… | |
… | |
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 | |
… | |
… | |
174 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
175 | |
175 | |
176 | 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 |
177 | 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 |
178 | you actually want to know. Also interesting is the combination of |
178 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
179 | C<ev_now_update> and C<ev_now>. |
180 | |
180 | |
181 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
182 | |
182 | |
183 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
184 | 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 >>. |
|
|
187 | |
185 | 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 >>). |
186 | |
192 | |
187 | =item int ev_version_major () |
193 | =item int ev_version_major () |
188 | |
194 | |
189 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
190 | |
196 | |
… | |
… | |
241 | 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 () |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
243 | |
249 | |
244 | See the description of C<ev_embed> watchers for more info. |
250 | See the description of C<ev_embed> watchers for more info. |
245 | |
251 | |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
247 | |
253 | |
248 | Sets the allocation function to use (the prototype is similar - the |
254 | Sets the allocation function to use (the prototype is similar - the |
249 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
255 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
250 | used to allocate and free memory (no surprises here). If it returns zero |
256 | used to allocate and free memory (no surprises here). If it returns zero |
251 | when memory needs to be allocated (C<size != 0>), the library might abort |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
277 | } |
283 | } |
278 | |
284 | |
279 | ... |
285 | ... |
280 | ev_set_allocator (persistent_realloc); |
286 | ev_set_allocator (persistent_realloc); |
281 | |
287 | |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
283 | |
289 | |
284 | 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 |
285 | 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 |
286 | indicating the system call or subsystem causing the problem. If this |
292 | indicating the system call or subsystem causing the problem. If this |
287 | callback is set, then libev will expect it to remedy the situation, no |
293 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
299 | } |
305 | } |
300 | |
306 | |
301 | ... |
307 | ... |
302 | ev_set_syserr_cb (fatal_error); |
308 | ev_set_syserr_cb (fatal_error); |
303 | |
309 | |
|
|
310 | =item ev_feed_signal (int signum) |
|
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311 | |
|
|
312 | This function can be used to "simulate" a signal receive. It is completely |
|
|
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 | |
|
|
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 | |
304 | =back |
323 | =back |
305 | |
324 | |
306 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
325 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
307 | |
326 | |
308 | 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 |
… | |
… | |
355 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
374 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
356 | |
375 | |
357 | 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 |
358 | could not be initialised, returns false. |
377 | could not be initialised, returns false. |
359 | |
378 | |
360 | 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 |
361 | 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 |
362 | default loop in the "main" or "initial" thread. |
381 | loop in the "main" or "initial" thread. |
363 | |
382 | |
364 | 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 |
365 | 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>). |
366 | |
385 | |
367 | The following flags are supported: |
386 | The following flags are supported: |
… | |
… | |
402 | environment variable. |
421 | environment variable. |
403 | |
422 | |
404 | =item C<EVFLAG_NOINOTIFY> |
423 | =item C<EVFLAG_NOINOTIFY> |
405 | |
424 | |
406 | 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 |
407 | 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 |
408 | 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 |
409 | 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. |
410 | |
429 | |
411 | =item C<EVFLAG_SIGNALFD> |
430 | =item C<EVFLAG_SIGNALFD> |
412 | |
431 | |
413 | 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 |
414 | 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 |
415 | delivers signals synchronously, which makes it both faster and might make |
434 | delivers signals synchronously, which makes it both faster and might make |
416 | it possible to get the queued signal data. It can also simplify signal |
435 | it possible to get the queued signal data. It can also simplify signal |
417 | handling with threads, as long as you properly block signals in your |
436 | handling with threads, as long as you properly block signals in your |
418 | threads that are not interested in handling them. |
437 | threads that are not interested in handling them. |
419 | |
438 | |
420 | 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 |
421 | 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 |
422 | example) that can't properly initialise their signal masks. |
441 | example) that can't properly initialise their signal masks. |
|
|
442 | |
|
|
443 | =item C<EVFLAG_NOSIGMASK> |
|
|
444 | |
|
|
445 | When this flag is specified, then libev will avoid to modify the signal |
|
|
446 | mask. Specifically, this means you have to make sure signals are unblocked |
|
|
447 | when you want to receive them. |
|
|
448 | |
|
|
449 | This behaviour is useful when you want to do your own signal handling, or |
|
|
450 | want to handle signals only in specific threads and want to avoid libev |
|
|
451 | unblocking the signals. |
|
|
452 | |
|
|
453 | It's also required by POSIX in a threaded program, as libev calls |
|
|
454 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
|
455 | |
|
|
456 | This flag's behaviour will become the default in future versions of libev. |
423 | |
457 | |
424 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
425 | |
459 | |
426 | 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 |
427 | 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, |
… | |
… | |
455 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
456 | |
490 | |
457 | 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 |
458 | kernels). |
492 | kernels). |
459 | |
493 | |
460 | 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 |
461 | but it scales phenomenally better. While poll and select usually scale |
495 | it scales phenomenally better. While poll and select usually scale like |
462 | like O(total_fds) where n is the total number of fds (or the highest fd), |
496 | O(total_fds) where total_fds is the total number of fds (or the highest |
463 | epoll scales either O(1) or O(active_fds). |
497 | fd), epoll scales either O(1) or O(active_fds). |
464 | |
498 | |
465 | The epoll mechanism deserves honorable mention as the most misdesigned |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
466 | of the more advanced event mechanisms: mere annoyances include silently |
500 | of the more advanced event mechanisms: mere annoyances include silently |
467 | dropping file descriptors, requiring a system call per change per file |
501 | dropping file descriptors, requiring a system call per change per file |
468 | descriptor (and unnecessary guessing of parameters), problems with dup and |
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
503 | returning before the timeout value, resulting in additional iterations |
|
|
504 | (and only giving 5ms accuracy while select on the same platform gives |
469 | 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 |
470 | 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 |
471 | take considerable time (one syscall per file descriptor) and is of course |
507 | set, which can take considerable time (one syscall per file descriptor) |
472 | hard to detect. |
508 | and is of course hard to detect. |
473 | |
509 | |
474 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
475 | 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 |
476 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
477 | 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 |
478 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
479 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
480 | 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 |
|
|
517 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
518 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
519 | because epoll returns immediately despite a nonzero timeout. And last |
481 | 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 |
482 | perfectly fine with C<select> (files, many character devices...). |
521 | perfectly fine with C<select> (files, many character devices...). |
|
|
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 |
|
|
525 | others. Oh, the pain, will it ever stop... |
483 | |
526 | |
484 | 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 |
485 | 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 |
486 | 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 |
487 | 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 |
… | |
… | |
553 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
596 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
554 | |
597 | |
555 | 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, |
556 | 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)). |
557 | |
600 | |
558 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
559 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
560 | blocking when no data (or space) is available. |
|
|
561 | |
|
|
562 | 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 |
563 | 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 |
564 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
603 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
565 | might perform better. |
604 | might perform better. |
566 | |
605 | |
567 | On the positive side, with the exception of the spurious readiness |
606 | On the positive side, this backend actually performed fully to |
568 | notifications, this backend actually performed fully to specification |
|
|
569 | 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 |
570 | OS-specific backends (I vastly prefer correctness over speed hacks). |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
609 | hacks). |
|
|
610 | |
|
|
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
612 | even sun itself gets it wrong in their code examples: The event polling |
|
|
613 | function sometimes returns events to the caller even though an error |
|
|
614 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
615 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
616 | absolutely have to know whether an event occurred or not because you have |
|
|
617 | to re-arm the watcher. |
|
|
618 | |
|
|
619 | Fortunately libev seems to be able to work around these idiocies. |
571 | |
620 | |
572 | 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 |
573 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
574 | |
623 | |
575 | =item C<EVBACKEND_ALL> |
624 | =item C<EVBACKEND_ALL> |
576 | |
625 | |
577 | 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 |
578 | 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 |
579 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
628 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
580 | |
629 | |
581 | 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 |
|
|
632 | at all. |
|
|
633 | |
|
|
634 | =item C<EVBACKEND_MASK> |
|
|
635 | |
|
|
636 | Not a backend at all, but a mask to select all backend bits from a |
|
|
637 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
638 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
582 | |
639 | |
583 | =back |
640 | =back |
584 | |
641 | |
585 | 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, |
586 | 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 |
… | |
… | |
615 | This function is normally used on loop objects allocated by |
672 | This function is normally used on loop objects allocated by |
616 | 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 |
617 | 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. |
618 | |
675 | |
619 | 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 |
620 | 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. |
621 | 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> |
622 | and C<ev_loop_destroy>. |
679 | and C<ev_loop_destroy>. |
623 | |
680 | |
624 | =item ev_loop_fork (loop) |
681 | =item ev_loop_fork (loop) |
625 | |
682 | |
… | |
… | |
673 | prepare and check phases. |
730 | prepare and check phases. |
674 | |
731 | |
675 | =item unsigned int ev_depth (loop) |
732 | =item unsigned int ev_depth (loop) |
676 | |
733 | |
677 | 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 |
678 | 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. |
679 | |
736 | |
680 | 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 |
681 | 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), |
682 | in which case it is higher. |
739 | in which case it is higher. |
683 | |
740 | |
684 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
741 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
685 | 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 |
686 | 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. |
687 | |
745 | |
688 | =item unsigned int ev_backend (loop) |
746 | =item unsigned int ev_backend (loop) |
689 | |
747 | |
690 | 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 |
691 | use. |
