… | |
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58 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
59 | |
59 | |
60 | // now wait for events to arrive |
60 | // now wait for events to arrive |
61 | ev_run (loop, 0); |
61 | ev_run (loop, 0); |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // break was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 ABOUT THIS DOCUMENT |
67 | =head1 ABOUT THIS DOCUMENT |
68 | |
68 | |
… | |
… | |
77 | on event-based programming, nor will it introduce event-based programming |
77 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
78 | with libev. |
79 | |
79 | |
80 | Familiarity with event based programming techniques in general is assumed |
80 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
81 | throughout this document. |
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82 | |
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83 | =head1 WHAT TO READ WHEN IN A HURRY |
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84 | |
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85 | This manual tries to be very detailed, but unfortunately, this also makes |
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86 | it very long. If you just want to know the basics of libev, I suggest |
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87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
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88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
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89 | C<ev_timer> sections in L<WATCHER TYPES>. |
82 | |
90 | |
83 | =head1 ABOUT LIBEV |
91 | =head1 ABOUT LIBEV |
84 | |
92 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
93 | 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 |
94 | file descriptor being readable or a timeout occurring), and it will manage |
… | |
… | |
166 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
167 | |
175 | |
168 | Returns the current time as libev would use it. Please note that the |
176 | 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 |
177 | 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 |
178 | you actually want to know. Also interesting is the combination of |
171 | C<ev_update_now> and C<ev_now>. |
179 | C<ev_now_update> and C<ev_now>. |
172 | |
180 | |
173 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
174 | |
182 | |
175 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
176 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
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185 | passed (approximately - it might return a bit earlier even if not |
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186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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187 | |
177 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
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189 | |
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190 | The range of the C<interval> is limited - libev only guarantees to work |
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191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
178 | |
192 | |
179 | =item int ev_version_major () |
193 | =item int ev_version_major () |
180 | |
194 | |
181 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
182 | |
196 | |
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… | |
233 | the current system, you would need to look at C<ev_embeddable_backends () |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
234 | & ev_supported_backends ()>, likewise for recommended ones. |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
235 | |
249 | |
236 | See the description of C<ev_embed> watchers for more info. |
250 | See the description of C<ev_embed> watchers for more info. |
237 | |
251 | |
238 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
239 | |
253 | |
240 | Sets the allocation function to use (the prototype is similar - the |
254 | 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 |
255 | 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 |
256 | 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 |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
269 | } |
283 | } |
270 | |
284 | |
271 | ... |
285 | ... |
272 | ev_set_allocator (persistent_realloc); |
286 | ev_set_allocator (persistent_realloc); |
273 | |
287 | |
274 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
275 | |
289 | |
276 | Set the callback function to call on a retryable system call error (such |
290 | 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 |
291 | as failed select, poll, epoll_wait). The message is a printable string |
278 | indicating the system call or subsystem causing the problem. If this |
292 | 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 |
293 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
291 | } |
305 | } |
292 | |
306 | |
293 | ... |
307 | ... |
294 | ev_set_syserr_cb (fatal_error); |
308 | ev_set_syserr_cb (fatal_error); |
295 | |
309 | |
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310 | =item ev_feed_signal (int signum) |
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311 | |
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312 | This function can be used to "simulate" a signal receive. It is completely |
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313 | safe to call this function at any time, from any context, including signal |
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314 | handlers or random threads. |
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315 | |
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316 | Its main use is to customise signal handling in your process, especially |
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317 | in the presence of threads. For example, you could block signals |
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318 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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319 | creating any loops), and in one thread, use C<sigwait> or any other |
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320 | mechanism to wait for signals, then "deliver" them to libev by calling |
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321 | C<ev_feed_signal>. |
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322 | |
296 | =back |
323 | =back |
297 | |
324 | |
298 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
325 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
299 | |
326 | |
300 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
327 | 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 |
328 | 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). |
329 | libev 3 had an C<ev_loop> function colliding with the struct name). |
303 | |
330 | |
304 | The library knows two types of such loops, the I<default> loop, which |
331 | The library knows two types of such loops, the I<default> loop, which |
305 | supports signals and child events, and dynamically created event loops |
332 | supports child process events, and dynamically created event loops which |
306 | which do not. |
333 | do not. |
307 | |
334 | |
308 | =over 4 |
335 | =over 4 |
309 | |
336 | |
310 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
337 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
311 | |
338 | |
… | |
… | |
347 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
374 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
348 | |
375 | |
349 | This will create and initialise a new event loop object. If the loop |
376 | This will create and initialise a new event loop object. If the loop |
350 | could not be initialised, returns false. |
377 | could not be initialised, returns false. |
351 | |
378 | |
352 | Note that this function I<is> thread-safe, and one common way to use |
379 | 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 |
380 | threads is indeed to create one loop per thread, and using the default |
354 | default loop in the "main" or "initial" thread. |
381 | loop in the "main" or "initial" thread. |
355 | |
382 | |
356 | The flags argument can be used to specify special behaviour or specific |
383 | 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>). |
384 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
358 | |
385 | |
359 | The following flags are supported: |
386 | The following flags are supported: |
… | |
… | |
394 | environment variable. |
421 | environment variable. |
395 | |
422 | |
396 | =item C<EVFLAG_NOINOTIFY> |
423 | =item C<EVFLAG_NOINOTIFY> |
397 | |
424 | |
398 | When this flag is specified, then libev will not attempt to use the |
425 | 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 |
426 | 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 |
427 | 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. |
428 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
402 | |
429 | |
403 | =item C<EVFLAG_SIGNALFD> |
430 | =item C<EVFLAG_SIGNALFD> |
404 | |
431 | |
405 | When this flag is specified, then libev will attempt to use the |
432 | 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 |
433 | 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 |
434 | 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 |
435 | 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 |
436 | handling with threads, as long as you properly block signals in your |
410 | threads that are not interested in handling them. |
437 | threads that are not interested in handling them. |
411 | |
438 | |
412 | Signalfd will not be used by default as this changes your signal mask, and |
439 | 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 |
440 | there are a lot of shoddy libraries and programs (glib's threadpool for |
414 | example) that can't properly initialise their signal masks. |
441 | example) that can't properly initialise their signal masks. |
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442 | |
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443 | =item C<EVFLAG_NOSIGMASK> |
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444 | |
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445 | When this flag is specified, then libev will avoid to modify the signal |
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446 | mask. Specifically, this means you have to make sure signals are unblocked |
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447 | when you want to receive them. |
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448 | |
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449 | This behaviour is useful when you want to do your own signal handling, or |
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450 | want to handle signals only in specific threads and want to avoid libev |
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451 | unblocking the signals. |
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452 | |
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453 | It's also required by POSIX in a threaded program, as libev calls |
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454 | C<sigprocmask>, whose behaviour is officially unspecified. |
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455 | |
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456 | This flag's behaviour will become the default in future versions of libev. |
415 | |
457 | |
416 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
417 | |
459 | |
418 | This is your standard select(2) backend. Not I<completely> standard, as |
460 | 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, |
461 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
447 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
448 | |
490 | |
449 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
450 | kernels). |
492 | kernels). |
451 | |
493 | |
452 | For few fds, this backend is a bit little slower than poll and select, |
494 | 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 |
495 | 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), |
496 | 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). |
497 | fd), epoll scales either O(1) or O(active_fds). |
456 | |
498 | |
457 | The epoll mechanism deserves honorable mention as the most misdesigned |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
458 | of the more advanced event mechanisms: mere annoyances include silently |
500 | of the more advanced event mechanisms: mere annoyances include silently |
459 | dropping file descriptors, requiring a system call per change per file |
501 | dropping file descriptors, requiring a system call per change per file |
460 | descriptor (and unnecessary guessing of parameters), problems with dup and |
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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503 | returning before the timeout value, resulting in additional iterations |
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504 | (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 |
505 | 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 |
506 | 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 |
507 | set, which can take considerable time (one syscall per file descriptor) |
464 | hard to detect. |
508 | and is of course hard to detect. |
465 | |
509 | |
466 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | 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 |
511 | 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 |
512 | totally I<different> file descriptors (even already closed ones, so |
469 | even remove them from the set) than registered in the set (especially |
513 | 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 |
514 | (especially on SMP systems). Libev tries to counter these spurious |
471 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
472 | events to filter out spurious ones, recreating the set when required. Last |
516 | that against the events to filter out spurious ones, recreating the set |
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517 | when required. Epoll also erroneously rounds down timeouts, but gives you |
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518 | no way to know when and by how much, so sometimes you have to busy-wait |
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519 | because epoll returns immediately despite a nonzero timeout. And last |
473 | not least, it also refuses to work with some file descriptors which work |
520 | not least, it also refuses to work with some file descriptors which work |
474 | perfectly fine with C<select> (files, many character devices...). |
521 | perfectly fine with C<select> (files, many character devices...). |
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522 | |
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523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
