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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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77 | on event-based programming, nor will it introduce event-based programming |
79 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
80 | with libev. |
79 | |
81 | |
80 | Familiarity with event based programming techniques in general is assumed |
82 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
83 | throughout this document. |
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84 | |
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85 | =head1 WHAT TO READ WHEN IN A HURRY |
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86 | |
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87 | This manual tries to be very detailed, but unfortunately, this also makes |
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88 | it very long. If you just want to know the basics of libev, I suggest |
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89 | reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and |
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90 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
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91 | C<ev_timer> sections in L</WATCHER TYPES>. |
82 | |
92 | |
83 | =head1 ABOUT LIBEV |
93 | =head1 ABOUT LIBEV |
84 | |
94 | |
85 | 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 |
86 | 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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166 | =item ev_tstamp ev_time () |
176 | =item ev_tstamp ev_time () |
167 | |
177 | |
168 | Returns the current time as libev would use it. Please note that the |
178 | Returns the current time as libev would use it. Please note that the |
169 | C<ev_now> function is usually faster and also often returns the timestamp |
179 | C<ev_now> function is usually faster and also often returns the timestamp |
170 | you actually want to know. Also interesting is the combination of |
180 | you actually want to know. Also interesting is the combination of |
171 | C<ev_update_now> and C<ev_now>. |
181 | C<ev_now_update> and C<ev_now>. |
172 | |
182 | |
173 | =item ev_sleep (ev_tstamp interval) |
183 | =item ev_sleep (ev_tstamp interval) |
174 | |
184 | |
175 | Sleep for the given interval: The current thread will be blocked until |
185 | Sleep for the given interval: The current thread will be blocked |
176 | either it is interrupted or the given time interval has passed. Basically |
186 | until either it is interrupted or the given time interval has |
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187 | passed (approximately - it might return a bit earlier even if not |
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188 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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189 | |
177 | this is a sub-second-resolution C<sleep ()>. |
190 | Basically this is a sub-second-resolution C<sleep ()>. |
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191 | |
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192 | The range of the C<interval> is limited - libev only guarantees to work |
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193 | with sleep times of up to one day (C<< interval <= 86400 >>). |
178 | |
194 | |
179 | =item int ev_version_major () |
195 | =item int ev_version_major () |
180 | |
196 | |
181 | =item int ev_version_minor () |
197 | =item int ev_version_minor () |
182 | |
198 | |
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233 | the current system, you would need to look at C<ev_embeddable_backends () |
249 | the current system, you would need to look at C<ev_embeddable_backends () |
234 | & ev_supported_backends ()>, likewise for recommended ones. |
250 | & ev_supported_backends ()>, likewise for recommended ones. |
235 | |
251 | |
236 | See the description of C<ev_embed> watchers for more info. |
252 | See the description of C<ev_embed> watchers for more info. |
237 | |
253 | |
238 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
254 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
239 | |
255 | |
240 | Sets the allocation function to use (the prototype is similar - the |
256 | Sets the allocation function to use (the prototype is similar - the |
241 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
257 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
242 | used to allocate and free memory (no surprises here). If it returns zero |
258 | used to allocate and free memory (no surprises here). If it returns zero |
243 | when memory needs to be allocated (C<size != 0>), the library might abort |
259 | when memory needs to be allocated (C<size != 0>), the library might abort |
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269 | } |
285 | } |
270 | |
286 | |
271 | ... |
287 | ... |
272 | ev_set_allocator (persistent_realloc); |
288 | ev_set_allocator (persistent_realloc); |
273 | |
289 | |
274 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
290 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
275 | |
291 | |
276 | Set the callback function to call on a retryable system call error (such |
292 | Set the callback function to call on a retryable system call error (such |
277 | as failed select, poll, epoll_wait). The message is a printable string |
293 | as failed select, poll, epoll_wait). The message is a printable string |
278 | indicating the system call or subsystem causing the problem. If this |
294 | indicating the system call or subsystem causing the problem. If this |
279 | callback is set, then libev will expect it to remedy the situation, no |
295 | callback is set, then libev will expect it to remedy the situation, no |
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291 | } |
307 | } |
292 | |
308 | |
293 | ... |
309 | ... |
294 | ev_set_syserr_cb (fatal_error); |
310 | ev_set_syserr_cb (fatal_error); |
295 | |
311 | |
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312 | =item ev_feed_signal (int signum) |
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313 | |
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314 | This function can be used to "simulate" a signal receive. It is completely |
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315 | safe to call this function at any time, from any context, including signal |
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316 | handlers or random threads. |
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317 | |
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318 | Its main use is to customise signal handling in your process, especially |
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319 | in the presence of threads. For example, you could block signals |
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320 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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321 | creating any loops), and in one thread, use C<sigwait> or any other |
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322 | mechanism to wait for signals, then "deliver" them to libev by calling |
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323 | C<ev_feed_signal>. |
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324 | |
296 | =back |
325 | =back |
297 | |
326 | |
298 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
327 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
299 | |
328 | |
300 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
329 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
301 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
330 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
302 | libev 3 had an C<ev_loop> function colliding with the struct name). |
331 | libev 3 had an C<ev_loop> function colliding with the struct name). |
303 | |
332 | |
304 | The library knows two types of such loops, the I<default> loop, which |
333 | The library knows two types of such loops, the I<default> loop, which |
305 | supports signals and child events, and dynamically created event loops |
334 | supports child process events, and dynamically created event loops which |
306 | which do not. |
335 | do not. |
307 | |
336 | |
308 | =over 4 |
337 | =over 4 |
309 | |
338 | |
310 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
339 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
311 | |
340 | |
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347 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
376 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
348 | |
377 | |
349 | This will create and initialise a new event loop object. If the loop |
378 | This will create and initialise a new event loop object. If the loop |
350 | could not be initialised, returns false. |
379 | could not be initialised, returns false. |
351 | |
380 | |
352 | Note that this function I<is> thread-safe, and one common way to use |
381 | This function is thread-safe, and one common way to use libev with |
353 | libev with threads is indeed to create one loop per thread, and using the |
382 | threads is indeed to create one loop per thread, and using the default |
354 | default loop in the "main" or "initial" thread. |
383 | loop in the "main" or "initial" thread. |
355 | |
384 | |
356 | The flags argument can be used to specify special behaviour or specific |
385 | The flags argument can be used to specify special behaviour or specific |
357 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
386 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
358 | |
387 | |
359 | The following flags are supported: |
388 | The following flags are supported: |
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369 | |
398 | |
370 | If this flag bit is or'ed into the flag value (or the program runs setuid |
399 | If this flag bit is or'ed into the flag value (or the program runs setuid |
371 | or setgid) then libev will I<not> look at the environment variable |
400 | or setgid) then libev will I<not> look at the environment variable |
372 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
401 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
373 | override the flags completely if it is found in the environment. This is |
402 | override the flags completely if it is found in the environment. This is |
374 | useful to try out specific backends to test their performance, or to work |
403 | useful to try out specific backends to test their performance, to work |
375 | around bugs. |
404 | around bugs, or to make libev threadsafe (accessing environment variables |
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405 | cannot be done in a threadsafe way, but usually it works if no other |
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406 | thread modifies them). |
376 | |
407 | |
377 | =item C<EVFLAG_FORKCHECK> |
408 | =item C<EVFLAG_FORKCHECK> |
378 | |
409 | |
379 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
410 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
380 | make libev check for a fork in each iteration by enabling this flag. |
411 | make libev check for a fork in each iteration by enabling this flag. |
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394 | environment variable. |
425 | environment variable. |
395 | |
426 | |
396 | =item C<EVFLAG_NOINOTIFY> |
427 | =item C<EVFLAG_NOINOTIFY> |
397 | |
428 | |
398 | When this flag is specified, then libev will not attempt to use the |
429 | When this flag is specified, then libev will not attempt to use the |
399 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
430 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
400 | testing, this flag can be useful to conserve inotify file descriptors, as |
431 | testing, this flag can be useful to conserve inotify file descriptors, as |
401 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
432 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
402 | |
433 | |
403 | =item C<EVFLAG_SIGNALFD> |
434 | =item C<EVFLAG_SIGNALFD> |
404 | |
435 | |
405 | When this flag is specified, then libev will attempt to use the |
436 | When this flag is specified, then libev will attempt to use the |
406 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
437 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
407 | delivers signals synchronously, which makes it both faster and might make |
438 | delivers signals synchronously, which makes it both faster and might make |
408 | it possible to get the queued signal data. It can also simplify signal |
439 | it possible to get the queued signal data. It can also simplify signal |
409 | handling with threads, as long as you properly block signals in your |
440 | handling with threads, as long as you properly block signals in your |
410 | threads that are not interested in handling them. |
441 | threads that are not interested in handling them. |
411 | |
442 | |
412 | Signalfd will not be used by default as this changes your signal mask, and |
443 | Signalfd will not be used by default as this changes your signal mask, and |
413 | there are a lot of shoddy libraries and programs (glib's threadpool for |
444 | there are a lot of shoddy libraries and programs (glib's threadpool for |
414 | example) that can't properly initialise their signal masks. |
445 | example) that can't properly initialise their signal masks. |
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446 | |
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447 | =item C<EVFLAG_NOSIGMASK> |
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448 | |
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449 | When this flag is specified, then libev will avoid to modify the signal |
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450 | mask. Specifically, this means you have to make sure signals are unblocked |
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451 | when you want to receive them. |
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452 | |
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453 | This behaviour is useful when you want to do your own signal handling, or |
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454 | want to handle signals only in specific threads and want to avoid libev |
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455 | unblocking the signals. |
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456 | |
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457 | It's also required by POSIX in a threaded program, as libev calls |
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458 | C<sigprocmask>, whose behaviour is officially unspecified. |
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459 | |
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460 | This flag's behaviour will become the default in future versions of libev. |
415 | |
461 | |
416 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
462 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
417 | |
463 | |
418 | This is your standard select(2) backend. Not I<completely> standard, as |
464 | This is your standard select(2) backend. Not I<completely> standard, as |
419 | libev tries to roll its own fd_set with no limits on the number of fds, |
465 | libev tries to roll its own fd_set with no limits on the number of fds, |
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447 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
493 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
448 | |
494 | |
449 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
495 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
450 | kernels). |
496 | kernels). |
451 | |
497 | |
452 | For few fds, this backend is a bit little slower than poll and select, |
498 | For few fds, this backend is a bit little slower than poll and select, but |
453 | but it scales phenomenally better. While poll and select usually scale |
499 | it scales phenomenally better. While poll and select usually scale like |
454 | like O(total_fds) where n is the total number of fds (or the highest fd), |
500 | O(total_fds) where total_fds is the total number of fds (or the highest |
455 | epoll scales either O(1) or O(active_fds). |
501 | fd), epoll scales either O(1) or O(active_fds). |
456 | |
502 | |
457 | The epoll mechanism deserves honorable mention as the most misdesigned |
503 | The epoll mechanism deserves honorable mention as the most misdesigned |
458 | of the more advanced event mechanisms: mere annoyances include silently |
504 | of the more advanced event mechanisms: mere annoyances include silently |
459 | dropping file descriptors, requiring a system call per change per file |
505 | dropping file descriptors, requiring a system call per change per file |
460 | descriptor (and unnecessary guessing of parameters), problems with dup and |
506 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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507 | returning before the timeout value, resulting in additional iterations |
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508 | (and only giving 5ms accuracy while select on the same platform gives |
461 | so on. The biggest issue is fork races, however - if a program forks then |
509 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
462 | I<both> parent and child process have to recreate the epoll set, which can |
510 | forks then I<both> parent and child process have to recreate the epoll |
463 | take considerable time (one syscall per file descriptor) and is of course |
511 | set, which can take considerable time (one syscall per file descriptor) |
464 | hard to detect. |
512 | and is of course hard to detect. |
465 | |
513 | |
466 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
514 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
467 | of course I<doesn't>, and epoll just loves to report events for totally |
515 | but of course I<doesn't>, and epoll just loves to report events for |
468 | I<different> file descriptors (even already closed ones, so one cannot |
516 | totally I<different> file descriptors (even already closed ones, so |
469 | even remove them from the set) than registered in the set (especially |
517 | one cannot even remove them from the set) than registered in the set |
470 | on SMP systems). Libev tries to counter these spurious notifications by |
518 | (especially on SMP systems). Libev tries to counter these spurious |
471 | employing an additional generation counter and comparing that against the |
519 | notifications by employing an additional generation counter and comparing |
472 | events to filter out spurious ones, recreating the set when required. Last |
520 | that against the events to filter out spurious ones, recreating the set |
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521 | when required. Epoll also erroneously rounds down timeouts, but gives you |
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522 | no way to know when and by how much, so sometimes you have to busy-wait |
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523 | because epoll returns immediately despite a nonzero timeout. And last |
473 | not least, it also refuses to work with some file descriptors which work |
524 | not least, it also refuses to work with some file descriptors which work |
474 | perfectly fine with C<select> (files, many character devices...). |
525 | perfectly fine with C<select> (files, many character devices...). |
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526 | |
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527 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
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528 | cobbled together in a hurry, no thought to design or interaction with |
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529 | others. Oh, the pain, will it ever stop... |
475 | |
530 | |
476 | While stopping, setting and starting an I/O watcher in the same iteration |
531 | While stopping, setting and starting an I/O watcher in the same iteration |
477 | will result in some caching, there is still a system call per such |
532 | will result in some caching, there is still a system call per such |
478 | incident (because the same I<file descriptor> could point to a different |
533 | incident (because the same I<file descriptor> could point to a different |
479 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
534 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
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516 | |
571 | |
517 | It scales in the same way as the epoll backend, but the interface to the |
572 | It scales in the same way as the epoll backend, but the interface to the |
518 | kernel is more efficient (which says nothing about its actual speed, of |
573 | kernel is more efficient (which says nothing about its actual speed, of |
519 | course). While stopping, setting and starting an I/O watcher does never |
574 | course). While stopping, setting and starting an I/O watcher does never |
520 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
575 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
521 | two event changes per incident. Support for C<fork ()> is very bad (but |
