… | |
… | |
105 | 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 |
106 | watcher. |
106 | watcher. |
107 | |
107 | |
108 | =head2 FEATURES |
108 | =head2 FEATURES |
109 | |
109 | |
110 | 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> |
111 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
111 | interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port |
112 | 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> |
113 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
113 | interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
114 | 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 |
115 | timers (C<ev_timer>), absolute timers with customised rescheduling |
115 | timers (C<ev_timer>), absolute timers with customised rescheduling |
116 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
116 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
117 | 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 |
118 | 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 |
… | |
… | |
265 | |
265 | |
266 | You could override this function in high-availability programs to, say, |
266 | You could override this function in high-availability programs to, say, |
267 | free some memory if it cannot allocate memory, to use a special allocator, |
267 | free some memory if it cannot allocate memory, to use a special allocator, |
268 | or even to sleep a while and retry until some memory is available. |
268 | or even to sleep a while and retry until some memory is available. |
269 | |
269 | |
|
|
270 | Example: The following is the C<realloc> function that libev itself uses |
|
|
271 | which should work with C<realloc> and C<free> functions of all kinds and |
|
|
272 | is probably a good basis for your own implementation. |
|
|
273 | |
|
|
274 | static void * |
|
|
275 | ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT |
|
|
276 | { |
|
|
277 | if (size) |
|
|
278 | return realloc (ptr, size); |
|
|
279 | |
|
|
280 | free (ptr); |
|
|
281 | return 0; |
|
|
282 | } |
|
|
283 | |
270 | Example: Replace the libev allocator with one that waits a bit and then |
284 | Example: Replace the libev allocator with one that waits a bit and then |
271 | retries (example requires a standards-compliant C<realloc>). |
285 | retries. |
272 | |
286 | |
273 | static void * |
287 | static void * |
274 | persistent_realloc (void *ptr, size_t size) |
288 | persistent_realloc (void *ptr, size_t size) |
275 | { |
289 | { |
|
|
290 | if (!size) |
|
|
291 | { |
|
|
292 | free (ptr); |
|
|
293 | return 0; |
|
|
294 | } |
|
|
295 | |
276 | for (;;) |
296 | for (;;) |
277 | { |
297 | { |
278 | void *newptr = realloc (ptr, size); |
298 | void *newptr = realloc (ptr, size); |
279 | |
299 | |
280 | if (newptr) |
300 | if (newptr) |
… | |
… | |
411 | make libev check for a fork in each iteration by enabling this flag. |
431 | make libev check for a fork in each iteration by enabling this flag. |
412 | |
432 | |
413 | This works by calling C<getpid ()> on every iteration of the loop, |
433 | This works by calling C<getpid ()> on every iteration of the loop, |
414 | and thus this might slow down your event loop if you do a lot of loop |
434 | and thus this might slow down your event loop if you do a lot of loop |
415 | iterations and little real work, but is usually not noticeable (on my |
435 | iterations and little real work, but is usually not noticeable (on my |
416 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
436 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
417 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
437 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
418 | C<pthread_atfork> which is even faster). |
438 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
|
|
439 | versions 2.25 apparently removed the C<getpid> optimisation again). |
419 | |
440 | |
420 | The big advantage of this flag is that you can forget about fork (and |
441 | The big advantage of this flag is that you can forget about fork (and |
421 | forget about forgetting to tell libev about forking) when you use this |
442 | forget about forgetting to tell libev about forking, although you still |
422 | flag. |
443 | have to ignore C<SIGPIPE>) when you use this flag. |
423 | |
444 | |
424 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
445 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
425 | environment variable. |
446 | environment variable. |
426 | |
447 | |
427 | =item C<EVFLAG_NOINOTIFY> |
448 | =item C<EVFLAG_NOINOTIFY> |
… | |
… | |
546 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
567 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
547 | faster than epoll for maybe up to a hundred file descriptors, depending on |
568 | faster than epoll for maybe up to a hundred file descriptors, depending on |
548 | the usage. So sad. |
569 | the usage. So sad. |
549 | |
570 | |
550 | While nominally embeddable in other event loops, this feature is broken in |
571 | While nominally embeddable in other event loops, this feature is broken in |
