… | |
… | |
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 | |
… | |
… | |
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 |
… | |
… | |
299 | } |
305 | } |
300 | |
306 | |
301 | ... |
307 | ... |
302 | ev_set_syserr_cb (fatal_error); |
308 | ev_set_syserr_cb (fatal_error); |
303 | |
309 | |
|
|
310 | =item ev_feed_signal (int signum) |
|
|
311 | |
|
|
312 | This function can be used to "simulate" a signal receive. It is completely |
|
|
313 | safe to call this function at any time, from any context, including signal |
|
|
314 | handlers or random threads. |
|
|
315 | |
|
|
316 | Its main use is to customise signal handling in your process, especially |
|
|
317 | in the presence of threads. For example, you could block signals |
|
|
318 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
|
|
319 | creating any loops), and in one thread, use C<sigwait> or any other |
|
|
320 | mechanism to wait for signals, then "deliver" them to libev by calling |
|
|
321 | C<ev_feed_signal>. |
|
|
322 | |
304 | =back |
323 | =back |
305 | |
324 | |
306 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
325 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
307 | |
326 | |
308 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
327 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
… | |
… | |
419 | |
438 | |
420 | Signalfd will not be used by default as this changes your signal mask, and |
439 | Signalfd will not be used by default as this changes your signal mask, and |
421 | there are a lot of shoddy libraries and programs (glib's threadpool for |
440 | there are a lot of shoddy libraries and programs (glib's threadpool for |
422 | example) that can't properly initialise their signal masks. |
441 | example) that can't properly initialise their signal masks. |
423 | |
442 | |
|
|
443 | =item C<EVFLAG_NOSIGMASK> |
|
|
444 | |
|
|
445 | When this flag is specified, then libev will avoid to modify the signal |
|
|
446 | mask. Specifically, this means you have to make sure signals are unblocked |
|
|
447 | when you want to receive them. |
|
|
448 | |
|
|
449 | This behaviour is useful when you want to do your own signal handling, or |
|
|
450 | want to handle signals only in specific threads and want to avoid libev |
|
|
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. |
|
|
455 | |
|
|
456 | This flag's behaviour will become the default in future versions of libev. |
|
|
457 | |
424 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
425 | |
459 | |
426 | This is your standard select(2) backend. Not I<completely> standard, as |
460 | This is your standard select(2) backend. Not I<completely> standard, as |
427 | libev tries to roll its own fd_set with no limits on the number of fds, |
461 | libev tries to roll its own fd_set with no limits on the number of fds, |
428 | but if that fails, expect a fairly low limit on the number of fds when |
462 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
455 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
456 | |
490 | |
457 | 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 |
458 | kernels). |
492 | kernels). |
459 | |
493 | |
460 | 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 |
461 | but it scales phenomenally better. While poll and select usually scale |
495 | it scales phenomenally better. While poll and select usually scale like |
462 | 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 |
463 | epoll scales either O(1) or O(active_fds). |
497 | fd), epoll scales either O(1) or O(active_fds). |
464 | |
498 | |
465 | The epoll mechanism deserves honorable mention as the most misdesigned |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
466 | of the more advanced event mechanisms: mere annoyances include silently |
500 | of the more advanced event mechanisms: mere annoyances include silently |
467 | dropping file descriptors, requiring a system call per change per file |
501 | dropping file descriptors, requiring a system call per change per file |
468 | descriptor (and unnecessary guessing of parameters), problems with dup, |
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
… | |
… | |
471 | 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 |
472 | 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 |
473 | set, which can take considerable time (one syscall per file descriptor) |
507 | set, which can take considerable time (one syscall per file descriptor) |
474 | and is of course hard to detect. |
508 | and is of course hard to detect. |
475 | |
509 | |
476 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
477 | 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 |
478 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
479 | 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 |
480 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
481 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
482 | 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 |
483 | 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 |
484 | perfectly fine with C<select> (files, many character devices...). |
521 | perfectly fine with C<select> (files, many character devices...). |
485 | |
522 | |
486 | 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... |
487 | |
526 | |
488 | 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 |
489 | 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 |
490 | 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 |
491 | 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 |
… | |
… | |
528 | |
567 | |
529 | 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 |
530 | 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 |
531 | 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 |
532 | 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 |
533 | 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 |
534 | 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 |
535 | cases |
574 | drops fds silently in similarly hard-to-detect cases |
536 | |
575 | |
537 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
538 | |
577 | |
539 | While nominally embeddable in other event loops, this doesn't work |
578 | While nominally embeddable in other event loops, this doesn't work |
540 | 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 |
… | |
… | |
557 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
596 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
558 | |
597 | |
559 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
598 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
560 | it's really slow, but it still scales very well (O(active_fds)). |
599 | it's really slow, but it still scales very well (O(active_fds)). |
561 | |
600 | |
562 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
563 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
564 | blocking when no data (or space) is available. |
|
|
565 | |
|
|
566 | While this backend scales well, it requires one system call per active |
601 | While this backend scales well, it requires one system call per active |
567 | file descriptor per loop iteration. For small and medium numbers of file |
602 | file descriptor per loop iteration. For small and medium numbers of file |
568 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
603 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
569 | might perform better. |
604 | might perform better. |
570 | |
605 | |
571 | On the positive side, with the exception of the spurious readiness |
606 | On the positive side, this backend actually performed fully to |
572 | notifications, this backend actually performed fully to specification |
|
|
573 | in all tests and is fully embeddable, which is a rare feat among the |
607 | specification in all tests and is fully embeddable, which is a rare feat |
574 | OS-specific backends (I vastly prefer correctness over speed hacks). |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
609 | hacks). |
|
|
610 | |
|
|
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
612 | even sun itself gets it wrong in their code examples: The event polling |
|
|
613 | function sometimes returns events to the caller even though an error |
|
|
614 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
615 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
616 | absolutely have to know whether an event occurred or not because you have |
|
|
617 | to re-arm the watcher. |
|
|
618 | |
|
|
619 | Fortunately libev seems to be able to work around these idiocies. |
575 | |
620 | |
576 | 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 |
577 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
578 | |
623 | |
579 | =item C<EVBACKEND_ALL> |
624 | =item C<EVBACKEND_ALL> |
580 | |
625 | |
581 | Try all backends (even potentially broken ones that wouldn't be tried |
626 | Try all backends (even potentially broken ones that wouldn't be tried |
582 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
627 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
583 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
628 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
584 | |
629 | |
585 | It is definitely not recommended to use this flag. |
630 | It is definitely not recommended to use this flag, use whatever |
|
|
631 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
632 | at all. |
|
|
633 | |
|
|
634 | =item C<EVBACKEND_MASK> |
|
|
635 | |
|
|
636 | Not a backend at all, but a mask to select all backend bits from a |
|
|
637 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
638 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
586 | |
639 | |
587 | =back |
640 | =back |
588 | |
641 | |
589 | If one or more of the backend flags are or'ed into the flags value, |
642 | If one or more of the backend flags are or'ed into the flags value, |
590 | then only these backends will be tried (in the reverse order as listed |
643 | then only these backends will be tried (in the reverse order as listed |
… | |
… | |
739 | without a previous call to C<ev_suspend>. |
792 | without a previous call to C<ev_suspend>. |
740 | |
793 | |
741 | 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 |
742 | event loop time (see C<ev_now_update>). |
795 | event loop time (see C<ev_now_update>). |
743 | |
796 | |
744 | =item ev_run (loop, int flags) |
797 | =item bool ev_run (loop, int flags) |
745 | |
798 | |
746 | 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 |
747 | 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 |
748 | 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 |
749 | the watcher callbacks, an then repeat the whole process indefinitely: This |
802 | the watcher callbacks, and then repeat the whole process indefinitely: This |
750 | is why event loops are called I<loops>. |
803 | is why event loops are called I<loops>. |
751 | |
804 | |
752 | 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 |
753 | 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 |
754 | 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"). |
755 | |
812 | |
756 | 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 |
757 | 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 |
758 | finished (especially in interactive programs), but having a program |
815 | finished (especially in interactive programs), but having a program |
759 | 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 |
760 | 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 |
761 | beauty. |
818 | beauty. |
762 | |
819 | |
763 | 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 |
764 | 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++ |
765 | 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 |
766 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
823 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
767 | |
824 | |
768 | 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 |
769 | 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 |
… | |
… | |
781 | 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 |
782 | 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 |
