… | |
… | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
|
|
14 | #include <stdio.h> // for puts |
|
|
15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
18 | |
20 | |
19 | // all watcher callbacks have a similar signature |
21 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
22 | // this callback is called when data is readable on stdin |
21 | static void |
23 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
24 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
25 | { |
24 | puts ("stdin ready"); |
26 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
27 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
28 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
29 | ev_io_stop (EV_A_ w); |
… | |
… | |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
31 | } |
33 | } |
32 | |
34 | |
33 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
34 | static void |
36 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
38 | { |
37 | puts ("timeout"); |
39 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_loop to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
40 | } |
42 | } |
… | |
… | |
103 | Libev is very configurable. In this manual the default (and most common) |
105 | Libev is very configurable. In this manual the default (and most common) |
104 | configuration will be described, which supports multiple event loops. For |
106 | configuration will be described, which supports multiple event loops. For |
105 | more info about various configuration options please have a look at |
107 | more info about various configuration options please have a look at |
106 | B<EMBED> section in this manual. If libev was configured without support |
108 | B<EMBED> section in this manual. If libev was configured without support |
107 | for multiple event loops, then all functions taking an initial argument of |
109 | for multiple event loops, then all functions taking an initial argument of |
108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
110 | name C<loop> (which is always of type C<ev_loop *>) will not have |
109 | this argument. |
111 | this argument. |
110 | |
112 | |
111 | =head2 TIME REPRESENTATION |
113 | =head2 TIME REPRESENTATION |
112 | |
114 | |
113 | Libev represents time as a single floating point number, representing the |
115 | Libev represents time as a single floating point number, representing the |
… | |
… | |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
216 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
215 | recommended ones. |
217 | recommended ones. |
216 | |
218 | |
217 | See the description of C<ev_embed> watchers for more info. |
219 | See the description of C<ev_embed> watchers for more info. |
218 | |
220 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
221 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
220 | |
222 | |
221 | Sets the allocation function to use (the prototype is similar - the |
223 | Sets the allocation function to use (the prototype is similar - the |
222 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
224 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
223 | used to allocate and free memory (no surprises here). If it returns zero |
225 | used to allocate and free memory (no surprises here). If it returns zero |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
226 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
250 | } |
252 | } |
251 | |
253 | |
252 | ... |
254 | ... |
253 | ev_set_allocator (persistent_realloc); |
255 | ev_set_allocator (persistent_realloc); |
254 | |
256 | |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
257 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
256 | |
258 | |
257 | Set the callback function to call on a retryable system call error (such |
259 | Set the callback function to call on a retryable system call error (such |
258 | as failed select, poll, epoll_wait). The message is a printable string |
260 | as failed select, poll, epoll_wait). The message is a printable string |
259 | indicating the system call or subsystem causing the problem. If this |
261 | indicating the system call or subsystem causing the problem. If this |
260 | callback is set, then libev will expect it to remedy the situation, no |
262 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
276 | |
278 | |
277 | =back |
279 | =back |
278 | |
280 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
281 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
280 | |
282 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
283 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
282 | types of such loops, the I<default> loop, which supports signals and child |
284 | is I<not> optional in this case, as there is also an C<ev_loop> |
283 | events, and dynamically created loops which do not. |
285 | I<function>). |
|
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286 | |
|
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287 | The library knows two types of such loops, the I<default> loop, which |
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288 | supports signals and child events, and dynamically created loops which do |
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289 | not. |
284 | |
290 | |
285 | =over 4 |
291 | =over 4 |
286 | |
292 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
293 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
294 | |
… | |
… | |
294 | If you don't know what event loop to use, use the one returned from this |
300 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
301 | function. |
296 | |
302 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
303 | Note that this function is I<not> thread-safe, so if you want to use it |
298 | from multiple threads, you have to lock (note also that this is unlikely, |
304 | from multiple threads, you have to lock (note also that this is unlikely, |
299 | as loops cannot bes hared easily between threads anyway). |
305 | as loops cannot be shared easily between threads anyway). |
300 | |
306 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
307 | The default loop is the only loop that can handle C<ev_signal> and |
302 | C<ev_child> watchers, and to do this, it always registers a handler |
308 | C<ev_child> watchers, and to do this, it always registers a handler |
303 | for C<SIGCHLD>. If this is a problem for your application you can either |
309 | for C<SIGCHLD>. If this is a problem for your application you can either |
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
310 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
… | |
380 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
386 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
381 | |
387 | |
382 | For few fds, this backend is a bit little slower than poll and select, |
388 | For few fds, this backend is a bit little slower than poll and select, |
383 | but it scales phenomenally better. While poll and select usually scale |
389 | but it scales phenomenally better. While poll and select usually scale |
384 | like O(total_fds) where n is the total number of fds (or the highest fd), |
390 | like O(total_fds) where n is the total number of fds (or the highest fd), |
385 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
391 | epoll scales either O(1) or O(active_fds). |
386 | of shortcomings, such as silently dropping events in some hard-to-detect |
392 | |
387 | cases and requiring a system call per fd change, no fork support and bad |
393 | The epoll mechanism deserves honorable mention as the most misdesigned |
388 | support for dup. |
394 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
395 | dropping file descriptors, requiring a system call per change per file |
|
|
396 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
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397 | so on. The biggest issue is fork races, however - if a program forks then |
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398 | I<both> parent and child process have to recreate the epoll set, which can |
|
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399 | take considerable time (one syscall per file descriptor) and is of course |
|
|
400 | hard to detect. |
|
|
401 | |
|
|
402 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
|
|
403 | of course I<doesn't>, and epoll just loves to report events for totally |
|
|
404 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
405 | even remove them from the set) than registered in the set (especially |
|
|
406 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
407 | employing an additional generation counter and comparing that against the |
|
|
408 | events to filter out spurious ones, recreating the set when required. |
389 | |
409 | |
390 | While stopping, setting and starting an I/O watcher in the same iteration |
410 | While stopping, setting and starting an I/O watcher in the same iteration |
391 | will result in some caching, there is still a system call per such incident |
411 | will result in some caching, there is still a system call per such |
392 | (because the fd could point to a different file description now), so its |
412 | incident (because the same I<file descriptor> could point to a different |
393 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
413 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
394 | very well if you register events for both fds. |
414 | file descriptors might not work very well if you register events for both |
395 | |
415 | file descriptors. |
396 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
397 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
398 | (or space) is available. |
|
|
399 | |
416 | |
400 | Best performance from this backend is achieved by not unregistering all |
417 | Best performance from this backend is achieved by not unregistering all |
401 | watchers for a file descriptor until it has been closed, if possible, |
418 | watchers for a file descriptor until it has been closed, if possible, |
402 | i.e. keep at least one watcher active per fd at all times. Stopping and |
419 | i.e. keep at least one watcher active per fd at all times. Stopping and |
403 | starting a watcher (without re-setting it) also usually doesn't cause |
420 | starting a watcher (without re-setting it) also usually doesn't cause |
404 | extra overhead. |
421 | extra overhead. A fork can both result in spurious notifications as well |
|
|
422 | as in libev having to destroy and recreate the epoll object, which can |
|
|
423 | take considerable time and thus should be avoided. |
|
|
424 | |
|
|
425 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
426 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
427 | the usage. So sad. |
405 | |
428 | |
406 | While nominally embeddable in other event loops, this feature is broken in |
429 | While nominally embeddable in other event loops, this feature is broken in |
407 | all kernel versions tested so far. |
430 | all kernel versions tested so far. |
408 | |
431 | |
409 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
432 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
410 | C<EVBACKEND_POLL>. |
433 | C<EVBACKEND_POLL>. |
411 | |
434 | |
412 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
435 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
413 | |
436 | |
414 | Kqueue deserves special mention, as at the time of this writing, it was |
437 | Kqueue deserves special mention, as at the time of this writing, it |
415 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
438 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
416 | anything but sockets and pipes, except on Darwin, where of course it's |
439 | with anything but sockets and pipes, except on Darwin, where of course |
417 | completely useless). For this reason it's not being "auto-detected" unless |
440 | it's completely useless). Unlike epoll, however, whose brokenness |
418 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
441 | is by design, these kqueue bugs can (and eventually will) be fixed |
419 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
442 | without API changes to existing programs. For this reason it's not being |
|
|
443 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
|
|
444 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
445 | system like NetBSD. |
420 | |
446 | |
421 | You still can embed kqueue into a normal poll or select backend and use it |
447 | You still can embed kqueue into a normal poll or select backend and use it |
422 | only for sockets (after having made sure that sockets work with kqueue on |
448 | only for sockets (after having made sure that sockets work with kqueue on |
423 | the target platform). See C<ev_embed> watchers for more info. |
449 | the target platform). See C<ev_embed> watchers for more info. |
424 | |
450 | |
425 | It scales in the same way as the epoll backend, but the interface to the |
451 | It scales in the same way as the epoll backend, but the interface to the |
426 | kernel is more efficient (which says nothing about its actual speed, of |
452 | kernel is more efficient (which says nothing about its actual speed, of |
427 | course). While stopping, setting and starting an I/O watcher does never |
453 | course). While stopping, setting and starting an I/O watcher does never |
428 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
454 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
429 | two event changes per incident. Support for C<fork ()> is very bad and it |
455 | two event changes per incident. Support for C<fork ()> is very bad (but |
430 | drops fds silently in similarly hard-to-detect cases. |
456 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
457 | cases |
431 | |
458 | |
432 | This backend usually performs well under most conditions. |
459 | This backend usually performs well under most conditions. |
433 | |
460 | |
434 | While nominally embeddable in other event loops, this doesn't work |
461 | While nominally embeddable in other event loops, this doesn't work |
435 | everywhere, so you might need to test for this. And since it is broken |
462 | everywhere, so you might need to test for this. And since it is broken |
436 | almost everywhere, you should only use it when you have a lot of sockets |
463 | almost everywhere, you should only use it when you have a lot of sockets |
437 | (for which it usually works), by embedding it into another event loop |
464 | (for which it usually works), by embedding it into another event loop |
438 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
465 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
439 | using it only for sockets. |
466 | also broken on OS X)) and, did I mention it, using it only for sockets. |
440 | |
467 | |
441 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
468 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
442 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
469 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
443 | C<NOTE_EOF>. |
470 | C<NOTE_EOF>. |
444 | |
471 | |
… | |
… | |
464 | might perform better. |
491 | might perform better. |
465 | |
492 | |
466 | On the positive side, with the exception of the spurious readiness |
493 | On the positive side, with the exception of the spurious readiness |
467 | notifications, this backend actually performed fully to specification |
494 | notifications, this backend actually performed fully to specification |
468 | in all tests and is fully embeddable, which is a rare feat among the |
495 | in all tests and is fully embeddable, which is a rare feat among the |
469 | OS-specific backends. |
496 | OS-specific backends (I vastly prefer correctness over speed hacks). |
470 | |
497 | |
471 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
498 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
472 | C<EVBACKEND_POLL>. |
