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1 | =encoding utf-8 |
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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 |
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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 |
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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 |
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157 | When libev detects a usage error such as a negative timer interval, then |
159 | When libev detects a usage error such as a negative timer interval, then |
158 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
160 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
159 | so C<NDEBUG> will disable this checking): these are programming errors in |
161 | so C<NDEBUG> will disable this checking): these are programming errors in |
160 | the libev caller and need to be fixed there. |
162 | the libev caller and need to be fixed there. |
161 | |
163 | |
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164 | Via the C<EV_FREQUENT> macro you can compile in and/or enable extensive |
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165 | consistency checking code inside libev that can be used to check for |
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166 | internal inconsistencies, suually caused by application bugs. |
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167 | |
162 | Libev also has a few internal error-checking C<assert>ions, and also has |
168 | Libev also has a few internal error-checking C<assert>ions. These do not |
163 | extensive consistency checking code. These do not trigger under normal |
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164 | circumstances, as they indicate either a bug in libev or worse. |
169 | trigger under normal circumstances, as they indicate either a bug in libev |
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170 | or worse. |
165 | |
171 | |
166 | |
172 | |
167 | =head1 GLOBAL FUNCTIONS |
173 | =head1 GLOBAL FUNCTIONS |
168 | |
174 | |
169 | These functions can be called anytime, even before initialising the |
175 | These functions can be called anytime, even before initialising the |
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263 | |
269 | |
264 | You could override this function in high-availability programs to, say, |
270 | 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, |
271 | 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. |
272 | or even to sleep a while and retry until some memory is available. |
267 | |
273 | |
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274 | Example: The following is the C<realloc> function that libev itself uses |
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275 | which should work with C<realloc> and C<free> functions of all kinds and |
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276 | is probably a good basis for your own implementation. |
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277 | |
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278 | static void * |
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279 | ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT |
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280 | { |
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281 | if (size) |
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282 | return realloc (ptr, size); |
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283 | |
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284 | free (ptr); |
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285 | return 0; |
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286 | } |
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287 | |
268 | Example: Replace the libev allocator with one that waits a bit and then |
288 | Example: Replace the libev allocator with one that waits a bit and then |
269 | retries (example requires a standards-compliant C<realloc>). |
289 | retries. |
270 | |
290 | |
271 | static void * |
291 | static void * |
272 | persistent_realloc (void *ptr, size_t size) |
292 | persistent_realloc (void *ptr, size_t size) |
273 | { |
293 | { |
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294 | if (!size) |
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295 | { |
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296 | free (ptr); |
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297 | return 0; |
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298 | } |
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299 | |
274 | for (;;) |
300 | for (;;) |
275 | { |
301 | { |
276 | void *newptr = realloc (ptr, size); |
302 | void *newptr = realloc (ptr, size); |
277 | |
303 | |
278 | if (newptr) |
304 | if (newptr) |
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396 | |
422 | |
397 | If this flag bit is or'ed into the flag value (or the program runs setuid |
423 | 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 |
424 | or setgid) then libev will I<not> look at the environment variable |
399 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
425 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
400 | override the flags completely if it is found in the environment. This is |
426 | 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 |
427 | useful to try out specific backends to test their performance, to work |
402 | around bugs. |
428 | around bugs, or to make libev threadsafe (accessing environment variables |
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429 | cannot be done in a threadsafe way, but usually it works if no other |
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430 | thread modifies them). |
403 | |
431 | |
404 | =item C<EVFLAG_FORKCHECK> |
432 | =item C<EVFLAG_FORKCHECK> |
405 | |
433 | |
406 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
434 | 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. |
435 | make libev check for a fork in each iteration by enabling this flag. |
408 | |
436 | |
409 | This works by calling C<getpid ()> on every iteration of the loop, |
437 | 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 |
438 | 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 |
439 | 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 |
440 | 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 |
441 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
414 | C<pthread_atfork> which is even faster). |
442 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
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443 | versions 2.25 apparently removed the C<getpid> optimisation again). |
415 | |
444 | |
416 | The big advantage of this flag is that you can forget about fork (and |
445 | 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 |
446 | forget about forgetting to tell libev about forking, although you still |
418 | flag. |
447 | have to ignore C<SIGPIPE>) when you use this flag. |
419 | |
448 | |
420 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
449 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
421 | environment variable. |
450 | environment variable. |
422 | |
451 | |
423 | =item C<EVFLAG_NOINOTIFY> |
452 | =item C<EVFLAG_NOINOTIFY> |
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451 | unblocking the signals. |
480 | unblocking the signals. |
452 | |
481 | |
453 | It's also required by POSIX in a threaded program, as libev calls |
482 | It's also required by POSIX in a threaded program, as libev calls |
454 | C<sigprocmask>, whose behaviour is officially unspecified. |
483 | C<sigprocmask>, whose behaviour is officially unspecified. |
455 | |
484 | |
456 | This flag's behaviour will become the default in future versions of libev. |
485 | =item C<EVFLAG_NOTIMERFD> |
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486 | |
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487 | When this flag is specified, the libev will avoid using a C<timerfd> to |
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488 | detect time jumps. It will still be able to detect time jumps, but takes |
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489 | longer and has a lower accuracy in doing so, but saves a file descriptor |
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490 | per loop. |
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491 | |
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492 | The current implementation only tries to use a C<timerfd> when the first |
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493 | C<ev_periodic> watcher is started and falls back on other methods if it |
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494 | cannot be created, but this behaviour might change in the future. |
457 | |
495 | |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
496 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
459 | |
497 | |
460 | This is your standard select(2) backend. Not I<completely> standard, as |
498 | This is your standard select(2) backend. Not I<completely> standard, as |
461 | libev tries to roll its own fd_set with no limits on the number of fds, |
499 | libev tries to roll its own fd_set with no limits on the number of fds, |
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486 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
524 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
487 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
525 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
488 | |
526 | |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
527 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
490 | |
528 | |
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
529 | Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
492 | kernels). |
530 | kernels). |
493 | |
531 | |
494 | For few fds, this backend is a bit little slower than poll and select, but |
532 | For few fds, this backend is a bit little slower than poll and select, but |
495 | it scales phenomenally better. While poll and select usually scale like |
533 | it scales phenomenally better. While poll and select usually scale like |
496 | O(total_fds) where total_fds is the total number of fds (or the highest |
534 | O(total_fds) where total_fds is the total number of fds (or the highest |
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542 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
580 | 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 |
581 | faster than epoll for maybe up to a hundred file descriptors, depending on |
544 | the usage. So sad. |
582 | the usage. So sad. |
545 | |
583 | |
546 | While nominally embeddable in other event loops, this feature is broken in |
584 | While nominally embeddable in other event loops, this feature is broken in |
547 | all kernel versions tested so far. |
585 | a lot of kernel revisions, but probably(!) works in current versions. |
548 | |
586 | |
549 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
587 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
550 | C<EVBACKEND_POLL>. |
588 | C<EVBACKEND_POLL>. |
551 | |
589 | |
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590 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
