… | |
… | |
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 >>. |
|
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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) throw ()) |
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) throw ()) |
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) |
|
|
311 | |
|
|
312 | This function can be used to "simulate" a signal receive. It is completely |
|
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313 | safe to call this function at any time, from any context, including signal |
|
|
314 | handlers or random threads. |
|
|
315 | |
|
|
316 | Its main use is to customise signal handling in your process, especially |
|
|
317 | in the presence of threads. For example, you could block signals |
|
|
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, |
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
469 | returning before the timeout value requiring additional iterations and so |
503 | returning before the timeout value, resulting in additional iterations |
|
|
504 | (and only giving 5ms accuracy while select on the same platform gives |
470 | 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 |
471 | 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 |
472 | take considerable time (one syscall per file descriptor) and is of course |
507 | set, which can take considerable time (one syscall per file descriptor) |
473 | hard to detect. |
508 | and is of course hard to detect. |
474 | |
509 | |
475 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
476 | 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 |
477 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
478 | 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 |
479 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
480 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
481 | 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 |
482 | 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 |
483 | perfectly fine with C<select> (files, many character devices...). |
521 | perfectly fine with C<select> (files, many character devices...). |
|
|
522 | |
|
|
523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
524 | cobbled together in a hurry, no thought to design or interaction with |
|
|
525 | others. Oh, the pain, will it ever stop... |
484 | |
526 | |
485 | 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 |
486 | 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 |
487 | 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 |
488 | 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 |
… | |
… | |
525 | |
567 | |
526 | It scales in the same way as the epoll backend, but the interface to the |
568 | It scales in the same way as the epoll backend, but the interface to the |
527 | kernel is more efficient (which says nothing about its actual speed, of |
569 | kernel is more efficient (which says nothing about its actual speed, of |
528 | course). While stopping, setting and starting an I/O watcher does never |
570 | course). While stopping, setting and starting an I/O watcher does never |
529 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
530 | two event changes per incident. Support for C<fork ()> is very bad (but |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
531 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
532 | cases |
574 | drops fds silently in similarly hard-to-detect cases |
533 | |
575 | |
534 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
535 | |
577 | |
536 | While nominally embeddable in other event loops, this doesn't work |
578 | While nominally embeddable in other event loops, this doesn't work |
537 | everywhere, so you might need to test for this. And since it is broken |
579 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
554 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
596 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
555 | |
597 | |
556 | 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, |
557 | 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)). |
558 | |
600 | |
559 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
560 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
561 | blocking when no data (or space) is available. |
|
|
562 | |
|
|
563 | 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 |
564 | 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 |
565 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
603 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
566 | might perform better. |
604 | might perform better. |
567 | |
605 | |
568 | On the positive side, with the exception of the spurious readiness |
606 | On the positive side, this backend actually performed fully to |
569 | notifications, this backend actually performed fully to specification |
|
|
570 | 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 |
571 | 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. |
572 | |
620 | |
573 | 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 |
574 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
575 | |
623 | |
576 | =item C<EVBACKEND_ALL> |
624 | =item C<EVBACKEND_ALL> |
577 | |
625 | |
578 | 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 |
579 | 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 |
580 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
628 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
581 | |
629 | |
582 | 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). |
583 | |
639 | |
584 | =back |
640 | =back |
585 | |
641 | |
586 | 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, |
587 | 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 |
… | |
… | |
616 | This function is normally used on loop objects allocated by |
672 | This function is normally used on loop objects allocated by |
617 | 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 |
618 | 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. |
619 | |
675 | |
620 | 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 |
621 | 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. |
622 | 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> |
623 | and C<ev_loop_destroy>. |
679 | and C<ev_loop_destroy>. |
624 | |
680 | |
625 | =item ev_loop_fork (loop) |
681 | =item ev_loop_fork (loop) |
626 | |
682 | |
… | |
… | |
674 | prepare and check phases. |
730 | prepare and check phases. |
675 | |
731 | |
676 | =item unsigned int ev_depth (loop) |
732 | =item unsigned int ev_depth (loop) |
677 | |
733 | |
678 | 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 |
679 | 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. |
680 | |
736 | |
681 | 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 |
682 | 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), |
683 | in which case it is higher. |
739 | in which case it is higher. |
684 | |
740 | |
685 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
741 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
686 | 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 |
687 | 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. |
688 | |
745 | |
689 | =item unsigned int ev_backend (loop) |
746 | =item unsigned int ev_backend (loop) |
690 | |
747 | |
691 | 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 |
692 | use. |
749 | use. |
… | |
… | |
735 | without a previous call to C<ev_suspend>. |
792 | without a previous call to C<ev_suspend>. |
736 | |
793 | |
737 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
738 | event loop time (see C<ev_now_update>). |
795 | event loop time (see C<ev_now_update>). |
739 | |
796 | |
740 | =item ev_run (loop, int flags) |
797 | =item bool ev_run (loop, int flags) |
741 | |
798 | |
742 | Finally, this is it, the event handler. This function usually is called |
799 | Finally, this is it, the event handler. This function usually is called |
743 | after you have initialised all your watchers and you want to start |
800 | after you have initialised all your watchers and you want to start |
744 | handling events. It will ask the operating system for any new events, call |
801 | handling events. It will ask the operating system for any new events, call |
745 | the watcher callbacks, an then repeat the whole process indefinitely: This |
802 | the watcher callbacks, and then repeat the whole process indefinitely: This |
746 | is why event loops are called I<loops>. |
803 | is why event loops are called I<loops>. |
747 | |
804 | |
748 | If the flags argument is specified as C<0>, it will keep handling events |
805 | If the flags argument is specified as C<0>, it will keep handling events |
749 | until either no event watchers are active anymore or C<ev_break> was |
806 | until either no event watchers are active anymore or C<ev_break> was |
750 | called. |
807 | called. |
|
|
808 | |
|
|
809 | The return value is false if there are no more active watchers (which |
|
|
810 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
811 | (which usually means " you should call C<ev_run> again"). |
751 | |
812 | |
752 | Please note that an explicit C<ev_break> is usually better than |
813 | Please note that an explicit C<ev_break> is usually better than |
753 | relying on all watchers to be stopped when deciding when a program has |
814 | relying on all watchers to be stopped when deciding when a program has |
754 | finished (especially in interactive programs), but having a program |
815 | finished (especially in interactive programs), but having a program |
755 | that automatically loops as long as it has to and no longer by virtue |
816 | that automatically loops as long as it has to and no longer by virtue |
756 | of relying on its watchers stopping correctly, that is truly a thing of |
817 | of relying on its watchers stopping correctly, that is truly a thing of |
757 | beauty. |
818 | beauty. |
758 | |
819 | |
|
|
820 | This function is I<mostly> exception-safe - you can break out of a |
|
|
821 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
822 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
823 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
824 | |
759 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
825 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
760 | those events and any already outstanding ones, but will not wait and |
826 | those events and any already outstanding ones, but will not wait and |
761 | block your process in case there are no events and will return after one |
827 | block your process in case there are no events and will return after one |
762 | iteration of the loop. This is sometimes useful to poll and handle new |
828 | iteration of the loop. This is sometimes useful to poll and handle new |
763 | events while doing lengthy calculations, to keep the program responsive. |
829 | events while doing lengthy calculations, to keep the program responsive. |
… | |
… | |
772 | This is useful if you are waiting for some external event in conjunction |
838 | This is useful if you are waiting for some external event in conjunction |
773 | with something not expressible using other libev watchers (i.e. "roll your |
839 | with something not expressible using other libev watchers (i.e. "roll your |
774 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
840 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
775 | usually a better approach for this kind of thing. |
841 | usually a better approach for this kind of thing. |
776 | |
842 | |
777 | Here are the gory details of what C<ev_run> does: |
843 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
844 | understanding, not a guarantee that things will work exactly like this in |
|
|
845 | future versions): |
778 | |
846 | |
779 | - Increment loop depth. |
847 | - Increment loop depth. |
780 | - Reset the ev_break status. |