499 | C<EVBACKEND_POLL>. |
473 | |
500 | |
474 | =item C<EVBACKEND_ALL> |
501 | =item C<EVBACKEND_ALL> |
… | |
… | |
527 | responsibility to either stop all watchers cleanly yourself I<before> |
554 | responsibility to either stop all watchers cleanly yourself I<before> |
528 | calling this function, or cope with the fact afterwards (which is usually |
555 | calling this function, or cope with the fact afterwards (which is usually |
529 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
556 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
530 | for example). |
557 | for example). |
531 | |
558 | |
532 | Note that certain global state, such as signal state, will not be freed by |
559 | Note that certain global state, such as signal state (and installed signal |
533 | this function, and related watchers (such as signal and child watchers) |
560 | handlers), will not be freed by this function, and related watchers (such |
534 | would need to be stopped manually. |
561 | as signal and child watchers) would need to be stopped manually. |
535 | |
562 | |
536 | In general it is not advisable to call this function except in the |
563 | In general it is not advisable to call this function except in the |
537 | rare occasion where you really need to free e.g. the signal handling |
564 | rare occasion where you really need to free e.g. the signal handling |
538 | pipe fds. If you need dynamically allocated loops it is better to use |
565 | pipe fds. If you need dynamically allocated loops it is better to use |
539 | C<ev_loop_new> and C<ev_loop_destroy>). |
566 | C<ev_loop_new> and C<ev_loop_destroy>). |
… | |
… | |
631 | the loop. |
658 | the loop. |
632 | |
659 | |
633 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
660 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
634 | necessary) and will handle those and any already outstanding ones. It |
661 | necessary) and will handle those and any already outstanding ones. It |
635 | will block your process until at least one new event arrives (which could |
662 | will block your process until at least one new event arrives (which could |
636 | be an event internal to libev itself, so there is no guarentee that a |
663 | be an event internal to libev itself, so there is no guarantee that a |
637 | user-registered callback will be called), and will return after one |
664 | user-registered callback will be called), and will return after one |
638 | iteration of the loop. |
665 | iteration of the loop. |
639 | |
666 | |
640 | This is useful if you are waiting for some external event in conjunction |
667 | This is useful if you are waiting for some external event in conjunction |
641 | with something not expressible using other libev watchers (i.e. "roll your |
668 | with something not expressible using other libev watchers (i.e. "roll your |
… | |
… | |
685 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
712 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
686 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
713 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
687 | |
714 | |
688 | This "unloop state" will be cleared when entering C<ev_loop> again. |
715 | This "unloop state" will be cleared when entering C<ev_loop> again. |
689 | |
716 | |
|
|
717 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
718 | |
690 | =item ev_ref (loop) |
719 | =item ev_ref (loop) |
691 | |
720 | |
692 | =item ev_unref (loop) |
721 | =item ev_unref (loop) |
693 | |
722 | |
694 | Ref/unref can be used to add or remove a reference count on the event |
723 | Ref/unref can be used to add or remove a reference count on the event |
… | |
… | |
697 | |
726 | |
698 | If you have a watcher you never unregister that should not keep C<ev_loop> |
727 | If you have a watcher you never unregister that should not keep C<ev_loop> |
699 | from returning, call ev_unref() after starting, and ev_ref() before |
728 | from returning, call ev_unref() after starting, and ev_ref() before |
700 | stopping it. |
729 | stopping it. |
701 | |
730 | |
702 | As an example, libev itself uses this for its internal signal pipe: It is |
731 | As an example, libev itself uses this for its internal signal pipe: It |
703 | not visible to the libev user and should not keep C<ev_loop> from exiting |
732 | is not visible to the libev user and should not keep C<ev_loop> from |
704 | if no event watchers registered by it are active. It is also an excellent |
733 | exiting if no event watchers registered by it are active. It is also an |
705 | way to do this for generic recurring timers or from within third-party |
734 | excellent way to do this for generic recurring timers or from within |
706 | libraries. Just remember to I<unref after start> and I<ref before stop> |
735 | third-party libraries. Just remember to I<unref after start> and I<ref |
707 | (but only if the watcher wasn't active before, or was active before, |
736 | before stop> (but only if the watcher wasn't active before, or was active |
708 | respectively). |
737 | before, respectively. Note also that libev might stop watchers itself |
|
|
738 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
739 | in the callback). |
709 | |
740 | |
710 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
741 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
711 | running when nothing else is active. |
742 | running when nothing else is active. |
712 | |
743 | |
713 | struct ev_signal exitsig; |
744 | ev_signal exitsig; |
714 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
745 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
715 | ev_signal_start (loop, &exitsig); |
746 | ev_signal_start (loop, &exitsig); |
716 | evf_unref (loop); |
747 | evf_unref (loop); |
717 | |
748 | |
718 | Example: For some weird reason, unregister the above signal handler again. |
749 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
766 | they fire on, say, one-second boundaries only. |
797 | they fire on, say, one-second boundaries only. |
767 | |
798 | |
768 | =item ev_loop_verify (loop) |
799 | =item ev_loop_verify (loop) |
769 | |
800 | |
770 | This function only does something when C<EV_VERIFY> support has been |
801 | This function only does something when C<EV_VERIFY> support has been |
771 | compiled in. which is the default for non-minimal builds. It tries to go |
802 | compiled in, which is the default for non-minimal builds. It tries to go |
772 | through all internal structures and checks them for validity. If anything |
803 | through all internal structures and checks them for validity. If anything |
773 | is found to be inconsistent, it will print an error message to standard |
804 | is found to be inconsistent, it will print an error message to standard |
774 | error and call C<abort ()>. |
805 | error and call C<abort ()>. |
775 | |
806 | |
776 | This can be used to catch bugs inside libev itself: under normal |
807 | This can be used to catch bugs inside libev itself: under normal |
… | |
… | |
780 | =back |
811 | =back |
781 | |
812 | |
782 | |
813 | |
783 | =head1 ANATOMY OF A WATCHER |
814 | =head1 ANATOMY OF A WATCHER |
784 | |
815 | |
|
|
816 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
817 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
818 | watchers and C<ev_io_start> for I/O watchers. |
|
|
819 | |
785 | A watcher is a structure that you create and register to record your |
820 | A watcher is a structure that you create and register to record your |
786 | interest in some event. For instance, if you want to wait for STDIN to |
821 | interest in some event. For instance, if you want to wait for STDIN to |
787 | become readable, you would create an C<ev_io> watcher for that: |
822 | become readable, you would create an C<ev_io> watcher for that: |
788 | |
823 | |
789 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
824 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
790 | { |
825 | { |
791 | ev_io_stop (w); |
826 | ev_io_stop (w); |
792 | ev_unloop (loop, EVUNLOOP_ALL); |
827 | ev_unloop (loop, EVUNLOOP_ALL); |
793 | } |
828 | } |
794 | |
829 | |
795 | struct ev_loop *loop = ev_default_loop (0); |
830 | struct ev_loop *loop = ev_default_loop (0); |
|
|
831 | |
796 | struct ev_io stdin_watcher; |
832 | ev_io stdin_watcher; |
|
|
833 | |
797 | ev_init (&stdin_watcher, my_cb); |
834 | ev_init (&stdin_watcher, my_cb); |
798 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
835 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
799 | ev_io_start (loop, &stdin_watcher); |
836 | ev_io_start (loop, &stdin_watcher); |
|
|
837 | |
800 | ev_loop (loop, 0); |
838 | ev_loop (loop, 0); |
801 | |
839 | |
802 | As you can see, you are responsible for allocating the memory for your |
840 | As you can see, you are responsible for allocating the memory for your |
803 | watcher structures (and it is usually a bad idea to do this on the stack, |
841 | watcher structures (and it is I<usually> a bad idea to do this on the |
804 | although this can sometimes be quite valid). |
842 | stack). |
|
|
843 | |
|
|
844 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
845 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
805 | |
846 | |
806 | Each watcher structure must be initialised by a call to C<ev_init |
847 | Each watcher structure must be initialised by a call to C<ev_init |
807 | (watcher *, callback)>, which expects a callback to be provided. This |
848 | (watcher *, callback)>, which expects a callback to be provided. This |
808 | callback gets invoked each time the event occurs (or, in the case of I/O |
849 | callback gets invoked each time the event occurs (or, in the case of I/O |
809 | watchers, each time the event loop detects that the file descriptor given |
850 | watchers, each time the event loop detects that the file descriptor given |
810 | is readable and/or writable). |
851 | is readable and/or writable). |
811 | |
852 | |
812 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
853 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
813 | with arguments specific to this watcher type. There is also a macro |
854 | macro to configure it, with arguments specific to the watcher type. There |
814 | to combine initialisation and setting in one call: C<< ev_<type>_init |
855 | is also a macro to combine initialisation and setting in one call: C<< |
815 | (watcher *, callback, ...) >>. |
856 | ev_TYPE_init (watcher *, callback, ...) >>. |
816 | |
857 | |
817 | To make the watcher actually watch out for events, you have to start it |
858 | To make the watcher actually watch out for events, you have to start it |
818 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
859 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
819 | *) >>), and you can stop watching for events at any time by calling the |
860 | *) >>), and you can stop watching for events at any time by calling the |
820 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
861 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
821 | |
862 | |
822 | As long as your watcher is active (has been started but not stopped) you |
863 | As long as your watcher is active (has been started but not stopped) you |
823 | must not touch the values stored in it. Most specifically you must never |
864 | must not touch the values stored in it. Most specifically you must never |
824 | reinitialise it or call its C<set> macro. |
865 | reinitialise it or call its C<ev_TYPE_set> macro. |
825 | |
866 | |
826 | Each and every callback receives the event loop pointer as first, the |
867 | Each and every callback receives the event loop pointer as first, the |
827 | registered watcher structure as second, and a bitset of received events as |
868 | registered watcher structure as second, and a bitset of received events as |
828 | third argument. |
869 | third argument. |
829 | |
870 | |
… | |
… | |
887 | |
928 | |
888 | =item C<EV_ASYNC> |
929 | =item C<EV_ASYNC> |
889 | |
930 | |
890 | The given async watcher has been asynchronously notified (see C<ev_async>). |
931 | The given async watcher has been asynchronously notified (see C<ev_async>). |
891 | |
932 | |
|
|
933 | =item C<EV_CUSTOM> |
|
|
934 | |
|
|
935 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
936 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
937 | |
892 | =item C<EV_ERROR> |
938 | =item C<EV_ERROR> |
893 | |
939 | |
894 | An unspecified error has occurred, the watcher has been stopped. This might |
940 | An unspecified error has occurred, the watcher has been stopped. This might |
895 | happen because the watcher could not be properly started because libev |
941 | happen because the watcher could not be properly started because libev |
896 | ran out of memory, a file descriptor was found to be closed or any other |
942 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
943 | problem. Libev considers these application bugs. |
|
|
944 | |
897 | problem. You best act on it by reporting the problem and somehow coping |
945 | You best act on it by reporting the problem and somehow coping with the |
898 | with the watcher being stopped. |
946 | watcher being stopped. Note that well-written programs should not receive |
|
|
947 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
948 | bug in your program. |
899 | |
949 | |
900 | Libev will usually signal a few "dummy" events together with an error, for |
950 | Libev will usually signal a few "dummy" events together with an error, for |
901 | example it might indicate that a fd is readable or writable, and if your |
951 | example it might indicate that a fd is readable or writable, and if your |
902 | callbacks is well-written it can just attempt the operation and cope with |
952 | callbacks is well-written it can just attempt the operation and cope with |
903 | the error from read() or write(). This will not work in multi-threaded |
953 | the error from read() or write(). This will not work in multi-threaded |
… | |
… | |
906 | |
956 | |
907 | =back |
957 | =back |
908 | |
958 | |
909 | =head2 GENERIC WATCHER FUNCTIONS |
959 | =head2 GENERIC WATCHER FUNCTIONS |
910 | |
960 | |
911 | In the following description, C<TYPE> stands for the watcher type, |
|
|
912 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
913 | |
|
|
914 | =over 4 |
961 | =over 4 |
915 | |
962 | |
916 | =item C<ev_init> (ev_TYPE *watcher, callback) |
963 | =item C<ev_init> (ev_TYPE *watcher, callback) |
917 | |
964 | |
918 | This macro initialises the generic portion of a watcher. The contents |
965 | This macro initialises the generic portion of a watcher. The contents |
… | |
… | |
923 | which rolls both calls into one. |
970 | which rolls both calls into one. |
924 | |
971 | |
925 | You can reinitialise a watcher at any time as long as it has been stopped |
972 | You can reinitialise a watcher at any time as long as it has been stopped |
926 | (or never started) and there are no pending events outstanding. |
973 | (or never started) and there are no pending events outstanding. |
927 | |
974 | |
928 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
975 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
929 | int revents)>. |
976 | int revents)>. |
930 | |
977 | |
931 | Example: Initialise an C<ev_io> watcher in two steps. |
978 | Example: Initialise an C<ev_io> watcher in two steps. |
932 | |
979 | |
933 | ev_io w; |
980 | ev_io w; |
… | |
… | |
967 | |
1014 | |
968 | ev_io_start (EV_DEFAULT_UC, &w); |
1015 | ev_io_start (EV_DEFAULT_UC, &w); |
969 | |
1016 | |
970 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1017 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
971 | |
1018 | |
972 | Stops the given watcher again (if active) and clears the pending |
1019 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1020 | the watcher was active or not). |
|
|
1021 | |
973 | status. It is possible that stopped watchers are pending (for example, |
