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1 | =encoding utf-8 |
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2 | |
1 | =head1 NAME |
3 | =head1 NAME |
2 | |
4 | |
3 | libev - a high performance full-featured event loop written in C |
5 | libev - a high performance full-featured event loop written in C |
4 | |
6 | |
5 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
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82 | |
84 | |
83 | =head1 WHAT TO READ WHEN IN A HURRY |
85 | =head1 WHAT TO READ WHEN IN A HURRY |
84 | |
86 | |
85 | This manual tries to be very detailed, but unfortunately, this also makes |
87 | 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 |
88 | 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 |
89 | 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 |
90 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
89 | C<ev_timer> sections in L<WATCHER TYPES>. |
91 | C<ev_timer> sections in L</WATCHER TYPES>. |
90 | |
92 | |
91 | =head1 ABOUT LIBEV |
93 | =head1 ABOUT LIBEV |
92 | |
94 | |
93 | Libev is an event loop: you register interest in certain events (such as a |
95 | Libev is an event loop: you register interest in certain events (such as a |
94 | file descriptor being readable or a timeout occurring), and it will manage |
96 | file descriptor being readable or a timeout occurring), and it will manage |
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174 | =item ev_tstamp ev_time () |
176 | =item ev_tstamp ev_time () |
175 | |
177 | |
176 | Returns the current time as libev would use it. Please note that the |
178 | Returns the current time as libev would use it. Please note that the |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
179 | C<ev_now> function is usually faster and also often returns the timestamp |
178 | you actually want to know. Also interesting is the combination of |
180 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
181 | C<ev_now_update> and C<ev_now>. |
180 | |
182 | |
181 | =item ev_sleep (ev_tstamp interval) |
183 | =item ev_sleep (ev_tstamp interval) |
182 | |
184 | |
183 | Sleep for the given interval: The current thread will be blocked |
185 | Sleep for the given interval: The current thread will be blocked |
184 | until either it is interrupted or the given time interval has |
186 | until either it is interrupted or the given time interval has |
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247 | the current system, you would need to look at C<ev_embeddable_backends () |
249 | the current system, you would need to look at C<ev_embeddable_backends () |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
250 | & ev_supported_backends ()>, likewise for recommended ones. |
249 | |
251 | |
250 | See the description of C<ev_embed> watchers for more info. |
252 | See the description of C<ev_embed> watchers for more info. |
251 | |
253 | |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
254 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
253 | |
255 | |
254 | Sets the allocation function to use (the prototype is similar - the |
256 | Sets the allocation function to use (the prototype is similar - the |
255 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
257 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
256 | used to allocate and free memory (no surprises here). If it returns zero |
258 | used to allocate and free memory (no surprises here). If it returns zero |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
259 | when memory needs to be allocated (C<size != 0>), the library might abort |
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283 | } |
285 | } |
284 | |
286 | |
285 | ... |
287 | ... |
286 | ev_set_allocator (persistent_realloc); |
288 | ev_set_allocator (persistent_realloc); |
287 | |
289 | |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
290 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
289 | |
291 | |
290 | Set the callback function to call on a retryable system call error (such |
292 | Set the callback function to call on a retryable system call error (such |
291 | as failed select, poll, epoll_wait). The message is a printable string |
293 | as failed select, poll, epoll_wait). The message is a printable string |
292 | indicating the system call or subsystem causing the problem. If this |
294 | indicating the system call or subsystem causing the problem. If this |
293 | callback is set, then libev will expect it to remedy the situation, no |
295 | callback is set, then libev will expect it to remedy the situation, no |
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396 | |
398 | |
397 | If this flag bit is or'ed into the flag value (or the program runs setuid |
399 | If this flag bit is or'ed into the flag value (or the program runs setuid |
398 | or setgid) then libev will I<not> look at the environment variable |
400 | or setgid) then libev will I<not> look at the environment variable |
399 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
401 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
400 | override the flags completely if it is found in the environment. This is |
402 | override the flags completely if it is found in the environment. This is |
401 | useful to try out specific backends to test their performance, or to work |
403 | useful to try out specific backends to test their performance, to work |
402 | around bugs. |
404 | around bugs, or to make libev threadsafe (accessing environment variables |
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405 | cannot be done in a threadsafe way, but usually it works if no other |
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406 | thread modifies them). |
403 | |
407 | |
404 | =item C<EVFLAG_FORKCHECK> |
408 | =item C<EVFLAG_FORKCHECK> |
405 | |
409 | |
406 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
410 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
407 | make libev check for a fork in each iteration by enabling this flag. |
411 | make libev check for a fork in each iteration by enabling this flag. |
408 | |
412 | |
409 | This works by calling C<getpid ()> on every iteration of the loop, |
413 | This works by calling C<getpid ()> on every iteration of the loop, |
410 | and thus this might slow down your event loop if you do a lot of loop |
414 | and thus this might slow down your event loop if you do a lot of loop |
411 | iterations and little real work, but is usually not noticeable (on my |
415 | iterations and little real work, but is usually not noticeable (on my |
412 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
416 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
413 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
417 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
414 | C<pthread_atfork> which is even faster). |
418 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
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419 | versions 2.25 apparently removed the C<getpid> optimisation again). |
415 | |
420 | |
416 | The big advantage of this flag is that you can forget about fork (and |
421 | The big advantage of this flag is that you can forget about fork (and |
417 | forget about forgetting to tell libev about forking) when you use this |
422 | forget about forgetting to tell libev about forking, although you still |
418 | flag. |
423 | have to ignore C<SIGPIPE>) when you use this flag. |
419 | |
424 | |
420 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
425 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
421 | environment variable. |
426 | environment variable. |
422 | |
427 | |
423 | =item C<EVFLAG_NOINOTIFY> |
428 | =item C<EVFLAG_NOINOTIFY> |
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567 | |
572 | |
568 | It scales in the same way as the epoll backend, but the interface to the |
573 | It scales in the same way as the epoll backend, but the interface to the |
569 | kernel is more efficient (which says nothing about its actual speed, of |
574 | kernel is more efficient (which says nothing about its actual speed, of |
570 | course). While stopping, setting and starting an I/O watcher does never |
575 | course). While stopping, setting and starting an I/O watcher does never |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
576 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
572 | two event changes per incident. Support for C<fork ()> is very bad (but |
577 | two event changes per incident. Support for C<fork ()> is very bad (you |
573 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
578 | might have to leak fd's on fork, but it's more sane than epoll) and it |
574 | cases |
579 | drops fds silently in similarly hard-to-detect cases. |
575 | |
580 | |
576 | This backend usually performs well under most conditions. |
581 | This backend usually performs well under most conditions. |
577 | |
582 | |
578 | While nominally embeddable in other event loops, this doesn't work |
583 | While nominally embeddable in other event loops, this doesn't work |
579 | everywhere, so you might need to test for this. And since it is broken |
584 | everywhere, so you might need to test for this. And since it is broken |
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608 | among the OS-specific backends (I vastly prefer correctness over speed |
613 | among the OS-specific backends (I vastly prefer correctness over speed |
609 | hacks). |
614 | hacks). |
610 | |
615 | |
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
616 | On the negative side, the interface is I<bizarre> - so bizarre that |
612 | even sun itself gets it wrong in their code examples: The event polling |
617 | even sun itself gets it wrong in their code examples: The event polling |
613 | function sometimes returning events to the caller even though an error |
618 | function sometimes returns events to the caller even though an error |
614 | occurred, but with no indication whether it has done so or not (yes, it's |
619 | occurred, but with no indication whether it has done so or not (yes, it's |
615 | even documented that way) - deadly for edge-triggered interfaces where |
620 | even documented that way) - deadly for edge-triggered interfaces where you |
616 | you absolutely have to know whether an event occurred or not because you |
621 | absolutely have to know whether an event occurred or not because you have |
617 | have to re-arm the watcher. |
622 | to re-arm the watcher. |
618 | |
623 | |
619 | Fortunately libev seems to be able to work around these idiocies. |
624 | Fortunately libev seems to be able to work around these idiocies. |
620 | |
625 | |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
626 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
622 | C<EVBACKEND_POLL>. |
627 | C<EVBACKEND_POLL>. |
… | |
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678 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
683 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
679 | and C<ev_loop_destroy>. |
684 | and C<ev_loop_destroy>. |
680 | |
685 | |
681 | =item ev_loop_fork (loop) |
686 | =item ev_loop_fork (loop) |
682 | |
687 | |
683 | This function sets a flag that causes subsequent C<ev_run> iterations to |
688 | This function sets a flag that causes subsequent C<ev_run> iterations |
684 | reinitialise the kernel state for backends that have one. Despite the |
689 | to reinitialise the kernel state for backends that have one. Despite |
685 | name, you can call it anytime, but it makes most sense after forking, in |
690 | the name, you can call it anytime you are allowed to start or stop |
686 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
691 | watchers (except inside an C<ev_prepare> callback), but it makes most |
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692 | sense after forking, in the child process. You I<must> call it (or use |
687 | child before resuming or calling C<ev_run>. |
693 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
688 | |
694 | |
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695 | In addition, if you want to reuse a loop (via this function or |
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696 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
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697 | |
689 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
698 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
690 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
699 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
691 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
700 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
692 | during fork. |
701 | during fork. |
693 | |
702 | |
