|
|
1 | =encoding utf-8 |
|
|
2 | |
1 | =head1 NAME |
3 | =head1 NAME |
2 | |
4 | |
3 | libev - a high performance full-featured event loop written in C |
5 | libev - a high performance full-featured event loop written in C |
4 | |
6 | |
5 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
… | |
… | |
82 | |
84 | |
83 | =head1 WHAT TO READ WHEN IN A HURRY |
85 | =head1 WHAT TO READ WHEN IN A HURRY |
84 | |
86 | |
85 | This manual tries to be very detailed, but unfortunately, this also makes |
87 | This manual tries to be very detailed, but unfortunately, this also makes |
86 | it very long. If you just want to know the basics of libev, I suggest |
88 | it very long. If you just want to know the basics of libev, I suggest |
87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
89 | reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and |
88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
90 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
89 | C<ev_timer> sections in L<WATCHER TYPES>. |
91 | C<ev_timer> sections in L</WATCHER TYPES>. |
90 | |
92 | |
91 | =head1 ABOUT LIBEV |
93 | =head1 ABOUT LIBEV |
92 | |
94 | |
93 | Libev is an event loop: you register interest in certain events (such as a |
95 | Libev is an event loop: you register interest in certain events (such as a |
94 | file descriptor being readable or a timeout occurring), and it will manage |
96 | file descriptor being readable or a timeout occurring), and it will manage |
… | |
… | |
103 | details of the event, and then hand it over to libev by I<starting> the |
105 | details of the event, and then hand it over to libev by I<starting> the |
104 | watcher. |
106 | watcher. |
105 | |
107 | |
106 | =head2 FEATURES |
108 | =head2 FEATURES |
107 | |
109 | |
108 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
110 | Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll> |
109 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
111 | interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port |
110 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
112 | mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify> |
111 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
113 | interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
112 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
114 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
113 | timers (C<ev_timer>), absolute timers with customised rescheduling |
115 | timers (C<ev_timer>), absolute timers with customised rescheduling |
114 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
116 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
115 | change events (C<ev_child>), and event watchers dealing with the event |
117 | change events (C<ev_child>), and event watchers dealing with the event |
116 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
118 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
… | |
… | |
263 | |
265 | |
264 | You could override this function in high-availability programs to, say, |
266 | You could override this function in high-availability programs to, say, |
265 | free some memory if it cannot allocate memory, to use a special allocator, |
267 | free some memory if it cannot allocate memory, to use a special allocator, |
266 | or even to sleep a while and retry until some memory is available. |
268 | or even to sleep a while and retry until some memory is available. |
267 | |
269 | |
|
|
270 | Example: The following is the C<realloc> function that libev itself uses |
|
|
271 | which should work with C<realloc> and C<free> functions of all kinds and |
|
|
272 | is probably a good basis for your own implementation. |
|
|
273 | |
|
|
274 | static void * |
|
|
275 | ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT |
|
|
276 | { |
|
|
277 | if (size) |
|
|
278 | return realloc (ptr, size); |
|
|
279 | |
|
|
280 | free (ptr); |
|
|
281 | return 0; |
|
|
282 | } |
|
|
283 | |
268 | Example: Replace the libev allocator with one that waits a bit and then |
284 | Example: Replace the libev allocator with one that waits a bit and then |
269 | retries (example requires a standards-compliant C<realloc>). |
285 | retries. |
270 | |
286 | |
271 | static void * |
287 | static void * |
272 | persistent_realloc (void *ptr, size_t size) |
288 | persistent_realloc (void *ptr, size_t size) |
273 | { |
289 | { |
|
|
290 | if (!size) |
|
|
291 | { |
|
|
292 | free (ptr); |
|
|
293 | return 0; |
|
|
294 | } |
|
|
295 | |
274 | for (;;) |
296 | for (;;) |
275 | { |
297 | { |
276 | void *newptr = realloc (ptr, size); |
298 | void *newptr = realloc (ptr, size); |
277 | |
299 | |
278 | if (newptr) |
300 | if (newptr) |
… | |
… | |
396 | |
418 | |
397 | If this flag bit is or'ed into the flag value (or the program runs setuid |
419 | If this flag bit is or'ed into the flag value (or the program runs setuid |
398 | or setgid) then libev will I<not> look at the environment variable |
420 | or setgid) then libev will I<not> look at the environment variable |
399 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
421 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
400 | override the flags completely if it is found in the environment. This is |
422 | override the flags completely if it is found in the environment. This is |
401 | useful to try out specific backends to test their performance, or to work |
423 | useful to try out specific backends to test their performance, to work |
402 | around bugs. |
424 | around bugs, or to make libev threadsafe (accessing environment variables |
|
|
425 | cannot be done in a threadsafe way, but usually it works if no other |
|
|
426 | thread modifies them). |
403 | |
427 | |
404 | =item C<EVFLAG_FORKCHECK> |
428 | =item C<EVFLAG_FORKCHECK> |
405 | |
429 | |
406 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
430 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
407 | make libev check for a fork in each iteration by enabling this flag. |
431 | make libev check for a fork in each iteration by enabling this flag. |
408 | |
432 | |
409 | This works by calling C<getpid ()> on every iteration of the loop, |
433 | This works by calling C<getpid ()> on every iteration of the loop, |
410 | and thus this might slow down your event loop if you do a lot of loop |
434 | and thus this might slow down your event loop if you do a lot of loop |
411 | iterations and little real work, but is usually not noticeable (on my |
435 | iterations and little real work, but is usually not noticeable (on my |
412 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
436 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
413 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
437 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
414 | C<pthread_atfork> which is even faster). |
438 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
|
|
439 | versions 2.25 apparently removed the C<getpid> optimisation again). |
415 | |
440 | |
416 | The big advantage of this flag is that you can forget about fork (and |
441 | The big advantage of this flag is that you can forget about fork (and |
417 | forget about forgetting to tell libev about forking) when you use this |
442 | forget about forgetting to tell libev about forking, although you still |
418 | flag. |
443 | have to ignore C<SIGPIPE>) when you use this flag. |
419 | |
444 | |
420 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
445 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
421 | environment variable. |
446 | environment variable. |
422 | |
447 | |
423 | =item C<EVFLAG_NOINOTIFY> |
448 | =item C<EVFLAG_NOINOTIFY> |
… | |
… | |
542 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
567 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
543 | faster than epoll for maybe up to a hundred file descriptors, depending on |
568 | faster than epoll for maybe up to a hundred file descriptors, depending on |
544 | the usage. So sad. |
569 | the usage. So sad. |
545 | |
570 | |
546 | While nominally embeddable in other event loops, this feature is broken in |
