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1 | =encoding utf-8 |
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2 | |
1 | =head1 NAME |
3 | =head1 NAME |
2 | |
4 | |
3 | libev - a high performance full-featured event loop written in C |
5 | libev - a high performance full-featured event loop written in C |
4 | |
6 | |
5 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
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58 | ev_timer_start (loop, &timeout_watcher); |
60 | ev_timer_start (loop, &timeout_watcher); |
59 | |
61 | |
60 | // now wait for events to arrive |
62 | // now wait for events to arrive |
61 | ev_run (loop, 0); |
63 | ev_run (loop, 0); |
62 | |
64 | |
63 | // unloop was called, so exit |
65 | // break was called, so exit |
64 | return 0; |
66 | return 0; |
65 | } |
67 | } |
66 | |
68 | |
67 | =head1 ABOUT THIS DOCUMENT |
69 | =head1 ABOUT THIS DOCUMENT |
68 | |
70 | |
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82 | |
84 | |
83 | =head1 WHAT TO READ WHEN IN A HURRY |
85 | =head1 WHAT TO READ WHEN IN A HURRY |
84 | |
86 | |
85 | This manual tries to be very detailed, but unfortunately, this also makes |
87 | This manual tries to be very detailed, but unfortunately, this also makes |
86 | it very long. If you just want to know the basics of libev, I suggest |
88 | it very long. If you just want to know the basics of libev, I suggest |
87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
89 | reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and |
88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
90 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
89 | C<ev_timer> sections in L<WATCHER TYPES>. |
91 | C<ev_timer> sections in L</WATCHER TYPES>. |
90 | |
92 | |
91 | =head1 ABOUT LIBEV |
93 | =head1 ABOUT LIBEV |
92 | |
94 | |
93 | Libev is an event loop: you register interest in certain events (such as a |
95 | Libev is an event loop: you register interest in certain events (such as a |
94 | file descriptor being readable or a timeout occurring), and it will manage |
96 | file descriptor being readable or a timeout occurring), and it will manage |
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103 | details of the event, and then hand it over to libev by I<starting> the |
105 | details of the event, and then hand it over to libev by I<starting> the |
104 | watcher. |
106 | watcher. |
105 | |
107 | |
106 | =head2 FEATURES |
108 | =head2 FEATURES |
107 | |
109 | |
108 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
110 | Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll> |
109 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
111 | interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port |
110 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
112 | mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify> |
111 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
113 | interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
112 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
114 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
113 | timers (C<ev_timer>), absolute timers with customised rescheduling |
115 | timers (C<ev_timer>), absolute timers with customised rescheduling |
114 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
116 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
115 | change events (C<ev_child>), and event watchers dealing with the event |
117 | change events (C<ev_child>), and event watchers dealing with the event |
116 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
118 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
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157 | When libev detects a usage error such as a negative timer interval, then |
159 | When libev detects a usage error such as a negative timer interval, then |
158 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
160 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
159 | so C<NDEBUG> will disable this checking): these are programming errors in |
161 | so C<NDEBUG> will disable this checking): these are programming errors in |
160 | the libev caller and need to be fixed there. |
162 | the libev caller and need to be fixed there. |
161 | |
163 | |
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164 | Via the C<EV_FREQUENT> macro you can compile in and/or enable extensive |
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165 | consistency checking code inside libev that can be used to check for |
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166 | internal inconsistencies, suually caused by application bugs. |
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167 | |
162 | Libev also has a few internal error-checking C<assert>ions, and also has |
168 | Libev also has a few internal error-checking C<assert>ions. These do not |
163 | extensive consistency checking code. These do not trigger under normal |
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164 | circumstances, as they indicate either a bug in libev or worse. |
169 | trigger under normal circumstances, as they indicate either a bug in libev |
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170 | or worse. |
165 | |
171 | |
166 | |
172 | |
167 | =head1 GLOBAL FUNCTIONS |
173 | =head1 GLOBAL FUNCTIONS |
168 | |
174 | |
169 | These functions can be called anytime, even before initialising the |
175 | These functions can be called anytime, even before initialising the |
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174 | =item ev_tstamp ev_time () |
180 | =item ev_tstamp ev_time () |
175 | |
181 | |
176 | Returns the current time as libev would use it. Please note that the |
182 | Returns the current time as libev would use it. Please note that the |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
183 | C<ev_now> function is usually faster and also often returns the timestamp |
178 | you actually want to know. Also interesting is the combination of |
184 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
185 | C<ev_now_update> and C<ev_now>. |
180 | |
186 | |
181 | =item ev_sleep (ev_tstamp interval) |
187 | =item ev_sleep (ev_tstamp interval) |
182 | |
188 | |
183 | Sleep for the given interval: The current thread will be blocked until |
189 | Sleep for the given interval: The current thread will be blocked |
184 | either it is interrupted or the given time interval has passed. Basically |
190 | until either it is interrupted or the given time interval has |
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191 | passed (approximately - it might return a bit earlier even if not |
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192 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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193 | |
185 | this is a sub-second-resolution C<sleep ()>. |
194 | Basically this is a sub-second-resolution C<sleep ()>. |
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195 | |
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196 | The range of the C<interval> is limited - libev only guarantees to work |
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197 | with sleep times of up to one day (C<< interval <= 86400 >>). |
186 | |
198 | |
187 | =item int ev_version_major () |
199 | =item int ev_version_major () |
188 | |
200 | |
189 | =item int ev_version_minor () |
201 | =item int ev_version_minor () |
190 | |
202 | |
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241 | the current system, you would need to look at C<ev_embeddable_backends () |
253 | the current system, you would need to look at C<ev_embeddable_backends () |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
254 | & ev_supported_backends ()>, likewise for recommended ones. |
243 | |
255 | |
244 | See the description of C<ev_embed> watchers for more info. |
256 | See the description of C<ev_embed> watchers for more info. |
245 | |
257 | |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
258 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
247 | |
259 | |
248 | Sets the allocation function to use (the prototype is similar - the |
260 | Sets the allocation function to use (the prototype is similar - the |
249 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
261 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
250 | used to allocate and free memory (no surprises here). If it returns zero |
262 | used to allocate and free memory (no surprises here). If it returns zero |
251 | when memory needs to be allocated (C<size != 0>), the library might abort |
263 | when memory needs to be allocated (C<size != 0>), the library might abort |
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257 | |
269 | |
258 | You could override this function in high-availability programs to, say, |
270 | You could override this function in high-availability programs to, say, |
259 | free some memory if it cannot allocate memory, to use a special allocator, |
271 | free some memory if it cannot allocate memory, to use a special allocator, |
260 | or even to sleep a while and retry until some memory is available. |
272 | or even to sleep a while and retry until some memory is available. |
261 | |
273 | |
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274 | Example: The following is the C<realloc> function that libev itself uses |
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275 | which should work with C<realloc> and C<free> functions of all kinds and |
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276 | is probably a good basis for your own implementation. |
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277 | |
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278 | static void * |
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279 | ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT |
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280 | { |
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281 | if (size) |
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282 | return realloc (ptr, size); |
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283 | |
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284 | free (ptr); |
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285 | return 0; |
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286 | } |
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287 | |
262 | Example: Replace the libev allocator with one that waits a bit and then |
288 | Example: Replace the libev allocator with one that waits a bit and then |
263 | retries (example requires a standards-compliant C<realloc>). |
289 | retries. |
264 | |
290 | |
265 | static void * |
291 | static void * |
266 | persistent_realloc (void *ptr, size_t size) |
292 | persistent_realloc (void *ptr, size_t size) |
267 | { |
293 | { |
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294 | if (!size) |
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295 | { |
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296 | free (ptr); |
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297 | return 0; |
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298 | } |
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299 | |
268 | for (;;) |
300 | for (;;) |
269 | { |
301 | { |
270 | void *newptr = realloc (ptr, size); |
302 | void *newptr = realloc (ptr, size); |
271 | |
303 | |
272 | if (newptr) |
304 | if (newptr) |
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277 | } |
309 | } |
278 | |
310 | |
279 | ... |
311 | ... |
280 | ev_set_allocator (persistent_realloc); |
312 | ev_set_allocator (persistent_realloc); |
281 | |
313 | |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
314 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
283 | |
315 | |
284 | Set the callback function to call on a retryable system call error (such |
316 | Set the callback function to call on a retryable system call error (such |
285 | as failed select, poll, epoll_wait). The message is a printable string |
317 | as failed select, poll, epoll_wait). The message is a printable string |
286 | indicating the system call or subsystem causing the problem. If this |
318 | indicating the system call or subsystem causing the problem. If this |
287 | callback is set, then libev will expect it to remedy the situation, no |
319 | callback is set, then libev will expect it to remedy the situation, no |
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299 | } |
331 | } |
300 | |
332 | |
301 | ... |
333 | ... |
302 | ev_set_syserr_cb (fatal_error); |
334 | ev_set_syserr_cb (fatal_error); |
303 | |
335 | |
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336 | =item ev_feed_signal (int signum) |
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337 | |
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338 | This function can be used to "simulate" a signal receive. It is completely |
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339 | safe to call this function at any time, from any context, including signal |
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340 | handlers or random threads. |
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341 | |
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342 | Its main use is to customise signal handling in your process, especially |
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343 | in the presence of threads. For example, you could block signals |
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344 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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345 | creating any loops), and in one thread, use C<sigwait> or any other |
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346 | mechanism to wait for signals, then "deliver" them to libev by calling |
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347 | C<ev_feed_signal>. |
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348 | |
304 | =back |
349 | =back |
305 | |
350 | |
306 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
351 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
307 | |
352 | |
308 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
353 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
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355 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
400 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
356 | |
401 | |
357 | This will create and initialise a new event loop object. If the loop |
402 | This will create and initialise a new event loop object. If the loop |
358 | could not be initialised, returns false. |
403 | could not be initialised, returns false. |
359 | |
404 | |
360 | Note that this function I<is> thread-safe, and one common way to use |
405 | This function is thread-safe, and one common way to use libev with |
361 | libev with threads is indeed to create one loop per thread, and using the |
406 | threads is indeed to create one loop per thread, and using the default |
362 | default loop in the "main" or "initial" thread. |
407 | loop in the "main" or "initial" thread. |
363 | |
408 | |
364 | The flags argument can be used to specify special behaviour or specific |
409 | The flags argument can be used to specify special behaviour or specific |
365 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
410 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
366 | |
411 | |
367 | The following flags are supported: |
412 | The following flags are supported: |
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377 | |
422 | |
378 | If this flag bit is or'ed into the flag value (or the program runs setuid |
423 | If this flag bit is or'ed into the flag value (or the program runs setuid |
379 | or setgid) then libev will I<not> look at the environment variable |
424 | or setgid) then libev will I<not> look at the environment variable |
380 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
425 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
381 | override the flags completely if it is found in the environment. This is |
426 | override the flags completely if it is found in the environment. This is |
382 | useful to try out specific backends to test their performance, or to work |
427 | useful to try out specific backends to test their performance, to work |
383 | around bugs. |
428 | around bugs, or to make libev threadsafe (accessing environment variables |
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429 | cannot be done in a threadsafe way, but usually it works if no other |
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430 | thread modifies them). |
384 | |
431 | |
385 | =item C<EVFLAG_FORKCHECK> |
432 | =item C<EVFLAG_FORKCHECK> |
386 | |
433 | |
387 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
434 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
388 | make libev check for a fork in each iteration by enabling this flag. |
435 | make libev check for a fork in each iteration by enabling this flag. |
389 | |
436 | |
390 | This works by calling C<getpid ()> on every iteration of the loop, |
437 | This works by calling C<getpid ()> on every iteration of the loop, |
391 | and thus this might slow down your event loop if you do a lot of loop |
438 | and thus this might slow down your event loop if you do a lot of loop |
392 | iterations and little real work, but is usually not noticeable (on my |
439 | iterations and little real work, but is usually not noticeable (on my |
393 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
440 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
394 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
441 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
395 | C<pthread_atfork> which is even faster). |
442 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
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443 | versions 2.25 apparently removed the C<getpid> optimisation again). |
396 | |
444 | |
397 | The big advantage of this flag is that you can forget about fork (and |
445 | The big advantage of this flag is that you can forget about fork (and |
398 | forget about forgetting to tell libev about forking) when you use this |
446 | forget about forgetting to tell libev about forking, although you still |
399 | flag. |
447 | have to ignore C<SIGPIPE>) when you use this flag. |
400 | |
448 | |
401 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
449 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
402 | environment variable. |
450 | environment variable. |
403 | |
451 | |
404 | =item C<EVFLAG_NOINOTIFY> |
452 | =item C<EVFLAG_NOINOTIFY> |
405 | |
453 | |
406 | When this flag is specified, then libev will not attempt to use the |
454 | When this flag is specified, then libev will not attempt to use the |
407 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
455 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
408 | testing, this flag can be useful to conserve inotify file descriptors, as |
456 | testing, this flag can be useful to conserve inotify file descriptors, as |
409 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
457 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
410 | |
458 | |
411 | =item C<EVFLAG_SIGNALFD> |
459 | =item C<EVFLAG_SIGNALFD> |
412 | |
460 | |
413 | When this flag is specified, then libev will attempt to use the |
461 | When this flag is specified, then libev will attempt to use the |
414 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
462 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
415 | delivers signals synchronously, which makes it both faster and might make |
463 | delivers signals synchronously, which makes it both faster and might make |
416 | it possible to get the queued signal data. It can also simplify signal |
464 | it possible to get the queued signal data. It can also simplify signal |
417 | handling with threads, as long as you properly block signals in your |
465 | handling with threads, as long as you properly block signals in your |
418 | threads that are not interested in handling them. |
466 | threads that are not interested in handling them. |
419 | |
467 | |
420 | Signalfd will not be used by default as this changes your signal mask, and |
468 | Signalfd will not be used by default as this changes your signal mask, and |
421 | there are a lot of shoddy libraries and programs (glib's threadpool for |
469 | there are a lot of shoddy libraries and programs (glib's threadpool for |
422 | example) that can't properly initialise their signal masks. |
470 | example) that can't properly initialise their signal masks. |
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471 | |
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472 | =item C<EVFLAG_NOSIGMASK> |
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473 | |
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474 | When this flag is specified, then libev will avoid to modify the signal |
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475 | mask. Specifically, this means you have to make sure signals are unblocked |
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476 | when you want to receive them. |
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477 | |
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478 | This behaviour is useful when you want to do your own signal handling, or |
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479 | want to handle signals only in specific threads and want to avoid libev |
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480 | unblocking the signals. |
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481 | |
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482 | It's also required by POSIX in a threaded program, as libev calls |
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483 | C<sigprocmask>, whose behaviour is officially unspecified. |
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484 | |
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485 | =item C<EVFLAG_NOTIMERFD> |
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486 | |
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487 | When this flag is specified, the libev will avoid using a C<timerfd> to |
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488 | detect time jumps. It will still be able to detect time jumps, but takes |
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489 | longer and has a lower accuracy in doing so, but saves a file descriptor |
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490 | per loop. |
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491 | |
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492 | The current implementation only tries to use a C<timerfd> when the first |
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493 | C<ev_periodic> watcher is started and falls back on other methods if it |
