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134 | .IX Title "LIBEV 3" |
126 | .IX Title "LIBEV 3" |
135 | .TH LIBEV 3 "2008-06-19" "libev-3.43" "libev - high performance full featured event loop" |
127 | .TH LIBEV 3 "2009-07-27" "libev-3.8" "libev - high performance full featured event loop" |
136 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
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138 | .if n .ad l |
130 | .if n .ad l |
139 | .nh |
131 | .nh |
140 | .SH "NAME" |
132 | .SH "NAME" |
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142 | .SH "SYNOPSIS" |
134 | .SH "SYNOPSIS" |
143 | .IX Header "SYNOPSIS" |
135 | .IX Header "SYNOPSIS" |
144 | .Vb 1 |
136 | .Vb 1 |
145 | \& #include <ev.h> |
137 | \& #include <ev.h> |
146 | .Ve |
138 | .Ve |
147 | .Sh "\s-1EXAMPLE\s0 \s-1PROGRAM\s0" |
139 | .SS "\s-1EXAMPLE\s0 \s-1PROGRAM\s0" |
148 | .IX Subsection "EXAMPLE PROGRAM" |
140 | .IX Subsection "EXAMPLE PROGRAM" |
149 | .Vb 2 |
141 | .Vb 2 |
150 | \& // a single header file is required |
142 | \& // a single header file is required |
151 | \& #include <ev.h> |
143 | \& #include <ev.h> |
152 | \& |
144 | \& |
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145 | \& #include <stdio.h> // for puts |
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146 | \& |
153 | \& // every watcher type has its own typedef\*(Aqd struct |
147 | \& // every watcher type has its own typedef\*(Aqd struct |
154 | \& // with the name ev_<type> |
148 | \& // with the name ev_TYPE |
155 | \& ev_io stdin_watcher; |
149 | \& ev_io stdin_watcher; |
156 | \& ev_timer timeout_watcher; |
150 | \& ev_timer timeout_watcher; |
157 | \& |
151 | \& |
158 | \& // all watcher callbacks have a similar signature |
152 | \& // all watcher callbacks have a similar signature |
159 | \& // this callback is called when data is readable on stdin |
153 | \& // this callback is called when data is readable on stdin |
160 | \& static void |
154 | \& static void |
161 | \& stdin_cb (EV_P_ struct ev_io *w, int revents) |
155 | \& stdin_cb (EV_P_ ev_io *w, int revents) |
162 | \& { |
156 | \& { |
163 | \& puts ("stdin ready"); |
157 | \& puts ("stdin ready"); |
164 | \& // for one\-shot events, one must manually stop the watcher |
158 | \& // for one\-shot events, one must manually stop the watcher |
165 | \& // with its corresponding stop function. |
159 | \& // with its corresponding stop function. |
166 | \& ev_io_stop (EV_A_ w); |
160 | \& ev_io_stop (EV_A_ w); |
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169 | \& ev_unloop (EV_A_ EVUNLOOP_ALL); |
163 | \& ev_unloop (EV_A_ EVUNLOOP_ALL); |
170 | \& } |
164 | \& } |
171 | \& |
165 | \& |
172 | \& // another callback, this time for a time\-out |
166 | \& // another callback, this time for a time\-out |
173 | \& static void |
167 | \& static void |
174 | \& timeout_cb (EV_P_ struct ev_timer *w, int revents) |
168 | \& timeout_cb (EV_P_ ev_timer *w, int revents) |
175 | \& { |
169 | \& { |
176 | \& puts ("timeout"); |
170 | \& puts ("timeout"); |
177 | \& // this causes the innermost ev_loop to stop iterating |
171 | \& // this causes the innermost ev_loop to stop iterating |
178 | \& ev_unloop (EV_A_ EVUNLOOP_ONE); |
172 | \& ev_unloop (EV_A_ EVUNLOOP_ONE); |
179 | \& } |
173 | \& } |
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199 | \& |
193 | \& |
200 | \& // unloop was called, so exit |
194 | \& // unloop was called, so exit |
201 | \& return 0; |
195 | \& return 0; |
202 | \& } |
196 | \& } |
203 | .Ve |
197 | .Ve |
204 | .SH "DESCRIPTION" |
198 | .SH "ABOUT THIS DOCUMENT" |
205 | .IX Header "DESCRIPTION" |
199 | .IX Header "ABOUT THIS DOCUMENT" |
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200 | This document documents the libev software package. |
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201 | .PP |
206 | The newest version of this document is also available as an html-formatted |
202 | The newest version of this document is also available as an html-formatted |
207 | web page you might find easier to navigate when reading it for the first |
203 | web page you might find easier to navigate when reading it for the first |
208 | time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
204 | time: <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
209 | .PP |
205 | .PP |
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206 | While this document tries to be as complete as possible in documenting |
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207 | libev, its usage and the rationale behind its design, it is not a tutorial |
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208 | on event-based programming, nor will it introduce event-based programming |
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209 | with libev. |
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210 | .PP |
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211 | Familarity with event based programming techniques in general is assumed |
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212 | throughout this document. |
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213 | .SH "ABOUT LIBEV" |
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214 | .IX Header "ABOUT LIBEV" |
210 | Libev is an event loop: you register interest in certain events (such as a |
215 | Libev is an event loop: you register interest in certain events (such as a |
211 | file descriptor being readable or a timeout occurring), and it will manage |
216 | file descriptor being readable or a timeout occurring), and it will manage |
212 | these event sources and provide your program with events. |
217 | these event sources and provide your program with events. |
213 | .PP |
218 | .PP |
214 | To do this, it must take more or less complete control over your process |
219 | To do this, it must take more or less complete control over your process |
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217 | .PP |
222 | .PP |
218 | You register interest in certain events by registering so-called \fIevent |
223 | You register interest in certain events by registering so-called \fIevent |
219 | watchers\fR, which are relatively small C structures you initialise with the |
224 | watchers\fR, which are relatively small C structures you initialise with the |
220 | details of the event, and then hand it over to libev by \fIstarting\fR the |
225 | details of the event, and then hand it over to libev by \fIstarting\fR the |
221 | watcher. |
226 | watcher. |
222 | .Sh "\s-1FEATURES\s0" |
227 | .SS "\s-1FEATURES\s0" |
223 | .IX Subsection "FEATURES" |
228 | .IX Subsection "FEATURES" |
224 | Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the |
229 | Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the |
225 | BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms |
230 | BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms |
226 | for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface |
231 | for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface |
227 | (for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers |
232 | (for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner |
228 | with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals |
233 | inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative |
229 | (\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event |
234 | timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling |
230 | watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, |
235 | (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status |
231 | \&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as |
236 | change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event |
232 | file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events |
237 | loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and |
233 | (\f(CW\*(C`ev_fork\*(C'\fR). |
238 | \&\f(CW\*(C`ev_check\*(C'\fR watchers) as well as file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even |
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239 | limited support for fork events (\f(CW\*(C`ev_fork\*(C'\fR). |
234 | .PP |
240 | .PP |
235 | It also is quite fast (see this |
241 | It also is quite fast (see this |
236 | benchmark comparing it to libevent |
242 | <benchmark> comparing it to libevent |
237 | for example). |
243 | for example). |
238 | .Sh "\s-1CONVENTIONS\s0" |
244 | .SS "\s-1CONVENTIONS\s0" |
239 | .IX Subsection "CONVENTIONS" |
245 | .IX Subsection "CONVENTIONS" |
240 | Libev is very configurable. In this manual the default (and most common) |
246 | Libev is very configurable. In this manual the default (and most common) |
241 | configuration will be described, which supports multiple event loops. For |
247 | configuration will be described, which supports multiple event loops. For |
242 | more info about various configuration options please have a look at |
248 | more info about various configuration options please have a look at |
243 | \&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support |
249 | \&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support |
244 | for multiple event loops, then all functions taking an initial argument of |
250 | for multiple event loops, then all functions taking an initial argument of |
245 | name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have |
251 | name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`ev_loop *\*(C'\fR) will not have |
246 | this argument. |
252 | this argument. |
247 | .Sh "\s-1TIME\s0 \s-1REPRESENTATION\s0" |
253 | .SS "\s-1TIME\s0 \s-1REPRESENTATION\s0" |
248 | .IX Subsection "TIME REPRESENTATION" |
254 | .IX Subsection "TIME REPRESENTATION" |
249 | Libev represents time as a single floating point number, representing the |
255 | Libev represents time as a single floating point number, representing |
250 | (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near |
256 | the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere |
251 | the beginning of 1970, details are complicated, don't ask). This type is |
257 | near the beginning of 1970, details are complicated, don't ask). This |
252 | called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases |
258 | type is called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually |
253 | to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on |
259 | aliases to the \f(CW\*(C`double\*(C'\fR type in C. When you need to do any calculations |
254 | it, you should treat it as some floating point value. Unlike the name |
260 | on it, you should treat it as some floating point value. Unlike the name |
255 | component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences |
261 | component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences |
256 | throughout libev. |
262 | throughout libev. |
257 | .SH "ERROR HANDLING" |
263 | .SH "ERROR HANDLING" |
258 | .IX Header "ERROR HANDLING" |
264 | .IX Header "ERROR HANDLING" |
259 | Libev knows three classes of errors: operating system errors, usage errors |
265 | Libev knows three classes of errors: operating system errors, usage errors |
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344 | might be supported on the current system, you would need to look at |
350 | might be supported on the current system, you would need to look at |
345 | \&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for |
351 | \&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for |
346 | recommended ones. |
352 | recommended ones. |
347 | .Sp |
353 | .Sp |
348 | See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
354 | See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
349 | .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 |
355 | .IP "ev_set_allocator (void *(*cb)(void *ptr, long size)) [\s-1NOT\s0 \s-1REENTRANT\s0]" 4 |
350 | .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" |
356 | .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]" |
351 | Sets the allocation function to use (the prototype is similar \- the |
357 | Sets the allocation function to use (the prototype is similar \- the |
352 | semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is |
358 | semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is |
353 | used to allocate and free memory (no surprises here). If it returns zero |
359 | used to allocate and free memory (no surprises here). If it returns zero |
354 | when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort |
360 | when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort |
355 | or take some potentially destructive action. |
361 | or take some potentially destructive action. |
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381 | \& } |
387 | \& } |
382 | \& |
388 | \& |
383 | \& ... |
389 | \& ... |
384 | \& ev_set_allocator (persistent_realloc); |
390 | \& ev_set_allocator (persistent_realloc); |
385 | .Ve |
391 | .Ve |
386 | .IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 |
392 | .IP "ev_set_syserr_cb (void (*cb)(const char *msg)); [\s-1NOT\s0 \s-1REENTRANT\s0]" 4 |
387 | .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" |
393 | .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]" |
388 | Set the callback function to call on a retryable system call error (such |
394 | Set the callback function to call on a retryable system call error (such |
389 | as failed select, poll, epoll_wait). The message is a printable string |
395 | as failed select, poll, epoll_wait). The message is a printable string |
390 | indicating the system call or subsystem causing the problem. If this |
396 | indicating the system call or subsystem causing the problem. If this |
391 | callback is set, then libev will expect it to remedy the situation, no |
397 | callback is set, then libev will expect it to remedy the situation, no |
392 | matter what, when it returns. That is, libev will generally retry the |
398 | matter what, when it returns. That is, libev will generally retry the |
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406 | \& ... |
412 | \& ... |
407 | \& ev_set_syserr_cb (fatal_error); |
413 | \& ev_set_syserr_cb (fatal_error); |
408 | .Ve |
414 | .Ve |
409 | .SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
415 | .SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
410 | .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
416 | .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
411 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two |
417 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR |
412 | types of such loops, the \fIdefault\fR loop, which supports signals and child |
418 | is \fInot\fR optional in this case, as there is also an \f(CW\*(C`ev_loop\*(C'\fR |
413 | events, and dynamically created loops which do not. |
419 | \&\fIfunction\fR). |
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420 | .PP |
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421 | The library knows two types of such loops, the \fIdefault\fR loop, which |
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422 | supports signals and child events, and dynamically created loops which do |
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423 | not. |
414 | .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
424 | .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
415 | .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
425 | .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
416 | This will initialise the default event loop if it hasn't been initialised |
426 | This will initialise the default event loop if it hasn't been initialised |
417 | yet and return it. If the default loop could not be initialised, returns |
427 | yet and return it. If the default loop could not be initialised, returns |
418 | false. If it already was initialised it simply returns it (and ignores the |
428 | false. If it already was initialised it simply returns it (and ignores the |
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421 | If you don't know what event loop to use, use the one returned from this |
431 | If you don't know what event loop to use, use the one returned from this |
422 | function. |
432 | function. |
423 | .Sp |
433 | .Sp |
424 | Note that this function is \fInot\fR thread-safe, so if you want to use it |
434 | Note that this function is \fInot\fR thread-safe, so if you want to use it |
425 | from multiple threads, you have to lock (note also that this is unlikely, |
435 | from multiple threads, you have to lock (note also that this is unlikely, |
426 | as loops cannot bes hared easily between threads anyway). |
436 | as loops cannot be shared easily between threads anyway). |
427 | .Sp |
437 | .Sp |
428 | The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and |
438 | The default loop is the only loop that can handle \f(CW\*(C`ev_signal\*(C'\fR and |
429 | \&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler |
439 | \&\f(CW\*(C`ev_child\*(C'\fR watchers, and to do this, it always registers a handler |
430 | for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your application you can either |
440 | for \f(CW\*(C`SIGCHLD\*(C'\fR. If this is a problem for your application you can either |
431 | create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you |
441 | create a dynamic loop with \f(CW\*(C`ev_loop_new\*(C'\fR that doesn't do that, or you |
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469 | forget about forgetting to tell libev about forking) when you use this |
479 | forget about forgetting to tell libev about forking) when you use this |
470 | flag. |
480 | flag. |
471 | .Sp |
481 | .Sp |
472 | This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR |
482 | This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR |
473 | environment variable. |
483 | environment variable. |
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484 | .ie n .IP """EVFLAG_NOINOTIFY""" 4 |
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485 | .el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4 |
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486 | .IX Item "EVFLAG_NOINOTIFY" |
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487 | When this flag is specified, then libev will not attempt to use the |
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488 | \&\fIinotify\fR \s-1API\s0 for it's \f(CW\*(C`ev_stat\*(C'\fR watchers. Apart from debugging and |
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489 | testing, this flag can be useful to conserve inotify file descriptors, as |
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490 | otherwise each loop using \f(CW\*(C`ev_stat\*(C'\fR watchers consumes one inotify handle. |
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491 | .ie n .IP """EVFLAG_NOSIGNALFD""" 4 |
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492 | .el .IP "\f(CWEVFLAG_NOSIGNALFD\fR" 4 |
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493 | .IX Item "EVFLAG_NOSIGNALFD" |
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494 | When this flag is specified, then libev will not attempt to use the |
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495 | \&\fIsignalfd\fR \s-1API\s0 for it's \f(CW\*(C`ev_signal\*(C'\fR (and \f(CW\*(C`ev_child\*(C'\fR) watchers. This is |
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496 | probably only useful to work around any bugs in libev. Consequently, this |
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497 | flag might go away once the signalfd functionality is considered stable, |
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498 | so it's useful mostly in environment variables and not in program code. |
474 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
499 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
475 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
500 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
476 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
501 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
477 | This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
502 | This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
478 | libev tries to roll its own fd_set with no limits on the number of fds, |
503 | libev tries to roll its own fd_set with no limits on the number of fds, |
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484 | parallelism (most of the file descriptors should be busy). If you are |
509 | parallelism (most of the file descriptors should be busy). If you are |
485 | writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many |
510 | writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many |
486 | connections as possible during one iteration. You might also want to have |
511 | connections as possible during one iteration. You might also want to have |
487 | a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of |
512 | a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of |
488 | readiness notifications you get per iteration. |
513 | readiness notifications you get per iteration. |
|
|
514 | .Sp |
|
|
515 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR to the \f(CW\*(C`readfds\*(C'\fR set and \f(CW\*(C`EV_WRITE\*(C'\fR to the |
|
|
516 | \&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the |
|
|
517 | \&\f(CW\*(C`exceptfds\*(C'\fR set on that platform). |
489 | .ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
518 | .ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
490 | .el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
519 | .el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
491 | .IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" |
520 | .IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" |
492 | And this is your standard \fIpoll\fR\|(2) backend. It's more complicated |
521 | And this is your standard \fIpoll\fR\|(2) backend. It's more complicated |
493 | than select, but handles sparse fds better and has no artificial |
522 | than select, but handles sparse fds better and has no artificial |
494 | limit on the number of fds you can use (except it will slow down |
523 | limit on the number of fds you can use (except it will slow down |
495 | considerably with a lot of inactive fds). It scales similarly to select, |
524 | considerably with a lot of inactive fds). It scales similarly to select, |
496 | i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for |
525 | i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for |
497 | performance tips. |
526 | performance tips. |
|
|
527 | .Sp |
|
|
528 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and |
|
|
529 | \&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR. |
498 | .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
530 | .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
499 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
531 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
500 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
532 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
501 | For few fds, this backend is a bit little slower than poll and select, |
533 | For few fds, this backend is a bit little slower than poll and select, |
502 | but it scales phenomenally better. While poll and select usually scale |
534 | but it scales phenomenally better. While poll and select usually scale |
503 | like O(total_fds) where n is the total number of fds (or the highest fd), |
535 | like O(total_fds) where n is the total number of fds (or the highest fd), |
504 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
536 | epoll scales either O(1) or O(active_fds). |
505 | of shortcomings, such as silently dropping events in some hard-to-detect |
537 | .Sp |
506 | cases and requiring a system call per fd change, no fork support and bad |
538 | The epoll mechanism deserves honorable mention as the most misdesigned |
507 | support for dup. |
539 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
540 | dropping file descriptors, requiring a system call per change per file |
|
|
541 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
542 | so on. The biggest issue is fork races, however \- if a program forks then |
|
|
543 | \&\fIboth\fR parent and child process have to recreate the epoll set, which can |
|
|
544 | take considerable time (one syscall per file descriptor) and is of course |
|
|
545 | hard to detect. |
|
|
546 | .Sp |
|
|
547 | Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work, but |
|
|
548 | of course \fIdoesn't\fR, and epoll just loves to report events for totally |
|
|
549 | \&\fIdifferent\fR file descriptors (even already closed ones, so one cannot |
|
|
550 | even remove them from the set) than registered in the set (especially |
|
|
551 | on \s-1SMP\s0 systems). Libev tries to counter these spurious notifications by |
|
|
552 | employing an additional generation counter and comparing that against the |
|
|
553 | events to filter out spurious ones, recreating the set when required. |
508 | .Sp |
554 | .Sp |
509 | While stopping, setting and starting an I/O watcher in the same iteration |
555 | While stopping, setting and starting an I/O watcher in the same iteration |
510 | will result in some caching, there is still a system call per such incident |
556 | will result in some caching, there is still a system call per such |
511 | (because the fd could point to a different file description now), so its |
557 | incident (because the same \fIfile descriptor\fR could point to a different |
512 | best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work |
558 | \&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed |
513 | very well if you register events for both fds. |
559 | file descriptors might not work very well if you register events for both |
514 | .Sp |
560 | file descriptors. |
515 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
516 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
517 | (or space) is available. |
|
|
518 | .Sp |
561 | .Sp |
519 | Best performance from this backend is achieved by not unregistering all |
562 | Best performance from this backend is achieved by not unregistering all |
520 | watchers for a file descriptor until it has been closed, if possible, i.e. |
563 | watchers for a file descriptor until it has been closed, if possible, |
521 | keep at least one watcher active per fd at all times. |
564 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
565 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
566 | extra overhead. A fork can both result in spurious notifications as well |
|
|
567 | as in libev having to destroy and recreate the epoll object, which can |
|
|
568 | take considerable time and thus should be avoided. |
|
|
569 | .Sp |
|
|
570 | All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or |
|
|
571 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
572 | the usage. So sad. |
522 | .Sp |
573 | .Sp |
523 | While nominally embeddable in other event loops, this feature is broken in |
574 | While nominally embeddable in other event loops, this feature is broken in |
524 | all kernel versions tested so far. |
575 | all kernel versions tested so far. |
|
|
576 | .Sp |
|
|
577 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
|
|
578 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
525 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
579 | .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
526 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
580 | .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
527 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
581 | .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
528 | Kqueue deserves special mention, as at the time of this writing, it |
582 | Kqueue deserves special mention, as at the time of this writing, it |
529 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
583 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
530 | with anything but sockets and pipes, except on Darwin, where of course |
584 | with anything but sockets and pipes, except on Darwin, where of course |
531 | it's completely useless). For this reason it's not being \*(L"auto-detected\*(R" |
585 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
586 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
587 | without \s-1API\s0 changes to existing programs. For this reason it's not being |
532 | unless you explicitly specify it explicitly in the flags (i.e. using |
588 | \&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using |
533 | \&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough) |
589 | \&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough) |
534 | system like NetBSD. |
590 | system like NetBSD. |
535 | .Sp |
591 | .Sp |
536 | You still can embed kqueue into a normal poll or select backend and use it |
592 | You still can embed kqueue into a normal poll or select backend and use it |
537 | only for sockets (after having made sure that sockets work with kqueue on |
593 | only for sockets (after having made sure that sockets work with kqueue on |
… | |
… | |
539 | .Sp |
595 | .Sp |
540 | It scales in the same way as the epoll backend, but the interface to the |
596 | It scales in the same way as the epoll backend, but the interface to the |
541 | kernel is more efficient (which says nothing about its actual speed, of |
597 | kernel is more efficient (which says nothing about its actual speed, of |
542 | course). While stopping, setting and starting an I/O watcher does never |
598 | course). While stopping, setting and starting an I/O watcher does never |
543 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
599 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
544 | two event changes per incident, support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it |
600 | two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (but |
545 | drops fds silently in similarly hard-to-detect cases. |
601 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
602 | cases |
546 | .Sp |
603 | .Sp |
547 | This backend usually performs well under most conditions. |
604 | This backend usually performs well under most conditions. |
548 | .Sp |
605 | .Sp |
549 | While nominally embeddable in other event loops, this doesn't work |
606 | While nominally embeddable in other event loops, this doesn't work |
550 | everywhere, so you might need to test for this. And since it is broken |
607 | everywhere, so you might need to test for this. And since it is broken |
551 | almost everywhere, you should only use it when you have a lot of sockets |
608 | almost everywhere, you should only use it when you have a lot of sockets |
552 | (for which it usually works), by embedding it into another event loop |
609 | (for which it usually works), by embedding it into another event loop |
553 | (e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR) and using it only for |
610 | (e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR (but \f(CW\*(C`poll\*(C'\fR is of course |
554 | sockets. |
611 | also broken on \s-1OS\s0 X)) and, did I mention it, using it only for sockets. |
|
|
612 | .Sp |
|
|
613 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR into an \f(CW\*(C`EVFILT_READ\*(C'\fR kevent with |
|
|
614 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR, and \f(CW\*(C`EV_WRITE\*(C'\fR into an \f(CW\*(C`EVFILT_WRITE\*(C'\fR kevent with |
|
|
615 | \&\f(CW\*(C`NOTE_EOF\*(C'\fR. |
555 | .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
616 | .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
556 | .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 |
617 | .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 |
557 | .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" |
618 | .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" |
558 | This is not implemented yet (and might never be, unless you send me an |
619 | This is not implemented yet (and might never be, unless you send me an |
559 | implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets |
620 | implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets |
… | |
… | |
572 | While this backend scales well, it requires one system call per active |
633 | While this backend scales well, it requires one system call per active |
573 | file descriptor per loop iteration. For small and medium numbers of file |
634 | file descriptor per loop iteration. For small and medium numbers of file |
574 | descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend |
635 | descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend |
575 | might perform better. |
636 | might perform better. |
576 | .Sp |
637 | .Sp |
577 | On the positive side, ignoring the spurious readiness notifications, this |
638 | On the positive side, with the exception of the spurious readiness |
578 | backend actually performed to specification in all tests and is fully |
639 | notifications, this backend actually performed fully to specification |
579 | embeddable, which is a rare feat among the OS-specific backends. |
640 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
641 | OS-specific backends (I vastly prefer correctness over speed hacks). |
|
|
642 | .Sp |
|
|
643 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
|
|
644 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
580 | .ie n .IP """EVBACKEND_ALL""" 4 |
645 | .ie n .IP """EVBACKEND_ALL""" 4 |
581 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
646 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
582 | .IX Item "EVBACKEND_ALL" |
647 | .IX Item "EVBACKEND_ALL" |
583 | Try all backends (even potentially broken ones that wouldn't be tried |
648 | Try all backends (even potentially broken ones that wouldn't be tried |
584 | with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
649 | with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
… | |
… | |
586 | .Sp |
651 | .Sp |
587 | It is definitely not recommended to use this flag. |
652 | It is definitely not recommended to use this flag. |
588 | .RE |
653 | .RE |
589 | .RS 4 |
654 | .RS 4 |
590 | .Sp |
655 | .Sp |
591 | If one or more of these are or'ed into the flags value, then only these |
656 | If one or more of the backend flags are or'ed into the flags value, |
592 | backends will be tried (in the reverse order as listed here). If none are |
657 | then only these backends will be tried (in the reverse order as listed |
593 | specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried. |
658 | here). If none are specified, all backends in \f(CW\*(C`ev_recommended_backends |
|
|
659 | ()\*(C'\fR will be tried. |
594 | .Sp |
660 | .Sp |
595 | The most typical usage is like this: |
661 | Example: This is the most typical usage. |
596 | .Sp |
662 | .Sp |
597 | .Vb 2 |
663 | .Vb 2 |
598 | \& if (!ev_default_loop (0)) |
664 | \& if (!ev_default_loop (0)) |
599 | \& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
665 | \& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
600 | .Ve |
666 | .Ve |
601 | .Sp |
667 | .Sp |
602 | Restrict libev to the select and poll backends, and do not allow |
668 | Example: Restrict libev to the select and poll backends, and do not allow |
603 | environment settings to be taken into account: |
669 | environment settings to be taken into account: |
604 | .Sp |
670 | .Sp |
605 | .Vb 1 |
671 | .Vb 1 |
606 | \& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
672 | \& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
607 | .Ve |
673 | .Ve |
608 | .Sp |
674 | .Sp |
609 | Use whatever libev has to offer, but make sure that kqueue is used if |
675 | Example: Use whatever libev has to offer, but make sure that kqueue is |
610 | available (warning, breaks stuff, best use only with your own private |
676 | used if available (warning, breaks stuff, best use only with your own |
611 | event loop and only if you know the \s-1OS\s0 supports your types of fds): |
677 | private event loop and only if you know the \s-1OS\s0 supports your types of |
|
|
678 | fds): |
612 | .Sp |
679 | .Sp |
613 | .Vb 1 |
680 | .Vb 1 |
614 | \& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
681 | \& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
615 | .Ve |
682 | .Ve |
616 | .RE |
683 | .RE |
… | |
… | |
640 | responsibility to either stop all watchers cleanly yourself \fIbefore\fR |
707 | responsibility to either stop all watchers cleanly yourself \fIbefore\fR |
641 | calling this function, or cope with the fact afterwards (which is usually |
708 | calling this function, or cope with the fact afterwards (which is usually |
642 | the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
709 | the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
643 | for example). |
710 | for example). |
644 | .Sp |
711 | .Sp |
645 | Note that certain global state, such as signal state, will not be freed by |
712 | Note that certain global state, such as signal state (and installed signal |
646 | this function, and related watchers (such as signal and child watchers) |
713 | handlers), will not be freed by this function, and related watchers (such |
647 | would need to be stopped manually. |
