… | |
… | |
17 | ev_timer timeout_watcher; |
17 | ev_timer timeout_watcher; |
18 | |
18 | |
19 | // all watcher callbacks have a similar signature |
19 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
20 | // this callback is called when data is readable on stdin |
21 | static void |
21 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
22 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
23 | { |
24 | puts ("stdin ready"); |
24 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
25 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
26 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
27 | ev_io_stop (EV_A_ w); |
… | |
… | |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
31 | } |
31 | } |
32 | |
32 | |
33 | // another callback, this time for a time-out |
33 | // another callback, this time for a time-out |
34 | static void |
34 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
35 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
36 | { |
37 | puts ("timeout"); |
37 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
38 | // this causes the innermost ev_loop to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
40 | } |
40 | } |
41 | |
41 | |
42 | int |
42 | int |
43 | main (void) |
43 | main (void) |
44 | { |
44 | { |
45 | // use the default event loop unless you have special needs |
45 | // use the default event loop unless you have special needs |
46 | struct ev_loop *loop = ev_default_loop (0); |
46 | ev_loop *loop = ev_default_loop (0); |
47 | |
47 | |
48 | // initialise an io watcher, then start it |
48 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
49 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
51 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
103 | Libev is very configurable. In this manual the default (and most common) |
103 | Libev is very configurable. In this manual the default (and most common) |
104 | configuration will be described, which supports multiple event loops. For |
104 | configuration will be described, which supports multiple event loops. For |
105 | more info about various configuration options please have a look at |
105 | more info about various configuration options please have a look at |
106 | B<EMBED> section in this manual. If libev was configured without support |
106 | B<EMBED> section in this manual. If libev was configured without support |
107 | for multiple event loops, then all functions taking an initial argument of |
107 | for multiple event loops, then all functions taking an initial argument of |
108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
108 | name C<loop> (which is always of type C<ev_loop *>) will not have |
109 | this argument. |
109 | this argument. |
110 | |
110 | |
111 | =head2 TIME REPRESENTATION |
111 | =head2 TIME REPRESENTATION |
112 | |
112 | |
113 | Libev represents time as a single floating point number, representing the |
113 | Libev represents time as a single floating point number, representing the |
… | |
… | |
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 |
… | |
… | |
276 | |
276 | |
277 | =back |
277 | =back |
278 | |
278 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
280 | |
280 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
281 | An event loop is described by a C<ev_loop *>. The library knows two |
282 | types of such loops, the I<default> loop, which supports signals and child |
282 | types of such loops, the I<default> loop, which supports signals and child |
283 | events, and dynamically created loops which do not. |
283 | events, and dynamically created loops which do not. |
284 | |
284 | |
285 | =over 4 |
285 | =over 4 |
286 | |
286 | |
… | |
… | |
396 | Please note that epoll sometimes generates spurious notifications, so you |
396 | Please note that epoll sometimes generates spurious notifications, so you |
397 | 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 |
398 | (or space) is available. |
398 | (or space) is available. |
399 | |
399 | |
400 | Best performance from this backend is achieved by not unregistering all |
400 | Best performance from this backend is achieved by not unregistering all |
401 | 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, |
402 | 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. |
403 | |
405 | |
404 | 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 |
405 | all kernel versions tested so far. |
407 | all kernel versions tested so far. |
406 | |
408 | |
407 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
409 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
408 | C<EVBACKEND_POLL>. |
410 | C<EVBACKEND_POLL>. |
409 | |
411 | |
410 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
412 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
411 | |
413 | |
412 | 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 |
413 | 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 |
414 | 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 |
415 | 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 |
416 | 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 |
417 | 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. |
418 | system like NetBSD. |
|
|
419 | |
420 | |
420 | 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 |
421 | 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 |
422 | the target platform). See C<ev_embed> watchers for more info. |
423 | the target platform). See C<ev_embed> watchers for more info. |
423 | |
424 | |
424 | 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 |
425 | 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 |
426 | 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 |
427 | 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 |
428 | 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 |
429 | drops fds silently in similarly hard-to-detect cases. |
430 | drops fds silently in similarly hard-to-detect cases. |
430 | |
431 | |
431 | This backend usually performs well under most conditions. |
432 | This backend usually performs well under most conditions. |
432 | |
433 | |
433 | While nominally embeddable in other event loops, this doesn't work |
434 | While nominally embeddable in other event loops, this doesn't work |
434 | 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 |
435 | 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 |
436 | (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 |
437 | (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, |
438 | sockets. |
439 | using it only for sockets. |
439 | |
440 | |
440 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
441 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
441 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
442 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
442 | C<NOTE_EOF>. |
443 | C<NOTE_EOF>. |
443 | |
444 | |
… | |
… | |
460 | 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 |
461 | 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 |
462 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
463 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
463 | might perform better. |
464 | might perform better. |
464 | |
465 | |
465 | On the positive side, ignoring the spurious readiness notifications, this |
466 | On the positive side, with the exception of the spurious readiness |
466 | backend actually performed to specification in all tests and is fully |
467 | notifications, this backend actually performed fully to specification |
467 | 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. |
468 | |
470 | |
469 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
471 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
470 | C<EVBACKEND_POLL>. |
472 | C<EVBACKEND_POLL>. |
471 | |
473 | |
472 | =item C<EVBACKEND_ALL> |
474 | =item C<EVBACKEND_ALL> |
… | |
… | |
481 | |
483 | |
482 | 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 |
483 | 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 |
484 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
486 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
485 | |
487 | |
486 | The most typical usage is like this: |
488 | Example: This is the most typical usage. |
487 | |
489 | |
488 | if (!ev_default_loop (0)) |
490 | if (!ev_default_loop (0)) |
489 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
491 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
490 | |
492 | |
491 | 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 |
492 | environment settings to be taken into account: |
494 | environment settings to be taken into account: |
493 | |
495 | |
494 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
496 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
495 | |
497 | |
496 | 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 |
497 | available (warning, breaks stuff, best use only with your own private |
499 | used if available (warning, breaks stuff, best use only with your own |
498 | 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): |
499 | |
502 | |
500 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
503 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
501 | |
504 | |
502 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
505 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
503 | |
506 | |
… | |
… | |
561 | |
564 | |
562 | =item ev_loop_fork (loop) |
565 | =item ev_loop_fork (loop) |
563 | |
566 | |
564 | 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 |
565 | 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 |
566 | 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. |
567 | |
571 | |
568 | =item int ev_is_default_loop (loop) |
572 | =item int ev_is_default_loop (loop) |
569 | |
573 | |
570 | 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. |
571 | |
576 | |
572 | =item unsigned int ev_loop_count (loop) |
577 | =item unsigned int ev_loop_count (loop) |
573 | |
578 | |
574 | 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 |
575 | 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 |
… | |
… | |
613 | 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 |
614 | 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. |
615 | |
620 | |
616 | 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 |
617 | 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 |
618 | finished (especially in interactive programs), but having a program that |
623 | finished (especially in interactive programs), but having a program |
619 | 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 |
620 | 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. |
621 | |
627 | |
622 | 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 |
623 | 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 |
624 | 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. |
625 | |
632 | |
626 | 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 |
627 | necessary) and will handle those and any outstanding ones. It will block |
634 | necessary) and will handle those and any already outstanding ones. It |
628 | 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 |
629 | 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 |
630 | 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 |
631 | 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 |
632 | usually a better approach for this kind of thing. |
643 | usually a better approach for this kind of thing. |
633 | |
644 | |
634 | Here are the gory details of what C<ev_loop> does: |
645 | Here are the gory details of what C<ev_loop> does: |
635 | |
646 | |
636 | - Before the first iteration, call any pending watchers. |
647 | - Before the first iteration, call any pending watchers. |
… | |
… | |
646 | any active watchers at all will result in not sleeping). |
657 | any active watchers at all will result in not sleeping). |
647 | - Sleep if the I/O and timer collect interval say so. |
658 | - Sleep if the I/O and timer collect interval say so. |
648 | - Block the process, waiting for any events. |
659 | - Block the process, waiting for any events. |
649 | - Queue all outstanding I/O (fd) events. |
660 | - Queue all outstanding I/O (fd) events. |
650 | - 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. |
651 | - Queue all outstanding timers. |
662 | - Queue all expired timers. |
652 | - Queue all outstanding periodics. |
663 | - Queue all expired periodics. |
653 | - Unless any events are pending now, queue all idle watchers. |
664 | - Unless any events are pending now, queue all idle watchers. |
654 | - Queue all check watchers. |
665 | - Queue all check watchers. |
655 | - 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). |
656 | 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 |
657 | be handled here by queueing them when their watcher gets executed. |
668 | be handled here by queueing them when their watcher gets executed. |
… | |
… | |
674 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
685 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
675 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
686 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
676 | |
687 | |
677 | This "unloop state" will be cleared when entering C<ev_loop> again. |
688 | This "unloop state" will be cleared when entering C<ev_loop> again. |
678 | |
689 | |
|
|
690 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
691 | |
679 | =item ev_ref (loop) |
692 | =item ev_ref (loop) |
680 | |
693 | |
681 | =item ev_unref (loop) |
694 | =item ev_unref (loop) |
682 | |
695 | |
683 | Ref/unref can be used to add or remove a reference count on the event |
696 | Ref/unref can be used to add or remove a reference count on the event |
684 | loop: Every watcher keeps one reference, and as long as the reference |
697 | loop: Every watcher keeps one reference, and as long as the reference |
685 | count is nonzero, C<ev_loop> will not return on its own. If you have |
698 | count is nonzero, C<ev_loop> will not return on its own. |
|
|
699 | |
686 | a watcher you never unregister that should not keep C<ev_loop> from |
700 | If you have a watcher you never unregister that should not keep C<ev_loop> |
687 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
701 | from returning, call ev_unref() after starting, and ev_ref() before |
|
|
702 | stopping it. |
|
|
703 | |
688 | example, libev itself uses this for its internal signal pipe: It is not |
704 | As an example, libev itself uses this for its internal signal pipe: It is |
689 | visible to the libev user and should not keep C<ev_loop> from exiting if |
705 | not visible to the libev user and should not keep C<ev_loop> from exiting |
690 | no event watchers registered by it are active. It is also an excellent |
706 | if no event watchers registered by it are active. It is also an excellent |
691 | way to do this for generic recurring timers or from within third-party |
707 | way to do this for generic recurring timers or from within third-party |
692 | libraries. Just remember to I<unref after start> and I<ref before stop> |
708 | libraries. Just remember to I<unref after start> and I<ref before stop> |
693 | (but only if the watcher wasn't active before, or was active before, |
709 | (but only if the watcher wasn't active before, or was active before, |
694 | respectively). |
710 | respectively). |
695 | |
711 | |
696 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
712 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
697 | running when nothing else is active. |
713 | running when nothing else is active. |
698 | |
714 | |
699 | struct ev_signal exitsig; |
715 | ev_signal exitsig; |
700 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
716 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
701 | ev_signal_start (loop, &exitsig); |
717 | ev_signal_start (loop, &exitsig); |
702 | evf_unref (loop); |
718 | evf_unref (loop); |
703 | |
719 | |
704 | Example: For some weird reason, unregister the above signal handler again. |
720 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
718 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
734 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
719 | allows libev to delay invocation of I/O and timer/periodic callbacks |
735 | allows libev to delay invocation of I/O and timer/periodic callbacks |
720 | to increase efficiency of loop iterations (or to increase power-saving |
736 | to increase efficiency of loop iterations (or to increase power-saving |
721 | opportunities). |
737 | opportunities). |
722 | |
738 | |
723 | The background is that sometimes your program runs just fast enough to |
739 | The idea is that sometimes your program runs just fast enough to handle |
724 | handle one (or very few) event(s) per loop iteration. While this makes |
740 | one (or very few) event(s) per loop iteration. While this makes the |
725 | the program responsive, it also wastes a lot of CPU time to poll for new |
741 | program responsive, it also wastes a lot of CPU time to poll for new |
726 | events, especially with backends like C<select ()> which have a high |
742 | events, especially with backends like C<select ()> which have a high |
727 | overhead for the actual polling but can deliver many events at once. |
743 | overhead for the actual polling but can deliver many events at once. |
728 | |
744 | |
