… | |
… | |
2 | |
2 | |
3 | libev - a high performance full-featured event loop written in C |
3 | libev - a high performance full-featured event loop written in C |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
8 | |
8 | |
9 | =head1 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
|
|
11 | // a single header file is required |
11 | #include <ev.h> |
12 | #include <ev.h> |
12 | |
13 | |
|
|
14 | #include <stdio.h> // for puts |
|
|
15 | |
|
|
16 | // every watcher type has its own typedef'd struct |
|
|
17 | // with the name ev_TYPE |
13 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
14 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
15 | |
20 | |
16 | /* called when data readable on stdin */ |
21 | // all watcher callbacks have a similar signature |
|
|
22 | // this callback is called when data is readable on stdin |
17 | static void |
23 | static void |
18 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
24 | stdin_cb (EV_P_ ev_io *w, int revents) |
19 | { |
25 | { |
20 | /* puts ("stdin ready"); */ |
26 | puts ("stdin ready"); |
21 | ev_io_stop (EV_A_ w); /* just a syntax example */ |
27 | // for one-shot events, one must manually stop the watcher |
22 | ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */ |
28 | // with its corresponding stop function. |
|
|
29 | ev_io_stop (EV_A_ w); |
|
|
30 | |
|
|
31 | // this causes all nested ev_loop's to stop iterating |
|
|
32 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
23 | } |
33 | } |
24 | |
34 | |
|
|
35 | // another callback, this time for a time-out |
25 | static void |
36 | static void |
26 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
27 | { |
38 | { |
28 | /* puts ("timeout"); */ |
39 | puts ("timeout"); |
29 | ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */ |
40 | // this causes the innermost ev_loop to stop iterating |
|
|
41 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
30 | } |
42 | } |
31 | |
43 | |
32 | int |
44 | int |
33 | main (void) |
45 | main (void) |
34 | { |
46 | { |
|
|
47 | // use the default event loop unless you have special needs |
35 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
36 | |
49 | |
37 | /* initialise an io watcher, then start it */ |
50 | // initialise an io watcher, then start it |
|
|
51 | // this one will watch for stdin to become readable |
38 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
39 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
40 | |
54 | |
|
|
55 | // initialise a timer watcher, then start it |
41 | /* simple non-repeating 5.5 second timeout */ |
56 | // simple non-repeating 5.5 second timeout |
42 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
43 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
44 | |
59 | |
45 | /* loop till timeout or data ready */ |
60 | // now wait for events to arrive |
46 | ev_loop (loop, 0); |
61 | ev_loop (loop, 0); |
47 | |
62 | |
|
|
63 | // unloop was called, so exit |
48 | return 0; |
64 | return 0; |
49 | } |
65 | } |
50 | |
66 | |
51 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
52 | |
68 | |
|
|
69 | This document documents the libev software package. |
|
|
70 | |
53 | The newest version of this document is also available as a html-formatted |
71 | The newest version of this document is also available as an html-formatted |
54 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
55 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
|
|
74 | |
|
|
75 | While this document tries to be as complete as possible in documenting |
|
|
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
|
|
77 | on event-based programming, nor will it introduce event-based programming |
|
|
78 | with libev. |
|
|
79 | |
|
|
80 | Familarity with event based programming techniques in general is assumed |
|
|
81 | throughout this document. |
|
|
82 | |
|
|
83 | =head1 ABOUT LIBEV |
56 | |
84 | |
57 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
58 | file descriptor being readable or a timeout occuring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
59 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
60 | |
88 | |
61 | To do this, it must take more or less complete control over your process |
89 | To do this, it must take more or less complete control over your process |
62 | (or thread) by executing the I<event loop> handler, and will then |
90 | (or thread) by executing the I<event loop> handler, and will then |
63 | communicate events via a callback mechanism. |
91 | communicate events via a callback mechanism. |
… | |
… | |
65 | You register interest in certain events by registering so-called I<event |
93 | You register interest in certain events by registering so-called I<event |
66 | watchers>, which are relatively small C structures you initialise with the |
94 | watchers>, which are relatively small C structures you initialise with the |
67 | details of the event, and then hand it over to libev by I<starting> the |
95 | details of the event, and then hand it over to libev by I<starting> the |
68 | watcher. |
96 | watcher. |
69 | |
97 | |
70 | =head1 FEATURES |
98 | =head2 FEATURES |
71 | |
99 | |
72 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
73 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
74 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
75 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
… | |
… | |
82 | |
110 | |
83 | It also is quite fast (see this |
111 | It also is quite fast (see this |
84 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
112 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
85 | for example). |
113 | for example). |
86 | |
114 | |
87 | =head1 CONVENTIONS |
115 | =head2 CONVENTIONS |
88 | |
116 | |
89 | Libev is very configurable. In this manual the default configuration will |
117 | Libev is very configurable. In this manual the default (and most common) |
90 | be described, which supports multiple event loops. For more info about |
118 | configuration will be described, which supports multiple event loops. For |
91 | various configuration options please have a look at B<EMBED> section in |
119 | more info about various configuration options please have a look at |
92 | this manual. If libev was configured without support for multiple event |
120 | B<EMBED> section in this manual. If libev was configured without support |
93 | loops, then all functions taking an initial argument of name C<loop> |
121 | for multiple event loops, then all functions taking an initial argument of |
94 | (which is always of type C<struct ev_loop *>) will not have this argument. |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
|
|
123 | this argument. |
95 | |
124 | |
96 | =head1 TIME REPRESENTATION |
125 | =head2 TIME REPRESENTATION |
97 | |
126 | |
98 | Libev represents time as a single floating point number, representing the |
127 | Libev represents time as a single floating point number, representing |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
100 | the beginning of 1970, details are complicated, don't ask). This type is |
129 | near the beginning of 1970, details are complicated, don't ask). This |
101 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
130 | type is called C<ev_tstamp>, which is what you should use too. It usually |
102 | to the C<double> type in C, and when you need to do any calculations on |
131 | aliases to the C<double> type in C. When you need to do any calculations |
103 | it, you should treat it as such. |
132 | on it, you should treat it as some floating point value. Unlike the name |
|
|
133 | component C<stamp> might indicate, it is also used for time differences |
|
|
134 | throughout libev. |
|
|
135 | |
|
|
136 | =head1 ERROR HANDLING |
|
|
137 | |
|
|
138 | Libev knows three classes of errors: operating system errors, usage errors |
|
|
139 | and internal errors (bugs). |
|
|
140 | |
|
|
141 | When libev catches an operating system error it cannot handle (for example |
|
|
142 | a system call indicating a condition libev cannot fix), it calls the callback |
|
|
143 | set via C<ev_set_syserr_cb>, which is supposed to fix the problem or |
|
|
144 | abort. The default is to print a diagnostic message and to call C<abort |
|
|
145 | ()>. |
|
|
146 | |
|
|
147 | When libev detects a usage error such as a negative timer interval, then |
|
|
148 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
|
|
149 | so C<NDEBUG> will disable this checking): these are programming errors in |
|
|
150 | the libev caller and need to be fixed there. |
|
|
151 | |
|
|
152 | Libev also has a few internal error-checking C<assert>ions, and also has |
|
|
153 | extensive consistency checking code. These do not trigger under normal |
|
|
154 | circumstances, as they indicate either a bug in libev or worse. |
|
|
155 | |
104 | |
156 | |
105 | =head1 GLOBAL FUNCTIONS |
157 | =head1 GLOBAL FUNCTIONS |
106 | |
158 | |
107 | These functions can be called anytime, even before initialising the |
159 | These functions can be called anytime, even before initialising the |
108 | library in any way. |
160 | library in any way. |
… | |
… | |
113 | |
165 | |
114 | Returns the current time as libev would use it. Please note that the |
166 | Returns the current time as libev would use it. Please note that the |
115 | C<ev_now> function is usually faster and also often returns the timestamp |
167 | C<ev_now> function is usually faster and also often returns the timestamp |
116 | you actually want to know. |
168 | you actually want to know. |
117 | |
169 | |
|
|
170 | =item ev_sleep (ev_tstamp interval) |
|
|
171 | |
|
|
172 | Sleep for the given interval: The current thread will be blocked until |
|
|
173 | either it is interrupted or the given time interval has passed. Basically |
|
|
174 | this is a sub-second-resolution C<sleep ()>. |
|
|
175 | |
118 | =item int ev_version_major () |
176 | =item int ev_version_major () |
119 | |
177 | |
120 | =item int ev_version_minor () |
178 | =item int ev_version_minor () |
121 | |
179 | |
122 | You can find out the major and minor version numbers of the library |
180 | You can find out the major and minor ABI version numbers of the library |
123 | you linked against by calling the functions C<ev_version_major> and |
181 | you linked against by calling the functions C<ev_version_major> and |
124 | C<ev_version_minor>. If you want, you can compare against the global |
182 | C<ev_version_minor>. If you want, you can compare against the global |
125 | symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the |
183 | symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the |
126 | version of the library your program was compiled against. |
184 | version of the library your program was compiled against. |
127 | |
185 | |
|
|
186 | These version numbers refer to the ABI version of the library, not the |
|
|
187 | release version. |
|
|
188 | |
128 | Usually, it's a good idea to terminate if the major versions mismatch, |
189 | Usually, it's a good idea to terminate if the major versions mismatch, |
129 | as this indicates an incompatible change. Minor versions are usually |
190 | as this indicates an incompatible change. Minor versions are usually |
130 | compatible to older versions, so a larger minor version alone is usually |
191 | compatible to older versions, so a larger minor version alone is usually |
131 | not a problem. |
192 | not a problem. |
132 | |
193 | |
133 | Example: Make sure we haven't accidentally been linked against the wrong |
194 | Example: Make sure we haven't accidentally been linked against the wrong |
134 | version. |
195 | version. |
135 | |
196 | |
136 | assert (("libev version mismatch", |
197 | assert (("libev version mismatch", |
137 | ev_version_major () == EV_VERSION_MAJOR |
198 | ev_version_major () == EV_VERSION_MAJOR |
138 | && ev_version_minor () >= EV_VERSION_MINOR)); |
199 | && ev_version_minor () >= EV_VERSION_MINOR)); |
139 | |
200 | |
140 | =item unsigned int ev_supported_backends () |
201 | =item unsigned int ev_supported_backends () |
141 | |
202 | |
142 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
203 | Return the set of all backends (i.e. their corresponding C<EV_BACKEND_*> |
143 | value) compiled into this binary of libev (independent of their |
204 | value) compiled into this binary of libev (independent of their |
… | |
… | |
145 | a description of the set values. |
206 | a description of the set values. |
146 | |
207 | |
147 | Example: make sure we have the epoll method, because yeah this is cool and |
208 | Example: make sure we have the epoll method, because yeah this is cool and |
148 | a must have and can we have a torrent of it please!!!11 |
209 | a must have and can we have a torrent of it please!!!11 |
149 | |
210 | |
150 | assert (("sorry, no epoll, no sex", |
211 | assert (("sorry, no epoll, no sex", |
151 | ev_supported_backends () & EVBACKEND_EPOLL)); |
212 | ev_supported_backends () & EVBACKEND_EPOLL)); |
152 | |
213 | |
153 | =item unsigned int ev_recommended_backends () |
214 | =item unsigned int ev_recommended_backends () |
154 | |
215 | |
155 | Return the set of all backends compiled into this binary of libev and also |
216 | Return the set of all backends compiled into this binary of libev and also |
156 | recommended for this platform. This set is often smaller than the one |
217 | recommended for this platform. This set is often smaller than the one |
157 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
218 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
158 | most BSDs and will not be autodetected unless you explicitly request it |
219 | most BSDs and will not be auto-detected unless you explicitly request it |
159 | (assuming you know what you are doing). This is the set of backends that |
220 | (assuming you know what you are doing). This is the set of backends that |
160 | libev will probe for if you specify no backends explicitly. |
221 | libev will probe for if you specify no backends explicitly. |
161 | |
222 | |
162 | =item unsigned int ev_embeddable_backends () |
223 | =item unsigned int ev_embeddable_backends () |
163 | |
224 | |
… | |
… | |
167 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
228 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
168 | recommended ones. |
229 | recommended ones. |
169 | |
230 | |
170 | See the description of C<ev_embed> watchers for more info. |
231 | See the description of C<ev_embed> watchers for more info. |
171 | |
232 | |
172 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
233 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
173 | |
234 | |
174 | Sets the allocation function to use (the prototype is similar - the |
235 | Sets the allocation function to use (the prototype is similar - the |
175 | semantics is identical - to the realloc C function). It is used to |
236 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
176 | allocate and free memory (no surprises here). If it returns zero when |
237 | used to allocate and free memory (no surprises here). If it returns zero |
177 | memory needs to be allocated, the library might abort or take some |
238 | when memory needs to be allocated (C<size != 0>), the library might abort |
178 | potentially destructive action. The default is your system realloc |
239 | or take some potentially destructive action. |
179 | function. |
240 | |
|
|
241 | Since some systems (at least OpenBSD and Darwin) fail to implement |
|
|
242 | correct C<realloc> semantics, libev will use a wrapper around the system |
|
|
243 | C<realloc> and C<free> functions by default. |
180 | |
244 | |
181 | You could override this function in high-availability programs to, say, |
245 | You could override this function in high-availability programs to, say, |
182 | free some memory if it cannot allocate memory, to use a special allocator, |
246 | free some memory if it cannot allocate memory, to use a special allocator, |
183 | or even to sleep a while and retry until some memory is available. |
247 | or even to sleep a while and retry until some memory is available. |
184 | |
248 | |
185 | Example: Replace the libev allocator with one that waits a bit and then |
249 | Example: Replace the libev allocator with one that waits a bit and then |
186 | retries). |
250 | retries (example requires a standards-compliant C<realloc>). |
187 | |
251 | |
188 | static void * |
252 | static void * |
189 | persistent_realloc (void *ptr, size_t size) |
253 | persistent_realloc (void *ptr, size_t size) |
190 | { |
254 | { |
191 | for (;;) |
255 | for (;;) |
… | |
… | |
200 | } |
264 | } |
201 | |
265 | |
202 | ... |
266 | ... |
203 | ev_set_allocator (persistent_realloc); |
267 | ev_set_allocator (persistent_realloc); |
204 | |
268 | |
205 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
269 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
206 | |
270 | |
207 | Set the callback function to call on a retryable syscall error (such |
271 | Set the callback function to call on a retryable system call error (such |
208 | as failed select, poll, epoll_wait). The message is a printable string |
272 | as failed select, poll, epoll_wait). The message is a printable string |
209 | indicating the system call or subsystem causing the problem. If this |
273 | indicating the system call or subsystem causing the problem. If this |
210 | callback is set, then libev will expect it to remedy the sitution, no |
274 | callback is set, then libev will expect it to remedy the situation, no |
211 | matter what, when it returns. That is, libev will generally retry the |
275 | matter what, when it returns. That is, libev will generally retry the |
212 | requested operation, or, if the condition doesn't go away, do bad stuff |
276 | requested operation, or, if the condition doesn't go away, do bad stuff |
213 | (such as abort). |
277 | (such as abort). |
214 | |
278 | |
215 | Example: This is basically the same thing that libev does internally, too. |
279 | Example: This is basically the same thing that libev does internally, too. |
… | |
… | |
226 | |
290 | |
227 | =back |
291 | =back |
228 | |
292 | |
229 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
293 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
230 | |
294 | |
231 | An event loop is described by a C<struct ev_loop *>. The library knows two |
295 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
232 | types of such loops, the I<default> loop, which supports signals and child |
296 | is I<not> optional in this case, as there is also an C<ev_loop> |
233 | events, and dynamically created loops which do not. |
297 | I<function>). |
234 | |
298 | |
235 | If you use threads, a common model is to run the default event loop |
299 | The library knows two types of such loops, the I<default> loop, which |
236 | in your main thread (or in a separate thread) and for each thread you |
300 | supports signals and child events, and dynamically created loops which do |
237 | create, you also create another event loop. Libev itself does no locking |
301 | not. |
238 | whatsoever, so if you mix calls to the same event loop in different |
|
|
239 | threads, make sure you lock (this is usually a bad idea, though, even if |
|
|
240 | done correctly, because it's hideous and inefficient). |
|
|
241 | |
302 | |
242 | =over 4 |
303 | =over 4 |
243 | |
304 | |
244 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
305 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
245 | |
306 | |
… | |
… | |
249 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
310 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
250 | |
311 | |
251 | If you don't know what event loop to use, use the one returned from this |
312 | If you don't know what event loop to use, use the one returned from this |
252 | function. |
313 | function. |
253 | |
314 | |
|
|
315 | Note that this function is I<not> thread-safe, so if you want to use it |
|
|
316 | from multiple threads, you have to lock (note also that this is unlikely, |
|
|
317 | as loops cannot be shared easily between threads anyway). |
|
|
318 | |
|
|
319 | The default loop is the only loop that can handle C<ev_signal> and |
|
|
320 | C<ev_child> watchers, and to do this, it always registers a handler |
|
|
321 | for C<SIGCHLD>. If this is a problem for your application you can either |
|
|
322 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
|
|
323 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
|
|
324 | C<ev_default_init>. |
|
|
325 | |
254 | The flags argument can be used to specify special behaviour or specific |
326 | The flags argument can be used to specify special behaviour or specific |
255 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
327 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
256 | |
328 | |
257 | The following flags are supported: |
329 | The following flags are supported: |
258 | |
330 | |
… | |
… | |
263 | The default flags value. Use this if you have no clue (it's the right |
335 | The default flags value. Use this if you have no clue (it's the right |
264 | thing, believe me). |
336 | thing, believe me). |
265 | |
337 | |
266 | =item C<EVFLAG_NOENV> |
338 | =item C<EVFLAG_NOENV> |
267 | |
339 | |
268 | If this flag bit is ored into the flag value (or the program runs setuid |
340 | If this flag bit is or'ed into the flag value (or the program runs setuid |
269 | or setgid) then libev will I<not> look at the environment variable |
341 | or setgid) then libev will I<not> look at the environment variable |
270 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
342 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
271 | override the flags completely if it is found in the environment. This is |
343 | override the flags completely if it is found in the environment. This is |
272 | useful to try out specific backends to test their performance, or to work |
344 | useful to try out specific backends to test their performance, or to work |
273 | around bugs. |
345 | around bugs. |
… | |
… | |
279 | enabling this flag. |
351 | enabling this flag. |
280 | |
352 | |
281 | This works by calling C<getpid ()> on every iteration of the loop, |
353 | This works by calling C<getpid ()> on every iteration of the loop, |
282 | and thus this might slow down your event loop if you do a lot of loop |
354 | and thus this might slow down your event loop if you do a lot of loop |
283 | iterations and little real work, but is usually not noticeable (on my |
355 | iterations and little real work, but is usually not noticeable (on my |
284 | Linux system for example, C<getpid> is actually a simple 5-insn sequence |
356 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
285 | without a syscall and thus I<very> fast, but my Linux system also has |
357 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
286 | C<pthread_atfork> which is even faster). |
358 | C<pthread_atfork> which is even faster). |
287 | |
359 | |
288 | The big advantage of this flag is that you can forget about fork (and |
360 | The big advantage of this flag is that you can forget about fork (and |
289 | forget about forgetting to tell libev about forking) when you use this |
361 | forget about forgetting to tell libev about forking) when you use this |
290 | flag. |
362 | flag. |
291 | |
363 | |
292 | This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS> |
364 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
293 | environment variable. |
365 | environment variable. |
294 | |
366 | |
295 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
367 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
296 | |
368 | |
297 | This is your standard select(2) backend. Not I<completely> standard, as |
369 | This is your standard select(2) backend. Not I<completely> standard, as |
298 | libev tries to roll its own fd_set with no limits on the number of fds, |
370 | libev tries to roll its own fd_set with no limits on the number of fds, |
299 | but if that fails, expect a fairly low limit on the number of fds when |
371 | but if that fails, expect a fairly low limit on the number of fds when |
300 | using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
372 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
301 | the fastest backend for a low number of fds. |
373 | usually the fastest backend for a low number of (low-numbered :) fds. |
|
|
374 | |
|
|
375 | To get good performance out of this backend you need a high amount of |
|
|
376 | parallelism (most of the file descriptors should be busy). If you are |
|
|
377 | writing a server, you should C<accept ()> in a loop to accept as many |
|
|
378 | connections as possible during one iteration. You might also want to have |
|
|
379 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
|
|
380 | readiness notifications you get per iteration. |
|
|
381 | |
|
|
382 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
|
|
383 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
|
|
384 | C<exceptfds> set on that platform). |
302 | |
385 | |
303 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
386 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
304 | |
387 | |
305 | And this is your standard poll(2) backend. It's more complicated than |
388 | And this is your standard poll(2) backend. It's more complicated |
306 | select, but handles sparse fds better and has no artificial limit on the |
389 | than select, but handles sparse fds better and has no artificial |
307 | number of fds you can use (except it will slow down considerably with a |
390 | limit on the number of fds you can use (except it will slow down |
308 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds). |
391 | considerably with a lot of inactive fds). It scales similarly to select, |
|
|
392 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
|
|
393 | performance tips. |
|
|
394 | |
|
|
395 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
|
|
396 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
309 | |
397 | |
310 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
398 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
311 | |
399 | |
312 | For few fds, this backend is a bit little slower than poll and select, |
400 | For few fds, this backend is a bit little slower than poll and select, |
313 | but it scales phenomenally better. While poll and select usually scale like |
401 | but it scales phenomenally better. While poll and select usually scale |
314 | O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
402 | like O(total_fds) where n is the total number of fds (or the highest fd), |
315 | either O(1) or O(active_fds). |
403 | epoll scales either O(1) or O(active_fds). |
316 | |
404 | |
|
|
405 | The epoll mechanism deserves honorable mention as the most misdesigned |
|
|
406 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
407 | dropping file descriptors, requiring a system call per change per file |
|
|
408 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
409 | so on. The biggest issue is fork races, however - if a program forks then |
|
|
410 | I<both> parent and child process have to recreate the epoll set, which can |
|
|
411 | take considerable time (one syscall per file descriptor) and is of course |
|
|
412 | hard to detect. |
|
|
413 | |
|
|
414 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
|
|
415 | of course I<doesn't>, and epoll just loves to report events for totally |
|
|
416 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
417 | even remove them from the set) than registered in the set (especially |
|
|
418 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
419 | employing an additional generation counter and comparing that against the |
|
|
420 | events to filter out spurious ones, recreating the set when required. |
|
|
421 | |
317 | While stopping and starting an I/O watcher in the same iteration will |
422 | While stopping, setting and starting an I/O watcher in the same iteration |
318 | result in some caching, there is still a syscall per such incident |
423 | will result in some caching, there is still a system call per such |
319 | (because the fd could point to a different file description now), so its |
424 | incident (because the same I<file descriptor> could point to a different |
320 | best to avoid that. Also, dup()ed file descriptors might not work very |
425 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
321 | well if you register events for both fds. |
426 | file descriptors might not work very well if you register events for both |
|
|
427 | file descriptors. |
322 | |
428 | |
323 | Please note that epoll sometimes generates spurious notifications, so you |
429 | Best performance from this backend is achieved by not unregistering all |
324 | need to use non-blocking I/O or other means to avoid blocking when no data |
430 | watchers for a file descriptor until it has been closed, if possible, |
325 | (or space) is available. |
431 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
432 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
433 | extra overhead. A fork can both result in spurious notifications as well |
|
|
434 | as in libev having to destroy and recreate the epoll object, which can |
|
|
435 | take considerable time and thus should be avoided. |
|
|
436 | |
|
|
437 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
438 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
439 | the usage. So sad. |
|
|
440 | |
|
|
441 | While nominally embeddable in other event loops, this feature is broken in |
|
|
442 | all kernel versions tested so far. |
|
|
443 | |
|
|
444 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
445 | C<EVBACKEND_POLL>. |
326 | |
446 | |
327 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
447 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
328 | |
448 | |
329 | Kqueue deserves special mention, as at the time of this writing, it |
449 | Kqueue deserves special mention, as at the time of this writing, it |
330 | was broken on all BSDs except NetBSD (usually it doesn't work with |
450 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
331 | anything but sockets and pipes, except on Darwin, where of course its |
451 | with anything but sockets and pipes, except on Darwin, where of course |
332 | completely useless). For this reason its not being "autodetected" |
452 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
453 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
454 | without API changes to existing programs. For this reason it's not being |
333 | unless you explicitly specify it explicitly in the flags (i.e. using |
455 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
334 | C<EVBACKEND_KQUEUE>). |
456 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
457 | system like NetBSD. |
|
|
458 | |
|
|
459 | You still can embed kqueue into a normal poll or select backend and use it |
|
|
460 | only for sockets (after having made sure that sockets work with kqueue on |
|
|
461 | the target platform). See C<ev_embed> watchers for more info. |
335 | |
462 | |
336 | It scales in the same way as the epoll backend, but the interface to the |
463 | It scales in the same way as the epoll backend, but the interface to the |
337 | kernel is more efficient (which says nothing about its actual speed, of |
464 | kernel is more efficient (which says nothing about its actual speed, of |
338 | course). While starting and stopping an I/O watcher does not cause an |
465 | course). While stopping, setting and starting an I/O watcher does never |
339 | extra syscall as with epoll, it still adds up to four event changes per |
466 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
340 | incident, so its best to avoid that. |
467 | two event changes per incident. Support for C<fork ()> is very bad (but |
|
|
468 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
469 | cases |
|
|
470 | |
|
|
471 | This backend usually performs well under most conditions. |
|
|
472 | |
|
|
473 | While nominally embeddable in other event loops, this doesn't work |
|
|
474 | everywhere, so you might need to test for this. And since it is broken |
|
|
475 | almost everywhere, you should only use it when you have a lot of sockets |
|
|
476 | (for which it usually works), by embedding it into another event loop |
|
|
477 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
|
|
478 | also broken on OS X)) and, did I mention it, using it only for sockets. |
|
|
479 | |
|
|
480 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
481 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
482 | C<NOTE_EOF>. |
341 | |
483 | |
342 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