714 | as signal and child watchers) would need to be stopped manually. |
648 | .Sp |
715 | .Sp |
649 | In general it is not advisable to call this function except in the |
716 | In general it is not advisable to call this function except in the |
650 | rare occasion where you really need to free e.g. the signal handling |
717 | rare occasion where you really need to free e.g. the signal handling |
651 | pipe fds. If you need dynamically allocated loops it is better to use |
718 | pipe fds. If you need dynamically allocated loops it is better to use |
652 | \&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR). |
719 | \&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR). |
… | |
… | |
676 | .Ve |
743 | .Ve |
677 | .IP "ev_loop_fork (loop)" 4 |
744 | .IP "ev_loop_fork (loop)" 4 |
678 | .IX Item "ev_loop_fork (loop)" |
745 | .IX Item "ev_loop_fork (loop)" |
679 | Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by |
746 | Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by |
680 | \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop |
747 | \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop |
681 | after fork, and how you do this is entirely your own problem. |
748 | after fork that you want to re-use in the child, and how you do this is |
|
|
749 | entirely your own problem. |
682 | .IP "int ev_is_default_loop (loop)" 4 |
750 | .IP "int ev_is_default_loop (loop)" 4 |
683 | .IX Item "int ev_is_default_loop (loop)" |
751 | .IX Item "int ev_is_default_loop (loop)" |
684 | Returns true when the given loop actually is the default loop, false otherwise. |
752 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
753 | otherwise. |
685 | .IP "unsigned int ev_loop_count (loop)" 4 |
754 | .IP "unsigned int ev_loop_count (loop)" 4 |
686 | .IX Item "unsigned int ev_loop_count (loop)" |
755 | .IX Item "unsigned int ev_loop_count (loop)" |
687 | Returns the count of loop iterations for the loop, which is identical to |
756 | Returns the count of loop iterations for the loop, which is identical to |
688 | the number of times libev did poll for new events. It starts at \f(CW0\fR and |
757 | the number of times libev did poll for new events. It starts at \f(CW0\fR and |
689 | happily wraps around with enough iterations. |
758 | happily wraps around with enough iterations. |
690 | .Sp |
759 | .Sp |
691 | This value can sometimes be useful as a generation counter of sorts (it |
760 | This value can sometimes be useful as a generation counter of sorts (it |
692 | \&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with |
761 | \&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with |
693 | \&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls. |
762 | \&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls. |
|
|
763 | .IP "unsigned int ev_loop_depth (loop)" 4 |
|
|
764 | .IX Item "unsigned int ev_loop_depth (loop)" |
|
|
765 | Returns the number of times \f(CW\*(C`ev_loop\*(C'\fR was entered minus the number of |
|
|
766 | times \f(CW\*(C`ev_loop\*(C'\fR was exited, in other words, the recursion depth. |
|
|
767 | .Sp |
|
|
768 | Outside \f(CW\*(C`ev_loop\*(C'\fR, this number is zero. In a callback, this number is |
|
|
769 | \&\f(CW1\fR, unless \f(CW\*(C`ev_loop\*(C'\fR was invoked recursively (or from another thread), |
|
|
770 | in which case it is higher. |
|
|
771 | .Sp |
|
|
772 | Leaving \f(CW\*(C`ev_loop\*(C'\fR abnormally (setjmp/longjmp, cancelling the thread |
|
|
773 | etc.), doesn't count as exit. |
694 | .IP "unsigned int ev_backend (loop)" 4 |
774 | .IP "unsigned int ev_backend (loop)" 4 |
695 | .IX Item "unsigned int ev_backend (loop)" |
775 | .IX Item "unsigned int ev_backend (loop)" |
696 | Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
776 | Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
697 | use. |
777 | use. |
698 | .IP "ev_tstamp ev_now (loop)" 4 |
778 | .IP "ev_tstamp ev_now (loop)" 4 |
… | |
… | |
700 | Returns the current \*(L"event loop time\*(R", which is the time the event loop |
780 | Returns the current \*(L"event loop time\*(R", which is the time the event loop |
701 | received events and started processing them. This timestamp does not |
781 | received events and started processing them. This timestamp does not |
702 | change as long as callbacks are being processed, and this is also the base |
782 | change as long as callbacks are being processed, and this is also the base |
703 | time used for relative timers. You can treat it as the timestamp of the |
783 | time used for relative timers. You can treat it as the timestamp of the |
704 | event occurring (or more correctly, libev finding out about it). |
784 | event occurring (or more correctly, libev finding out about it). |
|
|
785 | .IP "ev_now_update (loop)" 4 |
|
|
786 | .IX Item "ev_now_update (loop)" |
|
|
787 | Establishes the current time by querying the kernel, updating the time |
|
|
788 | returned by \f(CW\*(C`ev_now ()\*(C'\fR in the progress. This is a costly operation and |
|
|
789 | is usually done automatically within \f(CW\*(C`ev_loop ()\*(C'\fR. |
|
|
790 | .Sp |
|
|
791 | This function is rarely useful, but when some event callback runs for a |
|
|
792 | very long time without entering the event loop, updating libev's idea of |
|
|
793 | the current time is a good idea. |
|
|
794 | .Sp |
|
|
795 | See also \*(L"The special problem of time updates\*(R" in the \f(CW\*(C`ev_timer\*(C'\fR section. |
|
|
796 | .IP "ev_suspend (loop)" 4 |
|
|
797 | .IX Item "ev_suspend (loop)" |
|
|
798 | .PD 0 |
|
|
799 | .IP "ev_resume (loop)" 4 |
|
|
800 | .IX Item "ev_resume (loop)" |
|
|
801 | .PD |
|
|
802 | These two functions suspend and resume a loop, for use when the loop is |
|
|
803 | not used for a while and timeouts should not be processed. |
|
|
804 | .Sp |
|
|
805 | A typical use case would be an interactive program such as a game: When |
|
|
806 | the user presses \f(CW\*(C`^Z\*(C'\fR to suspend the game and resumes it an hour later it |
|
|
807 | would be best to handle timeouts as if no time had actually passed while |
|
|
808 | the program was suspended. This can be achieved by calling \f(CW\*(C`ev_suspend\*(C'\fR |
|
|
809 | in your \f(CW\*(C`SIGTSTP\*(C'\fR handler, sending yourself a \f(CW\*(C`SIGSTOP\*(C'\fR and calling |
|
|
810 | \&\f(CW\*(C`ev_resume\*(C'\fR directly afterwards to resume timer processing. |
|
|
811 | .Sp |
|
|
812 | Effectively, all \f(CW\*(C`ev_timer\*(C'\fR watchers will be delayed by the time spend |
|
|
813 | between \f(CW\*(C`ev_suspend\*(C'\fR and \f(CW\*(C`ev_resume\*(C'\fR, and all \f(CW\*(C`ev_periodic\*(C'\fR watchers |
|
|
814 | will be rescheduled (that is, they will lose any events that would have |
|
|
815 | occured while suspended). |
|
|
816 | .Sp |
|
|
817 | After calling \f(CW\*(C`ev_suspend\*(C'\fR you \fBmust not\fR call \fIany\fR function on the |
|
|
818 | given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR |
|
|
819 | without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR. |
|
|
820 | .Sp |
|
|
821 | Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the |
|
|
822 | event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR). |
705 | .IP "ev_loop (loop, int flags)" 4 |
823 | .IP "ev_loop (loop, int flags)" 4 |
706 | .IX Item "ev_loop (loop, int flags)" |
824 | .IX Item "ev_loop (loop, int flags)" |
707 | Finally, this is it, the event handler. This function usually is called |
825 | Finally, this is it, the event handler. This function usually is called |
708 | after you initialised all your watchers and you want to start handling |
826 | after you initialised all your watchers and you want to start handling |
709 | events. |
827 | events. |
… | |
… | |
711 | If the flags argument is specified as \f(CW0\fR, it will not return until |
829 | If the flags argument is specified as \f(CW0\fR, it will not return until |
712 | either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. |
830 | either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. |
713 | .Sp |
831 | .Sp |
714 | Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than |
832 | Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than |
715 | relying on all watchers to be stopped when deciding when a program has |
833 | relying on all watchers to be stopped when deciding when a program has |
716 | finished (especially in interactive programs), but having a program that |
834 | finished (especially in interactive programs), but having a program |
717 | automatically loops as long as it has to and no longer by virtue of |
835 | that automatically loops as long as it has to and no longer by virtue |
718 | relying on its watchers stopping correctly is a thing of beauty. |
836 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
837 | beauty. |
719 | .Sp |
838 | .Sp |
720 | A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle |
839 | A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle |
721 | those events and any outstanding ones, but will not block your process in |
840 | those events and any already outstanding ones, but will not block your |
722 | case there are no events and will return after one iteration of the loop. |
841 | process in case there are no events and will return after one iteration of |
|
|
842 | the loop. |
723 | .Sp |
843 | .Sp |
724 | A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
844 | A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
725 | necessary) and will handle those and any outstanding ones. It will block |
845 | necessary) and will handle those and any already outstanding ones. It |
726 | your process until at least one new event arrives, and will return after |
846 | will block your process until at least one new event arrives (which could |
727 | one iteration of the loop. This is useful if you are waiting for some |
847 | be an event internal to libev itself, so there is no guarantee that a |
728 | external event in conjunction with something not expressible using other |
848 | user-registered callback will be called), and will return after one |
|
|
849 | iteration of the loop. |
|
|
850 | .Sp |
|
|
851 | This is useful if you are waiting for some external event in conjunction |
|
|
852 | with something not expressible using other libev watchers (i.e. "roll your |
729 | libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
853 | own \f(CW\*(C`ev_loop\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
730 | usually a better approach for this kind of thing. |
854 | usually a better approach for this kind of thing. |
731 | .Sp |
855 | .Sp |
732 | Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: |
856 | Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: |
733 | .Sp |
857 | .Sp |
734 | .Vb 10 |
858 | .Vb 10 |
735 | \& \- Before the first iteration, call any pending watchers. |
859 | \& \- Before the first iteration, call any pending watchers. |
736 | \& * If EVFLAG_FORKCHECK was used, check for a fork. |
860 | \& * If EVFLAG_FORKCHECK was used, check for a fork. |
737 | \& \- If a fork was detected, queue and call all fork watchers. |
861 | \& \- If a fork was detected (by any means), queue and call all fork watchers. |
738 | \& \- Queue and call all prepare watchers. |
862 | \& \- Queue and call all prepare watchers. |
739 | \& \- If we have been forked, recreate the kernel state. |
863 | \& \- If we have been forked, detach and recreate the kernel state |
|
|
864 | \& as to not disturb the other process. |
740 | \& \- Update the kernel state with all outstanding changes. |
865 | \& \- Update the kernel state with all outstanding changes. |
741 | \& \- Update the "event loop time". |
866 | \& \- Update the "event loop time" (ev_now ()). |
742 | \& \- Calculate for how long to sleep or block, if at all |
867 | \& \- Calculate for how long to sleep or block, if at all |
743 | \& (active idle watchers, EVLOOP_NONBLOCK or not having |
868 | \& (active idle watchers, EVLOOP_NONBLOCK or not having |
744 | \& any active watchers at all will result in not sleeping). |
869 | \& any active watchers at all will result in not sleeping). |
745 | \& \- Sleep if the I/O and timer collect interval say so. |
870 | \& \- Sleep if the I/O and timer collect interval say so. |
746 | \& \- Block the process, waiting for any events. |
871 | \& \- Block the process, waiting for any events. |
747 | \& \- Queue all outstanding I/O (fd) events. |
872 | \& \- Queue all outstanding I/O (fd) events. |
748 | \& \- Update the "event loop time" and do time jump handling. |
873 | \& \- Update the "event loop time" (ev_now ()), and do time jump adjustments. |
749 | \& \- Queue all outstanding timers. |
874 | \& \- Queue all expired timers. |
750 | \& \- Queue all outstanding periodics. |
875 | \& \- Queue all expired periodics. |
751 | \& \- If no events are pending now, queue all idle watchers. |
876 | \& \- Unless any events are pending now, queue all idle watchers. |
752 | \& \- Queue all check watchers. |
877 | \& \- Queue all check watchers. |
753 | \& \- Call all queued watchers in reverse order (i.e. check watchers first). |
878 | \& \- Call all queued watchers in reverse order (i.e. check watchers first). |
754 | \& Signals and child watchers are implemented as I/O watchers, and will |
879 | \& Signals and child watchers are implemented as I/O watchers, and will |
755 | \& be handled here by queueing them when their watcher gets executed. |
880 | \& be handled here by queueing them when their watcher gets executed. |
756 | \& \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
881 | \& \- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
… | |
… | |
763 | .Sp |
888 | .Sp |
764 | .Vb 4 |
889 | .Vb 4 |
765 | \& ... queue jobs here, make sure they register event watchers as long |
890 | \& ... queue jobs here, make sure they register event watchers as long |
766 | \& ... as they still have work to do (even an idle watcher will do..) |
891 | \& ... as they still have work to do (even an idle watcher will do..) |
767 | \& ev_loop (my_loop, 0); |
892 | \& ev_loop (my_loop, 0); |
768 | \& ... jobs done. yeah! |
893 | \& ... jobs done or somebody called unloop. yeah! |
769 | .Ve |
894 | .Ve |
770 | .IP "ev_unloop (loop, how)" 4 |
895 | .IP "ev_unloop (loop, how)" 4 |
771 | .IX Item "ev_unloop (loop, how)" |
896 | .IX Item "ev_unloop (loop, how)" |
772 | Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it |
897 | Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it |
773 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
898 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
774 | \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
899 | \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
775 | \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
900 | \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
776 | .Sp |
901 | .Sp |
777 | This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again. |
902 | This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_loop\*(C'\fR again. |
|
|
903 | .Sp |
|
|
904 | It is safe to call \f(CW\*(C`ev_unloop\*(C'\fR from otuside any \f(CW\*(C`ev_loop\*(C'\fR calls. |
778 | .IP "ev_ref (loop)" 4 |
905 | .IP "ev_ref (loop)" 4 |
779 | .IX Item "ev_ref (loop)" |
906 | .IX Item "ev_ref (loop)" |
780 | .PD 0 |
907 | .PD 0 |
781 | .IP "ev_unref (loop)" 4 |
908 | .IP "ev_unref (loop)" 4 |
782 | .IX Item "ev_unref (loop)" |
909 | .IX Item "ev_unref (loop)" |
783 | .PD |
910 | .PD |
784 | Ref/unref can be used to add or remove a reference count on the event |
911 | Ref/unref can be used to add or remove a reference count on the event |
785 | loop: Every watcher keeps one reference, and as long as the reference |
912 | loop: Every watcher keeps one reference, and as long as the reference |
786 | count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have |
913 | count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. |
|
|
914 | .Sp |
787 | a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from |
915 | If you have a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR |
788 | returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For |
916 | from returning, call \fIev_unref()\fR after starting, and \fIev_ref()\fR before |
|
|
917 | stopping it. |
|
|
918 | .Sp |
789 | example, libev itself uses this for its internal signal pipe: It is not |
919 | As an example, libev itself uses this for its internal signal pipe: It |
790 | visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if |
920 | is not visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from |
791 | no event watchers registered by it are active. It is also an excellent |
921 | exiting if no event watchers registered by it are active. It is also an |
792 | way to do this for generic recurring timers or from within third-party |
922 | excellent way to do this for generic recurring timers or from within |
793 | libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR |
923 | third-party libraries. Just remember to \fIunref after start\fR and \fIref |
794 | (but only if the watcher wasn't active before, or was active before, |
924 | before stop\fR (but only if the watcher wasn't active before, or was active |
795 | respectively). |
925 | before, respectively. Note also that libev might stop watchers itself |
|
|
926 | (e.g. non-repeating timers) in which case you have to \f(CW\*(C`ev_ref\*(C'\fR |
|
|
927 | in the callback). |
796 | .Sp |
928 | .Sp |
797 | Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR |
929 | Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR |
798 | running when nothing else is active. |
930 | running when nothing else is active. |
799 | .Sp |
931 | .Sp |
800 | .Vb 4 |
932 | .Vb 4 |
801 | \& struct ev_signal exitsig; |
933 | \& ev_signal exitsig; |
802 | \& ev_signal_init (&exitsig, sig_cb, SIGINT); |
934 | \& ev_signal_init (&exitsig, sig_cb, SIGINT); |
803 | \& ev_signal_start (loop, &exitsig); |
935 | \& ev_signal_start (loop, &exitsig); |
804 | \& evf_unref (loop); |
936 | \& evf_unref (loop); |
805 | .Ve |
937 | .Ve |
806 | .Sp |
938 | .Sp |
… | |
… | |
815 | .PD 0 |
947 | .PD 0 |
816 | .IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4 |
948 | .IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4 |
817 | .IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" |
949 | .IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" |
818 | .PD |
950 | .PD |
819 | These advanced functions influence the time that libev will spend waiting |
951 | These advanced functions influence the time that libev will spend waiting |
820 | for events. Both are by default \f(CW0\fR, meaning that libev will try to |
952 | for events. Both time intervals are by default \f(CW0\fR, meaning that libev |
821 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
953 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
954 | latency. |
822 | .Sp |
955 | .Sp |
823 | Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR) |
956 | Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR) |
824 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
957 | allows libev to delay invocation of I/O and timer/periodic callbacks |
825 | increase efficiency of loop iterations. |
958 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
959 | opportunities). |
826 | .Sp |
960 | .Sp |
827 | The background is that sometimes your program runs just fast enough to |
961 | The idea is that sometimes your program runs just fast enough to handle |
828 | handle one (or very few) event(s) per loop iteration. While this makes |
962 | one (or very few) event(s) per loop iteration. While this makes the |
829 | the program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new |
963 | program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new |
830 | events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high |
964 | events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high |
831 | overhead for the actual polling but can deliver many events at once. |
965 | overhead for the actual polling but can deliver many events at once. |
832 | .Sp |
966 | .Sp |
833 | By setting a higher \fIio collect interval\fR you allow libev to spend more |
967 | By setting a higher \fIio collect interval\fR you allow libev to spend more |
834 | time collecting I/O events, so you can handle more events per iteration, |
968 | time collecting I/O events, so you can handle more events per iteration, |
835 | at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and |
969 | at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and |
836 | \&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will |
970 | \&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will |
837 | introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. |
971 | introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The |
|
|
972 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
973 | once per this interval, on average. |
838 | .Sp |
974 | .Sp |
839 | Likewise, by setting a higher \fItimeout collect interval\fR you allow libev |
975 | Likewise, by setting a higher \fItimeout collect interval\fR you allow libev |
840 | to spend more time collecting timeouts, at the expense of increased |
976 | to spend more time collecting timeouts, at the expense of increased |
841 | latency (the watcher callback will be called later). \f(CW\*(C`ev_io\*(C'\fR watchers |
977 | latency/jitter/inexactness (the watcher callback will be called |
842 | will not be affected. Setting this to a non-null value will not introduce |
978 | later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null |
843 | any overhead in libev. |
979 | value will not introduce any overhead in libev. |
844 | .Sp |
980 | .Sp |
845 | Many (busy) programs can usually benefit by setting the I/O collect |
981 | Many (busy) programs can usually benefit by setting the I/O collect |
846 | interval to a value near \f(CW0.1\fR or so, which is often enough for |
982 | interval to a value near \f(CW0.1\fR or so, which is often enough for |
847 | interactive servers (of course not for games), likewise for timeouts. It |
983 | interactive servers (of course not for games), likewise for timeouts. It |
848 | usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR, |
984 | usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR, |
849 | as this approaches the timing granularity of most systems. |
985 | as this approaches the timing granularity of most systems. Note that if |
|
|
986 | you do transactions with the outside world and you can't increase the |
|
|
987 | parallelity, then this setting will limit your transaction rate (if you |
|
|
988 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
989 | then you can't do more than 100 transations per second). |
|
|
990 | .Sp |
|
|
991 | Setting the \fItimeout collect interval\fR can improve the opportunity for |
|
|
992 | saving power, as the program will \*(L"bundle\*(R" timer callback invocations that |
|
|
993 | are \*(L"near\*(R" in time together, by delaying some, thus reducing the number of |
|
|
994 | times the process sleeps and wakes up again. Another useful technique to |
|
|
995 | reduce iterations/wake\-ups is to use \f(CW\*(C`ev_periodic\*(C'\fR watchers and make sure |
|
|
996 | they fire on, say, one-second boundaries only. |
|
|
997 | .Sp |
|
|
998 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
999 | more often than 100 times per second: |
|
|
1000 | .Sp |
|
|
1001 | .Vb 2 |
|
|
1002 | \& ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
1003 | \& ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
1004 | .Ve |
|
|
1005 | .IP "ev_invoke_pending (loop)" 4 |
|
|
1006 | .IX Item "ev_invoke_pending (loop)" |
|
|
1007 | This call will simply invoke all pending watchers while resetting their |
|
|
1008 | pending state. Normally, \f(CW\*(C`ev_loop\*(C'\fR does this automatically when required, |
|
|
1009 | but when overriding the invoke callback this call comes handy. |
|
|
1010 | .IP "int ev_pending_count (loop)" 4 |
|
|
1011 | .IX Item "int ev_pending_count (loop)" |
|
|
1012 | Returns the number of pending watchers \- zero indicates that no watchers |
|
|
1013 | are pending. |
|
|
1014 | .IP "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(\s-1EV_P\s0))" 4 |
|
|
1015 | .IX Item "ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))" |
|
|
1016 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
1017 | invoking all pending watchers when there are any, \f(CW\*(C`ev_loop\*(C'\fR will call |
|
|
1018 | this callback instead. This is useful, for example, when you want to |
|
|
1019 | invoke the actual watchers inside another context (another thread etc.). |
|
|
1020 | .Sp |
|
|
1021 | If you want to reset the callback, use \f(CW\*(C`ev_invoke_pending\*(C'\fR as new |
|
|
1022 | callback. |
|
|
1023 | .IP "ev_set_loop_release_cb (loop, void (*release)(\s-1EV_P\s0), void (*acquire)(\s-1EV_P\s0))" 4 |
|
|
1024 | .IX Item "ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))" |
|
|
1025 | Sometimes you want to share the same loop between multiple threads. This |
|
|
1026 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
1027 | each call to a libev function. |
|
|
1028 | .Sp |
|
|
1029 | However, \f(CW\*(C`ev_loop\*(C'\fR can run an indefinite time, so it is not feasible to |
|
|
1030 | wait for it to return. One way around this is to wake up the loop via |
|
|
1031 | \&\f(CW\*(C`ev_unloop\*(C'\fR and \f(CW\*(C`av_async_send\*(C'\fR, another way is to set these \fIrelease\fR |
|
|
1032 | and \fIacquire\fR callbacks on the loop. |
|
|
1033 | .Sp |
|
|
1034 | When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is |
|
|
1035 | suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just |
|
|
1036 | afterwards. |
|
|
1037 | .Sp |
|
|
1038 | Ideally, \f(CW\*(C`release\*(C'\fR will just call your mutex_unlock function, and |
|
|
1039 | \&\f(CW\*(C`acquire\*(C'\fR will just call the mutex_lock function again. |
|
|
1040 | .Sp |
|
|
1041 | While event loop modifications are allowed between invocations of |
|
|
1042 | \&\f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR (that's their only purpose after all), no |
|
|
1043 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
1044 | have no effect on the set of file descriptors being watched, or the time |
|
|
1045 | waited. USe an \f(CW\*(C`ev_async\*(C'\fR watcher to wake up \f(CW\*(C`ev_loop\*(C'\fR when you want it |
|
|
1046 | to take note of any changes you made. |
|
|
1047 | .Sp |
|
|
1048 | In theory, threads executing \f(CW\*(C`ev_loop\*(C'\fR will be async-cancel safe between |
|
|
1049 | invocations of \f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR. |
|
|
1050 | .Sp |
|
|
1051 | See also the locking example in the \f(CW\*(C`THREADS\*(C'\fR section later in this |
|
|
1052 | document. |
|
|
1053 | .IP "ev_set_userdata (loop, void *data)" 4 |
|
|
1054 | .IX Item "ev_set_userdata (loop, void *data)" |
|
|
1055 | .PD 0 |
|
|
1056 | .IP "ev_userdata (loop)" 4 |
|
|
1057 | .IX Item "ev_userdata (loop)" |
|
|
1058 | .PD |
|
|
1059 | Set and retrieve a single \f(CW\*(C`void *\*(C'\fR associated with a loop. When |
|
|
1060 | \&\f(CW\*(C`ev_set_userdata\*(C'\fR has never been called, then \f(CW\*(C`ev_userdata\*(C'\fR returns |
|
|
1061 | \&\f(CW0.\fR |
|
|
1062 | .Sp |
|
|
1063 | These two functions can be used to associate arbitrary data with a loop, |
|
|
1064 | and are intended solely for the \f(CW\*(C`invoke_pending_cb\*(C'\fR, \f(CW\*(C`release\*(C'\fR and |
|
|
1065 | \&\f(CW\*(C`acquire\*(C'\fR callbacks described above, but of course can be (ab\-)used for |
|
|
1066 | any other purpose as well. |
850 | .IP "ev_loop_verify (loop)" 4 |
1067 | .IP "ev_loop_verify (loop)" 4 |
851 | .IX Item "ev_loop_verify (loop)" |
1068 | .IX Item "ev_loop_verify (loop)" |
852 | This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been |
1069 | This function only does something when \f(CW\*(C`EV_VERIFY\*(C'\fR support has been |
853 | compiled in. It tries to go through all internal structures and checks |
1070 | compiled in, which is the default for non-minimal builds. It tries to go |
854 | them for validity. If anything is found to be inconsistent, it will print |
1071 | through all internal structures and checks them for validity. If anything |
855 | an error message to standard error and call \f(CW\*(C`abort ()\*(C'\fR. |
1072 | is found to be inconsistent, it will print an error message to standard |
|
|
1073 | error and call \f(CW\*(C`abort ()\*(C'\fR. |
856 | .Sp |
1074 | .Sp |
857 | This can be used to catch bugs inside libev itself: under normal |
1075 | This can be used to catch bugs inside libev itself: under normal |
858 | circumstances, this function will never abort as of course libev keeps its |
1076 | circumstances, this function will never abort as of course libev keeps its |
859 | data structures consistent. |
1077 | data structures consistent. |
860 | .SH "ANATOMY OF A WATCHER" |
1078 | .SH "ANATOMY OF A WATCHER" |
861 | .IX Header "ANATOMY OF A WATCHER" |
1079 | .IX Header "ANATOMY OF A WATCHER" |
|
|
1080 | In the following description, uppercase \f(CW\*(C`TYPE\*(C'\fR in names stands for the |
|
|
1081 | watcher type, e.g. \f(CW\*(C`ev_TYPE_start\*(C'\fR can mean \f(CW\*(C`ev_timer_start\*(C'\fR for timer |
|
|
1082 | watchers and \f(CW\*(C`ev_io_start\*(C'\fR for I/O watchers. |
|
|
1083 | .PP |
862 | A watcher is a structure that you create and register to record your |
1084 | A watcher is a structure that you create and register to record your |
863 | interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
1085 | interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
864 | become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
1086 | become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
865 | .PP |
1087 | .PP |
866 | .Vb 5 |
1088 | .Vb 5 |
867 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1089 | \& static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
868 | \& { |
1090 | \& { |
869 | \& ev_io_stop (w); |
1091 | \& ev_io_stop (w); |
870 | \& ev_unloop (loop, EVUNLOOP_ALL); |
1092 | \& ev_unloop (loop, EVUNLOOP_ALL); |
871 | \& } |
1093 | \& } |
872 | \& |
1094 | \& |
873 | \& struct ev_loop *loop = ev_default_loop (0); |
1095 | \& struct ev_loop *loop = ev_default_loop (0); |
|
|
1096 | \& |
874 | \& struct ev_io stdin_watcher; |
1097 | \& ev_io stdin_watcher; |
|
|
1098 | \& |
875 | \& ev_init (&stdin_watcher, my_cb); |
1099 | \& ev_init (&stdin_watcher, my_cb); |
876 | \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1100 | \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
877 | \& ev_io_start (loop, &stdin_watcher); |
1101 | \& ev_io_start (loop, &stdin_watcher); |
|
|
1102 | \& |
878 | \& ev_loop (loop, 0); |
1103 | \& ev_loop (loop, 0); |
879 | .Ve |
1104 | .Ve |
880 | .PP |
1105 | .PP |
881 | As you can see, you are responsible for allocating the memory for your |
1106 | As you can see, you are responsible for allocating the memory for your |
882 | watcher structures (and it is usually a bad idea to do this on the stack, |
1107 | watcher structures (and it is \fIusually\fR a bad idea to do this on the |
883 | although this can sometimes be quite valid). |
1108 | stack). |
|
|
1109 | .PP |
|
|
1110 | Each watcher has an associated watcher structure (called \f(CW\*(C`struct ev_TYPE\*(C'\fR |
|
|
1111 | or simply \f(CW\*(C`ev_TYPE\*(C'\fR, as typedefs are provided for all watcher structs). |
884 | .PP |
1112 | .PP |
885 | Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
1113 | Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
886 | (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
1114 | (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
887 | callback gets invoked each time the event occurs (or, in the case of I/O |
1115 | callback gets invoked each time the event occurs (or, in the case of I/O |
888 | watchers, each time the event loop detects that the file descriptor given |
1116 | watchers, each time the event loop detects that the file descriptor given |
889 | is readable and/or writable). |
1117 | is readable and/or writable). |
890 | .PP |
1118 | .PP |
891 | Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro |
1119 | Each watcher type further has its own \f(CW\*(C`ev_TYPE_set (watcher *, ...)\*(C'\fR |
892 | with arguments specific to this watcher type. There is also a macro |
1120 | macro to configure it, with arguments specific to the watcher type. There |
893 | to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init |
1121 | is also a macro to combine initialisation and setting in one call: \f(CW\*(C`ev_TYPE_init (watcher *, callback, ...)\*(C'\fR. |
894 | (watcher *, callback, ...)\*(C'\fR. |
|
|
895 | .PP |
1122 | .PP |
896 | To make the watcher actually watch out for events, you have to start it |
1123 | To make the watcher actually watch out for events, you have to start it |
897 | with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher |
1124 | with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher |
898 | *)\*(C'\fR), and you can stop watching for events at any time by calling the |
1125 | *)\*(C'\fR), and you can stop watching for events at any time by calling the |
899 | corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. |
1126 | corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR. |
900 | .PP |
1127 | .PP |
901 | As long as your watcher is active (has been started but not stopped) you |
1128 | As long as your watcher is active (has been started but not stopped) you |
902 | must not touch the values stored in it. Most specifically you must never |
1129 | must not touch the values stored in it. Most specifically you must never |
903 | reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro. |
1130 | reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro. |
904 | .PP |
1131 | .PP |
905 | Each and every callback receives the event loop pointer as first, the |
1132 | Each and every callback receives the event loop pointer as first, the |
906 | registered watcher structure as second, and a bitset of received events as |
1133 | registered watcher structure as second, and a bitset of received events as |
907 | third argument. |
1134 | third argument. |
908 | .PP |
1135 | .PP |
… | |
… | |
969 | \&\f(CW\*(C`ev_fork\*(C'\fR). |
1196 | \&\f(CW\*(C`ev_fork\*(C'\fR). |
970 | .ie n .IP """EV_ASYNC""" 4 |
1197 | .ie n .IP """EV_ASYNC""" 4 |
971 | .el .IP "\f(CWEV_ASYNC\fR" 4 |
1198 | .el .IP "\f(CWEV_ASYNC\fR" 4 |
972 | .IX Item "EV_ASYNC" |
1199 | .IX Item "EV_ASYNC" |
973 | The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR). |
1200 | The given async watcher has been asynchronously notified (see \f(CW\*(C`ev_async\*(C'\fR). |
|
|
1201 | .ie n .IP """EV_CUSTOM""" 4 |
|
|
1202 | .el .IP "\f(CWEV_CUSTOM\fR" 4 |
|
|
1203 | .IX Item "EV_CUSTOM" |
|
|
1204 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1205 | by libev users to signal watchers (e.g. via \f(CW\*(C`ev_feed_event\*(C'\fR). |
974 | .ie n .IP """EV_ERROR""" 4 |
1206 | .ie n .IP """EV_ERROR""" 4 |
975 | .el .IP "\f(CWEV_ERROR\fR" 4 |
1207 | .el .IP "\f(CWEV_ERROR\fR" 4 |
976 | .IX Item "EV_ERROR" |
1208 | .IX Item "EV_ERROR" |
977 | An unspecified error has occurred, the watcher has been stopped. This might |
1209 | An unspecified error has occurred, the watcher has been stopped. This might |
978 | happen because the watcher could not be properly started because libev |
1210 | happen because the watcher could not be properly started because libev |
979 | ran out of memory, a file descriptor was found to be closed or any other |
1211 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1212 | problem. Libev considers these application bugs. |
|
|
1213 | .Sp |
980 | problem. You best act on it by reporting the problem and somehow coping |
1214 | You best act on it by reporting the problem and somehow coping with the |
981 | with the watcher being stopped. |
1215 | watcher being stopped. Note that well-written programs should not receive |
|
|
1216 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1217 | bug in your program. |
982 | .Sp |
1218 | .Sp |
983 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, |
1219 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for |
984 | for example it might indicate that a fd is readable or writable, and if |
1220 | example it might indicate that a fd is readable or writable, and if your |
985 | your callbacks is well-written it can just attempt the operation and cope |
1221 | callbacks is well-written it can just attempt the operation and cope with |
986 | with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded |
1222 | the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded |
987 | programs, though, so beware. |
1223 | programs, though, as the fd could already be closed and reused for another |
|
|
1224 | thing, so beware. |
988 | .Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
1225 | .SS "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
989 | .IX Subsection "GENERIC WATCHER FUNCTIONS" |
1226 | .IX Subsection "GENERIC WATCHER FUNCTIONS" |
990 | In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, |
|
|
991 | e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers. |
|
|
