… | |
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9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
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14 | #include <stdio.h> // for puts |
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15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
18 | |
20 | |
19 | // all watcher callbacks have a similar signature |
21 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
22 | // this callback is called when data is readable on stdin |
21 | static void |
23 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
24 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
25 | { |
24 | puts ("stdin ready"); |
26 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
27 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
28 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
29 | ev_io_stop (EV_A_ w); |
… | |
… | |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
31 | } |
33 | } |
32 | |
34 | |
33 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
34 | static void |
36 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
38 | { |
37 | puts ("timeout"); |
39 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_loop to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
40 | } |
42 | } |
… | |
… | |
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 | |
… | |
… | |
103 | Libev is very configurable. In this manual the default (and most common) |
117 | Libev is very configurable. In this manual the default (and most common) |
104 | configuration will be described, which supports multiple event loops. For |
118 | configuration will be described, which supports multiple event loops. For |
105 | more info about various configuration options please have a look at |
119 | more info about various configuration options please have a look at |
106 | B<EMBED> section in this manual. If libev was configured without support |
120 | 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 |
121 | for multiple event loops, then all functions taking an initial argument of |
108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
109 | this argument. |
123 | this argument. |
110 | |
124 | |
111 | =head2 TIME REPRESENTATION |
125 | =head2 TIME REPRESENTATION |
112 | |
126 | |
113 | Libev represents time as a single floating point number, representing the |
127 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
129 | near the beginning of 1970, details are complicated, don't ask). This |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
130 | type is called C<ev_tstamp>, which is what you should use too. It usually |
117 | to the C<double> type in C, and when you need to do any calculations on |
131 | aliases to the C<double> type in C. When you need to do any calculations |
118 | it, you should treat it as some floating point value. Unlike the name |
132 | on it, you should treat it as some floating point value. Unlike the name |
119 | component C<stamp> might indicate, it is also used for time differences |
133 | component C<stamp> might indicate, it is also used for time differences |
120 | throughout libev. |
134 | throughout libev. |
121 | |
135 | |
122 | =head1 ERROR HANDLING |
136 | =head1 ERROR HANDLING |
123 | |
137 | |
… | |
… | |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
228 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
215 | recommended ones. |
229 | recommended ones. |
216 | |
230 | |
217 | See the description of C<ev_embed> watchers for more info. |
231 | See the description of C<ev_embed> watchers for more info. |
218 | |
232 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
233 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
220 | |
234 | |
221 | Sets the allocation function to use (the prototype is similar - the |
235 | Sets the allocation function to use (the prototype is similar - the |
222 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
236 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
223 | used to allocate and free memory (no surprises here). If it returns zero |
237 | used to allocate and free memory (no surprises here). If it returns zero |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
238 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
250 | } |
264 | } |
251 | |
265 | |
252 | ... |
266 | ... |
253 | ev_set_allocator (persistent_realloc); |
267 | ev_set_allocator (persistent_realloc); |
254 | |
268 | |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
269 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
256 | |
270 | |
257 | Set the callback function to call on a retryable system call error (such |
271 | Set the callback function to call on a retryable system call error (such |
258 | as failed select, poll, epoll_wait). The message is a printable string |
272 | as failed select, poll, epoll_wait). The message is a printable string |
259 | indicating the system call or subsystem causing the problem. If this |
273 | indicating the system call or subsystem causing the problem. If this |
260 | callback is set, then libev will expect it to remedy the situation, no |
274 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
276 | |
290 | |
277 | =back |
291 | =back |
278 | |
292 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
293 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
280 | |
294 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
295 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
282 | types of such loops, the I<default> loop, which supports signals and child |
296 | is I<not> optional in this case, as there is also an C<ev_loop> |
283 | events, and dynamically created loops which do not. |
297 | I<function>). |
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298 | |
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299 | The library knows two types of such loops, the I<default> loop, which |
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300 | supports signals and child events, and dynamically created loops which do |
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301 | not. |
284 | |
302 | |
285 | =over 4 |
303 | =over 4 |
286 | |
304 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
305 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
306 | |
… | |
… | |
294 | If you don't know what event loop to use, use the one returned from this |
312 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
313 | function. |
296 | |
314 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
315 | Note that this function is I<not> thread-safe, so if you want to use it |
298 | from multiple threads, you have to lock (note also that this is unlikely, |
316 | from multiple threads, you have to lock (note also that this is unlikely, |
299 | as loops cannot bes hared easily between threads anyway). |
317 | as loops cannot be shared easily between threads anyway). |
300 | |
318 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
319 | The default loop is the only loop that can handle C<ev_signal> and |
302 | C<ev_child> watchers, and to do this, it always registers a handler |
320 | C<ev_child> watchers, and to do this, it always registers a handler |
303 | for C<SIGCHLD>. If this is a problem for your application you can either |
321 | for C<SIGCHLD>. If this is a problem for your application you can either |
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
322 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
… | |
380 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
398 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
381 | |
399 | |
382 | For few fds, this backend is a bit little slower than poll and select, |
400 | For few fds, this backend is a bit little slower than poll and select, |
383 | but it scales phenomenally better. While poll and select usually scale |
401 | but it scales phenomenally better. While poll and select usually scale |
384 | like O(total_fds) where n is the total number of fds (or the highest fd), |
402 | like O(total_fds) where n is the total number of fds (or the highest fd), |
385 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
403 | epoll scales either O(1) or O(active_fds). |
386 | of shortcomings, such as silently dropping events in some hard-to-detect |
404 | |
387 | cases and requiring a system call per fd change, no fork support and bad |
405 | The epoll mechanism deserves honorable mention as the most misdesigned |
388 | support for dup. |
406 | of the more advanced event mechanisms: mere annoyances include silently |
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407 | dropping file descriptors, requiring a system call per change per file |
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408 | descriptor (and unnecessary guessing of parameters), problems with dup and |
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409 | so on. The biggest issue is fork races, however - if a program forks then |
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410 | I<both> parent and child process have to recreate the epoll set, which can |
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411 | take considerable time (one syscall per file descriptor) and is of course |
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412 | hard to detect. |
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413 | |
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414 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
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415 | of course I<doesn't>, and epoll just loves to report events for totally |
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416 | I<different> file descriptors (even already closed ones, so one cannot |
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417 | even remove them from the set) than registered in the set (especially |
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418 | on SMP systems). Libev tries to counter these spurious notifications by |
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419 | employing an additional generation counter and comparing that against the |
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420 | events to filter out spurious ones, recreating the set when required. |
389 | |
421 | |
390 | While stopping, setting and starting an I/O watcher in the same iteration |
422 | While stopping, setting and starting an I/O watcher in the same iteration |
391 | will result in some caching, there is still a system call per such incident |
423 | will result in some caching, there is still a system call per such |
392 | (because the fd could point to a different file description now), so its |
424 | incident (because the same I<file descriptor> could point to a different |
393 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
425 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
394 | very well if you register events for both fds. |
426 | file descriptors might not work very well if you register events for both |
395 | |
427 | file descriptors. |
396 | Please note that epoll sometimes generates spurious notifications, so you |
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397 | need to use non-blocking I/O or other means to avoid blocking when no data |
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398 | (or space) is available. |
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399 | |
428 | |
400 | Best performance from this backend is achieved by not unregistering all |
429 | Best performance from this backend is achieved by not unregistering all |
401 | watchers for a file descriptor until it has been closed, if possible, |
430 | watchers for a file descriptor until it has been closed, if possible, |
402 | i.e. keep at least one watcher active per fd at all times. Stopping and |
431 | i.e. keep at least one watcher active per fd at all times. Stopping and |
403 | starting a watcher (without re-setting it) also usually doesn't cause |
432 | starting a watcher (without re-setting it) also usually doesn't cause |
404 | extra overhead. |
433 | extra overhead. A fork can both result in spurious notifications as well |
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434 | as in libev having to destroy and recreate the epoll object, which can |
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435 | take considerable time and thus should be avoided. |
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436 | |
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437 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
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438 | faster than epoll for maybe up to a hundred file descriptors, depending on |
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439 | the usage. So sad. |
405 | |
440 | |
406 | While nominally embeddable in other event loops, this feature is broken in |
441 | While nominally embeddable in other event loops, this feature is broken in |
407 | all kernel versions tested so far. |
442 | all kernel versions tested so far. |
408 | |
443 | |
409 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
444 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
410 | C<EVBACKEND_POLL>. |
445 | C<EVBACKEND_POLL>. |
411 | |
446 | |
412 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
447 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
413 | |
448 | |
414 | Kqueue deserves special mention, as at the time of this writing, it was |
449 | Kqueue deserves special mention, as at the time of this writing, it |
415 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
450 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
416 | anything but sockets and pipes, except on Darwin, where of course it's |
451 | with anything but sockets and pipes, except on Darwin, where of course |
417 | completely useless). For this reason it's not being "auto-detected" unless |
452 | it's completely useless). Unlike epoll, however, whose brokenness |
418 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
453 | is by design, these kqueue bugs can (and eventually will) be fixed |
419 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
454 | without API changes to existing programs. For this reason it's not being |
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455 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
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456 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
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457 | system like NetBSD. |
420 | |
458 | |
421 | You still can embed kqueue into a normal poll or select backend and use it |
459 | You still can embed kqueue into a normal poll or select backend and use it |
422 | only for sockets (after having made sure that sockets work with kqueue on |
460 | only for sockets (after having made sure that sockets work with kqueue on |
423 | the target platform). See C<ev_embed> watchers for more info. |
461 | the target platform). See C<ev_embed> watchers for more info. |
424 | |
462 | |
425 | It scales in the same way as the epoll backend, but the interface to the |
463 | It scales in the same way as the epoll backend, but the interface to the |
426 | kernel is more efficient (which says nothing about its actual speed, of |
464 | kernel is more efficient (which says nothing about its actual speed, of |
427 | course). While stopping, setting and starting an I/O watcher does never |
465 | course). While stopping, setting and starting an I/O watcher does never |
428 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
466 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
429 | two event changes per incident. Support for C<fork ()> is very bad and it |
467 | two event changes per incident. Support for C<fork ()> is very bad (but |
430 | drops fds silently in similarly hard-to-detect cases. |
468 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
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469 | cases |
431 | |
470 | |
432 | This backend usually performs well under most conditions. |
471 | This backend usually performs well under most conditions. |
433 | |
472 | |
434 | While nominally embeddable in other event loops, this doesn't work |
473 | While nominally embeddable in other event loops, this doesn't work |
435 | everywhere, so you might need to test for this. And since it is broken |
474 | everywhere, so you might need to test for this. And since it is broken |
436 | almost everywhere, you should only use it when you have a lot of sockets |
475 | almost everywhere, you should only use it when you have a lot of sockets |
437 | (for which it usually works), by embedding it into another event loop |
476 | (for which it usually works), by embedding it into another event loop |
438 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
477 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
439 | using it only for sockets. |
478 | also broken on OS X)) and, did I mention it, using it only for sockets. |
440 | |
479 | |
441 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
480 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
442 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
481 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
443 | C<NOTE_EOF>. |
482 | C<NOTE_EOF>. |
444 | |
483 | |
… | |
… | |
464 | might perform better. |
503 | might perform better. |
465 | |
504 | |
466 | On the positive side, with the exception of the spurious readiness |
505 | On the positive side, with the exception of the spurious readiness |
467 | notifications, this backend actually performed fully to specification |
506 | notifications, this backend actually performed fully to specification |
468 | in all tests and is fully embeddable, which is a rare feat among the |
507 | in all tests and is fully embeddable, which is a rare feat among the |
469 | OS-specific backends. |
508 | OS-specific backends (I vastly prefer correctness over speed hacks). |
470 | |
509 | |
471 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
510 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
472 | C<EVBACKEND_POLL>. |
511 | C<EVBACKEND_POLL>. |
473 | |
512 | |
474 | =item C<EVBACKEND_ALL> |
513 | =item C<EVBACKEND_ALL> |
… | |
… | |
527 | responsibility to either stop all watchers cleanly yourself I<before> |
566 | responsibility to either stop all watchers cleanly yourself I<before> |
528 | calling this function, or cope with the fact afterwards (which is usually |
567 | calling this function, or cope with the fact afterwards (which is usually |
529 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
568 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
530 | for example). |
569 | for example). |
531 | |
570 | |
532 | Note that certain global state, such as signal state, will not be freed by |
571 | Note that certain global state, such as signal state (and installed signal |
533 | this function, and related watchers (such as signal and child watchers) |
572 | handlers), will not be freed by this function, and related watchers (such |
534 | would need to be stopped manually. |
573 | as signal and child watchers) would need to be stopped manually. |
535 | |
574 | |
536 | In general it is not advisable to call this function except in the |
575 | In general it is not advisable to call this function except in the |
537 | rare occasion where you really need to free e.g. the signal handling |
576 | rare occasion where you really need to free e.g. the signal handling |
538 | pipe fds. If you need dynamically allocated loops it is better to use |
577 | pipe fds. If you need dynamically allocated loops it is better to use |
539 | C<ev_loop_new> and C<ev_loop_destroy>). |
578 | C<ev_loop_new> and C<ev_loop_destroy>). |
… | |
… | |
582 | |
621 | |
583 | This value can sometimes be useful as a generation counter of sorts (it |
622 | This value can sometimes be useful as a generation counter of sorts (it |
584 | "ticks" the number of loop iterations), as it roughly corresponds with |
623 | "ticks" the number of loop iterations), as it roughly corresponds with |
585 | C<ev_prepare> and C<ev_check> calls. |
624 | C<ev_prepare> and C<ev_check> calls. |
586 | |
625 | |
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626 | =item unsigned int ev_loop_depth (loop) |
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627 | |
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628 | Returns the number of times C<ev_loop> was entered minus the number of |
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629 | times C<ev_loop> was exited, in other words, the recursion depth. |
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630 | |
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631 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
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632 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
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633 | in which case it is higher. |
|
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634 | |
|
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635 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