848 | - Reset the ev_break status. |
781 | - Before the first iteration, call any pending watchers. |
849 | - Before the first iteration, call any pending watchers. |
782 | LOOP: |
850 | LOOP: |
… | |
… | |
815 | anymore. |
883 | anymore. |
816 | |
884 | |
817 | ... queue jobs here, make sure they register event watchers as long |
885 | ... queue jobs here, make sure they register event watchers as long |
818 | ... as they still have work to do (even an idle watcher will do..) |
886 | ... as they still have work to do (even an idle watcher will do..) |
819 | ev_run (my_loop, 0); |
887 | ev_run (my_loop, 0); |
820 | ... jobs done or somebody called unloop. yeah! |
888 | ... jobs done or somebody called break. yeah! |
821 | |
889 | |
822 | =item ev_break (loop, how) |
890 | =item ev_break (loop, how) |
823 | |
891 | |
824 | Can be used to make a call to C<ev_run> return early (but only after it |
892 | Can be used to make a call to C<ev_run> return early (but only after it |
825 | has processed all outstanding events). The C<how> argument must be either |
893 | has processed all outstanding events). The C<how> argument must be either |
826 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
894 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
827 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
895 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
828 | |
896 | |
829 | This "break state" will be cleared when entering C<ev_run> again. |
897 | This "break state" will be cleared on the next call to C<ev_run>. |
830 | |
898 | |
831 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too. |
899 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
900 | which case it will have no effect. |
832 | |
901 | |
833 | =item ev_ref (loop) |
902 | =item ev_ref (loop) |
834 | |
903 | |
835 | =item ev_unref (loop) |
904 | =item ev_unref (loop) |
836 | |
905 | |
… | |
… | |
857 | running when nothing else is active. |
926 | running when nothing else is active. |
858 | |
927 | |
859 | ev_signal exitsig; |
928 | ev_signal exitsig; |
860 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
929 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
861 | ev_signal_start (loop, &exitsig); |
930 | ev_signal_start (loop, &exitsig); |
862 | evf_unref (loop); |
931 | ev_unref (loop); |
863 | |
932 | |
864 | Example: For some weird reason, unregister the above signal handler again. |
933 | Example: For some weird reason, unregister the above signal handler again. |
865 | |
934 | |
866 | ev_ref (loop); |
935 | ev_ref (loop); |
867 | ev_signal_stop (loop, &exitsig); |
936 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
887 | overhead for the actual polling but can deliver many events at once. |
956 | overhead for the actual polling but can deliver many events at once. |
888 | |
957 | |
889 | By setting a higher I<io collect interval> you allow libev to spend more |
958 | By setting a higher I<io collect interval> you allow libev to spend more |
890 | time collecting I/O events, so you can handle more events per iteration, |
959 | time collecting I/O events, so you can handle more events per iteration, |
891 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
960 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
892 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
961 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
893 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
962 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
894 | sleep time ensures that libev will not poll for I/O events more often then |
963 | sleep time ensures that libev will not poll for I/O events more often then |
895 | once per this interval, on average. |
964 | once per this interval, on average (as long as the host time resolution is |
|
|
965 | good enough). |
896 | |
966 | |
897 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
967 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
898 | to spend more time collecting timeouts, at the expense of increased |
968 | to spend more time collecting timeouts, at the expense of increased |
899 | latency/jitter/inexactness (the watcher callback will be called |
969 | latency/jitter/inexactness (the watcher callback will be called |
900 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
970 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
946 | invoke the actual watchers inside another context (another thread etc.). |
1016 | invoke the actual watchers inside another context (another thread etc.). |
947 | |
1017 | |
948 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1018 | If you want to reset the callback, use C<ev_invoke_pending> as new |
949 | callback. |
1019 | callback. |
950 | |
1020 | |
951 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1021 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
952 | |
1022 | |
953 | Sometimes you want to share the same loop between multiple threads. This |
1023 | Sometimes you want to share the same loop between multiple threads. This |
954 | can be done relatively simply by putting mutex_lock/unlock calls around |
1024 | can be done relatively simply by putting mutex_lock/unlock calls around |
955 | each call to a libev function. |
1025 | each call to a libev function. |
956 | |
1026 | |
957 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1027 | However, C<ev_run> can run an indefinite time, so it is not feasible |
958 | to wait for it to return. One way around this is to wake up the event |
1028 | to wait for it to return. One way around this is to wake up the event |
959 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1029 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
960 | I<release> and I<acquire> callbacks on the loop. |
1030 | I<release> and I<acquire> callbacks on the loop. |
961 | |
1031 | |
962 | When set, then C<release> will be called just before the thread is |
1032 | When set, then C<release> will be called just before the thread is |
963 | suspended waiting for new events, and C<acquire> is called just |
1033 | suspended waiting for new events, and C<acquire> is called just |
964 | afterwards. |
1034 | afterwards. |
… | |
… | |
979 | See also the locking example in the C<THREADS> section later in this |
1049 | See also the locking example in the C<THREADS> section later in this |
980 | document. |
1050 | document. |
981 | |
1051 | |
982 | =item ev_set_userdata (loop, void *data) |
1052 | =item ev_set_userdata (loop, void *data) |
983 | |
1053 | |
984 | =item ev_userdata (loop) |
1054 | =item void *ev_userdata (loop) |
985 | |
1055 | |
986 | Set and retrieve a single C<void *> associated with a loop. When |
1056 | Set and retrieve a single C<void *> associated with a loop. When |
987 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1057 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
988 | C<0.> |
1058 | C<0>. |
989 | |
1059 | |
990 | These two functions can be used to associate arbitrary data with a loop, |
1060 | These two functions can be used to associate arbitrary data with a loop, |
991 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1061 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
992 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1062 | C<acquire> callbacks described above, but of course can be (ab-)used for |
993 | any other purpose as well. |
1063 | any other purpose as well. |
… | |
… | |
1104 | |
1174 | |
1105 | =item C<EV_PREPARE> |
1175 | =item C<EV_PREPARE> |
1106 | |
1176 | |
1107 | =item C<EV_CHECK> |
1177 | =item C<EV_CHECK> |
1108 | |
1178 | |
1109 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1179 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1110 | to gather new events, and all C<ev_check> watchers are invoked just after |
1180 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1111 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1181 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1182 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1183 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1184 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1185 | or lower priority within an event loop iteration. |
|
|
1186 | |
1112 | received events. Callbacks of both watcher types can start and stop as |
1187 | Callbacks of both watcher types can start and stop as many watchers as |
1113 | many watchers as they want, and all of them will be taken into account |
1188 | they want, and all of them will be taken into account (for example, a |
1114 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1189 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1115 | C<ev_run> from blocking). |
1190 | blocking). |
1116 | |
1191 | |
1117 | =item C<EV_EMBED> |
1192 | =item C<EV_EMBED> |
1118 | |
1193 | |
1119 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1194 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1120 | |
1195 | |
… | |
… | |
1306 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1381 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1307 | functions that do not need a watcher. |
1382 | functions that do not need a watcher. |
1308 | |
1383 | |
1309 | =back |
1384 | =back |
1310 | |
1385 | |
1311 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1386 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
1312 | |
1387 | OWN COMPOSITE WATCHERS> idioms. |
1313 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1314 | and read at any time: libev will completely ignore it. This can be used |
|
|
1315 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1316 | don't want to allocate memory and store a pointer to it in that data |
|
|
1317 | member, you can also "subclass" the watcher type and provide your own |
|
|
1318 | data: |
|
|
1319 | |
|
|
1320 | struct my_io |
|
|
1321 | { |
|
|
1322 | ev_io io; |
|
|
1323 | int otherfd; |
|
|
1324 | void *somedata; |
|
|
1325 | struct whatever *mostinteresting; |
|
|
1326 | }; |
|
|
1327 | |
|
|
1328 | ... |
|
|
1329 | struct my_io w; |
|
|
1330 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1331 | |
|
|
1332 | And since your callback will be called with a pointer to the watcher, you |
|
|
1333 | can cast it back to your own type: |
|
|
1334 | |
|
|
1335 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1336 | { |
|
|
1337 | struct my_io *w = (struct my_io *)w_; |
|
|
1338 | ... |
|
|
1339 | } |
|
|
1340 | |
|
|
1341 | More interesting and less C-conformant ways of casting your callback type |
|
|
1342 | instead have been omitted. |
|
|
1343 | |
|
|
1344 | Another common scenario is to use some data structure with multiple |
|
|
1345 | embedded watchers: |
|
|
1346 | |
|
|
1347 | struct my_biggy |
|
|
1348 | { |
|
|
1349 | int some_data; |
|
|
1350 | ev_timer t1; |
|
|
1351 | ev_timer t2; |
|
|
1352 | } |
|
|
1353 | |
|
|
1354 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1355 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1356 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1357 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1358 | programmers): |
|
|
1359 | |
|
|
1360 | #include <stddef.h> |
|
|
1361 | |
|
|
1362 | static void |
|
|
1363 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1364 | { |
|
|
1365 | struct my_biggy big = (struct my_biggy *) |
|
|
1366 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1367 | } |
|
|
1368 | |
|
|
1369 | static void |
|
|
1370 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1371 | { |
|
|
1372 | struct my_biggy big = (struct my_biggy *) |
|
|
1373 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1374 | } |
|
|
1375 | |
1388 | |
1376 | =head2 WATCHER STATES |
1389 | =head2 WATCHER STATES |
1377 | |
1390 | |
1378 | There are various watcher states mentioned throughout this manual - |
1391 | There are various watcher states mentioned throughout this manual - |