484 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
343 | |
485 | |
344 | This is not implemented yet (and might never be). |
486 | This is not implemented yet (and might never be, unless you send me an |
|
|
487 | implementation). According to reports, C</dev/poll> only supports sockets |
|
|
488 | and is not embeddable, which would limit the usefulness of this backend |
|
|
489 | immensely. |
345 | |
490 | |
346 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
491 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
347 | |
492 | |
348 | This uses the Solaris 10 port mechanism. As with everything on Solaris, |
493 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
349 | it's really slow, but it still scales very well (O(active_fds)). |
494 | it's really slow, but it still scales very well (O(active_fds)). |
350 | |
495 | |
351 | Please note that solaris ports can result in a lot of spurious |
496 | Please note that Solaris event ports can deliver a lot of spurious |
352 | notifications, so you need to use non-blocking I/O or other means to avoid |
497 | notifications, so you need to use non-blocking I/O or other means to avoid |
353 | blocking when no data (or space) is available. |
498 | blocking when no data (or space) is available. |
|
|
499 | |
|
|
500 | While this backend scales well, it requires one system call per active |
|
|
501 | file descriptor per loop iteration. For small and medium numbers of file |
|
|
502 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
|
|
503 | might perform better. |
|
|
504 | |
|
|
505 | On the positive side, with the exception of the spurious readiness |
|
|
506 | notifications, this backend actually performed fully to specification |
|
|
507 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
508 | OS-specific backends (I vastly prefer correctness over speed hacks). |
|
|
509 | |
|
|
510 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
511 | C<EVBACKEND_POLL>. |
354 | |
512 | |
355 | =item C<EVBACKEND_ALL> |
513 | =item C<EVBACKEND_ALL> |
356 | |
514 | |
357 | Try all backends (even potentially broken ones that wouldn't be tried |
515 | Try all backends (even potentially broken ones that wouldn't be tried |
358 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
516 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
359 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
517 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
360 | |
518 | |
|
|
519 | It is definitely not recommended to use this flag. |
|
|
520 | |
361 | =back |
521 | =back |
362 | |
522 | |
363 | If one or more of these are ored into the flags value, then only these |
523 | If one or more of these are or'ed into the flags value, then only these |
364 | backends will be tried (in the reverse order as given here). If none are |
524 | backends will be tried (in the reverse order as listed here). If none are |
365 | specified, most compiled-in backend will be tried, usually in reverse |
525 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
366 | order of their flag values :) |
|
|
367 | |
526 | |
368 | The most typical usage is like this: |
527 | Example: This is the most typical usage. |
369 | |
528 | |
370 | if (!ev_default_loop (0)) |
529 | if (!ev_default_loop (0)) |
371 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
530 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
372 | |
531 | |
373 | Restrict libev to the select and poll backends, and do not allow |
532 | Example: Restrict libev to the select and poll backends, and do not allow |
374 | environment settings to be taken into account: |
533 | environment settings to be taken into account: |
375 | |
534 | |
376 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
535 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
377 | |
536 | |
378 | Use whatever libev has to offer, but make sure that kqueue is used if |
537 | Example: Use whatever libev has to offer, but make sure that kqueue is |
379 | available (warning, breaks stuff, best use only with your own private |
538 | used if available (warning, breaks stuff, best use only with your own |
380 | event loop and only if you know the OS supports your types of fds): |
539 | private event loop and only if you know the OS supports your types of |
|
|
540 | fds): |
381 | |
541 | |
382 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
542 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
383 | |
543 | |
384 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
544 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
385 | |
545 | |
386 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
546 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
387 | always distinct from the default loop. Unlike the default loop, it cannot |
547 | always distinct from the default loop. Unlike the default loop, it cannot |
388 | handle signal and child watchers, and attempts to do so will be greeted by |
548 | handle signal and child watchers, and attempts to do so will be greeted by |
389 | undefined behaviour (or a failed assertion if assertions are enabled). |
549 | undefined behaviour (or a failed assertion if assertions are enabled). |
390 | |
550 | |
|
|
551 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
552 | libev with threads is indeed to create one loop per thread, and using the |
|
|
553 | default loop in the "main" or "initial" thread. |
|
|
554 | |
391 | Example: Try to create a event loop that uses epoll and nothing else. |
555 | Example: Try to create a event loop that uses epoll and nothing else. |
392 | |
556 | |
393 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
557 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
394 | if (!epoller) |
558 | if (!epoller) |
395 | fatal ("no epoll found here, maybe it hides under your chair"); |
559 | fatal ("no epoll found here, maybe it hides under your chair"); |
396 | |
560 | |
397 | =item ev_default_destroy () |
561 | =item ev_default_destroy () |
398 | |
562 | |
399 | Destroys the default loop again (frees all memory and kernel state |
563 | Destroys the default loop again (frees all memory and kernel state |
400 | etc.). None of the active event watchers will be stopped in the normal |
564 | etc.). None of the active event watchers will be stopped in the normal |
401 | sense, so e.g. C<ev_is_active> might still return true. It is your |
565 | sense, so e.g. C<ev_is_active> might still return true. It is your |
402 | responsibility to either stop all watchers cleanly yoursef I<before> |
566 | responsibility to either stop all watchers cleanly yourself I<before> |
403 | calling this function, or cope with the fact afterwards (which is usually |
567 | calling this function, or cope with the fact afterwards (which is usually |
404 | the easiest thing, youc na just ignore the watchers and/or C<free ()> them |
568 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
405 | for example). |
569 | for example). |
|
|
570 | |
|
|
571 | Note that certain global state, such as signal state (and installed signal |
|
|
572 | handlers), will not be freed by this function, and related watchers (such |
|
|
573 | as signal and child watchers) would need to be stopped manually. |
|
|
574 | |
|
|
575 | In general it is not advisable to call this function except in the |
|
|
576 | rare occasion where you really need to free e.g. the signal handling |
|
|
577 | pipe fds. If you need dynamically allocated loops it is better to use |
|
|
578 | C<ev_loop_new> and C<ev_loop_destroy>). |
406 | |
579 | |
407 | =item ev_loop_destroy (loop) |
580 | =item ev_loop_destroy (loop) |
408 | |
581 | |
409 | Like C<ev_default_destroy>, but destroys an event loop created by an |
582 | Like C<ev_default_destroy>, but destroys an event loop created by an |
410 | earlier call to C<ev_loop_new>. |
583 | earlier call to C<ev_loop_new>. |
411 | |
584 | |
412 | =item ev_default_fork () |
585 | =item ev_default_fork () |
413 | |
586 | |
|
|
587 | This function sets a flag that causes subsequent C<ev_loop> iterations |
414 | This function reinitialises the kernel state for backends that have |
588 | to reinitialise the kernel state for backends that have one. Despite the |
415 | one. Despite the name, you can call it anytime, but it makes most sense |
589 | name, you can call it anytime, but it makes most sense after forking, in |
416 | after forking, in either the parent or child process (or both, but that |
590 | the child process (or both child and parent, but that again makes little |
417 | again makes little sense). |
591 | sense). You I<must> call it in the child before using any of the libev |
|
|
592 | functions, and it will only take effect at the next C<ev_loop> iteration. |
418 | |
593 | |
419 | You I<must> call this function in the child process after forking if and |
594 | On the other hand, you only need to call this function in the child |
420 | only if you want to use the event library in both processes. If you just |
595 | process if and only if you want to use the event library in the child. If |
421 | fork+exec, you don't have to call it. |
596 | you just fork+exec, you don't have to call it at all. |
422 | |
597 | |
423 | The function itself is quite fast and it's usually not a problem to call |
598 | The function itself is quite fast and it's usually not a problem to call |
424 | it just in case after a fork. To make this easy, the function will fit in |
599 | it just in case after a fork. To make this easy, the function will fit in |
425 | quite nicely into a call to C<pthread_atfork>: |
600 | quite nicely into a call to C<pthread_atfork>: |
426 | |
601 | |
427 | pthread_atfork (0, 0, ev_default_fork); |
602 | pthread_atfork (0, 0, ev_default_fork); |
428 | |
603 | |
429 | At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use |
|
|
430 | without calling this function, so if you force one of those backends you |
|
|
431 | do not need to care. |
|
|
432 | |
|
|
433 | =item ev_loop_fork (loop) |
604 | =item ev_loop_fork (loop) |
434 | |
605 | |
435 | Like C<ev_default_fork>, but acts on an event loop created by |
606 | Like C<ev_default_fork>, but acts on an event loop created by |
436 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
607 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
437 | after fork, and how you do this is entirely your own problem. |
608 | after fork that you want to re-use in the child, and how you do this is |
|
|
609 | entirely your own problem. |
|
|
610 | |
|
|
611 | =item int ev_is_default_loop (loop) |
|
|
612 | |
|
|
613 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
614 | otherwise. |
438 | |
615 | |
439 | =item unsigned int ev_loop_count (loop) |
616 | =item unsigned int ev_loop_count (loop) |
440 | |
617 | |
441 | Returns the count of loop iterations for the loop, which is identical to |
618 | Returns the count of loop iterations for the loop, which is identical to |
442 | the number of times libev did poll for new events. It starts at C<0> and |
619 | the number of times libev did poll for new events. It starts at C<0> and |
… | |
… | |
455 | |
632 | |
456 | Returns the current "event loop time", which is the time the event loop |
633 | Returns the current "event loop time", which is the time the event loop |
457 | received events and started processing them. This timestamp does not |
634 | received events and started processing them. This timestamp does not |
458 | change as long as callbacks are being processed, and this is also the base |
635 | change as long as callbacks are being processed, and this is also the base |
459 | time used for relative timers. You can treat it as the timestamp of the |
636 | time used for relative timers. You can treat it as the timestamp of the |
460 | event occuring (or more correctly, libev finding out about it). |
637 | event occurring (or more correctly, libev finding out about it). |
|
|
638 | |
|
|
639 | =item ev_now_update (loop) |
|
|
640 | |
|
|
641 | Establishes the current time by querying the kernel, updating the time |
|
|
642 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
643 | is usually done automatically within C<ev_loop ()>. |
|
|
644 | |
|
|
645 | This function is rarely useful, but when some event callback runs for a |
|
|
646 | very long time without entering the event loop, updating libev's idea of |
|
|
647 | the current time is a good idea. |
|
|
648 | |
|
|
649 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
650 | |
|
|
651 | =item ev_suspend (loop) |
|
|
652 | |
|
|
653 | =item ev_resume (loop) |
|
|
654 | |
|
|
655 | These two functions suspend and resume a loop, for use when the loop is |
|
|
656 | not used for a while and timeouts should not be processed. |
|
|
657 | |
|
|
658 | A typical use case would be an interactive program such as a game: When |
|
|
659 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
660 | would be best to handle timeouts as if no time had actually passed while |
|
|
661 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
662 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
663 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
664 | |
|
|
665 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
666 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
667 | will be rescheduled (that is, they will lose any events that would have |
|
|
668 | occured while suspended). |
|
|
669 | |
|
|
670 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
671 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
672 | without a previous call to C<ev_suspend>. |
|
|
673 | |
|
|
674 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
675 | event loop time (see C<ev_now_update>). |
461 | |
676 | |
462 | =item ev_loop (loop, int flags) |
677 | =item ev_loop (loop, int flags) |
463 | |
678 | |
464 | Finally, this is it, the event handler. This function usually is called |
679 | Finally, this is it, the event handler. This function usually is called |
465 | after you initialised all your watchers and you want to start handling |
680 | after you initialised all your watchers and you want to start handling |
… | |
… | |
468 | If the flags argument is specified as C<0>, it will not return until |
683 | If the flags argument is specified as C<0>, it will not return until |
469 | either no event watchers are active anymore or C<ev_unloop> was called. |
684 | either no event watchers are active anymore or C<ev_unloop> was called. |
470 | |
685 | |
471 | Please note that an explicit C<ev_unloop> is usually better than |
686 | Please note that an explicit C<ev_unloop> is usually better than |
472 | relying on all watchers to be stopped when deciding when a program has |
687 | relying on all watchers to be stopped when deciding when a program has |
473 | finished (especially in interactive programs), but having a program that |
688 | finished (especially in interactive programs), but having a program |
474 | automatically loops as long as it has to and no longer by virtue of |
689 | that automatically loops as long as it has to and no longer by virtue |
475 | relying on its watchers stopping correctly is a thing of beauty. |
690 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
691 | beauty. |
476 | |
692 | |
477 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
693 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
478 | those events and any outstanding ones, but will not block your process in |
694 | those events and any already outstanding ones, but will not block your |
479 | case there are no events and will return after one iteration of the loop. |
695 | process in case there are no events and will return after one iteration of |
|
|
696 | the loop. |
480 | |
697 | |
481 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
698 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
482 | neccessary) and will handle those and any outstanding ones. It will block |
699 | necessary) and will handle those and any already outstanding ones. It |
483 | your process until at least one new event arrives, and will return after |
700 | will block your process until at least one new event arrives (which could |
484 | one iteration of the loop. This is useful if you are waiting for some |
701 | be an event internal to libev itself, so there is no guarantee that a |
485 | external event in conjunction with something not expressible using other |
702 | user-registered callback will be called), and will return after one |
|
|
703 | iteration of the loop. |
|
|
704 | |
|
|
705 | This is useful if you are waiting for some external event in conjunction |
|
|
706 | with something not expressible using other libev watchers (i.e. "roll your |
486 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
707 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
487 | usually a better approach for this kind of thing. |
708 | usually a better approach for this kind of thing. |
488 | |
709 | |
489 | Here are the gory details of what C<ev_loop> does: |
710 | Here are the gory details of what C<ev_loop> does: |
490 | |
711 | |
491 | * If there are no active watchers (reference count is zero), return. |
712 | - Before the first iteration, call any pending watchers. |
492 | - Queue prepare watchers and then call all outstanding watchers. |
713 | * If EVFLAG_FORKCHECK was used, check for a fork. |
|
|
714 | - If a fork was detected (by any means), queue and call all fork watchers. |
|
|
715 | - Queue and call all prepare watchers. |
493 | - If we have been forked, recreate the kernel state. |
716 | - If we have been forked, detach and recreate the kernel state |
|
|
717 | as to not disturb the other process. |
494 | - Update the kernel state with all outstanding changes. |
718 | - Update the kernel state with all outstanding changes. |
495 | - Update the "event loop time". |
719 | - Update the "event loop time" (ev_now ()). |
496 | - Calculate for how long to block. |
720 | - Calculate for how long to sleep or block, if at all |
|
|
721 | (active idle watchers, EVLOOP_NONBLOCK or not having |
|
|
722 | any active watchers at all will result in not sleeping). |
|
|
723 | - Sleep if the I/O and timer collect interval say so. |
497 | - Block the process, waiting for any events. |
724 | - Block the process, waiting for any events. |
498 | - Queue all outstanding I/O (fd) events. |
725 | - Queue all outstanding I/O (fd) events. |
499 | - Update the "event loop time" and do time jump handling. |
726 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
500 | - Queue all outstanding timers. |
727 | - Queue all expired timers. |
501 | - Queue all outstanding periodics. |
728 | - Queue all expired periodics. |
502 | - If no events are pending now, queue all idle watchers. |
729 | - Unless any events are pending now, queue all idle watchers. |
503 | - Queue all check watchers. |
730 | - Queue all check watchers. |
504 | - Call all queued watchers in reverse order (i.e. check watchers first). |
731 | - Call all queued watchers in reverse order (i.e. check watchers first). |
505 | Signals and child watchers are implemented as I/O watchers, and will |
732 | Signals and child watchers are implemented as I/O watchers, and will |
506 | be handled here by queueing them when their watcher gets executed. |
733 | be handled here by queueing them when their watcher gets executed. |
507 | - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
734 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
508 | were used, return, otherwise continue with step *. |
735 | were used, or there are no active watchers, return, otherwise |
|
|
736 | continue with step *. |
509 | |
737 | |
510 | Example: Queue some jobs and then loop until no events are outsanding |
738 | Example: Queue some jobs and then loop until no events are outstanding |
511 | anymore. |
739 | anymore. |
512 | |
740 | |
513 | ... queue jobs here, make sure they register event watchers as long |
741 | ... queue jobs here, make sure they register event watchers as long |
514 | ... as they still have work to do (even an idle watcher will do..) |
742 | ... as they still have work to do (even an idle watcher will do..) |
515 | ev_loop (my_loop, 0); |
743 | ev_loop (my_loop, 0); |
516 | ... jobs done. yeah! |
744 | ... jobs done or somebody called unloop. yeah! |
517 | |
745 | |
518 | =item ev_unloop (loop, how) |
746 | =item ev_unloop (loop, how) |
519 | |
747 | |
520 | Can be used to make a call to C<ev_loop> return early (but only after it |
748 | Can be used to make a call to C<ev_loop> return early (but only after it |
521 | has processed all outstanding events). The C<how> argument must be either |
749 | has processed all outstanding events). The C<how> argument must be either |
522 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
750 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
523 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
751 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
524 | |
752 | |
|
|
753 | This "unloop state" will be cleared when entering C<ev_loop> again. |
|
|
754 | |
|
|
755 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
756 | |
525 | =item ev_ref (loop) |
757 | =item ev_ref (loop) |
526 | |
758 | |
527 | =item ev_unref (loop) |
759 | =item ev_unref (loop) |
528 | |
760 | |
529 | Ref/unref can be used to add or remove a reference count on the event |
761 | Ref/unref can be used to add or remove a reference count on the event |
530 | loop: Every watcher keeps one reference, and as long as the reference |
762 | loop: Every watcher keeps one reference, and as long as the reference |
531 | count is nonzero, C<ev_loop> will not return on its own. If you have |
763 | count is nonzero, C<ev_loop> will not return on its own. |
|
|
764 | |
532 | a watcher you never unregister that should not keep C<ev_loop> from |
765 | If you have a watcher you never unregister that should not keep C<ev_loop> |
533 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
766 | from returning, call ev_unref() after starting, and ev_ref() before |
|
|
767 | stopping it. |
|
|
768 | |
534 | example, libev itself uses this for its internal signal pipe: It is not |
769 | As an example, libev itself uses this for its internal signal pipe: It |
535 | visible to the libev user and should not keep C<ev_loop> from exiting if |
770 | is not visible to the libev user and should not keep C<ev_loop> from |
536 | no event watchers registered by it are active. It is also an excellent |
771 | exiting if no event watchers registered by it are active. It is also an |
537 | way to do this for generic recurring timers or from within third-party |
772 | excellent way to do this for generic recurring timers or from within |
538 | libraries. Just remember to I<unref after start> and I<ref before stop>. |
773 | third-party libraries. Just remember to I<unref after start> and I<ref |
|
|
774 | before stop> (but only if the watcher wasn't active before, or was active |
|
|
775 | before, respectively. Note also that libev might stop watchers itself |
|
|
776 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
777 | in the callback). |
539 | |
778 | |
540 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
779 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
541 | running when nothing else is active. |
780 | running when nothing else is active. |
542 | |
781 | |
543 | struct ev_signal exitsig; |
782 | ev_signal exitsig; |
544 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
783 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
545 | ev_signal_start (loop, &exitsig); |
784 | ev_signal_start (loop, &exitsig); |
546 | evf_unref (loop); |
785 | evf_unref (loop); |
547 | |
786 | |
548 | Example: For some weird reason, unregister the above signal handler again. |
787 | Example: For some weird reason, unregister the above signal handler again. |
549 | |
788 | |
550 | ev_ref (loop); |
789 | ev_ref (loop); |
551 | ev_signal_stop (loop, &exitsig); |
790 | ev_signal_stop (loop, &exitsig); |
|
|
791 | |
|
|
792 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
|
|
793 | |
|
|
794 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
|
|
795 | |
|
|
796 | These advanced functions influence the time that libev will spend waiting |
|
|
797 | for events. Both time intervals are by default C<0>, meaning that libev |
|
|
798 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
799 | latency. |
|
|
800 | |
|
|
801 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
|
|
802 | allows libev to delay invocation of I/O and timer/periodic callbacks |
|
|
803 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
804 | opportunities). |
|
|
805 | |
|
|
806 | The idea is that sometimes your program runs just fast enough to handle |
|
|
807 | one (or very few) event(s) per loop iteration. While this makes the |
|
|
808 | program responsive, it also wastes a lot of CPU time to poll for new |
|
|
809 | events, especially with backends like C<select ()> which have a high |
|
|
810 | overhead for the actual polling but can deliver many events at once. |
|
|
811 | |
|
|
812 | By setting a higher I<io collect interval> you allow libev to spend more |
|
|
813 | time collecting I/O events, so you can handle more events per iteration, |
|
|
814 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
|
|
815 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
|
|
816 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
|
|
817 | |
|
|
818 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
|
|
819 | to spend more time collecting timeouts, at the expense of increased |
|
|
820 | latency/jitter/inexactness (the watcher callback will be called |
|
|
821 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
|
|
822 | value will not introduce any overhead in libev. |
|
|
823 | |
|
|
824 | Many (busy) programs can usually benefit by setting the I/O collect |
|
|
825 | interval to a value near C<0.1> or so, which is often enough for |
|
|
826 | interactive servers (of course not for games), likewise for timeouts. It |
|
|
827 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
|
|
828 | as this approaches the timing granularity of most systems. |
|
|
829 | |
|
|
830 | Setting the I<timeout collect interval> can improve the opportunity for |
|
|
831 | saving power, as the program will "bundle" timer callback invocations that |
|
|
832 | are "near" in time together, by delaying some, thus reducing the number of |
|
|
833 | times the process sleeps and wakes up again. Another useful technique to |
|
|
834 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
|
|
835 | they fire on, say, one-second boundaries only. |
|
|
836 | |
|
|
837 | =item ev_loop_verify (loop) |
|
|
838 | |
|
|
839 | This function only does something when C<EV_VERIFY> support has been |
|
|
840 | compiled in, which is the default for non-minimal builds. It tries to go |
|
|
841 | through all internal structures and checks them for validity. If anything |
|
|
842 | is found to be inconsistent, it will print an error message to standard |
|
|
843 | error and call C<abort ()>. |
|
|
844 | |
|
|
845 | This can be used to catch bugs inside libev itself: under normal |
|
|
846 | circumstances, this function will never abort as of course libev keeps its |
|
|
847 | data structures consistent. |
552 | |
848 | |
553 | =back |
849 | =back |
554 | |
850 | |
555 | |
851 | |
556 | =head1 ANATOMY OF A WATCHER |
852 | =head1 ANATOMY OF A WATCHER |
|
|
853 | |
|
|
854 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
855 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
856 | watchers and C<ev_io_start> for I/O watchers. |
557 | |
857 | |
558 | A watcher is a structure that you create and register to record your |
858 | A watcher is a structure that you create and register to record your |
559 | interest in some event. For instance, if you want to wait for STDIN to |
859 | interest in some event. For instance, if you want to wait for STDIN to |
560 | become readable, you would create an C<ev_io> watcher for that: |
860 | become readable, you would create an C<ev_io> watcher for that: |
561 | |
861 | |
562 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
862 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
563 | { |
863 | { |
564 | ev_io_stop (w); |
864 | ev_io_stop (w); |
565 | ev_unloop (loop, EVUNLOOP_ALL); |
865 | ev_unloop (loop, EVUNLOOP_ALL); |
566 | } |
866 | } |
567 | |
867 | |
568 | struct ev_loop *loop = ev_default_loop (0); |
868 | struct ev_loop *loop = ev_default_loop (0); |
|
|
869 | |
569 | struct ev_io stdin_watcher; |
870 | ev_io stdin_watcher; |
|
|
871 | |
570 | ev_init (&stdin_watcher, my_cb); |
872 | ev_init (&stdin_watcher, my_cb); |
571 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
873 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
572 | ev_io_start (loop, &stdin_watcher); |
874 | ev_io_start (loop, &stdin_watcher); |
|
|
875 | |
573 | ev_loop (loop, 0); |
876 | ev_loop (loop, 0); |
574 | |
877 | |
575 | As you can see, you are responsible for allocating the memory for your |
878 | As you can see, you are responsible for allocating the memory for your |
576 | watcher structures (and it is usually a bad idea to do this on the stack, |
879 | watcher structures (and it is I<usually> a bad idea to do this on the |
577 | although this can sometimes be quite valid). |
880 | stack). |
|
|
881 | |
|
|
882 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
883 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
578 | |
884 | |
579 | Each watcher structure must be initialised by a call to C<ev_init |
885 | Each watcher structure must be initialised by a call to C<ev_init |
580 | (watcher *, callback)>, which expects a callback to be provided. This |
886 | (watcher *, callback)>, which expects a callback to be provided. This |
581 | callback gets invoked each time the event occurs (or, in the case of io |
887 | callback gets invoked each time the event occurs (or, in the case of I/O |
582 | watchers, each time the event loop detects that the file descriptor given |
888 | watchers, each time the event loop detects that the file descriptor given |
583 | is readable and/or writable). |
889 | is readable and/or writable). |
584 | |
890 | |
585 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
891 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
586 | with arguments specific to this watcher type. There is also a macro |
892 | macro to configure it, with arguments specific to the watcher type. There |
587 | to combine initialisation and setting in one call: C<< ev_<type>_init |
893 | is also a macro to combine initialisation and setting in one call: C<< |
588 | (watcher *, callback, ...) >>. |
894 | ev_TYPE_init (watcher *, callback, ...) >>. |
589 | |
895 | |
590 | To make the watcher actually watch out for events, you have to start it |
896 | To make the watcher actually watch out for events, you have to start it |
591 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
897 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
592 | *) >>), and you can stop watching for events at any time by calling the |
898 | *) >>), and you can stop watching for events at any time by calling the |
593 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
899 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
594 | |
900 | |
595 | As long as your watcher is active (has been started but not stopped) you |
901 | As long as your watcher is active (has been started but not stopped) you |
596 | must not touch the values stored in it. Most specifically you must never |
902 | must not touch the values stored in it. Most specifically you must never |
597 | reinitialise it or call its C<set> macro. |
903 | reinitialise it or call its C<ev_TYPE_set> macro. |
598 | |
904 | |
599 | Each and every callback receives the event loop pointer as first, the |
905 | Each and every callback receives the event loop pointer as first, the |
600 | registered watcher structure as second, and a bitset of received events as |
906 | registered watcher structure as second, and a bitset of received events as |
601 | third argument. |
907 | third argument. |
602 | |
908 | |
… | |
… | |
656 | =item C<EV_FORK> |
962 | =item C<EV_FORK> |
657 | |
963 | |
658 | The event loop has been resumed in the child process after fork (see |
964 | The event loop has been resumed in the child process after fork (see |
659 | C<ev_fork>). |
965 | C<ev_fork>). |
660 | |
966 | |
|
|
967 | =item C<EV_ASYNC> |
|
|
968 | |
|
|
969 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
970 | |
|
|
971 | =item C<EV_CUSTOM> |
|
|
972 | |
|
|
973 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