992 | .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
1227 | .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
993 | .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
1228 | .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
994 | .IX Item "ev_init (ev_TYPE *watcher, callback)" |
1229 | .IX Item "ev_init (ev_TYPE *watcher, callback)" |
995 | This macro initialises the generic portion of a watcher. The contents |
1230 | This macro initialises the generic portion of a watcher. The contents |
996 | of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
1231 | of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
… | |
… | |
1000 | which rolls both calls into one. |
1235 | which rolls both calls into one. |
1001 | .Sp |
1236 | .Sp |
1002 | You can reinitialise a watcher at any time as long as it has been stopped |
1237 | You can reinitialise a watcher at any time as long as it has been stopped |
1003 | (or never started) and there are no pending events outstanding. |
1238 | (or never started) and there are no pending events outstanding. |
1004 | .Sp |
1239 | .Sp |
1005 | The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, |
1240 | The callback is always of type \f(CW\*(C`void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
1006 | int revents)\*(C'\fR. |
1241 | int revents)\*(C'\fR. |
|
|
1242 | .Sp |
|
|
1243 | Example: Initialise an \f(CW\*(C`ev_io\*(C'\fR watcher in two steps. |
|
|
1244 | .Sp |
|
|
1245 | .Vb 3 |
|
|
1246 | \& ev_io w; |
|
|
1247 | \& ev_init (&w, my_cb); |
|
|
1248 | \& ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1249 | .Ve |
1007 | .ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 |
1250 | .ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 |
1008 | .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 |
1251 | .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 |
1009 | .IX Item "ev_TYPE_set (ev_TYPE *, [args])" |
1252 | .IX Item "ev_TYPE_set (ev_TYPE *, [args])" |
1010 | This macro initialises the type-specific parts of a watcher. You need to |
1253 | This macro initialises the type-specific parts of a watcher. You need to |
1011 | call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can |
1254 | call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can |
… | |
… | |
1013 | macro on a watcher that is active (it can be pending, however, which is a |
1256 | macro on a watcher that is active (it can be pending, however, which is a |
1014 | difference to the \f(CW\*(C`ev_init\*(C'\fR macro). |
1257 | difference to the \f(CW\*(C`ev_init\*(C'\fR macro). |
1015 | .Sp |
1258 | .Sp |
1016 | Although some watcher types do not have type-specific arguments |
1259 | Although some watcher types do not have type-specific arguments |
1017 | (e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro. |
1260 | (e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro. |
|
|
1261 | .Sp |
|
|
1262 | See \f(CW\*(C`ev_init\*(C'\fR, above, for an example. |
1018 | .ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4 |
1263 | .ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4 |
1019 | .el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4 |
1264 | .el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4 |
1020 | .IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])" |
1265 | .IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])" |
1021 | This convenience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro |
1266 | This convenience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro |
1022 | calls into a single call. This is the most convenient method to initialise |
1267 | calls into a single call. This is the most convenient method to initialise |
1023 | a watcher. The same limitations apply, of course. |
1268 | a watcher. The same limitations apply, of course. |
|
|
1269 | .Sp |
|
|
1270 | Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step. |
|
|
1271 | .Sp |
|
|
1272 | .Vb 1 |
|
|
1273 | \& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1274 | .Ve |
1024 | .ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 |
1275 | .ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 |
1025 | .el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 |
1276 | .el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 |
1026 | .IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" |
1277 | .IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" |
1027 | Starts (activates) the given watcher. Only active watchers will receive |
1278 | Starts (activates) the given watcher. Only active watchers will receive |
1028 | events. If the watcher is already active nothing will happen. |
1279 | events. If the watcher is already active nothing will happen. |
|
|
1280 | .Sp |
|
|
1281 | Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this |
|
|
1282 | whole section. |
|
|
1283 | .Sp |
|
|
1284 | .Vb 1 |
|
|
1285 | \& ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1286 | .Ve |
1029 | .ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 |
1287 | .ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 |
1030 | .el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 |
1288 | .el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 |
1031 | .IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" |
1289 | .IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" |
1032 | Stops the given watcher again (if active) and clears the pending |
1290 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1291 | the watcher was active or not). |
|
|
1292 | .Sp |
1033 | status. It is possible that stopped watchers are pending (for example, |
1293 | It is possible that stopped watchers are pending \- for example, |
1034 | non-repeating timers are being stopped when they become pending), but |
1294 | non-repeating timers are being stopped when they become pending \- but |
1035 | \&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If |
1295 | calling \f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor |
1036 | you want to free or reuse the memory used by the watcher it is therefore a |
1296 | pending. If you want to free or reuse the memory used by the watcher it is |
1037 | good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
1297 | therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
1038 | .IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
1298 | .IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
1039 | .IX Item "bool ev_is_active (ev_TYPE *watcher)" |
1299 | .IX Item "bool ev_is_active (ev_TYPE *watcher)" |
1040 | Returns a true value iff the watcher is active (i.e. it has been started |
1300 | Returns a true value iff the watcher is active (i.e. it has been started |
1041 | and not yet been stopped). As long as a watcher is active you must not modify |
1301 | and not yet been stopped). As long as a watcher is active you must not modify |
1042 | it. |
1302 | it. |
… | |
… | |
1065 | integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR |
1325 | integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR |
1066 | (default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked |
1326 | (default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked |
1067 | before watchers with lower priority, but priority will not keep watchers |
1327 | before watchers with lower priority, but priority will not keep watchers |
1068 | from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). |
1328 | from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers). |
1069 | .Sp |
1329 | .Sp |
1070 | This means that priorities are \fIonly\fR used for ordering callback |
|
|
1071 | invocation after new events have been received. This is useful, for |
|
|
1072 | example, to reduce latency after idling, or more often, to bind two |
|
|
1073 | watchers on the same event and make sure one is called first. |
|
|
1074 | .Sp |
|
|
1075 | If you need to suppress invocation when higher priority events are pending |
1330 | If you need to suppress invocation when higher priority events are pending |
1076 | you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. |
1331 | you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality. |
1077 | .Sp |
1332 | .Sp |
1078 | You \fImust not\fR change the priority of a watcher as long as it is active or |
1333 | You \fImust not\fR change the priority of a watcher as long as it is active or |
1079 | pending. |
1334 | pending. |
1080 | .Sp |
1335 | .Sp |
|
|
1336 | Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is |
|
|
1337 | fine, as long as you do not mind that the priority value you query might |
|
|
1338 | or might not have been clamped to the valid range. |
|
|
1339 | .Sp |
1081 | The default priority used by watchers when no priority has been set is |
1340 | The default priority used by watchers when no priority has been set is |
1082 | always \f(CW0\fR, which is supposed to not be too high and not be too low :). |
1341 | always \f(CW0\fR, which is supposed to not be too high and not be too low :). |
1083 | .Sp |
1342 | .Sp |
1084 | Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is |
1343 | See \*(L"\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0\*(R", below, for a more thorough treatment of |
1085 | fine, as long as you do not mind that the priority value you query might |
1344 | priorities. |
1086 | or might not have been adjusted to be within valid range. |
|
|
1087 | .IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 |
1345 | .IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4 |
1088 | .IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" |
1346 | .IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)" |
1089 | Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither |
1347 | Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither |
1090 | \&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback |
1348 | \&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback |
1091 | can deal with that fact. |
1349 | can deal with that fact, as both are simply passed through to the |
|
|
1350 | callback. |
1092 | .IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4 |
1351 | .IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4 |
1093 | .IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)" |
1352 | .IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)" |
1094 | If the watcher is pending, this function returns clears its pending status |
1353 | If the watcher is pending, this function clears its pending status and |
1095 | and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the |
1354 | returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the |
1096 | watcher isn't pending it does nothing and returns \f(CW0\fR. |
1355 | watcher isn't pending it does nothing and returns \f(CW0\fR. |
|
|
1356 | .Sp |
|
|
1357 | Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its |
|
|
1358 | callback to be invoked, which can be accomplished with this function. |
1097 | .Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
1359 | .SS "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
1098 | .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
1360 | .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
1099 | Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change |
1361 | Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change |
1100 | and read at any time, libev will completely ignore it. This can be used |
1362 | and read at any time: libev will completely ignore it. This can be used |
1101 | to associate arbitrary data with your watcher. If you need more data and |
1363 | to associate arbitrary data with your watcher. If you need more data and |
1102 | don't want to allocate memory and store a pointer to it in that data |
1364 | don't want to allocate memory and store a pointer to it in that data |
1103 | member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
1365 | member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
1104 | data: |
1366 | data: |
1105 | .PP |
1367 | .PP |
1106 | .Vb 7 |
1368 | .Vb 7 |
1107 | \& struct my_io |
1369 | \& struct my_io |
1108 | \& { |
1370 | \& { |
1109 | \& struct ev_io io; |
1371 | \& ev_io io; |
1110 | \& int otherfd; |
1372 | \& int otherfd; |
1111 | \& void *somedata; |
1373 | \& void *somedata; |
1112 | \& struct whatever *mostinteresting; |
1374 | \& struct whatever *mostinteresting; |
1113 | \& } |
1375 | \& }; |
|
|
1376 | \& |
|
|
1377 | \& ... |
|
|
1378 | \& struct my_io w; |
|
|
1379 | \& ev_io_init (&w.io, my_cb, fd, EV_READ); |
1114 | .Ve |
1380 | .Ve |
1115 | .PP |
1381 | .PP |
1116 | And since your callback will be called with a pointer to the watcher, you |
1382 | And since your callback will be called with a pointer to the watcher, you |
1117 | can cast it back to your own type: |
1383 | can cast it back to your own type: |
1118 | .PP |
1384 | .PP |
1119 | .Vb 5 |
1385 | .Vb 5 |
1120 | \& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1386 | \& static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1121 | \& { |
1387 | \& { |
1122 | \& struct my_io *w = (struct my_io *)w_; |
1388 | \& struct my_io *w = (struct my_io *)w_; |
1123 | \& ... |
1389 | \& ... |
1124 | \& } |
1390 | \& } |
1125 | .Ve |
1391 | .Ve |
1126 | .PP |
1392 | .PP |
1127 | More interesting and less C\-conformant ways of casting your callback type |
1393 | More interesting and less C\-conformant ways of casting your callback type |
1128 | instead have been omitted. |
1394 | instead have been omitted. |
1129 | .PP |
1395 | .PP |
1130 | Another common scenario is having some data structure with multiple |
1396 | Another common scenario is to use some data structure with multiple |
1131 | watchers: |
1397 | embedded watchers: |
1132 | .PP |
1398 | .PP |
1133 | .Vb 6 |
1399 | .Vb 6 |
1134 | \& struct my_biggy |
1400 | \& struct my_biggy |
1135 | \& { |
1401 | \& { |
1136 | \& int some_data; |
1402 | \& int some_data; |
1137 | \& ev_timer t1; |
1403 | \& ev_timer t1; |
1138 | \& ev_timer t2; |
1404 | \& ev_timer t2; |
1139 | \& } |
1405 | \& } |
1140 | .Ve |
1406 | .Ve |
1141 | .PP |
1407 | .PP |
1142 | In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated, |
1408 | In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more |
1143 | you need to use \f(CW\*(C`offsetof\*(C'\fR: |
1409 | complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct |
|
|
1410 | in the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies), or you need to use |
|
|
1411 | some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for real |
|
|
1412 | programmers): |
1144 | .PP |
1413 | .PP |
1145 | .Vb 1 |
1414 | .Vb 1 |
1146 | \& #include <stddef.h> |
1415 | \& #include <stddef.h> |
1147 | \& |
1416 | \& |
1148 | \& static void |
1417 | \& static void |
1149 | \& t1_cb (EV_P_ struct ev_timer *w, int revents) |
1418 | \& t1_cb (EV_P_ ev_timer *w, int revents) |
1150 | \& { |
1419 | \& { |
1151 | \& struct my_biggy big = (struct my_biggy * |
1420 | \& struct my_biggy big = (struct my_biggy *) |
1152 | \& (((char *)w) \- offsetof (struct my_biggy, t1)); |
1421 | \& (((char *)w) \- offsetof (struct my_biggy, t1)); |
1153 | \& } |
1422 | \& } |
1154 | \& |
1423 | \& |
1155 | \& static void |
1424 | \& static void |
1156 | \& t2_cb (EV_P_ struct ev_timer *w, int revents) |
1425 | \& t2_cb (EV_P_ ev_timer *w, int revents) |
1157 | \& { |
1426 | \& { |
1158 | \& struct my_biggy big = (struct my_biggy * |
1427 | \& struct my_biggy big = (struct my_biggy *) |
1159 | \& (((char *)w) \- offsetof (struct my_biggy, t2)); |
1428 | \& (((char *)w) \- offsetof (struct my_biggy, t2)); |
1160 | \& } |
1429 | \& } |
1161 | .Ve |
1430 | .Ve |
|
|
1431 | .SS "\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0" |
|
|
1432 | .IX Subsection "WATCHER PRIORITY MODELS" |
|
|
1433 | Many event loops support \fIwatcher priorities\fR, which are usually small |
|
|
1434 | integers that influence the ordering of event callback invocation |
|
|
1435 | between watchers in some way, all else being equal. |
|
|
1436 | .PP |
|
|
1437 | In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its |
|
|
1438 | description for the more technical details such as the actual priority |
|
|
1439 | range. |
|
|
1440 | .PP |
|
|
1441 | There are two common ways how these these priorities are being interpreted |
|
|
1442 | by event loops: |
|
|
1443 | .PP |
|
|
1444 | In the more common lock-out model, higher priorities \*(L"lock out\*(R" invocation |
|
|
1445 | of lower priority watchers, which means as long as higher priority |
|
|
1446 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1447 | .PP |
|
|
1448 | The less common only-for-ordering model uses priorities solely to order |
|
|
1449 | callback invocation within a single event loop iteration: Higher priority |
|
|
1450 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1451 | before polling for new events. |
|
|
1452 | .PP |
|
|
1453 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1454 | except for idle watchers (which use the lock-out model). |
|
|
1455 | .PP |
|
|
1456 | The rationale behind this is that implementing the lock-out model for |
|
|
1457 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1458 | libraries will just poll for the same events again and again as long as |
|
|
1459 | their callbacks have not been executed, which is very inefficient in the |
|
|
1460 | common case of one high-priority watcher locking out a mass of lower |
|
|
1461 | priority ones. |
|
|
1462 | .PP |
|
|
1463 | Static (ordering) priorities are most useful when you have two or more |
|
|
1464 | watchers handling the same resource: a typical usage example is having an |
|
|
1465 | \&\f(CW\*(C`ev_io\*(C'\fR watcher to receive data, and an associated \f(CW\*(C`ev_timer\*(C'\fR to handle |
|
|
1466 | timeouts. Under load, data might be received while the program handles |
|
|
1467 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1468 | handler will be executed before checking for data. In that case, giving |
|
|
1469 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1470 | handled first even under adverse conditions (which is usually, but not |
|
|
1471 | always, what you want). |
|
|
1472 | .PP |
|
|
1473 | Since idle watchers use the \*(L"lock-out\*(R" model, meaning that idle watchers |
|
|
1474 | will only be executed when no same or higher priority watchers have |
|
|
1475 | received events, they can be used to implement the \*(L"lock-out\*(R" model when |
|
|
1476 | required. |
|
|
1477 | .PP |
|
|
1478 | For example, to emulate how many other event libraries handle priorities, |
|
|
1479 | you can associate an \f(CW\*(C`ev_idle\*(C'\fR watcher to each such watcher, and in |
|
|
1480 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1481 | processing is done in the idle watcher callback. This causes libev to |
|
|
1482 | continously poll and process kernel event data for the watcher, but when |
|
|
1483 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1484 | workable. |
|
|
1485 | .PP |
|
|
1486 | Usually, however, the lock-out model implemented that way will perform |
|
|
1487 | miserably under the type of load it was designed to handle. In that case, |
|
|
1488 | it might be preferable to stop the real watcher before starting the |
|
|
1489 | idle watcher, so the kernel will not have to process the event in case |
|
|
1490 | the actual processing will be delayed for considerable time. |
|
|
1491 | .PP |
|
|
1492 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1493 | priority than the default, and which should only process data when no |
|
|
1494 | other events are pending: |
|
|
1495 | .PP |
|
|
1496 | .Vb 2 |
|
|
1497 | \& ev_idle idle; // actual processing watcher |
|
|
1498 | \& ev_io io; // actual event watcher |
|
|
1499 | \& |
|
|
1500 | \& static void |
|
|
1501 | \& io_cb (EV_P_ ev_io *w, int revents) |
|
|
1502 | \& { |
|
|
1503 | \& // stop the I/O watcher, we received the event, but |
|
|
1504 | \& // are not yet ready to handle it. |
|
|
1505 | \& ev_io_stop (EV_A_ w); |
|
|
1506 | \& |
|
|
1507 | \& // start the idle watcher to ahndle the actual event. |
|
|
1508 | \& // it will not be executed as long as other watchers |
|
|
1509 | \& // with the default priority are receiving events. |
|
|
1510 | \& ev_idle_start (EV_A_ &idle); |
|
|
1511 | \& } |
|
|
1512 | \& |
|
|
1513 | \& static void |
|
|
1514 | \& idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1515 | \& { |
|
|
1516 | \& // actual processing |
|
|
1517 | \& read (STDIN_FILENO, ...); |
|
|
1518 | \& |
|
|
1519 | \& // have to start the I/O watcher again, as |
|
|
1520 | \& // we have handled the event |
|
|
1521 | \& ev_io_start (EV_P_ &io); |
|
|
1522 | \& } |
|
|
1523 | \& |
|
|
1524 | \& // initialisation |
|
|
1525 | \& ev_idle_init (&idle, idle_cb); |
|
|
1526 | \& ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1527 | \& ev_io_start (EV_DEFAULT_ &io); |
|
|
1528 | .Ve |
|
|
1529 | .PP |
|
|
1530 | In the \*(L"real\*(R" world, it might also be beneficial to start a timer, so that |
|
|
1531 | low-priority connections can not be locked out forever under load. This |
|
|
1532 | enables your program to keep a lower latency for important connections |
|
|
1533 | during short periods of high load, while not completely locking out less |
|
|
1534 | important ones. |
1162 | .SH "WATCHER TYPES" |
1535 | .SH "WATCHER TYPES" |
1163 | .IX Header "WATCHER TYPES" |
1536 | .IX Header "WATCHER TYPES" |
1164 | This section describes each watcher in detail, but will not repeat |
1537 | This section describes each watcher in detail, but will not repeat |
1165 | information given in the last section. Any initialisation/set macros, |
1538 | information given in the last section. Any initialisation/set macros, |
1166 | functions and members specific to the watcher type are explained. |
1539 | functions and members specific to the watcher type are explained. |
… | |
… | |
1171 | watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
1544 | watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
1172 | means you can expect it to have some sensible content while the watcher |
1545 | means you can expect it to have some sensible content while the watcher |
1173 | is active, but you can also modify it. Modifying it may not do something |
1546 | is active, but you can also modify it. Modifying it may not do something |
1174 | sensible or take immediate effect (or do anything at all), but libev will |
1547 | sensible or take immediate effect (or do anything at all), but libev will |
1175 | not crash or malfunction in any way. |
1548 | not crash or malfunction in any way. |
1176 | .ie n .Sh """ev_io"" \- is this file descriptor readable or writable?" |
1549 | .ie n .SS """ev_io"" \- is this file descriptor readable or writable?" |
1177 | .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
1550 | .el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
1178 | .IX Subsection "ev_io - is this file descriptor readable or writable?" |
1551 | .IX Subsection "ev_io - is this file descriptor readable or writable?" |
1179 | I/O watchers check whether a file descriptor is readable or writable |
1552 | I/O watchers check whether a file descriptor is readable or writable |
1180 | in each iteration of the event loop, or, more precisely, when reading |
1553 | in each iteration of the event loop, or, more precisely, when reading |
1181 | would not block the process and writing would at least be able to write |
1554 | would not block the process and writing would at least be able to write |
1182 | some data. This behaviour is called level-triggering because you keep |
1555 | some data. This behaviour is called level-triggering because you keep |
… | |
… | |
1187 | In general you can register as many read and/or write event watchers per |
1560 | In general you can register as many read and/or write event watchers per |
1188 | fd as you want (as long as you don't confuse yourself). Setting all file |
1561 | fd as you want (as long as you don't confuse yourself). Setting all file |
1189 | descriptors to non-blocking mode is also usually a good idea (but not |
1562 | descriptors to non-blocking mode is also usually a good idea (but not |
1190 | required if you know what you are doing). |
1563 | required if you know what you are doing). |
1191 | .PP |
1564 | .PP |
1192 | If you must do this, then force the use of a known-to-be-good backend |
1565 | If you cannot use non-blocking mode, then force the use of a |
1193 | (at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and |
1566 | known-to-be-good backend (at the time of this writing, this includes only |
1194 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). |
1567 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR). The same applies to file |
|
|
1568 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1569 | files) \- libev doesn't guarentee any specific behaviour in that case. |
1195 | .PP |
1570 | .PP |
1196 | Another thing you have to watch out for is that it is quite easy to |
1571 | Another thing you have to watch out for is that it is quite easy to |
1197 | receive \*(L"spurious\*(R" readiness notifications, that is your callback might |
1572 | receive \*(L"spurious\*(R" readiness notifications, that is your callback might |
1198 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
1573 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
1199 | because there is no data. Not only are some backends known to create a |
1574 | because there is no data. Not only are some backends known to create a |
1200 | lot of those (for example Solaris ports), it is very easy to get into |
1575 | lot of those (for example Solaris ports), it is very easy to get into |
1201 | this situation even with a relatively standard program structure. Thus |
1576 | this situation even with a relatively standard program structure. Thus |
1202 | it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning |
1577 | it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning |
1203 | \&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. |
1578 | \&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. |
1204 | .PP |
1579 | .PP |
1205 | If you cannot run the fd in non-blocking mode (for example you should not |
1580 | If you cannot run the fd in non-blocking mode (for example you should |
1206 | play around with an Xlib connection), then you have to separately re-test |
1581 | not play around with an Xlib connection), then you have to separately |
1207 | whether a file descriptor is really ready with a known-to-be good interface |
1582 | re-test whether a file descriptor is really ready with a known-to-be good |
1208 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1583 | interface such as poll (fortunately in our Xlib example, Xlib already |
1209 | its own, so its quite safe to use). |
1584 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1585 | use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block |
|
|
1586 | indefinitely. |
|
|
1587 | .PP |
|
|
1588 | But really, best use non-blocking mode. |
1210 | .PP |
1589 | .PP |
1211 | \fIThe special problem of disappearing file descriptors\fR |
1590 | \fIThe special problem of disappearing file descriptors\fR |
1212 | .IX Subsection "The special problem of disappearing file descriptors" |
1591 | .IX Subsection "The special problem of disappearing file descriptors" |
1213 | .PP |
1592 | .PP |
1214 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1593 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1215 | descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means, |
1594 | descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means, |
1216 | such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file |
1595 | such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file |
1217 | descriptor, but when it goes away, the operating system will silently drop |
1596 | descriptor, but when it goes away, the operating system will silently drop |
1218 | this interest. If another file descriptor with the same number then is |
1597 | this interest. If another file descriptor with the same number then is |
1219 | registered with libev, there is no efficient way to see that this is, in |
1598 | registered with libev, there is no efficient way to see that this is, in |
1220 | fact, a different file descriptor. |
1599 | fact, a different file descriptor. |
1221 | .PP |
1600 | .PP |
… | |
… | |
1255 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1634 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1256 | .PP |
1635 | .PP |
1257 | \fIThe special problem of \s-1SIGPIPE\s0\fR |
1636 | \fIThe special problem of \s-1SIGPIPE\s0\fR |
1258 | .IX Subsection "The special problem of SIGPIPE" |
1637 | .IX Subsection "The special problem of SIGPIPE" |
1259 | .PP |
1638 | .PP |
1260 | While not really specific to libev, it is easy to forget about \s-1SIGPIPE:\s0 |
1639 | While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR: |
1261 | when reading from a pipe whose other end has been closed, your program |
1640 | when writing to a pipe whose other end has been closed, your program gets |
1262 | gets send a \s-1SIGPIPE\s0, which, by default, aborts your program. For most |
1641 | sent a \s-1SIGPIPE\s0, which, by default, aborts your program. For most programs |
1263 | programs this is sensible behaviour, for daemons, this is usually |
1642 | this is sensible behaviour, for daemons, this is usually undesirable. |
1264 | undesirable. |
|
|
1265 | .PP |
1643 | .PP |
1266 | So when you encounter spurious, unexplained daemon exits, make sure you |
1644 | So when you encounter spurious, unexplained daemon exits, make sure you |
1267 | ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon |
1645 | ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon |
1268 | somewhere, as that would have given you a big clue). |
1646 | somewhere, as that would have given you a big clue). |
1269 | .PP |
1647 | .PP |
… | |
… | |
1274 | .PD 0 |
1652 | .PD 0 |
1275 | .IP "ev_io_set (ev_io *, int fd, int events)" 4 |
1653 | .IP "ev_io_set (ev_io *, int fd, int events)" 4 |
1276 | .IX Item "ev_io_set (ev_io *, int fd, int events)" |
1654 | .IX Item "ev_io_set (ev_io *, int fd, int events)" |
1277 | .PD |
1655 | .PD |
1278 | Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to |
1656 | Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to |
1279 | receive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or |
1657 | receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or |
1280 | \&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events. |
1658 | \&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events. |
1281 | .IP "int fd [read\-only]" 4 |
1659 | .IP "int fd [read\-only]" 4 |
1282 | .IX Item "int fd [read-only]" |
1660 | .IX Item "int fd [read-only]" |
1283 | The file descriptor being watched. |
1661 | The file descriptor being watched. |
1284 | .IP "int events [read\-only]" 4 |
1662 | .IP "int events [read\-only]" 4 |
1285 | .IX Item "int events [read-only]" |
1663 | .IX Item "int events [read-only]" |
… | |
… | |
1292 | readable, but only once. Since it is likely line-buffered, you could |
1670 | readable, but only once. Since it is likely line-buffered, you could |
1293 | attempt to read a whole line in the callback. |
1671 | attempt to read a whole line in the callback. |
1294 | .PP |
1672 | .PP |
1295 | .Vb 6 |
1673 | .Vb 6 |
1296 | \& static void |
1674 | \& static void |
1297 | \& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1675 | \& stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1298 | \& { |
1676 | \& { |
1299 | \& ev_io_stop (loop, w); |
1677 | \& ev_io_stop (loop, w); |
1300 | \& .. read from stdin here (or from w\->fd) and haqndle any I/O errors |
1678 | \& .. read from stdin here (or from w\->fd) and handle any I/O errors |
1301 | \& } |
1679 | \& } |
1302 | \& |
1680 | \& |
1303 | \& ... |
1681 | \& ... |
1304 | \& struct ev_loop *loop = ev_default_init (0); |
1682 | \& struct ev_loop *loop = ev_default_init (0); |
1305 | \& struct ev_io stdin_readable; |
1683 | \& ev_io stdin_readable; |
1306 | \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1684 | \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1307 | \& ev_io_start (loop, &stdin_readable); |
1685 | \& ev_io_start (loop, &stdin_readable); |
1308 | \& ev_loop (loop, 0); |
1686 | \& ev_loop (loop, 0); |
1309 | .Ve |
1687 | .Ve |
1310 | .ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" |
1688 | .ie n .SS """ev_timer"" \- relative and optionally repeating timeouts" |
1311 | .el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts" |
1689 | .el .SS "\f(CWev_timer\fP \- relative and optionally repeating timeouts" |
1312 | .IX Subsection "ev_timer - relative and optionally repeating timeouts" |
1690 | .IX Subsection "ev_timer - relative and optionally repeating timeouts" |
1313 | Timer watchers are simple relative timers that generate an event after a |
1691 | Timer watchers are simple relative timers that generate an event after a |
1314 | given time, and optionally repeating in regular intervals after that. |
1692 | given time, and optionally repeating in regular intervals after that. |
1315 | .PP |
1693 | .PP |
1316 | The timers are based on real time, that is, if you register an event that |
1694 | The timers are based on real time, that is, if you register an event that |
1317 | times out after an hour and you reset your system clock to January last |
1695 | times out after an hour and you reset your system clock to January last |
1318 | year, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because |
1696 | year, it will still time out after (roughly) one hour. \*(L"Roughly\*(R" because |
1319 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1697 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1320 | monotonic clock option helps a lot here). |
1698 | monotonic clock option helps a lot here). |
|
|
1699 | .PP |
|
|
1700 | The callback is guaranteed to be invoked only \fIafter\fR its timeout has |
|
|
1701 | passed (not \fIat\fR, so on systems with very low-resolution clocks this |
|
|
1702 | might introduce a small delay). If multiple timers become ready during the |
|
|
1703 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1704 | before ones of the same priority with later time-out values (but this is |
|
|
1705 | no longer true when a callback calls \f(CW\*(C`ev_loop\*(C'\fR recursively). |
|
|
1706 | .PP |
|
|
1707 | \fIBe smart about timeouts\fR |
|
|
1708 | .IX Subsection "Be smart about timeouts" |
|
|
1709 | .PP |
|
|
1710 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1711 | recovery. A typical example is an \s-1HTTP\s0 request \- if the other side hangs, |
|
|
1712 | you want to raise some error after a while. |
|
|
1713 | .PP |
|
|
1714 | What follows are some ways to handle this problem, from obvious and |
|
|
1715 | inefficient to smart and efficient. |
|
|
1716 | .PP |
|
|
1717 | In the following, a 60 second activity timeout is assumed \- a timeout that |
|
|
1718 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1719 | data or other life sign was received). |
|
|
1720 | .IP "1. Use a timer and stop, reinitialise and start it on activity." 4 |
|
|
1721 | .IX Item "1. Use a timer and stop, reinitialise and start it on activity." |
|
|
1722 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1723 | start the watcher: |
|
|
1724 | .Sp |
|
|
1725 | .Vb 2 |
|
|
1726 | \& ev_timer_init (timer, callback, 60., 0.); |
|
|
1727 | \& ev_timer_start (loop, timer); |
|
|
1728 | .Ve |
|
|
1729 | .Sp |
|
|
1730 | Then, each time there is some activity, \f(CW\*(C`ev_timer_stop\*(C'\fR it, initialise it |
|
|
1731 | and start it again: |
|
|
1732 | .Sp |
|
|
1733 | .Vb 3 |
|
|
1734 | \& ev_timer_stop (loop, timer); |
|
|
1735 | \& ev_timer_set (timer, 60., 0.); |
|
|
1736 | \& ev_timer_start (loop, timer); |
|
|
1737 | .Ve |
|
|
1738 | .Sp |
|
|
1739 | This is relatively simple to implement, but means that each time there is |
|
|
1740 | some activity, libev will first have to remove the timer from its internal |
|
|
1741 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1742 | still not a constant-time operation. |
|
|
1743 | .ie n .IP "2. Use a timer and re-start it with ""ev_timer_again"" inactivity." 4 |
|
|
1744 | .el .IP "2. Use a timer and re-start it with \f(CWev_timer_again\fR inactivity." 4 |
|
|
1745 | .IX Item "2. Use a timer and re-start it with ev_timer_again inactivity." |
|
|
1746 | This is the easiest way, and involves using \f(CW\*(C`ev_timer_again\*(C'\fR instead of |
|
|
1747 | \&\f(CW\*(C`ev_timer_start\*(C'\fR. |
|
|
1748 | .Sp |
|
|
1749 | To implement this, configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value |
|
|
1750 | of \f(CW60\fR and then call \f(CW\*(C`ev_timer_again\*(C'\fR at start and each time you |
|
|
1751 | successfully read or write some data. If you go into an idle state where |
|
|
1752 | you do not expect data to travel on the socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR |
|
|
1753 | the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will automatically restart it if need be. |
|
|
1754 | .Sp |
|
|
