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8 | |
8 | |
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> |
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13 | |
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14 | #include <stdio.h> // for puts |
13 | |
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; |
… | |
… | |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // unloop was called, so exit |
62 | return 0; |
64 | return 0; |
63 | } |
65 | } |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
66 | |
70 | |
67 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 ABOUT LIBEV |
70 | |
84 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
74 | |
88 | |
… | |
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108 | name C<loop> (which is always of type C<ev_loop *>) will not have |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
109 | this argument. |
123 | this argument. |
110 | |
124 | |
111 | =head2 TIME REPRESENTATION |
125 | =head2 TIME REPRESENTATION |
112 | |
126 | |
113 | Libev represents time as a single floating point number, representing the |
127 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
129 | near the beginning of 1970, details are complicated, don't ask). This |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
130 | type is called C<ev_tstamp>, which is what you should use too. It usually |
117 | to the C<double> type in C, and when you need to do any calculations on |
131 | aliases to the C<double> type in C. When you need to do any calculations |
118 | it, you should treat it as some floating point value. Unlike the name |
132 | on it, you should treat it as some floating point value. Unlike the name |
119 | component C<stamp> might indicate, it is also used for time differences |
133 | component C<stamp> might indicate, it is also used for time differences |
120 | throughout libev. |
134 | throughout libev. |
121 | |
135 | |
122 | =head1 ERROR HANDLING |
136 | =head1 ERROR HANDLING |
123 | |
137 | |
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298 | If you don't know what event loop to use, use the one returned from this |
312 | If you don't know what event loop to use, use the one returned from this |
299 | function. |
313 | function. |
300 | |
314 | |
301 | Note that this function is I<not> thread-safe, so if you want to use it |
315 | Note that this function is I<not> thread-safe, so if you want to use it |
302 | from multiple threads, you have to lock (note also that this is unlikely, |
316 | from multiple threads, you have to lock (note also that this is unlikely, |
303 | as loops cannot bes hared easily between threads anyway). |
317 | as loops cannot be shared easily between threads anyway). |
304 | |
318 | |
305 | The default loop is the only loop that can handle C<ev_signal> and |
319 | The default loop is the only loop that can handle C<ev_signal> and |
306 | C<ev_child> watchers, and to do this, it always registers a handler |
320 | C<ev_child> watchers, and to do this, it always registers a handler |
307 | for C<SIGCHLD>. If this is a problem for your application you can either |
321 | for C<SIGCHLD>. If this is a problem for your application you can either |
308 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
322 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
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386 | For few fds, this backend is a bit little slower than poll and select, |
400 | For few fds, this backend is a bit little slower than poll and select, |
387 | but it scales phenomenally better. While poll and select usually scale |
401 | but it scales phenomenally better. While poll and select usually scale |
388 | like O(total_fds) where n is the total number of fds (or the highest fd), |
402 | like O(total_fds) where n is the total number of fds (or the highest fd), |
389 | epoll scales either O(1) or O(active_fds). |
403 | epoll scales either O(1) or O(active_fds). |
390 | |
404 | |
391 | The epoll syscalls are the most misdesigned of the more advanced event |
405 | The epoll mechanism deserves honorable mention as the most misdesigned |
392 | mechanisms: problems include silently dropping fds, requiring a system |
406 | of the more advanced event mechanisms: mere annoyances include silently |
393 | call per change per fd (and unnecessary guessing of parameters), problems |
407 | dropping file descriptors, requiring a system call per change per file |
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408 | descriptor (and unnecessary guessing of parameters), problems with dup and |
394 | with dup and so on. The biggest issue is fork races, however - if a |
409 | so on. The biggest issue is fork races, however - if a program forks then |
395 | program forks then I<both> parent and child process have to recreate the |
410 | I<both> parent and child process have to recreate the epoll set, which can |
396 | epoll set, which can take considerable time (one syscall per fd) and is of |
411 | take considerable time (one syscall per file descriptor) and is of course |
397 | course hard to detect. |
412 | hard to detect. |
398 | |
413 | |
399 | Epoll is also notoriously buggy - embedding epoll fds should work, but |
414 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
400 | of course doesn't, and epoll just loves to report events for totally |
415 | of course I<doesn't>, and epoll just loves to report events for totally |
401 | I<different> file descriptors (even already closed ones, so one cannot |
416 | I<different> file descriptors (even already closed ones, so one cannot |
402 | even remove them from the set) than registered in the set (especially |
417 | even remove them from the set) than registered in the set (especially |
403 | on SMP systems). Libev tries to counter these spurious notifications by |
418 | on SMP systems). Libev tries to counter these spurious notifications by |
404 | employing an additional generation counter and comparing that against the |
419 | employing an additional generation counter and comparing that against the |
405 | events to filter out spurious ones. |
420 | events to filter out spurious ones, recreating the set when required. |
406 | |
421 | |
407 | While stopping, setting and starting an I/O watcher in the same iteration |
422 | While stopping, setting and starting an I/O watcher in the same iteration |
408 | will result in some caching, there is still a system call per such incident |
423 | will result in some caching, there is still a system call per such |
409 | (because the fd could point to a different file description now), so its |
424 | incident (because the same I<file descriptor> could point to a different |
410 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
425 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
411 | very well if you register events for both fds. |
426 | file descriptors might not work very well if you register events for both |
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427 | file descriptors. |
412 | |
428 | |
413 | Best performance from this backend is achieved by not unregistering all |
429 | Best performance from this backend is achieved by not unregistering all |
414 | watchers for a file descriptor until it has been closed, if possible, |
430 | watchers for a file descriptor until it has been closed, if possible, |
415 | i.e. keep at least one watcher active per fd at all times. Stopping and |
431 | i.e. keep at least one watcher active per fd at all times. Stopping and |
416 | starting a watcher (without re-setting it) also usually doesn't cause |
432 | starting a watcher (without re-setting it) also usually doesn't cause |
417 | extra overhead. A fork can both result in spurious notifications as well |
433 | extra overhead. A fork can both result in spurious notifications as well |
418 | as in libev having to destroy and recreate the epoll object, which can |
434 | as in libev having to destroy and recreate the epoll object, which can |
419 | take considerable time and thus should be avoided. |
435 | take considerable time and thus should be avoided. |
420 | |
436 | |
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437 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
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438 | faster than epoll for maybe up to a hundred file descriptors, depending on |
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439 | the usage. So sad. |
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440 | |
421 | While nominally embeddable in other event loops, this feature is broken in |
441 | While nominally embeddable in other event loops, this feature is broken in |
422 | all kernel versions tested so far. |
442 | all kernel versions tested so far. |
423 | |
443 | |
424 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
444 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
425 | C<EVBACKEND_POLL>. |
445 | C<EVBACKEND_POLL>. |
426 | |
446 | |
427 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
447 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
428 | |
448 | |
429 | Kqueue deserves special mention, as at the time of this writing, it was |
449 | Kqueue deserves special mention, as at the time of this writing, it |
430 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
450 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
431 | anything but sockets and pipes, except on Darwin, where of course it's |
451 | with anything but sockets and pipes, except on Darwin, where of course |
432 | completely useless). For this reason it's not being "auto-detected" unless |
452 | it's completely useless). Unlike epoll, however, whose brokenness |
433 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
453 | is by design, these kqueue bugs can (and eventually will) be fixed |
434 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
454 | without API changes to existing programs. For this reason it's not being |
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455 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
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456 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
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457 | system like NetBSD. |
435 | |
458 | |
436 | You still can embed kqueue into a normal poll or select backend and use it |
459 | You still can embed kqueue into a normal poll or select backend and use it |
437 | only for sockets (after having made sure that sockets work with kqueue on |
460 | only for sockets (after having made sure that sockets work with kqueue on |
438 | the target platform). See C<ev_embed> watchers for more info. |
461 | the target platform). See C<ev_embed> watchers for more info. |
439 | |
462 | |
… | |
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449 | |
472 | |
450 | While nominally embeddable in other event loops, this doesn't work |
473 | While nominally embeddable in other event loops, this doesn't work |
451 | everywhere, so you might need to test for this. And since it is broken |
474 | everywhere, so you might need to test for this. And since it is broken |
452 | almost everywhere, you should only use it when you have a lot of sockets |
475 | almost everywhere, you should only use it when you have a lot of sockets |
453 | (for which it usually works), by embedding it into another event loop |
476 | (for which it usually works), by embedding it into another event loop |
