… | |
… | |
77 | on event-based programming, nor will it introduce event-based programming |
77 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
78 | with libev. |
79 | |
79 | |
80 | Familiarity with event based programming techniques in general is assumed |
80 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
81 | throughout this document. |
|
|
82 | |
|
|
83 | =head1 WHAT TO READ WHEN IN A HURRY |
|
|
84 | |
|
|
85 | This manual tries to be very detailed, but unfortunately, this also makes |
|
|
86 | it very long. If you just want to know the basics of libev, I suggest |
|
|
87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
|
|
88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
|
|
89 | C<ev_timer> sections in L<WATCHER TYPES>. |
82 | |
90 | |
83 | =head1 ABOUT LIBEV |
91 | =head1 ABOUT LIBEV |
84 | |
92 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
93 | Libev is an event loop: you register interest in certain events (such as a |
86 | file descriptor being readable or a timeout occurring), and it will manage |
94 | file descriptor being readable or a timeout occurring), and it will manage |
… | |
… | |
233 | the current system, you would need to look at C<ev_embeddable_backends () |
241 | the current system, you would need to look at C<ev_embeddable_backends () |
234 | & ev_supported_backends ()>, likewise for recommended ones. |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
235 | |
243 | |
236 | See the description of C<ev_embed> watchers for more info. |
244 | See the description of C<ev_embed> watchers for more info. |
237 | |
245 | |
238 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
239 | |
247 | |
240 | Sets the allocation function to use (the prototype is similar - the |
248 | Sets the allocation function to use (the prototype is similar - the |
241 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
249 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
242 | used to allocate and free memory (no surprises here). If it returns zero |
250 | used to allocate and free memory (no surprises here). If it returns zero |
243 | when memory needs to be allocated (C<size != 0>), the library might abort |
251 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
269 | } |
277 | } |
270 | |
278 | |
271 | ... |
279 | ... |
272 | ev_set_allocator (persistent_realloc); |
280 | ev_set_allocator (persistent_realloc); |
273 | |
281 | |
274 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
275 | |
283 | |
276 | Set the callback function to call on a retryable system call error (such |
284 | Set the callback function to call on a retryable system call error (such |
277 | as failed select, poll, epoll_wait). The message is a printable string |
285 | as failed select, poll, epoll_wait). The message is a printable string |
278 | indicating the system call or subsystem causing the problem. If this |
286 | indicating the system call or subsystem causing the problem. If this |
279 | callback is set, then libev will expect it to remedy the situation, no |
287 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
300 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
308 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
301 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
309 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
302 | libev 3 had an C<ev_loop> function colliding with the struct name). |
310 | libev 3 had an C<ev_loop> function colliding with the struct name). |
303 | |
311 | |
304 | The library knows two types of such loops, the I<default> loop, which |
312 | The library knows two types of such loops, the I<default> loop, which |
305 | supports signals and child events, and dynamically created event loops |
313 | supports child process events, and dynamically created event loops which |
306 | which do not. |
314 | do not. |
307 | |
315 | |
308 | =over 4 |
316 | =over 4 |
309 | |
317 | |
310 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
318 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
311 | |
319 | |
… | |
… | |
342 | Example: Restrict libev to the select and poll backends, and do not allow |
350 | Example: Restrict libev to the select and poll backends, and do not allow |
343 | environment settings to be taken into account: |
351 | environment settings to be taken into account: |
344 | |
352 | |
345 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
353 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
346 | |
354 | |
347 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
348 | used if available (warning, breaks stuff, best use only with your own |
|
|
349 | private event loop and only if you know the OS supports your types of |
|
|
350 | fds): |
|
|
351 | |
|
|
352 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
353 | |
|
|
354 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
355 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
355 | |
356 | |
356 | This will create and initialise a new event loop object. If the loop |
357 | This will create and initialise a new event loop object. If the loop |
357 | could not be initialised, returns false. |
358 | could not be initialised, returns false. |