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591 | |
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592 | Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<< |
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593 | io_submit(2) >>) event interface available in post-4.18 kernels (but libev |
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594 | only tries to use it in 4.19+). |
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595 | |
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596 | This is another Linux train wreck of an event interface. |
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597 | |
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598 | If this backend works for you (as of this writing, it was very |
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599 | experimental), it is the best event interface available on Linux and might |
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600 | be well worth enabling it - if it isn't available in your kernel this will |
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601 | be detected and this backend will be skipped. |
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602 | |
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603 | This backend can batch oneshot requests and supports a user-space ring |
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604 | buffer to receive events. It also doesn't suffer from most of the design |
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605 | problems of epoll (such as not being able to remove event sources from |
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606 | the epoll set), and generally sounds too good to be true. Because, this |
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607 | being the Linux kernel, of course it suffers from a whole new set of |
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608 | limitations, forcing you to fall back to epoll, inheriting all its design |
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609 | issues. |
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610 | |
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611 | For one, it is not easily embeddable (but probably could be done using |
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612 | an event fd at some extra overhead). It also is subject to a system wide |
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613 | limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO |
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614 | requests are left, this backend will be skipped during initialisation, and |
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615 | will switch to epoll when the loop is active. |
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616 | |
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617 | Most problematic in practice, however, is that not all file descriptors |
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618 | work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds, |
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619 | files, F</dev/null> and many others are supported, but ttys do not work |
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620 | properly (a known bug that the kernel developers don't care about, see |
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621 | L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
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622 | (yet?) a generic event polling interface. |
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623 | |
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624 | Overall, it seems the Linux developers just don't want it to have a |
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625 | generic event handling mechanism other than C<select> or C<poll>. |
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626 | |
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627 | To work around all these problem, the current version of libev uses its |
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628 | epoll backend as a fallback for file descriptor types that do not work. Or |
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629 | falls back completely to epoll if the kernel acts up. |
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630 | |
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631 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
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632 | C<EVBACKEND_POLL>. |
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633 | |
552 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
634 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
553 | |
635 | |
554 | Kqueue deserves special mention, as at the time of this writing, it |
636 | Kqueue deserves special mention, as at the time this backend was |
555 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
637 | implemented, it was broken on all BSDs except NetBSD (usually it doesn't |
556 | with anything but sockets and pipes, except on Darwin, where of course |
638 | work reliably with anything but sockets and pipes, except on Darwin, |
557 | it's completely useless). Unlike epoll, however, whose brokenness |
639 | where of course it's completely useless). Unlike epoll, however, whose |
558 | is by design, these kqueue bugs can (and eventually will) be fixed |
640 | brokenness is by design, these kqueue bugs can be (and mostly have been) |
559 | without API changes to existing programs. For this reason it's not being |
641 | fixed without API changes to existing programs. For this reason it's not |
560 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
642 | being "auto-detected" on all platforms unless you explicitly specify it |
561 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
643 | in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a |
562 | system like NetBSD. |
644 | known-to-be-good (-enough) system like NetBSD. |
563 | |
645 | |
564 | You still can embed kqueue into a normal poll or select backend and use it |
646 | You still can embed kqueue into a normal poll or select backend and use it |
565 | only for sockets (after having made sure that sockets work with kqueue on |
647 | only for sockets (after having made sure that sockets work with kqueue on |
566 | the target platform). See C<ev_embed> watchers for more info. |
648 | the target platform). See C<ev_embed> watchers for more info. |
567 | |
649 | |
568 | It scales in the same way as the epoll backend, but the interface to the |
650 | It scales in the same way as the epoll backend, but the interface to the |
569 | kernel is more efficient (which says nothing about its actual speed, of |
651 | 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 |
652 | 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 |
653 | 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 |
654 | 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 |
655 | might have to leak fds on fork, but it's more sane than epoll) and it |
574 | drops fds silently in similarly hard-to-detect cases |
656 | drops fds silently in similarly hard-to-detect cases. |
575 | |
657 | |
576 | This backend usually performs well under most conditions. |
658 | This backend usually performs well under most conditions. |
577 | |
659 | |
578 | While nominally embeddable in other event loops, this doesn't work |
660 | 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 |
661 | everywhere, so you might need to test for this. And since it is broken |
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653 | Example: Use whatever libev has to offer, but make sure that kqueue is |
735 | Example: Use whatever libev has to offer, but make sure that kqueue is |
654 | used if available. |
736 | used if available. |
655 | |
737 | |
656 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
738 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
657 | |
739 | |
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740 | Example: Similarly, on linux, you mgiht want to take advantage of the |
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741 | linux aio backend if possible, but fall back to something else if that |
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742 | isn't available. |
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743 | |
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744 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO); |
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745 | |
658 | =item ev_loop_destroy (loop) |
746 | =item ev_loop_destroy (loop) |
659 | |
747 | |
660 | Destroys an event loop object (frees all memory and kernel state |
748 | 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 |
749 | 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 |
750 | sense, so e.g. C<ev_is_active> might still return true. It is your |
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678 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
766 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
679 | and C<ev_loop_destroy>. |
767 | and C<ev_loop_destroy>. |
680 | |
768 | |
681 | =item ev_loop_fork (loop) |
769 | =item ev_loop_fork (loop) |
682 | |
770 | |
683 | This function sets a flag that causes subsequent C<ev_run> iterations to |
771 | This function sets a flag that causes subsequent C<ev_run> iterations |
684 | reinitialise the kernel state for backends that have one. Despite the |
772 | 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 |
773 | 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 |
774 | watchers (except inside an C<ev_prepare> callback), but it makes most |
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775 | sense after forking, in the child process. You I<must> call it (or use |
687 | child before resuming or calling C<ev_run>. |
776 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
688 | |
777 | |
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778 | In addition, if you want to reuse a loop (via this function or |
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779 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
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780 | |
689 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
781 | 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 |
782 | 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 |
783 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
692 | during fork. |
784 | during fork. |
693 | |
785 | |
694 | On the other hand, you only need to call this function in the child |
786 | On the other hand, you only need to call this function in the child |
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764 | |
856 | |
765 | This function is rarely useful, but when some event callback runs for a |
857 | 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 |
858 | very long time without entering the event loop, updating libev's idea of |
767 | the current time is a good idea. |
859 | the current time is a good idea. |
768 | |
860 | |
769 | See also L<The special problem of time updates> in the C<ev_timer> section. |