576 | two event changes per incident. Support for C<fork ()> is very bad (you |
522 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
577 | might have to leak fd's on fork, but it's more sane than epoll) and it |
523 | cases |
578 | drops fds silently in similarly hard-to-detect cases. |
524 | |
579 | |
525 | This backend usually performs well under most conditions. |
580 | This backend usually performs well under most conditions. |
526 | |
581 | |
527 | While nominally embeddable in other event loops, this doesn't work |
582 | While nominally embeddable in other event loops, this doesn't work |
528 | everywhere, so you might need to test for this. And since it is broken |
583 | everywhere, so you might need to test for this. And since it is broken |
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545 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
600 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
546 | |
601 | |
547 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
602 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
548 | it's really slow, but it still scales very well (O(active_fds)). |
603 | it's really slow, but it still scales very well (O(active_fds)). |
549 | |
604 | |
550 | Please note that Solaris event ports can deliver a lot of spurious |
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551 | notifications, so you need to use non-blocking I/O or other means to avoid |
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552 | blocking when no data (or space) is available. |
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553 | |
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554 | While this backend scales well, it requires one system call per active |
605 | While this backend scales well, it requires one system call per active |
555 | file descriptor per loop iteration. For small and medium numbers of file |
606 | file descriptor per loop iteration. For small and medium numbers of file |
556 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
607 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
557 | might perform better. |
608 | might perform better. |
558 | |
609 | |
559 | On the positive side, with the exception of the spurious readiness |
610 | On the positive side, this backend actually performed fully to |
560 | notifications, this backend actually performed fully to specification |
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561 | in all tests and is fully embeddable, which is a rare feat among the |
611 | specification in all tests and is fully embeddable, which is a rare feat |
562 | OS-specific backends (I vastly prefer correctness over speed hacks). |
612 | among the OS-specific backends (I vastly prefer correctness over speed |
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613 | hacks). |
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614 | |
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615 | On the negative side, the interface is I<bizarre> - so bizarre that |
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616 | even sun itself gets it wrong in their code examples: The event polling |
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617 | function sometimes returns events to the caller even though an error |
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618 | occurred, but with no indication whether it has done so or not (yes, it's |
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619 | even documented that way) - deadly for edge-triggered interfaces where you |
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620 | absolutely have to know whether an event occurred or not because you have |
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621 | to re-arm the watcher. |
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622 | |
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623 | Fortunately libev seems to be able to work around these idiocies. |
563 | |
624 | |
564 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
625 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
565 | C<EVBACKEND_POLL>. |
626 | C<EVBACKEND_POLL>. |
566 | |
627 | |
567 | =item C<EVBACKEND_ALL> |
628 | =item C<EVBACKEND_ALL> |
568 | |
629 | |
569 | Try all backends (even potentially broken ones that wouldn't be tried |
630 | Try all backends (even potentially broken ones that wouldn't be tried |
570 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
631 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
571 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
632 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
572 | |
633 | |
573 | It is definitely not recommended to use this flag. |
634 | It is definitely not recommended to use this flag, use whatever |
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635 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
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636 | at all. |
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637 | |
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638 | =item C<EVBACKEND_MASK> |
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639 | |
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640 | Not a backend at all, but a mask to select all backend bits from a |
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641 | C<flags> value, in case you want to mask out any backends from a flags |
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642 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
574 | |
643 | |
575 | =back |
644 | =back |
576 | |
645 | |
577 | If one or more of the backend flags are or'ed into the flags value, |
646 | If one or more of the backend flags are or'ed into the flags value, |
578 | then only these backends will be tried (in the reverse order as listed |
647 | then only these backends will be tried (in the reverse order as listed |
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607 | This function is normally used on loop objects allocated by |
676 | This function is normally used on loop objects allocated by |
608 | C<ev_loop_new>, but it can also be used on the default loop returned by |
677 | C<ev_loop_new>, but it can also be used on the default loop returned by |
609 | C<ev_default_loop>, in which case it is not thread-safe. |
678 | C<ev_default_loop>, in which case it is not thread-safe. |
610 | |
679 | |
611 | Note that it is not advisable to call this function on the default loop |
680 | Note that it is not advisable to call this function on the default loop |
612 | except in the rare occasion where you really need to free it's resources. |
681 | except in the rare occasion where you really need to free its resources. |
613 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
682 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
614 | and C<ev_loop_destroy>. |
683 | and C<ev_loop_destroy>. |
615 | |
684 | |
616 | =item ev_loop_fork (loop) |
685 | =item ev_loop_fork (loop) |
617 | |
686 | |
618 | This function sets a flag that causes subsequent C<ev_run> iterations to |
687 | This function sets a flag that causes subsequent C<ev_run> iterations |
619 | reinitialise the kernel state for backends that have one. Despite the |
688 | to reinitialise the kernel state for backends that have one. Despite |
620 | name, you can call it anytime, but it makes most sense after forking, in |
689 | the name, you can call it anytime you are allowed to start or stop |
621 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
690 | watchers (except inside an C<ev_prepare> callback), but it makes most |
|
|
691 | sense after forking, in the child process. You I<must> call it (or use |
622 | child before resuming or calling C<ev_run>. |
692 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
623 | |
693 | |
624 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
694 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
625 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
695 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
626 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
696 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
627 | during fork. |
697 | during fork. |
628 | |
698 | |
629 | On the other hand, you only need to call this function in the child |
699 | On the other hand, you only need to call this function in the child |
… | |
… | |
665 | prepare and check phases. |
735 | prepare and check phases. |
666 | |
736 | |
667 | =item unsigned int ev_depth (loop) |
737 | =item unsigned int ev_depth (loop) |
668 | |
738 | |
669 | Returns the number of times C<ev_run> was entered minus the number of |
739 | Returns the number of times C<ev_run> was entered minus the number of |
670 | times C<ev_run> was exited, in other words, the recursion depth. |
740 | times C<ev_run> was exited normally, in other words, the recursion depth. |
671 | |
741 | |
672 | Outside C<ev_run>, this number is zero. In a callback, this number is |
742 | Outside C<ev_run>, this number is zero. In a callback, this number is |
673 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
743 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
674 | in which case it is higher. |
744 | in which case it is higher. |
675 | |
745 | |
676 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
746 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
677 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
747 | throwing an exception etc.), doesn't count as "exit" - consider this |
678 | ungentleman-like behaviour unless it's really convenient. |
748 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
749 | convenient, in which case it is fully supported. |
679 | |
750 | |
680 | =item unsigned int ev_backend (loop) |
751 | =item unsigned int ev_backend (loop) |
681 | |
752 | |
682 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
753 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
683 | use. |
754 | use. |
… | |
… | |
698 | |
769 | |
699 | This function is rarely useful, but when some event callback runs for a |
770 | This function is rarely useful, but when some event callback runs for a |
700 | very long time without entering the event loop, updating libev's idea of |
771 | very long time without entering the event loop, updating libev's idea of |
701 | the current time is a good idea. |
772 | the current time is a good idea. |
702 | |
773 | |
703 | See also L<The special problem of time updates> in the C<ev_timer> section. |
774 | See also L</The special problem of time updates> in the C<ev_timer> section. |
704 | |
775 | |
705 | =item ev_suspend (loop) |
776 | =item ev_suspend (loop) |
706 | |
777 | |
707 | =item ev_resume (loop) |
778 | =item ev_resume (loop) |
708 | |
779 | |
… | |
… | |
726 | without a previous call to C<ev_suspend>. |
797 | without a previous call to C<ev_suspend>. |
727 | |
798 | |
728 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
799 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
729 | event loop time (see C<ev_now_update>). |
800 | event loop time (see C<ev_now_update>). |
730 | |
801 | |
731 | =item ev_run (loop, int flags) |
802 | =item bool ev_run (loop, int flags) |
732 | |
803 | |
733 | Finally, this is it, the event handler. This function usually is called |
804 | Finally, this is it, the event handler. This function usually is called |
734 | after you have initialised all your watchers and you want to start |
805 | after you have initialised all your watchers and you want to start |
735 | handling events. It will ask the operating system for any new events, call |
806 | handling events. It will ask the operating system for any new events, call |
736 | the watcher callbacks, an then repeat the whole process indefinitely: This |
807 | the watcher callbacks, and then repeat the whole process indefinitely: This |
737 | is why event loops are called I<loops>. |
808 | is why event loops are called I<loops>. |
738 | |
809 | |
739 | If the flags argument is specified as C<0>, it will keep handling events |
810 | If the flags argument is specified as C<0>, it will keep handling events |
740 | until either no event watchers are active anymore or C<ev_break> was |
811 | until either no event watchers are active anymore or C<ev_break> was |
741 | called. |
812 | called. |
|
|
813 | |
|
|
814 | The return value is false if there are no more active watchers (which |
|
|
815 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
816 | (which usually means " you should call C<ev_run> again"). |
742 | |
817 | |
743 | Please note that an explicit C<ev_break> is usually better than |
818 | Please note that an explicit C<ev_break> is usually better than |
744 | relying on all watchers to be stopped when deciding when a program has |
819 | relying on all watchers to be stopped when deciding when a program has |
745 | finished (especially in interactive programs), but having a program |
820 | finished (especially in interactive programs), but having a program |
746 | that automatically loops as long as it has to and no longer by virtue |
821 | that automatically loops as long as it has to and no longer by virtue |
747 | of relying on its watchers stopping correctly, that is truly a thing of |
822 | of relying on its watchers stopping correctly, that is truly a thing of |
748 | beauty. |
823 | beauty. |
749 | |
824 | |
|
|
825 | This function is I<mostly> exception-safe - you can break out of a |
|
|
826 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
827 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
828 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
829 | |
750 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
830 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
751 | those events and any already outstanding ones, but will not wait and |
831 | those events and any already outstanding ones, but will not wait and |
752 | block your process in case there are no events and will return after one |
832 | block your process in case there are no events and will return after one |
753 | iteration of the loop. This is sometimes useful to poll and handle new |
833 | iteration of the loop. This is sometimes useful to poll and handle new |
754 | events while doing lengthy calculations, to keep the program responsive. |
834 | events while doing lengthy calculations, to keep the program responsive. |
… | |
… | |
763 | This is useful if you are waiting for some external event in conjunction |
843 | This is useful if you are waiting for some external event in conjunction |
764 | with something not expressible using other libev watchers (i.e. "roll your |
844 | with something not expressible using other libev watchers (i.e. "roll your |
765 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
845 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
766 | usually a better approach for this kind of thing. |
846 | usually a better approach for this kind of thing. |
767 | |
847 | |
768 | Here are the gory details of what C<ev_run> does: |
848 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
849 | understanding, not a guarantee that things will work exactly like this in |
|
|
850 | future versions): |
769 | |
851 | |
770 | - Increment loop depth. |
852 | - Increment loop depth. |
771 | - Reset the ev_break status. |
853 | - Reset the ev_break status. |
772 | - Before the first iteration, call any pending watchers. |
854 | - Before the first iteration, call any pending watchers. |
773 | LOOP: |
855 | LOOP: |
… | |
… | |
806 | anymore. |
888 | anymore. |
807 | |
889 | |
808 | ... queue jobs here, make sure they register event watchers as long |
890 | ... queue jobs here, make sure they register event watchers as long |
809 | ... as they still have work to do (even an idle watcher will do..) |
891 | ... as they still have work to do (even an idle watcher will do..) |
810 | ev_run (my_loop, 0); |
892 | ev_run (my_loop, 0); |
811 | ... jobs done or somebody called unloop. yeah! |
893 | ... jobs done or somebody called break. yeah! |
812 | |
894 | |
813 | =item ev_break (loop, how) |
895 | =item ev_break (loop, how) |
814 | |
896 | |
815 | Can be used to make a call to C<ev_run> return early (but only after it |
897 | Can be used to make a call to C<ev_run> return early (but only after it |
816 | has processed all outstanding events). The C<how> argument must be either |
898 | has processed all outstanding events). The C<how> argument must be either |
817 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
899 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
818 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
900 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
819 | |
901 | |
820 | This "unloop state" will be cleared when entering C<ev_run> again. |
902 | This "break state" will be cleared on the next call to C<ev_run>. |
821 | |
903 | |
822 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
904 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
905 | which case it will have no effect. |
823 | |
906 | |
824 | =item ev_ref (loop) |
907 | =item ev_ref (loop) |
825 | |
908 | |
826 | =item ev_unref (loop) |
909 | =item ev_unref (loop) |
827 | |
910 | |
… | |
… | |
848 | running when nothing else is active. |
931 | running when nothing else is active. |
849 | |
932 | |
850 | ev_signal exitsig; |
933 | ev_signal exitsig; |
851 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
934 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
852 | ev_signal_start (loop, &exitsig); |
935 | ev_signal_start (loop, &exitsig); |
853 | evf_unref (loop); |
936 | ev_unref (loop); |
854 | |
937 | |
855 | Example: For some weird reason, unregister the above signal handler again. |
938 | Example: For some weird reason, unregister the above signal handler again. |
856 | |
939 | |
857 | ev_ref (loop); |
940 | ev_ref (loop); |
858 | ev_signal_stop (loop, &exitsig); |
941 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
878 | overhead for the actual polling but can deliver many events at once. |
961 | overhead for the actual polling but can deliver many events at once. |
879 | |
962 | |
880 | By setting a higher I<io collect interval> you allow libev to spend more |
963 | By setting a higher I<io collect interval> you allow libev to spend more |
881 | time collecting I/O events, so you can handle more events per iteration, |
964 | time collecting I/O events, so you can handle more events per iteration, |
882 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
965 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
883 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
966 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
884 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
967 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
885 | sleep time ensures that libev will not poll for I/O events more often then |
968 | sleep time ensures that libev will not poll for I/O events more often then |
886 | once per this interval, on average. |
969 | once per this interval, on average (as long as the host time resolution is |
|
|
970 | good enough). |
887 | |
971 | |
888 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
972 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
889 | to spend more time collecting timeouts, at the expense of increased |
973 | to spend more time collecting timeouts, at the expense of increased |
890 | latency/jitter/inexactness (the watcher callback will be called |
974 | latency/jitter/inexactness (the watcher callback will be called |
891 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
975 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
937 | invoke the actual watchers inside another context (another thread etc.). |
1021 | invoke the actual watchers inside another context (another thread etc.). |
938 | |
1022 | |
939 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1023 | If you want to reset the callback, use C<ev_invoke_pending> as new |
940 | callback. |
1024 | callback. |
941 | |
1025 | |
942 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1026 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
943 | |
1027 | |
944 | Sometimes you want to share the same loop between multiple threads. This |
1028 | Sometimes you want to share the same loop between multiple threads. This |
945 | can be done relatively simply by putting mutex_lock/unlock calls around |
1029 | can be done relatively simply by putting mutex_lock/unlock calls around |
946 | each call to a libev function. |
1030 | each call to a libev function. |
947 | |
1031 | |
948 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1032 | However, C<ev_run> can run an indefinite time, so it is not feasible |
949 | to wait for it to return. One way around this is to wake up the event |
1033 | to wait for it to return. One way around this is to wake up the event |
950 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1034 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
951 | I<release> and I<acquire> callbacks on the loop. |
1035 | I<release> and I<acquire> callbacks on the loop. |
952 | |
1036 | |
953 | When set, then C<release> will be called just before the thread is |
1037 | When set, then C<release> will be called just before the thread is |
