… | |
… | |
58 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
59 | |
59 | |
60 | // now wait for events to arrive |
60 | // now wait for events to arrive |
61 | ev_run (loop, 0); |
61 | ev_run (loop, 0); |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // break was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 ABOUT THIS DOCUMENT |
67 | =head1 ABOUT THIS DOCUMENT |
68 | |
68 | |
… | |
… | |
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 |
… | |
… | |
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 |
|
|
185 | passed (approximately - it might return a bit earlier even if not |
|
|
186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
|
|
187 | |
185 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
|
|
189 | |
|
|
190 | The range of the C<interval> is limited - libev only guarantees to work |
|
|
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 | |
… | |
… | |
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 |
… | |
… | |
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 |
… | |
… | |
435 | example) that can't properly initialise their signal masks. |
441 | example) that can't properly initialise their signal masks. |
436 | |
442 | |
437 | =item C<EVFLAG_NOSIGMASK> |
443 | =item C<EVFLAG_NOSIGMASK> |
438 | |
444 | |
439 | When this flag is specified, then libev will avoid to modify the signal |
445 | 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 |
446 | mask. Specifically, this means you have to make sure signals are unblocked |
441 | when you want to receive them. |
447 | when you want to receive them. |
442 | |
448 | |
443 | This behaviour is useful when you want to do your own signal handling, or |
449 | 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 |
450 | want to handle signals only in specific threads and want to avoid libev |
445 | unblocking the signals. |
451 | unblocking the signals. |
|
|
452 | |
|
|
453 | It's also required by POSIX in a threaded program, as libev calls |
|
|
454 | C<sigprocmask>, whose behaviour is officially unspecified. |
446 | |
455 | |
447 | This flag's behaviour will become the default in future versions of libev. |
456 | This flag's behaviour will become the default in future versions of libev. |
448 | |
457 | |
449 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
450 | |
459 | |
… | |
… | |
480 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
481 | |
490 | |
482 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
483 | kernels). |
492 | kernels). |
484 | |
493 | |
485 | For few fds, this backend is a bit little slower than poll and select, |
494 | For few fds, this backend is a bit little slower than poll and select, but |
486 | but it scales phenomenally better. While poll and select usually scale |
495 | it scales phenomenally better. While poll and select usually scale like |
487 | like O(total_fds) where n is the total number of fds (or the highest fd), |
496 | O(total_fds) where total_fds is the total number of fds (or the highest |
488 | epoll scales either O(1) or O(active_fds). |
497 | fd), epoll scales either O(1) or O(active_fds). |
489 | |
498 | |
490 | The epoll mechanism deserves honorable mention as the most misdesigned |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
491 | of the more advanced event mechanisms: mere annoyances include silently |
500 | of the more advanced event mechanisms: mere annoyances include silently |
492 | dropping file descriptors, requiring a system call per change per file |
501 | dropping file descriptors, requiring a system call per change per file |
493 | descriptor (and unnecessary guessing of parameters), problems with dup, |
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
… | |
… | |
496 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
505 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
497 | forks then I<both> parent and child process have to recreate the epoll |
506 | forks then I<both> parent and child process have to recreate the epoll |
498 | set, which can take considerable time (one syscall per file descriptor) |
507 | set, which can take considerable time (one syscall per file descriptor) |
499 | and is of course hard to detect. |
508 | and is of course hard to detect. |
500 | |
509 | |
501 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
502 | of course I<doesn't>, and epoll just loves to report events for totally |
511 | but of course I<doesn't>, and epoll just loves to report events for |
503 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
504 | even remove them from the set) than registered in the set (especially |
513 | one cannot even remove them from the set) than registered in the set |
505 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
506 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
507 | events to filter out spurious ones, recreating the set when required. Last |
516 | that against the events to filter out spurious ones, recreating the set |
|
|
517 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
518 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
519 | because epoll returns immediately despite a nonzero timeout. And last |
508 | not least, it also refuses to work with some file descriptors which work |
520 | not least, it also refuses to work with some file descriptors which work |
509 | perfectly fine with C<select> (files, many character devices...). |
521 | perfectly fine with C<select> (files, many character devices...). |
510 | |
522 | |
511 | Epoll is truly the train wreck analog among event poll mechanisms. |
523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
524 | cobbled together in a hurry, no thought to design or interaction with |
|
|
525 | others. Oh, the pain, will it ever stop... |
512 | |
526 | |
513 | While stopping, setting and starting an I/O watcher in the same iteration |
527 | While stopping, setting and starting an I/O watcher in the same iteration |
514 | will result in some caching, there is still a system call per such |
528 | will result in some caching, there is still a system call per such |
515 | incident (because the same I<file descriptor> could point to a different |
529 | incident (because the same I<file descriptor> could point to a different |
516 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
530 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
553 | |
567 | |
554 | It scales in the same way as the epoll backend, but the interface to the |
568 | It scales in the same way as the epoll backend, but the interface to the |
555 | kernel is more efficient (which says nothing about its actual speed, of |
569 | kernel is more efficient (which says nothing about its actual speed, of |
556 | course). While stopping, setting and starting an I/O watcher does never |
570 | course). While stopping, setting and starting an I/O watcher does never |
557 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
558 | two event changes per incident. Support for C<fork ()> is very bad (but |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
559 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
560 | cases |
574 | drops fds silently in similarly hard-to-detect cases. |
561 | |
575 | |
562 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
563 | |
577 | |
564 | While nominally embeddable in other event loops, this doesn't work |
578 | While nominally embeddable in other event loops, this doesn't work |
565 | everywhere, so you might need to test for this. And since it is broken |
579 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
594 | among the OS-specific backends (I vastly prefer correctness over speed |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
595 | hacks). |
609 | hacks). |
596 | |
610 | |
597 | On the negative side, the interface is I<bizarre> - so bizarre that |
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
598 | even sun itself gets it wrong in their code examples: The event polling |
612 | even sun itself gets it wrong in their code examples: The event polling |
599 | function sometimes returning events to the caller even though an error |
613 | function sometimes returns events to the caller even though an error |
600 | occured, but with no indication whether it has done so or not (yes, it's |
614 | occurred, but with no indication whether it has done so or not (yes, it's |
601 | even documented that way) - deadly for edge-triggered interfaces where |
615 | even documented that way) - deadly for edge-triggered interfaces where you |
602 | you absolutely have to know whether an event occured or not because you |
616 | absolutely have to know whether an event occurred or not because you have |
603 | have to re-arm the watcher. |
617 | to re-arm the watcher. |
604 | |
618 | |
605 | Fortunately libev seems to be able to work around these idiocies. |
619 | Fortunately libev seems to be able to work around these idiocies. |
606 | |
620 | |
607 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
608 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
… | |
… | |
750 | |
764 | |
751 | This function is rarely useful, but when some event callback runs for a |
765 | This function is rarely useful, but when some event callback runs for a |
752 | very long time without entering the event loop, updating libev's idea of |
766 | very long time without entering the event loop, updating libev's idea of |
753 | the current time is a good idea. |
767 | the current time is a good idea. |
754 | |
768 | |
755 | See also L<The special problem of time updates> in the C<ev_timer> section. |
769 | See also L</The special problem of time updates> in the C<ev_timer> section. |
756 | |
770 | |
757 | =item ev_suspend (loop) |
771 | =item ev_suspend (loop) |
758 | |
772 | |
759 | =item ev_resume (loop) |
773 | =item ev_resume (loop) |
760 | |
774 | |
… | |
… | |
778 | without a previous call to C<ev_suspend>. |
792 | without a previous call to C<ev_suspend>. |
779 | |
793 | |
780 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
781 | event loop time (see C<ev_now_update>). |
795 | event loop time (see C<ev_now_update>). |
782 | |
796 | |
783 | =item ev_run (loop, int flags) |
797 | =item bool ev_run (loop, int flags) |
784 | |
798 | |
785 | Finally, this is it, the event handler. This function usually is called |
799 | Finally, this is it, the event handler. This function usually is called |
786 | after you have initialised all your watchers and you want to start |
800 | after you have initialised all your watchers and you want to start |
787 | handling events. It will ask the operating system for any new events, call |
801 | handling events. It will ask the operating system for any new events, call |
788 | the watcher callbacks, an then repeat the whole process indefinitely: This |
802 | the watcher callbacks, and then repeat the whole process indefinitely: This |
789 | is why event loops are called I<loops>. |
803 | is why event loops are called I<loops>. |
790 | |
804 | |
791 | If the flags argument is specified as C<0>, it will keep handling events |
805 | If the flags argument is specified as C<0>, it will keep handling events |
792 | until either no event watchers are active anymore or C<ev_break> was |
806 | until either no event watchers are active anymore or C<ev_break> was |
793 | called. |
807 | called. |
|
|
808 | |
|
|
809 | The return value is false if there are no more active watchers (which |
|
|
810 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
811 | (which usually means " you should call C<ev_run> again"). |
794 | |
812 | |
795 | Please note that an explicit C<ev_break> is usually better than |
813 | Please note that an explicit C<ev_break> is usually better than |
796 | relying on all watchers to be stopped when deciding when a program has |
814 | relying on all watchers to be stopped when deciding when a program has |
797 | finished (especially in interactive programs), but having a program |
815 | finished (especially in interactive programs), but having a program |
798 | that automatically loops as long as it has to and no longer by virtue |
816 | that automatically loops as long as it has to and no longer by virtue |
799 | of relying on its watchers stopping correctly, that is truly a thing of |
817 | of relying on its watchers stopping correctly, that is truly a thing of |
800 | beauty. |
818 | beauty. |
801 | |
819 | |
802 | This function is also I<mostly> exception-safe - you can break out of |
820 | This function is I<mostly> exception-safe - you can break out of a |
803 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
821 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
804 | exception and so on. This does not decrement the C<ev_depth> value, nor |
822 | exception and so on. This does not decrement the C<ev_depth> value, nor |
805 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
823 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
806 | |
824 | |
807 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
825 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
808 | those events and any already outstanding ones, but will not wait and |
826 | those events and any already outstanding ones, but will not wait and |
… | |
… | |
820 | This is useful if you are waiting for some external event in conjunction |
838 | This is useful if you are waiting for some external event in conjunction |
821 | with something not expressible using other libev watchers (i.e. "roll your |
839 | with something not expressible using other libev watchers (i.e. "roll your |
822 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
840 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
823 | usually a better approach for this kind of thing. |
841 | usually a better approach for this kind of thing. |
824 | |
842 | |
825 | Here are the gory details of what C<ev_run> does: |
843 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
844 | understanding, not a guarantee that things will work exactly like this in |
|
|
845 | future versions): |
826 | |
846 | |
827 | - Increment loop depth. |
847 | - Increment loop depth. |
828 | - Reset the ev_break status. |
848 | - Reset the ev_break status. |
829 | - Before the first iteration, call any pending watchers. |
849 | - Before the first iteration, call any pending watchers. |
830 | LOOP: |
850 | LOOP: |
… | |
… | |
863 | anymore. |
883 | anymore. |
864 | |
884 | |
865 | ... queue jobs here, make sure they register event watchers as long |
885 | ... queue jobs here, make sure they register event watchers as long |
866 | ... as they still have work to do (even an idle watcher will do..) |