974 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
975 | |
661 | =item C<EV_ERROR> |
976 | =item C<EV_ERROR> |
662 | |
977 | |
663 | An unspecified error has occured, the watcher has been stopped. This might |
978 | An unspecified error has occurred, the watcher has been stopped. This might |
664 | happen because the watcher could not be properly started because libev |
979 | happen because the watcher could not be properly started because libev |
665 | ran out of memory, a file descriptor was found to be closed or any other |
980 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
981 | problem. Libev considers these application bugs. |
|
|
982 | |
666 | problem. You best act on it by reporting the problem and somehow coping |
983 | You best act on it by reporting the problem and somehow coping with the |
667 | with the watcher being stopped. |
984 | watcher being stopped. Note that well-written programs should not receive |
|
|
985 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
986 | bug in your program. |
668 | |
987 | |
669 | Libev will usually signal a few "dummy" events together with an error, |
988 | Libev will usually signal a few "dummy" events together with an error, for |
670 | for example it might indicate that a fd is readable or writable, and if |
989 | example it might indicate that a fd is readable or writable, and if your |
671 | your callbacks is well-written it can just attempt the operation and cope |
990 | callbacks is well-written it can just attempt the operation and cope with |
672 | with the error from read() or write(). This will not work in multithreaded |
991 | the error from read() or write(). This will not work in multi-threaded |
673 | programs, though, so beware. |
992 | programs, though, as the fd could already be closed and reused for another |
|
|
993 | thing, so beware. |
674 | |
994 | |
675 | =back |
995 | =back |
676 | |
996 | |
677 | =head2 GENERIC WATCHER FUNCTIONS |
997 | =head2 GENERIC WATCHER FUNCTIONS |
678 | |
|
|
679 | In the following description, C<TYPE> stands for the watcher type, |
|
|
680 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
681 | |
998 | |
682 | =over 4 |
999 | =over 4 |
683 | |
1000 | |
684 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1001 | =item C<ev_init> (ev_TYPE *watcher, callback) |
685 | |
1002 | |
… | |
… | |
691 | which rolls both calls into one. |
1008 | which rolls both calls into one. |
692 | |
1009 | |
693 | You can reinitialise a watcher at any time as long as it has been stopped |
1010 | You can reinitialise a watcher at any time as long as it has been stopped |
694 | (or never started) and there are no pending events outstanding. |
1011 | (or never started) and there are no pending events outstanding. |
695 | |
1012 | |
696 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1013 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
697 | int revents)>. |
1014 | int revents)>. |
|
|
1015 | |
|
|
1016 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1017 | |
|
|
1018 | ev_io w; |
|
|
1019 | ev_init (&w, my_cb); |
|
|
1020 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
698 | |
1021 | |
699 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1022 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
700 | |
1023 | |
701 | This macro initialises the type-specific parts of a watcher. You need to |
1024 | This macro initialises the type-specific parts of a watcher. You need to |
702 | call C<ev_init> at least once before you call this macro, but you can |
1025 | call C<ev_init> at least once before you call this macro, but you can |
… | |
… | |
705 | difference to the C<ev_init> macro). |
1028 | difference to the C<ev_init> macro). |
706 | |
1029 | |
707 | Although some watcher types do not have type-specific arguments |
1030 | Although some watcher types do not have type-specific arguments |
708 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
1031 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
709 | |
1032 | |
|
|
1033 | See C<ev_init>, above, for an example. |
|
|
1034 | |
710 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
1035 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
711 | |
1036 | |
712 | This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
1037 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
713 | calls into a single call. This is the most convinient method to initialise |
1038 | calls into a single call. This is the most convenient method to initialise |
714 | a watcher. The same limitations apply, of course. |
1039 | a watcher. The same limitations apply, of course. |
|
|
1040 | |
|
|
1041 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1042 | |
|
|
1043 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
715 | |
1044 | |
716 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1045 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
717 | |
1046 | |
718 | Starts (activates) the given watcher. Only active watchers will receive |
1047 | Starts (activates) the given watcher. Only active watchers will receive |
719 | events. If the watcher is already active nothing will happen. |
1048 | events. If the watcher is already active nothing will happen. |
720 | |
1049 | |
|
|
1050 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1051 | whole section. |
|
|
1052 | |
|
|
1053 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1054 | |
721 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1055 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
722 | |
1056 | |
723 | Stops the given watcher again (if active) and clears the pending |
1057 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1058 | the watcher was active or not). |
|
|
1059 | |
724 | status. It is possible that stopped watchers are pending (for example, |
1060 | It is possible that stopped watchers are pending - for example, |
725 | non-repeating timers are being stopped when they become pending), but |
1061 | non-repeating timers are being stopped when they become pending - but |
726 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1062 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
727 | you want to free or reuse the memory used by the watcher it is therefore a |
1063 | pending. If you want to free or reuse the memory used by the watcher it is |
728 | good idea to always call its C<ev_TYPE_stop> function. |
1064 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
729 | |
1065 | |
730 | =item bool ev_is_active (ev_TYPE *watcher) |
1066 | =item bool ev_is_active (ev_TYPE *watcher) |
731 | |
1067 | |
732 | Returns a true value iff the watcher is active (i.e. it has been started |
1068 | Returns a true value iff the watcher is active (i.e. it has been started |
733 | and not yet been stopped). As long as a watcher is active you must not modify |
1069 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
759 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1095 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
760 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1096 | (default: C<-2>). Pending watchers with higher priority will be invoked |
761 | before watchers with lower priority, but priority will not keep watchers |
1097 | before watchers with lower priority, but priority will not keep watchers |
762 | from being executed (except for C<ev_idle> watchers). |
1098 | from being executed (except for C<ev_idle> watchers). |
763 | |
1099 | |
764 | This means that priorities are I<only> used for ordering callback |
|
|
765 | invocation after new events have been received. This is useful, for |
|
|
766 | example, to reduce latency after idling, or more often, to bind two |
|
|
767 | watchers on the same event and make sure one is called first. |
|
|
768 | |
|
|
769 | If you need to suppress invocation when higher priority events are pending |
1100 | If you need to suppress invocation when higher priority events are pending |
770 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1101 | you need to look at C<ev_idle> watchers, which provide this functionality. |
771 | |
1102 | |
772 | You I<must not> change the priority of a watcher as long as it is active or |
1103 | You I<must not> change the priority of a watcher as long as it is active or |
773 | pending. |
1104 | pending. |
774 | |
1105 | |
|
|
1106 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1107 | fine, as long as you do not mind that the priority value you query might |
|
|
1108 | or might not have been clamped to the valid range. |
|
|
1109 | |
775 | The default priority used by watchers when no priority has been set is |
1110 | The default priority used by watchers when no priority has been set is |
776 | always C<0>, which is supposed to not be too high and not be too low :). |
1111 | always C<0>, which is supposed to not be too high and not be too low :). |
777 | |
1112 | |
778 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1113 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
779 | fine, as long as you do not mind that the priority value you query might |
1114 | priorities. |
780 | or might not have been adjusted to be within valid range. |
1115 | |
|
|
1116 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1117 | |
|
|
1118 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1119 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1120 | can deal with that fact, as both are simply passed through to the |
|
|
1121 | callback. |
|
|
1122 | |
|
|
1123 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1124 | |
|
|
1125 | If the watcher is pending, this function clears its pending status and |
|
|
1126 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1127 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1128 | |
|
|
1129 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1130 | callback to be invoked, which can be accomplished with this function. |
781 | |
1131 | |
782 | =back |
1132 | =back |
783 | |
1133 | |
784 | |
1134 | |
785 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1135 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
786 | |
1136 | |
787 | Each watcher has, by default, a member C<void *data> that you can change |
1137 | Each watcher has, by default, a member C<void *data> that you can change |
788 | and read at any time, libev will completely ignore it. This can be used |
1138 | and read at any time: libev will completely ignore it. This can be used |
789 | to associate arbitrary data with your watcher. If you need more data and |
1139 | to associate arbitrary data with your watcher. If you need more data and |
790 | don't want to allocate memory and store a pointer to it in that data |
1140 | don't want to allocate memory and store a pointer to it in that data |
791 | member, you can also "subclass" the watcher type and provide your own |
1141 | member, you can also "subclass" the watcher type and provide your own |
792 | data: |
1142 | data: |
793 | |
1143 | |
794 | struct my_io |
1144 | struct my_io |
795 | { |
1145 | { |
796 | struct ev_io io; |
1146 | ev_io io; |
797 | int otherfd; |
1147 | int otherfd; |
798 | void *somedata; |
1148 | void *somedata; |
799 | struct whatever *mostinteresting; |
1149 | struct whatever *mostinteresting; |
800 | } |
1150 | }; |
|
|
1151 | |
|
|
1152 | ... |
|
|
1153 | struct my_io w; |
|
|
1154 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
801 | |
1155 | |
802 | And since your callback will be called with a pointer to the watcher, you |
1156 | And since your callback will be called with a pointer to the watcher, you |
803 | can cast it back to your own type: |
1157 | can cast it back to your own type: |
804 | |
1158 | |
805 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1159 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
806 | { |
1160 | { |
807 | struct my_io *w = (struct my_io *)w_; |
1161 | struct my_io *w = (struct my_io *)w_; |
808 | ... |
1162 | ... |
809 | } |
1163 | } |
810 | |
1164 | |
811 | More interesting and less C-conformant ways of casting your callback type |
1165 | More interesting and less C-conformant ways of casting your callback type |
812 | instead have been omitted. |
1166 | instead have been omitted. |
813 | |
1167 | |
814 | Another common scenario is having some data structure with multiple |
1168 | Another common scenario is to use some data structure with multiple |
815 | watchers: |
1169 | embedded watchers: |
816 | |
1170 | |
817 | struct my_biggy |
1171 | struct my_biggy |
818 | { |
1172 | { |
819 | int some_data; |
1173 | int some_data; |
820 | ev_timer t1; |
1174 | ev_timer t1; |
821 | ev_timer t2; |
1175 | ev_timer t2; |
822 | } |
1176 | } |
823 | |
1177 | |
824 | In this case getting the pointer to C<my_biggy> is a bit more complicated, |
1178 | In this case getting the pointer to C<my_biggy> is a bit more |
825 | you need to use C<offsetof>: |
1179 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1180 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1181 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1182 | programmers): |
826 | |
1183 | |
827 | #include <stddef.h> |
1184 | #include <stddef.h> |
828 | |
1185 | |
829 | static void |
1186 | static void |
830 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1187 | t1_cb (EV_P_ ev_timer *w, int revents) |
831 | { |
1188 | { |
832 | struct my_biggy big = (struct my_biggy * |
1189 | struct my_biggy big = (struct my_biggy *) |
833 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1190 | (((char *)w) - offsetof (struct my_biggy, t1)); |
834 | } |
1191 | } |
835 | |
1192 | |
836 | static void |
1193 | static void |
837 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1194 | t2_cb (EV_P_ ev_timer *w, int revents) |
838 | { |
1195 | { |
839 | struct my_biggy big = (struct my_biggy * |
1196 | struct my_biggy big = (struct my_biggy *) |
840 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1197 | (((char *)w) - offsetof (struct my_biggy, t2)); |
841 | } |
1198 | } |
|
|
1199 | |
|
|
1200 | =head2 WATCHER PRIORITY MODELS |
|
|
1201 | |
|
|
1202 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1203 | integers that influence the ordering of event callback invocation |
|
|
1204 | between watchers in some way, all else being equal. |
|
|
1205 | |
|
|
1206 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1207 | description for the more technical details such as the actual priority |
|
|
1208 | range. |
|
|
1209 | |
|
|
1210 | There are two common ways how these these priorities are being interpreted |
|
|
1211 | by event loops: |
|
|
1212 | |
|
|
1213 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1214 | of lower priority watchers, which means as long as higher priority |
|
|
1215 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1216 | |
|
|
1217 | The less common only-for-ordering model uses priorities solely to order |
|
|
1218 | callback invocation within a single event loop iteration: Higher priority |
|
|
1219 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1220 | before polling for new events. |
|
|
1221 | |
|
|
1222 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1223 | except for idle watchers (which use the lock-out model). |
|
|
1224 | |
|
|
1225 | The rationale behind this is that implementing the lock-out model for |
|
|
1226 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1227 | libraries will just poll for the same events again and again as long as |
|
|
1228 | their callbacks have not been executed, which is very inefficient in the |
|
|
1229 | common case of one high-priority watcher locking out a mass of lower |
|
|
1230 | priority ones. |
|
|
1231 | |
|
|
1232 | Static (ordering) priorities are most useful when you have two or more |
|
|
1233 | watchers handling the same resource: a typical usage example is having an |
|
|
1234 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1235 | timeouts. Under load, data might be received while the program handles |
|
|
1236 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1237 | handler will be executed before checking for data. In that case, giving |
|
|
1238 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1239 | handled first even under adverse conditions (which is usually, but not |
|
|
1240 | always, what you want). |
|
|
1241 | |
|
|
1242 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1243 | will only be executed when no same or higher priority watchers have |
|
|
1244 | received events, they can be used to implement the "lock-out" model when |
|
|
1245 | required. |
|
|
1246 | |
|
|
1247 | For example, to emulate how many other event libraries handle priorities, |
|
|
1248 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1249 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1250 | processing is done in the idle watcher callback. This causes libev to |
|
|
1251 | continously poll and process kernel event data for the watcher, but when |
|
|
1252 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1253 | workable. |
|
|
1254 | |
|
|
1255 | Usually, however, the lock-out model implemented that way will perform |
|
|
1256 | miserably under the type of load it was designed to handle. In that case, |
|
|
1257 | it might be preferable to stop the real watcher before starting the |
|
|
1258 | idle watcher, so the kernel will not have to process the event in case |
|
|
1259 | the actual processing will be delayed for considerable time. |
|
|
1260 | |
|
|
1261 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1262 | priority than the default, and which should only process data when no |
|
|
1263 | other events are pending: |
|
|
1264 | |
|
|
1265 | ev_idle idle; // actual processing watcher |
|
|
1266 | ev_io io; // actual event watcher |
|
|
1267 | |
|
|
1268 | static void |
|
|
1269 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1270 | { |
|
|
1271 | // stop the I/O watcher, we received the event, but |
|
|
1272 | // are not yet ready to handle it. |
|
|
1273 | ev_io_stop (EV_A_ w); |
|
|
1274 | |
|
|
1275 | // start the idle watcher to ahndle the actual event. |
|
|
1276 | // it will not be executed as long as other watchers |
|
|
1277 | // with the default priority are receiving events. |
|
|
1278 | ev_idle_start (EV_A_ &idle); |
|
|
1279 | } |
|
|
1280 | |
|
|
1281 | static void |
|
|
1282 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1283 | { |
|
|
1284 | // actual processing |
|
|
1285 | read (STDIN_FILENO, ...); |
|
|
1286 | |
|
|
1287 | // have to start the I/O watcher again, as |
|
|
1288 | // we have handled the event |
|
|
1289 | ev_io_start (EV_P_ &io); |
|
|
1290 | } |
|
|
1291 | |
|
|
1292 | // initialisation |
|
|
1293 | ev_idle_init (&idle, idle_cb); |
|
|
1294 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1295 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1296 | |
|
|
1297 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1298 | low-priority connections can not be locked out forever under load. This |
|
|
1299 | enables your program to keep a lower latency for important connections |
|
|
1300 | during short periods of high load, while not completely locking out less |
|
|
1301 | important ones. |
842 | |
1302 | |
843 | |
1303 | |
844 | =head1 WATCHER TYPES |
1304 | =head1 WATCHER TYPES |
845 | |
1305 | |
846 | This section describes each watcher in detail, but will not repeat |
1306 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
870 | In general you can register as many read and/or write event watchers per |
1330 | In general you can register as many read and/or write event watchers per |
871 | fd as you want (as long as you don't confuse yourself). Setting all file |
1331 | fd as you want (as long as you don't confuse yourself). Setting all file |
872 | descriptors to non-blocking mode is also usually a good idea (but not |
1332 | descriptors to non-blocking mode is also usually a good idea (but not |
873 | required if you know what you are doing). |
1333 | required if you know what you are doing). |
874 | |
1334 | |
875 | You have to be careful with dup'ed file descriptors, though. Some backends |
1335 | If you cannot use non-blocking mode, then force the use of a |
876 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
1336 | known-to-be-good backend (at the time of this writing, this includes only |
877 | descriptors correctly if you register interest in two or more fds pointing |
1337 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
878 | to the same underlying file/socket/etc. description (that is, they share |
1338 | descriptors for which non-blocking operation makes no sense (such as |
879 | the same underlying "file open"). |
1339 | files) - libev doesn't guarentee any specific behaviour in that case. |
880 | |
|
|
881 | If you must do this, then force the use of a known-to-be-good backend |
|
|
882 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
|
|
883 | C<EVBACKEND_POLL>). |
|
|
884 | |
1340 | |
885 | Another thing you have to watch out for is that it is quite easy to |
1341 | Another thing you have to watch out for is that it is quite easy to |
886 | receive "spurious" readyness notifications, that is your callback might |
1342 | receive "spurious" readiness notifications, that is your callback might |
887 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1343 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
888 | because there is no data. Not only are some backends known to create a |
1344 | because there is no data. Not only are some backends known to create a |
889 | lot of those (for example solaris ports), it is very easy to get into |
1345 | lot of those (for example Solaris ports), it is very easy to get into |
890 | this situation even with a relatively standard program structure. Thus |
1346 | this situation even with a relatively standard program structure. Thus |
891 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1347 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
892 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1348 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
893 | |
1349 | |
894 | If you cannot run the fd in non-blocking mode (for example you should not |
1350 | If you cannot run the fd in non-blocking mode (for example you should |
895 | play around with an Xlib connection), then you have to seperately re-test |
1351 | not play around with an Xlib connection), then you have to separately |
896 | whether a file descriptor is really ready with a known-to-be good interface |
1352 | re-test whether a file descriptor is really ready with a known-to-be good |
897 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1353 | interface such as poll (fortunately in our Xlib example, Xlib already |
898 | its own, so its quite safe to use). |
1354 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1355 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1356 | indefinitely. |
|
|
1357 | |
|
|
1358 | But really, best use non-blocking mode. |
|
|
1359 | |
|
|
1360 | =head3 The special problem of disappearing file descriptors |
|
|
1361 | |
|
|
1362 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
|
|
1363 | descriptor (either due to calling C<close> explicitly or any other means, |
|
|
1364 | such as C<dup2>). The reason is that you register interest in some file |
|
|
1365 | descriptor, but when it goes away, the operating system will silently drop |
|
|
1366 | this interest. If another file descriptor with the same number then is |
|
|
1367 | registered with libev, there is no efficient way to see that this is, in |
|
|
1368 | fact, a different file descriptor. |
|
|
1369 | |
|
|
1370 | To avoid having to explicitly tell libev about such cases, libev follows |
|
|
1371 | the following policy: Each time C<ev_io_set> is being called, libev |
|
|
1372 | will assume that this is potentially a new file descriptor, otherwise |
|
|
1373 | it is assumed that the file descriptor stays the same. That means that |
|
|
1374 | you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the |
|
|
1375 | descriptor even if the file descriptor number itself did not change. |
|
|
1376 | |
|
|
1377 | This is how one would do it normally anyway, the important point is that |
|
|
1378 | the libev application should not optimise around libev but should leave |
|
|
1379 | optimisations to libev. |
|
|
1380 | |
|
|
1381 | =head3 The special problem of dup'ed file descriptors |
|
|
1382 | |
|
|
1383 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
1384 | but only events for the underlying file descriptions. That means when you |
|
|
1385 | have C<dup ()>'ed file descriptors or weirder constellations, and register |
|
|
1386 | events for them, only one file descriptor might actually receive events. |
|
|
1387 | |
|
|
1388 | There is no workaround possible except not registering events |
|
|
1389 | for potentially C<dup ()>'ed file descriptors, or to resort to |
|
|
1390 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
|
|
1391 | |
|
|
1392 | =head3 The special problem of fork |
|
|
1393 | |
|
|
1394 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
|
|
1395 | useless behaviour. Libev fully supports fork, but needs to be told about |
|
|
1396 | it in the child. |
|
|
1397 | |
|
|
1398 | To support fork in your programs, you either have to call |
|
|
1399 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
|
|
1400 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
|
|
1401 | C<EVBACKEND_POLL>. |
|
|
1402 | |
|
|
1403 | =head3 The special problem of SIGPIPE |
|
|
1404 | |
|
|
1405 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
|
|
1406 | when writing to a pipe whose other end has been closed, your program gets |
|
|
1407 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
|
|
1408 | this is sensible behaviour, for daemons, this is usually undesirable. |
|
|
1409 | |
|
|
1410 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1411 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1412 | somewhere, as that would have given you a big clue). |
|
|
1413 | |
|
|
1414 | |
|
|
1415 | =head3 Watcher-Specific Functions |
899 | |
1416 | |
900 | =over 4 |
1417 | =over 4 |
901 | |
1418 | |
902 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1419 | =item ev_io_init (ev_io *, callback, int fd, int events) |
903 | |
1420 | |
904 | =item ev_io_set (ev_io *, int fd, int events) |
1421 | =item ev_io_set (ev_io *, int fd, int events) |
905 | |
1422 | |
906 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1423 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
907 | rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1424 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
908 | C<EV_READ | EV_WRITE> to receive the given events. |
1425 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
909 | |
1426 | |
910 | =item int fd [read-only] |
1427 | =item int fd [read-only] |
911 | |
1428 | |
912 | The file descriptor being watched. |
1429 | The file descriptor being watched. |
913 | |
1430 | |
914 | =item int events [read-only] |
1431 | =item int events [read-only] |
915 | |
1432 | |
916 | The events being watched. |
1433 | The events being watched. |
917 | |
1434 | |
918 | =back |
1435 | =back |
|
|
1436 | |
|
|
1437 | =head3 Examples |
919 | |
1438 | |
920 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1439 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
921 | readable, but only once. Since it is likely line-buffered, you could |
1440 | readable, but only once. Since it is likely line-buffered, you could |
922 | attempt to read a whole line in the callback. |
1441 | attempt to read a whole line in the callback. |
923 | |
1442 | |
924 | static void |
1443 | static void |
925 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1444 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
926 | { |
1445 | { |
927 | ev_io_stop (loop, w); |
1446 | ev_io_stop (loop, w); |
928 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1447 | .. read from stdin here (or from w->fd) and handle any I/O errors |
929 | } |
1448 | } |
930 | |
1449 | |
931 | ... |
1450 | ... |
932 | struct ev_loop *loop = ev_default_init (0); |
1451 | struct ev_loop *loop = ev_default_init (0); |
933 | struct ev_io stdin_readable; |
1452 | ev_io stdin_readable; |
934 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1453 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
935 | ev_io_start (loop, &stdin_readable); |
1454 | ev_io_start (loop, &stdin_readable); |
936 | ev_loop (loop, 0); |
1455 | ev_loop (loop, 0); |
937 | |
1456 | |
938 | |
1457 | |
939 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1458 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
940 | |
1459 | |
941 | Timer watchers are simple relative timers that generate an event after a |
1460 | Timer watchers are simple relative timers that generate an event after a |
942 | given time, and optionally repeating in regular intervals after that. |
1461 | given time, and optionally repeating in regular intervals after that. |
943 | |
1462 | |
944 | The timers are based on real time, that is, if you register an event that |
1463 | The timers are based on real time, that is, if you register an event that |
945 | times out after an hour and you reset your system clock to last years |
1464 | times out after an hour and you reset your system clock to January last |
946 | time, it will still time out after (roughly) and hour. "Roughly" because |
1465 | year, it will still time out after (roughly) one hour. "Roughly" because |
947 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1466 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
948 | monotonic clock option helps a lot here). |
1467 | monotonic clock option helps a lot here). |
|
|
1468 | |
|
|
1469 | The callback is guaranteed to be invoked only I<after> its timeout has |
|
|
1470 | passed (not I<at>, so on systems with very low-resolution clocks this |
|
|
1471 | might introduce a small delay). If multiple timers become ready during the |
|
|
1472 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1473 | before ones with later time-out values (but this is no longer true when a |
|
|
1474 | callback calls C<ev_loop> recursively). |
|
|
1475 | |
|
|
1476 | =head3 Be smart about timeouts |
|
|
1477 | |
|
|
1478 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1479 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1480 | you want to raise some error after a while. |
|
|
1481 | |
|
|
1482 | What follows are some ways to handle this problem, from obvious and |
|
|
1483 | inefficient to smart and efficient. |
|
|
1484 | |
|
|
1485 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1486 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1487 | data or other life sign was received). |
|
|
1488 | |
|
|
1489 | =over 4 |
|
|
1490 | |
|
|
1491 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1492 | |
|
|
1493 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1494 | start the watcher: |
|
|
1495 | |
|
|
1496 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1497 | ev_timer_start (loop, timer); |
|
|
1498 | |
|
|
1499 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1500 | and start it again: |
|
|
1501 | |
|
|
1502 | ev_timer_stop (loop, timer); |
|
|
1503 | ev_timer_set (timer, 60., 0.); |
|
|
1504 | ev_timer_start (loop, timer); |
|
|
1505 | |
|
|
1506 | This is relatively simple to implement, but means that each time there is |
|
|
1507 | some activity, libev will first have to remove the timer from its internal |
|
|
1508 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1509 | still not a constant-time operation. |
|
|
1510 | |
|
|
1511 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1512 | |
|
|
1513 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1514 | C<ev_timer_start>. |
|
|
1515 | |
|
|
1516 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1517 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1518 | successfully read or write some data. If you go into an idle state where |
|
|
1519 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1520 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1521 | |
|
|
1522 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1523 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1524 | member and C<ev_timer_again>. |
|
|
1525 | |
|
|
1526 | At start: |
|
|
1527 | |
|
|
1528 | ev_init (timer, callback); |
|
|
1529 | timer->repeat = 60.; |
|
|
1530 | ev_timer_again (loop, timer); |
|
|
1531 | |
|
|
1532 | Each time there is some activity: |
|
|
1533 | |
|
|
1534 | ev_timer_again (loop, timer); |
|
|
1535 | |
|
|
1536 | It is even possible to change the time-out on the fly, regardless of |
|
|
1537 | whether the watcher is active or not: |