1022 | It is possible that stopped watchers are pending - for example, |
974 | non-repeating timers are being stopped when they become pending), but |
1023 | non-repeating timers are being stopped when they become pending - but |
975 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1024 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
976 | you want to free or reuse the memory used by the watcher it is therefore a |
1025 | pending. If you want to free or reuse the memory used by the watcher it is |
977 | good idea to always call its C<ev_TYPE_stop> function. |
1026 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
978 | |
1027 | |
979 | =item bool ev_is_active (ev_TYPE *watcher) |
1028 | =item bool ev_is_active (ev_TYPE *watcher) |
980 | |
1029 | |
981 | Returns a true value iff the watcher is active (i.e. it has been started |
1030 | Returns a true value iff the watcher is active (i.e. it has been started |
982 | and not yet been stopped). As long as a watcher is active you must not modify |
1031 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
1024 | The default priority used by watchers when no priority has been set is |
1073 | The default priority used by watchers when no priority has been set is |
1025 | always C<0>, which is supposed to not be too high and not be too low :). |
1074 | always C<0>, which is supposed to not be too high and not be too low :). |
1026 | |
1075 | |
1027 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1076 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1028 | fine, as long as you do not mind that the priority value you query might |
1077 | fine, as long as you do not mind that the priority value you query might |
1029 | or might not have been adjusted to be within valid range. |
1078 | or might not have been clamped to the valid range. |
1030 | |
1079 | |
1031 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1080 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1032 | |
1081 | |
1033 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1082 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1034 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1083 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1056 | member, you can also "subclass" the watcher type and provide your own |
1105 | member, you can also "subclass" the watcher type and provide your own |
1057 | data: |
1106 | data: |
1058 | |
1107 | |
1059 | struct my_io |
1108 | struct my_io |
1060 | { |
1109 | { |
1061 | struct ev_io io; |
1110 | ev_io io; |
1062 | int otherfd; |
1111 | int otherfd; |
1063 | void *somedata; |
1112 | void *somedata; |
1064 | struct whatever *mostinteresting; |
1113 | struct whatever *mostinteresting; |
1065 | }; |
1114 | }; |
1066 | |
1115 | |
… | |
… | |
1069 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1118 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1070 | |
1119 | |
1071 | And since your callback will be called with a pointer to the watcher, you |
1120 | And since your callback will be called with a pointer to the watcher, you |
1072 | can cast it back to your own type: |
1121 | can cast it back to your own type: |
1073 | |
1122 | |
1074 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1123 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1075 | { |
1124 | { |
1076 | struct my_io *w = (struct my_io *)w_; |
1125 | struct my_io *w = (struct my_io *)w_; |
1077 | ... |
1126 | ... |
1078 | } |
1127 | } |
1079 | |
1128 | |
… | |
… | |
1097 | programmers): |
1146 | programmers): |
1098 | |
1147 | |
1099 | #include <stddef.h> |
1148 | #include <stddef.h> |
1100 | |
1149 | |
1101 | static void |
1150 | static void |
1102 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1151 | t1_cb (EV_P_ ev_timer *w, int revents) |
1103 | { |
1152 | { |
1104 | struct my_biggy big = (struct my_biggy * |
1153 | struct my_biggy big = (struct my_biggy * |
1105 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1154 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1106 | } |
1155 | } |
1107 | |
1156 | |
1108 | static void |
1157 | static void |
1109 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1158 | t2_cb (EV_P_ ev_timer *w, int revents) |
1110 | { |
1159 | { |
1111 | struct my_biggy big = (struct my_biggy * |
1160 | struct my_biggy big = (struct my_biggy * |
1112 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1161 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1113 | } |
1162 | } |
1114 | |
1163 | |
… | |
… | |
1249 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1298 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1250 | readable, but only once. Since it is likely line-buffered, you could |
1299 | readable, but only once. Since it is likely line-buffered, you could |
1251 | attempt to read a whole line in the callback. |
1300 | attempt to read a whole line in the callback. |
1252 | |
1301 | |
1253 | static void |
1302 | static void |
1254 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1303 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1255 | { |
1304 | { |
1256 | ev_io_stop (loop, w); |
1305 | ev_io_stop (loop, w); |
1257 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1306 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1258 | } |
1307 | } |
1259 | |
1308 | |
1260 | ... |
1309 | ... |
1261 | struct ev_loop *loop = ev_default_init (0); |
1310 | struct ev_loop *loop = ev_default_init (0); |
1262 | struct ev_io stdin_readable; |
1311 | ev_io stdin_readable; |
1263 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1312 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1264 | ev_io_start (loop, &stdin_readable); |
1313 | ev_io_start (loop, &stdin_readable); |
1265 | ev_loop (loop, 0); |
1314 | ev_loop (loop, 0); |
1266 | |
1315 | |
1267 | |
1316 | |
… | |
… | |
1275 | year, it will still time out after (roughly) one hour. "Roughly" because |
1324 | year, it will still time out after (roughly) one hour. "Roughly" because |
1276 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1325 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1277 | monotonic clock option helps a lot here). |
1326 | monotonic clock option helps a lot here). |
1278 | |
1327 | |
1279 | The callback is guaranteed to be invoked only I<after> its timeout has |
1328 | The callback is guaranteed to be invoked only I<after> its timeout has |
1280 | passed, but if multiple timers become ready during the same loop iteration |
1329 | passed. If multiple timers become ready during the same loop iteration |
1281 | then order of execution is undefined. |
1330 | then the ones with earlier time-out values are invoked before ones with |
|
|
1331 | later time-out values (but this is no longer true when a callback calls |
|
|
1332 | C<ev_loop> recursively). |
|
|
1333 | |
|
|
1334 | =head3 Be smart about timeouts |
|
|
1335 | |
|
|
1336 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1337 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1338 | you want to raise some error after a while. |
|
|
1339 | |
|
|
1340 | What follows are some ways to handle this problem, from obvious and |
|
|
1341 | inefficient to smart and efficient. |
|
|
1342 | |
|
|
1343 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1344 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1345 | data or other life sign was received). |
|
|
1346 | |
|
|
1347 | =over 4 |
|
|
1348 | |
|
|
1349 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1350 | |
|
|
1351 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1352 | start the watcher: |
|
|
1353 | |
|
|
1354 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1355 | ev_timer_start (loop, timer); |
|
|
1356 | |
|
|
1357 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1358 | and start it again: |
|
|
1359 | |
|
|
1360 | ev_timer_stop (loop, timer); |
|
|
1361 | ev_timer_set (timer, 60., 0.); |
|
|
1362 | ev_timer_start (loop, timer); |
|
|
1363 | |
|
|
1364 | This is relatively simple to implement, but means that each time there is |
|
|
1365 | some activity, libev will first have to remove the timer from its internal |
|
|
1366 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1367 | still not a constant-time operation. |
|
|
1368 | |
|
|
1369 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1370 | |
|
|
1371 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1372 | C<ev_timer_start>. |
|
|
1373 | |
|
|
1374 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1375 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1376 | successfully read or write some data. If you go into an idle state where |
|
|
1377 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1378 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1379 | |
|
|
1380 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1381 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1382 | member and C<ev_timer_again>. |
|
|
1383 | |
|
|
1384 | At start: |
|
|
1385 | |
|
|
1386 | ev_timer_init (timer, callback); |
|
|
1387 | timer->repeat = 60.; |
|
|
1388 | ev_timer_again (loop, timer); |
|
|
1389 | |
|
|
1390 | Each time there is some activity: |
|
|
1391 | |
|
|
1392 | ev_timer_again (loop, timer); |
|
|
1393 | |
|
|
1394 | It is even possible to change the time-out on the fly, regardless of |
|
|
1395 | whether the watcher is active or not: |
|
|
1396 | |
|
|
1397 | timer->repeat = 30.; |
|
|
1398 | ev_timer_again (loop, timer); |
|
|
1399 | |
|
|
1400 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1401 | you want to modify its timeout value, as libev does not have to completely |
|
|
1402 | remove and re-insert the timer from/into its internal data structure. |
|
|
1403 | |
|
|
1404 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1405 | |
|
|
1406 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1407 | |
|
|
1408 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1409 | relatively long compared to the intervals between other activity - in |
|
|
1410 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1411 | associated activity resets. |
|
|
1412 | |
|
|
1413 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1414 | but remember the time of last activity, and check for a real timeout only |
|
|
1415 | within the callback: |
|
|
1416 | |
|
|
1417 | ev_tstamp last_activity; // time of last activity |
|
|
1418 | |
|
|
1419 | static void |
|
|
1420 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1421 | { |
|
|
1422 | ev_tstamp now = ev_now (EV_A); |
|
|
1423 | ev_tstamp timeout = last_activity + 60.; |
|
|
1424 | |
|
|
1425 | // if last_activity + 60. is older than now, we did time out |
|
|
1426 | if (timeout < now) |
|
|
1427 | { |
|
|
1428 | // timeout occured, take action |
|
|
1429 | } |
|
|
1430 | else |
|
|
1431 | { |
|
|
1432 | // callback was invoked, but there was some activity, re-arm |
|
|
1433 | // the watcher to fire in last_activity + 60, which is |
|
|
1434 | // guaranteed to be in the future, so "again" is positive: |
|
|
1435 | w->repeat = timeout - now; |
|
|
1436 | ev_timer_again (EV_A_ w); |
|
|
1437 | } |
|
|
1438 | } |
|
|
1439 | |
|
|
1440 | To summarise the callback: first calculate the real timeout (defined |
|
|
1441 | as "60 seconds after the last activity"), then check if that time has |
|
|
1442 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1443 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1444 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1445 | a timeout then. |
|
|
1446 | |
|
|
1447 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1448 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1449 | |
|
|
1450 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1451 | minus half the average time between activity), but virtually no calls to |
|
|
1452 | libev to change the timeout. |
|
|
1453 | |
|
|
1454 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1455 | to the current time (meaning we just have some activity :), then call the |
|
|
1456 | callback, which will "do the right thing" and start the timer: |
|
|
1457 | |
|
|
1458 | ev_timer_init (timer, callback); |
|
|
1459 | last_activity = ev_now (loop); |
|
|
1460 | callback (loop, timer, EV_TIMEOUT); |
|
|
1461 | |
|
|
1462 | And when there is some activity, simply store the current time in |
|
|
1463 | C<last_activity>, no libev calls at all: |
|
|
1464 | |
|
|
1465 | last_actiivty = ev_now (loop); |
|
|
1466 | |
|
|
1467 | This technique is slightly more complex, but in most cases where the |
|
|
1468 | time-out is unlikely to be triggered, much more efficient. |
|
|
1469 | |
|
|
1470 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1471 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1472 | fix things for you. |
|
|
1473 | |
|
|
1474 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1475 | |
|
|
1476 | If there is not one request, but many thousands (millions...), all |
|
|
1477 | employing some kind of timeout with the same timeout value, then one can |
|
|
1478 | do even better: |
|
|
1479 | |
|
|
1480 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1481 | at the I<end> of the list. |
|
|
1482 | |
|
|
1483 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1484 | the list is expected to fire (for example, using the technique #3). |
|
|
1485 | |
|
|
1486 | When there is some activity, remove the timer from the list, recalculate |
|
|
1487 | the timeout, append it to the end of the list again, and make sure to |
|
|
1488 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1489 | |
|
|
1490 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1491 | starting, stopping and updating the timers, at the expense of a major |
|
|
1492 | complication, and having to use a constant timeout. The constant timeout |
|
|
1493 | ensures that the list stays sorted. |
|
|
1494 | |
|
|
1495 | =back |
|
|
1496 | |
|
|
1497 | So which method the best? |
|
|
1498 | |
|
|
1499 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1500 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1501 | better, and isn't very complicated either. In most case, choosing either |
|
|
1502 | one is fine, with #3 being better in typical situations. |
|
|
1503 | |
|
|
1504 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1505 | rather complicated, but extremely efficient, something that really pays |
|
|
1506 | off after the first million or so of active timers, i.e. it's usually |
|
|
1507 | overkill :) |
1282 | |
1508 | |
1283 | =head3 The special problem of time updates |
1509 | =head3 The special problem of time updates |
1284 | |
1510 | |
1285 | Establishing the current time is a costly operation (it usually takes at |
1511 | Establishing the current time is a costly operation (it usually takes at |
1286 | least two system calls): EV therefore updates its idea of the current |
1512 | least two system calls): EV therefore updates its idea of the current |
… | |
… | |
1330 | If the timer is started but non-repeating, stop it (as if it timed out). |
1556 | If the timer is started but non-repeating, stop it (as if it timed out). |
1331 | |
1557 | |
1332 | If the timer is repeating, either start it if necessary (with the |
1558 | If the timer is repeating, either start it if necessary (with the |
1333 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1559 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1334 | |
1560 | |
1335 | This sounds a bit complicated, but here is a useful and typical |
1561 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1336 | example: Imagine you have a TCP connection and you want a so-called idle |
1562 | usage example. |
1337 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1338 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1339 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1340 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1341 | you go into an idle state where you do not expect data to travel on the |
