… | |
… | |
8 | |
8 | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
|
|
13 | |
|
|
14 | #include <stdio.h> // for puts |
13 | |
15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_TYPE |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
… | |
… | |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // unloop was called, so exit |
62 | return 0; |
64 | return 0; |
63 | } |
65 | } |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
|
|
68 | |
|
|
69 | This document documents the libev software package. |
66 | |
70 | |
67 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
|
|
74 | |
|
|
75 | While this document tries to be as complete as possible in documenting |
|
|
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
|
|
77 | on event-based programming, nor will it introduce event-based programming |
|
|
78 | with libev. |
|
|
79 | |
|
|
80 | Familarity with event based programming techniques in general is assumed |
|
|
81 | throughout this document. |
|
|
82 | |
|
|
83 | =head1 ABOUT LIBEV |
70 | |
84 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
74 | |
88 | |
… | |
… | |
84 | =head2 FEATURES |
98 | =head2 FEATURES |
85 | |
99 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
107 | change events (C<ev_child>), and event watchers dealing with the event |
94 | file watchers (C<ev_stat>) and even limited support for fork events |
108 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
|
|
110 | limited support for fork events (C<ev_fork>). |
96 | |
111 | |
97 | It also is quite fast (see this |
112 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
113 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
114 | for example). |
100 | |
115 | |
… | |
… | |
108 | name C<loop> (which is always of type C<ev_loop *>) will not have |
123 | name C<loop> (which is always of type C<ev_loop *>) will not have |
109 | this argument. |
124 | this argument. |
110 | |
125 | |
111 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
112 | |
127 | |
113 | Libev represents time as a single floating point number, representing the |
128 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
129 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
130 | near the beginning of 1970, details are complicated, don't ask). This |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
131 | type is called C<ev_tstamp>, which is what you should use too. It usually |
117 | to the C<double> type in C, and when you need to do any calculations on |
132 | aliases to the C<double> type in C. When you need to do any calculations |
118 | it, you should treat it as some floating point value. Unlike the name |
133 | on it, you should treat it as some floating point value. Unlike the name |
119 | component C<stamp> might indicate, it is also used for time differences |
134 | component C<stamp> might indicate, it is also used for time differences |
120 | throughout libev. |
135 | throughout libev. |
121 | |
136 | |
122 | =head1 ERROR HANDLING |
137 | =head1 ERROR HANDLING |
123 | |
138 | |
… | |
… | |
347 | forget about forgetting to tell libev about forking) when you use this |
362 | forget about forgetting to tell libev about forking) when you use this |
348 | flag. |
363 | flag. |
349 | |
364 | |
350 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
365 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
351 | environment variable. |
366 | environment variable. |
|
|
367 | |
|
|
368 | =item C<EVFLAG_NOINOTIFY> |
|
|
369 | |
|
|
370 | When this flag is specified, then libev will not attempt to use the |
|
|
371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
|
|
372 | testing, this flag can be useful to conserve inotify file descriptors, as |
|
|
373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
|
|
374 | |
|
|
375 | =item C<EVFLAG_NOSIGNALFD> |
|
|
376 | |
|
|
377 | When this flag is specified, then libev will not attempt to use the |
|
|
378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is |
|
|
379 | probably only useful to work around any bugs in libev. Consequently, this |
|
|
380 | flag might go away once the signalfd functionality is considered stable, |
|
|
381 | so it's useful mostly in environment variables and not in program code. |
352 | |
382 | |
353 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
383 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
354 | |
384 | |
355 | This is your standard select(2) backend. Not I<completely> standard, as |
385 | This is your standard select(2) backend. Not I<completely> standard, as |
356 | libev tries to roll its own fd_set with no limits on the number of fds, |
386 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
417 | i.e. keep at least one watcher active per fd at all times. Stopping and |
447 | i.e. keep at least one watcher active per fd at all times. Stopping and |
418 | starting a watcher (without re-setting it) also usually doesn't cause |
448 | starting a watcher (without re-setting it) also usually doesn't cause |
419 | extra overhead. A fork can both result in spurious notifications as well |
449 | extra overhead. A fork can both result in spurious notifications as well |
420 | as in libev having to destroy and recreate the epoll object, which can |
450 | as in libev having to destroy and recreate the epoll object, which can |
421 | take considerable time and thus should be avoided. |
451 | take considerable time and thus should be avoided. |
|
|
452 | |
|
|
453 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