861 | See also L</The special problem of time updates> in the C<ev_timer> section. |
770 | |
862 | |
771 | =item ev_suspend (loop) |
863 | =item ev_suspend (loop) |
772 | |
864 | |
773 | =item ev_resume (loop) |
865 | =item ev_resume (loop) |
774 | |
866 | |
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1126 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
1218 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
1127 | *) >>), and you can stop watching for events at any time by calling the |
1219 | *) >>), and you can stop watching for events at any time by calling the |
1128 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
1220 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
1129 | |
1221 | |
1130 | As long as your watcher is active (has been started but not stopped) you |
1222 | As long as your watcher is active (has been started but not stopped) you |
1131 | must not touch the values stored in it. Most specifically you must never |
1223 | must not touch the values stored in it except when explicitly documented |
1132 | reinitialise it or call its C<ev_TYPE_set> macro. |
1224 | otherwise. Most specifically you must never reinitialise it or call its |
|
|
1225 | C<ev_TYPE_set> macro. |
1133 | |
1226 | |
1134 | Each and every callback receives the event loop pointer as first, the |
1227 | Each and every callback receives the event loop pointer as first, the |
1135 | registered watcher structure as second, and a bitset of received events as |
1228 | registered watcher structure as second, and a bitset of received events as |
1136 | third argument. |
1229 | third argument. |
1137 | |
1230 | |
… | |
… | |
1174 | |
1267 | |
1175 | =item C<EV_PREPARE> |
1268 | =item C<EV_PREPARE> |
1176 | |
1269 | |
1177 | =item C<EV_CHECK> |
1270 | =item C<EV_CHECK> |
1178 | |
1271 | |
1179 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1272 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1180 | to gather new events, and all C<ev_check> watchers are invoked just after |
1273 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1181 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1274 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1275 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1276 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1277 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1278 | or lower priority within an event loop iteration. |
|
|
1279 | |
1182 | received events. Callbacks of both watcher types can start and stop as |
1280 | Callbacks of both watcher types can start and stop as many watchers as |
1183 | many watchers as they want, and all of them will be taken into account |
1281 | they want, and all of them will be taken into account (for example, a |
1184 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1282 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1185 | C<ev_run> from blocking). |
1283 | blocking). |
1186 | |
1284 | |
1187 | =item C<EV_EMBED> |
1285 | =item C<EV_EMBED> |
1188 | |
1286 | |
1189 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1287 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1190 | |
1288 | |
… | |
… | |
1313 | |
1411 | |
1314 | =item callback ev_cb (ev_TYPE *watcher) |
1412 | =item callback ev_cb (ev_TYPE *watcher) |
1315 | |
1413 | |
1316 | Returns the callback currently set on the watcher. |
1414 | Returns the callback currently set on the watcher. |
1317 | |
1415 | |
1318 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1416 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1319 | |
1417 | |
1320 | Change the callback. You can change the callback at virtually any time |
1418 | Change the callback. You can change the callback at virtually any time |
1321 | (modulo threads). |
1419 | (modulo threads). |
1322 | |
1420 | |
1323 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1421 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
… | |
… | |
1341 | or might not have been clamped to the valid range. |
1439 | or might not have been clamped to the valid range. |
1342 | |
1440 | |
1343 | The default priority used by watchers when no priority has been set is |
1441 | The default priority used by watchers when no priority has been set is |
1344 | always C<0>, which is supposed to not be too high and not be too low :). |
1442 | always C<0>, which is supposed to not be too high and not be too low :). |
1345 | |
1443 | |
1346 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1444 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1347 | priorities. |
1445 | priorities. |
1348 | |
1446 | |
1349 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1447 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1350 | |
1448 | |
1351 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1449 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1376 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1474 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1377 | functions that do not need a watcher. |
1475 | functions that do not need a watcher. |
1378 | |
1476 | |
1379 | =back |
1477 | =back |
1380 | |
1478 | |
1381 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
1479 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
1382 | OWN COMPOSITE WATCHERS> idioms. |
1480 | OWN COMPOSITE WATCHERS> idioms. |
1383 | |
1481 | |
1384 | =head2 WATCHER STATES |
1482 | =head2 WATCHER STATES |
1385 | |
1483 | |
1386 | There are various watcher states mentioned throughout this manual - |
1484 | There are various watcher states mentioned throughout this manual - |
… | |
… | |
1388 | transition between them will be described in more detail - and while these |
1486 | transition between them will be described in more detail - and while these |
1389 | rules might look complicated, they usually do "the right thing". |
1487 | rules might look complicated, they usually do "the right thing". |
1390 | |
1488 | |
1391 | =over 4 |
1489 | =over 4 |
1392 | |
1490 | |
1393 | =item initialiased |
1491 | =item initialised |
1394 | |
1492 | |
1395 | Before a watcher can be registered with the event loop it has to be |
1493 | Before a watcher can be registered with the event loop it has to be |
1396 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1494 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1397 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1495 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1398 | |
1496 | |
… | |
… | |
1447 | |
1545 | |
1448 | Many event loops support I<watcher priorities>, which are usually small |
1546 | Many event loops support I<watcher priorities>, which are usually small |
1449 | integers that influence the ordering of event callback invocation |
1547 | integers that influence the ordering of event callback invocation |
1450 | between watchers in some way, all else being equal. |
1548 | between watchers in some way, all else being equal. |
1451 | |
1549 | |
1452 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
1550 | In libev, watcher priorities can be set using C<ev_set_priority>. See its |
1453 | description for the more technical details such as the actual priority |
1551 | description for the more technical details such as the actual priority |
1454 | range. |
1552 | range. |
1455 | |
1553 | |
1456 | There are two common ways how these these priorities are being interpreted |
1554 | There are two common ways how these these priorities are being interpreted |
1457 | by event loops: |
1555 | by event loops: |
… | |
… | |
1551 | |
1649 | |
1552 | This section describes each watcher in detail, but will not repeat |
1650 | This section describes each watcher in detail, but will not repeat |
1553 | information given in the last section. Any initialisation/set macros, |
1651 | information given in the last section. Any initialisation/set macros, |
1554 | functions and members specific to the watcher type are explained. |
1652 | functions and members specific to the watcher type are explained. |
1555 | |
1653 | |
1556 | Members are additionally marked with either I<[read-only]>, meaning that, |
1654 | Most members are additionally marked with either I<[read-only]>, meaning |
1557 | while the watcher is active, you can look at the member and expect some |
1655 | that, while the watcher is active, you can look at the member and expect |
1558 | sensible content, but you must not modify it (you can modify it while the |
1656 | some sensible content, but you must not modify it (you can modify it while |
1559 | watcher is stopped to your hearts content), or I<[read-write]>, which |
1657 | the watcher is stopped to your hearts content), or I<[read-write]>, which |
1560 | means you can expect it to have some sensible content while the watcher |
1658 | means you can expect it to have some sensible content while the watcher |
1561 | is active, but you can also modify it. Modifying it may not do something |
1659 | is active, but you can also modify it. Modifying it may not do something |
1562 | sensible or take immediate effect (or do anything at all), but libev will |
1660 | sensible or take immediate effect (or do anything at all), but libev will |
1563 | not crash or malfunction in any way. |
1661 | not crash or malfunction in any way. |
1564 | |
1662 | |
|
|
1663 | In any case, the documentation for each member will explain what the |
|
|
1664 | effects are, and if there are any additional access restrictions. |
1565 | |
1665 | |
1566 | =head2 C<ev_io> - is this file descriptor readable or writable? |
1666 | =head2 C<ev_io> - is this file descriptor readable or writable? |
1567 | |
1667 | |
1568 | I/O watchers check whether a file descriptor is readable or writable |
1668 | I/O watchers check whether a file descriptor is readable or writable |
1569 | in each iteration of the event loop, or, more precisely, when reading |
1669 | in each iteration of the event loop, or, more precisely, when reading |
… | |
… | |
1596 | |
1696 | |
1597 | But really, best use non-blocking mode. |
1697 | But really, best use non-blocking mode. |
1598 | |
1698 | |
1599 | =head3 The special problem of disappearing file descriptors |
1699 | =head3 The special problem of disappearing file descriptors |
1600 | |
1700 | |
1601 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1701 | Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing |
1602 | descriptor (either due to calling C<close> explicitly or any other means, |
1702 | a file descriptor (either due to calling C<close> explicitly or any other |
1603 | such as C<dup2>). The reason is that you register interest in some file |
1703 | means, such as C<dup2>). The reason is that you register interest in some |
1604 | descriptor, but when it goes away, the operating system will silently drop |
1704 | file descriptor, but when it goes away, the operating system will silently |
1605 | this interest. If another file descriptor with the same number then is |
1705 | drop this interest. If another file descriptor with the same number then |
1606 | registered with libev, there is no efficient way to see that this is, in |
1706 | is registered with libev, there is no efficient way to see that this is, |
1607 | fact, a different file descriptor. |