|
|
1342 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1343 | automatically restart it if need be. |
|
|
1344 | |
|
|
1345 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1346 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1347 | |
|
|
1348 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1349 | ev_timer_again (loop, timer); |
|
|
1350 | ... |
|
|
1351 | timer->again = 17.; |
|
|
1352 | ev_timer_again (loop, timer); |
|
|
1353 | ... |
|
|
1354 | timer->again = 10.; |
|
|
1355 | ev_timer_again (loop, timer); |
|
|
1356 | |
|
|
1357 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1358 | you want to modify its timeout value. |
|
|
1359 | |
|
|
1360 | Note, however, that it is often even more efficient to remember the |
|
|
1361 | time of the last activity and let the timer time-out naturally. In the |
|
|
1362 | callback, you then check whether the time-out is real, or, if there was |
|
|
1363 | some activity, you reschedule the watcher to time-out in "last_activity + |
|
|
1364 | timeout - ev_now ()" seconds. |
|
|
1365 | |
1563 | |
1366 | =item ev_tstamp repeat [read-write] |
1564 | =item ev_tstamp repeat [read-write] |
1367 | |
1565 | |
1368 | The current C<repeat> value. Will be used each time the watcher times out |
1566 | The current C<repeat> value. Will be used each time the watcher times out |
1369 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1567 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1374 | =head3 Examples |
1572 | =head3 Examples |
1375 | |
1573 | |
1376 | Example: Create a timer that fires after 60 seconds. |
1574 | Example: Create a timer that fires after 60 seconds. |
1377 | |
1575 | |
1378 | static void |
1576 | static void |
1379 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1577 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1380 | { |
1578 | { |
1381 | .. one minute over, w is actually stopped right here |
1579 | .. one minute over, w is actually stopped right here |
1382 | } |
1580 | } |
1383 | |
1581 | |
1384 | struct ev_timer mytimer; |
1582 | ev_timer mytimer; |
1385 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1583 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1386 | ev_timer_start (loop, &mytimer); |
1584 | ev_timer_start (loop, &mytimer); |
1387 | |
1585 | |
1388 | Example: Create a timeout timer that times out after 10 seconds of |
1586 | Example: Create a timeout timer that times out after 10 seconds of |
1389 | inactivity. |
1587 | inactivity. |
1390 | |
1588 | |
1391 | static void |
1589 | static void |
1392 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1590 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1393 | { |
1591 | { |
1394 | .. ten seconds without any activity |
1592 | .. ten seconds without any activity |
1395 | } |
1593 | } |
1396 | |
1594 | |
1397 | struct ev_timer mytimer; |
1595 | ev_timer mytimer; |
1398 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1596 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1399 | ev_timer_again (&mytimer); /* start timer */ |
1597 | ev_timer_again (&mytimer); /* start timer */ |
1400 | ev_loop (loop, 0); |
1598 | ev_loop (loop, 0); |
1401 | |
1599 | |
1402 | // and in some piece of code that gets executed on any "activity": |
1600 | // and in some piece of code that gets executed on any "activity": |
… | |
… | |
1407 | =head2 C<ev_periodic> - to cron or not to cron? |
1605 | =head2 C<ev_periodic> - to cron or not to cron? |
1408 | |
1606 | |
1409 | Periodic watchers are also timers of a kind, but they are very versatile |
1607 | Periodic watchers are also timers of a kind, but they are very versatile |
1410 | (and unfortunately a bit complex). |
1608 | (and unfortunately a bit complex). |
1411 | |
1609 | |
1412 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1610 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1413 | but on wall clock time (absolute time). You can tell a periodic watcher |
1611 | relative time, the physical time that passes) but on wall clock time |
1414 | to trigger after some specific point in time. For example, if you tell a |
1612 | (absolute time, the thing you can read on your calender or clock). The |
1415 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1613 | difference is that wall clock time can run faster or slower than real |
1416 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1614 | time, and time jumps are not uncommon (e.g. when you adjust your |
1417 | clock to January of the previous year, then it will take more than year |
1615 | wrist-watch). |
1418 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1419 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1420 | |
1616 | |
|
|
1617 | You can tell a periodic watcher to trigger after some specific point |
|
|
1618 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1619 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1620 | not a delay) and then reset your system clock to January of the previous |
|
|
1621 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1622 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1623 | it, as it uses a relative timeout). |
|
|
1624 | |
1421 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1625 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1422 | such as triggering an event on each "midnight, local time", or other |
1626 | timers, such as triggering an event on each "midnight, local time", or |
1423 | complicated rules. |
1627 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1628 | those cannot react to time jumps. |
1424 | |
1629 | |
1425 | As with timers, the callback is guaranteed to be invoked only when the |
1630 | As with timers, the callback is guaranteed to be invoked only when the |
1426 | time (C<at>) has passed, but if multiple periodic timers become ready |
1631 | point in time where it is supposed to trigger has passed. If multiple |
1427 | during the same loop iteration, then order of execution is undefined. |
1632 | timers become ready during the same loop iteration then the ones with |
|
|
1633 | earlier time-out values are invoked before ones with later time-out values |
|
|
1634 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1428 | |
1635 | |
1429 | =head3 Watcher-Specific Functions and Data Members |
1636 | =head3 Watcher-Specific Functions and Data Members |
1430 | |
1637 | |
1431 | =over 4 |
1638 | =over 4 |
1432 | |
1639 | |
1433 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1640 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1434 | |
1641 | |
1435 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1642 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1436 | |
1643 | |
1437 | Lots of arguments, lets sort it out... There are basically three modes of |
1644 | Lots of arguments, let's sort it out... There are basically three modes of |
1438 | operation, and we will explain them from simplest to most complex: |
1645 | operation, and we will explain them from simplest to most complex: |
1439 | |
1646 | |
1440 | =over 4 |
1647 | =over 4 |
1441 | |
1648 | |
1442 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1649 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1443 | |
1650 | |
1444 | In this configuration the watcher triggers an event after the wall clock |
1651 | In this configuration the watcher triggers an event after the wall clock |
1445 | time C<at> has passed. It will not repeat and will not adjust when a time |
1652 | time C<offset> has passed. It will not repeat and will not adjust when a |
1446 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1653 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1447 | only run when the system clock reaches or surpasses this time. |
1654 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1655 | this point in time. |
1448 | |
1656 | |
1449 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1657 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1450 | |
1658 | |
1451 | In this mode the watcher will always be scheduled to time out at the next |
1659 | In this mode the watcher will always be scheduled to time out at the next |
1452 | C<at + N * interval> time (for some integer N, which can also be negative) |
1660 | C<offset + N * interval> time (for some integer N, which can also be |
1453 | and then repeat, regardless of any time jumps. |
1661 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1662 | argument is merely an offset into the C<interval> periods. |
1454 | |
1663 | |
1455 | This can be used to create timers that do not drift with respect to the |
1664 | This can be used to create timers that do not drift with respect to the |
1456 | system clock, for example, here is a C<ev_periodic> that triggers each |
1665 | system clock, for example, here is an C<ev_periodic> that triggers each |
1457 | hour, on the hour: |
1666 | hour, on the hour (with respect to UTC): |
1458 | |
1667 | |
1459 | ev_periodic_set (&periodic, 0., 3600., 0); |
1668 | ev_periodic_set (&periodic, 0., 3600., 0); |
1460 | |
1669 | |
1461 | This doesn't mean there will always be 3600 seconds in between triggers, |
1670 | This doesn't mean there will always be 3600 seconds in between triggers, |
1462 | but only that the callback will be called when the system time shows a |
1671 | but only that the callback will be called when the system time shows a |
1463 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1672 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1464 | by 3600. |
1673 | by 3600. |
1465 | |
1674 | |
1466 | Another way to think about it (for the mathematically inclined) is that |
1675 | Another way to think about it (for the mathematically inclined) is that |
1467 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1676 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1468 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1677 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1469 | |
1678 | |
1470 | For numerical stability it is preferable that the C<at> value is near |
1679 | For numerical stability it is preferable that the C<offset> value is near |
1471 | C<ev_now ()> (the current time), but there is no range requirement for |
1680 | C<ev_now ()> (the current time), but there is no range requirement for |
1472 | this value, and in fact is often specified as zero. |
1681 | this value, and in fact is often specified as zero. |
1473 | |
1682 | |
1474 | Note also that there is an upper limit to how often a timer can fire (CPU |
1683 | Note also that there is an upper limit to how often a timer can fire (CPU |
1475 | speed for example), so if C<interval> is very small then timing stability |
1684 | speed for example), so if C<interval> is very small then timing stability |
1476 | will of course deteriorate. Libev itself tries to be exact to be about one |
1685 | will of course deteriorate. Libev itself tries to be exact to be about one |
1477 | millisecond (if the OS supports it and the machine is fast enough). |
1686 | millisecond (if the OS supports it and the machine is fast enough). |
1478 | |
1687 | |
1479 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1688 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1480 | |
1689 | |
1481 | In this mode the values for C<interval> and C<at> are both being |
1690 | In this mode the values for C<interval> and C<offset> are both being |
1482 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1691 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1483 | reschedule callback will be called with the watcher as first, and the |
1692 | reschedule callback will be called with the watcher as first, and the |
1484 | current time as second argument. |
1693 | current time as second argument. |
1485 | |
1694 | |
1486 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1695 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1487 | ever, or make ANY event loop modifications whatsoever>. |
1696 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1697 | allowed by documentation here>. |
1488 | |
1698 | |
1489 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1699 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1490 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1700 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1491 | only event loop modification you are allowed to do). |
1701 | only event loop modification you are allowed to do). |
1492 | |
1702 | |
1493 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1703 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1494 | *w, ev_tstamp now)>, e.g.: |
1704 | *w, ev_tstamp now)>, e.g.: |
1495 | |
1705 | |
|
|
1706 | static ev_tstamp |
1496 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1707 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1497 | { |
1708 | { |
1498 | return now + 60.; |
1709 | return now + 60.; |
1499 | } |
1710 | } |
1500 | |
1711 | |
1501 | It must return the next time to trigger, based on the passed time value |
1712 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1521 | a different time than the last time it was called (e.g. in a crond like |
1732 | a different time than the last time it was called (e.g. in a crond like |
1522 | program when the crontabs have changed). |
1733 | program when the crontabs have changed). |
1523 | |
1734 | |
1524 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1735 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1525 | |
1736 | |
1526 | When active, returns the absolute time that the watcher is supposed to |
1737 | When active, returns the absolute time that the watcher is supposed |
1527 | trigger next. |
1738 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1739 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1740 | rescheduling modes. |
1528 | |
1741 | |
1529 | =item ev_tstamp offset [read-write] |
1742 | =item ev_tstamp offset [read-write] |
1530 | |
1743 | |
1531 | When repeating, this contains the offset value, otherwise this is the |
1744 | When repeating, this contains the offset value, otherwise this is the |
1532 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1745 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1746 | although libev might modify this value for better numerical stability). |
1533 | |
1747 | |
1534 | Can be modified any time, but changes only take effect when the periodic |
1748 | Can be modified any time, but changes only take effect when the periodic |
1535 | timer fires or C<ev_periodic_again> is being called. |
1749 | timer fires or C<ev_periodic_again> is being called. |
1536 | |
1750 | |
1537 | =item ev_tstamp interval [read-write] |
1751 | =item ev_tstamp interval [read-write] |
1538 | |
1752 | |
1539 | The current interval value. Can be modified any time, but changes only |
1753 | The current interval value. Can be modified any time, but changes only |
1540 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1754 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1541 | called. |
1755 | called. |
1542 | |
1756 | |
1543 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1757 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1544 | |
1758 | |
1545 | The current reschedule callback, or C<0>, if this functionality is |
1759 | The current reschedule callback, or C<0>, if this functionality is |
1546 | switched off. Can be changed any time, but changes only take effect when |
1760 | switched off. Can be changed any time, but changes only take effect when |
1547 | the periodic timer fires or C<ev_periodic_again> is being called. |
1761 | the periodic timer fires or C<ev_periodic_again> is being called. |
1548 | |
1762 | |
… | |
… | |
1553 | Example: Call a callback every hour, or, more precisely, whenever the |
1767 | Example: Call a callback every hour, or, more precisely, whenever the |
1554 | system time is divisible by 3600. The callback invocation times have |