|
|
1538 | |
|
|
1539 | timer->repeat = 30.; |
|
|
1540 | ev_timer_again (loop, timer); |
|
|
1541 | |
|
|
1542 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1543 | you want to modify its timeout value, as libev does not have to completely |
|
|
1544 | remove and re-insert the timer from/into its internal data structure. |
|
|
1545 | |
|
|
1546 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1547 | |
|
|
1548 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1549 | |
|
|
1550 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1551 | relatively long compared to the intervals between other activity - in |
|
|
1552 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1553 | associated activity resets. |
|
|
1554 | |
|
|
1555 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1556 | but remember the time of last activity, and check for a real timeout only |
|
|
1557 | within the callback: |
|
|
1558 | |
|
|
1559 | ev_tstamp last_activity; // time of last activity |
|
|
1560 | |
|
|
1561 | static void |
|
|
1562 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1563 | { |
|
|
1564 | ev_tstamp now = ev_now (EV_A); |
|
|
1565 | ev_tstamp timeout = last_activity + 60.; |
|
|
1566 | |
|
|
1567 | // if last_activity + 60. is older than now, we did time out |
|
|
1568 | if (timeout < now) |
|
|
1569 | { |
|
|
1570 | // timeout occured, take action |
|
|
1571 | } |
|
|
1572 | else |
|
|
1573 | { |
|
|
1574 | // callback was invoked, but there was some activity, re-arm |
|
|
1575 | // the watcher to fire in last_activity + 60, which is |
|
|
1576 | // guaranteed to be in the future, so "again" is positive: |
|
|
1577 | w->repeat = timeout - now; |
|
|
1578 | ev_timer_again (EV_A_ w); |
|
|
1579 | } |
|
|
1580 | } |
|
|
1581 | |
|
|
1582 | To summarise the callback: first calculate the real timeout (defined |
|
|
1583 | as "60 seconds after the last activity"), then check if that time has |
|
|
1584 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1585 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1586 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1587 | a timeout then. |
|
|
1588 | |
|
|
1589 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1590 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1591 | |
|
|
1592 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1593 | minus half the average time between activity), but virtually no calls to |
|
|
1594 | libev to change the timeout. |
|
|
1595 | |
|
|
1596 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1597 | to the current time (meaning we just have some activity :), then call the |
|
|
1598 | callback, which will "do the right thing" and start the timer: |
|
|
1599 | |
|
|
1600 | ev_init (timer, callback); |
|
|
1601 | last_activity = ev_now (loop); |
|
|
1602 | callback (loop, timer, EV_TIMEOUT); |
|
|
1603 | |
|
|
1604 | And when there is some activity, simply store the current time in |
|
|
1605 | C<last_activity>, no libev calls at all: |
|
|
1606 | |
|
|
1607 | last_actiivty = ev_now (loop); |
|
|
1608 | |
|
|
1609 | This technique is slightly more complex, but in most cases where the |
|
|
1610 | time-out is unlikely to be triggered, much more efficient. |
|
|
1611 | |
|
|
1612 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1613 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1614 | fix things for you. |
|
|
1615 | |
|
|
1616 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1617 | |
|
|
1618 | If there is not one request, but many thousands (millions...), all |
|
|
1619 | employing some kind of timeout with the same timeout value, then one can |
|
|
1620 | do even better: |
|
|
1621 | |
|
|
1622 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1623 | at the I<end> of the list. |
|
|
1624 | |
|
|
1625 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1626 | the list is expected to fire (for example, using the technique #3). |
|
|
1627 | |
|
|
1628 | When there is some activity, remove the timer from the list, recalculate |
|
|
1629 | the timeout, append it to the end of the list again, and make sure to |
|
|
1630 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1631 | |
|
|
1632 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1633 | starting, stopping and updating the timers, at the expense of a major |
|
|
1634 | complication, and having to use a constant timeout. The constant timeout |
|
|
1635 | ensures that the list stays sorted. |
|
|
1636 | |
|
|
1637 | =back |
|
|
1638 | |
|
|
1639 | So which method the best? |
|
|
1640 | |
|
|
1641 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1642 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1643 | better, and isn't very complicated either. In most case, choosing either |
|
|
1644 | one is fine, with #3 being better in typical situations. |
|
|
1645 | |
|
|
1646 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1647 | rather complicated, but extremely efficient, something that really pays |
|
|
1648 | off after the first million or so of active timers, i.e. it's usually |
|
|
1649 | overkill :) |
|
|
1650 | |
|
|
1651 | =head3 The special problem of time updates |
|
|
1652 | |
|
|
1653 | Establishing the current time is a costly operation (it usually takes at |
|
|
1654 | least two system calls): EV therefore updates its idea of the current |
|
|
1655 | time only before and after C<ev_loop> collects new events, which causes a |
|
|
1656 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
1657 | lots of events in one iteration. |
949 | |
1658 | |
950 | The relative timeouts are calculated relative to the C<ev_now ()> |
1659 | The relative timeouts are calculated relative to the C<ev_now ()> |
951 | time. This is usually the right thing as this timestamp refers to the time |
1660 | time. This is usually the right thing as this timestamp refers to the time |
952 | of the event triggering whatever timeout you are modifying/starting. If |
1661 | of the event triggering whatever timeout you are modifying/starting. If |
953 | you suspect event processing to be delayed and you I<need> to base the timeout |
1662 | you suspect event processing to be delayed and you I<need> to base the |
954 | on the current time, use something like this to adjust for this: |
1663 | timeout on the current time, use something like this to adjust for this: |
955 | |
1664 | |
956 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1665 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
957 | |
1666 | |
958 | The callback is guarenteed to be invoked only when its timeout has passed, |
1667 | If the event loop is suspended for a long time, you can also force an |
959 | but if multiple timers become ready during the same loop iteration then |
1668 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
960 | order of execution is undefined. |
1669 | ()>. |
|
|
1670 | |
|
|
1671 | =head3 Watcher-Specific Functions and Data Members |
961 | |
1672 | |
962 | =over 4 |
1673 | =over 4 |
963 | |
1674 | |
964 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1675 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
965 | |
1676 | |
966 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1677 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
967 | |
1678 | |
968 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1679 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
969 | C<0.>, then it will automatically be stopped. If it is positive, then the |
1680 | is C<0.>, then it will automatically be stopped once the timeout is |
970 | timer will automatically be configured to trigger again C<repeat> seconds |
1681 | reached. If it is positive, then the timer will automatically be |
971 | later, again, and again, until stopped manually. |
1682 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1683 | until stopped manually. |
972 | |
1684 | |
973 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1685 | The timer itself will do a best-effort at avoiding drift, that is, if |
974 | configure a timer to trigger every 10 seconds, then it will trigger at |
1686 | you configure a timer to trigger every 10 seconds, then it will normally |
975 | exactly 10 second intervals. If, however, your program cannot keep up with |
1687 | trigger at exactly 10 second intervals. If, however, your program cannot |
976 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1688 | keep up with the timer (because it takes longer than those 10 seconds to |
977 | timer will not fire more than once per event loop iteration. |
1689 | do stuff) the timer will not fire more than once per event loop iteration. |
978 | |
1690 | |
979 | =item ev_timer_again (loop) |
1691 | =item ev_timer_again (loop, ev_timer *) |
980 | |
1692 | |
981 | This will act as if the timer timed out and restart it again if it is |
1693 | This will act as if the timer timed out and restart it again if it is |
982 | repeating. The exact semantics are: |
1694 | repeating. The exact semantics are: |
983 | |
1695 | |
984 | If the timer is pending, its pending status is cleared. |
1696 | If the timer is pending, its pending status is cleared. |
985 | |
1697 | |
986 | If the timer is started but nonrepeating, stop it (as if it timed out). |
1698 | If the timer is started but non-repeating, stop it (as if it timed out). |
987 | |
1699 | |
988 | If the timer is repeating, either start it if necessary (with the |
1700 | If the timer is repeating, either start it if necessary (with the |
989 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1701 | C<repeat> value), or reset the running timer to the C<repeat> value. |
990 | |
1702 | |
991 | This sounds a bit complicated, but here is a useful and typical |
1703 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
992 | example: Imagine you have a tcp connection and you want a so-called idle |
1704 | usage example. |
993 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
994 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
995 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
996 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
997 | you go into an idle state where you do not expect data to travel on the |
|
|
998 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
999 | automatically restart it if need be. |
|
|
1000 | |
|
|
1001 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1002 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1003 | |
|
|
1004 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1005 | ev_timer_again (loop, timer); |
|
|
1006 | ... |
|
|
1007 | timer->again = 17.; |
|
|
1008 | ev_timer_again (loop, timer); |
|
|
1009 | ... |
|
|
1010 | timer->again = 10.; |
|
|
1011 | ev_timer_again (loop, timer); |
|
|
1012 | |
|
|
1013 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1014 | you want to modify its timeout value. |
|
|
1015 | |
1705 | |
1016 | =item ev_tstamp repeat [read-write] |
1706 | =item ev_tstamp repeat [read-write] |
1017 | |
1707 | |
1018 | The current C<repeat> value. Will be used each time the watcher times out |
1708 | The current C<repeat> value. Will be used each time the watcher times out |
1019 | or C<ev_timer_again> is called and determines the next timeout (if any), |
1709 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1020 | which is also when any modifications are taken into account. |
1710 | which is also when any modifications are taken into account. |
1021 | |
1711 | |
1022 | =back |
1712 | =back |
1023 | |
1713 | |
|
|
1714 | =head3 Examples |
|
|
1715 | |
1024 | Example: Create a timer that fires after 60 seconds. |
1716 | Example: Create a timer that fires after 60 seconds. |
1025 | |
1717 | |
1026 | static void |
1718 | static void |
1027 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1719 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1028 | { |
1720 | { |
1029 | .. one minute over, w is actually stopped right here |
1721 | .. one minute over, w is actually stopped right here |
1030 | } |
1722 | } |
1031 | |
1723 | |
1032 | struct ev_timer mytimer; |
1724 | ev_timer mytimer; |
1033 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1725 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1034 | ev_timer_start (loop, &mytimer); |
1726 | ev_timer_start (loop, &mytimer); |
1035 | |
1727 | |
1036 | Example: Create a timeout timer that times out after 10 seconds of |
1728 | Example: Create a timeout timer that times out after 10 seconds of |
1037 | inactivity. |
1729 | inactivity. |
1038 | |
1730 | |
1039 | static void |
1731 | static void |
1040 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1732 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1041 | { |
1733 | { |
1042 | .. ten seconds without any activity |
1734 | .. ten seconds without any activity |
1043 | } |
1735 | } |
1044 | |
1736 | |
1045 | struct ev_timer mytimer; |
1737 | ev_timer mytimer; |
1046 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1738 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1047 | ev_timer_again (&mytimer); /* start timer */ |
1739 | ev_timer_again (&mytimer); /* start timer */ |
1048 | ev_loop (loop, 0); |
1740 | ev_loop (loop, 0); |
1049 | |
1741 | |
1050 | // and in some piece of code that gets executed on any "activity": |
1742 | // and in some piece of code that gets executed on any "activity": |
1051 | // reset the timeout to start ticking again at 10 seconds |
1743 | // reset the timeout to start ticking again at 10 seconds |
1052 | ev_timer_again (&mytimer); |
1744 | ev_timer_again (&mytimer); |
1053 | |
1745 | |
1054 | |
1746 | |
1055 | =head2 C<ev_periodic> - to cron or not to cron? |
1747 | =head2 C<ev_periodic> - to cron or not to cron? |
1056 | |
1748 | |
1057 | Periodic watchers are also timers of a kind, but they are very versatile |
1749 | Periodic watchers are also timers of a kind, but they are very versatile |
1058 | (and unfortunately a bit complex). |
1750 | (and unfortunately a bit complex). |
1059 | |
1751 | |
1060 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1752 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1061 | but on wallclock time (absolute time). You can tell a periodic watcher |
1753 | relative time, the physical time that passes) but on wall clock time |
1062 | to trigger "at" some specific point in time. For example, if you tell a |
1754 | (absolute time, the thing you can read on your calender or clock). The |
1063 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1755 | difference is that wall clock time can run faster or slower than real |
1064 | + 10.>) and then reset your system clock to the last year, then it will |
1756 | time, and time jumps are not uncommon (e.g. when you adjust your |
1065 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1757 | wrist-watch). |
1066 | roughly 10 seconds later and of course not if you reset your system time |
|
|
1067 | again). |
|
|
1068 | |
1758 | |
1069 | They can also be used to implement vastly more complex timers, such as |
1759 | You can tell a periodic watcher to trigger after some specific point |
|
|
1760 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1761 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1762 | not a delay) and then reset your system clock to January of the previous |
|
|
1763 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1764 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1765 | it, as it uses a relative timeout). |
|
|
1766 | |
|
|
1767 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1070 | triggering an event on eahc midnight, local time. |
1768 | timers, such as triggering an event on each "midnight, local time", or |
|
|
1769 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1770 | those cannot react to time jumps. |
1071 | |
1771 | |
1072 | As with timers, the callback is guarenteed to be invoked only when the |
1772 | As with timers, the callback is guaranteed to be invoked only when the |
1073 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1773 | point in time where it is supposed to trigger has passed. If multiple |
1074 | during the same loop iteration then order of execution is undefined. |
1774 | timers become ready during the same loop iteration then the ones with |
|
|
1775 | earlier time-out values are invoked before ones with later time-out values |
|
|
1776 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
|
|
1777 | |
|
|
1778 | =head3 Watcher-Specific Functions and Data Members |
1075 | |
1779 | |
1076 | =over 4 |
1780 | =over 4 |
1077 | |
1781 | |
1078 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1782 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1079 | |
1783 | |
1080 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1784 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1081 | |
1785 | |
1082 | Lots of arguments, lets sort it out... There are basically three modes of |
1786 | Lots of arguments, let's sort it out... There are basically three modes of |
1083 | operation, and we will explain them from simplest to complex: |
1787 | operation, and we will explain them from simplest to most complex: |
1084 | |
1788 | |
1085 | =over 4 |
1789 | =over 4 |
1086 | |
1790 | |
1087 | =item * absolute timer (interval = reschedule_cb = 0) |
1791 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1088 | |
1792 | |
1089 | In this configuration the watcher triggers an event at the wallclock time |
1793 | In this configuration the watcher triggers an event after the wall clock |
1090 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1794 | time C<offset> has passed. It will not repeat and will not adjust when a |
1091 | that is, if it is to be run at January 1st 2011 then it will run when the |
1795 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1092 | system time reaches or surpasses this time. |
1796 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1797 | this point in time. |
1093 | |
1798 | |
1094 | =item * non-repeating interval timer (interval > 0, reschedule_cb = 0) |
1799 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1095 | |
1800 | |
1096 | In this mode the watcher will always be scheduled to time out at the next |
1801 | In this mode the watcher will always be scheduled to time out at the next |
1097 | C<at + N * interval> time (for some integer N) and then repeat, regardless |
1802 | C<offset + N * interval> time (for some integer N, which can also be |
1098 | of any time jumps. |
1803 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1804 | argument is merely an offset into the C<interval> periods. |
1099 | |
1805 | |
1100 | This can be used to create timers that do not drift with respect to system |
1806 | This can be used to create timers that do not drift with respect to the |
1101 | time: |
1807 | system clock, for example, here is an C<ev_periodic> that triggers each |
|
|
1808 | hour, on the hour (with respect to UTC): |
1102 | |
1809 | |
1103 | ev_periodic_set (&periodic, 0., 3600., 0); |
1810 | ev_periodic_set (&periodic, 0., 3600., 0); |
1104 | |
1811 | |
1105 | This doesn't mean there will always be 3600 seconds in between triggers, |
1812 | This doesn't mean there will always be 3600 seconds in between triggers, |
1106 | but only that the the callback will be called when the system time shows a |
1813 | but only that the callback will be called when the system time shows a |
1107 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1814 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1108 | by 3600. |
1815 | by 3600. |
1109 | |
1816 | |
1110 | Another way to think about it (for the mathematically inclined) is that |
1817 | Another way to think about it (for the mathematically inclined) is that |
1111 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1818 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1112 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1819 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1113 | |
1820 | |
|
|
1821 | For numerical stability it is preferable that the C<offset> value is near |
|
|
1822 | C<ev_now ()> (the current time), but there is no range requirement for |
|
|
1823 | this value, and in fact is often specified as zero. |
|
|
1824 | |
|
|
1825 | Note also that there is an upper limit to how often a timer can fire (CPU |
|
|
1826 | speed for example), so if C<interval> is very small then timing stability |
|
|
1827 | will of course deteriorate. Libev itself tries to be exact to be about one |
|
|
1828 | millisecond (if the OS supports it and the machine is fast enough). |
|
|
1829 | |
1114 | =item * manual reschedule mode (reschedule_cb = callback) |
1830 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1115 | |
1831 | |
1116 | In this mode the values for C<interval> and C<at> are both being |
1832 | In this mode the values for C<interval> and C<offset> are both being |
1117 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1833 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1118 | reschedule callback will be called with the watcher as first, and the |
1834 | reschedule callback will be called with the watcher as first, and the |
1119 | current time as second argument. |
1835 | current time as second argument. |
1120 | |
1836 | |
1121 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1837 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1122 | ever, or make any event loop modifications>. If you need to stop it, |
1838 | or make ANY other event loop modifications whatsoever, unless explicitly |
1123 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
1839 | allowed by documentation here>. |
1124 | starting a prepare watcher). |
|
|
1125 | |
1840 | |
|
|
1841 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
1842 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
1843 | only event loop modification you are allowed to do). |
|
|
1844 | |
1126 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1845 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1127 | ev_tstamp now)>, e.g.: |
1846 | *w, ev_tstamp now)>, e.g.: |
1128 | |
1847 | |
|
|
1848 | static ev_tstamp |
1129 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1849 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1130 | { |
1850 | { |
1131 | return now + 60.; |
1851 | return now + 60.; |
1132 | } |
1852 | } |
1133 | |
1853 | |
1134 | It must return the next time to trigger, based on the passed time value |
1854 | It must return the next time to trigger, based on the passed time value |
1135 | (that is, the lowest time value larger than to the second argument). It |
1855 | (that is, the lowest time value larger than to the second argument). It |
1136 | will usually be called just before the callback will be triggered, but |
1856 | will usually be called just before the callback will be triggered, but |
1137 | might be called at other times, too. |
1857 | might be called at other times, too. |
1138 | |
1858 | |
1139 | NOTE: I<< This callback must always return a time that is later than the |
1859 | NOTE: I<< This callback must always return a time that is higher than or |
1140 | passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. |
1860 | equal to the passed C<now> value >>. |
1141 | |
1861 | |
1142 | This can be used to create very complex timers, such as a timer that |
1862 | This can be used to create very complex timers, such as a timer that |
1143 | triggers on each midnight, local time. To do this, you would calculate the |
1863 | triggers on "next midnight, local time". To do this, you would calculate the |
1144 | next midnight after C<now> and return the timestamp value for this. How |
1864 | next midnight after C<now> and return the timestamp value for this. How |
1145 | you do this is, again, up to you (but it is not trivial, which is the main |
1865 | you do this is, again, up to you (but it is not trivial, which is the main |
1146 | reason I omitted it as an example). |
1866 | reason I omitted it as an example). |
1147 | |
1867 | |
1148 | =back |
1868 | =back |
… | |
… | |
1152 | Simply stops and restarts the periodic watcher again. This is only useful |
1872 | Simply stops and restarts the periodic watcher again. This is only useful |
1153 | when you changed some parameters or the reschedule callback would return |
1873 | when you changed some parameters or the reschedule callback would return |
1154 | a different time than the last time it was called (e.g. in a crond like |
1874 | a different time than the last time it was called (e.g. in a crond like |
1155 | program when the crontabs have changed). |
1875 | program when the crontabs have changed). |
1156 | |
1876 | |
|
|
1877 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
1878 | |
|
|
1879 | When active, returns the absolute time that the watcher is supposed |
|
|
1880 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1881 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1882 | rescheduling modes. |
|
|
1883 | |
|
|
1884 | =item ev_tstamp offset [read-write] |
|
|
1885 | |
|
|
1886 | When repeating, this contains the offset value, otherwise this is the |
|
|
1887 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1888 | although libev might modify this value for better numerical stability). |
|
|
1889 | |
|
|
1890 | Can be modified any time, but changes only take effect when the periodic |
|
|
1891 | timer fires or C<ev_periodic_again> is being called. |
|
|
1892 | |
1157 | =item ev_tstamp interval [read-write] |
1893 | =item ev_tstamp interval [read-write] |
1158 | |
1894 | |
1159 | The current interval value. Can be modified any time, but changes only |
1895 | The current interval value. Can be modified any time, but changes only |
1160 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1896 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1161 | called. |
1897 | called. |
1162 | |
1898 | |
1163 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1899 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1164 | |
1900 | |
1165 | The current reschedule callback, or C<0>, if this functionality is |
1901 | The current reschedule callback, or C<0>, if this functionality is |
1166 | switched off. Can be changed any time, but changes only take effect when |
1902 | switched off. Can be changed any time, but changes only take effect when |
1167 | the periodic timer fires or C<ev_periodic_again> is being called. |
1903 | the periodic timer fires or C<ev_periodic_again> is being called. |
1168 | |
1904 | |
1169 | =back |
1905 | =back |
1170 | |
1906 | |
|
|
1907 | =head3 Examples |
|
|
1908 | |
1171 | Example: Call a callback every hour, or, more precisely, whenever the |
1909 | Example: Call a callback every hour, or, more precisely, whenever the |
1172 | system clock is divisible by 3600. The callback invocation times have |
1910 | system time is divisible by 3600. The callback invocation times have |
1173 | potentially a lot of jittering, but good long-term stability. |
1911 | potentially a lot of jitter, but good long-term stability. |
1174 | |
1912 | |
1175 | static void |
1913 | static void |
1176 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1914 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1177 | { |
1915 | { |
1178 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1916 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1179 | } |
1917 | } |
1180 | |
1918 | |
1181 | struct ev_periodic hourly_tick; |
1919 | ev_periodic hourly_tick; |
1182 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1920 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1183 | ev_periodic_start (loop, &hourly_tick); |
1921 | ev_periodic_start (loop, &hourly_tick); |
1184 | |
1922 | |
1185 | Example: The same as above, but use a reschedule callback to do it: |
1923 | Example: The same as above, but use a reschedule callback to do it: |
1186 | |
1924 | |
1187 | #include <math.h> |
1925 | #include <math.h> |
1188 | |
1926 | |
1189 | static ev_tstamp |
1927 | static ev_tstamp |
1190 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1928 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1191 | { |
1929 | { |
1192 | return fmod (now, 3600.) + 3600.; |
1930 | return now + (3600. - fmod (now, 3600.)); |
1193 | } |
1931 | } |
1194 | |
1932 | |
1195 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1933 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1196 | |
1934 | |
1197 | Example: Call a callback every hour, starting now: |
1935 | Example: Call a callback every hour, starting now: |
1198 | |
1936 | |
1199 | struct ev_periodic hourly_tick; |
1937 | ev_periodic hourly_tick; |
1200 | ev_periodic_init (&hourly_tick, clock_cb, |
1938 | ev_periodic_init (&hourly_tick, clock_cb, |
1201 | fmod (ev_now (loop), 3600.), 3600., 0); |
1939 | fmod (ev_now (loop), 3600.), 3600., 0); |
1202 | ev_periodic_start (loop, &hourly_tick); |
1940 | ev_periodic_start (loop, &hourly_tick); |
1203 | |
1941 | |
1204 | |
1942 | |
1205 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1943 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1206 | |
1944 | |
1207 | Signal watchers will trigger an event when the process receives a specific |
1945 | Signal watchers will trigger an event when the process receives a specific |
1208 | signal one or more times. Even though signals are very asynchronous, libev |
1946 | signal one or more times. Even though signals are very asynchronous, libev |
1209 | will try it's best to deliver signals synchronously, i.e. as part of the |
1947 | will try it's best to deliver signals synchronously, i.e. as part of the |
1210 | normal event processing, like any other event. |
1948 | normal event processing, like any other event. |
1211 | |
1949 | |
|
|
1950 | If you want signals asynchronously, just use C<sigaction> as you would |
|
|
1951 | do without libev and forget about sharing the signal. You can even use |
|
|
1952 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
|
|
1953 | |
1212 | You can configure as many watchers as you like per signal. Only when the |
1954 | You can configure as many watchers as you like per signal. Only when the |
1213 | first watcher gets started will libev actually register a signal watcher |
1955 | first watcher gets started will libev actually register a signal handler |
1214 | with the kernel (thus it coexists with your own signal handlers as long |
1956 | with the kernel (thus it coexists with your own signal handlers as long as |
1215 | as you don't register any with libev). Similarly, when the last signal |
1957 | you don't register any with libev for the same signal). Similarly, when |
1216 | watcher for a signal is stopped libev will reset the signal handler to |
1958 | the last signal watcher for a signal is stopped, libev will reset the |
1217 | SIG_DFL (regardless of what it was set to before). |
1959 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1960 | |
|
|
1961 | If possible and supported, libev will install its handlers with |
|
|
1962 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
|
|
1963 | interrupted. If you have a problem with system calls getting interrupted by |
|
|
1964 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1965 | them in an C<ev_prepare> watcher. |
|
|
1966 | |
|
|
1967 | =head3 Watcher-Specific Functions and Data Members |
1218 | |
1968 | |
1219 | =over 4 |
1969 | =over 4 |
1220 | |
1970 | |
1221 | =item ev_signal_init (ev_signal *, callback, int signum) |
1971 | =item ev_signal_init (ev_signal *, callback, int signum) |
1222 | |
1972 | |
… | |
… | |
1229 | |
1979 | |
1230 | The signal the watcher watches out for. |
1980 | The signal the watcher watches out for. |
1231 | |
1981 | |
1232 | =back |
1982 | =back |
1233 | |
1983 | |
|
|
1984 | =head3 Examples |
|
|
1985 | |
|
|
1986 | Example: Try to exit cleanly on SIGINT. |
|
|
1987 | |
|
|
1988 | static void |
|
|
1989 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
|
|
1990 | { |
|
|
1991 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1992 | } |
|
|
1993 | |
|
|
1994 | ev_signal signal_watcher; |
|
|
1995 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1996 | ev_signal_start (loop, &signal_watcher); |
|
|
1997 | |
1234 | |
1998 | |
1235 | =head2 C<ev_child> - watch out for process status changes |
1999 | =head2 C<ev_child> - watch out for process status changes |
1236 | |
2000 | |
1237 | Child watchers trigger when your process receives a SIGCHLD in response to |
2001 | Child watchers trigger when your process receives a SIGCHLD in response to |
1238 | some child status changes (most typically when a child of yours dies). |
2002 | some child status changes (most typically when a child of yours dies or |
|
|
2003 | exits). It is permissible to install a child watcher I<after> the child |
|
|
