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8 | |
8 | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
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13 | |
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14 | #include <stdio.h> // for puts |
13 | |
15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_TYPE |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
… | |
… | |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // unloop was called, so exit |
62 | return 0; |
64 | return 0; |
63 | } |
65 | } |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
66 | |
70 | |
67 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 ABOUT LIBEV |
70 | |
84 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
74 | |
88 | |
… | |
… | |
84 | =head2 FEATURES |
98 | =head2 FEATURES |
85 | |
99 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
107 | change events (C<ev_child>), and event watchers dealing with the event |
94 | file watchers (C<ev_stat>) and even limited support for fork events |
108 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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110 | limited support for fork events (C<ev_fork>). |
96 | |
111 | |
97 | It also is quite fast (see this |
112 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
113 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
114 | for example). |
100 | |
115 | |
… | |
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103 | Libev is very configurable. In this manual the default (and most common) |
118 | Libev is very configurable. In this manual the default (and most common) |
104 | configuration will be described, which supports multiple event loops. For |
119 | configuration will be described, which supports multiple event loops. For |
105 | more info about various configuration options please have a look at |
120 | more info about various configuration options please have a look at |
106 | B<EMBED> section in this manual. If libev was configured without support |
121 | B<EMBED> section in this manual. If libev was configured without support |
107 | for multiple event loops, then all functions taking an initial argument of |
122 | for multiple event loops, then all functions taking an initial argument of |
108 | name C<loop> (which is always of type C<ev_loop *>) will not have |
123 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
109 | this argument. |
124 | this argument. |
110 | |
125 | |
111 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
112 | |
127 | |
113 | Libev represents time as a single floating point number, representing the |
128 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
129 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
130 | 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 |
131 | 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 |
132 | 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 |
133 | 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 |
134 | component C<stamp> might indicate, it is also used for time differences |
120 | throughout libev. |
135 | throughout libev. |
121 | |
136 | |
122 | =head1 ERROR HANDLING |
137 | =head1 ERROR HANDLING |
123 | |
138 | |
… | |
… | |
298 | If you don't know what event loop to use, use the one returned from this |
313 | If you don't know what event loop to use, use the one returned from this |
299 | function. |
314 | function. |
300 | |
315 | |
301 | Note that this function is I<not> thread-safe, so if you want to use it |
316 | 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, |
317 | from multiple threads, you have to lock (note also that this is unlikely, |
303 | as loops cannot bes hared easily between threads anyway). |
318 | as loops cannot be shared easily between threads anyway). |
304 | |
319 | |
305 | The default loop is the only loop that can handle C<ev_signal> and |
320 | 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 |
321 | 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 |
322 | 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 |
323 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
… | |
348 | flag. |
363 | flag. |
349 | |
364 | |
350 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
365 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
351 | environment variable. |
366 | environment variable. |
352 | |
367 | |
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368 | =item C<EVFLAG_NOINOTIFY> |
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369 | |
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370 | When this flag is specified, then libev will not attempt to use the |
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371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
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372 | testing, this flag can be useful to conserve inotify file descriptors, as |
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373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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374 | |
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375 | =item C<EVFLAG_SIGNALFD> |
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376 | |
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377 | When this flag is specified, then libev will attempt to use the |
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378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
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379 | delivers signals synchronously, which makes it both faster and might make |
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380 | it possible to get the queued signal data. It can also simplify signal |
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381 | handling with threads, as long as you properly block signals in your |
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382 | threads that are not interested in handling them. |
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383 | |
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384 | Signalfd will not be used by default as this changes your signal mask, and |
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385 | there are a lot of shoddy libraries and programs (glib's threadpool for |
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386 | example) that can't properly initialise their signal masks. |
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387 | |
353 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
354 | |
389 | |
355 | This is your standard select(2) backend. Not I<completely> standard, as |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
356 | libev tries to roll its own fd_set with no limits on the number of fds, |
391 | libev tries to roll its own fd_set with no limits on the number of fds, |
357 | but if that fails, expect a fairly low limit on the number of fds when |
392 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
381 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
416 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
382 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
417 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
383 | |
418 | |
384 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
419 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
385 | |
420 | |
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421 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
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422 | kernels). |
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423 | |
386 | For few fds, this backend is a bit little slower than poll and select, |
424 | 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 |
425 | 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), |
426 | 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). |
427 | epoll scales either O(1) or O(active_fds). |
390 | |
428 | |
391 | The epoll syscalls are the most misdesigned of the more advanced event |
429 | The epoll mechanism deserves honorable mention as the most misdesigned |
392 | mechanisms: problems include silently dropping fds, requiring a system |
430 | of the more advanced event mechanisms: mere annoyances include silently |
393 | call per change per fd (and unnecessary guessing of parameters), problems |
431 | dropping file descriptors, requiring a system call per change per file |
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432 | descriptor (and unnecessary guessing of parameters), problems with dup and |
394 | with dup and so on. The biggest issue is fork races, however - if a |
433 | so on. The biggest issue is fork races, however - if a program forks then |
395 | program forks then I<both> parent and child process have to recreate the |
434 | I<both> parent and child process have to recreate the epoll set, which can |
396 | epoll set, which can take considerable time (one syscall per fd) and is of |
435 | take considerable time (one syscall per file descriptor) and is of course |
397 | course hard to detect. |
436 | hard to detect. |
398 | |
437 | |
399 | Epoll is also notoriously buggy - embedding epoll fds should work, but |
438 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
400 | of course doesn't, and epoll just loves to report events for totally |
439 | of course I<doesn't>, and epoll just loves to report events for totally |
401 | I<different> file descriptors (even already closed ones, so one cannot |
440 | I<different> file descriptors (even already closed ones, so one cannot |
402 | even remove them from the set) than registered in the set (especially |
441 | even remove them from the set) than registered in the set (especially |
403 | on SMP systems). Libev tries to counter these spurious notifications by |
442 | on SMP systems). Libev tries to counter these spurious notifications by |
404 | employing an additional generation counter and comparing that against the |
443 | employing an additional generation counter and comparing that against the |
405 | events to filter out spurious ones. |
444 | events to filter out spurious ones, recreating the set when required. |
406 | |
445 | |
407 | While stopping, setting and starting an I/O watcher in the same iteration |
446 | While stopping, setting and starting an I/O watcher in the same iteration |
408 | will result in some caching, there is still a system call per such incident |
447 | will result in some caching, there is still a system call per such |
409 | (because the fd could point to a different file description now), so its |
448 | incident (because the same I<file descriptor> could point to a different |
410 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
449 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
411 | very well if you register events for both fds. |
450 | file descriptors might not work very well if you register events for both |
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451 | file descriptors. |
412 | |
452 | |
413 | Best performance from this backend is achieved by not unregistering all |
453 | Best performance from this backend is achieved by not unregistering all |
414 | watchers for a file descriptor until it has been closed, if possible, |
454 | watchers for a file descriptor until it has been closed, if possible, |
415 | i.e. keep at least one watcher active per fd at all times. Stopping and |
455 | i.e. keep at least one watcher active per fd at all times. Stopping and |
416 | starting a watcher (without re-setting it) also usually doesn't cause |
456 | starting a watcher (without re-setting it) also usually doesn't cause |
417 | extra overhead. A fork can both result in spurious notifications as well |
457 | extra overhead. A fork can both result in spurious notifications as well |
418 | as in libev having to destroy and recreate the epoll object, which can |
458 | as in libev having to destroy and recreate the epoll object, which can |
419 | take considerable time and thus should be avoided. |
459 | take considerable time and thus should be avoided. |
420 | |
460 | |
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461 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
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462 | faster than epoll for maybe up to a hundred file descriptors, depending on |
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463 | the usage. So sad. |
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464 | |
421 | While nominally embeddable in other event loops, this feature is broken in |
465 | While nominally embeddable in other event loops, this feature is broken in |
422 | all kernel versions tested so far. |
466 | all kernel versions tested so far. |
423 | |
467 | |
424 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
468 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
425 | C<EVBACKEND_POLL>. |
469 | C<EVBACKEND_POLL>. |
426 | |
470 | |
427 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
471 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
428 | |
472 | |
429 | Kqueue deserves special mention, as at the time of this writing, it was |
473 | Kqueue deserves special mention, as at the time of this writing, it |
430 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
474 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
431 | anything but sockets and pipes, except on Darwin, where of course it's |
475 | with anything but sockets and pipes, except on Darwin, where of course |
432 | completely useless). For this reason it's not being "auto-detected" unless |
476 | it's completely useless). Unlike epoll, however, whose brokenness |
433 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
477 | is by design, these kqueue bugs can (and eventually will) be fixed |
434 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
478 | without API changes to existing programs. For this reason it's not being |
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479 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
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480 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
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481 | system like NetBSD. |
435 | |
482 | |
436 | You still can embed kqueue into a normal poll or select backend and use it |
483 | You still can embed kqueue into a normal poll or select backend and use it |
437 | only for sockets (after having made sure that sockets work with kqueue on |
484 | only for sockets (after having made sure that sockets work with kqueue on |
438 | the target platform). See C<ev_embed> watchers for more info. |
485 | the target platform). See C<ev_embed> watchers for more info. |
439 | |
486 | |
… | |
… | |
449 | |
496 | |
450 | While nominally embeddable in other event loops, this doesn't work |
497 | While nominally embeddable in other event loops, this doesn't work |
451 | everywhere, so you might need to test for this. And since it is broken |
498 | everywhere, so you might need to test for this. And since it is broken |
452 | almost everywhere, you should only use it when you have a lot of sockets |
499 | almost everywhere, you should only use it when you have a lot of sockets |
453 | (for which it usually works), by embedding it into another event loop |
500 | (for which it usually works), by embedding it into another event loop |
454 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
501 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
455 | using it only for sockets. |
502 | also broken on OS X)) and, did I mention it, using it only for sockets. |
456 | |
503 | |
457 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
504 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
458 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
505 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
459 | C<NOTE_EOF>. |
506 | C<NOTE_EOF>. |
460 | |
507 | |
… | |
… | |
495 | |
542 | |
496 | It is definitely not recommended to use this flag. |
543 | It is definitely not recommended to use this flag. |
497 | |
544 | |
498 | =back |
545 | =back |
499 | |
546 | |
500 | If one or more of these are or'ed into the flags value, then only these |
547 | If one or more of the backend flags are or'ed into the flags value, |
501 | backends will be tried (in the reverse order as listed here). If none are |
548 | then only these backends will be tried (in the reverse order as listed |
502 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
549 | here). If none are specified, all backends in C<ev_recommended_backends |
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550 | ()> will be tried. |
503 | |
551 | |
504 | Example: This is the most typical usage. |
552 | Example: This is the most typical usage. |
505 | |
553 | |
506 | if (!ev_default_loop (0)) |
554 | if (!ev_default_loop (0)) |
507 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