749 | use. |
… | |
… | |
753 | finished (especially in interactive programs), but having a program |
811 | finished (especially in interactive programs), but having a program |
754 | that automatically loops as long as it has to and no longer by virtue |
812 | that automatically loops as long as it has to and no longer by virtue |
755 | of relying on its watchers stopping correctly, that is truly a thing of |
813 | of relying on its watchers stopping correctly, that is truly a thing of |
756 | beauty. |
814 | beauty. |
757 | |
815 | |
|
|
816 | This function is also I<mostly> exception-safe - you can break out of |
|
|
817 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
818 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
819 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
820 | |
758 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
821 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
759 | those events and any already outstanding ones, but will not wait and |
822 | those events and any already outstanding ones, but will not wait and |
760 | block your process in case there are no events and will return after one |
823 | block your process in case there are no events and will return after one |
761 | iteration of the loop. This is sometimes useful to poll and handle new |
824 | iteration of the loop. This is sometimes useful to poll and handle new |
762 | events while doing lengthy calculations, to keep the program responsive. |
825 | events while doing lengthy calculations, to keep the program responsive. |
… | |
… | |
771 | This is useful if you are waiting for some external event in conjunction |
834 | This is useful if you are waiting for some external event in conjunction |
772 | with something not expressible using other libev watchers (i.e. "roll your |
835 | with something not expressible using other libev watchers (i.e. "roll your |
773 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
836 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
774 | usually a better approach for this kind of thing. |
837 | usually a better approach for this kind of thing. |
775 | |
838 | |
776 | Here are the gory details of what C<ev_run> does: |
839 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
840 | understanding, not a guarantee that things will work exactly like this in |
|
|
841 | future versions): |
777 | |
842 | |
778 | - Increment loop depth. |
843 | - Increment loop depth. |
779 | - Reset the ev_break status. |
844 | - Reset the ev_break status. |
780 | - Before the first iteration, call any pending watchers. |
845 | - Before the first iteration, call any pending watchers. |
781 | LOOP: |
846 | LOOP: |
… | |
… | |
814 | anymore. |
879 | anymore. |
815 | |
880 | |
816 | ... queue jobs here, make sure they register event watchers as long |
881 | ... queue jobs here, make sure they register event watchers as long |
817 | ... as they still have work to do (even an idle watcher will do..) |
882 | ... as they still have work to do (even an idle watcher will do..) |
818 | ev_run (my_loop, 0); |
883 | ev_run (my_loop, 0); |
819 | ... jobs done or somebody called unloop. yeah! |
884 | ... jobs done or somebody called break. yeah! |
820 | |
885 | |
821 | =item ev_break (loop, how) |
886 | =item ev_break (loop, how) |
822 | |
887 | |
823 | Can be used to make a call to C<ev_run> return early (but only after it |
888 | Can be used to make a call to C<ev_run> return early (but only after it |
824 | has processed all outstanding events). The C<how> argument must be either |
889 | has processed all outstanding events). The C<how> argument must be either |
825 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
890 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
826 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
891 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
827 | |
892 | |
828 | This "unloop state" will be cleared when entering C<ev_run> again. |
893 | This "break state" will be cleared on the next call to C<ev_run>. |
829 | |
894 | |
830 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
895 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
896 | which case it will have no effect. |
831 | |
897 | |
832 | =item ev_ref (loop) |
898 | =item ev_ref (loop) |
833 | |
899 | |
834 | =item ev_unref (loop) |
900 | =item ev_unref (loop) |
835 | |
901 | |
… | |
… | |
856 | running when nothing else is active. |
922 | running when nothing else is active. |
857 | |
923 | |
858 | ev_signal exitsig; |
924 | ev_signal exitsig; |
859 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
925 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
860 | ev_signal_start (loop, &exitsig); |
926 | ev_signal_start (loop, &exitsig); |
861 | evf_unref (loop); |
927 | ev_unref (loop); |
862 | |
928 | |
863 | Example: For some weird reason, unregister the above signal handler again. |
929 | Example: For some weird reason, unregister the above signal handler again. |
864 | |
930 | |
865 | ev_ref (loop); |
931 | ev_ref (loop); |
866 | ev_signal_stop (loop, &exitsig); |
932 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
886 | overhead for the actual polling but can deliver many events at once. |
952 | overhead for the actual polling but can deliver many events at once. |
887 | |
953 | |
888 | By setting a higher I<io collect interval> you allow libev to spend more |
954 | By setting a higher I<io collect interval> you allow libev to spend more |
889 | time collecting I/O events, so you can handle more events per iteration, |
955 | time collecting I/O events, so you can handle more events per iteration, |
890 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
956 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
891 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
957 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
892 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
958 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
893 | sleep time ensures that libev will not poll for I/O events more often then |
959 | sleep time ensures that libev will not poll for I/O events more often then |
894 | once per this interval, on average. |
960 | once per this interval, on average (as long as the host time resolution is |
|
|
961 | good enough). |
895 | |
962 | |
896 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
963 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
897 | to spend more time collecting timeouts, at the expense of increased |
964 | to spend more time collecting timeouts, at the expense of increased |
898 | latency/jitter/inexactness (the watcher callback will be called |
965 | latency/jitter/inexactness (the watcher callback will be called |
899 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
966 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
953 | can be done relatively simply by putting mutex_lock/unlock calls around |
1020 | can be done relatively simply by putting mutex_lock/unlock calls around |
954 | each call to a libev function. |
1021 | each call to a libev function. |
955 | |
1022 | |
956 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1023 | However, C<ev_run> can run an indefinite time, so it is not feasible |
957 | to wait for it to return. One way around this is to wake up the event |
1024 | to wait for it to return. One way around this is to wake up the event |
958 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1025 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
959 | I<release> and I<acquire> callbacks on the loop. |
1026 | I<release> and I<acquire> callbacks on the loop. |
960 | |
1027 | |
961 | When set, then C<release> will be called just before the thread is |
1028 | When set, then C<release> will be called just before the thread is |
962 | suspended waiting for new events, and C<acquire> is called just |
1029 | suspended waiting for new events, and C<acquire> is called just |
963 | afterwards. |
1030 | afterwards. |
… | |
… | |
978 | See also the locking example in the C<THREADS> section later in this |
1045 | See also the locking example in the C<THREADS> section later in this |
979 | document. |
1046 | document. |
980 | |
1047 | |
981 | =item ev_set_userdata (loop, void *data) |
1048 | =item ev_set_userdata (loop, void *data) |
982 | |
1049 | |
983 | =item ev_userdata (loop) |
1050 | =item void *ev_userdata (loop) |
984 | |
1051 | |
985 | Set and retrieve a single C<void *> associated with a loop. When |
1052 | Set and retrieve a single C<void *> associated with a loop. When |
986 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1053 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
987 | C<0.> |
1054 | C<0>. |
988 | |
1055 | |
989 | These two functions can be used to associate arbitrary data with a loop, |
1056 | These two functions can be used to associate arbitrary data with a loop, |
990 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1057 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
991 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1058 | C<acquire> callbacks described above, but of course can be (ab-)used for |
992 | any other purpose as well. |
1059 | any other purpose as well. |
… | |
… | |
1154 | programs, though, as the fd could already be closed and reused for another |
1221 | programs, though, as the fd could already be closed and reused for another |
1155 | thing, so beware. |
1222 | thing, so beware. |
1156 | |
1223 | |
1157 | =back |
1224 | =back |
1158 | |
1225 | |
|
|
1226 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1227 | |
|
|
1228 | =over 4 |
|
|
1229 | |
|
|
1230 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1231 | |
|
|
1232 | This macro initialises the generic portion of a watcher. The contents |
|
|
1233 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1234 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1235 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1236 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1237 | which rolls both calls into one. |
|
|
1238 | |
|
|
1239 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1240 | (or never started) and there are no pending events outstanding. |
|
|
1241 | |
|
|
1242 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1243 | int revents)>. |
|
|
1244 | |
|
|
1245 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1246 | |
|
|
1247 | ev_io w; |
|
|
1248 | ev_init (&w, my_cb); |
|
|
1249 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1250 | |
|
|
1251 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1252 | |
|
|
1253 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1254 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1255 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1256 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1257 | difference to the C<ev_init> macro). |
|
|
1258 | |
|
|
1259 | Although some watcher types do not have type-specific arguments |
|
|
1260 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1261 | |
|
|
1262 | See C<ev_init>, above, for an example. |
|
|
1263 | |
|
|
1264 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1265 | |
|
|
1266 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1267 | calls into a single call. This is the most convenient method to initialise |
|
|
1268 | a watcher. The same limitations apply, of course. |
|
|
1269 | |
|
|
1270 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1271 | |
|
|
1272 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1273 | |
|
|
1274 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1275 | |
|
|
1276 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1277 | events. If the watcher is already active nothing will happen. |
|
|
1278 | |
|
|
1279 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1280 | whole section. |
|
|
1281 | |
|
|
1282 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1283 | |
|
|
1284 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1285 | |
|
|
1286 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1287 | the watcher was active or not). |
|
|
1288 | |
|
|
1289 | It is possible that stopped watchers are pending - for example, |
|
|
1290 | non-repeating timers are being stopped when they become pending - but |
|
|
1291 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1292 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1293 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1294 | |
|
|
1295 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1296 | |
|
|
1297 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1298 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1299 | it. |
|
|
1300 | |
|
|
1301 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1302 | |
|
|
1303 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1304 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1305 | is pending (but not active) you must not call an init function on it (but |
|
|
1306 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1307 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1308 | it). |
|
|
1309 | |
|
|
1310 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1311 | |
|
|
1312 | Returns the callback currently set on the watcher. |
|
|
1313 | |
|
|
1314 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
1315 | |
|
|
1316 | Change the callback. You can change the callback at virtually any time |
|
|
1317 | (modulo threads). |
|
|
1318 | |
|
|
1319 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1320 | |
|
|
1321 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1322 | |
|
|
1323 | Set and query the priority of the watcher. The priority is a small |
|
|
1324 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1325 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1326 | before watchers with lower priority, but priority will not keep watchers |
|
|
1327 | from being executed (except for C<ev_idle> watchers). |
|
|
1328 | |
|
|