1379 | active, pending and so on. In this section these states and the rules to |
1392 | active, pending and so on. In this section these states and the rules to |
… | |
… | |
1382 | |
1395 | |
1383 | =over 4 |
1396 | =over 4 |
1384 | |
1397 | |
1385 | =item initialiased |
1398 | =item initialiased |
1386 | |
1399 | |
1387 | Before a watcher can be registered with the event looop it has to be |
1400 | Before a watcher can be registered with the event loop it has to be |
1388 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1401 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1389 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1402 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1390 | |
1403 | |
1391 | In this state it is simply some block of memory that is suitable for use |
1404 | In this state it is simply some block of memory that is suitable for |
1392 | in an event loop. It can be moved around, freed, reused etc. at will. |
1405 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1406 | will - as long as you either keep the memory contents intact, or call |
|
|
1407 | C<ev_TYPE_init> again. |
1393 | |
1408 | |
1394 | =item started/running/active |
1409 | =item started/running/active |
1395 | |
1410 | |
1396 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1411 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1397 | property of the event loop, and is actively waiting for events. While in |
1412 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1425 | latter will clear any pending state the watcher might be in, regardless |
1440 | latter will clear any pending state the watcher might be in, regardless |
1426 | of whether it was active or not, so stopping a watcher explicitly before |
1441 | of whether it was active or not, so stopping a watcher explicitly before |
1427 | freeing it is often a good idea. |
1442 | freeing it is often a good idea. |
1428 | |
1443 | |
1429 | While stopped (and not pending) the watcher is essentially in the |
1444 | While stopped (and not pending) the watcher is essentially in the |
1430 | initialised state, that is it can be reused, moved, modified in any way |
1445 | initialised state, that is, it can be reused, moved, modified in any way |
1431 | you wish. |
1446 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1447 | it again). |
1432 | |
1448 | |
1433 | =back |
1449 | =back |
1434 | |
1450 | |
1435 | =head2 WATCHER PRIORITY MODELS |
1451 | =head2 WATCHER PRIORITY MODELS |
1436 | |
1452 | |
… | |
… | |
1565 | In general you can register as many read and/or write event watchers per |
1581 | 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 |
1582 | 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 |
1583 | descriptors to non-blocking mode is also usually a good idea (but not |
1568 | required if you know what you are doing). |
1584 | required if you know what you are doing). |
1569 | |
1585 | |
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 |
1586 | 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 |
1587 | 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 |
1588 | 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 |
1589 | 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 |
1590 | with a relatively standard program structure. Thus it is best to always |
1581 | this situation even with a relatively standard program structure. Thus |
1591 | 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. |
1592 | preferable to a program hanging until some data arrives. |
1584 | |
1593 | |
1585 | If you cannot run the fd in non-blocking mode (for example you should |
1594 | 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 |
1595 | 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 |
1596 | 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 |
1597 | 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 |
1598 | 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 |
1599 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1591 | indefinitely. |
1600 | indefinitely. |
1592 | |
1601 | |
1593 | But really, best use non-blocking mode. |
1602 | But really, best use non-blocking mode. |
1594 | |
1603 | |
… | |
… | |
1622 | |
1631 | |
1623 | There is no workaround possible except not registering events |
1632 | There is no workaround possible except not registering events |
1624 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1633 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1625 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1634 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1626 | |
1635 | |
|
|
1636 | =head3 The special problem of files |
|
|
1637 | |
|
|
1638 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1639 | representing files, and expect it to become ready when their program |
|
|
1640 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1641 | |
|
|
1642 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1643 | notification as soon as the kernel knows whether and how much data is |
|
|
1644 | there, and in the case of open files, that's always the case, so you |
|
|
1645 | always get a readiness notification instantly, and your read (or possibly |
|
|
1646 | write) will still block on the disk I/O. |
|
|
1647 | |
|
|
1648 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1649 | devices and so on, there is another party (the sender) that delivers data |
|
|
1650 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1651 | will not send data on its own, simply because it doesn't know what you |
|
|
1652 | wish to read - you would first have to request some data. |
|
|
1653 | |
|
|
1654 | Since files are typically not-so-well supported by advanced notification |
|
|
1655 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1656 | to files, even though you should not use it. The reason for this is |
|
|
1657 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1658 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1659 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1660 | F</dev/urandom>), and even though the file might better be served with |
|
|
1661 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1662 | it "just works" instead of freezing. |
|
|
1663 | |
|
|
1664 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1665 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1666 | when you rarely read from a file instead of from a socket, and want to |
|
|
1667 | reuse the same code path. |
|
|
1668 | |
1627 | =head3 The special problem of fork |
1669 | =head3 The special problem of fork |
1628 | |
1670 | |
1629 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1671 | 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 |
1672 | useless behaviour. Libev fully supports fork, but needs to be told about |
1631 | it in the child. |
1673 | it in the child if you want to continue to use it in the child. |
1632 | |
1674 | |
1633 | To support fork in your programs, you either have to call |
1675 | 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, |
1676 | ()> 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 |
1677 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1636 | C<EVBACKEND_POLL>. |
|
|
1637 | |
1678 | |
1638 | =head3 The special problem of SIGPIPE |
1679 | =head3 The special problem of SIGPIPE |
1639 | |
1680 | |
1640 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1681 | 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 |
1682 | 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 |
1780 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1740 | monotonic clock option helps a lot here). |
1781 | monotonic clock option helps a lot here). |
1741 | |
1782 | |
1742 | The callback is guaranteed to be invoked only I<after> its timeout has |
1783 | 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 |
1784 | 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 |
1785 | might introduce a small delay, see "the special problem of being too |
|
|
1786 | 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 |
1787 | 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 |
1788 | 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). |
1789 | longer true when a callback calls C<ev_run> recursively). |
1748 | |
1790 | |
1749 | =head3 Be smart about timeouts |
1791 | =head3 Be smart about timeouts |
1750 | |
1792 | |
1751 | Many real-world problems involve some kind of timeout, usually for error |
1793 | 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, |
1794 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1827 | |
1869 | |
1828 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1870 | 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 |
1871 | but remember the time of last activity, and check for a real timeout only |
1830 | within the callback: |
1872 | within the callback: |
1831 | |
1873 | |
|
|
1874 | ev_tstamp timeout = 60.; |
1832 | ev_tstamp last_activity; // time of last activity |
1875 | ev_tstamp last_activity; // time of last activity |
|
|
1876 | ev_timer timer; |
1833 | |
1877 | |
1834 | static void |
1878 | static void |
1835 | callback (EV_P_ ev_timer *w, int revents) |
1879 | callback (EV_P_ ev_timer *w, int revents) |
1836 | { |
1880 | { |
1837 | ev_tstamp now = ev_now (EV_A); |
1881 | // calculate when the timeout would happen |
1838 | ev_tstamp timeout = last_activity + 60.; |
1882 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1839 | |
1883 | |
1840 | // if last_activity + 60. is older than now, we did time out |
1884 | // if negative, it means we the timeout already occurred |
1841 | if (timeout < now) |
1885 | if (after < 0.) |
1842 | { |
1886 | { |
1843 | // timeout occurred, take action |
1887 | // timeout occurred, take action |
1844 | } |
1888 | } |
1845 | else |
1889 | else |
1846 | { |
1890 | { |
1847 | // callback was invoked, but there was some activity, re-arm |
1891 | // callback was invoked, but there was some recent |
1848 | // the watcher to fire in last_activity + 60, which is |
1892 | // activity. simply restart the timer to time out |
1849 | // guaranteed to be in the future, so "again" is positive: |
1893 | // after "after" seconds, which is the earliest time |
1850 | w->repeat = timeout - now; |
1894 | // the timeout can occur. |
|
|
1895 | ev_timer_set (w, after, 0.); |
1851 | ev_timer_again (EV_A_ w); |
1896 | ev_timer_start (EV_A_ w); |
1852 | } |
1897 | } |
1853 | } |
1898 | } |
1854 | |
1899 | |
1855 | To summarise the callback: first calculate the real timeout (defined |
1900 | 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 |
1901 | 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 |
1902 | 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 |
1903 | (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 | |
1904 | |
1862 | Note how C<ev_timer_again> is used, taking advantage of the |
1905 | 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. |
1906 | timed out, and need to do whatever is needed in this case. |
|
|
1907 | |
|
|
1908 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1909 | and simply start the timer with this timeout value. |
|
|
1910 | |
|
|
1911 | In other words, each time the callback is invoked it will check whether |
|
|
1912 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1913 | again at the earliest time it could time out. Rinse. Repeat. |
1864 | |
1914 | |
1865 | This scheme causes more callback invocations (about one every 60 seconds |
1915 | This scheme causes more callback invocations (about one every 60 seconds |
1866 | minus half the average time between activity), but virtually no calls to |
1916 | minus half the average time between activity), but virtually no calls to |
1867 | libev to change the timeout. |
1917 | libev to change the timeout. |
1868 | |
1918 | |
1869 | To start the timer, simply initialise the watcher and set C<last_activity> |
