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82 | |
82 | |
83 | =head1 WHAT TO READ WHEN IN A HURRY |
83 | =head1 WHAT TO READ WHEN IN A HURRY |
84 | |
84 | |
85 | This manual tries to be very detailed, but unfortunately, this also makes |
85 | This manual tries to be very detailed, but unfortunately, this also makes |
86 | it very long. If you just want to know the basics of libev, I suggest |
86 | it very long. If you just want to know the basics of libev, I suggest |
87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
87 | reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and |
88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
88 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
89 | C<ev_timer> sections in L<WATCHER TYPES>. |
89 | C<ev_timer> sections in L</WATCHER TYPES>. |
90 | |
90 | |
91 | =head1 ABOUT LIBEV |
91 | =head1 ABOUT LIBEV |
92 | |
92 | |
93 | Libev is an event loop: you register interest in certain events (such as a |
93 | Libev is an event loop: you register interest in certain events (such as a |
94 | file descriptor being readable or a timeout occurring), and it will manage |
94 | file descriptor being readable or a timeout occurring), and it will manage |
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174 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
175 | |
175 | |
176 | Returns the current time as libev would use it. Please note that the |
176 | 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 |
177 | 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 |
178 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
179 | C<ev_now_update> and C<ev_now>. |
180 | |
180 | |
181 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
182 | |
182 | |
183 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
184 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
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185 | passed (approximately - it might return a bit earlier even if not |
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186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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187 | |
185 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
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189 | |
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190 | The range of the C<interval> is limited - libev only guarantees to work |
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191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
186 | |
192 | |
187 | =item int ev_version_major () |
193 | =item int ev_version_major () |
188 | |
194 | |
189 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
190 | |
196 | |
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241 | the current system, you would need to look at C<ev_embeddable_backends () |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
243 | |
249 | |
244 | See the description of C<ev_embed> watchers for more info. |
250 | See the description of C<ev_embed> watchers for more info. |
245 | |
251 | |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
247 | |
253 | |
248 | Sets the allocation function to use (the prototype is similar - the |
254 | Sets the allocation function to use (the prototype is similar - the |
249 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
255 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
250 | used to allocate and free memory (no surprises here). If it returns zero |
256 | used to allocate and free memory (no surprises here). If it returns zero |
251 | when memory needs to be allocated (C<size != 0>), the library might abort |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
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277 | } |
283 | } |
278 | |
284 | |
279 | ... |
285 | ... |
280 | ev_set_allocator (persistent_realloc); |
286 | ev_set_allocator (persistent_realloc); |
281 | |
287 | |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
283 | |
289 | |
284 | Set the callback function to call on a retryable system call error (such |
290 | Set the callback function to call on a retryable system call error (such |
285 | as failed select, poll, epoll_wait). The message is a printable string |
291 | as failed select, poll, epoll_wait). The message is a printable string |
286 | indicating the system call or subsystem causing the problem. If this |
292 | indicating the system call or subsystem causing the problem. If this |
287 | callback is set, then libev will expect it to remedy the situation, no |
293 | callback is set, then libev will expect it to remedy the situation, no |
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390 | |
396 | |
391 | If this flag bit is or'ed into the flag value (or the program runs setuid |
397 | If this flag bit is or'ed into the flag value (or the program runs setuid |
392 | or setgid) then libev will I<not> look at the environment variable |
398 | or setgid) then libev will I<not> look at the environment variable |
393 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
399 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
394 | override the flags completely if it is found in the environment. This is |
400 | override the flags completely if it is found in the environment. This is |
395 | useful to try out specific backends to test their performance, or to work |
401 | useful to try out specific backends to test their performance, to work |
396 | around bugs. |
402 | around bugs, or to make libev threadsafe (accessing environment variables |
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403 | cannot be done in a threadsafe way, but usually it works if no other |
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404 | thread modifies them). |
397 | |
405 | |
398 | =item C<EVFLAG_FORKCHECK> |
406 | =item C<EVFLAG_FORKCHECK> |
399 | |
407 | |
400 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
408 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
401 | make libev check for a fork in each iteration by enabling this flag. |
409 | make libev check for a fork in each iteration by enabling this flag. |
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435 | example) that can't properly initialise their signal masks. |
443 | example) that can't properly initialise their signal masks. |
436 | |
444 | |
437 | =item C<EVFLAG_NOSIGMASK> |
445 | =item C<EVFLAG_NOSIGMASK> |
438 | |
446 | |
439 | When this flag is specified, then libev will avoid to modify the signal |
447 | When this flag is specified, then libev will avoid to modify the signal |
440 | mask. Specifically, this means you ahve to make sure signals are unblocked |
448 | mask. Specifically, this means you have to make sure signals are unblocked |
441 | when you want to receive them. |
449 | when you want to receive them. |
442 | |
450 | |
443 | This behaviour is useful when you want to do your own signal handling, or |
451 | This behaviour is useful when you want to do your own signal handling, or |
444 | want to handle signals only in specific threads and want to avoid libev |
452 | want to handle signals only in specific threads and want to avoid libev |
445 | unblocking the signals. |
453 | unblocking the signals. |
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499 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
507 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
500 | forks then I<both> parent and child process have to recreate the epoll |
508 | forks then I<both> parent and child process have to recreate the epoll |
501 | set, which can take considerable time (one syscall per file descriptor) |
509 | set, which can take considerable time (one syscall per file descriptor) |
502 | and is of course hard to detect. |
510 | and is of course hard to detect. |
503 | |
511 | |
504 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
512 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
505 | of course I<doesn't>, and epoll just loves to report events for totally |
513 | but of course I<doesn't>, and epoll just loves to report events for |
506 | I<different> file descriptors (even already closed ones, so one cannot |
514 | totally I<different> file descriptors (even already closed ones, so |
507 | even remove them from the set) than registered in the set (especially |
515 | one cannot even remove them from the set) than registered in the set |
508 | on SMP systems). Libev tries to counter these spurious notifications by |
516 | (especially on SMP systems). Libev tries to counter these spurious |
509 | employing an additional generation counter and comparing that against the |
517 | notifications by employing an additional generation counter and comparing |
510 | events to filter out spurious ones, recreating the set when required. Last |
518 | that against the events to filter out spurious ones, recreating the set |
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519 | when required. Epoll also erroneously rounds down timeouts, but gives you |
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520 | no way to know when and by how much, so sometimes you have to busy-wait |
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521 | because epoll returns immediately despite a nonzero timeout. And last |
511 | not least, it also refuses to work with some file descriptors which work |
522 | not least, it also refuses to work with some file descriptors which work |
512 | perfectly fine with C<select> (files, many character devices...). |
523 | perfectly fine with C<select> (files, many character devices...). |
513 | |
524 | |
514 | Epoll is truly the train wreck analog among event poll mechanisms, |
525 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
515 | a frankenpoll, cobbled together in a hurry, no thought to design or |
526 | cobbled together in a hurry, no thought to design or interaction with |
516 | interaction with others. |
527 | others. Oh, the pain, will it ever stop... |
517 | |
528 | |
518 | While stopping, setting and starting an I/O watcher in the same iteration |
529 | While stopping, setting and starting an I/O watcher in the same iteration |
519 | will result in some caching, there is still a system call per such |
530 | will result in some caching, there is still a system call per such |
520 | incident (because the same I<file descriptor> could point to a different |
531 | incident (because the same I<file descriptor> could point to a different |
521 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
532 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
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558 | |
569 | |
559 | It scales in the same way as the epoll backend, but the interface to the |
570 | It scales in the same way as the epoll backend, but the interface to the |
560 | kernel is more efficient (which says nothing about its actual speed, of |
571 | kernel is more efficient (which says nothing about its actual speed, of |
561 | course). While stopping, setting and starting an I/O watcher does never |