1768 | system time is divisible by 3600. The callback invocation times have |
1555 | potentially a lot of jitter, but good long-term stability. |
1769 | potentially a lot of jitter, but good long-term stability. |
1556 | |
1770 | |
1557 | static void |
1771 | static void |
1558 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1772 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1559 | { |
1773 | { |
1560 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1774 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1561 | } |
1775 | } |
1562 | |
1776 | |
1563 | struct ev_periodic hourly_tick; |
1777 | ev_periodic hourly_tick; |
1564 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1778 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1565 | ev_periodic_start (loop, &hourly_tick); |
1779 | ev_periodic_start (loop, &hourly_tick); |
1566 | |
1780 | |
1567 | Example: The same as above, but use a reschedule callback to do it: |
1781 | Example: The same as above, but use a reschedule callback to do it: |
1568 | |
1782 | |
1569 | #include <math.h> |
1783 | #include <math.h> |
1570 | |
1784 | |
1571 | static ev_tstamp |
1785 | static ev_tstamp |
1572 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1786 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1573 | { |
1787 | { |
1574 | return now + (3600. - fmod (now, 3600.)); |
1788 | return now + (3600. - fmod (now, 3600.)); |
1575 | } |
1789 | } |
1576 | |
1790 | |
1577 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1791 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1578 | |
1792 | |
1579 | Example: Call a callback every hour, starting now: |
1793 | Example: Call a callback every hour, starting now: |
1580 | |
1794 | |
1581 | struct ev_periodic hourly_tick; |
1795 | ev_periodic hourly_tick; |
1582 | ev_periodic_init (&hourly_tick, clock_cb, |
1796 | ev_periodic_init (&hourly_tick, clock_cb, |
1583 | fmod (ev_now (loop), 3600.), 3600., 0); |
1797 | fmod (ev_now (loop), 3600.), 3600., 0); |
1584 | ev_periodic_start (loop, &hourly_tick); |
1798 | ev_periodic_start (loop, &hourly_tick); |
1585 | |
1799 | |
1586 | |
1800 | |
… | |
… | |
1625 | |
1839 | |
1626 | =back |
1840 | =back |
1627 | |
1841 | |
1628 | =head3 Examples |
1842 | =head3 Examples |
1629 | |
1843 | |
1630 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
1844 | Example: Try to exit cleanly on SIGINT. |
1631 | |
1845 | |
1632 | static void |
1846 | static void |
1633 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1847 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1634 | { |
1848 | { |
1635 | ev_unloop (loop, EVUNLOOP_ALL); |
1849 | ev_unloop (loop, EVUNLOOP_ALL); |
1636 | } |
1850 | } |
1637 | |
1851 | |
1638 | struct ev_signal signal_watcher; |
1852 | ev_signal signal_watcher; |
1639 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1853 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1640 | ev_signal_start (loop, &sigint_cb); |
1854 | ev_signal_start (loop, &signal_watcher); |
1641 | |
1855 | |
1642 | |
1856 | |
1643 | =head2 C<ev_child> - watch out for process status changes |
1857 | =head2 C<ev_child> - watch out for process status changes |
1644 | |
1858 | |
1645 | Child watchers trigger when your process receives a SIGCHLD in response to |
1859 | Child watchers trigger when your process receives a SIGCHLD in response to |
… | |
… | |
1718 | its completion. |
1932 | its completion. |
1719 | |
1933 | |
1720 | ev_child cw; |
1934 | ev_child cw; |
1721 | |
1935 | |
1722 | static void |
1936 | static void |
1723 | child_cb (EV_P_ struct ev_child *w, int revents) |
1937 | child_cb (EV_P_ ev_child *w, int revents) |
1724 | { |
1938 | { |
1725 | ev_child_stop (EV_A_ w); |
1939 | ev_child_stop (EV_A_ w); |
1726 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1940 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1727 | } |
1941 | } |
1728 | |
1942 | |
… | |
… | |
1743 | |
1957 | |
1744 | |
1958 | |
1745 | =head2 C<ev_stat> - did the file attributes just change? |
1959 | =head2 C<ev_stat> - did the file attributes just change? |
1746 | |
1960 | |
1747 | This watches a file system path for attribute changes. That is, it calls |
1961 | This watches a file system path for attribute changes. That is, it calls |
1748 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
1962 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1749 | compared to the last time, invoking the callback if it did. |
1963 | and sees if it changed compared to the last time, invoking the callback if |
|
|
1964 | it did. |
1750 | |
1965 | |
1751 | The path does not need to exist: changing from "path exists" to "path does |
1966 | The path does not need to exist: changing from "path exists" to "path does |
1752 | not exist" is a status change like any other. The condition "path does |
1967 | not exist" is a status change like any other. The condition "path does not |
1753 | not exist" is signified by the C<st_nlink> field being zero (which is |
1968 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1754 | otherwise always forced to be at least one) and all the other fields of |
1969 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1755 | the stat buffer having unspecified contents. |
1970 | least one) and all the other fields of the stat buffer having unspecified |
|
|
1971 | contents. |
1756 | |
1972 | |
1757 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1973 | The path I<must not> end in a slash or contain special components such as |
|
|
1974 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1758 | relative and your working directory changes, the behaviour is undefined. |
1975 | your working directory changes, then the behaviour is undefined. |
1759 | |
1976 | |
1760 | Since there is no standard kernel interface to do this, the portable |
1977 | Since there is no portable change notification interface available, the |
1761 | implementation simply calls C<stat (2)> regularly on the path to see if |
1978 | portable implementation simply calls C<stat(2)> regularly on the path |
1762 | it changed somehow. You can specify a recommended polling interval for |
1979 | to see if it changed somehow. You can specify a recommended polling |
1763 | this case. If you specify a polling interval of C<0> (highly recommended!) |
1980 | interval for this case. If you specify a polling interval of C<0> (highly |
1764 | then a I<suitable, unspecified default> value will be used (which |
1981 | recommended!) then a I<suitable, unspecified default> value will be used |
1765 | you can expect to be around five seconds, although this might change |
1982 | (which you can expect to be around five seconds, although this might |
1766 | dynamically). Libev will also impose a minimum interval which is currently |
1983 | change dynamically). Libev will also impose a minimum interval which is |
1767 | around C<0.1>, but thats usually overkill. |
1984 | currently around C<0.1>, but that's usually overkill. |
1768 | |
1985 | |
1769 | This watcher type is not meant for massive numbers of stat watchers, |
1986 | This watcher type is not meant for massive numbers of stat watchers, |
1770 | as even with OS-supported change notifications, this can be |
1987 | as even with OS-supported change notifications, this can be |
1771 | resource-intensive. |
1988 | resource-intensive. |
1772 | |
1989 | |
1773 | At the time of this writing, the only OS-specific interface implemented |
1990 | At the time of this writing, the only OS-specific interface implemented |
1774 | is the Linux inotify interface (implementing kqueue support is left as |
1991 | is the Linux inotify interface (implementing kqueue support is left as an |
1775 | an exercise for the reader. Note, however, that the author sees no way |
1992 | exercise for the reader. Note, however, that the author sees no way of |
1776 | of implementing C<ev_stat> semantics with kqueue). |
1993 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1777 | |
1994 | |
1778 | =head3 ABI Issues (Largefile Support) |
1995 | =head3 ABI Issues (Largefile Support) |
1779 | |
1996 | |
1780 | Libev by default (unless the user overrides this) uses the default |
1997 | Libev by default (unless the user overrides this) uses the default |
1781 | compilation environment, which means that on systems with large file |
1998 | compilation environment, which means that on systems with large file |
1782 | support disabled by default, you get the 32 bit version of the stat |
1999 | support disabled by default, you get the 32 bit version of the stat |
1783 | structure. When using the library from programs that change the ABI to |
2000 | structure. When using the library from programs that change the ABI to |
1784 | use 64 bit file offsets the programs will fail. In that case you have to |
2001 | use 64 bit file offsets the programs will fail. In that case you have to |
1785 | compile libev with the same flags to get binary compatibility. This is |
2002 | compile libev with the same flags to get binary compatibility. This is |
1786 | obviously the case with any flags that change the ABI, but the problem is |
2003 | obviously the case with any flags that change the ABI, but the problem is |
1787 | most noticeably disabled with ev_stat and large file support. |
2004 | most noticeably displayed with ev_stat and large file support. |
1788 | |
2005 | |
1789 | The solution for this is to lobby your distribution maker to make large |
2006 | The solution for this is to lobby your distribution maker to make large |
1790 | file interfaces available by default (as e.g. FreeBSD does) and not |
2007 | file interfaces available by default (as e.g. FreeBSD does) and not |
1791 | optional. Libev cannot simply switch on large file support because it has |
2008 | optional. Libev cannot simply switch on large file support because it has |
1792 | to exchange stat structures with application programs compiled using the |
2009 | to exchange stat structures with application programs compiled using the |
1793 | default compilation environment. |
2010 | default compilation environment. |
1794 | |
2011 | |
1795 | =head3 Inotify and Kqueue |
2012 | =head3 Inotify and Kqueue |
1796 | |
2013 | |
1797 | When C<inotify (7)> support has been compiled into libev (generally only |
2014 | When C<inotify (7)> support has been compiled into libev and present at |
1798 | available with Linux) and present at runtime, it will be used to speed up |
2015 | runtime, it will be used to speed up change detection where possible. The |
1799 | change detection where possible. The inotify descriptor will be created lazily |
2016 | inotify descriptor will be created lazily when the first C<ev_stat> |
1800 | when the first C<ev_stat> watcher is being started. |
2017 | watcher is being started. |
1801 | |
2018 | |
1802 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2019 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1803 | except that changes might be detected earlier, and in some cases, to avoid |
2020 | except that changes might be detected earlier, and in some cases, to avoid |
1804 | making regular C<stat> calls. Even in the presence of inotify support |
2021 | making regular C<stat> calls. Even in the presence of inotify support |
1805 | there are many cases where libev has to resort to regular C<stat> polling, |
2022 | there are many cases where libev has to resort to regular C<stat> polling, |
1806 | but as long as the path exists, libev usually gets away without polling. |
2023 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2024 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2025 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2026 | xfs are fully working) libev usually gets away without polling. |
1807 | |
2027 | |
1808 | There is no support for kqueue, as apparently it cannot be used to |
2028 | There is no support for kqueue, as apparently it cannot be used to |
1809 | implement this functionality, due to the requirement of having a file |
2029 | implement this functionality, due to the requirement of having a file |
1810 | descriptor open on the object at all times, and detecting renames, unlinks |
2030 | descriptor open on the object at all times, and detecting renames, unlinks |
1811 | etc. is difficult. |
2031 | etc. is difficult. |
1812 | |
2032 | |
|
|
2033 | =head3 C<stat ()> is a synchronous operation |
|
|
2034 | |
|
|
2035 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2036 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2037 | ()>, which is a synchronous operation. |
|
|
2038 | |
|
|
2039 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2040 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2041 | as the path data is usually in memory already (except when starting the |
|
|
2042 | watcher). |
|
|
2043 | |
|
|
2044 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2045 | time due to network issues, and even under good conditions, a stat call |
|
|
2046 | often takes multiple milliseconds. |
|
|
2047 | |
|
|
2048 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2049 | paths, although this is fully supported by libev. |
|
|
2050 | |
1813 | =head3 The special problem of stat time resolution |
2051 | =head3 The special problem of stat time resolution |
1814 | |
2052 | |
1815 | The C<stat ()> system call only supports full-second resolution portably, and |
2053 | The C<stat ()> system call only supports full-second resolution portably, |
1816 | even on systems where the resolution is higher, most file systems still |
2054 | and even on systems where the resolution is higher, most file systems |
1817 | only support whole seconds. |
2055 | still only support whole seconds. |
1818 | |
2056 | |
1819 | That means that, if the time is the only thing that changes, you can |
2057 | That means that, if the time is the only thing that changes, you can |
1820 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2058 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1821 | calls your callback, which does something. When there is another update |
2059 | calls your callback, which does something. When there is another update |
1822 | within the same second, C<ev_stat> will be unable to detect unless the |
2060 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
1965 | |
2203 | |
1966 | =head3 Watcher-Specific Functions and Data Members |
2204 | =head3 Watcher-Specific Functions and Data Members |
1967 | |
2205 | |
1968 | =over 4 |
2206 | =over 4 |
1969 | |
2207 | |
1970 | =item ev_idle_init (ev_signal *, callback) |
2208 | =item ev_idle_init (ev_idle *, callback) |
1971 | |
2209 | |
1972 | Initialises and configures the idle watcher - it has no parameters of any |
2210 | Initialises and configures the idle watcher - it has no parameters of any |
1973 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2211 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1974 | believe me. |
2212 | believe me. |
1975 | |
2213 | |
… | |
… | |
1979 | |
2217 | |
1980 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2218 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1981 | callback, free it. Also, use no error checking, as usual. |
2219 | callback, free it. Also, use no error checking, as usual. |
1982 | |
2220 | |
1983 | static void |
2221 | static void |
1984 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2222 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1985 | { |
2223 | { |
1986 | free (w); |
2224 | free (w); |
1987 | // now do something you wanted to do when the program has |
2225 | // now do something you wanted to do when the program has |
1988 | // no longer anything immediate to do. |
2226 | // no longer anything immediate to do. |
1989 | } |
2227 | } |
1990 | |
2228 | |
1991 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2229 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1992 | ev_idle_init (idle_watcher, idle_cb); |