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524 | cobbled together in a hurry, no thought to design or interaction with |
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525 | others. Oh, the pain, will it ever stop... |
475 | |
526 | |
476 | While stopping, setting and starting an I/O watcher in the same iteration |
527 | 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 |
528 | 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 |
529 | 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 |
530 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
516 | |
567 | |
517 | It scales in the same way as the epoll backend, but the interface to the |
568 | 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 |
569 | 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 |
570 | 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 |
571 | 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 |
572 | 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 |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
523 | cases |
574 | drops fds silently in similarly hard-to-detect cases |
524 | |
575 | |
525 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
526 | |
577 | |
527 | While nominally embeddable in other event loops, this doesn't work |
578 | 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 |
579 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
545 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
596 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
546 | |
597 | |
547 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
598 | 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)). |
599 | it's really slow, but it still scales very well (O(active_fds)). |
549 | |
600 | |
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 |
601 | 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 |
602 | file descriptor per loop iteration. For small and medium numbers of file |
556 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
603 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
557 | might perform better. |
604 | might perform better. |
558 | |
605 | |
559 | On the positive side, with the exception of the spurious readiness |
606 | 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 |
607 | specification in all tests and is fully embeddable, which is a rare feat |
562 | OS-specific backends (I vastly prefer correctness over speed hacks). |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
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609 | hacks). |
|
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610 | |
|
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611 | On the negative side, the interface is I<bizarre> - so bizarre that |
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612 | even sun itself gets it wrong in their code examples: The event polling |
|
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613 | function sometimes returns events to the caller even though an error |
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614 | occurred, but with no indication whether it has done so or not (yes, it's |
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615 | even documented that way) - deadly for edge-triggered interfaces where you |
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616 | absolutely have to know whether an event occurred or not because you have |
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617 | to re-arm the watcher. |
|
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618 | |
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619 | Fortunately libev seems to be able to work around these idiocies. |
563 | |
620 | |
564 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
565 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
566 | |
623 | |
567 | =item C<EVBACKEND_ALL> |
624 | =item C<EVBACKEND_ALL> |
568 | |
625 | |
569 | Try all backends (even potentially broken ones that wouldn't be tried |
626 | 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 |
627 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
571 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
628 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
572 | |
629 | |
573 | It is definitely not recommended to use this flag. |
630 | It is definitely not recommended to use this flag, use whatever |
|
|
631 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
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632 | at all. |
|
|
633 | |
|
|
634 | =item C<EVBACKEND_MASK> |
|
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635 | |
|
|
636 | Not a backend at all, but a mask to select all backend bits from a |
|
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637 | C<flags> value, in case you want to mask out any backends from a flags |
|
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638 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
574 | |
639 | |
575 | =back |
640 | =back |
576 | |
641 | |
577 | If one or more of the backend flags are or'ed into the flags value, |
642 | 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 |
643 | then only these backends will be tried (in the reverse order as listed |
… | |
… | |
607 | This function is normally used on loop objects allocated by |
672 | 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 |
673 | 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. |
674 | C<ev_default_loop>, in which case it is not thread-safe. |
610 | |
675 | |
611 | Note that it is not advisable to call this function on the default loop |
676 | 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. |
677 | 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> |
678 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
614 | and C<ev_loop_destroy>. |
679 | and C<ev_loop_destroy>. |
615 | |
680 | |
616 | =item ev_loop_fork (loop) |
681 | =item ev_loop_fork (loop) |
617 | |
682 | |
… | |
… | |
665 | prepare and check phases. |
730 | prepare and check phases. |
666 | |
731 | |
667 | =item unsigned int ev_depth (loop) |
732 | =item unsigned int ev_depth (loop) |
668 | |
733 | |
669 | Returns the number of times C<ev_run> was entered minus the number of |
734 | 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. |
735 | times C<ev_run> was exited normally, in other words, the recursion depth. |
671 | |
736 | |
672 | Outside C<ev_run>, this number is zero. In a callback, this number is |
737 | 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), |
738 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
674 | in which case it is higher. |
739 | in which case it is higher. |
675 | |
740 | |
676 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
741 | 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 |
742 | throwing an exception etc.), doesn't count as "exit" - consider this |
678 | ungentleman-like behaviour unless it's really convenient. |
743 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
744 | convenient, in which case it is fully supported. |
679 | |
745 | |
680 | =item unsigned int ev_backend (loop) |
746 | =item unsigned int ev_backend (loop) |
681 | |
747 | |
682 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
748 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
683 | use. |
749 | use. |
… | |
… | |
726 | without a previous call to C<ev_suspend>. |
792 | without a previous call to C<ev_suspend>. |
727 | |
793 | |
728 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
729 | event loop time (see C<ev_now_update>). |
795 | event loop time (see C<ev_now_update>). |
730 | |
796 | |
731 | =item ev_run (loop, int flags) |
797 | =item bool ev_run (loop, int flags) |
732 | |
798 | |
733 | Finally, this is it, the event handler. This function usually is called |
799 | 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 |
800 | 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 |
801 | 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 |
802 | the watcher callbacks, and then repeat the whole process indefinitely: This |
737 | is why event loops are called I<loops>. |
803 | is why event loops are called I<loops>. |
738 | |
804 | |
739 | If the flags argument is specified as C<0>, it will keep handling events |
805 | 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 |
806 | until either no event watchers are active anymore or C<ev_break> was |
741 | called. |
807 | called. |
|
|
808 | |
|
|
809 | The return value is false if there are no more active watchers (which |
|
|
810 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
811 | (which usually means " you should call C<ev_run> again"). |
742 | |
812 | |
743 | Please note that an explicit C<ev_break> is usually better than |
813 | 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 |
814 | relying on all watchers to be stopped when deciding when a program has |
745 | finished (especially in interactive programs), but having a program |
815 | finished (especially in interactive programs), but having a program |
746 | that automatically loops as long as it has to and no longer by virtue |
816 | 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 |
817 | of relying on its watchers stopping correctly, that is truly a thing of |
748 | beauty. |
818 | beauty. |
749 | |
819 | |
|
|
820 | This function is I<mostly> exception-safe - you can break out of a |
|
|
821 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
822 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
823 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
824 | |
750 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
825 | 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 |
826 | 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 |
827 | 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 |
828 | iteration of the loop. This is sometimes useful to poll and handle new |
754 | events while doing lengthy calculations, to keep the program responsive. |
829 | events while doing lengthy calculations, to keep the program responsive. |
… | |
… | |
763 | This is useful if you are waiting for some external event in conjunction |
838 | 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 |
839 | 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 |
840 | 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. |
841 | usually a better approach for this kind of thing. |
767 | |
842 | |
768 | Here are the gory details of what C<ev_run> does: |
843 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
844 | understanding, not a guarantee that things will work exactly like this in |
|
|
845 | future versions): |
769 | |
846 | |
770 | - Increment loop depth. |
847 | - Increment loop depth. |
771 | - Reset the ev_break status. |
848 | - Reset the ev_break status. |
772 | - Before the first iteration, call any pending watchers. |
849 | - Before the first iteration, call any pending watchers. |
773 | LOOP: |
850 | LOOP: |
… | |
… | |
806 | anymore. |
883 | anymore. |
807 | |
884 | |
808 | ... queue jobs here, make sure they register event watchers as long |
885 | ... 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..) |
886 | ... as they still have work to do (even an idle watcher will do..) |
810 | ev_run (my_loop, 0); |
887 | ev_run (my_loop, 0); |
811 | ... jobs done or somebody called unloop. yeah! |
888 | ... jobs done or somebody called break. yeah! |
812 | |
889 | |
813 | =item ev_break (loop, how) |
890 | =item ev_break (loop, how) |
814 | |
891 | |
815 | Can be used to make a call to C<ev_run> return early (but only after it |
892 | 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 |
893 | 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 |
894 | 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. |
895 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
819 | |
896 | |
820 | This "unloop state" will be cleared when entering C<ev_run> again. |
897 | This "break state" will be cleared on the next call to C<ev_run>. |
821 | |
898 | |
822 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
899 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
900 | which case it will have no effect. |
823 | |
901 | |
824 | =item ev_ref (loop) |
902 | =item ev_ref (loop) |
825 | |
903 | |
826 | =item ev_unref (loop) |
904 | =item ev_unref (loop) |
827 | |
905 | |
… | |
… | |
848 | running when nothing else is active. |
926 | running when nothing else is active. |
849 | |
927 | |
850 | ev_signal exitsig; |
928 | ev_signal exitsig; |
851 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
929 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
852 | ev_signal_start (loop, &exitsig); |
930 | ev_signal_start (loop, &exitsig); |
853 | evf_unref (loop); |
931 | ev_unref (loop); |
854 | |
932 | |
855 | Example: For some weird reason, unregister the above signal handler again. |
933 | Example: For some weird reason, unregister the above signal handler again. |
856 | |
934 | |
857 | ev_ref (loop); |
935 | ev_ref (loop); |
858 | ev_signal_stop (loop, &exitsig); |
936 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
878 | overhead for the actual polling but can deliver many events at once. |
956 | overhead for the actual polling but can deliver many events at once. |
879 | |
957 | |
880 | By setting a higher I<io collect interval> you allow libev to spend more |
958 | 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, |
959 | 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 |
960 | 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 |
961 | 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 |
962 | 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 |
963 | sleep time ensures that libev will not poll for I/O events more often then |
886 | once per this interval, on average. |
964 | once per this interval, on average (as long as the host time resolution is |
|
|
965 | good enough). |
887 | |
966 | |
888 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
967 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
889 | to spend more time collecting timeouts, at the expense of increased |
968 | to spend more time collecting timeouts, at the expense of increased |
890 | latency/jitter/inexactness (the watcher callback will be called |
969 | 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 |
970 | 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.). |
1016 | invoke the actual watchers inside another context (another thread etc.). |
938 | |
1017 | |
939 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1018 | If you want to reset the callback, use C<ev_invoke_pending> as new |
940 | callback. |
1019 | callback. |
941 | |
1020 | |
942 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1021 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
943 | |
1022 | |
944 | Sometimes you want to share the same loop between multiple threads. This |
1023 | 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 |