555 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
… | |
… | |
550 | as signal and child watchers) would need to be stopped manually. |
598 | as signal and child watchers) would need to be stopped manually. |
551 | |
599 | |
552 | In general it is not advisable to call this function except in the |
600 | In general it is not advisable to call this function except in the |
553 | rare occasion where you really need to free e.g. the signal handling |
601 | rare occasion where you really need to free e.g. the signal handling |
554 | pipe fds. If you need dynamically allocated loops it is better to use |
602 | pipe fds. If you need dynamically allocated loops it is better to use |
555 | C<ev_loop_new> and C<ev_loop_destroy>). |
603 | C<ev_loop_new> and C<ev_loop_destroy>. |
556 | |
604 | |
557 | =item ev_loop_destroy (loop) |
605 | =item ev_loop_destroy (loop) |
558 | |
606 | |
559 | Like C<ev_default_destroy>, but destroys an event loop created by an |
607 | Like C<ev_default_destroy>, but destroys an event loop created by an |
560 | earlier call to C<ev_loop_new>. |
608 | earlier call to C<ev_loop_new>. |
… | |
… | |
598 | |
646 | |
599 | This value can sometimes be useful as a generation counter of sorts (it |
647 | This value can sometimes be useful as a generation counter of sorts (it |
600 | "ticks" the number of loop iterations), as it roughly corresponds with |
648 | "ticks" the number of loop iterations), as it roughly corresponds with |
601 | C<ev_prepare> and C<ev_check> calls. |
649 | C<ev_prepare> and C<ev_check> calls. |
602 | |
650 | |
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651 | =item unsigned int ev_loop_depth (loop) |
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652 | |
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653 | Returns the number of times C<ev_loop> was entered minus the number of |
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654 | times C<ev_loop> was exited, in other words, the recursion depth. |
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655 | |
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656 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
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657 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
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658 | in which case it is higher. |
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659 | |
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660 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
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661 | etc.), doesn't count as exit. |
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662 | |
603 | =item unsigned int ev_backend (loop) |
663 | =item unsigned int ev_backend (loop) |
604 | |
664 | |
605 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
665 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
606 | use. |
666 | use. |
607 | |
667 | |
… | |
… | |
621 | |
681 | |
622 | This function is rarely useful, but when some event callback runs for a |
682 | This function is rarely useful, but when some event callback runs for a |
623 | very long time without entering the event loop, updating libev's idea of |
683 | very long time without entering the event loop, updating libev's idea of |
624 | the current time is a good idea. |
684 | the current time is a good idea. |
625 | |
685 | |
626 | See also "The special problem of time updates" in the C<ev_timer> section. |
686 | See also L<The special problem of time updates> in the C<ev_timer> section. |
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687 | |
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688 | =item ev_suspend (loop) |
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689 | |
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690 | =item ev_resume (loop) |
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691 | |
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692 | These two functions suspend and resume a loop, for use when the loop is |
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693 | not used for a while and timeouts should not be processed. |
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694 | |
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695 | A typical use case would be an interactive program such as a game: When |
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696 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
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697 | would be best to handle timeouts as if no time had actually passed while |
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698 | the program was suspended. This can be achieved by calling C<ev_suspend> |
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699 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
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700 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
701 | |
|
|
702 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
703 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
704 | will be rescheduled (that is, they will lose any events that would have |
|
|
705 | occured while suspended). |
|
|
706 | |
|
|
707 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
708 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
709 | without a previous call to C<ev_suspend>. |
|
|
710 | |
|
|
711 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
712 | event loop time (see C<ev_now_update>). |
627 | |
713 | |
628 | =item ev_loop (loop, int flags) |
714 | =item ev_loop (loop, int flags) |
629 | |
715 | |
630 | Finally, this is it, the event handler. This function usually is called |
716 | Finally, this is it, the event handler. This function usually is called |
631 | after you initialised all your watchers and you want to start handling |
717 | after you have initialised all your watchers and you want to start |
632 | events. |
718 | handling events. |
633 | |
719 | |
634 | If the flags argument is specified as C<0>, it will not return until |
720 | If the flags argument is specified as C<0>, it will not return until |
635 | either no event watchers are active anymore or C<ev_unloop> was called. |
721 | either no event watchers are active anymore or C<ev_unloop> was called. |
636 | |
722 | |
637 | Please note that an explicit C<ev_unloop> is usually better than |
723 | Please note that an explicit C<ev_unloop> is usually better than |
… | |
… | |
647 | the loop. |
733 | the loop. |
648 | |
734 | |
649 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
735 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
650 | necessary) and will handle those and any already outstanding ones. It |
736 | necessary) and will handle those and any already outstanding ones. It |
651 | will block your process until at least one new event arrives (which could |
737 | will block your process until at least one new event arrives (which could |
652 | be an event internal to libev itself, so there is no guarentee that a |
738 | be an event internal to libev itself, so there is no guarantee that a |
653 | user-registered callback will be called), and will return after one |
739 | user-registered callback will be called), and will return after one |
654 | iteration of the loop. |
740 | iteration of the loop. |
655 | |
741 | |
656 | This is useful if you are waiting for some external event in conjunction |
742 | This is useful if you are waiting for some external event in conjunction |
657 | with something not expressible using other libev watchers (i.e. "roll your |
743 | with something not expressible using other libev watchers (i.e. "roll your |
… | |
… | |
711 | |
797 | |
712 | Ref/unref can be used to add or remove a reference count on the event |
798 | Ref/unref can be used to add or remove a reference count on the event |
713 | loop: Every watcher keeps one reference, and as long as the reference |
799 | loop: Every watcher keeps one reference, and as long as the reference |
714 | count is nonzero, C<ev_loop> will not return on its own. |
800 | count is nonzero, C<ev_loop> will not return on its own. |
715 | |
801 | |
716 | If you have a watcher you never unregister that should not keep C<ev_loop> |
802 | This is useful when you have a watcher that you never intend to |
717 | from returning, call ev_unref() after starting, and ev_ref() before |
803 | unregister, but that nevertheless should not keep C<ev_loop> from |
|
|
804 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
718 | stopping it. |
805 | before stopping it. |
719 | |
806 | |
720 | As an example, libev itself uses this for its internal signal pipe: It is |
807 | As an example, libev itself uses this for its internal signal pipe: It |
721 | not visible to the libev user and should not keep C<ev_loop> from exiting |
808 | is not visible to the libev user and should not keep C<ev_loop> from |
722 | if no event watchers registered by it are active. It is also an excellent |
809 | exiting if no event watchers registered by it are active. It is also an |
723 | way to do this for generic recurring timers or from within third-party |
810 | excellent way to do this for generic recurring timers or from within |
724 | libraries. Just remember to I<unref after start> and I<ref before stop> |
811 | third-party libraries. Just remember to I<unref after start> and I<ref |
725 | (but only if the watcher wasn't active before, or was active before, |
812 | before stop> (but only if the watcher wasn't active before, or was active |
726 | respectively). |
813 | before, respectively. Note also that libev might stop watchers itself |
|
|
814 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
815 | in the callback). |
727 | |
816 | |
728 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
817 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
729 | running when nothing else is active. |
818 | running when nothing else is active. |
730 | |
819 | |
731 | ev_signal exitsig; |
820 | ev_signal exitsig; |
… | |
… | |
760 | |
849 | |
761 | By setting a higher I<io collect interval> you allow libev to spend more |
850 | By setting a higher I<io collect interval> you allow libev to spend more |
762 | time collecting I/O events, so you can handle more events per iteration, |
851 | time collecting I/O events, so you can handle more events per iteration, |
763 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
852 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
764 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
853 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
765 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
854 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
855 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
856 | once per this interval, on average. |
766 | |
857 | |
767 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
858 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
768 | to spend more time collecting timeouts, at the expense of increased |
859 | to spend more time collecting timeouts, at the expense of increased |
769 | latency/jitter/inexactness (the watcher callback will be called |
860 | latency/jitter/inexactness (the watcher callback will be called |
770 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
861 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
772 | |
863 | |
773 | Many (busy) programs can usually benefit by setting the I/O collect |
864 | Many (busy) programs can usually benefit by setting the I/O collect |
774 | interval to a value near C<0.1> or so, which is often enough for |
865 | interval to a value near C<0.1> or so, which is often enough for |
775 | interactive servers (of course not for games), likewise for timeouts. It |
866 | interactive servers (of course not for games), likewise for timeouts. It |
776 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
867 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
777 | as this approaches the timing granularity of most systems. |
868 | as this approaches the timing granularity of most systems. Note that if |
|
|
869 | you do transactions with the outside world and you can't increase the |
|
|
870 | parallelity, then this setting will limit your transaction rate (if you |
|
|
871 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
872 | then you can't do more than 100 transations per second). |
778 | |
873 | |
779 | Setting the I<timeout collect interval> can improve the opportunity for |
874 | Setting the I<timeout collect interval> can improve the opportunity for |
780 | saving power, as the program will "bundle" timer callback invocations that |
875 | saving power, as the program will "bundle" timer callback invocations that |
781 | are "near" in time together, by delaying some, thus reducing the number of |
876 | are "near" in time together, by delaying some, thus reducing the number of |
782 | times the process sleeps and wakes up again. Another useful technique to |
877 | times the process sleeps and wakes up again. Another useful technique to |
783 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
878 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
784 | they fire on, say, one-second boundaries only. |
879 | they fire on, say, one-second boundaries only. |
|
|
880 | |
|
|
881 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
882 | more often than 100 times per second: |
|
|
883 | |
|
|
884 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
885 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
886 | |
|
|
887 | =item ev_invoke_pending (loop) |
|
|
888 | |
|
|
889 | This call will simply invoke all pending watchers while resetting their |
|
|
890 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
|
891 | but when overriding the invoke callback this call comes handy. |
|
|
892 | |
|
|
893 | =item int ev_pending_count (loop) |
|
|
894 | |
|
|
895 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
896 | are pending. |
|
|
897 | |
|
|
898 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
899 | |
|
|
900 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
901 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
902 | this callback instead. This is useful, for example, when you want to |
|
|
903 | invoke the actual watchers inside another context (another thread etc.). |
|
|
904 | |
|
|
905 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
906 | callback. |
|
|
907 | |
|
|
908 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
909 | |
|
|
910 | Sometimes you want to share the same loop between multiple threads. This |
|
|
911 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
912 | each call to a libev function. |
|
|
913 | |
|
|
914 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
915 | wait for it to return. One way around this is to wake up the loop via |
|
|
916 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
917 | and I<acquire> callbacks on the loop. |
|
|
918 | |
|
|
919 | When set, then C<release> will be called just before the thread is |
|
|
920 | suspended waiting for new events, and C<acquire> is called just |
|
|
921 | afterwards. |
|
|
922 | |
|
|
923 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
924 | C<acquire> will just call the mutex_lock function again. |
|
|
925 | |
|
|
926 | While event loop modifications are allowed between invocations of |
|
|
927 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
928 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
929 | have no effect on the set of file descriptors being watched, or the time |
|
|
930 | waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
931 | to take note of any changes you made. |
|
|
932 | |
|
|
933 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
934 | invocations of C<release> and C<acquire>. |
|
|
935 | |
|
|
936 | See also the locking example in the C<THREADS> section later in this |
|
|
937 | document. |
|
|
938 | |
|
|
939 | =item ev_set_userdata (loop, void *data) |
|
|
940 | |
|
|
941 | =item ev_userdata (loop) |
|
|
942 | |
|
|
943 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
944 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
945 | C<0.> |
|
|
946 | |
|
|
947 | These two functions can be used to associate arbitrary data with a loop, |
|
|
948 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
949 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
950 | any other purpose as well. |
785 | |
951 | |
786 | =item ev_loop_verify (loop) |
952 | =item ev_loop_verify (loop) |
787 | |
953 | |
788 | This function only does something when C<EV_VERIFY> support has been |
954 | This function only does something when C<EV_VERIFY> support has been |
789 | compiled in, which is the default for non-minimal builds. It tries to go |
955 | compiled in, which is the default for non-minimal builds. It tries to go |
… | |
… | |
915 | |
1081 | |
916 | =item C<EV_ASYNC> |