1707 | in fact, a different file descriptor. |
1608 | |
1708 | |
1609 | To avoid having to explicitly tell libev about such cases, libev follows |
1709 | To avoid having to explicitly tell libev about such cases, libev follows |
1610 | the following policy: Each time C<ev_io_set> is being called, libev |
1710 | the following policy: Each time C<ev_io_set> is being called, libev |
1611 | will assume that this is potentially a new file descriptor, otherwise |
1711 | will assume that this is potentially a new file descriptor, otherwise |
1612 | it is assumed that the file descriptor stays the same. That means that |
1712 | it is assumed that the file descriptor stays the same. That means that |
… | |
… | |
1661 | when you rarely read from a file instead of from a socket, and want to |
1761 | when you rarely read from a file instead of from a socket, and want to |
1662 | reuse the same code path. |
1762 | reuse the same code path. |
1663 | |
1763 | |
1664 | =head3 The special problem of fork |
1764 | =head3 The special problem of fork |
1665 | |
1765 | |
1666 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1766 | Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()> |
1667 | useless behaviour. Libev fully supports fork, but needs to be told about |
1767 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1668 | it in the child if you want to continue to use it in the child. |
1768 | to be told about it in the child if you want to continue to use it in the |
|
|
1769 | child. |
1669 | |
1770 | |
1670 | To support fork in your child processes, you have to call C<ev_loop_fork |
1771 | To support fork in your child processes, you have to call C<ev_loop_fork |
1671 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1772 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1672 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1773 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1673 | |
1774 | |
… | |
… | |
1731 | |
1832 | |
1732 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1833 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1733 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1834 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1734 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1835 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1735 | |
1836 | |
1736 | =item int fd [read-only] |
1837 | =item ev_io_modify (ev_io *, int events) |
1737 | |
1838 | |
1738 | The file descriptor being watched. |
1839 | Similar to C<ev_io_set>, but only changes the event mask. Using this might |
|
|
1840 | be faster with some backends, as libev can assume that the C<fd> still |
|
|
1841 | refers to the same underlying file description, something it cannot do |
|
|
1842 | when using C<ev_io_set>. |
1739 | |
1843 | |
|
|
1844 | =item int fd [no-modify] |
|
|
1845 | |
|
|
1846 | The file descriptor being watched. While it can be read at any time, you |
|
|
1847 | must not modify this member even when the watcher is stopped - always use |
|
|
1848 | C<ev_io_set> for that. |
|
|
1849 | |
1740 | =item int events [read-only] |
1850 | =item int events [no-modify] |
1741 | |
1851 | |
1742 | The events being watched. |
1852 | The set of events the fd is being watched for, among other flags. Remember |
|
|
1853 | that this is a bit set - to test for C<EV_READ>, use C<< w->events & |
|
|
1854 | EV_READ >>, and similarly for C<EV_WRITE>. |
|
|
1855 | |
|
|
1856 | As with C<fd>, you must not modify this member even when the watcher is |
|
|
1857 | stopped, always use C<ev_io_set> or C<ev_io_modify> for that. |
1743 | |
1858 | |
1744 | =back |
1859 | =back |
1745 | |
1860 | |
1746 | =head3 Examples |
1861 | =head3 Examples |
1747 | |
1862 | |
… | |
… | |
2019 | |
2134 | |
2020 | The relative timeouts are calculated relative to the C<ev_now ()> |
2135 | The relative timeouts are calculated relative to the C<ev_now ()> |
2021 | time. This is usually the right thing as this timestamp refers to the time |
2136 | time. This is usually the right thing as this timestamp refers to the time |
2022 | of the event triggering whatever timeout you are modifying/starting. If |
2137 | of the event triggering whatever timeout you are modifying/starting. If |
2023 | you suspect event processing to be delayed and you I<need> to base the |
2138 | you suspect event processing to be delayed and you I<need> to base the |
2024 | timeout on the current time, use something like this to adjust for this: |
2139 | timeout on the current time, use something like the following to adjust |
|
|
2140 | for it: |
2025 | |
2141 | |
2026 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2142 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
2027 | |
2143 | |
2028 | If the event loop is suspended for a long time, you can also force an |
2144 | If the event loop is suspended for a long time, you can also force an |
2029 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2145 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2030 | ()>. |
2146 | ()>, although that will push the event time of all outstanding events |
|
|
2147 | further into the future. |
2031 | |
2148 | |
2032 | =head3 The special problem of unsynchronised clocks |
2149 | =head3 The special problem of unsynchronised clocks |
2033 | |
2150 | |
2034 | Modern systems have a variety of clocks - libev itself uses the normal |
2151 | Modern systems have a variety of clocks - libev itself uses the normal |
2035 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
2152 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
… | |
… | |
2098 | |
2215 | |
2099 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2216 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2100 | |
2217 | |
2101 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2218 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2102 | |
2219 | |
2103 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2220 | Configure the timer to trigger after C<after> seconds (fractional and |
2104 | is C<0.>, then it will automatically be stopped once the timeout is |
2221 | negative values are supported). If C<repeat> is C<0.>, then it will |
2105 | reached. If it is positive, then the timer will automatically be |
2222 | automatically be stopped once the timeout is reached. If it is positive, |
2106 | configured to trigger again C<repeat> seconds later, again, and again, |
2223 | then the timer will automatically be configured to trigger again C<repeat> |
2107 | until stopped manually. |
2224 | seconds later, again, and again, until stopped manually. |
2108 | |
2225 | |
2109 | The timer itself will do a best-effort at avoiding drift, that is, if |
2226 | The timer itself will do a best-effort at avoiding drift, that is, if |
2110 | you configure a timer to trigger every 10 seconds, then it will normally |
2227 | you configure a timer to trigger every 10 seconds, then it will normally |
2111 | trigger at exactly 10 second intervals. If, however, your program cannot |
2228 | trigger at exactly 10 second intervals. If, however, your program cannot |
2112 | keep up with the timer (because it takes longer than those 10 seconds to |
2229 | keep up with the timer (because it takes longer than those 10 seconds to |
… | |
… | |
2131 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2248 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2132 | and start the timer, if necessary. |
2249 | and start the timer, if necessary. |
2133 | |
2250 | |
2134 | =back |
2251 | =back |
2135 | |
2252 | |
2136 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2253 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
2137 | usage example. |
2254 | usage example. |
2138 | |
2255 | |
2139 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2256 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2140 | |
2257 | |
2141 | Returns the remaining time until a timer fires. If the timer is active, |
2258 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2194 | Periodic watchers are also timers of a kind, but they are very versatile |
2311 | Periodic watchers are also timers of a kind, but they are very versatile |
2195 | (and unfortunately a bit complex). |
2312 | (and unfortunately a bit complex). |
2196 | |
2313 | |
2197 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2314 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2198 | relative time, the physical time that passes) but on wall clock time |
2315 | relative time, the physical time that passes) but on wall clock time |
2199 | (absolute time, the thing you can read on your calender or clock). The |
2316 | (absolute time, the thing you can read on your calendar or clock). The |
2200 | difference is that wall clock time can run faster or slower than real |
2317 | difference is that wall clock time can run faster or slower than real |
2201 | time, and time jumps are not uncommon (e.g. when you adjust your |
2318 | time, and time jumps are not uncommon (e.g. when you adjust your |
2202 | wrist-watch). |
2319 | wrist-watch). |
2203 | |
2320 | |
2204 | You can tell a periodic watcher to trigger after some specific point |
2321 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
2209 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2326 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2210 | it, as it uses a relative timeout). |
2327 | it, as it uses a relative timeout). |
2211 | |
2328 | |
2212 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2329 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2213 | timers, such as triggering an event on each "midnight, local time", or |
2330 | timers, such as triggering an event on each "midnight, local time", or |
2214 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
2331 | other complicated rules. This cannot easily be done with C<ev_timer> |
2215 | those cannot react to time jumps. |
2332 | watchers, as those cannot react to time jumps. |
2216 | |
2333 | |
2217 | As with timers, the callback is guaranteed to be invoked only when the |
2334 | As with timers, the callback is guaranteed to be invoked only when the |
2218 | point in time where it is supposed to trigger has passed. If multiple |
2335 | point in time where it is supposed to trigger has passed. If multiple |
2219 | timers become ready during the same loop iteration then the ones with |
2336 | timers become ready during the same loop iteration then the ones with |
2220 | earlier time-out values are invoked before ones with later time-out values |
2337 | earlier time-out values are invoked before ones with later time-out values |
… | |
… | |
2306 | |
2423 | |
2307 | NOTE: I<< This callback must always return a time that is higher than or |
2424 | NOTE: I<< This callback must always return a time that is higher than or |
2308 | equal to the passed C<now> value >>. |
2425 | equal to the passed C<now> value >>. |
2309 | |
2426 | |
2310 | This can be used to create very complex timers, such as a timer that |
2427 | This can be used to create very complex timers, such as a timer that |
2311 | triggers on "next midnight, local time". To do this, you would calculate the |
2428 | triggers on "next midnight, local time". To do this, you would calculate |
2312 | next midnight after C<now> and return the timestamp value for this. How |