886 | ... as they still have work to do (even an idle watcher will do..) |
867 | ev_run (my_loop, 0); |
887 | ev_run (my_loop, 0); |
868 | ... jobs done or somebody called unloop. yeah! |
888 | ... jobs done or somebody called break. yeah! |
869 | |
889 | |
870 | =item ev_break (loop, how) |
890 | =item ev_break (loop, how) |
871 | |
891 | |
872 | Can be used to make a call to C<ev_run> return early (but only after it |
892 | Can be used to make a call to C<ev_run> return early (but only after it |
873 | has processed all outstanding events). The C<how> argument must be either |
893 | has processed all outstanding events). The C<how> argument must be either |
… | |
… | |
936 | overhead for the actual polling but can deliver many events at once. |
956 | overhead for the actual polling but can deliver many events at once. |
937 | |
957 | |
938 | By setting a higher I<io collect interval> you allow libev to spend more |
958 | By setting a higher I<io collect interval> you allow libev to spend more |
939 | time collecting I/O events, so you can handle more events per iteration, |
959 | time collecting I/O events, so you can handle more events per iteration, |
940 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
960 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
941 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
961 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
942 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
962 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
943 | sleep time ensures that libev will not poll for I/O events more often then |
963 | sleep time ensures that libev will not poll for I/O events more often then |
944 | once per this interval, on average. |
964 | once per this interval, on average (as long as the host time resolution is |
|
|
965 | good enough). |
945 | |
966 | |
946 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
967 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
947 | to spend more time collecting timeouts, at the expense of increased |
968 | to spend more time collecting timeouts, at the expense of increased |
948 | latency/jitter/inexactness (the watcher callback will be called |
969 | latency/jitter/inexactness (the watcher callback will be called |
949 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
970 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
995 | invoke the actual watchers inside another context (another thread etc.). |
1016 | invoke the actual watchers inside another context (another thread etc.). |
996 | |
1017 | |
997 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1018 | If you want to reset the callback, use C<ev_invoke_pending> as new |
998 | callback. |
1019 | callback. |
999 | |
1020 | |
1000 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1021 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
1001 | |
1022 | |
1002 | Sometimes you want to share the same loop between multiple threads. This |
1023 | Sometimes you want to share the same loop between multiple threads. This |
1003 | can be done relatively simply by putting mutex_lock/unlock calls around |
1024 | can be done relatively simply by putting mutex_lock/unlock calls around |
1004 | each call to a libev function. |
1025 | each call to a libev function. |
1005 | |
1026 | |
1006 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1027 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1007 | to wait for it to return. One way around this is to wake up the event |
1028 | to wait for it to return. One way around this is to wake up the event |
1008 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1029 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
1009 | I<release> and I<acquire> callbacks on the loop. |
1030 | I<release> and I<acquire> callbacks on the loop. |
1010 | |
1031 | |
1011 | When set, then C<release> will be called just before the thread is |
1032 | When set, then C<release> will be called just before the thread is |
1012 | suspended waiting for new events, and C<acquire> is called just |
1033 | suspended waiting for new events, and C<acquire> is called just |
1013 | afterwards. |
1034 | afterwards. |
… | |
… | |
1153 | |
1174 | |
1154 | =item C<EV_PREPARE> |
1175 | =item C<EV_PREPARE> |
1155 | |
1176 | |
1156 | =item C<EV_CHECK> |
1177 | =item C<EV_CHECK> |
1157 | |
1178 | |
1158 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1179 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1159 | to gather new events, and all C<ev_check> watchers are invoked just after |
1180 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1160 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1181 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1182 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1183 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1184 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1185 | or lower priority within an event loop iteration. |
|
|
1186 | |
1161 | received events. Callbacks of both watcher types can start and stop as |
1187 | Callbacks of both watcher types can start and stop as many watchers as |
1162 | many watchers as they want, and all of them will be taken into account |
1188 | they want, and all of them will be taken into account (for example, a |
1163 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1189 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1164 | C<ev_run> from blocking). |
1190 | blocking). |
1165 | |
1191 | |
1166 | =item C<EV_EMBED> |
1192 | =item C<EV_EMBED> |
1167 | |
1193 | |
1168 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1194 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1169 | |
1195 | |
… | |
… | |
1292 | |
1318 | |
1293 | =item callback ev_cb (ev_TYPE *watcher) |
1319 | =item callback ev_cb (ev_TYPE *watcher) |
1294 | |
1320 | |
1295 | Returns the callback currently set on the watcher. |
1321 | Returns the callback currently set on the watcher. |
1296 | |
1322 | |
1297 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1323 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1298 | |
1324 | |
1299 | Change the callback. You can change the callback at virtually any time |
1325 | Change the callback. You can change the callback at virtually any time |
1300 | (modulo threads). |
1326 | (modulo threads). |
1301 | |
1327 | |
1302 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1328 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
… | |
… | |
1320 | or might not have been clamped to the valid range. |
1346 | or might not have been clamped to the valid range. |
1321 | |
1347 | |
1322 | The default priority used by watchers when no priority has been set is |
1348 | The default priority used by watchers when no priority has been set is |
1323 | always C<0>, which is supposed to not be too high and not be too low :). |
1349 | always C<0>, which is supposed to not be too high and not be too low :). |
1324 | |
1350 | |
1325 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1351 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1326 | priorities. |
1352 | priorities. |
1327 | |
1353 | |
1328 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1354 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1329 | |
1355 | |
1330 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1356 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1355 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1381 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1356 | functions that do not need a watcher. |
1382 | functions that do not need a watcher. |
1357 | |
1383 | |
1358 | =back |
1384 | =back |
1359 | |
1385 | |
1360 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1386 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
1361 | |
1387 | OWN COMPOSITE WATCHERS> idioms. |
1362 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1363 | and read at any time: libev will completely ignore it. This can be used |
|
|
1364 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1365 | don't want to allocate memory and store a pointer to it in that data |
|
|
1366 | member, you can also "subclass" the watcher type and provide your own |
|
|
1367 | data: |
|
|
1368 | |
|
|
1369 | struct my_io |
|
|
1370 | { |
|
|
1371 | ev_io io; |
|
|
1372 | int otherfd; |
|
|
1373 | void *somedata; |
|
|
1374 | struct whatever *mostinteresting; |
|
|
1375 | }; |
|
|
1376 | |
|
|
1377 | ... |
|
|
1378 | struct my_io w; |
|
|
1379 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1380 | |
|
|
1381 | And since your callback will be called with a pointer to the watcher, you |
|
|
1382 | can cast it back to your own type: |
|
|
1383 | |
|
|
1384 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1385 | { |
|
|
1386 | struct my_io *w = (struct my_io *)w_; |
|
|
1387 | ... |
|
|
1388 | } |
|
|
1389 | |
|
|
1390 | More interesting and less C-conformant ways of casting your callback type |
|
|
1391 | instead have been omitted. |
|
|
1392 | |
|
|
1393 | Another common scenario is to use some data structure with multiple |
|
|
1394 | embedded watchers: |
|
|
1395 | |
|
|
1396 | struct my_biggy |
|
|
1397 | { |
|
|
1398 | int some_data; |
|
|
1399 | ev_timer t1; |
|
|
1400 | ev_timer t2; |
|
|
1401 | } |
|
|
1402 | |
|
|
1403 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1404 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1405 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1406 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1407 | programmers): |
|
|
1408 | |
|
|
1409 | #include <stddef.h> |
|
|
1410 | |
|
|
1411 | static void |
|
|
1412 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1413 | { |
|
|
1414 | struct my_biggy big = (struct my_biggy *) |
|
|
1415 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1416 | } |
|
|
1417 | |
|
|
1418 | static void |
|
|
1419 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1420 | { |
|
|
1421 | struct my_biggy big = (struct my_biggy *) |
|
|
1422 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1423 | } |
|
|
1424 | |
1388 | |
1425 | =head2 WATCHER STATES |
1389 | =head2 WATCHER STATES |
1426 | |
1390 | |
1427 | There are various watcher states mentioned throughout this manual - |
1391 | There are various watcher states mentioned throughout this manual - |
1428 | active, pending and so on. In this section these states and the rules to |
1392 | active, pending and so on. In this section these states and the rules to |
1429 | transition between them will be described in more detail - and while these |
1393 | transition between them will be described in more detail - and while these |
1430 | rules might look complicated, they usually do "the right thing". |
1394 | rules might look complicated, they usually do "the right thing". |
1431 | |
1395 | |
1432 | =over 4 |
1396 | =over 4 |
1433 | |
1397 | |
1434 | =item initialiased |
1398 | =item initialised |
1435 | |
1399 | |
1436 | Before a watcher can be registered with the event looop it has to be |
1400 | Before a watcher can be registered with the event loop it has to be |
1437 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1401 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1438 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1402 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1439 | |
1403 | |
1440 | In this state it is simply some block of memory that is suitable for use |
1404 | In this state it is simply some block of memory that is suitable for |
1441 | in an event loop. It can be moved around, freed, reused etc. at will. |
1405 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1406 | will - as long as you either keep the memory contents intact, or call |
|
|
1407 | C<ev_TYPE_init> again. |
1442 | |
1408 | |
1443 | =item started/running/active |
1409 | =item started/running/active |
1444 | |
1410 | |
1445 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1411 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1446 | property of the event loop, and is actively waiting for events. While in |
1412 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1474 | latter will clear any pending state the watcher might be in, regardless |
1440 | latter will clear any pending state the watcher might be in, regardless |
1475 | of whether it was active or not, so stopping a watcher explicitly before |
1441 | of whether it was active or not, so stopping a watcher explicitly before |
1476 | freeing it is often a good idea. |
1442 | freeing it is often a good idea. |
1477 | |
1443 | |
1478 | While stopped (and not pending) the watcher is essentially in the |
1444 | While stopped (and not pending) the watcher is essentially in the |
1479 | initialised state, that is it can be reused, moved, modified in any way |
1445 | initialised state, that is, it can be reused, moved, modified in any way |
1480 | you wish. |
1446 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1447 | it again). |
1481 | |
1448 | |
1482 | =back |
1449 | =back |
1483 | |
1450 | |
1484 | =head2 WATCHER PRIORITY MODELS |
1451 | =head2 WATCHER PRIORITY MODELS |
1485 | |
1452 | |
… | |
… | |
1614 | In general you can register as many read and/or write event watchers per |
1581 | In general you can register as many read and/or write event watchers per |
1615 | fd as you want (as long as you don't confuse yourself). Setting all file |
1582 | fd as you want (as long as you don't confuse yourself). Setting all file |
1616 | descriptors to non-blocking mode is also usually a good idea (but not |
1583 | descriptors to non-blocking mode is also usually a good idea (but not |
1617 | required if you know what you are doing). |
1584 | required if you know what you are doing). |
1618 | |
1585 | |
1619 | If you cannot use non-blocking mode, then force the use of a |
|
|
1620 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1621 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1622 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1623 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1624 | |
|
|
1625 | Another thing you have to watch out for is that it is quite easy to |
1586 | Another thing you have to watch out for is that it is quite easy to |
1626 | receive "spurious" readiness notifications, that is your callback might |
1587 | receive "spurious" readiness notifications, that is, your callback might |
1627 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1588 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1628 | because there is no data. Not only are some backends known to create a |
