… | |
… | |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
215 | recommended ones. |
215 | recommended ones. |
216 | |
216 | |
217 | See the description of C<ev_embed> watchers for more info. |
217 | See the description of C<ev_embed> watchers for more info. |
218 | |
218 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
220 | |
220 | |
221 | Sets the allocation function to use (the prototype is similar - the |
221 | Sets the allocation function to use (the prototype is similar - the |
222 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
222 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
223 | used to allocate and free memory (no surprises here). If it returns zero |
223 | used to allocate and free memory (no surprises here). If it returns zero |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
250 | } |
250 | } |
251 | |
251 | |
252 | ... |
252 | ... |
253 | ev_set_allocator (persistent_realloc); |
253 | ev_set_allocator (persistent_realloc); |
254 | |
254 | |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
256 | |
256 | |
257 | Set the callback function to call on a retryable system call error (such |
257 | Set the callback function to call on a retryable system call error (such |
258 | as failed select, poll, epoll_wait). The message is a printable string |
258 | as failed select, poll, epoll_wait). The message is a printable string |
259 | indicating the system call or subsystem causing the problem. If this |
259 | indicating the system call or subsystem causing the problem. If this |
260 | callback is set, then libev will expect it to remedy the situation, no |
260 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
359 | writing a server, you should C<accept ()> in a loop to accept as many |
359 | writing a server, you should C<accept ()> in a loop to accept as many |
360 | connections as possible during one iteration. You might also want to have |
360 | connections as possible during one iteration. You might also want to have |
361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
362 | readiness notifications you get per iteration. |
362 | readiness notifications you get per iteration. |
363 | |
363 | |
|
|
364 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
|
|
365 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
|
|
366 | C<exceptfds> set on that platform). |
|
|
367 | |
364 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
368 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
365 | |
369 | |
366 | And this is your standard poll(2) backend. It's more complicated |
370 | And this is your standard poll(2) backend. It's more complicated |
367 | than select, but handles sparse fds better and has no artificial |
371 | than select, but handles sparse fds better and has no artificial |
368 | limit on the number of fds you can use (except it will slow down |
372 | limit on the number of fds you can use (except it will slow down |
369 | considerably with a lot of inactive fds). It scales similarly to select, |
373 | considerably with a lot of inactive fds). It scales similarly to select, |
370 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
374 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
371 | performance tips. |
375 | performance tips. |
|
|
376 | |
|
|
377 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
|
|
378 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
372 | |
379 | |
373 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
380 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
374 | |
381 | |
375 | For few fds, this backend is a bit little slower than poll and select, |
382 | For few fds, this backend is a bit little slower than poll and select, |
376 | but it scales phenomenally better. While poll and select usually scale |
383 | but it scales phenomenally better. While poll and select usually scale |
… | |
… | |
389 | Please note that epoll sometimes generates spurious notifications, so you |
396 | Please note that epoll sometimes generates spurious notifications, so you |
390 | need to use non-blocking I/O or other means to avoid blocking when no data |
397 | need to use non-blocking I/O or other means to avoid blocking when no data |
391 | (or space) is available. |
398 | (or space) is available. |
392 | |
399 | |
393 | Best performance from this backend is achieved by not unregistering all |
400 | Best performance from this backend is achieved by not unregistering all |
394 | watchers for a file descriptor until it has been closed, if possible, i.e. |
401 | watchers for a file descriptor until it has been closed, if possible, |
395 | keep at least one watcher active per fd at all times. |
402 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
403 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
404 | extra overhead. |
396 | |
405 | |
397 | While nominally embeddable in other event loops, this feature is broken in |
406 | While nominally embeddable in other event loops, this feature is broken in |
398 | all kernel versions tested so far. |
407 | all kernel versions tested so far. |
399 | |
408 | |
|
|
409 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
410 | C<EVBACKEND_POLL>. |
|
|
411 | |
400 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
412 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
401 | |
413 | |
402 | Kqueue deserves special mention, as at the time of this writing, it |
414 | Kqueue deserves special mention, as at the time of this writing, it was |
403 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
415 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
404 | with anything but sockets and pipes, except on Darwin, where of course |
416 | anything but sockets and pipes, except on Darwin, where of course it's |
405 | it's completely useless). For this reason it's not being "auto-detected" |
417 | completely useless). For this reason it's not being "auto-detected" unless |
406 | unless you explicitly specify it explicitly in the flags (i.e. using |
418 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
407 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
419 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
408 | system like NetBSD. |
|
|
409 | |
420 | |
410 | You still can embed kqueue into a normal poll or select backend and use it |
421 | You still can embed kqueue into a normal poll or select backend and use it |
411 | only for sockets (after having made sure that sockets work with kqueue on |
422 | only for sockets (after having made sure that sockets work with kqueue on |
412 | the target platform). See C<ev_embed> watchers for more info. |
423 | the target platform). See C<ev_embed> watchers for more info. |
413 | |
424 | |
414 | It scales in the same way as the epoll backend, but the interface to the |
425 | It scales in the same way as the epoll backend, but the interface to the |
415 | kernel is more efficient (which says nothing about its actual speed, of |
426 | kernel is more efficient (which says nothing about its actual speed, of |
416 | course). While stopping, setting and starting an I/O watcher does never |
427 | course). While stopping, setting and starting an I/O watcher does never |
417 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
428 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
418 | two event changes per incident, support for C<fork ()> is very bad and it |
429 | two event changes per incident. Support for C<fork ()> is very bad and it |
419 | drops fds silently in similarly hard-to-detect cases. |
430 | drops fds silently in similarly hard-to-detect cases. |
420 | |
431 | |
421 | This backend usually performs well under most conditions. |
432 | This backend usually performs well under most conditions. |
422 | |
433 | |
423 | While nominally embeddable in other event loops, this doesn't work |
434 | While nominally embeddable in other event loops, this doesn't work |
424 | everywhere, so you might need to test for this. And since it is broken |
435 | everywhere, so you might need to test for this. And since it is broken |
425 | almost everywhere, you should only use it when you have a lot of sockets |
436 | almost everywhere, you should only use it when you have a lot of sockets |
426 | (for which it usually works), by embedding it into another event loop |
437 | (for which it usually works), by embedding it into another event loop |
427 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
438 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
428 | sockets. |
439 | using it only for sockets. |
|
|
440 | |
|
|
441 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
442 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
443 | C<NOTE_EOF>. |
429 | |
444 | |
430 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
445 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
431 | |
446 | |
432 | This is not implemented yet (and might never be, unless you send me an |
447 | This is not implemented yet (and might never be, unless you send me an |
433 | implementation). According to reports, C</dev/poll> only supports sockets |
448 | implementation). According to reports, C</dev/poll> only supports sockets |
… | |
… | |
446 | While this backend scales well, it requires one system call per active |
461 | While this backend scales well, it requires one system call per active |
447 | file descriptor per loop iteration. For small and medium numbers of file |
462 | file descriptor per loop iteration. For small and medium numbers of file |
448 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
463 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
449 | might perform better. |
464 | might perform better. |
450 | |
465 | |
451 | On the positive side, ignoring the spurious readiness notifications, this |
466 | On the positive side, with the exception of the spurious readiness |
452 | backend actually performed to specification in all tests and is fully |
467 | notifications, this backend actually performed fully to specification |
453 | embeddable, which is a rare feat among the OS-specific backends. |
468 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
469 | OS-specific backends. |
|
|
470 | |
|
|
471 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
472 | C<EVBACKEND_POLL>. |
454 | |
473 | |
455 | =item C<EVBACKEND_ALL> |
474 | =item C<EVBACKEND_ALL> |
456 | |
475 | |
457 | Try all backends (even potentially broken ones that wouldn't be tried |
476 | Try all backends (even potentially broken ones that wouldn't be tried |
458 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
477 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
… | |
… | |
464 | |
483 | |
465 | If one or more of these are or'ed into the flags value, then only these |
484 | If one or more of these are or'ed into the flags value, then only these |
466 | backends will be tried (in the reverse order as listed here). If none are |
485 | backends will be tried (in the reverse order as listed here). If none are |
467 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
486 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
468 | |
487 | |
469 | The most typical usage is like this: |
488 | Example: This is the most typical usage. |
470 | |
489 | |
471 | if (!ev_default_loop (0)) |
490 | if (!ev_default_loop (0)) |
472 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
491 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
473 | |
492 | |
474 | Restrict libev to the select and poll backends, and do not allow |
493 | Example: Restrict libev to the select and poll backends, and do not allow |
475 | environment settings to be taken into account: |
494 | environment settings to be taken into account: |
476 | |
495 | |
477 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
496 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
478 | |
497 | |
479 | Use whatever libev has to offer, but make sure that kqueue is used if |
498 | Example: Use whatever libev has to offer, but make sure that kqueue is |
480 | available (warning, breaks stuff, best use only with your own private |
499 | used if available (warning, breaks stuff, best use only with your own |
481 | event loop and only if you know the OS supports your types of fds): |
500 | private event loop and only if you know the OS supports your types of |
|
|
501 | fds): |
482 | |
502 | |
483 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
503 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
484 | |
504 | |
485 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
505 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
486 | |
506 | |
… | |
… | |
544 | |
564 | |
545 | =item ev_loop_fork (loop) |
565 | =item ev_loop_fork (loop) |
546 | |
566 | |
547 | Like C<ev_default_fork>, but acts on an event loop created by |
567 | Like C<ev_default_fork>, but acts on an event loop created by |
548 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
568 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
549 | after fork, and how you do this is entirely your own problem. |
569 | after fork that you want to re-use in the child, and how you do this is |
|
|
570 | entirely your own problem. |
550 | |
571 | |
551 | =item int ev_is_default_loop (loop) |
572 | =item int ev_is_default_loop (loop) |
552 | |
573 | |
553 | Returns true when the given loop actually is the default loop, false otherwise. |
574 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
575 | otherwise. |
554 | |
576 | |
555 | =item unsigned int ev_loop_count (loop) |
577 | =item unsigned int ev_loop_count (loop) |
556 | |
578 | |
557 | Returns the count of loop iterations for the loop, which is identical to |
579 | Returns the count of loop iterations for the loop, which is identical to |
558 | the number of times libev did poll for new events. It starts at C<0> and |
580 | the number of times libev did poll for new events. It starts at C<0> and |
… | |
… | |
573 | received events and started processing them. This timestamp does not |
595 | received events and started processing them. This timestamp does not |
574 | change as long as callbacks are being processed, and this is also the base |
596 | change as long as callbacks are being processed, and this is also the base |
575 | time used for relative timers. You can treat it as the timestamp of the |
597 | time used for relative timers. You can treat it as the timestamp of the |
576 | event occurring (or more correctly, libev finding out about it). |
598 | event occurring (or more correctly, libev finding out about it). |
577 | |
599 | |
|
|
600 | =item ev_now_update (loop) |
|
|
601 | |
|
|
602 | Establishes the current time by querying the kernel, updating the time |
|
|
603 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
604 | is usually done automatically within C<ev_loop ()>. |
|
|
605 | |
|
|
606 | This function is rarely useful, but when some event callback runs for a |
|
|
607 | very long time without entering the event loop, updating libev's idea of |
|
|
608 | the current time is a good idea. |
|
|
609 | |
|
|
610 | See also "The special problem of time updates" in the C<ev_timer> section. |
|
|
611 | |