1329 | If you need to suppress invocation when higher priority events are pending |
|
|
1330 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1331 | |
|
|
1332 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1333 | pending. |
|
|
1334 | |
|
|
1335 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1336 | fine, as long as you do not mind that the priority value you query might |
|
|
1337 | or might not have been clamped to the valid range. |
|
|
1338 | |
|
|
1339 | The default priority used by watchers when no priority has been set is |
|
|
1340 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1341 | |
|
|
1342 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1343 | priorities. |
|
|
1344 | |
|
|
1345 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1346 | |
|
|
1347 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1348 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1349 | can deal with that fact, as both are simply passed through to the |
|
|
1350 | callback. |
|
|
1351 | |
|
|
1352 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1353 | |
|
|
1354 | If the watcher is pending, this function clears its pending status and |
|
|
1355 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1356 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1357 | |
|
|
1358 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1359 | callback to be invoked, which can be accomplished with this function. |
|
|
1360 | |
|
|
1361 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1362 | |
|
|
1363 | Feeds the given event set into the event loop, as if the specified event |
|
|
1364 | had happened for the specified watcher (which must be a pointer to an |
|
|
1365 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1366 | not free the watcher as long as it has pending events. |
|
|
1367 | |
|
|
1368 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1369 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1370 | not started in the first place. |
|
|
1371 | |
|
|
1372 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1373 | functions that do not need a watcher. |
|
|
1374 | |
|
|
1375 | =back |
|
|
1376 | |
|
|
1377 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
|
|
1378 | OWN COMPOSITE WATCHERS> idioms. |
|
|
1379 | |
1159 | =head2 WATCHER STATES |
1380 | =head2 WATCHER STATES |
1160 | |
1381 | |
1161 | There are various watcher states mentioned throughout this manual - |
1382 | There are various watcher states mentioned throughout this manual - |
1162 | active, pending and so on. In this section these states and the rules to |
1383 | active, pending and so on. In this section these states and the rules to |
1163 | transition between them will be described in more detail - and while these |
1384 | transition between them will be described in more detail - and while these |
… | |
… | |
1165 | |
1386 | |
1166 | =over 4 |
1387 | =over 4 |
1167 | |
1388 | |
1168 | =item initialiased |
1389 | =item initialiased |
1169 | |
1390 | |
1170 | Before a watcher can be registered with the event looop it has to be |
1391 | Before a watcher can be registered with the event loop it has to be |
1171 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1392 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1172 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1393 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1173 | |
1394 | |
1174 | In this state it is simply some block of memory that is suitable for use |
1395 | In this state it is simply some block of memory that is suitable for |
1175 | in an event loop. It can be moved around, freed, reused etc. at will. |
1396 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1397 | will - as long as you either keep the memory contents intact, or call |
|
|
1398 | C<ev_TYPE_init> again. |
1176 | |
1399 | |
1177 | =item started/running/active |
1400 | =item started/running/active |
1178 | |
1401 | |
1179 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1402 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1180 | property of the event loop, and is actively waiting for events. While in |
1403 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1208 | latter will clear any pending state the watcher might be in, regardless |
1431 | latter will clear any pending state the watcher might be in, regardless |
1209 | of whether it was active or not, so stopping a watcher explicitly before |
1432 | of whether it was active or not, so stopping a watcher explicitly before |
1210 | freeing it is often a good idea. |
1433 | freeing it is often a good idea. |
1211 | |
1434 | |
1212 | While stopped (and not pending) the watcher is essentially in the |
1435 | While stopped (and not pending) the watcher is essentially in the |
1213 | initialised state, that is it can be reused, moved, modified in any way |
1436 | initialised state, that is, it can be reused, moved, modified in any way |
1214 | you wish. |
1437 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1438 | it again). |
1215 | |
1439 | |
1216 | =back |
1440 | =back |
1217 | |
|
|
1218 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1219 | |
|
|
1220 | =over 4 |
|
|
1221 | |
|
|
1222 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1223 | |
|
|
1224 | This macro initialises the generic portion of a watcher. The contents |
|
|
1225 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1226 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1227 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1228 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1229 | which rolls both calls into one. |
|
|
1230 | |
|
|
1231 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1232 | (or never started) and there are no pending events outstanding. |
|
|
1233 | |
|
|
1234 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1235 | int revents)>. |
|
|
1236 | |
|
|
1237 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1238 | |
|
|
1239 | ev_io w; |
|
|
1240 | ev_init (&w, my_cb); |
|
|
1241 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1242 | |
|
|
1243 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1244 | |
|
|
1245 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1246 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1247 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1248 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1249 | difference to the C<ev_init> macro). |
|
|
1250 | |
|
|
1251 | Although some watcher types do not have type-specific arguments |
|
|
1252 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1253 | |
|
|
1254 | See C<ev_init>, above, for an example. |
|
|
1255 | |
|
|
1256 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1257 | |
|
|
1258 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1259 | calls into a single call. This is the most convenient method to initialise |
|
|
1260 | a watcher. The same limitations apply, of course. |
|
|
1261 | |
|
|
1262 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1263 | |
|
|
1264 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1265 | |
|
|
1266 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1267 | |
|
|
1268 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1269 | events. If the watcher is already active nothing will happen. |
|
|
1270 | |
|
|
1271 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1272 | whole section. |
|
|
1273 | |
|
|
1274 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1275 | |
|
|
1276 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1277 | |
|
|
1278 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1279 | the watcher was active or not). |
|
|
1280 | |
|
|
1281 | It is possible that stopped watchers are pending - for example, |
|
|
1282 | non-repeating timers are being stopped when they become pending - but |
|
|
1283 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1284 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1285 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1286 | |
|
|
1287 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1288 | |
|
|
1289 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1290 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1291 | it. |
|
|
1292 | |
|
|
1293 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1294 | |
|
|
1295 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1296 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1297 | is pending (but not active) you must not call an init function on it (but |
|
|
1298 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1299 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1300 | it). |
|
|
1301 | |
|
|
1302 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1303 | |
|
|
1304 | Returns the callback currently set on the watcher. |
|
|
1305 | |
|
|
1306 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
1307 | |
|
|
1308 | Change the callback. You can change the callback at virtually any time |
|
|
1309 | (modulo threads). |
|
|
1310 | |
|
|
1311 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1312 | |
|
|
1313 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1314 | |
|
|
1315 | Set and query the priority of the watcher. The priority is a small |
|
|
1316 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1317 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1318 | before watchers with lower priority, but priority will not keep watchers |
|
|
1319 | from being executed (except for C<ev_idle> watchers). |
|
|
1320 | |
|
|
1321 | If you need to suppress invocation when higher priority events are pending |
|
|
1322 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1323 | |
|
|
1324 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1325 | pending. |
|
|
1326 | |
|
|
1327 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1328 | fine, as long as you do not mind that the priority value you query might |
|
|
1329 | or might not have been clamped to the valid range. |
|
|
1330 | |
|
|
1331 | The default priority used by watchers when no priority has been set is |
|
|
1332 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1333 | |
|
|
1334 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1335 | priorities. |
|
|
1336 | |
|
|
1337 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1338 | |
|
|
1339 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1340 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1341 | can deal with that fact, as both are simply passed through to the |
|
|
1342 | callback. |
|
|
1343 | |
|
|
1344 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1345 | |
|
|
1346 | If the watcher is pending, this function clears its pending status and |
|
|
1347 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1348 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1349 | |
|
|
1350 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1351 | callback to be invoked, which can be accomplished with this function. |
|
|
1352 | |
|
|
1353 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1354 | |
|
|
1355 | Feeds the given event set into the event loop, as if the specified event |
|
|
1356 | had happened for the specified watcher (which must be a pointer to an |
|
|
1357 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1358 | not free the watcher as long as it has pending events. |
|
|
1359 | |
|
|
1360 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1361 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1362 | not started in the first place. |
|
|
1363 | |
|
|
1364 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1365 | functions that do not need a watcher. |
|
|
1366 | |
|
|
1367 | =back |
|
|
1368 | |
|
|
1369 | |
|
|
1370 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
1371 | |
|
|
1372 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1373 | and read at any time: libev will completely ignore it. This can be used |
|
|
1374 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1375 | don't want to allocate memory and store a pointer to it in that data |
|
|
1376 | member, you can also "subclass" the watcher type and provide your own |
|
|
1377 | data: |
|
|
1378 | |
|
|
1379 | struct my_io |
|
|
1380 | { |
|
|
1381 | ev_io io; |
|
|
1382 | int otherfd; |
|
|
1383 | void *somedata; |
|
|
1384 | struct whatever *mostinteresting; |
|
|
1385 | }; |
|
|
1386 | |
|
|
1387 | ... |
|
|
1388 | struct my_io w; |
|
|
1389 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1390 | |
|
|
1391 | And since your callback will be called with a pointer to the watcher, you |
|
|
1392 | can cast it back to your own type: |
|
|
1393 | |
|
|
1394 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1395 | { |
|
|
1396 | struct my_io *w = (struct my_io *)w_; |
|
|
1397 | ... |
|
|
1398 | } |
|
|
1399 | |
|
|
1400 | More interesting and less C-conformant ways of casting your callback type |
|
|
1401 | instead have been omitted. |
|
|
1402 | |
|
|
1403 | Another common scenario is to use some data structure with multiple |
|
|
1404 | embedded watchers: |
|
|
1405 | |
|
|
1406 | struct my_biggy |
|
|
1407 | { |
|
|
1408 | int some_data; |
|
|
1409 | ev_timer t1; |
|
|
1410 | ev_timer t2; |
|
|
1411 | } |
|
|
1412 | |
|
|
1413 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1414 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1415 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1416 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1417 | programmers): |
|
|
1418 | |
|
|
1419 | #include <stddef.h> |
|
|
1420 | |
|
|
1421 | static void |
|
|
1422 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1423 | { |
|
|
1424 | struct my_biggy big = (struct my_biggy *) |
|
|
1425 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1426 | } |
|
|
1427 | |
|
|
1428 | static void |
|
|
1429 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1430 | { |
|
|
1431 | struct my_biggy big = (struct my_biggy *) |
|
|
