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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. |
… | |
… | |
617 | any active watchers at all will result in not sleeping). |
734 | any active watchers at all will result in not sleeping). |
618 | - Sleep if the I/O and timer collect interval say so. |
735 | - Sleep if the I/O and timer collect interval say so. |
619 | - Block the process, waiting for any events. |
736 | - Block the process, waiting for any events. |
620 | - Queue all outstanding I/O (fd) events. |
737 | - Queue all outstanding I/O (fd) events. |
621 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
738 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
622 | - Queue all outstanding timers. |
739 | - Queue all expired timers. |
623 | - Queue all outstanding periodics. |
740 | - Queue all expired periodics. |
624 | - Unless any events are pending now, queue all idle watchers. |
741 | - Unless any events are pending now, queue all idle watchers. |
625 | - Queue all check watchers. |
742 | - Queue all check watchers. |
626 | - 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). |
627 | 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 |
628 | be handled here by queueing them when their watcher gets executed. |
745 | be handled here by queueing them when their watcher gets executed. |
… | |
… | |
645 | 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 |
646 | 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. |
647 | |
764 | |
648 | 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. |
649 | |
766 | |
|
|
767 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
768 | |
650 | =item ev_ref (loop) |
769 | =item ev_ref (loop) |
651 | |
770 | |
652 | =item ev_unref (loop) |
771 | =item ev_unref (loop) |
653 | |
772 | |
654 | 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 |
655 | 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 |
656 | 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 | |
657 | 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> |
658 | 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 | |
659 | 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 |
660 | 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 |
661 | 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 |
662 | 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 |
663 | 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 |
664 | (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 |
665 | 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). |
666 | |
790 | |
667 | 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> |
668 | running when nothing else is active. |
792 | running when nothing else is active. |
669 | |
793 | |
670 | struct ev_signal exitsig; |
794 | ev_signal exitsig; |
671 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
795 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
672 | ev_signal_start (loop, &exitsig); |
796 | ev_signal_start (loop, &exitsig); |
673 | evf_unref (loop); |
797 | evf_unref (loop); |
674 | |
798 | |
675 | Example: For some weird reason, unregister the above signal handler again. |
799 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
689 | 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>) |
690 | allows libev to delay invocation of I/O and timer/periodic callbacks |
814 | allows libev to delay invocation of I/O and timer/periodic callbacks |
691 | to increase efficiency of loop iterations (or to increase power-saving |
815 | to increase efficiency of loop iterations (or to increase power-saving |
692 | opportunities). |
816 | opportunities). |
693 | |
817 | |
694 | 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 |
695 | 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 |
696 | 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 |
697 | events, especially with backends like C<select ()> which have a high |
821 | events, especially with backends like C<select ()> which have a high |
698 | 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. |
699 | |
823 | |
700 | 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 |
701 | 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, |
702 | 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 |
703 | 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 |
704 | 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. |
705 | |
831 | |
706 | 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 |
707 | to spend more time collecting timeouts, at the expense of increased |
833 | to spend more time collecting timeouts, at the expense of increased |
708 | latency (the watcher callback will be called later). C<ev_io> watchers |
834 | latency/jitter/inexactness (the watcher callback will be called |
709 | 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 |
710 | any overhead in libev. |
836 | value will not introduce any overhead in libev. |
711 | |
837 | |
712 | 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 |
713 | 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 |
714 | interactive servers (of course not for games), likewise for timeouts. It |
840 | interactive servers (of course not for games), likewise for timeouts. It |
715 | 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>, |
716 | 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). |
717 | |
847 | |
718 | Setting the I<timeout collect interval> can improve the opportunity for |
848 | Setting the I<timeout collect interval> can improve the opportunity for |
719 | saving power, as the program will "bundle" timer callback invocations that |
849 | saving power, as the program will "bundle" timer callback invocations that |
720 | are "near" in time together, by delaying some, thus reducing the number of |
850 | are "near" in time together, by delaying some, thus reducing the number of |
721 | times the process sleeps and wakes up again. Another useful technique to |
851 | times the process sleeps and wakes up again. Another useful technique to |
722 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
852 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
723 | they fire on, say, one-second boundaries only. |
853 | they fire on, say, one-second boundaries only. |
724 | |
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. |
|
|
925 | |
725 | =item ev_loop_verify (loop) |
926 | =item ev_loop_verify (loop) |
726 | |
927 | |
727 | 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 |
728 | 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 |
729 | 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 |
730 | 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 ()>. |
731 | |
933 | |
732 | 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 |
733 | 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 |
734 | data structures consistent. |
936 | data structures consistent. |
735 | |
937 | |
736 | =back |
938 | =back |
737 | |
939 | |
738 | |
940 | |
739 | =head1 ANATOMY OF A WATCHER |
941 | =head1 ANATOMY OF A WATCHER |
740 | |
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 | |
741 | 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 |
742 | 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 |
743 | 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: |
744 | |
950 | |
745 | 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) |
746 | { |
952 | { |
747 | ev_io_stop (w); |
953 | ev_io_stop (w); |
748 | ev_unloop (loop, EVUNLOOP_ALL); |
954 | ev_unloop (loop, EVUNLOOP_ALL); |
749 | } |
955 | } |
750 | |
956 | |
751 | struct ev_loop *loop = ev_default_loop (0); |
957 | struct ev_loop *loop = ev_default_loop (0); |
|
|
958 | |
752 | struct ev_io stdin_watcher; |
959 | ev_io stdin_watcher; |
|
|
960 | |
753 | ev_init (&stdin_watcher, my_cb); |
961 | ev_init (&stdin_watcher, my_cb); |
754 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
962 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
755 | ev_io_start (loop, &stdin_watcher); |
963 | ev_io_start (loop, &stdin_watcher); |
|
|
964 | |
756 | ev_loop (loop, 0); |
965 | ev_loop (loop, 0); |
757 | |
966 | |
758 | 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 |
759 | 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 |
760 | 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). |
761 | |
973 | |
762 | 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 |
763 | (watcher *, callback)>, which expects a callback to be provided. This |
975 | (watcher *, callback)>, which expects a callback to be provided. This |
764 | 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 |
765 | 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 |
766 | is readable and/or writable). |
978 | is readable and/or writable). |
767 | |
979 | |
768 | 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 *, ...) >> |
769 | 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 |
770 | 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<< |
771 | (watcher *, callback, ...) >>. |
983 | ev_TYPE_init (watcher *, callback, ...) >>. |
772 | |
984 | |
773 | 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 |
774 | 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 |
775 | *) >>), 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 |
776 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
988 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
777 | |
989 | |
778 | 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 |
779 | 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 |
780 | reinitialise it or call its C<set> macro. |
992 | reinitialise it or call its C<ev_TYPE_set> macro. |
781 | |
993 | |
782 | 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 |
783 | 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 |
784 | third argument. |
996 | third argument. |
785 | |
997 | |
… | |
… | |
843 | |
1055 | |
844 | =item C<EV_ASYNC> |
1056 | =item C<EV_ASYNC> |
845 | |
1057 | |
846 | 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>). |
847 | |
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 | |
848 | =item C<EV_ERROR> |
1065 | =item C<EV_ERROR> |
849 | |
1066 | |
850 | 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 |
851 | happen because the watcher could not be properly started because libev |
1068 | happen because the watcher could not be properly started because libev |
852 | 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 | |
853 | 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 |
854 | 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. |
855 | |
1076 | |
856 | 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 |
857 | 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 |
858 | 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 |
859 | 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 |
860 | programs, though, so beware. |
1081 | programs, though, as the fd could already be closed and reused for another |
|
|
1082 | thing, so beware. |
861 | |
1083 | |
862 | =back |
1084 | =back |
863 | |
1085 | |
864 | =head2 GENERIC WATCHER FUNCTIONS |
1086 | =head2 GENERIC WATCHER FUNCTIONS |
865 | |
|
|
866 | In the following description, C<TYPE> stands for the watcher type, |
|
|
867 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
868 | |
1087 | |
869 | =over 4 |
1088 | =over 4 |
870 | |
1089 | |
871 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1090 | =item C<ev_init> (ev_TYPE *watcher, callback) |
872 | |
1091 | |
… | |
… | |
878 | which rolls both calls into one. |
1097 | which rolls both calls into one. |
879 | |
1098 | |
880 | 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 |
881 | (or never started) and there are no pending events outstanding. |
1100 | (or never started) and there are no pending events outstanding. |
882 | |
1101 | |
883 | 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, |
884 | 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); |
885 | |
1110 | |
886 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1111 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
887 | |
1112 | |
888 | 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 |
889 | 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 |
… | |
… | |
892 | difference to the C<ev_init> macro). |
1117 | difference to the C<ev_init> macro). |
893 | |
1118 | |
894 | Although some watcher types do not have type-specific arguments |
1119 | Although some watcher types do not have type-specific arguments |
895 | (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. |
896 | |
1121 | |
|
|
1122 | See C<ev_init>, above, for an example. |
|
|
1123 | |
897 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
1124 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
898 | |
1125 | |
899 | 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 |
900 | 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 |
901 | a watcher. The same limitations apply, of course. |
1128 | a watcher. The same limitations apply, of course. |
902 | |
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 | |
903 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1134 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
904 | |
1135 | |
905 | Starts (activates) the given watcher. Only active watchers will receive |
1136 | Starts (activates) the given watcher. Only active watchers will receive |
906 | events. If the watcher is already active nothing will happen. |
1137 | events. If the watcher is already active nothing will happen. |
907 | |
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 | |
908 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1144 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
909 | |
1145 | |
910 | 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 | |
911 | status. It is possible that stopped watchers are pending (for example, |
1149 | It is possible that stopped watchers are pending - for example, |
912 | non-repeating timers are being stopped when they become pending), but |
1150 | non-repeating timers are being stopped when they become pending - but |
913 | 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 |
914 | 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 |
915 | 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. |
916 | |
1154 | |
917 | =item bool ev_is_active (ev_TYPE *watcher) |
1155 | =item bool ev_is_active (ev_TYPE *watcher) |
918 | |
1156 | |
919 | 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 |
920 | 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 |
… | |
… | |
946 | 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> |
947 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1185 | (default: C<-2>). Pending watchers with higher priority will be invoked |
948 | before watchers with lower priority, but priority will not keep watchers |
1186 | before watchers with lower priority, but priority will not keep watchers |
949 | from being executed (except for C<ev_idle> watchers). |
1187 | from being executed (except for C<ev_idle> watchers). |
950 | |
1188 | |
951 | This means that priorities are I<only> used for ordering callback |
|
|
952 | invocation after new events have been received. This is useful, for |
|
|
953 | example, to reduce latency after idling, or more often, to bind two |
|
|
954 | watchers on the same event and make sure one is called first. |
|
|
955 | |
|
|
956 | 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 |
957 | 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. |
958 | |
1191 | |
959 | 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 |
960 | pending. |
1193 | pending. |
961 | |
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 | |
962 | 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 |
963 | 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 :). |
964 | |
1201 | |
965 | 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 |
966 | fine, as long as you do not mind that the priority value you query might |
1203 | priorities. |
967 | or might not have been adjusted to be within valid range. |
|
|
968 | |
1204 | |
969 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1205 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
970 | |
1206 | |
971 | 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 |
972 | 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 |
973 | can deal with that fact. |
1209 | can deal with that fact, as both are simply passed through to the |
|
|
1210 | callback. |
974 | |
1211 | |
975 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1212 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
976 | |
1213 | |
977 | 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 |
978 | 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 |
979 | watcher isn't pending it does nothing and returns C<0>. |
1216 | watcher isn't pending it does nothing and returns C<0>. |
980 | |
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 | |
981 | =back |
1221 | =back |
982 | |
1222 | |
983 | |
1223 | |
984 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1224 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
985 | |
1225 | |
986 | 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 |
987 | 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 |
988 | 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 |
989 | 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 |
990 | 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 |
991 | data: |
1231 | data: |
992 | |
1232 | |
993 | struct my_io |
1233 | struct my_io |
994 | { |
1234 | { |
995 | struct ev_io io; |
1235 | ev_io io; |
996 | int otherfd; |
1236 | int otherfd; |
997 | void *somedata; |
1237 | void *somedata; |
998 | struct whatever *mostinteresting; |
1238 | struct whatever *mostinteresting; |
999 | } |
1239 | }; |
|
|
1240 | |
|
|
1241 | ... |
|
|
1242 | struct my_io w; |
|
|
1243 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1000 | |
1244 | |
1001 | 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 |
1002 | can cast it back to your own type: |
1246 | can cast it back to your own type: |
1003 | |
1247 | |
1004 | 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) |
1005 | { |
1249 | { |
1006 | struct my_io *w = (struct my_io *)w_; |
1250 | struct my_io *w = (struct my_io *)w_; |
1007 | ... |
1251 | ... |
1008 | } |
1252 | } |
1009 | |
1253 | |
1010 | 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 |
1011 | instead have been omitted. |
1255 | instead have been omitted. |
1012 | |
1256 | |
1013 | Another common scenario is having some data structure with multiple |
1257 | Another common scenario is to use some data structure with multiple |
1014 | watchers: |
1258 | embedded watchers: |
1015 | |
1259 | |
1016 | struct my_biggy |
1260 | struct my_biggy |
1017 | { |
1261 | { |
1018 | int some_data; |
1262 | int some_data; |
1019 | ev_timer t1; |
1263 | ev_timer t1; |
1020 | ev_timer t2; |
1264 | ev_timer t2; |
1021 | } |
1265 | } |
1022 | |
1266 | |
1023 | 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 |
1024 | 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): |
1025 | |
1272 | |
1026 | #include <stddef.h> |
1273 | #include <stddef.h> |
1027 | |
1274 | |
1028 | static void |
1275 | static void |
1029 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1276 | t1_cb (EV_P_ ev_timer *w, int revents) |
1030 | { |
1277 | { |
1031 | struct my_biggy big = (struct my_biggy * |
1278 | struct my_biggy big = (struct my_biggy *) |
1032 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1279 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1033 | } |
1280 | } |
1034 | |
1281 | |
1035 | static void |
1282 | static void |