578 | =item ev_loop (loop, int flags) |
612 | =item ev_loop (loop, int flags) |
579 | |
613 | |
580 | Finally, this is it, the event handler. This function usually is called |
614 | Finally, this is it, the event handler. This function usually is called |
581 | after you initialised all your watchers and you want to start handling |
615 | after you initialised all your watchers and you want to start handling |
582 | events. |
616 | events. |
… | |
… | |
584 | If the flags argument is specified as C<0>, it will not return until |
618 | If the flags argument is specified as C<0>, it will not return until |
585 | either no event watchers are active anymore or C<ev_unloop> was called. |
619 | either no event watchers are active anymore or C<ev_unloop> was called. |
586 | |
620 | |
587 | Please note that an explicit C<ev_unloop> is usually better than |
621 | Please note that an explicit C<ev_unloop> is usually better than |
588 | relying on all watchers to be stopped when deciding when a program has |
622 | relying on all watchers to be stopped when deciding when a program has |
589 | finished (especially in interactive programs), but having a program that |
623 | finished (especially in interactive programs), but having a program |
590 | automatically loops as long as it has to and no longer by virtue of |
624 | that automatically loops as long as it has to and no longer by virtue |
591 | relying on its watchers stopping correctly is a thing of beauty. |
625 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
626 | beauty. |
592 | |
627 | |
593 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
628 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
594 | those events and any outstanding ones, but will not block your process in |
629 | those events and any already outstanding ones, but will not block your |
595 | case there are no events and will return after one iteration of the loop. |
630 | process in case there are no events and will return after one iteration of |
|
|
631 | the loop. |
596 | |
632 | |
597 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
633 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
598 | necessary) and will handle those and any outstanding ones. It will block |
634 | necessary) and will handle those and any already outstanding ones. It |
599 | your process until at least one new event arrives, and will return after |
635 | will block your process until at least one new event arrives (which could |
600 | one iteration of the loop. This is useful if you are waiting for some |
636 | be an event internal to libev itself, so there is no guarentee that a |
601 | external event in conjunction with something not expressible using other |
637 | user-registered callback will be called), and will return after one |
|
|
638 | iteration of the loop. |
|
|
639 | |
|
|
640 | This is useful if you are waiting for some external event in conjunction |
|
|
641 | with something not expressible using other libev watchers (i.e. "roll your |
602 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
642 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
603 | usually a better approach for this kind of thing. |
643 | usually a better approach for this kind of thing. |
604 | |
644 | |
605 | Here are the gory details of what C<ev_loop> does: |
645 | Here are the gory details of what C<ev_loop> does: |
606 | |
646 | |
607 | - Before the first iteration, call any pending watchers. |
647 | - Before the first iteration, call any pending watchers. |
… | |
… | |
617 | any active watchers at all will result in not sleeping). |
657 | any active watchers at all will result in not sleeping). |
618 | - Sleep if the I/O and timer collect interval say so. |
658 | - Sleep if the I/O and timer collect interval say so. |
619 | - Block the process, waiting for any events. |
659 | - Block the process, waiting for any events. |
620 | - Queue all outstanding I/O (fd) events. |
660 | - Queue all outstanding I/O (fd) events. |
621 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
661 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
622 | - Queue all outstanding timers. |
662 | - Queue all expired timers. |
623 | - Queue all outstanding periodics. |
663 | - Queue all expired periodics. |
624 | - Unless any events are pending now, queue all idle watchers. |
664 | - Unless any events are pending now, queue all idle watchers. |
625 | - Queue all check watchers. |
665 | - Queue all check watchers. |
626 | - Call all queued watchers in reverse order (i.e. check watchers first). |
666 | - Call all queued watchers in reverse order (i.e. check watchers first). |
627 | Signals and child watchers are implemented as I/O watchers, and will |
667 | Signals and child watchers are implemented as I/O watchers, and will |
628 | be handled here by queueing them when their watcher gets executed. |
668 | be handled here by queueing them when their watcher gets executed. |
… | |
… | |
651 | |
691 | |
652 | =item ev_unref (loop) |
692 | =item ev_unref (loop) |
653 | |
693 | |
654 | Ref/unref can be used to add or remove a reference count on the event |
694 | Ref/unref can be used to add or remove a reference count on the event |
655 | loop: Every watcher keeps one reference, and as long as the reference |
695 | loop: Every watcher keeps one reference, and as long as the reference |
656 | count is nonzero, C<ev_loop> will not return on its own. If you have |
696 | count is nonzero, C<ev_loop> will not return on its own. |
|
|
697 | |
657 | a watcher you never unregister that should not keep C<ev_loop> from |
698 | If you have a watcher you never unregister that should not keep C<ev_loop> |
658 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
699 | from returning, call ev_unref() after starting, and ev_ref() before |
|
|
700 | stopping it. |
|
|
701 | |
659 | example, libev itself uses this for its internal signal pipe: It is not |
702 | As an example, libev itself uses this for its internal signal pipe: It is |
660 | visible to the libev user and should not keep C<ev_loop> from exiting if |
703 | not visible to the libev user and should not keep C<ev_loop> from exiting |
661 | no event watchers registered by it are active. It is also an excellent |
704 | if no event watchers registered by it are active. It is also an excellent |
662 | way to do this for generic recurring timers or from within third-party |
705 | way to do this for generic recurring timers or from within third-party |
663 | libraries. Just remember to I<unref after start> and I<ref before stop> |
706 | libraries. Just remember to I<unref after start> and I<ref before stop> |
664 | (but only if the watcher wasn't active before, or was active before, |
707 | (but only if the watcher wasn't active before, or was active before, |
665 | respectively). |
708 | respectively). |
666 | |
709 | |
… | |
… | |
689 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
732 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
690 | allows libev to delay invocation of I/O and timer/periodic callbacks |
733 | allows libev to delay invocation of I/O and timer/periodic callbacks |
691 | to increase efficiency of loop iterations (or to increase power-saving |
734 | to increase efficiency of loop iterations (or to increase power-saving |
692 | opportunities). |
735 | opportunities). |
693 | |
736 | |
694 | The background is that sometimes your program runs just fast enough to |
737 | The idea is that sometimes your program runs just fast enough to handle |
695 | handle one (or very few) event(s) per loop iteration. While this makes |
738 | one (or very few) event(s) per loop iteration. While this makes the |
696 | the program responsive, it also wastes a lot of CPU time to poll for new |
739 | program responsive, it also wastes a lot of CPU time to poll for new |
697 | events, especially with backends like C<select ()> which have a high |
740 | events, especially with backends like C<select ()> which have a high |
698 | overhead for the actual polling but can deliver many events at once. |
741 | overhead for the actual polling but can deliver many events at once. |
699 | |
742 | |
700 | By setting a higher I<io collect interval> you allow libev to spend more |
743 | By setting a higher I<io collect interval> you allow libev to spend more |
701 | time collecting I/O events, so you can handle more events per iteration, |
744 | time collecting I/O events, so you can handle more events per iteration, |
… | |
… | |
703 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
746 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
704 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
747 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
705 | |
748 | |
706 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
749 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
707 | to spend more time collecting timeouts, at the expense of increased |
750 | to spend more time collecting timeouts, at the expense of increased |
708 | latency (the watcher callback will be called later). C<ev_io> watchers |
751 | latency/jitter/inexactness (the watcher callback will be called |
709 | will not be affected. Setting this to a non-null value will not introduce |
752 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
710 | any overhead in libev. |
753 | value will not introduce any overhead in libev. |
711 | |
754 | |
712 | Many (busy) programs can usually benefit by setting the I/O collect |
755 | Many (busy) programs can usually benefit by setting the I/O collect |
713 | interval to a value near C<0.1> or so, which is often enough for |
756 | interval to a value near C<0.1> or so, which is often enough for |
714 | interactive servers (of course not for games), likewise for timeouts. It |
757 | interactive servers (of course not for games), likewise for timeouts. It |
715 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
758 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
… | |
… | |
723 | they fire on, say, one-second boundaries only. |
766 | they fire on, say, one-second boundaries only. |
724 | |
767 | |
725 | =item ev_loop_verify (loop) |
768 | =item ev_loop_verify (loop) |
726 | |
769 | |
727 | This function only does something when C<EV_VERIFY> support has been |
770 | This function only does something when C<EV_VERIFY> support has been |
728 | compiled in. It tries to go through all internal structures and checks |
771 | compiled in. which is the default for non-minimal builds. It tries to go |
729 | them for validity. If anything is found to be inconsistent, it will print |
772 | through all internal structures and checks them for validity. If anything |
730 | an error message to standard error and call C<abort ()>. |
773 | is found to be inconsistent, it will print an error message to standard |
|
|
774 | error and call C<abort ()>. |
731 | |
775 | |
732 | This can be used to catch bugs inside libev itself: under normal |
776 | This can be used to catch bugs inside libev itself: under normal |
733 | circumstances, this function will never abort as of course libev keeps its |
777 | circumstances, this function will never abort as of course libev keeps its |
734 | data structures consistent. |
778 | data structures consistent. |
735 | |
779 | |
… | |
… | |
851 | happen because the watcher could not be properly started because libev |
895 | happen because the watcher could not be properly started because libev |
852 | ran out of memory, a file descriptor was found to be closed or any other |
896 | ran out of memory, a file descriptor was found to be closed or any other |
853 | problem. You best act on it by reporting the problem and somehow coping |
897 | problem. You best act on it by reporting the problem and somehow coping |
854 | with the watcher being stopped. |
898 | with the watcher being stopped. |
855 | |
899 | |
856 | Libev will usually signal a few "dummy" events together with an error, |
900 | Libev will usually signal a few "dummy" events together with an error, for |
857 | for example it might indicate that a fd is readable or writable, and if |
901 | example it might indicate that a fd is readable or writable, and if your |
858 | your callbacks is well-written it can just attempt the operation and cope |
902 | callbacks is well-written it can just attempt the operation and cope with |
859 | with the error from read() or write(). This will not work in multi-threaded |
903 | the error from read() or write(). This will not work in multi-threaded |
860 | programs, though, so beware. |
904 | programs, though, as the fd could already be closed and reused for another |
|
|
905 | thing, so beware. |
861 | |
906 | |
862 | =back |
907 | =back |
863 | |
908 | |
864 | =head2 GENERIC WATCHER FUNCTIONS |
909 | =head2 GENERIC WATCHER FUNCTIONS |
865 | |
910 | |
… | |
… | |
881 | (or never started) and there are no pending events outstanding. |
926 | (or never started) and there are no pending events outstanding. |
882 | |
927 | |
883 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
928 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
884 | int revents)>. |
929 | int revents)>. |
885 | |
930 | |
|
|
931 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
932 | |
|
|
933 | ev_io w; |
|
|
934 | ev_init (&w, my_cb); |
|
|
935 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
936 | |
886 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
937 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
887 | |
938 | |
888 | This macro initialises the type-specific parts of a watcher. You need to |
939 | This macro initialises the type-specific parts of a watcher. You need to |
889 | call C<ev_init> at least once before you call this macro, but you can |
940 | call C<ev_init> at least once before you call this macro, but you can |
890 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
941 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
… | |
… | |
892 | difference to the C<ev_init> macro). |
943 | difference to the C<ev_init> macro). |
893 | |
944 | |
894 | Although some watcher types do not have type-specific arguments |
945 | Although some watcher types do not have type-specific arguments |
895 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
946 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
896 | |
947 | |
|
|
948 | See C<ev_init>, above, for an example. |
|
|
949 | |
897 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
950 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
898 | |
951 | |
899 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
952 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
900 | calls into a single call. This is the most convenient method to initialise |
953 | calls into a single call. This is the most convenient method to initialise |
901 | a watcher. The same limitations apply, of course. |
954 | a watcher. The same limitations apply, of course. |
902 | |
955 | |
|
|
956 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
957 | |
|
|
958 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
959 | |
903 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
960 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