572 | course). While stopping, setting and starting an I/O watcher does never |
562 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
573 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
563 | two event changes per incident. Support for C<fork ()> is very bad (but |
574 | two event changes per incident. Support for C<fork ()> is very bad (you |
564 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
575 | might have to leak fd's on fork, but it's more sane than epoll) and it |
565 | cases |
576 | drops fds silently in similarly hard-to-detect cases. |
566 | |
577 | |
567 | This backend usually performs well under most conditions. |
578 | This backend usually performs well under most conditions. |
568 | |
579 | |
569 | While nominally embeddable in other event loops, this doesn't work |
580 | While nominally embeddable in other event loops, this doesn't work |
570 | everywhere, so you might need to test for this. And since it is broken |
581 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
599 | among the OS-specific backends (I vastly prefer correctness over speed |
610 | among the OS-specific backends (I vastly prefer correctness over speed |
600 | hacks). |
611 | hacks). |
601 | |
612 | |
602 | On the negative side, the interface is I<bizarre> - so bizarre that |
613 | On the negative side, the interface is I<bizarre> - so bizarre that |
603 | even sun itself gets it wrong in their code examples: The event polling |
614 | even sun itself gets it wrong in their code examples: The event polling |
604 | function sometimes returning events to the caller even though an error |
615 | function sometimes returns events to the caller even though an error |
605 | occurred, but with no indication whether it has done so or not (yes, it's |
616 | occurred, but with no indication whether it has done so or not (yes, it's |
606 | even documented that way) - deadly for edge-triggered interfaces where |
617 | even documented that way) - deadly for edge-triggered interfaces where you |
607 | you absolutely have to know whether an event occurred or not because you |
618 | absolutely have to know whether an event occurred or not because you have |
608 | have to re-arm the watcher. |
619 | to re-arm the watcher. |
609 | |
620 | |
610 | Fortunately libev seems to be able to work around these idiocies. |
621 | Fortunately libev seems to be able to work around these idiocies. |
611 | |
622 | |
612 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
623 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
613 | C<EVBACKEND_POLL>. |
624 | C<EVBACKEND_POLL>. |
… | |
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755 | |
766 | |
756 | This function is rarely useful, but when some event callback runs for a |
767 | This function is rarely useful, but when some event callback runs for a |
757 | very long time without entering the event loop, updating libev's idea of |
768 | very long time without entering the event loop, updating libev's idea of |
758 | the current time is a good idea. |
769 | the current time is a good idea. |
759 | |
770 | |
760 | See also L<The special problem of time updates> in the C<ev_timer> section. |
771 | See also L</The special problem of time updates> in the C<ev_timer> section. |
761 | |
772 | |
762 | =item ev_suspend (loop) |
773 | =item ev_suspend (loop) |
763 | |
774 | |
764 | =item ev_resume (loop) |
775 | =item ev_resume (loop) |
765 | |
776 | |
… | |
… | |
783 | without a previous call to C<ev_suspend>. |
794 | without a previous call to C<ev_suspend>. |
784 | |
795 | |
785 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
796 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
786 | event loop time (see C<ev_now_update>). |
797 | event loop time (see C<ev_now_update>). |
787 | |
798 | |
788 | =item ev_run (loop, int flags) |
799 | =item bool ev_run (loop, int flags) |
789 | |
800 | |
790 | Finally, this is it, the event handler. This function usually is called |
801 | Finally, this is it, the event handler. This function usually is called |
791 | after you have initialised all your watchers and you want to start |
802 | after you have initialised all your watchers and you want to start |
792 | handling events. It will ask the operating system for any new events, call |
803 | handling events. It will ask the operating system for any new events, call |
793 | the watcher callbacks, an then repeat the whole process indefinitely: This |
804 | the watcher callbacks, and then repeat the whole process indefinitely: This |
794 | is why event loops are called I<loops>. |
805 | is why event loops are called I<loops>. |
795 | |
806 | |
796 | If the flags argument is specified as C<0>, it will keep handling events |
807 | If the flags argument is specified as C<0>, it will keep handling events |
797 | until either no event watchers are active anymore or C<ev_break> was |
808 | until either no event watchers are active anymore or C<ev_break> was |
798 | called. |
809 | called. |
|
|
810 | |
|
|
811 | The return value is false if there are no more active watchers (which |
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812 | usually means "all jobs done" or "deadlock"), and true in all other cases |
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|
813 | (which usually means " you should call C<ev_run> again"). |
799 | |
814 | |
800 | Please note that an explicit C<ev_break> is usually better than |
815 | Please note that an explicit C<ev_break> is usually better than |
801 | relying on all watchers to be stopped when deciding when a program has |
816 | relying on all watchers to be stopped when deciding when a program has |
802 | finished (especially in interactive programs), but having a program |
817 | finished (especially in interactive programs), but having a program |
803 | that automatically loops as long as it has to and no longer by virtue |
818 | that automatically loops as long as it has to and no longer by virtue |
804 | of relying on its watchers stopping correctly, that is truly a thing of |
819 | of relying on its watchers stopping correctly, that is truly a thing of |
805 | beauty. |
820 | beauty. |
806 | |
821 | |
807 | This function is also I<mostly> exception-safe - you can break out of |
822 | This function is I<mostly> exception-safe - you can break out of a |
808 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
823 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
809 | exception and so on. This does not decrement the C<ev_depth> value, nor |
824 | exception and so on. This does not decrement the C<ev_depth> value, nor |
810 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
825 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
811 | |
826 | |
812 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
827 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
813 | those events and any already outstanding ones, but will not wait and |
828 | those events and any already outstanding ones, but will not wait and |
… | |
… | |
943 | overhead for the actual polling but can deliver many events at once. |
958 | overhead for the actual polling but can deliver many events at once. |
944 | |
959 | |
945 | By setting a higher I<io collect interval> you allow libev to spend more |
960 | By setting a higher I<io collect interval> you allow libev to spend more |
946 | time collecting I/O events, so you can handle more events per iteration, |
961 | time collecting I/O events, so you can handle more events per iteration, |
947 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
962 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
948 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
963 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
949 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
964 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
950 | sleep time ensures that libev will not poll for I/O events more often then |
965 | sleep time ensures that libev will not poll for I/O events more often then |
951 | once per this interval, on average. |
966 | once per this interval, on average (as long as the host time resolution is |
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967 | good enough). |
952 | |
968 | |
953 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
969 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
954 | to spend more time collecting timeouts, at the expense of increased |
970 | to spend more time collecting timeouts, at the expense of increased |
955 | latency/jitter/inexactness (the watcher callback will be called |
971 | latency/jitter/inexactness (the watcher callback will be called |
956 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
972 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
1002 | invoke the actual watchers inside another context (another thread etc.). |
1018 | invoke the actual watchers inside another context (another thread etc.). |
1003 | |
1019 | |
1004 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1020 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1005 | callback. |
1021 | callback. |
1006 | |
1022 | |
1007 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1023 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
1008 | |
1024 | |
1009 | Sometimes you want to share the same loop between multiple threads. This |
1025 | Sometimes you want to share the same loop between multiple threads. This |
1010 | can be done relatively simply by putting mutex_lock/unlock calls around |
1026 | can be done relatively simply by putting mutex_lock/unlock calls around |
1011 | each call to a libev function. |
1027 | each call to a libev function. |
1012 | |
1028 | |
1013 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1029 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1014 | to wait for it to return. One way around this is to wake up the event |
1030 | to wait for it to return. One way around this is to wake up the event |
1015 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1031 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
1016 | I<release> and I<acquire> callbacks on the loop. |
1032 | I<release> and I<acquire> callbacks on the loop. |
1017 | |
1033 | |
1018 | When set, then C<release> will be called just before the thread is |
1034 | When set, then C<release> will be called just before the thread is |
1019 | suspended waiting for new events, and C<acquire> is called just |
1035 | suspended waiting for new events, and C<acquire> is called just |
1020 | afterwards. |
1036 | afterwards. |
… | |
… | |
1160 | |
1176 | |
1161 | =item C<EV_PREPARE> |
1177 | =item C<EV_PREPARE> |
1162 | |
1178 | |
1163 | =item C<EV_CHECK> |
1179 | =item C<EV_CHECK> |
1164 | |
1180 | |
1165 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1181 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1166 | to gather new events, and all C<ev_check> watchers are invoked just after |
1182 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1167 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1183 | just after C<ev_run> has gathered them, but before it queues any callbacks |