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636 | etc.), doesn't count as exit. |
|
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637 | |
587 | =item unsigned int ev_backend (loop) |
638 | =item unsigned int ev_backend (loop) |
588 | |
639 | |
589 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
640 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
590 | use. |
641 | use. |
591 | |
642 | |
… | |
… | |
605 | |
656 | |
606 | This function is rarely useful, but when some event callback runs for a |
657 | This function is rarely useful, but when some event callback runs for a |
607 | very long time without entering the event loop, updating libev's idea of |
658 | very long time without entering the event loop, updating libev's idea of |
608 | the current time is a good idea. |
659 | the current time is a good idea. |
609 | |
660 | |
610 | See also "The special problem of time updates" in the C<ev_timer> section. |
661 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
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662 | |
|
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663 | =item ev_suspend (loop) |
|
|
664 | |
|
|
665 | =item ev_resume (loop) |
|
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666 | |
|
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667 | These two functions suspend and resume a loop, for use when the loop is |
|
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668 | not used for a while and timeouts should not be processed. |
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669 | |
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670 | A typical use case would be an interactive program such as a game: When |
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671 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
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672 | would be best to handle timeouts as if no time had actually passed while |
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673 | the program was suspended. This can be achieved by calling C<ev_suspend> |
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674 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
675 | C<ev_resume> directly afterwards to resume timer processing. |
|
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676 | |
|
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677 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
678 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
679 | will be rescheduled (that is, they will lose any events that would have |
|
|
680 | occured while suspended). |
|
|
681 | |
|
|
682 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
683 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
684 | without a previous call to C<ev_suspend>. |
|
|
685 | |
|
|
686 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
687 | event loop time (see C<ev_now_update>). |
611 | |
688 | |
612 | =item ev_loop (loop, int flags) |
689 | =item ev_loop (loop, int flags) |
613 | |
690 | |
614 | Finally, this is it, the event handler. This function usually is called |
691 | Finally, this is it, the event handler. This function usually is called |
615 | after you initialised all your watchers and you want to start handling |
692 | after you initialised all your watchers and you want to start handling |
… | |
… | |
631 | the loop. |
708 | the loop. |
632 | |
709 | |
633 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
710 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
634 | necessary) and will handle those and any already outstanding ones. It |
711 | necessary) and will handle those and any already outstanding ones. It |
635 | will block your process until at least one new event arrives (which could |
712 | will block your process until at least one new event arrives (which could |
636 | be an event internal to libev itself, so there is no guarentee that a |
713 | be an event internal to libev itself, so there is no guarantee that a |
637 | user-registered callback will be called), and will return after one |
714 | user-registered callback will be called), and will return after one |
638 | iteration of the loop. |
715 | iteration of the loop. |
639 | |
716 | |
640 | This is useful if you are waiting for some external event in conjunction |
717 | This is useful if you are waiting for some external event in conjunction |
641 | with something not expressible using other libev watchers (i.e. "roll your |
718 | with something not expressible using other libev watchers (i.e. "roll your |
… | |
… | |
685 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
762 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
686 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
763 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
687 | |
764 | |
688 | This "unloop state" will be cleared when entering C<ev_loop> again. |
765 | This "unloop state" will be cleared when entering C<ev_loop> again. |
689 | |
766 | |
|
|
767 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
768 | |
690 | =item ev_ref (loop) |
769 | =item ev_ref (loop) |
691 | |
770 | |
692 | =item ev_unref (loop) |
771 | =item ev_unref (loop) |
693 | |
772 | |
694 | Ref/unref can be used to add or remove a reference count on the event |
773 | Ref/unref can be used to add or remove a reference count on the event |
… | |
… | |
697 | |
776 | |
698 | If you have a watcher you never unregister that should not keep C<ev_loop> |
777 | If you have a watcher you never unregister that should not keep C<ev_loop> |
699 | from returning, call ev_unref() after starting, and ev_ref() before |
778 | from returning, call ev_unref() after starting, and ev_ref() before |
700 | stopping it. |
779 | stopping it. |
701 | |
780 | |
702 | As an example, libev itself uses this for its internal signal pipe: It is |
781 | As an example, libev itself uses this for its internal signal pipe: It |
703 | not visible to the libev user and should not keep C<ev_loop> from exiting |
782 | is not visible to the libev user and should not keep C<ev_loop> from |
704 | if no event watchers registered by it are active. It is also an excellent |
783 | exiting if no event watchers registered by it are active. It is also an |
705 | way to do this for generic recurring timers or from within third-party |
784 | excellent way to do this for generic recurring timers or from within |
706 | libraries. Just remember to I<unref after start> and I<ref before stop> |
785 | third-party libraries. Just remember to I<unref after start> and I<ref |
707 | (but only if the watcher wasn't active before, or was active before, |
786 | before stop> (but only if the watcher wasn't active before, or was active |
708 | respectively). |
787 | before, respectively. Note also that libev might stop watchers itself |
|
|
788 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
789 | in the callback). |
709 | |
790 | |
710 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
791 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
711 | running when nothing else is active. |
792 | running when nothing else is active. |
712 | |
793 | |
713 | struct ev_signal exitsig; |
794 | ev_signal exitsig; |
714 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
795 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
715 | ev_signal_start (loop, &exitsig); |
796 | ev_signal_start (loop, &exitsig); |
716 | evf_unref (loop); |
797 | evf_unref (loop); |
717 | |
798 | |
718 | Example: For some weird reason, unregister the above signal handler again. |
799 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
742 | |
823 | |
743 | By setting a higher I<io collect interval> you allow libev to spend more |
824 | By setting a higher I<io collect interval> you allow libev to spend more |
744 | time collecting I/O events, so you can handle more events per iteration, |
825 | time collecting I/O events, so you can handle more events per iteration, |
745 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
826 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
746 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
827 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
747 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
828 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
829 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
830 | once per this interval, on average. |
748 | |
831 | |
749 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
832 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
750 | to spend more time collecting timeouts, at the expense of increased |
833 | to spend more time collecting timeouts, at the expense of increased |
751 | latency/jitter/inexactness (the watcher callback will be called |
834 | latency/jitter/inexactness (the watcher callback will be called |
752 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
835 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
754 | |
837 | |
755 | Many (busy) programs can usually benefit by setting the I/O collect |
838 | Many (busy) programs can usually benefit by setting the I/O collect |
756 | interval to a value near C<0.1> or so, which is often enough for |
839 | interval to a value near C<0.1> or so, which is often enough for |
757 | interactive servers (of course not for games), likewise for timeouts. It |
840 | interactive servers (of course not for games), likewise for timeouts. It |
758 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
841 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
759 | as this approaches the timing granularity of most systems. |
842 | as this approaches the timing granularity of most systems. Note that if |
|
|
843 | you do transactions with the outside world and you can't increase the |
|
|
844 | parallelity, then this setting will limit your transaction rate (if you |
|
|
845 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
846 | then you can't do more than 100 transations per second). |
760 | |
847 | |
761 | Setting the I<timeout collect interval> can improve the opportunity for |
848 | Setting the I<timeout collect interval> can improve the opportunity for |
762 | saving power, as the program will "bundle" timer callback invocations that |
849 | saving power, as the program will "bundle" timer callback invocations that |
763 | are "near" in time together, by delaying some, thus reducing the number of |
850 | are "near" in time together, by delaying some, thus reducing the number of |
764 | times the process sleeps and wakes up again. Another useful technique to |
851 | times the process sleeps and wakes up again. Another useful technique to |
765 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
852 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
766 | they fire on, say, one-second boundaries only. |
853 | they fire on, say, one-second boundaries only. |
767 | |
854 | |
|
|
855 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
856 | more often than 100 times per second: |
|
|
857 | |
|
|
858 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
859 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
860 | |
|
|
861 | =item ev_invoke_pending (loop) |
|
|
862 | |
|
|
863 | This call will simply invoke all pending watchers while resetting their |
|
|
864 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
|
865 | but when overriding the invoke callback this call comes handy. |
|
|
866 | |
|
|
867 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
868 | |
|
|
869 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
870 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
871 | this callback instead. This is useful, for example, when you want to |
|
|
872 | invoke the actual watchers inside another context (another thread etc.). |
|
|
873 | |
|
|
874 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
875 | callback. |
|
|
876 | |
|
|
877 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
878 | |
|
|
879 | Sometimes you want to share the same loop between multiple threads. This |
|
|
880 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
881 | each call to a libev function. |
|
|
882 | |
|
|
883 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
884 | wait for it to return. One way around this is to wake up the loop via |
|
|
885 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
886 | and I<acquire> callbacks on the loop. |
|
|
887 | |
|
|
888 | When set, then C<release> will be called just before the thread is |
|
|
889 | suspended waiting for new events, and C<acquire> is called just |
|
|
890 | afterwards. |
|
|
891 | |
|
|
892 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
893 | C<acquire> will just call the mutex_lock function again. |
|
|
894 | |
|
|
895 | While event loop modifications are allowed between invocations of |
|
|
896 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
897 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
898 | have no effect on the set of file descriptors being watched, or the time |
|
|
899 | waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
900 | to take note of any changes you made. |
|
|
901 | |
|
|
902 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
903 | invocations of C<release> and C<acquire>. |
|
|
904 | |
|
|
905 | See also the locking example in the C<THREADS> section later in this |
|
|
906 | document. |
|
|
907 | |
|
|
908 | =item ev_set_userdata (loop, void *data) |
|
|
909 | |
|
|
910 | =item ev_userdata (loop) |
|
|
911 | |
|
|
912 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
913 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
914 | C<0.> |
|
|
915 | |
|
|
916 | These two functions can be used to associate arbitrary data with a loop, |
|
|
917 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
918 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
919 | any other purpose as well. |
|
|
920 | |
768 | =item ev_loop_verify (loop) |
921 | =item ev_loop_verify (loop) |
769 | |
922 | |
770 | This function only does something when C<EV_VERIFY> support has been |
923 | This function only does something when C<EV_VERIFY> support has been |
771 | compiled in. which is the default for non-minimal builds. It tries to go |
924 | compiled in, which is the default for non-minimal builds. It tries to go |
772 | through all internal structures and checks them for validity. If anything |
925 | through all internal structures and checks them for validity. If anything |
773 | is found to be inconsistent, it will print an error message to standard |
926 | is found to be inconsistent, it will print an error message to standard |
774 | error and call C<abort ()>. |
927 | error and call C<abort ()>. |
775 | |
928 | |
776 | This can be used to catch bugs inside libev itself: under normal |
929 | This can be used to catch bugs inside libev itself: under normal |
… | |
… | |
780 | =back |
933 | =back |
781 | |
934 | |
782 | |
935 | |
783 | =head1 ANATOMY OF A WATCHER |
936 | =head1 ANATOMY OF A WATCHER |
784 | |
937 | |
|
|
938 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
939 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
940 | watchers and C<ev_io_start> for I/O watchers. |
|
|
941 | |
785 | A watcher is a structure that you create and register to record your |
942 | A watcher is a structure that you create and register to record your |
786 | interest in some event. For instance, if you want to wait for STDIN to |
943 | interest in some event. For instance, if you want to wait for STDIN to |
787 | become readable, you would create an C<ev_io> watcher for that: |
944 | become readable, you would create an C<ev_io> watcher for that: |
788 | |
945 | |
789 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
946 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
790 | { |
947 | { |
791 | ev_io_stop (w); |
948 | ev_io_stop (w); |
792 | ev_unloop (loop, EVUNLOOP_ALL); |
949 | ev_unloop (loop, EVUNLOOP_ALL); |
793 | } |
950 | } |
794 | |
951 | |
795 | struct ev_loop *loop = ev_default_loop (0); |
952 | struct ev_loop *loop = ev_default_loop (0); |
|
|
953 | |
796 | struct ev_io stdin_watcher; |
954 | ev_io stdin_watcher; |
|
|
955 | |
797 | ev_init (&stdin_watcher, my_cb); |
956 | ev_init (&stdin_watcher, my_cb); |
798 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
957 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
799 | ev_io_start (loop, &stdin_watcher); |
958 | ev_io_start (loop, &stdin_watcher); |
|
|
959 | |
800 | ev_loop (loop, 0); |
960 | ev_loop (loop, 0); |
801 | |
961 | |
802 | As you can see, you are responsible for allocating the memory for your |
962 | As you can see, you are responsible for allocating the memory for your |
803 | watcher structures (and it is usually a bad idea to do this on the stack, |
963 | watcher structures (and it is I<usually> a bad idea to do this on the |
804 | although this can sometimes be quite valid). |
964 | stack). |
|
|
965 | |
|
|
966 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
967 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
805 | |
968 | |
806 | Each watcher structure must be initialised by a call to C<ev_init |
969 | Each watcher structure must be initialised by a call to C<ev_init |
807 | (watcher *, callback)>, which expects a callback to be provided. This |
970 | (watcher *, callback)>, which expects a callback to be provided. This |
808 | callback gets invoked each time the event occurs (or, in the case of I/O |
971 | callback gets invoked each time the event occurs (or, in the case of I/O |
809 | watchers, each time the event loop detects that the file descriptor given |
972 | watchers, each time the event loop detects that the file descriptor given |
810 | is readable and/or writable). |
973 | is readable and/or writable). |
811 | |
974 | |
812 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
975 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
813 | with arguments specific to this watcher type. There is also a macro |
976 | macro to configure it, with arguments specific to the watcher type. There |
814 | to combine initialisation and setting in one call: C<< ev_<type>_init |
977 | is also a macro to combine initialisation and setting in one call: C<< |
815 | (watcher *, callback, ...) >>. |
978 | ev_TYPE_init (watcher *, callback, ...) >>. |
816 | |
979 | |
817 | To make the watcher actually watch out for events, you have to start it |
980 | To make the watcher actually watch out for events, you have to start it |
818 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
981 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
819 | *) >>), and you can stop watching for events at any time by calling the |
982 | *) >>), and you can stop watching for events at any time by calling the |
820 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
983 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
821 | |
984 | |
822 | As long as your watcher is active (has been started but not stopped) you |
985 | As long as your watcher is active (has been started but not stopped) you |
823 | must not touch the values stored in it. Most specifically you must never |
986 | must not touch the values stored in it. Most specifically you must never |
824 | reinitialise it or call its C<set> macro. |
987 | reinitialise it or call its C<ev_TYPE_set> macro. |
825 | |
988 | |
826 | Each and every callback receives the event loop pointer as first, the |
989 | Each and every callback receives the event loop pointer as first, the |
827 | registered watcher structure as second, and a bitset of received events as |
990 | registered watcher structure as second, and a bitset of received events as |
828 | third argument. |
991 | third argument. |
829 | |
992 | |
… | |
… | |
887 | |
1050 | |
888 | =item C<EV_ASYNC> |
1051 | =item C<EV_ASYNC> |
889 | |
1052 | |
890 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1053 | The given async watcher has been asynchronously notified (see C<ev_async>). |
891 | |
1054 | |
|
|
1055 | =item C<EV_CUSTOM> |
|
|
1056 | |
|
|
1057 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1058 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
1059 | |
892 | =item C<EV_ERROR> |
1060 | =item C<EV_ERROR> |
893 | |
1061 | |
894 | An unspecified error has occurred, the watcher has been stopped. This might |
1062 | An unspecified error has occurred, the watcher has been stopped. This might |
895 | happen because the watcher could not be properly started because libev |
1063 | happen because the watcher could not be properly started because libev |
896 | ran out of memory, a file descriptor was found to be closed or any other |
1064 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1065 | problem. Libev considers these application bugs. |
|
|
1066 | |
897 | problem. You best act on it by reporting the problem and somehow coping |
1067 | You best act on it by reporting the problem and somehow coping with the |
898 | with the watcher being stopped. |
1068 | watcher being stopped. Note that well-written programs should not receive |
|
|
1069 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1070 | bug in your program. |
899 | |
1071 | |