2429 | the next midnight after C<now> and return the timestamp value for |
2313 | you do this is, again, up to you (but it is not trivial, which is the main |
2430 | this. Here is a (completely untested, no error checking) example on how to |
2314 | reason I omitted it as an example). |
2431 | do this: |
|
|
2432 | |
|
|
2433 | #include <time.h> |
|
|
2434 | |
|
|
2435 | static ev_tstamp |
|
|
2436 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2437 | { |
|
|
2438 | time_t tnow = (time_t)now; |
|
|
2439 | struct tm tm; |
|
|
2440 | localtime_r (&tnow, &tm); |
|
|
2441 | |
|
|
2442 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2443 | ++tm.tm_mday; // midnight next day |
|
|
2444 | |
|
|
2445 | return mktime (&tm); |
|
|
2446 | } |
|
|
2447 | |
|
|
2448 | Note: this code might run into trouble on days that have more then two |
|
|
2449 | midnights (beginning and end). |
2315 | |
2450 | |
2316 | =back |
2451 | =back |
2317 | |
2452 | |
2318 | =item ev_periodic_again (loop, ev_periodic *) |
2453 | =item ev_periodic_again (loop, ev_periodic *) |
2319 | |
2454 | |
… | |
… | |
2384 | |
2519 | |
2385 | ev_periodic hourly_tick; |
2520 | ev_periodic hourly_tick; |
2386 | ev_periodic_init (&hourly_tick, clock_cb, |
2521 | ev_periodic_init (&hourly_tick, clock_cb, |
2387 | fmod (ev_now (loop), 3600.), 3600., 0); |
2522 | fmod (ev_now (loop), 3600.), 3600., 0); |
2388 | ev_periodic_start (loop, &hourly_tick); |
2523 | ev_periodic_start (loop, &hourly_tick); |
2389 | |
2524 | |
2390 | |
2525 | |
2391 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2526 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2392 | |
2527 | |
2393 | Signal watchers will trigger an event when the process receives a specific |
2528 | Signal watchers will trigger an event when the process receives a specific |
2394 | signal one or more times. Even though signals are very asynchronous, libev |
2529 | signal one or more times. Even though signals are very asynchronous, libev |
… | |
… | |
2404 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2539 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2405 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2540 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2406 | C<SIGINT> in both the default loop and another loop at the same time. At |
2541 | C<SIGINT> in both the default loop and another loop at the same time. At |
2407 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2542 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2408 | |
2543 | |
2409 | When the first watcher gets started will libev actually register something |
2544 | Only after the first watcher for a signal is started will libev actually |
2410 | with the kernel (thus it coexists with your own signal handlers as long as |
2545 | register something with the kernel. It thus coexists with your own signal |
2411 | you don't register any with libev for the same signal). |
2546 | handlers as long as you don't register any with libev for the same signal. |
2412 | |
2547 | |
2413 | If possible and supported, libev will install its handlers with |
2548 | If possible and supported, libev will install its handlers with |
2414 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2549 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2415 | not be unduly interrupted. If you have a problem with system calls getting |
2550 | not be unduly interrupted. If you have a problem with system calls getting |
2416 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2551 | interrupted by signals you can block all signals in an C<ev_check> watcher |
… | |
… | |
2601 | |
2736 | |
2602 | =head2 C<ev_stat> - did the file attributes just change? |
2737 | =head2 C<ev_stat> - did the file attributes just change? |
2603 | |
2738 | |
2604 | This watches a file system path for attribute changes. That is, it calls |
2739 | This watches a file system path for attribute changes. That is, it calls |
2605 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2740 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2606 | and sees if it changed compared to the last time, invoking the callback if |
2741 | and sees if it changed compared to the last time, invoking the callback |
2607 | it did. |
2742 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2743 | happen after the watcher has been started will be reported. |
2608 | |
2744 | |
2609 | The path does not need to exist: changing from "path exists" to "path does |
2745 | The path does not need to exist: changing from "path exists" to "path does |
2610 | not exist" is a status change like any other. The condition "path does not |
2746 | not exist" is a status change like any other. The condition "path does not |
2611 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2747 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2612 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2748 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2842 | Apart from keeping your process non-blocking (which is a useful |
2978 | Apart from keeping your process non-blocking (which is a useful |
2843 | effect on its own sometimes), idle watchers are a good place to do |
2979 | effect on its own sometimes), idle watchers are a good place to do |
2844 | "pseudo-background processing", or delay processing stuff to after the |
2980 | "pseudo-background processing", or delay processing stuff to after the |
2845 | event loop has handled all outstanding events. |
2981 | event loop has handled all outstanding events. |
2846 | |
2982 | |
|
|
2983 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2984 | |
|
|
2985 | As long as there is at least one active idle watcher, libev will never |
|
|
2986 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2987 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2988 | lowest priority will do. |
|
|
2989 | |
|
|
2990 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2991 | to do something on each event loop iteration - for example to balance load |
|
|
2992 | between different connections. |
|
|
2993 | |
|
|
2994 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2995 | example. |
|
|
2996 | |
2847 | =head3 Watcher-Specific Functions and Data Members |
2997 | =head3 Watcher-Specific Functions and Data Members |
2848 | |
2998 | |
2849 | =over 4 |
2999 | =over 4 |
2850 | |
3000 | |
2851 | =item ev_idle_init (ev_idle *, callback) |
3001 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2862 | callback, free it. Also, use no error checking, as usual. |
3012 | callback, free it. Also, use no error checking, as usual. |
2863 | |
3013 | |
2864 | static void |
3014 | static void |
2865 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
3015 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2866 | { |
3016 | { |
|
|
3017 | // stop the watcher |
|
|
3018 | ev_idle_stop (loop, w); |
|
|
3019 | |
|
|
3020 | // now we can free it |
2867 | free (w); |
3021 | free (w); |
|
|
3022 | |
2868 | // now do something you wanted to do when the program has |
3023 | // now do something you wanted to do when the program has |
2869 | // no longer anything immediate to do. |
3024 | // no longer anything immediate to do. |
2870 | } |
3025 | } |
2871 | |
3026 | |
2872 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
3027 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2874 | ev_idle_start (loop, idle_watcher); |
3029 | ev_idle_start (loop, idle_watcher); |
2875 | |
3030 | |
2876 | |
3031 | |
2877 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
3032 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2878 | |
3033 | |
2879 | Prepare and check watchers are usually (but not always) used in pairs: |
3034 | Prepare and check watchers are often (but not always) used in pairs: |
2880 | prepare watchers get invoked before the process blocks and check watchers |
3035 | prepare watchers get invoked before the process blocks and check watchers |
2881 | afterwards. |
3036 | afterwards. |
2882 | |
3037 | |
2883 | You I<must not> call C<ev_run> or similar functions that enter |
3038 | You I<must not> call C<ev_run> (or similar functions that enter the |
2884 | the current event loop from either C<ev_prepare> or C<ev_check> |
3039 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2885 | watchers. Other loops than the current one are fine, however. The |
3040 | C<ev_check> watchers. Other loops than the current one are fine, |
2886 | rationale behind this is that you do not need to check for recursion in |
3041 | however. The rationale behind this is that you do not need to check |
2887 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
3042 | for recursion in those watchers, i.e. the sequence will always be |
2888 | C<ev_check> so if you have one watcher of each kind they will always be |
3043 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2889 | called in pairs bracketing the blocking call. |
3044 | kind they will always be called in pairs bracketing the blocking call. |
2890 | |
3045 | |
2891 | Their main purpose is to integrate other event mechanisms into libev and |
3046 | Their main purpose is to integrate other event mechanisms into libev and |
2892 | their use is somewhat advanced. They could be used, for example, to track |
3047 | their use is somewhat advanced. They could be used, for example, to track |
2893 | variable changes, implement your own watchers, integrate net-snmp or a |
3048 | variable changes, implement your own watchers, integrate net-snmp or a |
2894 | coroutine library and lots more. They are also occasionally useful if |
3049 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
2912 | with priority higher than or equal to the event loop and one coroutine |
3067 | with priority higher than or equal to the event loop and one coroutine |
2913 | of lower priority, but only once, using idle watchers to keep the event |
3068 | of lower priority, but only once, using idle watchers to keep the event |
2914 | loop from blocking if lower-priority coroutines are active, thus mapping |
3069 | loop from blocking if lower-priority coroutines are active, thus mapping |
2915 | low-priority coroutines to idle/background tasks). |
3070 | low-priority coroutines to idle/background tasks). |
2916 | |
3071 | |
2917 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
3072 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2918 | priority, to ensure that they are being run before any other watchers |
3073 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2919 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
3074 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
3075 | watchers). |
2920 | |
3076 | |
2921 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
3077 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2922 | activate ("feed") events into libev. While libev fully supports this, they |
3078 | activate ("feed") events into libev. While libev fully supports this, they |
2923 | might get executed before other C<ev_check> watchers did their job. As |
3079 | might get executed before other C<ev_check> watchers did their job. As |
2924 | C<ev_check> watchers are often used to embed other (non-libev) event |