1755 | That means you can ignore both the \f(CW\*(C`ev_timer_start\*(C'\fR function and the |
|
|
1756 | \&\f(CW\*(C`after\*(C'\fR argument to \f(CW\*(C`ev_timer_set\*(C'\fR, and only ever use the \f(CW\*(C`repeat\*(C'\fR |
|
|
1757 | member and \f(CW\*(C`ev_timer_again\*(C'\fR. |
|
|
1758 | .Sp |
|
|
1759 | At start: |
|
|
1760 | .Sp |
|
|
1761 | .Vb 3 |
|
|
1762 | \& ev_init (timer, callback); |
|
|
1763 | \& timer\->repeat = 60.; |
|
|
1764 | \& ev_timer_again (loop, timer); |
|
|
1765 | .Ve |
|
|
1766 | .Sp |
|
|
1767 | Each time there is some activity: |
|
|
1768 | .Sp |
|
|
1769 | .Vb 1 |
|
|
1770 | \& ev_timer_again (loop, timer); |
|
|
1771 | .Ve |
|
|
1772 | .Sp |
|
|
1773 | It is even possible to change the time-out on the fly, regardless of |
|
|
1774 | whether the watcher is active or not: |
|
|
1775 | .Sp |
|
|
1776 | .Vb 2 |
|
|
1777 | \& timer\->repeat = 30.; |
|
|
1778 | \& ev_timer_again (loop, timer); |
|
|
1779 | .Ve |
|
|
1780 | .Sp |
|
|
1781 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1782 | you want to modify its timeout value, as libev does not have to completely |
|
|
1783 | remove and re-insert the timer from/into its internal data structure. |
|
|
1784 | .Sp |
|
|
1785 | It is, however, even simpler than the \*(L"obvious\*(R" way to do it. |
|
|
1786 | .IP "3. Let the timer time out, but then re-arm it as required." 4 |
|
|
1787 | .IX Item "3. Let the timer time out, but then re-arm it as required." |
|
|
1788 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1789 | relatively long compared to the intervals between other activity \- in |
|
|
1790 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1791 | associated activity resets. |
|
|
1792 | .Sp |
|
|
1793 | In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone, |
|
|
1794 | but remember the time of last activity, and check for a real timeout only |
|
|
1795 | within the callback: |
|
|
1796 | .Sp |
|
|
1797 | .Vb 1 |
|
|
1798 | \& ev_tstamp last_activity; // time of last activity |
|
|
1799 | \& |
|
|
1800 | \& static void |
|
|
1801 | \& callback (EV_P_ ev_timer *w, int revents) |
|
|
1802 | \& { |
|
|
1803 | \& ev_tstamp now = ev_now (EV_A); |
|
|
1804 | \& ev_tstamp timeout = last_activity + 60.; |
|
|
1805 | \& |
|
|
1806 | \& // if last_activity + 60. is older than now, we did time out |
|
|
1807 | \& if (timeout < now) |
|
|
1808 | \& { |
|
|
1809 | \& // timeout occured, take action |
|
|
1810 | \& } |
|
|
1811 | \& else |
|
|
1812 | \& { |
|
|
1813 | \& // callback was invoked, but there was some activity, re\-arm |
|
|
1814 | \& // the watcher to fire in last_activity + 60, which is |
|
|
1815 | \& // guaranteed to be in the future, so "again" is positive: |
|
|
1816 | \& w\->repeat = timeout \- now; |
|
|
1817 | \& ev_timer_again (EV_A_ w); |
|
|
1818 | \& } |
|
|
1819 | \& } |
|
|
1820 | .Ve |
|
|
1821 | .Sp |
|
|
1822 | To summarise the callback: first calculate the real timeout (defined |
|
|
1823 | as \*(L"60 seconds after the last activity\*(R"), then check if that time has |
|
|
1824 | been reached, which means something \fIdid\fR, in fact, time out. Otherwise |
|
|
1825 | the callback was invoked too early (\f(CW\*(C`timeout\*(C'\fR is in the future), so |
|
|
1826 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1827 | a timeout then. |
|
|
1828 | .Sp |
|
|
1829 | Note how \f(CW\*(C`ev_timer_again\*(C'\fR is used, taking advantage of the |
|
|
1830 | \&\f(CW\*(C`ev_timer_again\*(C'\fR optimisation when the timer is already running. |
|
|
1831 | .Sp |
|
|
1832 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1833 | minus half the average time between activity), but virtually no calls to |
|
|
1834 | libev to change the timeout. |
|
|
1835 | .Sp |
|
|
1836 | To start the timer, simply initialise the watcher and set \f(CW\*(C`last_activity\*(C'\fR |
|
|
1837 | to the current time (meaning we just have some activity :), then call the |
|
|
1838 | callback, which will \*(L"do the right thing\*(R" and start the timer: |
|
|
1839 | .Sp |
|
|
1840 | .Vb 3 |
|
|
1841 | \& ev_init (timer, callback); |
|
|
1842 | \& last_activity = ev_now (loop); |
|
|
1843 | \& callback (loop, timer, EV_TIMEOUT); |
|
|
1844 | .Ve |
|
|
1845 | .Sp |
|
|
1846 | And when there is some activity, simply store the current time in |
|
|
1847 | \&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all: |
|
|
1848 | .Sp |
|
|
1849 | .Vb 1 |
|
|
1850 | \& last_actiivty = ev_now (loop); |
|
|
1851 | .Ve |
|
|
1852 | .Sp |
|
|
1853 | This technique is slightly more complex, but in most cases where the |
|
|
1854 | time-out is unlikely to be triggered, much more efficient. |
|
|
1855 | .Sp |
|
|
1856 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1857 | callback :) \- just change the timeout and invoke the callback, which will |
|
|
1858 | fix things for you. |
|
|
1859 | .IP "4. Wee, just use a double-linked list for your timeouts." 4 |
|
|
1860 | .IX Item "4. Wee, just use a double-linked list for your timeouts." |
|
|
1861 | If there is not one request, but many thousands (millions...), all |
|
|
1862 | employing some kind of timeout with the same timeout value, then one can |
|
|
1863 | do even better: |
|
|
1864 | .Sp |
|
|
1865 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1866 | at the \fIend\fR of the list. |
|
|
1867 | .Sp |
|
|
1868 | Then use an \f(CW\*(C`ev_timer\*(C'\fR to fire when the timeout at the \fIbeginning\fR of |
|
|
1869 | the list is expected to fire (for example, using the technique #3). |
|
|
1870 | .Sp |
|
|
1871 | When there is some activity, remove the timer from the list, recalculate |
|
|
1872 | the timeout, append it to the end of the list again, and make sure to |
|
|
1873 | update the \f(CW\*(C`ev_timer\*(C'\fR if it was taken from the beginning of the list. |
|
|
1874 | .Sp |
|
|
1875 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1876 | starting, stopping and updating the timers, at the expense of a major |
|
|
1877 | complication, and having to use a constant timeout. The constant timeout |
|
|
1878 | ensures that the list stays sorted. |
|
|
1879 | .PP |
|
|
1880 | So which method the best? |
|
|
1881 | .PP |
|
|
1882 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1883 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1884 | better, and isn't very complicated either. In most case, choosing either |
|
|
1885 | one is fine, with #3 being better in typical situations. |
|
|
1886 | .PP |
|
|
1887 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1888 | rather complicated, but extremely efficient, something that really pays |
|
|
1889 | off after the first million or so of active timers, i.e. it's usually |
|
|
1890 | overkill :) |
|
|
1891 | .PP |
|
|
1892 | \fIThe special problem of time updates\fR |
|
|
1893 | .IX Subsection "The special problem of time updates" |
|
|
1894 | .PP |
|
|
1895 | Establishing the current time is a costly operation (it usually takes at |
|
|
1896 | least two system calls): \s-1EV\s0 therefore updates its idea of the current |
|
|
1897 | time only before and after \f(CW\*(C`ev_loop\*(C'\fR collects new events, which causes a |
|
|
1898 | growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling |
|
|
1899 | lots of events in one iteration. |
1321 | .PP |
1900 | .PP |
1322 | The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
1901 | The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
1323 | time. This is usually the right thing as this timestamp refers to the time |
1902 | time. This is usually the right thing as this timestamp refers to the time |
1324 | of the event triggering whatever timeout you are modifying/starting. If |
1903 | of the event triggering whatever timeout you are modifying/starting. If |
1325 | you suspect event processing to be delayed and you \fIneed\fR to base the timeout |
1904 | you suspect event processing to be delayed and you \fIneed\fR to base the |
1326 | on the current time, use something like this to adjust for this: |
1905 | timeout on the current time, use something like this to adjust for this: |
1327 | .PP |
1906 | .PP |
1328 | .Vb 1 |
1907 | .Vb 1 |
1329 | \& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.); |
1908 | \& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.); |
1330 | .Ve |
1909 | .Ve |
1331 | .PP |
1910 | .PP |
1332 | The callback is guaranteed to be invoked only after its timeout has passed, |
1911 | If the event loop is suspended for a long time, you can also force an |
1333 | but if multiple timers become ready during the same loop iteration then |
1912 | update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update |
1334 | order of execution is undefined. |
1913 | ()\*(C'\fR. |
|
|
1914 | .PP |
|
|
1915 | \fIThe special problems of suspended animation\fR |
|
|
1916 | .IX Subsection "The special problems of suspended animation" |
|
|
1917 | .PP |
|
|
1918 | When you leave the server world it is quite customary to hit machines that |
|
|
1919 | can suspend/hibernate \- what happens to the clocks during such a suspend? |
|
|
1920 | .PP |
|
|
1921 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1922 | all processes, while the clocks (\f(CW\*(C`times\*(C'\fR, \f(CW\*(C`CLOCK_MONOTONIC\*(C'\fR) continue |
|
|
1923 | to run until the system is suspended, but they will not advance while the |
|
|
1924 | system is suspended. That means, on resume, it will be as if the program |
|
|
1925 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1926 | towards \f(CW\*(C`ev_timer\*(C'\fR when a monotonic clock source is used. The real time |
|
|
1927 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1928 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1929 | be adjusted accordingly. |
|
|
1930 | .PP |
|
|
1931 | I would not be surprised to see different behaviour in different between |
|
|
1932 | operating systems, \s-1OS\s0 versions or even different hardware. |
|
|
1933 | .PP |
|
|
1934 | The other form of suspend (job control, or sending a \s-1SIGSTOP\s0) will see a |
|
|
1935 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1936 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1937 | then you can expect \f(CW\*(C`ev_timer\*(C'\fRs to expire as the full suspension time |
|
|
1938 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1939 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1940 | .PP |
|
|
1941 | It might be beneficial for this latter case to call \f(CW\*(C`ev_suspend\*(C'\fR |
|
|
1942 | and \f(CW\*(C`ev_resume\*(C'\fR in code that handles \f(CW\*(C`SIGTSTP\*(C'\fR, to at least get |
|
|
1943 | deterministic behaviour in this case (you can do nothing against |
|
|
1944 | \&\f(CW\*(C`SIGSTOP\*(C'\fR). |
1335 | .PP |
1945 | .PP |
1336 | \fIWatcher-Specific Functions and Data Members\fR |
1946 | \fIWatcher-Specific Functions and Data Members\fR |
1337 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1947 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1338 | .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
1948 | .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
1339 | .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
1949 | .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
… | |
… | |
1362 | If the timer is started but non-repeating, stop it (as if it timed out). |
1972 | If the timer is started but non-repeating, stop it (as if it timed out). |
1363 | .Sp |
1973 | .Sp |
1364 | If the timer is repeating, either start it if necessary (with the |
1974 | If the timer is repeating, either start it if necessary (with the |
1365 | \&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. |
1975 | \&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. |
1366 | .Sp |
1976 | .Sp |
1367 | This sounds a bit complicated, but here is a useful and typical |
1977 | This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a |
1368 | example: Imagine you have a \s-1TCP\s0 connection and you want a so-called idle |
1978 | usage example. |
1369 | timeout, that is, you want to be called when there have been, say, 60 |
1979 | .IP "ev_timer_remaining (loop, ev_timer *)" 4 |
1370 | seconds of inactivity on the socket. The easiest way to do this is to |
1980 | .IX Item "ev_timer_remaining (loop, ev_timer *)" |
1371 | configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call |
1981 | Returns the remaining time until a timer fires. If the timer is active, |
1372 | \&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If |
1982 | then this time is relative to the current event loop time, otherwise it's |
1373 | you go into an idle state where you do not expect data to travel on the |
1983 | the timeout value currently configured. |
1374 | socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will |
|
|
1375 | automatically restart it if need be. |
|
|
1376 | .Sp |
1984 | .Sp |
1377 | That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR |
1985 | That is, after an \f(CW\*(C`ev_timer_set (w, 5, 7)\*(C'\fR, \f(CW\*(C`ev_timer_remaining\*(C'\fR returns |
1378 | altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR: |
1986 | \&\f(CW5\fR. When the timer is started and one second passes, \f(CW\*(C`ev_timer_remain\*(C'\fR |
1379 | .Sp |
1987 | will return \f(CW4\fR. When the timer expires and is restarted, it will return |
1380 | .Vb 8 |
1988 | roughly \f(CW7\fR (likely slightly less as callback invocation takes some time, |
1381 | \& ev_timer_init (timer, callback, 0., 5.); |
1989 | too), and so on. |
1382 | \& ev_timer_again (loop, timer); |
|
|
1383 | \& ... |
|
|
1384 | \& timer\->again = 17.; |
|
|
1385 | \& ev_timer_again (loop, timer); |
|
|
1386 | \& ... |
|
|
1387 | \& timer\->again = 10.; |
|
|
1388 | \& ev_timer_again (loop, timer); |
|
|
1389 | .Ve |
|
|
1390 | .Sp |
|
|
1391 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1392 | you want to modify its timeout value. |
|
|
1393 | .IP "ev_tstamp repeat [read\-write]" 4 |
1990 | .IP "ev_tstamp repeat [read\-write]" 4 |
1394 | .IX Item "ev_tstamp repeat [read-write]" |
1991 | .IX Item "ev_tstamp repeat [read-write]" |
1395 | The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
1992 | The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
1396 | or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any), |
1993 | or \f(CW\*(C`ev_timer_again\*(C'\fR is called, and determines the next timeout (if any), |
1397 | which is also when any modifications are taken into account. |
1994 | which is also when any modifications are taken into account. |
1398 | .PP |
1995 | .PP |
1399 | \fIExamples\fR |
1996 | \fIExamples\fR |
1400 | .IX Subsection "Examples" |
1997 | .IX Subsection "Examples" |
1401 | .PP |
1998 | .PP |
1402 | Example: Create a timer that fires after 60 seconds. |
1999 | Example: Create a timer that fires after 60 seconds. |
1403 | .PP |
2000 | .PP |
1404 | .Vb 5 |
2001 | .Vb 5 |
1405 | \& static void |
2002 | \& static void |
1406 | \& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2003 | \& one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1407 | \& { |
2004 | \& { |
1408 | \& .. one minute over, w is actually stopped right here |
2005 | \& .. one minute over, w is actually stopped right here |
1409 | \& } |
2006 | \& } |
1410 | \& |
2007 | \& |
1411 | \& struct ev_timer mytimer; |
2008 | \& ev_timer mytimer; |
1412 | \& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
2009 | \& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1413 | \& ev_timer_start (loop, &mytimer); |
2010 | \& ev_timer_start (loop, &mytimer); |
1414 | .Ve |
2011 | .Ve |
1415 | .PP |
2012 | .PP |
1416 | Example: Create a timeout timer that times out after 10 seconds of |
2013 | Example: Create a timeout timer that times out after 10 seconds of |
1417 | inactivity. |
2014 | inactivity. |
1418 | .PP |
2015 | .PP |
1419 | .Vb 5 |
2016 | .Vb 5 |
1420 | \& static void |
2017 | \& static void |
1421 | \& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2018 | \& timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1422 | \& { |
2019 | \& { |
1423 | \& .. ten seconds without any activity |
2020 | \& .. ten seconds without any activity |
1424 | \& } |
2021 | \& } |
1425 | \& |
2022 | \& |
1426 | \& struct ev_timer mytimer; |
2023 | \& ev_timer mytimer; |
1427 | \& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2024 | \& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1428 | \& ev_timer_again (&mytimer); /* start timer */ |
2025 | \& ev_timer_again (&mytimer); /* start timer */ |
1429 | \& ev_loop (loop, 0); |
2026 | \& ev_loop (loop, 0); |
1430 | \& |
2027 | \& |
1431 | \& // and in some piece of code that gets executed on any "activity": |
2028 | \& // and in some piece of code that gets executed on any "activity": |
1432 | \& // reset the timeout to start ticking again at 10 seconds |
2029 | \& // reset the timeout to start ticking again at 10 seconds |
1433 | \& ev_timer_again (&mytimer); |
2030 | \& ev_timer_again (&mytimer); |
1434 | .Ve |
2031 | .Ve |
1435 | .ie n .Sh """ev_periodic"" \- to cron or not to cron?" |
2032 | .ie n .SS """ev_periodic"" \- to cron or not to cron?" |
1436 | .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" |
2033 | .el .SS "\f(CWev_periodic\fP \- to cron or not to cron?" |
1437 | .IX Subsection "ev_periodic - to cron or not to cron?" |
2034 | .IX Subsection "ev_periodic - to cron or not to cron?" |
1438 | Periodic watchers are also timers of a kind, but they are very versatile |
2035 | Periodic watchers are also timers of a kind, but they are very versatile |
1439 | (and unfortunately a bit complex). |
2036 | (and unfortunately a bit complex). |
1440 | .PP |
2037 | .PP |
1441 | Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) |
2038 | Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or |
1442 | but on wall clock time (absolute time). You can tell a periodic watcher |
2039 | relative time, the physical time that passes) but on wall clock time |
1443 | to trigger after some specific point in time. For example, if you tell a |
2040 | (absolute time, the thing you can read on your calender or clock). The |
1444 | periodic watcher to trigger in 10 seconds (by specifying e.g. \f(CW\*(C`ev_now () |
2041 | difference is that wall clock time can run faster or slower than real |
1445 | + 10.\*(C'\fR, that is, an absolute time not a delay) and then reset your system |
2042 | time, and time jumps are not uncommon (e.g. when you adjust your |
1446 | clock to January of the previous year, then it will take more than year |
2043 | wrist-watch). |
1447 | to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would still trigger |
|
|
1448 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1449 | .PP |
2044 | .PP |
|
|
2045 | You can tell a periodic watcher to trigger after some specific point |
|
|
2046 | in time: for example, if you tell a periodic watcher to trigger \*(L"in 10 |
|
|
2047 | seconds\*(R" (by specifying e.g. \f(CW\*(C`ev_now () + 10.\*(C'\fR, that is, an absolute time |
|
|
2048 | not a delay) and then reset your system clock to January of the previous |
|
|
2049 | year, then it will take a year or more to trigger the event (unlike an |
|
|
2050 | \&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting |
|
|
2051 | it, as it uses a relative timeout). |
|
|
2052 | .PP |
1450 | \&\f(CW\*(C`ev_periodic\*(C'\fRs can also be used to implement vastly more complex timers, |
2053 | \&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex |
1451 | such as triggering an event on each \*(L"midnight, local time\*(R", or other |
2054 | timers, such as triggering an event on each \*(L"midnight, local time\*(R", or |
1452 | complicated, rules. |
2055 | other complicated rules. This cannot be done with \f(CW\*(C`ev_timer\*(C'\fR watchers, as |
|
|
2056 | those cannot react to time jumps. |
1453 | .PP |
2057 | .PP |
1454 | As with timers, the callback is guaranteed to be invoked only when the |
2058 | As with timers, the callback is guaranteed to be invoked only when the |
1455 | time (\f(CW\*(C`at\*(C'\fR) has passed, but if multiple periodic timers become ready |
2059 | point in time where it is supposed to trigger has passed. If multiple |
1456 | during the same loop iteration then order of execution is undefined. |
2060 | timers become ready during the same loop iteration then the ones with |
|
|
2061 | earlier time-out values are invoked before ones with later time-out values |
|
|
2062 | (but this is no longer true when a callback calls \f(CW\*(C`ev_loop\*(C'\fR recursively). |
1457 | .PP |
2063 | .PP |
1458 | \fIWatcher-Specific Functions and Data Members\fR |
2064 | \fIWatcher-Specific Functions and Data Members\fR |
1459 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2065 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1460 | .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 |
2066 | .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4 |
1461 | .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" |
2067 | .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" |
1462 | .PD 0 |
2068 | .PD 0 |
1463 | .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 |
2069 | .IP "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" 4 |
1464 | .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" |
2070 | .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)" |
1465 | .PD |
2071 | .PD |
1466 | Lots of arguments, lets sort it out... There are basically three modes of |
2072 | Lots of arguments, let's sort it out... There are basically three modes of |
1467 | operation, and we will explain them from simplest to complex: |
2073 | operation, and we will explain them from simplest to most complex: |
1468 | .RS 4 |
2074 | .RS 4 |
1469 | .IP "\(bu" 4 |
2075 | .IP "\(bu" 4 |
1470 | absolute timer (at = time, interval = reschedule_cb = 0) |
2076 | absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1471 | .Sp |
2077 | .Sp |
1472 | In this configuration the watcher triggers an event after the wall clock |
2078 | In this configuration the watcher triggers an event after the wall clock |
1473 | time \f(CW\*(C`at\*(C'\fR has passed and doesn't repeat. It will not adjust when a time |
2079 | time \f(CW\*(C`offset\*(C'\fR has passed. It will not repeat and will not adjust when a |
1474 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
2080 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1475 | run when the system time reaches or surpasses this time. |
2081 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2082 | this point in time. |
1476 | .IP "\(bu" 4 |
2083 | .IP "\(bu" 4 |
1477 | repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2084 | repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1478 | .Sp |
2085 | .Sp |
1479 | In this mode the watcher will always be scheduled to time out at the next |
2086 | In this mode the watcher will always be scheduled to time out at the next |
1480 | \&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative) |
2087 | \&\f(CW\*(C`offset + N * interval\*(C'\fR time (for some integer N, which can also be |
1481 | and then repeat, regardless of any time jumps. |
2088 | negative) and then repeat, regardless of any time jumps. The \f(CW\*(C`offset\*(C'\fR |
|
|
2089 | argument is merely an offset into the \f(CW\*(C`interval\*(C'\fR periods. |
1482 | .Sp |
2090 | .Sp |
1483 | This can be used to create timers that do not drift with respect to system |
2091 | This can be used to create timers that do not drift with respect to the |
1484 | time, for example, here is a \f(CW\*(C`ev_periodic\*(C'\fR that triggers each hour, on |
2092 | system clock, for example, here is an \f(CW\*(C`ev_periodic\*(C'\fR that triggers each |
1485 | the hour: |
2093 | hour, on the hour (with respect to \s-1UTC\s0): |
1486 | .Sp |
2094 | .Sp |
1487 | .Vb 1 |
2095 | .Vb 1 |
1488 | \& ev_periodic_set (&periodic, 0., 3600., 0); |
2096 | \& ev_periodic_set (&periodic, 0., 3600., 0); |
1489 | .Ve |
2097 | .Ve |
1490 | .Sp |
2098 | .Sp |
… | |
… | |
1493 | full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
2101 | full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
1494 | by 3600. |
2102 | by 3600. |
1495 | .Sp |
2103 | .Sp |
1496 | Another way to think about it (for the mathematically inclined) is that |
2104 | Another way to think about it (for the mathematically inclined) is that |
1497 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
2105 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
1498 | time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. |
2106 | time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps. |
1499 | .Sp |
2107 | .Sp |
1500 | For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near |
2108 | For numerical stability it is preferable that the \f(CW\*(C`offset\*(C'\fR value is near |
1501 | \&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for |
2109 | \&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for |
1502 | this value, and in fact is often specified as zero. |
2110 | this value, and in fact is often specified as zero. |
1503 | .Sp |
2111 | .Sp |
1504 | Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0 |
2112 | Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0 |
1505 | speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability |
2113 | speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability |
1506 | will of course deteriorate. Libev itself tries to be exact to be about one |
2114 | will of course deteriorate. Libev itself tries to be exact to be about one |
1507 | millisecond (if the \s-1OS\s0 supports it and the machine is fast enough). |
2115 | millisecond (if the \s-1OS\s0 supports it and the machine is fast enough). |
1508 | .IP "\(bu" 4 |
2116 | .IP "\(bu" 4 |
1509 | manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2117 | manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1510 | .Sp |
2118 | .Sp |
1511 | In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being |
2119 | In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being |
1512 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2120 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1513 | reschedule callback will be called with the watcher as first, and the |
2121 | reschedule callback will be called with the watcher as first, and the |
1514 | current time as second argument. |
2122 | current time as second argument. |
1515 | .Sp |
2123 | .Sp |
1516 | \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, |
2124 | \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, ever, |
1517 | ever, or make \s-1ANY\s0 event loop modifications whatsoever\fR. |
2125 | or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly |
|
|
2126 | allowed by documentation here\fR. |
1518 | .Sp |
2127 | .Sp |
1519 | If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop |
2128 | If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop |
1520 | it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the |
2129 | it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the |
1521 | only event loop modification you are allowed to do). |
2130 | only event loop modification you are allowed to do). |
1522 | .Sp |
2131 | .Sp |
1523 | The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic |
2132 | The callback prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(ev_periodic |
1524 | *w, ev_tstamp now)\*(C'\fR, e.g.: |
2133 | *w, ev_tstamp now)\*(C'\fR, e.g.: |
1525 | .Sp |
2134 | .Sp |
1526 | .Vb 4 |
2135 | .Vb 5 |
|
|
2136 | \& static ev_tstamp |
1527 | \& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2137 | \& my_rescheduler (ev_periodic *w, ev_tstamp now) |
1528 | \& { |
2138 | \& { |
1529 | \& return now + 60.; |
2139 | \& return now + 60.; |
1530 | \& } |
2140 | \& } |
1531 | .Ve |
2141 | .Ve |
1532 | .Sp |
2142 | .Sp |
… | |
… | |
1552 | when you changed some parameters or the reschedule callback would return |
2162 | when you changed some parameters or the reschedule callback would return |
1553 | a different time than the last time it was called (e.g. in a crond like |
2163 | a different time than the last time it was called (e.g. in a crond like |
1554 | program when the crontabs have changed). |
2164 | program when the crontabs have changed). |
1555 | .IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4 |
2165 | .IP "ev_tstamp ev_periodic_at (ev_periodic *)" 4 |
1556 | .IX Item "ev_tstamp ev_periodic_at (ev_periodic *)" |
2166 | .IX Item "ev_tstamp ev_periodic_at (ev_periodic *)" |
1557 | When active, returns the absolute time that the watcher is supposed to |
2167 | When active, returns the absolute time that the watcher is supposed |
1558 | trigger next. |
2168 | to trigger next. This is not the same as the \f(CW\*(C`offset\*(C'\fR argument to |
|
|
2169 | \&\f(CW\*(C`ev_periodic_set\*(C'\fR, but indeed works even in interval and manual |
|
|
2170 | rescheduling modes. |
1559 | .IP "ev_tstamp offset [read\-write]" 4 |
2171 | .IP "ev_tstamp offset [read\-write]" 4 |
1560 | .IX Item "ev_tstamp offset [read-write]" |
2172 | .IX Item "ev_tstamp offset [read-write]" |
1561 | When repeating, this contains the offset value, otherwise this is the |
2173 | When repeating, this contains the offset value, otherwise this is the |
1562 | absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR). |
2174 | absolute point in time (the \f(CW\*(C`offset\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR, |
|
|
2175 | although libev might modify this value for better numerical stability). |
1563 | .Sp |
2176 | .Sp |
1564 | Can be modified any time, but changes only take effect when the periodic |
2177 | Can be modified any time, but changes only take effect when the periodic |
1565 | timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
2178 | timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
1566 | .IP "ev_tstamp interval [read\-write]" 4 |
2179 | .IP "ev_tstamp interval [read\-write]" 4 |
1567 | .IX Item "ev_tstamp interval [read-write]" |
2180 | .IX Item "ev_tstamp interval [read-write]" |
1568 | The current interval value. Can be modified any time, but changes only |
2181 | The current interval value. Can be modified any time, but changes only |
1569 | take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
2182 | take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
1570 | called. |
2183 | called. |
1571 | .IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
2184 | .IP "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
1572 | .IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]" |
2185 | .IX Item "ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]" |
1573 | The current reschedule callback, or \f(CW0\fR, if this functionality is |
2186 | The current reschedule callback, or \f(CW0\fR, if this functionality is |
1574 | switched off. Can be changed any time, but changes only take effect when |
2187 | switched off. Can be changed any time, but changes only take effect when |
1575 | the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
2188 | the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
1576 | .PP |
2189 | .PP |
1577 | \fIExamples\fR |
2190 | \fIExamples\fR |
1578 | .IX Subsection "Examples" |
2191 | .IX Subsection "Examples" |
1579 | .PP |
2192 | .PP |
1580 | Example: Call a callback every hour, or, more precisely, whenever the |
2193 | Example: Call a callback every hour, or, more precisely, whenever the |
1581 | system clock is divisible by 3600. The callback invocation times have |
2194 | system time is divisible by 3600. The callback invocation times have |
1582 | potentially a lot of jitter, but good long-term stability. |
2195 | potentially a lot of jitter, but good long-term stability. |
1583 | .PP |
2196 | .PP |
1584 | .Vb 5 |
2197 | .Vb 5 |
1585 | \& static void |
2198 | \& static void |
1586 | \& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2199 | \& clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1587 | \& { |
2200 | \& { |
1588 | \& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2201 | \& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1589 | \& } |
2202 | \& } |
1590 | \& |
2203 | \& |
1591 | \& struct ev_periodic hourly_tick; |
2204 | \& ev_periodic hourly_tick; |
1592 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2205 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1593 | \& ev_periodic_start (loop, &hourly_tick); |
2206 | \& ev_periodic_start (loop, &hourly_tick); |
1594 | .Ve |
2207 | .Ve |
1595 | .PP |
2208 | .PP |
1596 | Example: The same as above, but use a reschedule callback to do it: |
2209 | Example: The same as above, but use a reschedule callback to do it: |
1597 | .PP |
2210 | .PP |
1598 | .Vb 1 |
2211 | .Vb 1 |
1599 | \& #include <math.h> |
2212 | \& #include <math.h> |
1600 | \& |
2213 | \& |
1601 | \& static ev_tstamp |
2214 | \& static ev_tstamp |
1602 | \& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2215 | \& my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1603 | \& { |
2216 | \& { |
1604 | \& return fmod (now, 3600.) + 3600.; |
2217 | \& return now + (3600. \- fmod (now, 3600.)); |
1605 | \& } |
2218 | \& } |
1606 | \& |
2219 | \& |
1607 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2220 | \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1608 | .Ve |
2221 | .Ve |
1609 | .PP |
2222 | .PP |
1610 | Example: Call a callback every hour, starting now: |
2223 | Example: Call a callback every hour, starting now: |
1611 | .PP |
2224 | .PP |
1612 | .Vb 4 |
2225 | .Vb 4 |
1613 | \& struct ev_periodic hourly_tick; |
2226 | \& ev_periodic hourly_tick; |
1614 | \& ev_periodic_init (&hourly_tick, clock_cb, |
2227 | \& ev_periodic_init (&hourly_tick, clock_cb, |
1615 | \& fmod (ev_now (loop), 3600.), 3600., 0); |
2228 | \& fmod (ev_now (loop), 3600.), 3600., 0); |
1616 | \& ev_periodic_start (loop, &hourly_tick); |
2229 | \& ev_periodic_start (loop, &hourly_tick); |
1617 | .Ve |
2230 | .Ve |
1618 | .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" |
2231 | .ie n .SS """ev_signal"" \- signal me when a signal gets signalled!" |
1619 | .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
2232 | .el .SS "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
1620 | .IX Subsection "ev_signal - signal me when a signal gets signalled!" |
2233 | .IX Subsection "ev_signal - signal me when a signal gets signalled!" |
1621 | Signal watchers will trigger an event when the process receives a specific |
2234 | Signal watchers will trigger an event when the process receives a specific |
1622 | signal one or more times. Even though signals are very asynchronous, libev |
2235 | signal one or more times. Even though signals are very asynchronous, libev |
1623 | will try it's best to deliver signals synchronously, i.e. as part of the |
2236 | will try it's best to deliver signals synchronously, i.e. as part of the |
1624 | normal event processing, like any other event. |
2237 | normal event processing, like any other event. |
1625 | .PP |
2238 | .PP |
|
|
2239 | If you want signals to be delivered truly asynchronously, just use |
|
|
2240 | \&\f(CW\*(C`sigaction\*(C'\fR as you would do without libev and forget about sharing |
|
|
2241 | the signal. You can even use \f(CW\*(C`ev_async\*(C'\fR from a signal handler to |
|
|
2242 | synchronously wake up an event loop. |
|
|
2243 | .PP |
1626 | You can configure as many watchers as you like per signal. Only when the |
2244 | You can configure as many watchers as you like for the same signal, but |
|
|
2245 | only within the same loop, i.e. you can watch for \f(CW\*(C`SIGINT\*(C'\fR in your |
|
|
2246 | default loop and for \f(CW\*(C`SIGIO\*(C'\fR in another loop, but you cannot watch for |
|
|
2247 | \&\f(CW\*(C`SIGINT\*(C'\fR in both the default loop and another loop at the same time. At |
|
|
2248 | the moment, \f(CW\*(C`SIGCHLD\*(C'\fR is permanently tied to the default loop. |
|
|
2249 | .PP |
1627 | first watcher gets started will libev actually register a signal watcher |
2250 | When the first watcher gets started will libev actually register something |
1628 | with the kernel (thus it coexists with your own signal handlers as long |
2251 | with the kernel (thus it coexists with your own signal handlers as long as |
1629 | as you don't register any with libev). Similarly, when the last signal |
2252 | you don't register any with libev for the same signal). |
1630 | watcher for a signal is stopped libev will reset the signal handler to |
2253 | .PP |
1631 | \&\s-1SIG_DFL\s0 (regardless of what it was set to before). |
2254 | Both the signal mask state (\f(CW\*(C`sigprocmask\*(C'\fR) and the signal handler state |
|
|
2255 | (\f(CW\*(C`sigaction\*(C'\fR) are unspecified after starting a signal watcher (and after |
|
|
2256 | sotpping it again), that is, libev might or might not block the signal, |
|
|
2257 | and might or might not set or restore the installed signal handler. |
1632 | .PP |
2258 | .PP |
1633 | If possible and supported, libev will install its handlers with |
2259 | If possible and supported, libev will install its handlers with |
1634 | \&\f(CW\*(C`SA_RESTART\*(C'\fR behaviour enabled, so system calls should not be unduly |
2260 | \&\f(CW\*(C`SA_RESTART\*(C'\fR (or equivalent) behaviour enabled, so system calls should |
