1 | .\" Automatically generated by Pod::Man 2.16 (Pod::Simple 3.05) |
1 | .\" Automatically generated by Pod::Man 4.11 (Pod::Simple 3.35) |
2 | .\" |
2 | .\" |
3 | .\" Standard preamble: |
3 | .\" Standard preamble: |
4 | .\" ======================================================================== |
4 | .\" ======================================================================== |
5 | .de Sh \" Subsection heading |
|
|
6 | .br |
|
|
7 | .if t .Sp |
|
|
8 | .ne 5 |
|
|
9 | .PP |
|
|
10 | \fB\\$1\fR |
|
|
11 | .PP |
|
|
12 | .. |
|
|
13 | .de Sp \" Vertical space (when we can't use .PP) |
5 | .de Sp \" Vertical space (when we can't use .PP) |
14 | .if t .sp .5v |
6 | .if t .sp .5v |
15 | .if n .sp |
7 | .if n .sp |
16 | .. |
8 | .. |
17 | .de Vb \" Begin verbatim text |
9 | .de Vb \" Begin verbatim text |
… | |
… | |
44 | .el\{\ |
36 | .el\{\ |
45 | . ds -- \|\(em\| |
37 | . ds -- \|\(em\| |
46 | . ds PI \(*p |
38 | . ds PI \(*p |
47 | . ds L" `` |
39 | . ds L" `` |
48 | . ds R" '' |
40 | . ds R" '' |
|
|
41 | . ds C` |
|
|
42 | . ds C' |
49 | 'br\} |
43 | 'br\} |
50 | .\" |
44 | .\" |
51 | .\" Escape single quotes in literal strings from groff's Unicode transform. |
45 | .\" Escape single quotes in literal strings from groff's Unicode transform. |
52 | .ie \n(.g .ds Aq \(aq |
46 | .ie \n(.g .ds Aq \(aq |
53 | .el .ds Aq ' |
47 | .el .ds Aq ' |
54 | .\" |
48 | .\" |
55 | .\" If the F register is turned on, we'll generate index entries on stderr for |
49 | .\" If the F register is >0, we'll generate index entries on stderr for |
56 | .\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index |
50 | .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index |
57 | .\" entries marked with X<> in POD. Of course, you'll have to process the |
51 | .\" entries marked with X<> in POD. Of course, you'll have to process the |
58 | .\" output yourself in some meaningful fashion. |
52 | .\" output yourself in some meaningful fashion. |
59 | .ie \nF \{\ |
53 | .\" |
|
|
54 | .\" Avoid warning from groff about undefined register 'F'. |
60 | . de IX |
55 | .de IX |
61 | . tm Index:\\$1\t\\n%\t"\\$2" |
|
|
62 | .. |
56 | .. |
63 | . nr % 0 |
57 | .nr rF 0 |
64 | . rr F |
58 | .if \n(.g .if rF .nr rF 1 |
|
|
59 | .if (\n(rF:(\n(.g==0)) \{\ |
|
|
60 | . if \nF \{\ |
|
|
61 | . de IX |
|
|
62 | . tm Index:\\$1\t\\n%\t"\\$2" |
|
|
63 | .. |
|
|
64 | . if !\nF==2 \{\ |
|
|
65 | . nr % 0 |
|
|
66 | . nr F 2 |
|
|
67 | . \} |
|
|
68 | . \} |
65 | .\} |
69 | .\} |
66 | .el \{\ |
70 | .rr rF |
67 | . de IX |
|
|
68 | .. |
|
|
69 | .\} |
|
|
70 | .\" |
71 | .\" |
71 | .\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2). |
72 | .\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2). |
72 | .\" Fear. Run. Save yourself. No user-serviceable parts. |
73 | .\" Fear. Run. Save yourself. No user-serviceable parts. |
73 | . \" fudge factors for nroff and troff |
74 | . \" fudge factors for nroff and troff |
74 | .if n \{\ |
75 | .if n \{\ |
… | |
… | |
130 | .\} |
131 | .\} |
131 | .rm #[ #] #H #V #F C |
132 | .rm #[ #] #H #V #F C |
132 | .\" ======================================================================== |
133 | .\" ======================================================================== |
133 | .\" |
134 | .\" |
134 | .IX Title "LIBEV 3" |
135 | .IX Title "LIBEV 3" |
135 | .TH LIBEV 3 "2008-09-29" "libev-3.44" "libev - high performance full featured event loop" |
136 | .TH LIBEV 3 "2019-06-25" "libev-4.25" "libev - high performance full featured event loop" |
136 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
137 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
137 | .\" way too many mistakes in technical documents. |
138 | .\" way too many mistakes in technical documents. |
138 | .if n .ad l |
139 | .if n .ad l |
139 | .nh |
140 | .nh |
140 | .SH "NAME" |
141 | .SH "NAME" |
… | |
… | |
142 | .SH "SYNOPSIS" |
143 | .SH "SYNOPSIS" |
143 | .IX Header "SYNOPSIS" |
144 | .IX Header "SYNOPSIS" |
144 | .Vb 1 |
145 | .Vb 1 |
145 | \& #include <ev.h> |
146 | \& #include <ev.h> |
146 | .Ve |
147 | .Ve |
147 | .Sh "\s-1EXAMPLE\s0 \s-1PROGRAM\s0" |
148 | .SS "\s-1EXAMPLE PROGRAM\s0" |
148 | .IX Subsection "EXAMPLE PROGRAM" |
149 | .IX Subsection "EXAMPLE PROGRAM" |
149 | .Vb 2 |
150 | .Vb 2 |
150 | \& // a single header file is required |
151 | \& // a single header file is required |
151 | \& #include <ev.h> |
152 | \& #include <ev.h> |
152 | \& |
153 | \& |
|
|
154 | \& #include <stdio.h> // for puts |
|
|
155 | \& |
153 | \& // every watcher type has its own typedef\*(Aqd struct |
156 | \& // every watcher type has its own typedef\*(Aqd struct |
154 | \& // with the name ev_<type> |
157 | \& // with the name ev_TYPE |
155 | \& ev_io stdin_watcher; |
158 | \& ev_io stdin_watcher; |
156 | \& ev_timer timeout_watcher; |
159 | \& ev_timer timeout_watcher; |
157 | \& |
160 | \& |
158 | \& // all watcher callbacks have a similar signature |
161 | \& // all watcher callbacks have a similar signature |
159 | \& // this callback is called when data is readable on stdin |
162 | \& // this callback is called when data is readable on stdin |
160 | \& static void |
163 | \& static void |
161 | \& stdin_cb (EV_P_ struct ev_io *w, int revents) |
164 | \& stdin_cb (EV_P_ ev_io *w, int revents) |
162 | \& { |
165 | \& { |
163 | \& puts ("stdin ready"); |
166 | \& puts ("stdin ready"); |
164 | \& // for one\-shot events, one must manually stop the watcher |
167 | \& // for one\-shot events, one must manually stop the watcher |
165 | \& // with its corresponding stop function. |
168 | \& // with its corresponding stop function. |
166 | \& ev_io_stop (EV_A_ w); |
169 | \& ev_io_stop (EV_A_ w); |
167 | \& |
170 | \& |
168 | \& // this causes all nested ev_loop\*(Aqs to stop iterating |
171 | \& // this causes all nested ev_run\*(Aqs to stop iterating |
169 | \& ev_unloop (EV_A_ EVUNLOOP_ALL); |
172 | \& ev_break (EV_A_ EVBREAK_ALL); |
170 | \& } |
173 | \& } |
171 | \& |
174 | \& |
172 | \& // another callback, this time for a time\-out |
175 | \& // another callback, this time for a time\-out |
173 | \& static void |
176 | \& static void |
174 | \& timeout_cb (EV_P_ struct ev_timer *w, int revents) |
177 | \& timeout_cb (EV_P_ ev_timer *w, int revents) |
175 | \& { |
178 | \& { |
176 | \& puts ("timeout"); |
179 | \& puts ("timeout"); |
177 | \& // this causes the innermost ev_loop to stop iterating |
180 | \& // this causes the innermost ev_run to stop iterating |
178 | \& ev_unloop (EV_A_ EVUNLOOP_ONE); |
181 | \& ev_break (EV_A_ EVBREAK_ONE); |
179 | \& } |
182 | \& } |
180 | \& |
183 | \& |
181 | \& int |
184 | \& int |
182 | \& main (void) |
185 | \& main (void) |
183 | \& { |
186 | \& { |
184 | \& // use the default event loop unless you have special needs |
187 | \& // use the default event loop unless you have special needs |
185 | \& struct ev_loop *loop = ev_default_loop (0); |
188 | \& struct ev_loop *loop = EV_DEFAULT; |
186 | \& |
189 | \& |
187 | \& // initialise an io watcher, then start it |
190 | \& // initialise an io watcher, then start it |
188 | \& // this one will watch for stdin to become readable |
191 | \& // this one will watch for stdin to become readable |
189 | \& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
192 | \& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
190 | \& ev_io_start (loop, &stdin_watcher); |
193 | \& ev_io_start (loop, &stdin_watcher); |
… | |
… | |
193 | \& // simple non\-repeating 5.5 second timeout |
196 | \& // simple non\-repeating 5.5 second timeout |
194 | \& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
197 | \& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
195 | \& ev_timer_start (loop, &timeout_watcher); |
198 | \& ev_timer_start (loop, &timeout_watcher); |
196 | \& |
199 | \& |
197 | \& // now wait for events to arrive |
200 | \& // now wait for events to arrive |
198 | \& ev_loop (loop, 0); |
201 | \& ev_run (loop, 0); |
199 | \& |
202 | \& |
200 | \& // unloop was called, so exit |
203 | \& // break was called, so exit |
201 | \& return 0; |
204 | \& return 0; |
202 | \& } |
205 | \& } |
203 | .Ve |
206 | .Ve |
204 | .SH "DESCRIPTION" |
207 | .SH "ABOUT THIS DOCUMENT" |
205 | .IX Header "DESCRIPTION" |
208 | .IX Header "ABOUT THIS DOCUMENT" |
|
|
209 | This document documents the libev software package. |
|
|
210 | .PP |
206 | The newest version of this document is also available as an html-formatted |
211 | The newest version of this document is also available as an html-formatted |
207 | web page you might find easier to navigate when reading it for the first |
212 | web page you might find easier to navigate when reading it for the first |
208 | time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
213 | time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
209 | .PP |
214 | .PP |
|
|
215 | While this document tries to be as complete as possible in documenting |
|
|
216 | libev, its usage and the rationale behind its design, it is not a tutorial |
|
|
217 | on event-based programming, nor will it introduce event-based programming |
|
|
218 | with libev. |
|
|
219 | .PP |
|
|
220 | Familiarity with event based programming techniques in general is assumed |
|
|
221 | throughout this document. |
|
|
222 | .SH "WHAT TO READ WHEN IN A HURRY" |
|
|
223 | .IX Header "WHAT TO READ WHEN IN A HURRY" |
|
|
224 | This manual tries to be very detailed, but unfortunately, this also makes |
|
|
225 | it very long. If you just want to know the basics of libev, I suggest |
|
|
226 | reading \*(L"\s-1ANATOMY OF A WATCHER\*(R"\s0, then the \*(L"\s-1EXAMPLE PROGRAM\*(R"\s0 above and |
|
|
227 | look up the missing functions in \*(L"\s-1GLOBAL FUNCTIONS\*(R"\s0 and the \f(CW\*(C`ev_io\*(C'\fR and |
|
|
228 | \&\f(CW\*(C`ev_timer\*(C'\fR sections in \*(L"\s-1WATCHER TYPES\*(R"\s0. |
|
|
229 | .SH "ABOUT LIBEV" |
|
|
230 | .IX Header "ABOUT LIBEV" |
210 | Libev is an event loop: you register interest in certain events (such as a |
231 | Libev is an event loop: you register interest in certain events (such as a |
211 | file descriptor being readable or a timeout occurring), and it will manage |
232 | file descriptor being readable or a timeout occurring), and it will manage |
212 | these event sources and provide your program with events. |
233 | these event sources and provide your program with events. |
213 | .PP |
234 | .PP |
214 | To do this, it must take more or less complete control over your process |
235 | To do this, it must take more or less complete control over your process |
… | |
… | |
217 | .PP |
238 | .PP |
218 | You register interest in certain events by registering so-called \fIevent |
239 | You register interest in certain events by registering so-called \fIevent |
219 | watchers\fR, which are relatively small C structures you initialise with the |
240 | watchers\fR, which are relatively small C structures you initialise with the |
220 | details of the event, and then hand it over to libev by \fIstarting\fR the |
241 | details of the event, and then hand it over to libev by \fIstarting\fR the |
221 | watcher. |
242 | watcher. |
222 | .Sh "\s-1FEATURES\s0" |
243 | .SS "\s-1FEATURES\s0" |
223 | .IX Subsection "FEATURES" |
244 | .IX Subsection "FEATURES" |
224 | Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the |
245 | Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific aio and \f(CW\*(C`epoll\*(C'\fR |
225 | BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms |
246 | interfaces, the BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port |
226 | for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface |
247 | mechanisms for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR |
227 | (for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers |
248 | interface (for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner |
228 | with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals |
249 | inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative |
229 | (\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event |
250 | timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling |
230 | watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, |
251 | (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status |
231 | \&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as |
252 | change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event |
232 | file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events |
253 | loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and |
233 | (\f(CW\*(C`ev_fork\*(C'\fR). |
254 | \&\f(CW\*(C`ev_check\*(C'\fR watchers) as well as file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even |
|
|
255 | limited support for fork events (\f(CW\*(C`ev_fork\*(C'\fR). |
234 | .PP |
256 | .PP |
235 | It also is quite fast (see this |
257 | It also is quite fast (see this |
236 | benchmark comparing it to libevent |
258 | benchmark <http://libev.schmorp.de/bench.html> comparing it to libevent |
237 | for example). |
259 | for example). |
238 | .Sh "\s-1CONVENTIONS\s0" |
260 | .SS "\s-1CONVENTIONS\s0" |
239 | .IX Subsection "CONVENTIONS" |
261 | .IX Subsection "CONVENTIONS" |
240 | Libev is very configurable. In this manual the default (and most common) |
262 | Libev is very configurable. In this manual the default (and most common) |
241 | configuration will be described, which supports multiple event loops. For |
263 | configuration will be described, which supports multiple event loops. For |
242 | more info about various configuration options please have a look at |
264 | more info about various configuration options please have a look at |
243 | \&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support |
265 | \&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support |
244 | for multiple event loops, then all functions taking an initial argument of |
266 | for multiple event loops, then all functions taking an initial argument of |
245 | name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have |
267 | name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have |
246 | this argument. |
268 | this argument. |
247 | .Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0" |
269 | .SS "\s-1TIME REPRESENTATION\s0" |
248 | .IX Subsection "TIME REPRESENTATION" |
270 | .IX Subsection "TIME REPRESENTATION" |
249 | Libev represents time as a single floating point number, representing the |
271 | Libev represents time as a single floating point number, representing |
250 | (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near |
272 | the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (in practice |
251 | the beginning of 1970, details are complicated, don't ask). This type is |
273 | somewhere near the beginning of 1970, details are complicated, don't |
252 | called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases |
274 | ask). This type is called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use |
253 | to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on |
275 | too. It usually aliases to the \f(CW\*(C`double\*(C'\fR type in C. When you need to do |
254 | it, you should treat it as some floating point value. Unlike the name |
276 | any calculations on it, you should treat it as some floating point value. |
|
|
277 | .PP |
255 | component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences |
278 | Unlike the name component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for |
256 | throughout libev. |
279 | time differences (e.g. delays) throughout libev. |
257 | .SH "ERROR HANDLING" |
280 | .SH "ERROR HANDLING" |
258 | .IX Header "ERROR HANDLING" |
281 | .IX Header "ERROR HANDLING" |
259 | Libev knows three classes of errors: operating system errors, usage errors |
282 | Libev knows three classes of errors: operating system errors, usage errors |
260 | and internal errors (bugs). |
283 | and internal errors (bugs). |
261 | .PP |
284 | .PP |
… | |
… | |
279 | library in any way. |
302 | library in any way. |
280 | .IP "ev_tstamp ev_time ()" 4 |
303 | .IP "ev_tstamp ev_time ()" 4 |
281 | .IX Item "ev_tstamp ev_time ()" |
304 | .IX Item "ev_tstamp ev_time ()" |
282 | Returns the current time as libev would use it. Please note that the |
305 | Returns the current time as libev would use it. Please note that the |
283 | \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp |
306 | \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp |
284 | you actually want to know. |
307 | you actually want to know. Also interesting is the combination of |
|
|
308 | \&\f(CW\*(C`ev_now_update\*(C'\fR and \f(CW\*(C`ev_now\*(C'\fR. |
285 | .IP "ev_sleep (ev_tstamp interval)" 4 |
309 | .IP "ev_sleep (ev_tstamp interval)" 4 |
286 | .IX Item "ev_sleep (ev_tstamp interval)" |
310 | .IX Item "ev_sleep (ev_tstamp interval)" |
287 | Sleep for the given interval: The current thread will be blocked until |
311 | Sleep for the given interval: The current thread will be blocked |
288 | either it is interrupted or the given time interval has passed. Basically |
312 | until either it is interrupted or the given time interval has |
|
|
313 | passed (approximately \- it might return a bit earlier even if not |
|
|
314 | interrupted). Returns immediately if \f(CW\*(C`interval <= 0\*(C'\fR. |
|
|
315 | .Sp |
289 | this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR. |
316 | Basically this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR. |
|
|
317 | .Sp |
|
|
318 | The range of the \f(CW\*(C`interval\*(C'\fR is limited \- libev only guarantees to work |
|
|
319 | with sleep times of up to one day (\f(CW\*(C`interval <= 86400\*(C'\fR). |
290 | .IP "int ev_version_major ()" 4 |
320 | .IP "int ev_version_major ()" 4 |
291 | .IX Item "int ev_version_major ()" |
321 | .IX Item "int ev_version_major ()" |
292 | .PD 0 |
322 | .PD 0 |
293 | .IP "int ev_version_minor ()" 4 |
323 | .IP "int ev_version_minor ()" 4 |
294 | .IX Item "int ev_version_minor ()" |
324 | .IX Item "int ev_version_minor ()" |
… | |
… | |
306 | as this indicates an incompatible change. Minor versions are usually |
336 | as this indicates an incompatible change. Minor versions are usually |
307 | compatible to older versions, so a larger minor version alone is usually |
337 | compatible to older versions, so a larger minor version alone is usually |
308 | not a problem. |
338 | not a problem. |
309 | .Sp |
339 | .Sp |
310 | Example: Make sure we haven't accidentally been linked against the wrong |
340 | Example: Make sure we haven't accidentally been linked against the wrong |
311 | version. |
341 | version (note, however, that this will not detect other \s-1ABI\s0 mismatches, |
|
|
342 | such as \s-1LFS\s0 or reentrancy). |
312 | .Sp |
343 | .Sp |
313 | .Vb 3 |
344 | .Vb 3 |
314 | \& assert (("libev version mismatch", |
345 | \& assert (("libev version mismatch", |
315 | \& ev_version_major () == EV_VERSION_MAJOR |
346 | \& ev_version_major () == EV_VERSION_MAJOR |
316 | \& && ev_version_minor () >= EV_VERSION_MINOR)); |
347 | \& && ev_version_minor () >= EV_VERSION_MINOR)); |
… | |
… | |
329 | \& assert (("sorry, no epoll, no sex", |
360 | \& assert (("sorry, no epoll, no sex", |
330 | \& ev_supported_backends () & EVBACKEND_EPOLL)); |
361 | \& ev_supported_backends () & EVBACKEND_EPOLL)); |
331 | .Ve |
362 | .Ve |
332 | .IP "unsigned int ev_recommended_backends ()" 4 |
363 | .IP "unsigned int ev_recommended_backends ()" 4 |
333 | .IX Item "unsigned int ev_recommended_backends ()" |
364 | .IX Item "unsigned int ev_recommended_backends ()" |
334 | Return the set of all backends compiled into this binary of libev and also |
365 | Return the set of all backends compiled into this binary of libev and |
335 | recommended for this platform. This set is often smaller than the one |
366 | also recommended for this platform, meaning it will work for most file |
|
|
367 | descriptor types. This set is often smaller than the one returned by |
336 | returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on |
368 | \&\f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on most BSDs |
337 | most BSDs and will not be auto-detected unless you explicitly request it |
369 | and will not be auto-detected unless you explicitly request it (assuming |
338 | (assuming you know what you are doing). This is the set of backends that |
370 | you know what you are doing). This is the set of backends that libev will |
339 | libev will probe for if you specify no backends explicitly. |
371 | probe for if you specify no backends explicitly. |
340 | .IP "unsigned int ev_embeddable_backends ()" 4 |
372 | .IP "unsigned int ev_embeddable_backends ()" 4 |
341 | .IX Item "unsigned int ev_embeddable_backends ()" |
373 | .IX Item "unsigned int ev_embeddable_backends ()" |
342 | Returns the set of backends that are embeddable in other event loops. This |
374 | Returns the set of backends that are embeddable in other event loops. This |
343 | is the theoretical, all-platform, value. To find which backends |
375 | value is platform-specific but can include backends not available on the |
344 | might be supported on the current system, you would need to look at |
376 | current system. To find which embeddable backends might be supported on |
345 | \&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for |
377 | the current system, you would need to look at \f(CW\*(C`ev_embeddable_backends () |
346 | recommended ones. |
378 | & ev_supported_backends ()\*(C'\fR, likewise for recommended ones. |
347 | .Sp |
379 | .Sp |
348 | See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
380 | See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
349 | .IP "ev_set_allocator (void *(*cb)(void *ptr, long size)) [\s-1NOT\s0 \s-1REENTRANT\s0]" 4 |
381 | .IP "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())" 4 |
350 | .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]" |
382 | .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())" |
351 | Sets the allocation function to use (the prototype is similar \- the |
383 | Sets the allocation function to use (the prototype is similar \- the |
352 | semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is |
384 | semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is |
353 | used to allocate and free memory (no surprises here). If it returns zero |
385 | used to allocate and free memory (no surprises here). If it returns zero |
354 | when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort |
386 | when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort |
355 | or take some potentially destructive action. |
387 | or take some potentially destructive action. |
… | |
… | |
360 | .Sp |
392 | .Sp |
361 | You could override this function in high-availability programs to, say, |
393 | You could override this function in high-availability programs to, say, |
362 | free some memory if it cannot allocate memory, to use a special allocator, |
394 | free some memory if it cannot allocate memory, to use a special allocator, |
363 | or even to sleep a while and retry until some memory is available. |
395 | or even to sleep a while and retry until some memory is available. |
364 | .Sp |
396 | .Sp |
|
|
397 | Example: The following is the \f(CW\*(C`realloc\*(C'\fR function that libev itself uses |
|
|
398 | which should work with \f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions of all kinds and |
|
|
399 | is probably a good basis for your own implementation. |
|
|
400 | .Sp |
|
|
401 | .Vb 5 |
|
|
402 | \& static void * |
|
|
403 | \& ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT |
|
|
404 | \& { |
|
|
405 | \& if (size) |
|
|
406 | \& return realloc (ptr, size); |
|
|
407 | \& |
|
|
408 | \& free (ptr); |
|
|
409 | \& return 0; |
|
|
410 | \& } |
|
|
411 | .Ve |
|
|
412 | .Sp |
365 | Example: Replace the libev allocator with one that waits a bit and then |
413 | Example: Replace the libev allocator with one that waits a bit and then |
366 | retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR). |
414 | retries. |
367 | .Sp |
415 | .Sp |
368 | .Vb 6 |
416 | .Vb 8 |
369 | \& static void * |
417 | \& static void * |
370 | \& persistent_realloc (void *ptr, size_t size) |
418 | \& persistent_realloc (void *ptr, size_t size) |
371 | \& { |
419 | \& { |
|
|
420 | \& if (!size) |
|
|
421 | \& { |
|
|
422 | \& free (ptr); |
|
|
423 | \& return 0; |
|
|
424 | \& } |
|
|
425 | \& |
372 | \& for (;;) |
426 | \& for (;;) |
373 | \& { |
427 | \& { |
374 | \& void *newptr = realloc (ptr, size); |
428 | \& void *newptr = realloc (ptr, size); |
375 | \& |
429 | \& |
376 | \& if (newptr) |
430 | \& if (newptr) |
… | |
… | |
381 | \& } |
435 | \& } |
382 | \& |
436 | \& |
383 | \& ... |
437 | \& ... |
384 | \& ev_set_allocator (persistent_realloc); |
438 | \& ev_set_allocator (persistent_realloc); |
385 | .Ve |
439 | .Ve |
386 | .IP "ev_set_syserr_cb (void (*cb)(const char *msg)); [\s-1NOT\s0 \s-1REENTRANT\s0]" 4 |
440 | .IP "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())" 4 |
387 | .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]" |
441 | .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg) throw ())" |
388 | Set the callback function to call on a retryable system call error (such |
442 | Set the callback function to call on a retryable system call error (such |
389 | as failed select, poll, epoll_wait). The message is a printable string |
443 | as failed select, poll, epoll_wait). The message is a printable string |
390 | indicating the system call or subsystem causing the problem. If this |
444 | indicating the system call or subsystem causing the problem. If this |
391 | callback is set, then libev will expect it to remedy the situation, no |
445 | callback is set, then libev will expect it to remedy the situation, no |
392 | matter what, when it returns. That is, libev will generally retry the |
446 | matter what, when it returns. That is, libev will generally retry the |
… | |
… | |
404 | \& } |
458 | \& } |
405 | \& |
459 | \& |
406 | \& ... |
460 | \& ... |
407 | \& ev_set_syserr_cb (fatal_error); |
461 | \& ev_set_syserr_cb (fatal_error); |
408 | .Ve |
462 | .Ve |
|
|
463 | .IP "ev_feed_signal (int signum)" 4 |
|
|
464 | .IX Item "ev_feed_signal (int signum)" |
|
|
465 | This function can be used to \*(L"simulate\*(R" a signal receive. It is completely |
|
|
466 | safe to call this function at any time, from any context, including signal |
|
|
467 | handlers or random threads. |
|
|
468 | .Sp |
|
|
469 | Its main use is to customise signal handling in your process, especially |
|
|
470 | in the presence of threads. For example, you could block signals |
|
|
471 | by default in all threads (and specifying \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when |
|
|
472 | creating any loops), and in one thread, use \f(CW\*(C`sigwait\*(C'\fR or any other |
|
|
473 | mechanism to wait for signals, then \*(L"deliver\*(R" them to libev by calling |
|
|
474 | \&\f(CW\*(C`ev_feed_signal\*(C'\fR. |
409 | .SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
475 | .SH "FUNCTIONS CONTROLLING EVENT LOOPS" |
410 | .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
476 | .IX Header "FUNCTIONS CONTROLLING EVENT LOOPS" |
411 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two |
477 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR is |
412 | types of such loops, the \fIdefault\fR loop, which supports signals and child |
478 | \&\fInot\fR optional in this case unless libev 3 compatibility is disabled, as |
413 | events, and dynamically created loops which do not. |
479 | libev 3 had an \f(CW\*(C`ev_loop\*(C'\fR function colliding with the struct name). |
|
|
480 | .PP |
|
|
481 | The library knows two types of such loops, the \fIdefault\fR loop, which |
|
|
482 | supports child process events, and dynamically created event loops which |
|
|
483 | do not. |
414 | .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
484 | .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
415 | .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
485 | .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
416 | This will initialise the default event loop if it hasn't been initialised |
486 | This returns the \*(L"default\*(R" event loop object, which is what you should |
417 | yet and return it. If the default loop could not be initialised, returns |
487 | normally use when you just need \*(L"the event loop\*(R". Event loop objects and |
418 | false. If it already was initialised it simply returns it (and ignores the |
488 | the \f(CW\*(C`flags\*(C'\fR parameter are described in more detail in the entry for |
419 | flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards). |
489 | \&\f(CW\*(C`ev_loop_new\*(C'\fR. |
|
|
490 | .Sp |
|
|
491 | If the default loop is already initialised then this function simply |
|
|
492 | returns it (and ignores the flags. If that is troubling you, check |
|
|
493 | \&\f(CW\*(C`ev_backend ()\*(C'\fR afterwards). Otherwise it will create it with the given |
|
|
494 | flags, which should almost always be \f(CW0\fR, unless the caller is also the |
|
|
495 | one calling \f(CW\*(C`ev_run\*(C'\fR or otherwise qualifies as \*(L"the main program\*(R". |
420 | .Sp |
496 | .Sp |
421 | If you don't know what event loop to use, use the one returned from this |
497 | If you don't know what event loop to use, use the one returned from this |
422 | function. |
498 | function (or via the \f(CW\*(C`EV_DEFAULT\*(C'\fR macro). |
423 | .Sp |
499 | .Sp |
424 | Note that this function is \fInot\fR thread-safe, so if you want to use it |
500 | Note that this function is \fInot\fR thread-safe, so if you want to use it |
425 | from multiple threads, you have to lock (note also that this is unlikely, |
501 | from multiple threads, you have to employ some kind of mutex (note also |
426 | as loops cannot bes hared easily between threads anyway). |
502 | that this case is unlikely, as loops cannot be shared easily between |
|
|
503 | threads anyway). |
427 | .Sp |
504 | .Sp |
428 | The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and |
505 | The default loop is the only loop that can handle \f(CW\*(C`ev_child\*(C'\fR watchers, |
429 | \&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler |
506 | and to do this, it always registers a handler for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is |
430 | for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your application you can either |
507 | a problem for your application you can either create a dynamic loop with |
431 | create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you |
508 | \&\f(CW\*(C`ev_loop_new\*(C'\fR which doesn't do that, or you can simply overwrite the |
432 | can simply overwrite the \f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling |
509 | \&\f(CW\*(C`SIGCHLD\*(C'\fR signal handler \fIafter\fR calling \f(CW\*(C`ev_default_init\*(C'\fR. |
433 | \&\f(CW\*(C`ev_default_init\*(C'\fR. |
510 | .Sp |
|
|
511 | Example: This is the most typical usage. |
|
|
512 | .Sp |
|
|
513 | .Vb 2 |
|
|
514 | \& if (!ev_default_loop (0)) |
|
|
515 | \& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
516 | .Ve |
|
|
517 | .Sp |
|
|
518 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
519 | environment settings to be taken into account: |
|
|
520 | .Sp |
|
|
521 | .Vb 1 |
|
|
522 | \& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
523 | .Ve |
|
|
524 | .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
|
|
525 | .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
|
|
526 | This will create and initialise a new event loop object. If the loop |
|
|
527 | could not be initialised, returns false. |
|
|
528 | .Sp |
|
|
529 | This function is thread-safe, and one common way to use libev with |
|
|
530 | threads is indeed to create one loop per thread, and using the default |
|
|
531 | loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread. |
434 | .Sp |
532 | .Sp |
435 | The flags argument can be used to specify special behaviour or specific |
533 | The flags argument can be used to specify special behaviour or specific |
436 | backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). |
534 | backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). |
437 | .Sp |
535 | .Sp |
438 | The following flags are supported: |
536 | The following flags are supported: |
… | |
… | |
447 | .IX Item "EVFLAG_NOENV" |
545 | .IX Item "EVFLAG_NOENV" |
448 | If this flag bit is or'ed into the flag value (or the program runs setuid |
546 | If this flag bit is or'ed into the flag value (or the program runs setuid |
449 | or setgid) then libev will \fInot\fR look at the environment variable |
547 | or setgid) then libev will \fInot\fR look at the environment variable |
450 | \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will |
548 | \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will |
451 | override the flags completely if it is found in the environment. This is |
549 | override the flags completely if it is found in the environment. This is |
452 | useful to try out specific backends to test their performance, or to work |
550 | useful to try out specific backends to test their performance, to work |
453 | around bugs. |
551 | around bugs, or to make libev threadsafe (accessing environment variables |
|
|
552 | cannot be done in a threadsafe way, but usually it works if no other |
|
|
553 | thread modifies them). |
454 | .ie n .IP """EVFLAG_FORKCHECK""" 4 |
554 | .ie n .IP """EVFLAG_FORKCHECK""" 4 |
455 | .el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4 |
555 | .el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4 |
456 | .IX Item "EVFLAG_FORKCHECK" |
556 | .IX Item "EVFLAG_FORKCHECK" |
457 | Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after |
557 | Instead of calling \f(CW\*(C`ev_loop_fork\*(C'\fR manually after a fork, you can also |
458 | a fork, you can also make libev check for a fork in each iteration by |
558 | make libev check for a fork in each iteration by enabling this flag. |
459 | enabling this flag. |
|
|
460 | .Sp |
559 | .Sp |
461 | This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop, |
560 | This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop, |
462 | and thus this might slow down your event loop if you do a lot of loop |
561 | and thus this might slow down your event loop if you do a lot of loop |
463 | iterations and little real work, but is usually not noticeable (on my |
562 | iterations and little real work, but is usually not noticeable (on my |
464 | GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence |
563 | GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn |
465 | without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has |
564 | sequence without a system call and thus \fIvery\fR fast, but my GNU/Linux |
466 | \&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). |
565 | system also has \f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). (Update: glibc |
|
|
566 | versions 2.25 apparently removed the \f(CW\*(C`getpid\*(C'\fR optimisation again). |
467 | .Sp |
567 | .Sp |
468 | The big advantage of this flag is that you can forget about fork (and |
568 | The big advantage of this flag is that you can forget about fork (and |
469 | forget about forgetting to tell libev about forking) when you use this |
569 | forget about forgetting to tell libev about forking, although you still |
470 | flag. |
570 | have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR) when you use this flag. |
471 | .Sp |
571 | .Sp |
472 | This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR |
572 | This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR |
473 | environment variable. |
573 | environment variable. |
|
|
574 | .ie n .IP """EVFLAG_NOINOTIFY""" 4 |
|
|
575 | .el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4 |
|
|
576 | .IX Item "EVFLAG_NOINOTIFY" |
|
|
577 | When this flag is specified, then libev will not attempt to use the |
|
|
578 | \&\fIinotify\fR \s-1API\s0 for its \f(CW\*(C`ev_stat\*(C'\fR watchers. Apart from debugging and |
|
|
579 | testing, this flag can be useful to conserve inotify file descriptors, as |
|
|
580 | otherwise each loop using \f(CW\*(C`ev_stat\*(C'\fR watchers consumes one inotify handle. |
|
|
581 | .ie n .IP """EVFLAG_SIGNALFD""" 4 |
|
|
582 | .el .IP "\f(CWEVFLAG_SIGNALFD\fR" 4 |
|
|
583 | .IX Item "EVFLAG_SIGNALFD" |
|
|
584 | When this flag is specified, then libev will attempt to use the |
|
|
585 | \&\fIsignalfd\fR \s-1API\s0 for its \f(CW\*(C`ev_signal\*(C'\fR (and \f(CW\*(C`ev_child\*(C'\fR) watchers. This \s-1API\s0 |
|
|
586 | delivers signals synchronously, which makes it both faster and might make |
|
|
587 | it possible to get the queued signal data. It can also simplify signal |
|
|
588 | handling with threads, as long as you properly block signals in your |
|
|
589 | threads that are not interested in handling them. |
|
|
590 | .Sp |
|
|
591 | Signalfd will not be used by default as this changes your signal mask, and |
|
|
592 | there are a lot of shoddy libraries and programs (glib's threadpool for |
|
|
593 | example) that can't properly initialise their signal masks. |
|
|
594 | .ie n .IP """EVFLAG_NOSIGMASK""" 4 |
|
|
595 | .el .IP "\f(CWEVFLAG_NOSIGMASK\fR" 4 |
|
|
596 | .IX Item "EVFLAG_NOSIGMASK" |
|
|
597 | When this flag is specified, then libev will avoid to modify the signal |
|
|
598 | mask. Specifically, this means you have to make sure signals are unblocked |
|
|
599 | when you want to receive them. |
|
|
600 | .Sp |
|
|
601 | This behaviour is useful when you want to do your own signal handling, or |
|
|
602 | want to handle signals only in specific threads and want to avoid libev |
|
|
603 | unblocking the signals. |
|
|
604 | .Sp |
|
|
605 | It's also required by \s-1POSIX\s0 in a threaded program, as libev calls |
|
|
606 | \&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified. |
|
|
607 | .Sp |
|
|
608 | This flag's behaviour will become the default in future versions of libev. |
474 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
609 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
475 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
610 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
476 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
611 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
477 | This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
612 | This is your standard \fBselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
478 | libev tries to roll its own fd_set with no limits on the number of fds, |
613 | libev tries to roll its own fd_set with no limits on the number of fds, |
479 | but if that fails, expect a fairly low limit on the number of fds when |
614 | but if that fails, expect a fairly low limit on the number of fds when |
480 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
615 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
481 | usually the fastest backend for a low number of (low-numbered :) fds. |
616 | usually the fastest backend for a low number of (low-numbered :) fds. |
482 | .Sp |
617 | .Sp |
… | |
… | |
490 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR to the \f(CW\*(C`readfds\*(C'\fR set and \f(CW\*(C`EV_WRITE\*(C'\fR to the |
625 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR to the \f(CW\*(C`readfds\*(C'\fR set and \f(CW\*(C`EV_WRITE\*(C'\fR to the |
491 | \&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the |
626 | \&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the |
492 | \&\f(CW\*(C`exceptfds\*(C'\fR set on that platform). |
627 | \&\f(CW\*(C`exceptfds\*(C'\fR set on that platform). |
493 | .ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
628 | .ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
494 | .el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
629 | .el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
495 | .IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" |
630 | .IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" |
496 | And this is your standard \fIpoll\fR\|(2) backend. It's more complicated |
631 | And this is your standard \fBpoll\fR\|(2) backend. It's more complicated |
497 | than select, but handles sparse fds better and has no artificial |
632 | than select, but handles sparse fds better and has no artificial |
498 | limit on the number of fds you can use (except it will slow down |
633 | limit on the number of fds you can use (except it will slow down |
499 | considerably with a lot of inactive fds). It scales similarly to select, |
634 | considerably with a lot of inactive fds). It scales similarly to select, |
500 | i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for |
635 | i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for |
501 | performance tips. |
636 | performance tips. |
502 | .Sp |
637 | .Sp |
503 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and |
638 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and |
504 | \&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR. |
639 | \&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR. |
505 | .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
640 | .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
506 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
641 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
507 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
642 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
|
|
643 | Use the Linux-specific \fBepoll\fR\|(7) interface (for both pre\- and post\-2.6.9 |
|
|
644 | kernels). |
|
|
645 | .Sp |
508 | For few fds, this backend is a bit little slower than poll and select, |
646 | For few fds, this backend is a bit little slower than poll and select, but |
509 | but it scales phenomenally better. While poll and select usually scale |
647 | it scales phenomenally better. While poll and select usually scale like |
510 | like O(total_fds) where n is the total number of fds (or the highest fd), |
648 | O(total_fds) where total_fds is the total number of fds (or the highest |
511 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
649 | fd), epoll scales either O(1) or O(active_fds). |
512 | of shortcomings, such as silently dropping events in some hard-to-detect |
650 | .Sp |
513 | cases and requiring a system call per fd change, no fork support and bad |
651 | The epoll mechanism deserves honorable mention as the most misdesigned |
514 | support for dup. |
652 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
653 | dropping file descriptors, requiring a system call per change per file |
|
|
654 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
655 | returning before the timeout value, resulting in additional iterations |
|
|
656 | (and only giving 5ms accuracy while select on the same platform gives |
|
|
657 | 0.1ms) and so on. The biggest issue is fork races, however \- if a program |
|
|
658 | forks then \fIboth\fR parent and child process have to recreate the epoll |
|
|
659 | set, which can take considerable time (one syscall per file descriptor) |
|
|
660 | and is of course hard to detect. |
|
|
661 | .Sp |
|
|
662 | Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work, |
|
|
663 | but of course \fIdoesn't\fR, and epoll just loves to report events for |
|
|
664 | totally \fIdifferent\fR file descriptors (even already closed ones, so |
|
|
665 | one cannot even remove them from the set) than registered in the set |
|
|
666 | (especially on \s-1SMP\s0 systems). Libev tries to counter these spurious |
|
|
667 | notifications by employing an additional generation counter and comparing |
|
|
668 | that against the events to filter out spurious ones, recreating the set |
|
|
669 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
670 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
671 | because epoll returns immediately despite a nonzero timeout. And last |
|
|
672 | not least, it also refuses to work with some file descriptors which work |
|
|
673 | perfectly fine with \f(CW\*(C`select\*(C'\fR (files, many character devices...). |
|
|
674 | .Sp |
|
|
675 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
676 | cobbled together in a hurry, no thought to design or interaction with |
|
|
677 | others. Oh, the pain, will it ever stop... |
515 | .Sp |
678 | .Sp |
516 | While stopping, setting and starting an I/O watcher in the same iteration |
679 | While stopping, setting and starting an I/O watcher in the same iteration |
517 | will result in some caching, there is still a system call per such incident |
680 | will result in some caching, there is still a system call per such |
518 | (because the fd could point to a different file description now), so its |
681 | incident (because the same \fIfile descriptor\fR could point to a different |
519 | best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work |
682 | \&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed |
520 | very well if you register events for both fds. |
683 | file descriptors might not work very well if you register events for both |
521 | .Sp |
684 | file descriptors. |
522 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
523 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
524 | (or space) is available. |
|
|
525 | .Sp |
685 | .Sp |
526 | Best performance from this backend is achieved by not unregistering all |
686 | Best performance from this backend is achieved by not unregistering all |
527 | watchers for a file descriptor until it has been closed, if possible, |
687 | watchers for a file descriptor until it has been closed, if possible, |
528 | i.e. keep at least one watcher active per fd at all times. Stopping and |
688 | i.e. keep at least one watcher active per fd at all times. Stopping and |
529 | starting a watcher (without re-setting it) also usually doesn't cause |
689 | starting a watcher (without re-setting it) also usually doesn't cause |
530 | extra overhead. |
690 | extra overhead. A fork can both result in spurious notifications as well |
|
|
691 | as in libev having to destroy and recreate the epoll object, which can |
|
|
692 | take considerable time and thus should be avoided. |
|
|
693 | .Sp |
|
|
694 | All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or |
|
|
695 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
696 | the usage. So sad. |
531 | .Sp |
697 | .Sp |
532 | While nominally embeddable in other event loops, this feature is broken in |
698 | While nominally embeddable in other event loops, this feature is broken in |
533 | all kernel versions tested so far. |
699 | a lot of kernel revisions, but probably(!) works in current versions. |
|
|
700 | .Sp |
|
|
701 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
|
|
702 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
|
|
703 | .ie n .IP """EVBACKEND_LINUXAIO"" (value 64, Linux)" 4 |
|
|
704 | .el .IP "\f(CWEVBACKEND_LINUXAIO\fR (value 64, Linux)" 4 |
|
|
705 | .IX Item "EVBACKEND_LINUXAIO (value 64, Linux)" |
|
|
706 | Use the Linux-specific Linux \s-1AIO\s0 (\fInot\fR \f(CWaio(7)\fR but \f(CWio_submit(2)\fR) event interface available in post\-4.18 kernels (but libev |
|
|
707 | only tries to use it in 4.19+). |
|
|
708 | .Sp |
|
|
709 | This is another Linux train wreck of an event interface. |
|
|
710 | .Sp |
|
|
711 | If this backend works for you (as of this writing, it was very |
|
|
712 | experimental), it is the best event interface available on Linux and might |
|
|
713 | be well worth enabling it \- if it isn't available in your kernel this will |
|
|
714 | be detected and this backend will be skipped. |
|
|
715 | .Sp |
|
|
716 | This backend can batch oneshot requests and supports a user-space ring |
|
|
717 | buffer to receive events. It also doesn't suffer from most of the design |
|
|
718 | problems of epoll (such as not being able to remove event sources from |
|
|
719 | the epoll set), and generally sounds too good to be true. Because, this |
|
|
720 | being the Linux kernel, of course it suffers from a whole new set of |
|
|
721 | limitations, forcing you to fall back to epoll, inheriting all its design |
|
|
722 | issues. |
|
|
723 | .Sp |
|
|
724 | For one, it is not easily embeddable (but probably could be done using |
|
|
725 | an event fd at some extra overhead). It also is subject to a system wide |
|
|
726 | limit that can be configured in \fI/proc/sys/fs/aio\-max\-nr\fR. If no \s-1AIO\s0 |
|
|
727 | requests are left, this backend will be skipped during initialisation, and |
|
|
728 | will switch to epoll when the loop is active. |
|
|
729 | .Sp |
|
|
730 | Most problematic in practice, however, is that not all file descriptors |
|
|
731 | work with it. For example, in Linux 5.1, \s-1TCP\s0 sockets, pipes, event fds, |
|
|
732 | files, \fI/dev/null\fR and many others are supported, but ttys do not work |
|
|
733 | properly (a known bug that the kernel developers don't care about, see |
|
|
734 | <https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
|
|
735 | (yet?) a generic event polling interface. |
|
|
736 | .Sp |
|
|
737 | Overall, it seems the Linux developers just don't want it to have a |
|
|
738 | generic event handling mechanism other than \f(CW\*(C`select\*(C'\fR or \f(CW\*(C`poll\*(C'\fR. |
|
|
739 | .Sp |
|
|
740 | To work around all these problem, the current version of libev uses its |
|
|
741 | epoll backend as a fallback for file descriptor types that do not work. Or |
|
|
742 | falls back completely to epoll if the kernel acts up. |
534 | .Sp |
743 | .Sp |
535 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
744 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
536 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
745 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
537 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
746 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
538 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
747 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
539 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
748 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
540 | Kqueue deserves special mention, as at the time of this writing, it was |
749 | Kqueue deserves special mention, as at the time this backend was |
541 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
750 | implemented, it was broken on all BSDs except NetBSD (usually it doesn't |
542 | anything but sockets and pipes, except on Darwin, where of course it's |
751 | work reliably with anything but sockets and pipes, except on Darwin, |
543 | completely useless). For this reason it's not being \*(L"auto-detected\*(R" unless |
752 | where of course it's completely useless). Unlike epoll, however, whose |
544 | you explicitly specify it in the flags (i.e. using \f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or |
753 | brokenness is by design, these kqueue bugs can be (and mostly have been) |
|
|
754 | fixed without \s-1API\s0 changes to existing programs. For this reason it's not |
|
|
755 | being \*(L"auto-detected\*(R" on all platforms unless you explicitly specify it |
|
|