1432 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1433 | } |
|
|
1434 | |
1441 | |
1435 | =head2 WATCHER PRIORITY MODELS |
1442 | =head2 WATCHER PRIORITY MODELS |
1436 | |
1443 | |
1437 | Many event loops support I<watcher priorities>, which are usually small |
1444 | Many event loops support I<watcher priorities>, which are usually small |
1438 | integers that influence the ordering of event callback invocation |
1445 | integers that influence the ordering of event callback invocation |
… | |
… | |
1565 | In general you can register as many read and/or write event watchers per |
1572 | In general you can register as many read and/or write event watchers per |
1566 | fd as you want (as long as you don't confuse yourself). Setting all file |
1573 | fd as you want (as long as you don't confuse yourself). Setting all file |
1567 | descriptors to non-blocking mode is also usually a good idea (but not |
1574 | descriptors to non-blocking mode is also usually a good idea (but not |
1568 | required if you know what you are doing). |
1575 | required if you know what you are doing). |
1569 | |
1576 | |
1570 | If you cannot use non-blocking mode, then force the use of a |
|
|
1571 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1572 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1573 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1574 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1575 | |
|
|
1576 | Another thing you have to watch out for is that it is quite easy to |
1577 | Another thing you have to watch out for is that it is quite easy to |
1577 | receive "spurious" readiness notifications, that is your callback might |
1578 | receive "spurious" readiness notifications, that is, your callback might |
1578 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1579 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1579 | because there is no data. Not only are some backends known to create a |
1580 | because there is no data. It is very easy to get into this situation even |
1580 | lot of those (for example Solaris ports), it is very easy to get into |
1581 | with a relatively standard program structure. Thus it is best to always |
1581 | this situation even with a relatively standard program structure. Thus |
1582 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1582 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1583 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1583 | preferable to a program hanging until some data arrives. |
1584 | |
1584 | |
1585 | If you cannot run the fd in non-blocking mode (for example you should |
1585 | If you cannot run the fd in non-blocking mode (for example you should |
1586 | not play around with an Xlib connection), then you have to separately |
1586 | not play around with an Xlib connection), then you have to separately |
1587 | re-test whether a file descriptor is really ready with a known-to-be good |
1587 | re-test whether a file descriptor is really ready with a known-to-be good |
1588 | interface such as poll (fortunately in our Xlib example, Xlib already |
1588 | interface such as poll (fortunately in the case of Xlib, it already does |
1589 | does this on its own, so its quite safe to use). Some people additionally |
1589 | this on its own, so its quite safe to use). Some people additionally |
1590 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1590 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1591 | indefinitely. |
1591 | indefinitely. |
1592 | |
1592 | |
1593 | But really, best use non-blocking mode. |
1593 | But really, best use non-blocking mode. |
1594 | |
1594 | |
… | |
… | |
1622 | |
1622 | |
1623 | There is no workaround possible except not registering events |
1623 | There is no workaround possible except not registering events |
1624 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1624 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1625 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1625 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1626 | |
1626 | |
|
|
1627 | =head3 The special problem of files |
|
|
1628 | |
|
|
1629 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1630 | representing files, and expect it to become ready when their program |
|
|
1631 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1632 | |
|
|
1633 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1634 | notification as soon as the kernel knows whether and how much data is |
|
|
1635 | there, and in the case of open files, that's always the case, so you |
|
|
1636 | always get a readiness notification instantly, and your read (or possibly |
|
|
1637 | write) will still block on the disk I/O. |
|
|
1638 | |
|
|
1639 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1640 | devices and so on, there is another party (the sender) that delivers data |
|
|
1641 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1642 | will not send data on its own, simply because it doesn't know what you |
|
|
1643 | wish to read - you would first have to request some data. |
|
|
1644 | |
|
|
1645 | Since files are typically not-so-well supported by advanced notification |
|
|
1646 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1647 | to files, even though you should not use it. The reason for this is |
|
|
1648 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1649 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1650 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1651 | F</dev/urandom>), and even though the file might better be served with |
|
|
1652 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1653 | it "just works" instead of freezing. |
|
|
1654 | |
|
|
1655 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1656 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1657 | when you rarely read from a file instead of from a socket, and want to |
|
|
1658 | reuse the same code path. |
|
|
1659 | |
1627 | =head3 The special problem of fork |
1660 | =head3 The special problem of fork |
1628 | |
1661 | |
1629 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1662 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1630 | useless behaviour. Libev fully supports fork, but needs to be told about |
1663 | useless behaviour. Libev fully supports fork, but needs to be told about |
1631 | it in the child. |
1664 | it in the child if you want to continue to use it in the child. |
1632 | |
1665 | |
1633 | To support fork in your programs, you either have to call |
1666 | To support fork in your child processes, you have to call C<ev_loop_fork |
1634 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1667 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1635 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1668 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1636 | C<EVBACKEND_POLL>. |
|
|
1637 | |
1669 | |
1638 | =head3 The special problem of SIGPIPE |
1670 | =head3 The special problem of SIGPIPE |
1639 | |
1671 | |
1640 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1672 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1641 | when writing to a pipe whose other end has been closed, your program gets |
1673 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1739 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1771 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1740 | monotonic clock option helps a lot here). |
1772 | monotonic clock option helps a lot here). |
1741 | |
1773 | |
1742 | The callback is guaranteed to be invoked only I<after> its timeout has |
1774 | The callback is guaranteed to be invoked only I<after> its timeout has |
1743 | passed (not I<at>, so on systems with very low-resolution clocks this |
1775 | passed (not I<at>, so on systems with very low-resolution clocks this |
1744 | might introduce a small delay). If multiple timers become ready during the |
1776 | might introduce a small delay, see "the special problem of being too |
|
|
1777 | early", below). If multiple timers become ready during the same loop |
1745 | same loop iteration then the ones with earlier time-out values are invoked |
1778 | iteration then the ones with earlier time-out values are invoked before |
1746 | before ones of the same priority with later time-out values (but this is |
1779 | ones of the same priority with later time-out values (but this is no |
1747 | no longer true when a callback calls C<ev_run> recursively). |
1780 | longer true when a callback calls C<ev_run> recursively). |
1748 | |
1781 | |
1749 | =head3 Be smart about timeouts |
1782 | =head3 Be smart about timeouts |
1750 | |
1783 | |
1751 | Many real-world problems involve some kind of timeout, usually for error |
1784 | Many real-world problems involve some kind of timeout, usually for error |
1752 | recovery. A typical example is an HTTP request - if the other side hangs, |
1785 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1827 | |
1860 | |
1828 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1861 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1829 | but remember the time of last activity, and check for a real timeout only |
1862 | but remember the time of last activity, and check for a real timeout only |
1830 | within the callback: |
1863 | within the callback: |
1831 | |
1864 | |
|
|
1865 | ev_tstamp timeout = 60.; |
1832 | ev_tstamp last_activity; // time of last activity |
1866 | ev_tstamp last_activity; // time of last activity |
|
|
1867 | ev_timer timer; |
1833 | |
1868 | |
1834 | static void |
1869 | static void |
1835 | callback (EV_P_ ev_timer *w, int revents) |
1870 | callback (EV_P_ ev_timer *w, int revents) |
1836 | { |
1871 | { |
1837 | ev_tstamp now = ev_now (EV_A); |
1872 | // calculate when the timeout would happen |
1838 | ev_tstamp timeout = last_activity + 60.; |
1873 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1839 | |
1874 | |
1840 | // if last_activity + 60. is older than now, we did time out |
1875 | // if negative, it means we the timeout already occured |
1841 | if (timeout < now) |
1876 | if (after < 0.) |
1842 | { |
1877 | { |
1843 | // timeout occurred, take action |
1878 | // timeout occurred, take action |
1844 | } |
1879 | } |
1845 | else |
1880 | else |
1846 | { |
1881 | { |
1847 | // callback was invoked, but there was some activity, re-arm |
1882 | // callback was invoked, but there was some recent |
1848 | // the watcher to fire in last_activity + 60, which is |
1883 | // activity. simply restart the timer to time out |
1849 | // guaranteed to be in the future, so "again" is positive: |
1884 | // after "after" seconds, which is the earliest time |
1850 | w->repeat = timeout - now; |
1885 | // the timeout can occur. |
|
|
1886 | ev_timer_set (w, after, 0.); |
1851 | ev_timer_again (EV_A_ w); |
1887 | ev_timer_start (EV_A_ w); |
1852 | } |
1888 | } |
1853 | } |
1889 | } |
1854 | |
1890 | |
1855 | To summarise the callback: first calculate the real timeout (defined |
1891 | To summarise the callback: first calculate in how many seconds the |
1856 | as "60 seconds after the last activity"), then check if that time has |
1892 | timeout will occur (by calculating the absolute time when it would occur, |
1857 | been reached, which means something I<did>, in fact, time out. Otherwise |
1893 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1858 | the callback was invoked too early (C<timeout> is in the future), so |
1894 | (EV_A)> from that). |
1859 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1860 | a timeout then. |
|
|
1861 | |
1895 | |
1862 | Note how C<ev_timer_again> is used, taking advantage of the |
1896 | If this value is negative, then we are already past the timeout, i.e. we |
1863 | C<ev_timer_again> optimisation when the timer is already running. |
1897 | timed out, and need to do whatever is needed in this case. |
|
|
1898 | |
|
|
1899 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1900 | and simply start the timer with this timeout value. |
|
|
1901 | |
|
|
1902 | In other words, each time the callback is invoked it will check whether |
|
|
1903 | the timeout cocured. If not, it will simply reschedule itself to check |
|
|
1904 | again at the earliest time it could time out. Rinse. Repeat. |
1864 | |
1905 | |
1865 | This scheme causes more callback invocations (about one every 60 seconds |
1906 | This scheme causes more callback invocations (about one every 60 seconds |
1866 | minus half the average time between activity), but virtually no calls to |
1907 | minus half the average time between activity), but virtually no calls to |
1867 | libev to change the timeout. |
1908 | libev to change the timeout. |
1868 | |
1909 | |
1869 | To start the timer, simply initialise the watcher and set C<last_activity> |
1910 | To start the machinery, simply initialise the watcher and set |
1870 | to the current time (meaning we just have some activity :), then call the |
1911 | C<last_activity> to the current time (meaning there was some activity just |
1871 | callback, which will "do the right thing" and start the timer: |
1912 | now), then call the callback, which will "do the right thing" and start |
|
|
1913 | the timer: |
1872 | |
1914 | |
|
|
1915 | last_activity = ev_now (EV_A); |
1873 | ev_init (timer, callback); |
1916 | ev_init (&timer, callback); |
1874 | last_activity = ev_now (loop); |
1917 | callback (EV_A_ &timer, 0); |
1875 | callback (loop, timer, EV_TIMER); |
|
|
1876 | |
1918 | |
1877 | And when there is some activity, simply store the current time in |
1919 | When there is some activity, simply store the current time in |
1878 | C<last_activity>, no libev calls at all: |
1920 | C<last_activity>, no libev calls at all: |
1879 | |
1921 | |
|
|
1922 | if (activity detected) |
1880 | last_activity = ev_now (loop); |
1923 | last_activity = ev_now (EV_A); |
|
|
1924 | |
|
|
1925 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1926 | providing a new value, stopping the timer and calling the callback, which |