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1184 | for any received events. That means C<ev_prepare> watchers are the last |
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1185 | watchers invoked before the event loop sleeps or polls for new events, and |
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1186 | C<ev_check> watchers will be invoked before any other watchers of the same |
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|
1187 | or lower priority within an event loop iteration. |
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|
1188 | |
1168 | received events. Callbacks of both watcher types can start and stop as |
1189 | Callbacks of both watcher types can start and stop as many watchers as |
1169 | many watchers as they want, and all of them will be taken into account |
1190 | they want, and all of them will be taken into account (for example, a |
1170 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1191 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1171 | C<ev_run> from blocking). |
1192 | blocking). |
1172 | |
1193 | |
1173 | =item C<EV_EMBED> |
1194 | =item C<EV_EMBED> |
1174 | |
1195 | |
1175 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1196 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1176 | |
1197 | |
… | |
… | |
1299 | |
1320 | |
1300 | =item callback ev_cb (ev_TYPE *watcher) |
1321 | =item callback ev_cb (ev_TYPE *watcher) |
1301 | |
1322 | |
1302 | Returns the callback currently set on the watcher. |
1323 | Returns the callback currently set on the watcher. |
1303 | |
1324 | |
1304 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1325 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1305 | |
1326 | |
1306 | Change the callback. You can change the callback at virtually any time |
1327 | Change the callback. You can change the callback at virtually any time |
1307 | (modulo threads). |
1328 | (modulo threads). |
1308 | |
1329 | |
1309 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1330 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
… | |
… | |
1327 | or might not have been clamped to the valid range. |
1348 | or might not have been clamped to the valid range. |
1328 | |
1349 | |
1329 | The default priority used by watchers when no priority has been set is |
1350 | The default priority used by watchers when no priority has been set is |
1330 | always C<0>, which is supposed to not be too high and not be too low :). |
1351 | always C<0>, which is supposed to not be too high and not be too low :). |
1331 | |
1352 | |
1332 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1353 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1333 | priorities. |
1354 | priorities. |
1334 | |
1355 | |
1335 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1356 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1336 | |
1357 | |
1337 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1358 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1362 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1383 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1363 | functions that do not need a watcher. |
1384 | functions that do not need a watcher. |
1364 | |
1385 | |
1365 | =back |
1386 | =back |
1366 | |
1387 | |
1367 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
1388 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
1368 | OWN COMPOSITE WATCHERS> idioms. |
1389 | OWN COMPOSITE WATCHERS> idioms. |
1369 | |
1390 | |
1370 | =head2 WATCHER STATES |
1391 | =head2 WATCHER STATES |
1371 | |
1392 | |
1372 | There are various watcher states mentioned throughout this manual - |
1393 | There are various watcher states mentioned throughout this manual - |
… | |
… | |
1374 | transition between them will be described in more detail - and while these |
1395 | transition between them will be described in more detail - and while these |
1375 | rules might look complicated, they usually do "the right thing". |
1396 | rules might look complicated, they usually do "the right thing". |
1376 | |
1397 | |
1377 | =over 4 |
1398 | =over 4 |
1378 | |
1399 | |
1379 | =item initialiased |
1400 | =item initialised |
1380 | |
1401 | |
1381 | Before a watcher can be registered with the event looop it has to be |
1402 | Before a watcher can be registered with the event loop it has to be |
1382 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1403 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1383 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1404 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1384 | |
1405 | |
1385 | In this state it is simply some block of memory that is suitable for |
1406 | In this state it is simply some block of memory that is suitable for |
1386 | use in an event loop. It can be moved around, freed, reused etc. at |
1407 | use in an event loop. It can be moved around, freed, reused etc. at |
… | |
… | |
1761 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1782 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1762 | monotonic clock option helps a lot here). |
1783 | monotonic clock option helps a lot here). |
1763 | |
1784 | |
1764 | The callback is guaranteed to be invoked only I<after> its timeout has |
1785 | The callback is guaranteed to be invoked only I<after> its timeout has |
1765 | passed (not I<at>, so on systems with very low-resolution clocks this |
1786 | passed (not I<at>, so on systems with very low-resolution clocks this |
1766 | might introduce a small delay). If multiple timers become ready during the |
1787 | might introduce a small delay, see "the special problem of being too |
|
|
1788 | early", below). If multiple timers become ready during the same loop |
1767 | same loop iteration then the ones with earlier time-out values are invoked |
1789 | iteration then the ones with earlier time-out values are invoked before |
1768 | before ones of the same priority with later time-out values (but this is |
1790 | ones of the same priority with later time-out values (but this is no |
1769 | no longer true when a callback calls C<ev_run> recursively). |
1791 | longer true when a callback calls C<ev_run> recursively). |
1770 | |
1792 | |
1771 | =head3 Be smart about timeouts |
1793 | =head3 Be smart about timeouts |
1772 | |
1794 | |
1773 | Many real-world problems involve some kind of timeout, usually for error |
1795 | Many real-world problems involve some kind of timeout, usually for error |
1774 | recovery. A typical example is an HTTP request - if the other side hangs, |
1796 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1849 | |
1871 | |
1850 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1872 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1851 | but remember the time of last activity, and check for a real timeout only |
1873 | but remember the time of last activity, and check for a real timeout only |
1852 | within the callback: |
1874 | within the callback: |
1853 | |
1875 | |
|
|
1876 | ev_tstamp timeout = 60.; |
1854 | ev_tstamp last_activity; // time of last activity |
1877 | ev_tstamp last_activity; // time of last activity |
|
|
1878 | ev_timer timer; |
1855 | |
1879 | |
1856 | static void |
1880 | static void |
1857 | callback (EV_P_ ev_timer *w, int revents) |
1881 | callback (EV_P_ ev_timer *w, int revents) |
1858 | { |
1882 | { |
1859 | ev_tstamp now = ev_now (EV_A); |
1883 | // calculate when the timeout would happen |
1860 | ev_tstamp timeout = last_activity + 60.; |
1884 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1861 | |
1885 | |
1862 | // if last_activity + 60. is older than now, we did time out |
1886 | // if negative, it means we the timeout already occurred |
1863 | if (timeout < now) |
1887 | if (after < 0.) |
1864 | { |
1888 | { |
1865 | // timeout occurred, take action |
1889 | // timeout occurred, take action |
1866 | } |
1890 | } |
1867 | else |
1891 | else |
1868 | { |
1892 | { |
1869 | // callback was invoked, but there was some activity, re-arm |
1893 | // callback was invoked, but there was some recent |
1870 | // the watcher to fire in last_activity + 60, which is |
1894 | // activity. simply restart the timer to time out |
1871 | // guaranteed to be in the future, so "again" is positive: |
1895 | // after "after" seconds, which is the earliest time |
1872 | w->repeat = timeout - now; |
1896 | // the timeout can occur. |
|
|
1897 | ev_timer_set (w, after, 0.); |
1873 | ev_timer_again (EV_A_ w); |
1898 | ev_timer_start (EV_A_ w); |
1874 | } |
1899 | } |
1875 | } |
1900 | } |
1876 | |
1901 | |
1877 | To summarise the callback: first calculate the real timeout (defined |
1902 | To summarise the callback: first calculate in how many seconds the |
1878 | as "60 seconds after the last activity"), then check if that time has |
1903 | timeout will occur (by calculating the absolute time when it would occur, |
1879 | been reached, which means something I<did>, in fact, time out. Otherwise |
1904 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1880 | the callback was invoked too early (C<timeout> is in the future), so |
1905 | (EV_A)> from that). |
1881 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1882 | a timeout then. |
|
|
1883 | |
1906 | |
1884 | Note how C<ev_timer_again> is used, taking advantage of the |
1907 | If this value is negative, then we are already past the timeout, i.e. we |
1885 | C<ev_timer_again> optimisation when the timer is already running. |
1908 | timed out, and need to do whatever is needed in this case. |
|
|
1909 | |
|
|
1910 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1911 | and simply start the timer with this timeout value. |
|
|
1912 | |
|
|
1913 | In other words, each time the callback is invoked it will check whether |
|
|
1914 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1915 | again at the earliest time it could time out. Rinse. Repeat. |
1886 | |
1916 | |
1887 | This scheme causes more callback invocations (about one every 60 seconds |
1917 | This scheme causes more callback invocations (about one every 60 seconds |
1888 | minus half the average time between activity), but virtually no calls to |
1918 | minus half the average time between activity), but virtually no calls to |
1889 | libev to change the timeout. |
1919 | libev to change the timeout. |
1890 | |
1920 | |
1891 | To start the timer, simply initialise the watcher and set C<last_activity> |
1921 | To start the machinery, simply initialise the watcher and set |
1892 | to the current time (meaning we just have some activity :), then call the |
1922 | C<last_activity> to the current time (meaning there was some activity just |
1893 | callback, which will "do the right thing" and start the timer: |
1923 | now), then call the callback, which will "do the right thing" and start |
|
|
1924 | the timer: |
1894 | |
1925 | |
|
|
1926 | last_activity = ev_now (EV_A); |
1895 | ev_init (timer, callback); |
1927 | ev_init (&timer, callback); |
1896 | last_activity = ev_now (loop); |
