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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 | |
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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 | |
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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 | |
… | |
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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 |
… | |
… | |
359 | writing a server, you should C<accept ()> in a loop to accept as many |
377 | writing a server, you should C<accept ()> in a loop to accept as many |
360 | connections as possible during one iteration. You might also want to have |
378 | connections as possible during one iteration. You might also want to have |
361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
379 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
362 | readiness notifications you get per iteration. |
380 | readiness notifications you get per iteration. |
363 | |
381 | |
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382 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
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383 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
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384 | C<exceptfds> set on that platform). |
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385 | |
364 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
386 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
365 | |
387 | |
366 | And this is your standard poll(2) backend. It's more complicated |
388 | And this is your standard poll(2) backend. It's more complicated |
367 | than select, but handles sparse fds better and has no artificial |
389 | than select, but handles sparse fds better and has no artificial |
368 | limit on the number of fds you can use (except it will slow down |
390 | limit on the number of fds you can use (except it will slow down |
369 | considerably with a lot of inactive fds). It scales similarly to select, |
391 | considerably with a lot of inactive fds). It scales similarly to select, |
370 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
392 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
371 | performance tips. |
393 | performance tips. |
372 | |
394 | |
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395 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
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396 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
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397 | |
373 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
398 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
374 | |
399 | |
375 | 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, |
376 | but it scales phenomenally better. While poll and select usually scale |
401 | but it scales phenomenally better. While poll and select usually scale |
377 | 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), |
378 | 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). |
379 | of shortcomings, such as silently dropping events in some hard-to-detect |
404 | |
380 | 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 |
381 | 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. |
382 | |
421 | |
383 | 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 |
384 | 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 |
385 | (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 |
386 | 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 |
387 | very well if you register events for both fds. |
426 | file descriptors might not work very well if you register events for both |
388 | |
427 | file descriptors. |
389 | Please note that epoll sometimes generates spurious notifications, so you |
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390 | need to use non-blocking I/O or other means to avoid blocking when no data |
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391 | (or space) is available. |
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392 | |
428 | |
393 | Best performance from this backend is achieved by not unregistering all |
429 | Best performance from this backend is achieved by not unregistering all |
394 | watchers for a file descriptor until it has been closed, if possible, i.e. |
430 | watchers for a file descriptor until it has been closed, if possible, |
395 | keep at least one watcher active per fd at all times. |
431 | i.e. keep at least one watcher active per fd at all times. Stopping and |
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432 | starting a watcher (without re-setting it) also usually doesn't cause |
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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. |
396 | |
440 | |
397 | 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 |
398 | all kernel versions tested so far. |
442 | all kernel versions tested so far. |
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443 | |
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444 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
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445 | C<EVBACKEND_POLL>. |
399 | |
446 | |
400 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
447 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
401 | |
448 | |
402 | Kqueue deserves special mention, as at the time of this writing, it |
449 | Kqueue deserves special mention, as at the time of this writing, it |
403 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
450 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
404 | with anything but sockets and pipes, except on Darwin, where of course |
451 | with anything but sockets and pipes, except on Darwin, where of course |
405 | it's completely useless). For this reason it's not being "auto-detected" |
452 | it's completely useless). Unlike epoll, however, whose brokenness |
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453 | is by design, these kqueue bugs can (and eventually will) be fixed |
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454 | without API changes to existing programs. For this reason it's not being |
406 | unless you explicitly specify it explicitly in the flags (i.e. using |
455 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
407 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
456 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
408 | system like NetBSD. |
457 | system like NetBSD. |
409 | |
458 | |
410 | 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 |
411 | 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 |
… | |
… | |
413 | |
462 | |
414 | 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 |
415 | 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 |
416 | 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 |
417 | 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 |
418 | 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 |
419 | 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 |
420 | |
470 | |
421 | This backend usually performs well under most conditions. |
471 | This backend usually performs well under most conditions. |
422 | |
472 | |
423 | While nominally embeddable in other event loops, this doesn't work |
473 | While nominally embeddable in other event loops, this doesn't work |
424 | 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 |
425 | 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 |
426 | (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 |
427 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
477 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
428 | sockets. |
478 | also broken on OS X)) and, did I mention it, using it only for sockets. |
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479 | |
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480 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
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481 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
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482 | C<NOTE_EOF>. |
429 | |
483 | |
430 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
484 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
431 | |
485 | |
432 | This is not implemented yet (and might never be, unless you send me an |
486 | This is not implemented yet (and might never be, unless you send me an |
433 | implementation). According to reports, C</dev/poll> only supports sockets |
487 | implementation). According to reports, C</dev/poll> only supports sockets |
… | |
… | |
446 | While this backend scales well, it requires one system call per active |
500 | While this backend scales well, it requires one system call per active |
447 | file descriptor per loop iteration. For small and medium numbers of file |
501 | file descriptor per loop iteration. For small and medium numbers of file |
448 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
502 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
449 | might perform better. |
503 | might perform better. |
450 | |
504 | |
451 | On the positive side, ignoring the spurious readiness notifications, this |
505 | On the positive side, with the exception of the spurious readiness |
452 | backend actually performed to specification in all tests and is fully |
506 | notifications, this backend actually performed fully to specification |
453 | embeddable, which is a rare feat among the OS-specific backends. |
507 | in all tests and is fully embeddable, which is a rare feat among the |
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508 | OS-specific backends (I vastly prefer correctness over speed hacks). |
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509 | |
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510 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
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511 | C<EVBACKEND_POLL>. |
454 | |
512 | |
455 | =item C<EVBACKEND_ALL> |
513 | =item C<EVBACKEND_ALL> |
456 | |
514 | |
457 | Try all backends (even potentially broken ones that wouldn't be tried |
515 | Try all backends (even potentially broken ones that wouldn't be tried |
458 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
516 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
… | |
… | |
464 | |
522 | |
465 | If one or more of these are or'ed into the flags value, then only these |
523 | If one or more of these are or'ed into the flags value, then only these |
466 | backends will be tried (in the reverse order as listed here). If none are |
524 | backends will be tried (in the reverse order as listed here). If none are |
467 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
525 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
468 | |
526 | |
469 | The most typical usage is like this: |
527 | Example: This is the most typical usage. |
470 | |
528 | |
471 | if (!ev_default_loop (0)) |
529 | if (!ev_default_loop (0)) |
472 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
530 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
473 | |
531 | |
474 | Restrict libev to the select and poll backends, and do not allow |
532 | Example: Restrict libev to the select and poll backends, and do not allow |
475 | environment settings to be taken into account: |
533 | environment settings to be taken into account: |
476 | |
534 | |
477 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
535 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
478 | |
536 | |
479 | Use whatever libev has to offer, but make sure that kqueue is used if |
537 | Example: Use whatever libev has to offer, but make sure that kqueue is |
480 | available (warning, breaks stuff, best use only with your own private |
538 | used if available (warning, breaks stuff, best use only with your own |
481 | event loop and only if you know the OS supports your types of fds): |
539 | private event loop and only if you know the OS supports your types of |
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540 | fds): |
482 | |
541 | |
483 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
542 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
484 | |
543 | |
485 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
544 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
486 | |
545 | |
… | |
… | |
507 | responsibility to either stop all watchers cleanly yourself I<before> |
566 | responsibility to either stop all watchers cleanly yourself I<before> |
508 | 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 |
509 | 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 |
510 | for example). |
569 | for example). |
511 | |
570 | |
512 | 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 |
513 | this function, and related watchers (such as signal and child watchers) |
572 | handlers), will not be freed by this function, and related watchers (such |
514 | would need to be stopped manually. |
573 | as signal and child watchers) would need to be stopped manually. |
515 | |
574 | |
516 | 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 |
517 | 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 |
518 | 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 |
519 | C<ev_loop_new> and C<ev_loop_destroy>). |
578 | C<ev_loop_new> and C<ev_loop_destroy>). |
… | |
… | |
544 | |
603 | |
545 | =item ev_loop_fork (loop) |
604 | =item ev_loop_fork (loop) |
546 | |
605 | |
547 | Like C<ev_default_fork>, but acts on an event loop created by |
606 | Like C<ev_default_fork>, but acts on an event loop created by |
548 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
607 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
549 | after fork, and how you do this is entirely your own problem. |
608 | after fork that you want to re-use in the child, and how you do this is |
|
|
609 | entirely your own problem. |
550 | |
610 | |
551 | =item int ev_is_default_loop (loop) |
611 | =item int ev_is_default_loop (loop) |
552 | |
612 | |
553 | Returns true when the given loop actually is the default loop, false otherwise. |
613 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
614 | otherwise. |
554 | |
615 | |
555 | =item unsigned int ev_loop_count (loop) |
616 | =item unsigned int ev_loop_count (loop) |
556 | |
617 | |
557 | Returns the count of loop iterations for the loop, which is identical to |
618 | Returns the count of loop iterations for the loop, which is identical to |
558 | the number of times libev did poll for new events. It starts at C<0> and |
619 | the number of times libev did poll for new events. It starts at C<0> and |
559 | happily wraps around with enough iterations. |
620 | happily wraps around with enough iterations. |
560 | |
621 | |
561 | 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 |
562 | "ticks" the number of loop iterations), as it roughly corresponds with |
623 | "ticks" the number of loop iterations), as it roughly corresponds with |
563 | C<ev_prepare> and C<ev_check> calls. |
624 | C<ev_prepare> and C<ev_check> calls. |
|
|
625 | |
|
|
626 | =item unsigned int ev_loop_depth (loop) |
|
|
627 | |
|
|
628 | Returns the number of times C<ev_loop> was entered minus the number of |
|
|
629 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
630 | |
|
|
631 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
|
|
632 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
|
|
633 | in which case it is higher. |
|
|
634 | |
|
|
635 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
636 | etc.), doesn't count as exit. |
564 | |
637 | |
565 | =item unsigned int ev_backend (loop) |
638 | =item unsigned int ev_backend (loop) |
566 | |
639 | |
567 | 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 |
568 | use. |
641 | use. |
… | |
… | |
573 | received events and started processing them. This timestamp does not |
646 | received events and started processing them. This timestamp does not |
574 | change as long as callbacks are being processed, and this is also the base |
647 | change as long as callbacks are being processed, and this is also the base |
575 | time used for relative timers. You can treat it as the timestamp of the |
648 | time used for relative timers. You can treat it as the timestamp of the |
576 | event occurring (or more correctly, libev finding out about it). |
649 | event occurring (or more correctly, libev finding out about it). |
577 | |
650 | |
|
|
651 | =item ev_now_update (loop) |
|
|
652 | |
|
|
653 | Establishes the current time by querying the kernel, updating the time |
|
|
654 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
655 | is usually done automatically within C<ev_loop ()>. |
|
|
656 | |
|
|
657 | This function is rarely useful, but when some event callback runs for a |
|
|
658 | very long time without entering the event loop, updating libev's idea of |
|
|
659 | the current time is a good idea. |
|
|
660 | |
|
|
661 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
662 | |
|
|
663 | =item ev_suspend (loop) |
|
|
664 | |
|
|
665 | =item ev_resume (loop) |
|
|
666 | |
|
|
667 | These two functions suspend and resume a loop, for use when the loop is |
|
|
668 | not used for a while and timeouts should not be processed. |
|
|
669 | |
|
|
670 | A typical use case would be an interactive program such as a game: When |
|
|
671 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
672 | would be best to handle timeouts as if no time had actually passed while |
|
|
673 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
674 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
675 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
676 | |
|
|
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>). |
|
|
688 | |
578 | =item ev_loop (loop, int flags) |
689 | =item ev_loop (loop, int flags) |
579 | |
690 | |
580 | 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 |
581 | 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 |
582 | events. |
693 | events. |
… | |
… | |
584 | If the flags argument is specified as C<0>, it will not return until |
695 | If the flags argument is specified as C<0>, it will not return until |
585 | either no event watchers are active anymore or C<ev_unloop> was called. |
696 | either no event watchers are active anymore or C<ev_unloop> was called. |
586 | |
697 | |
587 | Please note that an explicit C<ev_unloop> is usually better than |
698 | Please note that an explicit C<ev_unloop> is usually better than |
588 | relying on all watchers to be stopped when deciding when a program has |
699 | relying on all watchers to be stopped when deciding when a program has |
589 | finished (especially in interactive programs), but having a program that |
700 | finished (especially in interactive programs), but having a program |
590 | automatically loops as long as it has to and no longer by virtue of |
701 | that automatically loops as long as it has to and no longer by virtue |
591 | relying on its watchers stopping correctly is a thing of beauty. |
702 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
703 | beauty. |
592 | |
704 | |
593 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
705 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
594 | those events and any outstanding ones, but will not block your process in |
706 | those events and any already outstanding ones, but will not block your |
595 | case there are no events and will return after one iteration of the loop. |
707 | process in case there are no events and will return after one iteration of |
|
|
708 | the loop. |
596 | |
709 | |
597 | 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 |
598 | necessary) and will handle those and any outstanding ones. It will block |
711 | necessary) and will handle those and any already outstanding ones. It |
599 | your process until at least one new event arrives, and will return after |
712 | will block your process until at least one new event arrives (which could |
600 | one iteration of the loop. This is useful if you are waiting for some |
713 | be an event internal to libev itself, so there is no guarantee that a |
601 | external event in conjunction with something not expressible using other |
714 | user-registered callback will be called), and will return after one |
|
|
715 | iteration of the loop. |
|
|
716 | |
|
|
717 | This is useful if you are waiting for some external event in conjunction |
|
|
718 | with something not expressible using other libev watchers (i.e. "roll your |
602 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
719 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
603 | usually a better approach for this kind of thing. |
720 | usually a better approach for this kind of thing. |
604 | |
721 | |
605 | Here are the gory details of what C<ev_loop> does: |
722 | Here are the gory details of what C<ev_loop> does: |
606 | |
723 | |
607 | - Before the first iteration, call any pending watchers. |
724 | - Before the first iteration, call any pending watchers. |
608 | * If EVFLAG_FORKCHECK was used, check for a fork. |
725 | * If EVFLAG_FORKCHECK was used, check for a fork. |
609 | - If a fork was detected, queue and call all fork watchers. |
726 | - If a fork was detected (by any means), queue and call all fork watchers. |
610 | - Queue and call all prepare watchers. |
727 | - Queue and call all prepare watchers. |
611 | - If we have been forked, recreate the kernel state. |
728 | - If we have been forked, detach and recreate the kernel state |
|
|
729 | as to not disturb the other process. |
612 | - Update the kernel state with all outstanding changes. |
730 | - Update the kernel state with all outstanding changes. |
613 | - Update the "event loop time". |
731 | - Update the "event loop time" (ev_now ()). |
614 | - Calculate for how long to sleep or block, if at all |
732 | - Calculate for how long to sleep or block, if at all |
615 | (active idle watchers, EVLOOP_NONBLOCK or not having |
733 | (active idle watchers, EVLOOP_NONBLOCK or not having |
616 | any active watchers at all will result in not sleeping). |
734 | any active watchers at all will result in not sleeping). |
617 | - Sleep if the I/O and timer collect interval say so. |
735 | - Sleep if the I/O and timer collect interval say so. |
618 | - Block the process, waiting for any events. |
736 | - Block the process, waiting for any events. |
619 | - Queue all outstanding I/O (fd) events. |
737 | - Queue all outstanding I/O (fd) events. |
620 | - Update the "event loop time" and do time jump handling. |
738 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
621 | - Queue all outstanding timers. |
739 | - Queue all expired timers. |
622 | - Queue all outstanding periodics. |
740 | - Queue all expired periodics. |
623 | - If no events are pending now, queue all idle watchers. |
741 | - Unless any events are pending now, queue all idle watchers. |
624 | - Queue all check watchers. |
742 | - Queue all check watchers. |
625 | - Call all queued watchers in reverse order (i.e. check watchers first). |
743 | - Call all queued watchers in reverse order (i.e. check watchers first). |
626 | Signals and child watchers are implemented as I/O watchers, and will |
744 | Signals and child watchers are implemented as I/O watchers, and will |
627 | be handled here by queueing them when their watcher gets executed. |
745 | be handled here by queueing them when their watcher gets executed. |
628 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
746 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
… | |
… | |
633 | anymore. |
751 | anymore. |
634 | |
752 | |
635 | ... queue jobs here, make sure they register event watchers as long |
753 | ... queue jobs here, make sure they register event watchers as long |
636 | ... as they still have work to do (even an idle watcher will do..) |
754 | ... as they still have work to do (even an idle watcher will do..) |
637 | ev_loop (my_loop, 0); |
755 | ev_loop (my_loop, 0); |
638 | ... jobs done. yeah! |
756 | ... jobs done or somebody called unloop. yeah! |
639 | |
757 | |
640 | =item ev_unloop (loop, how) |
758 | =item ev_unloop (loop, how) |
641 | |
759 | |
642 | Can be used to make a call to C<ev_loop> return early (but only after it |
760 | Can be used to make a call to C<ev_loop> return early (but only after it |
643 | has processed all outstanding events). The C<how> argument must be either |
761 | has processed all outstanding events). The C<how> argument must be either |
644 | 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 |
645 | 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. |
646 | |
764 | |
647 | 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. |
648 | |
766 | |
|
|
767 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
768 | |
649 | =item ev_ref (loop) |
769 | =item ev_ref (loop) |
650 | |
770 | |
651 | =item ev_unref (loop) |
771 | =item ev_unref (loop) |
652 | |
772 | |
653 | 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 |
654 | loop: Every watcher keeps one reference, and as long as the reference |
774 | loop: Every watcher keeps one reference, and as long as the reference |
655 | count is nonzero, C<ev_loop> will not return on its own. If you have |
775 | count is nonzero, C<ev_loop> will not return on its own. |
|
|
776 | |
656 | a watcher you never unregister that should not keep C<ev_loop> from |
777 | If you have a watcher you never unregister that should not keep C<ev_loop> |
657 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
778 | from returning, call ev_unref() after starting, and ev_ref() before |
|
|
779 | stopping it. |
|
|
780 | |
658 | example, libev itself uses this for its internal signal pipe: It is not |
781 | As an example, libev itself uses this for its internal signal pipe: It |