1036 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1283 | t2_cb (EV_P_ ev_timer *w, int revents) |
1037 | { |
1284 | { |
1038 | struct my_biggy big = (struct my_biggy * |
1285 | struct my_biggy big = (struct my_biggy *) |
1039 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1286 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1040 | } |
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. |
1041 | |
1391 | |
1042 | |
1392 | |
1043 | =head1 WATCHER TYPES |
1393 | =head1 WATCHER TYPES |
1044 | |
1394 | |
1045 | This section describes each watcher in detail, but will not repeat |
1395 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1069 | 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 |
1070 | 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 |
1071 | 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 |
1072 | required if you know what you are doing). |
1422 | required if you know what you are doing). |
1073 | |
1423 | |
1074 | 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 |
1075 | (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 |
1076 | 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. |
1077 | |
1429 | |
1078 | 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 |
1079 | receive "spurious" readiness notifications, that is your callback might |
1431 | receive "spurious" readiness notifications, that is your callback might |
1080 | 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 |
1081 | 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 |
1082 | 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 |
1083 | this situation even with a relatively standard program structure. Thus |
1435 | this situation even with a relatively standard program structure. Thus |
1084 | 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 |
1085 | 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. |
1086 | |
1438 | |
1087 | 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 |
1088 | 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 |
1089 | 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 |
1090 | 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 |
1091 | 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. |
1092 | |
1448 | |
1093 | =head3 The special problem of disappearing file descriptors |
1449 | =head3 The special problem of disappearing file descriptors |
1094 | |
1450 | |
1095 | 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 |
1096 | 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, |
1097 | 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 |
1098 | 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 |
1099 | 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 |
1100 | 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 |
1101 | fact, a different file descriptor. |
1457 | fact, a different file descriptor. |
1102 | |
1458 | |
… | |
… | |
1133 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1489 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1134 | C<EVBACKEND_POLL>. |
1490 | C<EVBACKEND_POLL>. |
1135 | |
1491 | |
1136 | =head3 The special problem of SIGPIPE |
1492 | =head3 The special problem of SIGPIPE |
1137 | |
1493 | |
1138 | 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>: |
1139 | 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 |
1140 | 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 |
1141 | programs this is sensible behaviour, for daemons, this is usually |
1497 | this is sensible behaviour, for daemons, this is usually undesirable. |
1142 | undesirable. |
|
|
1143 | |
1498 | |
1144 | So when you encounter spurious, unexplained daemon exits, make sure you |
1499 | So when you encounter spurious, unexplained daemon exits, make sure you |
1145 | 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 |
1146 | somewhere, as that would have given you a big clue). |
1501 | somewhere, as that would have given you a big clue). |
1147 | |
1502 | |
… | |
… | |
1153 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1508 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1154 | |
1509 | |
1155 | =item ev_io_set (ev_io *, int fd, int events) |
1510 | =item ev_io_set (ev_io *, int fd, int events) |
1156 | |
1511 | |
1157 | 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 |
1158 | 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 |
1159 | 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. |
1160 | |
1515 | |
1161 | =item int fd [read-only] |
1516 | =item int fd [read-only] |
1162 | |
1517 | |
1163 | The file descriptor being watched. |
1518 | The file descriptor being watched. |
1164 | |
1519 | |
… | |
… | |
1173 | 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 |
1174 | 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 |
1175 | attempt to read a whole line in the callback. |
1530 | attempt to read a whole line in the callback. |
1176 | |
1531 | |
1177 | static void |
1532 | static void |
1178 | 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) |
1179 | { |
1534 | { |
1180 | ev_io_stop (loop, w); |
1535 | ev_io_stop (loop, w); |
1181 | .. 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 |
1182 | } |
1537 | } |
1183 | |
1538 | |
1184 | ... |
1539 | ... |
1185 | struct ev_loop *loop = ev_default_init (0); |
1540 | struct ev_loop *loop = ev_default_init (0); |
1186 | struct ev_io stdin_readable; |
1541 | ev_io stdin_readable; |
1187 | 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); |
1188 | ev_io_start (loop, &stdin_readable); |
1543 | ev_io_start (loop, &stdin_readable); |
1189 | ev_loop (loop, 0); |
1544 | ev_loop (loop, 0); |
1190 | |
1545 | |
1191 | |
1546 | |
… | |
… | |
1194 | 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 |
1195 | given time, and optionally repeating in regular intervals after that. |
1550 | given time, and optionally repeating in regular intervals after that. |
1196 | |
1551 | |
1197 | 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 |
1198 | 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 |
1199 | 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 |
1200 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1555 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1201 | 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. |
1202 | |
1747 | |
1203 | The relative timeouts are calculated relative to the C<ev_now ()> |
1748 | The relative timeouts are calculated relative to the C<ev_now ()> |
1204 | 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 |
1205 | of the event triggering whatever timeout you are modifying/starting. If |
1750 | of the event triggering whatever timeout you are modifying/starting. If |
1206 | 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 |
1207 | 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: |
1208 | |
1753 | |
1209 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1754 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1210 | |
1755 | |
1211 | 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 |
1212 | 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 |
1213 | order of execution is undefined. |
1758 | ()>. |
|
|
1759 | |
|
|
1760 | =head3 The special problems of suspended animation |
|
|
1761 | |
|
|
1762 | When you leave the server world it is quite customary to hit machines that |
|
|
1763 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1764 | |
|
|
1765 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1766 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1767 | to run until the system is suspended, but they will not advance while the |
|
|
1768 | system is suspended. That means, on resume, it will be as if the program |
|
|
1769 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1770 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1771 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1772 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1773 | be adjusted accordingly. |
|
|
1774 | |
|
|
1775 | I would not be surprised to see different behaviour in different between |
|
|
1776 | operating systems, OS versions or even different hardware. |
|
|
1777 | |
|
|
1778 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1779 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1780 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1781 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1782 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1783 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1784 | |
|
|
1785 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1786 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1787 | deterministic behaviour in this case (you can do nothing against |
|
|
1788 | C<SIGSTOP>). |
1214 | |
1789 | |
1215 | =head3 Watcher-Specific Functions and Data Members |
1790 | =head3 Watcher-Specific Functions and Data Members |
1216 | |
1791 | |
1217 | =over 4 |
1792 | =over 4 |
1218 | |
1793 | |
… | |
… | |
1242 | If the timer is started but non-repeating, stop it (as if it timed out). |
1817 | If the timer is started but non-repeating, stop it (as if it timed out). |
1243 | |
1818 | |
1244 | If the timer is repeating, either start it if necessary (with the |
1819 | If the timer is repeating, either start it if necessary (with the |
1245 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1820 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1246 | |
1821 | |
1247 | This sounds a bit complicated, but here is a useful and typical |
1822 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1248 | example: Imagine you have a TCP connection and you want a so-called idle |
1823 | usage example. |
1249 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1250 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1251 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1252 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1253 | you go into an idle state where you do not expect data to travel on the |
|
|
1254 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1255 | automatically restart it if need be. |
|
|
1256 | |
1824 | |
1257 | That means you can ignore the C<after> value and C<ev_timer_start> |
1825 | =item ev_timer_remaining (loop, ev_timer *) |
1258 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1259 | |
1826 | |
1260 | ev_timer_init (timer, callback, 0., 5.); |
1827 | Returns the remaining time until a timer fires. If the timer is active, |
1261 | ev_timer_again (loop, timer); |
1828 | then this time is relative to the current event loop time, otherwise it's |
1262 | ... |
1829 | the timeout value currently configured. |
1263 | timer->again = 17.; |
|
|
1264 | ev_timer_again (loop, timer); |
|
|
1265 | ... |
|
|
1266 | timer->again = 10.; |
|
|
1267 | ev_timer_again (loop, timer); |
|
|
1268 | |
1830 | |
1269 | This is more slightly efficient then stopping/starting the timer each time |
1831 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1270 | you want to modify its timeout value. |
1832 | C<5>. When the timer is started and one second passes, C<ev_timer_remain> |
|
|
1833 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1834 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1835 | too), and so on. |
1271 | |
1836 | |
1272 | =item ev_tstamp repeat [read-write] |
1837 | =item ev_tstamp repeat [read-write] |
1273 | |
1838 | |
1274 | The current C<repeat> value. Will be used each time the watcher times out |
1839 | The current C<repeat> value. Will be used each time the watcher times out |
1275 | or C<ev_timer_again> is called and determines the next timeout (if any), |
1840 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1276 | which is also when any modifications are taken into account. |
1841 | which is also when any modifications are taken into account. |
1277 | |
1842 | |
1278 | =back |
1843 | =back |
1279 | |
1844 | |
1280 | =head3 Examples |
1845 | =head3 Examples |
1281 | |
1846 | |
1282 | Example: Create a timer that fires after 60 seconds. |
1847 | Example: Create a timer that fires after 60 seconds. |
1283 | |
1848 | |
1284 | static void |
1849 | static void |
1285 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1850 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1286 | { |
1851 | { |
1287 | .. one minute over, w is actually stopped right here |
1852 | .. one minute over, w is actually stopped right here |
1288 | } |
1853 | } |
1289 | |
1854 | |
1290 | struct ev_timer mytimer; |
1855 | ev_timer mytimer; |
1291 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1856 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1292 | ev_timer_start (loop, &mytimer); |
1857 | ev_timer_start (loop, &mytimer); |
1293 | |
1858 | |
1294 | Example: Create a timeout timer that times out after 10 seconds of |
1859 | Example: Create a timeout timer that times out after 10 seconds of |
1295 | inactivity. |
1860 | inactivity. |
1296 | |
1861 | |
1297 | static void |
1862 | static void |
1298 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1863 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1299 | { |
1864 | { |
1300 | .. ten seconds without any activity |
1865 | .. ten seconds without any activity |
1301 | } |
1866 | } |
1302 | |
1867 | |
1303 | struct ev_timer mytimer; |
1868 | ev_timer mytimer; |
1304 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1869 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1305 | ev_timer_again (&mytimer); /* start timer */ |
1870 | ev_timer_again (&mytimer); /* start timer */ |
1306 | ev_loop (loop, 0); |
1871 | ev_loop (loop, 0); |
1307 | |
1872 | |
1308 | // and in some piece of code that gets executed on any "activity": |
1873 | // and in some piece of code that gets executed on any "activity": |
… | |
… | |
1313 | =head2 C<ev_periodic> - to cron or not to cron? |
1878 | =head2 C<ev_periodic> - to cron or not to cron? |
1314 | |
1879 | |
1315 | Periodic watchers are also timers of a kind, but they are very versatile |
1880 | Periodic watchers are also timers of a kind, but they are very versatile |
1316 | (and unfortunately a bit complex). |
1881 | (and unfortunately a bit complex). |
1317 | |
1882 | |
1318 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1883 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1319 | but on wall clock time (absolute time). You can tell a periodic watcher |
1884 | relative time, the physical time that passes) but on wall clock time |
1320 | to trigger after some specific point in time. For example, if you tell a |
1885 | (absolute time, the thing you can read on your calender or clock). The |
1321 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1886 | difference is that wall clock time can run faster or slower than real |
1322 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1887 | time, and time jumps are not uncommon (e.g. when you adjust your |
1323 | clock to January of the previous year, then it will take more than year |
1888 | wrist-watch). |
1324 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1325 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1326 | |
1889 | |
|
|
1890 | You can tell a periodic watcher to trigger after some specific point |
|
|
1891 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1892 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1893 | not a delay) and then reset your system clock to January of the previous |
|
|
1894 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1895 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1896 | it, as it uses a relative timeout). |
|
|
1897 | |
1327 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1898 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1328 | such as triggering an event on each "midnight, local time", or other |
1899 | timers, such as triggering an event on each "midnight, local time", or |
1329 | complicated, rules. |
1900 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1901 | those cannot react to time jumps. |
1330 | |
1902 | |
1331 | As with timers, the callback is guaranteed to be invoked only when the |
1903 | As with timers, the callback is guaranteed to be invoked only when the |
1332 | time (C<at>) has passed, but if multiple periodic timers become ready |
1904 | point in time where it is supposed to trigger has passed. If multiple |
1333 | during the same loop iteration then order of execution is undefined. |
1905 | timers become ready during the same loop iteration then the ones with |
|
|
1906 | earlier time-out values are invoked before ones with later time-out values |
|
|
1907 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1334 | |
1908 | |
1335 | =head3 Watcher-Specific Functions and Data Members |
1909 | =head3 Watcher-Specific Functions and Data Members |
1336 | |
1910 | |
1337 | =over 4 |
1911 | =over 4 |
1338 | |
1912 | |
1339 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1913 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1340 | |
1914 | |
1341 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1915 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1342 | |
1916 | |
1343 | Lots of arguments, lets sort it out... There are basically three modes of |
1917 | Lots of arguments, let's sort it out... There are basically three modes of |
1344 | operation, and we will explain them from simplest to complex: |
1918 | operation, and we will explain them from simplest to most complex: |
1345 | |
1919 | |
1346 | =over 4 |
1920 | =over 4 |
1347 | |
1921 | |
1348 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1922 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1349 | |
1923 | |
1350 | In this configuration the watcher triggers an event after the wall clock |
1924 | In this configuration the watcher triggers an event after the wall clock |
1351 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
1925 | time C<offset> has passed. It will not repeat and will not adjust when a |
1352 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1926 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1353 | run when the system time reaches or surpasses this time. |
1927 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1928 | this point in time. |
1354 | |
1929 | |
1355 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1930 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1356 | |
1931 | |
1357 | In this mode the watcher will always be scheduled to time out at the next |
1932 | In this mode the watcher will always be scheduled to time out at the next |
1358 | C<at + N * interval> time (for some integer N, which can also be negative) |
1933 | C<offset + N * interval> time (for some integer N, which can also be |
1359 | and then repeat, regardless of any time jumps. |
1934 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1935 | argument is merely an offset into the C<interval> periods. |
1360 | |
1936 | |
1361 | This can be used to create timers that do not drift with respect to system |
1937 | This can be used to create timers that do not drift with respect to the |
1362 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
1938 | system clock, for example, here is an C<ev_periodic> that triggers each |
1363 | the hour: |
1939 | hour, on the hour (with respect to UTC): |
1364 | |
1940 | |
1365 | ev_periodic_set (&periodic, 0., 3600., 0); |
1941 | ev_periodic_set (&periodic, 0., 3600., 0); |
1366 | |
1942 | |
1367 | This doesn't mean there will always be 3600 seconds in between triggers, |
1943 | This doesn't mean there will always be 3600 seconds in between triggers, |
1368 | but only that the callback will be called when the system time shows a |
1944 | but only that the callback will be called when the system time shows a |