1928 | callback (EV_A_ &timer, 0); |
1897 | callback (loop, timer, EV_TIMER); |
|
|
1898 | |
1929 | |
1899 | And when there is some activity, simply store the current time in |
1930 | When there is some activity, simply store the current time in |
1900 | C<last_activity>, no libev calls at all: |
1931 | C<last_activity>, no libev calls at all: |
1901 | |
1932 | |
|
|
1933 | if (activity detected) |
1902 | last_activity = ev_now (loop); |
1934 | last_activity = ev_now (EV_A); |
|
|
1935 | |
|
|
1936 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1937 | providing a new value, stopping the timer and calling the callback, which |
|
|
1938 | will again do the right thing (for example, time out immediately :). |
|
|
1939 | |
|
|
1940 | timeout = new_value; |
|
|
1941 | ev_timer_stop (EV_A_ &timer); |
|
|
1942 | callback (EV_A_ &timer, 0); |
1903 | |
1943 | |
1904 | This technique is slightly more complex, but in most cases where the |
1944 | This technique is slightly more complex, but in most cases where the |
1905 | time-out is unlikely to be triggered, much more efficient. |
1945 | time-out is unlikely to be triggered, much more efficient. |
1906 | |
|
|
1907 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1908 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1909 | fix things for you. |
|
|
1910 | |
1946 | |
1911 | =item 4. Wee, just use a double-linked list for your timeouts. |
1947 | =item 4. Wee, just use a double-linked list for your timeouts. |
1912 | |
1948 | |
1913 | If there is not one request, but many thousands (millions...), all |
1949 | If there is not one request, but many thousands (millions...), all |
1914 | employing some kind of timeout with the same timeout value, then one can |
1950 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1941 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1977 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1942 | rather complicated, but extremely efficient, something that really pays |
1978 | rather complicated, but extremely efficient, something that really pays |
1943 | off after the first million or so of active timers, i.e. it's usually |
1979 | off after the first million or so of active timers, i.e. it's usually |
1944 | overkill :) |
1980 | overkill :) |
1945 | |
1981 | |
|
|
1982 | =head3 The special problem of being too early |
|
|
1983 | |
|
|
1984 | If you ask a timer to call your callback after three seconds, then |
|
|
1985 | you expect it to be invoked after three seconds - but of course, this |
|
|
1986 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1987 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1988 | process with a STOP signal for a few hours for example. |
|
|
1989 | |
|
|
1990 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1991 | delay has occurred, but cannot guarantee this. |
|
|
1992 | |
|
|
1993 | A less obvious failure mode is calling your callback too early: many event |
|
|
1994 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1995 | this can cause your callback to be invoked much earlier than you would |
|
|
1996 | expect. |
|
|
1997 | |
|
|
1998 | To see why, imagine a system with a clock that only offers full second |
|
|
1999 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2000 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2001 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2002 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2003 | |
|
|
2004 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2005 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2006 | one-second delay was requested - this is being "too early", despite best |
|
|
2007 | intentions. |
|
|
2008 | |
|
|
2009 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2010 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2011 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2012 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2013 | |
|
|
2014 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2015 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2016 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2017 | late" side of things. |
|
|
2018 | |
1946 | =head3 The special problem of time updates |
2019 | =head3 The special problem of time updates |
1947 | |
2020 | |
1948 | Establishing the current time is a costly operation (it usually takes at |
2021 | Establishing the current time is a costly operation (it usually takes |
1949 | least two system calls): EV therefore updates its idea of the current |
2022 | at least one system call): EV therefore updates its idea of the current |
1950 | time only before and after C<ev_run> collects new events, which causes a |
2023 | time only before and after C<ev_run> collects new events, which causes a |
1951 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2024 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1952 | lots of events in one iteration. |
2025 | lots of events in one iteration. |
1953 | |
2026 | |
1954 | The relative timeouts are calculated relative to the C<ev_now ()> |
2027 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1960 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2033 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1961 | |
2034 | |
1962 | If the event loop is suspended for a long time, you can also force an |
2035 | If the event loop is suspended for a long time, you can also force an |
1963 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2036 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1964 | ()>. |
2037 | ()>. |
|
|
2038 | |
|
|
2039 | =head3 The special problem of unsynchronised clocks |
|
|
2040 | |
|
|
2041 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2042 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2043 | jumps). |
|
|
2044 | |
|
|
2045 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2046 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2047 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2048 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2049 | than a directly following call to C<time>. |
|
|
2050 | |
|
|
2051 | The moral of this is to only compare libev-related timestamps with |
|
|
2052 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2053 | a second or so. |
|
|
2054 | |
|
|
2055 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2056 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2057 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2058 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2059 | |
|
|
2060 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2061 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2062 | I<measured according to the real time>, not the system clock. |
|
|
2063 | |
|
|
2064 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2065 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2066 | exactly the right behaviour. |
|
|
2067 | |
|
|
2068 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2069 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2070 | time, where your comparisons will always generate correct results. |
1965 | |
2071 | |
1966 | =head3 The special problems of suspended animation |
2072 | =head3 The special problems of suspended animation |
1967 | |
2073 | |
1968 | When you leave the server world it is quite customary to hit machines that |
2074 | When you leave the server world it is quite customary to hit machines that |
1969 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2075 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
2013 | keep up with the timer (because it takes longer than those 10 seconds to |
2119 | keep up with the timer (because it takes longer than those 10 seconds to |
2014 | do stuff) the timer will not fire more than once per event loop iteration. |
2120 | do stuff) the timer will not fire more than once per event loop iteration. |
2015 | |
2121 | |
2016 | =item ev_timer_again (loop, ev_timer *) |
2122 | =item ev_timer_again (loop, ev_timer *) |
2017 | |
2123 | |
2018 | This will act as if the timer timed out and restart it again if it is |
2124 | This will act as if the timer timed out, and restarts it again if it is |
2019 | repeating. The exact semantics are: |
2125 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2126 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
2020 | |
2127 | |
|
|
2128 | The exact semantics are as in the following rules, all of which will be |
|
|
2129 | applied to the watcher: |
|
|
2130 | |
|
|
2131 | =over 4 |
|
|
2132 | |
2021 | If the timer is pending, its pending status is cleared. |
2133 | =item If the timer is pending, the pending status is always cleared. |
2022 | |
2134 | |
2023 | If the timer is started but non-repeating, stop it (as if it timed out). |
2135 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2136 | out, without invoking it). |
2024 | |
2137 | |
2025 | If the timer is repeating, either start it if necessary (with the |
2138 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2026 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2139 | and start the timer, if necessary. |
2027 | |
2140 | |
|
|
2141 | =back |
|
|
2142 | |
2028 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2143 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
2029 | usage example. |
2144 | usage example. |
2030 | |
2145 | |
2031 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2146 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2032 | |
2147 | |
2033 | Returns the remaining time until a timer fires. If the timer is active, |
2148 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2493 | |
2608 | |
2494 | =head2 C<ev_stat> - did the file attributes just change? |
2609 | =head2 C<ev_stat> - did the file attributes just change? |
2495 | |
2610 | |
2496 | This watches a file system path for attribute changes. That is, it calls |
2611 | This watches a file system path for attribute changes. That is, it calls |
2497 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2612 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2498 | and sees if it changed compared to the last time, invoking the callback if |
2613 | and sees if it changed compared to the last time, invoking the callback |
2499 | it did. |
2614 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2615 | happen after the watcher has been started will be reported. |
2500 | |
2616 | |
2501 | The path does not need to exist: changing from "path exists" to "path does |
2617 | The path does not need to exist: changing from "path exists" to "path does |
2502 | not exist" is a status change like any other. The condition "path does not |
2618 | not exist" is a status change like any other. The condition "path does not |
2503 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2619 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2504 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2620 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2734 | Apart from keeping your process non-blocking (which is a useful |
2850 | Apart from keeping your process non-blocking (which is a useful |