904 | |
961 | |
905 | Starts (activates) the given watcher. Only active watchers will receive |
962 | Starts (activates) the given watcher. Only active watchers will receive |
906 | events. If the watcher is already active nothing will happen. |
963 | events. If the watcher is already active nothing will happen. |
|
|
964 | |
|
|
965 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
966 | whole section. |
|
|
967 | |
|
|
968 | ev_io_start (EV_DEFAULT_UC, &w); |
907 | |
969 | |
908 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
970 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
909 | |
971 | |
910 | Stops the given watcher again (if active) and clears the pending |
972 | Stops the given watcher again (if active) and clears the pending |
911 | status. It is possible that stopped watchers are pending (for example, |
973 | status. It is possible that stopped watchers are pending (for example, |
… | |
… | |
968 | |
1030 | |
969 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1031 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
970 | |
1032 | |
971 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1033 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
972 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1034 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
973 | can deal with that fact. |
1035 | can deal with that fact, as both are simply passed through to the |
|
|
1036 | callback. |
974 | |
1037 | |
975 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1038 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
976 | |
1039 | |
977 | If the watcher is pending, this function returns clears its pending status |
1040 | If the watcher is pending, this function clears its pending status and |
978 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1041 | returns its C<revents> bitset (as if its callback was invoked). If the |
979 | watcher isn't pending it does nothing and returns C<0>. |
1042 | watcher isn't pending it does nothing and returns C<0>. |
980 | |
1043 | |
|
|
1044 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1045 | callback to be invoked, which can be accomplished with this function. |
|
|
1046 | |
981 | =back |
1047 | =back |
982 | |
1048 | |
983 | |
1049 | |
984 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1050 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
985 | |
1051 | |
986 | Each watcher has, by default, a member C<void *data> that you can change |
1052 | Each watcher has, by default, a member C<void *data> that you can change |
987 | and read at any time, libev will completely ignore it. This can be used |
1053 | and read at any time: libev will completely ignore it. This can be used |
988 | to associate arbitrary data with your watcher. If you need more data and |
1054 | to associate arbitrary data with your watcher. If you need more data and |
989 | don't want to allocate memory and store a pointer to it in that data |
1055 | don't want to allocate memory and store a pointer to it in that data |
990 | member, you can also "subclass" the watcher type and provide your own |
1056 | member, you can also "subclass" the watcher type and provide your own |
991 | data: |
1057 | data: |
992 | |
1058 | |
… | |
… | |
994 | { |
1060 | { |
995 | struct ev_io io; |
1061 | struct ev_io io; |
996 | int otherfd; |
1062 | int otherfd; |
997 | void *somedata; |
1063 | void *somedata; |
998 | struct whatever *mostinteresting; |
1064 | struct whatever *mostinteresting; |
999 | } |
1065 | }; |
|
|
1066 | |
|
|
1067 | ... |
|
|
1068 | struct my_io w; |
|
|
1069 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1000 | |
1070 | |
1001 | And since your callback will be called with a pointer to the watcher, you |
1071 | And since your callback will be called with a pointer to the watcher, you |
1002 | can cast it back to your own type: |
1072 | can cast it back to your own type: |
1003 | |
1073 | |
1004 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1074 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
… | |
… | |
1008 | } |
1078 | } |
1009 | |
1079 | |
1010 | More interesting and less C-conformant ways of casting your callback type |
1080 | More interesting and less C-conformant ways of casting your callback type |
1011 | instead have been omitted. |
1081 | instead have been omitted. |
1012 | |
1082 | |
1013 | Another common scenario is having some data structure with multiple |
1083 | Another common scenario is to use some data structure with multiple |
1014 | watchers: |
1084 | embedded watchers: |
1015 | |
1085 | |
1016 | struct my_biggy |
1086 | struct my_biggy |
1017 | { |
1087 | { |
1018 | int some_data; |
1088 | int some_data; |
1019 | ev_timer t1; |
1089 | ev_timer t1; |
1020 | ev_timer t2; |
1090 | ev_timer t2; |
1021 | } |
1091 | } |
1022 | |
1092 | |
1023 | In this case getting the pointer to C<my_biggy> is a bit more complicated, |
1093 | In this case getting the pointer to C<my_biggy> is a bit more |
1024 | you need to use C<offsetof>: |
1094 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1095 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1096 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1097 | programmers): |
1025 | |
1098 | |
1026 | #include <stddef.h> |
1099 | #include <stddef.h> |
1027 | |
1100 | |
1028 | static void |
1101 | static void |
1029 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1102 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
… | |
… | |
1069 | In general you can register as many read and/or write event watchers per |
1142 | In general you can register as many read and/or write event watchers per |
1070 | fd as you want (as long as you don't confuse yourself). Setting all file |
1143 | fd as you want (as long as you don't confuse yourself). Setting all file |
1071 | descriptors to non-blocking mode is also usually a good idea (but not |
1144 | descriptors to non-blocking mode is also usually a good idea (but not |
1072 | required if you know what you are doing). |
1145 | required if you know what you are doing). |
1073 | |
1146 | |
1074 | If you must do this, then force the use of a known-to-be-good backend |
1147 | If you cannot use non-blocking mode, then force the use of a |
1075 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1148 | known-to-be-good backend (at the time of this writing, this includes only |
1076 | C<EVBACKEND_POLL>). |
1149 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1077 | |
1150 | |
1078 | Another thing you have to watch out for is that it is quite easy to |
1151 | Another thing you have to watch out for is that it is quite easy to |
1079 | receive "spurious" readiness notifications, that is your callback might |
1152 | receive "spurious" readiness notifications, that is your callback might |
1080 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1153 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1081 | because there is no data. Not only are some backends known to create a |
1154 | because there is no data. Not only are some backends known to create a |
1082 | lot of those (for example Solaris ports), it is very easy to get into |
1155 | lot of those (for example Solaris ports), it is very easy to get into |
1083 | this situation even with a relatively standard program structure. Thus |
1156 | this situation even with a relatively standard program structure. Thus |
1084 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1157 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1085 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1158 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1086 | |
1159 | |
1087 | If you cannot run the fd in non-blocking mode (for example you should not |
1160 | If you cannot run the fd in non-blocking mode (for example you should |
1088 | play around with an Xlib connection), then you have to separately re-test |
1161 | not play around with an Xlib connection), then you have to separately |
1089 | whether a file descriptor is really ready with a known-to-be good interface |
1162 | re-test whether a file descriptor is really ready with a known-to-be good |
1090 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1163 | interface such as poll (fortunately in our Xlib example, Xlib already |
1091 | its own, so its quite safe to use). |
1164 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1165 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1166 | indefinitely. |
|
|
1167 | |
|
|
1168 | But really, best use non-blocking mode. |
1092 | |
1169 | |
1093 | =head3 The special problem of disappearing file descriptors |
1170 | =head3 The special problem of disappearing file descriptors |
1094 | |
1171 | |
1095 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1172 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1096 | descriptor (either by calling C<close> explicitly or by any other means, |
1173 | descriptor (either due to calling C<close> explicitly or any other means, |
1097 | such as C<dup>). The reason is that you register interest in some file |
1174 | such as C<dup2>). The reason is that you register interest in some file |
1098 | descriptor, but when it goes away, the operating system will silently drop |
1175 | descriptor, but when it goes away, the operating system will silently drop |
1099 | this interest. If another file descriptor with the same number then is |
1176 | this interest. If another file descriptor with the same number then is |
1100 | registered with libev, there is no efficient way to see that this is, in |
1177 | registered with libev, there is no efficient way to see that this is, in |
1101 | fact, a different file descriptor. |
1178 | fact, a different file descriptor. |
1102 | |
1179 | |
… | |
… | |
1133 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1210 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1134 | C<EVBACKEND_POLL>. |
1211 | C<EVBACKEND_POLL>. |
1135 | |
1212 | |
1136 | =head3 The special problem of SIGPIPE |
1213 | =head3 The special problem of SIGPIPE |
1137 | |
1214 | |
1138 | While not really specific to libev, it is easy to forget about SIGPIPE: |
1215 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1139 | when writing to a pipe whose other end has been closed, your program gets |
1216 | when writing to a pipe whose other end has been closed, your program gets |
1140 | send a SIGPIPE, which, by default, aborts your program. For most programs |
1217 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
1141 | this is sensible behaviour, for daemons, this is usually undesirable. |
1218 | this is sensible behaviour, for daemons, this is usually undesirable. |
1142 | |
1219 | |
1143 | So when you encounter spurious, unexplained daemon exits, make sure you |
1220 | So when you encounter spurious, unexplained daemon exits, make sure you |
1144 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1221 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1145 | somewhere, as that would have given you a big clue). |
1222 | somewhere, as that would have given you a big clue). |
… | |
… | |
1152 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1229 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1153 | |
1230 | |
1154 | =item ev_io_set (ev_io *, int fd, int events) |
1231 | =item ev_io_set (ev_io *, int fd, int events) |
1155 | |
1232 | |
1156 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1233 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1157 | receive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1234 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1158 | C<EV_READ | EV_WRITE> to receive the given events. |
1235 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1159 | |
1236 | |
1160 | =item int fd [read-only] |
1237 | =item int fd [read-only] |
1161 | |
1238 | |
1162 | The file descriptor being watched. |
1239 | The file descriptor being watched. |
1163 | |
1240 | |
… | |
… | |
1175 | |
1252 | |
1176 | static void |
1253 | static void |
1177 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1254 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1178 | { |
1255 | { |
1179 | ev_io_stop (loop, w); |
1256 | ev_io_stop (loop, w); |
1180 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1257 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1181 | } |
1258 | } |
1182 | |
1259 | |
1183 | ... |
1260 | ... |
1184 | struct ev_loop *loop = ev_default_init (0); |
1261 | struct ev_loop *loop = ev_default_init (0); |
1185 | struct ev_io stdin_readable; |
1262 | struct ev_io stdin_readable; |
… | |
… | |
1193 | Timer watchers are simple relative timers that generate an event after a |
1270 | Timer watchers are simple relative timers that generate an event after a |
1194 | given time, and optionally repeating in regular intervals after that. |
1271 | given time, and optionally repeating in regular intervals after that. |
1195 | |
1272 | |
1196 | The timers are based on real time, that is, if you register an event that |
1273 | The timers are based on real time, that is, if you register an event that |
1197 | times out after an hour and you reset your system clock to January last |
1274 | times out after an hour and you reset your system clock to January last |
1198 | year, it will still time out after (roughly) and hour. "Roughly" because |
1275 | year, it will still time out after (roughly) one hour. "Roughly" because |
1199 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1276 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1200 | monotonic clock option helps a lot here). |
1277 | monotonic clock option helps a lot here). |
1201 | |
1278 | |
1202 | The callback is guaranteed to be invoked only after its timeout has passed, |
1279 | The callback is guaranteed to be invoked only I<after> its timeout has |
1203 | but if multiple timers become ready during the same loop iteration then |
1280 | passed, but if multiple timers become ready during the same loop iteration |
1204 | order of execution is undefined. |
1281 | then order of execution is undefined. |
1205 | |
1282 | |
1206 | =head3 The special problem of time updates |
1283 | =head3 The special problem of time updates |
1207 | |
1284 | |
1208 | Requesting the current time is a costly operation (it usually takes at |
1285 | Establishing the current time is a costly operation (it usually takes at |
1209 | least two syscalls): EV therefore updates it's idea of the current time |
1286 | least two system calls): EV therefore updates its idea of the current |
1210 | only before and after C<ev_loop> polls for new events, which causes the |
1287 | time only before and after C<ev_loop> collects new events, which causes a |
1211 | difference between C<ev_now ()> and C<ev_time ()>. |
1288 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
1289 | lots of events in one iteration. |
1212 | |
1290 | |
1213 | The relative timeouts are calculated relative to the C<ev_now ()> |
1291 | The relative timeouts are calculated relative to the C<ev_now ()> |
1214 | time. This is usually the right thing as this timestamp refers to the time |
1292 | time. This is usually the right thing as this timestamp refers to the time |