783 | 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 |
784 | usually a better approach for this kind of thing. |
841 | usually a better approach for this kind of thing. |
785 | |
842 | |
786 | 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): |
787 | |
846 | |
788 | - Increment loop depth. |
847 | - Increment loop depth. |
789 | - Reset the ev_break status. |
848 | - Reset the ev_break status. |
790 | - Before the first iteration, call any pending watchers. |
849 | - Before the first iteration, call any pending watchers. |
791 | LOOP: |
850 | LOOP: |
… | |
… | |
824 | anymore. |
883 | anymore. |
825 | |
884 | |
826 | ... queue jobs here, make sure they register event watchers as long |
885 | ... queue jobs here, make sure they register event watchers as long |
827 | ... 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..) |
828 | ev_run (my_loop, 0); |
887 | ev_run (my_loop, 0); |
829 | ... jobs done or somebody called unloop. yeah! |
888 | ... jobs done or somebody called break. yeah! |
830 | |
889 | |
831 | =item ev_break (loop, how) |
890 | =item ev_break (loop, how) |
832 | |
891 | |
833 | 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 |
834 | 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 |
… | |
… | |
867 | running when nothing else is active. |
926 | running when nothing else is active. |
868 | |
927 | |
869 | ev_signal exitsig; |
928 | ev_signal exitsig; |
870 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
929 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
871 | ev_signal_start (loop, &exitsig); |
930 | ev_signal_start (loop, &exitsig); |
872 | evf_unref (loop); |
931 | ev_unref (loop); |
873 | |
932 | |
874 | Example: For some weird reason, unregister the above signal handler again. |
933 | Example: For some weird reason, unregister the above signal handler again. |
875 | |
934 | |
876 | ev_ref (loop); |
935 | ev_ref (loop); |
877 | ev_signal_stop (loop, &exitsig); |
936 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
897 | 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. |
898 | |
957 | |
899 | 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 |
900 | 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, |
901 | 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 |
902 | 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 |
903 | 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 |
904 | 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 |
905 | once per this interval, on average. |
964 | once per this interval, on average (as long as the host time resolution is |
|
|
965 | good enough). |
906 | |
966 | |
907 | 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 |
908 | to spend more time collecting timeouts, at the expense of increased |
968 | to spend more time collecting timeouts, at the expense of increased |
909 | latency/jitter/inexactness (the watcher callback will be called |
969 | latency/jitter/inexactness (the watcher callback will be called |
910 | 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 |
… | |
… | |
956 | invoke the actual watchers inside another context (another thread etc.). |
1016 | invoke the actual watchers inside another context (another thread etc.). |
957 | |
1017 | |
958 | 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 |
959 | callback. |
1019 | callback. |
960 | |
1020 | |
961 | =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 ()) |
962 | |
1022 | |
963 | 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 |
964 | 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 |
965 | each call to a libev function. |
1025 | each call to a libev function. |
966 | |
1026 | |
967 | 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 |
968 | 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 |
969 | 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 |
970 | I<release> and I<acquire> callbacks on the loop. |
1030 | I<release> and I<acquire> callbacks on the loop. |
971 | |
1031 | |
972 | 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 |
973 | suspended waiting for new events, and C<acquire> is called just |
1033 | suspended waiting for new events, and C<acquire> is called just |
974 | afterwards. |
1034 | afterwards. |
… | |
… | |
989 | See also the locking example in the C<THREADS> section later in this |
1049 | See also the locking example in the C<THREADS> section later in this |
990 | document. |
1050 | document. |
991 | |
1051 | |
992 | =item ev_set_userdata (loop, void *data) |
1052 | =item ev_set_userdata (loop, void *data) |
993 | |
1053 | |
994 | =item ev_userdata (loop) |
1054 | =item void *ev_userdata (loop) |
995 | |
1055 | |
996 | Set and retrieve a single C<void *> associated with a loop. When |
1056 | Set and retrieve a single C<void *> associated with a loop. When |
997 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1057 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
998 | C<0>. |
1058 | C<0>. |
999 | |
1059 | |
… | |
… | |
1316 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1376 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1317 | functions that do not need a watcher. |
1377 | functions that do not need a watcher. |
1318 | |
1378 | |
1319 | =back |
1379 | =back |
1320 | |
1380 | |
1321 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1381 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
1322 | |
1382 | OWN COMPOSITE WATCHERS> idioms. |
1323 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1324 | and read at any time: libev will completely ignore it. This can be used |
|
|
1325 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1326 | don't want to allocate memory and store a pointer to it in that data |
|
|
1327 | member, you can also "subclass" the watcher type and provide your own |
|
|
1328 | data: |
|
|
1329 | |
|
|
1330 | struct my_io |
|
|
1331 | { |
|
|
1332 | ev_io io; |
|
|
1333 | int otherfd; |
|
|
1334 | void *somedata; |
|
|
1335 | struct whatever *mostinteresting; |
|
|
1336 | }; |
|
|
1337 | |
|
|
1338 | ... |
|
|
1339 | struct my_io w; |
|
|
1340 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1341 | |
|
|
1342 | And since your callback will be called with a pointer to the watcher, you |
|
|
1343 | can cast it back to your own type: |
|
|
1344 | |
|
|
1345 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1346 | { |
|
|
1347 | struct my_io *w = (struct my_io *)w_; |
|
|
1348 | ... |
|
|
1349 | } |
|
|
1350 | |
|
|
1351 | More interesting and less C-conformant ways of casting your callback type |
|
|
1352 | instead have been omitted. |
|
|
1353 | |
|
|
1354 | Another common scenario is to use some data structure with multiple |
|
|
1355 | embedded watchers: |
|
|
1356 | |
|
|
1357 | struct my_biggy |
|
|
1358 | { |
|
|
1359 | int some_data; |
|
|
1360 | ev_timer t1; |
|
|
1361 | ev_timer t2; |
|
|
1362 | } |
|
|
1363 | |
|
|
1364 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1365 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1366 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1367 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1368 | programmers): |
|
|
1369 | |
|
|
1370 | #include <stddef.h> |
|
|
1371 | |
|
|
1372 | static void |
|
|
1373 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1374 | { |
|
|
1375 | struct my_biggy big = (struct my_biggy *) |
|
|
1376 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1377 | } |
|
|
1378 | |
|
|
1379 | static void |
|
|
1380 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1381 | { |
|
|
1382 | struct my_biggy big = (struct my_biggy *) |
|
|
1383 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1384 | } |
|
|
1385 | |
1383 | |
1386 | =head2 WATCHER STATES |
1384 | =head2 WATCHER STATES |
1387 | |
1385 | |
1388 | There are various watcher states mentioned throughout this manual - |
1386 | There are various watcher states mentioned throughout this manual - |
1389 | active, pending and so on. In this section these states and the rules to |
1387 | active, pending and so on. In this section these states and the rules to |
… | |
… | |
1392 | |
1390 | |
1393 | =over 4 |
1391 | =over 4 |
1394 | |
1392 | |
1395 | =item initialiased |
1393 | =item initialiased |
1396 | |
1394 | |
1397 | Before a watcher can be registered with the event looop it has to be |
1395 | Before a watcher can be registered with the event loop it has to be |
1398 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1396 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1399 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1397 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1400 | |
1398 | |
1401 | In this state it is simply some block of memory that is suitable for use |
1399 | In this state it is simply some block of memory that is suitable for |
1402 | in an event loop. It can be moved around, freed, reused etc. at will. |
1400 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1401 | will - as long as you either keep the memory contents intact, or call |
|
|
1402 | C<ev_TYPE_init> again. |
1403 | |
1403 | |
1404 | =item started/running/active |
1404 | =item started/running/active |
1405 | |
1405 | |
1406 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1406 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1407 | property of the event loop, and is actively waiting for events. While in |
1407 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1435 | latter will clear any pending state the watcher might be in, regardless |
1435 | latter will clear any pending state the watcher might be in, regardless |
1436 | of whether it was active or not, so stopping a watcher explicitly before |
1436 | of whether it was active or not, so stopping a watcher explicitly before |
1437 | freeing it is often a good idea. |
1437 | freeing it is often a good idea. |
1438 | |
1438 | |
1439 | While stopped (and not pending) the watcher is essentially in the |
1439 | While stopped (and not pending) the watcher is essentially in the |
1440 | initialised state, that is it can be reused, moved, modified in any way |
1440 | initialised state, that is, it can be reused, moved, modified in any way |
1441 | you wish. |
1441 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1442 | it again). |
1442 | |
1443 | |
1443 | =back |
1444 | =back |
1444 | |
1445 | |
1445 | =head2 WATCHER PRIORITY MODELS |
1446 | =head2 WATCHER PRIORITY MODELS |
1446 | |
1447 | |
… | |
… | |
1575 | In general you can register as many read and/or write event watchers per |
1576 | In general you can register as many read and/or write event watchers per |
1576 | fd as you want (as long as you don't confuse yourself). Setting all file |
1577 | fd as you want (as long as you don't confuse yourself). Setting all file |
1577 | descriptors to non-blocking mode is also usually a good idea (but not |
1578 | descriptors to non-blocking mode is also usually a good idea (but not |
1578 | required if you know what you are doing). |
1579 | required if you know what you are doing). |
1579 | |
1580 | |
1580 | If you cannot use non-blocking mode, then force the use of a |
|
|
1581 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1582 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1583 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1584 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1585 | |
|
|
1586 | Another thing you have to watch out for is that it is quite easy to |
1581 | Another thing you have to watch out for is that it is quite easy to |
1587 | receive "spurious" readiness notifications, that is your callback might |
1582 | receive "spurious" readiness notifications, that is, your callback might |
1588 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1583 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1589 | because there is no data. Not only are some backends known to create a |
1584 | because there is no data. It is very easy to get into this situation even |
1590 | lot of those (for example Solaris ports), it is very easy to get into |
1585 | with a relatively standard program structure. Thus it is best to always |