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494 | cannot be created, but this behaviour might change in the future. |
423 | |
495 | |
424 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
496 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
425 | |
497 | |
426 | This is your standard select(2) backend. Not I<completely> standard, as |
498 | This is your standard select(2) backend. Not I<completely> standard, as |
427 | libev tries to roll its own fd_set with no limits on the number of fds, |
499 | libev tries to roll its own fd_set with no limits on the number of fds, |
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452 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
524 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
453 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
525 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
454 | |
526 | |
455 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
527 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
456 | |
528 | |
457 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
529 | Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
458 | kernels). |
530 | kernels). |
459 | |
531 | |
460 | For few fds, this backend is a bit little slower than poll and select, |
532 | For few fds, this backend is a bit little slower than poll and select, but |
461 | but it scales phenomenally better. While poll and select usually scale |
533 | it scales phenomenally better. While poll and select usually scale like |
462 | like O(total_fds) where n is the total number of fds (or the highest fd), |
534 | O(total_fds) where total_fds is the total number of fds (or the highest |
463 | epoll scales either O(1) or O(active_fds). |
535 | fd), epoll scales either O(1) or O(active_fds). |
464 | |
536 | |
465 | The epoll mechanism deserves honorable mention as the most misdesigned |
537 | The epoll mechanism deserves honorable mention as the most misdesigned |
466 | of the more advanced event mechanisms: mere annoyances include silently |
538 | of the more advanced event mechanisms: mere annoyances include silently |
467 | dropping file descriptors, requiring a system call per change per file |
539 | dropping file descriptors, requiring a system call per change per file |
468 | descriptor (and unnecessary guessing of parameters), problems with dup, |
540 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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471 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
543 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
472 | forks then I<both> parent and child process have to recreate the epoll |
544 | forks then I<both> parent and child process have to recreate the epoll |
473 | set, which can take considerable time (one syscall per file descriptor) |
545 | set, which can take considerable time (one syscall per file descriptor) |
474 | and is of course hard to detect. |
546 | and is of course hard to detect. |
475 | |
547 | |
476 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
548 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
477 | of course I<doesn't>, and epoll just loves to report events for totally |
549 | but of course I<doesn't>, and epoll just loves to report events for |
478 | I<different> file descriptors (even already closed ones, so one cannot |
550 | totally I<different> file descriptors (even already closed ones, so |
479 | even remove them from the set) than registered in the set (especially |
551 | one cannot even remove them from the set) than registered in the set |
480 | on SMP systems). Libev tries to counter these spurious notifications by |
552 | (especially on SMP systems). Libev tries to counter these spurious |
481 | employing an additional generation counter and comparing that against the |
553 | notifications by employing an additional generation counter and comparing |
482 | events to filter out spurious ones, recreating the set when required. Last |
554 | that against the events to filter out spurious ones, recreating the set |
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555 | when required. Epoll also erroneously rounds down timeouts, but gives you |
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556 | no way to know when and by how much, so sometimes you have to busy-wait |
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557 | because epoll returns immediately despite a nonzero timeout. And last |
483 | not least, it also refuses to work with some file descriptors which work |
558 | not least, it also refuses to work with some file descriptors which work |
484 | perfectly fine with C<select> (files, many character devices...). |
559 | perfectly fine with C<select> (files, many character devices...). |
485 | |
560 | |
486 | Epoll is truly the train wreck analog among event poll mechanisms. |
561 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
562 | cobbled together in a hurry, no thought to design or interaction with |
|
|
563 | others. Oh, the pain, will it ever stop... |
487 | |
564 | |
488 | While stopping, setting and starting an I/O watcher in the same iteration |
565 | While stopping, setting and starting an I/O watcher in the same iteration |
489 | will result in some caching, there is still a system call per such |
566 | will result in some caching, there is still a system call per such |
490 | incident (because the same I<file descriptor> could point to a different |
567 | incident (because the same I<file descriptor> could point to a different |
491 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
568 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
503 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
580 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
504 | faster than epoll for maybe up to a hundred file descriptors, depending on |
581 | faster than epoll for maybe up to a hundred file descriptors, depending on |
505 | the usage. So sad. |
582 | the usage. So sad. |
506 | |
583 | |
507 | While nominally embeddable in other event loops, this feature is broken in |
584 | While nominally embeddable in other event loops, this feature is broken in |
508 | all kernel versions tested so far. |
585 | a lot of kernel revisions, but probably(!) works in current versions. |
509 | |
586 | |
510 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
587 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
511 | C<EVBACKEND_POLL>. |
588 | C<EVBACKEND_POLL>. |
512 | |
589 | |
|
|
590 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
|
|
591 | |
|
|
592 | Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<< |
|
|
593 | io_submit(2) >>) event interface available in post-4.18 kernels (but libev |
|
|
594 | only tries to use it in 4.19+). |
|
|
595 | |
|
|
596 | This is another Linux train wreck of an event interface. |
|
|
597 | |
|
|
598 | If this backend works for you (as of this writing, it was very |
|
|
599 | experimental), it is the best event interface available on Linux and might |
|
|
600 | be well worth enabling it - if it isn't available in your kernel this will |
|
|
601 | be detected and this backend will be skipped. |
|
|
602 | |
|
|
603 | This backend can batch oneshot requests and supports a user-space ring |
|
|
604 | buffer to receive events. It also doesn't suffer from most of the design |
|
|
605 | problems of epoll (such as not being able to remove event sources from |
|
|
606 | the epoll set), and generally sounds too good to be true. Because, this |
|
|
607 | being the Linux kernel, of course it suffers from a whole new set of |
|
|
608 | limitations, forcing you to fall back to epoll, inheriting all its design |
|
|
609 | issues. |
|
|
610 | |
|
|
611 | For one, it is not easily embeddable (but probably could be done using |
|
|
612 | an event fd at some extra overhead). It also is subject to a system wide |
|
|
613 | limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO |
|
|
614 | requests are left, this backend will be skipped during initialisation, and |
|
|
615 | will switch to epoll when the loop is active. |
|
|
616 | |
|
|
617 | Most problematic in practice, however, is that not all file descriptors |
|
|
618 | work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds, |
|
|
619 | files, F</dev/null> and many others are supported, but ttys do not work |
|
|
620 | properly (a known bug that the kernel developers don't care about, see |
|
|
621 | L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
|
|
622 | (yet?) a generic event polling interface. |
|
|
623 | |
|
|
624 | Overall, it seems the Linux developers just don't want it to have a |
|
|
625 | generic event handling mechanism other than C<select> or C<poll>. |
|
|
626 | |
|
|
627 | To work around all these problem, the current version of libev uses its |
|
|
628 | epoll backend as a fallback for file descriptor types that do not work. Or |
|
|
629 | falls back completely to epoll if the kernel acts up. |
|
|
630 | |
|
|
631 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
632 | C<EVBACKEND_POLL>. |
|
|
633 | |
513 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
634 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
514 | |
635 | |
515 | Kqueue deserves special mention, as at the time of this writing, it |
636 | Kqueue deserves special mention, as at the time this backend was |
516 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
637 | implemented, it was broken on all BSDs except NetBSD (usually it doesn't |
517 | with anything but sockets and pipes, except on Darwin, where of course |
638 | work reliably with anything but sockets and pipes, except on Darwin, |
518 | it's completely useless). Unlike epoll, however, whose brokenness |
639 | where of course it's completely useless). Unlike epoll, however, whose |
519 | is by design, these kqueue bugs can (and eventually will) be fixed |
640 | brokenness is by design, these kqueue bugs can be (and mostly have been) |
520 | without API changes to existing programs. For this reason it's not being |
641 | fixed without API changes to existing programs. For this reason it's not |
521 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
642 | being "auto-detected" on all platforms unless you explicitly specify it |
522 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
643 | in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a |
523 | system like NetBSD. |
644 | known-to-be-good (-enough) system like NetBSD. |
524 | |
645 | |
525 | You still can embed kqueue into a normal poll or select backend and use it |
646 | You still can embed kqueue into a normal poll or select backend and use it |
526 | only for sockets (after having made sure that sockets work with kqueue on |
647 | only for sockets (after having made sure that sockets work with kqueue on |
527 | the target platform). See C<ev_embed> watchers for more info. |
648 | the target platform). See C<ev_embed> watchers for more info. |
528 | |
649 | |
529 | It scales in the same way as the epoll backend, but the interface to the |
650 | It scales in the same way as the epoll backend, but the interface to the |
530 | kernel is more efficient (which says nothing about its actual speed, of |
651 | kernel is more efficient (which says nothing about its actual speed, of |
531 | course). While stopping, setting and starting an I/O watcher does never |
652 | course). While stopping, setting and starting an I/O watcher does never |
532 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
653 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
533 | two event changes per incident. Support for C<fork ()> is very bad (but |
654 | two event changes per incident. Support for C<fork ()> is very bad (you |
534 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
655 | might have to leak fds on fork, but it's more sane than epoll) and it |
535 | cases |
656 | drops fds silently in similarly hard-to-detect cases. |
536 | |
657 | |
537 | This backend usually performs well under most conditions. |
658 | This backend usually performs well under most conditions. |
538 | |
659 | |
539 | While nominally embeddable in other event loops, this doesn't work |
660 | While nominally embeddable in other event loops, this doesn't work |
540 | everywhere, so you might need to test for this. And since it is broken |
661 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
557 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
678 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
558 | |
679 | |
559 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
680 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
560 | it's really slow, but it still scales very well (O(active_fds)). |
681 | it's really slow, but it still scales very well (O(active_fds)). |
561 | |
682 | |
562 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
563 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
564 | blocking when no data (or space) is available. |
|
|
565 | |
|
|
566 | While this backend scales well, it requires one system call per active |
683 | While this backend scales well, it requires one system call per active |
567 | file descriptor per loop iteration. For small and medium numbers of file |
684 | file descriptor per loop iteration. For small and medium numbers of file |
568 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
685 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
569 | might perform better. |
686 | might perform better. |
570 | |
687 | |
571 | On the positive side, with the exception of the spurious readiness |
688 | On the positive side, this backend actually performed fully to |
572 | notifications, this backend actually performed fully to specification |
|
|
573 | in all tests and is fully embeddable, which is a rare feat among the |
689 | specification in all tests and is fully embeddable, which is a rare feat |
574 | OS-specific backends (I vastly prefer correctness over speed hacks). |
690 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
691 | hacks). |
|
|
692 | |
|
|
693 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
694 | even sun itself gets it wrong in their code examples: The event polling |
|
|
695 | function sometimes returns events to the caller even though an error |
|
|
696 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
697 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
698 | absolutely have to know whether an event occurred or not because you have |
|
|
699 | to re-arm the watcher. |
|
|
700 | |
|
|
701 | Fortunately libev seems to be able to work around these idiocies. |
575 | |
702 | |
576 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
703 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
577 | C<EVBACKEND_POLL>. |
704 | C<EVBACKEND_POLL>. |
578 | |
705 | |
579 | =item C<EVBACKEND_ALL> |
706 | =item C<EVBACKEND_ALL> |
580 | |
707 | |
581 | Try all backends (even potentially broken ones that wouldn't be tried |
708 | Try all backends (even potentially broken ones that wouldn't be tried |
582 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
709 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
583 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
710 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
584 | |
711 | |
585 | It is definitely not recommended to use this flag. |
712 | It is definitely not recommended to use this flag, use whatever |
|
|
713 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
714 | at all. |
|
|
715 | |
|
|
716 | =item C<EVBACKEND_MASK> |
|
|
717 | |
|
|
718 | Not a backend at all, but a mask to select all backend bits from a |
|
|
719 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
720 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
586 | |
721 | |
587 | =back |
722 | =back |
588 | |
723 | |
589 | If one or more of the backend flags are or'ed into the flags value, |
724 | If one or more of the backend flags are or'ed into the flags value, |
590 | then only these backends will be tried (in the reverse order as listed |
725 | then only these backends will be tried (in the reverse order as listed |
… | |
… | |
599 | |
734 | |
600 | Example: Use whatever libev has to offer, but make sure that kqueue is |
735 | Example: Use whatever libev has to offer, but make sure that kqueue is |
601 | used if available. |
736 | used if available. |
602 | |
737 | |
603 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
738 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
739 | |
|
|
740 | Example: Similarly, on linux, you mgiht want to take advantage of the |
|
|
741 | linux aio backend if possible, but fall back to something else if that |
|
|
742 | isn't available. |
|
|
743 | |
|
|
744 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO); |
604 | |
745 | |
605 | =item ev_loop_destroy (loop) |
746 | =item ev_loop_destroy (loop) |
606 | |
747 | |
607 | Destroys an event loop object (frees all memory and kernel state |
748 | Destroys an event loop object (frees all memory and kernel state |
608 | etc.). None of the active event watchers will be stopped in the normal |
749 | etc.). None of the active event watchers will be stopped in the normal |
… | |
… | |
619 | This function is normally used on loop objects allocated by |
760 | This function is normally used on loop objects allocated by |
620 | C<ev_loop_new>, but it can also be used on the default loop returned by |
761 | C<ev_loop_new>, but it can also be used on the default loop returned by |
621 | C<ev_default_loop>, in which case it is not thread-safe. |
762 | C<ev_default_loop>, in which case it is not thread-safe. |
622 | |
763 | |
623 | Note that it is not advisable to call this function on the default loop |
764 | Note that it is not advisable to call this function on the default loop |
624 | except in the rare occasion where you really need to free it's resources. |
765 | except in the rare occasion where you really need to free its resources. |
625 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
766 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
626 | and C<ev_loop_destroy>. |
767 | and C<ev_loop_destroy>. |
627 | |
768 | |
628 | =item ev_loop_fork (loop) |
769 | =item ev_loop_fork (loop) |
629 | |
770 | |
630 | This function sets a flag that causes subsequent C<ev_run> iterations to |
771 | This function sets a flag that causes subsequent C<ev_run> iterations |
631 | reinitialise the kernel state for backends that have one. Despite the |
772 | to reinitialise the kernel state for backends that have one. Despite |
632 | name, you can call it anytime, but it makes most sense after forking, in |
773 | the name, you can call it anytime you are allowed to start or stop |
633 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
774 | watchers (except inside an C<ev_prepare> callback), but it makes most |
|
|
775 | sense after forking, in the child process. You I<must> call it (or use |
634 | child before resuming or calling C<ev_run>. |
776 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
635 | |
777 | |
|
|
778 | In addition, if you want to reuse a loop (via this function or |
|
|
779 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
|
|
780 | |
636 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
781 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
637 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
782 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
638 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
783 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
639 | during fork. |
784 | during fork. |
640 | |
785 | |
641 | On the other hand, you only need to call this function in the child |
786 | On the other hand, you only need to call this function in the child |
… | |
… | |
677 | prepare and check phases. |
822 | prepare and check phases. |
678 | |
823 | |
679 | =item unsigned int ev_depth (loop) |
824 | =item unsigned int ev_depth (loop) |
680 | |
825 | |
681 | Returns the number of times C<ev_run> was entered minus the number of |
826 | Returns the number of times C<ev_run> was entered minus the number of |
682 | times C<ev_run> was exited, in other words, the recursion depth. |
827 | times C<ev_run> was exited normally, in other words, the recursion depth. |
683 | |
828 | |
684 | Outside C<ev_run>, this number is zero. In a callback, this number is |
829 | Outside C<ev_run>, this number is zero. In a callback, this number is |
685 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
830 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
686 | in which case it is higher. |
831 | in which case it is higher. |
687 | |
832 | |
688 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
833 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
689 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
834 | throwing an exception etc.), doesn't count as "exit" - consider this |
690 | ungentleman-like behaviour unless it's really convenient. |
835 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
836 | convenient, in which case it is fully supported. |
691 | |
837 | |
692 | =item unsigned int ev_backend (loop) |
838 | =item unsigned int ev_backend (loop) |
693 | |
839 | |
694 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
840 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
695 | use. |
841 | use. |
… | |
… | |
710 | |
856 | |
711 | This function is rarely useful, but when some event callback runs for a |
857 | This function is rarely useful, but when some event callback runs for a |
712 | very long time without entering the event loop, updating libev's idea of |
858 | very long time without entering the event loop, updating libev's idea of |
713 | the current time is a good idea. |
859 | the current time is a good idea. |
714 | |
860 | |
715 | See also L<The special problem of time updates> in the C<ev_timer> section. |
861 | See also L</The special problem of time updates> in the C<ev_timer> section. |
716 | |
862 | |
717 | =item ev_suspend (loop) |
863 | =item ev_suspend (loop) |
718 | |
864 | |
719 | =item ev_resume (loop) |
865 | =item ev_resume (loop) |
720 | |
866 | |
… | |
… | |
738 | without a previous call to C<ev_suspend>. |
884 | without a previous call to C<ev_suspend>. |
739 | |
885 | |
740 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
886 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
741 | event loop time (see C<ev_now_update>). |
887 | event loop time (see C<ev_now_update>). |
742 | |
888 | |
743 | =item ev_run (loop, int flags) |
889 | =item bool ev_run (loop, int flags) |
744 | |
890 | |
745 | Finally, this is it, the event handler. This function usually is called |
891 | Finally, this is it, the event handler. This function usually is called |
746 | after you have initialised all your watchers and you want to start |
892 | after you have initialised all your watchers and you want to start |
747 | handling events. It will ask the operating system for any new events, call |
893 | handling events. It will ask the operating system for any new events, call |