571 | While nominally embeddable in other event loops, this feature is broken in |
547 | all kernel versions tested so far. |
572 | a lot of kernel revisions, but probably(!) works in current versions. |
|
|
573 | |
|
|
574 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
575 | C<EVBACKEND_POLL>. |
|
|
576 | |
|
|
577 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
|
|
578 | |
|
|
579 | Use the linux-specific linux aio (I<not> C<< aio(7) >> but C<< |
|
|
580 | io_submit(2) >>) event interface available in post-4.18 kernels. |
|
|
581 | |
|
|
582 | If this backend works for you (as of this writing, it was very |
|
|
583 | experimental), it is the best event interface available on linux and might |
|
|
584 | be well worth enabling it - if it isn't available in your kernel this will |
|
|
585 | be detected and this backend will be skipped. |
|
|
586 | |
|
|
587 | This backend can batch oneshot requests and supports a user-space ring |
|
|
588 | buffer to receive events. It also doesn't suffer from most of the design |
|
|
589 | problems of epoll (such as not being able to remove event sources from |
|
|
590 | the epoll set), and generally sounds too good to be true. Because, this |
|
|
591 | being the linux kernel, of course it suffers from a whole new set of |
|
|
592 | limitations. |
|
|
593 | |
|
|
594 | For one, it is not easily embeddable (but probably could be done using |
|
|
595 | an event fd at some extra overhead). It also is subject to a system wide |
|
|
596 | limit that can be configured in F</proc/sys/fs/aio-max-nr> - each loop |
|
|
597 | currently requires C<61> of this number. If no aio requests are left, this |
|
|
598 | backend will be skipped during initialisation. |
|
|
599 | |
|
|
600 | Most problematic in practise, however, is that not all file descriptors |
|
|
601 | work with it. For example, in linux 5.1, tcp sockets, pipes, event fds, |
|
|
602 | files, F</dev/null> and a few others are supported, but ttys do not work |
|
|
603 | (probably because of a bug), so this is not (yet?) a generic event polling |
|
|
604 | interface. |
|
|
605 | |
|
|
606 | To work around this latter problem, the current version of libev uses |
|
|
607 | epoll as a fallback for file deescriptor types that do not work. Epoll |
|
|
608 | is used in, kind of, slow mode that hopefully avoids most of its design |
|
|
609 | problems and requires 1-3 extra syscalls per active fd every iteration. |
548 | |
610 | |
549 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
611 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
550 | C<EVBACKEND_POLL>. |
612 | C<EVBACKEND_POLL>. |
551 | |
613 | |
552 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
614 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
… | |
… | |
569 | kernel is more efficient (which says nothing about its actual speed, of |
631 | kernel is more efficient (which says nothing about its actual speed, of |
570 | course). While stopping, setting and starting an I/O watcher does never |
632 | course). While stopping, setting and starting an I/O watcher does never |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
633 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
634 | two event changes per incident. Support for C<fork ()> is very bad (you |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
635 | might have to leak fd's on fork, but it's more sane than epoll) and it |
574 | drops fds silently in similarly hard-to-detect cases |
636 | drops fds silently in similarly hard-to-detect cases. |
575 | |
637 | |
576 | This backend usually performs well under most conditions. |
638 | This backend usually performs well under most conditions. |
577 | |
639 | |
578 | While nominally embeddable in other event loops, this doesn't work |
640 | While nominally embeddable in other event loops, this doesn't work |
579 | everywhere, so you might need to test for this. And since it is broken |
641 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
653 | Example: Use whatever libev has to offer, but make sure that kqueue is |
715 | Example: Use whatever libev has to offer, but make sure that kqueue is |
654 | used if available. |
716 | used if available. |
655 | |
717 | |
656 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
718 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
657 | |
719 | |
|
|
720 | Example: Similarly, on linux, you mgiht want to take advantage of the |
|
|
721 | linux aio backend if possible, but fall back to something else if that |
|
|
722 | isn't available. |
|
|
723 | |
|
|
724 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO); |
|
|
725 | |
658 | =item ev_loop_destroy (loop) |
726 | =item ev_loop_destroy (loop) |
659 | |
727 | |
660 | Destroys an event loop object (frees all memory and kernel state |
728 | Destroys an event loop object (frees all memory and kernel state |
661 | etc.). None of the active event watchers will be stopped in the normal |
729 | etc.). None of the active event watchers will be stopped in the normal |
662 | sense, so e.g. C<ev_is_active> might still return true. It is your |
730 | sense, so e.g. C<ev_is_active> might still return true. It is your |
… | |
… | |
678 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
746 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
679 | and C<ev_loop_destroy>. |
747 | and C<ev_loop_destroy>. |
680 | |
748 | |
681 | =item ev_loop_fork (loop) |
749 | =item ev_loop_fork (loop) |
682 | |
750 | |
683 | This function sets a flag that causes subsequent C<ev_run> iterations to |
751 | This function sets a flag that causes subsequent C<ev_run> iterations |
684 | reinitialise the kernel state for backends that have one. Despite the |
752 | to reinitialise the kernel state for backends that have one. Despite |
685 | name, you can call it anytime, but it makes most sense after forking, in |
753 | the name, you can call it anytime you are allowed to start or stop |
686 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
754 | watchers (except inside an C<ev_prepare> callback), but it makes most |
|
|
755 | sense after forking, in the child process. You I<must> call it (or use |
687 | child before resuming or calling C<ev_run>. |
756 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
688 | |
757 | |
|
|
758 | In addition, if you want to reuse a loop (via this function or |
|
|
759 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
|
|
760 | |
689 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
761 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
690 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
762 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
691 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
763 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
692 | during fork. |
764 | during fork. |
693 | |
765 | |
694 | On the other hand, you only need to call this function in the child |
766 | On the other hand, you only need to call this function in the child |
… | |
… | |
764 | |
836 | |
765 | This function is rarely useful, but when some event callback runs for a |
837 | This function is rarely useful, but when some event callback runs for a |
766 | very long time without entering the event loop, updating libev's idea of |
838 | very long time without entering the event loop, updating libev's idea of |
767 | the current time is a good idea. |
839 | the current time is a good idea. |
768 | |
840 | |
769 | See also L<The special problem of time updates> in the C<ev_timer> section. |
841 | See also L</The special problem of time updates> in the C<ev_timer> section. |
770 | |
842 | |
771 | =item ev_suspend (loop) |
843 | =item ev_suspend (loop) |
772 | |
844 | |
773 | =item ev_resume (loop) |
845 | =item ev_resume (loop) |
774 | |
846 | |
… | |
… | |
1346 | or might not have been clamped to the valid range. |
1418 | or might not have been clamped to the valid range. |
1347 | |
1419 | |
1348 | The default priority used by watchers when no priority has been set is |
1420 | The default priority used by watchers when no priority has been set is |