694 | On the other hand, you only need to call this function in the child |
703 | On the other hand, you only need to call this function in the child |
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764 | |
773 | |
765 | This function is rarely useful, but when some event callback runs for a |
774 | This function is rarely useful, but when some event callback runs for a |
766 | very long time without entering the event loop, updating libev's idea of |
775 | very long time without entering the event loop, updating libev's idea of |
767 | the current time is a good idea. |
776 | the current time is a good idea. |
768 | |
777 | |
769 | See also L<The special problem of time updates> in the C<ev_timer> section. |
778 | See also L</The special problem of time updates> in the C<ev_timer> section. |
770 | |
779 | |
771 | =item ev_suspend (loop) |
780 | =item ev_suspend (loop) |
772 | |
781 | |
773 | =item ev_resume (loop) |
782 | =item ev_resume (loop) |
774 | |
783 | |
… | |
… | |
792 | without a previous call to C<ev_suspend>. |
801 | without a previous call to C<ev_suspend>. |
793 | |
802 | |
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
803 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
795 | event loop time (see C<ev_now_update>). |
804 | event loop time (see C<ev_now_update>). |
796 | |
805 | |
797 | =item ev_run (loop, int flags) |
806 | =item bool ev_run (loop, int flags) |
798 | |
807 | |
799 | Finally, this is it, the event handler. This function usually is called |
808 | Finally, this is it, the event handler. This function usually is called |
800 | after you have initialised all your watchers and you want to start |
809 | after you have initialised all your watchers and you want to start |
801 | handling events. It will ask the operating system for any new events, call |
810 | handling events. It will ask the operating system for any new events, call |
802 | the watcher callbacks, an then repeat the whole process indefinitely: This |
811 | the watcher callbacks, and then repeat the whole process indefinitely: This |
803 | is why event loops are called I<loops>. |
812 | is why event loops are called I<loops>. |
804 | |
813 | |
805 | If the flags argument is specified as C<0>, it will keep handling events |
814 | If the flags argument is specified as C<0>, it will keep handling events |
806 | until either no event watchers are active anymore or C<ev_break> was |
815 | until either no event watchers are active anymore or C<ev_break> was |
807 | called. |
816 | called. |
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817 | |
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818 | The return value is false if there are no more active watchers (which |
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819 | usually means "all jobs done" or "deadlock"), and true in all other cases |
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820 | (which usually means " you should call C<ev_run> again"). |
808 | |
821 | |
809 | Please note that an explicit C<ev_break> is usually better than |
822 | Please note that an explicit C<ev_break> is usually better than |
810 | relying on all watchers to be stopped when deciding when a program has |
823 | relying on all watchers to be stopped when deciding when a program has |
811 | finished (especially in interactive programs), but having a program |
824 | finished (especially in interactive programs), but having a program |
812 | that automatically loops as long as it has to and no longer by virtue |
825 | that automatically loops as long as it has to and no longer by virtue |
813 | of relying on its watchers stopping correctly, that is truly a thing of |
826 | of relying on its watchers stopping correctly, that is truly a thing of |
814 | beauty. |
827 | beauty. |
815 | |
828 | |
816 | This function is also I<mostly> exception-safe - you can break out of |
829 | This function is I<mostly> exception-safe - you can break out of a |
817 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
830 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
818 | exception and so on. This does not decrement the C<ev_depth> value, nor |
831 | exception and so on. This does not decrement the C<ev_depth> value, nor |
819 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
832 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
820 | |
833 | |
821 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
834 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
822 | those events and any already outstanding ones, but will not wait and |
835 | those events and any already outstanding ones, but will not wait and |
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1012 | invoke the actual watchers inside another context (another thread etc.). |
1025 | invoke the actual watchers inside another context (another thread etc.). |
1013 | |
1026 | |
1014 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1027 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1015 | callback. |
1028 | callback. |
1016 | |
1029 | |
1017 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1030 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
1018 | |
1031 | |
1019 | Sometimes you want to share the same loop between multiple threads. This |
1032 | Sometimes you want to share the same loop between multiple threads. This |
1020 | can be done relatively simply by putting mutex_lock/unlock calls around |
1033 | can be done relatively simply by putting mutex_lock/unlock calls around |
1021 | each call to a libev function. |
1034 | each call to a libev function. |
1022 | |
1035 | |
1023 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1036 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1024 | to wait for it to return. One way around this is to wake up the event |
1037 | to wait for it to return. One way around this is to wake up the event |
1025 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1038 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
1026 | I<release> and I<acquire> callbacks on the loop. |
1039 | I<release> and I<acquire> callbacks on the loop. |
1027 | |
1040 | |
1028 | When set, then C<release> will be called just before the thread is |
1041 | When set, then C<release> will be called just before the thread is |
1029 | suspended waiting for new events, and C<acquire> is called just |
1042 | suspended waiting for new events, and C<acquire> is called just |
1030 | afterwards. |
1043 | afterwards. |
… | |
… | |
1170 | |
1183 | |
1171 | =item C<EV_PREPARE> |
1184 | =item C<EV_PREPARE> |
1172 | |
1185 | |
1173 | =item C<EV_CHECK> |
1186 | =item C<EV_CHECK> |
1174 | |
1187 | |
1175 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1188 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1176 | to gather new events, and all C<ev_check> watchers are invoked just after |
1189 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1177 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1190 | just after C<ev_run> has gathered them, but before it queues any callbacks |
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1191 | for any received events. That means C<ev_prepare> watchers are the last |
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1192 | watchers invoked before the event loop sleeps or polls for new events, and |
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1193 | C<ev_check> watchers will be invoked before any other watchers of the same |
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1194 | or lower priority within an event loop iteration. |
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1195 | |
1178 | received events. Callbacks of both watcher types can start and stop as |
1196 | Callbacks of both watcher types can start and stop as many watchers as |
1179 | many watchers as they want, and all of them will be taken into account |
1197 | they want, and all of them will be taken into account (for example, a |
1180 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1198 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1181 | C<ev_run> from blocking). |
1199 | blocking). |
1182 | |
1200 | |
1183 | =item C<EV_EMBED> |
1201 | =item C<EV_EMBED> |
1184 | |
1202 | |
1185 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1203 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1186 | |
1204 | |
… | |
… | |
1309 | |
1327 | |
1310 | =item callback ev_cb (ev_TYPE *watcher) |
1328 | =item callback ev_cb (ev_TYPE *watcher) |
1311 | |
1329 | |
1312 | Returns the callback currently set on the watcher. |
1330 | Returns the callback currently set on the watcher. |
1313 | |
1331 | |
1314 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1332 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1315 | |
1333 | |
1316 | Change the callback. You can change the callback at virtually any time |
1334 | Change the callback. You can change the callback at virtually any time |
1317 | (modulo threads). |
1335 | (modulo threads). |
1318 | |
1336 | |
1319 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1337 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
… | |
… | |
1337 | or might not have been clamped to the valid range. |
1355 | or might not have been clamped to the valid range. |
1338 | |
1356 | |
1339 | The default priority used by watchers when no priority has been set is |
1357 | The default priority used by watchers when no priority has been set is |
1340 | always C<0>, which is supposed to not be too high and not be too low :). |
1358 | always C<0>, which is supposed to not be too high and not be too low :). |
1341 | |
1359 | |
1342 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1360 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1343 | priorities. |
1361 | priorities. |
1344 | |
1362 | |
1345 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1363 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1346 | |
1364 | |
1347 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1365 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1372 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1390 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1373 | functions that do not need a watcher. |
1391 | functions that do not need a watcher. |
1374 | |
1392 | |
1375 | =back |
1393 | =back |
1376 | |
1394 | |
1377 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
1395 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
1378 | OWN COMPOSITE WATCHERS> idioms. |
1396 | OWN COMPOSITE WATCHERS> idioms. |
1379 | |
1397 | |
1380 | =head2 WATCHER STATES |
1398 | =head2 WATCHER STATES |
1381 | |
1399 | |
1382 | There are various watcher states mentioned throughout this manual - |
1400 | There are various watcher states mentioned throughout this manual - |
… | |
… | |
1384 | transition between them will be described in more detail - and while these |
1402 | transition between them will be described in more detail - and while these |
1385 | rules might look complicated, they usually do "the right thing". |
1403 | rules might look complicated, they usually do "the right thing". |
1386 | |
1404 | |
1387 | =over 4 |
1405 | =over 4 |
1388 | |
1406 | |
1389 | =item initialiased |
1407 | =item initialised |
1390 | |
1408 | |
1391 | Before a watcher can be registered with the event loop it has to be |
1409 | Before a watcher can be registered with the event loop it has to be |
1392 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1410 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1393 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1411 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1394 | |
1412 | |
… | |
… | |
1771 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1789 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1772 | monotonic clock option helps a lot here). |
1790 | monotonic clock option helps a lot here). |
1773 | |
1791 | |
1774 | The callback is guaranteed to be invoked only I<after> its timeout has |
1792 | The callback is guaranteed to be invoked only I<after> its timeout has |
1775 | passed (not I<at>, so on systems with very low-resolution clocks this |
1793 | passed (not I<at>, so on systems with very low-resolution clocks this |
1776 | might introduce a small delay). If multiple timers become ready during the |
1794 | might introduce a small delay, see "the special problem of being too |
|
|
1795 | early", below). If multiple timers become ready during the same loop |
1777 | same loop iteration then the ones with earlier time-out values are invoked |
1796 | iteration then the ones with earlier time-out values are invoked before |
1778 | before ones of the same priority with later time-out values (but this is |