1589 | because there is no data. It is very easy to get into this situation even |
1629 | lot of those (for example Solaris ports), it is very easy to get into |
1590 | with a relatively standard program structure. Thus it is best to always |
1630 | this situation even with a relatively standard program structure. Thus |
1591 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1631 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1632 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1592 | preferable to a program hanging until some data arrives. |
1633 | |
1593 | |
1634 | If you cannot run the fd in non-blocking mode (for example you should |
1594 | If you cannot run the fd in non-blocking mode (for example you should |
1635 | not play around with an Xlib connection), then you have to separately |
1595 | not play around with an Xlib connection), then you have to separately |
1636 | re-test whether a file descriptor is really ready with a known-to-be good |
1596 | re-test whether a file descriptor is really ready with a known-to-be good |
1637 | interface such as poll (fortunately in our Xlib example, Xlib already |
1597 | interface such as poll (fortunately in the case of Xlib, it already does |
1638 | does this on its own, so its quite safe to use). Some people additionally |
1598 | this on its own, so its quite safe to use). Some people additionally |
1639 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1599 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1640 | indefinitely. |
1600 | indefinitely. |
1641 | |
1601 | |
1642 | But really, best use non-blocking mode. |
1602 | But really, best use non-blocking mode. |
1643 | |
1603 | |
… | |
… | |
1671 | |
1631 | |
1672 | There is no workaround possible except not registering events |
1632 | There is no workaround possible except not registering events |
1673 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1633 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1674 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1634 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1675 | |
1635 | |
|
|
1636 | =head3 The special problem of files |
|
|
1637 | |
|
|
1638 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1639 | representing files, and expect it to become ready when their program |
|
|
1640 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1641 | |
|
|
1642 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1643 | notification as soon as the kernel knows whether and how much data is |
|
|
1644 | there, and in the case of open files, that's always the case, so you |
|
|
1645 | always get a readiness notification instantly, and your read (or possibly |
|
|
1646 | write) will still block on the disk I/O. |
|
|
1647 | |
|
|
1648 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1649 | devices and so on, there is another party (the sender) that delivers data |
|
|
1650 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1651 | will not send data on its own, simply because it doesn't know what you |
|
|
1652 | wish to read - you would first have to request some data. |
|
|
1653 | |
|
|
1654 | Since files are typically not-so-well supported by advanced notification |
|
|
1655 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1656 | to files, even though you should not use it. The reason for this is |
|
|
1657 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1658 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1659 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1660 | F</dev/urandom>), and even though the file might better be served with |
|
|
1661 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1662 | it "just works" instead of freezing. |
|
|
1663 | |
|
|
1664 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1665 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1666 | when you rarely read from a file instead of from a socket, and want to |
|
|
1667 | reuse the same code path. |
|
|
1668 | |
1676 | =head3 The special problem of fork |
1669 | =head3 The special problem of fork |
1677 | |
1670 | |
1678 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1671 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1679 | useless behaviour. Libev fully supports fork, but needs to be told about |
1672 | useless behaviour. Libev fully supports fork, but needs to be told about |
1680 | it in the child. |
1673 | it in the child if you want to continue to use it in the child. |
1681 | |
1674 | |
1682 | To support fork in your programs, you either have to call |
1675 | To support fork in your child processes, you have to call C<ev_loop_fork |
1683 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1676 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1684 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1677 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1685 | C<EVBACKEND_POLL>. |
|
|
1686 | |
1678 | |
1687 | =head3 The special problem of SIGPIPE |
1679 | =head3 The special problem of SIGPIPE |
1688 | |
1680 | |
1689 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1681 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1690 | when writing to a pipe whose other end has been closed, your program gets |
1682 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1788 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1780 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1789 | monotonic clock option helps a lot here). |
1781 | monotonic clock option helps a lot here). |
1790 | |
1782 | |
1791 | The callback is guaranteed to be invoked only I<after> its timeout has |
1783 | The callback is guaranteed to be invoked only I<after> its timeout has |
1792 | passed (not I<at>, so on systems with very low-resolution clocks this |
1784 | passed (not I<at>, so on systems with very low-resolution clocks this |
1793 | might introduce a small delay). If multiple timers become ready during the |
1785 | might introduce a small delay, see "the special problem of being too |
|
|
1786 | early", below). If multiple timers become ready during the same loop |
1794 | same loop iteration then the ones with earlier time-out values are invoked |
1787 | iteration then the ones with earlier time-out values are invoked before |
1795 | before ones of the same priority with later time-out values (but this is |
1788 | ones of the same priority with later time-out values (but this is no |
1796 | no longer true when a callback calls C<ev_run> recursively). |
1789 | longer true when a callback calls C<ev_run> recursively). |
1797 | |
1790 | |
1798 | =head3 Be smart about timeouts |
1791 | =head3 Be smart about timeouts |
1799 | |
1792 | |
1800 | Many real-world problems involve some kind of timeout, usually for error |
1793 | Many real-world problems involve some kind of timeout, usually for error |
1801 | recovery. A typical example is an HTTP request - if the other side hangs, |
1794 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1876 | |
1869 | |
1877 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1870 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1878 | but remember the time of last activity, and check for a real timeout only |
1871 | but remember the time of last activity, and check for a real timeout only |
1879 | within the callback: |
1872 | within the callback: |
1880 | |
1873 | |
|
|
1874 | ev_tstamp timeout = 60.; |
1881 | ev_tstamp last_activity; // time of last activity |
1875 | ev_tstamp last_activity; // time of last activity |
|
|
1876 | ev_timer timer; |
1882 | |
1877 | |
1883 | static void |
1878 | static void |
1884 | callback (EV_P_ ev_timer *w, int revents) |
1879 | callback (EV_P_ ev_timer *w, int revents) |
1885 | { |
1880 | { |
1886 | ev_tstamp now = ev_now (EV_A); |
1881 | // calculate when the timeout would happen |
1887 | ev_tstamp timeout = last_activity + 60.; |
1882 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1888 | |
1883 | |
1889 | // if last_activity + 60. is older than now, we did time out |
1884 | // if negative, it means we the timeout already occurred |
1890 | if (timeout < now) |
1885 | if (after < 0.) |
1891 | { |
1886 | { |
1892 | // timeout occurred, take action |
1887 | // timeout occurred, take action |
1893 | } |
1888 | } |
1894 | else |
1889 | else |
1895 | { |
1890 | { |
1896 | // callback was invoked, but there was some activity, re-arm |
1891 | // callback was invoked, but there was some recent |
1897 | // the watcher to fire in last_activity + 60, which is |
1892 | // activity. simply restart the timer to time out |
1898 | // guaranteed to be in the future, so "again" is positive: |
1893 | // after "after" seconds, which is the earliest time |
1899 | w->repeat = timeout - now; |
1894 | // the timeout can occur. |
|
|
1895 | ev_timer_set (w, after, 0.); |
1900 | ev_timer_again (EV_A_ w); |
1896 | ev_timer_start (EV_A_ w); |
1901 | } |
1897 | } |
1902 | } |
1898 | } |
1903 | |
1899 | |
1904 | To summarise the callback: first calculate the real timeout (defined |
1900 | To summarise the callback: first calculate in how many seconds the |
1905 | as "60 seconds after the last activity"), then check if that time has |
1901 | timeout will occur (by calculating the absolute time when it would occur, |
1906 | been reached, which means something I<did>, in fact, time out. Otherwise |
1902 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1907 | the callback was invoked too early (C<timeout> is in the future), so |
1903 | (EV_A)> from that). |
1908 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1909 | a timeout then. |
|
|
1910 | |
1904 | |
1911 | Note how C<ev_timer_again> is used, taking advantage of the |
1905 | If this value is negative, then we are already past the timeout, i.e. we |
1912 | C<ev_timer_again> optimisation when the timer is already running. |
1906 | timed out, and need to do whatever is needed in this case. |
|
|
1907 | |
|
|
1908 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1909 | and simply start the timer with this timeout value. |
|
|
1910 | |
|
|
1911 | In other words, each time the callback is invoked it will check whether |
|
|
1912 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1913 | again at the earliest time it could time out. Rinse. Repeat. |
1913 | |
1914 | |
1914 | This scheme causes more callback invocations (about one every 60 seconds |
1915 | This scheme causes more callback invocations (about one every 60 seconds |
1915 | minus half the average time between activity), but virtually no calls to |
1916 | minus half the average time between activity), but virtually no calls to |
1916 | libev to change the timeout. |
1917 | libev to change the timeout. |
1917 | |
1918 | |
1918 | To start the timer, simply initialise the watcher and set C<last_activity> |
1919 | To start the machinery, simply initialise the watcher and set |
1919 | to the current time (meaning we just have some activity :), then call the |
1920 | C<last_activity> to the current time (meaning there was some activity just |
1920 | callback, which will "do the right thing" and start the timer: |
1921 | now), then call the callback, which will "do the right thing" and start |
|
|
1922 | the timer: |
1921 | |
1923 | |
|
|
1924 | last_activity = ev_now (EV_A); |
1922 | ev_init (timer, callback); |
1925 | ev_init (&timer, callback); |
1923 | last_activity = ev_now (loop); |
1926 | callback (EV_A_ &timer, 0); |
1924 | callback (loop, timer, EV_TIMER); |
|
|
1925 | |
1927 | |
1926 | And when there is some activity, simply store the current time in |
1928 | When there is some activity, simply store the current time in |
1927 | C<last_activity>, no libev calls at all: |
1929 | C<last_activity>, no libev calls at all: |
1928 | |
1930 | |
|
|
1931 | if (activity detected) |
1929 | last_activity = ev_now (loop); |
1932 | last_activity = ev_now (EV_A); |
|
|
1933 | |
|
|
1934 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1935 | providing a new value, stopping the timer and calling the callback, which |
|
|
1936 | will again do the right thing (for example, time out immediately :). |
|
|
1937 | |
|
|
1938 | timeout = new_value; |
|
|
1939 | ev_timer_stop (EV_A_ &timer); |
|
|
1940 | callback (EV_A_ &timer, 0); |
1930 | |
1941 | |
1931 | This technique is slightly more complex, but in most cases where the |
1942 | This technique is slightly more complex, but in most cases where the |
1932 | time-out is unlikely to be triggered, much more efficient. |
1943 | time-out is unlikely to be triggered, much more efficient. |
1933 | |
|
|
1934 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1935 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1936 | fix things for you. |
|
|
1937 | |
1944 | |
1938 | =item 4. Wee, just use a double-linked list for your timeouts. |
1945 | =item 4. Wee, just use a double-linked list for your timeouts. |
1939 | |
1946 | |
1940 | If there is not one request, but many thousands (millions...), all |
1947 | If there is not one request, but many thousands (millions...), all |
1941 | employing some kind of timeout with the same timeout value, then one can |
1948 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1968 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1975 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1969 | rather complicated, but extremely efficient, something that really pays |
1976 | rather complicated, but extremely efficient, something that really pays |
1970 | off after the first million or so of active timers, i.e. it's usually |
1977 | off after the first million or so of active timers, i.e. it's usually |
1971 | overkill :) |
1978 | overkill :) |
1972 | |
1979 | |
|
|
1980 | =head3 The special problem of being too early |
|
|
1981 | |
|
|
1982 | If you ask a timer to call your callback after three seconds, then |
|
|
1983 | you expect it to be invoked after three seconds - but of course, this |
|
|
1984 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1985 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1986 | process with a STOP signal for a few hours for example. |
|
|
1987 | |
|
|
1988 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1989 | delay has occurred, but cannot guarantee this. |
|
|
1990 | |
|
|
1991 | A less obvious failure mode is calling your callback too early: many event |
|
|
1992 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1993 | this can cause your callback to be invoked much earlier than you would |
|
|
1994 | expect. |
|
|
1995 | |
|
|
1996 | To see why, imagine a system with a clock that only offers full second |
|
|