2004 | has been forked (which implies it might have already exited), as long |
|
|
2005 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2006 | forking and then immediately registering a watcher for the child is fine, |
|
|
2007 | but forking and registering a watcher a few event loop iterations later or |
|
|
2008 | in the next callback invocation is not. |
|
|
2009 | |
|
|
2010 | Only the default event loop is capable of handling signals, and therefore |
|
|
2011 | you can only register child watchers in the default event loop. |
|
|
2012 | |
|
|
2013 | =head3 Process Interaction |
|
|
2014 | |
|
|
2015 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
2016 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
2017 | the first child watcher is started after the child exits. The occurrence |
|
|
2018 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
2019 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
2020 | children, even ones not watched. |
|
|
2021 | |
|
|
2022 | =head3 Overriding the Built-In Processing |
|
|
2023 | |
|
|
2024 | Libev offers no special support for overriding the built-in child |
|
|
2025 | processing, but if your application collides with libev's default child |
|
|
2026 | handler, you can override it easily by installing your own handler for |
|
|
2027 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
2028 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
2029 | event-based approach to child reaping and thus use libev's support for |
|
|
2030 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
2031 | |
|
|
2032 | =head3 Stopping the Child Watcher |
|
|
2033 | |
|
|
2034 | Currently, the child watcher never gets stopped, even when the |
|
|
2035 | child terminates, so normally one needs to stop the watcher in the |
|
|
2036 | callback. Future versions of libev might stop the watcher automatically |
|
|
2037 | when a child exit is detected. |
|
|
2038 | |
|
|
2039 | =head3 Watcher-Specific Functions and Data Members |
1239 | |
2040 | |
1240 | =over 4 |
2041 | =over 4 |
1241 | |
2042 | |
1242 | =item ev_child_init (ev_child *, callback, int pid) |
2043 | =item ev_child_init (ev_child *, callback, int pid, int trace) |
1243 | |
2044 | |
1244 | =item ev_child_set (ev_child *, int pid) |
2045 | =item ev_child_set (ev_child *, int pid, int trace) |
1245 | |
2046 | |
1246 | Configures the watcher to wait for status changes of process C<pid> (or |
2047 | Configures the watcher to wait for status changes of process C<pid> (or |
1247 | I<any> process if C<pid> is specified as C<0>). The callback can look |
2048 | I<any> process if C<pid> is specified as C<0>). The callback can look |
1248 | at the C<rstatus> member of the C<ev_child> watcher structure to see |
2049 | at the C<rstatus> member of the C<ev_child> watcher structure to see |
1249 | the status word (use the macros from C<sys/wait.h> and see your systems |
2050 | the status word (use the macros from C<sys/wait.h> and see your systems |
1250 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
2051 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
1251 | process causing the status change. |
2052 | process causing the status change. C<trace> must be either C<0> (only |
|
|
2053 | activate the watcher when the process terminates) or C<1> (additionally |
|
|
2054 | activate the watcher when the process is stopped or continued). |
1252 | |
2055 | |
1253 | =item int pid [read-only] |
2056 | =item int pid [read-only] |
1254 | |
2057 | |
1255 | The process id this watcher watches out for, or C<0>, meaning any process id. |
2058 | The process id this watcher watches out for, or C<0>, meaning any process id. |
1256 | |
2059 | |
… | |
… | |
1263 | The process exit/trace status caused by C<rpid> (see your systems |
2066 | The process exit/trace status caused by C<rpid> (see your systems |
1264 | C<waitpid> and C<sys/wait.h> documentation for details). |
2067 | C<waitpid> and C<sys/wait.h> documentation for details). |
1265 | |
2068 | |
1266 | =back |
2069 | =back |
1267 | |
2070 | |
1268 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2071 | =head3 Examples |
1269 | |
2072 | |
|
|
2073 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
2074 | its completion. |
|
|
2075 | |
|
|
2076 | ev_child cw; |
|
|
2077 | |
1270 | static void |
2078 | static void |
1271 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2079 | child_cb (EV_P_ ev_child *w, int revents) |
1272 | { |
2080 | { |
1273 | ev_unloop (loop, EVUNLOOP_ALL); |
2081 | ev_child_stop (EV_A_ w); |
|
|
2082 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1274 | } |
2083 | } |
1275 | |
2084 | |
1276 | struct ev_signal signal_watcher; |
2085 | pid_t pid = fork (); |
1277 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2086 | |
1278 | ev_signal_start (loop, &sigint_cb); |
2087 | if (pid < 0) |
|
|
2088 | // error |
|
|
2089 | else if (pid == 0) |
|
|
2090 | { |
|
|
2091 | // the forked child executes here |
|
|
2092 | exit (1); |
|
|
2093 | } |
|
|
2094 | else |
|
|
2095 | { |
|
|
2096 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
2097 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
2098 | } |
1279 | |
2099 | |
1280 | |
2100 | |
1281 | =head2 C<ev_stat> - did the file attributes just change? |
2101 | =head2 C<ev_stat> - did the file attributes just change? |
1282 | |
2102 | |
1283 | This watches a filesystem path for attribute changes. That is, it calls |
2103 | This watches a file system path for attribute changes. That is, it calls |
1284 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2104 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1285 | compared to the last time, invoking the callback if it did. |
2105 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2106 | it did. |
1286 | |
2107 | |
1287 | The path does not need to exist: changing from "path exists" to "path does |
2108 | The path does not need to exist: changing from "path exists" to "path does |
1288 | not exist" is a status change like any other. The condition "path does |
2109 | not exist" is a status change like any other. The condition "path does not |
1289 | not exist" is signified by the C<st_nlink> field being zero (which is |
2110 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1290 | otherwise always forced to be at least one) and all the other fields of |
2111 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1291 | the stat buffer having unspecified contents. |
2112 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2113 | contents. |
1292 | |
2114 | |
1293 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2115 | The path I<must not> end in a slash or contain special components such as |
|
|
2116 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1294 | relative and your working directory changes, the behaviour is undefined. |
2117 | your working directory changes, then the behaviour is undefined. |
1295 | |
2118 | |
1296 | Since there is no standard to do this, the portable implementation simply |
2119 | Since there is no portable change notification interface available, the |
1297 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
2120 | portable implementation simply calls C<stat(2)> regularly on the path |
1298 | can specify a recommended polling interval for this case. If you specify |
2121 | to see if it changed somehow. You can specify a recommended polling |
1299 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
2122 | interval for this case. If you specify a polling interval of C<0> (highly |
1300 | unspecified default> value will be used (which you can expect to be around |
2123 | recommended!) then a I<suitable, unspecified default> value will be used |
1301 | five seconds, although this might change dynamically). Libev will also |
2124 | (which you can expect to be around five seconds, although this might |
1302 | impose a minimum interval which is currently around C<0.1>, but thats |
2125 | change dynamically). Libev will also impose a minimum interval which is |
1303 | usually overkill. |
2126 | currently around C<0.1>, but that's usually overkill. |
1304 | |
2127 | |
1305 | This watcher type is not meant for massive numbers of stat watchers, |
2128 | This watcher type is not meant for massive numbers of stat watchers, |
1306 | as even with OS-supported change notifications, this can be |
2129 | as even with OS-supported change notifications, this can be |
1307 | resource-intensive. |
2130 | resource-intensive. |
1308 | |
2131 | |
1309 | At the time of this writing, only the Linux inotify interface is |
2132 | At the time of this writing, the only OS-specific interface implemented |
1310 | implemented (implementing kqueue support is left as an exercise for the |
2133 | is the Linux inotify interface (implementing kqueue support is left as an |
1311 | reader). Inotify will be used to give hints only and should not change the |
2134 | exercise for the reader. Note, however, that the author sees no way of |
1312 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
2135 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1313 | to fall back to regular polling again even with inotify, but changes are |
2136 | |
1314 | usually detected immediately, and if the file exists there will be no |
2137 | =head3 ABI Issues (Largefile Support) |
1315 | polling. |
2138 | |
|
|
2139 | Libev by default (unless the user overrides this) uses the default |
|
|
2140 | compilation environment, which means that on systems with large file |
|
|
2141 | support disabled by default, you get the 32 bit version of the stat |
|
|
2142 | structure. When using the library from programs that change the ABI to |
|
|
2143 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
2144 | compile libev with the same flags to get binary compatibility. This is |
|
|
2145 | obviously the case with any flags that change the ABI, but the problem is |
|
|
2146 | most noticeably displayed with ev_stat and large file support. |
|
|
2147 | |
|
|
2148 | The solution for this is to lobby your distribution maker to make large |
|
|
2149 | file interfaces available by default (as e.g. FreeBSD does) and not |
|
|
2150 | optional. Libev cannot simply switch on large file support because it has |
|
|
2151 | to exchange stat structures with application programs compiled using the |
|
|
2152 | default compilation environment. |
|
|
2153 | |
|
|
2154 | =head3 Inotify and Kqueue |
|
|
2155 | |
|
|
2156 | When C<inotify (7)> support has been compiled into libev and present at |
|
|
2157 | runtime, it will be used to speed up change detection where possible. The |
|
|
2158 | inotify descriptor will be created lazily when the first C<ev_stat> |
|
|
2159 | watcher is being started. |
|
|
2160 | |
|
|
2161 | Inotify presence does not change the semantics of C<ev_stat> watchers |
|
|
2162 | except that changes might be detected earlier, and in some cases, to avoid |
|
|
2163 | making regular C<stat> calls. Even in the presence of inotify support |
|
|
2164 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2165 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2166 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2167 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2168 | xfs are fully working) libev usually gets away without polling. |
|
|
2169 | |
|
|
2170 | There is no support for kqueue, as apparently it cannot be used to |
|
|
2171 | implement this functionality, due to the requirement of having a file |
|
|
2172 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2173 | etc. is difficult. |
|
|
2174 | |
|
|
2175 | =head3 C<stat ()> is a synchronous operation |
|
|
2176 | |
|
|
2177 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2178 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2179 | ()>, which is a synchronous operation. |
|
|
2180 | |
|
|
2181 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2182 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2183 | as the path data is usually in memory already (except when starting the |
|
|
2184 | watcher). |
|
|
2185 | |
|
|
2186 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2187 | time due to network issues, and even under good conditions, a stat call |
|
|
2188 | often takes multiple milliseconds. |
|
|
2189 | |
|
|
2190 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2191 | paths, although this is fully supported by libev. |
|
|
2192 | |
|
|
2193 | =head3 The special problem of stat time resolution |
|
|
2194 | |
|
|
2195 | The C<stat ()> system call only supports full-second resolution portably, |
|
|
2196 | and even on systems where the resolution is higher, most file systems |
|
|
2197 | still only support whole seconds. |
|
|
2198 | |
|
|
2199 | That means that, if the time is the only thing that changes, you can |
|
|
2200 | easily miss updates: on the first update, C<ev_stat> detects a change and |
|
|
2201 | calls your callback, which does something. When there is another update |
|
|
2202 | within the same second, C<ev_stat> will be unable to detect unless the |
|
|
2203 | stat data does change in other ways (e.g. file size). |
|
|
2204 | |
|
|
2205 | The solution to this is to delay acting on a change for slightly more |
|
|
2206 | than a second (or till slightly after the next full second boundary), using |
|
|
2207 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
|
|
2208 | ev_timer_again (loop, w)>). |
|
|
2209 | |
|
|
2210 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
2211 | of some operating systems (where the second counter of the current time |
|
|
2212 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
2213 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
2214 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
2215 | update file times then there will be a small window where the kernel uses |
|
|
2216 | the previous second to update file times but libev might already execute |
|
|
2217 | the timer callback). |
|
|
2218 | |
|
|
2219 | =head3 Watcher-Specific Functions and Data Members |
1316 | |
2220 | |
1317 | =over 4 |
2221 | =over 4 |
1318 | |
2222 | |
1319 | =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) |
2223 | =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) |
1320 | |
2224 | |
… | |
… | |
1324 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2228 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1325 | be detected and should normally be specified as C<0> to let libev choose |
2229 | be detected and should normally be specified as C<0> to let libev choose |
1326 | a suitable value. The memory pointed to by C<path> must point to the same |
2230 | a suitable value. The memory pointed to by C<path> must point to the same |
1327 | path for as long as the watcher is active. |
2231 | path for as long as the watcher is active. |
1328 | |
2232 | |
1329 | The callback will be receive C<EV_STAT> when a change was detected, |
2233 | The callback will receive an C<EV_STAT> event when a change was detected, |
1330 | relative to the attributes at the time the watcher was started (or the |
2234 | relative to the attributes at the time the watcher was started (or the |
1331 | last change was detected). |
2235 | last change was detected). |
1332 | |
2236 | |
1333 | =item ev_stat_stat (ev_stat *) |
2237 | =item ev_stat_stat (loop, ev_stat *) |
1334 | |
2238 | |
1335 | Updates the stat buffer immediately with new values. If you change the |
2239 | Updates the stat buffer immediately with new values. If you change the |
1336 | watched path in your callback, you could call this fucntion to avoid |
2240 | watched path in your callback, you could call this function to avoid |
1337 | detecting this change (while introducing a race condition). Can also be |
2241 | detecting this change (while introducing a race condition if you are not |
1338 | useful simply to find out the new values. |
2242 | the only one changing the path). Can also be useful simply to find out the |
|
|
2243 | new values. |
1339 | |
2244 | |
1340 | =item ev_statdata attr [read-only] |
2245 | =item ev_statdata attr [read-only] |
1341 | |
2246 | |
1342 | The most-recently detected attributes of the file. Although the type is of |
2247 | The most-recently detected attributes of the file. Although the type is |
1343 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
2248 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1344 | suitable for your system. If the C<st_nlink> member is C<0>, then there |
2249 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
2250 | members to be present. If the C<st_nlink> member is C<0>, then there was |
1345 | was some error while C<stat>ing the file. |
2251 | some error while C<stat>ing the file. |
1346 | |
2252 | |
1347 | =item ev_statdata prev [read-only] |
2253 | =item ev_statdata prev [read-only] |
1348 | |
2254 | |
1349 | The previous attributes of the file. The callback gets invoked whenever |
2255 | The previous attributes of the file. The callback gets invoked whenever |
1350 | C<prev> != C<attr>. |
2256 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
2257 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
2258 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
1351 | |
2259 | |
1352 | =item ev_tstamp interval [read-only] |
2260 | =item ev_tstamp interval [read-only] |
1353 | |
2261 | |
1354 | The specified interval. |
2262 | The specified interval. |
1355 | |
2263 | |
1356 | =item const char *path [read-only] |
2264 | =item const char *path [read-only] |
1357 | |
2265 | |
1358 | The filesystem path that is being watched. |
2266 | The file system path that is being watched. |
1359 | |
2267 | |
1360 | =back |
2268 | =back |
1361 | |
2269 | |
|
|
2270 | =head3 Examples |
|
|
2271 | |
1362 | Example: Watch C</etc/passwd> for attribute changes. |
2272 | Example: Watch C</etc/passwd> for attribute changes. |
1363 | |
2273 | |
1364 | static void |
2274 | static void |
1365 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
2275 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
1366 | { |
2276 | { |
1367 | /* /etc/passwd changed in some way */ |
2277 | /* /etc/passwd changed in some way */ |
1368 | if (w->attr.st_nlink) |
2278 | if (w->attr.st_nlink) |
1369 | { |
2279 | { |
1370 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
2280 | printf ("passwd current size %ld\n", (long)w->attr.st_size); |
1371 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
2281 | printf ("passwd current atime %ld\n", (long)w->attr.st_mtime); |
1372 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
2282 | printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime); |
1373 | } |
2283 | } |
1374 | else |
2284 | else |
1375 | /* you shalt not abuse printf for puts */ |
2285 | /* you shalt not abuse printf for puts */ |
1376 | puts ("wow, /etc/passwd is not there, expect problems. " |
2286 | puts ("wow, /etc/passwd is not there, expect problems. " |
1377 | "if this is windows, they already arrived\n"); |
2287 | "if this is windows, they already arrived\n"); |
1378 | } |
2288 | } |
1379 | |
2289 | |
1380 | ... |
2290 | ... |
1381 | ev_stat passwd; |
2291 | ev_stat passwd; |
1382 | |
2292 | |
1383 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); |
2293 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
1384 | ev_stat_start (loop, &passwd); |
2294 | ev_stat_start (loop, &passwd); |
|
|
2295 | |
|
|
2296 | Example: Like above, but additionally use a one-second delay so we do not |
|
|
2297 | miss updates (however, frequent updates will delay processing, too, so |
|
|
2298 | one might do the work both on C<ev_stat> callback invocation I<and> on |
|
|
2299 | C<ev_timer> callback invocation). |
|
|
2300 | |
|
|
2301 | static ev_stat passwd; |
|
|
2302 | static ev_timer timer; |
|
|
2303 | |
|
|
2304 | static void |
|
|
2305 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2306 | { |
|
|
2307 | ev_timer_stop (EV_A_ w); |
|
|
2308 | |
|
|
2309 | /* now it's one second after the most recent passwd change */ |
|
|
2310 | } |
|
|
2311 | |
|
|
2312 | static void |
|
|
2313 | stat_cb (EV_P_ ev_stat *w, int revents) |
|
|
2314 | { |
|
|
2315 | /* reset the one-second timer */ |
|
|
2316 | ev_timer_again (EV_A_ &timer); |
|
|
2317 | } |
|
|
2318 | |
|
|
2319 | ... |
|
|
2320 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
|
|
2321 | ev_stat_start (loop, &passwd); |
|
|
2322 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1385 | |
2323 | |
1386 | |
2324 | |
1387 | =head2 C<ev_idle> - when you've got nothing better to do... |
2325 | =head2 C<ev_idle> - when you've got nothing better to do... |
1388 | |
2326 | |
1389 | Idle watchers trigger events when no other events of the same or higher |
2327 | Idle watchers trigger events when no other events of the same or higher |
1390 | priority are pending (prepare, check and other idle watchers do not |
2328 | priority are pending (prepare, check and other idle watchers do not count |
1391 | count). |
2329 | as receiving "events"). |
1392 | |
2330 | |
1393 | That is, as long as your process is busy handling sockets or timeouts |
2331 | That is, as long as your process is busy handling sockets or timeouts |
1394 | (or even signals, imagine) of the same or higher priority it will not be |
2332 | (or even signals, imagine) of the same or higher priority it will not be |
1395 | triggered. But when your process is idle (or only lower-priority watchers |
2333 | triggered. But when your process is idle (or only lower-priority watchers |
1396 | are pending), the idle watchers are being called once per event loop |
2334 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1403 | Apart from keeping your process non-blocking (which is a useful |
2341 | Apart from keeping your process non-blocking (which is a useful |
1404 | effect on its own sometimes), idle watchers are a good place to do |
2342 | effect on its own sometimes), idle watchers are a good place to do |
1405 | "pseudo-background processing", or delay processing stuff to after the |
2343 | "pseudo-background processing", or delay processing stuff to after the |
1406 | event loop has handled all outstanding events. |
2344 | event loop has handled all outstanding events. |
1407 | |
2345 | |
|
|
2346 | =head3 Watcher-Specific Functions and Data Members |
|
|
2347 | |
1408 | =over 4 |
2348 | =over 4 |
1409 | |
2349 | |
1410 | =item ev_idle_init (ev_signal *, callback) |
2350 | =item ev_idle_init (ev_idle *, callback) |
1411 | |
2351 | |
1412 | Initialises and configures the idle watcher - it has no parameters of any |
2352 | Initialises and configures the idle watcher - it has no parameters of any |
1413 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2353 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1414 | believe me. |
2354 | believe me. |
1415 | |
2355 | |
1416 | =back |
2356 | =back |
1417 | |
2357 | |
|
|
2358 | =head3 Examples |
|
|
2359 | |
1418 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2360 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1419 | callback, free it. Also, use no error checking, as usual. |
2361 | callback, free it. Also, use no error checking, as usual. |
1420 | |
2362 | |
1421 | static void |
2363 | static void |
1422 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2364 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1423 | { |
2365 | { |
1424 | free (w); |
2366 | free (w); |
1425 | // now do something you wanted to do when the program has |
2367 | // now do something you wanted to do when the program has |
1426 | // no longer asnything immediate to do. |
2368 | // no longer anything immediate to do. |
1427 | } |
2369 | } |
1428 | |
2370 | |
1429 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2371 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1430 | ev_idle_init (idle_watcher, idle_cb); |
2372 | ev_idle_init (idle_watcher, idle_cb); |
1431 | ev_idle_start (loop, idle_cb); |
2373 | ev_idle_start (loop, idle_watcher); |
1432 | |
2374 | |
1433 | |
2375 | |
1434 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2376 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1435 | |
2377 | |
1436 | Prepare and check watchers are usually (but not always) used in tandem: |
2378 | Prepare and check watchers are usually (but not always) used in pairs: |
1437 | prepare watchers get invoked before the process blocks and check watchers |
2379 | prepare watchers get invoked before the process blocks and check watchers |
1438 | afterwards. |
2380 | afterwards. |
1439 | |
2381 | |
1440 | You I<must not> call C<ev_loop> or similar functions that enter |
2382 | You I<must not> call C<ev_loop> or similar functions that enter |
1441 | the current event loop from either C<ev_prepare> or C<ev_check> |
2383 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
1444 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2386 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1445 | C<ev_check> so if you have one watcher of each kind they will always be |
2387 | C<ev_check> so if you have one watcher of each kind they will always be |
1446 | called in pairs bracketing the blocking call. |
2388 | called in pairs bracketing the blocking call. |
1447 | |
2389 | |
1448 | Their main purpose is to integrate other event mechanisms into libev and |
2390 | Their main purpose is to integrate other event mechanisms into libev and |
1449 | their use is somewhat advanced. This could be used, for example, to track |
2391 | their use is somewhat advanced. They could be used, for example, to track |
1450 | variable changes, implement your own watchers, integrate net-snmp or a |
2392 | variable changes, implement your own watchers, integrate net-snmp or a |
1451 | coroutine library and lots more. They are also occasionally useful if |
2393 | coroutine library and lots more. They are also occasionally useful if |
1452 | you cache some data and want to flush it before blocking (for example, |
2394 | you cache some data and want to flush it before blocking (for example, |
1453 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2395 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1454 | watcher). |
2396 | watcher). |
1455 | |
2397 | |
1456 | This is done by examining in each prepare call which file descriptors need |
2398 | This is done by examining in each prepare call which file descriptors |
1457 | to be watched by the other library, registering C<ev_io> watchers for |
2399 | need to be watched by the other library, registering C<ev_io> watchers |
1458 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2400 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1459 | provide just this functionality). Then, in the check watcher you check for |
2401 | libraries provide exactly this functionality). Then, in the check watcher, |
1460 | any events that occured (by checking the pending status of all watchers |
2402 | you check for any events that occurred (by checking the pending status |
1461 | and stopping them) and call back into the library. The I/O and timer |
2403 | of all watchers and stopping them) and call back into the library. The |
1462 | callbacks will never actually be called (but must be valid nevertheless, |
2404 | I/O and timer callbacks will never actually be called (but must be valid |
1463 | because you never know, you know?). |
2405 | nevertheless, because you never know, you know?). |
1464 | |
2406 | |
1465 | As another example, the Perl Coro module uses these hooks to integrate |
2407 | As another example, the Perl Coro module uses these hooks to integrate |
1466 | coroutines into libev programs, by yielding to other active coroutines |
2408 | coroutines into libev programs, by yielding to other active coroutines |
1467 | during each prepare and only letting the process block if no coroutines |
2409 | during each prepare and only letting the process block if no coroutines |
1468 | are ready to run (it's actually more complicated: it only runs coroutines |
2410 | are ready to run (it's actually more complicated: it only runs coroutines |
1469 | with priority higher than or equal to the event loop and one coroutine |
2411 | with priority higher than or equal to the event loop and one coroutine |
1470 | of lower priority, but only once, using idle watchers to keep the event |
2412 | of lower priority, but only once, using idle watchers to keep the event |
1471 | loop from blocking if lower-priority coroutines are active, thus mapping |
2413 | loop from blocking if lower-priority coroutines are active, thus mapping |
1472 | low-priority coroutines to idle/background tasks). |
2414 | low-priority coroutines to idle/background tasks). |
1473 | |
2415 | |
|
|
2416 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
|
|
2417 | priority, to ensure that they are being run before any other watchers |
|
|
2418 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2419 | |
|
|
2420 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
|
|
2421 | activate ("feed") events into libev. While libev fully supports this, they |
|
|
2422 | might get executed before other C<ev_check> watchers did their job. As |
|
|
2423 | C<ev_check> watchers are often used to embed other (non-libev) event |
|
|
2424 | loops those other event loops might be in an unusable state until their |
|
|
2425 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
|
|
2426 | others). |
|
|
2427 | |
|
|
2428 | =head3 Watcher-Specific Functions and Data Members |
|
|
2429 | |
1474 | =over 4 |
2430 | =over 4 |
1475 | |
2431 | |
1476 | =item ev_prepare_init (ev_prepare *, callback) |
2432 | =item ev_prepare_init (ev_prepare *, callback) |
1477 | |
2433 | |
1478 | =item ev_check_init (ev_check *, callback) |
2434 | =item ev_check_init (ev_check *, callback) |
1479 | |
2435 | |
1480 | Initialises and configures the prepare or check watcher - they have no |
2436 | Initialises and configures the prepare or check watcher - they have no |
1481 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2437 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1482 | macros, but using them is utterly, utterly and completely pointless. |
2438 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2439 | pointless. |
1483 | |
2440 | |
1484 | =back |
2441 | =back |
1485 | |
2442 | |
1486 | Example: To include a library such as adns, you would add IO watchers |
2443 | =head3 Examples |
1487 | and a timeout watcher in a prepare handler, as required by libadns, and |
2444 | |
|
|
2445 | There are a number of principal ways to embed other event loops or modules |
|
|
2446 | into libev. Here are some ideas on how to include libadns into libev |
|
|
2447 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
|
|
2448 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
|
|
2449 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
|
|
2450 | Glib event loop). |
|
|
2451 | |
|
|
2452 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1488 | in a check watcher, destroy them and call into libadns. What follows is |
2453 | and in a check watcher, destroy them and call into libadns. What follows |
1489 | pseudo-code only of course: |
2454 | is pseudo-code only of course. This requires you to either use a low |
|
|
2455 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
|
|
2456 | the callbacks for the IO/timeout watchers might not have been called yet. |
1490 | |
2457 | |
1491 | static ev_io iow [nfd]; |
2458 | static ev_io iow [nfd]; |
1492 | static ev_timer tw; |
2459 | static ev_timer tw; |
1493 | |
2460 | |
1494 | static void |
2461 | static void |
1495 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2462 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
1496 | { |
2463 | { |
1497 | // set the relevant poll flags |
|
|
1498 | // could also call adns_processreadable etc. here |
|
|
1499 | struct pollfd *fd = (struct pollfd *)w->data; |
|
|
1500 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
1501 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
1502 | } |
2464 | } |
1503 | |
2465 | |
1504 | // create io watchers for each fd and a timer before blocking |
2466 | // create io watchers for each fd and a timer before blocking |
1505 | static void |
2467 | static void |
1506 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2468 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
1507 | { |
2469 | { |
1508 | int timeout = 3600000; |
2470 | int timeout = 3600000; |
1509 | struct pollfd fds [nfd]; |
2471 | struct pollfd fds [nfd]; |
1510 | // actual code will need to loop here and realloc etc. |
2472 | // actual code will need to loop here and realloc etc. |
1511 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2473 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1512 | |
2474 | |