1024 | can be done relatively simply by putting mutex_lock/unlock calls around |
946 | each call to a libev function. |
1025 | each call to a libev function. |
947 | |
1026 | |
948 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1027 | 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 |
1028 | 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 |
1029 | 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. |
1030 | I<release> and I<acquire> callbacks on the loop. |
952 | |
1031 | |
953 | When set, then C<release> will be called just before the thread is |
1032 | 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 |
1033 | suspended waiting for new events, and C<acquire> is called just |
955 | afterwards. |
1034 | afterwards. |
… | |
… | |
970 | See also the locking example in the C<THREADS> section later in this |
1049 | See also the locking example in the C<THREADS> section later in this |
971 | document. |
1050 | document. |
972 | |
1051 | |
973 | =item ev_set_userdata (loop, void *data) |
1052 | =item ev_set_userdata (loop, void *data) |
974 | |
1053 | |
975 | =item ev_userdata (loop) |
1054 | =item void *ev_userdata (loop) |
976 | |
1055 | |
977 | Set and retrieve a single C<void *> associated with a loop. When |
1056 | 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 |
1057 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
979 | C<0.> |
1058 | C<0>. |
980 | |
1059 | |
981 | These two functions can be used to associate arbitrary data with a loop, |
1060 | 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 |
1061 | 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 |
1062 | C<acquire> callbacks described above, but of course can be (ab-)used for |
984 | any other purpose as well. |
1063 | any other purpose as well. |
… | |
… | |
1114 | The event loop has been resumed in the child process after fork (see |
1193 | The event loop has been resumed in the child process after fork (see |
1115 | C<ev_fork>). |
1194 | C<ev_fork>). |
1116 | |
1195 | |
1117 | =item C<EV_CLEANUP> |
1196 | =item C<EV_CLEANUP> |
1118 | |
1197 | |
1119 | The event loop is abotu to be destroyed (see C<ev_cleanup>). |
1198 | The event loop is about to be destroyed (see C<ev_cleanup>). |
1120 | |
1199 | |
1121 | =item C<EV_ASYNC> |
1200 | =item C<EV_ASYNC> |
1122 | |
1201 | |
1123 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1202 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1124 | |
1203 | |
… | |
… | |
1146 | programs, though, as the fd could already be closed and reused for another |
1225 | programs, though, as the fd could already be closed and reused for another |
1147 | thing, so beware. |
1226 | thing, so beware. |
1148 | |
1227 | |
1149 | =back |
1228 | =back |
1150 | |
1229 | |
|
|
1230 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1231 | |
|
|
1232 | =over 4 |
|
|
1233 | |
|
|
1234 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1235 | |
|
|
1236 | This macro initialises the generic portion of a watcher. The contents |
|
|
1237 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1238 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1239 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1240 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1241 | which rolls both calls into one. |
|
|
1242 | |
|
|
1243 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1244 | (or never started) and there are no pending events outstanding. |
|
|
1245 | |
|
|
1246 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1247 | int revents)>. |
|
|
1248 | |
|
|
1249 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1250 | |
|
|
1251 | ev_io w; |
|
|
1252 | ev_init (&w, my_cb); |
|
|
1253 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1254 | |
|
|
1255 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1256 | |
|
|
1257 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1258 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1259 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1260 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1261 | difference to the C<ev_init> macro). |
|
|
1262 | |
|
|
1263 | Although some watcher types do not have type-specific arguments |
|
|
1264 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1265 | |
|
|
1266 | See C<ev_init>, above, for an example. |
|
|
1267 | |
|
|
1268 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1269 | |
|
|
1270 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1271 | calls into a single call. This is the most convenient method to initialise |
|
|
1272 | a watcher. The same limitations apply, of course. |
|
|
1273 | |
|
|
1274 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1275 | |
|
|
1276 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1277 | |
|
|
1278 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1279 | |
|
|
1280 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1281 | events. If the watcher is already active nothing will happen. |
|
|
1282 | |
|
|
1283 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1284 | whole section. |
|
|
1285 | |
|
|
1286 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1287 | |
|
|
1288 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1289 | |
|
|
1290 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1291 | the watcher was active or not). |
|
|
1292 | |
|
|
1293 | It is possible that stopped watchers are pending - for example, |
|
|
1294 | non-repeating timers are being stopped when they become pending - but |
|
|
1295 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1296 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1297 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1298 | |
|
|
1299 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1300 | |
|
|
1301 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1302 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1303 | it. |
|
|
1304 | |
|
|
1305 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1306 | |
|
|
1307 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1308 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1309 | is pending (but not active) you must not call an init function on it (but |
|
|
1310 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1311 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1312 | it). |
|
|
1313 | |
|
|
1314 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1315 | |
|
|
1316 | Returns the callback currently set on the watcher. |
|
|
1317 | |
|
|
1318 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
1319 | |
|
|
1320 | Change the callback. You can change the callback at virtually any time |
|
|
1321 | (modulo threads). |
|
|
1322 | |
|
|
1323 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1324 | |
|
|
1325 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1326 | |
|
|
1327 | Set and query the priority of the watcher. The priority is a small |
|
|
1328 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1329 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1330 | before watchers with lower priority, but priority will not keep watchers |
|
|
1331 | from being executed (except for C<ev_idle> watchers). |
|
|
1332 | |
|
|
1333 | If you need to suppress invocation when higher priority events are pending |
|
|
1334 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1335 | |
|
|
1336 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1337 | pending. |
|
|
1338 | |
|
|
1339 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1340 | fine, as long as you do not mind that the priority value you query might |
|
|
1341 | or might not have been clamped to the valid range. |
|
|
1342 | |
|
|
1343 | The default priority used by watchers when no priority has been set is |
|
|
1344 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1345 | |
|
|
1346 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1347 | priorities. |
|
|
1348 | |
|
|
1349 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1350 | |
|
|
1351 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1352 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1353 | can deal with that fact, as both are simply passed through to the |
|
|
1354 | callback. |
|
|
1355 | |
|
|
1356 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1357 | |
|
|
1358 | If the watcher is pending, this function clears its pending status and |
|
|
1359 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1360 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1361 | |
|
|
1362 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1363 | callback to be invoked, which can be accomplished with this function. |
|
|
1364 | |
|
|
1365 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1366 | |
|
|
1367 | Feeds the given event set into the event loop, as if the specified event |
|
|
1368 | had happened for the specified watcher (which must be a pointer to an |
|
|
1369 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1370 | not free the watcher as long as it has pending events. |
|
|
1371 | |
|
|
1372 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1373 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1374 | not started in the first place. |
|
|
1375 | |
|
|
1376 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1377 | functions that do not need a watcher. |
|
|
1378 | |
|
|
1379 | =back |
|
|
1380 | |
|
|
1381 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
|
|
1382 | OWN COMPOSITE WATCHERS> idioms. |
|
|
1383 | |
1151 | =head2 WATCHER STATES |
1384 | =head2 WATCHER STATES |
1152 | |
1385 | |
1153 | There are various watcher states mentioned throughout this manual - |
1386 | There are various watcher states mentioned throughout this manual - |
1154 | active, pending and so on. In this section these states and the rules to |
1387 | 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 |
1388 | transition between them will be described in more detail - and while these |
… | |
… | |
1157 | |
1390 | |
1158 | =over 4 |
1391 | =over 4 |
1159 | |
1392 | |
1160 | =item initialiased |
1393 | =item initialiased |
1161 | |
1394 | |
1162 | Before a watcher can be registered with the event looop it has to be |
1395 | 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 |
1396 | 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. |
1397 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1165 | |
1398 | |
1166 | In this state it is simply some block of memory that is suitable for use |
1399 | 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. |
1400 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1401 | will - as long as you either keep the memory contents intact, or call |
|
|
1402 | C<ev_TYPE_init> again. |
1168 | |
1403 | |
1169 | =item started/running/active |
1404 | =item started/running/active |
1170 | |
1405 | |
1171 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1406 | 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 |
1407 | 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 |
1435 | 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 |
1436 | of whether it was active or not, so stopping a watcher explicitly before |
1202 | freeing it is often a good idea. |
1437 | freeing it is often a good idea. |
1203 | |
1438 | |
1204 | While stopped (and not pending) the watcher is essentially in the |
1439 | 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 |
1440 | initialised state, that is, it can be reused, moved, modified in any way |
1206 | you wish. |
1441 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1442 | it again). |
1207 | |
1443 | |
1208 | =back |
1444 | =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 | |
1445 | |
1427 | =head2 WATCHER PRIORITY MODELS |
1446 | =head2 WATCHER PRIORITY MODELS |
1428 | |
1447 | |
1429 | Many event loops support I<watcher priorities>, which are usually small |
1448 | Many event loops support I<watcher priorities>, which are usually small |
1430 | integers that influence the ordering of event callback invocation |
1449 | integers that influence the ordering of event callback invocation |
… | |
… | |
1557 | In general you can register as many read and/or write event watchers per |
1576 | 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 |
1577 | 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 |
1578 | descriptors to non-blocking mode is also usually a good idea (but not |
1560 | required if you know what you are doing). |
1579 | required if you know what you are doing). |
1561 | |
1580 | |
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 |
1581 | 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 |
1582 | 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 |
1583 | 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 |
1584 | 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 |
1585 | with a relatively standard program structure. Thus it is best to always |
1573 | this situation even with a relatively standard program structure. Thus |
1586 | 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. |
1587 | preferable to a program hanging until some data arrives. |
1576 | |
1588 | |
1577 | If you cannot run the fd in non-blocking mode (for example you should |
1589 | 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 |
1590 | 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 |
1591 | 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 |
1592 | 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 |
1593 | 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 |
1594 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1583 | indefinitely. |
1595 | indefinitely. |
1584 | |
1596 | |
1585 | But really, best use non-blocking mode. |
1597 | But really, best use non-blocking mode. |
1586 | |
1598 | |
… | |
… | |
1614 | |
1626 | |
1615 | There is no workaround possible except not registering events |
1627 | There is no workaround possible except not registering events |
1616 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1628 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1617 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1629 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1618 | |
1630 | |
|
|
1631 | =head3 The special problem of files |
|
|
1632 | |
|
|
1633 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1634 | representing files, and expect it to become ready when their program |
|
|
1635 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1636 | |
|
|
1637 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1638 | notification as soon as the kernel knows whether and how much data is |
|
|
1639 | there, and in the case of open files, that's always the case, so you |
|
|
1640 | always get a readiness notification instantly, and your read (or possibly |
|
|
1641 | write) will still block on the disk I/O. |
|
|
1642 | |
|
|
1643 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1644 | devices and so on, there is another party (the sender) that delivers data |