900 | Libev will usually signal a few "dummy" events together with an error, for |
1072 | Libev will usually signal a few "dummy" events together with an error, for |
901 | example it might indicate that a fd is readable or writable, and if your |
1073 | example it might indicate that a fd is readable or writable, and if your |
902 | callbacks is well-written it can just attempt the operation and cope with |
1074 | callbacks is well-written it can just attempt the operation and cope with |
903 | the error from read() or write(). This will not work in multi-threaded |
1075 | the error from read() or write(). This will not work in multi-threaded |
… | |
… | |
906 | |
1078 | |
907 | =back |
1079 | =back |
908 | |
1080 | |
909 | =head2 GENERIC WATCHER FUNCTIONS |
1081 | =head2 GENERIC WATCHER FUNCTIONS |
910 | |
1082 | |
911 | In the following description, C<TYPE> stands for the watcher type, |
|
|
912 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
913 | |
|
|
914 | =over 4 |
1083 | =over 4 |
915 | |
1084 | |
916 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1085 | =item C<ev_init> (ev_TYPE *watcher, callback) |
917 | |
1086 | |
918 | This macro initialises the generic portion of a watcher. The contents |
1087 | This macro initialises the generic portion of a watcher. The contents |
… | |
… | |
923 | which rolls both calls into one. |
1092 | which rolls both calls into one. |
924 | |
1093 | |
925 | You can reinitialise a watcher at any time as long as it has been stopped |
1094 | You can reinitialise a watcher at any time as long as it has been stopped |
926 | (or never started) and there are no pending events outstanding. |
1095 | (or never started) and there are no pending events outstanding. |
927 | |
1096 | |
928 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1097 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
929 | int revents)>. |
1098 | int revents)>. |
930 | |
1099 | |
931 | Example: Initialise an C<ev_io> watcher in two steps. |
1100 | Example: Initialise an C<ev_io> watcher in two steps. |
932 | |
1101 | |
933 | ev_io w; |
1102 | ev_io w; |
… | |
… | |
967 | |
1136 | |
968 | ev_io_start (EV_DEFAULT_UC, &w); |
1137 | ev_io_start (EV_DEFAULT_UC, &w); |
969 | |
1138 | |
970 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1139 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
971 | |
1140 | |
972 | Stops the given watcher again (if active) and clears the pending |
1141 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1142 | the watcher was active or not). |
|
|
1143 | |
973 | status. It is possible that stopped watchers are pending (for example, |
1144 | It is possible that stopped watchers are pending - for example, |
974 | non-repeating timers are being stopped when they become pending), but |
1145 | non-repeating timers are being stopped when they become pending - but |
975 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1146 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
976 | you want to free or reuse the memory used by the watcher it is therefore a |
1147 | pending. If you want to free or reuse the memory used by the watcher it is |
977 | good idea to always call its C<ev_TYPE_stop> function. |
1148 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
978 | |
1149 | |
979 | =item bool ev_is_active (ev_TYPE *watcher) |
1150 | =item bool ev_is_active (ev_TYPE *watcher) |
980 | |
1151 | |
981 | Returns a true value iff the watcher is active (i.e. it has been started |
1152 | Returns a true value iff the watcher is active (i.e. it has been started |
982 | and not yet been stopped). As long as a watcher is active you must not modify |
1153 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
1008 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1179 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1009 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1180 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1010 | before watchers with lower priority, but priority will not keep watchers |
1181 | before watchers with lower priority, but priority will not keep watchers |
1011 | from being executed (except for C<ev_idle> watchers). |
1182 | from being executed (except for C<ev_idle> watchers). |
1012 | |
1183 | |
1013 | This means that priorities are I<only> used for ordering callback |
|
|
1014 | invocation after new events have been received. This is useful, for |
|
|
1015 | example, to reduce latency after idling, or more often, to bind two |
|
|
1016 | watchers on the same event and make sure one is called first. |
|
|
1017 | |
|
|
1018 | If you need to suppress invocation when higher priority events are pending |
1184 | If you need to suppress invocation when higher priority events are pending |
1019 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1185 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1020 | |
1186 | |
1021 | You I<must not> change the priority of a watcher as long as it is active or |
1187 | You I<must not> change the priority of a watcher as long as it is active or |
1022 | pending. |
1188 | pending. |
1023 | |
1189 | |
|
|
1190 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1191 | fine, as long as you do not mind that the priority value you query might |
|
|
1192 | or might not have been clamped to the valid range. |
|
|
1193 | |
1024 | The default priority used by watchers when no priority has been set is |
1194 | The default priority used by watchers when no priority has been set is |
1025 | always C<0>, which is supposed to not be too high and not be too low :). |
1195 | always C<0>, which is supposed to not be too high and not be too low :). |
1026 | |
1196 | |
1027 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1197 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1028 | fine, as long as you do not mind that the priority value you query might |
1198 | priorities. |
1029 | or might not have been adjusted to be within valid range. |
|
|
1030 | |
1199 | |
1031 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1200 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1032 | |
1201 | |
1033 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1202 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1034 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1203 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1056 | member, you can also "subclass" the watcher type and provide your own |
1225 | member, you can also "subclass" the watcher type and provide your own |
1057 | data: |
1226 | data: |
1058 | |
1227 | |
1059 | struct my_io |
1228 | struct my_io |
1060 | { |
1229 | { |
1061 | struct ev_io io; |
1230 | ev_io io; |
1062 | int otherfd; |
1231 | int otherfd; |
1063 | void *somedata; |
1232 | void *somedata; |
1064 | struct whatever *mostinteresting; |
1233 | struct whatever *mostinteresting; |
1065 | }; |
1234 | }; |
1066 | |
1235 | |
… | |
… | |
1069 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1238 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1070 | |
1239 | |
1071 | And since your callback will be called with a pointer to the watcher, you |
1240 | And since your callback will be called with a pointer to the watcher, you |
1072 | can cast it back to your own type: |
1241 | can cast it back to your own type: |
1073 | |
1242 | |
1074 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1243 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1075 | { |
1244 | { |
1076 | struct my_io *w = (struct my_io *)w_; |
1245 | struct my_io *w = (struct my_io *)w_; |
1077 | ... |
1246 | ... |
1078 | } |
1247 | } |
1079 | |
1248 | |
… | |
… | |
1097 | programmers): |
1266 | programmers): |
1098 | |
1267 | |
1099 | #include <stddef.h> |
1268 | #include <stddef.h> |
1100 | |
1269 | |
1101 | static void |
1270 | static void |
1102 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1271 | t1_cb (EV_P_ ev_timer *w, int revents) |
1103 | { |
1272 | { |
1104 | struct my_biggy big = (struct my_biggy * |
1273 | struct my_biggy big = (struct my_biggy *) |
1105 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1274 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1106 | } |
1275 | } |
1107 | |
1276 | |
1108 | static void |
1277 | static void |
1109 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1278 | t2_cb (EV_P_ ev_timer *w, int revents) |
1110 | { |
1279 | { |
1111 | struct my_biggy big = (struct my_biggy * |
1280 | struct my_biggy big = (struct my_biggy *) |
1112 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1281 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1113 | } |
1282 | } |
|
|
1283 | |
|
|
1284 | =head2 WATCHER PRIORITY MODELS |
|
|
1285 | |
|
|
1286 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1287 | integers that influence the ordering of event callback invocation |
|
|
1288 | between watchers in some way, all else being equal. |
|
|
1289 | |
|
|
1290 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1291 | description for the more technical details such as the actual priority |
|
|
1292 | range. |
|
|
1293 | |
|
|
1294 | There are two common ways how these these priorities are being interpreted |
|
|
1295 | by event loops: |
|
|
1296 | |
|
|
1297 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1298 | of lower priority watchers, which means as long as higher priority |
|
|
1299 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1300 | |
|
|
1301 | The less common only-for-ordering model uses priorities solely to order |
|
|
1302 | callback invocation within a single event loop iteration: Higher priority |
|
|
1303 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1304 | before polling for new events. |
|
|
1305 | |
|
|
1306 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1307 | except for idle watchers (which use the lock-out model). |
|
|
1308 | |
|
|
1309 | The rationale behind this is that implementing the lock-out model for |
|
|
1310 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1311 | libraries will just poll for the same events again and again as long as |
|
|
1312 | their callbacks have not been executed, which is very inefficient in the |
|
|
1313 | common case of one high-priority watcher locking out a mass of lower |
|
|
1314 | priority ones. |
|
|
1315 | |
|
|
1316 | Static (ordering) priorities are most useful when you have two or more |
|
|
1317 | watchers handling the same resource: a typical usage example is having an |
|
|
1318 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1319 | timeouts. Under load, data might be received while the program handles |
|
|
1320 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1321 | handler will be executed before checking for data. In that case, giving |
|
|
1322 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1323 | handled first even under adverse conditions (which is usually, but not |
|
|
1324 | always, what you want). |
|
|
1325 | |
|
|
1326 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1327 | will only be executed when no same or higher priority watchers have |
|
|
1328 | received events, they can be used to implement the "lock-out" model when |
|
|
1329 | required. |
|
|
1330 | |
|
|
1331 | For example, to emulate how many other event libraries handle priorities, |
|
|
1332 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1333 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1334 | processing is done in the idle watcher callback. This causes libev to |
|
|
1335 | continously poll and process kernel event data for the watcher, but when |
|
|
1336 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1337 | workable. |
|
|
1338 | |
|
|
1339 | Usually, however, the lock-out model implemented that way will perform |
|
|
1340 | miserably under the type of load it was designed to handle. In that case, |
|
|
1341 | it might be preferable to stop the real watcher before starting the |
|
|
1342 | idle watcher, so the kernel will not have to process the event in case |
|
|
1343 | the actual processing will be delayed for considerable time. |
|
|
1344 | |
|
|
1345 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1346 | priority than the default, and which should only process data when no |
|
|
1347 | other events are pending: |
|
|
1348 | |
|
|
1349 | ev_idle idle; // actual processing watcher |
|
|
1350 | ev_io io; // actual event watcher |
|
|
1351 | |
|
|
1352 | static void |
|
|
1353 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1354 | { |
|
|
1355 | // stop the I/O watcher, we received the event, but |
|
|
1356 | // are not yet ready to handle it. |
|
|
1357 | ev_io_stop (EV_A_ w); |
|
|
1358 | |
|
|
1359 | // start the idle watcher to ahndle the actual event. |
|
|
1360 | // it will not be executed as long as other watchers |
|
|
1361 | // with the default priority are receiving events. |
|
|
1362 | ev_idle_start (EV_A_ &idle); |
|
|
1363 | } |
|
|
1364 | |
|
|
1365 | static void |
|
|
1366 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1367 | { |
|
|
1368 | // actual processing |
|
|
1369 | read (STDIN_FILENO, ...); |
|
|
1370 | |
|
|
1371 | // have to start the I/O watcher again, as |
|
|
1372 | // we have handled the event |
|
|
1373 | ev_io_start (EV_P_ &io); |
|
|
1374 | } |
|
|
1375 | |
|
|
1376 | // initialisation |
|
|
1377 | ev_idle_init (&idle, idle_cb); |
|
|
1378 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1379 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1380 | |
|
|
1381 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1382 | low-priority connections can not be locked out forever under load. This |
|
|
1383 | enables your program to keep a lower latency for important connections |
|
|
1384 | during short periods of high load, while not completely locking out less |
|
|
1385 | important ones. |
1114 | |
1386 | |
1115 | |
1387 | |
1116 | =head1 WATCHER TYPES |
1388 | =head1 WATCHER TYPES |
1117 | |
1389 | |
1118 | This section describes each watcher in detail, but will not repeat |
1390 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1144 | descriptors to non-blocking mode is also usually a good idea (but not |
1416 | descriptors to non-blocking mode is also usually a good idea (but not |
1145 | required if you know what you are doing). |
1417 | required if you know what you are doing). |
1146 | |
1418 | |
1147 | If you cannot use non-blocking mode, then force the use of a |
1419 | If you cannot use non-blocking mode, then force the use of a |
1148 | known-to-be-good backend (at the time of this writing, this includes only |
1420 | known-to-be-good backend (at the time of this writing, this includes only |
1149 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1421 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1422 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1423 | files) - libev doesn't guarentee any specific behaviour in that case. |
1150 | |
1424 | |
1151 | Another thing you have to watch out for is that it is quite easy to |
1425 | Another thing you have to watch out for is that it is quite easy to |
1152 | receive "spurious" readiness notifications, that is your callback might |
1426 | receive "spurious" readiness notifications, that is your callback might |
1153 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1427 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1154 | because there is no data. Not only are some backends known to create a |
1428 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1249 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1523 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1250 | readable, but only once. Since it is likely line-buffered, you could |
1524 | readable, but only once. Since it is likely line-buffered, you could |
1251 | attempt to read a whole line in the callback. |
1525 | attempt to read a whole line in the callback. |
1252 | |
1526 | |
1253 | static void |
1527 | static void |
1254 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1528 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1255 | { |
1529 | { |
1256 | ev_io_stop (loop, w); |
1530 | ev_io_stop (loop, w); |
1257 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1531 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1258 | } |
1532 | } |
1259 | |
1533 | |
1260 | ... |
1534 | ... |
1261 | struct ev_loop *loop = ev_default_init (0); |
1535 | struct ev_loop *loop = ev_default_init (0); |
1262 | struct ev_io stdin_readable; |
1536 | ev_io stdin_readable; |
1263 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1537 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1264 | ev_io_start (loop, &stdin_readable); |
1538 | ev_io_start (loop, &stdin_readable); |
1265 | ev_loop (loop, 0); |
1539 | ev_loop (loop, 0); |
1266 | |
1540 | |
1267 | |
1541 | |
… | |
… | |
1275 | year, it will still time out after (roughly) one hour. "Roughly" because |
1549 | year, it will still time out after (roughly) one hour. "Roughly" because |
1276 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1550 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1277 | monotonic clock option helps a lot here). |
1551 | monotonic clock option helps a lot here). |
1278 | |
1552 | |
1279 | The callback is guaranteed to be invoked only I<after> its timeout has |
1553 | The callback is guaranteed to be invoked only I<after> its timeout has |
1280 | passed, but if multiple timers become ready during the same loop iteration |
1554 | passed (not I<at>, so on systems with very low-resolution clocks this |
1281 | then order of execution is undefined. |
1555 | might introduce a small delay). If multiple timers become ready during the |
|
|
1556 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1557 | before ones of the same priority with later time-out values (but this is |
|
|
1558 | no longer true when a callback calls C<ev_loop> recursively). |
|
|
1559 | |
|
|
1560 | =head3 Be smart about timeouts |
|
|
1561 | |
|
|
1562 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1563 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1564 | you want to raise some error after a while. |
|
|
1565 | |
|
|
1566 | What follows are some ways to handle this problem, from obvious and |
|
|
1567 | inefficient to smart and efficient. |
|
|
1568 | |
|
|
1569 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1570 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1571 | data or other life sign was received). |
|
|
1572 | |
|
|
1573 | =over 4 |
|
|
1574 | |
|
|
1575 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1576 | |
|
|
1577 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1578 | start the watcher: |
|
|
1579 | |
|
|
1580 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1581 | ev_timer_start (loop, timer); |
|
|
1582 | |
|
|
1583 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1584 | and start it again: |
|
|
1585 | |
|
|
1586 | ev_timer_stop (loop, timer); |
|
|
1587 | ev_timer_set (timer, 60., 0.); |
|
|
1588 | ev_timer_start (loop, timer); |
|
|
1589 | |
|
|
1590 | This is relatively simple to implement, but means that each time there is |
|
|
1591 | some activity, libev will first have to remove the timer from its internal |
|
|
1592 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1593 | still not a constant-time operation. |
|
|
1594 | |
|
|
1595 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1596 | |
|
|
1597 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1598 | C<ev_timer_start>. |
|
|
1599 | |
|
|
1600 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1601 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1602 | successfully read or write some data. If you go into an idle state where |
|
|
1603 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1604 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1605 | |
|
|
1606 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1607 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1608 | member and C<ev_timer_again>. |
|
|
1609 | |
|
|
1610 | At start: |
|
|
1611 | |
|
|
1612 | ev_init (timer, callback); |
|
|
1613 | timer->repeat = 60.; |
|
|
1614 | ev_timer_again (loop, timer); |
|
|
1615 | |
|
|
1616 | Each time there is some activity: |
|
|
1617 | |
|
|
1618 | ev_timer_again (loop, timer); |
|
|
1619 | |
|
|
1620 | It is even possible to change the time-out on the fly, regardless of |
|
|
1621 | whether the watcher is active or not: |
|
|
1622 | |
|
|
1623 | timer->repeat = 30.; |
|
|
1624 | ev_timer_again (loop, timer); |
|
|
1625 | |
|
|
1626 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1627 | you want to modify its timeout value, as libev does not have to completely |
|
|
1628 | remove and re-insert the timer from/into its internal data structure. |
|
|
1629 | |
|
|
1630 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1631 | |
|
|
1632 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1633 | |
|
|
1634 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1635 | relatively long compared to the intervals between other activity - in |
|
|
1636 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1637 | associated activity resets. |
|
|
1638 | |
|
|
1639 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1640 | but remember the time of last activity, and check for a real timeout only |