1369 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1945 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1370 | by 3600. |
1946 | by 3600. |
1371 | |
1947 | |
1372 | Another way to think about it (for the mathematically inclined) is that |
1948 | Another way to think about it (for the mathematically inclined) is that |
1373 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1949 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1374 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1950 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1375 | |
1951 | |
1376 | For numerical stability it is preferable that the C<at> value is near |
1952 | For numerical stability it is preferable that the C<offset> value is near |
1377 | C<ev_now ()> (the current time), but there is no range requirement for |
1953 | C<ev_now ()> (the current time), but there is no range requirement for |
1378 | this value, and in fact is often specified as zero. |
1954 | this value, and in fact is often specified as zero. |
1379 | |
1955 | |
1380 | Note also that there is an upper limit to how often a timer can fire (CPU |
1956 | Note also that there is an upper limit to how often a timer can fire (CPU |
1381 | speed for example), so if C<interval> is very small then timing stability |
1957 | speed for example), so if C<interval> is very small then timing stability |
1382 | will of course deteriorate. Libev itself tries to be exact to be about one |
1958 | will of course deteriorate. Libev itself tries to be exact to be about one |
1383 | millisecond (if the OS supports it and the machine is fast enough). |
1959 | millisecond (if the OS supports it and the machine is fast enough). |
1384 | |
1960 | |
1385 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1961 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1386 | |
1962 | |
1387 | In this mode the values for C<interval> and C<at> are both being |
1963 | In this mode the values for C<interval> and C<offset> are both being |
1388 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1964 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1389 | reschedule callback will be called with the watcher as first, and the |
1965 | reschedule callback will be called with the watcher as first, and the |
1390 | current time as second argument. |
1966 | current time as second argument. |
1391 | |
1967 | |
1392 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1968 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1393 | ever, or make ANY event loop modifications whatsoever>. |
1969 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1970 | allowed by documentation here>. |
1394 | |
1971 | |
1395 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1972 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1396 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1973 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1397 | only event loop modification you are allowed to do). |
1974 | only event loop modification you are allowed to do). |
1398 | |
1975 | |
1399 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1976 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1400 | *w, ev_tstamp now)>, e.g.: |
1977 | *w, ev_tstamp now)>, e.g.: |
1401 | |
1978 | |
|
|
1979 | static ev_tstamp |
1402 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1980 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1403 | { |
1981 | { |
1404 | return now + 60.; |
1982 | return now + 60.; |
1405 | } |
1983 | } |
1406 | |
1984 | |
1407 | It must return the next time to trigger, based on the passed time value |
1985 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1427 | a different time than the last time it was called (e.g. in a crond like |
2005 | a different time than the last time it was called (e.g. in a crond like |
1428 | program when the crontabs have changed). |
2006 | program when the crontabs have changed). |
1429 | |
2007 | |
1430 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2008 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1431 | |
2009 | |
1432 | When active, returns the absolute time that the watcher is supposed to |
2010 | When active, returns the absolute time that the watcher is supposed |
1433 | trigger next. |
2011 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2012 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2013 | rescheduling modes. |
1434 | |
2014 | |
1435 | =item ev_tstamp offset [read-write] |
2015 | =item ev_tstamp offset [read-write] |
1436 | |
2016 | |
1437 | When repeating, this contains the offset value, otherwise this is the |
2017 | When repeating, this contains the offset value, otherwise this is the |
1438 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2018 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2019 | although libev might modify this value for better numerical stability). |
1439 | |
2020 | |
1440 | Can be modified any time, but changes only take effect when the periodic |
2021 | Can be modified any time, but changes only take effect when the periodic |
1441 | timer fires or C<ev_periodic_again> is being called. |
2022 | timer fires or C<ev_periodic_again> is being called. |
1442 | |
2023 | |
1443 | =item ev_tstamp interval [read-write] |
2024 | =item ev_tstamp interval [read-write] |
1444 | |
2025 | |
1445 | The current interval value. Can be modified any time, but changes only |
2026 | The current interval value. Can be modified any time, but changes only |
1446 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
2027 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1447 | called. |
2028 | called. |
1448 | |
2029 | |
1449 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
2030 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1450 | |
2031 | |
1451 | The current reschedule callback, or C<0>, if this functionality is |
2032 | The current reschedule callback, or C<0>, if this functionality is |
1452 | switched off. Can be changed any time, but changes only take effect when |
2033 | switched off. Can be changed any time, but changes only take effect when |
1453 | the periodic timer fires or C<ev_periodic_again> is being called. |
2034 | the periodic timer fires or C<ev_periodic_again> is being called. |
1454 | |
2035 | |
1455 | =back |
2036 | =back |
1456 | |
2037 | |
1457 | =head3 Examples |
2038 | =head3 Examples |
1458 | |
2039 | |
1459 | Example: Call a callback every hour, or, more precisely, whenever the |
2040 | Example: Call a callback every hour, or, more precisely, whenever the |
1460 | system clock is divisible by 3600. The callback invocation times have |
2041 | system time is divisible by 3600. The callback invocation times have |
1461 | potentially a lot of jitter, but good long-term stability. |
2042 | potentially a lot of jitter, but good long-term stability. |
1462 | |
2043 | |
1463 | static void |
2044 | static void |
1464 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2045 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1465 | { |
2046 | { |
1466 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2047 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1467 | } |
2048 | } |
1468 | |
2049 | |
1469 | struct ev_periodic hourly_tick; |
2050 | ev_periodic hourly_tick; |
1470 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2051 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1471 | ev_periodic_start (loop, &hourly_tick); |
2052 | ev_periodic_start (loop, &hourly_tick); |
1472 | |
2053 | |
1473 | Example: The same as above, but use a reschedule callback to do it: |
2054 | Example: The same as above, but use a reschedule callback to do it: |
1474 | |
2055 | |
1475 | #include <math.h> |
2056 | #include <math.h> |
1476 | |
2057 | |
1477 | static ev_tstamp |
2058 | static ev_tstamp |
1478 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2059 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1479 | { |
2060 | { |
1480 | return fmod (now, 3600.) + 3600.; |
2061 | return now + (3600. - fmod (now, 3600.)); |
1481 | } |
2062 | } |
1482 | |
2063 | |
1483 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2064 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1484 | |
2065 | |
1485 | Example: Call a callback every hour, starting now: |
2066 | Example: Call a callback every hour, starting now: |
1486 | |
2067 | |
1487 | struct ev_periodic hourly_tick; |
2068 | ev_periodic hourly_tick; |
1488 | ev_periodic_init (&hourly_tick, clock_cb, |
2069 | ev_periodic_init (&hourly_tick, clock_cb, |
1489 | fmod (ev_now (loop), 3600.), 3600., 0); |
2070 | fmod (ev_now (loop), 3600.), 3600., 0); |
1490 | ev_periodic_start (loop, &hourly_tick); |
2071 | ev_periodic_start (loop, &hourly_tick); |
1491 | |
2072 | |
1492 | |
2073 | |
… | |
… | |
1495 | Signal watchers will trigger an event when the process receives a specific |
2076 | Signal watchers will trigger an event when the process receives a specific |
1496 | signal one or more times. Even though signals are very asynchronous, libev |
2077 | signal one or more times. Even though signals are very asynchronous, libev |
1497 | will try it's best to deliver signals synchronously, i.e. as part of the |
2078 | will try it's best to deliver signals synchronously, i.e. as part of the |
1498 | normal event processing, like any other event. |
2079 | normal event processing, like any other event. |
1499 | |
2080 | |
|
|
2081 | If you want signals asynchronously, just use C<sigaction> as you would |
|
|
2082 | do without libev and forget about sharing the signal. You can even use |
|
|
2083 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
|
|
2084 | |
1500 | You can configure as many watchers as you like per signal. Only when the |
2085 | You can configure as many watchers as you like per signal. Only when the |
1501 | first watcher gets started will libev actually register a signal watcher |
2086 | first watcher gets started will libev actually register a signal handler |
1502 | with the kernel (thus it coexists with your own signal handlers as long |
2087 | with the kernel (thus it coexists with your own signal handlers as long as |
1503 | as you don't register any with libev). Similarly, when the last signal |
2088 | you don't register any with libev for the same signal). Similarly, when |
1504 | watcher for a signal is stopped libev will reset the signal handler to |
2089 | the last signal watcher for a signal is stopped, libev will reset the |
1505 | SIG_DFL (regardless of what it was set to before). |
2090 | signal handler to SIG_DFL (regardless of what it was set to before). |
1506 | |
2091 | |
1507 | If possible and supported, libev will install its handlers with |
2092 | If possible and supported, libev will install its handlers with |
1508 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2093 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
1509 | interrupted. If you have a problem with system calls getting interrupted by |
2094 | interrupted. If you have a problem with system calls getting interrupted by |
1510 | signals you can block all signals in an C<ev_check> watcher and unblock |
2095 | signals you can block all signals in an C<ev_check> watcher and unblock |
… | |
… | |
1527 | |
2112 | |
1528 | =back |
2113 | =back |
1529 | |
2114 | |
1530 | =head3 Examples |
2115 | =head3 Examples |
1531 | |
2116 | |
1532 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2117 | Example: Try to exit cleanly on SIGINT. |
1533 | |
2118 | |
1534 | static void |
2119 | static void |
1535 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2120 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1536 | { |
2121 | { |
1537 | ev_unloop (loop, EVUNLOOP_ALL); |
2122 | ev_unloop (loop, EVUNLOOP_ALL); |
1538 | } |
2123 | } |
1539 | |
2124 | |
1540 | struct ev_signal signal_watcher; |
2125 | ev_signal signal_watcher; |
1541 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2126 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1542 | ev_signal_start (loop, &sigint_cb); |
2127 | ev_signal_start (loop, &signal_watcher); |
1543 | |
2128 | |
1544 | |
2129 | |
1545 | =head2 C<ev_child> - watch out for process status changes |
2130 | =head2 C<ev_child> - watch out for process status changes |
1546 | |
2131 | |
1547 | Child watchers trigger when your process receives a SIGCHLD in response to |
2132 | Child watchers trigger when your process receives a SIGCHLD in response to |
1548 | some child status changes (most typically when a child of yours dies). It |
2133 | some child status changes (most typically when a child of yours dies or |
1549 | is permissible to install a child watcher I<after> the child has been |
2134 | exits). It is permissible to install a child watcher I<after> the child |
1550 | forked (which implies it might have already exited), as long as the event |
2135 | has been forked (which implies it might have already exited), as long |
1551 | loop isn't entered (or is continued from a watcher). |
2136 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2137 | forking and then immediately registering a watcher for the child is fine, |
|
|
2138 | but forking and registering a watcher a few event loop iterations later or |
|
|
2139 | in the next callback invocation is not. |
1552 | |
2140 | |
1553 | Only the default event loop is capable of handling signals, and therefore |
2141 | Only the default event loop is capable of handling signals, and therefore |
1554 | you can only register child watchers in the default event loop. |
2142 | you can only register child watchers in the default event loop. |
|
|
2143 | |
|
|
2144 | Due to some design glitches inside libev, child watchers will always be |
|
|
2145 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2146 | libev) |
1555 | |
2147 | |
1556 | =head3 Process Interaction |
2148 | =head3 Process Interaction |
1557 | |
2149 | |
1558 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2150 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1559 | initialised. This is necessary to guarantee proper behaviour even if |
2151 | initialised. This is necessary to guarantee proper behaviour even if |
… | |
… | |
1569 | handler, you can override it easily by installing your own handler for |
2161 | handler, you can override it easily by installing your own handler for |
1570 | C<SIGCHLD> after initialising the default loop, and making sure the |
2162 | C<SIGCHLD> after initialising the default loop, and making sure the |
1571 | default loop never gets destroyed. You are encouraged, however, to use an |
2163 | default loop never gets destroyed. You are encouraged, however, to use an |
1572 | event-based approach to child reaping and thus use libev's support for |
2164 | event-based approach to child reaping and thus use libev's support for |
1573 | that, so other libev users can use C<ev_child> watchers freely. |
2165 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
2166 | |
|
|
2167 | =head3 Stopping the Child Watcher |
|
|
2168 | |
|
|
2169 | Currently, the child watcher never gets stopped, even when the |
|
|
2170 | child terminates, so normally one needs to stop the watcher in the |
|
|
2171 | callback. Future versions of libev might stop the watcher automatically |
|
|
2172 | when a child exit is detected. |
1574 | |
2173 | |
1575 | =head3 Watcher-Specific Functions and Data Members |
2174 | =head3 Watcher-Specific Functions and Data Members |
1576 | |
2175 | |
1577 | =over 4 |
2176 | =over 4 |
1578 | |
2177 | |
… | |
… | |
1610 | its completion. |
2209 | its completion. |
1611 | |
2210 | |
1612 | ev_child cw; |
2211 | ev_child cw; |
1613 | |
2212 | |
1614 | static void |
2213 | static void |
1615 | child_cb (EV_P_ struct ev_child *w, int revents) |
2214 | child_cb (EV_P_ ev_child *w, int revents) |
1616 | { |
2215 | { |
1617 | ev_child_stop (EV_A_ w); |
2216 | ev_child_stop (EV_A_ w); |
1618 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2217 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1619 | } |
2218 | } |
1620 | |
2219 | |
… | |
… | |
1635 | |
2234 | |
1636 | |
2235 | |
1637 | =head2 C<ev_stat> - did the file attributes just change? |
2236 | =head2 C<ev_stat> - did the file attributes just change? |
1638 | |
2237 | |
1639 | This watches a file system path for attribute changes. That is, it calls |
2238 | This watches a file system path for attribute changes. That is, it calls |
1640 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2239 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1641 | compared to the last time, invoking the callback if it did. |
2240 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2241 | it did. |
1642 | |
2242 | |
1643 | The path does not need to exist: changing from "path exists" to "path does |
2243 | The path does not need to exist: changing from "path exists" to "path does |
1644 | not exist" is a status change like any other. The condition "path does |
2244 | not exist" is a status change like any other. The condition "path does not |
1645 | not exist" is signified by the C<st_nlink> field being zero (which is |
2245 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1646 | otherwise always forced to be at least one) and all the other fields of |
2246 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1647 | the stat buffer having unspecified contents. |
2247 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2248 | contents. |
1648 | |
2249 | |
1649 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2250 | The path I<must not> end in a slash or contain special components such as |
|
|
2251 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1650 | relative and your working directory changes, the behaviour is undefined. |
2252 | your working directory changes, then the behaviour is undefined. |
1651 | |
2253 | |
1652 | Since there is no standard to do this, the portable implementation simply |
2254 | Since there is no portable change notification interface available, the |
1653 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
2255 | portable implementation simply calls C<stat(2)> regularly on the path |
1654 | can specify a recommended polling interval for this case. If you specify |
2256 | to see if it changed somehow. You can specify a recommended polling |
1655 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
2257 | interval for this case. If you specify a polling interval of C<0> (highly |
1656 | unspecified default> value will be used (which you can expect to be around |
2258 | recommended!) then a I<suitable, unspecified default> value will be used |
1657 | five seconds, although this might change dynamically). Libev will also |
2259 | (which you can expect to be around five seconds, although this might |
1658 | impose a minimum interval which is currently around C<0.1>, but thats |
2260 | change dynamically). Libev will also impose a minimum interval which is |
1659 | usually overkill. |
2261 | currently around C<0.1>, but that's usually overkill. |
1660 | |
2262 | |
1661 | This watcher type is not meant for massive numbers of stat watchers, |
2263 | This watcher type is not meant for massive numbers of stat watchers, |
1662 | as even with OS-supported change notifications, this can be |
2264 | as even with OS-supported change notifications, this can be |
1663 | resource-intensive. |
2265 | resource-intensive. |
1664 | |
2266 | |
1665 | At the time of this writing, only the Linux inotify interface is |
2267 | At the time of this writing, the only OS-specific interface implemented |
1666 | implemented (implementing kqueue support is left as an exercise for the |
2268 | is the Linux inotify interface (implementing kqueue support is left as an |