1997 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1998 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1999 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2000 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2001 | |
|
|
2002 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2003 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2004 | one-second delay was requested - this is being "too early", despite best |
|
|
2005 | intentions. |
|
|
2006 | |
|
|
2007 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2008 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2009 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2010 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2011 | |
|
|
2012 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2013 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2014 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2015 | late" side of things. |
|
|
2016 | |
1973 | =head3 The special problem of time updates |
2017 | =head3 The special problem of time updates |
1974 | |
2018 | |
1975 | Establishing the current time is a costly operation (it usually takes at |
2019 | Establishing the current time is a costly operation (it usually takes |
1976 | least two system calls): EV therefore updates its idea of the current |
2020 | at least one system call): EV therefore updates its idea of the current |
1977 | time only before and after C<ev_run> collects new events, which causes a |
2021 | time only before and after C<ev_run> collects new events, which causes a |
1978 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2022 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1979 | lots of events in one iteration. |
2023 | lots of events in one iteration. |
1980 | |
2024 | |
1981 | The relative timeouts are calculated relative to the C<ev_now ()> |
2025 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1987 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2031 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1988 | |
2032 | |
1989 | If the event loop is suspended for a long time, you can also force an |
2033 | If the event loop is suspended for a long time, you can also force an |
1990 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2034 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1991 | ()>. |
2035 | ()>. |
|
|
2036 | |
|
|
2037 | =head3 The special problem of unsynchronised clocks |
|
|
2038 | |
|
|
2039 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2040 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2041 | jumps). |
|
|
2042 | |
|
|
2043 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2044 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2045 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2046 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2047 | than a directly following call to C<time>. |
|
|
2048 | |
|
|
2049 | The moral of this is to only compare libev-related timestamps with |
|
|
2050 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2051 | a second or so. |
|
|
2052 | |
|
|
2053 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2054 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2055 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2056 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2057 | |
|
|
2058 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2059 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2060 | I<measured according to the real time>, not the system clock. |
|
|
2061 | |
|
|
2062 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2063 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2064 | exactly the right behaviour. |
|
|
2065 | |
|
|
2066 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2067 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2068 | time, where your comparisons will always generate correct results. |
1992 | |
2069 | |
1993 | =head3 The special problems of suspended animation |
2070 | =head3 The special problems of suspended animation |
1994 | |
2071 | |
1995 | When you leave the server world it is quite customary to hit machines that |
2072 | When you leave the server world it is quite customary to hit machines that |
1996 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2073 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
2040 | keep up with the timer (because it takes longer than those 10 seconds to |
2117 | keep up with the timer (because it takes longer than those 10 seconds to |
2041 | do stuff) the timer will not fire more than once per event loop iteration. |
2118 | do stuff) the timer will not fire more than once per event loop iteration. |
2042 | |
2119 | |
2043 | =item ev_timer_again (loop, ev_timer *) |
2120 | =item ev_timer_again (loop, ev_timer *) |
2044 | |
2121 | |
2045 | This will act as if the timer timed out and restart it again if it is |
2122 | This will act as if the timer timed out, and restarts it again if it is |
2046 | repeating. The exact semantics are: |
2123 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2124 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
2047 | |
2125 | |
|
|
2126 | The exact semantics are as in the following rules, all of which will be |
|
|
2127 | applied to the watcher: |
|
|
2128 | |
|
|
2129 | =over 4 |
|
|
2130 | |
2048 | If the timer is pending, its pending status is cleared. |
2131 | =item If the timer is pending, the pending status is always cleared. |
2049 | |
2132 | |
2050 | If the timer is started but non-repeating, stop it (as if it timed out). |
2133 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2134 | out, without invoking it). |
2051 | |
2135 | |
2052 | If the timer is repeating, either start it if necessary (with the |
2136 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2053 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2137 | and start the timer, if necessary. |
2054 | |
2138 | |
|
|
2139 | =back |
|
|
2140 | |
2055 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2141 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
2056 | usage example. |
2142 | usage example. |
2057 | |
2143 | |
2058 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2144 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2059 | |
2145 | |
2060 | Returns the remaining time until a timer fires. If the timer is active, |
2146 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2180 | |
2266 | |
2181 | Another way to think about it (for the mathematically inclined) is that |
2267 | Another way to think about it (for the mathematically inclined) is that |
2182 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2268 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2183 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2269 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2184 | |
2270 | |
2185 | For numerical stability it is preferable that the C<offset> value is near |
2271 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2186 | C<ev_now ()> (the current time), but there is no range requirement for |
2272 | interval value should be higher than C<1/8192> (which is around 100 |
2187 | this value, and in fact is often specified as zero. |
2273 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2274 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2275 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2276 | C<0> and C<interval>, which is also the recommended range. |
2188 | |
2277 | |
2189 | Note also that there is an upper limit to how often a timer can fire (CPU |
2278 | Note also that there is an upper limit to how often a timer can fire (CPU |
2190 | speed for example), so if C<interval> is very small then timing stability |
2279 | speed for example), so if C<interval> is very small then timing stability |
2191 | will of course deteriorate. Libev itself tries to be exact to be about one |
2280 | will of course deteriorate. Libev itself tries to be exact to be about one |
2192 | millisecond (if the OS supports it and the machine is fast enough). |
2281 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2335 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2424 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2336 | |
2425 | |
2337 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2426 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2338 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2427 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2339 | stopping it again), that is, libev might or might not block the signal, |
2428 | stopping it again), that is, libev might or might not block the signal, |
2340 | and might or might not set or restore the installed signal handler. |
2429 | and might or might not set or restore the installed signal handler (but |
|
|
2430 | see C<EVFLAG_NOSIGMASK>). |
2341 | |
2431 | |
2342 | While this does not matter for the signal disposition (libev never |
2432 | While this does not matter for the signal disposition (libev never |
2343 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2433 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2344 | C<execve>), this matters for the signal mask: many programs do not expect |
2434 | C<execve>), this matters for the signal mask: many programs do not expect |
2345 | certain signals to be blocked. |
2435 | certain signals to be blocked. |
… | |
… | |
2516 | |
2606 | |
2517 | =head2 C<ev_stat> - did the file attributes just change? |
2607 | =head2 C<ev_stat> - did the file attributes just change? |
2518 | |
2608 | |
2519 | This watches a file system path for attribute changes. That is, it calls |
2609 | This watches a file system path for attribute changes. That is, it calls |
2520 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2610 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2521 | and sees if it changed compared to the last time, invoking the callback if |
2611 | and sees if it changed compared to the last time, invoking the callback |
2522 | it did. |
2612 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2613 | happen after the watcher has been started will be reported. |
2523 | |
2614 | |
2524 | The path does not need to exist: changing from "path exists" to "path does |
2615 | The path does not need to exist: changing from "path exists" to "path does |
2525 | not exist" is a status change like any other. The condition "path does not |
2616 | not exist" is a status change like any other. The condition "path does not |
2526 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2617 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2527 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2618 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2757 | Apart from keeping your process non-blocking (which is a useful |
2848 | Apart from keeping your process non-blocking (which is a useful |
2758 | effect on its own sometimes), idle watchers are a good place to do |
2849 | effect on its own sometimes), idle watchers are a good place to do |
2759 | "pseudo-background processing", or delay processing stuff to after the |
2850 | "pseudo-background processing", or delay processing stuff to after the |
2760 | event loop has handled all outstanding events. |
2851 | event loop has handled all outstanding events. |
2761 | |
2852 | |
|
|
2853 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2854 | |
|
|
2855 | As long as there is at least one active idle watcher, libev will never |
|
|
2856 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2857 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2858 | lowest priority will do. |
|
|
2859 | |
|
|
2860 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2861 | to do something on each event loop iteration - for example to balance load |
|
|
2862 | between different connections. |
|
|
2863 | |
|
|
2864 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2865 | example. |
|
|
2866 | |
2762 | =head3 Watcher-Specific Functions and Data Members |
2867 | =head3 Watcher-Specific Functions and Data Members |
2763 | |
2868 | |
2764 | =over 4 |
2869 | =over 4 |
2765 | |
2870 | |
2766 | =item ev_idle_init (ev_idle *, callback) |
2871 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2777 | callback, free it. Also, use no error checking, as usual. |
2882 | callback, free it. Also, use no error checking, as usual. |
2778 | |
2883 | |
2779 | static void |
2884 | static void |
2780 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2885 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2781 | { |
2886 | { |
|
|
2887 | // stop the watcher |
|
|
2888 | ev_idle_stop (loop, w); |
|
|
2889 | |
|
|
2890 | // now we can free it |
2782 | free (w); |
2891 | free (w); |
|
|
2892 | |
2783 | // now do something you wanted to do when the program has |
2893 | // now do something you wanted to do when the program has |
2784 | // no longer anything immediate to do. |
2894 | // no longer anything immediate to do. |
2785 | } |
2895 | } |
2786 | |
2896 | |
2787 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2897 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2789 | ev_idle_start (loop, idle_watcher); |
2899 | ev_idle_start (loop, idle_watcher); |
2790 | |
2900 | |
2791 | |
2901 | |
2792 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2902 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2793 | |
2903 | |
2794 | Prepare and check watchers are usually (but not always) used in pairs: |
2904 | Prepare and check watchers are often (but not always) used in pairs: |
2795 | prepare watchers get invoked before the process blocks and check watchers |
2905 | prepare watchers get invoked before the process blocks and check watchers |
2796 | afterwards. |
2906 | afterwards. |
2797 | |
2907 | |
2798 | You I<must not> call C<ev_run> or similar functions that enter |
2908 | You I<must not> call C<ev_run> or similar functions that enter |
2799 | the current event loop from either C<ev_prepare> or C<ev_check> |
2909 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
2827 | with priority higher than or equal to the event loop and one coroutine |
2937 | with priority higher than or equal to the event loop and one coroutine |
2828 | of lower priority, but only once, using idle watchers to keep the event |
2938 | of lower priority, but only once, using idle watchers to keep the event |
2829 | loop from blocking if lower-priority coroutines are active, thus mapping |
2939 | loop from blocking if lower-priority coroutines are active, thus mapping |
2830 | low-priority coroutines to idle/background tasks). |
2940 | low-priority coroutines to idle/background tasks). |
2831 | |
2941 | |