1349 | always C<0>, which is supposed to not be too high and not be too low :). |
1421 | always C<0>, which is supposed to not be too high and not be too low :). |
1350 | |
1422 | |
1351 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1423 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1352 | priorities. |
1424 | priorities. |
1353 | |
1425 | |
1354 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1426 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1355 | |
1427 | |
1356 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1428 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1381 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1453 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1382 | functions that do not need a watcher. |
1454 | functions that do not need a watcher. |
1383 | |
1455 | |
1384 | =back |
1456 | =back |
1385 | |
1457 | |
1386 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
1458 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
1387 | OWN COMPOSITE WATCHERS> idioms. |
1459 | OWN COMPOSITE WATCHERS> idioms. |
1388 | |
1460 | |
1389 | =head2 WATCHER STATES |
1461 | =head2 WATCHER STATES |
1390 | |
1462 | |
1391 | There are various watcher states mentioned throughout this manual - |
1463 | There are various watcher states mentioned throughout this manual - |
… | |
… | |
1393 | transition between them will be described in more detail - and while these |
1465 | transition between them will be described in more detail - and while these |
1394 | rules might look complicated, they usually do "the right thing". |
1466 | rules might look complicated, they usually do "the right thing". |
1395 | |
1467 | |
1396 | =over 4 |
1468 | =over 4 |
1397 | |
1469 | |
1398 | =item initialiased |
1470 | =item initialised |
1399 | |
1471 | |
1400 | Before a watcher can be registered with the event loop it has to be |
1472 | Before a watcher can be registered with the event loop it has to be |
1401 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1473 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1402 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1474 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1403 | |
1475 | |
… | |
… | |
1601 | |
1673 | |
1602 | But really, best use non-blocking mode. |
1674 | But really, best use non-blocking mode. |
1603 | |
1675 | |
1604 | =head3 The special problem of disappearing file descriptors |
1676 | =head3 The special problem of disappearing file descriptors |
1605 | |
1677 | |
1606 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1678 | Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing |
1607 | descriptor (either due to calling C<close> explicitly or any other means, |
1679 | a file descriptor (either due to calling C<close> explicitly or any other |
1608 | such as C<dup2>). The reason is that you register interest in some file |
1680 | means, such as C<dup2>). The reason is that you register interest in some |
1609 | descriptor, but when it goes away, the operating system will silently drop |
1681 | file descriptor, but when it goes away, the operating system will silently |
1610 | this interest. If another file descriptor with the same number then is |
1682 | drop this interest. If another file descriptor with the same number then |
1611 | registered with libev, there is no efficient way to see that this is, in |
1683 | is registered with libev, there is no efficient way to see that this is, |
1612 | fact, a different file descriptor. |
1684 | in fact, a different file descriptor. |
1613 | |
1685 | |
1614 | To avoid having to explicitly tell libev about such cases, libev follows |
1686 | To avoid having to explicitly tell libev about such cases, libev follows |
1615 | the following policy: Each time C<ev_io_set> is being called, libev |
1687 | the following policy: Each time C<ev_io_set> is being called, libev |
1616 | will assume that this is potentially a new file descriptor, otherwise |
1688 | will assume that this is potentially a new file descriptor, otherwise |
1617 | it is assumed that the file descriptor stays the same. That means that |
1689 | it is assumed that the file descriptor stays the same. That means that |
… | |
… | |
1666 | when you rarely read from a file instead of from a socket, and want to |
1738 | when you rarely read from a file instead of from a socket, and want to |
1667 | reuse the same code path. |
1739 | reuse the same code path. |
1668 | |
1740 | |
1669 | =head3 The special problem of fork |
1741 | =head3 The special problem of fork |
1670 | |
1742 | |
1671 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1743 | Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()> |
1672 | useless behaviour. Libev fully supports fork, but needs to be told about |
1744 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1673 | it in the child if you want to continue to use it in the child. |
1745 | to be told about it in the child if you want to continue to use it in the |
|
|
1746 | child. |
1674 | |
1747 | |
1675 | To support fork in your child processes, you have to call C<ev_loop_fork |
1748 | To support fork in your child processes, you have to call C<ev_loop_fork |
1676 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1749 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1677 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1750 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1678 | |
1751 | |
… | |
… | |
2024 | |
2097 | |
2025 | The relative timeouts are calculated relative to the C<ev_now ()> |
2098 | The relative timeouts are calculated relative to the C<ev_now ()> |
2026 | time. This is usually the right thing as this timestamp refers to the time |
2099 | time. This is usually the right thing as this timestamp refers to the time |
2027 | of the event triggering whatever timeout you are modifying/starting. If |
2100 | of the event triggering whatever timeout you are modifying/starting. If |
2028 | you suspect event processing to be delayed and you I<need> to base the |
2101 | you suspect event processing to be delayed and you I<need> to base the |
2029 | timeout on the current time, use something like this to adjust for this: |
2102 | timeout on the current time, use something like the following to adjust |
|
|
2103 | for it: |
2030 | |
2104 | |
2031 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2105 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
2032 | |
2106 | |
2033 | If the event loop is suspended for a long time, you can also force an |
2107 | If the event loop is suspended for a long time, you can also force an |
2034 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2108 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2035 | ()>. |
2109 | ()>, although that will push the event time of all outstanding events |
|
|
2110 | further into the future. |
2036 | |
2111 | |
2037 | =head3 The special problem of unsynchronised clocks |
2112 | =head3 The special problem of unsynchronised clocks |
2038 | |
2113 | |
2039 | Modern systems have a variety of clocks - libev itself uses the normal |
2114 | Modern systems have a variety of clocks - libev itself uses the normal |
2040 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
2115 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
… | |
… | |
2103 | |
2178 | |
2104 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2179 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2105 | |
2180 | |
2106 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2181 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2107 | |
2182 | |
2108 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2183 | Configure the timer to trigger after C<after> seconds (fractional and |
2109 | is C<0.>, then it will automatically be stopped once the timeout is |
2184 | negative values are supported). If C<repeat> is C<0.>, then it will |
2110 | reached. If it is positive, then the timer will automatically be |
2185 | automatically be stopped once the timeout is reached. If it is positive, |