454 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
477 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
455 | using it only for sockets. |
478 | also broken on OS X)) and, did I mention it, using it only for sockets. |
456 | |
479 | |
457 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
480 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
458 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
481 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
459 | C<NOTE_EOF>. |
482 | C<NOTE_EOF>. |
460 | |
483 | |
… | |
… | |
621 | |
644 | |
622 | This function is rarely useful, but when some event callback runs for a |
645 | This function is rarely useful, but when some event callback runs for a |
623 | very long time without entering the event loop, updating libev's idea of |
646 | very long time without entering the event loop, updating libev's idea of |
624 | the current time is a good idea. |
647 | the current time is a good idea. |
625 | |
648 | |
626 | See also "The special problem of time updates" in the C<ev_timer> section. |
649 | See also L<The special problem of time updates> in the C<ev_timer> section. |
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650 | |
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651 | =item ev_suspend (loop) |
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652 | |
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653 | =item ev_resume (loop) |
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654 | |
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655 | These two functions suspend and resume a loop, for use when the loop is |
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656 | not used for a while and timeouts should not be processed. |
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657 | |
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658 | A typical use case would be an interactive program such as a game: When |
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659 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
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660 | would be best to handle timeouts as if no time had actually passed while |
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661 | the program was suspended. This can be achieved by calling C<ev_suspend> |
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662 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
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663 | C<ev_resume> directly afterwards to resume timer processing. |
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664 | |
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665 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
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666 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
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667 | will be rescheduled (that is, they will lose any events that would have |
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668 | occured while suspended). |
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669 | |
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670 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
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671 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
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672 | without a previous call to C<ev_suspend>. |
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673 | |
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674 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
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675 | event loop time (see C<ev_now_update>). |
627 | |
676 | |
628 | =item ev_loop (loop, int flags) |
677 | =item ev_loop (loop, int flags) |
629 | |
678 | |
630 | Finally, this is it, the event handler. This function usually is called |
679 | Finally, this is it, the event handler. This function usually is called |
631 | after you initialised all your watchers and you want to start handling |
680 | after you initialised all your watchers and you want to start handling |
… | |
… | |
647 | the loop. |
696 | the loop. |
648 | |
697 | |
649 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
698 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
650 | necessary) and will handle those and any already outstanding ones. It |
699 | necessary) and will handle those and any already outstanding ones. It |
651 | will block your process until at least one new event arrives (which could |
700 | will block your process until at least one new event arrives (which could |
652 | be an event internal to libev itself, so there is no guarentee that a |
701 | be an event internal to libev itself, so there is no guarantee that a |
653 | user-registered callback will be called), and will return after one |
702 | user-registered callback will be called), and will return after one |
654 | iteration of the loop. |
703 | iteration of the loop. |
655 | |
704 | |
656 | This is useful if you are waiting for some external event in conjunction |
705 | This is useful if you are waiting for some external event in conjunction |
657 | with something not expressible using other libev watchers (i.e. "roll your |
706 | with something not expressible using other libev watchers (i.e. "roll your |
… | |
… | |
715 | |
764 | |
716 | If you have a watcher you never unregister that should not keep C<ev_loop> |
765 | If you have a watcher you never unregister that should not keep C<ev_loop> |
717 | from returning, call ev_unref() after starting, and ev_ref() before |
766 | from returning, call ev_unref() after starting, and ev_ref() before |
718 | stopping it. |
767 | stopping it. |
719 | |
768 | |
720 | As an example, libev itself uses this for its internal signal pipe: It is |
769 | As an example, libev itself uses this for its internal signal pipe: It |
721 | not visible to the libev user and should not keep C<ev_loop> from exiting |
770 | is not visible to the libev user and should not keep C<ev_loop> from |
722 | if no event watchers registered by it are active. It is also an excellent |
771 | exiting if no event watchers registered by it are active. It is also an |
723 | way to do this for generic recurring timers or from within third-party |
772 | excellent way to do this for generic recurring timers or from within |
724 | libraries. Just remember to I<unref after start> and I<ref before stop> |
773 | third-party libraries. Just remember to I<unref after start> and I<ref |
725 | (but only if the watcher wasn't active before, or was active before, |
774 | before stop> (but only if the watcher wasn't active before, or was active |
726 | respectively). |
775 | before, respectively. Note also that libev might stop watchers itself |
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776 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
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777 | in the callback). |
727 | |
778 | |
728 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
779 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
729 | running when nothing else is active. |
780 | running when nothing else is active. |
730 | |
781 | |
731 | ev_signal exitsig; |
782 | ev_signal exitsig; |
… | |
… | |
760 | |
811 | |
761 | By setting a higher I<io collect interval> you allow libev to spend more |
812 | By setting a higher I<io collect interval> you allow libev to spend more |
762 | time collecting I/O events, so you can handle more events per iteration, |
813 | time collecting I/O events, so you can handle more events per iteration, |
763 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
814 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
764 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
815 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
765 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
816 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
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817 | sleep time ensures that libev will not poll for I/O events more often then |
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818 | once per this interval, on average. |
766 | |
819 | |
767 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
820 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
768 | to spend more time collecting timeouts, at the expense of increased |
821 | to spend more time collecting timeouts, at the expense of increased |
769 | latency/jitter/inexactness (the watcher callback will be called |
822 | latency/jitter/inexactness (the watcher callback will be called |
770 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
823 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
772 | |
825 | |
773 | Many (busy) programs can usually benefit by setting the I/O collect |
826 | Many (busy) programs can usually benefit by setting the I/O collect |
774 | interval to a value near C<0.1> or so, which is often enough for |
827 | interval to a value near C<0.1> or so, which is often enough for |
775 | interactive servers (of course not for games), likewise for timeouts. It |
828 | interactive servers (of course not for games), likewise for timeouts. It |
776 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
829 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
777 | as this approaches the timing granularity of most systems. |
830 | as this approaches the timing granularity of most systems. Note that if |
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831 | you do transactions with the outside world and you can't increase the |
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832 | parallelity, then this setting will limit your transaction rate (if you |
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833 | need to poll once per transaction and the I/O collect interval is 0.01, |
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834 | then you can't do more than 100 transations per second). |
778 | |
835 | |
779 | Setting the I<timeout collect interval> can improve the opportunity for |
836 | Setting the I<timeout collect interval> can improve the opportunity for |
780 | saving power, as the program will "bundle" timer callback invocations that |
837 | saving power, as the program will "bundle" timer callback invocations that |
781 | are "near" in time together, by delaying some, thus reducing the number of |
838 | are "near" in time together, by delaying some, thus reducing the number of |
782 | times the process sleeps and wakes up again. Another useful technique to |
839 | times the process sleeps and wakes up again. Another useful technique to |
783 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
840 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
784 | they fire on, say, one-second boundaries only. |
841 | they fire on, say, one-second boundaries only. |
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842 | |
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843 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
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844 | more often than 100 times per second: |
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845 | |
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846 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
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847 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
785 | |
848 | |
786 | =item ev_loop_verify (loop) |