1215 | of the event triggering whatever timeout you are modifying/starting. If |
1293 | of the event triggering whatever timeout you are modifying/starting. If |
1216 | you suspect event processing to be delayed and you I<need> to base the |
1294 | you suspect event processing to be delayed and you I<need> to base the |
1217 | timeout on the current time, use something like this to adjust for this: |
1295 | timeout on the current time, use something like this to adjust for this: |
1218 | |
1296 | |
1219 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1297 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
|
|
1298 | |
|
|
1299 | If the event loop is suspended for a long time, you can also force an |
|
|
1300 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
|
|
1301 | ()>. |
1220 | |
1302 | |
1221 | =head3 Watcher-Specific Functions and Data Members |
1303 | =head3 Watcher-Specific Functions and Data Members |
1222 | |
1304 | |
1223 | =over 4 |
1305 | =over 4 |
1224 | |
1306 | |
… | |
… | |
1273 | ev_timer_again (loop, timer); |
1355 | ev_timer_again (loop, timer); |
1274 | |
1356 | |
1275 | This is more slightly efficient then stopping/starting the timer each time |
1357 | This is more slightly efficient then stopping/starting the timer each time |
1276 | you want to modify its timeout value. |
1358 | you want to modify its timeout value. |
1277 | |
1359 | |
|
|
1360 | Note, however, that it is often even more efficient to remember the |
|
|
1361 | time of the last activity and let the timer time-out naturally. In the |
|
|
1362 | callback, you then check whether the time-out is real, or, if there was |
|
|
1363 | some activity, you reschedule the watcher to time-out in "last_activity + |
|
|
1364 | timeout - ev_now ()" seconds. |
|
|
1365 | |
1278 | =item ev_tstamp repeat [read-write] |
1366 | =item ev_tstamp repeat [read-write] |
1279 | |
1367 | |
1280 | The current C<repeat> value. Will be used each time the watcher times out |
1368 | The current C<repeat> value. Will be used each time the watcher times out |
1281 | or C<ev_timer_again> is called and determines the next timeout (if any), |
1369 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1282 | which is also when any modifications are taken into account. |
1370 | which is also when any modifications are taken into account. |
1283 | |
1371 | |
1284 | =back |
1372 | =back |
1285 | |
1373 | |
1286 | =head3 Examples |
1374 | =head3 Examples |
… | |
… | |
1330 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
1418 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
1331 | roughly 10 seconds later as it uses a relative timeout). |
1419 | roughly 10 seconds later as it uses a relative timeout). |
1332 | |
1420 | |
1333 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1421 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1334 | such as triggering an event on each "midnight, local time", or other |
1422 | such as triggering an event on each "midnight, local time", or other |
1335 | complicated, rules. |
1423 | complicated rules. |
1336 | |
1424 | |
1337 | As with timers, the callback is guaranteed to be invoked only when the |
1425 | As with timers, the callback is guaranteed to be invoked only when the |
1338 | time (C<at>) has passed, but if multiple periodic timers become ready |
1426 | time (C<at>) has passed, but if multiple periodic timers become ready |
1339 | during the same loop iteration then order of execution is undefined. |
1427 | during the same loop iteration, then order of execution is undefined. |
1340 | |
1428 | |
1341 | =head3 Watcher-Specific Functions and Data Members |
1429 | =head3 Watcher-Specific Functions and Data Members |
1342 | |
1430 | |
1343 | =over 4 |
1431 | =over 4 |
1344 | |
1432 | |
1345 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1433 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1346 | |
1434 | |
1347 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1435 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1348 | |
1436 | |
1349 | Lots of arguments, lets sort it out... There are basically three modes of |
1437 | Lots of arguments, lets sort it out... There are basically three modes of |
1350 | operation, and we will explain them from simplest to complex: |
1438 | operation, and we will explain them from simplest to most complex: |
1351 | |
1439 | |
1352 | =over 4 |
1440 | =over 4 |
1353 | |
1441 | |
1354 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1442 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1355 | |
1443 | |
1356 | In this configuration the watcher triggers an event after the wall clock |
1444 | In this configuration the watcher triggers an event after the wall clock |
1357 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
1445 | time C<at> has passed. It will not repeat and will not adjust when a time |
1358 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1446 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1359 | run when the system time reaches or surpasses this time. |
1447 | only run when the system clock reaches or surpasses this time. |
1360 | |
1448 | |
1361 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1449 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1362 | |
1450 | |
1363 | In this mode the watcher will always be scheduled to time out at the next |
1451 | In this mode the watcher will always be scheduled to time out at the next |
1364 | C<at + N * interval> time (for some integer N, which can also be negative) |
1452 | C<at + N * interval> time (for some integer N, which can also be negative) |
1365 | and then repeat, regardless of any time jumps. |
1453 | and then repeat, regardless of any time jumps. |
1366 | |
1454 | |
1367 | This can be used to create timers that do not drift with respect to system |
1455 | This can be used to create timers that do not drift with respect to the |
1368 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
1456 | system clock, for example, here is a C<ev_periodic> that triggers each |
1369 | the hour: |
1457 | hour, on the hour: |
1370 | |
1458 | |
1371 | ev_periodic_set (&periodic, 0., 3600., 0); |
1459 | ev_periodic_set (&periodic, 0., 3600., 0); |
1372 | |
1460 | |
1373 | This doesn't mean there will always be 3600 seconds in between triggers, |
1461 | This doesn't mean there will always be 3600 seconds in between triggers, |
1374 | but only that the callback will be called when the system time shows a |
1462 | but only that the callback will be called when the system time shows a |
… | |
… | |
1461 | =back |
1549 | =back |
1462 | |
1550 | |
1463 | =head3 Examples |
1551 | =head3 Examples |
1464 | |
1552 | |
1465 | Example: Call a callback every hour, or, more precisely, whenever the |
1553 | Example: Call a callback every hour, or, more precisely, whenever the |
1466 | system clock is divisible by 3600. The callback invocation times have |
1554 | system time is divisible by 3600. The callback invocation times have |
1467 | potentially a lot of jitter, but good long-term stability. |
1555 | potentially a lot of jitter, but good long-term stability. |
1468 | |
1556 | |
1469 | static void |
1557 | static void |
1470 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1558 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1471 | { |
1559 | { |
… | |
… | |
1481 | #include <math.h> |
1569 | #include <math.h> |
1482 | |
1570 | |
1483 | static ev_tstamp |
1571 | static ev_tstamp |
1484 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1572 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1485 | { |
1573 | { |
1486 | return fmod (now, 3600.) + 3600.; |
1574 | return now + (3600. - fmod (now, 3600.)); |
1487 | } |
1575 | } |
1488 | |
1576 | |
1489 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1577 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1490 | |
1578 | |
1491 | Example: Call a callback every hour, starting now: |
1579 | Example: Call a callback every hour, starting now: |
… | |
… | |
1501 | Signal watchers will trigger an event when the process receives a specific |
1589 | Signal watchers will trigger an event when the process receives a specific |
1502 | signal one or more times. Even though signals are very asynchronous, libev |
1590 | signal one or more times. Even though signals are very asynchronous, libev |
1503 | will try it's best to deliver signals synchronously, i.e. as part of the |
1591 | will try it's best to deliver signals synchronously, i.e. as part of the |
1504 | normal event processing, like any other event. |
1592 | normal event processing, like any other event. |
1505 | |
1593 | |
|
|
1594 | If you want signals asynchronously, just use C<sigaction> as you would |
|
|
1595 | do without libev and forget about sharing the signal. You can even use |
|
|
1596 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
|
|
1597 | |
1506 | You can configure as many watchers as you like per signal. Only when the |
1598 | You can configure as many watchers as you like per signal. Only when the |
1507 | first watcher gets started will libev actually register a signal watcher |
1599 | first watcher gets started will libev actually register a signal handler |
1508 | with the kernel (thus it coexists with your own signal handlers as long |
1600 | with the kernel (thus it coexists with your own signal handlers as long as |
1509 | as you don't register any with libev). Similarly, when the last signal |
1601 | you don't register any with libev for the same signal). Similarly, when |
1510 | watcher for a signal is stopped libev will reset the signal handler to |
1602 | the last signal watcher for a signal is stopped, libev will reset the |
1511 | SIG_DFL (regardless of what it was set to before). |
1603 | signal handler to SIG_DFL (regardless of what it was set to before). |
1512 | |
1604 | |
1513 | If possible and supported, libev will install its handlers with |
1605 | If possible and supported, libev will install its handlers with |
1514 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
1606 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
1515 | interrupted. If you have a problem with system calls getting interrupted by |
1607 | interrupted. If you have a problem with system calls getting interrupted by |
1516 | signals you can block all signals in an C<ev_check> watcher and unblock |
1608 | signals you can block all signals in an C<ev_check> watcher and unblock |
… | |
… | |
1533 | |
1625 | |
1534 | =back |
1626 | =back |
1535 | |
1627 | |
1536 | =head3 Examples |
1628 | =head3 Examples |
1537 | |
1629 | |
1538 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
1630 | Example: Try to exit cleanly on SIGINT. |
1539 | |
1631 | |
1540 | static void |
1632 | static void |
1541 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1633 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1542 | { |
1634 | { |
1543 | ev_unloop (loop, EVUNLOOP_ALL); |
1635 | ev_unloop (loop, EVUNLOOP_ALL); |
1544 | } |
1636 | } |
1545 | |
1637 | |
1546 | struct ev_signal signal_watcher; |
1638 | struct ev_signal signal_watcher; |
1547 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1639 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1548 | ev_signal_start (loop, &sigint_cb); |
1640 | ev_signal_start (loop, &signal_watcher); |
1549 | |
1641 | |
1550 | |
1642 | |
1551 | =head2 C<ev_child> - watch out for process status changes |
1643 | =head2 C<ev_child> - watch out for process status changes |
1552 | |
1644 | |
1553 | Child watchers trigger when your process receives a SIGCHLD in response to |
1645 | Child watchers trigger when your process receives a SIGCHLD in response to |
1554 | some child status changes (most typically when a child of yours dies). It |
1646 | some child status changes (most typically when a child of yours dies or |
1555 | is permissible to install a child watcher I<after> the child has been |
1647 | exits). It is permissible to install a child watcher I<after> the child |
1556 | forked (which implies it might have already exited), as long as the event |
1648 | has been forked (which implies it might have already exited), as long |
1557 | loop isn't entered (or is continued from a watcher). |
1649 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
1650 | forking and then immediately registering a watcher for the child is fine, |
|
|
1651 | but forking and registering a watcher a few event loop iterations later is |
|
|
1652 | not. |
1558 | |
1653 | |
1559 | Only the default event loop is capable of handling signals, and therefore |
1654 | Only the default event loop is capable of handling signals, and therefore |
1560 | you can only register child watchers in the default event loop. |
1655 | you can only register child watchers in the default event loop. |
1561 | |
1656 | |
1562 | =head3 Process Interaction |
1657 | =head3 Process Interaction |
… | |
… | |
1660 | the stat buffer having unspecified contents. |
1755 | the stat buffer having unspecified contents. |
1661 | |
1756 | |
1662 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1757 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1663 | relative and your working directory changes, the behaviour is undefined. |
1758 | relative and your working directory changes, the behaviour is undefined. |
1664 | |
1759 | |
1665 | Since there is no standard to do this, the portable implementation simply |
1760 | Since there is no standard kernel interface to do this, the portable |
1666 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
1761 | implementation simply calls C<stat (2)> regularly on the path to see if |
1667 | can specify a recommended polling interval for this case. If you specify |
1762 | it changed somehow. You can specify a recommended polling interval for |
1668 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
1763 | this case. If you specify a polling interval of C<0> (highly recommended!) |
1669 | unspecified default> value will be used (which you can expect to be around |
1764 | then a I<suitable, unspecified default> value will be used (which |
1670 | five seconds, although this might change dynamically). Libev will also |
1765 | you can expect to be around five seconds, although this might change |
1671 | impose a minimum interval which is currently around C<0.1>, but thats |
1766 | dynamically). Libev will also impose a minimum interval which is currently |
1672 | usually overkill. |
1767 | around C<0.1>, but thats usually overkill. |
1673 | |
1768 | |
1674 | This watcher type is not meant for massive numbers of stat watchers, |
1769 | This watcher type is not meant for massive numbers of stat watchers, |
1675 | as even with OS-supported change notifications, this can be |
1770 | as even with OS-supported change notifications, this can be |
1676 | resource-intensive. |
1771 | resource-intensive. |
1677 | |
1772 | |
1678 | At the time of this writing, only the Linux inotify interface is |
1773 | At the time of this writing, the only OS-specific interface implemented |
1679 | implemented (implementing kqueue support is left as an exercise for the |
1774 | is the Linux inotify interface (implementing kqueue support is left as |