2111 | configured to trigger again C<repeat> seconds later, again, and again, |
2186 | then the timer will automatically be configured to trigger again C<repeat> |
2112 | until stopped manually. |
2187 | seconds later, again, and again, until stopped manually. |
2113 | |
2188 | |
2114 | The timer itself will do a best-effort at avoiding drift, that is, if |
2189 | The timer itself will do a best-effort at avoiding drift, that is, if |
2115 | you configure a timer to trigger every 10 seconds, then it will normally |
2190 | you configure a timer to trigger every 10 seconds, then it will normally |
2116 | trigger at exactly 10 second intervals. If, however, your program cannot |
2191 | trigger at exactly 10 second intervals. If, however, your program cannot |
2117 | keep up with the timer (because it takes longer than those 10 seconds to |
2192 | keep up with the timer (because it takes longer than those 10 seconds to |
… | |
… | |
2136 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2211 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2137 | and start the timer, if necessary. |
2212 | and start the timer, if necessary. |
2138 | |
2213 | |
2139 | =back |
2214 | =back |
2140 | |
2215 | |
2141 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2216 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
2142 | usage example. |
2217 | usage example. |
2143 | |
2218 | |
2144 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2219 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2145 | |
2220 | |
2146 | Returns the remaining time until a timer fires. If the timer is active, |
2221 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2199 | Periodic watchers are also timers of a kind, but they are very versatile |
2274 | Periodic watchers are also timers of a kind, but they are very versatile |
2200 | (and unfortunately a bit complex). |
2275 | (and unfortunately a bit complex). |
2201 | |
2276 | |
2202 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2277 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2203 | relative time, the physical time that passes) but on wall clock time |
2278 | relative time, the physical time that passes) but on wall clock time |
2204 | (absolute time, the thing you can read on your calender or clock). The |
2279 | (absolute time, the thing you can read on your calendar or clock). The |
2205 | difference is that wall clock time can run faster or slower than real |
2280 | difference is that wall clock time can run faster or slower than real |
2206 | time, and time jumps are not uncommon (e.g. when you adjust your |
2281 | time, and time jumps are not uncommon (e.g. when you adjust your |
2207 | wrist-watch). |
2282 | wrist-watch). |
2208 | |
2283 | |
2209 | You can tell a periodic watcher to trigger after some specific point |
2284 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
2214 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2289 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2215 | it, as it uses a relative timeout). |
2290 | it, as it uses a relative timeout). |
2216 | |
2291 | |
2217 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2292 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2218 | timers, such as triggering an event on each "midnight, local time", or |
2293 | timers, such as triggering an event on each "midnight, local time", or |
2219 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
2294 | other complicated rules. This cannot easily be done with C<ev_timer> |
2220 | those cannot react to time jumps. |
2295 | watchers, as those cannot react to time jumps. |
2221 | |
2296 | |
2222 | As with timers, the callback is guaranteed to be invoked only when the |
2297 | As with timers, the callback is guaranteed to be invoked only when the |
2223 | point in time where it is supposed to trigger has passed. If multiple |
2298 | point in time where it is supposed to trigger has passed. If multiple |
2224 | timers become ready during the same loop iteration then the ones with |
2299 | timers become ready during the same loop iteration then the ones with |
2225 | earlier time-out values are invoked before ones with later time-out values |
2300 | earlier time-out values are invoked before ones with later time-out values |
… | |
… | |
2311 | |
2386 | |
2312 | NOTE: I<< This callback must always return a time that is higher than or |
2387 | NOTE: I<< This callback must always return a time that is higher than or |
2313 | equal to the passed C<now> value >>. |
2388 | equal to the passed C<now> value >>. |
2314 | |
2389 | |
2315 | This can be used to create very complex timers, such as a timer that |
2390 | This can be used to create very complex timers, such as a timer that |
2316 | triggers on "next midnight, local time". To do this, you would calculate the |
2391 | triggers on "next midnight, local time". To do this, you would calculate |
2317 | next midnight after C<now> and return the timestamp value for this. How |
2392 | the next midnight after C<now> and return the timestamp value for |
2318 | you do this is, again, up to you (but it is not trivial, which is the main |
2393 | this. Here is a (completely untested, no error checking) example on how to |
2319 | reason I omitted it as an example). |
2394 | do this: |
|
|
2395 | |
|
|
2396 | #include <time.h> |
|
|
2397 | |
|
|
2398 | static ev_tstamp |
|
|
2399 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2400 | { |
|
|
2401 | time_t tnow = (time_t)now; |
|
|
2402 | struct tm tm; |
|
|
2403 | localtime_r (&tnow, &tm); |
|
|
2404 | |
|
|
2405 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2406 | ++tm.tm_mday; // midnight next day |
|
|
2407 | |
|
|
2408 | return mktime (&tm); |
|
|
2409 | } |
|
|
2410 | |
|
|
2411 | Note: this code might run into trouble on days that have more then two |
|
|
2412 | midnights (beginning and end). |
2320 | |
2413 | |
2321 | =back |
2414 | =back |
2322 | |
2415 | |
2323 | =item ev_periodic_again (loop, ev_periodic *) |
2416 | =item ev_periodic_again (loop, ev_periodic *) |
2324 | |
2417 | |
… | |
… | |
2389 | |
2482 | |
2390 | ev_periodic hourly_tick; |
2483 | ev_periodic hourly_tick; |
2391 | ev_periodic_init (&hourly_tick, clock_cb, |
2484 | ev_periodic_init (&hourly_tick, clock_cb, |
2392 | fmod (ev_now (loop), 3600.), 3600., 0); |
2485 | fmod (ev_now (loop), 3600.), 3600., 0); |
2393 | ev_periodic_start (loop, &hourly_tick); |
2486 | ev_periodic_start (loop, &hourly_tick); |
2394 | |
2487 | |
2395 | |
2488 | |
2396 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2489 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2397 | |
2490 | |
2398 | Signal watchers will trigger an event when the process receives a specific |
2491 | Signal watchers will trigger an event when the process receives a specific |
2399 | signal one or more times. Even though signals are very asynchronous, libev |
2492 | signal one or more times. Even though signals are very asynchronous, libev |
… | |
… | |
2409 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2502 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2410 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2503 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2411 | C<SIGINT> in both the default loop and another loop at the same time. At |
2504 | C<SIGINT> in both the default loop and another loop at the same time. At |
2412 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2505 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2413 | |
2506 | |
2414 | When the first watcher gets started will libev actually register something |
2507 | Only after the first watcher for a signal is started will libev actually |
2415 | with the kernel (thus it coexists with your own signal handlers as long as |
2508 | register something with the kernel. It thus coexists with your own signal |
2416 | you don't register any with libev for the same signal). |
2509 | handlers as long as you don't register any with libev for the same signal. |
2417 | |
2510 | |
2418 | If possible and supported, libev will install its handlers with |