756 | in the flags (i.e. using \f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a |
545 | libev was compiled on a known-to-be-good (\-enough) system like NetBSD. |
757 | known-to-be-good (\-enough) system like NetBSD. |
546 | .Sp |
758 | .Sp |
547 | You still can embed kqueue into a normal poll or select backend and use it |
759 | You still can embed kqueue into a normal poll or select backend and use it |
548 | only for sockets (after having made sure that sockets work with kqueue on |
760 | only for sockets (after having made sure that sockets work with kqueue on |
549 | the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
761 | the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
550 | .Sp |
762 | .Sp |
551 | It scales in the same way as the epoll backend, but the interface to the |
763 | It scales in the same way as the epoll backend, but the interface to the |
552 | kernel is more efficient (which says nothing about its actual speed, of |
764 | kernel is more efficient (which says nothing about its actual speed, of |
553 | course). While stopping, setting and starting an I/O watcher does never |
765 | course). While stopping, setting and starting an I/O watcher does never |
554 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
766 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
555 | two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it |
767 | two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you |
|
|
768 | might have to leak fds on fork, but it's more sane than epoll) and it |
556 | drops fds silently in similarly hard-to-detect cases. |
769 | drops fds silently in similarly hard-to-detect cases. |
557 | .Sp |
770 | .Sp |
558 | This backend usually performs well under most conditions. |
771 | This backend usually performs well under most conditions. |
559 | .Sp |
772 | .Sp |
560 | While nominally embeddable in other event loops, this doesn't work |
773 | While nominally embeddable in other event loops, this doesn't work |
561 | everywhere, so you might need to test for this. And since it is broken |
774 | everywhere, so you might need to test for this. And since it is broken |
562 | almost everywhere, you should only use it when you have a lot of sockets |
775 | almost everywhere, you should only use it when you have a lot of sockets |
563 | (for which it usually works), by embedding it into another event loop |
776 | (for which it usually works), by embedding it into another event loop |
564 | (e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR) and, did I mention it, |
777 | (e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR (but \f(CW\*(C`poll\*(C'\fR is of course |
565 | using it only for sockets. |
778 | also broken on \s-1OS X\s0)) and, did I mention it, using it only for sockets. |
566 | .Sp |
779 | .Sp |
567 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with |
780 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with |
568 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR, and \f(CW\*(C`EV_WRITE\*(C'\fR into an \f(CW\*(C`EVFILT_WRITE\*(C'\fR kevent with |
781 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR, and \f(CW\*(C`EV_WRITE\*(C'\fR into an \f(CW\*(C`EVFILT_WRITE\*(C'\fR kevent with |
569 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR. |
782 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR. |
570 | .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
783 | .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
… | |
… | |
574 | implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets |
787 | implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets |
575 | and is not embeddable, which would limit the usefulness of this backend |
788 | and is not embeddable, which would limit the usefulness of this backend |
576 | immensely. |
789 | immensely. |
577 | .ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 |
790 | .ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 |
578 | .el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 |
791 | .el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 |
579 | .IX Item "EVBACKEND_PORT (value 32, Solaris 10)" |
792 | .IX Item "EVBACKEND_PORT (value 32, Solaris 10)" |
580 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
793 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
581 | it's really slow, but it still scales very well (O(active_fds)). |
794 | it's really slow, but it still scales very well (O(active_fds)). |
582 | .Sp |
|
|
583 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
584 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
585 | blocking when no data (or space) is available. |
|
|
586 | .Sp |
795 | .Sp |
587 | While this backend scales well, it requires one system call per active |
796 | While this backend scales well, it requires one system call per active |
588 | file descriptor per loop iteration. For small and medium numbers of file |
797 | file descriptor per loop iteration. For small and medium numbers of file |
589 | descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend |
798 | descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend |
590 | might perform better. |
799 | might perform better. |
591 | .Sp |
800 | .Sp |
592 | On the positive side, with the exception of the spurious readiness |
801 | On the positive side, this backend actually performed fully to |
593 | notifications, this backend actually performed fully to specification |
|
|
594 | in all tests and is fully embeddable, which is a rare feat among the |
802 | specification in all tests and is fully embeddable, which is a rare feat |
595 | OS-specific backends. |
803 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
804 | hacks). |
|
|
805 | .Sp |
|
|
806 | On the negative side, the interface is \fIbizarre\fR \- so bizarre that |
|
|
807 | even sun itself gets it wrong in their code examples: The event polling |
|
|
808 | function sometimes returns events to the caller even though an error |
|
|
809 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
810 | even documented that way) \- deadly for edge-triggered interfaces where you |
|
|
811 | absolutely have to know whether an event occurred or not because you have |
|
|
812 | to re-arm the watcher. |
|
|
813 | .Sp |
|
|
814 | Fortunately libev seems to be able to work around these idiocies. |
596 | .Sp |
815 | .Sp |
597 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
816 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
598 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
817 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
599 | .ie n .IP """EVBACKEND_ALL""" 4 |
818 | .ie n .IP """EVBACKEND_ALL""" 4 |
600 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
819 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
601 | .IX Item "EVBACKEND_ALL" |
820 | .IX Item "EVBACKEND_ALL" |
602 | Try all backends (even potentially broken ones that wouldn't be tried |
821 | Try all backends (even potentially broken ones that wouldn't be tried |
603 | with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
822 | with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
604 | \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. |
823 | \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. |
605 | .Sp |
824 | .Sp |
606 | It is definitely not recommended to use this flag. |
825 | It is definitely not recommended to use this flag, use whatever |
|
|
826 | \&\f(CW\*(C`ev_recommended_backends ()\*(C'\fR returns, or simply do not specify a backend |
|
|
827 | at all. |
|
|
828 | .ie n .IP """EVBACKEND_MASK""" 4 |
|
|
829 | .el .IP "\f(CWEVBACKEND_MASK\fR" 4 |
|
|
830 | .IX Item "EVBACKEND_MASK" |
|
|
831 | Not a backend at all, but a mask to select all backend bits from a |
|
|
832 | \&\f(CW\*(C`flags\*(C'\fR value, in case you want to mask out any backends from a flags |
|
|
833 | value (e.g. when modifying the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR environment variable). |
607 | .RE |
834 | .RE |
608 | .RS 4 |
835 | .RS 4 |
609 | .Sp |
836 | .Sp |
610 | If one or more of these are or'ed into the flags value, then only these |
837 | If one or more of the backend flags are or'ed into the flags value, |
611 | backends will be tried (in the reverse order as listed here). If none are |
838 | then only these backends will be tried (in the reverse order as listed |
612 | specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried. |
839 | here). If none are specified, all backends in \f(CW\*(C`ev_recommended_backends |
613 | .Sp |
840 | ()\*(C'\fR will be tried. |
614 | Example: This is the most typical usage. |
|
|
615 | .Sp |
|
|
616 | .Vb 2 |
|
|
617 | \& if (!ev_default_loop (0)) |
|
|
618 | \& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
619 | .Ve |
|
|
620 | .Sp |
|
|
621 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
622 | environment settings to be taken into account: |
|
|
623 | .Sp |
|
|
624 | .Vb 1 |
|
|
625 | \& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
626 | .Ve |
|
|
627 | .Sp |
|
|
628 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
629 | used if available (warning, breaks stuff, best use only with your own |
|
|
630 | private event loop and only if you know the \s-1OS\s0 supports your types of |
|
|
631 | fds): |
|
|
632 | .Sp |
|
|
633 | .Vb 1 |
|
|
634 | \& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
635 | .Ve |
|
|
636 | .RE |
|
|
637 | .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
|
|
638 | .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
|
|
639 | Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is |
|
|
640 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
641 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
642 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
643 | .Sp |
|
|
644 | Note that this function \fIis\fR thread-safe, and the recommended way to use |
|
|
645 | libev with threads is indeed to create one loop per thread, and using the |
|
|
646 | default loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread. |
|
|
647 | .Sp |
841 | .Sp |
648 | Example: Try to create a event loop that uses epoll and nothing else. |
842 | Example: Try to create a event loop that uses epoll and nothing else. |
649 | .Sp |
843 | .Sp |
650 | .Vb 3 |
844 | .Vb 3 |
651 | \& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
845 | \& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
652 | \& if (!epoller) |
846 | \& if (!epoller) |
653 | \& fatal ("no epoll found here, maybe it hides under your chair"); |
847 | \& fatal ("no epoll found here, maybe it hides under your chair"); |
654 | .Ve |
848 | .Ve |
|
|
849 | .Sp |
|
|
850 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
851 | used if available. |
|
|
852 | .Sp |
|
|
853 | .Vb 1 |
|
|
854 | \& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
855 | .Ve |
|
|
856 | .Sp |
|
|
857 | Example: Similarly, on linux, you mgiht want to take advantage of the |
|
|
858 | linux aio backend if possible, but fall back to something else if that |
|
|
859 | isn't available. |
|
|
860 | .Sp |
|
|
861 | .Vb 1 |
|
|
862 | \& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO); |
|
|
863 | .Ve |
|
|
864 | .RE |
655 | .IP "ev_default_destroy ()" 4 |
865 | .IP "ev_loop_destroy (loop)" 4 |
656 | .IX Item "ev_default_destroy ()" |
866 | .IX Item "ev_loop_destroy (loop)" |
657 | Destroys the default loop again (frees all memory and kernel state |
867 | Destroys an event loop object (frees all memory and kernel state |
658 | etc.). None of the active event watchers will be stopped in the normal |
868 | etc.). None of the active event watchers will be stopped in the normal |
659 | sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your |
869 | sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your |
660 | responsibility to either stop all watchers cleanly yourself \fIbefore\fR |
870 | responsibility to either stop all watchers cleanly yourself \fIbefore\fR |
661 | calling this function, or cope with the fact afterwards (which is usually |
871 | calling this function, or cope with the fact afterwards (which is usually |
662 | the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
872 | the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
663 | for example). |
873 | for example). |
664 | .Sp |
874 | .Sp |
665 | Note that certain global state, such as signal state, will not be freed by |
875 | Note that certain global state, such as signal state (and installed signal |
666 | this function, and related watchers (such as signal and child watchers) |
876 | handlers), will not be freed by this function, and related watchers (such |
667 | would need to be stopped manually. |
877 | as signal and child watchers) would need to be stopped manually. |
668 | .Sp |
878 | .Sp |
669 | In general it is not advisable to call this function except in the |
879 | This function is normally used on loop objects allocated by |
670 | rare occasion where you really need to free e.g. the signal handling |
880 | \&\f(CW\*(C`ev_loop_new\*(C'\fR, but it can also be used on the default loop returned by |
671 | pipe fds. If you need dynamically allocated loops it is better to use |
881 | \&\f(CW\*(C`ev_default_loop\*(C'\fR, in which case it is not thread-safe. |
672 | \&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR). |
|
|
673 | .IP "ev_loop_destroy (loop)" 4 |
|
|
674 | .IX Item "ev_loop_destroy (loop)" |
|
|
675 | Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an |
|
|
676 | earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. |
|
|
677 | .IP "ev_default_fork ()" 4 |
|
|
678 | .IX Item "ev_default_fork ()" |
|
|
679 | This function sets a flag that causes subsequent \f(CW\*(C`ev_loop\*(C'\fR iterations |
|
|
680 | to reinitialise the kernel state for backends that have one. Despite the |
|
|
681 | name, you can call it anytime, but it makes most sense after forking, in |
|
|
682 | the child process (or both child and parent, but that again makes little |
|
|
683 | sense). You \fImust\fR call it in the child before using any of the libev |
|
|
684 | functions, and it will only take effect at the next \f(CW\*(C`ev_loop\*(C'\fR iteration. |
|
|
685 | .Sp |
882 | .Sp |
686 | On the other hand, you only need to call this function in the child |
883 | Note that it is not advisable to call this function on the default loop |
687 | process if and only if you want to use the event library in the child. If |
884 | except in the rare occasion where you really need to free its resources. |
688 | you just fork+exec, you don't have to call it at all. |
885 | If you need dynamically allocated loops it is better to use \f(CW\*(C`ev_loop_new\*(C'\fR |
689 | .Sp |
886 | and \f(CW\*(C`ev_loop_destroy\*(C'\fR. |
690 | The function itself is quite fast and it's usually not a problem to call |
|
|
691 | it just in case after a fork. To make this easy, the function will fit in |
|
|
692 | quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: |
|
|
693 | .Sp |
|
|
694 | .Vb 1 |
|
|
695 | \& pthread_atfork (0, 0, ev_default_fork); |
|
|
696 | .Ve |
|
|
697 | .IP "ev_loop_fork (loop)" 4 |
887 | .IP "ev_loop_fork (loop)" 4 |
698 | .IX Item "ev_loop_fork (loop)" |
888 | .IX Item "ev_loop_fork (loop)" |
699 | Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by |
889 | This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations |
700 | \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop |
890 | to reinitialise the kernel state for backends that have one. Despite |
701 | after fork that you want to re-use in the child, and how you do this is |
891 | the name, you can call it anytime you are allowed to start or stop |
702 | entirely your own problem. |
892 | watchers (except inside an \f(CW\*(C`ev_prepare\*(C'\fR callback), but it makes most |
|
|
893 | sense after forking, in the child process. You \fImust\fR call it (or use |
|
|
894 | \&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR. |
|
|
895 | .Sp |
|
|
896 | In addition, if you want to reuse a loop (via this function or |
|
|
897 | \&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR), you \fIalso\fR have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR. |
|
|
898 | .Sp |
|
|
899 | Again, you \fIhave\fR to call it on \fIany\fR loop that you want to re-use after |
|
|
900 | a fork, \fIeven if you do not plan to use the loop in the parent\fR. This is |
|
|
901 | because some kernel interfaces *cough* \fIkqueue\fR *cough* do funny things |
|
|
902 | during fork. |
|
|
903 | .Sp |
|
|
904 | On the other hand, you only need to call this function in the child |
|
|
905 | process if and only if you want to use the event loop in the child. If |
|
|
906 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
907 | call it at all (in fact, \f(CW\*(C`epoll\*(C'\fR is so badly broken that it makes a |
|
|
908 | difference, but libev will usually detect this case on its own and do a |
|
|
909 | costly reset of the backend). |
|
|
910 | .Sp |
|
|
911 | The function itself is quite fast and it's usually not a problem to call |
|
|
912 | it just in case after a fork. |
|
|
913 | .Sp |
|
|
914 | Example: Automate calling \f(CW\*(C`ev_loop_fork\*(C'\fR on the default loop when |
|
|
915 | using pthreads. |
|
|
916 | .Sp |
|
|
917 | .Vb 5 |
|
|
918 | \& static void |
|
|
919 | \& post_fork_child (void) |
|
|
920 | \& { |
|
|
921 | \& ev_loop_fork (EV_DEFAULT); |
|
|
922 | \& } |
|
|
923 | \& |
|
|
924 | \& ... |
|
|
925 | \& pthread_atfork (0, 0, post_fork_child); |
|
|
926 | .Ve |
703 | .IP "int ev_is_default_loop (loop)" 4 |
927 | .IP "int ev_is_default_loop (loop)" 4 |
704 | .IX Item "int ev_is_default_loop (loop)" |
928 | .IX Item "int ev_is_default_loop (loop)" |
705 | Returns true when the given loop is, in fact, the default loop, and false |
929 | Returns true when the given loop is, in fact, the default loop, and false |
706 | otherwise. |
930 | otherwise. |
707 | .IP "unsigned int ev_loop_count (loop)" 4 |
931 | .IP "unsigned int ev_iteration (loop)" 4 |
708 | .IX Item "unsigned int ev_loop_count (loop)" |
932 | .IX Item "unsigned int ev_iteration (loop)" |
709 | Returns the count of loop iterations for the loop, which is identical to |
933 | Returns the current iteration count for the event loop, which is identical |
710 | the number of times libev did poll for new events. It starts at \f(CW0\fR and |
934 | to the number of times libev did poll for new events. It starts at \f(CW0\fR |
711 | happily wraps around with enough iterations. |
935 | and happily wraps around with enough iterations. |
712 | .Sp |
936 | .Sp |
713 | This value can sometimes be useful as a generation counter of sorts (it |
937 | This value can sometimes be useful as a generation counter of sorts (it |
714 | \&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with |
938 | \&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with |
715 | \&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls. |
939 | \&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls \- and is incremented between the |
|
|
940 | prepare and check phases. |
|
|
941 | .IP "unsigned int ev_depth (loop)" 4 |
|
|
942 | .IX Item "unsigned int ev_depth (loop)" |
|
|
943 | Returns the number of times \f(CW\*(C`ev_run\*(C'\fR was entered minus the number of |
|
|
944 | times \f(CW\*(C`ev_run\*(C'\fR was exited normally, in other words, the recursion depth. |
|
|
945 | .Sp |
|
|
946 | Outside \f(CW\*(C`ev_run\*(C'\fR, this number is zero. In a callback, this number is |
|
|
947 | \&\f(CW1\fR, unless \f(CW\*(C`ev_run\*(C'\fR was invoked recursively (or from another thread), |
|
|
948 | in which case it is higher. |
|
|
949 | .Sp |
|
|
950 | Leaving \f(CW\*(C`ev_run\*(C'\fR abnormally (setjmp/longjmp, cancelling the thread, |
|
|
951 | throwing an exception etc.), doesn't count as \*(L"exit\*(R" \- consider this |
|
|
952 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
953 | convenient, in which case it is fully supported. |
716 | .IP "unsigned int ev_backend (loop)" 4 |
954 | .IP "unsigned int ev_backend (loop)" 4 |
717 | .IX Item "unsigned int ev_backend (loop)" |
955 | .IX Item "unsigned int ev_backend (loop)" |
718 | Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
956 | Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
719 | use. |
957 | use. |
720 | .IP "ev_tstamp ev_now (loop)" 4 |
958 | .IP "ev_tstamp ev_now (loop)" 4 |
… | |
… | |
726 | event occurring (or more correctly, libev finding out about it). |
964 | event occurring (or more correctly, libev finding out about it). |
727 | .IP "ev_now_update (loop)" 4 |
965 | .IP "ev_now_update (loop)" 4 |
728 | .IX Item "ev_now_update (loop)" |
966 | .IX Item "ev_now_update (loop)" |
729 | Establishes the current time by querying the kernel, updating the time |
967 | Establishes the current time by querying the kernel, updating the time |
730 | returned by \f(CW\*(C`ev_now ()\*(C'\fR in the progress. This is a costly operation and |
968 | returned by \f(CW\*(C`ev_now ()\*(C'\fR in the progress. This is a costly operation and |
731 | is usually done automatically within \f(CW\*(C`ev_loop ()\*(C'\fR. |
969 | is usually done automatically within \f(CW\*(C`ev_run ()\*(C'\fR. |
732 | .Sp |
970 | .Sp |
733 | This function is rarely useful, but when some event callback runs for a |
971 | This function is rarely useful, but when some event callback runs for a |
734 | very long time without entering the event loop, updating libev's idea of |
972 | very long time without entering the event loop, updating libev's idea of |
735 | the current time is a good idea. |
973 | the current time is a good idea. |
736 | .Sp |
974 | .Sp |
737 | See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section. |
975 | See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section. |
|
|
976 | .IP "ev_suspend (loop)" 4 |
|
|
977 | .IX Item "ev_suspend (loop)" |
|
|
978 | .PD 0 |
|
|
979 | .IP "ev_resume (loop)" 4 |
|
|
980 | .IX Item "ev_resume (loop)" |
|
|
981 | .PD |
|
|
982 | These two functions suspend and resume an event loop, for use when the |
|
|
983 | loop is not used for a while and timeouts should not be processed. |
|
|
984 | .Sp |
|
|
985 | A typical use case would be an interactive program such as a game: When |
|
|
986 | the user presses \f(CW\*(C`^Z\*(C'\fR to suspend the game and resumes it an hour later it |
|
|
987 | would be best to handle timeouts as if no time had actually passed while |
|
|
988 | the program was suspended. This can be achieved by calling \f(CW\*(C`ev_suspend\*(C'\fR |
|
|
989 | in your \f(CW\*(C`SIGTSTP\*(C'\fR handler, sending yourself a \f(CW\*(C`SIGSTOP\*(C'\fR and calling |
|
|
990 | \&\f(CW\*(C`ev_resume\*(C'\fR directly afterwards to resume timer processing. |
|
|
991 | .Sp |
|
|
992 | Effectively, all \f(CW\*(C`ev_timer\*(C'\fR watchers will be delayed by the time spend |
|
|
993 | between \f(CW\*(C`ev_suspend\*(C'\fR and \f(CW\*(C`ev_resume\*(C'\fR, and all \f(CW\*(C`ev_periodic\*(C'\fR watchers |
|
|
994 | will be rescheduled (that is, they will lose any events that would have |
|
|
995 | occurred while suspended). |
|
|
996 | .Sp |
|
|
997 | After calling \f(CW\*(C`ev_suspend\*(C'\fR you \fBmust not\fR call \fIany\fR function on the |
|
|
998 | given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR |
|
|
999 | without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR. |
|
|
1000 | .Sp |
|
|
1001 | Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the |
|
|
1002 | event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR). |
738 | .IP "ev_loop (loop, int flags)" 4 |
1003 | .IP "bool ev_run (loop, int flags)" 4 |
739 | .IX Item "ev_loop (loop, int flags)" |
1004 | .IX Item "bool ev_run (loop, int flags)" |
740 | Finally, this is it, the event handler. This function usually is called |
1005 | Finally, this is it, the event handler. This function usually is called |
741 | after you initialised all your watchers and you want to start handling |
1006 | after you have initialised all your watchers and you want to start |
742 | events. |
1007 | handling events. It will ask the operating system for any new events, call |
|
|
1008 | the watcher callbacks, and then repeat the whole process indefinitely: This |
|
|
1009 | is why event loops are called \fIloops\fR. |
743 | .Sp |
1010 | .Sp |
744 | If the flags argument is specified as \f(CW0\fR, it will not return until |
1011 | If the flags argument is specified as \f(CW0\fR, it will keep handling events |
745 | either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. |
1012 | until either no event watchers are active anymore or \f(CW\*(C`ev_break\*(C'\fR was |
|
|
1013 | called. |
746 | .Sp |
1014 | .Sp |
|
|
1015 | The return value is false if there are no more active watchers (which |
|
|
1016 | usually means \*(L"all jobs done\*(R" or \*(L"deadlock\*(R"), and true in all other cases |
|
|
1017 | (which usually means " you should call \f(CW\*(C`ev_run\*(C'\fR again"). |
|
|
1018 | .Sp |
747 | Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than |
1019 | Please note that an explicit \f(CW\*(C`ev_break\*(C'\fR is usually better than |
748 | relying on all watchers to be stopped when deciding when a program has |
1020 | relying on all watchers to be stopped when deciding when a program has |
749 | finished (especially in interactive programs), but having a program |
1021 | finished (especially in interactive programs), but having a program |
750 | that automatically loops as long as it has to and no longer by virtue |
1022 | that automatically loops as long as it has to and no longer by virtue |
751 | of relying on its watchers stopping correctly, that is truly a thing of |
1023 | of relying on its watchers stopping correctly, that is truly a thing of |
752 | beauty. |
1024 | beauty. |
753 | .Sp |
1025 | .Sp |
|
|
1026 | This function is \fImostly\fR exception-safe \- you can break out of a |
|
|
1027 | \&\f(CW\*(C`ev_run\*(C'\fR call by calling \f(CW\*(C`longjmp\*(C'\fR in a callback, throwing a \*(C+ |
|
|
1028 | exception and so on. This does not decrement the \f(CW\*(C`ev_depth\*(C'\fR value, nor |
|
|
1029 | will it clear any outstanding \f(CW\*(C`EVBREAK_ONE\*(C'\fR breaks. |
|
|
1030 | .Sp |
754 | A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle |
1031 | A flags value of \f(CW\*(C`EVRUN_NOWAIT\*(C'\fR will look for new events, will handle |
755 | those events and any already outstanding ones, but will not block your |
1032 | those events and any already outstanding ones, but will not wait and |
756 | process in case there are no events and will return after one iteration of |
1033 | block your process in case there are no events and will return after one |
757 | the loop. |
1034 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
1035 | events while doing lengthy calculations, to keep the program responsive. |
758 | .Sp |
1036 | .Sp |
759 | A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
1037 | A flags value of \f(CW\*(C`EVRUN_ONCE\*(C'\fR will look for new events (waiting if |
760 | necessary) and will handle those and any already outstanding ones. It |
1038 | necessary) and will handle those and any already outstanding ones. It |
761 | will block your process until at least one new event arrives (which could |
1039 | will block your process until at least one new event arrives (which could |
762 | be an event internal to libev itself, so there is no guarentee that a |
1040 | be an event internal to libev itself, so there is no guarantee that a |
763 | user-registered callback will be called), and will return after one |
1041 | user-registered callback will be called), and will return after one |
764 | iteration of the loop. |
1042 | iteration of the loop. |
765 | .Sp |
1043 | .Sp |
766 | This is useful if you are waiting for some external event in conjunction |
1044 | This is useful if you are waiting for some external event in conjunction |
767 | with something not expressible using other libev watchers (i.e. "roll your |
1045 | with something not expressible using other libev watchers (i.e. "roll your |
768 | own \f(CW\*(C`ev_loop\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
1046 | own \f(CW\*(C`ev_run\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
769 | usually a better approach for this kind of thing. |
1047 | usually a better approach for this kind of thing. |
770 | .Sp |
1048 | .Sp |
771 | Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: |
1049 | Here are the gory details of what \f(CW\*(C`ev_run\*(C'\fR does (this is for your |
|
|
1050 | understanding, not a guarantee that things will work exactly like this in |
|
|
1051 | future versions): |
772 | .Sp |
1052 | .Sp |
773 | .Vb 10 |
1053 | .Vb 10 |
|
|
1054 | \& \- Increment loop depth. |
|
|
1055 | \& \- Reset the ev_break status. |
774 | \& \- Before the first iteration, call any pending watchers. |
1056 | \& \- Before the first iteration, call any pending watchers. |
|
|
1057 | \& LOOP: |
775 | \& * If EVFLAG_FORKCHECK was used, check for a fork. |
1058 | \& \- If EVFLAG_FORKCHECK was used, check for a fork. |
776 | \& \- If a fork was detected (by any means), queue and call all fork watchers. |
1059 | \& \- If a fork was detected (by any means), queue and call all fork watchers. |
777 | \& \- Queue and call all prepare watchers. |
1060 | \& \- Queue and call all prepare watchers. |
|
|
1061 | \& \- If ev_break was called, goto FINISH. |
778 | \& \- If we have been forked, detach and recreate the kernel state |
1062 | \& \- If we have been forked, detach and recreate the kernel state |
779 | \& as to not disturb the other process. |
1063 | \& as to not disturb the other process. |
780 | \& \- Update the kernel state with all outstanding changes. |
1064 | \& \- Update the kernel state with all outstanding changes. |
781 | \& \- Update the "event loop time" (ev_now ()). |
1065 | \& \- Update the "event loop time" (ev_now ()). |
782 | \& \- Calculate for how long to sleep or block, if at all |
1066 | \& \- Calculate for how long to sleep or block, if at all |
783 | \& (active idle watchers, EVLOOP_NONBLOCK or not having |
1067 | \& (active idle watchers, EVRUN_NOWAIT or not having |
784 | \& any active watchers at all will result in not sleeping). |
1068 | \& any active watchers at all will result in not sleeping). |
785 | \& \- Sleep if the I/O and timer collect interval say so. |
1069 | \& \- Sleep if the I/O and timer collect interval say so. |
|
|
1070 | \& \- Increment loop iteration counter. |
786 | \& \- Block the process, waiting for any events. |
1071 | \& \- Block the process, waiting for any events. |
787 | \& \- Queue all outstanding I/O (fd) events. |
1072 | \& \- Queue all outstanding I/O (fd) events. |
788 | \& \- Update the "event loop time" (ev_now ()), and do time jump adjustments. |
1073 | \& \- Update the "event loop time" (ev_now ()), and do time jump adjustments. |
789 | \& \- Queue all expired timers. |
1074 | \& \- Queue all expired timers. |
790 | \& \- Queue all expired periodics. |
1075 | \& \- Queue all expired periodics. |
791 | \& \- Unless any events are pending now, queue all idle watchers. |
1076 | \& \- Queue all idle watchers with priority higher than that of pending events. |
792 | \& \- Queue all check watchers. |
1077 | \& \- Queue all check watchers. |
793 | \& \- Call all queued watchers in reverse order (i.e. check watchers first). |
1078 | \& \- Call all queued watchers in reverse order (i.e. check watchers first). |
794 | \& Signals and child watchers are implemented as I/O watchers, and will |
1079 | \& Signals and child watchers are implemented as I/O watchers, and will |
795 | \& be handled here by queueing them when their watcher gets executed. |
1080 | \& be handled here by queueing them when their watcher gets executed. |
796 | \& \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
1081 | \& \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
797 | \& were used, or there are no active watchers, return, otherwise |
1082 | \& were used, or there are no active watchers, goto FINISH, otherwise |
798 | \& continue with step *. |
1083 | \& continue with step LOOP. |
|
|
1084 | \& FINISH: |
|
|
1085 | \& \- Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
1086 | \& \- Decrement the loop depth. |
|
|
1087 | \& \- Return. |
799 | .Ve |
1088 | .Ve |
800 | .Sp |
1089 | .Sp |
801 | Example: Queue some jobs and then loop until no events are outstanding |
1090 | Example: Queue some jobs and then loop until no events are outstanding |
802 | anymore. |
1091 | anymore. |
803 | .Sp |
1092 | .Sp |
804 | .Vb 4 |
1093 | .Vb 4 |
805 | \& ... queue jobs here, make sure they register event watchers as long |
1094 | \& ... queue jobs here, make sure they register event watchers as long |
806 | \& ... as they still have work to do (even an idle watcher will do..) |
1095 | \& ... as they still have work to do (even an idle watcher will do..) |
807 | \& ev_loop (my_loop, 0); |
1096 | \& ev_run (my_loop, 0); |
808 | \& ... jobs done or somebody called unloop. yeah! |
1097 | \& ... jobs done or somebody called break. yeah! |
809 | .Ve |
1098 | .Ve |
810 | .IP "ev_unloop (loop, how)" 4 |
1099 | .IP "ev_break (loop, how)" 4 |
811 | .IX Item "ev_unloop (loop, how)" |
1100 | .IX Item "ev_break (loop, how)" |
812 | Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it |
1101 | Can be used to make a call to \f(CW\*(C`ev_run\*(C'\fR return early (but only after it |
813 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
1102 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
814 | \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
1103 | \&\f(CW\*(C`EVBREAK_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_run\*(C'\fR call return, or |
815 | \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
1104 | \&\f(CW\*(C`EVBREAK_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_run\*(C'\fR calls return. |
816 | .Sp |
1105 | .Sp |
817 | This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again. |
1106 | This \*(L"break state\*(R" will be cleared on the next call to \f(CW\*(C`ev_run\*(C'\fR. |
|
|
1107 | .Sp |
|
|
1108 | It is safe to call \f(CW\*(C`ev_break\*(C'\fR from outside any \f(CW\*(C`ev_run\*(C'\fR calls, too, in |
|
|
1109 | which case it will have no effect. |
818 | .IP "ev_ref (loop)" 4 |
1110 | .IP "ev_ref (loop)" 4 |
819 | .IX Item "ev_ref (loop)" |
1111 | .IX Item "ev_ref (loop)" |
820 | .PD 0 |
1112 | .PD 0 |
821 | .IP "ev_unref (loop)" 4 |
1113 | .IP "ev_unref (loop)" 4 |
822 | .IX Item "ev_unref (loop)" |
1114 | .IX Item "ev_unref (loop)" |
823 | .PD |
1115 | .PD |
824 | Ref/unref can be used to add or remove a reference count on the event |
1116 | Ref/unref can be used to add or remove a reference count on the event |
825 | loop: Every watcher keeps one reference, and as long as the reference |
1117 | loop: Every watcher keeps one reference, and as long as the reference |
826 | count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. |
1118 | count is nonzero, \f(CW\*(C`ev_run\*(C'\fR will not return on its own. |
827 | .Sp |
1119 | .Sp |
828 | If you have a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR |
1120 | This is useful when you have a watcher that you never intend to |
829 | from returning, call \fIev_unref()\fR after starting, and \fIev_ref()\fR before |
1121 | unregister, but that nevertheless should not keep \f(CW\*(C`ev_run\*(C'\fR from |
|
|
1122 | returning. In such a case, call \f(CW\*(C`ev_unref\*(C'\fR after starting, and \f(CW\*(C`ev_ref\*(C'\fR |
830 | stopping it. |
1123 | before stopping it. |
831 | .Sp |
1124 | .Sp |
832 | As an example, libev itself uses this for its internal signal pipe: It is |
1125 | As an example, libev itself uses this for its internal signal pipe: It |
833 | not visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting |
1126 | is not visible to the libev user and should not keep \f(CW\*(C`ev_run\*(C'\fR from |
834 | if no event watchers registered by it are active. It is also an excellent |
1127 | exiting if no event watchers registered by it are active. It is also an |
835 | way to do this for generic recurring timers or from within third-party |
1128 | excellent way to do this for generic recurring timers or from within |
836 | libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR |
1129 | third-party libraries. Just remember to \fIunref after start\fR and \fIref |
837 | (but only if the watcher wasn't active before, or was active before, |
1130 | before stop\fR (but only if the watcher wasn't active before, or was active |
838 | respectively). |
1131 | before, respectively. Note also that libev might stop watchers itself |
|
|
1132 | (e.g. non-repeating timers) in which case you have to \f(CW\*(C`ev_ref\*(C'\fR |
|
|
1133 | in the callback). |
839 | .Sp |
1134 | .Sp |
840 | Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR |
1135 | Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_run\*(C'\fR |
841 | running when nothing else is active. |
1136 | running when nothing else is active. |
842 | .Sp |
1137 | .Sp |
843 | .Vb 4 |
1138 | .Vb 4 |
844 | \& struct ev_signal exitsig; |
1139 | \& ev_signal exitsig; |
845 | \& ev_signal_init (&exitsig, sig_cb, SIGINT); |
1140 | \& ev_signal_init (&exitsig, sig_cb, SIGINT); |
846 | \& ev_signal_start (loop, &exitsig); |
1141 | \& ev_signal_start (loop, &exitsig); |
847 | \& evf_unref (loop); |
1142 | \& ev_unref (loop); |
848 | .Ve |
1143 | .Ve |
849 | .Sp |
1144 | .Sp |
850 | Example: For some weird reason, unregister the above signal handler again. |
1145 | Example: For some weird reason, unregister the above signal handler again. |
851 | .Sp |
1146 | .Sp |
852 | .Vb 2 |
1147 | .Vb 2 |
… | |
… | |
876 | overhead for the actual polling but can deliver many events at once. |
1171 | overhead for the actual polling but can deliver many events at once. |
877 | .Sp |
1172 | .Sp |
878 | By setting a higher \fIio collect interval\fR you allow libev to spend more |
1173 | By setting a higher \fIio collect interval\fR you allow libev to spend more |
879 | time collecting I/O events, so you can handle more events per iteration, |
1174 | time collecting I/O events, so you can handle more events per iteration, |
880 | at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and |
1175 | at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and |
881 | \&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will |
1176 | \&\f(CW\*(C`ev_timer\*(C'\fR) will not be affected. Setting this to a non-null value will |
882 | introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. |
1177 | introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The |
|
|
1178 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
1179 | once per this interval, on average (as long as the host time resolution is |
|
|
1180 | good enough). |
883 | .Sp |
1181 | .Sp |
884 | Likewise, by setting a higher \fItimeout collect interval\fR you allow libev |
1182 | Likewise, by setting a higher \fItimeout collect interval\fR you allow libev |
885 | to spend more time collecting timeouts, at the expense of increased |
1183 | to spend more time collecting timeouts, at the expense of increased |
886 | latency/jitter/inexactness (the watcher callback will be called |
1184 | latency/jitter/inexactness (the watcher callback will be called |
887 | later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null |
1185 | later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null |
… | |
… | |
889 | .Sp |
1187 | .Sp |
890 | Many (busy) programs can usually benefit by setting the I/O collect |
1188 | Many (busy) programs can usually benefit by setting the I/O collect |
891 | interval to a value near \f(CW0.1\fR or so, which is often enough for |
1189 | interval to a value near \f(CW0.1\fR or so, which is often enough for |
892 | interactive servers (of course not for games), likewise for timeouts. It |
1190 | interactive servers (of course not for games), likewise for timeouts. It |
893 | usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR, |
1191 | usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR, |
894 | as this approaches the timing granularity of most systems. |
1192 | as this approaches the timing granularity of most systems. Note that if |
|
|
1193 | you do transactions with the outside world and you can't increase the |
|
|
1194 | parallelity, then this setting will limit your transaction rate (if you |
|
|
1195 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
1196 | then you can't do more than 100 transactions per second). |
895 | .Sp |
1197 | .Sp |
896 | Setting the \fItimeout collect interval\fR can improve the opportunity for |
1198 | Setting the \fItimeout collect interval\fR can improve the opportunity for |
897 | saving power, as the program will \*(L"bundle\*(R" timer callback invocations that |
1199 | saving power, as the program will \*(L"bundle\*(R" timer callback invocations that |
898 | are \*(L"near\*(R" in time together, by delaying some, thus reducing the number of |
1200 | are \*(L"near\*(R" in time together, by delaying some, thus reducing the number of |
899 | times the process sleeps and wakes up again. Another useful technique to |
1201 | times the process sleeps and wakes up again. Another useful technique to |
900 | reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure |
1202 | reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure |
901 | they fire on, say, one-second boundaries only. |
1203 | they fire on, say, one-second boundaries only. |
|
|
1204 | .Sp |
|
|
1205 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
1206 | more often than 100 times per second: |
|
|
1207 | .Sp |
|
|
1208 | .Vb 2 |
|
|
1209 | \& ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
1210 | \& ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
1211 | .Ve |
|
|
1212 | .IP "ev_invoke_pending (loop)" 4 |
|
|
1213 | .IX Item "ev_invoke_pending (loop)" |
|
|
1214 | This call will simply invoke all pending watchers while resetting their |
|
|
1215 | pending state. Normally, \f(CW\*(C`ev_run\*(C'\fR does this automatically when required, |
|
|
1216 | but when overriding the invoke callback this call comes handy. This |
|
|
1217 | function can be invoked from a watcher \- this can be useful for example |
|
|
1218 | when you want to do some lengthy calculation and want to pass further |
|
|
1219 | event handling to another thread (you still have to make sure only one |
|
|
1220 | thread executes within \f(CW\*(C`ev_invoke_pending\*(C'\fR or \f(CW\*(C`ev_run\*(C'\fR of course). |
|
|
1221 | .IP "int ev_pending_count (loop)" 4 |
|
|
1222 | .IX Item "int ev_pending_count (loop)" |
|
|
1223 | Returns the number of pending watchers \- zero indicates that no watchers |
|
|
1224 | are pending. |
|
|
1225 | .IP "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(\s-1EV_P\s0))" 4 |
|
|
1226 | .IX Item "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))" |
|
|
1227 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
1228 | invoking all pending watchers when there are any, \f(CW\*(C`ev_run\*(C'\fR will call |
|
|
1229 | this callback instead. This is useful, for example, when you want to |
|
|
1230 | invoke the actual watchers inside another context (another thread etc.). |
|
|
1231 | .Sp |
|
|
1232 | If you want to reset the callback, use \f(CW\*(C`ev_invoke_pending\*(C'\fR as new |
|
|
1233 | callback. |
|
|
1234 | .IP "ev_set_loop_release_cb (loop, void (*release)(\s-1EV_P\s0) throw (), void (*acquire)(\s-1EV_P\s0) throw ())" 4 |
|
|
1235 | .IX Item "ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())" |
|
|
1236 | Sometimes you want to share the same loop between multiple threads. This |
|
|
1237 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
1238 | each call to a libev function. |
|
|
1239 | .Sp |
|
|
1240 | However, \f(CW\*(C`ev_run\*(C'\fR can run an indefinite time, so it is not feasible |
|
|
1241 | to wait for it to return. One way around this is to wake up the event |
|
|
1242 | loop via \f(CW\*(C`ev_break\*(C'\fR and \f(CW\*(C`ev_async_send\*(C'\fR, another way is to set these |
|
|
1243 | \&\fIrelease\fR and \fIacquire\fR callbacks on the loop. |
|
|
1244 | .Sp |
|
|
1245 | When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is |
|
|
1246 | suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just |
|
|
1247 | afterwards. |
|
|
1248 | .Sp |
|
|
1249 | Ideally, \f(CW\*(C`release\*(C'\fR will just call your mutex_unlock function, and |
|
|
1250 | \&\f(CW\*(C`acquire\*(C'\fR will just call the mutex_lock function again. |
|
|
1251 | .Sp |
|
|
1252 | While event loop modifications are allowed between invocations of |
|
|
1253 | \&\f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR (that's their only purpose after all), no |
|
|
1254 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
1255 | have no effect on the set of file descriptors being watched, or the time |
|
|
1256 | waited. Use an \f(CW\*(C`ev_async\*(C'\fR watcher to wake up \f(CW\*(C`ev_run\*(C'\fR when you want it |
|
|
1257 | to take note of any changes you made. |
|
|
1258 | .Sp |
|
|
1259 | In theory, threads executing \f(CW\*(C`ev_run\*(C'\fR will be async-cancel safe between |
|
|
1260 | invocations of \f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR. |
|
|
1261 | .Sp |
|
|
1262 | See also the locking example in the \f(CW\*(C`THREADS\*(C'\fR section later in this |
|
|
1263 | document. |
|
|
1264 | .IP "ev_set_userdata (loop, void *data)" 4 |
|
|
1265 | .IX Item "ev_set_userdata (loop, void *data)" |
|
|
1266 | .PD 0 |
|
|
1267 | .IP "void *ev_userdata (loop)" 4 |
|
|
1268 | .IX Item "void *ev_userdata (loop)" |
|
|
1269 | .PD |
|
|
1270 | Set and retrieve a single \f(CW\*(C`void *\*(C'\fR associated with a loop. When |
|
|
1271 | \&\f(CW\*(C`ev_set_userdata\*(C'\fR has never been called, then \f(CW\*(C`ev_userdata\*(C'\fR returns |
|
|
1272 | \&\f(CW0\fR. |
|
|
1273 | .Sp |
|
|
1274 | These two functions can be used to associate arbitrary data with a loop, |
|
|
1275 | and are intended solely for the \f(CW\*(C`invoke_pending_cb\*(C'\fR, \f(CW\*(C`release\*(C'\fR and |
|
|
1276 | \&\f(CW\*(C`acquire\*(C'\fR callbacks described above, but of course can be (ab\-)used for |
|
|
1277 | any other purpose as well. |
902 | .IP "ev_loop_verify (loop)" 4 |
1278 | .IP "ev_verify (loop)" 4 |
903 | .IX Item "ev_loop_verify (loop)" |
1279 | .IX Item "ev_verify (loop)" |
904 | This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been |
1280 | This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been |
905 | compiled in. which is the default for non-minimal builds. It tries to go |
1281 | compiled in, which is the default for non-minimal builds. It tries to go |
906 | through all internal structures and checks them for validity. If anything |
1282 | through all internal structures and checks them for validity. If anything |
907 | is found to be inconsistent, it will print an error message to standard |
1283 | is found to be inconsistent, it will print an error message to standard |
908 | error and call \f(CW\*(C`abort ()\*(C'\fR. |
1284 | error and call \f(CW\*(C`abort ()\*(C'\fR. |
909 | .Sp |
1285 | .Sp |
910 | This can be used to catch bugs inside libev itself: under normal |
1286 | This can be used to catch bugs inside libev itself: under normal |
911 | circumstances, this function will never abort as of course libev keeps its |
1287 | circumstances, this function will never abort as of course libev keeps its |
912 | data structures consistent. |
1288 | data structures consistent. |
913 | .SH "ANATOMY OF A WATCHER" |
1289 | .SH "ANATOMY OF A WATCHER" |
914 | .IX Header "ANATOMY OF A WATCHER" |
1290 | .IX Header "ANATOMY OF A WATCHER" |
|
|
1291 | In the following description, uppercase \f(CW\*(C`TYPE\*(C'\fR in names stands for the |
|
|
1292 | watcher type, e.g. \f(CW\*(C`ev_TYPE_start\*(C'\fR can mean \f(CW\*(C`ev_timer_start\*(C'\fR for timer |
|
|
1293 | watchers and \f(CW\*(C`ev_io_start\*(C'\fR for I/O watchers. |
|
|
1294 | .PP |
915 | A watcher is a structure that you create and register to record your |
1295 | A watcher is an opaque structure that you allocate and register to record |
916 | interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
1296 | your interest in some event. To make a concrete example, imagine you want |
917 | become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
1297 | to wait for \s-1STDIN\s0 to become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher |
|
|
1298 | for that: |
918 | .PP |
1299 | .PP |
919 | .Vb 5 |
1300 | .Vb 5 |
920 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1301 | \& static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
921 | \& { |
1302 | \& { |
922 | \& ev_io_stop (w); |
1303 | \& ev_io_stop (w); |
923 | \& ev_unloop (loop, EVUNLOOP_ALL); |
1304 | \& ev_break (loop, EVBREAK_ALL); |
924 | \& } |
1305 | \& } |
925 | \& |
1306 | \& |
926 | \& struct ev_loop *loop = ev_default_loop (0); |
1307 | \& struct ev_loop *loop = ev_default_loop (0); |
|
|
1308 | \& |
927 | \& struct ev_io stdin_watcher; |
1309 | \& ev_io stdin_watcher; |
|
|
1310 | \& |
928 | \& ev_init (&stdin_watcher, my_cb); |
1311 | \& ev_init (&stdin_watcher, my_cb); |
929 | \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1312 | \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
930 | \& ev_io_start (loop, &stdin_watcher); |
1313 | \& ev_io_start (loop, &stdin_watcher); |
|
|
1314 | \& |
931 | \& ev_loop (loop, 0); |
1315 | \& ev_run (loop, 0); |
932 | .Ve |
1316 | .Ve |
933 | .PP |
1317 | .PP |
934 | As you can see, you are responsible for allocating the memory for your |
1318 | As you can see, you are responsible for allocating the memory for your |
935 | watcher structures (and it is usually a bad idea to do this on the stack, |
1319 | watcher structures (and it is \fIusually\fR a bad idea to do this on the |
936 | although this can sometimes be quite valid). |
1320 | stack). |
937 | .PP |
1321 | .PP |
|
|
1322 | Each watcher has an associated watcher structure (called \f(CW\*(C`struct ev_TYPE\*(C'\fR |
|
|
1323 | or simply \f(CW\*(C`ev_TYPE\*(C'\fR, as typedefs are provided for all watcher structs). |
|
|
1324 | .PP |
938 | Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
1325 | Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init (watcher |
939 | (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
1326 | *, callback)\*(C'\fR, which expects a callback to be provided. This callback is |
940 | callback gets invoked each time the event occurs (or, in the case of I/O |
1327 | invoked each time the event occurs (or, in the case of I/O watchers, each |
941 | watchers, each time the event loop detects that the file descriptor given |
1328 | time the event loop detects that the file descriptor given is readable |
942 | is readable and/or writable). |
1329 | and/or writable). |
943 | .PP |
1330 | .PP |
944 | Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro |
1331 | Each watcher type further has its own \f(CW\*(C`ev_TYPE_set (watcher *, ...)\*(C'\fR |
945 | with arguments specific to this watcher type. There is also a macro |
1332 | macro to configure it, with arguments specific to the watcher type. There |
946 | to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init |