748 | the watcher callbacks, an then repeat the whole process indefinitely: This |
894 | the watcher callbacks, and then repeat the whole process indefinitely: This |
749 | is why event loops are called I<loops>. |
895 | is why event loops are called I<loops>. |
750 | |
896 | |
751 | If the flags argument is specified as C<0>, it will keep handling events |
897 | If the flags argument is specified as C<0>, it will keep handling events |
752 | until either no event watchers are active anymore or C<ev_break> was |
898 | until either no event watchers are active anymore or C<ev_break> was |
753 | called. |
899 | called. |
|
|
900 | |
|
|
901 | The return value is false if there are no more active watchers (which |
|
|
902 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
903 | (which usually means " you should call C<ev_run> again"). |
754 | |
904 | |
755 | Please note that an explicit C<ev_break> is usually better than |
905 | Please note that an explicit C<ev_break> is usually better than |
756 | relying on all watchers to be stopped when deciding when a program has |
906 | relying on all watchers to be stopped when deciding when a program has |
757 | finished (especially in interactive programs), but having a program |
907 | finished (especially in interactive programs), but having a program |
758 | that automatically loops as long as it has to and no longer by virtue |
908 | that automatically loops as long as it has to and no longer by virtue |
759 | of relying on its watchers stopping correctly, that is truly a thing of |
909 | of relying on its watchers stopping correctly, that is truly a thing of |
760 | beauty. |
910 | beauty. |
761 | |
911 | |
|
|
912 | This function is I<mostly> exception-safe - you can break out of a |
|
|
913 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
914 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
915 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
916 | |
762 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
917 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
763 | those events and any already outstanding ones, but will not wait and |
918 | those events and any already outstanding ones, but will not wait and |
764 | block your process in case there are no events and will return after one |
919 | block your process in case there are no events and will return after one |
765 | iteration of the loop. This is sometimes useful to poll and handle new |
920 | iteration of the loop. This is sometimes useful to poll and handle new |
766 | events while doing lengthy calculations, to keep the program responsive. |
921 | events while doing lengthy calculations, to keep the program responsive. |
… | |
… | |
775 | This is useful if you are waiting for some external event in conjunction |
930 | This is useful if you are waiting for some external event in conjunction |
776 | with something not expressible using other libev watchers (i.e. "roll your |
931 | with something not expressible using other libev watchers (i.e. "roll your |
777 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
932 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
778 | usually a better approach for this kind of thing. |
933 | usually a better approach for this kind of thing. |
779 | |
934 | |
780 | Here are the gory details of what C<ev_run> does: |
935 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
936 | understanding, not a guarantee that things will work exactly like this in |
|
|
937 | future versions): |
781 | |
938 | |
782 | - Increment loop depth. |
939 | - Increment loop depth. |
783 | - Reset the ev_break status. |
940 | - Reset the ev_break status. |
784 | - Before the first iteration, call any pending watchers. |
941 | - Before the first iteration, call any pending watchers. |
785 | LOOP: |
942 | LOOP: |
… | |
… | |
818 | anymore. |
975 | anymore. |
819 | |
976 | |
820 | ... queue jobs here, make sure they register event watchers as long |
977 | ... queue jobs here, make sure they register event watchers as long |
821 | ... as they still have work to do (even an idle watcher will do..) |
978 | ... as they still have work to do (even an idle watcher will do..) |
822 | ev_run (my_loop, 0); |
979 | ev_run (my_loop, 0); |
823 | ... jobs done or somebody called unloop. yeah! |
980 | ... jobs done or somebody called break. yeah! |
824 | |
981 | |
825 | =item ev_break (loop, how) |
982 | =item ev_break (loop, how) |
826 | |
983 | |
827 | Can be used to make a call to C<ev_run> return early (but only after it |
984 | Can be used to make a call to C<ev_run> return early (but only after it |
828 | has processed all outstanding events). The C<how> argument must be either |
985 | has processed all outstanding events). The C<how> argument must be either |
829 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
986 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
830 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
987 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
831 | |
988 | |
832 | This "break state" will be cleared when entering C<ev_run> again. |
989 | This "break state" will be cleared on the next call to C<ev_run>. |
833 | |
990 | |
834 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too. |
991 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
992 | which case it will have no effect. |
835 | |
993 | |
836 | =item ev_ref (loop) |
994 | =item ev_ref (loop) |
837 | |
995 | |
838 | =item ev_unref (loop) |
996 | =item ev_unref (loop) |
839 | |
997 | |
… | |
… | |
860 | running when nothing else is active. |
1018 | running when nothing else is active. |
861 | |
1019 | |
862 | ev_signal exitsig; |
1020 | ev_signal exitsig; |
863 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
1021 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
864 | ev_signal_start (loop, &exitsig); |
1022 | ev_signal_start (loop, &exitsig); |
865 | evf_unref (loop); |
1023 | ev_unref (loop); |
866 | |
1024 | |
867 | Example: For some weird reason, unregister the above signal handler again. |
1025 | Example: For some weird reason, unregister the above signal handler again. |
868 | |
1026 | |
869 | ev_ref (loop); |
1027 | ev_ref (loop); |
870 | ev_signal_stop (loop, &exitsig); |
1028 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
890 | overhead for the actual polling but can deliver many events at once. |
1048 | overhead for the actual polling but can deliver many events at once. |
891 | |
1049 | |
892 | By setting a higher I<io collect interval> you allow libev to spend more |
1050 | By setting a higher I<io collect interval> you allow libev to spend more |
893 | time collecting I/O events, so you can handle more events per iteration, |
1051 | time collecting I/O events, so you can handle more events per iteration, |
894 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
1052 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
895 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
1053 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
896 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
1054 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
897 | sleep time ensures that libev will not poll for I/O events more often then |
1055 | sleep time ensures that libev will not poll for I/O events more often then |
898 | once per this interval, on average. |
1056 | once per this interval, on average (as long as the host time resolution is |
|
|
1057 | good enough). |
899 | |
1058 | |
900 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
1059 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
901 | to spend more time collecting timeouts, at the expense of increased |
1060 | to spend more time collecting timeouts, at the expense of increased |
902 | latency/jitter/inexactness (the watcher callback will be called |
1061 | latency/jitter/inexactness (the watcher callback will be called |
903 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
1062 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
949 | invoke the actual watchers inside another context (another thread etc.). |
1108 | invoke the actual watchers inside another context (another thread etc.). |
950 | |
1109 | |
951 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1110 | If you want to reset the callback, use C<ev_invoke_pending> as new |
952 | callback. |
1111 | callback. |
953 | |
1112 | |
954 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1113 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
955 | |
1114 | |
956 | Sometimes you want to share the same loop between multiple threads. This |
1115 | Sometimes you want to share the same loop between multiple threads. This |
957 | can be done relatively simply by putting mutex_lock/unlock calls around |
1116 | can be done relatively simply by putting mutex_lock/unlock calls around |
958 | each call to a libev function. |
1117 | each call to a libev function. |
959 | |
1118 | |
960 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1119 | However, C<ev_run> can run an indefinite time, so it is not feasible |
961 | to wait for it to return. One way around this is to wake up the event |
1120 | to wait for it to return. One way around this is to wake up the event |
962 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1121 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
963 | I<release> and I<acquire> callbacks on the loop. |
1122 | I<release> and I<acquire> callbacks on the loop. |
964 | |
1123 | |
965 | When set, then C<release> will be called just before the thread is |
1124 | When set, then C<release> will be called just before the thread is |
966 | suspended waiting for new events, and C<acquire> is called just |
1125 | suspended waiting for new events, and C<acquire> is called just |
967 | afterwards. |
1126 | afterwards. |
… | |
… | |
982 | See also the locking example in the C<THREADS> section later in this |
1141 | See also the locking example in the C<THREADS> section later in this |
983 | document. |
1142 | document. |
984 | |
1143 | |
985 | =item ev_set_userdata (loop, void *data) |
1144 | =item ev_set_userdata (loop, void *data) |
986 | |
1145 | |
987 | =item ev_userdata (loop) |
1146 | =item void *ev_userdata (loop) |
988 | |
1147 | |
989 | Set and retrieve a single C<void *> associated with a loop. When |
1148 | Set and retrieve a single C<void *> associated with a loop. When |
990 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1149 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
991 | C<0.> |
1150 | C<0>. |
992 | |
1151 | |
993 | These two functions can be used to associate arbitrary data with a loop, |
1152 | These two functions can be used to associate arbitrary data with a loop, |
994 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1153 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
995 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1154 | C<acquire> callbacks described above, but of course can be (ab-)used for |
996 | any other purpose as well. |
1155 | any other purpose as well. |
… | |
… | |
1107 | |
1266 | |
1108 | =item C<EV_PREPARE> |
1267 | =item C<EV_PREPARE> |
1109 | |
1268 | |
1110 | =item C<EV_CHECK> |
1269 | =item C<EV_CHECK> |
1111 | |
1270 | |
1112 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1271 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1113 | to gather new events, and all C<ev_check> watchers are invoked just after |
1272 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1114 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1273 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1274 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1275 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1276 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1277 | or lower priority within an event loop iteration. |
|
|
1278 | |
1115 | received events. Callbacks of both watcher types can start and stop as |
1279 | Callbacks of both watcher types can start and stop as many watchers as |
1116 | many watchers as they want, and all of them will be taken into account |
1280 | they want, and all of them will be taken into account (for example, a |
1117 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1281 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1118 | C<ev_run> from blocking). |
1282 | blocking). |
1119 | |
1283 | |
1120 | =item C<EV_EMBED> |
1284 | =item C<EV_EMBED> |
1121 | |
1285 | |
1122 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1286 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1123 | |
1287 | |
… | |
… | |
1246 | |
1410 | |
1247 | =item callback ev_cb (ev_TYPE *watcher) |
1411 | =item callback ev_cb (ev_TYPE *watcher) |
1248 | |
1412 | |
1249 | Returns the callback currently set on the watcher. |
1413 | Returns the callback currently set on the watcher. |
1250 | |
1414 | |
1251 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1415 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1252 | |
1416 | |
1253 | Change the callback. You can change the callback at virtually any time |
1417 | Change the callback. You can change the callback at virtually any time |
1254 | (modulo threads). |
1418 | (modulo threads). |
1255 | |
1419 | |
1256 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1420 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
… | |
… | |
1274 | or might not have been clamped to the valid range. |
1438 | or might not have been clamped to the valid range. |
1275 | |
1439 | |
1276 | The default priority used by watchers when no priority has been set is |
1440 | The default priority used by watchers when no priority has been set is |
1277 | always C<0>, which is supposed to not be too high and not be too low :). |
1441 | always C<0>, which is supposed to not be too high and not be too low :). |
1278 | |
1442 | |
1279 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1443 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1280 | priorities. |
1444 | priorities. |
1281 | |
1445 | |
1282 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1446 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1283 | |
1447 | |
1284 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1448 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1309 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1473 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1310 | functions that do not need a watcher. |
1474 | functions that do not need a watcher. |
1311 | |
1475 | |
1312 | =back |
1476 | =back |
1313 | |
1477 | |
1314 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1478 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
1315 | |
1479 | OWN COMPOSITE WATCHERS> idioms. |
1316 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1317 | and read at any time: libev will completely ignore it. This can be used |
|
|
1318 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1319 | don't want to allocate memory and store a pointer to it in that data |
|
|
1320 | member, you can also "subclass" the watcher type and provide your own |
|
|
1321 | data: |
|
|
1322 | |
|
|
1323 | struct my_io |
|
|
1324 | { |
|
|
1325 | ev_io io; |
|
|
1326 | int otherfd; |
|
|
1327 | void *somedata; |
|
|
1328 | struct whatever *mostinteresting; |
|
|
1329 | }; |
|
|
1330 | |
|
|
1331 | ... |
|
|
1332 | struct my_io w; |
|
|
1333 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1334 | |
|
|
1335 | And since your callback will be called with a pointer to the watcher, you |
|
|
1336 | can cast it back to your own type: |
|
|
1337 | |
|
|
1338 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1339 | { |
|
|
1340 | struct my_io *w = (struct my_io *)w_; |
|
|
1341 | ... |
|
|
1342 | } |
|
|
1343 | |
|
|
1344 | More interesting and less C-conformant ways of casting your callback type |
|
|
1345 | instead have been omitted. |
|
|
1346 | |
|
|
1347 | Another common scenario is to use some data structure with multiple |
|
|
1348 | embedded watchers: |
|
|
1349 | |
|
|
1350 | struct my_biggy |
|
|
1351 | { |
|
|
1352 | int some_data; |
|
|
1353 | ev_timer t1; |
|
|
1354 | ev_timer t2; |
|
|
1355 | } |
|
|
1356 | |
|
|
1357 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1358 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1359 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1360 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1361 | programmers): |
|
|
1362 | |
|
|
1363 | #include <stddef.h> |
|
|
1364 | |
|
|
1365 | static void |
|
|
1366 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1367 | { |
|
|
1368 | struct my_biggy big = (struct my_biggy *) |
|
|
1369 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1370 | } |
|
|
1371 | |
|
|
1372 | static void |
|
|
1373 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1374 | { |
|
|
1375 | struct my_biggy big = (struct my_biggy *) |
|
|
1376 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1377 | } |
|
|
1378 | |
1480 | |
1379 | =head2 WATCHER STATES |
1481 | =head2 WATCHER STATES |
1380 | |
1482 | |
1381 | There are various watcher states mentioned throughout this manual - |
1483 | There are various watcher states mentioned throughout this manual - |
1382 | active, pending and so on. In this section these states and the rules to |
1484 | active, pending and so on. In this section these states and the rules to |
1383 | transition between them will be described in more detail - and while these |
1485 | transition between them will be described in more detail - and while these |
1384 | rules might look complicated, they usually do "the right thing". |
1486 | rules might look complicated, they usually do "the right thing". |
1385 | |
1487 | |
1386 | =over 4 |
1488 | =over 4 |
1387 | |
1489 | |
1388 | =item initialiased |
1490 | =item initialised |
1389 | |
1491 | |
1390 | Before a watcher can be registered with the event looop it has to be |
1492 | Before a watcher can be registered with the event loop it has to be |
1391 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1493 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1392 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1494 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1393 | |
1495 | |
1394 | In this state it is simply some block of memory that is suitable for use |
1496 | In this state it is simply some block of memory that is suitable for |
1395 | in an event loop. It can be moved around, freed, reused etc. at will. |
1497 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1498 | will - as long as you either keep the memory contents intact, or call |
|
|
1499 | C<ev_TYPE_init> again. |
1396 | |
1500 | |
1397 | =item started/running/active |
1501 | =item started/running/active |
1398 | |
1502 | |
1399 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1503 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1400 | property of the event loop, and is actively waiting for events. While in |
1504 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1428 | latter will clear any pending state the watcher might be in, regardless |
1532 | latter will clear any pending state the watcher might be in, regardless |
1429 | of whether it was active or not, so stopping a watcher explicitly before |
1533 | of whether it was active or not, so stopping a watcher explicitly before |
1430 | freeing it is often a good idea. |
1534 | freeing it is often a good idea. |
1431 | |
1535 | |
1432 | While stopped (and not pending) the watcher is essentially in the |
1536 | While stopped (and not pending) the watcher is essentially in the |
1433 | initialised state, that is it can be reused, moved, modified in any way |
1537 | initialised state, that is, it can be reused, moved, modified in any way |
1434 | you wish. |
1538 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1539 | it again). |
1435 | |
1540 | |
1436 | =back |
1541 | =back |
1437 | |
1542 | |
1438 | =head2 WATCHER PRIORITY MODELS |
1543 | =head2 WATCHER PRIORITY MODELS |
1439 | |
1544 | |
1440 | Many event loops support I<watcher priorities>, which are usually small |
1545 | Many event loops support I<watcher priorities>, which are usually small |
1441 | integers that influence the ordering of event callback invocation |
1546 | integers that influence the ordering of event callback invocation |
1442 | between watchers in some way, all else being equal. |
1547 | between watchers in some way, all else being equal. |
1443 | |
1548 | |
1444 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
1549 | In libev, watcher priorities can be set using C<ev_set_priority>. See its |
1445 | description for the more technical details such as the actual priority |
1550 | description for the more technical details such as the actual priority |
1446 | range. |
1551 | range. |
1447 | |
1552 | |
1448 | There are two common ways how these these priorities are being interpreted |
1553 | There are two common ways how these these priorities are being interpreted |
1449 | by event loops: |
1554 | by event loops: |
… | |
… | |
1568 | In general you can register as many read and/or write event watchers per |
1673 | In general you can register as many read and/or write event watchers per |
1569 | fd as you want (as long as you don't confuse yourself). Setting all file |
1674 | fd as you want (as long as you don't confuse yourself). Setting all file |
1570 | descriptors to non-blocking mode is also usually a good idea (but not |
1675 | descriptors to non-blocking mode is also usually a good idea (but not |
1571 | required if you know what you are doing). |
1676 | required if you know what you are doing). |
1572 | |
1677 | |
1573 | If you cannot use non-blocking mode, then force the use of a |
|
|
1574 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1575 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1576 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1577 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1578 | |
|
|
1579 | Another thing you have to watch out for is that it is quite easy to |
1678 | Another thing you have to watch out for is that it is quite easy to |
1580 | receive "spurious" readiness notifications, that is your callback might |
1679 | receive "spurious" readiness notifications, that is, your callback might |
1581 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1680 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1582 | because there is no data. Not only are some backends known to create a |
1681 | because there is no data. It is very easy to get into this situation even |
1583 | lot of those (for example Solaris ports), it is very easy to get into |
1682 | with a relatively standard program structure. Thus it is best to always |
1584 | this situation even with a relatively standard program structure. Thus |
1683 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1585 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1586 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1684 | preferable to a program hanging until some data arrives. |