1591 | this situation even with a relatively standard program structure. Thus |
1586 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1592 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1593 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1587 | preferable to a program hanging until some data arrives. |
1594 | |
1588 | |
1595 | If you cannot run the fd in non-blocking mode (for example you should |
1589 | If you cannot run the fd in non-blocking mode (for example you should |
1596 | not play around with an Xlib connection), then you have to separately |
1590 | not play around with an Xlib connection), then you have to separately |
1597 | re-test whether a file descriptor is really ready with a known-to-be good |
1591 | re-test whether a file descriptor is really ready with a known-to-be good |
1598 | interface such as poll (fortunately in our Xlib example, Xlib already |
1592 | interface such as poll (fortunately in the case of Xlib, it already does |
1599 | does this on its own, so its quite safe to use). Some people additionally |
1593 | this on its own, so its quite safe to use). Some people additionally |
1600 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1594 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1601 | indefinitely. |
1595 | indefinitely. |
1602 | |
1596 | |
1603 | But really, best use non-blocking mode. |
1597 | But really, best use non-blocking mode. |
1604 | |
1598 | |
… | |
… | |
1632 | |
1626 | |
1633 | There is no workaround possible except not registering events |
1627 | There is no workaround possible except not registering events |
1634 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1628 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1635 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1629 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1636 | |
1630 | |
|
|
1631 | =head3 The special problem of files |
|
|
1632 | |
|
|
1633 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1634 | representing files, and expect it to become ready when their program |
|
|
1635 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1636 | |
|
|
1637 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1638 | notification as soon as the kernel knows whether and how much data is |
|
|
1639 | there, and in the case of open files, that's always the case, so you |
|
|
1640 | always get a readiness notification instantly, and your read (or possibly |
|
|
1641 | write) will still block on the disk I/O. |
|
|
1642 | |
|
|
1643 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1644 | devices and so on, there is another party (the sender) that delivers data |
|
|
1645 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1646 | will not send data on its own, simply because it doesn't know what you |
|
|
1647 | wish to read - you would first have to request some data. |
|
|
1648 | |
|
|
1649 | Since files are typically not-so-well supported by advanced notification |
|
|
1650 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1651 | to files, even though you should not use it. The reason for this is |
|
|
1652 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1653 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1654 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1655 | F</dev/urandom>), and even though the file might better be served with |
|
|
1656 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1657 | it "just works" instead of freezing. |
|
|
1658 | |
|
|
1659 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1660 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1661 | when you rarely read from a file instead of from a socket, and want to |
|
|
1662 | reuse the same code path. |
|
|
1663 | |
1637 | =head3 The special problem of fork |
1664 | =head3 The special problem of fork |
1638 | |
1665 | |
1639 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1666 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1640 | useless behaviour. Libev fully supports fork, but needs to be told about |
1667 | useless behaviour. Libev fully supports fork, but needs to be told about |
1641 | it in the child. |
1668 | it in the child if you want to continue to use it in the child. |
1642 | |
1669 | |
1643 | To support fork in your programs, you either have to call |
1670 | To support fork in your child processes, you have to call C<ev_loop_fork |
1644 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1671 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1645 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1672 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1646 | C<EVBACKEND_POLL>. |
|
|
1647 | |
1673 | |
1648 | =head3 The special problem of SIGPIPE |
1674 | =head3 The special problem of SIGPIPE |
1649 | |
1675 | |
1650 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1676 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1651 | when writing to a pipe whose other end has been closed, your program gets |
1677 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1749 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1775 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1750 | monotonic clock option helps a lot here). |
1776 | monotonic clock option helps a lot here). |
1751 | |
1777 | |
1752 | The callback is guaranteed to be invoked only I<after> its timeout has |
1778 | The callback is guaranteed to be invoked only I<after> its timeout has |
1753 | passed (not I<at>, so on systems with very low-resolution clocks this |
1779 | passed (not I<at>, so on systems with very low-resolution clocks this |
1754 | might introduce a small delay). If multiple timers become ready during the |
1780 | might introduce a small delay, see "the special problem of being too |
|
|
1781 | early", below). If multiple timers become ready during the same loop |
1755 | same loop iteration then the ones with earlier time-out values are invoked |
1782 | iteration then the ones with earlier time-out values are invoked before |
1756 | before ones of the same priority with later time-out values (but this is |
1783 | ones of the same priority with later time-out values (but this is no |
1757 | no longer true when a callback calls C<ev_run> recursively). |
1784 | longer true when a callback calls C<ev_run> recursively). |
1758 | |
1785 | |
1759 | =head3 Be smart about timeouts |
1786 | =head3 Be smart about timeouts |
1760 | |
1787 | |
1761 | Many real-world problems involve some kind of timeout, usually for error |
1788 | Many real-world problems involve some kind of timeout, usually for error |
1762 | recovery. A typical example is an HTTP request - if the other side hangs, |
1789 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1837 | |
1864 | |
1838 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1865 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1839 | but remember the time of last activity, and check for a real timeout only |
1866 | but remember the time of last activity, and check for a real timeout only |
1840 | within the callback: |
1867 | within the callback: |
1841 | |
1868 | |
|
|
1869 | ev_tstamp timeout = 60.; |
1842 | ev_tstamp last_activity; // time of last activity |
1870 | ev_tstamp last_activity; // time of last activity |
|
|
1871 | ev_timer timer; |
1843 | |
1872 | |
1844 | static void |
1873 | static void |
1845 | callback (EV_P_ ev_timer *w, int revents) |
1874 | callback (EV_P_ ev_timer *w, int revents) |
1846 | { |
1875 | { |
1847 | ev_tstamp now = ev_now (EV_A); |
1876 | // calculate when the timeout would happen |
1848 | ev_tstamp timeout = last_activity + 60.; |
1877 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1849 | |
1878 | |
1850 | // if last_activity + 60. is older than now, we did time out |
1879 | // if negative, it means we the timeout already occured |
1851 | if (timeout < now) |
1880 | if (after < 0.) |
1852 | { |
1881 | { |
1853 | // timeout occurred, take action |
1882 | // timeout occurred, take action |
1854 | } |
1883 | } |
1855 | else |
1884 | else |
1856 | { |
1885 | { |
1857 | // callback was invoked, but there was some activity, re-arm |
1886 | // callback was invoked, but there was some recent |
1858 | // the watcher to fire in last_activity + 60, which is |
1887 | // activity. simply restart the timer to time out |
1859 | // guaranteed to be in the future, so "again" is positive: |
1888 | // after "after" seconds, which is the earliest time |
1860 | w->repeat = timeout - now; |
1889 | // the timeout can occur. |
|
|
1890 | ev_timer_set (w, after, 0.); |
1861 | ev_timer_again (EV_A_ w); |
1891 | ev_timer_start (EV_A_ w); |
1862 | } |
1892 | } |
1863 | } |
1893 | } |
1864 | |
1894 | |
1865 | To summarise the callback: first calculate the real timeout (defined |
1895 | To summarise the callback: first calculate in how many seconds the |
1866 | as "60 seconds after the last activity"), then check if that time has |
1896 | timeout will occur (by calculating the absolute time when it would occur, |
1867 | been reached, which means something I<did>, in fact, time out. Otherwise |
1897 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1868 | the callback was invoked too early (C<timeout> is in the future), so |
1898 | (EV_A)> from that). |
1869 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1870 | a timeout then. |
|
|
1871 | |
1899 | |
1872 | Note how C<ev_timer_again> is used, taking advantage of the |
1900 | If this value is negative, then we are already past the timeout, i.e. we |
1873 | C<ev_timer_again> optimisation when the timer is already running. |
1901 | timed out, and need to do whatever is needed in this case. |
|
|
1902 | |
|
|
1903 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1904 | and simply start the timer with this timeout value. |
|
|
1905 | |
|
|
1906 | In other words, each time the callback is invoked it will check whether |
|
|
1907 | the timeout cocured. If not, it will simply reschedule itself to check |
|
|
1908 | again at the earliest time it could time out. Rinse. Repeat. |
1874 | |
1909 | |
1875 | This scheme causes more callback invocations (about one every 60 seconds |
1910 | This scheme causes more callback invocations (about one every 60 seconds |
1876 | minus half the average time between activity), but virtually no calls to |
1911 | minus half the average time between activity), but virtually no calls to |
1877 | libev to change the timeout. |
1912 | libev to change the timeout. |
1878 | |
1913 | |
1879 | To start the timer, simply initialise the watcher and set C<last_activity> |
1914 | To start the machinery, simply initialise the watcher and set |
1880 | to the current time (meaning we just have some activity :), then call the |
1915 | C<last_activity> to the current time (meaning there was some activity just |
1881 | callback, which will "do the right thing" and start the timer: |
1916 | now), then call the callback, which will "do the right thing" and start |
|
|
1917 | the timer: |
1882 | |
1918 | |
|
|
1919 | last_activity = ev_now (EV_A); |
1883 | ev_init (timer, callback); |
1920 | ev_init (&timer, callback); |
1884 | last_activity = ev_now (loop); |
1921 | callback (EV_A_ &timer, 0); |
1885 | callback (loop, timer, EV_TIMER); |
|
|
1886 | |
1922 | |
1887 | And when there is some activity, simply store the current time in |
1923 | When there is some activity, simply store the current time in |
1888 | C<last_activity>, no libev calls at all: |
1924 | C<last_activity>, no libev calls at all: |
1889 | |
1925 | |
|
|
1926 | if (activity detected) |
1890 | last_activity = ev_now (loop); |
1927 | last_activity = ev_now (EV_A); |
|
|
1928 | |
|
|
1929 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1930 | providing a new value, stopping the timer and calling the callback, which |
|
|
1931 | will agaion do the right thing (for example, time out immediately :). |
|
|
1932 | |
|
|
1933 | timeout = new_value; |
|
|
1934 | ev_timer_stop (EV_A_ &timer); |
|
|
1935 | callback (EV_A_ &timer, 0); |
1891 | |
1936 | |