|
|
1645 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1646 | will not send data on its own, simply because it doesn't know what you |
|
|
1647 | wish to read - you would first have to request some data. |
|
|
1648 | |
|
|
1649 | Since files are typically not-so-well supported by advanced notification |
|
|
1650 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1651 | to files, even though you should not use it. The reason for this is |
|
|
1652 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1653 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1654 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1655 | F</dev/urandom>), and even though the file might better be served with |
|
|
1656 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1657 | it "just works" instead of freezing. |
|
|
1658 | |
|
|
1659 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1660 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1661 | when you rarely read from a file instead of from a socket, and want to |
|
|
1662 | reuse the same code path. |
|
|
1663 | |
1619 | =head3 The special problem of fork |
1664 | =head3 The special problem of fork |
1620 | |
1665 | |
1621 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1666 | 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 |
1667 | useless behaviour. Libev fully supports fork, but needs to be told about |
1623 | it in the child. |
1668 | it in the child if you want to continue to use it in the child. |
1624 | |
1669 | |
1625 | To support fork in your programs, you either have to call |
1670 | 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, |
1671 | ()> 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 |
1672 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1628 | C<EVBACKEND_POLL>. |
|
|
1629 | |
1673 | |
1630 | =head3 The special problem of SIGPIPE |
1674 | =head3 The special problem of SIGPIPE |
1631 | |
1675 | |
1632 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1676 | 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 |
1677 | 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 |
1775 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1732 | monotonic clock option helps a lot here). |
1776 | monotonic clock option helps a lot here). |
1733 | |
1777 | |
1734 | The callback is guaranteed to be invoked only I<after> its timeout has |
1778 | 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 |
1779 | 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 |
1780 | might introduce a small delay, see "the special problem of being too |
|
|
1781 | 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 |
1782 | 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 |
1783 | 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). |
1784 | longer true when a callback calls C<ev_run> recursively). |
1740 | |
1785 | |
1741 | =head3 Be smart about timeouts |
1786 | =head3 Be smart about timeouts |
1742 | |
1787 | |
1743 | Many real-world problems involve some kind of timeout, usually for error |
1788 | 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, |
1789 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1819 | |
1864 | |
1820 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1865 | 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 |
1866 | but remember the time of last activity, and check for a real timeout only |
1822 | within the callback: |
1867 | within the callback: |
1823 | |
1868 | |
|
|
1869 | ev_tstamp timeout = 60.; |
1824 | ev_tstamp last_activity; // time of last activity |
1870 | ev_tstamp last_activity; // time of last activity |
|
|
1871 | ev_timer timer; |
1825 | |
1872 | |
1826 | static void |
1873 | static void |
1827 | callback (EV_P_ ev_timer *w, int revents) |
1874 | callback (EV_P_ ev_timer *w, int revents) |
1828 | { |
1875 | { |
1829 | ev_tstamp now = ev_now (EV_A); |
1876 | // calculate when the timeout would happen |
1830 | ev_tstamp timeout = last_activity + 60.; |
1877 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1831 | |
1878 | |
1832 | // if last_activity + 60. is older than now, we did time out |
1879 | // if negative, it means we the timeout already occured |
1833 | if (timeout < now) |
1880 | if (after < 0.) |
1834 | { |
1881 | { |
1835 | // timeout occurred, take action |
1882 | // timeout occurred, take action |
1836 | } |
1883 | } |
1837 | else |
1884 | else |
1838 | { |
1885 | { |
1839 | // callback was invoked, but there was some activity, re-arm |
1886 | // callback was invoked, but there was some recent |
1840 | // the watcher to fire in last_activity + 60, which is |
1887 | // activity. simply restart the timer to time out |
1841 | // guaranteed to be in the future, so "again" is positive: |
1888 | // after "after" seconds, which is the earliest time |
1842 | w->repeat = timeout - now; |
1889 | // the timeout can occur. |
|
|
1890 | ev_timer_set (w, after, 0.); |
1843 | ev_timer_again (EV_A_ w); |
1891 | ev_timer_start (EV_A_ w); |
1844 | } |
1892 | } |
1845 | } |
1893 | } |
1846 | |
1894 | |
1847 | To summarise the callback: first calculate the real timeout (defined |
1895 | 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 |
1896 | 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 |
1897 | 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 |
1898 | (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 | |
1899 | |
1854 | Note how C<ev_timer_again> is used, taking advantage of the |
1900 | 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. |
1901 | timed out, and need to do whatever is needed in this case. |
|
|
1902 | |
|
|
1903 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1904 | and simply start the timer with this timeout value. |
|
|
1905 | |
|
|
1906 | In other words, each time the callback is invoked it will check whether |
|
|
1907 | the timeout cocured. If not, it will simply reschedule itself to check |
|
|
1908 | again at the earliest time it could time out. Rinse. Repeat. |
1856 | |
1909 | |
1857 | This scheme causes more callback invocations (about one every 60 seconds |
1910 | This scheme causes more callback invocations (about one every 60 seconds |
1858 | minus half the average time between activity), but virtually no calls to |
1911 | minus half the average time between activity), but virtually no calls to |
1859 | libev to change the timeout. |
1912 | libev to change the timeout. |
1860 | |
1913 | |
1861 | To start the timer, simply initialise the watcher and set C<last_activity> |
1914 | To start the machinery, simply initialise the watcher and set |
1862 | to the current time (meaning we just have some activity :), then call the |
1915 | 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: |
1916 | now), then call the callback, which will "do the right thing" and start |
|
|
1917 | the timer: |
1864 | |
1918 | |
|
|
1919 | last_activity = ev_now (EV_A); |
1865 | ev_init (timer, callback); |
1920 | ev_init (&timer, callback); |
1866 | last_activity = ev_now (loop); |
1921 | callback (EV_A_ &timer, 0); |
1867 | callback (loop, timer, EV_TIMER); |
|
|
1868 | |
1922 | |
1869 | And when there is some activity, simply store the current time in |
1923 | When there is some activity, simply store the current time in |
1870 | C<last_activity>, no libev calls at all: |
1924 | C<last_activity>, no libev calls at all: |
1871 | |
1925 | |
|
|
1926 | if (activity detected) |
1872 | last_activity = ev_now (loop); |
1927 | last_activity = ev_now (EV_A); |
|
|
1928 | |
|
|
1929 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1930 | providing a new value, stopping the timer and calling the callback, which |
|
|
1931 | will agaion do the right thing (for example, time out immediately :). |
|
|
1932 | |
|
|
1933 | timeout = new_value; |
|
|
1934 | ev_timer_stop (EV_A_ &timer); |
|
|
1935 | callback (EV_A_ &timer, 0); |
1873 | |
1936 | |
1874 | This technique is slightly more complex, but in most cases where the |
1937 | This technique is slightly more complex, but in most cases where the |
1875 | time-out is unlikely to be triggered, much more efficient. |
1938 | 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 | |
1939 | |
1881 | =item 4. Wee, just use a double-linked list for your timeouts. |
1940 | =item 4. Wee, just use a double-linked list for your timeouts. |
1882 | |
1941 | |
1883 | If there is not one request, but many thousands (millions...), all |
1942 | 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 |
1943 | 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 |
1970 | 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 |
1971 | 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 |
1972 | off after the first million or so of active timers, i.e. it's usually |
1914 | overkill :) |
1973 | overkill :) |
1915 | |
1974 | |
|
|
1975 | =head3 The special problem of being too early |
|
|
1976 | |
|
|
1977 | If you ask a timer to call your callback after three seconds, then |
|
|
1978 | you expect it to be invoked after three seconds - but of course, this |
|
|
1979 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1980 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1981 | process with a STOP signal for a few hours for example. |
|
|
1982 | |
|
|
1983 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1984 | delay has occurred, but cannot guarantee this. |
|
|
1985 | |
|
|
1986 | A less obvious failure mode is calling your callback too early: many event |
|
|
1987 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1988 | this can cause your callback to be invoked much earlier than you would |
|
|
1989 | expect. |
|
|
1990 | |
|
|
1991 | To see why, imagine a system with a clock that only offers full second |
|
|
1992 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1993 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1994 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
1995 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
1996 | |
|
|
1997 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
1998 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
1999 | one-second delay was requested - this is being "too early", despite best |
|
|
2000 | intentions. |
|
|
2001 | |
|
|
2002 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2003 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2004 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2005 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2006 | |
|
|
2007 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2008 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2009 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2010 | late" side of things. |
|
|
2011 | |
1916 | =head3 The special problem of time updates |
2012 | =head3 The special problem of time updates |
1917 | |
2013 | |
1918 | Establishing the current time is a costly operation (it usually takes at |
2014 | Establishing the current time is a costly operation (it usually takes |
1919 | least two system calls): EV therefore updates its idea of the current |
2015 | 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 |
2016 | 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 |
2017 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1922 | lots of events in one iteration. |
2018 | lots of events in one iteration. |
1923 | |
2019 | |
1924 | The relative timeouts are calculated relative to the C<ev_now ()> |
2020 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1930 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2026 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1931 | |
2027 | |
1932 | If the event loop is suspended for a long time, you can also force an |
2028 | 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 |
2029 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1934 | ()>. |
2030 | ()>. |
|
|
2031 | |
|
|
2032 | =head3 The special problem of unsynchronised clocks |
|
|
2033 | |
|
|
2034 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2035 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2036 | jumps). |
|
|
2037 | |
|
|
2038 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2039 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2040 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2041 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2042 | than a directly following call to C<time>. |
|
|
2043 | |
|
|
2044 | The moral of this is to only compare libev-related timestamps with |
|
|
2045 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2046 | a second or so. |
|
|
2047 | |
|
|
2048 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2049 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2050 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2051 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2052 | |
|
|
2053 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2054 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2055 | I<measured according to the real time>, not the system clock. |
|
|
2056 | |
|
|
2057 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2058 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2059 | exactly the right behaviour. |
|
|
2060 | |
|
|
2061 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2062 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2063 | time, where your comparisons will always generate correct results. |
1935 | |
2064 | |
1936 | =head3 The special problems of suspended animation |
2065 | =head3 The special problems of suspended animation |
1937 | |
2066 | |
1938 | When you leave the server world it is quite customary to hit machines that |
2067 | 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? |
2068 | 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 |
2112 | 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. |
2113 | do stuff) the timer will not fire more than once per event loop iteration. |
1985 | |
2114 | |
1986 | =item ev_timer_again (loop, ev_timer *) |
2115 | =item ev_timer_again (loop, ev_timer *) |
1987 | |
2116 | |
1988 | This will act as if the timer timed out and restart it again if it is |
2117 | This will act as if the timer timed out, and restarts it again if it is |
1989 | repeating. The exact semantics are: |
2118 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2119 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1990 | |
2120 | |
|
|
2121 | The exact semantics are as in the following rules, all of which will be |
|
|
2122 | applied to the watcher: |
|
|
2123 | |
|
|
2124 | =over 4 |
|
|
2125 | |
1991 | If the timer is pending, its pending status is cleared. |
2126 | =item If the timer is pending, the pending status is always cleared. |
1992 | |
2127 | |
1993 | If the timer is started but non-repeating, stop it (as if it timed out). |
2128 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2129 | out, without invoking it). |
1994 | |
2130 | |