1513 | /* the callback is illegal, but won't be called as we stop during check */ |
2475 | /* the callback is illegal, but won't be called as we stop during check */ |
1514 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2476 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
1515 | ev_timer_start (loop, &tw); |
2477 | ev_timer_start (loop, &tw); |
1516 | |
2478 | |
1517 | // create on ev_io per pollfd |
2479 | // create one ev_io per pollfd |
1518 | for (int i = 0; i < nfd; ++i) |
2480 | for (int i = 0; i < nfd; ++i) |
1519 | { |
2481 | { |
1520 | ev_io_init (iow + i, io_cb, fds [i].fd, |
2482 | ev_io_init (iow + i, io_cb, fds [i].fd, |
1521 | ((fds [i].events & POLLIN ? EV_READ : 0) |
2483 | ((fds [i].events & POLLIN ? EV_READ : 0) |
1522 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
2484 | | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1523 | |
2485 | |
1524 | fds [i].revents = 0; |
2486 | fds [i].revents = 0; |
1525 | iow [i].data = fds + i; |
|
|
1526 | ev_io_start (loop, iow + i); |
2487 | ev_io_start (loop, iow + i); |
1527 | } |
2488 | } |
1528 | } |
2489 | } |
1529 | |
2490 | |
1530 | // stop all watchers after blocking |
2491 | // stop all watchers after blocking |
1531 | static void |
2492 | static void |
1532 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2493 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
1533 | { |
2494 | { |
1534 | ev_timer_stop (loop, &tw); |
2495 | ev_timer_stop (loop, &tw); |
1535 | |
2496 | |
1536 | for (int i = 0; i < nfd; ++i) |
2497 | for (int i = 0; i < nfd; ++i) |
|
|
2498 | { |
|
|
2499 | // set the relevant poll flags |
|
|
2500 | // could also call adns_processreadable etc. here |
|
|
2501 | struct pollfd *fd = fds + i; |
|
|
2502 | int revents = ev_clear_pending (iow + i); |
|
|
2503 | if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
|
|
2504 | if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
|
|
2505 | |
|
|
2506 | // now stop the watcher |
1537 | ev_io_stop (loop, iow + i); |
2507 | ev_io_stop (loop, iow + i); |
|
|
2508 | } |
1538 | |
2509 | |
1539 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
2510 | adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1540 | } |
2511 | } |
|
|
2512 | |
|
|
2513 | Method 2: This would be just like method 1, but you run C<adns_afterpoll> |
|
|
2514 | in the prepare watcher and would dispose of the check watcher. |
|
|
2515 | |
|
|
2516 | Method 3: If the module to be embedded supports explicit event |
|
|
2517 | notification (libadns does), you can also make use of the actual watcher |
|
|
2518 | callbacks, and only destroy/create the watchers in the prepare watcher. |
|
|
2519 | |
|
|
2520 | static void |
|
|
2521 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
2522 | { |
|
|
2523 | adns_state ads = (adns_state)w->data; |
|
|
2524 | update_now (EV_A); |
|
|
2525 | |
|
|
2526 | adns_processtimeouts (ads, &tv_now); |
|
|
2527 | } |
|
|
2528 | |
|
|
2529 | static void |
|
|
2530 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
2531 | { |
|
|
2532 | adns_state ads = (adns_state)w->data; |
|
|
2533 | update_now (EV_A); |
|
|
2534 | |
|
|
2535 | if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now); |
|
|
2536 | if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now); |
|
|
2537 | } |
|
|
2538 | |
|
|
2539 | // do not ever call adns_afterpoll |
|
|
2540 | |
|
|
2541 | Method 4: Do not use a prepare or check watcher because the module you |
|
|
2542 | want to embed is not flexible enough to support it. Instead, you can |
|
|
2543 | override their poll function. The drawback with this solution is that the |
|
|
2544 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
|
|
2545 | this approach, effectively embedding EV as a client into the horrible |
|
|
2546 | libglib event loop. |
|
|
2547 | |
|
|
2548 | static gint |
|
|
2549 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
|
|
2550 | { |
|
|
2551 | int got_events = 0; |
|
|
2552 | |
|
|
2553 | for (n = 0; n < nfds; ++n) |
|
|
2554 | // create/start io watcher that sets the relevant bits in fds[n] and increment got_events |
|
|
2555 | |
|
|
2556 | if (timeout >= 0) |
|
|
2557 | // create/start timer |
|
|
2558 | |
|
|
2559 | // poll |
|
|
2560 | ev_loop (EV_A_ 0); |
|
|
2561 | |
|
|
2562 | // stop timer again |
|
|
2563 | if (timeout >= 0) |
|
|
2564 | ev_timer_stop (EV_A_ &to); |
|
|
2565 | |
|
|
2566 | // stop io watchers again - their callbacks should have set |
|
|
2567 | for (n = 0; n < nfds; ++n) |
|
|
2568 | ev_io_stop (EV_A_ iow [n]); |
|
|
2569 | |
|
|
2570 | return got_events; |
|
|
2571 | } |
1541 | |
2572 | |
1542 | |
2573 | |
1543 | =head2 C<ev_embed> - when one backend isn't enough... |
2574 | =head2 C<ev_embed> - when one backend isn't enough... |
1544 | |
2575 | |
1545 | This is a rather advanced watcher type that lets you embed one event loop |
2576 | This is a rather advanced watcher type that lets you embed one event loop |
… | |
… | |
1551 | prioritise I/O. |
2582 | prioritise I/O. |
1552 | |
2583 | |
1553 | As an example for a bug workaround, the kqueue backend might only support |
2584 | As an example for a bug workaround, the kqueue backend might only support |
1554 | sockets on some platform, so it is unusable as generic backend, but you |
2585 | sockets on some platform, so it is unusable as generic backend, but you |
1555 | still want to make use of it because you have many sockets and it scales |
2586 | still want to make use of it because you have many sockets and it scales |
1556 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2587 | so nicely. In this case, you would create a kqueue-based loop and embed |
1557 | into your default loop (which might use e.g. poll). Overall operation will |
2588 | it into your default loop (which might use e.g. poll). Overall operation |
1558 | be a bit slower because first libev has to poll and then call kevent, but |
2589 | will be a bit slower because first libev has to call C<poll> and then |
1559 | at least you can use both at what they are best. |
2590 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2591 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
1560 | |
2592 | |
1561 | As for prioritising I/O: rarely you have the case where some fds have |
2593 | As for prioritising I/O: under rare circumstances you have the case where |
1562 | to be watched and handled very quickly (with low latency), and even |
2594 | some fds have to be watched and handled very quickly (with low latency), |
1563 | priorities and idle watchers might have too much overhead. In this case |
2595 | and even priorities and idle watchers might have too much overhead. In |
1564 | you would put all the high priority stuff in one loop and all the rest in |
2596 | this case you would put all the high priority stuff in one loop and all |
1565 | a second one, and embed the second one in the first. |
2597 | the rest in a second one, and embed the second one in the first. |
1566 | |
2598 | |
1567 | As long as the watcher is active, the callback will be invoked every time |
2599 | As long as the watcher is active, the callback will be invoked every |
1568 | there might be events pending in the embedded loop. The callback must then |
2600 | time there might be events pending in the embedded loop. The callback |
1569 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2601 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
1570 | their callbacks (you could also start an idle watcher to give the embedded |
2602 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
1571 | loop strictly lower priority for example). You can also set the callback |
2603 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
1572 | to C<0>, in which case the embed watcher will automatically execute the |
2604 | to give the embedded loop strictly lower priority for example). |
1573 | embedded loop sweep. |
|
|
1574 | |
2605 | |
1575 | As long as the watcher is started it will automatically handle events. The |
2606 | You can also set the callback to C<0>, in which case the embed watcher |
1576 | callback will be invoked whenever some events have been handled. You can |
2607 | will automatically execute the embedded loop sweep whenever necessary. |
1577 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
1578 | interested in that. |
|
|
1579 | |
2608 | |
1580 | Also, there have not currently been made special provisions for forking: |
2609 | Fork detection will be handled transparently while the C<ev_embed> watcher |
1581 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2610 | is active, i.e., the embedded loop will automatically be forked when the |
1582 | but you will also have to stop and restart any C<ev_embed> watchers |
2611 | embedding loop forks. In other cases, the user is responsible for calling |
1583 | yourself. |
2612 | C<ev_loop_fork> on the embedded loop. |
1584 | |
2613 | |
1585 | Unfortunately, not all backends are embeddable, only the ones returned by |
2614 | Unfortunately, not all backends are embeddable: only the ones returned by |
1586 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2615 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
1587 | portable one. |
2616 | portable one. |
1588 | |
2617 | |
1589 | So when you want to use this feature you will always have to be prepared |
2618 | So when you want to use this feature you will always have to be prepared |
1590 | that you cannot get an embeddable loop. The recommended way to get around |
2619 | that you cannot get an embeddable loop. The recommended way to get around |
1591 | this is to have a separate variables for your embeddable loop, try to |
2620 | this is to have a separate variables for your embeddable loop, try to |
1592 | create it, and if that fails, use the normal loop for everything: |
2621 | create it, and if that fails, use the normal loop for everything. |
1593 | |
2622 | |
1594 | struct ev_loop *loop_hi = ev_default_init (0); |
2623 | =head3 C<ev_embed> and fork |
1595 | struct ev_loop *loop_lo = 0; |
|
|
1596 | struct ev_embed embed; |
|
|
1597 | |
|
|
1598 | // see if there is a chance of getting one that works |
|
|
1599 | // (remember that a flags value of 0 means autodetection) |
|
|
1600 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
1601 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
1602 | : 0; |
|
|
1603 | |
2624 | |
1604 | // if we got one, then embed it, otherwise default to loop_hi |
2625 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
1605 | if (loop_lo) |
2626 | automatically be applied to the embedded loop as well, so no special |
1606 | { |
2627 | fork handling is required in that case. When the watcher is not running, |
1607 | ev_embed_init (&embed, 0, loop_lo); |
2628 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
1608 | ev_embed_start (loop_hi, &embed); |
2629 | as applicable. |
1609 | } |
2630 | |
1610 | else |
2631 | =head3 Watcher-Specific Functions and Data Members |
1611 | loop_lo = loop_hi; |
|
|
1612 | |
2632 | |
1613 | =over 4 |
2633 | =over 4 |
1614 | |
2634 | |
1615 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2635 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
1616 | |
2636 | |
… | |
… | |
1618 | |
2638 | |
1619 | Configures the watcher to embed the given loop, which must be |
2639 | Configures the watcher to embed the given loop, which must be |
1620 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2640 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
1621 | invoked automatically, otherwise it is the responsibility of the callback |
2641 | invoked automatically, otherwise it is the responsibility of the callback |
1622 | to invoke it (it will continue to be called until the sweep has been done, |
2642 | to invoke it (it will continue to be called until the sweep has been done, |
1623 | if you do not want thta, you need to temporarily stop the embed watcher). |
2643 | if you do not want that, you need to temporarily stop the embed watcher). |
1624 | |
2644 | |
1625 | =item ev_embed_sweep (loop, ev_embed *) |
2645 | =item ev_embed_sweep (loop, ev_embed *) |
1626 | |
2646 | |
1627 | Make a single, non-blocking sweep over the embedded loop. This works |
2647 | Make a single, non-blocking sweep over the embedded loop. This works |
1628 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
2648 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
1629 | apropriate way for embedded loops. |
2649 | appropriate way for embedded loops. |
1630 | |
2650 | |
1631 | =item struct ev_loop *loop [read-only] |
2651 | =item struct ev_loop *other [read-only] |
1632 | |
2652 | |
1633 | The embedded event loop. |
2653 | The embedded event loop. |
1634 | |
2654 | |
1635 | =back |
2655 | =back |
|
|
2656 | |
|
|
2657 | =head3 Examples |
|
|
2658 | |
|
|
2659 | Example: Try to get an embeddable event loop and embed it into the default |
|
|
2660 | event loop. If that is not possible, use the default loop. The default |
|
|
2661 | loop is stored in C<loop_hi>, while the embeddable loop is stored in |
|
|
2662 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
|
|
2663 | used). |
|
|
2664 | |
|
|
2665 | struct ev_loop *loop_hi = ev_default_init (0); |
|
|
2666 | struct ev_loop *loop_lo = 0; |
|
|
2667 | ev_embed embed; |
|
|
2668 | |
|
|
2669 | // see if there is a chance of getting one that works |
|
|
2670 | // (remember that a flags value of 0 means autodetection) |
|
|
2671 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
|
|
2672 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
|
|
2673 | : 0; |
|
|
2674 | |
|
|
2675 | // if we got one, then embed it, otherwise default to loop_hi |
|
|
2676 | if (loop_lo) |
|
|
2677 | { |
|
|
2678 | ev_embed_init (&embed, 0, loop_lo); |
|
|
2679 | ev_embed_start (loop_hi, &embed); |
|
|
2680 | } |
|
|
2681 | else |
|
|
2682 | loop_lo = loop_hi; |
|
|
2683 | |
|
|
2684 | Example: Check if kqueue is available but not recommended and create |
|
|
2685 | a kqueue backend for use with sockets (which usually work with any |
|
|
2686 | kqueue implementation). Store the kqueue/socket-only event loop in |
|
|
2687 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
|
|
2688 | |
|
|
2689 | struct ev_loop *loop = ev_default_init (0); |
|
|
2690 | struct ev_loop *loop_socket = 0; |
|
|
2691 | ev_embed embed; |
|
|
2692 | |
|
|
2693 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
|
|
2694 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
|
|
2695 | { |
|
|
2696 | ev_embed_init (&embed, 0, loop_socket); |
|
|
2697 | ev_embed_start (loop, &embed); |
|
|
2698 | } |
|
|
2699 | |
|
|
2700 | if (!loop_socket) |
|
|
2701 | loop_socket = loop; |
|
|
2702 | |
|
|
2703 | // now use loop_socket for all sockets, and loop for everything else |
1636 | |
2704 | |
1637 | |
2705 | |
1638 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
2706 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
1639 | |
2707 | |
1640 | Fork watchers are called when a C<fork ()> was detected (usually because |
2708 | Fork watchers are called when a C<fork ()> was detected (usually because |
… | |
… | |
1643 | event loop blocks next and before C<ev_check> watchers are being called, |
2711 | event loop blocks next and before C<ev_check> watchers are being called, |
1644 | and only in the child after the fork. If whoever good citizen calling |
2712 | and only in the child after the fork. If whoever good citizen calling |
1645 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2713 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
1646 | handlers will be invoked, too, of course. |
2714 | handlers will be invoked, too, of course. |
1647 | |
2715 | |
|
|
2716 | =head3 The special problem of life after fork - how is it possible? |
|
|
2717 | |
|
|
2718 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2719 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2720 | sequence should be handled by libev without any problems. |
|
|
2721 | |
|
|
2722 | This changes when the application actually wants to do event handling |
|
|
2723 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2724 | fork. |
|
|
2725 | |
|
|
2726 | The default mode of operation (for libev, with application help to detect |
|
|
2727 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2728 | when I<either> the parent I<or> the child process continues. |
|
|
2729 | |
|
|
2730 | When both processes want to continue using libev, then this is usually the |
|
|
2731 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2732 | supposed to continue with all watchers in place as before, while the other |
|
|
2733 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2734 | |
|
|
2735 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2736 | simply create a new event loop, which of course will be "empty", and |
|
|
2737 | use that for new watchers. This has the advantage of not touching more |
|
|
2738 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2739 | disadvantage of having to use multiple event loops (which do not support |
|
|
2740 | signal watchers). |
|
|
2741 | |
|
|
2742 | When this is not possible, or you want to use the default loop for |
|
|
2743 | other reasons, then in the process that wants to start "fresh", call |
|
|
2744 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2745 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2746 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2747 | also that in that case, you have to re-register any signal watchers. |
|
|
2748 | |
|
|
2749 | =head3 Watcher-Specific Functions and Data Members |
|
|
2750 | |
1648 | =over 4 |
2751 | =over 4 |
1649 | |
2752 | |
1650 | =item ev_fork_init (ev_signal *, callback) |
2753 | =item ev_fork_init (ev_signal *, callback) |
1651 | |
2754 | |
1652 | Initialises and configures the fork watcher - it has no parameters of any |
2755 | Initialises and configures the fork watcher - it has no parameters of any |
… | |
… | |
1654 | believe me. |
2757 | believe me. |
1655 | |
2758 | |
1656 | =back |
2759 | =back |
1657 | |
2760 | |
1658 | |
2761 | |
|
|
2762 | =head2 C<ev_async> - how to wake up another event loop |
|
|
2763 | |
|
|
2764 | In general, you cannot use an C<ev_loop> from multiple threads or other |
|
|
2765 | asynchronous sources such as signal handlers (as opposed to multiple event |
|
|
2766 | loops - those are of course safe to use in different threads). |
|
|
2767 | |
|
|
2768 | Sometimes, however, you need to wake up another event loop you do not |
|
|
2769 | control, for example because it belongs to another thread. This is what |
|
|
2770 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
|
|
2771 | can signal it by calling C<ev_async_send>, which is thread- and signal |
|
|
2772 | safe. |
|
|
2773 | |
|
|
2774 | This functionality is very similar to C<ev_signal> watchers, as signals, |
|
|
2775 | too, are asynchronous in nature, and signals, too, will be compressed |
|
|
2776 | (i.e. the number of callback invocations may be less than the number of |
|
|
2777 | C<ev_async_sent> calls). |
|
|
2778 | |
|
|
2779 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
2780 | just the default loop. |
|
|
2781 | |
|
|
2782 | =head3 Queueing |
|
|
2783 | |
|
|
2784 | C<ev_async> does not support queueing of data in any way. The reason |
|
|
2785 | is that the author does not know of a simple (or any) algorithm for a |
|
|
2786 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
2787 | need elaborate support such as pthreads. |
|
|
2788 | |
|
|
2789 | That means that if you want to queue data, you have to provide your own |
|
|
2790 | queue. But at least I can tell you how to implement locking around your |
|
|
2791 | queue: |
|
|
2792 | |
|
|
2793 | =over 4 |
|
|
2794 | |
|
|
2795 | =item queueing from a signal handler context |
|
|
2796 | |
|
|
2797 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
2798 | handler but you block the signal handler in the watcher callback. Here is |
|
|
2799 | an example that does that for some fictitious SIGUSR1 handler: |
|
|
2800 | |
|
|
2801 | static ev_async mysig; |
|
|
2802 | |
|
|
2803 | static void |
|
|
2804 | sigusr1_handler (void) |
|
|
2805 | { |
|
|
2806 | sometype data; |
|
|
2807 | |
|
|
2808 | // no locking etc. |
|
|
2809 | queue_put (data); |
|
|
2810 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2811 | } |
|
|
2812 | |
|
|
2813 | static void |
|
|
2814 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2815 | { |
|
|
2816 | sometype data; |
|
|
2817 | sigset_t block, prev; |
|
|
2818 | |
|
|
2819 | sigemptyset (&block); |
|
|
2820 | sigaddset (&block, SIGUSR1); |
|
|
2821 | sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
2822 | |
|
|
2823 | while (queue_get (&data)) |
|
|
2824 | process (data); |
|
|
2825 | |
|
|
2826 | if (sigismember (&prev, SIGUSR1) |
|
|
2827 | sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
2828 | } |
|
|
2829 | |
|
|
2830 | (Note: pthreads in theory requires you to use C<pthread_setmask> |
|
|
2831 | instead of C<sigprocmask> when you use threads, but libev doesn't do it |
|
|
2832 | either...). |
|
|
2833 | |
|
|
2834 | =item queueing from a thread context |
|
|
2835 | |
|
|
2836 | The strategy for threads is different, as you cannot (easily) block |
|
|
2837 | threads but you can easily preempt them, so to queue safely you need to |
|
|
2838 | employ a traditional mutex lock, such as in this pthread example: |
|
|
2839 | |
|
|
2840 | static ev_async mysig; |
|
|
2841 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
2842 | |
|
|
2843 | static void |
|
|
2844 | otherthread (void) |
|
|
2845 | { |
|
|
2846 | // only need to lock the actual queueing operation |
|
|
2847 | pthread_mutex_lock (&mymutex); |
|
|
2848 | queue_put (data); |
|
|
2849 | pthread_mutex_unlock (&mymutex); |
|
|
2850 | |
|
|
2851 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2852 | } |
|
|
2853 | |
|
|
2854 | static void |
|
|
2855 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2856 | { |
|
|
2857 | pthread_mutex_lock (&mymutex); |
|
|
2858 | |
|
|
2859 | while (queue_get (&data)) |
|
|
2860 | process (data); |
|
|
2861 | |
|
|
2862 | pthread_mutex_unlock (&mymutex); |
|
|
2863 | } |
|
|
2864 | |
|
|
2865 | =back |
|
|
2866 | |
|
|
2867 | |
|
|
2868 | =head3 Watcher-Specific Functions and Data Members |
|
|
2869 | |
|
|
2870 | =over 4 |
|
|
2871 | |
|
|
2872 | =item ev_async_init (ev_async *, callback) |
|
|
2873 | |
|
|
2874 | Initialises and configures the async watcher - it has no parameters of any |
|
|
2875 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
|
|
2876 | trust me. |
|
|
2877 | |
|
|
2878 | =item ev_async_send (loop, ev_async *) |
|
|
2879 | |
|
|
2880 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
|
|
2881 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
|
|
2882 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
|
|
2883 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
|
|
2884 | section below on what exactly this means). |
|
|
2885 | |
|
|
2886 | Note that, as with other watchers in libev, multiple events might get |
|
|
2887 | compressed into a single callback invocation (another way to look at this |
|
|
2888 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2889 | reset when the event loop detects that). |
|
|
2890 | |
|
|
2891 | This call incurs the overhead of a system call only once per event loop |
|
|
2892 | iteration, so while the overhead might be noticeable, it doesn't apply to |
|
|
2893 | repeated calls to C<ev_async_send> for the same event loop. |
|
|
2894 | |
|
|
2895 | =item bool = ev_async_pending (ev_async *) |
|
|
2896 | |
|
|
2897 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
2898 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2899 | event loop. |
|
|
2900 | |
|
|
2901 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
2902 | the loop iterates next and checks for the watcher to have become active, |
|
|
2903 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
2904 | quickly check whether invoking the loop might be a good idea. |
|
|
2905 | |
|
|
2906 | Not that this does I<not> check whether the watcher itself is pending, |
|
|
2907 | only whether it has been requested to make this watcher pending: there |
|
|
2908 | is a time window between the event loop checking and resetting the async |
|
|
2909 | notification, and the callback being invoked. |
|
|
2910 | |
|
|
2911 | =back |
|
|
2912 | |
|
|
2913 | |
1659 | =head1 OTHER FUNCTIONS |
2914 | =head1 OTHER FUNCTIONS |
1660 | |
2915 | |
1661 | There are some other functions of possible interest. Described. Here. Now. |
2916 | There are some other functions of possible interest. Described. Here. Now. |
1662 | |
2917 | |
1663 | =over 4 |
2918 | =over 4 |
1664 | |
2919 | |
1665 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2920 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
1666 | |
2921 | |
1667 | This function combines a simple timer and an I/O watcher, calls your |
2922 | This function combines a simple timer and an I/O watcher, calls your |
1668 | callback on whichever event happens first and automatically stop both |
2923 | callback on whichever event happens first and automatically stops both |
1669 | watchers. This is useful if you want to wait for a single event on an fd |
2924 | watchers. This is useful if you want to wait for a single event on an fd |
1670 | or timeout without having to allocate/configure/start/stop/free one or |
2925 | or timeout without having to allocate/configure/start/stop/free one or |
1671 | more watchers yourself. |
2926 | more watchers yourself. |
1672 | |
2927 | |
1673 | If C<fd> is less than 0, then no I/O watcher will be started and events |
2928 | If C<fd> is less than 0, then no I/O watcher will be started and the |
1674 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
2929 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
1675 | C<events> set will be craeted and started. |
2930 | the given C<fd> and C<events> set will be created and started. |
1676 | |
2931 | |
1677 | If C<timeout> is less than 0, then no timeout watcher will be |
2932 | If C<timeout> is less than 0, then no timeout watcher will be |
1678 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2933 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
1679 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
2934 | repeat = 0) will be started. C<0> is a valid timeout. |
1680 | dubious value. |
|
|
1681 | |
2935 | |
1682 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2936 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
1683 | passed an C<revents> set like normal event callbacks (a combination of |
2937 | passed an C<revents> set like normal event callbacks (a combination of |
1684 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2938 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
1685 | value passed to C<ev_once>: |
2939 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
2940 | a timeout and an io event at the same time - you probably should give io |
|
|
2941 | events precedence. |
1686 | |
2942 | |
|
|
2943 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
|
|
2944 | |
1687 | static void stdin_ready (int revents, void *arg) |
2945 | static void stdin_ready (int revents, void *arg) |
1688 | { |
2946 | { |
1689 | if (revents & EV_TIMEOUT) |
|
|
1690 | /* doh, nothing entered */; |
|
|
1691 | else if (revents & EV_READ) |
2947 | if (revents & EV_READ) |
1692 | /* stdin might have data for us, joy! */; |
2948 | /* stdin might have data for us, joy! */; |
|
|
2949 | else if (revents & EV_TIMEOUT) |
|
|
2950 | /* doh, nothing entered */; |
1693 | } |
2951 | } |
1694 | |
2952 | |
1695 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2953 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
1696 | |
2954 | |
1697 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
2955 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
1698 | |
2956 | |
1699 | Feeds the given event set into the event loop, as if the specified event |
2957 | Feeds the given event set into the event loop, as if the specified event |
1700 | had happened for the specified watcher (which must be a pointer to an |
2958 | had happened for the specified watcher (which must be a pointer to an |
1701 | initialised but not necessarily started event watcher). |
2959 | initialised but not necessarily started event watcher). |
1702 | |
2960 | |
1703 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
2961 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
1704 | |
2962 | |
1705 | Feed an event on the given fd, as if a file descriptor backend detected |
2963 | Feed an event on the given fd, as if a file descriptor backend detected |
1706 | the given events it. |
2964 | the given events it. |
1707 | |
2965 | |
1708 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
2966 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
1709 | |
2967 | |
1710 | Feed an event as if the given signal occured (C<loop> must be the default |
2968 | Feed an event as if the given signal occurred (C<loop> must be the default |
1711 | loop!). |
2969 | loop!). |
1712 | |
2970 | |
1713 | =back |
2971 | =back |
1714 | |
2972 | |
1715 | |
2973 | |
… | |
… | |
1731 | |
2989 | |
1732 | =item * Priorities are not currently supported. Initialising priorities |
2990 | =item * Priorities are not currently supported. Initialising priorities |
1733 | will fail and all watchers will have the same priority, even though there |
2991 | will fail and all watchers will have the same priority, even though there |
1734 | is an ev_pri field. |
2992 | is an ev_pri field. |
1735 | |
2993 | |
|
|
2994 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
2995 | first base created (== the default loop) gets the signals. |
|
|
2996 | |
1736 | =item * Other members are not supported. |
2997 | =item * Other members are not supported. |
1737 | |
2998 | |
1738 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2999 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
1739 | to use the libev header file and library. |
3000 | to use the libev header file and library. |
1740 | |
3001 | |
1741 | =back |
3002 | =back |
1742 | |
3003 | |
1743 | =head1 C++ SUPPORT |
3004 | =head1 C++ SUPPORT |
1744 | |
3005 | |
1745 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3006 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
1746 | you to use some convinience methods to start/stop watchers and also change |
3007 | you to use some convenience methods to start/stop watchers and also change |
1747 | the callback model to a model using method callbacks on objects. |
3008 | the callback model to a model using method callbacks on objects. |
1748 | |
3009 | |
1749 | To use it, |
3010 | To use it, |
1750 | |
3011 | |
1751 | #include <ev++.h> |
3012 | #include <ev++.h> |
1752 | |
3013 | |
1753 | This automatically includes F<ev.h> and puts all of its definitions (many |
3014 | This automatically includes F<ev.h> and puts all of its definitions (many |
1754 | of them macros) into the global namespace. All C++ specific things are |
3015 | of them macros) into the global namespace. All C++ specific things are |
1755 | put into the C<ev> namespace. It should support all the same embedding |
3016 | put into the C<ev> namespace. It should support all the same embedding |
1756 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
3017 | options as F<ev.h>, most notably C<EV_MULTIPLICITY>. |
… | |
… | |
1823 | your compiler is good :), then the method will be fully inlined into the |
3084 | your compiler is good :), then the method will be fully inlined into the |
1824 | thunking function, making it as fast as a direct C callback. |
3085 | thunking function, making it as fast as a direct C callback. |
1825 | |
3086 | |
1826 | Example: simple class declaration and watcher initialisation |
3087 | Example: simple class declaration and watcher initialisation |
1827 | |
3088 | |
1828 | struct myclass |
3089 | struct myclass |
1829 | { |
3090 | { |
1830 | void io_cb (ev::io &w, int revents) { } |
3091 | void io_cb (ev::io &w, int revents) { } |
1831 | } |
3092 | } |
1832 | |
3093 | |
1833 | myclass obj; |
3094 | myclass obj; |
1834 | ev::io iow; |
3095 | ev::io iow; |
1835 | iow.set <myclass, &myclass::io_cb> (&obj); |
3096 | iow.set <myclass, &myclass::io_cb> (&obj); |
1836 | |
3097 | |
1837 | =item w->set (void (*function)(watcher &w, int), void *data = 0) |
3098 | =item w->set (object *) |
|
|
3099 | |
|
|
3100 | This is an B<experimental> feature that might go away in a future version. |
|
|
3101 | |
|
|
3102 | This is a variation of a method callback - leaving out the method to call |
|
|