2511 | If possible and supported, libev will install its handlers with |
2419 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2512 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2420 | not be unduly interrupted. If you have a problem with system calls getting |
2513 | not be unduly interrupted. If you have a problem with system calls getting |
2421 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2514 | interrupted by signals you can block all signals in an C<ev_check> watcher |
… | |
… | |
2606 | |
2699 | |
2607 | =head2 C<ev_stat> - did the file attributes just change? |
2700 | =head2 C<ev_stat> - did the file attributes just change? |
2608 | |
2701 | |
2609 | This watches a file system path for attribute changes. That is, it calls |
2702 | This watches a file system path for attribute changes. That is, it calls |
2610 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2703 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2611 | and sees if it changed compared to the last time, invoking the callback if |
2704 | and sees if it changed compared to the last time, invoking the callback |
2612 | it did. |
2705 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2706 | happen after the watcher has been started will be reported. |
2613 | |
2707 | |
2614 | The path does not need to exist: changing from "path exists" to "path does |
2708 | The path does not need to exist: changing from "path exists" to "path does |
2615 | not exist" is a status change like any other. The condition "path does not |
2709 | not exist" is a status change like any other. The condition "path does not |
2616 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2710 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2617 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2711 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2858 | |
2952 | |
2859 | This mode of operation can be useful together with an C<ev_check> watcher, |
2953 | This mode of operation can be useful together with an C<ev_check> watcher, |
2860 | to do something on each event loop iteration - for example to balance load |
2954 | to do something on each event loop iteration - for example to balance load |
2861 | between different connections. |
2955 | between different connections. |
2862 | |
2956 | |
2863 | See L<< Abusing an C<ev_check> watcher for its side-effect >> for a longer |
2957 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
2864 | example. |
2958 | example. |
2865 | |
2959 | |
2866 | =head3 Watcher-Specific Functions and Data Members |
2960 | =head3 Watcher-Specific Functions and Data Members |
2867 | |
2961 | |
2868 | =over 4 |
2962 | =over 4 |
… | |
… | |
2902 | |
2996 | |
2903 | Prepare and check watchers are often (but not always) used in pairs: |
2997 | Prepare and check watchers are often (but not always) used in pairs: |
2904 | prepare watchers get invoked before the process blocks and check watchers |
2998 | prepare watchers get invoked before the process blocks and check watchers |
2905 | afterwards. |
2999 | afterwards. |
2906 | |
3000 | |
2907 | You I<must not> call C<ev_run> or similar functions that enter |
3001 | You I<must not> call C<ev_run> (or similar functions that enter the |
2908 | the current event loop from either C<ev_prepare> or C<ev_check> |
3002 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2909 | watchers. Other loops than the current one are fine, however. The |
3003 | C<ev_check> watchers. Other loops than the current one are fine, |
2910 | rationale behind this is that you do not need to check for recursion in |
3004 | however. The rationale behind this is that you do not need to check |
2911 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
3005 | for recursion in those watchers, i.e. the sequence will always be |
2912 | C<ev_check> so if you have one watcher of each kind they will always be |
3006 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2913 | called in pairs bracketing the blocking call. |
3007 | kind they will always be called in pairs bracketing the blocking call. |
2914 | |
3008 | |
2915 | Their main purpose is to integrate other event mechanisms into libev and |
3009 | Their main purpose is to integrate other event mechanisms into libev and |
2916 | their use is somewhat advanced. They could be used, for example, to track |
3010 | their use is somewhat advanced. They could be used, for example, to track |
2917 | variable changes, implement your own watchers, integrate net-snmp or a |
3011 | variable changes, implement your own watchers, integrate net-snmp or a |
2918 | coroutine library and lots more. They are also occasionally useful if |
3012 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
2962 | |
3056 | |
2963 | Using an C<ev_check> watcher is almost enough: it will be called on the |
3057 | Using an C<ev_check> watcher is almost enough: it will be called on the |
2964 | next event loop iteration. However, that isn't as soon as possible - |
3058 | next event loop iteration. However, that isn't as soon as possible - |
2965 | without external events, your C<ev_check> watcher will not be invoked. |
3059 | without external events, your C<ev_check> watcher will not be invoked. |
2966 | |
3060 | |
2967 | |
|
|
2968 | This is where C<ev_idle> watchers come in handy - all you need is a |
3061 | This is where C<ev_idle> watchers come in handy - all you need is a |
2969 | single global idle watcher that is active as long as you have one active |
3062 | single global idle watcher that is active as long as you have one active |
2970 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
3063 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
2971 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
3064 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
2972 | invoked. Neither watcher alone can do that. |
3065 | invoked. Neither watcher alone can do that. |
… | |
… | |
3178 | |
3271 | |
3179 | =over 4 |
3272 | =over 4 |
3180 | |
3273 | |
3181 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3274 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3182 | |
3275 | |
3183 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3276 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
3184 | |
3277 | |
3185 | Configures the watcher to embed the given loop, which must be |
3278 | Configures the watcher to embed the given loop, which must be |
3186 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3279 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3187 | invoked automatically, otherwise it is the responsibility of the callback |
3280 | invoked automatically, otherwise it is the responsibility of the callback |
3188 | to invoke it (it will continue to be called until the sweep has been done, |
3281 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3209 | used). |
3302 | used). |
3210 | |
3303 | |
3211 | struct ev_loop *loop_hi = ev_default_init (0); |
3304 | struct ev_loop *loop_hi = ev_default_init (0); |
3212 | struct ev_loop *loop_lo = 0; |
3305 | struct ev_loop *loop_lo = 0; |
3213 | ev_embed embed; |
3306 | ev_embed embed; |
3214 | |
3307 | |
3215 | // see if there is a chance of getting one that works |
3308 | // see if there is a chance of getting one that works |
3216 | // (remember that a flags value of 0 means autodetection) |
3309 | // (remember that a flags value of 0 means autodetection) |
3217 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3310 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3218 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3311 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3219 | : 0; |
3312 | : 0; |
… | |
… | |
3233 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3326 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3234 | |
3327 | |
3235 | struct ev_loop *loop = ev_default_init (0); |
3328 | struct ev_loop *loop = ev_default_init (0); |
3236 | struct ev_loop *loop_socket = 0; |
3329 | struct ev_loop *loop_socket = 0; |
3237 | ev_embed embed; |
3330 | ev_embed embed; |
3238 | |
3331 | |