|
|
1641 | within the callback: |
|
|
1642 | |
|
|
1643 | ev_tstamp last_activity; // time of last activity |
|
|
1644 | |
|
|
1645 | static void |
|
|
1646 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1647 | { |
|
|
1648 | ev_tstamp now = ev_now (EV_A); |
|
|
1649 | ev_tstamp timeout = last_activity + 60.; |
|
|
1650 | |
|
|
1651 | // if last_activity + 60. is older than now, we did time out |
|
|
1652 | if (timeout < now) |
|
|
1653 | { |
|
|
1654 | // timeout occured, take action |
|
|
1655 | } |
|
|
1656 | else |
|
|
1657 | { |
|
|
1658 | // callback was invoked, but there was some activity, re-arm |
|
|
1659 | // the watcher to fire in last_activity + 60, which is |
|
|
1660 | // guaranteed to be in the future, so "again" is positive: |
|
|
1661 | w->repeat = timeout - now; |
|
|
1662 | ev_timer_again (EV_A_ w); |
|
|
1663 | } |
|
|
1664 | } |
|
|
1665 | |
|
|
1666 | To summarise the callback: first calculate the real timeout (defined |
|
|
1667 | as "60 seconds after the last activity"), then check if that time has |
|
|
1668 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1669 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1670 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1671 | a timeout then. |
|
|
1672 | |
|
|
1673 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1674 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1675 | |
|
|
1676 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1677 | minus half the average time between activity), but virtually no calls to |
|
|
1678 | libev to change the timeout. |
|
|
1679 | |
|
|
1680 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1681 | to the current time (meaning we just have some activity :), then call the |
|
|
1682 | callback, which will "do the right thing" and start the timer: |
|
|
1683 | |
|
|
1684 | ev_init (timer, callback); |
|
|
1685 | last_activity = ev_now (loop); |
|
|
1686 | callback (loop, timer, EV_TIMEOUT); |
|
|
1687 | |
|
|
1688 | And when there is some activity, simply store the current time in |
|
|
1689 | C<last_activity>, no libev calls at all: |
|
|
1690 | |
|
|
1691 | last_actiivty = ev_now (loop); |
|
|
1692 | |
|
|
1693 | This technique is slightly more complex, but in most cases where the |
|
|
1694 | time-out is unlikely to be triggered, much more efficient. |
|
|
1695 | |
|
|
1696 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1697 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1698 | fix things for you. |
|
|
1699 | |
|
|
1700 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1701 | |
|
|
1702 | If there is not one request, but many thousands (millions...), all |
|
|
1703 | employing some kind of timeout with the same timeout value, then one can |
|
|
1704 | do even better: |
|
|
1705 | |
|
|
1706 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1707 | at the I<end> of the list. |
|
|
1708 | |
|
|
1709 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1710 | the list is expected to fire (for example, using the technique #3). |
|
|
1711 | |
|
|
1712 | When there is some activity, remove the timer from the list, recalculate |
|
|
1713 | the timeout, append it to the end of the list again, and make sure to |
|
|
1714 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1715 | |
|
|
1716 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1717 | starting, stopping and updating the timers, at the expense of a major |
|
|
1718 | complication, and having to use a constant timeout. The constant timeout |
|
|
1719 | ensures that the list stays sorted. |
|
|
1720 | |
|
|
1721 | =back |
|
|
1722 | |
|
|
1723 | So which method the best? |
|
|
1724 | |
|
|
1725 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1726 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1727 | better, and isn't very complicated either. In most case, choosing either |
|
|
1728 | one is fine, with #3 being better in typical situations. |
|
|
1729 | |
|
|
1730 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1731 | rather complicated, but extremely efficient, something that really pays |
|
|
1732 | off after the first million or so of active timers, i.e. it's usually |
|
|
1733 | overkill :) |
1282 | |
1734 | |
1283 | =head3 The special problem of time updates |
1735 | =head3 The special problem of time updates |
1284 | |
1736 | |
1285 | Establishing the current time is a costly operation (it usually takes at |
1737 | Establishing the current time is a costly operation (it usually takes at |
1286 | least two system calls): EV therefore updates its idea of the current |
1738 | least two system calls): EV therefore updates its idea of the current |
… | |
… | |
1330 | If the timer is started but non-repeating, stop it (as if it timed out). |
1782 | If the timer is started but non-repeating, stop it (as if it timed out). |
1331 | |
1783 | |
1332 | If the timer is repeating, either start it if necessary (with the |
1784 | If the timer is repeating, either start it if necessary (with the |
1333 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1785 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1334 | |
1786 | |
1335 | This sounds a bit complicated, but here is a useful and typical |
1787 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1336 | example: Imagine you have a TCP connection and you want a so-called idle |
1788 | usage example. |
1337 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1338 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1339 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1340 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1341 | you go into an idle state where you do not expect data to travel on the |
|
|
1342 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1343 | automatically restart it if need be. |
|
|
1344 | |
|
|
1345 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1346 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1347 | |
|
|
1348 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1349 | ev_timer_again (loop, timer); |
|
|
1350 | ... |
|
|
1351 | timer->again = 17.; |
|
|
1352 | ev_timer_again (loop, timer); |
|
|
1353 | ... |
|
|
1354 | timer->again = 10.; |
|
|
1355 | ev_timer_again (loop, timer); |
|
|
1356 | |
|
|
1357 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1358 | you want to modify its timeout value. |
|
|
1359 | |
|
|
1360 | Note, however, that it is often even more efficient to remember the |
|
|
1361 | time of the last activity and let the timer time-out naturally. In the |
|
|
1362 | callback, you then check whether the time-out is real, or, if there was |
|
|
1363 | some activity, you reschedule the watcher to time-out in "last_activity + |
|
|
1364 | timeout - ev_now ()" seconds. |
|
|
1365 | |
1789 | |
1366 | =item ev_tstamp repeat [read-write] |
1790 | =item ev_tstamp repeat [read-write] |
1367 | |
1791 | |
1368 | The current C<repeat> value. Will be used each time the watcher times out |
1792 | The current C<repeat> value. Will be used each time the watcher times out |
1369 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1793 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1374 | =head3 Examples |
1798 | =head3 Examples |
1375 | |
1799 | |
1376 | Example: Create a timer that fires after 60 seconds. |
1800 | Example: Create a timer that fires after 60 seconds. |
1377 | |
1801 | |
1378 | static void |
1802 | static void |
1379 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1803 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1380 | { |
1804 | { |
1381 | .. one minute over, w is actually stopped right here |
1805 | .. one minute over, w is actually stopped right here |
1382 | } |
1806 | } |
1383 | |
1807 | |
1384 | struct ev_timer mytimer; |
1808 | ev_timer mytimer; |
1385 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1809 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1386 | ev_timer_start (loop, &mytimer); |
1810 | ev_timer_start (loop, &mytimer); |
1387 | |
1811 | |
1388 | Example: Create a timeout timer that times out after 10 seconds of |
1812 | Example: Create a timeout timer that times out after 10 seconds of |
1389 | inactivity. |
1813 | inactivity. |
1390 | |
1814 | |
1391 | static void |
1815 | static void |
1392 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1816 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1393 | { |
1817 | { |
1394 | .. ten seconds without any activity |
1818 | .. ten seconds without any activity |
1395 | } |
1819 | } |
1396 | |
1820 | |
1397 | struct ev_timer mytimer; |
1821 | ev_timer mytimer; |
1398 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1822 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1399 | ev_timer_again (&mytimer); /* start timer */ |
1823 | ev_timer_again (&mytimer); /* start timer */ |
1400 | ev_loop (loop, 0); |
1824 | ev_loop (loop, 0); |
1401 | |
1825 | |
1402 | // and in some piece of code that gets executed on any "activity": |
1826 | // and in some piece of code that gets executed on any "activity": |
… | |
… | |
1407 | =head2 C<ev_periodic> - to cron or not to cron? |
1831 | =head2 C<ev_periodic> - to cron or not to cron? |
1408 | |
1832 | |
1409 | Periodic watchers are also timers of a kind, but they are very versatile |
1833 | Periodic watchers are also timers of a kind, but they are very versatile |
1410 | (and unfortunately a bit complex). |
1834 | (and unfortunately a bit complex). |
1411 | |
1835 | |
1412 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1836 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1413 | but on wall clock time (absolute time). You can tell a periodic watcher |
1837 | relative time, the physical time that passes) but on wall clock time |
1414 | to trigger after some specific point in time. For example, if you tell a |
1838 | (absolute time, the thing you can read on your calender or clock). The |
1415 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1839 | difference is that wall clock time can run faster or slower than real |
1416 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1840 | time, and time jumps are not uncommon (e.g. when you adjust your |
1417 | clock to January of the previous year, then it will take more than year |
1841 | wrist-watch). |
1418 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1419 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1420 | |
1842 | |
|
|
1843 | You can tell a periodic watcher to trigger after some specific point |
|
|
1844 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1845 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1846 | not a delay) and then reset your system clock to January of the previous |
|
|
1847 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1848 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1849 | it, as it uses a relative timeout). |
|
|
1850 | |
1421 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1851 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1422 | such as triggering an event on each "midnight, local time", or other |
1852 | timers, such as triggering an event on each "midnight, local time", or |
1423 | complicated rules. |
1853 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1854 | those cannot react to time jumps. |
1424 | |
1855 | |
1425 | As with timers, the callback is guaranteed to be invoked only when the |
1856 | As with timers, the callback is guaranteed to be invoked only when the |
1426 | time (C<at>) has passed, but if multiple periodic timers become ready |
1857 | point in time where it is supposed to trigger has passed. If multiple |
1427 | during the same loop iteration, then order of execution is undefined. |
1858 | timers become ready during the same loop iteration then the ones with |
|
|
1859 | earlier time-out values are invoked before ones with later time-out values |
|
|
1860 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1428 | |
1861 | |
1429 | =head3 Watcher-Specific Functions and Data Members |
1862 | =head3 Watcher-Specific Functions and Data Members |
1430 | |
1863 | |
1431 | =over 4 |
1864 | =over 4 |
1432 | |
1865 | |
1433 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1866 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1434 | |
1867 | |
1435 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1868 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1436 | |
1869 | |
1437 | Lots of arguments, lets sort it out... There are basically three modes of |
1870 | Lots of arguments, let's sort it out... There are basically three modes of |
1438 | operation, and we will explain them from simplest to most complex: |
1871 | operation, and we will explain them from simplest to most complex: |
1439 | |
1872 | |
1440 | =over 4 |
1873 | =over 4 |
1441 | |
1874 | |
1442 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1875 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1443 | |
1876 | |
1444 | In this configuration the watcher triggers an event after the wall clock |
1877 | In this configuration the watcher triggers an event after the wall clock |
1445 | time C<at> has passed. It will not repeat and will not adjust when a time |
1878 | time C<offset> has passed. It will not repeat and will not adjust when a |
1446 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1879 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1447 | only run when the system clock reaches or surpasses this time. |
1880 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1881 | this point in time. |
1448 | |
1882 | |
1449 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1883 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1450 | |
1884 | |
1451 | In this mode the watcher will always be scheduled to time out at the next |
1885 | In this mode the watcher will always be scheduled to time out at the next |
1452 | C<at + N * interval> time (for some integer N, which can also be negative) |
1886 | C<offset + N * interval> time (for some integer N, which can also be |
1453 | and then repeat, regardless of any time jumps. |
1887 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1888 | argument is merely an offset into the C<interval> periods. |
1454 | |
1889 | |
1455 | This can be used to create timers that do not drift with respect to the |
1890 | This can be used to create timers that do not drift with respect to the |
1456 | system clock, for example, here is a C<ev_periodic> that triggers each |
1891 | system clock, for example, here is an C<ev_periodic> that triggers each |
1457 | hour, on the hour: |
1892 | hour, on the hour (with respect to UTC): |
1458 | |
1893 | |
1459 | ev_periodic_set (&periodic, 0., 3600., 0); |
1894 | ev_periodic_set (&periodic, 0., 3600., 0); |
1460 | |
1895 | |
1461 | This doesn't mean there will always be 3600 seconds in between triggers, |
1896 | This doesn't mean there will always be 3600 seconds in between triggers, |
1462 | but only that the callback will be called when the system time shows a |
1897 | but only that the callback will be called when the system time shows a |
1463 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1898 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1464 | by 3600. |
1899 | by 3600. |
1465 | |
1900 | |
1466 | Another way to think about it (for the mathematically inclined) is that |
1901 | Another way to think about it (for the mathematically inclined) is that |
1467 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1902 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1468 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1903 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1469 | |
1904 | |
1470 | For numerical stability it is preferable that the C<at> value is near |
1905 | For numerical stability it is preferable that the C<offset> value is near |
1471 | C<ev_now ()> (the current time), but there is no range requirement for |
1906 | C<ev_now ()> (the current time), but there is no range requirement for |
1472 | this value, and in fact is often specified as zero. |
1907 | this value, and in fact is often specified as zero. |
1473 | |
1908 | |
1474 | Note also that there is an upper limit to how often a timer can fire (CPU |
1909 | Note also that there is an upper limit to how often a timer can fire (CPU |
1475 | speed for example), so if C<interval> is very small then timing stability |
1910 | speed for example), so if C<interval> is very small then timing stability |
1476 | will of course deteriorate. Libev itself tries to be exact to be about one |
1911 | will of course deteriorate. Libev itself tries to be exact to be about one |
1477 | millisecond (if the OS supports it and the machine is fast enough). |
1912 | millisecond (if the OS supports it and the machine is fast enough). |
1478 | |
1913 | |
1479 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1914 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1480 | |
1915 | |
1481 | In this mode the values for C<interval> and C<at> are both being |
1916 | In this mode the values for C<interval> and C<offset> are both being |
1482 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1917 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1483 | reschedule callback will be called with the watcher as first, and the |
1918 | reschedule callback will be called with the watcher as first, and the |
1484 | current time as second argument. |
1919 | current time as second argument. |
1485 | |
1920 | |
1486 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1921 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1487 | ever, or make ANY event loop modifications whatsoever>. |
1922 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1923 | allowed by documentation here>. |
1488 | |
1924 | |
1489 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1925 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1490 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1926 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1491 | only event loop modification you are allowed to do). |
1927 | only event loop modification you are allowed to do). |
1492 | |
1928 | |
1493 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1929 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1494 | *w, ev_tstamp now)>, e.g.: |
1930 | *w, ev_tstamp now)>, e.g.: |
1495 | |
1931 | |
|
|
1932 | static ev_tstamp |
1496 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1933 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1497 | { |
1934 | { |
1498 | return now + 60.; |
1935 | return now + 60.; |
1499 | } |
1936 | } |
1500 | |
1937 | |
1501 | It must return the next time to trigger, based on the passed time value |
1938 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1521 | a different time than the last time it was called (e.g. in a crond like |
1958 | a different time than the last time it was called (e.g. in a crond like |
1522 | program when the crontabs have changed). |
1959 | program when the crontabs have changed). |
1523 | |
1960 | |
1524 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1961 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1525 | |
1962 | |
1526 | When active, returns the absolute time that the watcher is supposed to |
1963 | When active, returns the absolute time that the watcher is supposed |
1527 | trigger next. |
1964 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1965 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1966 | rescheduling modes. |
1528 | |
1967 | |
1529 | =item ev_tstamp offset [read-write] |
1968 | =item ev_tstamp offset [read-write] |
1530 | |
1969 | |
1531 | When repeating, this contains the offset value, otherwise this is the |
1970 | When repeating, this contains the offset value, otherwise this is the |
1532 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1971 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1972 | although libev might modify this value for better numerical stability). |
1533 | |
1973 | |
1534 | Can be modified any time, but changes only take effect when the periodic |
1974 | Can be modified any time, but changes only take effect when the periodic |
1535 | timer fires or C<ev_periodic_again> is being called. |
1975 | timer fires or C<ev_periodic_again> is being called. |
1536 | |
1976 | |
1537 | =item ev_tstamp interval [read-write] |
1977 | =item ev_tstamp interval [read-write] |
1538 | |
1978 | |
1539 | The current interval value. Can be modified any time, but changes only |
1979 | The current interval value. Can be modified any time, but changes only |
1540 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1980 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1541 | called. |
1981 | called. |
1542 | |
1982 | |
1543 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1983 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1544 | |
1984 | |
1545 | The current reschedule callback, or C<0>, if this functionality is |
1985 | The current reschedule callback, or C<0>, if this functionality is |
1546 | switched off. Can be changed any time, but changes only take effect when |
1986 | switched off. Can be changed any time, but changes only take effect when |
1547 | the periodic timer fires or C<ev_periodic_again> is being called. |