849 | =item ev_loop_verify (loop) |
787 | |
850 | |
788 | This function only does something when C<EV_VERIFY> support has been |
851 | This function only does something when C<EV_VERIFY> support has been |
789 | compiled in, which is the default for non-minimal builds. It tries to go |
852 | compiled in, which is the default for non-minimal builds. It tries to go |
… | |
… | |
915 | |
978 | |
916 | =item C<EV_ASYNC> |
979 | =item C<EV_ASYNC> |
917 | |
980 | |
918 | The given async watcher has been asynchronously notified (see C<ev_async>). |
981 | The given async watcher has been asynchronously notified (see C<ev_async>). |
919 | |
982 | |
|
|
983 | =item C<EV_CUSTOM> |
|
|
984 | |
|
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985 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
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986 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
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987 | |
920 | =item C<EV_ERROR> |
988 | =item C<EV_ERROR> |
921 | |
989 | |
922 | An unspecified error has occurred, the watcher has been stopped. This might |
990 | An unspecified error has occurred, the watcher has been stopped. This might |
923 | happen because the watcher could not be properly started because libev |
991 | happen because the watcher could not be properly started because libev |
924 | ran out of memory, a file descriptor was found to be closed or any other |
992 | ran out of memory, a file descriptor was found to be closed or any other |
… | |
… | |
1039 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1107 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1040 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1108 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1041 | before watchers with lower priority, but priority will not keep watchers |
1109 | before watchers with lower priority, but priority will not keep watchers |
1042 | from being executed (except for C<ev_idle> watchers). |
1110 | from being executed (except for C<ev_idle> watchers). |
1043 | |
1111 | |
1044 | This means that priorities are I<only> used for ordering callback |
|
|
1045 | invocation after new events have been received. This is useful, for |
|
|
1046 | example, to reduce latency after idling, or more often, to bind two |
|
|
1047 | watchers on the same event and make sure one is called first. |
|
|
1048 | |
|
|
1049 | If you need to suppress invocation when higher priority events are pending |
1112 | If you need to suppress invocation when higher priority events are pending |
1050 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1113 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1051 | |
1114 | |
1052 | You I<must not> change the priority of a watcher as long as it is active or |
1115 | You I<must not> change the priority of a watcher as long as it is active or |
1053 | pending. |
1116 | pending. |
1054 | |
|
|
1055 | The default priority used by watchers when no priority has been set is |
|
|
1056 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1057 | |
1117 | |
1058 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1118 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1059 | fine, as long as you do not mind that the priority value you query might |
1119 | fine, as long as you do not mind that the priority value you query might |
1060 | or might not have been clamped to the valid range. |
1120 | or might not have been clamped to the valid range. |
|
|
1121 | |
|
|
1122 | The default priority used by watchers when no priority has been set is |
|
|
1123 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1124 | |
|
|
1125 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1126 | priorities. |
1061 | |
1127 | |
1062 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1128 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1063 | |
1129 | |
1064 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1130 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1065 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1131 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1130 | #include <stddef.h> |
1196 | #include <stddef.h> |
1131 | |
1197 | |
1132 | static void |
1198 | static void |
1133 | t1_cb (EV_P_ ev_timer *w, int revents) |
1199 | t1_cb (EV_P_ ev_timer *w, int revents) |
1134 | { |
1200 | { |
1135 | struct my_biggy big = (struct my_biggy * |
1201 | struct my_biggy big = (struct my_biggy *) |
1136 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1202 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1137 | } |
1203 | } |
1138 | |
1204 | |
1139 | static void |
1205 | static void |
1140 | t2_cb (EV_P_ ev_timer *w, int revents) |
1206 | t2_cb (EV_P_ ev_timer *w, int revents) |
1141 | { |
1207 | { |
1142 | struct my_biggy big = (struct my_biggy * |
1208 | struct my_biggy big = (struct my_biggy *) |
1143 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1209 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1144 | } |
1210 | } |
|
|
1211 | |
|
|
1212 | =head2 WATCHER PRIORITY MODELS |
|
|
1213 | |
|
|
1214 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1215 | integers that influence the ordering of event callback invocation |
|
|
1216 | between watchers in some way, all else being equal. |
|
|
1217 | |
|
|
1218 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1219 | description for the more technical details such as the actual priority |
|
|
1220 | range. |
|
|
1221 | |
|
|
1222 | There are two common ways how these these priorities are being interpreted |
|
|
1223 | by event loops: |
|
|
1224 | |
|
|
1225 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1226 | of lower priority watchers, which means as long as higher priority |
|
|
1227 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1228 | |
|
|
1229 | The less common only-for-ordering model uses priorities solely to order |
|
|
1230 | callback invocation within a single event loop iteration: Higher priority |
|
|
1231 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1232 | before polling for new events. |
|
|
1233 | |
|
|
1234 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1235 | except for idle watchers (which use the lock-out model). |
|
|
1236 | |
|
|
1237 | The rationale behind this is that implementing the lock-out model for |
|
|
1238 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1239 | libraries will just poll for the same events again and again as long as |
|
|
1240 | their callbacks have not been executed, which is very inefficient in the |
|
|
1241 | common case of one high-priority watcher locking out a mass of lower |
|
|
1242 | priority ones. |
|
|
1243 | |
|
|
1244 | Static (ordering) priorities are most useful when you have two or more |
|
|
1245 | watchers handling the same resource: a typical usage example is having an |
|
|
1246 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1247 | timeouts. Under load, data might be received while the program handles |
|
|
1248 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1249 | handler will be executed before checking for data. In that case, giving |
|
|
1250 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1251 | handled first even under adverse conditions (which is usually, but not |
|
|
1252 | always, what you want). |
|
|
1253 | |
|
|
1254 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1255 | will only be executed when no same or higher priority watchers have |
|
|
1256 | received events, they can be used to implement the "lock-out" model when |
|
|
1257 | required. |
|
|
1258 | |
|
|
1259 | For example, to emulate how many other event libraries handle priorities, |
|
|
1260 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1261 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1262 | processing is done in the idle watcher callback. This causes libev to |
|
|
1263 | continously poll and process kernel event data for the watcher, but when |
|
|
1264 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1265 | workable. |
|
|
1266 | |
|
|
1267 | Usually, however, the lock-out model implemented that way will perform |
|
|
1268 | miserably under the type of load it was designed to handle. In that case, |
|
|
1269 | it might be preferable to stop the real watcher before starting the |
|
|
1270 | idle watcher, so the kernel will not have to process the event in case |
|
|
1271 | the actual processing will be delayed for considerable time. |
|
|
1272 | |
|
|
1273 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1274 | priority than the default, and which should only process data when no |
|
|
1275 | other events are pending: |
|
|
1276 | |
|
|
1277 | ev_idle idle; // actual processing watcher |
|
|
1278 | ev_io io; // actual event watcher |
|
|
1279 | |
|
|
1280 | static void |
|
|
1281 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1282 | { |
|
|
1283 | // stop the I/O watcher, we received the event, but |
|
|
1284 | // are not yet ready to handle it. |
|
|
1285 | ev_io_stop (EV_A_ w); |
|
|
1286 | |
|
|
1287 | // start the idle watcher to ahndle the actual event. |
|
|
1288 | // it will not be executed as long as other watchers |
|
|
1289 | // with the default priority are receiving events. |
|
|
1290 | ev_idle_start (EV_A_ &idle); |
|
|
1291 | } |
|
|
1292 | |
|
|
1293 | static void |
|
|
1294 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1295 | { |
|
|
1296 | // actual processing |
|
|
1297 | read (STDIN_FILENO, ...); |
|
|
1298 | |
|
|
1299 | // have to start the I/O watcher again, as |
|
|
1300 | // we have handled the event |
|
|
1301 | ev_io_start (EV_P_ &io); |
|
|
1302 | } |
|
|
1303 | |
|
|
1304 | // initialisation |
|
|
1305 | ev_idle_init (&idle, idle_cb); |
|
|
1306 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1307 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1308 | |
|
|
1309 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1310 | low-priority connections can not be locked out forever under load. This |
|
|
1311 | enables your program to keep a lower latency for important connections |
|
|
1312 | during short periods of high load, while not completely locking out less |
|
|
1313 | important ones. |
1145 | |
1314 | |
1146 | |
1315 | |
1147 | =head1 WATCHER TYPES |
1316 | =head1 WATCHER TYPES |
1148 | |
1317 | |
1149 | This section describes each watcher in detail, but will not repeat |
1318 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1175 | descriptors to non-blocking mode is also usually a good idea (but not |
1344 | descriptors to non-blocking mode is also usually a good idea (but not |
1176 | required if you know what you are doing). |
1345 | required if you know what you are doing). |
1177 | |
1346 | |
1178 | If you cannot use non-blocking mode, then force the use of a |
1347 | If you cannot use non-blocking mode, then force the use of a |
1179 | known-to-be-good backend (at the time of this writing, this includes only |
1348 | known-to-be-good backend (at the time of this writing, this includes only |
1180 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1349 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1350 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1351 | files) - libev doesn't guarentee any specific behaviour in that case. |
1181 | |
1352 | |
1182 | Another thing you have to watch out for is that it is quite easy to |
1353 | Another thing you have to watch out for is that it is quite easy to |