551 | all kernel versions tested so far. |
572 | a lot of kernel revisions, but probably(!) works in current versions. |
|
|
573 | |
|
|
574 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
575 | C<EVBACKEND_POLL>. |
|
|
576 | |
|
|
577 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
|
|
578 | |
|
|
579 | Use the linux-specific linux aio (I<not> C<< aio(7) >> but C<< |
|
|
580 | io_submit(2) >>) event interface available in post-4.18 kernels. |
|
|
581 | |
|
|
582 | If this backend works for you (as of this writing, it was very |
|
|
583 | experimental), it is the best event interface available on linux and might |
|
|
584 | be well worth enabling it - if it isn't available in your kernel this will |
|
|
585 | be detected and this backend will be skipped. |
|
|
586 | |
|
|
587 | This backend can batch oneshot requests and supports a user-space ring |
|
|
588 | buffer to receive events. It also doesn't suffer from most of the design |
|
|
589 | problems of epoll (such as not being able to remove event sources from |
|
|
590 | the epoll set), and generally sounds too good to be true. Because, this |
|
|
591 | being the linux kernel, of course it suffers from a whole new set of |
|
|
592 | limitations. |
|
|
593 | |
|
|
594 | For one, it is not easily embeddable (but probably could be done using |
|
|
595 | an event fd at some extra overhead). It also is subject to a system wide |
|
|
596 | limit that can be configured in F</proc/sys/fs/aio-max-nr> - each loop |
|
|
597 | currently requires C<61> of this number. If no aio requests are left, this |
|
|
598 | backend will be skipped during initialisation. |
|
|
599 | |
|
|
600 | Most problematic in practise, however, is that not all file descriptors |
|
|
601 | work with it. For example, in linux 5.1, tcp sockets, pipes, event fds, |
|
|
602 | files, F</dev/null> and a few others are supported, but ttys do not work |
|
|
603 | properly (a known bug that the kernel developers don't care about, see |
|
|
604 | L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
|
|
605 | (yet?) a generic event polling interface. |
|
|
606 | |
|
|
607 | To work around this latter problem, the current version of libev uses |
|
|
608 | epoll as a fallback for file deescriptor types that do not work. Epoll |
|
|
609 | is used in, kind of, slow mode that hopefully avoids most of its design |
|
|
610 | problems and requires 1-3 extra syscalls per active fd every iteration. |
552 | |
611 | |
553 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
612 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
554 | C<EVBACKEND_POLL>. |
613 | C<EVBACKEND_POLL>. |
555 | |
614 | |
556 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
615 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
… | |
… | |
657 | Example: Use whatever libev has to offer, but make sure that kqueue is |
716 | Example: Use whatever libev has to offer, but make sure that kqueue is |
658 | used if available. |
717 | used if available. |
659 | |
718 | |
660 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
719 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
661 | |
720 | |
|
|
721 | Example: Similarly, on linux, you mgiht want to take advantage of the |
|
|
722 | linux aio backend if possible, but fall back to something else if that |
|
|
723 | isn't available. |
|
|
724 | |
|
|
725 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO); |
|
|
726 | |
662 | =item ev_loop_destroy (loop) |
727 | =item ev_loop_destroy (loop) |
663 | |
728 | |
664 | Destroys an event loop object (frees all memory and kernel state |
729 | Destroys an event loop object (frees all memory and kernel state |
665 | etc.). None of the active event watchers will be stopped in the normal |
730 | etc.). None of the active event watchers will be stopped in the normal |
666 | sense, so e.g. C<ev_is_active> might still return true. It is your |
731 | sense, so e.g. C<ev_is_active> might still return true. It is your |
… | |
… | |
682 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
747 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
683 | and C<ev_loop_destroy>. |
748 | and C<ev_loop_destroy>. |
684 | |
749 | |
685 | =item ev_loop_fork (loop) |
750 | =item ev_loop_fork (loop) |
686 | |
751 | |
687 | This function sets a flag that causes subsequent C<ev_run> iterations to |
752 | This function sets a flag that causes subsequent C<ev_run> iterations |
688 | reinitialise the kernel state for backends that have one. Despite the |
753 | to reinitialise the kernel state for backends that have one. Despite |
689 | name, you can call it anytime, but it makes most sense after forking, in |
754 | the name, you can call it anytime you are allowed to start or stop |
690 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
755 | watchers (except inside an C<ev_prepare> callback), but it makes most |
|
|
756 | sense after forking, in the child process. You I<must> call it (or use |
691 | child before resuming or calling C<ev_run>. |