729 | By setting a higher I<io collect interval> you allow libev to spend more |
745 | By setting a higher I<io collect interval> you allow libev to spend more |
730 | time collecting I/O events, so you can handle more events per iteration, |
746 | time collecting I/O events, so you can handle more events per iteration, |
… | |
… | |
732 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
748 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
733 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
749 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
734 | |
750 | |
735 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
751 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
736 | to spend more time collecting timeouts, at the expense of increased |
752 | to spend more time collecting timeouts, at the expense of increased |
737 | latency (the watcher callback will be called later). C<ev_io> watchers |
753 | latency/jitter/inexactness (the watcher callback will be called |
738 | will not be affected. Setting this to a non-null value will not introduce |
754 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
739 | any overhead in libev. |
755 | value will not introduce any overhead in libev. |
740 | |
756 | |
741 | Many (busy) programs can usually benefit by setting the I/O collect |
757 | Many (busy) programs can usually benefit by setting the I/O collect |
742 | interval to a value near C<0.1> or so, which is often enough for |
758 | interval to a value near C<0.1> or so, which is often enough for |
743 | interactive servers (of course not for games), likewise for timeouts. It |
759 | interactive servers (of course not for games), likewise for timeouts. It |
744 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
760 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
… | |
… | |
752 | they fire on, say, one-second boundaries only. |
768 | they fire on, say, one-second boundaries only. |
753 | |
769 | |
754 | =item ev_loop_verify (loop) |
770 | =item ev_loop_verify (loop) |
755 | |
771 | |
756 | This function only does something when C<EV_VERIFY> support has been |
772 | This function only does something when C<EV_VERIFY> support has been |
757 | compiled in. It tries to go through all internal structures and checks |
773 | compiled in. which is the default for non-minimal builds. It tries to go |
758 | them for validity. If anything is found to be inconsistent, it will print |
774 | through all internal structures and checks them for validity. If anything |
759 | an error message to standard error and call C<abort ()>. |
775 | is found to be inconsistent, it will print an error message to standard |
|
|
776 | error and call C<abort ()>. |
760 | |
777 | |
761 | This can be used to catch bugs inside libev itself: under normal |
778 | This can be used to catch bugs inside libev itself: under normal |
762 | circumstances, this function will never abort as of course libev keeps its |
779 | circumstances, this function will never abort as of course libev keeps its |
763 | data structures consistent. |
780 | data structures consistent. |
764 | |
781 | |
… | |
… | |
769 | |
786 | |
770 | A watcher is a structure that you create and register to record your |
787 | A watcher is a structure that you create and register to record your |
771 | interest in some event. For instance, if you want to wait for STDIN to |
788 | interest in some event. For instance, if you want to wait for STDIN to |
772 | become readable, you would create an C<ev_io> watcher for that: |
789 | become readable, you would create an C<ev_io> watcher for that: |
773 | |
790 | |
774 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
791 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
775 | { |
792 | { |
776 | ev_io_stop (w); |
793 | ev_io_stop (w); |
777 | ev_unloop (loop, EVUNLOOP_ALL); |
794 | ev_unloop (loop, EVUNLOOP_ALL); |
778 | } |
795 | } |
779 | |
796 | |
780 | struct ev_loop *loop = ev_default_loop (0); |
797 | struct ev_loop *loop = ev_default_loop (0); |
781 | struct ev_io stdin_watcher; |
798 | ev_io stdin_watcher; |
782 | ev_init (&stdin_watcher, my_cb); |
799 | ev_init (&stdin_watcher, my_cb); |
783 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
800 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
784 | ev_io_start (loop, &stdin_watcher); |
801 | ev_io_start (loop, &stdin_watcher); |
785 | ev_loop (loop, 0); |
802 | ev_loop (loop, 0); |
786 | |
803 | |
… | |
… | |
877 | =item C<EV_ERROR> |
894 | =item C<EV_ERROR> |
878 | |
895 | |
879 | An unspecified error has occurred, the watcher has been stopped. This might |
896 | An unspecified error has occurred, the watcher has been stopped. This might |
880 | happen because the watcher could not be properly started because libev |
897 | happen because the watcher could not be properly started because libev |
881 | ran out of memory, a file descriptor was found to be closed or any other |
898 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
899 | problem. Libev considers these application bugs. |
|
|
900 | |
882 | problem. You best act on it by reporting the problem and somehow coping |
901 | You best act on it by reporting the problem and somehow coping with the |
883 | with the watcher being stopped. |
902 | watcher being stopped. Note that well-written programs should not receive |
|
|
903 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
904 | bug in your program. |
884 | |
905 | |
885 | Libev will usually signal a few "dummy" events together with an error, |
906 | Libev will usually signal a few "dummy" events together with an error, for |
886 | for example it might indicate that a fd is readable or writable, and if |
907 | example it might indicate that a fd is readable or writable, and if your |
887 | your callbacks is well-written it can just attempt the operation and cope |
908 | callbacks is well-written it can just attempt the operation and cope with |
888 | with the error from read() or write(). This will not work in multi-threaded |
909 | the error from read() or write(). This will not work in multi-threaded |
889 | programs, though, so beware. |
910 | programs, though, as the fd could already be closed and reused for another |
|
|
911 | thing, so beware. |
890 | |
912 | |
891 | =back |
913 | =back |
892 | |
914 | |
893 | =head2 GENERIC WATCHER FUNCTIONS |
915 | =head2 GENERIC WATCHER FUNCTIONS |
894 | |
916 | |
… | |
… | |
907 | which rolls both calls into one. |
929 | which rolls both calls into one. |
908 | |
930 | |
909 | You can reinitialise a watcher at any time as long as it has been stopped |
931 | You can reinitialise a watcher at any time as long as it has been stopped |
910 | (or never started) and there are no pending events outstanding. |
932 | (or never started) and there are no pending events outstanding. |
911 | |
933 | |
912 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
934 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
913 | int revents)>. |
935 | int revents)>. |
|
|
936 | |
|
|
937 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
938 | |
|
|
939 | ev_io w; |
|
|
940 | ev_init (&w, my_cb); |
|
|
941 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
914 | |
942 | |
915 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
943 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
916 | |
944 | |
917 | This macro initialises the type-specific parts of a watcher. You need to |
945 | This macro initialises the type-specific parts of a watcher. You need to |
918 | call C<ev_init> at least once before you call this macro, but you can |
946 | call C<ev_init> at least once before you call this macro, but you can |
… | |
… | |
921 | difference to the C<ev_init> macro). |
949 | difference to the C<ev_init> macro). |
922 | |
950 | |
923 | Although some watcher types do not have type-specific arguments |
951 | Although some watcher types do not have type-specific arguments |
924 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
952 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
925 | |
953 | |
|
|
954 | See C<ev_init>, above, for an example. |
|
|
955 | |
926 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
956 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
927 | |
957 | |
928 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
958 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
929 | calls into a single call. This is the most convenient method to initialise |
959 | calls into a single call. This is the most convenient method to initialise |
930 | a watcher. The same limitations apply, of course. |
960 | a watcher. The same limitations apply, of course. |
931 | |
961 | |
|
|
962 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
963 | |
|
|
964 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
965 | |
932 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
966 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
933 | |
967 | |
934 | Starts (activates) the given watcher. Only active watchers will receive |
968 | Starts (activates) the given watcher. Only active watchers will receive |
935 | events. If the watcher is already active nothing will happen. |
969 | events. If the watcher is already active nothing will happen. |
936 | |
970 | |
|
|
971 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
972 | whole section. |
|
|
973 | |
|
|
974 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
975 | |
937 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
976 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
938 | |
977 | |
939 | Stops the given watcher again (if active) and clears the pending |
978 | Stops the given watcher if active, and clears the pending status (whether |
|
|
979 | the watcher was active or not). |
|
|
980 | |
940 | status. It is possible that stopped watchers are pending (for example, |
981 | It is possible that stopped watchers are pending - for example, |
941 | non-repeating timers are being stopped when they become pending), but |
982 | non-repeating timers are being stopped when they become pending - but |
942 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
983 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
943 | you want to free or reuse the memory used by the watcher it is therefore a |
984 | pending. If you want to free or reuse the memory used by the watcher it is |
944 | good idea to always call its C<ev_TYPE_stop> function. |
985 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
945 | |
986 | |
946 | =item bool ev_is_active (ev_TYPE *watcher) |
987 | =item bool ev_is_active (ev_TYPE *watcher) |
947 | |
988 | |
948 | Returns a true value iff the watcher is active (i.e. it has been started |
989 | Returns a true value iff the watcher is active (i.e. it has been started |
949 | and not yet been stopped). As long as a watcher is active you must not modify |
990 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
997 | |
1038 | |
998 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1039 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
999 | |
1040 | |
1000 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1041 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1001 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1042 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1002 | can deal with that fact. |
1043 | can deal with that fact, as both are simply passed through to the |
|
|
1044 | callback. |
1003 | |
1045 | |
1004 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1046 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1005 | |
1047 | |
1006 | If the watcher is pending, this function returns clears its pending status |
1048 | If the watcher is pending, this function clears its pending status and |
1007 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1049 | returns its C<revents> bitset (as if its callback was invoked). If the |
1008 | watcher isn't pending it does nothing and returns C<0>. |
1050 | watcher isn't pending it does nothing and returns C<0>. |
1009 | |
1051 | |
|
|
1052 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1053 | callback to be invoked, which can be accomplished with this function. |
|
|
1054 | |
1010 | =back |
1055 | =back |
1011 | |
1056 | |
1012 | |
1057 | |
1013 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1058 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1014 | |
1059 | |
1015 | Each watcher has, by default, a member C<void *data> that you can change |
1060 | Each watcher has, by default, a member C<void *data> that you can change |
1016 | and read at any time, libev will completely ignore it. This can be used |
1061 | and read at any time: libev will completely ignore it. This can be used |
1017 | to associate arbitrary data with your watcher. If you need more data and |
1062 | to associate arbitrary data with your watcher. If you need more data and |
1018 | don't want to allocate memory and store a pointer to it in that data |
1063 | don't want to allocate memory and store a pointer to it in that data |
1019 | member, you can also "subclass" the watcher type and provide your own |
1064 | member, you can also "subclass" the watcher type and provide your own |
1020 | data: |
1065 | data: |
1021 | |
1066 | |
1022 | struct my_io |
1067 | struct my_io |
1023 | { |
1068 | { |
1024 | struct ev_io io; |
1069 | ev_io io; |
1025 | int otherfd; |
1070 | int otherfd; |
1026 | void *somedata; |
1071 | void *somedata; |
1027 | struct whatever *mostinteresting; |
1072 | struct whatever *mostinteresting; |
1028 | }; |
1073 | }; |
1029 | |
1074 | |
… | |
… | |
1032 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1077 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1033 | |
1078 | |
1034 | And since your callback will be called with a pointer to the watcher, you |
1079 | And since your callback will be called with a pointer to the watcher, you |
1035 | can cast it back to your own type: |
1080 | can cast it back to your own type: |
1036 | |
1081 | |
1037 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1082 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1038 | { |
1083 | { |
1039 | struct my_io *w = (struct my_io *)w_; |
1084 | struct my_io *w = (struct my_io *)w_; |
1040 | ... |
1085 | ... |
1041 | } |
1086 | } |
1042 | |
1087 | |
… | |
… | |
1053 | ev_timer t2; |
1098 | ev_timer t2; |
1054 | } |
1099 | } |
1055 | |
1100 | |
1056 | In this case getting the pointer to C<my_biggy> is a bit more |
1101 | In this case getting the pointer to C<my_biggy> is a bit more |
1057 | complicated: Either you store the address of your C<my_biggy> struct |
1102 | complicated: Either you store the address of your C<my_biggy> struct |
1058 | in the C<data> member of the watcher, or you need to use some pointer |
1103 | in the C<data> member of the watcher (for woozies), or you need to use |
1059 | arithmetic using C<offsetof> inside your watchers: |
1104 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1105 | programmers): |
1060 | |
1106 | |
1061 | #include <stddef.h> |
1107 | #include <stddef.h> |
1062 | |
1108 | |
1063 | static void |
1109 | static void |
1064 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1110 | t1_cb (EV_P_ ev_timer *w, int revents) |
1065 | { |
1111 | { |
1066 | struct my_biggy big = (struct my_biggy * |
1112 | struct my_biggy big = (struct my_biggy * |
1067 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1113 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1068 | } |
1114 | } |
1069 | |
1115 | |
1070 | static void |
1116 | static void |
1071 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1117 | t2_cb (EV_P_ ev_timer *w, int revents) |
1072 | { |
1118 | { |
1073 | struct my_biggy big = (struct my_biggy * |
1119 | struct my_biggy big = (struct my_biggy * |
1074 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1120 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1075 | } |
1121 | } |
1076 | |
1122 | |
… | |
… | |
1104 | In general you can register as many read and/or write event watchers per |
1150 | In general you can register as many read and/or write event watchers per |
1105 | fd as you want (as long as you don't confuse yourself). Setting all file |
1151 | fd as you want (as long as you don't confuse yourself). Setting all file |
1106 | descriptors to non-blocking mode is also usually a good idea (but not |
1152 | descriptors to non-blocking mode is also usually a good idea (but not |
1107 | required if you know what you are doing). |
1153 | required if you know what you are doing). |
1108 | |
1154 | |
1109 | If you must do this, then force the use of a known-to-be-good backend |
1155 | If you cannot use non-blocking mode, then force the use of a |
1110 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1156 | known-to-be-good backend (at the time of this writing, this includes only |
1111 | C<EVBACKEND_POLL>). |
1157 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1112 | |
1158 | |
1113 | Another thing you have to watch out for is that it is quite easy to |
1159 | Another thing you have to watch out for is that it is quite easy to |
1114 | receive "spurious" readiness notifications, that is your callback might |
1160 | receive "spurious" readiness notifications, that is your callback might |