1680 | reader, note, however, that the author sees no way of implementing ev_stat |
1775 | an exercise for the reader. Note, however, that the author sees no way |
1681 | semantics with kqueue). Inotify will be used to give hints only and should |
1776 | of implementing C<ev_stat> semantics with kqueue). |
1682 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1683 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1684 | but changes are usually detected immediately, and if the file exists there |
|
|
1685 | will be no polling. |
|
|
1686 | |
1777 | |
1687 | =head3 ABI Issues (Largefile Support) |
1778 | =head3 ABI Issues (Largefile Support) |
1688 | |
1779 | |
1689 | Libev by default (unless the user overrides this) uses the default |
1780 | Libev by default (unless the user overrides this) uses the default |
1690 | compilation environment, which means that on systems with large file |
1781 | compilation environment, which means that on systems with large file |
… | |
… | |
1699 | file interfaces available by default (as e.g. FreeBSD does) and not |
1790 | file interfaces available by default (as e.g. FreeBSD does) and not |
1700 | optional. Libev cannot simply switch on large file support because it has |
1791 | optional. Libev cannot simply switch on large file support because it has |
1701 | to exchange stat structures with application programs compiled using the |
1792 | to exchange stat structures with application programs compiled using the |
1702 | default compilation environment. |
1793 | default compilation environment. |
1703 | |
1794 | |
1704 | =head3 Inotify |
1795 | =head3 Inotify and Kqueue |
1705 | |
1796 | |
1706 | When C<inotify (7)> support has been compiled into libev (generally only |
1797 | When C<inotify (7)> support has been compiled into libev (generally only |
1707 | available on Linux) and present at runtime, it will be used to speed up |
1798 | available with Linux) and present at runtime, it will be used to speed up |
1708 | change detection where possible. The inotify descriptor will be created lazily |
1799 | change detection where possible. The inotify descriptor will be created lazily |
1709 | when the first C<ev_stat> watcher is being started. |
1800 | when the first C<ev_stat> watcher is being started. |
1710 | |
1801 | |
1711 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1802 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1712 | except that changes might be detected earlier, and in some cases, to avoid |
1803 | except that changes might be detected earlier, and in some cases, to avoid |
1713 | making regular C<stat> calls. Even in the presence of inotify support |
1804 | making regular C<stat> calls. Even in the presence of inotify support |
1714 | there are many cases where libev has to resort to regular C<stat> polling. |
1805 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
1806 | but as long as the path exists, libev usually gets away without polling. |
1715 | |
1807 | |
1716 | (There is no support for kqueue, as apparently it cannot be used to |
1808 | There is no support for kqueue, as apparently it cannot be used to |
1717 | implement this functionality, due to the requirement of having a file |
1809 | implement this functionality, due to the requirement of having a file |
1718 | descriptor open on the object at all times). |
1810 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
1811 | etc. is difficult. |
1719 | |
1812 | |
1720 | =head3 The special problem of stat time resolution |
1813 | =head3 The special problem of stat time resolution |
1721 | |
1814 | |
1722 | The C<stat ()> system call only supports full-second resolution portably, and |
1815 | The C<stat ()> system call only supports full-second resolution portably, and |
1723 | even on systems where the resolution is higher, many file systems still |
1816 | even on systems where the resolution is higher, most file systems still |
1724 | only support whole seconds. |
1817 | only support whole seconds. |
1725 | |
1818 | |
1726 | That means that, if the time is the only thing that changes, you can |
1819 | That means that, if the time is the only thing that changes, you can |
1727 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1820 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1728 | calls your callback, which does something. When there is another update |
1821 | calls your callback, which does something. When there is another update |
1729 | within the same second, C<ev_stat> will be unable to detect it as the stat |
1822 | within the same second, C<ev_stat> will be unable to detect unless the |
1730 | data does not change. |
1823 | stat data does change in other ways (e.g. file size). |
1731 | |
1824 | |
1732 | The solution to this is to delay acting on a change for slightly more |
1825 | The solution to this is to delay acting on a change for slightly more |
1733 | than a second (or till slightly after the next full second boundary), using |
1826 | than a second (or till slightly after the next full second boundary), using |
1734 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1827 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1735 | ev_timer_again (loop, w)>). |
1828 | ev_timer_again (loop, w)>). |
… | |
… | |
1755 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1848 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1756 | be detected and should normally be specified as C<0> to let libev choose |
1849 | be detected and should normally be specified as C<0> to let libev choose |
1757 | a suitable value. The memory pointed to by C<path> must point to the same |
1850 | a suitable value. The memory pointed to by C<path> must point to the same |
1758 | path for as long as the watcher is active. |
1851 | path for as long as the watcher is active. |
1759 | |
1852 | |
1760 | The callback will receive C<EV_STAT> when a change was detected, relative |
1853 | The callback will receive an C<EV_STAT> event when a change was detected, |
1761 | to the attributes at the time the watcher was started (or the last change |
1854 | relative to the attributes at the time the watcher was started (or the |
1762 | was detected). |
1855 | last change was detected). |
1763 | |
1856 | |
1764 | =item ev_stat_stat (loop, ev_stat *) |
1857 | =item ev_stat_stat (loop, ev_stat *) |
1765 | |
1858 | |
1766 | Updates the stat buffer immediately with new values. If you change the |
1859 | Updates the stat buffer immediately with new values. If you change the |
1767 | watched path in your callback, you could call this function to avoid |
1860 | watched path in your callback, you could call this function to avoid |
… | |
… | |
1850 | |
1943 | |
1851 | |
1944 | |
1852 | =head2 C<ev_idle> - when you've got nothing better to do... |
1945 | =head2 C<ev_idle> - when you've got nothing better to do... |
1853 | |
1946 | |
1854 | Idle watchers trigger events when no other events of the same or higher |
1947 | Idle watchers trigger events when no other events of the same or higher |
1855 | priority are pending (prepare, check and other idle watchers do not |
1948 | priority are pending (prepare, check and other idle watchers do not count |
1856 | count). |
1949 | as receiving "events"). |
1857 | |
1950 | |
1858 | That is, as long as your process is busy handling sockets or timeouts |
1951 | That is, as long as your process is busy handling sockets or timeouts |
1859 | (or even signals, imagine) of the same or higher priority it will not be |
1952 | (or even signals, imagine) of the same or higher priority it will not be |
1860 | triggered. But when your process is idle (or only lower-priority watchers |
1953 | triggered. But when your process is idle (or only lower-priority watchers |
1861 | are pending), the idle watchers are being called once per event loop |
1954 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1900 | ev_idle_start (loop, idle_cb); |
1993 | ev_idle_start (loop, idle_cb); |
1901 | |
1994 | |
1902 | |
1995 | |
1903 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1996 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1904 | |
1997 | |
1905 | Prepare and check watchers are usually (but not always) used in tandem: |
1998 | Prepare and check watchers are usually (but not always) used in pairs: |
1906 | prepare watchers get invoked before the process blocks and check watchers |
1999 | prepare watchers get invoked before the process blocks and check watchers |
1907 | afterwards. |
2000 | afterwards. |
1908 | |
2001 | |
1909 | You I<must not> call C<ev_loop> or similar functions that enter |
2002 | You I<must not> call C<ev_loop> or similar functions that enter |
1910 | the current event loop from either C<ev_prepare> or C<ev_check> |
2003 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
1913 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2006 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1914 | C<ev_check> so if you have one watcher of each kind they will always be |
2007 | C<ev_check> so if you have one watcher of each kind they will always be |
1915 | called in pairs bracketing the blocking call. |
2008 | called in pairs bracketing the blocking call. |
1916 | |
2009 | |
1917 | Their main purpose is to integrate other event mechanisms into libev and |
2010 | Their main purpose is to integrate other event mechanisms into libev and |
1918 | their use is somewhat advanced. This could be used, for example, to track |
2011 | their use is somewhat advanced. They could be used, for example, to track |
1919 | variable changes, implement your own watchers, integrate net-snmp or a |
2012 | variable changes, implement your own watchers, integrate net-snmp or a |
1920 | coroutine library and lots more. They are also occasionally useful if |
2013 | coroutine library and lots more. They are also occasionally useful if |
1921 | you cache some data and want to flush it before blocking (for example, |
2014 | you cache some data and want to flush it before blocking (for example, |
1922 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2015 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1923 | watcher). |
2016 | watcher). |
1924 | |
2017 | |
1925 | This is done by examining in each prepare call which file descriptors need |
2018 | This is done by examining in each prepare call which file descriptors |
1926 | to be watched by the other library, registering C<ev_io> watchers for |
2019 | need to be watched by the other library, registering C<ev_io> watchers |
1927 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2020 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1928 | provide just this functionality). Then, in the check watcher you check for |
2021 | libraries provide exactly this functionality). Then, in the check watcher, |
1929 | any events that occurred (by checking the pending status of all watchers |
2022 | you check for any events that occurred (by checking the pending status |
1930 | and stopping them) and call back into the library. The I/O and timer |
2023 | of all watchers and stopping them) and call back into the library. The |
1931 | callbacks will never actually be called (but must be valid nevertheless, |
2024 | I/O and timer callbacks will never actually be called (but must be valid |
1932 | because you never know, you know?). |
2025 | nevertheless, because you never know, you know?). |
1933 | |
2026 | |
1934 | As another example, the Perl Coro module uses these hooks to integrate |
2027 | As another example, the Perl Coro module uses these hooks to integrate |
1935 | coroutines into libev programs, by yielding to other active coroutines |
2028 | coroutines into libev programs, by yielding to other active coroutines |
1936 | during each prepare and only letting the process block if no coroutines |
2029 | during each prepare and only letting the process block if no coroutines |
1937 | are ready to run (it's actually more complicated: it only runs coroutines |
2030 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
1940 | loop from blocking if lower-priority coroutines are active, thus mapping |
2033 | loop from blocking if lower-priority coroutines are active, thus mapping |
1941 | low-priority coroutines to idle/background tasks). |
2034 | low-priority coroutines to idle/background tasks). |
1942 | |
2035 | |
1943 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2036 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1944 | priority, to ensure that they are being run before any other watchers |
2037 | priority, to ensure that they are being run before any other watchers |
|
|
2038 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2039 | |
1945 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2040 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1946 | too) should not activate ("feed") events into libev. While libev fully |
2041 | activate ("feed") events into libev. While libev fully supports this, they |
1947 | supports this, they might get executed before other C<ev_check> watchers |
2042 | might get executed before other C<ev_check> watchers did their job. As |
1948 | did their job. As C<ev_check> watchers are often used to embed other |
2043 | C<ev_check> watchers are often used to embed other (non-libev) event |
1949 | (non-libev) event loops those other event loops might be in an unusable |
2044 | loops those other event loops might be in an unusable state until their |
1950 | state until their C<ev_check> watcher ran (always remind yourself to |
2045 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1951 | coexist peacefully with others). |
2046 | others). |
1952 | |
2047 | |
1953 | =head3 Watcher-Specific Functions and Data Members |
2048 | =head3 Watcher-Specific Functions and Data Members |
1954 | |
2049 | |
1955 | =over 4 |
2050 | =over 4 |
1956 | |
2051 | |
… | |
… | |
1958 | |
2053 | |
1959 | =item ev_check_init (ev_check *, callback) |
2054 | =item ev_check_init (ev_check *, callback) |
1960 | |
2055 | |
1961 | Initialises and configures the prepare or check watcher - they have no |
2056 | Initialises and configures the prepare or check watcher - they have no |
1962 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2057 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1963 | macros, but using them is utterly, utterly and completely pointless. |
2058 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2059 | pointless. |
1964 | |
2060 | |
1965 | =back |
2061 | =back |
1966 | |
2062 | |
1967 | =head3 Examples |
2063 | =head3 Examples |
1968 | |
2064 | |
… | |
… | |
2061 | } |
2157 | } |
2062 | |
2158 | |
2063 | // do not ever call adns_afterpoll |
2159 | // do not ever call adns_afterpoll |
2064 | |
2160 | |
2065 | Method 4: Do not use a prepare or check watcher because the module you |
2161 | Method 4: Do not use a prepare or check watcher because the module you |
2066 | want to embed is too inflexible to support it. Instead, you can override |
2162 | want to embed is not flexible enough to support it. Instead, you can |
2067 | their poll function. The drawback with this solution is that the main |
2163 | override their poll function. The drawback with this solution is that the |