757 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
|
|
758 | |
|
|
759 | In addition, if you want to reuse a loop (via this function or |
|
|
760 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
692 | |
761 | |
693 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
762 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
694 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
763 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
695 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
764 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
696 | during fork. |
765 | during fork. |
… | |
… | |
1605 | |
1674 | |
1606 | But really, best use non-blocking mode. |
1675 | But really, best use non-blocking mode. |
1607 | |
1676 | |
1608 | =head3 The special problem of disappearing file descriptors |
1677 | =head3 The special problem of disappearing file descriptors |
1609 | |
1678 | |
1610 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1679 | Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing |
1611 | descriptor (either due to calling C<close> explicitly or any other means, |
1680 | a file descriptor (either due to calling C<close> explicitly or any other |
1612 | such as C<dup2>). The reason is that you register interest in some file |
1681 | means, such as C<dup2>). The reason is that you register interest in some |
1613 | descriptor, but when it goes away, the operating system will silently drop |
1682 | file descriptor, but when it goes away, the operating system will silently |
1614 | this interest. If another file descriptor with the same number then is |
1683 | drop this interest. If another file descriptor with the same number then |
1615 | registered with libev, there is no efficient way to see that this is, in |
1684 | is registered with libev, there is no efficient way to see that this is, |
1616 | fact, a different file descriptor. |
1685 | in fact, a different file descriptor. |
1617 | |
1686 | |
1618 | To avoid having to explicitly tell libev about such cases, libev follows |
1687 | To avoid having to explicitly tell libev about such cases, libev follows |
1619 | the following policy: Each time C<ev_io_set> is being called, libev |
1688 | the following policy: Each time C<ev_io_set> is being called, libev |
1620 | will assume that this is potentially a new file descriptor, otherwise |
1689 | will assume that this is potentially a new file descriptor, otherwise |
1621 | it is assumed that the file descriptor stays the same. That means that |
1690 | it is assumed that the file descriptor stays the same. That means that |
… | |
… | |
1670 | when you rarely read from a file instead of from a socket, and want to |
1739 | when you rarely read from a file instead of from a socket, and want to |
1671 | reuse the same code path. |
1740 | reuse the same code path. |
1672 | |
1741 | |
1673 | =head3 The special problem of fork |
1742 | =head3 The special problem of fork |
1674 | |
1743 | |
1675 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1744 | Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()> |
1676 | useless behaviour. Libev fully supports fork, but needs to be told about |
1745 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1677 | it in the child if you want to continue to use it in the child. |
1746 | to be told about it in the child if you want to continue to use it in the |
|
|
1747 | child. |
1678 | |
1748 | |
1679 | To support fork in your child processes, you have to call C<ev_loop_fork |
1749 | To support fork in your child processes, you have to call C<ev_loop_fork |
1680 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1750 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1681 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1751 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1682 | |
1752 | |
… | |
… | |
2028 | |
2098 | |
2029 | The relative timeouts are calculated relative to the C<ev_now ()> |
2099 | The relative timeouts are calculated relative to the C<ev_now ()> |
2030 | time. This is usually the right thing as this timestamp refers to the time |
2100 | time. This is usually the right thing as this timestamp refers to the time |
2031 | of the event triggering whatever timeout you are modifying/starting. If |
2101 | of the event triggering whatever timeout you are modifying/starting. If |
2032 | you suspect event processing to be delayed and you I<need> to base the |
2102 | you suspect event processing to be delayed and you I<need> to base the |
2033 | timeout on the current time, use something like this to adjust for this: |
2103 | timeout on the current time, use something like the following to adjust |
|
|
2104 | for it: |
2034 | |
2105 | |
2035 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2106 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
2036 | |
2107 | |
2037 | If the event loop is suspended for a long time, you can also force an |
2108 | If the event loop is suspended for a long time, you can also force an |