1995 | If the timer is repeating, either start it if necessary (with the |
2131 | =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. |
2132 | and start the timer, if necessary. |
|
|
2133 | |
|
|
2134 | =back |
1997 | |
2135 | |
1998 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2136 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1999 | usage example. |
2137 | usage example. |
2000 | |
2138 | |
2001 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2139 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
… | |
… | |
2123 | |
2261 | |
2124 | Another way to think about it (for the mathematically inclined) is that |
2262 | 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 |
2263 | 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. |
2264 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2127 | |
2265 | |
2128 | For numerical stability it is preferable that the C<offset> value is near |
2266 | 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 |
2267 | interval value should be higher than C<1/8192> (which is around 100 |
2130 | this value, and in fact is often specified as zero. |
2268 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2269 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2270 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2271 | C<0> and C<interval>, which is also the recommended range. |
2131 | |
2272 | |
2132 | Note also that there is an upper limit to how often a timer can fire (CPU |
2273 | 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 |
2274 | 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 |
2275 | 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). |
2276 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2249 | |
2390 | |
2250 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2391 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2251 | |
2392 | |
2252 | Signal watchers will trigger an event when the process receives a specific |
2393 | 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 |
2394 | 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 |
2395 | will try its best to deliver signals synchronously, i.e. as part of the |
2255 | normal event processing, like any other event. |
2396 | normal event processing, like any other event. |
2256 | |
2397 | |
2257 | If you want signals to be delivered truly asynchronously, just use |
2398 | If you want signals to be delivered truly asynchronously, just use |
2258 | C<sigaction> as you would do without libev and forget about sharing |
2399 | 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 |
2400 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2278 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2419 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2279 | |
2420 | |
2280 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2421 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2281 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2422 | (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, |
2423 | 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. |
2424 | and might or might not set or restore the installed signal handler (but |
|
|
2425 | see C<EVFLAG_NOSIGMASK>). |
2284 | |
2426 | |
2285 | While this does not matter for the signal disposition (libev never |
2427 | 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 |
2428 | 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 |
2429 | C<execve>), this matters for the signal mask: many programs do not expect |
2288 | certain signals to be blocked. |
2430 | certain signals to be blocked. |
… | |
… | |
2301 | I<has> to modify the signal mask, at least temporarily. |
2443 | I<has> to modify the signal mask, at least temporarily. |
2302 | |
2444 | |
2303 | So I can't stress this enough: I<If you do not reset your signal mask when |
2445 | 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 |
2446 | 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. |
2447 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2448 | |
|
|
2449 | =head3 The special problem of threads signal handling |
|
|
2450 | |
|
|
2451 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2452 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2453 | threads in a process block signals, which is hard to achieve. |
|
|
2454 | |
|
|
2455 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2456 | for the same signals), you can tackle this problem by globally blocking |
|
|
2457 | all signals before creating any threads (or creating them with a fully set |
|
|
2458 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2459 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2460 | these signals. You can pass on any signals that libev might be interested |
|
|
2461 | in by calling C<ev_feed_signal>. |
2306 | |
2462 | |
2307 | =head3 Watcher-Specific Functions and Data Members |
2463 | =head3 Watcher-Specific Functions and Data Members |
2308 | |
2464 | |
2309 | =over 4 |
2465 | =over 4 |
2310 | |
2466 | |
… | |
… | |
3098 | |
3254 | |
3099 | =item ev_fork_init (ev_fork *, callback) |
3255 | =item ev_fork_init (ev_fork *, callback) |
3100 | |
3256 | |
3101 | Initialises and configures the fork watcher - it has no parameters of any |
3257 | 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, |
3258 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3103 | believe me. |
3259 | really. |
3104 | |
3260 | |
3105 | =back |
3261 | =back |
3106 | |
3262 | |
3107 | |
3263 | |
3108 | =head2 C<ev_cleanup> - even the best things end |
3264 | =head2 C<ev_cleanup> - even the best things end |
3109 | |
3265 | |
3110 | Cleanup watchers are called just before the event loop they are registered |
3266 | Cleanup watchers are called just before the event loop is being destroyed |
3111 | with is being destroyed. |
3267 | by a call to C<ev_loop_destroy>. |
3112 | |
3268 | |
3113 | While there is no guarantee that the event loop gets destroyed, cleanup |
3269 | While there is no guarantee that the event loop gets destroyed, cleanup |
3114 | watchers provide a convenient method to install cleanup hooks for your |
3270 | watchers provide a convenient method to install cleanup hooks for your |
3115 | program, worker threads and so on - you just to make sure to destroy the |
3271 | program, worker threads and so on - you just to make sure to destroy the |
3116 | loop when you want them to be invoked. |
3272 | loop when you want them to be invoked. |
3117 | |
3273 | |
|
|
3274 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3275 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3276 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3277 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3278 | |
3118 | =head3 Watcher-Specific Functions and Data Members |
3279 | =head3 Watcher-Specific Functions and Data Members |
3119 | |
3280 | |
3120 | =over 4 |
3281 | =over 4 |
3121 | |
3282 | |
3122 | =item ev_cleanup_init (ev_cleanup *, callback) |
3283 | =item ev_cleanup_init (ev_cleanup *, callback) |
3123 | |
3284 | |
3124 | Initialises and configures the cleanup watcher - it has no parameters of |
3285 | Initialises and configures the cleanup watcher - it has no parameters of |
3125 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
3286 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
3126 | pointless, believe me. |
3287 | pointless, I assure you. |
3127 | |
3288 | |
3128 | =back |
3289 | =back |
3129 | |
3290 | |
3130 | Example: Register an atexit handler to destroy the default loop, so any |
3291 | Example: Register an atexit handler to destroy the default loop, so any |
3131 | cleanup functions are called. |
3292 | cleanup functions are called. |
… | |
… | |
3140 | atexit (program_exits); |
3301 | atexit (program_exits); |
3141 | |
3302 | |
3142 | |
3303 | |
3143 | =head2 C<ev_async> - how to wake up an event loop |
3304 | =head2 C<ev_async> - how to wake up an event loop |
3144 | |
3305 | |
3145 | In general, you cannot use an C<ev_run> from multiple threads or other |
3306 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3146 | asynchronous sources such as signal handlers (as opposed to multiple event |
3307 | asynchronous sources such as signal handlers (as opposed to multiple event |
3147 | loops - those are of course safe to use in different threads). |
3308 | loops - those are of course safe to use in different threads). |
3148 | |
3309 | |
3149 | Sometimes, however, you need to wake up an event loop you do not control, |
3310 | Sometimes, however, you need to wake up an event loop you do not control, |
3150 | for example because it belongs to another thread. This is what C<ev_async> |
3311 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3152 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3313 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3153 | |
3314 | |
3154 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3315 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3155 | too, are asynchronous in nature, and signals, too, will be compressed |
3316 | too, are asynchronous in nature, and signals, too, will be compressed |
3156 | (i.e. the number of callback invocations may be less than the number of |
3317 | (i.e. the number of callback invocations may be less than the number of |
3157 | C<ev_async_sent> calls). |
3318 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3158 | |
3319 | of "global async watchers" by using a watcher on an otherwise unused |
3159 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3320 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3160 | just the default loop. |
3321 | even without knowing which loop owns the signal. |
3161 | |
3322 | |
3162 | =head3 Queueing |
3323 | =head3 Queueing |
3163 | |
3324 | |
3164 | C<ev_async> does not support queueing of data in any way. The reason |
3325 | C<ev_async> does not support queueing of data in any way. The reason |
3165 | is that the author does not know of a simple (or any) algorithm for a |
3326 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3257 | trust me. |
3418 | trust me. |
3258 | |
3419 | |
3259 | =item ev_async_send (loop, ev_async *) |
3420 | =item ev_async_send (loop, ev_async *) |
3260 | |
3421 | |
3261 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3422 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3262 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3423 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3424 | returns. |
|
|
3425 | |
3263 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3426 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3264 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3427 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3265 | section below on what exactly this means). |
3428 | embedding section below on what exactly this means). |
3266 | |
3429 | |
3267 | Note that, as with other watchers in libev, multiple events might get |
3430 | Note that, as with other watchers in libev, multiple events might get |
3268 | compressed into a single callback invocation (another way to look at this |
3431 | compressed into a single callback invocation (another way to look at |
3269 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3432 | this is that C<ev_async> watchers are level-triggered: they are set on |
3270 | reset when the event loop detects that). |
3433 | C<ev_async_send>, reset when the event loop detects that). |
3271 | |
3434 | |
3272 | This call incurs the overhead of a system call only once per event loop |
3435 | This call incurs the overhead of at most one extra system call per event |
3273 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3436 | loop iteration, if the event loop is blocked, and no syscall at all if |
3274 | repeated calls to C<ev_async_send> for the same event loop. |
3437 | the event loop (or your program) is processing events. That means that |
|
|
3438 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3439 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3440 | zero) under load. |
3275 | |
3441 | |
3276 | =item bool = ev_async_pending (ev_async *) |
3442 | =item bool = ev_async_pending (ev_async *) |
3277 | |
3443 | |
3278 | Returns a non-zero value when C<ev_async_send> has been called on the |
3444 | Returns a non-zero value when C<ev_async_send> has been called on the |
3279 | watcher but the event has not yet been processed (or even noted) by the |
3445 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3334 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3500 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3335 | |
3501 | |
3336 | =item ev_feed_fd_event (loop, int fd, int revents) |
3502 | =item ev_feed_fd_event (loop, int fd, int revents) |
3337 | |
3503 | |
3338 | Feed an event on the given fd, as if a file descriptor backend detected |
3504 | Feed an event on the given fd, as if a file descriptor backend detected |
3339 | the given events it. |
3505 | the given events. |
3340 | |
3506 | |
3341 | =item ev_feed_signal_event (loop, int signum) |
3507 | =item ev_feed_signal_event (loop, int signum) |
3342 | |
3508 | |
3343 | Feed an event as if the given signal occurred (C<loop> must be the default |
3509 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3344 | loop!). |
3510 | which is async-safe. |
3345 | |
3511 | |
3346 | =back |
3512 | =back |
|
|
3513 | |
|
|
3514 | |
|
|
3515 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3516 | |
|
|
3517 | This section explains some common idioms that are not immediately |
|
|
3518 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3519 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3520 | |
|
|
3521 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3522 | |
|
|
3523 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3524 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3525 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3526 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3527 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3528 | data: |
|
|
3529 | |
|
|
3530 | struct my_io |
|
|
3531 | { |
|
|
3532 | ev_io io; |
|
|
3533 | int otherfd; |
|
|
3534 | void *somedata; |
|
|
3535 | struct whatever *mostinteresting; |
|
|
3536 | }; |
|
|
3537 | |
|
|
3538 | ... |
|
|
3539 | struct my_io w; |
|
|
3540 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3541 | |
|
|
3542 | And since your callback will be called with a pointer to the watcher, you |
|
|
3543 | can cast it back to your own type: |
|
|
3544 | |
|
|
3545 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3546 | { |
|
|
3547 | struct my_io *w = (struct my_io *)w_; |
|
|
3548 | ... |
|
|
3549 | } |
|
|
3550 | |
|
|
3551 | More interesting and less C-conformant ways of casting your callback |
|
|
3552 | function type instead have been omitted. |
|
|
3553 | |
|
|
3554 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3555 | |
|
|