1115 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1161 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1116 | because there is no data. Not only are some backends known to create a |
1162 | because there is no data. Not only are some backends known to create a |
1117 | lot of those (for example Solaris ports), it is very easy to get into |
1163 | lot of those (for example Solaris ports), it is very easy to get into |
1118 | this situation even with a relatively standard program structure. Thus |
1164 | this situation even with a relatively standard program structure. Thus |
1119 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1165 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1120 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1166 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1121 | |
1167 | |
1122 | If you cannot run the fd in non-blocking mode (for example you should not |
1168 | If you cannot run the fd in non-blocking mode (for example you should |
1123 | play around with an Xlib connection), then you have to separately re-test |
1169 | not play around with an Xlib connection), then you have to separately |
1124 | whether a file descriptor is really ready with a known-to-be good interface |
1170 | re-test whether a file descriptor is really ready with a known-to-be good |
1125 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1171 | interface such as poll (fortunately in our Xlib example, Xlib already |
1126 | its own, so its quite safe to use). |
1172 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1173 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1174 | indefinitely. |
|
|
1175 | |
|
|
1176 | But really, best use non-blocking mode. |
1127 | |
1177 | |
1128 | =head3 The special problem of disappearing file descriptors |
1178 | =head3 The special problem of disappearing file descriptors |
1129 | |
1179 | |
1130 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1180 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1131 | descriptor (either by calling C<close> explicitly or by any other means, |
1181 | descriptor (either due to calling C<close> explicitly or any other means, |
1132 | such as C<dup>). The reason is that you register interest in some file |
1182 | such as C<dup2>). The reason is that you register interest in some file |
1133 | descriptor, but when it goes away, the operating system will silently drop |
1183 | descriptor, but when it goes away, the operating system will silently drop |
1134 | this interest. If another file descriptor with the same number then is |
1184 | this interest. If another file descriptor with the same number then is |
1135 | registered with libev, there is no efficient way to see that this is, in |
1185 | registered with libev, there is no efficient way to see that this is, in |
1136 | fact, a different file descriptor. |
1186 | fact, a different file descriptor. |
1137 | |
1187 | |
… | |
… | |
1168 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1218 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1169 | C<EVBACKEND_POLL>. |
1219 | C<EVBACKEND_POLL>. |
1170 | |
1220 | |
1171 | =head3 The special problem of SIGPIPE |
1221 | =head3 The special problem of SIGPIPE |
1172 | |
1222 | |
1173 | While not really specific to libev, it is easy to forget about SIGPIPE: |
1223 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1174 | when writing to a pipe whose other end has been closed, your program gets |
1224 | when writing to a pipe whose other end has been closed, your program gets |
1175 | send a SIGPIPE, which, by default, aborts your program. For most programs |
1225 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
1176 | this is sensible behaviour, for daemons, this is usually undesirable. |
1226 | this is sensible behaviour, for daemons, this is usually undesirable. |
1177 | |
1227 | |
1178 | So when you encounter spurious, unexplained daemon exits, make sure you |
1228 | So when you encounter spurious, unexplained daemon exits, make sure you |
1179 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1229 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1180 | somewhere, as that would have given you a big clue). |
1230 | somewhere, as that would have given you a big clue). |
… | |
… | |
1187 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1237 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1188 | |
1238 | |
1189 | =item ev_io_set (ev_io *, int fd, int events) |
1239 | =item ev_io_set (ev_io *, int fd, int events) |
1190 | |
1240 | |
1191 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1241 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1192 | receive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1242 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1193 | C<EV_READ | EV_WRITE> to receive the given events. |
1243 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1194 | |
1244 | |
1195 | =item int fd [read-only] |
1245 | =item int fd [read-only] |
1196 | |
1246 | |
1197 | The file descriptor being watched. |
1247 | The file descriptor being watched. |
1198 | |
1248 | |
… | |
… | |
1207 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1257 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1208 | readable, but only once. Since it is likely line-buffered, you could |
1258 | readable, but only once. Since it is likely line-buffered, you could |
1209 | attempt to read a whole line in the callback. |
1259 | attempt to read a whole line in the callback. |
1210 | |
1260 | |
1211 | static void |
1261 | static void |
1212 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1262 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1213 | { |
1263 | { |
1214 | ev_io_stop (loop, w); |
1264 | ev_io_stop (loop, w); |
1215 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1265 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1216 | } |
1266 | } |
1217 | |
1267 | |
1218 | ... |
1268 | ... |
1219 | struct ev_loop *loop = ev_default_init (0); |
1269 | struct ev_loop *loop = ev_default_init (0); |
1220 | struct ev_io stdin_readable; |
1270 | ev_io stdin_readable; |
1221 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1271 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1222 | ev_io_start (loop, &stdin_readable); |
1272 | ev_io_start (loop, &stdin_readable); |
1223 | ev_loop (loop, 0); |
1273 | ev_loop (loop, 0); |
1224 | |
1274 | |
1225 | |
1275 | |
… | |
… | |
1228 | Timer watchers are simple relative timers that generate an event after a |
1278 | Timer watchers are simple relative timers that generate an event after a |
1229 | given time, and optionally repeating in regular intervals after that. |
1279 | given time, and optionally repeating in regular intervals after that. |
1230 | |
1280 | |
1231 | The timers are based on real time, that is, if you register an event that |
1281 | The timers are based on real time, that is, if you register an event that |
1232 | times out after an hour and you reset your system clock to January last |
1282 | times out after an hour and you reset your system clock to January last |
1233 | year, it will still time out after (roughly) and hour. "Roughly" because |
1283 | year, it will still time out after (roughly) one hour. "Roughly" because |
1234 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1284 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1235 | monotonic clock option helps a lot here). |
1285 | monotonic clock option helps a lot here). |
1236 | |
1286 | |
1237 | The callback is guaranteed to be invoked only after its timeout has passed, |
1287 | The callback is guaranteed to be invoked only I<after> its timeout has |
1238 | but if multiple timers become ready during the same loop iteration then |
1288 | passed, but if multiple timers become ready during the same loop iteration |
1239 | order of execution is undefined. |
1289 | then order of execution is undefined. |
|
|
1290 | |
|
|
1291 | =head3 Be smart about timeouts |
|
|
1292 | |
|
|
1293 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1294 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1295 | you want to raise some error after a while. |
|
|
1296 | |
|
|
1297 | What follows are some ways to handle this problem, from obvious and |
|
|
1298 | inefficient to smart and efficient. |
|
|
1299 | |
|
|
1300 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1301 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1302 | data or other life sign was received). |
|
|
1303 | |
|
|
1304 | =over 4 |
|
|
1305 | |
|
|
1306 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1307 | |
|
|
1308 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1309 | start the watcher: |
|
|
1310 | |
|
|
1311 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1312 | ev_timer_start (loop, timer); |
|
|
1313 | |
|
|
1314 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1315 | and start it again: |
|
|
1316 | |
|
|
1317 | ev_timer_stop (loop, timer); |
|
|
1318 | ev_timer_set (timer, 60., 0.); |
|
|
1319 | ev_timer_start (loop, timer); |
|
|
1320 | |
|
|
1321 | This is relatively simple to implement, but means that each time there is |
|
|
1322 | some activity, libev will first have to remove the timer from its internal |
|
|
1323 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1324 | still not a constant-time operation. |
|
|
1325 | |
|
|
1326 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1327 | |
|
|
1328 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1329 | C<ev_timer_start>. |
|
|
1330 | |
|
|
1331 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1332 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1333 | successfully read or write some data. If you go into an idle state where |
|
|
1334 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1335 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1336 | |
|
|
1337 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1338 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1339 | member and C<ev_timer_again>. |
|
|
1340 | |
|
|
1341 | At start: |
|
|
1342 | |
|
|
1343 | ev_timer_init (timer, callback); |
|
|
1344 | timer->repeat = 60.; |
|
|
1345 | ev_timer_again (loop, timer); |
|
|
1346 | |
|
|
1347 | Each time there is some activity: |
|
|
1348 | |
|
|
1349 | ev_timer_again (loop, timer); |
|
|
1350 | |
|
|
1351 | It is even possible to change the time-out on the fly, regardless of |
|
|
1352 | whether the watcher is active or not: |
|
|
1353 | |
|
|
1354 | timer->repeat = 30.; |
|
|
1355 | ev_timer_again (loop, timer); |
|
|
1356 | |
|
|
1357 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1358 | you want to modify its timeout value, as libev does not have to completely |
|
|
1359 | remove and re-insert the timer from/into its internal data structure. |
|
|
1360 | |
|
|
1361 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1362 | |
|
|
1363 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1364 | |
|
|
1365 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1366 | relatively long compared to the intervals between other activity - in |
|
|
1367 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1368 | associated activity resets. |
|
|
1369 | |
|
|
1370 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1371 | but remember the time of last activity, and check for a real timeout only |
|
|
1372 | within the callback: |
|
|
1373 | |
|
|
1374 | ev_tstamp last_activity; // time of last activity |
|
|
1375 | |
|
|
1376 | static void |
|
|
1377 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1378 | { |
|
|
1379 | ev_tstamp now = ev_now (EV_A); |
|
|
1380 | ev_tstamp timeout = last_activity + 60.; |
|
|
1381 | |
|
|
1382 | // if last_activity + 60. is older than now, we did time out |
|
|
1383 | if (timeout < now) |
|
|
1384 | { |
|
|
1385 | // timeout occured, take action |
|
|
1386 | } |
|
|
1387 | else |
|
|
1388 | { |
|
|
1389 | // callback was invoked, but there was some activity, re-arm |
|
|
1390 | // the watcher to fire in last_activity + 60, which is |
|
|
1391 | // guaranteed to be in the future, so "again" is positive: |
|
|
1392 | w->again = timeout - now; |
|
|
1393 | ev_timer_again (EV_A_ w); |
|
|
1394 | } |
|
|
1395 | } |
|
|
1396 | |
|
|
1397 | To summarise the callback: first calculate the real timeout (defined |
|
|
1398 | as "60 seconds after the last activity"), then check if that time has |
|
|
1399 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1400 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1401 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1402 | a timeout then. |
|
|
1403 | |
|
|
1404 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1405 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1406 | |
|
|
1407 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1408 | minus half the average time between activity), but virtually no calls to |
|
|
1409 | libev to change the timeout. |
|
|
1410 | |
|
|
1411 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1412 | to the current time (meaning we just have some activity :), then call the |
|
|
1413 | callback, which will "do the right thing" and start the timer: |
|
|
1414 | |
|
|
1415 | ev_timer_init (timer, callback); |
|
|
1416 | last_activity = ev_now (loop); |
|
|
1417 | callback (loop, timer, EV_TIMEOUT); |
|
|
1418 | |
|
|
1419 | And when there is some activity, simply store the current time in |
|
|
1420 | C<last_activity>, no libev calls at all: |
|
|
1421 | |
|
|
1422 | last_actiivty = ev_now (loop); |
|
|
1423 | |
|
|
1424 | This technique is slightly more complex, but in most cases where the |
|
|
1425 | time-out is unlikely to be triggered, much more efficient. |
|
|
1426 | |
|
|
1427 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1428 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1429 | fix things for you. |
|
|
1430 | |
|
|
1431 | =item 4. Whee, use a double-linked list for your timeouts. |
|
|
1432 | |
|
|
1433 | If there is not one request, but many thousands, all employing some kind |
|
|
1434 | of timeout with the same timeout value, then one can do even better: |
|
|
1435 | |
|
|
1436 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1437 | at the I<end> of the list. |
|
|
1438 | |
|
|
1439 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1440 | the list is expected to fire (for example, using the technique #3). |
|
|
1441 | |
|
|
1442 | When there is some activity, remove the timer from the list, recalculate |
|
|
1443 | the timeout, append it to the end of the list again, and make sure to |
|
|
1444 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1445 | |
|
|
1446 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1447 | starting, stopping and updating the timers, at the expense of a major |
|
|
1448 | complication, and having to use a constant timeout. The constant timeout |
|
|
1449 | ensures that the list stays sorted. |
|
|
1450 | |
|
|
1451 | =back |
|
|
1452 | |
|
|
1453 | So what method is the best? |
|
|
1454 | |
|
|
1455 | The method #2 is a simple no-brain-required solution that is adequate in |
|
|
1456 | most situations. Method #3 requires a bit more thinking, but handles many |
|
|
1457 | cases better, and isn't very complicated either. In most case, choosing |
|
|
1458 | either one is fine. |
|
|
1459 | |
|
|
1460 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1461 | rather complicated, but extremely efficient, something that really pays |
|
|
1462 | off after the first or so million of active timers, i.e. it's usually |
|
|
1463 | overkill :) |
1240 | |
1464 | |
1241 | =head3 The special problem of time updates |
1465 | =head3 The special problem of time updates |
1242 | |
1466 | |
1243 | Establishing the current time is a costly operation (it usually takes at |
1467 | Establishing the current time is a costly operation (it usually takes at |
1244 | least two system calls): EV therefore updates its idea of the current |
1468 | least two system calls): EV therefore updates its idea of the current |
1245 | time only before and after C<ev_loop> polls for new events, which causes |
1469 | time only before and after C<ev_loop> collects new events, which causes a |
1246 | a growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1470 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1247 | lots of events. |
1471 | lots of events in one iteration. |
1248 | |
1472 | |
1249 | The relative timeouts are calculated relative to the C<ev_now ()> |
1473 | The relative timeouts are calculated relative to the C<ev_now ()> |
1250 | time. This is usually the right thing as this timestamp refers to the time |
1474 | time. This is usually the right thing as this timestamp refers to the time |
1251 | of the event triggering whatever timeout you are modifying/starting. If |
1475 | of the event triggering whatever timeout you are modifying/starting. If |
1252 | you suspect event processing to be delayed and you I<need> to base the |
1476 | you suspect event processing to be delayed and you I<need> to base the |
… | |
… | |
1288 | If the timer is started but non-repeating, stop it (as if it timed out). |
1512 | If the timer is started but non-repeating, stop it (as if it timed out). |
1289 | |
1513 | |
1290 | If the timer is repeating, either start it if necessary (with the |
1514 | If the timer is repeating, either start it if necessary (with the |