1919 | To start the machinery, simply initialise the watcher and set |
1870 | to the current time (meaning we just have some activity :), then call the |
1920 | 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: |
1921 | now), then call the callback, which will "do the right thing" and start |
|
|
1922 | the timer: |
1872 | |
1923 | |
|
|
1924 | last_activity = ev_now (EV_A); |
1873 | ev_init (timer, callback); |
1925 | ev_init (&timer, callback); |
1874 | last_activity = ev_now (loop); |
1926 | callback (EV_A_ &timer, 0); |
1875 | callback (loop, timer, EV_TIMER); |
|
|
1876 | |
1927 | |
1877 | And when there is some activity, simply store the current time in |
1928 | When there is some activity, simply store the current time in |
1878 | C<last_activity>, no libev calls at all: |
1929 | C<last_activity>, no libev calls at all: |
1879 | |
1930 | |
|
|
1931 | if (activity detected) |
1880 | last_activity = ev_now (loop); |
1932 | last_activity = ev_now (EV_A); |
|
|
1933 | |
|
|
1934 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1935 | providing a new value, stopping the timer and calling the callback, which |
|
|
1936 | will again do the right thing (for example, time out immediately :). |
|
|
1937 | |
|
|
1938 | timeout = new_value; |
|
|
1939 | ev_timer_stop (EV_A_ &timer); |
|
|
1940 | callback (EV_A_ &timer, 0); |
1881 | |
1941 | |
1882 | This technique is slightly more complex, but in most cases where the |
1942 | This technique is slightly more complex, but in most cases where the |
1883 | time-out is unlikely to be triggered, much more efficient. |
1943 | 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 | |
1944 | |
1889 | =item 4. Wee, just use a double-linked list for your timeouts. |
1945 | =item 4. Wee, just use a double-linked list for your timeouts. |
1890 | |
1946 | |
1891 | If there is not one request, but many thousands (millions...), all |
1947 | 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 |
1948 | 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 |
1975 | 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 |
1976 | 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 |
1977 | off after the first million or so of active timers, i.e. it's usually |
1922 | overkill :) |
1978 | overkill :) |
1923 | |
1979 | |
|
|
1980 | =head3 The special problem of being too early |
|
|
1981 | |
|
|
1982 | If you ask a timer to call your callback after three seconds, then |
|
|
1983 | you expect it to be invoked after three seconds - but of course, this |
|
|
1984 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1985 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1986 | process with a STOP signal for a few hours for example. |
|
|
1987 | |
|
|
1988 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1989 | delay has occurred, but cannot guarantee this. |
|
|
1990 | |
|
|
1991 | A less obvious failure mode is calling your callback too early: many event |
|
|
1992 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1993 | this can cause your callback to be invoked much earlier than you would |
|
|
1994 | expect. |
|
|
1995 | |
|
|
1996 | To see why, imagine a system with a clock that only offers full second |
|
|
1997 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1998 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1999 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2000 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2001 | |
|
|
2002 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2003 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2004 | one-second delay was requested - this is being "too early", despite best |
|
|
2005 | intentions. |
|
|
2006 | |
|
|
2007 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2008 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2009 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2010 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2011 | |
|
|
2012 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2013 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2014 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2015 | late" side of things. |
|
|
2016 | |
1924 | =head3 The special problem of time updates |
2017 | =head3 The special problem of time updates |
1925 | |
2018 | |
1926 | Establishing the current time is a costly operation (it usually takes at |
2019 | Establishing the current time is a costly operation (it usually takes |
1927 | least two system calls): EV therefore updates its idea of the current |
2020 | 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 |
2021 | 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 |
2022 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1930 | lots of events in one iteration. |
2023 | lots of events in one iteration. |
1931 | |
2024 | |
1932 | The relative timeouts are calculated relative to the C<ev_now ()> |
2025 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1938 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2031 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1939 | |
2032 | |
1940 | If the event loop is suspended for a long time, you can also force an |
2033 | 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 |
2034 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1942 | ()>. |
2035 | ()>. |
|
|
2036 | |
|
|
2037 | =head3 The special problem of unsynchronised clocks |
|
|
2038 | |
|
|
2039 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2040 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2041 | jumps). |
|
|
2042 | |
|
|
2043 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2044 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2045 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2046 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2047 | than a directly following call to C<time>. |
|
|
2048 | |
|
|
2049 | The moral of this is to only compare libev-related timestamps with |
|
|
2050 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2051 | a second or so. |
|
|
2052 | |
|
|
2053 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2054 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2055 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2056 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2057 | |
|
|
2058 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2059 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2060 | I<measured according to the real time>, not the system clock. |
|
|
2061 | |
|
|
2062 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2063 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2064 | exactly the right behaviour. |
|
|
2065 | |
|
|
2066 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2067 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2068 | time, where your comparisons will always generate correct results. |
1943 | |
2069 | |
1944 | =head3 The special problems of suspended animation |
2070 | =head3 The special problems of suspended animation |
1945 | |
2071 | |
1946 | When you leave the server world it is quite customary to hit machines that |
2072 | 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? |
2073 | 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 |
2117 | 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. |
2118 | do stuff) the timer will not fire more than once per event loop iteration. |
1993 | |
2119 | |
1994 | =item ev_timer_again (loop, ev_timer *) |
2120 | =item ev_timer_again (loop, ev_timer *) |
1995 | |
2121 | |
1996 | This will act as if the timer timed out and restart it again if it is |
2122 | This will act as if the timer timed out, and restarts it again if it is |
1997 | repeating. The exact semantics are: |
2123 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2124 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1998 | |
2125 | |
|
|
2126 | The exact semantics are as in the following rules, all of which will be |
|
|
2127 | applied to the watcher: |
|
|
2128 | |
|
|
2129 | =over 4 |
|
|
2130 | |
1999 | If the timer is pending, its pending status is cleared. |
2131 | =item If the timer is pending, the pending status is always cleared. |
2000 | |
2132 | |
2001 | If the timer is started but non-repeating, stop it (as if it timed out). |
2133 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2134 | out, without invoking it). |
2002 | |
2135 | |
2003 | If the timer is repeating, either start it if necessary (with the |
2136 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2004 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2137 | and start the timer, if necessary. |
|
|
2138 | |
|
|
2139 | =back |
2005 | |
2140 | |
2006 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2141 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2007 | usage example. |
2142 | usage example. |
2008 | |
2143 | |
2009 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2144 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
… | |
… | |
2131 | |
2266 | |
2132 | Another way to think about it (for the mathematically inclined) is that |
2267 | 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 |
2268 | 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. |
2269 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2135 | |
2270 | |
2136 | For numerical stability it is preferable that the C<offset> value is near |
2271 | 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 |
2272 | interval value should be higher than C<1/8192> (which is around 100 |
2138 | this value, and in fact is often specified as zero. |
2273 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2274 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2275 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2276 | C<0> and C<interval>, which is also the recommended range. |
2139 | |
2277 | |
2140 | Note also that there is an upper limit to how often a timer can fire (CPU |
2278 | 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 |
2279 | 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 |
2280 | 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). |
2281 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2257 | |
2395 | |
2258 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2396 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2259 | |
2397 | |
2260 | Signal watchers will trigger an event when the process receives a specific |
2398 | 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 |
2399 | 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 |
2400 | will try its best to deliver signals synchronously, i.e. as part of the |
2263 | normal event processing, like any other event. |
2401 | normal event processing, like any other event. |
2264 | |
2402 | |
2265 | If you want signals to be delivered truly asynchronously, just use |
2403 | If you want signals to be delivered truly asynchronously, just use |
2266 | C<sigaction> as you would do without libev and forget about sharing |
2404 | 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 |
2405 | 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 |
2424 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2287 | |
2425 | |
2288 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2426 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2289 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2427 | (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, |
2428 | 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. |
2429 | and might or might not set or restore the installed signal handler (but |
|
|
2430 | see C<EVFLAG_NOSIGMASK>). |
2292 | |
2431 | |
2293 | While this does not matter for the signal disposition (libev never |
2432 | 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 |
2433 | 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 |
2434 | C<execve>), this matters for the signal mask: many programs do not expect |