1333 | is also a macro to combine initialisation and setting in one call: \f(CW\*(C`ev_TYPE_init (watcher *, callback, ...)\*(C'\fR. |
947 | (watcher *, callback, ...)\*(C'\fR. |
|
|
948 | .PP |
1334 | .PP |
949 | To make the watcher actually watch out for events, you have to start it |
1335 | To make the watcher actually watch out for events, you have to start it |
950 | with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher |
1336 | with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher |
951 | *)\*(C'\fR), and you can stop watching for events at any time by calling the |
1337 | *)\*(C'\fR), and you can stop watching for events at any time by calling the |
952 | corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. |
1338 | corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR. |
953 | .PP |
1339 | .PP |
954 | As long as your watcher is active (has been started but not stopped) you |
1340 | As long as your watcher is active (has been started but not stopped) you |
955 | must not touch the values stored in it. Most specifically you must never |
1341 | must not touch the values stored in it. Most specifically you must never |
956 | reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro. |
1342 | reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro. |
957 | .PP |
1343 | .PP |
958 | Each and every callback receives the event loop pointer as first, the |
1344 | Each and every callback receives the event loop pointer as first, the |
959 | registered watcher structure as second, and a bitset of received events as |
1345 | registered watcher structure as second, and a bitset of received events as |
960 | third argument. |
1346 | third argument. |
961 | .PP |
1347 | .PP |
… | |
… | |
970 | .el .IP "\f(CWEV_WRITE\fR" 4 |
1356 | .el .IP "\f(CWEV_WRITE\fR" 4 |
971 | .IX Item "EV_WRITE" |
1357 | .IX Item "EV_WRITE" |
972 | .PD |
1358 | .PD |
973 | The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or |
1359 | The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or |
974 | writable. |
1360 | writable. |
975 | .ie n .IP """EV_TIMEOUT""" 4 |
1361 | .ie n .IP """EV_TIMER""" 4 |
976 | .el .IP "\f(CWEV_TIMEOUT\fR" 4 |
1362 | .el .IP "\f(CWEV_TIMER\fR" 4 |
977 | .IX Item "EV_TIMEOUT" |
1363 | .IX Item "EV_TIMER" |
978 | The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out. |
1364 | The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out. |
979 | .ie n .IP """EV_PERIODIC""" 4 |
1365 | .ie n .IP """EV_PERIODIC""" 4 |
980 | .el .IP "\f(CWEV_PERIODIC\fR" 4 |
1366 | .el .IP "\f(CWEV_PERIODIC\fR" 4 |
981 | .IX Item "EV_PERIODIC" |
1367 | .IX Item "EV_PERIODIC" |
982 | The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out. |
1368 | The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out. |
… | |
… | |
1002 | .PD 0 |
1388 | .PD 0 |
1003 | .ie n .IP """EV_CHECK""" 4 |
1389 | .ie n .IP """EV_CHECK""" 4 |
1004 | .el .IP "\f(CWEV_CHECK\fR" 4 |
1390 | .el .IP "\f(CWEV_CHECK\fR" 4 |
1005 | .IX Item "EV_CHECK" |
1391 | .IX Item "EV_CHECK" |
1006 | .PD |
1392 | .PD |
1007 | All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts |
1393 | All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_run\*(C'\fR starts to |
1008 | to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after |
1394 | gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are queued (not invoked) |
1009 | \&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any |
1395 | just after \f(CW\*(C`ev_run\*(C'\fR has gathered them, but before it queues any callbacks |
|
|
1396 | for any received events. That means \f(CW\*(C`ev_prepare\*(C'\fR watchers are the last |
|
|
1397 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1398 | \&\f(CW\*(C`ev_check\*(C'\fR watchers will be invoked before any other watchers of the same |
|
|
1399 | or lower priority within an event loop iteration. |
|
|
1400 | .Sp |
1010 | received events. Callbacks of both watcher types can start and stop as |
1401 | Callbacks of both watcher types can start and stop as many watchers as |
1011 | many watchers as they want, and all of them will be taken into account |
1402 | they want, and all of them will be taken into account (for example, a |
1012 | (for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep |
1403 | \&\f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep \f(CW\*(C`ev_run\*(C'\fR from |
1013 | \&\f(CW\*(C`ev_loop\*(C'\fR from blocking). |
1404 | blocking). |
1014 | .ie n .IP """EV_EMBED""" 4 |
1405 | .ie n .IP """EV_EMBED""" 4 |
1015 | .el .IP "\f(CWEV_EMBED\fR" 4 |
1406 | .el .IP "\f(CWEV_EMBED\fR" 4 |
1016 | .IX Item "EV_EMBED" |
1407 | .IX Item "EV_EMBED" |
1017 | The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention. |
1408 | The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention. |
1018 | .ie n .IP """EV_FORK""" 4 |
1409 | .ie n .IP """EV_FORK""" 4 |
1019 | .el .IP "\f(CWEV_FORK\fR" 4 |
1410 | .el .IP "\f(CWEV_FORK\fR" 4 |
1020 | .IX Item "EV_FORK" |
1411 | .IX Item "EV_FORK" |
1021 | The event loop has been resumed in the child process after fork (see |
1412 | The event loop has been resumed in the child process after fork (see |
1022 | \&\f(CW\*(C`ev_fork\*(C'\fR). |
1413 | \&\f(CW\*(C`ev_fork\*(C'\fR). |
|
|
1414 | .ie n .IP """EV_CLEANUP""" 4 |
|
|
1415 | .el .IP "\f(CWEV_CLEANUP\fR" 4 |
|
|
1416 | .IX Item "EV_CLEANUP" |
|
|
1417 | The event loop is about to be destroyed (see \f(CW\*(C`ev_cleanup\*(C'\fR). |
1023 | .ie n .IP """EV_ASYNC""" 4 |
1418 | .ie n .IP """EV_ASYNC""" 4 |
1024 | .el .IP "\f(CWEV_ASYNC\fR" 4 |
1419 | .el .IP "\f(CWEV_ASYNC\fR" 4 |
1025 | .IX Item "EV_ASYNC" |
1420 | .IX Item "EV_ASYNC" |
1026 | The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR). |
1421 | The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR). |
|
|
1422 | .ie n .IP """EV_CUSTOM""" 4 |
|
|
1423 | .el .IP "\f(CWEV_CUSTOM\fR" 4 |
|
|
1424 | .IX Item "EV_CUSTOM" |
|
|
1425 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1426 | by libev users to signal watchers (e.g. via \f(CW\*(C`ev_feed_event\*(C'\fR). |
1027 | .ie n .IP """EV_ERROR""" 4 |
1427 | .ie n .IP """EV_ERROR""" 4 |
1028 | .el .IP "\f(CWEV_ERROR\fR" 4 |
1428 | .el .IP "\f(CWEV_ERROR\fR" 4 |
1029 | .IX Item "EV_ERROR" |
1429 | .IX Item "EV_ERROR" |
1030 | An unspecified error has occurred, the watcher has been stopped. This might |
1430 | An unspecified error has occurred, the watcher has been stopped. This might |
1031 | happen because the watcher could not be properly started because libev |
1431 | happen because the watcher could not be properly started because libev |
1032 | ran out of memory, a file descriptor was found to be closed or any other |
1432 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1433 | problem. Libev considers these application bugs. |
|
|
1434 | .Sp |
1033 | problem. You best act on it by reporting the problem and somehow coping |
1435 | You best act on it by reporting the problem and somehow coping with the |
1034 | with the watcher being stopped. |
1436 | watcher being stopped. Note that well-written programs should not receive |
|
|
1437 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1438 | bug in your program. |
1035 | .Sp |
1439 | .Sp |
1036 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for |
1440 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for |
1037 | example it might indicate that a fd is readable or writable, and if your |
1441 | example it might indicate that a fd is readable or writable, and if your |
1038 | callbacks is well-written it can just attempt the operation and cope with |
1442 | callbacks is well-written it can just attempt the operation and cope with |
1039 | the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded |
1443 | the error from \fBread()\fR or \fBwrite()\fR. This will not work in multi-threaded |
1040 | programs, though, as the fd could already be closed and reused for another |
1444 | programs, though, as the fd could already be closed and reused for another |
1041 | thing, so beware. |
1445 | thing, so beware. |
1042 | .Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
1446 | .SS "\s-1GENERIC WATCHER FUNCTIONS\s0" |
1043 | .IX Subsection "GENERIC WATCHER FUNCTIONS" |
1447 | .IX Subsection "GENERIC WATCHER FUNCTIONS" |
1044 | In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, |
|
|
1045 | e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers. |
|
|
1046 | .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
1448 | .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
1047 | .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
1449 | .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
1048 | .IX Item "ev_init (ev_TYPE *watcher, callback)" |
1450 | .IX Item "ev_init (ev_TYPE *watcher, callback)" |
1049 | This macro initialises the generic portion of a watcher. The contents |
1451 | This macro initialises the generic portion of a watcher. The contents |
1050 | of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
1452 | of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
… | |
… | |
1054 | which rolls both calls into one. |
1456 | which rolls both calls into one. |
1055 | .Sp |
1457 | .Sp |
1056 | You can reinitialise a watcher at any time as long as it has been stopped |
1458 | You can reinitialise a watcher at any time as long as it has been stopped |
1057 | (or never started) and there are no pending events outstanding. |
1459 | (or never started) and there are no pending events outstanding. |
1058 | .Sp |
1460 | .Sp |
1059 | The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, |
1461 | The callback is always of type \f(CW\*(C`void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
1060 | int revents)\*(C'\fR. |
1462 | int revents)\*(C'\fR. |
1061 | .Sp |
1463 | .Sp |
1062 | Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps. |
1464 | Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps. |
1063 | .Sp |
1465 | .Sp |
1064 | .Vb 3 |
1466 | .Vb 3 |
1065 | \& ev_io w; |
1467 | \& ev_io w; |
1066 | \& ev_init (&w, my_cb); |
1468 | \& ev_init (&w, my_cb); |
1067 | \& ev_io_set (&w, STDIN_FILENO, EV_READ); |
1469 | \& ev_io_set (&w, STDIN_FILENO, EV_READ); |
1068 | .Ve |
1470 | .Ve |
1069 | .ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 |
1471 | .ie n .IP """ev_TYPE_set"" (ev_TYPE *watcher, [args])" 4 |
1070 | .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 |
1472 | .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *watcher, [args])" 4 |
1071 | .IX Item "ev_TYPE_set (ev_TYPE *, [args])" |
1473 | .IX Item "ev_TYPE_set (ev_TYPE *watcher, [args])" |
1072 | This macro initialises the type-specific parts of a watcher. You need to |
1474 | This macro initialises the type-specific parts of a watcher. You need to |
1073 | call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can |
1475 | call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can |
1074 | call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this |
1476 | call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this |
1075 | macro on a watcher that is active (it can be pending, however, which is a |
1477 | macro on a watcher that is active (it can be pending, however, which is a |
1076 | difference to the \f(CW\*(C`ev_init\*(C'\fR macro). |
1478 | difference to the \f(CW\*(C`ev_init\*(C'\fR macro). |
… | |
… | |
1089 | Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step. |
1491 | Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step. |
1090 | .Sp |
1492 | .Sp |
1091 | .Vb 1 |
1493 | .Vb 1 |
1092 | \& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1494 | \& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1093 | .Ve |
1495 | .Ve |
1094 | .ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 |
1496 | .ie n .IP """ev_TYPE_start"" (loop, ev_TYPE *watcher)" 4 |
1095 | .el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 |
1497 | .el .IP "\f(CWev_TYPE_start\fR (loop, ev_TYPE *watcher)" 4 |
1096 | .IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" |
1498 | .IX Item "ev_TYPE_start (loop, ev_TYPE *watcher)" |
1097 | Starts (activates) the given watcher. Only active watchers will receive |
1499 | Starts (activates) the given watcher. Only active watchers will receive |
1098 | events. If the watcher is already active nothing will happen. |
1500 | events. If the watcher is already active nothing will happen. |
1099 | .Sp |
1501 | .Sp |
1100 | Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this |
1502 | Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this |
1101 | whole section. |
1503 | whole section. |
1102 | .Sp |
1504 | .Sp |
1103 | .Vb 1 |
1505 | .Vb 1 |
1104 | \& ev_io_start (EV_DEFAULT_UC, &w); |
1506 | \& ev_io_start (EV_DEFAULT_UC, &w); |
1105 | .Ve |
1507 | .Ve |
1106 | .ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 |
1508 | .ie n .IP """ev_TYPE_stop"" (loop, ev_TYPE *watcher)" 4 |
1107 | .el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 |
1509 | .el .IP "\f(CWev_TYPE_stop\fR (loop, ev_TYPE *watcher)" 4 |
1108 | .IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" |
1510 | .IX Item "ev_TYPE_stop (loop, ev_TYPE *watcher)" |
1109 | Stops the given watcher again (if active) and clears the pending |
1511 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1512 | the watcher was active or not). |
|
|
1513 | .Sp |
1110 | status. It is possible that stopped watchers are pending (for example, |
1514 | It is possible that stopped watchers are pending \- for example, |
1111 | non-repeating timers are being stopped when they become pending), but |
1515 | non-repeating timers are being stopped when they become pending \- but |
1112 | \&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If |
1516 | calling \f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor |
1113 | you want to free or reuse the memory used by the watcher it is therefore a |
1517 | pending. If you want to free or reuse the memory used by the watcher it is |
1114 | good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
1518 | therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
1115 | .IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
1519 | .IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
1116 | .IX Item "bool ev_is_active (ev_TYPE *watcher)" |
1520 | .IX Item "bool ev_is_active (ev_TYPE *watcher)" |
1117 | Returns a true value iff the watcher is active (i.e. it has been started |
1521 | Returns a true value iff the watcher is active (i.e. it has been started |
1118 | and not yet been stopped). As long as a watcher is active you must not modify |
1522 | and not yet been stopped). As long as a watcher is active you must not modify |
1119 | it. |
1523 | it. |
… | |
… | |
1126 | make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR |
1530 | make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR |
1127 | it). |
1531 | it). |
1128 | .IP "callback ev_cb (ev_TYPE *watcher)" 4 |
1532 | .IP "callback ev_cb (ev_TYPE *watcher)" 4 |
1129 | .IX Item "callback ev_cb (ev_TYPE *watcher)" |
1533 | .IX Item "callback ev_cb (ev_TYPE *watcher)" |
1130 | Returns the callback currently set on the watcher. |
1534 | Returns the callback currently set on the watcher. |
1131 | .IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 |
1535 | .IP "ev_set_cb (ev_TYPE *watcher, callback)" 4 |
1132 | .IX Item "ev_cb_set (ev_TYPE *watcher, callback)" |
1536 | .IX Item "ev_set_cb (ev_TYPE *watcher, callback)" |
1133 | Change the callback. You can change the callback at virtually any time |
1537 | Change the callback. You can change the callback at virtually any time |
1134 | (modulo threads). |
1538 | (modulo threads). |
1135 | .IP "ev_set_priority (ev_TYPE *watcher, priority)" 4 |
1539 | .IP "ev_set_priority (ev_TYPE *watcher, int priority)" 4 |
1136 | .IX Item "ev_set_priority (ev_TYPE *watcher, priority)" |
1540 | .IX Item "ev_set_priority (ev_TYPE *watcher, int priority)" |
1137 | .PD 0 |
1541 | .PD 0 |
1138 | .IP "int ev_priority (ev_TYPE *watcher)" 4 |
1542 | .IP "int ev_priority (ev_TYPE *watcher)" 4 |
1139 | .IX Item "int ev_priority (ev_TYPE *watcher)" |
1543 | .IX Item "int ev_priority (ev_TYPE *watcher)" |
1140 | .PD |
1544 | .PD |
1141 | Set and query the priority of the watcher. The priority is a small |
1545 | Set and query the priority of the watcher. The priority is a small |
1142 | integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR |
1546 | integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR |
1143 | (default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked |
1547 | (default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked |
1144 | before watchers with lower priority, but priority will not keep watchers |
1548 | before watchers with lower priority, but priority will not keep watchers |
1145 | from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). |
1549 | from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). |
1146 | .Sp |
1550 | .Sp |
1147 | This means that priorities are \fIonly\fR used for ordering callback |
|
|
1148 | invocation after new events have been received. This is useful, for |
|
|
1149 | example, to reduce latency after idling, or more often, to bind two |
|
|
1150 | watchers on the same event and make sure one is called first. |
|
|
1151 | .Sp |
|
|
1152 | If you need to suppress invocation when higher priority events are pending |
1551 | If you need to suppress invocation when higher priority events are pending |
1153 | you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. |
1552 | you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. |
1154 | .Sp |
1553 | .Sp |
1155 | You \fImust not\fR change the priority of a watcher as long as it is active or |
1554 | You \fImust not\fR change the priority of a watcher as long as it is active or |
1156 | pending. |
1555 | pending. |
1157 | .Sp |
1556 | .Sp |
|
|
1557 | Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is |
|
|
1558 | fine, as long as you do not mind that the priority value you query might |
|
|
1559 | or might not have been clamped to the valid range. |
|
|
1560 | .Sp |
1158 | The default priority used by watchers when no priority has been set is |
1561 | The default priority used by watchers when no priority has been set is |
1159 | always \f(CW0\fR, which is supposed to not be too high and not be too low :). |
1562 | always \f(CW0\fR, which is supposed to not be too high and not be too low :). |
1160 | .Sp |
1563 | .Sp |
1161 | Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is |
1564 | See \*(L"\s-1WATCHER PRIORITY MODELS\*(R"\s0, below, for a more thorough treatment of |
1162 | fine, as long as you do not mind that the priority value you query might |
1565 | priorities. |
1163 | or might not have been adjusted to be within valid range. |
|
|
1164 | .IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 |
1566 | .IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 |
1165 | .IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" |
1567 | .IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" |
1166 | Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither |
1568 | Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither |
1167 | \&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback |
1569 | \&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback |
1168 | can deal with that fact, as both are simply passed through to the |
1570 | can deal with that fact, as both are simply passed through to the |
… | |
… | |
1173 | returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the |
1575 | returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the |
1174 | watcher isn't pending it does nothing and returns \f(CW0\fR. |
1576 | watcher isn't pending it does nothing and returns \f(CW0\fR. |
1175 | .Sp |
1577 | .Sp |
1176 | Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its |
1578 | Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its |
1177 | callback to be invoked, which can be accomplished with this function. |
1579 | callback to be invoked, which can be accomplished with this function. |
1178 | .Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
1580 | .IP "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 4 |
1179 | .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
1581 | .IX Item "ev_feed_event (loop, ev_TYPE *watcher, int revents)" |
1180 | Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change |
1582 | Feeds the given event set into the event loop, as if the specified event |
1181 | and read at any time: libev will completely ignore it. This can be used |
1583 | had happened for the specified watcher (which must be a pointer to an |
1182 | to associate arbitrary data with your watcher. If you need more data and |
1584 | initialised but not necessarily started event watcher). Obviously you must |
1183 | don't want to allocate memory and store a pointer to it in that data |
1585 | not free the watcher as long as it has pending events. |
1184 | member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
1586 | .Sp |
1185 | data: |
1587 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1588 | \&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was |
|
|
1589 | not started in the first place. |
|
|
1590 | .Sp |
|
|
1591 | See also \f(CW\*(C`ev_feed_fd_event\*(C'\fR and \f(CW\*(C`ev_feed_signal_event\*(C'\fR for related |
|
|
1592 | functions that do not need a watcher. |
1186 | .PP |
1593 | .PP |
|
|
1594 | See also the \*(L"\s-1ASSOCIATING CUSTOM DATA WITH A WATCHER\*(R"\s0 and \*(L"\s-1BUILDING YOUR |
|
|
1595 | OWN COMPOSITE WATCHERS\*(R"\s0 idioms. |
|
|
1596 | .SS "\s-1WATCHER STATES\s0" |
|
|
1597 | .IX Subsection "WATCHER STATES" |
|
|
1598 | There are various watcher states mentioned throughout this manual \- |
|
|
1599 | active, pending and so on. In this section these states and the rules to |
|
|
1600 | transition between them will be described in more detail \- and while these |
|
|
1601 | rules might look complicated, they usually do \*(L"the right thing\*(R". |
|
|
1602 | .IP "initialised" 4 |
|
|
1603 | .IX Item "initialised" |
|
|
1604 | Before a watcher can be registered with the event loop it has to be |
|
|
1605 | initialised. This can be done with a call to \f(CW\*(C`ev_TYPE_init\*(C'\fR, or calls to |
|
|
1606 | \&\f(CW\*(C`ev_init\*(C'\fR followed by the watcher-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR function. |
|
|
1607 | .Sp |
|
|
1608 | In this state it is simply some block of memory that is suitable for |
|
|
1609 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1610 | will \- as long as you either keep the memory contents intact, or call |
|
|
1611 | \&\f(CW\*(C`ev_TYPE_init\*(C'\fR again. |
|
|
1612 | .IP "started/running/active" 4 |
|
|
1613 | .IX Item "started/running/active" |
|
|
1614 | Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes |
|
|
1615 | property of the event loop, and is actively waiting for events. While in |
|
|
1616 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1617 | freed or anything else \- the only legal thing is to keep a pointer to it, |
|
|
1618 | and call libev functions on it that are documented to work on active watchers. |
|
|
1619 | .IP "pending" 4 |
|
|
1620 | .IX Item "pending" |
|
|
1621 | If a watcher is active and libev determines that an event it is interested |
|
|
1622 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1623 | stay in this pending state until either it is stopped or its callback is |
|
|
1624 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1625 | callback. |
|
|
1626 | .Sp |
|
|
1627 | The watcher might or might not be active while it is pending (for example, |
|
|
1628 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1629 | is stopped, it can be freely accessed (e.g. by calling \f(CW\*(C`ev_TYPE_set\*(C'\fR), |
|
|
1630 | but it is still property of the event loop at this time, so cannot be |
|
|
1631 | moved, freed or reused. And if it is active the rules described in the |
|
|
1632 | previous item still apply. |
|
|
1633 | .Sp |
|
|
1634 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1635 | via \f(CW\*(C`ev_feed_event\*(C'\fR), in which case it becomes pending without being |
|
|
1636 | active. |
|
|
1637 | .IP "stopped" 4 |
|
|
1638 | .IX Item "stopped" |
|
|
1639 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1640 | be pending), or explicitly by calling its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. The |
|
|
1641 | latter will clear any pending state the watcher might be in, regardless |
|
|
1642 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1643 | freeing it is often a good idea. |
|
|
1644 | .Sp |
|
|
1645 | While stopped (and not pending) the watcher is essentially in the |
|
|
1646 | initialised state, that is, it can be reused, moved, modified in any way |
|
|
1647 | you wish (but when you trash the memory block, you need to \f(CW\*(C`ev_TYPE_init\*(C'\fR |
|
|
1648 | it again). |
|
|
1649 | .SS "\s-1WATCHER PRIORITY MODELS\s0" |
|
|
1650 | .IX Subsection "WATCHER PRIORITY MODELS" |
|
|
1651 | Many event loops support \fIwatcher priorities\fR, which are usually small |
|
|
1652 | integers that influence the ordering of event callback invocation |
|
|
1653 | between watchers in some way, all else being equal. |
|
|
1654 | .PP |
|
|
1655 | In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its |
|
|
1656 | description for the more technical details such as the actual priority |
|
|
1657 | range. |
|
|
1658 | .PP |
|
|
1659 | There are two common ways how these these priorities are being interpreted |
|
|
1660 | by event loops: |
|
|
1661 | .PP |
|
|
1662 | In the more common lock-out model, higher priorities \*(L"lock out\*(R" invocation |
|
|
1663 | of lower priority watchers, which means as long as higher priority |
|
|
1664 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1665 | .PP |
|
|
1666 | The less common only-for-ordering model uses priorities solely to order |
|
|
1667 | callback invocation within a single event loop iteration: Higher priority |
|
|
1668 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1669 | before polling for new events. |
|
|
1670 | .PP |
|
|
1671 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1672 | except for idle watchers (which use the lock-out model). |
|
|
1673 | .PP |
|
|
1674 | The rationale behind this is that implementing the lock-out model for |
|
|
1675 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1676 | libraries will just poll for the same events again and again as long as |
|
|
1677 | their callbacks have not been executed, which is very inefficient in the |
|
|
1678 | common case of one high-priority watcher locking out a mass of lower |
|
|
1679 | priority ones. |
|
|
1680 | .PP |
|
|
1681 | Static (ordering) priorities are most useful when you have two or more |
|
|
1682 | watchers handling the same resource: a typical usage example is having an |
|
|
1683 | \&\f(CW\*(C`ev_io\*(C'\fR watcher to receive data, and an associated \f(CW\*(C`ev_timer\*(C'\fR to handle |
|
|
1684 | timeouts. Under load, data might be received while the program handles |
|
|
1685 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1686 | handler will be executed before checking for data. In that case, giving |
|
|
1687 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1688 | handled first even under adverse conditions (which is usually, but not |
|
|
1689 | always, what you want). |
|
|
1690 | .PP |
|
|
1691 | Since idle watchers use the \*(L"lock-out\*(R" model, meaning that idle watchers |
|
|
1692 | will only be executed when no same or higher priority watchers have |
|
|
1693 | received events, they can be used to implement the \*(L"lock-out\*(R" model when |
|
|
1694 | required. |
|
|
1695 | .PP |
|
|
1696 | For example, to emulate how many other event libraries handle priorities, |
|
|
1697 | you can associate an \f(CW\*(C`ev_idle\*(C'\fR watcher to each such watcher, and in |
|
|
1698 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1699 | processing is done in the idle watcher callback. This causes libev to |
|
|
1700 | continuously poll and process kernel event data for the watcher, but when |
|
|
1701 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1702 | workable. |
|
|
1703 | .PP |
|
|
1704 | Usually, however, the lock-out model implemented that way will perform |
|
|
1705 | miserably under the type of load it was designed to handle. In that case, |
|
|
1706 | it might be preferable to stop the real watcher before starting the |
|
|
1707 | idle watcher, so the kernel will not have to process the event in case |
|
|
1708 | the actual processing will be delayed for considerable time. |
|
|
1709 | .PP |
|
|
1710 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1711 | priority than the default, and which should only process data when no |
|
|
1712 | other events are pending: |
|
|
1713 | .PP |
1187 | .Vb 7 |
1714 | .Vb 2 |
1188 | \& struct my_io |
1715 | \& ev_idle idle; // actual processing watcher |
|
|
1716 | \& ev_io io; // actual event watcher |
|
|
1717 | \& |
|
|
1718 | \& static void |
|
|
1719 | \& io_cb (EV_P_ ev_io *w, int revents) |
1189 | \& { |
1720 | \& { |
1190 | \& struct ev_io io; |
1721 | \& // stop the I/O watcher, we received the event, but |
1191 | \& int otherfd; |
1722 | \& // are not yet ready to handle it. |
1192 | \& void *somedata; |
1723 | \& ev_io_stop (EV_A_ w); |
1193 | \& struct whatever *mostinteresting; |
1724 | \& |
|
|
1725 | \& // start the idle watcher to handle the actual event. |
|
|
1726 | \& // it will not be executed as long as other watchers |
|
|
1727 | \& // with the default priority are receiving events. |
|
|
1728 | \& ev_idle_start (EV_A_ &idle); |
1194 | \& }; |
1729 | \& } |
1195 | \& |
1730 | \& |
1196 | \& ... |
1731 | \& static void |
1197 | \& struct my_io w; |
1732 | \& idle_cb (EV_P_ ev_idle *w, int revents) |
1198 | \& ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1199 | .Ve |
|
|
1200 | .PP |
|
|
1201 | And since your callback will be called with a pointer to the watcher, you |
|
|
1202 | can cast it back to your own type: |
|
|
1203 | .PP |
|
|
1204 | .Vb 5 |
|
|
1205 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
|
|
1206 | \& { |
1733 | \& { |
1207 | \& struct my_io *w = (struct my_io *)w_; |
1734 | \& // actual processing |
1208 | \& ... |
1735 | \& read (STDIN_FILENO, ...); |
|
|
1736 | \& |
|
|
1737 | \& // have to start the I/O watcher again, as |
|
|
1738 | \& // we have handled the event |
|
|
1739 | \& ev_io_start (EV_P_ &io); |
1209 | \& } |
1740 | \& } |
1210 | .Ve |
|
|
1211 | .PP |
|
|
1212 | More interesting and less C\-conformant ways of casting your callback type |
|
|
1213 | instead have been omitted. |
|
|
1214 | .PP |
|
|
1215 | Another common scenario is to use some data structure with multiple |
|
|
1216 | embedded watchers: |
|
|
1217 | .PP |
|
|
1218 | .Vb 6 |
|
|
1219 | \& struct my_biggy |
|
|
1220 | \& { |
|
|
1221 | \& int some_data; |
|
|
1222 | \& ev_timer t1; |
|
|
1223 | \& ev_timer t2; |
|
|
1224 | \& } |
|
|
1225 | .Ve |
|
|
1226 | .PP |
|
|
1227 | In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more |
|
|
1228 | complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct |
|
|
1229 | in the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies), or you need to use |
|
|
1230 | some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for real |
|
|
1231 | programmers): |
|
|
1232 | .PP |
|
|
1233 | .Vb 1 |
|
|
1234 | \& #include <stddef.h> |
|
|
1235 | \& |
1741 | \& |
1236 | \& static void |
1742 | \& // initialisation |
1237 | \& t1_cb (EV_P_ struct ev_timer *w, int revents) |
1743 | \& ev_idle_init (&idle, idle_cb); |
1238 | \& { |
1744 | \& ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
1239 | \& struct my_biggy big = (struct my_biggy * |
1745 | \& ev_io_start (EV_DEFAULT_ &io); |
1240 | \& (((char *)w) \- offsetof (struct my_biggy, t1)); |
|
|
1241 | \& } |
|
|
1242 | \& |
|
|
1243 | \& static void |
|
|
1244 | \& t2_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
1245 | \& { |
|
|
1246 | \& struct my_biggy big = (struct my_biggy * |
|
|
1247 | \& (((char *)w) \- offsetof (struct my_biggy, t2)); |
|
|
1248 | \& } |
|
|
1249 | .Ve |
1746 | .Ve |
|
|
1747 | .PP |
|
|
1748 | In the \*(L"real\*(R" world, it might also be beneficial to start a timer, so that |
|
|
1749 | low-priority connections can not be locked out forever under load. This |
|
|
1750 | enables your program to keep a lower latency for important connections |
|
|
1751 | during short periods of high load, while not completely locking out less |
|
|
1752 | important ones. |
1250 | .SH "WATCHER TYPES" |
1753 | .SH "WATCHER TYPES" |
1251 | .IX Header "WATCHER TYPES" |
1754 | .IX Header "WATCHER TYPES" |
1252 | This section describes each watcher in detail, but will not repeat |
1755 | This section describes each watcher in detail, but will not repeat |
1253 | information given in the last section. Any initialisation/set macros, |
1756 | information given in the last section. Any initialisation/set macros, |
1254 | functions and members specific to the watcher type are explained. |
1757 | functions and members specific to the watcher type are explained. |
… | |
… | |
1259 | watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
1762 | watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
1260 | means you can expect it to have some sensible content while the watcher |
1763 | means you can expect it to have some sensible content while the watcher |
1261 | is active, but you can also modify it. Modifying it may not do something |
1764 | is active, but you can also modify it. Modifying it may not do something |
1262 | sensible or take immediate effect (or do anything at all), but libev will |
1765 | sensible or take immediate effect (or do anything at all), but libev will |
1263 | not crash or malfunction in any way. |
1766 | not crash or malfunction in any way. |
1264 | .ie n .Sh """ev_io"" \- is this file descriptor readable or writable?" |
1767 | .ie n .SS """ev_io"" \- is this file descriptor readable or writable?" |
1265 | .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
1768 | .el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
1266 | .IX Subsection "ev_io - is this file descriptor readable or writable?" |
1769 | .IX Subsection "ev_io - is this file descriptor readable or writable?" |
1267 | I/O watchers check whether a file descriptor is readable or writable |
1770 | I/O watchers check whether a file descriptor is readable or writable |
1268 | in each iteration of the event loop, or, more precisely, when reading |
1771 | in each iteration of the event loop, or, more precisely, when reading |
1269 | would not block the process and writing would at least be able to write |
1772 | would not block the process and writing would at least be able to write |
1270 | some data. This behaviour is called level-triggering because you keep |
1773 | some data. This behaviour is called level-triggering because you keep |
… | |
… | |
1275 | In general you can register as many read and/or write event watchers per |
1778 | In general you can register as many read and/or write event watchers per |
1276 | fd as you want (as long as you don't confuse yourself). Setting all file |
1779 | fd as you want (as long as you don't confuse yourself). Setting all file |
1277 | descriptors to non-blocking mode is also usually a good idea (but not |
1780 | descriptors to non-blocking mode is also usually a good idea (but not |
1278 | required if you know what you are doing). |
1781 | required if you know what you are doing). |
1279 | .PP |
1782 | .PP |
1280 | If you cannot use non-blocking mode, then force the use of a |
|
|
1281 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1282 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR). |
|
|
1283 | .PP |
|
|
1284 | Another thing you have to watch out for is that it is quite easy to |
1783 | Another thing you have to watch out for is that it is quite easy to |
1285 | receive \*(L"spurious\*(R" readiness notifications, that is your callback might |
1784 | receive \*(L"spurious\*(R" readiness notifications, that is, your callback might |
1286 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
1785 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
1287 | because there is no data. Not only are some backends known to create a |
1786 | because there is no data. It is very easy to get into this situation even |
1288 | lot of those (for example Solaris ports), it is very easy to get into |
1787 | with a relatively standard program structure. Thus it is best to always |
1289 | this situation even with a relatively standard program structure. Thus |
1788 | use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning \f(CW\*(C`EAGAIN\*(C'\fR is far |
1290 | it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning |
|
|
1291 | \&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. |
1789 | preferable to a program hanging until some data arrives. |
1292 | .PP |
1790 | .PP |
1293 | If you cannot run the fd in non-blocking mode (for example you should |
1791 | If you cannot run the fd in non-blocking mode (for example you should |
1294 | not play around with an Xlib connection), then you have to separately |
1792 | not play around with an Xlib connection), then you have to separately |
1295 | re-test whether a file descriptor is really ready with a known-to-be good |
1793 | re-test whether a file descriptor is really ready with a known-to-be good |
1296 | interface such as poll (fortunately in our Xlib example, Xlib already |
1794 | interface such as poll (fortunately in the case of Xlib, it already does |
1297 | does this on its own, so its quite safe to use). Some people additionally |
1795 | this on its own, so its quite safe to use). Some people additionally |
1298 | use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block |
1796 | use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block |
1299 | indefinitely. |
1797 | indefinitely. |
1300 | .PP |
1798 | .PP |
1301 | But really, best use non-blocking mode. |
1799 | But really, best use non-blocking mode. |
1302 | .PP |
1800 | .PP |
1303 | \fIThe special problem of disappearing file descriptors\fR |
1801 | \fIThe special problem of disappearing file descriptors\fR |
1304 | .IX Subsection "The special problem of disappearing file descriptors" |
1802 | .IX Subsection "The special problem of disappearing file descriptors" |
1305 | .PP |
1803 | .PP |
1306 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1804 | Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing |
1307 | descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means, |
1805 | a file descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other |
1308 | such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file |
1806 | means, such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some |
1309 | descriptor, but when it goes away, the operating system will silently drop |
1807 | file descriptor, but when it goes away, the operating system will silently |
1310 | this interest. If another file descriptor with the same number then is |
1808 | drop this interest. If another file descriptor with the same number then |
1311 | registered with libev, there is no efficient way to see that this is, in |
1809 | is registered with libev, there is no efficient way to see that this is, |
1312 | fact, a different file descriptor. |
1810 | in fact, a different file descriptor. |
1313 | .PP |
1811 | .PP |
1314 | To avoid having to explicitly tell libev about such cases, libev follows |
1812 | To avoid having to explicitly tell libev about such cases, libev follows |
1315 | the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev |
1813 | the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev |
1316 | will assume that this is potentially a new file descriptor, otherwise |
1814 | will assume that this is potentially a new file descriptor, otherwise |
1317 | it is assumed that the file descriptor stays the same. That means that |
1815 | it is assumed that the file descriptor stays the same. That means that |
… | |
… | |
1332 | .PP |
1830 | .PP |
1333 | There is no workaround possible except not registering events |
1831 | There is no workaround possible except not registering events |
1334 | for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to |
1832 | for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to |
1335 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1833 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1336 | .PP |
1834 | .PP |
|
|
1835 | \fIThe special problem of files\fR |
|
|
1836 | .IX Subsection "The special problem of files" |
|
|
1837 | .PP |
|
|
1838 | Many people try to use \f(CW\*(C`select\*(C'\fR (or libev) on file descriptors |
|
|
1839 | representing files, and expect it to become ready when their program |
|
|
1840 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1841 | .PP |
|
|
1842 | However, this cannot ever work in the \*(L"expected\*(R" way \- you get a readiness |
|
|
1843 | notification as soon as the kernel knows whether and how much data is |
|
|
1844 | there, and in the case of open files, that's always the case, so you |
|
|
1845 | always get a readiness notification instantly, and your read (or possibly |
|
|
1846 | write) will still block on the disk I/O. |
|
|
1847 | .PP |
|
|
1848 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1849 | devices and so on, there is another party (the sender) that delivers data |
|
|
1850 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1851 | will not send data on its own, simply because it doesn't know what you |
|
|
1852 | wish to read \- you would first have to request some data. |
|
|
1853 | .PP |
|
|
1854 | Since files are typically not-so-well supported by advanced notification |
|
|
1855 | mechanism, libev tries hard to emulate \s-1POSIX\s0 behaviour with respect |
|
|
1856 | to files, even though you should not use it. The reason for this is |
|
|
1857 | convenience: sometimes you want to watch \s-1STDIN\s0 or \s-1STDOUT,\s0 which is |
|
|
1858 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1859 | (for example, \f(CW\*(C`epoll\*(C'\fR on Linux works with \fI/dev/random\fR but not with |
|
|
1860 | \&\fI/dev/urandom\fR), and even though the file might better be served with |
|
|
1861 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1862 | it \*(L"just works\*(R" instead of freezing. |
|
|
1863 | .PP |
|
|
1864 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1865 | libeio), but use them when it is convenient, e.g. for \s-1STDIN/STDOUT,\s0 or |
|
|
1866 | when you rarely read from a file instead of from a socket, and want to |
|
|
1867 | reuse the same code path. |
|
|
1868 | .PP |
1337 | \fIThe special problem of fork\fR |
1869 | \fIThe special problem of fork\fR |
1338 | .IX Subsection "The special problem of fork" |
1870 | .IX Subsection "The special problem of fork" |
1339 | .PP |
1871 | .PP |
1340 | Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit |
1872 | Some backends (epoll, kqueue, probably linuxaio) do not support \f(CW\*(C`fork ()\*(C'\fR |
1341 | useless behaviour. Libev fully supports fork, but needs to be told about |
1873 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1342 | it in the child. |
1874 | to be told about it in the child if you want to continue to use it in the |
|
|
1875 | child. |
1343 | .PP |
1876 | .PP |
1344 | To support fork in your programs, you either have to call |
1877 | To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork |
1345 | \&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child, |
1878 | ()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to |
1346 | enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or |
1879 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1347 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
|
|
1348 | .PP |
1880 | .PP |
1349 | \fIThe special problem of \s-1SIGPIPE\s0\fR |
1881 | \fIThe special problem of \s-1SIGPIPE\s0\fR |
1350 | .IX Subsection "The special problem of SIGPIPE" |
1882 | .IX Subsection "The special problem of SIGPIPE" |
1351 | .PP |
1883 | .PP |
1352 | While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR: |
1884 | While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR: |
1353 | when writing to a pipe whose other end has been closed, your program gets |
1885 | when writing to a pipe whose other end has been closed, your program gets |
1354 | sent a \s-1SIGPIPE\s0, which, by default, aborts your program. For most programs |
1886 | sent a \s-1SIGPIPE,\s0 which, by default, aborts your program. For most programs |
1355 | this is sensible behaviour, for daemons, this is usually undesirable. |
1887 | this is sensible behaviour, for daemons, this is usually undesirable. |
1356 | .PP |
1888 | .PP |
1357 | So when you encounter spurious, unexplained daemon exits, make sure you |
1889 | So when you encounter spurious, unexplained daemon exits, make sure you |
1358 | ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon |
1890 | ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon |
1359 | somewhere, as that would have given you a big clue). |
1891 | somewhere, as that would have given you a big clue). |
|
|
1892 | .PP |
|
|
1893 | \fIThe special problem of \f(BIaccept()\fIing when you can't\fR |
|
|
1894 | .IX Subsection "The special problem of accept()ing when you can't" |
|
|
1895 | .PP |
|
|
1896 | Many implementations of the \s-1POSIX\s0 \f(CW\*(C`accept\*(C'\fR function (for example, |
|
|
1897 | found in post\-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1898 | connection from the pending queue in all error cases. |
|
|
1899 | .PP |
|
|
1900 | For example, larger servers often run out of file descriptors (because |
|
|
1901 | of resource limits), causing \f(CW\*(C`accept\*(C'\fR to fail with \f(CW\*(C`ENFILE\*(C'\fR but not |
|
|
1902 | rejecting the connection, leading to libev signalling readiness on |
|
|
1903 | the next iteration again (the connection still exists after all), and |
|
|
1904 | typically causing the program to loop at 100% \s-1CPU\s0 usage. |
|
|
1905 | .PP |
|
|
1906 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1907 | operating systems, there is usually little the app can do to remedy the |
|
|
1908 | situation, and no known thread-safe method of removing the connection to |
|
|
1909 | cope with overload is known (to me). |
|
|
1910 | .PP |
|
|
1911 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1912 | \&\- when the program encounters an overload, it will just loop until the |
|
|
1913 | situation is over. While this is a form of busy waiting, no \s-1OS\s0 offers an |
|
|
1914 | event-based way to handle this situation, so it's the best one can do. |
|
|
1915 | .PP |
|
|
1916 | A better way to handle the situation is to log any errors other than |
|
|
1917 | \&\f(CW\*(C`EAGAIN\*(C'\fR and \f(CW\*(C`EWOULDBLOCK\*(C'\fR, making sure not to flood the log with such |
|
|
1918 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1919 | what could be wrong (\*(L"raise the ulimit!\*(R"). For extra points one could stop |
|
|
1920 | the \f(CW\*(C`ev_io\*(C'\fR watcher on the listening fd \*(L"for a while\*(R", which reduces \s-1CPU\s0 |
|
|
1921 | usage. |
|
|
1922 | .PP |
|
|
1923 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1924 | descriptor for overload situations (e.g. by opening \fI/dev/null\fR), and |
|
|
1925 | when you run into \f(CW\*(C`ENFILE\*(C'\fR or \f(CW\*(C`EMFILE\*(C'\fR, close it, run \f(CW\*(C`accept\*(C'\fR, |
|
|
1926 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1927 | clients under typical overload conditions. |
|
|
1928 | .PP |
|
|
1929 | The last way to handle it is to simply log the error and \f(CW\*(C`exit\*(C'\fR, as |
|
|
1930 | is often done with \f(CW\*(C`malloc\*(C'\fR failures, but this results in an easy |
|
|
1931 | opportunity for a DoS attack. |
1360 | .PP |
1932 | .PP |
1361 | \fIWatcher-Specific Functions\fR |
1933 | \fIWatcher-Specific Functions\fR |
1362 | .IX Subsection "Watcher-Specific Functions" |
1934 | .IX Subsection "Watcher-Specific Functions" |
1363 | .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
1935 | .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
1364 | .IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
1936 | .IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
… | |
… | |
1383 | readable, but only once. Since it is likely line-buffered, you could |
1955 | readable, but only once. Since it is likely line-buffered, you could |
1384 | attempt to read a whole line in the callback. |
1956 | attempt to read a whole line in the callback. |
1385 | .PP |
1957 | .PP |
1386 | .Vb 6 |
1958 | .Vb 6 |
1387 | \& static void |
1959 | \& static void |
1388 | \& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1960 | \& stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1389 | \& { |
1961 | \& { |
1390 | \& ev_io_stop (loop, w); |
1962 | \& ev_io_stop (loop, w); |
1391 | \& .. read from stdin here (or from w\->fd) and handle any I/O errors |
1963 | \& .. read from stdin here (or from w\->fd) and handle any I/O errors |
1392 | \& } |
1964 | \& } |
1393 | \& |
1965 | \& |
1394 | \& ... |
1966 | \& ... |
1395 | \& struct ev_loop *loop = ev_default_init (0); |
1967 | \& struct ev_loop *loop = ev_default_init (0); |
1396 | \& struct ev_io stdin_readable; |
1968 | \& ev_io stdin_readable; |
1397 | \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1969 | \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1398 | \& ev_io_start (loop, &stdin_readable); |
1970 | \& ev_io_start (loop, &stdin_readable); |
1399 | \& ev_loop (loop, 0); |
1971 | \& ev_run (loop, 0); |
1400 | .Ve |
1972 | .Ve |
1401 | .ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" |
1973 | .ie n .SS """ev_timer"" \- relative and optionally repeating timeouts" |
1402 | .el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts" |
1974 | .el .SS "\f(CWev_timer\fP \- relative and optionally repeating timeouts" |
1403 | .IX Subsection "ev_timer - relative and optionally repeating timeouts" |
1975 | .IX Subsection "ev_timer - relative and optionally repeating timeouts" |
1404 | Timer watchers are simple relative timers that generate an event after a |
1976 | Timer watchers are simple relative timers that generate an event after a |
1405 | given time, and optionally repeating in regular intervals after that. |
1977 | given time, and optionally repeating in regular intervals after that. |
1406 | .PP |
1978 | .PP |
1407 | The timers are based on real time, that is, if you register an event that |
1979 | The timers are based on real time, that is, if you register an event that |
… | |
… | |
1409 | year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because |
1981 | year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because |
1410 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1982 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1411 | monotonic clock option helps a lot here). |
1983 | monotonic clock option helps a lot here). |
1412 | .PP |
1984 | .PP |
1413 | The callback is guaranteed to be invoked only \fIafter\fR its timeout has |