3103 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3104 | functor objects without having to manually specify the C<operator ()> all |
|
|
3105 | the time. Incidentally, you can then also leave out the template argument |
|
|
3106 | list. |
|
|
3107 | |
|
|
3108 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3109 | int revents)>. |
|
|
3110 | |
|
|
3111 | See the method-C<set> above for more details. |
|
|
3112 | |
|
|
3113 | Example: use a functor object as callback. |
|
|
3114 | |
|
|
3115 | struct myfunctor |
|
|
3116 | { |
|
|
3117 | void operator() (ev::io &w, int revents) |
|
|
3118 | { |
|
|
3119 | ... |
|
|
3120 | } |
|
|
3121 | } |
|
|
3122 | |
|
|
3123 | myfunctor f; |
|
|
3124 | |
|
|
3125 | ev::io w; |
|
|
3126 | w.set (&f); |
|
|
3127 | |
|
|
3128 | =item w->set<function> (void *data = 0) |
1838 | |
3129 | |
1839 | Also sets a callback, but uses a static method or plain function as |
3130 | Also sets a callback, but uses a static method or plain function as |
1840 | callback. The optional C<data> argument will be stored in the watcher's |
3131 | callback. The optional C<data> argument will be stored in the watcher's |
1841 | C<data> member and is free for you to use. |
3132 | C<data> member and is free for you to use. |
1842 | |
3133 | |
|
|
3134 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
|
|
3135 | |
1843 | See the method-C<set> above for more details. |
3136 | See the method-C<set> above for more details. |
|
|
3137 | |
|
|
3138 | Example: Use a plain function as callback. |
|
|
3139 | |
|
|
3140 | static void io_cb (ev::io &w, int revents) { } |
|
|
3141 | iow.set <io_cb> (); |
1844 | |
3142 | |
1845 | =item w->set (struct ev_loop *) |
3143 | =item w->set (struct ev_loop *) |
1846 | |
3144 | |
1847 | Associates a different C<struct ev_loop> with this watcher. You can only |
3145 | Associates a different C<struct ev_loop> with this watcher. You can only |
1848 | do this when the watcher is inactive (and not pending either). |
3146 | do this when the watcher is inactive (and not pending either). |
1849 | |
3147 | |
1850 | =item w->set ([args]) |
3148 | =item w->set ([arguments]) |
1851 | |
3149 | |
1852 | Basically the same as C<ev_TYPE_set>, with the same args. Must be |
3150 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
1853 | called at least once. Unlike the C counterpart, an active watcher gets |
3151 | called at least once. Unlike the C counterpart, an active watcher gets |
1854 | automatically stopped and restarted when reconfiguring it with this |
3152 | automatically stopped and restarted when reconfiguring it with this |
1855 | method. |
3153 | method. |
1856 | |
3154 | |
1857 | =item w->start () |
3155 | =item w->start () |
… | |
… | |
1861 | |
3159 | |
1862 | =item w->stop () |
3160 | =item w->stop () |
1863 | |
3161 | |
1864 | Stops the watcher if it is active. Again, no C<loop> argument. |
3162 | Stops the watcher if it is active. Again, no C<loop> argument. |
1865 | |
3163 | |
1866 | =item w->again () C<ev::timer>, C<ev::periodic> only |
3164 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
1867 | |
3165 | |
1868 | For C<ev::timer> and C<ev::periodic>, this invokes the corresponding |
3166 | For C<ev::timer> and C<ev::periodic>, this invokes the corresponding |
1869 | C<ev_TYPE_again> function. |
3167 | C<ev_TYPE_again> function. |
1870 | |
3168 | |
1871 | =item w->sweep () C<ev::embed> only |
3169 | =item w->sweep () (C<ev::embed> only) |
1872 | |
3170 | |
1873 | Invokes C<ev_embed_sweep>. |
3171 | Invokes C<ev_embed_sweep>. |
1874 | |
3172 | |
1875 | =item w->update () C<ev::stat> only |
3173 | =item w->update () (C<ev::stat> only) |
1876 | |
3174 | |
1877 | Invokes C<ev_stat_stat>. |
3175 | Invokes C<ev_stat_stat>. |
1878 | |
3176 | |
1879 | =back |
3177 | =back |
1880 | |
3178 | |
1881 | =back |
3179 | =back |
1882 | |
3180 | |
1883 | Example: Define a class with an IO and idle watcher, start one of them in |
3181 | Example: Define a class with an IO and idle watcher, start one of them in |
1884 | the constructor. |
3182 | the constructor. |
1885 | |
3183 | |
1886 | class myclass |
3184 | class myclass |
1887 | { |
3185 | { |
1888 | ev_io io; void io_cb (ev::io &w, int revents); |
3186 | ev::io io ; void io_cb (ev::io &w, int revents); |
1889 | ev_idle idle void idle_cb (ev::idle &w, int revents); |
3187 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
1890 | |
3188 | |
1891 | myclass (); |
3189 | myclass (int fd) |
1892 | } |
3190 | { |
1893 | |
|
|
1894 | myclass::myclass (int fd) |
|
|
1895 | { |
|
|
1896 | io .set <myclass, &myclass::io_cb > (this); |
3191 | io .set <myclass, &myclass::io_cb > (this); |
1897 | idle.set <myclass, &myclass::idle_cb> (this); |
3192 | idle.set <myclass, &myclass::idle_cb> (this); |
1898 | |
3193 | |
1899 | io.start (fd, ev::READ); |
3194 | io.start (fd, ev::READ); |
|
|
3195 | } |
1900 | } |
3196 | }; |
|
|
3197 | |
|
|
3198 | |
|
|
3199 | =head1 OTHER LANGUAGE BINDINGS |
|
|
3200 | |
|
|
3201 | Libev does not offer other language bindings itself, but bindings for a |
|
|
3202 | number of languages exist in the form of third-party packages. If you know |
|
|
3203 | any interesting language binding in addition to the ones listed here, drop |
|
|
3204 | me a note. |
|
|
3205 | |
|
|
3206 | =over 4 |
|
|
3207 | |
|
|
3208 | =item Perl |
|
|
3209 | |
|
|
3210 | The EV module implements the full libev API and is actually used to test |
|
|
3211 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
3212 | there are additional modules that implement libev-compatible interfaces |
|
|
3213 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
|
|
3214 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
3215 | and C<EV::Glib>). |
|
|
3216 | |
|
|
3217 | It can be found and installed via CPAN, its homepage is at |
|
|
3218 | L<http://software.schmorp.de/pkg/EV>. |
|
|
3219 | |
|
|
3220 | =item Python |
|
|
3221 | |
|
|
3222 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
|
|
3223 | seems to be quite complete and well-documented. |
|
|
3224 | |
|
|
3225 | =item Ruby |
|
|
3226 | |
|
|
3227 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
3228 | of the libev API and adds file handle abstractions, asynchronous DNS and |
|
|
3229 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
3230 | L<http://rev.rubyforge.org/>. |
|
|
3231 | |
|
|
3232 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3233 | makes rev work even on mingw. |
|
|
3234 | |
|
|
3235 | =item Haskell |
|
|
3236 | |
|
|
3237 | A haskell binding to libev is available at |
|
|
3238 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3239 | |
|
|
3240 | =item D |
|
|
3241 | |
|
|
3242 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
3243 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3244 | |
|
|
3245 | =item Ocaml |
|
|
3246 | |
|
|
3247 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3248 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3249 | |
|
|
3250 | =back |
1901 | |
3251 | |
1902 | |
3252 | |
1903 | =head1 MACRO MAGIC |
3253 | =head1 MACRO MAGIC |
1904 | |
3254 | |
1905 | Libev can be compiled with a variety of options, the most fundemantal is |
3255 | Libev can be compiled with a variety of options, the most fundamental |
1906 | C<EV_MULTIPLICITY>. This option determines whether (most) functions and |
3256 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
1907 | callbacks have an initial C<struct ev_loop *> argument. |
3257 | functions and callbacks have an initial C<struct ev_loop *> argument. |
1908 | |
3258 | |
1909 | To make it easier to write programs that cope with either variant, the |
3259 | To make it easier to write programs that cope with either variant, the |
1910 | following macros are defined: |
3260 | following macros are defined: |
1911 | |
3261 | |
1912 | =over 4 |
3262 | =over 4 |
… | |
… | |
1915 | |
3265 | |
1916 | This provides the loop I<argument> for functions, if one is required ("ev |
3266 | This provides the loop I<argument> for functions, if one is required ("ev |
1917 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3267 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
1918 | C<EV_A_> is used when other arguments are following. Example: |
3268 | C<EV_A_> is used when other arguments are following. Example: |
1919 | |
3269 | |
1920 | ev_unref (EV_A); |
3270 | ev_unref (EV_A); |
1921 | ev_timer_add (EV_A_ watcher); |
3271 | ev_timer_add (EV_A_ watcher); |
1922 | ev_loop (EV_A_ 0); |
3272 | ev_loop (EV_A_ 0); |
1923 | |
3273 | |
1924 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3274 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
1925 | which is often provided by the following macro. |
3275 | which is often provided by the following macro. |
1926 | |
3276 | |
1927 | =item C<EV_P>, C<EV_P_> |
3277 | =item C<EV_P>, C<EV_P_> |
1928 | |
3278 | |
1929 | This provides the loop I<parameter> for functions, if one is required ("ev |
3279 | This provides the loop I<parameter> for functions, if one is required ("ev |
1930 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
3280 | loop parameter"). The C<EV_P> form is used when this is the sole parameter, |
1931 | C<EV_P_> is used when other parameters are following. Example: |
3281 | C<EV_P_> is used when other parameters are following. Example: |
1932 | |
3282 | |
1933 | // this is how ev_unref is being declared |
3283 | // this is how ev_unref is being declared |
1934 | static void ev_unref (EV_P); |
3284 | static void ev_unref (EV_P); |
1935 | |
3285 | |
1936 | // this is how you can declare your typical callback |
3286 | // this is how you can declare your typical callback |
1937 | static void cb (EV_P_ ev_timer *w, int revents) |
3287 | static void cb (EV_P_ ev_timer *w, int revents) |
1938 | |
3288 | |
1939 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
3289 | It declares a parameter C<loop> of type C<struct ev_loop *>, quite |
1940 | suitable for use with C<EV_A>. |
3290 | suitable for use with C<EV_A>. |
1941 | |
3291 | |
1942 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3292 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
1943 | |
3293 | |
1944 | Similar to the other two macros, this gives you the value of the default |
3294 | Similar to the other two macros, this gives you the value of the default |
1945 | loop, if multiple loops are supported ("ev loop default"). |
3295 | loop, if multiple loops are supported ("ev loop default"). |
|
|
3296 | |
|
|
3297 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
3298 | |
|
|
3299 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
3300 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
3301 | is undefined when the default loop has not been initialised by a previous |
|
|
3302 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
3303 | |
|
|
3304 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
3305 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
1946 | |
3306 | |
1947 | =back |
3307 | =back |
1948 | |
3308 | |
1949 | Example: Declare and initialise a check watcher, utilising the above |
3309 | Example: Declare and initialise a check watcher, utilising the above |
1950 | macros so it will work regardless of whether multiple loops are supported |
3310 | macros so it will work regardless of whether multiple loops are supported |
1951 | or not. |
3311 | or not. |
1952 | |
3312 | |
1953 | static void |
3313 | static void |
1954 | check_cb (EV_P_ ev_timer *w, int revents) |
3314 | check_cb (EV_P_ ev_timer *w, int revents) |
1955 | { |
3315 | { |
1956 | ev_check_stop (EV_A_ w); |
3316 | ev_check_stop (EV_A_ w); |
1957 | } |
3317 | } |
1958 | |
3318 | |
1959 | ev_check check; |
3319 | ev_check check; |
1960 | ev_check_init (&check, check_cb); |
3320 | ev_check_init (&check, check_cb); |
1961 | ev_check_start (EV_DEFAULT_ &check); |
3321 | ev_check_start (EV_DEFAULT_ &check); |
1962 | ev_loop (EV_DEFAULT_ 0); |
3322 | ev_loop (EV_DEFAULT_ 0); |
1963 | |
3323 | |
1964 | =head1 EMBEDDING |
3324 | =head1 EMBEDDING |
1965 | |
3325 | |
1966 | Libev can (and often is) directly embedded into host |
3326 | Libev can (and often is) directly embedded into host |
1967 | applications. Examples of applications that embed it include the Deliantra |
3327 | applications. Examples of applications that embed it include the Deliantra |
1968 | Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
3328 | Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) |
1969 | and rxvt-unicode. |
3329 | and rxvt-unicode. |
1970 | |
3330 | |
1971 | The goal is to enable you to just copy the neecssary files into your |
3331 | The goal is to enable you to just copy the necessary files into your |
1972 | source directory without having to change even a single line in them, so |
3332 | source directory without having to change even a single line in them, so |
1973 | you can easily upgrade by simply copying (or having a checked-out copy of |
3333 | you can easily upgrade by simply copying (or having a checked-out copy of |
1974 | libev somewhere in your source tree). |
3334 | libev somewhere in your source tree). |
1975 | |
3335 | |
1976 | =head2 FILESETS |
3336 | =head2 FILESETS |
1977 | |
3337 | |
1978 | Depending on what features you need you need to include one or more sets of files |
3338 | Depending on what features you need you need to include one or more sets of files |
1979 | in your app. |
3339 | in your application. |
1980 | |
3340 | |
1981 | =head3 CORE EVENT LOOP |
3341 | =head3 CORE EVENT LOOP |
1982 | |
3342 | |
1983 | To include only the libev core (all the C<ev_*> functions), with manual |
3343 | To include only the libev core (all the C<ev_*> functions), with manual |
1984 | configuration (no autoconf): |
3344 | configuration (no autoconf): |
1985 | |
3345 | |
1986 | #define EV_STANDALONE 1 |
3346 | #define EV_STANDALONE 1 |
1987 | #include "ev.c" |
3347 | #include "ev.c" |
1988 | |
3348 | |
1989 | This will automatically include F<ev.h>, too, and should be done in a |
3349 | This will automatically include F<ev.h>, too, and should be done in a |
1990 | single C source file only to provide the function implementations. To use |
3350 | single C source file only to provide the function implementations. To use |
1991 | it, do the same for F<ev.h> in all files wishing to use this API (best |
3351 | it, do the same for F<ev.h> in all files wishing to use this API (best |
1992 | done by writing a wrapper around F<ev.h> that you can include instead and |
3352 | done by writing a wrapper around F<ev.h> that you can include instead and |
1993 | where you can put other configuration options): |
3353 | where you can put other configuration options): |
1994 | |
3354 | |
1995 | #define EV_STANDALONE 1 |
3355 | #define EV_STANDALONE 1 |
1996 | #include "ev.h" |
3356 | #include "ev.h" |
1997 | |
3357 | |
1998 | Both header files and implementation files can be compiled with a C++ |
3358 | Both header files and implementation files can be compiled with a C++ |
1999 | compiler (at least, thats a stated goal, and breakage will be treated |
3359 | compiler (at least, that's a stated goal, and breakage will be treated |
2000 | as a bug). |
3360 | as a bug). |
2001 | |
3361 | |
2002 | You need the following files in your source tree, or in a directory |
3362 | You need the following files in your source tree, or in a directory |
2003 | in your include path (e.g. in libev/ when using -Ilibev): |
3363 | in your include path (e.g. in libev/ when using -Ilibev): |
2004 | |
3364 | |
2005 | ev.h |
3365 | ev.h |
2006 | ev.c |
3366 | ev.c |
2007 | ev_vars.h |
3367 | ev_vars.h |
2008 | ev_wrap.h |
3368 | ev_wrap.h |
2009 | |
3369 | |
2010 | ev_win32.c required on win32 platforms only |
3370 | ev_win32.c required on win32 platforms only |
2011 | |
3371 | |
2012 | ev_select.c only when select backend is enabled (which is enabled by default) |
3372 | ev_select.c only when select backend is enabled (which is enabled by default) |
2013 | ev_poll.c only when poll backend is enabled (disabled by default) |
3373 | ev_poll.c only when poll backend is enabled (disabled by default) |
2014 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
3374 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
2015 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
3375 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
2016 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
3376 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
2017 | |
3377 | |
2018 | F<ev.c> includes the backend files directly when enabled, so you only need |
3378 | F<ev.c> includes the backend files directly when enabled, so you only need |
2019 | to compile this single file. |
3379 | to compile this single file. |
2020 | |
3380 | |
2021 | =head3 LIBEVENT COMPATIBILITY API |
3381 | =head3 LIBEVENT COMPATIBILITY API |
2022 | |
3382 | |
2023 | To include the libevent compatibility API, also include: |
3383 | To include the libevent compatibility API, also include: |
2024 | |
3384 | |
2025 | #include "event.c" |
3385 | #include "event.c" |
2026 | |
3386 | |
2027 | in the file including F<ev.c>, and: |
3387 | in the file including F<ev.c>, and: |
2028 | |
3388 | |
2029 | #include "event.h" |
3389 | #include "event.h" |
2030 | |
3390 | |
2031 | in the files that want to use the libevent API. This also includes F<ev.h>. |
3391 | in the files that want to use the libevent API. This also includes F<ev.h>. |
2032 | |
3392 | |
2033 | You need the following additional files for this: |
3393 | You need the following additional files for this: |
2034 | |
3394 | |
2035 | event.h |
3395 | event.h |
2036 | event.c |
3396 | event.c |
2037 | |
3397 | |
2038 | =head3 AUTOCONF SUPPORT |
3398 | =head3 AUTOCONF SUPPORT |
2039 | |
3399 | |
2040 | Instead of using C<EV_STANDALONE=1> and providing your config in |
3400 | Instead of using C<EV_STANDALONE=1> and providing your configuration in |
2041 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
3401 | whatever way you want, you can also C<m4_include([libev.m4])> in your |
2042 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
3402 | F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then |
2043 | include F<config.h> and configure itself accordingly. |
3403 | include F<config.h> and configure itself accordingly. |
2044 | |
3404 | |
2045 | For this of course you need the m4 file: |
3405 | For this of course you need the m4 file: |
2046 | |
3406 | |
2047 | libev.m4 |
3407 | libev.m4 |
2048 | |
3408 | |
2049 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3409 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2050 | |
3410 | |
2051 | Libev can be configured via a variety of preprocessor symbols you have to define |
3411 | Libev can be configured via a variety of preprocessor symbols you have to |
2052 | before including any of its files. The default is not to build for multiplicity |
3412 | define before including any of its files. The default in the absence of |
2053 | and only include the select backend. |
3413 | autoconf is documented for every option. |
2054 | |
3414 | |
2055 | =over 4 |
3415 | =over 4 |
2056 | |
3416 | |
2057 | =item EV_STANDALONE |
3417 | =item EV_STANDALONE |
2058 | |
3418 | |
… | |
… | |
2060 | keeps libev from including F<config.h>, and it also defines dummy |
3420 | keeps libev from including F<config.h>, and it also defines dummy |
2061 | implementations for some libevent functions (such as logging, which is not |
3421 | implementations for some libevent functions (such as logging, which is not |
2062 | supported). It will also not define any of the structs usually found in |
3422 | supported). It will also not define any of the structs usually found in |
2063 | F<event.h> that are not directly supported by the libev core alone. |
3423 | F<event.h> that are not directly supported by the libev core alone. |
2064 | |
3424 | |
|
|
3425 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3426 | configuration, but has to be more conservative. |
|
|
3427 | |
2065 | =item EV_USE_MONOTONIC |
3428 | =item EV_USE_MONOTONIC |
2066 | |
3429 | |
2067 | If defined to be C<1>, libev will try to detect the availability of the |
3430 | If defined to be C<1>, libev will try to detect the availability of the |
2068 | monotonic clock option at both compiletime and runtime. Otherwise no use |
3431 | monotonic clock option at both compile time and runtime. Otherwise no |
2069 | of the monotonic clock option will be attempted. If you enable this, you |
3432 | use of the monotonic clock option will be attempted. If you enable this, |
2070 | usually have to link against librt or something similar. Enabling it when |
3433 | you usually have to link against librt or something similar. Enabling it |
2071 | the functionality isn't available is safe, though, althoguh you have |
3434 | when the functionality isn't available is safe, though, although you have |
2072 | to make sure you link against any libraries where the C<clock_gettime> |
3435 | to make sure you link against any libraries where the C<clock_gettime> |
2073 | function is hiding in (often F<-lrt>). |
3436 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2074 | |
3437 | |
2075 | =item EV_USE_REALTIME |
3438 | =item EV_USE_REALTIME |
2076 | |
3439 | |
2077 | If defined to be C<1>, libev will try to detect the availability of the |
3440 | If defined to be C<1>, libev will try to detect the availability of the |
2078 | realtime clock option at compiletime (and assume its availability at |
3441 | real-time clock option at compile time (and assume its availability |
2079 | runtime if successful). Otherwise no use of the realtime clock option will |
3442 | at runtime if successful). Otherwise no use of the real-time clock |
2080 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3443 | option will be attempted. This effectively replaces C<gettimeofday> |
2081 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries |
3444 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2082 | in the description of C<EV_USE_MONOTONIC>, though. |
3445 | correctness. See the note about libraries in the description of |
|
|
3446 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3447 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3448 | |
|
|
3449 | =item EV_USE_CLOCK_SYSCALL |
|
|
3450 | |
|
|
3451 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3452 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3453 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3454 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3455 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3456 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3457 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3458 | higher, as it simplifies linking (no need for C<-lrt>). |
|
|
3459 | |
|
|
3460 | =item EV_USE_NANOSLEEP |
|
|
3461 | |
|
|
3462 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
|
|
3463 | and will use it for delays. Otherwise it will use C<select ()>. |
|
|
3464 | |
|
|
3465 | =item EV_USE_EVENTFD |
|
|
3466 | |
|
|
3467 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
3468 | available and will probe for kernel support at runtime. This will improve |
|
|
3469 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
3470 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
3471 | 2.7 or newer, otherwise disabled. |
2083 | |
3472 | |
2084 | =item EV_USE_SELECT |
3473 | =item EV_USE_SELECT |
2085 | |
3474 | |
2086 | If undefined or defined to be C<1>, libev will compile in support for the |
3475 | If undefined or defined to be C<1>, libev will compile in support for the |
2087 | C<select>(2) backend. No attempt at autodetection will be done: if no |
3476 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
2088 | other method takes over, select will be it. Otherwise the select backend |
3477 | other method takes over, select will be it. Otherwise the select backend |
2089 | will not be compiled in. |
3478 | will not be compiled in. |
2090 | |
3479 | |
2091 | =item EV_SELECT_USE_FD_SET |
3480 | =item EV_SELECT_USE_FD_SET |
2092 | |
3481 | |
2093 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3482 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2094 | structure. This is useful if libev doesn't compile due to a missing |
3483 | structure. This is useful if libev doesn't compile due to a missing |
2095 | C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on |
3484 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
2096 | exotic systems. This usually limits the range of file descriptors to some |
3485 | on exotic systems. This usually limits the range of file descriptors to |
2097 | low limit such as 1024 or might have other limitations (winsocket only |
3486 | some low limit such as 1024 or might have other limitations (winsocket |
2098 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3487 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
2099 | influence the size of the C<fd_set> used. |
3488 | configures the maximum size of the C<fd_set>. |
2100 | |
3489 | |
2101 | =item EV_SELECT_IS_WINSOCKET |
3490 | =item EV_SELECT_IS_WINSOCKET |
2102 | |
3491 | |
2103 | When defined to C<1>, the select backend will assume that |
3492 | When defined to C<1>, the select backend will assume that |
2104 | select/socket/connect etc. don't understand file descriptors but |
3493 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
2106 | be used is the winsock select). This means that it will call |
3495 | be used is the winsock select). This means that it will call |
2107 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3496 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
2108 | it is assumed that all these functions actually work on fds, even |
3497 | it is assumed that all these functions actually work on fds, even |
2109 | on win32. Should not be defined on non-win32 platforms. |
3498 | on win32. Should not be defined on non-win32 platforms. |
2110 | |
3499 | |
|
|
3500 | =item EV_FD_TO_WIN32_HANDLE |
|
|
3501 | |
|
|
3502 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
|
|
3503 | file descriptors to socket handles. When not defining this symbol (the |
|
|
3504 | default), then libev will call C<_get_osfhandle>, which is usually |
|
|
3505 | correct. In some cases, programs use their own file descriptor management, |
|
|
3506 | in which case they can provide this function to map fds to socket handles. |
|
|
3507 | |
2111 | =item EV_USE_POLL |
3508 | =item EV_USE_POLL |
2112 | |
3509 | |
2113 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3510 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
2114 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3511 | backend. Otherwise it will be enabled on non-win32 platforms. It |
2115 | takes precedence over select. |
3512 | takes precedence over select. |
2116 | |
3513 | |
2117 | =item EV_USE_EPOLL |
3514 | =item EV_USE_EPOLL |
2118 | |
3515 | |
2119 | If defined to be C<1>, libev will compile in support for the Linux |
3516 | If defined to be C<1>, libev will compile in support for the Linux |
2120 | C<epoll>(7) backend. Its availability will be detected at runtime, |
3517 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2121 | otherwise another method will be used as fallback. This is the |
3518 | otherwise another method will be used as fallback. This is the preferred |
2122 | preferred backend for GNU/Linux systems. |
3519 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
3520 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2123 | |
3521 | |
2124 | =item EV_USE_KQUEUE |
3522 | =item EV_USE_KQUEUE |
2125 | |
3523 | |
2126 | If defined to be C<1>, libev will compile in support for the BSD style |
3524 | If defined to be C<1>, libev will compile in support for the BSD style |
2127 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
3525 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
2140 | otherwise another method will be used as fallback. This is the preferred |
3538 | otherwise another method will be used as fallback. This is the preferred |
2141 | backend for Solaris 10 systems. |
3539 | backend for Solaris 10 systems. |
2142 | |
3540 | |
2143 | =item EV_USE_DEVPOLL |
3541 | =item EV_USE_DEVPOLL |
2144 | |
3542 | |
2145 | reserved for future expansion, works like the USE symbols above. |
3543 | Reserved for future expansion, works like the USE symbols above. |
2146 | |
3544 | |
2147 | =item EV_USE_INOTIFY |
3545 | =item EV_USE_INOTIFY |
2148 | |
3546 | |
2149 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3547 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2150 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3548 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2151 | be detected at runtime. |
3549 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
3550 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
3551 | |
|
|
3552 | =item EV_ATOMIC_T |
|
|
3553 | |
|
|
3554 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
|
|
3555 | access is atomic with respect to other threads or signal contexts. No such |
|
|
3556 | type is easily found in the C language, so you can provide your own type |
|
|
3557 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
3558 | as well as for signal and thread safety in C<ev_async> watchers. |
|
|
3559 | |
|
|
3560 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
|
|
3561 | (from F<signal.h>), which is usually good enough on most platforms. |
2152 | |
3562 | |
2153 | =item EV_H |
3563 | =item EV_H |
2154 | |
3564 | |
2155 | The name of the F<ev.h> header file used to include it. The default if |
3565 | The name of the F<ev.h> header file used to include it. The default if |
2156 | undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This |
3566 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2157 | can be used to virtually rename the F<ev.h> header file in case of conflicts. |
3567 | used to virtually rename the F<ev.h> header file in case of conflicts. |
2158 | |
3568 | |
2159 | =item EV_CONFIG_H |
3569 | =item EV_CONFIG_H |
2160 | |
3570 | |
2161 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3571 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
2162 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3572 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
2163 | C<EV_H>, above. |
3573 | C<EV_H>, above. |
2164 | |
3574 | |
2165 | =item EV_EVENT_H |
3575 | =item EV_EVENT_H |
2166 | |
3576 | |
2167 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3577 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
2168 | of how the F<event.h> header can be found. |
3578 | of how the F<event.h> header can be found, the default is C<"event.h">. |
2169 | |
3579 | |
2170 | =item EV_PROTOTYPES |
3580 | =item EV_PROTOTYPES |
2171 | |
3581 | |
2172 | If defined to be C<0>, then F<ev.h> will not define any function |
3582 | If defined to be C<0>, then F<ev.h> will not define any function |
2173 | prototypes, but still define all the structs and other symbols. This is |
3583 | prototypes, but still define all the structs and other symbols. This is |
… | |
… | |
2194 | When doing priority-based operations, libev usually has to linearly search |
3604 | When doing priority-based operations, libev usually has to linearly search |
2195 | all the priorities, so having many of them (hundreds) uses a lot of space |
3605 | all the priorities, so having many of them (hundreds) uses a lot of space |
2196 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3606 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
2197 | fine. |
3607 | fine. |
2198 | |
3608 | |
2199 | If your embedding app does not need any priorities, defining these both to |
3609 | If your embedding application does not need any priorities, defining these |
2200 | C<0> will save some memory and cpu. |
3610 | both to C<0> will save some memory and CPU. |
2201 | |
3611 | |
2202 | =item EV_PERIODIC_ENABLE |
3612 | =item EV_PERIODIC_ENABLE |
2203 | |
3613 | |
2204 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3614 | If undefined or defined to be C<1>, then periodic timers are supported. If |
2205 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3615 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
… | |
… | |
2212 | code. |
3622 | code. |
2213 | |
3623 | |
2214 | =item EV_EMBED_ENABLE |
3624 | =item EV_EMBED_ENABLE |
2215 | |
3625 | |
2216 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3626 | If undefined or defined to be C<1>, then embed watchers are supported. If |
2217 | defined to be C<0>, then they are not. |
3627 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3628 | watcher types, which therefore must not be disabled. |
2218 | |
3629 | |
2219 | =item EV_STAT_ENABLE |
3630 | =item EV_STAT_ENABLE |