1892 | This technique is slightly more complex, but in most cases where the |
1937 | This technique is slightly more complex, but in most cases where the |
1893 | time-out is unlikely to be triggered, much more efficient. |
1938 | time-out is unlikely to be triggered, much more efficient. |
1894 | |
|
|
1895 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1896 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1897 | fix things for you. |
|
|
1898 | |
1939 | |
1899 | =item 4. Wee, just use a double-linked list for your timeouts. |
1940 | =item 4. Wee, just use a double-linked list for your timeouts. |
1900 | |
1941 | |
1901 | If there is not one request, but many thousands (millions...), all |
1942 | If there is not one request, but many thousands (millions...), all |
1902 | employing some kind of timeout with the same timeout value, then one can |
1943 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1929 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1970 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1930 | rather complicated, but extremely efficient, something that really pays |
1971 | rather complicated, but extremely efficient, something that really pays |
1931 | off after the first million or so of active timers, i.e. it's usually |
1972 | off after the first million or so of active timers, i.e. it's usually |
1932 | overkill :) |
1973 | overkill :) |
1933 | |
1974 | |
|
|
1975 | =head3 The special problem of being too early |
|
|
1976 | |
|
|
1977 | If you ask a timer to call your callback after three seconds, then |
|
|
1978 | you expect it to be invoked after three seconds - but of course, this |
|
|
1979 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1980 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1981 | process with a STOP signal for a few hours for example. |
|
|
1982 | |
|
|
1983 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1984 | delay has occurred, but cannot guarantee this. |
|
|
1985 | |
|
|
1986 | A less obvious failure mode is calling your callback too early: many event |
|
|
1987 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1988 | this can cause your callback to be invoked much earlier than you would |
|
|
1989 | expect. |
|
|
1990 | |
|
|
1991 | To see why, imagine a system with a clock that only offers full second |
|
|
1992 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1993 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1994 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
1995 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
1996 | |
|
|
1997 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
1998 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
1999 | one-second delay was requested - this is being "too early", despite best |
|
|
2000 | intentions. |
|
|
2001 | |
|
|
2002 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2003 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2004 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2005 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2006 | |
|
|
2007 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2008 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2009 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2010 | late" side of things. |
|
|
2011 | |
1934 | =head3 The special problem of time updates |
2012 | =head3 The special problem of time updates |
1935 | |
2013 | |
1936 | Establishing the current time is a costly operation (it usually takes at |
2014 | Establishing the current time is a costly operation (it usually takes |
1937 | least two system calls): EV therefore updates its idea of the current |
2015 | at least one system call): EV therefore updates its idea of the current |
1938 | time only before and after C<ev_run> collects new events, which causes a |
2016 | time only before and after C<ev_run> collects new events, which causes a |
1939 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2017 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1940 | lots of events in one iteration. |
2018 | lots of events in one iteration. |
1941 | |
2019 | |
1942 | The relative timeouts are calculated relative to the C<ev_now ()> |
2020 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1948 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2026 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1949 | |
2027 | |
1950 | If the event loop is suspended for a long time, you can also force an |
2028 | If the event loop is suspended for a long time, you can also force an |
1951 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2029 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1952 | ()>. |
2030 | ()>. |
|
|
2031 | |
|
|
2032 | =head3 The special problem of unsynchronised clocks |
|
|
2033 | |
|
|
2034 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2035 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2036 | jumps). |
|
|
2037 | |
|
|
2038 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2039 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2040 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2041 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2042 | than a directly following call to C<time>. |
|
|
2043 | |
|
|
2044 | The moral of this is to only compare libev-related timestamps with |
|
|
2045 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2046 | a second or so. |
|
|
2047 | |
|
|
2048 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2049 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2050 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2051 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2052 | |
|
|
2053 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2054 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2055 | I<measured according to the real time>, not the system clock. |
|
|
2056 | |
|
|
2057 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2058 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2059 | exactly the right behaviour. |
|
|
2060 | |
|
|
2061 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2062 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2063 | time, where your comparisons will always generate correct results. |
1953 | |
2064 | |
1954 | =head3 The special problems of suspended animation |
2065 | =head3 The special problems of suspended animation |
1955 | |
2066 | |
1956 | When you leave the server world it is quite customary to hit machines that |
2067 | When you leave the server world it is quite customary to hit machines that |
1957 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2068 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
2001 | keep up with the timer (because it takes longer than those 10 seconds to |
2112 | keep up with the timer (because it takes longer than those 10 seconds to |
2002 | do stuff) the timer will not fire more than once per event loop iteration. |
2113 | do stuff) the timer will not fire more than once per event loop iteration. |
2003 | |
2114 | |
2004 | =item ev_timer_again (loop, ev_timer *) |
2115 | =item ev_timer_again (loop, ev_timer *) |
2005 | |
2116 | |
2006 | This will act as if the timer timed out and restart it again if it is |
2117 | This will act as if the timer timed out, and restarts it again if it is |
2007 | repeating. The exact semantics are: |
2118 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2119 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
2008 | |
2120 | |
|
|
2121 | The exact semantics are as in the following rules, all of which will be |
|
|
2122 | applied to the watcher: |
|
|
2123 | |
|
|
2124 | =over 4 |
|
|
2125 | |
2009 | If the timer is pending, its pending status is cleared. |
2126 | =item If the timer is pending, the pending status is always cleared. |
2010 | |
2127 | |
2011 | If the timer is started but non-repeating, stop it (as if it timed out). |
2128 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2129 | out, without invoking it). |
2012 | |
2130 | |
2013 | If the timer is repeating, either start it if necessary (with the |
2131 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2014 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2132 | and start the timer, if necessary. |
|
|
2133 | |
|
|
2134 | =back |
2015 | |
2135 | |
2016 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2136 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2017 | usage example. |
2137 | usage example. |
2018 | |
2138 | |
2019 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2139 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
… | |
… | |
2141 | |
2261 | |
2142 | Another way to think about it (for the mathematically inclined) is that |
2262 | Another way to think about it (for the mathematically inclined) is that |
2143 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2263 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2144 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2264 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2145 | |
2265 | |
2146 | For numerical stability it is preferable that the C<offset> value is near |
2266 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2147 | C<ev_now ()> (the current time), but there is no range requirement for |
2267 | interval value should be higher than C<1/8192> (which is around 100 |
2148 | this value, and in fact is often specified as zero. |
2268 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2269 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2270 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2271 | C<0> and C<interval>, which is also the recommended range. |
2149 | |
2272 | |
2150 | Note also that there is an upper limit to how often a timer can fire (CPU |
2273 | Note also that there is an upper limit to how often a timer can fire (CPU |
2151 | speed for example), so if C<interval> is very small then timing stability |
2274 | speed for example), so if C<interval> is very small then timing stability |
2152 | will of course deteriorate. Libev itself tries to be exact to be about one |
2275 | will of course deteriorate. Libev itself tries to be exact to be about one |
2153 | millisecond (if the OS supports it and the machine is fast enough). |
2276 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2296 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2419 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2297 | |
2420 | |
2298 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2421 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2299 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2422 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2300 | stopping it again), that is, libev might or might not block the signal, |
2423 | stopping it again), that is, libev might or might not block the signal, |
2301 | and might or might not set or restore the installed signal handler. |
2424 | and might or might not set or restore the installed signal handler (but |
|
|
2425 | see C<EVFLAG_NOSIGMASK>). |
2302 | |
2426 | |
2303 | While this does not matter for the signal disposition (libev never |
2427 | While this does not matter for the signal disposition (libev never |
2304 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2428 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2305 | C<execve>), this matters for the signal mask: many programs do not expect |
2429 | C<execve>), this matters for the signal mask: many programs do not expect |
2306 | certain signals to be blocked. |
2430 | certain signals to be blocked. |
… | |
… | |
2319 | I<has> to modify the signal mask, at least temporarily. |
2443 | I<has> to modify the signal mask, at least temporarily. |
2320 | |
2444 | |
2321 | So I can't stress this enough: I<If you do not reset your signal mask when |
2445 | So I can't stress this enough: I<If you do not reset your signal mask when |
2322 | you expect it to be empty, you have a race condition in your code>. This |
2446 | you expect it to be empty, you have a race condition in your code>. This |
2323 | is not a libev-specific thing, this is true for most event libraries. |