358 | |
359 | |
359 | Note that this function I<is> thread-safe, and one common way to use |
360 | This function is thread-safe, and one common way to use libev with |
360 | libev with threads is indeed to create one loop per thread, and using the |
361 | threads is indeed to create one loop per thread, and using the default |
361 | default loop in the "main" or "initial" thread. |
362 | loop in the "main" or "initial" thread. |
362 | |
363 | |
363 | The flags argument can be used to specify special behaviour or specific |
364 | The flags argument can be used to specify special behaviour or specific |
364 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
365 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
365 | |
366 | |
366 | The following flags are supported: |
367 | The following flags are supported: |
… | |
… | |
401 | environment variable. |
402 | environment variable. |
402 | |
403 | |
403 | =item C<EVFLAG_NOINOTIFY> |
404 | =item C<EVFLAG_NOINOTIFY> |
404 | |
405 | |
405 | When this flag is specified, then libev will not attempt to use the |
406 | When this flag is specified, then libev will not attempt to use the |
406 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
407 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
407 | testing, this flag can be useful to conserve inotify file descriptors, as |
408 | testing, this flag can be useful to conserve inotify file descriptors, as |
408 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
409 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
409 | |
410 | |
410 | =item C<EVFLAG_SIGNALFD> |
411 | =item C<EVFLAG_SIGNALFD> |
411 | |
412 | |
412 | When this flag is specified, then libev will attempt to use the |
413 | When this flag is specified, then libev will attempt to use the |
413 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
414 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
414 | delivers signals synchronously, which makes it both faster and might make |
415 | delivers signals synchronously, which makes it both faster and might make |
415 | it possible to get the queued signal data. It can also simplify signal |
416 | it possible to get the queued signal data. It can also simplify signal |
416 | handling with threads, as long as you properly block signals in your |
417 | handling with threads, as long as you properly block signals in your |
417 | threads that are not interested in handling them. |
418 | threads that are not interested in handling them. |
418 | |
419 | |
… | |
… | |
462 | epoll scales either O(1) or O(active_fds). |
463 | epoll scales either O(1) or O(active_fds). |
463 | |
464 | |
464 | The epoll mechanism deserves honorable mention as the most misdesigned |
465 | The epoll mechanism deserves honorable mention as the most misdesigned |
465 | of the more advanced event mechanisms: mere annoyances include silently |
466 | of the more advanced event mechanisms: mere annoyances include silently |
466 | dropping file descriptors, requiring a system call per change per file |
467 | dropping file descriptors, requiring a system call per change per file |
467 | descriptor (and unnecessary guessing of parameters), problems with dup and |
468 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
469 | returning before the timeout value, resulting in additional iterations |
|
|
470 | (and only giving 5ms accuracy while select on the same platform gives |
468 | so on. The biggest issue is fork races, however - if a program forks then |
471 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
469 | I<both> parent and child process have to recreate the epoll set, which can |
472 | forks then I<both> parent and child process have to recreate the epoll |
470 | take considerable time (one syscall per file descriptor) and is of course |
473 | set, which can take considerable time (one syscall per file descriptor) |
471 | hard to detect. |
474 | and is of course hard to detect. |
472 | |
475 | |
473 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
476 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
474 | of course I<doesn't>, and epoll just loves to report events for totally |
477 | of course I<doesn't>, and epoll just loves to report events for totally |
475 | I<different> file descriptors (even already closed ones, so one cannot |
478 | I<different> file descriptors (even already closed ones, so one cannot |
476 | even remove them from the set) than registered in the set (especially |
479 | even remove them from the set) than registered in the set (especially |
… | |
… | |
478 | employing an additional generation counter and comparing that against the |
481 | employing an additional generation counter and comparing that against the |
479 | events to filter out spurious ones, recreating the set when required. Last |
482 | events to filter out spurious ones, recreating the set when required. Last |
480 | not least, it also refuses to work with some file descriptors which work |
483 | not least, it also refuses to work with some file descriptors which work |
481 | perfectly fine with C<select> (files, many character devices...). |