3080 | C<ev_check> watchers are often used to embed other (non-libev) event |
2925 | loops those other event loops might be in an unusable state until their |
3081 | loops those other event loops might be in an unusable state until their |
2926 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
3082 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2927 | others). |
3083 | others). |
|
|
3084 | |
|
|
3085 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
3086 | |
|
|
3087 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
3088 | useful because they are called once per event loop iteration. For |
|
|
3089 | example, if you want to handle a large number of connections fairly, you |
|
|
3090 | normally only do a bit of work for each active connection, and if there |
|
|
3091 | is more work to do, you wait for the next event loop iteration, so other |
|
|
3092 | connections have a chance of making progress. |
|
|
3093 | |
|
|
3094 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
3095 | next event loop iteration. However, that isn't as soon as possible - |
|
|
3096 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
3097 | |
|
|
3098 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
3099 | single global idle watcher that is active as long as you have one active |
|
|
3100 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
3101 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
3102 | invoked. Neither watcher alone can do that. |
2928 | |
3103 | |
2929 | =head3 Watcher-Specific Functions and Data Members |
3104 | =head3 Watcher-Specific Functions and Data Members |
2930 | |
3105 | |
2931 | =over 4 |
3106 | =over 4 |
2932 | |
3107 | |
… | |
… | |
3133 | |
3308 | |
3134 | =over 4 |
3309 | =over 4 |
3135 | |
3310 | |
3136 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3311 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3137 | |
3312 | |
3138 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3313 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
3139 | |
3314 | |
3140 | Configures the watcher to embed the given loop, which must be |
3315 | Configures the watcher to embed the given loop, which must be |
3141 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3316 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3142 | invoked automatically, otherwise it is the responsibility of the callback |
3317 | invoked automatically, otherwise it is the responsibility of the callback |
3143 | to invoke it (it will continue to be called until the sweep has been done, |
3318 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3164 | used). |
3339 | used). |
3165 | |
3340 | |
3166 | struct ev_loop *loop_hi = ev_default_init (0); |
3341 | struct ev_loop *loop_hi = ev_default_init (0); |
3167 | struct ev_loop *loop_lo = 0; |
3342 | struct ev_loop *loop_lo = 0; |
3168 | ev_embed embed; |
3343 | ev_embed embed; |
3169 | |
3344 | |
3170 | // see if there is a chance of getting one that works |
3345 | // see if there is a chance of getting one that works |
3171 | // (remember that a flags value of 0 means autodetection) |
3346 | // (remember that a flags value of 0 means autodetection) |
3172 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3347 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3173 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3348 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3174 | : 0; |
3349 | : 0; |
… | |
… | |
3188 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3363 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3189 | |
3364 | |
3190 | struct ev_loop *loop = ev_default_init (0); |
3365 | struct ev_loop *loop = ev_default_init (0); |
3191 | struct ev_loop *loop_socket = 0; |
3366 | struct ev_loop *loop_socket = 0; |
3192 | ev_embed embed; |
3367 | ev_embed embed; |
3193 | |
3368 | |
3194 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3369 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3195 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3370 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3196 | { |
3371 | { |
3197 | ev_embed_init (&embed, 0, loop_socket); |
3372 | ev_embed_init (&embed, 0, loop_socket); |
3198 | ev_embed_start (loop, &embed); |
3373 | ev_embed_start (loop, &embed); |
… | |
… | |
3206 | |
3381 | |
3207 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3382 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3208 | |
3383 | |
3209 | Fork watchers are called when a C<fork ()> was detected (usually because |
3384 | Fork watchers are called when a C<fork ()> was detected (usually because |
3210 | whoever is a good citizen cared to tell libev about it by calling |
3385 | whoever is a good citizen cared to tell libev about it by calling |
3211 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3386 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3212 | event loop blocks next and before C<ev_check> watchers are being called, |
3387 | and before C<ev_check> watchers are being called, and only in the child |
3213 | and only in the child after the fork. If whoever good citizen calling |
3388 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3214 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3389 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3215 | handlers will be invoked, too, of course. |
3390 | of course. |
3216 | |
3391 | |
3217 | =head3 The special problem of life after fork - how is it possible? |
3392 | =head3 The special problem of life after fork - how is it possible? |
3218 | |
3393 | |
3219 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3394 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3220 | up/change the process environment, followed by a call to C<exec()>. This |
3395 | up/change the process environment, followed by a call to C<exec()>. This |
3221 | sequence should be handled by libev without any problems. |
3396 | sequence should be handled by libev without any problems. |
3222 | |
3397 | |
3223 | This changes when the application actually wants to do event handling |
3398 | This changes when the application actually wants to do event handling |
3224 | in the child, or both parent in child, in effect "continuing" after the |
3399 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3313 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3488 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3314 | |
3489 | |
3315 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3490 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3316 | too, are asynchronous in nature, and signals, too, will be compressed |
3491 | too, are asynchronous in nature, and signals, too, will be compressed |
3317 | (i.e. the number of callback invocations may be less than the number of |
3492 | (i.e. the number of callback invocations may be less than the number of |
3318 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3493 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3319 | of "global async watchers" by using a watcher on an otherwise unused |
3494 | of "global async watchers" by using a watcher on an otherwise unused |
3320 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3495 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3321 | even without knowing which loop owns the signal. |
3496 | even without knowing which loop owns the signal. |
3322 | |
3497 | |
3323 | =head3 Queueing |
3498 | =head3 Queueing |
… | |
… | |
3462 | |
3637 | |
3463 | There are some other functions of possible interest. Described. Here. Now. |
3638 | There are some other functions of possible interest. Described. Here. Now. |
3464 | |
3639 | |
3465 | =over 4 |
3640 | =over 4 |
3466 | |
3641 | |
3467 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3642 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
3468 | |
3643 | |
3469 | This function combines a simple timer and an I/O watcher, calls your |
3644 | This function combines a simple timer and an I/O watcher, calls your |
3470 | callback on whichever event happens first and automatically stops both |
3645 | callback on whichever event happens first and automatically stops both |
3471 | watchers. This is useful if you want to wait for a single event on an fd |
3646 | watchers. This is useful if you want to wait for a single event on an fd |
3472 | or timeout without having to allocate/configure/start/stop/free one or |
3647 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
3614 | already been invoked. |
3789 | already been invoked. |
3615 | |
3790 | |
3616 | A common way around all these issues is to make sure that |
3791 | A common way around all these issues is to make sure that |
3617 | C<start_new_request> I<always> returns before the callback is invoked. If |
3792 | C<start_new_request> I<always> returns before the callback is invoked. If |
3618 | C<start_new_request> immediately knows the result, it can artificially |
3793 | C<start_new_request> immediately knows the result, it can artificially |
3619 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
3794 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
3620 | for example, or more sneakily, by reusing an existing (stopped) watcher |
3795 | example, or more sneakily, by reusing an existing (stopped) watcher and |
3621 | and pushing it into the pending queue: |
3796 | pushing it into the pending queue: |
3622 | |
3797 | |
3623 | ev_set_cb (watcher, callback); |
3798 | ev_set_cb (watcher, callback); |
3624 | ev_feed_event (EV_A_ watcher, 0); |
3799 | ev_feed_event (EV_A_ watcher, 0); |
3625 | |
3800 | |
3626 | This way, C<start_new_request> can safely return before the callback is |
3801 | This way, C<start_new_request> can safely return before the callback is |
… | |
… | |
3634 | |
3809 | |
3635 | This brings the problem of exiting - a callback might want to finish the |
3810 | This brings the problem of exiting - a callback might want to finish the |
3636 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3811 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3637 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3812 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3638 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3813 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3639 | other combination: In these cases, C<ev_break> will not work alone. |
3814 | other combination: In these cases, a simple C<ev_break> will not work. |
3640 | |
3815 | |
3641 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3816 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3642 | invocation, and use a loop around C<ev_run> until the condition is |
3817 | invocation, and use a loop around C<ev_run> until the condition is |
3643 | triggered, using C<EVRUN_ONCE>: |
3818 | triggered, using C<EVRUN_ONCE>: |
3644 | |
3819 | |
… | |
… | |
3830 | called): |
4005 | called): |
3831 | |
4006 | |
3832 | void |
4007 | void |
3833 | wait_for_event (ev_watcher *w) |
4008 | wait_for_event (ev_watcher *w) |
3834 | { |
4009 | { |
3835 | ev_cb_set (w) = current_coro; |
4010 | ev_set_cb (w, current_coro); |
3836 | switch_to (libev_coro); |
4011 | switch_to (libev_coro); |
3837 | } |
4012 | } |
3838 | |
4013 | |
3839 | That basically suspends the coroutine inside C<wait_for_event> and |