2447 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2448 | |
|
|
2449 | =head3 The special problem of threads signal handling |
|
|
2450 | |
|
|
2451 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2452 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2453 | threads in a process block signals, which is hard to achieve. |
|
|
2454 | |
|
|
2455 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2456 | for the same signals), you can tackle this problem by globally blocking |
|
|
2457 | all signals before creating any threads (or creating them with a fully set |
|
|
2458 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2459 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2460 | these signals. You can pass on any signals that libev might be interested |
|
|
2461 | in by calling C<ev_feed_signal>. |
2324 | |
2462 | |
2325 | =head3 Watcher-Specific Functions and Data Members |
2463 | =head3 Watcher-Specific Functions and Data Members |
2326 | |
2464 | |
2327 | =over 4 |
2465 | =over 4 |
2328 | |
2466 | |
… | |
… | |
3163 | atexit (program_exits); |
3301 | atexit (program_exits); |
3164 | |
3302 | |
3165 | |
3303 | |
3166 | =head2 C<ev_async> - how to wake up an event loop |
3304 | =head2 C<ev_async> - how to wake up an event loop |
3167 | |
3305 | |
3168 | In general, you cannot use an C<ev_run> from multiple threads or other |
3306 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3169 | asynchronous sources such as signal handlers (as opposed to multiple event |
3307 | asynchronous sources such as signal handlers (as opposed to multiple event |
3170 | loops - those are of course safe to use in different threads). |
3308 | loops - those are of course safe to use in different threads). |
3171 | |
3309 | |
3172 | Sometimes, however, you need to wake up an event loop you do not control, |
3310 | Sometimes, however, you need to wake up an event loop you do not control, |
3173 | for example because it belongs to another thread. This is what C<ev_async> |
3311 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3175 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3313 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3176 | |
3314 | |
3177 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3315 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3178 | too, are asynchronous in nature, and signals, too, will be compressed |
3316 | too, are asynchronous in nature, and signals, too, will be compressed |
3179 | (i.e. the number of callback invocations may be less than the number of |
3317 | (i.e. the number of callback invocations may be less than the number of |
3180 | C<ev_async_sent> calls). |
3318 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3181 | |
3319 | of "global async watchers" by using a watcher on an otherwise unused |
3182 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3320 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3183 | just the default loop. |
3321 | even without knowing which loop owns the signal. |
3184 | |
3322 | |
3185 | =head3 Queueing |
3323 | =head3 Queueing |
3186 | |
3324 | |
3187 | C<ev_async> does not support queueing of data in any way. The reason |
3325 | C<ev_async> does not support queueing of data in any way. The reason |
3188 | is that the author does not know of a simple (or any) algorithm for a |
3326 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3280 | trust me. |
3418 | trust me. |
3281 | |
3419 | |
3282 | =item ev_async_send (loop, ev_async *) |
3420 | =item ev_async_send (loop, ev_async *) |
3283 | |
3421 | |
3284 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3422 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3285 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3423 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3424 | returns. |
|
|
3425 | |
3286 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3426 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3287 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3427 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3288 | section below on what exactly this means). |
3428 | embedding section below on what exactly this means). |
3289 | |
3429 | |
3290 | Note that, as with other watchers in libev, multiple events might get |
3430 | Note that, as with other watchers in libev, multiple events might get |
3291 | compressed into a single callback invocation (another way to look at this |
3431 | compressed into a single callback invocation (another way to look at |
3292 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3432 | this is that C<ev_async> watchers are level-triggered: they are set on |
3293 | reset when the event loop detects that). |
3433 | C<ev_async_send>, reset when the event loop detects that). |
3294 | |
3434 | |
3295 | This call incurs the overhead of a system call only once per event loop |
3435 | This call incurs the overhead of at most one extra system call per event |
3296 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3436 | loop iteration, if the event loop is blocked, and no syscall at all if |
3297 | repeated calls to C<ev_async_send> for the same event loop. |
3437 | the event loop (or your program) is processing events. That means that |
|
|
3438 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3439 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3440 | zero) under load. |
3298 | |
3441 | |
3299 | =item bool = ev_async_pending (ev_async *) |
3442 | =item bool = ev_async_pending (ev_async *) |
3300 | |
3443 | |
3301 | Returns a non-zero value when C<ev_async_send> has been called on the |
3444 | Returns a non-zero value when C<ev_async_send> has been called on the |
3302 | watcher but the event has not yet been processed (or even noted) by the |
3445 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3357 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3500 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3358 | |
3501 | |
3359 | =item ev_feed_fd_event (loop, int fd, int revents) |
3502 | =item ev_feed_fd_event (loop, int fd, int revents) |
3360 | |
3503 | |
3361 | Feed an event on the given fd, as if a file descriptor backend detected |
3504 | Feed an event on the given fd, as if a file descriptor backend detected |
3362 | the given events it. |
3505 | the given events. |
3363 | |
3506 | |
3364 | =item ev_feed_signal_event (loop, int signum) |
3507 | =item ev_feed_signal_event (loop, int signum) |
3365 | |
3508 | |
3366 | Feed an event as if the given signal occurred (C<loop> must be the default |
3509 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3367 | loop!). |
3510 | which is async-safe. |
3368 | |
3511 | |
3369 | =back |
3512 | =back |
|
|
3513 | |
|
|
3514 | |
|
|
3515 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3516 | |
|
|
3517 | This section explains some common idioms that are not immediately |
|
|
3518 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3519 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3520 | |
|
|
3521 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3522 | |
|
|
3523 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3524 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3525 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3526 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3527 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3528 | data: |
|
|
3529 | |
|
|
3530 | struct my_io |
|
|
3531 | { |
|
|
3532 | ev_io io; |
|
|
3533 | int otherfd; |
|
|
3534 | void *somedata; |
|
|
3535 | struct whatever *mostinteresting; |
|
|
3536 | }; |
|
|
3537 | |
|
|
3538 | ... |
|
|
3539 | struct my_io w; |
|
|
3540 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3541 | |
|
|
3542 | And since your callback will be called with a pointer to the watcher, you |
|
|
3543 | can cast it back to your own type: |
|
|
3544 | |
|
|
3545 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3546 | { |
|
|
3547 | struct my_io *w = (struct my_io *)w_; |
|
|
3548 | ... |
|
|
3549 | } |
|
|
3550 | |
|
|
3551 | More interesting and less C-conformant ways of casting your callback |
|
|
3552 | function type instead have been omitted. |
|
|
3553 | |
|
|
3554 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3555 | |
|
|
3556 | Another common scenario is to use some data structure with multiple |
|
|
3557 | embedded watchers, in effect creating your own watcher that combines |
|
|
3558 | multiple libev event sources into one "super-watcher": |
|
|
3559 | |
|
|
3560 | struct my_biggy |
|
|
3561 | { |
|
|
3562 | int some_data; |
|
|
3563 | ev_timer t1; |
|
|
3564 | ev_timer t2; |
|
|
3565 | } |
|
|
3566 | |
|
|
3567 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3568 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3569 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3570 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3571 | real programmers): |
|
|
3572 | |
|
|
3573 | #include <stddef.h> |
|
|
3574 | |
|
|
3575 | static void |
|
|
3576 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3577 | { |
|
|
3578 | struct my_biggy big = (struct my_biggy *) |
|
|
3579 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3580 | } |
|
|
3581 | |
|
|
3582 | static void |
|
|
3583 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3584 | { |
|
|
3585 | struct my_biggy big = (struct my_biggy *) |
|
|
3586 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3587 | } |
|
|
3588 | |
|
|
3589 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3590 | |
|
|
3591 | Often you have structures like this in event-based programs: |
|
|
3592 | |
|
|
3593 | callback () |
|
|
3594 | { |
|
|
3595 | free (request); |
|
|
3596 | } |
|
|
3597 | |
|
|
3598 | request = start_new_request (..., callback); |
|
|
3599 | |
|
|
3600 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3601 | used to cancel the operation, or do other things with it. |
|
|
3602 | |
|
|
3603 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3604 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3605 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3606 | operation and simply invoke the callback with the result. |
|
|
3607 | |
|
|
3608 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3609 | has returned, so C<request> is not set. |
|
|
3610 | |
|
|
3611 | Even if you pass the request by some safer means to the callback, you |
|
|
3612 | might want to do something to the request after starting it, such as |
|
|
3613 | canceling it, which probably isn't working so well when the callback has |
|
|
3614 | already been invoked. |
|
|
3615 | |
|
|
3616 | A common way around all these issues is to make sure that |
|
|
3617 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3618 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3619 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
|
|
3620 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3621 | and pushing it into the pending queue: |
|
|
3622 | |
|
|
3623 | ev_set_cb (watcher, callback); |
|
|
3624 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3625 | |
|
|
3626 | This way, C<start_new_request> can safely return before the callback is |
|
|
3627 | invoked, while not delaying callback invocation too much. |
|
|
3628 | |
|
|
3629 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3630 | |
|
|
3631 | Often (especially in GUI toolkits) there are places where you have |
|
|
3632 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3633 | invoking C<ev_run>. |
|
|
3634 | |
|
|
3635 | This brings the problem of exiting - a callback might want to finish the |
|
|
3636 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3637 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3638 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3639 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3640 | |
|
|
3641 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3642 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3643 | triggered, using C<EVRUN_ONCE>: |
|
|
3644 | |
|
|
3645 | // main loop |
|
|
3646 | int exit_main_loop = 0; |