1635 | interrupted. If you have a problem with system calls getting interrupted by |
2261 | not be unduly interrupted. If you have a problem with system calls getting |
1636 | signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher and unblock |
2262 | interrupted by signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher |
1637 | them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher. |
2263 | and unblock them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher. |
1638 | .PP |
2264 | .PP |
1639 | \fIWatcher-Specific Functions and Data Members\fR |
2265 | \fIWatcher-Specific Functions and Data Members\fR |
1640 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2266 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1641 | .IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
2267 | .IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
1642 | .IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
2268 | .IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
… | |
… | |
1651 | The signal the watcher watches out for. |
2277 | The signal the watcher watches out for. |
1652 | .PP |
2278 | .PP |
1653 | \fIExamples\fR |
2279 | \fIExamples\fR |
1654 | .IX Subsection "Examples" |
2280 | .IX Subsection "Examples" |
1655 | .PP |
2281 | .PP |
1656 | Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. |
2282 | Example: Try to exit cleanly on \s-1SIGINT\s0. |
1657 | .PP |
2283 | .PP |
1658 | .Vb 5 |
2284 | .Vb 5 |
1659 | \& static void |
2285 | \& static void |
1660 | \& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2286 | \& sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1661 | \& { |
2287 | \& { |
1662 | \& ev_unloop (loop, EVUNLOOP_ALL); |
2288 | \& ev_unloop (loop, EVUNLOOP_ALL); |
1663 | \& } |
2289 | \& } |
1664 | \& |
2290 | \& |
1665 | \& struct ev_signal signal_watcher; |
2291 | \& ev_signal signal_watcher; |
1666 | \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2292 | \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1667 | \& ev_signal_start (loop, &sigint_cb); |
2293 | \& ev_signal_start (loop, &signal_watcher); |
1668 | .Ve |
2294 | .Ve |
1669 | .ie n .Sh """ev_child"" \- watch out for process status changes" |
2295 | .ie n .SS """ev_child"" \- watch out for process status changes" |
1670 | .el .Sh "\f(CWev_child\fP \- watch out for process status changes" |
2296 | .el .SS "\f(CWev_child\fP \- watch out for process status changes" |
1671 | .IX Subsection "ev_child - watch out for process status changes" |
2297 | .IX Subsection "ev_child - watch out for process status changes" |
1672 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
2298 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
1673 | some child status changes (most typically when a child of yours dies). It |
2299 | some child status changes (most typically when a child of yours dies or |
1674 | is permissible to install a child watcher \fIafter\fR the child has been |
2300 | exits). It is permissible to install a child watcher \fIafter\fR the child |
1675 | forked (which implies it might have already exited), as long as the event |
2301 | has been forked (which implies it might have already exited), as long |
1676 | loop isn't entered (or is continued from a watcher). |
2302 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2303 | forking and then immediately registering a watcher for the child is fine, |
|
|
2304 | but forking and registering a watcher a few event loop iterations later or |
|
|
2305 | in the next callback invocation is not. |
1677 | .PP |
2306 | .PP |
1678 | Only the default event loop is capable of handling signals, and therefore |
2307 | Only the default event loop is capable of handling signals, and therefore |
1679 | you can only register child watchers in the default event loop. |
2308 | you can only register child watchers in the default event loop. |
1680 | .PP |
2309 | .PP |
|
|
2310 | Due to some design glitches inside libev, child watchers will always be |
|
|
2311 | handled at maximum priority (their priority is set to \f(CW\*(C`EV_MAXPRI\*(C'\fR by |
|
|
2312 | libev) |
|
|
2313 | .PP |
1681 | \fIProcess Interaction\fR |
2314 | \fIProcess Interaction\fR |
1682 | .IX Subsection "Process Interaction" |
2315 | .IX Subsection "Process Interaction" |
1683 | .PP |
2316 | .PP |
1684 | Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is |
2317 | Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is |
1685 | initialised. This is necessary to guarantee proper behaviour even if |
2318 | initialised. This is necessary to guarantee proper behaviour even if the |
1686 | the first child watcher is started after the child exits. The occurrence |
2319 | first child watcher is started after the child exits. The occurrence |
1687 | of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done |
2320 | of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done |
1688 | synchronously as part of the event loop processing. Libev always reaps all |
2321 | synchronously as part of the event loop processing. Libev always reaps all |
1689 | children, even ones not watched. |
2322 | children, even ones not watched. |
1690 | .PP |
2323 | .PP |
1691 | \fIOverriding the Built-In Processing\fR |
2324 | \fIOverriding the Built-In Processing\fR |
… | |
… | |
1696 | handler, you can override it easily by installing your own handler for |
2329 | handler, you can override it easily by installing your own handler for |
1697 | \&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the |
2330 | \&\f(CW\*(C`SIGCHLD\*(C'\fR after initialising the default loop, and making sure the |
1698 | default loop never gets destroyed. You are encouraged, however, to use an |
2331 | default loop never gets destroyed. You are encouraged, however, to use an |
1699 | event-based approach to child reaping and thus use libev's support for |
2332 | event-based approach to child reaping and thus use libev's support for |
1700 | that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely. |
2333 | that, so other libev users can use \f(CW\*(C`ev_child\*(C'\fR watchers freely. |
|
|
2334 | .PP |
|
|
2335 | \fIStopping the Child Watcher\fR |
|
|
2336 | .IX Subsection "Stopping the Child Watcher" |
|
|
2337 | .PP |
|
|
2338 | Currently, the child watcher never gets stopped, even when the |
|
|
2339 | child terminates, so normally one needs to stop the watcher in the |
|
|
2340 | callback. Future versions of libev might stop the watcher automatically |
|
|
2341 | when a child exit is detected (calling \f(CW\*(C`ev_child_stop\*(C'\fR twice is not a |
|
|
2342 | problem). |
1701 | .PP |
2343 | .PP |
1702 | \fIWatcher-Specific Functions and Data Members\fR |
2344 | \fIWatcher-Specific Functions and Data Members\fR |
1703 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2345 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1704 | .IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4 |
2346 | .IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4 |
1705 | .IX Item "ev_child_init (ev_child *, callback, int pid, int trace)" |
2347 | .IX Item "ev_child_init (ev_child *, callback, int pid, int trace)" |
… | |
… | |
1734 | .PP |
2376 | .PP |
1735 | .Vb 1 |
2377 | .Vb 1 |
1736 | \& ev_child cw; |
2378 | \& ev_child cw; |
1737 | \& |
2379 | \& |
1738 | \& static void |
2380 | \& static void |
1739 | \& child_cb (EV_P_ struct ev_child *w, int revents) |
2381 | \& child_cb (EV_P_ ev_child *w, int revents) |
1740 | \& { |
2382 | \& { |
1741 | \& ev_child_stop (EV_A_ w); |
2383 | \& ev_child_stop (EV_A_ w); |
1742 | \& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus); |
2384 | \& printf ("process %d exited with status %x\en", w\->rpid, w\->rstatus); |
1743 | \& } |
2385 | \& } |
1744 | \& |
2386 | \& |
… | |
… | |
1755 | \& { |
2397 | \& { |
1756 | \& ev_child_init (&cw, child_cb, pid, 0); |
2398 | \& ev_child_init (&cw, child_cb, pid, 0); |
1757 | \& ev_child_start (EV_DEFAULT_ &cw); |
2399 | \& ev_child_start (EV_DEFAULT_ &cw); |
1758 | \& } |
2400 | \& } |
1759 | .Ve |
2401 | .Ve |
1760 | .ie n .Sh """ev_stat"" \- did the file attributes just change?" |
2402 | .ie n .SS """ev_stat"" \- did the file attributes just change?" |
1761 | .el .Sh "\f(CWev_stat\fP \- did the file attributes just change?" |
2403 | .el .SS "\f(CWev_stat\fP \- did the file attributes just change?" |
1762 | .IX Subsection "ev_stat - did the file attributes just change?" |
2404 | .IX Subsection "ev_stat - did the file attributes just change?" |
1763 | This watches a file system path for attribute changes. That is, it calls |
2405 | This watches a file system path for attribute changes. That is, it calls |
1764 | \&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed |
2406 | \&\f(CW\*(C`stat\*(C'\fR on that path in regular intervals (or when the \s-1OS\s0 says it changed) |
1765 | compared to the last time, invoking the callback if it did. |
2407 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2408 | it did. |
1766 | .PP |
2409 | .PP |
1767 | The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
2410 | The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
1768 | not exist\*(R" is a status change like any other. The condition \*(L"path does |
2411 | not exist\*(R" is a status change like any other. The condition \*(L"path does not |
1769 | not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is |
2412 | exist\*(R" (or more correctly \*(L"path cannot be stat'ed\*(R") is signified by the |
1770 | otherwise always forced to be at least one) and all the other fields of |
2413 | \&\f(CW\*(C`st_nlink\*(C'\fR field being zero (which is otherwise always forced to be at |
1771 | the stat buffer having unspecified contents. |
2414 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2415 | contents. |
1772 | .PP |
2416 | .PP |
1773 | The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is |
2417 | The path \fImust not\fR end in a slash or contain special components such as |
|
|
2418 | \&\f(CW\*(C`.\*(C'\fR or \f(CW\*(C`..\*(C'\fR. The path \fIshould\fR be absolute: If it is relative and |
1774 | relative and your working directory changes, the behaviour is undefined. |
2419 | your working directory changes, then the behaviour is undefined. |
1775 | .PP |
2420 | .PP |
1776 | Since there is no standard to do this, the portable implementation simply |
2421 | Since there is no portable change notification interface available, the |
1777 | calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You |
2422 | portable implementation simply calls \f(CWstat(2)\fR regularly on the path |
1778 | can specify a recommended polling interval for this case. If you specify |
2423 | to see if it changed somehow. You can specify a recommended polling |
1779 | a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable, |
2424 | interval for this case. If you specify a polling interval of \f(CW0\fR (highly |
1780 | unspecified default\fR value will be used (which you can expect to be around |
2425 | recommended!) then a \fIsuitable, unspecified default\fR value will be used |
1781 | five seconds, although this might change dynamically). Libev will also |
2426 | (which you can expect to be around five seconds, although this might |
1782 | impose a minimum interval which is currently around \f(CW0.1\fR, but thats |
2427 | change dynamically). Libev will also impose a minimum interval which is |
1783 | usually overkill. |
2428 | currently around \f(CW0.1\fR, but that's usually overkill. |
1784 | .PP |
2429 | .PP |
1785 | This watcher type is not meant for massive numbers of stat watchers, |
2430 | This watcher type is not meant for massive numbers of stat watchers, |
1786 | as even with OS-supported change notifications, this can be |
2431 | as even with OS-supported change notifications, this can be |
1787 | resource-intensive. |
2432 | resource-intensive. |
1788 | .PP |
2433 | .PP |
1789 | At the time of this writing, only the Linux inotify interface is |
2434 | At the time of this writing, the only OS-specific interface implemented |
1790 | implemented (implementing kqueue support is left as an exercise for the |
2435 | is the Linux inotify interface (implementing kqueue support is left as an |
1791 | reader, note, however, that the author sees no way of implementing ev_stat |
2436 | exercise for the reader. Note, however, that the author sees no way of |
1792 | semantics with kqueue). Inotify will be used to give hints only and should |
2437 | implementing \f(CW\*(C`ev_stat\*(C'\fR semantics with kqueue, except as a hint). |
1793 | not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev |
|
|
1794 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1795 | but changes are usually detected immediately, and if the file exists there |
|
|
1796 | will be no polling. |
|
|
1797 | .PP |
2438 | .PP |
1798 | \fI\s-1ABI\s0 Issues (Largefile Support)\fR |
2439 | \fI\s-1ABI\s0 Issues (Largefile Support)\fR |
1799 | .IX Subsection "ABI Issues (Largefile Support)" |
2440 | .IX Subsection "ABI Issues (Largefile Support)" |
1800 | .PP |
2441 | .PP |
1801 | Libev by default (unless the user overrides this) uses the default |
2442 | Libev by default (unless the user overrides this) uses the default |
… | |
… | |
1803 | support disabled by default, you get the 32 bit version of the stat |
2444 | support disabled by default, you get the 32 bit version of the stat |
1804 | structure. When using the library from programs that change the \s-1ABI\s0 to |
2445 | structure. When using the library from programs that change the \s-1ABI\s0 to |
1805 | use 64 bit file offsets the programs will fail. In that case you have to |
2446 | use 64 bit file offsets the programs will fail. In that case you have to |
1806 | compile libev with the same flags to get binary compatibility. This is |
2447 | compile libev with the same flags to get binary compatibility. This is |
1807 | obviously the case with any flags that change the \s-1ABI\s0, but the problem is |
2448 | obviously the case with any flags that change the \s-1ABI\s0, but the problem is |
1808 | most noticeably disabled with ev_stat and large file support. |
2449 | most noticeably displayed with ev_stat and large file support. |
1809 | .PP |
2450 | .PP |
1810 | The solution for this is to lobby your distribution maker to make large |
2451 | The solution for this is to lobby your distribution maker to make large |
1811 | file interfaces available by default (as e.g. FreeBSD does) and not |
2452 | file interfaces available by default (as e.g. FreeBSD does) and not |
1812 | optional. Libev cannot simply switch on large file support because it has |
2453 | optional. Libev cannot simply switch on large file support because it has |
1813 | to exchange stat structures with application programs compiled using the |
2454 | to exchange stat structures with application programs compiled using the |
1814 | default compilation environment. |
2455 | default compilation environment. |
1815 | .PP |
2456 | .PP |
1816 | \fIInotify\fR |
2457 | \fIInotify and Kqueue\fR |
1817 | .IX Subsection "Inotify" |
2458 | .IX Subsection "Inotify and Kqueue" |
1818 | .PP |
2459 | .PP |
1819 | When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev (generally only |
2460 | When \f(CW\*(C`inotify (7)\*(C'\fR support has been compiled into libev and present at |
1820 | available on Linux) and present at runtime, it will be used to speed up |
2461 | runtime, it will be used to speed up change detection where possible. The |
1821 | change detection where possible. The inotify descriptor will be created lazily |
2462 | inotify descriptor will be created lazily when the first \f(CW\*(C`ev_stat\*(C'\fR |
1822 | when the first \f(CW\*(C`ev_stat\*(C'\fR watcher is being started. |
2463 | watcher is being started. |
1823 | .PP |
2464 | .PP |
1824 | Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers |
2465 | Inotify presence does not change the semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers |
1825 | except that changes might be detected earlier, and in some cases, to avoid |
2466 | except that changes might be detected earlier, and in some cases, to avoid |
1826 | making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support |
2467 | making regular \f(CW\*(C`stat\*(C'\fR calls. Even in the presence of inotify support |
1827 | there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling. |
2468 | there are many cases where libev has to resort to regular \f(CW\*(C`stat\*(C'\fR polling, |
|
|
2469 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2470 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2471 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2472 | xfs are fully working) libev usually gets away without polling. |
1828 | .PP |
2473 | .PP |
1829 | (There is no support for kqueue, as apparently it cannot be used to |
2474 | There is no support for kqueue, as apparently it cannot be used to |
1830 | implement this functionality, due to the requirement of having a file |
2475 | implement this functionality, due to the requirement of having a file |
1831 | descriptor open on the object at all times). |
2476 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2477 | etc. is difficult. |
|
|
2478 | .PP |
|
|
2479 | \fI\f(CI\*(C`stat ()\*(C'\fI is a synchronous operation\fR |
|
|
2480 | .IX Subsection "stat () is a synchronous operation" |
|
|
2481 | .PP |
|
|
2482 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2483 | the process. The exception are \f(CW\*(C`ev_stat\*(C'\fR watchers \- those call \f(CW\*(C`stat |
|
|
2484 | ()\*(C'\fR, which is a synchronous operation. |
|
|
2485 | .PP |
|
|
2486 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2487 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2488 | as the path data is usually in memory already (except when starting the |
|
|
2489 | watcher). |
|
|
2490 | .PP |
|
|
2491 | For networked file systems, calling \f(CW\*(C`stat ()\*(C'\fR can block an indefinite |
|
|
2492 | time due to network issues, and even under good conditions, a stat call |
|
|
2493 | often takes multiple milliseconds. |
|
|
2494 | .PP |
|
|
2495 | Therefore, it is best to avoid using \f(CW\*(C`ev_stat\*(C'\fR watchers on networked |
|
|
2496 | paths, although this is fully supported by libev. |
1832 | .PP |
2497 | .PP |
1833 | \fIThe special problem of stat time resolution\fR |
2498 | \fIThe special problem of stat time resolution\fR |
1834 | .IX Subsection "The special problem of stat time resolution" |
2499 | .IX Subsection "The special problem of stat time resolution" |
1835 | .PP |
2500 | .PP |
1836 | The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably, and |
2501 | The \f(CW\*(C`stat ()\*(C'\fR system call only supports full-second resolution portably, |
1837 | even on systems where the resolution is higher, many file systems still |
2502 | and even on systems where the resolution is higher, most file systems |
1838 | only support whole seconds. |
2503 | still only support whole seconds. |
1839 | .PP |
2504 | .PP |
1840 | That means that, if the time is the only thing that changes, you can |
2505 | That means that, if the time is the only thing that changes, you can |
1841 | easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and |
2506 | easily miss updates: on the first update, \f(CW\*(C`ev_stat\*(C'\fR detects a change and |
1842 | calls your callback, which does something. When there is another update |
2507 | calls your callback, which does something. When there is another update |
1843 | within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect it as the stat |
2508 | within the same second, \f(CW\*(C`ev_stat\*(C'\fR will be unable to detect unless the |
1844 | data does not change. |
2509 | stat data does change in other ways (e.g. file size). |
1845 | .PP |
2510 | .PP |
1846 | The solution to this is to delay acting on a change for slightly more |
2511 | The solution to this is to delay acting on a change for slightly more |
1847 | than a second (or till slightly after the next full second boundary), using |
2512 | than a second (or till slightly after the next full second boundary), using |
1848 | a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02); |
2513 | a roughly one-second-delay \f(CW\*(C`ev_timer\*(C'\fR (e.g. \f(CW\*(C`ev_timer_set (w, 0., 1.02); |
1849 | ev_timer_again (loop, w)\*(C'\fR). |
2514 | ev_timer_again (loop, w)\*(C'\fR). |
… | |
… | |
1869 | \&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to |
2534 | \&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to |
1870 | be detected and should normally be specified as \f(CW0\fR to let libev choose |
2535 | be detected and should normally be specified as \f(CW0\fR to let libev choose |
1871 | a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same |
2536 | a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same |
1872 | path for as long as the watcher is active. |
2537 | path for as long as the watcher is active. |
1873 | .Sp |
2538 | .Sp |
1874 | The callback will receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected, relative |
2539 | The callback will receive an \f(CW\*(C`EV_STAT\*(C'\fR event when a change was detected, |
1875 | to the attributes at the time the watcher was started (or the last change |
2540 | relative to the attributes at the time the watcher was started (or the |
1876 | was detected). |
2541 | last change was detected). |
1877 | .IP "ev_stat_stat (loop, ev_stat *)" 4 |
2542 | .IP "ev_stat_stat (loop, ev_stat *)" 4 |
1878 | .IX Item "ev_stat_stat (loop, ev_stat *)" |
2543 | .IX Item "ev_stat_stat (loop, ev_stat *)" |
1879 | Updates the stat buffer immediately with new values. If you change the |
2544 | Updates the stat buffer immediately with new values. If you change the |
1880 | watched path in your callback, you could call this function to avoid |
2545 | watched path in your callback, you could call this function to avoid |
1881 | detecting this change (while introducing a race condition if you are not |
2546 | detecting this change (while introducing a race condition if you are not |
… | |
… | |
1957 | \& ... |
2622 | \& ... |
1958 | \& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
2623 | \& ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1959 | \& ev_stat_start (loop, &passwd); |
2624 | \& ev_stat_start (loop, &passwd); |
1960 | \& ev_timer_init (&timer, timer_cb, 0., 1.02); |
2625 | \& ev_timer_init (&timer, timer_cb, 0., 1.02); |
1961 | .Ve |
2626 | .Ve |
1962 | .ie n .Sh """ev_idle"" \- when you've got nothing better to do..." |
2627 | .ie n .SS """ev_idle"" \- when you've got nothing better to do..." |
1963 | .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." |
2628 | .el .SS "\f(CWev_idle\fP \- when you've got nothing better to do..." |
1964 | .IX Subsection "ev_idle - when you've got nothing better to do..." |
2629 | .IX Subsection "ev_idle - when you've got nothing better to do..." |
1965 | Idle watchers trigger events when no other events of the same or higher |
2630 | Idle watchers trigger events when no other events of the same or higher |
1966 | priority are pending (prepare, check and other idle watchers do not |
2631 | priority are pending (prepare, check and other idle watchers do not count |
1967 | count). |
2632 | as receiving \*(L"events\*(R"). |
1968 | .PP |
2633 | .PP |
1969 | That is, as long as your process is busy handling sockets or timeouts |
2634 | That is, as long as your process is busy handling sockets or timeouts |
1970 | (or even signals, imagine) of the same or higher priority it will not be |
2635 | (or even signals, imagine) of the same or higher priority it will not be |
1971 | triggered. But when your process is idle (or only lower-priority watchers |
2636 | triggered. But when your process is idle (or only lower-priority watchers |
1972 | are pending), the idle watchers are being called once per event loop |
2637 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1981 | \&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the |
2646 | \&\*(L"pseudo-background processing\*(R", or delay processing stuff to after the |
1982 | event loop has handled all outstanding events. |
2647 | event loop has handled all outstanding events. |
1983 | .PP |
2648 | .PP |
1984 | \fIWatcher-Specific Functions and Data Members\fR |
2649 | \fIWatcher-Specific Functions and Data Members\fR |
1985 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2650 | .IX Subsection "Watcher-Specific Functions and Data Members" |
1986 | .IP "ev_idle_init (ev_signal *, callback)" 4 |
2651 | .IP "ev_idle_init (ev_idle *, callback)" 4 |
1987 | .IX Item "ev_idle_init (ev_signal *, callback)" |
2652 | .IX Item "ev_idle_init (ev_idle *, callback)" |
1988 | Initialises and configures the idle watcher \- it has no parameters of any |
2653 | Initialises and configures the idle watcher \- it has no parameters of any |
1989 | kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
2654 | kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
1990 | believe me. |
2655 | believe me. |
1991 | .PP |
2656 | .PP |
1992 | \fIExamples\fR |
2657 | \fIExamples\fR |
… | |
… | |
1995 | Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the |
2660 | Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the |
1996 | callback, free it. Also, use no error checking, as usual. |
2661 | callback, free it. Also, use no error checking, as usual. |
1997 | .PP |
2662 | .PP |
1998 | .Vb 7 |
2663 | .Vb 7 |
1999 | \& static void |
2664 | \& static void |
2000 | \& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2665 | \& idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2001 | \& { |
2666 | \& { |
2002 | \& free (w); |
2667 | \& free (w); |
2003 | \& // now do something you wanted to do when the program has |
2668 | \& // now do something you wanted to do when the program has |
2004 | \& // no longer anything immediate to do. |
2669 | \& // no longer anything immediate to do. |
2005 | \& } |
2670 | \& } |
2006 | \& |
2671 | \& |
2007 | \& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2672 | \& ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2008 | \& ev_idle_init (idle_watcher, idle_cb); |
2673 | \& ev_idle_init (idle_watcher, idle_cb); |
2009 | \& ev_idle_start (loop, idle_cb); |
2674 | \& ev_idle_start (loop, idle_watcher); |
2010 | .Ve |
2675 | .Ve |
2011 | .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" |
2676 | .ie n .SS """ev_prepare"" and ""ev_check"" \- customise your event loop!" |
2012 | .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
2677 | .el .SS "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
2013 | .IX Subsection "ev_prepare and ev_check - customise your event loop!" |
2678 | .IX Subsection "ev_prepare and ev_check - customise your event loop!" |
2014 | Prepare and check watchers are usually (but not always) used in tandem: |
2679 | Prepare and check watchers are usually (but not always) used in pairs: |
2015 | prepare watchers get invoked before the process blocks and check watchers |
2680 | prepare watchers get invoked before the process blocks and check watchers |
2016 | afterwards. |
2681 | afterwards. |
2017 | .PP |
2682 | .PP |
2018 | You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter |
2683 | You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter |
2019 | the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR |
2684 | the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR |
… | |
… | |
2022 | those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, |
2687 | those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, |
2023 | \&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be |
2688 | \&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be |
2024 | called in pairs bracketing the blocking call. |
2689 | called in pairs bracketing the blocking call. |
2025 | .PP |
2690 | .PP |
2026 | Their main purpose is to integrate other event mechanisms into libev and |
2691 | Their main purpose is to integrate other event mechanisms into libev and |
2027 | their use is somewhat advanced. This could be used, for example, to track |
2692 | their use is somewhat advanced. They could be used, for example, to track |
2028 | variable changes, implement your own watchers, integrate net-snmp or a |
2693 | variable changes, implement your own watchers, integrate net-snmp or a |
2029 | coroutine library and lots more. They are also occasionally useful if |
2694 | coroutine library and lots more. They are also occasionally useful if |
2030 | you cache some data and want to flush it before blocking (for example, |
2695 | you cache some data and want to flush it before blocking (for example, |
2031 | in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR |
2696 | in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR |
2032 | watcher). |
2697 | watcher). |
2033 | .PP |
2698 | .PP |
2034 | This is done by examining in each prepare call which file descriptors need |
2699 | This is done by examining in each prepare call which file descriptors |
2035 | to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for |
2700 | need to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers |
2036 | them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries |
2701 | for them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many |
2037 | provide just this functionality). Then, in the check watcher you check for |
2702 | libraries provide exactly this functionality). Then, in the check watcher, |
2038 | any events that occurred (by checking the pending status of all watchers |
2703 | you check for any events that occurred (by checking the pending status |
2039 | and stopping them) and call back into the library. The I/O and timer |
2704 | of all watchers and stopping them) and call back into the library. The |
2040 | callbacks will never actually be called (but must be valid nevertheless, |
2705 | I/O and timer callbacks will never actually be called (but must be valid |
2041 | because you never know, you know?). |
2706 | nevertheless, because you never know, you know?). |
2042 | .PP |
2707 | .PP |
2043 | As another example, the Perl Coro module uses these hooks to integrate |
2708 | As another example, the Perl Coro module uses these hooks to integrate |
2044 | coroutines into libev programs, by yielding to other active coroutines |
2709 | coroutines into libev programs, by yielding to other active coroutines |
2045 | during each prepare and only letting the process block if no coroutines |
2710 | during each prepare and only letting the process block if no coroutines |
2046 | are ready to run (it's actually more complicated: it only runs coroutines |
2711 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
2049 | loop from blocking if lower-priority coroutines are active, thus mapping |
2714 | loop from blocking if lower-priority coroutines are active, thus mapping |
2050 | low-priority coroutines to idle/background tasks). |
2715 | low-priority coroutines to idle/background tasks). |
2051 | .PP |
2716 | .PP |
2052 | It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) |
2717 | It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR) |
2053 | priority, to ensure that they are being run before any other watchers |
2718 | priority, to ensure that they are being run before any other watchers |
|
|
2719 | after the poll (this doesn't matter for \f(CW\*(C`ev_prepare\*(C'\fR watchers). |
|
|
2720 | .PP |
2054 | after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, |
2721 | Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers, too) should not |
2055 | too) should not activate (\*(L"feed\*(R") events into libev. While libev fully |
2722 | activate (\*(L"feed\*(R") events into libev. While libev fully supports this, they |
2056 | supports this, they might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers |
2723 | might get executed before other \f(CW\*(C`ev_check\*(C'\fR watchers did their job. As |
2057 | did their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other |
2724 | \&\f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other (non-libev) event |
2058 | (non-libev) event loops those other event loops might be in an unusable |
2725 | loops those other event loops might be in an unusable state until their |
2059 | state until their \f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to |
2726 | \&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with |
2060 | coexist peacefully with others). |
2727 | others). |
2061 | .PP |
2728 | .PP |
2062 | \fIWatcher-Specific Functions and Data Members\fR |
2729 | \fIWatcher-Specific Functions and Data Members\fR |
2063 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2730 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2064 | .IP "ev_prepare_init (ev_prepare *, callback)" 4 |
2731 | .IP "ev_prepare_init (ev_prepare *, callback)" 4 |
2065 | .IX Item "ev_prepare_init (ev_prepare *, callback)" |
2732 | .IX Item "ev_prepare_init (ev_prepare *, callback)" |
… | |
… | |
2067 | .IP "ev_check_init (ev_check *, callback)" 4 |
2734 | .IP "ev_check_init (ev_check *, callback)" 4 |
2068 | .IX Item "ev_check_init (ev_check *, callback)" |
2735 | .IX Item "ev_check_init (ev_check *, callback)" |
2069 | .PD |
2736 | .PD |
2070 | Initialises and configures the prepare or check watcher \- they have no |
2737 | Initialises and configures the prepare or check watcher \- they have no |
2071 | parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
2738 | parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
2072 | macros, but using them is utterly, utterly and completely pointless. |
2739 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2740 | pointless. |
2073 | .PP |
2741 | .PP |
2074 | \fIExamples\fR |
2742 | \fIExamples\fR |
2075 | .IX Subsection "Examples" |
2743 | .IX Subsection "Examples" |
2076 | .PP |
2744 | .PP |
2077 | There are a number of principal ways to embed other event loops or modules |
2745 | There are a number of principal ways to embed other event loops or modules |
… | |
… | |
2090 | .Vb 2 |
2758 | .Vb 2 |
2091 | \& static ev_io iow [nfd]; |
2759 | \& static ev_io iow [nfd]; |
2092 | \& static ev_timer tw; |
2760 | \& static ev_timer tw; |
2093 | \& |
2761 | \& |
2094 | \& static void |
2762 | \& static void |
2095 | \& io_cb (ev_loop *loop, ev_io *w, int revents) |
2763 | \& io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2096 | \& { |
2764 | \& { |
2097 | \& } |
2765 | \& } |
2098 | \& |
2766 | \& |
2099 | \& // create io watchers for each fd and a timer before blocking |
2767 | \& // create io watchers for each fd and a timer before blocking |
2100 | \& static void |
2768 | \& static void |
2101 | \& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2769 | \& adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2102 | \& { |
2770 | \& { |
2103 | \& int timeout = 3600000; |
2771 | \& int timeout = 3600000; |
2104 | \& struct pollfd fds [nfd]; |
2772 | \& struct pollfd fds [nfd]; |
2105 | \& // actual code will need to loop here and realloc etc. |
2773 | \& // actual code will need to loop here and realloc etc. |
2106 | \& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2774 | \& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2107 | \& |
2775 | \& |
2108 | \& /* the callback is illegal, but won\*(Aqt be called as we stop during check */ |
2776 | \& /* the callback is illegal, but won\*(Aqt be called as we stop during check */ |
2109 | \& ev_timer_init (&tw, 0, timeout * 1e\-3); |
2777 | \& ev_timer_init (&tw, 0, timeout * 1e\-3, 0.); |
2110 | \& ev_timer_start (loop, &tw); |
2778 | \& ev_timer_start (loop, &tw); |
2111 | \& |
2779 | \& |
2112 | \& // create one ev_io per pollfd |
2780 | \& // create one ev_io per pollfd |
2113 | \& for (int i = 0; i < nfd; ++i) |
2781 | \& for (int i = 0; i < nfd; ++i) |
2114 | \& { |
2782 | \& { |
… | |
… | |
2121 | \& } |
2789 | \& } |
2122 | \& } |
2790 | \& } |
2123 | \& |
2791 | \& |
2124 | \& // stop all watchers after blocking |
2792 | \& // stop all watchers after blocking |
2125 | \& static void |
2793 | \& static void |
2126 | \& adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2794 | \& adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2127 | \& { |
2795 | \& { |
2128 | \& ev_timer_stop (loop, &tw); |
2796 | \& ev_timer_stop (loop, &tw); |
2129 | \& |
2797 | \& |
2130 | \& for (int i = 0; i < nfd; ++i) |
2798 | \& for (int i = 0; i < nfd; ++i) |
2131 | \& { |
2799 | \& { |
… | |
… | |
2173 | \& |
2841 | \& |
2174 | \& // do not ever call adns_afterpoll |
2842 | \& // do not ever call adns_afterpoll |
2175 | .Ve |
2843 | .Ve |
2176 | .PP |
2844 | .PP |
2177 | Method 4: Do not use a prepare or check watcher because the module you |
2845 | Method 4: Do not use a prepare or check watcher because the module you |
2178 | want to embed is too inflexible to support it. Instead, you can override |
2846 | want to embed is not flexible enough to support it. Instead, you can |
2179 | their poll function. The drawback with this solution is that the main |
2847 | override their poll function. The drawback with this solution is that the |
2180 | loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does |
2848 | main loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module uses |