1797 | ones of the same priority with later time-out values (but this is no |
1779 | no longer true when a callback calls C<ev_run> recursively). |
1798 | longer true when a callback calls C<ev_run> recursively). |
1780 | |
1799 | |
1781 | =head3 Be smart about timeouts |
1800 | =head3 Be smart about timeouts |
1782 | |
1801 | |
1783 | Many real-world problems involve some kind of timeout, usually for error |
1802 | Many real-world problems involve some kind of timeout, usually for error |
1784 | recovery. A typical example is an HTTP request - if the other side hangs, |
1803 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1859 | |
1878 | |
1860 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1879 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1861 | but remember the time of last activity, and check for a real timeout only |
1880 | but remember the time of last activity, and check for a real timeout only |
1862 | within the callback: |
1881 | within the callback: |
1863 | |
1882 | |
|
|
1883 | ev_tstamp timeout = 60.; |
1864 | ev_tstamp last_activity; // time of last activity |
1884 | ev_tstamp last_activity; // time of last activity |
|
|
1885 | ev_timer timer; |
1865 | |
1886 | |
1866 | static void |
1887 | static void |
1867 | callback (EV_P_ ev_timer *w, int revents) |
1888 | callback (EV_P_ ev_timer *w, int revents) |
1868 | { |
1889 | { |
1869 | ev_tstamp now = ev_now (EV_A); |
1890 | // calculate when the timeout would happen |
1870 | ev_tstamp timeout = last_activity + 60.; |
1891 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1871 | |
1892 | |
1872 | // if last_activity + 60. is older than now, we did time out |
1893 | // if negative, it means we the timeout already occurred |
1873 | if (timeout < now) |
1894 | if (after < 0.) |
1874 | { |
1895 | { |
1875 | // timeout occurred, take action |
1896 | // timeout occurred, take action |
1876 | } |
1897 | } |
1877 | else |
1898 | else |
1878 | { |
1899 | { |
1879 | // callback was invoked, but there was some activity, re-arm |
1900 | // callback was invoked, but there was some recent |
1880 | // the watcher to fire in last_activity + 60, which is |
1901 | // activity. simply restart the timer to time out |
1881 | // guaranteed to be in the future, so "again" is positive: |
1902 | // after "after" seconds, which is the earliest time |
1882 | w->repeat = timeout - now; |
1903 | // the timeout can occur. |
|
|
1904 | ev_timer_set (w, after, 0.); |
1883 | ev_timer_again (EV_A_ w); |
1905 | ev_timer_start (EV_A_ w); |
1884 | } |
1906 | } |
1885 | } |
1907 | } |
1886 | |
1908 | |
1887 | To summarise the callback: first calculate the real timeout (defined |
1909 | To summarise the callback: first calculate in how many seconds the |
1888 | as "60 seconds after the last activity"), then check if that time has |
1910 | timeout will occur (by calculating the absolute time when it would occur, |
1889 | been reached, which means something I<did>, in fact, time out. Otherwise |
1911 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1890 | the callback was invoked too early (C<timeout> is in the future), so |
1912 | (EV_A)> from that). |
1891 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1892 | a timeout then. |
|
|
1893 | |
1913 | |
1894 | Note how C<ev_timer_again> is used, taking advantage of the |
1914 | If this value is negative, then we are already past the timeout, i.e. we |
1895 | C<ev_timer_again> optimisation when the timer is already running. |
1915 | timed out, and need to do whatever is needed in this case. |
|
|
1916 | |
|
|
1917 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1918 | and simply start the timer with this timeout value. |
|
|
1919 | |
|
|
1920 | In other words, each time the callback is invoked it will check whether |
|
|
1921 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1922 | again at the earliest time it could time out. Rinse. Repeat. |
1896 | |
1923 | |
1897 | This scheme causes more callback invocations (about one every 60 seconds |
1924 | This scheme causes more callback invocations (about one every 60 seconds |
1898 | minus half the average time between activity), but virtually no calls to |
1925 | minus half the average time between activity), but virtually no calls to |
1899 | libev to change the timeout. |
1926 | libev to change the timeout. |
1900 | |
1927 | |
1901 | To start the timer, simply initialise the watcher and set C<last_activity> |
1928 | To start the machinery, simply initialise the watcher and set |
1902 | to the current time (meaning we just have some activity :), then call the |
1929 | C<last_activity> to the current time (meaning there was some activity just |
1903 | callback, which will "do the right thing" and start the timer: |
1930 | now), then call the callback, which will "do the right thing" and start |
|
|
1931 | the timer: |
1904 | |
1932 | |
|
|
1933 | last_activity = ev_now (EV_A); |
1905 | ev_init (timer, callback); |
1934 | ev_init (&timer, callback); |
1906 | last_activity = ev_now (loop); |
1935 | callback (EV_A_ &timer, 0); |
1907 | callback (loop, timer, EV_TIMER); |
|
|
1908 | |
1936 | |
1909 | And when there is some activity, simply store the current time in |
1937 | When there is some activity, simply store the current time in |
1910 | C<last_activity>, no libev calls at all: |
1938 | C<last_activity>, no libev calls at all: |
1911 | |
1939 | |
|
|
1940 | if (activity detected) |
1912 | last_activity = ev_now (loop); |
1941 | last_activity = ev_now (EV_A); |
|
|
1942 | |
|
|
1943 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1944 | providing a new value, stopping the timer and calling the callback, which |
|
|
1945 | will again do the right thing (for example, time out immediately :). |
|
|
1946 | |
|
|
1947 | timeout = new_value; |
|
|
1948 | ev_timer_stop (EV_A_ &timer); |
|
|
1949 | callback (EV_A_ &timer, 0); |
1913 | |
1950 | |
1914 | This technique is slightly more complex, but in most cases where the |
1951 | This technique is slightly more complex, but in most cases where the |
1915 | time-out is unlikely to be triggered, much more efficient. |
1952 | time-out is unlikely to be triggered, much more efficient. |
1916 | |
|
|
1917 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1918 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1919 | fix things for you. |
|
|
1920 | |
1953 | |
1921 | =item 4. Wee, just use a double-linked list for your timeouts. |
1954 | =item 4. Wee, just use a double-linked list for your timeouts. |
1922 | |
1955 | |
1923 | If there is not one request, but many thousands (millions...), all |
1956 | If there is not one request, but many thousands (millions...), all |
1924 | employing some kind of timeout with the same timeout value, then one can |
1957 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1951 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1984 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1952 | rather complicated, but extremely efficient, something that really pays |
1985 | rather complicated, but extremely efficient, something that really pays |
1953 | off after the first million or so of active timers, i.e. it's usually |
1986 | off after the first million or so of active timers, i.e. it's usually |
1954 | overkill :) |
1987 | overkill :) |
1955 | |
1988 | |
|
|
1989 | =head3 The special problem of being too early |
|
|
1990 | |
|
|
1991 | If you ask a timer to call your callback after three seconds, then |
|
|
1992 | you expect it to be invoked after three seconds - but of course, this |
|
|
1993 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1994 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1995 | process with a STOP signal for a few hours for example. |
|
|
1996 | |
|
|
1997 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1998 | delay has occurred, but cannot guarantee this. |
|
|
1999 | |
|
|
2000 | A less obvious failure mode is calling your callback too early: many event |
|
|
2001 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
2002 | this can cause your callback to be invoked much earlier than you would |
|
|
2003 | expect. |
|
|
2004 | |
|
|
2005 | To see why, imagine a system with a clock that only offers full second |
|
|
2006 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2007 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2008 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2009 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2010 | |
|
|
2011 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2012 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2013 | one-second delay was requested - this is being "too early", despite best |
|
|
2014 | intentions. |
|
|
2015 | |
|
|
2016 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2017 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2018 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2019 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2020 | |
|
|
2021 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2022 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2023 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2024 | late" side of things. |
|
|
2025 | |
1956 | =head3 The special problem of time updates |
2026 | =head3 The special problem of time updates |
1957 | |
2027 | |
1958 | Establishing the current time is a costly operation (it usually takes at |
2028 | Establishing the current time is a costly operation (it usually takes |
1959 | least two system calls): EV therefore updates its idea of the current |
2029 | at least one system call): EV therefore updates its idea of the current |
1960 | time only before and after C<ev_run> collects new events, which causes a |
2030 | time only before and after C<ev_run> collects new events, which causes a |
1961 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2031 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1962 | lots of events in one iteration. |
2032 | lots of events in one iteration. |
1963 | |
2033 | |
1964 | The relative timeouts are calculated relative to the C<ev_now ()> |
2034 | The relative timeouts are calculated relative to the C<ev_now ()> |
1965 | time. This is usually the right thing as this timestamp refers to the time |
2035 | time. This is usually the right thing as this timestamp refers to the time |
1966 | of the event triggering whatever timeout you are modifying/starting. If |
2036 | of the event triggering whatever timeout you are modifying/starting. If |
1967 | you suspect event processing to be delayed and you I<need> to base the |
2037 | you suspect event processing to be delayed and you I<need> to base the |
1968 | timeout on the current time, use something like this to adjust for this: |
2038 | timeout on the current time, use something like the following to adjust |
|
|
2039 | for it: |
1969 | |
2040 | |
1970 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2041 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
1971 | |
2042 | |
1972 | If the event loop is suspended for a long time, you can also force an |
2043 | If the event loop is suspended for a long time, you can also force an |
1973 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2044 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1974 | ()>. |
2045 | ()>, although that will push the event time of all outstanding events |
|
|
2046 | further into the future. |
|
|
2047 | |
|
|
2048 | =head3 The special problem of unsynchronised clocks |
|
|
2049 | |
|
|
2050 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2051 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2052 | jumps). |
|
|
2053 | |
|
|
2054 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2055 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2056 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2057 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2058 | than a directly following call to C<time>. |
|
|
2059 | |
|
|
2060 | The moral of this is to only compare libev-related timestamps with |
|
|
2061 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2062 | a second or so. |
|
|
2063 | |
|
|
2064 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2065 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2066 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2067 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2068 | |
|
|
2069 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2070 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2071 | I<measured according to the real time>, not the system clock. |
|
|
2072 | |
|
|
2073 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2074 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2075 | exactly the right behaviour. |
|
|
2076 | |
|
|