2038 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2109 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2039 | ()>. |
2110 | ()>, although that will push the event time of all outstanding events |
|
|
2111 | further into the future. |
2040 | |
2112 | |
2041 | =head3 The special problem of unsynchronised clocks |
2113 | =head3 The special problem of unsynchronised clocks |
2042 | |
2114 | |
2043 | Modern systems have a variety of clocks - libev itself uses the normal |
2115 | Modern systems have a variety of clocks - libev itself uses the normal |
2044 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
2116 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
… | |
… | |
2107 | |
2179 | |
2108 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2180 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2109 | |
2181 | |
2110 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2182 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2111 | |
2183 | |
2112 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2184 | Configure the timer to trigger after C<after> seconds (fractional and |
2113 | is C<0.>, then it will automatically be stopped once the timeout is |
2185 | negative values are supported). If C<repeat> is C<0.>, then it will |
2114 | reached. If it is positive, then the timer will automatically be |
2186 | automatically be stopped once the timeout is reached. If it is positive, |
2115 | configured to trigger again C<repeat> seconds later, again, and again, |
2187 | then the timer will automatically be configured to trigger again C<repeat> |
2116 | until stopped manually. |
2188 | seconds later, again, and again, until stopped manually. |
2117 | |
2189 | |
2118 | The timer itself will do a best-effort at avoiding drift, that is, if |
2190 | The timer itself will do a best-effort at avoiding drift, that is, if |
2119 | you configure a timer to trigger every 10 seconds, then it will normally |
2191 | you configure a timer to trigger every 10 seconds, then it will normally |
2120 | trigger at exactly 10 second intervals. If, however, your program cannot |
2192 | trigger at exactly 10 second intervals. If, however, your program cannot |
2121 | keep up with the timer (because it takes longer than those 10 seconds to |
2193 | keep up with the timer (because it takes longer than those 10 seconds to |
… | |
… | |
2203 | Periodic watchers are also timers of a kind, but they are very versatile |
2275 | Periodic watchers are also timers of a kind, but they are very versatile |
2204 | (and unfortunately a bit complex). |
2276 | (and unfortunately a bit complex). |
2205 | |
2277 | |
2206 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2278 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2207 | relative time, the physical time that passes) but on wall clock time |
2279 | relative time, the physical time that passes) but on wall clock time |
2208 | (absolute time, the thing you can read on your calender or clock). The |
2280 | (absolute time, the thing you can read on your calendar or clock). The |
2209 | difference is that wall clock time can run faster or slower than real |
2281 | difference is that wall clock time can run faster or slower than real |
2210 | time, and time jumps are not uncommon (e.g. when you adjust your |
2282 | time, and time jumps are not uncommon (e.g. when you adjust your |
2211 | wrist-watch). |
2283 | wrist-watch). |
2212 | |
2284 | |
2213 | You can tell a periodic watcher to trigger after some specific point |
2285 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
2218 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2290 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2219 | it, as it uses a relative timeout). |
2291 | it, as it uses a relative timeout). |
2220 | |
2292 | |
2221 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2293 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2222 | timers, such as triggering an event on each "midnight, local time", or |
2294 | timers, such as triggering an event on each "midnight, local time", or |
2223 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
2295 | other complicated rules. This cannot easily be done with C<ev_timer> |
2224 | those cannot react to time jumps. |
2296 | watchers, as those cannot react to time jumps. |
2225 | |
2297 | |
2226 | As with timers, the callback is guaranteed to be invoked only when the |
2298 | As with timers, the callback is guaranteed to be invoked only when the |
2227 | point in time where it is supposed to trigger has passed. If multiple |
2299 | point in time where it is supposed to trigger has passed. If multiple |
2228 | timers become ready during the same loop iteration then the ones with |
2300 | timers become ready during the same loop iteration then the ones with |
2229 | earlier time-out values are invoked before ones with later time-out values |
2301 | earlier time-out values are invoked before ones with later time-out values |
… | |
… | |
2315 | |
2387 | |
2316 | NOTE: I<< This callback must always return a time that is higher than or |