454 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
455 | the usage. So sad. |
422 | |
456 | |
423 | While nominally embeddable in other event loops, this feature is broken in |
457 | While nominally embeddable in other event loops, this feature is broken in |
424 | all kernel versions tested so far. |
458 | all kernel versions tested so far. |
425 | |
459 | |
426 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
460 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
… | |
… | |
454 | |
488 | |
455 | While nominally embeddable in other event loops, this doesn't work |
489 | While nominally embeddable in other event loops, this doesn't work |
456 | everywhere, so you might need to test for this. And since it is broken |
490 | everywhere, so you might need to test for this. And since it is broken |
457 | almost everywhere, you should only use it when you have a lot of sockets |
491 | almost everywhere, you should only use it when you have a lot of sockets |
458 | (for which it usually works), by embedding it into another event loop |
492 | (for which it usually works), by embedding it into another event loop |
459 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
493 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
460 | using it only for sockets. |
494 | also broken on OS X)) and, did I mention it, using it only for sockets. |
461 | |
495 | |
462 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
496 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
463 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
497 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
464 | C<NOTE_EOF>. |
498 | C<NOTE_EOF>. |
465 | |
499 | |
… | |
… | |
500 | |
534 | |
501 | It is definitely not recommended to use this flag. |
535 | It is definitely not recommended to use this flag. |
502 | |
536 | |
503 | =back |
537 | =back |
504 | |
538 | |
505 | If one or more of these are or'ed into the flags value, then only these |
539 | If one or more of the backend flags are or'ed into the flags value, |
506 | backends will be tried (in the reverse order as listed here). If none are |
540 | then only these backends will be tried (in the reverse order as listed |
507 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
541 | here). If none are specified, all backends in C<ev_recommended_backends |
|
|
542 | ()> will be tried. |
508 | |
543 | |
509 | Example: This is the most typical usage. |
544 | Example: This is the most typical usage. |
510 | |
545 | |
511 | if (!ev_default_loop (0)) |
546 | if (!ev_default_loop (0)) |
512 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
547 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
… | |
… | |
603 | |
638 | |
604 | This value can sometimes be useful as a generation counter of sorts (it |
639 | This value can sometimes be useful as a generation counter of sorts (it |
605 | "ticks" the number of loop iterations), as it roughly corresponds with |
640 | "ticks" the number of loop iterations), as it roughly corresponds with |
606 | C<ev_prepare> and C<ev_check> calls. |
641 | C<ev_prepare> and C<ev_check> calls. |
607 | |
642 | |
|
|
643 | =item unsigned int ev_loop_depth (loop) |
|
|
644 | |
|
|
645 | Returns the number of times C<ev_loop> was entered minus the number of |
|
|
646 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
647 | |
|
|
648 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
|
|
649 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
|
|
650 | in which case it is higher. |
|
|
651 | |
|
|
652 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
653 | etc.), doesn't count as exit. |
|
|
654 | |
608 | =item unsigned int ev_backend (loop) |
655 | =item unsigned int ev_backend (loop) |
609 | |
656 | |
610 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
657 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
611 | use. |
658 | use. |
612 | |
659 | |
… | |
… | |
626 | |
673 | |
627 | This function is rarely useful, but when some event callback runs for a |
674 | This function is rarely useful, but when some event callback runs for a |
628 | very long time without entering the event loop, updating libev's idea of |
675 | very long time without entering the event loop, updating libev's idea of |
629 | the current time is a good idea. |
676 | the current time is a good idea. |
630 | |
677 | |
631 | See also "The special problem of time updates" in the C<ev_timer> section. |
678 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
679 | |
|
|
680 | =item ev_suspend (loop) |
|
|
681 | |
|
|
682 | =item ev_resume (loop) |
|
|
683 | |
|
|
684 | These two functions suspend and resume a loop, for use when the loop is |
|
|
685 | not used for a while and timeouts should not be processed. |
|
|
686 | |
|
|
687 | A typical use case would be an interactive program such as a game: When |
|
|
688 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
689 | would be best to handle timeouts as if no time had actually passed while |
|
|
690 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
691 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
692 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
693 | |
|
|
694 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
695 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
696 | will be rescheduled (that is, they will lose any events that would have |
|
|
697 | occured while suspended). |
|
|
698 | |
|
|
699 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