659 | visible to the libev user and should not keep C<ev_loop> from exiting if |
782 | is not visible to the libev user and should not keep C<ev_loop> from |
660 | 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 |
661 | 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 |
662 | 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 |
663 | (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 |
664 | 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). |
665 | |
790 | |
666 | 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> |
667 | running when nothing else is active. |
792 | running when nothing else is active. |
668 | |
793 | |
669 | struct ev_signal exitsig; |
794 | ev_signal exitsig; |
670 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
795 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
671 | ev_signal_start (loop, &exitsig); |
796 | ev_signal_start (loop, &exitsig); |
672 | evf_unref (loop); |
797 | evf_unref (loop); |
673 | |
798 | |
674 | Example: For some weird reason, unregister the above signal handler again. |
799 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
679 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
804 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
680 | |
805 | |
681 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
806 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
682 | |
807 | |
683 | These advanced functions influence the time that libev will spend waiting |
808 | These advanced functions influence the time that libev will spend waiting |
684 | for events. Both are by default C<0>, meaning that libev will try to |
809 | for events. Both time intervals are by default C<0>, meaning that libev |
685 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
810 | will try to invoke timer/periodic callbacks and I/O callbacks with minimum |
|
|
811 | latency. |
686 | |
812 | |
687 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
813 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
688 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
814 | allows libev to delay invocation of I/O and timer/periodic callbacks |
689 | increase efficiency of loop iterations. |
815 | to increase efficiency of loop iterations (or to increase power-saving |
|
|
816 | opportunities). |
690 | |
817 | |
691 | The background is that sometimes your program runs just fast enough to |
818 | The idea is that sometimes your program runs just fast enough to handle |
692 | handle one (or very few) event(s) per loop iteration. While this makes |
819 | one (or very few) event(s) per loop iteration. While this makes the |
693 | the program responsive, it also wastes a lot of CPU time to poll for new |
820 | program responsive, it also wastes a lot of CPU time to poll for new |
694 | events, especially with backends like C<select ()> which have a high |
821 | events, especially with backends like C<select ()> which have a high |
695 | overhead for the actual polling but can deliver many events at once. |
822 | overhead for the actual polling but can deliver many events at once. |
696 | |
823 | |
697 | 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 |
698 | 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, |
699 | 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 |
700 | 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 |
701 | 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. |
702 | |
831 | |
703 | 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 |
704 | to spend more time collecting timeouts, at the expense of increased |
833 | to spend more time collecting timeouts, at the expense of increased |
705 | latency (the watcher callback will be called later). C<ev_io> watchers |
834 | latency/jitter/inexactness (the watcher callback will be called |
706 | will not be affected. Setting this to a non-null value will not introduce |
835 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
707 | any overhead in libev. |
836 | value will not introduce any overhead in libev. |
708 | |
837 | |
709 | 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 |
710 | 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 |
711 | interactive servers (of course not for games), likewise for timeouts. It |
840 | interactive servers (of course not for games), likewise for timeouts. It |
712 | 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>, |
713 | 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). |
|
|
847 | |
|
|
848 | Setting the I<timeout collect interval> can improve the opportunity for |
|
|
849 | saving power, as the program will "bundle" timer callback invocations that |
|
|
850 | are "near" in time together, by delaying some, thus reducing the number of |
|
|
851 | times the process sleeps and wakes up again. Another useful technique to |
|
|
852 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
|
|
853 | they fire on, say, one-second boundaries only. |
|
|
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 int ev_pending_count (loop) |
|
|
868 | |
|
|
869 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
870 | are pending. |
|
|
871 | |
|
|
872 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
873 | |
|
|
874 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
875 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
876 | this callback instead. This is useful, for example, when you want to |
|
|
877 | invoke the actual watchers inside another context (another thread etc.). |
|
|
878 | |
|
|
879 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
880 | callback. |
|
|
881 | |
|
|
882 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
883 | |
|
|
884 | Sometimes you want to share the same loop between multiple threads. This |
|
|
885 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
886 | each call to a libev function. |
|
|
887 | |
|
|
888 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
889 | wait for it to return. One way around this is to wake up the loop via |
|
|
890 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
891 | and I<acquire> callbacks on the loop. |
|
|
892 | |
|
|
893 | When set, then C<release> will be called just before the thread is |
|
|
894 | suspended waiting for new events, and C<acquire> is called just |
|
|
895 | afterwards. |
|
|
896 | |
|
|
897 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
898 | C<acquire> will just call the mutex_lock function again. |
|
|
899 | |
|
|
900 | While event loop modifications are allowed between invocations of |
|
|
901 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
902 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
903 | have no effect on the set of file descriptors being watched, or the time |
|
|
904 | waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
905 | to take note of any changes you made. |
|
|
906 | |
|
|
907 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
908 | invocations of C<release> and C<acquire>. |
|
|
909 | |
|
|
910 | See also the locking example in the C<THREADS> section later in this |
|
|
911 | document. |
|
|
912 | |
|
|
913 | =item ev_set_userdata (loop, void *data) |
|
|
914 | |
|
|
915 | =item ev_userdata (loop) |
|
|
916 | |
|
|
917 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
918 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
919 | C<0.> |
|
|
920 | |
|
|
921 | These two functions can be used to associate arbitrary data with a loop, |
|
|
922 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
923 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
924 | any other purpose as well. |
714 | |
925 | |
715 | =item ev_loop_verify (loop) |
926 | =item ev_loop_verify (loop) |
716 | |
927 | |
717 | This function only does something when C<EV_VERIFY> support has been |
928 | This function only does something when C<EV_VERIFY> support has been |
718 | compiled in. It tries to go through all internal structures and checks |
929 | compiled in, which is the default for non-minimal builds. It tries to go |
719 | them for validity. If anything is found to be inconsistent, it will print |
930 | through all internal structures and checks them for validity. If anything |
720 | an error message to standard error and call C<abort ()>. |
931 | is found to be inconsistent, it will print an error message to standard |
|
|
932 | error and call C<abort ()>. |
721 | |
933 | |
722 | This can be used to catch bugs inside libev itself: under normal |
934 | This can be used to catch bugs inside libev itself: under normal |
723 | circumstances, this function will never abort as of course libev keeps its |
935 | circumstances, this function will never abort as of course libev keeps its |
724 | data structures consistent. |
936 | data structures consistent. |
725 | |
937 | |
726 | =back |
938 | =back |
727 | |
939 | |
728 | |
940 | |
729 | =head1 ANATOMY OF A WATCHER |
941 | =head1 ANATOMY OF A WATCHER |
730 | |
942 | |
|
|
943 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
944 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
945 | watchers and C<ev_io_start> for I/O watchers. |
|
|
946 | |
731 | A watcher is a structure that you create and register to record your |
947 | A watcher is a structure that you create and register to record your |
732 | interest in some event. For instance, if you want to wait for STDIN to |
948 | interest in some event. For instance, if you want to wait for STDIN to |
733 | become readable, you would create an C<ev_io> watcher for that: |
949 | become readable, you would create an C<ev_io> watcher for that: |
734 | |
950 | |
735 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
951 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
736 | { |
952 | { |
737 | ev_io_stop (w); |
953 | ev_io_stop (w); |
738 | ev_unloop (loop, EVUNLOOP_ALL); |
954 | ev_unloop (loop, EVUNLOOP_ALL); |
739 | } |
955 | } |
740 | |
956 | |
741 | struct ev_loop *loop = ev_default_loop (0); |
957 | struct ev_loop *loop = ev_default_loop (0); |
|
|
958 | |
742 | struct ev_io stdin_watcher; |
959 | ev_io stdin_watcher; |
|
|
960 | |
743 | ev_init (&stdin_watcher, my_cb); |
961 | ev_init (&stdin_watcher, my_cb); |
744 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
962 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
745 | ev_io_start (loop, &stdin_watcher); |
963 | ev_io_start (loop, &stdin_watcher); |
|
|
964 | |
746 | ev_loop (loop, 0); |
965 | ev_loop (loop, 0); |
747 | |
966 | |
748 | As you can see, you are responsible for allocating the memory for your |
967 | As you can see, you are responsible for allocating the memory for your |
749 | watcher structures (and it is usually a bad idea to do this on the stack, |
968 | watcher structures (and it is I<usually> a bad idea to do this on the |
750 | although this can sometimes be quite valid). |
969 | stack). |
|
|
970 | |
|
|
971 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
972 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
751 | |
973 | |
752 | Each watcher structure must be initialised by a call to C<ev_init |
974 | Each watcher structure must be initialised by a call to C<ev_init |
753 | (watcher *, callback)>, which expects a callback to be provided. This |
975 | (watcher *, callback)>, which expects a callback to be provided. This |
754 | callback gets invoked each time the event occurs (or, in the case of I/O |
976 | callback gets invoked each time the event occurs (or, in the case of I/O |
755 | watchers, each time the event loop detects that the file descriptor given |
977 | watchers, each time the event loop detects that the file descriptor given |
756 | is readable and/or writable). |
978 | is readable and/or writable). |
757 | |
979 | |
758 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
980 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
759 | with arguments specific to this watcher type. There is also a macro |
981 | macro to configure it, with arguments specific to the watcher type. There |
760 | to combine initialisation and setting in one call: C<< ev_<type>_init |
982 | is also a macro to combine initialisation and setting in one call: C<< |
761 | (watcher *, callback, ...) >>. |
983 | ev_TYPE_init (watcher *, callback, ...) >>. |
762 | |
984 | |
763 | To make the watcher actually watch out for events, you have to start it |
985 | To make the watcher actually watch out for events, you have to start it |
764 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
986 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
765 | *) >>), and you can stop watching for events at any time by calling the |
987 | *) >>), and you can stop watching for events at any time by calling the |
766 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
988 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
767 | |
989 | |
768 | As long as your watcher is active (has been started but not stopped) you |
990 | As long as your watcher is active (has been started but not stopped) you |
769 | must not touch the values stored in it. Most specifically you must never |
991 | must not touch the values stored in it. Most specifically you must never |
770 | reinitialise it or call its C<set> macro. |
992 | reinitialise it or call its C<ev_TYPE_set> macro. |
771 | |
993 | |
772 | Each and every callback receives the event loop pointer as first, the |
994 | Each and every callback receives the event loop pointer as first, the |
773 | registered watcher structure as second, and a bitset of received events as |
995 | registered watcher structure as second, and a bitset of received events as |
774 | third argument. |
996 | third argument. |
775 | |
997 | |
… | |
… | |
833 | |
1055 | |
834 | =item C<EV_ASYNC> |
1056 | =item C<EV_ASYNC> |
835 | |
1057 | |
836 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1058 | The given async watcher has been asynchronously notified (see C<ev_async>). |
837 | |
1059 | |
|
|
1060 | =item C<EV_CUSTOM> |
|
|
1061 | |
|
|
1062 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1063 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
1064 | |
838 | =item C<EV_ERROR> |
1065 | =item C<EV_ERROR> |
839 | |
1066 | |
840 | An unspecified error has occurred, the watcher has been stopped. This might |
1067 | An unspecified error has occurred, the watcher has been stopped. This might |
841 | happen because the watcher could not be properly started because libev |
1068 | happen because the watcher could not be properly started because libev |
842 | ran out of memory, a file descriptor was found to be closed or any other |
1069 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1070 | problem. Libev considers these application bugs. |
|
|
1071 | |
843 | problem. You best act on it by reporting the problem and somehow coping |
1072 | You best act on it by reporting the problem and somehow coping with the |
844 | with the watcher being stopped. |
1073 | watcher being stopped. Note that well-written programs should not receive |
|
|
1074 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1075 | bug in your program. |
845 | |
1076 | |
846 | Libev will usually signal a few "dummy" events together with an error, |
1077 | Libev will usually signal a few "dummy" events together with an error, for |
847 | for example it might indicate that a fd is readable or writable, and if |
1078 | example it might indicate that a fd is readable or writable, and if your |
848 | your callbacks is well-written it can just attempt the operation and cope |
1079 | callbacks is well-written it can just attempt the operation and cope with |
849 | with the error from read() or write(). This will not work in multi-threaded |
1080 | the error from read() or write(). This will not work in multi-threaded |
850 | programs, though, so beware. |
1081 | programs, though, as the fd could already be closed and reused for another |
|
|
1082 | thing, so beware. |
851 | |
1083 | |
852 | =back |
1084 | =back |
853 | |
1085 | |
854 | =head2 GENERIC WATCHER FUNCTIONS |
1086 | =head2 GENERIC WATCHER FUNCTIONS |
855 | |
|
|
856 | In the following description, C<TYPE> stands for the watcher type, |
|
|
857 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
858 | |
1087 | |
859 | =over 4 |
1088 | =over 4 |
860 | |
1089 | |
861 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1090 | =item C<ev_init> (ev_TYPE *watcher, callback) |
862 | |
1091 | |
… | |
… | |
868 | which rolls both calls into one. |
1097 | which rolls both calls into one. |
869 | |
1098 | |
870 | You can reinitialise a watcher at any time as long as it has been stopped |
1099 | You can reinitialise a watcher at any time as long as it has been stopped |
871 | (or never started) and there are no pending events outstanding. |
1100 | (or never started) and there are no pending events outstanding. |
872 | |
1101 | |
873 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1102 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
874 | int revents)>. |
1103 | int revents)>. |
|
|
1104 | |
|
|
1105 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1106 | |
|
|
1107 | ev_io w; |
|
|
1108 | ev_init (&w, my_cb); |
|
|
1109 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
875 | |
1110 | |
876 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1111 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
877 | |
1112 | |
878 | This macro initialises the type-specific parts of a watcher. You need to |
1113 | This macro initialises the type-specific parts of a watcher. You need to |
879 | call C<ev_init> at least once before you call this macro, but you can |
1114 | call C<ev_init> at least once before you call this macro, but you can |
… | |
… | |
882 | difference to the C<ev_init> macro). |
1117 | difference to the C<ev_init> macro). |
883 | |
1118 | |
884 | Although some watcher types do not have type-specific arguments |
1119 | Although some watcher types do not have type-specific arguments |
885 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
1120 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
886 | |
1121 | |
|
|
1122 | See C<ev_init>, above, for an example. |
|
|
1123 | |
887 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
1124 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
888 | |
1125 | |
889 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
1126 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
890 | calls into a single call. This is the most convenient method to initialise |
1127 | calls into a single call. This is the most convenient method to initialise |
891 | a watcher. The same limitations apply, of course. |
1128 | a watcher. The same limitations apply, of course. |
892 | |
1129 | |
|
|
1130 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1131 | |
|
|
1132 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1133 | |
893 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1134 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
894 | |
1135 | |
895 | Starts (activates) the given watcher. Only active watchers will receive |
1136 | Starts (activates) the given watcher. Only active watchers will receive |
896 | events. If the watcher is already active nothing will happen. |
1137 | events. If the watcher is already active nothing will happen. |
897 | |
1138 | |
|
|
1139 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1140 | whole section. |
|
|
1141 | |
|
|
1142 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1143 | |
898 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1144 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
899 | |
1145 | |
900 | Stops the given watcher again (if active) and clears the pending |
1146 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1147 | the watcher was active or not). |
|
|
1148 | |
901 | status. It is possible that stopped watchers are pending (for example, |
1149 | It is possible that stopped watchers are pending - for example, |
902 | non-repeating timers are being stopped when they become pending), but |
1150 | non-repeating timers are being stopped when they become pending - but |
903 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1151 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
904 | you want to free or reuse the memory used by the watcher it is therefore a |
1152 | pending. If you want to free or reuse the memory used by the watcher it is |
905 | good idea to always call its C<ev_TYPE_stop> function. |
1153 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
906 | |
1154 | |
907 | =item bool ev_is_active (ev_TYPE *watcher) |
1155 | =item bool ev_is_active (ev_TYPE *watcher) |
908 | |
1156 | |
909 | Returns a true value iff the watcher is active (i.e. it has been started |
1157 | Returns a true value iff the watcher is active (i.e. it has been started |
910 | and not yet been stopped). As long as a watcher is active you must not modify |
1158 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
936 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1184 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
937 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1185 | (default: C<-2>). Pending watchers with higher priority will be invoked |
938 | before watchers with lower priority, but priority will not keep watchers |
1186 | before watchers with lower priority, but priority will not keep watchers |
939 | from being executed (except for C<ev_idle> watchers). |
1187 | from being executed (except for C<ev_idle> watchers). |
940 | |
1188 | |
941 | This means that priorities are I<only> used for ordering callback |
|
|
942 | invocation after new events have been received. This is useful, for |
|
|
943 | example, to reduce latency after idling, or more often, to bind two |
|
|
944 | watchers on the same event and make sure one is called first. |
|
|
945 | |
|
|
946 | If you need to suppress invocation when higher priority events are pending |
1189 | If you need to suppress invocation when higher priority events are pending |
947 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1190 | you need to look at C<ev_idle> watchers, which provide this functionality. |
948 | |
1191 | |
949 | You I<must not> change the priority of a watcher as long as it is active or |
1192 | You I<must not> change the priority of a watcher as long as it is active or |
950 | pending. |
1193 | pending. |
951 | |
1194 | |
|
|
1195 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1196 | fine, as long as you do not mind that the priority value you query might |
|
|
1197 | or might not have been clamped to the valid range. |
|
|
1198 | |
952 | The default priority used by watchers when no priority has been set is |
1199 | The default priority used by watchers when no priority has been set is |
953 | always C<0>, which is supposed to not be too high and not be too low :). |
1200 | always C<0>, which is supposed to not be too high and not be too low :). |
954 | |
1201 | |
955 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1202 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
956 | fine, as long as you do not mind that the priority value you query might |
1203 | priorities. |
957 | or might not have been adjusted to be within valid range. |
|
|
958 | |
1204 | |
959 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1205 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
960 | |
1206 | |
961 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1207 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
962 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1208 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
963 | can deal with that fact. |
1209 | can deal with that fact, as both are simply passed through to the |
|
|
1210 | callback. |
964 | |
1211 | |
965 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1212 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
966 | |
1213 | |
967 | If the watcher is pending, this function returns clears its pending status |
1214 | If the watcher is pending, this function clears its pending status and |
968 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1215 | returns its C<revents> bitset (as if its callback was invoked). If the |
969 | watcher isn't pending it does nothing and returns C<0>. |
1216 | watcher isn't pending it does nothing and returns C<0>. |
970 | |
1217 | |
|
|
1218 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1219 | callback to be invoked, which can be accomplished with this function. |
|
|
1220 | |
971 | =back |
1221 | =back |
972 | |
1222 | |
973 | |
1223 | |
974 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1224 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
975 | |
1225 | |
976 | Each watcher has, by default, a member C<void *data> that you can change |
1226 | Each watcher has, by default, a member C<void *data> that you can change |
977 | and read at any time, libev will completely ignore it. This can be used |
1227 | and read at any time: libev will completely ignore it. This can be used |
978 | to associate arbitrary data with your watcher. If you need more data and |
1228 | to associate arbitrary data with your watcher. If you need more data and |
979 | don't want to allocate memory and store a pointer to it in that data |
1229 | don't want to allocate memory and store a pointer to it in that data |
980 | member, you can also "subclass" the watcher type and provide your own |
1230 | member, you can also "subclass" the watcher type and provide your own |
981 | data: |
1231 | data: |
982 | |
1232 | |
983 | struct my_io |
1233 | struct my_io |
984 | { |
1234 | { |
985 | struct ev_io io; |
1235 | ev_io io; |
986 | int otherfd; |
1236 | int otherfd; |
987 | void *somedata; |
1237 | void *somedata; |
988 | struct whatever *mostinteresting; |
1238 | struct whatever *mostinteresting; |
989 | } |
1239 | }; |
|
|
1240 | |
|
|
1241 | ... |
|
|
1242 | struct my_io w; |
|
|
1243 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