2077 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2078 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2079 | time, where your comparisons will always generate correct results. |
1975 | |
2080 | |
1976 | =head3 The special problems of suspended animation |
2081 | =head3 The special problems of suspended animation |
1977 | |
2082 | |
1978 | When you leave the server world it is quite customary to hit machines that |
2083 | When you leave the server world it is quite customary to hit machines that |
1979 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2084 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
2009 | |
2114 | |
2010 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2115 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2011 | |
2116 | |
2012 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2117 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2013 | |
2118 | |
2014 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2119 | Configure the timer to trigger after C<after> seconds (fractional and |
2015 | is C<0.>, then it will automatically be stopped once the timeout is |
2120 | negative values are supported). If C<repeat> is C<0.>, then it will |
2016 | reached. If it is positive, then the timer will automatically be |
2121 | automatically be stopped once the timeout is reached. If it is positive, |
2017 | configured to trigger again C<repeat> seconds later, again, and again, |
2122 | then the timer will automatically be configured to trigger again C<repeat> |
2018 | until stopped manually. |
2123 | seconds later, again, and again, until stopped manually. |
2019 | |
2124 | |
2020 | The timer itself will do a best-effort at avoiding drift, that is, if |
2125 | The timer itself will do a best-effort at avoiding drift, that is, if |
2021 | you configure a timer to trigger every 10 seconds, then it will normally |
2126 | you configure a timer to trigger every 10 seconds, then it will normally |
2022 | trigger at exactly 10 second intervals. If, however, your program cannot |
2127 | trigger at exactly 10 second intervals. If, however, your program cannot |
2023 | keep up with the timer (because it takes longer than those 10 seconds to |
2128 | keep up with the timer (because it takes longer than those 10 seconds to |
2024 | do stuff) the timer will not fire more than once per event loop iteration. |
2129 | do stuff) the timer will not fire more than once per event loop iteration. |
2025 | |
2130 | |
2026 | =item ev_timer_again (loop, ev_timer *) |
2131 | =item ev_timer_again (loop, ev_timer *) |
2027 | |
2132 | |
2028 | This will act as if the timer timed out and restart it again if it is |
2133 | This will act as if the timer timed out, and restarts it again if it is |
2029 | repeating. The exact semantics are: |
2134 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2135 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
2030 | |
2136 | |
|
|
2137 | The exact semantics are as in the following rules, all of which will be |
|
|
2138 | applied to the watcher: |
|
|
2139 | |
|
|
2140 | =over 4 |
|
|
2141 | |
2031 | If the timer is pending, its pending status is cleared. |
2142 | =item If the timer is pending, the pending status is always cleared. |
2032 | |
2143 | |
2033 | If the timer is started but non-repeating, stop it (as if it timed out). |
2144 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2145 | out, without invoking it). |
2034 | |
2146 | |
2035 | If the timer is repeating, either start it if necessary (with the |
2147 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2036 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2148 | and start the timer, if necessary. |
2037 | |
2149 | |
|
|
2150 | =back |
|
|
2151 | |
2038 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2152 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
2039 | usage example. |
2153 | usage example. |
2040 | |
2154 | |
2041 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2155 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2042 | |
2156 | |
2043 | Returns the remaining time until a timer fires. If the timer is active, |
2157 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2096 | Periodic watchers are also timers of a kind, but they are very versatile |
2210 | Periodic watchers are also timers of a kind, but they are very versatile |
2097 | (and unfortunately a bit complex). |
2211 | (and unfortunately a bit complex). |
2098 | |
2212 | |
2099 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2213 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2100 | relative time, the physical time that passes) but on wall clock time |
2214 | relative time, the physical time that passes) but on wall clock time |
2101 | (absolute time, the thing you can read on your calender or clock). The |
2215 | (absolute time, the thing you can read on your calendar or clock). The |
2102 | difference is that wall clock time can run faster or slower than real |
2216 | difference is that wall clock time can run faster or slower than real |
2103 | time, and time jumps are not uncommon (e.g. when you adjust your |
2217 | time, and time jumps are not uncommon (e.g. when you adjust your |
2104 | wrist-watch). |
2218 | wrist-watch). |
2105 | |
2219 | |
2106 | You can tell a periodic watcher to trigger after some specific point |
2220 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
2111 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2225 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2112 | it, as it uses a relative timeout). |
2226 | it, as it uses a relative timeout). |
2113 | |
2227 | |
2114 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2228 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2115 | timers, such as triggering an event on each "midnight, local time", or |
2229 | timers, such as triggering an event on each "midnight, local time", or |
2116 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
2230 | other complicated rules. This cannot easily be done with C<ev_timer> |
2117 | those cannot react to time jumps. |
2231 | watchers, as those cannot react to time jumps. |
2118 | |
2232 | |
2119 | As with timers, the callback is guaranteed to be invoked only when the |
2233 | As with timers, the callback is guaranteed to be invoked only when the |
2120 | point in time where it is supposed to trigger has passed. If multiple |
2234 | point in time where it is supposed to trigger has passed. If multiple |
2121 | timers become ready during the same loop iteration then the ones with |
2235 | timers become ready during the same loop iteration then the ones with |
2122 | earlier time-out values are invoked before ones with later time-out values |
2236 | earlier time-out values are invoked before ones with later time-out values |
… | |
… | |
2208 | |
2322 | |
2209 | NOTE: I<< This callback must always return a time that is higher than or |
2323 | NOTE: I<< This callback must always return a time that is higher than or |
2210 | equal to the passed C<now> value >>. |
2324 | equal to the passed C<now> value >>. |
2211 | |
2325 | |
2212 | This can be used to create very complex timers, such as a timer that |
2326 | This can be used to create very complex timers, such as a timer that |
2213 | triggers on "next midnight, local time". To do this, you would calculate the |
2327 | triggers on "next midnight, local time". To do this, you would calculate |
2214 | next midnight after C<now> and return the timestamp value for this. How |
2328 | the next midnight after C<now> and return the timestamp value for |
2215 | you do this is, again, up to you (but it is not trivial, which is the main |
2329 | this. Here is a (completely untested, no error checking) example on how to |
2216 | reason I omitted it as an example). |
2330 | do this: |
|
|
2331 | |
|
|
2332 | #include <time.h> |
|
|
2333 | |
|
|
2334 | static ev_tstamp |
|
|
2335 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2336 | { |
|
|
2337 | time_t tnow = (time_t)now; |
|
|
2338 | struct tm tm; |
|
|
2339 | localtime_r (&tnow, &tm); |
|
|
2340 | |
|
|
2341 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2342 | ++tm.tm_mday; // midnight next day |
|
|
2343 | |
|
|
2344 | return mktime (&tm); |
|
|
2345 | } |
|
|
2346 | |
|
|
2347 | Note: this code might run into trouble on days that have more then two |
|
|
2348 | midnights (beginning and end). |
2217 | |
2349 | |
2218 | =back |
2350 | =back |
2219 | |
2351 | |
2220 | =item ev_periodic_again (loop, ev_periodic *) |
2352 | =item ev_periodic_again (loop, ev_periodic *) |
2221 | |
2353 | |
… | |
… | |
2286 | |
2418 | |
2287 | ev_periodic hourly_tick; |
2419 | ev_periodic hourly_tick; |
2288 | ev_periodic_init (&hourly_tick, clock_cb, |
2420 | ev_periodic_init (&hourly_tick, clock_cb, |
2289 | fmod (ev_now (loop), 3600.), 3600., 0); |
2421 | fmod (ev_now (loop), 3600.), 3600., 0); |
2290 | ev_periodic_start (loop, &hourly_tick); |
2422 | ev_periodic_start (loop, &hourly_tick); |
2291 | |
2423 | |
2292 | |
2424 | |
2293 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2425 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2294 | |
2426 | |
2295 | Signal watchers will trigger an event when the process receives a specific |
2427 | Signal watchers will trigger an event when the process receives a specific |
2296 | signal one or more times. Even though signals are very asynchronous, libev |
2428 | signal one or more times. Even though signals are very asynchronous, libev |
… | |
… | |
2306 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2438 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2307 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2439 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2308 | C<SIGINT> in both the default loop and another loop at the same time. At |
2440 | C<SIGINT> in both the default loop and another loop at the same time. At |
2309 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2441 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2310 | |
2442 | |
2311 | When the first watcher gets started will libev actually register something |
2443 | Only after the first watcher for a signal is started will libev actually |
2312 | with the kernel (thus it coexists with your own signal handlers as long as |
2444 | register something with the kernel. It thus coexists with your own signal |
2313 | you don't register any with libev for the same signal). |
2445 | handlers as long as you don't register any with libev for the same signal. |
2314 | |
2446 | |
2315 | If possible and supported, libev will install its handlers with |
2447 | If possible and supported, libev will install its handlers with |
2316 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2448 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2317 | not be unduly interrupted. If you have a problem with system calls getting |
2449 | not be unduly interrupted. If you have a problem with system calls getting |
2318 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2450 | interrupted by signals you can block all signals in an C<ev_check> watcher |
… | |
… | |
2503 | |
2635 | |
2504 | =head2 C<ev_stat> - did the file attributes just change? |
2636 | =head2 C<ev_stat> - did the file attributes just change? |
2505 | |
2637 | |
2506 | This watches a file system path for attribute changes. That is, it calls |
2638 | This watches a file system path for attribute changes. That is, it calls |
2507 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2639 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2508 | and sees if it changed compared to the last time, invoking the callback if |
2640 | and sees if it changed compared to the last time, invoking the callback |
2509 | it did. |
2641 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2642 | happen after the watcher has been started will be reported. |
2510 | |
2643 | |
2511 | The path does not need to exist: changing from "path exists" to "path does |
2644 | The path does not need to exist: changing from "path exists" to "path does |
2512 | not exist" is a status change like any other. The condition "path does not |
2645 | not exist" is a status change like any other. The condition "path does not |
2513 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2646 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2514 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2647 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2744 | Apart from keeping your process non-blocking (which is a useful |
2877 | Apart from keeping your process non-blocking (which is a useful |
2745 | effect on its own sometimes), idle watchers are a good place to do |