1667 | reader, note, however, that the author sees no way of implementing ev_stat |
2269 | exercise for the reader. Note, however, that the author sees no way of |
1668 | semantics with kqueue). Inotify will be used to give hints only and should |
2270 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1669 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1670 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1671 | but changes are usually detected immediately, and if the file exists there |
|
|
1672 | will be no polling. |
|
|
1673 | |
2271 | |
1674 | =head3 ABI Issues (Largefile Support) |
2272 | =head3 ABI Issues (Largefile Support) |
1675 | |
2273 | |
1676 | Libev by default (unless the user overrides this) uses the default |
2274 | Libev by default (unless the user overrides this) uses the default |
1677 | compilation environment, which means that on systems with large file |
2275 | compilation environment, which means that on systems with large file |
1678 | support disabled by default, you get the 32 bit version of the stat |
2276 | support disabled by default, you get the 32 bit version of the stat |
1679 | structure. When using the library from programs that change the ABI to |
2277 | structure. When using the library from programs that change the ABI to |
1680 | use 64 bit file offsets the programs will fail. In that case you have to |
2278 | use 64 bit file offsets the programs will fail. In that case you have to |
1681 | compile libev with the same flags to get binary compatibility. This is |
2279 | compile libev with the same flags to get binary compatibility. This is |
1682 | obviously the case with any flags that change the ABI, but the problem is |
2280 | obviously the case with any flags that change the ABI, but the problem is |
1683 | most noticeably disabled with ev_stat and large file support. |
2281 | most noticeably displayed with ev_stat and large file support. |
1684 | |
2282 | |
1685 | The solution for this is to lobby your distribution maker to make large |
2283 | The solution for this is to lobby your distribution maker to make large |
1686 | file interfaces available by default (as e.g. FreeBSD does) and not |
2284 | file interfaces available by default (as e.g. FreeBSD does) and not |
1687 | optional. Libev cannot simply switch on large file support because it has |
2285 | optional. Libev cannot simply switch on large file support because it has |
1688 | to exchange stat structures with application programs compiled using the |
2286 | to exchange stat structures with application programs compiled using the |
1689 | default compilation environment. |
2287 | default compilation environment. |
1690 | |
2288 | |
1691 | =head3 Inotify |
2289 | =head3 Inotify and Kqueue |
1692 | |
2290 | |
1693 | When C<inotify (7)> support has been compiled into libev (generally only |
2291 | When C<inotify (7)> support has been compiled into libev and present at |
1694 | available on Linux) and present at runtime, it will be used to speed up |
2292 | runtime, it will be used to speed up change detection where possible. The |
1695 | change detection where possible. The inotify descriptor will be created lazily |
2293 | inotify descriptor will be created lazily when the first C<ev_stat> |
1696 | when the first C<ev_stat> watcher is being started. |
2294 | watcher is being started. |
1697 | |
2295 | |
1698 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2296 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1699 | except that changes might be detected earlier, and in some cases, to avoid |
2297 | except that changes might be detected earlier, and in some cases, to avoid |
1700 | making regular C<stat> calls. Even in the presence of inotify support |
2298 | making regular C<stat> calls. Even in the presence of inotify support |
1701 | there are many cases where libev has to resort to regular C<stat> polling. |
2299 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2300 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2301 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2302 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2303 | xfs are fully working) libev usually gets away without polling. |
1702 | |
2304 | |
1703 | (There is no support for kqueue, as apparently it cannot be used to |
2305 | There is no support for kqueue, as apparently it cannot be used to |
1704 | implement this functionality, due to the requirement of having a file |
2306 | implement this functionality, due to the requirement of having a file |
1705 | descriptor open on the object at all times). |
2307 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2308 | etc. is difficult. |
|
|
2309 | |
|
|
2310 | =head3 C<stat ()> is a synchronous operation |
|
|
2311 | |
|
|
2312 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2313 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2314 | ()>, which is a synchronous operation. |
|
|
2315 | |
|
|
2316 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2317 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2318 | as the path data is usually in memory already (except when starting the |
|
|
2319 | watcher). |
|
|
2320 | |
|
|
2321 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2322 | time due to network issues, and even under good conditions, a stat call |
|
|
2323 | often takes multiple milliseconds. |
|
|
2324 | |
|
|
2325 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2326 | paths, although this is fully supported by libev. |
1706 | |
2327 | |
1707 | =head3 The special problem of stat time resolution |
2328 | =head3 The special problem of stat time resolution |
1708 | |
2329 | |
1709 | The C<stat ()> system call only supports full-second resolution portably, and |
2330 | The C<stat ()> system call only supports full-second resolution portably, |
1710 | even on systems where the resolution is higher, many file systems still |
2331 | and even on systems where the resolution is higher, most file systems |
1711 | only support whole seconds. |
2332 | still only support whole seconds. |
1712 | |
2333 | |
1713 | That means that, if the time is the only thing that changes, you can |
2334 | That means that, if the time is the only thing that changes, you can |
1714 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2335 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1715 | calls your callback, which does something. When there is another update |
2336 | calls your callback, which does something. When there is another update |
1716 | within the same second, C<ev_stat> will be unable to detect it as the stat |
2337 | within the same second, C<ev_stat> will be unable to detect unless the |
1717 | data does not change. |
2338 | stat data does change in other ways (e.g. file size). |
1718 | |
2339 | |
1719 | The solution to this is to delay acting on a change for slightly more |
2340 | The solution to this is to delay acting on a change for slightly more |
1720 | than a second (or till slightly after the next full second boundary), using |
2341 | than a second (or till slightly after the next full second boundary), using |
1721 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
2342 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1722 | ev_timer_again (loop, w)>). |
2343 | ev_timer_again (loop, w)>). |
… | |
… | |
1742 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2363 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1743 | be detected and should normally be specified as C<0> to let libev choose |
2364 | be detected and should normally be specified as C<0> to let libev choose |
1744 | a suitable value. The memory pointed to by C<path> must point to the same |
2365 | a suitable value. The memory pointed to by C<path> must point to the same |
1745 | path for as long as the watcher is active. |
2366 | path for as long as the watcher is active. |
1746 | |
2367 | |
1747 | The callback will receive C<EV_STAT> when a change was detected, relative |
2368 | The callback will receive an C<EV_STAT> event when a change was detected, |
1748 | to the attributes at the time the watcher was started (or the last change |
2369 | relative to the attributes at the time the watcher was started (or the |
1749 | was detected). |
2370 | last change was detected). |
1750 | |
2371 | |
1751 | =item ev_stat_stat (loop, ev_stat *) |
2372 | =item ev_stat_stat (loop, ev_stat *) |
1752 | |
2373 | |
1753 | Updates the stat buffer immediately with new values. If you change the |
2374 | Updates the stat buffer immediately with new values. If you change the |
1754 | watched path in your callback, you could call this function to avoid |
2375 | watched path in your callback, you could call this function to avoid |
… | |
… | |
1837 | |
2458 | |
1838 | |
2459 | |
1839 | =head2 C<ev_idle> - when you've got nothing better to do... |
2460 | =head2 C<ev_idle> - when you've got nothing better to do... |
1840 | |
2461 | |
1841 | Idle watchers trigger events when no other events of the same or higher |
2462 | Idle watchers trigger events when no other events of the same or higher |
1842 | priority are pending (prepare, check and other idle watchers do not |
2463 | priority are pending (prepare, check and other idle watchers do not count |
1843 | count). |
2464 | as receiving "events"). |
1844 | |
2465 | |
1845 | That is, as long as your process is busy handling sockets or timeouts |
2466 | That is, as long as your process is busy handling sockets or timeouts |
1846 | (or even signals, imagine) of the same or higher priority it will not be |
2467 | (or even signals, imagine) of the same or higher priority it will not be |
1847 | triggered. But when your process is idle (or only lower-priority watchers |
2468 | triggered. But when your process is idle (or only lower-priority watchers |
1848 | are pending), the idle watchers are being called once per event loop |
2469 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1859 | |
2480 | |
1860 | =head3 Watcher-Specific Functions and Data Members |
2481 | =head3 Watcher-Specific Functions and Data Members |
1861 | |
2482 | |
1862 | =over 4 |
2483 | =over 4 |
1863 | |
2484 | |
1864 | =item ev_idle_init (ev_signal *, callback) |
2485 | =item ev_idle_init (ev_idle *, callback) |
1865 | |
2486 | |
1866 | Initialises and configures the idle watcher - it has no parameters of any |
2487 | Initialises and configures the idle watcher - it has no parameters of any |
1867 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2488 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1868 | believe me. |
2489 | believe me. |
1869 | |
2490 | |
… | |
… | |
1873 | |
2494 | |
1874 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2495 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1875 | callback, free it. Also, use no error checking, as usual. |
2496 | callback, free it. Also, use no error checking, as usual. |
1876 | |
2497 | |
1877 | static void |
2498 | static void |
1878 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2499 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1879 | { |
2500 | { |
1880 | free (w); |
2501 | free (w); |
1881 | // now do something you wanted to do when the program has |
2502 | // now do something you wanted to do when the program has |
1882 | // no longer anything immediate to do. |
2503 | // no longer anything immediate to do. |
1883 | } |
2504 | } |
1884 | |
2505 | |
1885 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2506 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1886 | ev_idle_init (idle_watcher, idle_cb); |
2507 | ev_idle_init (idle_watcher, idle_cb); |
1887 | ev_idle_start (loop, idle_cb); |
2508 | ev_idle_start (loop, idle_watcher); |
1888 | |
2509 | |
1889 | |
2510 | |
1890 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2511 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1891 | |
2512 | |
1892 | Prepare and check watchers are usually (but not always) used in tandem: |
2513 | Prepare and check watchers are usually (but not always) used in pairs: |
1893 | prepare watchers get invoked before the process blocks and check watchers |
2514 | prepare watchers get invoked before the process blocks and check watchers |
1894 | afterwards. |
2515 | afterwards. |
1895 | |
2516 | |
1896 | You I<must not> call C<ev_loop> or similar functions that enter |
2517 | You I<must not> call C<ev_loop> or similar functions that enter |
1897 | the current event loop from either C<ev_prepare> or C<ev_check> |
2518 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
1900 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2521 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1901 | C<ev_check> so if you have one watcher of each kind they will always be |
2522 | C<ev_check> so if you have one watcher of each kind they will always be |
1902 | called in pairs bracketing the blocking call. |
2523 | called in pairs bracketing the blocking call. |
1903 | |
2524 | |
1904 | Their main purpose is to integrate other event mechanisms into libev and |
2525 | Their main purpose is to integrate other event mechanisms into libev and |
1905 | their use is somewhat advanced. This could be used, for example, to track |
2526 | their use is somewhat advanced. They could be used, for example, to track |
1906 | variable changes, implement your own watchers, integrate net-snmp or a |
2527 | variable changes, implement your own watchers, integrate net-snmp or a |
1907 | coroutine library and lots more. They are also occasionally useful if |
2528 | coroutine library and lots more. They are also occasionally useful if |
1908 | you cache some data and want to flush it before blocking (for example, |
2529 | you cache some data and want to flush it before blocking (for example, |
1909 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2530 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1910 | watcher). |
2531 | watcher). |
1911 | |
2532 | |
1912 | This is done by examining in each prepare call which file descriptors need |
2533 | This is done by examining in each prepare call which file descriptors |
1913 | to be watched by the other library, registering C<ev_io> watchers for |
2534 | need to be watched by the other library, registering C<ev_io> watchers |
1914 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2535 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1915 | provide just this functionality). Then, in the check watcher you check for |
2536 | libraries provide exactly this functionality). Then, in the check watcher, |
1916 | any events that occurred (by checking the pending status of all watchers |
2537 | you check for any events that occurred (by checking the pending status |
1917 | and stopping them) and call back into the library. The I/O and timer |
2538 | of all watchers and stopping them) and call back into the library. The |
1918 | callbacks will never actually be called (but must be valid nevertheless, |
2539 | I/O and timer callbacks will never actually be called (but must be valid |
1919 | because you never know, you know?). |
2540 | nevertheless, because you never know, you know?). |
1920 | |
2541 | |
1921 | As another example, the Perl Coro module uses these hooks to integrate |
2542 | As another example, the Perl Coro module uses these hooks to integrate |
1922 | coroutines into libev programs, by yielding to other active coroutines |
2543 | coroutines into libev programs, by yielding to other active coroutines |
1923 | during each prepare and only letting the process block if no coroutines |
2544 | during each prepare and only letting the process block if no coroutines |
1924 | are ready to run (it's actually more complicated: it only runs coroutines |
2545 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
1927 | loop from blocking if lower-priority coroutines are active, thus mapping |
2548 | loop from blocking if lower-priority coroutines are active, thus mapping |
1928 | low-priority coroutines to idle/background tasks). |
2549 | low-priority coroutines to idle/background tasks). |
1929 | |
2550 | |
1930 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2551 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1931 | priority, to ensure that they are being run before any other watchers |
2552 | priority, to ensure that they are being run before any other watchers |
|
|
2553 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2554 | |
1932 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2555 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1933 | too) should not activate ("feed") events into libev. While libev fully |
2556 | activate ("feed") events into libev. While libev fully supports this, they |
1934 | supports this, they might get executed before other C<ev_check> watchers |
2557 | might get executed before other C<ev_check> watchers did their job. As |
1935 | did their job. As C<ev_check> watchers are often used to embed other |
2558 | C<ev_check> watchers are often used to embed other (non-libev) event |
1936 | (non-libev) event loops those other event loops might be in an unusable |
2559 | loops those other event loops might be in an unusable state until their |
1937 | state until their C<ev_check> watcher ran (always remind yourself to |
2560 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1938 | coexist peacefully with others). |
2561 | others). |
1939 | |
2562 | |
1940 | =head3 Watcher-Specific Functions and Data Members |
2563 | =head3 Watcher-Specific Functions and Data Members |
1941 | |
2564 | |
1942 | =over 4 |
2565 | =over 4 |
1943 | |
2566 | |
… | |
… | |
1945 | |
2568 | |
1946 | =item ev_check_init (ev_check *, callback) |
2569 | =item ev_check_init (ev_check *, callback) |
1947 | |
2570 | |
1948 | Initialises and configures the prepare or check watcher - they have no |
2571 | Initialises and configures the prepare or check watcher - they have no |
1949 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2572 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1950 | macros, but using them is utterly, utterly and completely pointless. |
2573 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2574 | pointless. |
1951 | |
2575 | |
1952 | =back |
2576 | =back |
1953 | |
2577 | |
1954 | =head3 Examples |
2578 | =head3 Examples |
1955 | |
2579 | |
… | |
… | |
1968 | |
2592 | |
1969 | static ev_io iow [nfd]; |
2593 | static ev_io iow [nfd]; |
1970 | static ev_timer tw; |
2594 | static ev_timer tw; |
1971 | |
2595 | |
1972 | static void |
2596 | static void |
1973 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2597 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
1974 | { |
2598 | { |
1975 | } |
2599 | } |
1976 | |
2600 | |
1977 | // create io watchers for each fd and a timer before blocking |
2601 | // create io watchers for each fd and a timer before blocking |
1978 | static void |
2602 | static void |
1979 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2603 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
1980 | { |
2604 | { |
1981 | int timeout = 3600000; |
2605 | int timeout = 3600000; |
1982 | struct pollfd fds [nfd]; |
2606 | struct pollfd fds [nfd]; |
1983 | // actual code will need to loop here and realloc etc. |
2607 | // actual code will need to loop here and realloc etc. |
1984 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2608 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1985 | |
2609 | |
1986 | /* the callback is illegal, but won't be called as we stop during check */ |
2610 | /* the callback is illegal, but won't be called as we stop during check */ |
1987 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2611 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