1291 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1515 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1292 | |
1516 | |
1293 | This sounds a bit complicated, but here is a useful and typical |
1517 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1294 | example: Imagine you have a TCP connection and you want a so-called idle |
1518 | usage example. |
1295 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1296 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1297 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1298 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1299 | you go into an idle state where you do not expect data to travel on the |
|
|
1300 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1301 | automatically restart it if need be. |
|
|
1302 | |
|
|
1303 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1304 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1305 | |
|
|
1306 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1307 | ev_timer_again (loop, timer); |
|
|
1308 | ... |
|
|
1309 | timer->again = 17.; |
|
|
1310 | ev_timer_again (loop, timer); |
|
|
1311 | ... |
|
|
1312 | timer->again = 10.; |
|
|
1313 | ev_timer_again (loop, timer); |
|
|
1314 | |
|
|
1315 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1316 | you want to modify its timeout value. |
|
|
1317 | |
1519 | |
1318 | =item ev_tstamp repeat [read-write] |
1520 | =item ev_tstamp repeat [read-write] |
1319 | |
1521 | |
1320 | The current C<repeat> value. Will be used each time the watcher times out |
1522 | The current C<repeat> value. Will be used each time the watcher times out |
1321 | or C<ev_timer_again> is called and determines the next timeout (if any), |
1523 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1322 | which is also when any modifications are taken into account. |
1524 | which is also when any modifications are taken into account. |
1323 | |
1525 | |
1324 | =back |
1526 | =back |
1325 | |
1527 | |
1326 | =head3 Examples |
1528 | =head3 Examples |
1327 | |
1529 | |
1328 | Example: Create a timer that fires after 60 seconds. |
1530 | Example: Create a timer that fires after 60 seconds. |
1329 | |
1531 | |
1330 | static void |
1532 | static void |
1331 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1533 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1332 | { |
1534 | { |
1333 | .. one minute over, w is actually stopped right here |
1535 | .. one minute over, w is actually stopped right here |
1334 | } |
1536 | } |
1335 | |
1537 | |
1336 | struct ev_timer mytimer; |
1538 | ev_timer mytimer; |
1337 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1539 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1338 | ev_timer_start (loop, &mytimer); |
1540 | ev_timer_start (loop, &mytimer); |
1339 | |
1541 | |
1340 | Example: Create a timeout timer that times out after 10 seconds of |
1542 | Example: Create a timeout timer that times out after 10 seconds of |
1341 | inactivity. |
1543 | inactivity. |
1342 | |
1544 | |
1343 | static void |
1545 | static void |
1344 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1546 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1345 | { |
1547 | { |
1346 | .. ten seconds without any activity |
1548 | .. ten seconds without any activity |
1347 | } |
1549 | } |
1348 | |
1550 | |
1349 | struct ev_timer mytimer; |
1551 | ev_timer mytimer; |
1350 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1552 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1351 | ev_timer_again (&mytimer); /* start timer */ |
1553 | ev_timer_again (&mytimer); /* start timer */ |
1352 | ev_loop (loop, 0); |
1554 | ev_loop (loop, 0); |
1353 | |
1555 | |
1354 | // and in some piece of code that gets executed on any "activity": |
1556 | // and in some piece of code that gets executed on any "activity": |
… | |
… | |
1370 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
1572 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
1371 | roughly 10 seconds later as it uses a relative timeout). |
1573 | roughly 10 seconds later as it uses a relative timeout). |
1372 | |
1574 | |
1373 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1575 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1374 | such as triggering an event on each "midnight, local time", or other |
1576 | such as triggering an event on each "midnight, local time", or other |
1375 | complicated, rules. |
1577 | complicated rules. |
1376 | |
1578 | |
1377 | As with timers, the callback is guaranteed to be invoked only when the |
1579 | As with timers, the callback is guaranteed to be invoked only when the |
1378 | time (C<at>) has passed, but if multiple periodic timers become ready |
1580 | time (C<at>) has passed, but if multiple periodic timers become ready |
1379 | during the same loop iteration then order of execution is undefined. |
1581 | during the same loop iteration, then order of execution is undefined. |
1380 | |
1582 | |
1381 | =head3 Watcher-Specific Functions and Data Members |
1583 | =head3 Watcher-Specific Functions and Data Members |
1382 | |
1584 | |
1383 | =over 4 |
1585 | =over 4 |
1384 | |
1586 | |
1385 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1587 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1386 | |
1588 | |
1387 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1589 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1388 | |
1590 | |
1389 | Lots of arguments, lets sort it out... There are basically three modes of |
1591 | Lots of arguments, lets sort it out... There are basically three modes of |
1390 | operation, and we will explain them from simplest to complex: |
1592 | operation, and we will explain them from simplest to most complex: |
1391 | |
1593 | |
1392 | =over 4 |
1594 | =over 4 |
1393 | |
1595 | |
1394 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1596 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1395 | |
1597 | |
1396 | In this configuration the watcher triggers an event after the wall clock |
1598 | In this configuration the watcher triggers an event after the wall clock |
1397 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
1599 | time C<at> has passed. It will not repeat and will not adjust when a time |
1398 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1600 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1399 | run when the system time reaches or surpasses this time. |
1601 | only run when the system clock reaches or surpasses this time. |
1400 | |
1602 | |
1401 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1603 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1402 | |
1604 | |
1403 | In this mode the watcher will always be scheduled to time out at the next |
1605 | In this mode the watcher will always be scheduled to time out at the next |
1404 | C<at + N * interval> time (for some integer N, which can also be negative) |
1606 | C<at + N * interval> time (for some integer N, which can also be negative) |
1405 | and then repeat, regardless of any time jumps. |
1607 | and then repeat, regardless of any time jumps. |
1406 | |
1608 | |
1407 | This can be used to create timers that do not drift with respect to system |
1609 | This can be used to create timers that do not drift with respect to the |
1408 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
1610 | system clock, for example, here is a C<ev_periodic> that triggers each |
1409 | the hour: |
1611 | hour, on the hour: |
1410 | |
1612 | |
1411 | ev_periodic_set (&periodic, 0., 3600., 0); |
1613 | ev_periodic_set (&periodic, 0., 3600., 0); |
1412 | |
1614 | |
1413 | This doesn't mean there will always be 3600 seconds in between triggers, |
1615 | This doesn't mean there will always be 3600 seconds in between triggers, |
1414 | but only that the callback will be called when the system time shows a |
1616 | but only that the callback will be called when the system time shows a |
… | |
… | |
1440 | |
1642 | |
1441 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1643 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1442 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1644 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1443 | only event loop modification you are allowed to do). |
1645 | only event loop modification you are allowed to do). |
1444 | |
1646 | |
1445 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1647 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1446 | *w, ev_tstamp now)>, e.g.: |
1648 | *w, ev_tstamp now)>, e.g.: |
1447 | |
1649 | |
|
|
1650 | static ev_tstamp |
1448 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1651 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1449 | { |
1652 | { |
1450 | return now + 60.; |
1653 | return now + 60.; |
1451 | } |
1654 | } |
1452 | |
1655 | |
1453 | It must return the next time to trigger, based on the passed time value |
1656 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1490 | |
1693 | |
1491 | The current interval value. Can be modified any time, but changes only |
1694 | The current interval value. Can be modified any time, but changes only |
1492 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1695 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1493 | called. |
1696 | called. |
1494 | |
1697 | |
1495 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1698 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1496 | |
1699 | |
1497 | The current reschedule callback, or C<0>, if this functionality is |
1700 | The current reschedule callback, or C<0>, if this functionality is |
1498 | switched off. Can be changed any time, but changes only take effect when |
1701 | switched off. Can be changed any time, but changes only take effect when |
1499 | the periodic timer fires or C<ev_periodic_again> is being called. |
1702 | the periodic timer fires or C<ev_periodic_again> is being called. |
1500 | |
1703 | |
1501 | =back |
1704 | =back |
1502 | |
1705 | |
1503 | =head3 Examples |
1706 | =head3 Examples |
1504 | |
1707 | |
1505 | Example: Call a callback every hour, or, more precisely, whenever the |
1708 | Example: Call a callback every hour, or, more precisely, whenever the |
1506 | system clock is divisible by 3600. The callback invocation times have |
1709 | system time is divisible by 3600. The callback invocation times have |
1507 | potentially a lot of jitter, but good long-term stability. |
1710 | potentially a lot of jitter, but good long-term stability. |
1508 | |
1711 | |
1509 | static void |
1712 | static void |
1510 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1713 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1511 | { |
1714 | { |
1512 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1715 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1513 | } |
1716 | } |
1514 | |
1717 | |
1515 | struct ev_periodic hourly_tick; |
1718 | ev_periodic hourly_tick; |
1516 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1719 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1517 | ev_periodic_start (loop, &hourly_tick); |
1720 | ev_periodic_start (loop, &hourly_tick); |
1518 | |
1721 | |
1519 | Example: The same as above, but use a reschedule callback to do it: |
1722 | Example: The same as above, but use a reschedule callback to do it: |
1520 | |
1723 | |
1521 | #include <math.h> |
1724 | #include <math.h> |
1522 | |
1725 | |
1523 | static ev_tstamp |
1726 | static ev_tstamp |
1524 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1727 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1525 | { |
1728 | { |
1526 | return fmod (now, 3600.) + 3600.; |
1729 | return now + (3600. - fmod (now, 3600.)); |
1527 | } |
1730 | } |
1528 | |
1731 | |
1529 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1732 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1530 | |
1733 | |
1531 | Example: Call a callback every hour, starting now: |
1734 | Example: Call a callback every hour, starting now: |
1532 | |
1735 | |
1533 | struct ev_periodic hourly_tick; |
1736 | ev_periodic hourly_tick; |
1534 | ev_periodic_init (&hourly_tick, clock_cb, |
1737 | ev_periodic_init (&hourly_tick, clock_cb, |
1535 | fmod (ev_now (loop), 3600.), 3600., 0); |
1738 | fmod (ev_now (loop), 3600.), 3600., 0); |
1536 | ev_periodic_start (loop, &hourly_tick); |
1739 | ev_periodic_start (loop, &hourly_tick); |
1537 | |
1740 | |
1538 | |
1741 | |
… | |
… | |
1541 | Signal watchers will trigger an event when the process receives a specific |
1744 | Signal watchers will trigger an event when the process receives a specific |
1542 | signal one or more times. Even though signals are very asynchronous, libev |
1745 | signal one or more times. Even though signals are very asynchronous, libev |
1543 | will try it's best to deliver signals synchronously, i.e. as part of the |
1746 | will try it's best to deliver signals synchronously, i.e. as part of the |
1544 | normal event processing, like any other event. |
1747 | normal event processing, like any other event. |
1545 | |
1748 | |
|
|
1749 | If you want signals asynchronously, just use C<sigaction> as you would |
|
|
1750 | do without libev and forget about sharing the signal. You can even use |
|
|
1751 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
|
|
1752 | |
1546 | You can configure as many watchers as you like per signal. Only when the |
1753 | You can configure as many watchers as you like per signal. Only when the |
1547 | first watcher gets started will libev actually register a signal watcher |
1754 | first watcher gets started will libev actually register a signal handler |
1548 | with the kernel (thus it coexists with your own signal handlers as long |
1755 | with the kernel (thus it coexists with your own signal handlers as long as |
1549 | as you don't register any with libev). Similarly, when the last signal |
1756 | you don't register any with libev for the same signal). Similarly, when |
1550 | watcher for a signal is stopped libev will reset the signal handler to |
1757 | the last signal watcher for a signal is stopped, libev will reset the |
1551 | SIG_DFL (regardless of what it was set to before). |
1758 | signal handler to SIG_DFL (regardless of what it was set to before). |
1552 | |
1759 | |
1553 | If possible and supported, libev will install its handlers with |
1760 | If possible and supported, libev will install its handlers with |
1554 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
1761 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
1555 | interrupted. If you have a problem with system calls getting interrupted by |
1762 | interrupted. If you have a problem with system calls getting interrupted by |
1556 | signals you can block all signals in an C<ev_check> watcher and unblock |
1763 | signals you can block all signals in an C<ev_check> watcher and unblock |
… | |
… | |
1573 | |
1780 | |
1574 | =back |
1781 | =back |
1575 | |
1782 | |
1576 | =head3 Examples |
1783 | =head3 Examples |
1577 | |
1784 | |
1578 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
1785 | Example: Try to exit cleanly on SIGINT. |
1579 | |
1786 | |
1580 | static void |
1787 | static void |
1581 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1788 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1582 | { |
1789 | { |
1583 | ev_unloop (loop, EVUNLOOP_ALL); |
1790 | ev_unloop (loop, EVUNLOOP_ALL); |
1584 | } |
1791 | } |
1585 | |
1792 | |
1586 | struct ev_signal signal_watcher; |
1793 | ev_signal signal_watcher; |
1587 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1794 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1588 | ev_signal_start (loop, &sigint_cb); |
1795 | ev_signal_start (loop, &signal_watcher); |
1589 | |
1796 | |
1590 | |
1797 | |
1591 | =head2 C<ev_child> - watch out for process status changes |
1798 | =head2 C<ev_child> - watch out for process status changes |
1592 | |
1799 | |
1593 | Child watchers trigger when your process receives a SIGCHLD in response to |
1800 | Child watchers trigger when your process receives a SIGCHLD in response to |
1594 | some child status changes (most typically when a child of yours dies). It |
1801 | some child status changes (most typically when a child of yours dies or |
1595 | is permissible to install a child watcher I<after> the child has been |
1802 | exits). It is permissible to install a child watcher I<after> the child |
1596 | forked (which implies it might have already exited), as long as the event |
1803 | has been forked (which implies it might have already exited), as long |
1597 | loop isn't entered (or is continued from a watcher). |
1804 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
1805 | forking and then immediately registering a watcher for the child is fine, |
|
|
1806 | but forking and registering a watcher a few event loop iterations later is |
|
|
1807 | not. |
1598 | |
1808 | |
1599 | Only the default event loop is capable of handling signals, and therefore |
1809 | Only the default event loop is capable of handling signals, and therefore |
1600 | you can only register child watchers in the default event loop. |
1810 | you can only register child watchers in the default event loop. |
1601 | |
1811 | |
1602 | =head3 Process Interaction |
1812 | =head3 Process Interaction |
… | |
… | |
1663 | its completion. |
1873 | its completion. |