990 | |
1244 | |
991 | And since your callback will be called with a pointer to the watcher, you |
1245 | And since your callback will be called with a pointer to the watcher, you |
992 | can cast it back to your own type: |
1246 | can cast it back to your own type: |
993 | |
1247 | |
994 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1248 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
995 | { |
1249 | { |
996 | struct my_io *w = (struct my_io *)w_; |
1250 | struct my_io *w = (struct my_io *)w_; |
997 | ... |
1251 | ... |
998 | } |
1252 | } |
999 | |
1253 | |
1000 | More interesting and less C-conformant ways of casting your callback type |
1254 | More interesting and less C-conformant ways of casting your callback type |
1001 | instead have been omitted. |
1255 | instead have been omitted. |
1002 | |
1256 | |
1003 | Another common scenario is having some data structure with multiple |
1257 | Another common scenario is to use some data structure with multiple |
1004 | watchers: |
1258 | embedded watchers: |
1005 | |
1259 | |
1006 | struct my_biggy |
1260 | struct my_biggy |
1007 | { |
1261 | { |
1008 | int some_data; |
1262 | int some_data; |
1009 | ev_timer t1; |
1263 | ev_timer t1; |
1010 | ev_timer t2; |
1264 | ev_timer t2; |
1011 | } |
1265 | } |
1012 | |
1266 | |
1013 | In this case getting the pointer to C<my_biggy> is a bit more complicated, |
1267 | In this case getting the pointer to C<my_biggy> is a bit more |
1014 | you need to use C<offsetof>: |
1268 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1269 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1270 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1271 | programmers): |
1015 | |
1272 | |
1016 | #include <stddef.h> |
1273 | #include <stddef.h> |
1017 | |
1274 | |
1018 | static void |
1275 | static void |
1019 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1276 | t1_cb (EV_P_ ev_timer *w, int revents) |
1020 | { |
1277 | { |
1021 | struct my_biggy big = (struct my_biggy * |
1278 | struct my_biggy big = (struct my_biggy *) |
1022 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1279 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1023 | } |
1280 | } |
1024 | |
1281 | |
1025 | static void |
1282 | static void |
1026 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1283 | t2_cb (EV_P_ ev_timer *w, int revents) |
1027 | { |
1284 | { |
1028 | struct my_biggy big = (struct my_biggy * |
1285 | struct my_biggy big = (struct my_biggy *) |
1029 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1286 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1030 | } |
1287 | } |
|
|
1288 | |
|
|
1289 | =head2 WATCHER PRIORITY MODELS |
|
|
1290 | |
|
|
1291 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1292 | integers that influence the ordering of event callback invocation |
|
|
1293 | between watchers in some way, all else being equal. |
|
|
1294 | |
|
|
1295 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1296 | description for the more technical details such as the actual priority |
|
|
1297 | range. |
|
|
1298 | |
|
|
1299 | There are two common ways how these these priorities are being interpreted |
|
|
1300 | by event loops: |
|
|
1301 | |
|
|
1302 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1303 | of lower priority watchers, which means as long as higher priority |
|
|
1304 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1305 | |
|
|
1306 | The less common only-for-ordering model uses priorities solely to order |
|
|
1307 | callback invocation within a single event loop iteration: Higher priority |
|
|
1308 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1309 | before polling for new events. |
|
|
1310 | |
|
|
1311 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1312 | except for idle watchers (which use the lock-out model). |
|
|
1313 | |
|
|
1314 | The rationale behind this is that implementing the lock-out model for |
|
|
1315 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1316 | libraries will just poll for the same events again and again as long as |
|
|
1317 | their callbacks have not been executed, which is very inefficient in the |
|
|
1318 | common case of one high-priority watcher locking out a mass of lower |
|
|
1319 | priority ones. |
|
|
1320 | |
|
|
1321 | Static (ordering) priorities are most useful when you have two or more |
|
|
1322 | watchers handling the same resource: a typical usage example is having an |
|
|
1323 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1324 | timeouts. Under load, data might be received while the program handles |
|
|
1325 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1326 | handler will be executed before checking for data. In that case, giving |
|
|
1327 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1328 | handled first even under adverse conditions (which is usually, but not |
|
|
1329 | always, what you want). |
|
|
1330 | |
|
|
1331 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1332 | will only be executed when no same or higher priority watchers have |
|
|
1333 | received events, they can be used to implement the "lock-out" model when |
|
|
1334 | required. |
|
|
1335 | |
|
|
1336 | For example, to emulate how many other event libraries handle priorities, |
|
|
1337 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1338 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1339 | processing is done in the idle watcher callback. This causes libev to |
|
|
1340 | continously poll and process kernel event data for the watcher, but when |
|
|
1341 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1342 | workable. |
|
|
1343 | |
|
|
1344 | Usually, however, the lock-out model implemented that way will perform |
|
|
1345 | miserably under the type of load it was designed to handle. In that case, |
|
|
1346 | it might be preferable to stop the real watcher before starting the |
|
|
1347 | idle watcher, so the kernel will not have to process the event in case |
|
|
1348 | the actual processing will be delayed for considerable time. |
|
|
1349 | |
|
|
1350 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1351 | priority than the default, and which should only process data when no |
|
|
1352 | other events are pending: |
|
|
1353 | |
|
|
1354 | ev_idle idle; // actual processing watcher |
|
|
1355 | ev_io io; // actual event watcher |
|
|
1356 | |
|
|
1357 | static void |
|
|
1358 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1359 | { |
|
|
1360 | // stop the I/O watcher, we received the event, but |
|
|
1361 | // are not yet ready to handle it. |
|
|
1362 | ev_io_stop (EV_A_ w); |
|
|
1363 | |
|
|
1364 | // start the idle watcher to ahndle the actual event. |
|
|
1365 | // it will not be executed as long as other watchers |
|
|
1366 | // with the default priority are receiving events. |
|
|
1367 | ev_idle_start (EV_A_ &idle); |
|
|
1368 | } |
|
|
1369 | |
|
|
1370 | static void |
|
|
1371 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1372 | { |
|
|
1373 | // actual processing |
|
|
1374 | read (STDIN_FILENO, ...); |
|
|
1375 | |
|
|
1376 | // have to start the I/O watcher again, as |
|
|
1377 | // we have handled the event |
|
|
1378 | ev_io_start (EV_P_ &io); |
|
|
1379 | } |
|
|
1380 | |
|
|
1381 | // initialisation |
|
|
1382 | ev_idle_init (&idle, idle_cb); |
|
|
1383 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1384 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1385 | |
|
|
1386 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1387 | low-priority connections can not be locked out forever under load. This |
|
|
1388 | enables your program to keep a lower latency for important connections |
|
|
1389 | during short periods of high load, while not completely locking out less |
|
|
1390 | important ones. |
1031 | |
1391 | |
1032 | |
1392 | |
1033 | =head1 WATCHER TYPES |
1393 | =head1 WATCHER TYPES |
1034 | |
1394 | |
1035 | This section describes each watcher in detail, but will not repeat |
1395 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1059 | In general you can register as many read and/or write event watchers per |
1419 | In general you can register as many read and/or write event watchers per |
1060 | fd as you want (as long as you don't confuse yourself). Setting all file |
1420 | fd as you want (as long as you don't confuse yourself). Setting all file |
1061 | descriptors to non-blocking mode is also usually a good idea (but not |
1421 | descriptors to non-blocking mode is also usually a good idea (but not |
1062 | required if you know what you are doing). |
1422 | required if you know what you are doing). |
1063 | |
1423 | |
1064 | If you must do this, then force the use of a known-to-be-good backend |
1424 | If you cannot use non-blocking mode, then force the use of a |
1065 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1425 | known-to-be-good backend (at the time of this writing, this includes only |
1066 | C<EVBACKEND_POLL>). |
1426 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1427 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1428 | files) - libev doesn't guarentee any specific behaviour in that case. |
1067 | |
1429 | |
1068 | Another thing you have to watch out for is that it is quite easy to |
1430 | Another thing you have to watch out for is that it is quite easy to |
1069 | receive "spurious" readiness notifications, that is your callback might |
1431 | receive "spurious" readiness notifications, that is your callback might |
1070 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1432 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1071 | because there is no data. Not only are some backends known to create a |
1433 | because there is no data. Not only are some backends known to create a |
1072 | lot of those (for example Solaris ports), it is very easy to get into |
1434 | lot of those (for example Solaris ports), it is very easy to get into |
1073 | this situation even with a relatively standard program structure. Thus |
1435 | this situation even with a relatively standard program structure. Thus |
1074 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1436 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1075 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1437 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1076 | |
1438 | |
1077 | If you cannot run the fd in non-blocking mode (for example you should not |
1439 | If you cannot run the fd in non-blocking mode (for example you should |
1078 | play around with an Xlib connection), then you have to separately re-test |
1440 | not play around with an Xlib connection), then you have to separately |
1079 | whether a file descriptor is really ready with a known-to-be good interface |
1441 | re-test whether a file descriptor is really ready with a known-to-be good |
1080 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1442 | interface such as poll (fortunately in our Xlib example, Xlib already |
1081 | its own, so its quite safe to use). |
1443 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1444 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1445 | indefinitely. |
|
|
1446 | |
|
|
1447 | But really, best use non-blocking mode. |
1082 | |
1448 | |
1083 | =head3 The special problem of disappearing file descriptors |
1449 | =head3 The special problem of disappearing file descriptors |
1084 | |
1450 | |
1085 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1451 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1086 | descriptor (either by calling C<close> explicitly or by any other means, |
1452 | descriptor (either due to calling C<close> explicitly or any other means, |
1087 | such as C<dup>). The reason is that you register interest in some file |
1453 | such as C<dup2>). The reason is that you register interest in some file |
1088 | descriptor, but when it goes away, the operating system will silently drop |
1454 | descriptor, but when it goes away, the operating system will silently drop |
1089 | this interest. If another file descriptor with the same number then is |
1455 | this interest. If another file descriptor with the same number then is |
1090 | registered with libev, there is no efficient way to see that this is, in |
1456 | registered with libev, there is no efficient way to see that this is, in |
1091 | fact, a different file descriptor. |
1457 | fact, a different file descriptor. |
1092 | |
1458 | |
… | |
… | |
1123 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1489 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1124 | C<EVBACKEND_POLL>. |
1490 | C<EVBACKEND_POLL>. |
1125 | |
1491 | |
1126 | =head3 The special problem of SIGPIPE |
1492 | =head3 The special problem of SIGPIPE |
1127 | |
1493 | |
1128 | While not really specific to libev, it is easy to forget about SIGPIPE: |
1494 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1129 | when reading from a pipe whose other end has been closed, your program |
1495 | when writing to a pipe whose other end has been closed, your program gets |
1130 | gets send a SIGPIPE, which, by default, aborts your program. For most |
1496 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
1131 | programs this is sensible behaviour, for daemons, this is usually |
1497 | this is sensible behaviour, for daemons, this is usually undesirable. |
1132 | undesirable. |
|
|
1133 | |
1498 | |
1134 | So when you encounter spurious, unexplained daemon exits, make sure you |
1499 | So when you encounter spurious, unexplained daemon exits, make sure you |
1135 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1500 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1136 | somewhere, as that would have given you a big clue). |
1501 | somewhere, as that would have given you a big clue). |
1137 | |
1502 | |
… | |
… | |
1143 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1508 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1144 | |
1509 | |
1145 | =item ev_io_set (ev_io *, int fd, int events) |
1510 | =item ev_io_set (ev_io *, int fd, int events) |
1146 | |
1511 | |
1147 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1512 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1148 | receive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1513 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1149 | C<EV_READ | EV_WRITE> to receive the given events. |
1514 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1150 | |
1515 | |
1151 | =item int fd [read-only] |
1516 | =item int fd [read-only] |
1152 | |
1517 | |
1153 | The file descriptor being watched. |
1518 | The file descriptor being watched. |
1154 | |
1519 | |
… | |
… | |
1163 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1528 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1164 | readable, but only once. Since it is likely line-buffered, you could |
1529 | readable, but only once. Since it is likely line-buffered, you could |
1165 | attempt to read a whole line in the callback. |
1530 | attempt to read a whole line in the callback. |
1166 | |
1531 | |
1167 | static void |
1532 | static void |
1168 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1533 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1169 | { |
1534 | { |
1170 | ev_io_stop (loop, w); |
1535 | ev_io_stop (loop, w); |
1171 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1536 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1172 | } |
1537 | } |
1173 | |
1538 | |
1174 | ... |
1539 | ... |
1175 | struct ev_loop *loop = ev_default_init (0); |
1540 | struct ev_loop *loop = ev_default_init (0); |
1176 | struct ev_io stdin_readable; |
1541 | ev_io stdin_readable; |
1177 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1542 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1178 | ev_io_start (loop, &stdin_readable); |
1543 | ev_io_start (loop, &stdin_readable); |
1179 | ev_loop (loop, 0); |
1544 | ev_loop (loop, 0); |
1180 | |
1545 | |
1181 | |
1546 | |
… | |
… | |
1184 | Timer watchers are simple relative timers that generate an event after a |
1549 | Timer watchers are simple relative timers that generate an event after a |
1185 | given time, and optionally repeating in regular intervals after that. |
1550 | given time, and optionally repeating in regular intervals after that. |
1186 | |
1551 | |
1187 | The timers are based on real time, that is, if you register an event that |
1552 | The timers are based on real time, that is, if you register an event that |
1188 | times out after an hour and you reset your system clock to January last |
1553 | times out after an hour and you reset your system clock to January last |
1189 | year, it will still time out after (roughly) and hour. "Roughly" because |
1554 | year, it will still time out after (roughly) one hour. "Roughly" because |
1190 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1555 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1191 | monotonic clock option helps a lot here). |
1556 | monotonic clock option helps a lot here). |
|
|
1557 | |
|
|
1558 | The callback is guaranteed to be invoked only I<after> its timeout has |
|
|
1559 | passed (not I<at>, so on systems with very low-resolution clocks this |
|
|
1560 | might introduce a small delay). If multiple timers become ready during the |
|
|
1561 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1562 | before ones of the same priority with later time-out values (but this is |
|
|
1563 | no longer true when a callback calls C<ev_loop> recursively). |
|
|
1564 | |
|
|
1565 | =head3 Be smart about timeouts |
|
|
1566 | |
|
|
1567 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1568 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1569 | you want to raise some error after a while. |
|
|
1570 | |
|
|
1571 | What follows are some ways to handle this problem, from obvious and |
|
|
1572 | inefficient to smart and efficient. |
|
|
1573 | |
|
|
1574 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1575 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1576 | data or other life sign was received). |
|
|
1577 | |
|
|
1578 | =over 4 |
|
|
1579 | |
|
|
1580 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1581 | |
|
|
1582 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1583 | start the watcher: |
|
|
1584 | |
|
|
1585 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1586 | ev_timer_start (loop, timer); |
|
|
1587 | |
|
|
1588 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1589 | and start it again: |
|
|
1590 | |
|
|
1591 | ev_timer_stop (loop, timer); |
|
|
1592 | ev_timer_set (timer, 60., 0.); |
|
|
1593 | ev_timer_start (loop, timer); |
|
|
1594 | |
|
|
1595 | This is relatively simple to implement, but means that each time there is |
|
|
1596 | some activity, libev will first have to remove the timer from its internal |
|
|
1597 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1598 | still not a constant-time operation. |
|
|
1599 | |
|
|
1600 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1601 | |
|
|
1602 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1603 | C<ev_timer_start>. |
|
|
1604 | |
|
|
1605 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1606 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1607 | successfully read or write some data. If you go into an idle state where |
|
|
1608 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1609 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1610 | |
|
|
1611 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1612 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1613 | member and C<ev_timer_again>. |
|
|
1614 | |
|
|
1615 | At start: |
|
|
1616 | |
|
|
1617 | ev_init (timer, callback); |
|
|
1618 | timer->repeat = 60.; |
|
|
1619 | ev_timer_again (loop, timer); |
|
|
1620 | |
|
|
1621 | Each time there is some activity: |
|
|
1622 | |
|
|
1623 | ev_timer_again (loop, timer); |
|
|
1624 | |
|
|
1625 | It is even possible to change the time-out on the fly, regardless of |
|
|
1626 | whether the watcher is active or not: |
|
|
1627 | |
|
|
1628 | timer->repeat = 30.; |
|
|
1629 | ev_timer_again (loop, timer); |
|
|
1630 | |
|
|
1631 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1632 | you want to modify its timeout value, as libev does not have to completely |
|
|
1633 | remove and re-insert the timer from/into its internal data structure. |
|
|
1634 | |
|
|
1635 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1636 | |
|
|
1637 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1638 | |
|
|
1639 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1640 | relatively long compared to the intervals between other activity - in |
|
|
1641 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1642 | associated activity resets. |
|
|
1643 | |
|
|
1644 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1645 | but remember the time of last activity, and check for a real timeout only |
|
|
1646 | within the callback: |
|
|
1647 | |
|
|
1648 | ev_tstamp last_activity; // time of last activity |
|
|
1649 | |
|
|
1650 | static void |
|
|
1651 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1652 | { |
|
|
1653 | ev_tstamp now = ev_now (EV_A); |
|
|
1654 | ev_tstamp timeout = last_activity + 60.; |
|
|
1655 | |
|
|
1656 | // if last_activity + 60. is older than now, we did time out |
|
|
1657 | if (timeout < now) |
|
|
1658 | { |
|
|
1659 | // timeout occured, take action |
|
|
1660 | } |
|
|
1661 | else |
|
|
1662 | { |
|
|
1663 | // callback was invoked, but there was some activity, re-arm |
|
|
1664 | // the watcher to fire in last_activity + 60, which is |
|
|
1665 | // guaranteed to be in the future, so "again" is positive: |
|
|
1666 | w->repeat = timeout - now; |
|
|
1667 | ev_timer_again (EV_A_ w); |
|
|
1668 | } |
|
|
1669 | } |
|
|
1670 | |
|
|
1671 | To summarise the callback: first calculate the real timeout (defined |
|
|
1672 | as "60 seconds after the last activity"), then check if that time has |
|
|
1673 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1674 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1675 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1676 | a timeout then. |
|
|
1677 | |
|
|
1678 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1679 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1680 | |
|
|
1681 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1682 | minus half the average time between activity), but virtually no calls to |
|
|
1683 | libev to change the timeout. |
|
|
1684 | |
|
|
1685 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1686 | to the current time (meaning we just have some activity :), then call the |
|
|
1687 | callback, which will "do the right thing" and start the timer: |
|
|
1688 | |
|
|
1689 | ev_init (timer, callback); |
|
|
1690 | last_activity = ev_now (loop); |
|
|
1691 | callback (loop, timer, EV_TIMEOUT); |
|
|
1692 | |
|
|
1693 | And when there is some activity, simply store the current time in |
|
|
1694 | C<last_activity>, no libev calls at all: |
|
|
1695 | |
|
|
1696 | last_actiivty = ev_now (loop); |
|
|
1697 | |
|
|
1698 | This technique is slightly more complex, but in most cases where the |
|
|
1699 | time-out is unlikely to be triggered, much more efficient. |
|
|
1700 | |
|
|
1701 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1702 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1703 | fix things for you. |
|
|
1704 | |
|
|
1705 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1706 | |
|
|
1707 | If there is not one request, but many thousands (millions...), all |
|
|
1708 | employing some kind of timeout with the same timeout value, then one can |
|
|
1709 | do even better: |
|
|
1710 | |
|
|
1711 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1712 | at the I<end> of the list. |
|
|
1713 | |
|
|
1714 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1715 | the list is expected to fire (for example, using the technique #3). |
|
|
1716 | |
|
|
1717 | When there is some activity, remove the timer from the list, recalculate |
|
|
1718 | the timeout, append it to the end of the list again, and make sure to |
|
|
1719 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1720 | |
|
|
1721 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1722 | starting, stopping and updating the timers, at the expense of a major |
|
|
1723 | complication, and having to use a constant timeout. The constant timeout |
|
|
1724 | ensures that the list stays sorted. |
|
|
1725 | |
|
|
1726 | =back |
|
|
1727 | |
|
|
1728 | So which method the best? |
|
|
1729 | |
|
|
1730 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1731 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1732 | better, and isn't very complicated either. In most case, choosing either |
|
|
1733 | one is fine, with #3 being better in typical situations. |
|
|
1734 | |
|
|
1735 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1736 | rather complicated, but extremely efficient, something that really pays |
|
|
1737 | off after the first million or so of active timers, i.e. it's usually |
|
|
1738 | overkill :) |
|
|
1739 | |
|
|
1740 | =head3 The special problem of time updates |
|
|
1741 | |
|
|
1742 | Establishing the current time is a costly operation (it usually takes at |
|
|
1743 | least two system calls): EV therefore updates its idea of the current |
|
|
1744 | time only before and after C<ev_loop> collects new events, which causes a |
|
|
1745 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
1746 | lots of events in one iteration. |
1192 | |
1747 | |
1193 | The relative timeouts are calculated relative to the C<ev_now ()> |
1748 | The relative timeouts are calculated relative to the C<ev_now ()> |
1194 | time. This is usually the right thing as this timestamp refers to the time |