1587 | |
1685 | |
1588 | If you cannot run the fd in non-blocking mode (for example you should |
1686 | If you cannot run the fd in non-blocking mode (for example you should |
1589 | not play around with an Xlib connection), then you have to separately |
1687 | not play around with an Xlib connection), then you have to separately |
1590 | re-test whether a file descriptor is really ready with a known-to-be good |
1688 | re-test whether a file descriptor is really ready with a known-to-be good |
1591 | interface such as poll (fortunately in our Xlib example, Xlib already |
1689 | interface such as poll (fortunately in the case of Xlib, it already does |
1592 | does this on its own, so its quite safe to use). Some people additionally |
1690 | this on its own, so its quite safe to use). Some people additionally |
1593 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1691 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1594 | indefinitely. |
1692 | indefinitely. |
1595 | |
1693 | |
1596 | But really, best use non-blocking mode. |
1694 | But really, best use non-blocking mode. |
1597 | |
1695 | |
1598 | =head3 The special problem of disappearing file descriptors |
1696 | =head3 The special problem of disappearing file descriptors |
1599 | |
1697 | |
1600 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1698 | Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing |
1601 | descriptor (either due to calling C<close> explicitly or any other means, |
1699 | a file descriptor (either due to calling C<close> explicitly or any other |
1602 | such as C<dup2>). The reason is that you register interest in some file |
1700 | means, such as C<dup2>). The reason is that you register interest in some |
1603 | descriptor, but when it goes away, the operating system will silently drop |
1701 | file descriptor, but when it goes away, the operating system will silently |
1604 | this interest. If another file descriptor with the same number then is |
1702 | drop this interest. If another file descriptor with the same number then |
1605 | registered with libev, there is no efficient way to see that this is, in |
1703 | is registered with libev, there is no efficient way to see that this is, |
1606 | fact, a different file descriptor. |
1704 | in fact, a different file descriptor. |
1607 | |
1705 | |
1608 | To avoid having to explicitly tell libev about such cases, libev follows |
1706 | To avoid having to explicitly tell libev about such cases, libev follows |
1609 | the following policy: Each time C<ev_io_set> is being called, libev |
1707 | the following policy: Each time C<ev_io_set> is being called, libev |
1610 | will assume that this is potentially a new file descriptor, otherwise |
1708 | will assume that this is potentially a new file descriptor, otherwise |
1611 | it is assumed that the file descriptor stays the same. That means that |
1709 | it is assumed that the file descriptor stays the same. That means that |
… | |
… | |
1625 | |
1723 | |
1626 | There is no workaround possible except not registering events |
1724 | There is no workaround possible except not registering events |
1627 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1725 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1628 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1726 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1629 | |
1727 | |
|
|
1728 | =head3 The special problem of files |
|
|
1729 | |
|
|
1730 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1731 | representing files, and expect it to become ready when their program |
|
|
1732 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1733 | |
|
|
1734 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1735 | notification as soon as the kernel knows whether and how much data is |
|
|
1736 | there, and in the case of open files, that's always the case, so you |
|
|
1737 | always get a readiness notification instantly, and your read (or possibly |
|
|
1738 | write) will still block on the disk I/O. |
|
|
1739 | |
|
|
1740 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1741 | devices and so on, there is another party (the sender) that delivers data |
|
|
1742 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1743 | will not send data on its own, simply because it doesn't know what you |
|
|
1744 | wish to read - you would first have to request some data. |
|
|
1745 | |
|
|
1746 | Since files are typically not-so-well supported by advanced notification |
|
|
1747 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1748 | to files, even though you should not use it. The reason for this is |
|
|
1749 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1750 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1751 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1752 | F</dev/urandom>), and even though the file might better be served with |
|
|
1753 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1754 | it "just works" instead of freezing. |
|
|
1755 | |
|
|
1756 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1757 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1758 | when you rarely read from a file instead of from a socket, and want to |
|
|
1759 | reuse the same code path. |
|
|
1760 | |
1630 | =head3 The special problem of fork |
1761 | =head3 The special problem of fork |
1631 | |
1762 | |
1632 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1763 | Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()> |
1633 | useless behaviour. Libev fully supports fork, but needs to be told about |
1764 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1634 | it in the child. |
1765 | to be told about it in the child if you want to continue to use it in the |
|
|
1766 | child. |
1635 | |
1767 | |
1636 | To support fork in your programs, you either have to call |
1768 | To support fork in your child processes, you have to call C<ev_loop_fork |
1637 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1769 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1638 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1770 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1639 | C<EVBACKEND_POLL>. |
|
|
1640 | |
1771 | |
1641 | =head3 The special problem of SIGPIPE |
1772 | =head3 The special problem of SIGPIPE |
1642 | |
1773 | |
1643 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1774 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1644 | when writing to a pipe whose other end has been closed, your program gets |
1775 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1742 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1873 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1743 | monotonic clock option helps a lot here). |
1874 | monotonic clock option helps a lot here). |
1744 | |
1875 | |
1745 | The callback is guaranteed to be invoked only I<after> its timeout has |
1876 | The callback is guaranteed to be invoked only I<after> its timeout has |
1746 | passed (not I<at>, so on systems with very low-resolution clocks this |
1877 | passed (not I<at>, so on systems with very low-resolution clocks this |
1747 | might introduce a small delay). If multiple timers become ready during the |
1878 | might introduce a small delay, see "the special problem of being too |
|
|
1879 | early", below). If multiple timers become ready during the same loop |
1748 | same loop iteration then the ones with earlier time-out values are invoked |
1880 | iteration then the ones with earlier time-out values are invoked before |
1749 | before ones of the same priority with later time-out values (but this is |
1881 | ones of the same priority with later time-out values (but this is no |
1750 | no longer true when a callback calls C<ev_run> recursively). |
1882 | longer true when a callback calls C<ev_run> recursively). |
1751 | |
1883 | |
1752 | =head3 Be smart about timeouts |
1884 | =head3 Be smart about timeouts |
1753 | |
1885 | |
1754 | Many real-world problems involve some kind of timeout, usually for error |
1886 | Many real-world problems involve some kind of timeout, usually for error |
1755 | recovery. A typical example is an HTTP request - if the other side hangs, |
1887 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1830 | |
1962 | |
1831 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1963 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1832 | but remember the time of last activity, and check for a real timeout only |
1964 | but remember the time of last activity, and check for a real timeout only |
1833 | within the callback: |
1965 | within the callback: |
1834 | |
1966 | |
|
|
1967 | ev_tstamp timeout = 60.; |
1835 | ev_tstamp last_activity; // time of last activity |
1968 | ev_tstamp last_activity; // time of last activity |
|
|
1969 | ev_timer timer; |
1836 | |
1970 | |
1837 | static void |
1971 | static void |
1838 | callback (EV_P_ ev_timer *w, int revents) |
1972 | callback (EV_P_ ev_timer *w, int revents) |
1839 | { |
1973 | { |
1840 | ev_tstamp now = ev_now (EV_A); |
1974 | // calculate when the timeout would happen |
1841 | ev_tstamp timeout = last_activity + 60.; |
1975 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1842 | |
1976 | |
1843 | // if last_activity + 60. is older than now, we did time out |
1977 | // if negative, it means we the timeout already occurred |
1844 | if (timeout < now) |
1978 | if (after < 0.) |
1845 | { |
1979 | { |
1846 | // timeout occurred, take action |
1980 | // timeout occurred, take action |
1847 | } |
1981 | } |
1848 | else |
1982 | else |
1849 | { |
1983 | { |
1850 | // callback was invoked, but there was some activity, re-arm |
1984 | // callback was invoked, but there was some recent |
1851 | // the watcher to fire in last_activity + 60, which is |
1985 | // activity. simply restart the timer to time out |
1852 | // guaranteed to be in the future, so "again" is positive: |
1986 | // after "after" seconds, which is the earliest time |
1853 | w->repeat = timeout - now; |
1987 | // the timeout can occur. |
|
|
1988 | ev_timer_set (w, after, 0.); |
1854 | ev_timer_again (EV_A_ w); |
1989 | ev_timer_start (EV_A_ w); |
1855 | } |
1990 | } |
1856 | } |
1991 | } |
1857 | |
1992 | |
1858 | To summarise the callback: first calculate the real timeout (defined |
1993 | To summarise the callback: first calculate in how many seconds the |
1859 | as "60 seconds after the last activity"), then check if that time has |
1994 | timeout will occur (by calculating the absolute time when it would occur, |
1860 | been reached, which means something I<did>, in fact, time out. Otherwise |
1995 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1861 | the callback was invoked too early (C<timeout> is in the future), so |
1996 | (EV_A)> from that). |
1862 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1863 | a timeout then. |
|
|
1864 | |
1997 | |
1865 | Note how C<ev_timer_again> is used, taking advantage of the |
1998 | If this value is negative, then we are already past the timeout, i.e. we |
1866 | C<ev_timer_again> optimisation when the timer is already running. |
1999 | timed out, and need to do whatever is needed in this case. |
|
|
2000 | |
|
|
2001 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
2002 | and simply start the timer with this timeout value. |
|
|
2003 | |
|
|
2004 | In other words, each time the callback is invoked it will check whether |
|
|
2005 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
2006 | again at the earliest time it could time out. Rinse. Repeat. |
1867 | |
2007 | |
1868 | This scheme causes more callback invocations (about one every 60 seconds |
2008 | This scheme causes more callback invocations (about one every 60 seconds |
1869 | minus half the average time between activity), but virtually no calls to |
2009 | minus half the average time between activity), but virtually no calls to |
1870 | libev to change the timeout. |
2010 | libev to change the timeout. |
1871 | |
2011 | |
1872 | To start the timer, simply initialise the watcher and set C<last_activity> |
2012 | To start the machinery, simply initialise the watcher and set |
1873 | to the current time (meaning we just have some activity :), then call the |
2013 | C<last_activity> to the current time (meaning there was some activity just |
1874 | callback, which will "do the right thing" and start the timer: |
2014 | now), then call the callback, which will "do the right thing" and start |
|
|
2015 | the timer: |
1875 | |
2016 | |
|
|
2017 | last_activity = ev_now (EV_A); |
1876 | ev_init (timer, callback); |
2018 | ev_init (&timer, callback); |
1877 | last_activity = ev_now (loop); |
2019 | callback (EV_A_ &timer, 0); |
1878 | callback (loop, timer, EV_TIMER); |
|
|
1879 | |
2020 | |
1880 | And when there is some activity, simply store the current time in |
2021 | When there is some activity, simply store the current time in |
1881 | C<last_activity>, no libev calls at all: |
2022 | C<last_activity>, no libev calls at all: |
1882 | |
2023 | |
|
|
2024 | if (activity detected) |
1883 | last_activity = ev_now (loop); |
2025 | last_activity = ev_now (EV_A); |
|
|
2026 | |
|
|
2027 | When your timeout value changes, then the timeout can be changed by simply |
|
|
2028 | providing a new value, stopping the timer and calling the callback, which |
|
|
2029 | will again do the right thing (for example, time out immediately :). |
|
|
2030 | |
|
|
2031 | timeout = new_value; |
|
|
2032 | ev_timer_stop (EV_A_ &timer); |
|
|
2033 | callback (EV_A_ &timer, 0); |
1884 | |
2034 | |
1885 | This technique is slightly more complex, but in most cases where the |
2035 | This technique is slightly more complex, but in most cases where the |
1886 | time-out is unlikely to be triggered, much more efficient. |
2036 | time-out is unlikely to be triggered, much more efficient. |
1887 | |
|
|
1888 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1889 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1890 | fix things for you. |
|
|
1891 | |
2037 | |
1892 | =item 4. Wee, just use a double-linked list for your timeouts. |
2038 | =item 4. Wee, just use a double-linked list for your timeouts. |
1893 | |
2039 | |
1894 | If there is not one request, but many thousands (millions...), all |
2040 | If there is not one request, but many thousands (millions...), all |
1895 | employing some kind of timeout with the same timeout value, then one can |
2041 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1922 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
2068 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1923 | rather complicated, but extremely efficient, something that really pays |
2069 | rather complicated, but extremely efficient, something that really pays |
1924 | off after the first million or so of active timers, i.e. it's usually |
2070 | off after the first million or so of active timers, i.e. it's usually |
1925 | overkill :) |
2071 | overkill :) |
1926 | |
2072 | |
|
|
2073 | =head3 The special problem of being too early |
|
|
2074 | |
|
|
2075 | If you ask a timer to call your callback after three seconds, then |
|
|
2076 | you expect it to be invoked after three seconds - but of course, this |
|
|
2077 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
2078 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
2079 | process with a STOP signal for a few hours for example. |
|
|
2080 | |
|
|
2081 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
2082 | delay has occurred, but cannot guarantee this. |
|
|
2083 | |
|
|
2084 | A less obvious failure mode is calling your callback too early: many event |
|
|
2085 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
2086 | this can cause your callback to be invoked much earlier than you would |
|
|
2087 | expect. |
|
|
2088 | |
|
|
2089 | To see why, imagine a system with a clock that only offers full second |
|
|
2090 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2091 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2092 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2093 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2094 | |
|
|
2095 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2096 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2097 | one-second delay was requested - this is being "too early", despite best |
|
|
2098 | intentions. |
|
|
2099 | |
|
|
2100 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2101 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2102 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2103 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2104 | |
|
|
2105 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2106 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2107 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2108 | late" side of things. |
|
|
2109 | |
1927 | =head3 The special problem of time updates |
2110 | =head3 The special problem of time updates |
1928 | |
2111 | |
1929 | Establishing the current time is a costly operation (it usually takes at |
2112 | Establishing the current time is a costly operation (it usually takes |
1930 | least two system calls): EV therefore updates its idea of the current |
2113 | at least one system call): EV therefore updates its idea of the current |
1931 | time only before and after C<ev_run> collects new events, which causes a |
2114 | time only before and after C<ev_run> collects new events, which causes a |
1932 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2115 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1933 | lots of events in one iteration. |
2116 | lots of events in one iteration. |
1934 | |
2117 | |
1935 | The relative timeouts are calculated relative to the C<ev_now ()> |
2118 | The relative timeouts are calculated relative to the C<ev_now ()> |
1936 | time. This is usually the right thing as this timestamp refers to the time |
2119 | time. This is usually the right thing as this timestamp refers to the time |
1937 | of the event triggering whatever timeout you are modifying/starting. If |
2120 | of the event triggering whatever timeout you are modifying/starting. If |
1938 | you suspect event processing to be delayed and you I<need> to base the |
2121 | you suspect event processing to be delayed and you I<need> to base the |
1939 | timeout on the current time, use something like this to adjust for this: |
2122 | timeout on the current time, use something like the following to adjust |
|
|
2123 | for it: |
1940 | |
2124 | |
1941 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2125 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
1942 | |
2126 | |
1943 | If the event loop is suspended for a long time, you can also force an |
2127 | If the event loop is suspended for a long time, you can also force an |
1944 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2128 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1945 | ()>. |
2129 | ()>, although that will push the event time of all outstanding events |
|
|
2130 | further into the future. |
|
|
2131 | |
|
|
2132 | =head3 The special problem of unsynchronised clocks |
|
|
2133 | |
|
|
2134 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2135 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2136 | jumps). |
|
|
2137 | |
|
|
2138 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2139 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2140 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2141 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2142 | than a directly following call to C<time>. |
|
|
2143 | |
|
|
2144 | The moral of this is to only compare libev-related timestamps with |
|
|
2145 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2146 | a second or so. |
|
|
2147 | |
|
|
2148 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2149 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2150 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2151 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2152 | |
|
|
2153 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2154 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2155 | I<measured according to the real time>, not the system clock. |
|
|
2156 | |
|
|
2157 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2158 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2159 | exactly the right behaviour. |
|
|
2160 | |
|
|
2161 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2162 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2163 | time, where your comparisons will always generate correct results. |
1946 | |
2164 | |
1947 | =head3 The special problems of suspended animation |
2165 | =head3 The special problems of suspended animation |
1948 | |
2166 | |
1949 | When you leave the server world it is quite customary to hit machines that |
2167 | When you leave the server world it is quite customary to hit machines that |
1950 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2168 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
1980 | |
2198 | |
1981 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2199 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1982 | |
2200 | |
1983 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2201 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1984 | |
2202 | |
1985 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2203 | Configure the timer to trigger after C<after> seconds (fractional and |
1986 | is C<0.>, then it will automatically be stopped once the timeout is |
2204 | negative values are supported). If C<repeat> is C<0.>, then it will |
1987 | reached. If it is positive, then the timer will automatically be |
2205 | automatically be stopped once the timeout is reached. If it is positive, |
1988 | configured to trigger again C<repeat> seconds later, again, and again, |
2206 | then the timer will automatically be configured to trigger again C<repeat> |
1989 | until stopped manually. |
2207 | seconds later, again, and again, until stopped manually. |
1990 | |
2208 | |
1991 | The timer itself will do a best-effort at avoiding drift, that is, if |
2209 | The timer itself will do a best-effort at avoiding drift, that is, if |
1992 | you configure a timer to trigger every 10 seconds, then it will normally |
2210 | you configure a timer to trigger every 10 seconds, then it will normally |
1993 | trigger at exactly 10 second intervals. If, however, your program cannot |
2211 | trigger at exactly 10 second intervals. If, however, your program cannot |
1994 | keep up with the timer (because it takes longer than those 10 seconds to |
2212 | keep up with the timer (because it takes longer than those 10 seconds to |
1995 | do stuff) the timer will not fire more than once per event loop iteration. |
2213 | do stuff) the timer will not fire more than once per event loop iteration. |
1996 | |
2214 | |
1997 | =item ev_timer_again (loop, ev_timer *) |
2215 | =item ev_timer_again (loop, ev_timer *) |