2230 | ev_idle_init (idle_watcher, idle_cb); |
1993 | ev_idle_start (loop, idle_cb); |
2231 | ev_idle_start (loop, idle_cb); |
1994 | |
2232 | |
1995 | |
2233 | |
1996 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2234 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
… | |
… | |
2077 | |
2315 | |
2078 | static ev_io iow [nfd]; |
2316 | static ev_io iow [nfd]; |
2079 | static ev_timer tw; |
2317 | static ev_timer tw; |
2080 | |
2318 | |
2081 | static void |
2319 | static void |
2082 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2320 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2083 | { |
2321 | { |
2084 | } |
2322 | } |
2085 | |
2323 | |
2086 | // create io watchers for each fd and a timer before blocking |
2324 | // create io watchers for each fd and a timer before blocking |
2087 | static void |
2325 | static void |
2088 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2326 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2089 | { |
2327 | { |
2090 | int timeout = 3600000; |
2328 | int timeout = 3600000; |
2091 | struct pollfd fds [nfd]; |
2329 | struct pollfd fds [nfd]; |
2092 | // actual code will need to loop here and realloc etc. |
2330 | // actual code will need to loop here and realloc etc. |
2093 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2331 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
… | |
… | |
2108 | } |
2346 | } |
2109 | } |
2347 | } |
2110 | |
2348 | |
2111 | // stop all watchers after blocking |
2349 | // stop all watchers after blocking |
2112 | static void |
2350 | static void |
2113 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2351 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2114 | { |
2352 | { |
2115 | ev_timer_stop (loop, &tw); |
2353 | ev_timer_stop (loop, &tw); |
2116 | |
2354 | |
2117 | for (int i = 0; i < nfd; ++i) |
2355 | for (int i = 0; i < nfd; ++i) |
2118 | { |
2356 | { |
… | |
… | |
2214 | some fds have to be watched and handled very quickly (with low latency), |
2452 | some fds have to be watched and handled very quickly (with low latency), |
2215 | and even priorities and idle watchers might have too much overhead. In |
2453 | and even priorities and idle watchers might have too much overhead. In |
2216 | this case you would put all the high priority stuff in one loop and all |
2454 | this case you would put all the high priority stuff in one loop and all |
2217 | the rest in a second one, and embed the second one in the first. |
2455 | the rest in a second one, and embed the second one in the first. |
2218 | |
2456 | |
2219 | As long as the watcher is active, the callback will be invoked every time |
2457 | As long as the watcher is active, the callback will be invoked every |
2220 | there might be events pending in the embedded loop. The callback must then |
2458 | time there might be events pending in the embedded loop. The callback |
2221 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2459 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2222 | their callbacks (you could also start an idle watcher to give the embedded |
2460 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2223 | loop strictly lower priority for example). You can also set the callback |
2461 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2224 | to C<0>, in which case the embed watcher will automatically execute the |
2462 | to give the embedded loop strictly lower priority for example). |
2225 | embedded loop sweep. |
|
|
2226 | |
2463 | |
2227 | As long as the watcher is started it will automatically handle events. The |
2464 | You can also set the callback to C<0>, in which case the embed watcher |
2228 | callback will be invoked whenever some events have been handled. You can |
2465 | will automatically execute the embedded loop sweep whenever necessary. |
2229 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2230 | interested in that. |
|
|
2231 | |
2466 | |
2232 | Also, there have not currently been made special provisions for forking: |
2467 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2233 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2468 | is active, i.e., the embedded loop will automatically be forked when the |
2234 | but you will also have to stop and restart any C<ev_embed> watchers |
2469 | embedding loop forks. In other cases, the user is responsible for calling |
2235 | yourself - but you can use a fork watcher to handle this automatically, |
2470 | C<ev_loop_fork> on the embedded loop. |
2236 | and future versions of libev might do just that. |
|
|
2237 | |
2471 | |
2238 | Unfortunately, not all backends are embeddable: only the ones returned by |
2472 | Unfortunately, not all backends are embeddable: only the ones returned by |
2239 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2473 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2240 | portable one. |
2474 | portable one. |
2241 | |
2475 | |
2242 | So when you want to use this feature you will always have to be prepared |
2476 | So when you want to use this feature you will always have to be prepared |
2243 | that you cannot get an embeddable loop. The recommended way to get around |
2477 | that you cannot get an embeddable loop. The recommended way to get around |
2244 | this is to have a separate variables for your embeddable loop, try to |
2478 | this is to have a separate variables for your embeddable loop, try to |
2245 | create it, and if that fails, use the normal loop for everything. |
2479 | create it, and if that fails, use the normal loop for everything. |
|
|
2480 | |
|
|
2481 | =head3 C<ev_embed> and fork |
|
|
2482 | |
|
|
2483 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2484 | automatically be applied to the embedded loop as well, so no special |
|
|
2485 | fork handling is required in that case. When the watcher is not running, |
|
|
2486 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2487 | as applicable. |
2246 | |
2488 | |
2247 | =head3 Watcher-Specific Functions and Data Members |
2489 | =head3 Watcher-Specific Functions and Data Members |
2248 | |
2490 | |
2249 | =over 4 |
2491 | =over 4 |
2250 | |
2492 | |
… | |
… | |
2278 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2520 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2279 | used). |
2521 | used). |
2280 | |
2522 | |
2281 | struct ev_loop *loop_hi = ev_default_init (0); |
2523 | struct ev_loop *loop_hi = ev_default_init (0); |
2282 | struct ev_loop *loop_lo = 0; |
2524 | struct ev_loop *loop_lo = 0; |
2283 | struct ev_embed embed; |
2525 | ev_embed embed; |
2284 | |
2526 | |
2285 | // see if there is a chance of getting one that works |
2527 | // see if there is a chance of getting one that works |
2286 | // (remember that a flags value of 0 means autodetection) |
2528 | // (remember that a flags value of 0 means autodetection) |
2287 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2529 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2288 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2530 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2302 | kqueue implementation). Store the kqueue/socket-only event loop in |
2544 | kqueue implementation). Store the kqueue/socket-only event loop in |
2303 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2545 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2304 | |
2546 | |
2305 | struct ev_loop *loop = ev_default_init (0); |
2547 | struct ev_loop *loop = ev_default_init (0); |
2306 | struct ev_loop *loop_socket = 0; |
2548 | struct ev_loop *loop_socket = 0; |
2307 | struct ev_embed embed; |
2549 | ev_embed embed; |
2308 | |
2550 | |
2309 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2551 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2310 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2552 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2311 | { |
2553 | { |
2312 | ev_embed_init (&embed, 0, loop_socket); |
2554 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2376 | =over 4 |
2618 | =over 4 |
2377 | |
2619 | |
2378 | =item queueing from a signal handler context |
2620 | =item queueing from a signal handler context |
2379 | |
2621 | |
2380 | To implement race-free queueing, you simply add to the queue in the signal |
2622 | To implement race-free queueing, you simply add to the queue in the signal |
2381 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
2623 | handler but you block the signal handler in the watcher callback. Here is |
2382 | some fictitious SIGUSR1 handler: |
2624 | an example that does that for some fictitious SIGUSR1 handler: |
2383 | |
2625 | |
2384 | static ev_async mysig; |
2626 | static ev_async mysig; |
2385 | |
2627 | |
2386 | static void |
2628 | static void |
2387 | sigusr1_handler (void) |
2629 | sigusr1_handler (void) |
… | |
… | |
2453 | =over 4 |
2695 | =over 4 |
2454 | |
2696 | |
2455 | =item ev_async_init (ev_async *, callback) |
2697 | =item ev_async_init (ev_async *, callback) |
2456 | |
2698 | |
2457 | Initialises and configures the async watcher - it has no parameters of any |
2699 | Initialises and configures the async watcher - it has no parameters of any |
2458 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2700 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2459 | trust me. |
2701 | trust me. |
2460 | |
2702 | |
2461 | =item ev_async_send (loop, ev_async *) |
2703 | =item ev_async_send (loop, ev_async *) |
2462 | |
2704 | |
2463 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2705 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2464 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2706 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2465 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2707 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2466 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2708 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2467 | section below on what exactly this means). |
2709 | section below on what exactly this means). |
2468 | |
2710 | |
|
|
2711 | Note that, as with other watchers in libev, multiple events might get |
|
|
2712 | compressed into a single callback invocation (another way to look at this |
|
|
2713 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2714 | reset when the event loop detects that). |
|
|
2715 | |
2469 | This call incurs the overhead of a system call only once per loop iteration, |
2716 | This call incurs the overhead of a system call only once per event loop |
2470 | so while the overhead might be noticeable, it doesn't apply to repeated |
2717 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2471 | calls to C<ev_async_send>. |
2718 | repeated calls to C<ev_async_send> for the same event loop. |
2472 | |
2719 | |
2473 | =item bool = ev_async_pending (ev_async *) |
2720 | =item bool = ev_async_pending (ev_async *) |
2474 | |
2721 | |
2475 | Returns a non-zero value when C<ev_async_send> has been called on the |
2722 | Returns a non-zero value when C<ev_async_send> has been called on the |
2476 | watcher but the event has not yet been processed (or even noted) by the |
2723 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2479 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2726 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2480 | the loop iterates next and checks for the watcher to have become active, |
2727 | the loop iterates next and checks for the watcher to have become active, |
2481 | it will reset the flag again. C<ev_async_pending> can be used to very |
2728 | it will reset the flag again. C<ev_async_pending> can be used to very |
2482 | quickly check whether invoking the loop might be a good idea. |
2729 | quickly check whether invoking the loop might be a good idea. |
2483 | |
2730 | |
2484 | Not that this does I<not> check whether the watcher itself is pending, only |
2731 | Not that this does I<not> check whether the watcher itself is pending, |
2485 | whether it has been requested to make this watcher pending. |
2732 | only whether it has been requested to make this watcher pending: there |
|
|
2733 | is a time window between the event loop checking and resetting the async |
|
|
2734 | notification, and the callback being invoked. |
2486 | |
2735 | |
2487 | =back |
2736 | =back |
2488 | |
2737 | |
2489 | |
2738 | |
2490 | =head1 OTHER FUNCTIONS |
2739 | =head1 OTHER FUNCTIONS |
… | |
… | |
2494 | =over 4 |
2743 | =over 4 |
2495 | |
2744 | |
2496 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2745 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2497 | |
2746 | |
2498 | This function combines a simple timer and an I/O watcher, calls your |
2747 | This function combines a simple timer and an I/O watcher, calls your |
2499 | callback on whichever event happens first and automatically stop both |
2748 | callback on whichever event happens first and automatically stops both |
2500 | watchers. This is useful if you want to wait for a single event on an fd |
2749 | watchers. This is useful if you want to wait for a single event on an fd |
2501 | or timeout without having to allocate/configure/start/stop/free one or |
2750 | or timeout without having to allocate/configure/start/stop/free one or |
2502 | more watchers yourself. |
2751 | more watchers yourself. |
2503 | |
2752 | |
2504 | If C<fd> is less than 0, then no I/O watcher will be started and events |
2753 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2505 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
2754 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2506 | C<events> set will be created and started. |
2755 | the given C<fd> and C<events> set will be created and started. |
2507 | |
2756 | |
2508 | If C<timeout> is less than 0, then no timeout watcher will be |
2757 | If C<timeout> is less than 0, then no timeout watcher will be |
2509 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2758 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2510 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
2759 | repeat = 0) will be started. C<0> is a valid timeout. |
2511 | dubious value. |
|
|
2512 | |
2760 | |
2513 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2761 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2514 | passed an C<revents> set like normal event callbacks (a combination of |
2762 | passed an C<revents> set like normal event callbacks (a combination of |
2515 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2763 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2516 | value passed to C<ev_once>: |
2764 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
2765 | a timeout and an io event at the same time - you probably should give io |
|
|
2766 | events precedence. |
|
|
2767 | |
|
|
2768 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2517 | |
2769 | |
2518 | static void stdin_ready (int revents, void *arg) |
2770 | static void stdin_ready (int revents, void *arg) |
2519 | { |
2771 | { |
|
|
2772 | if (revents & EV_READ) |
|
|
2773 | /* stdin might have data for us, joy! */; |
2520 | if (revents & EV_TIMEOUT) |
2774 | else if (revents & EV_TIMEOUT) |
2521 | /* doh, nothing entered */; |
2775 | /* doh, nothing entered */; |
2522 | else if (revents & EV_READ) |
|
|
2523 | /* stdin might have data for us, joy! */; |
|
|
2524 | } |
2776 | } |
2525 | |
2777 | |
2526 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2778 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2527 | |
2779 | |
2528 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
2780 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
2529 | |
2781 | |
2530 | Feeds the given event set into the event loop, as if the specified event |
2782 | Feeds the given event set into the event loop, as if the specified event |
2531 | had happened for the specified watcher (which must be a pointer to an |
2783 | had happened for the specified watcher (which must be a pointer to an |