1987 | the periodic timer fires or C<ev_periodic_again> is being called. |
1548 | |
1988 | |
… | |
… | |
1553 | Example: Call a callback every hour, or, more precisely, whenever the |
1993 | Example: Call a callback every hour, or, more precisely, whenever the |
1554 | system time is divisible by 3600. The callback invocation times have |
1994 | system time is divisible by 3600. The callback invocation times have |
1555 | potentially a lot of jitter, but good long-term stability. |
1995 | potentially a lot of jitter, but good long-term stability. |
1556 | |
1996 | |
1557 | static void |
1997 | static void |
1558 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1998 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1559 | { |
1999 | { |
1560 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2000 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1561 | } |
2001 | } |
1562 | |
2002 | |
1563 | struct ev_periodic hourly_tick; |
2003 | ev_periodic hourly_tick; |
1564 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2004 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1565 | ev_periodic_start (loop, &hourly_tick); |
2005 | ev_periodic_start (loop, &hourly_tick); |
1566 | |
2006 | |
1567 | Example: The same as above, but use a reschedule callback to do it: |
2007 | Example: The same as above, but use a reschedule callback to do it: |
1568 | |
2008 | |
1569 | #include <math.h> |
2009 | #include <math.h> |
1570 | |
2010 | |
1571 | static ev_tstamp |
2011 | static ev_tstamp |
1572 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2012 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1573 | { |
2013 | { |
1574 | return now + (3600. - fmod (now, 3600.)); |
2014 | return now + (3600. - fmod (now, 3600.)); |
1575 | } |
2015 | } |
1576 | |
2016 | |
1577 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2017 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1578 | |
2018 | |
1579 | Example: Call a callback every hour, starting now: |
2019 | Example: Call a callback every hour, starting now: |
1580 | |
2020 | |
1581 | struct ev_periodic hourly_tick; |
2021 | ev_periodic hourly_tick; |
1582 | ev_periodic_init (&hourly_tick, clock_cb, |
2022 | ev_periodic_init (&hourly_tick, clock_cb, |
1583 | fmod (ev_now (loop), 3600.), 3600., 0); |
2023 | fmod (ev_now (loop), 3600.), 3600., 0); |
1584 | ev_periodic_start (loop, &hourly_tick); |
2024 | ev_periodic_start (loop, &hourly_tick); |
1585 | |
2025 | |
1586 | |
2026 | |
… | |
… | |
1625 | |
2065 | |
1626 | =back |
2066 | =back |
1627 | |
2067 | |
1628 | =head3 Examples |
2068 | =head3 Examples |
1629 | |
2069 | |
1630 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2070 | Example: Try to exit cleanly on SIGINT. |
1631 | |
2071 | |
1632 | static void |
2072 | static void |
1633 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2073 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1634 | { |
2074 | { |
1635 | ev_unloop (loop, EVUNLOOP_ALL); |
2075 | ev_unloop (loop, EVUNLOOP_ALL); |
1636 | } |
2076 | } |
1637 | |
2077 | |
1638 | struct ev_signal signal_watcher; |
2078 | ev_signal signal_watcher; |
1639 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2079 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1640 | ev_signal_start (loop, &sigint_cb); |
2080 | ev_signal_start (loop, &signal_watcher); |
1641 | |
2081 | |
1642 | |
2082 | |
1643 | =head2 C<ev_child> - watch out for process status changes |
2083 | =head2 C<ev_child> - watch out for process status changes |
1644 | |
2084 | |
1645 | Child watchers trigger when your process receives a SIGCHLD in response to |
2085 | Child watchers trigger when your process receives a SIGCHLD in response to |
1646 | some child status changes (most typically when a child of yours dies or |
2086 | some child status changes (most typically when a child of yours dies or |
1647 | exits). It is permissible to install a child watcher I<after> the child |
2087 | exits). It is permissible to install a child watcher I<after> the child |
1648 | has been forked (which implies it might have already exited), as long |
2088 | has been forked (which implies it might have already exited), as long |
1649 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2089 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1650 | forking and then immediately registering a watcher for the child is fine, |
2090 | forking and then immediately registering a watcher for the child is fine, |
1651 | but forking and registering a watcher a few event loop iterations later is |
2091 | but forking and registering a watcher a few event loop iterations later or |
1652 | not. |
2092 | in the next callback invocation is not. |
1653 | |
2093 | |
1654 | Only the default event loop is capable of handling signals, and therefore |
2094 | Only the default event loop is capable of handling signals, and therefore |
1655 | you can only register child watchers in the default event loop. |
2095 | you can only register child watchers in the default event loop. |
|
|
2096 | |
|
|
2097 | Due to some design glitches inside libev, child watchers will always be |
|
|
2098 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2099 | libev) |
1656 | |
2100 | |
1657 | =head3 Process Interaction |
2101 | =head3 Process Interaction |
1658 | |
2102 | |
1659 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2103 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1660 | initialised. This is necessary to guarantee proper behaviour even if |
2104 | initialised. This is necessary to guarantee proper behaviour even if |
… | |
… | |
1718 | its completion. |
2162 | its completion. |
1719 | |
2163 | |
1720 | ev_child cw; |
2164 | ev_child cw; |
1721 | |
2165 | |
1722 | static void |
2166 | static void |
1723 | child_cb (EV_P_ struct ev_child *w, int revents) |
2167 | child_cb (EV_P_ ev_child *w, int revents) |
1724 | { |
2168 | { |
1725 | ev_child_stop (EV_A_ w); |
2169 | ev_child_stop (EV_A_ w); |
1726 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2170 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1727 | } |
2171 | } |
1728 | |
2172 | |
… | |
… | |
1743 | |
2187 | |
1744 | |
2188 | |
1745 | =head2 C<ev_stat> - did the file attributes just change? |
2189 | =head2 C<ev_stat> - did the file attributes just change? |
1746 | |
2190 | |
1747 | This watches a file system path for attribute changes. That is, it calls |
2191 | This watches a file system path for attribute changes. That is, it calls |
1748 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2192 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1749 | compared to the last time, invoking the callback if it did. |
2193 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2194 | it did. |
1750 | |
2195 | |
1751 | The path does not need to exist: changing from "path exists" to "path does |
2196 | The path does not need to exist: changing from "path exists" to "path does |
1752 | not exist" is a status change like any other. The condition "path does |
2197 | not exist" is a status change like any other. The condition "path does not |
1753 | not exist" is signified by the C<st_nlink> field being zero (which is |
2198 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1754 | otherwise always forced to be at least one) and all the other fields of |
2199 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1755 | the stat buffer having unspecified contents. |
2200 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2201 | contents. |
1756 | |
2202 | |
1757 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2203 | The path I<must not> end in a slash or contain special components such as |
|
|
2204 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1758 | relative and your working directory changes, the behaviour is undefined. |
2205 | your working directory changes, then the behaviour is undefined. |
1759 | |
2206 | |
1760 | Since there is no standard kernel interface to do this, the portable |
2207 | Since there is no portable change notification interface available, the |
1761 | implementation simply calls C<stat (2)> regularly on the path to see if |
2208 | portable implementation simply calls C<stat(2)> regularly on the path |
1762 | it changed somehow. You can specify a recommended polling interval for |
2209 | to see if it changed somehow. You can specify a recommended polling |
1763 | this case. If you specify a polling interval of C<0> (highly recommended!) |
2210 | interval for this case. If you specify a polling interval of C<0> (highly |
1764 | then a I<suitable, unspecified default> value will be used (which |
2211 | recommended!) then a I<suitable, unspecified default> value will be used |
1765 | you can expect to be around five seconds, although this might change |
2212 | (which you can expect to be around five seconds, although this might |
1766 | dynamically). Libev will also impose a minimum interval which is currently |
2213 | change dynamically). Libev will also impose a minimum interval which is |
1767 | around C<0.1>, but thats usually overkill. |
2214 | currently around C<0.1>, but that's usually overkill. |
1768 | |
2215 | |
1769 | This watcher type is not meant for massive numbers of stat watchers, |
2216 | This watcher type is not meant for massive numbers of stat watchers, |
1770 | as even with OS-supported change notifications, this can be |
2217 | as even with OS-supported change notifications, this can be |
1771 | resource-intensive. |
2218 | resource-intensive. |
1772 | |
2219 | |
1773 | At the time of this writing, the only OS-specific interface implemented |
2220 | At the time of this writing, the only OS-specific interface implemented |
1774 | is the Linux inotify interface (implementing kqueue support is left as |
2221 | is the Linux inotify interface (implementing kqueue support is left as an |
1775 | an exercise for the reader. Note, however, that the author sees no way |
2222 | exercise for the reader. Note, however, that the author sees no way of |
1776 | of implementing C<ev_stat> semantics with kqueue). |
2223 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1777 | |
2224 | |
1778 | =head3 ABI Issues (Largefile Support) |
2225 | =head3 ABI Issues (Largefile Support) |
1779 | |
2226 | |
1780 | Libev by default (unless the user overrides this) uses the default |
2227 | Libev by default (unless the user overrides this) uses the default |
1781 | compilation environment, which means that on systems with large file |
2228 | compilation environment, which means that on systems with large file |
1782 | support disabled by default, you get the 32 bit version of the stat |
2229 | support disabled by default, you get the 32 bit version of the stat |
1783 | structure. When using the library from programs that change the ABI to |
2230 | structure. When using the library from programs that change the ABI to |
1784 | use 64 bit file offsets the programs will fail. In that case you have to |
2231 | use 64 bit file offsets the programs will fail. In that case you have to |
1785 | compile libev with the same flags to get binary compatibility. This is |
2232 | compile libev with the same flags to get binary compatibility. This is |
1786 | obviously the case with any flags that change the ABI, but the problem is |
2233 | obviously the case with any flags that change the ABI, but the problem is |
1787 | most noticeably disabled with ev_stat and large file support. |
2234 | most noticeably displayed with ev_stat and large file support. |
1788 | |
2235 | |
1789 | The solution for this is to lobby your distribution maker to make large |
2236 | The solution for this is to lobby your distribution maker to make large |
1790 | file interfaces available by default (as e.g. FreeBSD does) and not |
2237 | file interfaces available by default (as e.g. FreeBSD does) and not |
1791 | optional. Libev cannot simply switch on large file support because it has |
2238 | optional. Libev cannot simply switch on large file support because it has |
1792 | to exchange stat structures with application programs compiled using the |
2239 | to exchange stat structures with application programs compiled using the |
1793 | default compilation environment. |
2240 | default compilation environment. |
1794 | |
2241 | |
1795 | =head3 Inotify and Kqueue |
2242 | =head3 Inotify and Kqueue |
1796 | |
2243 | |
1797 | When C<inotify (7)> support has been compiled into libev (generally only |
2244 | When C<inotify (7)> support has been compiled into libev and present at |
1798 | available with Linux) and present at runtime, it will be used to speed up |
2245 | runtime, it will be used to speed up change detection where possible. The |
1799 | change detection where possible. The inotify descriptor will be created lazily |
2246 | inotify descriptor will be created lazily when the first C<ev_stat> |
1800 | when the first C<ev_stat> watcher is being started. |
2247 | watcher is being started. |
1801 | |
2248 | |
1802 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2249 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1803 | except that changes might be detected earlier, and in some cases, to avoid |
2250 | except that changes might be detected earlier, and in some cases, to avoid |
1804 | making regular C<stat> calls. Even in the presence of inotify support |
2251 | making regular C<stat> calls. Even in the presence of inotify support |
1805 | there are many cases where libev has to resort to regular C<stat> polling, |
2252 | there are many cases where libev has to resort to regular C<stat> polling, |
1806 | but as long as the path exists, libev usually gets away without polling. |
2253 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2254 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2255 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2256 | xfs are fully working) libev usually gets away without polling. |
1807 | |
2257 | |
1808 | There is no support for kqueue, as apparently it cannot be used to |
2258 | There is no support for kqueue, as apparently it cannot be used to |
1809 | implement this functionality, due to the requirement of having a file |
2259 | implement this functionality, due to the requirement of having a file |
1810 | descriptor open on the object at all times, and detecting renames, unlinks |
2260 | descriptor open on the object at all times, and detecting renames, unlinks |
1811 | etc. is difficult. |
2261 | etc. is difficult. |
1812 | |
2262 | |
|
|
2263 | =head3 C<stat ()> is a synchronous operation |
|
|
2264 | |
|
|
2265 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2266 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2267 | ()>, which is a synchronous operation. |
|
|
2268 | |
|
|
2269 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2270 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2271 | as the path data is usually in memory already (except when starting the |
|
|
2272 | watcher). |
|
|
2273 | |
|
|
2274 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2275 | time due to network issues, and even under good conditions, a stat call |
|
|
2276 | often takes multiple milliseconds. |
|
|
2277 | |
|
|
2278 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2279 | paths, although this is fully supported by libev. |
|
|
2280 | |
1813 | =head3 The special problem of stat time resolution |
2281 | =head3 The special problem of stat time resolution |
1814 | |
2282 | |
1815 | The C<stat ()> system call only supports full-second resolution portably, and |
2283 | The C<stat ()> system call only supports full-second resolution portably, |
1816 | even on systems where the resolution is higher, most file systems still |
2284 | and even on systems where the resolution is higher, most file systems |
1817 | only support whole seconds. |
2285 | still only support whole seconds. |
1818 | |
2286 | |
1819 | That means that, if the time is the only thing that changes, you can |
2287 | That means that, if the time is the only thing that changes, you can |
1820 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2288 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1821 | calls your callback, which does something. When there is another update |
2289 | calls your callback, which does something. When there is another update |
1822 | within the same second, C<ev_stat> will be unable to detect unless the |
2290 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
1965 | |
2433 | |
1966 | =head3 Watcher-Specific Functions and Data Members |
2434 | =head3 Watcher-Specific Functions and Data Members |
1967 | |
2435 | |
1968 | =over 4 |
2436 | =over 4 |
1969 | |
2437 | |
1970 | =item ev_idle_init (ev_signal *, callback) |
2438 | =item ev_idle_init (ev_idle *, callback) |
1971 | |
2439 | |
1972 | Initialises and configures the idle watcher - it has no parameters of any |
2440 | Initialises and configures the idle watcher - it has no parameters of any |
1973 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2441 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1974 | believe me. |
2442 | believe me. |
1975 | |
2443 | |
… | |
… | |
1979 | |
2447 | |
1980 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2448 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1981 | callback, free it. Also, use no error checking, as usual. |
2449 | callback, free it. Also, use no error checking, as usual. |
1982 | |
2450 | |
1983 | static void |
2451 | static void |
1984 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2452 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1985 | { |
2453 | { |
1986 | free (w); |
2454 | free (w); |
1987 | // now do something you wanted to do when the program has |
2455 | // now do something you wanted to do when the program has |
1988 | // no longer anything immediate to do. |
2456 | // no longer anything immediate to do. |
1989 | } |
2457 | } |
1990 | |
2458 | |
1991 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2459 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1992 | ev_idle_init (idle_watcher, idle_cb); |
2460 | ev_idle_init (idle_watcher, idle_cb); |
1993 | ev_idle_start (loop, idle_cb); |
2461 | ev_idle_start (loop, idle_watcher); |
1994 | |
2462 | |
1995 | |
2463 | |
1996 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2464 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1997 | |
2465 | |
1998 | Prepare and check watchers are usually (but not always) used in pairs: |
2466 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2077 | |
2545 | |
2078 | static ev_io iow [nfd]; |
2546 | static ev_io iow [nfd]; |
2079 | static ev_timer tw; |
2547 | static ev_timer tw; |
2080 | |
2548 | |
2081 | static void |
2549 | static void |
2082 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2550 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2083 | { |
2551 | { |
2084 | } |
2552 | } |
2085 | |
2553 | |
2086 | // create io watchers for each fd and a timer before blocking |
2554 | // create io watchers for each fd and a timer before blocking |
2087 | static void |
2555 | static void |
2088 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2556 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2089 | { |
2557 | { |
2090 | int timeout = 3600000; |
2558 | int timeout = 3600000; |
2091 | struct pollfd fds [nfd]; |
2559 | struct pollfd fds [nfd]; |
2092 | // actual code will need to loop here and realloc etc. |
2560 | // actual code will need to loop here and realloc etc. |
2093 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2561 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2094 | |
2562 | |
2095 | /* the callback is illegal, but won't be called as we stop during check */ |
2563 | /* the callback is illegal, but won't be called as we stop during check */ |
2096 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2564 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2097 | ev_timer_start (loop, &tw); |
2565 | ev_timer_start (loop, &tw); |
2098 | |
2566 | |
2099 | // create one ev_io per pollfd |
2567 | // create one ev_io per pollfd |
2100 | for (int i = 0; i < nfd; ++i) |
2568 | for (int i = 0; i < nfd; ++i) |
2101 | { |
2569 | { |
… | |
… | |
2108 | } |
2576 | } |
2109 | } |
2577 | } |
2110 | |
2578 | |
2111 | // stop all watchers after blocking |
2579 | // stop all watchers after blocking |
2112 | static void |
2580 | static void |
2113 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2581 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2114 | { |
2582 | { |
2115 | ev_timer_stop (loop, &tw); |
2583 | ev_timer_stop (loop, &tw); |
2116 | |
2584 | |
2117 | for (int i = 0; i < nfd; ++i) |
2585 | for (int i = 0; i < nfd; ++i) |
2118 | { |
2586 | { |
… | |
… | |
2214 | some fds have to be watched and handled very quickly (with low latency), |
2682 | some fds have to be watched and handled very quickly (with low latency), |
2215 | and even priorities and idle watchers might have too much overhead. In |
2683 | and even priorities and idle watchers might have too much overhead. In |
2216 | this case you would put all the high priority stuff in one loop and all |
2684 | this case you would put all the high priority stuff in one loop and all |