2878 | effect on its own sometimes), idle watchers are a good place to do |
2746 | "pseudo-background processing", or delay processing stuff to after the |
2879 | "pseudo-background processing", or delay processing stuff to after the |
2747 | event loop has handled all outstanding events. |
2880 | event loop has handled all outstanding events. |
2748 | |
2881 | |
|
|
2882 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2883 | |
|
|
2884 | As long as there is at least one active idle watcher, libev will never |
|
|
2885 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2886 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2887 | lowest priority will do. |
|
|
2888 | |
|
|
2889 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2890 | to do something on each event loop iteration - for example to balance load |
|
|
2891 | between different connections. |
|
|
2892 | |
|
|
2893 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2894 | example. |
|
|
2895 | |
2749 | =head3 Watcher-Specific Functions and Data Members |
2896 | =head3 Watcher-Specific Functions and Data Members |
2750 | |
2897 | |
2751 | =over 4 |
2898 | =over 4 |
2752 | |
2899 | |
2753 | =item ev_idle_init (ev_idle *, callback) |
2900 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2764 | callback, free it. Also, use no error checking, as usual. |
2911 | callback, free it. Also, use no error checking, as usual. |
2765 | |
2912 | |
2766 | static void |
2913 | static void |
2767 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2914 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2768 | { |
2915 | { |
|
|
2916 | // stop the watcher |
|
|
2917 | ev_idle_stop (loop, w); |
|
|
2918 | |
|
|
2919 | // now we can free it |
2769 | free (w); |
2920 | free (w); |
|
|
2921 | |
2770 | // now do something you wanted to do when the program has |
2922 | // now do something you wanted to do when the program has |
2771 | // no longer anything immediate to do. |
2923 | // no longer anything immediate to do. |
2772 | } |
2924 | } |
2773 | |
2925 | |
2774 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2926 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2776 | ev_idle_start (loop, idle_watcher); |
2928 | ev_idle_start (loop, idle_watcher); |
2777 | |
2929 | |
2778 | |
2930 | |
2779 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2931 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2780 | |
2932 | |
2781 | Prepare and check watchers are usually (but not always) used in pairs: |
2933 | Prepare and check watchers are often (but not always) used in pairs: |
2782 | prepare watchers get invoked before the process blocks and check watchers |
2934 | prepare watchers get invoked before the process blocks and check watchers |
2783 | afterwards. |
2935 | afterwards. |
2784 | |
2936 | |
2785 | You I<must not> call C<ev_run> or similar functions that enter |
2937 | You I<must not> call C<ev_run> (or similar functions that enter the |
2786 | the current event loop from either C<ev_prepare> or C<ev_check> |
2938 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2787 | watchers. Other loops than the current one are fine, however. The |
2939 | C<ev_check> watchers. Other loops than the current one are fine, |
2788 | rationale behind this is that you do not need to check for recursion in |
2940 | however. The rationale behind this is that you do not need to check |
2789 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2941 | for recursion in those watchers, i.e. the sequence will always be |
2790 | C<ev_check> so if you have one watcher of each kind they will always be |
2942 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2791 | called in pairs bracketing the blocking call. |
2943 | kind they will always be called in pairs bracketing the blocking call. |
2792 | |
2944 | |
2793 | Their main purpose is to integrate other event mechanisms into libev and |
2945 | Their main purpose is to integrate other event mechanisms into libev and |
2794 | their use is somewhat advanced. They could be used, for example, to track |
2946 | their use is somewhat advanced. They could be used, for example, to track |
2795 | variable changes, implement your own watchers, integrate net-snmp or a |
2947 | variable changes, implement your own watchers, integrate net-snmp or a |
2796 | coroutine library and lots more. They are also occasionally useful if |
2948 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
2814 | with priority higher than or equal to the event loop and one coroutine |
2966 | with priority higher than or equal to the event loop and one coroutine |
2815 | of lower priority, but only once, using idle watchers to keep the event |
2967 | of lower priority, but only once, using idle watchers to keep the event |
2816 | loop from blocking if lower-priority coroutines are active, thus mapping |
2968 | loop from blocking if lower-priority coroutines are active, thus mapping |
2817 | low-priority coroutines to idle/background tasks). |
2969 | low-priority coroutines to idle/background tasks). |
2818 | |
2970 | |
2819 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2971 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2820 | priority, to ensure that they are being run before any other watchers |
2972 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2821 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
2973 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
2974 | watchers). |
2822 | |
2975 | |
2823 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2976 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2824 | activate ("feed") events into libev. While libev fully supports this, they |
2977 | activate ("feed") events into libev. While libev fully supports this, they |
2825 | might get executed before other C<ev_check> watchers did their job. As |
2978 | might get executed before other C<ev_check> watchers did their job. As |
2826 | C<ev_check> watchers are often used to embed other (non-libev) event |
2979 | C<ev_check> watchers are often used to embed other (non-libev) event |
2827 | loops those other event loops might be in an unusable state until their |
2980 | loops those other event loops might be in an unusable state until their |
2828 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2981 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2829 | others). |
2982 | others). |
|
|
2983 | |
|
|
2984 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
2985 | |
|
|
2986 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
2987 | useful because they are called once per event loop iteration. For |
|
|
2988 | example, if you want to handle a large number of connections fairly, you |
|
|
2989 | normally only do a bit of work for each active connection, and if there |
|
|
2990 | is more work to do, you wait for the next event loop iteration, so other |
|
|
2991 | connections have a chance of making progress. |
|
|
2992 | |
|
|
2993 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
2994 | next event loop iteration. However, that isn't as soon as possible - |
|
|
2995 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
2996 | |
|
|
2997 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2998 | single global idle watcher that is active as long as you have one active |
|
|
2999 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
3000 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
3001 | invoked. Neither watcher alone can do that. |
2830 | |
3002 | |
2831 | =head3 Watcher-Specific Functions and Data Members |
3003 | =head3 Watcher-Specific Functions and Data Members |
2832 | |
3004 | |
2833 | =over 4 |
3005 | =over 4 |
2834 | |
3006 | |
… | |
… | |
3035 | |
3207 | |
3036 | =over 4 |
3208 | =over 4 |
3037 | |
3209 | |
3038 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3210 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3039 | |
3211 | |
3040 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3212 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
3041 | |
3213 | |
3042 | Configures the watcher to embed the given loop, which must be |
3214 | Configures the watcher to embed the given loop, which must be |
3043 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3215 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3044 | invoked automatically, otherwise it is the responsibility of the callback |
3216 | invoked automatically, otherwise it is the responsibility of the callback |
3045 | to invoke it (it will continue to be called until the sweep has been done, |
3217 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3066 | used). |
3238 | used). |
3067 | |
3239 | |
3068 | struct ev_loop *loop_hi = ev_default_init (0); |
3240 | struct ev_loop *loop_hi = ev_default_init (0); |
3069 | struct ev_loop *loop_lo = 0; |
3241 | struct ev_loop *loop_lo = 0; |
3070 | ev_embed embed; |
3242 | ev_embed embed; |
3071 | |
3243 | |
3072 | // see if there is a chance of getting one that works |
3244 | // see if there is a chance of getting one that works |
3073 | // (remember that a flags value of 0 means autodetection) |
3245 | // (remember that a flags value of 0 means autodetection) |
3074 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3246 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3075 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3247 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3076 | : 0; |
3248 | : 0; |
… | |
… | |
3090 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3262 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3091 | |
3263 | |
3092 | struct ev_loop *loop = ev_default_init (0); |
3264 | struct ev_loop *loop = ev_default_init (0); |
3093 | struct ev_loop *loop_socket = 0; |
3265 | struct ev_loop *loop_socket = 0; |
3094 | ev_embed embed; |
3266 | ev_embed embed; |
3095 | |
3267 | |
3096 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3268 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3097 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3269 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3098 | { |
3270 | { |
3099 | ev_embed_init (&embed, 0, loop_socket); |
3271 | ev_embed_init (&embed, 0, loop_socket); |
3100 | ev_embed_start (loop, &embed); |
3272 | ev_embed_start (loop, &embed); |
… | |
… | |
3108 | |
3280 | |
3109 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3281 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3110 | |
3282 | |
3111 | Fork watchers are called when a C<fork ()> was detected (usually because |
3283 | Fork watchers are called when a C<fork ()> was detected (usually because |
3112 | whoever is a good citizen cared to tell libev about it by calling |
3284 | whoever is a good citizen cared to tell libev about it by calling |
3113 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3285 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3114 | event loop blocks next and before C<ev_check> watchers are being called, |
3286 | and before C<ev_check> watchers are being called, and only in the child |
3115 | and only in the child after the fork. If whoever good citizen calling |
3287 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3116 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3288 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3117 | handlers will be invoked, too, of course. |
3289 | of course. |
3118 | |
3290 | |
3119 | =head3 The special problem of life after fork - how is it possible? |
3291 | =head3 The special problem of life after fork - how is it possible? |
3120 | |
3292 | |
3121 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3293 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3122 | up/change the process environment, followed by a call to C<exec()>. This |
3294 | up/change the process environment, followed by a call to C<exec()>. This |
3123 | sequence should be handled by libev without any problems. |
3295 | sequence should be handled by libev without any problems. |
3124 | |
3296 | |
3125 | This changes when the application actually wants to do event handling |
3297 | This changes when the application actually wants to do event handling |
3126 | in the child, or both parent in child, in effect "continuing" after the |
3298 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3215 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3387 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3216 | |
3388 | |
3217 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3389 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3218 | too, are asynchronous in nature, and signals, too, will be compressed |
3390 | too, are asynchronous in nature, and signals, too, will be compressed |
3219 | (i.e. the number of callback invocations may be less than the number of |