1183 | receive "spurious" readiness notifications, that is your callback might |
1354 | receive "spurious" readiness notifications, that is your callback might |
1184 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1355 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1185 | because there is no data. Not only are some backends known to create a |
1356 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1306 | year, it will still time out after (roughly) one hour. "Roughly" because |
1477 | year, it will still time out after (roughly) one hour. "Roughly" because |
1307 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1478 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1308 | monotonic clock option helps a lot here). |
1479 | monotonic clock option helps a lot here). |
1309 | |
1480 | |
1310 | The callback is guaranteed to be invoked only I<after> its timeout has |
1481 | The callback is guaranteed to be invoked only I<after> its timeout has |
1311 | passed, but if multiple timers become ready during the same loop iteration |
1482 | passed (not I<at>, so on systems with very low-resolution clocks this |
1312 | then order of execution is undefined. |
1483 | might introduce a small delay). If multiple timers become ready during the |
|
|
1484 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1485 | before ones with later time-out values (but this is no longer true when a |
|
|
1486 | callback calls C<ev_loop> recursively). |
1313 | |
1487 | |
1314 | =head3 Be smart about timeouts |
1488 | =head3 Be smart about timeouts |
1315 | |
1489 | |
1316 | Many real-world problems involve some kind of timeout, usually for error |
1490 | Many real-world problems involve some kind of timeout, usually for error |
1317 | recovery. A typical example is an HTTP request - if the other side hangs, |
1491 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1361 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1535 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1362 | member and C<ev_timer_again>. |
1536 | member and C<ev_timer_again>. |
1363 | |
1537 | |
1364 | At start: |
1538 | At start: |
1365 | |
1539 | |
1366 | ev_timer_init (timer, callback); |
1540 | ev_init (timer, callback); |
1367 | timer->repeat = 60.; |
1541 | timer->repeat = 60.; |
1368 | ev_timer_again (loop, timer); |
1542 | ev_timer_again (loop, timer); |
1369 | |
1543 | |
1370 | Each time there is some activity: |
1544 | Each time there is some activity: |
1371 | |
1545 | |
… | |
… | |
1410 | else |
1584 | else |
1411 | { |
1585 | { |
1412 | // callback was invoked, but there was some activity, re-arm |
1586 | // callback was invoked, but there was some activity, re-arm |
1413 | // the watcher to fire in last_activity + 60, which is |
1587 | // the watcher to fire in last_activity + 60, which is |
1414 | // guaranteed to be in the future, so "again" is positive: |
1588 | // guaranteed to be in the future, so "again" is positive: |
1415 | w->again = timeout - now; |
1589 | w->repeat = timeout - now; |
1416 | ev_timer_again (EV_A_ w); |
1590 | ev_timer_again (EV_A_ w); |
1417 | } |
1591 | } |
1418 | } |
1592 | } |
1419 | |
1593 | |
1420 | To summarise the callback: first calculate the real timeout (defined |
1594 | To summarise the callback: first calculate the real timeout (defined |
… | |
… | |
1433 | |
1607 | |
1434 | To start the timer, simply initialise the watcher and set C<last_activity> |
1608 | To start the timer, simply initialise the watcher and set C<last_activity> |
1435 | to the current time (meaning we just have some activity :), then call the |
1609 | to the current time (meaning we just have some activity :), then call the |
1436 | callback, which will "do the right thing" and start the timer: |
1610 | callback, which will "do the right thing" and start the timer: |
1437 | |
1611 | |
1438 | ev_timer_init (timer, callback); |
1612 | ev_init (timer, callback); |
1439 | last_activity = ev_now (loop); |
1613 | last_activity = ev_now (loop); |
1440 | callback (loop, timer, EV_TIMEOUT); |
1614 | callback (loop, timer, EV_TIMEOUT); |
1441 | |
1615 | |
1442 | And when there is some activity, simply store the current time in |
1616 | And when there is some activity, simply store the current time in |
1443 | C<last_activity>, no libev calls at all: |
1617 | C<last_activity>, no libev calls at all: |
… | |
… | |
1536 | If the timer is started but non-repeating, stop it (as if it timed out). |
1710 | If the timer is started but non-repeating, stop it (as if it timed out). |
1537 | |
1711 | |
1538 | If the timer is repeating, either start it if necessary (with the |
1712 | If the timer is repeating, either start it if necessary (with the |
1539 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1713 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1540 | |
1714 | |
1541 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1715 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1542 | usage example. |
1716 | usage example. |
1543 | |
1717 | |
1544 | =item ev_tstamp repeat [read-write] |
1718 | =item ev_tstamp repeat [read-write] |
1545 | |
1719 | |
1546 | The current C<repeat> value. Will be used each time the watcher times out |
1720 | The current C<repeat> value. Will be used each time the watcher times out |
… | |
… | |
1585 | =head2 C<ev_periodic> - to cron or not to cron? |
1759 | =head2 C<ev_periodic> - to cron or not to cron? |
1586 | |
1760 | |
1587 | Periodic watchers are also timers of a kind, but they are very versatile |
1761 | Periodic watchers are also timers of a kind, but they are very versatile |
1588 | (and unfortunately a bit complex). |
1762 | (and unfortunately a bit complex). |
1589 | |
1763 | |
1590 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1764 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1591 | but on wall clock time (absolute time). You can tell a periodic watcher |
1765 | relative time, the physical time that passes) but on wall clock time |
1592 | to trigger after some specific point in time. For example, if you tell a |
1766 | (absolute time, the thing you can read on your calender or clock). The |
1593 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1767 | difference is that wall clock time can run faster or slower than real |
1594 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1768 | time, and time jumps are not uncommon (e.g. when you adjust your |
1595 | clock to January of the previous year, then it will take more than year |
1769 | wrist-watch). |
1596 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1597 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1598 | |
1770 | |
|
|
1771 | You can tell a periodic watcher to trigger after some specific point |
|
|
1772 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1773 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1774 | not a delay) and then reset your system clock to January of the previous |
|
|
1775 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1776 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1777 | it, as it uses a relative timeout). |
|
|
1778 | |
1599 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1779 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1600 | such as triggering an event on each "midnight, local time", or other |
1780 | timers, such as triggering an event on each "midnight, local time", or |
1601 | complicated rules. |
1781 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1782 | those cannot react to time jumps. |
1602 | |
1783 | |
1603 | As with timers, the callback is guaranteed to be invoked only when the |
1784 | As with timers, the callback is guaranteed to be invoked only when the |
1604 | time (C<at>) has passed, but if multiple periodic timers become ready |
1785 | point in time where it is supposed to trigger has passed. If multiple |
1605 | during the same loop iteration, then order of execution is undefined. |
1786 | timers become ready during the same loop iteration then the ones with |
|
|
1787 | earlier time-out values are invoked before ones with later time-out values |
|
|
1788 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1606 | |
1789 | |
1607 | =head3 Watcher-Specific Functions and Data Members |
1790 | =head3 Watcher-Specific Functions and Data Members |
1608 | |
1791 | |
1609 | =over 4 |
1792 | =over 4 |
1610 | |
1793 | |
1611 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1794 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1612 | |
1795 | |
1613 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1796 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1614 | |
1797 | |
1615 | Lots of arguments, lets sort it out... There are basically three modes of |
1798 | Lots of arguments, let's sort it out... There are basically three modes of |
1616 | operation, and we will explain them from simplest to most complex: |
1799 | operation, and we will explain them from simplest to most complex: |
1617 | |
1800 | |
1618 | =over 4 |
1801 | =over 4 |
1619 | |
1802 | |
1620 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1803 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1621 | |
1804 | |
1622 | In this configuration the watcher triggers an event after the wall clock |
1805 | In this configuration the watcher triggers an event after the wall clock |
1623 | time C<at> has passed. It will not repeat and will not adjust when a time |
1806 | time C<offset> has passed. It will not repeat and will not adjust when a |
1624 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1807 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1625 | only run when the system clock reaches or surpasses this time. |
1808 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1809 | this point in time. |
1626 | |
1810 | |
1627 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1811 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1628 | |
1812 | |
1629 | In this mode the watcher will always be scheduled to time out at the next |
1813 | In this mode the watcher will always be scheduled to time out at the next |
1630 | C<at + N * interval> time (for some integer N, which can also be negative) |
1814 | C<offset + N * interval> time (for some integer N, which can also be |
1631 | and then repeat, regardless of any time jumps. |
1815 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1816 | argument is merely an offset into the C<interval> periods. |
1632 | |
1817 | |
1633 | This can be used to create timers that do not drift with respect to the |
1818 | This can be used to create timers that do not drift with respect to the |
1634 | system clock, for example, here is a C<ev_periodic> that triggers each |
1819 | system clock, for example, here is an C<ev_periodic> that triggers each |
1635 | hour, on the hour: |
1820 | hour, on the hour (with respect to UTC): |
1636 | |
1821 | |
1637 | ev_periodic_set (&periodic, 0., 3600., 0); |
1822 | ev_periodic_set (&periodic, 0., 3600., 0); |
1638 | |
1823 | |
1639 | This doesn't mean there will always be 3600 seconds in between triggers, |
1824 | This doesn't mean there will always be 3600 seconds in between triggers, |
1640 | but only that the callback will be called when the system time shows a |
1825 | but only that the callback will be called when the system time shows a |
1641 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1826 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1642 | by 3600. |
1827 | by 3600. |
1643 | |
1828 | |
1644 | Another way to think about it (for the mathematically inclined) is that |