484 | perfectly fine with C<select> (files, many character devices...). |
482 | |
485 | |
|
|
486 | Epoll is truly the train wreck analog among event poll mechanisms. |
|
|
487 | |
483 | While stopping, setting and starting an I/O watcher in the same iteration |
488 | While stopping, setting and starting an I/O watcher in the same iteration |
484 | will result in some caching, there is still a system call per such |
489 | will result in some caching, there is still a system call per such |
485 | incident (because the same I<file descriptor> could point to a different |
490 | incident (because the same I<file descriptor> could point to a different |
486 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
491 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
487 | file descriptors might not work very well if you register events for both |
492 | file descriptors might not work very well if you register events for both |
… | |
… | |
590 | |
595 | |
591 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
596 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
592 | if (!epoller) |
597 | if (!epoller) |
593 | fatal ("no epoll found here, maybe it hides under your chair"); |
598 | fatal ("no epoll found here, maybe it hides under your chair"); |
594 | |
599 | |
|
|
600 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
601 | used if available. |
|
|
602 | |
|
|
603 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
604 | |
595 | =item ev_loop_destroy (loop) |
605 | =item ev_loop_destroy (loop) |
596 | |
606 | |
597 | Destroys an event loop object (frees all memory and kernel state |
607 | Destroys an event loop object (frees all memory and kernel state |
598 | etc.). None of the active event watchers will be stopped in the normal |
608 | etc.). None of the active event watchers will be stopped in the normal |
599 | sense, so e.g. C<ev_is_active> might still return true. It is your |
609 | sense, so e.g. C<ev_is_active> might still return true. It is your |
… | |
… | |
609 | This function is normally used on loop objects allocated by |
619 | This function is normally used on loop objects allocated by |
610 | C<ev_loop_new>, but it can also be used on the default loop returned by |
620 | C<ev_loop_new>, but it can also be used on the default loop returned by |
611 | C<ev_default_loop>, in which case it is not thread-safe. |
621 | C<ev_default_loop>, in which case it is not thread-safe. |
612 | |
622 | |
613 | Note that it is not advisable to call this function on the default loop |
623 | Note that it is not advisable to call this function on the default loop |
614 | except in the rare occasion where you really need to free it's resources. |
624 | except in the rare occasion where you really need to free its resources. |
615 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
625 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
616 | and C<ev_loop_destroy>. |
626 | and C<ev_loop_destroy>. |
617 | |
627 | |
618 | =item ev_loop_fork (loop) |
628 | =item ev_loop_fork (loop) |
619 | |
629 | |
… | |
… | |
667 | prepare and check phases. |
677 | prepare and check phases. |
668 | |
678 | |
669 | =item unsigned int ev_depth (loop) |
679 | =item unsigned int ev_depth (loop) |
670 | |
680 | |
671 | Returns the number of times C<ev_run> was entered minus the number of |
681 | Returns the number of times C<ev_run> was entered minus the number of |
672 | times C<ev_run> was exited, in other words, the recursion depth. |
682 | times C<ev_run> was exited normally, in other words, the recursion depth. |
673 | |
683 | |
674 | Outside C<ev_run>, this number is zero. In a callback, this number is |
684 | Outside C<ev_run>, this number is zero. In a callback, this number is |
675 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
685 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
676 | in which case it is higher. |
686 | in which case it is higher. |
677 | |
687 | |
678 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
688 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
679 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
689 | throwing an exception etc.), doesn't count as "exit" - consider this |
680 | ungentleman-like behaviour unless it's really convenient. |
690 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
691 | convenient, in which case it is fully supported. |
681 | |
692 | |
682 | =item unsigned int ev_backend (loop) |
693 | =item unsigned int ev_backend (loop) |
683 | |
694 | |
684 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
695 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
685 | use. |
696 | use. |
… | |
… | |
746 | relying on all watchers to be stopped when deciding when a program has |
757 | relying on all watchers to be stopped when deciding when a program has |
747 | finished (especially in interactive programs), but having a program |
758 | finished (especially in interactive programs), but having a program |
748 | that automatically loops as long as it has to and no longer by virtue |
759 | that automatically loops as long as it has to and no longer by virtue |
749 | of relying on its watchers stopping correctly, that is truly a thing of |