2832 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2942 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2833 | priority, to ensure that they are being run before any other watchers |
2943 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2834 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
2944 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
2945 | watchers). |
2835 | |
2946 | |
2836 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2947 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2837 | activate ("feed") events into libev. While libev fully supports this, they |
2948 | activate ("feed") events into libev. While libev fully supports this, they |
2838 | might get executed before other C<ev_check> watchers did their job. As |
2949 | might get executed before other C<ev_check> watchers did their job. As |
2839 | C<ev_check> watchers are often used to embed other (non-libev) event |
2950 | C<ev_check> watchers are often used to embed other (non-libev) event |
2840 | loops those other event loops might be in an unusable state until their |
2951 | loops those other event loops might be in an unusable state until their |
2841 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2952 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2842 | others). |
2953 | others). |
|
|
2954 | |
|
|
2955 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
2956 | |
|
|
2957 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
2958 | useful because they are called once per event loop iteration. For |
|
|
2959 | example, if you want to handle a large number of connections fairly, you |
|
|
2960 | normally only do a bit of work for each active connection, and if there |
|
|
2961 | is more work to do, you wait for the next event loop iteration, so other |
|
|
2962 | connections have a chance of making progress. |
|
|
2963 | |
|
|
2964 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
2965 | next event loop iteration. However, that isn't as soon as possible - |
|
|
2966 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
2967 | |
|
|
2968 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2969 | single global idle watcher that is active as long as you have one active |
|
|
2970 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
2971 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
2972 | invoked. Neither watcher alone can do that. |
2843 | |
2973 | |
2844 | =head3 Watcher-Specific Functions and Data Members |
2974 | =head3 Watcher-Specific Functions and Data Members |
2845 | |
2975 | |
2846 | =over 4 |
2976 | =over 4 |
2847 | |
2977 | |
… | |
… | |
3048 | |
3178 | |
3049 | =over 4 |
3179 | =over 4 |
3050 | |
3180 | |
3051 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3181 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3052 | |
3182 | |
3053 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3183 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
3054 | |
3184 | |
3055 | Configures the watcher to embed the given loop, which must be |
3185 | Configures the watcher to embed the given loop, which must be |
3056 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3186 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3057 | invoked automatically, otherwise it is the responsibility of the callback |
3187 | invoked automatically, otherwise it is the responsibility of the callback |
3058 | to invoke it (it will continue to be called until the sweep has been done, |
3188 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3121 | |
3251 | |
3122 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3252 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3123 | |
3253 | |
3124 | Fork watchers are called when a C<fork ()> was detected (usually because |
3254 | Fork watchers are called when a C<fork ()> was detected (usually because |
3125 | whoever is a good citizen cared to tell libev about it by calling |
3255 | whoever is a good citizen cared to tell libev about it by calling |
3126 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3256 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3127 | event loop blocks next and before C<ev_check> watchers are being called, |
3257 | and before C<ev_check> watchers are being called, and only in the child |
3128 | and only in the child after the fork. If whoever good citizen calling |
3258 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3129 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3259 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3130 | handlers will be invoked, too, of course. |
3260 | of course. |
3131 | |
3261 | |
3132 | =head3 The special problem of life after fork - how is it possible? |
3262 | =head3 The special problem of life after fork - how is it possible? |
3133 | |
3263 | |
3134 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3264 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3135 | up/change the process environment, followed by a call to C<exec()>. This |
3265 | up/change the process environment, followed by a call to C<exec()>. This |
… | |
… | |
3216 | atexit (program_exits); |
3346 | atexit (program_exits); |
3217 | |
3347 | |
3218 | |
3348 | |
3219 | =head2 C<ev_async> - how to wake up an event loop |
3349 | =head2 C<ev_async> - how to wake up an event loop |
3220 | |
3350 | |
3221 | In general, you cannot use an C<ev_run> from multiple threads or other |
3351 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3222 | asynchronous sources such as signal handlers (as opposed to multiple event |
3352 | asynchronous sources such as signal handlers (as opposed to multiple event |
3223 | loops - those are of course safe to use in different threads). |
3353 | loops - those are of course safe to use in different threads). |
3224 | |
3354 | |
3225 | Sometimes, however, you need to wake up an event loop you do not control, |
3355 | Sometimes, however, you need to wake up an event loop you do not control, |
3226 | for example because it belongs to another thread. This is what C<ev_async> |
3356 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3228 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3358 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3229 | |
3359 | |
3230 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3360 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3231 | too, are asynchronous in nature, and signals, too, will be compressed |
3361 | too, are asynchronous in nature, and signals, too, will be compressed |
3232 | (i.e. the number of callback invocations may be less than the number of |
3362 | (i.e. the number of callback invocations may be less than the number of |
3233 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3363 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3234 | of "global async watchers" by using a watcher on an otherwise unused |
3364 | of "global async watchers" by using a watcher on an otherwise unused |
3235 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3365 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3236 | even without knowing which loop owns the signal. |
3366 | even without knowing which loop owns the signal. |
3237 | |
|
|
3238 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
3239 | just the default loop. |
|
|
3240 | |
3367 | |
3241 | =head3 Queueing |
3368 | =head3 Queueing |
3242 | |
3369 | |
3243 | C<ev_async> does not support queueing of data in any way. The reason |
3370 | C<ev_async> does not support queueing of data in any way. The reason |
3244 | is that the author does not know of a simple (or any) algorithm for a |
3371 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3336 | trust me. |
3463 | trust me. |
3337 | |
3464 | |
3338 | =item ev_async_send (loop, ev_async *) |
3465 | =item ev_async_send (loop, ev_async *) |
3339 | |
3466 | |
3340 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3467 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3341 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3468 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3469 | returns. |
|
|
3470 | |
3342 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3471 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3343 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3472 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3344 | section below on what exactly this means). |
3473 | embedding section below on what exactly this means). |
3345 | |
3474 | |
3346 | Note that, as with other watchers in libev, multiple events might get |
3475 | Note that, as with other watchers in libev, multiple events might get |
3347 | compressed into a single callback invocation (another way to look at this |
3476 | compressed into a single callback invocation (another way to look at |
3348 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3477 | this is that C<ev_async> watchers are level-triggered: they are set on |
3349 | reset when the event loop detects that). |
3478 | C<ev_async_send>, reset when the event loop detects that). |
3350 | |
3479 | |
3351 | This call incurs the overhead of a system call only once per event loop |
3480 | This call incurs the overhead of at most one extra system call per event |
3352 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3481 | loop iteration, if the event loop is blocked, and no syscall at all if |
3353 | repeated calls to C<ev_async_send> for the same event loop. |
3482 | the event loop (or your program) is processing events. That means that |
|
|
3483 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3484 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3485 | zero) under load. |
3354 | |
3486 | |
3355 | =item bool = ev_async_pending (ev_async *) |
3487 | =item bool = ev_async_pending (ev_async *) |
3356 | |
3488 | |
3357 | Returns a non-zero value when C<ev_async_send> has been called on the |
3489 | Returns a non-zero value when C<ev_async_send> has been called on the |
3358 | watcher but the event has not yet been processed (or even noted) by the |
3490 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3413 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3545 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3414 | |
3546 | |
3415 | =item ev_feed_fd_event (loop, int fd, int revents) |
3547 | =item ev_feed_fd_event (loop, int fd, int revents) |
3416 | |
3548 | |
3417 | Feed an event on the given fd, as if a file descriptor backend detected |
3549 | Feed an event on the given fd, as if a file descriptor backend detected |
3418 | the given events it. |
3550 | the given events. |
3419 | |
3551 | |
3420 | =item ev_feed_signal_event (loop, int signum) |
3552 | =item ev_feed_signal_event (loop, int signum) |
3421 | |
3553 | |
3422 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3554 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3423 | which is async-safe. |
3555 | which is async-safe. |
… | |
… | |
3429 | |
3561 | |
3430 | This section explains some common idioms that are not immediately |
3562 | This section explains some common idioms that are not immediately |
3431 | obvious. Note that examples are sprinkled over the whole manual, and this |
3563 | obvious. Note that examples are sprinkled over the whole manual, and this |
3432 | section only contains stuff that wouldn't fit anywhere else. |
3564 | section only contains stuff that wouldn't fit anywhere else. |
3433 | |
3565 | |
3434 | =over 4 |
3566 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
3435 | |
3567 | |
3436 | =item Model/nested event loop invocations and exit conditions. |
3568 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3569 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3570 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3571 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3572 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3573 | data: |
|
|
3574 | |
|
|
3575 | struct my_io |
|
|
3576 | { |
|
|
3577 | ev_io io; |
|
|
3578 | int otherfd; |
|
|
3579 | void *somedata; |
|
|
3580 | struct whatever *mostinteresting; |
|
|
3581 | }; |
|
|
3582 | |
|
|
3583 | ... |
|
|
3584 | struct my_io w; |
|
|
3585 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3586 | |
|
|
3587 | And since your callback will be called with a pointer to the watcher, you |
|
|
3588 | can cast it back to your own type: |
|
|
3589 | |
|
|
3590 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3591 | { |
|
|
3592 | struct my_io *w = (struct my_io *)w_; |
|
|
3593 | ... |
|
|
3594 | } |
|
|
3595 | |
|
|
3596 | More interesting and less C-conformant ways of casting your callback |
|
|
3597 | function type instead have been omitted. |
|
|
3598 | |
|
|
3599 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3600 | |
|
|
3601 | Another common scenario is to use some data structure with multiple |
|
|
3602 | embedded watchers, in effect creating your own watcher that combines |
|
|
3603 | multiple libev event sources into one "super-watcher": |
|
|
3604 | |
|
|
3605 | struct my_biggy |
|
|
3606 | { |
|
|
3607 | int some_data; |
|
|
3608 | ev_timer t1; |
|
|
3609 | ev_timer t2; |
|
|
3610 | } |
|
|
3611 | |
|
|
3612 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3613 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3614 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3615 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3616 | real programmers): |
|
|
3617 | |
|
|
3618 | #include <stddef.h> |
|
|
3619 | |
|
|
3620 | static void |
|
|
3621 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3622 | { |
|
|
3623 | struct my_biggy big = (struct my_biggy *) |
|
|
3624 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3625 | } |
|
|
3626 | |
|
|
3627 | static void |
|
|
3628 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3629 | { |
|
|
3630 | struct my_biggy big = (struct my_biggy *) |
|
|
3631 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3632 | } |
|
|
3633 | |
|
|
3634 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3635 | |
|
|
3636 | Often you have structures like this in event-based programs: |
|
|
3637 | |
|
|
3638 | callback () |
|
|
3639 | { |
|
|
3640 | free (request); |
|
|
3641 | } |
|
|
3642 | |
|
|
3643 | request = start_new_request (..., callback); |
|
|
3644 | |
|
|
3645 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3646 | used to cancel the operation, or do other things with it. |
|
|
3647 | |
|
|
3648 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3649 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3650 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3651 | operation and simply invoke the callback with the result. |