3556 | Another common scenario is to use some data structure with multiple |
|
|
3557 | embedded watchers, in effect creating your own watcher that combines |
|
|
3558 | multiple libev event sources into one "super-watcher": |
|
|
3559 | |
|
|
3560 | struct my_biggy |
|
|
3561 | { |
|
|
3562 | int some_data; |
|
|
3563 | ev_timer t1; |
|
|
3564 | ev_timer t2; |
|
|
3565 | } |
|
|
3566 | |
|
|
3567 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3568 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3569 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3570 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3571 | real programmers): |
|
|
3572 | |
|
|
3573 | #include <stddef.h> |
|
|
3574 | |
|
|
3575 | static void |
|
|
3576 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3577 | { |
|
|
3578 | struct my_biggy big = (struct my_biggy *) |
|
|
3579 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3580 | } |
|
|
3581 | |
|
|
3582 | static void |
|
|
3583 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3584 | { |
|
|
3585 | struct my_biggy big = (struct my_biggy *) |
|
|
3586 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3587 | } |
|
|
3588 | |
|
|
3589 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3590 | |
|
|
3591 | Often you have structures like this in event-based programs: |
|
|
3592 | |
|
|
3593 | callback () |
|
|
3594 | { |
|
|
3595 | free (request); |
|
|
3596 | } |
|
|
3597 | |
|
|
3598 | request = start_new_request (..., callback); |
|
|
3599 | |
|
|
3600 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3601 | used to cancel the operation, or do other things with it. |
|
|
3602 | |
|
|
3603 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3604 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3605 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3606 | operation and simply invoke the callback with the result. |
|
|
3607 | |
|
|
3608 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3609 | has returned, so C<request> is not set. |
|
|
3610 | |
|
|
3611 | Even if you pass the request by some safer means to the callback, you |
|
|
3612 | might want to do something to the request after starting it, such as |
|
|
3613 | canceling it, which probably isn't working so well when the callback has |
|
|
3614 | already been invoked. |
|
|
3615 | |
|
|
3616 | A common way around all these issues is to make sure that |
|
|
3617 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3618 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3619 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
|
|
3620 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3621 | and pushing it into the pending queue: |
|
|
3622 | |
|
|
3623 | ev_set_cb (watcher, callback); |
|
|
3624 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3625 | |
|
|
3626 | This way, C<start_new_request> can safely return before the callback is |
|
|
3627 | invoked, while not delaying callback invocation too much. |
|
|
3628 | |
|
|
3629 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3630 | |
|
|
3631 | Often (especially in GUI toolkits) there are places where you have |
|
|
3632 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3633 | invoking C<ev_run>. |
|
|
3634 | |
|
|
3635 | This brings the problem of exiting - a callback might want to finish the |
|
|
3636 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3637 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3638 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3639 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3640 | |
|
|
3641 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3642 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3643 | triggered, using C<EVRUN_ONCE>: |
|
|
3644 | |
|
|
3645 | // main loop |
|
|
3646 | int exit_main_loop = 0; |
|
|
3647 | |
|
|
3648 | while (!exit_main_loop) |
|
|
3649 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3650 | |
|
|
3651 | // in a modal watcher |
|
|
3652 | int exit_nested_loop = 0; |
|
|
3653 | |
|
|
3654 | while (!exit_nested_loop) |
|
|
3655 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3656 | |
|
|
3657 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3658 | |
|
|
3659 | // exit modal loop |
|
|
3660 | exit_nested_loop = 1; |
|
|
3661 | |
|
|
3662 | // exit main program, after modal loop is finished |
|
|
3663 | exit_main_loop = 1; |
|
|
3664 | |
|
|
3665 | // exit both |
|
|
3666 | exit_main_loop = exit_nested_loop = 1; |
|
|
3667 | |
|
|
3668 | =head2 THREAD LOCKING EXAMPLE |
|
|
3669 | |
|
|
3670 | Here is a fictitious example of how to run an event loop in a different |
|
|
3671 | thread from where callbacks are being invoked and watchers are |
|
|
3672 | created/added/removed. |
|
|
3673 | |
|
|
3674 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3675 | which uses exactly this technique (which is suited for many high-level |
|
|
3676 | languages). |
|
|
3677 | |
|
|
3678 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3679 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3680 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3681 | |
|
|
3682 | First, you need to associate some data with the event loop: |
|
|
3683 | |
|
|
3684 | typedef struct { |
|
|
3685 | mutex_t lock; /* global loop lock */ |
|
|
3686 | ev_async async_w; |
|
|
3687 | thread_t tid; |
|
|
3688 | cond_t invoke_cv; |
|
|
3689 | } userdata; |
|
|
3690 | |
|
|
3691 | void prepare_loop (EV_P) |
|
|
3692 | { |
|
|
3693 | // for simplicity, we use a static userdata struct. |
|
|
3694 | static userdata u; |
|
|
3695 | |
|
|
3696 | ev_async_init (&u->async_w, async_cb); |
|
|
3697 | ev_async_start (EV_A_ &u->async_w); |
|
|
3698 | |
|
|
3699 | pthread_mutex_init (&u->lock, 0); |
|
|
3700 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3701 | |
|
|
3702 | // now associate this with the loop |
|
|
3703 | ev_set_userdata (EV_A_ u); |
|
|
3704 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3705 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3706 | |
|
|
3707 | // then create the thread running ev_run |
|
|
3708 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3709 | } |
|
|
3710 | |
|
|
3711 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3712 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3713 | that might have been added: |
|
|
3714 | |
|
|
3715 | static void |
|
|
3716 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3717 | { |
|
|
3718 | // just used for the side effects |
|
|
3719 | } |
|
|
3720 | |
|
|
3721 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3722 | protecting the loop data, respectively. |
|
|
3723 | |
|
|
3724 | static void |
|
|
3725 | l_release (EV_P) |
|
|
3726 | { |
|
|
3727 | userdata *u = ev_userdata (EV_A); |
|
|
3728 | pthread_mutex_unlock (&u->lock); |
|
|
3729 | } |
|
|
3730 | |
|
|
3731 | static void |
|
|
3732 | l_acquire (EV_P) |
|
|
3733 | { |
|
|
3734 | userdata *u = ev_userdata (EV_A); |
|
|
3735 | pthread_mutex_lock (&u->lock); |
|
|
3736 | } |
|
|
3737 | |
|
|
3738 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3739 | into C<ev_run>: |
|
|
3740 | |
|
|
3741 | void * |
|
|
3742 | l_run (void *thr_arg) |
|
|
3743 | { |
|
|
3744 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3745 | |
|
|
3746 | l_acquire (EV_A); |
|
|
3747 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3748 | ev_run (EV_A_ 0); |
|
|
3749 | l_release (EV_A); |
|
|
3750 | |
|
|
3751 | return 0; |
|
|
3752 | } |
|
|
3753 | |
|
|
3754 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3755 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3756 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3757 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3758 | and b) skipping inter-thread-communication when there are no pending |
|
|
3759 | watchers is very beneficial): |
|
|
3760 | |
|
|
3761 | static void |
|
|
3762 | l_invoke (EV_P) |
|
|
3763 | { |
|
|
3764 | userdata *u = ev_userdata (EV_A); |
|
|
3765 | |
|
|
3766 | while (ev_pending_count (EV_A)) |
|
|
3767 | { |
|
|
3768 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3769 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3770 | } |
|
|
3771 | } |
|
|
3772 | |
|
|
3773 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3774 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3775 | thread to continue: |
|
|
3776 | |
|
|
3777 | static void |
|
|
3778 | real_invoke_pending (EV_P) |
|
|
3779 | { |
|
|
3780 | userdata *u = ev_userdata (EV_A); |
|
|
3781 | |
|
|
3782 | pthread_mutex_lock (&u->lock); |
|
|
3783 | ev_invoke_pending (EV_A); |
|
|
3784 | pthread_cond_signal (&u->invoke_cv); |
|
|
3785 | pthread_mutex_unlock (&u->lock); |
|
|
3786 | } |
|
|
3787 | |
|
|
3788 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3789 | event loop, you will now have to lock: |
|
|
3790 | |
|
|
3791 | ev_timer timeout_watcher; |
|
|
3792 | userdata *u = ev_userdata (EV_A); |
|
|
3793 | |
|
|
3794 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3795 | |
|
|
3796 | pthread_mutex_lock (&u->lock); |
|
|
3797 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3798 | ev_async_send (EV_A_ &u->async_w); |
|
|
3799 | pthread_mutex_unlock (&u->lock); |
|
|
3800 | |
|
|
3801 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3802 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3803 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3804 | watchers in the next event loop iteration. |
|
|
3805 | |
|
|
3806 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3807 | |
|
|
3808 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3809 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3810 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3811 | doesn't need callbacks anymore. |
|
|
3812 | |
|
|
3813 | Imagine you have coroutines that you can switch to using a function |
|
|
3814 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3815 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3816 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3817 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3818 | the differing C<;> conventions): |
|
|
3819 | |
|
|
3820 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3821 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3822 | |
|
|
3823 | That means instead of having a C callback function, you store the |
|
|
3824 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3825 | your callback, you instead have it switch to that coroutine. |
|
|
3826 | |
|
|
3827 | A coroutine might now wait for an event with a function called |
|
|
3828 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3829 | matter when, or whether the watcher is active or not when this function is |
|
|
3830 | called): |
|
|
3831 | |
|
|
3832 | void |
|
|
3833 | wait_for_event (ev_watcher *w) |
|
|
3834 | { |
|
|
3835 | ev_cb_set (w) = current_coro; |
|
|
3836 | switch_to (libev_coro); |
|
|
3837 | } |
|
|
3838 | |
|
|
3839 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3840 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3841 | this or any other coroutine. |
|
|
3842 | |
|
|
3843 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3844 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3845 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3846 | any waiters. |
|
|
3847 | |
|
|
3848 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3849 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3850 | |
|
|
3851 | // my_ev.h |
|
|
3852 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3853 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3854 | #include "../libev/ev.h" |
|
|
3855 | |
|
|
3856 | // my_ev.c |
|
|
3857 | #define EV_H "my_ev.h" |
|
|
3858 | #include "../libev/ev.c" |
|
|
3859 | |
|
|
3860 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3861 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3862 | can even use F<ev.h> as header file name directly. |
3347 | |
3863 | |
3348 | |
3864 | |
3349 | =head1 LIBEVENT EMULATION |
3865 | =head1 LIBEVENT EMULATION |
3350 | |
3866 | |
3351 | Libev offers a compatibility emulation layer for libevent. It cannot |
3867 | Libev offers a compatibility emulation layer for libevent. It cannot |
3352 | emulate the internals of libevent, so here are some usage hints: |
3868 | emulate the internals of libevent, so here are some usage hints: |
3353 | |
3869 | |
3354 | =over 4 |
3870 | =over 4 |
|
|
3871 | |
|
|
3872 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3873 | |
|
|
3874 | This was the newest libevent version available when libev was implemented, |
|
|
3875 | and is still mostly unchanged in 2010. |
3355 | |
3876 | |
3356 | =item * Use it by including <event.h>, as usual. |
3877 | =item * Use it by including <event.h>, as usual. |
3357 | |
3878 | |
3358 | =item * The following members are fully supported: ev_base, ev_callback, |
3879 | =item * The following members are fully supported: ev_base, ev_callback, |
3359 | ev_arg, ev_fd, ev_res, ev_events. |
3880 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3365 | =item * Priorities are not currently supported. Initialising priorities |
3886 | =item * Priorities are not currently supported. Initialising priorities |
3366 | will fail and all watchers will have the same priority, even though there |
3887 | will fail and all watchers will have the same priority, even though there |
3367 | is an ev_pri field. |
3888 | is an ev_pri field. |
3368 | |
3889 | |
3369 | =item * In libevent, the last base created gets the signals, in libev, the |
3890 | =item * In libevent, the last base created gets the signals, in libev, the |
3370 | first base created (== the default loop) gets the signals. |
3891 | base that registered the signal gets the signals. |
3371 | |
3892 | |
3372 | =item * Other members are not supported. |
3893 | =item * Other members are not supported. |
3373 | |
3894 | |
3374 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3895 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3375 | to use the libev header file and library. |
3896 | to use the libev header file and library. |
3376 | |
3897 | |
3377 | =back |
3898 | =back |
3378 | |
3899 | |
3379 | =head1 C++ SUPPORT |
3900 | =head1 C++ SUPPORT |
|
|
3901 | |
|
|
3902 | =head2 C API |
|
|
3903 | |
|
|
3904 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3905 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3906 | will work fine. |
|
|
3907 | |
|
|
3908 | Proper exception specifications might have to be added to callbacks passed |
|
|
3909 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3910 | other callbacks (allocator, syserr, loop acquire/release and periodioc |
|
|
3911 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3912 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3913 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3914 | |
|
|
3915 | static void |
|
|
3916 | fatal_error (const char *msg) EV_THROW |
|
|
3917 | { |
|
|
3918 | perror (msg); |