954 | suspended waiting for new events, and C<acquire> is called just |
1038 | suspended waiting for new events, and C<acquire> is called just |
955 | afterwards. |
1039 | afterwards. |
… | |
… | |
970 | See also the locking example in the C<THREADS> section later in this |
1054 | See also the locking example in the C<THREADS> section later in this |
971 | document. |
1055 | document. |
972 | |
1056 | |
973 | =item ev_set_userdata (loop, void *data) |
1057 | =item ev_set_userdata (loop, void *data) |
974 | |
1058 | |
975 | =item ev_userdata (loop) |
1059 | =item void *ev_userdata (loop) |
976 | |
1060 | |
977 | Set and retrieve a single C<void *> associated with a loop. When |
1061 | Set and retrieve a single C<void *> associated with a loop. When |
978 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1062 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
979 | C<0.> |
1063 | C<0>. |
980 | |
1064 | |
981 | These two functions can be used to associate arbitrary data with a loop, |
1065 | These two functions can be used to associate arbitrary data with a loop, |
982 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1066 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
983 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1067 | C<acquire> callbacks described above, but of course can be (ab-)used for |
984 | any other purpose as well. |
1068 | any other purpose as well. |
… | |
… | |
1095 | |
1179 | |
1096 | =item C<EV_PREPARE> |
1180 | =item C<EV_PREPARE> |
1097 | |
1181 | |
1098 | =item C<EV_CHECK> |
1182 | =item C<EV_CHECK> |
1099 | |
1183 | |
1100 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1184 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1101 | to gather new events, and all C<ev_check> watchers are invoked just after |
1185 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1102 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1186 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1187 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1188 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1189 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1190 | or lower priority within an event loop iteration. |
|
|
1191 | |
1103 | received events. Callbacks of both watcher types can start and stop as |
1192 | Callbacks of both watcher types can start and stop as many watchers as |
1104 | many watchers as they want, and all of them will be taken into account |
1193 | they want, and all of them will be taken into account (for example, a |
1105 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1194 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1106 | C<ev_run> from blocking). |
1195 | blocking). |
1107 | |
1196 | |
1108 | =item C<EV_EMBED> |
1197 | =item C<EV_EMBED> |
1109 | |
1198 | |
1110 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1199 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1111 | |
1200 | |
… | |
… | |
1114 | The event loop has been resumed in the child process after fork (see |
1203 | The event loop has been resumed in the child process after fork (see |
1115 | C<ev_fork>). |
1204 | C<ev_fork>). |
1116 | |
1205 | |
1117 | =item C<EV_CLEANUP> |
1206 | =item C<EV_CLEANUP> |
1118 | |
1207 | |
1119 | The event loop is abotu to be destroyed (see C<ev_cleanup>). |
1208 | The event loop is about to be destroyed (see C<ev_cleanup>). |
1120 | |
1209 | |
1121 | =item C<EV_ASYNC> |
1210 | =item C<EV_ASYNC> |
1122 | |
1211 | |
1123 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1212 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1124 | |
1213 | |
… | |
… | |
1146 | programs, though, as the fd could already be closed and reused for another |
1235 | programs, though, as the fd could already be closed and reused for another |
1147 | thing, so beware. |
1236 | thing, so beware. |
1148 | |
1237 | |
1149 | =back |
1238 | =back |
1150 | |
1239 | |
|
|
1240 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1241 | |
|
|
1242 | =over 4 |
|
|
1243 | |
|
|
1244 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1245 | |
|
|
1246 | This macro initialises the generic portion of a watcher. The contents |
|
|
1247 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1248 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1249 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1250 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1251 | which rolls both calls into one. |
|
|
1252 | |
|
|
1253 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1254 | (or never started) and there are no pending events outstanding. |
|
|
1255 | |
|
|
1256 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1257 | int revents)>. |
|
|
1258 | |
|
|
1259 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1260 | |
|
|
1261 | ev_io w; |
|
|
1262 | ev_init (&w, my_cb); |
|
|
1263 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1264 | |
|
|
1265 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1266 | |
|
|
1267 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1268 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1269 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1270 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1271 | difference to the C<ev_init> macro). |
|
|
1272 | |
|
|
1273 | Although some watcher types do not have type-specific arguments |
|
|
1274 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1275 | |
|
|
1276 | See C<ev_init>, above, for an example. |
|
|
1277 | |
|
|
1278 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1279 | |
|
|
1280 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1281 | calls into a single call. This is the most convenient method to initialise |
|
|
1282 | a watcher. The same limitations apply, of course. |
|
|
1283 | |
|
|
1284 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1285 | |
|
|
1286 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1287 | |
|
|
1288 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1289 | |
|
|
1290 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1291 | events. If the watcher is already active nothing will happen. |
|
|
1292 | |
|
|
1293 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1294 | whole section. |
|
|
1295 | |
|
|
1296 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1297 | |
|
|
1298 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1299 | |
|
|
1300 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1301 | the watcher was active or not). |
|
|
1302 | |
|
|
1303 | It is possible that stopped watchers are pending - for example, |
|
|
1304 | non-repeating timers are being stopped when they become pending - but |
|
|
1305 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1306 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1307 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1308 | |
|
|
1309 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1310 | |
|
|
1311 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1312 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1313 | it. |
|
|
1314 | |
|
|
1315 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1316 | |
|
|
1317 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1318 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1319 | is pending (but not active) you must not call an init function on it (but |
|
|
1320 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1321 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1322 | it). |
|
|
1323 | |
|
|
1324 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1325 | |
|
|
1326 | Returns the callback currently set on the watcher. |
|
|
1327 | |
|
|
1328 | =item ev_set_cb (ev_TYPE *watcher, callback) |
|
|
1329 | |
|
|
1330 | Change the callback. You can change the callback at virtually any time |
|
|
1331 | (modulo threads). |
|
|
1332 | |
|
|
1333 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1334 | |
|
|
1335 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1336 | |
|
|
1337 | Set and query the priority of the watcher. The priority is a small |
|
|
1338 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1339 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1340 | before watchers with lower priority, but priority will not keep watchers |
|
|
1341 | from being executed (except for C<ev_idle> watchers). |
|
|
1342 | |
|
|
1343 | If you need to suppress invocation when higher priority events are pending |
|
|
1344 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1345 | |
|
|
1346 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1347 | pending. |
|
|
1348 | |
|
|
1349 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1350 | fine, as long as you do not mind that the priority value you query might |
|
|
1351 | or might not have been clamped to the valid range. |
|
|
1352 | |
|
|
1353 | The default priority used by watchers when no priority has been set is |
|
|
1354 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1355 | |
|
|
1356 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1357 | priorities. |
|
|
1358 | |
|
|
1359 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1360 | |
|
|
1361 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1362 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1363 | can deal with that fact, as both are simply passed through to the |
|
|
1364 | callback. |
|
|
1365 | |
|
|
1366 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1367 | |
|
|
1368 | If the watcher is pending, this function clears its pending status and |
|
|
1369 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1370 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1371 | |
|
|
1372 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1373 | callback to be invoked, which can be accomplished with this function. |
|
|
1374 | |
|
|
1375 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1376 | |
|
|
1377 | Feeds the given event set into the event loop, as if the specified event |
|
|
1378 | had happened for the specified watcher (which must be a pointer to an |
|
|
1379 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1380 | not free the watcher as long as it has pending events. |
|
|
1381 | |
|
|
1382 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1383 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1384 | not started in the first place. |
|
|
1385 | |
|
|
1386 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1387 | functions that do not need a watcher. |
|
|
1388 | |
|
|
1389 | =back |
|
|
1390 | |
|
|
1391 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
|
|
1392 | OWN COMPOSITE WATCHERS> idioms. |
|
|
1393 | |
1151 | =head2 WATCHER STATES |
1394 | =head2 WATCHER STATES |
1152 | |
1395 | |
1153 | There are various watcher states mentioned throughout this manual - |
1396 | There are various watcher states mentioned throughout this manual - |
1154 | active, pending and so on. In this section these states and the rules to |
1397 | active, pending and so on. In this section these states and the rules to |
1155 | transition between them will be described in more detail - and while these |
1398 | transition between them will be described in more detail - and while these |
1156 | rules might look complicated, they usually do "the right thing". |
1399 | rules might look complicated, they usually do "the right thing". |
1157 | |
1400 | |
1158 | =over 4 |
1401 | =over 4 |
1159 | |
1402 | |
1160 | =item initialiased |
1403 | =item initialised |
1161 | |
1404 | |
1162 | Before a watcher can be registered with the event looop it has to be |
1405 | Before a watcher can be registered with the event loop it has to be |
1163 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1406 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1164 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1407 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1165 | |
1408 | |
1166 | In this state it is simply some block of memory that is suitable for use |
1409 | In this state it is simply some block of memory that is suitable for |
1167 | in an event loop. It can be moved around, freed, reused etc. at will. |
1410 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1411 | will - as long as you either keep the memory contents intact, or call |
|
|
1412 | C<ev_TYPE_init> again. |
1168 | |
1413 | |
1169 | =item started/running/active |
1414 | =item started/running/active |
1170 | |
1415 | |
1171 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1416 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1172 | property of the event loop, and is actively waiting for events. While in |
1417 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1200 | latter will clear any pending state the watcher might be in, regardless |
1445 | latter will clear any pending state the watcher might be in, regardless |
1201 | of whether it was active or not, so stopping a watcher explicitly before |
1446 | of whether it was active or not, so stopping a watcher explicitly before |
1202 | freeing it is often a good idea. |
1447 | freeing it is often a good idea. |
1203 | |
1448 | |
1204 | While stopped (and not pending) the watcher is essentially in the |
1449 | While stopped (and not pending) the watcher is essentially in the |
1205 | initialised state, that is it can be reused, moved, modified in any way |
1450 | initialised state, that is, it can be reused, moved, modified in any way |
1206 | you wish. |
1451 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1452 | it again). |
1207 | |
1453 | |
1208 | =back |
1454 | =back |
1209 | |
|
|
1210 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1211 | |
|
|
1212 | =over 4 |
|
|
1213 | |
|
|
1214 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1215 | |
|
|
1216 | This macro initialises the generic portion of a watcher. The contents |
|
|
1217 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1218 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1219 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1220 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1221 | which rolls both calls into one. |
|
|
1222 | |
|
|
1223 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1224 | (or never started) and there are no pending events outstanding. |
|
|
1225 | |
|
|
1226 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1227 | int revents)>. |
|
|
1228 | |
|
|
1229 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1230 | |
|
|
1231 | ev_io w; |
|
|
1232 | ev_init (&w, my_cb); |
|
|
1233 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1234 | |
|
|
1235 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1236 | |
|
|
1237 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1238 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1239 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1240 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1241 | difference to the C<ev_init> macro). |
|
|
1242 | |
|
|
1243 | Although some watcher types do not have type-specific arguments |
|
|
1244 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1245 | |
|
|
1246 | See C<ev_init>, above, for an example. |
|
|
1247 | |
|
|
1248 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1249 | |
|
|
1250 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1251 | calls into a single call. This is the most convenient method to initialise |
|
|
1252 | a watcher. The same limitations apply, of course. |
|
|
1253 | |
|
|
1254 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1255 | |
|
|
1256 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1257 | |
|
|
1258 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1259 | |
|
|
1260 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1261 | events. If the watcher is already active nothing will happen. |
|
|
1262 | |
|
|
1263 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1264 | whole section. |
|
|
1265 | |
|
|
1266 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1267 | |
|
|
1268 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1269 | |
|
|
1270 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1271 | the watcher was active or not). |
|
|
1272 | |
|
|
1273 | It is possible that stopped watchers are pending - for example, |
|
|
1274 | non-repeating timers are being stopped when they become pending - but |
|
|
1275 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1276 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1277 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1278 | |
|
|
1279 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1280 | |
|
|
1281 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1282 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1283 | it. |
|
|
1284 | |
|
|
1285 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1286 | |
|
|
1287 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1288 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1289 | is pending (but not active) you must not call an init function on it (but |
|
|
1290 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1291 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1292 | it). |
|
|
1293 | |
|
|
1294 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1295 | |
|
|
1296 | Returns the callback currently set on the watcher. |
|
|
1297 | |
|
|
1298 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
1299 | |
|
|
1300 | Change the callback. You can change the callback at virtually any time |
|
|
1301 | (modulo threads). |
|
|
1302 | |
|
|
1303 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1304 | |
|
|
1305 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1306 | |
|
|
1307 | Set and query the priority of the watcher. The priority is a small |
|
|
1308 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1309 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1310 | before watchers with lower priority, but priority will not keep watchers |
|
|
1311 | from being executed (except for C<ev_idle> watchers). |
|
|
1312 | |
|
|
1313 | If you need to suppress invocation when higher priority events are pending |
|
|
1314 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1315 | |
|
|
1316 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1317 | pending. |
|
|
1318 | |
|
|
1319 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1320 | fine, as long as you do not mind that the priority value you query might |
|
|
1321 | or might not have been clamped to the valid range. |
|
|
1322 | |
|
|
1323 | The default priority used by watchers when no priority has been set is |
|
|
1324 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1325 | |
|
|
1326 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1327 | priorities. |
|
|
1328 | |
|
|
1329 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1330 | |
|
|
1331 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1332 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1333 | can deal with that fact, as both are simply passed through to the |
|
|
1334 | callback. |
|
|
1335 | |
|
|
1336 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1337 | |
|
|
1338 | If the watcher is pending, this function clears its pending status and |
|
|
1339 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1340 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1341 | |
|
|
1342 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1343 | callback to be invoked, which can be accomplished with this function. |
|
|
1344 | |
|
|
1345 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1346 | |
|
|
1347 | Feeds the given event set into the event loop, as if the specified event |
|
|
1348 | had happened for the specified watcher (which must be a pointer to an |
|
|
1349 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1350 | not free the watcher as long as it has pending events. |
|
|
1351 | |
|
|
1352 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1353 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1354 | not started in the first place. |
|
|
1355 | |
|
|
1356 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1357 | functions that do not need a watcher. |
|
|
1358 | |
|
|
1359 | =back |
|
|
1360 | |
|
|
1361 | |
|
|
1362 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
1363 | |
|
|
1364 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1365 | and read at any time: libev will completely ignore it. This can be used |
|
|
1366 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1367 | don't want to allocate memory and store a pointer to it in that data |
|
|
1368 | member, you can also "subclass" the watcher type and provide your own |
|
|
1369 | data: |
|
|
1370 | |
|
|
1371 | struct my_io |
|
|
1372 | { |
|
|
1373 | ev_io io; |
|
|
1374 | int otherfd; |
|
|
1375 | void *somedata; |
|
|
1376 | struct whatever *mostinteresting; |
|
|
1377 | }; |
|
|
1378 | |
|
|
1379 | ... |
|
|
1380 | struct my_io w; |
|
|
1381 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1382 | |
|
|
1383 | And since your callback will be called with a pointer to the watcher, you |
|
|
1384 | can cast it back to your own type: |
|
|
1385 | |
|
|
1386 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1387 | { |
|
|
1388 | struct my_io *w = (struct my_io *)w_; |
|
|
1389 | ... |
|
|
1390 | } |
|
|
1391 | |
|
|