1664 | |
1874 | |
1665 | ev_child cw; |
1875 | ev_child cw; |
1666 | |
1876 | |
1667 | static void |
1877 | static void |
1668 | child_cb (EV_P_ struct ev_child *w, int revents) |
1878 | child_cb (EV_P_ ev_child *w, int revents) |
1669 | { |
1879 | { |
1670 | ev_child_stop (EV_A_ w); |
1880 | ev_child_stop (EV_A_ w); |
1671 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1881 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1672 | } |
1882 | } |
1673 | |
1883 | |
… | |
… | |
1700 | the stat buffer having unspecified contents. |
1910 | the stat buffer having unspecified contents. |
1701 | |
1911 | |
1702 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1912 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1703 | relative and your working directory changes, the behaviour is undefined. |
1913 | relative and your working directory changes, the behaviour is undefined. |
1704 | |
1914 | |
1705 | Since there is no standard to do this, the portable implementation simply |
1915 | Since there is no standard kernel interface to do this, the portable |
1706 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
1916 | implementation simply calls C<stat (2)> regularly on the path to see if |
1707 | can specify a recommended polling interval for this case. If you specify |
1917 | it changed somehow. You can specify a recommended polling interval for |
1708 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
1918 | this case. If you specify a polling interval of C<0> (highly recommended!) |
1709 | unspecified default> value will be used (which you can expect to be around |
1919 | then a I<suitable, unspecified default> value will be used (which |
1710 | five seconds, although this might change dynamically). Libev will also |
1920 | you can expect to be around five seconds, although this might change |
1711 | impose a minimum interval which is currently around C<0.1>, but thats |
1921 | dynamically). Libev will also impose a minimum interval which is currently |
1712 | usually overkill. |
1922 | around C<0.1>, but thats usually overkill. |
1713 | |
1923 | |
1714 | This watcher type is not meant for massive numbers of stat watchers, |
1924 | This watcher type is not meant for massive numbers of stat watchers, |
1715 | as even with OS-supported change notifications, this can be |
1925 | as even with OS-supported change notifications, this can be |
1716 | resource-intensive. |
1926 | resource-intensive. |
1717 | |
1927 | |
1718 | At the time of this writing, only the Linux inotify interface is |
1928 | At the time of this writing, the only OS-specific interface implemented |
1719 | implemented (implementing kqueue support is left as an exercise for the |
1929 | is the Linux inotify interface (implementing kqueue support is left as |
1720 | reader, note, however, that the author sees no way of implementing ev_stat |
1930 | an exercise for the reader. Note, however, that the author sees no way |
1721 | semantics with kqueue). Inotify will be used to give hints only and should |
1931 | of implementing C<ev_stat> semantics with kqueue). |
1722 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1723 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1724 | but changes are usually detected immediately, and if the file exists there |
|
|
1725 | will be no polling. |
|
|
1726 | |
1932 | |
1727 | =head3 ABI Issues (Largefile Support) |
1933 | =head3 ABI Issues (Largefile Support) |
1728 | |
1934 | |
1729 | Libev by default (unless the user overrides this) uses the default |
1935 | Libev by default (unless the user overrides this) uses the default |
1730 | compilation environment, which means that on systems with large file |
1936 | compilation environment, which means that on systems with large file |
… | |
… | |
1739 | file interfaces available by default (as e.g. FreeBSD does) and not |
1945 | file interfaces available by default (as e.g. FreeBSD does) and not |
1740 | optional. Libev cannot simply switch on large file support because it has |
1946 | optional. Libev cannot simply switch on large file support because it has |
1741 | to exchange stat structures with application programs compiled using the |
1947 | to exchange stat structures with application programs compiled using the |
1742 | default compilation environment. |
1948 | default compilation environment. |
1743 | |
1949 | |
1744 | =head3 Inotify |
1950 | =head3 Inotify and Kqueue |
1745 | |
1951 | |
1746 | When C<inotify (7)> support has been compiled into libev (generally only |
1952 | When C<inotify (7)> support has been compiled into libev (generally |
|
|
1953 | only available with Linux 2.6.25 or above due to bugs in earlier |
1747 | available on Linux) and present at runtime, it will be used to speed up |
1954 | implementations) and present at runtime, it will be used to speed up |
1748 | change detection where possible. The inotify descriptor will be created lazily |
1955 | change detection where possible. The inotify descriptor will be created |
1749 | when the first C<ev_stat> watcher is being started. |
1956 | lazily when the first C<ev_stat> watcher is being started. |
1750 | |
1957 | |
1751 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1958 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1752 | except that changes might be detected earlier, and in some cases, to avoid |
1959 | except that changes might be detected earlier, and in some cases, to avoid |
1753 | making regular C<stat> calls. Even in the presence of inotify support |
1960 | making regular C<stat> calls. Even in the presence of inotify support |
1754 | there are many cases where libev has to resort to regular C<stat> polling. |
1961 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
1962 | but as long as the path exists, libev usually gets away without polling. |
1755 | |
1963 | |
1756 | (There is no support for kqueue, as apparently it cannot be used to |
1964 | There is no support for kqueue, as apparently it cannot be used to |
1757 | implement this functionality, due to the requirement of having a file |
1965 | implement this functionality, due to the requirement of having a file |
1758 | descriptor open on the object at all times). |
1966 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
1967 | etc. is difficult. |
1759 | |
1968 | |
1760 | =head3 The special problem of stat time resolution |
1969 | =head3 The special problem of stat time resolution |
1761 | |
1970 | |
1762 | The C<stat ()> system call only supports full-second resolution portably, and |
1971 | The C<stat ()> system call only supports full-second resolution portably, and |
1763 | even on systems where the resolution is higher, many file systems still |
1972 | even on systems where the resolution is higher, most file systems still |
1764 | only support whole seconds. |
1973 | only support whole seconds. |
1765 | |
1974 | |
1766 | That means that, if the time is the only thing that changes, you can |
1975 | That means that, if the time is the only thing that changes, you can |
1767 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1976 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1768 | calls your callback, which does something. When there is another update |
1977 | calls your callback, which does something. When there is another update |
1769 | within the same second, C<ev_stat> will be unable to detect it as the stat |
1978 | within the same second, C<ev_stat> will be unable to detect unless the |
1770 | data does not change. |
1979 | stat data does change in other ways (e.g. file size). |
1771 | |
1980 | |
1772 | The solution to this is to delay acting on a change for slightly more |
1981 | The solution to this is to delay acting on a change for slightly more |
1773 | than a second (or till slightly after the next full second boundary), using |
1982 | than a second (or till slightly after the next full second boundary), using |
1774 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1983 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1775 | ev_timer_again (loop, w)>). |
1984 | ev_timer_again (loop, w)>). |
… | |
… | |
1795 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2004 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1796 | be detected and should normally be specified as C<0> to let libev choose |
2005 | be detected and should normally be specified as C<0> to let libev choose |
1797 | a suitable value. The memory pointed to by C<path> must point to the same |
2006 | a suitable value. The memory pointed to by C<path> must point to the same |
1798 | path for as long as the watcher is active. |
2007 | path for as long as the watcher is active. |
1799 | |
2008 | |
1800 | The callback will receive C<EV_STAT> when a change was detected, relative |
2009 | The callback will receive an C<EV_STAT> event when a change was detected, |
1801 | to the attributes at the time the watcher was started (or the last change |
2010 | relative to the attributes at the time the watcher was started (or the |
1802 | was detected). |
2011 | last change was detected). |
1803 | |
2012 | |
1804 | =item ev_stat_stat (loop, ev_stat *) |
2013 | =item ev_stat_stat (loop, ev_stat *) |
1805 | |
2014 | |
1806 | Updates the stat buffer immediately with new values. If you change the |
2015 | Updates the stat buffer immediately with new values. If you change the |
1807 | watched path in your callback, you could call this function to avoid |
2016 | watched path in your callback, you could call this function to avoid |
… | |
… | |
1890 | |
2099 | |
1891 | |
2100 | |
1892 | =head2 C<ev_idle> - when you've got nothing better to do... |
2101 | =head2 C<ev_idle> - when you've got nothing better to do... |
1893 | |
2102 | |
1894 | Idle watchers trigger events when no other events of the same or higher |
2103 | Idle watchers trigger events when no other events of the same or higher |
1895 | priority are pending (prepare, check and other idle watchers do not |
2104 | priority are pending (prepare, check and other idle watchers do not count |
1896 | count). |
2105 | as receiving "events"). |
1897 | |
2106 | |
1898 | That is, as long as your process is busy handling sockets or timeouts |
2107 | That is, as long as your process is busy handling sockets or timeouts |
1899 | (or even signals, imagine) of the same or higher priority it will not be |
2108 | (or even signals, imagine) of the same or higher priority it will not be |
1900 | triggered. But when your process is idle (or only lower-priority watchers |
2109 | triggered. But when your process is idle (or only lower-priority watchers |
1901 | are pending), the idle watchers are being called once per event loop |
2110 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1926 | |
2135 | |
1927 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2136 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1928 | callback, free it. Also, use no error checking, as usual. |
2137 | callback, free it. Also, use no error checking, as usual. |
1929 | |
2138 | |
1930 | static void |
2139 | static void |
1931 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2140 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1932 | { |
2141 | { |
1933 | free (w); |
2142 | free (w); |
1934 | // now do something you wanted to do when the program has |
2143 | // now do something you wanted to do when the program has |
1935 | // no longer anything immediate to do. |
2144 | // no longer anything immediate to do. |
1936 | } |
2145 | } |
1937 | |
2146 | |
1938 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2147 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1939 | ev_idle_init (idle_watcher, idle_cb); |
2148 | ev_idle_init (idle_watcher, idle_cb); |
1940 | ev_idle_start (loop, idle_cb); |
2149 | ev_idle_start (loop, idle_cb); |
1941 | |
2150 | |
1942 | |
2151 | |
1943 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2152 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1944 | |
2153 | |
1945 | Prepare and check watchers are usually (but not always) used in tandem: |
2154 | Prepare and check watchers are usually (but not always) used in pairs: |
1946 | prepare watchers get invoked before the process blocks and check watchers |
2155 | prepare watchers get invoked before the process blocks and check watchers |
1947 | afterwards. |
2156 | afterwards. |
1948 | |
2157 | |
1949 | You I<must not> call C<ev_loop> or similar functions that enter |
2158 | You I<must not> call C<ev_loop> or similar functions that enter |
1950 | the current event loop from either C<ev_prepare> or C<ev_check> |
2159 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
1953 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2162 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1954 | C<ev_check> so if you have one watcher of each kind they will always be |
2163 | C<ev_check> so if you have one watcher of each kind they will always be |
1955 | called in pairs bracketing the blocking call. |
2164 | called in pairs bracketing the blocking call. |
1956 | |
2165 | |
1957 | Their main purpose is to integrate other event mechanisms into libev and |
2166 | Their main purpose is to integrate other event mechanisms into libev and |
1958 | their use is somewhat advanced. This could be used, for example, to track |
2167 | their use is somewhat advanced. They could be used, for example, to track |
1959 | variable changes, implement your own watchers, integrate net-snmp or a |
2168 | variable changes, implement your own watchers, integrate net-snmp or a |
1960 | coroutine library and lots more. They are also occasionally useful if |
2169 | coroutine library and lots more. They are also occasionally useful if |
1961 | you cache some data and want to flush it before blocking (for example, |
2170 | you cache some data and want to flush it before blocking (for example, |
1962 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2171 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1963 | watcher). |
2172 | watcher). |
1964 | |
2173 | |
1965 | This is done by examining in each prepare call which file descriptors need |
2174 | This is done by examining in each prepare call which file descriptors |
1966 | to be watched by the other library, registering C<ev_io> watchers for |
2175 | need to be watched by the other library, registering C<ev_io> watchers |
1967 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2176 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1968 | provide just this functionality). Then, in the check watcher you check for |
2177 | libraries provide exactly this functionality). Then, in the check watcher, |
1969 | any events that occurred (by checking the pending status of all watchers |
2178 | you check for any events that occurred (by checking the pending status |
1970 | and stopping them) and call back into the library. The I/O and timer |
2179 | of all watchers and stopping them) and call back into the library. The |
1971 | callbacks will never actually be called (but must be valid nevertheless, |
2180 | I/O and timer callbacks will never actually be called (but must be valid |
1972 | because you never know, you know?). |
2181 | nevertheless, because you never know, you know?). |
1973 | |
2182 | |
1974 | As another example, the Perl Coro module uses these hooks to integrate |
2183 | As another example, the Perl Coro module uses these hooks to integrate |
1975 | coroutines into libev programs, by yielding to other active coroutines |
2184 | coroutines into libev programs, by yielding to other active coroutines |
1976 | during each prepare and only letting the process block if no coroutines |
2185 | during each prepare and only letting the process block if no coroutines |
1977 | are ready to run (it's actually more complicated: it only runs coroutines |
2186 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
1980 | loop from blocking if lower-priority coroutines are active, thus mapping |
2189 | loop from blocking if lower-priority coroutines are active, thus mapping |
1981 | low-priority coroutines to idle/background tasks). |
2190 | low-priority coroutines to idle/background tasks). |
1982 | |
2191 | |
1983 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2192 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1984 | priority, to ensure that they are being run before any other watchers |
2193 | priority, to ensure that they are being run before any other watchers |
|
|
2194 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2195 | |
1985 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2196 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1986 | too) should not activate ("feed") events into libev. While libev fully |
2197 | activate ("feed") events into libev. While libev fully supports this, they |
1987 | supports this, they might get executed before other C<ev_check> watchers |
2198 | might get executed before other C<ev_check> watchers did their job. As |
1988 | did their job. As C<ev_check> watchers are often used to embed other |
2199 | C<ev_check> watchers are often used to embed other (non-libev) event |
1989 | (non-libev) event loops those other event loops might be in an unusable |
2200 | loops those other event loops might be in an unusable state until their |
1990 | state until their C<ev_check> watcher ran (always remind yourself to |