2217 | the rest in a second one, and embed the second one in the first. |
2685 | the rest in a second one, and embed the second one in the first. |
2218 | |
2686 | |
2219 | As long as the watcher is active, the callback will be invoked every time |
2687 | As long as the watcher is active, the callback will be invoked every |
2220 | there might be events pending in the embedded loop. The callback must then |
2688 | time there might be events pending in the embedded loop. The callback |
2221 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2689 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2222 | their callbacks (you could also start an idle watcher to give the embedded |
2690 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2223 | loop strictly lower priority for example). You can also set the callback |
2691 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2224 | to C<0>, in which case the embed watcher will automatically execute the |
2692 | to give the embedded loop strictly lower priority for example). |
2225 | embedded loop sweep. |
|
|
2226 | |
2693 | |
2227 | As long as the watcher is started it will automatically handle events. The |
2694 | You can also set the callback to C<0>, in which case the embed watcher |
2228 | callback will be invoked whenever some events have been handled. You can |
2695 | will automatically execute the embedded loop sweep whenever necessary. |
2229 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2230 | interested in that. |
|
|
2231 | |
2696 | |
2232 | Also, there have not currently been made special provisions for forking: |
2697 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2233 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2698 | is active, i.e., the embedded loop will automatically be forked when the |
2234 | but you will also have to stop and restart any C<ev_embed> watchers |
2699 | embedding loop forks. In other cases, the user is responsible for calling |
2235 | yourself - but you can use a fork watcher to handle this automatically, |
2700 | C<ev_loop_fork> on the embedded loop. |
2236 | and future versions of libev might do just that. |
|
|
2237 | |
2701 | |
2238 | Unfortunately, not all backends are embeddable: only the ones returned by |
2702 | Unfortunately, not all backends are embeddable: only the ones returned by |
2239 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2703 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2240 | portable one. |
2704 | portable one. |
2241 | |
2705 | |
2242 | So when you want to use this feature you will always have to be prepared |
2706 | So when you want to use this feature you will always have to be prepared |
2243 | that you cannot get an embeddable loop. The recommended way to get around |
2707 | that you cannot get an embeddable loop. The recommended way to get around |
2244 | this is to have a separate variables for your embeddable loop, try to |
2708 | this is to have a separate variables for your embeddable loop, try to |
2245 | create it, and if that fails, use the normal loop for everything. |
2709 | create it, and if that fails, use the normal loop for everything. |
|
|
2710 | |
|
|
2711 | =head3 C<ev_embed> and fork |
|
|
2712 | |
|
|
2713 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2714 | automatically be applied to the embedded loop as well, so no special |
|
|
2715 | fork handling is required in that case. When the watcher is not running, |
|
|
2716 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2717 | as applicable. |
2246 | |
2718 | |
2247 | =head3 Watcher-Specific Functions and Data Members |
2719 | =head3 Watcher-Specific Functions and Data Members |
2248 | |
2720 | |
2249 | =over 4 |
2721 | =over 4 |
2250 | |
2722 | |
… | |
… | |
2278 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2750 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2279 | used). |
2751 | used). |
2280 | |
2752 | |
2281 | struct ev_loop *loop_hi = ev_default_init (0); |
2753 | struct ev_loop *loop_hi = ev_default_init (0); |
2282 | struct ev_loop *loop_lo = 0; |
2754 | struct ev_loop *loop_lo = 0; |
2283 | struct ev_embed embed; |
2755 | ev_embed embed; |
2284 | |
2756 | |
2285 | // see if there is a chance of getting one that works |
2757 | // see if there is a chance of getting one that works |
2286 | // (remember that a flags value of 0 means autodetection) |
2758 | // (remember that a flags value of 0 means autodetection) |
2287 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2759 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2288 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2760 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2302 | kqueue implementation). Store the kqueue/socket-only event loop in |
2774 | kqueue implementation). Store the kqueue/socket-only event loop in |
2303 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2775 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2304 | |
2776 | |
2305 | struct ev_loop *loop = ev_default_init (0); |
2777 | struct ev_loop *loop = ev_default_init (0); |
2306 | struct ev_loop *loop_socket = 0; |
2778 | struct ev_loop *loop_socket = 0; |
2307 | struct ev_embed embed; |
2779 | ev_embed embed; |
2308 | |
2780 | |
2309 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2781 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2310 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2782 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2311 | { |
2783 | { |
2312 | ev_embed_init (&embed, 0, loop_socket); |
2784 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2327 | event loop blocks next and before C<ev_check> watchers are being called, |
2799 | event loop blocks next and before C<ev_check> watchers are being called, |
2328 | and only in the child after the fork. If whoever good citizen calling |
2800 | and only in the child after the fork. If whoever good citizen calling |
2329 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2801 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2330 | handlers will be invoked, too, of course. |
2802 | handlers will be invoked, too, of course. |
2331 | |
2803 | |
|
|
2804 | =head3 The special problem of life after fork - how is it possible? |
|
|
2805 | |
|
|
2806 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2807 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2808 | sequence should be handled by libev without any problems. |
|
|
2809 | |
|
|
2810 | This changes when the application actually wants to do event handling |
|
|
2811 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2812 | fork. |
|
|
2813 | |
|
|
2814 | The default mode of operation (for libev, with application help to detect |
|
|
2815 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2816 | when I<either> the parent I<or> the child process continues. |
|
|
2817 | |
|
|
2818 | When both processes want to continue using libev, then this is usually the |
|
|
2819 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2820 | supposed to continue with all watchers in place as before, while the other |
|
|
2821 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2822 | |
|
|
2823 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2824 | simply create a new event loop, which of course will be "empty", and |
|
|
2825 | use that for new watchers. This has the advantage of not touching more |
|
|
2826 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2827 | disadvantage of having to use multiple event loops (which do not support |
|
|
2828 | signal watchers). |
|
|
2829 | |
|
|
2830 | When this is not possible, or you want to use the default loop for |
|
|
2831 | other reasons, then in the process that wants to start "fresh", call |
|
|
2832 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2833 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2834 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2835 | also that in that case, you have to re-register any signal watchers. |
|
|
2836 | |
2332 | =head3 Watcher-Specific Functions and Data Members |
2837 | =head3 Watcher-Specific Functions and Data Members |
2333 | |
2838 | |
2334 | =over 4 |
2839 | =over 4 |
2335 | |
2840 | |
2336 | =item ev_fork_init (ev_signal *, callback) |
2841 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2376 | =over 4 |
2881 | =over 4 |
2377 | |
2882 | |
2378 | =item queueing from a signal handler context |
2883 | =item queueing from a signal handler context |
2379 | |
2884 | |
2380 | To implement race-free queueing, you simply add to the queue in the signal |
2885 | To implement race-free queueing, you simply add to the queue in the signal |
2381 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
2886 | handler but you block the signal handler in the watcher callback. Here is |
2382 | some fictitious SIGUSR1 handler: |
2887 | an example that does that for some fictitious SIGUSR1 handler: |
2383 | |
2888 | |
2384 | static ev_async mysig; |
2889 | static ev_async mysig; |
2385 | |
2890 | |
2386 | static void |
2891 | static void |
2387 | sigusr1_handler (void) |
2892 | sigusr1_handler (void) |
… | |
… | |
2453 | =over 4 |
2958 | =over 4 |
2454 | |
2959 | |
2455 | =item ev_async_init (ev_async *, callback) |
2960 | =item ev_async_init (ev_async *, callback) |
2456 | |
2961 | |
2457 | Initialises and configures the async watcher - it has no parameters of any |
2962 | Initialises and configures the async watcher - it has no parameters of any |
2458 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2963 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2459 | trust me. |
2964 | trust me. |
2460 | |
2965 | |
2461 | =item ev_async_send (loop, ev_async *) |
2966 | =item ev_async_send (loop, ev_async *) |
2462 | |
2967 | |
2463 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2968 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2464 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2969 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2465 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2970 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2466 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2971 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2467 | section below on what exactly this means). |
2972 | section below on what exactly this means). |
2468 | |
2973 | |
|
|
2974 | Note that, as with other watchers in libev, multiple events might get |
|
|
2975 | compressed into a single callback invocation (another way to look at this |
|
|
2976 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2977 | reset when the event loop detects that). |
|
|
2978 | |
2469 | This call incurs the overhead of a system call only once per loop iteration, |
2979 | This call incurs the overhead of a system call only once per event loop |
2470 | so while the overhead might be noticeable, it doesn't apply to repeated |
2980 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2471 | calls to C<ev_async_send>. |
2981 | repeated calls to C<ev_async_send> for the same event loop. |
2472 | |
2982 | |
2473 | =item bool = ev_async_pending (ev_async *) |
2983 | =item bool = ev_async_pending (ev_async *) |
2474 | |
2984 | |
2475 | Returns a non-zero value when C<ev_async_send> has been called on the |
2985 | Returns a non-zero value when C<ev_async_send> has been called on the |
2476 | watcher but the event has not yet been processed (or even noted) by the |
2986 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2479 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2989 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2480 | the loop iterates next and checks for the watcher to have become active, |
2990 | the loop iterates next and checks for the watcher to have become active, |
2481 | it will reset the flag again. C<ev_async_pending> can be used to very |
2991 | it will reset the flag again. C<ev_async_pending> can be used to very |
2482 | quickly check whether invoking the loop might be a good idea. |
2992 | quickly check whether invoking the loop might be a good idea. |
2483 | |
2993 | |
2484 | Not that this does I<not> check whether the watcher itself is pending, only |
2994 | Not that this does I<not> check whether the watcher itself is pending, |
2485 | whether it has been requested to make this watcher pending. |
2995 | only whether it has been requested to make this watcher pending: there |
|
|
2996 | is a time window between the event loop checking and resetting the async |
|
|
2997 | notification, and the callback being invoked. |
2486 | |
2998 | |
2487 | =back |
2999 | =back |
2488 | |
3000 | |
2489 | |
3001 | |
2490 | =head1 OTHER FUNCTIONS |
3002 | =head1 OTHER FUNCTIONS |
… | |
… | |
2494 | =over 4 |
3006 | =over 4 |
2495 | |
3007 | |
2496 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3008 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2497 | |
3009 | |
2498 | This function combines a simple timer and an I/O watcher, calls your |
3010 | This function combines a simple timer and an I/O watcher, calls your |
2499 | callback on whichever event happens first and automatically stop both |
3011 | callback on whichever event happens first and automatically stops both |
2500 | watchers. This is useful if you want to wait for a single event on an fd |
3012 | watchers. This is useful if you want to wait for a single event on an fd |
2501 | or timeout without having to allocate/configure/start/stop/free one or |
3013 | or timeout without having to allocate/configure/start/stop/free one or |
2502 | more watchers yourself. |
3014 | more watchers yourself. |
2503 | |
3015 | |
2504 | If C<fd> is less than 0, then no I/O watcher will be started and events |
3016 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2505 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
3017 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2506 | C<events> set will be created and started. |
3018 | the given C<fd> and C<events> set will be created and started. |
2507 | |
3019 | |
2508 | If C<timeout> is less than 0, then no timeout watcher will be |
3020 | If C<timeout> is less than 0, then no timeout watcher will be |
2509 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3021 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2510 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
3022 | repeat = 0) will be started. C<0> is a valid timeout. |
2511 | dubious value. |
|
|
2512 | |
3023 | |
2513 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3024 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2514 | passed an C<revents> set like normal event callbacks (a combination of |
3025 | passed an C<revents> set like normal event callbacks (a combination of |
2515 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3026 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2516 | value passed to C<ev_once>: |
3027 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
3028 | a timeout and an io event at the same time - you probably should give io |
|
|
3029 | events precedence. |
|
|
3030 | |
|
|
3031 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2517 | |
3032 | |
2518 | static void stdin_ready (int revents, void *arg) |
3033 | static void stdin_ready (int revents, void *arg) |
2519 | { |
3034 | { |
|
|
3035 | if (revents & EV_READ) |
|
|
3036 | /* stdin might have data for us, joy! */; |
2520 | if (revents & EV_TIMEOUT) |
3037 | else if (revents & EV_TIMEOUT) |
2521 | /* doh, nothing entered */; |
3038 | /* doh, nothing entered */; |
2522 | else if (revents & EV_READ) |
|
|
2523 | /* stdin might have data for us, joy! */; |
|
|
2524 | } |
3039 | } |
2525 | |
3040 | |
2526 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3041 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2527 | |
3042 | |
2528 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
3043 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
2529 | |
3044 | |
2530 | Feeds the given event set into the event loop, as if the specified event |
3045 | Feeds the given event set into the event loop, as if the specified event |
2531 | had happened for the specified watcher (which must be a pointer to an |
3046 | had happened for the specified watcher (which must be a pointer to an |
2532 | initialised but not necessarily started event watcher). |
3047 | initialised but not necessarily started event watcher). |
2533 | |
3048 | |
2534 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3049 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
2535 | |
3050 | |
2536 | Feed an event on the given fd, as if a file descriptor backend detected |
3051 | Feed an event on the given fd, as if a file descriptor backend detected |
2537 | the given events it. |
3052 | the given events it. |
2538 | |
3053 | |
2539 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3054 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
2540 | |
3055 | |
2541 | Feed an event as if the given signal occurred (C<loop> must be the default |
3056 | Feed an event as if the given signal occurred (C<loop> must be the default |
2542 | loop!). |
3057 | loop!). |
2543 | |
3058 | |
2544 | =back |
3059 | =back |
… | |
… | |
2665 | } |
3180 | } |
2666 | |
3181 | |
2667 | myclass obj; |
3182 | myclass obj; |
2668 | ev::io iow; |
3183 | ev::io iow; |
2669 | iow.set <myclass, &myclass::io_cb> (&obj); |
3184 | iow.set <myclass, &myclass::io_cb> (&obj); |
|
|
3185 | |
|
|
3186 | =item w->set (object *) |
|
|
3187 | |
|
|
3188 | This is an B<experimental> feature that might go away in a future version. |
|
|
3189 | |
|
|
3190 | This is a variation of a method callback - leaving out the method to call |
|
|
3191 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3192 | functor objects without having to manually specify the C<operator ()> all |
|
|
3193 | the time. Incidentally, you can then also leave out the template argument |
|
|
3194 | list. |
|
|
3195 | |
|
|
3196 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3197 | int revents)>. |
|
|
3198 | |
|
|
3199 | See the method-C<set> above for more details. |
|
|
3200 | |
|
|
3201 | Example: use a functor object as callback. |
|
|
3202 | |
|
|
3203 | struct myfunctor |
|
|
3204 | { |
|
|
3205 | void operator() (ev::io &w, int revents) |
|
|
3206 | { |
|
|
3207 | ... |
|
|
3208 | } |
|
|
3209 | } |
|
|
3210 | |
|
|
3211 | myfunctor f; |
|
|
3212 | |
|
|
3213 | ev::io w; |
|
|
3214 | w.set (&f); |
2670 | |
3215 | |
2671 | =item w->set<function> (void *data = 0) |
3216 | =item w->set<function> (void *data = 0) |
2672 | |
3217 | |
2673 | Also sets a callback, but uses a static method or plain function as |
3218 | Also sets a callback, but uses a static method or plain function as |
2674 | callback. The optional C<data> argument will be stored in the watcher's |
3219 | callback. The optional C<data> argument will be stored in the watcher's |
… | |
… | |
2761 | L<http://software.schmorp.de/pkg/EV>. |
3306 | L<http://software.schmorp.de/pkg/EV>. |
2762 | |
3307 | |
2763 | =item Python |
3308 | =item Python |
2764 | |
3309 | |
2765 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3310 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2766 | seems to be quite complete and well-documented. Note, however, that the |
3311 | seems to be quite complete and well-documented. |
2767 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2768 | for everybody else, and therefore, should never be applied in an installed |
|
|
2769 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2770 | libev). |
|
|
2771 | |
3312 | |
2772 | =item Ruby |
3313 | =item Ruby |
2773 | |
3314 | |
2774 | Tony Arcieri has written a ruby extension that offers access to a subset |
3315 | Tony Arcieri has written a ruby extension that offers access to a subset |
2775 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3316 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2776 | more on top of it. It can be found via gem servers. Its homepage is at |
3317 | more on top of it. It can be found via gem servers. Its homepage is at |
2777 | L<http://rev.rubyforge.org/>. |
3318 | L<http://rev.rubyforge.org/>. |
2778 | |
3319 | |
|
|
3320 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3321 | makes rev work even on mingw. |
|
|
3322 | |
|
|
3323 | =item Haskell |
|
|
3324 | |
|
|
3325 | A haskell binding to libev is available at |
|
|
3326 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3327 | |
2779 | =item D |
3328 | =item D |
2780 | |
3329 | |
2781 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3330 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2782 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3331 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3332 | |
|
|
3333 | =item Ocaml |
|
|
3334 | |
|
|
3335 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3336 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
2783 | |
3337 | |
2784 | =back |
3338 | =back |
2785 | |
3339 | |
2786 | |
3340 | |
2787 | =head1 MACRO MAGIC |
3341 | =head1 MACRO MAGIC |
… | |
… | |
2888 | |
3442 | |
2889 | #define EV_STANDALONE 1 |
3443 | #define EV_STANDALONE 1 |
2890 | #include "ev.h" |
3444 | #include "ev.h" |
2891 | |
3445 | |
2892 | Both header files and implementation files can be compiled with a C++ |