|
|
1927 | will agaion do the right thing (for example, time out immediately :). |
|
|
1928 | |
|
|
1929 | timeout = new_value; |
|
|
1930 | ev_timer_stop (EV_A_ &timer); |
|
|
1931 | callback (EV_A_ &timer, 0); |
1881 | |
1932 | |
1882 | This technique is slightly more complex, but in most cases where the |
1933 | This technique is slightly more complex, but in most cases where the |
1883 | time-out is unlikely to be triggered, much more efficient. |
1934 | time-out is unlikely to be triggered, much more efficient. |
1884 | |
|
|
1885 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1886 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1887 | fix things for you. |
|
|
1888 | |
1935 | |
1889 | =item 4. Wee, just use a double-linked list for your timeouts. |
1936 | =item 4. Wee, just use a double-linked list for your timeouts. |
1890 | |
1937 | |
1891 | If there is not one request, but many thousands (millions...), all |
1938 | If there is not one request, but many thousands (millions...), all |
1892 | employing some kind of timeout with the same timeout value, then one can |
1939 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1919 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1966 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1920 | rather complicated, but extremely efficient, something that really pays |
1967 | rather complicated, but extremely efficient, something that really pays |
1921 | off after the first million or so of active timers, i.e. it's usually |
1968 | off after the first million or so of active timers, i.e. it's usually |
1922 | overkill :) |
1969 | overkill :) |
1923 | |
1970 | |
|
|
1971 | =head3 The special problem of being too early |
|
|
1972 | |
|
|
1973 | If you ask a timer to call your callback after three seconds, then |
|
|
1974 | you expect it to be invoked after three seconds - but of course, this |
|
|
1975 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1976 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1977 | process with a STOP signal for a few hours for example. |
|
|
1978 | |
|
|
1979 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1980 | delay has occurred, but cannot guarantee this. |
|
|
1981 | |
|
|
1982 | A less obvious failure mode is calling your callback too early: many event |
|
|
1983 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1984 | this can cause your callback to be invoked much earlier than you would |
|
|
1985 | expect. |
|
|
1986 | |
|
|
1987 | To see why, imagine a system with a clock that only offers full second |
|
|
1988 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1989 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1990 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
1991 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
1992 | |
|
|
1993 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
1994 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
1995 | one-second delay was requested - this is being "too early", despite best |
|
|
1996 | intentions. |
|
|
1997 | |
|
|
1998 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
1999 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2000 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2001 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2002 | |
|
|
2003 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2004 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2005 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2006 | late" side of things. |
|
|
2007 | |
1924 | =head3 The special problem of time updates |
2008 | =head3 The special problem of time updates |
1925 | |
2009 | |
1926 | Establishing the current time is a costly operation (it usually takes at |
2010 | Establishing the current time is a costly operation (it usually takes |
1927 | least two system calls): EV therefore updates its idea of the current |
2011 | at least one system call): EV therefore updates its idea of the current |
1928 | time only before and after C<ev_run> collects new events, which causes a |
2012 | time only before and after C<ev_run> collects new events, which causes a |
1929 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2013 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1930 | lots of events in one iteration. |
2014 | lots of events in one iteration. |
1931 | |
2015 | |
1932 | The relative timeouts are calculated relative to the C<ev_now ()> |
2016 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1938 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2022 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1939 | |
2023 | |
1940 | If the event loop is suspended for a long time, you can also force an |
2024 | If the event loop is suspended for a long time, you can also force an |
1941 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2025 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1942 | ()>. |
2026 | ()>. |
|
|
2027 | |
|
|
2028 | =head3 The special problem of unsynchronised clocks |
|
|
2029 | |
|
|
2030 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2031 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2032 | jumps). |
|
|
2033 | |
|
|
2034 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2035 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2036 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2037 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2038 | than a directly following call to C<time>. |
|
|
2039 | |
|
|
2040 | The moral of this is to only compare libev-related timestamps with |
|
|
2041 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2042 | a second or so. |
|
|
2043 | |
|
|
2044 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2045 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2046 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2047 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2048 | |
|
|
2049 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2050 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2051 | I<measured according to the real time>, not the system clock. |
|
|
2052 | |
|
|
2053 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2054 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2055 | exactly the right behaviour. |
|
|
2056 | |
|
|
2057 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2058 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2059 | time, where your comparisons will always generate correct results. |
1943 | |
2060 | |
1944 | =head3 The special problems of suspended animation |
2061 | =head3 The special problems of suspended animation |
1945 | |
2062 | |
1946 | When you leave the server world it is quite customary to hit machines that |
2063 | When you leave the server world it is quite customary to hit machines that |
1947 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2064 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
1991 | keep up with the timer (because it takes longer than those 10 seconds to |
2108 | keep up with the timer (because it takes longer than those 10 seconds to |
1992 | do stuff) the timer will not fire more than once per event loop iteration. |
2109 | do stuff) the timer will not fire more than once per event loop iteration. |
1993 | |
2110 | |
1994 | =item ev_timer_again (loop, ev_timer *) |
2111 | =item ev_timer_again (loop, ev_timer *) |
1995 | |
2112 | |
1996 | This will act as if the timer timed out and restart it again if it is |
2113 | This will act as if the timer timed out and restarts it again if it is |
1997 | repeating. The exact semantics are: |
2114 | repeating. The exact semantics are: |
1998 | |
2115 | |
1999 | If the timer is pending, its pending status is cleared. |
2116 | If the timer is pending, its pending status is cleared. |
2000 | |
2117 | |
2001 | If the timer is started but non-repeating, stop it (as if it timed out). |
2118 | If the timer is started but non-repeating, stop it (as if it timed out). |
… | |
… | |
2131 | |
2248 | |
2132 | Another way to think about it (for the mathematically inclined) is that |
2249 | Another way to think about it (for the mathematically inclined) is that |
2133 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2250 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2134 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2251 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2135 | |
2252 | |
2136 | For numerical stability it is preferable that the C<offset> value is near |
2253 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2137 | C<ev_now ()> (the current time), but there is no range requirement for |
2254 | interval value should be higher than C<1/8192> (which is around 100 |
2138 | this value, and in fact is often specified as zero. |
2255 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2256 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2257 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2258 | C<0> and C<interval>, which is also the recommended range. |
2139 | |
2259 | |
2140 | Note also that there is an upper limit to how often a timer can fire (CPU |
2260 | Note also that there is an upper limit to how often a timer can fire (CPU |
2141 | speed for example), so if C<interval> is very small then timing stability |
2261 | speed for example), so if C<interval> is very small then timing stability |
2142 | will of course deteriorate. Libev itself tries to be exact to be about one |
2262 | will of course deteriorate. Libev itself tries to be exact to be about one |
2143 | millisecond (if the OS supports it and the machine is fast enough). |
2263 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2257 | |
2377 | |
2258 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2378 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2259 | |
2379 | |
2260 | Signal watchers will trigger an event when the process receives a specific |
2380 | Signal watchers will trigger an event when the process receives a specific |
2261 | signal one or more times. Even though signals are very asynchronous, libev |
2381 | signal one or more times. Even though signals are very asynchronous, libev |
2262 | will try it's best to deliver signals synchronously, i.e. as part of the |
2382 | will try its best to deliver signals synchronously, i.e. as part of the |
2263 | normal event processing, like any other event. |
2383 | normal event processing, like any other event. |
2264 | |
2384 | |
2265 | If you want signals to be delivered truly asynchronously, just use |
2385 | If you want signals to be delivered truly asynchronously, just use |
2266 | C<sigaction> as you would do without libev and forget about sharing |
2386 | C<sigaction> as you would do without libev and forget about sharing |
2267 | the signal. You can even use C<ev_async> from a signal handler to |
2387 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2286 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2406 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2287 | |
2407 | |
2288 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2408 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2289 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2409 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2290 | stopping it again), that is, libev might or might not block the signal, |
2410 | stopping it again), that is, libev might or might not block the signal, |
2291 | and might or might not set or restore the installed signal handler. |
2411 | and might or might not set or restore the installed signal handler (but |
|
|
2412 | see C<EVFLAG_NOSIGMASK>). |
2292 | |
2413 | |
2293 | While this does not matter for the signal disposition (libev never |
2414 | While this does not matter for the signal disposition (libev never |
2294 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2415 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2295 | C<execve>), this matters for the signal mask: many programs do not expect |
2416 | C<execve>), this matters for the signal mask: many programs do not expect |
2296 | certain signals to be blocked. |
2417 | certain signals to be blocked. |
… | |
… | |
2309 | I<has> to modify the signal mask, at least temporarily. |
2430 | I<has> to modify the signal mask, at least temporarily. |
2310 | |
2431 | |
2311 | So I can't stress this enough: I<If you do not reset your signal mask when |
2432 | So I can't stress this enough: I<If you do not reset your signal mask when |
2312 | you expect it to be empty, you have a race condition in your code>. This |
2433 | you expect it to be empty, you have a race condition in your code>. This |
2313 | is not a libev-specific thing, this is true for most event libraries. |
2434 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2435 | |
|
|
2436 | =head3 The special problem of threads signal handling |
|
|
2437 | |
|
|
2438 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2439 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2440 | threads in a process block signals, which is hard to achieve. |
|
|
2441 | |
|
|
2442 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2443 | for the same signals), you can tackle this problem by globally blocking |
|
|
2444 | all signals before creating any threads (or creating them with a fully set |
|
|
2445 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2446 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2447 | these signals. You can pass on any signals that libev might be interested |
|
|
2448 | in by calling C<ev_feed_signal>. |
2314 | |
2449 | |
2315 | =head3 Watcher-Specific Functions and Data Members |
2450 | =head3 Watcher-Specific Functions and Data Members |
2316 | |
2451 | |
2317 | =over 4 |
2452 | =over 4 |
2318 | |
2453 | |
… | |
… | |
3153 | atexit (program_exits); |
3288 | atexit (program_exits); |
3154 | |
3289 | |
3155 | |
3290 | |
3156 | =head2 C<ev_async> - how to wake up an event loop |