2388 | NOTE: I<< This callback must always return a time that is higher than or |
2317 | equal to the passed C<now> value >>. |
2389 | equal to the passed C<now> value >>. |
2318 | |
2390 | |
2319 | This can be used to create very complex timers, such as a timer that |
2391 | This can be used to create very complex timers, such as a timer that |
2320 | triggers on "next midnight, local time". To do this, you would calculate the |
2392 | triggers on "next midnight, local time". To do this, you would calculate |
2321 | next midnight after C<now> and return the timestamp value for this. How |
2393 | the next midnight after C<now> and return the timestamp value for |
2322 | you do this is, again, up to you (but it is not trivial, which is the main |
2394 | this. Here is a (completely untested, no error checking) example on how to |
2323 | reason I omitted it as an example). |
2395 | do this: |
|
|
2396 | |
|
|
2397 | #include <time.h> |
|
|
2398 | |
|
|
2399 | static ev_tstamp |
|
|
2400 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2401 | { |
|
|
2402 | time_t tnow = (time_t)now; |
|
|
2403 | struct tm tm; |
|
|
2404 | localtime_r (&tnow, &tm); |
|
|
2405 | |
|
|
2406 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2407 | ++tm.tm_mday; // midnight next day |
|
|
2408 | |
|
|
2409 | return mktime (&tm); |
|
|
2410 | } |
|
|
2411 | |
|
|
2412 | Note: this code might run into trouble on days that have more then two |
|
|
2413 | midnights (beginning and end). |
2324 | |
2414 | |
2325 | =back |
2415 | =back |
2326 | |
2416 | |
2327 | =item ev_periodic_again (loop, ev_periodic *) |
2417 | =item ev_periodic_again (loop, ev_periodic *) |
2328 | |
2418 | |
… | |
… | |
2393 | |
2483 | |
2394 | ev_periodic hourly_tick; |
2484 | ev_periodic hourly_tick; |
2395 | ev_periodic_init (&hourly_tick, clock_cb, |
2485 | ev_periodic_init (&hourly_tick, clock_cb, |
2396 | fmod (ev_now (loop), 3600.), 3600., 0); |
2486 | fmod (ev_now (loop), 3600.), 3600., 0); |
2397 | ev_periodic_start (loop, &hourly_tick); |
2487 | ev_periodic_start (loop, &hourly_tick); |
2398 | |
2488 | |
2399 | |
2489 | |
2400 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2490 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2401 | |
2491 | |
2402 | Signal watchers will trigger an event when the process receives a specific |
2492 | Signal watchers will trigger an event when the process receives a specific |
2403 | signal one or more times. Even though signals are very asynchronous, libev |
2493 | signal one or more times. Even though signals are very asynchronous, libev |
… | |
… | |
2907 | |
2997 | |
2908 | Prepare and check watchers are often (but not always) used in pairs: |
2998 | Prepare and check watchers are often (but not always) used in pairs: |
2909 | prepare watchers get invoked before the process blocks and check watchers |
2999 | prepare watchers get invoked before the process blocks and check watchers |
2910 | afterwards. |
3000 | afterwards. |
2911 | |
3001 | |
2912 | You I<must not> call C<ev_run> or similar functions that enter |
3002 | You I<must not> call C<ev_run> (or similar functions that enter the |
2913 | the current event loop from either C<ev_prepare> or C<ev_check> |
3003 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2914 | watchers. Other loops than the current one are fine, however. The |
3004 | C<ev_check> watchers. Other loops than the current one are fine, |
2915 | rationale behind this is that you do not need to check for recursion in |
3005 | however. The rationale behind this is that you do not need to check |
2916 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
3006 | for recursion in those watchers, i.e. the sequence will always be |
2917 | C<ev_check> so if you have one watcher of each kind they will always be |
3007 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2918 | called in pairs bracketing the blocking call. |
3008 | kind they will always be called in pairs bracketing the blocking call. |
2919 | |
3009 | |
2920 | Their main purpose is to integrate other event mechanisms into libev and |
3010 | Their main purpose is to integrate other event mechanisms into libev and |
2921 | their use is somewhat advanced. They could be used, for example, to track |
3011 | their use is somewhat advanced. They could be used, for example, to track |
2922 | variable changes, implement your own watchers, integrate net-snmp or a |
3012 | variable changes, implement your own watchers, integrate net-snmp or a |
2923 | coroutine library and lots more. They are also occasionally useful if |
3013 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
3213 | used). |
3303 | used). |
3214 | |
3304 | |
3215 | struct ev_loop *loop_hi = ev_default_init (0); |
3305 | struct ev_loop *loop_hi = ev_default_init (0); |
3216 | struct ev_loop *loop_lo = 0; |
3306 | struct ev_loop *loop_lo = 0; |
3217 | ev_embed embed; |
3307 | ev_embed embed; |
3218 | |
3308 | |
3219 | // see if there is a chance of getting one that works |