|
|
3647 | |
|
|
3648 | while (!exit_main_loop) |
|
|
3649 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3650 | |
|
|
3651 | // in a modal watcher |
|
|
3652 | int exit_nested_loop = 0; |
|
|
3653 | |
|
|
3654 | while (!exit_nested_loop) |
|
|
3655 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3656 | |
|
|
3657 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3658 | |
|
|
3659 | // exit modal loop |
|
|
3660 | exit_nested_loop = 1; |
|
|
3661 | |
|
|
3662 | // exit main program, after modal loop is finished |
|
|
3663 | exit_main_loop = 1; |
|
|
3664 | |
|
|
3665 | // exit both |
|
|
3666 | exit_main_loop = exit_nested_loop = 1; |
|
|
3667 | |
|
|
3668 | =head2 THREAD LOCKING EXAMPLE |
|
|
3669 | |
|
|
3670 | Here is a fictitious example of how to run an event loop in a different |
|
|
3671 | thread from where callbacks are being invoked and watchers are |
|
|
3672 | created/added/removed. |
|
|
3673 | |
|
|
3674 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3675 | which uses exactly this technique (which is suited for many high-level |
|
|
3676 | languages). |
|
|
3677 | |
|
|
3678 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3679 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3680 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3681 | |
|
|
3682 | First, you need to associate some data with the event loop: |
|
|
3683 | |
|
|
3684 | typedef struct { |
|
|
3685 | mutex_t lock; /* global loop lock */ |
|
|
3686 | ev_async async_w; |
|
|
3687 | thread_t tid; |
|
|
3688 | cond_t invoke_cv; |
|
|
3689 | } userdata; |
|
|
3690 | |
|
|
3691 | void prepare_loop (EV_P) |
|
|
3692 | { |
|
|
3693 | // for simplicity, we use a static userdata struct. |
|
|
3694 | static userdata u; |
|
|
3695 | |
|
|
3696 | ev_async_init (&u->async_w, async_cb); |
|
|
3697 | ev_async_start (EV_A_ &u->async_w); |
|
|
3698 | |
|
|
3699 | pthread_mutex_init (&u->lock, 0); |
|
|
3700 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3701 | |
|
|
3702 | // now associate this with the loop |
|
|
3703 | ev_set_userdata (EV_A_ u); |
|
|
3704 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3705 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3706 | |
|
|
3707 | // then create the thread running ev_run |
|
|
3708 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3709 | } |
|
|
3710 | |
|
|
3711 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3712 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3713 | that might have been added: |
|
|
3714 | |
|
|
3715 | static void |
|
|
3716 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3717 | { |
|
|
3718 | // just used for the side effects |
|
|
3719 | } |
|
|
3720 | |
|
|
3721 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3722 | protecting the loop data, respectively. |
|
|
3723 | |
|
|
3724 | static void |
|
|
3725 | l_release (EV_P) |
|
|
3726 | { |
|
|
3727 | userdata *u = ev_userdata (EV_A); |
|
|
3728 | pthread_mutex_unlock (&u->lock); |
|
|
3729 | } |
|
|
3730 | |
|
|
3731 | static void |
|
|
3732 | l_acquire (EV_P) |
|
|
3733 | { |
|
|
3734 | userdata *u = ev_userdata (EV_A); |
|
|
3735 | pthread_mutex_lock (&u->lock); |
|
|
3736 | } |
|
|
3737 | |
|
|
3738 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3739 | into C<ev_run>: |
|
|
3740 | |
|
|
3741 | void * |
|
|
3742 | l_run (void *thr_arg) |
|
|
3743 | { |
|
|
3744 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3745 | |
|
|
3746 | l_acquire (EV_A); |
|
|
3747 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3748 | ev_run (EV_A_ 0); |
|
|
3749 | l_release (EV_A); |
|
|
3750 | |
|
|
3751 | return 0; |
|
|
3752 | } |
|
|
3753 | |
|
|
3754 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3755 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3756 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3757 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3758 | and b) skipping inter-thread-communication when there are no pending |
|
|
3759 | watchers is very beneficial): |
|
|
3760 | |
|
|
3761 | static void |
|
|
3762 | l_invoke (EV_P) |
|
|
3763 | { |
|
|
3764 | userdata *u = ev_userdata (EV_A); |
|
|
3765 | |
|
|
3766 | while (ev_pending_count (EV_A)) |
|
|
3767 | { |
|
|
3768 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3769 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3770 | } |
|
|
3771 | } |
|
|
3772 | |
|
|
3773 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3774 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3775 | thread to continue: |
|
|
3776 | |
|
|
3777 | static void |
|
|
3778 | real_invoke_pending (EV_P) |
|
|
3779 | { |
|
|
3780 | userdata *u = ev_userdata (EV_A); |
|
|
3781 | |
|
|
3782 | pthread_mutex_lock (&u->lock); |
|
|
3783 | ev_invoke_pending (EV_A); |
|
|
3784 | pthread_cond_signal (&u->invoke_cv); |
|
|
3785 | pthread_mutex_unlock (&u->lock); |
|
|
3786 | } |
|
|
3787 | |
|
|
3788 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3789 | event loop, you will now have to lock: |
|
|
3790 | |
|
|
3791 | ev_timer timeout_watcher; |
|
|
3792 | userdata *u = ev_userdata (EV_A); |
|
|
3793 | |
|
|
3794 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3795 | |
|
|
3796 | pthread_mutex_lock (&u->lock); |
|
|
3797 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3798 | ev_async_send (EV_A_ &u->async_w); |
|
|
3799 | pthread_mutex_unlock (&u->lock); |
|
|
3800 | |
|
|
3801 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3802 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3803 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3804 | watchers in the next event loop iteration. |
|
|
3805 | |
|
|
3806 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3807 | |
|
|
3808 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3809 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3810 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3811 | doesn't need callbacks anymore. |
|
|
3812 | |
|
|
3813 | Imagine you have coroutines that you can switch to using a function |
|
|
3814 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3815 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3816 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3817 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3818 | the differing C<;> conventions): |
|
|
3819 | |
|
|
3820 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3821 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3822 | |
|
|
3823 | That means instead of having a C callback function, you store the |
|
|
3824 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3825 | your callback, you instead have it switch to that coroutine. |
|
|
3826 | |
|
|
3827 | A coroutine might now wait for an event with a function called |
|
|
3828 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3829 | matter when, or whether the watcher is active or not when this function is |
|
|
3830 | called): |
|
|
3831 | |
|
|
3832 | void |
|
|
3833 | wait_for_event (ev_watcher *w) |
|
|
3834 | { |
|
|
3835 | ev_cb_set (w) = current_coro; |
|
|
3836 | switch_to (libev_coro); |
|
|
3837 | } |
|
|
3838 | |
|
|
3839 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3840 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3841 | this or any other coroutine. |
|
|
3842 | |
|
|
3843 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3844 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3845 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3846 | any waiters. |
|
|
3847 | |
|
|
3848 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3849 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3850 | |
|
|
3851 | // my_ev.h |
|
|
3852 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3853 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3854 | #include "../libev/ev.h" |
|
|
3855 | |
|
|
3856 | // my_ev.c |
|
|
3857 | #define EV_H "my_ev.h" |
|
|
3858 | #include "../libev/ev.c" |
|
|
3859 | |
|
|
3860 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3861 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3862 | can even use F<ev.h> as header file name directly. |
3370 | |
3863 | |
3371 | |
3864 | |
3372 | =head1 LIBEVENT EMULATION |
3865 | =head1 LIBEVENT EMULATION |
3373 | |
3866 | |
3374 | Libev offers a compatibility emulation layer for libevent. It cannot |
3867 | Libev offers a compatibility emulation layer for libevent. It cannot |
3375 | emulate the internals of libevent, so here are some usage hints: |
3868 | emulate the internals of libevent, so here are some usage hints: |
3376 | |
3869 | |
3377 | =over 4 |
3870 | =over 4 |
|
|
3871 | |
|
|
3872 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3873 | |
|
|
3874 | This was the newest libevent version available when libev was implemented, |
|
|
3875 | and is still mostly unchanged in 2010. |
3378 | |
3876 | |
3379 | =item * Use it by including <event.h>, as usual. |
3877 | =item * Use it by including <event.h>, as usual. |
3380 | |
3878 | |
3381 | =item * The following members are fully supported: ev_base, ev_callback, |
3879 | =item * The following members are fully supported: ev_base, ev_callback, |
3382 | ev_arg, ev_fd, ev_res, ev_events. |
3880 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3398 | to use the libev header file and library. |
3896 | to use the libev header file and library. |
3399 | |
3897 | |
3400 | =back |
3898 | =back |
3401 | |
3899 | |
3402 | =head1 C++ SUPPORT |
3900 | =head1 C++ SUPPORT |
|
|
3901 | |
|
|
3902 | =head2 C API |
|
|
3903 | |
|
|
3904 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3905 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3906 | will work fine. |
|
|
3907 | |
|
|
3908 | Proper exception specifications might have to be added to callbacks passed |
|
|
3909 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3910 | other callbacks (allocator, syserr, loop acquire/release and periodioc |
|
|
3911 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3912 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3913 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3914 | |
|
|
3915 | static void |
|
|
3916 | fatal_error (const char *msg) EV_THROW |
|
|
3917 | { |
|
|
3918 | perror (msg); |
|
|
3919 | abort (); |
|
|
3920 | } |
|
|
3921 | |
|
|
3922 | ... |
|
|
3923 | ev_set_syserr_cb (fatal_error); |
|
|
3924 | |
|
|
3925 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3926 | C<ev_inoke> and C<ev_invoke_pending>. |
|
|
3927 | |
|
|
3928 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3929 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3930 | throwing exceptions through C libraries (most do). |
|
|
3931 | |
|
|
3932 | =head2 C++ API |
3403 | |
3933 | |
3404 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3934 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3405 | you to use some convenience methods to start/stop watchers and also change |
3935 | you to use some convenience methods to start/stop watchers and also change |
3406 | the callback model to a model using method callbacks on objects. |
3936 | the callback model to a model using method callbacks on objects. |
3407 | |
3937 | |
… | |
… | |
3417 | Care has been taken to keep the overhead low. The only data member the C++ |
3947 | Care has been taken to keep the overhead low. The only data member the C++ |
3418 | classes add (compared to plain C-style watchers) is the event loop pointer |
3948 | classes add (compared to plain C-style watchers) is the event loop pointer |
3419 | that the watcher is associated with (or no additional members at all if |
3949 | that the watcher is associated with (or no additional members at all if |
3420 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3950 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3421 | |
3951 | |
3422 | Currently, functions, and static and non-static member functions can be |
3952 | Currently, functions, static and non-static member functions and classes |
3423 | used as callbacks. Other types should be easy to add as long as they only |
3953 | with C<operator ()> can be used as callbacks. Other types should be easy |