1985 | The callback is guaranteed to be invoked only \fIafter\fR its timeout has |
1414 | passed, but if multiple timers become ready during the same loop iteration |
1986 | passed (not \fIat\fR, so on systems with very low-resolution clocks this |
1415 | then order of execution is undefined. |
1987 | might introduce a small delay, see \*(L"the special problem of being too |
|
|
1988 | early\*(R", below). If multiple timers become ready during the same loop |
|
|
1989 | iteration then the ones with earlier time-out values are invoked before |
|
|
1990 | ones of the same priority with later time-out values (but this is no |
|
|
1991 | longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively). |
|
|
1992 | .PP |
|
|
1993 | \fIBe smart about timeouts\fR |
|
|
1994 | .IX Subsection "Be smart about timeouts" |
|
|
1995 | .PP |
|
|
1996 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1997 | recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs, |
|
|
1998 | you want to raise some error after a while. |
|
|
1999 | .PP |
|
|
2000 | What follows are some ways to handle this problem, from obvious and |
|
|
2001 | inefficient to smart and efficient. |
|
|
2002 | .PP |
|
|
2003 | In the following, a 60 second activity timeout is assumed \- a timeout that |
|
|
2004 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
2005 | data or other life sign was received). |
|
|
2006 | .IP "1. Use a timer and stop, reinitialise and start it on activity." 4 |
|
|
2007 | .IX Item "1. Use a timer and stop, reinitialise and start it on activity." |
|
|
2008 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
2009 | start the watcher: |
|
|
2010 | .Sp |
|
|
2011 | .Vb 2 |
|
|
2012 | \& ev_timer_init (timer, callback, 60., 0.); |
|
|
2013 | \& ev_timer_start (loop, timer); |
|
|
2014 | .Ve |
|
|
2015 | .Sp |
|
|
2016 | Then, each time there is some activity, \f(CW\*(C`ev_timer_stop\*(C'\fR it, initialise it |
|
|
2017 | and start it again: |
|
|
2018 | .Sp |
|
|
2019 | .Vb 3 |
|
|
2020 | \& ev_timer_stop (loop, timer); |
|
|
2021 | \& ev_timer_set (timer, 60., 0.); |
|
|
2022 | \& ev_timer_start (loop, timer); |
|
|
2023 | .Ve |
|
|
2024 | .Sp |
|
|
2025 | This is relatively simple to implement, but means that each time there is |
|
|
2026 | some activity, libev will first have to remove the timer from its internal |
|
|
2027 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
2028 | still not a constant-time operation. |
|
|
2029 | .ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4 |
|
|
2030 | .el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4 |
|
|
2031 | .IX Item "2. Use a timer and re-start it with ev_timer_again inactivity." |
|
|
2032 | This is the easiest way, and involves using \f(CW\*(C`ev_timer_again\*(C'\fR instead of |
|
|
2033 | \&\f(CW\*(C`ev_timer_start\*(C'\fR. |
|
|
2034 | .Sp |
|
|
2035 | To implement this, configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value |
|
|
2036 | of \f(CW60\fR and then call \f(CW\*(C`ev_timer_again\*(C'\fR at start and each time you |
|
|
2037 | successfully read or write some data. If you go into an idle state where |
|
|
2038 | you do not expect data to travel on the socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR |
|
|
2039 | the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will automatically restart it if need be. |
|
|
2040 | .Sp |
|
|
2041 | That means you can ignore both the \f(CW\*(C`ev_timer_start\*(C'\fR function and the |
|
|
2042 | \&\f(CW\*(C`after\*(C'\fR argument to \f(CW\*(C`ev_timer_set\*(C'\fR, and only ever use the \f(CW\*(C`repeat\*(C'\fR |
|
|
2043 | member and \f(CW\*(C`ev_timer_again\*(C'\fR. |
|
|
2044 | .Sp |
|
|
2045 | At start: |
|
|
2046 | .Sp |
|
|
2047 | .Vb 3 |
|
|
2048 | \& ev_init (timer, callback); |
|
|
2049 | \& timer\->repeat = 60.; |
|
|
2050 | \& ev_timer_again (loop, timer); |
|
|
2051 | .Ve |
|
|
2052 | .Sp |
|
|
2053 | Each time there is some activity: |
|
|
2054 | .Sp |
|
|
2055 | .Vb 1 |
|
|
2056 | \& ev_timer_again (loop, timer); |
|
|
2057 | .Ve |
|
|
2058 | .Sp |
|
|
2059 | It is even possible to change the time-out on the fly, regardless of |
|
|
2060 | whether the watcher is active or not: |
|
|
2061 | .Sp |
|
|
2062 | .Vb 2 |
|
|
2063 | \& timer\->repeat = 30.; |
|
|
2064 | \& ev_timer_again (loop, timer); |
|
|
2065 | .Ve |
|
|
2066 | .Sp |
|
|
2067 | This is slightly more efficient then stopping/starting the timer each time |
|
|
2068 | you want to modify its timeout value, as libev does not have to completely |
|
|
2069 | remove and re-insert the timer from/into its internal data structure. |
|
|
2070 | .Sp |
|
|
2071 | It is, however, even simpler than the \*(L"obvious\*(R" way to do it. |
|
|
2072 | .IP "3. Let the timer time out, but then re-arm it as required." 4 |
|
|
2073 | .IX Item "3. Let the timer time out, but then re-arm it as required." |
|
|
2074 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
2075 | relatively long compared to the intervals between other activity \- in |
|
|
2076 | our example, within 60 seconds, there are usually many I/O events with |
|
|
2077 | associated activity resets. |
|
|
2078 | .Sp |
|
|
2079 | In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone, |
|
|
2080 | but remember the time of last activity, and check for a real timeout only |
|
|
2081 | within the callback: |
|
|
2082 | .Sp |
|
|
2083 | .Vb 3 |
|
|
2084 | \& ev_tstamp timeout = 60.; |
|
|
2085 | \& ev_tstamp last_activity; // time of last activity |
|
|
2086 | \& ev_timer timer; |
|
|
2087 | \& |
|
|
2088 | \& static void |
|
|
2089 | \& callback (EV_P_ ev_timer *w, int revents) |
|
|
2090 | \& { |
|
|
2091 | \& // calculate when the timeout would happen |
|
|
2092 | \& ev_tstamp after = last_activity \- ev_now (EV_A) + timeout; |
|
|
2093 | \& |
|
|
2094 | \& // if negative, it means we the timeout already occurred |
|
|
2095 | \& if (after < 0.) |
|
|
2096 | \& { |
|
|
2097 | \& // timeout occurred, take action |
|
|
2098 | \& } |
|
|
2099 | \& else |
|
|
2100 | \& { |
|
|
2101 | \& // callback was invoked, but there was some recent |
|
|
2102 | \& // activity. simply restart the timer to time out |
|
|
2103 | \& // after "after" seconds, which is the earliest time |
|
|
2104 | \& // the timeout can occur. |
|
|
2105 | \& ev_timer_set (w, after, 0.); |
|
|
2106 | \& ev_timer_start (EV_A_ w); |
|
|
2107 | \& } |
|
|
2108 | \& } |
|
|
2109 | .Ve |
|
|
2110 | .Sp |
|
|
2111 | To summarise the callback: first calculate in how many seconds the |
|
|
2112 | timeout will occur (by calculating the absolute time when it would occur, |
|
|
2113 | \&\f(CW\*(C`last_activity + timeout\*(C'\fR, and subtracting the current time, \f(CW\*(C`ev_now |
|
|
2114 | (EV_A)\*(C'\fR from that). |
|
|
2115 | .Sp |
|
|
2116 | If this value is negative, then we are already past the timeout, i.e. we |
|
|
2117 | timed out, and need to do whatever is needed in this case. |
|
|
2118 | .Sp |
|
|
2119 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
2120 | and simply start the timer with this timeout value. |
|
|
2121 | .Sp |
|
|
2122 | In other words, each time the callback is invoked it will check whether |
|
|
2123 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
2124 | again at the earliest time it could time out. Rinse. Repeat. |
|
|
2125 | .Sp |
|
|
2126 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
2127 | minus half the average time between activity), but virtually no calls to |
|
|
2128 | libev to change the timeout. |
|
|
2129 | .Sp |
|
|
2130 | To start the machinery, simply initialise the watcher and set |
|
|
2131 | \&\f(CW\*(C`last_activity\*(C'\fR to the current time (meaning there was some activity just |
|
|
2132 | now), then call the callback, which will \*(L"do the right thing\*(R" and start |
|
|
2133 | the timer: |
|
|
2134 | .Sp |
|
|
2135 | .Vb 3 |
|
|
2136 | \& last_activity = ev_now (EV_A); |
|
|
2137 | \& ev_init (&timer, callback); |
|
|
2138 | \& callback (EV_A_ &timer, 0); |
|
|
2139 | .Ve |
|
|
2140 | .Sp |
|
|
2141 | When there is some activity, simply store the current time in |
|
|
2142 | \&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all: |
|
|
2143 | .Sp |
|
|
2144 | .Vb 2 |
|
|
2145 | \& if (activity detected) |
|
|
2146 | \& last_activity = ev_now (EV_A); |
|
|
2147 | .Ve |
|
|
2148 | .Sp |
|
|
2149 | When your timeout value changes, then the timeout can be changed by simply |
|
|
2150 | providing a new value, stopping the timer and calling the callback, which |
|
|
2151 | will again do the right thing (for example, time out immediately :). |
|
|
2152 | .Sp |
|
|
2153 | .Vb 3 |
|
|
2154 | \& timeout = new_value; |
|
|
2155 | \& ev_timer_stop (EV_A_ &timer); |
|
|
2156 | \& callback (EV_A_ &timer, 0); |
|
|
2157 | .Ve |
|
|
2158 | .Sp |
|
|
2159 | This technique is slightly more complex, but in most cases where the |
|
|
2160 | time-out is unlikely to be triggered, much more efficient. |
|
|
2161 | .IP "4. Wee, just use a double-linked list for your timeouts." 4 |
|
|
2162 | .IX Item "4. Wee, just use a double-linked list for your timeouts." |
|
|
2163 | If there is not one request, but many thousands (millions...), all |
|
|
2164 | employing some kind of timeout with the same timeout value, then one can |
|
|
2165 | do even better: |
|
|
2166 | .Sp |
|
|
2167 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
2168 | at the \fIend\fR of the list. |
|
|
2169 | .Sp |
|
|
2170 | Then use an \f(CW\*(C`ev_timer\*(C'\fR to fire when the timeout at the \fIbeginning\fR of |
|
|
2171 | the list is expected to fire (for example, using the technique #3). |
|
|
2172 | .Sp |
|
|
2173 | When there is some activity, remove the timer from the list, recalculate |
|
|
2174 | the timeout, append it to the end of the list again, and make sure to |
|
|
2175 | update the \f(CW\*(C`ev_timer\*(C'\fR if it was taken from the beginning of the list. |
|
|
2176 | .Sp |
|
|
2177 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
2178 | starting, stopping and updating the timers, at the expense of a major |
|
|
2179 | complication, and having to use a constant timeout. The constant timeout |
|
|
2180 | ensures that the list stays sorted. |
|
|
2181 | .PP |
|
|
2182 | So which method the best? |
|
|
2183 | .PP |
|
|
2184 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
2185 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
2186 | better, and isn't very complicated either. In most case, choosing either |
|
|
2187 | one is fine, with #3 being better in typical situations. |
|
|
2188 | .PP |
|
|
2189 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
2190 | rather complicated, but extremely efficient, something that really pays |
|
|
2191 | off after the first million or so of active timers, i.e. it's usually |
|
|
2192 | overkill :) |
|
|
2193 | .PP |
|
|
2194 | \fIThe special problem of being too early\fR |
|
|
2195 | .IX Subsection "The special problem of being too early" |
|
|
2196 | .PP |
|
|
2197 | If you ask a timer to call your callback after three seconds, then |
|
|
2198 | you expect it to be invoked after three seconds \- but of course, this |
|
|
2199 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
2200 | guaranteed to any precision by libev \- imagine somebody suspending the |
|
|
2201 | process with a \s-1STOP\s0 signal for a few hours for example. |
|
|
2202 | .PP |
|
|
2203 | So, libev tries to invoke your callback as soon as possible \fIafter\fR the |
|
|
2204 | delay has occurred, but cannot guarantee this. |
|
|
2205 | .PP |
|
|
2206 | A less obvious failure mode is calling your callback too early: many event |
|
|
2207 | loops compare timestamps with a \*(L"elapsed delay >= requested delay\*(R", but |
|
|
2208 | this can cause your callback to be invoked much earlier than you would |
|
|
2209 | expect. |
|
|
2210 | .PP |
|
|
2211 | To see why, imagine a system with a clock that only offers full second |
|
|
2212 | resolution (think windows if you can't come up with a broken enough \s-1OS\s0 |
|
|
2213 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2214 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2215 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2216 | .PP |
|
|
2217 | If an event library looks at the timeout 0.1s later, it will see \*(L"501 >= |
|
|
2218 | 501\*(R" and invoke the callback 0.1s after it was started, even though a |
|
|
2219 | one-second delay was requested \- this is being \*(L"too early\*(R", despite best |
|
|
2220 | intentions. |
|
|
2221 | .PP |
|
|
2222 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2223 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2224 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2225 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2226 | .PP |
|
|
2227 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2228 | exactly when requested, it \fIcan\fR and \fIdoes\fR guarantee that the requested |
|
|
2229 | delay has actually elapsed, or in other words, it always errs on the \*(L"too |
|
|
2230 | late\*(R" side of things. |
1416 | .PP |
2231 | .PP |
1417 | \fIThe special problem of time updates\fR |
2232 | \fIThe special problem of time updates\fR |
1418 | .IX Subsection "The special problem of time updates" |
2233 | .IX Subsection "The special problem of time updates" |
1419 | .PP |
2234 | .PP |
1420 | Establishing the current time is a costly operation (it usually takes at |
2235 | Establishing the current time is a costly operation (it usually takes |
1421 | least two system calls): \s-1EV\s0 therefore updates its idea of the current |
2236 | at least one system call): \s-1EV\s0 therefore updates its idea of the current |
1422 | time only before and after \f(CW\*(C`ev_loop\*(C'\fR collects new events, which causes a |
2237 | time only before and after \f(CW\*(C`ev_run\*(C'\fR collects new events, which causes a |
1423 | growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling |
2238 | growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling |
1424 | lots of events in one iteration. |
2239 | lots of events in one iteration. |
1425 | .PP |
2240 | .PP |
1426 | The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
2241 | The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
1427 | time. This is usually the right thing as this timestamp refers to the time |
2242 | time. This is usually the right thing as this timestamp refers to the time |
1428 | of the event triggering whatever timeout you are modifying/starting. If |
2243 | of the event triggering whatever timeout you are modifying/starting. If |
1429 | you suspect event processing to be delayed and you \fIneed\fR to base the |
2244 | you suspect event processing to be delayed and you \fIneed\fR to base the |
1430 | timeout on the current time, use something like this to adjust for this: |
2245 | timeout on the current time, use something like the following to adjust |
|
|
2246 | for it: |
1431 | .PP |
2247 | .PP |
1432 | .Vb 1 |
2248 | .Vb 1 |
1433 | \& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.); |
2249 | \& ev_timer_set (&timer, after + (ev_time () \- ev_now ()), 0.); |
1434 | .Ve |
2250 | .Ve |
1435 | .PP |
2251 | .PP |
1436 | If the event loop is suspended for a long time, you can also force an |
2252 | If the event loop is suspended for a long time, you can also force an |
1437 | update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update |
2253 | update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update |
1438 | ()\*(C'\fR. |
2254 | ()\*(C'\fR, although that will push the event time of all outstanding events |
|
|
2255 | further into the future. |
|
|
2256 | .PP |
|
|
2257 | \fIThe special problem of unsynchronised clocks\fR |
|
|
2258 | .IX Subsection "The special problem of unsynchronised clocks" |
|
|
2259 | .PP |
|
|
2260 | Modern systems have a variety of clocks \- libev itself uses the normal |
|
|
2261 | \&\*(L"wall clock\*(R" clock and, if available, the monotonic clock (to avoid time |
|
|
2262 | jumps). |
|
|
2263 | .PP |
|
|
2264 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2265 | on the system, so \f(CW\*(C`ev_time ()\*(C'\fR might return a considerably different time |
|
|
2266 | than \f(CW\*(C`gettimeofday ()\*(C'\fR or \f(CW\*(C`time ()\*(C'\fR. On a GNU/Linux system, for example, |
|
|
2267 | a call to \f(CW\*(C`gettimeofday\*(C'\fR might return a second count that is one higher |
|
|
2268 | than a directly following call to \f(CW\*(C`time\*(C'\fR. |
|
|
2269 | .PP |
|
|
2270 | The moral of this is to only compare libev-related timestamps with |
|
|
2271 | \&\f(CW\*(C`ev_time ()\*(C'\fR and \f(CW\*(C`ev_now ()\*(C'\fR, at least if you want better precision than |
|
|
2272 | a second or so. |
|
|
2273 | .PP |
|
|
2274 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2275 | the system monotonic clock and you compare timestamps from \f(CW\*(C`ev_time\*(C'\fR |
|
|
2276 | or \f(CW\*(C`ev_now\*(C'\fR from when you started your timer and when your callback is |
|
|
2277 | invoked, you will find that sometimes the callback is a bit \*(L"early\*(R". |
|
|
2278 | .PP |
|
|
2279 | This is because \f(CW\*(C`ev_timer\*(C'\fRs work in real time, not wall clock time, so |
|
|
2280 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2281 | \&\fImeasured according to the real time\fR, not the system clock. |
|
|
2282 | .PP |
|
|
2283 | If your timeouts are based on a physical timescale (e.g. \*(L"time out this |
|
|
2284 | connection after 100 seconds\*(R") then this shouldn't bother you as it is |
|
|
2285 | exactly the right behaviour. |
|
|
2286 | .PP |
|
|
2287 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2288 | you need to use \f(CW\*(C`ev_periodic\*(C'\fRs, as these are based on the wall clock |
|
|
2289 | time, where your comparisons will always generate correct results. |
|
|
2290 | .PP |
|
|
2291 | \fIThe special problems of suspended animation\fR |
|
|
2292 | .IX Subsection "The special problems of suspended animation" |
|
|
2293 | .PP |
|
|
2294 | When you leave the server world it is quite customary to hit machines that |
|
|
2295 | can suspend/hibernate \- what happens to the clocks during such a suspend? |
|
|
2296 | .PP |
|
|
2297 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
2298 | all processes, while the clocks (\f(CW\*(C`times\*(C'\fR, \f(CW\*(C`CLOCK_MONOTONIC\*(C'\fR) continue |
|
|
2299 | to run until the system is suspended, but they will not advance while the |
|
|
2300 | system is suspended. That means, on resume, it will be as if the program |
|
|
2301 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
2302 | towards \f(CW\*(C`ev_timer\*(C'\fR when a monotonic clock source is used. The real time |
|
|
2303 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
2304 | long suspend would be detected as a time jump by libev, and timers would |
|
|
2305 | be adjusted accordingly. |
|
|
2306 | .PP |
|
|
2307 | I would not be surprised to see different behaviour in different between |
|
|
2308 | operating systems, \s-1OS\s0 versions or even different hardware. |
|
|
2309 | .PP |
|
|
2310 | The other form of suspend (job control, or sending a \s-1SIGSTOP\s0) will see a |
|
|
2311 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
2312 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
2313 | then you can expect \f(CW\*(C`ev_timer\*(C'\fRs to expire as the full suspension time |
|
|
2314 | will be counted towards the timers. When no monotonic clock source is in |
|
|
2315 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
2316 | .PP |
|
|
2317 | It might be beneficial for this latter case to call \f(CW\*(C`ev_suspend\*(C'\fR |
|
|
2318 | and \f(CW\*(C`ev_resume\*(C'\fR in code that handles \f(CW\*(C`SIGTSTP\*(C'\fR, to at least get |
|
|
2319 | deterministic behaviour in this case (you can do nothing against |
|
|
2320 | \&\f(CW\*(C`SIGSTOP\*(C'\fR). |
1439 | .PP |
2321 | .PP |
1440 | \fIWatcher-Specific Functions and Data Members\fR |
2322 | \fIWatcher-Specific Functions and Data Members\fR |
1441 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2323 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1442 | .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
2324 | .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
1443 | .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
2325 | .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
1444 | .PD 0 |
2326 | .PD 0 |
1445 | .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 |
2327 | .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 |
1446 | .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" |
2328 | .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" |
1447 | .PD |
2329 | .PD |
1448 | Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR |
2330 | Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds (fractional and |
1449 | is \f(CW0.\fR, then it will automatically be stopped once the timeout is |
2331 | negative values are supported). If \f(CW\*(C`repeat\*(C'\fR is \f(CW0.\fR, then it will |
1450 | reached. If it is positive, then the timer will automatically be |
2332 | automatically be stopped once the timeout is reached. If it is positive, |
1451 | configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds later, again, and again, |
2333 | then the timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR |
1452 | until stopped manually. |
2334 | seconds later, again, and again, until stopped manually. |
1453 | .Sp |
2335 | .Sp |
1454 | The timer itself will do a best-effort at avoiding drift, that is, if |
2336 | The timer itself will do a best-effort at avoiding drift, that is, if |
1455 | you configure a timer to trigger every 10 seconds, then it will normally |
2337 | you configure a timer to trigger every 10 seconds, then it will normally |
1456 | trigger at exactly 10 second intervals. If, however, your program cannot |
2338 | trigger at exactly 10 second intervals. If, however, your program cannot |
1457 | keep up with the timer (because it takes longer than those 10 seconds to |
2339 | keep up with the timer (because it takes longer than those 10 seconds to |
1458 | do stuff) the timer will not fire more than once per event loop iteration. |
2340 | do stuff) the timer will not fire more than once per event loop iteration. |
1459 | .IP "ev_timer_again (loop, ev_timer *)" 4 |
2341 | .IP "ev_timer_again (loop, ev_timer *)" 4 |
1460 | .IX Item "ev_timer_again (loop, ev_timer *)" |
2342 | .IX Item "ev_timer_again (loop, ev_timer *)" |
1461 | This will act as if the timer timed out and restart it again if it is |
2343 | This will act as if the timer timed out, and restarts it again if it is |
1462 | repeating. The exact semantics are: |
2344 | repeating. It basically works like calling \f(CW\*(C`ev_timer_stop\*(C'\fR, updating the |
|
|
2345 | timeout to the \f(CW\*(C`repeat\*(C'\fR value and calling \f(CW\*(C`ev_timer_start\*(C'\fR. |
1463 | .Sp |
2346 | .Sp |
|
|
2347 | The exact semantics are as in the following rules, all of which will be |
|
|
2348 | applied to the watcher: |
|
|
2349 | .RS 4 |
1464 | If the timer is pending, its pending status is cleared. |
2350 | .IP "If the timer is pending, the pending status is always cleared." 4 |
1465 | .Sp |
2351 | .IX Item "If the timer is pending, the pending status is always cleared." |
|
|
2352 | .PD 0 |
1466 | If the timer is started but non-repeating, stop it (as if it timed out). |
2353 | .IP "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)." 4 |
|
|
2354 | .IX Item "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)." |
|
|
2355 | .ie n .IP "If the timer is repeating, make the ""repeat"" value the new timeout and start the timer, if necessary." 4 |
|
|
2356 | .el .IP "If the timer is repeating, make the \f(CWrepeat\fR value the new timeout and start the timer, if necessary." 4 |
|
|
2357 | .IX Item "If the timer is repeating, make the repeat value the new timeout and start the timer, if necessary." |
|
|
2358 | .RE |
|
|
2359 | .RS 4 |
|
|
2360 | .PD |
1467 | .Sp |
2361 | .Sp |
1468 | If the timer is repeating, either start it if necessary (with the |
2362 | This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a |
1469 | \&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. |
2363 | usage example. |
|
|
2364 | .RE |
|
|
2365 | .IP "ev_tstamp ev_timer_remaining (loop, ev_timer *)" 4 |
|
|
2366 | .IX Item "ev_tstamp ev_timer_remaining (loop, ev_timer *)" |
|
|
2367 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
2368 | then this time is relative to the current event loop time, otherwise it's |
|
|
2369 | the timeout value currently configured. |
1470 | .Sp |
2370 | .Sp |
1471 | This sounds a bit complicated, but here is a useful and typical |
2371 | That is, after an \f(CW\*(C`ev_timer_set (w, 5, 7)\*(C'\fR, \f(CW\*(C`ev_timer_remaining\*(C'\fR returns |
1472 | example: Imagine you have a \s-1TCP\s0 connection and you want a so-called idle |
2372 | \&\f(CW5\fR. When the timer is started and one second passes, \f(CW\*(C`ev_timer_remaining\*(C'\fR |
1473 | timeout, that is, you want to be called when there have been, say, 60 |
2373 | will return \f(CW4\fR. When the timer expires and is restarted, it will return |
1474 | seconds of inactivity on the socket. The easiest way to do this is to |
2374 | roughly \f(CW7\fR (likely slightly less as callback invocation takes some time, |
1475 | configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call |
2375 | too), and so on. |
1476 | \&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If |
|
|
1477 | you go into an idle state where you do not expect data to travel on the |
|
|
1478 | socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will |
|
|
1479 | automatically restart it if need be. |
|
|
1480 | .Sp |
|
|
1481 | That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR |
|
|
1482 | altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR: |
|
|
1483 | .Sp |
|
|
1484 | .Vb 8 |
|
|
1485 | \& ev_timer_init (timer, callback, 0., 5.); |
|
|
1486 | \& ev_timer_again (loop, timer); |
|
|
1487 | \& ... |
|
|
1488 | \& timer\->again = 17.; |
|
|
1489 | \& ev_timer_again (loop, timer); |
|
|
1490 | \& ... |
|
|
1491 | \& timer\->again = 10.; |
|
|
1492 | \& ev_timer_again (loop, timer); |
|
|
1493 | .Ve |
|
|
1494 | .Sp |
|
|
1495 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1496 | you want to modify its timeout value. |
|
|
1497 | .Sp |
|
|
1498 | Note, however, that it is often even more efficient to remember the |
|
|
1499 | time of the last activity and let the timer time-out naturally. In the |
|
|
1500 | callback, you then check whether the time-out is real, or, if there was |
|
|
1501 | some activity, you reschedule the watcher to time-out in \*(L"last_activity + |
|
|
1502 | timeout \- ev_now ()\*(R" seconds. |
|
|
1503 | .IP "ev_tstamp repeat [read\-write]" 4 |
2376 | .IP "ev_tstamp repeat [read\-write]" 4 |
1504 | .IX Item "ev_tstamp repeat [read-write]" |
2377 | .IX Item "ev_tstamp repeat [read-write]" |
1505 | The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
2378 | The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
1506 | or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any), |
2379 | or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any), |
1507 | which is also when any modifications are taken into account. |
2380 | which is also when any modifications are taken into account. |
… | |
… | |
1511 | .PP |
2384 | .PP |
1512 | Example: Create a timer that fires after 60 seconds. |
2385 | Example: Create a timer that fires after 60 seconds. |
1513 | .PP |
2386 | .PP |
1514 | .Vb 5 |
2387 | .Vb 5 |
1515 | \& static void |
2388 | \& static void |
1516 | \& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2389 | \& one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1517 | \& { |
2390 | \& { |
1518 | \& .. one minute over, w is actually stopped right here |
2391 | \& .. one minute over, w is actually stopped right here |
1519 | \& } |
2392 | \& } |
1520 | \& |
2393 | \& |
1521 | \& struct ev_timer mytimer; |
2394 | \& ev_timer mytimer; |
1522 | \& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
2395 | \& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1523 | \& ev_timer_start (loop, &mytimer); |
2396 | \& ev_timer_start (loop, &mytimer); |
1524 | .Ve |
2397 | .Ve |
1525 | .PP |
2398 | .PP |
1526 | Example: Create a timeout timer that times out after 10 seconds of |
2399 | Example: Create a timeout timer that times out after 10 seconds of |
1527 | inactivity. |
2400 | inactivity. |
1528 | .PP |
2401 | .PP |
1529 | .Vb 5 |
2402 | .Vb 5 |
1530 | \& static void |
2403 | \& static void |
1531 | \& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2404 | \& timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1532 | \& { |
2405 | \& { |
1533 | \& .. ten seconds without any activity |
2406 | \& .. ten seconds without any activity |
1534 | \& } |
2407 | \& } |
1535 | \& |
2408 | \& |
1536 | \& struct ev_timer mytimer; |
2409 | \& ev_timer mytimer; |
1537 | \& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2410 | \& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1538 | \& ev_timer_again (&mytimer); /* start timer */ |
2411 | \& ev_timer_again (&mytimer); /* start timer */ |
1539 | \& ev_loop (loop, 0); |
2412 | \& ev_run (loop, 0); |
1540 | \& |
2413 | \& |
1541 | \& // and in some piece of code that gets executed on any "activity": |
2414 | \& // and in some piece of code that gets executed on any "activity": |
1542 | \& // reset the timeout to start ticking again at 10 seconds |
2415 | \& // reset the timeout to start ticking again at 10 seconds |
1543 | \& ev_timer_again (&mytimer); |
2416 | \& ev_timer_again (&mytimer); |
1544 | .Ve |
2417 | .Ve |
1545 | .ie n .Sh """ev_periodic"" \- to cron or not to cron?" |
2418 | .ie n .SS """ev_periodic"" \- to cron or not to cron?" |
1546 | .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" |
2419 | .el .SS "\f(CWev_periodic\fP \- to cron or not to cron?" |
1547 | .IX Subsection "ev_periodic - to cron or not to cron?" |
2420 | .IX Subsection "ev_periodic - to cron or not to cron?" |
1548 | Periodic watchers are also timers of a kind, but they are very versatile |
2421 | Periodic watchers are also timers of a kind, but they are very versatile |
1549 | (and unfortunately a bit complex). |
2422 | (and unfortunately a bit complex). |
1550 | .PP |
2423 | .PP |
1551 | Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) |
2424 | Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or |
1552 | but on wall clock time (absolute time). You can tell a periodic watcher |
2425 | relative time, the physical time that passes) but on wall clock time |
1553 | to trigger after some specific point in time. For example, if you tell a |
2426 | (absolute time, the thing you can read on your calendar or clock). The |
1554 | periodic watcher to trigger in 10 seconds (by specifying e.g. \f(CW\*(C`ev_now () |
2427 | difference is that wall clock time can run faster or slower than real |
1555 | + 10.\*(C'\fR, that is, an absolute time not a delay) and then reset your system |
2428 | time, and time jumps are not uncommon (e.g. when you adjust your |
1556 | clock to January of the previous year, then it will take more than year |
2429 | wrist-watch). |
1557 | to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would still trigger |
|
|
1558 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1559 | .PP |
2430 | .PP |
|
|
2431 | You can tell a periodic watcher to trigger after some specific point |
|
|
2432 | in time: for example, if you tell a periodic watcher to trigger \*(L"in 10 |
|
|
2433 | seconds\*(R" (by specifying e.g. \f(CW\*(C`ev_now () + 10.\*(C'\fR, that is, an absolute time |
|
|
2434 | not a delay) and then reset your system clock to January of the previous |
|
|
2435 | year, then it will take a year or more to trigger the event (unlike an |
|
|
2436 | \&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting |
|
|
2437 | it, as it uses a relative timeout). |
|
|
2438 | .PP |
1560 | \&\f(CW\*(C`ev_periodic\*(C'\fRs can also be used to implement vastly more complex timers, |
2439 | \&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex |
1561 | such as triggering an event on each \*(L"midnight, local time\*(R", or other |
2440 | timers, such as triggering an event on each \*(L"midnight, local time\*(R", or |
1562 | complicated rules. |
2441 | other complicated rules. This cannot easily be done with \f(CW\*(C`ev_timer\*(C'\fR |
|
|
2442 | watchers, as those cannot react to time jumps. |
1563 | .PP |
2443 | .PP |
1564 | As with timers, the callback is guaranteed to be invoked only when the |
2444 | As with timers, the callback is guaranteed to be invoked only when the |
1565 | time (\f(CW\*(C`at\*(C'\fR) has passed, but if multiple periodic timers become ready |
2445 | point in time where it is supposed to trigger has passed. If multiple |
1566 | during the same loop iteration, then order of execution is undefined. |
2446 | timers become ready during the same loop iteration then the ones with |
|
|
2447 | earlier time-out values are invoked before ones with later time-out values |
|
|
2448 | (but this is no longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively). |
1567 | .PP |
2449 | .PP |
1568 | \fIWatcher-Specific Functions and Data Members\fR |
2450 | \fIWatcher-Specific Functions and Data Members\fR |
1569 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2451 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1570 | .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 |
2452 | .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4 |
1571 | .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" |
2453 | .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" |
1572 | .PD 0 |
2454 | .PD 0 |
1573 | .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 |
2455 | .IP "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4 |
1574 | .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" |
2456 | .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" |
1575 | .PD |
2457 | .PD |
1576 | Lots of arguments, lets sort it out... There are basically three modes of |
2458 | Lots of arguments, let's sort it out... There are basically three modes of |
1577 | operation, and we will explain them from simplest to most complex: |
2459 | operation, and we will explain them from simplest to most complex: |
1578 | .RS 4 |
2460 | .RS 4 |
1579 | .IP "\(bu" 4 |
2461 | .IP "\(bu" 4 |
1580 | absolute timer (at = time, interval = reschedule_cb = 0) |
2462 | absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1581 | .Sp |
2463 | .Sp |
1582 | In this configuration the watcher triggers an event after the wall clock |
2464 | In this configuration the watcher triggers an event after the wall clock |
1583 | time \f(CW\*(C`at\*(C'\fR has passed. It will not repeat and will not adjust when a time |
2465 | time \f(CW\*(C`offset\*(C'\fR has passed. It will not repeat and will not adjust when a |
1584 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
2466 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1585 | only run when the system clock reaches or surpasses this time. |
2467 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2468 | this point in time. |
1586 | .IP "\(bu" 4 |
2469 | .IP "\(bu" 4 |
1587 | repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2470 | repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1588 | .Sp |
2471 | .Sp |
1589 | In this mode the watcher will always be scheduled to time out at the next |
2472 | In this mode the watcher will always be scheduled to time out at the next |
1590 | \&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative) |
2473 | \&\f(CW\*(C`offset + N * interval\*(C'\fR time (for some integer N, which can also be |
1591 | and then repeat, regardless of any time jumps. |
2474 | negative) and then repeat, regardless of any time jumps. The \f(CW\*(C`offset\*(C'\fR |
|
|
2475 | argument is merely an offset into the \f(CW\*(C`interval\*(C'\fR periods. |
1592 | .Sp |
2476 | .Sp |
1593 | This can be used to create timers that do not drift with respect to the |
2477 | This can be used to create timers that do not drift with respect to the |
1594 | system clock, for example, here is a \f(CW\*(C`ev_periodic\*(C'\fR that triggers each |
2478 | system clock, for example, here is an \f(CW\*(C`ev_periodic\*(C'\fR that triggers each |
1595 | hour, on the hour: |
2479 | hour, on the hour (with respect to \s-1UTC\s0): |
1596 | .Sp |
2480 | .Sp |
1597 | .Vb 1 |
2481 | .Vb 1 |
1598 | \& ev_periodic_set (&periodic, 0., 3600., 0); |
2482 | \& ev_periodic_set (&periodic, 0., 3600., 0); |
1599 | .Ve |
2483 | .Ve |
1600 | .Sp |
2484 | .Sp |
… | |
… | |
1603 | full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
2487 | full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
1604 | by 3600. |
2488 | by 3600. |
1605 | .Sp |
2489 | .Sp |
1606 | Another way to think about it (for the mathematically inclined) is that |
2490 | Another way to think about it (for the mathematically inclined) is that |
1607 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
2491 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
1608 | time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. |
2492 | time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps. |
1609 | .Sp |
2493 | .Sp |
1610 | For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near |
2494 | The \f(CW\*(C`interval\*(C'\fR \fI\s-1MUST\s0\fR be positive, and for numerical stability, the |
1611 | \&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for |
2495 | interval value should be higher than \f(CW\*(C`1/8192\*(C'\fR (which is around 100 |
1612 | this value, and in fact is often specified as zero. |
2496 | microseconds) and \f(CW\*(C`offset\*(C'\fR should be higher than \f(CW0\fR and should have |
|
|
2497 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2498 | ten). Typical values for offset are, in fact, \f(CW0\fR or something between |
|
|
2499 | \&\f(CW0\fR and \f(CW\*(C`interval\*(C'\fR, which is also the recommended range. |
1613 | .Sp |
2500 | .Sp |
1614 | Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0 |
2501 | Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0 |
1615 | speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability |
2502 | speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability |
1616 | will of course deteriorate. Libev itself tries to be exact to be about one |
2503 | will of course deteriorate. Libev itself tries to be exact to be about one |
1617 | millisecond (if the \s-1OS\s0 supports it and the machine is fast enough). |
2504 | millisecond (if the \s-1OS\s0 supports it and the machine is fast enough). |
1618 | .IP "\(bu" 4 |
2505 | .IP "\(bu" 4 |
1619 | manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2506 | manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1620 | .Sp |
2507 | .Sp |
1621 | In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being |
2508 | In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being |
1622 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2509 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1623 | reschedule callback will be called with the watcher as first, and the |
2510 | reschedule callback will be called with the watcher as first, and the |
1624 | current time as second argument. |
2511 | current time as second argument. |
1625 | .Sp |
2512 | .Sp |
1626 | \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, |
2513 | \&\s-1NOTE:\s0 \fIThis callback \s-1MUST NOT\s0 stop or destroy any periodic watcher, ever, |
1627 | ever, or make \s-1ANY\s0 event loop modifications whatsoever\fR. |
2514 | or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly |
|
|
2515 | allowed by documentation here\fR. |
1628 | .Sp |
2516 | .Sp |
1629 | If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop |
2517 | If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop |
1630 | it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the |
2518 | it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the |
1631 | only event loop modification you are allowed to do). |
2519 | only event loop modification you are allowed to do). |
1632 | .Sp |
2520 | .Sp |
1633 | The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic |
2521 | The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(ev_periodic |
1634 | *w, ev_tstamp now)\*(C'\fR, e.g.: |
2522 | *w, ev_tstamp now)\*(C'\fR, e.g.: |
1635 | .Sp |
2523 | .Sp |
1636 | .Vb 4 |
2524 | .Vb 5 |
|
|
2525 | \& static ev_tstamp |
1637 | \& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2526 | \& my_rescheduler (ev_periodic *w, ev_tstamp now) |
1638 | \& { |
2527 | \& { |
1639 | \& return now + 60.; |
2528 | \& return now + 60.; |
1640 | \& } |
2529 | \& } |
1641 | .Ve |
2530 | .Ve |
1642 | .Sp |
2531 | .Sp |
… | |
… | |
1647 | .Sp |
2536 | .Sp |
1648 | \&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or |
2537 | \&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or |
1649 | equal to the passed \f(CI\*(C`now\*(C'\fI value\fR. |
2538 | equal to the passed \f(CI\*(C`now\*(C'\fI value\fR. |
1650 | .Sp |
2539 | .Sp |
1651 | This can be used to create very complex timers, such as a timer that |
2540 | This can be used to create very complex timers, such as a timer that |
1652 | triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate the |
2541 | triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate |
1653 | next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How |
2542 | the next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for |
1654 | you do this is, again, up to you (but it is not trivial, which is the main |
2543 | this. Here is a (completely untested, no error checking) example on how to |
1655 | reason I omitted it as an example). |
2544 | do this: |
|
|
2545 | .Sp |
|
|
2546 | .Vb 1 |
|
|
2547 | \& #include <time.h> |
|
|
2548 | \& |
|
|
2549 | \& static ev_tstamp |
|
|
2550 | \& my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2551 | \& { |
|
|
2552 | \& time_t tnow = (time_t)now; |
|
|
2553 | \& struct tm tm; |
|
|
2554 | \& localtime_r (&tnow, &tm); |
|
|
2555 | \& |
|
|
2556 | \& tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2557 | \& ++tm.tm_mday; // midnight next day |
|
|
2558 | \& |
|
|
2559 | \& return mktime (&tm); |
|
|
2560 | \& } |
|
|
2561 | .Ve |
|
|
2562 | .Sp |
|
|
2563 | Note: this code might run into trouble on days that have more then two |
|
|
2564 | midnights (beginning and end). |
1656 | .RE |
2565 | .RE |
1657 | .RS 4 |
2566 | .RS 4 |
1658 | .RE |
2567 | .RE |
1659 | .IP "ev_periodic_again (loop, ev_periodic *)" 4 |
2568 | .IP "ev_periodic_again (loop, ev_periodic *)" 4 |
1660 | .IX Item "ev_periodic_again (loop, ev_periodic *)" |
2569 | .IX Item "ev_periodic_again (loop, ev_periodic *)" |
… | |
… | |
1662 | when you changed some parameters or the reschedule callback would return |
2571 | when you changed some parameters or the reschedule callback would return |
1663 | a different time than the last time it was called (e.g. in a crond like |
2572 | a different time than the last time it was called (e.g. in a crond like |
1664 | program when the crontabs have changed). |
2573 | program when the crontabs have changed). |
1665 | .IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4 |
2574 | .IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4 |
1666 | .IX Item "ev_tstamp ev_periodic_at (ev_periodic *)" |
2575 | .IX Item "ev_tstamp ev_periodic_at (ev_periodic *)" |
1667 | When active, returns the absolute time that the watcher is supposed to |
2576 | When active, returns the absolute time that the watcher is supposed |
1668 | trigger next. |
2577 | to trigger next. This is not the same as the \f(CW\*(C`offset\*(C'\fR argument to |
|
|
2578 | \&\f(CW\*(C`ev_periodic_set\*(C'\fR, but indeed works even in interval and manual |
|
|
2579 | rescheduling modes. |
1669 | .IP "ev_tstamp offset [read\-write]" 4 |
2580 | .IP "ev_tstamp offset [read\-write]" 4 |
1670 | .IX Item "ev_tstamp offset [read-write]" |
2581 | .IX Item "ev_tstamp offset [read-write]" |
1671 | When repeating, this contains the offset value, otherwise this is the |
2582 | When repeating, this contains the offset value, otherwise this is the |
1672 | absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR). |
2583 | absolute point in time (the \f(CW\*(C`offset\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR, |
|
|
2584 | although libev might modify this value for better numerical stability). |
1673 | .Sp |
2585 | .Sp |
1674 | Can be modified any time, but changes only take effect when the periodic |
2586 | Can be modified any time, but changes only take effect when the periodic |
1675 | timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
2587 | timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
1676 | .IP "ev_tstamp interval [read\-write]" 4 |
2588 | .IP "ev_tstamp interval [read\-write]" 4 |
1677 | .IX Item "ev_tstamp interval [read-write]" |
2589 | .IX Item "ev_tstamp interval [read-write]" |
1678 | The current interval value. Can be modified any time, but changes only |
2590 | The current interval value. Can be modified any time, but changes only |
1679 | take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
2591 | take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
1680 | called. |
2592 | called. |
1681 | .IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
2593 | .IP "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
1682 | .IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]" |
2594 | .IX Item "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]" |
1683 | The current reschedule callback, or \f(CW0\fR, if this functionality is |
2595 | The current reschedule callback, or \f(CW0\fR, if this functionality is |
1684 | switched off. Can be changed any time, but changes only take effect when |
2596 | switched off. Can be changed any time, but changes only take effect when |
1685 | the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
2597 | the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
1686 | .PP |
2598 | .PP |
1687 | \fIExamples\fR |
2599 | \fIExamples\fR |
… | |
… | |
1691 | system time is divisible by 3600. The callback invocation times have |
2603 | system time is divisible by 3600. The callback invocation times have |
1692 | potentially a lot of jitter, but good long-term stability. |
2604 | potentially a lot of jitter, but good long-term stability. |
1693 | .PP |
2605 | .PP |
1694 | .Vb 5 |
2606 | .Vb 5 |
1695 | \& static void |
2607 | \& static void |
1696 | \& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2608 | \& clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1697 | \& { |
2609 | \& { |
1698 | \& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2610 | \& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1699 | \& } |
2611 | \& } |
1700 | \& |
2612 | \& |
1701 | \& struct ev_periodic hourly_tick; |
2613 | \& ev_periodic hourly_tick; |
1702 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2614 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1703 | \& ev_periodic_start (loop, &hourly_tick); |
2615 | \& ev_periodic_start (loop, &hourly_tick); |
1704 | .Ve |
2616 | .Ve |
1705 | .PP |
2617 | .PP |
1706 | Example: The same as above, but use a reschedule callback to do it: |
2618 | Example: The same as above, but use a reschedule callback to do it: |
1707 | .PP |
2619 | .PP |
1708 | .Vb 1 |
2620 | .Vb 1 |
1709 | \& #include <math.h> |
2621 | \& #include <math.h> |
1710 | \& |
2622 | \& |
1711 | \& static ev_tstamp |
2623 | \& static ev_tstamp |
1712 | \& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2624 | \& my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1713 | \& { |
2625 | \& { |
1714 | \& return now + (3600. \- fmod (now, 3600.)); |
2626 | \& return now + (3600. \- fmod (now, 3600.)); |
1715 | \& } |
2627 | \& } |
1716 | \& |
2628 | \& |
1717 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2629 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1718 | .Ve |
2630 | .Ve |
1719 | .PP |
2631 | .PP |
1720 | Example: Call a callback every hour, starting now: |
2632 | Example: Call a callback every hour, starting now: |
1721 | .PP |
2633 | .PP |
1722 | .Vb 4 |
2634 | .Vb 4 |
1723 | \& struct ev_periodic hourly_tick; |
2635 | \& ev_periodic hourly_tick; |
1724 | \& ev_periodic_init (&hourly_tick, clock_cb, |
2636 | \& ev_periodic_init (&hourly_tick, clock_cb, |
1725 | \& fmod (ev_now (loop), 3600.), 3600., 0); |
2637 | \& fmod (ev_now (loop), 3600.), 3600., 0); |
1726 | \& ev_periodic_start (loop, &hourly_tick); |
2638 | \& ev_periodic_start (loop, &hourly_tick); |
1727 | .Ve |
2639 | .Ve |
1728 | .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" |
2640 | .ie n .SS """ev_signal"" \- signal me when a signal gets signalled!" |
1729 | .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
2641 | .el .SS "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
1730 | .IX Subsection "ev_signal - signal me when a signal gets signalled!" |
2642 | .IX Subsection "ev_signal - signal me when a signal gets signalled!" |
1731 | Signal watchers will trigger an event when the process receives a specific |
2643 | Signal watchers will trigger an event when the process receives a specific |
1732 | signal one or more times. Even though signals are very asynchronous, libev |
2644 | signal one or more times. Even though signals are very asynchronous, libev |
1733 | will try it's best to deliver signals synchronously, i.e. as part of the |
2645 | will try its best to deliver signals synchronously, i.e. as part of the |
1734 | normal event processing, like any other event. |
2646 | normal event processing, like any other event. |
1735 | .PP |
2647 | .PP |
1736 | If you want signals asynchronously, just use \f(CW\*(C`sigaction\*(C'\fR as you would |
2648 | If you want signals to be delivered truly asynchronously, just use |
1737 | do without libev and forget about sharing the signal. You can even use |
2649 | \&\f(CW\*(C`sigaction\*(C'\fR as you would do without libev and forget about sharing |
1738 | \&\f(CW\*(C`ev_async\*(C'\fR from a signal handler to synchronously wake up an event loop. |
2650 | the signal. You can even use \f(CW\*(C`ev_async\*(C'\fR from a signal handler to |
|
|
2651 | synchronously wake up an event loop. |
1739 | .PP |
2652 | .PP |
1740 | You can configure as many watchers as you like per signal. Only when the |
2653 | You can configure as many watchers as you like for the same signal, but |
1741 | first watcher gets started will libev actually register a signal handler |
2654 | only within the same loop, i.e. you can watch for \f(CW\*(C`SIGINT\*(C'\fR in your |
1742 | with the kernel (thus it coexists with your own signal handlers as long as |
2655 | default loop and for \f(CW\*(C`SIGIO\*(C'\fR in another loop, but you cannot watch for |
1743 | you don't register any with libev for the same signal). Similarly, when |
2656 | \&\f(CW\*(C`SIGINT\*(C'\fR in both the default loop and another loop at the same time. At |
1744 | the last signal watcher for a signal is stopped, libev will reset the |