1988 | ev_timer_start (loop, &tw); |
2612 | ev_timer_start (loop, &tw); |
1989 | |
2613 | |
1990 | // create one ev_io per pollfd |
2614 | // create one ev_io per pollfd |
1991 | for (int i = 0; i < nfd; ++i) |
2615 | for (int i = 0; i < nfd; ++i) |
1992 | { |
2616 | { |
… | |
… | |
1999 | } |
2623 | } |
2000 | } |
2624 | } |
2001 | |
2625 | |
2002 | // stop all watchers after blocking |
2626 | // stop all watchers after blocking |
2003 | static void |
2627 | static void |
2004 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2628 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2005 | { |
2629 | { |
2006 | ev_timer_stop (loop, &tw); |
2630 | ev_timer_stop (loop, &tw); |
2007 | |
2631 | |
2008 | for (int i = 0; i < nfd; ++i) |
2632 | for (int i = 0; i < nfd; ++i) |
2009 | { |
2633 | { |
… | |
… | |
2048 | } |
2672 | } |
2049 | |
2673 | |
2050 | // do not ever call adns_afterpoll |
2674 | // do not ever call adns_afterpoll |
2051 | |
2675 | |
2052 | Method 4: Do not use a prepare or check watcher because the module you |
2676 | Method 4: Do not use a prepare or check watcher because the module you |
2053 | want to embed is too inflexible to support it. Instead, you can override |
2677 | want to embed is not flexible enough to support it. Instead, you can |
2054 | their poll function. The drawback with this solution is that the main |
2678 | override their poll function. The drawback with this solution is that the |
2055 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
2679 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
2056 | this. |
2680 | this approach, effectively embedding EV as a client into the horrible |
|
|
2681 | libglib event loop. |
2057 | |
2682 | |
2058 | static gint |
2683 | static gint |
2059 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2684 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2060 | { |
2685 | { |
2061 | int got_events = 0; |
2686 | int got_events = 0; |
… | |
… | |
2092 | prioritise I/O. |
2717 | prioritise I/O. |
2093 | |
2718 | |
2094 | As an example for a bug workaround, the kqueue backend might only support |
2719 | As an example for a bug workaround, the kqueue backend might only support |
2095 | sockets on some platform, so it is unusable as generic backend, but you |
2720 | sockets on some platform, so it is unusable as generic backend, but you |
2096 | still want to make use of it because you have many sockets and it scales |
2721 | still want to make use of it because you have many sockets and it scales |
2097 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2722 | so nicely. In this case, you would create a kqueue-based loop and embed |
2098 | into your default loop (which might use e.g. poll). Overall operation will |
2723 | it into your default loop (which might use e.g. poll). Overall operation |
2099 | be a bit slower because first libev has to poll and then call kevent, but |
2724 | will be a bit slower because first libev has to call C<poll> and then |
2100 | at least you can use both at what they are best. |
2725 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2726 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2101 | |
2727 | |
2102 | As for prioritising I/O: rarely you have the case where some fds have |
2728 | As for prioritising I/O: under rare circumstances you have the case where |
2103 | to be watched and handled very quickly (with low latency), and even |
2729 | some fds have to be watched and handled very quickly (with low latency), |
2104 | priorities and idle watchers might have too much overhead. In this case |
2730 | and even priorities and idle watchers might have too much overhead. In |
2105 | you would put all the high priority stuff in one loop and all the rest in |
2731 | this case you would put all the high priority stuff in one loop and all |
2106 | a second one, and embed the second one in the first. |
2732 | the rest in a second one, and embed the second one in the first. |
2107 | |
2733 | |
2108 | As long as the watcher is active, the callback will be invoked every time |
2734 | As long as the watcher is active, the callback will be invoked every |
2109 | there might be events pending in the embedded loop. The callback must then |
2735 | time there might be events pending in the embedded loop. The callback |
2110 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2736 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2111 | their callbacks (you could also start an idle watcher to give the embedded |
2737 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2112 | loop strictly lower priority for example). You can also set the callback |
2738 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2113 | to C<0>, in which case the embed watcher will automatically execute the |
2739 | to give the embedded loop strictly lower priority for example). |
2114 | embedded loop sweep. |
|
|
2115 | |
2740 | |
2116 | As long as the watcher is started it will automatically handle events. The |
2741 | You can also set the callback to C<0>, in which case the embed watcher |
2117 | callback will be invoked whenever some events have been handled. You can |
2742 | will automatically execute the embedded loop sweep whenever necessary. |
2118 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2119 | interested in that. |
|
|
2120 | |
2743 | |
2121 | Also, there have not currently been made special provisions for forking: |
2744 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2122 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2745 | is active, i.e., the embedded loop will automatically be forked when the |
2123 | but you will also have to stop and restart any C<ev_embed> watchers |
2746 | embedding loop forks. In other cases, the user is responsible for calling |
2124 | yourself. |
2747 | C<ev_loop_fork> on the embedded loop. |
2125 | |
2748 | |
2126 | Unfortunately, not all backends are embeddable, only the ones returned by |
2749 | Unfortunately, not all backends are embeddable: only the ones returned by |
2127 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2750 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2128 | portable one. |
2751 | portable one. |
2129 | |
2752 | |
2130 | So when you want to use this feature you will always have to be prepared |
2753 | So when you want to use this feature you will always have to be prepared |
2131 | that you cannot get an embeddable loop. The recommended way to get around |
2754 | that you cannot get an embeddable loop. The recommended way to get around |
2132 | this is to have a separate variables for your embeddable loop, try to |
2755 | this is to have a separate variables for your embeddable loop, try to |
2133 | create it, and if that fails, use the normal loop for everything. |
2756 | create it, and if that fails, use the normal loop for everything. |
|
|
2757 | |
|
|
2758 | =head3 C<ev_embed> and fork |
|
|
2759 | |
|
|
2760 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2761 | automatically be applied to the embedded loop as well, so no special |
|
|
2762 | fork handling is required in that case. When the watcher is not running, |
|
|
2763 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2764 | as applicable. |
2134 | |
2765 | |
2135 | =head3 Watcher-Specific Functions and Data Members |
2766 | =head3 Watcher-Specific Functions and Data Members |
2136 | |
2767 | |
2137 | =over 4 |
2768 | =over 4 |
2138 | |
2769 | |
… | |
… | |
2166 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2797 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2167 | used). |
2798 | used). |
2168 | |
2799 | |
2169 | struct ev_loop *loop_hi = ev_default_init (0); |
2800 | struct ev_loop *loop_hi = ev_default_init (0); |
2170 | struct ev_loop *loop_lo = 0; |
2801 | struct ev_loop *loop_lo = 0; |
2171 | struct ev_embed embed; |
2802 | ev_embed embed; |
2172 | |
2803 | |
2173 | // see if there is a chance of getting one that works |
2804 | // see if there is a chance of getting one that works |
2174 | // (remember that a flags value of 0 means autodetection) |
2805 | // (remember that a flags value of 0 means autodetection) |
2175 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2806 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2176 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2807 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2190 | kqueue implementation). Store the kqueue/socket-only event loop in |
2821 | kqueue implementation). Store the kqueue/socket-only event loop in |
2191 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2822 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2192 | |
2823 | |
2193 | struct ev_loop *loop = ev_default_init (0); |
2824 | struct ev_loop *loop = ev_default_init (0); |
2194 | struct ev_loop *loop_socket = 0; |
2825 | struct ev_loop *loop_socket = 0; |
2195 | struct ev_embed embed; |
2826 | ev_embed embed; |
2196 | |
2827 | |
2197 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2828 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2198 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2829 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2199 | { |
2830 | { |
2200 | ev_embed_init (&embed, 0, loop_socket); |
2831 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2215 | event loop blocks next and before C<ev_check> watchers are being called, |
2846 | event loop blocks next and before C<ev_check> watchers are being called, |
2216 | and only in the child after the fork. If whoever good citizen calling |
2847 | and only in the child after the fork. If whoever good citizen calling |
2217 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2848 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2218 | handlers will be invoked, too, of course. |
2849 | handlers will be invoked, too, of course. |
2219 | |
2850 | |
|
|
2851 | =head3 The special problem of life after fork - how is it possible? |
|
|
2852 | |
|
|
2853 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2854 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2855 | sequence should be handled by libev without any problems. |
|
|
2856 | |
|
|
2857 | This changes when the application actually wants to do event handling |
|
|
2858 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2859 | fork. |
|
|
2860 | |
|
|
2861 | The default mode of operation (for libev, with application help to detect |
|
|
2862 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2863 | when I<either> the parent I<or> the child process continues. |
|
|
2864 | |
|
|
2865 | When both processes want to continue using libev, then this is usually the |
|
|
2866 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2867 | supposed to continue with all watchers in place as before, while the other |
|
|
2868 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2869 | |
|
|
2870 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2871 | simply create a new event loop, which of course will be "empty", and |
|
|
2872 | use that for new watchers. This has the advantage of not touching more |
|
|
2873 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2874 | disadvantage of having to use multiple event loops (which do not support |
|
|
2875 | signal watchers). |
|
|
2876 | |
|
|
2877 | When this is not possible, or you want to use the default loop for |
|
|
2878 | other reasons, then in the process that wants to start "fresh", call |
|
|
2879 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2880 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2881 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2882 | also that in that case, you have to re-register any signal watchers. |
|
|
2883 | |
2220 | =head3 Watcher-Specific Functions and Data Members |
2884 | =head3 Watcher-Specific Functions and Data Members |
2221 | |
2885 | |
2222 | =over 4 |
2886 | =over 4 |
2223 | |
2887 | |
2224 | =item ev_fork_init (ev_signal *, callback) |
2888 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2256 | is that the author does not know of a simple (or any) algorithm for a |
2920 | is that the author does not know of a simple (or any) algorithm for a |
2257 | multiple-writer-single-reader queue that works in all cases and doesn't |
2921 | multiple-writer-single-reader queue that works in all cases and doesn't |
2258 | need elaborate support such as pthreads. |
2922 | need elaborate support such as pthreads. |
2259 | |
2923 | |
2260 | That means that if you want to queue data, you have to provide your own |
2924 | That means that if you want to queue data, you have to provide your own |
2261 | queue. But at least I can tell you would implement locking around your |
2925 | queue. But at least I can tell you how to implement locking around your |
2262 | queue: |
2926 | queue: |
2263 | |
2927 | |
2264 | =over 4 |
2928 | =over 4 |
2265 | |
2929 | |
2266 | =item queueing from a signal handler context |
2930 | =item queueing from a signal handler context |
2267 | |
2931 | |
2268 | To implement race-free queueing, you simply add to the queue in the signal |
2932 | To implement race-free queueing, you simply add to the queue in the signal |
2269 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
2933 | handler but you block the signal handler in the watcher callback. Here is |
2270 | some fictitious SIGUSR1 handler: |
2934 | an example that does that for some fictitious SIGUSR1 handler: |
2271 | |
2935 | |
2272 | static ev_async mysig; |
2936 | static ev_async mysig; |
2273 | |
2937 | |
2274 | static void |
2938 | static void |
2275 | sigusr1_handler (void) |
2939 | sigusr1_handler (void) |
… | |
… | |
2341 | =over 4 |
3005 | =over 4 |
2342 | |
3006 | |
2343 | =item ev_async_init (ev_async *, callback) |
3007 | =item ev_async_init (ev_async *, callback) |
2344 | |
3008 | |
2345 | Initialises and configures the async watcher - it has no parameters of any |
3009 | Initialises and configures the async watcher - it has no parameters of any |
2346 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3010 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2347 | believe me. |
3011 | trust me. |
2348 | |
3012 | |
2349 | =item ev_async_send (loop, ev_async *) |
3013 | =item ev_async_send (loop, ev_async *) |
2350 | |
3014 | |
2351 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3015 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2352 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3016 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2353 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
3017 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2354 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3018 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2355 | section below on what exactly this means). |
3019 | section below on what exactly this means). |
2356 | |
3020 | |
|
|
3021 | Note that, as with other watchers in libev, multiple events might get |
|
|
3022 | compressed into a single callback invocation (another way to look at this |
|
|
3023 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3024 | reset when the event loop detects that). |
|
|
3025 | |
2357 | This call incurs the overhead of a system call only once per loop iteration, |
3026 | This call incurs the overhead of a system call only once per event loop |
2358 | so while the overhead might be noticeable, it doesn't apply to repeated |
3027 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2359 | calls to C<ev_async_send>. |
3028 | repeated calls to C<ev_async_send> for the same event loop. |
2360 | |
3029 | |
2361 | =item bool = ev_async_pending (ev_async *) |
3030 | =item bool = ev_async_pending (ev_async *) |
2362 | |
3031 | |
2363 | Returns a non-zero value when C<ev_async_send> has been called on the |
3032 | Returns a non-zero value when C<ev_async_send> has been called on the |
2364 | watcher but the event has not yet been processed (or even noted) by the |
3033 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2367 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3036 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2368 | the loop iterates next and checks for the watcher to have become active, |
3037 | the loop iterates next and checks for the watcher to have become active, |
2369 | it will reset the flag again. C<ev_async_pending> can be used to very |
3038 | it will reset the flag again. C<ev_async_pending> can be used to very |
2370 | quickly check whether invoking the loop might be a good idea. |
3039 | quickly check whether invoking the loop might be a good idea. |
2371 | |
3040 | |
2372 | Not that this does I<not> check whether the watcher itself is pending, only |
3041 | Not that this does I<not> check whether the watcher itself is pending, |
2373 | whether it has been requested to make this watcher pending. |
3042 | only whether it has been requested to make this watcher pending: there |
|
|
3043 | is a time window between the event loop checking and resetting the async |
|
|
3044 | notification, and the callback being invoked. |
2374 | |
3045 | |
2375 | =back |
3046 | =back |
2376 | |
3047 | |
2377 | |
3048 | |
2378 | =head1 OTHER FUNCTIONS |
3049 | =head1 OTHER FUNCTIONS |
… | |
… | |
2382 | =over 4 |
3053 | =over 4 |
2383 | |
3054 | |
2384 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3055 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2385 | |
3056 | |
2386 | This function combines a simple timer and an I/O watcher, calls your |
3057 | This function combines a simple timer and an I/O watcher, calls your |
2387 | callback on whichever event happens first and automatically stop both |
3058 | callback on whichever event happens first and automatically stops both |
2388 | watchers. This is useful if you want to wait for a single event on an fd |
3059 | watchers. This is useful if you want to wait for a single event on an fd |
2389 | or timeout without having to allocate/configure/start/stop/free one or |
3060 | or timeout without having to allocate/configure/start/stop/free one or |
2390 | more watchers yourself. |
3061 | more watchers yourself. |
2391 | |
3062 | |
2392 | If C<fd> is less than 0, then no I/O watcher will be started and events |
3063 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2393 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
3064 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2394 | C<events> set will be created and started. |
3065 | the given C<fd> and C<events> set will be created and started. |
2395 | |
3066 | |
2396 | If C<timeout> is less than 0, then no timeout watcher will be |
3067 | If C<timeout> is less than 0, then no timeout watcher will be |
2397 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3068 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2398 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
3069 | repeat = 0) will be started. C<0> is a valid timeout. |
2399 | dubious value. |
|
|
2400 | |
3070 | |
2401 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3071 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2402 | passed an C<revents> set like normal event callbacks (a combination of |
3072 | passed an C<revents> set like normal event callbacks (a combination of |
2403 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3073 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2404 | value passed to C<ev_once>: |
3074 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
3075 | a timeout and an io event at the same time - you probably should give io |
|
|
3076 | events precedence. |
|
|
3077 | |
|
|
3078 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2405 | |