1829 | Another way to think about it (for the mathematically inclined) is that |
1645 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1830 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1646 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1831 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1647 | |
1832 | |
1648 | For numerical stability it is preferable that the C<at> value is near |
1833 | For numerical stability it is preferable that the C<offset> value is near |
1649 | C<ev_now ()> (the current time), but there is no range requirement for |
1834 | C<ev_now ()> (the current time), but there is no range requirement for |
1650 | this value, and in fact is often specified as zero. |
1835 | this value, and in fact is often specified as zero. |
1651 | |
1836 | |
1652 | Note also that there is an upper limit to how often a timer can fire (CPU |
1837 | Note also that there is an upper limit to how often a timer can fire (CPU |
1653 | speed for example), so if C<interval> is very small then timing stability |
1838 | speed for example), so if C<interval> is very small then timing stability |
1654 | will of course deteriorate. Libev itself tries to be exact to be about one |
1839 | will of course deteriorate. Libev itself tries to be exact to be about one |
1655 | millisecond (if the OS supports it and the machine is fast enough). |
1840 | millisecond (if the OS supports it and the machine is fast enough). |
1656 | |
1841 | |
1657 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1842 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1658 | |
1843 | |
1659 | In this mode the values for C<interval> and C<at> are both being |
1844 | In this mode the values for C<interval> and C<offset> are both being |
1660 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1845 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1661 | reschedule callback will be called with the watcher as first, and the |
1846 | reschedule callback will be called with the watcher as first, and the |
1662 | current time as second argument. |
1847 | current time as second argument. |
1663 | |
1848 | |
1664 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1849 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1665 | ever, or make ANY event loop modifications whatsoever>. |
1850 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1851 | allowed by documentation here>. |
1666 | |
1852 | |
1667 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1853 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1668 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1854 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1669 | only event loop modification you are allowed to do). |
1855 | only event loop modification you are allowed to do). |
1670 | |
1856 | |
… | |
… | |
1700 | a different time than the last time it was called (e.g. in a crond like |
1886 | a different time than the last time it was called (e.g. in a crond like |
1701 | program when the crontabs have changed). |
1887 | program when the crontabs have changed). |
1702 | |
1888 | |
1703 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1889 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1704 | |
1890 | |
1705 | When active, returns the absolute time that the watcher is supposed to |
1891 | When active, returns the absolute time that the watcher is supposed |
1706 | trigger next. |
1892 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1893 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1894 | rescheduling modes. |
1707 | |
1895 | |
1708 | =item ev_tstamp offset [read-write] |
1896 | =item ev_tstamp offset [read-write] |
1709 | |
1897 | |
1710 | When repeating, this contains the offset value, otherwise this is the |
1898 | When repeating, this contains the offset value, otherwise this is the |
1711 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1899 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1900 | although libev might modify this value for better numerical stability). |
1712 | |
1901 | |
1713 | Can be modified any time, but changes only take effect when the periodic |
1902 | Can be modified any time, but changes only take effect when the periodic |
1714 | timer fires or C<ev_periodic_again> is being called. |
1903 | timer fires or C<ev_periodic_again> is being called. |
1715 | |
1904 | |
1716 | =item ev_tstamp interval [read-write] |
1905 | =item ev_tstamp interval [read-write] |
… | |
… | |
1825 | some child status changes (most typically when a child of yours dies or |
2014 | some child status changes (most typically when a child of yours dies or |
1826 | exits). It is permissible to install a child watcher I<after> the child |
2015 | exits). It is permissible to install a child watcher I<after> the child |
1827 | has been forked (which implies it might have already exited), as long |
2016 | has been forked (which implies it might have already exited), as long |
1828 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2017 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1829 | forking and then immediately registering a watcher for the child is fine, |
2018 | forking and then immediately registering a watcher for the child is fine, |
1830 | but forking and registering a watcher a few event loop iterations later is |
2019 | but forking and registering a watcher a few event loop iterations later or |
1831 | not. |
2020 | in the next callback invocation is not. |
1832 | |
2021 | |
1833 | Only the default event loop is capable of handling signals, and therefore |
2022 | Only the default event loop is capable of handling signals, and therefore |
1834 | you can only register child watchers in the default event loop. |
2023 | you can only register child watchers in the default event loop. |
1835 | |
2024 | |
1836 | =head3 Process Interaction |
2025 | =head3 Process Interaction |
… | |
… | |
1927 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2116 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1928 | and sees if it changed compared to the last time, invoking the callback if |
2117 | and sees if it changed compared to the last time, invoking the callback if |
1929 | it did. |
2118 | it did. |
1930 | |
2119 | |
1931 | The path does not need to exist: changing from "path exists" to "path does |
2120 | The path does not need to exist: changing from "path exists" to "path does |
1932 | not exist" is a status change like any other. The condition "path does |
2121 | not exist" is a status change like any other. The condition "path does not |
1933 | not exist" is signified by the C<st_nlink> field being zero (which is |
2122 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1934 | otherwise always forced to be at least one) and all the other fields of |
2123 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1935 | the stat buffer having unspecified contents. |
2124 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2125 | contents. |
1936 | |
2126 | |
1937 | The path I<must not> end in a slash or contain special components such as |
2127 | The path I<must not> end in a slash or contain special components such as |
1938 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
2128 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1939 | your working directory changes, then the behaviour is undefined. |
2129 | your working directory changes, then the behaviour is undefined. |
1940 | |
2130 | |
… | |
… | |
1943 | to see if it changed somehow. You can specify a recommended polling |
2133 | to see if it changed somehow. You can specify a recommended polling |
1944 | interval for this case. If you specify a polling interval of C<0> (highly |
2134 | interval for this case. If you specify a polling interval of C<0> (highly |
1945 | recommended!) then a I<suitable, unspecified default> value will be used |
2135 | recommended!) then a I<suitable, unspecified default> value will be used |
1946 | (which you can expect to be around five seconds, although this might |
2136 | (which you can expect to be around five seconds, although this might |
1947 | change dynamically). Libev will also impose a minimum interval which is |
2137 | change dynamically). Libev will also impose a minimum interval which is |
1948 | currently around C<0.1>, but thats usually overkill. |
2138 | currently around C<0.1>, but that's usually overkill. |
1949 | |
2139 | |
1950 | This watcher type is not meant for massive numbers of stat watchers, |
2140 | This watcher type is not meant for massive numbers of stat watchers, |
1951 | as even with OS-supported change notifications, this can be |
2141 | as even with OS-supported change notifications, this can be |
1952 | resource-intensive. |
2142 | resource-intensive. |
1953 | |
2143 | |
1954 | At the time of this writing, the only OS-specific interface implemented |
2144 | At the time of this writing, the only OS-specific interface implemented |
1955 | is the Linux inotify interface (implementing kqueue support is left as |
2145 | is the Linux inotify interface (implementing kqueue support is left as an |
1956 | an exercise for the reader. Note, however, that the author sees no way |
2146 | exercise for the reader. Note, however, that the author sees no way of |
1957 | of implementing C<ev_stat> semantics with kqueue). |
2147 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1958 | |
2148 | |
1959 | =head3 ABI Issues (Largefile Support) |
2149 | =head3 ABI Issues (Largefile Support) |
1960 | |
2150 | |
1961 | Libev by default (unless the user overrides this) uses the default |
2151 | Libev by default (unless the user overrides this) uses the default |
1962 | compilation environment, which means that on systems with large file |
2152 | compilation environment, which means that on systems with large file |
… | |
… | |
1973 | to exchange stat structures with application programs compiled using the |
2163 | to exchange stat structures with application programs compiled using the |
1974 | default compilation environment. |
2164 | default compilation environment. |
1975 | |
2165 | |
1976 | =head3 Inotify and Kqueue |
2166 | =head3 Inotify and Kqueue |
1977 | |
2167 | |
1978 | When C<inotify (7)> support has been compiled into libev (generally |
2168 | When C<inotify (7)> support has been compiled into libev and present at |
1979 | only available with Linux 2.6.25 or above due to bugs in earlier |
2169 | runtime, it will be used to speed up change detection where possible. The |
1980 | implementations) and present at runtime, it will be used to speed up |
2170 | inotify descriptor will be created lazily when the first C<ev_stat> |
1981 | change detection where possible. The inotify descriptor will be created |
2171 | watcher is being started. |
1982 | lazily when the first C<ev_stat> watcher is being started. |
|
|
1983 | |
2172 | |
1984 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2173 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1985 | except that changes might be detected earlier, and in some cases, to avoid |
2174 | except that changes might be detected earlier, and in some cases, to avoid |
1986 | making regular C<stat> calls. Even in the presence of inotify support |
2175 | making regular C<stat> calls. Even in the presence of inotify support |
1987 | there are many cases where libev has to resort to regular C<stat> polling, |
2176 | there are many cases where libev has to resort to regular C<stat> polling, |
1988 | but as long as the path exists, libev usually gets away without polling. |