760 | of relying on its watchers stopping correctly, that is truly a thing of |
750 | beauty. |
761 | beauty. |
|
|
762 | |
|
|
763 | This function is also I<mostly> exception-safe - you can break out of |
|
|
764 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
765 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
766 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
751 | |
767 | |
752 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
768 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
753 | those events and any already outstanding ones, but will not wait and |
769 | those events and any already outstanding ones, but will not wait and |
754 | block your process in case there are no events and will return after one |
770 | block your process in case there are no events and will return after one |
755 | iteration of the loop. This is sometimes useful to poll and handle new |
771 | iteration of the loop. This is sometimes useful to poll and handle new |
… | |
… | |
817 | Can be used to make a call to C<ev_run> return early (but only after it |
833 | Can be used to make a call to C<ev_run> return early (but only after it |
818 | has processed all outstanding events). The C<how> argument must be either |
834 | has processed all outstanding events). The C<how> argument must be either |
819 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
835 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
820 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
836 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
821 | |
837 | |
822 | This "unloop state" will be cleared when entering C<ev_run> again. |
838 | This "break state" will be cleared on the next call to C<ev_run>. |
823 | |
839 | |
824 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
840 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
841 | which case it will have no effect. |
825 | |
842 | |
826 | =item ev_ref (loop) |
843 | =item ev_ref (loop) |
827 | |
844 | |
828 | =item ev_unref (loop) |
845 | =item ev_unref (loop) |
829 | |
846 | |
… | |
… | |
972 | See also the locking example in the C<THREADS> section later in this |
989 | See also the locking example in the C<THREADS> section later in this |
973 | document. |
990 | document. |
974 | |
991 | |
975 | =item ev_set_userdata (loop, void *data) |
992 | =item ev_set_userdata (loop, void *data) |
976 | |
993 | |
977 | =item ev_userdata (loop) |
994 | =item void *ev_userdata (loop) |
978 | |
995 | |
979 | Set and retrieve a single C<void *> associated with a loop. When |
996 | Set and retrieve a single C<void *> associated with a loop. When |
980 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
997 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
981 | C<0.> |
998 | C<0>. |
982 | |
999 | |
983 | These two functions can be used to associate arbitrary data with a loop, |
1000 | These two functions can be used to associate arbitrary data with a loop, |
984 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1001 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
985 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1002 | C<acquire> callbacks described above, but of course can be (ab-)used for |
986 | any other purpose as well. |
1003 | any other purpose as well. |
… | |
… | |
1114 | =item C<EV_FORK> |
1131 | =item C<EV_FORK> |
1115 | |
1132 | |
1116 | The event loop has been resumed in the child process after fork (see |
1133 | The event loop has been resumed in the child process after fork (see |
1117 | C<ev_fork>). |
1134 | C<ev_fork>). |
1118 | |
1135 | |
|
|
1136 | =item C<EV_CLEANUP> |
|
|
1137 | |
|
|
1138 | The event loop is about to be destroyed (see C<ev_cleanup>). |
|
|
1139 | |
1119 | =item C<EV_ASYNC> |
1140 | =item C<EV_ASYNC> |
1120 | |
1141 | |
1121 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1142 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1122 | |
1143 | |
1123 | =item C<EV_CUSTOM> |
1144 | =item C<EV_CUSTOM> |
… | |
… | |
1144 | programs, though, as the fd could already be closed and reused for another |
1165 | programs, though, as the fd could already be closed and reused for another |
1145 | thing, so beware. |
1166 | thing, so beware. |
1146 | |
1167 | |
1147 | =back |
1168 | =back |
1148 | |
1169 | |
1149 | =head2 WATCHER STATES |
|
|
1150 | |
|
|
1151 | There are various watcher states mentioned throughout this manual - |
|
|
1152 | active, pending and so on. In this section these states and the rules to |
|
|
1153 | transition between them will be described in more detail - and while these |
|
|
1154 | rules might look complicated, they usually do "the right thing". |
|
|
1155 | |
|
|
1156 | =over 4 |
|
|
1157 | |
|
|
1158 | =item initialiased |
|
|
1159 | |
|
|
1160 | Before a watcher can be registered with the event looop it has to be |
|
|
1161 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1162 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1163 | |
|
|
1164 | In this state it is simply some block of memory that is suitable for use |
|
|
1165 | in an event loop. It can be moved around, freed, reused etc. at will. |
|
|
1166 | |
|
|