4014 | That basically suspends the coroutine inside C<wait_for_event> and |
3840 | continues the libev coroutine, which, when appropriate, switches back to |
4015 | continues the libev coroutine, which, when appropriate, switches back to |
… | |
… | |
3843 | You can do similar tricks if you have, say, threads with an event queue - |
4018 | You can do similar tricks if you have, say, threads with an event queue - |
3844 | instead of storing a coroutine, you store the queue object and instead of |
4019 | instead of storing a coroutine, you store the queue object and instead of |
3845 | switching to a coroutine, you push the watcher onto the queue and notify |
4020 | switching to a coroutine, you push the watcher onto the queue and notify |
3846 | any waiters. |
4021 | any waiters. |
3847 | |
4022 | |
3848 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
4023 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3849 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
4024 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3850 | |
4025 | |
3851 | // my_ev.h |
4026 | // my_ev.h |
3852 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
4027 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3853 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
4028 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
3854 | #include "../libev/ev.h" |
4029 | #include "../libev/ev.h" |
3855 | |
4030 | |
3856 | // my_ev.c |
4031 | // my_ev.c |
3857 | #define EV_H "my_ev.h" |
4032 | #define EV_H "my_ev.h" |
3858 | #include "../libev/ev.c" |
4033 | #include "../libev/ev.c" |
… | |
… | |
3904 | The normal C API should work fine when used from C++: both ev.h and the |
4079 | The normal C API should work fine when used from C++: both ev.h and the |
3905 | libev sources can be compiled as C++. Therefore, code that uses the C API |
4080 | libev sources can be compiled as C++. Therefore, code that uses the C API |
3906 | will work fine. |
4081 | will work fine. |
3907 | |
4082 | |
3908 | Proper exception specifications might have to be added to callbacks passed |
4083 | Proper exception specifications might have to be added to callbacks passed |
3909 | to libev: exceptions may be thrown only from watcher callbacks, all |
4084 | to libev: exceptions may be thrown only from watcher callbacks, all other |
3910 | other callbacks (allocator, syserr, loop acquire/release and periodioc |
4085 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
3911 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
4086 | callbacks) must not throw exceptions, and might need a C<noexcept> |
3912 | ()> specification. If you have code that needs to be compiled as both C |
4087 | specification. If you have code that needs to be compiled as both C and |
3913 | and C++ you can use the C<EV_THROW> macro for this: |
4088 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
3914 | |
4089 | |
3915 | static void |
4090 | static void |
3916 | fatal_error (const char *msg) EV_THROW |
4091 | fatal_error (const char *msg) EV_NOEXCEPT |
3917 | { |
4092 | { |
3918 | perror (msg); |
4093 | perror (msg); |
3919 | abort (); |
4094 | abort (); |
3920 | } |
4095 | } |
3921 | |
4096 | |
… | |
… | |
3935 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
4110 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3936 | you to use some convenience methods to start/stop watchers and also change |
4111 | you to use some convenience methods to start/stop watchers and also change |
3937 | the callback model to a model using method callbacks on objects. |
4112 | the callback model to a model using method callbacks on objects. |
3938 | |
4113 | |
3939 | To use it, |
4114 | To use it, |
3940 | |
4115 | |
3941 | #include <ev++.h> |
4116 | #include <ev++.h> |
3942 | |
4117 | |
3943 | This automatically includes F<ev.h> and puts all of its definitions (many |
4118 | This automatically includes F<ev.h> and puts all of its definitions (many |
3944 | of them macros) into the global namespace. All C++ specific things are |
4119 | of them macros) into the global namespace. All C++ specific things are |
3945 | put into the C<ev> namespace. It should support all the same embedding |
4120 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
4048 | void operator() (ev::io &w, int revents) |
4223 | void operator() (ev::io &w, int revents) |
4049 | { |
4224 | { |
4050 | ... |
4225 | ... |
4051 | } |
4226 | } |
4052 | } |
4227 | } |
4053 | |
4228 | |
4054 | myfunctor f; |
4229 | myfunctor f; |
4055 | |
4230 | |
4056 | ev::io w; |
4231 | ev::io w; |
4057 | w.set (&f); |
4232 | w.set (&f); |
4058 | |
4233 | |
… | |
… | |
4076 | Associates a different C<struct ev_loop> with this watcher. You can only |
4251 | Associates a different C<struct ev_loop> with this watcher. You can only |
4077 | do this when the watcher is inactive (and not pending either). |
4252 | do this when the watcher is inactive (and not pending either). |
4078 | |
4253 | |
4079 | =item w->set ([arguments]) |
4254 | =item w->set ([arguments]) |
4080 | |
4255 | |
4081 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4256 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
4082 | method or a suitable start method must be called at least once. Unlike the |
4257 | with the same arguments. Either this method or a suitable start method |
4083 | C counterpart, an active watcher gets automatically stopped and restarted |
4258 | must be called at least once. Unlike the C counterpart, an active watcher |
4084 | when reconfiguring it with this method. |
4259 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4260 | method. |
|
|
4261 | |
|
|
4262 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4263 | clashing with the C<set (loop)> method. |
4085 | |
4264 | |
4086 | =item w->start () |
4265 | =item w->start () |
4087 | |
4266 | |
4088 | Starts the watcher. Note that there is no C<loop> argument, as the |
4267 | Starts the watcher. Note that there is no C<loop> argument, as the |
4089 | constructor already stores the event loop. |
4268 | constructor already stores the event loop. |
… | |
… | |
4193 | |
4372 | |
4194 | Brian Maher has written a partial interface to libev for lua (at the |
4373 | Brian Maher has written a partial interface to libev for lua (at the |
4195 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4374 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4196 | L<http://github.com/brimworks/lua-ev>. |
4375 | L<http://github.com/brimworks/lua-ev>. |
4197 | |
4376 | |
|
|
4377 | =item Javascript |
|
|
4378 | |
|
|
4379 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4380 | |
|
|
4381 | =item Others |
|
|
4382 | |
|
|
4383 | There are others, and I stopped counting. |
|
|
4384 | |
4198 | =back |
4385 | =back |
4199 | |
4386 | |
4200 | |
4387 | |
4201 | =head1 MACRO MAGIC |
4388 | =head1 MACRO MAGIC |
4202 | |
4389 | |
… | |
… | |
4319 | ev_vars.h |
4506 | ev_vars.h |
4320 | ev_wrap.h |
4507 | ev_wrap.h |
4321 | |
4508 | |
4322 | ev_win32.c required on win32 platforms only |
4509 | ev_win32.c required on win32 platforms only |
4323 | |
4510 | |
4324 | ev_select.c only when select backend is enabled (which is enabled by default) |
4511 | ev_select.c only when select backend is enabled |
4325 | ev_poll.c only when poll backend is enabled (disabled by default) |
4512 | ev_poll.c only when poll backend is enabled |
4326 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4513 | ev_epoll.c only when the epoll backend is enabled |
|
|
4514 | ev_linuxaio.c only when the linux aio backend is enabled |
|
|
4515 | ev_iouring.c only when the linux io_uring backend is enabled |
4327 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4516 | ev_kqueue.c only when the kqueue backend is enabled |
4328 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4517 | ev_port.c only when the solaris port backend is enabled |
4329 | |
4518 | |
4330 | F<ev.c> includes the backend files directly when enabled, so you only need |
4519 | F<ev.c> includes the backend files directly when enabled, so you only need |
4331 | to compile this single file. |
4520 | to compile this single file. |
4332 | |
4521 | |
4333 | =head3 LIBEVENT COMPATIBILITY API |
4522 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
4452 | available and will probe for kernel support at runtime. This will improve |
4641 | available and will probe for kernel support at runtime. This will improve |
4453 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
4642 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
4454 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
4643 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
4455 | 2.7 or newer, otherwise disabled. |
4644 | 2.7 or newer, otherwise disabled. |
4456 | |
4645 | |
|
|
4646 | =item EV_USE_SIGNALFD |
|
|
4647 | |
|
|
4648 | If defined to be C<1>, then libev will assume that C<signalfd ()> is |
|
|
4649 | available and will probe for kernel support at runtime. This enables |
|
|
4650 | the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If |
|
|
4651 | undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4652 | 2.7 or newer, otherwise disabled. |
|
|
4653 | |
|
|
4654 | =item EV_USE_TIMERFD |
|
|
4655 | |
|
|
4656 | If defined to be C<1>, then libev will assume that C<timerfd ()> is |
|
|
4657 | available and will probe for kernel support at runtime. This allows |
|
|
4658 | libev to detect time jumps accurately. If undefined, it will be enabled |
|
|
4659 | if the headers indicate GNU/Linux + Glibc 2.8 or newer and define |
|
|
4660 | C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled. |
|
|
4661 | |
|
|
4662 | =item EV_USE_EVENTFD |
|
|
4663 | |
|
|
4664 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
4665 | available and will probe for kernel support at runtime. This will improve |
|
|
4666 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
4667 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4668 | 2.7 or newer, otherwise disabled. |
|
|
4669 | |
4457 | =item EV_USE_SELECT |
4670 | =item EV_USE_SELECT |
4458 | |
4671 | |
4459 | If undefined or defined to be C<1>, libev will compile in support for the |
4672 | If undefined or defined to be C<1>, libev will compile in support for the |
4460 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
4673 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
4461 | other method takes over, select will be it. Otherwise the select backend |
4674 | other method takes over, select will be it. Otherwise the select backend |
… | |
… | |
4501 | If programs implement their own fd to handle mapping on win32, then this |
4714 | If programs implement their own fd to handle mapping on win32, then this |
4502 | macro can be used to override the C<close> function, useful to unregister |
4715 | macro can be used to override the C<close> function, useful to unregister |
4503 | file descriptors again. Note that the replacement function has to close |
4716 | file descriptors again. Note that the replacement function has to close |
4504 | the underlying OS handle. |
4717 | the underlying OS handle. |
4505 | |
4718 | |
|
|
4719 | =item EV_USE_WSASOCKET |
|
|
4720 | |
|
|
4721 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4722 | communication socket, which works better in some environments. Otherwise, |