2657 | the moment, \f(CW\*(C`SIGCHLD\*(C'\fR is permanently tied to the default loop. |
1745 | signal handler to \s-1SIG_DFL\s0 (regardless of what it was set to before). |
2658 | .PP |
|
|
2659 | Only after the first watcher for a signal is started will libev actually |
|
|
2660 | register something with the kernel. It thus coexists with your own signal |
|
|
2661 | handlers as long as you don't register any with libev for the same signal. |
1746 | .PP |
2662 | .PP |
1747 | If possible and supported, libev will install its handlers with |
2663 | If possible and supported, libev will install its handlers with |
1748 | \&\f(CW\*(C`SA_RESTART\*(C'\fR behaviour enabled, so system calls should not be unduly |
2664 | \&\f(CW\*(C`SA_RESTART\*(C'\fR (or equivalent) behaviour enabled, so system calls should |
1749 | interrupted. If you have a problem with system calls getting interrupted by |
2665 | not be unduly interrupted. If you have a problem with system calls getting |
1750 | signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher and unblock |
2666 | interrupted by signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher |
1751 | them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher. |
2667 | and unblock them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher. |
|
|
2668 | .PP |
|
|
2669 | \fIThe special problem of inheritance over fork/execve/pthread_create\fR |
|
|
2670 | .IX Subsection "The special problem of inheritance over fork/execve/pthread_create" |
|
|
2671 | .PP |
|
|
2672 | Both the signal mask (\f(CW\*(C`sigprocmask\*(C'\fR) and the signal disposition |
|
|
2673 | (\f(CW\*(C`sigaction\*(C'\fR) are unspecified after starting a signal watcher (and after |
|
|
2674 | stopping it again), that is, libev might or might not block the signal, |
|
|
2675 | and might or might not set or restore the installed signal handler (but |
|
|
2676 | see \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR). |
|
|
2677 | .PP |
|
|
2678 | While this does not matter for the signal disposition (libev never |
|
|
2679 | sets signals to \f(CW\*(C`SIG_IGN\*(C'\fR, so handlers will be reset to \f(CW\*(C`SIG_DFL\*(C'\fR on |
|
|
2680 | \&\f(CW\*(C`execve\*(C'\fR), this matters for the signal mask: many programs do not expect |
|
|
2681 | certain signals to be blocked. |
|
|
2682 | .PP |
|
|
2683 | This means that before calling \f(CW\*(C`exec\*(C'\fR (from the child) you should reset |
|
|
2684 | the signal mask to whatever \*(L"default\*(R" you expect (all clear is a good |
|
|
2685 | choice usually). |
|
|
2686 | .PP |
|
|
2687 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2688 | to install a fork handler with \f(CW\*(C`pthread_atfork\*(C'\fR that resets it. That will |
|
|
2689 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2690 | .PP |
|
|
2691 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2692 | unless you use the \f(CW\*(C`signalfd\*(C'\fR \s-1API\s0 (\f(CW\*(C`EV_SIGNALFD\*(C'\fR). While this reduces |
|
|
2693 | the window of opportunity for problems, it will not go away, as libev |
|
|
2694 | \&\fIhas\fR to modify the signal mask, at least temporarily. |
|
|
2695 | .PP |
|
|
2696 | So I can't stress this enough: \fIIf you do not reset your signal mask when |
|
|
2697 | you expect it to be empty, you have a race condition in your code\fR. This |
|
|
2698 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2699 | .PP |
|
|
2700 | \fIThe special problem of threads signal handling\fR |
|
|
2701 | .IX Subsection "The special problem of threads signal handling" |
|
|
2702 | .PP |
|
|
2703 | \&\s-1POSIX\s0 threads has problematic signal handling semantics, specifically, |
|
|
2704 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2705 | threads in a process block signals, which is hard to achieve. |
|
|
2706 | .PP |
|
|
2707 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2708 | for the same signals), you can tackle this problem by globally blocking |
|
|
2709 | all signals before creating any threads (or creating them with a fully set |
|
|
2710 | sigprocmask) and also specifying the \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when creating |
|
|
2711 | loops. Then designate one thread as \*(L"signal receiver thread\*(R" which handles |
|
|
2712 | these signals. You can pass on any signals that libev might be interested |
|
|
2713 | in by calling \f(CW\*(C`ev_feed_signal\*(C'\fR. |
1752 | .PP |
2714 | .PP |
1753 | \fIWatcher-Specific Functions and Data Members\fR |
2715 | \fIWatcher-Specific Functions and Data Members\fR |
1754 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2716 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1755 | .IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
2717 | .IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
1756 | .IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
2718 | .IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
… | |
… | |
1765 | The signal the watcher watches out for. |
2727 | The signal the watcher watches out for. |
1766 | .PP |
2728 | .PP |
1767 | \fIExamples\fR |
2729 | \fIExamples\fR |
1768 | .IX Subsection "Examples" |
2730 | .IX Subsection "Examples" |
1769 | .PP |
2731 | .PP |
1770 | Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. |
2732 | Example: Try to exit cleanly on \s-1SIGINT.\s0 |
1771 | .PP |
2733 | .PP |
1772 | .Vb 5 |
2734 | .Vb 5 |
1773 | \& static void |
2735 | \& static void |
1774 | \& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2736 | \& sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1775 | \& { |
2737 | \& { |
1776 | \& ev_unloop (loop, EVUNLOOP_ALL); |
2738 | \& ev_break (loop, EVBREAK_ALL); |
1777 | \& } |
2739 | \& } |
1778 | \& |
2740 | \& |
1779 | \& struct ev_signal signal_watcher; |
2741 | \& ev_signal signal_watcher; |
1780 | \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2742 | \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1781 | \& ev_signal_start (loop, &sigint_cb); |
2743 | \& ev_signal_start (loop, &signal_watcher); |
1782 | .Ve |
2744 | .Ve |
1783 | .ie n .Sh """ev_child"" \- watch out for process status changes" |
2745 | .ie n .SS """ev_child"" \- watch out for process status changes" |
1784 | .el .Sh "\f(CWev_child\fP \- watch out for process status changes" |
2746 | .el .SS "\f(CWev_child\fP \- watch out for process status changes" |
1785 | .IX Subsection "ev_child - watch out for process status changes" |
2747 | .IX Subsection "ev_child - watch out for process status changes" |
1786 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
2748 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
1787 | some child status changes (most typically when a child of yours dies or |
2749 | some child status changes (most typically when a child of yours dies or |
1788 | exits). It is permissible to install a child watcher \fIafter\fR the child |
2750 | exits). It is permissible to install a child watcher \fIafter\fR the child |
1789 | has been forked (which implies it might have already exited), as long |
2751 | has been forked (which implies it might have already exited), as long |
1790 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2752 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1791 | forking and then immediately registering a watcher for the child is fine, |
2753 | forking and then immediately registering a watcher for the child is fine, |
1792 | but forking and registering a watcher a few event loop iterations later is |
2754 | but forking and registering a watcher a few event loop iterations later or |
1793 | not. |
2755 | in the next callback invocation is not. |
1794 | .PP |
2756 | .PP |
1795 | Only the default event loop is capable of handling signals, and therefore |
2757 | Only the default event loop is capable of handling signals, and therefore |
1796 | you can only register child watchers in the default event loop. |
2758 | you can only register child watchers in the default event loop. |
1797 | .PP |
2759 | .PP |
|
|
2760 | Due to some design glitches inside libev, child watchers will always be |
|
|
2761 | handled at maximum priority (their priority is set to \f(CW\*(C`EV_MAXPRI\*(C'\fR by |
|
|
2762 | libev) |
|
|
2763 | .PP |
1798 | \fIProcess Interaction\fR |
2764 | \fIProcess Interaction\fR |
1799 | .IX Subsection "Process Interaction" |
2765 | .IX Subsection "Process Interaction" |
1800 | .PP |
2766 | .PP |
1801 | Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is |
2767 | Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is |
1802 | initialised. This is necessary to guarantee proper behaviour even if |
2768 | initialised. This is necessary to guarantee proper behaviour even if the |
1803 | the first child watcher is started after the child exits. The occurrence |
2769 | first child watcher is started after the child exits. The occurrence |
1804 | of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done |
2770 | of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done |
1805 | synchronously as part of the event loop processing. Libev always reaps all |
2771 | synchronously as part of the event loop processing. Libev always reaps all |
1806 | children, even ones not watched. |
2772 | children, even ones not watched. |
1807 | .PP |
2773 | .PP |
1808 | \fIOverriding the Built-In Processing\fR |
2774 | \fIOverriding the Built-In Processing\fR |
… | |
… | |
1820 | .IX Subsection "Stopping the Child Watcher" |
2786 | .IX Subsection "Stopping the Child Watcher" |
1821 | .PP |
2787 | .PP |
1822 | Currently, the child watcher never gets stopped, even when the |
2788 | Currently, the child watcher never gets stopped, even when the |
1823 | child terminates, so normally one needs to stop the watcher in the |
2789 | child terminates, so normally one needs to stop the watcher in the |
1824 | callback. Future versions of libev might stop the watcher automatically |
2790 | callback. Future versions of libev might stop the watcher automatically |
1825 | when a child exit is detected. |
2791 | when a child exit is detected (calling \f(CW\*(C`ev_child_stop\*(C'\fR twice is not a |
|
|
2792 | problem). |
1826 | .PP |
2793 | .PP |
1827 | \fIWatcher-Specific Functions and Data Members\fR |
2794 | \fIWatcher-Specific Functions and Data Members\fR |
1828 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2795 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1829 | .IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4 |
2796 | .IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4 |
1830 | .IX Item "ev_child_init (ev_child *, callback, int pid, int trace)" |
2797 | .IX Item "ev_child_init (ev_child *, callback, int pid, int trace)" |
… | |
… | |
1859 | .PP |
2826 | .PP |
1860 | .Vb 1 |
2827 | .Vb 1 |
1861 | \& ev_child cw; |
2828 | \& ev_child cw; |
1862 | \& |
2829 | \& |
1863 | \& static void |
2830 | \& static void |
1864 | \& child_cb (EV_P_ struct ev_child *w, int revents) |
2831 | \& child_cb (EV_P_ ev_child *w, int revents) |
1865 | \& { |
2832 | \& { |
1866 | \& ev_child_stop (EV_A_ w); |
2833 | \& ev_child_stop (EV_A_ w); |
1867 | \& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus); |
2834 | \& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus); |
1868 | \& } |
2835 | \& } |
1869 | \& |
2836 | \& |
… | |
… | |
1880 | \& { |
2847 | \& { |
1881 | \& ev_child_init (&cw, child_cb, pid, 0); |
2848 | \& ev_child_init (&cw, child_cb, pid, 0); |
1882 | \& ev_child_start (EV_DEFAULT_ &cw); |
2849 | \& ev_child_start (EV_DEFAULT_ &cw); |
1883 | \& } |
2850 | \& } |
1884 | .Ve |
2851 | .Ve |
1885 | .ie n .Sh """ev_stat"" \- did the file attributes just change?" |
2852 | .ie n .SS """ev_stat"" \- did the file attributes just change?" |
1886 | .el .Sh "\f(CWev_stat\fP \- did the file attributes just change?" |
2853 | .el .SS "\f(CWev_stat\fP \- did the file attributes just change?" |
1887 | .IX Subsection "ev_stat - did the file attributes just change?" |
2854 | .IX Subsection "ev_stat - did the file attributes just change?" |
1888 | This watches a file system path for attribute changes. That is, it calls |
2855 | This watches a file system path for attribute changes. That is, it calls |
1889 | \&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed |
2856 | \&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed) |
1890 | compared to the last time, invoking the callback if it did. |
2857 | and sees if it changed compared to the last time, invoking the callback |
|
|
2858 | if it did. Starting the watcher \f(CW\*(C`stat\*(C'\fR's the file, so only changes that |
|
|
2859 | happen after the watcher has been started will be reported. |
1891 | .PP |
2860 | .PP |
1892 | The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
2861 | The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
1893 | not exist\*(R" is a status change like any other. The condition \*(L"path does |
2862 | not exist\*(R" is a status change like any other. The condition \*(L"path does not |
1894 | not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is |
2863 | exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the |
1895 | otherwise always forced to be at least one) and all the other fields of |
2864 | \&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at |
1896 | the stat buffer having unspecified contents. |
2865 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2866 | contents. |
1897 | .PP |
2867 | .PP |
1898 | The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is |
2868 | The path \fImust not\fR end in a slash or contain special components such as |
|
|
2869 | \&\f(CW\*(C`.\*(C'\fR or \f(CW\*(C`..\*(C'\fR. The path \fIshould\fR be absolute: If it is relative and |
1899 | relative and your working directory changes, the behaviour is undefined. |
2870 | your working directory changes, then the behaviour is undefined. |
1900 | .PP |
2871 | .PP |
1901 | Since there is no standard kernel interface to do this, the portable |
2872 | Since there is no portable change notification interface available, the |
1902 | implementation simply calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if |
2873 | portable implementation simply calls \f(CWstat(2)\fR regularly on the path |
1903 | it changed somehow. You can specify a recommended polling interval for |
2874 | to see if it changed somehow. You can specify a recommended polling |
1904 | this case. If you specify a polling interval of \f(CW0\fR (highly recommended!) |
2875 | interval for this case. If you specify a polling interval of \f(CW0\fR (highly |
1905 | then a \fIsuitable, unspecified default\fR value will be used (which |
2876 | recommended!) then a \fIsuitable, unspecified default\fR value will be used |
1906 | you can expect to be around five seconds, although this might change |
2877 | (which you can expect to be around five seconds, although this might |
1907 | dynamically). Libev will also impose a minimum interval which is currently |
2878 | change dynamically). Libev will also impose a minimum interval which is |
1908 | around \f(CW0.1\fR, but thats usually overkill. |
2879 | currently around \f(CW0.1\fR, but that's usually overkill. |
1909 | .PP |
2880 | .PP |
1910 | This watcher type is not meant for massive numbers of stat watchers, |
2881 | This watcher type is not meant for massive numbers of stat watchers, |
1911 | as even with OS-supported change notifications, this can be |
2882 | as even with OS-supported change notifications, this can be |
1912 | resource-intensive. |
2883 | resource-intensive. |
1913 | .PP |
2884 | .PP |
1914 | At the time of this writing, the only OS-specific interface implemented |
2885 | At the time of this writing, the only OS-specific interface implemented |
1915 | is the Linux inotify interface (implementing kqueue support is left as |
2886 | is the Linux inotify interface (implementing kqueue support is left as an |
1916 | an exercise for the reader. Note, however, that the author sees no way |
2887 | exercise for the reader. Note, however, that the author sees no way of |
1917 | of implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue). |
2888 | implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue, except as a hint). |
1918 | .PP |
2889 | .PP |
1919 | \fI\s-1ABI\s0 Issues (Largefile Support)\fR |
2890 | \fI\s-1ABI\s0 Issues (Largefile Support)\fR |
1920 | .IX Subsection "ABI Issues (Largefile Support)" |
2891 | .IX Subsection "ABI Issues (Largefile Support)" |
1921 | .PP |
2892 | .PP |
1922 | Libev by default (unless the user overrides this) uses the default |
2893 | Libev by default (unless the user overrides this) uses the default |
1923 | compilation environment, which means that on systems with large file |
2894 | compilation environment, which means that on systems with large file |
1924 | support disabled by default, you get the 32 bit version of the stat |
2895 | support disabled by default, you get the 32 bit version of the stat |
1925 | structure. When using the library from programs that change the \s-1ABI\s0 to |
2896 | structure. When using the library from programs that change the \s-1ABI\s0 to |
1926 | use 64 bit file offsets the programs will fail. In that case you have to |
2897 | use 64 bit file offsets the programs will fail. In that case you have to |
1927 | compile libev with the same flags to get binary compatibility. This is |
2898 | compile libev with the same flags to get binary compatibility. This is |
1928 | obviously the case with any flags that change the \s-1ABI\s0, but the problem is |
2899 | obviously the case with any flags that change the \s-1ABI,\s0 but the problem is |
1929 | most noticeably disabled with ev_stat and large file support. |
2900 | most noticeably displayed with ev_stat and large file support. |
1930 | .PP |
2901 | .PP |
1931 | The solution for this is to lobby your distribution maker to make large |
2902 | The solution for this is to lobby your distribution maker to make large |
1932 | file interfaces available by default (as e.g. FreeBSD does) and not |
2903 | file interfaces available by default (as e.g. FreeBSD does) and not |
1933 | optional. Libev cannot simply switch on large file support because it has |
2904 | optional. Libev cannot simply switch on large file support because it has |
1934 | to exchange stat structures with application programs compiled using the |
2905 | to exchange stat structures with application programs compiled using the |
1935 | default compilation environment. |
2906 | default compilation environment. |
1936 | .PP |
2907 | .PP |
1937 | \fIInotify and Kqueue\fR |
2908 | \fIInotify and Kqueue\fR |
1938 | .IX Subsection "Inotify and Kqueue" |
2909 | .IX Subsection "Inotify and Kqueue" |
1939 | .PP |
2910 | .PP |
1940 | When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev (generally only |
2911 | When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at |
1941 | available with Linux) and present at runtime, it will be used to speed up |
2912 | runtime, it will be used to speed up change detection where possible. The |
1942 | change detection where possible. The inotify descriptor will be created lazily |
2913 | inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR |
1943 | when the first \f(CW\*(C`ev_stat\*(C'\fR watcher is being started. |
2914 | watcher is being started. |
1944 | .PP |
2915 | .PP |
1945 | Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers |
2916 | Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers |
1946 | except that changes might be detected earlier, and in some cases, to avoid |
2917 | except that changes might be detected earlier, and in some cases, to avoid |
1947 | making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support |
2918 | making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support |
1948 | there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling, |
2919 | there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling, |
1949 | but as long as the path exists, libev usually gets away without polling. |
2920 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2921 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2922 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2923 | xfs are fully working) libev usually gets away without polling. |
1950 | .PP |
2924 | .PP |
1951 | There is no support for kqueue, as apparently it cannot be used to |
2925 | There is no support for kqueue, as apparently it cannot be used to |
1952 | implement this functionality, due to the requirement of having a file |
2926 | implement this functionality, due to the requirement of having a file |
1953 | descriptor open on the object at all times, and detecting renames, unlinks |
2927 | descriptor open on the object at all times, and detecting renames, unlinks |
1954 | etc. is difficult. |
2928 | etc. is difficult. |
1955 | .PP |
2929 | .PP |
|
|
2930 | \fI\f(CI\*(C`stat ()\*(C'\fI is a synchronous operation\fR |
|
|
2931 | .IX Subsection "stat () is a synchronous operation" |
|
|
2932 | .PP |
|
|
2933 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2934 | the process. The exception are \f(CW\*(C`ev_stat\*(C'\fR watchers \- those call \f(CW\*(C`stat |
|
|
2935 | ()\*(C'\fR, which is a synchronous operation. |
|
|
2936 | .PP |
|
|
2937 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2938 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2939 | as the path data is usually in memory already (except when starting the |
|
|
2940 | watcher). |
|
|
2941 | .PP |
|
|
2942 | For networked file systems, calling \f(CW\*(C`stat ()\*(C'\fR can block an indefinite |
|
|
2943 | time due to network issues, and even under good conditions, a stat call |
|
|
2944 | often takes multiple milliseconds. |
|
|
2945 | .PP |
|
|
2946 | Therefore, it is best to avoid using \f(CW\*(C`ev_stat\*(C'\fR watchers on networked |
|
|
2947 | paths, although this is fully supported by libev. |
|
|
2948 | .PP |
1956 | \fIThe special problem of stat time resolution\fR |
2949 | \fIThe special problem of stat time resolution\fR |
1957 | .IX Subsection "The special problem of stat time resolution" |
2950 | .IX Subsection "The special problem of stat time resolution" |
1958 | .PP |
2951 | .PP |
1959 | The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably, and |
2952 | The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably, |
1960 | even on systems where the resolution is higher, most file systems still |
2953 | and even on systems where the resolution is higher, most file systems |
1961 | only support whole seconds. |
2954 | still only support whole seconds. |
1962 | .PP |
2955 | .PP |
1963 | That means that, if the time is the only thing that changes, you can |
2956 | That means that, if the time is the only thing that changes, you can |
1964 | easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and |
2957 | easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and |
1965 | calls your callback, which does something. When there is another update |
2958 | calls your callback, which does something. When there is another update |
1966 | within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the |
2959 | within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the |
… | |
… | |
2080 | \& ... |
3073 | \& ... |
2081 | \& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
3074 | \& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
2082 | \& ev_stat_start (loop, &passwd); |
3075 | \& ev_stat_start (loop, &passwd); |
2083 | \& ev_timer_init (&timer, timer_cb, 0., 1.02); |
3076 | \& ev_timer_init (&timer, timer_cb, 0., 1.02); |
2084 | .Ve |
3077 | .Ve |
2085 | .ie n .Sh """ev_idle"" \- when you've got nothing better to do..." |
3078 | .ie n .SS """ev_idle"" \- when you've got nothing better to do..." |
2086 | .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." |
3079 | .el .SS "\f(CWev_idle\fP \- when you've got nothing better to do..." |
2087 | .IX Subsection "ev_idle - when you've got nothing better to do..." |
3080 | .IX Subsection "ev_idle - when you've got nothing better to do..." |
2088 | Idle watchers trigger events when no other events of the same or higher |
3081 | Idle watchers trigger events when no other events of the same or higher |
2089 | priority are pending (prepare, check and other idle watchers do not count |
3082 | priority are pending (prepare, check and other idle watchers do not count |
2090 | as receiving \*(L"events\*(R"). |
3083 | as receiving \*(L"events\*(R"). |
2091 | .PP |
3084 | .PP |
… | |
… | |
2102 | Apart from keeping your process non-blocking (which is a useful |
3095 | Apart from keeping your process non-blocking (which is a useful |
2103 | effect on its own sometimes), idle watchers are a good place to do |
3096 | effect on its own sometimes), idle watchers are a good place to do |
2104 | \&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the |
3097 | \&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the |
2105 | event loop has handled all outstanding events. |
3098 | event loop has handled all outstanding events. |
2106 | .PP |
3099 | .PP |
|
|
3100 | \fIAbusing an \f(CI\*(C`ev_idle\*(C'\fI watcher for its side-effect\fR |
|
|
3101 | .IX Subsection "Abusing an ev_idle watcher for its side-effect" |
|
|
3102 | .PP |
|
|
3103 | As long as there is at least one active idle watcher, libev will never |
|
|
3104 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
3105 | For this to work, the idle watcher doesn't need to be invoked at all \- the |
|
|
3106 | lowest priority will do. |
|
|
3107 | .PP |
|
|
3108 | This mode of operation can be useful together with an \f(CW\*(C`ev_check\*(C'\fR watcher, |
|
|
3109 | to do something on each event loop iteration \- for example to balance load |
|
|
3110 | between different connections. |
|
|
3111 | .PP |
|
|
3112 | See \*(L"Abusing an ev_check watcher for its side-effect\*(R" for a longer |
|
|
3113 | example. |
|
|
3114 | .PP |
2107 | \fIWatcher-Specific Functions and Data Members\fR |
3115 | \fIWatcher-Specific Functions and Data Members\fR |
2108 | .IX Subsection "Watcher-Specific Functions and Data Members" |
3116 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2109 | .IP "ev_idle_init (ev_signal *, callback)" 4 |
3117 | .IP "ev_idle_init (ev_idle *, callback)" 4 |
2110 | .IX Item "ev_idle_init (ev_signal *, callback)" |
3118 | .IX Item "ev_idle_init (ev_idle *, callback)" |
2111 | Initialises and configures the idle watcher \- it has no parameters of any |
3119 | Initialises and configures the idle watcher \- it has no parameters of any |
2112 | kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
3120 | kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
2113 | believe me. |
3121 | believe me. |
2114 | .PP |
3122 | .PP |
2115 | \fIExamples\fR |
3123 | \fIExamples\fR |
2116 | .IX Subsection "Examples" |
3124 | .IX Subsection "Examples" |
2117 | .PP |
3125 | .PP |
2118 | Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the |
3126 | Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the |
2119 | callback, free it. Also, use no error checking, as usual. |
3127 | callback, free it. Also, use no error checking, as usual. |
2120 | .PP |
3128 | .PP |
2121 | .Vb 7 |
3129 | .Vb 5 |
2122 | \& static void |
3130 | \& static void |
2123 | \& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
3131 | \& idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2124 | \& { |
3132 | \& { |
|
|
3133 | \& // stop the watcher |
|
|
3134 | \& ev_idle_stop (loop, w); |
|
|
3135 | \& |
|
|
3136 | \& // now we can free it |
2125 | \& free (w); |
3137 | \& free (w); |
|
|
3138 | \& |
2126 | \& // now do something you wanted to do when the program has |
3139 | \& // now do something you wanted to do when the program has |
2127 | \& // no longer anything immediate to do. |
3140 | \& // no longer anything immediate to do. |
2128 | \& } |
3141 | \& } |
2129 | \& |
3142 | \& |
2130 | \& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
3143 | \& ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2131 | \& ev_idle_init (idle_watcher, idle_cb); |
3144 | \& ev_idle_init (idle_watcher, idle_cb); |
2132 | \& ev_idle_start (loop, idle_cb); |
3145 | \& ev_idle_start (loop, idle_watcher); |
2133 | .Ve |
3146 | .Ve |
2134 | .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" |
3147 | .ie n .SS """ev_prepare"" and ""ev_check"" \- customise your event loop!" |
2135 | .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
3148 | .el .SS "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
2136 | .IX Subsection "ev_prepare and ev_check - customise your event loop!" |
3149 | .IX Subsection "ev_prepare and ev_check - customise your event loop!" |
2137 | Prepare and check watchers are usually (but not always) used in pairs: |
3150 | Prepare and check watchers are often (but not always) used in pairs: |
2138 | prepare watchers get invoked before the process blocks and check watchers |
3151 | prepare watchers get invoked before the process blocks and check watchers |
2139 | afterwards. |
3152 | afterwards. |
2140 | .PP |
3153 | .PP |
2141 | You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter |
3154 | You \fImust not\fR call \f(CW\*(C`ev_run\*(C'\fR (or similar functions that enter the |
2142 | the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR |
3155 | current event loop) or \f(CW\*(C`ev_loop_fork\*(C'\fR from either \f(CW\*(C`ev_prepare\*(C'\fR or |
2143 | watchers. Other loops than the current one are fine, however. The |
3156 | \&\f(CW\*(C`ev_check\*(C'\fR watchers. Other loops than the current one are fine, |
2144 | rationale behind this is that you do not need to check for recursion in |
3157 | however. The rationale behind this is that you do not need to check |
2145 | those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, |
3158 | for recursion in those watchers, i.e. the sequence will always be |
2146 | \&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be |
3159 | \&\f(CW\*(C`ev_prepare\*(C'\fR, blocking, \f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each |
2147 | called in pairs bracketing the blocking call. |
3160 | kind they will always be called in pairs bracketing the blocking call. |
2148 | .PP |
3161 | .PP |
2149 | Their main purpose is to integrate other event mechanisms into libev and |
3162 | Their main purpose is to integrate other event mechanisms into libev and |
2150 | their use is somewhat advanced. They could be used, for example, to track |
3163 | their use is somewhat advanced. They could be used, for example, to track |
2151 | variable changes, implement your own watchers, integrate net-snmp or a |
3164 | variable changes, implement your own watchers, integrate net-snmp or a |
2152 | coroutine library and lots more. They are also occasionally useful if |
3165 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
2170 | with priority higher than or equal to the event loop and one coroutine |
3183 | with priority higher than or equal to the event loop and one coroutine |
2171 | of lower priority, but only once, using idle watchers to keep the event |
3184 | of lower priority, but only once, using idle watchers to keep the event |
2172 | loop from blocking if lower-priority coroutines are active, thus mapping |
3185 | loop from blocking if lower-priority coroutines are active, thus mapping |
2173 | low-priority coroutines to idle/background tasks). |
3186 | low-priority coroutines to idle/background tasks). |
2174 | .PP |
3187 | .PP |
2175 | It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) |
3188 | When used for this purpose, it is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers |
2176 | priority, to ensure that they are being run before any other watchers |
3189 | highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) priority, to ensure that they are being run before |
2177 | after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR watchers). |
3190 | any other watchers after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR |
|
|
3191 | watchers). |
2178 | .PP |
3192 | .PP |
2179 | Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not |
3193 | Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not |
2180 | activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they |
3194 | activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they |
2181 | might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As |
3195 | might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As |
2182 | \&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event |
3196 | \&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event |
2183 | loops those other event loops might be in an unusable state until their |
3197 | loops those other event loops might be in an unusable state until their |
2184 | \&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with |
3198 | \&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with |
2185 | others). |
3199 | others). |
|
|
3200 | .PP |
|
|
3201 | \fIAbusing an \f(CI\*(C`ev_check\*(C'\fI watcher for its side-effect\fR |
|
|
3202 | .IX Subsection "Abusing an ev_check watcher for its side-effect" |
|
|
3203 | .PP |
|
|
3204 | \&\f(CW\*(C`ev_check\*(C'\fR (and less often also \f(CW\*(C`ev_prepare\*(C'\fR) watchers can also be |
|
|
3205 | useful because they are called once per event loop iteration. For |
|
|
3206 | example, if you want to handle a large number of connections fairly, you |
|
|
3207 | normally only do a bit of work for each active connection, and if there |
|
|
3208 | is more work to do, you wait for the next event loop iteration, so other |
|
|
3209 | connections have a chance of making progress. |
|
|
3210 | .PP |
|
|
3211 | Using an \f(CW\*(C`ev_check\*(C'\fR watcher is almost enough: it will be called on the |
|
|
3212 | next event loop iteration. However, that isn't as soon as possible \- |
|
|
3213 | without external events, your \f(CW\*(C`ev_check\*(C'\fR watcher will not be invoked. |
|
|
3214 | .PP |
|
|
3215 | This is where \f(CW\*(C`ev_idle\*(C'\fR watchers come in handy \- all you need is a |
|
|
3216 | single global idle watcher that is active as long as you have one active |
|
|
3217 | \&\f(CW\*(C`ev_check\*(C'\fR watcher. The \f(CW\*(C`ev_idle\*(C'\fR watcher makes sure the event loop |
|
|
3218 | will not sleep, and the \f(CW\*(C`ev_check\*(C'\fR watcher makes sure a callback gets |
|
|
3219 | invoked. Neither watcher alone can do that. |
2186 | .PP |
3220 | .PP |
2187 | \fIWatcher-Specific Functions and Data Members\fR |
3221 | \fIWatcher-Specific Functions and Data Members\fR |
2188 | .IX Subsection "Watcher-Specific Functions and Data Members" |
3222 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2189 | .IP "ev_prepare_init (ev_prepare *, callback)" 4 |
3223 | .IP "ev_prepare_init (ev_prepare *, callback)" 4 |
2190 | .IX Item "ev_prepare_init (ev_prepare *, callback)" |
3224 | .IX Item "ev_prepare_init (ev_prepare *, callback)" |
… | |
… | |
2216 | .Vb 2 |
3250 | .Vb 2 |
2217 | \& static ev_io iow [nfd]; |
3251 | \& static ev_io iow [nfd]; |
2218 | \& static ev_timer tw; |
3252 | \& static ev_timer tw; |
2219 | \& |
3253 | \& |
2220 | \& static void |
3254 | \& static void |
2221 | \& io_cb (ev_loop *loop, ev_io *w, int revents) |
3255 | \& io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2222 | \& { |
3256 | \& { |
2223 | \& } |
3257 | \& } |
2224 | \& |
3258 | \& |
2225 | \& // create io watchers for each fd and a timer before blocking |
3259 | \& // create io watchers for each fd and a timer before blocking |
2226 | \& static void |
3260 | \& static void |
2227 | \& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
3261 | \& adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2228 | \& { |
3262 | \& { |
2229 | \& int timeout = 3600000; |
3263 | \& int timeout = 3600000; |
2230 | \& struct pollfd fds [nfd]; |
3264 | \& struct pollfd fds [nfd]; |
2231 | \& // actual code will need to loop here and realloc etc. |
3265 | \& // actual code will need to loop here and realloc etc. |
2232 | \& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
3266 | \& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2233 | \& |
3267 | \& |
2234 | \& /* the callback is illegal, but won\*(Aqt be called as we stop during check */ |
3268 | \& /* the callback is illegal, but won\*(Aqt be called as we stop during check */ |
2235 | \& ev_timer_init (&tw, 0, timeout * 1e\-3); |
3269 | \& ev_timer_init (&tw, 0, timeout * 1e\-3, 0.); |
2236 | \& ev_timer_start (loop, &tw); |
3270 | \& ev_timer_start (loop, &tw); |
2237 | \& |
3271 | \& |
2238 | \& // create one ev_io per pollfd |
3272 | \& // create one ev_io per pollfd |
2239 | \& for (int i = 0; i < nfd; ++i) |
3273 | \& for (int i = 0; i < nfd; ++i) |
2240 | \& { |
3274 | \& { |
… | |
… | |
2247 | \& } |
3281 | \& } |
2248 | \& } |
3282 | \& } |
2249 | \& |
3283 | \& |
2250 | \& // stop all watchers after blocking |
3284 | \& // stop all watchers after blocking |
2251 | \& static void |
3285 | \& static void |
2252 | \& adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
3286 | \& adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2253 | \& { |
3287 | \& { |
2254 | \& ev_timer_stop (loop, &tw); |
3288 | \& ev_timer_stop (loop, &tw); |
2255 | \& |
3289 | \& |
2256 | \& for (int i = 0; i < nfd; ++i) |
3290 | \& for (int i = 0; i < nfd; ++i) |
2257 | \& { |
3291 | \& { |
… | |
… | |
2301 | .Ve |
3335 | .Ve |
2302 | .PP |
3336 | .PP |
2303 | Method 4: Do not use a prepare or check watcher because the module you |
3337 | Method 4: Do not use a prepare or check watcher because the module you |
2304 | want to embed is not flexible enough to support it. Instead, you can |
3338 | want to embed is not flexible enough to support it. Instead, you can |
2305 | override their poll function. The drawback with this solution is that the |
3339 | override their poll function. The drawback with this solution is that the |
2306 | main loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module uses |
3340 | main loop is now no longer controllable by \s-1EV.\s0 The \f(CW\*(C`Glib::EV\*(C'\fR module uses |
2307 | this approach, effectively embedding \s-1EV\s0 as a client into the horrible |
3341 | this approach, effectively embedding \s-1EV\s0 as a client into the horrible |
2308 | libglib event loop. |
3342 | libglib event loop. |
2309 | .PP |
3343 | .PP |
2310 | .Vb 4 |
3344 | .Vb 4 |
2311 | \& static gint |
3345 | \& static gint |
… | |
… | |
2318 | \& |
3352 | \& |
2319 | \& if (timeout >= 0) |
3353 | \& if (timeout >= 0) |
2320 | \& // create/start timer |
3354 | \& // create/start timer |
2321 | \& |
3355 | \& |
2322 | \& // poll |
3356 | \& // poll |
2323 | \& ev_loop (EV_A_ 0); |
3357 | \& ev_run (EV_A_ 0); |
2324 | \& |
3358 | \& |
2325 | \& // stop timer again |
3359 | \& // stop timer again |
2326 | \& if (timeout >= 0) |
3360 | \& if (timeout >= 0) |
2327 | \& ev_timer_stop (EV_A_ &to); |
3361 | \& ev_timer_stop (EV_A_ &to); |
2328 | \& |
3362 | \& |
… | |
… | |
2331 | \& ev_io_stop (EV_A_ iow [n]); |
3365 | \& ev_io_stop (EV_A_ iow [n]); |
2332 | \& |
3366 | \& |
2333 | \& return got_events; |
3367 | \& return got_events; |
2334 | \& } |
3368 | \& } |
2335 | .Ve |
3369 | .Ve |
2336 | .ie n .Sh """ev_embed"" \- when one backend isn't enough..." |
3370 | .ie n .SS """ev_embed"" \- when one backend isn't enough..." |
2337 | .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." |
3371 | .el .SS "\f(CWev_embed\fP \- when one backend isn't enough..." |
2338 | .IX Subsection "ev_embed - when one backend isn't enough..." |
3372 | .IX Subsection "ev_embed - when one backend isn't enough..." |
2339 | This is a rather advanced watcher type that lets you embed one event loop |
3373 | This is a rather advanced watcher type that lets you embed one event loop |
2340 | into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
3374 | into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
2341 | loop, other types of watchers might be handled in a delayed or incorrect |
3375 | loop, other types of watchers might be handled in a delayed or incorrect |
2342 | fashion and must not be used). |
3376 | fashion and must not be used). |
… | |
… | |
2357 | some fds have to be watched and handled very quickly (with low latency), |
3391 | some fds have to be watched and handled very quickly (with low latency), |
2358 | and even priorities and idle watchers might have too much overhead. In |
3392 | and even priorities and idle watchers might have too much overhead. In |
2359 | this case you would put all the high priority stuff in one loop and all |
3393 | this case you would put all the high priority stuff in one loop and all |
2360 | the rest in a second one, and embed the second one in the first. |
3394 | the rest in a second one, and embed the second one in the first. |
2361 | .PP |
3395 | .PP |
2362 | As long as the watcher is active, the callback will be invoked every time |
3396 | As long as the watcher is active, the callback will be invoked every |
2363 | there might be events pending in the embedded loop. The callback must then |
3397 | time there might be events pending in the embedded loop. The callback |
2364 | call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke |
3398 | must then call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single |
2365 | their callbacks (you could also start an idle watcher to give the embedded |
3399 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2366 | loop strictly lower priority for example). You can also set the callback |
3400 | \&\f(CW\*(C`ev_embed_sweep\*(C'\fR function directly, it could also start an idle watcher |
2367 | to \f(CW0\fR, in which case the embed watcher will automatically execute the |
3401 | to give the embedded loop strictly lower priority for example). |
2368 | embedded loop sweep. |
|
|
2369 | .PP |
3402 | .PP |
2370 | As long as the watcher is started it will automatically handle events. The |
3403 | You can also set the callback to \f(CW0\fR, in which case the embed watcher |
2371 | callback will be invoked whenever some events have been handled. You can |
3404 | will automatically execute the embedded loop sweep whenever necessary. |
2372 | set the callback to \f(CW0\fR to avoid having to specify one if you are not |
|
|
2373 | interested in that. |
|
|
2374 | .PP |
3405 | .PP |
2375 | Also, there have not currently been made special provisions for forking: |
3406 | Fork detection will be handled transparently while the \f(CW\*(C`ev_embed\*(C'\fR watcher |
2376 | when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops, |
3407 | is active, i.e., the embedded loop will automatically be forked when the |
2377 | but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers |
3408 | embedding loop forks. In other cases, the user is responsible for calling |
2378 | yourself \- but you can use a fork watcher to handle this automatically, |
3409 | \&\f(CW\*(C`ev_loop_fork\*(C'\fR on the embedded loop. |
2379 | and future versions of libev might do just that. |
|
|
2380 | .PP |
3410 | .PP |
2381 | Unfortunately, not all backends are embeddable: only the ones returned by |
3411 | Unfortunately, not all backends are embeddable: only the ones returned by |
2382 | \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
3412 | \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
2383 | portable one. |
3413 | portable one. |
2384 | .PP |
3414 | .PP |
… | |
… | |
2399 | \fIWatcher-Specific Functions and Data Members\fR |
3429 | \fIWatcher-Specific Functions and Data Members\fR |
2400 | .IX Subsection "Watcher-Specific Functions and Data Members" |
3430 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2401 | .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
3431 | .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
2402 | .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" |
3432 | .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" |
2403 | .PD 0 |
3433 | .PD 0 |
2404 | .IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
3434 | .IP "ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)" 4 |
2405 | .IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" |
3435 | .IX Item "ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)" |
2406 | .PD |
3436 | .PD |
2407 | Configures the watcher to embed the given loop, which must be |
3437 | Configures the watcher to embed the given loop, which must be |
2408 | embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be |
3438 | embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be |
2409 | invoked automatically, otherwise it is the responsibility of the callback |
3439 | invoked automatically, otherwise it is the responsibility of the callback |
2410 | to invoke it (it will continue to be called until the sweep has been done, |
3440 | to invoke it (it will continue to be called until the sweep has been done, |
2411 | if you do not want that, you need to temporarily stop the embed watcher). |
3441 | if you do not want that, you need to temporarily stop the embed watcher). |
2412 | .IP "ev_embed_sweep (loop, ev_embed *)" 4 |
3442 | .IP "ev_embed_sweep (loop, ev_embed *)" 4 |
2413 | .IX Item "ev_embed_sweep (loop, ev_embed *)" |
3443 | .IX Item "ev_embed_sweep (loop, ev_embed *)" |
2414 | Make a single, non-blocking sweep over the embedded loop. This works |
3444 | Make a single, non-blocking sweep over the embedded loop. This works |
2415 | similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most |
3445 | similarly to \f(CW\*(C`ev_run (embedded_loop, EVRUN_NOWAIT)\*(C'\fR, but in the most |
2416 | appropriate way for embedded loops. |
3446 | appropriate way for embedded loops. |
2417 | .IP "struct ev_loop *other [read\-only]" 4 |
3447 | .IP "struct ev_loop *other [read\-only]" 4 |
2418 | .IX Item "struct ev_loop *other [read-only]" |
3448 | .IX Item "struct ev_loop *other [read-only]" |
2419 | The embedded event loop. |
3449 | The embedded event loop. |
2420 | .PP |
3450 | .PP |
… | |
… | |
2428 | used). |
3458 | used). |
2429 | .PP |
3459 | .PP |
2430 | .Vb 3 |
3460 | .Vb 3 |
2431 | \& struct ev_loop *loop_hi = ev_default_init (0); |
3461 | \& struct ev_loop *loop_hi = ev_default_init (0); |
2432 | \& struct ev_loop *loop_lo = 0; |
3462 | \& struct ev_loop *loop_lo = 0; |
2433 | \& struct ev_embed embed; |
3463 | \& ev_embed embed; |
2434 | \& |
3464 | \& |
2435 | \& // see if there is a chance of getting one that works |
3465 | \& // see if there is a chance of getting one that works |
2436 | \& // (remember that a flags value of 0 means autodetection) |
3466 | \& // (remember that a flags value of 0 means autodetection) |
2437 | \& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3467 | \& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2438 | \& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3468 | \& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2439 | \& : 0; |
3469 | \& : 0; |
… | |
… | |
2454 | \&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too). |
3484 | \&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too). |
2455 | .PP |
3485 | .PP |
2456 | .Vb 3 |
3486 | .Vb 3 |
2457 | \& struct ev_loop *loop = ev_default_init (0); |
3487 | \& struct ev_loop *loop = ev_default_init (0); |
2458 | \& struct ev_loop *loop_socket = 0; |
3488 | \& struct ev_loop *loop_socket = 0; |
2459 | \& struct ev_embed embed; |
3489 | \& ev_embed embed; |
2460 | \& |
3490 | \& |
2461 | \& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3491 | \& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2462 | \& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3492 | \& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2463 | \& { |
3493 | \& { |
2464 | \& ev_embed_init (&embed, 0, loop_socket); |
3494 | \& ev_embed_init (&embed, 0, loop_socket); |
2465 | \& ev_embed_start (loop, &embed); |
3495 | \& ev_embed_start (loop, &embed); |
… | |
… | |
2468 | \& if (!loop_socket) |
3498 | \& if (!loop_socket) |
2469 | \& loop_socket = loop; |
3499 | \& loop_socket = loop; |
2470 | \& |
3500 | \& |
2471 | \& // now use loop_socket for all sockets, and loop for everything else |
3501 | \& // now use loop_socket for all sockets, and loop for everything else |
2472 | .Ve |
3502 | .Ve |
2473 | .ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork" |
3503 | .ie n .SS """ev_fork"" \- the audacity to resume the event loop after a fork" |
2474 | .el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" |
3504 | .el .SS "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" |
2475 | .IX Subsection "ev_fork - the audacity to resume the event loop after a fork" |
3505 | .IX Subsection "ev_fork - the audacity to resume the event loop after a fork" |
2476 | Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because |
3506 | Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because |
2477 | whoever is a good citizen cared to tell libev about it by calling |
3507 | whoever is a good citizen cared to tell libev about it by calling |
2478 | \&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the |
3508 | \&\f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the event loop blocks next |
2479 | event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, |
3509 | and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, and only in the child |
2480 | and only in the child after the fork. If whoever good citizen calling |
3510 | after the fork. If whoever good citizen calling \f(CW\*(C`ev_default_fork\*(C'\fR cheats |
2481 | \&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork |
3511 | and calls it in the wrong process, the fork handlers will be invoked, too, |
2482 | handlers will be invoked, too, of course. |
3512 | of course. |
|
|
3513 | .PP |
|
|
3514 | \fIThe special problem of life after fork \- how is it possible?\fR |
|
|
3515 | .IX Subsection "The special problem of life after fork - how is it possible?" |
|
|
3516 | .PP |
|
|
3517 | Most uses of \f(CW\*(C`fork ()\*(C'\fR consist of forking, then some simple calls to set |
|
|
3518 | up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This |
|
|
3519 | sequence should be handled by libev without any problems. |
|
|
3520 | .PP |
|
|
3521 | This changes when the application actually wants to do event handling |
|
|
3522 | in the child, or both parent in child, in effect \*(L"continuing\*(R" after the |
|
|
3523 | fork. |
|
|
3524 | .PP |
|
|
3525 | The default mode of operation (for libev, with application help to detect |
|
|
3526 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3527 | when \fIeither\fR the parent \fIor\fR the child process continues. |
|
|
3528 | .PP |
|
|
3529 | When both processes want to continue using libev, then this is usually the |
|
|
3530 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3531 | supposed to continue with all watchers in place as before, while the other |
|
|
3532 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3533 | .PP |
|
|
3534 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3535 | simply create a new event loop, which of course will be \*(L"empty\*(R", and |
|
|
3536 | use that for new watchers. This has the advantage of not touching more |
|
|
3537 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3538 | disadvantage of having to use multiple event loops (which do not support |