2532 | initialised but not necessarily started event watcher). |
2784 | initialised but not necessarily started event watcher). |
2533 | |
2785 | |
2534 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
2786 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
2535 | |
2787 | |
2536 | Feed an event on the given fd, as if a file descriptor backend detected |
2788 | Feed an event on the given fd, as if a file descriptor backend detected |
2537 | the given events it. |
2789 | the given events it. |
2538 | |
2790 | |
2539 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
2791 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
2540 | |
2792 | |
2541 | Feed an event as if the given signal occurred (C<loop> must be the default |
2793 | Feed an event as if the given signal occurred (C<loop> must be the default |
2542 | loop!). |
2794 | loop!). |
2543 | |
2795 | |
2544 | =back |
2796 | =back |
… | |
… | |
2665 | } |
2917 | } |
2666 | |
2918 | |
2667 | myclass obj; |
2919 | myclass obj; |
2668 | ev::io iow; |
2920 | ev::io iow; |
2669 | iow.set <myclass, &myclass::io_cb> (&obj); |
2921 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
2922 | |
|
|
2923 | =item w->set (object *) |
|
|
2924 | |
|
|
2925 | This is an B<experimental> feature that might go away in a future version. |
|
|
2926 | |
|
|
2927 | This is a variation of a method callback - leaving out the method to call |
|
|
2928 | will default the method to C<operator ()>, which makes it possible to use |
|
|
2929 | functor objects without having to manually specify the C<operator ()> all |
|
|
2930 | the time. Incidentally, you can then also leave out the template argument |
|
|
2931 | list. |
|
|
2932 | |
|
|
2933 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
2934 | int revents)>. |
|
|
2935 | |
|
|
2936 | See the method-C<set> above for more details. |
|
|
2937 | |
|
|
2938 | Example: use a functor object as callback. |
|
|
2939 | |
|
|
2940 | struct myfunctor |
|
|
2941 | { |
|
|
2942 | void operator() (ev::io &w, int revents) |
|
|
2943 | { |
|
|
2944 | ... |
|
|
2945 | } |
|
|
2946 | } |
|
|
2947 | |
|
|
2948 | myfunctor f; |
|
|
2949 | |
|
|
2950 | ev::io w; |
|
|
2951 | w.set (&f); |
2670 | |
2952 | |
2671 | =item w->set<function> (void *data = 0) |
2953 | =item w->set<function> (void *data = 0) |
2672 | |
2954 | |
2673 | Also sets a callback, but uses a static method or plain function as |
2955 | Also sets a callback, but uses a static method or plain function as |
2674 | callback. The optional C<data> argument will be stored in the watcher's |
2956 | callback. The optional C<data> argument will be stored in the watcher's |
… | |
… | |
2761 | L<http://software.schmorp.de/pkg/EV>. |
3043 | L<http://software.schmorp.de/pkg/EV>. |
2762 | |
3044 | |
2763 | =item Python |
3045 | =item Python |
2764 | |
3046 | |
2765 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3047 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2766 | seems to be quite complete and well-documented. Note, however, that the |
3048 | seems to be quite complete and well-documented. |
2767 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2768 | for everybody else, and therefore, should never be applied in an installed |
|
|
2769 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2770 | libev). |
|
|
2771 | |
3049 | |
2772 | =item Ruby |
3050 | =item Ruby |
2773 | |
3051 | |
2774 | Tony Arcieri has written a ruby extension that offers access to a subset |
3052 | Tony Arcieri has written a ruby extension that offers access to a subset |
2775 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3053 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2776 | more on top of it. It can be found via gem servers. Its homepage is at |
3054 | more on top of it. It can be found via gem servers. Its homepage is at |
2777 | L<http://rev.rubyforge.org/>. |
3055 | L<http://rev.rubyforge.org/>. |
2778 | |
3056 | |
|
|
3057 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3058 | makes rev work even on mingw. |
|
|
3059 | |
|
|
3060 | =item Haskell |
|
|
3061 | |
|
|
3062 | A haskell binding to libev is available at |
|
|
3063 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3064 | |
2779 | =item D |
3065 | =item D |
2780 | |
3066 | |
2781 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3067 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2782 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3068 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3069 | |
|
|
3070 | =item Ocaml |
|
|
3071 | |
|
|
3072 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3073 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
2783 | |
3074 | |
2784 | =back |
3075 | =back |
2785 | |
3076 | |
2786 | |
3077 | |
2787 | =head1 MACRO MAGIC |
3078 | =head1 MACRO MAGIC |
… | |
… | |
2888 | |
3179 | |
2889 | #define EV_STANDALONE 1 |
3180 | #define EV_STANDALONE 1 |
2890 | #include "ev.h" |
3181 | #include "ev.h" |
2891 | |
3182 | |
2892 | Both header files and implementation files can be compiled with a C++ |
3183 | Both header files and implementation files can be compiled with a C++ |
2893 | compiler (at least, thats a stated goal, and breakage will be treated |
3184 | compiler (at least, that's a stated goal, and breakage will be treated |
2894 | as a bug). |
3185 | as a bug). |
2895 | |
3186 | |
2896 | You need the following files in your source tree, or in a directory |
3187 | You need the following files in your source tree, or in a directory |
2897 | in your include path (e.g. in libev/ when using -Ilibev): |
3188 | in your include path (e.g. in libev/ when using -Ilibev): |
2898 | |
3189 | |
… | |
… | |
2954 | keeps libev from including F<config.h>, and it also defines dummy |
3245 | keeps libev from including F<config.h>, and it also defines dummy |
2955 | implementations for some libevent functions (such as logging, which is not |
3246 | implementations for some libevent functions (such as logging, which is not |
2956 | supported). It will also not define any of the structs usually found in |
3247 | supported). It will also not define any of the structs usually found in |
2957 | F<event.h> that are not directly supported by the libev core alone. |
3248 | F<event.h> that are not directly supported by the libev core alone. |
2958 | |
3249 | |
|
|
3250 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3251 | configuration, but has to be more conservative. |
|
|
3252 | |
2959 | =item EV_USE_MONOTONIC |
3253 | =item EV_USE_MONOTONIC |
2960 | |
3254 | |
2961 | If defined to be C<1>, libev will try to detect the availability of the |
3255 | If defined to be C<1>, libev will try to detect the availability of the |
2962 | monotonic clock option at both compile time and runtime. Otherwise no use |
3256 | monotonic clock option at both compile time and runtime. Otherwise no |
2963 | of the monotonic clock option will be attempted. If you enable this, you |
3257 | use of the monotonic clock option will be attempted. If you enable this, |
2964 | usually have to link against librt or something similar. Enabling it when |
3258 | you usually have to link against librt or something similar. Enabling it |
2965 | the functionality isn't available is safe, though, although you have |
3259 | when the functionality isn't available is safe, though, although you have |
2966 | to make sure you link against any libraries where the C<clock_gettime> |
3260 | to make sure you link against any libraries where the C<clock_gettime> |
2967 | function is hiding in (often F<-lrt>). |
3261 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2968 | |
3262 | |
2969 | =item EV_USE_REALTIME |
3263 | =item EV_USE_REALTIME |
2970 | |
3264 | |
2971 | If defined to be C<1>, libev will try to detect the availability of the |
3265 | If defined to be C<1>, libev will try to detect the availability of the |
2972 | real-time clock option at compile time (and assume its availability at |
3266 | real-time clock option at compile time (and assume its availability |
2973 | runtime if successful). Otherwise no use of the real-time clock option will |
3267 | at runtime if successful). Otherwise no use of the real-time clock |
2974 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3268 | option will be attempted. This effectively replaces C<gettimeofday> |
2975 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3269 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2976 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3270 | correctness. See the note about libraries in the description of |
|
|
3271 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3272 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3273 | |
|
|
3274 | =item EV_USE_CLOCK_SYSCALL |
|
|
3275 | |
|
|
3276 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3277 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3278 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3279 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3280 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3281 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3282 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3283 | higher, as it simplifies linking (no need for C<-lrt>). |
2977 | |
3284 | |
2978 | =item EV_USE_NANOSLEEP |
3285 | =item EV_USE_NANOSLEEP |
2979 | |
3286 | |
2980 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3287 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2981 | and will use it for delays. Otherwise it will use C<select ()>. |
3288 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
2997 | |
3304 | |
2998 | =item EV_SELECT_USE_FD_SET |
3305 | =item EV_SELECT_USE_FD_SET |
2999 | |
3306 | |
3000 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3307 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3001 | structure. This is useful if libev doesn't compile due to a missing |
3308 | structure. This is useful if libev doesn't compile due to a missing |
3002 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3309 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3003 | exotic systems. This usually limits the range of file descriptors to some |
3310 | on exotic systems. This usually limits the range of file descriptors to |
3004 | low limit such as 1024 or might have other limitations (winsocket only |
3311 | some low limit such as 1024 or might have other limitations (winsocket |
3005 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3312 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3006 | influence the size of the C<fd_set> used. |
3313 | configures the maximum size of the C<fd_set>. |
3007 | |
3314 | |
3008 | =item EV_SELECT_IS_WINSOCKET |
3315 | =item EV_SELECT_IS_WINSOCKET |
3009 | |
3316 | |
3010 | When defined to C<1>, the select backend will assume that |
3317 | When defined to C<1>, the select backend will assume that |
3011 | select/socket/connect etc. don't understand file descriptors but |
3318 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3298 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3605 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3299 | |
3606 | |
3300 | #include "ev_cpp.h" |
3607 | #include "ev_cpp.h" |
3301 | #include "ev.c" |
3608 | #include "ev.c" |
3302 | |
3609 | |
|
|
3610 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3303 | |
3611 | |
3304 | =head1 THREADS AND COROUTINES |
3612 | =head2 THREADS AND COROUTINES |
3305 | |
3613 | |
3306 | =head2 THREADS |
3614 | =head3 THREADS |
3307 | |
3615 | |
3308 | Libev itself is thread-safe (unless the opposite is specifically |
3616 | All libev functions are reentrant and thread-safe unless explicitly |
3309 | documented for a function), but it uses no locking itself. This means that |
3617 | documented otherwise, but libev implements no locking itself. This means |
3310 | you can use as many loops as you want in parallel, as long as only one |
3618 | that you can use as many loops as you want in parallel, as long as there |
3311 | thread ever calls into one libev function with the same loop parameter: |
3619 | are no concurrent calls into any libev function with the same loop |
|
|
3620 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
3312 | libev guarantees that different event loops share no data structures that |
3621 | of course): libev guarantees that different event loops share no data |
3313 | need locking. |
3622 | structures that need any locking. |
3314 | |
3623 | |
3315 | Or to put it differently: calls with different loop parameters can be done |
3624 | Or to put it differently: calls with different loop parameters can be done |
3316 | concurrently from multiple threads, calls with the same loop parameter |
3625 | concurrently from multiple threads, calls with the same loop parameter |
3317 | must be done serially (but can be done from different threads, as long as |
3626 | must be done serially (but can be done from different threads, as long as |
3318 | only one thread ever is inside a call at any point in time, e.g. by using |
3627 | only one thread ever is inside a call at any point in time, e.g. by using |
3319 | a mutex per loop). |
3628 | a mutex per loop). |
3320 | |
3629 | |
3321 | Specifically to support threads (and signal handlers), libev implements |
3630 | Specifically to support threads (and signal handlers), libev implements |
3322 | so-called C<ev_async> watchers, which allow some limited form of |
3631 | so-called C<ev_async> watchers, which allow some limited form of |
3323 | concurrency on the same event loop. |
3632 | concurrency on the same event loop, namely waking it up "from the |
|
|
3633 | outside". |
3324 | |
3634 | |
3325 | If you want to know which design (one loop, locking, or multiple loops |
3635 | If you want to know which design (one loop, locking, or multiple loops |
3326 | without or something else still) is best for your problem, then I cannot |
3636 | without or something else still) is best for your problem, then I cannot |
3327 | help you. I can give some generic advice however: |
3637 | help you, but here is some generic advice: |
3328 | |
3638 | |
3329 | =over 4 |
3639 | =over 4 |
3330 | |
3640 | |
3331 | =item * most applications have a main thread: use the default libev loop |
3641 | =item * most applications have a main thread: use the default libev loop |
3332 | in that thread, or create a separate thread running only the default loop. |
3642 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3356 | default loop and triggering an C<ev_async> watcher from the default loop |
3666 | default loop and triggering an C<ev_async> watcher from the default loop |
3357 | watcher callback into the event loop interested in the signal. |
3667 | watcher callback into the event loop interested in the signal. |
3358 | |
3668 | |
3359 | =back |
3669 | =back |
3360 | |
3670 | |
3361 | =head2 COROUTINES |
3671 | =head3 COROUTINES |
3362 | |
3672 | |
3363 | Libev is much more accommodating to coroutines ("cooperative threads"): |
3673 | Libev is very accommodating to coroutines ("cooperative threads"): |
3364 | libev fully supports nesting calls to it's functions from different |
3674 | libev fully supports nesting calls to its functions from different |
3365 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3675 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3366 | different coroutines and switch freely between both coroutines running the |
3676 | different coroutines, and switch freely between both coroutines running the |
3367 | loop, as long as you don't confuse yourself). The only exception is that |
3677 | loop, as long as you don't confuse yourself). The only exception is that |
3368 | you must not do this from C<ev_periodic> reschedule callbacks. |
3678 | you must not do this from C<ev_periodic> reschedule callbacks. |
3369 | |
3679 | |