700 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
701 | without a previous call to C<ev_suspend>. |
|
|
702 | |
|
|
703 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
704 | event loop time (see C<ev_now_update>). |
632 | |
705 | |
633 | =item ev_loop (loop, int flags) |
706 | =item ev_loop (loop, int flags) |
634 | |
707 | |
635 | Finally, this is it, the event handler. This function usually is called |
708 | Finally, this is it, the event handler. This function usually is called |
636 | after you initialised all your watchers and you want to start handling |
709 | after you initialised all your watchers and you want to start handling |
… | |
… | |
720 | |
793 | |
721 | If you have a watcher you never unregister that should not keep C<ev_loop> |
794 | If you have a watcher you never unregister that should not keep C<ev_loop> |
722 | from returning, call ev_unref() after starting, and ev_ref() before |
795 | from returning, call ev_unref() after starting, and ev_ref() before |
723 | stopping it. |
796 | stopping it. |
724 | |
797 | |
725 | As an example, libev itself uses this for its internal signal pipe: It is |
798 | As an example, libev itself uses this for its internal signal pipe: It |
726 | not visible to the libev user and should not keep C<ev_loop> from exiting |
799 | is not visible to the libev user and should not keep C<ev_loop> from |
727 | if no event watchers registered by it are active. It is also an excellent |
800 | exiting if no event watchers registered by it are active. It is also an |
728 | way to do this for generic recurring timers or from within third-party |
801 | excellent way to do this for generic recurring timers or from within |
729 | libraries. Just remember to I<unref after start> and I<ref before stop> |
802 | third-party libraries. Just remember to I<unref after start> and I<ref |
730 | (but only if the watcher wasn't active before, or was active before, |
803 | before stop> (but only if the watcher wasn't active before, or was active |
731 | respectively). |
804 | before, respectively. Note also that libev might stop watchers itself |
|
|
805 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
806 | in the callback). |
732 | |
807 | |
733 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
808 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
734 | running when nothing else is active. |
809 | running when nothing else is active. |
735 | |
810 | |
736 | ev_signal exitsig; |
811 | ev_signal exitsig; |
… | |
… | |
765 | |
840 | |
766 | By setting a higher I<io collect interval> you allow libev to spend more |
841 | By setting a higher I<io collect interval> you allow libev to spend more |
767 | time collecting I/O events, so you can handle more events per iteration, |
842 | time collecting I/O events, so you can handle more events per iteration, |
768 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
843 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
769 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
844 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
770 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
845 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
846 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
847 | once per this interval, on average. |
771 | |
848 | |
772 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
849 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
773 | to spend more time collecting timeouts, at the expense of increased |
850 | to spend more time collecting timeouts, at the expense of increased |
774 | latency/jitter/inexactness (the watcher callback will be called |
851 | latency/jitter/inexactness (the watcher callback will be called |
775 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
852 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
777 | |
854 | |
778 | Many (busy) programs can usually benefit by setting the I/O collect |
855 | Many (busy) programs can usually benefit by setting the I/O collect |
779 | interval to a value near C<0.1> or so, which is often enough for |
856 | interval to a value near C<0.1> or so, which is often enough for |
780 | interactive servers (of course not for games), likewise for timeouts. It |
857 | interactive servers (of course not for games), likewise for timeouts. It |
781 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
858 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
782 | as this approaches the timing granularity of most systems. |
859 | as this approaches the timing granularity of most systems. Note that if |
|
|
860 | you do transactions with the outside world and you can't increase the |
|
|
861 | parallelity, then this setting will limit your transaction rate (if you |
|
|
862 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
863 | then you can't do more than 100 transations per second). |
783 | |
864 | |
784 | Setting the I<timeout collect interval> can improve the opportunity for |
865 | Setting the I<timeout collect interval> can improve the opportunity for |
785 | saving power, as the program will "bundle" timer callback invocations that |
866 | saving power, as the program will "bundle" timer callback invocations that |
786 | are "near" in time together, by delaying some, thus reducing the number of |
867 | are "near" in time together, by delaying some, thus reducing the number of |
787 | times the process sleeps and wakes up again. Another useful technique to |
868 | times the process sleeps and wakes up again. Another useful technique to |