3309 | // see if there is a chance of getting one that works |
3220 | // (remember that a flags value of 0 means autodetection) |
3310 | // (remember that a flags value of 0 means autodetection) |
3221 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3311 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3222 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3312 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3223 | : 0; |
3313 | : 0; |
… | |
… | |
3237 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3327 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3238 | |
3328 | |
3239 | struct ev_loop *loop = ev_default_init (0); |
3329 | struct ev_loop *loop = ev_default_init (0); |
3240 | struct ev_loop *loop_socket = 0; |
3330 | struct ev_loop *loop_socket = 0; |
3241 | ev_embed embed; |
3331 | ev_embed embed; |
3242 | |
3332 | |
3243 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3333 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3244 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3334 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3245 | { |
3335 | { |
3246 | ev_embed_init (&embed, 0, loop_socket); |
3336 | ev_embed_init (&embed, 0, loop_socket); |
3247 | ev_embed_start (loop, &embed); |
3337 | ev_embed_start (loop, &embed); |
… | |
… | |
3263 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3353 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3264 | of course. |
3354 | of course. |
3265 | |
3355 | |
3266 | =head3 The special problem of life after fork - how is it possible? |
3356 | =head3 The special problem of life after fork - how is it possible? |
3267 | |
3357 | |
3268 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3358 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3269 | up/change the process environment, followed by a call to C<exec()>. This |
3359 | up/change the process environment, followed by a call to C<exec()>. This |
3270 | sequence should be handled by libev without any problems. |
3360 | sequence should be handled by libev without any problems. |
3271 | |
3361 | |
3272 | This changes when the application actually wants to do event handling |
3362 | This changes when the application actually wants to do event handling |
3273 | in the child, or both parent in child, in effect "continuing" after the |
3363 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3511 | |
3601 | |
3512 | There are some other functions of possible interest. Described. Here. Now. |
3602 | There are some other functions of possible interest. Described. Here. Now. |
3513 | |
3603 | |
3514 | =over 4 |
3604 | =over 4 |
3515 | |
3605 | |
3516 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3606 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
3517 | |
3607 | |
3518 | This function combines a simple timer and an I/O watcher, calls your |
3608 | This function combines a simple timer and an I/O watcher, calls your |
3519 | callback on whichever event happens first and automatically stops both |
3609 | callback on whichever event happens first and automatically stops both |
3520 | watchers. This is useful if you want to wait for a single event on an fd |
3610 | watchers. This is useful if you want to wait for a single event on an fd |
3521 | or timeout without having to allocate/configure/start/stop/free one or |
3611 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
3897 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3987 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3898 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3988 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3899 | |
3989 | |
3900 | // my_ev.h |
3990 | // my_ev.h |
3901 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3991 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3902 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
3992 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
3903 | #include "../libev/ev.h" |
3993 | #include "../libev/ev.h" |
3904 | |
3994 | |
3905 | // my_ev.c |
3995 | // my_ev.c |
3906 | #define EV_H "my_ev.h" |
3996 | #define EV_H "my_ev.h" |
3907 | #include "../libev/ev.c" |
3997 | #include "../libev/ev.c" |
… | |
… | |
3953 | The normal C API should work fine when used from C++: both ev.h and the |
4043 | The normal C API should work fine when used from C++: both ev.h and the |
3954 | libev sources can be compiled as C++. Therefore, code that uses the C API |
4044 | libev sources can be compiled as C++. Therefore, code that uses the C API |
3955 | will work fine. |
4045 | will work fine. |
3956 | |
4046 | |
3957 | Proper exception specifications might have to be added to callbacks passed |
4047 | Proper exception specifications might have to be added to callbacks passed |
3958 | to libev: exceptions may be thrown only from watcher callbacks, all |
4048 | to libev: exceptions may be thrown only from watcher callbacks, all other |
3959 | other callbacks (allocator, syserr, loop acquire/release and periodic |