3079 | |
2406 | static void stdin_ready (int revents, void *arg) |
3080 | static void stdin_ready (int revents, void *arg) |
2407 | { |
3081 | { |
|
|
3082 | if (revents & EV_READ) |
|
|
3083 | /* stdin might have data for us, joy! */; |
2408 | if (revents & EV_TIMEOUT) |
3084 | else if (revents & EV_TIMEOUT) |
2409 | /* doh, nothing entered */; |
3085 | /* doh, nothing entered */; |
2410 | else if (revents & EV_READ) |
|
|
2411 | /* stdin might have data for us, joy! */; |
|
|
2412 | } |
3086 | } |
2413 | |
3087 | |
2414 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3088 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2415 | |
3089 | |
2416 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
3090 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
2417 | |
3091 | |
2418 | Feeds the given event set into the event loop, as if the specified event |
3092 | Feeds the given event set into the event loop, as if the specified event |
2419 | had happened for the specified watcher (which must be a pointer to an |
3093 | had happened for the specified watcher (which must be a pointer to an |
2420 | initialised but not necessarily started event watcher). |
3094 | initialised but not necessarily started event watcher). |
2421 | |
3095 | |
2422 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3096 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
2423 | |
3097 | |
2424 | Feed an event on the given fd, as if a file descriptor backend detected |
3098 | Feed an event on the given fd, as if a file descriptor backend detected |
2425 | the given events it. |
3099 | the given events it. |
2426 | |
3100 | |
2427 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3101 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
2428 | |
3102 | |
2429 | Feed an event as if the given signal occurred (C<loop> must be the default |
3103 | Feed an event as if the given signal occurred (C<loop> must be the default |
2430 | loop!). |
3104 | loop!). |
2431 | |
3105 | |
2432 | =back |
3106 | =back |
… | |
… | |
2554 | |
3228 | |
2555 | myclass obj; |
3229 | myclass obj; |
2556 | ev::io iow; |
3230 | ev::io iow; |
2557 | iow.set <myclass, &myclass::io_cb> (&obj); |
3231 | iow.set <myclass, &myclass::io_cb> (&obj); |
2558 | |
3232 | |
|
|
3233 | =item w->set (object *) |
|
|
3234 | |
|
|
3235 | This is an B<experimental> feature that might go away in a future version. |
|
|
3236 | |
|
|
3237 | This is a variation of a method callback - leaving out the method to call |
|
|
3238 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3239 | functor objects without having to manually specify the C<operator ()> all |
|
|
3240 | the time. Incidentally, you can then also leave out the template argument |
|
|
3241 | list. |
|
|
3242 | |
|
|
3243 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3244 | int revents)>. |
|
|
3245 | |
|
|
3246 | See the method-C<set> above for more details. |
|
|
3247 | |
|
|
3248 | Example: use a functor object as callback. |
|
|
3249 | |
|
|
3250 | struct myfunctor |
|
|
3251 | { |
|
|
3252 | void operator() (ev::io &w, int revents) |
|
|
3253 | { |
|
|
3254 | ... |
|
|
3255 | } |
|
|
3256 | } |
|
|
3257 | |
|
|
3258 | myfunctor f; |
|
|
3259 | |
|
|
3260 | ev::io w; |
|
|
3261 | w.set (&f); |
|
|
3262 | |
2559 | =item w->set<function> (void *data = 0) |
3263 | =item w->set<function> (void *data = 0) |
2560 | |
3264 | |
2561 | Also sets a callback, but uses a static method or plain function as |
3265 | Also sets a callback, but uses a static method or plain function as |
2562 | callback. The optional C<data> argument will be stored in the watcher's |
3266 | callback. The optional C<data> argument will be stored in the watcher's |
2563 | C<data> member and is free for you to use. |
3267 | C<data> member and is free for you to use. |
2564 | |
3268 | |
2565 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
3269 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2566 | |
3270 | |
2567 | See the method-C<set> above for more details. |
3271 | See the method-C<set> above for more details. |
2568 | |
3272 | |
2569 | Example: |
3273 | Example: Use a plain function as callback. |
2570 | |
3274 | |
2571 | static void io_cb (ev::io &w, int revents) { } |
3275 | static void io_cb (ev::io &w, int revents) { } |
2572 | iow.set <io_cb> (); |
3276 | iow.set <io_cb> (); |
2573 | |
3277 | |
2574 | =item w->set (struct ev_loop *) |
3278 | =item w->set (struct ev_loop *) |
… | |
… | |
2612 | Example: Define a class with an IO and idle watcher, start one of them in |
3316 | Example: Define a class with an IO and idle watcher, start one of them in |
2613 | the constructor. |
3317 | the constructor. |
2614 | |
3318 | |
2615 | class myclass |
3319 | class myclass |
2616 | { |
3320 | { |
2617 | ev::io io; void io_cb (ev::io &w, int revents); |
3321 | ev::io io ; void io_cb (ev::io &w, int revents); |
2618 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
3322 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2619 | |
3323 | |
2620 | myclass (int fd) |
3324 | myclass (int fd) |
2621 | { |
3325 | { |
2622 | io .set <myclass, &myclass::io_cb > (this); |
3326 | io .set <myclass, &myclass::io_cb > (this); |
2623 | idle.set <myclass, &myclass::idle_cb> (this); |
3327 | idle.set <myclass, &myclass::idle_cb> (this); |
… | |
… | |
2639 | =item Perl |
3343 | =item Perl |
2640 | |
3344 | |
2641 | The EV module implements the full libev API and is actually used to test |
3345 | The EV module implements the full libev API and is actually used to test |
2642 | libev. EV is developed together with libev. Apart from the EV core module, |
3346 | libev. EV is developed together with libev. Apart from the EV core module, |
2643 | there are additional modules that implement libev-compatible interfaces |
3347 | there are additional modules that implement libev-compatible interfaces |
2644 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
3348 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2645 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
3349 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
3350 | and C<EV::Glib>). |
2646 | |
3351 | |
2647 | It can be found and installed via CPAN, its homepage is at |
3352 | It can be found and installed via CPAN, its homepage is at |
2648 | L<http://software.schmorp.de/pkg/EV>. |
3353 | L<http://software.schmorp.de/pkg/EV>. |
2649 | |
3354 | |
2650 | =item Python |
3355 | =item Python |
2651 | |
3356 | |
2652 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3357 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2653 | seems to be quite complete and well-documented. Note, however, that the |
3358 | seems to be quite complete and well-documented. |
2654 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2655 | for everybody else, and therefore, should never be applied in an installed |
|
|
2656 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2657 | libev). |
|
|
2658 | |
3359 | |
2659 | =item Ruby |
3360 | =item Ruby |
2660 | |
3361 | |
2661 | Tony Arcieri has written a ruby extension that offers access to a subset |
3362 | Tony Arcieri has written a ruby extension that offers access to a subset |
2662 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3363 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2663 | more on top of it. It can be found via gem servers. Its homepage is at |
3364 | more on top of it. It can be found via gem servers. Its homepage is at |
2664 | L<http://rev.rubyforge.org/>. |
3365 | L<http://rev.rubyforge.org/>. |
2665 | |
3366 | |
|
|
3367 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3368 | makes rev work even on mingw. |
|
|
3369 | |
|
|
3370 | =item Haskell |
|
|
3371 | |
|
|
3372 | A haskell binding to libev is available at |
|
|
3373 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3374 | |
2666 | =item D |
3375 | =item D |
2667 | |
3376 | |
2668 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3377 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2669 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3378 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3379 | |
|
|
3380 | =item Ocaml |
|
|
3381 | |
|
|
3382 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3383 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
2670 | |
3384 | |
2671 | =back |
3385 | =back |
2672 | |
3386 | |
2673 | |
3387 | |
2674 | =head1 MACRO MAGIC |
3388 | =head1 MACRO MAGIC |
… | |
… | |
2775 | |
3489 | |
2776 | #define EV_STANDALONE 1 |
3490 | #define EV_STANDALONE 1 |
2777 | #include "ev.h" |
3491 | #include "ev.h" |
2778 | |
3492 | |
2779 | Both header files and implementation files can be compiled with a C++ |
3493 | Both header files and implementation files can be compiled with a C++ |
2780 | compiler (at least, thats a stated goal, and breakage will be treated |
3494 | compiler (at least, that's a stated goal, and breakage will be treated |
2781 | as a bug). |
3495 | as a bug). |
2782 | |
3496 | |
2783 | You need the following files in your source tree, or in a directory |
3497 | You need the following files in your source tree, or in a directory |
2784 | in your include path (e.g. in libev/ when using -Ilibev): |
3498 | in your include path (e.g. in libev/ when using -Ilibev): |
2785 | |
3499 | |
… | |
… | |
2829 | |
3543 | |
2830 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3544 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2831 | |
3545 | |
2832 | Libev can be configured via a variety of preprocessor symbols you have to |
3546 | Libev can be configured via a variety of preprocessor symbols you have to |
2833 | define before including any of its files. The default in the absence of |
3547 | define before including any of its files. The default in the absence of |
2834 | autoconf is noted for every option. |
3548 | autoconf is documented for every option. |
2835 | |
3549 | |
2836 | =over 4 |
3550 | =over 4 |
2837 | |
3551 | |
2838 | =item EV_STANDALONE |
3552 | =item EV_STANDALONE |
2839 | |
3553 | |
… | |
… | |
2841 | keeps libev from including F<config.h>, and it also defines dummy |
3555 | keeps libev from including F<config.h>, and it also defines dummy |
2842 | implementations for some libevent functions (such as logging, which is not |
3556 | implementations for some libevent functions (such as logging, which is not |
2843 | supported). It will also not define any of the structs usually found in |
3557 | supported). It will also not define any of the structs usually found in |
2844 | F<event.h> that are not directly supported by the libev core alone. |
3558 | F<event.h> that are not directly supported by the libev core alone. |
2845 | |
3559 | |
|
|
3560 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3561 | configuration, but has to be more conservative. |
|
|
3562 | |
2846 | =item EV_USE_MONOTONIC |
3563 | =item EV_USE_MONOTONIC |
2847 | |
3564 | |
2848 | If defined to be C<1>, libev will try to detect the availability of the |
3565 | If defined to be C<1>, libev will try to detect the availability of the |
2849 | monotonic clock option at both compile time and runtime. Otherwise no use |
3566 | monotonic clock option at both compile time and runtime. Otherwise no |
2850 | of the monotonic clock option will be attempted. If you enable this, you |
3567 | use of the monotonic clock option will be attempted. If you enable this, |
2851 | usually have to link against librt or something similar. Enabling it when |
3568 | you usually have to link against librt or something similar. Enabling it |
2852 | the functionality isn't available is safe, though, although you have |
3569 | when the functionality isn't available is safe, though, although you have |
2853 | to make sure you link against any libraries where the C<clock_gettime> |
3570 | to make sure you link against any libraries where the C<clock_gettime> |
2854 | function is hiding in (often F<-lrt>). |
3571 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2855 | |
3572 | |
2856 | =item EV_USE_REALTIME |
3573 | =item EV_USE_REALTIME |
2857 | |
3574 | |
2858 | If defined to be C<1>, libev will try to detect the availability of the |
3575 | If defined to be C<1>, libev will try to detect the availability of the |
2859 | real-time clock option at compile time (and assume its availability at |
3576 | real-time clock option at compile time (and assume its availability |
2860 | runtime if successful). Otherwise no use of the real-time clock option will |
3577 | at runtime if successful). Otherwise no use of the real-time clock |
2861 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3578 | option will be attempted. This effectively replaces C<gettimeofday> |
2862 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3579 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2863 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3580 | correctness. See the note about libraries in the description of |
|
|
3581 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3582 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3583 | |
|
|
3584 | =item EV_USE_CLOCK_SYSCALL |
|
|
3585 | |
|
|
3586 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3587 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3588 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3589 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3590 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3591 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3592 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3593 | higher, as it simplifies linking (no need for C<-lrt>). |
2864 | |
3594 | |
2865 | =item EV_USE_NANOSLEEP |
3595 | =item EV_USE_NANOSLEEP |
2866 | |
3596 | |
2867 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3597 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2868 | and will use it for delays. Otherwise it will use C<select ()>. |
3598 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
2884 | |
3614 | |
2885 | =item EV_SELECT_USE_FD_SET |
3615 | =item EV_SELECT_USE_FD_SET |
2886 | |
3616 | |
2887 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3617 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2888 | structure. This is useful if libev doesn't compile due to a missing |
3618 | structure. This is useful if libev doesn't compile due to a missing |
2889 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3619 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
2890 | exotic systems. This usually limits the range of file descriptors to some |
3620 | on exotic systems. This usually limits the range of file descriptors to |
2891 | low limit such as 1024 or might have other limitations (winsocket only |
3621 | some low limit such as 1024 or might have other limitations (winsocket |
2892 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3622 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
2893 | influence the size of the C<fd_set> used. |
3623 | configures the maximum size of the C<fd_set>. |
2894 | |
3624 | |
2895 | =item EV_SELECT_IS_WINSOCKET |
3625 | =item EV_SELECT_IS_WINSOCKET |
2896 | |
3626 | |
2897 | When defined to C<1>, the select backend will assume that |
3627 | When defined to C<1>, the select backend will assume that |
2898 | select/socket/connect etc. don't understand file descriptors but |
3628 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3009 | When doing priority-based operations, libev usually has to linearly search |
3739 | When doing priority-based operations, libev usually has to linearly search |
3010 | all the priorities, so having many of them (hundreds) uses a lot of space |
3740 | all the priorities, so having many of them (hundreds) uses a lot of space |
3011 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3741 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3012 | fine. |
3742 | fine. |
3013 | |
3743 | |
3014 | If your embedding application does not need any priorities, defining these both to |
3744 | If your embedding application does not need any priorities, defining these |
3015 | C<0> will save some memory and CPU. |
3745 | both to C<0> will save some memory and CPU. |
3016 | |
3746 | |
3017 | =item EV_PERIODIC_ENABLE |
3747 | =item EV_PERIODIC_ENABLE |
3018 | |
3748 | |
3019 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3749 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3020 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3750 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
… | |
… | |
3027 | code. |
3757 | code. |
3028 | |
3758 | |
3029 | =item EV_EMBED_ENABLE |
3759 | =item EV_EMBED_ENABLE |
3030 | |
3760 | |
3031 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3761 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3032 | defined to be C<0>, then they are not. |
3762 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3763 | watcher types, which therefore must not be disabled. |
3033 | |
3764 | |
3034 | =item EV_STAT_ENABLE |
3765 | =item EV_STAT_ENABLE |
3035 | |
3766 | |
3036 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3767 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3037 | defined to be C<0>, then they are not. |
3768 | defined to be C<0>, then they are not. |
… | |
… | |
3047 | defined to be C<0>, then they are not. |
3778 | defined to be C<0>, then they are not. |
3048 | |
3779 | |
3049 | =item EV_MINIMAL |
3780 | =item EV_MINIMAL |
3050 | |
3781 | |
3051 | If you need to shave off some kilobytes of code at the expense of some |
3782 | If you need to shave off some kilobytes of code at the expense of some |
3052 | speed, define this symbol to C<1>. Currently this is used to override some |
3783 | speed (but with the full API), define this symbol to C<1>. Currently this |
3053 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3784 | is used to override some inlining decisions, saves roughly 30% code size |
3054 | much smaller 2-heap for timer management over the default 4-heap. |
3785 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3786 | the default 4-heap. |
|
|
3787 | |
|
|
3788 | You can save even more by disabling watcher types you do not need |
|
|
3789 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3790 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3791 | |
|
|
3792 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3793 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3794 | of the API are still available, and do not complain if this subset changes |
|
|
3795 | over time. |
3055 | |
3796 | |
3056 | =item EV_PID_HASHSIZE |
3797 | =item EV_PID_HASHSIZE |
3057 | |
3798 | |
3058 | C<ev_child> watchers use a small hash table to distribute workload by |
3799 | C<ev_child> watchers use a small hash table to distribute workload by |
3059 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3800 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3069 | two). |
3810 | two). |
3070 | |
3811 | |
3071 | =item EV_USE_4HEAP |
3812 | =item EV_USE_4HEAP |
3072 | |
3813 | |
3073 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3814 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3074 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
3815 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3075 | to C<1>. The 4-heap uses more complicated (longer) code but has |
3816 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3076 | noticeably faster performance with many (thousands) of watchers. |
3817 | faster performance with many (thousands) of watchers. |
3077 | |
3818 | |
3078 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3819 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3079 | (disabled). |