2181 | this. |
2849 | this approach, effectively embedding \s-1EV\s0 as a client into the horrible |
|
|
2850 | libglib event loop. |
2182 | .PP |
2851 | .PP |
2183 | .Vb 4 |
2852 | .Vb 4 |
2184 | \& static gint |
2853 | \& static gint |
2185 | \& event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2854 | \& event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2186 | \& { |
2855 | \& { |
… | |
… | |
2204 | \& ev_io_stop (EV_A_ iow [n]); |
2873 | \& ev_io_stop (EV_A_ iow [n]); |
2205 | \& |
2874 | \& |
2206 | \& return got_events; |
2875 | \& return got_events; |
2207 | \& } |
2876 | \& } |
2208 | .Ve |
2877 | .Ve |
2209 | .ie n .Sh """ev_embed"" \- when one backend isn't enough..." |
2878 | .ie n .SS """ev_embed"" \- when one backend isn't enough..." |
2210 | .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." |
2879 | .el .SS "\f(CWev_embed\fP \- when one backend isn't enough..." |
2211 | .IX Subsection "ev_embed - when one backend isn't enough..." |
2880 | .IX Subsection "ev_embed - when one backend isn't enough..." |
2212 | This is a rather advanced watcher type that lets you embed one event loop |
2881 | This is a rather advanced watcher type that lets you embed one event loop |
2213 | into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
2882 | into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
2214 | loop, other types of watchers might be handled in a delayed or incorrect |
2883 | loop, other types of watchers might be handled in a delayed or incorrect |
2215 | fashion and must not be used). |
2884 | fashion and must not be used). |
… | |
… | |
2218 | prioritise I/O. |
2887 | prioritise I/O. |
2219 | .PP |
2888 | .PP |
2220 | As an example for a bug workaround, the kqueue backend might only support |
2889 | As an example for a bug workaround, the kqueue backend might only support |
2221 | sockets on some platform, so it is unusable as generic backend, but you |
2890 | sockets on some platform, so it is unusable as generic backend, but you |
2222 | still want to make use of it because you have many sockets and it scales |
2891 | still want to make use of it because you have many sockets and it scales |
2223 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2892 | so nicely. In this case, you would create a kqueue-based loop and embed |
2224 | into your default loop (which might use e.g. poll). Overall operation will |
2893 | it into your default loop (which might use e.g. poll). Overall operation |
2225 | be a bit slower because first libev has to poll and then call kevent, but |
2894 | will be a bit slower because first libev has to call \f(CW\*(C`poll\*(C'\fR and then |
2226 | at least you can use both at what they are best. |
2895 | \&\f(CW\*(C`kevent\*(C'\fR, but at least you can use both mechanisms for what they are |
|
|
2896 | best: \f(CW\*(C`kqueue\*(C'\fR for scalable sockets and \f(CW\*(C`poll\*(C'\fR if you want it to work :) |
2227 | .PP |
2897 | .PP |
2228 | As for prioritising I/O: rarely you have the case where some fds have |
2898 | As for prioritising I/O: under rare circumstances you have the case where |
2229 | to be watched and handled very quickly (with low latency), and even |
2899 | some fds have to be watched and handled very quickly (with low latency), |
2230 | priorities and idle watchers might have too much overhead. In this case |
2900 | and even priorities and idle watchers might have too much overhead. In |
2231 | you would put all the high priority stuff in one loop and all the rest in |
2901 | this case you would put all the high priority stuff in one loop and all |
2232 | a second one, and embed the second one in the first. |
2902 | the rest in a second one, and embed the second one in the first. |
2233 | .PP |
2903 | .PP |
2234 | As long as the watcher is active, the callback will be invoked every time |
2904 | As long as the watcher is active, the callback will be invoked every |
2235 | there might be events pending in the embedded loop. The callback must then |
2905 | time there might be events pending in the embedded loop. The callback |
2236 | call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke |
2906 | must then call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single |
2237 | their callbacks (you could also start an idle watcher to give the embedded |
2907 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2238 | loop strictly lower priority for example). You can also set the callback |
2908 | \&\f(CW\*(C`ev_embed_sweep\*(C'\fR function directly, it could also start an idle watcher |
2239 | to \f(CW0\fR, in which case the embed watcher will automatically execute the |
2909 | to give the embedded loop strictly lower priority for example). |
2240 | embedded loop sweep. |
|
|
2241 | .PP |
2910 | .PP |
2242 | As long as the watcher is started it will automatically handle events. The |
2911 | You can also set the callback to \f(CW0\fR, in which case the embed watcher |
2243 | callback will be invoked whenever some events have been handled. You can |
2912 | will automatically execute the embedded loop sweep whenever necessary. |
2244 | set the callback to \f(CW0\fR to avoid having to specify one if you are not |
|
|
2245 | interested in that. |
|
|
2246 | .PP |
2913 | .PP |
2247 | Also, there have not currently been made special provisions for forking: |
2914 | Fork detection will be handled transparently while the \f(CW\*(C`ev_embed\*(C'\fR watcher |
2248 | when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops, |
2915 | is active, i.e., the embedded loop will automatically be forked when the |
2249 | but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers |
2916 | embedding loop forks. In other cases, the user is responsible for calling |
2250 | yourself. |
2917 | \&\f(CW\*(C`ev_loop_fork\*(C'\fR on the embedded loop. |
2251 | .PP |
2918 | .PP |
2252 | Unfortunately, not all backends are embeddable, only the ones returned by |
2919 | Unfortunately, not all backends are embeddable: only the ones returned by |
2253 | \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
2920 | \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
2254 | portable one. |
2921 | portable one. |
2255 | .PP |
2922 | .PP |
2256 | So when you want to use this feature you will always have to be prepared |
2923 | So when you want to use this feature you will always have to be prepared |
2257 | that you cannot get an embeddable loop. The recommended way to get around |
2924 | that you cannot get an embeddable loop. The recommended way to get around |
2258 | this is to have a separate variables for your embeddable loop, try to |
2925 | this is to have a separate variables for your embeddable loop, try to |
2259 | create it, and if that fails, use the normal loop for everything. |
2926 | create it, and if that fails, use the normal loop for everything. |
|
|
2927 | .PP |
|
|
2928 | \fI\f(CI\*(C`ev_embed\*(C'\fI and fork\fR |
|
|
2929 | .IX Subsection "ev_embed and fork" |
|
|
2930 | .PP |
|
|
2931 | While the \f(CW\*(C`ev_embed\*(C'\fR watcher is running, forks in the embedding loop will |
|
|
2932 | automatically be applied to the embedded loop as well, so no special |
|
|
2933 | fork handling is required in that case. When the watcher is not running, |
|
|
2934 | however, it is still the task of the libev user to call \f(CW\*(C`ev_loop_fork ()\*(C'\fR |
|
|
2935 | as applicable. |
2260 | .PP |
2936 | .PP |
2261 | \fIWatcher-Specific Functions and Data Members\fR |
2937 | \fIWatcher-Specific Functions and Data Members\fR |
2262 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2938 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2263 | .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
2939 | .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
2264 | .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" |
2940 | .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" |
… | |
… | |
2290 | used). |
2966 | used). |
2291 | .PP |
2967 | .PP |
2292 | .Vb 3 |
2968 | .Vb 3 |
2293 | \& struct ev_loop *loop_hi = ev_default_init (0); |
2969 | \& struct ev_loop *loop_hi = ev_default_init (0); |
2294 | \& struct ev_loop *loop_lo = 0; |
2970 | \& struct ev_loop *loop_lo = 0; |
2295 | \& struct ev_embed embed; |
2971 | \& ev_embed embed; |
2296 | \& |
2972 | \& |
2297 | \& // see if there is a chance of getting one that works |
2973 | \& // see if there is a chance of getting one that works |
2298 | \& // (remember that a flags value of 0 means autodetection) |
2974 | \& // (remember that a flags value of 0 means autodetection) |
2299 | \& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2975 | \& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2300 | \& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2976 | \& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2316 | \&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too). |
2992 | \&\f(CW\*(C`loop_socket\*(C'\fR. (One might optionally use \f(CW\*(C`EVFLAG_NOENV\*(C'\fR, too). |
2317 | .PP |
2993 | .PP |
2318 | .Vb 3 |
2994 | .Vb 3 |
2319 | \& struct ev_loop *loop = ev_default_init (0); |
2995 | \& struct ev_loop *loop = ev_default_init (0); |
2320 | \& struct ev_loop *loop_socket = 0; |
2996 | \& struct ev_loop *loop_socket = 0; |
2321 | \& struct ev_embed embed; |
2997 | \& ev_embed embed; |
2322 | \& |
2998 | \& |
2323 | \& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2999 | \& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2324 | \& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3000 | \& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2325 | \& { |
3001 | \& { |
2326 | \& ev_embed_init (&embed, 0, loop_socket); |
3002 | \& ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2330 | \& if (!loop_socket) |
3006 | \& if (!loop_socket) |
2331 | \& loop_socket = loop; |
3007 | \& loop_socket = loop; |
2332 | \& |
3008 | \& |
2333 | \& // now use loop_socket for all sockets, and loop for everything else |
3009 | \& // now use loop_socket for all sockets, and loop for everything else |
2334 | .Ve |
3010 | .Ve |
2335 | .ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork" |
3011 | .ie n .SS """ev_fork"" \- the audacity to resume the event loop after a fork" |
2336 | .el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" |
3012 | .el .SS "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" |
2337 | .IX Subsection "ev_fork - the audacity to resume the event loop after a fork" |
3013 | .IX Subsection "ev_fork - the audacity to resume the event loop after a fork" |
2338 | Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because |
3014 | Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because |
2339 | whoever is a good citizen cared to tell libev about it by calling |
3015 | whoever is a good citizen cared to tell libev about it by calling |
2340 | \&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the |
3016 | \&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the |
2341 | event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, |
3017 | event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, |
2342 | and only in the child after the fork. If whoever good citizen calling |
3018 | and only in the child after the fork. If whoever good citizen calling |
2343 | \&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork |
3019 | \&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork |
2344 | handlers will be invoked, too, of course. |
3020 | handlers will be invoked, too, of course. |
2345 | .PP |
3021 | .PP |
|
|
3022 | \fIThe special problem of life after fork \- how is it possible?\fR |
|
|
3023 | .IX Subsection "The special problem of life after fork - how is it possible?" |
|
|
3024 | .PP |
|
|
3025 | Most uses of \f(CW\*(C`fork()\*(C'\fR consist of forking, then some simple calls to ste |
|
|
3026 | up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This |
|
|
3027 | sequence should be handled by libev without any problems. |
|
|
3028 | .PP |
|
|
3029 | This changes when the application actually wants to do event handling |
|
|
3030 | in the child, or both parent in child, in effect \*(L"continuing\*(R" after the |
|
|
3031 | fork. |
|
|
3032 | .PP |
|
|
3033 | The default mode of operation (for libev, with application help to detect |
|
|
3034 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3035 | when \fIeither\fR the parent \fIor\fR the child process continues. |
|
|
3036 | .PP |
|
|
3037 | When both processes want to continue using libev, then this is usually the |
|
|
3038 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3039 | supposed to continue with all watchers in place as before, while the other |
|
|
3040 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3041 | .PP |
|
|
3042 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3043 | simply create a new event loop, which of course will be \*(L"empty\*(R", and |
|
|
3044 | use that for new watchers. This has the advantage of not touching more |
|
|
3045 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3046 | disadvantage of having to use multiple event loops (which do not support |
|
|
3047 | signal watchers). |
|
|
3048 | .PP |
|
|
3049 | When this is not possible, or you want to use the default loop for |
|
|
3050 | other reasons, then in the process that wants to start \*(L"fresh\*(R", call |
|
|
3051 | \&\f(CW\*(C`ev_default_destroy ()\*(C'\fR followed by \f(CW\*(C`ev_default_loop (...)\*(C'\fR. Destroying |
|
|
3052 | the default loop will \*(L"orphan\*(R" (not stop) all registered watchers, so you |
|
|
3053 | have to be careful not to execute code that modifies those watchers. Note |
|
|
3054 | also that in that case, you have to re-register any signal watchers. |
|
|
3055 | .PP |
2346 | \fIWatcher-Specific Functions and Data Members\fR |
3056 | \fIWatcher-Specific Functions and Data Members\fR |
2347 | .IX Subsection "Watcher-Specific Functions and Data Members" |
3057 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2348 | .IP "ev_fork_init (ev_signal *, callback)" 4 |
3058 | .IP "ev_fork_init (ev_signal *, callback)" 4 |
2349 | .IX Item "ev_fork_init (ev_signal *, callback)" |
3059 | .IX Item "ev_fork_init (ev_signal *, callback)" |
2350 | Initialises and configures the fork watcher \- it has no parameters of any |
3060 | Initialises and configures the fork watcher \- it has no parameters of any |
2351 | kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, |
3061 | kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, |
2352 | believe me. |
3062 | believe me. |
2353 | .ie n .Sh """ev_async"" \- how to wake up another event loop" |
3063 | .ie n .SS """ev_async"" \- how to wake up another event loop" |
2354 | .el .Sh "\f(CWev_async\fP \- how to wake up another event loop" |
3064 | .el .SS "\f(CWev_async\fP \- how to wake up another event loop" |
2355 | .IX Subsection "ev_async - how to wake up another event loop" |
3065 | .IX Subsection "ev_async - how to wake up another event loop" |
2356 | In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other |
3066 | In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other |
2357 | asynchronous sources such as signal handlers (as opposed to multiple event |
3067 | asynchronous sources such as signal handlers (as opposed to multiple event |
2358 | loops \- those are of course safe to use in different threads). |
3068 | loops \- those are of course safe to use in different threads). |
2359 | .PP |
3069 | .PP |
… | |
… | |
2378 | is that the author does not know of a simple (or any) algorithm for a |
3088 | is that the author does not know of a simple (or any) algorithm for a |
2379 | multiple-writer-single-reader queue that works in all cases and doesn't |
3089 | multiple-writer-single-reader queue that works in all cases and doesn't |
2380 | need elaborate support such as pthreads. |
3090 | need elaborate support such as pthreads. |
2381 | .PP |
3091 | .PP |
2382 | That means that if you want to queue data, you have to provide your own |
3092 | That means that if you want to queue data, you have to provide your own |
2383 | queue. But at least I can tell you would implement locking around your |
3093 | queue. But at least I can tell you how to implement locking around your |
2384 | queue: |
3094 | queue: |
2385 | .IP "queueing from a signal handler context" 4 |
3095 | .IP "queueing from a signal handler context" 4 |
2386 | .IX Item "queueing from a signal handler context" |
3096 | .IX Item "queueing from a signal handler context" |
2387 | To implement race-free queueing, you simply add to the queue in the signal |
3097 | To implement race-free queueing, you simply add to the queue in the signal |
2388 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
3098 | handler but you block the signal handler in the watcher callback. Here is |
2389 | some fictitious \s-1SIGUSR1\s0 handler: |
3099 | an example that does that for some fictitious \s-1SIGUSR1\s0 handler: |
2390 | .Sp |
3100 | .Sp |
2391 | .Vb 1 |
3101 | .Vb 1 |
2392 | \& static ev_async mysig; |
3102 | \& static ev_async mysig; |
2393 | \& |
3103 | \& |
2394 | \& static void |
3104 | \& static void |
… | |
… | |
2458 | \fIWatcher-Specific Functions and Data Members\fR |
3168 | \fIWatcher-Specific Functions and Data Members\fR |
2459 | .IX Subsection "Watcher-Specific Functions and Data Members" |
3169 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2460 | .IP "ev_async_init (ev_async *, callback)" 4 |
3170 | .IP "ev_async_init (ev_async *, callback)" 4 |
2461 | .IX Item "ev_async_init (ev_async *, callback)" |
3171 | .IX Item "ev_async_init (ev_async *, callback)" |
2462 | Initialises and configures the async watcher \- it has no parameters of any |
3172 | Initialises and configures the async watcher \- it has no parameters of any |
2463 | kind. There is a \f(CW\*(C`ev_asynd_set\*(C'\fR macro, but using it is utterly pointless, |
3173 | kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless, |
2464 | believe me. |
3174 | trust me. |
2465 | .IP "ev_async_send (loop, ev_async *)" 4 |
3175 | .IP "ev_async_send (loop, ev_async *)" 4 |
2466 | .IX Item "ev_async_send (loop, ev_async *)" |
3176 | .IX Item "ev_async_send (loop, ev_async *)" |
2467 | Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
3177 | Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
2468 | an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike |
3178 | an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike |
2469 | \&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do in other threads, signal or |
3179 | \&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, signal or |
2470 | similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding |
3180 | similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding |
2471 | section below on what exactly this means). |
3181 | section below on what exactly this means). |
2472 | .Sp |
3182 | .Sp |
|
|
3183 | Note that, as with other watchers in libev, multiple events might get |
|
|
3184 | compressed into a single callback invocation (another way to look at this |
|
|
3185 | is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered, set on \f(CW\*(C`ev_async_send\*(C'\fR, |
|
|
3186 | reset when the event loop detects that). |
|
|
3187 | .Sp |
2473 | This call incurs the overhead of a system call only once per loop iteration, |
3188 | This call incurs the overhead of a system call only once per event loop |
2474 | so while the overhead might be noticeable, it doesn't apply to repeated |
3189 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2475 | calls to \f(CW\*(C`ev_async_send\*(C'\fR. |
3190 | repeated calls to \f(CW\*(C`ev_async_send\*(C'\fR for the same event loop. |
2476 | .IP "bool = ev_async_pending (ev_async *)" 4 |
3191 | .IP "bool = ev_async_pending (ev_async *)" 4 |
2477 | .IX Item "bool = ev_async_pending (ev_async *)" |
3192 | .IX Item "bool = ev_async_pending (ev_async *)" |
2478 | Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
3193 | Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
2479 | watcher but the event has not yet been processed (or even noted) by the |
3194 | watcher but the event has not yet been processed (or even noted) by the |
2480 | event loop. |
3195 | event loop. |
… | |
… | |
2482 | \&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When |
3197 | \&\f(CW\*(C`ev_async_send\*(C'\fR sets a flag in the watcher and wakes up the loop. When |
2483 | the loop iterates next and checks for the watcher to have become active, |
3198 | the loop iterates next and checks for the watcher to have become active, |
2484 | it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very |
3199 | it will reset the flag again. \f(CW\*(C`ev_async_pending\*(C'\fR can be used to very |
2485 | quickly check whether invoking the loop might be a good idea. |
3200 | quickly check whether invoking the loop might be a good idea. |
2486 | .Sp |
3201 | .Sp |
2487 | Not that this does \fInot\fR check whether the watcher itself is pending, only |
3202 | Not that this does \fInot\fR check whether the watcher itself is pending, |
2488 | whether it has been requested to make this watcher pending. |
3203 | only whether it has been requested to make this watcher pending: there |
|
|
3204 | is a time window between the event loop checking and resetting the async |
|
|
3205 | notification, and the callback being invoked. |
2489 | .SH "OTHER FUNCTIONS" |
3206 | .SH "OTHER FUNCTIONS" |
2490 | .IX Header "OTHER FUNCTIONS" |
3207 | .IX Header "OTHER FUNCTIONS" |
2491 | There are some other functions of possible interest. Described. Here. Now. |
3208 | There are some other functions of possible interest. Described. Here. Now. |
2492 | .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
3209 | .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
2493 | .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
3210 | .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
2494 | This function combines a simple timer and an I/O watcher, calls your |
3211 | This function combines a simple timer and an I/O watcher, calls your |
2495 | callback on whichever event happens first and automatically stop both |
3212 | callback on whichever event happens first and automatically stops both |
2496 | watchers. This is useful if you want to wait for a single event on an fd |
3213 | watchers. This is useful if you want to wait for a single event on an fd |
2497 | or timeout without having to allocate/configure/start/stop/free one or |
3214 | or timeout without having to allocate/configure/start/stop/free one or |
2498 | more watchers yourself. |
3215 | more watchers yourself. |
2499 | .Sp |
3216 | .Sp |
2500 | If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events |
3217 | If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and the |
2501 | is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and |
3218 | \&\f(CW\*(C`events\*(C'\fR argument is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for |
2502 | \&\f(CW\*(C`events\*(C'\fR set will be created and started. |
3219 | the given \f(CW\*(C`fd\*(C'\fR and \f(CW\*(C`events\*(C'\fR set will be created and started. |
2503 | .Sp |
3220 | .Sp |
2504 | If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
3221 | If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
2505 | started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
3222 | started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
2506 | repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of |
3223 | repeat = 0) will be started. \f(CW0\fR is a valid timeout. |
2507 | dubious value. |
|
|
2508 | .Sp |
3224 | .Sp |
2509 | The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets |
3225 | The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets |
2510 | passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
3226 | passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
2511 | \&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR |
3227 | \&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR |
2512 | value passed to \f(CW\*(C`ev_once\*(C'\fR: |
3228 | value passed to \f(CW\*(C`ev_once\*(C'\fR. Note that it is possible to receive \fIboth\fR |
|
|
3229 | a timeout and an io event at the same time \- you probably should give io |
|
|
3230 | events precedence. |
|
|
3231 | .Sp |
|
|
3232 | Example: wait up to ten seconds for data to appear on \s-1STDIN_FILENO\s0. |
2513 | .Sp |
3233 | .Sp |
2514 | .Vb 7 |
3234 | .Vb 7 |
2515 | \& static void stdin_ready (int revents, void *arg) |
3235 | \& static void stdin_ready (int revents, void *arg) |
2516 | \& { |
3236 | \& { |
|
|
3237 | \& if (revents & EV_READ) |
|
|
3238 | \& /* stdin might have data for us, joy! */; |
2517 | \& if (revents & EV_TIMEOUT) |
3239 | \& else if (revents & EV_TIMEOUT) |
2518 | \& /* doh, nothing entered */; |
3240 | \& /* doh, nothing entered */; |
2519 | \& else if (revents & EV_READ) |
|
|
2520 | \& /* stdin might have data for us, joy! */; |
|
|
2521 | \& } |
3241 | \& } |
2522 | \& |
3242 | \& |
2523 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3243 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2524 | .Ve |
3244 | .Ve |
2525 | .IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4 |
3245 | .IP "ev_feed_event (struct ev_loop *, watcher *, int revents)" 4 |
2526 | .IX Item "ev_feed_event (ev_loop *, watcher *, int revents)" |
3246 | .IX Item "ev_feed_event (struct ev_loop *, watcher *, int revents)" |
2527 | Feeds the given event set into the event loop, as if the specified event |
3247 | Feeds the given event set into the event loop, as if the specified event |
2528 | had happened for the specified watcher (which must be a pointer to an |
3248 | had happened for the specified watcher (which must be a pointer to an |
2529 | initialised but not necessarily started event watcher). |
3249 | initialised but not necessarily started event watcher). |
2530 | .IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4 |
3250 | .IP "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" 4 |
2531 | .IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)" |
3251 | .IX Item "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" |
2532 | Feed an event on the given fd, as if a file descriptor backend detected |
3252 | Feed an event on the given fd, as if a file descriptor backend detected |
2533 | the given events it. |
3253 | the given events it. |
2534 | .IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4 |
3254 | .IP "ev_feed_signal_event (struct ev_loop *loop, int signum)" 4 |
2535 | .IX Item "ev_feed_signal_event (ev_loop *loop, int signum)" |
3255 | .IX Item "ev_feed_signal_event (struct ev_loop *loop, int signum)" |
2536 | Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default |
3256 | Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default |
2537 | loop!). |
3257 | loop!). |
2538 | .SH "LIBEVENT EMULATION" |
3258 | .SH "LIBEVENT EMULATION" |
2539 | .IX Header "LIBEVENT EMULATION" |
3259 | .IX Header "LIBEVENT EMULATION" |
2540 | Libev offers a compatibility emulation layer for libevent. It cannot |
3260 | Libev offers a compatibility emulation layer for libevent. It cannot |
… | |
… | |
2587 | need one additional pointer for context. If you need support for other |
3307 | need one additional pointer for context. If you need support for other |
2588 | types of functors please contact the author (preferably after implementing |
3308 | types of functors please contact the author (preferably after implementing |
2589 | it). |
3309 | it). |
2590 | .PP |
3310 | .PP |
2591 | Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
3311 | Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
2592 | .ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 |
3312 | .ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4 |
2593 | .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
3313 | .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
2594 | .IX Item "ev::READ, ev::WRITE etc." |
3314 | .IX Item "ev::READ, ev::WRITE etc." |
2595 | These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. |
3315 | These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. |
2596 | macros from \fIev.h\fR. |
3316 | macros from \fIev.h\fR. |
2597 | .ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4 |
3317 | .ie n .IP """ev::tstamp"", ""ev::now""" 4 |
2598 | .el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 |
3318 | .el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 |
2599 | .IX Item "ev::tstamp, ev::now" |
3319 | .IX Item "ev::tstamp, ev::now" |
2600 | Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. |
3320 | Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. |
2601 | .ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4 |
3321 | .ie n .IP """ev::io"", ""ev::timer"", ""ev::periodic"", ""ev::idle"", ""ev::sig"" etc." 4 |
2602 | .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
3322 | .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
2603 | .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
3323 | .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
2604 | For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
3324 | For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
2605 | the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
3325 | the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
2606 | which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
3326 | which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
… | |
… | |
2652 | \& |
3372 | \& |
2653 | \& myclass obj; |
3373 | \& myclass obj; |
2654 | \& ev::io iow; |
3374 | \& ev::io iow; |
2655 | \& iow.set <myclass, &myclass::io_cb> (&obj); |
3375 | \& iow.set <myclass, &myclass::io_cb> (&obj); |
2656 | .Ve |
3376 | .Ve |
|
|
3377 | .IP "w\->set (object *)" 4 |
|
|
3378 | .IX Item "w->set (object *)" |
|
|
3379 | This is an \fBexperimental\fR feature that might go away in a future version. |
|
|
3380 | .Sp |
|
|
3381 | This is a variation of a method callback \- leaving out the method to call |
|
|
3382 | will default the method to \f(CW\*(C`operator ()\*(C'\fR, which makes it possible to use |
|
|
3383 | functor objects without having to manually specify the \f(CW\*(C`operator ()\*(C'\fR all |
|
|
3384 | the time. Incidentally, you can then also leave out the template argument |
|
|
3385 | list. |
|
|
3386 | .Sp |
|
|
3387 | The \f(CW\*(C`operator ()\*(C'\fR method prototype must be \f(CW\*(C`void operator ()(watcher &w, |
|
|
3388 | int revents)\*(C'\fR. |
|
|
3389 | .Sp |
|
|
3390 | See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
|
|
3391 | .Sp |
|
|
3392 | Example: use a functor object as callback. |
|
|
3393 | .Sp |
|
|
3394 | .Vb 7 |
|
|
3395 | \& struct myfunctor |
|
|
3396 | \& { |
|
|
3397 | \& void operator() (ev::io &w, int revents) |
|
|
3398 | \& { |
|
|
3399 | \& ... |
|
|
3400 | \& } |
|
|
3401 | \& } |
|
|
3402 | \& |
|
|
3403 | \& myfunctor f; |
|
|
3404 | \& |
|
|
3405 | \& ev::io w; |
|
|
3406 | \& w.set (&f); |
|
|
3407 | .Ve |
2657 | .IP "w\->set<function> (void *data = 0)" 4 |
3408 | .IP "w\->set<function> (void *data = 0)" 4 |
2658 | .IX Item "w->set<function> (void *data = 0)" |
3409 | .IX Item "w->set<function> (void *data = 0)" |
2659 | Also sets a callback, but uses a static method or plain function as |
3410 | Also sets a callback, but uses a static method or plain function as |
2660 | callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's |
3411 | callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's |
2661 | \&\f(CW\*(C`data\*(C'\fR member and is free for you to use. |
3412 | \&\f(CW\*(C`data\*(C'\fR member and is free for you to use. |
2662 | .Sp |
3413 | .Sp |
2663 | The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR. |
3414 | The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR. |
2664 | .Sp |
3415 | .Sp |
2665 | See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
3416 | See the method\-\f(CW\*(C`set\*(C'\fR above for more details. |
2666 | .Sp |
3417 | .Sp |
2667 | Example: |
3418 | Example: Use a plain function as callback. |
2668 | .Sp |
3419 | .Sp |
2669 | .Vb 2 |
3420 | .Vb 2 |
2670 | \& static void io_cb (ev::io &w, int revents) { } |
3421 | \& static void io_cb (ev::io &w, int revents) { } |
2671 | \& iow.set <io_cb> (); |
3422 | \& iow.set <io_cb> (); |
2672 | .Ve |
3423 | .Ve |
… | |
… | |
2685 | Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the |
3436 | Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the |
2686 | constructor already stores the event loop. |
3437 | constructor already stores the event loop. |
2687 | .IP "w\->stop ()" 4 |
3438 | .IP "w\->stop ()" 4 |
2688 | .IX Item "w->stop ()" |
3439 | .IX Item "w->stop ()" |
2689 | Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. |
3440 | Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. |
2690 | .ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4 |
3441 | .ie n .IP "w\->again () (""ev::timer"", ""ev::periodic"" only)" 4 |
2691 | .el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4 |
3442 | .el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4 |
2692 | .IX Item "w->again () (ev::timer, ev::periodic only)" |
3443 | .IX Item "w->again () (ev::timer, ev::periodic only)" |
2693 | For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding |
3444 | For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding |
2694 | \&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. |
3445 | \&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. |
2695 | .ie n .IP "w\->sweep () (""ev::embed"" only)" 4 |
3446 | .ie n .IP "w\->sweep () (""ev::embed"" only)" 4 |
… | |
… | |
2708 | the constructor. |
3459 | the constructor. |
2709 | .PP |
3460 | .PP |
2710 | .Vb 4 |
3461 | .Vb 4 |
2711 | \& class myclass |
3462 | \& class myclass |
2712 | \& { |
3463 | \& { |
2713 | \& ev::io io; void io_cb (ev::io &w, int revents); |
3464 | \& ev::io io ; void io_cb (ev::io &w, int revents); |
2714 | \& ev:idle idle void idle_cb (ev::idle &w, int revents); |
3465 | \& ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2715 | \& |
3466 | \& |
2716 | \& myclass (int fd) |
3467 | \& myclass (int fd) |
2717 | \& { |
3468 | \& { |
2718 | \& io .set <myclass, &myclass::io_cb > (this); |
3469 | \& io .set <myclass, &myclass::io_cb > (this); |
2719 | \& idle.set <myclass, &myclass::idle_cb> (this); |
3470 | \& idle.set <myclass, &myclass::idle_cb> (this); |
… | |
… | |
2731 | .IP "Perl" 4 |
3482 | .IP "Perl" 4 |
2732 | .IX Item "Perl" |
3483 | .IX Item "Perl" |
2733 | The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test |
3484 | The \s-1EV\s0 module implements the full libev \s-1API\s0 and is actually used to test |
2734 | libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module, |
3485 | libev. \s-1EV\s0 is developed together with libev. Apart from the \s-1EV\s0 core module, |
2735 | there are additional modules that implement libev-compatible interfaces |
3486 | there are additional modules that implement libev-compatible interfaces |
2736 | to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR), \f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the |
3487 | to \f(CW\*(C`libadns\*(C'\fR (\f(CW\*(C`EV::ADNS\*(C'\fR, but \f(CW\*(C`AnyEvent::DNS\*(C'\fR is preferred nowadays), |
2737 | \&\f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR and \f(CW\*(C`EV::Glib\*(C'\fR). |
3488 | \&\f(CW\*(C`Net::SNMP\*(C'\fR (\f(CW\*(C`Net::SNMP::EV\*(C'\fR) and the \f(CW\*(C`libglib\*(C'\fR event core (\f(CW\*(C`Glib::EV\*(C'\fR |
|
|
3489 | and \f(CW\*(C`EV::Glib\*(C'\fR). |
2738 | .Sp |
3490 | .Sp |
2739 | It can be found and installed via \s-1CPAN\s0, its homepage is at |
3491 | It can be found and installed via \s-1CPAN\s0, its homepage is at |
2740 | <http://software.schmorp.de/pkg/EV>. |
3492 | <http://software.schmorp.de/pkg/EV>. |
2741 | .IP "Python" 4 |
3493 | .IP "Python" 4 |
2742 | .IX Item "Python" |
3494 | .IX Item "Python" |
2743 | Python bindings can be found at <http://code.google.com/p/pyev/>. It |
3495 | Python bindings can be found at <http://code.google.com/p/pyev/>. It |
2744 | seems to be quite complete and well-documented. Note, however, that the |
3496 | seems to be quite complete and well-documented. |
2745 | patch they require for libev is outright dangerous as it breaks the \s-1ABI\s0 |
|
|
2746 | for everybody else, and therefore, should never be applied in an installed |
|
|
2747 | libev (if python requires an incompatible \s-1ABI\s0 then it needs to embed |
|
|
2748 | libev). |
|
|
2749 | .IP "Ruby" 4 |
3497 | .IP "Ruby" 4 |
2750 | .IX Item "Ruby" |
3498 | .IX Item "Ruby" |
2751 | Tony Arcieri has written a ruby extension that offers access to a subset |
3499 | Tony Arcieri has written a ruby extension that offers access to a subset |
2752 | of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and |
3500 | of the libev \s-1API\s0 and adds file handle abstractions, asynchronous \s-1DNS\s0 and |
2753 | more on top of it. It can be found via gem servers. Its homepage is at |
3501 | more on top of it. It can be found via gem servers. Its homepage is at |
2754 | <http://rev.rubyforge.org/>. |
3502 | <http://rev.rubyforge.org/>. |
|
|
3503 | .Sp |
|
|