1082 | =item C<EV_ASYNC> |
917 | |
1083 | |
918 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1084 | The given async watcher has been asynchronously notified (see C<ev_async>). |
919 | |
1085 | |
|
|
1086 | =item C<EV_CUSTOM> |
|
|
1087 | |
|
|
1088 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1089 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
1090 | |
920 | =item C<EV_ERROR> |
1091 | =item C<EV_ERROR> |
921 | |
1092 | |
922 | An unspecified error has occurred, the watcher has been stopped. This might |
1093 | An unspecified error has occurred, the watcher has been stopped. This might |
923 | happen because the watcher could not be properly started because libev |
1094 | happen because the watcher could not be properly started because libev |
924 | ran out of memory, a file descriptor was found to be closed or any other |
1095 | ran out of memory, a file descriptor was found to be closed or any other |
… | |
… | |
961 | |
1132 | |
962 | ev_io w; |
1133 | ev_io w; |
963 | ev_init (&w, my_cb); |
1134 | ev_init (&w, my_cb); |
964 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1135 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
965 | |
1136 | |
966 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1137 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
967 | |
1138 | |
968 | This macro initialises the type-specific parts of a watcher. You need to |
1139 | This macro initialises the type-specific parts of a watcher. You need to |
969 | call C<ev_init> at least once before you call this macro, but you can |
1140 | call C<ev_init> at least once before you call this macro, but you can |
970 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1141 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
971 | macro on a watcher that is active (it can be pending, however, which is a |
1142 | macro on a watcher that is active (it can be pending, however, which is a |
… | |
… | |
984 | |
1155 | |
985 | Example: Initialise and set an C<ev_io> watcher in one step. |
1156 | Example: Initialise and set an C<ev_io> watcher in one step. |
986 | |
1157 | |
987 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1158 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
988 | |
1159 | |
989 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1160 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
990 | |
1161 | |
991 | Starts (activates) the given watcher. Only active watchers will receive |
1162 | Starts (activates) the given watcher. Only active watchers will receive |
992 | events. If the watcher is already active nothing will happen. |
1163 | events. If the watcher is already active nothing will happen. |
993 | |
1164 | |
994 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1165 | Example: Start the C<ev_io> watcher that is being abused as example in this |
995 | whole section. |
1166 | whole section. |
996 | |
1167 | |
997 | ev_io_start (EV_DEFAULT_UC, &w); |
1168 | ev_io_start (EV_DEFAULT_UC, &w); |
998 | |
1169 | |
999 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1170 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
1000 | |
1171 | |
1001 | Stops the given watcher if active, and clears the pending status (whether |
1172 | Stops the given watcher if active, and clears the pending status (whether |
1002 | the watcher was active or not). |
1173 | the watcher was active or not). |
1003 | |
1174 | |
1004 | It is possible that stopped watchers are pending - for example, |
1175 | It is possible that stopped watchers are pending - for example, |
… | |
… | |
1029 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1200 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1030 | |
1201 | |
1031 | Change the callback. You can change the callback at virtually any time |
1202 | Change the callback. You can change the callback at virtually any time |
1032 | (modulo threads). |
1203 | (modulo threads). |
1033 | |
1204 | |
1034 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1205 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1035 | |
1206 | |
1036 | =item int ev_priority (ev_TYPE *watcher) |
1207 | =item int ev_priority (ev_TYPE *watcher) |
1037 | |
1208 | |
1038 | Set and query the priority of the watcher. The priority is a small |
1209 | Set and query the priority of the watcher. The priority is a small |
1039 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1210 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1040 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1211 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1041 | before watchers with lower priority, but priority will not keep watchers |
1212 | before watchers with lower priority, but priority will not keep watchers |
1042 | from being executed (except for C<ev_idle> watchers). |
1213 | from being executed (except for C<ev_idle> watchers). |
1043 | |
1214 | |
1044 | This means that priorities are I<only> used for ordering callback |
|
|
1045 | invocation after new events have been received. This is useful, for |
|
|
1046 | example, to reduce latency after idling, or more often, to bind two |
|
|
1047 | watchers on the same event and make sure one is called first. |
|
|
1048 | |
|
|
1049 | If you need to suppress invocation when higher priority events are pending |
1215 | If you need to suppress invocation when higher priority events are pending |
1050 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1216 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1051 | |
1217 | |
1052 | You I<must not> change the priority of a watcher as long as it is active or |
1218 | You I<must not> change the priority of a watcher as long as it is active or |
1053 | pending. |
1219 | pending. |
1054 | |
|
|
1055 | The default priority used by watchers when no priority has been set is |
|
|
1056 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1057 | |
1220 | |
1058 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1221 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1059 | fine, as long as you do not mind that the priority value you query might |
1222 | fine, as long as you do not mind that the priority value you query might |
1060 | or might not have been clamped to the valid range. |
1223 | or might not have been clamped to the valid range. |
|
|
1224 | |
|
|
1225 | The default priority used by watchers when no priority has been set is |
|
|
1226 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1227 | |
|
|
1228 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1229 | priorities. |
1061 | |
1230 | |
1062 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1231 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1063 | |
1232 | |
1064 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1233 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1065 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1234 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1072 | returns its C<revents> bitset (as if its callback was invoked). If the |
1241 | returns its C<revents> bitset (as if its callback was invoked). If the |
1073 | watcher isn't pending it does nothing and returns C<0>. |
1242 | watcher isn't pending it does nothing and returns C<0>. |
1074 | |
1243 | |
1075 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1244 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1076 | callback to be invoked, which can be accomplished with this function. |
1245 | callback to be invoked, which can be accomplished with this function. |
|
|
1246 | |
|
|
1247 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1248 | |
|
|
1249 | Feeds the given event set into the event loop, as if the specified event |
|
|
1250 | had happened for the specified watcher (which must be a pointer to an |
|
|
1251 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1252 | not free the watcher as long as it has pending events. |
|
|
1253 | |
|
|
1254 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1255 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1256 | not started in the first place. |
|
|
1257 | |
|
|
1258 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1259 | functions that do not need a watcher. |
1077 | |
1260 | |
1078 | =back |
1261 | =back |
1079 | |
1262 | |
1080 | |
1263 | |
1081 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1264 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
… | |
… | |
1130 | #include <stddef.h> |
1313 | #include <stddef.h> |
1131 | |
1314 | |
1132 | static void |
1315 | static void |
1133 | t1_cb (EV_P_ ev_timer *w, int revents) |
1316 | t1_cb (EV_P_ ev_timer *w, int revents) |
1134 | { |
1317 | { |
1135 | struct my_biggy big = (struct my_biggy * |
1318 | struct my_biggy big = (struct my_biggy *) |
1136 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1319 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1137 | } |
1320 | } |
1138 | |
1321 | |
1139 | static void |
1322 | static void |
1140 | t2_cb (EV_P_ ev_timer *w, int revents) |
1323 | t2_cb (EV_P_ ev_timer *w, int revents) |
1141 | { |
1324 | { |
1142 | struct my_biggy big = (struct my_biggy * |
1325 | struct my_biggy big = (struct my_biggy *) |
1143 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1326 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1144 | } |
1327 | } |
|
|
1328 | |
|
|
1329 | =head2 WATCHER PRIORITY MODELS |
|
|
1330 | |
|
|
1331 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1332 | integers that influence the ordering of event callback invocation |
|
|
1333 | between watchers in some way, all else being equal. |
|
|
1334 | |
|
|
1335 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1336 | description for the more technical details such as the actual priority |
|
|
1337 | range. |
|
|
1338 | |
|
|
1339 | There are two common ways how these these priorities are being interpreted |
|
|
1340 | by event loops: |
|
|
1341 | |
|
|
1342 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1343 | of lower priority watchers, which means as long as higher priority |
|
|
1344 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1345 | |
|
|
1346 | The less common only-for-ordering model uses priorities solely to order |
|
|
1347 | callback invocation within a single event loop iteration: Higher priority |
|
|
1348 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1349 | before polling for new events. |
|
|
1350 | |
|
|
1351 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1352 | except for idle watchers (which use the lock-out model). |
|
|
1353 | |
|
|
1354 | The rationale behind this is that implementing the lock-out model for |
|
|
1355 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1356 | libraries will just poll for the same events again and again as long as |
|
|
1357 | their callbacks have not been executed, which is very inefficient in the |
|
|
1358 | common case of one high-priority watcher locking out a mass of lower |
|
|
1359 | priority ones. |
|
|
1360 | |
|
|
1361 | Static (ordering) priorities are most useful when you have two or more |
|
|
1362 | watchers handling the same resource: a typical usage example is having an |
|
|
1363 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1364 | timeouts. Under load, data might be received while the program handles |
|
|
1365 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1366 | handler will be executed before checking for data. In that case, giving |
|
|
1367 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1368 | handled first even under adverse conditions (which is usually, but not |
|
|
1369 | always, what you want). |
|
|
1370 | |
|
|
1371 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1372 | will only be executed when no same or higher priority watchers have |
|
|
1373 | received events, they can be used to implement the "lock-out" model when |
|
|
1374 | required. |
|
|
1375 | |
|
|
1376 | For example, to emulate how many other event libraries handle priorities, |
|
|
1377 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1378 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1379 | processing is done in the idle watcher callback. This causes libev to |
|
|
1380 | continously poll and process kernel event data for the watcher, but when |
|
|
1381 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1382 | workable. |
|
|
1383 | |
|
|
1384 | Usually, however, the lock-out model implemented that way will perform |
|
|
1385 | miserably under the type of load it was designed to handle. In that case, |
|
|
1386 | it might be preferable to stop the real watcher before starting the |
|
|
1387 | idle watcher, so the kernel will not have to process the event in case |
|
|
1388 | the actual processing will be delayed for considerable time. |
|
|
1389 | |
|
|
1390 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1391 | priority than the default, and which should only process data when no |
|
|
1392 | other events are pending: |
|
|
1393 | |
|
|
1394 | ev_idle idle; // actual processing watcher |
|
|
1395 | ev_io io; // actual event watcher |
|
|
1396 | |
|
|
1397 | static void |
|
|
1398 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1399 | { |
|
|
1400 | // stop the I/O watcher, we received the event, but |
|
|
1401 | // are not yet ready to handle it. |
|
|
1402 | ev_io_stop (EV_A_ w); |
|
|
1403 | |
|
|
1404 | // start the idle watcher to ahndle the actual event. |
|
|
1405 | // it will not be executed as long as other watchers |
|
|
1406 | // with the default priority are receiving events. |
|
|
1407 | ev_idle_start (EV_A_ &idle); |
|
|
1408 | } |
|
|
1409 | |
|
|
1410 | static void |
|
|
1411 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1412 | { |
|
|
1413 | // actual processing |
|
|
1414 | read (STDIN_FILENO, ...); |
|
|
1415 | |
|
|
1416 | // have to start the I/O watcher again, as |
|
|
1417 | // we have handled the event |
|
|
1418 | ev_io_start (EV_P_ &io); |
|
|
1419 | } |
|
|
1420 | |
|
|
1421 | // initialisation |
|
|
1422 | ev_idle_init (&idle, idle_cb); |
|
|
1423 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1424 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1425 | |
|
|
1426 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1427 | low-priority connections can not be locked out forever under load. This |
|
|
1428 | enables your program to keep a lower latency for important connections |
|
|
1429 | during short periods of high load, while not completely locking out less |
|
|
1430 | important ones. |
1145 | |
1431 | |
1146 | |
1432 | |
1147 | =head1 WATCHER TYPES |
1433 | =head1 WATCHER TYPES |
1148 | |
1434 | |
1149 | This section describes each watcher in detail, but will not repeat |
1435 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1175 | descriptors to non-blocking mode is also usually a good idea (but not |
1461 | descriptors to non-blocking mode is also usually a good idea (but not |
1176 | required if you know what you are doing). |
1462 | required if you know what you are doing). |
1177 | |
1463 | |
1178 | If you cannot use non-blocking mode, then force the use of a |
1464 | If you cannot use non-blocking mode, then force the use of a |
1179 | known-to-be-good backend (at the time of this writing, this includes only |
1465 | known-to-be-good backend (at the time of this writing, this includes only |
1180 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1466 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1467 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1468 | files) - libev doesn't guarentee any specific behaviour in that case. |
1181 | |
1469 | |
1182 | Another thing you have to watch out for is that it is quite easy to |
1470 | Another thing you have to watch out for is that it is quite easy to |
1183 | receive "spurious" readiness notifications, that is your callback might |
1471 | receive "spurious" readiness notifications, that is your callback might |
1184 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1472 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1185 | because there is no data. Not only are some backends known to create a |
1473 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1306 | year, it will still time out after (roughly) one hour. "Roughly" because |
1594 | year, it will still time out after (roughly) one hour. "Roughly" because |
1307 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1595 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1308 | monotonic clock option helps a lot here). |
1596 | monotonic clock option helps a lot here). |
1309 | |
1597 | |
1310 | The callback is guaranteed to be invoked only I<after> its timeout has |
1598 | The callback is guaranteed to be invoked only I<after> its timeout has |
1311 | passed, but if multiple timers become ready during the same loop iteration |
1599 | passed (not I<at>, so on systems with very low-resolution clocks this |
1312 | then order of execution is undefined. |