3820 | (disabled). |
3080 | |
3821 | |
3081 | =item EV_HEAP_CACHE_AT |
3822 | =item EV_HEAP_CACHE_AT |
3082 | |
3823 | |
3083 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3824 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3084 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
3825 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3085 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3826 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3086 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3827 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3087 | but avoids random read accesses on heap changes. This improves performance |
3828 | but avoids random read accesses on heap changes. This improves performance |
3088 | noticeably with with many (hundreds) of watchers. |
3829 | noticeably with many (hundreds) of watchers. |
3089 | |
3830 | |
3090 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3831 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3091 | (disabled). |
3832 | (disabled). |
3092 | |
3833 | |
3093 | =item EV_VERIFY |
3834 | =item EV_VERIFY |
… | |
… | |
3099 | called once per loop, which can slow down libev. If set to C<3>, then the |
3840 | called once per loop, which can slow down libev. If set to C<3>, then the |
3100 | verification code will be called very frequently, which will slow down |
3841 | verification code will be called very frequently, which will slow down |
3101 | libev considerably. |
3842 | libev considerably. |
3102 | |
3843 | |
3103 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
3844 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
3104 | C<0.> |
3845 | C<0>. |
3105 | |
3846 | |
3106 | =item EV_COMMON |
3847 | =item EV_COMMON |
3107 | |
3848 | |
3108 | By default, all watchers have a C<void *data> member. By redefining |
3849 | By default, all watchers have a C<void *data> member. By redefining |
3109 | this macro to a something else you can include more and other types of |
3850 | this macro to a something else you can include more and other types of |
… | |
… | |
3126 | and the way callbacks are invoked and set. Must expand to a struct member |
3867 | and the way callbacks are invoked and set. Must expand to a struct member |
3127 | definition and a statement, respectively. See the F<ev.h> header file for |
3868 | definition and a statement, respectively. See the F<ev.h> header file for |
3128 | their default definitions. One possible use for overriding these is to |
3869 | their default definitions. One possible use for overriding these is to |
3129 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3870 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3130 | method calls instead of plain function calls in C++. |
3871 | method calls instead of plain function calls in C++. |
|
|
3872 | |
|
|
3873 | =back |
3131 | |
3874 | |
3132 | =head2 EXPORTED API SYMBOLS |
3875 | =head2 EXPORTED API SYMBOLS |
3133 | |
3876 | |
3134 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3877 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3135 | exported symbols, you can use the provided F<Symbol.*> files which list |
3878 | exported symbols, you can use the provided F<Symbol.*> files which list |
… | |
… | |
3182 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3925 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3183 | |
3926 | |
3184 | #include "ev_cpp.h" |
3927 | #include "ev_cpp.h" |
3185 | #include "ev.c" |
3928 | #include "ev.c" |
3186 | |
3929 | |
|
|
3930 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3187 | |
3931 | |
3188 | =head1 THREADS AND COROUTINES |
3932 | =head2 THREADS AND COROUTINES |
3189 | |
3933 | |
3190 | =head2 THREADS |
3934 | =head3 THREADS |
3191 | |
3935 | |
3192 | Libev itself is completely thread-safe, but it uses no locking. This |
3936 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
3937 | documented otherwise, but libev implements no locking itself. This means |
3193 | means that you can use as many loops as you want in parallel, as long as |
3938 | that you can use as many loops as you want in parallel, as long as there |
3194 | only one thread ever calls into one libev function with the same loop |
3939 | are no concurrent calls into any libev function with the same loop |
3195 | parameter. |
3940 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
3941 | of course): libev guarantees that different event loops share no data |
|
|
3942 | structures that need any locking. |
3196 | |
3943 | |
3197 | Or put differently: calls with different loop parameters can be done in |
3944 | Or to put it differently: calls with different loop parameters can be done |
3198 | parallel from multiple threads, calls with the same loop parameter must be |
3945 | concurrently from multiple threads, calls with the same loop parameter |
3199 | done serially (but can be done from different threads, as long as only one |
3946 | must be done serially (but can be done from different threads, as long as |
3200 | thread ever is inside a call at any point in time, e.g. by using a mutex |
3947 | only one thread ever is inside a call at any point in time, e.g. by using |
3201 | per loop). |
3948 | a mutex per loop). |
|
|
3949 | |
|
|
3950 | Specifically to support threads (and signal handlers), libev implements |
|
|
3951 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
3952 | concurrency on the same event loop, namely waking it up "from the |
|
|
3953 | outside". |
3202 | |
3954 | |
3203 | If you want to know which design (one loop, locking, or multiple loops |
3955 | If you want to know which design (one loop, locking, or multiple loops |
3204 | without or something else still) is best for your problem, then I cannot |
3956 | without or something else still) is best for your problem, then I cannot |
3205 | help you. I can give some generic advice however: |
3957 | help you, but here is some generic advice: |
3206 | |
3958 | |
3207 | =over 4 |
3959 | =over 4 |
3208 | |
3960 | |
3209 | =item * most applications have a main thread: use the default libev loop |
3961 | =item * most applications have a main thread: use the default libev loop |
3210 | in that thread, or create a separate thread running only the default loop. |
3962 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3222 | |
3974 | |
3223 | Choosing a model is hard - look around, learn, know that usually you can do |
3975 | Choosing a model is hard - look around, learn, know that usually you can do |
3224 | better than you currently do :-) |
3976 | better than you currently do :-) |
3225 | |
3977 | |
3226 | =item * often you need to talk to some other thread which blocks in the |
3978 | =item * often you need to talk to some other thread which blocks in the |
|
|
3979 | event loop. |
|
|
3980 | |
3227 | event loop - C<ev_async> watchers can be used to wake them up from other |
3981 | C<ev_async> watchers can be used to wake them up from other threads safely |
3228 | threads safely (or from signal contexts...). |
3982 | (or from signal contexts...). |
|
|
3983 | |
|
|
3984 | An example use would be to communicate signals or other events that only |
|
|
3985 | work in the default loop by registering the signal watcher with the |
|
|
3986 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
3987 | watcher callback into the event loop interested in the signal. |
3229 | |
3988 | |
3230 | =back |
3989 | =back |
3231 | |
3990 | |
|
|
3991 | =head4 THREAD LOCKING EXAMPLE |
|
|
3992 | |
|
|
3993 | Here is a fictitious example of how to run an event loop in a different |
|
|
3994 | thread than where callbacks are being invoked and watchers are |
|
|
3995 | created/added/removed. |
|
|
3996 | |
|
|
3997 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3998 | which uses exactly this technique (which is suited for many high-level |
|
|
3999 | languages). |
|
|
4000 | |
|
|
4001 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4002 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4003 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4004 | |
|
|
4005 | First, you need to associate some data with the event loop: |
|
|
4006 | |
|
|
4007 | typedef struct { |
|
|
4008 | mutex_t lock; /* global loop lock */ |
|
|
4009 | ev_async async_w; |
|
|
4010 | thread_t tid; |
|
|
4011 | cond_t invoke_cv; |
|
|
4012 | } userdata; |
|
|
4013 | |
|
|
4014 | void prepare_loop (EV_P) |
|
|
4015 | { |
|
|
4016 | // for simplicity, we use a static userdata struct. |
|
|
4017 | static userdata u; |
|
|
4018 | |
|
|
4019 | ev_async_init (&u->async_w, async_cb); |
|
|
4020 | ev_async_start (EV_A_ &u->async_w); |
|
|
4021 | |
|
|
4022 | pthread_mutex_init (&u->lock, 0); |
|
|
4023 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4024 | |
|
|
4025 | // now associate this with the loop |
|
|
4026 | ev_set_userdata (EV_A_ u); |
|
|
4027 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4028 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4029 | |
|
|
4030 | // then create the thread running ev_loop |
|
|
4031 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4032 | } |
|
|
4033 | |
|
|
4034 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4035 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4036 | that might have been added: |
|
|
4037 | |
|
|
4038 | static void |
|
|
4039 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4040 | { |
|
|
4041 | // just used for the side effects |
|
|
4042 | } |
|
|
4043 | |
|
|
4044 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4045 | protecting the loop data, respectively. |
|
|
4046 | |
|
|
4047 | static void |
|
|
4048 | l_release (EV_P) |
|
|
4049 | { |
|
|
4050 | userdata *u = ev_userdata (EV_A); |
|
|
4051 | pthread_mutex_unlock (&u->lock); |
|
|
4052 | } |
|
|
4053 | |
|
|
4054 | static void |
|
|
4055 | l_acquire (EV_P) |
|
|
4056 | { |
|
|
4057 | userdata *u = ev_userdata (EV_A); |
|
|
4058 | pthread_mutex_lock (&u->lock); |
|
|
4059 | } |
|
|
4060 | |
|
|
4061 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4062 | into C<ev_loop>: |
|
|
4063 | |
|
|
4064 | void * |
|
|
4065 | l_run (void *thr_arg) |
|
|
4066 | { |
|
|
4067 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4068 | |
|
|
4069 | l_acquire (EV_A); |
|
|
4070 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4071 | ev_loop (EV_A_ 0); |
|
|
4072 | l_release (EV_A); |
|
|
4073 | |
|
|
4074 | return 0; |
|
|
4075 | } |
|
|
4076 | |
|
|
4077 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4078 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4079 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4080 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4081 | and b) skipping inter-thread-communication when there are no pending |
|
|
4082 | watchers is very beneficial): |
|
|
4083 | |
|
|
4084 | static void |
|
|
4085 | l_invoke (EV_P) |
|
|
4086 | { |
|
|
4087 | userdata *u = ev_userdata (EV_A); |
|
|
4088 | |
|
|
4089 | while (ev_pending_count (EV_A)) |
|
|
4090 | { |
|
|
4091 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4092 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4093 | } |
|
|
4094 | } |
|
|
4095 | |
|
|
4096 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4097 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4098 | thread to continue: |
|
|
4099 | |
|
|
4100 | static void |
|
|
4101 | real_invoke_pending (EV_P) |
|
|
4102 | { |
|
|
4103 | userdata *u = ev_userdata (EV_A); |
|
|
4104 | |
|
|
4105 | pthread_mutex_lock (&u->lock); |
|
|
4106 | ev_invoke_pending (EV_A); |
|
|
4107 | pthread_cond_signal (&u->invoke_cv); |
|
|
4108 | pthread_mutex_unlock (&u->lock); |
|
|
4109 | } |
|
|
4110 | |
|
|
4111 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4112 | event loop, you will now have to lock: |
|
|
4113 | |
|
|
4114 | ev_timer timeout_watcher; |
|
|
4115 | userdata *u = ev_userdata (EV_A); |
|
|
4116 | |
|
|
4117 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4118 | |
|
|
4119 | pthread_mutex_lock (&u->lock); |
|
|
4120 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4121 | ev_async_send (EV_A_ &u->async_w); |
|
|
4122 | pthread_mutex_unlock (&u->lock); |
|
|
4123 | |
|
|
4124 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4125 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4126 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4127 | watchers in the next event loop iteration. |
|
|
4128 | |
3232 | =head2 COROUTINES |
4129 | =head3 COROUTINES |
3233 | |
4130 | |
3234 | Libev is much more accommodating to coroutines ("cooperative threads"): |
4131 | Libev is very accommodating to coroutines ("cooperative threads"): |
3235 | libev fully supports nesting calls to it's functions from different |
4132 | libev fully supports nesting calls to its functions from different |
3236 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4133 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3237 | different coroutines and switch freely between both coroutines running the |
4134 | different coroutines, and switch freely between both coroutines running |
3238 | loop, as long as you don't confuse yourself). The only exception is that |
4135 | the loop, as long as you don't confuse yourself). The only exception is |
3239 | you must not do this from C<ev_periodic> reschedule callbacks. |
4136 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3240 | |
4137 | |
3241 | Care has been invested into making sure that libev does not keep local |
4138 | Care has been taken to ensure that libev does not keep local state inside |
3242 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
4139 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3243 | switches. |
4140 | they do not call any callbacks. |
3244 | |
4141 | |
|
|
4142 | =head2 COMPILER WARNINGS |
3245 | |
4143 | |
3246 | =head1 COMPLEXITIES |
4144 | Depending on your compiler and compiler settings, you might get no or a |
|
|
4145 | lot of warnings when compiling libev code. Some people are apparently |
|
|
4146 | scared by this. |
3247 | |
4147 | |
3248 | In this section the complexities of (many of) the algorithms used inside |
4148 | However, these are unavoidable for many reasons. For one, each compiler |
3249 | libev will be explained. For complexity discussions about backends see the |
4149 | has different warnings, and each user has different tastes regarding |
3250 | documentation for C<ev_default_init>. |
4150 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
4151 | targeting a specific compiler and compiler-version. |
3251 | |
4152 | |
3252 | All of the following are about amortised time: If an array needs to be |
4153 | Another reason is that some compiler warnings require elaborate |
3253 | extended, libev needs to realloc and move the whole array, but this |
4154 | workarounds, or other changes to the code that make it less clear and less |
3254 | happens asymptotically never with higher number of elements, so O(1) might |
4155 | maintainable. |
3255 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3256 | it is much faster and asymptotically approaches constant time. |
|
|
3257 | |
4156 | |
3258 | =over 4 |
4157 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
4158 | wrong (because they don't actually warn about the condition their message |
|
|
4159 | seems to warn about). For example, certain older gcc versions had some |
|
|
4160 | warnings that resulted an extreme number of false positives. These have |
|
|
4161 | been fixed, but some people still insist on making code warn-free with |
|
|
4162 | such buggy versions. |
3259 | |
4163 | |
3260 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
4164 | While libev is written to generate as few warnings as possible, |
|
|
4165 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
4166 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
4167 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
4168 | warnings, not errors, or proof of bugs. |
3261 | |
4169 | |
3262 | This means that, when you have a watcher that triggers in one hour and |
|
|
3263 | there are 100 watchers that would trigger before that then inserting will |
|
|
3264 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3265 | |
4170 | |
3266 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
4171 | =head2 VALGRIND |
3267 | |
4172 | |
3268 | That means that changing a timer costs less than removing/adding them |
4173 | Valgrind has a special section here because it is a popular tool that is |
3269 | as only the relative motion in the event queue has to be paid for. |
4174 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3270 | |
4175 | |
3271 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
4176 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
4177 | in libev, then check twice: If valgrind reports something like: |
3272 | |
4178 | |
3273 | These just add the watcher into an array or at the head of a list. |
4179 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
4180 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
4181 | ==2274== still reachable: 256 bytes in 1 blocks. |
3274 | |
4182 | |
3275 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
4183 | Then there is no memory leak, just as memory accounted to global variables |
|
|
4184 | is not a memleak - the memory is still being referenced, and didn't leak. |
3276 | |
4185 | |
3277 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
4186 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
4187 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
4188 | although an acceptable workaround has been found here), or it might be |
|
|
4189 | confused. |
3278 | |
4190 | |
3279 | These watchers are stored in lists then need to be walked to find the |
4191 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3280 | correct watcher to remove. The lists are usually short (you don't usually |
4192 | make it into some kind of religion. |
3281 | have many watchers waiting for the same fd or signal). |
|
|
3282 | |
4193 | |
3283 | =item Finding the next timer in each loop iteration: O(1) |
4194 | If you are unsure about something, feel free to contact the mailing list |
|
|
4195 | with the full valgrind report and an explanation on why you think this |
|
|
4196 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
4197 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
4198 | of learning how to interpret valgrind properly. |
3284 | |
4199 | |
3285 | By virtue of using a binary or 4-heap, the next timer is always found at a |
4200 | If you need, for some reason, empty reports from valgrind for your project |
3286 | fixed position in the storage array. |
4201 | I suggest using suppression lists. |
3287 | |
4202 | |
3288 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3289 | |
4203 | |
3290 | A change means an I/O watcher gets started or stopped, which requires |
4204 | =head1 PORTABILITY NOTES |
3291 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3292 | on backend and whether C<ev_io_set> was used). |
|
|
3293 | |
4205 | |
3294 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3295 | |
|
|
3296 | =item Priority handling: O(number_of_priorities) |
|
|
3297 | |
|
|
3298 | Priorities are implemented by allocating some space for each |
|
|
3299 | priority. When doing priority-based operations, libev usually has to |
|
|
3300 | linearly search all the priorities, but starting/stopping and activating |
|
|
3301 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3302 | |
|
|
3303 | =item Sending an ev_async: O(1) |
|
|
3304 | |
|
|
3305 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3306 | |
|
|