3239 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3332 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3240 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3333 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3241 | { |
3334 | { |
3242 | ev_embed_init (&embed, 0, loop_socket); |
3335 | ev_embed_init (&embed, 0, loop_socket); |
3243 | ev_embed_start (loop, &embed); |
3336 | ev_embed_start (loop, &embed); |
… | |
… | |
3251 | |
3344 | |
3252 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3345 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3253 | |
3346 | |
3254 | Fork watchers are called when a C<fork ()> was detected (usually because |
3347 | Fork watchers are called when a C<fork ()> was detected (usually because |
3255 | whoever is a good citizen cared to tell libev about it by calling |
3348 | whoever is a good citizen cared to tell libev about it by calling |
3256 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3349 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3257 | event loop blocks next and before C<ev_check> watchers are being called, |
3350 | and before C<ev_check> watchers are being called, and only in the child |
3258 | and only in the child after the fork. If whoever good citizen calling |
3351 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3259 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3352 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3260 | handlers will be invoked, too, of course. |
3353 | of course. |
3261 | |
3354 | |
3262 | =head3 The special problem of life after fork - how is it possible? |
3355 | =head3 The special problem of life after fork - how is it possible? |
3263 | |
3356 | |
3264 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3357 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3265 | up/change the process environment, followed by a call to C<exec()>. This |
3358 | up/change the process environment, followed by a call to C<exec()>. This |
3266 | sequence should be handled by libev without any problems. |
3359 | sequence should be handled by libev without any problems. |
3267 | |
3360 | |
3268 | This changes when the application actually wants to do event handling |
3361 | This changes when the application actually wants to do event handling |
3269 | in the child, or both parent in child, in effect "continuing" after the |
3362 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3507 | |
3600 | |
3508 | There are some other functions of possible interest. Described. Here. Now. |
3601 | There are some other functions of possible interest. Described. Here. Now. |
3509 | |
3602 | |
3510 | =over 4 |
3603 | =over 4 |
3511 | |
3604 | |
3512 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3605 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
3513 | |
3606 | |
3514 | This function combines a simple timer and an I/O watcher, calls your |
3607 | This function combines a simple timer and an I/O watcher, calls your |
3515 | callback on whichever event happens first and automatically stops both |
3608 | callback on whichever event happens first and automatically stops both |
3516 | watchers. This is useful if you want to wait for a single event on an fd |
3609 | watchers. This is useful if you want to wait for a single event on an fd |
3517 | or timeout without having to allocate/configure/start/stop/free one or |
3610 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
3659 | already been invoked. |
3752 | already been invoked. |
3660 | |
3753 | |
3661 | A common way around all these issues is to make sure that |
3754 | A common way around all these issues is to make sure that |
3662 | C<start_new_request> I<always> returns before the callback is invoked. If |
3755 | C<start_new_request> I<always> returns before the callback is invoked. If |
3663 | C<start_new_request> immediately knows the result, it can artificially |
3756 | C<start_new_request> immediately knows the result, it can artificially |
3664 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
3757 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
3665 | for example, or more sneakily, by reusing an existing (stopped) watcher |
3758 | example, or more sneakily, by reusing an existing (stopped) watcher and |
3666 | and pushing it into the pending queue: |
3759 | pushing it into the pending queue: |
3667 | |
3760 | |
3668 | ev_set_cb (watcher, callback); |
3761 | ev_set_cb (watcher, callback); |
3669 | ev_feed_event (EV_A_ watcher, 0); |
3762 | ev_feed_event (EV_A_ watcher, 0); |
3670 | |
3763 | |
3671 | This way, C<start_new_request> can safely return before the callback is |
3764 | This way, C<start_new_request> can safely return before the callback is |
… | |
… | |
3679 | |
3772 | |
3680 | This brings the problem of exiting - a callback might want to finish the |
3773 | This brings the problem of exiting - a callback might want to finish the |
3681 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3774 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3682 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3775 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3683 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3776 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3684 | other combination: In these cases, C<ev_break> will not work alone. |
3777 | other combination: In these cases, a simple C<ev_break> will not work. |
3685 | |
3778 | |
3686 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3779 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3687 | invocation, and use a loop around C<ev_run> until the condition is |
3780 | invocation, and use a loop around C<ev_run> until the condition is |
3688 | triggered, using C<EVRUN_ONCE>: |
3781 | triggered, using C<EVRUN_ONCE>: |
3689 | |
3782 | |
… | |
… | |
3888 | You can do similar tricks if you have, say, threads with an event queue - |
3981 | You can do similar tricks if you have, say, threads with an event queue - |
3889 | instead of storing a coroutine, you store the queue object and instead of |
3982 | instead of storing a coroutine, you store the queue object and instead of |
3890 | switching to a coroutine, you push the watcher onto the queue and notify |
3983 | switching to a coroutine, you push the watcher onto the queue and notify |
3891 | any waiters. |
3984 | any waiters. |
3892 | |
3985 | |
3893 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
3986 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3894 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3987 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3895 | |
3988 | |
3896 | // my_ev.h |
3989 | // my_ev.h |
3897 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3990 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3898 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
3991 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
3899 | #include "../libev/ev.h" |
3992 | #include "../libev/ev.h" |
3900 | |
3993 | |
3901 | // my_ev.c |
3994 | // my_ev.c |
3902 | #define EV_H "my_ev.h" |
3995 | #define EV_H "my_ev.h" |
3903 | #include "../libev/ev.c" |
3996 | #include "../libev/ev.c" |
… | |
… | |
3949 | The normal C API should work fine when used from C++: both ev.h and the |
4042 | The normal C API should work fine when used from C++: both ev.h and the |
3950 | libev sources can be compiled as C++. Therefore, code that uses the C API |
4043 | libev sources can be compiled as C++. Therefore, code that uses the C API |
3951 | will work fine. |
4044 | will work fine. |
3952 | |
4045 | |
3953 | Proper exception specifications might have to be added to callbacks passed |
4046 | Proper exception specifications might have to be added to callbacks passed |
3954 | to libev: exceptions may be thrown only from watcher callbacks, all |
4047 | to libev: exceptions may be thrown only from watcher callbacks, all other |
3955 | other callbacks (allocator, syserr, loop acquire/release and periodioc |
4048 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
3956 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