3391 | (i.e. the number of callback invocations may be less than the number of |
3220 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3392 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3221 | of "global async watchers" by using a watcher on an otherwise unused |
3393 | of "global async watchers" by using a watcher on an otherwise unused |
3222 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3394 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3223 | even without knowing which loop owns the signal. |
3395 | even without knowing which loop owns the signal. |
3224 | |
|
|
3225 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
3226 | just the default loop. |
|
|
3227 | |
3396 | |
3228 | =head3 Queueing |
3397 | =head3 Queueing |
3229 | |
3398 | |
3230 | C<ev_async> does not support queueing of data in any way. The reason |
3399 | C<ev_async> does not support queueing of data in any way. The reason |
3231 | is that the author does not know of a simple (or any) algorithm for a |
3400 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3331 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3500 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3332 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3501 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3333 | embedding section below on what exactly this means). |
3502 | embedding section below on what exactly this means). |
3334 | |
3503 | |
3335 | Note that, as with other watchers in libev, multiple events might get |
3504 | Note that, as with other watchers in libev, multiple events might get |
3336 | compressed into a single callback invocation (another way to look at this |
3505 | compressed into a single callback invocation (another way to look at |
3337 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3506 | this is that C<ev_async> watchers are level-triggered: they are set on |
3338 | reset when the event loop detects that). |
3507 | C<ev_async_send>, reset when the event loop detects that). |
3339 | |
3508 | |
3340 | This call incurs the overhead of a system call only once per event loop |
3509 | This call incurs the overhead of at most one extra system call per event |
3341 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3510 | loop iteration, if the event loop is blocked, and no syscall at all if |
3342 | repeated calls to C<ev_async_send> for the same event loop. |
3511 | the event loop (or your program) is processing events. That means that |
|
|
3512 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3513 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3514 | zero) under load. |
3343 | |
3515 | |
3344 | =item bool = ev_async_pending (ev_async *) |
3516 | =item bool = ev_async_pending (ev_async *) |
3345 | |
3517 | |
3346 | Returns a non-zero value when C<ev_async_send> has been called on the |
3518 | Returns a non-zero value when C<ev_async_send> has been called on the |
3347 | watcher but the event has not yet been processed (or even noted) by the |
3519 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3364 | |
3536 | |
3365 | There are some other functions of possible interest. Described. Here. Now. |
3537 | There are some other functions of possible interest. Described. Here. Now. |
3366 | |
3538 | |
3367 | =over 4 |
3539 | =over 4 |
3368 | |
3540 | |
3369 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3541 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
3370 | |
3542 | |
3371 | This function combines a simple timer and an I/O watcher, calls your |
3543 | This function combines a simple timer and an I/O watcher, calls your |
3372 | callback on whichever event happens first and automatically stops both |
3544 | callback on whichever event happens first and automatically stops both |
3373 | watchers. This is useful if you want to wait for a single event on an fd |
3545 | watchers. This is useful if you want to wait for a single event on an fd |
3374 | or timeout without having to allocate/configure/start/stop/free one or |
3546 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
3402 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3574 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3403 | |
3575 | |
3404 | =item ev_feed_fd_event (loop, int fd, int revents) |
3576 | =item ev_feed_fd_event (loop, int fd, int revents) |
3405 | |
3577 | |
3406 | Feed an event on the given fd, as if a file descriptor backend detected |
3578 | Feed an event on the given fd, as if a file descriptor backend detected |
3407 | the given events it. |
3579 | the given events. |
3408 | |
3580 | |
3409 | =item ev_feed_signal_event (loop, int signum) |
3581 | =item ev_feed_signal_event (loop, int signum) |
3410 | |
3582 | |
3411 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3583 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3412 | which is async-safe. |
3584 | which is async-safe. |
… | |
… | |
3486 | { |
3658 | { |
3487 | struct my_biggy big = (struct my_biggy *) |
3659 | struct my_biggy big = (struct my_biggy *) |
3488 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3660 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3489 | } |
3661 | } |
3490 | |
3662 | |
|
|
3663 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3664 | |
|
|
3665 | Often you have structures like this in event-based programs: |
|
|
3666 | |
|
|
3667 | callback () |
|
|
3668 | { |
|
|
3669 | free (request); |
|
|
3670 | } |
|
|
3671 | |
|
|
3672 | request = start_new_request (..., callback); |
|
|
3673 | |
|
|
3674 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3675 | used to cancel the operation, or do other things with it. |
|
|
3676 | |
|
|
3677 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3678 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3679 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3680 | operation and simply invoke the callback with the result. |
|
|
3681 | |
|
|
3682 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3683 | has returned, so C<request> is not set. |
|
|
3684 | |
|
|
3685 | Even if you pass the request by some safer means to the callback, you |
|
|
3686 | might want to do something to the request after starting it, such as |
|
|
3687 | canceling it, which probably isn't working so well when the callback has |
|
|
3688 | already been invoked. |
|
|
3689 | |
|
|
3690 | A common way around all these issues is to make sure that |
|
|
3691 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3692 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3693 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3694 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3695 | pushing it into the pending queue: |
|
|
3696 | |
|
|
3697 | ev_set_cb (watcher, callback); |
|
|
3698 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3699 | |
|
|
3700 | This way, C<start_new_request> can safely return before the callback is |
|
|
3701 | invoked, while not delaying callback invocation too much. |
|
|
3702 | |
3491 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3703 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3492 | |
3704 | |
3493 | Often (especially in GUI toolkits) there are places where you have |
3705 | Often (especially in GUI toolkits) there are places where you have |
3494 | I<modal> interaction, which is most easily implemented by recursively |
3706 | I<modal> interaction, which is most easily implemented by recursively |
3495 | invoking C<ev_run>. |
3707 | invoking C<ev_run>. |
3496 | |
3708 | |
3497 | This brings the problem of exiting - a callback might want to finish the |
3709 | This brings the problem of exiting - a callback might want to finish the |
3498 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3710 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3499 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3711 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3500 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3712 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3501 | other combination: In these cases, C<ev_break> will not work alone. |
3713 | other combination: In these cases, a simple C<ev_break> will not work. |
3502 | |
3714 | |
3503 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3715 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3504 | invocation, and use a loop around C<ev_run> until the condition is |
3716 | invocation, and use a loop around C<ev_run> until the condition is |
3505 | triggered, using C<EVRUN_ONCE>: |
3717 | triggered, using C<EVRUN_ONCE>: |
3506 | |
3718 | |
… | |
… | |
3508 | int exit_main_loop = 0; |
3720 | int exit_main_loop = 0; |
3509 | |
3721 | |
3510 | while (!exit_main_loop) |
3722 | while (!exit_main_loop) |
3511 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3723 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3512 | |
3724 | |
3513 | // in a model watcher |
3725 | // in a modal watcher |
3514 | int exit_nested_loop = 0; |
3726 | int exit_nested_loop = 0; |
3515 | |
3727 | |
3516 | while (!exit_nested_loop) |
3728 | while (!exit_nested_loop) |
3517 | ev_run (EV_A_ EVRUN_ONCE); |
3729 | ev_run (EV_A_ EVRUN_ONCE); |
3518 | |
3730 | |
… | |
… | |
3692 | called): |
3904 | called): |
3693 | |
3905 | |
3694 | void |
3906 | void |
3695 | wait_for_event (ev_watcher *w) |
3907 | wait_for_event (ev_watcher *w) |
3696 | { |
3908 | { |
3697 | ev_cb_set (w) = current_coro; |
3909 | ev_set_cb (w, current_coro); |
3698 | switch_to (libev_coro); |
3910 | switch_to (libev_coro); |
3699 | } |
3911 | } |
3700 | |
3912 | |
3701 | That basically suspends the coroutine inside C<wait_for_event> and |
3913 | That basically suspends the coroutine inside C<wait_for_event> and |
3702 | continues the libev coroutine, which, when appropriate, switches back to |
3914 | continues the libev coroutine, which, when appropriate, switches back to |
3703 | this or any other coroutine. I am sure if you sue this your own :) |
3915 | this or any other coroutine. |
3704 | |
3916 | |
3705 | You can do similar tricks if you have, say, threads with an event queue - |
3917 | You can do similar tricks if you have, say, threads with an event queue - |
3706 | instead of storing a coroutine, you store the queue object and instead of |
3918 | instead of storing a coroutine, you store the queue object and instead of |
3707 | switching to a coroutine, you push the watcher onto the queue and notify |
3919 | switching to a coroutine, you push the watcher onto the queue and notify |
3708 | any waiters. |
3920 | any waiters. |
3709 | |
3921 | |
3710 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
3922 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3711 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3923 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3712 | |
3924 | |
3713 | // my_ev.h |
3925 | // my_ev.h |
3714 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3926 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3715 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
3927 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
3716 | #include "../libev/ev.h" |
3928 | #include "../libev/ev.h" |
3717 | |
3929 | |
3718 | // my_ev.c |
3930 | // my_ev.c |
3719 | #define EV_H "my_ev.h" |
3931 | #define EV_H "my_ev.h" |
3720 | #include "../libev/ev.c" |
3932 | #include "../libev/ev.c" |
… | |
… | |
3759 | |
3971 | |
3760 | =back |
3972 | =back |
3761 | |
3973 | |
3762 | =head1 C++ SUPPORT |
3974 | =head1 C++ SUPPORT |
3763 | |
3975 | |
|
|
3976 | =head2 C API |
|
|
3977 | |
|
|
3978 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3979 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3980 | will work fine. |
|
|
3981 | |
|
|
3982 | Proper exception specifications might have to be added to callbacks passed |
|
|
3983 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3984 | other callbacks (allocator, syserr, loop acquire/release and periodic |
|
|
3985 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3986 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3987 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3988 | |
|
|
3989 | static void |
|
|
3990 | fatal_error (const char *msg) EV_THROW |
|
|
3991 | { |
|
|
3992 | perror (msg); |
|
|
3993 | abort (); |
|
|
3994 | } |
|
|
3995 | |
|
|
3996 | ... |
|
|
3997 | ev_set_syserr_cb (fatal_error); |
|
|
3998 | |
|
|
3999 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
4000 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
4001 | because it runs cleanup watchers). |
|
|
4002 | |
|
|
4003 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
4004 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
4005 | throwing exceptions through C libraries (most do). |
|
|
4006 | |
|
|