1167 | =item started/running/active |
|
|
1168 | |
|
|
1169 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1170 | property of the event loop, and is actively waiting for events. While in |
|
|
1171 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1172 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1173 | and call libev functions on it that are documented to work on active watchers. |
|
|
1174 | |
|
|
1175 | =item pending |
|
|
1176 | |
|
|
1177 | If a watcher is active and libev determines that an event it is interested |
|
|
1178 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1179 | stay in this pending state until either it is stopped or its callback is |
|
|
1180 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1181 | callback. |
|
|
1182 | |
|
|
1183 | The watcher might or might not be active while it is pending (for example, |
|
|
1184 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1185 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1186 | but it is still property of the event loop at this time, so cannot be |
|
|
1187 | moved, freed or reused. And if it is active the rules described in the |
|
|
1188 | previous item still apply. |
|
|
1189 | |
|
|
1190 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1191 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1192 | active. |
|
|
1193 | |
|
|
1194 | =item stopped |
|
|
1195 | |
|
|
1196 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1197 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1198 | latter will clear any pending state the watcher might be in, regardless |
|
|
1199 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1200 | freeing it is often a good idea. |
|
|
1201 | |
|
|
1202 | While stopped (and not pending) the watcher is essentially in the |
|
|
1203 | initialised state, that is it can be reused, moved, modified in any way |
|
|
1204 | you wish. |
|
|
1205 | |
|
|
1206 | =back |
|
|
1207 | |
|
|
1208 | =head2 GENERIC WATCHER FUNCTIONS |
1170 | =head2 GENERIC WATCHER FUNCTIONS |
1209 | |
1171 | |
1210 | =over 4 |
1172 | =over 4 |
1211 | |
1173 | |
1212 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1174 | =item C<ev_init> (ev_TYPE *watcher, callback) |
… | |
… | |
1353 | |
1315 | |
1354 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1316 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1355 | functions that do not need a watcher. |
1317 | functions that do not need a watcher. |
1356 | |
1318 | |
1357 | =back |
1319 | =back |
1358 | |
|
|
1359 | |
1320 | |
1360 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1321 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1361 | |
1322 | |
1362 | Each watcher has, by default, a member C<void *data> that you can change |
1323 | Each watcher has, by default, a member C<void *data> that you can change |
1363 | and read at any time: libev will completely ignore it. This can be used |
1324 | and read at any time: libev will completely ignore it. This can be used |
… | |
… | |
1419 | t2_cb (EV_P_ ev_timer *w, int revents) |
1380 | t2_cb (EV_P_ ev_timer *w, int revents) |
1420 | { |
1381 | { |
1421 | struct my_biggy big = (struct my_biggy *) |
1382 | struct my_biggy big = (struct my_biggy *) |
1422 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1383 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1423 | } |
1384 | } |
|
|
1385 | |
|
|
1386 | =head2 WATCHER STATES |
|
|
1387 | |
|
|
1388 | There are various watcher states mentioned throughout this manual - |
|
|
1389 | active, pending and so on. In this section these states and the rules to |
|
|
1390 | transition between them will be described in more detail - and while these |
|
|
1391 | rules might look complicated, they usually do "the right thing". |
|
|
1392 | |
|
|
1393 | =over 4 |
|
|
1394 | |
|
|
1395 | =item initialiased |
|
|
1396 | |
|
|
1397 | Before a watcher can be registered with the event looop it has to be |
|
|
1398 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1399 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1400 | |
|
|
1401 | In this state it is simply some block of memory that is suitable for use |
|
|
1402 | in an event loop. It can be moved around, freed, reused etc. at will. |
|
|
1403 | |
|
|
1404 | =item started/running/active |
|
|
1405 | |
|
|
1406 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1407 | property of the event loop, and is actively waiting for events. While in |
|
|
1408 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1409 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1410 | and call libev functions on it that are documented to work on active watchers. |
|
|
1411 | |
|
|
1412 | =item pending |
|
|
1413 | |
|
|
1414 | If a watcher is active and libev determines that an event it is interested |
|
|
1415 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1416 | stay in this pending state until either it is stopped or its callback is |
|
|
1417 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1418 | callback. |
|
|
1419 | |
|
|
1420 | The watcher might or might not be active while it is pending (for example, |
|
|