1749 | time. This is usually the right thing as this timestamp refers to the time |
1195 | of the event triggering whatever timeout you are modifying/starting. If |
1750 | of the event triggering whatever timeout you are modifying/starting. If |
1196 | you suspect event processing to be delayed and you I<need> to base the timeout |
1751 | you suspect event processing to be delayed and you I<need> to base the |
1197 | on the current time, use something like this to adjust for this: |
1752 | timeout on the current time, use something like this to adjust for this: |
1198 | |
1753 | |
1199 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1754 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1200 | |
1755 | |
1201 | The callback is guaranteed to be invoked only after its timeout has passed, |
1756 | If the event loop is suspended for a long time, you can also force an |
1202 | but if multiple timers become ready during the same loop iteration then |
1757 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1203 | order of execution is undefined. |
1758 | ()>. |
1204 | |
1759 | |
1205 | =head3 Watcher-Specific Functions and Data Members |
1760 | =head3 Watcher-Specific Functions and Data Members |
1206 | |
1761 | |
1207 | =over 4 |
1762 | =over 4 |
1208 | |
1763 | |
… | |
… | |
1232 | If the timer is started but non-repeating, stop it (as if it timed out). |
1787 | If the timer is started but non-repeating, stop it (as if it timed out). |
1233 | |
1788 | |
1234 | If the timer is repeating, either start it if necessary (with the |
1789 | If the timer is repeating, either start it if necessary (with the |
1235 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1790 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1236 | |
1791 | |
1237 | This sounds a bit complicated, but here is a useful and typical |
1792 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1238 | example: Imagine you have a TCP connection and you want a so-called idle |
1793 | usage example. |
1239 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1240 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1241 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1242 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1243 | you go into an idle state where you do not expect data to travel on the |
|
|
1244 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1245 | automatically restart it if need be. |
|
|
1246 | |
|
|
1247 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1248 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1249 | |
|
|
1250 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1251 | ev_timer_again (loop, timer); |
|
|
1252 | ... |
|
|
1253 | timer->again = 17.; |
|
|
1254 | ev_timer_again (loop, timer); |
|
|
1255 | ... |
|
|
1256 | timer->again = 10.; |
|
|
1257 | ev_timer_again (loop, timer); |
|
|
1258 | |
|
|
1259 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1260 | you want to modify its timeout value. |
|
|
1261 | |
1794 | |
1262 | =item ev_tstamp repeat [read-write] |
1795 | =item ev_tstamp repeat [read-write] |
1263 | |
1796 | |
1264 | The current C<repeat> value. Will be used each time the watcher times out |
1797 | The current C<repeat> value. Will be used each time the watcher times out |
1265 | or C<ev_timer_again> is called and determines the next timeout (if any), |
1798 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1266 | which is also when any modifications are taken into account. |
1799 | which is also when any modifications are taken into account. |
1267 | |
1800 | |
1268 | =back |
1801 | =back |
1269 | |
1802 | |
1270 | =head3 Examples |
1803 | =head3 Examples |
1271 | |
1804 | |
1272 | Example: Create a timer that fires after 60 seconds. |
1805 | Example: Create a timer that fires after 60 seconds. |
1273 | |
1806 | |
1274 | static void |
1807 | static void |
1275 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1808 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1276 | { |
1809 | { |
1277 | .. one minute over, w is actually stopped right here |
1810 | .. one minute over, w is actually stopped right here |
1278 | } |
1811 | } |
1279 | |
1812 | |
1280 | struct ev_timer mytimer; |
1813 | ev_timer mytimer; |
1281 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1814 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1282 | ev_timer_start (loop, &mytimer); |
1815 | ev_timer_start (loop, &mytimer); |
1283 | |
1816 | |
1284 | Example: Create a timeout timer that times out after 10 seconds of |
1817 | Example: Create a timeout timer that times out after 10 seconds of |
1285 | inactivity. |
1818 | inactivity. |
1286 | |
1819 | |
1287 | static void |
1820 | static void |
1288 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1821 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1289 | { |
1822 | { |
1290 | .. ten seconds without any activity |
1823 | .. ten seconds without any activity |
1291 | } |
1824 | } |
1292 | |
1825 | |
1293 | struct ev_timer mytimer; |
1826 | ev_timer mytimer; |
1294 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1827 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1295 | ev_timer_again (&mytimer); /* start timer */ |
1828 | ev_timer_again (&mytimer); /* start timer */ |
1296 | ev_loop (loop, 0); |
1829 | ev_loop (loop, 0); |
1297 | |
1830 | |
1298 | // and in some piece of code that gets executed on any "activity": |
1831 | // and in some piece of code that gets executed on any "activity": |
… | |
… | |
1303 | =head2 C<ev_periodic> - to cron or not to cron? |
1836 | =head2 C<ev_periodic> - to cron or not to cron? |
1304 | |
1837 | |
1305 | Periodic watchers are also timers of a kind, but they are very versatile |
1838 | Periodic watchers are also timers of a kind, but they are very versatile |
1306 | (and unfortunately a bit complex). |
1839 | (and unfortunately a bit complex). |
1307 | |
1840 | |
1308 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1841 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1309 | but on wall clock time (absolute time). You can tell a periodic watcher |
1842 | relative time, the physical time that passes) but on wall clock time |
1310 | to trigger after some specific point in time. For example, if you tell a |
1843 | (absolute time, the thing you can read on your calender or clock). The |
1311 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1844 | difference is that wall clock time can run faster or slower than real |
1312 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1845 | time, and time jumps are not uncommon (e.g. when you adjust your |
1313 | clock to January of the previous year, then it will take more than year |
1846 | wrist-watch). |
1314 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1315 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1316 | |
1847 | |
|
|
1848 | You can tell a periodic watcher to trigger after some specific point |
|
|
1849 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1850 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1851 | not a delay) and then reset your system clock to January of the previous |
|
|
1852 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1853 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1854 | it, as it uses a relative timeout). |
|
|
1855 | |
1317 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1856 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1318 | such as triggering an event on each "midnight, local time", or other |
1857 | timers, such as triggering an event on each "midnight, local time", or |
1319 | complicated, rules. |
1858 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1859 | those cannot react to time jumps. |
1320 | |
1860 | |
1321 | As with timers, the callback is guaranteed to be invoked only when the |
1861 | As with timers, the callback is guaranteed to be invoked only when the |
1322 | time (C<at>) has passed, but if multiple periodic timers become ready |
1862 | point in time where it is supposed to trigger has passed. If multiple |
1323 | during the same loop iteration then order of execution is undefined. |
1863 | timers become ready during the same loop iteration then the ones with |
|
|
1864 | earlier time-out values are invoked before ones with later time-out values |
|
|
1865 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1324 | |
1866 | |
1325 | =head3 Watcher-Specific Functions and Data Members |
1867 | =head3 Watcher-Specific Functions and Data Members |
1326 | |
1868 | |
1327 | =over 4 |
1869 | =over 4 |
1328 | |
1870 | |
1329 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1871 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1330 | |
1872 | |
1331 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1873 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1332 | |
1874 | |
1333 | Lots of arguments, lets sort it out... There are basically three modes of |
1875 | Lots of arguments, let's sort it out... There are basically three modes of |
1334 | operation, and we will explain them from simplest to complex: |
1876 | operation, and we will explain them from simplest to most complex: |
1335 | |
1877 | |
1336 | =over 4 |
1878 | =over 4 |
1337 | |
1879 | |
1338 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1880 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1339 | |
1881 | |
1340 | In this configuration the watcher triggers an event after the wall clock |
1882 | In this configuration the watcher triggers an event after the wall clock |
1341 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
1883 | time C<offset> has passed. It will not repeat and will not adjust when a |
1342 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1884 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1343 | run when the system time reaches or surpasses this time. |
1885 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1886 | this point in time. |
1344 | |
1887 | |
1345 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1888 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1346 | |
1889 | |
1347 | In this mode the watcher will always be scheduled to time out at the next |
1890 | In this mode the watcher will always be scheduled to time out at the next |
1348 | C<at + N * interval> time (for some integer N, which can also be negative) |
1891 | C<offset + N * interval> time (for some integer N, which can also be |
1349 | and then repeat, regardless of any time jumps. |
1892 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1893 | argument is merely an offset into the C<interval> periods. |
1350 | |
1894 | |
1351 | This can be used to create timers that do not drift with respect to system |
1895 | This can be used to create timers that do not drift with respect to the |
1352 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
1896 | system clock, for example, here is an C<ev_periodic> that triggers each |
1353 | the hour: |
1897 | hour, on the hour (with respect to UTC): |
1354 | |
1898 | |
1355 | ev_periodic_set (&periodic, 0., 3600., 0); |
1899 | ev_periodic_set (&periodic, 0., 3600., 0); |
1356 | |
1900 | |
1357 | This doesn't mean there will always be 3600 seconds in between triggers, |
1901 | This doesn't mean there will always be 3600 seconds in between triggers, |
1358 | but only that the callback will be called when the system time shows a |
1902 | but only that the callback will be called when the system time shows a |
1359 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1903 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1360 | by 3600. |
1904 | by 3600. |
1361 | |
1905 | |
1362 | Another way to think about it (for the mathematically inclined) is that |
1906 | Another way to think about it (for the mathematically inclined) is that |
1363 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1907 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1364 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1908 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1365 | |
1909 | |
1366 | For numerical stability it is preferable that the C<at> value is near |
1910 | For numerical stability it is preferable that the C<offset> value is near |
1367 | C<ev_now ()> (the current time), but there is no range requirement for |
1911 | C<ev_now ()> (the current time), but there is no range requirement for |
1368 | this value, and in fact is often specified as zero. |
1912 | this value, and in fact is often specified as zero. |
1369 | |
1913 | |
1370 | Note also that there is an upper limit to how often a timer can fire (CPU |
1914 | Note also that there is an upper limit to how often a timer can fire (CPU |
1371 | speed for example), so if C<interval> is very small then timing stability |
1915 | speed for example), so if C<interval> is very small then timing stability |
1372 | will of course deteriorate. Libev itself tries to be exact to be about one |
1916 | will of course deteriorate. Libev itself tries to be exact to be about one |
1373 | millisecond (if the OS supports it and the machine is fast enough). |
1917 | millisecond (if the OS supports it and the machine is fast enough). |
1374 | |
1918 | |
1375 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1919 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1376 | |
1920 | |
1377 | In this mode the values for C<interval> and C<at> are both being |
1921 | In this mode the values for C<interval> and C<offset> are both being |
1378 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1922 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1379 | reschedule callback will be called with the watcher as first, and the |
1923 | reschedule callback will be called with the watcher as first, and the |
1380 | current time as second argument. |
1924 | current time as second argument. |
1381 | |
1925 | |
1382 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1926 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1383 | ever, or make ANY event loop modifications whatsoever>. |
1927 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1928 | allowed by documentation here>. |
1384 | |
1929 | |
1385 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1930 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1386 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1931 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1387 | only event loop modification you are allowed to do). |
1932 | only event loop modification you are allowed to do). |
1388 | |
1933 | |
1389 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1934 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1390 | *w, ev_tstamp now)>, e.g.: |
1935 | *w, ev_tstamp now)>, e.g.: |
1391 | |
1936 | |
|
|
1937 | static ev_tstamp |
1392 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1938 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1393 | { |
1939 | { |
1394 | return now + 60.; |
1940 | return now + 60.; |
1395 | } |
1941 | } |
1396 | |
1942 | |
1397 | It must return the next time to trigger, based on the passed time value |
1943 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1417 | a different time than the last time it was called (e.g. in a crond like |
1963 | a different time than the last time it was called (e.g. in a crond like |
1418 | program when the crontabs have changed). |
1964 | program when the crontabs have changed). |
1419 | |
1965 | |
1420 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1966 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1421 | |
1967 | |
1422 | When active, returns the absolute time that the watcher is supposed to |
1968 | When active, returns the absolute time that the watcher is supposed |
1423 | trigger next. |
1969 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1970 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1971 | rescheduling modes. |
1424 | |
1972 | |
1425 | =item ev_tstamp offset [read-write] |
1973 | =item ev_tstamp offset [read-write] |
1426 | |
1974 | |
1427 | When repeating, this contains the offset value, otherwise this is the |
1975 | When repeating, this contains the offset value, otherwise this is the |
1428 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1976 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1977 | although libev might modify this value for better numerical stability). |
1429 | |
1978 | |
1430 | Can be modified any time, but changes only take effect when the periodic |
1979 | Can be modified any time, but changes only take effect when the periodic |
1431 | timer fires or C<ev_periodic_again> is being called. |
1980 | timer fires or C<ev_periodic_again> is being called. |
1432 | |
1981 | |
1433 | =item ev_tstamp interval [read-write] |
1982 | =item ev_tstamp interval [read-write] |
1434 | |
1983 | |
1435 | The current interval value. Can be modified any time, but changes only |
1984 | The current interval value. Can be modified any time, but changes only |
1436 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1985 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1437 | called. |
1986 | called. |
1438 | |
1987 | |
1439 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1988 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1440 | |
1989 | |
1441 | The current reschedule callback, or C<0>, if this functionality is |
1990 | The current reschedule callback, or C<0>, if this functionality is |
1442 | switched off. Can be changed any time, but changes only take effect when |
1991 | switched off. Can be changed any time, but changes only take effect when |
1443 | the periodic timer fires or C<ev_periodic_again> is being called. |
1992 | the periodic timer fires or C<ev_periodic_again> is being called. |
1444 | |
1993 | |
1445 | =back |
1994 | =back |
1446 | |
1995 | |
1447 | =head3 Examples |
1996 | =head3 Examples |
1448 | |
1997 | |
1449 | Example: Call a callback every hour, or, more precisely, whenever the |
1998 | Example: Call a callback every hour, or, more precisely, whenever the |
1450 | system clock is divisible by 3600. The callback invocation times have |
1999 | system time is divisible by 3600. The callback invocation times have |
1451 | potentially a lot of jitter, but good long-term stability. |
2000 | potentially a lot of jitter, but good long-term stability. |
1452 | |
2001 | |
1453 | static void |
2002 | static void |
1454 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2003 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1455 | { |
2004 | { |
1456 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2005 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1457 | } |
2006 | } |
1458 | |
2007 | |
1459 | struct ev_periodic hourly_tick; |
2008 | ev_periodic hourly_tick; |
1460 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2009 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1461 | ev_periodic_start (loop, &hourly_tick); |
2010 | ev_periodic_start (loop, &hourly_tick); |
1462 | |
2011 | |
1463 | Example: The same as above, but use a reschedule callback to do it: |
2012 | Example: The same as above, but use a reschedule callback to do it: |
1464 | |
2013 | |
1465 | #include <math.h> |
2014 | #include <math.h> |
1466 | |
2015 | |
1467 | static ev_tstamp |
2016 | static ev_tstamp |
1468 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2017 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1469 | { |
2018 | { |
1470 | return fmod (now, 3600.) + 3600.; |
2019 | return now + (3600. - fmod (now, 3600.)); |
1471 | } |
2020 | } |
1472 | |
2021 | |
1473 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2022 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1474 | |
2023 | |
1475 | Example: Call a callback every hour, starting now: |
2024 | Example: Call a callback every hour, starting now: |
1476 | |
2025 | |
1477 | struct ev_periodic hourly_tick; |
2026 | ev_periodic hourly_tick; |
1478 | ev_periodic_init (&hourly_tick, clock_cb, |
2027 | ev_periodic_init (&hourly_tick, clock_cb, |
1479 | fmod (ev_now (loop), 3600.), 3600., 0); |
2028 | fmod (ev_now (loop), 3600.), 3600., 0); |
1480 | ev_periodic_start (loop, &hourly_tick); |
2029 | ev_periodic_start (loop, &hourly_tick); |
1481 | |
2030 | |
1482 | |
2031 | |
… | |
… | |
1485 | Signal watchers will trigger an event when the process receives a specific |
2034 | Signal watchers will trigger an event when the process receives a specific |
1486 | signal one or more times. Even though signals are very asynchronous, libev |
2035 | signal one or more times. Even though signals are very asynchronous, libev |
1487 | will try it's best to deliver signals synchronously, i.e. as part of the |
2036 | will try it's best to deliver signals synchronously, i.e. as part of the |
1488 | normal event processing, like any other event. |
2037 | normal event processing, like any other event. |
1489 | |
2038 | |
|
|
2039 | If you want signals asynchronously, just use C<sigaction> as you would |
|
|
2040 | do without libev and forget about sharing the signal. You can even use |
|
|
2041 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
|
|
2042 | |
1490 | You can configure as many watchers as you like per signal. Only when the |
2043 | You can configure as many watchers as you like per signal. Only when the |
1491 | first watcher gets started will libev actually register a signal watcher |
2044 | first watcher gets started will libev actually register a signal handler |
1492 | with the kernel (thus it coexists with your own signal handlers as long |
2045 | with the kernel (thus it coexists with your own signal handlers as long as |
1493 | as you don't register any with libev). Similarly, when the last signal |
2046 | you don't register any with libev for the same signal). Similarly, when |
1494 | watcher for a signal is stopped libev will reset the signal handler to |
2047 | the last signal watcher for a signal is stopped, libev will reset the |
1495 | SIG_DFL (regardless of what it was set to before). |
2048 | signal handler to SIG_DFL (regardless of what it was set to before). |
1496 | |
2049 | |
1497 | If possible and supported, libev will install its handlers with |
2050 | If possible and supported, libev will install its handlers with |
1498 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2051 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
1499 | interrupted. If you have a problem with system calls getting interrupted by |
2052 | interrupted. If you have a problem with system calls getting interrupted by |
1500 | signals you can block all signals in an C<ev_check> watcher and unblock |
2053 | signals you can block all signals in an C<ev_check> watcher and unblock |
… | |
… | |
1517 | |
2070 | |
1518 | =back |
2071 | =back |
1519 | |
2072 | |
1520 | =head3 Examples |
2073 | =head3 Examples |
1521 | |
2074 | |
1522 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2075 | Example: Try to exit cleanly on SIGINT. |
1523 | |
2076 | |
1524 | static void |
2077 | static void |
1525 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2078 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1526 | { |
2079 | { |
1527 | ev_unloop (loop, EVUNLOOP_ALL); |
2080 | ev_unloop (loop, EVUNLOOP_ALL); |
1528 | } |
2081 | } |
1529 | |
2082 | |
1530 | struct ev_signal signal_watcher; |
2083 | ev_signal signal_watcher; |
1531 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2084 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1532 | ev_signal_start (loop, &sigint_cb); |
2085 | ev_signal_start (loop, &signal_watcher); |
1533 | |
2086 | |
1534 | |
2087 | |
1535 | =head2 C<ev_child> - watch out for process status changes |
2088 | =head2 C<ev_child> - watch out for process status changes |
1536 | |
2089 | |
1537 | Child watchers trigger when your process receives a SIGCHLD in response to |
2090 | Child watchers trigger when your process receives a SIGCHLD in response to |
1538 | some child status changes (most typically when a child of yours dies). It |
2091 | some child status changes (most typically when a child of yours dies or |
1539 | is permissible to install a child watcher I<after> the child has been |
2092 | exits). It is permissible to install a child watcher I<after> the child |
1540 | forked (which implies it might have already exited), as long as the event |
2093 | has been forked (which implies it might have already exited), as long |
1541 | loop isn't entered (or is continued from a watcher). |
2094 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2095 | forking and then immediately registering a watcher for the child is fine, |
|
|
2096 | but forking and registering a watcher a few event loop iterations later or |
|
|
2097 | in the next callback invocation is not. |
1542 | |
2098 | |
1543 | Only the default event loop is capable of handling signals, and therefore |
2099 | Only the default event loop is capable of handling signals, and therefore |
1544 | you can only register child watchers in the default event loop. |
2100 | you can only register child watchers in the default event loop. |
|
|
2101 | |
|
|
2102 | Due to some design glitches inside libev, child watchers will always be |
|
|
2103 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2104 | libev) |
1545 | |
2105 | |
1546 | =head3 Process Interaction |
2106 | =head3 Process Interaction |
1547 | |
2107 | |
1548 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2108 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1549 | initialised. This is necessary to guarantee proper behaviour even if |
2109 | initialised. This is necessary to guarantee proper behaviour even if |
… | |
… | |
1559 | handler, you can override it easily by installing your own handler for |
2119 | handler, you can override it easily by installing your own handler for |
1560 | C<SIGCHLD> after initialising the default loop, and making sure the |
2120 | C<SIGCHLD> after initialising the default loop, and making sure the |