788 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
869 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
789 | they fire on, say, one-second boundaries only. |
870 | they fire on, say, one-second boundaries only. |
|
|
871 | |
|
|
872 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
873 | more often than 100 times per second: |
|
|
874 | |
|
|
875 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
876 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
877 | |
|
|
878 | =item ev_invoke_pending (loop) |
|
|
879 | |
|
|
880 | This call will simply invoke all pending watchers while resetting their |
|
|
881 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
|
882 | but when overriding the invoke callback this call comes handy. |
|
|
883 | |
|
|
884 | =item int ev_pending_count (loop) |
|
|
885 | |
|
|
886 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
887 | are pending. |
|
|
888 | |
|
|
889 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
890 | |
|
|
891 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
892 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
893 | this callback instead. This is useful, for example, when you want to |
|
|
894 | invoke the actual watchers inside another context (another thread etc.). |
|
|
895 | |
|
|
896 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
897 | callback. |
|
|
898 | |
|
|
899 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
900 | |
|
|
901 | Sometimes you want to share the same loop between multiple threads. This |
|
|
902 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
903 | each call to a libev function. |
|
|
904 | |
|
|
905 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
906 | wait for it to return. One way around this is to wake up the loop via |
|
|
907 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
908 | and I<acquire> callbacks on the loop. |
|
|
909 | |
|
|
910 | When set, then C<release> will be called just before the thread is |
|
|
911 | suspended waiting for new events, and C<acquire> is called just |
|
|
912 | afterwards. |
|
|
913 | |
|
|
914 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
915 | C<acquire> will just call the mutex_lock function again. |
|
|
916 | |
|
|
917 | While event loop modifications are allowed between invocations of |
|
|
918 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
919 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
920 | have no effect on the set of file descriptors being watched, or the time |
|
|
921 | waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
922 | to take note of any changes you made. |
|
|
923 | |
|
|
924 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
925 | invocations of C<release> and C<acquire>. |
|
|
926 | |
|
|
927 | See also the locking example in the C<THREADS> section later in this |
|
|
928 | document. |
|
|
929 | |
|
|
930 | =item ev_set_userdata (loop, void *data) |
|
|
931 | |
|
|
932 | =item ev_userdata (loop) |
|
|
933 | |
|
|
934 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
935 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
936 | C<0.> |
|
|
937 | |
|
|
938 | These two functions can be used to associate arbitrary data with a loop, |
|
|
939 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
940 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
941 | any other purpose as well. |
790 | |
942 | |
791 | =item ev_loop_verify (loop) |
943 | =item ev_loop_verify (loop) |
792 | |
944 | |
793 | This function only does something when C<EV_VERIFY> support has been |
945 | This function only does something when C<EV_VERIFY> support has been |
794 | compiled in, which is the default for non-minimal builds. It tries to go |
946 | compiled in, which is the default for non-minimal builds. It tries to go |
… | |
… | |
920 | |
1072 | |
921 | =item C<EV_ASYNC> |
1073 | =item C<EV_ASYNC> |
922 | |
1074 | |
923 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1075 | The given async watcher has been asynchronously notified (see C<ev_async>). |
924 | |
1076 | |
|
|
1077 | =item C<EV_CUSTOM> |
|
|
1078 | |
|
|
1079 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1080 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
1081 | |
925 | =item C<EV_ERROR> |
1082 | =item C<EV_ERROR> |
926 | |
1083 | |
927 | An unspecified error has occurred, the watcher has been stopped. This might |
1084 | An unspecified error has occurred, the watcher has been stopped. This might |
928 | happen because the watcher could not be properly started because libev |
1085 | happen because the watcher could not be properly started because libev |
929 | ran out of memory, a file descriptor was found to be closed or any other |
1086 | ran out of memory, a file descriptor was found to be closed or any other |
… | |
… | |
1044 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1201 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1045 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1202 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1046 | before watchers with lower priority, but priority will not keep watchers |
1203 | before watchers with lower priority, but priority will not keep watchers |
1047 | from being executed (except for C<ev_idle> watchers). |
1204 | from being executed (except for C<ev_idle> watchers). |
1048 | |
1205 | |
1049 | This means that priorities are I<only> used for ordering callback |
|
|
1050 | invocation after new events have been received. This is useful, for |