1421 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1422 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1423 | but it is still property of the event loop at this time, so cannot be |
|
|
1424 | moved, freed or reused. And if it is active the rules described in the |
|
|
1425 | previous item still apply. |
|
|
1426 | |
|
|
1427 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1428 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1429 | active. |
|
|
1430 | |
|
|
1431 | =item stopped |
|
|
1432 | |
|
|
1433 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1434 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1435 | latter will clear any pending state the watcher might be in, regardless |
|
|
1436 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1437 | freeing it is often a good idea. |
|
|
1438 | |
|
|
1439 | While stopped (and not pending) the watcher is essentially in the |
|
|
1440 | initialised state, that is it can be reused, moved, modified in any way |
|
|
1441 | you wish. |
|
|
1442 | |
|
|
1443 | =back |
1424 | |
1444 | |
1425 | =head2 WATCHER PRIORITY MODELS |
1445 | =head2 WATCHER PRIORITY MODELS |
1426 | |
1446 | |
1427 | Many event loops support I<watcher priorities>, which are usually small |
1447 | Many event loops support I<watcher priorities>, which are usually small |
1428 | integers that influence the ordering of event callback invocation |
1448 | integers that influence the ordering of event callback invocation |
… | |
… | |
2247 | |
2267 | |
2248 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2268 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2249 | |
2269 | |
2250 | Signal watchers will trigger an event when the process receives a specific |
2270 | Signal watchers will trigger an event when the process receives a specific |
2251 | signal one or more times. Even though signals are very asynchronous, libev |
2271 | signal one or more times. Even though signals are very asynchronous, libev |
2252 | will try it's best to deliver signals synchronously, i.e. as part of the |
2272 | will try its best to deliver signals synchronously, i.e. as part of the |
2253 | normal event processing, like any other event. |
2273 | normal event processing, like any other event. |
2254 | |
2274 | |
2255 | If you want signals to be delivered truly asynchronously, just use |
2275 | If you want signals to be delivered truly asynchronously, just use |
2256 | C<sigaction> as you would do without libev and forget about sharing |
2276 | C<sigaction> as you would do without libev and forget about sharing |
2257 | the signal. You can even use C<ev_async> from a signal handler to |
2277 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
3092 | |
3112 | |
3093 | =head3 Watcher-Specific Functions and Data Members |
3113 | =head3 Watcher-Specific Functions and Data Members |
3094 | |
3114 | |
3095 | =over 4 |
3115 | =over 4 |
3096 | |
3116 | |
3097 | =item ev_fork_init (ev_signal *, callback) |
3117 | =item ev_fork_init (ev_fork *, callback) |
3098 | |
3118 | |
3099 | Initialises and configures the fork watcher - it has no parameters of any |
3119 | Initialises and configures the fork watcher - it has no parameters of any |
3100 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3120 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3101 | believe me. |
3121 | really. |
3102 | |
3122 | |
3103 | =back |
3123 | =back |
|
|
3124 | |
|
|
3125 | |
|
|
3126 | =head2 C<ev_cleanup> - even the best things end |
|
|
3127 | |
|
|
3128 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3129 | by a call to C<ev_loop_destroy>. |
|
|
3130 | |
|
|
3131 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3132 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3133 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3134 | loop when you want them to be invoked. |
|
|
3135 | |
|
|
3136 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3137 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3138 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3139 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3140 | |
|
|
3141 | =head3 Watcher-Specific Functions and Data Members |
|
|
3142 | |
|
|
3143 | =over 4 |
|
|
3144 | |
|
|
3145 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3146 | |
|
|
3147 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3148 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3149 | pointless, I assure you. |
|
|
3150 | |
|
|
3151 | =back |
|
|
3152 | |
|
|
3153 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3154 | cleanup functions are called. |
|
|
3155 | |
|
|
3156 | static void |
|
|
3157 | program_exits (void) |
|
|
3158 | { |
|
|
3159 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3160 | } |
|
|
3161 | |
|
|
3162 | ... |
|
|
3163 | atexit (program_exits); |
3104 | |
3164 | |
3105 | |
3165 | |
3106 | =head2 C<ev_async> - how to wake up an event loop |
3166 | =head2 C<ev_async> - how to wake up an event loop |
3107 | |
3167 | |
3108 | In general, you cannot use an C<ev_run> from multiple threads or other |
3168 | In general, you cannot use an C<ev_run> from multiple threads or other |
… | |
… | |
3307 | loop!). |
3367 | loop!). |
3308 | |
3368 | |
3309 | =back |