|
|
3539 | signal watchers). |
|
|
3540 | .PP |
|
|
3541 | When this is not possible, or you want to use the default loop for |
|
|
3542 | other reasons, then in the process that wants to start \*(L"fresh\*(R", call |
|
|
3543 | \&\f(CW\*(C`ev_loop_destroy (EV_DEFAULT)\*(C'\fR followed by \f(CW\*(C`ev_default_loop (...)\*(C'\fR. |
|
|
3544 | Destroying the default loop will \*(L"orphan\*(R" (not stop) all registered |
|
|
3545 | watchers, so you have to be careful not to execute code that modifies |
|
|
3546 | those watchers. Note also that in that case, you have to re-register any |
|
|
3547 | signal watchers. |
2483 | .PP |
3548 | .PP |
2484 | \fIWatcher-Specific Functions and Data Members\fR |
3549 | \fIWatcher-Specific Functions and Data Members\fR |
2485 | .IX Subsection "Watcher-Specific Functions and Data Members" |
3550 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2486 | .IP "ev_fork_init (ev_signal *, callback)" 4 |
3551 | .IP "ev_fork_init (ev_fork *, callback)" 4 |
2487 | .IX Item "ev_fork_init (ev_signal *, callback)" |
3552 | .IX Item "ev_fork_init (ev_fork *, callback)" |
2488 | Initialises and configures the fork watcher \- it has no parameters of any |
3553 | Initialises and configures the fork watcher \- it has no parameters of any |
2489 | kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, |
3554 | kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, |
2490 | believe me. |
3555 | really. |
|
|
3556 | .ie n .SS """ev_cleanup"" \- even the best things end" |
|
|
3557 | .el .SS "\f(CWev_cleanup\fP \- even the best things end" |
|
|
3558 | .IX Subsection "ev_cleanup - even the best things end" |
|
|
3559 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3560 | by a call to \f(CW\*(C`ev_loop_destroy\*(C'\fR. |
|
|
3561 | .PP |
|
|
3562 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3563 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3564 | program, worker threads and so on \- you just to make sure to destroy the |
|
|
3565 | loop when you want them to be invoked. |
|
|
3566 | .PP |
|
|
3567 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3568 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3569 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3570 | can call libev functions in the callback, except \f(CW\*(C`ev_cleanup_start\*(C'\fR. |
|
|
3571 | .PP |
|
|
3572 | \fIWatcher-Specific Functions and Data Members\fR |
|
|
3573 | .IX Subsection "Watcher-Specific Functions and Data Members" |
|
|
3574 | .IP "ev_cleanup_init (ev_cleanup *, callback)" 4 |
|
|
3575 | .IX Item "ev_cleanup_init (ev_cleanup *, callback)" |
|
|
3576 | Initialises and configures the cleanup watcher \- it has no parameters of |
|
|
3577 | any kind. There is a \f(CW\*(C`ev_cleanup_set\*(C'\fR macro, but using it is utterly |
|
|
3578 | pointless, I assure you. |
|
|
3579 | .PP |
|
|
3580 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3581 | cleanup functions are called. |
|
|
3582 | .PP |
|
|
3583 | .Vb 5 |
|
|
3584 | \& static void |
|
|
3585 | \& program_exits (void) |
|
|
3586 | \& { |
|
|
3587 | \& ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3588 | \& } |
|
|
3589 | \& |
|
|
3590 | \& ... |
|
|
3591 | \& atexit (program_exits); |
|
|
3592 | .Ve |
2491 | .ie n .Sh """ev_async"" \- how to wake up another event loop" |
3593 | .ie n .SS """ev_async"" \- how to wake up an event loop" |
2492 | .el .Sh "\f(CWev_async\fP \- how to wake up another event loop" |
3594 | .el .SS "\f(CWev_async\fP \- how to wake up an event loop" |
2493 | .IX Subsection "ev_async - how to wake up another event loop" |
3595 | .IX Subsection "ev_async - how to wake up an event loop" |
2494 | In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other |
3596 | In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other |
2495 | asynchronous sources such as signal handlers (as opposed to multiple event |
3597 | asynchronous sources such as signal handlers (as opposed to multiple event |
2496 | loops \- those are of course safe to use in different threads). |
3598 | loops \- those are of course safe to use in different threads). |
2497 | .PP |
3599 | .PP |
2498 | Sometimes, however, you need to wake up another event loop you do not |
3600 | Sometimes, however, you need to wake up an event loop you do not control, |
2499 | control, for example because it belongs to another thread. This is what |
3601 | for example because it belongs to another thread. This is what \f(CW\*(C`ev_async\*(C'\fR |
2500 | \&\f(CW\*(C`ev_async\*(C'\fR watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you |
3602 | watchers do: as long as the \f(CW\*(C`ev_async\*(C'\fR watcher is active, you can signal |
2501 | can signal it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal |
3603 | it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal safe. |
2502 | safe. |
|
|
2503 | .PP |
3604 | .PP |
2504 | This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals, |
3605 | This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals, |
2505 | too, are asynchronous in nature, and signals, too, will be compressed |
3606 | too, are asynchronous in nature, and signals, too, will be compressed |
2506 | (i.e. the number of callback invocations may be less than the number of |
3607 | (i.e. the number of callback invocations may be less than the number of |
2507 | \&\f(CW\*(C`ev_async_sent\*(C'\fR calls). |
3608 | \&\f(CW\*(C`ev_async_send\*(C'\fR calls). In fact, you could use signal watchers as a kind |
2508 | .PP |
3609 | of \*(L"global async watchers\*(R" by using a watcher on an otherwise unused |
2509 | Unlike \f(CW\*(C`ev_signal\*(C'\fR watchers, \f(CW\*(C`ev_async\*(C'\fR works with any event loop, not |
3610 | signal, and \f(CW\*(C`ev_feed_signal\*(C'\fR to signal this watcher from another thread, |
2510 | just the default loop. |
3611 | even without knowing which loop owns the signal. |
2511 | .PP |
3612 | .PP |
2512 | \fIQueueing\fR |
3613 | \fIQueueing\fR |
2513 | .IX Subsection "Queueing" |
3614 | .IX Subsection "Queueing" |
2514 | .PP |
3615 | .PP |
2515 | \&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason |
3616 | \&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason |
2516 | is that the author does not know of a simple (or any) algorithm for a |
3617 | is that the author does not know of a simple (or any) algorithm for a |
2517 | multiple-writer-single-reader queue that works in all cases and doesn't |
3618 | multiple-writer-single-reader queue that works in all cases and doesn't |
2518 | need elaborate support such as pthreads. |
3619 | need elaborate support such as pthreads or unportable memory access |
|
|
3620 | semantics. |
2519 | .PP |
3621 | .PP |
2520 | That means that if you want to queue data, you have to provide your own |
3622 | That means that if you want to queue data, you have to provide your own |
2521 | queue. But at least I can tell you how to implement locking around your |
3623 | queue. But at least I can tell you how to implement locking around your |
2522 | queue: |
3624 | queue: |
2523 | .IP "queueing from a signal handler context" 4 |
3625 | .IP "queueing from a signal handler context" 4 |
2524 | .IX Item "queueing from a signal handler context" |
3626 | .IX Item "queueing from a signal handler context" |
2525 | To implement race-free queueing, you simply add to the queue in the signal |
3627 | To implement race-free queueing, you simply add to the queue in the signal |
2526 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
3628 | handler but you block the signal handler in the watcher callback. Here is |
2527 | some fictitious \s-1SIGUSR1\s0 handler: |
3629 | an example that does that for some fictitious \s-1SIGUSR1\s0 handler: |
2528 | .Sp |
3630 | .Sp |
2529 | .Vb 1 |
3631 | .Vb 1 |
2530 | \& static ev_async mysig; |
3632 | \& static ev_async mysig; |
2531 | \& |
3633 | \& |
2532 | \& static void |
3634 | \& static void |
… | |
… | |
2596 | \fIWatcher-Specific Functions and Data Members\fR |
3698 | \fIWatcher-Specific Functions and Data Members\fR |
2597 | .IX Subsection "Watcher-Specific Functions and Data Members" |
3699 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2598 | .IP "ev_async_init (ev_async *, callback)" 4 |
3700 | .IP "ev_async_init (ev_async *, callback)" 4 |
2599 | .IX Item "ev_async_init (ev_async *, callback)" |
3701 | .IX Item "ev_async_init (ev_async *, callback)" |
2600 | Initialises and configures the async watcher \- it has no parameters of any |
3702 | Initialises and configures the async watcher \- it has no parameters of any |
2601 | kind. There is a \f(CW\*(C`ev_asynd_set\*(C'\fR macro, but using it is utterly pointless, |
3703 | kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless, |
2602 | trust me. |
3704 | trust me. |
2603 | .IP "ev_async_send (loop, ev_async *)" 4 |
3705 | .IP "ev_async_send (loop, ev_async *)" 4 |
2604 | .IX Item "ev_async_send (loop, ev_async *)" |
3706 | .IX Item "ev_async_send (loop, ev_async *)" |
2605 | Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
3707 | Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
2606 | an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike |
3708 | an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop, and instantly |
|
|
3709 | returns. |
|
|
3710 | .Sp |
2607 | \&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, signal or |
3711 | Unlike \f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, |
2608 | similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding |
3712 | signal or similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the |
2609 | section below on what exactly this means). |
3713 | embedding section below on what exactly this means). |
2610 | .Sp |
3714 | .Sp |
2611 | This call incurs the overhead of a system call only once per loop iteration, |
3715 | Note that, as with other watchers in libev, multiple events might get |
2612 | so while the overhead might be noticeable, it doesn't apply to repeated |
3716 | compressed into a single callback invocation (another way to look at |
2613 | calls to \f(CW\*(C`ev_async_send\*(C'\fR. |
3717 | this is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered: they are set on |
|
|
3718 | \&\f(CW\*(C`ev_async_send\*(C'\fR, reset when the event loop detects that). |
|
|
3719 | .Sp |
|
|
3720 | This call incurs the overhead of at most one extra system call per event |
|
|
3721 | loop iteration, if the event loop is blocked, and no syscall at all if |
|
|
3722 | the event loop (or your program) is processing events. That means that |
|
|
3723 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3724 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3725 | zero) under load. |
2614 | .IP "bool = ev_async_pending (ev_async *)" 4 |
3726 | .IP "bool = ev_async_pending (ev_async *)" 4 |
2615 | .IX Item "bool = ev_async_pending (ev_async *)" |
3727 | .IX Item "bool = ev_async_pending (ev_async *)" |
2616 | Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
3728 | Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
2617 | watcher but the event has not yet been processed (or even noted) by the |
3729 | watcher but the event has not yet been processed (or even noted) by the |
2618 | event loop. |
3730 | event loop. |
… | |
… | |
2620 | \&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When |
3732 | \&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When |
2621 | the loop iterates next and checks for the watcher to have become active, |
3733 | the loop iterates next and checks for the watcher to have become active, |
2622 | it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very |
3734 | it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very |
2623 | quickly check whether invoking the loop might be a good idea. |
3735 | quickly check whether invoking the loop might be a good idea. |
2624 | .Sp |
3736 | .Sp |
2625 | Not that this does \fInot\fR check whether the watcher itself is pending, only |
3737 | Not that this does \fInot\fR check whether the watcher itself is pending, |
2626 | whether it has been requested to make this watcher pending. |
3738 | only whether it has been requested to make this watcher pending: there |
|
|
3739 | is a time window between the event loop checking and resetting the async |
|
|
3740 | notification, and the callback being invoked. |
2627 | .SH "OTHER FUNCTIONS" |
3741 | .SH "OTHER FUNCTIONS" |
2628 | .IX Header "OTHER FUNCTIONS" |
3742 | .IX Header "OTHER FUNCTIONS" |
2629 | There are some other functions of possible interest. Described. Here. Now. |
3743 | There are some other functions of possible interest. Described. Here. Now. |
2630 | .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
3744 | .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)" 4 |
2631 | .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
3745 | .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)" |
2632 | This function combines a simple timer and an I/O watcher, calls your |
3746 | This function combines a simple timer and an I/O watcher, calls your |
2633 | callback on whichever event happens first and automatically stop both |
3747 | callback on whichever event happens first and automatically stops both |
2634 | watchers. This is useful if you want to wait for a single event on an fd |
3748 | watchers. This is useful if you want to wait for a single event on an fd |
2635 | or timeout without having to allocate/configure/start/stop/free one or |
3749 | or timeout without having to allocate/configure/start/stop/free one or |
2636 | more watchers yourself. |
3750 | more watchers yourself. |
2637 | .Sp |
3751 | .Sp |
2638 | If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events |
3752 | If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and the |
2639 | is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and |
3753 | \&\f(CW\*(C`events\*(C'\fR argument is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for |
2640 | \&\f(CW\*(C`events\*(C'\fR set will be created and started. |
3754 | the given \f(CW\*(C`fd\*(C'\fR and \f(CW\*(C`events\*(C'\fR set will be created and started. |
2641 | .Sp |
3755 | .Sp |
2642 | If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
3756 | If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
2643 | started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
3757 | started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
2644 | repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of |
3758 | repeat = 0) will be started. \f(CW0\fR is a valid timeout. |
2645 | dubious value. |
|
|
2646 | .Sp |
3759 | .Sp |
2647 | The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets |
3760 | The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and is |
2648 | passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
3761 | passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
2649 | \&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR |
3762 | \&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMER\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR |
2650 | value passed to \f(CW\*(C`ev_once\*(C'\fR: |
3763 | value passed to \f(CW\*(C`ev_once\*(C'\fR. Note that it is possible to receive \fIboth\fR |
|
|
3764 | a timeout and an io event at the same time \- you probably should give io |
|
|
3765 | events precedence. |
|
|
3766 | .Sp |
|
|
3767 | Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO.\s0 |
2651 | .Sp |
3768 | .Sp |
2652 | .Vb 7 |
3769 | .Vb 7 |
2653 | \& static void stdin_ready (int revents, void *arg) |
3770 | \& static void stdin_ready (int revents, void *arg) |
2654 | \& { |
3771 | \& { |
|
|
3772 | \& if (revents & EV_READ) |
|
|
3773 | \& /* stdin might have data for us, joy! */; |
2655 | \& if (revents & EV_TIMEOUT) |
3774 | \& else if (revents & EV_TIMER) |
2656 | \& /* doh, nothing entered */; |
3775 | \& /* doh, nothing entered */; |
2657 | \& else if (revents & EV_READ) |
|
|
2658 | \& /* stdin might have data for us, joy! */; |
|
|
2659 | \& } |
3776 | \& } |
2660 | \& |
3777 | \& |
2661 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3778 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2662 | .Ve |
3779 | .Ve |
2663 | .IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4 |
|
|
2664 | .IX Item "ev_feed_event (ev_loop *, watcher *, int revents)" |
|
|
2665 | Feeds the given event set into the event loop, as if the specified event |
|
|
2666 | had happened for the specified watcher (which must be a pointer to an |
|
|
2667 | initialised but not necessarily started event watcher). |
|
|
2668 | .IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4 |
3780 | .IP "ev_feed_fd_event (loop, int fd, int revents)" 4 |
2669 | .IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)" |
3781 | .IX Item "ev_feed_fd_event (loop, int fd, int revents)" |
2670 | Feed an event on the given fd, as if a file descriptor backend detected |
3782 | Feed an event on the given fd, as if a file descriptor backend detected |
2671 | the given events it. |
3783 | the given events. |
2672 | .IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4 |
3784 | .IP "ev_feed_signal_event (loop, int signum)" 4 |
2673 | .IX Item "ev_feed_signal_event (ev_loop *loop, int signum)" |
3785 | .IX Item "ev_feed_signal_event (loop, int signum)" |
2674 | Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default |
3786 | Feed an event as if the given signal occurred. See also \f(CW\*(C`ev_feed_signal\*(C'\fR, |
2675 | loop!). |
3787 | which is async-safe. |
|
|
3788 | .SH "COMMON OR USEFUL IDIOMS (OR BOTH)" |
|
|
3789 | .IX Header "COMMON OR USEFUL IDIOMS (OR BOTH)" |
|
|
3790 | This section explains some common idioms that are not immediately |
|
|
3791 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3792 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3793 | .SS "\s-1ASSOCIATING CUSTOM DATA WITH A WATCHER\s0" |
|
|
3794 | .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
|
|
3795 | Each watcher has, by default, a \f(CW\*(C`void *data\*(C'\fR member that you can read |
|
|
3796 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3797 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3798 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3799 | data member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
|
|
3800 | data: |
|
|
3801 | .PP |
|
|
3802 | .Vb 7 |
|
|
3803 | \& struct my_io |
|
|
3804 | \& { |
|
|
3805 | \& ev_io io; |
|
|
3806 | \& int otherfd; |
|
|
3807 | \& void *somedata; |
|
|
3808 | \& struct whatever *mostinteresting; |
|
|
3809 | \& }; |
|
|
3810 | \& |
|
|
3811 | \& ... |
|
|
3812 | \& struct my_io w; |
|
|
3813 | \& ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3814 | .Ve |
|
|
3815 | .PP |
|
|
3816 | And since your callback will be called with a pointer to the watcher, you |
|
|
3817 | can cast it back to your own type: |
|
|
3818 | .PP |
|
|
3819 | .Vb 5 |
|
|
3820 | \& static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3821 | \& { |
|
|
3822 | \& struct my_io *w = (struct my_io *)w_; |
|
|
3823 | \& ... |
|
|
3824 | \& } |
|
|
3825 | .Ve |
|
|
3826 | .PP |
|
|
3827 | More interesting and less C\-conformant ways of casting your callback |
|
|
3828 | function type instead have been omitted. |
|
|
3829 | .SS "\s-1BUILDING YOUR OWN COMPOSITE WATCHERS\s0" |
|
|
3830 | .IX Subsection "BUILDING YOUR OWN COMPOSITE WATCHERS" |
|
|
3831 | Another common scenario is to use some data structure with multiple |
|
|
3832 | embedded watchers, in effect creating your own watcher that combines |
|
|
3833 | multiple libev event sources into one \*(L"super-watcher\*(R": |
|
|
3834 | .PP |
|
|
3835 | .Vb 6 |
|
|
3836 | \& struct my_biggy |
|
|
3837 | \& { |
|
|
3838 | \& int some_data; |
|
|
3839 | \& ev_timer t1; |
|
|
3840 | \& ev_timer t2; |
|
|
3841 | \& } |
|
|
3842 | .Ve |
|
|
3843 | .PP |
|
|
3844 | In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more |
|
|
3845 | complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct in |
|
|
3846 | the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies or \*(C+ coders), or you need |
|
|
3847 | to use some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for |
|
|
3848 | real programmers): |
|
|
3849 | .PP |
|
|
3850 | .Vb 1 |
|
|
3851 | \& #include <stddef.h> |
|
|
3852 | \& |
|
|
3853 | \& static void |
|
|
3854 | \& t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3855 | \& { |
|
|
3856 | \& struct my_biggy big = (struct my_biggy *) |
|
|
3857 | \& (((char *)w) \- offsetof (struct my_biggy, t1)); |
|
|
3858 | \& } |
|
|
3859 | \& |
|
|
3860 | \& static void |
|
|
3861 | \& t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3862 | \& { |
|
|
3863 | \& struct my_biggy big = (struct my_biggy *) |
|
|
3864 | \& (((char *)w) \- offsetof (struct my_biggy, t2)); |
|
|
3865 | \& } |
|
|
3866 | .Ve |
|
|
3867 | .SS "\s-1AVOIDING FINISHING BEFORE RETURNING\s0" |
|
|
3868 | .IX Subsection "AVOIDING FINISHING BEFORE RETURNING" |
|
|
3869 | Often you have structures like this in event-based programs: |
|
|
3870 | .PP |
|
|
3871 | .Vb 4 |
|
|
3872 | \& callback () |
|
|
3873 | \& { |
|
|
3874 | \& free (request); |
|
|
3875 | \& } |
|
|
3876 | \& |
|
|
3877 | \& request = start_new_request (..., callback); |
|
|
3878 | .Ve |
|
|
3879 | .PP |
|
|
3880 | The intent is to start some \*(L"lengthy\*(R" operation. The \f(CW\*(C`request\*(C'\fR could be |
|
|
3881 | used to cancel the operation, or do other things with it. |
|
|
3882 | .PP |
|
|
3883 | It's not uncommon to have code paths in \f(CW\*(C`start_new_request\*(C'\fR that |
|
|
3884 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3885 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3886 | operation and simply invoke the callback with the result. |
|
|
3887 | .PP |
|
|
3888 | The problem here is that this will happen \fIbefore\fR \f(CW\*(C`start_new_request\*(C'\fR |
|
|
3889 | has returned, so \f(CW\*(C`request\*(C'\fR is not set. |
|
|
3890 | .PP |
|
|
3891 | Even if you pass the request by some safer means to the callback, you |
|
|
3892 | might want to do something to the request after starting it, such as |
|
|
3893 | canceling it, which probably isn't working so well when the callback has |
|
|
3894 | already been invoked. |
|
|
3895 | .PP |
|
|
3896 | A common way around all these issues is to make sure that |
|
|
3897 | \&\f(CW\*(C`start_new_request\*(C'\fR \fIalways\fR returns before the callback is invoked. If |
|
|
3898 | \&\f(CW\*(C`start_new_request\*(C'\fR immediately knows the result, it can artificially |
|
|
3899 | delay invoking the callback by using a \f(CW\*(C`prepare\*(C'\fR or \f(CW\*(C`idle\*(C'\fR watcher for |
|
|
3900 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3901 | pushing it into the pending queue: |
|
|
3902 | .PP |
|
|
3903 | .Vb 2 |
|
|
3904 | \& ev_set_cb (watcher, callback); |
|
|
3905 | \& ev_feed_event (EV_A_ watcher, 0); |
|
|
3906 | .Ve |
|
|
3907 | .PP |
|
|
3908 | This way, \f(CW\*(C`start_new_request\*(C'\fR can safely return before the callback is |
|
|
3909 | invoked, while not delaying callback invocation too much. |
|
|
3910 | .SS "\s-1MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS\s0" |
|
|
3911 | .IX Subsection "MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS" |
|
|
3912 | Often (especially in \s-1GUI\s0 toolkits) there are places where you have |
|
|
3913 | \&\fImodal\fR interaction, which is most easily implemented by recursively |
|
|
3914 | invoking \f(CW\*(C`ev_run\*(C'\fR. |
|
|
3915 | .PP |
|
|
3916 | This brings the problem of exiting \- a callback might want to finish the |
|
|
3917 | main \f(CW\*(C`ev_run\*(C'\fR call, but not the nested one (e.g. user clicked \*(L"Quit\*(R", but |
|
|
3918 | a modal \*(L"Are you sure?\*(R" dialog is still waiting), or just the nested one |
|
|
3919 | and not the main one (e.g. user clocked \*(L"Ok\*(R" in a modal dialog), or some |
|
|
3920 | other combination: In these cases, a simple \f(CW\*(C`ev_break\*(C'\fR will not work. |
|
|
3921 | .PP |
|
|
3922 | The solution is to maintain \*(L"break this loop\*(R" variable for each \f(CW\*(C`ev_run\*(C'\fR |
|
|
3923 | invocation, and use a loop around \f(CW\*(C`ev_run\*(C'\fR until the condition is |
|
|
3924 | triggered, using \f(CW\*(C`EVRUN_ONCE\*(C'\fR: |
|
|
3925 | .PP |
|
|
3926 | .Vb 2 |
|
|
3927 | \& // main loop |
|
|
3928 | \& int exit_main_loop = 0; |
|
|
3929 | \& |
|
|
3930 | \& while (!exit_main_loop) |
|
|
3931 | \& ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3932 | \& |
|
|
3933 | \& // in a modal watcher |
|
|
3934 | \& int exit_nested_loop = 0; |
|
|
3935 | \& |
|
|
3936 | \& while (!exit_nested_loop) |
|
|
3937 | \& ev_run (EV_A_ EVRUN_ONCE); |
|
|
3938 | .Ve |
|
|
3939 | .PP |
|
|
3940 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3941 | .PP |
|
|
3942 | .Vb 2 |
|
|
3943 | \& // exit modal loop |
|
|
3944 | \& exit_nested_loop = 1; |
|
|
3945 | \& |
|
|
3946 | \& // exit main program, after modal loop is finished |
|
|
3947 | \& exit_main_loop = 1; |
|
|
3948 | \& |
|
|
3949 | \& // exit both |
|
|
3950 | \& exit_main_loop = exit_nested_loop = 1; |
|
|
3951 | .Ve |
|
|
3952 | .SS "\s-1THREAD LOCKING EXAMPLE\s0" |
|
|
3953 | .IX Subsection "THREAD LOCKING EXAMPLE" |
|
|
3954 | Here is a fictitious example of how to run an event loop in a different |
|
|
3955 | thread from where callbacks are being invoked and watchers are |
|
|
3956 | created/added/removed. |
|
|
3957 | .PP |
|
|
3958 | For a real-world example, see the \f(CW\*(C`EV::Loop::Async\*(C'\fR perl module, |
|
|
3959 | which uses exactly this technique (which is suited for many high-level |
|
|
3960 | languages). |
|
|
3961 | .PP |
|
|
3962 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3963 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3964 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3965 | .PP |
|
|
3966 | First, you need to associate some data with the event loop: |
|
|
3967 | .PP |
|
|
3968 | .Vb 6 |
|
|
3969 | \& typedef struct { |
|
|
3970 | \& mutex_t lock; /* global loop lock */ |
|
|
3971 | \& ev_async async_w; |
|
|
3972 | \& thread_t tid; |
|
|
3973 | \& cond_t invoke_cv; |
|
|
3974 | \& } userdata; |
|
|
3975 | \& |
|
|
3976 | \& void prepare_loop (EV_P) |
|
|
3977 | \& { |
|
|
3978 | \& // for simplicity, we use a static userdata struct. |
|
|
3979 | \& static userdata u; |
|
|
3980 | \& |
|
|
3981 | \& ev_async_init (&u\->async_w, async_cb); |
|
|
3982 | \& ev_async_start (EV_A_ &u\->async_w); |
|
|
3983 | \& |
|
|
3984 | \& pthread_mutex_init (&u\->lock, 0); |
|
|
3985 | \& pthread_cond_init (&u\->invoke_cv, 0); |
|
|
3986 | \& |
|
|
3987 | \& // now associate this with the loop |
|
|
3988 | \& ev_set_userdata (EV_A_ u); |
|
|
3989 | \& ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3990 | \& ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3991 | \& |
|
|
3992 | \& // then create the thread running ev_run |
|
|
3993 | \& pthread_create (&u\->tid, 0, l_run, EV_A); |
|
|
3994 | \& } |
|
|
3995 | .Ve |
|
|
3996 | .PP |
|
|
3997 | The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used |
|
|
3998 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3999 | that might have been added: |
|
|
4000 | .PP |
|
|
4001 | .Vb 5 |
|
|
4002 | \& static void |
|
|
4003 | \& async_cb (EV_P_ ev_async *w, int revents) |
|
|
4004 | \& { |
|
|
4005 | \& // just used for the side effects |
|
|
4006 | \& } |
|
|
4007 | .Ve |
|
|
4008 | .PP |
|
|
4009 | The \f(CW\*(C`l_release\*(C'\fR and \f(CW\*(C`l_acquire\*(C'\fR callbacks simply unlock/lock the mutex |
|
|
4010 | protecting the loop data, respectively. |
|
|
4011 | .PP |
|
|
4012 | .Vb 6 |
|
|
4013 | \& static void |
|
|
4014 | \& l_release (EV_P) |
|
|
4015 | \& { |
|
|
4016 | \& userdata *u = ev_userdata (EV_A); |
|
|
4017 | \& pthread_mutex_unlock (&u\->lock); |
|
|
4018 | \& } |
|
|
4019 | \& |
|
|
4020 | \& static void |
|
|
4021 | \& l_acquire (EV_P) |
|
|
4022 | \& { |
|
|
4023 | \& userdata *u = ev_userdata (EV_A); |
|
|
4024 | \& pthread_mutex_lock (&u\->lock); |
|
|
4025 | \& } |
|
|
4026 | .Ve |
|
|
4027 | .PP |
|
|
4028 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4029 | into \f(CW\*(C`ev_run\*(C'\fR: |
|
|
4030 | .PP |
|
|
4031 | .Vb 4 |
|
|
4032 | \& void * |
|
|
4033 | \& l_run (void *thr_arg) |
|
|
4034 | \& { |
|
|
4035 | \& struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4036 | \& |
|
|
4037 | \& l_acquire (EV_A); |
|
|
4038 | \& pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4039 | \& ev_run (EV_A_ 0); |
|
|
4040 | \& l_release (EV_A); |
|
|
4041 | \& |
|
|
4042 | \& return 0; |
|
|
4043 | \& } |
|
|
4044 | .Ve |
|
|
4045 | .PP |
|
|
4046 | Instead of invoking all pending watchers, the \f(CW\*(C`l_invoke\*(C'\fR callback will |
|
|
4047 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4048 | writes? \f(CW\*(C`Async::Interrupt\*(C'\fR?) and then waits until all pending watchers |
|
|
4049 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4050 | and b) skipping inter-thread-communication when there are no pending |
|
|
4051 | watchers is very beneficial): |
|
|
4052 | .PP |
|
|
4053 | .Vb 4 |
|
|
4054 | \& static void |
|
|
4055 | \& l_invoke (EV_P) |
|
|
4056 | \& { |
|
|
4057 | \& userdata *u = ev_userdata (EV_A); |
|
|
4058 | \& |
|
|
4059 | \& while (ev_pending_count (EV_A)) |
|
|
4060 | \& { |
|
|
4061 | \& wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4062 | \& pthread_cond_wait (&u\->invoke_cv, &u\->lock); |
|
|
4063 | \& } |
|
|
4064 | \& } |
|
|
4065 | .Ve |
|
|
4066 | .PP |
|
|
4067 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4068 | will grab the lock, call \f(CW\*(C`ev_invoke_pending\*(C'\fR and then signal the loop |
|
|
4069 | thread to continue: |
|
|
4070 | .PP |
|
|
4071 | .Vb 4 |
|
|
4072 | \& static void |
|
|
4073 | \& real_invoke_pending (EV_P) |
|
|
4074 | \& { |
|
|
4075 | \& userdata *u = ev_userdata (EV_A); |
|
|
4076 | \& |
|
|
4077 | \& pthread_mutex_lock (&u\->lock); |
|
|
4078 | \& ev_invoke_pending (EV_A); |
|
|
4079 | \& pthread_cond_signal (&u\->invoke_cv); |
|
|
4080 | \& pthread_mutex_unlock (&u\->lock); |
|
|
4081 | \& } |
|
|
4082 | .Ve |
|
|
4083 | .PP |
|
|
4084 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4085 | event loop, you will now have to lock: |
|
|
4086 | .PP |
|
|
4087 | .Vb 2 |
|
|
4088 | \& ev_timer timeout_watcher; |
|
|
4089 | \& userdata *u = ev_userdata (EV_A); |
|
|
4090 | \& |
|
|
4091 | \& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4092 | \& |
|
|
4093 | \& pthread_mutex_lock (&u\->lock); |
|
|
4094 | \& ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4095 | \& ev_async_send (EV_A_ &u\->async_w); |
|
|
4096 | \& pthread_mutex_unlock (&u\->lock); |
|
|
4097 | .Ve |
|
|
4098 | .PP |
|
|
4099 | Note that sending the \f(CW\*(C`ev_async\*(C'\fR watcher is required because otherwise |
|
|
4100 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4101 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4102 | watchers in the next event loop iteration. |
|
|
4103 | .SS "\s-1THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS\s0" |
|
|
4104 | .IX Subsection "THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS" |
|
|
4105 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
4106 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
4107 | kind of threads or coroutines, you might want to customise libev so that |
|
|
4108 | doesn't need callbacks anymore. |
|
|
4109 | .PP |
|
|
4110 | Imagine you have coroutines that you can switch to using a function |
|
|
4111 | \&\f(CW\*(C`switch_to (coro)\*(C'\fR, that libev runs in a coroutine called \f(CW\*(C`libev_coro\*(C'\fR |
|
|
4112 | and that due to some magic, the currently active coroutine is stored in a |
|
|
4113 | global called \f(CW\*(C`current_coro\*(C'\fR. Then you can build your own \*(L"wait for libev |
|
|
4114 | event\*(R" primitive by changing \f(CW\*(C`EV_CB_DECLARE\*(C'\fR and \f(CW\*(C`EV_CB_INVOKE\*(C'\fR (note |
|
|
4115 | the differing \f(CW\*(C`;\*(C'\fR conventions): |
|
|
4116 | .PP |
|
|
4117 | .Vb 2 |
|
|
4118 | \& #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
4119 | \& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb) |
|
|
4120 | .Ve |
|
|
4121 | .PP |
|
|
4122 | That means instead of having a C callback function, you store the |
|
|
4123 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
4124 | your callback, you instead have it switch to that coroutine. |
|
|
4125 | .PP |
|
|
4126 | A coroutine might now wait for an event with a function called |
|
|
4127 | \&\f(CW\*(C`wait_for_event\*(C'\fR. (the watcher needs to be started, as always, but it doesn't |
|
|
4128 | matter when, or whether the watcher is active or not when this function is |
|
|
4129 | called): |
|
|
4130 | .PP |
|
|
4131 | .Vb 6 |
|
|
4132 | \& void |
|
|
4133 | \& wait_for_event (ev_watcher *w) |
|
|
4134 | \& { |
|
|
4135 | \& ev_set_cb (w, current_coro); |
|
|
4136 | \& switch_to (libev_coro); |
|
|
4137 | \& } |
|
|
4138 | .Ve |
|
|
4139 | .PP |
|
|
4140 | That basically suspends the coroutine inside \f(CW\*(C`wait_for_event\*(C'\fR and |
|
|
4141 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
4142 | this or any other coroutine. |
|
|
4143 | .PP |
|
|
4144 | You can do similar tricks if you have, say, threads with an event queue \- |
|
|
4145 | instead of storing a coroutine, you store the queue object and instead of |
|
|
4146 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
4147 | any waiters. |
|
|
4148 | .PP |
|
|
4149 | To embed libev, see \*(L"\s-1EMBEDDING\*(R"\s0, but in short, it's easiest to create two |
|
|
4150 | files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files: |
|
|
4151 | .PP |
|
|
4152 | .Vb 4 |
|
|
4153 | \& // my_ev.h |
|
|
4154 | \& #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
4155 | \& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb) |
|
|
4156 | \& #include "../libev/ev.h" |
|
|
4157 | \& |
|
|
4158 | \& // my_ev.c |
|
|
4159 | \& #define EV_H "my_ev.h" |
|
|
4160 | \& #include "../libev/ev.c" |
|
|
4161 | .Ve |
|
|
4162 | .PP |
|
|
4163 | And then use \fImy_ev.h\fR when you would normally use \fIev.h\fR, and compile |
|
|
4164 | \&\fImy_ev.c\fR into your project. When properly specifying include paths, you |
|
|
4165 | can even use \fIev.h\fR as header file name directly. |
2676 | .SH "LIBEVENT EMULATION" |
4166 | .SH "LIBEVENT EMULATION" |
2677 | .IX Header "LIBEVENT EMULATION" |
4167 | .IX Header "LIBEVENT EMULATION" |
2678 | Libev offers a compatibility emulation layer for libevent. It cannot |
4168 | Libev offers a compatibility emulation layer for libevent. It cannot |
2679 | emulate the internals of libevent, so here are some usage hints: |
4169 | emulate the internals of libevent, so here are some usage hints: |
|
|
4170 | .IP "\(bu" 4 |
|
|
4171 | Only the libevent\-1.4.1\-beta \s-1API\s0 is being emulated. |
|
|
4172 | .Sp |
|
|
4173 | This was the newest libevent version available when libev was implemented, |
|
|
4174 | and is still mostly unchanged in 2010. |
2680 | .IP "\(bu" 4 |
4175 | .IP "\(bu" 4 |
2681 | Use it by including <event.h>, as usual. |
4176 | Use it by including <event.h>, as usual. |
2682 | .IP "\(bu" 4 |
4177 | .IP "\(bu" 4 |
2683 | The following members are fully supported: ev_base, ev_callback, |
4178 | The following members are fully supported: ev_base, ev_callback, |
2684 | ev_arg, ev_fd, ev_res, ev_events. |
4179 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
2690 | Priorities are not currently supported. Initialising priorities |
4185 | Priorities are not currently supported. Initialising priorities |
2691 | will fail and all watchers will have the same priority, even though there |
4186 | will fail and all watchers will have the same priority, even though there |
2692 | is an ev_pri field. |
4187 | is an ev_pri field. |
2693 | .IP "\(bu" 4 |
4188 | .IP "\(bu" 4 |
2694 | In libevent, the last base created gets the signals, in libev, the |
4189 | In libevent, the last base created gets the signals, in libev, the |
2695 | first base created (== the default loop) gets the signals. |
4190 | base that registered the signal gets the signals. |
2696 | .IP "\(bu" 4 |
4191 | .IP "\(bu" 4 |
2697 | Other members are not supported. |
4192 | Other members are not supported. |
2698 | .IP "\(bu" 4 |
4193 | .IP "\(bu" 4 |
2699 | The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need |
4194 | The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need |
2700 | to use the libev header file and library. |
4195 | to use the libev header file and library. |
2701 | .SH "\*(C+ SUPPORT" |
4196 | .SH "\*(C+ SUPPORT" |
2702 | .IX Header " SUPPORT" |
4197 | .IX Header " SUPPORT" |
|
|
4198 | .SS "C \s-1API\s0" |
|
|
4199 | .IX Subsection "C API" |
|
|
4200 | The normal C \s-1API\s0 should work fine when used from \*(C+: both ev.h and the |
|
|
4201 | libev sources can be compiled as \*(C+. Therefore, code that uses the C \s-1API\s0 |
|
|
4202 | will work fine. |
|
|
4203 | .PP |
|
|
4204 | Proper exception specifications might have to be added to callbacks passed |
|
|
4205 | to libev: exceptions may be thrown only from watcher callbacks, all other |
|
|
4206 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
|
|
4207 | callbacks) must not throw exceptions, and might need a \f(CW\*(C`noexcept\*(C'\fR |
|
|
4208 | specification. If you have code that needs to be compiled as both C and |
|
|
4209 | \&\*(C+ you can use the \f(CW\*(C`EV_NOEXCEPT\*(C'\fR macro for this: |
|
|
4210 | .PP |
|
|
4211 | .Vb 6 |
|
|
4212 | \& static void |
|
|
4213 | \& fatal_error (const char *msg) EV_NOEXCEPT |
|
|
4214 | \& { |
|
|
4215 | \& perror (msg); |
|
|
4216 | \& abort (); |
|
|
4217 | \& } |
|
|
4218 | \& |
|
|
4219 | \& ... |
|
|
4220 | \& ev_set_syserr_cb (fatal_error); |
|
|
4221 | .Ve |
|
|
4222 | .PP |
|
|
4223 | The only \s-1API\s0 functions that can currently throw exceptions are \f(CW\*(C`ev_run\*(C'\fR, |
|
|
4224 | \&\f(CW\*(C`ev_invoke\*(C'\fR, \f(CW\*(C`ev_invoke_pending\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR (the latter |
|
|
4225 | because it runs cleanup watchers). |
|
|
4226 | .PP |
|
|
4227 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
4228 | is compiled with a \*(C+ compiler or your C and \*(C+ environments allow |
|
|
4229 | throwing exceptions through C libraries (most do). |
|
|
4230 | .SS "\*(C+ \s-1API\s0" |
|
|
4231 | .IX Subsection " API" |
2703 | Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow |
4232 | Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow |
2704 | you to use some convenience methods to start/stop watchers and also change |
4233 | you to use some convenience methods to start/stop watchers and also change |
2705 | the callback model to a model using method callbacks on objects. |
4234 | the callback model to a model using method callbacks on objects. |
2706 | .PP |
4235 | .PP |
2707 | To use it, |
4236 | To use it, |
… | |
… | |
2718 | Care has been taken to keep the overhead low. The only data member the \*(C+ |
4247 | Care has been taken to keep the overhead low. The only data member the \*(C+ |
2719 | classes add (compared to plain C\-style watchers) is the event loop pointer |
4248 | classes add (compared to plain C\-style watchers) is the event loop pointer |
2720 | that the watcher is associated with (or no additional members at all if |
4249 | that the watcher is associated with (or no additional members at all if |
2721 | you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev). |
4250 | you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev). |
2722 | .PP |
4251 | .PP |
2723 | Currently, functions, and static and non-static member functions can be |
4252 | Currently, functions, static and non-static member functions and classes |
2724 | used as callbacks. Other types should be easy to add as long as they only |
4253 | with \f(CW\*(C`operator ()\*(C'\fR can be used as callbacks. Other types should be easy |
2725 | need one additional pointer for context. If you need support for other |
4254 | to add as long as they only need one additional pointer for context. If |
2726 | types of functors please contact the author (preferably after implementing |
4255 | you need support for other types of functors please contact the author |
2727 | it). |
4256 | (preferably after implementing it). |
|
|
4257 | .PP |
|
|
4258 | For all this to work, your \*(C+ compiler either has to use the same calling |
|
|
4259 | conventions as your C compiler (for static member functions), or you have |
|
|
4260 | to embed libev and compile libev itself as \*(C+. |
2728 | .PP |
4261 | .PP |
2729 | Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
4262 | Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
2730 | .ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 |
4263 | .ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4 |
2731 | .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
4264 | .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
2732 | .IX Item "ev::READ, ev::WRITE etc." |
4265 | .IX Item "ev::READ, ev::WRITE etc." |
2733 | These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. |
4266 | These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. |
2734 | macros from \fIev.h\fR. |
4267 | macros from \fIev.h\fR. |
2735 | .ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4 |
4268 | .ie n .IP """ev::tstamp"", ""ev::now""" 4 |
2736 | .el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 |
4269 | .el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 |
2737 | .IX Item "ev::tstamp, ev::now" |
4270 | .IX Item "ev::tstamp, ev::now" |
2738 | Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. |
4271 | Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. |
2739 | .ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4 |
4272 | .ie n .IP """ev::io"", ""ev::timer"", ""ev::periodic"", ""ev::idle"", ""ev::sig"" etc." 4 |
2740 | .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
4273 | .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
2741 | .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
4274 | .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
2742 | For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
4275 | For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
2743 | the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
4276 | the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
2744 | which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
4277 | which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
2745 | defines by many implementations. |
4278 | defined by many implementations. |
2746 | .Sp |
4279 | .Sp |
2747 | All of those classes have these methods: |
4280 | All of those classes have these methods: |
2748 | .RS 4 |
4281 | .RS 4 |
2749 | .IP "ev::TYPE::TYPE ()" 4 |
4282 | .IP "ev::TYPE::TYPE ()" 4 |
2750 | .IX Item "ev::TYPE::TYPE ()" |
4283 | .IX Item "ev::TYPE::TYPE ()" |
2751 | .PD 0 |
4284 | .PD 0 |
2752 | .IP "ev::TYPE::TYPE (struct ev_loop *)" 4 |
4285 | .IP "ev::TYPE::TYPE (loop)" 4 |
2753 | .IX Item "ev::TYPE::TYPE (struct ev_loop *)" |
4286 | .IX Item "ev::TYPE::TYPE (loop)" |
2754 | .IP "ev::TYPE::~TYPE" 4 |
4287 | .IP "ev::TYPE::~TYPE" 4 |
2755 | .IX Item "ev::TYPE::~TYPE" |
4288 | .IX Item "ev::TYPE::~TYPE" |
2756 | .PD |
4289 | .PD |
2757 | The constructor (optionally) takes an event loop to associate the watcher |
4290 | The constructor (optionally) takes an event loop to associate the watcher |
2758 | with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR. |
4291 | with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR. |
… | |
… | |
2790 | \& |
4323 | \& |
2791 | \& myclass obj; |
4324 | \& myclass obj; |
2792 | \& ev::io iow; |
4325 | \& ev::io iow; |
2793 | \& iow.set <myclass, &myclass::io_cb> (&obj); |
4326 | \& iow.set <myclass, &myclass::io_cb> (&obj); |
2794 | .Ve |
4327 | .Ve |
|
|
4328 | .IP "w\->set (object *)" 4 |
|
|
4329 | .IX Item "w->set (object *)" |
|
|
4330 | This is a variation of a method callback \- leaving out the method to call |
|
|
4331 | will default the method to \f(CW\*(C`operator ()\*(C'\fR, which makes it possible to use |
|
|
4332 | functor objects without having to manually specify the \f(CW\*(C`operator ()\*(C'\fR all |
|
|
4333 | the time. Incidentally, you can then also leave out the template argument |
|
|
4334 | list. |
|
|
4335 | .Sp |
|
|
4336 | The \f(CW\*(C`operator ()\*(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w, |
|
|
4337 | int revents)\*(C'\fR. |
|
|
4338 | .Sp |
|
|
4339 | See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
|
|
4340 | .Sp |
|
|
4341 | Example: use a functor object as callback. |
|
|
4342 | .Sp |
|
|
4343 | .Vb 7 |
|
|
4344 | \& struct myfunctor |
|
|
4345 | \& { |
|
|
4346 | \& void operator() (ev::io &w, int revents) |
|
|
4347 | \& { |
|
|
4348 | \& ... |
|
|
4349 | \& } |
|
|
4350 | \& } |
|
|
4351 | \& |
|
|
4352 | \& myfunctor f; |
|
|
4353 | \& |
|
|
4354 | \& ev::io w; |
|
|
4355 | \& w.set (&f); |
|
|
4356 | .Ve |
2795 | .IP "w\->set<function> (void *data = 0)" 4 |
4357 | .IP "w\->set<function> (void *data = 0)" 4 |
2796 | .IX Item "w->set<function> (void *data = 0)" |
4358 | .IX Item "w->set<function> (void *data = 0)" |
2797 | Also sets a callback, but uses a static method or plain function as |
4359 | Also sets a callback, but uses a static method or plain function as |
2798 | callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's |
4360 | callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's |
2799 | \&\f(CW\*(C`data\*(C'\fR member and is free for you to use. |
4361 | \&\f(CW\*(C`data\*(C'\fR member and is free for you to use. |
… | |
… | |
2806 | .Sp |
4368 | .Sp |
2807 | .Vb 2 |
4369 | .Vb 2 |
2808 | \& static void io_cb (ev::io &w, int revents) { } |
4370 | \& static void io_cb (ev::io &w, int revents) { } |
2809 | \& iow.set <io_cb> (); |
4371 | \& iow.set <io_cb> (); |
2810 | .Ve |
4372 | .Ve |
2811 | .IP "w\->set (struct ev_loop *)" 4 |
4373 | .IP "w\->set (loop)" 4 |
2812 | .IX Item "w->set (struct ev_loop *)" |
4374 | .IX Item "w->set (loop)" |
2813 | Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only |
4375 | Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only |
2814 | do this when the watcher is inactive (and not pending either). |
4376 | do this when the watcher is inactive (and not pending either). |
2815 | .IP "w\->set ([arguments])" 4 |
4377 | .IP "w\->set ([arguments])" 4 |
2816 | .IX Item "w->set ([arguments])" |
4378 | .IX Item "w->set ([arguments])" |
2817 | Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same arguments. Must be |
4379 | Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR (except for \f(CW\*(C`ev::embed\*(C'\fR watchers>), |
|
|
4380 | with the same arguments. Either this method or a suitable start method |
2818 | called at least once. Unlike the C counterpart, an active watcher gets |
4381 | must be called at least once. Unlike the C counterpart, an active watcher |
2819 | automatically stopped and restarted when reconfiguring it with this |
4382 | gets automatically stopped and restarted when reconfiguring it with this |
2820 | method. |
4383 | method. |
|
|
4384 | .Sp |
|
|
4385 | For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid |
|
|
4386 | clashing with the \f(CW\*(C`set (loop)\*(C'\fR method. |
2821 | .IP "w\->start ()" 4 |
4387 | .IP "w\->start ()" 4 |
2822 | .IX Item "w->start ()" |
4388 | .IX Item "w->start ()" |
2823 | Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the |
4389 | Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the |
2824 | constructor already stores the event loop. |
4390 | constructor already stores the event loop. |
|
|
4391 | .IP "w\->start ([arguments])" 4 |
|
|
4392 | .IX Item "w->start ([arguments])" |
|
|
4393 | Instead of calling \f(CW\*(C`set\*(C'\fR and \f(CW\*(C`start\*(C'\fR methods separately, it is often |
|
|
4394 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
4395 | the configure \f(CW\*(C`set\*(C'\fR method of the watcher. |
2825 | .IP "w\->stop ()" 4 |
4396 | .IP "w\->stop ()" 4 |
2826 | .IX Item "w->stop ()" |
4397 | .IX Item "w->stop ()" |
2827 | Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. |
4398 | Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. |
2828 | .ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4 |
4399 | .ie n .IP "w\->again () (""ev::timer"", ""ev::periodic"" only)" 4 |
2829 | .el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4 |
4400 | .el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4 |
2830 | .IX Item "w->again () (ev::timer, ev::periodic only)" |
4401 | .IX Item "w->again () (ev::timer, ev::periodic only)" |
2831 | For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding |
4402 | For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding |
2832 | \&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. |
4403 | \&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. |
2833 | .ie n .IP "w\->sweep () (""ev::embed"" only)" 4 |
4404 | .ie n .IP "w\->sweep () (""ev::embed"" only)" 4 |
… | |
… | |
2840 | Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. |
4411 | Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. |
2841 | .RE |
4412 | .RE |
2842 | .RS 4 |
4413 | .RS 4 |
2843 | .RE |
4414 | .RE |
2844 | .PP |
4415 | .PP |
2845 | Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in |
4416 | Example: Define a class with two I/O and idle watchers, start the I/O |
2846 | the constructor. |
4417 | watchers in the constructor. |
2847 | .PP |
4418 | .PP |
2848 | .Vb 4 |
4419 | .Vb 5 |
2849 | \& class myclass |
4420 | \& class myclass |
2850 | \& { |
4421 | \& { |
2851 | \& ev::io io ; void io_cb (ev::io &w, int revents); |
4422 | \& ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
4423 | \& ev::io io2 ; void io2_cb (ev::io &w, int revents); |
2852 | \& ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4424 | \& ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2853 | \& |
4425 | \& |
2854 | \& myclass (int fd) |
4426 | \& myclass (int fd) |
2855 | \& { |
4427 | \& { |
2856 | \& io .set <myclass, &myclass::io_cb > (this); |
4428 | \& io .set <myclass, &myclass::io_cb > (this); |
|
|
4429 | \& io2 .set <myclass, &myclass::io2_cb > (this); |
2857 | \& idle.set <myclass, &myclass::idle_cb> (this); |
4430 | \& idle.set <myclass, &myclass::idle_cb> (this); |
2858 | \& |
4431 | \& |
2859 | \& io.start (fd, ev::READ); |
4432 | \& io.set (fd, ev::WRITE); // configure the watcher |
|
|
4433 | \& io.start (); // start it whenever convenient |
|
|
4434 | \& |
|
|
4435 | \& io2.start (fd, ev::READ); // set + start in one call |
2860 | \& } |
4436 | \& } |
2861 | \& }; |
4437 | \& }; |
2862 | .Ve |
4438 | .Ve |
2863 | .SH "OTHER LANGUAGE BINDINGS" |
4439 | .SH "OTHER LANGUAGE BINDINGS" |
2864 | .IX Header "OTHER LANGUAGE BINDINGS" |
4440 | .IX Header "OTHER LANGUAGE BINDINGS" |
… | |
… | |
2873 | there are additional modules that implement libev-compatible interfaces |
4449 | there are additional modules that implement libev-compatible interfaces |
2874 | to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR, but \f(CW\*(C`AnyEvent::DNS\*(C'\fR is preferred nowadays), |