3446 | Both header files and implementation files can be compiled with a C++ |
2893 | compiler (at least, thats a stated goal, and breakage will be treated |
3447 | compiler (at least, that's a stated goal, and breakage will be treated |
2894 | as a bug). |
3448 | as a bug). |
2895 | |
3449 | |
2896 | You need the following files in your source tree, or in a directory |
3450 | You need the following files in your source tree, or in a directory |
2897 | in your include path (e.g. in libev/ when using -Ilibev): |
3451 | in your include path (e.g. in libev/ when using -Ilibev): |
2898 | |
3452 | |
… | |
… | |
2954 | keeps libev from including F<config.h>, and it also defines dummy |
3508 | keeps libev from including F<config.h>, and it also defines dummy |
2955 | implementations for some libevent functions (such as logging, which is not |
3509 | implementations for some libevent functions (such as logging, which is not |
2956 | supported). It will also not define any of the structs usually found in |
3510 | supported). It will also not define any of the structs usually found in |
2957 | F<event.h> that are not directly supported by the libev core alone. |
3511 | F<event.h> that are not directly supported by the libev core alone. |
2958 | |
3512 | |
|
|
3513 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3514 | configuration, but has to be more conservative. |
|
|
3515 | |
2959 | =item EV_USE_MONOTONIC |
3516 | =item EV_USE_MONOTONIC |
2960 | |
3517 | |
2961 | If defined to be C<1>, libev will try to detect the availability of the |
3518 | If defined to be C<1>, libev will try to detect the availability of the |
2962 | monotonic clock option at both compile time and runtime. Otherwise no use |
3519 | monotonic clock option at both compile time and runtime. Otherwise no |
2963 | of the monotonic clock option will be attempted. If you enable this, you |
3520 | use of the monotonic clock option will be attempted. If you enable this, |
2964 | usually have to link against librt or something similar. Enabling it when |
3521 | you usually have to link against librt or something similar. Enabling it |
2965 | the functionality isn't available is safe, though, although you have |
3522 | when the functionality isn't available is safe, though, although you have |
2966 | to make sure you link against any libraries where the C<clock_gettime> |
3523 | to make sure you link against any libraries where the C<clock_gettime> |
2967 | function is hiding in (often F<-lrt>). |
3524 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2968 | |
3525 | |
2969 | =item EV_USE_REALTIME |
3526 | =item EV_USE_REALTIME |
2970 | |
3527 | |
2971 | If defined to be C<1>, libev will try to detect the availability of the |
3528 | If defined to be C<1>, libev will try to detect the availability of the |
2972 | real-time clock option at compile time (and assume its availability at |
3529 | real-time clock option at compile time (and assume its availability |
2973 | runtime if successful). Otherwise no use of the real-time clock option will |
3530 | at runtime if successful). Otherwise no use of the real-time clock |
2974 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3531 | option will be attempted. This effectively replaces C<gettimeofday> |
2975 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3532 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2976 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3533 | correctness. See the note about libraries in the description of |
|
|
3534 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3535 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3536 | |
|
|
3537 | =item EV_USE_CLOCK_SYSCALL |
|
|
3538 | |
|
|
3539 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3540 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3541 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3542 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3543 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3544 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3545 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3546 | higher, as it simplifies linking (no need for C<-lrt>). |
2977 | |
3547 | |
2978 | =item EV_USE_NANOSLEEP |
3548 | =item EV_USE_NANOSLEEP |
2979 | |
3549 | |
2980 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3550 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2981 | and will use it for delays. Otherwise it will use C<select ()>. |
3551 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
2997 | |
3567 | |
2998 | =item EV_SELECT_USE_FD_SET |
3568 | =item EV_SELECT_USE_FD_SET |
2999 | |
3569 | |
3000 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3570 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3001 | structure. This is useful if libev doesn't compile due to a missing |
3571 | structure. This is useful if libev doesn't compile due to a missing |
3002 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3572 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3003 | exotic systems. This usually limits the range of file descriptors to some |
3573 | on exotic systems. This usually limits the range of file descriptors to |
3004 | low limit such as 1024 or might have other limitations (winsocket only |
3574 | some low limit such as 1024 or might have other limitations (winsocket |
3005 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3575 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3006 | influence the size of the C<fd_set> used. |
3576 | configures the maximum size of the C<fd_set>. |
3007 | |
3577 | |
3008 | =item EV_SELECT_IS_WINSOCKET |
3578 | =item EV_SELECT_IS_WINSOCKET |
3009 | |
3579 | |
3010 | When defined to C<1>, the select backend will assume that |
3580 | When defined to C<1>, the select backend will assume that |
3011 | select/socket/connect etc. don't understand file descriptors but |
3581 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3161 | defined to be C<0>, then they are not. |
3731 | defined to be C<0>, then they are not. |
3162 | |
3732 | |
3163 | =item EV_MINIMAL |
3733 | =item EV_MINIMAL |
3164 | |
3734 | |
3165 | If you need to shave off some kilobytes of code at the expense of some |
3735 | If you need to shave off some kilobytes of code at the expense of some |
3166 | speed, define this symbol to C<1>. Currently this is used to override some |
3736 | speed (but with the full API), define this symbol to C<1>. Currently this |
3167 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3737 | is used to override some inlining decisions, saves roughly 30% code size |
3168 | much smaller 2-heap for timer management over the default 4-heap. |
3738 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3739 | the default 4-heap. |
|
|
3740 | |
|
|
3741 | You can save even more by disabling watcher types you do not need |
|
|
3742 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3743 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3744 | |
|
|
3745 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3746 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3747 | of the API are still available, and do not complain if this subset changes |
|
|
3748 | over time. |
3169 | |
3749 | |
3170 | =item EV_PID_HASHSIZE |
3750 | =item EV_PID_HASHSIZE |
3171 | |
3751 | |
3172 | C<ev_child> watchers use a small hash table to distribute workload by |
3752 | C<ev_child> watchers use a small hash table to distribute workload by |
3173 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3753 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3240 | and the way callbacks are invoked and set. Must expand to a struct member |
3820 | and the way callbacks are invoked and set. Must expand to a struct member |
3241 | definition and a statement, respectively. See the F<ev.h> header file for |
3821 | definition and a statement, respectively. See the F<ev.h> header file for |
3242 | their default definitions. One possible use for overriding these is to |
3822 | their default definitions. One possible use for overriding these is to |
3243 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3823 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3244 | method calls instead of plain function calls in C++. |
3824 | method calls instead of plain function calls in C++. |
|
|
3825 | |
|
|
3826 | =back |
3245 | |
3827 | |
3246 | =head2 EXPORTED API SYMBOLS |
3828 | =head2 EXPORTED API SYMBOLS |
3247 | |
3829 | |
3248 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3830 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3249 | exported symbols, you can use the provided F<Symbol.*> files which list |
3831 | exported symbols, you can use the provided F<Symbol.*> files which list |
… | |
… | |
3296 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3878 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3297 | |
3879 | |
3298 | #include "ev_cpp.h" |
3880 | #include "ev_cpp.h" |
3299 | #include "ev.c" |
3881 | #include "ev.c" |
3300 | |
3882 | |
|
|
3883 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3301 | |
3884 | |
3302 | =head1 THREADS AND COROUTINES |
3885 | =head2 THREADS AND COROUTINES |
3303 | |
3886 | |
3304 | =head2 THREADS |
3887 | =head3 THREADS |
3305 | |
3888 | |
3306 | Libev itself is thread-safe (unless the opposite is specifically |
3889 | All libev functions are reentrant and thread-safe unless explicitly |
3307 | documented for a function), but it uses no locking itself. This means that |
3890 | documented otherwise, but libev implements no locking itself. This means |
3308 | you can use as many loops as you want in parallel, as long as only one |
3891 | that you can use as many loops as you want in parallel, as long as there |
3309 | thread ever calls into one libev function with the same loop parameter: |
3892 | are no concurrent calls into any libev function with the same loop |
|
|
3893 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
3310 | libev guarantees that different event loops share no data structures that |
3894 | of course): libev guarantees that different event loops share no data |
3311 | need locking. |
3895 | structures that need any locking. |
3312 | |
3896 | |
3313 | Or to put it differently: calls with different loop parameters can be done |
3897 | Or to put it differently: calls with different loop parameters can be done |
3314 | concurrently from multiple threads, calls with the same loop parameter |
3898 | concurrently from multiple threads, calls with the same loop parameter |
3315 | must be done serially (but can be done from different threads, as long as |
3899 | must be done serially (but can be done from different threads, as long as |
3316 | only one thread ever is inside a call at any point in time, e.g. by using |
3900 | only one thread ever is inside a call at any point in time, e.g. by using |
3317 | a mutex per loop). |
3901 | a mutex per loop). |
3318 | |
3902 | |
3319 | Specifically to support threads (and signal handlers), libev implements |
3903 | Specifically to support threads (and signal handlers), libev implements |
3320 | so-called C<ev_async> watchers, which allow some limited form of |
3904 | so-called C<ev_async> watchers, which allow some limited form of |
3321 | concurrency on the same event loop. |
3905 | concurrency on the same event loop, namely waking it up "from the |
|
|
3906 | outside". |
3322 | |
3907 | |
3323 | If you want to know which design (one loop, locking, or multiple loops |
3908 | If you want to know which design (one loop, locking, or multiple loops |
3324 | without or something else still) is best for your problem, then I cannot |
3909 | without or something else still) is best for your problem, then I cannot |
3325 | help you. I can give some generic advice however: |
3910 | help you, but here is some generic advice: |
3326 | |
3911 | |
3327 | =over 4 |
3912 | =over 4 |
3328 | |
3913 | |
3329 | =item * most applications have a main thread: use the default libev loop |
3914 | =item * most applications have a main thread: use the default libev loop |
3330 | in that thread, or create a separate thread running only the default loop. |
3915 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3354 | default loop and triggering an C<ev_async> watcher from the default loop |
3939 | default loop and triggering an C<ev_async> watcher from the default loop |
3355 | watcher callback into the event loop interested in the signal. |
3940 | watcher callback into the event loop interested in the signal. |
3356 | |
3941 | |
3357 | =back |
3942 | =back |
3358 | |
3943 | |
|
|
3944 | =head4 THREAD LOCKING EXAMPLE |
|
|
3945 | |
|
|
3946 | Here is a fictitious example of how to run an event loop in a different |
|
|
3947 | thread than where callbacks are being invoked and watchers are |
|
|
3948 | created/added/removed. |
|
|
3949 | |
|
|
3950 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3951 | which uses exactly this technique (which is suited for many high-level |
|
|
3952 | languages). |
|
|
3953 | |
|
|
3954 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3955 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3956 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3957 | |
|
|
3958 | First, you need to associate some data with the event loop: |
|
|
3959 | |
|
|
3960 | typedef struct { |
|
|
3961 | mutex_t lock; /* global loop lock */ |
|
|
3962 | ev_async async_w; |
|
|
3963 | thread_t tid; |
|
|
3964 | cond_t invoke_cv; |
|
|
3965 | } userdata; |
|
|
3966 | |
|
|
3967 | void prepare_loop (EV_P) |
|
|
3968 | { |
|
|
3969 | // for simplicity, we use a static userdata struct. |
|
|
3970 | static userdata u; |
|
|
3971 | |
|
|
3972 | ev_async_init (&u->async_w, async_cb); |
|
|
3973 | ev_async_start (EV_A_ &u->async_w); |
|
|
3974 | |
|
|
3975 | pthread_mutex_init (&u->lock, 0); |
|
|
3976 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3977 | |
|
|
3978 | // now associate this with the loop |
|
|
3979 | ev_set_userdata (EV_A_ u); |
|
|
3980 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3981 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3982 | |
|
|
3983 | // then create the thread running ev_loop |
|
|
3984 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3985 | } |
|
|
3986 | |
|
|
3987 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3988 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3989 | that might have been added: |
|
|
3990 | |
|
|
3991 | static void |
|
|
3992 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3993 | { |
|
|
3994 | // just used for the side effects |
|
|
3995 | } |
|
|
3996 | |
|
|
3997 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3998 | protecting the loop data, respectively. |
|
|
3999 | |
|
|
4000 | static void |
|
|
4001 | l_release (EV_P) |
|
|
4002 | { |
|
|
4003 | userdata *u = ev_userdata (EV_A); |
|
|
4004 | pthread_mutex_unlock (&u->lock); |
|
|
4005 | } |
|
|
4006 | |
|
|
4007 | static void |
|
|
4008 | l_acquire (EV_P) |
|
|
4009 | { |
|
|
4010 | userdata *u = ev_userdata (EV_A); |
|
|
4011 | pthread_mutex_lock (&u->lock); |
|
|
4012 | } |
|
|
4013 | |
|
|
4014 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4015 | into C<ev_loop>: |
|
|
4016 | |
|
|
4017 | void * |
|
|
4018 | l_run (void *thr_arg) |
|
|
4019 | { |
|
|
4020 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4021 | |
|
|
4022 | l_acquire (EV_A); |
|
|
4023 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4024 | ev_loop (EV_A_ 0); |
|
|
4025 | l_release (EV_A); |
|
|
4026 | |
|
|
4027 | return 0; |
|
|
4028 | } |
|
|
4029 | |
|
|
4030 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4031 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4032 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4033 | have been called: |
|
|
4034 | |
|
|
4035 | static void |
|
|
4036 | l_invoke (EV_P) |
|
|
4037 | { |
|
|
4038 | userdata *u = ev_userdata (EV_A); |
|
|
4039 | |
|
|
4040 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4041 | |
|
|
4042 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4043 | } |
|
|
4044 | |
|
|
4045 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4046 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4047 | thread to continue: |
|
|
4048 | |
|
|
4049 | static void |
|
|
4050 | real_invoke_pending (EV_P) |
|
|
4051 | { |
|
|
4052 | userdata *u = ev_userdata (EV_A); |
|
|
4053 | |
|
|
4054 | pthread_mutex_lock (&u->lock); |
|
|
4055 | ev_invoke_pending (EV_A); |
|
|
4056 | pthread_cond_signal (&u->invoke_cv); |
|
|
4057 | pthread_mutex_unlock (&u->lock); |
|
|
4058 | } |
|
|
4059 | |
|
|
4060 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4061 | event loop, you will now have to lock: |
|
|
4062 | |
|
|
4063 | ev_timer timeout_watcher; |
|
|
4064 | userdata *u = ev_userdata (EV_A); |
|
|
4065 | |
|
|
4066 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4067 | |
|
|
4068 | pthread_mutex_lock (&u->lock); |
|
|
4069 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4070 | ev_async_send (EV_A_ &u->async_w); |
|
|
4071 | pthread_mutex_unlock (&u->lock); |
|
|
4072 | |
|
|
4073 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4074 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4075 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4076 | watchers in the next event loop iteration. |
|
|
4077 | |
3359 | =head2 COROUTINES |
4078 | =head3 COROUTINES |
3360 | |
4079 | |
3361 | Libev is much more accommodating to coroutines ("cooperative threads"): |
4080 | Libev is very accommodating to coroutines ("cooperative threads"): |
3362 | libev fully supports nesting calls to it's functions from different |
4081 | libev fully supports nesting calls to its functions from different |
3363 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4082 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3364 | different coroutines and switch freely between both coroutines running the |
4083 | different coroutines, and switch freely between both coroutines running |
3365 | loop, as long as you don't confuse yourself). The only exception is that |
4084 | the loop, as long as you don't confuse yourself). The only exception is |
3366 | you must not do this from C<ev_periodic> reschedule callbacks. |
4085 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3367 | |
4086 | |
3368 | Care has been taken to ensure that libev does not keep local state inside |
4087 | Care has been taken to ensure that libev does not keep local state inside |
3369 | C<ev_loop>, and other calls do not usually allow coroutine switches. |
4088 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
|
|
4089 | they do not call any callbacks. |
3370 | |
4090 | |
|
|
4091 | =head2 COMPILER WARNINGS |
3371 | |
4092 | |
3372 | =head1 COMPLEXITIES |
4093 | Depending on your compiler and compiler settings, you might get no or a |
|
|
4094 | lot of warnings when compiling libev code. Some people are apparently |
|
|
4095 | scared by this. |
3373 | |
4096 | |
3374 | In this section the complexities of (many of) the algorithms used inside |
4097 | However, these are unavoidable for many reasons. For one, each compiler |
3375 | libev will be explained. For complexity discussions about backends see the |
4098 | has different warnings, and each user has different tastes regarding |
3376 | documentation for C<ev_default_init>. |
4099 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
4100 | targeting a specific compiler and compiler-version. |
3377 | |
4101 | |
3378 | All of the following are about amortised time: If an array needs to be |
4102 | Another reason is that some compiler warnings require elaborate |
3379 | extended, libev needs to realloc and move the whole array, but this |
4103 | workarounds, or other changes to the code that make it less clear and less |
3380 | happens asymptotically never with higher number of elements, so O(1) might |
4104 | maintainable. |
3381 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3382 | it is much faster and asymptotically approaches constant time. |
|
|
3383 | |
4105 | |
3384 | =over 4 |
4106 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
4107 | wrong (because they don't actually warn about the condition their message |
|
|
4108 | seems to warn about). For example, certain older gcc versions had some |
|
|
4109 | warnings that resulted an extreme number of false positives. These have |
|
|
4110 | been fixed, but some people still insist on making code warn-free with |
|
|
4111 | such buggy versions. |
3385 | |
4112 | |
3386 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
4113 | While libev is written to generate as few warnings as possible, |
|
|
4114 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
4115 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
4116 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
4117 | warnings, not errors, or proof of bugs. |
3387 | |
4118 | |
3388 | This means that, when you have a watcher that triggers in one hour and |
|
|
3389 | there are 100 watchers that would trigger before that then inserting will |
|
|
3390 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3391 | |
4119 | |
3392 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