1600 | might introduce a small delay). If multiple timers become ready during the |
|
|
1601 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1602 | before ones of the same priority with later time-out values (but this is |
|
|
1603 | no longer true when a callback calls C<ev_loop> recursively). |
1313 | |
1604 | |
1314 | =head3 Be smart about timeouts |
1605 | =head3 Be smart about timeouts |
1315 | |
1606 | |
1316 | Many real-world problems involve some kind of timeout, usually for error |
1607 | Many real-world problems involve some kind of timeout, usually for error |
1317 | recovery. A typical example is an HTTP request - if the other side hangs, |
1608 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1361 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1652 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1362 | member and C<ev_timer_again>. |
1653 | member and C<ev_timer_again>. |
1363 | |
1654 | |
1364 | At start: |
1655 | At start: |
1365 | |
1656 | |
1366 | ev_timer_init (timer, callback); |
1657 | ev_init (timer, callback); |
1367 | timer->repeat = 60.; |
1658 | timer->repeat = 60.; |
1368 | ev_timer_again (loop, timer); |
1659 | ev_timer_again (loop, timer); |
1369 | |
1660 | |
1370 | Each time there is some activity: |
1661 | Each time there is some activity: |
1371 | |
1662 | |
… | |
… | |
1410 | else |
1701 | else |
1411 | { |
1702 | { |
1412 | // callback was invoked, but there was some activity, re-arm |
1703 | // callback was invoked, but there was some activity, re-arm |
1413 | // the watcher to fire in last_activity + 60, which is |
1704 | // the watcher to fire in last_activity + 60, which is |
1414 | // guaranteed to be in the future, so "again" is positive: |
1705 | // guaranteed to be in the future, so "again" is positive: |
1415 | w->again = timeout - now; |
1706 | w->repeat = timeout - now; |
1416 | ev_timer_again (EV_A_ w); |
1707 | ev_timer_again (EV_A_ w); |
1417 | } |
1708 | } |
1418 | } |
1709 | } |
1419 | |
1710 | |
1420 | To summarise the callback: first calculate the real timeout (defined |
1711 | To summarise the callback: first calculate the real timeout (defined |
… | |
… | |
1433 | |
1724 | |
1434 | To start the timer, simply initialise the watcher and set C<last_activity> |
1725 | To start the timer, simply initialise the watcher and set C<last_activity> |
1435 | to the current time (meaning we just have some activity :), then call the |
1726 | to the current time (meaning we just have some activity :), then call the |
1436 | callback, which will "do the right thing" and start the timer: |
1727 | callback, which will "do the right thing" and start the timer: |
1437 | |
1728 | |
1438 | ev_timer_init (timer, callback); |
1729 | ev_init (timer, callback); |
1439 | last_activity = ev_now (loop); |
1730 | last_activity = ev_now (loop); |
1440 | callback (loop, timer, EV_TIMEOUT); |
1731 | callback (loop, timer, EV_TIMEOUT); |
1441 | |
1732 | |
1442 | And when there is some activity, simply store the current time in |
1733 | And when there is some activity, simply store the current time in |
1443 | C<last_activity>, no libev calls at all: |
1734 | C<last_activity>, no libev calls at all: |
… | |
… | |
1504 | |
1795 | |
1505 | If the event loop is suspended for a long time, you can also force an |
1796 | If the event loop is suspended for a long time, you can also force an |
1506 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1797 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1507 | ()>. |
1798 | ()>. |
1508 | |
1799 | |
|
|
1800 | =head3 The special problems of suspended animation |
|
|
1801 | |
|
|
1802 | When you leave the server world it is quite customary to hit machines that |
|
|
1803 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1804 | |
|
|
1805 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1806 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1807 | to run until the system is suspended, but they will not advance while the |
|
|
1808 | system is suspended. That means, on resume, it will be as if the program |
|
|
1809 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1810 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1811 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1812 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1813 | be adjusted accordingly. |
|
|
1814 | |
|
|
1815 | I would not be surprised to see different behaviour in different between |
|
|
1816 | operating systems, OS versions or even different hardware. |
|
|
1817 | |
|
|
1818 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1819 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1820 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1821 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1822 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1823 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1824 | |
|
|
1825 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1826 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1827 | deterministic behaviour in this case (you can do nothing against |
|
|
1828 | C<SIGSTOP>). |
|
|
1829 | |
1509 | =head3 Watcher-Specific Functions and Data Members |
1830 | =head3 Watcher-Specific Functions and Data Members |
1510 | |
1831 | |
1511 | =over 4 |
1832 | =over 4 |
1512 | |
1833 | |
1513 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1834 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1536 | If the timer is started but non-repeating, stop it (as if it timed out). |
1857 | If the timer is started but non-repeating, stop it (as if it timed out). |
1537 | |
1858 | |
1538 | If the timer is repeating, either start it if necessary (with the |
1859 | If the timer is repeating, either start it if necessary (with the |
1539 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1860 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1540 | |
1861 | |
1541 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1862 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1542 | usage example. |
1863 | usage example. |
|
|
1864 | |
|
|
1865 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
|
|
1866 | |
|
|
1867 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
1868 | then this time is relative to the current event loop time, otherwise it's |
|
|
1869 | the timeout value currently configured. |
|
|
1870 | |
|
|
1871 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
1872 | C<5>. When the timer is started and one second passes, C<ev_timer_remain> |
|
|
1873 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1874 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1875 | too), and so on. |
1543 | |
1876 | |
1544 | =item ev_tstamp repeat [read-write] |
1877 | =item ev_tstamp repeat [read-write] |
1545 | |
1878 | |
1546 | The current C<repeat> value. Will be used each time the watcher times out |
1879 | The current C<repeat> value. Will be used each time the watcher times out |
1547 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1880 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1585 | =head2 C<ev_periodic> - to cron or not to cron? |
1918 | =head2 C<ev_periodic> - to cron or not to cron? |
1586 | |
1919 | |
1587 | Periodic watchers are also timers of a kind, but they are very versatile |
1920 | Periodic watchers are also timers of a kind, but they are very versatile |
1588 | (and unfortunately a bit complex). |
1921 | (and unfortunately a bit complex). |
1589 | |
1922 | |
1590 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1923 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1591 | but on wall clock time (absolute time). You can tell a periodic watcher |
1924 | relative time, the physical time that passes) but on wall clock time |
1592 | to trigger after some specific point in time. For example, if you tell a |
1925 | (absolute time, the thing you can read on your calender or clock). The |
1593 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1926 | difference is that wall clock time can run faster or slower than real |
1594 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1927 | time, and time jumps are not uncommon (e.g. when you adjust your |
1595 | clock to January of the previous year, then it will take more than year |
1928 | wrist-watch). |
1596 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1597 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1598 | |
1929 | |
|
|
1930 | You can tell a periodic watcher to trigger after some specific point |
|
|
1931 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1932 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1933 | not a delay) and then reset your system clock to January of the previous |
|
|
1934 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1935 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1936 | it, as it uses a relative timeout). |
|
|
1937 | |
1599 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1938 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1600 | such as triggering an event on each "midnight, local time", or other |
1939 | timers, such as triggering an event on each "midnight, local time", or |
1601 | complicated rules. |
1940 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1941 | those cannot react to time jumps. |
1602 | |
1942 | |
1603 | As with timers, the callback is guaranteed to be invoked only when the |
1943 | As with timers, the callback is guaranteed to be invoked only when the |
1604 | time (C<at>) has passed, but if multiple periodic timers become ready |
1944 | point in time where it is supposed to trigger has passed. If multiple |
1605 | during the same loop iteration, then order of execution is undefined. |
1945 | timers become ready during the same loop iteration then the ones with |
|
|
1946 | earlier time-out values are invoked before ones with later time-out values |
|
|
1947 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1606 | |
1948 | |
1607 | =head3 Watcher-Specific Functions and Data Members |
1949 | =head3 Watcher-Specific Functions and Data Members |
1608 | |
1950 | |
1609 | =over 4 |
1951 | =over 4 |
1610 | |
1952 | |
1611 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1953 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1612 | |
1954 | |
1613 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1955 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1614 | |
1956 | |
1615 | Lots of arguments, lets sort it out... There are basically three modes of |
1957 | Lots of arguments, let's sort it out... There are basically three modes of |
1616 | operation, and we will explain them from simplest to most complex: |
1958 | operation, and we will explain them from simplest to most complex: |
1617 | |
1959 | |
1618 | =over 4 |
1960 | =over 4 |
1619 | |
1961 | |
1620 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1962 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1621 | |
1963 | |
1622 | In this configuration the watcher triggers an event after the wall clock |
1964 | In this configuration the watcher triggers an event after the wall clock |
1623 | time C<at> has passed. It will not repeat and will not adjust when a time |
1965 | time C<offset> has passed. It will not repeat and will not adjust when a |
1624 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1966 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1625 | only run when the system clock reaches or surpasses this time. |
1967 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1968 | this point in time. |
1626 | |
1969 | |
1627 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1970 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1628 | |
1971 | |
1629 | In this mode the watcher will always be scheduled to time out at the next |
1972 | In this mode the watcher will always be scheduled to time out at the next |
1630 | C<at + N * interval> time (for some integer N, which can also be negative) |
1973 | C<offset + N * interval> time (for some integer N, which can also be |
1631 | and then repeat, regardless of any time jumps. |
1974 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1975 | argument is merely an offset into the C<interval> periods. |
1632 | |
1976 | |
1633 | This can be used to create timers that do not drift with respect to the |
1977 | This can be used to create timers that do not drift with respect to the |
1634 | system clock, for example, here is a C<ev_periodic> that triggers each |
1978 | system clock, for example, here is an C<ev_periodic> that triggers each |
1635 | hour, on the hour: |
1979 | hour, on the hour (with respect to UTC): |
1636 | |
1980 | |
1637 | ev_periodic_set (&periodic, 0., 3600., 0); |
1981 | ev_periodic_set (&periodic, 0., 3600., 0); |
1638 | |
1982 | |
1639 | This doesn't mean there will always be 3600 seconds in between triggers, |
1983 | This doesn't mean there will always be 3600 seconds in between triggers, |
1640 | but only that the callback will be called when the system time shows a |
1984 | but only that the callback will be called when the system time shows a |
1641 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1985 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1642 | by 3600. |
1986 | by 3600. |
1643 | |
1987 | |
1644 | Another way to think about it (for the mathematically inclined) is that |
1988 | Another way to think about it (for the mathematically inclined) is that |
1645 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1989 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1646 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1990 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1647 | |
1991 | |
1648 | For numerical stability it is preferable that the C<at> value is near |
1992 | For numerical stability it is preferable that the C<offset> value is near |
1649 | C<ev_now ()> (the current time), but there is no range requirement for |
1993 | C<ev_now ()> (the current time), but there is no range requirement for |
1650 | this value, and in fact is often specified as zero. |
1994 | this value, and in fact is often specified as zero. |
1651 | |
1995 | |
1652 | Note also that there is an upper limit to how often a timer can fire (CPU |
1996 | Note also that there is an upper limit to how often a timer can fire (CPU |
1653 | speed for example), so if C<interval> is very small then timing stability |
1997 | speed for example), so if C<interval> is very small then timing stability |
1654 | will of course deteriorate. Libev itself tries to be exact to be about one |
1998 | will of course deteriorate. Libev itself tries to be exact to be about one |
1655 | millisecond (if the OS supports it and the machine is fast enough). |
1999 | millisecond (if the OS supports it and the machine is fast enough). |
1656 | |
2000 | |
1657 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2001 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1658 | |
2002 | |
1659 | In this mode the values for C<interval> and C<at> are both being |
2003 | In this mode the values for C<interval> and C<offset> are both being |
1660 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2004 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1661 | reschedule callback will be called with the watcher as first, and the |
2005 | reschedule callback will be called with the watcher as first, and the |
1662 | current time as second argument. |
2006 | current time as second argument. |
1663 | |
2007 | |
1664 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2008 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1665 | ever, or make ANY event loop modifications whatsoever>. |
2009 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
2010 | allowed by documentation here>. |
1666 | |
2011 | |
1667 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
2012 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1668 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
2013 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1669 | only event loop modification you are allowed to do). |
2014 | only event loop modification you are allowed to do). |
1670 | |
2015 | |
… | |
… | |
1700 | a different time than the last time it was called (e.g. in a crond like |
2045 | a different time than the last time it was called (e.g. in a crond like |
1701 | program when the crontabs have changed). |
2046 | program when the crontabs have changed). |
1702 | |
2047 | |
1703 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2048 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1704 | |
2049 | |
1705 | When active, returns the absolute time that the watcher is supposed to |
2050 | When active, returns the absolute time that the watcher is supposed |
1706 | trigger next. |
2051 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2052 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2053 | rescheduling modes. |
1707 | |
2054 | |
1708 | =item ev_tstamp offset [read-write] |