4007 | =head2 C++ API |
|
|
4008 | |
3764 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
4009 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3765 | you to use some convenience methods to start/stop watchers and also change |
4010 | you to use some convenience methods to start/stop watchers and also change |
3766 | the callback model to a model using method callbacks on objects. |
4011 | the callback model to a model using method callbacks on objects. |
3767 | |
4012 | |
3768 | To use it, |
4013 | To use it, |
3769 | |
4014 | |
3770 | #include <ev++.h> |
4015 | #include <ev++.h> |
3771 | |
4016 | |
3772 | This automatically includes F<ev.h> and puts all of its definitions (many |
4017 | This automatically includes F<ev.h> and puts all of its definitions (many |
3773 | of them macros) into the global namespace. All C++ specific things are |
4018 | of them macros) into the global namespace. All C++ specific things are |
3774 | put into the C<ev> namespace. It should support all the same embedding |
4019 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
3783 | with C<operator ()> can be used as callbacks. Other types should be easy |
4028 | with C<operator ()> can be used as callbacks. Other types should be easy |
3784 | to add as long as they only need one additional pointer for context. If |
4029 | to add as long as they only need one additional pointer for context. If |
3785 | you need support for other types of functors please contact the author |
4030 | you need support for other types of functors please contact the author |
3786 | (preferably after implementing it). |
4031 | (preferably after implementing it). |
3787 | |
4032 | |
|
|
4033 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4034 | conventions as your C compiler (for static member functions), or you have |
|
|
4035 | to embed libev and compile libev itself as C++. |
|
|
4036 | |
3788 | Here is a list of things available in the C<ev> namespace: |
4037 | Here is a list of things available in the C<ev> namespace: |
3789 | |
4038 | |
3790 | =over 4 |
4039 | =over 4 |
3791 | |
4040 | |
3792 | =item C<ev::READ>, C<ev::WRITE> etc. |
4041 | =item C<ev::READ>, C<ev::WRITE> etc. |
… | |
… | |
3801 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4050 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3802 | |
4051 | |
3803 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4052 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3804 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4053 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3805 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4054 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3806 | defines by many implementations. |
4055 | defined by many implementations. |
3807 | |
4056 | |
3808 | All of those classes have these methods: |
4057 | All of those classes have these methods: |
3809 | |
4058 | |
3810 | =over 4 |
4059 | =over 4 |
3811 | |
4060 | |
… | |
… | |
3873 | void operator() (ev::io &w, int revents) |
4122 | void operator() (ev::io &w, int revents) |
3874 | { |
4123 | { |
3875 | ... |
4124 | ... |
3876 | } |
4125 | } |
3877 | } |
4126 | } |
3878 | |
4127 | |
3879 | myfunctor f; |
4128 | myfunctor f; |
3880 | |
4129 | |
3881 | ev::io w; |
4130 | ev::io w; |
3882 | w.set (&f); |
4131 | w.set (&f); |
3883 | |
4132 | |
… | |
… | |
3901 | Associates a different C<struct ev_loop> with this watcher. You can only |
4150 | Associates a different C<struct ev_loop> with this watcher. You can only |
3902 | do this when the watcher is inactive (and not pending either). |
4151 | do this when the watcher is inactive (and not pending either). |
3903 | |
4152 | |
3904 | =item w->set ([arguments]) |
4153 | =item w->set ([arguments]) |
3905 | |
4154 | |
3906 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4155 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
3907 | method or a suitable start method must be called at least once. Unlike the |
4156 | with the same arguments. Either this method or a suitable start method |
3908 | C counterpart, an active watcher gets automatically stopped and restarted |
4157 | must be called at least once. Unlike the C counterpart, an active watcher |
3909 | when reconfiguring it with this method. |
4158 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4159 | method. |
|
|
4160 | |
|
|
4161 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4162 | clashing with the C<set (loop)> method. |
3910 | |
4163 | |
3911 | =item w->start () |
4164 | =item w->start () |
3912 | |
4165 | |
3913 | Starts the watcher. Note that there is no C<loop> argument, as the |
4166 | Starts the watcher. Note that there is no C<loop> argument, as the |
3914 | constructor already stores the event loop. |
4167 | constructor already stores the event loop. |
… | |
… | |
3944 | watchers in the constructor. |
4197 | watchers in the constructor. |
3945 | |
4198 | |
3946 | class myclass |
4199 | class myclass |
3947 | { |
4200 | { |
3948 | ev::io io ; void io_cb (ev::io &w, int revents); |
4201 | ev::io io ; void io_cb (ev::io &w, int revents); |
3949 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4202 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3950 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4203 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3951 | |
4204 | |
3952 | myclass (int fd) |
4205 | myclass (int fd) |
3953 | { |
4206 | { |
3954 | io .set <myclass, &myclass::io_cb > (this); |
4207 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
4005 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4258 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4006 | |
4259 | |
4007 | =item D |
4260 | =item D |
4008 | |
4261 | |
4009 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4262 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4010 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4263 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
4011 | |
4264 | |
4012 | =item Ocaml |
4265 | =item Ocaml |
4013 | |
4266 | |
4014 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4267 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4015 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4268 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
4018 | |
4271 | |
4019 | Brian Maher has written a partial interface to libev for lua (at the |
4272 | Brian Maher has written a partial interface to libev for lua (at the |
4020 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4273 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4021 | L<http://github.com/brimworks/lua-ev>. |
4274 | L<http://github.com/brimworks/lua-ev>. |
4022 | |
4275 | |
|
|
4276 | =item Javascript |
|
|
4277 | |
|
|
4278 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4279 | |
|
|
4280 | =item Others |
|
|
4281 | |
|
|
4282 | There are others, and I stopped counting. |
|
|
4283 | |
4023 | =back |
4284 | =back |
4024 | |
4285 | |
4025 | |
4286 | |
4026 | =head1 MACRO MAGIC |
4287 | =head1 MACRO MAGIC |
4027 | |
4288 | |
… | |
… | |
4063 | suitable for use with C<EV_A>. |
4324 | suitable for use with C<EV_A>. |
4064 | |
4325 | |
4065 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4326 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4066 | |
4327 | |
4067 | Similar to the other two macros, this gives you the value of the default |
4328 | Similar to the other two macros, this gives you the value of the default |
4068 | loop, if multiple loops are supported ("ev loop default"). |
4329 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4330 | will be initialised if it isn't already initialised. |
|
|
4331 | |
|
|
4332 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4333 | to initialise the loop somewhere. |
4069 | |
4334 | |
4070 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4335 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4071 | |
4336 | |
4072 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4337 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4073 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4338 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
4140 | ev_vars.h |
4405 | ev_vars.h |
4141 | ev_wrap.h |
4406 | ev_wrap.h |
4142 | |
4407 | |
4143 | ev_win32.c required on win32 platforms only |
4408 | ev_win32.c required on win32 platforms only |
4144 | |
4409 | |
4145 | ev_select.c only when select backend is enabled (which is enabled by default) |
4410 | ev_select.c only when select backend is enabled |
4146 | ev_poll.c only when poll backend is enabled (disabled by default) |
4411 | ev_poll.c only when poll backend is enabled |
4147 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4412 | ev_epoll.c only when the epoll backend is enabled |
4148 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4413 | ev_kqueue.c only when the kqueue backend is enabled |
4149 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4414 | ev_port.c only when the solaris port backend is enabled |
4150 | |
4415 | |
4151 | F<ev.c> includes the backend files directly when enabled, so you only need |
4416 | F<ev.c> includes the backend files directly when enabled, so you only need |
4152 | to compile this single file. |
4417 | to compile this single file. |
4153 | |
4418 | |
4154 | =head3 LIBEVENT COMPATIBILITY API |
4419 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
4321 | |
4586 | |
4322 | If programs implement their own fd to handle mapping on win32, then this |
4587 | If programs implement their own fd to handle mapping on win32, then this |
4323 | macro can be used to override the C<close> function, useful to unregister |
4588 | macro can be used to override the C<close> function, useful to unregister |
4324 | file descriptors again. Note that the replacement function has to close |
4589 | file descriptors again. Note that the replacement function has to close |
4325 | the underlying OS handle. |
4590 | the underlying OS handle. |
|
|
4591 | |
|
|
4592 | =item EV_USE_WSASOCKET |
|
|
4593 | |
|
|
4594 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4595 | communication socket, which works better in some environments. Otherwise, |
|
|
4596 | the normal C<socket> function will be used, which works better in other |
|
|
4597 | environments. |
4326 | |
4598 | |
4327 | =item EV_USE_POLL |
4599 | =item EV_USE_POLL |
4328 | |
4600 | |
4329 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4601 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4330 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4602 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
4366 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4638 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4367 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4639 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4368 | be detected at runtime. If undefined, it will be enabled if the headers |
4640 | be detected at runtime. If undefined, it will be enabled if the headers |
4369 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4641 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4370 | |
4642 | |
|
|
4643 | =item EV_NO_SMP |
|
|
4644 | |
|
|
4645 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4646 | between threads, that is, threads can be used, but threads never run on |
|
|
4647 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4648 | and makes libev faster. |
|
|
4649 | |
|
|
4650 | =item EV_NO_THREADS |
|
|
4651 | |
|
|
4652 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4653 | different threads (that includes signal handlers), which is a stronger |
|
|
4654 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4655 | libev faster. |
|
|
4656 | |
4371 | =item EV_ATOMIC_T |
4657 | =item EV_ATOMIC_T |
4372 | |
4658 | |
4373 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4659 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4374 | access is atomic with respect to other threads or signal contexts. No such |
4660 | access is atomic with respect to other threads or signal contexts. No |
4375 | type is easily found in the C language, so you can provide your own type |
4661 | such type is easily found in the C language, so you can provide your own |
4376 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4662 | type that you know is safe for your purposes. It is used both for signal |
4377 | as well as for signal and thread safety in C<ev_async> watchers. |
4663 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4664 | watchers. |
4378 | |
4665 | |
4379 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4666 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4380 | (from F<signal.h>), which is usually good enough on most platforms. |