3291 | =head2 C<ev_async> - how to wake up an event loop |
3157 | |
3292 | |
3158 | In general, you cannot use an C<ev_run> from multiple threads or other |
3293 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3159 | asynchronous sources such as signal handlers (as opposed to multiple event |
3294 | asynchronous sources such as signal handlers (as opposed to multiple event |
3160 | loops - those are of course safe to use in different threads). |
3295 | loops - those are of course safe to use in different threads). |
3161 | |
3296 | |
3162 | Sometimes, however, you need to wake up an event loop you do not control, |
3297 | Sometimes, however, you need to wake up an event loop you do not control, |
3163 | for example because it belongs to another thread. This is what C<ev_async> |
3298 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3165 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3300 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3166 | |
3301 | |
3167 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3302 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3168 | too, are asynchronous in nature, and signals, too, will be compressed |
3303 | too, are asynchronous in nature, and signals, too, will be compressed |
3169 | (i.e. the number of callback invocations may be less than the number of |
3304 | (i.e. the number of callback invocations may be less than the number of |
3170 | C<ev_async_sent> calls). |
3305 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3171 | |
3306 | of "global async watchers" by using a watcher on an otherwise unused |
3172 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3307 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3173 | just the default loop. |
3308 | even without knowing which loop owns the signal. |
3174 | |
3309 | |
3175 | =head3 Queueing |
3310 | =head3 Queueing |
3176 | |
3311 | |
3177 | C<ev_async> does not support queueing of data in any way. The reason |
3312 | C<ev_async> does not support queueing of data in any way. The reason |
3178 | is that the author does not know of a simple (or any) algorithm for a |
3313 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3270 | trust me. |
3405 | trust me. |
3271 | |
3406 | |
3272 | =item ev_async_send (loop, ev_async *) |
3407 | =item ev_async_send (loop, ev_async *) |
3273 | |
3408 | |
3274 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3409 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3275 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3410 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3411 | returns. |
|
|
3412 | |
3276 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3413 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3277 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3414 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3278 | section below on what exactly this means). |
3415 | embedding section below on what exactly this means). |
3279 | |
3416 | |
3280 | Note that, as with other watchers in libev, multiple events might get |
3417 | Note that, as with other watchers in libev, multiple events might get |
3281 | compressed into a single callback invocation (another way to look at this |
3418 | compressed into a single callback invocation (another way to look at |
3282 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3419 | this is that C<ev_async> watchers are level-triggered: they are set on |
3283 | reset when the event loop detects that). |
3420 | C<ev_async_send>, reset when the event loop detects that). |
3284 | |
3421 | |
3285 | This call incurs the overhead of a system call only once per event loop |
3422 | This call incurs the overhead of at most one extra system call per event |
3286 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3423 | loop iteration, if the event loop is blocked, and no syscall at all if |
3287 | repeated calls to C<ev_async_send> for the same event loop. |
3424 | the event loop (or your program) is processing events. That means that |
|
|
3425 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3426 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3427 | zero) under load. |
3288 | |
3428 | |
3289 | =item bool = ev_async_pending (ev_async *) |
3429 | =item bool = ev_async_pending (ev_async *) |
3290 | |
3430 | |
3291 | Returns a non-zero value when C<ev_async_send> has been called on the |
3431 | Returns a non-zero value when C<ev_async_send> has been called on the |
3292 | watcher but the event has not yet been processed (or even noted) by the |
3432 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3347 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3487 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3348 | |
3488 | |
3349 | =item ev_feed_fd_event (loop, int fd, int revents) |
3489 | =item ev_feed_fd_event (loop, int fd, int revents) |
3350 | |
3490 | |
3351 | Feed an event on the given fd, as if a file descriptor backend detected |
3491 | Feed an event on the given fd, as if a file descriptor backend detected |
3352 | the given events it. |
3492 | the given events. |
3353 | |
3493 | |
3354 | =item ev_feed_signal_event (loop, int signum) |
3494 | =item ev_feed_signal_event (loop, int signum) |
3355 | |
3495 | |
3356 | Feed an event as if the given signal occurred (C<loop> must be the default |
3496 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3357 | loop!). |
3497 | which is async-safe. |
3358 | |
3498 | |
3359 | =back |
3499 | =back |
|
|
3500 | |
|
|
3501 | |
|
|
3502 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3503 | |
|
|
3504 | This section explains some common idioms that are not immediately |
|
|
3505 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3506 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3507 | |
|
|
3508 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3509 | |
|
|
3510 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3511 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3512 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3513 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3514 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3515 | data: |
|
|
3516 | |
|
|
3517 | struct my_io |
|
|
3518 | { |
|
|
3519 | ev_io io; |
|
|
3520 | int otherfd; |
|
|
3521 | void *somedata; |
|
|
3522 | struct whatever *mostinteresting; |
|
|
3523 | }; |
|
|
3524 | |
|
|
3525 | ... |
|
|
3526 | struct my_io w; |
|
|
3527 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3528 | |
|
|
3529 | And since your callback will be called with a pointer to the watcher, you |
|
|
3530 | can cast it back to your own type: |
|
|
3531 | |
|
|
3532 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3533 | { |
|
|
3534 | struct my_io *w = (struct my_io *)w_; |
|
|
3535 | ... |
|
|
3536 | } |
|
|
3537 | |
|
|
3538 | More interesting and less C-conformant ways of casting your callback |
|
|
3539 | function type instead have been omitted. |
|
|
3540 | |
|
|
3541 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3542 | |
|
|
3543 | Another common scenario is to use some data structure with multiple |
|
|
3544 | embedded watchers, in effect creating your own watcher that combines |
|
|
3545 | multiple libev event sources into one "super-watcher": |
|
|
3546 | |
|
|
3547 | struct my_biggy |
|
|
3548 | { |
|
|
3549 | int some_data; |
|
|
3550 | ev_timer t1; |
|
|
3551 | ev_timer t2; |
|
|
3552 | } |
|
|
3553 | |
|
|
3554 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3555 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3556 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3557 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3558 | real programmers): |
|
|
3559 | |
|
|
3560 | #include <stddef.h> |
|
|
3561 | |
|
|
3562 | static void |
|
|
3563 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3564 | { |
|
|
3565 | struct my_biggy big = (struct my_biggy *) |
|
|
3566 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3567 | } |
|
|
3568 | |
|
|
3569 | static void |
|
|
3570 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3571 | { |
|
|
3572 | struct my_biggy big = (struct my_biggy *) |
|
|
3573 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3574 | } |
|
|
3575 | |
|
|
3576 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3577 | |
|
|
3578 | Often you have structures like this in event-based programs: |
|
|
3579 | |
|
|
3580 | callback () |
|
|
3581 | { |
|
|
3582 | free (request); |
|
|
3583 | } |
|
|
3584 | |
|
|
3585 | request = start_new_request (..., callback); |
|
|
3586 | |
|
|
3587 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3588 | used to cancel the operation, or do other things with it. |
|
|
3589 | |
|
|
3590 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3591 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3592 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3593 | operation and simply invoke the callback with the result. |
|
|
3594 | |
|
|
3595 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3596 | has returned, so C<request> is not set. |
|
|
3597 | |
|
|
3598 | Even if you pass the request by some safer means to the callback, you |
|
|
3599 | might want to do something to the request after starting it, such as |
|
|
3600 | canceling it, which probably isn't working so well when the callback has |
|
|
3601 | already been invoked. |
|
|
3602 | |
|
|
3603 | A common way around all these issues is to make sure that |
|
|
3604 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3605 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3606 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
|
|
3607 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3608 | and pushing it into the pending queue: |
|
|
3609 | |
|
|
3610 | ev_set_cb (watcher, callback); |
|
|
3611 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3612 | |
|
|
3613 | This way, C<start_new_request> can safely return before the callback is |
|
|
3614 | invoked, while not delaying callback invocation too much. |
|
|
3615 | |
|
|
3616 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3617 | |
|
|
3618 | Often (especially in GUI toolkits) there are places where you have |
|
|
3619 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3620 | invoking C<ev_run>. |
|
|
3621 | |
|
|
3622 | This brings the problem of exiting - a callback might want to finish the |
|
|
3623 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3624 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3625 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3626 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3627 | |
|
|
3628 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3629 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3630 | triggered, using C<EVRUN_ONCE>: |
|
|
3631 | |
|
|
3632 | // main loop |
|
|
3633 | int exit_main_loop = 0; |
|
|
3634 | |
|
|
3635 | while (!exit_main_loop) |
|
|
3636 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3637 | |
|
|
3638 | // in a modal watcher |
|
|
3639 | int exit_nested_loop = 0; |
|
|
3640 | |
|
|
3641 | while (!exit_nested_loop) |
|
|
3642 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3643 | |
|
|
3644 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3645 | |
|
|
3646 | // exit modal loop |
|
|
3647 | exit_nested_loop = 1; |
|
|
3648 | |
|
|
3649 | // exit main program, after modal loop is finished |
|
|
3650 | exit_main_loop = 1; |
|
|
3651 | |
|
|
3652 | // exit both |
|
|
3653 | exit_main_loop = exit_nested_loop = 1; |
|
|
3654 | |
|
|
3655 | =head2 THREAD LOCKING EXAMPLE |
|
|
3656 | |
|
|
3657 | Here is a fictitious example of how to run an event loop in a different |
|
|
3658 | thread from where callbacks are being invoked and watchers are |
|
|
3659 | created/added/removed. |
|
|
3660 | |
|
|
3661 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3662 | which uses exactly this technique (which is suited for many high-level |
|
|
3663 | languages). |
|
|
3664 | |
|
|
3665 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3666 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3667 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3668 | |
|
|
3669 | First, you need to associate some data with the event loop: |
|
|
3670 | |
|
|
3671 | typedef struct { |
|
|
3672 | mutex_t lock; /* global loop lock */ |
|
|
3673 | ev_async async_w; |
|
|
3674 | thread_t tid; |
|
|
3675 | cond_t invoke_cv; |
|
|
3676 | } userdata; |
|
|
3677 | |
|
|
3678 | void prepare_loop (EV_P) |
|
|
3679 | { |
|
|
3680 | // for simplicity, we use a static userdata struct. |
|
|
3681 | static userdata u; |
|
|
3682 | |
|
|
3683 | ev_async_init (&u->async_w, async_cb); |
|
|
3684 | ev_async_start (EV_A_ &u->async_w); |
|
|
3685 | |
|
|
3686 | pthread_mutex_init (&u->lock, 0); |
|
|
3687 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3688 | |
|
|
3689 | // now associate this with the loop |
|
|
3690 | ev_set_userdata (EV_A_ u); |
|
|
3691 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3692 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3693 | |
|
|
3694 | // then create the thread running ev_run |
|
|
3695 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3696 | } |
|
|
3697 | |
|
|
3698 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3699 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3700 | that might have been added: |
|
|
3701 | |
|
|
3702 | static void |
|
|
3703 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3704 | { |
|
|
3705 | // just used for the side effects |
|
|
3706 | } |
|
|
3707 | |
|
|
3708 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3709 | protecting the loop data, respectively. |
|
|
3710 | |
|
|
3711 | static void |
|
|
3712 | l_release (EV_P) |
|
|
3713 | { |
|
|
3714 | userdata *u = ev_userdata (EV_A); |
|
|
3715 | pthread_mutex_unlock (&u->lock); |
|
|
3716 | } |
|
|
3717 | |
|
|
3718 | static void |
|
|
3719 | l_acquire (EV_P) |
|
|
3720 | { |
|
|