4450 | to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR, but \f(CW\*(C`AnyEvent::DNS\*(C'\fR is preferred nowadays), |
2875 | \&\f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the \f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR |
4451 | \&\f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the \f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR |
2876 | and \f(CW\*(C`EV::Glib\*(C'\fR). |
4452 | and \f(CW\*(C`EV::Glib\*(C'\fR). |
2877 | .Sp |
4453 | .Sp |
2878 | It can be found and installed via \s-1CPAN\s0, its homepage is at |
4454 | It can be found and installed via \s-1CPAN,\s0 its homepage is at |
2879 | <http://software.schmorp.de/pkg/EV>. |
4455 | <http://software.schmorp.de/pkg/EV>. |
2880 | .IP "Python" 4 |
4456 | .IP "Python" 4 |
2881 | .IX Item "Python" |
4457 | .IX Item "Python" |
2882 | Python bindings can be found at <http://code.google.com/p/pyev/>. It |
4458 | Python bindings can be found at <http://code.google.com/p/pyev/>. It |
2883 | seems to be quite complete and well-documented. Note, however, that the |
4459 | seems to be quite complete and well-documented. |
2884 | patch they require for libev is outright dangerous as it breaks the \s-1ABI\s0 |
|
|
2885 | for everybody else, and therefore, should never be applied in an installed |
|
|
2886 | libev (if python requires an incompatible \s-1ABI\s0 then it needs to embed |
|
|
2887 | libev). |
|
|
2888 | .IP "Ruby" 4 |
4460 | .IP "Ruby" 4 |
2889 | .IX Item "Ruby" |
4461 | .IX Item "Ruby" |
2890 | Tony Arcieri has written a ruby extension that offers access to a subset |
4462 | Tony Arcieri has written a ruby extension that offers access to a subset |
2891 | of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and |
4463 | of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and |
2892 | more on top of it. It can be found via gem servers. Its homepage is at |
4464 | more on top of it. It can be found via gem servers. Its homepage is at |
2893 | <http://rev.rubyforge.org/>. |
4465 | <http://rev.rubyforge.org/>. |
|
|
4466 | .Sp |
|
|
4467 | Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR |
|
|
4468 | makes rev work even on mingw. |
|
|
4469 | .IP "Haskell" 4 |
|
|
4470 | .IX Item "Haskell" |
|
|
4471 | A haskell binding to libev is available at |
|
|
4472 | <http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev>. |
2894 | .IP "D" 4 |
4473 | .IP "D" 4 |
2895 | .IX Item "D" |
4474 | .IX Item "D" |
2896 | Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
4475 | Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
2897 | be found at <http://proj.llucax.com.ar/wiki/evd>. |
4476 | be found at <http://www.llucax.com.ar/proj/ev.d/index.html>. |
|
|
4477 | .IP "Ocaml" 4 |
|
|
4478 | .IX Item "Ocaml" |
|
|
4479 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
4480 | <http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>. |
|
|
4481 | .IP "Lua" 4 |
|
|
4482 | .IX Item "Lua" |
|
|
4483 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
4484 | time of this writing, only \f(CW\*(C`ev_io\*(C'\fR and \f(CW\*(C`ev_timer\*(C'\fR), to be found at |
|
|
4485 | <http://github.com/brimworks/lua\-ev>. |
|
|
4486 | .IP "Javascript" 4 |
|
|
4487 | .IX Item "Javascript" |
|
|
4488 | Node.js (<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4489 | .IP "Others" 4 |
|
|
4490 | .IX Item "Others" |
|
|
4491 | There are others, and I stopped counting. |
2898 | .SH "MACRO MAGIC" |
4492 | .SH "MACRO MAGIC" |
2899 | .IX Header "MACRO MAGIC" |
4493 | .IX Header "MACRO MAGIC" |
2900 | Libev can be compiled with a variety of options, the most fundamental |
4494 | Libev can be compiled with a variety of options, the most fundamental |
2901 | of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
4495 | of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
2902 | functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
4496 | functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
2903 | .PP |
4497 | .PP |
2904 | To make it easier to write programs that cope with either variant, the |
4498 | To make it easier to write programs that cope with either variant, the |
2905 | following macros are defined: |
4499 | following macros are defined: |
2906 | .ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4 |
4500 | .ie n .IP """EV_A"", ""EV_A_""" 4 |
2907 | .el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 |
4501 | .el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 |
2908 | .IX Item "EV_A, EV_A_" |
4502 | .IX Item "EV_A, EV_A_" |
2909 | This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev |
4503 | This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev |
2910 | loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, |
4504 | loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, |
2911 | \&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: |
4505 | \&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: |
2912 | .Sp |
4506 | .Sp |
2913 | .Vb 3 |
4507 | .Vb 3 |
2914 | \& ev_unref (EV_A); |
4508 | \& ev_unref (EV_A); |
2915 | \& ev_timer_add (EV_A_ watcher); |
4509 | \& ev_timer_add (EV_A_ watcher); |
2916 | \& ev_loop (EV_A_ 0); |
4510 | \& ev_run (EV_A_ 0); |
2917 | .Ve |
4511 | .Ve |
2918 | .Sp |
4512 | .Sp |
2919 | It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, |
4513 | It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, |
2920 | which is often provided by the following macro. |
4514 | which is often provided by the following macro. |
2921 | .ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4 |
4515 | .ie n .IP """EV_P"", ""EV_P_""" 4 |
2922 | .el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 |
4516 | .el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 |
2923 | .IX Item "EV_P, EV_P_" |
4517 | .IX Item "EV_P, EV_P_" |
2924 | This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev |
4518 | This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev |
2925 | loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, |
4519 | loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, |
2926 | \&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: |
4520 | \&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: |
… | |
… | |
2933 | \& static void cb (EV_P_ ev_timer *w, int revents) |
4527 | \& static void cb (EV_P_ ev_timer *w, int revents) |
2934 | .Ve |
4528 | .Ve |
2935 | .Sp |
4529 | .Sp |
2936 | It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite |
4530 | It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite |
2937 | suitable for use with \f(CW\*(C`EV_A\*(C'\fR. |
4531 | suitable for use with \f(CW\*(C`EV_A\*(C'\fR. |
2938 | .ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4 |
4532 | .ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4 |
2939 | .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 |
4533 | .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 |
2940 | .IX Item "EV_DEFAULT, EV_DEFAULT_" |
4534 | .IX Item "EV_DEFAULT, EV_DEFAULT_" |
2941 | Similar to the other two macros, this gives you the value of the default |
4535 | Similar to the other two macros, this gives you the value of the default |
2942 | loop, if multiple loops are supported (\*(L"ev loop default\*(R"). |
4536 | loop, if multiple loops are supported (\*(L"ev loop default\*(R"). The default loop |
|
|
4537 | will be initialised if it isn't already initialised. |
|
|
4538 | .Sp |
|
|
4539 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4540 | to initialise the loop somewhere. |
2943 | .ie n .IP """EV_DEFAULT_UC""\fR, \f(CW""EV_DEFAULT_UC_""" 4 |
4541 | .ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4 |
2944 | .el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4 |
4542 | .el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4 |
2945 | .IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_" |
4543 | .IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_" |
2946 | Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the |
4544 | Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the |
2947 | default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour |
4545 | default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour |
2948 | is undefined when the default loop has not been initialised by a previous |
4546 | is undefined when the default loop has not been initialised by a previous |
… | |
… | |
2963 | \& } |
4561 | \& } |
2964 | \& |
4562 | \& |
2965 | \& ev_check check; |
4563 | \& ev_check check; |
2966 | \& ev_check_init (&check, check_cb); |
4564 | \& ev_check_init (&check, check_cb); |
2967 | \& ev_check_start (EV_DEFAULT_ &check); |
4565 | \& ev_check_start (EV_DEFAULT_ &check); |
2968 | \& ev_loop (EV_DEFAULT_ 0); |
4566 | \& ev_run (EV_DEFAULT_ 0); |
2969 | .Ve |
4567 | .Ve |
2970 | .SH "EMBEDDING" |
4568 | .SH "EMBEDDING" |
2971 | .IX Header "EMBEDDING" |
4569 | .IX Header "EMBEDDING" |
2972 | Libev can (and often is) directly embedded into host |
4570 | Libev can (and often is) directly embedded into host |
2973 | applications. Examples of applications that embed it include the Deliantra |
4571 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
2976 | .PP |
4574 | .PP |
2977 | The goal is to enable you to just copy the necessary files into your |
4575 | The goal is to enable you to just copy the necessary files into your |
2978 | source directory without having to change even a single line in them, so |
4576 | source directory without having to change even a single line in them, so |
2979 | you can easily upgrade by simply copying (or having a checked-out copy of |
4577 | you can easily upgrade by simply copying (or having a checked-out copy of |
2980 | libev somewhere in your source tree). |
4578 | libev somewhere in your source tree). |
2981 | .Sh "\s-1FILESETS\s0" |
4579 | .SS "\s-1FILESETS\s0" |
2982 | .IX Subsection "FILESETS" |
4580 | .IX Subsection "FILESETS" |
2983 | Depending on what features you need you need to include one or more sets of files |
4581 | Depending on what features you need you need to include one or more sets of files |
2984 | in your application. |
4582 | in your application. |
2985 | .PP |
4583 | .PP |
2986 | \fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR |
4584 | \fI\s-1CORE EVENT LOOP\s0\fR |
2987 | .IX Subsection "CORE EVENT LOOP" |
4585 | .IX Subsection "CORE EVENT LOOP" |
2988 | .PP |
4586 | .PP |
2989 | To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual |
4587 | To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual |
2990 | configuration (no autoconf): |
4588 | configuration (no autoconf): |
2991 | .PP |
4589 | .PP |
… | |
… | |
3004 | \& #define EV_STANDALONE 1 |
4602 | \& #define EV_STANDALONE 1 |
3005 | \& #include "ev.h" |
4603 | \& #include "ev.h" |
3006 | .Ve |
4604 | .Ve |
3007 | .PP |
4605 | .PP |
3008 | Both header files and implementation files can be compiled with a \*(C+ |
4606 | Both header files and implementation files can be compiled with a \*(C+ |
3009 | compiler (at least, thats a stated goal, and breakage will be treated |
4607 | compiler (at least, that's a stated goal, and breakage will be treated |
3010 | as a bug). |
4608 | as a bug). |
3011 | .PP |
4609 | .PP |
3012 | You need the following files in your source tree, or in a directory |
4610 | You need the following files in your source tree, or in a directory |
3013 | in your include path (e.g. in libev/ when using \-Ilibev): |
4611 | in your include path (e.g. in libev/ when using \-Ilibev): |
3014 | .PP |
4612 | .PP |
… | |
… | |
3018 | \& ev_vars.h |
4616 | \& ev_vars.h |
3019 | \& ev_wrap.h |
4617 | \& ev_wrap.h |
3020 | \& |
4618 | \& |
3021 | \& ev_win32.c required on win32 platforms only |
4619 | \& ev_win32.c required on win32 platforms only |
3022 | \& |
4620 | \& |
3023 | \& ev_select.c only when select backend is enabled (which is enabled by default) |
4621 | \& ev_select.c only when select backend is enabled |
3024 | \& ev_poll.c only when poll backend is enabled (disabled by default) |
4622 | \& ev_poll.c only when poll backend is enabled |
3025 | \& ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4623 | \& ev_epoll.c only when the epoll backend is enabled |
|
|
4624 | \& ev_linuxaio.c only when the linux aio backend is enabled |
3026 | \& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4625 | \& ev_kqueue.c only when the kqueue backend is enabled |
3027 | \& ev_port.c only when the solaris port backend is enabled (disabled by default) |
4626 | \& ev_port.c only when the solaris port backend is enabled |
3028 | .Ve |
4627 | .Ve |
3029 | .PP |
4628 | .PP |
3030 | \&\fIev.c\fR includes the backend files directly when enabled, so you only need |
4629 | \&\fIev.c\fR includes the backend files directly when enabled, so you only need |
3031 | to compile this single file. |
4630 | to compile this single file. |
3032 | .PP |
4631 | .PP |
3033 | \fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR |
4632 | \fI\s-1LIBEVENT COMPATIBILITY API\s0\fR |
3034 | .IX Subsection "LIBEVENT COMPATIBILITY API" |
4633 | .IX Subsection "LIBEVENT COMPATIBILITY API" |
3035 | .PP |
4634 | .PP |
3036 | To include the libevent compatibility \s-1API\s0, also include: |
4635 | To include the libevent compatibility \s-1API,\s0 also include: |
3037 | .PP |
4636 | .PP |
3038 | .Vb 1 |
4637 | .Vb 1 |
3039 | \& #include "event.c" |
4638 | \& #include "event.c" |
3040 | .Ve |
4639 | .Ve |
3041 | .PP |
4640 | .PP |
… | |
… | |
3043 | .PP |
4642 | .PP |
3044 | .Vb 1 |
4643 | .Vb 1 |
3045 | \& #include "event.h" |
4644 | \& #include "event.h" |
3046 | .Ve |
4645 | .Ve |
3047 | .PP |
4646 | .PP |
3048 | in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR. |
4647 | in the files that want to use the libevent \s-1API.\s0 This also includes \fIev.h\fR. |
3049 | .PP |
4648 | .PP |
3050 | You need the following additional files for this: |
4649 | You need the following additional files for this: |
3051 | .PP |
4650 | .PP |
3052 | .Vb 2 |
4651 | .Vb 2 |
3053 | \& event.h |
4652 | \& event.h |
3054 | \& event.c |
4653 | \& event.c |
3055 | .Ve |
4654 | .Ve |
3056 | .PP |
4655 | .PP |
3057 | \fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR |
4656 | \fI\s-1AUTOCONF SUPPORT\s0\fR |
3058 | .IX Subsection "AUTOCONF SUPPORT" |
4657 | .IX Subsection "AUTOCONF SUPPORT" |
3059 | .PP |
4658 | .PP |
3060 | Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your configuration in |
4659 | Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your configuration in |
3061 | whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your |
4660 | whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your |
3062 | \&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then |
4661 | \&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then |
… | |
… | |
3065 | For this of course you need the m4 file: |
4664 | For this of course you need the m4 file: |
3066 | .PP |
4665 | .PP |
3067 | .Vb 1 |
4666 | .Vb 1 |
3068 | \& libev.m4 |
4667 | \& libev.m4 |
3069 | .Ve |
4668 | .Ve |
3070 | .Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" |
4669 | .SS "\s-1PREPROCESSOR SYMBOLS/MACROS\s0" |
3071 | .IX Subsection "PREPROCESSOR SYMBOLS/MACROS" |
4670 | .IX Subsection "PREPROCESSOR SYMBOLS/MACROS" |
3072 | Libev can be configured via a variety of preprocessor symbols you have to |
4671 | Libev can be configured via a variety of preprocessor symbols you have to |
3073 | define before including any of its files. The default in the absence of |
4672 | define before including (or compiling) any of its files. The default in |
3074 | autoconf is documented for every option. |
4673 | the absence of autoconf is documented for every option. |
|
|
4674 | .PP |
|
|
4675 | Symbols marked with \*(L"(h)\*(R" do not change the \s-1ABI,\s0 and can have different |
|
|
4676 | values when compiling libev vs. including \fIev.h\fR, so it is permissible |
|
|
4677 | to redefine them before including \fIev.h\fR without breaking compatibility |
|
|
4678 | to a compiled library. All other symbols change the \s-1ABI,\s0 which means all |
|
|
4679 | users of libev and the libev code itself must be compiled with compatible |
|
|
4680 | settings. |
|
|
4681 | .IP "\s-1EV_COMPAT3\s0 (h)" 4 |
|
|
4682 | .IX Item "EV_COMPAT3 (h)" |
|
|
4683 | Backwards compatibility is a major concern for libev. This is why this |
|
|
4684 | release of libev comes with wrappers for the functions and symbols that |
|
|
4685 | have been renamed between libev version 3 and 4. |
|
|
4686 | .Sp |
|
|
4687 | You can disable these wrappers (to test compatibility with future |
|
|
4688 | versions) by defining \f(CW\*(C`EV_COMPAT3\*(C'\fR to \f(CW0\fR when compiling your |
|
|
4689 | sources. This has the additional advantage that you can drop the \f(CW\*(C`struct\*(C'\fR |
|
|
4690 | from \f(CW\*(C`struct ev_loop\*(C'\fR declarations, as libev will provide an \f(CW\*(C`ev_loop\*(C'\fR |
|
|
4691 | typedef in that case. |
|
|
4692 | .Sp |
|
|
4693 | In some future version, the default for \f(CW\*(C`EV_COMPAT3\*(C'\fR will become \f(CW0\fR, |
|
|
4694 | and in some even more future version the compatibility code will be |
|
|
4695 | removed completely. |
3075 | .IP "\s-1EV_STANDALONE\s0" 4 |
4696 | .IP "\s-1EV_STANDALONE\s0 (h)" 4 |
3076 | .IX Item "EV_STANDALONE" |
4697 | .IX Item "EV_STANDALONE (h)" |
3077 | Must always be \f(CW1\fR if you do not use autoconf configuration, which |
4698 | Must always be \f(CW1\fR if you do not use autoconf configuration, which |
3078 | keeps libev from including \fIconfig.h\fR, and it also defines dummy |
4699 | keeps libev from including \fIconfig.h\fR, and it also defines dummy |
3079 | implementations for some libevent functions (such as logging, which is not |
4700 | implementations for some libevent functions (such as logging, which is not |
3080 | supported). It will also not define any of the structs usually found in |
4701 | supported). It will also not define any of the structs usually found in |
3081 | \&\fIevent.h\fR that are not directly supported by the libev core alone. |
4702 | \&\fIevent.h\fR that are not directly supported by the libev core alone. |
|
|
4703 | .Sp |
|
|
4704 | In standalone mode, libev will still try to automatically deduce the |
|
|
4705 | configuration, but has to be more conservative. |
|
|
4706 | .IP "\s-1EV_USE_FLOOR\s0" 4 |
|
|
4707 | .IX Item "EV_USE_FLOOR" |
|
|
4708 | If defined to be \f(CW1\fR, libev will use the \f(CW\*(C`floor ()\*(C'\fR function for its |
|
|
4709 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4710 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4711 | link against libm or something equivalent. Enabling this when the \f(CW\*(C`floor\*(C'\fR |
|
|
4712 | function is not available will fail, so the safe default is to not enable |
|
|
4713 | this. |
3082 | .IP "\s-1EV_USE_MONOTONIC\s0" 4 |
4714 | .IP "\s-1EV_USE_MONOTONIC\s0" 4 |
3083 | .IX Item "EV_USE_MONOTONIC" |
4715 | .IX Item "EV_USE_MONOTONIC" |
3084 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
4716 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
3085 | monotonic clock option at both compile time and runtime. Otherwise no use |
4717 | monotonic clock option at both compile time and runtime. Otherwise no |
3086 | of the monotonic clock option will be attempted. If you enable this, you |
4718 | use of the monotonic clock option will be attempted. If you enable this, |
3087 | usually have to link against librt or something similar. Enabling it when |
4719 | you usually have to link against librt or something similar. Enabling it |
3088 | the functionality isn't available is safe, though, although you have |
4720 | when the functionality isn't available is safe, though, although you have |
3089 | to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
4721 | to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
3090 | function is hiding in (often \fI\-lrt\fR). |
4722 | function is hiding in (often \fI\-lrt\fR). See also \f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR. |
3091 | .IP "\s-1EV_USE_REALTIME\s0" 4 |
4723 | .IP "\s-1EV_USE_REALTIME\s0" 4 |
3092 | .IX Item "EV_USE_REALTIME" |
4724 | .IX Item "EV_USE_REALTIME" |
3093 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
4725 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
3094 | real-time clock option at compile time (and assume its availability at |
4726 | real-time clock option at compile time (and assume its availability |
3095 | runtime if successful). Otherwise no use of the real-time clock option will |
4727 | at runtime if successful). Otherwise no use of the real-time clock |
3096 | be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get |
4728 | option will be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR |
3097 | (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the |
4729 | by \f(CW\*(C`clock_get (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect |
3098 | note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. |
4730 | correctness. See the note about libraries in the description of |
|
|
4731 | \&\f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. Defaults to the opposite value of |
|
|
4732 | \&\f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR. |
|
|
4733 | .IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4 |
|
|
4734 | .IX Item "EV_USE_CLOCK_SYSCALL" |
|
|
4735 | If defined to be \f(CW1\fR, libev will try to use a direct syscall instead |
|
|
4736 | of calling the system-provided \f(CW\*(C`clock_gettime\*(C'\fR function. This option |
|
|
4737 | exists because on GNU/Linux, \f(CW\*(C`clock_gettime\*(C'\fR is in \f(CW\*(C`librt\*(C'\fR, but \f(CW\*(C`librt\*(C'\fR |
|
|
4738 | unconditionally pulls in \f(CW\*(C`libpthread\*(C'\fR, slowing down single-threaded |
|
|
4739 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
4740 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
4741 | the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or |
|
|
4742 | higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR). |
3099 | .IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
4743 | .IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
3100 | .IX Item "EV_USE_NANOSLEEP" |
4744 | .IX Item "EV_USE_NANOSLEEP" |
3101 | If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
4745 | If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
3102 | and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
4746 | and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
3103 | .IP "\s-1EV_USE_EVENTFD\s0" 4 |
4747 | .IP "\s-1EV_USE_EVENTFD\s0" 4 |
… | |
… | |
3115 | will not be compiled in. |
4759 | will not be compiled in. |
3116 | .IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
4760 | .IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
3117 | .IX Item "EV_SELECT_USE_FD_SET" |
4761 | .IX Item "EV_SELECT_USE_FD_SET" |
3118 | If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
4762 | If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
3119 | structure. This is useful if libev doesn't compile due to a missing |
4763 | structure. This is useful if libev doesn't compile due to a missing |
3120 | \&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout on |
4764 | \&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout |
3121 | exotic systems. This usually limits the range of file descriptors to some |
4765 | on exotic systems. This usually limits the range of file descriptors to |
3122 | low limit such as 1024 or might have other limitations (winsocket only |
4766 | some low limit such as 1024 or might have other limitations (winsocket |
3123 | allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might |
4767 | only allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, |
3124 | influence the size of the \f(CW\*(C`fd_set\*(C'\fR used. |
4768 | configures the maximum size of the \f(CW\*(C`fd_set\*(C'\fR. |
3125 | .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
4769 | .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
3126 | .IX Item "EV_SELECT_IS_WINSOCKET" |
4770 | .IX Item "EV_SELECT_IS_WINSOCKET" |
3127 | When defined to \f(CW1\fR, the select backend will assume that |
4771 | When defined to \f(CW1\fR, the select backend will assume that |
3128 | select/socket/connect etc. don't understand file descriptors but |
4772 | select/socket/connect etc. don't understand file descriptors but |
3129 | wants osf handles on win32 (this is the case when the select to |
4773 | wants osf handles on win32 (this is the case when the select to |
3130 | be used is the winsock select). This means that it will call |
4774 | be used is the winsock select). This means that it will call |
3131 | \&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, |
4775 | \&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, |
3132 | it is assumed that all these functions actually work on fds, even |
4776 | it is assumed that all these functions actually work on fds, even |
3133 | on win32. Should not be defined on non\-win32 platforms. |
4777 | on win32. Should not be defined on non\-win32 platforms. |
3134 | .IP "\s-1EV_FD_TO_WIN32_HANDLE\s0" 4 |
4778 | .IP "\s-1EV_FD_TO_WIN32_HANDLE\s0(fd)" 4 |
3135 | .IX Item "EV_FD_TO_WIN32_HANDLE" |
4779 | .IX Item "EV_FD_TO_WIN32_HANDLE(fd)" |
3136 | If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map |
4780 | If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map |
3137 | file descriptors to socket handles. When not defining this symbol (the |
4781 | file descriptors to socket handles. When not defining this symbol (the |
3138 | default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually |
4782 | default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually |
3139 | correct. In some cases, programs use their own file descriptor management, |
4783 | correct. In some cases, programs use their own file descriptor management, |
3140 | in which case they can provide this function to map fds to socket handles. |
4784 | in which case they can provide this function to map fds to socket handles. |
|
|
4785 | .IP "\s-1EV_WIN32_HANDLE_TO_FD\s0(handle)" 4 |
|
|
4786 | .IX Item "EV_WIN32_HANDLE_TO_FD(handle)" |
|
|
4787 | If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR then libev maps handles to file descriptors |
|
|
4788 | using the standard \f(CW\*(C`_open_osfhandle\*(C'\fR function. For programs implementing |
|
|
4789 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
4790 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
4791 | .IP "\s-1EV_WIN32_CLOSE_FD\s0(fd)" 4 |
|
|
4792 | .IX Item "EV_WIN32_CLOSE_FD(fd)" |
|
|
4793 | If programs implement their own fd to handle mapping on win32, then this |
|
|
4794 | macro can be used to override the \f(CW\*(C`close\*(C'\fR function, useful to unregister |
|
|
4795 | file descriptors again. Note that the replacement function has to close |
|
|
4796 | the underlying \s-1OS\s0 handle. |
|
|
4797 | .IP "\s-1EV_USE_WSASOCKET\s0" 4 |
|
|
4798 | .IX Item "EV_USE_WSASOCKET" |
|
|
4799 | If defined to be \f(CW1\fR, libev will use \f(CW\*(C`WSASocket\*(C'\fR to create its internal |
|
|
4800 | communication socket, which works better in some environments. Otherwise, |
|
|
4801 | the normal \f(CW\*(C`socket\*(C'\fR function will be used, which works better in other |
|
|
4802 | environments. |
3141 | .IP "\s-1EV_USE_POLL\s0" 4 |
4803 | .IP "\s-1EV_USE_POLL\s0" 4 |
3142 | .IX Item "EV_USE_POLL" |
4804 | .IX Item "EV_USE_POLL" |
3143 | If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) |
4805 | If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) |
3144 | backend. Otherwise it will be enabled on non\-win32 platforms. It |
4806 | backend. Otherwise it will be enabled on non\-win32 platforms. It |
3145 | takes precedence over select. |
4807 | takes precedence over select. |
… | |
… | |
3148 | If defined to be \f(CW1\fR, libev will compile in support for the Linux |
4810 | If defined to be \f(CW1\fR, libev will compile in support for the Linux |
3149 | \&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, |
4811 | \&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, |
3150 | otherwise another method will be used as fallback. This is the preferred |
4812 | otherwise another method will be used as fallback. This is the preferred |
3151 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4813 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
3152 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4814 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4815 | .IP "\s-1EV_USE_LINUXAIO\s0" 4 |
|
|
4816 | .IX Item "EV_USE_LINUXAIO" |
|
|
4817 | If defined to be \f(CW1\fR, libev will compile in support for the Linux |
|
|
4818 | aio backend. Due to it's currenbt limitations it has to be requested |
|
|
4819 | explicitly. If undefined, it will be enabled on linux, otherwise |
|
|
4820 | disabled. |
3153 | .IP "\s-1EV_USE_KQUEUE\s0" 4 |
4821 | .IP "\s-1EV_USE_KQUEUE\s0" 4 |
3154 | .IX Item "EV_USE_KQUEUE" |
4822 | .IX Item "EV_USE_KQUEUE" |
3155 | If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style |
4823 | If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style |
3156 | \&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, |
4824 | \&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, |
3157 | otherwise another method will be used as fallback. This is the preferred |
4825 | otherwise another method will be used as fallback. This is the preferred |
… | |
… | |
3174 | .IX Item "EV_USE_INOTIFY" |
4842 | .IX Item "EV_USE_INOTIFY" |
3175 | If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify |
4843 | If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify |
3176 | interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will |
4844 | interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will |
3177 | be detected at runtime. If undefined, it will be enabled if the headers |
4845 | be detected at runtime. If undefined, it will be enabled if the headers |
3178 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4846 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4847 | .IP "\s-1EV_NO_SMP\s0" 4 |
|
|
4848 | .IX Item "EV_NO_SMP" |
|
|
4849 | If defined to be \f(CW1\fR, libev will assume that memory is always coherent |
|
|
4850 | between threads, that is, threads can be used, but threads never run on |
|
|
4851 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4852 | and makes libev faster. |
|
|
4853 | .IP "\s-1EV_NO_THREADS\s0" 4 |
|
|
4854 | .IX Item "EV_NO_THREADS" |
|
|
4855 | If defined to be \f(CW1\fR, libev will assume that it will never be called from |
|
|
4856 | different threads (that includes signal handlers), which is a stronger |
|
|
4857 | assumption than \f(CW\*(C`EV_NO_SMP\*(C'\fR, above. This reduces dependencies and makes |
|
|
4858 | libev faster. |
3179 | .IP "\s-1EV_ATOMIC_T\s0" 4 |
4859 | .IP "\s-1EV_ATOMIC_T\s0" 4 |
3180 | .IX Item "EV_ATOMIC_T" |
4860 | .IX Item "EV_ATOMIC_T" |
3181 | Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose |
4861 | Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose |
3182 | access is atomic with respect to other threads or signal contexts. No such |
4862 | access is atomic with respect to other threads or signal contexts. No |
3183 | type is easily found in the C language, so you can provide your own type |
4863 | such type is easily found in the C language, so you can provide your own |
3184 | that you know is safe for your purposes. It is used both for signal handler \*(L"locking\*(R" |
4864 | type that you know is safe for your purposes. It is used both for signal |
3185 | as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR watchers. |
4865 | handler \*(L"locking\*(R" as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR |
|
|
4866 | watchers. |
3186 | .Sp |
4867 | .Sp |
3187 | In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR |
4868 | In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR |
3188 | (from \fIsignal.h\fR), which is usually good enough on most platforms. |
4869 | (from \fIsignal.h\fR), which is usually good enough on most platforms. |
3189 | .IP "\s-1EV_H\s0" 4 |
4870 | .IP "\s-1EV_H\s0 (h)" 4 |
3190 | .IX Item "EV_H" |
4871 | .IX Item "EV_H (h)" |
3191 | The name of the \fIev.h\fR header file used to include it. The default if |
4872 | The name of the \fIev.h\fR header file used to include it. The default if |
3192 | undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be |
4873 | undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be |
3193 | used to virtually rename the \fIev.h\fR header file in case of conflicts. |
4874 | used to virtually rename the \fIev.h\fR header file in case of conflicts. |
3194 | .IP "\s-1EV_CONFIG_H\s0" 4 |
4875 | .IP "\s-1EV_CONFIG_H\s0 (h)" 4 |
3195 | .IX Item "EV_CONFIG_H" |
4876 | .IX Item "EV_CONFIG_H (h)" |
3196 | If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override |
4877 | If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override |
3197 | \&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to |
4878 | \&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to |
3198 | \&\f(CW\*(C`EV_H\*(C'\fR, above. |
4879 | \&\f(CW\*(C`EV_H\*(C'\fR, above. |
3199 | .IP "\s-1EV_EVENT_H\s0" 4 |
4880 | .IP "\s-1EV_EVENT_H\s0 (h)" 4 |
3200 | .IX Item "EV_EVENT_H" |
4881 | .IX Item "EV_EVENT_H (h)" |
3201 | Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea |
4882 | Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea |
3202 | of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR. |
4883 | of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR. |
3203 | .IP "\s-1EV_PROTOTYPES\s0" 4 |
4884 | .IP "\s-1EV_PROTOTYPES\s0 (h)" 4 |
3204 | .IX Item "EV_PROTOTYPES" |
4885 | .IX Item "EV_PROTOTYPES (h)" |
3205 | If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function |
4886 | If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function |
3206 | prototypes, but still define all the structs and other symbols. This is |
4887 | prototypes, but still define all the structs and other symbols. This is |
3207 | occasionally useful if you want to provide your own wrapper functions |
4888 | occasionally useful if you want to provide your own wrapper functions |
3208 | around libev functions. |
4889 | around libev functions. |
3209 | .IP "\s-1EV_MULTIPLICITY\s0" 4 |
4890 | .IP "\s-1EV_MULTIPLICITY\s0" 4 |
… | |
… | |
3211 | If undefined or defined to \f(CW1\fR, then all event-loop-specific functions |
4892 | If undefined or defined to \f(CW1\fR, then all event-loop-specific functions |
3212 | will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create |
4893 | will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create |
3213 | additional independent event loops. Otherwise there will be no support |
4894 | additional independent event loops. Otherwise there will be no support |
3214 | for multiple event loops and there is no first event loop pointer |
4895 | for multiple event loops and there is no first event loop pointer |
3215 | argument. Instead, all functions act on the single default loop. |
4896 | argument. Instead, all functions act on the single default loop. |
|
|
4897 | .Sp |
|
|
4898 | Note that \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR will no longer provide a |
|
|
4899 | default loop when multiplicity is switched off \- you always have to |
|
|
4900 | initialise the loop manually in this case. |
3216 | .IP "\s-1EV_MINPRI\s0" 4 |
4901 | .IP "\s-1EV_MINPRI\s0" 4 |
3217 | .IX Item "EV_MINPRI" |
4902 | .IX Item "EV_MINPRI" |
3218 | .PD 0 |
4903 | .PD 0 |
3219 | .IP "\s-1EV_MAXPRI\s0" 4 |
4904 | .IP "\s-1EV_MAXPRI\s0" 4 |
3220 | .IX Item "EV_MAXPRI" |
4905 | .IX Item "EV_MAXPRI" |
… | |
… | |
3228 | all the priorities, so having many of them (hundreds) uses a lot of space |
4913 | all the priorities, so having many of them (hundreds) uses a lot of space |
3229 | and time, so using the defaults of five priorities (\-2 .. +2) is usually |
4914 | and time, so using the defaults of five priorities (\-2 .. +2) is usually |
3230 | fine. |
4915 | fine. |
3231 | .Sp |
4916 | .Sp |
3232 | If your embedding application does not need any priorities, defining these |
4917 | If your embedding application does not need any priorities, defining these |
3233 | both to \f(CW0\fR will save some memory and \s-1CPU\s0. |
4918 | both to \f(CW0\fR will save some memory and \s-1CPU.\s0 |
3234 | .IP "\s-1EV_PERIODIC_ENABLE\s0" 4 |
4919 | .IP "\s-1EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, EV_ASYNC_ENABLE, EV_CHILD_ENABLE.\s0" 4 |
3235 | .IX Item "EV_PERIODIC_ENABLE" |
4920 | .IX Item "EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, EV_ASYNC_ENABLE, EV_CHILD_ENABLE." |
3236 | If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If |
4921 | If undefined or defined to be \f(CW1\fR (and the platform supports it), then |
3237 | defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
4922 | the respective watcher type is supported. If defined to be \f(CW0\fR, then it |
3238 | code. |
4923 | is not. Disabling watcher types mainly saves code size. |
3239 | .IP "\s-1EV_IDLE_ENABLE\s0" 4 |
|
|
3240 | .IX Item "EV_IDLE_ENABLE" |
|
|
3241 | If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If |
|
|
3242 | defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
|
|
3243 | code. |
|
|
3244 | .IP "\s-1EV_EMBED_ENABLE\s0" 4 |
|
|
3245 | .IX Item "EV_EMBED_ENABLE" |
|
|
3246 | If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If |
|
|
3247 | defined to be \f(CW0\fR, then they are not. Embed watchers rely on most other |
|
|
3248 | watcher types, which therefore must not be disabled. |
|
|
3249 | .IP "\s-1EV_STAT_ENABLE\s0" 4 |
4924 | .IP "\s-1EV_FEATURES\s0" 4 |
3250 | .IX Item "EV_STAT_ENABLE" |
4925 | .IX Item "EV_FEATURES" |
3251 | If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If |
|
|
3252 | defined to be \f(CW0\fR, then they are not. |
|
|
3253 | .IP "\s-1EV_FORK_ENABLE\s0" 4 |
|
|
3254 | .IX Item "EV_FORK_ENABLE" |
|
|
3255 | If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If |
|
|
3256 | defined to be \f(CW0\fR, then they are not. |
|
|
3257 | .IP "\s-1EV_ASYNC_ENABLE\s0" 4 |
|
|
3258 | .IX Item "EV_ASYNC_ENABLE" |
|
|
3259 | If undefined or defined to be \f(CW1\fR, then async watchers are supported. If |
|
|
3260 | defined to be \f(CW0\fR, then they are not. |
|
|
3261 | .IP "\s-1EV_MINIMAL\s0" 4 |
|
|
3262 | .IX Item "EV_MINIMAL" |
|
|
3263 | If you need to shave off some kilobytes of code at the expense of some |
4926 | If you need to shave off some kilobytes of code at the expense of some |
3264 | speed, define this symbol to \f(CW1\fR. Currently this is used to override some |
4927 | speed (but with the full \s-1API\s0), you can define this symbol to request |
3265 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
4928 | certain subsets of functionality. The default is to enable all features |
3266 | much smaller 2\-heap for timer management over the default 4\-heap. |
4929 | that can be enabled on the platform. |
|
|
4930 | .Sp |
|
|
4931 | A typical way to use this symbol is to define it to \f(CW0\fR (or to a bitset |
|
|
4932 | with some broad features you want) and then selectively re-enable |
|
|
4933 | additional parts you want, for example if you want everything minimal, |
|
|
4934 | but multiple event loop support, async and child watchers and the poll |
|
|
4935 | backend, use this: |
|
|
4936 | .Sp |
|
|
4937 | .Vb 5 |
|
|
4938 | \& #define EV_FEATURES 0 |
|
|
4939 | \& #define EV_MULTIPLICITY 1 |
|
|
4940 | \& #define EV_USE_POLL 1 |
|
|
4941 | \& #define EV_CHILD_ENABLE 1 |
|
|
4942 | \& #define EV_ASYNC_ENABLE 1 |
|
|
4943 | .Ve |
|
|
4944 | .Sp |
|
|
4945 | The actual value is a bitset, it can be a combination of the following |
|
|
4946 | values (by default, all of these are enabled): |
|
|
4947 | .RS 4 |
|
|
4948 | .ie n .IP "1 \- faster/larger code" 4 |
|
|
4949 | .el .IP "\f(CW1\fR \- faster/larger code" 4 |
|
|
4950 | .IX Item "1 - faster/larger code" |
|
|
4951 | Use larger code to speed up some operations. |
|
|
4952 | .Sp |
|
|
4953 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4954 | code size by roughly 30% on amd64). |
|
|
4955 | .Sp |
|
|
4956 | When optimising for size, use of compiler flags such as \f(CW\*(C`\-Os\*(C'\fR with |
|
|
4957 | gcc is recommended, as well as \f(CW\*(C`\-DNDEBUG\*(C'\fR, as libev contains a number of |
|
|
4958 | assertions. |
|
|
4959 | .Sp |
|
|
4960 | The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler |
|
|
4961 | (e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR). |
|
|
4962 | .ie n .IP "2 \- faster/larger data structures" 4 |
|
|
4963 | .el .IP "\f(CW2\fR \- faster/larger data structures" 4 |
|
|
4964 | .IX Item "2 - faster/larger data structures" |
|
|
4965 | Replaces the small 2\-heap for timer management by a faster 4\-heap, larger |
|
|
4966 | hash table sizes and so on. This will usually further increase code size |
|
|
4967 | and can additionally have an effect on the size of data structures at |
|
|
4968 | runtime. |
|
|
4969 | .Sp |
|
|
4970 | The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler |
|
|
4971 | (e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR). |
|
|
4972 | .ie n .IP "4 \- full \s-1API\s0 configuration" 4 |
|
|
4973 | .el .IP "\f(CW4\fR \- full \s-1API\s0 configuration" 4 |
|
|
4974 | .IX Item "4 - full API configuration" |
|
|
4975 | This enables priorities (sets \f(CW\*(C`EV_MAXPRI\*(C'\fR=2 and \f(CW\*(C`EV_MINPRI\*(C'\fR=\-2), and |
|
|
4976 | enables multiplicity (\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR=1). |
|
|
4977 | .ie n .IP "8 \- full \s-1API\s0" 4 |
|
|
4978 | .el .IP "\f(CW8\fR \- full \s-1API\s0" 4 |
|
|
4979 | .IX Item "8 - full API" |
|
|
4980 | This enables a lot of the \*(L"lesser used\*(R" \s-1API\s0 functions. See \f(CW\*(C`ev.h\*(C'\fR for |
|
|
4981 | details on which parts of the \s-1API\s0 are still available without this |
|
|
4982 | feature, and do not complain if this subset changes over time. |
|
|
4983 | .ie n .IP "16 \- enable all optional watcher types" 4 |
|
|
4984 | .el .IP "\f(CW16\fR \- enable all optional watcher types" 4 |
|
|
4985 | .IX Item "16 - enable all optional watcher types" |
|
|
4986 | Enables all optional watcher types. If you want to selectively enable |
|
|
4987 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4988 | embed, async, child...) you can enable them manually by defining |
|
|
4989 | \&\f(CW\*(C`EV_watchertype_ENABLE\*(C'\fR to \f(CW1\fR instead. |
|
|
4990 | .ie n .IP "32 \- enable all backends" 4 |
|
|
4991 | .el .IP "\f(CW32\fR \- enable all backends" 4 |
|
|
4992 | .IX Item "32 - enable all backends" |
|
|
4993 | This enables all backends \- without this feature, you need to enable at |
|
|
4994 | least one backend manually (\f(CW\*(C`EV_USE_SELECT\*(C'\fR is a good choice). |
|
|
4995 | .ie n .IP "64 \- enable OS-specific ""helper"" APIs" 4 |
|
|
4996 | .el .IP "\f(CW64\fR \- enable OS-specific ``helper'' APIs" 4 |
|
|
4997 | .IX Item "64 - enable OS-specific helper APIs" |
|
|
4998 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4999 | default. |
|
|
5000 | .RE |
|
|
5001 | .RS 4 |
|
|
5002 | .Sp |
|
|
5003 | Compiling with \f(CW\*(C`gcc \-Os \-DEV_STANDALONE \-DEV_USE_EPOLL=1 \-DEV_FEATURES=0\*(C'\fR |
|
|
5004 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
5005 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
5006 | watchers, timers and monotonic clock support. |
|
|
5007 | .Sp |
|
|
5008 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
5009 | when you use \f(CW\*(C`\-Wl,\-\-gc\-sections \-ffunction\-sections\*(C'\fR) functions unused by |
|
|
5010 | your program might be left out as well \- a binary starting a timer and an |
|
|
5011 | I/O watcher then might come out at only 5Kb. |
|
|
5012 | .RE |
|
|
5013 | .IP "\s-1EV_API_STATIC\s0" 4 |
|
|
5014 | .IX Item "EV_API_STATIC" |
|
|
5015 | If this symbol is defined (by default it is not), then all identifiers |
|
|
5016 | will have static linkage. This means that libev will not export any |
|
|
5017 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
5018 | when you embed libev, only want to use libev functions in a single file, |
|
|
5019 | and do not want its identifiers to be visible. |
|
|
5020 | .Sp |
|
|
5021 | To use this, define \f(CW\*(C`EV_API_STATIC\*(C'\fR and include \fIev.c\fR in the file that |
|
|
5022 | wants to use libev. |
|
|
5023 | .Sp |
|
|
5024 | This option only works when libev is compiled with a C compiler, as \*(C+ |
|
|
5025 | doesn't support the required declaration syntax. |
|
|
5026 | .IP "\s-1EV_AVOID_STDIO\s0" 4 |
|
|
5027 | .IX Item "EV_AVOID_STDIO" |
|
|
5028 | If this is set to \f(CW1\fR at compiletime, then libev will avoid using stdio |
|
|
5029 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
5030 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
5031 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
5032 | big. |
|
|
5033 | .Sp |
|
|
5034 | Note that error messages might become less precise when this option is |
|
|
5035 | enabled. |
|
|
5036 | .IP "\s-1EV_NSIG\s0" 4 |
|
|
5037 | .IX Item "EV_NSIG" |
|
|
5038 | The highest supported signal number, +1 (or, the number of |
|
|
5039 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
5040 | automatically, but sometimes this fails, in which case it can be |
|
|
5041 | specified. Also, using a lower number than detected (\f(CW32\fR should be |
|
|
5042 | good for about any system in existence) can save some memory, as libev |
|
|
5043 | statically allocates some 12\-24 bytes per signal number. |
3267 | .IP "\s-1EV_PID_HASHSIZE\s0" 4 |
5044 | .IP "\s-1EV_PID_HASHSIZE\s0" 4 |
3268 | .IX Item "EV_PID_HASHSIZE" |
5045 | .IX Item "EV_PID_HASHSIZE" |
3269 | \&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by |
5046 | \&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by |
3270 | pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more |
5047 | pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR disabled), |
3271 | than enough. If you need to manage thousands of children you might want to |
5048 | usually more than enough. If you need to manage thousands of children you |
3272 | increase this value (\fImust\fR be a power of two). |
5049 | might want to increase this value (\fImust\fR be a power of two). |
3273 | .IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4 |
5050 | .IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4 |
3274 | .IX Item "EV_INOTIFY_HASHSIZE" |
5051 | .IX Item "EV_INOTIFY_HASHSIZE" |
3275 | \&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by |
5052 | \&\f(CW\*(C`ev_stat\*(C'\fR watchers use a small hash table to distribute workload by |
3276 | inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), |
5053 | inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_FEATURES\*(C'\fR |
3277 | usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR |
5054 | disabled), usually more than enough. If you need to manage thousands of |
3278 | watchers you might want to increase this value (\fImust\fR be a power of |
5055 | \&\f(CW\*(C`ev_stat\*(C'\fR watchers you might want to increase this value (\fImust\fR be a |
3279 | two). |
5056 | power of two). |
3280 | .IP "\s-1EV_USE_4HEAP\s0" 4 |
5057 | .IP "\s-1EV_USE_4HEAP\s0" 4 |
3281 | .IX Item "EV_USE_4HEAP" |
5058 | .IX Item "EV_USE_4HEAP" |
3282 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
5059 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3283 | timer and periodics heaps, libev uses a 4\-heap when this symbol is defined |
5060 | timer and periodics heaps, libev uses a 4\-heap when this symbol is defined |
3284 | to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably |
5061 | to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably |
3285 | faster performance with many (thousands) of watchers. |
5062 | faster performance with many (thousands) of watchers. |
3286 | .Sp |
5063 | .Sp |
3287 | The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
5064 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it |
3288 | (disabled). |
5065 | will be \f(CW0\fR. |
3289 | .IP "\s-1EV_HEAP_CACHE_AT\s0" 4 |
5066 | .IP "\s-1EV_HEAP_CACHE_AT\s0" 4 |
3290 | .IX Item "EV_HEAP_CACHE_AT" |
5067 | .IX Item "EV_HEAP_CACHE_AT" |
3291 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
5068 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3292 | timer and periodics heaps, libev can cache the timestamp (\fIat\fR) within |
5069 | timer and periodics heaps, libev can cache the timestamp (\fIat\fR) within |
3293 | the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR), |
5070 | the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR), |
3294 | which uses 8\-12 bytes more per watcher and a few hundred bytes more code, |
5071 | which uses 8\-12 bytes more per watcher and a few hundred bytes more code, |
3295 | but avoids random read accesses on heap changes. This improves performance |
5072 | but avoids random read accesses on heap changes. This improves performance |
3296 | noticeably with many (hundreds) of watchers. |
5073 | noticeably with many (hundreds) of watchers. |
3297 | .Sp |
5074 | .Sp |
3298 | The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
5075 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it |
3299 | (disabled). |
5076 | will be \f(CW0\fR. |
3300 | .IP "\s-1EV_VERIFY\s0" 4 |
5077 | .IP "\s-1EV_VERIFY\s0" 4 |
3301 | .IX Item "EV_VERIFY" |
5078 | .IX Item "EV_VERIFY" |
3302 | Controls how much internal verification (see \f(CW\*(C`ev_loop_verify ()\*(C'\fR) will |
5079 | Controls how much internal verification (see \f(CW\*(C`ev_verify ()\*(C'\fR) will |
3303 | be done: If set to \f(CW0\fR, no internal verification code will be compiled |
5080 | be done: If set to \f(CW0\fR, no internal verification code will be compiled |
3304 | in. If set to \f(CW1\fR, then verification code will be compiled in, but not |
5081 | in. If set to \f(CW1\fR, then verification code will be compiled in, but not |
3305 | called. If set to \f(CW2\fR, then the internal verification code will be |
5082 | called. If set to \f(CW2\fR, then the internal verification code will be |
3306 | called once per loop, which can slow down libev. If set to \f(CW3\fR, then the |
5083 | called once per loop, which can slow down libev. If set to \f(CW3\fR, then the |
3307 | verification code will be called very frequently, which will slow down |
5084 | verification code will be called very frequently, which will slow down |
3308 | libev considerably. |
5085 | libev considerably. |
3309 | .Sp |
5086 | .Sp |
3310 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set, in which case it will be |
5087 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it |
3311 | \&\f(CW0\fR. |
5088 | will be \f(CW0\fR. |
3312 | .IP "\s-1EV_COMMON\s0" 4 |
5089 | .IP "\s-1EV_COMMON\s0" 4 |
3313 | .IX Item "EV_COMMON" |
5090 | .IX Item "EV_COMMON" |
3314 | By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining |
5091 | By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining |
3315 | this macro to a something else you can include more and other types of |
5092 | this macro to something else you can include more and other types of |
3316 | members. You have to define it each time you include one of the files, |