4667 | (from F<signal.h>), which is usually good enough on most platforms. |
4381 | |
4668 | |
4382 | =item EV_H (h) |
4669 | =item EV_H (h) |
… | |
… | |
4409 | will have the C<struct ev_loop *> as first argument, and you can create |
4696 | will have the C<struct ev_loop *> as first argument, and you can create |
4410 | additional independent event loops. Otherwise there will be no support |
4697 | additional independent event loops. Otherwise there will be no support |
4411 | for multiple event loops and there is no first event loop pointer |
4698 | for multiple event loops and there is no first event loop pointer |
4412 | argument. Instead, all functions act on the single default loop. |
4699 | argument. Instead, all functions act on the single default loop. |
4413 | |
4700 | |
|
|
4701 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4702 | default loop when multiplicity is switched off - you always have to |
|
|
4703 | initialise the loop manually in this case. |
|
|
4704 | |
4414 | =item EV_MINPRI |
4705 | =item EV_MINPRI |
4415 | |
4706 | |
4416 | =item EV_MAXPRI |
4707 | =item EV_MAXPRI |
4417 | |
4708 | |
4418 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4709 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4454 | #define EV_USE_POLL 1 |
4745 | #define EV_USE_POLL 1 |
4455 | #define EV_CHILD_ENABLE 1 |
4746 | #define EV_CHILD_ENABLE 1 |
4456 | #define EV_ASYNC_ENABLE 1 |
4747 | #define EV_ASYNC_ENABLE 1 |
4457 | |
4748 | |
4458 | The actual value is a bitset, it can be a combination of the following |
4749 | The actual value is a bitset, it can be a combination of the following |
4459 | values: |
4750 | values (by default, all of these are enabled): |
4460 | |
4751 | |
4461 | =over 4 |
4752 | =over 4 |
4462 | |
4753 | |
4463 | =item C<1> - faster/larger code |
4754 | =item C<1> - faster/larger code |
4464 | |
4755 | |
… | |
… | |
4468 | code size by roughly 30% on amd64). |
4759 | code size by roughly 30% on amd64). |
4469 | |
4760 | |
4470 | When optimising for size, use of compiler flags such as C<-Os> with |
4761 | When optimising for size, use of compiler flags such as C<-Os> with |
4471 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4762 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4472 | assertions. |
4763 | assertions. |
|
|
4764 | |
|
|
4765 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4766 | (e.g. gcc with C<-Os>). |
4473 | |
4767 | |
4474 | =item C<2> - faster/larger data structures |
4768 | =item C<2> - faster/larger data structures |
4475 | |
4769 | |
4476 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4770 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4477 | hash table sizes and so on. This will usually further increase code size |
4771 | hash table sizes and so on. This will usually further increase code size |
4478 | and can additionally have an effect on the size of data structures at |
4772 | and can additionally have an effect on the size of data structures at |
4479 | runtime. |
4773 | runtime. |
4480 | |
4774 | |
|
|
4775 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4776 | (e.g. gcc with C<-Os>). |
|
|
4777 | |
4481 | =item C<4> - full API configuration |
4778 | =item C<4> - full API configuration |
4482 | |
4779 | |
4483 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4780 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4484 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4781 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4485 | |
4782 | |
… | |
… | |
4515 | |
4812 | |
4516 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4813 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4517 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4814 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4518 | your program might be left out as well - a binary starting a timer and an |
4815 | your program might be left out as well - a binary starting a timer and an |
4519 | I/O watcher then might come out at only 5Kb. |
4816 | I/O watcher then might come out at only 5Kb. |
|
|
4817 | |
|
|
4818 | =item EV_API_STATIC |
|
|
4819 | |
|
|
4820 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4821 | will have static linkage. This means that libev will not export any |
|
|
4822 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4823 | when you embed libev, only want to use libev functions in a single file, |
|
|
4824 | and do not want its identifiers to be visible. |
|
|
4825 | |
|
|
4826 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4827 | wants to use libev. |
|
|
4828 | |
|
|
4829 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4830 | doesn't support the required declaration syntax. |
4520 | |
4831 | |
4521 | =item EV_AVOID_STDIO |
4832 | =item EV_AVOID_STDIO |
4522 | |
4833 | |
4523 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4834 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4524 | functions (printf, scanf, perror etc.). This will increase the code size |
4835 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4729 | default loop and triggering an C<ev_async> watcher from the default loop |
5040 | default loop and triggering an C<ev_async> watcher from the default loop |
4730 | watcher callback into the event loop interested in the signal. |
5041 | watcher callback into the event loop interested in the signal. |
4731 | |
5042 | |
4732 | =back |
5043 | =back |
4733 | |
5044 | |
4734 | See also L<THREAD LOCKING EXAMPLE>. |
5045 | See also L</THREAD LOCKING EXAMPLE>. |
4735 | |
5046 | |
4736 | =head3 COROUTINES |
5047 | =head3 COROUTINES |
4737 | |
5048 | |
4738 | Libev is very accommodating to coroutines ("cooperative threads"): |
5049 | Libev is very accommodating to coroutines ("cooperative threads"): |
4739 | libev fully supports nesting calls to its functions from different |
5050 | libev fully supports nesting calls to its functions from different |
… | |
… | |
5008 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5319 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5009 | assumes that the same (machine) code can be used to call any watcher |
5320 | assumes that the same (machine) code can be used to call any watcher |
5010 | callback: The watcher callbacks have different type signatures, but libev |
5321 | callback: The watcher callbacks have different type signatures, but libev |
5011 | calls them using an C<ev_watcher *> internally. |
5322 | calls them using an C<ev_watcher *> internally. |
5012 | |
5323 | |
|
|
5324 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5325 | |
|
|
5326 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5327 | relies on this setting pointers and integers to null. |
|
|
5328 | |
5013 | =item pointer accesses must be thread-atomic |
5329 | =item pointer accesses must be thread-atomic |
5014 | |
5330 | |
5015 | Accessing a pointer value must be atomic, it must both be readable and |
5331 | Accessing a pointer value must be atomic, it must both be readable and |
5016 | writable in one piece - this is the case on all current architectures. |
5332 | writable in one piece - this is the case on all current architectures. |
5017 | |
5333 | |
… | |
… | |
5030 | thread" or will block signals process-wide, both behaviours would |
5346 | thread" or will block signals process-wide, both behaviours would |
5031 | be compatible with libev. Interaction between C<sigprocmask> and |
5347 | be compatible with libev. Interaction between C<sigprocmask> and |
5032 | C<pthread_sigmask> could complicate things, however. |
5348 | C<pthread_sigmask> could complicate things, however. |
5033 | |
5349 | |
5034 | The most portable way to handle signals is to block signals in all threads |
5350 | The most portable way to handle signals is to block signals in all threads |
5035 | except the initial one, and run the default loop in the initial thread as |
5351 | except the initial one, and run the signal handling loop in the initial |
5036 | well. |
5352 | thread as well. |
5037 | |
5353 | |
5038 | =item C<long> must be large enough for common memory allocation sizes |
5354 | =item C<long> must be large enough for common memory allocation sizes |
5039 | |
5355 | |
5040 | To improve portability and simplify its API, libev uses C<long> internally |
5356 | To improve portability and simplify its API, libev uses C<long> internally |
5041 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5357 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
5047 | |
5363 | |
5048 | The type C<double> is used to represent timestamps. It is required to |
5364 | The type C<double> is used to represent timestamps. It is required to |
5049 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5365 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5050 | good enough for at least into the year 4000 with millisecond accuracy |
5366 | good enough for at least into the year 4000 with millisecond accuracy |
5051 | (the design goal for libev). This requirement is overfulfilled by |
5367 | (the design goal for libev). This requirement is overfulfilled by |
5052 | implementations using IEEE 754, which is basically all existing ones. With |
5368 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5369 | |
5053 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5370 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5371 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5372 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5373 | something like that, just kidding). |
5054 | |
5374 | |
5055 | =back |
5375 | =back |
5056 | |
5376 | |
5057 | If you know of other additional requirements drop me a note. |
5377 | If you know of other additional requirements drop me a note. |
5058 | |
5378 | |
… | |
… | |
5120 | =item Processing ev_async_send: O(number_of_async_watchers) |
5440 | =item Processing ev_async_send: O(number_of_async_watchers) |
5121 | |
5441 | |
5122 | =item Processing signals: O(max_signal_number) |
5442 | =item Processing signals: O(max_signal_number) |
5123 | |
5443 | |
5124 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5444 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5125 | calls in the current loop iteration. Checking for async and signal events |
5445 | calls in the current loop iteration and the loop is currently |
|
|
5446 | blocked. Checking for async and signal events involves iterating over all |
5126 | involves iterating over all running async watchers or all signal numbers. |
5447 | running async watchers or all signal numbers. |
5127 | |
5448 | |
5128 | =back |
5449 | =back |
5129 | |
5450 | |
5130 | |
5451 | |
5131 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5452 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
5140 | =over 4 |
5461 | =over 4 |
5141 | |
5462 | |
5142 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5463 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5143 | |
5464 | |
5144 | The backward compatibility mechanism can be controlled by |
5465 | The backward compatibility mechanism can be controlled by |
5145 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
5466 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
5146 | section. |
5467 | section. |
5147 | |
5468 | |
5148 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5469 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5149 | |
5470 | |
5150 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5471 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
… | |
… | |
5193 | =over 4 |
5514 | =over 4 |
5194 | |
5515 | |
5195 | =item active |
5516 | =item active |
5196 | |
5517 | |
5197 | A watcher is active as long as it has been started and not yet stopped. |
5518 | A watcher is active as long as it has been started and not yet stopped. |
5198 | See L<WATCHER STATES> for details. |
5519 | See L</WATCHER STATES> for details. |
5199 | |
5520 | |
5200 | =item application |
5521 | =item application |
5201 | |
5522 | |
5202 | In this document, an application is whatever is using libev. |
5523 | In this document, an application is whatever is using libev. |
5203 | |
5524 | |
… | |
… | |
5239 | watchers and events. |
5560 | watchers and events. |
5240 | |
5561 | |
5241 | =item pending |
5562 | =item pending |
5242 | |
5563 | |
5243 | A watcher is pending as soon as the corresponding event has been |
5564 | A watcher is pending as soon as the corresponding event has been |
5244 | detected. See L<WATCHER STATES> for details. |
5565 | detected. See L</WATCHER STATES> for details. |
5245 | |
5566 | |
5246 | =item real time |
5567 | =item real time |
5247 | |
5568 | |
5248 | The physical time that is observed. It is apparently strictly monotonic :) |
5569 | The physical time that is observed. It is apparently strictly monotonic :) |
5249 | |
5570 | |