3504 | Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR |
|
|
3505 | makes rev work even on mingw. |
|
|
3506 | .IP "Haskell" 4 |
|
|
3507 | .IX Item "Haskell" |
|
|
3508 | A haskell binding to libev is available at |
|
|
3509 | <http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev>. |
2755 | .IP "D" 4 |
3510 | .IP "D" 4 |
2756 | .IX Item "D" |
3511 | .IX Item "D" |
2757 | Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
3512 | Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
2758 | be found at <http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
3513 | be found at <http://proj.llucax.com.ar/wiki/evd>. |
|
|
3514 | .IP "Ocaml" 4 |
|
|
3515 | .IX Item "Ocaml" |
|
|
3516 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3517 | <http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>. |
|
|
3518 | .IP "Lua" 4 |
|
|
3519 | .IX Item "Lua" |
|
|
3520 | Brian Maher has written a partial interface to libev |
|
|
3521 | for lua (only \f(CW\*(C`ev_io\*(C'\fR and \f(CW\*(C`ev_timer\*(C'\fR), to be found at |
|
|
3522 | <http://github.com/brimworks/lua\-ev>. |
2759 | .SH "MACRO MAGIC" |
3523 | .SH "MACRO MAGIC" |
2760 | .IX Header "MACRO MAGIC" |
3524 | .IX Header "MACRO MAGIC" |
2761 | Libev can be compiled with a variety of options, the most fundamental |
3525 | Libev can be compiled with a variety of options, the most fundamental |
2762 | of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
3526 | of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
2763 | functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
3527 | functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
2764 | .PP |
3528 | .PP |
2765 | To make it easier to write programs that cope with either variant, the |
3529 | To make it easier to write programs that cope with either variant, the |
2766 | following macros are defined: |
3530 | following macros are defined: |
2767 | .ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4 |
3531 | .ie n .IP """EV_A"", ""EV_A_""" 4 |
2768 | .el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 |
3532 | .el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 |
2769 | .IX Item "EV_A, EV_A_" |
3533 | .IX Item "EV_A, EV_A_" |
2770 | This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev |
3534 | This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev |
2771 | loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, |
3535 | loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, |
2772 | \&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: |
3536 | \&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: |
… | |
… | |
2777 | \& ev_loop (EV_A_ 0); |
3541 | \& ev_loop (EV_A_ 0); |
2778 | .Ve |
3542 | .Ve |
2779 | .Sp |
3543 | .Sp |
2780 | It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, |
3544 | It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, |
2781 | which is often provided by the following macro. |
3545 | which is often provided by the following macro. |
2782 | .ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4 |
3546 | .ie n .IP """EV_P"", ""EV_P_""" 4 |
2783 | .el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 |
3547 | .el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 |
2784 | .IX Item "EV_P, EV_P_" |
3548 | .IX Item "EV_P, EV_P_" |
2785 | This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev |
3549 | This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev |
2786 | loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, |
3550 | loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, |
2787 | \&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: |
3551 | \&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: |
… | |
… | |
2794 | \& static void cb (EV_P_ ev_timer *w, int revents) |
3558 | \& static void cb (EV_P_ ev_timer *w, int revents) |
2795 | .Ve |
3559 | .Ve |
2796 | .Sp |
3560 | .Sp |
2797 | It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite |
3561 | It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite |
2798 | suitable for use with \f(CW\*(C`EV_A\*(C'\fR. |
3562 | suitable for use with \f(CW\*(C`EV_A\*(C'\fR. |
2799 | .ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4 |
3563 | .ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4 |
2800 | .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 |
3564 | .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 |
2801 | .IX Item "EV_DEFAULT, EV_DEFAULT_" |
3565 | .IX Item "EV_DEFAULT, EV_DEFAULT_" |
2802 | Similar to the other two macros, this gives you the value of the default |
3566 | Similar to the other two macros, this gives you the value of the default |
2803 | loop, if multiple loops are supported (\*(L"ev loop default\*(R"). |
3567 | loop, if multiple loops are supported (\*(L"ev loop default\*(R"). |
2804 | .ie n .IP """EV_DEFAULT_UC""\fR, \f(CW""EV_DEFAULT_UC_""" 4 |
3568 | .ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4 |
2805 | .el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4 |
3569 | .el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4 |
2806 | .IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_" |
3570 | .IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_" |
2807 | Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the |
3571 | Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the |
2808 | default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour |
3572 | default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour |
2809 | is undefined when the default loop has not been initialised by a previous |
3573 | is undefined when the default loop has not been initialised by a previous |
… | |
… | |
2837 | .PP |
3601 | .PP |
2838 | The goal is to enable you to just copy the necessary files into your |
3602 | The goal is to enable you to just copy the necessary files into your |
2839 | source directory without having to change even a single line in them, so |
3603 | source directory without having to change even a single line in them, so |
2840 | you can easily upgrade by simply copying (or having a checked-out copy of |
3604 | you can easily upgrade by simply copying (or having a checked-out copy of |
2841 | libev somewhere in your source tree). |
3605 | libev somewhere in your source tree). |
2842 | .Sh "\s-1FILESETS\s0" |
3606 | .SS "\s-1FILESETS\s0" |
2843 | .IX Subsection "FILESETS" |
3607 | .IX Subsection "FILESETS" |
2844 | Depending on what features you need you need to include one or more sets of files |
3608 | Depending on what features you need you need to include one or more sets of files |
2845 | in your application. |
3609 | in your application. |
2846 | .PP |
3610 | .PP |
2847 | \fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR |
3611 | \fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR |
… | |
… | |
2865 | \& #define EV_STANDALONE 1 |
3629 | \& #define EV_STANDALONE 1 |
2866 | \& #include "ev.h" |
3630 | \& #include "ev.h" |
2867 | .Ve |
3631 | .Ve |
2868 | .PP |
3632 | .PP |
2869 | Both header files and implementation files can be compiled with a \*(C+ |
3633 | Both header files and implementation files can be compiled with a \*(C+ |
2870 | compiler (at least, thats a stated goal, and breakage will be treated |
3634 | compiler (at least, that's a stated goal, and breakage will be treated |
2871 | as a bug). |
3635 | as a bug). |
2872 | .PP |
3636 | .PP |
2873 | You need the following files in your source tree, or in a directory |
3637 | You need the following files in your source tree, or in a directory |
2874 | in your include path (e.g. in libev/ when using \-Ilibev): |
3638 | in your include path (e.g. in libev/ when using \-Ilibev): |
2875 | .PP |
3639 | .PP |
… | |
… | |
2926 | For this of course you need the m4 file: |
3690 | For this of course you need the m4 file: |
2927 | .PP |
3691 | .PP |
2928 | .Vb 1 |
3692 | .Vb 1 |
2929 | \& libev.m4 |
3693 | \& libev.m4 |
2930 | .Ve |
3694 | .Ve |
2931 | .Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" |
3695 | .SS "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" |
2932 | .IX Subsection "PREPROCESSOR SYMBOLS/MACROS" |
3696 | .IX Subsection "PREPROCESSOR SYMBOLS/MACROS" |
2933 | Libev can be configured via a variety of preprocessor symbols you have to |
3697 | Libev can be configured via a variety of preprocessor symbols you have to |
2934 | define before including any of its files. The default in the absence of |
3698 | define before including any of its files. The default in the absence of |
2935 | autoconf is noted for every option. |
3699 | autoconf is documented for every option. |
2936 | .IP "\s-1EV_STANDALONE\s0" 4 |
3700 | .IP "\s-1EV_STANDALONE\s0" 4 |
2937 | .IX Item "EV_STANDALONE" |
3701 | .IX Item "EV_STANDALONE" |
2938 | Must always be \f(CW1\fR if you do not use autoconf configuration, which |
3702 | Must always be \f(CW1\fR if you do not use autoconf configuration, which |
2939 | keeps libev from including \fIconfig.h\fR, and it also defines dummy |
3703 | keeps libev from including \fIconfig.h\fR, and it also defines dummy |
2940 | implementations for some libevent functions (such as logging, which is not |
3704 | implementations for some libevent functions (such as logging, which is not |
2941 | supported). It will also not define any of the structs usually found in |
3705 | supported). It will also not define any of the structs usually found in |
2942 | \&\fIevent.h\fR that are not directly supported by the libev core alone. |
3706 | \&\fIevent.h\fR that are not directly supported by the libev core alone. |
|
|
3707 | .Sp |
|
|
3708 | In standalone mode, libev will still try to automatically deduce the |
|
|
3709 | configuration, but has to be more conservative. |
2943 | .IP "\s-1EV_USE_MONOTONIC\s0" 4 |
3710 | .IP "\s-1EV_USE_MONOTONIC\s0" 4 |
2944 | .IX Item "EV_USE_MONOTONIC" |
3711 | .IX Item "EV_USE_MONOTONIC" |
2945 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
3712 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
2946 | monotonic clock option at both compile time and runtime. Otherwise no use |
3713 | monotonic clock option at both compile time and runtime. Otherwise no |
2947 | of the monotonic clock option will be attempted. If you enable this, you |
3714 | use of the monotonic clock option will be attempted. If you enable this, |
2948 | usually have to link against librt or something similar. Enabling it when |
3715 | you usually have to link against librt or something similar. Enabling it |
2949 | the functionality isn't available is safe, though, although you have |
3716 | when the functionality isn't available is safe, though, although you have |
2950 | to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
3717 | to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
2951 | function is hiding in (often \fI\-lrt\fR). |
3718 | function is hiding in (often \fI\-lrt\fR). See also \f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR. |
2952 | .IP "\s-1EV_USE_REALTIME\s0" 4 |
3719 | .IP "\s-1EV_USE_REALTIME\s0" 4 |
2953 | .IX Item "EV_USE_REALTIME" |
3720 | .IX Item "EV_USE_REALTIME" |
2954 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
3721 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
2955 | real-time clock option at compile time (and assume its availability at |
3722 | real-time clock option at compile time (and assume its availability |
2956 | runtime if successful). Otherwise no use of the real-time clock option will |
3723 | at runtime if successful). Otherwise no use of the real-time clock |
2957 | be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get |
3724 | option will be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR |
2958 | (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the |
3725 | by \f(CW\*(C`clock_get (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect |
2959 | note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. |
3726 | correctness. See the note about libraries in the description of |
|
|
3727 | \&\f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. Defaults to the opposite value of |
|
|
3728 | \&\f(CW\*(C`EV_USE_CLOCK_SYSCALL\*(C'\fR. |
|
|
3729 | .IP "\s-1EV_USE_CLOCK_SYSCALL\s0" 4 |
|
|
3730 | .IX Item "EV_USE_CLOCK_SYSCALL" |
|
|
3731 | If defined to be \f(CW1\fR, libev will try to use a direct syscall instead |
|
|
3732 | of calling the system-provided \f(CW\*(C`clock_gettime\*(C'\fR function. This option |
|
|
3733 | exists because on GNU/Linux, \f(CW\*(C`clock_gettime\*(C'\fR is in \f(CW\*(C`librt\*(C'\fR, but \f(CW\*(C`librt\*(C'\fR |
|
|
3734 | unconditionally pulls in \f(CW\*(C`libpthread\*(C'\fR, slowing down single-threaded |
|
|
3735 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3736 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3737 | the pthread dependency. Defaults to \f(CW1\fR on GNU/Linux with glibc 2.x or |
|
|
3738 | higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR). |
2960 | .IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
3739 | .IP "\s-1EV_USE_NANOSLEEP\s0" 4 |
2961 | .IX Item "EV_USE_NANOSLEEP" |
3740 | .IX Item "EV_USE_NANOSLEEP" |
2962 | If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
3741 | If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available |
2963 | and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
3742 | and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. |
2964 | .IP "\s-1EV_USE_EVENTFD\s0" 4 |
3743 | .IP "\s-1EV_USE_EVENTFD\s0" 4 |
… | |
… | |
2976 | will not be compiled in. |
3755 | will not be compiled in. |
2977 | .IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
3756 | .IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
2978 | .IX Item "EV_SELECT_USE_FD_SET" |
3757 | .IX Item "EV_SELECT_USE_FD_SET" |
2979 | If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
3758 | If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
2980 | structure. This is useful if libev doesn't compile due to a missing |
3759 | structure. This is useful if libev doesn't compile due to a missing |
2981 | \&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout on |
3760 | \&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it mis-guesses the bitset layout |
2982 | exotic systems. This usually limits the range of file descriptors to some |
3761 | on exotic systems. This usually limits the range of file descriptors to |
2983 | low limit such as 1024 or might have other limitations (winsocket only |
3762 | some low limit such as 1024 or might have other limitations (winsocket |
2984 | allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might |
3763 | only allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, |
2985 | influence the size of the \f(CW\*(C`fd_set\*(C'\fR used. |
3764 | configures the maximum size of the \f(CW\*(C`fd_set\*(C'\fR. |
2986 | .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
3765 | .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
2987 | .IX Item "EV_SELECT_IS_WINSOCKET" |
3766 | .IX Item "EV_SELECT_IS_WINSOCKET" |
2988 | When defined to \f(CW1\fR, the select backend will assume that |
3767 | When defined to \f(CW1\fR, the select backend will assume that |
2989 | select/socket/connect etc. don't understand file descriptors but |
3768 | select/socket/connect etc. don't understand file descriptors but |
2990 | wants osf handles on win32 (this is the case when the select to |
3769 | wants osf handles on win32 (this is the case when the select to |
… | |
… | |
3088 | When doing priority-based operations, libev usually has to linearly search |
3867 | When doing priority-based operations, libev usually has to linearly search |
3089 | all the priorities, so having many of them (hundreds) uses a lot of space |
3868 | all the priorities, so having many of them (hundreds) uses a lot of space |
3090 | and time, so using the defaults of five priorities (\-2 .. +2) is usually |
3869 | and time, so using the defaults of five priorities (\-2 .. +2) is usually |
3091 | fine. |
3870 | fine. |
3092 | .Sp |
3871 | .Sp |
3093 | If your embedding application does not need any priorities, defining these both to |
3872 | If your embedding application does not need any priorities, defining these |
3094 | \&\f(CW0\fR will save some memory and \s-1CPU\s0. |
3873 | both to \f(CW0\fR will save some memory and \s-1CPU\s0. |
3095 | .IP "\s-1EV_PERIODIC_ENABLE\s0" 4 |
3874 | .IP "\s-1EV_PERIODIC_ENABLE\s0" 4 |
3096 | .IX Item "EV_PERIODIC_ENABLE" |
3875 | .IX Item "EV_PERIODIC_ENABLE" |
3097 | If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If |
3876 | If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If |
3098 | defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
3877 | defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
3099 | code. |
3878 | code. |
… | |
… | |
3103 | defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
3882 | defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
3104 | code. |
3883 | code. |
3105 | .IP "\s-1EV_EMBED_ENABLE\s0" 4 |
3884 | .IP "\s-1EV_EMBED_ENABLE\s0" 4 |
3106 | .IX Item "EV_EMBED_ENABLE" |
3885 | .IX Item "EV_EMBED_ENABLE" |
3107 | If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If |
3886 | If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If |
3108 | defined to be \f(CW0\fR, then they are not. |
3887 | defined to be \f(CW0\fR, then they are not. Embed watchers rely on most other |
|
|
3888 | watcher types, which therefore must not be disabled. |
3109 | .IP "\s-1EV_STAT_ENABLE\s0" 4 |
3889 | .IP "\s-1EV_STAT_ENABLE\s0" 4 |
3110 | .IX Item "EV_STAT_ENABLE" |
3890 | .IX Item "EV_STAT_ENABLE" |
3111 | If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If |
3891 | If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If |
3112 | defined to be \f(CW0\fR, then they are not. |
3892 | defined to be \f(CW0\fR, then they are not. |
3113 | .IP "\s-1EV_FORK_ENABLE\s0" 4 |
3893 | .IP "\s-1EV_FORK_ENABLE\s0" 4 |
… | |
… | |
3119 | If undefined or defined to be \f(CW1\fR, then async watchers are supported. If |
3899 | If undefined or defined to be \f(CW1\fR, then async watchers are supported. If |
3120 | defined to be \f(CW0\fR, then they are not. |
3900 | defined to be \f(CW0\fR, then they are not. |
3121 | .IP "\s-1EV_MINIMAL\s0" 4 |
3901 | .IP "\s-1EV_MINIMAL\s0" 4 |
3122 | .IX Item "EV_MINIMAL" |
3902 | .IX Item "EV_MINIMAL" |
3123 | If you need to shave off some kilobytes of code at the expense of some |
3903 | If you need to shave off some kilobytes of code at the expense of some |
3124 | speed, define this symbol to \f(CW1\fR. Currently this is used to override some |
3904 | speed (but with the full \s-1API\s0), define this symbol to \f(CW1\fR. Currently this |
3125 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3905 | is used to override some inlining decisions, saves roughly 30% code size |
3126 | much smaller 2\-heap for timer management over the default 4\-heap. |
3906 | on amd64. It also selects a much smaller 2\-heap for timer management over |
|
|
3907 | the default 4\-heap. |
|
|
3908 | .Sp |
|
|
3909 | You can save even more by disabling watcher types you do not need |
|
|
3910 | and setting \f(CW\*(C`EV_MAXPRI\*(C'\fR == \f(CW\*(C`EV_MINPRI\*(C'\fR. Also, disabling \f(CW\*(C`assert\*(C'\fR |
|
|
3911 | (\f(CW\*(C`\-DNDEBUG\*(C'\fR) will usually reduce code size a lot. |
|
|
3912 | .Sp |
|
|
3913 | Defining \f(CW\*(C`EV_MINIMAL\*(C'\fR to \f(CW2\fR will additionally reduce the core \s-1API\s0 to |
|
|
3914 | provide a bare-bones event library. See \f(CW\*(C`ev.h\*(C'\fR for details on what parts |
|
|
3915 | of the \s-1API\s0 are still available, and do not complain if this subset changes |
|
|
3916 | over time. |
|
|
3917 | .IP "\s-1EV_NSIG\s0" 4 |
|
|
3918 | .IX Item "EV_NSIG" |
|
|
3919 | The highest supported signal number, +1 (or, the number of |
|
|
3920 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
3921 | automatically, but sometimes this fails, in which case it can be |
|
|
3922 | specified. Also, using a lower number than detected (\f(CW32\fR should be |
|
|
3923 | good for about any system in existance) can save some memory, as libev |
|
|
3924 | statically allocates some 12\-24 bytes per signal number. |
3127 | .IP "\s-1EV_PID_HASHSIZE\s0" 4 |
3925 | .IP "\s-1EV_PID_HASHSIZE\s0" 4 |
3128 | .IX Item "EV_PID_HASHSIZE" |
3926 | .IX Item "EV_PID_HASHSIZE" |
3129 | \&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by |
3927 | \&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by |
3130 | pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more |
3928 | pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more |
3131 | than enough. If you need to manage thousands of children you might want to |
3929 | than enough. If you need to manage thousands of children you might want to |
… | |
… | |
3138 | watchers you might want to increase this value (\fImust\fR be a power of |
3936 | watchers you might want to increase this value (\fImust\fR be a power of |
3139 | two). |
3937 | two). |
3140 | .IP "\s-1EV_USE_4HEAP\s0" 4 |
3938 | .IP "\s-1EV_USE_4HEAP\s0" 4 |
3141 | .IX Item "EV_USE_4HEAP" |
3939 | .IX Item "EV_USE_4HEAP" |
3142 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3940 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3143 | timer and periodics heap, libev uses a 4\-heap when this symbol is defined |
3941 | timer and periodics heaps, libev uses a 4\-heap when this symbol is defined |
3144 | to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has |
3942 | to \f(CW1\fR. The 4\-heap uses more complicated (longer) code but has noticeably |
3145 | noticeably faster performance with many (thousands) of watchers. |
3943 | faster performance with many (thousands) of watchers. |
3146 | .Sp |
3944 | .Sp |
3147 | The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
3945 | The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
3148 | (disabled). |
3946 | (disabled). |
3149 | .IP "\s-1EV_HEAP_CACHE_AT\s0" 4 |
3947 | .IP "\s-1EV_HEAP_CACHE_AT\s0" 4 |
3150 | .IX Item "EV_HEAP_CACHE_AT" |
3948 | .IX Item "EV_HEAP_CACHE_AT" |
3151 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3949 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3152 | timer and periodics heap, libev can cache the timestamp (\fIat\fR) within |
3950 | timer and periodics heaps, libev can cache the timestamp (\fIat\fR) within |
3153 | the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR), |
3951 | the heap structure (selected by defining \f(CW\*(C`EV_HEAP_CACHE_AT\*(C'\fR to \f(CW1\fR), |
3154 | which uses 8\-12 bytes more per watcher and a few hundred bytes more code, |
3952 | which uses 8\-12 bytes more per watcher and a few hundred bytes more code, |
3155 | but avoids random read accesses on heap changes. This improves performance |
3953 | but avoids random read accesses on heap changes. This improves performance |
3156 | noticeably with with many (hundreds) of watchers. |
3954 | noticeably with many (hundreds) of watchers. |
3157 | .Sp |
3955 | .Sp |
3158 | The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
3956 | The default is \f(CW1\fR unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set in which case it is \f(CW0\fR |
3159 | (disabled). |
3957 | (disabled). |
3160 | .IP "\s-1EV_VERIFY\s0" 4 |
3958 | .IP "\s-1EV_VERIFY\s0" 4 |
3161 | .IX Item "EV_VERIFY" |
3959 | .IX Item "EV_VERIFY" |
… | |
… | |
3166 | called once per loop, which can slow down libev. If set to \f(CW3\fR, then the |
3964 | called once per loop, which can slow down libev. If set to \f(CW3\fR, then the |
3167 | verification code will be called very frequently, which will slow down |
3965 | verification code will be called very frequently, which will slow down |
3168 | libev considerably. |
3966 | libev considerably. |
3169 | .Sp |
3967 | .Sp |
3170 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set, in which case it will be |
3968 | The default is \f(CW1\fR, unless \f(CW\*(C`EV_MINIMAL\*(C'\fR is set, in which case it will be |
3171 | \&\f(CW0.\fR |
3969 | \&\f(CW0\fR. |
3172 | .IP "\s-1EV_COMMON\s0" 4 |
3970 | .IP "\s-1EV_COMMON\s0" 4 |
3173 | .IX Item "EV_COMMON" |
3971 | .IX Item "EV_COMMON" |
3174 | By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining |
3972 | By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining |
3175 | this macro to a something else you can include more and other types of |
3973 | this macro to a something else you can include more and other types of |
3176 | members. You have to define it each time you include one of the files, |
3974 | members. You have to define it each time you include one of the files, |
… | |
… | |
3195 | and the way callbacks are invoked and set. Must expand to a struct member |
3993 | and the way callbacks are invoked and set. Must expand to a struct member |
3196 | definition and a statement, respectively. See the \fIev.h\fR header file for |
3994 | definition and a statement, respectively. See the \fIev.h\fR header file for |
3197 | their default definitions. One possible use for overriding these is to |
3995 | their default definitions. One possible use for overriding these is to |
3198 | avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use |
3996 | avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use |
3199 | method calls instead of plain function calls in \*(C+. |
3997 | method calls instead of plain function calls in \*(C+. |
3200 | .Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0" |
3998 | .SS "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0" |
3201 | .IX Subsection "EXPORTED API SYMBOLS" |
3999 | .IX Subsection "EXPORTED API SYMBOLS" |
3202 | If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of |
4000 | If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of |
3203 | exported symbols, you can use the provided \fISymbol.*\fR files which list |
4001 | exported symbols, you can use the provided \fISymbol.*\fR files which list |
3204 | all public symbols, one per line: |
4002 | all public symbols, one per line: |
3205 | .PP |
4003 | .PP |
… | |
… | |
3225 | \& #define ev_backend myprefix_ev_backend |
4023 | \& #define ev_backend myprefix_ev_backend |
3226 | \& #define ev_check_start myprefix_ev_check_start |
4024 | \& #define ev_check_start myprefix_ev_check_start |
3227 | \& #define ev_check_stop myprefix_ev_check_stop |
4025 | \& #define ev_check_stop myprefix_ev_check_stop |
3228 | \& ... |
4026 | \& ... |
3229 | .Ve |
4027 | .Ve |
3230 | .Sh "\s-1EXAMPLES\s0" |
4028 | .SS "\s-1EXAMPLES\s0" |
3231 | .IX Subsection "EXAMPLES" |
4029 | .IX Subsection "EXAMPLES" |
3232 | For a real-world example of a program the includes libev |
4030 | For a real-world example of a program the includes libev |
3233 | verbatim, you can have a look at the \s-1EV\s0 perl module |
4031 | verbatim, you can have a look at the \s-1EV\s0 perl module |
3234 | (<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
4032 | (<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
3235 | the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public |
4033 | the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public |
… | |
… | |
3258 | .PP |
4056 | .PP |
3259 | .Vb 2 |
4057 | .Vb 2 |
3260 | \& #include "ev_cpp.h" |
4058 | \& #include "ev_cpp.h" |
3261 | \& #include "ev.c" |
4059 | \& #include "ev.c" |
3262 | .Ve |
4060 | .Ve |
3263 | .SH "THREADS AND COROUTINES" |
4061 | .SH "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES" |
|
|
4062 | .IX Header "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES" |
|
|
4063 | .SS "\s-1THREADS\s0 \s-1AND\s0 \s-1COROUTINES\s0" |
3264 | .IX Header "THREADS AND COROUTINES" |
4064 | .IX Subsection "THREADS AND COROUTINES" |
3265 | .Sh "\s-1THREADS\s0" |
4065 | \fI\s-1THREADS\s0\fR |
3266 | .IX Subsection "THREADS" |
4066 | .IX Subsection "THREADS" |
3267 | Libev itself is completely thread-safe, but it uses no locking. This |
4067 | .PP |
|
|
4068 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
4069 | documented otherwise, but libev implements no locking itself. This means |
3268 | means that you can use as many loops as you want in parallel, as long as |
4070 | that you can use as many loops as you want in parallel, as long as there |
3269 | only one thread ever calls into one libev function with the same loop |
4071 | are no concurrent calls into any libev function with the same loop |
3270 | parameter. |
4072 | parameter (\f(CW\*(C`ev_default_*\*(C'\fR calls have an implicit default loop parameter, |
|
|
4073 | of course): libev guarantees that different event loops share no data |
|
|
4074 | structures that need any locking. |
3271 | .PP |
4075 | .PP |
3272 | Or put differently: calls with different loop parameters can be done in |
4076 | Or to put it differently: calls with different loop parameters can be done |
3273 | parallel from multiple threads, calls with the same loop parameter must be |
4077 | concurrently from multiple threads, calls with the same loop parameter |
3274 | done serially (but can be done from different threads, as long as only one |
4078 | must be done serially (but can be done from different threads, as long as |
3275 | thread ever is inside a call at any point in time, e.g. by using a mutex |
4079 | only one thread ever is inside a call at any point in time, e.g. by using |
3276 | per loop). |
4080 | a mutex per loop). |
3277 | .PP |
4081 | .PP |
3278 | If you want to know which design is best for your problem, then I cannot |
4082 | Specifically to support threads (and signal handlers), libev implements |
|
|
4083 | so-called \f(CW\*(C`ev_async\*(C'\fR watchers, which allow some limited form of |
|
|
4084 | concurrency on the same event loop, namely waking it up \*(L"from the |
|
|
4085 | outside\*(R". |
|
|
4086 | .PP |
|
|
4087 | If you want to know which design (one loop, locking, or multiple loops |
|
|
4088 | without or something else still) is best for your problem, then I cannot |
3279 | help you but by giving some generic advice: |
4089 | help you, but here is some generic advice: |
3280 | .IP "\(bu" 4 |
4090 | .IP "\(bu" 4 |
3281 | most applications have a main thread: use the default libev loop |
4091 | most applications have a main thread: use the default libev loop |
3282 | in that thread, or create a separate thread running only the default loop. |
4092 | in that thread, or create a separate thread running only the default loop. |
3283 | .Sp |
4093 | .Sp |
3284 | This helps integrating other libraries or software modules that use libev |
4094 | This helps integrating other libraries or software modules that use libev |
… | |
… | |
3294 | .Sp |
4104 | .Sp |
3295 | Choosing a model is hard \- look around, learn, know that usually you can do |
4105 | Choosing a model is hard \- look around, learn, know that usually you can do |
3296 | better than you currently do :\-) |
4106 | better than you currently do :\-) |
3297 | .IP "\(bu" 4 |
4107 | .IP "\(bu" 4 |
3298 | often you need to talk to some other thread which blocks in the |
4108 | often you need to talk to some other thread which blocks in the |
|
|
4109 | event loop. |
|
|
4110 | .Sp |
3299 | event loop \- \f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other |
4111 | \&\f(CW\*(C`ev_async\*(C'\fR watchers can be used to wake them up from other threads safely |
3300 | threads safely (or from signal contexts...). |
4112 | (or from signal contexts...). |
3301 | .Sh "\s-1COROUTINES\s0" |
4113 | .Sp |
|
|
4114 | An example use would be to communicate signals or other events that only |
|
|
4115 | work in the default loop by registering the signal watcher with the |
|
|
4116 | default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop |
|
|
4117 | watcher callback into the event loop interested in the signal. |
|
|
4118 | .PP |
|
|
4119 | \s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0 |
|
|
4120 | .IX Subsection "THREAD LOCKING EXAMPLE" |
|
|
4121 | .PP |
|
|
4122 | Here is a fictitious example of how to run an event loop in a different |
|
|
4123 | thread than where callbacks are being invoked and watchers are |
|
|
4124 | created/added/removed. |
|
|
4125 | .PP |
|
|
4126 | For a real-world example, see the \f(CW\*(C`EV::Loop::Async\*(C'\fR perl module, |
|
|
4127 | which uses exactly this technique (which is suited for many high-level |
|
|
4128 | languages). |
|
|
4129 | .PP |
|
|
4130 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4131 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4132 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4133 | .PP |
|
|
4134 | First, you need to associate some data with the event loop: |
|
|
4135 | .PP |
|
|
4136 | .Vb 6 |
|
|
4137 | \& typedef struct { |
|
|
4138 | \& mutex_t lock; /* global loop lock */ |
|
|
4139 | \& ev_async async_w; |
|
|
4140 | \& thread_t tid; |
|
|
4141 | \& cond_t invoke_cv; |
|
|
4142 | \& } userdata; |
|
|
4143 | \& |
|
|
4144 | \& void prepare_loop (EV_P) |
|
|
4145 | \& { |
|
|
4146 | \& // for simplicity, we use a static userdata struct. |
|
|
4147 | \& static userdata u; |
|
|
4148 | \& |
|
|
4149 | \& ev_async_init (&u\->async_w, async_cb); |
|
|
4150 | \& ev_async_start (EV_A_ &u\->async_w); |
|
|
4151 | \& |
|
|
4152 | \& pthread_mutex_init (&u\->lock, 0); |
|
|
4153 | \& pthread_cond_init (&u\->invoke_cv, 0); |
|
|
4154 | \& |
|
|
4155 | \& // now associate this with the loop |
|
|
4156 | \& ev_set_userdata (EV_A_ u); |
|
|
4157 | \& ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4158 | \& ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4159 | \& |
|
|
4160 | \& // then create the thread running ev_loop |
|
|
4161 | \& pthread_create (&u\->tid, 0, l_run, EV_A); |
|
|
4162 | \& } |
|
|
4163 | .Ve |
|
|
4164 | .PP |
|
|
4165 | The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used |
|
|
4166 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4167 | that might have been added: |
|
|
4168 | .PP |
|
|
4169 | .Vb 5 |
|
|
4170 | \& static void |
|
|
4171 | \& async_cb (EV_P_ ev_async *w, int revents) |
|
|
4172 | \& { |
|
|
4173 | \& // just used for the side effects |
|
|
4174 | \& } |
|
|
4175 | .Ve |
|
|
4176 | .PP |
|
|
4177 | The \f(CW\*(C`l_release\*(C'\fR and \f(CW\*(C`l_acquire\*(C'\fR callbacks simply unlock/lock the mutex |
|
|
4178 | protecting the loop data, respectively. |
|
|
4179 | .PP |
|
|
4180 | .Vb 6 |
|
|
4181 | \& static void |
|
|
4182 | \& l_release (EV_P) |
|
|
4183 | \& { |
|
|
4184 | \& userdata *u = ev_userdata (EV_A); |
|
|
4185 | \& pthread_mutex_unlock (&u\->lock); |
|
|
4186 | \& } |
|
|
4187 | \& |
|
|
4188 | \& static void |
|
|
4189 | \& l_acquire (EV_P) |
|
|
4190 | \& { |
|
|
4191 | \& userdata *u = ev_userdata (EV_A); |
|
|
4192 | \& pthread_mutex_lock (&u\->lock); |
|
|
4193 | \& } |
|
|
4194 | .Ve |
|
|
4195 | .PP |
|
|
4196 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4197 | into \f(CW\*(C`ev_loop\*(C'\fR: |
|
|
4198 | .PP |
|
|
4199 | .Vb 4 |
|
|
4200 | \& void * |
|
|
4201 | \& l_run (void *thr_arg) |
|
|
4202 | \& { |
|
|
4203 | \& struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4204 | \& |
|
|
4205 | \& l_acquire (EV_A); |
|
|
4206 | \& pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4207 | \& ev_loop (EV_A_ 0); |
|
|
4208 | \& l_release (EV_A); |
|
|
4209 | \& |
|
|
4210 | \& return 0; |
|
|
4211 | \& } |
|
|
4212 | .Ve |
|
|
4213 | .PP |
|
|
4214 | Instead of invoking all pending watchers, the \f(CW\*(C`l_invoke\*(C'\fR callback will |
|
|
4215 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4216 | writes? \f(CW\*(C`Async::Interrupt\*(C'\fR?) and then waits until all pending watchers |
|
|
4217 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4218 | and b) skipping inter-thread-communication when there are no pending |
|
|
4219 | watchers is very beneficial): |
|
|
4220 | .PP |
|
|
4221 | .Vb 4 |
|
|
4222 | \& static void |
|
|
4223 | \& l_invoke (EV_P) |
|
|
4224 | \& { |
|
|
4225 | \& userdata *u = ev_userdata (EV_A); |
|
|
4226 | \& |
|
|
4227 | \& while (ev_pending_count (EV_A)) |
|
|
4228 | \& { |
|
|
4229 | \& wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4230 | \& pthread_cond_wait (&u\->invoke_cv, &u\->lock); |
|
|
4231 | \& } |
|
|
4232 | \& } |
|
|
4233 | .Ve |
|
|
4234 | .PP |
|
|
4235 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4236 | will grab the lock, call \f(CW\*(C`ev_invoke_pending\*(C'\fR and then signal the loop |
|
|
4237 | thread to continue: |
|
|
4238 | .PP |
|
|
4239 | .Vb 4 |
|
|
4240 | \& static void |
|
|
4241 | \& real_invoke_pending (EV_P) |
|
|
4242 | \& { |
|
|
4243 | \& userdata *u = ev_userdata (EV_A); |
|
|
4244 | \& |
|
|
4245 | \& pthread_mutex_lock (&u\->lock); |
|
|
4246 | \& ev_invoke_pending (EV_A); |
|
|
4247 | \& pthread_cond_signal (&u\->invoke_cv); |
|
|
4248 | \& pthread_mutex_unlock (&u\->lock); |
|
|
4249 | \& } |
|
|
4250 | .Ve |
|
|
4251 | .PP |
|
|
4252 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4253 | event loop, you will now have to lock: |
|
|
4254 | .PP |
|
|
4255 | .Vb 2 |
|
|
4256 | \& ev_timer timeout_watcher; |
|
|
4257 | \& userdata *u = ev_userdata (EV_A); |
|
|
4258 | \& |
|
|
4259 | \& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4260 | \& |
|
|
4261 | \& pthread_mutex_lock (&u\->lock); |
|
|
4262 | \& ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4263 | \& ev_async_send (EV_A_ &u\->async_w); |