|
|
3919 | abort (); |
|
|
3920 | } |
|
|
3921 | |
|
|
3922 | ... |
|
|
3923 | ev_set_syserr_cb (fatal_error); |
|
|
3924 | |
|
|
3925 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3926 | C<ev_inoke> and C<ev_invoke_pending>. |
|
|
3927 | |
|
|
3928 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3929 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3930 | throwing exceptions through C libraries (most do). |
|
|
3931 | |
|
|
3932 | =head2 C++ API |
3380 | |
3933 | |
3381 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3934 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3382 | you to use some convenience methods to start/stop watchers and also change |
3935 | you to use some convenience methods to start/stop watchers and also change |
3383 | the callback model to a model using method callbacks on objects. |
3936 | the callback model to a model using method callbacks on objects. |
3384 | |
3937 | |
… | |
… | |
3394 | Care has been taken to keep the overhead low. The only data member the C++ |
3947 | Care has been taken to keep the overhead low. The only data member the C++ |
3395 | classes add (compared to plain C-style watchers) is the event loop pointer |
3948 | classes add (compared to plain C-style watchers) is the event loop pointer |
3396 | that the watcher is associated with (or no additional members at all if |
3949 | that the watcher is associated with (or no additional members at all if |
3397 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3950 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3398 | |
3951 | |
3399 | Currently, functions, and static and non-static member functions can be |
3952 | Currently, functions, static and non-static member functions and classes |
3400 | used as callbacks. Other types should be easy to add as long as they only |
3953 | with C<operator ()> can be used as callbacks. Other types should be easy |
3401 | need one additional pointer for context. If you need support for other |
3954 | to add as long as they only need one additional pointer for context. If |
3402 | types of functors please contact the author (preferably after implementing |
3955 | you need support for other types of functors please contact the author |
3403 | it). |
3956 | (preferably after implementing it). |
|
|
3957 | |
|
|
3958 | For all this to work, your C++ compiler either has to use the same calling |
|
|
3959 | conventions as your C compiler (for static member functions), or you have |
|
|
3960 | to embed libev and compile libev itself as C++. |
3404 | |
3961 | |
3405 | Here is a list of things available in the C<ev> namespace: |
3962 | Here is a list of things available in the C<ev> namespace: |
3406 | |
3963 | |
3407 | =over 4 |
3964 | =over 4 |
3408 | |
3965 | |
… | |
… | |
3418 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3975 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3419 | |
3976 | |
3420 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3977 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3421 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3978 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3422 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3979 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3423 | defines by many implementations. |
3980 | defined by many implementations. |
3424 | |
3981 | |
3425 | All of those classes have these methods: |
3982 | All of those classes have these methods: |
3426 | |
3983 | |
3427 | =over 4 |
3984 | =over 4 |
3428 | |
3985 | |
… | |
… | |
3561 | watchers in the constructor. |
4118 | watchers in the constructor. |
3562 | |
4119 | |
3563 | class myclass |
4120 | class myclass |
3564 | { |
4121 | { |
3565 | ev::io io ; void io_cb (ev::io &w, int revents); |
4122 | ev::io io ; void io_cb (ev::io &w, int revents); |
3566 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4123 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3567 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4124 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3568 | |
4125 | |
3569 | myclass (int fd) |
4126 | myclass (int fd) |
3570 | { |
4127 | { |
3571 | io .set <myclass, &myclass::io_cb > (this); |
4128 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3622 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4179 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3623 | |
4180 | |
3624 | =item D |
4181 | =item D |
3625 | |
4182 | |
3626 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4183 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3627 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4184 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3628 | |
4185 | |
3629 | =item Ocaml |
4186 | =item Ocaml |
3630 | |
4187 | |
3631 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4188 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3632 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4189 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3680 | suitable for use with C<EV_A>. |
4237 | suitable for use with C<EV_A>. |
3681 | |
4238 | |
3682 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4239 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3683 | |
4240 | |
3684 | Similar to the other two macros, this gives you the value of the default |
4241 | Similar to the other two macros, this gives you the value of the default |
3685 | loop, if multiple loops are supported ("ev loop default"). |
4242 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4243 | will be initialised if it isn't already initialised. |
|
|
4244 | |
|
|
4245 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4246 | to initialise the loop somewhere. |
3686 | |
4247 | |
3687 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4248 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3688 | |
4249 | |
3689 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4250 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3690 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4251 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3835 | supported). It will also not define any of the structs usually found in |
4396 | supported). It will also not define any of the structs usually found in |
3836 | F<event.h> that are not directly supported by the libev core alone. |
4397 | F<event.h> that are not directly supported by the libev core alone. |
3837 | |
4398 | |
3838 | In standalone mode, libev will still try to automatically deduce the |
4399 | In standalone mode, libev will still try to automatically deduce the |
3839 | configuration, but has to be more conservative. |
4400 | configuration, but has to be more conservative. |
|
|
4401 | |
|
|
4402 | =item EV_USE_FLOOR |
|
|
4403 | |
|
|
4404 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4405 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4406 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4407 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4408 | function is not available will fail, so the safe default is to not enable |
|
|
4409 | this. |
3840 | |
4410 | |
3841 | =item EV_USE_MONOTONIC |
4411 | =item EV_USE_MONOTONIC |
3842 | |
4412 | |
3843 | If defined to be C<1>, libev will try to detect the availability of the |
4413 | If defined to be C<1>, libev will try to detect the availability of the |
3844 | monotonic clock option at both compile time and runtime. Otherwise no |
4414 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3974 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4544 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3975 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4545 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3976 | be detected at runtime. If undefined, it will be enabled if the headers |
4546 | be detected at runtime. If undefined, it will be enabled if the headers |
3977 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4547 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3978 | |
4548 | |
|
|
4549 | =item EV_NO_SMP |
|
|
4550 | |
|
|
4551 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4552 | between threads, that is, threads can be used, but threads never run on |
|
|
4553 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4554 | and makes libev faster. |
|
|
4555 | |
|
|
4556 | =item EV_NO_THREADS |
|
|
4557 | |
|
|
4558 | If defined to be C<1>, libev will assume that it will never be called |
|
|
4559 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
|
|
4560 | above. This reduces dependencies and makes libev faster. |
|
|
4561 | |
3979 | =item EV_ATOMIC_T |
4562 | =item EV_ATOMIC_T |
3980 | |
4563 | |
3981 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4564 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3982 | access is atomic with respect to other threads or signal contexts. No such |
4565 | access is atomic and serialised with respect to other threads or signal |
3983 | type is easily found in the C language, so you can provide your own type |
4566 | contexts. No such type is easily found in the C language, so you can |
3984 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4567 | provide your own type that you know is safe for your purposes. It is used |
3985 | as well as for signal and thread safety in C<ev_async> watchers. |
4568 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4569 | in C<ev_async> watchers. |
3986 | |
4570 | |
3987 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4571 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3988 | (from F<signal.h>), which is usually good enough on most platforms. |
4572 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4573 | although strictly speaking using a type that also implies a memory fence |
|
|
4574 | is required. |
3989 | |
4575 | |
3990 | =item EV_H (h) |
4576 | =item EV_H (h) |
3991 | |
4577 | |
3992 | The name of the F<ev.h> header file used to include it. The default if |
4578 | The name of the F<ev.h> header file used to include it. The default if |
3993 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4579 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
4017 | will have the C<struct ev_loop *> as first argument, and you can create |
4603 | will have the C<struct ev_loop *> as first argument, and you can create |
4018 | additional independent event loops. Otherwise there will be no support |
4604 | additional independent event loops. Otherwise there will be no support |
4019 | for multiple event loops and there is no first event loop pointer |
4605 | for multiple event loops and there is no first event loop pointer |
4020 | argument. Instead, all functions act on the single default loop. |
4606 | argument. Instead, all functions act on the single default loop. |
4021 | |
4607 | |
|
|
4608 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4609 | default loop when multiplicity is switched off - you always have to |
|
|
4610 | initialise the loop manually in this case. |
|
|
4611 | |
4022 | =item EV_MINPRI |
4612 | =item EV_MINPRI |
4023 | |
4613 | |
4024 | =item EV_MAXPRI |
4614 | =item EV_MAXPRI |
4025 | |
4615 | |
4026 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4616 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4062 | #define EV_USE_POLL 1 |
4652 | #define EV_USE_POLL 1 |
4063 | #define EV_CHILD_ENABLE 1 |
4653 | #define EV_CHILD_ENABLE 1 |
4064 | #define EV_ASYNC_ENABLE 1 |
4654 | #define EV_ASYNC_ENABLE 1 |
4065 | |
4655 | |
4066 | The actual value is a bitset, it can be a combination of the following |
4656 | The actual value is a bitset, it can be a combination of the following |
4067 | values: |
4657 | values (by default, all of these are enabled): |
4068 | |
4658 | |
4069 | =over 4 |
4659 | =over 4 |
4070 | |
4660 | |
4071 | =item C<1> - faster/larger code |
4661 | =item C<1> - faster/larger code |
4072 | |
4662 | |
… | |
… | |
4076 | code size by roughly 30% on amd64). |
4666 | code size by roughly 30% on amd64). |
4077 | |
4667 | |
4078 | When optimising for size, use of compiler flags such as C<-Os> with |
4668 | When optimising for size, use of compiler flags such as C<-Os> with |
4079 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4669 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4080 | assertions. |
4670 | assertions. |
|
|
4671 | |
|
|
4672 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4673 | (e.g. gcc with C<-Os>). |
4081 | |
4674 | |
4082 | =item C<2> - faster/larger data structures |
4675 | =item C<2> - faster/larger data structures |
4083 | |
4676 | |
4084 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4677 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4085 | hash table sizes and so on. This will usually further increase code size |
4678 | hash table sizes and so on. This will usually further increase code size |
4086 | and can additionally have an effect on the size of data structures at |
4679 | and can additionally have an effect on the size of data structures at |
4087 | runtime. |
4680 | runtime. |
4088 | |
4681 | |
|
|
4682 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4683 | (e.g. gcc with C<-Os>). |
|
|
4684 | |
4089 | =item C<4> - full API configuration |
4685 | =item C<4> - full API configuration |
4090 | |
4686 | |
4091 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4687 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4092 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4688 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4093 | |
4689 | |
… | |
… | |
4123 | |
4719 | |
4124 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4720 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4125 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4721 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4126 | your program might be left out as well - a binary starting a timer and an |
4722 | your program might be left out as well - a binary starting a timer and an |
4127 | I/O watcher then might come out at only 5Kb. |
4723 | I/O watcher then might come out at only 5Kb. |
|
|
4724 | |
|
|
4725 | =item EV_API_STATIC |
|
|
4726 | |
|
|
4727 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4728 | will have static linkage. This means that libev will not export any |
|
|
4729 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4730 | when you embed libev, only want to use libev functions in a single file, |
|
|
4731 | and do not want its identifiers to be visible. |
|
|
4732 | |
|
|
4733 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4734 | wants to use libev. |
|
|
4735 | |
|
|
4736 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4737 | doesn't support the required declaration syntax. |
4128 | |
4738 | |
4129 | =item EV_AVOID_STDIO |
4739 | =item EV_AVOID_STDIO |
4130 | |
4740 | |
4131 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4741 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4132 | functions (printf, scanf, perror etc.). This will increase the code size |