1392 | More interesting and less C-conformant ways of casting your callback type |
|
|
1393 | instead have been omitted. |
|
|
1394 | |
|
|
1395 | Another common scenario is to use some data structure with multiple |
|
|
1396 | embedded watchers: |
|
|
1397 | |
|
|
1398 | struct my_biggy |
|
|
1399 | { |
|
|
1400 | int some_data; |
|
|
1401 | ev_timer t1; |
|
|
1402 | ev_timer t2; |
|
|
1403 | } |
|
|
1404 | |
|
|
1405 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1406 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1407 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1408 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1409 | programmers): |
|
|
1410 | |
|
|
1411 | #include <stddef.h> |
|
|
1412 | |
|
|
1413 | static void |
|
|
1414 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1415 | { |
|
|
1416 | struct my_biggy big = (struct my_biggy *) |
|
|
1417 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1418 | } |
|
|
1419 | |
|
|
1420 | static void |
|
|
1421 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1422 | { |
|
|
1423 | struct my_biggy big = (struct my_biggy *) |
|
|
1424 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1425 | } |
|
|
1426 | |
1455 | |
1427 | =head2 WATCHER PRIORITY MODELS |
1456 | =head2 WATCHER PRIORITY MODELS |
1428 | |
1457 | |
1429 | Many event loops support I<watcher priorities>, which are usually small |
1458 | Many event loops support I<watcher priorities>, which are usually small |
1430 | integers that influence the ordering of event callback invocation |
1459 | integers that influence the ordering of event callback invocation |
… | |
… | |
1557 | In general you can register as many read and/or write event watchers per |
1586 | In general you can register as many read and/or write event watchers per |
1558 | fd as you want (as long as you don't confuse yourself). Setting all file |
1587 | fd as you want (as long as you don't confuse yourself). Setting all file |
1559 | descriptors to non-blocking mode is also usually a good idea (but not |
1588 | descriptors to non-blocking mode is also usually a good idea (but not |
1560 | required if you know what you are doing). |
1589 | required if you know what you are doing). |
1561 | |
1590 | |
1562 | If you cannot use non-blocking mode, then force the use of a |
|
|
1563 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1564 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1565 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1566 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1567 | |
|
|
1568 | Another thing you have to watch out for is that it is quite easy to |
1591 | Another thing you have to watch out for is that it is quite easy to |
1569 | receive "spurious" readiness notifications, that is your callback might |
1592 | receive "spurious" readiness notifications, that is, your callback might |
1570 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1593 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1571 | because there is no data. Not only are some backends known to create a |
1594 | because there is no data. It is very easy to get into this situation even |
1572 | lot of those (for example Solaris ports), it is very easy to get into |
1595 | with a relatively standard program structure. Thus it is best to always |
1573 | this situation even with a relatively standard program structure. Thus |
1596 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1574 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1575 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1597 | preferable to a program hanging until some data arrives. |
1576 | |
1598 | |
1577 | If you cannot run the fd in non-blocking mode (for example you should |
1599 | If you cannot run the fd in non-blocking mode (for example you should |
1578 | not play around with an Xlib connection), then you have to separately |
1600 | not play around with an Xlib connection), then you have to separately |
1579 | re-test whether a file descriptor is really ready with a known-to-be good |
1601 | re-test whether a file descriptor is really ready with a known-to-be good |
1580 | interface such as poll (fortunately in our Xlib example, Xlib already |
1602 | interface such as poll (fortunately in the case of Xlib, it already does |
1581 | does this on its own, so its quite safe to use). Some people additionally |
1603 | this on its own, so its quite safe to use). Some people additionally |
1582 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1604 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1583 | indefinitely. |
1605 | indefinitely. |
1584 | |
1606 | |
1585 | But really, best use non-blocking mode. |
1607 | But really, best use non-blocking mode. |
1586 | |
1608 | |
… | |
… | |
1614 | |
1636 | |
1615 | There is no workaround possible except not registering events |
1637 | There is no workaround possible except not registering events |
1616 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1638 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1617 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1639 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1618 | |
1640 | |
|
|
1641 | =head3 The special problem of files |
|
|
1642 | |
|
|
1643 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1644 | representing files, and expect it to become ready when their program |
|
|
1645 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1646 | |
|
|
1647 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1648 | notification as soon as the kernel knows whether and how much data is |
|
|
1649 | there, and in the case of open files, that's always the case, so you |
|
|
1650 | always get a readiness notification instantly, and your read (or possibly |
|
|
1651 | write) will still block on the disk I/O. |
|
|
1652 | |
|
|
1653 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1654 | devices and so on, there is another party (the sender) that delivers data |
|
|
1655 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1656 | will not send data on its own, simply because it doesn't know what you |
|
|
1657 | wish to read - you would first have to request some data. |
|
|
1658 | |
|
|
1659 | Since files are typically not-so-well supported by advanced notification |
|
|
1660 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1661 | to files, even though you should not use it. The reason for this is |
|
|
1662 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1663 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1664 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1665 | F</dev/urandom>), and even though the file might better be served with |
|
|
1666 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1667 | it "just works" instead of freezing. |
|
|
1668 | |
|
|
1669 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1670 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1671 | when you rarely read from a file instead of from a socket, and want to |
|
|
1672 | reuse the same code path. |
|
|
1673 | |
1619 | =head3 The special problem of fork |
1674 | =head3 The special problem of fork |
1620 | |
1675 | |
1621 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1676 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1622 | useless behaviour. Libev fully supports fork, but needs to be told about |
1677 | useless behaviour. Libev fully supports fork, but needs to be told about |
1623 | it in the child. |
1678 | it in the child if you want to continue to use it in the child. |
1624 | |
1679 | |
1625 | To support fork in your programs, you either have to call |
1680 | To support fork in your child processes, you have to call C<ev_loop_fork |
1626 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1681 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1627 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1682 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1628 | C<EVBACKEND_POLL>. |
|
|
1629 | |
1683 | |
1630 | =head3 The special problem of SIGPIPE |
1684 | =head3 The special problem of SIGPIPE |
1631 | |
1685 | |
1632 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1686 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1633 | when writing to a pipe whose other end has been closed, your program gets |
1687 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1731 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1785 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1732 | monotonic clock option helps a lot here). |
1786 | monotonic clock option helps a lot here). |
1733 | |
1787 | |
1734 | The callback is guaranteed to be invoked only I<after> its timeout has |
1788 | The callback is guaranteed to be invoked only I<after> its timeout has |
1735 | passed (not I<at>, so on systems with very low-resolution clocks this |
1789 | passed (not I<at>, so on systems with very low-resolution clocks this |
1736 | might introduce a small delay). If multiple timers become ready during the |
1790 | might introduce a small delay, see "the special problem of being too |
|
|
1791 | early", below). If multiple timers become ready during the same loop |
1737 | same loop iteration then the ones with earlier time-out values are invoked |
1792 | iteration then the ones with earlier time-out values are invoked before |
1738 | before ones of the same priority with later time-out values (but this is |
1793 | ones of the same priority with later time-out values (but this is no |
1739 | no longer true when a callback calls C<ev_run> recursively). |
1794 | longer true when a callback calls C<ev_run> recursively). |
1740 | |
1795 | |
1741 | =head3 Be smart about timeouts |
1796 | =head3 Be smart about timeouts |
1742 | |
1797 | |
1743 | Many real-world problems involve some kind of timeout, usually for error |
1798 | Many real-world problems involve some kind of timeout, usually for error |
1744 | recovery. A typical example is an HTTP request - if the other side hangs, |
1799 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1819 | |
1874 | |
1820 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1875 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1821 | but remember the time of last activity, and check for a real timeout only |
1876 | but remember the time of last activity, and check for a real timeout only |
1822 | within the callback: |
1877 | within the callback: |
1823 | |
1878 | |
|
|
1879 | ev_tstamp timeout = 60.; |
1824 | ev_tstamp last_activity; // time of last activity |
1880 | ev_tstamp last_activity; // time of last activity |
|
|
1881 | ev_timer timer; |
1825 | |
1882 | |
1826 | static void |
1883 | static void |
1827 | callback (EV_P_ ev_timer *w, int revents) |
1884 | callback (EV_P_ ev_timer *w, int revents) |
1828 | { |
1885 | { |
1829 | ev_tstamp now = ev_now (EV_A); |
1886 | // calculate when the timeout would happen |
1830 | ev_tstamp timeout = last_activity + 60.; |
1887 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1831 | |
1888 | |
1832 | // if last_activity + 60. is older than now, we did time out |
1889 | // if negative, it means we the timeout already occurred |
1833 | if (timeout < now) |
1890 | if (after < 0.) |
1834 | { |
1891 | { |
1835 | // timeout occurred, take action |
1892 | // timeout occurred, take action |
1836 | } |
1893 | } |
1837 | else |
1894 | else |
1838 | { |
1895 | { |
1839 | // callback was invoked, but there was some activity, re-arm |
1896 | // callback was invoked, but there was some recent |
1840 | // the watcher to fire in last_activity + 60, which is |
1897 | // activity. simply restart the timer to time out |
1841 | // guaranteed to be in the future, so "again" is positive: |
1898 | // after "after" seconds, which is the earliest time |
1842 | w->repeat = timeout - now; |
1899 | // the timeout can occur. |
|
|
1900 | ev_timer_set (w, after, 0.); |
1843 | ev_timer_again (EV_A_ w); |
1901 | ev_timer_start (EV_A_ w); |
1844 | } |
1902 | } |
1845 | } |
1903 | } |
1846 | |
1904 | |
1847 | To summarise the callback: first calculate the real timeout (defined |
1905 | To summarise the callback: first calculate in how many seconds the |
1848 | as "60 seconds after the last activity"), then check if that time has |
1906 | timeout will occur (by calculating the absolute time when it would occur, |
1849 | been reached, which means something I<did>, in fact, time out. Otherwise |
1907 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1850 | the callback was invoked too early (C<timeout> is in the future), so |
1908 | (EV_A)> from that). |
1851 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1852 | a timeout then. |
|
|
1853 | |
1909 | |
1854 | Note how C<ev_timer_again> is used, taking advantage of the |
1910 | If this value is negative, then we are already past the timeout, i.e. we |
1855 | C<ev_timer_again> optimisation when the timer is already running. |
1911 | timed out, and need to do whatever is needed in this case. |
|
|
1912 | |
|
|
1913 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1914 | and simply start the timer with this timeout value. |
|
|
1915 | |
|
|
1916 | In other words, each time the callback is invoked it will check whether |
|
|
1917 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1918 | again at the earliest time it could time out. Rinse. Repeat. |
1856 | |
1919 | |
1857 | This scheme causes more callback invocations (about one every 60 seconds |
1920 | This scheme causes more callback invocations (about one every 60 seconds |
1858 | minus half the average time between activity), but virtually no calls to |
1921 | minus half the average time between activity), but virtually no calls to |
1859 | libev to change the timeout. |
1922 | libev to change the timeout. |
1860 | |
1923 | |
1861 | To start the timer, simply initialise the watcher and set C<last_activity> |
1924 | To start the machinery, simply initialise the watcher and set |
1862 | to the current time (meaning we just have some activity :), then call the |
1925 | C<last_activity> to the current time (meaning there was some activity just |
1863 | callback, which will "do the right thing" and start the timer: |
1926 | now), then call the callback, which will "do the right thing" and start |
|
|
1927 | the timer: |
1864 | |
1928 | |
|
|
1929 | last_activity = ev_now (EV_A); |
1865 | ev_init (timer, callback); |
1930 | ev_init (&timer, callback); |
1866 | last_activity = ev_now (loop); |
1931 | callback (EV_A_ &timer, 0); |
1867 | callback (loop, timer, EV_TIMER); |
|
|
1868 | |
1932 | |
1869 | And when there is some activity, simply store the current time in |
1933 | When there is some activity, simply store the current time in |
1870 | C<last_activity>, no libev calls at all: |
1934 | C<last_activity>, no libev calls at all: |
1871 | |
1935 | |
|
|
1936 | if (activity detected) |
1872 | last_activity = ev_now (loop); |
1937 | last_activity = ev_now (EV_A); |
|
|
1938 | |
|
|
1939 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1940 | providing a new value, stopping the timer and calling the callback, which |
|
|
1941 | will again do the right thing (for example, time out immediately :). |
|
|
1942 | |
|
|
1943 | timeout = new_value; |
|
|
1944 | ev_timer_stop (EV_A_ &timer); |
|
|
1945 | callback (EV_A_ &timer, 0); |
1873 | |
1946 | |
1874 | This technique is slightly more complex, but in most cases where the |
1947 | This technique is slightly more complex, but in most cases where the |
1875 | time-out is unlikely to be triggered, much more efficient. |
1948 | time-out is unlikely to be triggered, much more efficient. |
1876 | |
|
|
1877 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1878 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1879 | fix things for you. |
|
|
1880 | |
1949 | |
1881 | =item 4. Wee, just use a double-linked list for your timeouts. |
1950 | =item 4. Wee, just use a double-linked list for your timeouts. |
1882 | |
1951 | |
1883 | If there is not one request, but many thousands (millions...), all |
1952 | If there is not one request, but many thousands (millions...), all |
1884 | employing some kind of timeout with the same timeout value, then one can |
1953 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1911 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1980 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1912 | rather complicated, but extremely efficient, something that really pays |
1981 | rather complicated, but extremely efficient, something that really pays |
1913 | off after the first million or so of active timers, i.e. it's usually |
1982 | off after the first million or so of active timers, i.e. it's usually |
1914 | overkill :) |
1983 | overkill :) |
1915 | |
1984 | |
|
|
1985 | =head3 The special problem of being too early |
|
|
1986 | |
|
|
1987 | If you ask a timer to call your callback after three seconds, then |
|
|
1988 | you expect it to be invoked after three seconds - but of course, this |
|
|
1989 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1990 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1991 | process with a STOP signal for a few hours for example. |
|
|
1992 | |
|
|
1993 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1994 | delay has occurred, but cannot guarantee this. |
|
|
1995 | |
|
|
1996 | A less obvious failure mode is calling your callback too early: many event |
|
|
1997 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1998 | this can cause your callback to be invoked much earlier than you would |
|
|
1999 | expect. |
|
|
2000 | |
|
|
2001 | To see why, imagine a system with a clock that only offers full second |
|
|
2002 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2003 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2004 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2005 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2006 | |
|
|
2007 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2008 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2009 | one-second delay was requested - this is being "too early", despite best |
|
|
2010 | intentions. |
|
|
2011 | |
|
|
2012 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2013 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2014 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2015 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2016 | |
|
|
2017 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2018 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2019 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2020 | late" side of things. |
|
|
2021 | |
1916 | =head3 The special problem of time updates |
2022 | =head3 The special problem of time updates |
1917 | |
2023 | |
1918 | Establishing the current time is a costly operation (it usually takes at |
2024 | Establishing the current time is a costly operation (it usually takes |
1919 | least two system calls): EV therefore updates its idea of the current |
2025 | at least one system call): EV therefore updates its idea of the current |
1920 | time only before and after C<ev_run> collects new events, which causes a |
2026 | time only before and after C<ev_run> collects new events, which causes a |
1921 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2027 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1922 | lots of events in one iteration. |
2028 | lots of events in one iteration. |
1923 | |
2029 | |
1924 | The relative timeouts are calculated relative to the C<ev_now ()> |
2030 | The relative timeouts are calculated relative to the C<ev_now ()> |
1925 | time. This is usually the right thing as this timestamp refers to the time |
2031 | time. This is usually the right thing as this timestamp refers to the time |
1926 | of the event triggering whatever timeout you are modifying/starting. If |
2032 | of the event triggering whatever timeout you are modifying/starting. If |
1927 | you suspect event processing to be delayed and you I<need> to base the |
2033 | you suspect event processing to be delayed and you I<need> to base the |
1928 | timeout on the current time, use something like this to adjust for this: |
2034 | timeout on the current time, use something like the following to adjust |
|
|
2035 | for it: |
1929 | |
2036 | |
1930 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2037 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
1931 | |
2038 | |
1932 | If the event loop is suspended for a long time, you can also force an |
2039 | If the event loop is suspended for a long time, you can also force an |
1933 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2040 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1934 | ()>. |
2041 | ()>, although that will push the event time of all outstanding events |
|
|
2042 | further into the future. |
|
|
2043 | |
|
|
2044 | =head3 The special problem of unsynchronised clocks |
|
|
2045 | |
|
|
2046 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2047 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2048 | jumps). |
|
|
2049 | |
|
|
2050 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2051 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2052 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2053 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2054 | than a directly following call to C<time>. |