2296 | certain signals to be blocked. |
2435 | certain signals to be blocked. |
… | |
… | |
2309 | I<has> to modify the signal mask, at least temporarily. |
2448 | I<has> to modify the signal mask, at least temporarily. |
2310 | |
2449 | |
2311 | So I can't stress this enough: I<If you do not reset your signal mask when |
2450 | 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 |
2451 | 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. |
2452 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2453 | |
|
|
2454 | =head3 The special problem of threads signal handling |
|
|
2455 | |
|
|
2456 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2457 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2458 | threads in a process block signals, which is hard to achieve. |
|
|
2459 | |
|
|
2460 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2461 | for the same signals), you can tackle this problem by globally blocking |
|
|
2462 | all signals before creating any threads (or creating them with a fully set |
|
|
2463 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2464 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2465 | these signals. You can pass on any signals that libev might be interested |
|
|
2466 | in by calling C<ev_feed_signal>. |
2314 | |
2467 | |
2315 | =head3 Watcher-Specific Functions and Data Members |
2468 | =head3 Watcher-Specific Functions and Data Members |
2316 | |
2469 | |
2317 | =over 4 |
2470 | =over 4 |
2318 | |
2471 | |
… | |
… | |
2694 | Apart from keeping your process non-blocking (which is a useful |
2847 | Apart from keeping your process non-blocking (which is a useful |
2695 | effect on its own sometimes), idle watchers are a good place to do |
2848 | effect on its own sometimes), idle watchers are a good place to do |
2696 | "pseudo-background processing", or delay processing stuff to after the |
2849 | "pseudo-background processing", or delay processing stuff to after the |
2697 | event loop has handled all outstanding events. |
2850 | event loop has handled all outstanding events. |
2698 | |
2851 | |
|
|
2852 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2853 | |
|
|
2854 | As long as there is at least one active idle watcher, libev will never |
|
|
2855 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2856 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2857 | lowest priority will do. |
|
|
2858 | |
|
|
2859 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2860 | to do something on each event loop iteration - for example to balance load |
|
|
2861 | between different connections. |
|
|
2862 | |
|
|
2863 | See L<Abusing an C<ev_check> watcher for its side-effect> for a longer |
|
|
2864 | example. |
|
|
2865 | |
2699 | =head3 Watcher-Specific Functions and Data Members |
2866 | =head3 Watcher-Specific Functions and Data Members |
2700 | |
2867 | |
2701 | =over 4 |
2868 | =over 4 |
2702 | |
2869 | |
2703 | =item ev_idle_init (ev_idle *, callback) |
2870 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2726 | ev_idle_start (loop, idle_watcher); |
2893 | ev_idle_start (loop, idle_watcher); |
2727 | |
2894 | |
2728 | |
2895 | |
2729 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2896 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2730 | |
2897 | |
2731 | Prepare and check watchers are usually (but not always) used in pairs: |
2898 | Prepare and check watchers are often (but not always) used in pairs: |
2732 | prepare watchers get invoked before the process blocks and check watchers |
2899 | prepare watchers get invoked before the process blocks and check watchers |
2733 | afterwards. |
2900 | afterwards. |
2734 | |
2901 | |
2735 | You I<must not> call C<ev_run> or similar functions that enter |
2902 | You I<must not> call C<ev_run> or similar functions that enter |
2736 | the current event loop from either C<ev_prepare> or C<ev_check> |
2903 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
2764 | with priority higher than or equal to the event loop and one coroutine |
2931 | with priority higher than or equal to the event loop and one coroutine |
2765 | of lower priority, but only once, using idle watchers to keep the event |
2932 | of lower priority, but only once, using idle watchers to keep the event |
2766 | loop from blocking if lower-priority coroutines are active, thus mapping |
2933 | loop from blocking if lower-priority coroutines are active, thus mapping |
2767 | low-priority coroutines to idle/background tasks). |
2934 | low-priority coroutines to idle/background tasks). |
2768 | |
2935 | |
2769 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2936 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2770 | priority, to ensure that they are being run before any other watchers |
2937 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2771 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
2938 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
2939 | watchers). |
2772 | |
2940 | |
2773 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2941 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2774 | activate ("feed") events into libev. While libev fully supports this, they |
2942 | activate ("feed") events into libev. While libev fully supports this, they |
2775 | might get executed before other C<ev_check> watchers did their job. As |
2943 | might get executed before other C<ev_check> watchers did their job. As |
2776 | C<ev_check> watchers are often used to embed other (non-libev) event |
2944 | C<ev_check> watchers are often used to embed other (non-libev) event |
2777 | loops those other event loops might be in an unusable state until their |
2945 | loops those other event loops might be in an unusable state until their |
2778 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2946 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2779 | others). |
2947 | others). |
|
|
2948 | |
|
|
2949 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
2950 | |
|
|
2951 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
2952 | useful because they are called once per event loop iteration. For |
|
|
2953 | example, if you want to handle a large number of connections fairly, you |
|
|
2954 | normally only do a bit of work for each active connection, and if there |
|
|
2955 | is more work to do, you wait for the next event loop iteration, so other |
|
|
2956 | connections have a chance of making progress. |
|
|
2957 | |
|
|
2958 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
2959 | next event loop iteration. However, that isn't as soon as possible - |
|
|
2960 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
2961 | |
|
|
2962 | |
|
|
2963 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2964 | single global idle watcher that is active as long as you have one active |
|
|
2965 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
2966 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
2967 | invoked. Neither watcher alone can do that. |
2780 | |
2968 | |
2781 | =head3 Watcher-Specific Functions and Data Members |
2969 | =head3 Watcher-Specific Functions and Data Members |
2782 | |
2970 | |
2783 | =over 4 |
2971 | =over 4 |
2784 | |
2972 | |
… | |
… | |
3153 | atexit (program_exits); |
3341 | atexit (program_exits); |
3154 | |
3342 | |
3155 | |
3343 | |
3156 | =head2 C<ev_async> - how to wake up an event loop |
3344 | =head2 C<ev_async> - how to wake up an event loop |
3157 | |
3345 | |
3158 | In general, you cannot use an C<ev_run> from multiple threads or other |
3346 | 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 |
3347 | asynchronous sources such as signal handlers (as opposed to multiple event |
3160 | loops - those are of course safe to use in different threads). |
3348 | loops - those are of course safe to use in different threads). |
3161 | |
3349 | |
3162 | Sometimes, however, you need to wake up an event loop you do not control, |
3350 | 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> |
3351 | 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. |
3353 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3166 | |
3354 | |
3167 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3355 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3168 | too, are asynchronous in nature, and signals, too, will be compressed |
3356 | 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 |
3357 | (i.e. the number of callback invocations may be less than the number of |
3170 | C<ev_async_sent> calls). |
3358 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3171 | |
3359 | 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 |
3360 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3173 | just the default loop. |
3361 | even without knowing which loop owns the signal. |
3174 | |
3362 | |
3175 | =head3 Queueing |
3363 | =head3 Queueing |
3176 | |
3364 | |
3177 | C<ev_async> does not support queueing of data in any way. The reason |
3365 | 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 |
3366 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3270 | trust me. |
3458 | trust me. |
3271 | |
3459 | |
3272 | =item ev_async_send (loop, ev_async *) |
3460 | =item ev_async_send (loop, ev_async *) |
3273 | |
3461 | |
3274 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3462 | 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 |
3463 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3464 | returns. |
|
|
3465 | |
3276 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3466 | 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 |
3467 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3278 | section below on what exactly this means). |
3468 | embedding section below on what exactly this means). |
3279 | |
3469 | |
3280 | Note that, as with other watchers in libev, multiple events might get |
3470 | 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 |
3471 | 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>, |
3472 | this is that C<ev_async> watchers are level-triggered: they are set on |
3283 | reset when the event loop detects that). |
3473 | C<ev_async_send>, reset when the event loop detects that). |
3284 | |
3474 | |
3285 | This call incurs the overhead of a system call only once per event loop |
3475 | 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 |
3476 | 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. |
3477 | the event loop (or your program) is processing events. That means that |
|
|
3478 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3479 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3480 | zero) under load. |
3288 | |
3481 | |
3289 | =item bool = ev_async_pending (ev_async *) |
3482 | =item bool = ev_async_pending (ev_async *) |
3290 | |
3483 | |
3291 | Returns a non-zero value when C<ev_async_send> has been called on the |
3484 | 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 |
3485 | 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); |
3540 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3348 | |
3541 | |
3349 | =item ev_feed_fd_event (loop, int fd, int revents) |
3542 | =item ev_feed_fd_event (loop, int fd, int revents) |
3350 | |
3543 | |
3351 | Feed an event on the given fd, as if a file descriptor backend detected |
3544 | Feed an event on the given fd, as if a file descriptor backend detected |
3352 | the given events it. |
3545 | the given events. |
3353 | |
3546 | |
3354 | =item ev_feed_signal_event (loop, int signum) |
3547 | =item ev_feed_signal_event (loop, int signum) |
3355 | |
3548 | |
3356 | Feed an event as if the given signal occurred (C<loop> must be the default |
3549 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3357 | loop!). |
3550 | which is async-safe. |
3358 | |
3551 | |
3359 | =back |
3552 | =back |
|
|
3553 | |
|
|