2201 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1991 | coexist peacefully with others). |
2202 | others). |
1992 | |
2203 | |
1993 | =head3 Watcher-Specific Functions and Data Members |
2204 | =head3 Watcher-Specific Functions and Data Members |
1994 | |
2205 | |
1995 | =over 4 |
2206 | =over 4 |
1996 | |
2207 | |
… | |
… | |
1998 | |
2209 | |
1999 | =item ev_check_init (ev_check *, callback) |
2210 | =item ev_check_init (ev_check *, callback) |
2000 | |
2211 | |
2001 | Initialises and configures the prepare or check watcher - they have no |
2212 | Initialises and configures the prepare or check watcher - they have no |
2002 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2213 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2003 | macros, but using them is utterly, utterly and completely pointless. |
2214 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2215 | pointless. |
2004 | |
2216 | |
2005 | =back |
2217 | =back |
2006 | |
2218 | |
2007 | =head3 Examples |
2219 | =head3 Examples |
2008 | |
2220 | |
… | |
… | |
2021 | |
2233 | |
2022 | static ev_io iow [nfd]; |
2234 | static ev_io iow [nfd]; |
2023 | static ev_timer tw; |
2235 | static ev_timer tw; |
2024 | |
2236 | |
2025 | static void |
2237 | static void |
2026 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2238 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2027 | { |
2239 | { |
2028 | } |
2240 | } |
2029 | |
2241 | |
2030 | // create io watchers for each fd and a timer before blocking |
2242 | // create io watchers for each fd and a timer before blocking |
2031 | static void |
2243 | static void |
2032 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2244 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2033 | { |
2245 | { |
2034 | int timeout = 3600000; |
2246 | int timeout = 3600000; |
2035 | struct pollfd fds [nfd]; |
2247 | struct pollfd fds [nfd]; |
2036 | // actual code will need to loop here and realloc etc. |
2248 | // actual code will need to loop here and realloc etc. |
2037 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2249 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
… | |
… | |
2052 | } |
2264 | } |
2053 | } |
2265 | } |
2054 | |
2266 | |
2055 | // stop all watchers after blocking |
2267 | // stop all watchers after blocking |
2056 | static void |
2268 | static void |
2057 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2269 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2058 | { |
2270 | { |
2059 | ev_timer_stop (loop, &tw); |
2271 | ev_timer_stop (loop, &tw); |
2060 | |
2272 | |
2061 | for (int i = 0; i < nfd; ++i) |
2273 | for (int i = 0; i < nfd; ++i) |
2062 | { |
2274 | { |
… | |
… | |
2101 | } |
2313 | } |
2102 | |
2314 | |
2103 | // do not ever call adns_afterpoll |
2315 | // do not ever call adns_afterpoll |
2104 | |
2316 | |
2105 | Method 4: Do not use a prepare or check watcher because the module you |
2317 | Method 4: Do not use a prepare or check watcher because the module you |
2106 | want to embed is too inflexible to support it. Instead, you can override |
2318 | want to embed is not flexible enough to support it. Instead, you can |
2107 | their poll function. The drawback with this solution is that the main |
2319 | override their poll function. The drawback with this solution is that the |
2108 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
2320 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
2109 | this. |
2321 | this approach, effectively embedding EV as a client into the horrible |
|
|
2322 | libglib event loop. |
2110 | |
2323 | |
2111 | static gint |
2324 | static gint |
2112 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2325 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2113 | { |
2326 | { |
2114 | int got_events = 0; |
2327 | int got_events = 0; |
… | |
… | |
2145 | prioritise I/O. |
2358 | prioritise I/O. |
2146 | |
2359 | |
2147 | As an example for a bug workaround, the kqueue backend might only support |
2360 | As an example for a bug workaround, the kqueue backend might only support |
2148 | sockets on some platform, so it is unusable as generic backend, but you |
2361 | sockets on some platform, so it is unusable as generic backend, but you |
2149 | still want to make use of it because you have many sockets and it scales |
2362 | still want to make use of it because you have many sockets and it scales |
2150 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2363 | so nicely. In this case, you would create a kqueue-based loop and embed |
2151 | into your default loop (which might use e.g. poll). Overall operation will |
2364 | it into your default loop (which might use e.g. poll). Overall operation |
2152 | be a bit slower because first libev has to poll and then call kevent, but |
2365 | will be a bit slower because first libev has to call C<poll> and then |
2153 | at least you can use both at what they are best. |
2366 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2367 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2154 | |
2368 | |
2155 | As for prioritising I/O: rarely you have the case where some fds have |
2369 | As for prioritising I/O: under rare circumstances you have the case where |
2156 | to be watched and handled very quickly (with low latency), and even |
2370 | some fds have to be watched and handled very quickly (with low latency), |
2157 | priorities and idle watchers might have too much overhead. In this case |
2371 | and even priorities and idle watchers might have too much overhead. In |
2158 | you would put all the high priority stuff in one loop and all the rest in |
2372 | this case you would put all the high priority stuff in one loop and all |
2159 | a second one, and embed the second one in the first. |
2373 | the rest in a second one, and embed the second one in the first. |
2160 | |
2374 | |
2161 | As long as the watcher is active, the callback will be invoked every time |
2375 | As long as the watcher is active, the callback will be invoked every time |
2162 | there might be events pending in the embedded loop. The callback must then |
2376 | there might be events pending in the embedded loop. The callback must then |
2163 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2377 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2164 | their callbacks (you could also start an idle watcher to give the embedded |
2378 | their callbacks (you could also start an idle watcher to give the embedded |
… | |
… | |
2172 | interested in that. |
2386 | interested in that. |
2173 | |
2387 | |
2174 | Also, there have not currently been made special provisions for forking: |
2388 | Also, there have not currently been made special provisions for forking: |
2175 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2389 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2176 | but you will also have to stop and restart any C<ev_embed> watchers |
2390 | but you will also have to stop and restart any C<ev_embed> watchers |
2177 | yourself. |
2391 | yourself - but you can use a fork watcher to handle this automatically, |
|
|
2392 | and future versions of libev might do just that. |
2178 | |
2393 | |
2179 | Unfortunately, not all backends are embeddable, only the ones returned by |
2394 | Unfortunately, not all backends are embeddable: only the ones returned by |
2180 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2395 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2181 | portable one. |
2396 | portable one. |
2182 | |
2397 | |
2183 | So when you want to use this feature you will always have to be prepared |
2398 | So when you want to use this feature you will always have to be prepared |
2184 | that you cannot get an embeddable loop. The recommended way to get around |
2399 | that you cannot get an embeddable loop. The recommended way to get around |
2185 | this is to have a separate variables for your embeddable loop, try to |
2400 | this is to have a separate variables for your embeddable loop, try to |
2186 | create it, and if that fails, use the normal loop for everything. |
2401 | create it, and if that fails, use the normal loop for everything. |
|
|
2402 | |
|
|
2403 | =head3 C<ev_embed> and fork |
|
|
2404 | |
|
|
2405 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2406 | automatically be applied to the embedded loop as well, so no special |
|
|
2407 | fork handling is required in that case. When the watcher is not running, |
|
|
2408 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2409 | as applicable. |
2187 | |
2410 | |
2188 | =head3 Watcher-Specific Functions and Data Members |
2411 | =head3 Watcher-Specific Functions and Data Members |
2189 | |
2412 | |
2190 | =over 4 |
2413 | =over 4 |
2191 | |
2414 | |
… | |
… | |
2219 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2442 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2220 | used). |
2443 | used). |
2221 | |
2444 | |
2222 | struct ev_loop *loop_hi = ev_default_init (0); |
2445 | struct ev_loop *loop_hi = ev_default_init (0); |
2223 | struct ev_loop *loop_lo = 0; |
2446 | struct ev_loop *loop_lo = 0; |
2224 | struct ev_embed embed; |
2447 | ev_embed embed; |
2225 | |
2448 | |
2226 | // see if there is a chance of getting one that works |
2449 | // see if there is a chance of getting one that works |
2227 | // (remember that a flags value of 0 means autodetection) |
2450 | // (remember that a flags value of 0 means autodetection) |
2228 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2451 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2229 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2452 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2243 | kqueue implementation). Store the kqueue/socket-only event loop in |
2466 | kqueue implementation). Store the kqueue/socket-only event loop in |
2244 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2467 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2245 | |
2468 | |
2246 | struct ev_loop *loop = ev_default_init (0); |
2469 | struct ev_loop *loop = ev_default_init (0); |
2247 | struct ev_loop *loop_socket = 0; |
2470 | struct ev_loop *loop_socket = 0; |
2248 | struct ev_embed embed; |
2471 | ev_embed embed; |
2249 | |
2472 | |
2250 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2473 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2251 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2474 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2252 | { |
2475 | { |
2253 | ev_embed_init (&embed, 0, loop_socket); |
2476 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2309 | is that the author does not know of a simple (or any) algorithm for a |
2532 | is that the author does not know of a simple (or any) algorithm for a |
2310 | multiple-writer-single-reader queue that works in all cases and doesn't |
2533 | multiple-writer-single-reader queue that works in all cases and doesn't |
2311 | need elaborate support such as pthreads. |
2534 | need elaborate support such as pthreads. |
2312 | |
2535 | |
2313 | That means that if you want to queue data, you have to provide your own |
2536 | That means that if you want to queue data, you have to provide your own |
2314 | queue. But at least I can tell you would implement locking around your |
2537 | queue. But at least I can tell you how to implement locking around your |
2315 | queue: |
2538 | queue: |
2316 | |
2539 | |
2317 | =over 4 |
2540 | =over 4 |
2318 | |
2541 | |
2319 | =item queueing from a signal handler context |
2542 | =item queueing from a signal handler context |
2320 | |
2543 | |
2321 | To implement race-free queueing, you simply add to the queue in the signal |
2544 | To implement race-free queueing, you simply add to the queue in the signal |
2322 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
2545 | handler but you block the signal handler in the watcher callback. Here is |
2323 | some fictitious SIGUSR1 handler: |
2546 | an example that does that for some fictitious SIGUSR1 handler: |
2324 | |
2547 | |
2325 | static ev_async mysig; |
2548 | static ev_async mysig; |
2326 | |
2549 | |
2327 | static void |
2550 | static void |
2328 | sigusr1_handler (void) |
2551 | sigusr1_handler (void) |
… | |
… | |
2395 | |
2618 | |
2396 | =item ev_async_init (ev_async *, callback) |
2619 | =item ev_async_init (ev_async *, callback) |
2397 | |
2620 | |
2398 | Initialises and configures the async watcher - it has no parameters of any |
2621 | Initialises and configures the async watcher - it has no parameters of any |
2399 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2622 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2400 | believe me. |
2623 | trust me. |
2401 | |
2624 | |
2402 | =item ev_async_send (loop, ev_async *) |
2625 | =item ev_async_send (loop, ev_async *) |
2403 | |
2626 | |
2404 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2627 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2405 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2628 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2406 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
2629 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2407 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2630 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2408 | section below on what exactly this means). |
2631 | section below on what exactly this means). |
2409 | |
2632 | |
2410 | This call incurs the overhead of a system call only once per loop iteration, |
2633 | This call incurs the overhead of a system call only once per loop iteration, |
2411 | so while the overhead might be noticeable, it doesn't apply to repeated |
2634 | so while the overhead might be noticeable, it doesn't apply to repeated |
… | |
… | |
2435 | =over 4 |
2658 | =over 4 |
2436 | |
2659 | |
2437 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2660 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2438 | |
2661 | |
2439 | This function combines a simple timer and an I/O watcher, calls your |
2662 | This function combines a simple timer and an I/O watcher, calls your |
2440 | callback on whichever event happens first and automatically stop both |
2663 | callback on whichever event happens first and automatically stops both |
2441 | watchers. This is useful if you want to wait for a single event on an fd |
2664 | watchers. This is useful if you want to wait for a single event on an fd |
2442 | or timeout without having to allocate/configure/start/stop/free one or |
2665 | or timeout without having to allocate/configure/start/stop/free one or |
2443 | more watchers yourself. |
2666 | more watchers yourself. |
2444 | |
2667 | |
2445 | If C<fd> is less than 0, then no I/O watcher will be started and events |
2668 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2446 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
2669 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2447 | C<events> set will be created and started. |
2670 | the given C<fd> and C<events> set will be created and started. |
2448 | |
2671 | |
2449 | If C<timeout> is less than 0, then no timeout watcher will be |
2672 | If C<timeout> is less than 0, then no timeout watcher will be |
2450 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2673 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2451 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
2674 | repeat = 0) will be started. C<0> is a valid timeout. |
2452 | dubious value. |
|
|
2453 | |
2675 | |
2454 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2676 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2455 | passed an C<revents> set like normal event callbacks (a combination of |
2677 | passed an C<revents> set like normal event callbacks (a combination of |
2456 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2678 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2457 | value passed to C<ev_once>: |
2679 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
2680 | a timeout and an io event at the same time - you probably should give io |
|
|
2681 | events precedence. |
|
|
2682 | |
|
|
2683 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2458 | |
2684 | |
2459 | static void stdin_ready (int revents, void *arg) |
2685 | static void stdin_ready (int revents, void *arg) |
2460 | { |
2686 | { |
|
|
2687 | if (revents & EV_READ) |
|
|
2688 | /* stdin might have data for us, joy! */; |
2461 | if (revents & EV_TIMEOUT) |
2689 | else if (revents & EV_TIMEOUT) |
2462 | /* doh, nothing entered */; |
2690 | /* doh, nothing entered */; |
2463 | else if (revents & EV_READ) |
|
|
2464 | /* stdin might have data for us, joy! */; |
|
|
2465 | } |
2691 | } |
2466 | |
2692 | |
2467 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2693 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2468 | |
2694 | |
2469 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
2695 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
2470 | |
2696 | |
2471 | Feeds the given event set into the event loop, as if the specified event |
2697 | Feeds the given event set into the event loop, as if the specified event |
2472 | had happened for the specified watcher (which must be a pointer to an |
2698 | had happened for the specified watcher (which must be a pointer to an |