1561 | default loop never gets destroyed. You are encouraged, however, to use an |
2121 | default loop never gets destroyed. You are encouraged, however, to use an |
1562 | event-based approach to child reaping and thus use libev's support for |
2122 | event-based approach to child reaping and thus use libev's support for |
1563 | that, so other libev users can use C<ev_child> watchers freely. |
2123 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
2124 | |
|
|
2125 | =head3 Stopping the Child Watcher |
|
|
2126 | |
|
|
2127 | Currently, the child watcher never gets stopped, even when the |
|
|
2128 | child terminates, so normally one needs to stop the watcher in the |
|
|
2129 | callback. Future versions of libev might stop the watcher automatically |
|
|
2130 | when a child exit is detected. |
1564 | |
2131 | |
1565 | =head3 Watcher-Specific Functions and Data Members |
2132 | =head3 Watcher-Specific Functions and Data Members |
1566 | |
2133 | |
1567 | =over 4 |
2134 | =over 4 |
1568 | |
2135 | |
… | |
… | |
1600 | its completion. |
2167 | its completion. |
1601 | |
2168 | |
1602 | ev_child cw; |
2169 | ev_child cw; |
1603 | |
2170 | |
1604 | static void |
2171 | static void |
1605 | child_cb (EV_P_ struct ev_child *w, int revents) |
2172 | child_cb (EV_P_ ev_child *w, int revents) |
1606 | { |
2173 | { |
1607 | ev_child_stop (EV_A_ w); |
2174 | ev_child_stop (EV_A_ w); |
1608 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2175 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1609 | } |
2176 | } |
1610 | |
2177 | |
… | |
… | |
1625 | |
2192 | |
1626 | |
2193 | |
1627 | =head2 C<ev_stat> - did the file attributes just change? |
2194 | =head2 C<ev_stat> - did the file attributes just change? |
1628 | |
2195 | |
1629 | This watches a file system path for attribute changes. That is, it calls |
2196 | This watches a file system path for attribute changes. That is, it calls |
1630 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2197 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1631 | compared to the last time, invoking the callback if it did. |
2198 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2199 | it did. |
1632 | |
2200 | |
1633 | The path does not need to exist: changing from "path exists" to "path does |
2201 | The path does not need to exist: changing from "path exists" to "path does |
1634 | not exist" is a status change like any other. The condition "path does |
2202 | not exist" is a status change like any other. The condition "path does not |
1635 | not exist" is signified by the C<st_nlink> field being zero (which is |
2203 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1636 | otherwise always forced to be at least one) and all the other fields of |
2204 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1637 | the stat buffer having unspecified contents. |
2205 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2206 | contents. |
1638 | |
2207 | |
1639 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2208 | The path I<must not> end in a slash or contain special components such as |
|
|
2209 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1640 | relative and your working directory changes, the behaviour is undefined. |
2210 | your working directory changes, then the behaviour is undefined. |
1641 | |
2211 | |
1642 | Since there is no standard to do this, the portable implementation simply |
2212 | Since there is no portable change notification interface available, the |
1643 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
2213 | portable implementation simply calls C<stat(2)> regularly on the path |
1644 | can specify a recommended polling interval for this case. If you specify |
2214 | to see if it changed somehow. You can specify a recommended polling |
1645 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
2215 | interval for this case. If you specify a polling interval of C<0> (highly |
1646 | unspecified default> value will be used (which you can expect to be around |
2216 | recommended!) then a I<suitable, unspecified default> value will be used |
1647 | five seconds, although this might change dynamically). Libev will also |
2217 | (which you can expect to be around five seconds, although this might |
1648 | impose a minimum interval which is currently around C<0.1>, but thats |
2218 | change dynamically). Libev will also impose a minimum interval which is |
1649 | usually overkill. |
2219 | currently around C<0.1>, but that's usually overkill. |
1650 | |
2220 | |
1651 | This watcher type is not meant for massive numbers of stat watchers, |
2221 | This watcher type is not meant for massive numbers of stat watchers, |
1652 | as even with OS-supported change notifications, this can be |
2222 | as even with OS-supported change notifications, this can be |
1653 | resource-intensive. |
2223 | resource-intensive. |
1654 | |
2224 | |
1655 | At the time of this writing, only the Linux inotify interface is |
2225 | At the time of this writing, the only OS-specific interface implemented |
1656 | implemented (implementing kqueue support is left as an exercise for the |
2226 | is the Linux inotify interface (implementing kqueue support is left as an |
1657 | reader, note, however, that the author sees no way of implementing ev_stat |
2227 | exercise for the reader. Note, however, that the author sees no way of |
1658 | semantics with kqueue). Inotify will be used to give hints only and should |
2228 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1659 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1660 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1661 | but changes are usually detected immediately, and if the file exists there |
|
|
1662 | will be no polling. |
|
|
1663 | |
2229 | |
1664 | =head3 ABI Issues (Largefile Support) |
2230 | =head3 ABI Issues (Largefile Support) |
1665 | |
2231 | |
1666 | Libev by default (unless the user overrides this) uses the default |
2232 | Libev by default (unless the user overrides this) uses the default |
1667 | compilation environment, which means that on systems with large file |
2233 | compilation environment, which means that on systems with large file |
1668 | support disabled by default, you get the 32 bit version of the stat |
2234 | support disabled by default, you get the 32 bit version of the stat |
1669 | structure. When using the library from programs that change the ABI to |
2235 | structure. When using the library from programs that change the ABI to |
1670 | use 64 bit file offsets the programs will fail. In that case you have to |
2236 | use 64 bit file offsets the programs will fail. In that case you have to |
1671 | compile libev with the same flags to get binary compatibility. This is |
2237 | compile libev with the same flags to get binary compatibility. This is |
1672 | obviously the case with any flags that change the ABI, but the problem is |
2238 | obviously the case with any flags that change the ABI, but the problem is |
1673 | most noticeably disabled with ev_stat and large file support. |
2239 | most noticeably displayed with ev_stat and large file support. |
1674 | |
2240 | |
1675 | The solution for this is to lobby your distribution maker to make large |
2241 | The solution for this is to lobby your distribution maker to make large |
1676 | file interfaces available by default (as e.g. FreeBSD does) and not |
2242 | file interfaces available by default (as e.g. FreeBSD does) and not |
1677 | optional. Libev cannot simply switch on large file support because it has |
2243 | optional. Libev cannot simply switch on large file support because it has |
1678 | to exchange stat structures with application programs compiled using the |
2244 | to exchange stat structures with application programs compiled using the |
1679 | default compilation environment. |
2245 | default compilation environment. |
1680 | |
2246 | |
1681 | =head3 Inotify |
2247 | =head3 Inotify and Kqueue |
1682 | |
2248 | |
1683 | When C<inotify (7)> support has been compiled into libev (generally only |
2249 | When C<inotify (7)> support has been compiled into libev and present at |
1684 | available on Linux) and present at runtime, it will be used to speed up |
2250 | runtime, it will be used to speed up change detection where possible. The |
1685 | change detection where possible. The inotify descriptor will be created lazily |
2251 | inotify descriptor will be created lazily when the first C<ev_stat> |
1686 | when the first C<ev_stat> watcher is being started. |
2252 | watcher is being started. |
1687 | |
2253 | |
1688 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2254 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1689 | except that changes might be detected earlier, and in some cases, to avoid |
2255 | except that changes might be detected earlier, and in some cases, to avoid |
1690 | making regular C<stat> calls. Even in the presence of inotify support |
2256 | making regular C<stat> calls. Even in the presence of inotify support |
1691 | there are many cases where libev has to resort to regular C<stat> polling. |
2257 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2258 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2259 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2260 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2261 | xfs are fully working) libev usually gets away without polling. |
1692 | |
2262 | |
1693 | (There is no support for kqueue, as apparently it cannot be used to |
2263 | There is no support for kqueue, as apparently it cannot be used to |
1694 | implement this functionality, due to the requirement of having a file |
2264 | implement this functionality, due to the requirement of having a file |
1695 | descriptor open on the object at all times). |
2265 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2266 | etc. is difficult. |
|
|
2267 | |
|
|
2268 | =head3 C<stat ()> is a synchronous operation |
|
|
2269 | |
|
|
2270 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2271 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2272 | ()>, which is a synchronous operation. |
|
|
2273 | |
|
|
2274 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2275 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2276 | as the path data is usually in memory already (except when starting the |
|
|
2277 | watcher). |
|
|
2278 | |
|
|
2279 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2280 | time due to network issues, and even under good conditions, a stat call |
|
|
2281 | often takes multiple milliseconds. |
|
|
2282 | |
|
|
2283 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2284 | paths, although this is fully supported by libev. |
1696 | |
2285 | |
1697 | =head3 The special problem of stat time resolution |
2286 | =head3 The special problem of stat time resolution |
1698 | |
2287 | |
1699 | The C<stat ()> system call only supports full-second resolution portably, and |
2288 | The C<stat ()> system call only supports full-second resolution portably, |
1700 | even on systems where the resolution is higher, many file systems still |
2289 | and even on systems where the resolution is higher, most file systems |
1701 | only support whole seconds. |
2290 | still only support whole seconds. |
1702 | |
2291 | |
1703 | That means that, if the time is the only thing that changes, you can |
2292 | That means that, if the time is the only thing that changes, you can |
1704 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2293 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1705 | calls your callback, which does something. When there is another update |
2294 | calls your callback, which does something. When there is another update |
1706 | within the same second, C<ev_stat> will be unable to detect it as the stat |
2295 | within the same second, C<ev_stat> will be unable to detect unless the |
1707 | data does not change. |
2296 | stat data does change in other ways (e.g. file size). |
1708 | |
2297 | |
1709 | The solution to this is to delay acting on a change for slightly more |
2298 | The solution to this is to delay acting on a change for slightly more |
1710 | than a second (or till slightly after the next full second boundary), using |
2299 | than a second (or till slightly after the next full second boundary), using |
1711 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
2300 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1712 | ev_timer_again (loop, w)>). |
2301 | ev_timer_again (loop, w)>). |
… | |
… | |
1732 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2321 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1733 | be detected and should normally be specified as C<0> to let libev choose |
2322 | be detected and should normally be specified as C<0> to let libev choose |
1734 | a suitable value. The memory pointed to by C<path> must point to the same |
2323 | a suitable value. The memory pointed to by C<path> must point to the same |
1735 | path for as long as the watcher is active. |
2324 | path for as long as the watcher is active. |
1736 | |
2325 | |
1737 | The callback will receive C<EV_STAT> when a change was detected, relative |
2326 | The callback will receive an C<EV_STAT> event when a change was detected, |
1738 | to the attributes at the time the watcher was started (or the last change |
2327 | relative to the attributes at the time the watcher was started (or the |
1739 | was detected). |
2328 | last change was detected). |
1740 | |
2329 | |
1741 | =item ev_stat_stat (loop, ev_stat *) |
2330 | =item ev_stat_stat (loop, ev_stat *) |
1742 | |
2331 | |
1743 | Updates the stat buffer immediately with new values. If you change the |
2332 | Updates the stat buffer immediately with new values. If you change the |
1744 | watched path in your callback, you could call this function to avoid |
2333 | watched path in your callback, you could call this function to avoid |
… | |
… | |
1827 | |
2416 | |
1828 | |
2417 | |
1829 | =head2 C<ev_idle> - when you've got nothing better to do... |
2418 | =head2 C<ev_idle> - when you've got nothing better to do... |
1830 | |
2419 | |
1831 | Idle watchers trigger events when no other events of the same or higher |
2420 | Idle watchers trigger events when no other events of the same or higher |
1832 | priority are pending (prepare, check and other idle watchers do not |
2421 | priority are pending (prepare, check and other idle watchers do not count |
1833 | count). |
2422 | as receiving "events"). |
1834 | |
2423 | |
1835 | That is, as long as your process is busy handling sockets or timeouts |
2424 | That is, as long as your process is busy handling sockets or timeouts |
1836 | (or even signals, imagine) of the same or higher priority it will not be |
2425 | (or even signals, imagine) of the same or higher priority it will not be |
1837 | triggered. But when your process is idle (or only lower-priority watchers |
2426 | triggered. But when your process is idle (or only lower-priority watchers |
1838 | are pending), the idle watchers are being called once per event loop |
2427 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1849 | |
2438 | |
1850 | =head3 Watcher-Specific Functions and Data Members |
2439 | =head3 Watcher-Specific Functions and Data Members |
1851 | |
2440 | |
1852 | =over 4 |
2441 | =over 4 |
1853 | |
2442 | |
1854 | =item ev_idle_init (ev_signal *, callback) |
2443 | =item ev_idle_init (ev_idle *, callback) |
1855 | |
2444 | |
1856 | Initialises and configures the idle watcher - it has no parameters of any |
2445 | Initialises and configures the idle watcher - it has no parameters of any |
1857 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2446 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1858 | believe me. |
2447 | believe me. |
1859 | |
2448 | |
… | |
… | |
1863 | |
2452 | |
1864 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2453 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1865 | callback, free it. Also, use no error checking, as usual. |
2454 | callback, free it. Also, use no error checking, as usual. |
1866 | |
2455 | |
1867 | static void |
2456 | static void |
1868 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2457 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1869 | { |
2458 | { |
1870 | free (w); |
2459 | free (w); |
1871 | // now do something you wanted to do when the program has |
2460 | // now do something you wanted to do when the program has |
1872 | // no longer anything immediate to do. |
2461 | // no longer anything immediate to do. |
1873 | } |
2462 | } |
1874 | |
2463 | |
1875 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2464 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1876 | ev_idle_init (idle_watcher, idle_cb); |
2465 | ev_idle_init (idle_watcher, idle_cb); |
1877 | ev_idle_start (loop, idle_cb); |
2466 | ev_idle_start (loop, idle_watcher); |
1878 | |
2467 | |
1879 | |
2468 | |
1880 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2469 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1881 | |
2470 | |
1882 | Prepare and check watchers are usually (but not always) used in tandem: |
2471 | Prepare and check watchers are usually (but not always) used in pairs: |
1883 | prepare watchers get invoked before the process blocks and check watchers |
2472 | prepare watchers get invoked before the process blocks and check watchers |
1884 | afterwards. |
2473 | afterwards. |
1885 | |
2474 | |
1886 | You I<must not> call C<ev_loop> or similar functions that enter |
2475 | You I<must not> call C<ev_loop> or similar functions that enter |
1887 | the current event loop from either C<ev_prepare> or C<ev_check> |
2476 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
1890 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2479 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1891 | C<ev_check> so if you have one watcher of each kind they will always be |
2480 | C<ev_check> so if you have one watcher of each kind they will always be |
1892 | called in pairs bracketing the blocking call. |
2481 | called in pairs bracketing the blocking call. |
1893 | |
2482 | |
1894 | Their main purpose is to integrate other event mechanisms into libev and |
2483 | Their main purpose is to integrate other event mechanisms into libev and |
1895 | their use is somewhat advanced. This could be used, for example, to track |
2484 | their use is somewhat advanced. They could be used, for example, to track |
1896 | variable changes, implement your own watchers, integrate net-snmp or a |
2485 | variable changes, implement your own watchers, integrate net-snmp or a |
1897 | coroutine library and lots more. They are also occasionally useful if |
2486 | coroutine library and lots more. They are also occasionally useful if |
1898 | you cache some data and want to flush it before blocking (for example, |
2487 | you cache some data and want to flush it before blocking (for example, |
1899 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2488 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1900 | watcher). |
2489 | watcher). |
1901 | |
2490 | |
1902 | This is done by examining in each prepare call which file descriptors need |
2491 | This is done by examining in each prepare call which file descriptors |
1903 | to be watched by the other library, registering C<ev_io> watchers for |
2492 | need to be watched by the other library, registering C<ev_io> watchers |
1904 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2493 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1905 | provide just this functionality). Then, in the check watcher you check for |
2494 | libraries provide exactly this functionality). Then, in the check watcher, |
1906 | any events that occurred (by checking the pending status of all watchers |
2495 | you check for any events that occurred (by checking the pending status |
1907 | and stopping them) and call back into the library. The I/O and timer |
2496 | of all watchers and stopping them) and call back into the library. The |
1908 | callbacks will never actually be called (but must be valid nevertheless, |
2497 | I/O and timer callbacks will never actually be called (but must be valid |
1909 | because you never know, you know?). |
2498 | nevertheless, because you never know, you know?). |
1910 | |
2499 | |
1911 | As another example, the Perl Coro module uses these hooks to integrate |
2500 | As another example, the Perl Coro module uses these hooks to integrate |
1912 | coroutines into libev programs, by yielding to other active coroutines |
2501 | coroutines into libev programs, by yielding to other active coroutines |
1913 | during each prepare and only letting the process block if no coroutines |
2502 | during each prepare and only letting the process block if no coroutines |
1914 | are ready to run (it's actually more complicated: it only runs coroutines |
2503 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
1917 | loop from blocking if lower-priority coroutines are active, thus mapping |
2506 | loop from blocking if lower-priority coroutines are active, thus mapping |
1918 | low-priority coroutines to idle/background tasks). |
2507 | low-priority coroutines to idle/background tasks). |
1919 | |
2508 | |
1920 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2509 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1921 | priority, to ensure that they are being run before any other watchers |
2510 | priority, to ensure that they are being run before any other watchers |
|
|
2511 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2512 | |
1922 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2513 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1923 | too) should not activate ("feed") events into libev. While libev fully |
2514 | activate ("feed") events into libev. While libev fully supports this, they |
1924 | supports this, they might get executed before other C<ev_check> watchers |
2515 | might get executed before other C<ev_check> watchers did their job. As |
1925 | did their job. As C<ev_check> watchers are often used to embed other |
2516 | C<ev_check> watchers are often used to embed other (non-libev) event |
1926 | (non-libev) event loops those other event loops might be in an unusable |
2517 | loops those other event loops might be in an unusable state until their |
1927 | state until their C<ev_check> watcher ran (always remind yourself to |
2518 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1928 | coexist peacefully with others). |
2519 | others). |
1929 | |
2520 | |
1930 | =head3 Watcher-Specific Functions and Data Members |
2521 | =head3 Watcher-Specific Functions and Data Members |
1931 | |
2522 | |
1932 | =over 4 |
2523 | =over 4 |
1933 | |
2524 | |
… | |
… | |
1935 | |
2526 | |
1936 | =item ev_check_init (ev_check *, callback) |
2527 | =item ev_check_init (ev_check *, callback) |
1937 | |
2528 | |
1938 | Initialises and configures the prepare or check watcher - they have no |
2529 | Initialises and configures the prepare or check watcher - they have no |
1939 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2530 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1940 | macros, but using them is utterly, utterly and completely pointless. |
2531 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2532 | pointless. |
1941 | |
2533 | |
1942 | =back |
2534 | =back |
1943 | |
2535 | |
1944 | =head3 Examples |
2536 | =head3 Examples |
1945 | |
2537 | |
… | |
… | |
1958 | |
2550 | |
1959 | static ev_io iow [nfd]; |
2551 | static ev_io iow [nfd]; |
1960 | static ev_timer tw; |
2552 | static ev_timer tw; |
1961 | |
2553 | |
1962 | static void |
2554 | static void |
1963 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2555 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
1964 | { |
2556 | { |
1965 | } |
2557 | } |
1966 | |
2558 | |
1967 | // create io watchers for each fd and a timer before blocking |
2559 | // create io watchers for each fd and a timer before blocking |
1968 | static void |
2560 | static void |
1969 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2561 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
1970 | { |
2562 | { |
1971 | int timeout = 3600000; |
2563 | int timeout = 3600000; |
1972 | struct pollfd fds [nfd]; |
2564 | struct pollfd fds [nfd]; |
1973 | // actual code will need to loop here and realloc etc. |
2565 | // actual code will need to loop here and realloc etc. |
1974 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2566 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1975 | |
2567 | |
1976 | /* the callback is illegal, but won't be called as we stop during check */ |
2568 | /* the callback is illegal, but won't be called as we stop during check */ |
1977 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2569 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
1978 | ev_timer_start (loop, &tw); |
2570 | ev_timer_start (loop, &tw); |
1979 | |
2571 | |
1980 | // create one ev_io per pollfd |
2572 | // create one ev_io per pollfd |
1981 | for (int i = 0; i < nfd; ++i) |
2573 | for (int i = 0; i < nfd; ++i) |
1982 | { |
2574 | { |
… | |
… | |
1989 | } |
2581 | } |
1990 | } |
2582 | } |
1991 | |
2583 | |
1992 | // stop all watchers after blocking |
2584 | // stop all watchers after blocking |
1993 | static void |
2585 | static void |
1994 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2586 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
1995 | { |
2587 | { |
1996 | ev_timer_stop (loop, &tw); |
2588 | ev_timer_stop (loop, &tw); |
1997 | |
2589 | |
1998 | for (int i = 0; i < nfd; ++i) |
2590 | for (int i = 0; i < nfd; ++i) |
1999 | { |
2591 | { |
… | |
… | |
2038 | } |
2630 | } |
2039 | |
2631 | |
2040 | // do not ever call adns_afterpoll |