3554 | |
|
|
3555 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3556 | |
|
|
3557 | This section explains some common idioms that are not immediately |
|
|
3558 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3559 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3560 | |
|
|
3561 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3562 | |
|
|
3563 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3564 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3565 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3566 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3567 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3568 | data: |
|
|
3569 | |
|
|
3570 | struct my_io |
|
|
3571 | { |
|
|
3572 | ev_io io; |
|
|
3573 | int otherfd; |
|
|
3574 | void *somedata; |
|
|
3575 | struct whatever *mostinteresting; |
|
|
3576 | }; |
|
|
3577 | |
|
|
3578 | ... |
|
|
3579 | struct my_io w; |
|
|
3580 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3581 | |
|
|
3582 | And since your callback will be called with a pointer to the watcher, you |
|
|
3583 | can cast it back to your own type: |
|
|
3584 | |
|
|
3585 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3586 | { |
|
|
3587 | struct my_io *w = (struct my_io *)w_; |
|
|
3588 | ... |
|
|
3589 | } |
|
|
3590 | |
|
|
3591 | More interesting and less C-conformant ways of casting your callback |
|
|
3592 | function type instead have been omitted. |
|
|
3593 | |
|
|
3594 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3595 | |
|
|
3596 | Another common scenario is to use some data structure with multiple |
|
|
3597 | embedded watchers, in effect creating your own watcher that combines |
|
|
3598 | multiple libev event sources into one "super-watcher": |
|
|
3599 | |
|
|
3600 | struct my_biggy |
|
|
3601 | { |
|
|
3602 | int some_data; |
|
|
3603 | ev_timer t1; |
|
|
3604 | ev_timer t2; |
|
|
3605 | } |
|
|
3606 | |
|
|
3607 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3608 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3609 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3610 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3611 | real programmers): |
|
|
3612 | |
|
|
3613 | #include <stddef.h> |
|
|
3614 | |
|
|
3615 | static void |
|
|
3616 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3617 | { |
|
|
3618 | struct my_biggy big = (struct my_biggy *) |
|
|
3619 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3620 | } |
|
|
3621 | |
|
|
3622 | static void |
|
|
3623 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3624 | { |
|
|
3625 | struct my_biggy big = (struct my_biggy *) |
|
|
3626 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3627 | } |
|
|
3628 | |
|
|
3629 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3630 | |
|
|
3631 | Often you have structures like this in event-based programs: |
|
|
3632 | |
|
|
3633 | callback () |
|
|
3634 | { |
|
|
3635 | free (request); |
|
|
3636 | } |
|
|
3637 | |
|
|
3638 | request = start_new_request (..., callback); |
|
|
3639 | |
|
|
3640 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3641 | used to cancel the operation, or do other things with it. |
|
|
3642 | |
|
|
3643 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3644 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3645 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3646 | operation and simply invoke the callback with the result. |
|
|
3647 | |
|
|
3648 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3649 | has returned, so C<request> is not set. |
|
|
3650 | |
|
|
3651 | Even if you pass the request by some safer means to the callback, you |
|
|
3652 | might want to do something to the request after starting it, such as |
|
|
3653 | canceling it, which probably isn't working so well when the callback has |
|
|
3654 | already been invoked. |
|
|
3655 | |
|
|
3656 | A common way around all these issues is to make sure that |
|
|
3657 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3658 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3659 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
|
|
3660 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3661 | and pushing it into the pending queue: |
|
|
3662 | |
|
|
3663 | ev_set_cb (watcher, callback); |
|
|
3664 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3665 | |
|
|
3666 | This way, C<start_new_request> can safely return before the callback is |
|
|
3667 | invoked, while not delaying callback invocation too much. |
|
|
3668 | |
|
|
3669 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3670 | |
|
|
3671 | Often (especially in GUI toolkits) there are places where you have |
|
|
3672 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3673 | invoking C<ev_run>. |
|
|
3674 | |
|
|
3675 | This brings the problem of exiting - a callback might want to finish the |
|
|
3676 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3677 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3678 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3679 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3680 | |
|
|
3681 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3682 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3683 | triggered, using C<EVRUN_ONCE>: |
|
|
3684 | |
|
|
3685 | // main loop |
|
|
3686 | int exit_main_loop = 0; |
|
|
3687 | |
|
|
3688 | while (!exit_main_loop) |
|
|
3689 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3690 | |
|
|
3691 | // in a modal watcher |
|
|
3692 | int exit_nested_loop = 0; |
|
|
3693 | |
|
|
3694 | while (!exit_nested_loop) |
|
|
3695 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3696 | |
|
|
3697 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3698 | |
|
|
3699 | // exit modal loop |
|
|
3700 | exit_nested_loop = 1; |
|
|
3701 | |
|
|
3702 | // exit main program, after modal loop is finished |
|
|
3703 | exit_main_loop = 1; |
|
|
3704 | |
|
|
3705 | // exit both |
|
|
3706 | exit_main_loop = exit_nested_loop = 1; |
|
|
3707 | |
|
|
3708 | =head2 THREAD LOCKING EXAMPLE |
|
|
3709 | |
|
|
3710 | Here is a fictitious example of how to run an event loop in a different |
|
|
3711 | thread from where callbacks are being invoked and watchers are |
|
|
3712 | created/added/removed. |
|
|
3713 | |
|
|
3714 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3715 | which uses exactly this technique (which is suited for many high-level |
|
|
3716 | languages). |
|
|
3717 | |
|
|
3718 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3719 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3720 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3721 | |
|
|
3722 | First, you need to associate some data with the event loop: |
|
|
3723 | |
|
|
3724 | typedef struct { |
|
|
3725 | mutex_t lock; /* global loop lock */ |
|
|
3726 | ev_async async_w; |
|
|
3727 | thread_t tid; |
|
|
3728 | cond_t invoke_cv; |
|
|
3729 | } userdata; |
|
|
3730 | |
|
|
3731 | void prepare_loop (EV_P) |
|
|
3732 | { |
|
|
3733 | // for simplicity, we use a static userdata struct. |
|
|
3734 | static userdata u; |
|
|
3735 | |
|
|
3736 | ev_async_init (&u->async_w, async_cb); |
|
|
3737 | ev_async_start (EV_A_ &u->async_w); |
|
|
3738 | |
|
|
3739 | pthread_mutex_init (&u->lock, 0); |
|
|
3740 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3741 | |
|
|
3742 | // now associate this with the loop |
|
|
3743 | ev_set_userdata (EV_A_ u); |
|
|
3744 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3745 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3746 | |
|
|
3747 | // then create the thread running ev_run |
|
|
3748 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3749 | } |
|
|
3750 | |
|
|
3751 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3752 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3753 | that might have been added: |
|
|
3754 | |
|
|
3755 | static void |
|
|
3756 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3757 | { |
|
|
3758 | // just used for the side effects |
|
|
3759 | } |
|
|
3760 | |
|
|
3761 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3762 | protecting the loop data, respectively. |
|
|
3763 | |
|
|
3764 | static void |
|
|
3765 | l_release (EV_P) |
|
|
3766 | { |
|
|
3767 | userdata *u = ev_userdata (EV_A); |
|
|
3768 | pthread_mutex_unlock (&u->lock); |
|
|
3769 | } |
|
|
3770 | |
|
|
3771 | static void |
|
|
3772 | l_acquire (EV_P) |
|
|
3773 | { |
|
|
3774 | userdata *u = ev_userdata (EV_A); |
|
|
3775 | pthread_mutex_lock (&u->lock); |
|
|
3776 | } |
|
|
3777 | |
|
|
3778 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3779 | into C<ev_run>: |
|
|
3780 | |
|
|
3781 | void * |
|
|
3782 | l_run (void *thr_arg) |
|
|
3783 | { |
|
|
3784 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3785 | |
|
|
3786 | l_acquire (EV_A); |
|
|
3787 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3788 | ev_run (EV_A_ 0); |
|
|
3789 | l_release (EV_A); |
|
|
3790 | |
|
|
3791 | return 0; |
|
|
3792 | } |
|
|
3793 | |
|
|
3794 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3795 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3796 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3797 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3798 | and b) skipping inter-thread-communication when there are no pending |
|
|
3799 | watchers is very beneficial): |
|
|
3800 | |
|
|
3801 | static void |
|
|
3802 | l_invoke (EV_P) |
|
|
3803 | { |
|
|
3804 | userdata *u = ev_userdata (EV_A); |
|
|
3805 | |
|
|
3806 | while (ev_pending_count (EV_A)) |
|
|
3807 | { |
|
|
3808 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3809 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3810 | } |
|
|
3811 | } |
|
|
3812 | |
|
|
3813 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3814 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3815 | thread to continue: |
|
|
3816 | |
|
|
3817 | static void |
|
|
3818 | real_invoke_pending (EV_P) |
|
|
3819 | { |
|
|
3820 | userdata *u = ev_userdata (EV_A); |
|
|
3821 | |
|
|
3822 | pthread_mutex_lock (&u->lock); |
|
|
3823 | ev_invoke_pending (EV_A); |
|
|
3824 | pthread_cond_signal (&u->invoke_cv); |
|
|
3825 | pthread_mutex_unlock (&u->lock); |
|
|
3826 | } |
|
|
3827 | |
|
|
3828 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3829 | event loop, you will now have to lock: |
|
|
3830 | |
|
|
3831 | ev_timer timeout_watcher; |
|
|
3832 | userdata *u = ev_userdata (EV_A); |
|
|
3833 | |
|
|
3834 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3835 | |
|
|
3836 | pthread_mutex_lock (&u->lock); |
|
|
3837 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3838 | ev_async_send (EV_A_ &u->async_w); |
|
|
3839 | pthread_mutex_unlock (&u->lock); |
|
|
3840 | |
|
|
3841 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3842 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3843 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3844 | watchers in the next event loop iteration. |
|
|
3845 | |
|
|
3846 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3847 | |
|
|
3848 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3849 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3850 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3851 | doesn't need callbacks anymore. |
|
|
3852 | |
|
|
3853 | Imagine you have coroutines that you can switch to using a function |
|
|
3854 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3855 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3856 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3857 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3858 | the differing C<;> conventions): |
|
|
3859 | |
|
|
3860 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3861 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3862 | |
|
|
3863 | That means instead of having a C callback function, you store the |