1998 | |
2216 | |
1999 | This will act as if the timer timed out and restart it again if it is |
2217 | This will act as if the timer timed out, and restarts it again if it is |
2000 | repeating. The exact semantics are: |
2218 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2219 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
2001 | |
2220 | |
|
|
2221 | The exact semantics are as in the following rules, all of which will be |
|
|
2222 | applied to the watcher: |
|
|
2223 | |
|
|
2224 | =over 4 |
|
|
2225 | |
2002 | If the timer is pending, its pending status is cleared. |
2226 | =item If the timer is pending, the pending status is always cleared. |
2003 | |
2227 | |
2004 | If the timer is started but non-repeating, stop it (as if it timed out). |
2228 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2229 | out, without invoking it). |
2005 | |
2230 | |
2006 | If the timer is repeating, either start it if necessary (with the |
2231 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2007 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2232 | and start the timer, if necessary. |
2008 | |
2233 | |
|
|
2234 | =back |
|
|
2235 | |
2009 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2236 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
2010 | usage example. |
2237 | usage example. |
2011 | |
2238 | |
2012 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2239 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2013 | |
2240 | |
2014 | Returns the remaining time until a timer fires. If the timer is active, |
2241 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2067 | Periodic watchers are also timers of a kind, but they are very versatile |
2294 | Periodic watchers are also timers of a kind, but they are very versatile |
2068 | (and unfortunately a bit complex). |
2295 | (and unfortunately a bit complex). |
2069 | |
2296 | |
2070 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2297 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2071 | relative time, the physical time that passes) but on wall clock time |
2298 | relative time, the physical time that passes) but on wall clock time |
2072 | (absolute time, the thing you can read on your calender or clock). The |
2299 | (absolute time, the thing you can read on your calendar or clock). The |
2073 | difference is that wall clock time can run faster or slower than real |
2300 | difference is that wall clock time can run faster or slower than real |
2074 | time, and time jumps are not uncommon (e.g. when you adjust your |
2301 | time, and time jumps are not uncommon (e.g. when you adjust your |
2075 | wrist-watch). |
2302 | wrist-watch). |
2076 | |
2303 | |
2077 | You can tell a periodic watcher to trigger after some specific point |
2304 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
2082 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2309 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2083 | it, as it uses a relative timeout). |
2310 | it, as it uses a relative timeout). |
2084 | |
2311 | |
2085 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2312 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2086 | timers, such as triggering an event on each "midnight, local time", or |
2313 | timers, such as triggering an event on each "midnight, local time", or |
2087 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
2314 | other complicated rules. This cannot easily be done with C<ev_timer> |
2088 | those cannot react to time jumps. |
2315 | watchers, as those cannot react to time jumps. |
2089 | |
2316 | |
2090 | As with timers, the callback is guaranteed to be invoked only when the |
2317 | As with timers, the callback is guaranteed to be invoked only when the |
2091 | point in time where it is supposed to trigger has passed. If multiple |
2318 | point in time where it is supposed to trigger has passed. If multiple |
2092 | timers become ready during the same loop iteration then the ones with |
2319 | timers become ready during the same loop iteration then the ones with |
2093 | earlier time-out values are invoked before ones with later time-out values |
2320 | earlier time-out values are invoked before ones with later time-out values |
… | |
… | |
2134 | |
2361 | |
2135 | Another way to think about it (for the mathematically inclined) is that |
2362 | Another way to think about it (for the mathematically inclined) is that |
2136 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2363 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2137 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2364 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2138 | |
2365 | |
2139 | For numerical stability it is preferable that the C<offset> value is near |
2366 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2140 | C<ev_now ()> (the current time), but there is no range requirement for |
2367 | interval value should be higher than C<1/8192> (which is around 100 |
2141 | this value, and in fact is often specified as zero. |
2368 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2369 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2370 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2371 | C<0> and C<interval>, which is also the recommended range. |
2142 | |
2372 | |
2143 | Note also that there is an upper limit to how often a timer can fire (CPU |
2373 | Note also that there is an upper limit to how often a timer can fire (CPU |
2144 | speed for example), so if C<interval> is very small then timing stability |
2374 | speed for example), so if C<interval> is very small then timing stability |
2145 | will of course deteriorate. Libev itself tries to be exact to be about one |
2375 | will of course deteriorate. Libev itself tries to be exact to be about one |
2146 | millisecond (if the OS supports it and the machine is fast enough). |
2376 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2176 | |
2406 | |
2177 | NOTE: I<< This callback must always return a time that is higher than or |
2407 | NOTE: I<< This callback must always return a time that is higher than or |
2178 | equal to the passed C<now> value >>. |
2408 | equal to the passed C<now> value >>. |
2179 | |
2409 | |
2180 | This can be used to create very complex timers, such as a timer that |
2410 | This can be used to create very complex timers, such as a timer that |
2181 | triggers on "next midnight, local time". To do this, you would calculate the |
2411 | triggers on "next midnight, local time". To do this, you would calculate |
2182 | next midnight after C<now> and return the timestamp value for this. How |
2412 | the next midnight after C<now> and return the timestamp value for |
2183 | you do this is, again, up to you (but it is not trivial, which is the main |
2413 | this. Here is a (completely untested, no error checking) example on how to |
2184 | reason I omitted it as an example). |
2414 | do this: |
|
|
2415 | |
|
|
2416 | #include <time.h> |
|
|
2417 | |
|
|
2418 | static ev_tstamp |
|
|
2419 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2420 | { |
|
|
2421 | time_t tnow = (time_t)now; |
|
|
2422 | struct tm tm; |
|
|
2423 | localtime_r (&tnow, &tm); |
|
|
2424 | |
|
|
2425 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2426 | ++tm.tm_mday; // midnight next day |
|
|
2427 | |
|
|
2428 | return mktime (&tm); |
|
|
2429 | } |
|
|
2430 | |
|
|
2431 | Note: this code might run into trouble on days that have more then two |
|
|
2432 | midnights (beginning and end). |
2185 | |
2433 | |
2186 | =back |
2434 | =back |
2187 | |
2435 | |
2188 | =item ev_periodic_again (loop, ev_periodic *) |
2436 | =item ev_periodic_again (loop, ev_periodic *) |
2189 | |
2437 | |
… | |
… | |
2254 | |
2502 | |
2255 | ev_periodic hourly_tick; |
2503 | ev_periodic hourly_tick; |
2256 | ev_periodic_init (&hourly_tick, clock_cb, |
2504 | ev_periodic_init (&hourly_tick, clock_cb, |
2257 | fmod (ev_now (loop), 3600.), 3600., 0); |
2505 | fmod (ev_now (loop), 3600.), 3600., 0); |
2258 | ev_periodic_start (loop, &hourly_tick); |
2506 | ev_periodic_start (loop, &hourly_tick); |
2259 | |
2507 | |
2260 | |
2508 | |
2261 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2509 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2262 | |
2510 | |
2263 | Signal watchers will trigger an event when the process receives a specific |
2511 | Signal watchers will trigger an event when the process receives a specific |
2264 | signal one or more times. Even though signals are very asynchronous, libev |
2512 | signal one or more times. Even though signals are very asynchronous, libev |
2265 | will try it's best to deliver signals synchronously, i.e. as part of the |
2513 | will try its best to deliver signals synchronously, i.e. as part of the |
2266 | normal event processing, like any other event. |
2514 | normal event processing, like any other event. |
2267 | |
2515 | |
2268 | If you want signals to be delivered truly asynchronously, just use |
2516 | If you want signals to be delivered truly asynchronously, just use |
2269 | C<sigaction> as you would do without libev and forget about sharing |
2517 | C<sigaction> as you would do without libev and forget about sharing |
2270 | the signal. You can even use C<ev_async> from a signal handler to |
2518 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2274 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2522 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2275 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2523 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2276 | C<SIGINT> in both the default loop and another loop at the same time. At |
2524 | C<SIGINT> in both the default loop and another loop at the same time. At |
2277 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2525 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2278 | |
2526 | |
2279 | When the first watcher gets started will libev actually register something |
2527 | Only after the first watcher for a signal is started will libev actually |
2280 | with the kernel (thus it coexists with your own signal handlers as long as |
2528 | register something with the kernel. It thus coexists with your own signal |
2281 | you don't register any with libev for the same signal). |
2529 | handlers as long as you don't register any with libev for the same signal. |
2282 | |
2530 | |
2283 | If possible and supported, libev will install its handlers with |
2531 | If possible and supported, libev will install its handlers with |
2284 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2532 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2285 | not be unduly interrupted. If you have a problem with system calls getting |
2533 | not be unduly interrupted. If you have a problem with system calls getting |
2286 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2534 | interrupted by signals you can block all signals in an C<ev_check> watcher |
… | |
… | |
2289 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2537 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2290 | |
2538 | |
2291 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2539 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2292 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2540 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2293 | stopping it again), that is, libev might or might not block the signal, |
2541 | stopping it again), that is, libev might or might not block the signal, |
2294 | and might or might not set or restore the installed signal handler. |
2542 | and might or might not set or restore the installed signal handler (but |
|
|
2543 | see C<EVFLAG_NOSIGMASK>). |
2295 | |
2544 | |
2296 | While this does not matter for the signal disposition (libev never |
2545 | While this does not matter for the signal disposition (libev never |
2297 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2546 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2298 | C<execve>), this matters for the signal mask: many programs do not expect |
2547 | C<execve>), this matters for the signal mask: many programs do not expect |
2299 | certain signals to be blocked. |
2548 | certain signals to be blocked. |
… | |
… | |
2312 | I<has> to modify the signal mask, at least temporarily. |
2561 | I<has> to modify the signal mask, at least temporarily. |
2313 | |
2562 | |
2314 | So I can't stress this enough: I<If you do not reset your signal mask when |
2563 | So I can't stress this enough: I<If you do not reset your signal mask when |
2315 | you expect it to be empty, you have a race condition in your code>. This |
2564 | you expect it to be empty, you have a race condition in your code>. This |
2316 | is not a libev-specific thing, this is true for most event libraries. |
2565 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2566 | |
|
|
2567 | =head3 The special problem of threads signal handling |
|
|
2568 | |
|
|
2569 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2570 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2571 | threads in a process block signals, which is hard to achieve. |
|
|
2572 | |
|
|
2573 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2574 | for the same signals), you can tackle this problem by globally blocking |
|
|
2575 | all signals before creating any threads (or creating them with a fully set |
|
|
2576 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2577 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2578 | these signals. You can pass on any signals that libev might be interested |
|
|
2579 | in by calling C<ev_feed_signal>. |
2317 | |
2580 | |
2318 | =head3 Watcher-Specific Functions and Data Members |
2581 | =head3 Watcher-Specific Functions and Data Members |
2319 | |
2582 | |
2320 | =over 4 |
2583 | =over 4 |
2321 | |
2584 | |
… | |
… | |
2456 | |
2719 | |
2457 | =head2 C<ev_stat> - did the file attributes just change? |
2720 | =head2 C<ev_stat> - did the file attributes just change? |
2458 | |
2721 | |
2459 | This watches a file system path for attribute changes. That is, it calls |
2722 | This watches a file system path for attribute changes. That is, it calls |
2460 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2723 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2461 | and sees if it changed compared to the last time, invoking the callback if |
2724 | and sees if it changed compared to the last time, invoking the callback |
2462 | it did. |
2725 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2726 | happen after the watcher has been started will be reported. |
2463 | |
2727 | |
2464 | The path does not need to exist: changing from "path exists" to "path does |
2728 | The path does not need to exist: changing from "path exists" to "path does |
2465 | not exist" is a status change like any other. The condition "path does not |
2729 | not exist" is a status change like any other. The condition "path does not |
2466 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2730 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2467 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2731 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2697 | Apart from keeping your process non-blocking (which is a useful |
2961 | Apart from keeping your process non-blocking (which is a useful |
2698 | effect on its own sometimes), idle watchers are a good place to do |
2962 | effect on its own sometimes), idle watchers are a good place to do |
2699 | "pseudo-background processing", or delay processing stuff to after the |
2963 | "pseudo-background processing", or delay processing stuff to after the |
2700 | event loop has handled all outstanding events. |
2964 | event loop has handled all outstanding events. |
2701 | |
2965 | |
|
|
2966 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2967 | |
|
|
2968 | As long as there is at least one active idle watcher, libev will never |
|
|
2969 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2970 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2971 | lowest priority will do. |
|
|
2972 | |
|
|
2973 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2974 | to do something on each event loop iteration - for example to balance load |
|
|
2975 | between different connections. |
|
|
2976 | |
|
|
2977 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2978 | example. |
|
|
2979 | |
2702 | =head3 Watcher-Specific Functions and Data Members |
2980 | =head3 Watcher-Specific Functions and Data Members |
2703 | |
2981 | |
2704 | =over 4 |
2982 | =over 4 |
2705 | |
2983 | |
2706 | =item ev_idle_init (ev_idle *, callback) |
2984 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2717 | callback, free it. Also, use no error checking, as usual. |
2995 | callback, free it. Also, use no error checking, as usual. |
2718 | |
2996 | |
2719 | static void |
2997 | static void |
2720 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2998 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2721 | { |
2999 | { |
|
|
3000 | // stop the watcher |
|
|
3001 | ev_idle_stop (loop, w); |
|
|
3002 | |
|
|
3003 | // now we can free it |
2722 | free (w); |
3004 | free (w); |
|
|
3005 | |
2723 | // now do something you wanted to do when the program has |
3006 | // now do something you wanted to do when the program has |
2724 | // no longer anything immediate to do. |
3007 | // no longer anything immediate to do. |
2725 | } |
3008 | } |
2726 | |
3009 | |
2727 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
3010 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2729 | ev_idle_start (loop, idle_watcher); |
3012 | ev_idle_start (loop, idle_watcher); |
2730 | |
3013 | |
2731 | |
3014 | |
2732 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
3015 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2733 | |
3016 | |
2734 | Prepare and check watchers are usually (but not always) used in pairs: |
3017 | Prepare and check watchers are often (but not always) used in pairs: |
2735 | prepare watchers get invoked before the process blocks and check watchers |
3018 | prepare watchers get invoked before the process blocks and check watchers |
2736 | afterwards. |
3019 | afterwards. |
2737 | |
3020 | |
2738 | You I<must not> call C<ev_run> or similar functions that enter |
3021 | You I<must not> call C<ev_run> (or similar functions that enter the |
2739 | the current event loop from either C<ev_prepare> or C<ev_check> |
3022 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2740 | watchers. Other loops than the current one are fine, however. The |
3023 | C<ev_check> watchers. Other loops than the current one are fine, |
2741 | rationale behind this is that you do not need to check for recursion in |
3024 | however. The rationale behind this is that you do not need to check |
2742 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
3025 | for recursion in those watchers, i.e. the sequence will always be |
2743 | C<ev_check> so if you have one watcher of each kind they will always be |
3026 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2744 | called in pairs bracketing the blocking call. |
3027 | kind they will always be called in pairs bracketing the blocking call. |
2745 | |
3028 | |
2746 | Their main purpose is to integrate other event mechanisms into libev and |
3029 | Their main purpose is to integrate other event mechanisms into libev and |
2747 | their use is somewhat advanced. They could be used, for example, to track |
3030 | their use is somewhat advanced. They could be used, for example, to track |
2748 | variable changes, implement your own watchers, integrate net-snmp or a |
3031 | variable changes, implement your own watchers, integrate net-snmp or a |
2749 | coroutine library and lots more. They are also occasionally useful if |
3032 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
2767 | with priority higher than or equal to the event loop and one coroutine |
3050 | with priority higher than or equal to the event loop and one coroutine |
2768 | of lower priority, but only once, using idle watchers to keep the event |
3051 | of lower priority, but only once, using idle watchers to keep the event |
2769 | loop from blocking if lower-priority coroutines are active, thus mapping |
3052 | loop from blocking if lower-priority coroutines are active, thus mapping |
2770 | low-priority coroutines to idle/background tasks). |
3053 | low-priority coroutines to idle/background tasks). |
2771 | |
3054 | |
2772 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
3055 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2773 | priority, to ensure that they are being run before any other watchers |
3056 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2774 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
3057 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
3058 | watchers). |
2775 | |
3059 | |
2776 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
3060 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2777 | activate ("feed") events into libev. While libev fully supports this, they |
3061 | activate ("feed") events into libev. While libev fully supports this, they |
2778 | might get executed before other C<ev_check> watchers did their job. As |
3062 | might get executed before other C<ev_check> watchers did their job. As |
2779 | C<ev_check> watchers are often used to embed other (non-libev) event |
3063 | C<ev_check> watchers are often used to embed other (non-libev) event |
2780 | loops those other event loops might be in an unusable state until their |
3064 | loops those other event loops might be in an unusable state until their |
2781 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
3065 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2782 | others). |
3066 | others). |
|
|
3067 | |
|
|
3068 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
3069 | |
|
|
3070 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
3071 | useful because they are called once per event loop iteration. For |
|
|
3072 | example, if you want to handle a large number of connections fairly, you |
|
|
3073 | normally only do a bit of work for each active connection, and if there |
|
|
3074 | is more work to do, you wait for the next event loop iteration, so other |
|
|
3075 | connections have a chance of making progress. |
|
|
3076 | |
|
|
3077 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
3078 | next event loop iteration. However, that isn't as soon as possible - |
|
|
3079 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
3080 | |
|
|
3081 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
3082 | single global idle watcher that is active as long as you have one active |
|
|
3083 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
3084 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
3085 | invoked. Neither watcher alone can do that. |
2783 | |
3086 | |
2784 | =head3 Watcher-Specific Functions and Data Members |
3087 | =head3 Watcher-Specific Functions and Data Members |