2055 | =item ev_tstamp offset [read-write] |
1709 | |
2056 | |
1710 | When repeating, this contains the offset value, otherwise this is the |
2057 | When repeating, this contains the offset value, otherwise this is the |
1711 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2058 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2059 | although libev might modify this value for better numerical stability). |
1712 | |
2060 | |
1713 | Can be modified any time, but changes only take effect when the periodic |
2061 | Can be modified any time, but changes only take effect when the periodic |
1714 | timer fires or C<ev_periodic_again> is being called. |
2062 | timer fires or C<ev_periodic_again> is being called. |
1715 | |
2063 | |
1716 | =item ev_tstamp interval [read-write] |
2064 | =item ev_tstamp interval [read-write] |
… | |
… | |
1768 | Signal watchers will trigger an event when the process receives a specific |
2116 | Signal watchers will trigger an event when the process receives a specific |
1769 | signal one or more times. Even though signals are very asynchronous, libev |
2117 | signal one or more times. Even though signals are very asynchronous, libev |
1770 | will try it's best to deliver signals synchronously, i.e. as part of the |
2118 | will try it's best to deliver signals synchronously, i.e. as part of the |
1771 | normal event processing, like any other event. |
2119 | normal event processing, like any other event. |
1772 | |
2120 | |
1773 | If you want signals asynchronously, just use C<sigaction> as you would |
2121 | If you want signals to be delivered truly asynchronously, just use |
1774 | do without libev and forget about sharing the signal. You can even use |
2122 | C<sigaction> as you would do without libev and forget about sharing |
1775 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
2123 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2124 | synchronously wake up an event loop. |
1776 | |
2125 | |
1777 | You can configure as many watchers as you like per signal. Only when the |
2126 | You can configure as many watchers as you like for the same signal, but |
|
|
2127 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2128 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2129 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2130 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2131 | |
1778 | first watcher gets started will libev actually register a signal handler |
2132 | When the first watcher gets started will libev actually register something |
1779 | with the kernel (thus it coexists with your own signal handlers as long as |
2133 | with the kernel (thus it coexists with your own signal handlers as long as |
1780 | you don't register any with libev for the same signal). Similarly, when |
2134 | you don't register any with libev for the same signal). |
1781 | the last signal watcher for a signal is stopped, libev will reset the |
|
|
1782 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1783 | |
2135 | |
1784 | If possible and supported, libev will install its handlers with |
2136 | If possible and supported, libev will install its handlers with |
1785 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2137 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1786 | interrupted. If you have a problem with system calls getting interrupted by |
2138 | not be unduly interrupted. If you have a problem with system calls getting |
1787 | signals you can block all signals in an C<ev_check> watcher and unblock |
2139 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1788 | them in an C<ev_prepare> watcher. |
2140 | and unblock them in an C<ev_prepare> watcher. |
|
|
2141 | |
|
|
2142 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2143 | |
|
|
2144 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2145 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2146 | stopping it again), that is, libev might or might not block the signal, |
|
|
2147 | and might or might not set or restore the installed signal handler. |
|
|
2148 | |
|
|
2149 | While this does not matter for the signal disposition (libev never |
|
|
2150 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2151 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2152 | certain signals to be blocked. |
|
|
2153 | |
|
|
2154 | This means that before calling C<exec> (from the child) you should reset |
|
|
2155 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2156 | choice usually). |
|
|
2157 | |
|
|
2158 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2159 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2160 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2161 | |
|
|
2162 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2163 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2164 | the window of opportunity for problems, it will not go away, as libev |
|
|
2165 | I<has> to modify the signal mask, at least temporarily. |
|
|
2166 | |
|
|
2167 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2168 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2169 | is not a libev-specific thing, this is true for most event libraries. |
1789 | |
2170 | |
1790 | =head3 Watcher-Specific Functions and Data Members |
2171 | =head3 Watcher-Specific Functions and Data Members |
1791 | |
2172 | |
1792 | =over 4 |
2173 | =over 4 |
1793 | |
2174 | |
… | |
… | |
1825 | some child status changes (most typically when a child of yours dies or |
2206 | some child status changes (most typically when a child of yours dies or |
1826 | exits). It is permissible to install a child watcher I<after> the child |
2207 | exits). It is permissible to install a child watcher I<after> the child |
1827 | has been forked (which implies it might have already exited), as long |
2208 | has been forked (which implies it might have already exited), as long |
1828 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2209 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1829 | forking and then immediately registering a watcher for the child is fine, |
2210 | forking and then immediately registering a watcher for the child is fine, |
1830 | but forking and registering a watcher a few event loop iterations later is |
2211 | but forking and registering a watcher a few event loop iterations later or |
1831 | not. |
2212 | in the next callback invocation is not. |
1832 | |
2213 | |
1833 | Only the default event loop is capable of handling signals, and therefore |
2214 | Only the default event loop is capable of handling signals, and therefore |
1834 | you can only register child watchers in the default event loop. |
2215 | you can only register child watchers in the default event loop. |
1835 | |
2216 | |
|
|
2217 | Due to some design glitches inside libev, child watchers will always be |
|
|
2218 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2219 | libev) |
|
|
2220 | |
1836 | =head3 Process Interaction |
2221 | =head3 Process Interaction |
1837 | |
2222 | |
1838 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2223 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1839 | initialised. This is necessary to guarantee proper behaviour even if |
2224 | initialised. This is necessary to guarantee proper behaviour even if the |
1840 | the first child watcher is started after the child exits. The occurrence |
2225 | first child watcher is started after the child exits. The occurrence |
1841 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2226 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1842 | synchronously as part of the event loop processing. Libev always reaps all |
2227 | synchronously as part of the event loop processing. Libev always reaps all |
1843 | children, even ones not watched. |
2228 | children, even ones not watched. |
1844 | |
2229 | |
1845 | =head3 Overriding the Built-In Processing |
2230 | =head3 Overriding the Built-In Processing |
… | |
… | |
1855 | =head3 Stopping the Child Watcher |
2240 | =head3 Stopping the Child Watcher |
1856 | |
2241 | |
1857 | Currently, the child watcher never gets stopped, even when the |
2242 | Currently, the child watcher never gets stopped, even when the |
1858 | child terminates, so normally one needs to stop the watcher in the |
2243 | child terminates, so normally one needs to stop the watcher in the |
1859 | callback. Future versions of libev might stop the watcher automatically |
2244 | callback. Future versions of libev might stop the watcher automatically |
1860 | when a child exit is detected. |
2245 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2246 | problem). |
1861 | |
2247 | |
1862 | =head3 Watcher-Specific Functions and Data Members |
2248 | =head3 Watcher-Specific Functions and Data Members |
1863 | |
2249 | |
1864 | =over 4 |
2250 | =over 4 |
1865 | |
2251 | |
… | |
… | |
1922 | |
2308 | |
1923 | |
2309 | |
1924 | =head2 C<ev_stat> - did the file attributes just change? |
2310 | =head2 C<ev_stat> - did the file attributes just change? |
1925 | |
2311 | |
1926 | This watches a file system path for attribute changes. That is, it calls |
2312 | This watches a file system path for attribute changes. That is, it calls |
1927 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2313 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1928 | compared to the last time, invoking the callback if it did. |
2314 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2315 | it did. |
1929 | |
2316 | |
1930 | The path does not need to exist: changing from "path exists" to "path does |
2317 | The path does not need to exist: changing from "path exists" to "path does |
1931 | not exist" is a status change like any other. The condition "path does |
2318 | not exist" is a status change like any other. The condition "path does not |
1932 | not exist" is signified by the C<st_nlink> field being zero (which is |
2319 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1933 | otherwise always forced to be at least one) and all the other fields of |
2320 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1934 | the stat buffer having unspecified contents. |
2321 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2322 | contents. |
1935 | |
2323 | |
1936 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2324 | The path I<must not> end in a slash or contain special components such as |
|
|
2325 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1937 | relative and your working directory changes, the behaviour is undefined. |
2326 | your working directory changes, then the behaviour is undefined. |
1938 | |
2327 | |
1939 | Since there is no standard kernel interface to do this, the portable |
2328 | Since there is no portable change notification interface available, the |
1940 | implementation simply calls C<stat (2)> regularly on the path to see if |
2329 | portable implementation simply calls C<stat(2)> regularly on the path |
1941 | it changed somehow. You can specify a recommended polling interval for |
2330 | to see if it changed somehow. You can specify a recommended polling |
1942 | this case. If you specify a polling interval of C<0> (highly recommended!) |
2331 | interval for this case. If you specify a polling interval of C<0> (highly |
1943 | then a I<suitable, unspecified default> value will be used (which |
2332 | recommended!) then a I<suitable, unspecified default> value will be used |
1944 | you can expect to be around five seconds, although this might change |
2333 | (which you can expect to be around five seconds, although this might |
1945 | dynamically). Libev will also impose a minimum interval which is currently |
2334 | change dynamically). Libev will also impose a minimum interval which is |
1946 | around C<0.1>, but thats usually overkill. |
2335 | currently around C<0.1>, but that's usually overkill. |
1947 | |
2336 | |
1948 | This watcher type is not meant for massive numbers of stat watchers, |
2337 | This watcher type is not meant for massive numbers of stat watchers, |
1949 | as even with OS-supported change notifications, this can be |
2338 | as even with OS-supported change notifications, this can be |
1950 | resource-intensive. |
2339 | resource-intensive. |
1951 | |
2340 | |
1952 | At the time of this writing, the only OS-specific interface implemented |
2341 | At the time of this writing, the only OS-specific interface implemented |
1953 | is the Linux inotify interface (implementing kqueue support is left as |
2342 | is the Linux inotify interface (implementing kqueue support is left as an |
1954 | an exercise for the reader. Note, however, that the author sees no way |
2343 | exercise for the reader. Note, however, that the author sees no way of |
1955 | of implementing C<ev_stat> semantics with kqueue). |
2344 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1956 | |
2345 | |
1957 | =head3 ABI Issues (Largefile Support) |
2346 | =head3 ABI Issues (Largefile Support) |
1958 | |
2347 | |
1959 | Libev by default (unless the user overrides this) uses the default |
2348 | Libev by default (unless the user overrides this) uses the default |
1960 | compilation environment, which means that on systems with large file |
2349 | compilation environment, which means that on systems with large file |
1961 | support disabled by default, you get the 32 bit version of the stat |
2350 | support disabled by default, you get the 32 bit version of the stat |
1962 | structure. When using the library from programs that change the ABI to |
2351 | structure. When using the library from programs that change the ABI to |
1963 | use 64 bit file offsets the programs will fail. In that case you have to |
2352 | use 64 bit file offsets the programs will fail. In that case you have to |
1964 | compile libev with the same flags to get binary compatibility. This is |
2353 | compile libev with the same flags to get binary compatibility. This is |
1965 | obviously the case with any flags that change the ABI, but the problem is |
2354 | obviously the case with any flags that change the ABI, but the problem is |
1966 | most noticeably disabled with ev_stat and large file support. |
2355 | most noticeably displayed with ev_stat and large file support. |
1967 | |
2356 | |
1968 | The solution for this is to lobby your distribution maker to make large |
2357 | The solution for this is to lobby your distribution maker to make large |
1969 | file interfaces available by default (as e.g. FreeBSD does) and not |
2358 | file interfaces available by default (as e.g. FreeBSD does) and not |
1970 | optional. Libev cannot simply switch on large file support because it has |
2359 | optional. Libev cannot simply switch on large file support because it has |
1971 | to exchange stat structures with application programs compiled using the |
2360 | to exchange stat structures with application programs compiled using the |
1972 | default compilation environment. |
2361 | default compilation environment. |
1973 | |
2362 | |
1974 | =head3 Inotify and Kqueue |
2363 | =head3 Inotify and Kqueue |
1975 | |
2364 | |
1976 | When C<inotify (7)> support has been compiled into libev (generally |
2365 | When C<inotify (7)> support has been compiled into libev and present at |
1977 | only available with Linux 2.6.25 or above due to bugs in earlier |
2366 | runtime, it will be used to speed up change detection where possible. The |
1978 | implementations) and present at runtime, it will be used to speed up |
2367 | inotify descriptor will be created lazily when the first C<ev_stat> |
1979 | change detection where possible. The inotify descriptor will be created |
2368 | watcher is being started. |
1980 | lazily when the first C<ev_stat> watcher is being started. |
|
|
1981 | |
2369 | |
1982 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2370 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1983 | except that changes might be detected earlier, and in some cases, to avoid |
2371 | except that changes might be detected earlier, and in some cases, to avoid |
1984 | making regular C<stat> calls. Even in the presence of inotify support |
2372 | making regular C<stat> calls. Even in the presence of inotify support |
1985 | there are many cases where libev has to resort to regular C<stat> polling, |
2373 | there are many cases where libev has to resort to regular C<stat> polling, |
1986 | but as long as the path exists, libev usually gets away without polling. |
2374 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2375 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2376 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2377 | xfs are fully working) libev usually gets away without polling. |
1987 | |
2378 | |
1988 | There is no support for kqueue, as apparently it cannot be used to |
2379 | There is no support for kqueue, as apparently it cannot be used to |
1989 | implement this functionality, due to the requirement of having a file |