2632 | // do not ever call adns_afterpoll |
2041 | |
2633 | |
2042 | Method 4: Do not use a prepare or check watcher because the module you |
2634 | Method 4: Do not use a prepare or check watcher because the module you |
2043 | want to embed is too inflexible to support it. Instead, you can override |
2635 | want to embed is not flexible enough to support it. Instead, you can |
2044 | their poll function. The drawback with this solution is that the main |
2636 | override their poll function. The drawback with this solution is that the |
2045 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
2637 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
2046 | this. |
2638 | this approach, effectively embedding EV as a client into the horrible |
|
|
2639 | libglib event loop. |
2047 | |
2640 | |
2048 | static gint |
2641 | static gint |
2049 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2642 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2050 | { |
2643 | { |
2051 | int got_events = 0; |
2644 | int got_events = 0; |
… | |
… | |
2082 | prioritise I/O. |
2675 | prioritise I/O. |
2083 | |
2676 | |
2084 | As an example for a bug workaround, the kqueue backend might only support |
2677 | As an example for a bug workaround, the kqueue backend might only support |
2085 | sockets on some platform, so it is unusable as generic backend, but you |
2678 | sockets on some platform, so it is unusable as generic backend, but you |
2086 | still want to make use of it because you have many sockets and it scales |
2679 | still want to make use of it because you have many sockets and it scales |
2087 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2680 | so nicely. In this case, you would create a kqueue-based loop and embed |
2088 | into your default loop (which might use e.g. poll). Overall operation will |
2681 | it into your default loop (which might use e.g. poll). Overall operation |
2089 | be a bit slower because first libev has to poll and then call kevent, but |
2682 | will be a bit slower because first libev has to call C<poll> and then |
2090 | at least you can use both at what they are best. |
2683 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2684 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2091 | |
2685 | |
2092 | As for prioritising I/O: rarely you have the case where some fds have |
2686 | As for prioritising I/O: under rare circumstances you have the case where |
2093 | to be watched and handled very quickly (with low latency), and even |
2687 | some fds have to be watched and handled very quickly (with low latency), |
2094 | priorities and idle watchers might have too much overhead. In this case |
2688 | and even priorities and idle watchers might have too much overhead. In |
2095 | you would put all the high priority stuff in one loop and all the rest in |
2689 | this case you would put all the high priority stuff in one loop and all |
2096 | a second one, and embed the second one in the first. |
2690 | the rest in a second one, and embed the second one in the first. |
2097 | |
2691 | |
2098 | As long as the watcher is active, the callback will be invoked every time |
2692 | As long as the watcher is active, the callback will be invoked every |
2099 | there might be events pending in the embedded loop. The callback must then |
2693 | time there might be events pending in the embedded loop. The callback |
2100 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2694 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2101 | their callbacks (you could also start an idle watcher to give the embedded |
2695 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2102 | loop strictly lower priority for example). You can also set the callback |
2696 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2103 | to C<0>, in which case the embed watcher will automatically execute the |
2697 | to give the embedded loop strictly lower priority for example). |
2104 | embedded loop sweep. |
|
|
2105 | |
2698 | |
2106 | As long as the watcher is started it will automatically handle events. The |
2699 | You can also set the callback to C<0>, in which case the embed watcher |
2107 | callback will be invoked whenever some events have been handled. You can |
2700 | will automatically execute the embedded loop sweep whenever necessary. |
2108 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2109 | interested in that. |
|
|
2110 | |
2701 | |
2111 | Also, there have not currently been made special provisions for forking: |
2702 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2112 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2703 | is active, i.e., the embedded loop will automatically be forked when the |
2113 | but you will also have to stop and restart any C<ev_embed> watchers |
2704 | embedding loop forks. In other cases, the user is responsible for calling |
2114 | yourself. |
2705 | C<ev_loop_fork> on the embedded loop. |
2115 | |
2706 | |
2116 | Unfortunately, not all backends are embeddable, only the ones returned by |
2707 | Unfortunately, not all backends are embeddable: only the ones returned by |
2117 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2708 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2118 | portable one. |
2709 | portable one. |
2119 | |
2710 | |
2120 | So when you want to use this feature you will always have to be prepared |
2711 | So when you want to use this feature you will always have to be prepared |
2121 | that you cannot get an embeddable loop. The recommended way to get around |
2712 | that you cannot get an embeddable loop. The recommended way to get around |
2122 | this is to have a separate variables for your embeddable loop, try to |
2713 | this is to have a separate variables for your embeddable loop, try to |
2123 | create it, and if that fails, use the normal loop for everything. |
2714 | create it, and if that fails, use the normal loop for everything. |
|
|
2715 | |
|
|
2716 | =head3 C<ev_embed> and fork |
|
|
2717 | |
|
|
2718 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2719 | automatically be applied to the embedded loop as well, so no special |
|
|
2720 | fork handling is required in that case. When the watcher is not running, |
|
|
2721 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2722 | as applicable. |
2124 | |
2723 | |
2125 | =head3 Watcher-Specific Functions and Data Members |
2724 | =head3 Watcher-Specific Functions and Data Members |
2126 | |
2725 | |
2127 | =over 4 |
2726 | =over 4 |
2128 | |
2727 | |
… | |
… | |
2156 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2755 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2157 | used). |
2756 | used). |
2158 | |
2757 | |
2159 | struct ev_loop *loop_hi = ev_default_init (0); |
2758 | struct ev_loop *loop_hi = ev_default_init (0); |
2160 | struct ev_loop *loop_lo = 0; |
2759 | struct ev_loop *loop_lo = 0; |
2161 | struct ev_embed embed; |
2760 | ev_embed embed; |
2162 | |
2761 | |
2163 | // see if there is a chance of getting one that works |
2762 | // see if there is a chance of getting one that works |
2164 | // (remember that a flags value of 0 means autodetection) |
2763 | // (remember that a flags value of 0 means autodetection) |
2165 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2764 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2166 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2765 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2180 | kqueue implementation). Store the kqueue/socket-only event loop in |
2779 | kqueue implementation). Store the kqueue/socket-only event loop in |
2181 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2780 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2182 | |
2781 | |
2183 | struct ev_loop *loop = ev_default_init (0); |
2782 | struct ev_loop *loop = ev_default_init (0); |
2184 | struct ev_loop *loop_socket = 0; |
2783 | struct ev_loop *loop_socket = 0; |
2185 | struct ev_embed embed; |
2784 | ev_embed embed; |
2186 | |
2785 | |
2187 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2786 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2188 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2787 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2189 | { |
2788 | { |
2190 | ev_embed_init (&embed, 0, loop_socket); |
2789 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2205 | event loop blocks next and before C<ev_check> watchers are being called, |
2804 | event loop blocks next and before C<ev_check> watchers are being called, |
2206 | and only in the child after the fork. If whoever good citizen calling |
2805 | and only in the child after the fork. If whoever good citizen calling |
2207 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2806 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2208 | handlers will be invoked, too, of course. |
2807 | handlers will be invoked, too, of course. |
2209 | |
2808 | |
|
|
2809 | =head3 The special problem of life after fork - how is it possible? |
|
|
2810 | |
|
|
2811 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2812 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2813 | sequence should be handled by libev without any problems. |
|
|
2814 | |
|
|
2815 | This changes when the application actually wants to do event handling |
|
|
2816 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2817 | fork. |
|
|
2818 | |
|
|
2819 | The default mode of operation (for libev, with application help to detect |
|
|
2820 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2821 | when I<either> the parent I<or> the child process continues. |
|
|
2822 | |
|
|
2823 | When both processes want to continue using libev, then this is usually the |
|
|
2824 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2825 | supposed to continue with all watchers in place as before, while the other |
|
|
2826 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2827 | |
|
|
2828 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2829 | simply create a new event loop, which of course will be "empty", and |
|
|
2830 | use that for new watchers. This has the advantage of not touching more |
|
|
2831 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2832 | disadvantage of having to use multiple event loops (which do not support |
|
|
2833 | signal watchers). |
|
|
2834 | |
|
|
2835 | When this is not possible, or you want to use the default loop for |
|
|
2836 | other reasons, then in the process that wants to start "fresh", call |
|
|
2837 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2838 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2839 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2840 | also that in that case, you have to re-register any signal watchers. |
|
|
2841 | |
2210 | =head3 Watcher-Specific Functions and Data Members |
2842 | =head3 Watcher-Specific Functions and Data Members |
2211 | |
2843 | |
2212 | =over 4 |
2844 | =over 4 |
2213 | |
2845 | |
2214 | =item ev_fork_init (ev_signal *, callback) |
2846 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2246 | is that the author does not know of a simple (or any) algorithm for a |
2878 | is that the author does not know of a simple (or any) algorithm for a |
2247 | multiple-writer-single-reader queue that works in all cases and doesn't |
2879 | multiple-writer-single-reader queue that works in all cases and doesn't |
2248 | need elaborate support such as pthreads. |
2880 | need elaborate support such as pthreads. |
2249 | |
2881 | |
2250 | That means that if you want to queue data, you have to provide your own |
2882 | That means that if you want to queue data, you have to provide your own |
2251 | queue. But at least I can tell you would implement locking around your |
2883 | queue. But at least I can tell you how to implement locking around your |
2252 | queue: |
2884 | queue: |
2253 | |
2885 | |
2254 | =over 4 |
2886 | =over 4 |
2255 | |
2887 | |
2256 | =item queueing from a signal handler context |
2888 | =item queueing from a signal handler context |
2257 | |
2889 | |
2258 | To implement race-free queueing, you simply add to the queue in the signal |
2890 | To implement race-free queueing, you simply add to the queue in the signal |
2259 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
2891 | handler but you block the signal handler in the watcher callback. Here is |
2260 | some fictitious SIGUSR1 handler: |
2892 | an example that does that for some fictitious SIGUSR1 handler: |
2261 | |
2893 | |
2262 | static ev_async mysig; |
2894 | static ev_async mysig; |
2263 | |
2895 | |
2264 | static void |
2896 | static void |
2265 | sigusr1_handler (void) |
2897 | sigusr1_handler (void) |
… | |
… | |
2331 | =over 4 |
2963 | =over 4 |
2332 | |
2964 | |
2333 | =item ev_async_init (ev_async *, callback) |
2965 | =item ev_async_init (ev_async *, callback) |
2334 | |
2966 | |
2335 | Initialises and configures the async watcher - it has no parameters of any |
2967 | Initialises and configures the async watcher - it has no parameters of any |
2336 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2968 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2337 | believe me. |
2969 | trust me. |
2338 | |
2970 | |
2339 | =item ev_async_send (loop, ev_async *) |
2971 | =item ev_async_send (loop, ev_async *) |
2340 | |
2972 | |
2341 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2973 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2342 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2974 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2343 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
2975 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2344 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2976 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2345 | section below on what exactly this means). |
2977 | section below on what exactly this means). |
2346 | |
2978 | |
|
|
2979 | Note that, as with other watchers in libev, multiple events might get |
|
|
2980 | compressed into a single callback invocation (another way to look at this |
|
|
2981 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2982 | reset when the event loop detects that). |
|
|
2983 | |
2347 | This call incurs the overhead of a system call only once per loop iteration, |
2984 | This call incurs the overhead of a system call only once per event loop |
2348 | so while the overhead might be noticeable, it doesn't apply to repeated |
2985 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2349 | calls to C<ev_async_send>. |
2986 | repeated calls to C<ev_async_send> for the same event loop. |
2350 | |
2987 | |
2351 | =item bool = ev_async_pending (ev_async *) |
2988 | =item bool = ev_async_pending (ev_async *) |
2352 | |
2989 | |
2353 | Returns a non-zero value when C<ev_async_send> has been called on the |
2990 | Returns a non-zero value when C<ev_async_send> has been called on the |
2354 | watcher but the event has not yet been processed (or even noted) by the |
2991 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2357 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2994 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2358 | the loop iterates next and checks for the watcher to have become active, |
2995 | the loop iterates next and checks for the watcher to have become active, |
2359 | it will reset the flag again. C<ev_async_pending> can be used to very |
2996 | it will reset the flag again. C<ev_async_pending> can be used to very |
2360 | quickly check whether invoking the loop might be a good idea. |
2997 | quickly check whether invoking the loop might be a good idea. |
2361 | |
2998 | |
2362 | Not that this does I<not> check whether the watcher itself is pending, only |
2999 | Not that this does I<not> check whether the watcher itself is pending, |
2363 | whether it has been requested to make this watcher pending. |
3000 | only whether it has been requested to make this watcher pending: there |
|
|
3001 | is a time window between the event loop checking and resetting the async |
|
|
3002 | notification, and the callback being invoked. |
2364 | |
3003 | |
2365 | =back |
3004 | =back |
2366 | |
3005 | |
2367 | |
3006 | |
2368 | =head1 OTHER FUNCTIONS |
3007 | =head1 OTHER FUNCTIONS |
… | |
… | |
2372 | =over 4 |
3011 | =over 4 |
2373 | |
3012 | |
2374 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3013 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2375 | |
3014 | |
2376 | This function combines a simple timer and an I/O watcher, calls your |
3015 | This function combines a simple timer and an I/O watcher, calls your |
2377 | callback on whichever event happens first and automatically stop both |
3016 | callback on whichever event happens first and automatically stops both |
2378 | watchers. This is useful if you want to wait for a single event on an fd |
3017 | watchers. This is useful if you want to wait for a single event on an fd |
2379 | or timeout without having to allocate/configure/start/stop/free one or |
3018 | or timeout without having to allocate/configure/start/stop/free one or |
2380 | more watchers yourself. |
3019 | more watchers yourself. |
2381 | |
3020 | |
2382 | If C<fd> is less than 0, then no I/O watcher will be started and events |
3021 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2383 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
3022 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2384 | C<events> set will be created and started. |
3023 | the given C<fd> and C<events> set will be created and started. |
2385 | |
3024 | |
2386 | If C<timeout> is less than 0, then no timeout watcher will be |
3025 | If C<timeout> is less than 0, then no timeout watcher will be |
2387 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3026 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2388 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
3027 | repeat = 0) will be started. C<0> is a valid timeout. |
2389 | dubious value. |
|
|
2390 | |
3028 | |
2391 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3029 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2392 | passed an C<revents> set like normal event callbacks (a combination of |
3030 | passed an C<revents> set like normal event callbacks (a combination of |
2393 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3031 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2394 | value passed to C<ev_once>: |
3032 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
3033 | a timeout and an io event at the same time - you probably should give io |
|
|
3034 | events precedence. |
|
|
3035 | |
|
|
3036 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2395 | |
3037 | |
2396 | static void stdin_ready (int revents, void *arg) |
3038 | static void stdin_ready (int revents, void *arg) |
2397 | { |
3039 | { |
|
|
3040 | if (revents & EV_READ) |
|
|
3041 | /* stdin might have data for us, joy! */; |
2398 | if (revents & EV_TIMEOUT) |
3042 | else if (revents & EV_TIMEOUT) |
2399 | /* doh, nothing entered */; |
3043 | /* doh, nothing entered */; |
2400 | else if (revents & EV_READ) |
|
|
2401 | /* stdin might have data for us, joy! */; |
|
|
2402 | } |
3044 | } |
2403 | |
3045 | |
2404 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3046 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2405 | |
3047 | |
2406 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
3048 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
2407 | |
3049 | |
2408 | Feeds the given event set into the event loop, as if the specified event |
3050 | Feeds the given event set into the event loop, as if the specified event |
2409 | had happened for the specified watcher (which must be a pointer to an |
3051 | had happened for the specified watcher (which must be a pointer to an |
2410 | initialised but not necessarily started event watcher). |
3052 | initialised but not necessarily started event watcher). |
2411 | |
3053 | |
2412 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3054 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
2413 | |
3055 | |
2414 | Feed an event on the given fd, as if a file descriptor backend detected |
3056 | Feed an event on the given fd, as if a file descriptor backend detected |
2415 | the given events it. |
3057 | the given events it. |
2416 | |
3058 | |
2417 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3059 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
2418 | |
3060 | |
2419 | Feed an event as if the given signal occurred (C<loop> must be the default |
3061 | Feed an event as if the given signal occurred (C<loop> must be the default |
2420 | loop!). |
3062 | loop!). |
2421 | |
3063 | |
2422 | =back |
3064 | =back |
… | |
… | |
2544 | |
3186 | |
2545 | myclass obj; |
3187 | myclass obj; |
2546 | ev::io iow; |
3188 | ev::io iow; |
2547 | iow.set <myclass, &myclass::io_cb> (&obj); |
3189 | iow.set <myclass, &myclass::io_cb> (&obj); |
2548 | |
3190 | |
|
|
3191 | =item w->set (object *) |
|
|
3192 | |
|
|
3193 | This is an B<experimental> feature that might go away in a future version. |
|
|
3194 | |
|
|
3195 | This is a variation of a method callback - leaving out the method to call |
|
|
3196 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3197 | functor objects without having to manually specify the C<operator ()> all |
|
|
3198 | the time. Incidentally, you can then also leave out the template argument |
|
|
3199 | list. |
|
|
3200 | |
|
|
3201 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3202 | int revents)>. |
|
|
3203 | |
|
|
3204 | See the method-C<set> above for more details. |
|
|
3205 | |
|
|
3206 | Example: use a functor object as callback. |
|
|
3207 | |
|
|
3208 | struct myfunctor |
|
|
3209 | { |
|
|
3210 | void operator() (ev::io &w, int revents) |
|
|
3211 | { |
|
|
3212 | ... |
|
|
3213 | } |
|
|
3214 | } |
|
|
3215 | |
|
|
3216 | myfunctor f; |
|
|
3217 | |
|
|
3218 | ev::io w; |
|
|
3219 | w.set (&f); |
|
|
3220 | |
2549 | =item w->set<function> (void *data = 0) |
3221 | =item w->set<function> (void *data = 0) |
2550 | |
3222 | |
2551 | Also sets a callback, but uses a static method or plain function as |
3223 | Also sets a callback, but uses a static method or plain function as |
2552 | callback. The optional C<data> argument will be stored in the watcher's |
3224 | callback. The optional C<data> argument will be stored in the watcher's |
2553 | C<data> member and is free for you to use. |
3225 | C<data> member and is free for you to use. |
2554 | |
3226 | |
2555 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
3227 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2556 | |
3228 | |
2557 | See the method-C<set> above for more details. |
3229 | See the method-C<set> above for more details. |
2558 | |
3230 | |
2559 | Example: |
3231 | Example: Use a plain function as callback. |
2560 | |
3232 | |
2561 | static void io_cb (ev::io &w, int revents) { } |
3233 | static void io_cb (ev::io &w, int revents) { } |
2562 | iow.set <io_cb> (); |
3234 | iow.set <io_cb> (); |
2563 | |
3235 | |
2564 | =item w->set (struct ev_loop *) |
3236 | =item w->set (struct ev_loop *) |
… | |
… | |
2602 | Example: Define a class with an IO and idle watcher, start one of them in |
3274 | Example: Define a class with an IO and idle watcher, start one of them in |
2603 | the constructor. |
3275 | the constructor. |
2604 | |
3276 | |
2605 | class myclass |
3277 | class myclass |
2606 | { |
3278 | { |
2607 | ev::io io; void io_cb (ev::io &w, int revents); |
3279 | ev::io io ; void io_cb (ev::io &w, int revents); |
2608 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
3280 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2609 | |
3281 | |
2610 | myclass (int fd) |
3282 | myclass (int fd) |
2611 | { |
3283 | { |
2612 | io .set <myclass, &myclass::io_cb > (this); |
3284 | io .set <myclass, &myclass::io_cb > (this); |
2613 | idle.set <myclass, &myclass::idle_cb> (this); |
3285 | idle.set <myclass, &myclass::idle_cb> (this); |
… | |
… | |
2629 | =item Perl |
3301 | =item Perl |
2630 | |
3302 | |
2631 | The EV module implements the full libev API and is actually used to test |
3303 | The EV module implements the full libev API and is actually used to test |
2632 | libev. EV is developed together with libev. Apart from the EV core module, |
3304 | libev. EV is developed together with libev. Apart from the EV core module, |
2633 | there are additional modules that implement libev-compatible interfaces |
3305 | there are additional modules that implement libev-compatible interfaces |
2634 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
3306 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2635 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
3307 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
3308 | and C<EV::Glib>). |
2636 | |
3309 | |
2637 | It can be found and installed via CPAN, its homepage is at |
3310 | It can be found and installed via CPAN, its homepage is at |
2638 | L<http://software.schmorp.de/pkg/EV>. |
3311 | L<http://software.schmorp.de/pkg/EV>. |
2639 | |
3312 | |
2640 | =item Python |
3313 | =item Python |
2641 | |
3314 | |
2642 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3315 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2643 | seems to be quite complete and well-documented. Note, however, that the |
3316 | seems to be quite complete and well-documented. |
2644 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2645 | for everybody else, and therefore, should never be applied in an installed |
|
|
2646 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2647 | libev). |
|
|
2648 | |
3317 | |
2649 | =item Ruby |
3318 | =item Ruby |
2650 | |
3319 | |
2651 | Tony Arcieri has written a ruby extension that offers access to a subset |
3320 | Tony Arcieri has written a ruby extension that offers access to a subset |