2785 | |
3088 | |
2786 | =over 4 |
3089 | =over 4 |
2787 | |
3090 | |
… | |
… | |
2988 | |
3291 | |
2989 | =over 4 |
3292 | =over 4 |
2990 | |
3293 | |
2991 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3294 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2992 | |
3295 | |
2993 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3296 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
2994 | |
3297 | |
2995 | Configures the watcher to embed the given loop, which must be |
3298 | Configures the watcher to embed the given loop, which must be |
2996 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3299 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2997 | invoked automatically, otherwise it is the responsibility of the callback |
3300 | invoked automatically, otherwise it is the responsibility of the callback |
2998 | to invoke it (it will continue to be called until the sweep has been done, |
3301 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3019 | used). |
3322 | used). |
3020 | |
3323 | |
3021 | struct ev_loop *loop_hi = ev_default_init (0); |
3324 | struct ev_loop *loop_hi = ev_default_init (0); |
3022 | struct ev_loop *loop_lo = 0; |
3325 | struct ev_loop *loop_lo = 0; |
3023 | ev_embed embed; |
3326 | ev_embed embed; |
3024 | |
3327 | |
3025 | // see if there is a chance of getting one that works |
3328 | // see if there is a chance of getting one that works |
3026 | // (remember that a flags value of 0 means autodetection) |
3329 | // (remember that a flags value of 0 means autodetection) |
3027 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3330 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3028 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3331 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3029 | : 0; |
3332 | : 0; |
… | |
… | |
3043 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3346 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3044 | |
3347 | |
3045 | struct ev_loop *loop = ev_default_init (0); |
3348 | struct ev_loop *loop = ev_default_init (0); |
3046 | struct ev_loop *loop_socket = 0; |
3349 | struct ev_loop *loop_socket = 0; |
3047 | ev_embed embed; |
3350 | ev_embed embed; |
3048 | |
3351 | |
3049 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3352 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3050 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3353 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3051 | { |
3354 | { |
3052 | ev_embed_init (&embed, 0, loop_socket); |
3355 | ev_embed_init (&embed, 0, loop_socket); |
3053 | ev_embed_start (loop, &embed); |
3356 | ev_embed_start (loop, &embed); |
… | |
… | |
3061 | |
3364 | |
3062 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3365 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3063 | |
3366 | |
3064 | Fork watchers are called when a C<fork ()> was detected (usually because |
3367 | Fork watchers are called when a C<fork ()> was detected (usually because |
3065 | whoever is a good citizen cared to tell libev about it by calling |
3368 | whoever is a good citizen cared to tell libev about it by calling |
3066 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3369 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3067 | event loop blocks next and before C<ev_check> watchers are being called, |
3370 | and before C<ev_check> watchers are being called, and only in the child |
3068 | and only in the child after the fork. If whoever good citizen calling |
3371 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3069 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3372 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3070 | handlers will be invoked, too, of course. |
3373 | of course. |
3071 | |
3374 | |
3072 | =head3 The special problem of life after fork - how is it possible? |
3375 | =head3 The special problem of life after fork - how is it possible? |
3073 | |
3376 | |
3074 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3377 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3075 | up/change the process environment, followed by a call to C<exec()>. This |
3378 | up/change the process environment, followed by a call to C<exec()>. This |
3076 | sequence should be handled by libev without any problems. |
3379 | sequence should be handled by libev without any problems. |
3077 | |
3380 | |
3078 | This changes when the application actually wants to do event handling |
3381 | This changes when the application actually wants to do event handling |
3079 | in the child, or both parent in child, in effect "continuing" after the |
3382 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3156 | atexit (program_exits); |
3459 | atexit (program_exits); |
3157 | |
3460 | |
3158 | |
3461 | |
3159 | =head2 C<ev_async> - how to wake up an event loop |
3462 | =head2 C<ev_async> - how to wake up an event loop |
3160 | |
3463 | |
3161 | In general, you cannot use an C<ev_run> from multiple threads or other |
3464 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3162 | asynchronous sources such as signal handlers (as opposed to multiple event |
3465 | asynchronous sources such as signal handlers (as opposed to multiple event |
3163 | loops - those are of course safe to use in different threads). |
3466 | loops - those are of course safe to use in different threads). |
3164 | |
3467 | |
3165 | Sometimes, however, you need to wake up an event loop you do not control, |
3468 | Sometimes, however, you need to wake up an event loop you do not control, |
3166 | for example because it belongs to another thread. This is what C<ev_async> |
3469 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3168 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3471 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3169 | |
3472 | |
3170 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3473 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3171 | too, are asynchronous in nature, and signals, too, will be compressed |
3474 | too, are asynchronous in nature, and signals, too, will be compressed |
3172 | (i.e. the number of callback invocations may be less than the number of |
3475 | (i.e. the number of callback invocations may be less than the number of |
3173 | C<ev_async_sent> calls). |
3476 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3174 | |
3477 | of "global async watchers" by using a watcher on an otherwise unused |
3175 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3478 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3176 | just the default loop. |
3479 | even without knowing which loop owns the signal. |
3177 | |
3480 | |
3178 | =head3 Queueing |
3481 | =head3 Queueing |
3179 | |
3482 | |
3180 | C<ev_async> does not support queueing of data in any way. The reason |
3483 | C<ev_async> does not support queueing of data in any way. The reason |
3181 | is that the author does not know of a simple (or any) algorithm for a |
3484 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3273 | trust me. |
3576 | trust me. |
3274 | |
3577 | |
3275 | =item ev_async_send (loop, ev_async *) |
3578 | =item ev_async_send (loop, ev_async *) |
3276 | |
3579 | |
3277 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3580 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3278 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3581 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3582 | returns. |
|
|
3583 | |
3279 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3584 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3280 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3585 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3281 | section below on what exactly this means). |
3586 | embedding section below on what exactly this means). |
3282 | |
3587 | |
3283 | Note that, as with other watchers in libev, multiple events might get |
3588 | Note that, as with other watchers in libev, multiple events might get |
3284 | compressed into a single callback invocation (another way to look at this |
3589 | compressed into a single callback invocation (another way to look at |
3285 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3590 | this is that C<ev_async> watchers are level-triggered: they are set on |
3286 | reset when the event loop detects that). |
3591 | C<ev_async_send>, reset when the event loop detects that). |
3287 | |
3592 | |
3288 | This call incurs the overhead of a system call only once per event loop |
3593 | This call incurs the overhead of at most one extra system call per event |
3289 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3594 | loop iteration, if the event loop is blocked, and no syscall at all if |
3290 | repeated calls to C<ev_async_send> for the same event loop. |
3595 | the event loop (or your program) is processing events. That means that |
|
|
3596 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3597 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3598 | zero) under load. |
3291 | |
3599 | |
3292 | =item bool = ev_async_pending (ev_async *) |
3600 | =item bool = ev_async_pending (ev_async *) |
3293 | |
3601 | |
3294 | Returns a non-zero value when C<ev_async_send> has been called on the |
3602 | Returns a non-zero value when C<ev_async_send> has been called on the |
3295 | watcher but the event has not yet been processed (or even noted) by the |
3603 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3312 | |
3620 | |
3313 | There are some other functions of possible interest. Described. Here. Now. |
3621 | There are some other functions of possible interest. Described. Here. Now. |
3314 | |
3622 | |
3315 | =over 4 |
3623 | =over 4 |
3316 | |
3624 | |
3317 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3625 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
3318 | |
3626 | |
3319 | This function combines a simple timer and an I/O watcher, calls your |
3627 | This function combines a simple timer and an I/O watcher, calls your |
3320 | callback on whichever event happens first and automatically stops both |
3628 | callback on whichever event happens first and automatically stops both |
3321 | watchers. This is useful if you want to wait for a single event on an fd |
3629 | watchers. This is useful if you want to wait for a single event on an fd |
3322 | or timeout without having to allocate/configure/start/stop/free one or |
3630 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
3350 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3658 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3351 | |
3659 | |
3352 | =item ev_feed_fd_event (loop, int fd, int revents) |
3660 | =item ev_feed_fd_event (loop, int fd, int revents) |
3353 | |
3661 | |
3354 | Feed an event on the given fd, as if a file descriptor backend detected |
3662 | Feed an event on the given fd, as if a file descriptor backend detected |
3355 | the given events it. |
3663 | the given events. |
3356 | |
3664 | |
3357 | =item ev_feed_signal_event (loop, int signum) |
3665 | =item ev_feed_signal_event (loop, int signum) |
3358 | |
3666 | |
3359 | Feed an event as if the given signal occurred (C<loop> must be the default |
3667 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3360 | loop!). |
3668 | which is async-safe. |
3361 | |
3669 | |
3362 | =back |
3670 | =back |
|
|
3671 | |
|
|
3672 | |
|
|
3673 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3674 | |
|
|
3675 | This section explains some common idioms that are not immediately |
|
|
3676 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3677 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3678 | |
|
|
3679 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3680 | |
|
|
3681 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3682 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3683 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3684 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3685 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3686 | data: |
|
|
3687 | |
|
|
3688 | struct my_io |
|
|
3689 | { |
|
|
3690 | ev_io io; |
|
|
3691 | int otherfd; |
|
|
3692 | void *somedata; |
|
|
3693 | struct whatever *mostinteresting; |
|
|
3694 | }; |
|
|
3695 | |
|
|
3696 | ... |
|
|
3697 | struct my_io w; |
|
|
3698 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3699 | |
|
|
3700 | And since your callback will be called with a pointer to the watcher, you |
|
|
3701 | can cast it back to your own type: |
|
|
3702 | |
|
|
3703 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3704 | { |
|
|
3705 | struct my_io *w = (struct my_io *)w_; |
|
|
3706 | ... |
|
|
3707 | } |
|
|
3708 | |
|
|
3709 | More interesting and less C-conformant ways of casting your callback |
|
|
3710 | function type instead have been omitted. |
|
|
3711 | |
|
|
3712 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3713 | |
|
|
3714 | Another common scenario is to use some data structure with multiple |
|
|
3715 | embedded watchers, in effect creating your own watcher that combines |
|
|
3716 | multiple libev event sources into one "super-watcher": |
|
|
3717 | |
|
|
3718 | struct my_biggy |
|
|
3719 | { |
|
|
3720 | int some_data; |
|
|
3721 | ev_timer t1; |
|
|
3722 | ev_timer t2; |
|
|
3723 | } |
|
|
3724 | |
|
|
3725 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3726 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3727 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3728 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3729 | real programmers): |
|
|
3730 | |
|
|
3731 | #include <stddef.h> |
|
|
3732 | |
|
|
3733 | static void |
|
|
3734 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3735 | { |
|
|
3736 | struct my_biggy big = (struct my_biggy *) |
|
|
3737 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3738 | } |
|
|
3739 | |
|
|
3740 | static void |
|
|
3741 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3742 | { |
|
|
3743 | struct my_biggy big = (struct my_biggy *) |
|
|
3744 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3745 | } |
|
|
3746 | |
|
|
3747 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3748 | |
|
|
3749 | Often you have structures like this in event-based programs: |
|
|
3750 | |
|
|
3751 | callback () |
|
|
3752 | { |
|
|
3753 | free (request); |
|
|
3754 | } |
|
|
3755 | |
|
|
3756 | request = start_new_request (..., callback); |
|
|
3757 | |
|
|
3758 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3759 | used to cancel the operation, or do other things with it. |
|
|
3760 | |
|
|
3761 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3762 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3763 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3764 | operation and simply invoke the callback with the result. |
|
|
3765 | |
|
|
3766 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3767 | has returned, so C<request> is not set. |
|
|
3768 | |
|
|
3769 | Even if you pass the request by some safer means to the callback, you |
|
|
3770 | might want to do something to the request after starting it, such as |
|
|
3771 | canceling it, which probably isn't working so well when the callback has |
|
|
3772 | already been invoked. |
|
|
3773 | |
|
|
3774 | A common way around all these issues is to make sure that |
|
|
3775 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3776 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3777 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3778 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3779 | pushing it into the pending queue: |
|
|
3780 | |
|
|
3781 | ev_set_cb (watcher, callback); |
|
|
3782 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3783 | |
|
|
3784 | This way, C<start_new_request> can safely return before the callback is |
|
|
3785 | invoked, while not delaying callback invocation too much. |
|
|
3786 | |
|
|
3787 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3788 | |
|
|
3789 | Often (especially in GUI toolkits) there are places where you have |
|
|
3790 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3791 | invoking C<ev_run>. |
|
|
3792 | |
|
|
3793 | This brings the problem of exiting - a callback might want to finish the |
|
|
3794 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3795 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3796 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3797 | other combination: In these cases, a simple C<ev_break> will not work. |
|
|
3798 | |
|
|
3799 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3800 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3801 | triggered, using C<EVRUN_ONCE>: |
|
|
3802 | |
|
|
3803 | // main loop |
|
|
3804 | int exit_main_loop = 0; |
|
|
3805 | |
|
|
3806 | while (!exit_main_loop) |
|
|
3807 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3808 | |
|
|
3809 | // in a modal watcher |
|
|
3810 | int exit_nested_loop = 0; |
|
|
3811 | |
|
|
3812 | while (!exit_nested_loop) |
|
|
3813 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3814 | |
|
|
3815 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3816 | |
|
|
3817 | // exit modal loop |
|
|
3818 | exit_nested_loop = 1; |
|
|
3819 | |
|
|
3820 | // exit main program, after modal loop is finished |
|
|
3821 | exit_main_loop = 1; |
|
|
3822 | |
|
|
3823 | // exit both |
|
|
3824 | exit_main_loop = exit_nested_loop = 1; |
|
|
3825 | |
|
|
3826 | =head2 THREAD LOCKING EXAMPLE |
|
|
3827 | |
|
|
3828 | Here is a fictitious example of how to run an event loop in a different |
|
|
3829 | thread from where callbacks are being invoked and watchers are |
|
|
3830 | created/added/removed. |
|
|
3831 | |
|
|
3832 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3833 | which uses exactly this technique (which is suited for many high-level |
|
|
3834 | languages). |
|
|
3835 | |
|
|
3836 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3837 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3838 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3839 | |
|
|
3840 | First, you need to associate some data with the event loop: |
|
|
3841 | |
|
|
3842 | typedef struct { |
|
|
3843 | mutex_t lock; /* global loop lock */ |
|
|
3844 | ev_async async_w; |
|
|
3845 | thread_t tid; |
|
|
3846 | cond_t invoke_cv; |
|
|
3847 | } userdata; |
|
|
3848 | |
|
|
3849 | void prepare_loop (EV_P) |
|
|
3850 | { |
|
|
3851 | // for simplicity, we use a static userdata struct. |
|
|
3852 | static userdata u; |
|
|
3853 | |
|
|
3854 | ev_async_init (&u->async_w, async_cb); |
|
|
3855 | ev_async_start (EV_A_ &u->async_w); |
|
|
3856 | |
|
|
3857 | pthread_mutex_init (&u->lock, 0); |
|
|
3858 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3859 | |
|
|
3860 | // now associate this with the loop |
|
|
3861 | ev_set_userdata (EV_A_ u); |
|
|
3862 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3863 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3864 | |
|
|
3865 | // then create the thread running ev_run |
|
|
3866 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3867 | } |
|
|
3868 | |
|
|
3869 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3870 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3871 | that might have been added: |
|
|
3872 | |
|
|
3873 | static void |
|
|
3874 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3875 | { |
|
|
3876 | // just used for the side effects |
|
|
3877 | } |
|
|
3878 | |
|
|
3879 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3880 | protecting the loop data, respectively. |
|
|
3881 | |
|
|
3882 | static void |
|
|
3883 | l_release (EV_P) |
|
|
3884 | { |
|
|
3885 | userdata *u = ev_userdata (EV_A); |
|
|
3886 | pthread_mutex_unlock (&u->lock); |
|
|
3887 | } |
|
|
3888 | |
|
|
3889 | static void |
|
|
3890 | l_acquire (EV_P) |
|
|
3891 | { |
|
|
3892 | userdata *u = ev_userdata (EV_A); |
|
|
3893 | pthread_mutex_lock (&u->lock); |
|
|
3894 | } |
|
|
3895 | |
|
|
3896 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3897 | into C<ev_run>: |
|
|
3898 | |
|
|
3899 | void * |
|
|
3900 | l_run (void *thr_arg) |
|
|
3901 | { |
|
|
3902 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3903 | |
|
|
3904 | l_acquire (EV_A); |
|
|
3905 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3906 | ev_run (EV_A_ 0); |
|
|
3907 | l_release (EV_A); |
|
|
3908 | |
|
|
3909 | return 0; |
|
|
3910 | } |
|
|
3911 | |
|
|
3912 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3913 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3914 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3915 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3916 | and b) skipping inter-thread-communication when there are no pending |
|
|
3917 | watchers is very beneficial): |
|
|
3918 | |
|
|
3919 | static void |
|
|
3920 | l_invoke (EV_P) |
|
|
3921 | { |
|
|
3922 | userdata *u = ev_userdata (EV_A); |
|
|
3923 | |
|
|
3924 | while (ev_pending_count (EV_A)) |
|
|
3925 | { |
|
|
3926 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3927 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3928 | } |
|
|
3929 | } |
|
|
3930 | |
|
|
3931 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3932 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3933 | thread to continue: |
|
|
3934 | |
|
|
3935 | static void |
|
|
3936 | real_invoke_pending (EV_P) |
|
|
3937 | { |
|
|
3938 | userdata *u = ev_userdata (EV_A); |
|
|
3939 | |
|
|
3940 | pthread_mutex_lock (&u->lock); |
|
|
3941 | ev_invoke_pending (EV_A); |
|
|
3942 | pthread_cond_signal (&u->invoke_cv); |
|
|
3943 | pthread_mutex_unlock (&u->lock); |
|
|
3944 | } |
|
|
3945 | |
|
|
3946 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3947 | event loop, you will now have to lock: |
|
|
3948 | |
|
|
3949 | ev_timer timeout_watcher; |
|
|
3950 | userdata *u = ev_userdata (EV_A); |
|
|
3951 | |
|
|
3952 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3953 | |
|
|
3954 | pthread_mutex_lock (&u->lock); |
|
|
3955 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3956 | ev_async_send (EV_A_ &u->async_w); |
|
|
3957 | pthread_mutex_unlock (&u->lock); |
|
|
3958 | |
|
|
3959 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3960 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3961 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3962 | watchers in the next event loop iteration. |
|
|
3963 | |
|
|
3964 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3965 | |
|
|
3966 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3967 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3968 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3969 | doesn't need callbacks anymore. |
|
|
3970 | |
|
|
3971 | Imagine you have coroutines that you can switch to using a function |
|
|
3972 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3973 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3974 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3975 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3976 | the differing C<;> conventions): |
|
|