2220 | |
3631 | |
2221 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3632 | If undefined or defined to be C<1>, then stat watchers are supported. If |
2222 | defined to be C<0>, then they are not. |
3633 | defined to be C<0>, then they are not. |
… | |
… | |
2224 | =item EV_FORK_ENABLE |
3635 | =item EV_FORK_ENABLE |
2225 | |
3636 | |
2226 | If undefined or defined to be C<1>, then fork watchers are supported. If |
3637 | If undefined or defined to be C<1>, then fork watchers are supported. If |
2227 | defined to be C<0>, then they are not. |
3638 | defined to be C<0>, then they are not. |
2228 | |
3639 | |
|
|
3640 | =item EV_ASYNC_ENABLE |
|
|
3641 | |
|
|
3642 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3643 | defined to be C<0>, then they are not. |
|
|
3644 | |
2229 | =item EV_MINIMAL |
3645 | =item EV_MINIMAL |
2230 | |
3646 | |
2231 | If you need to shave off some kilobytes of code at the expense of some |
3647 | If you need to shave off some kilobytes of code at the expense of some |
2232 | speed, define this symbol to C<1>. Currently only used for gcc to override |
3648 | speed, define this symbol to C<1>. Currently this is used to override some |
2233 | some inlining decisions, saves roughly 30% codesize of amd64. |
3649 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
|
|
3650 | much smaller 2-heap for timer management over the default 4-heap. |
2234 | |
3651 | |
2235 | =item EV_PID_HASHSIZE |
3652 | =item EV_PID_HASHSIZE |
2236 | |
3653 | |
2237 | C<ev_child> watchers use a small hash table to distribute workload by |
3654 | C<ev_child> watchers use a small hash table to distribute workload by |
2238 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3655 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
2239 | than enough. If you need to manage thousands of children you might want to |
3656 | than enough. If you need to manage thousands of children you might want to |
2240 | increase this value (I<must> be a power of two). |
3657 | increase this value (I<must> be a power of two). |
2241 | |
3658 | |
2242 | =item EV_INOTIFY_HASHSIZE |
3659 | =item EV_INOTIFY_HASHSIZE |
2243 | |
3660 | |
2244 | C<ev_staz> watchers use a small hash table to distribute workload by |
3661 | C<ev_stat> watchers use a small hash table to distribute workload by |
2245 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
3662 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2246 | usually more than enough. If you need to manage thousands of C<ev_stat> |
3663 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2247 | watchers you might want to increase this value (I<must> be a power of |
3664 | watchers you might want to increase this value (I<must> be a power of |
2248 | two). |
3665 | two). |
2249 | |
3666 | |
|
|
3667 | =item EV_USE_4HEAP |
|
|
3668 | |
|
|
3669 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3670 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
|
|
3671 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
|
|
3672 | faster performance with many (thousands) of watchers. |
|
|
3673 | |
|
|
3674 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3675 | (disabled). |
|
|
3676 | |
|
|
3677 | =item EV_HEAP_CACHE_AT |
|
|
3678 | |
|
|
3679 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3680 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
|
|
3681 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3682 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3683 | but avoids random read accesses on heap changes. This improves performance |
|
|
3684 | noticeably with many (hundreds) of watchers. |
|
|
3685 | |
|
|
3686 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3687 | (disabled). |
|
|
3688 | |
|
|
3689 | =item EV_VERIFY |
|
|
3690 | |
|
|
3691 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
|
|
3692 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
3693 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
3694 | called. If set to C<2>, then the internal verification code will be |
|
|
3695 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
3696 | verification code will be called very frequently, which will slow down |
|
|
3697 | libev considerably. |
|
|
3698 | |
|
|
3699 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
|
|
3700 | C<0>. |
|
|
3701 | |
2250 | =item EV_COMMON |
3702 | =item EV_COMMON |
2251 | |
3703 | |
2252 | By default, all watchers have a C<void *data> member. By redefining |
3704 | By default, all watchers have a C<void *data> member. By redefining |
2253 | this macro to a something else you can include more and other types of |
3705 | this macro to a something else you can include more and other types of |
2254 | members. You have to define it each time you include one of the files, |
3706 | members. You have to define it each time you include one of the files, |
2255 | though, and it must be identical each time. |
3707 | though, and it must be identical each time. |
2256 | |
3708 | |
2257 | For example, the perl EV module uses something like this: |
3709 | For example, the perl EV module uses something like this: |
2258 | |
3710 | |
2259 | #define EV_COMMON \ |
3711 | #define EV_COMMON \ |
2260 | SV *self; /* contains this struct */ \ |
3712 | SV *self; /* contains this struct */ \ |
2261 | SV *cb_sv, *fh /* note no trailing ";" */ |
3713 | SV *cb_sv, *fh /* note no trailing ";" */ |
2262 | |
3714 | |
2263 | =item EV_CB_DECLARE (type) |
3715 | =item EV_CB_DECLARE (type) |
2264 | |
3716 | |
2265 | =item EV_CB_INVOKE (watcher, revents) |
3717 | =item EV_CB_INVOKE (watcher, revents) |
2266 | |
3718 | |
2267 | =item ev_set_cb (ev, cb) |
3719 | =item ev_set_cb (ev, cb) |
2268 | |
3720 | |
2269 | Can be used to change the callback member declaration in each watcher, |
3721 | Can be used to change the callback member declaration in each watcher, |
2270 | and the way callbacks are invoked and set. Must expand to a struct member |
3722 | and the way callbacks are invoked and set. Must expand to a struct member |
2271 | definition and a statement, respectively. See the F<ev.v> header file for |
3723 | definition and a statement, respectively. See the F<ev.h> header file for |
2272 | their default definitions. One possible use for overriding these is to |
3724 | their default definitions. One possible use for overriding these is to |
2273 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3725 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
2274 | method calls instead of plain function calls in C++. |
3726 | method calls instead of plain function calls in C++. |
|
|
3727 | |
|
|
3728 | =back |
|
|
3729 | |
|
|
3730 | =head2 EXPORTED API SYMBOLS |
|
|
3731 | |
|
|
3732 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
|
|
3733 | exported symbols, you can use the provided F<Symbol.*> files which list |
|
|
3734 | all public symbols, one per line: |
|
|
3735 | |
|
|
3736 | Symbols.ev for libev proper |
|
|
3737 | Symbols.event for the libevent emulation |
|
|
3738 | |
|
|
3739 | This can also be used to rename all public symbols to avoid clashes with |
|
|
3740 | multiple versions of libev linked together (which is obviously bad in |
|
|
3741 | itself, but sometimes it is inconvenient to avoid this). |
|
|
3742 | |
|
|
3743 | A sed command like this will create wrapper C<#define>'s that you need to |
|
|
3744 | include before including F<ev.h>: |
|
|
3745 | |
|
|
3746 | <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h |
|
|
3747 | |
|
|
3748 | This would create a file F<wrap.h> which essentially looks like this: |
|
|
3749 | |
|
|
3750 | #define ev_backend myprefix_ev_backend |
|
|
3751 | #define ev_check_start myprefix_ev_check_start |
|
|
3752 | #define ev_check_stop myprefix_ev_check_stop |
|
|
3753 | ... |
2275 | |
3754 | |
2276 | =head2 EXAMPLES |
3755 | =head2 EXAMPLES |
2277 | |
3756 | |
2278 | For a real-world example of a program the includes libev |
3757 | For a real-world example of a program the includes libev |
2279 | verbatim, you can have a look at the EV perl module |
3758 | verbatim, you can have a look at the EV perl module |
… | |
… | |
2284 | file. |
3763 | file. |
2285 | |
3764 | |
2286 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3765 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
2287 | that everybody includes and which overrides some configure choices: |
3766 | that everybody includes and which overrides some configure choices: |
2288 | |
3767 | |
2289 | #define EV_MINIMAL 1 |
3768 | #define EV_MINIMAL 1 |
2290 | #define EV_USE_POLL 0 |
3769 | #define EV_USE_POLL 0 |
2291 | #define EV_MULTIPLICITY 0 |
3770 | #define EV_MULTIPLICITY 0 |
2292 | #define EV_PERIODIC_ENABLE 0 |
3771 | #define EV_PERIODIC_ENABLE 0 |
2293 | #define EV_STAT_ENABLE 0 |
3772 | #define EV_STAT_ENABLE 0 |
2294 | #define EV_FORK_ENABLE 0 |
3773 | #define EV_FORK_ENABLE 0 |
2295 | #define EV_CONFIG_H <config.h> |
3774 | #define EV_CONFIG_H <config.h> |
2296 | #define EV_MINPRI 0 |
3775 | #define EV_MINPRI 0 |
2297 | #define EV_MAXPRI 0 |
3776 | #define EV_MAXPRI 0 |
2298 | |
3777 | |
2299 | #include "ev++.h" |
3778 | #include "ev++.h" |
2300 | |
3779 | |
2301 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3780 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
2302 | |
3781 | |
2303 | #include "ev_cpp.h" |
3782 | #include "ev_cpp.h" |
2304 | #include "ev.c" |
3783 | #include "ev.c" |
2305 | |
3784 | |
|
|
3785 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
2306 | |
3786 | |
|
|
3787 | =head2 THREADS AND COROUTINES |
|
|
3788 | |
|
|
3789 | =head3 THREADS |
|
|
3790 | |
|
|
3791 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
3792 | documented otherwise, but libev implements no locking itself. This means |
|
|
3793 | that you can use as many loops as you want in parallel, as long as there |
|
|
3794 | are no concurrent calls into any libev function with the same loop |
|
|
3795 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
3796 | of course): libev guarantees that different event loops share no data |
|
|
3797 | structures that need any locking. |
|
|
3798 | |
|
|
3799 | Or to put it differently: calls with different loop parameters can be done |
|
|
3800 | concurrently from multiple threads, calls with the same loop parameter |
|
|
3801 | must be done serially (but can be done from different threads, as long as |
|
|
3802 | only one thread ever is inside a call at any point in time, e.g. by using |
|
|
3803 | a mutex per loop). |
|
|
3804 | |
|
|
3805 | Specifically to support threads (and signal handlers), libev implements |
|
|
3806 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
3807 | concurrency on the same event loop, namely waking it up "from the |
|
|
3808 | outside". |
|
|
3809 | |
|
|
3810 | If you want to know which design (one loop, locking, or multiple loops |
|
|
3811 | without or something else still) is best for your problem, then I cannot |
|
|
3812 | help you, but here is some generic advice: |
|
|
3813 | |
|
|
3814 | =over 4 |
|
|
3815 | |
|
|
3816 | =item * most applications have a main thread: use the default libev loop |
|
|
3817 | in that thread, or create a separate thread running only the default loop. |
|
|
3818 | |
|
|
3819 | This helps integrating other libraries or software modules that use libev |
|
|
3820 | themselves and don't care/know about threading. |
|
|
3821 | |
|
|
3822 | =item * one loop per thread is usually a good model. |
|
|
3823 | |
|
|
3824 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3825 | exists, but it is always a good start. |
|
|
3826 | |
|
|
3827 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
3828 | loop is handed through multiple threads in a kind of round-robin fashion. |
|
|
3829 | |
|
|
3830 | Choosing a model is hard - look around, learn, know that usually you can do |
|
|
3831 | better than you currently do :-) |
|
|
3832 | |
|
|
3833 | =item * often you need to talk to some other thread which blocks in the |
|
|
3834 | event loop. |
|
|
3835 | |
|
|
3836 | C<ev_async> watchers can be used to wake them up from other threads safely |
|
|
3837 | (or from signal contexts...). |
|
|
3838 | |
|
|
3839 | An example use would be to communicate signals or other events that only |
|
|
3840 | work in the default loop by registering the signal watcher with the |
|
|
3841 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
3842 | watcher callback into the event loop interested in the signal. |
|
|
3843 | |
|
|
3844 | =back |
|
|
3845 | |
|
|
3846 | =head3 COROUTINES |
|
|
3847 | |
|
|
3848 | Libev is very accommodating to coroutines ("cooperative threads"): |
|
|
3849 | libev fully supports nesting calls to its functions from different |
|
|
3850 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
3851 | different coroutines, and switch freely between both coroutines running the |
|
|
3852 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3853 | you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
3854 | |
|
|
3855 | Care has been taken to ensure that libev does not keep local state inside |
|
|
3856 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
|
|
3857 | they do not call any callbacks. |
|
|
3858 | |
|
|
3859 | =head2 COMPILER WARNINGS |
|
|
3860 | |
|
|
3861 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3862 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3863 | scared by this. |
|
|
3864 | |
|
|
3865 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3866 | has different warnings, and each user has different tastes regarding |
|
|
3867 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3868 | targeting a specific compiler and compiler-version. |
|
|
3869 | |
|
|
3870 | Another reason is that some compiler warnings require elaborate |
|
|
3871 | workarounds, or other changes to the code that make it less clear and less |
|
|
3872 | maintainable. |
|
|
3873 | |
|
|
3874 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3875 | wrong (because they don't actually warn about the condition their message |
|
|
3876 | seems to warn about). For example, certain older gcc versions had some |
|
|
3877 | warnings that resulted an extreme number of false positives. These have |
|
|
3878 | been fixed, but some people still insist on making code warn-free with |
|
|
3879 | such buggy versions. |
|
|
3880 | |
|
|
3881 | While libev is written to generate as few warnings as possible, |
|
|
3882 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3883 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3884 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3885 | warnings, not errors, or proof of bugs. |
|
|
3886 | |
|
|
3887 | |
|
|
3888 | =head2 VALGRIND |
|
|
3889 | |
|
|
3890 | Valgrind has a special section here because it is a popular tool that is |
|
|
3891 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
|
|
3892 | |
|
|
3893 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3894 | in libev, then check twice: If valgrind reports something like: |
|
|
3895 | |
|
|
3896 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3897 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3898 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3899 | |
|
|
3900 | Then there is no memory leak, just as memory accounted to global variables |
|
|
3901 | is not a memleak - the memory is still being referenced, and didn't leak. |
|
|
3902 | |
|
|
3903 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
3904 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
3905 | although an acceptable workaround has been found here), or it might be |
|
|
3906 | confused. |
|
|
3907 | |
|
|
3908 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
|
|
3909 | make it into some kind of religion. |
|
|
3910 | |
|
|
3911 | If you are unsure about something, feel free to contact the mailing list |
|
|
3912 | with the full valgrind report and an explanation on why you think this |
|
|
3913 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
3914 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
3915 | of learning how to interpret valgrind properly. |
|
|
3916 | |
|
|
3917 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3918 | I suggest using suppression lists. |
|
|
3919 | |
|
|
3920 | |
|
|
3921 | =head1 PORTABILITY NOTES |
|
|
3922 | |
|
|
3923 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
3924 | |
|
|
3925 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
|
|
3926 | requires, and its I/O model is fundamentally incompatible with the POSIX |
|
|
3927 | model. Libev still offers limited functionality on this platform in |
|
|
3928 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
|
|
3929 | descriptors. This only applies when using Win32 natively, not when using |
|
|
3930 | e.g. cygwin. |
|
|
3931 | |
|
|
3932 | Lifting these limitations would basically require the full |
|
|
3933 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3934 | things, then note that glib does exactly that for you in a very portable |
|
|
3935 | way (note also that glib is the slowest event library known to man). |
|
|
3936 | |
|
|
3937 | There is no supported compilation method available on windows except |
|
|
3938 | embedding it into other applications. |
|
|
3939 | |
|
|
3940 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
3941 | tries its best, but under most conditions, signals will simply not work. |
|
|
3942 | |
|
|
3943 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
3944 | accept large writes: instead of resulting in a partial write, windows will |
|
|
3945 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
|
|
3946 | so make sure you only write small amounts into your sockets (less than a |
|
|
3947 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
3948 | available). |
|
|
3949 | |
|
|
3950 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
3951 | the abysmal performance of winsockets, using a large number of sockets |
|
|
3952 | is not recommended (and not reasonable). If your program needs to use |
|
|
3953 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
3954 | different implementation for windows, as libev offers the POSIX readiness |
|
|
3955 | notification model, which cannot be implemented efficiently on windows |
|
|
3956 | (due to Microsoft monopoly games). |
|
|
3957 | |
|
|
3958 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
3959 | section for details) and use the following F<evwrap.h> header file instead |
|
|
3960 | of F<ev.h>: |
|
|
3961 | |
|
|
3962 | #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
3963 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
3964 | |
|
|
3965 | #include "ev.h" |
|
|
3966 | |
|
|
3967 | And compile the following F<evwrap.c> file into your project (make sure |
|
|
3968 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
|
|
3969 | |
|
|
3970 | #include "evwrap.h" |
|
|
3971 | #include "ev.c" |
|
|
3972 | |
|
|
3973 | =over 4 |
|
|
3974 | |
|
|
3975 | =item The winsocket select function |
|
|
3976 | |
|
|
3977 | The winsocket C<select> function doesn't follow POSIX in that it |
|
|
3978 | requires socket I<handles> and not socket I<file descriptors> (it is |
|
|
3979 | also extremely buggy). This makes select very inefficient, and also |
|
|
3980 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
3981 | C runtime provides the function C<_open_osfhandle> for this). See the |
|
|
3982 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
|
|
3983 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
|
|
3984 | |
|
|
3985 | The configuration for a "naked" win32 using the Microsoft runtime |
|
|
3986 | libraries and raw winsocket select is: |
|
|
3987 | |
|
|
3988 | #define EV_USE_SELECT 1 |
|
|
3989 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
3990 | |
|
|
3991 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
3992 | complexity in the O(n²) range when using win32. |
|
|
3993 | |
|
|
3994 | =item Limited number of file descriptors |
|
|
3995 | |
|
|
3996 | Windows has numerous arbitrary (and low) limits on things. |
|
|
3997 | |
|
|
3998 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
3999 | of C<64> handles (probably owning to the fact that all windows kernels |
|
|
4000 | can only wait for C<64> things at the same time internally; Microsoft |
|
|
4001 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
4002 | previous thread in each. Sounds great!). |
|
|
4003 | |
|
|
4004 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
|
|
4005 | to some high number (e.g. C<2048>) before compiling the winsocket select |
|
|
4006 | call (which might be in libev or elsewhere, for example, perl and many |
|
|
4007 | other interpreters do their own select emulation on windows). |
|
|
4008 | |
|
|
4009 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
4010 | libraries, which by default is C<64> (there must be a hidden I<64> |
|
|
4011 | fetish or something like this inside Microsoft). You can increase this |
|
|
4012 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
|
|
4013 | (another arbitrary limit), but is broken in many versions of the Microsoft |
|
|
4014 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
|
|
4015 | (depending on windows version and/or the phase of the moon). To get more, |
|
|
4016 | you need to wrap all I/O functions and provide your own fd management, but |
|
|
4017 | the cost of calling select (O(n²)) will likely make this unworkable. |
|
|
4018 | |
|
|
4019 | =back |
|
|
4020 | |
|
|
4021 | =head2 PORTABILITY REQUIREMENTS |
|
|
4022 | |
|
|
4023 | In addition to a working ISO-C implementation and of course the |
|
|
4024 | backend-specific APIs, libev relies on a few additional extensions: |
|
|
4025 | |
|
|
4026 | =over 4 |
|
|
4027 | |
|
|
4028 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
|
|
4029 | calling conventions regardless of C<ev_watcher_type *>. |
|
|
4030 | |
|
|
4031 | Libev assumes not only that all watcher pointers have the same internal |
|
|
4032 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
|
|
4033 | assumes that the same (machine) code can be used to call any watcher |
|
|
4034 | callback: The watcher callbacks have different type signatures, but libev |
|
|
4035 | calls them using an C<ev_watcher *> internally. |
|
|
4036 | |
|
|
4037 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
4038 | |
|
|
4039 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
4040 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
|
|
4041 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
4042 | believed to be sufficiently portable. |
|
|
4043 | |
|
|
4044 | =item C<sigprocmask> must work in a threaded environment |
|
|
4045 | |
|
|
4046 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
4047 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
4048 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
4049 | thread" or will block signals process-wide, both behaviours would |
|
|
4050 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
4051 | C<pthread_sigmask> could complicate things, however. |
|
|
4052 | |
|
|
4053 | The most portable way to handle signals is to block signals in all threads |
|
|
4054 | except the initial one, and run the default loop in the initial thread as |
|
|
4055 | well. |
|
|
4056 | |
|
|
4057 | =item C<long> must be large enough for common memory allocation sizes |
|
|
4058 | |
|
|
4059 | To improve portability and simplify its API, libev uses C<long> internally |
|
|
4060 | instead of C<size_t> when allocating its data structures. On non-POSIX |
|
|
4061 | systems (Microsoft...) this might be unexpectedly low, but is still at |
|
|
4062 | least 31 bits everywhere, which is enough for hundreds of millions of |
|
|
4063 | watchers. |
|
|
4064 | |
|
|
4065 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
4066 | |
|
|
4067 | The type C<double> is used to represent timestamps. It is required to |
|
|
4068 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
4069 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
4070 | implementations implementing IEEE 754 (basically all existing ones). |
|
|
4071 | |
|
|
4072 | =back |
|
|
4073 | |
|
|
4074 | If you know of other additional requirements drop me a note. |
|
|
4075 | |
|
|
4076 | |
2307 | =head1 COMPLEXITIES |
4077 | =head1 ALGORITHMIC COMPLEXITIES |
2308 | |
4078 | |
2309 | In this section the complexities of (many of) the algorithms used inside |
4079 | In this section the complexities of (many of) the algorithms used inside |
2310 | libev will be explained. For complexity discussions about backends see the |
4080 | libev will be documented. For complexity discussions about backends see |
2311 | documentation for C<ev_default_init>. |
4081 | the documentation for C<ev_default_init>. |
2312 | |
4082 | |
2313 | All of the following are about amortised time: If an array needs to be |
4083 | All of the following are about amortised time: If an array needs to be |
2314 | extended, libev needs to realloc and move the whole array, but this |
4084 | extended, libev needs to realloc and move the whole array, but this |
2315 | happens asymptotically never with higher number of elements, so O(1) might |
4085 | happens asymptotically rarer with higher number of elements, so O(1) might |
2316 | mean it might do a lengthy realloc operation in rare cases, but on average |
4086 | mean that libev does a lengthy realloc operation in rare cases, but on |
2317 | it is much faster and asymptotically approaches constant time. |
4087 | average it is much faster and asymptotically approaches constant time. |
2318 | |
4088 | |
2319 | =over 4 |
4089 | =over 4 |
2320 | |
4090 | |
2321 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
4091 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
2322 | |
4092 | |
2323 | This means that, when you have a watcher that triggers in one hour and |
4093 | This means that, when you have a watcher that triggers in one hour and |
2324 | there are 100 watchers that would trigger before that then inserting will |
4094 | there are 100 watchers that would trigger before that, then inserting will |
2325 | have to skip those 100 watchers. |
4095 | have to skip roughly seven (C<ld 100>) of these watchers. |
2326 | |
4096 | |
2327 | =item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) |
4097 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
2328 | |
4098 | |
2329 | That means that for changing a timer costs less than removing/adding them |
4099 | That means that changing a timer costs less than removing/adding them, |
2330 | as only the relative motion in the event queue has to be paid for. |
4100 | as only the relative motion in the event queue has to be paid for. |
2331 | |
4101 | |
2332 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
4102 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
2333 | |
4103 | |
2334 | These just add the watcher into an array or at the head of a list. |
4104 | These just add the watcher into an array or at the head of a list. |
|
|
4105 | |
2335 | =item Stopping check/prepare/idle watchers: O(1) |
4106 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
2336 | |
4107 | |
2337 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
4108 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2338 | |
4109 | |
2339 | These watchers are stored in lists then need to be walked to find the |
4110 | These watchers are stored in lists, so they need to be walked to find the |
2340 | correct watcher to remove. The lists are usually short (you don't usually |
4111 | correct watcher to remove. The lists are usually short (you don't usually |
2341 | have many watchers waiting for the same fd or signal). |
4112 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
4113 | is rare). |
2342 | |
4114 | |
2343 | =item Finding the next timer per loop iteration: O(1) |
4115 | =item Finding the next timer in each loop iteration: O(1) |
|
|
4116 | |
|
|
4117 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
4118 | fixed position in the storage array. |
2344 | |
4119 | |
2345 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
4120 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
2346 | |
4121 | |
2347 | A change means an I/O watcher gets started or stopped, which requires |
4122 | A change means an I/O watcher gets started or stopped, which requires |
2348 | libev to recalculate its status (and possibly tell the kernel). |
4123 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
4124 | on backend and whether C<ev_io_set> was used). |
2349 | |
4125 | |
2350 | =item Activating one watcher: O(1) |
4126 | =item Activating one watcher (putting it into the pending state): O(1) |
2351 | |
4127 | |
2352 | =item Priority handling: O(number_of_priorities) |
4128 | =item Priority handling: O(number_of_priorities) |
2353 | |
4129 | |
2354 | Priorities are implemented by allocating some space for each |
4130 | Priorities are implemented by allocating some space for each |
2355 | priority. When doing priority-based operations, libev usually has to |
4131 | priority. When doing priority-based operations, libev usually has to |
2356 | linearly search all the priorities. |
4132 | linearly search all the priorities, but starting/stopping and activating |
|
|
4133 | watchers becomes O(1) with respect to priority handling. |
|
|
4134 | |
|
|
4135 | =item Sending an ev_async: O(1) |
|
|
4136 | |
|
|
4137 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
4138 | |
|
|
4139 | =item Processing signals: O(max_signal_number) |
|
|
4140 | |
|
|
4141 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
4142 | calls in the current loop iteration. Checking for async and signal events |
|
|
4143 | involves iterating over all running async watchers or all signal numbers. |
2357 | |
4144 | |
2358 | =back |
4145 | =back |
2359 | |
4146 | |
2360 | |
4147 | |
|
|
4148 | =head1 GLOSSARY |
|
|
4149 | |
|
|
4150 | =over 4 |
|
|
4151 | |
|
|
4152 | =item active |
|
|
4153 | |
|
|
4154 | A watcher is active as long as it has been started (has been attached to |
|
|
4155 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4156 | |
|
|
4157 | =item application |
|
|
4158 | |
|
|
4159 | In this document, an application is whatever is using libev. |
|
|
4160 | |
|
|
4161 | =item callback |
|
|
4162 | |
|
|
4163 | The address of a function that is called when some event has been |
|
|
4164 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4165 | received the event, and the actual event bitset. |
|
|
4166 | |
|
|
4167 | =item callback invocation |
|
|
4168 | |
|
|
4169 | The act of calling the callback associated with a watcher. |
|
|
4170 | |
|
|
4171 | =item event |
|
|
4172 | |
|
|
4173 | A change of state of some external event, such as data now being available |
|
|
4174 | for reading on a file descriptor, time having passed or simply not having |
|
|
4175 | any other events happening anymore. |
|
|
4176 | |
|
|
4177 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4178 | C<EV_TIMEOUT>). |
|
|
4179 | |
|
|
4180 | =item event library |
|
|
4181 | |
|
|
4182 | A software package implementing an event model and loop. |
|
|
4183 | |
|
|
4184 | =item event loop |
|
|
4185 | |
|
|
4186 | An entity that handles and processes external events and converts them |
|
|
4187 | into callback invocations. |
|
|
4188 | |
|
|
4189 | =item event model |
|
|
4190 | |
|
|
4191 | The model used to describe how an event loop handles and processes |
|
|
4192 | watchers and events. |
|
|
4193 | |
|
|
4194 | =item pending |
|
|
4195 | |
|
|
4196 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4197 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4198 | pending status is explicitly cleared by the application. |
|
|
4199 | |
|
|
4200 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4201 | its pending status. |
|
|
4202 | |
|
|
4203 | =item real time |
|
|
4204 | |
|
|
4205 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4206 | |
|
|
4207 | =item wall-clock time |
|
|
4208 | |
|
|
4209 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4210 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4211 | clock. |
|
|
4212 | |
|
|
4213 | =item watcher |
|
|
4214 | |
|
|
4215 | A data structure that describes interest in certain events. Watchers need |
|
|
4216 | to be started (attached to an event loop) before they can receive events. |
|
|
4217 | |
|
|
4218 | =item watcher invocation |
|
|
4219 | |
|
|
4220 | The act of calling the callback associated with a watcher. |
|
|
4221 | |
|
|
4222 | =back |
|
|
4223 | |
2361 | =head1 AUTHOR |
4224 | =head1 AUTHOR |
2362 | |
4225 | |
2363 | Marc Lehmann <libev@schmorp.de>. |
4226 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
2364 | |
4227 | |