|
|
2055 | |
|
|
2056 | The moral of this is to only compare libev-related timestamps with |
|
|
2057 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2058 | a second or so. |
|
|
2059 | |
|
|
2060 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2061 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2062 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2063 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2064 | |
|
|
2065 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2066 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2067 | I<measured according to the real time>, not the system clock. |
|
|
2068 | |
|
|
2069 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2070 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2071 | exactly the right behaviour. |
|
|
2072 | |
|
|
2073 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2074 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2075 | time, where your comparisons will always generate correct results. |
1935 | |
2076 | |
1936 | =head3 The special problems of suspended animation |
2077 | =head3 The special problems of suspended animation |
1937 | |
2078 | |
1938 | When you leave the server world it is quite customary to hit machines that |
2079 | When you leave the server world it is quite customary to hit machines that |
1939 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2080 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
1983 | keep up with the timer (because it takes longer than those 10 seconds to |
2124 | keep up with the timer (because it takes longer than those 10 seconds to |
1984 | do stuff) the timer will not fire more than once per event loop iteration. |
2125 | do stuff) the timer will not fire more than once per event loop iteration. |
1985 | |
2126 | |
1986 | =item ev_timer_again (loop, ev_timer *) |
2127 | =item ev_timer_again (loop, ev_timer *) |
1987 | |
2128 | |
1988 | This will act as if the timer timed out and restart it again if it is |
2129 | This will act as if the timer timed out, and restarts it again if it is |
1989 | repeating. The exact semantics are: |
2130 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2131 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1990 | |
2132 | |
|
|
2133 | The exact semantics are as in the following rules, all of which will be |
|
|
2134 | applied to the watcher: |
|
|
2135 | |
|
|
2136 | =over 4 |
|
|
2137 | |
1991 | If the timer is pending, its pending status is cleared. |
2138 | =item If the timer is pending, the pending status is always cleared. |
1992 | |
2139 | |
1993 | If the timer is started but non-repeating, stop it (as if it timed out). |
2140 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2141 | out, without invoking it). |
1994 | |
2142 | |
1995 | If the timer is repeating, either start it if necessary (with the |
2143 | =item If the timer is repeating, make the C<repeat> value the new timeout |
1996 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2144 | and start the timer, if necessary. |
1997 | |
2145 | |
|
|
2146 | =back |
|
|
2147 | |
1998 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2148 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
1999 | usage example. |
2149 | usage example. |
2000 | |
2150 | |
2001 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2151 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2002 | |
2152 | |
2003 | Returns the remaining time until a timer fires. If the timer is active, |
2153 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2123 | |
2273 | |
2124 | Another way to think about it (for the mathematically inclined) is that |
2274 | Another way to think about it (for the mathematically inclined) is that |
2125 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2275 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2126 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2276 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2127 | |
2277 | |
2128 | For numerical stability it is preferable that the C<offset> value is near |
2278 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2129 | C<ev_now ()> (the current time), but there is no range requirement for |
2279 | interval value should be higher than C<1/8192> (which is around 100 |
2130 | this value, and in fact is often specified as zero. |
2280 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2281 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2282 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2283 | C<0> and C<interval>, which is also the recommended range. |
2131 | |
2284 | |
2132 | Note also that there is an upper limit to how often a timer can fire (CPU |
2285 | Note also that there is an upper limit to how often a timer can fire (CPU |
2133 | speed for example), so if C<interval> is very small then timing stability |
2286 | speed for example), so if C<interval> is very small then timing stability |
2134 | will of course deteriorate. Libev itself tries to be exact to be about one |
2287 | will of course deteriorate. Libev itself tries to be exact to be about one |
2135 | millisecond (if the OS supports it and the machine is fast enough). |
2288 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2243 | |
2396 | |
2244 | ev_periodic hourly_tick; |
2397 | ev_periodic hourly_tick; |
2245 | ev_periodic_init (&hourly_tick, clock_cb, |
2398 | ev_periodic_init (&hourly_tick, clock_cb, |
2246 | fmod (ev_now (loop), 3600.), 3600., 0); |
2399 | fmod (ev_now (loop), 3600.), 3600., 0); |
2247 | ev_periodic_start (loop, &hourly_tick); |
2400 | ev_periodic_start (loop, &hourly_tick); |
2248 | |
2401 | |
2249 | |
2402 | |
2250 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2403 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2251 | |
2404 | |
2252 | Signal watchers will trigger an event when the process receives a specific |
2405 | Signal watchers will trigger an event when the process receives a specific |
2253 | signal one or more times. Even though signals are very asynchronous, libev |
2406 | signal one or more times. Even though signals are very asynchronous, libev |
2254 | will try it's best to deliver signals synchronously, i.e. as part of the |
2407 | will try its best to deliver signals synchronously, i.e. as part of the |
2255 | normal event processing, like any other event. |
2408 | normal event processing, like any other event. |
2256 | |
2409 | |
2257 | If you want signals to be delivered truly asynchronously, just use |
2410 | If you want signals to be delivered truly asynchronously, just use |
2258 | C<sigaction> as you would do without libev and forget about sharing |
2411 | C<sigaction> as you would do without libev and forget about sharing |
2259 | the signal. You can even use C<ev_async> from a signal handler to |
2412 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2263 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2416 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2264 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2417 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2265 | C<SIGINT> in both the default loop and another loop at the same time. At |
2418 | C<SIGINT> in both the default loop and another loop at the same time. At |
2266 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2419 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2267 | |
2420 | |
2268 | When the first watcher gets started will libev actually register something |
2421 | Only after the first watcher for a signal is started will libev actually |
2269 | with the kernel (thus it coexists with your own signal handlers as long as |
2422 | register something with the kernel. It thus coexists with your own signal |
2270 | you don't register any with libev for the same signal). |
2423 | handlers as long as you don't register any with libev for the same signal. |
2271 | |
2424 | |
2272 | If possible and supported, libev will install its handlers with |
2425 | If possible and supported, libev will install its handlers with |
2273 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2426 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2274 | not be unduly interrupted. If you have a problem with system calls getting |
2427 | not be unduly interrupted. If you have a problem with system calls getting |
2275 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2428 | interrupted by signals you can block all signals in an C<ev_check> watcher |
… | |
… | |
2278 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2431 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2279 | |
2432 | |
2280 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2433 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2281 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2434 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2282 | stopping it again), that is, libev might or might not block the signal, |
2435 | stopping it again), that is, libev might or might not block the signal, |
2283 | and might or might not set or restore the installed signal handler. |
2436 | and might or might not set or restore the installed signal handler (but |
|
|
2437 | see C<EVFLAG_NOSIGMASK>). |
2284 | |
2438 | |
2285 | While this does not matter for the signal disposition (libev never |
2439 | While this does not matter for the signal disposition (libev never |
2286 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2440 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2287 | C<execve>), this matters for the signal mask: many programs do not expect |
2441 | C<execve>), this matters for the signal mask: many programs do not expect |
2288 | certain signals to be blocked. |
2442 | certain signals to be blocked. |
… | |
… | |
2301 | I<has> to modify the signal mask, at least temporarily. |
2455 | I<has> to modify the signal mask, at least temporarily. |
2302 | |
2456 | |
2303 | So I can't stress this enough: I<If you do not reset your signal mask when |
2457 | So I can't stress this enough: I<If you do not reset your signal mask when |
2304 | you expect it to be empty, you have a race condition in your code>. This |
2458 | you expect it to be empty, you have a race condition in your code>. This |
2305 | is not a libev-specific thing, this is true for most event libraries. |
2459 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2460 | |
|
|
2461 | =head3 The special problem of threads signal handling |
|
|
2462 | |
|
|
2463 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2464 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2465 | threads in a process block signals, which is hard to achieve. |
|
|
2466 | |
|
|
2467 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2468 | for the same signals), you can tackle this problem by globally blocking |
|
|
2469 | all signals before creating any threads (or creating them with a fully set |
|
|
2470 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2471 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2472 | these signals. You can pass on any signals that libev might be interested |
|
|
2473 | in by calling C<ev_feed_signal>. |
2306 | |
2474 | |
2307 | =head3 Watcher-Specific Functions and Data Members |
2475 | =head3 Watcher-Specific Functions and Data Members |
2308 | |
2476 | |
2309 | =over 4 |
2477 | =over 4 |
2310 | |
2478 | |
… | |
… | |
2445 | |
2613 | |
2446 | =head2 C<ev_stat> - did the file attributes just change? |
2614 | =head2 C<ev_stat> - did the file attributes just change? |
2447 | |
2615 | |
2448 | This watches a file system path for attribute changes. That is, it calls |
2616 | This watches a file system path for attribute changes. That is, it calls |
2449 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2617 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2450 | and sees if it changed compared to the last time, invoking the callback if |
2618 | and sees if it changed compared to the last time, invoking the callback |
2451 | it did. |
2619 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2620 | happen after the watcher has been started will be reported. |
2452 | |
2621 | |
2453 | The path does not need to exist: changing from "path exists" to "path does |
2622 | The path does not need to exist: changing from "path exists" to "path does |
2454 | not exist" is a status change like any other. The condition "path does not |
2623 | not exist" is a status change like any other. The condition "path does not |
2455 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2624 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2456 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2625 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2686 | Apart from keeping your process non-blocking (which is a useful |
2855 | Apart from keeping your process non-blocking (which is a useful |
2687 | effect on its own sometimes), idle watchers are a good place to do |
2856 | effect on its own sometimes), idle watchers are a good place to do |
2688 | "pseudo-background processing", or delay processing stuff to after the |
2857 | "pseudo-background processing", or delay processing stuff to after the |
2689 | event loop has handled all outstanding events. |
2858 | event loop has handled all outstanding events. |
2690 | |
2859 | |
|
|
2860 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2861 | |
|
|
2862 | As long as there is at least one active idle watcher, libev will never |
|
|
2863 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2864 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2865 | lowest priority will do. |
|
|
2866 | |
|
|
2867 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2868 | to do something on each event loop iteration - for example to balance load |
|
|
2869 | between different connections. |
|
|
2870 | |
|
|
2871 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2872 | example. |
|
|
2873 | |
2691 | =head3 Watcher-Specific Functions and Data Members |
2874 | =head3 Watcher-Specific Functions and Data Members |
2692 | |
2875 | |
2693 | =over 4 |
2876 | =over 4 |
2694 | |
2877 | |
2695 | =item ev_idle_init (ev_idle *, callback) |
2878 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2706 | callback, free it. Also, use no error checking, as usual. |
2889 | callback, free it. Also, use no error checking, as usual. |
2707 | |
2890 | |
2708 | static void |
2891 | static void |
2709 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2892 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2710 | { |
2893 | { |
|
|
2894 | // stop the watcher |
|
|
2895 | ev_idle_stop (loop, w); |
|
|
2896 | |
|
|
2897 | // now we can free it |
2711 | free (w); |
2898 | free (w); |
|
|
2899 | |
2712 | // now do something you wanted to do when the program has |
2900 | // now do something you wanted to do when the program has |
2713 | // no longer anything immediate to do. |
2901 | // no longer anything immediate to do. |
2714 | } |
2902 | } |
2715 | |
2903 | |
2716 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2904 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2718 | ev_idle_start (loop, idle_watcher); |
2906 | ev_idle_start (loop, idle_watcher); |
2719 | |
2907 | |
2720 | |
2908 | |
2721 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2909 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2722 | |
2910 | |
2723 | Prepare and check watchers are usually (but not always) used in pairs: |
2911 | Prepare and check watchers are often (but not always) used in pairs: |
2724 | prepare watchers get invoked before the process blocks and check watchers |
2912 | prepare watchers get invoked before the process blocks and check watchers |
2725 | afterwards. |
2913 | afterwards. |
2726 | |
2914 | |
2727 | You I<must not> call C<ev_run> or similar functions that enter |
2915 | You I<must not> call C<ev_run> (or similar functions that enter the |
2728 | the current event loop from either C<ev_prepare> or C<ev_check> |
2916 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2729 | watchers. Other loops than the current one are fine, however. The |
2917 | C<ev_check> watchers. Other loops than the current one are fine, |
2730 | rationale behind this is that you do not need to check for recursion in |
2918 | however. The rationale behind this is that you do not need to check |
2731 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2919 | for recursion in those watchers, i.e. the sequence will always be |
2732 | C<ev_check> so if you have one watcher of each kind they will always be |
2920 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2733 | called in pairs bracketing the blocking call. |
2921 | kind they will always be called in pairs bracketing the blocking call. |
2734 | |
2922 | |
2735 | Their main purpose is to integrate other event mechanisms into libev and |
2923 | Their main purpose is to integrate other event mechanisms into libev and |
2736 | their use is somewhat advanced. They could be used, for example, to track |
2924 | their use is somewhat advanced. They could be used, for example, to track |
2737 | variable changes, implement your own watchers, integrate net-snmp or a |
2925 | variable changes, implement your own watchers, integrate net-snmp or a |
2738 | coroutine library and lots more. They are also occasionally useful if |
2926 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
2756 | with priority higher than or equal to the event loop and one coroutine |
2944 | with priority higher than or equal to the event loop and one coroutine |
2757 | of lower priority, but only once, using idle watchers to keep the event |
2945 | of lower priority, but only once, using idle watchers to keep the event |
2758 | loop from blocking if lower-priority coroutines are active, thus mapping |
2946 | loop from blocking if lower-priority coroutines are active, thus mapping |
2759 | low-priority coroutines to idle/background tasks). |
2947 | low-priority coroutines to idle/background tasks). |
2760 | |
2948 | |
2761 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2949 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2762 | priority, to ensure that they are being run before any other watchers |
2950 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2763 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
2951 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
2952 | watchers). |
2764 | |
2953 | |
2765 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2954 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2766 | activate ("feed") events into libev. While libev fully supports this, they |
2955 | activate ("feed") events into libev. While libev fully supports this, they |
2767 | might get executed before other C<ev_check> watchers did their job. As |
2956 | might get executed before other C<ev_check> watchers did their job. As |
2768 | C<ev_check> watchers are often used to embed other (non-libev) event |
2957 | C<ev_check> watchers are often used to embed other (non-libev) event |
2769 | loops those other event loops might be in an unusable state until their |
2958 | loops those other event loops might be in an unusable state until their |
2770 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2959 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2771 | others). |
2960 | others). |
|
|
2961 | |
|
|
2962 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
2963 | |
|
|
2964 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
2965 | useful because they are called once per event loop iteration. For |
|
|
2966 | example, if you want to handle a large number of connections fairly, you |
|
|
2967 | normally only do a bit of work for each active connection, and if there |
|
|
2968 | is more work to do, you wait for the next event loop iteration, so other |
|
|
2969 | connections have a chance of making progress. |
|
|
2970 | |
|
|
2971 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
2972 | next event loop iteration. However, that isn't as soon as possible - |
|
|
2973 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
2974 | |
|
|
2975 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2976 | single global idle watcher that is active as long as you have one active |
|
|
2977 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
2978 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
2979 | invoked. Neither watcher alone can do that. |
2772 | |
2980 | |
2773 | =head3 Watcher-Specific Functions and Data Members |
2981 | =head3 Watcher-Specific Functions and Data Members |
2774 | |
2982 | |
2775 | =over 4 |
2983 | =over 4 |
2776 | |
2984 | |
… | |
… | |
2977 | |
3185 | |
2978 | =over 4 |
3186 | =over 4 |
2979 | |
3187 | |
2980 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3188 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2981 | |
3189 | |
2982 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3190 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
2983 | |
3191 | |
2984 | Configures the watcher to embed the given loop, which must be |
3192 | Configures the watcher to embed the given loop, which must be |
2985 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3193 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2986 | invoked automatically, otherwise it is the responsibility of the callback |