2473 | initialised but not necessarily started event watcher). |
2699 | initialised but not necessarily started event watcher). |
2474 | |
2700 | |
2475 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
2701 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
2476 | |
2702 | |
2477 | Feed an event on the given fd, as if a file descriptor backend detected |
2703 | Feed an event on the given fd, as if a file descriptor backend detected |
2478 | the given events it. |
2704 | the given events it. |
2479 | |
2705 | |
2480 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
2706 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
2481 | |
2707 | |
2482 | Feed an event as if the given signal occurred (C<loop> must be the default |
2708 | Feed an event as if the given signal occurred (C<loop> must be the default |
2483 | loop!). |
2709 | loop!). |
2484 | |
2710 | |
2485 | =back |
2711 | =back |
… | |
… | |
2617 | |
2843 | |
2618 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2844 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2619 | |
2845 | |
2620 | See the method-C<set> above for more details. |
2846 | See the method-C<set> above for more details. |
2621 | |
2847 | |
2622 | Example: |
2848 | Example: Use a plain function as callback. |
2623 | |
2849 | |
2624 | static void io_cb (ev::io &w, int revents) { } |
2850 | static void io_cb (ev::io &w, int revents) { } |
2625 | iow.set <io_cb> (); |
2851 | iow.set <io_cb> (); |
2626 | |
2852 | |
2627 | =item w->set (struct ev_loop *) |
2853 | =item w->set (struct ev_loop *) |
… | |
… | |
2665 | Example: Define a class with an IO and idle watcher, start one of them in |
2891 | Example: Define a class with an IO and idle watcher, start one of them in |
2666 | the constructor. |
2892 | the constructor. |
2667 | |
2893 | |
2668 | class myclass |
2894 | class myclass |
2669 | { |
2895 | { |
2670 | ev::io io; void io_cb (ev::io &w, int revents); |
2896 | ev::io io ; void io_cb (ev::io &w, int revents); |
2671 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
2897 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2672 | |
2898 | |
2673 | myclass (int fd) |
2899 | myclass (int fd) |
2674 | { |
2900 | { |
2675 | io .set <myclass, &myclass::io_cb > (this); |
2901 | io .set <myclass, &myclass::io_cb > (this); |
2676 | idle.set <myclass, &myclass::idle_cb> (this); |
2902 | idle.set <myclass, &myclass::idle_cb> (this); |
… | |
… | |
2692 | =item Perl |
2918 | =item Perl |
2693 | |
2919 | |
2694 | The EV module implements the full libev API and is actually used to test |
2920 | The EV module implements the full libev API and is actually used to test |
2695 | libev. EV is developed together with libev. Apart from the EV core module, |
2921 | libev. EV is developed together with libev. Apart from the EV core module, |
2696 | there are additional modules that implement libev-compatible interfaces |
2922 | there are additional modules that implement libev-compatible interfaces |
2697 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
2923 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2698 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
2924 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
2925 | and C<EV::Glib>). |
2699 | |
2926 | |
2700 | It can be found and installed via CPAN, its homepage is at |
2927 | It can be found and installed via CPAN, its homepage is at |
2701 | L<http://software.schmorp.de/pkg/EV>. |
2928 | L<http://software.schmorp.de/pkg/EV>. |
2702 | |
2929 | |
2703 | =item Python |
2930 | =item Python |
… | |
… | |
2882 | |
3109 | |
2883 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3110 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2884 | |
3111 | |
2885 | Libev can be configured via a variety of preprocessor symbols you have to |
3112 | Libev can be configured via a variety of preprocessor symbols you have to |
2886 | define before including any of its files. The default in the absence of |
3113 | define before including any of its files. The default in the absence of |
2887 | autoconf is noted for every option. |
3114 | autoconf is documented for every option. |
2888 | |
3115 | |
2889 | =over 4 |
3116 | =over 4 |
2890 | |
3117 | |
2891 | =item EV_STANDALONE |
3118 | =item EV_STANDALONE |
2892 | |
3119 | |
… | |
… | |
3062 | When doing priority-based operations, libev usually has to linearly search |
3289 | When doing priority-based operations, libev usually has to linearly search |
3063 | all the priorities, so having many of them (hundreds) uses a lot of space |
3290 | all the priorities, so having many of them (hundreds) uses a lot of space |
3064 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3291 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3065 | fine. |
3292 | fine. |
3066 | |
3293 | |
3067 | If your embedding application does not need any priorities, defining these both to |
3294 | If your embedding application does not need any priorities, defining these |
3068 | C<0> will save some memory and CPU. |
3295 | both to C<0> will save some memory and CPU. |
3069 | |
3296 | |
3070 | =item EV_PERIODIC_ENABLE |
3297 | =item EV_PERIODIC_ENABLE |
3071 | |
3298 | |
3072 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3299 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3073 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3300 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
… | |
… | |
3080 | code. |
3307 | code. |
3081 | |
3308 | |
3082 | =item EV_EMBED_ENABLE |
3309 | =item EV_EMBED_ENABLE |
3083 | |
3310 | |
3084 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3311 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3085 | defined to be C<0>, then they are not. |
3312 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3313 | watcher types, which therefore must not be disabled. |
3086 | |
3314 | |
3087 | =item EV_STAT_ENABLE |
3315 | =item EV_STAT_ENABLE |
3088 | |
3316 | |
3089 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3317 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3090 | defined to be C<0>, then they are not. |
3318 | defined to be C<0>, then they are not. |
… | |
… | |
3122 | two). |
3350 | two). |
3123 | |
3351 | |
3124 | =item EV_USE_4HEAP |
3352 | =item EV_USE_4HEAP |
3125 | |
3353 | |
3126 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3354 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3127 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
3355 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3128 | to C<1>. The 4-heap uses more complicated (longer) code but has |
3356 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3129 | noticeably faster performance with many (thousands) of watchers. |
3357 | faster performance with many (thousands) of watchers. |
3130 | |
3358 | |
3131 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3359 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3132 | (disabled). |
3360 | (disabled). |
3133 | |
3361 | |
3134 | =item EV_HEAP_CACHE_AT |
3362 | =item EV_HEAP_CACHE_AT |
3135 | |
3363 | |
3136 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3364 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3137 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
3365 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3138 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3366 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3139 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3367 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3140 | but avoids random read accesses on heap changes. This improves performance |
3368 | but avoids random read accesses on heap changes. This improves performance |
3141 | noticeably with with many (hundreds) of watchers. |
3369 | noticeably with many (hundreds) of watchers. |
3142 | |
3370 | |
3143 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3371 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3144 | (disabled). |
3372 | (disabled). |
3145 | |
3373 | |
3146 | =item EV_VERIFY |
3374 | =item EV_VERIFY |
… | |
… | |
3152 | called once per loop, which can slow down libev. If set to C<3>, then the |
3380 | called once per loop, which can slow down libev. If set to C<3>, then the |
3153 | verification code will be called very frequently, which will slow down |
3381 | verification code will be called very frequently, which will slow down |
3154 | libev considerably. |
3382 | libev considerably. |
3155 | |
3383 | |
3156 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
3384 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
3157 | C<0.> |
3385 | C<0>. |
3158 | |
3386 | |
3159 | =item EV_COMMON |
3387 | =item EV_COMMON |
3160 | |
3388 | |
3161 | By default, all watchers have a C<void *data> member. By redefining |
3389 | By default, all watchers have a C<void *data> member. By redefining |
3162 | this macro to a something else you can include more and other types of |
3390 | this macro to a something else you can include more and other types of |
… | |
… | |
3179 | and the way callbacks are invoked and set. Must expand to a struct member |
3407 | and the way callbacks are invoked and set. Must expand to a struct member |
3180 | definition and a statement, respectively. See the F<ev.h> header file for |
3408 | definition and a statement, respectively. See the F<ev.h> header file for |
3181 | their default definitions. One possible use for overriding these is to |
3409 | their default definitions. One possible use for overriding these is to |
3182 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3410 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3183 | method calls instead of plain function calls in C++. |
3411 | method calls instead of plain function calls in C++. |
|
|
3412 | |
|
|
3413 | =back |
3184 | |
3414 | |
3185 | =head2 EXPORTED API SYMBOLS |
3415 | =head2 EXPORTED API SYMBOLS |
3186 | |
3416 | |
3187 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3417 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3188 | exported symbols, you can use the provided F<Symbol.*> files which list |
3418 | exported symbols, you can use the provided F<Symbol.*> files which list |
… | |
… | |
3235 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3465 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3236 | |
3466 | |
3237 | #include "ev_cpp.h" |
3467 | #include "ev_cpp.h" |
3238 | #include "ev.c" |
3468 | #include "ev.c" |
3239 | |
3469 | |
|
|
3470 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3240 | |
3471 | |
3241 | =head1 THREADS AND COROUTINES |
3472 | =head2 THREADS AND COROUTINES |
3242 | |
3473 | |
3243 | =head2 THREADS |
3474 | =head3 THREADS |
3244 | |
3475 | |
3245 | Libev itself is thread-safe (unless the opposite is specifically |
3476 | All libev functions are reentrant and thread-safe unless explicitly |
3246 | documented for a function), but it uses no locking itself. This means that |
3477 | documented otherwise, but libev implements no locking itself. This means |
3247 | you can use as many loops as you want in parallel, as long as only one |
3478 | that you can use as many loops as you want in parallel, as long as there |
3248 | thread ever calls into one libev function with the same loop parameter: |
3479 | are no concurrent calls into any libev function with the same loop |
|
|
3480 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
3249 | libev guarentees that different event loops share no data structures that |
3481 | of course): libev guarantees that different event loops share no data |
3250 | need locking. |
3482 | structures that need any locking. |
3251 | |
3483 | |
3252 | Or to put it differently: calls with different loop parameters can be done |
3484 | Or to put it differently: calls with different loop parameters can be done |
3253 | concurrently from multiple threads, calls with the same loop parameter |
3485 | concurrently from multiple threads, calls with the same loop parameter |
3254 | must be done serially (but can be done from different threads, as long as |
3486 | must be done serially (but can be done from different threads, as long as |
3255 | only one thread ever is inside a call at any point in time, e.g. by using |
3487 | only one thread ever is inside a call at any point in time, e.g. by using |
3256 | a mutex per loop). |
3488 | a mutex per loop). |
3257 | |
3489 | |
3258 | Specifically to support threads (and signal handlers), libev implements |
3490 | Specifically to support threads (and signal handlers), libev implements |
3259 | so-called C<ev_async> watchers, which allow some limited form of |
3491 | so-called C<ev_async> watchers, which allow some limited form of |
3260 | concurrency on the same event loop. |
3492 | concurrency on the same event loop, namely waking it up "from the |
|
|
3493 | outside". |
3261 | |
3494 | |
3262 | If you want to know which design (one loop, locking, or multiple loops |
3495 | If you want to know which design (one loop, locking, or multiple loops |
3263 | without or something else still) is best for your problem, then I cannot |
3496 | without or something else still) is best for your problem, then I cannot |
3264 | help you. I can give some generic advice however: |
3497 | help you, but here is some generic advice: |
3265 | |
3498 | |
3266 | =over 4 |
3499 | =over 4 |
3267 | |
3500 | |
3268 | =item * most applications have a main thread: use the default libev loop |
3501 | =item * most applications have a main thread: use the default libev loop |
3269 | in that thread, or create a separate thread running only the default loop. |
3502 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3281 | |
3514 | |
3282 | Choosing a model is hard - look around, learn, know that usually you can do |
3515 | Choosing a model is hard - look around, learn, know that usually you can do |
3283 | better than you currently do :-) |
3516 | better than you currently do :-) |
3284 | |
3517 | |
3285 | =item * often you need to talk to some other thread which blocks in the |
3518 | =item * often you need to talk to some other thread which blocks in the |
|
|
3519 | event loop. |
|
|
3520 | |
3286 | event loop - C<ev_async> watchers can be used to wake them up from other |
3521 | C<ev_async> watchers can be used to wake them up from other threads safely |
3287 | threads safely (or from signal contexts...). |
3522 | (or from signal contexts...). |
3288 | |
3523 | |
3289 | =item * some watcher types are only supported in the default loop - use |
3524 | An example use would be to communicate signals or other events that only |
3290 | C<ev_async> watchers to tell your other loops about any such events. |
3525 | work in the default loop by registering the signal watcher with the |
|
|
3526 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
3527 | watcher callback into the event loop interested in the signal. |
3291 | |
3528 | |
3292 | =back |
3529 | =back |
3293 | |
3530 | |
3294 | =head2 COROUTINES |
3531 | =head3 COROUTINES |
3295 | |
3532 | |
3296 | Libev is much more accommodating to coroutines ("cooperative threads"): |
3533 | Libev is very accommodating to coroutines ("cooperative threads"): |
3297 | libev fully supports nesting calls to it's functions from different |
3534 | libev fully supports nesting calls to its functions from different |
3298 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3535 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3299 | different coroutines and switch freely between both coroutines running the |
3536 | different coroutines, and switch freely between both coroutines running the |
3300 | loop, as long as you don't confuse yourself). The only exception is that |
3537 | loop, as long as you don't confuse yourself). The only exception is that |
3301 | you must not do this from C<ev_periodic> reschedule callbacks. |
3538 | you must not do this from C<ev_periodic> reschedule callbacks. |
3302 | |
3539 | |
3303 | Care has been invested into making sure that libev does not keep local |
3540 | Care has been taken to ensure that libev does not keep local state inside |
3304 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
3541 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3305 | switches. |
3542 | they do not clal any callbacks. |
3306 | |
3543 | |
|
|
3544 | =head2 COMPILER WARNINGS |
3307 | |
3545 | |
3308 | =head1 COMPLEXITIES |
3546 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3547 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3548 | scared by this. |
3309 | |
3549 | |
3310 | In this section the complexities of (many of) the algorithms used inside |
3550 | However, these are unavoidable for many reasons. For one, each compiler |
3311 | libev will be explained. For complexity discussions about backends see the |
3551 | has different warnings, and each user has different tastes regarding |
3312 | documentation for C<ev_default_init>. |
3552 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3553 | targeting a specific compiler and compiler-version. |
3313 | |
3554 | |
3314 | All of the following are about amortised time: If an array needs to be |
3555 | Another reason is that some compiler warnings require elaborate |
3315 | extended, libev needs to realloc and move the whole array, but this |
3556 | workarounds, or other changes to the code that make it less clear and less |