|
|
3864 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3865 | your callback, you instead have it switch to that coroutine. |
|
|
3866 | |
|
|
3867 | A coroutine might now wait for an event with a function called |
|
|
3868 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3869 | matter when, or whether the watcher is active or not when this function is |
|
|
3870 | called): |
|
|
3871 | |
|
|
3872 | void |
|
|
3873 | wait_for_event (ev_watcher *w) |
|
|
3874 | { |
|
|
3875 | ev_cb_set (w) = current_coro; |
|
|
3876 | switch_to (libev_coro); |
|
|
3877 | } |
|
|
3878 | |
|
|
3879 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3880 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3881 | this or any other coroutine. |
|
|
3882 | |
|
|
3883 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3884 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3885 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3886 | any waiters. |
|
|
3887 | |
|
|
3888 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3889 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3890 | |
|
|
3891 | // my_ev.h |
|
|
3892 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3893 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3894 | #include "../libev/ev.h" |
|
|
3895 | |
|
|
3896 | // my_ev.c |
|
|
3897 | #define EV_H "my_ev.h" |
|
|
3898 | #include "../libev/ev.c" |
|
|
3899 | |
|
|
3900 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3901 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3902 | can even use F<ev.h> as header file name directly. |
3360 | |
3903 | |
3361 | |
3904 | |
3362 | =head1 LIBEVENT EMULATION |
3905 | =head1 LIBEVENT EMULATION |
3363 | |
3906 | |
3364 | Libev offers a compatibility emulation layer for libevent. It cannot |
3907 | Libev offers a compatibility emulation layer for libevent. It cannot |
3365 | emulate the internals of libevent, so here are some usage hints: |
3908 | emulate the internals of libevent, so here are some usage hints: |
3366 | |
3909 | |
3367 | =over 4 |
3910 | =over 4 |
|
|
3911 | |
|
|
3912 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3913 | |
|
|
3914 | This was the newest libevent version available when libev was implemented, |
|
|
3915 | and is still mostly unchanged in 2010. |
3368 | |
3916 | |
3369 | =item * Use it by including <event.h>, as usual. |
3917 | =item * Use it by including <event.h>, as usual. |
3370 | |
3918 | |
3371 | =item * The following members are fully supported: ev_base, ev_callback, |
3919 | =item * The following members are fully supported: ev_base, ev_callback, |
3372 | ev_arg, ev_fd, ev_res, ev_events. |
3920 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3378 | =item * Priorities are not currently supported. Initialising priorities |
3926 | =item * Priorities are not currently supported. Initialising priorities |
3379 | will fail and all watchers will have the same priority, even though there |
3927 | will fail and all watchers will have the same priority, even though there |
3380 | is an ev_pri field. |
3928 | is an ev_pri field. |
3381 | |
3929 | |
3382 | =item * In libevent, the last base created gets the signals, in libev, the |
3930 | =item * In libevent, the last base created gets the signals, in libev, the |
3383 | first base created (== the default loop) gets the signals. |
3931 | base that registered the signal gets the signals. |
3384 | |
3932 | |
3385 | =item * Other members are not supported. |
3933 | =item * Other members are not supported. |
3386 | |
3934 | |
3387 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3935 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3388 | to use the libev header file and library. |
3936 | to use the libev header file and library. |
3389 | |
3937 | |
3390 | =back |
3938 | =back |
3391 | |
3939 | |
3392 | =head1 C++ SUPPORT |
3940 | =head1 C++ SUPPORT |
|
|
3941 | |
|
|
3942 | =head2 C API |
|
|
3943 | |
|
|
3944 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3945 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3946 | will work fine. |
|
|
3947 | |
|
|
3948 | Proper exception specifications might have to be added to callbacks passed |
|
|
3949 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3950 | other callbacks (allocator, syserr, loop acquire/release and periodioc |
|
|
3951 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3952 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3953 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3954 | |
|
|
3955 | static void |
|
|
3956 | fatal_error (const char *msg) EV_THROW |
|
|
3957 | { |
|
|
3958 | perror (msg); |
|
|
3959 | abort (); |
|
|
3960 | } |
|
|
3961 | |
|
|
3962 | ... |
|
|
3963 | ev_set_syserr_cb (fatal_error); |
|
|
3964 | |
|
|
3965 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3966 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
3967 | because it runs cleanup watchers). |
|
|
3968 | |
|
|
3969 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3970 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3971 | throwing exceptions through C libraries (most do). |
|
|
3972 | |
|
|
3973 | =head2 C++ API |
3393 | |
3974 | |
3394 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3975 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3395 | you to use some convenience methods to start/stop watchers and also change |
3976 | you to use some convenience methods to start/stop watchers and also change |
3396 | the callback model to a model using method callbacks on objects. |
3977 | the callback model to a model using method callbacks on objects. |
3397 | |
3978 | |
… | |
… | |
3407 | Care has been taken to keep the overhead low. The only data member the C++ |
3988 | 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 |
3989 | 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 |
3990 | that the watcher is associated with (or no additional members at all if |
3410 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3991 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3411 | |
3992 | |
3412 | Currently, functions, and static and non-static member functions can be |
3993 | 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 |
3994 | 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 |
3995 | 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 |
3996 | you need support for other types of functors please contact the author |
3416 | it). |
3997 | (preferably after implementing it). |
|
|
3998 | |
|
|
3999 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4000 | conventions as your C compiler (for static member functions), or you have |
|
|
4001 | to embed libev and compile libev itself as C++. |
3417 | |
4002 | |
3418 | Here is a list of things available in the C<ev> namespace: |
4003 | Here is a list of things available in the C<ev> namespace: |
3419 | |
4004 | |
3420 | =over 4 |
4005 | =over 4 |
3421 | |
4006 | |
… | |
… | |
3431 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4016 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3432 | |
4017 | |
3433 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4018 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3434 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4019 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3435 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4020 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3436 | defines by many implementations. |
4021 | defined by many implementations. |
3437 | |
4022 | |
3438 | All of those classes have these methods: |
4023 | All of those classes have these methods: |
3439 | |
4024 | |
3440 | =over 4 |
4025 | =over 4 |
3441 | |
4026 | |
… | |
… | |
3574 | watchers in the constructor. |
4159 | watchers in the constructor. |
3575 | |
4160 | |
3576 | class myclass |
4161 | class myclass |
3577 | { |
4162 | { |
3578 | ev::io io ; void io_cb (ev::io &w, int revents); |
4163 | ev::io io ; void io_cb (ev::io &w, int revents); |
3579 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4164 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3580 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4165 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3581 | |
4166 | |
3582 | myclass (int fd) |
4167 | myclass (int fd) |
3583 | { |
4168 | { |
3584 | io .set <myclass, &myclass::io_cb > (this); |
4169 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3635 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4220 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3636 | |
4221 | |
3637 | =item D |
4222 | =item D |
3638 | |
4223 | |
3639 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4224 | 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>. |
4225 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3641 | |
4226 | |
3642 | =item Ocaml |
4227 | =item Ocaml |
3643 | |
4228 | |
3644 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4229 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3645 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4230 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3693 | suitable for use with C<EV_A>. |
4278 | suitable for use with C<EV_A>. |
3694 | |
4279 | |
3695 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4280 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3696 | |
4281 | |
3697 | Similar to the other two macros, this gives you the value of the default |
4282 | Similar to the other two macros, this gives you the value of the default |
3698 | loop, if multiple loops are supported ("ev loop default"). |
4283 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4284 | will be initialised if it isn't already initialised. |
|
|
4285 | |
|
|
4286 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4287 | to initialise the loop somewhere. |
3699 | |
4288 | |
3700 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4289 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3701 | |
4290 | |
3702 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4291 | 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 |
4292 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3848 | supported). It will also not define any of the structs usually found in |
4437 | 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. |
4438 | F<event.h> that are not directly supported by the libev core alone. |
3850 | |
4439 | |
3851 | In standalone mode, libev will still try to automatically deduce the |
4440 | In standalone mode, libev will still try to automatically deduce the |
3852 | configuration, but has to be more conservative. |
4441 | configuration, but has to be more conservative. |
|
|
4442 | |
|
|
4443 | =item EV_USE_FLOOR |
|
|
4444 | |
|
|
4445 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4446 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4447 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4448 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4449 | function is not available will fail, so the safe default is to not enable |
|
|
4450 | this. |
3853 | |
4451 | |
3854 | =item EV_USE_MONOTONIC |
4452 | =item EV_USE_MONOTONIC |
3855 | |
4453 | |
3856 | If defined to be C<1>, libev will try to detect the availability of the |
4454 | 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 |
4455 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3987 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4585 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3988 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4586 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3989 | be detected at runtime. If undefined, it will be enabled if the headers |
4587 | be detected at runtime. If undefined, it will be enabled if the headers |
3990 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4588 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3991 | |