3424 | need one additional pointer for context. If you need support for other |
3954 | to add as long as they only need one additional pointer for context. If |
3425 | types of functors please contact the author (preferably after implementing |
3955 | you need support for other types of functors please contact the author |
3426 | it). |
3956 | (preferably after implementing it). |
|
|
3957 | |
|
|
3958 | For all this to work, your C++ compiler either has to use the same calling |
|
|
3959 | conventions as your C compiler (for static member functions), or you have |
|
|
3960 | to embed libev and compile libev itself as C++. |
3427 | |
3961 | |
3428 | Here is a list of things available in the C<ev> namespace: |
3962 | Here is a list of things available in the C<ev> namespace: |
3429 | |
3963 | |
3430 | =over 4 |
3964 | =over 4 |
3431 | |
3965 | |
… | |
… | |
3441 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3975 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3442 | |
3976 | |
3443 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3977 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3444 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3978 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3445 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3979 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3446 | defines by many implementations. |
3980 | defined by many implementations. |
3447 | |
3981 | |
3448 | All of those classes have these methods: |
3982 | All of those classes have these methods: |
3449 | |
3983 | |
3450 | =over 4 |
3984 | =over 4 |
3451 | |
3985 | |
… | |
… | |
3584 | watchers in the constructor. |
4118 | watchers in the constructor. |
3585 | |
4119 | |
3586 | class myclass |
4120 | class myclass |
3587 | { |
4121 | { |
3588 | ev::io io ; void io_cb (ev::io &w, int revents); |
4122 | ev::io io ; void io_cb (ev::io &w, int revents); |
3589 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4123 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3590 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4124 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3591 | |
4125 | |
3592 | myclass (int fd) |
4126 | myclass (int fd) |
3593 | { |
4127 | { |
3594 | io .set <myclass, &myclass::io_cb > (this); |
4128 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3645 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4179 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3646 | |
4180 | |
3647 | =item D |
4181 | =item D |
3648 | |
4182 | |
3649 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4183 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3650 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4184 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3651 | |
4185 | |
3652 | =item Ocaml |
4186 | =item Ocaml |
3653 | |
4187 | |
3654 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4188 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3655 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4189 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3703 | suitable for use with C<EV_A>. |
4237 | suitable for use with C<EV_A>. |
3704 | |
4238 | |
3705 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4239 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3706 | |
4240 | |
3707 | Similar to the other two macros, this gives you the value of the default |
4241 | Similar to the other two macros, this gives you the value of the default |
3708 | loop, if multiple loops are supported ("ev loop default"). |
4242 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4243 | will be initialised if it isn't already initialised. |
|
|
4244 | |
|
|
4245 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4246 | to initialise the loop somewhere. |
3709 | |
4247 | |
3710 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4248 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3711 | |
4249 | |
3712 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4250 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3713 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4251 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3858 | supported). It will also not define any of the structs usually found in |
4396 | supported). It will also not define any of the structs usually found in |
3859 | F<event.h> that are not directly supported by the libev core alone. |
4397 | F<event.h> that are not directly supported by the libev core alone. |
3860 | |
4398 | |
3861 | In standalone mode, libev will still try to automatically deduce the |
4399 | In standalone mode, libev will still try to automatically deduce the |
3862 | configuration, but has to be more conservative. |
4400 | configuration, but has to be more conservative. |
|
|
4401 | |
|
|
4402 | =item EV_USE_FLOOR |
|
|
4403 | |
|
|
4404 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4405 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4406 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4407 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4408 | function is not available will fail, so the safe default is to not enable |
|
|
4409 | this. |
3863 | |
4410 | |
3864 | =item EV_USE_MONOTONIC |
4411 | =item EV_USE_MONOTONIC |
3865 | |
4412 | |
3866 | If defined to be C<1>, libev will try to detect the availability of the |
4413 | If defined to be C<1>, libev will try to detect the availability of the |
3867 | monotonic clock option at both compile time and runtime. Otherwise no |
4414 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3997 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4544 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3998 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4545 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3999 | be detected at runtime. If undefined, it will be enabled if the headers |
4546 | be detected at runtime. If undefined, it will be enabled if the headers |
4000 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4547 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4001 | |
4548 | |
|
|
4549 | =item EV_NO_SMP |
|
|
4550 | |
|
|
4551 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4552 | between threads, that is, threads can be used, but threads never run on |
|
|
4553 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4554 | and makes libev faster. |
|
|
4555 | |
|
|
4556 | =item EV_NO_THREADS |
|
|
4557 | |
|
|
4558 | If defined to be C<1>, libev will assume that it will never be called |
|
|
4559 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
|
|
4560 | above. This reduces dependencies and makes libev faster. |
|
|
4561 | |
4002 | =item EV_ATOMIC_T |
4562 | =item EV_ATOMIC_T |
4003 | |
4563 | |
4004 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4564 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4005 | access is atomic with respect to other threads or signal contexts. No such |
4565 | access is atomic and serialised with respect to other threads or signal |
4006 | type is easily found in the C language, so you can provide your own type |
4566 | contexts. No such type is easily found in the C language, so you can |
4007 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4567 | provide your own type that you know is safe for your purposes. It is used |
4008 | as well as for signal and thread safety in C<ev_async> watchers. |
4568 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4569 | in C<ev_async> watchers. |
4009 | |
4570 | |
4010 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4571 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4011 | (from F<signal.h>), which is usually good enough on most platforms. |
4572 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4573 | although strictly speaking using a type that also implies a memory fence |
|
|
4574 | is required. |
4012 | |
4575 | |
4013 | =item EV_H (h) |
4576 | =item EV_H (h) |
4014 | |
4577 | |
4015 | The name of the F<ev.h> header file used to include it. The default if |
4578 | The name of the F<ev.h> header file used to include it. The default if |
4016 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4579 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
4040 | will have the C<struct ev_loop *> as first argument, and you can create |
4603 | will have the C<struct ev_loop *> as first argument, and you can create |
4041 | additional independent event loops. Otherwise there will be no support |
4604 | additional independent event loops. Otherwise there will be no support |
4042 | for multiple event loops and there is no first event loop pointer |
4605 | for multiple event loops and there is no first event loop pointer |
4043 | argument. Instead, all functions act on the single default loop. |
4606 | argument. Instead, all functions act on the single default loop. |
4044 | |
4607 | |
|
|
4608 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4609 | default loop when multiplicity is switched off - you always have to |
|
|
4610 | initialise the loop manually in this case. |
|
|
4611 | |
4045 | =item EV_MINPRI |
4612 | =item EV_MINPRI |
4046 | |
4613 | |
4047 | =item EV_MAXPRI |
4614 | =item EV_MAXPRI |
4048 | |
4615 | |
4049 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4616 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4085 | #define EV_USE_POLL 1 |
4652 | #define EV_USE_POLL 1 |
4086 | #define EV_CHILD_ENABLE 1 |
4653 | #define EV_CHILD_ENABLE 1 |
4087 | #define EV_ASYNC_ENABLE 1 |
4654 | #define EV_ASYNC_ENABLE 1 |
4088 | |
4655 | |
4089 | The actual value is a bitset, it can be a combination of the following |
4656 | The actual value is a bitset, it can be a combination of the following |
4090 | values: |
4657 | values (by default, all of these are enabled): |
4091 | |
4658 | |
4092 | =over 4 |
4659 | =over 4 |
4093 | |
4660 | |
4094 | =item C<1> - faster/larger code |
4661 | =item C<1> - faster/larger code |
4095 | |
4662 | |
… | |
… | |
4099 | code size by roughly 30% on amd64). |
4666 | code size by roughly 30% on amd64). |
4100 | |
4667 | |
4101 | When optimising for size, use of compiler flags such as C<-Os> with |
4668 | When optimising for size, use of compiler flags such as C<-Os> with |
4102 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4669 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4103 | assertions. |
4670 | assertions. |
|
|
4671 | |
|
|
4672 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4673 | (e.g. gcc with C<-Os>). |
4104 | |
4674 | |
4105 | =item C<2> - faster/larger data structures |
4675 | =item C<2> - faster/larger data structures |
4106 | |
4676 | |
4107 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4677 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4108 | hash table sizes and so on. This will usually further increase code size |
4678 | hash table sizes and so on. This will usually further increase code size |
4109 | and can additionally have an effect on the size of data structures at |
4679 | and can additionally have an effect on the size of data structures at |
4110 | runtime. |
4680 | runtime. |
4111 | |
4681 | |
|
|
4682 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4683 | (e.g. gcc with C<-Os>). |
|
|
4684 | |
4112 | =item C<4> - full API configuration |
4685 | =item C<4> - full API configuration |
4113 | |
4686 | |
4114 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4687 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4115 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4688 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4116 | |
4689 | |
… | |
… | |
4146 | |
4719 | |
4147 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4720 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4148 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4721 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4149 | your program might be left out as well - a binary starting a timer and an |
4722 | your program might be left out as well - a binary starting a timer and an |
4150 | I/O watcher then might come out at only 5Kb. |