2177 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2178 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2179 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2180 | xfs are fully working) libev usually gets away without polling. |
1989 | |
2181 | |
1990 | There is no support for kqueue, as apparently it cannot be used to |
2182 | There is no support for kqueue, as apparently it cannot be used to |
1991 | implement this functionality, due to the requirement of having a file |
2183 | implement this functionality, due to the requirement of having a file |
1992 | descriptor open on the object at all times, and detecting renames, unlinks |
2184 | descriptor open on the object at all times, and detecting renames, unlinks |
1993 | etc. is difficult. |
2185 | etc. is difficult. |
|
|
2186 | |
|
|
2187 | =head3 C<stat ()> is a synchronous operation |
|
|
2188 | |
|
|
2189 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2190 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2191 | ()>, which is a synchronous operation. |
|
|
2192 | |
|
|
2193 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2194 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2195 | as the path data is usually in memory already (except when starting the |
|
|
2196 | watcher). |
|
|
2197 | |
|
|
2198 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2199 | time due to network issues, and even under good conditions, a stat call |
|
|
2200 | often takes multiple milliseconds. |
|
|
2201 | |
|
|
2202 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2203 | paths, although this is fully supported by libev. |
1994 | |
2204 | |
1995 | =head3 The special problem of stat time resolution |
2205 | =head3 The special problem of stat time resolution |
1996 | |
2206 | |
1997 | The C<stat ()> system call only supports full-second resolution portably, |
2207 | The C<stat ()> system call only supports full-second resolution portably, |
1998 | and even on systems where the resolution is higher, most file systems |
2208 | and even on systems where the resolution is higher, most file systems |
… | |
… | |
2147 | |
2357 | |
2148 | =head3 Watcher-Specific Functions and Data Members |
2358 | =head3 Watcher-Specific Functions and Data Members |
2149 | |
2359 | |
2150 | =over 4 |
2360 | =over 4 |
2151 | |
2361 | |
2152 | =item ev_idle_init (ev_signal *, callback) |
2362 | =item ev_idle_init (ev_idle *, callback) |
2153 | |
2363 | |
2154 | Initialises and configures the idle watcher - it has no parameters of any |
2364 | Initialises and configures the idle watcher - it has no parameters of any |
2155 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2365 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2156 | believe me. |
2366 | believe me. |
2157 | |
2367 | |
… | |
… | |
2170 | // no longer anything immediate to do. |
2380 | // no longer anything immediate to do. |
2171 | } |
2381 | } |
2172 | |
2382 | |
2173 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2383 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2174 | ev_idle_init (idle_watcher, idle_cb); |
2384 | ev_idle_init (idle_watcher, idle_cb); |
2175 | ev_idle_start (loop, idle_cb); |
2385 | ev_idle_start (loop, idle_watcher); |
2176 | |
2386 | |
2177 | |
2387 | |
2178 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2388 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2179 | |
2389 | |
2180 | Prepare and check watchers are usually (but not always) used in pairs: |
2390 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2273 | struct pollfd fds [nfd]; |
2483 | struct pollfd fds [nfd]; |
2274 | // actual code will need to loop here and realloc etc. |
2484 | // actual code will need to loop here and realloc etc. |
2275 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2485 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2276 | |
2486 | |
2277 | /* the callback is illegal, but won't be called as we stop during check */ |
2487 | /* the callback is illegal, but won't be called as we stop during check */ |
2278 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2488 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2279 | ev_timer_start (loop, &tw); |
2489 | ev_timer_start (loop, &tw); |
2280 | |
2490 | |
2281 | // create one ev_io per pollfd |
2491 | // create one ev_io per pollfd |
2282 | for (int i = 0; i < nfd; ++i) |
2492 | for (int i = 0; i < nfd; ++i) |
2283 | { |
2493 | { |
… | |
… | |
2396 | some fds have to be watched and handled very quickly (with low latency), |
2606 | some fds have to be watched and handled very quickly (with low latency), |
2397 | and even priorities and idle watchers might have too much overhead. In |
2607 | and even priorities and idle watchers might have too much overhead. In |
2398 | this case you would put all the high priority stuff in one loop and all |
2608 | this case you would put all the high priority stuff in one loop and all |
2399 | the rest in a second one, and embed the second one in the first. |
2609 | the rest in a second one, and embed the second one in the first. |
2400 | |
2610 | |
2401 | As long as the watcher is active, the callback will be invoked every time |
2611 | As long as the watcher is active, the callback will be invoked every |
2402 | there might be events pending in the embedded loop. The callback must then |
2612 | time there might be events pending in the embedded loop. The callback |
2403 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2613 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2404 | their callbacks (you could also start an idle watcher to give the embedded |
2614 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2405 | loop strictly lower priority for example). You can also set the callback |
2615 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2406 | to C<0>, in which case the embed watcher will automatically execute the |
2616 | to give the embedded loop strictly lower priority for example). |
2407 | embedded loop sweep. |
|
|
2408 | |
2617 | |
2409 | As long as the watcher is started it will automatically handle events. The |
2618 | You can also set the callback to C<0>, in which case the embed watcher |
2410 | callback will be invoked whenever some events have been handled. You can |
2619 | will automatically execute the embedded loop sweep whenever necessary. |
2411 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2412 | interested in that. |
|
|
2413 | |
2620 | |
2414 | Also, there have not currently been made special provisions for forking: |
2621 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2415 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2622 | is active, i.e., the embedded loop will automatically be forked when the |
2416 | but you will also have to stop and restart any C<ev_embed> watchers |
2623 | embedding loop forks. In other cases, the user is responsible for calling |
2417 | yourself - but you can use a fork watcher to handle this automatically, |
2624 | C<ev_loop_fork> on the embedded loop. |
2418 | and future versions of libev might do just that. |
|
|
2419 | |
2625 | |
2420 | Unfortunately, not all backends are embeddable: only the ones returned by |
2626 | Unfortunately, not all backends are embeddable: only the ones returned by |
2421 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2627 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2422 | portable one. |
2628 | portable one. |
2423 | |
2629 | |
… | |
… | |
2517 | event loop blocks next and before C<ev_check> watchers are being called, |
2723 | event loop blocks next and before C<ev_check> watchers are being called, |
2518 | and only in the child after the fork. If whoever good citizen calling |
2724 | and only in the child after the fork. If whoever good citizen calling |
2519 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2725 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2520 | handlers will be invoked, too, of course. |
2726 | handlers will be invoked, too, of course. |
2521 | |
2727 | |
|
|
2728 | =head3 The special problem of life after fork - how is it possible? |
|
|
2729 | |
|
|
2730 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2731 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2732 | sequence should be handled by libev without any problems. |
|
|
2733 | |
|
|
2734 | This changes when the application actually wants to do event handling |
|
|
2735 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2736 | fork. |
|
|
2737 | |
|
|
2738 | The default mode of operation (for libev, with application help to detect |
|
|
2739 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2740 | when I<either> the parent I<or> the child process continues. |
|
|
2741 | |
|
|
2742 | When both processes want to continue using libev, then this is usually the |
|
|
2743 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2744 | supposed to continue with all watchers in place as before, while the other |
|
|
2745 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2746 | |
|
|
2747 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2748 | simply create a new event loop, which of course will be "empty", and |
|
|
2749 | use that for new watchers. This has the advantage of not touching more |
|
|
2750 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2751 | disadvantage of having to use multiple event loops (which do not support |
|
|
2752 | signal watchers). |
|
|
2753 | |
|
|
2754 | When this is not possible, or you want to use the default loop for |
|
|
2755 | other reasons, then in the process that wants to start "fresh", call |
|
|
2756 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2757 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2758 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2759 | also that in that case, you have to re-register any signal watchers. |
|
|
2760 | |
2522 | =head3 Watcher-Specific Functions and Data Members |
2761 | =head3 Watcher-Specific Functions and Data Members |
2523 | |
2762 | |
2524 | =over 4 |
2763 | =over 4 |
2525 | |
2764 | |
2526 | =item ev_fork_init (ev_signal *, callback) |
2765 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2643 | =over 4 |
2882 | =over 4 |
2644 | |
2883 | |
2645 | =item ev_async_init (ev_async *, callback) |
2884 | =item ev_async_init (ev_async *, callback) |
2646 | |
2885 | |
2647 | Initialises and configures the async watcher - it has no parameters of any |
2886 | Initialises and configures the async watcher - it has no parameters of any |
2648 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2887 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2649 | trust me. |
2888 | trust me. |
2650 | |
2889 | |
2651 | =item ev_async_send (loop, ev_async *) |
2890 | =item ev_async_send (loop, ev_async *) |
2652 | |
2891 | |
2653 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2892 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2654 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2893 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2655 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2894 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2656 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2895 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2657 | section below on what exactly this means). |
2896 | section below on what exactly this means). |
2658 | |
2897 | |
|
|
2898 | Note that, as with other watchers in libev, multiple events might get |
|
|