|
|
1051 | example, to reduce latency after idling, or more often, to bind two |
|
|
1052 | watchers on the same event and make sure one is called first. |
|
|
1053 | |
|
|
1054 | If you need to suppress invocation when higher priority events are pending |
1206 | If you need to suppress invocation when higher priority events are pending |
1055 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1207 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1056 | |
1208 | |
1057 | You I<must not> change the priority of a watcher as long as it is active or |
1209 | You I<must not> change the priority of a watcher as long as it is active or |
1058 | pending. |
1210 | pending. |
1059 | |
|
|
1060 | The default priority used by watchers when no priority has been set is |
|
|
1061 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1062 | |
1211 | |
1063 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1212 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1064 | fine, as long as you do not mind that the priority value you query might |
1213 | fine, as long as you do not mind that the priority value you query might |
1065 | or might not have been clamped to the valid range. |
1214 | or might not have been clamped to the valid range. |
|
|
1215 | |
|
|
1216 | The default priority used by watchers when no priority has been set is |
|
|
1217 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1218 | |
|
|
1219 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1220 | priorities. |
1066 | |
1221 | |
1067 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1222 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1068 | |
1223 | |
1069 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1224 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1070 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1225 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1135 | #include <stddef.h> |
1290 | #include <stddef.h> |
1136 | |
1291 | |
1137 | static void |
1292 | static void |
1138 | t1_cb (EV_P_ ev_timer *w, int revents) |
1293 | t1_cb (EV_P_ ev_timer *w, int revents) |
1139 | { |
1294 | { |
1140 | struct my_biggy big = (struct my_biggy * |
1295 | struct my_biggy big = (struct my_biggy *) |
1141 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1296 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1142 | } |
1297 | } |
1143 | |
1298 | |
1144 | static void |
1299 | static void |
1145 | t2_cb (EV_P_ ev_timer *w, int revents) |
1300 | t2_cb (EV_P_ ev_timer *w, int revents) |
1146 | { |
1301 | { |
1147 | struct my_biggy big = (struct my_biggy * |
1302 | struct my_biggy big = (struct my_biggy *) |
1148 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1303 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1149 | } |
1304 | } |
|
|
1305 | |
|
|
1306 | =head2 WATCHER PRIORITY MODELS |
|
|
1307 | |
|
|
1308 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1309 | integers that influence the ordering of event callback invocation |
|
|
1310 | between watchers in some way, all else being equal. |
|
|
1311 | |
|
|
1312 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1313 | description for the more technical details such as the actual priority |
|
|
1314 | range. |
|
|
1315 | |
|
|
1316 | There are two common ways how these these priorities are being interpreted |
|
|
1317 | by event loops: |
|
|
1318 | |
|
|
1319 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1320 | of lower priority watchers, which means as long as higher priority |
|
|
1321 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1322 | |
|
|
1323 | The less common only-for-ordering model uses priorities solely to order |
|
|
1324 | callback invocation within a single event loop iteration: Higher priority |
|
|
1325 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1326 | before polling for new events. |
|
|
1327 | |
|
|
1328 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1329 | except for idle watchers (which use the lock-out model). |
|
|
1330 | |
|
|
1331 | The rationale behind this is that implementing the lock-out model for |
|
|
1332 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1333 | libraries will just poll for the same events again and again as long as |
|
|
1334 | their callbacks have not been executed, which is very inefficient in the |
|
|
1335 | common case of one high-priority watcher locking out a mass of lower |
|
|
1336 | priority ones. |
|
|
1337 | |
|
|
1338 | Static (ordering) priorities are most useful when you have two or more |
|
|
1339 | watchers handling the same resource: a typical usage example is having an |
|
|
1340 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1341 | timeouts. Under load, data might be received while the program handles |
|
|
1342 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1343 | handler will be executed before checking for data. In that case, giving |
|
|
1344 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1345 | handled first even under adverse conditions (which is usually, but not |
|
|
1346 | always, what you want). |
|
|
1347 | |
|
|
1348 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1349 | will only be executed when no same or higher priority watchers have |
|
|
1350 | received events, they can be used to implement the "lock-out" model when |
|
|
1351 | required. |
|
|
1352 | |
|
|
1353 | For example, to emulate how many other event libraries handle priorities, |
|
|