4742 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4276 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4886 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4277 | |
4887 | |
4278 | #include "ev_cpp.h" |
4888 | #include "ev_cpp.h" |
4279 | #include "ev.c" |
4889 | #include "ev.c" |
4280 | |
4890 | |
4281 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4891 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4282 | |
4892 | |
4283 | =head2 THREADS AND COROUTINES |
4893 | =head2 THREADS AND COROUTINES |
4284 | |
4894 | |
4285 | =head3 THREADS |
4895 | =head3 THREADS |
4286 | |
4896 | |
… | |
… | |
4337 | default loop and triggering an C<ev_async> watcher from the default loop |
4947 | default loop and triggering an C<ev_async> watcher from the default loop |
4338 | watcher callback into the event loop interested in the signal. |
4948 | watcher callback into the event loop interested in the signal. |
4339 | |
4949 | |
4340 | =back |
4950 | =back |
4341 | |
4951 | |
4342 | =head4 THREAD LOCKING EXAMPLE |
4952 | See also L<THREAD LOCKING EXAMPLE>. |
4343 | |
|
|
4344 | Here is a fictitious example of how to run an event loop in a different |
|
|
4345 | thread than where callbacks are being invoked and watchers are |
|
|
4346 | created/added/removed. |
|
|
4347 | |
|
|
4348 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4349 | which uses exactly this technique (which is suited for many high-level |
|
|
4350 | languages). |
|
|
4351 | |
|
|
4352 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4353 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4354 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4355 | |
|
|
4356 | First, you need to associate some data with the event loop: |
|
|
4357 | |
|
|
4358 | typedef struct { |
|
|
4359 | mutex_t lock; /* global loop lock */ |
|
|
4360 | ev_async async_w; |
|
|
4361 | thread_t tid; |
|
|
4362 | cond_t invoke_cv; |
|
|
4363 | } userdata; |
|
|
4364 | |
|
|
4365 | void prepare_loop (EV_P) |
|
|
4366 | { |
|
|
4367 | // for simplicity, we use a static userdata struct. |
|
|
4368 | static userdata u; |
|
|
4369 | |
|
|
4370 | ev_async_init (&u->async_w, async_cb); |
|
|
4371 | ev_async_start (EV_A_ &u->async_w); |
|
|
4372 | |
|
|
4373 | pthread_mutex_init (&u->lock, 0); |
|
|
4374 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4375 | |
|
|
4376 | // now associate this with the loop |
|
|
4377 | ev_set_userdata (EV_A_ u); |
|
|
4378 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4379 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4380 | |
|
|
4381 | // then create the thread running ev_loop |
|
|
4382 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4383 | } |
|
|
4384 | |
|
|
4385 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4386 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4387 | that might have been added: |
|
|
4388 | |
|
|
4389 | static void |
|
|
4390 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4391 | { |
|
|
4392 | // just used for the side effects |
|
|
4393 | } |
|
|
4394 | |
|
|
4395 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4396 | protecting the loop data, respectively. |
|
|
4397 | |
|
|
4398 | static void |
|
|
4399 | l_release (EV_P) |
|
|
4400 | { |
|
|
4401 | userdata *u = ev_userdata (EV_A); |
|
|
4402 | pthread_mutex_unlock (&u->lock); |
|
|
4403 | } |
|
|
4404 | |
|
|
4405 | static void |
|
|
4406 | l_acquire (EV_P) |
|
|
4407 | { |
|
|
4408 | userdata *u = ev_userdata (EV_A); |
|
|
4409 | pthread_mutex_lock (&u->lock); |
|
|
4410 | } |
|
|
4411 | |
|
|
4412 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4413 | into C<ev_run>: |
|
|
4414 | |
|
|
4415 | void * |
|
|
4416 | l_run (void *thr_arg) |
|
|
4417 | { |
|
|
4418 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4419 | |
|
|
4420 | l_acquire (EV_A); |
|
|
4421 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4422 | ev_run (EV_A_ 0); |
|
|
4423 | l_release (EV_A); |
|
|
4424 | |
|
|
4425 | return 0; |
|
|
4426 | } |
|
|
4427 | |
|
|
4428 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4429 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4430 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4431 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4432 | and b) skipping inter-thread-communication when there are no pending |
|
|
4433 | watchers is very beneficial): |
|
|
4434 | |
|
|
4435 | static void |
|
|
4436 | l_invoke (EV_P) |
|
|
4437 | { |
|
|
4438 | userdata *u = ev_userdata (EV_A); |
|
|
4439 | |
|
|
4440 | while (ev_pending_count (EV_A)) |
|
|
4441 | { |
|
|
4442 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4443 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4444 | } |
|
|
4445 | } |
|
|
4446 | |
|
|
4447 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4448 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4449 | thread to continue: |
|
|
4450 | |
|
|
4451 | static void |
|
|
4452 | real_invoke_pending (EV_P) |
|
|
4453 | { |
|
|
4454 | userdata *u = ev_userdata (EV_A); |
|
|
4455 | |
|
|
4456 | pthread_mutex_lock (&u->lock); |
|
|
4457 | ev_invoke_pending (EV_A); |
|
|
4458 | pthread_cond_signal (&u->invoke_cv); |
|
|
4459 | pthread_mutex_unlock (&u->lock); |
|
|
4460 | } |
|
|
4461 | |
|
|
4462 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4463 | event loop, you will now have to lock: |
|
|
4464 | |
|
|
4465 | ev_timer timeout_watcher; |
|
|
4466 | userdata *u = ev_userdata (EV_A); |
|
|
4467 | |
|
|
4468 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4469 | |
|
|
4470 | pthread_mutex_lock (&u->lock); |
|
|
4471 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4472 | ev_async_send (EV_A_ &u->async_w); |
|
|
4473 | pthread_mutex_unlock (&u->lock); |
|
|
4474 | |
|
|
4475 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4476 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4477 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4478 | watchers in the next event loop iteration. |
|
|
4479 | |
4953 | |
4480 | =head3 COROUTINES |
4954 | =head3 COROUTINES |
4481 | |
4955 | |
4482 | Libev is very accommodating to coroutines ("cooperative threads"): |
4956 | Libev is very accommodating to coroutines ("cooperative threads"): |
4483 | libev fully supports nesting calls to its functions from different |
4957 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4648 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5122 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4649 | model. Libev still offers limited functionality on this platform in |
5123 | model. Libev still offers limited functionality on this platform in |
4650 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5124 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4651 | descriptors. This only applies when using Win32 natively, not when using |
5125 | descriptors. This only applies when using Win32 natively, not when using |
4652 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5126 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4653 | as every compielr comes with a slightly differently broken/incompatible |
5127 | as every compiler comes with a slightly differently broken/incompatible |
4654 | environment. |
5128 | environment. |
4655 | |
5129 | |
4656 | Lifting these limitations would basically require the full |
5130 | Lifting these limitations would basically require the full |
4657 | re-implementation of the I/O system. If you are into this kind of thing, |
5131 | re-implementation of the I/O system. If you are into this kind of thing, |
4658 | then note that glib does exactly that for you in a very portable way (note |
5132 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4752 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5226 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4753 | assumes that the same (machine) code can be used to call any watcher |
5227 | assumes that the same (machine) code can be used to call any watcher |
4754 | callback: The watcher callbacks have different type signatures, but libev |
5228 | callback: The watcher callbacks have different type signatures, but libev |
4755 | calls them using an C<ev_watcher *> internally. |
5229 | calls them using an C<ev_watcher *> internally. |
4756 | |
5230 | |
|
|
5231 | =item pointer accesses must be thread-atomic |
|
|
5232 | |
|
|
5233 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5234 | writable in one piece - this is the case on all current architectures. |
|
|
5235 | |
4757 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5236 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4758 | |
5237 | |
4759 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5238 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4760 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
5239 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4761 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
5240 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
… | |
… | |
4786 | |
5265 | |
4787 | The type C<double> is used to represent timestamps. It is required to |
5266 | The type C<double> is used to represent timestamps. It is required to |
4788 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5267 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4789 | good enough for at least into the year 4000 with millisecond accuracy |
5268 | good enough for at least into the year 4000 with millisecond accuracy |
4790 | (the design goal for libev). This requirement is overfulfilled by |
5269 | (the design goal for libev). This requirement is overfulfilled by |
4791 | implementations using IEEE 754, which is basically all existing ones. With |
5270 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5271 | |
4792 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5272 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5273 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5274 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5275 | something like that, just kidding). |
4793 | |
5276 | |
4794 | =back |
5277 | =back |
4795 | |
5278 | |
4796 | If you know of other additional requirements drop me a note. |
5279 | If you know of other additional requirements drop me a note. |
4797 | |
5280 | |
… | |
… | |
4859 | =item Processing ev_async_send: O(number_of_async_watchers) |
5342 | =item Processing ev_async_send: O(number_of_async_watchers) |
4860 | |
5343 | |
4861 | =item Processing signals: O(max_signal_number) |
5344 | =item Processing signals: O(max_signal_number) |
4862 | |
5345 | |
4863 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5346 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4864 | calls in the current loop iteration. Checking for async and signal events |
5347 | calls in the current loop iteration and the loop is currently |
|
|
5348 | blocked. Checking for async and signal events involves iterating over all |
4865 | involves iterating over all running async watchers or all signal numbers. |
5349 | running async watchers or all signal numbers. |
4866 | |
5350 | |
4867 | =back |
5351 | =back |
4868 | |
5352 | |
4869 | |
5353 | |
4870 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5354 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4871 | |
5355 | |
4872 | The major version 4 introduced some minor incompatible changes to the API. |
5356 | The major version 4 introduced some incompatible changes to the API. |
4873 | |
5357 | |
4874 | At the moment, the C<ev.h> header file tries to implement superficial |
5358 | At the moment, the C<ev.h> header file provides compatibility definitions |
4875 | compatibility, so most programs should still compile. Those might be |
5359 | for all changes, so most programs should still compile. The compatibility |
4876 | removed in later versions of libev, so better update early than late. |
5360 | layer might be removed in later versions of libev, so better update to the |
|
|
5361 | new API early than late. |
4877 | |
5362 | |
4878 | =over 4 |
5363 | =over 4 |
|
|
5364 | |
|
|
5365 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5366 | |
|
|
5367 | The backward compatibility mechanism can be controlled by |
|
|
5368 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
5369 | section. |
4879 | |
5370 | |
4880 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5371 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
4881 | |
5372 | |
4882 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5373 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
4883 | |
5374 | |
… | |
… | |
4909 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
5400 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
4910 | as all other watcher types. Note that C<ev_loop_fork> is still called |
5401 | as all other watcher types. Note that C<ev_loop_fork> is still called |
4911 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
5402 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
4912 | typedef. |
5403 | typedef. |
4913 | |
5404 | |
4914 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4915 | |
|
|
4916 | The backward compatibility mechanism can be controlled by |
|
|
4917 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4918 | section. |
|
|
4919 | |
|
|
4920 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
5405 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4921 | |
5406 | |
4922 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
5407 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4923 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
5408 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
4924 | and work, but the library code will of course be larger. |
5409 | and work, but the library code will of course be larger. |
… | |
… | |
4986 | The physical time that is observed. It is apparently strictly monotonic :) |
5471 | The physical time that is observed. It is apparently strictly monotonic :) |
4987 | |
5472 | |
4988 | =item wall-clock time |
5473 | =item wall-clock time |
4989 | |
5474 | |
4990 | The time and date as shown on clocks. Unlike real time, it can actually |
5475 | The time and date as shown on clocks. Unlike real time, it can actually |
4991 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5476 | be wrong and jump forwards and backwards, e.g. when you adjust your |
4992 | clock. |
5477 | clock. |
4993 | |
5478 | |
4994 | =item watcher |
5479 | =item watcher |
4995 | |
5480 | |
4996 | A data structure that describes interest in certain events. Watchers need |
5481 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
4998 | |
5483 | |
4999 | =back |
5484 | =back |
5000 | |
5485 | |
5001 | =head1 AUTHOR |
5486 | =head1 AUTHOR |
5002 | |
5487 | |
5003 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5488 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5489 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5004 | |
5490 | |