3370 | Care has been taken to ensure that libev does not keep local state inside |
3680 | Care has been taken to ensure that libev does not keep local state inside |
3371 | C<ev_loop>, and other calls do not usually allow coroutine switches. |
3681 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
|
|
3682 | they do not call any callbacks. |
3372 | |
3683 | |
|
|
3684 | =head2 COMPILER WARNINGS |
3373 | |
3685 | |
3374 | =head1 COMPLEXITIES |
3686 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3687 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3688 | scared by this. |
3375 | |
3689 | |
3376 | In this section the complexities of (many of) the algorithms used inside |
3690 | However, these are unavoidable for many reasons. For one, each compiler |
3377 | libev will be explained. For complexity discussions about backends see the |
3691 | has different warnings, and each user has different tastes regarding |
3378 | documentation for C<ev_default_init>. |
3692 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3693 | targeting a specific compiler and compiler-version. |
3379 | |
3694 | |
3380 | All of the following are about amortised time: If an array needs to be |
3695 | Another reason is that some compiler warnings require elaborate |
3381 | extended, libev needs to realloc and move the whole array, but this |
3696 | workarounds, or other changes to the code that make it less clear and less |
3382 | happens asymptotically never with higher number of elements, so O(1) might |
3697 | maintainable. |
3383 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3384 | it is much faster and asymptotically approaches constant time. |
|
|
3385 | |
3698 | |
3386 | =over 4 |
3699 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3700 | wrong (because they don't actually warn about the condition their message |
|
|
3701 | seems to warn about). For example, certain older gcc versions had some |
|
|
3702 | warnings that resulted an extreme number of false positives. These have |
|
|
3703 | been fixed, but some people still insist on making code warn-free with |
|
|
3704 | such buggy versions. |
3387 | |
3705 | |
3388 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3706 | While libev is written to generate as few warnings as possible, |
|
|
3707 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3708 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3709 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3710 | warnings, not errors, or proof of bugs. |
3389 | |
3711 | |
3390 | This means that, when you have a watcher that triggers in one hour and |
|
|
3391 | there are 100 watchers that would trigger before that then inserting will |
|
|
3392 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3393 | |
3712 | |
3394 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3713 | =head2 VALGRIND |
3395 | |
3714 | |
3396 | That means that changing a timer costs less than removing/adding them |
3715 | Valgrind has a special section here because it is a popular tool that is |
3397 | as only the relative motion in the event queue has to be paid for. |
3716 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3398 | |
3717 | |
3399 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3718 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3719 | in libev, then check twice: If valgrind reports something like: |
3400 | |
3720 | |
3401 | These just add the watcher into an array or at the head of a list. |
3721 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3722 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3723 | ==2274== still reachable: 256 bytes in 1 blocks. |
3402 | |
3724 | |
3403 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3725 | Then there is no memory leak, just as memory accounted to global variables |
|
|
3726 | is not a memleak - the memory is still being referenced, and didn't leak. |
3404 | |
3727 | |
3405 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3728 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
3729 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
3730 | although an acceptable workaround has been found here), or it might be |
|
|
3731 | confused. |
3406 | |
3732 | |
3407 | These watchers are stored in lists then need to be walked to find the |
3733 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3408 | correct watcher to remove. The lists are usually short (you don't usually |
3734 | make it into some kind of religion. |
3409 | have many watchers waiting for the same fd or signal). |
|
|
3410 | |
3735 | |
3411 | =item Finding the next timer in each loop iteration: O(1) |
3736 | If you are unsure about something, feel free to contact the mailing list |
|
|
3737 | with the full valgrind report and an explanation on why you think this |
|
|
3738 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
3739 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
3740 | of learning how to interpret valgrind properly. |
3412 | |
3741 | |
3413 | By virtue of using a binary or 4-heap, the next timer is always found at a |
3742 | If you need, for some reason, empty reports from valgrind for your project |
3414 | fixed position in the storage array. |
3743 | I suggest using suppression lists. |
3415 | |
3744 | |
3416 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3417 | |
3745 | |
3418 | A change means an I/O watcher gets started or stopped, which requires |
3746 | =head1 PORTABILITY NOTES |
3419 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3420 | on backend and whether C<ev_io_set> was used). |
|
|
3421 | |
3747 | |
3422 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3423 | |
|
|
3424 | =item Priority handling: O(number_of_priorities) |
|
|
3425 | |
|
|
3426 | Priorities are implemented by allocating some space for each |
|
|
3427 | priority. When doing priority-based operations, libev usually has to |
|
|
3428 | linearly search all the priorities, but starting/stopping and activating |
|
|
3429 | watchers becomes O(1) with respect to priority handling. |
|
|
3430 | |
|
|
3431 | =item Sending an ev_async: O(1) |
|
|
3432 | |
|
|
3433 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3434 | |
|
|
3435 | =item Processing signals: O(max_signal_number) |
|
|
3436 | |
|
|
3437 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3438 | calls in the current loop iteration. Checking for async and signal events |
|
|
3439 | involves iterating over all running async watchers or all signal numbers. |
|
|
3440 | |
|
|
3441 | =back |
|
|
3442 | |
|
|
3443 | |
|
|
3444 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3748 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3445 | |
3749 | |
3446 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3750 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3447 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3751 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3448 | model. Libev still offers limited functionality on this platform in |
3752 | model. Libev still offers limited functionality on this platform in |
3449 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3753 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
… | |
… | |
3536 | wrap all I/O functions and provide your own fd management, but the cost of |
3840 | wrap all I/O functions and provide your own fd management, but the cost of |
3537 | calling select (O(n²)) will likely make this unworkable. |
3841 | calling select (O(n²)) will likely make this unworkable. |
3538 | |
3842 | |
3539 | =back |
3843 | =back |
3540 | |
3844 | |
3541 | |
|
|
3542 | =head1 PORTABILITY REQUIREMENTS |
3845 | =head2 PORTABILITY REQUIREMENTS |
3543 | |
3846 | |
3544 | In addition to a working ISO-C implementation, libev relies on a few |
3847 | In addition to a working ISO-C implementation and of course the |
3545 | additional extensions: |
3848 | backend-specific APIs, libev relies on a few additional extensions: |
3546 | |
3849 | |
3547 | =over 4 |
3850 | =over 4 |
3548 | |
3851 | |
3549 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3852 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3550 | calling conventions regardless of C<ev_watcher_type *>. |
3853 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3575 | except the initial one, and run the default loop in the initial thread as |
3878 | except the initial one, and run the default loop in the initial thread as |
3576 | well. |
3879 | well. |
3577 | |
3880 | |
3578 | =item C<long> must be large enough for common memory allocation sizes |
3881 | =item C<long> must be large enough for common memory allocation sizes |
3579 | |
3882 | |
3580 | To improve portability and simplify using libev, libev uses C<long> |
3883 | To improve portability and simplify its API, libev uses C<long> internally |
3581 | internally instead of C<size_t> when allocating its data structures. On |
3884 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3582 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
3885 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3583 | is still at least 31 bits everywhere, which is enough for hundreds of |
3886 | least 31 bits everywhere, which is enough for hundreds of millions of |
3584 | millions of watchers. |
3887 | watchers. |
3585 | |
3888 | |
3586 | =item C<double> must hold a time value in seconds with enough accuracy |
3889 | =item C<double> must hold a time value in seconds with enough accuracy |
3587 | |
3890 | |
3588 | The type C<double> is used to represent timestamps. It is required to |
3891 | The type C<double> is used to represent timestamps. It is required to |
3589 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3892 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
… | |
… | |
3593 | =back |
3896 | =back |
3594 | |
3897 | |
3595 | If you know of other additional requirements drop me a note. |
3898 | If you know of other additional requirements drop me a note. |
3596 | |
3899 | |
3597 | |
3900 | |
3598 | =head1 COMPILER WARNINGS |
3901 | =head1 ALGORITHMIC COMPLEXITIES |
3599 | |
3902 | |
3600 | Depending on your compiler and compiler settings, you might get no or a |
3903 | In this section the complexities of (many of) the algorithms used inside |
3601 | lot of warnings when compiling libev code. Some people are apparently |
3904 | libev will be documented. For complexity discussions about backends see |
3602 | scared by this. |
3905 | the documentation for C<ev_default_init>. |
3603 | |
3906 | |
3604 | However, these are unavoidable for many reasons. For one, each compiler |
3907 | All of the following are about amortised time: If an array needs to be |
3605 | has different warnings, and each user has different tastes regarding |
3908 | extended, libev needs to realloc and move the whole array, but this |
3606 | warning options. "Warn-free" code therefore cannot be a goal except when |
3909 | happens asymptotically rarer with higher number of elements, so O(1) might |
3607 | targeting a specific compiler and compiler-version. |
3910 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
3911 | average it is much faster and asymptotically approaches constant time. |
3608 | |
3912 | |
3609 | Another reason is that some compiler warnings require elaborate |
3913 | =over 4 |
3610 | workarounds, or other changes to the code that make it less clear and less |
|
|
3611 | maintainable. |
|
|
3612 | |
3914 | |
3613 | And of course, some compiler warnings are just plain stupid, or simply |
3915 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3614 | wrong (because they don't actually warn about the condition their message |
|
|
3615 | seems to warn about). |
|
|
3616 | |
3916 | |
3617 | While libev is written to generate as few warnings as possible, |
3917 | This means that, when you have a watcher that triggers in one hour and |
3618 | "warn-free" code is not a goal, and it is recommended not to build libev |
3918 | there are 100 watchers that would trigger before that, then inserting will |
3619 | with any compiler warnings enabled unless you are prepared to cope with |
3919 | have to skip roughly seven (C<ld 100>) of these watchers. |
3620 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3621 | warnings, not errors, or proof of bugs. |
|
|
3622 | |
3920 | |
|
|
3921 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3623 | |
3922 | |
3624 | =head1 VALGRIND |
3923 | That means that changing a timer costs less than removing/adding them, |
|
|
3924 | as only the relative motion in the event queue has to be paid for. |
3625 | |
3925 | |
3626 | Valgrind has a special section here because it is a popular tool that is |
3926 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3627 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3628 | |
3927 | |
3629 | If you think you found a bug (memory leak, uninitialised data access etc.) |
3928 | These just add the watcher into an array or at the head of a list. |
3630 | in libev, then check twice: If valgrind reports something like: |
|
|
3631 | |
3929 | |
3632 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3930 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3633 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3634 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3635 | |
3931 | |
3636 | Then there is no memory leak. Similarly, under some circumstances, |
3932 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3637 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3638 | might be confused (it is a very good tool, but only a tool). |
|
|
3639 | |
3933 | |
3640 | If you are unsure about something, feel free to contact the mailing list |
3934 | These watchers are stored in lists, so they need to be walked to find the |
3641 | with the full valgrind report and an explanation on why you think this is |
3935 | correct watcher to remove. The lists are usually short (you don't usually |
3642 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
3936 | have many watchers waiting for the same fd or signal: one is typical, two |
3643 | no bug" answer and take the chance of learning how to interpret valgrind |
3937 | is rare). |
3644 | properly. |
|
|
3645 | |
3938 | |
3646 | If you need, for some reason, empty reports from valgrind for your project |
3939 | =item Finding the next timer in each loop iteration: O(1) |
3647 | I suggest using suppression lists. |
3940 | |
|
|
3941 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
3942 | fixed position in the storage array. |
|
|
3943 | |
|
|
3944 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3945 | |
|
|
3946 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3947 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3948 | on backend and whether C<ev_io_set> was used). |
|
|
3949 | |
|
|
3950 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3951 | |
|
|
3952 | =item Priority handling: O(number_of_priorities) |
|
|
3953 | |
|
|
3954 | Priorities are implemented by allocating some space for each |
|
|
3955 | priority. When doing priority-based operations, libev usually has to |
|
|
3956 | linearly search all the priorities, but starting/stopping and activating |
|
|
3957 | watchers becomes O(1) with respect to priority handling. |
|
|
3958 | |
|
|
3959 | =item Sending an ev_async: O(1) |
|
|
3960 | |
|
|
3961 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3962 | |
|
|
3963 | =item Processing signals: O(max_signal_number) |
|
|
3964 | |
|
|
3965 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3966 | calls in the current loop iteration. Checking for async and signal events |
|
|
3967 | involves iterating over all running async watchers or all signal numbers. |
|
|
3968 | |
|
|
3969 | =back |
3648 | |
3970 | |
3649 | |
3971 | |
3650 | =head1 AUTHOR |
3972 | =head1 AUTHOR |
3651 | |
3973 | |
3652 | Marc Lehmann <libev@schmorp.de>. |
3974 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3653 | |
3975 | |