|
|
4264 | \& pthread_mutex_unlock (&u\->lock); |
|
|
4265 | .Ve |
|
|
4266 | .PP |
|
|
4267 | Note that sending the \f(CW\*(C`ev_async\*(C'\fR watcher is required because otherwise |
|
|
4268 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4269 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4270 | watchers in the next event loop iteration. |
|
|
4271 | .PP |
|
|
4272 | \fI\s-1COROUTINES\s0\fR |
3302 | .IX Subsection "COROUTINES" |
4273 | .IX Subsection "COROUTINES" |
|
|
4274 | .PP |
3303 | Libev is much more accommodating to coroutines (\*(L"cooperative threads\*(R"): |
4275 | Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"): |
3304 | libev fully supports nesting calls to it's functions from different |
4276 | libev fully supports nesting calls to its functions from different |
3305 | coroutines (e.g. you can call \f(CW\*(C`ev_loop\*(C'\fR on the same loop from two |
4277 | coroutines (e.g. you can call \f(CW\*(C`ev_loop\*(C'\fR on the same loop from two |
3306 | different coroutines and switch freely between both coroutines running the |
4278 | different coroutines, and switch freely between both coroutines running |
3307 | loop, as long as you don't confuse yourself). The only exception is that |
4279 | the loop, as long as you don't confuse yourself). The only exception is |
3308 | you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks. |
4280 | that you must not do this from \f(CW\*(C`ev_periodic\*(C'\fR reschedule callbacks. |
3309 | .PP |
4281 | .PP |
3310 | Care has been invested into making sure that libev does not keep local |
4282 | Care has been taken to ensure that libev does not keep local state inside |
3311 | state inside \f(CW\*(C`ev_loop\*(C'\fR, and other calls do not usually allow coroutine |
4283 | \&\f(CW\*(C`ev_loop\*(C'\fR, and other calls do not usually allow for coroutine switches as |
|
|
4284 | they do not call any callbacks. |
|
|
4285 | .SS "\s-1COMPILER\s0 \s-1WARNINGS\s0" |
|
|
4286 | .IX Subsection "COMPILER WARNINGS" |
|
|
4287 | Depending on your compiler and compiler settings, you might get no or a |
|
|
4288 | lot of warnings when compiling libev code. Some people are apparently |
|
|
4289 | scared by this. |
|
|
4290 | .PP |
|
|
4291 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
4292 | has different warnings, and each user has different tastes regarding |
|
|
4293 | warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when |
|
|
4294 | targeting a specific compiler and compiler-version. |
|
|
4295 | .PP |
|
|
4296 | Another reason is that some compiler warnings require elaborate |
|
|
4297 | workarounds, or other changes to the code that make it less clear and less |
|
|
4298 | maintainable. |
|
|
4299 | .PP |
|
|
4300 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
4301 | wrong (because they don't actually warn about the condition their message |
|
|
4302 | seems to warn about). For example, certain older gcc versions had some |
|
|
4303 | warnings that resulted an extreme number of false positives. These have |
|
|
4304 | been fixed, but some people still insist on making code warn-free with |
|
|
4305 | such buggy versions. |
|
|
4306 | .PP |
|
|
4307 | While libev is written to generate as few warnings as possible, |
|
|
4308 | \&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev |
|
|
4309 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
4310 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
4311 | warnings, not errors, or proof of bugs. |
|
|
4312 | .SS "\s-1VALGRIND\s0" |
|
|
4313 | .IX Subsection "VALGRIND" |
|
|
4314 | Valgrind has a special section here because it is a popular tool that is |
|
|
4315 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
|
|
4316 | .PP |
|
|
4317 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
4318 | in libev, then check twice: If valgrind reports something like: |
|
|
4319 | .PP |
|
|
4320 | .Vb 3 |
|
|
4321 | \& ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
4322 | \& ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
4323 | \& ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
4324 | .Ve |
|
|
4325 | .PP |
|
|
4326 | Then there is no memory leak, just as memory accounted to global variables |
|
|
4327 | is not a memleak \- the memory is still being referenced, and didn't leak. |
|
|
4328 | .PP |
|
|
4329 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
4330 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
4331 | although an acceptable workaround has been found here), or it might be |
|
|
4332 | confused. |
|
|
4333 | .PP |
|
|
4334 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
|
|
4335 | make it into some kind of religion. |
|
|
4336 | .PP |
|
|
4337 | If you are unsure about something, feel free to contact the mailing list |
|
|
4338 | with the full valgrind report and an explanation on why you think this |
|
|
4339 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
4340 | annoyed when you get a brisk \*(L"this is no bug\*(R" answer and take the chance |
|
|
4341 | of learning how to interpret valgrind properly. |
|
|
4342 | .PP |
|
|
4343 | If you need, for some reason, empty reports from valgrind for your project |
|
|
4344 | I suggest using suppression lists. |
|
|
4345 | .SH "PORTABILITY NOTES" |
|
|
4346 | .IX Header "PORTABILITY NOTES" |
|
|
4347 | .SS "\s-1WIN32\s0 \s-1PLATFORM\s0 \s-1LIMITATIONS\s0 \s-1AND\s0 \s-1WORKAROUNDS\s0" |
|
|
4348 | .IX Subsection "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
|
|
4349 | Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev |
|
|
4350 | requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0 |
|
|
4351 | model. Libev still offers limited functionality on this platform in |
|
|
4352 | the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket |
|
|
4353 | descriptors. This only applies when using Win32 natively, not when using |
|
|
4354 | e.g. cygwin. |
|
|
4355 | .PP |
|
|
4356 | Lifting these limitations would basically require the full |
|
|
4357 | re-implementation of the I/O system. If you are into these kinds of |
|
|
4358 | things, then note that glib does exactly that for you in a very portable |
|
|
4359 | way (note also that glib is the slowest event library known to man). |
|
|
4360 | .PP |
|
|
4361 | There is no supported compilation method available on windows except |
|
|
4362 | embedding it into other applications. |
|
|
4363 | .PP |
|
|
4364 | Sensible signal handling is officially unsupported by Microsoft \- libev |
|
|
4365 | tries its best, but under most conditions, signals will simply not work. |
|
|
4366 | .PP |
|
|
4367 | Not a libev limitation but worth mentioning: windows apparently doesn't |
|
|
4368 | accept large writes: instead of resulting in a partial write, windows will |
|
|
4369 | either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large, |
|
|
4370 | so make sure you only write small amounts into your sockets (less than a |
|
|
4371 | megabyte seems safe, but this apparently depends on the amount of memory |
|
|
4372 | available). |
|
|
4373 | .PP |
|
|
4374 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
4375 | the abysmal performance of winsockets, using a large number of sockets |
|
|
4376 | is not recommended (and not reasonable). If your program needs to use |
|
|
4377 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
4378 | different implementation for windows, as libev offers the \s-1POSIX\s0 readiness |
|
|
4379 | notification model, which cannot be implemented efficiently on windows |
|
|
4380 | (due to Microsoft monopoly games). |
|
|
4381 | .PP |
|
|
4382 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
4383 | section for details) and use the following \fIevwrap.h\fR header file instead |
|
|
4384 | of \fIev.h\fR: |
|
|
4385 | .PP |
|
|
4386 | .Vb 2 |
|
|
4387 | \& #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
4388 | \& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
4389 | \& |
|
|
4390 | \& #include "ev.h" |
|
|
4391 | .Ve |
|
|
4392 | .PP |
|
|
4393 | And compile the following \fIevwrap.c\fR file into your project (make sure |
|
|
4394 | you do \fInot\fR compile the \fIev.c\fR or any other embedded source files!): |
|
|
4395 | .PP |
|
|
4396 | .Vb 2 |
|
|
4397 | \& #include "evwrap.h" |
|
|
4398 | \& #include "ev.c" |
|
|
4399 | .Ve |
|
|
4400 | .IP "The winsocket select function" 4 |
|
|
4401 | .IX Item "The winsocket select function" |
|
|
4402 | The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it |
|
|
4403 | requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is |
|
|
4404 | also extremely buggy). This makes select very inefficient, and also |
|
|
4405 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
4406 | C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the |
|
|
4407 | discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and |
|
|
4408 | \&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info. |
|
|
4409 | .Sp |
|
|
4410 | The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime |
|
|
4411 | libraries and raw winsocket select is: |
|
|
4412 | .Sp |
|
|
4413 | .Vb 2 |
|
|
4414 | \& #define EV_USE_SELECT 1 |
|
|
4415 | \& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
|
|
4416 | .Ve |
|
|
4417 | .Sp |
|
|
4418 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
|
|
4419 | complexity in the O(nA\*^X) range when using win32. |
|
|
4420 | .IP "Limited number of file descriptors" 4 |
|
|
4421 | .IX Item "Limited number of file descriptors" |
|
|
4422 | Windows has numerous arbitrary (and low) limits on things. |
|
|
4423 | .Sp |
|
|
4424 | Early versions of winsocket's select only supported waiting for a maximum |
|
|
4425 | of \f(CW64\fR handles (probably owning to the fact that all windows kernels |
|
|
4426 | can only wait for \f(CW64\fR things at the same time internally; Microsoft |
|
|
4427 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
4428 | previous thread in each. Sounds great!). |
|
|
4429 | .Sp |
|
|
4430 | Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR |
|
|
4431 | to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select |
|
|
4432 | call (which might be in libev or elsewhere, for example, perl and many |
|
|
4433 | other interpreters do their own select emulation on windows). |
|
|
4434 | .Sp |
|
|
4435 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
4436 | libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR |
|
|
4437 | fetish or something like this inside Microsoft). You can increase this |
|
|
4438 | by calling \f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR |
|
|
4439 | (another arbitrary limit), but is broken in many versions of the Microsoft |
|
|
4440 | runtime libraries. This might get you to about \f(CW512\fR or \f(CW2048\fR sockets |
|
|
4441 | (depending on windows version and/or the phase of the moon). To get more, |
|
|
4442 | you need to wrap all I/O functions and provide your own fd management, but |
|
|
4443 | the cost of calling select (O(nA\*^X)) will likely make this unworkable. |
|
|
4444 | .SS "\s-1PORTABILITY\s0 \s-1REQUIREMENTS\s0" |
|
|
4445 | .IX Subsection "PORTABILITY REQUIREMENTS" |
|
|
4446 | In addition to a working ISO-C implementation and of course the |
|
|
4447 | backend-specific APIs, libev relies on a few additional extensions: |
|
|
4448 | .ie n .IP """void (*)(ev_watcher_type *, int revents)"" must have compatible calling conventions regardless of ""ev_watcher_type *""." 4 |
|
|
4449 | .el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4 |
|
|
4450 | .IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *." |
|
|
4451 | Libev assumes not only that all watcher pointers have the same internal |
|
|
4452 | structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also |
|
|
4453 | assumes that the same (machine) code can be used to call any watcher |
|
|
4454 | callback: The watcher callbacks have different type signatures, but libev |
|
|
4455 | calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally. |
|
|
4456 | .ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4 |
|
|
4457 | .el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4 |
|
|
4458 | .IX Item "sig_atomic_t volatile must be thread-atomic as well" |
|
|
4459 | The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as |
|
|
4460 | \&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic with respect to accesses from different |
|
|
4461 | threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is |
|
|
4462 | believed to be sufficiently portable. |
|
|
4463 | .ie n .IP """sigprocmask"" must work in a threaded environment" 4 |
|
|
4464 | .el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4 |
|
|
4465 | .IX Item "sigprocmask must work in a threaded environment" |
|
|
4466 | Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not |
|
|
4467 | allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical |
|
|
4468 | pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main |
|
|
4469 | thread\*(R" or will block signals process-wide, both behaviours would |
|
|
4470 | be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and |
|
|
4471 | \&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however. |
|
|
4472 | .Sp |
|
|
4473 | The most portable way to handle signals is to block signals in all threads |
|
|
4474 | except the initial one, and run the default loop in the initial thread as |
|
|
4475 | well. |
|
|
4476 | .ie n .IP """long"" must be large enough for common memory allocation sizes" 4 |
|
|
4477 | .el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4 |
|
|
4478 | .IX Item "long must be large enough for common memory allocation sizes" |
|
|
4479 | To improve portability and simplify its \s-1API\s0, libev uses \f(CW\*(C`long\*(C'\fR internally |
|
|
4480 | instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On non-POSIX |
|
|
4481 | systems (Microsoft...) this might be unexpectedly low, but is still at |
|
|
4482 | least 31 bits everywhere, which is enough for hundreds of millions of |
3312 | switches. |
4483 | watchers. |
|
|
4484 | .ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4 |
|
|
4485 | .el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4 |
|
|
4486 | .IX Item "double must hold a time value in seconds with enough accuracy" |
|
|
4487 | The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to |
|
|
4488 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
4489 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
4490 | implementations implementing \s-1IEEE\s0 754, which is basically all existing |
|
|
4491 | ones. With \s-1IEEE\s0 754 doubles, you get microsecond accuracy until at least |
|
|
4492 | 2200. |
|
|
4493 | .PP |
|
|
4494 | If you know of other additional requirements drop me a note. |
3313 | .SH "COMPLEXITIES" |
4495 | .SH "ALGORITHMIC COMPLEXITIES" |
3314 | .IX Header "COMPLEXITIES" |
4496 | .IX Header "ALGORITHMIC COMPLEXITIES" |
3315 | In this section the complexities of (many of) the algorithms used inside |
4497 | In this section the complexities of (many of) the algorithms used inside |
3316 | libev will be explained. For complexity discussions about backends see the |
4498 | libev will be documented. For complexity discussions about backends see |
3317 | documentation for \f(CW\*(C`ev_default_init\*(C'\fR. |
4499 | the documentation for \f(CW\*(C`ev_default_init\*(C'\fR. |
3318 | .PP |
4500 | .PP |
3319 | All of the following are about amortised time: If an array needs to be |
4501 | All of the following are about amortised time: If an array needs to be |
3320 | extended, libev needs to realloc and move the whole array, but this |
4502 | extended, libev needs to realloc and move the whole array, but this |
3321 | happens asymptotically never with higher number of elements, so O(1) might |
4503 | happens asymptotically rarer with higher number of elements, so O(1) might |
3322 | mean it might do a lengthy realloc operation in rare cases, but on average |
4504 | mean that libev does a lengthy realloc operation in rare cases, but on |
3323 | it is much faster and asymptotically approaches constant time. |
4505 | average it is much faster and asymptotically approaches constant time. |
3324 | .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 |
4506 | .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 |
3325 | .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" |
4507 | .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" |
3326 | This means that, when you have a watcher that triggers in one hour and |
4508 | This means that, when you have a watcher that triggers in one hour and |
3327 | there are 100 watchers that would trigger before that then inserting will |
4509 | there are 100 watchers that would trigger before that, then inserting will |
3328 | have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers. |
4510 | have to skip roughly seven (\f(CW\*(C`ld 100\*(C'\fR) of these watchers. |
3329 | .IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4 |
4511 | .IP "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" 4 |
3330 | .IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" |
4512 | .IX Item "Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)" |
3331 | That means that changing a timer costs less than removing/adding them |
4513 | That means that changing a timer costs less than removing/adding them, |
3332 | as only the relative motion in the event queue has to be paid for. |
4514 | as only the relative motion in the event queue has to be paid for. |
3333 | .IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4 |
4515 | .IP "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" 4 |
3334 | .IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" |
4516 | .IX Item "Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)" |
3335 | These just add the watcher into an array or at the head of a list. |
4517 | These just add the watcher into an array or at the head of a list. |
3336 | .IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4 |
4518 | .IP "Stopping check/prepare/idle/fork/async watchers: O(1)" 4 |
3337 | .IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)" |
4519 | .IX Item "Stopping check/prepare/idle/fork/async watchers: O(1)" |
3338 | .PD 0 |
4520 | .PD 0 |
3339 | .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 |
4521 | .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 |
3340 | .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" |
4522 | .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" |
3341 | .PD |
4523 | .PD |
3342 | These watchers are stored in lists then need to be walked to find the |
4524 | These watchers are stored in lists, so they need to be walked to find the |
3343 | correct watcher to remove. The lists are usually short (you don't usually |
4525 | correct watcher to remove. The lists are usually short (you don't usually |
3344 | have many watchers waiting for the same fd or signal). |
4526 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
4527 | is rare). |
3345 | .IP "Finding the next timer in each loop iteration: O(1)" 4 |
4528 | .IP "Finding the next timer in each loop iteration: O(1)" 4 |
3346 | .IX Item "Finding the next timer in each loop iteration: O(1)" |
4529 | .IX Item "Finding the next timer in each loop iteration: O(1)" |
3347 | By virtue of using a binary or 4\-heap, the next timer is always found at a |
4530 | By virtue of using a binary or 4\-heap, the next timer is always found at a |
3348 | fixed position in the storage array. |
4531 | fixed position in the storage array. |
3349 | .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 |
4532 | .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 |
… | |
… | |
3358 | .IX Item "Priority handling: O(number_of_priorities)" |
4541 | .IX Item "Priority handling: O(number_of_priorities)" |
3359 | .PD |
4542 | .PD |
3360 | Priorities are implemented by allocating some space for each |
4543 | Priorities are implemented by allocating some space for each |
3361 | priority. When doing priority-based operations, libev usually has to |
4544 | priority. When doing priority-based operations, libev usually has to |
3362 | linearly search all the priorities, but starting/stopping and activating |
4545 | linearly search all the priorities, but starting/stopping and activating |
3363 | watchers becomes O(1) w.r.t. priority handling. |
4546 | watchers becomes O(1) with respect to priority handling. |
3364 | .IP "Sending an ev_async: O(1)" 4 |
4547 | .IP "Sending an ev_async: O(1)" 4 |
3365 | .IX Item "Sending an ev_async: O(1)" |
4548 | .IX Item "Sending an ev_async: O(1)" |
3366 | .PD 0 |
4549 | .PD 0 |
3367 | .IP "Processing ev_async_send: O(number_of_async_watchers)" 4 |
4550 | .IP "Processing ev_async_send: O(number_of_async_watchers)" 4 |
3368 | .IX Item "Processing ev_async_send: O(number_of_async_watchers)" |
4551 | .IX Item "Processing ev_async_send: O(number_of_async_watchers)" |
… | |
… | |
3370 | .IX Item "Processing signals: O(max_signal_number)" |
4553 | .IX Item "Processing signals: O(max_signal_number)" |
3371 | .PD |
4554 | .PD |
3372 | Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR |
4555 | Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR |
3373 | calls in the current loop iteration. Checking for async and signal events |
4556 | calls in the current loop iteration. Checking for async and signal events |
3374 | involves iterating over all running async watchers or all signal numbers. |
4557 | involves iterating over all running async watchers or all signal numbers. |
3375 | .SH "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
4558 | .SH "GLOSSARY" |
3376 | .IX Header "WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS" |
4559 | .IX Header "GLOSSARY" |
3377 | Win32 doesn't support any of the standards (e.g. \s-1POSIX\s0) that libev |
4560 | .IP "active" 4 |
3378 | requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0 |
4561 | .IX Item "active" |
3379 | model. Libev still offers limited functionality on this platform in |
4562 | A watcher is active as long as it has been started (has been attached to |
3380 | the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket |
4563 | an event loop) but not yet stopped (disassociated from the event loop). |
3381 | descriptors. This only applies when using Win32 natively, not when using |
4564 | .IP "application" 4 |
3382 | e.g. cygwin. |
4565 | .IX Item "application" |
3383 | .PP |
4566 | In this document, an application is whatever is using libev. |
3384 | Lifting these limitations would basically require the full |
4567 | .IP "callback" 4 |
3385 | re-implementation of the I/O system. If you are into these kinds of |
4568 | .IX Item "callback" |
3386 | things, then note that glib does exactly that for you in a very portable |
4569 | The address of a function that is called when some event has been |
3387 | way (note also that glib is the slowest event library known to man). |
4570 | detected. Callbacks are being passed the event loop, the watcher that |
3388 | .PP |
4571 | received the event, and the actual event bitset. |
3389 | There is no supported compilation method available on windows except |
4572 | .IP "callback invocation" 4 |
3390 | embedding it into other applications. |
4573 | .IX Item "callback invocation" |
3391 | .PP |
4574 | The act of calling the callback associated with a watcher. |
3392 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4575 | .IP "event" 4 |
3393 | accept large writes: instead of resulting in a partial write, windows will |
4576 | .IX Item "event" |
3394 | either accept everything or return \f(CW\*(C`ENOBUFS\*(C'\fR if the buffer is too large, |
4577 | A change of state of some external event, such as data now being available |
3395 | so make sure you only write small amounts into your sockets (less than a |
4578 | for reading on a file descriptor, time having passed or simply not having |
3396 | megabyte seems safe, but thsi apparently depends on the amount of memory |
4579 | any other events happening anymore. |
3397 | available). |
|
|
3398 | .PP |
|
|
3399 | Due to the many, low, and arbitrary limits on the win32 platform and |
|
|
3400 | the abysmal performance of winsockets, using a large number of sockets |
|
|
3401 | is not recommended (and not reasonable). If your program needs to use |
|
|
3402 | more than a hundred or so sockets, then likely it needs to use a totally |
|
|
3403 | different implementation for windows, as libev offers the \s-1POSIX\s0 readiness |
|
|
3404 | notification model, which cannot be implemented efficiently on windows |
|
|
3405 | (Microsoft monopoly games). |
|
|
3406 | .PP |
|
|
3407 | A typical way to use libev under windows is to embed it (see the embedding |
|
|
3408 | section for details) and use the following \fIevwrap.h\fR header file instead |
|
|
3409 | of \fIev.h\fR: |
|
|
3410 | .PP |
|
|
3411 | .Vb 2 |
|
|
3412 | \& #define EV_STANDALONE /* keeps ev from requiring config.h */ |
|
|
3413 | \& #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
|
|
3414 | \& |
|
|
3415 | \& #include "ev.h" |
|
|
3416 | .Ve |
|
|
3417 | .PP |
|
|
3418 | And compile the following \fIevwrap.c\fR file into your project (make sure |
|
|
3419 | you do \fInot\fR compile the \fIev.c\fR or any other embedded soruce files!): |
|
|
3420 | .PP |
|
|
3421 | .Vb 2 |
|
|
3422 | \& #include "evwrap.h" |
|
|
3423 | \& #include "ev.c" |
|
|
3424 | .Ve |
|
|
3425 | .IP "The winsocket select function" 4 |
|
|
3426 | .IX Item "The winsocket select function" |
|
|
3427 | The winsocket \f(CW\*(C`select\*(C'\fR function doesn't follow \s-1POSIX\s0 in that it |
|
|
3428 | requires socket \fIhandles\fR and not socket \fIfile descriptors\fR (it is |
|
|
3429 | also extremely buggy). This makes select very inefficient, and also |
|
|
3430 | requires a mapping from file descriptors to socket handles (the Microsoft |
|
|
3431 | C runtime provides the function \f(CW\*(C`_open_osfhandle\*(C'\fR for this). See the |
|
|
3432 | discussion of the \f(CW\*(C`EV_SELECT_USE_FD_SET\*(C'\fR, \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR and |
|
|
3433 | \&\f(CW\*(C`EV_FD_TO_WIN32_HANDLE\*(C'\fR preprocessor symbols for more info. |
|
|
3434 | .Sp |
4580 | .Sp |
3435 | The configuration for a \*(L"naked\*(R" win32 using the Microsoft runtime |
4581 | In libev, events are represented as single bits (such as \f(CW\*(C`EV_READ\*(C'\fR or |
3436 | libraries and raw winsocket select is: |
4582 | \&\f(CW\*(C`EV_TIMEOUT\*(C'\fR). |
|
|
4583 | .IP "event library" 4 |
|
|
4584 | .IX Item "event library" |
|
|
4585 | A software package implementing an event model and loop. |
|
|
4586 | .IP "event loop" 4 |
|
|
4587 | .IX Item "event loop" |
|
|
4588 | An entity that handles and processes external events and converts them |
|
|
4589 | into callback invocations. |
|
|
4590 | .IP "event model" 4 |
|
|
4591 | .IX Item "event model" |
|
|
4592 | The model used to describe how an event loop handles and processes |
|
|
4593 | watchers and events. |
|
|
4594 | .IP "pending" 4 |
|
|
4595 | .IX Item "pending" |
|
|
4596 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4597 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4598 | pending status is explicitly cleared by the application. |
3437 | .Sp |
4599 | .Sp |
3438 | .Vb 2 |
4600 | A watcher can be pending, but not active. Stopping a watcher also clears |
3439 | \& #define EV_USE_SELECT 1 |
4601 | its pending status. |
3440 | \& #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4602 | .IP "real time" 4 |
3441 | .Ve |
4603 | .IX Item "real time" |
3442 | .Sp |
4604 | The physical time that is observed. It is apparently strictly monotonic :) |
3443 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4605 | .IP "wall-clock time" 4 |
3444 | complexity in the O(nA\*^X) range when using win32. |
4606 | .IX Item "wall-clock time" |
3445 | .IP "Limited number of file descriptors" 4 |
4607 | The time and date as shown on clocks. Unlike real time, it can actually |
3446 | .IX Item "Limited number of file descriptors" |
4608 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
3447 | Windows has numerous arbitrary (and low) limits on things. |
4609 | clock. |
3448 | .Sp |
4610 | .IP "watcher" 4 |
3449 | Early versions of winsocket's select only supported waiting for a maximum |
4611 | .IX Item "watcher" |
3450 | of \f(CW64\fR handles (probably owning to the fact that all windows kernels |
4612 | A data structure that describes interest in certain events. Watchers need |
3451 | can only wait for \f(CW64\fR things at the same time internally; Microsoft |
4613 | to be started (attached to an event loop) before they can receive events. |
3452 | recommends spawning a chain of threads and wait for 63 handles and the |
4614 | .IP "watcher invocation" 4 |
3453 | previous thread in each. Great). |
4615 | .IX Item "watcher invocation" |
3454 | .Sp |
4616 | The act of calling the callback associated with a watcher. |
3455 | Newer versions support more handles, but you need to define \f(CW\*(C`FD_SETSIZE\*(C'\fR |
|
|
3456 | to some high number (e.g. \f(CW2048\fR) before compiling the winsocket select |
|
|
3457 | call (which might be in libev or elsewhere, for example, perl does its own |
|
|
3458 | select emulation on windows). |
|
|
3459 | .Sp |
|
|
3460 | Another limit is the number of file descriptors in the Microsoft runtime |
|
|
3461 | libraries, which by default is \f(CW64\fR (there must be a hidden \fI64\fR fetish |
|
|
3462 | or something like this inside Microsoft). You can increase this by calling |
|
|
3463 | \&\f(CW\*(C`_setmaxstdio\*(C'\fR, which can increase this limit to \f(CW2048\fR (another |
|
|
3464 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
|
|
3465 | libraries. |
|
|
3466 | .Sp |
|
|
3467 | This might get you to about \f(CW512\fR or \f(CW2048\fR sockets (depending on |
|
|
3468 | windows version and/or the phase of the moon). To get more, you need to |
|
|
3469 | wrap all I/O functions and provide your own fd management, but the cost of |
|
|
3470 | calling select (O(nA\*^X)) will likely make this unworkable. |
|
|
3471 | .SH "PORTABILITY REQUIREMENTS" |
|
|
3472 | .IX Header "PORTABILITY REQUIREMENTS" |
|
|
3473 | In addition to a working ISO-C implementation, libev relies on a few |
|
|
3474 | additional extensions: |
|
|
3475 | .ie n .IP """void (*)(ev_watcher_type *, int revents)""\fR must have compatible calling conventions regardless of \f(CW""ev_watcher_type *""." 4 |
|
|
3476 | .el .IP "\f(CWvoid (*)(ev_watcher_type *, int revents)\fR must have compatible calling conventions regardless of \f(CWev_watcher_type *\fR." 4 |
|
|
3477 | .IX Item "void (*)(ev_watcher_type *, int revents) must have compatible calling conventions regardless of ev_watcher_type *." |
|
|
3478 | Libev assumes not only that all watcher pointers have the same internal |
|
|
3479 | structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO\s0 C for example), but it also |
|
|
3480 | assumes that the same (machine) code can be used to call any watcher |
|
|
3481 | callback: The watcher callbacks have different type signatures, but libev |
|
|
3482 | calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally. |
|
|
3483 | .ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4 |
|
|
3484 | .el .IP "\f(CWsig_atomic_t volatile\fR must be thread-atomic as well" 4 |
|
|
3485 | .IX Item "sig_atomic_t volatile must be thread-atomic as well" |
|
|
3486 | The type \f(CW\*(C`sig_atomic_t volatile\*(C'\fR (or whatever is defined as |
|
|
3487 | \&\f(CW\*(C`EV_ATOMIC_T\*(C'\fR) must be atomic w.r.t. accesses from different |
|
|
3488 | threads. This is not part of the specification for \f(CW\*(C`sig_atomic_t\*(C'\fR, but is |
|
|
3489 | believed to be sufficiently portable. |
|
|
3490 | .ie n .IP """sigprocmask"" must work in a threaded environment" 4 |
|
|
3491 | .el .IP "\f(CWsigprocmask\fR must work in a threaded environment" 4 |
|
|
3492 | .IX Item "sigprocmask must work in a threaded environment" |
|
|
3493 | Libev uses \f(CW\*(C`sigprocmask\*(C'\fR to temporarily block signals. This is not |
|
|
3494 | allowed in a threaded program (\f(CW\*(C`pthread_sigmask\*(C'\fR has to be used). Typical |
|
|
3495 | pthread implementations will either allow \f(CW\*(C`sigprocmask\*(C'\fR in the \*(L"main |
|
|
3496 | thread\*(R" or will block signals process-wide, both behaviours would |
|
|
3497 | be compatible with libev. Interaction between \f(CW\*(C`sigprocmask\*(C'\fR and |
|
|
3498 | \&\f(CW\*(C`pthread_sigmask\*(C'\fR could complicate things, however. |
|
|
3499 | .Sp |
|
|
3500 | The most portable way to handle signals is to block signals in all threads |
|
|
3501 | except the initial one, and run the default loop in the initial thread as |
|
|
3502 | well. |
|
|
3503 | .ie n .IP """long"" must be large enough for common memory allocation sizes" 4 |
|
|
3504 | .el .IP "\f(CWlong\fR must be large enough for common memory allocation sizes" 4 |
|
|
3505 | .IX Item "long must be large enough for common memory allocation sizes" |
|
|
3506 | To improve portability and simplify using libev, libev uses \f(CW\*(C`long\*(C'\fR |
|
|
3507 | internally instead of \f(CW\*(C`size_t\*(C'\fR when allocating its data structures. On |
|
|
3508 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3509 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3510 | millions of watchers. |
|
|
3511 | .ie n .IP """double"" must hold a time value in seconds with enough accuracy" 4 |
|
|
3512 | .el .IP "\f(CWdouble\fR must hold a time value in seconds with enough accuracy" 4 |
|
|
3513 | .IX Item "double must hold a time value in seconds with enough accuracy" |
|
|
3514 | The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to |
|
|
3515 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3516 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3517 | implementations implementing \s-1IEEE\s0 754 (basically all existing ones). |
|
|
3518 | .PP |
|
|
3519 | If you know of other additional requirements drop me a note. |
|
|
3520 | .SH "COMPILER WARNINGS" |
|
|
3521 | .IX Header "COMPILER WARNINGS" |
|
|
3522 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3523 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3524 | scared by this. |
|
|
3525 | .PP |
|
|
3526 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3527 | has different warnings, and each user has different tastes regarding |
|
|
3528 | warning options. \*(L"Warn-free\*(R" code therefore cannot be a goal except when |
|
|
3529 | targeting a specific compiler and compiler-version. |
|
|
3530 | .PP |
|
|
3531 | Another reason is that some compiler warnings require elaborate |
|
|
3532 | workarounds, or other changes to the code that make it less clear and less |
|
|
3533 | maintainable. |
|
|
3534 | .PP |
|
|
3535 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3536 | wrong (because they don't actually warn about the condition their message |
|
|
3537 | seems to warn about). |
|
|
3538 | .PP |
|
|
3539 | While libev is written to generate as few warnings as possible, |
|
|
3540 | \&\*(L"warn-free\*(R" code is not a goal, and it is recommended not to build libev |
|
|
3541 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3542 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3543 | warnings, not errors, or proof of bugs. |
|
|
3544 | .SH "VALGRIND" |
|
|
3545 | .IX Header "VALGRIND" |
|
|
3546 | Valgrind has a special section here because it is a popular tool that is |
|
|
3547 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3548 | .PP |
|
|
3549 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3550 | in libev, then check twice: If valgrind reports something like: |
|
|
3551 | .PP |
|
|
3552 | .Vb 3 |
|
|
3553 | \& ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3554 | \& ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3555 | \& ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3556 | .Ve |
|
|
3557 | .PP |
|
|
3558 | Then there is no memory leak. Similarly, under some circumstances, |
|
|
3559 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3560 | might be confused (it is a very good tool, but only a tool). |
|
|
3561 | .PP |
|
|
3562 | If you are unsure about something, feel free to contact the mailing list |
|
|
3563 | with the full valgrind report and an explanation on why you think this is |
|
|
3564 | a bug in libev. However, don't be annoyed when you get a brisk \*(L"this is |
|
|
3565 | no bug\*(R" answer and take the chance of learning how to interpret valgrind |
|
|
3566 | properly. |
|
|
3567 | .PP |
|
|
3568 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3569 | I suggest using suppression lists. |
|
|
3570 | .SH "AUTHOR" |
4617 | .SH "AUTHOR" |
3571 | .IX Header "AUTHOR" |
4618 | .IX Header "AUTHOR" |
3572 | Marc Lehmann <libev@schmorp.de>. |
4619 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3573 | .SH "POD ERRORS" |
|
|
3574 | .IX Header "POD ERRORS" |
|
|
3575 | Hey! \fBThe above document had some coding errors, which are explained below:\fR |
|
|
3576 | .IP "Around line 3122:" 4 |
|
|
3577 | .IX Item "Around line 3122:" |
|
|
3578 | You forgot a '=back' before '=head2' |
|
|