4049 | callbacks) must not throw exceptions, and might need a C<noexcept> |
3957 | ()> specification. If you have code that needs to be compiled as both C |
4050 | specification. If you have code that needs to be compiled as both C and |
3958 | and C++ you can use the C<EV_THROW> macro for this: |
4051 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
3959 | |
4052 | |
3960 | static void |
4053 | static void |
3961 | fatal_error (const char *msg) EV_THROW |
4054 | fatal_error (const char *msg) EV_NOEXCEPT |
3962 | { |
4055 | { |
3963 | perror (msg); |
4056 | perror (msg); |
3964 | abort (); |
4057 | abort (); |
3965 | } |
4058 | } |
3966 | |
4059 | |
… | |
… | |
3980 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
4073 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3981 | you to use some convenience methods to start/stop watchers and also change |
4074 | you to use some convenience methods to start/stop watchers and also change |
3982 | the callback model to a model using method callbacks on objects. |
4075 | the callback model to a model using method callbacks on objects. |
3983 | |
4076 | |
3984 | To use it, |
4077 | To use it, |
3985 | |
4078 | |
3986 | #include <ev++.h> |
4079 | #include <ev++.h> |
3987 | |
4080 | |
3988 | This automatically includes F<ev.h> and puts all of its definitions (many |
4081 | This automatically includes F<ev.h> and puts all of its definitions (many |
3989 | of them macros) into the global namespace. All C++ specific things are |
4082 | of them macros) into the global namespace. All C++ specific things are |
3990 | put into the C<ev> namespace. It should support all the same embedding |
4083 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
4093 | void operator() (ev::io &w, int revents) |
4186 | void operator() (ev::io &w, int revents) |
4094 | { |
4187 | { |
4095 | ... |
4188 | ... |
4096 | } |
4189 | } |
4097 | } |
4190 | } |
4098 | |
4191 | |
4099 | myfunctor f; |
4192 | myfunctor f; |
4100 | |
4193 | |
4101 | ev::io w; |
4194 | ev::io w; |
4102 | w.set (&f); |
4195 | w.set (&f); |
4103 | |
4196 | |
… | |
… | |
4121 | Associates a different C<struct ev_loop> with this watcher. You can only |
4214 | Associates a different C<struct ev_loop> with this watcher. You can only |
4122 | do this when the watcher is inactive (and not pending either). |
4215 | do this when the watcher is inactive (and not pending either). |
4123 | |
4216 | |
4124 | =item w->set ([arguments]) |
4217 | =item w->set ([arguments]) |
4125 | |
4218 | |
4126 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4219 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
4127 | method or a suitable start method must be called at least once. Unlike the |
4220 | with the same arguments. Either this method or a suitable start method |
4128 | C counterpart, an active watcher gets automatically stopped and restarted |
4221 | must be called at least once. Unlike the C counterpart, an active watcher |
4129 | when reconfiguring it with this method. |
4222 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4223 | method. |
|
|
4224 | |
|
|
4225 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4226 | clashing with the C<set (loop)> method. |
4130 | |
4227 | |
4131 | =item w->start () |
4228 | =item w->start () |
4132 | |
4229 | |
4133 | Starts the watcher. Note that there is no C<loop> argument, as the |
4230 | Starts the watcher. Note that there is no C<loop> argument, as the |
4134 | constructor already stores the event loop. |
4231 | constructor already stores the event loop. |
… | |
… | |
4238 | |
4335 | |
4239 | Brian Maher has written a partial interface to libev for lua (at the |
4336 | Brian Maher has written a partial interface to libev for lua (at the |
4240 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4337 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4241 | L<http://github.com/brimworks/lua-ev>. |
4338 | L<http://github.com/brimworks/lua-ev>. |
4242 | |
4339 | |
|
|
4340 | =item Javascript |
|
|
4341 | |
|
|
4342 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4343 | |
|
|
4344 | =item Others |
|
|
4345 | |
|
|
4346 | There are others, and I stopped counting. |
|
|
4347 | |
4243 | =back |
4348 | =back |
4244 | |
4349 | |
4245 | |
4350 | |
4246 | =head1 MACRO MAGIC |
4351 | =head1 MACRO MAGIC |
4247 | |
4352 | |
… | |
… | |
4364 | ev_vars.h |
4469 | ev_vars.h |
4365 | ev_wrap.h |
4470 | ev_wrap.h |
4366 | |
4471 | |
4367 | ev_win32.c required on win32 platforms only |
4472 | ev_win32.c required on win32 platforms only |
4368 | |
4473 | |
4369 | ev_select.c only when select backend is enabled (which is enabled by default) |
4474 | ev_select.c only when select backend is enabled |
4370 | ev_poll.c only when poll backend is enabled (disabled by default) |
4475 | ev_poll.c only when poll backend is enabled |
4371 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4476 | ev_epoll.c only when the epoll backend is enabled |
|
|
4477 | ev_linuxaio.c only when the linux aio backend is enabled |
4372 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4478 | ev_kqueue.c only when the kqueue backend is enabled |
4373 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4479 | ev_port.c only when the solaris port backend is enabled |
4374 | |
4480 | |
4375 | F<ev.c> includes the backend files directly when enabled, so you only need |
4481 | F<ev.c> includes the backend files directly when enabled, so you only need |
4376 | to compile this single file. |
4482 | to compile this single file. |
4377 | |
4483 | |
4378 | =head3 LIBEVENT COMPATIBILITY API |
4484 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
4546 | If programs implement their own fd to handle mapping on win32, then this |
4652 | If programs implement their own fd to handle mapping on win32, then this |
4547 | macro can be used to override the C<close> function, useful to unregister |
4653 | macro can be used to override the C<close> function, useful to unregister |
4548 | file descriptors again. Note that the replacement function has to close |
4654 | file descriptors again. Note that the replacement function has to close |
4549 | the underlying OS handle. |
4655 | the underlying OS handle. |
4550 | |
4656 | |
|
|
4657 | =item EV_USE_WSASOCKET |
|
|
4658 | |
|
|
4659 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4660 | communication socket, which works better in some environments. Otherwise, |
|
|
4661 | the normal C<socket> function will be used, which works better in other |
|
|
4662 | environments. |
|
|
4663 | |
4551 | =item EV_USE_POLL |
4664 | =item EV_USE_POLL |
4552 | |
4665 | |
4553 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4666 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4554 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4667 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4555 | takes precedence over select. |
4668 | takes precedence over select. |
… | |
… | |
4559 | If defined to be C<1>, libev will compile in support for the Linux |
4672 | If defined to be C<1>, libev will compile in support for the Linux |
4560 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4673 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4561 | otherwise another method will be used as fallback. This is the preferred |
4674 | otherwise another method will be used as fallback. This is the preferred |
4562 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4675 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4563 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4676 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4677 | |
|
|
4678 | =item EV_USE_LINUXAIO |
|
|
4679 | |
|
|
4680 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
4681 | aio backend. Due to it's currenbt limitations it has to be requested |
|
|
4682 | explicitly. If undefined, it will be enabled on linux, otherwise |
|
|
4683 | disabled. |
4564 | |
4684 | |
4565 | =item EV_USE_KQUEUE |
4685 | =item EV_USE_KQUEUE |
4566 | |
4686 | |
4567 | If defined to be C<1>, libev will compile in support for the BSD style |