4723 | I/O watcher then might come out at only 5Kb. |
|
|
4724 | |
|
|
4725 | =item EV_API_STATIC |
|
|
4726 | |
|
|
4727 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4728 | will have static linkage. This means that libev will not export any |
|
|
4729 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4730 | when you embed libev, only want to use libev functions in a single file, |
|
|
4731 | and do not want its identifiers to be visible. |
|
|
4732 | |
|
|
4733 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4734 | wants to use libev. |
|
|
4735 | |
|
|
4736 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4737 | doesn't support the required declaration syntax. |
4151 | |
4738 | |
4152 | =item EV_AVOID_STDIO |
4739 | =item EV_AVOID_STDIO |
4153 | |
4740 | |
4154 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4741 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4155 | functions (printf, scanf, perror etc.). This will increase the code size |
4742 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4299 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4886 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4300 | |
4887 | |
4301 | #include "ev_cpp.h" |
4888 | #include "ev_cpp.h" |
4302 | #include "ev.c" |
4889 | #include "ev.c" |
4303 | |
4890 | |
4304 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4891 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4305 | |
4892 | |
4306 | =head2 THREADS AND COROUTINES |
4893 | =head2 THREADS AND COROUTINES |
4307 | |
4894 | |
4308 | =head3 THREADS |
4895 | =head3 THREADS |
4309 | |
4896 | |
… | |
… | |
4360 | default loop and triggering an C<ev_async> watcher from the default loop |
4947 | default loop and triggering an C<ev_async> watcher from the default loop |
4361 | watcher callback into the event loop interested in the signal. |
4948 | watcher callback into the event loop interested in the signal. |
4362 | |
4949 | |
4363 | =back |
4950 | =back |
4364 | |
4951 | |
4365 | =head4 THREAD LOCKING EXAMPLE |
4952 | See also L<THREAD LOCKING EXAMPLE>. |
4366 | |
|
|
4367 | Here is a fictitious example of how to run an event loop in a different |
|
|
4368 | thread than where callbacks are being invoked and watchers are |
|
|
4369 | created/added/removed. |
|
|
4370 | |
|
|
4371 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4372 | which uses exactly this technique (which is suited for many high-level |
|
|
4373 | languages). |
|
|
4374 | |
|
|
4375 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4376 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4377 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4378 | |
|
|
4379 | First, you need to associate some data with the event loop: |
|
|
4380 | |
|
|
4381 | typedef struct { |
|
|
4382 | mutex_t lock; /* global loop lock */ |
|
|
4383 | ev_async async_w; |
|
|
4384 | thread_t tid; |
|
|
4385 | cond_t invoke_cv; |
|
|
4386 | } userdata; |
|
|
4387 | |
|
|
4388 | void prepare_loop (EV_P) |
|
|
4389 | { |
|
|
4390 | // for simplicity, we use a static userdata struct. |
|
|
4391 | static userdata u; |
|
|
4392 | |
|
|
4393 | ev_async_init (&u->async_w, async_cb); |
|
|
4394 | ev_async_start (EV_A_ &u->async_w); |
|
|
4395 | |
|
|
4396 | pthread_mutex_init (&u->lock, 0); |
|
|
4397 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4398 | |
|
|
4399 | // now associate this with the loop |
|
|
4400 | ev_set_userdata (EV_A_ u); |
|
|
4401 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4402 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4403 | |
|
|
4404 | // then create the thread running ev_loop |
|
|
4405 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4406 | } |
|
|
4407 | |
|
|
4408 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4409 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4410 | that might have been added: |
|
|
4411 | |
|
|
4412 | static void |
|
|
4413 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4414 | { |
|
|
4415 | // just used for the side effects |
|
|
4416 | } |
|
|
4417 | |
|
|
4418 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4419 | protecting the loop data, respectively. |
|
|
4420 | |
|
|
4421 | static void |
|
|
4422 | l_release (EV_P) |
|
|
4423 | { |
|
|
4424 | userdata *u = ev_userdata (EV_A); |
|
|
4425 | pthread_mutex_unlock (&u->lock); |
|
|
4426 | } |
|
|
4427 | |
|
|
4428 | static void |
|
|
4429 | l_acquire (EV_P) |
|
|
4430 | { |
|
|
4431 | userdata *u = ev_userdata (EV_A); |
|
|
4432 | pthread_mutex_lock (&u->lock); |
|
|
4433 | } |
|
|
4434 | |
|
|
4435 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4436 | into C<ev_run>: |
|
|
4437 | |
|
|
4438 | void * |
|
|
4439 | l_run (void *thr_arg) |
|
|
4440 | { |
|
|
4441 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4442 | |
|
|
4443 | l_acquire (EV_A); |
|
|
4444 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4445 | ev_run (EV_A_ 0); |
|
|
4446 | l_release (EV_A); |
|
|
4447 | |
|
|
4448 | return 0; |
|
|
4449 | } |
|
|
4450 | |
|
|
4451 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4452 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4453 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4454 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4455 | and b) skipping inter-thread-communication when there are no pending |
|
|
4456 | watchers is very beneficial): |
|
|
4457 | |
|
|
4458 | static void |
|
|
4459 | l_invoke (EV_P) |
|
|
4460 | { |
|
|
4461 | userdata *u = ev_userdata (EV_A); |
|
|
4462 | |
|
|
4463 | while (ev_pending_count (EV_A)) |
|
|
4464 | { |
|
|
4465 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4466 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4467 | } |
|
|
4468 | } |
|
|
4469 | |
|
|
4470 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4471 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4472 | thread to continue: |
|
|
4473 | |
|
|
4474 | static void |
|
|
4475 | real_invoke_pending (EV_P) |
|
|
4476 | { |
|
|
4477 | userdata *u = ev_userdata (EV_A); |
|
|
4478 | |
|
|
4479 | pthread_mutex_lock (&u->lock); |
|
|
4480 | ev_invoke_pending (EV_A); |
|
|
4481 | pthread_cond_signal (&u->invoke_cv); |
|
|
4482 | pthread_mutex_unlock (&u->lock); |
|
|
4483 | } |
|
|
4484 | |
|
|
4485 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4486 | event loop, you will now have to lock: |
|
|
4487 | |
|
|
4488 | ev_timer timeout_watcher; |
|
|
4489 | userdata *u = ev_userdata (EV_A); |
|
|
4490 | |
|
|
4491 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4492 | |
|
|
4493 | pthread_mutex_lock (&u->lock); |
|
|
4494 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4495 | ev_async_send (EV_A_ &u->async_w); |
|
|
4496 | pthread_mutex_unlock (&u->lock); |
|
|
4497 | |
|
|
4498 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4499 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4500 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4501 | watchers in the next event loop iteration. |
|
|
4502 | |
4953 | |
4503 | =head3 COROUTINES |
4954 | =head3 COROUTINES |
4504 | |
4955 | |
4505 | Libev is very accommodating to coroutines ("cooperative threads"): |
4956 | Libev is very accommodating to coroutines ("cooperative threads"): |
4506 | libev fully supports nesting calls to its functions from different |
4957 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4671 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5122 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4672 | model. Libev still offers limited functionality on this platform in |
5123 | model. Libev still offers limited functionality on this platform in |
4673 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5124 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4674 | descriptors. This only applies when using Win32 natively, not when using |
5125 | descriptors. This only applies when using Win32 natively, not when using |
4675 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5126 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4676 | as every compielr comes with a slightly differently broken/incompatible |
5127 | as every compiler comes with a slightly differently broken/incompatible |
4677 | environment. |
5128 | environment. |
4678 | |
5129 | |
4679 | Lifting these limitations would basically require the full |
5130 | Lifting these limitations would basically require the full |
4680 | re-implementation of the I/O system. If you are into this kind of thing, |
5131 | re-implementation of the I/O system. If you are into this kind of thing, |
4681 | then note that glib does exactly that for you in a very portable way (note |
5132 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4814 | |
5265 | |
4815 | The type C<double> is used to represent timestamps. It is required to |
5266 | The type C<double> is used to represent timestamps. It is required to |
4816 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5267 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4817 | good enough for at least into the year 4000 with millisecond accuracy |
5268 | good enough for at least into the year 4000 with millisecond accuracy |
4818 | (the design goal for libev). This requirement is overfulfilled by |
5269 | (the design goal for libev). This requirement is overfulfilled by |
4819 | implementations using IEEE 754, which is basically all existing ones. With |
5270 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5271 | |
4820 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5272 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5273 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5274 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5275 | something like that, just kidding). |
4821 | |
5276 | |
4822 | =back |
5277 | =back |
4823 | |
5278 | |
4824 | If you know of other additional requirements drop me a note. |
5279 | If you know of other additional requirements drop me a note. |
4825 | |
5280 | |
… | |
… | |
4887 | =item Processing ev_async_send: O(number_of_async_watchers) |
5342 | =item Processing ev_async_send: O(number_of_async_watchers) |
4888 | |
5343 | |
4889 | =item Processing signals: O(max_signal_number) |
5344 | =item Processing signals: O(max_signal_number) |
4890 | |
5345 | |
4891 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5346 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4892 | calls in the current loop iteration. Checking for async and signal events |
5347 | calls in the current loop iteration and the loop is currently |
|
|
5348 | blocked. Checking for async and signal events involves iterating over all |
4893 | involves iterating over all running async watchers or all signal numbers. |
5349 | running async watchers or all signal numbers. |
4894 | |
5350 | |
4895 | =back |
5351 | =back |
4896 | |
5352 | |
4897 | |
5353 | |
4898 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5354 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
5015 | The physical time that is observed. It is apparently strictly monotonic :) |
5471 | The physical time that is observed. It is apparently strictly monotonic :) |
5016 | |
5472 | |
5017 | =item wall-clock time |
5473 | =item wall-clock time |
5018 | |
5474 | |
5019 | The time and date as shown on clocks. Unlike real time, it can actually |
5475 | The time and date as shown on clocks. Unlike real time, it can actually |
5020 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5476 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5021 | clock. |
5477 | clock. |
5022 | |
5478 | |
5023 | =item watcher |
5479 | =item watcher |
5024 | |
5480 | |
5025 | A data structure that describes interest in certain events. Watchers need |
5481 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5028 | =back |
5484 | =back |
5029 | |
5485 | |
5030 | =head1 AUTHOR |
5486 | =head1 AUTHOR |
5031 | |
5487 | |
5032 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5488 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5033 | Magnusson and Emanuele Giaquinta. |
5489 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5034 | |
5490 | |