3307 | =item Processing signals: O(max_signal_number) |
|
|
3308 | |
|
|
3309 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3310 | calls in the current loop iteration. Checking for async and signal events |
|
|
3311 | involves iterating over all running async watchers or all signal numbers. |
|
|
3312 | |
|
|
3313 | =back |
|
|
3314 | |
|
|
3315 | |
|
|
3316 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4206 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3317 | |
4207 | |
3318 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4208 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3319 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4209 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3320 | model. Libev still offers limited functionality on this platform in |
4210 | model. Libev still offers limited functionality on this platform in |
3321 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4211 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
… | |
… | |
3328 | way (note also that glib is the slowest event library known to man). |
4218 | way (note also that glib is the slowest event library known to man). |
3329 | |
4219 | |
3330 | There is no supported compilation method available on windows except |
4220 | There is no supported compilation method available on windows except |
3331 | embedding it into other applications. |
4221 | embedding it into other applications. |
3332 | |
4222 | |
|
|
4223 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4224 | tries its best, but under most conditions, signals will simply not work. |
|
|
4225 | |
3333 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4226 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3334 | accept large writes: instead of resulting in a partial write, windows will |
4227 | accept large writes: instead of resulting in a partial write, windows will |
3335 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4228 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3336 | so make sure you only write small amounts into your sockets (less than a |
4229 | so make sure you only write small amounts into your sockets (less than a |
3337 | megabyte seems safe, but thsi apparently depends on the amount of memory |
4230 | megabyte seems safe, but this apparently depends on the amount of memory |
3338 | available). |
4231 | available). |
3339 | |
4232 | |
3340 | Due to the many, low, and arbitrary limits on the win32 platform and |
4233 | Due to the many, low, and arbitrary limits on the win32 platform and |
3341 | the abysmal performance of winsockets, using a large number of sockets |
4234 | the abysmal performance of winsockets, using a large number of sockets |
3342 | is not recommended (and not reasonable). If your program needs to use |
4235 | is not recommended (and not reasonable). If your program needs to use |
3343 | more than a hundred or so sockets, then likely it needs to use a totally |
4236 | more than a hundred or so sockets, then likely it needs to use a totally |
3344 | different implementation for windows, as libev offers the POSIX readiness |
4237 | different implementation for windows, as libev offers the POSIX readiness |
3345 | notification model, which cannot be implemented efficiently on windows |
4238 | notification model, which cannot be implemented efficiently on windows |
3346 | (Microsoft monopoly games). |
4239 | (due to Microsoft monopoly games). |
3347 | |
4240 | |
3348 | A typical way to use libev under windows is to embed it (see the embedding |
4241 | A typical way to use libev under windows is to embed it (see the embedding |
3349 | section for details) and use the following F<evwrap.h> header file instead |
4242 | section for details) and use the following F<evwrap.h> header file instead |
3350 | of F<ev.h>: |
4243 | of F<ev.h>: |
3351 | |
4244 | |
… | |
… | |
3353 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
4246 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3354 | |
4247 | |
3355 | #include "ev.h" |
4248 | #include "ev.h" |
3356 | |
4249 | |
3357 | And compile the following F<evwrap.c> file into your project (make sure |
4250 | And compile the following F<evwrap.c> file into your project (make sure |
3358 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
4251 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3359 | |
4252 | |
3360 | #include "evwrap.h" |
4253 | #include "evwrap.h" |
3361 | #include "ev.c" |
4254 | #include "ev.c" |
3362 | |
4255 | |
3363 | =over 4 |
4256 | =over 4 |
… | |
… | |
3387 | |
4280 | |
3388 | Early versions of winsocket's select only supported waiting for a maximum |
4281 | Early versions of winsocket's select only supported waiting for a maximum |
3389 | of C<64> handles (probably owning to the fact that all windows kernels |
4282 | of C<64> handles (probably owning to the fact that all windows kernels |
3390 | can only wait for C<64> things at the same time internally; Microsoft |
4283 | can only wait for C<64> things at the same time internally; Microsoft |
3391 | recommends spawning a chain of threads and wait for 63 handles and the |
4284 | recommends spawning a chain of threads and wait for 63 handles and the |
3392 | previous thread in each. Great). |
4285 | previous thread in each. Sounds great!). |
3393 | |
4286 | |
3394 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4287 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3395 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4288 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3396 | call (which might be in libev or elsewhere, for example, perl does its own |
4289 | call (which might be in libev or elsewhere, for example, perl and many |
3397 | select emulation on windows). |
4290 | other interpreters do their own select emulation on windows). |
3398 | |
4291 | |
3399 | Another limit is the number of file descriptors in the Microsoft runtime |
4292 | Another limit is the number of file descriptors in the Microsoft runtime |
3400 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4293 | libraries, which by default is C<64> (there must be a hidden I<64> |
3401 | or something like this inside Microsoft). You can increase this by calling |
4294 | fetish or something like this inside Microsoft). You can increase this |
3402 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4295 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3403 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4296 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3404 | libraries. |
|
|
3405 | |
|
|
3406 | This might get you to about C<512> or C<2048> sockets (depending on |
4297 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3407 | windows version and/or the phase of the moon). To get more, you need to |
4298 | (depending on windows version and/or the phase of the moon). To get more, |
3408 | wrap all I/O functions and provide your own fd management, but the cost of |
4299 | you need to wrap all I/O functions and provide your own fd management, but |
3409 | calling select (O(n²)) will likely make this unworkable. |
4300 | the cost of calling select (O(n²)) will likely make this unworkable. |
3410 | |
4301 | |
3411 | =back |
4302 | =back |
3412 | |
4303 | |
3413 | |
|
|
3414 | =head1 PORTABILITY REQUIREMENTS |
4304 | =head2 PORTABILITY REQUIREMENTS |
3415 | |
4305 | |
3416 | In addition to a working ISO-C implementation, libev relies on a few |
4306 | In addition to a working ISO-C implementation and of course the |
3417 | additional extensions: |
4307 | backend-specific APIs, libev relies on a few additional extensions: |
3418 | |
4308 | |
3419 | =over 4 |
4309 | =over 4 |
3420 | |
4310 | |
3421 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
4311 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3422 | calling conventions regardless of C<ev_watcher_type *>. |
4312 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3428 | calls them using an C<ev_watcher *> internally. |
4318 | calls them using an C<ev_watcher *> internally. |
3429 | |
4319 | |
3430 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4320 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3431 | |
4321 | |
3432 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4322 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3433 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
4323 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
3434 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
4324 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3435 | believed to be sufficiently portable. |
4325 | believed to be sufficiently portable. |
3436 | |
4326 | |
3437 | =item C<sigprocmask> must work in a threaded environment |
4327 | =item C<sigprocmask> must work in a threaded environment |
3438 | |
4328 | |
… | |
… | |
3447 | except the initial one, and run the default loop in the initial thread as |
4337 | except the initial one, and run the default loop in the initial thread as |
3448 | well. |
4338 | well. |
3449 | |
4339 | |
3450 | =item C<long> must be large enough for common memory allocation sizes |
4340 | =item C<long> must be large enough for common memory allocation sizes |
3451 | |
4341 | |
3452 | To improve portability and simplify using libev, libev uses C<long> |
4342 | To improve portability and simplify its API, libev uses C<long> internally |
3453 | internally instead of C<size_t> when allocating its data structures. On |
4343 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3454 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
4344 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3455 | is still at least 31 bits everywhere, which is enough for hundreds of |
4345 | least 31 bits everywhere, which is enough for hundreds of millions of |
3456 | millions of watchers. |
4346 | watchers. |
3457 | |
4347 | |
3458 | =item C<double> must hold a time value in seconds with enough accuracy |
4348 | =item C<double> must hold a time value in seconds with enough accuracy |
3459 | |
4349 | |
3460 | The type C<double> is used to represent timestamps. It is required to |
4350 | The type C<double> is used to represent timestamps. It is required to |
3461 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4351 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3462 | enough for at least into the year 4000. This requirement is fulfilled by |
4352 | enough for at least into the year 4000. This requirement is fulfilled by |
3463 | implementations implementing IEEE 754 (basically all existing ones). |
4353 | implementations implementing IEEE 754, which is basically all existing |
|
|
4354 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4355 | 2200. |
3464 | |
4356 | |
3465 | =back |
4357 | =back |
3466 | |
4358 | |
3467 | If you know of other additional requirements drop me a note. |
4359 | If you know of other additional requirements drop me a note. |
3468 | |
4360 | |
3469 | |
4361 | |
3470 | =head1 COMPILER WARNINGS |
4362 | =head1 ALGORITHMIC COMPLEXITIES |
3471 | |
4363 | |
3472 | Depending on your compiler and compiler settings, you might get no or a |
4364 | In this section the complexities of (many of) the algorithms used inside |
3473 | lot of warnings when compiling libev code. Some people are apparently |
4365 | libev will be documented. For complexity discussions about backends see |
3474 | scared by this. |
4366 | the documentation for C<ev_default_init>. |
3475 | |
4367 | |
3476 | However, these are unavoidable for many reasons. For one, each compiler |
4368 | All of the following are about amortised time: If an array needs to be |
3477 | has different warnings, and each user has different tastes regarding |
4369 | extended, libev needs to realloc and move the whole array, but this |
3478 | warning options. "Warn-free" code therefore cannot be a goal except when |
4370 | happens asymptotically rarer with higher number of elements, so O(1) might |
3479 | targeting a specific compiler and compiler-version. |
4371 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
4372 | average it is much faster and asymptotically approaches constant time. |
3480 | |
4373 | |
3481 | Another reason is that some compiler warnings require elaborate |
4374 | =over 4 |
3482 | workarounds, or other changes to the code that make it less clear and less |
|
|
3483 | maintainable. |
|
|
3484 | |
4375 | |
3485 | And of course, some compiler warnings are just plain stupid, or simply |
4376 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3486 | wrong (because they don't actually warn about the condition their message |
|
|
3487 | seems to warn about). |
|
|
3488 | |
4377 | |
3489 | While libev is written to generate as few warnings as possible, |
4378 | This means that, when you have a watcher that triggers in one hour and |
3490 | "warn-free" code is not a goal, and it is recommended not to build libev |
4379 | there are 100 watchers that would trigger before that, then inserting will |
3491 | with any compiler warnings enabled unless you are prepared to cope with |
4380 | have to skip roughly seven (C<ld 100>) of these watchers. |
3492 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3493 | warnings, not errors, or proof of bugs. |
|
|
3494 | |
4381 | |
|
|
4382 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3495 | |
4383 | |
3496 | =head1 VALGRIND |
4384 | That means that changing a timer costs less than removing/adding them, |
|
|
4385 | as only the relative motion in the event queue has to be paid for. |
3497 | |
4386 | |
3498 | Valgrind has a special section here because it is a popular tool that is |
4387 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3499 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3500 | |
4388 | |
3501 | If you think you found a bug (memory leak, uninitialised data access etc.) |
4389 | These just add the watcher into an array or at the head of a list. |
3502 | in libev, then check twice: If valgrind reports something like: |
|
|
3503 | |
4390 | |
3504 | ==2274== definitely lost: 0 bytes in 0 blocks. |
4391 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3505 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3506 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3507 | |
4392 | |
3508 | Then there is no memory leak. Similarly, under some circumstances, |
4393 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3509 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3510 | might be confused (it is a very good tool, but only a tool). |
|
|
3511 | |
4394 | |
3512 | If you are unsure about something, feel free to contact the mailing list |
4395 | These watchers are stored in lists, so they need to be walked to find the |
3513 | with the full valgrind report and an explanation on why you think this is |
4396 | correct watcher to remove. The lists are usually short (you don't usually |
3514 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
4397 | have many watchers waiting for the same fd or signal: one is typical, two |
3515 | no bug" answer and take the chance of learning how to interpret valgrind |
4398 | is rare). |
3516 | properly. |
|
|
3517 | |
4399 | |
3518 | If you need, for some reason, empty reports from valgrind for your project |
4400 | =item Finding the next timer in each loop iteration: O(1) |
3519 | I suggest using suppression lists. |
|
|
3520 | |
4401 | |
|
|
4402 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
4403 | fixed position in the storage array. |
|
|
4404 | |
|
|
4405 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
4406 | |
|
|
4407 | A change means an I/O watcher gets started or stopped, which requires |
|
|
4408 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
4409 | on backend and whether C<ev_io_set> was used). |
|
|
4410 | |
|
|
4411 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
4412 | |
|
|
4413 | =item Priority handling: O(number_of_priorities) |
|
|
4414 | |
|
|
4415 | Priorities are implemented by allocating some space for each |
|
|
4416 | priority. When doing priority-based operations, libev usually has to |
|
|
4417 | linearly search all the priorities, but starting/stopping and activating |
|
|
4418 | watchers becomes O(1) with respect to priority handling. |
|
|
4419 | |
|
|
4420 | =item Sending an ev_async: O(1) |
|
|
4421 | |
|
|
4422 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
4423 | |
|
|
4424 | =item Processing signals: O(max_signal_number) |
|
|
4425 | |
|
|
4426 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
4427 | calls in the current loop iteration. Checking for async and signal events |
|
|
4428 | involves iterating over all running async watchers or all signal numbers. |
|
|
4429 | |
|
|
4430 | =back |
|
|
4431 | |
|
|
4432 | |
|
|
4433 | =head1 GLOSSARY |
|
|
4434 | |
|
|
4435 | =over 4 |
|
|
4436 | |
|
|
4437 | =item active |
|
|
4438 | |
|
|
4439 | A watcher is active as long as it has been started (has been attached to |
|
|
4440 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4441 | |
|
|
4442 | =item application |
|
|
4443 | |
|
|
4444 | In this document, an application is whatever is using libev. |
|
|
4445 | |
|
|
4446 | =item callback |
|
|
4447 | |
|
|
4448 | The address of a function that is called when some event has been |
|
|
4449 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4450 | received the event, and the actual event bitset. |
|
|
4451 | |
|
|
4452 | =item callback invocation |
|
|
4453 | |
|
|
4454 | The act of calling the callback associated with a watcher. |
|
|
4455 | |
|
|
4456 | =item event |
|
|
4457 | |
|
|
4458 | A change of state of some external event, such as data now being available |
|
|
4459 | for reading on a file descriptor, time having passed or simply not having |
|
|
4460 | any other events happening anymore. |
|
|
4461 | |
|
|
4462 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4463 | C<EV_TIMEOUT>). |
|
|
4464 | |
|
|
4465 | =item event library |
|
|
4466 | |
|
|
4467 | A software package implementing an event model and loop. |
|
|
4468 | |
|
|
4469 | =item event loop |
|
|
4470 | |
|
|
4471 | An entity that handles and processes external events and converts them |
|
|
4472 | into callback invocations. |
|
|
4473 | |
|
|
4474 | =item event model |
|
|
4475 | |
|
|
4476 | The model used to describe how an event loop handles and processes |
|
|
4477 | watchers and events. |
|
|
4478 | |
|
|
4479 | =item pending |
|
|
4480 | |
|
|
4481 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4482 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4483 | pending status is explicitly cleared by the application. |
|
|
4484 | |
|
|
4485 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4486 | its pending status. |
|
|
4487 | |
|
|
4488 | =item real time |
|
|
4489 | |
|
|
4490 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4491 | |
|
|
4492 | =item wall-clock time |
|
|
4493 | |
|
|
4494 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4495 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4496 | clock. |
|
|
4497 | |
|
|
4498 | =item watcher |
|
|
4499 | |
|
|
4500 | A data structure that describes interest in certain events. Watchers need |
|
|
4501 | to be started (attached to an event loop) before they can receive events. |
|
|
4502 | |
|
|
4503 | =item watcher invocation |
|
|
4504 | |
|
|
4505 | The act of calling the callback associated with a watcher. |
|
|
4506 | |
|
|
4507 | =back |
3521 | |
4508 | |
3522 | =head1 AUTHOR |
4509 | =head1 AUTHOR |
3523 | |
4510 | |
3524 | Marc Lehmann <libev@schmorp.de>. |
4511 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3525 | |
4512 | |