4687 | If defined to be C<1>, libev will compile in support for the BSD style |
4568 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4688 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
4599 | different cpus (or different cpu cores). This reduces dependencies |
4719 | different cpus (or different cpu cores). This reduces dependencies |
4600 | and makes libev faster. |
4720 | and makes libev faster. |
4601 | |
4721 | |
4602 | =item EV_NO_THREADS |
4722 | =item EV_NO_THREADS |
4603 | |
4723 | |
4604 | If defined to be C<1>, libev will assume that it will never be called |
4724 | If defined to be C<1>, libev will assume that it will never be called from |
4605 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
4725 | different threads (that includes signal handlers), which is a stronger |
4606 | above. This reduces dependencies and makes libev faster. |
4726 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4727 | libev faster. |
4607 | |
4728 | |
4608 | =item EV_ATOMIC_T |
4729 | =item EV_ATOMIC_T |
4609 | |
4730 | |
4610 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4731 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4611 | access is atomic and serialised with respect to other threads or signal |
4732 | access is atomic with respect to other threads or signal contexts. No |
4612 | contexts. No such type is easily found in the C language, so you can |
4733 | such type is easily found in the C language, so you can provide your own |
4613 | provide your own type that you know is safe for your purposes. It is used |
4734 | type that you know is safe for your purposes. It is used both for signal |
4614 | both for signal handler "locking" as well as for signal and thread safety |
4735 | handler "locking" as well as for signal and thread safety in C<ev_async> |
4615 | in C<ev_async> watchers. |
4736 | watchers. |
4616 | |
4737 | |
4617 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4738 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4618 | (from F<signal.h>), which is usually good enough on most platforms, |
4739 | (from F<signal.h>), which is usually good enough on most platforms. |
4619 | although strictly speaking using a type that also implies a memory fence |
|
|
4620 | is required. |
|
|
4621 | |
4740 | |
4622 | =item EV_H (h) |
4741 | =item EV_H (h) |
4623 | |
4742 | |
4624 | The name of the F<ev.h> header file used to include it. The default if |
4743 | The name of the F<ev.h> header file used to include it. The default if |
4625 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4744 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
4993 | default loop and triggering an C<ev_async> watcher from the default loop |
5112 | default loop and triggering an C<ev_async> watcher from the default loop |
4994 | watcher callback into the event loop interested in the signal. |
5113 | watcher callback into the event loop interested in the signal. |
4995 | |
5114 | |
4996 | =back |
5115 | =back |
4997 | |
5116 | |
4998 | See also L<THREAD LOCKING EXAMPLE>. |
5117 | See also L</THREAD LOCKING EXAMPLE>. |
4999 | |
5118 | |
5000 | =head3 COROUTINES |
5119 | =head3 COROUTINES |
5001 | |
5120 | |
5002 | Libev is very accommodating to coroutines ("cooperative threads"): |
5121 | Libev is very accommodating to coroutines ("cooperative threads"): |
5003 | libev fully supports nesting calls to its functions from different |
5122 | libev fully supports nesting calls to its functions from different |
… | |
… | |
5272 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5391 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5273 | assumes that the same (machine) code can be used to call any watcher |
5392 | assumes that the same (machine) code can be used to call any watcher |
5274 | callback: The watcher callbacks have different type signatures, but libev |
5393 | callback: The watcher callbacks have different type signatures, but libev |
5275 | calls them using an C<ev_watcher *> internally. |
5394 | calls them using an C<ev_watcher *> internally. |
5276 | |
5395 | |
|
|
5396 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5397 | |
|
|
5398 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5399 | relies on this setting pointers and integers to null. |
|
|
5400 | |
5277 | =item pointer accesses must be thread-atomic |
5401 | =item pointer accesses must be thread-atomic |
5278 | |
5402 | |
5279 | Accessing a pointer value must be atomic, it must both be readable and |
5403 | Accessing a pointer value must be atomic, it must both be readable and |
5280 | writable in one piece - this is the case on all current architectures. |
5404 | writable in one piece - this is the case on all current architectures. |
5281 | |
5405 | |
… | |
… | |
5294 | thread" or will block signals process-wide, both behaviours would |
5418 | thread" or will block signals process-wide, both behaviours would |
5295 | be compatible with libev. Interaction between C<sigprocmask> and |
5419 | be compatible with libev. Interaction between C<sigprocmask> and |
5296 | C<pthread_sigmask> could complicate things, however. |
5420 | C<pthread_sigmask> could complicate things, however. |
5297 | |
5421 | |
5298 | The most portable way to handle signals is to block signals in all threads |
5422 | The most portable way to handle signals is to block signals in all threads |
5299 | except the initial one, and run the default loop in the initial thread as |
5423 | except the initial one, and run the signal handling loop in the initial |
5300 | well. |
5424 | thread as well. |
5301 | |
5425 | |
5302 | =item C<long> must be large enough for common memory allocation sizes |
5426 | =item C<long> must be large enough for common memory allocation sizes |
5303 | |
5427 | |
5304 | To improve portability and simplify its API, libev uses C<long> internally |
5428 | To improve portability and simplify its API, libev uses C<long> internally |
5305 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5429 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
5409 | =over 4 |
5533 | =over 4 |
5410 | |
5534 | |
5411 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5535 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5412 | |
5536 | |
5413 | The backward compatibility mechanism can be controlled by |
5537 | The backward compatibility mechanism can be controlled by |
5414 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
5538 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
5415 | section. |
5539 | section. |
5416 | |
5540 | |
5417 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5541 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5418 | |
5542 | |
5419 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5543 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
… | |
… | |
5462 | =over 4 |
5586 | =over 4 |
5463 | |
5587 | |
5464 | =item active |
5588 | =item active |
5465 | |
5589 | |
5466 | A watcher is active as long as it has been started and not yet stopped. |
5590 | A watcher is active as long as it has been started and not yet stopped. |
5467 | See L<WATCHER STATES> for details. |
5591 | See L</WATCHER STATES> for details. |
5468 | |
5592 | |
5469 | =item application |
5593 | =item application |
5470 | |
5594 | |
5471 | In this document, an application is whatever is using libev. |
5595 | In this document, an application is whatever is using libev. |
5472 | |
5596 | |
… | |
… | |
5508 | watchers and events. |
5632 | watchers and events. |
5509 | |
5633 | |
5510 | =item pending |
5634 | =item pending |
5511 | |
5635 | |
5512 | A watcher is pending as soon as the corresponding event has been |
5636 | A watcher is pending as soon as the corresponding event has been |
5513 | detected. See L<WATCHER STATES> for details. |
5637 | detected. See L</WATCHER STATES> for details. |
5514 | |
5638 | |
5515 | =item real time |
5639 | =item real time |
5516 | |
5640 | |
5517 | The physical time that is observed. It is apparently strictly monotonic :) |
5641 | The physical time that is observed. It is apparently strictly monotonic :) |
5518 | |
5642 | |