5093 | members. You have to define it each time you include one of the files, |
3317 | though, and it must be identical each time. |
5094 | though, and it must be identical each time. |
3318 | .Sp |
5095 | .Sp |
3319 | For example, the perl \s-1EV\s0 module uses something like this: |
5096 | For example, the perl \s-1EV\s0 module uses something like this: |
3320 | .Sp |
5097 | .Sp |
… | |
… | |
3335 | and the way callbacks are invoked and set. Must expand to a struct member |
5112 | and the way callbacks are invoked and set. Must expand to a struct member |
3336 | definition and a statement, respectively. See the \fIev.h\fR header file for |
5113 | definition and a statement, respectively. See the \fIev.h\fR header file for |
3337 | their default definitions. One possible use for overriding these is to |
5114 | their default definitions. One possible use for overriding these is to |
3338 | avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use |
5115 | avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use |
3339 | method calls instead of plain function calls in \*(C+. |
5116 | method calls instead of plain function calls in \*(C+. |
3340 | .Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0" |
5117 | .SS "\s-1EXPORTED API SYMBOLS\s0" |
3341 | .IX Subsection "EXPORTED API SYMBOLS" |
5118 | .IX Subsection "EXPORTED API SYMBOLS" |
3342 | If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of |
5119 | If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of |
3343 | exported symbols, you can use the provided \fISymbol.*\fR files which list |
5120 | exported symbols, you can use the provided \fISymbol.*\fR files which list |
3344 | all public symbols, one per line: |
5121 | all public symbols, one per line: |
3345 | .PP |
5122 | .PP |
… | |
… | |
3365 | \& #define ev_backend myprefix_ev_backend |
5142 | \& #define ev_backend myprefix_ev_backend |
3366 | \& #define ev_check_start myprefix_ev_check_start |
5143 | \& #define ev_check_start myprefix_ev_check_start |
3367 | \& #define ev_check_stop myprefix_ev_check_stop |
5144 | \& #define ev_check_stop myprefix_ev_check_stop |
3368 | \& ... |
5145 | \& ... |
3369 | .Ve |
5146 | .Ve |
3370 | .Sh "\s-1EXAMPLES\s0" |
5147 | .SS "\s-1EXAMPLES\s0" |
3371 | .IX Subsection "EXAMPLES" |
5148 | .IX Subsection "EXAMPLES" |
3372 | For a real-world example of a program the includes libev |
5149 | For a real-world example of a program the includes libev |
3373 | verbatim, you can have a look at the \s-1EV\s0 perl module |
5150 | verbatim, you can have a look at the \s-1EV\s0 perl module |
3374 | (<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
5151 | (<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
3375 | the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public |
5152 | the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public |
… | |
… | |
3378 | file. |
5155 | file. |
3379 | .PP |
5156 | .PP |
3380 | The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file |
5157 | The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file |
3381 | that everybody includes and which overrides some configure choices: |
5158 | that everybody includes and which overrides some configure choices: |
3382 | .PP |
5159 | .PP |
3383 | .Vb 9 |
5160 | .Vb 8 |
3384 | \& #define EV_MINIMAL 1 |
5161 | \& #define EV_FEATURES 8 |
3385 | \& #define EV_USE_POLL 0 |
5162 | \& #define EV_USE_SELECT 1 |
3386 | \& #define EV_MULTIPLICITY 0 |
|
|
3387 | \& #define EV_PERIODIC_ENABLE 0 |
5163 | \& #define EV_PREPARE_ENABLE 1 |
|
|
5164 | \& #define EV_IDLE_ENABLE 1 |
3388 | \& #define EV_STAT_ENABLE 0 |
5165 | \& #define EV_SIGNAL_ENABLE 1 |
3389 | \& #define EV_FORK_ENABLE 0 |
5166 | \& #define EV_CHILD_ENABLE 1 |
|
|
5167 | \& #define EV_USE_STDEXCEPT 0 |
3390 | \& #define EV_CONFIG_H <config.h> |
5168 | \& #define EV_CONFIG_H <config.h> |
3391 | \& #define EV_MINPRI 0 |
|
|
3392 | \& #define EV_MAXPRI 0 |
|
|
3393 | \& |
5169 | \& |
3394 | \& #include "ev++.h" |
5170 | \& #include "ev++.h" |
3395 | .Ve |
5171 | .Ve |
3396 | .PP |
5172 | .PP |
3397 | And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled: |
5173 | And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled: |
3398 | .PP |
5174 | .PP |
3399 | .Vb 2 |
5175 | .Vb 2 |
3400 | \& #include "ev_cpp.h" |
5176 | \& #include "ev_cpp.h" |
3401 | \& #include "ev.c" |
5177 | \& #include "ev.c" |
3402 | .Ve |
5178 | .Ve |
|
|
5179 | .SH "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT" |
|
|
5180 | .IX Header "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT" |
3403 | .SH "THREADS AND COROUTINES" |
5181 | .SS "\s-1THREADS AND COROUTINES\s0" |
3404 | .IX Header "THREADS AND COROUTINES" |
5182 | .IX Subsection "THREADS AND COROUTINES" |
3405 | .Sh "\s-1THREADS\s0" |
5183 | \fI\s-1THREADS\s0\fR |
3406 | .IX Subsection "THREADS" |
5184 | .IX Subsection "THREADS" |
|
|
5185 | .PP |
3407 | All libev functions are reentrant and thread-safe unless explicitly |
5186 | All libev functions are reentrant and thread-safe unless explicitly |
3408 | documented otherwise, but it uses no locking itself. This means that you |
5187 | documented otherwise, but libev implements no locking itself. This means |
3409 | can use as many loops as you want in parallel, as long as there are no |
5188 | that you can use as many loops as you want in parallel, as long as there |
3410 | concurrent calls into any libev function with the same loop parameter |
5189 | are no concurrent calls into any libev function with the same loop |
3411 | (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter, of |
5190 | parameter (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter, |
3412 | course): libev guarantees that different event loops share no data |
5191 | of course): libev guarantees that different event loops share no data |
3413 | structures that need any locking. |
5192 | structures that need any locking. |
3414 | .PP |
5193 | .PP |
3415 | Or to put it differently: calls with different loop parameters can be done |
5194 | Or to put it differently: calls with different loop parameters can be done |
3416 | concurrently from multiple threads, calls with the same loop parameter |
5195 | concurrently from multiple threads, calls with the same loop parameter |
3417 | must be done serially (but can be done from different threads, as long as |
5196 | must be done serially (but can be done from different threads, as long as |
… | |
… | |
3452 | .Sp |
5231 | .Sp |
3453 | An example use would be to communicate signals or other events that only |
5232 | An example use would be to communicate signals or other events that only |
3454 | work in the default loop by registering the signal watcher with the |
5233 | work in the default loop by registering the signal watcher with the |
3455 | default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop |
5234 | default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop |
3456 | watcher callback into the event loop interested in the signal. |
5235 | watcher callback into the event loop interested in the signal. |
3457 | .Sh "\s-1COROUTINES\s0" |
5236 | .PP |
|
|
5237 | See also \*(L"\s-1THREAD LOCKING EXAMPLE\*(R"\s0. |
|
|
5238 | .PP |
|
|
5239 | \fI\s-1COROUTINES\s0\fR |
3458 | .IX Subsection "COROUTINES" |
5240 | .IX Subsection "COROUTINES" |
|
|
5241 | .PP |
3459 | Libev is much more accommodating to coroutines (\*(L"cooperative threads\*(R"): |
5242 | Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"): |
3460 | libev fully supports nesting calls to it's functions from different |
5243 | libev fully supports nesting calls to its functions from different |
3461 | coroutines (e.g. you can call \f(CW\*(C`ev_loop\*(C'\fR on the same loop from two |
5244 | coroutines (e.g. you can call \f(CW\*(C`ev_run\*(C'\fR on the same loop from two |
3462 | different coroutines and switch freely between both coroutines running the |
5245 | different coroutines, and switch freely between both coroutines running |
3463 | loop, as long as you don't confuse yourself). The only exception is that |
5246 | the loop, as long as you don't confuse yourself). The only exception is |
3464 | you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks. |
5247 | that you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks. |
3465 | .PP |
5248 | .PP |
3466 | Care has been taken to ensure that libev does not keep local state inside |
5249 | Care has been taken to ensure that libev does not keep local state inside |
3467 | \&\f(CW\*(C`ev_loop\*(C'\fR, and other calls do not usually allow coroutine switches. |
5250 | \&\f(CW\*(C`ev_run\*(C'\fR, and other calls do not usually allow for coroutine switches as |
|
|
5251 | they do not call any callbacks. |
|
|
5252 | .SS "\s-1COMPILER WARNINGS\s0" |
|
|
5253 | .IX Subsection "COMPILER WARNINGS" |
|
|
5254 | Depending on your compiler and compiler settings, you might get no or a |
|
|
5255 | lot of warnings when compiling libev code. Some people are apparently |
|
|
5256 | scared by this. |
|
|
5257 | .PP |
|
|
5258 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
5259 | has different warnings, and each user has different tastes regarding |
|
|
5260 | warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when |
|
|
5261 | targeting a specific compiler and compiler-version. |
|
|
5262 | .PP |
|
|
5263 | Another reason is that some compiler warnings require elaborate |
|
|
5264 | workarounds, or other changes to the code that make it less clear and less |
|
|
5265 | maintainable. |
|
|
5266 | .PP |
|
|
5267 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
5268 | wrong (because they don't actually warn about the condition their message |
|
|
5269 | seems to warn about). For example, certain older gcc versions had some |
|
|
5270 | warnings that resulted in an extreme number of false positives. These have |
|
|
5271 | been fixed, but some people still insist on making code warn-free with |
|
|
5272 | such buggy versions. |
|
|
5273 | .PP |
|
|
5274 | While libev is written to generate as few warnings as possible, |
|
|
5275 | \&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev |
|
|
5276 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
5277 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
5278 | warnings, not errors, or proof of bugs. |
|
|
5279 | .SS "\s-1VALGRIND\s0" |
|
|
5280 | .IX Subsection "VALGRIND" |
|
|
5281 | Valgrind has a special section here because it is a popular tool that is |
|
|
5282 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
|
|
5283 | .PP |
|
|
5284 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
5285 | in libev, then check twice: If valgrind reports something like: |
|
|
5286 | .PP |
|
|
5287 | .Vb 3 |
|
|
5288 | \& ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
5289 | \& ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
5290 | \& ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
5291 | .Ve |
|
|
5292 | .PP |
|
|
5293 | Then there is no memory leak, just as memory accounted to global variables |
|
|
5294 | is not a memleak \- the memory is still being referenced, and didn't leak. |
|
|
5295 | .PP |
|
|
5296 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
5297 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
5298 | although an acceptable workaround has been found here), or it might be |
|
|
5299 | confused. |
|
|
5300 | .PP |
|
|
5301 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
|
|
5302 | make it into some kind of religion. |
|
|
5303 | .PP |
|
|
5304 | If you are unsure about something, feel free to contact the mailing list |
|
|
5305 | with the full valgrind report and an explanation on why you think this |
|
|
5306 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
5307 | annoyed when you get a brisk \*(L"this is no bug\*(R" answer and take the chance |
|
|
5308 | of learning how to interpret valgrind properly. |
|
|
5309 | .PP |
|
|
5310 | If you need, for some reason, empty reports from valgrind for your project |
|
|
5311 | I suggest using suppression lists. |
|
|
5312 | .SH "PORTABILITY NOTES" |
|
|
5313 | .IX Header "PORTABILITY NOTES" |
|
|
5314 | .SS "\s-1GNU/LINUX 32 BIT LIMITATIONS\s0" |
|
|
5315 | .IX Subsection "GNU/LINUX 32 BIT LIMITATIONS" |
|
|
5316 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
5317 | interfaces but \fIdisables\fR them by default. |
|
|
5318 | .PP |
|
|
5319 | That means that libev compiled in the default environment doesn't support |
|
|
5320 | files larger than 2GiB or so, which mainly affects \f(CW\*(C`ev_stat\*(C'\fR watchers. |
|
|
5321 | .PP |
|
|
5322 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
5323 | by enabling the large file \s-1API,\s0 which makes them incompatible with the |
|
|
5324 | standard libev compiled for their system. |
|
|
5325 | .PP |
|
|
5326 | Likewise, libev cannot enable the large file \s-1API\s0 itself as this would |
|
|
5327 | suddenly make it incompatible to the default compile time environment, |
|
|
5328 | i.e. all programs not using special compile switches. |
|
|
5329 | .SS "\s-1OS/X AND DARWIN BUGS\s0" |
|
|
5330 | .IX Subsection "OS/X AND DARWIN BUGS" |
|
|
5331 | The whole thing is a bug if you ask me \- basically any system interface |
|
|
5332 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
5333 | OpenGL drivers. |
|
|
5334 | .PP |
|
|
5335 | \fI\f(CI\*(C`kqueue\*(C'\fI is buggy\fR |
|
|
5336 | .IX Subsection "kqueue is buggy" |
|
|
5337 | .PP |
|
|
5338 | The kqueue syscall is broken in all known versions \- most versions support |
|
|
5339 | only sockets, many support pipes. |
|
|
5340 | .PP |
|
|
5341 | Libev tries to work around this by not using \f(CW\*(C`kqueue\*(C'\fR by default on this |
|
|
5342 | rotten platform, but of course you can still ask for it when creating a |
|
|
5343 | loop \- embedding a socket-only kqueue loop into a select-based one is |
|
|
5344 | probably going to work well. |
|
|
5345 | .PP |
|
|
5346 | \fI\f(CI\*(C`poll\*(C'\fI is buggy\fR |
|
|
5347 | .IX Subsection "poll is buggy" |
|
|
5348 | .PP |
|
|
5349 | Instead of fixing \f(CW\*(C`kqueue\*(C'\fR, Apple replaced their (working) \f(CW\*(C`poll\*(C'\fR |
|
|
5350 | implementation by something calling \f(CW\*(C`kqueue\*(C'\fR internally around the 10.5.6 |
|
|
5351 | release, so now \f(CW\*(C`kqueue\*(C'\fR \fIand\fR \f(CW\*(C`poll\*(C'\fR are broken. |
|
|
5352 | .PP |
|
|
5353 | Libev tries to work around this by not using \f(CW\*(C`poll\*(C'\fR by default on |
|
|
5354 | this rotten platform, but of course you can still ask for it when creating |
|
|
5355 | a loop. |
|
|
5356 | .PP |
|
|
5357 | \fI\f(CI\*(C`select\*(C'\fI is buggy\fR |
|
|
5358 | .IX Subsection "select is buggy" |
|
|
5359 | .PP |
|
|
5360 | All that's left is \f(CW\*(C`select\*(C'\fR, and of course Apple found a way to fuck this |
|
|
5361 | one up as well: On \s-1OS/X,\s0 \f(CW\*(C`select\*(C'\fR actively limits the number of file |
|
|
5362 | descriptors you can pass in to 1024 \- your program suddenly crashes when |
|
|
5363 | you use more. |
|
|
5364 | .PP |
|
|
5365 | There is an undocumented \*(L"workaround\*(R" for this \- defining |
|
|
5366 | \&\f(CW\*(C`_DARWIN_UNLIMITED_SELECT\*(C'\fR, which libev tries to use, so select \fIshould\fR |
|
|
5367 | work on \s-1OS/X.\s0 |
|
|
5368 | .SS "\s-1SOLARIS PROBLEMS AND WORKAROUNDS\s0" |
|
|
5369 | .IX Subsection "SOLARIS PROBLEMS AND WORKAROUNDS" |
|
|
5370 | \fI\f(CI\*(C`errno\*(C'\fI reentrancy\fR |
|
|
5371 | .IX Subsection "errno reentrancy" |
|
|
5372 | .PP |
|
|
5373 | The default compile environment on Solaris is unfortunately so |
|
|
5374 | thread-unsafe that you can't even use components/libraries compiled |
|
|
5375 | without \f(CW\*(C`\-D_REENTRANT\*(C'\fR in a threaded program, which, of course, isn't |
|
|
5376 | defined by default. A valid, if stupid, implementation choice. |
|
|
5377 | .PP |
|
|
5378 | If you want to use libev in threaded environments you have to make sure |
|
|
5379 | it's compiled with \f(CW\*(C`_REENTRANT\*(C'\fR defined. |
|
|
5380 | .PP |
|
|
5381 | \fIEvent port backend\fR |
|
|
5382 | .IX Subsection "Event port backend" |
|
|
5383 | .PP |
|
|
5384 | The scalable event interface for Solaris is called \*(L"event |
|
|
5385 | ports\*(R". Unfortunately, this mechanism is very buggy in all major |
|
|
5386 | releases. If you run into high \s-1CPU\s0 usage, your program freezes or you get |
|
|
5387 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
5388 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
5389 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
5390 | great. |
|
|
5391 | .PP |
|
|
5392 | If you can't get it to work, you can try running the program by setting |
|
|
5393 | the environment variable \f(CW\*(C`LIBEV_FLAGS=3\*(C'\fR to only allow \f(CW\*(C`poll\*(C'\fR and |
|
|
5394 | \&\f(CW\*(C`select\*(C'\fR backends. |
|
|
5395 | .SS "\s-1AIX POLL BUG\s0" |
|
|
5396 | .IX Subsection "AIX POLL BUG" |
|
|
5397 | \&\s-1AIX\s0 unfortunately has a broken \f(CW\*(C`poll.h\*(C'\fR header. Libev works around |
|
|
5398 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
5399 | compiled in), which normally isn't a big problem as \f(CW\*(C`select\*(C'\fR works fine |
|
|
5400 | with large bitsets on \s-1AIX,\s0 and \s-1AIX\s0 is dead anyway. |
|
|
5401 | .SS "\s-1WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS\s0" |
|
|
5402 | .IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
|
|
5403 | \fIGeneral issues\fR |
|
|
5404 | .IX Subsection "General issues" |
|
|
5405 | .PP |
|
|
5406 | Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev |
|
|
5407 | requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0 |
|
|
5408 | model. Libev still offers limited functionality on this platform in |
|
|
5409 | the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket |
|
|
5410 | descriptors. This only applies when using Win32 natively, not when using |
|
|
5411 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
5412 | as every compiler comes with a slightly differently broken/incompatible |
|
|
5413 | environment. |
|
|
5414 | .PP |
|
|
5415 | Lifting these limitations would basically require the full |
|
|
5416 | re-implementation of the I/O system. If you are into this kind of thing, |
|
|
5417 | then note that glib does exactly that for you in a very portable way (note |
|
|
5418 | also that glib is the slowest event library known to man). |
|
|
5419 | .PP |
|
|
5420 | There is no supported compilation method available on windows except |
|
|
5421 | embedding it into other applications. |
|
|
5422 | .PP |
|
|
5423 | Sensible signal handling is officially unsupported by Microsoft \- libev |
|
|
5424 | tries its best, but under most conditions, signals will simply not work. |
|
|
5425 | .PP |
|
|
5426 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
5427 | accept large writes: instead of resulting in a partial write, windows will |
|
|
5428 | either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large, |
|
|
5429 | so make sure you only write small amounts into your sockets (less than a |
|
|
5430 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
5431 | available). |
|
|
5432 | .PP |
|
|
5433 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
5434 | the abysmal performance of winsockets, using a large number of sockets |
|
|
5435 | is not recommended (and not reasonable). If your program needs to use |
|
|
5436 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
5437 | different implementation for windows, as libev offers the \s-1POSIX\s0 readiness |
|
|
5438 | notification model, which cannot be implemented efficiently on windows |
|
|
5439 | (due to Microsoft monopoly games). |
|
|
5440 | .PP |
|
|
5441 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
5442 | section for details) and use the following \fIevwrap.h\fR header file instead |
|
|
5443 | of \fIev.h\fR: |
|
|
5444 | .PP |
|
|
5445 | .Vb 2 |
|
|
5446 | \& #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
5447 | \& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
5448 | \& |
|
|
5449 | \& #include "ev.h" |
|
|
5450 | .Ve |
|
|
5451 | .PP |
|
|
5452 | And compile the following \fIevwrap.c\fR file into your project (make sure |
|
|
5453 | you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!): |
|
|
5454 | .PP |
|
|
5455 | .Vb 2 |
|
|
5456 | \& #include "evwrap.h" |
|
|
5457 | \& #include "ev.c" |
|
|
5458 | .Ve |
|
|
5459 | .PP |
|
|
5460 | \fIThe winsocket \f(CI\*(C`select\*(C'\fI function\fR |
|
|
5461 | .IX Subsection "The winsocket select function" |
|
|
5462 | .PP |
|
|
5463 | The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it |
|
|
5464 | requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is |
|
|
5465 | also extremely buggy). This makes select very inefficient, and also |
|
|
5466 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
5467 | C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the |
|
|
5468 | discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and |
|
|
5469 | \&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info. |
|
|
5470 | .PP |
|
|
5471 | The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime |
|
|
5472 | libraries and raw winsocket select is: |
|
|
5473 | .PP |
|
|
5474 | .Vb 2 |
|
|
5475 | \& #define EV_USE_SELECT 1 |
|
|
5476 | \& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
5477 | .Ve |
|
|
5478 | .PP |
|
|
5479 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
5480 | complexity in the O(nX) range when using win32. |
|
|
5481 | .PP |
|
|
5482 | \fILimited number of file descriptors\fR |
|
|
5483 | .IX Subsection "Limited number of file descriptors" |
|
|
5484 | .PP |
|
|
5485 | Windows has numerous arbitrary (and low) limits on things. |
|
|
5486 | .PP |
|
|
5487 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
5488 | of \f(CW64\fR handles (probably owning to the fact that all windows kernels |
|
|
5489 | can only wait for \f(CW64\fR things at the same time internally; Microsoft |
|
|
5490 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
5491 | previous thread in each. Sounds great!). |
|
|
5492 | .PP |
|
|
5493 | Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR |
|
|
5494 | to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select |
|
|
5495 | call (which might be in libev or elsewhere, for example, perl and many |
|
|
5496 | other interpreters do their own select emulation on windows). |
|
|
5497 | .PP |
|
|
5498 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
5499 | libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR |
|
|
5500 | fetish or something like this inside Microsoft). You can increase this |
|
|
5501 | by calling \f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR |
|
|
5502 | (another arbitrary limit), but is broken in many versions of the Microsoft |
|
|
5503 | runtime libraries. This might get you to about \f(CW512\fR or \f(CW2048\fR sockets |
|
|
5504 | (depending on windows version and/or the phase of the moon). To get more, |
|
|
5505 | you need to wrap all I/O functions and provide your own fd management, but |
|
|
5506 | the cost of calling select (O(nX)) will likely make this unworkable. |
|
|
5507 | .SS "\s-1PORTABILITY REQUIREMENTS\s0" |
|
|
5508 | .IX Subsection "PORTABILITY REQUIREMENTS" |
|
|
5509 | In addition to a working ISO-C implementation and of course the |
|
|
5510 | backend-specific APIs, libev relies on a few additional extensions: |
|
|
5511 | .ie n .IP """void (*)(ev_watcher_type *, int revents)"" must have compatible calling conventions regardless of ""ev_watcher_type *""." 4 |
|
|
5512 | .el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4 |
|
|
5513 | .IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *." |
|
|
5514 | Libev assumes not only that all watcher pointers have the same internal |
|
|
5515 | structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO C\s0 for example), but it also |
|
|
5516 | assumes that the same (machine) code can be used to call any watcher |
|
|
5517 | callback: The watcher callbacks have different type signatures, but libev |
|
|
5518 | calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally. |
|
|
5519 | .IP "null pointers and integer zero are represented by 0 bytes" 4 |
|
|
5520 | .IX Item "null pointers and integer zero are represented by 0 bytes" |
|
|
5521 | Libev uses \f(CW\*(C`memset\*(C'\fR to initialise structs and arrays to \f(CW0\fR bytes, and |
|
|
5522 | relies on this setting pointers and integers to null. |
|
|
5523 | .IP "pointer accesses must be thread-atomic" 4 |
|
|
5524 | .IX Item "pointer accesses must be thread-atomic" |
|
|
5525 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5526 | writable in one piece \- this is the case on all current architectures. |
|
|
5527 | .ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4 |
|
|
5528 | .el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4 |
|
|
5529 | .IX Item "sig_atomic_t volatile must be thread-atomic as well" |
|
|
5530 | The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as |
|
|
5531 | \&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different |
|
|
5532 | threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is |
|
|
5533 | believed to be sufficiently portable. |
|
|
5534 | .ie n .IP """sigprocmask"" must work in a threaded environment" 4 |
|
|
5535 | .el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4 |
|
|
5536 | .IX Item "sigprocmask must work in a threaded environment" |
|
|
5537 | Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not |
|
|
5538 | allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical |
|
|
5539 | pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main |
|
|
5540 | thread\*(R" or will block signals process-wide, both behaviours would |
|
|
5541 | be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and |
|
|
5542 | \&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however. |
|
|
5543 | .Sp |
|
|
5544 | The most portable way to handle signals is to block signals in all threads |
|
|
5545 | except the initial one, and run the signal handling loop in the initial |
|
|
5546 | thread as well. |
|
|
5547 | .ie n .IP """long"" must be large enough for common memory allocation sizes" 4 |
|
|
5548 | .el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4 |
|
|
5549 | .IX Item "long must be large enough for common memory allocation sizes" |
|
|
5550 | To improve portability and simplify its \s-1API,\s0 libev uses \f(CW\*(C`long\*(C'\fR internally |
|
|
5551 | instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On non-POSIX |
|
|
5552 | systems (Microsoft...) this might be unexpectedly low, but is still at |
|
|
5553 | least 31 bits everywhere, which is enough for hundreds of millions of |
|
|
5554 | watchers. |
|
|
5555 | .ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4 |
|
|
5556 | .el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4 |
|
|
5557 | .IX Item "double must hold a time value in seconds with enough accuracy" |
|
|
5558 | The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to |
|
|
5559 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
|
|
5560 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
5561 | (the design goal for libev). This requirement is overfulfilled by |
|
|
5562 | implementations using \s-1IEEE 754,\s0 which is basically all existing ones. |
|
|
5563 | .Sp |
|
|
5564 | With \s-1IEEE 754\s0 doubles, you get microsecond accuracy until at least the |
|
|
5565 | year 2255 (and millisecond accuracy till the year 287396 \- by then, libev |
|
|
5566 | is either obsolete or somebody patched it to use \f(CW\*(C`long double\*(C'\fR or |
|
|
5567 | something like that, just kidding). |
|
|
5568 | .PP |
|
|
5569 | If you know of other additional requirements drop me a note. |
3468 | .SH "COMPLEXITIES" |
5570 | .SH "ALGORITHMIC COMPLEXITIES" |
3469 | .IX Header "COMPLEXITIES" |
5571 | .IX Header "ALGORITHMIC COMPLEXITIES" |
3470 | In this section the complexities of (many of) the algorithms used inside |
5572 | In this section the complexities of (many of) the algorithms used inside |
3471 | libev will be explained. For complexity discussions about backends see the |
5573 | libev will be documented. For complexity discussions about backends see |
3472 | documentation for \f(CW\*(C`ev_default_init\*(C'\fR. |
5574 | the documentation for \f(CW\*(C`ev_default_init\*(C'\fR. |
3473 | .PP |
5575 | .PP |
3474 | All of the following are about amortised time: If an array needs to be |
5576 | All of the following are about amortised time: If an array needs to be |
3475 | extended, libev needs to realloc and move the whole array, but this |
5577 | extended, libev needs to realloc and move the whole array, but this |
3476 | happens asymptotically never with higher number of elements, so O(1) might |
5578 | happens asymptotically rarer with higher number of elements, so O(1) might |
3477 | mean it might do a lengthy realloc operation in rare cases, but on average |
5579 | mean that libev does a lengthy realloc operation in rare cases, but on |
3478 | it is much faster and asymptotically approaches constant time. |
5580 | average it is much faster and asymptotically approaches constant time. |
3479 | .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 |
5581 | .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 |
3480 | .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" |
5582 | .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" |
3481 | This means that, when you have a watcher that triggers in one hour and |
5583 | This means that, when you have a watcher that triggers in one hour and |
3482 | there are 100 watchers that would trigger before that then inserting will |
5584 | there are 100 watchers that would trigger before that, then inserting will |
3483 | have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers. |
5585 | have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers. |
3484 | .IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4 |
5586 | .IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4 |
3485 | .IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" |
5587 | .IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" |
3486 | That means that changing a timer costs less than removing/adding them |
5588 | That means that changing a timer costs less than removing/adding them, |
3487 | as only the relative motion in the event queue has to be paid for. |
5589 | as only the relative motion in the event queue has to be paid for. |
3488 | .IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4 |
5590 | .IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4 |
3489 | .IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" |
5591 | .IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" |
3490 | These just add the watcher into an array or at the head of a list. |
5592 | These just add the watcher into an array or at the head of a list. |
3491 | .IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4 |
5593 | .IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4 |
3492 | .IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)" |
5594 | .IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)" |
3493 | .PD 0 |
5595 | .PD 0 |
3494 | .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 |
5596 | .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 |
3495 | .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" |
5597 | .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" |
3496 | .PD |
5598 | .PD |
3497 | These watchers are stored in lists then need to be walked to find the |
5599 | These watchers are stored in lists, so they need to be walked to find the |
3498 | correct watcher to remove. The lists are usually short (you don't usually |
5600 | correct watcher to remove. The lists are usually short (you don't usually |
3499 | have many watchers waiting for the same fd or signal). |
5601 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
5602 | is rare). |
3500 | .IP "Finding the next timer in each loop iteration: O(1)" 4 |
5603 | .IP "Finding the next timer in each loop iteration: O(1)" 4 |
3501 | .IX Item "Finding the next timer in each loop iteration: O(1)" |
5604 | .IX Item "Finding the next timer in each loop iteration: O(1)" |
3502 | By virtue of using a binary or 4\-heap, the next timer is always found at a |
5605 | By virtue of using a binary or 4\-heap, the next timer is always found at a |
3503 | fixed position in the storage array. |
5606 | fixed position in the storage array. |
3504 | .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 |
5607 | .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 |
… | |
… | |
3523 | .IX Item "Processing ev_async_send: O(number_of_async_watchers)" |
5626 | .IX Item "Processing ev_async_send: O(number_of_async_watchers)" |
3524 | .IP "Processing signals: O(max_signal_number)" 4 |
5627 | .IP "Processing signals: O(max_signal_number)" 4 |
3525 | .IX Item "Processing signals: O(max_signal_number)" |
5628 | .IX Item "Processing signals: O(max_signal_number)" |
3526 | .PD |
5629 | .PD |
3527 | Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR |
5630 | Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR |
3528 | calls in the current loop iteration. Checking for async and signal events |
5631 | calls in the current loop iteration and the loop is currently |
|
|
5632 | blocked. Checking for async and signal events involves iterating over all |
3529 | involves iterating over all running async watchers or all signal numbers. |
5633 | running async watchers or all signal numbers. |
3530 | .SH "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
5634 | .SH "PORTING FROM LIBEV 3.X TO 4.X" |
3531 | .IX Header "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
5635 | .IX Header "PORTING FROM LIBEV 3.X TO 4.X" |
3532 | Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev |
5636 | The major version 4 introduced some incompatible changes to the \s-1API.\s0 |
3533 | requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0 |
|
|
3534 | model. Libev still offers limited functionality on this platform in |
|
|
3535 | the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket |
|
|
3536 | descriptors. This only applies when using Win32 natively, not when using |
|
|
3537 | e.g. cygwin. |
|
|
3538 | .PP |
5637 | .PP |
3539 | Lifting these limitations would basically require the full |
5638 | At the moment, the \f(CW\*(C`ev.h\*(C'\fR header file provides compatibility definitions |
3540 | re-implementation of the I/O system. If you are into these kinds of |
5639 | for all changes, so most programs should still compile. The compatibility |
3541 | things, then note that glib does exactly that for you in a very portable |
5640 | layer might be removed in later versions of libev, so better update to the |
3542 | way (note also that glib is the slowest event library known to man). |
5641 | new \s-1API\s0 early than late. |
3543 | .PP |
5642 | .ie n .IP """EV_COMPAT3"" backwards compatibility mechanism" 4 |
3544 | There is no supported compilation method available on windows except |
5643 | .el .IP "\f(CWEV_COMPAT3\fR backwards compatibility mechanism" 4 |
3545 | embedding it into other applications. |
5644 | .IX Item "EV_COMPAT3 backwards compatibility mechanism" |
3546 | .PP |
5645 | The backward compatibility mechanism can be controlled by |
3547 | Not a libev limitation but worth mentioning: windows apparently doesn't |
5646 | \&\f(CW\*(C`EV_COMPAT3\*(C'\fR. See \*(L"\s-1PREPROCESSOR SYMBOLS/MACROS\*(R"\s0 in the \*(L"\s-1EMBEDDING\*(R"\s0 |
3548 | accept large writes: instead of resulting in a partial write, windows will |
5647 | section. |
3549 | either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large, |
5648 | .ie n .IP """ev_default_destroy"" and ""ev_default_fork"" have been removed" 4 |
3550 | so make sure you only write small amounts into your sockets (less than a |
5649 | .el .IP "\f(CWev_default_destroy\fR and \f(CWev_default_fork\fR have been removed" 4 |
3551 | megabyte seems safe, but this apparently depends on the amount of memory |
5650 | .IX Item "ev_default_destroy and ev_default_fork have been removed" |
3552 | available). |
5651 | These calls can be replaced easily by their \f(CW\*(C`ev_loop_xxx\*(C'\fR counterparts: |
3553 | .PP |
5652 | .Sp |
3554 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
3555 | the abysmal performance of winsockets, using a large number of sockets |
|
|
3556 | is not recommended (and not reasonable). If your program needs to use |
|
|
3557 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
3558 | different implementation for windows, as libev offers the \s-1POSIX\s0 readiness |
|
|
3559 | notification model, which cannot be implemented efficiently on windows |
|
|
3560 | (Microsoft monopoly games). |
|
|
3561 | .PP |
|
|
3562 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
3563 | section for details) and use the following \fIevwrap.h\fR header file instead |
|
|
3564 | of \fIev.h\fR: |
|
|
3565 | .PP |
|
|
3566 | .Vb 2 |
5653 | .Vb 2 |
3567 | \& #define EV_STANDALONE /* keeps ev from requiring config.h */ |
5654 | \& ev_loop_destroy (EV_DEFAULT_UC); |
3568 | \& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
5655 | \& ev_loop_fork (EV_DEFAULT); |
3569 | \& |
|
|
3570 | \& #include "ev.h" |
|
|
3571 | .Ve |
5656 | .Ve |
3572 | .PP |
5657 | .IP "function/symbol renames" 4 |
3573 | And compile the following \fIevwrap.c\fR file into your project (make sure |
5658 | .IX Item "function/symbol renames" |
3574 | you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!): |
5659 | A number of functions and symbols have been renamed: |
3575 | .PP |
|
|
3576 | .Vb 2 |
|
|
3577 | \& #include "evwrap.h" |
|
|
3578 | \& #include "ev.c" |
|
|
3579 | .Ve |
|
|
3580 | .IP "The winsocket select function" 4 |
|
|
3581 | .IX Item "The winsocket select function" |
|
|
3582 | The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it |
|
|
3583 | requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is |
|
|
3584 | also extremely buggy). This makes select very inefficient, and also |
|
|
3585 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
3586 | C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the |
|
|
3587 | discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and |
|
|
3588 | \&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info. |
|
|
3589 | .Sp |
5660 | .Sp |
3590 | The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime |
|
|
3591 | libraries and raw winsocket select is: |
|
|
3592 | .Sp |
|
|
3593 | .Vb 2 |
|
|
3594 | \& #define EV_USE_SELECT 1 |
|
|
3595 | \& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
3596 | .Ve |
|
|
3597 | .Sp |
|
|
3598 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
3599 | complexity in the O(nA\*^X) range when using win32. |
|
|
3600 | .IP "Limited number of file descriptors" 4 |
|
|
3601 | .IX Item "Limited number of file descriptors" |
|
|
3602 | Windows has numerous arbitrary (and low) limits on things. |
|
|
3603 | .Sp |
|
|
3604 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
3605 | of \f(CW64\fR handles (probably owning to the fact that all windows kernels |
|
|
3606 | can only wait for \f(CW64\fR things at the same time internally; Microsoft |
|
|
3607 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3608 | previous thread in each. Great). |
|
|
3609 | .Sp |
|
|
3610 | Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR |
|
|
3611 | to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select |
|
|
3612 | call (which might be in libev or elsewhere, for example, perl does its own |
|
|
3613 | select emulation on windows). |
|
|
3614 | .Sp |
|
|
3615 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
3616 | libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR fetish |
|
|
3617 | or something like this inside Microsoft). You can increase this by calling |
|
|
3618 | \&\f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR (another |
|
|
3619 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
|
|
3620 | libraries. |
|
|
3621 | .Sp |
|
|
3622 | This might get you to about \f(CW512\fR or \f(CW2048\fR sockets (depending on |
|
|
3623 | windows version and/or the phase of the moon). To get more, you need to |
|
|
3624 | wrap all I/O functions and provide your own fd management, but the cost of |
|
|
3625 | calling select (O(nA\*^X)) will likely make this unworkable. |
|
|
3626 | .SH "PORTABILITY REQUIREMENTS" |
|
|
3627 | .IX Header "PORTABILITY REQUIREMENTS" |
|
|
3628 | In addition to a working ISO-C implementation, libev relies on a few |
|
|
3629 | additional extensions: |
|
|
3630 | .ie n .IP """void (*)(ev_watcher_type *, int revents)""\fR must have compatible calling conventions regardless of \f(CW""ev_watcher_type *""." 4 |
|
|
3631 | .el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4 |
|
|
3632 | .IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *." |
|
|
3633 | Libev assumes not only that all watcher pointers have the same internal |
|
|
3634 | structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also |
|
|
3635 | assumes that the same (machine) code can be used to call any watcher |
|
|
3636 | callback: The watcher callbacks have different type signatures, but libev |
|
|
3637 | calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally. |
|
|
3638 | .ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4 |
|
|
3639 | .el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4 |
|
|
3640 | .IX Item "sig_atomic_t volatile must be thread-atomic as well" |
|
|
3641 | The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as |
|
|
3642 | \&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different |
|
|
3643 | threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is |
|
|
3644 | believed to be sufficiently portable. |
|
|
3645 | .ie n .IP """sigprocmask"" must work in a threaded environment" 4 |
|
|
3646 | .el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4 |
|
|
3647 | .IX Item "sigprocmask must work in a threaded environment" |
|
|
3648 | Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not |
|
|
3649 | allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical |
|
|
3650 | pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main |
|
|
3651 | thread\*(R" or will block signals process-wide, both behaviours would |
|
|
3652 | be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and |
|
|
3653 | \&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however. |
|
|
3654 | .Sp |
|
|
3655 | The most portable way to handle signals is to block signals in all threads |
|
|
3656 | except the initial one, and run the default loop in the initial thread as |
|
|
3657 | well. |
|
|
3658 | .ie n .IP """long"" must be large enough for common memory allocation sizes" 4 |
|
|
3659 | .el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4 |
|
|
3660 | .IX Item "long must be large enough for common memory allocation sizes" |
|
|
3661 | To improve portability and simplify using libev, libev uses \f(CW\*(C`long\*(C'\fR |
|
|
3662 | internally instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On |
|
|
3663 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3664 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3665 | millions of watchers. |
|
|
3666 | .ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4 |
|
|
3667 | .el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4 |
|
|
3668 | .IX Item "double must hold a time value in seconds with enough accuracy" |
|
|
3669 | The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to |
|
|
3670 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3671 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3672 | implementations implementing \s-1IEEE\s0 754 (basically all existing ones). |
|
|
3673 | .PP |
|
|
3674 | If you know of other additional requirements drop me a note. |
|
|
3675 | .SH "COMPILER WARNINGS" |
|
|
3676 | .IX Header "COMPILER WARNINGS" |
|
|
3677 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3678 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3679 | scared by this. |
|
|
3680 | .PP |
|
|
3681 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3682 | has different warnings, and each user has different tastes regarding |
|
|
3683 | warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when |
|
|
3684 | targeting a specific compiler and compiler-version. |
|
|
3685 | .PP |
|
|
3686 | Another reason is that some compiler warnings require elaborate |
|
|
3687 | workarounds, or other changes to the code that make it less clear and less |
|
|
3688 | maintainable. |
|
|
3689 | .PP |
|
|
3690 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3691 | wrong (because they don't actually warn about the condition their message |
|
|
3692 | seems to warn about). |
|
|
3693 | .PP |
|
|
3694 | While libev is written to generate as few warnings as possible, |
|
|
3695 | \&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev |
|
|
3696 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3697 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3698 | warnings, not errors, or proof of bugs. |
|
|
3699 | .SH "VALGRIND" |
|
|
3700 | .IX Header "VALGRIND" |
|
|
3701 | Valgrind has a special section here because it is a popular tool that is |
|
|
3702 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3703 | .PP |
|
|
3704 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3705 | in libev, then check twice: If valgrind reports something like: |
|
|
3706 | .PP |
|
|
3707 | .Vb 3 |
5661 | .Vb 3 |
3708 | \& ==2274== definitely lost: 0 bytes in 0 blocks. |
5662 | \& ev_loop => ev_run |
3709 | \& ==2274== possibly lost: 0 bytes in 0 blocks. |
5663 | \& EVLOOP_NONBLOCK => EVRUN_NOWAIT |
3710 | \& ==2274== still reachable: 256 bytes in 1 blocks. |
5664 | \& EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5665 | \& |
|
|
5666 | \& ev_unloop => ev_break |
|
|
5667 | \& EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5668 | \& EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5669 | \& EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5670 | \& |
|
|
5671 | \& EV_TIMEOUT => EV_TIMER |
|
|
5672 | \& |
|
|
5673 | \& ev_loop_count => ev_iteration |
|
|
5674 | \& ev_loop_depth => ev_depth |
|
|
5675 | \& ev_loop_verify => ev_verify |
3711 | .Ve |
5676 | .Ve |
3712 | .PP |
5677 | .Sp |
3713 | Then there is no memory leak. Similarly, under some circumstances, |
5678 | Most functions working on \f(CW\*(C`struct ev_loop\*(C'\fR objects don't have an |
3714 | valgrind might report kernel bugs as if it were a bug in libev, or it |
5679 | \&\f(CW\*(C`ev_loop_\*(C'\fR prefix, so it was removed; \f(CW\*(C`ev_loop\*(C'\fR, \f(CW\*(C`ev_unloop\*(C'\fR and |
3715 | might be confused (it is a very good tool, but only a tool). |
5680 | associated constants have been renamed to not collide with the \f(CW\*(C`struct |
3716 | .PP |
5681 | ev_loop\*(C'\fR anymore and \f(CW\*(C`EV_TIMER\*(C'\fR now follows the same naming scheme |
3717 | If you are unsure about something, feel free to contact the mailing list |
5682 | as all other watcher types. Note that \f(CW\*(C`ev_loop_fork\*(C'\fR is still called |
3718 | with the full valgrind report and an explanation on why you think this is |
5683 | \&\f(CW\*(C`ev_loop_fork\*(C'\fR because it would otherwise clash with the \f(CW\*(C`ev_fork\*(C'\fR |
3719 | a bug in libev. However, don't be annoyed when you get a brisk \*(L"this is |
5684 | typedef. |
3720 | no bug\*(R" answer and take the chance of learning how to interpret valgrind |
5685 | .ie n .IP """EV_MINIMAL"" mechanism replaced by ""EV_FEATURES""" 4 |
3721 | properly. |
5686 | .el .IP "\f(CWEV_MINIMAL\fR mechanism replaced by \f(CWEV_FEATURES\fR" 4 |
3722 | .PP |
5687 | .IX Item "EV_MINIMAL mechanism replaced by EV_FEATURES" |
3723 | If you need, for some reason, empty reports from valgrind for your project |
5688 | The preprocessor symbol \f(CW\*(C`EV_MINIMAL\*(C'\fR has been replaced by a different |
3724 | I suggest using suppression lists. |
5689 | mechanism, \f(CW\*(C`EV_FEATURES\*(C'\fR. Programs using \f(CW\*(C`EV_MINIMAL\*(C'\fR usually compile |
|
|
5690 | and work, but the library code will of course be larger. |
|
|
5691 | .SH "GLOSSARY" |
|
|
5692 | .IX Header "GLOSSARY" |
|
|
5693 | .IP "active" 4 |
|
|
5694 | .IX Item "active" |
|
|
5695 | A watcher is active as long as it has been started and not yet stopped. |
|
|
5696 | See \*(L"\s-1WATCHER STATES\*(R"\s0 for details. |
|
|
5697 | .IP "application" 4 |
|
|
5698 | .IX Item "application" |
|
|
5699 | In this document, an application is whatever is using libev. |
|
|
5700 | .IP "backend" 4 |
|
|
5701 | .IX Item "backend" |
|
|
5702 | The part of the code dealing with the operating system interfaces. |
|
|
5703 | .IP "callback" 4 |
|
|
5704 | .IX Item "callback" |
|
|
5705 | The address of a function that is called when some event has been |
|
|
5706 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
5707 | received the event, and the actual event bitset. |
|
|
5708 | .IP "callback/watcher invocation" 4 |
|
|
5709 | .IX Item "callback/watcher invocation" |
|
|
5710 | The act of calling the callback associated with a watcher. |
|
|
5711 | .IP "event" 4 |
|
|
5712 | .IX Item "event" |
|
|
5713 | A change of state of some external event, such as data now being available |
|
|
5714 | for reading on a file descriptor, time having passed or simply not having |
|
|
5715 | any other events happening anymore. |
|
|
5716 | .Sp |
|
|
5717 | In libev, events are represented as single bits (such as \f(CW\*(C`EV_READ\*(C'\fR or |
|
|
5718 | \&\f(CW\*(C`EV_TIMER\*(C'\fR). |
|
|
5719 | .IP "event library" 4 |
|
|
5720 | .IX Item "event library" |
|
|
5721 | A software package implementing an event model and loop. |
|
|
5722 | .IP "event loop" 4 |
|
|
5723 | .IX Item "event loop" |
|
|
5724 | An entity that handles and processes external events and converts them |
|
|
5725 | into callback invocations. |
|
|
5726 | .IP "event model" 4 |
|
|
5727 | .IX Item "event model" |
|
|
5728 | The model used to describe how an event loop handles and processes |
|
|
5729 | watchers and events. |
|
|
5730 | .IP "pending" 4 |
|
|
5731 | .IX Item "pending" |
|
|
5732 | A watcher is pending as soon as the corresponding event has been |
|
|
5733 | detected. See \*(L"\s-1WATCHER STATES\*(R"\s0 for details. |
|
|
5734 | .IP "real time" 4 |
|
|
5735 | .IX Item "real time" |
|
|
5736 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
5737 | .IP "wall-clock time" 4 |
|
|
5738 | .IX Item "wall-clock time" |
|
|
5739 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
5740 | be wrong and jump forwards and backwards, e.g. when you adjust your |
|
|
5741 | clock. |
|
|
5742 | .IP "watcher" 4 |
|
|
5743 | .IX Item "watcher" |
|
|
5744 | A data structure that describes interest in certain events. Watchers need |
|
|
5745 | to be started (attached to an event loop) before they can receive events. |
3725 | .SH "AUTHOR" |
5746 | .SH "AUTHOR" |
3726 | .IX Header "AUTHOR" |
5747 | .IX Header "AUTHOR" |
3727 | Marc Lehmann <libev@schmorp.de>. |
5748 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5749 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |