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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; |
… | |
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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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384 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
398 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
385 | |
399 | |
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). The epoll design has a number |
403 | epoll scales either O(1) or O(active_fds). |
390 | of shortcomings, such as silently dropping events in some hard-to-detect |
404 | |
391 | cases and requiring a system call per fd change, no fork support and bad |
405 | The epoll mechanism deserves honorable mention as the most misdesigned |
392 | support for dup. |
406 | of the more advanced event mechanisms: mere annoyances include silently |
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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 |
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409 | so on. The biggest issue is fork races, however - if a program forks then |
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410 | I<both> parent and child process have to recreate the epoll set, which can |
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411 | take considerable time (one syscall per file descriptor) and is of course |
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412 | hard to detect. |
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413 | |
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414 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
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415 | of course I<doesn't>, and epoll just loves to report events for totally |
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416 | I<different> file descriptors (even already closed ones, so one cannot |
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417 | even remove them from the set) than registered in the set (especially |
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418 | on SMP systems). Libev tries to counter these spurious notifications by |
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419 | employing an additional generation counter and comparing that against the |
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420 | events to filter out spurious ones, recreating the set when required. |
393 | |
421 | |
394 | 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 |
395 | 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 |
396 | (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 |
397 | 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 |
398 | very well if you register events for both fds. |
426 | file descriptors might not work very well if you register events for both |
399 | |
427 | file descriptors. |
400 | Please note that epoll sometimes generates spurious notifications, so you |
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401 | need to use non-blocking I/O or other means to avoid blocking when no data |
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402 | (or space) is available. |
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403 | |
428 | |
404 | Best performance from this backend is achieved by not unregistering all |
429 | Best performance from this backend is achieved by not unregistering all |
405 | 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, |
406 | 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 |
407 | 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 |
408 | extra overhead. |
433 | extra overhead. A fork can both result in spurious notifications as well |
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434 | as in libev having to destroy and recreate the epoll object, which can |
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435 | take considerable time and thus should be avoided. |
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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. |
409 | |
440 | |
410 | 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 |
411 | all kernel versions tested so far. |
442 | all kernel versions tested so far. |
412 | |
443 | |
413 | 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 |
414 | C<EVBACKEND_POLL>. |
445 | C<EVBACKEND_POLL>. |
415 | |
446 | |
416 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
447 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
417 | |
448 | |
418 | 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 |
419 | 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 |
420 | 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 |
421 | completely useless). For this reason it's not being "auto-detected" unless |
452 | it's completely useless). Unlike epoll, however, whose brokenness |
422 | 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 |
423 | 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. |
424 | |
458 | |
425 | 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 |
426 | 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 |
427 | the target platform). See C<ev_embed> watchers for more info. |
461 | the target platform). See C<ev_embed> watchers for more info. |
428 | |
462 | |
429 | It scales in the same way as the epoll backend, but the interface to the |
463 | It scales in the same way as the epoll backend, but the interface to the |
430 | kernel is more efficient (which says nothing about its actual speed, of |
464 | kernel is more efficient (which says nothing about its actual speed, of |
431 | course). While stopping, setting and starting an I/O watcher does never |
465 | course). While stopping, setting and starting an I/O watcher does never |
432 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
466 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
433 | two event changes per incident. Support for C<fork ()> is very bad and it |
467 | two event changes per incident. Support for C<fork ()> is very bad (but |
434 | drops fds silently in similarly hard-to-detect cases. |
468 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
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469 | cases |
435 | |
470 | |
436 | This backend usually performs well under most conditions. |
471 | This backend usually performs well under most conditions. |
437 | |
472 | |
438 | While nominally embeddable in other event loops, this doesn't work |
473 | While nominally embeddable in other event loops, this doesn't work |
439 | 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 |
440 | 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 |
441 | (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 |
442 | (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 |
443 | using it only for sockets. |
478 | also broken on OS X)) and, did I mention it, using it only for sockets. |
444 | |
479 | |
445 | 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 |
446 | 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 |
447 | C<NOTE_EOF>. |
482 | C<NOTE_EOF>. |
448 | |
483 | |
… | |
… | |
468 | might perform better. |
503 | might perform better. |
469 | |
504 | |
470 | On the positive side, with the exception of the spurious readiness |
505 | On the positive side, with the exception of the spurious readiness |
471 | notifications, this backend actually performed fully to specification |
506 | notifications, this backend actually performed fully to specification |
472 | in all tests and is fully embeddable, which is a rare feat among the |
507 | in all tests and is fully embeddable, which is a rare feat among the |
473 | OS-specific backends. |
508 | OS-specific backends (I vastly prefer correctness over speed hacks). |
474 | |
509 | |
475 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
510 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
476 | C<EVBACKEND_POLL>. |
511 | C<EVBACKEND_POLL>. |
477 | |
512 | |
478 | =item C<EVBACKEND_ALL> |
513 | =item C<EVBACKEND_ALL> |
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609 | |
644 | |
610 | 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 |
611 | 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 |
612 | the current time is a good idea. |
647 | the current time is a good idea. |
613 | |
648 | |
614 | 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>). |
615 | |
676 | |
616 | =item ev_loop (loop, int flags) |
677 | =item ev_loop (loop, int flags) |
617 | |
678 | |
618 | 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 |
619 | 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 |
… | |
… | |
635 | the loop. |
696 | the loop. |
636 | |
697 | |
637 | 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 |
638 | necessary) and will handle those and any already outstanding ones. It |
699 | necessary) and will handle those and any already outstanding ones. It |
639 | 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 |
640 | 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 |
641 | user-registered callback will be called), and will return after one |
702 | user-registered callback will be called), and will return after one |
642 | iteration of the loop. |
703 | iteration of the loop. |
643 | |
704 | |
644 | 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 |
645 | 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 |
… | |
… | |
703 | |
764 | |
704 | 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> |
705 | from returning, call ev_unref() after starting, and ev_ref() before |
766 | from returning, call ev_unref() after starting, and ev_ref() before |
706 | stopping it. |
767 | stopping it. |
707 | |
768 | |
708 | 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 |
709 | 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 |
710 | 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 |
711 | 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 |
712 | 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 |
713 | (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 |
714 | 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). |
715 | |
778 | |
716 | 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> |
717 | running when nothing else is active. |
780 | running when nothing else is active. |
718 | |
781 | |
719 | ev_signal exitsig; |
782 | ev_signal exitsig; |
… | |
… | |
903 | |
966 | |
904 | =item C<EV_ASYNC> |
967 | =item C<EV_ASYNC> |
905 | |
968 | |
906 | The given async watcher has been asynchronously notified (see C<ev_async>). |
969 | The given async watcher has been asynchronously notified (see C<ev_async>). |
907 | |
970 | |
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971 | =item C<EV_CUSTOM> |
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972 | |
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973 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
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974 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
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975 | |
908 | =item C<EV_ERROR> |
976 | =item C<EV_ERROR> |
909 | |
977 | |
910 | An unspecified error has occurred, the watcher has been stopped. This might |
978 | An unspecified error has occurred, the watcher has been stopped. This might |
911 | happen because the watcher could not be properly started because libev |
979 | happen because the watcher could not be properly started because libev |
912 | ran out of memory, a file descriptor was found to be closed or any other |
980 | ran out of memory, a file descriptor was found to be closed or any other |
… | |
… | |
1027 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1095 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1028 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1096 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1029 | before watchers with lower priority, but priority will not keep watchers |
1097 | before watchers with lower priority, but priority will not keep watchers |
1030 | from being executed (except for C<ev_idle> watchers). |
1098 | from being executed (except for C<ev_idle> watchers). |
1031 | |
1099 | |
1032 | This means that priorities are I<only> used for ordering callback |
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1033 | invocation after new events have been received. This is useful, for |
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1034 | example, to reduce latency after idling, or more often, to bind two |
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1035 | watchers on the same event and make sure one is called first. |
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1036 | |
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1037 | If you need to suppress invocation when higher priority events are pending |
1100 | If you need to suppress invocation when higher priority events are pending |
1038 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1101 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1039 | |
1102 | |
1040 | You I<must not> change the priority of a watcher as long as it is active or |
1103 | You I<must not> change the priority of a watcher as long as it is active or |
1041 | pending. |
1104 | pending. |
1042 | |
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1043 | The default priority used by watchers when no priority has been set is |
|
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1044 | always C<0>, which is supposed to not be too high and not be too low :). |
|
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1045 | |
1105 | |
1046 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1106 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1047 | fine, as long as you do not mind that the priority value you query might |
1107 | fine, as long as you do not mind that the priority value you query might |
1048 | or might not have been clamped to the valid range. |
1108 | or might not have been clamped to the valid range. |
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1109 | |
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1110 | The default priority used by watchers when no priority has been set is |
|
|
1111 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1112 | |
|
|
1113 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1114 | priorities. |
1049 | |
1115 | |
1050 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1116 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1051 | |
1117 | |
1052 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1118 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1053 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1119 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1118 | #include <stddef.h> |
1184 | #include <stddef.h> |
1119 | |
1185 | |
1120 | static void |
1186 | static void |
1121 | t1_cb (EV_P_ ev_timer *w, int revents) |
1187 | t1_cb (EV_P_ ev_timer *w, int revents) |
1122 | { |
1188 | { |
1123 | struct my_biggy big = (struct my_biggy * |
1189 | struct my_biggy big = (struct my_biggy *) |
1124 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1190 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1125 | } |
1191 | } |
1126 | |
1192 | |
1127 | static void |
1193 | static void |
1128 | t2_cb (EV_P_ ev_timer *w, int revents) |
1194 | t2_cb (EV_P_ ev_timer *w, int revents) |
1129 | { |
1195 | { |
1130 | struct my_biggy big = (struct my_biggy * |
1196 | struct my_biggy big = (struct my_biggy *) |
1131 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1197 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1132 | } |
1198 | } |
|
|
1199 | |
|
|
1200 | =head2 WATCHER PRIORITY MODELS |
|
|
1201 | |
|
|
1202 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1203 | integers that influence the ordering of event callback invocation |
|
|
1204 | between watchers in some way, all else being equal. |
|
|
1205 | |
|
|
1206 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1207 | description for the more technical details such as the actual priority |
|
|
1208 | range. |
|
|
1209 | |
|
|
1210 | There are two common ways how these these priorities are being interpreted |
|
|
1211 | by event loops: |
|
|
1212 | |
|
|
1213 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1214 | of lower priority watchers, which means as long as higher priority |
|
|
1215 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1216 | |
|
|
1217 | The less common only-for-ordering model uses priorities solely to order |
|
|
1218 | callback invocation within a single event loop iteration: Higher priority |
|
|
1219 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1220 | before polling for new events. |
|
|
1221 | |
|
|
1222 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1223 | except for idle watchers (which use the lock-out model). |
|
|
1224 | |
|
|
1225 | The rationale behind this is that implementing the lock-out model for |
|
|
1226 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1227 | libraries will just poll for the same events again and again as long as |
|
|
1228 | their callbacks have not been executed, which is very inefficient in the |
|
|
1229 | common case of one high-priority watcher locking out a mass of lower |
|
|
1230 | priority ones. |
|
|
1231 | |
|
|
1232 | Static (ordering) priorities are most useful when you have two or more |
|
|
1233 | watchers handling the same resource: a typical usage example is having an |
|
|
1234 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1235 | timeouts. Under load, data might be received while the program handles |
|
|
1236 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1237 | handler will be executed before checking for data. In that case, giving |
|
|
1238 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1239 | handled first even under adverse conditions (which is usually, but not |
|
|
1240 | always, what you want). |
|
|
1241 | |
|
|
1242 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1243 | will only be executed when no same or higher priority watchers have |
|
|
1244 | received events, they can be used to implement the "lock-out" model when |
|
|
1245 | required. |
|
|
1246 | |
|
|
1247 | For example, to emulate how many other event libraries handle priorities, |
|
|
1248 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1249 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1250 | processing is done in the idle watcher callback. This causes libev to |
|
|
1251 | continously poll and process kernel event data for the watcher, but when |
|
|
1252 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1253 | workable. |
|
|
1254 | |
|
|
1255 | Usually, however, the lock-out model implemented that way will perform |
|
|
1256 | miserably under the type of load it was designed to handle. In that case, |
|
|
1257 | it might be preferable to stop the real watcher before starting the |
|
|
1258 | idle watcher, so the kernel will not have to process the event in case |
|
|
1259 | the actual processing will be delayed for considerable time. |
|
|
1260 | |
|
|
1261 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1262 | priority than the default, and which should only process data when no |
|
|
1263 | other events are pending: |
|
|
1264 | |
|
|
1265 | ev_idle idle; // actual processing watcher |
|
|
1266 | ev_io io; // actual event watcher |
|
|
1267 | |
|
|
1268 | static void |
|
|
1269 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1270 | { |
|
|
1271 | // stop the I/O watcher, we received the event, but |
|
|
1272 | // are not yet ready to handle it. |
|
|
1273 | ev_io_stop (EV_A_ w); |
|
|
1274 | |
|
|
1275 | // start the idle watcher to ahndle the actual event. |
|
|
1276 | // it will not be executed as long as other watchers |
|
|
1277 | // with the default priority are receiving events. |
|
|
1278 | ev_idle_start (EV_A_ &idle); |
|
|
1279 | } |
|
|
1280 | |
|
|
1281 | static void |
|
|
1282 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1283 | { |
|
|
1284 | // actual processing |
|
|
1285 | read (STDIN_FILENO, ...); |
|
|
1286 | |
|
|
1287 | // have to start the I/O watcher again, as |
|
|
1288 | // we have handled the event |
|
|
1289 | ev_io_start (EV_P_ &io); |
|
|
1290 | } |
|
|
1291 | |
|
|
1292 | // initialisation |
|
|
1293 | ev_idle_init (&idle, idle_cb); |
|
|
1294 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1295 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1296 | |
|
|
1297 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1298 | low-priority connections can not be locked out forever under load. This |
|
|
1299 | enables your program to keep a lower latency for important connections |
|
|
1300 | during short periods of high load, while not completely locking out less |
|
|
1301 | important ones. |
1133 | |
1302 | |
1134 | |
1303 | |
1135 | =head1 WATCHER TYPES |
1304 | =head1 WATCHER TYPES |
1136 | |
1305 | |
1137 | This section describes each watcher in detail, but will not repeat |
1306 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1163 | descriptors to non-blocking mode is also usually a good idea (but not |
1332 | descriptors to non-blocking mode is also usually a good idea (but not |
1164 | required if you know what you are doing). |
1333 | required if you know what you are doing). |
1165 | |
1334 | |
1166 | If you cannot use non-blocking mode, then force the use of a |
1335 | If you cannot use non-blocking mode, then force the use of a |
1167 | known-to-be-good backend (at the time of this writing, this includes only |
1336 | known-to-be-good backend (at the time of this writing, this includes only |
1168 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1337 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1338 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1339 | files) - libev doesn't guarentee any specific behaviour in that case. |
1169 | |
1340 | |
1170 | Another thing you have to watch out for is that it is quite easy to |
1341 | Another thing you have to watch out for is that it is quite easy to |
1171 | receive "spurious" readiness notifications, that is your callback might |
1342 | receive "spurious" readiness notifications, that is your callback might |
1172 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1343 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1173 | because there is no data. Not only are some backends known to create a |
1344 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1294 | year, it will still time out after (roughly) one hour. "Roughly" because |
1465 | year, it will still time out after (roughly) one hour. "Roughly" because |
1295 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1466 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1296 | monotonic clock option helps a lot here). |
1467 | monotonic clock option helps a lot here). |
1297 | |
1468 | |
1298 | The callback is guaranteed to be invoked only I<after> its timeout has |
1469 | The callback is guaranteed to be invoked only I<after> its timeout has |
1299 | passed, but if multiple timers become ready during the same loop iteration |
1470 | passed (not I<at>, so on systems with very low-resolution clocks this |
1300 | then order of execution is undefined. |
1471 | might introduce a small delay). If multiple timers become ready during the |
|
|
1472 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1473 | before ones with later time-out values (but this is no longer true when a |
|
|
1474 | callback calls C<ev_loop> recursively). |
1301 | |
1475 | |
1302 | =head3 Be smart about timeouts |
1476 | =head3 Be smart about timeouts |
1303 | |
1477 | |
1304 | Many real-world problems involve some kind of timeout, usually for error |
1478 | Many real-world problems involve some kind of timeout, usually for error |
1305 | recovery. A typical example is an HTTP request - if the other side hangs, |
1479 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1349 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1523 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1350 | member and C<ev_timer_again>. |
1524 | member and C<ev_timer_again>. |
1351 | |
1525 | |
1352 | At start: |
1526 | At start: |
1353 | |
1527 | |
1354 | ev_timer_init (timer, callback); |
1528 | ev_init (timer, callback); |
1355 | timer->repeat = 60.; |
1529 | timer->repeat = 60.; |
1356 | ev_timer_again (loop, timer); |
1530 | ev_timer_again (loop, timer); |
1357 | |
1531 | |
1358 | Each time there is some activity: |
1532 | Each time there is some activity: |
1359 | |
1533 | |
… | |
… | |
1398 | else |
1572 | else |
1399 | { |
1573 | { |
1400 | // callback was invoked, but there was some activity, re-arm |
1574 | // callback was invoked, but there was some activity, re-arm |
1401 | // the watcher to fire in last_activity + 60, which is |
1575 | // the watcher to fire in last_activity + 60, which is |
1402 | // guaranteed to be in the future, so "again" is positive: |
1576 | // guaranteed to be in the future, so "again" is positive: |
1403 | w->again = timeout - now; |
1577 | w->repeat = timeout - now; |
1404 | ev_timer_again (EV_A_ w); |
1578 | ev_timer_again (EV_A_ w); |
1405 | } |
1579 | } |
1406 | } |
1580 | } |
1407 | |
1581 | |
1408 | To summarise the callback: first calculate the real timeout (defined |
1582 | To summarise the callback: first calculate the real timeout (defined |
… | |
… | |
1421 | |
1595 | |
1422 | To start the timer, simply initialise the watcher and set C<last_activity> |
1596 | To start the timer, simply initialise the watcher and set C<last_activity> |
1423 | to the current time (meaning we just have some activity :), then call the |
1597 | to the current time (meaning we just have some activity :), then call the |
1424 | callback, which will "do the right thing" and start the timer: |
1598 | callback, which will "do the right thing" and start the timer: |
1425 | |
1599 | |
1426 | ev_timer_init (timer, callback); |
1600 | ev_init (timer, callback); |
1427 | last_activity = ev_now (loop); |
1601 | last_activity = ev_now (loop); |
1428 | callback (loop, timer, EV_TIMEOUT); |
1602 | callback (loop, timer, EV_TIMEOUT); |
1429 | |
1603 | |
1430 | And when there is some activity, simply store the current time in |
1604 | And when there is some activity, simply store the current time in |
1431 | C<last_activity>, no libev calls at all: |
1605 | C<last_activity>, no libev calls at all: |
… | |
… | |
1524 | If the timer is started but non-repeating, stop it (as if it timed out). |
1698 | If the timer is started but non-repeating, stop it (as if it timed out). |
1525 | |
1699 | |
1526 | If the timer is repeating, either start it if necessary (with the |
1700 | If the timer is repeating, either start it if necessary (with the |
1527 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1701 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1528 | |
1702 | |
1529 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1703 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1530 | usage example. |
1704 | usage example. |
1531 | |
1705 | |
1532 | =item ev_tstamp repeat [read-write] |
1706 | =item ev_tstamp repeat [read-write] |
1533 | |
1707 | |
1534 | The current C<repeat> value. Will be used each time the watcher times out |
1708 | The current C<repeat> value. Will be used each time the watcher times out |
… | |
… | |
1573 | =head2 C<ev_periodic> - to cron or not to cron? |
1747 | =head2 C<ev_periodic> - to cron or not to cron? |
1574 | |
1748 | |
1575 | Periodic watchers are also timers of a kind, but they are very versatile |
1749 | Periodic watchers are also timers of a kind, but they are very versatile |
1576 | (and unfortunately a bit complex). |
1750 | (and unfortunately a bit complex). |
1577 | |
1751 | |
1578 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1752 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1579 | but on wall clock time (absolute time). You can tell a periodic watcher |
1753 | relative time, the physical time that passes) but on wall clock time |
1580 | to trigger after some specific point in time. For example, if you tell a |
1754 | (absolute time, the thing you can read on your calender or clock). The |
1581 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1755 | difference is that wall clock time can run faster or slower than real |
1582 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1756 | time, and time jumps are not uncommon (e.g. when you adjust your |
1583 | clock to January of the previous year, then it will take more than year |
1757 | wrist-watch). |
1584 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1585 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1586 | |
1758 | |
|
|
1759 | You can tell a periodic watcher to trigger after some specific point |
|
|
1760 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1761 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1762 | not a delay) and then reset your system clock to January of the previous |
|
|
1763 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1764 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1765 | it, as it uses a relative timeout). |
|
|
1766 | |
1587 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1767 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1588 | such as triggering an event on each "midnight, local time", or other |
1768 | timers, such as triggering an event on each "midnight, local time", or |
1589 | complicated rules. |
1769 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1770 | those cannot react to time jumps. |
1590 | |
1771 | |
1591 | As with timers, the callback is guaranteed to be invoked only when the |
1772 | As with timers, the callback is guaranteed to be invoked only when the |
1592 | time (C<at>) has passed, but if multiple periodic timers become ready |
1773 | point in time where it is supposed to trigger has passed. If multiple |
1593 | during the same loop iteration, then order of execution is undefined. |
1774 | timers become ready during the same loop iteration then the ones with |
|
|
1775 | earlier time-out values are invoked before ones with later time-out values |
|
|
1776 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1594 | |
1777 | |
1595 | =head3 Watcher-Specific Functions and Data Members |
1778 | =head3 Watcher-Specific Functions and Data Members |
1596 | |
1779 | |
1597 | =over 4 |
1780 | =over 4 |
1598 | |
1781 | |
1599 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1782 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1600 | |
1783 | |
1601 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1784 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1602 | |
1785 | |
1603 | Lots of arguments, lets sort it out... There are basically three modes of |
1786 | Lots of arguments, let's sort it out... There are basically three modes of |
1604 | operation, and we will explain them from simplest to most complex: |
1787 | operation, and we will explain them from simplest to most complex: |
1605 | |
1788 | |
1606 | =over 4 |
1789 | =over 4 |
1607 | |
1790 | |
1608 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1791 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1609 | |
1792 | |
1610 | In this configuration the watcher triggers an event after the wall clock |
1793 | In this configuration the watcher triggers an event after the wall clock |
1611 | time C<at> has passed. It will not repeat and will not adjust when a time |
1794 | time C<offset> has passed. It will not repeat and will not adjust when a |
1612 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1795 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1613 | only run when the system clock reaches or surpasses this time. |
1796 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1797 | this point in time. |
1614 | |
1798 | |
1615 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1799 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1616 | |
1800 | |
1617 | In this mode the watcher will always be scheduled to time out at the next |
1801 | In this mode the watcher will always be scheduled to time out at the next |
1618 | C<at + N * interval> time (for some integer N, which can also be negative) |
1802 | C<offset + N * interval> time (for some integer N, which can also be |
1619 | and then repeat, regardless of any time jumps. |
1803 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1804 | argument is merely an offset into the C<interval> periods. |
1620 | |
1805 | |
1621 | This can be used to create timers that do not drift with respect to the |
1806 | This can be used to create timers that do not drift with respect to the |
1622 | system clock, for example, here is a C<ev_periodic> that triggers each |
1807 | system clock, for example, here is an C<ev_periodic> that triggers each |
1623 | hour, on the hour: |
1808 | hour, on the hour (with respect to UTC): |
1624 | |
1809 | |
1625 | ev_periodic_set (&periodic, 0., 3600., 0); |
1810 | ev_periodic_set (&periodic, 0., 3600., 0); |
1626 | |
1811 | |
1627 | This doesn't mean there will always be 3600 seconds in between triggers, |
1812 | This doesn't mean there will always be 3600 seconds in between triggers, |
1628 | but only that the callback will be called when the system time shows a |
1813 | but only that the callback will be called when the system time shows a |
1629 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1814 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1630 | by 3600. |
1815 | by 3600. |
1631 | |
1816 | |
1632 | Another way to think about it (for the mathematically inclined) is that |
1817 | Another way to think about it (for the mathematically inclined) is that |
1633 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1818 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1634 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1819 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1635 | |
1820 | |
1636 | For numerical stability it is preferable that the C<at> value is near |
1821 | For numerical stability it is preferable that the C<offset> value is near |
1637 | C<ev_now ()> (the current time), but there is no range requirement for |
1822 | C<ev_now ()> (the current time), but there is no range requirement for |
1638 | this value, and in fact is often specified as zero. |
1823 | this value, and in fact is often specified as zero. |
1639 | |
1824 | |
1640 | Note also that there is an upper limit to how often a timer can fire (CPU |
1825 | Note also that there is an upper limit to how often a timer can fire (CPU |
1641 | speed for example), so if C<interval> is very small then timing stability |
1826 | speed for example), so if C<interval> is very small then timing stability |
1642 | will of course deteriorate. Libev itself tries to be exact to be about one |
1827 | will of course deteriorate. Libev itself tries to be exact to be about one |
1643 | millisecond (if the OS supports it and the machine is fast enough). |
1828 | millisecond (if the OS supports it and the machine is fast enough). |
1644 | |
1829 | |
1645 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1830 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1646 | |
1831 | |
1647 | In this mode the values for C<interval> and C<at> are both being |
1832 | In this mode the values for C<interval> and C<offset> are both being |
1648 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1833 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1649 | reschedule callback will be called with the watcher as first, and the |
1834 | reschedule callback will be called with the watcher as first, and the |
1650 | current time as second argument. |
1835 | current time as second argument. |
1651 | |
1836 | |
1652 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1837 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1653 | ever, or make ANY event loop modifications whatsoever>. |
1838 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1839 | allowed by documentation here>. |
1654 | |
1840 | |
1655 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1841 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1656 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1842 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1657 | only event loop modification you are allowed to do). |
1843 | only event loop modification you are allowed to do). |
1658 | |
1844 | |
… | |
… | |
1688 | a different time than the last time it was called (e.g. in a crond like |
1874 | a different time than the last time it was called (e.g. in a crond like |
1689 | program when the crontabs have changed). |
1875 | program when the crontabs have changed). |
1690 | |
1876 | |
1691 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1877 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1692 | |
1878 | |
1693 | When active, returns the absolute time that the watcher is supposed to |
1879 | When active, returns the absolute time that the watcher is supposed |
1694 | trigger next. |
1880 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1881 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1882 | rescheduling modes. |
1695 | |
1883 | |
1696 | =item ev_tstamp offset [read-write] |
1884 | =item ev_tstamp offset [read-write] |
1697 | |
1885 | |
1698 | When repeating, this contains the offset value, otherwise this is the |
1886 | When repeating, this contains the offset value, otherwise this is the |
1699 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1887 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1888 | although libev might modify this value for better numerical stability). |
1700 | |
1889 | |
1701 | Can be modified any time, but changes only take effect when the periodic |
1890 | Can be modified any time, but changes only take effect when the periodic |
1702 | timer fires or C<ev_periodic_again> is being called. |
1891 | timer fires or C<ev_periodic_again> is being called. |
1703 | |
1892 | |
1704 | =item ev_tstamp interval [read-write] |
1893 | =item ev_tstamp interval [read-write] |
… | |
… | |
1910 | |
2099 | |
1911 | |
2100 | |
1912 | =head2 C<ev_stat> - did the file attributes just change? |
2101 | =head2 C<ev_stat> - did the file attributes just change? |
1913 | |
2102 | |
1914 | This watches a file system path for attribute changes. That is, it calls |
2103 | This watches a file system path for attribute changes. That is, it calls |
1915 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2104 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1916 | compared to the last time, invoking the callback if it did. |
2105 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2106 | it did. |
1917 | |
2107 | |
1918 | The path does not need to exist: changing from "path exists" to "path does |
2108 | The path does not need to exist: changing from "path exists" to "path does |
1919 | not exist" is a status change like any other. The condition "path does |
2109 | not exist" is a status change like any other. The condition "path does not |
1920 | not exist" is signified by the C<st_nlink> field being zero (which is |
2110 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1921 | otherwise always forced to be at least one) and all the other fields of |
2111 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1922 | the stat buffer having unspecified contents. |
2112 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2113 | contents. |
1923 | |
2114 | |
1924 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2115 | The path I<must not> end in a slash or contain special components such as |
|
|
2116 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1925 | relative and your working directory changes, the behaviour is undefined. |
2117 | your working directory changes, then the behaviour is undefined. |
1926 | |
2118 | |
1927 | Since there is no standard kernel interface to do this, the portable |
2119 | Since there is no portable change notification interface available, the |
1928 | implementation simply calls C<stat (2)> regularly on the path to see if |
2120 | portable implementation simply calls C<stat(2)> regularly on the path |
1929 | it changed somehow. You can specify a recommended polling interval for |
2121 | to see if it changed somehow. You can specify a recommended polling |
1930 | this case. If you specify a polling interval of C<0> (highly recommended!) |
2122 | interval for this case. If you specify a polling interval of C<0> (highly |
1931 | then a I<suitable, unspecified default> value will be used (which |
2123 | recommended!) then a I<suitable, unspecified default> value will be used |
1932 | you can expect to be around five seconds, although this might change |
2124 | (which you can expect to be around five seconds, although this might |
1933 | dynamically). Libev will also impose a minimum interval which is currently |
2125 | change dynamically). Libev will also impose a minimum interval which is |
1934 | around C<0.1>, but thats usually overkill. |
2126 | currently around C<0.1>, but that's usually overkill. |
1935 | |
2127 | |
1936 | This watcher type is not meant for massive numbers of stat watchers, |
2128 | This watcher type is not meant for massive numbers of stat watchers, |
1937 | as even with OS-supported change notifications, this can be |
2129 | as even with OS-supported change notifications, this can be |
1938 | resource-intensive. |
2130 | resource-intensive. |
1939 | |
2131 | |
1940 | At the time of this writing, the only OS-specific interface implemented |
2132 | At the time of this writing, the only OS-specific interface implemented |
1941 | is the Linux inotify interface (implementing kqueue support is left as |
2133 | is the Linux inotify interface (implementing kqueue support is left as an |
1942 | an exercise for the reader. Note, however, that the author sees no way |
2134 | exercise for the reader. Note, however, that the author sees no way of |
1943 | of implementing C<ev_stat> semantics with kqueue). |
2135 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1944 | |
2136 | |
1945 | =head3 ABI Issues (Largefile Support) |
2137 | =head3 ABI Issues (Largefile Support) |
1946 | |
2138 | |
1947 | Libev by default (unless the user overrides this) uses the default |
2139 | Libev by default (unless the user overrides this) uses the default |
1948 | compilation environment, which means that on systems with large file |
2140 | compilation environment, which means that on systems with large file |
1949 | support disabled by default, you get the 32 bit version of the stat |
2141 | support disabled by default, you get the 32 bit version of the stat |
1950 | structure. When using the library from programs that change the ABI to |
2142 | structure. When using the library from programs that change the ABI to |
1951 | use 64 bit file offsets the programs will fail. In that case you have to |
2143 | use 64 bit file offsets the programs will fail. In that case you have to |
1952 | compile libev with the same flags to get binary compatibility. This is |
2144 | compile libev with the same flags to get binary compatibility. This is |
1953 | obviously the case with any flags that change the ABI, but the problem is |
2145 | obviously the case with any flags that change the ABI, but the problem is |
1954 | most noticeably disabled with ev_stat and large file support. |
2146 | most noticeably displayed with ev_stat and large file support. |
1955 | |
2147 | |
1956 | The solution for this is to lobby your distribution maker to make large |
2148 | The solution for this is to lobby your distribution maker to make large |
1957 | file interfaces available by default (as e.g. FreeBSD does) and not |
2149 | file interfaces available by default (as e.g. FreeBSD does) and not |
1958 | optional. Libev cannot simply switch on large file support because it has |
2150 | optional. Libev cannot simply switch on large file support because it has |
1959 | to exchange stat structures with application programs compiled using the |
2151 | to exchange stat structures with application programs compiled using the |
1960 | default compilation environment. |
2152 | default compilation environment. |
1961 | |
2153 | |
1962 | =head3 Inotify and Kqueue |
2154 | =head3 Inotify and Kqueue |
1963 | |
2155 | |
1964 | When C<inotify (7)> support has been compiled into libev (generally |
2156 | When C<inotify (7)> support has been compiled into libev and present at |
1965 | only available with Linux 2.6.25 or above due to bugs in earlier |
2157 | runtime, it will be used to speed up change detection where possible. The |
1966 | implementations) and present at runtime, it will be used to speed up |
2158 | inotify descriptor will be created lazily when the first C<ev_stat> |
1967 | change detection where possible. The inotify descriptor will be created |
2159 | watcher is being started. |
1968 | lazily when the first C<ev_stat> watcher is being started. |
|
|
1969 | |
2160 | |
1970 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2161 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1971 | except that changes might be detected earlier, and in some cases, to avoid |
2162 | except that changes might be detected earlier, and in some cases, to avoid |
1972 | making regular C<stat> calls. Even in the presence of inotify support |
2163 | making regular C<stat> calls. Even in the presence of inotify support |
1973 | there are many cases where libev has to resort to regular C<stat> polling, |
2164 | there are many cases where libev has to resort to regular C<stat> polling, |
1974 | but as long as the path exists, libev usually gets away without polling. |
2165 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2166 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2167 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2168 | xfs are fully working) libev usually gets away without polling. |
1975 | |
2169 | |
1976 | There is no support for kqueue, as apparently it cannot be used to |
2170 | There is no support for kqueue, as apparently it cannot be used to |
1977 | implement this functionality, due to the requirement of having a file |
2171 | implement this functionality, due to the requirement of having a file |
1978 | descriptor open on the object at all times, and detecting renames, unlinks |
2172 | descriptor open on the object at all times, and detecting renames, unlinks |
1979 | etc. is difficult. |
2173 | etc. is difficult. |
1980 | |
2174 | |
|
|
2175 | =head3 C<stat ()> is a synchronous operation |
|
|
2176 | |
|
|
2177 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2178 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2179 | ()>, which is a synchronous operation. |
|
|
2180 | |
|
|
2181 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2182 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2183 | as the path data is usually in memory already (except when starting the |
|
|
2184 | watcher). |
|
|
2185 | |
|
|
2186 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2187 | time due to network issues, and even under good conditions, a stat call |
|
|
2188 | often takes multiple milliseconds. |
|
|
2189 | |
|
|
2190 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2191 | paths, although this is fully supported by libev. |
|
|
2192 | |
1981 | =head3 The special problem of stat time resolution |
2193 | =head3 The special problem of stat time resolution |
1982 | |
2194 | |
1983 | The C<stat ()> system call only supports full-second resolution portably, and |
2195 | The C<stat ()> system call only supports full-second resolution portably, |
1984 | even on systems where the resolution is higher, most file systems still |
2196 | and even on systems where the resolution is higher, most file systems |
1985 | only support whole seconds. |
2197 | still only support whole seconds. |
1986 | |
2198 | |
1987 | That means that, if the time is the only thing that changes, you can |
2199 | That means that, if the time is the only thing that changes, you can |
1988 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2200 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1989 | calls your callback, which does something. When there is another update |
2201 | calls your callback, which does something. When there is another update |
1990 | within the same second, C<ev_stat> will be unable to detect unless the |
2202 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
2133 | |
2345 | |
2134 | =head3 Watcher-Specific Functions and Data Members |
2346 | =head3 Watcher-Specific Functions and Data Members |
2135 | |
2347 | |
2136 | =over 4 |
2348 | =over 4 |
2137 | |
2349 | |
2138 | =item ev_idle_init (ev_signal *, callback) |
2350 | =item ev_idle_init (ev_idle *, callback) |
2139 | |
2351 | |
2140 | Initialises and configures the idle watcher - it has no parameters of any |
2352 | Initialises and configures the idle watcher - it has no parameters of any |
2141 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2353 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2142 | believe me. |
2354 | believe me. |
2143 | |
2355 | |
… | |
… | |
2156 | // no longer anything immediate to do. |
2368 | // no longer anything immediate to do. |
2157 | } |
2369 | } |
2158 | |
2370 | |
2159 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2371 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2160 | ev_idle_init (idle_watcher, idle_cb); |
2372 | ev_idle_init (idle_watcher, idle_cb); |
2161 | ev_idle_start (loop, idle_cb); |
2373 | ev_idle_start (loop, idle_watcher); |
2162 | |
2374 | |
2163 | |
2375 | |
2164 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2376 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2165 | |
2377 | |
2166 | Prepare and check watchers are usually (but not always) used in pairs: |
2378 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2259 | struct pollfd fds [nfd]; |
2471 | struct pollfd fds [nfd]; |
2260 | // actual code will need to loop here and realloc etc. |
2472 | // actual code will need to loop here and realloc etc. |
2261 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2473 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2262 | |
2474 | |
2263 | /* the callback is illegal, but won't be called as we stop during check */ |
2475 | /* the callback is illegal, but won't be called as we stop during check */ |
2264 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2476 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2265 | ev_timer_start (loop, &tw); |
2477 | ev_timer_start (loop, &tw); |
2266 | |
2478 | |
2267 | // create one ev_io per pollfd |
2479 | // create one ev_io per pollfd |
2268 | for (int i = 0; i < nfd; ++i) |
2480 | for (int i = 0; i < nfd; ++i) |
2269 | { |
2481 | { |
… | |
… | |
2382 | some fds have to be watched and handled very quickly (with low latency), |
2594 | some fds have to be watched and handled very quickly (with low latency), |
2383 | and even priorities and idle watchers might have too much overhead. In |
2595 | and even priorities and idle watchers might have too much overhead. In |
2384 | this case you would put all the high priority stuff in one loop and all |
2596 | this case you would put all the high priority stuff in one loop and all |
2385 | the rest in a second one, and embed the second one in the first. |
2597 | the rest in a second one, and embed the second one in the first. |
2386 | |
2598 | |
2387 | As long as the watcher is active, the callback will be invoked every time |
2599 | As long as the watcher is active, the callback will be invoked every |
2388 | there might be events pending in the embedded loop. The callback must then |
2600 | time there might be events pending in the embedded loop. The callback |
2389 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2601 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2390 | their callbacks (you could also start an idle watcher to give the embedded |
2602 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2391 | loop strictly lower priority for example). You can also set the callback |
2603 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2392 | to C<0>, in which case the embed watcher will automatically execute the |
2604 | to give the embedded loop strictly lower priority for example). |
2393 | embedded loop sweep. |
|
|
2394 | |
2605 | |
2395 | As long as the watcher is started it will automatically handle events. The |
2606 | You can also set the callback to C<0>, in which case the embed watcher |
2396 | callback will be invoked whenever some events have been handled. You can |
2607 | will automatically execute the embedded loop sweep whenever necessary. |
2397 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2398 | interested in that. |
|
|
2399 | |
2608 | |
2400 | Also, there have not currently been made special provisions for forking: |
2609 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2401 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2610 | is active, i.e., the embedded loop will automatically be forked when the |
2402 | but you will also have to stop and restart any C<ev_embed> watchers |
2611 | embedding loop forks. In other cases, the user is responsible for calling |
2403 | yourself - but you can use a fork watcher to handle this automatically, |
2612 | C<ev_loop_fork> on the embedded loop. |
2404 | and future versions of libev might do just that. |
|
|
2405 | |
2613 | |
2406 | Unfortunately, not all backends are embeddable: only the ones returned by |
2614 | Unfortunately, not all backends are embeddable: only the ones returned by |
2407 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2615 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2408 | portable one. |
2616 | portable one. |
2409 | |
2617 | |
… | |
… | |
2503 | event loop blocks next and before C<ev_check> watchers are being called, |
2711 | event loop blocks next and before C<ev_check> watchers are being called, |
2504 | and only in the child after the fork. If whoever good citizen calling |
2712 | and only in the child after the fork. If whoever good citizen calling |
2505 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2713 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2506 | handlers will be invoked, too, of course. |
2714 | handlers will be invoked, too, of course. |
2507 | |
2715 | |
|
|
2716 | =head3 The special problem of life after fork - how is it possible? |
|
|
2717 | |
|
|
2718 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2719 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2720 | sequence should be handled by libev without any problems. |
|
|
2721 | |
|
|
2722 | This changes when the application actually wants to do event handling |
|
|
2723 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2724 | fork. |
|
|
2725 | |
|
|
2726 | The default mode of operation (for libev, with application help to detect |
|
|
2727 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2728 | when I<either> the parent I<or> the child process continues. |
|
|
2729 | |
|
|
2730 | When both processes want to continue using libev, then this is usually the |
|
|
2731 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2732 | supposed to continue with all watchers in place as before, while the other |
|
|
2733 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2734 | |
|
|
2735 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2736 | simply create a new event loop, which of course will be "empty", and |
|
|
2737 | use that for new watchers. This has the advantage of not touching more |
|
|
2738 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2739 | disadvantage of having to use multiple event loops (which do not support |
|
|
2740 | signal watchers). |
|
|
2741 | |
|
|
2742 | When this is not possible, or you want to use the default loop for |
|
|
2743 | other reasons, then in the process that wants to start "fresh", call |
|
|
2744 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2745 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2746 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2747 | also that in that case, you have to re-register any signal watchers. |
|
|
2748 | |
2508 | =head3 Watcher-Specific Functions and Data Members |
2749 | =head3 Watcher-Specific Functions and Data Members |
2509 | |
2750 | |
2510 | =over 4 |
2751 | =over 4 |
2511 | |
2752 | |
2512 | =item ev_fork_init (ev_signal *, callback) |
2753 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2629 | =over 4 |
2870 | =over 4 |
2630 | |
2871 | |
2631 | =item ev_async_init (ev_async *, callback) |
2872 | =item ev_async_init (ev_async *, callback) |
2632 | |
2873 | |
2633 | Initialises and configures the async watcher - it has no parameters of any |
2874 | Initialises and configures the async watcher - it has no parameters of any |
2634 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2875 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2635 | trust me. |
2876 | trust me. |
2636 | |
2877 | |
2637 | =item ev_async_send (loop, ev_async *) |
2878 | =item ev_async_send (loop, ev_async *) |
2638 | |
2879 | |
2639 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2880 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2640 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2881 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2641 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2882 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2642 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2883 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2643 | section below on what exactly this means). |
2884 | section below on what exactly this means). |
2644 | |
2885 | |
|
|
2886 | Note that, as with other watchers in libev, multiple events might get |
|
|
2887 | compressed into a single callback invocation (another way to look at this |
|
|
2888 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2889 | reset when the event loop detects that). |
|
|
2890 | |
2645 | This call incurs the overhead of a system call only once per loop iteration, |
2891 | This call incurs the overhead of a system call only once per event loop |
2646 | so while the overhead might be noticeable, it doesn't apply to repeated |
2892 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2647 | calls to C<ev_async_send>. |
2893 | repeated calls to C<ev_async_send> for the same event loop. |
2648 | |
2894 | |
2649 | =item bool = ev_async_pending (ev_async *) |
2895 | =item bool = ev_async_pending (ev_async *) |
2650 | |
2896 | |
2651 | Returns a non-zero value when C<ev_async_send> has been called on the |
2897 | Returns a non-zero value when C<ev_async_send> has been called on the |
2652 | watcher but the event has not yet been processed (or even noted) by the |
2898 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2655 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2901 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2656 | the loop iterates next and checks for the watcher to have become active, |
2902 | the loop iterates next and checks for the watcher to have become active, |
2657 | it will reset the flag again. C<ev_async_pending> can be used to very |
2903 | it will reset the flag again. C<ev_async_pending> can be used to very |
2658 | quickly check whether invoking the loop might be a good idea. |
2904 | quickly check whether invoking the loop might be a good idea. |
2659 | |
2905 | |
2660 | Not that this does I<not> check whether the watcher itself is pending, only |
2906 | Not that this does I<not> check whether the watcher itself is pending, |
2661 | whether it has been requested to make this watcher pending. |
2907 | only whether it has been requested to make this watcher pending: there |
|
|
2908 | is a time window between the event loop checking and resetting the async |
|
|
2909 | notification, and the callback being invoked. |
2662 | |
2910 | |
2663 | =back |
2911 | =back |
2664 | |
2912 | |
2665 | |
2913 | |
2666 | =head1 OTHER FUNCTIONS |
2914 | =head1 OTHER FUNCTIONS |
… | |
… | |
2845 | |
3093 | |
2846 | myclass obj; |
3094 | myclass obj; |
2847 | ev::io iow; |
3095 | ev::io iow; |
2848 | iow.set <myclass, &myclass::io_cb> (&obj); |
3096 | iow.set <myclass, &myclass::io_cb> (&obj); |
2849 | |
3097 | |
|
|
3098 | =item w->set (object *) |
|
|
3099 | |
|
|
3100 | This is an B<experimental> feature that might go away in a future version. |
|
|
3101 | |
|
|
3102 | This is a variation of a method callback - leaving out the method to call |
|
|
3103 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3104 | functor objects without having to manually specify the C<operator ()> all |
|
|
3105 | the time. Incidentally, you can then also leave out the template argument |
|
|
3106 | list. |
|
|
3107 | |
|
|
3108 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3109 | int revents)>. |
|
|
3110 | |
|
|
3111 | See the method-C<set> above for more details. |
|
|
3112 | |
|
|
3113 | Example: use a functor object as callback. |
|
|
3114 | |
|
|
3115 | struct myfunctor |
|
|
3116 | { |
|
|
3117 | void operator() (ev::io &w, int revents) |
|
|
3118 | { |
|
|
3119 | ... |
|
|
3120 | } |
|
|
3121 | } |
|
|
3122 | |
|
|
3123 | myfunctor f; |
|
|
3124 | |
|
|
3125 | ev::io w; |
|
|
3126 | w.set (&f); |
|
|
3127 | |
2850 | =item w->set<function> (void *data = 0) |
3128 | =item w->set<function> (void *data = 0) |
2851 | |
3129 | |
2852 | Also sets a callback, but uses a static method or plain function as |
3130 | Also sets a callback, but uses a static method or plain function as |
2853 | callback. The optional C<data> argument will be stored in the watcher's |
3131 | callback. The optional C<data> argument will be stored in the watcher's |
2854 | C<data> member and is free for you to use. |
3132 | C<data> member and is free for you to use. |
… | |
… | |
2940 | L<http://software.schmorp.de/pkg/EV>. |
3218 | L<http://software.schmorp.de/pkg/EV>. |
2941 | |
3219 | |
2942 | =item Python |
3220 | =item Python |
2943 | |
3221 | |
2944 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3222 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2945 | seems to be quite complete and well-documented. Note, however, that the |
3223 | seems to be quite complete and well-documented. |
2946 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2947 | for everybody else, and therefore, should never be applied in an installed |
|
|
2948 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2949 | libev). |
|
|
2950 | |
3224 | |
2951 | =item Ruby |
3225 | =item Ruby |
2952 | |
3226 | |
2953 | Tony Arcieri has written a ruby extension that offers access to a subset |
3227 | Tony Arcieri has written a ruby extension that offers access to a subset |
2954 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3228 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2955 | more on top of it. It can be found via gem servers. Its homepage is at |
3229 | more on top of it. It can be found via gem servers. Its homepage is at |
2956 | L<http://rev.rubyforge.org/>. |
3230 | L<http://rev.rubyforge.org/>. |
|
|
3231 | |
|
|
3232 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3233 | makes rev work even on mingw. |
|
|
3234 | |
|
|
3235 | =item Haskell |
|
|
3236 | |
|
|
3237 | A haskell binding to libev is available at |
|
|
3238 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
2957 | |
3239 | |
2958 | =item D |
3240 | =item D |
2959 | |
3241 | |
2960 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3242 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2961 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3243 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
… | |
… | |
3072 | |
3354 | |
3073 | #define EV_STANDALONE 1 |
3355 | #define EV_STANDALONE 1 |
3074 | #include "ev.h" |
3356 | #include "ev.h" |
3075 | |
3357 | |
3076 | Both header files and implementation files can be compiled with a C++ |
3358 | Both header files and implementation files can be compiled with a C++ |
3077 | compiler (at least, thats a stated goal, and breakage will be treated |
3359 | compiler (at least, that's a stated goal, and breakage will be treated |
3078 | as a bug). |
3360 | as a bug). |
3079 | |
3361 | |
3080 | You need the following files in your source tree, or in a directory |
3362 | You need the following files in your source tree, or in a directory |
3081 | in your include path (e.g. in libev/ when using -Ilibev): |
3363 | in your include path (e.g. in libev/ when using -Ilibev): |
3082 | |
3364 | |
… | |
… | |
3138 | keeps libev from including F<config.h>, and it also defines dummy |
3420 | keeps libev from including F<config.h>, and it also defines dummy |
3139 | implementations for some libevent functions (such as logging, which is not |
3421 | implementations for some libevent functions (such as logging, which is not |
3140 | supported). It will also not define any of the structs usually found in |
3422 | supported). It will also not define any of the structs usually found in |
3141 | F<event.h> that are not directly supported by the libev core alone. |
3423 | F<event.h> that are not directly supported by the libev core alone. |
3142 | |
3424 | |
|
|
3425 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3426 | configuration, but has to be more conservative. |
|
|
3427 | |
3143 | =item EV_USE_MONOTONIC |
3428 | =item EV_USE_MONOTONIC |
3144 | |
3429 | |
3145 | If defined to be C<1>, libev will try to detect the availability of the |
3430 | If defined to be C<1>, libev will try to detect the availability of the |
3146 | monotonic clock option at both compile time and runtime. Otherwise no use |
3431 | monotonic clock option at both compile time and runtime. Otherwise no |
3147 | of the monotonic clock option will be attempted. If you enable this, you |
3432 | use of the monotonic clock option will be attempted. If you enable this, |
3148 | usually have to link against librt or something similar. Enabling it when |
3433 | you usually have to link against librt or something similar. Enabling it |
3149 | the functionality isn't available is safe, though, although you have |
3434 | when the functionality isn't available is safe, though, although you have |
3150 | to make sure you link against any libraries where the C<clock_gettime> |
3435 | to make sure you link against any libraries where the C<clock_gettime> |
3151 | function is hiding in (often F<-lrt>). |
3436 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3152 | |
3437 | |
3153 | =item EV_USE_REALTIME |
3438 | =item EV_USE_REALTIME |
3154 | |
3439 | |
3155 | If defined to be C<1>, libev will try to detect the availability of the |
3440 | If defined to be C<1>, libev will try to detect the availability of the |
3156 | real-time clock option at compile time (and assume its availability at |
3441 | real-time clock option at compile time (and assume its availability |
3157 | runtime if successful). Otherwise no use of the real-time clock option will |
3442 | at runtime if successful). Otherwise no use of the real-time clock |
3158 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3443 | option will be attempted. This effectively replaces C<gettimeofday> |
3159 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3444 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3160 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3445 | correctness. See the note about libraries in the description of |
|
|
3446 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3447 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3448 | |
|
|
3449 | =item EV_USE_CLOCK_SYSCALL |
|
|
3450 | |
|
|
3451 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3452 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3453 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3454 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3455 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3456 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3457 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3458 | higher, as it simplifies linking (no need for C<-lrt>). |
3161 | |
3459 | |
3162 | =item EV_USE_NANOSLEEP |
3460 | =item EV_USE_NANOSLEEP |
3163 | |
3461 | |
3164 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3462 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3165 | and will use it for delays. Otherwise it will use C<select ()>. |
3463 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3181 | |
3479 | |
3182 | =item EV_SELECT_USE_FD_SET |
3480 | =item EV_SELECT_USE_FD_SET |
3183 | |
3481 | |
3184 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3482 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3185 | structure. This is useful if libev doesn't compile due to a missing |
3483 | structure. This is useful if libev doesn't compile due to a missing |
3186 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3484 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3187 | exotic systems. This usually limits the range of file descriptors to some |
3485 | on exotic systems. This usually limits the range of file descriptors to |
3188 | low limit such as 1024 or might have other limitations (winsocket only |
3486 | some low limit such as 1024 or might have other limitations (winsocket |
3189 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3487 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3190 | influence the size of the C<fd_set> used. |
3488 | configures the maximum size of the C<fd_set>. |
3191 | |
3489 | |
3192 | =item EV_SELECT_IS_WINSOCKET |
3490 | =item EV_SELECT_IS_WINSOCKET |
3193 | |
3491 | |
3194 | When defined to C<1>, the select backend will assume that |
3492 | When defined to C<1>, the select backend will assume that |
3195 | select/socket/connect etc. don't understand file descriptors but |
3493 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3554 | loop, as long as you don't confuse yourself). The only exception is that |
3852 | loop, as long as you don't confuse yourself). The only exception is that |
3555 | you must not do this from C<ev_periodic> reschedule callbacks. |
3853 | you must not do this from C<ev_periodic> reschedule callbacks. |
3556 | |
3854 | |
3557 | Care has been taken to ensure that libev does not keep local state inside |
3855 | Care has been taken to ensure that libev does not keep local state inside |
3558 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3856 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3559 | they do not clal any callbacks. |
3857 | they do not call any callbacks. |
3560 | |
3858 | |
3561 | =head2 COMPILER WARNINGS |
3859 | =head2 COMPILER WARNINGS |
3562 | |
3860 | |
3563 | Depending on your compiler and compiler settings, you might get no or a |
3861 | Depending on your compiler and compiler settings, you might get no or a |
3564 | lot of warnings when compiling libev code. Some people are apparently |
3862 | lot of warnings when compiling libev code. Some people are apparently |
… | |
… | |
3598 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3896 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3599 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3897 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3600 | ==2274== still reachable: 256 bytes in 1 blocks. |