3977 | |
|
|
3978 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3979 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3980 | |
|
|
3981 | That means instead of having a C callback function, you store the |
|
|
3982 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3983 | your callback, you instead have it switch to that coroutine. |
|
|
3984 | |
|
|
3985 | A coroutine might now wait for an event with a function called |
|
|
3986 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3987 | matter when, or whether the watcher is active or not when this function is |
|
|
3988 | called): |
|
|
3989 | |
|
|
3990 | void |
|
|
3991 | wait_for_event (ev_watcher *w) |
|
|
3992 | { |
|
|
3993 | ev_set_cb (w, current_coro); |
|
|
3994 | switch_to (libev_coro); |
|
|
3995 | } |
|
|
3996 | |
|
|
3997 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3998 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3999 | this or any other coroutine. |
|
|
4000 | |
|
|
4001 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
4002 | instead of storing a coroutine, you store the queue object and instead of |
|
|
4003 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
4004 | any waiters. |
|
|
4005 | |
|
|
4006 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
|
|
4007 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
4008 | |
|
|
4009 | // my_ev.h |
|
|
4010 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
4011 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
4012 | #include "../libev/ev.h" |
|
|
4013 | |
|
|
4014 | // my_ev.c |
|
|
4015 | #define EV_H "my_ev.h" |
|
|
4016 | #include "../libev/ev.c" |
|
|
4017 | |
|
|
4018 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
4019 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
4020 | can even use F<ev.h> as header file name directly. |
3363 | |
4021 | |
3364 | |
4022 | |
3365 | =head1 LIBEVENT EMULATION |
4023 | =head1 LIBEVENT EMULATION |
3366 | |
4024 | |
3367 | Libev offers a compatibility emulation layer for libevent. It cannot |
4025 | Libev offers a compatibility emulation layer for libevent. It cannot |
3368 | emulate the internals of libevent, so here are some usage hints: |
4026 | emulate the internals of libevent, so here are some usage hints: |
3369 | |
4027 | |
3370 | =over 4 |
4028 | =over 4 |
|
|
4029 | |
|
|
4030 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
4031 | |
|
|
4032 | This was the newest libevent version available when libev was implemented, |
|
|
4033 | and is still mostly unchanged in 2010. |
3371 | |
4034 | |
3372 | =item * Use it by including <event.h>, as usual. |
4035 | =item * Use it by including <event.h>, as usual. |
3373 | |
4036 | |
3374 | =item * The following members are fully supported: ev_base, ev_callback, |
4037 | =item * The following members are fully supported: ev_base, ev_callback, |
3375 | ev_arg, ev_fd, ev_res, ev_events. |
4038 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3381 | =item * Priorities are not currently supported. Initialising priorities |
4044 | =item * Priorities are not currently supported. Initialising priorities |
3382 | will fail and all watchers will have the same priority, even though there |
4045 | will fail and all watchers will have the same priority, even though there |
3383 | is an ev_pri field. |
4046 | is an ev_pri field. |
3384 | |
4047 | |
3385 | =item * In libevent, the last base created gets the signals, in libev, the |
4048 | =item * In libevent, the last base created gets the signals, in libev, the |
3386 | first base created (== the default loop) gets the signals. |
4049 | base that registered the signal gets the signals. |
3387 | |
4050 | |
3388 | =item * Other members are not supported. |
4051 | =item * Other members are not supported. |
3389 | |
4052 | |
3390 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
4053 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3391 | to use the libev header file and library. |
4054 | to use the libev header file and library. |
3392 | |
4055 | |
3393 | =back |
4056 | =back |
3394 | |
4057 | |
3395 | =head1 C++ SUPPORT |
4058 | =head1 C++ SUPPORT |
|
|
4059 | |
|
|
4060 | =head2 C API |
|
|
4061 | |
|
|
4062 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
4063 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
4064 | will work fine. |
|
|
4065 | |
|
|
4066 | Proper exception specifications might have to be added to callbacks passed |
|
|
4067 | to libev: exceptions may be thrown only from watcher callbacks, all other |
|
|
4068 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
|
|
4069 | callbacks) must not throw exceptions, and might need a C<noexcept> |
|
|
4070 | specification. If you have code that needs to be compiled as both C and |
|
|
4071 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
|
|
4072 | |
|
|
4073 | static void |
|
|
4074 | fatal_error (const char *msg) EV_NOEXCEPT |
|
|
4075 | { |
|
|
4076 | perror (msg); |
|
|
4077 | abort (); |
|
|
4078 | } |
|
|
4079 | |
|
|
4080 | ... |
|
|
4081 | ev_set_syserr_cb (fatal_error); |
|
|
4082 | |
|
|
4083 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
4084 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
4085 | because it runs cleanup watchers). |
|
|
4086 | |
|
|
4087 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
4088 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
4089 | throwing exceptions through C libraries (most do). |
|
|
4090 | |
|
|
4091 | =head2 C++ API |
3396 | |
4092 | |
3397 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
4093 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3398 | you to use some convenience methods to start/stop watchers and also change |
4094 | you to use some convenience methods to start/stop watchers and also change |
3399 | the callback model to a model using method callbacks on objects. |
4095 | the callback model to a model using method callbacks on objects. |
3400 | |
4096 | |
3401 | To use it, |
4097 | To use it, |
3402 | |
4098 | |
3403 | #include <ev++.h> |
4099 | #include <ev++.h> |
3404 | |
4100 | |
3405 | This automatically includes F<ev.h> and puts all of its definitions (many |
4101 | This automatically includes F<ev.h> and puts all of its definitions (many |
3406 | of them macros) into the global namespace. All C++ specific things are |
4102 | of them macros) into the global namespace. All C++ specific things are |
3407 | put into the C<ev> namespace. It should support all the same embedding |
4103 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
3410 | Care has been taken to keep the overhead low. The only data member the C++ |
4106 | Care has been taken to keep the overhead low. The only data member the C++ |
3411 | classes add (compared to plain C-style watchers) is the event loop pointer |
4107 | classes add (compared to plain C-style watchers) is the event loop pointer |
3412 | that the watcher is associated with (or no additional members at all if |
4108 | that the watcher is associated with (or no additional members at all if |
3413 | you disable C<EV_MULTIPLICITY> when embedding libev). |
4109 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3414 | |
4110 | |
3415 | Currently, functions, and static and non-static member functions can be |
4111 | Currently, functions, static and non-static member functions and classes |
3416 | used as callbacks. Other types should be easy to add as long as they only |
4112 | with C<operator ()> can be used as callbacks. Other types should be easy |
3417 | need one additional pointer for context. If you need support for other |
4113 | to add as long as they only need one additional pointer for context. If |
3418 | types of functors please contact the author (preferably after implementing |
4114 | you need support for other types of functors please contact the author |
3419 | it). |
4115 | (preferably after implementing it). |
|
|
4116 | |
|
|
4117 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4118 | conventions as your C compiler (for static member functions), or you have |
|
|
4119 | to embed libev and compile libev itself as C++. |
3420 | |
4120 | |
3421 | Here is a list of things available in the C<ev> namespace: |
4121 | Here is a list of things available in the C<ev> namespace: |
3422 | |
4122 | |
3423 | =over 4 |
4123 | =over 4 |
3424 | |
4124 | |
… | |
… | |
3434 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4134 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3435 | |
4135 | |
3436 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4136 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3437 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4137 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3438 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4138 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3439 | defines by many implementations. |
4139 | defined by many implementations. |
3440 | |
4140 | |
3441 | All of those classes have these methods: |
4141 | All of those classes have these methods: |
3442 | |
4142 | |
3443 | =over 4 |
4143 | =over 4 |
3444 | |
4144 | |
… | |
… | |
3506 | void operator() (ev::io &w, int revents) |
4206 | void operator() (ev::io &w, int revents) |
3507 | { |
4207 | { |
3508 | ... |
4208 | ... |
3509 | } |
4209 | } |
3510 | } |
4210 | } |
3511 | |
4211 | |
3512 | myfunctor f; |
4212 | myfunctor f; |
3513 | |
4213 | |
3514 | ev::io w; |
4214 | ev::io w; |
3515 | w.set (&f); |
4215 | w.set (&f); |
3516 | |
4216 | |
… | |
… | |
3534 | Associates a different C<struct ev_loop> with this watcher. You can only |
4234 | Associates a different C<struct ev_loop> with this watcher. You can only |
3535 | do this when the watcher is inactive (and not pending either). |
4235 | do this when the watcher is inactive (and not pending either). |
3536 | |
4236 | |
3537 | =item w->set ([arguments]) |
4237 | =item w->set ([arguments]) |
3538 | |
4238 | |
3539 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4239 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
3540 | method or a suitable start method must be called at least once. Unlike the |
4240 | with the same arguments. Either this method or a suitable start method |
3541 | C counterpart, an active watcher gets automatically stopped and restarted |
4241 | must be called at least once. Unlike the C counterpart, an active watcher |
3542 | when reconfiguring it with this method. |
4242 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4243 | method. |
|
|
4244 | |
|
|
4245 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4246 | clashing with the C<set (loop)> method. |
3543 | |
4247 | |
3544 | =item w->start () |
4248 | =item w->start () |
3545 | |
4249 | |
3546 | Starts the watcher. Note that there is no C<loop> argument, as the |
4250 | Starts the watcher. Note that there is no C<loop> argument, as the |
3547 | constructor already stores the event loop. |
4251 | constructor already stores the event loop. |
… | |
… | |
3577 | watchers in the constructor. |
4281 | watchers in the constructor. |
3578 | |
4282 | |
3579 | class myclass |
4283 | class myclass |
3580 | { |
4284 | { |
3581 | ev::io io ; void io_cb (ev::io &w, int revents); |
4285 | ev::io io ; void io_cb (ev::io &w, int revents); |
3582 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4286 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3583 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4287 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3584 | |
4288 | |
3585 | myclass (int fd) |
4289 | myclass (int fd) |
3586 | { |
4290 | { |
3587 | io .set <myclass, &myclass::io_cb > (this); |
4291 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3638 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4342 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3639 | |
4343 | |
3640 | =item D |
4344 | =item D |
3641 | |
4345 | |
3642 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4346 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3643 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4347 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3644 | |
4348 | |
3645 | =item Ocaml |
4349 | =item Ocaml |
3646 | |
4350 | |
3647 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4351 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3648 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4352 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3651 | |
4355 | |
3652 | Brian Maher has written a partial interface to libev for lua (at the |
4356 | Brian Maher has written a partial interface to libev for lua (at the |
3653 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4357 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3654 | L<http://github.com/brimworks/lua-ev>. |
4358 | L<http://github.com/brimworks/lua-ev>. |
3655 | |
4359 | |
|
|
4360 | =item Javascript |
|
|
4361 | |
|
|
4362 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4363 | |
|
|
4364 | =item Others |
|
|
4365 | |
|
|
4366 | There are others, and I stopped counting. |
|
|
4367 | |
3656 | =back |
4368 | =back |
3657 | |
4369 | |
3658 | |
4370 | |
3659 | =head1 MACRO MAGIC |
4371 | =head1 MACRO MAGIC |
3660 | |
4372 | |
… | |
… | |
3696 | suitable for use with C<EV_A>. |
4408 | suitable for use with C<EV_A>. |
3697 | |
4409 | |
3698 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4410 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3699 | |
4411 | |
3700 | Similar to the other two macros, this gives you the value of the default |
4412 | Similar to the other two macros, this gives you the value of the default |
3701 | loop, if multiple loops are supported ("ev loop default"). |
4413 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4414 | will be initialised if it isn't already initialised. |
|
|
4415 | |
|
|
4416 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4417 | to initialise the loop somewhere. |
3702 | |
4418 | |
3703 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4419 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3704 | |
4420 | |
3705 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4421 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3706 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4422 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3773 | ev_vars.h |
4489 | ev_vars.h |
3774 | ev_wrap.h |
4490 | ev_wrap.h |
3775 | |
4491 | |
3776 | ev_win32.c required on win32 platforms only |
4492 | ev_win32.c required on win32 platforms only |
3777 | |
4493 | |
3778 | ev_select.c only when select backend is enabled (which is enabled by default) |
4494 | ev_select.c only when select backend is enabled |
3779 | ev_poll.c only when poll backend is enabled (disabled by default) |
4495 | ev_poll.c only when poll backend is enabled |
3780 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4496 | ev_epoll.c only when the epoll backend is enabled |
|
|
4497 | ev_linuxaio.c only when the linux aio backend is enabled |
|
|
4498 | ev_iouring.c only when the linux io_uring backend is enabled |
3781 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4499 | ev_kqueue.c only when the kqueue backend is enabled |
3782 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4500 | ev_port.c only when the solaris port backend is enabled |
3783 | |
4501 | |
3784 | F<ev.c> includes the backend files directly when enabled, so you only need |
4502 | F<ev.c> includes the backend files directly when enabled, so you only need |
3785 | to compile this single file. |
4503 | to compile this single file. |
3786 | |
4504 | |
3787 | =head3 LIBEVENT COMPATIBILITY API |
4505 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
3851 | supported). It will also not define any of the structs usually found in |
4569 | supported). It will also not define any of the structs usually found in |
3852 | F<event.h> that are not directly supported by the libev core alone. |
4570 | F<event.h> that are not directly supported by the libev core alone. |
3853 | |
4571 | |
3854 | In standalone mode, libev will still try to automatically deduce the |
4572 | In standalone mode, libev will still try to automatically deduce the |
3855 | configuration, but has to be more conservative. |
4573 | configuration, but has to be more conservative. |
|
|
4574 | |
|
|
4575 | =item EV_USE_FLOOR |
|
|
4576 | |
|
|
4577 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4578 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4579 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4580 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4581 | function is not available will fail, so the safe default is to not enable |
|
|
4582 | this. |
3856 | |
4583 | |
3857 | =item EV_USE_MONOTONIC |
4584 | =item EV_USE_MONOTONIC |
3858 | |
4585 | |
3859 | If defined to be C<1>, libev will try to detect the availability of the |
4586 | If defined to be C<1>, libev will try to detect the availability of the |
3860 | monotonic clock option at both compile time and runtime. Otherwise no |
4587 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3897 | available and will probe for kernel support at runtime. This will improve |
4624 | available and will probe for kernel support at runtime. This will improve |
3898 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
4625 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
3899 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
4626 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
3900 | 2.7 or newer, otherwise disabled. |
4627 | 2.7 or newer, otherwise disabled. |
3901 | |
4628 | |
|
|
4629 | =item EV_USE_SIGNALFD |
|
|
4630 | |
|
|
4631 | If defined to be C<1>, then libev will assume that C<signalfd ()> is |
|
|
4632 | available and will probe for kernel support at runtime. This enables |
|
|
4633 | the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If |
|
|
4634 | undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4635 | 2.7 or newer, otherwise disabled. |
|
|
4636 | |
|
|
4637 | =item EV_USE_TIMERFD |
|
|
4638 | |
|
|
4639 | If defined to be C<1>, then libev will assume that C<timerfd ()> is |
|
|
4640 | available and will probe for kernel support at runtime. This allows |
|
|
4641 | libev to detect time jumps accurately. If undefined, it will be enabled |
|
|
4642 | if the headers indicate GNU/Linux + Glibc 2.8 or newer and define |
|
|
4643 | C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled. |
|
|
4644 | |
|
|
4645 | =item EV_USE_EVENTFD |
|
|
4646 | |
|
|
4647 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
4648 | available and will probe for kernel support at runtime. This will improve |
|
|
4649 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
4650 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4651 | 2.7 or newer, otherwise disabled. |
|
|
4652 | |
3902 | =item EV_USE_SELECT |
4653 | =item EV_USE_SELECT |
3903 | |
4654 | |
3904 | If undefined or defined to be C<1>, libev will compile in support for the |
4655 | If undefined or defined to be C<1>, libev will compile in support for the |
3905 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
4656 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
3906 | other method takes over, select will be it. Otherwise the select backend |
4657 | other method takes over, select will be it. Otherwise the select backend |
… | |
… | |
3946 | If programs implement their own fd to handle mapping on win32, then this |
4697 | If programs implement their own fd to handle mapping on win32, then this |
3947 | macro can be used to override the C<close> function, useful to unregister |
4698 | macro can be used to override the C<close> function, useful to unregister |
3948 | file descriptors again. Note that the replacement function has to close |
4699 | file descriptors again. Note that the replacement function has to close |
3949 | the underlying OS handle. |
4700 | the underlying OS handle. |
3950 | |
4701 | |
|
|
4702 | =item EV_USE_WSASOCKET |
|
|
4703 | |
|
|
4704 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4705 | communication socket, which works better in some environments. Otherwise, |
|
|
4706 | the normal C<socket> function will be used, which works better in other |
|
|
4707 | environments. |
|
|
4708 | |
3951 | =item EV_USE_POLL |
4709 | =item EV_USE_POLL |
3952 | |
4710 | |
3953 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4711 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3954 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4712 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3955 | takes precedence over select. |
4713 | takes precedence over select. |
… | |
… | |
3959 | If defined to be C<1>, libev will compile in support for the Linux |
4717 | If defined to be C<1>, libev will compile in support for the Linux |
3960 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4718 | C<epoll>(7) backend. Its availability will be detected at runtime, |
3961 | otherwise another method will be used as fallback. This is the preferred |
4719 | otherwise another method will be used as fallback. This is the preferred |
3962 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4720 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
3963 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4721 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4722 | |
|
|
4723 | =item EV_USE_LINUXAIO |
|
|
4724 | |
|
|
4725 | If defined to be C<1>, libev will compile in support for the Linux aio |
|
|
4726 | backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be |
|
|
4727 | enabled on linux, otherwise disabled. |
|
|
4728 | |
|
|
4729 | =item EV_USE_IOURING |
|
|
4730 | |
|
|
4731 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
4732 | io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's |
|
|
4733 | current limitations it has to be requested explicitly. If undefined, it |
|
|
4734 | will be enabled on linux, otherwise disabled. |
3964 | |
4735 | |
3965 | =item EV_USE_KQUEUE |
4736 | =item EV_USE_KQUEUE |
3966 | |
4737 | |
3967 | If defined to be C<1>, libev will compile in support for the BSD style |
4738 | If defined to be C<1>, libev will compile in support for the BSD style |
3968 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4739 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
3990 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4761 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3991 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4762 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3992 | be detected at runtime. If undefined, it will be enabled if the headers |
4763 | be detected at runtime. If undefined, it will be enabled if the headers |
3993 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4764 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3994 | |
4765 | |
|
|
4766 | =item EV_NO_SMP |
|
|
4767 | |
|
|
4768 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4769 | between threads, that is, threads can be used, but threads never run on |
|
|