|
|
3652 | |
|
|
3653 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3654 | has returned, so C<request> is not set. |
|
|
3655 | |
|
|
3656 | Even if you pass the request by some safer means to the callback, you |
|
|
3657 | might want to do something to the request after starting it, such as |
|
|
3658 | canceling it, which probably isn't working so well when the callback has |
|
|
3659 | already been invoked. |
|
|
3660 | |
|
|
3661 | A common way around all these issues is to make sure that |
|
|
3662 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3663 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3664 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3665 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3666 | pushing it into the pending queue: |
|
|
3667 | |
|
|
3668 | ev_set_cb (watcher, callback); |
|
|
3669 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3670 | |
|
|
3671 | This way, C<start_new_request> can safely return before the callback is |
|
|
3672 | invoked, while not delaying callback invocation too much. |
|
|
3673 | |
|
|
3674 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3437 | |
3675 | |
3438 | Often (especially in GUI toolkits) there are places where you have |
3676 | Often (especially in GUI toolkits) there are places where you have |
3439 | I<modal> interaction, which is most easily implemented by recursively |
3677 | I<modal> interaction, which is most easily implemented by recursively |
3440 | invoking C<ev_run>. |
3678 | invoking C<ev_run>. |
3441 | |
3679 | |
3442 | This brings the problem of exiting - a callback might want to finish the |
3680 | This brings the problem of exiting - a callback might want to finish the |
3443 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3681 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3444 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3682 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3445 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3683 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3446 | other combination: In these cases, C<ev_break> will not work alone. |
3684 | other combination: In these cases, a simple C<ev_break> will not work. |
3447 | |
3685 | |
3448 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3686 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3449 | invocation, and use a loop around C<ev_run> until the condition is |
3687 | invocation, and use a loop around C<ev_run> until the condition is |
3450 | triggered, using C<EVRUN_ONCE>: |
3688 | triggered, using C<EVRUN_ONCE>: |
3451 | |
3689 | |
… | |
… | |
3453 | int exit_main_loop = 0; |
3691 | int exit_main_loop = 0; |
3454 | |
3692 | |
3455 | while (!exit_main_loop) |
3693 | while (!exit_main_loop) |
3456 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3694 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3457 | |
3695 | |
3458 | // in a model watcher |
3696 | // in a modal watcher |
3459 | int exit_nested_loop = 0; |
3697 | int exit_nested_loop = 0; |
3460 | |
3698 | |
3461 | while (!exit_nested_loop) |
3699 | while (!exit_nested_loop) |
3462 | ev_run (EV_A_ EVRUN_ONCE); |
3700 | ev_run (EV_A_ EVRUN_ONCE); |
3463 | |
3701 | |
… | |
… | |
3470 | exit_main_loop = 1; |
3708 | exit_main_loop = 1; |
3471 | |
3709 | |
3472 | // exit both |
3710 | // exit both |
3473 | exit_main_loop = exit_nested_loop = 1; |
3711 | exit_main_loop = exit_nested_loop = 1; |
3474 | |
3712 | |
3475 | =back |
3713 | =head2 THREAD LOCKING EXAMPLE |
|
|
3714 | |
|
|
3715 | Here is a fictitious example of how to run an event loop in a different |
|
|
3716 | thread from where callbacks are being invoked and watchers are |
|
|
3717 | created/added/removed. |
|
|
3718 | |
|
|
3719 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3720 | which uses exactly this technique (which is suited for many high-level |
|
|
3721 | languages). |
|
|
3722 | |
|
|
3723 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3724 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3725 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3726 | |
|
|
3727 | First, you need to associate some data with the event loop: |
|
|
3728 | |
|
|
3729 | typedef struct { |
|
|
3730 | mutex_t lock; /* global loop lock */ |
|
|
3731 | ev_async async_w; |
|
|
3732 | thread_t tid; |
|
|
3733 | cond_t invoke_cv; |
|
|
3734 | } userdata; |
|
|
3735 | |
|
|
3736 | void prepare_loop (EV_P) |
|
|
3737 | { |
|
|
3738 | // for simplicity, we use a static userdata struct. |
|
|
3739 | static userdata u; |
|
|
3740 | |
|
|
3741 | ev_async_init (&u->async_w, async_cb); |
|
|
3742 | ev_async_start (EV_A_ &u->async_w); |
|
|
3743 | |
|
|
3744 | pthread_mutex_init (&u->lock, 0); |
|
|
3745 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3746 | |
|
|
3747 | // now associate this with the loop |
|
|
3748 | ev_set_userdata (EV_A_ u); |
|
|
3749 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3750 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3751 | |
|
|
3752 | // then create the thread running ev_run |
|
|
3753 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3754 | } |
|
|
3755 | |
|
|
3756 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3757 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3758 | that might have been added: |
|
|
3759 | |
|
|
3760 | static void |
|
|
3761 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3762 | { |
|
|
3763 | // just used for the side effects |
|
|
3764 | } |
|
|
3765 | |
|
|
3766 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3767 | protecting the loop data, respectively. |
|
|
3768 | |
|
|
3769 | static void |
|
|
3770 | l_release (EV_P) |
|
|
3771 | { |
|
|
3772 | userdata *u = ev_userdata (EV_A); |
|
|
3773 | pthread_mutex_unlock (&u->lock); |
|
|
3774 | } |
|
|
3775 | |
|
|
3776 | static void |
|
|
3777 | l_acquire (EV_P) |
|
|
3778 | { |
|
|
3779 | userdata *u = ev_userdata (EV_A); |
|
|
3780 | pthread_mutex_lock (&u->lock); |
|
|
3781 | } |
|
|
3782 | |
|
|
3783 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3784 | into C<ev_run>: |
|
|
3785 | |
|
|
3786 | void * |
|
|
3787 | l_run (void *thr_arg) |
|
|
3788 | { |
|
|
3789 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3790 | |
|
|
3791 | l_acquire (EV_A); |
|
|
3792 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3793 | ev_run (EV_A_ 0); |
|
|
3794 | l_release (EV_A); |
|
|
3795 | |
|
|
3796 | return 0; |
|
|
3797 | } |
|
|
3798 | |
|
|
3799 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3800 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3801 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3802 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3803 | and b) skipping inter-thread-communication when there are no pending |
|
|
3804 | watchers is very beneficial): |
|
|
3805 | |
|
|
3806 | static void |
|
|
3807 | l_invoke (EV_P) |
|
|
3808 | { |
|
|
3809 | userdata *u = ev_userdata (EV_A); |
|
|
3810 | |
|
|
3811 | while (ev_pending_count (EV_A)) |
|
|
3812 | { |
|
|
3813 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3814 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3815 | } |
|
|
3816 | } |
|
|
3817 | |
|
|
3818 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3819 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3820 | thread to continue: |
|
|
3821 | |
|
|
3822 | static void |
|
|
3823 | real_invoke_pending (EV_P) |
|
|
3824 | { |
|
|
3825 | userdata *u = ev_userdata (EV_A); |
|
|
3826 | |
|
|
3827 | pthread_mutex_lock (&u->lock); |
|
|
3828 | ev_invoke_pending (EV_A); |
|
|
3829 | pthread_cond_signal (&u->invoke_cv); |
|
|
3830 | pthread_mutex_unlock (&u->lock); |
|
|
3831 | } |
|
|
3832 | |
|
|
3833 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3834 | event loop, you will now have to lock: |
|
|
3835 | |
|
|
3836 | ev_timer timeout_watcher; |
|
|
3837 | userdata *u = ev_userdata (EV_A); |
|
|
3838 | |
|
|
3839 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3840 | |
|
|
3841 | pthread_mutex_lock (&u->lock); |
|
|
3842 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3843 | ev_async_send (EV_A_ &u->async_w); |
|
|
3844 | pthread_mutex_unlock (&u->lock); |
|
|
3845 | |
|
|
3846 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3847 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3848 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3849 | watchers in the next event loop iteration. |
|
|
3850 | |
|
|
3851 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3852 | |
|
|
3853 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3854 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3855 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3856 | doesn't need callbacks anymore. |
|
|
3857 | |
|
|
3858 | Imagine you have coroutines that you can switch to using a function |
|
|
3859 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3860 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3861 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3862 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3863 | the differing C<;> conventions): |
|
|
3864 | |
|
|
3865 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3866 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3867 | |
|
|
3868 | That means instead of having a C callback function, you store the |
|
|
3869 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3870 | your callback, you instead have it switch to that coroutine. |
|
|
3871 | |
|
|
3872 | A coroutine might now wait for an event with a function called |
|
|
3873 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3874 | matter when, or whether the watcher is active or not when this function is |
|
|
3875 | called): |
|
|
3876 | |
|
|
3877 | void |
|
|
3878 | wait_for_event (ev_watcher *w) |
|
|
3879 | { |
|
|
3880 | ev_set_cb (w, current_coro); |
|
|
3881 | switch_to (libev_coro); |
|
|
3882 | } |
|
|
3883 | |
|
|
3884 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3885 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3886 | this or any other coroutine. |
|
|
3887 | |
|
|
3888 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3889 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3890 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3891 | any waiters. |
|
|
3892 | |
|
|
3893 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
|
|
3894 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3895 | |
|
|
3896 | // my_ev.h |
|
|
3897 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3898 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3899 | #include "../libev/ev.h" |
|
|
3900 | |
|
|
3901 | // my_ev.c |
|
|
3902 | #define EV_H "my_ev.h" |
|
|
3903 | #include "../libev/ev.c" |
|
|
3904 | |
|
|
3905 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3906 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3907 | can even use F<ev.h> as header file name directly. |
3476 | |
3908 | |
3477 | |
3909 | |
3478 | =head1 LIBEVENT EMULATION |
3910 | =head1 LIBEVENT EMULATION |
3479 | |
3911 | |
3480 | Libev offers a compatibility emulation layer for libevent. It cannot |
3912 | Libev offers a compatibility emulation layer for libevent. It cannot |
… | |
… | |
3509 | to use the libev header file and library. |
3941 | to use the libev header file and library. |
3510 | |
3942 | |
3511 | =back |
3943 | =back |
3512 | |
3944 | |
3513 | =head1 C++ SUPPORT |
3945 | =head1 C++ SUPPORT |
|
|
3946 | |
|
|
3947 | =head2 C API |
|
|
3948 | |
|
|
3949 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3950 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3951 | will work fine. |
|
|
3952 | |
|
|
3953 | Proper exception specifications might have to be added to callbacks passed |
|
|
3954 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3955 | other callbacks (allocator, syserr, loop acquire/release and periodic |
|
|
3956 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3957 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3958 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3959 | |
|
|
3960 | static void |
|
|
3961 | fatal_error (const char *msg) EV_THROW |
|
|
3962 | { |
|
|
3963 | perror (msg); |
|
|
3964 | abort (); |
|
|
3965 | } |
|
|
3966 | |
|
|
3967 | ... |
|
|
3968 | ev_set_syserr_cb (fatal_error); |
|
|
3969 | |
|
|
3970 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3971 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
3972 | because it runs cleanup watchers). |
|
|
3973 | |
|
|
3974 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3975 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3976 | throwing exceptions through C libraries (most do). |
|
|
3977 | |
|
|
3978 | =head2 C++ API |
3514 | |
3979 | |
3515 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3980 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3516 | you to use some convenience methods to start/stop watchers and also change |
3981 | you to use some convenience methods to start/stop watchers and also change |
3517 | the callback model to a model using method callbacks on objects. |
3982 | the callback model to a model using method callbacks on objects. |
3518 | |
3983 | |
… | |
… | |
3534 | with C<operator ()> can be used as callbacks. Other types should be easy |
3999 | with C<operator ()> can be used as callbacks. Other types should be easy |
3535 | to add as long as they only need one additional pointer for context. If |
4000 | to add as long as they only need one additional pointer for context. If |
3536 | you need support for other types of functors please contact the author |
4001 | you need support for other types of functors please contact the author |
3537 | (preferably after implementing it). |
4002 | (preferably after implementing it). |
3538 | |
4003 | |
|
|
4004 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4005 | conventions as your C compiler (for static member functions), or you have |
|
|
4006 | to embed libev and compile libev itself as C++. |
|
|
4007 | |
3539 | Here is a list of things available in the C<ev> namespace: |
4008 | Here is a list of things available in the C<ev> namespace: |
3540 | |
4009 | |
3541 | =over 4 |
4010 | =over 4 |
3542 | |
4011 | |
3543 | =item C<ev::READ>, C<ev::WRITE> etc. |
4012 | =item C<ev::READ>, C<ev::WRITE> etc. |
… | |
… | |
3552 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4021 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3553 | |
4022 | |