2652 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3321 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2653 | more on top of it. It can be found via gem servers. Its homepage is at |
3322 | more on top of it. It can be found via gem servers. Its homepage is at |
2654 | L<http://rev.rubyforge.org/>. |
3323 | L<http://rev.rubyforge.org/>. |
2655 | |
3324 | |
|
|
3325 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3326 | makes rev work even on mingw. |
|
|
3327 | |
|
|
3328 | =item Haskell |
|
|
3329 | |
|
|
3330 | A haskell binding to libev is available at |
|
|
3331 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3332 | |
2656 | =item D |
3333 | =item D |
2657 | |
3334 | |
2658 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3335 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2659 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
3336 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3337 | |
|
|
3338 | =item Ocaml |
|
|
3339 | |
|
|
3340 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3341 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
2660 | |
3342 | |
2661 | =back |
3343 | =back |
2662 | |
3344 | |
2663 | |
3345 | |
2664 | =head1 MACRO MAGIC |
3346 | =head1 MACRO MAGIC |
… | |
… | |
2765 | |
3447 | |
2766 | #define EV_STANDALONE 1 |
3448 | #define EV_STANDALONE 1 |
2767 | #include "ev.h" |
3449 | #include "ev.h" |
2768 | |
3450 | |
2769 | Both header files and implementation files can be compiled with a C++ |
3451 | Both header files and implementation files can be compiled with a C++ |
2770 | compiler (at least, thats a stated goal, and breakage will be treated |
3452 | compiler (at least, that's a stated goal, and breakage will be treated |
2771 | as a bug). |
3453 | as a bug). |
2772 | |
3454 | |
2773 | You need the following files in your source tree, or in a directory |
3455 | You need the following files in your source tree, or in a directory |
2774 | in your include path (e.g. in libev/ when using -Ilibev): |
3456 | in your include path (e.g. in libev/ when using -Ilibev): |
2775 | |
3457 | |
… | |
… | |
2819 | |
3501 | |
2820 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3502 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2821 | |
3503 | |
2822 | Libev can be configured via a variety of preprocessor symbols you have to |
3504 | Libev can be configured via a variety of preprocessor symbols you have to |
2823 | define before including any of its files. The default in the absence of |
3505 | define before including any of its files. The default in the absence of |
2824 | autoconf is noted for every option. |
3506 | autoconf is documented for every option. |
2825 | |
3507 | |
2826 | =over 4 |
3508 | =over 4 |
2827 | |
3509 | |
2828 | =item EV_STANDALONE |
3510 | =item EV_STANDALONE |
2829 | |
3511 | |
… | |
… | |
2831 | keeps libev from including F<config.h>, and it also defines dummy |
3513 | keeps libev from including F<config.h>, and it also defines dummy |
2832 | implementations for some libevent functions (such as logging, which is not |
3514 | implementations for some libevent functions (such as logging, which is not |
2833 | supported). It will also not define any of the structs usually found in |
3515 | supported). It will also not define any of the structs usually found in |
2834 | F<event.h> that are not directly supported by the libev core alone. |
3516 | F<event.h> that are not directly supported by the libev core alone. |
2835 | |
3517 | |
|
|
3518 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3519 | configuration, but has to be more conservative. |
|
|
3520 | |
2836 | =item EV_USE_MONOTONIC |
3521 | =item EV_USE_MONOTONIC |
2837 | |
3522 | |
2838 | If defined to be C<1>, libev will try to detect the availability of the |
3523 | If defined to be C<1>, libev will try to detect the availability of the |
2839 | monotonic clock option at both compile time and runtime. Otherwise no use |
3524 | monotonic clock option at both compile time and runtime. Otherwise no |
2840 | of the monotonic clock option will be attempted. If you enable this, you |
3525 | use of the monotonic clock option will be attempted. If you enable this, |
2841 | usually have to link against librt or something similar. Enabling it when |
3526 | you usually have to link against librt or something similar. Enabling it |
2842 | the functionality isn't available is safe, though, although you have |
3527 | when the functionality isn't available is safe, though, although you have |
2843 | to make sure you link against any libraries where the C<clock_gettime> |
3528 | to make sure you link against any libraries where the C<clock_gettime> |
2844 | function is hiding in (often F<-lrt>). |
3529 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2845 | |
3530 | |
2846 | =item EV_USE_REALTIME |
3531 | =item EV_USE_REALTIME |
2847 | |
3532 | |
2848 | If defined to be C<1>, libev will try to detect the availability of the |
3533 | If defined to be C<1>, libev will try to detect the availability of the |
2849 | real-time clock option at compile time (and assume its availability at |
3534 | real-time clock option at compile time (and assume its availability |
2850 | runtime if successful). Otherwise no use of the real-time clock option will |
3535 | at runtime if successful). Otherwise no use of the real-time clock |
2851 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3536 | option will be attempted. This effectively replaces C<gettimeofday> |
2852 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3537 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2853 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3538 | correctness. See the note about libraries in the description of |
|
|
3539 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3540 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3541 | |
|
|
3542 | =item EV_USE_CLOCK_SYSCALL |
|
|
3543 | |
|
|
3544 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3545 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3546 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3547 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3548 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3549 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3550 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3551 | higher, as it simplifies linking (no need for C<-lrt>). |
2854 | |
3552 | |
2855 | =item EV_USE_NANOSLEEP |
3553 | =item EV_USE_NANOSLEEP |
2856 | |
3554 | |
2857 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3555 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2858 | and will use it for delays. Otherwise it will use C<select ()>. |
3556 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
2874 | |
3572 | |
2875 | =item EV_SELECT_USE_FD_SET |
3573 | =item EV_SELECT_USE_FD_SET |
2876 | |
3574 | |
2877 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3575 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2878 | structure. This is useful if libev doesn't compile due to a missing |
3576 | structure. This is useful if libev doesn't compile due to a missing |
2879 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3577 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
2880 | exotic systems. This usually limits the range of file descriptors to some |
3578 | on exotic systems. This usually limits the range of file descriptors to |
2881 | low limit such as 1024 or might have other limitations (winsocket only |
3579 | some low limit such as 1024 or might have other limitations (winsocket |
2882 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3580 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
2883 | influence the size of the C<fd_set> used. |
3581 | configures the maximum size of the C<fd_set>. |
2884 | |
3582 | |
2885 | =item EV_SELECT_IS_WINSOCKET |
3583 | =item EV_SELECT_IS_WINSOCKET |
2886 | |
3584 | |
2887 | When defined to C<1>, the select backend will assume that |
3585 | When defined to C<1>, the select backend will assume that |
2888 | select/socket/connect etc. don't understand file descriptors but |
3586 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
2999 | When doing priority-based operations, libev usually has to linearly search |
3697 | When doing priority-based operations, libev usually has to linearly search |
3000 | all the priorities, so having many of them (hundreds) uses a lot of space |
3698 | all the priorities, so having many of them (hundreds) uses a lot of space |
3001 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3699 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3002 | fine. |
3700 | fine. |
3003 | |
3701 | |
3004 | If your embedding application does not need any priorities, defining these both to |
3702 | If your embedding application does not need any priorities, defining these |
3005 | C<0> will save some memory and CPU. |
3703 | both to C<0> will save some memory and CPU. |
3006 | |
3704 | |
3007 | =item EV_PERIODIC_ENABLE |
3705 | =item EV_PERIODIC_ENABLE |
3008 | |
3706 | |
3009 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3707 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3010 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3708 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
… | |
… | |
3017 | code. |
3715 | code. |
3018 | |
3716 | |
3019 | =item EV_EMBED_ENABLE |
3717 | =item EV_EMBED_ENABLE |
3020 | |
3718 | |
3021 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3719 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3022 | defined to be C<0>, then they are not. |
3720 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3721 | watcher types, which therefore must not be disabled. |
3023 | |
3722 | |
3024 | =item EV_STAT_ENABLE |
3723 | =item EV_STAT_ENABLE |
3025 | |
3724 | |
3026 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3725 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3027 | defined to be C<0>, then they are not. |
3726 | defined to be C<0>, then they are not. |
… | |
… | |
3037 | defined to be C<0>, then they are not. |
3736 | defined to be C<0>, then they are not. |
3038 | |
3737 | |
3039 | =item EV_MINIMAL |
3738 | =item EV_MINIMAL |
3040 | |
3739 | |
3041 | If you need to shave off some kilobytes of code at the expense of some |
3740 | If you need to shave off some kilobytes of code at the expense of some |
3042 | speed, define this symbol to C<1>. Currently this is used to override some |
3741 | speed (but with the full API), define this symbol to C<1>. Currently this |
3043 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3742 | is used to override some inlining decisions, saves roughly 30% code size |
3044 | much smaller 2-heap for timer management over the default 4-heap. |
3743 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3744 | the default 4-heap. |
|
|
3745 | |
|
|
3746 | You can save even more by disabling watcher types you do not need |
|
|
3747 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3748 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3749 | |
|
|
3750 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3751 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3752 | of the API are still available, and do not complain if this subset changes |
|
|
3753 | over time. |
3045 | |
3754 | |
3046 | =item EV_PID_HASHSIZE |
3755 | =item EV_PID_HASHSIZE |
3047 | |
3756 | |
3048 | C<ev_child> watchers use a small hash table to distribute workload by |
3757 | C<ev_child> watchers use a small hash table to distribute workload by |
3049 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3758 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3059 | two). |
3768 | two). |
3060 | |
3769 | |
3061 | =item EV_USE_4HEAP |
3770 | =item EV_USE_4HEAP |
3062 | |
3771 | |
3063 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3772 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3064 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
3773 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3065 | to C<1>. The 4-heap uses more complicated (longer) code but has |
3774 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3066 | noticeably faster performance with many (thousands) of watchers. |
3775 | faster performance with many (thousands) of watchers. |
3067 | |
3776 | |
3068 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3777 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3069 | (disabled). |
3778 | (disabled). |
3070 | |
3779 | |
3071 | =item EV_HEAP_CACHE_AT |
3780 | =item EV_HEAP_CACHE_AT |
3072 | |
3781 | |
3073 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3782 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3074 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
3783 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3075 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3784 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3076 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3785 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3077 | but avoids random read accesses on heap changes. This improves performance |
3786 | but avoids random read accesses on heap changes. This improves performance |
3078 | noticeably with with many (hundreds) of watchers. |
3787 | noticeably with many (hundreds) of watchers. |
3079 | |
3788 | |
3080 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3789 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3081 | (disabled). |
3790 | (disabled). |
3082 | |
3791 | |
3083 | =item EV_VERIFY |
3792 | =item EV_VERIFY |
… | |
… | |
3089 | called once per loop, which can slow down libev. If set to C<3>, then the |
3798 | called once per loop, which can slow down libev. If set to C<3>, then the |
3090 | verification code will be called very frequently, which will slow down |
3799 | verification code will be called very frequently, which will slow down |
3091 | libev considerably. |
3800 | libev considerably. |
3092 | |
3801 | |
3093 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
3802 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
3094 | C<0.> |
3803 | C<0>. |
3095 | |
3804 | |
3096 | =item EV_COMMON |
3805 | =item EV_COMMON |
3097 | |
3806 | |
3098 | By default, all watchers have a C<void *data> member. By redefining |
3807 | By default, all watchers have a C<void *data> member. By redefining |
3099 | this macro to a something else you can include more and other types of |
3808 | this macro to a something else you can include more and other types of |
… | |
… | |
3116 | and the way callbacks are invoked and set. Must expand to a struct member |
3825 | and the way callbacks are invoked and set. Must expand to a struct member |
3117 | definition and a statement, respectively. See the F<ev.h> header file for |
3826 | definition and a statement, respectively. See the F<ev.h> header file for |
3118 | their default definitions. One possible use for overriding these is to |
3827 | their default definitions. One possible use for overriding these is to |
3119 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3828 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3120 | method calls instead of plain function calls in C++. |
3829 | method calls instead of plain function calls in C++. |
|
|
3830 | |
|
|
3831 | =back |
3121 | |
3832 | |
3122 | =head2 EXPORTED API SYMBOLS |
3833 | =head2 EXPORTED API SYMBOLS |
3123 | |
3834 | |
3124 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3835 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3125 | exported symbols, you can use the provided F<Symbol.*> files which list |
3836 | exported symbols, you can use the provided F<Symbol.*> files which list |
… | |
… | |
3172 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3883 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3173 | |
3884 | |
3174 | #include "ev_cpp.h" |
3885 | #include "ev_cpp.h" |
3175 | #include "ev.c" |
3886 | #include "ev.c" |
3176 | |
3887 | |
|
|
3888 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3177 | |
3889 | |
3178 | =head1 THREADS AND COROUTINES |
3890 | =head2 THREADS AND COROUTINES |
3179 | |
3891 | |
3180 | =head2 THREADS |
3892 | =head3 THREADS |
3181 | |
3893 | |
3182 | Libev itself is completely thread-safe, but it uses no locking. This |
3894 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
3895 | documented otherwise, but libev implements no locking itself. This means |
3183 | means that you can use as many loops as you want in parallel, as long as |
3896 | that you can use as many loops as you want in parallel, as long as there |
3184 | only one thread ever calls into one libev function with the same loop |
3897 | are no concurrent calls into any libev function with the same loop |
3185 | parameter. |
3898 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
3899 | of course): libev guarantees that different event loops share no data |
|
|
3900 | structures that need any locking. |
3186 | |
3901 | |
3187 | Or put differently: calls with different loop parameters can be done in |
3902 | Or to put it differently: calls with different loop parameters can be done |
3188 | parallel from multiple threads, calls with the same loop parameter must be |
3903 | concurrently from multiple threads, calls with the same loop parameter |
3189 | done serially (but can be done from different threads, as long as only one |
3904 | must be done serially (but can be done from different threads, as long as |
3190 | thread ever is inside a call at any point in time, e.g. by using a mutex |
3905 | only one thread ever is inside a call at any point in time, e.g. by using |
3191 | per loop). |
3906 | a mutex per loop). |
|
|
3907 | |
|
|
3908 | Specifically to support threads (and signal handlers), libev implements |
|
|
3909 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
3910 | concurrency on the same event loop, namely waking it up "from the |
|
|
3911 | outside". |
3192 | |
3912 | |
3193 | If you want to know which design (one loop, locking, or multiple loops |
3913 | If you want to know which design (one loop, locking, or multiple loops |
3194 | without or something else still) is best for your problem, then I cannot |
3914 | without or something else still) is best for your problem, then I cannot |
3195 | help you. I can give some generic advice however: |
3915 | help you, but here is some generic advice: |
3196 | |
3916 | |
3197 | =over 4 |
3917 | =over 4 |
3198 | |
3918 | |
3199 | =item * most applications have a main thread: use the default libev loop |
3919 | =item * most applications have a main thread: use the default libev loop |
3200 | in that thread, or create a separate thread running only the default loop. |
3920 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3212 | |
3932 | |
3213 | Choosing a model is hard - look around, learn, know that usually you can do |
3933 | Choosing a model is hard - look around, learn, know that usually you can do |
3214 | better than you currently do :-) |
3934 | better than you currently do :-) |
3215 | |
3935 | |
3216 | =item * often you need to talk to some other thread which blocks in the |
3936 | =item * often you need to talk to some other thread which blocks in the |
|
|
3937 | event loop. |
|
|
3938 | |
3217 | event loop - C<ev_async> watchers can be used to wake them up from other |
3939 | C<ev_async> watchers can be used to wake them up from other threads safely |
3218 | threads safely (or from signal contexts...). |
3940 | (or from signal contexts...). |
|
|
3941 | |
|
|
3942 | An example use would be to communicate signals or other events that only |
|
|
3943 | work in the default loop by registering the signal watcher with the |
|
|
3944 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
3945 | watcher callback into the event loop interested in the signal. |
3219 | |
3946 | |
3220 | =back |
3947 | =back |
3221 | |
3948 | |
|
|
3949 | =head4 THREAD LOCKING EXAMPLE |
|
|
3950 | |
|
|
3951 | Here is a fictitious example of how to run an event loop in a different |
|
|
3952 | thread than where callbacks are being invoked and watchers are |
|
|
3953 | created/added/removed. |
|
|
3954 | |
|
|
3955 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3956 | which uses exactly this technique (which is suited for many high-level |
|
|
3957 | languages). |
|
|
3958 | |
|
|
3959 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3960 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3961 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3962 | |
|
|
3963 | First, you need to associate some data with the event loop: |
|
|
3964 | |
|
|
3965 | typedef struct { |
|
|
3966 | mutex_t lock; /* global loop lock */ |
|
|
3967 | ev_async async_w; |
|
|
3968 | thread_t tid; |
|
|
3969 | cond_t invoke_cv; |
|
|
3970 | } userdata; |
|
|
3971 | |
|
|
3972 | void prepare_loop (EV_P) |
|
|
3973 | { |
|
|
3974 | // for simplicity, we use a static userdata struct. |
|
|
3975 | static userdata u; |
|
|
3976 | |
|
|
3977 | ev_async_init (&u->async_w, async_cb); |
|
|
3978 | ev_async_start (EV_A_ &u->async_w); |
|
|
3979 | |
|
|
3980 | pthread_mutex_init (&u->lock, 0); |
|
|
3981 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3982 | |
|
|
3983 | // now associate this with the loop |
|
|
3984 | ev_set_userdata (EV_A_ u); |
|
|
3985 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3986 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3987 | |
|
|
3988 | // then create the thread running ev_loop |
|
|
3989 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3990 | } |
|
|
3991 | |
|
|
3992 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3993 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3994 | that might have been added: |
|
|
3995 | |
|
|
3996 | static void |
|
|
3997 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3998 | { |
|
|
3999 | // just used for the side effects |
|
|
4000 | } |
|
|
4001 | |
|
|
4002 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4003 | protecting the loop data, respectively. |
|
|
4004 | |
|
|
4005 | static void |
|
|
4006 | l_release (EV_P) |
|
|
4007 | { |
|
|
4008 | userdata *u = ev_userdata (EV_A); |
|
|
4009 | pthread_mutex_unlock (&u->lock); |
|
|
4010 | } |
|
|
4011 | |
|
|
4012 | static void |
|
|
4013 | l_acquire (EV_P) |
|
|
4014 | { |
|
|
4015 | userdata *u = ev_userdata (EV_A); |
|
|
4016 | pthread_mutex_lock (&u->lock); |
|
|
4017 | } |
|
|
4018 | |
|
|
4019 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4020 | into C<ev_loop>: |
|
|
4021 | |
|
|
4022 | void * |
|
|
4023 | l_run (void *thr_arg) |
|
|
4024 | { |
|
|
4025 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4026 | |
|
|
4027 | l_acquire (EV_A); |
|
|
4028 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4029 | ev_loop (EV_A_ 0); |
|
|
4030 | l_release (EV_A); |
|
|
4031 | |
|
|
4032 | return 0; |
|
|
4033 | } |
|
|
4034 | |
|
|
4035 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4036 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4037 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4038 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4039 | and b) skipping inter-thread-communication when there are no pending |
|
|
4040 | watchers is very beneficial): |
|
|
4041 | |
|
|
4042 | static void |
|
|
4043 | l_invoke (EV_P) |
|
|
4044 | { |
|
|
4045 | userdata *u = ev_userdata (EV_A); |
|
|
4046 | |
|
|
4047 | while (ev_pending_count (EV_A)) |
|
|
4048 | { |
|
|
4049 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4050 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4051 | } |
|
|
4052 | } |
|
|
4053 | |
|
|
4054 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4055 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4056 | thread to continue: |
|
|
4057 | |
|
|
4058 | static void |
|
|
4059 | real_invoke_pending (EV_P) |
|
|
4060 | { |
|
|
4061 | userdata *u = ev_userdata (EV_A); |
|
|
4062 | |
|
|
4063 | pthread_mutex_lock (&u->lock); |
|
|
4064 | ev_invoke_pending (EV_A); |
|
|
4065 | pthread_cond_signal (&u->invoke_cv); |
|
|
4066 | pthread_mutex_unlock (&u->lock); |
|
|
4067 | } |
|
|
4068 | |
|
|
4069 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4070 | event loop, you will now have to lock: |
|
|
4071 | |
|
|
4072 | ev_timer timeout_watcher; |
|
|
4073 | userdata *u = ev_userdata (EV_A); |
|
|
4074 | |
|
|
4075 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4076 | |
|
|
4077 | pthread_mutex_lock (&u->lock); |
|
|
4078 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4079 | ev_async_send (EV_A_ &u->async_w); |
|
|
4080 | pthread_mutex_unlock (&u->lock); |
|
|
4081 | |
|
|
4082 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4083 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4084 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4085 | watchers in the next event loop iteration. |
|
|
4086 | |
3222 | =head2 COROUTINES |
4087 | =head3 COROUTINES |
3223 | |
4088 | |
3224 | Libev is much more accommodating to coroutines ("cooperative threads"): |
4089 | Libev is very accommodating to coroutines ("cooperative threads"): |
3225 | libev fully supports nesting calls to it's functions from different |
4090 | libev fully supports nesting calls to its functions from different |
3226 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4091 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3227 | different coroutines and switch freely between both coroutines running the |
4092 | different coroutines, and switch freely between both coroutines running |
3228 | loop, as long as you don't confuse yourself). The only exception is that |
4093 | the loop, as long as you don't confuse yourself). The only exception is |
3229 | you must not do this from C<ev_periodic> reschedule callbacks. |
4094 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3230 | |
4095 | |