4120 | =head2 VALGRIND |
3393 | |
4121 | |
3394 | That means that changing a timer costs less than removing/adding them |
4122 | Valgrind has a special section here because it is a popular tool that is |
3395 | as only the relative motion in the event queue has to be paid for. |
4123 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3396 | |
4124 | |
3397 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
4125 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
4126 | in libev, then check twice: If valgrind reports something like: |
3398 | |
4127 | |
3399 | These just add the watcher into an array or at the head of a list. |
4128 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
4129 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
4130 | ==2274== still reachable: 256 bytes in 1 blocks. |
3400 | |
4131 | |
3401 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
4132 | Then there is no memory leak, just as memory accounted to global variables |
|
|
4133 | is not a memleak - the memory is still being referenced, and didn't leak. |
3402 | |
4134 | |
3403 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
4135 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
4136 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
4137 | although an acceptable workaround has been found here), or it might be |
|
|
4138 | confused. |
3404 | |
4139 | |
3405 | These watchers are stored in lists then need to be walked to find the |
4140 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3406 | correct watcher to remove. The lists are usually short (you don't usually |
4141 | make it into some kind of religion. |
3407 | have many watchers waiting for the same fd or signal). |
|
|
3408 | |
4142 | |
3409 | =item Finding the next timer in each loop iteration: O(1) |
4143 | If you are unsure about something, feel free to contact the mailing list |
|
|
4144 | with the full valgrind report and an explanation on why you think this |
|
|
4145 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
4146 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
4147 | of learning how to interpret valgrind properly. |
3410 | |
4148 | |
3411 | By virtue of using a binary or 4-heap, the next timer is always found at a |
4149 | If you need, for some reason, empty reports from valgrind for your project |
3412 | fixed position in the storage array. |
4150 | I suggest using suppression lists. |
3413 | |
4151 | |
3414 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3415 | |
4152 | |
3416 | A change means an I/O watcher gets started or stopped, which requires |
4153 | =head1 PORTABILITY NOTES |
3417 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3418 | on backend and whether C<ev_io_set> was used). |
|
|
3419 | |
4154 | |
3420 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3421 | |
|
|
3422 | =item Priority handling: O(number_of_priorities) |
|
|
3423 | |
|
|
3424 | Priorities are implemented by allocating some space for each |
|
|
3425 | priority. When doing priority-based operations, libev usually has to |
|
|
3426 | linearly search all the priorities, but starting/stopping and activating |
|
|
3427 | watchers becomes O(1) with respect to priority handling. |
|
|
3428 | |
|
|
3429 | =item Sending an ev_async: O(1) |
|
|
3430 | |
|
|
3431 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3432 | |
|
|
3433 | =item Processing signals: O(max_signal_number) |
|
|
3434 | |
|
|
3435 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3436 | calls in the current loop iteration. Checking for async and signal events |
|
|
3437 | involves iterating over all running async watchers or all signal numbers. |
|
|
3438 | |
|
|
3439 | =back |
|
|
3440 | |
|
|
3441 | |
|
|
3442 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4155 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3443 | |
4156 | |
3444 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4157 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3445 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4158 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3446 | model. Libev still offers limited functionality on this platform in |
4159 | model. Libev still offers limited functionality on this platform in |
3447 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4160 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
… | |
… | |
3454 | way (note also that glib is the slowest event library known to man). |
4167 | way (note also that glib is the slowest event library known to man). |
3455 | |
4168 | |
3456 | There is no supported compilation method available on windows except |
4169 | There is no supported compilation method available on windows except |
3457 | embedding it into other applications. |
4170 | embedding it into other applications. |
3458 | |
4171 | |
|
|
4172 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4173 | tries its best, but under most conditions, signals will simply not work. |
|
|
4174 | |
3459 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4175 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3460 | accept large writes: instead of resulting in a partial write, windows will |
4176 | accept large writes: instead of resulting in a partial write, windows will |
3461 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4177 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3462 | so make sure you only write small amounts into your sockets (less than a |
4178 | so make sure you only write small amounts into your sockets (less than a |
3463 | megabyte seems safe, but this apparently depends on the amount of memory |
4179 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3467 | the abysmal performance of winsockets, using a large number of sockets |
4183 | the abysmal performance of winsockets, using a large number of sockets |
3468 | is not recommended (and not reasonable). If your program needs to use |
4184 | is not recommended (and not reasonable). If your program needs to use |
3469 | more than a hundred or so sockets, then likely it needs to use a totally |
4185 | more than a hundred or so sockets, then likely it needs to use a totally |
3470 | different implementation for windows, as libev offers the POSIX readiness |
4186 | different implementation for windows, as libev offers the POSIX readiness |
3471 | notification model, which cannot be implemented efficiently on windows |
4187 | notification model, which cannot be implemented efficiently on windows |
3472 | (Microsoft monopoly games). |
4188 | (due to Microsoft monopoly games). |
3473 | |
4189 | |
3474 | A typical way to use libev under windows is to embed it (see the embedding |
4190 | A typical way to use libev under windows is to embed it (see the embedding |
3475 | section for details) and use the following F<evwrap.h> header file instead |
4191 | section for details) and use the following F<evwrap.h> header file instead |
3476 | of F<ev.h>: |
4192 | of F<ev.h>: |
3477 | |
4193 | |
… | |
… | |
3513 | |
4229 | |
3514 | Early versions of winsocket's select only supported waiting for a maximum |
4230 | Early versions of winsocket's select only supported waiting for a maximum |
3515 | of C<64> handles (probably owning to the fact that all windows kernels |
4231 | of C<64> handles (probably owning to the fact that all windows kernels |
3516 | can only wait for C<64> things at the same time internally; Microsoft |
4232 | can only wait for C<64> things at the same time internally; Microsoft |
3517 | recommends spawning a chain of threads and wait for 63 handles and the |
4233 | recommends spawning a chain of threads and wait for 63 handles and the |
3518 | previous thread in each. Great). |
4234 | previous thread in each. Sounds great!). |
3519 | |
4235 | |
3520 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4236 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3521 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4237 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3522 | call (which might be in libev or elsewhere, for example, perl does its own |
4238 | call (which might be in libev or elsewhere, for example, perl and many |
3523 | select emulation on windows). |
4239 | other interpreters do their own select emulation on windows). |
3524 | |
4240 | |
3525 | Another limit is the number of file descriptors in the Microsoft runtime |
4241 | Another limit is the number of file descriptors in the Microsoft runtime |
3526 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4242 | libraries, which by default is C<64> (there must be a hidden I<64> |
3527 | or something like this inside Microsoft). You can increase this by calling |
4243 | fetish or something like this inside Microsoft). You can increase this |
3528 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4244 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3529 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4245 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3530 | libraries. |
|
|
3531 | |
|
|
3532 | This might get you to about C<512> or C<2048> sockets (depending on |
4246 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3533 | windows version and/or the phase of the moon). To get more, you need to |
4247 | (depending on windows version and/or the phase of the moon). To get more, |
3534 | wrap all I/O functions and provide your own fd management, but the cost of |
4248 | you need to wrap all I/O functions and provide your own fd management, but |
3535 | calling select (O(n²)) will likely make this unworkable. |
4249 | the cost of calling select (O(n²)) will likely make this unworkable. |
3536 | |
4250 | |
3537 | =back |
4251 | =back |
3538 | |
4252 | |
3539 | |
|
|
3540 | =head1 PORTABILITY REQUIREMENTS |
4253 | =head2 PORTABILITY REQUIREMENTS |
3541 | |
4254 | |
3542 | In addition to a working ISO-C implementation, libev relies on a few |
4255 | In addition to a working ISO-C implementation and of course the |
3543 | additional extensions: |
4256 | backend-specific APIs, libev relies on a few additional extensions: |
3544 | |
4257 | |
3545 | =over 4 |
4258 | =over 4 |
3546 | |
4259 | |
3547 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
4260 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3548 | calling conventions regardless of C<ev_watcher_type *>. |
4261 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3573 | except the initial one, and run the default loop in the initial thread as |
4286 | except the initial one, and run the default loop in the initial thread as |
3574 | well. |
4287 | well. |
3575 | |
4288 | |
3576 | =item C<long> must be large enough for common memory allocation sizes |
4289 | =item C<long> must be large enough for common memory allocation sizes |
3577 | |
4290 | |
3578 | To improve portability and simplify using libev, libev uses C<long> |
4291 | To improve portability and simplify its API, libev uses C<long> internally |
3579 | internally instead of C<size_t> when allocating its data structures. On |
4292 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3580 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
4293 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3581 | is still at least 31 bits everywhere, which is enough for hundreds of |
4294 | least 31 bits everywhere, which is enough for hundreds of millions of |
3582 | millions of watchers. |
4295 | watchers. |
3583 | |
4296 | |
3584 | =item C<double> must hold a time value in seconds with enough accuracy |
4297 | =item C<double> must hold a time value in seconds with enough accuracy |
3585 | |
4298 | |
3586 | The type C<double> is used to represent timestamps. It is required to |
4299 | The type C<double> is used to represent timestamps. It is required to |
3587 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4300 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3588 | enough for at least into the year 4000. This requirement is fulfilled by |
4301 | enough for at least into the year 4000. This requirement is fulfilled by |
3589 | implementations implementing IEEE 754 (basically all existing ones). |
4302 | implementations implementing IEEE 754, which is basically all existing |
|
|
4303 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4304 | 2200. |
3590 | |
4305 | |
3591 | =back |
4306 | =back |
3592 | |
4307 | |
3593 | If you know of other additional requirements drop me a note. |
4308 | If you know of other additional requirements drop me a note. |
3594 | |
4309 | |
3595 | |
4310 | |
3596 | =head1 COMPILER WARNINGS |
4311 | =head1 ALGORITHMIC COMPLEXITIES |
3597 | |
4312 | |
3598 | Depending on your compiler and compiler settings, you might get no or a |
4313 | In this section the complexities of (many of) the algorithms used inside |
3599 | lot of warnings when compiling libev code. Some people are apparently |
4314 | libev will be documented. For complexity discussions about backends see |
3600 | scared by this. |
4315 | the documentation for C<ev_default_init>. |
3601 | |
4316 | |
3602 | However, these are unavoidable for many reasons. For one, each compiler |
4317 | All of the following are about amortised time: If an array needs to be |
3603 | has different warnings, and each user has different tastes regarding |
4318 | extended, libev needs to realloc and move the whole array, but this |
3604 | warning options. "Warn-free" code therefore cannot be a goal except when |
4319 | happens asymptotically rarer with higher number of elements, so O(1) might |
3605 | targeting a specific compiler and compiler-version. |
4320 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
4321 | average it is much faster and asymptotically approaches constant time. |
3606 | |
4322 | |
3607 | Another reason is that some compiler warnings require elaborate |
4323 | =over 4 |
3608 | workarounds, or other changes to the code that make it less clear and less |
|
|
3609 | maintainable. |
|
|
3610 | |
4324 | |
3611 | And of course, some compiler warnings are just plain stupid, or simply |
4325 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3612 | wrong (because they don't actually warn about the condition their message |
|
|
3613 | seems to warn about). |
|
|
3614 | |
4326 | |
3615 | While libev is written to generate as few warnings as possible, |
4327 | This means that, when you have a watcher that triggers in one hour and |
3616 | "warn-free" code is not a goal, and it is recommended not to build libev |
4328 | there are 100 watchers that would trigger before that, then inserting will |
3617 | with any compiler warnings enabled unless you are prepared to cope with |
4329 | have to skip roughly seven (C<ld 100>) of these watchers. |
3618 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3619 | warnings, not errors, or proof of bugs. |
|
|
3620 | |
4330 | |
|
|
4331 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3621 | |
4332 | |
3622 | =head1 VALGRIND |
4333 | That means that changing a timer costs less than removing/adding them, |
|
|
4334 | as only the relative motion in the event queue has to be paid for. |
3623 | |
4335 | |
3624 | Valgrind has a special section here because it is a popular tool that is |
4336 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3625 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3626 | |
4337 | |
3627 | If you think you found a bug (memory leak, uninitialised data access etc.) |
4338 | These just add the watcher into an array or at the head of a list. |
3628 | in libev, then check twice: If valgrind reports something like: |
|
|
3629 | |
4339 | |
3630 | ==2274== definitely lost: 0 bytes in 0 blocks. |
4340 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3631 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3632 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3633 | |
4341 | |
3634 | Then there is no memory leak. Similarly, under some circumstances, |
4342 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3635 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3636 | might be confused (it is a very good tool, but only a tool). |
|
|
3637 | |
4343 | |
3638 | If you are unsure about something, feel free to contact the mailing list |
4344 | These watchers are stored in lists, so they need to be walked to find the |
3639 | with the full valgrind report and an explanation on why you think this is |
4345 | correct watcher to remove. The lists are usually short (you don't usually |
3640 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
4346 | have many watchers waiting for the same fd or signal: one is typical, two |
3641 | no bug" answer and take the chance of learning how to interpret valgrind |
4347 | is rare). |
3642 | properly. |
|
|
3643 | |
4348 | |
3644 | If you need, for some reason, empty reports from valgrind for your project |
4349 | =item Finding the next timer in each loop iteration: O(1) |
3645 | I suggest using suppression lists. |
|
|
3646 | |
4350 | |
|
|
4351 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
4352 | fixed position in the storage array. |
|
|
4353 | |
|
|
4354 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
4355 | |
|
|
4356 | A change means an I/O watcher gets started or stopped, which requires |
|
|
4357 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
4358 | on backend and whether C<ev_io_set> was used). |
|
|
4359 | |
|
|
4360 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
4361 | |
|
|
4362 | =item Priority handling: O(number_of_priorities) |
|
|
4363 | |
|
|
4364 | Priorities are implemented by allocating some space for each |
|
|
4365 | priority. When doing priority-based operations, libev usually has to |
|
|
4366 | linearly search all the priorities, but starting/stopping and activating |
|
|
4367 | watchers becomes O(1) with respect to priority handling. |
|
|
4368 | |
|
|
4369 | =item Sending an ev_async: O(1) |
|
|
4370 | |
|
|
4371 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
4372 | |
|
|
4373 | =item Processing signals: O(max_signal_number) |
|
|
4374 | |
|
|
4375 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
4376 | calls in the current loop iteration. Checking for async and signal events |
|
|
4377 | involves iterating over all running async watchers or all signal numbers. |
|
|
4378 | |
|
|
4379 | =back |
|
|
4380 | |
|
|
4381 | |
|
|
4382 | =head1 GLOSSARY |
|
|
4383 | |
|
|
4384 | =over 4 |
|
|
4385 | |
|
|
4386 | =item active |
|
|
4387 | |
|
|
4388 | A watcher is active as long as it has been started (has been attached to |
|
|
4389 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4390 | |
|
|
4391 | =item application |
|
|
4392 | |
|
|
4393 | In this document, an application is whatever is using libev. |
|
|
4394 | |
|
|
4395 | =item callback |
|
|
4396 | |
|
|
4397 | The address of a function that is called when some event has been |
|
|
4398 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4399 | received the event, and the actual event bitset. |
|
|
4400 | |
|
|
4401 | =item callback invocation |
|
|
4402 | |
|
|
4403 | The act of calling the callback associated with a watcher. |
|
|
4404 | |
|
|
4405 | =item event |
|
|
4406 | |
|
|
4407 | A change of state of some external event, such as data now being available |
|
|
4408 | for reading on a file descriptor, time having passed or simply not having |
|
|
4409 | any other events happening anymore. |
|
|
4410 | |
|
|
4411 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4412 | C<EV_TIMEOUT>). |
|
|
4413 | |
|
|
4414 | =item event library |
|
|
4415 | |
|
|
4416 | A software package implementing an event model and loop. |
|
|
4417 | |
|
|
4418 | =item event loop |
|
|
4419 | |
|
|
4420 | An entity that handles and processes external events and converts them |
|
|
4421 | into callback invocations. |
|
|
4422 | |
|
|
4423 | =item event model |
|
|
4424 | |
|
|
4425 | The model used to describe how an event loop handles and processes |
|
|
4426 | watchers and events. |
|
|
4427 | |
|
|
4428 | =item pending |
|
|
4429 | |
|
|
4430 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4431 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4432 | pending status is explicitly cleared by the application. |
|
|
4433 | |
|
|
4434 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4435 | its pending status. |
|
|
4436 | |
|
|
4437 | =item real time |
|
|
4438 | |
|
|
4439 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4440 | |
|
|
4441 | =item wall-clock time |
|
|
4442 | |
|
|
4443 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4444 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4445 | clock. |
|
|
4446 | |
|
|
4447 | =item watcher |
|
|
4448 | |
|
|
4449 | A data structure that describes interest in certain events. Watchers need |
|
|
4450 | to be started (attached to an event loop) before they can receive events. |
|
|
4451 | |
|
|
4452 | =item watcher invocation |
|
|
4453 | |
|
|
4454 | The act of calling the callback associated with a watcher. |
|
|
4455 | |
|
|
4456 | =back |
3647 | |
4457 | |
3648 | =head1 AUTHOR |
4458 | =head1 AUTHOR |
3649 | |
4459 | |
3650 | Marc Lehmann <libev@schmorp.de>. |
4460 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3651 | |
4461 | |