2899 | compressed into a single callback invocation (another way to look at this |
|
|
2900 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2901 | reset when the event loop detects that). |
|
|
2902 | |
2659 | This call incurs the overhead of a system call only once per loop iteration, |
2903 | This call incurs the overhead of a system call only once per event loop |
2660 | so while the overhead might be noticeable, it doesn't apply to repeated |
2904 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2661 | calls to C<ev_async_send>. |
2905 | repeated calls to C<ev_async_send> for the same event loop. |
2662 | |
2906 | |
2663 | =item bool = ev_async_pending (ev_async *) |
2907 | =item bool = ev_async_pending (ev_async *) |
2664 | |
2908 | |
2665 | Returns a non-zero value when C<ev_async_send> has been called on the |
2909 | Returns a non-zero value when C<ev_async_send> has been called on the |
2666 | watcher but the event has not yet been processed (or even noted) by the |
2910 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2669 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2913 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2670 | the loop iterates next and checks for the watcher to have become active, |
2914 | the loop iterates next and checks for the watcher to have become active, |
2671 | it will reset the flag again. C<ev_async_pending> can be used to very |
2915 | it will reset the flag again. C<ev_async_pending> can be used to very |
2672 | quickly check whether invoking the loop might be a good idea. |
2916 | quickly check whether invoking the loop might be a good idea. |
2673 | |
2917 | |
2674 | Not that this does I<not> check whether the watcher itself is pending, only |
2918 | Not that this does I<not> check whether the watcher itself is pending, |
2675 | whether it has been requested to make this watcher pending. |
2919 | only whether it has been requested to make this watcher pending: there |
|
|
2920 | is a time window between the event loop checking and resetting the async |
|
|
2921 | notification, and the callback being invoked. |
2676 | |
2922 | |
2677 | =back |
2923 | =back |
2678 | |
2924 | |
2679 | |
2925 | |
2680 | =head1 OTHER FUNCTIONS |
2926 | =head1 OTHER FUNCTIONS |
… | |
… | |
2859 | |
3105 | |
2860 | myclass obj; |
3106 | myclass obj; |
2861 | ev::io iow; |
3107 | ev::io iow; |
2862 | iow.set <myclass, &myclass::io_cb> (&obj); |
3108 | iow.set <myclass, &myclass::io_cb> (&obj); |
2863 | |
3109 | |
|
|
3110 | =item w->set (object *) |
|
|
3111 | |
|
|
3112 | This is an B<experimental> feature that might go away in a future version. |
|
|
3113 | |
|
|
3114 | This is a variation of a method callback - leaving out the method to call |
|
|
3115 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3116 | functor objects without having to manually specify the C<operator ()> all |
|
|
3117 | the time. Incidentally, you can then also leave out the template argument |
|
|
3118 | list. |
|
|
3119 | |
|
|
3120 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3121 | int revents)>. |
|
|
3122 | |
|
|
3123 | See the method-C<set> above for more details. |
|
|
3124 | |
|
|
3125 | Example: use a functor object as callback. |
|
|
3126 | |
|
|
3127 | struct myfunctor |
|
|
3128 | { |
|
|
3129 | void operator() (ev::io &w, int revents) |
|
|
3130 | { |
|
|
3131 | ... |
|
|
3132 | } |
|
|
3133 | } |
|
|
3134 | |
|
|
3135 | myfunctor f; |
|
|
3136 | |
|
|
3137 | ev::io w; |
|
|
3138 | w.set (&f); |
|
|
3139 | |
2864 | =item w->set<function> (void *data = 0) |
3140 | =item w->set<function> (void *data = 0) |
2865 | |
3141 | |
2866 | Also sets a callback, but uses a static method or plain function as |
3142 | Also sets a callback, but uses a static method or plain function as |
2867 | callback. The optional C<data> argument will be stored in the watcher's |
3143 | callback. The optional C<data> argument will be stored in the watcher's |
2868 | C<data> member and is free for you to use. |
3144 | C<data> member and is free for you to use. |
… | |
… | |
2954 | L<http://software.schmorp.de/pkg/EV>. |
3230 | L<http://software.schmorp.de/pkg/EV>. |
2955 | |
3231 | |
2956 | =item Python |
3232 | =item Python |
2957 | |
3233 | |
2958 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3234 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2959 | seems to be quite complete and well-documented. Note, however, that the |
3235 | seems to be quite complete and well-documented. |
2960 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2961 | for everybody else, and therefore, should never be applied in an installed |
|
|
2962 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2963 | libev). |
|
|
2964 | |
3236 | |
2965 | =item Ruby |
3237 | =item Ruby |
2966 | |
3238 | |
2967 | Tony Arcieri has written a ruby extension that offers access to a subset |
3239 | Tony Arcieri has written a ruby extension that offers access to a subset |
2968 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3240 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2969 | more on top of it. It can be found via gem servers. Its homepage is at |
3241 | more on top of it. It can be found via gem servers. Its homepage is at |
2970 | L<http://rev.rubyforge.org/>. |
3242 | L<http://rev.rubyforge.org/>. |
|
|
3243 | |
|
|
3244 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3245 | makes rev work even on mingw. |
|
|
3246 | |
|
|
3247 | =item Haskell |
|
|
3248 | |
|
|
3249 | A haskell binding to libev is available at |
|
|
3250 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
2971 | |
3251 | |
2972 | =item D |
3252 | =item D |
2973 | |
3253 | |
2974 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3254 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2975 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3255 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
… | |
… | |
3086 | |
3366 | |
3087 | #define EV_STANDALONE 1 |
3367 | #define EV_STANDALONE 1 |
3088 | #include "ev.h" |
3368 | #include "ev.h" |
3089 | |
3369 | |
3090 | Both header files and implementation files can be compiled with a C++ |
3370 | Both header files and implementation files can be compiled with a C++ |
3091 | compiler (at least, thats a stated goal, and breakage will be treated |
3371 | compiler (at least, that's a stated goal, and breakage will be treated |
3092 | as a bug). |
3372 | as a bug). |
3093 | |
3373 | |
3094 | You need the following files in your source tree, or in a directory |
3374 | You need the following files in your source tree, or in a directory |
3095 | in your include path (e.g. in libev/ when using -Ilibev): |
3375 | in your include path (e.g. in libev/ when using -Ilibev): |
3096 | |
3376 | |
… | |
… | |
3152 | keeps libev from including F<config.h>, and it also defines dummy |
3432 | keeps libev from including F<config.h>, and it also defines dummy |
3153 | implementations for some libevent functions (such as logging, which is not |
3433 | implementations for some libevent functions (such as logging, which is not |
3154 | supported). It will also not define any of the structs usually found in |
3434 | supported). It will also not define any of the structs usually found in |
3155 | F<event.h> that are not directly supported by the libev core alone. |
3435 | F<event.h> that are not directly supported by the libev core alone. |
3156 | |
3436 | |
|
|
3437 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3438 | configuration, but has to be more conservative. |
|
|
3439 | |
3157 | =item EV_USE_MONOTONIC |
3440 | =item EV_USE_MONOTONIC |
3158 | |
3441 | |
3159 | If defined to be C<1>, libev will try to detect the availability of the |
3442 | If defined to be C<1>, libev will try to detect the availability of the |
3160 | monotonic clock option at both compile time and runtime. Otherwise no use |
3443 | monotonic clock option at both compile time and runtime. Otherwise no |
3161 | of the monotonic clock option will be attempted. If you enable this, you |
3444 | use of the monotonic clock option will be attempted. If you enable this, |
3162 | usually have to link against librt or something similar. Enabling it when |
3445 | you usually have to link against librt or something similar. Enabling it |
3163 | the functionality isn't available is safe, though, although you have |
3446 | when the functionality isn't available is safe, though, although you have |
3164 | to make sure you link against any libraries where the C<clock_gettime> |
3447 | to make sure you link against any libraries where the C<clock_gettime> |
3165 | function is hiding in (often F<-lrt>). |
3448 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3166 | |
3449 | |
3167 | =item EV_USE_REALTIME |
3450 | =item EV_USE_REALTIME |
3168 | |
3451 | |
3169 | If defined to be C<1>, libev will try to detect the availability of the |
3452 | If defined to be C<1>, libev will try to detect the availability of the |
3170 | real-time clock option at compile time (and assume its availability at |
3453 | real-time clock option at compile time (and assume its availability |
3171 | runtime if successful). Otherwise no use of the real-time clock option will |
3454 | at runtime if successful). Otherwise no use of the real-time clock |
3172 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3455 | option will be attempted. This effectively replaces C<gettimeofday> |
3173 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3456 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3174 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3457 | correctness. See the note about libraries in the description of |
|
|
3458 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3459 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3460 | |
|
|
3461 | =item EV_USE_CLOCK_SYSCALL |
|
|
3462 | |
|
|
3463 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3464 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3465 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3466 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3467 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3468 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3469 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3470 | higher, as it simplifies linking (no need for C<-lrt>). |
3175 | |
3471 | |
3176 | =item EV_USE_NANOSLEEP |
3472 | =item EV_USE_NANOSLEEP |
3177 | |
3473 | |
3178 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3474 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3179 | and will use it for delays. Otherwise it will use C<select ()>. |
3475 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3195 | |
3491 | |
3196 | =item EV_SELECT_USE_FD_SET |
3492 | =item EV_SELECT_USE_FD_SET |
3197 | |
3493 | |
3198 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3494 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3199 | structure. This is useful if libev doesn't compile due to a missing |
3495 | structure. This is useful if libev doesn't compile due to a missing |
3200 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3496 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3201 | exotic systems. This usually limits the range of file descriptors to some |
3497 | on exotic systems. This usually limits the range of file descriptors to |
3202 | low limit such as 1024 or might have other limitations (winsocket only |
3498 | some low limit such as 1024 or might have other limitations (winsocket |