3316 | happens asymptotically never with higher number of elements, so O(1) might |
3557 | maintainable. |
3317 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3318 | it is much faster and asymptotically approaches constant time. |
|
|
3319 | |
3558 | |
3320 | =over 4 |
3559 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3560 | wrong (because they don't actually warn about the condition their message |
|
|
3561 | seems to warn about). For example, certain older gcc versions had some |
|
|
3562 | warnings that resulted an extreme number of false positives. These have |
|
|
3563 | been fixed, but some people still insist on making code warn-free with |
|
|
3564 | such buggy versions. |
3321 | |
3565 | |
3322 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3566 | While libev is written to generate as few warnings as possible, |
|
|
3567 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3568 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3569 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3570 | warnings, not errors, or proof of bugs. |
3323 | |
3571 | |
3324 | This means that, when you have a watcher that triggers in one hour and |
|
|
3325 | there are 100 watchers that would trigger before that then inserting will |
|
|
3326 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3327 | |
3572 | |
3328 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3573 | =head2 VALGRIND |
3329 | |
3574 | |
3330 | That means that changing a timer costs less than removing/adding them |
3575 | Valgrind has a special section here because it is a popular tool that is |
3331 | as only the relative motion in the event queue has to be paid for. |
3576 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3332 | |
3577 | |
3333 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3578 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3579 | in libev, then check twice: If valgrind reports something like: |
3334 | |
3580 | |
3335 | These just add the watcher into an array or at the head of a list. |
3581 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3582 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3583 | ==2274== still reachable: 256 bytes in 1 blocks. |
3336 | |
3584 | |
3337 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3585 | Then there is no memory leak, just as memory accounted to global variables |
|
|
3586 | is not a memleak - the memory is still being refernced, and didn't leak. |
3338 | |
3587 | |
3339 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3588 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
3589 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
3590 | although an acceptable workaround has been found here), or it might be |
|
|
3591 | confused. |
3340 | |
3592 | |
3341 | These watchers are stored in lists then need to be walked to find the |
3593 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3342 | correct watcher to remove. The lists are usually short (you don't usually |
3594 | make it into some kind of religion. |
3343 | have many watchers waiting for the same fd or signal). |
|
|
3344 | |
3595 | |
3345 | =item Finding the next timer in each loop iteration: O(1) |
3596 | If you are unsure about something, feel free to contact the mailing list |
|
|
3597 | with the full valgrind report and an explanation on why you think this |
|
|
3598 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
3599 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
3600 | of learning how to interpret valgrind properly. |
3346 | |
3601 | |
3347 | By virtue of using a binary or 4-heap, the next timer is always found at a |
3602 | If you need, for some reason, empty reports from valgrind for your project |
3348 | fixed position in the storage array. |
3603 | I suggest using suppression lists. |
3349 | |
3604 | |
3350 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3351 | |
3605 | |
3352 | A change means an I/O watcher gets started or stopped, which requires |
3606 | =head1 PORTABILITY NOTES |
3353 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3354 | on backend and whether C<ev_io_set> was used). |
|
|
3355 | |
3607 | |
3356 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3357 | |
|
|
3358 | =item Priority handling: O(number_of_priorities) |
|
|
3359 | |
|
|
3360 | Priorities are implemented by allocating some space for each |
|
|
3361 | priority. When doing priority-based operations, libev usually has to |
|
|
3362 | linearly search all the priorities, but starting/stopping and activating |
|
|
3363 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3364 | |
|
|
3365 | =item Sending an ev_async: O(1) |
|
|
3366 | |
|
|
3367 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3368 | |
|
|
3369 | =item Processing signals: O(max_signal_number) |
|
|
3370 | |
|
|
3371 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3372 | calls in the current loop iteration. Checking for async and signal events |
|
|
3373 | involves iterating over all running async watchers or all signal numbers. |
|
|
3374 | |
|
|
3375 | =back |
|
|
3376 | |
|
|
3377 | |
|
|
3378 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3608 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3379 | |
3609 | |
3380 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3610 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3381 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3611 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3382 | model. Libev still offers limited functionality on this platform in |
3612 | model. Libev still offers limited functionality on this platform in |
3383 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3613 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
… | |
… | |
3394 | |
3624 | |
3395 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3625 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3396 | accept large writes: instead of resulting in a partial write, windows will |
3626 | accept large writes: instead of resulting in a partial write, windows will |
3397 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3627 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3398 | so make sure you only write small amounts into your sockets (less than a |
3628 | so make sure you only write small amounts into your sockets (less than a |
3399 | megabyte seems safe, but thsi apparently depends on the amount of memory |
3629 | megabyte seems safe, but this apparently depends on the amount of memory |
3400 | available). |
3630 | available). |
3401 | |
3631 | |
3402 | Due to the many, low, and arbitrary limits on the win32 platform and |
3632 | Due to the many, low, and arbitrary limits on the win32 platform and |
3403 | the abysmal performance of winsockets, using a large number of sockets |
3633 | the abysmal performance of winsockets, using a large number of sockets |
3404 | is not recommended (and not reasonable). If your program needs to use |
3634 | is not recommended (and not reasonable). If your program needs to use |
… | |
… | |
3415 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3645 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3416 | |
3646 | |
3417 | #include "ev.h" |
3647 | #include "ev.h" |
3418 | |
3648 | |
3419 | And compile the following F<evwrap.c> file into your project (make sure |
3649 | And compile the following F<evwrap.c> file into your project (make sure |
3420 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
3650 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3421 | |
3651 | |
3422 | #include "evwrap.h" |
3652 | #include "evwrap.h" |
3423 | #include "ev.c" |
3653 | #include "ev.c" |
3424 | |
3654 | |
3425 | =over 4 |
3655 | =over 4 |
… | |
… | |
3470 | wrap all I/O functions and provide your own fd management, but the cost of |
3700 | wrap all I/O functions and provide your own fd management, but the cost of |
3471 | calling select (O(n²)) will likely make this unworkable. |
3701 | calling select (O(n²)) will likely make this unworkable. |
3472 | |
3702 | |
3473 | =back |
3703 | =back |
3474 | |
3704 | |
3475 | |
|
|
3476 | =head1 PORTABILITY REQUIREMENTS |
3705 | =head2 PORTABILITY REQUIREMENTS |
3477 | |
3706 | |
3478 | In addition to a working ISO-C implementation, libev relies on a few |
3707 | In addition to a working ISO-C implementation and of course the |
3479 | additional extensions: |
3708 | backend-specific APIs, libev relies on a few additional extensions: |
3480 | |
3709 | |
3481 | =over 4 |
3710 | =over 4 |
3482 | |
3711 | |
3483 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3712 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3484 | calling conventions regardless of C<ev_watcher_type *>. |
3713 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3490 | calls them using an C<ev_watcher *> internally. |
3719 | calls them using an C<ev_watcher *> internally. |
3491 | |
3720 | |
3492 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3721 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3493 | |
3722 | |
3494 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3723 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3495 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
3724 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
3496 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3725 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3497 | believed to be sufficiently portable. |
3726 | believed to be sufficiently portable. |
3498 | |
3727 | |
3499 | =item C<sigprocmask> must work in a threaded environment |
3728 | =item C<sigprocmask> must work in a threaded environment |
3500 | |
3729 | |
… | |
… | |
3509 | except the initial one, and run the default loop in the initial thread as |
3738 | except the initial one, and run the default loop in the initial thread as |
3510 | well. |
3739 | well. |
3511 | |
3740 | |
3512 | =item C<long> must be large enough for common memory allocation sizes |
3741 | =item C<long> must be large enough for common memory allocation sizes |
3513 | |
3742 | |
3514 | To improve portability and simplify using libev, libev uses C<long> |
3743 | To improve portability and simplify its API, libev uses C<long> internally |
3515 | internally instead of C<size_t> when allocating its data structures. On |
3744 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3516 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
3745 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3517 | is still at least 31 bits everywhere, which is enough for hundreds of |
3746 | least 31 bits everywhere, which is enough for hundreds of millions of |
3518 | millions of watchers. |
3747 | watchers. |
3519 | |
3748 | |
3520 | =item C<double> must hold a time value in seconds with enough accuracy |
3749 | =item C<double> must hold a time value in seconds with enough accuracy |
3521 | |
3750 | |
3522 | The type C<double> is used to represent timestamps. It is required to |
3751 | The type C<double> is used to represent timestamps. It is required to |
3523 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3752 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
… | |
… | |
3527 | =back |
3756 | =back |
3528 | |
3757 | |
3529 | If you know of other additional requirements drop me a note. |
3758 | If you know of other additional requirements drop me a note. |
3530 | |
3759 | |
3531 | |
3760 | |
3532 | =head1 COMPILER WARNINGS |
3761 | =head1 ALGORITHMIC COMPLEXITIES |
3533 | |
3762 | |
3534 | Depending on your compiler and compiler settings, you might get no or a |
3763 | In this section the complexities of (many of) the algorithms used inside |
3535 | lot of warnings when compiling libev code. Some people are apparently |
3764 | libev will be documented. For complexity discussions about backends see |
3536 | scared by this. |
3765 | the documentation for C<ev_default_init>. |
3537 | |
3766 | |
3538 | However, these are unavoidable for many reasons. For one, each compiler |
3767 | All of the following are about amortised time: If an array needs to be |
3539 | has different warnings, and each user has different tastes regarding |
3768 | extended, libev needs to realloc and move the whole array, but this |
3540 | warning options. "Warn-free" code therefore cannot be a goal except when |
3769 | happens asymptotically rarer with higher number of elements, so O(1) might |
3541 | targeting a specific compiler and compiler-version. |
3770 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
3771 | average it is much faster and asymptotically approaches constant time. |
3542 | |
3772 | |
3543 | Another reason is that some compiler warnings require elaborate |
3773 | =over 4 |
3544 | workarounds, or other changes to the code that make it less clear and less |
|
|
3545 | maintainable. |
|
|
3546 | |
3774 | |
3547 | And of course, some compiler warnings are just plain stupid, or simply |
3775 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3548 | wrong (because they don't actually warn about the condition their message |
|
|
3549 | seems to warn about). |
|
|
3550 | |
3776 | |
3551 | While libev is written to generate as few warnings as possible, |
3777 | This means that, when you have a watcher that triggers in one hour and |
3552 | "warn-free" code is not a goal, and it is recommended not to build libev |
3778 | there are 100 watchers that would trigger before that, then inserting will |
3553 | with any compiler warnings enabled unless you are prepared to cope with |
3779 | have to skip roughly seven (C<ld 100>) of these watchers. |
3554 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3555 | warnings, not errors, or proof of bugs. |
|
|
3556 | |
3780 | |
|
|
3781 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3557 | |
3782 | |
3558 | =head1 VALGRIND |
3783 | That means that changing a timer costs less than removing/adding them, |
|
|
3784 | as only the relative motion in the event queue has to be paid for. |
3559 | |
3785 | |
3560 | Valgrind has a special section here because it is a popular tool that is |
3786 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3561 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3562 | |
3787 | |
3563 | If you think you found a bug (memory leak, uninitialised data access etc.) |
3788 | These just add the watcher into an array or at the head of a list. |
3564 | in libev, then check twice: If valgrind reports something like: |
|
|
3565 | |
3789 | |
3566 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3790 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3567 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3568 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3569 | |
3791 | |
3570 | Then there is no memory leak. Similarly, under some circumstances, |
3792 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3571 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3572 | might be confused (it is a very good tool, but only a tool). |
|
|
3573 | |
3793 | |
3574 | If you are unsure about something, feel free to contact the mailing list |
3794 | These watchers are stored in lists, so they need to be walked to find the |
3575 | with the full valgrind report and an explanation on why you think this is |
3795 | correct watcher to remove. The lists are usually short (you don't usually |
3576 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
3796 | have many watchers waiting for the same fd or signal: one is typical, two |
3577 | no bug" answer and take the chance of learning how to interpret valgrind |
3797 | is rare). |
3578 | properly. |
|
|
3579 | |
3798 | |
3580 | If you need, for some reason, empty reports from valgrind for your project |
3799 | =item Finding the next timer in each loop iteration: O(1) |
3581 | I suggest using suppression lists. |
3800 | |
|
|
3801 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
3802 | fixed position in the storage array. |
|
|
3803 | |
|
|
3804 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3805 | |
|
|
3806 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3807 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3808 | on backend and whether C<ev_io_set> was used). |
|
|
3809 | |
|
|
3810 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3811 | |
|
|
3812 | =item Priority handling: O(number_of_priorities) |
|
|
3813 | |
|
|
3814 | Priorities are implemented by allocating some space for each |
|
|
3815 | priority. When doing priority-based operations, libev usually has to |
|
|
3816 | linearly search all the priorities, but starting/stopping and activating |
|
|
3817 | watchers becomes O(1) with respect to priority handling. |
|
|
3818 | |
|
|
3819 | =item Sending an ev_async: O(1) |
|
|
3820 | |
|
|
3821 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3822 | |
|
|
3823 | =item Processing signals: O(max_signal_number) |
|
|
3824 | |
|
|
3825 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3826 | calls in the current loop iteration. Checking for async and signal events |
|
|
3827 | involves iterating over all running async watchers or all signal numbers. |
|
|
3828 | |
|
|
3829 | =back |
3582 | |
3830 | |
3583 | |
3831 | |
3584 | =head1 AUTHOR |
3832 | =head1 AUTHOR |
3585 | |
3833 | |
3586 | Marc Lehmann <libev@schmorp.de>. |
3834 | Marc Lehmann <libev@schmorp.de>. |