2380 | implement this functionality, due to the requirement of having a file |
1990 | descriptor open on the object at all times, and detecting renames, unlinks |
2381 | descriptor open on the object at all times, and detecting renames, unlinks |
1991 | etc. is difficult. |
2382 | etc. is difficult. |
1992 | |
2383 | |
|
|
2384 | =head3 C<stat ()> is a synchronous operation |
|
|
2385 | |
|
|
2386 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2387 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2388 | ()>, which is a synchronous operation. |
|
|
2389 | |
|
|
2390 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2391 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2392 | as the path data is usually in memory already (except when starting the |
|
|
2393 | watcher). |
|
|
2394 | |
|
|
2395 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2396 | time due to network issues, and even under good conditions, a stat call |
|
|
2397 | often takes multiple milliseconds. |
|
|
2398 | |
|
|
2399 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2400 | paths, although this is fully supported by libev. |
|
|
2401 | |
1993 | =head3 The special problem of stat time resolution |
2402 | =head3 The special problem of stat time resolution |
1994 | |
2403 | |
1995 | The C<stat ()> system call only supports full-second resolution portably, and |
2404 | The C<stat ()> system call only supports full-second resolution portably, |
1996 | even on systems where the resolution is higher, most file systems still |
2405 | and even on systems where the resolution is higher, most file systems |
1997 | only support whole seconds. |
2406 | still only support whole seconds. |
1998 | |
2407 | |
1999 | That means that, if the time is the only thing that changes, you can |
2408 | That means that, if the time is the only thing that changes, you can |
2000 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2409 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2001 | calls your callback, which does something. When there is another update |
2410 | calls your callback, which does something. When there is another update |
2002 | within the same second, C<ev_stat> will be unable to detect unless the |
2411 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
2145 | |
2554 | |
2146 | =head3 Watcher-Specific Functions and Data Members |
2555 | =head3 Watcher-Specific Functions and Data Members |
2147 | |
2556 | |
2148 | =over 4 |
2557 | =over 4 |
2149 | |
2558 | |
2150 | =item ev_idle_init (ev_signal *, callback) |
2559 | =item ev_idle_init (ev_idle *, callback) |
2151 | |
2560 | |
2152 | Initialises and configures the idle watcher - it has no parameters of any |
2561 | Initialises and configures the idle watcher - it has no parameters of any |
2153 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2562 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2154 | believe me. |
2563 | believe me. |
2155 | |
2564 | |
… | |
… | |
2168 | // no longer anything immediate to do. |
2577 | // no longer anything immediate to do. |
2169 | } |
2578 | } |
2170 | |
2579 | |
2171 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2580 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2172 | ev_idle_init (idle_watcher, idle_cb); |
2581 | ev_idle_init (idle_watcher, idle_cb); |
2173 | ev_idle_start (loop, idle_cb); |
2582 | ev_idle_start (loop, idle_watcher); |
2174 | |
2583 | |
2175 | |
2584 | |
2176 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2585 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2177 | |
2586 | |
2178 | Prepare and check watchers are usually (but not always) used in pairs: |
2587 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2271 | struct pollfd fds [nfd]; |
2680 | struct pollfd fds [nfd]; |
2272 | // actual code will need to loop here and realloc etc. |
2681 | // actual code will need to loop here and realloc etc. |
2273 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2682 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2274 | |
2683 | |
2275 | /* the callback is illegal, but won't be called as we stop during check */ |
2684 | /* the callback is illegal, but won't be called as we stop during check */ |
2276 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2685 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2277 | ev_timer_start (loop, &tw); |
2686 | ev_timer_start (loop, &tw); |
2278 | |
2687 | |
2279 | // create one ev_io per pollfd |
2688 | // create one ev_io per pollfd |
2280 | for (int i = 0; i < nfd; ++i) |
2689 | for (int i = 0; i < nfd; ++i) |
2281 | { |
2690 | { |
… | |
… | |
2394 | some fds have to be watched and handled very quickly (with low latency), |
2803 | some fds have to be watched and handled very quickly (with low latency), |
2395 | and even priorities and idle watchers might have too much overhead. In |
2804 | and even priorities and idle watchers might have too much overhead. In |
2396 | this case you would put all the high priority stuff in one loop and all |
2805 | this case you would put all the high priority stuff in one loop and all |
2397 | the rest in a second one, and embed the second one in the first. |
2806 | the rest in a second one, and embed the second one in the first. |
2398 | |
2807 | |
2399 | As long as the watcher is active, the callback will be invoked every time |
2808 | As long as the watcher is active, the callback will be invoked every |
2400 | there might be events pending in the embedded loop. The callback must then |
2809 | time there might be events pending in the embedded loop. The callback |
2401 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2810 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2402 | their callbacks (you could also start an idle watcher to give the embedded |
2811 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2403 | loop strictly lower priority for example). You can also set the callback |
2812 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2404 | to C<0>, in which case the embed watcher will automatically execute the |
2813 | to give the embedded loop strictly lower priority for example). |
2405 | embedded loop sweep. |
|
|
2406 | |
2814 | |
2407 | As long as the watcher is started it will automatically handle events. The |
2815 | You can also set the callback to C<0>, in which case the embed watcher |
2408 | callback will be invoked whenever some events have been handled. You can |
2816 | will automatically execute the embedded loop sweep whenever necessary. |
2409 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2410 | interested in that. |
|
|
2411 | |
2817 | |
2412 | Also, there have not currently been made special provisions for forking: |
2818 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2413 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2819 | is active, i.e., the embedded loop will automatically be forked when the |
2414 | but you will also have to stop and restart any C<ev_embed> watchers |
2820 | embedding loop forks. In other cases, the user is responsible for calling |
2415 | yourself - but you can use a fork watcher to handle this automatically, |
2821 | C<ev_loop_fork> on the embedded loop. |
2416 | and future versions of libev might do just that. |
|
|
2417 | |
2822 | |
2418 | Unfortunately, not all backends are embeddable: only the ones returned by |
2823 | Unfortunately, not all backends are embeddable: only the ones returned by |
2419 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2824 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2420 | portable one. |
2825 | portable one. |
2421 | |
2826 | |
… | |
… | |
2515 | event loop blocks next and before C<ev_check> watchers are being called, |
2920 | event loop blocks next and before C<ev_check> watchers are being called, |
2516 | and only in the child after the fork. If whoever good citizen calling |
2921 | and only in the child after the fork. If whoever good citizen calling |
2517 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2922 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2518 | handlers will be invoked, too, of course. |
2923 | handlers will be invoked, too, of course. |
2519 | |
2924 | |
|
|
2925 | =head3 The special problem of life after fork - how is it possible? |
|
|
2926 | |
|
|
2927 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2928 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2929 | sequence should be handled by libev without any problems. |
|
|
2930 | |
|
|
2931 | This changes when the application actually wants to do event handling |
|
|
2932 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2933 | fork. |
|
|
2934 | |
|
|
2935 | The default mode of operation (for libev, with application help to detect |
|
|
2936 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2937 | when I<either> the parent I<or> the child process continues. |
|
|
2938 | |
|
|
2939 | When both processes want to continue using libev, then this is usually the |
|
|
2940 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2941 | supposed to continue with all watchers in place as before, while the other |
|
|
2942 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2943 | |
|
|
2944 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2945 | simply create a new event loop, which of course will be "empty", and |
|
|
2946 | use that for new watchers. This has the advantage of not touching more |
|
|
2947 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2948 | disadvantage of having to use multiple event loops (which do not support |
|
|
2949 | signal watchers). |
|
|
2950 | |
|
|
2951 | When this is not possible, or you want to use the default loop for |
|
|
2952 | other reasons, then in the process that wants to start "fresh", call |
|
|
2953 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2954 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2955 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2956 | also that in that case, you have to re-register any signal watchers. |
|
|
2957 | |
2520 | =head3 Watcher-Specific Functions and Data Members |
2958 | =head3 Watcher-Specific Functions and Data Members |
2521 | |
2959 | |
2522 | =over 4 |
2960 | =over 4 |
2523 | |
2961 | |
2524 | =item ev_fork_init (ev_signal *, callback) |
2962 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2553 | =head3 Queueing |
2991 | =head3 Queueing |
2554 | |
2992 | |
2555 | C<ev_async> does not support queueing of data in any way. The reason |
2993 | C<ev_async> does not support queueing of data in any way. The reason |
2556 | is that the author does not know of a simple (or any) algorithm for a |
2994 | is that the author does not know of a simple (or any) algorithm for a |
2557 | multiple-writer-single-reader queue that works in all cases and doesn't |
2995 | multiple-writer-single-reader queue that works in all cases and doesn't |
2558 | need elaborate support such as pthreads. |
2996 | need elaborate support such as pthreads or unportable memory access |
|
|
2997 | semantics. |
2559 | |
2998 | |
2560 | That means that if you want to queue data, you have to provide your own |
2999 | That means that if you want to queue data, you have to provide your own |
2561 | queue. But at least I can tell you how to implement locking around your |
3000 | queue. But at least I can tell you how to implement locking around your |
2562 | queue: |
3001 | queue: |
2563 | |
3002 | |
… | |
… | |
2641 | =over 4 |
3080 | =over 4 |
2642 | |
3081 | |
2643 | =item ev_async_init (ev_async *, callback) |
3082 | =item ev_async_init (ev_async *, callback) |
2644 | |
3083 | |
2645 | Initialises and configures the async watcher - it has no parameters of any |
3084 | Initialises and configures the async watcher - it has no parameters of any |
2646 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3085 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2647 | trust me. |
3086 | trust me. |
2648 | |
3087 | |
2649 | =item ev_async_send (loop, ev_async *) |
3088 | =item ev_async_send (loop, ev_async *) |
2650 | |
3089 | |
2651 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3090 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2652 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3091 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2653 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3092 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2654 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3093 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2655 | section below on what exactly this means). |
3094 | section below on what exactly this means). |
2656 | |
3095 | |
|
|
3096 | Note that, as with other watchers in libev, multiple events might get |
|
|
3097 | compressed into a single callback invocation (another way to look at this |
|
|
3098 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3099 | reset when the event loop detects that). |
|
|
3100 | |
2657 | This call incurs the overhead of a system call only once per loop iteration, |
3101 | This call incurs the overhead of a system call only once per event loop |
2658 | so while the overhead might be noticeable, it doesn't apply to repeated |
3102 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2659 | calls to C<ev_async_send>. |
3103 | repeated calls to C<ev_async_send> for the same event loop. |
2660 | |
3104 | |
2661 | =item bool = ev_async_pending (ev_async *) |
3105 | =item bool = ev_async_pending (ev_async *) |
2662 | |
3106 | |
2663 | Returns a non-zero value when C<ev_async_send> has been called on the |
3107 | Returns a non-zero value when C<ev_async_send> has been called on the |
2664 | watcher but the event has not yet been processed (or even noted) by the |
3108 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2667 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3111 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2668 | the loop iterates next and checks for the watcher to have become active, |
3112 | the loop iterates next and checks for the watcher to have become active, |
2669 | it will reset the flag again. C<ev_async_pending> can be used to very |
3113 | it will reset the flag again. C<ev_async_pending> can be used to very |
2670 | quickly check whether invoking the loop might be a good idea. |
3114 | quickly check whether invoking the loop might be a good idea. |
2671 | |
3115 | |
2672 | Not that this does I<not> check whether the watcher itself is pending, only |
3116 | Not that this does I<not> check whether the watcher itself is pending, |
2673 | whether it has been requested to make this watcher pending. |
3117 | only whether it has been requested to make this watcher pending: there |
|
|
3118 | is a time window between the event loop checking and resetting the async |
|
|
3119 | notification, and the callback being invoked. |
2674 | |
3120 | |
2675 | =back |
3121 | =back |
2676 | |
3122 | |
2677 | |
3123 | |
2678 | =head1 OTHER FUNCTIONS |
3124 | =head1 OTHER FUNCTIONS |
… | |
… | |
2714 | /* doh, nothing entered */; |
3160 | /* doh, nothing entered */; |
2715 | } |
3161 | } |
2716 | |
3162 | |
2717 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3163 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2718 | |
3164 | |
2719 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
|
|
2720 | |
|
|
2721 | Feeds the given event set into the event loop, as if the specified event |
|
|
2722 | had happened for the specified watcher (which must be a pointer to an |
|
|
2723 | initialised but not necessarily started event watcher). |
|
|
2724 | |
|
|
2725 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
3165 | =item ev_feed_fd_event (loop, int fd, int revents) |
2726 | |
3166 | |
2727 | Feed an event on the given fd, as if a file descriptor backend detected |
3167 | Feed an event on the given fd, as if a file descriptor backend detected |
2728 | the given events it. |
3168 | the given events it. |
2729 | |
3169 | |
2730 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
3170 | =item ev_feed_signal_event (loop, int signum) |
2731 | |
3171 | |
2732 | Feed an event as if the given signal occurred (C<loop> must be the default |
3172 | Feed an event as if the given signal occurred (C<loop> must be the default |
2733 | loop!). |
3173 | loop!). |
2734 | |
3174 | |
2735 | =back |
3175 | =back |
… | |
… | |
2815 | |
3255 | |
2816 | =over 4 |
3256 | =over 4 |
2817 | |
3257 | |
2818 | =item ev::TYPE::TYPE () |
3258 | =item ev::TYPE::TYPE () |
2819 | |
3259 | |
2820 | =item ev::TYPE::TYPE (struct ev_loop *) |
3260 | =item ev::TYPE::TYPE (loop) |
2821 | |
3261 | |
2822 | =item ev::TYPE::~TYPE |
3262 | =item ev::TYPE::~TYPE |
2823 | |
3263 | |
2824 | The constructor (optionally) takes an event loop to associate the watcher |
3264 | The constructor (optionally) takes an event loop to associate the watcher |
2825 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3265 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2857 | |