3554 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4023 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3555 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4024 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3556 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4025 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3557 | defines by many implementations. |
4026 | defined by many implementations. |
3558 | |
4027 | |
3559 | All of those classes have these methods: |
4028 | All of those classes have these methods: |
3560 | |
4029 | |
3561 | =over 4 |
4030 | =over 4 |
3562 | |
4031 | |
… | |
… | |
3652 | Associates a different C<struct ev_loop> with this watcher. You can only |
4121 | Associates a different C<struct ev_loop> with this watcher. You can only |
3653 | do this when the watcher is inactive (and not pending either). |
4122 | do this when the watcher is inactive (and not pending either). |
3654 | |
4123 | |
3655 | =item w->set ([arguments]) |
4124 | =item w->set ([arguments]) |
3656 | |
4125 | |
3657 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4126 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
3658 | method or a suitable start method must be called at least once. Unlike the |
4127 | with the same arguments. Either this method or a suitable start method |
3659 | C counterpart, an active watcher gets automatically stopped and restarted |
4128 | must be called at least once. Unlike the C counterpart, an active watcher |
3660 | when reconfiguring it with this method. |
4129 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4130 | method. |
|
|
4131 | |
|
|
4132 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4133 | clashing with the C<set (loop)> method. |
3661 | |
4134 | |
3662 | =item w->start () |
4135 | =item w->start () |
3663 | |
4136 | |
3664 | Starts the watcher. Note that there is no C<loop> argument, as the |
4137 | Starts the watcher. Note that there is no C<loop> argument, as the |
3665 | constructor already stores the event loop. |
4138 | constructor already stores the event loop. |
… | |
… | |
3695 | watchers in the constructor. |
4168 | watchers in the constructor. |
3696 | |
4169 | |
3697 | class myclass |
4170 | class myclass |
3698 | { |
4171 | { |
3699 | ev::io io ; void io_cb (ev::io &w, int revents); |
4172 | ev::io io ; void io_cb (ev::io &w, int revents); |
3700 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4173 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3701 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4174 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3702 | |
4175 | |
3703 | myclass (int fd) |
4176 | myclass (int fd) |
3704 | { |
4177 | { |
3705 | io .set <myclass, &myclass::io_cb > (this); |
4178 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3756 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4229 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3757 | |
4230 | |
3758 | =item D |
4231 | =item D |
3759 | |
4232 | |
3760 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4233 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3761 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4234 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3762 | |
4235 | |
3763 | =item Ocaml |
4236 | =item Ocaml |
3764 | |
4237 | |
3765 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4238 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3766 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4239 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3769 | |
4242 | |
3770 | Brian Maher has written a partial interface to libev for lua (at the |
4243 | Brian Maher has written a partial interface to libev for lua (at the |
3771 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4244 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3772 | L<http://github.com/brimworks/lua-ev>. |
4245 | L<http://github.com/brimworks/lua-ev>. |
3773 | |
4246 | |
|
|
4247 | =item Javascript |
|
|
4248 | |
|
|
4249 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4250 | |
|
|
4251 | =item Others |
|
|
4252 | |
|
|
4253 | There are others, and I stopped counting. |
|
|
4254 | |
3774 | =back |
4255 | =back |
3775 | |
4256 | |
3776 | |
4257 | |
3777 | =head1 MACRO MAGIC |
4258 | =head1 MACRO MAGIC |
3778 | |
4259 | |
… | |
… | |
3814 | suitable for use with C<EV_A>. |
4295 | suitable for use with C<EV_A>. |
3815 | |
4296 | |
3816 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4297 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3817 | |
4298 | |
3818 | Similar to the other two macros, this gives you the value of the default |
4299 | Similar to the other two macros, this gives you the value of the default |
3819 | loop, if multiple loops are supported ("ev loop default"). |
4300 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4301 | will be initialised if it isn't already initialised. |
|
|
4302 | |
|
|
4303 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4304 | to initialise the loop somewhere. |
3820 | |
4305 | |
3821 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4306 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3822 | |
4307 | |
3823 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4308 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3824 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4309 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3969 | supported). It will also not define any of the structs usually found in |
4454 | supported). It will also not define any of the structs usually found in |
3970 | F<event.h> that are not directly supported by the libev core alone. |
4455 | F<event.h> that are not directly supported by the libev core alone. |
3971 | |
4456 | |
3972 | In standalone mode, libev will still try to automatically deduce the |
4457 | In standalone mode, libev will still try to automatically deduce the |
3973 | configuration, but has to be more conservative. |
4458 | configuration, but has to be more conservative. |
|
|
4459 | |
|
|
4460 | =item EV_USE_FLOOR |
|
|
4461 | |
|
|
4462 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4463 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4464 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4465 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4466 | function is not available will fail, so the safe default is to not enable |
|
|
4467 | this. |
3974 | |
4468 | |
3975 | =item EV_USE_MONOTONIC |
4469 | =item EV_USE_MONOTONIC |
3976 | |
4470 | |
3977 | If defined to be C<1>, libev will try to detect the availability of the |
4471 | If defined to be C<1>, libev will try to detect the availability of the |
3978 | monotonic clock option at both compile time and runtime. Otherwise no |
4472 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
4063 | |
4557 | |
4064 | If programs implement their own fd to handle mapping on win32, then this |
4558 | If programs implement their own fd to handle mapping on win32, then this |
4065 | macro can be used to override the C<close> function, useful to unregister |
4559 | macro can be used to override the C<close> function, useful to unregister |
4066 | file descriptors again. Note that the replacement function has to close |
4560 | file descriptors again. Note that the replacement function has to close |
4067 | the underlying OS handle. |
4561 | the underlying OS handle. |
|
|
4562 | |
|
|
4563 | =item EV_USE_WSASOCKET |
|
|
4564 | |
|
|
4565 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4566 | communication socket, which works better in some environments. Otherwise, |
|
|
4567 | the normal C<socket> function will be used, which works better in other |
|
|
4568 | environments. |
4068 | |
4569 | |
4069 | =item EV_USE_POLL |
4570 | =item EV_USE_POLL |
4070 | |
4571 | |
4071 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4572 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4072 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4573 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
4108 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4609 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4109 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4610 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4110 | be detected at runtime. If undefined, it will be enabled if the headers |
4611 | be detected at runtime. If undefined, it will be enabled if the headers |
4111 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4612 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4112 | |
4613 | |
|
|
4614 | =item EV_NO_SMP |
|
|
4615 | |
|
|
4616 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4617 | between threads, that is, threads can be used, but threads never run on |
|
|
4618 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4619 | and makes libev faster. |
|
|
4620 | |
|
|
4621 | =item EV_NO_THREADS |
|
|
4622 | |
|
|
4623 | If defined to be C<1>, libev will assume that it will never be called |
|
|
4624 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
|
|
4625 | above. This reduces dependencies and makes libev faster. |
|
|
4626 | |
4113 | =item EV_ATOMIC_T |
4627 | =item EV_ATOMIC_T |
4114 | |
4628 | |
4115 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4629 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4116 | access is atomic with respect to other threads or signal contexts. No such |
4630 | access is atomic with respect to other threads or signal contexts. No |
4117 | type is easily found in the C language, so you can provide your own type |
4631 | such type is easily found in the C language, so you can provide your own |
4118 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4632 | type that you know is safe for your purposes. It is used both for signal |
4119 | as well as for signal and thread safety in C<ev_async> watchers. |
4633 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4634 | watchers. |
4120 | |
4635 | |
4121 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4636 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4122 | (from F<signal.h>), which is usually good enough on most platforms. |
4637 | (from F<signal.h>), which is usually good enough on most platforms. |
4123 | |
4638 | |
4124 | =item EV_H (h) |
4639 | =item EV_H (h) |
… | |
… | |
4151 | will have the C<struct ev_loop *> as first argument, and you can create |
4666 | will have the C<struct ev_loop *> as first argument, and you can create |
4152 | additional independent event loops. Otherwise there will be no support |
4667 | additional independent event loops. Otherwise there will be no support |
4153 | for multiple event loops and there is no first event loop pointer |
4668 | for multiple event loops and there is no first event loop pointer |
4154 | argument. Instead, all functions act on the single default loop. |
4669 | argument. Instead, all functions act on the single default loop. |
4155 | |
4670 | |
|
|
4671 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4672 | default loop when multiplicity is switched off - you always have to |
|
|
4673 | initialise the loop manually in this case. |
|
|
4674 | |
4156 | =item EV_MINPRI |
4675 | =item EV_MINPRI |
4157 | |
4676 | |
4158 | =item EV_MAXPRI |
4677 | =item EV_MAXPRI |
4159 | |
4678 | |
4160 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4679 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4196 | #define EV_USE_POLL 1 |
4715 | #define EV_USE_POLL 1 |
4197 | #define EV_CHILD_ENABLE 1 |
4716 | #define EV_CHILD_ENABLE 1 |
4198 | #define EV_ASYNC_ENABLE 1 |
4717 | #define EV_ASYNC_ENABLE 1 |
4199 | |
4718 | |
4200 | The actual value is a bitset, it can be a combination of the following |
4719 | The actual value is a bitset, it can be a combination of the following |
4201 | values: |
4720 | values (by default, all of these are enabled): |
4202 | |
4721 | |
4203 | =over 4 |
4722 | =over 4 |
4204 | |
4723 | |
4205 | =item C<1> - faster/larger code |
4724 | =item C<1> - faster/larger code |
4206 | |
4725 | |
… | |
… | |
4210 | code size by roughly 30% on amd64). |
4729 | code size by roughly 30% on amd64). |
4211 | |
4730 | |
4212 | When optimising for size, use of compiler flags such as C<-Os> with |
4731 | When optimising for size, use of compiler flags such as C<-Os> with |
4213 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4732 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4214 | assertions. |
4733 | assertions. |
|
|
4734 | |
|
|
4735 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4736 | (e.g. gcc with C<-Os>). |
4215 | |
4737 | |
4216 | =item C<2> - faster/larger data structures |
4738 | =item C<2> - faster/larger data structures |
4217 | |
4739 | |
4218 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4740 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4219 | hash table sizes and so on. This will usually further increase code size |
4741 | hash table sizes and so on. This will usually further increase code size |
4220 | and can additionally have an effect on the size of data structures at |
4742 | and can additionally have an effect on the size of data structures at |
4221 | runtime. |
4743 | runtime. |
4222 | |
4744 | |
|
|
4745 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4746 | (e.g. gcc with C<-Os>). |
|
|
4747 | |
4223 | =item C<4> - full API configuration |
4748 | =item C<4> - full API configuration |
4224 | |
4749 | |
4225 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4750 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4226 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4751 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4227 | |
4752 | |
… | |
… | |
4257 | |
4782 | |
4258 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4783 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4259 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4784 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4260 | your program might be left out as well - a binary starting a timer and an |
4785 | your program might be left out as well - a binary starting a timer and an |
4261 | I/O watcher then might come out at only 5Kb. |
4786 | I/O watcher then might come out at only 5Kb. |
|
|
4787 | |
|
|
4788 | =item EV_API_STATIC |
|
|
4789 | |
|
|
4790 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4791 | will have static linkage. This means that libev will not export any |
|
|
4792 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4793 | when you embed libev, only want to use libev functions in a single file, |
|
|
4794 | and do not want its identifiers to be visible. |
|
|
4795 | |
|
|
4796 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4797 | wants to use libev. |
|
|
4798 | |
|
|