4770 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4771 | and makes libev faster. |
|
|
4772 | |
|
|
4773 | =item EV_NO_THREADS |
|
|
4774 | |
|
|
4775 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4776 | different threads (that includes signal handlers), which is a stronger |
|
|
4777 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4778 | libev faster. |
|
|
4779 | |
3995 | =item EV_ATOMIC_T |
4780 | =item EV_ATOMIC_T |
3996 | |
4781 | |
3997 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4782 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3998 | access is atomic with respect to other threads or signal contexts. No such |
4783 | access is atomic with respect to other threads or signal contexts. No |
3999 | type is easily found in the C language, so you can provide your own type |
4784 | such type is easily found in the C language, so you can provide your own |
4000 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4785 | type that you know is safe for your purposes. It is used both for signal |
4001 | as well as for signal and thread safety in C<ev_async> watchers. |
4786 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4787 | watchers. |
4002 | |
4788 | |
4003 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4789 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4004 | (from F<signal.h>), which is usually good enough on most platforms. |
4790 | (from F<signal.h>), which is usually good enough on most platforms. |
4005 | |
4791 | |
4006 | =item EV_H (h) |
4792 | =item EV_H (h) |
… | |
… | |
4033 | will have the C<struct ev_loop *> as first argument, and you can create |
4819 | will have the C<struct ev_loop *> as first argument, and you can create |
4034 | additional independent event loops. Otherwise there will be no support |
4820 | additional independent event loops. Otherwise there will be no support |
4035 | for multiple event loops and there is no first event loop pointer |
4821 | for multiple event loops and there is no first event loop pointer |
4036 | argument. Instead, all functions act on the single default loop. |
4822 | argument. Instead, all functions act on the single default loop. |
4037 | |
4823 | |
|
|
4824 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4825 | default loop when multiplicity is switched off - you always have to |
|
|
4826 | initialise the loop manually in this case. |
|
|
4827 | |
4038 | =item EV_MINPRI |
4828 | =item EV_MINPRI |
4039 | |
4829 | |
4040 | =item EV_MAXPRI |
4830 | =item EV_MAXPRI |
4041 | |
4831 | |
4042 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4832 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4078 | #define EV_USE_POLL 1 |
4868 | #define EV_USE_POLL 1 |
4079 | #define EV_CHILD_ENABLE 1 |
4869 | #define EV_CHILD_ENABLE 1 |
4080 | #define EV_ASYNC_ENABLE 1 |
4870 | #define EV_ASYNC_ENABLE 1 |
4081 | |
4871 | |
4082 | The actual value is a bitset, it can be a combination of the following |
4872 | The actual value is a bitset, it can be a combination of the following |
4083 | values: |
4873 | values (by default, all of these are enabled): |
4084 | |
4874 | |
4085 | =over 4 |
4875 | =over 4 |
4086 | |
4876 | |
4087 | =item C<1> - faster/larger code |
4877 | =item C<1> - faster/larger code |
4088 | |
4878 | |
… | |
… | |
4092 | code size by roughly 30% on amd64). |
4882 | code size by roughly 30% on amd64). |
4093 | |
4883 | |
4094 | When optimising for size, use of compiler flags such as C<-Os> with |
4884 | When optimising for size, use of compiler flags such as C<-Os> with |
4095 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4885 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4096 | assertions. |
4886 | assertions. |
|
|
4887 | |
|
|
4888 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4889 | (e.g. gcc with C<-Os>). |
4097 | |
4890 | |
4098 | =item C<2> - faster/larger data structures |
4891 | =item C<2> - faster/larger data structures |
4099 | |
4892 | |
4100 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4893 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4101 | hash table sizes and so on. This will usually further increase code size |
4894 | hash table sizes and so on. This will usually further increase code size |
4102 | and can additionally have an effect on the size of data structures at |
4895 | and can additionally have an effect on the size of data structures at |
4103 | runtime. |
4896 | runtime. |
4104 | |
4897 | |
|
|
4898 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4899 | (e.g. gcc with C<-Os>). |
|
|
4900 | |
4105 | =item C<4> - full API configuration |
4901 | =item C<4> - full API configuration |
4106 | |
4902 | |
4107 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4903 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4108 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4904 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4109 | |
4905 | |
… | |
… | |
4139 | |
4935 | |
4140 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4936 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4141 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4937 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4142 | your program might be left out as well - a binary starting a timer and an |
4938 | your program might be left out as well - a binary starting a timer and an |
4143 | I/O watcher then might come out at only 5Kb. |
4939 | I/O watcher then might come out at only 5Kb. |
|
|
4940 | |
|
|
4941 | =item EV_API_STATIC |
|
|
4942 | |
|
|
4943 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4944 | will have static linkage. This means that libev will not export any |
|
|
4945 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4946 | when you embed libev, only want to use libev functions in a single file, |
|
|
4947 | and do not want its identifiers to be visible. |
|
|
4948 | |
|
|
4949 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4950 | wants to use libev. |
|
|
4951 | |
|
|
4952 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4953 | doesn't support the required declaration syntax. |
4144 | |
4954 | |
4145 | =item EV_AVOID_STDIO |
4955 | =item EV_AVOID_STDIO |
4146 | |
4956 | |
4147 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4957 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4148 | functions (printf, scanf, perror etc.). This will increase the code size |
4958 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4206 | in. If set to C<1>, then verification code will be compiled in, but not |
5016 | in. If set to C<1>, then verification code will be compiled in, but not |
4207 | called. If set to C<2>, then the internal verification code will be |
5017 | called. If set to C<2>, then the internal verification code will be |
4208 | called once per loop, which can slow down libev. If set to C<3>, then the |
5018 | called once per loop, which can slow down libev. If set to C<3>, then the |
4209 | verification code will be called very frequently, which will slow down |
5019 | verification code will be called very frequently, which will slow down |
4210 | libev considerably. |
5020 | libev considerably. |
|
|
5021 | |
|
|
5022 | Verification errors are reported via C's C<assert> mechanism, so if you |
|
|
5023 | disable that (e.g. by defining C<NDEBUG>) then no errors will be reported. |
4211 | |
5024 | |
4212 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
5025 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
4213 | will be C<0>. |
5026 | will be C<0>. |
4214 | |
5027 | |
4215 | =item EV_COMMON |
5028 | =item EV_COMMON |
… | |
… | |
4292 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
5105 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4293 | |
5106 | |
4294 | #include "ev_cpp.h" |
5107 | #include "ev_cpp.h" |
4295 | #include "ev.c" |
5108 | #include "ev.c" |
4296 | |
5109 | |
4297 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
5110 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4298 | |
5111 | |
4299 | =head2 THREADS AND COROUTINES |
5112 | =head2 THREADS AND COROUTINES |
4300 | |
5113 | |
4301 | =head3 THREADS |
5114 | =head3 THREADS |
4302 | |
5115 | |
… | |
… | |
4353 | default loop and triggering an C<ev_async> watcher from the default loop |
5166 | default loop and triggering an C<ev_async> watcher from the default loop |
4354 | watcher callback into the event loop interested in the signal. |
5167 | watcher callback into the event loop interested in the signal. |
4355 | |
5168 | |
4356 | =back |
5169 | =back |
4357 | |
5170 | |
4358 | =head4 THREAD LOCKING EXAMPLE |
5171 | See also L</THREAD LOCKING EXAMPLE>. |
4359 | |
|
|
4360 | Here is a fictitious example of how to run an event loop in a different |
|
|
4361 | thread than where callbacks are being invoked and watchers are |
|
|
4362 | created/added/removed. |
|
|
4363 | |
|
|
4364 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4365 | which uses exactly this technique (which is suited for many high-level |
|
|
4366 | languages). |
|
|
4367 | |
|
|
4368 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4369 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4370 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4371 | |
|
|
4372 | First, you need to associate some data with the event loop: |
|
|
4373 | |
|
|
4374 | typedef struct { |
|
|
4375 | mutex_t lock; /* global loop lock */ |
|
|
4376 | ev_async async_w; |
|
|
4377 | thread_t tid; |
|
|
4378 | cond_t invoke_cv; |
|
|
4379 | } userdata; |
|
|
4380 | |
|
|
4381 | void prepare_loop (EV_P) |
|
|
4382 | { |
|
|
4383 | // for simplicity, we use a static userdata struct. |
|
|
4384 | static userdata u; |
|
|
4385 | |
|
|
4386 | ev_async_init (&u->async_w, async_cb); |
|
|
4387 | ev_async_start (EV_A_ &u->async_w); |
|
|
4388 | |
|
|
4389 | pthread_mutex_init (&u->lock, 0); |
|
|
4390 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4391 | |
|
|
4392 | // now associate this with the loop |
|
|
4393 | ev_set_userdata (EV_A_ u); |
|
|
4394 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4395 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4396 | |
|
|
4397 | // then create the thread running ev_loop |
|
|
4398 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4399 | } |
|
|
4400 | |
|
|
4401 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4402 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4403 | that might have been added: |
|
|
4404 | |
|
|
4405 | static void |
|
|
4406 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4407 | { |
|
|
4408 | // just used for the side effects |
|
|
4409 | } |
|
|
4410 | |
|
|
4411 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4412 | protecting the loop data, respectively. |
|
|
4413 | |
|
|
4414 | static void |
|
|
4415 | l_release (EV_P) |
|
|
4416 | { |
|
|
4417 | userdata *u = ev_userdata (EV_A); |
|
|
4418 | pthread_mutex_unlock (&u->lock); |
|
|
4419 | } |
|
|
4420 | |
|
|
4421 | static void |
|
|
4422 | l_acquire (EV_P) |
|
|
4423 | { |
|
|
4424 | userdata *u = ev_userdata (EV_A); |
|
|
4425 | pthread_mutex_lock (&u->lock); |
|
|
4426 | } |
|
|
4427 | |
|
|
4428 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4429 | into C<ev_run>: |
|
|
4430 | |
|
|
4431 | void * |
|
|
4432 | l_run (void *thr_arg) |
|
|
4433 | { |
|
|
4434 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4435 | |
|
|
4436 | l_acquire (EV_A); |
|
|
4437 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4438 | ev_run (EV_A_ 0); |
|
|
4439 | l_release (EV_A); |
|
|
4440 | |
|
|
4441 | return 0; |
|
|
4442 | } |
|
|
4443 | |
|
|
4444 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4445 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4446 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4447 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4448 | and b) skipping inter-thread-communication when there are no pending |
|
|
4449 | watchers is very beneficial): |
|
|
4450 | |
|
|
4451 | static void |
|
|
4452 | l_invoke (EV_P) |
|
|
4453 | { |
|
|
4454 | userdata *u = ev_userdata (EV_A); |
|
|
4455 | |
|
|
4456 | while (ev_pending_count (EV_A)) |
|
|
4457 | { |
|
|
4458 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4459 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4460 | } |
|
|
4461 | } |
|
|
4462 | |
|
|
4463 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4464 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4465 | thread to continue: |
|
|
4466 | |
|
|
4467 | static void |
|
|
4468 | real_invoke_pending (EV_P) |
|
|
4469 | { |
|
|
4470 | userdata *u = ev_userdata (EV_A); |
|
|
4471 | |
|
|
4472 | pthread_mutex_lock (&u->lock); |
|
|
4473 | ev_invoke_pending (EV_A); |
|
|
4474 | pthread_cond_signal (&u->invoke_cv); |
|
|
4475 | pthread_mutex_unlock (&u->lock); |
|
|
4476 | } |
|
|
4477 | |
|
|
4478 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4479 | event loop, you will now have to lock: |
|
|
4480 | |
|
|
4481 | ev_timer timeout_watcher; |
|
|
4482 | userdata *u = ev_userdata (EV_A); |
|
|
4483 | |
|
|
4484 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4485 | |
|
|
4486 | pthread_mutex_lock (&u->lock); |
|
|
4487 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4488 | ev_async_send (EV_A_ &u->async_w); |
|
|
4489 | pthread_mutex_unlock (&u->lock); |
|
|
4490 | |
|
|
4491 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4492 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4493 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4494 | watchers in the next event loop iteration. |
|
|
4495 | |
5172 | |
4496 | =head3 COROUTINES |
5173 | =head3 COROUTINES |
4497 | |
5174 | |
4498 | Libev is very accommodating to coroutines ("cooperative threads"): |
5175 | Libev is very accommodating to coroutines ("cooperative threads"): |
4499 | libev fully supports nesting calls to its functions from different |
5176 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4664 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5341 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4665 | model. Libev still offers limited functionality on this platform in |
5342 | model. Libev still offers limited functionality on this platform in |
4666 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5343 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4667 | descriptors. This only applies when using Win32 natively, not when using |
5344 | descriptors. This only applies when using Win32 natively, not when using |
4668 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5345 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4669 | as every compielr comes with a slightly differently broken/incompatible |
5346 | as every compiler comes with a slightly differently broken/incompatible |
4670 | environment. |
5347 | environment. |
4671 | |
5348 | |
4672 | Lifting these limitations would basically require the full |
5349 | Lifting these limitations would basically require the full |
4673 | re-implementation of the I/O system. If you are into this kind of thing, |
5350 | re-implementation of the I/O system. If you are into this kind of thing, |
4674 | then note that glib does exactly that for you in a very portable way (note |
5351 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4768 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5445 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4769 | assumes that the same (machine) code can be used to call any watcher |
5446 | assumes that the same (machine) code can be used to call any watcher |
4770 | callback: The watcher callbacks have different type signatures, but libev |
5447 | callback: The watcher callbacks have different type signatures, but libev |
4771 | calls them using an C<ev_watcher *> internally. |
5448 | calls them using an C<ev_watcher *> internally. |
4772 | |
5449 | |
|
|
5450 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5451 | |
|
|
5452 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5453 | relies on this setting pointers and integers to null. |
|
|
5454 | |
4773 | =item pointer accesses must be thread-atomic |
5455 | =item pointer accesses must be thread-atomic |
4774 | |
5456 | |
4775 | Accessing a pointer value must be atomic, it must both be readable and |
5457 | Accessing a pointer value must be atomic, it must both be readable and |
4776 | writable in one piece - this is the case on all current architectures. |
5458 | writable in one piece - this is the case on all current architectures. |
4777 | |
5459 | |
… | |
… | |
4790 | thread" or will block signals process-wide, both behaviours would |
5472 | thread" or will block signals process-wide, both behaviours would |
4791 | be compatible with libev. Interaction between C<sigprocmask> and |
5473 | be compatible with libev. Interaction between C<sigprocmask> and |
4792 | C<pthread_sigmask> could complicate things, however. |
5474 | C<pthread_sigmask> could complicate things, however. |
4793 | |
5475 | |
4794 | The most portable way to handle signals is to block signals in all threads |
5476 | The most portable way to handle signals is to block signals in all threads |
4795 | except the initial one, and run the default loop in the initial thread as |
5477 | except the initial one, and run the signal handling loop in the initial |
4796 | well. |
5478 | thread as well. |
4797 | |
5479 | |
4798 | =item C<long> must be large enough for common memory allocation sizes |
5480 | =item C<long> must be large enough for common memory allocation sizes |
4799 | |
5481 | |
4800 | To improve portability and simplify its API, libev uses C<long> internally |
5482 | To improve portability and simplify its API, libev uses C<long> internally |
4801 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5483 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
4807 | |
5489 | |
4808 | The type C<double> is used to represent timestamps. It is required to |
5490 | The type C<double> is used to represent timestamps. It is required to |
4809 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5491 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4810 | good enough for at least into the year 4000 with millisecond accuracy |
5492 | good enough for at least into the year 4000 with millisecond accuracy |
4811 | (the design goal for libev). This requirement is overfulfilled by |
5493 | (the design goal for libev). This requirement is overfulfilled by |
4812 | implementations using IEEE 754, which is basically all existing ones. With |
5494 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5495 | |
4813 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5496 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5497 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5498 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5499 | something like that, just kidding). |
4814 | |
5500 | |
4815 | =back |
5501 | =back |
4816 | |
5502 | |
4817 | If you know of other additional requirements drop me a note. |
5503 | If you know of other additional requirements drop me a note. |
4818 | |
5504 | |
… | |
… | |
4880 | =item Processing ev_async_send: O(number_of_async_watchers) |
5566 | =item Processing ev_async_send: O(number_of_async_watchers) |
4881 | |
5567 | |
4882 | =item Processing signals: O(max_signal_number) |
5568 | =item Processing signals: O(max_signal_number) |
4883 | |
5569 | |
4884 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5570 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4885 | calls in the current loop iteration. Checking for async and signal events |
5571 | calls in the current loop iteration and the loop is currently |
|
|
5572 | blocked. Checking for async and signal events involves iterating over all |
4886 | involves iterating over all running async watchers or all signal numbers. |
5573 | running async watchers or all signal numbers. |
4887 | |
5574 | |
4888 | =back |
5575 | =back |
4889 | |
5576 | |
4890 | |
5577 | |
4891 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5578 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
4900 | =over 4 |
5587 | =over 4 |
4901 | |
5588 | |
4902 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5589 | =item C<EV_COMPAT3> backwards compatibility mechanism |
4903 | |
5590 | |
4904 | The backward compatibility mechanism can be controlled by |
5591 | The backward compatibility mechanism can be controlled by |
4905 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
5592 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
4906 | section. |
5593 | section. |
4907 | |
5594 | |
4908 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5595 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
4909 | |
5596 | |
4910 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5597 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
… | |
… | |
4953 | =over 4 |
5640 | =over 4 |
4954 | |
5641 | |
4955 | =item active |
5642 | =item active |
4956 | |
5643 | |
4957 | A watcher is active as long as it has been started and not yet stopped. |
5644 | A watcher is active as long as it has been started and not yet stopped. |
4958 | See L<WATCHER STATES> for details. |
5645 | See L</WATCHER STATES> for details. |
4959 | |
5646 | |
4960 | =item application |
5647 | =item application |
4961 | |
5648 | |
4962 | In this document, an application is whatever is using libev. |
5649 | In this document, an application is whatever is using libev. |
4963 | |
5650 | |
… | |
… | |
4999 | watchers and events. |
5686 | watchers and events. |
5000 | |
5687 | |
5001 | =item pending |
5688 | =item pending |
5002 | |
5689 | |
5003 | A watcher is pending as soon as the corresponding event has been |
5690 | A watcher is pending as soon as the corresponding event has been |
5004 | detected. See L<WATCHER STATES> for details. |
5691 | detected. See L</WATCHER STATES> for details. |
5005 | |
5692 | |
5006 | =item real time |
5693 | =item real time |
5007 | |
5694 | |
5008 | The physical time that is observed. It is apparently strictly monotonic :) |
5695 | The physical time that is observed. It is apparently strictly monotonic :) |
5009 | |
5696 | |
5010 | =item wall-clock time |
5697 | =item wall-clock time |
5011 | |
5698 | |
5012 | The time and date as shown on clocks. Unlike real time, it can actually |
5699 | The time and date as shown on clocks. Unlike real time, it can actually |
5013 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5700 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5014 | clock. |
5701 | clock. |
5015 | |
5702 | |
5016 | =item watcher |
5703 | =item watcher |
5017 | |
5704 | |
5018 | A data structure that describes interest in certain events. Watchers need |
5705 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5021 | =back |
5708 | =back |
5022 | |
5709 | |
5023 | =head1 AUTHOR |
5710 | =head1 AUTHOR |
5024 | |
5711 | |
5025 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5712 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5026 | Magnusson and Emanuele Giaquinta. |
5713 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5027 | |
5714 | |