3898 | ==2274== still reachable: 256 bytes in 1 blocks. |
3601 | |
3899 | |
3602 | Then there is no memory leak, just as memory accounted to global variables |
3900 | Then there is no memory leak, just as memory accounted to global variables |
3603 | is not a memleak - the memory is still being refernced, and didn't leak. |
3901 | is not a memleak - the memory is still being referenced, and didn't leak. |
3604 | |
3902 | |
3605 | Similarly, under some circumstances, valgrind might report kernel bugs |
3903 | Similarly, under some circumstances, valgrind might report kernel bugs |
3606 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3904 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3607 | although an acceptable workaround has been found here), or it might be |
3905 | although an acceptable workaround has been found here), or it might be |
3608 | confused. |
3906 | confused. |
… | |
… | |
3637 | way (note also that glib is the slowest event library known to man). |
3935 | way (note also that glib is the slowest event library known to man). |
3638 | |
3936 | |
3639 | There is no supported compilation method available on windows except |
3937 | There is no supported compilation method available on windows except |
3640 | embedding it into other applications. |
3938 | embedding it into other applications. |
3641 | |
3939 | |
|
|
3940 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
3941 | tries its best, but under most conditions, signals will simply not work. |
|
|
3942 | |
3642 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3943 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3643 | accept large writes: instead of resulting in a partial write, windows will |
3944 | accept large writes: instead of resulting in a partial write, windows will |
3644 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3945 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3645 | so make sure you only write small amounts into your sockets (less than a |
3946 | so make sure you only write small amounts into your sockets (less than a |
3646 | megabyte seems safe, but this apparently depends on the amount of memory |
3947 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3650 | the abysmal performance of winsockets, using a large number of sockets |
3951 | the abysmal performance of winsockets, using a large number of sockets |
3651 | is not recommended (and not reasonable). If your program needs to use |
3952 | is not recommended (and not reasonable). If your program needs to use |
3652 | more than a hundred or so sockets, then likely it needs to use a totally |
3953 | more than a hundred or so sockets, then likely it needs to use a totally |
3653 | different implementation for windows, as libev offers the POSIX readiness |
3954 | different implementation for windows, as libev offers the POSIX readiness |
3654 | notification model, which cannot be implemented efficiently on windows |
3955 | notification model, which cannot be implemented efficiently on windows |
3655 | (Microsoft monopoly games). |
3956 | (due to Microsoft monopoly games). |
3656 | |
3957 | |
3657 | A typical way to use libev under windows is to embed it (see the embedding |
3958 | A typical way to use libev under windows is to embed it (see the embedding |
3658 | section for details) and use the following F<evwrap.h> header file instead |
3959 | section for details) and use the following F<evwrap.h> header file instead |
3659 | of F<ev.h>: |
3960 | of F<ev.h>: |
3660 | |
3961 | |
… | |
… | |
3696 | |
3997 | |
3697 | Early versions of winsocket's select only supported waiting for a maximum |
3998 | Early versions of winsocket's select only supported waiting for a maximum |
3698 | of C<64> handles (probably owning to the fact that all windows kernels |
3999 | of C<64> handles (probably owning to the fact that all windows kernels |
3699 | can only wait for C<64> things at the same time internally; Microsoft |
4000 | can only wait for C<64> things at the same time internally; Microsoft |
3700 | recommends spawning a chain of threads and wait for 63 handles and the |
4001 | recommends spawning a chain of threads and wait for 63 handles and the |
3701 | previous thread in each. Great). |
4002 | previous thread in each. Sounds great!). |
3702 | |
4003 | |
3703 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4004 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3704 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4005 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3705 | call (which might be in libev or elsewhere, for example, perl does its own |
4006 | call (which might be in libev or elsewhere, for example, perl and many |
3706 | select emulation on windows). |
4007 | other interpreters do their own select emulation on windows). |
3707 | |
4008 | |
3708 | Another limit is the number of file descriptors in the Microsoft runtime |
4009 | Another limit is the number of file descriptors in the Microsoft runtime |
3709 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4010 | libraries, which by default is C<64> (there must be a hidden I<64> |
3710 | or something like this inside Microsoft). You can increase this by calling |
4011 | fetish or something like this inside Microsoft). You can increase this |
3711 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4012 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3712 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4013 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3713 | libraries. |
|
|
3714 | |
|
|
3715 | This might get you to about C<512> or C<2048> sockets (depending on |
4014 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3716 | windows version and/or the phase of the moon). To get more, you need to |
4015 | (depending on windows version and/or the phase of the moon). To get more, |
3717 | wrap all I/O functions and provide your own fd management, but the cost of |
4016 | you need to wrap all I/O functions and provide your own fd management, but |
3718 | calling select (O(n²)) will likely make this unworkable. |
4017 | the cost of calling select (O(n²)) will likely make this unworkable. |
3719 | |
4018 | |
3720 | =back |
4019 | =back |
3721 | |
4020 | |
3722 | =head2 PORTABILITY REQUIREMENTS |
4021 | =head2 PORTABILITY REQUIREMENTS |
3723 | |
4022 | |
… | |
… | |
3844 | involves iterating over all running async watchers or all signal numbers. |
4143 | involves iterating over all running async watchers or all signal numbers. |
3845 | |
4144 | |
3846 | =back |
4145 | =back |
3847 | |
4146 | |
3848 | |
4147 | |
|
|
4148 | =head1 GLOSSARY |
|
|
4149 | |
|
|
4150 | =over 4 |
|
|
4151 | |
|
|
4152 | =item active |
|
|
4153 | |
|
|
4154 | A watcher is active as long as it has been started (has been attached to |
|
|
4155 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4156 | |
|
|
4157 | =item application |
|
|
4158 | |
|
|
4159 | In this document, an application is whatever is using libev. |
|
|
4160 | |
|
|
4161 | =item callback |
|
|
4162 | |
|
|
4163 | The address of a function that is called when some event has been |
|
|
4164 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4165 | received the event, and the actual event bitset. |
|
|
4166 | |
|
|
4167 | =item callback invocation |
|
|
4168 | |
|
|
4169 | The act of calling the callback associated with a watcher. |
|
|
4170 | |
|
|
4171 | =item event |
|
|
4172 | |
|
|
4173 | A change of state of some external event, such as data now being available |
|
|
4174 | for reading on a file descriptor, time having passed or simply not having |
|
|
4175 | any other events happening anymore. |
|
|
4176 | |
|
|
4177 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4178 | C<EV_TIMEOUT>). |
|
|
4179 | |
|
|
4180 | =item event library |
|
|
4181 | |
|
|
4182 | A software package implementing an event model and loop. |
|
|
4183 | |
|
|
4184 | =item event loop |
|
|
4185 | |
|
|
4186 | An entity that handles and processes external events and converts them |
|
|
4187 | into callback invocations. |
|
|
4188 | |
|
|
4189 | =item event model |
|
|
4190 | |
|
|
4191 | The model used to describe how an event loop handles and processes |
|
|
4192 | watchers and events. |
|
|
4193 | |
|
|
4194 | =item pending |
|
|
4195 | |
|
|
4196 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4197 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4198 | pending status is explicitly cleared by the application. |
|
|
4199 | |
|
|
4200 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4201 | its pending status. |
|
|
4202 | |
|
|
4203 | =item real time |
|
|
4204 | |
|
|
4205 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4206 | |
|
|
4207 | =item wall-clock time |
|
|
4208 | |
|
|
4209 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4210 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
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4211 | clock. |
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4212 | |
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4213 | =item watcher |
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4214 | |
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4215 | A data structure that describes interest in certain events. Watchers need |
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4216 | to be started (attached to an event loop) before they can receive events. |
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4217 | |
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4218 | =item watcher invocation |
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4219 | |
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4220 | The act of calling the callback associated with a watcher. |
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4221 | |
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4222 | =back |
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4223 | |
3849 | =head1 AUTHOR |
4224 | =head1 AUTHOR |
3850 | |
4225 | |
3851 | Marc Lehmann <libev@schmorp.de>. |
4226 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3852 | |
4227 | |