2068 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
2164 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
2069 | this. |
2165 | this approach, effectively embedding EV as a client into the horrible |
|
|
2166 | libglib event loop. |
2070 | |
2167 | |
2071 | static gint |
2168 | static gint |
2072 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2169 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2073 | { |
2170 | { |
2074 | int got_events = 0; |
2171 | int got_events = 0; |
… | |
… | |
2105 | prioritise I/O. |
2202 | prioritise I/O. |
2106 | |
2203 | |
2107 | As an example for a bug workaround, the kqueue backend might only support |
2204 | As an example for a bug workaround, the kqueue backend might only support |
2108 | sockets on some platform, so it is unusable as generic backend, but you |
2205 | sockets on some platform, so it is unusable as generic backend, but you |
2109 | still want to make use of it because you have many sockets and it scales |
2206 | still want to make use of it because you have many sockets and it scales |
2110 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2207 | so nicely. In this case, you would create a kqueue-based loop and embed |
2111 | into your default loop (which might use e.g. poll). Overall operation will |
2208 | it into your default loop (which might use e.g. poll). Overall operation |
2112 | be a bit slower because first libev has to poll and then call kevent, but |
2209 | will be a bit slower because first libev has to call C<poll> and then |
2113 | at least you can use both at what they are best. |
2210 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2211 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2114 | |
2212 | |
2115 | As for prioritising I/O: rarely you have the case where some fds have |
2213 | As for prioritising I/O: under rare circumstances you have the case where |
2116 | to be watched and handled very quickly (with low latency), and even |
2214 | some fds have to be watched and handled very quickly (with low latency), |
2117 | priorities and idle watchers might have too much overhead. In this case |
2215 | and even priorities and idle watchers might have too much overhead. In |
2118 | you would put all the high priority stuff in one loop and all the rest in |
2216 | this case you would put all the high priority stuff in one loop and all |
2119 | a second one, and embed the second one in the first. |
2217 | the rest in a second one, and embed the second one in the first. |
2120 | |
2218 | |
2121 | As long as the watcher is active, the callback will be invoked every time |
2219 | As long as the watcher is active, the callback will be invoked every time |
2122 | there might be events pending in the embedded loop. The callback must then |
2220 | there might be events pending in the embedded loop. The callback must then |
2123 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2221 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2124 | their callbacks (you could also start an idle watcher to give the embedded |
2222 | their callbacks (you could also start an idle watcher to give the embedded |
… | |
… | |
2132 | interested in that. |
2230 | interested in that. |
2133 | |
2231 | |
2134 | Also, there have not currently been made special provisions for forking: |
2232 | Also, there have not currently been made special provisions for forking: |
2135 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2233 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2136 | but you will also have to stop and restart any C<ev_embed> watchers |
2234 | but you will also have to stop and restart any C<ev_embed> watchers |
2137 | yourself. |
2235 | yourself - but you can use a fork watcher to handle this automatically, |
|
|
2236 | and future versions of libev might do just that. |
2138 | |
2237 | |
2139 | Unfortunately, not all backends are embeddable, only the ones returned by |
2238 | Unfortunately, not all backends are embeddable: only the ones returned by |
2140 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2239 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2141 | portable one. |
2240 | portable one. |
2142 | |
2241 | |
2143 | So when you want to use this feature you will always have to be prepared |
2242 | So when you want to use this feature you will always have to be prepared |
2144 | that you cannot get an embeddable loop. The recommended way to get around |
2243 | that you cannot get an embeddable loop. The recommended way to get around |
2145 | this is to have a separate variables for your embeddable loop, try to |
2244 | this is to have a separate variables for your embeddable loop, try to |
2146 | create it, and if that fails, use the normal loop for everything. |
2245 | create it, and if that fails, use the normal loop for everything. |
|
|
2246 | |
|
|
2247 | =head3 C<ev_embed> and fork |
|
|
2248 | |
|
|
2249 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2250 | automatically be applied to the embedded loop as well, so no special |
|
|
2251 | fork handling is required in that case. When the watcher is not running, |
|
|
2252 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2253 | as applicable. |
2147 | |
2254 | |
2148 | =head3 Watcher-Specific Functions and Data Members |
2255 | =head3 Watcher-Specific Functions and Data Members |
2149 | |
2256 | |
2150 | =over 4 |
2257 | =over 4 |
2151 | |
2258 | |
… | |
… | |
2269 | is that the author does not know of a simple (or any) algorithm for a |
2376 | is that the author does not know of a simple (or any) algorithm for a |
2270 | multiple-writer-single-reader queue that works in all cases and doesn't |
2377 | multiple-writer-single-reader queue that works in all cases and doesn't |
2271 | need elaborate support such as pthreads. |
2378 | need elaborate support such as pthreads. |
2272 | |
2379 | |
2273 | That means that if you want to queue data, you have to provide your own |
2380 | That means that if you want to queue data, you have to provide your own |
2274 | queue. But at least I can tell you would implement locking around your |
2381 | queue. But at least I can tell you how to implement locking around your |
2275 | queue: |
2382 | queue: |
2276 | |
2383 | |
2277 | =over 4 |
2384 | =over 4 |
2278 | |
2385 | |
2279 | =item queueing from a signal handler context |
2386 | =item queueing from a signal handler context |
2280 | |
2387 | |
2281 | To implement race-free queueing, you simply add to the queue in the signal |
2388 | To implement race-free queueing, you simply add to the queue in the signal |
2282 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
2389 | handler but you block the signal handler in the watcher callback. Here is |
2283 | some fictitious SIGUSR1 handler: |
2390 | an example that does that for some fictitious SIGUSR1 handler: |
2284 | |
2391 | |
2285 | static ev_async mysig; |
2392 | static ev_async mysig; |
2286 | |
2393 | |
2287 | static void |
2394 | static void |
2288 | sigusr1_handler (void) |
2395 | sigusr1_handler (void) |
… | |
… | |
2355 | |
2462 | |
2356 | =item ev_async_init (ev_async *, callback) |
2463 | =item ev_async_init (ev_async *, callback) |
2357 | |
2464 | |
2358 | Initialises and configures the async watcher - it has no parameters of any |
2465 | Initialises and configures the async watcher - it has no parameters of any |
2359 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2466 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2360 | believe me. |
2467 | trust me. |
2361 | |
2468 | |
2362 | =item ev_async_send (loop, ev_async *) |
2469 | =item ev_async_send (loop, ev_async *) |
2363 | |
2470 | |
2364 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2471 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2365 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2472 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2366 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
2473 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2367 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2474 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2368 | section below on what exactly this means). |
2475 | section below on what exactly this means). |
2369 | |
2476 | |
2370 | This call incurs the overhead of a system call only once per loop iteration, |
2477 | This call incurs the overhead of a system call only once per loop iteration, |
2371 | so while the overhead might be noticeable, it doesn't apply to repeated |
2478 | so while the overhead might be noticeable, it doesn't apply to repeated |
… | |
… | |
2395 | =over 4 |
2502 | =over 4 |
2396 | |
2503 | |
2397 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2504 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2398 | |
2505 | |
2399 | This function combines a simple timer and an I/O watcher, calls your |
2506 | This function combines a simple timer and an I/O watcher, calls your |
2400 | callback on whichever event happens first and automatically stop both |
2507 | callback on whichever event happens first and automatically stops both |
2401 | watchers. This is useful if you want to wait for a single event on an fd |
2508 | watchers. This is useful if you want to wait for a single event on an fd |
2402 | or timeout without having to allocate/configure/start/stop/free one or |
2509 | or timeout without having to allocate/configure/start/stop/free one or |
2403 | more watchers yourself. |
2510 | more watchers yourself. |
2404 | |
2511 | |
2405 | If C<fd> is less than 0, then no I/O watcher will be started and events |
2512 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2406 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
2513 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2407 | C<events> set will be created and started. |
2514 | the given C<fd> and C<events> set will be created and started. |
2408 | |
2515 | |
2409 | If C<timeout> is less than 0, then no timeout watcher will be |
2516 | If C<timeout> is less than 0, then no timeout watcher will be |
2410 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2517 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2411 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
2518 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
2412 | dubious value. |
2519 | dubious value. |
… | |
… | |
2577 | |
2684 | |
2578 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2685 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2579 | |
2686 | |
2580 | See the method-C<set> above for more details. |
2687 | See the method-C<set> above for more details. |
2581 | |
2688 | |
2582 | Example: |
2689 | Example: Use a plain function as callback. |
2583 | |
2690 | |
2584 | static void io_cb (ev::io &w, int revents) { } |
2691 | static void io_cb (ev::io &w, int revents) { } |
2585 | iow.set <io_cb> (); |
2692 | iow.set <io_cb> (); |
2586 | |
2693 | |
2587 | =item w->set (struct ev_loop *) |
2694 | =item w->set (struct ev_loop *) |
… | |
… | |
2625 | Example: Define a class with an IO and idle watcher, start one of them in |
2732 | Example: Define a class with an IO and idle watcher, start one of them in |
2626 | the constructor. |
2733 | the constructor. |
2627 | |
2734 | |
2628 | class myclass |
2735 | class myclass |
2629 | { |
2736 | { |
2630 | ev::io io; void io_cb (ev::io &w, int revents); |
2737 | ev::io io ; void io_cb (ev::io &w, int revents); |
2631 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
2738 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2632 | |
2739 | |
2633 | myclass (int fd) |
2740 | myclass (int fd) |
2634 | { |
2741 | { |
2635 | io .set <myclass, &myclass::io_cb > (this); |
2742 | io .set <myclass, &myclass::io_cb > (this); |
2636 | idle.set <myclass, &myclass::idle_cb> (this); |
2743 | idle.set <myclass, &myclass::idle_cb> (this); |
… | |
… | |
2652 | =item Perl |
2759 | =item Perl |
2653 | |
2760 | |
2654 | The EV module implements the full libev API and is actually used to test |
2761 | The EV module implements the full libev API and is actually used to test |
2655 | libev. EV is developed together with libev. Apart from the EV core module, |
2762 | libev. EV is developed together with libev. Apart from the EV core module, |
2656 | there are additional modules that implement libev-compatible interfaces |
2763 | there are additional modules that implement libev-compatible interfaces |
2657 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
2764 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2658 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
2765 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
2766 | and C<EV::Glib>). |
2659 | |
2767 | |
2660 | It can be found and installed via CPAN, its homepage is at |
2768 | It can be found and installed via CPAN, its homepage is at |
2661 | L<http://software.schmorp.de/pkg/EV>. |
2769 | L<http://software.schmorp.de/pkg/EV>. |
2662 | |
2770 | |
2663 | =item Python |
2771 | =item Python |
… | |
… | |
2842 | |
2950 | |
2843 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2951 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2844 | |
2952 | |
2845 | Libev can be configured via a variety of preprocessor symbols you have to |
2953 | Libev can be configured via a variety of preprocessor symbols you have to |
2846 | define before including any of its files. The default in the absence of |
2954 | define before including any of its files. The default in the absence of |
2847 | autoconf is noted for every option. |
2955 | autoconf is documented for every option. |
2848 | |
2956 | |
2849 | =over 4 |
2957 | =over 4 |
2850 | |
2958 | |
2851 | =item EV_STANDALONE |
2959 | =item EV_STANDALONE |
2852 | |
2960 | |
… | |
… | |
3022 | When doing priority-based operations, libev usually has to linearly search |
3130 | When doing priority-based operations, libev usually has to linearly search |
3023 | all the priorities, so having many of them (hundreds) uses a lot of space |
3131 | all the priorities, so having many of them (hundreds) uses a lot of space |
3024 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3132 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3025 | fine. |
3133 | fine. |
3026 | |
3134 | |
3027 | If your embedding application does not need any priorities, defining these both to |
3135 | If your embedding application does not need any priorities, defining these |
3028 | C<0> will save some memory and CPU. |
3136 | both to C<0> will save some memory and CPU. |
3029 | |
3137 | |
3030 | =item EV_PERIODIC_ENABLE |
3138 | =item EV_PERIODIC_ENABLE |
3031 | |
3139 | |
3032 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3140 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3033 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3141 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
… | |
… | |
3040 | code. |
3148 | code. |
3041 | |
3149 | |
3042 | =item EV_EMBED_ENABLE |
3150 | =item EV_EMBED_ENABLE |
3043 | |
3151 | |
3044 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3152 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3045 | defined to be C<0>, then they are not. |