3203 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3499 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3204 | influence the size of the C<fd_set> used. |
3500 | configures the maximum size of the C<fd_set>. |
3205 | |
3501 | |
3206 | =item EV_SELECT_IS_WINSOCKET |
3502 | =item EV_SELECT_IS_WINSOCKET |
3207 | |
3503 | |
3208 | When defined to C<1>, the select backend will assume that |
3504 | When defined to C<1>, the select backend will assume that |
3209 | select/socket/connect etc. don't understand file descriptors but |
3505 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3568 | loop, as long as you don't confuse yourself). The only exception is that |
3864 | loop, as long as you don't confuse yourself). The only exception is that |
3569 | you must not do this from C<ev_periodic> reschedule callbacks. |
3865 | you must not do this from C<ev_periodic> reschedule callbacks. |
3570 | |
3866 | |
3571 | Care has been taken to ensure that libev does not keep local state inside |
3867 | Care has been taken to ensure that libev does not keep local state inside |
3572 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3868 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3573 | they do not clal any callbacks. |
3869 | they do not call any callbacks. |
3574 | |
3870 | |
3575 | =head2 COMPILER WARNINGS |
3871 | =head2 COMPILER WARNINGS |
3576 | |
3872 | |
3577 | Depending on your compiler and compiler settings, you might get no or a |
3873 | Depending on your compiler and compiler settings, you might get no or a |
3578 | lot of warnings when compiling libev code. Some people are apparently |
3874 | lot of warnings when compiling libev code. Some people are apparently |
… | |
… | |
3612 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3908 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3613 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3909 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3614 | ==2274== still reachable: 256 bytes in 1 blocks. |
3910 | ==2274== still reachable: 256 bytes in 1 blocks. |
3615 | |
3911 | |
3616 | Then there is no memory leak, just as memory accounted to global variables |
3912 | Then there is no memory leak, just as memory accounted to global variables |
3617 | is not a memleak - the memory is still being refernced, and didn't leak. |
3913 | is not a memleak - the memory is still being referenced, and didn't leak. |
3618 | |
3914 | |
3619 | Similarly, under some circumstances, valgrind might report kernel bugs |
3915 | Similarly, under some circumstances, valgrind might report kernel bugs |
3620 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3916 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3621 | although an acceptable workaround has been found here), or it might be |
3917 | although an acceptable workaround has been found here), or it might be |
3622 | confused. |
3918 | confused. |
… | |
… | |
3651 | way (note also that glib is the slowest event library known to man). |
3947 | way (note also that glib is the slowest event library known to man). |
3652 | |
3948 | |
3653 | There is no supported compilation method available on windows except |
3949 | There is no supported compilation method available on windows except |
3654 | embedding it into other applications. |
3950 | embedding it into other applications. |
3655 | |
3951 | |
|
|
3952 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
3953 | tries its best, but under most conditions, signals will simply not work. |
|
|
3954 | |
3656 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3955 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3657 | accept large writes: instead of resulting in a partial write, windows will |
3956 | accept large writes: instead of resulting in a partial write, windows will |
3658 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3957 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3659 | so make sure you only write small amounts into your sockets (less than a |
3958 | so make sure you only write small amounts into your sockets (less than a |
3660 | megabyte seems safe, but this apparently depends on the amount of memory |
3959 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3664 | the abysmal performance of winsockets, using a large number of sockets |
3963 | the abysmal performance of winsockets, using a large number of sockets |
3665 | is not recommended (and not reasonable). If your program needs to use |
3964 | is not recommended (and not reasonable). If your program needs to use |
3666 | more than a hundred or so sockets, then likely it needs to use a totally |
3965 | more than a hundred or so sockets, then likely it needs to use a totally |
3667 | different implementation for windows, as libev offers the POSIX readiness |
3966 | different implementation for windows, as libev offers the POSIX readiness |
3668 | notification model, which cannot be implemented efficiently on windows |
3967 | notification model, which cannot be implemented efficiently on windows |
3669 | (Microsoft monopoly games). |
3968 | (due to Microsoft monopoly games). |
3670 | |
3969 | |
3671 | A typical way to use libev under windows is to embed it (see the embedding |
3970 | A typical way to use libev under windows is to embed it (see the embedding |
3672 | section for details) and use the following F<evwrap.h> header file instead |
3971 | section for details) and use the following F<evwrap.h> header file instead |
3673 | of F<ev.h>: |
3972 | of F<ev.h>: |
3674 | |
3973 | |
… | |
… | |
3710 | |
4009 | |
3711 | Early versions of winsocket's select only supported waiting for a maximum |
4010 | Early versions of winsocket's select only supported waiting for a maximum |
3712 | of C<64> handles (probably owning to the fact that all windows kernels |
4011 | of C<64> handles (probably owning to the fact that all windows kernels |
3713 | can only wait for C<64> things at the same time internally; Microsoft |
4012 | can only wait for C<64> things at the same time internally; Microsoft |
3714 | recommends spawning a chain of threads and wait for 63 handles and the |
4013 | recommends spawning a chain of threads and wait for 63 handles and the |
3715 | previous thread in each. Great). |
4014 | previous thread in each. Sounds great!). |
3716 | |
4015 | |
3717 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4016 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3718 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4017 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3719 | call (which might be in libev or elsewhere, for example, perl does its own |
4018 | call (which might be in libev or elsewhere, for example, perl and many |
3720 | select emulation on windows). |
4019 | other interpreters do their own select emulation on windows). |
3721 | |
4020 | |
3722 | Another limit is the number of file descriptors in the Microsoft runtime |
4021 | Another limit is the number of file descriptors in the Microsoft runtime |
3723 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4022 | libraries, which by default is C<64> (there must be a hidden I<64> |
3724 | or something like this inside Microsoft). You can increase this by calling |
4023 | fetish or something like this inside Microsoft). You can increase this |
3725 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4024 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3726 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4025 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3727 | libraries. |
|
|
3728 | |
|
|
3729 | This might get you to about C<512> or C<2048> sockets (depending on |
4026 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3730 | windows version and/or the phase of the moon). To get more, you need to |
4027 | (depending on windows version and/or the phase of the moon). To get more, |
3731 | wrap all I/O functions and provide your own fd management, but the cost of |
4028 | you need to wrap all I/O functions and provide your own fd management, but |
3732 | calling select (O(n²)) will likely make this unworkable. |
4029 | the cost of calling select (O(n²)) will likely make this unworkable. |
3733 | |
4030 | |
3734 | =back |
4031 | =back |
3735 | |
4032 | |
3736 | =head2 PORTABILITY REQUIREMENTS |
4033 | =head2 PORTABILITY REQUIREMENTS |
3737 | |
4034 | |
… | |
… | |
3858 | involves iterating over all running async watchers or all signal numbers. |
4155 | involves iterating over all running async watchers or all signal numbers. |
3859 | |
4156 | |
3860 | =back |
4157 | =back |
3861 | |
4158 | |
3862 | |
4159 | |
|
|
4160 | =head1 GLOSSARY |
|
|
4161 | |
|
|
4162 | =over 4 |
|
|
4163 | |
|
|
4164 | =item active |
|
|
4165 | |
|
|
4166 | A watcher is active as long as it has been started (has been attached to |
|
|
4167 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4168 | |
|
|
4169 | =item application |
|
|
4170 | |
|
|
4171 | In this document, an application is whatever is using libev. |
|
|
4172 | |
|
|
4173 | =item callback |
|
|
4174 | |
|
|
4175 | The address of a function that is called when some event has been |
|
|
4176 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4177 | received the event, and the actual event bitset. |
|
|
4178 | |
|
|
4179 | =item callback invocation |
|
|
4180 | |
|
|
4181 | The act of calling the callback associated with a watcher. |
|
|
4182 | |
|
|
4183 | =item event |
|
|
4184 | |
|
|
4185 | A change of state of some external event, such as data now being available |
|
|
4186 | for reading on a file descriptor, time having passed or simply not having |
|
|
4187 | any other events happening anymore. |
|
|
4188 | |
|
|
4189 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4190 | C<EV_TIMEOUT>). |
|
|
4191 | |
|
|
4192 | =item event library |
|
|
4193 | |
|
|
4194 | A software package implementing an event model and loop. |
|
|
4195 | |
|
|
4196 | =item event loop |
|
|
4197 | |
|
|
4198 | An entity that handles and processes external events and converts them |
|
|
4199 | into callback invocations. |
|
|
4200 | |
|
|
4201 | =item event model |
|
|
4202 | |
|
|
4203 | The model used to describe how an event loop handles and processes |
|
|
4204 | watchers and events. |
|
|
4205 | |
|
|
4206 | =item pending |
|
|
4207 | |
|
|
4208 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4209 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4210 | pending status is explicitly cleared by the application. |
|
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4211 | |
|
|
4212 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4213 | its pending status. |
|
|
4214 | |
|
|
4215 | =item real time |
|
|
4216 | |
|
|
4217 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4218 | |
|
|
4219 | =item wall-clock time |
|
|
4220 | |
|
|
4221 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4222 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4223 | clock. |
|
|
4224 | |
|
|
4225 | =item watcher |
|
|
4226 | |
|
|
4227 | A data structure that describes interest in certain events. Watchers need |
|
|
4228 | to be started (attached to an event loop) before they can receive events. |
|
|
4229 | |
|
|
4230 | =item watcher invocation |
|
|
4231 | |
|
|
4232 | The act of calling the callback associated with a watcher. |
|
|
4233 | |
|
|
4234 | =back |
|
|
4235 | |
3863 | =head1 AUTHOR |
4236 | =head1 AUTHOR |
3864 | |
4237 | |
3865 | Marc Lehmann <libev@schmorp.de>. |
4238 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3866 | |
4239 | |