3369 | =back |
3310 | |
3370 | |
3311 | |
3371 | |
|
|
3372 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3373 | |
|
|
3374 | This section explains some common idioms that are not immediately |
|
|
3375 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3376 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3377 | |
|
|
3378 | =over 4 |
|
|
3379 | |
|
|
3380 | =item Model/nested event loop invocations and exit conditions. |
|
|
3381 | |
|
|
3382 | Often (especially in GUI toolkits) there are places where you have |
|
|
3383 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3384 | invoking C<ev_run>. |
|
|
3385 | |
|
|
3386 | This brings the problem of exiting - a callback might want to finish the |
|
|
3387 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3388 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3389 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3390 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3391 | |
|
|
3392 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3393 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3394 | triggered, using C<EVRUN_ONCE>: |
|
|
3395 | |
|
|
3396 | // main loop |
|
|
3397 | int exit_main_loop = 0; |
|
|
3398 | |
|
|
3399 | while (!exit_main_loop) |
|
|
3400 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3401 | |
|
|
3402 | // in a model watcher |
|
|
3403 | int exit_nested_loop = 0; |
|
|
3404 | |
|
|
3405 | while (!exit_nested_loop) |
|
|
3406 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3407 | |
|
|
3408 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3409 | |
|
|
3410 | // exit modal loop |
|
|
3411 | exit_nested_loop = 1; |
|
|
3412 | |
|
|
3413 | // exit main program, after modal loop is finished |
|
|
3414 | exit_main_loop = 1; |
|
|
3415 | |
|
|
3416 | // exit both |
|
|
3417 | exit_main_loop = exit_nested_loop = 1; |
|
|
3418 | |
|
|
3419 | =back |
|
|
3420 | |
|
|
3421 | |
3312 | =head1 LIBEVENT EMULATION |
3422 | =head1 LIBEVENT EMULATION |
3313 | |
3423 | |
3314 | Libev offers a compatibility emulation layer for libevent. It cannot |
3424 | Libev offers a compatibility emulation layer for libevent. It cannot |
3315 | emulate the internals of libevent, so here are some usage hints: |
3425 | emulate the internals of libevent, so here are some usage hints: |
3316 | |
3426 | |
3317 | =over 4 |
3427 | =over 4 |
|
|
3428 | |
|
|
3429 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3430 | |
|
|
3431 | This was the newest libevent version available when libev was implemented, |
|
|
3432 | and is still mostly unchanged in 2010. |
3318 | |
3433 | |
3319 | =item * Use it by including <event.h>, as usual. |
3434 | =item * Use it by including <event.h>, as usual. |
3320 | |
3435 | |
3321 | =item * The following members are fully supported: ev_base, ev_callback, |
3436 | =item * The following members are fully supported: ev_base, ev_callback, |
3322 | ev_arg, ev_fd, ev_res, ev_events. |
3437 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3328 | =item * Priorities are not currently supported. Initialising priorities |
3443 | =item * Priorities are not currently supported. Initialising priorities |
3329 | will fail and all watchers will have the same priority, even though there |
3444 | will fail and all watchers will have the same priority, even though there |
3330 | is an ev_pri field. |
3445 | is an ev_pri field. |
3331 | |
3446 | |
3332 | =item * In libevent, the last base created gets the signals, in libev, the |
3447 | =item * In libevent, the last base created gets the signals, in libev, the |
3333 | first base created (== the default loop) gets the signals. |
3448 | base that registered the signal gets the signals. |
3334 | |
3449 | |
3335 | =item * Other members are not supported. |
3450 | =item * Other members are not supported. |
3336 | |
3451 | |
3337 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3452 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3338 | to use the libev header file and library. |
3453 | to use the libev header file and library. |
… | |
… | |
3357 | Care has been taken to keep the overhead low. The only data member the C++ |
3472 | Care has been taken to keep the overhead low. The only data member the C++ |
3358 | classes add (compared to plain C-style watchers) is the event loop pointer |
3473 | classes add (compared to plain C-style watchers) is the event loop pointer |
3359 | that the watcher is associated with (or no additional members at all if |
3474 | that the watcher is associated with (or no additional members at all if |
3360 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3475 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3361 | |
3476 | |
3362 | Currently, functions, and static and non-static member functions can be |
3477 | Currently, functions, static and non-static member functions and classes |
3363 | used as callbacks. Other types should be easy to add as long as they only |
3478 | with C<operator ()> can be used as callbacks. Other types should be easy |
3364 | need one additional pointer for context. If you need support for other |
3479 | to add as long as they only need one additional pointer for context. If |