2735 | effect on its own sometimes), idle watchers are a good place to do |
2851 | effect on its own sometimes), idle watchers are a good place to do |
2736 | "pseudo-background processing", or delay processing stuff to after the |
2852 | "pseudo-background processing", or delay processing stuff to after the |
2737 | event loop has handled all outstanding events. |
2853 | event loop has handled all outstanding events. |
2738 | |
2854 | |
|
|
2855 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2856 | |
|
|
2857 | As long as there is at least one active idle watcher, libev will never |
|
|
2858 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2859 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2860 | lowest priority will do. |
|
|
2861 | |
|
|
2862 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2863 | to do something on each event loop iteration - for example to balance load |
|
|
2864 | between different connections. |
|
|
2865 | |
|
|
2866 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2867 | example. |
|
|
2868 | |
2739 | =head3 Watcher-Specific Functions and Data Members |
2869 | =head3 Watcher-Specific Functions and Data Members |
2740 | |
2870 | |
2741 | =over 4 |
2871 | =over 4 |
2742 | |
2872 | |
2743 | =item ev_idle_init (ev_idle *, callback) |
2873 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2754 | callback, free it. Also, use no error checking, as usual. |
2884 | callback, free it. Also, use no error checking, as usual. |
2755 | |
2885 | |
2756 | static void |
2886 | static void |
2757 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2887 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2758 | { |
2888 | { |
|
|
2889 | // stop the watcher |
|
|
2890 | ev_idle_stop (loop, w); |
|
|
2891 | |
|
|
2892 | // now we can free it |
2759 | free (w); |
2893 | free (w); |
|
|
2894 | |
2760 | // now do something you wanted to do when the program has |
2895 | // now do something you wanted to do when the program has |
2761 | // no longer anything immediate to do. |
2896 | // no longer anything immediate to do. |
2762 | } |
2897 | } |
2763 | |
2898 | |
2764 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2899 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2766 | ev_idle_start (loop, idle_watcher); |
2901 | ev_idle_start (loop, idle_watcher); |
2767 | |
2902 | |
2768 | |
2903 | |
2769 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2904 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2770 | |
2905 | |
2771 | Prepare and check watchers are usually (but not always) used in pairs: |
2906 | Prepare and check watchers are often (but not always) used in pairs: |
2772 | prepare watchers get invoked before the process blocks and check watchers |
2907 | prepare watchers get invoked before the process blocks and check watchers |
2773 | afterwards. |
2908 | afterwards. |
2774 | |
2909 | |
2775 | You I<must not> call C<ev_run> or similar functions that enter |
2910 | You I<must not> call C<ev_run> or similar functions that enter |
2776 | the current event loop from either C<ev_prepare> or C<ev_check> |
2911 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
2804 | with priority higher than or equal to the event loop and one coroutine |
2939 | with priority higher than or equal to the event loop and one coroutine |
2805 | of lower priority, but only once, using idle watchers to keep the event |
2940 | of lower priority, but only once, using idle watchers to keep the event |
2806 | loop from blocking if lower-priority coroutines are active, thus mapping |
2941 | loop from blocking if lower-priority coroutines are active, thus mapping |
2807 | low-priority coroutines to idle/background tasks). |
2942 | low-priority coroutines to idle/background tasks). |
2808 | |
2943 | |
2809 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2944 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2810 | priority, to ensure that they are being run before any other watchers |
2945 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2811 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
2946 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
2947 | watchers). |
2812 | |
2948 | |
2813 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2949 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2814 | activate ("feed") events into libev. While libev fully supports this, they |
2950 | activate ("feed") events into libev. While libev fully supports this, they |
2815 | might get executed before other C<ev_check> watchers did their job. As |
2951 | might get executed before other C<ev_check> watchers did their job. As |
2816 | C<ev_check> watchers are often used to embed other (non-libev) event |
2952 | C<ev_check> watchers are often used to embed other (non-libev) event |
2817 | loops those other event loops might be in an unusable state until their |
2953 | loops those other event loops might be in an unusable state until their |
2818 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2954 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2819 | others). |
2955 | others). |
|
|
2956 | |
|
|
2957 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
2958 | |
|
|
2959 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
2960 | useful because they are called once per event loop iteration. For |
|
|
2961 | example, if you want to handle a large number of connections fairly, you |
|
|
2962 | normally only do a bit of work for each active connection, and if there |
|
|
2963 | is more work to do, you wait for the next event loop iteration, so other |
|
|
2964 | connections have a chance of making progress. |
|
|
2965 | |
|
|
2966 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
2967 | next event loop iteration. However, that isn't as soon as possible - |
|
|
2968 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
2969 | |
|
|
2970 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2971 | single global idle watcher that is active as long as you have one active |
|
|
2972 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
2973 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
2974 | invoked. Neither watcher alone can do that. |
2820 | |
2975 | |
2821 | =head3 Watcher-Specific Functions and Data Members |
2976 | =head3 Watcher-Specific Functions and Data Members |
2822 | |
2977 | |
2823 | =over 4 |
2978 | =over 4 |
2824 | |
2979 | |
… | |
… | |
3025 | |
3180 | |
3026 | =over 4 |
3181 | =over 4 |
3027 | |
3182 | |
3028 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3183 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3029 | |
3184 | |
3030 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3185 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
3031 | |
3186 | |
3032 | Configures the watcher to embed the given loop, which must be |
3187 | Configures the watcher to embed the given loop, which must be |
3033 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3188 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3034 | invoked automatically, otherwise it is the responsibility of the callback |
3189 | invoked automatically, otherwise it is the responsibility of the callback |
3035 | to invoke it (it will continue to be called until the sweep has been done, |
3190 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3098 | |
3253 | |
3099 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3254 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3100 | |
3255 | |
3101 | Fork watchers are called when a C<fork ()> was detected (usually because |
3256 | Fork watchers are called when a C<fork ()> was detected (usually because |
3102 | whoever is a good citizen cared to tell libev about it by calling |
3257 | whoever is a good citizen cared to tell libev about it by calling |
3103 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3258 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3104 | event loop blocks next and before C<ev_check> watchers are being called, |
3259 | and before C<ev_check> watchers are being called, and only in the child |
3105 | and only in the child after the fork. If whoever good citizen calling |
3260 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3106 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3261 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3107 | handlers will be invoked, too, of course. |
3262 | of course. |
3108 | |
3263 | |
3109 | =head3 The special problem of life after fork - how is it possible? |
3264 | =head3 The special problem of life after fork - how is it possible? |
3110 | |
3265 | |
3111 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3266 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3112 | up/change the process environment, followed by a call to C<exec()>. This |
3267 | up/change the process environment, followed by a call to C<exec()>. This |
… | |
… | |
3205 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3360 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3206 | |
3361 | |
3207 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3362 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3208 | too, are asynchronous in nature, and signals, too, will be compressed |
3363 | too, are asynchronous in nature, and signals, too, will be compressed |
3209 | (i.e. the number of callback invocations may be less than the number of |
3364 | (i.e. the number of callback invocations may be less than the number of |
3210 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3365 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3211 | of "global async watchers" by using a watcher on an otherwise unused |
3366 | of "global async watchers" by using a watcher on an otherwise unused |
3212 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3367 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3213 | even without knowing which loop owns the signal. |
3368 | even without knowing which loop owns the signal. |
3214 | |
|
|
3215 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
3216 | just the default loop. |
|
|
3217 | |
3369 | |
3218 | =head3 Queueing |
3370 | =head3 Queueing |
3219 | |
3371 | |
3220 | C<ev_async> does not support queueing of data in any way. The reason |
3372 | C<ev_async> does not support queueing of data in any way. The reason |
3221 | is that the author does not know of a simple (or any) algorithm for a |
3373 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3321 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3473 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3322 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3474 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3323 | embedding section below on what exactly this means). |
3475 | embedding section below on what exactly this means). |
3324 | |
3476 | |
3325 | Note that, as with other watchers in libev, multiple events might get |
3477 | Note that, as with other watchers in libev, multiple events might get |
3326 | compressed into a single callback invocation (another way to look at this |