3721 | userdata *u = ev_userdata (EV_A); |
|
|
3722 | pthread_mutex_lock (&u->lock); |
|
|
3723 | } |
|
|
3724 | |
|
|
3725 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3726 | into C<ev_run>: |
|
|
3727 | |
|
|
3728 | void * |
|
|
3729 | l_run (void *thr_arg) |
|
|
3730 | { |
|
|
3731 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3732 | |
|
|
3733 | l_acquire (EV_A); |
|
|
3734 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3735 | ev_run (EV_A_ 0); |
|
|
3736 | l_release (EV_A); |
|
|
3737 | |
|
|
3738 | return 0; |
|
|
3739 | } |
|
|
3740 | |
|
|
3741 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3742 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3743 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3744 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3745 | and b) skipping inter-thread-communication when there are no pending |
|
|
3746 | watchers is very beneficial): |
|
|
3747 | |
|
|
3748 | static void |
|
|
3749 | l_invoke (EV_P) |
|
|
3750 | { |
|
|
3751 | userdata *u = ev_userdata (EV_A); |
|
|
3752 | |
|
|
3753 | while (ev_pending_count (EV_A)) |
|
|
3754 | { |
|
|
3755 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3756 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3757 | } |
|
|
3758 | } |
|
|
3759 | |
|
|
3760 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3761 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3762 | thread to continue: |
|
|
3763 | |
|
|
3764 | static void |
|
|
3765 | real_invoke_pending (EV_P) |
|
|
3766 | { |
|
|
3767 | userdata *u = ev_userdata (EV_A); |
|
|
3768 | |
|
|
3769 | pthread_mutex_lock (&u->lock); |
|
|
3770 | ev_invoke_pending (EV_A); |
|
|
3771 | pthread_cond_signal (&u->invoke_cv); |
|
|
3772 | pthread_mutex_unlock (&u->lock); |
|
|
3773 | } |
|
|
3774 | |
|
|
3775 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3776 | event loop, you will now have to lock: |
|
|
3777 | |
|
|
3778 | ev_timer timeout_watcher; |
|
|
3779 | userdata *u = ev_userdata (EV_A); |
|
|
3780 | |
|
|
3781 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3782 | |
|
|
3783 | pthread_mutex_lock (&u->lock); |
|
|
3784 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3785 | ev_async_send (EV_A_ &u->async_w); |
|
|
3786 | pthread_mutex_unlock (&u->lock); |
|
|
3787 | |
|
|
3788 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3789 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3790 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3791 | watchers in the next event loop iteration. |
|
|
3792 | |
|
|
3793 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3794 | |
|
|
3795 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3796 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3797 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3798 | doesn't need callbacks anymore. |
|
|
3799 | |
|
|
3800 | Imagine you have coroutines that you can switch to using a function |
|
|
3801 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3802 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3803 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3804 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3805 | the differing C<;> conventions): |
|
|
3806 | |
|
|
3807 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3808 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3809 | |
|
|
3810 | That means instead of having a C callback function, you store the |
|
|
3811 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3812 | your callback, you instead have it switch to that coroutine. |
|
|
3813 | |
|
|
3814 | A coroutine might now wait for an event with a function called |
|
|
3815 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3816 | matter when, or whether the watcher is active or not when this function is |
|
|
3817 | called): |
|
|
3818 | |
|
|
3819 | void |
|
|
3820 | wait_for_event (ev_watcher *w) |
|
|
3821 | { |
|
|
3822 | ev_cb_set (w) = current_coro; |
|
|
3823 | switch_to (libev_coro); |
|
|
3824 | } |
|
|
3825 | |
|
|
3826 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3827 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3828 | this or any other coroutine. |
|
|
3829 | |
|
|
3830 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3831 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3832 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3833 | any waiters. |
|
|
3834 | |
|
|
3835 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3836 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3837 | |
|
|
3838 | // my_ev.h |
|
|
3839 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3840 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3841 | #include "../libev/ev.h" |
|
|
3842 | |
|
|
3843 | // my_ev.c |
|
|
3844 | #define EV_H "my_ev.h" |
|
|
3845 | #include "../libev/ev.c" |
|
|
3846 | |
|
|
3847 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3848 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3849 | can even use F<ev.h> as header file name directly. |
3360 | |
3850 | |
3361 | |
3851 | |
3362 | =head1 LIBEVENT EMULATION |
3852 | =head1 LIBEVENT EMULATION |
3363 | |
3853 | |
3364 | Libev offers a compatibility emulation layer for libevent. It cannot |
3854 | Libev offers a compatibility emulation layer for libevent. It cannot |
3365 | emulate the internals of libevent, so here are some usage hints: |
3855 | emulate the internals of libevent, so here are some usage hints: |
3366 | |
3856 | |
3367 | =over 4 |
3857 | =over 4 |
|
|
3858 | |
|
|
3859 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3860 | |
|
|
3861 | This was the newest libevent version available when libev was implemented, |
|
|
3862 | and is still mostly unchanged in 2010. |
3368 | |
3863 | |
3369 | =item * Use it by including <event.h>, as usual. |
3864 | =item * Use it by including <event.h>, as usual. |
3370 | |
3865 | |
3371 | =item * The following members are fully supported: ev_base, ev_callback, |
3866 | =item * The following members are fully supported: ev_base, ev_callback, |
3372 | ev_arg, ev_fd, ev_res, ev_events. |
3867 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3378 | =item * Priorities are not currently supported. Initialising priorities |
3873 | =item * Priorities are not currently supported. Initialising priorities |
3379 | will fail and all watchers will have the same priority, even though there |
3874 | will fail and all watchers will have the same priority, even though there |
3380 | is an ev_pri field. |
3875 | is an ev_pri field. |
3381 | |
3876 | |
3382 | =item * In libevent, the last base created gets the signals, in libev, the |
3877 | =item * In libevent, the last base created gets the signals, in libev, the |
3383 | first base created (== the default loop) gets the signals. |
3878 | base that registered the signal gets the signals. |
3384 | |
3879 | |
3385 | =item * Other members are not supported. |
3880 | =item * Other members are not supported. |
3386 | |
3881 | |
3387 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3882 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3388 | to use the libev header file and library. |
3883 | to use the libev header file and library. |
… | |
… | |
3407 | Care has been taken to keep the overhead low. The only data member the C++ |
3902 | Care has been taken to keep the overhead low. The only data member the C++ |
3408 | classes add (compared to plain C-style watchers) is the event loop pointer |
3903 | classes add (compared to plain C-style watchers) is the event loop pointer |
3409 | that the watcher is associated with (or no additional members at all if |
3904 | that the watcher is associated with (or no additional members at all if |
3410 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3905 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3411 | |
3906 | |
3412 | Currently, functions, and static and non-static member functions can be |
3907 | Currently, functions, static and non-static member functions and classes |
3413 | used as callbacks. Other types should be easy to add as long as they only |
3908 | with C<operator ()> can be used as callbacks. Other types should be easy |
3414 | need one additional pointer for context. If you need support for other |
3909 | to add as long as they only need one additional pointer for context. If |
3415 | types of functors please contact the author (preferably after implementing |
3910 | you need support for other types of functors please contact the author |
3416 | it). |
3911 | (preferably after implementing it). |
3417 | |
3912 | |
3418 | Here is a list of things available in the C<ev> namespace: |
3913 | Here is a list of things available in the C<ev> namespace: |
3419 | |
3914 | |
3420 | =over 4 |
3915 | =over 4 |
3421 | |
3916 | |
… | |
… | |
3574 | watchers in the constructor. |
4069 | watchers in the constructor. |
3575 | |
4070 | |
3576 | class myclass |
4071 | class myclass |
3577 | { |
4072 | { |
3578 | ev::io io ; void io_cb (ev::io &w, int revents); |
4073 | ev::io io ; void io_cb (ev::io &w, int revents); |
3579 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4074 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3580 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4075 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3581 | |
4076 | |
3582 | myclass (int fd) |
4077 | myclass (int fd) |
3583 | { |
4078 | { |
3584 | io .set <myclass, &myclass::io_cb > (this); |
4079 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3635 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4130 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3636 | |
4131 | |
3637 | =item D |
4132 | =item D |
3638 | |
4133 | |
3639 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4134 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3640 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4135 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3641 | |
4136 | |
3642 | =item Ocaml |
4137 | =item Ocaml |
3643 | |
4138 | |
3644 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4139 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3645 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4140 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3693 | suitable for use with C<EV_A>. |
4188 | suitable for use with C<EV_A>. |
3694 | |
4189 | |
3695 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4190 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3696 | |
4191 | |
3697 | Similar to the other two macros, this gives you the value of the default |
4192 | Similar to the other two macros, this gives you the value of the default |
3698 | loop, if multiple loops are supported ("ev loop default"). |
4193 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4194 | will be initialised if it isn't already initialised. |
|
|
4195 | |
|
|
4196 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4197 | to initialise the loop somewhere. |
3699 | |
4198 | |
3700 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4199 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3701 | |
4200 | |
3702 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4201 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3703 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4202 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3848 | supported). It will also not define any of the structs usually found in |
4347 | supported). It will also not define any of the structs usually found in |
3849 | F<event.h> that are not directly supported by the libev core alone. |
4348 | F<event.h> that are not directly supported by the libev core alone. |
3850 | |
4349 | |
3851 | In standalone mode, libev will still try to automatically deduce the |
4350 | In standalone mode, libev will still try to automatically deduce the |
3852 | configuration, but has to be more conservative. |
4351 | configuration, but has to be more conservative. |
|
|
4352 | |
|
|
4353 | =item EV_USE_FLOOR |
|
|
4354 | |
|
|
4355 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4356 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4357 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4358 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4359 | function is not available will fail, so the safe default is to not enable |
|
|
4360 | this. |
3853 | |
4361 | |
3854 | =item EV_USE_MONOTONIC |
4362 | =item EV_USE_MONOTONIC |
3855 | |
4363 | |
3856 | If defined to be C<1>, libev will try to detect the availability of the |
4364 | If defined to be C<1>, libev will try to detect the availability of the |
3857 | monotonic clock option at both compile time and runtime. Otherwise no |
4365 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3990 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4498 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3991 | |
4499 | |
3992 | =item EV_ATOMIC_T |
4500 | =item EV_ATOMIC_T |
3993 | |
4501 | |
3994 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4502 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3995 | access is atomic with respect to other threads or signal contexts. No such |
4503 | access is atomic and serialised with respect to other threads or signal |
3996 | type is easily found in the C language, so you can provide your own type |
4504 | contexts. No such type is easily found in the C language, so you can |
3997 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4505 | provide your own type that you know is safe for your purposes. It is used |
3998 | as well as for signal and thread safety in C<ev_async> watchers. |
4506 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4507 | in C<ev_async> watchers. |
3999 | |
4508 | |
4000 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4509 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4001 | (from F<signal.h>), which is usually good enough on most platforms. |
4510 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4511 | although strictly speaking using a type that also implies a memory fence |