3153 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3154 | watcher types, which therefore must not be disabled. |
3046 | |
3155 | |
3047 | =item EV_STAT_ENABLE |
3156 | =item EV_STAT_ENABLE |
3048 | |
3157 | |
3049 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3158 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3050 | defined to be C<0>, then they are not. |
3159 | defined to be C<0>, then they are not. |
… | |
… | |
3082 | two). |
3191 | two). |
3083 | |
3192 | |
3084 | =item EV_USE_4HEAP |
3193 | =item EV_USE_4HEAP |
3085 | |
3194 | |
3086 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3195 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3087 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
3196 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3088 | to C<1>. The 4-heap uses more complicated (longer) code but has |
3197 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3089 | noticeably faster performance with many (thousands) of watchers. |
3198 | faster performance with many (thousands) of watchers. |
3090 | |
3199 | |
3091 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3200 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3092 | (disabled). |
3201 | (disabled). |
3093 | |
3202 | |
3094 | =item EV_HEAP_CACHE_AT |
3203 | =item EV_HEAP_CACHE_AT |
3095 | |
3204 | |
3096 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3205 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3097 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
3206 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3098 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3207 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3099 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3208 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3100 | but avoids random read accesses on heap changes. This improves performance |
3209 | but avoids random read accesses on heap changes. This improves performance |
3101 | noticeably with with many (hundreds) of watchers. |
3210 | noticeably with many (hundreds) of watchers. |
3102 | |
3211 | |
3103 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3212 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3104 | (disabled). |
3213 | (disabled). |
3105 | |
3214 | |
3106 | =item EV_VERIFY |
3215 | =item EV_VERIFY |
… | |
… | |
3112 | called once per loop, which can slow down libev. If set to C<3>, then the |
3221 | called once per loop, which can slow down libev. If set to C<3>, then the |
3113 | verification code will be called very frequently, which will slow down |
3222 | verification code will be called very frequently, which will slow down |
3114 | libev considerably. |
3223 | libev considerably. |
3115 | |
3224 | |
3116 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
3225 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
3117 | C<0.> |
3226 | C<0>. |
3118 | |
3227 | |
3119 | =item EV_COMMON |
3228 | =item EV_COMMON |
3120 | |
3229 | |
3121 | By default, all watchers have a C<void *data> member. By redefining |
3230 | By default, all watchers have a C<void *data> member. By redefining |
3122 | this macro to a something else you can include more and other types of |
3231 | this macro to a something else you can include more and other types of |
… | |
… | |
3139 | and the way callbacks are invoked and set. Must expand to a struct member |
3248 | and the way callbacks are invoked and set. Must expand to a struct member |
3140 | definition and a statement, respectively. See the F<ev.h> header file for |
3249 | definition and a statement, respectively. See the F<ev.h> header file for |
3141 | their default definitions. One possible use for overriding these is to |
3250 | their default definitions. One possible use for overriding these is to |
3142 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3251 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3143 | method calls instead of plain function calls in C++. |
3252 | method calls instead of plain function calls in C++. |
|
|
3253 | |
|
|
3254 | =back |
3144 | |
3255 | |
3145 | =head2 EXPORTED API SYMBOLS |
3256 | =head2 EXPORTED API SYMBOLS |
3146 | |
3257 | |
3147 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3258 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3148 | exported symbols, you can use the provided F<Symbol.*> files which list |
3259 | exported symbols, you can use the provided F<Symbol.*> files which list |
… | |
… | |
3195 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3306 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3196 | |
3307 | |
3197 | #include "ev_cpp.h" |
3308 | #include "ev_cpp.h" |
3198 | #include "ev.c" |
3309 | #include "ev.c" |
3199 | |
3310 | |
|
|
3311 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3200 | |
3312 | |
3201 | =head1 THREADS AND COROUTINES |
3313 | =head2 THREADS AND COROUTINES |
3202 | |
3314 | |
3203 | =head2 THREADS |
3315 | =head3 THREADS |
3204 | |
3316 | |
3205 | Libev itself is completely thread-safe, but it uses no locking. This |
3317 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
3318 | documented otherwise, but libev implements no locking itself. This means |
3206 | means that you can use as many loops as you want in parallel, as long as |
3319 | that you can use as many loops as you want in parallel, as long as there |
3207 | only one thread ever calls into one libev function with the same loop |
3320 | are no concurrent calls into any libev function with the same loop |
3208 | parameter. |
3321 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
3322 | of course): libev guarantees that different event loops share no data |
|
|
3323 | structures that need any locking. |
3209 | |
3324 | |
3210 | Or put differently: calls with different loop parameters can be done in |
3325 | Or to put it differently: calls with different loop parameters can be done |
3211 | parallel from multiple threads, calls with the same loop parameter must be |
3326 | concurrently from multiple threads, calls with the same loop parameter |
3212 | done serially (but can be done from different threads, as long as only one |
3327 | must be done serially (but can be done from different threads, as long as |
3213 | thread ever is inside a call at any point in time, e.g. by using a mutex |
3328 | only one thread ever is inside a call at any point in time, e.g. by using |
3214 | per loop). |
3329 | a mutex per loop). |
|
|
3330 | |
|
|
3331 | Specifically to support threads (and signal handlers), libev implements |
|
|
3332 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
3333 | concurrency on the same event loop, namely waking it up "from the |
|
|
3334 | outside". |
3215 | |
3335 | |
3216 | If you want to know which design (one loop, locking, or multiple loops |
3336 | If you want to know which design (one loop, locking, or multiple loops |
3217 | without or something else still) is best for your problem, then I cannot |
3337 | without or something else still) is best for your problem, then I cannot |
3218 | help you. I can give some generic advice however: |
3338 | help you, but here is some generic advice: |
3219 | |
3339 | |
3220 | =over 4 |
3340 | =over 4 |
3221 | |
3341 | |
3222 | =item * most applications have a main thread: use the default libev loop |
3342 | =item * most applications have a main thread: use the default libev loop |
3223 | in that thread, or create a separate thread running only the default loop. |
3343 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3235 | |
3355 | |
3236 | Choosing a model is hard - look around, learn, know that usually you can do |
3356 | Choosing a model is hard - look around, learn, know that usually you can do |
3237 | better than you currently do :-) |
3357 | better than you currently do :-) |
3238 | |
3358 | |
3239 | =item * often you need to talk to some other thread which blocks in the |
3359 | =item * often you need to talk to some other thread which blocks in the |
|
|
3360 | event loop. |
|
|
3361 | |
3240 | event loop - C<ev_async> watchers can be used to wake them up from other |
3362 | C<ev_async> watchers can be used to wake them up from other threads safely |
3241 | threads safely (or from signal contexts...). |
3363 | (or from signal contexts...). |
|
|
3364 | |
|
|
3365 | An example use would be to communicate signals or other events that only |
|
|
3366 | work in the default loop by registering the signal watcher with the |
|
|
3367 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
3368 | watcher callback into the event loop interested in the signal. |
3242 | |
3369 | |
3243 | =back |
3370 | =back |
3244 | |
3371 | |
3245 | =head2 COROUTINES |
3372 | =head3 COROUTINES |
3246 | |
3373 | |
3247 | Libev is much more accommodating to coroutines ("cooperative threads"): |
3374 | Libev is very accommodating to coroutines ("cooperative threads"): |
3248 | libev fully supports nesting calls to it's functions from different |
3375 | libev fully supports nesting calls to its functions from different |
3249 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3376 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3250 | different coroutines and switch freely between both coroutines running the |
3377 | different coroutines, and switch freely between both coroutines running the |
3251 | loop, as long as you don't confuse yourself). The only exception is that |
3378 | loop, as long as you don't confuse yourself). The only exception is that |
3252 | you must not do this from C<ev_periodic> reschedule callbacks. |
3379 | you must not do this from C<ev_periodic> reschedule callbacks. |
3253 | |
3380 | |
3254 | Care has been invested into making sure that libev does not keep local |
3381 | Care has been taken to ensure that libev does not keep local state inside |
3255 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
3382 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3256 | switches. |
3383 | they do not clal any callbacks. |
3257 | |
3384 | |
|
|
3385 | =head2 COMPILER WARNINGS |
3258 | |
3386 | |
3259 | =head1 COMPLEXITIES |
3387 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3388 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3389 | scared by this. |
3260 | |
3390 | |
3261 | In this section the complexities of (many of) the algorithms used inside |
3391 | However, these are unavoidable for many reasons. For one, each compiler |
3262 | libev will be explained. For complexity discussions about backends see the |
3392 | has different warnings, and each user has different tastes regarding |
3263 | documentation for C<ev_default_init>. |
3393 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3394 | targeting a specific compiler and compiler-version. |
3264 | |
3395 | |
3265 | All of the following are about amortised time: If an array needs to be |
3396 | Another reason is that some compiler warnings require elaborate |
3266 | extended, libev needs to realloc and move the whole array, but this |
3397 | workarounds, or other changes to the code that make it less clear and less |
3267 | happens asymptotically never with higher number of elements, so O(1) might |
3398 | maintainable. |
3268 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3269 | it is much faster and asymptotically approaches constant time. |
|
|
3270 | |
3399 | |
3271 | =over 4 |
3400 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3401 | wrong (because they don't actually warn about the condition their message |
|
|
3402 | seems to warn about). For example, certain older gcc versions had some |
|
|
3403 | warnings that resulted an extreme number of false positives. These have |
|
|
3404 | been fixed, but some people still insist on making code warn-free with |
|
|
3405 | such buggy versions. |
3272 | |
3406 | |
3273 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3407 | While libev is written to generate as few warnings as possible, |
|
|
3408 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3409 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3410 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3411 | warnings, not errors, or proof of bugs. |
3274 | |
3412 | |
3275 | This means that, when you have a watcher that triggers in one hour and |
|
|
3276 | there are 100 watchers that would trigger before that then inserting will |
|
|
3277 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3278 | |
3413 | |
3279 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3414 | =head2 VALGRIND |
3280 | |
3415 | |
3281 | That means that changing a timer costs less than removing/adding them |
3416 | Valgrind has a special section here because it is a popular tool that is |
3282 | as only the relative motion in the event queue has to be paid for. |
3417 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3283 | |
3418 | |
3284 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3419 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3420 | in libev, then check twice: If valgrind reports something like: |
3285 | |
3421 | |
3286 | These just add the watcher into an array or at the head of a list. |
3422 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3423 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3424 | ==2274== still reachable: 256 bytes in 1 blocks. |
3287 | |
3425 | |
3288 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3426 | Then there is no memory leak, just as memory accounted to global variables |
|
|
3427 | is not a memleak - the memory is still being refernced, and didn't leak. |
3289 | |
3428 | |
3290 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3429 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
3430 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
3431 | although an acceptable workaround has been found here), or it might be |
|
|
3432 | confused. |
3291 | |
3433 | |
3292 | These watchers are stored in lists then need to be walked to find the |
3434 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3293 | correct watcher to remove. The lists are usually short (you don't usually |
3435 | make it into some kind of religion. |
3294 | have many watchers waiting for the same fd or signal). |
|
|
3295 | |
3436 | |
3296 | =item Finding the next timer in each loop iteration: O(1) |
3437 | If you are unsure about something, feel free to contact the mailing list |
|
|
3438 | with the full valgrind report and an explanation on why you think this |
|
|
3439 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
3440 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
3441 | of learning how to interpret valgrind properly. |
3297 | |
3442 | |
3298 | By virtue of using a binary or 4-heap, the next timer is always found at a |
3443 | If you need, for some reason, empty reports from valgrind for your project |
3299 | fixed position in the storage array. |
3444 | I suggest using suppression lists. |
3300 | |
3445 | |
3301 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3302 | |
3446 | |
3303 | A change means an I/O watcher gets started or stopped, which requires |
3447 | =head1 PORTABILITY NOTES |
3304 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3305 | on backend and whether C<ev_io_set> was used). |