3478 | compressed into a single callback invocation (another way to look at |
3327 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3479 | this is that C<ev_async> watchers are level-triggered: they are set on |
3328 | reset when the event loop detects that). |
3480 | C<ev_async_send>, reset when the event loop detects that). |
3329 | |
3481 | |
3330 | This call incurs the overhead of a system call only once per event loop |
3482 | This call incurs the overhead of at most one extra system call per event |
3331 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3483 | loop iteration, if the event loop is blocked, and no syscall at all if |
3332 | repeated calls to C<ev_async_send> for the same event loop. |
3484 | the event loop (or your program) is processing events. That means that |
|
|
3485 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3486 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3487 | zero) under load. |
3333 | |
3488 | |
3334 | =item bool = ev_async_pending (ev_async *) |
3489 | =item bool = ev_async_pending (ev_async *) |
3335 | |
3490 | |
3336 | Returns a non-zero value when C<ev_async_send> has been called on the |
3491 | Returns a non-zero value when C<ev_async_send> has been called on the |
3337 | watcher but the event has not yet been processed (or even noted) by the |
3492 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3392 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3547 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3393 | |
3548 | |
3394 | =item ev_feed_fd_event (loop, int fd, int revents) |
3549 | =item ev_feed_fd_event (loop, int fd, int revents) |
3395 | |
3550 | |
3396 | Feed an event on the given fd, as if a file descriptor backend detected |
3551 | Feed an event on the given fd, as if a file descriptor backend detected |
3397 | the given events it. |
3552 | the given events. |
3398 | |
3553 | |
3399 | =item ev_feed_signal_event (loop, int signum) |
3554 | =item ev_feed_signal_event (loop, int signum) |
3400 | |
3555 | |
3401 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3556 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3402 | which is async-safe. |
3557 | which is async-safe. |
… | |
… | |
3476 | { |
3631 | { |
3477 | struct my_biggy big = (struct my_biggy *) |
3632 | struct my_biggy big = (struct my_biggy *) |
3478 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3633 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3479 | } |
3634 | } |
3480 | |
3635 | |
|
|
3636 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3637 | |
|
|
3638 | Often you have structures like this in event-based programs: |
|
|
3639 | |
|
|
3640 | callback () |
|
|
3641 | { |
|
|
3642 | free (request); |
|
|
3643 | } |
|
|
3644 | |
|
|
3645 | request = start_new_request (..., callback); |
|
|
3646 | |
|
|
3647 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3648 | used to cancel the operation, or do other things with it. |
|
|
3649 | |
|
|
3650 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3651 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3652 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3653 | operation and simply invoke the callback with the result. |
|
|
3654 | |
|
|
3655 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3656 | has returned, so C<request> is not set. |
|
|
3657 | |
|
|
3658 | Even if you pass the request by some safer means to the callback, you |
|
|
3659 | might want to do something to the request after starting it, such as |
|
|
3660 | canceling it, which probably isn't working so well when the callback has |
|
|
3661 | already been invoked. |
|
|
3662 | |
|
|
3663 | A common way around all these issues is to make sure that |
|
|
3664 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3665 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3666 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3667 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3668 | pushing it into the pending queue: |
|
|
3669 | |
|
|
3670 | ev_set_cb (watcher, callback); |
|
|
3671 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3672 | |
|
|
3673 | This way, C<start_new_request> can safely return before the callback is |
|
|
3674 | invoked, while not delaying callback invocation too much. |
|
|
3675 | |
3481 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3676 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3482 | |
3677 | |
3483 | Often (especially in GUI toolkits) there are places where you have |
3678 | Often (especially in GUI toolkits) there are places where you have |
3484 | I<modal> interaction, which is most easily implemented by recursively |
3679 | I<modal> interaction, which is most easily implemented by recursively |
3485 | invoking C<ev_run>. |
3680 | invoking C<ev_run>. |
3486 | |
3681 | |
3487 | This brings the problem of exiting - a callback might want to finish the |
3682 | This brings the problem of exiting - a callback might want to finish the |
3488 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3683 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3489 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3684 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3490 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3685 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3491 | other combination: In these cases, C<ev_break> will not work alone. |
3686 | other combination: In these cases, a simple C<ev_break> will not work. |
3492 | |
3687 | |
3493 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3688 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3494 | invocation, and use a loop around C<ev_run> until the condition is |
3689 | invocation, and use a loop around C<ev_run> until the condition is |
3495 | triggered, using C<EVRUN_ONCE>: |
3690 | triggered, using C<EVRUN_ONCE>: |
3496 | |
3691 | |
… | |
… | |
3498 | int exit_main_loop = 0; |
3693 | int exit_main_loop = 0; |
3499 | |
3694 | |
3500 | while (!exit_main_loop) |
3695 | while (!exit_main_loop) |
3501 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3696 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3502 | |
3697 | |
3503 | // in a model watcher |
3698 | // in a modal watcher |
3504 | int exit_nested_loop = 0; |
3699 | int exit_nested_loop = 0; |
3505 | |
3700 | |
3506 | while (!exit_nested_loop) |
3701 | while (!exit_nested_loop) |
3507 | ev_run (EV_A_ EVRUN_ONCE); |
3702 | ev_run (EV_A_ EVRUN_ONCE); |
3508 | |
3703 | |
… | |
… | |
3682 | called): |
3877 | called): |
3683 | |
3878 | |
3684 | void |
3879 | void |
3685 | wait_for_event (ev_watcher *w) |
3880 | wait_for_event (ev_watcher *w) |
3686 | { |
3881 | { |
3687 | ev_cb_set (w) = current_coro; |
3882 | ev_set_cb (w, current_coro); |
3688 | switch_to (libev_coro); |
3883 | switch_to (libev_coro); |
3689 | } |
3884 | } |
3690 | |
3885 | |
3691 | That basically suspends the coroutine inside C<wait_for_event> and |
3886 | That basically suspends the coroutine inside C<wait_for_event> and |
3692 | continues the libev coroutine, which, when appropriate, switches back to |
3887 | continues the libev coroutine, which, when appropriate, switches back to |
3693 | this or any other coroutine. I am sure if you sue this your own :) |
3888 | this or any other coroutine. |
3694 | |
3889 | |
3695 | You can do similar tricks if you have, say, threads with an event queue - |
3890 | You can do similar tricks if you have, say, threads with an event queue - |
3696 | instead of storing a coroutine, you store the queue object and instead of |
3891 | instead of storing a coroutine, you store the queue object and instead of |
3697 | switching to a coroutine, you push the watcher onto the queue and notify |
3892 | switching to a coroutine, you push the watcher onto the queue and notify |
3698 | any waiters. |
3893 | any waiters. |
3699 | |
3894 | |
3700 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
3895 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3701 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3896 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3702 | |
3897 | |
3703 | // my_ev.h |
3898 | // my_ev.h |
3704 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3899 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3705 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
3900 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
… | |
… | |
3748 | to use the libev header file and library. |
3943 | to use the libev header file and library. |
3749 | |
3944 | |
3750 | =back |
3945 | =back |
3751 | |
3946 | |
3752 | =head1 C++ SUPPORT |
3947 | =head1 C++ SUPPORT |
|
|
3948 | |
|
|
3949 | =head2 C API |
|
|
3950 | |
|
|
3951 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3952 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3953 | will work fine. |
|
|
3954 | |
|
|
3955 | Proper exception specifications might have to be added to callbacks passed |
|
|
3956 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3957 | other callbacks (allocator, syserr, loop acquire/release and periodic |
|
|
3958 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3959 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3960 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3961 | |
|
|
3962 | static void |
|
|
3963 | fatal_error (const char *msg) EV_THROW |
|
|
3964 | { |
|
|
3965 | perror (msg); |
|
|
3966 | abort (); |
|
|
3967 | } |
|
|
3968 | |
|
|
3969 | ... |
|
|
3970 | ev_set_syserr_cb (fatal_error); |
|
|
3971 | |
|
|
3972 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3973 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
3974 | because it runs cleanup watchers). |
|
|
3975 | |
|
|
3976 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3977 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3978 | throwing exceptions through C libraries (most do). |
|
|
3979 | |
|
|
3980 | =head2 C++ API |
3753 | |
3981 | |
3754 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3982 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3755 | you to use some convenience methods to start/stop watchers and also change |
3983 | you to use some convenience methods to start/stop watchers and also change |
3756 | the callback model to a model using method callbacks on objects. |
3984 | the callback model to a model using method callbacks on objects. |
3757 | |
3985 | |
… | |
… | |
3773 | with C<operator ()> can be used as callbacks. Other types should be easy |
4001 | with C<operator ()> can be used as callbacks. Other types should be easy |
3774 | to add as long as they only need one additional pointer for context. If |
4002 | to add as long as they only need one additional pointer for context. If |
3775 | you need support for other types of functors please contact the author |
4003 | you need support for other types of functors please contact the author |
3776 | (preferably after implementing it). |
4004 | (preferably after implementing it). |
3777 | |
4005 | |
|
|
4006 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4007 | conventions as your C compiler (for static member functions), or you have |