3194 | invoked automatically, otherwise it is the responsibility of the callback |
2987 | to invoke it (it will continue to be called until the sweep has been done, |
3195 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3008 | used). |
3216 | used). |
3009 | |
3217 | |
3010 | struct ev_loop *loop_hi = ev_default_init (0); |
3218 | struct ev_loop *loop_hi = ev_default_init (0); |
3011 | struct ev_loop *loop_lo = 0; |
3219 | struct ev_loop *loop_lo = 0; |
3012 | ev_embed embed; |
3220 | ev_embed embed; |
3013 | |
3221 | |
3014 | // see if there is a chance of getting one that works |
3222 | // see if there is a chance of getting one that works |
3015 | // (remember that a flags value of 0 means autodetection) |
3223 | // (remember that a flags value of 0 means autodetection) |
3016 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3224 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3017 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3225 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3018 | : 0; |
3226 | : 0; |
… | |
… | |
3032 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3240 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3033 | |
3241 | |
3034 | struct ev_loop *loop = ev_default_init (0); |
3242 | struct ev_loop *loop = ev_default_init (0); |
3035 | struct ev_loop *loop_socket = 0; |
3243 | struct ev_loop *loop_socket = 0; |
3036 | ev_embed embed; |
3244 | ev_embed embed; |
3037 | |
3245 | |
3038 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3246 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3039 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3247 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3040 | { |
3248 | { |
3041 | ev_embed_init (&embed, 0, loop_socket); |
3249 | ev_embed_init (&embed, 0, loop_socket); |
3042 | ev_embed_start (loop, &embed); |
3250 | ev_embed_start (loop, &embed); |
… | |
… | |
3050 | |
3258 | |
3051 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3259 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3052 | |
3260 | |
3053 | Fork watchers are called when a C<fork ()> was detected (usually because |
3261 | Fork watchers are called when a C<fork ()> was detected (usually because |
3054 | whoever is a good citizen cared to tell libev about it by calling |
3262 | whoever is a good citizen cared to tell libev about it by calling |
3055 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3263 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3056 | event loop blocks next and before C<ev_check> watchers are being called, |
3264 | and before C<ev_check> watchers are being called, and only in the child |
3057 | and only in the child after the fork. If whoever good citizen calling |
3265 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3058 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3266 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3059 | handlers will be invoked, too, of course. |
3267 | of course. |
3060 | |
3268 | |
3061 | =head3 The special problem of life after fork - how is it possible? |
3269 | =head3 The special problem of life after fork - how is it possible? |
3062 | |
3270 | |
3063 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3271 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3064 | up/change the process environment, followed by a call to C<exec()>. This |
3272 | up/change the process environment, followed by a call to C<exec()>. This |
3065 | sequence should be handled by libev without any problems. |
3273 | sequence should be handled by libev without any problems. |
3066 | |
3274 | |
3067 | This changes when the application actually wants to do event handling |
3275 | This changes when the application actually wants to do event handling |
3068 | in the child, or both parent in child, in effect "continuing" after the |
3276 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3098 | |
3306 | |
3099 | =item ev_fork_init (ev_fork *, callback) |
3307 | =item ev_fork_init (ev_fork *, callback) |
3100 | |
3308 | |
3101 | Initialises and configures the fork watcher - it has no parameters of any |
3309 | Initialises and configures the fork watcher - it has no parameters of any |
3102 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3310 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3103 | believe me. |
3311 | really. |
3104 | |
3312 | |
3105 | =back |
3313 | =back |
3106 | |
3314 | |
3107 | |
3315 | |
3108 | =head2 C<ev_cleanup> - even the best things end |
3316 | =head2 C<ev_cleanup> - even the best things end |
… | |
… | |
3126 | |
3334 | |
3127 | =item ev_cleanup_init (ev_cleanup *, callback) |
3335 | =item ev_cleanup_init (ev_cleanup *, callback) |
3128 | |
3336 | |
3129 | Initialises and configures the cleanup watcher - it has no parameters of |
3337 | Initialises and configures the cleanup watcher - it has no parameters of |
3130 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
3338 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
3131 | pointless, believe me. |
3339 | pointless, I assure you. |
3132 | |
3340 | |
3133 | =back |
3341 | =back |
3134 | |
3342 | |
3135 | Example: Register an atexit handler to destroy the default loop, so any |
3343 | Example: Register an atexit handler to destroy the default loop, so any |
3136 | cleanup functions are called. |
3344 | cleanup functions are called. |
… | |
… | |
3145 | atexit (program_exits); |
3353 | atexit (program_exits); |
3146 | |
3354 | |
3147 | |
3355 | |
3148 | =head2 C<ev_async> - how to wake up an event loop |
3356 | =head2 C<ev_async> - how to wake up an event loop |
3149 | |
3357 | |
3150 | In general, you cannot use an C<ev_run> from multiple threads or other |
3358 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3151 | asynchronous sources such as signal handlers (as opposed to multiple event |
3359 | asynchronous sources such as signal handlers (as opposed to multiple event |
3152 | loops - those are of course safe to use in different threads). |
3360 | loops - those are of course safe to use in different threads). |
3153 | |
3361 | |
3154 | Sometimes, however, you need to wake up an event loop you do not control, |
3362 | Sometimes, however, you need to wake up an event loop you do not control, |
3155 | for example because it belongs to another thread. This is what C<ev_async> |
3363 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3157 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3365 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3158 | |
3366 | |
3159 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3367 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3160 | too, are asynchronous in nature, and signals, too, will be compressed |
3368 | too, are asynchronous in nature, and signals, too, will be compressed |
3161 | (i.e. the number of callback invocations may be less than the number of |
3369 | (i.e. the number of callback invocations may be less than the number of |
3162 | C<ev_async_sent> calls). |
3370 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3163 | |
3371 | of "global async watchers" by using a watcher on an otherwise unused |
3164 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3372 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3165 | just the default loop. |
3373 | even without knowing which loop owns the signal. |
3166 | |
3374 | |
3167 | =head3 Queueing |
3375 | =head3 Queueing |
3168 | |
3376 | |
3169 | C<ev_async> does not support queueing of data in any way. The reason |
3377 | C<ev_async> does not support queueing of data in any way. The reason |
3170 | is that the author does not know of a simple (or any) algorithm for a |
3378 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3262 | trust me. |
3470 | trust me. |
3263 | |
3471 | |
3264 | =item ev_async_send (loop, ev_async *) |
3472 | =item ev_async_send (loop, ev_async *) |
3265 | |
3473 | |
3266 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3474 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3267 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3475 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3476 | returns. |
|
|
3477 | |
3268 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3478 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3269 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3479 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3270 | section below on what exactly this means). |
3480 | embedding section below on what exactly this means). |
3271 | |
3481 | |
3272 | Note that, as with other watchers in libev, multiple events might get |
3482 | Note that, as with other watchers in libev, multiple events might get |
3273 | compressed into a single callback invocation (another way to look at this |
3483 | compressed into a single callback invocation (another way to look at |
3274 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3484 | this is that C<ev_async> watchers are level-triggered: they are set on |
3275 | reset when the event loop detects that). |
3485 | C<ev_async_send>, reset when the event loop detects that). |
3276 | |
3486 | |
3277 | This call incurs the overhead of a system call only once per event loop |
3487 | This call incurs the overhead of at most one extra system call per event |
3278 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3488 | loop iteration, if the event loop is blocked, and no syscall at all if |
3279 | repeated calls to C<ev_async_send> for the same event loop. |
3489 | the event loop (or your program) is processing events. That means that |
|
|
3490 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3491 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3492 | zero) under load. |
3280 | |
3493 | |
3281 | =item bool = ev_async_pending (ev_async *) |
3494 | =item bool = ev_async_pending (ev_async *) |
3282 | |
3495 | |
3283 | Returns a non-zero value when C<ev_async_send> has been called on the |
3496 | Returns a non-zero value when C<ev_async_send> has been called on the |
3284 | watcher but the event has not yet been processed (or even noted) by the |
3497 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3339 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3552 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3340 | |
3553 | |
3341 | =item ev_feed_fd_event (loop, int fd, int revents) |
3554 | =item ev_feed_fd_event (loop, int fd, int revents) |
3342 | |
3555 | |
3343 | Feed an event on the given fd, as if a file descriptor backend detected |
3556 | Feed an event on the given fd, as if a file descriptor backend detected |
3344 | the given events it. |
3557 | the given events. |
3345 | |
3558 | |
3346 | =item ev_feed_signal_event (loop, int signum) |
3559 | =item ev_feed_signal_event (loop, int signum) |
3347 | |
3560 | |
3348 | Feed an event as if the given signal occurred (C<loop> must be the default |
3561 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3349 | loop!). |
3562 | which is async-safe. |
3350 | |
3563 | |
3351 | =back |
3564 | =back |
|
|
3565 | |
|
|
3566 | |
|
|
3567 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3568 | |
|
|
3569 | This section explains some common idioms that are not immediately |
|
|
3570 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3571 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3572 | |
|
|
3573 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3574 | |
|
|
3575 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3576 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3577 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3578 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3579 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3580 | data: |
|
|
3581 | |
|
|
3582 | struct my_io |
|
|
3583 | { |
|
|
3584 | ev_io io; |
|
|
3585 | int otherfd; |
|
|
3586 | void *somedata; |
|
|
3587 | struct whatever *mostinteresting; |
|
|
3588 | }; |
|
|
3589 | |
|
|
3590 | ... |
|
|
3591 | struct my_io w; |
|
|
3592 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3593 | |
|
|
3594 | And since your callback will be called with a pointer to the watcher, you |
|
|
3595 | can cast it back to your own type: |
|
|
3596 | |
|
|
3597 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3598 | { |
|
|
3599 | struct my_io *w = (struct my_io *)w_; |
|
|
3600 | ... |
|
|
3601 | } |
|
|
3602 | |
|
|
3603 | More interesting and less C-conformant ways of casting your callback |
|
|
3604 | function type instead have been omitted. |
|
|
3605 | |
|
|
3606 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3607 | |
|
|
3608 | Another common scenario is to use some data structure with multiple |
|
|
3609 | embedded watchers, in effect creating your own watcher that combines |
|
|
3610 | multiple libev event sources into one "super-watcher": |
|
|
3611 | |
|
|
3612 | struct my_biggy |
|
|
3613 | { |
|
|
3614 | int some_data; |
|
|
3615 | ev_timer t1; |
|
|
3616 | ev_timer t2; |
|
|
3617 | } |
|
|
3618 | |
|
|
3619 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3620 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3621 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3622 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3623 | real programmers): |
|
|
3624 | |
|
|
3625 | #include <stddef.h> |
|
|
3626 | |
|
|
3627 | static void |
|
|
3628 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3629 | { |
|
|
3630 | struct my_biggy big = (struct my_biggy *) |
|
|
3631 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3632 | } |
|
|
3633 | |
|
|
3634 | static void |
|
|
3635 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3636 | { |
|
|
3637 | struct my_biggy big = (struct my_biggy *) |
|
|
3638 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3639 | } |
|
|
3640 | |
|
|
3641 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3642 | |
|
|
3643 | Often you have structures like this in event-based programs: |
|
|
3644 | |
|
|
3645 | callback () |
|
|
3646 | { |
|
|
3647 | free (request); |
|
|
3648 | } |
|
|
3649 | |
|
|
3650 | request = start_new_request (..., callback); |
|
|
3651 | |
|
|
3652 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3653 | used to cancel the operation, or do other things with it. |
|
|
3654 | |
|
|
3655 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3656 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3657 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3658 | operation and simply invoke the callback with the result. |
|
|
3659 | |
|
|
3660 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3661 | has returned, so C<request> is not set. |
|
|
3662 | |
|
|
3663 | Even if you pass the request by some safer means to the callback, you |
|
|
3664 | might want to do something to the request after starting it, such as |
|
|
3665 | canceling it, which probably isn't working so well when the callback has |
|
|
3666 | already been invoked. |
|
|
3667 | |
|
|
3668 | A common way around all these issues is to make sure that |
|
|
3669 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3670 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3671 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3672 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3673 | pushing it into the pending queue: |
|
|
3674 | |
|
|
3675 | ev_set_cb (watcher, callback); |
|
|
3676 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3677 | |
|
|
3678 | This way, C<start_new_request> can safely return before the callback is |
|
|
3679 | invoked, while not delaying callback invocation too much. |
|
|
3680 | |
|
|
3681 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3682 | |
|
|
3683 | Often (especially in GUI toolkits) there are places where you have |
|
|
3684 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3685 | invoking C<ev_run>. |
|
|
3686 | |
|
|
3687 | This brings the problem of exiting - a callback might want to finish the |
|
|
3688 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3689 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3690 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3691 | other combination: In these cases, a simple C<ev_break> will not work. |
|
|
3692 | |
|
|
3693 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3694 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3695 | triggered, using C<EVRUN_ONCE>: |
|
|
3696 | |
|
|
3697 | // main loop |
|
|
3698 | int exit_main_loop = 0; |
|
|
3699 | |
|
|
3700 | while (!exit_main_loop) |
|
|
3701 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3702 | |
|
|
3703 | // in a modal watcher |
|
|
3704 | int exit_nested_loop = 0; |
|
|
3705 | |
|
|
3706 | while (!exit_nested_loop) |
|
|
3707 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3708 | |
|
|
3709 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3710 | |
|
|
3711 | // exit modal loop |
|
|
3712 | exit_nested_loop = 1; |
|
|
3713 | |
|
|
3714 | // exit main program, after modal loop is finished |
|
|
3715 | exit_main_loop = 1; |
|
|
3716 | |
|
|
3717 | // exit both |
|
|
3718 | exit_main_loop = exit_nested_loop = 1; |
|
|
3719 | |
|
|
3720 | =head2 THREAD LOCKING EXAMPLE |
|
|
3721 | |
|
|
3722 | Here is a fictitious example of how to run an event loop in a different |
|
|
3723 | thread from where callbacks are being invoked and watchers are |
|
|
3724 | created/added/removed. |
|
|
3725 | |
|
|
3726 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3727 | which uses exactly this technique (which is suited for many high-level |
|
|
3728 | languages). |
|
|
3729 | |
|
|
3730 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3731 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3732 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3733 | |
|
|
3734 | First, you need to associate some data with the event loop: |
|
|
3735 | |
|
|
3736 | typedef struct { |
|
|
3737 | mutex_t lock; /* global loop lock */ |
|
|
3738 | ev_async async_w; |
|
|
3739 | thread_t tid; |
|
|
3740 | cond_t invoke_cv; |
|
|
3741 | } userdata; |
|
|
3742 | |
|
|
3743 | void prepare_loop (EV_P) |
|
|
3744 | { |
|
|
3745 | // for simplicity, we use a static userdata struct. |
|
|
3746 | static userdata u; |
|
|
3747 | |
|
|
3748 | ev_async_init (&u->async_w, async_cb); |
|
|
3749 | ev_async_start (EV_A_ &u->async_w); |
|
|
3750 | |
|
|
3751 | pthread_mutex_init (&u->lock, 0); |
|
|
3752 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3753 | |
|
|
3754 | // now associate this with the loop |
|
|
3755 | ev_set_userdata (EV_A_ u); |
|
|
3756 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3757 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3758 | |
|
|
3759 | // then create the thread running ev_run |
|
|
3760 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3761 | } |
|
|
3762 | |
|
|
3763 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3764 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3765 | that might have been added: |
|
|
3766 | |
|
|
3767 | static void |
|
|
3768 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3769 | { |
|
|
3770 | // just used for the side effects |
|
|
3771 | } |
|
|
3772 | |
|
|
3773 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3774 | protecting the loop data, respectively. |
|
|
3775 | |
|
|
3776 | static void |
|
|
3777 | l_release (EV_P) |
|
|
3778 | { |
|
|
3779 | userdata *u = ev_userdata (EV_A); |
|
|
3780 | pthread_mutex_unlock (&u->lock); |
|
|
3781 | } |
|
|
3782 | |
|
|
3783 | static void |
|
|
3784 | l_acquire (EV_P) |
|
|
3785 | { |
|
|
3786 | userdata *u = ev_userdata (EV_A); |
|
|
3787 | pthread_mutex_lock (&u->lock); |
|
|
3788 | } |
|
|
3789 | |
|
|
3790 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3791 | into C<ev_run>: |
|
|
3792 | |
|
|
3793 | void * |
|
|
3794 | l_run (void *thr_arg) |
|
|
3795 | { |
|
|
3796 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3797 | |
|
|
3798 | l_acquire (EV_A); |
|
|
3799 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3800 | ev_run (EV_A_ 0); |
|
|
3801 | l_release (EV_A); |
|
|
3802 | |
|
|
3803 | return 0; |
|
|
3804 | } |
|
|
3805 | |
|
|
3806 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3807 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3808 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3809 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3810 | and b) skipping inter-thread-communication when there are no pending |
|
|
3811 | watchers is very beneficial): |
|
|
3812 | |
|
|
3813 | static void |
|
|
3814 | l_invoke (EV_P) |
|
|
3815 | { |
|
|
3816 | userdata *u = ev_userdata (EV_A); |
|
|
3817 | |
|
|
3818 | while (ev_pending_count (EV_A)) |
|
|
3819 | { |
|
|
3820 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3821 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3822 | } |
|
|
3823 | } |
|
|
3824 | |
|
|
3825 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3826 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3827 | thread to continue: |
|
|
3828 | |
|
|
3829 | static void |
|
|
3830 | real_invoke_pending (EV_P) |
|
|
3831 | { |
|
|
3832 | userdata *u = ev_userdata (EV_A); |
|
|
3833 | |
|
|
3834 | pthread_mutex_lock (&u->lock); |
|
|
3835 | ev_invoke_pending (EV_A); |
|
|
3836 | pthread_cond_signal (&u->invoke_cv); |
|
|
3837 | pthread_mutex_unlock (&u->lock); |
|
|
3838 | } |
|
|