3231 | Care has been invested into making sure that libev does not keep local |
4096 | Care has been taken to ensure that libev does not keep local state inside |
3232 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
4097 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3233 | switches. |
4098 | they do not call any callbacks. |
3234 | |
4099 | |
|
|
4100 | =head2 COMPILER WARNINGS |
3235 | |
4101 | |
3236 | =head1 COMPLEXITIES |
4102 | Depending on your compiler and compiler settings, you might get no or a |
|
|
4103 | lot of warnings when compiling libev code. Some people are apparently |
|
|
4104 | scared by this. |
3237 | |
4105 | |
3238 | In this section the complexities of (many of) the algorithms used inside |
4106 | However, these are unavoidable for many reasons. For one, each compiler |
3239 | libev will be explained. For complexity discussions about backends see the |
4107 | has different warnings, and each user has different tastes regarding |
3240 | documentation for C<ev_default_init>. |
4108 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
4109 | targeting a specific compiler and compiler-version. |
3241 | |
4110 | |
3242 | All of the following are about amortised time: If an array needs to be |
4111 | Another reason is that some compiler warnings require elaborate |
3243 | extended, libev needs to realloc and move the whole array, but this |
4112 | workarounds, or other changes to the code that make it less clear and less |
3244 | happens asymptotically never with higher number of elements, so O(1) might |
4113 | maintainable. |
3245 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3246 | it is much faster and asymptotically approaches constant time. |
|
|
3247 | |
4114 | |
3248 | =over 4 |
4115 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
4116 | wrong (because they don't actually warn about the condition their message |
|
|
4117 | seems to warn about). For example, certain older gcc versions had some |
|
|
4118 | warnings that resulted an extreme number of false positives. These have |
|
|
4119 | been fixed, but some people still insist on making code warn-free with |
|
|
4120 | such buggy versions. |
3249 | |
4121 | |
3250 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
4122 | While libev is written to generate as few warnings as possible, |
|
|
4123 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
4124 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
4125 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
4126 | warnings, not errors, or proof of bugs. |
3251 | |
4127 | |
3252 | This means that, when you have a watcher that triggers in one hour and |
|
|
3253 | there are 100 watchers that would trigger before that then inserting will |
|
|
3254 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3255 | |
4128 | |
3256 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
4129 | =head2 VALGRIND |
3257 | |
4130 | |
3258 | That means that changing a timer costs less than removing/adding them |
4131 | Valgrind has a special section here because it is a popular tool that is |
3259 | as only the relative motion in the event queue has to be paid for. |
4132 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3260 | |
4133 | |
3261 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
4134 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
4135 | in libev, then check twice: If valgrind reports something like: |
3262 | |
4136 | |
3263 | These just add the watcher into an array or at the head of a list. |
4137 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
4138 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
4139 | ==2274== still reachable: 256 bytes in 1 blocks. |
3264 | |
4140 | |
3265 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
4141 | Then there is no memory leak, just as memory accounted to global variables |
|
|
4142 | is not a memleak - the memory is still being referenced, and didn't leak. |
3266 | |
4143 | |
3267 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
4144 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
4145 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
4146 | although an acceptable workaround has been found here), or it might be |
|
|
4147 | confused. |
3268 | |
4148 | |
3269 | These watchers are stored in lists then need to be walked to find the |
4149 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3270 | correct watcher to remove. The lists are usually short (you don't usually |
4150 | make it into some kind of religion. |
3271 | have many watchers waiting for the same fd or signal). |
|
|
3272 | |
4151 | |
3273 | =item Finding the next timer in each loop iteration: O(1) |
4152 | If you are unsure about something, feel free to contact the mailing list |
|
|
4153 | with the full valgrind report and an explanation on why you think this |
|
|
4154 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
4155 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
4156 | of learning how to interpret valgrind properly. |
3274 | |
4157 | |
3275 | By virtue of using a binary or 4-heap, the next timer is always found at a |
4158 | If you need, for some reason, empty reports from valgrind for your project |
3276 | fixed position in the storage array. |
4159 | I suggest using suppression lists. |
3277 | |
4160 | |
3278 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3279 | |
4161 | |
3280 | A change means an I/O watcher gets started or stopped, which requires |
4162 | =head1 PORTABILITY NOTES |
3281 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3282 | on backend and whether C<ev_io_set> was used). |
|
|
3283 | |
4163 | |
3284 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3285 | |
|
|
3286 | =item Priority handling: O(number_of_priorities) |
|
|
3287 | |
|
|
3288 | Priorities are implemented by allocating some space for each |
|
|
3289 | priority. When doing priority-based operations, libev usually has to |
|
|
3290 | linearly search all the priorities, but starting/stopping and activating |
|
|
3291 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3292 | |
|
|
3293 | =item Sending an ev_async: O(1) |
|
|
3294 | |
|
|
3295 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3296 | |
|
|
3297 | =item Processing signals: O(max_signal_number) |
|
|
3298 | |
|
|
3299 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3300 | calls in the current loop iteration. Checking for async and signal events |
|
|
3301 | involves iterating over all running async watchers or all signal numbers. |
|
|
3302 | |
|
|
3303 | =back |
|
|
3304 | |
|
|
3305 | |
|
|
3306 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4164 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3307 | |
4165 | |
3308 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4166 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3309 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4167 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3310 | model. Libev still offers limited functionality on this platform in |
4168 | model. Libev still offers limited functionality on this platform in |
3311 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4169 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
… | |
… | |
3318 | way (note also that glib is the slowest event library known to man). |
4176 | way (note also that glib is the slowest event library known to man). |
3319 | |
4177 | |
3320 | There is no supported compilation method available on windows except |
4178 | There is no supported compilation method available on windows except |
3321 | embedding it into other applications. |
4179 | embedding it into other applications. |
3322 | |
4180 | |
|
|
4181 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4182 | tries its best, but under most conditions, signals will simply not work. |
|
|
4183 | |
3323 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4184 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3324 | accept large writes: instead of resulting in a partial write, windows will |
4185 | accept large writes: instead of resulting in a partial write, windows will |
3325 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4186 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3326 | so make sure you only write small amounts into your sockets (less than a |
4187 | so make sure you only write small amounts into your sockets (less than a |
3327 | megabyte seems safe, but thsi apparently depends on the amount of memory |
4188 | megabyte seems safe, but this apparently depends on the amount of memory |
3328 | available). |
4189 | available). |
3329 | |
4190 | |
3330 | Due to the many, low, and arbitrary limits on the win32 platform and |
4191 | Due to the many, low, and arbitrary limits on the win32 platform and |
3331 | the abysmal performance of winsockets, using a large number of sockets |
4192 | the abysmal performance of winsockets, using a large number of sockets |
3332 | is not recommended (and not reasonable). If your program needs to use |
4193 | is not recommended (and not reasonable). If your program needs to use |
3333 | more than a hundred or so sockets, then likely it needs to use a totally |
4194 | more than a hundred or so sockets, then likely it needs to use a totally |
3334 | different implementation for windows, as libev offers the POSIX readiness |
4195 | different implementation for windows, as libev offers the POSIX readiness |
3335 | notification model, which cannot be implemented efficiently on windows |
4196 | notification model, which cannot be implemented efficiently on windows |
3336 | (Microsoft monopoly games). |
4197 | (due to Microsoft monopoly games). |
3337 | |
4198 | |
3338 | A typical way to use libev under windows is to embed it (see the embedding |
4199 | A typical way to use libev under windows is to embed it (see the embedding |
3339 | section for details) and use the following F<evwrap.h> header file instead |
4200 | section for details) and use the following F<evwrap.h> header file instead |
3340 | of F<ev.h>: |
4201 | of F<ev.h>: |
3341 | |
4202 | |
… | |
… | |
3343 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
4204 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3344 | |
4205 | |
3345 | #include "ev.h" |
4206 | #include "ev.h" |
3346 | |
4207 | |
3347 | And compile the following F<evwrap.c> file into your project (make sure |
4208 | And compile the following F<evwrap.c> file into your project (make sure |
3348 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
4209 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3349 | |
4210 | |
3350 | #include "evwrap.h" |
4211 | #include "evwrap.h" |
3351 | #include "ev.c" |
4212 | #include "ev.c" |
3352 | |
4213 | |
3353 | =over 4 |
4214 | =over 4 |
… | |
… | |
3377 | |
4238 | |
3378 | Early versions of winsocket's select only supported waiting for a maximum |
4239 | Early versions of winsocket's select only supported waiting for a maximum |
3379 | of C<64> handles (probably owning to the fact that all windows kernels |
4240 | of C<64> handles (probably owning to the fact that all windows kernels |
3380 | can only wait for C<64> things at the same time internally; Microsoft |
4241 | can only wait for C<64> things at the same time internally; Microsoft |
3381 | recommends spawning a chain of threads and wait for 63 handles and the |
4242 | recommends spawning a chain of threads and wait for 63 handles and the |
3382 | previous thread in each. Great). |
4243 | previous thread in each. Sounds great!). |
3383 | |
4244 | |
3384 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4245 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3385 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4246 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3386 | call (which might be in libev or elsewhere, for example, perl does its own |
4247 | call (which might be in libev or elsewhere, for example, perl and many |
3387 | select emulation on windows). |
4248 | other interpreters do their own select emulation on windows). |
3388 | |
4249 | |
3389 | Another limit is the number of file descriptors in the Microsoft runtime |
4250 | Another limit is the number of file descriptors in the Microsoft runtime |
3390 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4251 | libraries, which by default is C<64> (there must be a hidden I<64> |
3391 | or something like this inside Microsoft). You can increase this by calling |
4252 | fetish or something like this inside Microsoft). You can increase this |
3392 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4253 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3393 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4254 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3394 | libraries. |
|
|
3395 | |
|
|
3396 | This might get you to about C<512> or C<2048> sockets (depending on |
4255 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3397 | windows version and/or the phase of the moon). To get more, you need to |
4256 | (depending on windows version and/or the phase of the moon). To get more, |
3398 | wrap all I/O functions and provide your own fd management, but the cost of |
4257 | you need to wrap all I/O functions and provide your own fd management, but |
3399 | calling select (O(n²)) will likely make this unworkable. |
4258 | the cost of calling select (O(n²)) will likely make this unworkable. |
3400 | |
4259 | |
3401 | =back |
4260 | =back |
3402 | |
4261 | |
3403 | |
|
|
3404 | =head1 PORTABILITY REQUIREMENTS |
4262 | =head2 PORTABILITY REQUIREMENTS |
3405 | |
4263 | |
3406 | In addition to a working ISO-C implementation, libev relies on a few |
4264 | In addition to a working ISO-C implementation and of course the |
3407 | additional extensions: |
4265 | backend-specific APIs, libev relies on a few additional extensions: |
3408 | |
4266 | |
3409 | =over 4 |
4267 | =over 4 |
3410 | |
4268 | |
3411 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
4269 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3412 | calling conventions regardless of C<ev_watcher_type *>. |
4270 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3418 | calls them using an C<ev_watcher *> internally. |
4276 | calls them using an C<ev_watcher *> internally. |
3419 | |
4277 | |
3420 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4278 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3421 | |
4279 | |
3422 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4280 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3423 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
4281 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
3424 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
4282 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3425 | believed to be sufficiently portable. |
4283 | believed to be sufficiently portable. |
3426 | |
4284 | |
3427 | =item C<sigprocmask> must work in a threaded environment |
4285 | =item C<sigprocmask> must work in a threaded environment |
3428 | |
4286 | |
… | |
… | |
3437 | except the initial one, and run the default loop in the initial thread as |
4295 | except the initial one, and run the default loop in the initial thread as |
3438 | well. |
4296 | well. |
3439 | |
4297 | |
3440 | =item C<long> must be large enough for common memory allocation sizes |
4298 | =item C<long> must be large enough for common memory allocation sizes |
3441 | |
4299 | |
3442 | To improve portability and simplify using libev, libev uses C<long> |
4300 | To improve portability and simplify its API, libev uses C<long> internally |
3443 | internally instead of C<size_t> when allocating its data structures. On |
4301 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3444 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
4302 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3445 | is still at least 31 bits everywhere, which is enough for hundreds of |
4303 | least 31 bits everywhere, which is enough for hundreds of millions of |
3446 | millions of watchers. |
4304 | watchers. |
3447 | |
4305 | |
3448 | =item C<double> must hold a time value in seconds with enough accuracy |
4306 | =item C<double> must hold a time value in seconds with enough accuracy |
3449 | |
4307 | |
3450 | The type C<double> is used to represent timestamps. It is required to |
4308 | The type C<double> is used to represent timestamps. It is required to |
3451 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4309 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3452 | enough for at least into the year 4000. This requirement is fulfilled by |
4310 | enough for at least into the year 4000. This requirement is fulfilled by |
3453 | implementations implementing IEEE 754 (basically all existing ones). |
4311 | implementations implementing IEEE 754, which is basically all existing |
|
|
4312 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4313 | 2200. |
3454 | |
4314 | |
3455 | =back |
4315 | =back |
3456 | |
4316 | |
3457 | If you know of other additional requirements drop me a note. |
4317 | If you know of other additional requirements drop me a note. |
3458 | |
4318 | |
3459 | |
4319 | |
3460 | =head1 COMPILER WARNINGS |
4320 | =head1 ALGORITHMIC COMPLEXITIES |
3461 | |
4321 | |
3462 | Depending on your compiler and compiler settings, you might get no or a |
4322 | In this section the complexities of (many of) the algorithms used inside |
3463 | lot of warnings when compiling libev code. Some people are apparently |
4323 | libev will be documented. For complexity discussions about backends see |
3464 | scared by this. |
4324 | the documentation for C<ev_default_init>. |
3465 | |
4325 | |
3466 | However, these are unavoidable for many reasons. For one, each compiler |
4326 | All of the following are about amortised time: If an array needs to be |
3467 | has different warnings, and each user has different tastes regarding |
4327 | extended, libev needs to realloc and move the whole array, but this |
3468 | warning options. "Warn-free" code therefore cannot be a goal except when |
4328 | happens asymptotically rarer with higher number of elements, so O(1) might |
3469 | targeting a specific compiler and compiler-version. |
4329 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
4330 | average it is much faster and asymptotically approaches constant time. |
3470 | |
4331 | |
3471 | Another reason is that some compiler warnings require elaborate |
4332 | =over 4 |
3472 | workarounds, or other changes to the code that make it less clear and less |
|
|
3473 | maintainable. |
|
|
3474 | |
4333 | |
3475 | And of course, some compiler warnings are just plain stupid, or simply |
4334 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3476 | wrong (because they don't actually warn about the condition their message |
|
|
3477 | seems to warn about). |
|
|
3478 | |
4335 | |
3479 | While libev is written to generate as few warnings as possible, |
4336 | This means that, when you have a watcher that triggers in one hour and |
3480 | "warn-free" code is not a goal, and it is recommended not to build libev |
4337 | there are 100 watchers that would trigger before that, then inserting will |
3481 | with any compiler warnings enabled unless you are prepared to cope with |
4338 | have to skip roughly seven (C<ld 100>) of these watchers. |
3482 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3483 | warnings, not errors, or proof of bugs. |
|
|
3484 | |
4339 | |
|
|
4340 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3485 | |
4341 | |
3486 | =head1 VALGRIND |
4342 | That means that changing a timer costs less than removing/adding them, |
|
|
4343 | as only the relative motion in the event queue has to be paid for. |
3487 | |
4344 | |
3488 | Valgrind has a special section here because it is a popular tool that is |
4345 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3489 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3490 | |
4346 | |
3491 | If you think you found a bug (memory leak, uninitialised data access etc.) |
4347 | These just add the watcher into an array or at the head of a list. |
3492 | in libev, then check twice: If valgrind reports something like: |
|
|
3493 | |
4348 | |
3494 | ==2274== definitely lost: 0 bytes in 0 blocks. |
4349 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3495 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3496 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3497 | |
4350 | |
3498 | Then there is no memory leak. Similarly, under some circumstances, |
4351 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3499 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3500 | might be confused (it is a very good tool, but only a tool). |
|
|
3501 | |
4352 | |
3502 | If you are unsure about something, feel free to contact the mailing list |
4353 | These watchers are stored in lists, so they need to be walked to find the |
3503 | with the full valgrind report and an explanation on why you think this is |
4354 | correct watcher to remove. The lists are usually short (you don't usually |
3504 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
4355 | have many watchers waiting for the same fd or signal: one is typical, two |
3505 | no bug" answer and take the chance of learning how to interpret valgrind |
4356 | is rare). |
3506 | properly. |
|
|
3507 | |
4357 | |
3508 | If you need, for some reason, empty reports from valgrind for your project |
4358 | =item Finding the next timer in each loop iteration: O(1) |
3509 | I suggest using suppression lists. |
|
|
3510 | |
4359 | |
|
|
4360 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
4361 | fixed position in the storage array. |
|
|
4362 | |
|
|
4363 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
4364 | |
|
|
4365 | A change means an I/O watcher gets started or stopped, which requires |
|
|
4366 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
4367 | on backend and whether C<ev_io_set> was used). |
|
|
4368 | |
|
|
4369 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
4370 | |
|
|
4371 | =item Priority handling: O(number_of_priorities) |
|
|
4372 | |
|
|
4373 | Priorities are implemented by allocating some space for each |
|
|
4374 | priority. When doing priority-based operations, libev usually has to |
|
|
4375 | linearly search all the priorities, but starting/stopping and activating |
|
|
4376 | watchers becomes O(1) with respect to priority handling. |
|
|
4377 | |
|
|
4378 | =item Sending an ev_async: O(1) |
|
|
4379 | |
|
|
4380 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
4381 | |
|
|
4382 | =item Processing signals: O(max_signal_number) |
|
|
4383 | |
|
|
4384 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
4385 | calls in the current loop iteration. Checking for async and signal events |
|
|
4386 | involves iterating over all running async watchers or all signal numbers. |
|
|
4387 | |
|
|
4388 | =back |
|
|
4389 | |
|
|
4390 | |
|
|
4391 | =head1 GLOSSARY |
|
|
4392 | |
|
|
4393 | =over 4 |
|
|
4394 | |
|
|
4395 | =item active |
|
|
4396 | |
|
|
4397 | A watcher is active as long as it has been started (has been attached to |
|
|
4398 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4399 | |
|
|
4400 | =item application |
|
|
4401 | |
|
|
4402 | In this document, an application is whatever is using libev. |
|
|
4403 | |
|
|
4404 | =item callback |
|
|
4405 | |
|
|
4406 | The address of a function that is called when some event has been |
|
|
4407 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4408 | received the event, and the actual event bitset. |
|
|
4409 | |
|
|
4410 | =item callback invocation |
|
|
4411 | |
|
|
4412 | The act of calling the callback associated with a watcher. |
|
|
4413 | |
|
|
4414 | =item event |
|
|
4415 | |
|
|
4416 | A change of state of some external event, such as data now being available |
|
|
4417 | for reading on a file descriptor, time having passed or simply not having |
|
|
4418 | any other events happening anymore. |
|
|
4419 | |
|
|
4420 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4421 | C<EV_TIMEOUT>). |
|
|
4422 | |
|
|
4423 | =item event library |
|
|
4424 | |
|
|
4425 | A software package implementing an event model and loop. |
|
|
4426 | |
|
|
4427 | =item event loop |
|
|
4428 | |
|
|
4429 | An entity that handles and processes external events and converts them |
|
|
4430 | into callback invocations. |
|
|
4431 | |
|
|
4432 | =item event model |
|
|
4433 | |
|
|
4434 | The model used to describe how an event loop handles and processes |
|
|
4435 | watchers and events. |
|
|
4436 | |
|
|
4437 | =item pending |
|
|
4438 | |
|
|
4439 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4440 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4441 | pending status is explicitly cleared by the application. |
|
|
4442 | |
|
|
4443 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4444 | its pending status. |
|
|
4445 | |
|
|
4446 | =item real time |
|
|
4447 | |
|
|
4448 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4449 | |
|
|
4450 | =item wall-clock time |
|
|
4451 | |
|
|
4452 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4453 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4454 | clock. |
|
|
4455 | |
|
|
4456 | =item watcher |
|
|
4457 | |
|
|
4458 | A data structure that describes interest in certain events. Watchers need |
|
|
4459 | to be started (attached to an event loop) before they can receive events. |
|
|
4460 | |
|
|
4461 | =item watcher invocation |
|
|
4462 | |
|
|
4463 | The act of calling the callback associated with a watcher. |
|
|
4464 | |
|
|
4465 | =back |
3511 | |
4466 | |
3512 | =head1 AUTHOR |
4467 | =head1 AUTHOR |
3513 | |
4468 | |
3514 | Marc Lehmann <libev@schmorp.de>. |
4469 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3515 | |
4470 | |