|
|
4008 | to embed libev and compile libev itself as C++. |
|
|
4009 | |
3778 | Here is a list of things available in the C<ev> namespace: |
4010 | Here is a list of things available in the C<ev> namespace: |
3779 | |
4011 | |
3780 | =over 4 |
4012 | =over 4 |
3781 | |
4013 | |
3782 | =item C<ev::READ>, C<ev::WRITE> etc. |
4014 | =item C<ev::READ>, C<ev::WRITE> etc. |
… | |
… | |
3791 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4023 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3792 | |
4024 | |
3793 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4025 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3794 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4026 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3795 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4027 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3796 | defines by many implementations. |
4028 | defined by many implementations. |
3797 | |
4029 | |
3798 | All of those classes have these methods: |
4030 | All of those classes have these methods: |
3799 | |
4031 | |
3800 | =over 4 |
4032 | =over 4 |
3801 | |
4033 | |
… | |
… | |
3891 | Associates a different C<struct ev_loop> with this watcher. You can only |
4123 | Associates a different C<struct ev_loop> with this watcher. You can only |
3892 | do this when the watcher is inactive (and not pending either). |
4124 | do this when the watcher is inactive (and not pending either). |
3893 | |
4125 | |
3894 | =item w->set ([arguments]) |
4126 | =item w->set ([arguments]) |
3895 | |
4127 | |
3896 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4128 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
3897 | method or a suitable start method must be called at least once. Unlike the |
4129 | with the same arguments. Either this method or a suitable start method |
3898 | C counterpart, an active watcher gets automatically stopped and restarted |
4130 | must be called at least once. Unlike the C counterpart, an active watcher |
3899 | when reconfiguring it with this method. |
4131 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4132 | method. |
|
|
4133 | |
|
|
4134 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4135 | clashing with the C<set (loop)> method. |
3900 | |
4136 | |
3901 | =item w->start () |
4137 | =item w->start () |
3902 | |
4138 | |
3903 | Starts the watcher. Note that there is no C<loop> argument, as the |
4139 | Starts the watcher. Note that there is no C<loop> argument, as the |
3904 | constructor already stores the event loop. |
4140 | constructor already stores the event loop. |
… | |
… | |
3934 | watchers in the constructor. |
4170 | watchers in the constructor. |
3935 | |
4171 | |
3936 | class myclass |
4172 | class myclass |
3937 | { |
4173 | { |
3938 | ev::io io ; void io_cb (ev::io &w, int revents); |
4174 | ev::io io ; void io_cb (ev::io &w, int revents); |
3939 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4175 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3940 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4176 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3941 | |
4177 | |
3942 | myclass (int fd) |
4178 | myclass (int fd) |
3943 | { |
4179 | { |
3944 | io .set <myclass, &myclass::io_cb > (this); |
4180 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3995 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4231 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3996 | |
4232 | |
3997 | =item D |
4233 | =item D |
3998 | |
4234 | |
3999 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4235 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4000 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4236 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
4001 | |
4237 | |
4002 | =item Ocaml |
4238 | =item Ocaml |
4003 | |
4239 | |
4004 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4240 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4005 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4241 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
4008 | |
4244 | |
4009 | Brian Maher has written a partial interface to libev for lua (at the |
4245 | Brian Maher has written a partial interface to libev for lua (at the |
4010 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4246 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4011 | L<http://github.com/brimworks/lua-ev>. |
4247 | L<http://github.com/brimworks/lua-ev>. |
4012 | |
4248 | |
|
|
4249 | =item Javascript |
|
|
4250 | |
|
|
4251 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4252 | |
|
|
4253 | =item Others |
|
|
4254 | |
|
|
4255 | There are others, and I stopped counting. |
|
|
4256 | |
4013 | =back |
4257 | =back |
4014 | |
4258 | |
4015 | |
4259 | |
4016 | =head1 MACRO MAGIC |
4260 | =head1 MACRO MAGIC |
4017 | |
4261 | |
… | |
… | |
4053 | suitable for use with C<EV_A>. |
4297 | suitable for use with C<EV_A>. |
4054 | |
4298 | |
4055 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4299 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4056 | |
4300 | |
4057 | Similar to the other two macros, this gives you the value of the default |
4301 | Similar to the other two macros, this gives you the value of the default |
4058 | loop, if multiple loops are supported ("ev loop default"). |
4302 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4303 | will be initialised if it isn't already initialised. |
|
|
4304 | |
|
|
4305 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4306 | to initialise the loop somewhere. |
4059 | |
4307 | |
4060 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4308 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4061 | |
4309 | |
4062 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4310 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4063 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4311 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
4311 | |
4559 | |
4312 | If programs implement their own fd to handle mapping on win32, then this |
4560 | If programs implement their own fd to handle mapping on win32, then this |
4313 | macro can be used to override the C<close> function, useful to unregister |
4561 | macro can be used to override the C<close> function, useful to unregister |
4314 | file descriptors again. Note that the replacement function has to close |
4562 | file descriptors again. Note that the replacement function has to close |
4315 | the underlying OS handle. |
4563 | the underlying OS handle. |
|
|
4564 | |
|
|
4565 | =item EV_USE_WSASOCKET |
|
|
4566 | |
|
|
4567 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4568 | communication socket, which works better in some environments. Otherwise, |
|
|
4569 | the normal C<socket> function will be used, which works better in other |
|
|
4570 | environments. |
4316 | |
4571 | |
4317 | =item EV_USE_POLL |
4572 | =item EV_USE_POLL |
4318 | |
4573 | |
4319 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4574 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4320 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4575 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
4356 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4611 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4357 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4612 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4358 | be detected at runtime. If undefined, it will be enabled if the headers |
4613 | be detected at runtime. If undefined, it will be enabled if the headers |
4359 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4614 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4360 | |
4615 | |
|
|
4616 | =item EV_NO_SMP |
|
|
4617 | |
|
|
4618 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4619 | between threads, that is, threads can be used, but threads never run on |
|
|
4620 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4621 | and makes libev faster. |
|
|
4622 | |
|
|
4623 | =item EV_NO_THREADS |
|
|
4624 | |
|
|
4625 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4626 | different threads (that includes signal handlers), which is a stronger |
|
|
4627 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4628 | libev faster. |
|
|
4629 | |
4361 | =item EV_ATOMIC_T |
4630 | =item EV_ATOMIC_T |
4362 | |
4631 | |
4363 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4632 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4364 | access is atomic with respect to other threads or signal contexts. No such |
4633 | access is atomic with respect to other threads or signal contexts. No |
4365 | type is easily found in the C language, so you can provide your own type |
4634 | such type is easily found in the C language, so you can provide your own |
4366 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4635 | type that you know is safe for your purposes. It is used both for signal |
4367 | as well as for signal and thread safety in C<ev_async> watchers. |
4636 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4637 | watchers. |
4368 | |
4638 | |
4369 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4639 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4370 | (from F<signal.h>), which is usually good enough on most platforms. |
4640 | (from F<signal.h>), which is usually good enough on most platforms. |
4371 | |
4641 | |
4372 | =item EV_H (h) |
4642 | =item EV_H (h) |
… | |
… | |
4399 | will have the C<struct ev_loop *> as first argument, and you can create |
4669 | will have the C<struct ev_loop *> as first argument, and you can create |
4400 | additional independent event loops. Otherwise there will be no support |
4670 | additional independent event loops. Otherwise there will be no support |
4401 | for multiple event loops and there is no first event loop pointer |
4671 | for multiple event loops and there is no first event loop pointer |
4402 | argument. Instead, all functions act on the single default loop. |
4672 | argument. Instead, all functions act on the single default loop. |
4403 | |
4673 | |
|
|
4674 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4675 | default loop when multiplicity is switched off - you always have to |
|
|
4676 | initialise the loop manually in this case. |
|
|
4677 | |
4404 | =item EV_MINPRI |
4678 | =item EV_MINPRI |
4405 | |
4679 | |
4406 | =item EV_MAXPRI |
4680 | =item EV_MAXPRI |
4407 | |
4681 | |
4408 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4682 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4444 | #define EV_USE_POLL 1 |
4718 | #define EV_USE_POLL 1 |
4445 | #define EV_CHILD_ENABLE 1 |
4719 | #define EV_CHILD_ENABLE 1 |
4446 | #define EV_ASYNC_ENABLE 1 |
4720 | #define EV_ASYNC_ENABLE 1 |
4447 | |
4721 | |
4448 | The actual value is a bitset, it can be a combination of the following |
4722 | The actual value is a bitset, it can be a combination of the following |
4449 | values: |
4723 | values (by default, all of these are enabled): |
4450 | |
4724 | |
4451 | =over 4 |
4725 | =over 4 |