3839 | |
|
|
3840 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3841 | event loop, you will now have to lock: |
|
|
3842 | |
|
|
3843 | ev_timer timeout_watcher; |
|
|
3844 | userdata *u = ev_userdata (EV_A); |
|
|
3845 | |
|
|
3846 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3847 | |
|
|
3848 | pthread_mutex_lock (&u->lock); |
|
|
3849 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3850 | ev_async_send (EV_A_ &u->async_w); |
|
|
3851 | pthread_mutex_unlock (&u->lock); |
|
|
3852 | |
|
|
3853 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3854 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3855 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3856 | watchers in the next event loop iteration. |
|
|
3857 | |
|
|
3858 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3859 | |
|
|
3860 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3861 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3862 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3863 | doesn't need callbacks anymore. |
|
|
3864 | |
|
|
3865 | Imagine you have coroutines that you can switch to using a function |
|
|
3866 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3867 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3868 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3869 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3870 | the differing C<;> conventions): |
|
|
3871 | |
|
|
3872 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3873 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3874 | |
|
|
3875 | That means instead of having a C callback function, you store the |
|
|
3876 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3877 | your callback, you instead have it switch to that coroutine. |
|
|
3878 | |
|
|
3879 | A coroutine might now wait for an event with a function called |
|
|
3880 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3881 | matter when, or whether the watcher is active or not when this function is |
|
|
3882 | called): |
|
|
3883 | |
|
|
3884 | void |
|
|
3885 | wait_for_event (ev_watcher *w) |
|
|
3886 | { |
|
|
3887 | ev_set_cb (w, current_coro); |
|
|
3888 | switch_to (libev_coro); |
|
|
3889 | } |
|
|
3890 | |
|
|
3891 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3892 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3893 | this or any other coroutine. |
|
|
3894 | |
|
|
3895 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3896 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3897 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3898 | any waiters. |
|
|
3899 | |
|
|
3900 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
|
|
3901 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3902 | |
|
|
3903 | // my_ev.h |
|
|
3904 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3905 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3906 | #include "../libev/ev.h" |
|
|
3907 | |
|
|
3908 | // my_ev.c |
|
|
3909 | #define EV_H "my_ev.h" |
|
|
3910 | #include "../libev/ev.c" |
|
|
3911 | |
|
|
3912 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3913 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3914 | can even use F<ev.h> as header file name directly. |
3352 | |
3915 | |
3353 | |
3916 | |
3354 | =head1 LIBEVENT EMULATION |
3917 | =head1 LIBEVENT EMULATION |
3355 | |
3918 | |
3356 | Libev offers a compatibility emulation layer for libevent. It cannot |
3919 | Libev offers a compatibility emulation layer for libevent. It cannot |
3357 | emulate the internals of libevent, so here are some usage hints: |
3920 | emulate the internals of libevent, so here are some usage hints: |
3358 | |
3921 | |
3359 | =over 4 |
3922 | =over 4 |
|
|
3923 | |
|
|
3924 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3925 | |
|
|
3926 | This was the newest libevent version available when libev was implemented, |
|
|
3927 | and is still mostly unchanged in 2010. |
3360 | |
3928 | |
3361 | =item * Use it by including <event.h>, as usual. |
3929 | =item * Use it by including <event.h>, as usual. |
3362 | |
3930 | |
3363 | =item * The following members are fully supported: ev_base, ev_callback, |
3931 | =item * The following members are fully supported: ev_base, ev_callback, |
3364 | ev_arg, ev_fd, ev_res, ev_events. |
3932 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3370 | =item * Priorities are not currently supported. Initialising priorities |
3938 | =item * Priorities are not currently supported. Initialising priorities |
3371 | will fail and all watchers will have the same priority, even though there |
3939 | will fail and all watchers will have the same priority, even though there |
3372 | is an ev_pri field. |
3940 | is an ev_pri field. |
3373 | |
3941 | |
3374 | =item * In libevent, the last base created gets the signals, in libev, the |
3942 | =item * In libevent, the last base created gets the signals, in libev, the |
3375 | first base created (== the default loop) gets the signals. |
3943 | base that registered the signal gets the signals. |
3376 | |
3944 | |
3377 | =item * Other members are not supported. |
3945 | =item * Other members are not supported. |
3378 | |
3946 | |
3379 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3947 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3380 | to use the libev header file and library. |
3948 | to use the libev header file and library. |
3381 | |
3949 | |
3382 | =back |
3950 | =back |
3383 | |
3951 | |
3384 | =head1 C++ SUPPORT |
3952 | =head1 C++ SUPPORT |
|
|
3953 | |
|
|
3954 | =head2 C API |
|
|
3955 | |
|
|
3956 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3957 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3958 | will work fine. |
|
|
3959 | |
|
|
3960 | Proper exception specifications might have to be added to callbacks passed |
|
|
3961 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3962 | other callbacks (allocator, syserr, loop acquire/release and periodic |
|
|
3963 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3964 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3965 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3966 | |
|
|
3967 | static void |
|
|
3968 | fatal_error (const char *msg) EV_THROW |
|
|
3969 | { |
|
|
3970 | perror (msg); |
|
|
3971 | abort (); |
|
|
3972 | } |
|
|
3973 | |
|
|
3974 | ... |
|
|
3975 | ev_set_syserr_cb (fatal_error); |
|
|
3976 | |
|
|
3977 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3978 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
3979 | because it runs cleanup watchers). |
|
|
3980 | |
|
|
3981 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3982 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3983 | throwing exceptions through C libraries (most do). |
|
|
3984 | |
|
|
3985 | =head2 C++ API |
3385 | |
3986 | |
3386 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3987 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3387 | you to use some convenience methods to start/stop watchers and also change |
3988 | you to use some convenience methods to start/stop watchers and also change |
3388 | the callback model to a model using method callbacks on objects. |
3989 | the callback model to a model using method callbacks on objects. |
3389 | |
3990 | |
3390 | To use it, |
3991 | To use it, |
3391 | |
3992 | |
3392 | #include <ev++.h> |
3993 | #include <ev++.h> |
3393 | |
3994 | |
3394 | This automatically includes F<ev.h> and puts all of its definitions (many |
3995 | This automatically includes F<ev.h> and puts all of its definitions (many |
3395 | of them macros) into the global namespace. All C++ specific things are |
3996 | of them macros) into the global namespace. All C++ specific things are |
3396 | put into the C<ev> namespace. It should support all the same embedding |
3997 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
3399 | Care has been taken to keep the overhead low. The only data member the C++ |
4000 | Care has been taken to keep the overhead low. The only data member the C++ |
3400 | classes add (compared to plain C-style watchers) is the event loop pointer |
4001 | classes add (compared to plain C-style watchers) is the event loop pointer |
3401 | that the watcher is associated with (or no additional members at all if |
4002 | that the watcher is associated with (or no additional members at all if |
3402 | you disable C<EV_MULTIPLICITY> when embedding libev). |
4003 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3403 | |
4004 | |
3404 | Currently, functions, and static and non-static member functions can be |
4005 | Currently, functions, static and non-static member functions and classes |
3405 | used as callbacks. Other types should be easy to add as long as they only |
4006 | with C<operator ()> can be used as callbacks. Other types should be easy |
3406 | need one additional pointer for context. If you need support for other |
4007 | to add as long as they only need one additional pointer for context. If |
3407 | types of functors please contact the author (preferably after implementing |
4008 | you need support for other types of functors please contact the author |
3408 | it). |
4009 | (preferably after implementing it). |
|
|
4010 | |
|
|
4011 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4012 | conventions as your C compiler (for static member functions), or you have |
|
|
4013 | to embed libev and compile libev itself as C++. |
3409 | |
4014 | |
3410 | Here is a list of things available in the C<ev> namespace: |
4015 | Here is a list of things available in the C<ev> namespace: |
3411 | |
4016 | |
3412 | =over 4 |
4017 | =over 4 |
3413 | |
4018 | |
… | |
… | |
3423 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4028 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3424 | |
4029 | |
3425 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4030 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3426 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4031 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3427 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4032 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3428 | defines by many implementations. |
4033 | defined by many implementations. |
3429 | |
4034 | |
3430 | All of those classes have these methods: |
4035 | All of those classes have these methods: |
3431 | |
4036 | |
3432 | =over 4 |
4037 | =over 4 |
3433 | |
4038 | |
… | |
… | |
3495 | void operator() (ev::io &w, int revents) |
4100 | void operator() (ev::io &w, int revents) |
3496 | { |
4101 | { |
3497 | ... |
4102 | ... |
3498 | } |
4103 | } |
3499 | } |
4104 | } |
3500 | |
4105 | |
3501 | myfunctor f; |
4106 | myfunctor f; |
3502 | |
4107 | |
3503 | ev::io w; |
4108 | ev::io w; |
3504 | w.set (&f); |
4109 | w.set (&f); |
3505 | |
4110 | |
… | |
… | |
3523 | Associates a different C<struct ev_loop> with this watcher. You can only |
4128 | Associates a different C<struct ev_loop> with this watcher. You can only |
3524 | do this when the watcher is inactive (and not pending either). |
4129 | do this when the watcher is inactive (and not pending either). |
3525 | |
4130 | |
3526 | =item w->set ([arguments]) |
4131 | =item w->set ([arguments]) |
3527 | |
4132 | |
3528 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4133 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
3529 | method or a suitable start method must be called at least once. Unlike the |
4134 | with the same arguments. Either this method or a suitable start method |
3530 | C counterpart, an active watcher gets automatically stopped and restarted |
4135 | must be called at least once. Unlike the C counterpart, an active watcher |
3531 | when reconfiguring it with this method. |
4136 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4137 | method. |
|
|
4138 | |
|
|
4139 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4140 | clashing with the C<set (loop)> method. |
3532 | |
4141 | |
3533 | =item w->start () |
4142 | =item w->start () |
3534 | |
4143 | |
3535 | Starts the watcher. Note that there is no C<loop> argument, as the |
4144 | Starts the watcher. Note that there is no C<loop> argument, as the |
3536 | constructor already stores the event loop. |
4145 | constructor already stores the event loop. |
… | |
… | |
3566 | watchers in the constructor. |
4175 | watchers in the constructor. |
3567 | |
4176 | |
3568 | class myclass |
4177 | class myclass |
3569 | { |
4178 | { |
3570 | ev::io io ; void io_cb (ev::io &w, int revents); |
4179 | ev::io io ; void io_cb (ev::io &w, int revents); |
3571 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4180 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3572 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4181 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3573 | |
4182 | |
3574 | myclass (int fd) |
4183 | myclass (int fd) |
3575 | { |
4184 | { |
3576 | io .set <myclass, &myclass::io_cb > (this); |
4185 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3627 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4236 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3628 | |
4237 | |
3629 | =item D |
4238 | =item D |
3630 | |
4239 | |
3631 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4240 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3632 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4241 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3633 | |
4242 | |
3634 | =item Ocaml |
4243 | =item Ocaml |
3635 | |
4244 | |
3636 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4245 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3637 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4246 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3640 | |
4249 | |
3641 | Brian Maher has written a partial interface to libev for lua (at the |
4250 | Brian Maher has written a partial interface to libev for lua (at the |
3642 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4251 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3643 | L<http://github.com/brimworks/lua-ev>. |
4252 | L<http://github.com/brimworks/lua-ev>. |
3644 | |
4253 | |
|
|
4254 | =item Javascript |
|
|
4255 | |
|
|
4256 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4257 | |
|
|
4258 | =item Others |
|
|
4259 | |
|
|
4260 | There are others, and I stopped counting. |
|
|
4261 | |
3645 | =back |
4262 | =back |
3646 | |
4263 | |
3647 | |
4264 | |
3648 | =head1 MACRO MAGIC |
4265 | =head1 MACRO MAGIC |
3649 | |
4266 | |
… | |
… | |
3685 | suitable for use with C<EV_A>. |
4302 | suitable for use with C<EV_A>. |
3686 | |
4303 | |
3687 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4304 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3688 | |
4305 | |
3689 | Similar to the other two macros, this gives you the value of the default |
4306 | Similar to the other two macros, this gives you the value of the default |
3690 | loop, if multiple loops are supported ("ev loop default"). |
4307 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4308 | will be initialised if it isn't already initialised. |
|
|
4309 | |
|
|
4310 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4311 | to initialise the loop somewhere. |
3691 | |
4312 | |
3692 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4313 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3693 | |
4314 | |
3694 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4315 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3695 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4316 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3840 | supported). It will also not define any of the structs usually found in |
4461 | supported). It will also not define any of the structs usually found in |
3841 | F<event.h> that are not directly supported by the libev core alone. |
4462 | F<event.h> that are not directly supported by the libev core alone. |
3842 | |
4463 | |
3843 | In standalone mode, libev will still try to automatically deduce the |
4464 | In standalone mode, libev will still try to automatically deduce the |
3844 | configuration, but has to be more conservative. |
4465 | configuration, but has to be more conservative. |
|
|
4466 | |
|
|
4467 | =item EV_USE_FLOOR |
|
|
4468 | |
|
|
4469 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4470 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4471 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4472 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4473 | function is not available will fail, so the safe default is to not enable |
|
|
4474 | this. |
3845 | |
4475 | |
3846 | =item EV_USE_MONOTONIC |
4476 | =item EV_USE_MONOTONIC |
3847 | |
4477 | |
3848 | If defined to be C<1>, libev will try to detect the availability of the |
4478 | If defined to be C<1>, libev will try to detect the availability of the |
3849 | monotonic clock option at both compile time and runtime. Otherwise no |
4479 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3934 | |
4564 | |
3935 | If programs implement their own fd to handle mapping on win32, then this |
4565 | If programs implement their own fd to handle mapping on win32, then this |
3936 | macro can be used to override the C<close> function, useful to unregister |
4566 | macro can be used to override the C<close> function, useful to unregister |
3937 | file descriptors again. Note that the replacement function has to close |
4567 | file descriptors again. Note that the replacement function has to close |
3938 | the underlying OS handle. |
4568 | the underlying OS handle. |
|
|
4569 | |
|
|
4570 | =item EV_USE_WSASOCKET |
|
|
4571 | |
|
|
4572 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4573 | communication socket, which works better in some environments. Otherwise, |
|
|
4574 | the normal C<socket> function will be used, which works better in other |
|
|
4575 | environments. |
3939 | |
4576 | |
3940 | =item EV_USE_POLL |
4577 | =item EV_USE_POLL |
3941 | |
4578 | |
3942 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4579 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3943 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4580 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3979 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4616 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3980 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4617 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3981 | be detected at runtime. If undefined, it will be enabled if the headers |
4618 | be detected at runtime. If undefined, it will be enabled if the headers |
3982 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4619 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3983 | |
4620 | |
|
|
4621 | =item EV_NO_SMP |
|
|
4622 | |
|
|
4623 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4624 | between threads, that is, threads can be used, but threads never run on |
|
|
4625 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4626 | and makes libev faster. |
|
|
4627 | |
|
|
4628 | =item EV_NO_THREADS |
|
|
4629 | |
|
|
4630 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4631 | different threads (that includes signal handlers), which is a stronger |
|
|
4632 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4633 | libev faster. |
|
|
4634 | |
3984 | =item EV_ATOMIC_T |
4635 | =item EV_ATOMIC_T |
3985 | |
4636 | |
3986 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4637 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3987 | access is atomic with respect to other threads or signal contexts. No such |
4638 | access is atomic with respect to other threads or signal contexts. No |
3988 | type is easily found in the C language, so you can provide your own type |
4639 | such type is easily found in the C language, so you can provide your own |
3989 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4640 | type that you know is safe for your purposes. It is used both for signal |
3990 | as well as for signal and thread safety in C<ev_async> watchers. |
4641 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4642 | watchers. |
3991 | |
4643 | |
3992 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4644 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3993 | (from F<signal.h>), which is usually good enough on most platforms. |
4645 | (from F<signal.h>), which is usually good enough on most platforms. |
3994 | |
4646 | |
3995 | =item EV_H (h) |
4647 | =item EV_H (h) |
… | |
… | |
4022 | will have the C<struct ev_loop *> as first argument, and you can create |
4674 | will have the C<struct ev_loop *> as first argument, and you can create |
4023 | additional independent event loops. Otherwise there will be no support |
4675 | additional independent event loops. Otherwise there will be no support |
4024 | for multiple event loops and there is no first event loop pointer |
4676 | for multiple event loops and there is no first event loop pointer |
4025 | argument. Instead, all functions act on the single default loop. |
4677 | argument. Instead, all functions act on the single default loop. |
4026 | |
4678 | |
|
|
4679 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4680 | default loop when multiplicity is switched off - you always have to |
|
|
4681 | initialise the loop manually in this case. |