3365 | types of functors please contact the author (preferably after implementing |
3480 | you need support for other types of functors please contact the author |
3366 | it). |
3481 | (preferably after implementing it). |
3367 | |
3482 | |
3368 | Here is a list of things available in the C<ev> namespace: |
3483 | Here is a list of things available in the C<ev> namespace: |
3369 | |
3484 | |
3370 | =over 4 |
3485 | =over 4 |
3371 | |
3486 | |
… | |
… | |
4715 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4830 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4716 | assumes that the same (machine) code can be used to call any watcher |
4831 | assumes that the same (machine) code can be used to call any watcher |
4717 | callback: The watcher callbacks have different type signatures, but libev |
4832 | callback: The watcher callbacks have different type signatures, but libev |
4718 | calls them using an C<ev_watcher *> internally. |
4833 | calls them using an C<ev_watcher *> internally. |
4719 | |
4834 | |
|
|
4835 | =item pointer accesses must be thread-atomic |
|
|
4836 | |
|
|
4837 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
4838 | writable in one piece - this is the case on all current architectures. |
|
|
4839 | |
4720 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4840 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4721 | |
4841 | |
4722 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4842 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4723 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4843 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4724 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
4844 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
… | |
… | |
4830 | =back |
4950 | =back |
4831 | |
4951 | |
4832 | |
4952 | |
4833 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4953 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4834 | |
4954 | |
4835 | The major version 4 introduced some minor incompatible changes to the API. |
4955 | The major version 4 introduced some incompatible changes to the API. |
4836 | |
4956 | |
4837 | At the moment, the C<ev.h> header file tries to implement superficial |
4957 | At the moment, the C<ev.h> header file provides compatibility definitions |
4838 | compatibility, so most programs should still compile. Those might be |
4958 | for all changes, so most programs should still compile. The compatibility |
4839 | removed in later versions of libev, so better update early than late. |
4959 | layer might be removed in later versions of libev, so better update to the |
|
|
4960 | new API early than late. |
4840 | |
4961 | |
4841 | =over 4 |
4962 | =over 4 |
4842 | |
4963 | |
|
|
4964 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4965 | |
|
|
4966 | The backward compatibility mechanism can be controlled by |
|
|
4967 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4968 | section. |
|
|
4969 | |
4843 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
4970 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
4844 | |
4971 | |
4845 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
4972 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
4846 | |
4973 | |
4847 | ev_loop_destroy (EV_DEFAULT); |
4974 | ev_loop_destroy (EV_DEFAULT_UC); |
4848 | ev_loop_fork (EV_DEFAULT); |
4975 | ev_loop_fork (EV_DEFAULT); |
4849 | |
4976 | |
4850 | =item function/symbol renames |
4977 | =item function/symbol renames |
4851 | |
4978 | |
4852 | A number of functions and symbols have been renamed: |
4979 | A number of functions and symbols have been renamed: |
… | |
… | |
4872 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
4999 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
4873 | as all other watcher types. Note that C<ev_loop_fork> is still called |
5000 | as all other watcher types. Note that C<ev_loop_fork> is still called |
4874 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
5001 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
4875 | typedef. |
5002 | typedef. |
4876 | |
5003 | |
4877 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4878 | |
|
|
4879 | The backward compatibility mechanism can be controlled by |
|
|
4880 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4881 | section. |
|
|
4882 | |
|
|
4883 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
5004 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4884 | |
5005 | |
4885 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
5006 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4886 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
5007 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
4887 | and work, but the library code will of course be larger. |
5008 | and work, but the library code will of course be larger. |
… | |
… | |
4961 | |
5082 | |
4962 | =back |
5083 | =back |
4963 | |
5084 | |
4964 | =head1 AUTHOR |
5085 | =head1 AUTHOR |
4965 | |
5086 | |
4966 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5087 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5088 | Magnusson and Emanuele Giaquinta. |
4967 | |
5089 | |