4452 | |
4726 | |
4453 | =item C<1> - faster/larger code |
4727 | =item C<1> - faster/larger code |
4454 | |
4728 | |
… | |
… | |
4458 | code size by roughly 30% on amd64). |
4732 | code size by roughly 30% on amd64). |
4459 | |
4733 | |
4460 | When optimising for size, use of compiler flags such as C<-Os> with |
4734 | When optimising for size, use of compiler flags such as C<-Os> with |
4461 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4735 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4462 | assertions. |
4736 | assertions. |
|
|
4737 | |
|
|
4738 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4739 | (e.g. gcc with C<-Os>). |
4463 | |
4740 | |
4464 | =item C<2> - faster/larger data structures |
4741 | =item C<2> - faster/larger data structures |
4465 | |
4742 | |
4466 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4743 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4467 | hash table sizes and so on. This will usually further increase code size |
4744 | hash table sizes and so on. This will usually further increase code size |
4468 | and can additionally have an effect on the size of data structures at |
4745 | and can additionally have an effect on the size of data structures at |
4469 | runtime. |
4746 | runtime. |
4470 | |
4747 | |
|
|
4748 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4749 | (e.g. gcc with C<-Os>). |
|
|
4750 | |
4471 | =item C<4> - full API configuration |
4751 | =item C<4> - full API configuration |
4472 | |
4752 | |
4473 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4753 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4474 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4754 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4475 | |
4755 | |
… | |
… | |
4505 | |
4785 | |
4506 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4786 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4507 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4787 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4508 | your program might be left out as well - a binary starting a timer and an |
4788 | your program might be left out as well - a binary starting a timer and an |
4509 | I/O watcher then might come out at only 5Kb. |
4789 | I/O watcher then might come out at only 5Kb. |
|
|
4790 | |
|
|
4791 | =item EV_API_STATIC |
|
|
4792 | |
|
|
4793 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4794 | will have static linkage. This means that libev will not export any |
|
|
4795 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4796 | when you embed libev, only want to use libev functions in a single file, |
|
|
4797 | and do not want its identifiers to be visible. |
|
|
4798 | |
|
|
4799 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4800 | wants to use libev. |
|
|
4801 | |
|
|
4802 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4803 | doesn't support the required declaration syntax. |
4510 | |
4804 | |
4511 | =item EV_AVOID_STDIO |
4805 | =item EV_AVOID_STDIO |
4512 | |
4806 | |
4513 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4807 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4514 | functions (printf, scanf, perror etc.). This will increase the code size |
4808 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4719 | default loop and triggering an C<ev_async> watcher from the default loop |
5013 | default loop and triggering an C<ev_async> watcher from the default loop |
4720 | watcher callback into the event loop interested in the signal. |
5014 | watcher callback into the event loop interested in the signal. |
4721 | |
5015 | |
4722 | =back |
5016 | =back |
4723 | |
5017 | |
4724 | See also L<THREAD LOCKING EXAMPLE>. |
5018 | See also L</THREAD LOCKING EXAMPLE>. |
4725 | |
5019 | |
4726 | =head3 COROUTINES |
5020 | =head3 COROUTINES |
4727 | |
5021 | |
4728 | Libev is very accommodating to coroutines ("cooperative threads"): |
5022 | Libev is very accommodating to coroutines ("cooperative threads"): |
4729 | libev fully supports nesting calls to its functions from different |
5023 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4894 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5188 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4895 | model. Libev still offers limited functionality on this platform in |
5189 | model. Libev still offers limited functionality on this platform in |
4896 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5190 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4897 | descriptors. This only applies when using Win32 natively, not when using |
5191 | descriptors. This only applies when using Win32 natively, not when using |
4898 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5192 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4899 | as every compielr comes with a slightly differently broken/incompatible |
5193 | as every compiler comes with a slightly differently broken/incompatible |
4900 | environment. |
5194 | environment. |
4901 | |
5195 | |
4902 | Lifting these limitations would basically require the full |
5196 | Lifting these limitations would basically require the full |
4903 | re-implementation of the I/O system. If you are into this kind of thing, |
5197 | re-implementation of the I/O system. If you are into this kind of thing, |
4904 | then note that glib does exactly that for you in a very portable way (note |
5198 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
5020 | thread" or will block signals process-wide, both behaviours would |
5314 | thread" or will block signals process-wide, both behaviours would |
5021 | be compatible with libev. Interaction between C<sigprocmask> and |
5315 | be compatible with libev. Interaction between C<sigprocmask> and |
5022 | C<pthread_sigmask> could complicate things, however. |
5316 | C<pthread_sigmask> could complicate things, however. |
5023 | |
5317 | |
5024 | The most portable way to handle signals is to block signals in all threads |
5318 | The most portable way to handle signals is to block signals in all threads |
5025 | except the initial one, and run the default loop in the initial thread as |
5319 | except the initial one, and run the signal handling loop in the initial |
5026 | well. |
5320 | thread as well. |
5027 | |
5321 | |
5028 | =item C<long> must be large enough for common memory allocation sizes |
5322 | =item C<long> must be large enough for common memory allocation sizes |
5029 | |
5323 | |
5030 | To improve portability and simplify its API, libev uses C<long> internally |
5324 | To improve portability and simplify its API, libev uses C<long> internally |
5031 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5325 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
5037 | |
5331 | |
5038 | The type C<double> is used to represent timestamps. It is required to |
5332 | The type C<double> is used to represent timestamps. It is required to |
5039 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5333 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5040 | good enough for at least into the year 4000 with millisecond accuracy |
5334 | good enough for at least into the year 4000 with millisecond accuracy |
5041 | (the design goal for libev). This requirement is overfulfilled by |
5335 | (the design goal for libev). This requirement is overfulfilled by |
5042 | implementations using IEEE 754, which is basically all existing ones. With |
5336 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5337 | |
5043 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5338 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5339 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5340 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5341 | something like that, just kidding). |
5044 | |
5342 | |
5045 | =back |
5343 | =back |
5046 | |
5344 | |
5047 | If you know of other additional requirements drop me a note. |
5345 | If you know of other additional requirements drop me a note. |
5048 | |
5346 | |
… | |
… | |
5110 | =item Processing ev_async_send: O(number_of_async_watchers) |
5408 | =item Processing ev_async_send: O(number_of_async_watchers) |
5111 | |
5409 | |
5112 | =item Processing signals: O(max_signal_number) |
5410 | =item Processing signals: O(max_signal_number) |
5113 | |
5411 | |
5114 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5412 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5115 | calls in the current loop iteration. Checking for async and signal events |
5413 | calls in the current loop iteration and the loop is currently |
|
|
5414 | blocked. Checking for async and signal events involves iterating over all |
5116 | involves iterating over all running async watchers or all signal numbers. |
5415 | running async watchers or all signal numbers. |
5117 | |
5416 | |
5118 | =back |
5417 | =back |
5119 | |
5418 | |
5120 | |
5419 | |
5121 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5420 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
5130 | =over 4 |
5429 | =over 4 |
5131 | |
5430 | |
5132 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5431 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5133 | |
5432 | |
5134 | The backward compatibility mechanism can be controlled by |
5433 | The backward compatibility mechanism can be controlled by |
5135 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
5434 | C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING> |
5136 | section. |
5435 | section. |
5137 | |
5436 | |
5138 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5437 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5139 | |
5438 | |
5140 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5439 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
… | |
… | |
5183 | =over 4 |
5482 | =over 4 |
5184 | |
5483 | |
5185 | =item active |
5484 | =item active |
5186 | |
5485 | |
5187 | A watcher is active as long as it has been started and not yet stopped. |
5486 | A watcher is active as long as it has been started and not yet stopped. |
5188 | See L<WATCHER STATES> for details. |
5487 | See L</WATCHER STATES> for details. |
5189 | |
5488 | |
5190 | =item application |
5489 | =item application |
5191 | |
5490 | |
5192 | In this document, an application is whatever is using libev. |
5491 | In this document, an application is whatever is using libev. |
5193 | |
5492 | |
… | |
… | |
5229 | watchers and events. |
5528 | watchers and events. |
5230 | |
5529 | |
5231 | =item pending |
5530 | =item pending |
5232 | |
5531 | |
5233 | A watcher is pending as soon as the corresponding event has been |
5532 | A watcher is pending as soon as the corresponding event has been |
5234 | detected. See L<WATCHER STATES> for details. |
5533 | detected. See L</WATCHER STATES> for details. |
5235 | |
5534 | |
5236 | =item real time |
5535 | =item real time |
5237 | |
5536 | |
5238 | The physical time that is observed. It is apparently strictly monotonic :) |
5537 | The physical time that is observed. It is apparently strictly monotonic :) |
5239 | |
5538 | |