|
|
3306 | |
3448 | |
3307 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3308 | |
|
|
3309 | =item Priority handling: O(number_of_priorities) |
|
|
3310 | |
|
|
3311 | Priorities are implemented by allocating some space for each |
|
|
3312 | priority. When doing priority-based operations, libev usually has to |
|
|
3313 | linearly search all the priorities, but starting/stopping and activating |
|
|
3314 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3315 | |
|
|
3316 | =item Sending an ev_async: O(1) |
|
|
3317 | |
|
|
3318 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3319 | |
|
|
3320 | =item Processing signals: O(max_signal_number) |
|
|
3321 | |
|
|
3322 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3323 | calls in the current loop iteration. Checking for async and signal events |
|
|
3324 | involves iterating over all running async watchers or all signal numbers. |
|
|
3325 | |
|
|
3326 | =back |
|
|
3327 | |
|
|
3328 | |
|
|
3329 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3449 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3330 | |
3450 | |
3331 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3451 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3332 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3452 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3333 | model. Libev still offers limited functionality on this platform in |
3453 | model. Libev still offers limited functionality on this platform in |
3334 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3454 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
… | |
… | |
3345 | |
3465 | |
3346 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3466 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3347 | accept large writes: instead of resulting in a partial write, windows will |
3467 | accept large writes: instead of resulting in a partial write, windows will |
3348 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3468 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3349 | so make sure you only write small amounts into your sockets (less than a |
3469 | so make sure you only write small amounts into your sockets (less than a |
3350 | megabyte seems safe, but thsi apparently depends on the amount of memory |
3470 | megabyte seems safe, but this apparently depends on the amount of memory |
3351 | available). |
3471 | available). |
3352 | |
3472 | |
3353 | Due to the many, low, and arbitrary limits on the win32 platform and |
3473 | Due to the many, low, and arbitrary limits on the win32 platform and |
3354 | the abysmal performance of winsockets, using a large number of sockets |
3474 | the abysmal performance of winsockets, using a large number of sockets |
3355 | is not recommended (and not reasonable). If your program needs to use |
3475 | is not recommended (and not reasonable). If your program needs to use |
… | |
… | |
3366 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3486 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3367 | |
3487 | |
3368 | #include "ev.h" |
3488 | #include "ev.h" |
3369 | |
3489 | |
3370 | And compile the following F<evwrap.c> file into your project (make sure |
3490 | And compile the following F<evwrap.c> file into your project (make sure |
3371 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
3491 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3372 | |
3492 | |
3373 | #include "evwrap.h" |
3493 | #include "evwrap.h" |
3374 | #include "ev.c" |
3494 | #include "ev.c" |
3375 | |
3495 | |
3376 | =over 4 |
3496 | =over 4 |
… | |
… | |
3421 | wrap all I/O functions and provide your own fd management, but the cost of |
3541 | wrap all I/O functions and provide your own fd management, but the cost of |
3422 | calling select (O(n²)) will likely make this unworkable. |
3542 | calling select (O(n²)) will likely make this unworkable. |
3423 | |
3543 | |
3424 | =back |
3544 | =back |
3425 | |
3545 | |
3426 | |
|
|
3427 | =head1 PORTABILITY REQUIREMENTS |
3546 | =head2 PORTABILITY REQUIREMENTS |
3428 | |
3547 | |
3429 | In addition to a working ISO-C implementation, libev relies on a few |
3548 | In addition to a working ISO-C implementation and of course the |
3430 | additional extensions: |
3549 | backend-specific APIs, libev relies on a few additional extensions: |
3431 | |
3550 | |
3432 | =over 4 |
3551 | =over 4 |
3433 | |
3552 | |
3434 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3553 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3435 | calling conventions regardless of C<ev_watcher_type *>. |
3554 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3441 | calls them using an C<ev_watcher *> internally. |
3560 | calls them using an C<ev_watcher *> internally. |
3442 | |
3561 | |
3443 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3562 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3444 | |
3563 | |
3445 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3564 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3446 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
3565 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
3447 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3566 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3448 | believed to be sufficiently portable. |
3567 | believed to be sufficiently portable. |
3449 | |
3568 | |
3450 | =item C<sigprocmask> must work in a threaded environment |
3569 | =item C<sigprocmask> must work in a threaded environment |
3451 | |
3570 | |
… | |
… | |
3460 | except the initial one, and run the default loop in the initial thread as |
3579 | except the initial one, and run the default loop in the initial thread as |
3461 | well. |
3580 | well. |
3462 | |
3581 | |
3463 | =item C<long> must be large enough for common memory allocation sizes |
3582 | =item C<long> must be large enough for common memory allocation sizes |
3464 | |
3583 | |
3465 | To improve portability and simplify using libev, libev uses C<long> |
3584 | To improve portability and simplify its API, libev uses C<long> internally |
3466 | internally instead of C<size_t> when allocating its data structures. On |
3585 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3467 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
3586 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3468 | is still at least 31 bits everywhere, which is enough for hundreds of |
3587 | least 31 bits everywhere, which is enough for hundreds of millions of |
3469 | millions of watchers. |
3588 | watchers. |
3470 | |
3589 | |
3471 | =item C<double> must hold a time value in seconds with enough accuracy |
3590 | =item C<double> must hold a time value in seconds with enough accuracy |
3472 | |
3591 | |
3473 | The type C<double> is used to represent timestamps. It is required to |
3592 | The type C<double> is used to represent timestamps. It is required to |
3474 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3593 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
… | |
… | |
3478 | =back |
3597 | =back |
3479 | |
3598 | |
3480 | If you know of other additional requirements drop me a note. |
3599 | If you know of other additional requirements drop me a note. |
3481 | |
3600 | |
3482 | |
3601 | |
3483 | =head1 COMPILER WARNINGS |
3602 | =head1 ALGORITHMIC COMPLEXITIES |
3484 | |
3603 | |
3485 | Depending on your compiler and compiler settings, you might get no or a |
3604 | In this section the complexities of (many of) the algorithms used inside |
3486 | lot of warnings when compiling libev code. Some people are apparently |
3605 | libev will be documented. For complexity discussions about backends see |
3487 | scared by this. |
3606 | the documentation for C<ev_default_init>. |
3488 | |
3607 | |
3489 | However, these are unavoidable for many reasons. For one, each compiler |
3608 | All of the following are about amortised time: If an array needs to be |
3490 | has different warnings, and each user has different tastes regarding |
3609 | extended, libev needs to realloc and move the whole array, but this |
3491 | warning options. "Warn-free" code therefore cannot be a goal except when |
3610 | happens asymptotically rarer with higher number of elements, so O(1) might |
3492 | targeting a specific compiler and compiler-version. |
3611 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
3612 | average it is much faster and asymptotically approaches constant time. |
3493 | |
3613 | |
3494 | Another reason is that some compiler warnings require elaborate |
3614 | =over 4 |
3495 | workarounds, or other changes to the code that make it less clear and less |
|
|
3496 | maintainable. |
|
|
3497 | |
3615 | |
3498 | And of course, some compiler warnings are just plain stupid, or simply |
3616 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3499 | wrong (because they don't actually warn about the condition their message |
|
|
3500 | seems to warn about). |
|
|
3501 | |
3617 | |
3502 | While libev is written to generate as few warnings as possible, |
3618 | This means that, when you have a watcher that triggers in one hour and |
3503 | "warn-free" code is not a goal, and it is recommended not to build libev |
3619 | there are 100 watchers that would trigger before that, then inserting will |
3504 | with any compiler warnings enabled unless you are prepared to cope with |
3620 | have to skip roughly seven (C<ld 100>) of these watchers. |
3505 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3506 | warnings, not errors, or proof of bugs. |
|
|
3507 | |
3621 | |
|
|
3622 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3508 | |
3623 | |
3509 | =head1 VALGRIND |
3624 | That means that changing a timer costs less than removing/adding them, |
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3625 | as only the relative motion in the event queue has to be paid for. |
3510 | |
3626 | |
3511 | Valgrind has a special section here because it is a popular tool that is |
3627 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3512 | highly useful, but valgrind reports are very hard to interpret. |
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3513 | |
3628 | |
3514 | If you think you found a bug (memory leak, uninitialised data access etc.) |
3629 | These just add the watcher into an array or at the head of a list. |
3515 | in libev, then check twice: If valgrind reports something like: |
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3516 | |
3630 | |
3517 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3631 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3518 | ==2274== possibly lost: 0 bytes in 0 blocks. |
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3519 | ==2274== still reachable: 256 bytes in 1 blocks. |
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3520 | |
3632 | |
3521 | Then there is no memory leak. Similarly, under some circumstances, |
3633 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3522 | valgrind might report kernel bugs as if it were a bug in libev, or it |
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3523 | might be confused (it is a very good tool, but only a tool). |
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3524 | |
3634 | |
3525 | If you are unsure about something, feel free to contact the mailing list |
3635 | These watchers are stored in lists, so they need to be walked to find the |
3526 | with the full valgrind report and an explanation on why you think this is |
3636 | correct watcher to remove. The lists are usually short (you don't usually |
3527 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
3637 | have many watchers waiting for the same fd or signal: one is typical, two |
3528 | no bug" answer and take the chance of learning how to interpret valgrind |
3638 | is rare). |
3529 | properly. |
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3530 | |
3639 | |
3531 | If you need, for some reason, empty reports from valgrind for your project |
3640 | =item Finding the next timer in each loop iteration: O(1) |
3532 | I suggest using suppression lists. |
3641 | |
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3642 | By virtue of using a binary or 4-heap, the next timer is always found at a |
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3643 | fixed position in the storage array. |
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3644 | |
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3645 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
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3646 | |
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3647 | A change means an I/O watcher gets started or stopped, which requires |
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3648 | libev to recalculate its status (and possibly tell the kernel, depending |
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3649 | on backend and whether C<ev_io_set> was used). |
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3650 | |
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3651 | =item Activating one watcher (putting it into the pending state): O(1) |
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3652 | |
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3653 | =item Priority handling: O(number_of_priorities) |
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3654 | |
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3655 | Priorities are implemented by allocating some space for each |
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3656 | priority. When doing priority-based operations, libev usually has to |
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3657 | linearly search all the priorities, but starting/stopping and activating |
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3658 | watchers becomes O(1) with respect to priority handling. |
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3659 | |
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3660 | =item Sending an ev_async: O(1) |
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3661 | |
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3662 | =item Processing ev_async_send: O(number_of_async_watchers) |
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3663 | |
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3664 | =item Processing signals: O(max_signal_number) |
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3665 | |
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3666 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
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3667 | calls in the current loop iteration. Checking for async and signal events |
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3668 | involves iterating over all running async watchers or all signal numbers. |
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3669 | |
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3670 | =back |
3533 | |
3671 | |
3534 | |
3672 | |
3535 | =head1 AUTHOR |
3673 | =head1 AUTHOR |
3536 | |
3674 | |
3537 | Marc Lehmann <libev@schmorp.de>. |
3675 | Marc Lehmann <libev@schmorp.de>. |