4049 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
3960 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
4050 | callbacks) must not throw exceptions, and might need a C<noexcept> |
3961 | ()> specification. If you have code that needs to be compiled as both C |
4051 | specification. If you have code that needs to be compiled as both C and |
3962 | and C++ you can use the C<EV_THROW> macro for this: |
4052 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
3963 | |
4053 | |
3964 | static void |
4054 | static void |
3965 | fatal_error (const char *msg) EV_THROW |
4055 | fatal_error (const char *msg) EV_NOEXCEPT |
3966 | { |
4056 | { |
3967 | perror (msg); |
4057 | perror (msg); |
3968 | abort (); |
4058 | abort (); |
3969 | } |
4059 | } |
3970 | |
4060 | |
… | |
… | |
4097 | void operator() (ev::io &w, int revents) |
4187 | void operator() (ev::io &w, int revents) |
4098 | { |
4188 | { |
4099 | ... |
4189 | ... |
4100 | } |
4190 | } |
4101 | } |
4191 | } |
4102 | |
4192 | |
4103 | myfunctor f; |
4193 | myfunctor f; |
4104 | |
4194 | |
4105 | ev::io w; |
4195 | ev::io w; |
4106 | w.set (&f); |
4196 | w.set (&f); |
4107 | |
4197 | |
… | |
… | |
4380 | ev_vars.h |
4470 | ev_vars.h |
4381 | ev_wrap.h |
4471 | ev_wrap.h |
4382 | |
4472 | |
4383 | ev_win32.c required on win32 platforms only |
4473 | ev_win32.c required on win32 platforms only |
4384 | |
4474 | |
4385 | ev_select.c only when select backend is enabled (which is enabled by default) |
4475 | ev_select.c only when select backend is enabled |
4386 | ev_poll.c only when poll backend is enabled (disabled by default) |
4476 | ev_poll.c only when poll backend is enabled |
4387 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4477 | ev_epoll.c only when the epoll backend is enabled |
|
|
4478 | ev_linuxaio.c only when the linux aio backend is enabled |
4388 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4479 | ev_kqueue.c only when the kqueue backend is enabled |
4389 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4480 | ev_port.c only when the solaris port backend is enabled |
4390 | |
4481 | |
4391 | F<ev.c> includes the backend files directly when enabled, so you only need |
4482 | F<ev.c> includes the backend files directly when enabled, so you only need |
4392 | to compile this single file. |
4483 | to compile this single file. |
4393 | |
4484 | |
4394 | =head3 LIBEVENT COMPATIBILITY API |
4485 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
4582 | If defined to be C<1>, libev will compile in support for the Linux |
4673 | If defined to be C<1>, libev will compile in support for the Linux |
4583 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4674 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4584 | otherwise another method will be used as fallback. This is the preferred |
4675 | otherwise another method will be used as fallback. This is the preferred |
4585 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4676 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4586 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4677 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4678 | |
|
|
4679 | =item EV_USE_LINUXAIO |
|
|
4680 | |
|
|
4681 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
4682 | aio backend. Due to it's currenbt limitations it has to be requested |
|
|
4683 | explicitly. If undefined, it will be enabled on linux, otherwise |
|
|
4684 | disabled. |
4587 | |
4685 | |
4588 | =item EV_USE_KQUEUE |
4686 | =item EV_USE_KQUEUE |
4589 | |
4687 | |
4590 | If defined to be C<1>, libev will compile in support for the BSD style |
4688 | If defined to be C<1>, libev will compile in support for the BSD style |
4591 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4689 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
5294 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5392 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5295 | assumes that the same (machine) code can be used to call any watcher |
5393 | assumes that the same (machine) code can be used to call any watcher |
5296 | callback: The watcher callbacks have different type signatures, but libev |
5394 | callback: The watcher callbacks have different type signatures, but libev |
5297 | calls them using an C<ev_watcher *> internally. |
5395 | calls them using an C<ev_watcher *> internally. |
5298 | |
5396 | |
|
|
5397 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5398 | |
|
|
5399 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5400 | relies on this setting pointers and integers to null. |
|
|
5401 | |
5299 | =item pointer accesses must be thread-atomic |
5402 | =item pointer accesses must be thread-atomic |
5300 | |
5403 | |
5301 | Accessing a pointer value must be atomic, it must both be readable and |
5404 | Accessing a pointer value must be atomic, it must both be readable and |
5302 | writable in one piece - this is the case on all current architectures. |
5405 | writable in one piece - this is the case on all current architectures. |
5303 | |
5406 | |