|
|
4682 | |
4027 | =item EV_MINPRI |
4683 | =item EV_MINPRI |
4028 | |
4684 | |
4029 | =item EV_MAXPRI |
4685 | =item EV_MAXPRI |
4030 | |
4686 | |
4031 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4687 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4067 | #define EV_USE_POLL 1 |
4723 | #define EV_USE_POLL 1 |
4068 | #define EV_CHILD_ENABLE 1 |
4724 | #define EV_CHILD_ENABLE 1 |
4069 | #define EV_ASYNC_ENABLE 1 |
4725 | #define EV_ASYNC_ENABLE 1 |
4070 | |
4726 | |
4071 | The actual value is a bitset, it can be a combination of the following |
4727 | The actual value is a bitset, it can be a combination of the following |
4072 | values: |
4728 | values (by default, all of these are enabled): |
4073 | |
4729 | |
4074 | =over 4 |
4730 | =over 4 |
4075 | |
4731 | |
4076 | =item C<1> - faster/larger code |
4732 | =item C<1> - faster/larger code |
4077 | |
4733 | |
… | |
… | |
4081 | code size by roughly 30% on amd64). |
4737 | code size by roughly 30% on amd64). |
4082 | |
4738 | |
4083 | When optimising for size, use of compiler flags such as C<-Os> with |
4739 | When optimising for size, use of compiler flags such as C<-Os> with |
4084 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4740 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4085 | assertions. |
4741 | assertions. |
|
|
4742 | |
|
|
4743 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4744 | (e.g. gcc with C<-Os>). |
4086 | |
4745 | |
4087 | =item C<2> - faster/larger data structures |
4746 | =item C<2> - faster/larger data structures |
4088 | |
4747 | |
4089 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4748 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4090 | hash table sizes and so on. This will usually further increase code size |
4749 | hash table sizes and so on. This will usually further increase code size |
4091 | and can additionally have an effect on the size of data structures at |
4750 | and can additionally have an effect on the size of data structures at |
4092 | runtime. |
4751 | runtime. |
4093 | |
4752 | |
|
|
4753 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4754 | (e.g. gcc with C<-Os>). |
|
|
4755 | |
4094 | =item C<4> - full API configuration |
4756 | =item C<4> - full API configuration |
4095 | |
4757 | |
4096 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4758 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4097 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4759 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4098 | |
4760 | |
… | |
… | |
4128 | |
4790 | |
4129 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4791 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4130 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4792 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4131 | your program might be left out as well - a binary starting a timer and an |
4793 | your program might be left out as well - a binary starting a timer and an |
4132 | I/O watcher then might come out at only 5Kb. |
4794 | I/O watcher then might come out at only 5Kb. |
|
|
4795 | |
|
|
4796 | =item EV_API_STATIC |
|
|
4797 | |
|
|
4798 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4799 | will have static linkage. This means that libev will not export any |
|
|
4800 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4801 | when you embed libev, only want to use libev functions in a single file, |
|
|
4802 | and do not want its identifiers to be visible. |
|
|
4803 | |
|
|
4804 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4805 | wants to use libev. |
|
|
4806 | |
|
|
4807 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4808 | doesn't support the required declaration syntax. |
4133 | |
4809 | |
4134 | =item EV_AVOID_STDIO |
4810 | =item EV_AVOID_STDIO |
4135 | |
4811 | |
4136 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4812 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4137 | functions (printf, scanf, perror etc.). This will increase the code size |
4813 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4281 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4957 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4282 | |
4958 | |
4283 | #include "ev_cpp.h" |
4959 | #include "ev_cpp.h" |
4284 | #include "ev.c" |
4960 | #include "ev.c" |
4285 | |
4961 | |
4286 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4962 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4287 | |
4963 | |
4288 | =head2 THREADS AND COROUTINES |
4964 | =head2 THREADS AND COROUTINES |
4289 | |
4965 | |
4290 | =head3 THREADS |
4966 | =head3 THREADS |
4291 | |
4967 | |
… | |
… | |
4342 | default loop and triggering an C<ev_async> watcher from the default loop |
5018 | default loop and triggering an C<ev_async> watcher from the default loop |
4343 | watcher callback into the event loop interested in the signal. |
5019 | watcher callback into the event loop interested in the signal. |
4344 | |
5020 | |
4345 | =back |
5021 | =back |
4346 | |
5022 | |
4347 | =head4 THREAD LOCKING EXAMPLE |
5023 | See also L</THREAD LOCKING EXAMPLE>. |
4348 | |
|
|
4349 | Here is a fictitious example of how to run an event loop in a different |
|
|
4350 | thread than where callbacks are being invoked and watchers are |
|
|
4351 | created/added/removed. |
|
|
4352 | |
|
|
4353 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4354 | which uses exactly this technique (which is suited for many high-level |
|
|
4355 | languages). |
|
|
4356 | |
|
|
4357 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4358 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4359 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4360 | |
|
|
4361 | First, you need to associate some data with the event loop: |
|
|
4362 | |
|
|
4363 | typedef struct { |
|
|
4364 | mutex_t lock; /* global loop lock */ |
|
|
4365 | ev_async async_w; |
|
|
4366 | thread_t tid; |
|
|
4367 | cond_t invoke_cv; |
|
|
4368 | } userdata; |
|
|
4369 | |
|
|
4370 | void prepare_loop (EV_P) |
|
|
4371 | { |
|
|
4372 | // for simplicity, we use a static userdata struct. |
|
|
4373 | static userdata u; |
|
|
4374 | |
|
|
4375 | ev_async_init (&u->async_w, async_cb); |
|
|
4376 | ev_async_start (EV_A_ &u->async_w); |
|
|
4377 | |
|
|
4378 | pthread_mutex_init (&u->lock, 0); |
|
|
4379 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4380 | |
|
|
4381 | // now associate this with the loop |
|
|
4382 | ev_set_userdata (EV_A_ u); |
|
|
4383 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4384 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4385 | |
|
|
4386 | // then create the thread running ev_loop |
|
|
4387 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4388 | } |
|
|
4389 | |
|
|
4390 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4391 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4392 | that might have been added: |
|
|
4393 | |
|
|
4394 | static void |
|
|
4395 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4396 | { |
|
|
4397 | // just used for the side effects |
|
|
4398 | } |
|
|
4399 | |
|
|
4400 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4401 | protecting the loop data, respectively. |
|
|
4402 | |
|
|
4403 | static void |
|
|
4404 | l_release (EV_P) |
|
|
4405 | { |
|
|
4406 | userdata *u = ev_userdata (EV_A); |
|
|
4407 | pthread_mutex_unlock (&u->lock); |
|
|
4408 | } |
|
|
4409 | |
|
|
4410 | static void |
|
|
4411 | l_acquire (EV_P) |
|
|
4412 | { |
|
|
4413 | userdata *u = ev_userdata (EV_A); |
|
|
4414 | pthread_mutex_lock (&u->lock); |
|
|
4415 | } |
|
|
4416 | |
|
|
4417 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4418 | into C<ev_run>: |
|
|
4419 | |
|
|
4420 | void * |
|
|
4421 | l_run (void *thr_arg) |
|
|
4422 | { |
|
|
4423 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4424 | |
|
|
4425 | l_acquire (EV_A); |
|
|
4426 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4427 | ev_run (EV_A_ 0); |
|
|
4428 | l_release (EV_A); |
|
|
4429 | |
|
|
4430 | return 0; |
|
|
4431 | } |
|
|
4432 | |
|
|
4433 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4434 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4435 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4436 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4437 | and b) skipping inter-thread-communication when there are no pending |
|
|
4438 | watchers is very beneficial): |
|
|
4439 | |
|
|
4440 | static void |
|
|
4441 | l_invoke (EV_P) |
|
|
4442 | { |
|
|
4443 | userdata *u = ev_userdata (EV_A); |
|
|
4444 | |
|
|
4445 | while (ev_pending_count (EV_A)) |
|
|
4446 | { |
|
|
4447 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4448 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4449 | } |
|
|
4450 | } |
|
|
4451 | |
|
|
4452 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4453 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4454 | thread to continue: |
|
|
4455 | |
|
|
4456 | static void |
|
|
4457 | real_invoke_pending (EV_P) |
|
|
4458 | { |
|
|
4459 | userdata *u = ev_userdata (EV_A); |
|
|
4460 | |
|
|
4461 | pthread_mutex_lock (&u->lock); |
|
|
4462 | ev_invoke_pending (EV_A); |
|
|
4463 | pthread_cond_signal (&u->invoke_cv); |
|
|
4464 | pthread_mutex_unlock (&u->lock); |
|
|
4465 | } |
|
|
4466 | |
|
|
4467 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4468 | event loop, you will now have to lock: |
|
|
4469 | |
|
|
4470 | ev_timer timeout_watcher; |
|
|
4471 | userdata *u = ev_userdata (EV_A); |
|
|
4472 | |
|
|
4473 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4474 | |
|
|
4475 | pthread_mutex_lock (&u->lock); |
|
|
4476 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4477 | ev_async_send (EV_A_ &u->async_w); |
|
|
4478 | pthread_mutex_unlock (&u->lock); |
|
|
4479 | |
|
|
4480 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4481 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4482 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4483 | watchers in the next event loop iteration. |
|
|
4484 | |
5024 | |
4485 | =head3 COROUTINES |
5025 | =head3 COROUTINES |
4486 | |
5026 | |
4487 | Libev is very accommodating to coroutines ("cooperative threads"): |
5027 | Libev is very accommodating to coroutines ("cooperative threads"): |
4488 | libev fully supports nesting calls to its functions from different |
5028 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4653 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5193 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4654 | model. Libev still offers limited functionality on this platform in |
5194 | model. Libev still offers limited functionality on this platform in |
4655 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5195 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4656 | descriptors. This only applies when using Win32 natively, not when using |
5196 | descriptors. This only applies when using Win32 natively, not when using |
4657 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5197 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4658 | as every compielr comes with a slightly differently broken/incompatible |
5198 | as every compiler comes with a slightly differently broken/incompatible |
4659 | environment. |
5199 | environment. |
4660 | |
5200 | |
4661 | Lifting these limitations would basically require the full |
5201 | Lifting these limitations would basically require the full |
4662 | re-implementation of the I/O system. If you are into this kind of thing, |
5202 | re-implementation of the I/O system. If you are into this kind of thing, |
4663 | then note that glib does exactly that for you in a very portable way (note |
5203 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4757 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5297 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4758 | assumes that the same (machine) code can be used to call any watcher |
5298 | assumes that the same (machine) code can be used to call any watcher |
4759 | callback: The watcher callbacks have different type signatures, but libev |
5299 | callback: The watcher callbacks have different type signatures, but libev |
4760 | calls them using an C<ev_watcher *> internally. |
5300 | calls them using an C<ev_watcher *> internally. |
4761 | |
5301 | |
|
|
5302 | =item pointer accesses must be thread-atomic |
|
|
5303 | |
|
|
5304 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5305 | writable in one piece - this is the case on all current architectures. |
|
|
5306 | |
4762 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5307 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4763 | |
5308 | |
4764 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5309 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4765 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
5310 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4766 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
5311 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
… | |
… | |
4774 | thread" or will block signals process-wide, both behaviours would |
5319 | thread" or will block signals process-wide, both behaviours would |
4775 | be compatible with libev. Interaction between C<sigprocmask> and |
5320 | be compatible with libev. Interaction between C<sigprocmask> and |
4776 | C<pthread_sigmask> could complicate things, however. |
5321 | C<pthread_sigmask> could complicate things, however. |
4777 | |
5322 | |
4778 | The most portable way to handle signals is to block signals in all threads |
5323 | The most portable way to handle signals is to block signals in all threads |
4779 | except the initial one, and run the default loop in the initial thread as |
5324 | except the initial one, and run the signal handling loop in the initial |
4780 | well. |
5325 | thread as well. |
4781 | |
5326 | |
4782 | =item C<long> must be large enough for common memory allocation sizes |
5327 | =item C<long> must be large enough for common memory allocation sizes |
4783 | |
5328 | |
4784 | To improve portability and simplify its API, libev uses C<long> internally |
5329 | To improve portability and simplify its API, libev uses C<long> internally |
4785 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5330 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
4791 | |
5336 | |
4792 | The type C<double> is used to represent timestamps. It is required to |
5337 | The type C<double> is used to represent timestamps. It is required to |
4793 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5338 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4794 | good enough for at least into the year 4000 with millisecond accuracy |
5339 | good enough for at least into the year 4000 with millisecond accuracy |
4795 | (the design goal for libev). This requirement is overfulfilled by |
5340 | (the design goal for libev). This requirement is overfulfilled by |
4796 | implementations using IEEE 754, which is basically all existing ones. With |
5341 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5342 | |
4797 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5343 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5344 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5345 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5346 | something like that, just kidding). |
4798 | |
5347 | |
4799 | =back |
5348 | =back |
4800 | |
5349 | |
4801 | If you know of other additional requirements drop me a note. |
5350 | If you know of other additional requirements drop me a note. |
4802 | |
5351 | |
… | |
… | |
4864 | =item Processing ev_async_send: O(number_of_async_watchers) |
5413 | =item Processing ev_async_send: O(number_of_async_watchers) |
4865 | |
5414 | |
4866 | =item Processing signals: O(max_signal_number) |
5415 | =item Processing signals: O(max_signal_number) |
4867 | |
5416 | |
4868 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5417 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4869 | calls in the current loop iteration. Checking for async and signal events |
5418 | calls in the current loop iteration and the loop is currently |
|
|
5419 | blocked. Checking for async and signal events involves iterating over all |
4870 | involves iterating over all running async watchers or all signal numbers. |
5420 | running async watchers or all signal numbers. |
4871 | |
5421 | |
4872 | =back |
5422 | =back |
4873 | |
5423 | |
4874 | |
5424 | |
4875 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5425 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4876 | |
5426 | |
4877 | The major version 4 introduced some minor incompatible changes to the API. |
5427 | The major version 4 introduced some incompatible changes to the API. |
4878 | |
5428 | |
4879 | At the moment, the C<ev.h> header file tries to implement superficial |
5429 | At the moment, the C<ev.h> header file provides compatibility definitions |
4880 | compatibility, so most programs should still compile. Those might be |
5430 | for all changes, so most programs should still compile. The compatibility |
4881 | removed in later versions of libev, so better update early than late. |
5431 | layer might be removed in later versions of libev, so better update to the |
|
|
5432 | new API early than late. |
4882 | |
5433 | |
4883 | =over 4 |
5434 | =over 4 |
|
|
5435 | |
|
|
5436 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5437 | |
|
|
5438 | The backward compatibility mechanism can be controlled by |
|
|
5439 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
|
|
5440 | section. |
4884 | |
5441 | |
4885 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5442 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
4886 | |
5443 | |
4887 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5444 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
4888 | |
5445 | |
… | |
… | |
4914 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
5471 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
4915 | as all other watcher types. Note that C<ev_loop_fork> is still called |
5472 | as all other watcher types. Note that C<ev_loop_fork> is still called |
4916 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
5473 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
4917 | typedef. |
5474 | typedef. |
4918 | |
5475 | |
4919 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4920 | |
|
|
4921 | The backward compatibility mechanism can be controlled by |
|
|
4922 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4923 | section. |
|
|
4924 | |
|
|
4925 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
5476 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4926 | |
5477 | |
4927 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
5478 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4928 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
5479 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
4929 | and work, but the library code will of course be larger. |
5480 | and work, but the library code will of course be larger. |
… | |
… | |
4936 | =over 4 |
5487 | =over 4 |
4937 | |
5488 | |
4938 | =item active |
5489 | =item active |
4939 | |
5490 | |
4940 | A watcher is active as long as it has been started and not yet stopped. |
5491 | A watcher is active as long as it has been started and not yet stopped. |
4941 | See L<WATCHER STATES> for details. |
5492 | See L</WATCHER STATES> for details. |
4942 | |
5493 | |
4943 | =item application |
5494 | =item application |
4944 | |
5495 | |
4945 | In this document, an application is whatever is using libev. |
5496 | In this document, an application is whatever is using libev. |
4946 | |
5497 | |
… | |
… | |
4982 | watchers and events. |
5533 | watchers and events. |
4983 | |
5534 | |
4984 | =item pending |
5535 | =item pending |
4985 | |
5536 | |
4986 | A watcher is pending as soon as the corresponding event has been |
5537 | A watcher is pending as soon as the corresponding event has been |
4987 | detected. See L<WATCHER STATES> for details. |
5538 | detected. See L</WATCHER STATES> for details. |
4988 | |
5539 | |
4989 | =item real time |
5540 | =item real time |
4990 | |
5541 | |
4991 | The physical time that is observed. It is apparently strictly monotonic :) |
5542 | The physical time that is observed. It is apparently strictly monotonic :) |
4992 | |
5543 | |
4993 | =item wall-clock time |
5544 | =item wall-clock time |
4994 | |
5545 | |
4995 | The time and date as shown on clocks. Unlike real time, it can actually |
5546 | The time and date as shown on clocks. Unlike real time, it can actually |
4996 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5547 | be wrong and jump forwards and backwards, e.g. when you adjust your |
4997 | clock. |
5548 | clock. |
4998 | |
5549 | |
4999 | =item watcher |
5550 | =item watcher |
5000 | |
5551 | |
5001 | A data structure that describes interest in certain events. Watchers need |
5552 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5003 | |
5554 | |
5004 | =back |
5555 | =back |
5005 | |
5556 | |
5006 | =head1 AUTHOR |
5557 | =head1 AUTHOR |
5007 | |
5558 | |
5008 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5559 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5560 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5009 | |
5561 | |