|
|
4723 | the normal C<socket> function will be used, which works better in other |
|
|
4724 | environments. |
|
|
4725 | |
4506 | =item EV_USE_POLL |
4726 | =item EV_USE_POLL |
4507 | |
4727 | |
4508 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4728 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4509 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4729 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4510 | takes precedence over select. |
4730 | takes precedence over select. |
… | |
… | |
4514 | If defined to be C<1>, libev will compile in support for the Linux |
4734 | If defined to be C<1>, libev will compile in support for the Linux |
4515 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4735 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4516 | otherwise another method will be used as fallback. This is the preferred |
4736 | otherwise another method will be used as fallback. This is the preferred |
4517 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4737 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4518 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4738 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4739 | |
|
|
4740 | =item EV_USE_LINUXAIO |
|
|
4741 | |
|
|
4742 | If defined to be C<1>, libev will compile in support for the Linux aio |
|
|
4743 | backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be |
|
|
4744 | enabled on linux, otherwise disabled. |
|
|
4745 | |
|
|
4746 | =item EV_USE_IOURING |
|
|
4747 | |
|
|
4748 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
4749 | io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's |
|
|
4750 | current limitations it has to be requested explicitly. If undefined, it |
|
|
4751 | will be enabled on linux, otherwise disabled. |
4519 | |
4752 | |
4520 | =item EV_USE_KQUEUE |
4753 | =item EV_USE_KQUEUE |
4521 | |
4754 | |
4522 | If defined to be C<1>, libev will compile in support for the BSD style |
4755 | If defined to be C<1>, libev will compile in support for the BSD style |
4523 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4756 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
4554 | different cpus (or different cpu cores). This reduces dependencies |
4787 | different cpus (or different cpu cores). This reduces dependencies |
4555 | and makes libev faster. |
4788 | and makes libev faster. |
4556 | |
4789 | |
4557 | =item EV_NO_THREADS |
4790 | =item EV_NO_THREADS |
4558 | |
4791 | |
4559 | If defined to be C<1>, libev will assume that it will never be called |
4792 | If defined to be C<1>, libev will assume that it will never be called from |
4560 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
4793 | different threads (that includes signal handlers), which is a stronger |
4561 | above. This reduces dependencies and makes libev faster. |
4794 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4795 | libev faster. |
4562 | |
4796 | |
4563 | =item EV_ATOMIC_T |
4797 | =item EV_ATOMIC_T |
4564 | |
4798 | |
4565 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4799 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4566 | access is atomic and serialised with respect to other threads or signal |
4800 | access is atomic with respect to other threads or signal contexts. No |
4567 | contexts. No such type is easily found in the C language, so you can |
4801 | such type is easily found in the C language, so you can provide your own |
4568 | provide your own type that you know is safe for your purposes. It is used |
4802 | type that you know is safe for your purposes. It is used both for signal |
4569 | both for signal handler "locking" as well as for signal and thread safety |
4803 | handler "locking" as well as for signal and thread safety in C<ev_async> |
4570 | in C<ev_async> watchers. |
4804 | watchers. |
4571 | |
4805 | |
4572 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4806 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4573 | (from F<signal.h>), which is usually good enough on most platforms, |
4807 | (from F<signal.h>), which is usually good enough on most platforms. |
4574 | although strictly speaking using a type that also implies a memory fence |
|
|
4575 | is required. |
|
|
4576 | |
4808 | |
4577 | =item EV_H (h) |
4809 | =item EV_H (h) |
4578 | |
4810 | |
4579 | The name of the F<ev.h> header file used to include it. The default if |
4811 | The name of the F<ev.h> header file used to include it. The default if |
4580 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4812 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
4801 | in. If set to C<1>, then verification code will be compiled in, but not |
5033 | in. If set to C<1>, then verification code will be compiled in, but not |
4802 | called. If set to C<2>, then the internal verification code will be |
5034 | called. If set to C<2>, then the internal verification code will be |
4803 | called once per loop, which can slow down libev. If set to C<3>, then the |
5035 | called once per loop, which can slow down libev. If set to C<3>, then the |
4804 | verification code will be called very frequently, which will slow down |
5036 | verification code will be called very frequently, which will slow down |
4805 | libev considerably. |
5037 | libev considerably. |
|
|
5038 | |
|
|
5039 | Verification errors are reported via C's C<assert> mechanism, so if you |
|
|
5040 | disable that (e.g. by defining C<NDEBUG>) then no errors will be reported. |
4806 | |
5041 | |
4807 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
5042 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
4808 | will be C<0>. |
5043 | will be C<0>. |
4809 | |
5044 | |
4810 | =item EV_COMMON |
5045 | =item EV_COMMON |
… | |
… | |
4948 | default loop and triggering an C<ev_async> watcher from the default loop |
5183 | default loop and triggering an C<ev_async> watcher from the default loop |
4949 | watcher callback into the event loop interested in the signal. |
5184 | watcher callback into the event loop interested in the signal. |
4950 | |
5185 | |
4951 | =back |
5186 | =back |
4952 | |
5187 | |
4953 | See also L<THREAD LOCKING EXAMPLE>. |
5188 | See also L</THREAD LOCKING EXAMPLE>. |
4954 | |
5189 | |
4955 | =head3 COROUTINES |
5190 | =head3 COROUTINES |
4956 | |
5191 | |
4957 | Libev is very accommodating to coroutines ("cooperative threads"): |
5192 | Libev is very accommodating to coroutines ("cooperative threads"): |
4958 | libev fully supports nesting calls to its functions from different |
5193 | libev fully supports nesting calls to its functions from different |
… | |
… | |
5227 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5462 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5228 | assumes that the same (machine) code can be used to call any watcher |
5463 | assumes that the same (machine) code can be used to call any watcher |
5229 | callback: The watcher callbacks have different type signatures, but libev |
5464 | callback: The watcher callbacks have different type signatures, but libev |
5230 | calls them using an C<ev_watcher *> internally. |
5465 | calls them using an C<ev_watcher *> internally. |
5231 | |
5466 | |
|
|
5467 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5468 | |
|
|
5469 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5470 | relies on this setting pointers and integers to null. |
|
|
5471 | |
5232 | =item pointer accesses must be thread-atomic |
5472 | =item pointer accesses must be thread-atomic |
5233 | |
5473 | |
5234 | Accessing a pointer value must be atomic, it must both be readable and |
5474 | Accessing a pointer value must be atomic, it must both be readable and |
5235 | writable in one piece - this is the case on all current architectures. |
5475 | writable in one piece - this is the case on all current architectures. |
5236 | |
5476 | |
… | |
… | |
5249 | thread" or will block signals process-wide, both behaviours would |
5489 | thread" or will block signals process-wide, both behaviours would |
5250 | be compatible with libev. Interaction between C<sigprocmask> and |
5490 | be compatible with libev. Interaction between C<sigprocmask> and |
5251 | C<pthread_sigmask> could complicate things, however. |
5491 | C<pthread_sigmask> could complicate things, however. |
5252 | |
5492 | |
5253 | The most portable way to handle signals is to block signals in all threads |
5493 | The most portable way to handle signals is to block signals in all threads |
5254 | except the initial one, and run the default loop in the initial thread as |
5494 | except the initial one, and run the signal handling loop in the initial |
5255 | well. |
5495 | thread as well. |
5256 | |
5496 | |
5257 | =item C<long> must be large enough for common memory allocation sizes |
5497 | =item C<long> must be large enough for common memory allocation sizes |
5258 | |
5498 | |
5259 | To improve portability and simplify its API, libev uses C<long> internally |
5499 | To improve portability and simplify its API, libev uses C<long> internally |
5260 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5500 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
5364 | =over 4 |
5604 | =over 4 |
5365 | |
5605 | |
5366 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5606 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5367 | |
5607 | |
5368 | The backward compatibility mechanism can be controlled by |
5608 | The backward compatibility mechanism can be controlled by |
5369 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
5609 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
5370 | section. |
5610 | section. |
5371 | |
5611 | |
5372 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5612 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5373 | |
5613 | |
5374 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5614 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
… | |
… | |
5417 | =over 4 |
5657 | =over 4 |
5418 | |
5658 | |
5419 | =item active |
5659 | =item active |
5420 | |
5660 | |
5421 | A watcher is active as long as it has been started and not yet stopped. |
5661 | A watcher is active as long as it has been started and not yet stopped. |
5422 | See L<WATCHER STATES> for details. |
5662 | See L</WATCHER STATES> for details. |
5423 | |
5663 | |
5424 | =item application |
5664 | =item application |
5425 | |
5665 | |
5426 | In this document, an application is whatever is using libev. |
5666 | In this document, an application is whatever is using libev. |
5427 | |
5667 | |
… | |
… | |
5463 | watchers and events. |
5703 | watchers and events. |
5464 | |
5704 | |
5465 | =item pending |
5705 | =item pending |
5466 | |
5706 | |
5467 | A watcher is pending as soon as the corresponding event has been |
5707 | A watcher is pending as soon as the corresponding event has been |
5468 | detected. See L<WATCHER STATES> for details. |
5708 | detected. See L</WATCHER STATES> for details. |
5469 | |
5709 | |
5470 | =item real time |
5710 | =item real time |
5471 | |
5711 | |
5472 | The physical time that is observed. It is apparently strictly monotonic :) |
5712 | The physical time that is observed. It is apparently strictly monotonic :) |
5473 | |
5713 | |