3297 | |
2858 | myclass obj; |
3298 | myclass obj; |
2859 | ev::io iow; |
3299 | ev::io iow; |
2860 | iow.set <myclass, &myclass::io_cb> (&obj); |
3300 | iow.set <myclass, &myclass::io_cb> (&obj); |
2861 | |
3301 | |
|
|
3302 | =item w->set (object *) |
|
|
3303 | |
|
|
3304 | This is an B<experimental> feature that might go away in a future version. |
|
|
3305 | |
|
|
3306 | This is a variation of a method callback - leaving out the method to call |
|
|
3307 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3308 | functor objects without having to manually specify the C<operator ()> all |
|
|
3309 | the time. Incidentally, you can then also leave out the template argument |
|
|
3310 | list. |
|
|
3311 | |
|
|
3312 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3313 | int revents)>. |
|
|
3314 | |
|
|
3315 | See the method-C<set> above for more details. |
|
|
3316 | |
|
|
3317 | Example: use a functor object as callback. |
|
|
3318 | |
|
|
3319 | struct myfunctor |
|
|
3320 | { |
|
|
3321 | void operator() (ev::io &w, int revents) |
|
|
3322 | { |
|
|
3323 | ... |
|
|
3324 | } |
|
|
3325 | } |
|
|
3326 | |
|
|
3327 | myfunctor f; |
|
|
3328 | |
|
|
3329 | ev::io w; |
|
|
3330 | w.set (&f); |
|
|
3331 | |
2862 | =item w->set<function> (void *data = 0) |
3332 | =item w->set<function> (void *data = 0) |
2863 | |
3333 | |
2864 | Also sets a callback, but uses a static method or plain function as |
3334 | Also sets a callback, but uses a static method or plain function as |
2865 | callback. The optional C<data> argument will be stored in the watcher's |
3335 | callback. The optional C<data> argument will be stored in the watcher's |
2866 | C<data> member and is free for you to use. |
3336 | C<data> member and is free for you to use. |
… | |
… | |
2872 | Example: Use a plain function as callback. |
3342 | Example: Use a plain function as callback. |
2873 | |
3343 | |
2874 | static void io_cb (ev::io &w, int revents) { } |
3344 | static void io_cb (ev::io &w, int revents) { } |
2875 | iow.set <io_cb> (); |
3345 | iow.set <io_cb> (); |
2876 | |
3346 | |
2877 | =item w->set (struct ev_loop *) |
3347 | =item w->set (loop) |
2878 | |
3348 | |
2879 | Associates a different C<struct ev_loop> with this watcher. You can only |
3349 | Associates a different C<struct ev_loop> with this watcher. You can only |
2880 | do this when the watcher is inactive (and not pending either). |
3350 | do this when the watcher is inactive (and not pending either). |
2881 | |
3351 | |
2882 | =item w->set ([arguments]) |
3352 | =item w->set ([arguments]) |
… | |
… | |
2952 | L<http://software.schmorp.de/pkg/EV>. |
3422 | L<http://software.schmorp.de/pkg/EV>. |
2953 | |
3423 | |
2954 | =item Python |
3424 | =item Python |
2955 | |
3425 | |
2956 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3426 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2957 | seems to be quite complete and well-documented. Note, however, that the |
3427 | seems to be quite complete and well-documented. |
2958 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2959 | for everybody else, and therefore, should never be applied in an installed |
|
|
2960 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2961 | libev). |
|
|
2962 | |
3428 | |
2963 | =item Ruby |
3429 | =item Ruby |
2964 | |
3430 | |
2965 | Tony Arcieri has written a ruby extension that offers access to a subset |
3431 | Tony Arcieri has written a ruby extension that offers access to a subset |
2966 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3432 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2967 | more on top of it. It can be found via gem servers. Its homepage is at |
3433 | more on top of it. It can be found via gem servers. Its homepage is at |
2968 | L<http://rev.rubyforge.org/>. |
3434 | L<http://rev.rubyforge.org/>. |
2969 | |
3435 | |
|
|
3436 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3437 | makes rev work even on mingw. |
|
|
3438 | |
|
|
3439 | =item Haskell |
|
|
3440 | |
|
|
3441 | A haskell binding to libev is available at |
|
|
3442 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3443 | |
2970 | =item D |
3444 | =item D |
2971 | |
3445 | |
2972 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3446 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2973 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3447 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
2974 | |
3448 | |
2975 | =item Ocaml |
3449 | =item Ocaml |
2976 | |
3450 | |
2977 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3451 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
2978 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3452 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3453 | |
|
|
3454 | =item Lua |
|
|
3455 | |
|
|
3456 | Brian Maher has written a partial interface to libev |
|
|
3457 | for lua (only C<ev_io> and C<ev_timer>), to be found at |
|
|
3458 | L<http://github.com/brimworks/lua-ev>. |
2979 | |
3459 | |
2980 | =back |
3460 | =back |
2981 | |
3461 | |
2982 | |
3462 | |
2983 | =head1 MACRO MAGIC |
3463 | =head1 MACRO MAGIC |
… | |
… | |
3084 | |
3564 | |
3085 | #define EV_STANDALONE 1 |
3565 | #define EV_STANDALONE 1 |
3086 | #include "ev.h" |
3566 | #include "ev.h" |
3087 | |
3567 | |
3088 | Both header files and implementation files can be compiled with a C++ |
3568 | Both header files and implementation files can be compiled with a C++ |
3089 | compiler (at least, thats a stated goal, and breakage will be treated |
3569 | compiler (at least, that's a stated goal, and breakage will be treated |
3090 | as a bug). |
3570 | as a bug). |
3091 | |
3571 | |
3092 | You need the following files in your source tree, or in a directory |
3572 | You need the following files in your source tree, or in a directory |
3093 | in your include path (e.g. in libev/ when using -Ilibev): |
3573 | in your include path (e.g. in libev/ when using -Ilibev): |
3094 | |
3574 | |
… | |
… | |
3150 | keeps libev from including F<config.h>, and it also defines dummy |
3630 | keeps libev from including F<config.h>, and it also defines dummy |
3151 | implementations for some libevent functions (such as logging, which is not |
3631 | implementations for some libevent functions (such as logging, which is not |
3152 | supported). It will also not define any of the structs usually found in |
3632 | supported). It will also not define any of the structs usually found in |
3153 | F<event.h> that are not directly supported by the libev core alone. |
3633 | F<event.h> that are not directly supported by the libev core alone. |
3154 | |
3634 | |
|
|
3635 | In standalone mode, libev will still try to automatically deduce the |
|
|
3636 | configuration, but has to be more conservative. |
|
|
3637 | |
3155 | =item EV_USE_MONOTONIC |
3638 | =item EV_USE_MONOTONIC |
3156 | |
3639 | |
3157 | If defined to be C<1>, libev will try to detect the availability of the |
3640 | If defined to be C<1>, libev will try to detect the availability of the |
3158 | monotonic clock option at both compile time and runtime. Otherwise no use |
3641 | monotonic clock option at both compile time and runtime. Otherwise no |
3159 | of the monotonic clock option will be attempted. If you enable this, you |
3642 | use of the monotonic clock option will be attempted. If you enable this, |
3160 | usually have to link against librt or something similar. Enabling it when |
3643 | you usually have to link against librt or something similar. Enabling it |
3161 | the functionality isn't available is safe, though, although you have |
3644 | when the functionality isn't available is safe, though, although you have |
3162 | to make sure you link against any libraries where the C<clock_gettime> |
3645 | to make sure you link against any libraries where the C<clock_gettime> |
3163 | function is hiding in (often F<-lrt>). |
3646 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3164 | |
3647 | |
3165 | =item EV_USE_REALTIME |
3648 | =item EV_USE_REALTIME |
3166 | |
3649 | |
3167 | If defined to be C<1>, libev will try to detect the availability of the |
3650 | If defined to be C<1>, libev will try to detect the availability of the |
3168 | real-time clock option at compile time (and assume its availability at |
3651 | real-time clock option at compile time (and assume its availability |
3169 | runtime if successful). Otherwise no use of the real-time clock option will |
3652 | at runtime if successful). Otherwise no use of the real-time clock |
3170 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3653 | option will be attempted. This effectively replaces C<gettimeofday> |
3171 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3654 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3172 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3655 | correctness. See the note about libraries in the description of |
|
|
3656 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3657 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3658 | |
|
|
3659 | =item EV_USE_CLOCK_SYSCALL |
|
|
3660 | |
|
|
3661 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3662 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3663 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3664 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3665 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3666 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3667 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3668 | higher, as it simplifies linking (no need for C<-lrt>). |
3173 | |
3669 | |
3174 | =item EV_USE_NANOSLEEP |
3670 | =item EV_USE_NANOSLEEP |
3175 | |
3671 | |
3176 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3672 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3177 | and will use it for delays. Otherwise it will use C<select ()>. |
3673 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3193 | |
3689 | |
3194 | =item EV_SELECT_USE_FD_SET |
3690 | =item EV_SELECT_USE_FD_SET |
3195 | |
3691 | |
3196 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3692 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3197 | structure. This is useful if libev doesn't compile due to a missing |
3693 | structure. This is useful if libev doesn't compile due to a missing |
3198 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3694 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3199 | exotic systems. This usually limits the range of file descriptors to some |
3695 | on exotic systems. This usually limits the range of file descriptors to |
3200 | low limit such as 1024 or might have other limitations (winsocket only |
3696 | some low limit such as 1024 or might have other limitations (winsocket |
3201 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3697 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3202 | influence the size of the C<fd_set> used. |
3698 | configures the maximum size of the C<fd_set>. |
3203 | |
3699 | |
3204 | =item EV_SELECT_IS_WINSOCKET |
3700 | =item EV_SELECT_IS_WINSOCKET |
3205 | |
3701 | |
3206 | When defined to C<1>, the select backend will assume that |
3702 | When defined to C<1>, the select backend will assume that |
3207 | select/socket/connect etc. don't understand file descriptors but |
3703 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3209 | be used is the winsock select). This means that it will call |
3705 | be used is the winsock select). This means that it will call |
3210 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3706 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3211 | it is assumed that all these functions actually work on fds, even |
3707 | it is assumed that all these functions actually work on fds, even |
3212 | on win32. Should not be defined on non-win32 platforms. |
3708 | on win32. Should not be defined on non-win32 platforms. |
3213 | |
3709 | |
3214 | =item EV_FD_TO_WIN32_HANDLE |
3710 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3215 | |
3711 | |
3216 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3712 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3217 | file descriptors to socket handles. When not defining this symbol (the |
3713 | file descriptors to socket handles. When not defining this symbol (the |
3218 | default), then libev will call C<_get_osfhandle>, which is usually |
3714 | default), then libev will call C<_get_osfhandle>, which is usually |
3219 | correct. In some cases, programs use their own file descriptor management, |
3715 | correct. In some cases, programs use their own file descriptor management, |
3220 | in which case they can provide this function to map fds to socket handles. |
3716 | in which case they can provide this function to map fds to socket handles. |
|
|
3717 | |
|
|
3718 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3719 | |
|
|
3720 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3721 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3722 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3723 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3724 | |
|
|
3725 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3726 | |
|
|
3727 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3728 | macro can be used to override the C<close> function, useful to unregister |
|
|
3729 | file descriptors again. Note that the replacement function has to close |
|
|
3730 | the underlying OS handle. |
3221 | |
3731 | |
3222 | =item EV_USE_POLL |
3732 | =item EV_USE_POLL |
3223 | |
3733 | |
3224 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3734 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3225 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3735 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3357 | defined to be C<0>, then they are not. |
3867 | defined to be C<0>, then they are not. |
3358 | |
3868 | |
3359 | =item EV_MINIMAL |
3869 | =item EV_MINIMAL |
3360 | |
3870 | |
3361 | If you need to shave off some kilobytes of code at the expense of some |
3871 | If you need to shave off some kilobytes of code at the expense of some |
3362 | speed, define this symbol to C<1>. Currently this is used to override some |
3872 | speed (but with the full API), define this symbol to C<1>. Currently this |
3363 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3873 | is used to override some inlining decisions, saves roughly 30% code size |
3364 | much smaller 2-heap for timer management over the default 4-heap. |
3874 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3875 | the default 4-heap. |
|
|
3876 | |
|
|
3877 | You can save even more by disabling watcher types you do not need |
|
|
3878 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3879 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3880 | |
|
|
3881 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3882 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3883 | of the API are still available, and do not complain if this subset changes |
|
|
3884 | over time. |
|
|
3885 | |
|
|
3886 | =item EV_NSIG |
|
|
3887 | |
|
|
3888 | The highest supported signal number, +1 (or, the number of |
|
|
3889 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
3890 | automatically, but sometimes this fails, in which case it can be |
|
|
3891 | specified. Also, using a lower number than detected (C<32> should be |
|
|
3892 | good for about any system in existance) can save some memory, as libev |
|
|
3893 | statically allocates some 12-24 bytes per signal number. |
3365 | |
3894 | |
3366 | =item EV_PID_HASHSIZE |
3895 | =item EV_PID_HASHSIZE |
3367 | |
3896 | |
3368 | C<ev_child> watchers use a small hash table to distribute workload by |
3897 | C<ev_child> watchers use a small hash table to distribute workload by |
3369 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3898 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3555 | default loop and triggering an C<ev_async> watcher from the default loop |
4084 | default loop and triggering an C<ev_async> watcher from the default loop |
3556 | watcher callback into the event loop interested in the signal. |
4085 | watcher callback into the event loop interested in the signal. |
3557 | |
4086 | |
3558 | =back |
4087 | =back |
3559 | |
4088 | |
|
|
4089 | =head4 THREAD LOCKING EXAMPLE |
|
|
4090 | |
|
|
4091 | Here is a fictitious example of how to run an event loop in a different |
|
|
4092 | thread than where callbacks are being invoked and watchers are |
|
|
4093 | created/added/removed. |
|
|
4094 | |
|
|
4095 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4096 | which uses exactly this technique (which is suited for many high-level |
|
|
4097 | languages). |
|
|
4098 | |
|
|
4099 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4100 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4101 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4102 | |
|
|