4799 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4800 | doesn't support the required declaration syntax. |
4262 | |
4801 | |
4263 | =item EV_AVOID_STDIO |
4802 | =item EV_AVOID_STDIO |
4264 | |
4803 | |
4265 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4804 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4266 | functions (printf, scanf, perror etc.). This will increase the code size |
4805 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4410 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4949 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4411 | |
4950 | |
4412 | #include "ev_cpp.h" |
4951 | #include "ev_cpp.h" |
4413 | #include "ev.c" |
4952 | #include "ev.c" |
4414 | |
4953 | |
4415 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4954 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4416 | |
4955 | |
4417 | =head2 THREADS AND COROUTINES |
4956 | =head2 THREADS AND COROUTINES |
4418 | |
4957 | |
4419 | =head3 THREADS |
4958 | =head3 THREADS |
4420 | |
4959 | |
… | |
… | |
4471 | default loop and triggering an C<ev_async> watcher from the default loop |
5010 | default loop and triggering an C<ev_async> watcher from the default loop |
4472 | watcher callback into the event loop interested in the signal. |
5011 | watcher callback into the event loop interested in the signal. |
4473 | |
5012 | |
4474 | =back |
5013 | =back |
4475 | |
5014 | |
4476 | =head4 THREAD LOCKING EXAMPLE |
5015 | See also L</THREAD LOCKING EXAMPLE>. |
4477 | |
|
|
4478 | Here is a fictitious example of how to run an event loop in a different |
|
|
4479 | thread than where callbacks are being invoked and watchers are |
|
|
4480 | created/added/removed. |
|
|
4481 | |
|
|
4482 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4483 | which uses exactly this technique (which is suited for many high-level |
|
|
4484 | languages). |
|
|
4485 | |
|
|
4486 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4487 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4488 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4489 | |
|
|
4490 | First, you need to associate some data with the event loop: |
|
|
4491 | |
|
|
4492 | typedef struct { |
|
|
4493 | mutex_t lock; /* global loop lock */ |
|
|
4494 | ev_async async_w; |
|
|
4495 | thread_t tid; |
|
|
4496 | cond_t invoke_cv; |
|
|
4497 | } userdata; |
|
|
4498 | |
|
|
4499 | void prepare_loop (EV_P) |
|
|
4500 | { |
|
|
4501 | // for simplicity, we use a static userdata struct. |
|
|
4502 | static userdata u; |
|
|
4503 | |
|
|
4504 | ev_async_init (&u->async_w, async_cb); |
|
|
4505 | ev_async_start (EV_A_ &u->async_w); |
|
|
4506 | |
|
|
4507 | pthread_mutex_init (&u->lock, 0); |
|
|
4508 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4509 | |
|
|
4510 | // now associate this with the loop |
|
|
4511 | ev_set_userdata (EV_A_ u); |
|
|
4512 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4513 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4514 | |
|
|
4515 | // then create the thread running ev_loop |
|
|
4516 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4517 | } |
|
|
4518 | |
|
|
4519 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4520 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4521 | that might have been added: |
|
|
4522 | |
|
|
4523 | static void |
|
|
4524 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4525 | { |
|
|
4526 | // just used for the side effects |
|
|
4527 | } |
|
|
4528 | |
|
|
4529 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4530 | protecting the loop data, respectively. |
|
|
4531 | |
|
|
4532 | static void |
|
|
4533 | l_release (EV_P) |
|
|
4534 | { |
|
|
4535 | userdata *u = ev_userdata (EV_A); |
|
|
4536 | pthread_mutex_unlock (&u->lock); |
|
|
4537 | } |
|
|
4538 | |
|
|
4539 | static void |
|
|
4540 | l_acquire (EV_P) |
|
|
4541 | { |
|
|
4542 | userdata *u = ev_userdata (EV_A); |
|
|
4543 | pthread_mutex_lock (&u->lock); |
|
|
4544 | } |
|
|
4545 | |
|
|
4546 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4547 | into C<ev_run>: |
|
|
4548 | |
|
|
4549 | void * |
|
|
4550 | l_run (void *thr_arg) |
|
|
4551 | { |
|
|
4552 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4553 | |
|
|
4554 | l_acquire (EV_A); |
|
|
4555 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4556 | ev_run (EV_A_ 0); |
|
|
4557 | l_release (EV_A); |
|
|
4558 | |
|
|
4559 | return 0; |
|
|
4560 | } |
|
|
4561 | |
|
|
4562 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4563 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4564 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4565 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4566 | and b) skipping inter-thread-communication when there are no pending |
|
|
4567 | watchers is very beneficial): |
|
|
4568 | |
|
|
4569 | static void |
|
|
4570 | l_invoke (EV_P) |
|
|
4571 | { |
|
|
4572 | userdata *u = ev_userdata (EV_A); |
|
|
4573 | |
|
|
4574 | while (ev_pending_count (EV_A)) |
|
|
4575 | { |
|
|
4576 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4577 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4578 | } |
|
|
4579 | } |
|
|
4580 | |
|
|
4581 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4582 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4583 | thread to continue: |
|
|
4584 | |
|
|
4585 | static void |
|
|
4586 | real_invoke_pending (EV_P) |
|
|
4587 | { |
|
|
4588 | userdata *u = ev_userdata (EV_A); |
|
|
4589 | |
|
|
4590 | pthread_mutex_lock (&u->lock); |
|
|
4591 | ev_invoke_pending (EV_A); |
|
|
4592 | pthread_cond_signal (&u->invoke_cv); |
|
|
4593 | pthread_mutex_unlock (&u->lock); |
|
|
4594 | } |
|
|
4595 | |
|
|
4596 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4597 | event loop, you will now have to lock: |
|
|
4598 | |
|
|
4599 | ev_timer timeout_watcher; |
|
|
4600 | userdata *u = ev_userdata (EV_A); |
|
|
4601 | |
|
|
4602 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4603 | |
|
|
4604 | pthread_mutex_lock (&u->lock); |
|
|
4605 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4606 | ev_async_send (EV_A_ &u->async_w); |
|
|
4607 | pthread_mutex_unlock (&u->lock); |
|
|
4608 | |
|
|
4609 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4610 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4611 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4612 | watchers in the next event loop iteration. |
|
|
4613 | |
5016 | |
4614 | =head3 COROUTINES |
5017 | =head3 COROUTINES |
4615 | |
5018 | |
4616 | Libev is very accommodating to coroutines ("cooperative threads"): |
5019 | Libev is very accommodating to coroutines ("cooperative threads"): |
4617 | libev fully supports nesting calls to its functions from different |
5020 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4782 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5185 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4783 | model. Libev still offers limited functionality on this platform in |
5186 | model. Libev still offers limited functionality on this platform in |
4784 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5187 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4785 | descriptors. This only applies when using Win32 natively, not when using |
5188 | descriptors. This only applies when using Win32 natively, not when using |
4786 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5189 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4787 | as every compielr comes with a slightly differently broken/incompatible |
5190 | as every compiler comes with a slightly differently broken/incompatible |
4788 | environment. |
5191 | environment. |
4789 | |
5192 | |
4790 | Lifting these limitations would basically require the full |
5193 | Lifting these limitations would basically require the full |
4791 | re-implementation of the I/O system. If you are into this kind of thing, |
5194 | re-implementation of the I/O system. If you are into this kind of thing, |
4792 | then note that glib does exactly that for you in a very portable way (note |
5195 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4908 | thread" or will block signals process-wide, both behaviours would |
5311 | thread" or will block signals process-wide, both behaviours would |
4909 | be compatible with libev. Interaction between C<sigprocmask> and |
5312 | be compatible with libev. Interaction between C<sigprocmask> and |
4910 | C<pthread_sigmask> could complicate things, however. |
5313 | C<pthread_sigmask> could complicate things, however. |
4911 | |
5314 | |
4912 | The most portable way to handle signals is to block signals in all threads |
5315 | The most portable way to handle signals is to block signals in all threads |
4913 | except the initial one, and run the default loop in the initial thread as |
5316 | except the initial one, and run the signal handling loop in the initial |
4914 | well. |
5317 | thread as well. |
4915 | |
5318 | |
4916 | =item C<long> must be large enough for common memory allocation sizes |
5319 | =item C<long> must be large enough for common memory allocation sizes |
4917 | |
5320 | |
4918 | To improve portability and simplify its API, libev uses C<long> internally |
5321 | To improve portability and simplify its API, libev uses C<long> internally |
4919 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5322 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
4925 | |
5328 | |
4926 | The type C<double> is used to represent timestamps. It is required to |
5329 | The type C<double> is used to represent timestamps. It is required to |
4927 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5330 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4928 | good enough for at least into the year 4000 with millisecond accuracy |
5331 | good enough for at least into the year 4000 with millisecond accuracy |
4929 | (the design goal for libev). This requirement is overfulfilled by |
5332 | (the design goal for libev). This requirement is overfulfilled by |
4930 | implementations using IEEE 754, which is basically all existing ones. With |
5333 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5334 | |
4931 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5335 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5336 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5337 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5338 | something like that, just kidding). |
4932 | |
5339 | |
4933 | =back |
5340 | =back |
4934 | |
5341 | |
4935 | If you know of other additional requirements drop me a note. |
5342 | If you know of other additional requirements drop me a note. |
4936 | |
5343 | |
… | |
… | |
4998 | =item Processing ev_async_send: O(number_of_async_watchers) |
5405 | =item Processing ev_async_send: O(number_of_async_watchers) |
4999 | |
5406 | |
5000 | =item Processing signals: O(max_signal_number) |
5407 | =item Processing signals: O(max_signal_number) |
5001 | |
5408 | |
5002 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5409 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5003 | calls in the current loop iteration. Checking for async and signal events |
5410 | calls in the current loop iteration and the loop is currently |
|
|
5411 | blocked. Checking for async and signal events involves iterating over all |
5004 | involves iterating over all running async watchers or all signal numbers. |
5412 | running async watchers or all signal numbers. |
5005 | |
5413 | |
5006 | =back |
5414 | =back |
5007 | |
5415 | |
5008 | |
5416 | |
5009 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5417 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
5018 | =over 4 |
5426 | =over 4 |
5019 | |
5427 | |
5020 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5428 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5021 | |
5429 | |
5022 | The backward compatibility mechanism can be controlled by |
5430 | The backward compatibility mechanism can be controlled by |
5023 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
5431 | C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING> |
5024 | section. |
5432 | section. |
5025 | |
5433 | |
5026 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5434 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5027 | |
5435 | |
5028 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5436 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
… | |
… | |
5071 | =over 4 |
5479 | =over 4 |
5072 | |
5480 | |
5073 | =item active |
5481 | =item active |
5074 | |
5482 | |
5075 | A watcher is active as long as it has been started and not yet stopped. |
5483 | A watcher is active as long as it has been started and not yet stopped. |
5076 | See L<WATCHER STATES> for details. |
5484 | See L</WATCHER STATES> for details. |
5077 | |
5485 | |
5078 | =item application |
5486 | =item application |
5079 | |
5487 | |
5080 | In this document, an application is whatever is using libev. |
5488 | In this document, an application is whatever is using libev. |
5081 | |
5489 | |
… | |
… | |
5117 | watchers and events. |
5525 | watchers and events. |
5118 | |
5526 | |
5119 | =item pending |
5527 | =item pending |
5120 | |
5528 | |
5121 | A watcher is pending as soon as the corresponding event has been |
5529 | A watcher is pending as soon as the corresponding event has been |
5122 | detected. See L<WATCHER STATES> for details. |
5530 | detected. See L</WATCHER STATES> for details. |
5123 | |
5531 | |
5124 | =item real time |
5532 | =item real time |
5125 | |
5533 | |
5126 | The physical time that is observed. It is apparently strictly monotonic :) |
5534 | The physical time that is observed. It is apparently strictly monotonic :) |
5127 | |
5535 | |
5128 | =item wall-clock time |
5536 | =item wall-clock time |
5129 | |
5537 | |
5130 | The time and date as shown on clocks. Unlike real time, it can actually |
5538 | The time and date as shown on clocks. Unlike real time, it can actually |
5131 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5539 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5132 | clock. |
5540 | clock. |
5133 | |
5541 | |
5134 | =item watcher |
5542 | =item watcher |
5135 | |
5543 | |
5136 | A data structure that describes interest in certain events. Watchers need |
5544 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5139 | =back |
5547 | =back |
5140 | |
5548 | |
5141 | =head1 AUTHOR |
5549 | =head1 AUTHOR |
5142 | |
5550 | |
5143 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5551 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5144 | Magnusson and Emanuele Giaquinta. |
5552 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5145 | |
5553 | |