4589 | |
|
|
4590 | =item EV_NO_SMP |
|
|
4591 | |
|
|
4592 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4593 | between threads, that is, threads can be used, but threads never run on |
|
|
4594 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4595 | and makes libev faster. |
|
|
4596 | |
|
|
4597 | =item EV_NO_THREADS |
|
|
4598 | |
|
|
4599 | If defined to be C<1>, libev will assume that it will never be called |
|
|
4600 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
|
|
4601 | above. This reduces dependencies and makes libev faster. |
|
|
4602 | |
3992 | =item EV_ATOMIC_T |
4603 | =item EV_ATOMIC_T |
3993 | |
4604 | |
3994 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4605 | 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 |
4606 | 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 |
4607 | 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" |
4608 | 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. |
4609 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4610 | in C<ev_async> watchers. |
3999 | |
4611 | |
4000 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4612 | 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. |
4613 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4614 | although strictly speaking using a type that also implies a memory fence |
|
|
4615 | is required. |
4002 | |
4616 | |
4003 | =item EV_H (h) |
4617 | =item EV_H (h) |
4004 | |
4618 | |
4005 | The name of the F<ev.h> header file used to include it. The default if |
4619 | 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 |
4620 | 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 |
4644 | 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 |
4645 | additional independent event loops. Otherwise there will be no support |
4032 | for multiple event loops and there is no first event loop pointer |
4646 | for multiple event loops and there is no first event loop pointer |
4033 | argument. Instead, all functions act on the single default loop. |
4647 | argument. Instead, all functions act on the single default loop. |
4034 | |
4648 | |
|
|
4649 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4650 | default loop when multiplicity is switched off - you always have to |
|
|
4651 | initialise the loop manually in this case. |
|
|
4652 | |
4035 | =item EV_MINPRI |
4653 | =item EV_MINPRI |
4036 | |
4654 | |
4037 | =item EV_MAXPRI |
4655 | =item EV_MAXPRI |
4038 | |
4656 | |
4039 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4657 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4075 | #define EV_USE_POLL 1 |
4693 | #define EV_USE_POLL 1 |
4076 | #define EV_CHILD_ENABLE 1 |
4694 | #define EV_CHILD_ENABLE 1 |
4077 | #define EV_ASYNC_ENABLE 1 |
4695 | #define EV_ASYNC_ENABLE 1 |
4078 | |
4696 | |
4079 | The actual value is a bitset, it can be a combination of the following |
4697 | The actual value is a bitset, it can be a combination of the following |
4080 | values: |
4698 | values (by default, all of these are enabled): |
4081 | |
4699 | |
4082 | =over 4 |
4700 | =over 4 |
4083 | |
4701 | |
4084 | =item C<1> - faster/larger code |
4702 | =item C<1> - faster/larger code |
4085 | |
4703 | |
… | |
… | |
4089 | code size by roughly 30% on amd64). |
4707 | code size by roughly 30% on amd64). |
4090 | |
4708 | |
4091 | When optimising for size, use of compiler flags such as C<-Os> with |
4709 | When optimising for size, use of compiler flags such as C<-Os> with |
4092 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4710 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4093 | assertions. |
4711 | assertions. |
|
|
4712 | |
|
|
4713 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4714 | (e.g. gcc with C<-Os>). |
4094 | |
4715 | |
4095 | =item C<2> - faster/larger data structures |
4716 | =item C<2> - faster/larger data structures |
4096 | |
4717 | |
4097 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4718 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4098 | hash table sizes and so on. This will usually further increase code size |
4719 | hash table sizes and so on. This will usually further increase code size |
4099 | and can additionally have an effect on the size of data structures at |
4720 | and can additionally have an effect on the size of data structures at |
4100 | runtime. |
4721 | runtime. |
4101 | |
4722 | |
|
|
4723 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4724 | (e.g. gcc with C<-Os>). |
|
|
4725 | |
4102 | =item C<4> - full API configuration |
4726 | =item C<4> - full API configuration |
4103 | |
4727 | |
4104 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4728 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4105 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4729 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4106 | |
4730 | |
… | |
… | |
4136 | |
4760 | |
4137 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4761 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4138 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4762 | 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 |
4763 | 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. |
4764 | I/O watcher then might come out at only 5Kb. |
|
|
4765 | |
|
|
4766 | =item EV_API_STATIC |
|
|
4767 | |
|
|
4768 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4769 | will have static linkage. This means that libev will not export any |
|
|
4770 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4771 | when you embed libev, only want to use libev functions in a single file, |
|
|
4772 | and do not want its identifiers to be visible. |
|
|
4773 | |
|
|
4774 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4775 | wants to use libev. |
|
|
4776 | |
|
|
4777 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4778 | doesn't support the required declaration syntax. |
4141 | |
4779 | |
4142 | =item EV_AVOID_STDIO |
4780 | =item EV_AVOID_STDIO |
4143 | |
4781 | |
4144 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4782 | 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 |
4783 | 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: |
4927 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4290 | |
4928 | |
4291 | #include "ev_cpp.h" |
4929 | #include "ev_cpp.h" |
4292 | #include "ev.c" |
4930 | #include "ev.c" |
4293 | |
4931 | |
4294 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4932 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4295 | |
4933 | |
4296 | =head2 THREADS AND COROUTINES |
4934 | =head2 THREADS AND COROUTINES |
4297 | |
4935 | |
4298 | =head3 THREADS |
4936 | =head3 THREADS |
4299 | |
4937 | |
… | |
… | |
4350 | default loop and triggering an C<ev_async> watcher from the default loop |
4988 | default loop and triggering an C<ev_async> watcher from the default loop |
4351 | watcher callback into the event loop interested in the signal. |
4989 | watcher callback into the event loop interested in the signal. |
4352 | |
4990 | |
4353 | =back |
4991 | =back |
4354 | |
4992 | |
4355 | =head4 THREAD LOCKING EXAMPLE |
4993 | 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 | |
4994 | |
4493 | =head3 COROUTINES |
4995 | =head3 COROUTINES |
4494 | |
4996 | |
4495 | Libev is very accommodating to coroutines ("cooperative threads"): |
4997 | Libev is very accommodating to coroutines ("cooperative threads"): |
4496 | libev fully supports nesting calls to its functions from different |
4998 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4661 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5163 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4662 | model. Libev still offers limited functionality on this platform in |
5164 | model. Libev still offers limited functionality on this platform in |
4663 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5165 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4664 | descriptors. This only applies when using Win32 natively, not when using |
5166 | descriptors. This only applies when using Win32 natively, not when using |
4665 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5167 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4666 | as every compielr comes with a slightly differently broken/incompatible |
5168 | as every compiler comes with a slightly differently broken/incompatible |
4667 | environment. |
5169 | environment. |
4668 | |
5170 | |
4669 | Lifting these limitations would basically require the full |
5171 | Lifting these limitations would basically require the full |
4670 | re-implementation of the I/O system. If you are into this kind of thing, |
5172 | 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 |
5173 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4804 | |
5306 | |
4805 | The type C<double> is used to represent timestamps. It is required to |
5307 | 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 |
5308 | 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 |
5309 | good enough for at least into the year 4000 with millisecond accuracy |
4808 | (the design goal for libev). This requirement is overfulfilled by |
5310 | (the design goal for libev). This requirement is overfulfilled by |
4809 | implementations using IEEE 754, which is basically all existing ones. With |
5311 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5312 | |
4810 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5313 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5314 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5315 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5316 | something like that, just kidding). |
4811 | |
5317 | |
4812 | =back |
5318 | =back |
4813 | |
5319 | |
4814 | If you know of other additional requirements drop me a note. |
5320 | If you know of other additional requirements drop me a note. |
4815 | |
5321 | |
… | |
… | |
4877 | =item Processing ev_async_send: O(number_of_async_watchers) |
5383 | =item Processing ev_async_send: O(number_of_async_watchers) |
4878 | |
5384 | |
4879 | =item Processing signals: O(max_signal_number) |
5385 | =item Processing signals: O(max_signal_number) |
4880 | |
5386 | |
4881 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5387 | 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 |
5388 | calls in the current loop iteration and the loop is currently |
|
|
5389 | blocked. Checking for async and signal events involves iterating over all |
4883 | involves iterating over all running async watchers or all signal numbers. |
5390 | running async watchers or all signal numbers. |
4884 | |
5391 | |
4885 | =back |
5392 | =back |
4886 | |
5393 | |
4887 | |
5394 | |
4888 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5395 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
5005 | The physical time that is observed. It is apparently strictly monotonic :) |
5512 | The physical time that is observed. It is apparently strictly monotonic :) |
5006 | |
5513 | |
5007 | =item wall-clock time |
5514 | =item wall-clock time |
5008 | |
5515 | |
5009 | The time and date as shown on clocks. Unlike real time, it can actually |
5516 | 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 |
5517 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5011 | clock. |
5518 | clock. |
5012 | |
5519 | |
5013 | =item watcher |
5520 | =item watcher |
5014 | |
5521 | |
5015 | A data structure that describes interest in certain events. Watchers need |
5522 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5018 | =back |
5525 | =back |
5019 | |
5526 | |
5020 | =head1 AUTHOR |
5527 | =head1 AUTHOR |
5021 | |
5528 | |
5022 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5529 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5023 | Magnusson and Emanuele Giaquinta. |
5530 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5024 | |
5531 | |