4103 | First, you need to associate some data with the event loop: |
|
|
4104 | |
|
|
4105 | typedef struct { |
|
|
4106 | mutex_t lock; /* global loop lock */ |
|
|
4107 | ev_async async_w; |
|
|
4108 | thread_t tid; |
|
|
4109 | cond_t invoke_cv; |
|
|
4110 | } userdata; |
|
|
4111 | |
|
|
4112 | void prepare_loop (EV_P) |
|
|
4113 | { |
|
|
4114 | // for simplicity, we use a static userdata struct. |
|
|
4115 | static userdata u; |
|
|
4116 | |
|
|
4117 | ev_async_init (&u->async_w, async_cb); |
|
|
4118 | ev_async_start (EV_A_ &u->async_w); |
|
|
4119 | |
|
|
4120 | pthread_mutex_init (&u->lock, 0); |
|
|
4121 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4122 | |
|
|
4123 | // now associate this with the loop |
|
|
4124 | ev_set_userdata (EV_A_ u); |
|
|
4125 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4126 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4127 | |
|
|
4128 | // then create the thread running ev_loop |
|
|
4129 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4130 | } |
|
|
4131 | |
|
|
4132 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4133 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4134 | that might have been added: |
|
|
4135 | |
|
|
4136 | static void |
|
|
4137 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4138 | { |
|
|
4139 | // just used for the side effects |
|
|
4140 | } |
|
|
4141 | |
|
|
4142 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4143 | protecting the loop data, respectively. |
|
|
4144 | |
|
|
4145 | static void |
|
|
4146 | l_release (EV_P) |
|
|
4147 | { |
|
|
4148 | userdata *u = ev_userdata (EV_A); |
|
|
4149 | pthread_mutex_unlock (&u->lock); |
|
|
4150 | } |
|
|
4151 | |
|
|
4152 | static void |
|
|
4153 | l_acquire (EV_P) |
|
|
4154 | { |
|
|
4155 | userdata *u = ev_userdata (EV_A); |
|
|
4156 | pthread_mutex_lock (&u->lock); |
|
|
4157 | } |
|
|
4158 | |
|
|
4159 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4160 | into C<ev_loop>: |
|
|
4161 | |
|
|
4162 | void * |
|
|
4163 | l_run (void *thr_arg) |
|
|
4164 | { |
|
|
4165 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4166 | |
|
|
4167 | l_acquire (EV_A); |
|
|
4168 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4169 | ev_loop (EV_A_ 0); |
|
|
4170 | l_release (EV_A); |
|
|
4171 | |
|
|
4172 | return 0; |
|
|
4173 | } |
|
|
4174 | |
|
|
4175 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4176 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4177 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4178 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4179 | and b) skipping inter-thread-communication when there are no pending |
|
|
4180 | watchers is very beneficial): |
|
|
4181 | |
|
|
4182 | static void |
|
|
4183 | l_invoke (EV_P) |
|
|
4184 | { |
|
|
4185 | userdata *u = ev_userdata (EV_A); |
|
|
4186 | |
|
|
4187 | while (ev_pending_count (EV_A)) |
|
|
4188 | { |
|
|
4189 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4190 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4191 | } |
|
|
4192 | } |
|
|
4193 | |
|
|
4194 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4195 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4196 | thread to continue: |
|
|
4197 | |
|
|
4198 | static void |
|
|
4199 | real_invoke_pending (EV_P) |
|
|
4200 | { |
|
|
4201 | userdata *u = ev_userdata (EV_A); |
|
|
4202 | |
|
|
4203 | pthread_mutex_lock (&u->lock); |
|
|
4204 | ev_invoke_pending (EV_A); |
|
|
4205 | pthread_cond_signal (&u->invoke_cv); |
|
|
4206 | pthread_mutex_unlock (&u->lock); |
|
|
4207 | } |
|
|
4208 | |
|
|
4209 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4210 | event loop, you will now have to lock: |
|
|
4211 | |
|
|
4212 | ev_timer timeout_watcher; |
|
|
4213 | userdata *u = ev_userdata (EV_A); |
|
|
4214 | |
|
|
4215 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4216 | |
|
|
4217 | pthread_mutex_lock (&u->lock); |
|
|
4218 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4219 | ev_async_send (EV_A_ &u->async_w); |
|
|
4220 | pthread_mutex_unlock (&u->lock); |
|
|
4221 | |
|
|
4222 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4223 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4224 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4225 | watchers in the next event loop iteration. |
|
|
4226 | |
3560 | =head3 COROUTINES |
4227 | =head3 COROUTINES |
3561 | |
4228 | |
3562 | Libev is very accommodating to coroutines ("cooperative threads"): |
4229 | Libev is very accommodating to coroutines ("cooperative threads"): |
3563 | libev fully supports nesting calls to its functions from different |
4230 | libev fully supports nesting calls to its functions from different |
3564 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4231 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3565 | different coroutines, and switch freely between both coroutines running the |
4232 | different coroutines, and switch freely between both coroutines running |
3566 | loop, as long as you don't confuse yourself). The only exception is that |
4233 | the loop, as long as you don't confuse yourself). The only exception is |
3567 | you must not do this from C<ev_periodic> reschedule callbacks. |
4234 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3568 | |
4235 | |
3569 | Care has been taken to ensure that libev does not keep local state inside |
4236 | Care has been taken to ensure that libev does not keep local state inside |
3570 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4237 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3571 | they do not clal any callbacks. |
4238 | they do not call any callbacks. |
3572 | |
4239 | |
3573 | =head2 COMPILER WARNINGS |
4240 | =head2 COMPILER WARNINGS |
3574 | |
4241 | |
3575 | Depending on your compiler and compiler settings, you might get no or a |
4242 | Depending on your compiler and compiler settings, you might get no or a |
3576 | lot of warnings when compiling libev code. Some people are apparently |
4243 | lot of warnings when compiling libev code. Some people are apparently |
… | |
… | |
3610 | ==2274== definitely lost: 0 bytes in 0 blocks. |
4277 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3611 | ==2274== possibly lost: 0 bytes in 0 blocks. |
4278 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3612 | ==2274== still reachable: 256 bytes in 1 blocks. |
4279 | ==2274== still reachable: 256 bytes in 1 blocks. |
3613 | |
4280 | |
3614 | Then there is no memory leak, just as memory accounted to global variables |
4281 | Then there is no memory leak, just as memory accounted to global variables |
3615 | is not a memleak - the memory is still being refernced, and didn't leak. |
4282 | is not a memleak - the memory is still being referenced, and didn't leak. |
3616 | |
4283 | |
3617 | Similarly, under some circumstances, valgrind might report kernel bugs |
4284 | Similarly, under some circumstances, valgrind might report kernel bugs |
3618 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
4285 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3619 | although an acceptable workaround has been found here), or it might be |
4286 | although an acceptable workaround has been found here), or it might be |
3620 | confused. |
4287 | confused. |
… | |
… | |
3649 | way (note also that glib is the slowest event library known to man). |
4316 | way (note also that glib is the slowest event library known to man). |
3650 | |
4317 | |
3651 | There is no supported compilation method available on windows except |
4318 | There is no supported compilation method available on windows except |
3652 | embedding it into other applications. |
4319 | embedding it into other applications. |
3653 | |
4320 | |
|
|
4321 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4322 | tries its best, but under most conditions, signals will simply not work. |
|
|
4323 | |
3654 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4324 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3655 | accept large writes: instead of resulting in a partial write, windows will |
4325 | accept large writes: instead of resulting in a partial write, windows will |
3656 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4326 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3657 | so make sure you only write small amounts into your sockets (less than a |
4327 | so make sure you only write small amounts into your sockets (less than a |
3658 | megabyte seems safe, but this apparently depends on the amount of memory |
4328 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3662 | the abysmal performance of winsockets, using a large number of sockets |
4332 | the abysmal performance of winsockets, using a large number of sockets |
3663 | is not recommended (and not reasonable). If your program needs to use |
4333 | is not recommended (and not reasonable). If your program needs to use |
3664 | more than a hundred or so sockets, then likely it needs to use a totally |
4334 | more than a hundred or so sockets, then likely it needs to use a totally |
3665 | different implementation for windows, as libev offers the POSIX readiness |
4335 | different implementation for windows, as libev offers the POSIX readiness |
3666 | notification model, which cannot be implemented efficiently on windows |
4336 | notification model, which cannot be implemented efficiently on windows |
3667 | (Microsoft monopoly games). |
4337 | (due to Microsoft monopoly games). |
3668 | |
4338 | |
3669 | A typical way to use libev under windows is to embed it (see the embedding |
4339 | A typical way to use libev under windows is to embed it (see the embedding |
3670 | section for details) and use the following F<evwrap.h> header file instead |
4340 | section for details) and use the following F<evwrap.h> header file instead |
3671 | of F<ev.h>: |
4341 | of F<ev.h>: |
3672 | |
4342 | |
… | |
… | |
3708 | |
4378 | |
3709 | Early versions of winsocket's select only supported waiting for a maximum |
4379 | Early versions of winsocket's select only supported waiting for a maximum |
3710 | of C<64> handles (probably owning to the fact that all windows kernels |
4380 | of C<64> handles (probably owning to the fact that all windows kernels |
3711 | can only wait for C<64> things at the same time internally; Microsoft |
4381 | can only wait for C<64> things at the same time internally; Microsoft |
3712 | recommends spawning a chain of threads and wait for 63 handles and the |
4382 | recommends spawning a chain of threads and wait for 63 handles and the |
3713 | previous thread in each. Great). |
4383 | previous thread in each. Sounds great!). |
3714 | |
4384 | |
3715 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4385 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3716 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4386 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3717 | call (which might be in libev or elsewhere, for example, perl does its own |
4387 | call (which might be in libev or elsewhere, for example, perl and many |
3718 | select emulation on windows). |
4388 | other interpreters do their own select emulation on windows). |
3719 | |
4389 | |
3720 | Another limit is the number of file descriptors in the Microsoft runtime |
4390 | Another limit is the number of file descriptors in the Microsoft runtime |
3721 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4391 | libraries, which by default is C<64> (there must be a hidden I<64> |
3722 | or something like this inside Microsoft). You can increase this by calling |
4392 | fetish or something like this inside Microsoft). You can increase this |
3723 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4393 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3724 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4394 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3725 | libraries. |
|
|
3726 | |
|
|
3727 | This might get you to about C<512> or C<2048> sockets (depending on |
4395 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3728 | windows version and/or the phase of the moon). To get more, you need to |
4396 | (depending on windows version and/or the phase of the moon). To get more, |
3729 | wrap all I/O functions and provide your own fd management, but the cost of |
4397 | you need to wrap all I/O functions and provide your own fd management, but |
3730 | calling select (O(n²)) will likely make this unworkable. |
4398 | the cost of calling select (O(n²)) will likely make this unworkable. |
3731 | |
4399 | |
3732 | =back |
4400 | =back |
3733 | |
4401 | |
3734 | =head2 PORTABILITY REQUIREMENTS |
4402 | =head2 PORTABILITY REQUIREMENTS |
3735 | |
4403 | |
… | |
… | |
3778 | =item C<double> must hold a time value in seconds with enough accuracy |
4446 | =item C<double> must hold a time value in seconds with enough accuracy |
3779 | |
4447 | |
3780 | The type C<double> is used to represent timestamps. It is required to |
4448 | The type C<double> is used to represent timestamps. It is required to |
3781 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4449 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3782 | enough for at least into the year 4000. This requirement is fulfilled by |
4450 | enough for at least into the year 4000. This requirement is fulfilled by |
3783 | implementations implementing IEEE 754 (basically all existing ones). |
4451 | implementations implementing IEEE 754, which is basically all existing |
|
|
4452 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4453 | 2200. |
3784 | |
4454 | |
3785 | =back |
4455 | =back |
3786 | |
4456 | |
3787 | If you know of other additional requirements drop me a note. |
4457 | If you know of other additional requirements drop me a note. |
3788 | |
4458 | |
… | |
… | |
3856 | involves iterating over all running async watchers or all signal numbers. |
4526 | involves iterating over all running async watchers or all signal numbers. |
3857 | |
4527 | |
3858 | =back |
4528 | =back |
3859 | |
4529 | |
3860 | |
4530 | |
|
|
4531 | =head1 GLOSSARY |
|
|
4532 | |
|
|
4533 | =over 4 |
|
|
4534 | |
|
|
4535 | =item active |
|
|
4536 | |
|
|
4537 | A watcher is active as long as it has been started (has been attached to |
|
|
4538 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4539 | |
|
|
4540 | =item application |
|
|
4541 | |
|
|
4542 | In this document, an application is whatever is using libev. |
|
|
4543 | |
|
|
4544 | =item callback |
|
|
4545 | |
|
|
4546 | The address of a function that is called when some event has been |
|
|
4547 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4548 | received the event, and the actual event bitset. |
|
|
4549 | |
|
|
4550 | =item callback invocation |
|
|
4551 | |
|
|
4552 | The act of calling the callback associated with a watcher. |
|
|
4553 | |
|
|
4554 | =item event |
|
|
4555 | |
|
|
4556 | A change of state of some external event, such as data now being available |
|
|
4557 | for reading on a file descriptor, time having passed or simply not having |
|
|
4558 | any other events happening anymore. |
|
|
4559 | |
|
|
4560 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4561 | C<EV_TIMEOUT>). |
|
|
4562 | |
|
|
4563 | =item event library |
|
|
4564 | |
|
|
4565 | A software package implementing an event model and loop. |
|
|
4566 | |
|
|
4567 | =item event loop |
|
|
4568 | |
|
|
4569 | An entity that handles and processes external events and converts them |
|
|
4570 | into callback invocations. |
|
|
4571 | |
|
|
4572 | =item event model |
|
|
4573 | |
|
|
4574 | The model used to describe how an event loop handles and processes |
|
|
4575 | watchers and events. |
|
|
4576 | |
|
|
4577 | =item pending |
|
|
4578 | |
|
|
4579 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4580 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4581 | pending status is explicitly cleared by the application. |
|
|
4582 | |
|
|
4583 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4584 | its pending status. |
|
|
4585 | |
|
|
4586 | =item real time |
|
|
4587 | |
|
|
4588 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4589 | |
|
|
4590 | =item wall-clock time |
|
|
4591 | |
|
|
4592 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4593 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4594 | clock. |
|
|
4595 | |
|
|
4596 | =item watcher |
|
|
4597 | |
|
|
4598 | A data structure that describes interest in certain events. Watchers need |
|
|
4599 | to be started (attached to an event loop) before they can receive events. |
|
|
4600 | |
|
|
4601 | =item watcher invocation |
|
|
4602 | |
|
|
4603 | The act of calling the callback associated with a watcher. |
|
|
4604 | |
|
|
4605 | =back |
|
|
4606 | |
3861 | =head1 AUTHOR |
4607 | =head1 AUTHOR |
3862 | |
4608 | |
3863 | Marc Lehmann <libev@schmorp.de>. |
4609 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3864 | |
4610 | |