|
|
4512 | is required. |
4002 | |
4513 | |
4003 | =item EV_H (h) |
4514 | =item EV_H (h) |
4004 | |
4515 | |
4005 | The name of the F<ev.h> header file used to include it. The default if |
4516 | The name of the F<ev.h> header file used to include it. The default if |
4006 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4517 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
4030 | will have the C<struct ev_loop *> as first argument, and you can create |
4541 | will have the C<struct ev_loop *> as first argument, and you can create |
4031 | additional independent event loops. Otherwise there will be no support |
4542 | additional independent event loops. Otherwise there will be no support |
4032 | for multiple event loops and there is no first event loop pointer |
4543 | for multiple event loops and there is no first event loop pointer |
4033 | argument. Instead, all functions act on the single default loop. |
4544 | argument. Instead, all functions act on the single default loop. |
4034 | |
4545 | |
|
|
4546 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4547 | default loop when multiplicity is switched off - you always have to |
|
|
4548 | initialise the loop manually in this case. |
|
|
4549 | |
4035 | =item EV_MINPRI |
4550 | =item EV_MINPRI |
4036 | |
4551 | |
4037 | =item EV_MAXPRI |
4552 | =item EV_MAXPRI |
4038 | |
4553 | |
4039 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4554 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4136 | |
4651 | |
4137 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4652 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4138 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4653 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4139 | your program might be left out as well - a binary starting a timer and an |
4654 | your program might be left out as well - a binary starting a timer and an |
4140 | I/O watcher then might come out at only 5Kb. |
4655 | I/O watcher then might come out at only 5Kb. |
|
|
4656 | |
|
|
4657 | =item EV_API_STATIC |
|
|
4658 | |
|
|
4659 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4660 | will have static linkage. This means that libev will not export any |
|
|
4661 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4662 | when you embed libev, only want to use libev functions in a single file, |
|
|
4663 | and do not want its identifiers to be visible. |
|
|
4664 | |
|
|
4665 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4666 | wants to use libev. |
4141 | |
4667 | |
4142 | =item EV_AVOID_STDIO |
4668 | =item EV_AVOID_STDIO |
4143 | |
4669 | |
4144 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4670 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4145 | functions (printf, scanf, perror etc.). This will increase the code size |
4671 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4289 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4815 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4290 | |
4816 | |
4291 | #include "ev_cpp.h" |
4817 | #include "ev_cpp.h" |
4292 | #include "ev.c" |
4818 | #include "ev.c" |
4293 | |
4819 | |
4294 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4820 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4295 | |
4821 | |
4296 | =head2 THREADS AND COROUTINES |
4822 | =head2 THREADS AND COROUTINES |
4297 | |
4823 | |
4298 | =head3 THREADS |
4824 | =head3 THREADS |
4299 | |
4825 | |
… | |
… | |
4350 | default loop and triggering an C<ev_async> watcher from the default loop |
4876 | default loop and triggering an C<ev_async> watcher from the default loop |
4351 | watcher callback into the event loop interested in the signal. |
4877 | watcher callback into the event loop interested in the signal. |
4352 | |
4878 | |
4353 | =back |
4879 | =back |
4354 | |
4880 | |
4355 | =head4 THREAD LOCKING EXAMPLE |
4881 | See also L<THREAD LOCKING EXAMPLE>. |
4356 | |
|
|
4357 | Here is a fictitious example of how to run an event loop in a different |
|
|
4358 | thread than where callbacks are being invoked and watchers are |
|
|
4359 | created/added/removed. |
|
|
4360 | |
|
|
4361 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4362 | which uses exactly this technique (which is suited for many high-level |
|
|
4363 | languages). |
|
|
4364 | |
|
|
4365 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4366 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4367 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4368 | |
|
|
4369 | First, you need to associate some data with the event loop: |
|
|
4370 | |
|
|
4371 | typedef struct { |
|
|
4372 | mutex_t lock; /* global loop lock */ |
|
|
4373 | ev_async async_w; |
|
|
4374 | thread_t tid; |
|
|
4375 | cond_t invoke_cv; |
|
|
4376 | } userdata; |
|
|
4377 | |
|
|
4378 | void prepare_loop (EV_P) |
|
|
4379 | { |
|
|
4380 | // for simplicity, we use a static userdata struct. |
|
|
4381 | static userdata u; |
|
|
4382 | |
|
|
4383 | ev_async_init (&u->async_w, async_cb); |
|
|
4384 | ev_async_start (EV_A_ &u->async_w); |
|
|
4385 | |
|
|
4386 | pthread_mutex_init (&u->lock, 0); |
|
|
4387 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4388 | |
|
|
4389 | // now associate this with the loop |
|
|
4390 | ev_set_userdata (EV_A_ u); |
|
|
4391 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4392 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4393 | |
|
|
4394 | // then create the thread running ev_loop |
|
|
4395 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4396 | } |
|
|
4397 | |
|
|
4398 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4399 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4400 | that might have been added: |
|
|
4401 | |
|
|
4402 | static void |
|
|
4403 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4404 | { |
|
|
4405 | // just used for the side effects |
|
|
4406 | } |
|
|
4407 | |
|
|
4408 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4409 | protecting the loop data, respectively. |
|
|
4410 | |
|
|
4411 | static void |
|
|
4412 | l_release (EV_P) |
|
|
4413 | { |
|
|
4414 | userdata *u = ev_userdata (EV_A); |
|
|
4415 | pthread_mutex_unlock (&u->lock); |
|
|
4416 | } |
|
|
4417 | |
|
|
4418 | static void |
|
|
4419 | l_acquire (EV_P) |
|
|
4420 | { |
|
|
4421 | userdata *u = ev_userdata (EV_A); |
|
|
4422 | pthread_mutex_lock (&u->lock); |
|
|
4423 | } |
|
|
4424 | |
|
|
4425 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4426 | into C<ev_run>: |
|
|
4427 | |
|
|
4428 | void * |
|
|
4429 | l_run (void *thr_arg) |
|
|
4430 | { |
|
|
4431 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4432 | |
|
|
4433 | l_acquire (EV_A); |
|
|
4434 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4435 | ev_run (EV_A_ 0); |
|
|
4436 | l_release (EV_A); |
|
|
4437 | |
|
|
4438 | return 0; |
|
|
4439 | } |
|
|
4440 | |
|
|
4441 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4442 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4443 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4444 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4445 | and b) skipping inter-thread-communication when there are no pending |
|
|
4446 | watchers is very beneficial): |
|
|
4447 | |
|
|
4448 | static void |
|
|
4449 | l_invoke (EV_P) |
|
|
4450 | { |
|
|
4451 | userdata *u = ev_userdata (EV_A); |
|
|
4452 | |
|
|
4453 | while (ev_pending_count (EV_A)) |
|
|
4454 | { |
|
|
4455 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4456 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4457 | } |
|
|
4458 | } |
|
|
4459 | |
|
|
4460 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4461 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4462 | thread to continue: |
|
|
4463 | |
|
|
4464 | static void |
|
|
4465 | real_invoke_pending (EV_P) |
|
|
4466 | { |
|
|
4467 | userdata *u = ev_userdata (EV_A); |
|
|
4468 | |
|
|
4469 | pthread_mutex_lock (&u->lock); |
|
|
4470 | ev_invoke_pending (EV_A); |
|
|
4471 | pthread_cond_signal (&u->invoke_cv); |
|
|
4472 | pthread_mutex_unlock (&u->lock); |
|
|
4473 | } |
|
|
4474 | |
|
|
4475 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4476 | event loop, you will now have to lock: |
|
|
4477 | |
|
|
4478 | ev_timer timeout_watcher; |
|
|
4479 | userdata *u = ev_userdata (EV_A); |
|
|
4480 | |
|
|
4481 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4482 | |
|
|
4483 | pthread_mutex_lock (&u->lock); |
|
|
4484 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4485 | ev_async_send (EV_A_ &u->async_w); |
|
|
4486 | pthread_mutex_unlock (&u->lock); |
|
|
4487 | |
|
|
4488 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4489 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4490 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4491 | watchers in the next event loop iteration. |
|
|
4492 | |
4882 | |
4493 | =head3 COROUTINES |
4883 | =head3 COROUTINES |
4494 | |
4884 | |
4495 | Libev is very accommodating to coroutines ("cooperative threads"): |
4885 | Libev is very accommodating to coroutines ("cooperative threads"): |
4496 | libev fully supports nesting calls to its functions from different |
4886 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4661 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5051 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4662 | model. Libev still offers limited functionality on this platform in |
5052 | model. Libev still offers limited functionality on this platform in |
4663 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5053 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4664 | descriptors. This only applies when using Win32 natively, not when using |
5054 | descriptors. This only applies when using Win32 natively, not when using |
4665 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5055 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4666 | as every compielr comes with a slightly differently broken/incompatible |
5056 | as every compiler comes with a slightly differently broken/incompatible |
4667 | environment. |
5057 | environment. |
4668 | |
5058 | |
4669 | Lifting these limitations would basically require the full |
5059 | Lifting these limitations would basically require the full |
4670 | re-implementation of the I/O system. If you are into this kind of thing, |
5060 | re-implementation of the I/O system. If you are into this kind of thing, |
4671 | then note that glib does exactly that for you in a very portable way (note |
5061 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4804 | |
5194 | |
4805 | The type C<double> is used to represent timestamps. It is required to |
5195 | The type C<double> is used to represent timestamps. It is required to |
4806 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5196 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4807 | good enough for at least into the year 4000 with millisecond accuracy |
5197 | good enough for at least into the year 4000 with millisecond accuracy |
4808 | (the design goal for libev). This requirement is overfulfilled by |
5198 | (the design goal for libev). This requirement is overfulfilled by |
4809 | implementations using IEEE 754, which is basically all existing ones. With |
5199 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5200 | |
4810 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5201 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5202 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5203 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5204 | something like that, just kidding). |
4811 | |
5205 | |
4812 | =back |
5206 | =back |
4813 | |
5207 | |
4814 | If you know of other additional requirements drop me a note. |
5208 | If you know of other additional requirements drop me a note. |
4815 | |
5209 | |
… | |
… | |
4877 | =item Processing ev_async_send: O(number_of_async_watchers) |
5271 | =item Processing ev_async_send: O(number_of_async_watchers) |
4878 | |
5272 | |
4879 | =item Processing signals: O(max_signal_number) |
5273 | =item Processing signals: O(max_signal_number) |
4880 | |
5274 | |
4881 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5275 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4882 | calls in the current loop iteration. Checking for async and signal events |
5276 | calls in the current loop iteration and the loop is currently |
|
|
5277 | blocked. Checking for async and signal events involves iterating over all |
4883 | involves iterating over all running async watchers or all signal numbers. |
5278 | running async watchers or all signal numbers. |
4884 | |
5279 | |
4885 | =back |
5280 | =back |
4886 | |
5281 | |
4887 | |
5282 | |
4888 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5283 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
5005 | The physical time that is observed. It is apparently strictly monotonic :) |
5400 | The physical time that is observed. It is apparently strictly monotonic :) |
5006 | |
5401 | |
5007 | =item wall-clock time |
5402 | =item wall-clock time |
5008 | |
5403 | |
5009 | The time and date as shown on clocks. Unlike real time, it can actually |
5404 | The time and date as shown on clocks. Unlike real time, it can actually |
5010 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5405 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5011 | clock. |
5406 | clock. |
5012 | |
5407 | |
5013 | =item watcher |
5408 | =item watcher |
5014 | |
5409 | |
5015 | A data structure that describes interest in certain events. Watchers need |
5410 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5018 | =back |
5413 | =back |
5019 | |
5414 | |
5020 | =head1 AUTHOR |
5415 | =head1 AUTHOR |
5021 | |
5416 | |
5022 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5417 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5023 | Magnusson and Emanuele Giaquinta. |
5418 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5024 | |
5419 | |