1354 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1355 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1356 | processing is done in the idle watcher callback. This causes libev to |
|
|
1357 | continously poll and process kernel event data for the watcher, but when |
|
|
1358 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1359 | workable. |
|
|
1360 | |
|
|
1361 | Usually, however, the lock-out model implemented that way will perform |
|
|
1362 | miserably under the type of load it was designed to handle. In that case, |
|
|
1363 | it might be preferable to stop the real watcher before starting the |
|
|
1364 | idle watcher, so the kernel will not have to process the event in case |
|
|
1365 | the actual processing will be delayed for considerable time. |
|
|
1366 | |
|
|
1367 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1368 | priority than the default, and which should only process data when no |
|
|
1369 | other events are pending: |
|
|
1370 | |
|
|
1371 | ev_idle idle; // actual processing watcher |
|
|
1372 | ev_io io; // actual event watcher |
|
|
1373 | |
|
|
1374 | static void |
|
|
1375 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1376 | { |
|
|
1377 | // stop the I/O watcher, we received the event, but |
|
|
1378 | // are not yet ready to handle it. |
|
|
1379 | ev_io_stop (EV_A_ w); |
|
|
1380 | |
|
|
1381 | // start the idle watcher to ahndle the actual event. |
|
|
1382 | // it will not be executed as long as other watchers |
|
|
1383 | // with the default priority are receiving events. |
|
|
1384 | ev_idle_start (EV_A_ &idle); |
|
|
1385 | } |
|
|
1386 | |
|
|
1387 | static void |
|
|
1388 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1389 | { |
|
|
1390 | // actual processing |
|
|
1391 | read (STDIN_FILENO, ...); |
|
|
1392 | |
|
|
1393 | // have to start the I/O watcher again, as |
|
|
1394 | // we have handled the event |
|
|
1395 | ev_io_start (EV_P_ &io); |
|
|
1396 | } |
|
|
1397 | |
|
|
1398 | // initialisation |
|
|
1399 | ev_idle_init (&idle, idle_cb); |
|
|
1400 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1401 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1402 | |
|
|
1403 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1404 | low-priority connections can not be locked out forever under load. This |
|
|
1405 | enables your program to keep a lower latency for important connections |
|
|
1406 | during short periods of high load, while not completely locking out less |
|
|
1407 | important ones. |
1150 | |
1408 | |
1151 | |
1409 | |
1152 | =head1 WATCHER TYPES |
1410 | =head1 WATCHER TYPES |
1153 | |
1411 | |
1154 | This section describes each watcher in detail, but will not repeat |
1412 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1180 | descriptors to non-blocking mode is also usually a good idea (but not |
1438 | descriptors to non-blocking mode is also usually a good idea (but not |
1181 | required if you know what you are doing). |
1439 | required if you know what you are doing). |
1182 | |
1440 | |
1183 | If you cannot use non-blocking mode, then force the use of a |
1441 | If you cannot use non-blocking mode, then force the use of a |
1184 | known-to-be-good backend (at the time of this writing, this includes only |
1442 | known-to-be-good backend (at the time of this writing, this includes only |
1185 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1443 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1444 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1445 | files) - libev doesn't guarentee any specific behaviour in that case. |
1186 | |
1446 | |
1187 | Another thing you have to watch out for is that it is quite easy to |
1447 | Another thing you have to watch out for is that it is quite easy to |
1188 | receive "spurious" readiness notifications, that is your callback might |
1448 | receive "spurious" readiness notifications, that is your callback might |
1189 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1449 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1190 | because there is no data. Not only are some backends known to create a |
1450 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1311 | year, it will still time out after (roughly) one hour. "Roughly" because |
1571 | year, it will still time out after (roughly) one hour. "Roughly" because |
1312 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1572 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1313 | monotonic clock option helps a lot here). |
1573 | monotonic clock option helps a lot here). |
1314 | |
1574 | |
1315 | The callback is guaranteed to be invoked only I<after> its timeout has |
1575 | The callback is guaranteed to be invoked only I<after> its timeout has |
1316 | passed, but if multiple timers become ready during the same loop iteration |
1576 | passed (not I<at>, so on systems with very low-resolution clocks this |
1317 | then order of execution is undefined. |
1577 | might introduce a small delay). If multiple timers become ready during the |
|
|
1578 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1579 | before ones of the same priority with later time-out values (but this is |
|
|
1580 | no longer true when a callback calls C<ev_loop> recursively). |
1318 | |
1581 | |
1319 | =head3 Be smart about timeouts |
1582 | =head3 Be smart about timeouts |
1320 | |
1583 | |
1321 | Many real-world problems involve some kind of timeout, usually for error |
1584 | Many real-world problems involve some kind of timeout, usually for error |
1322 | recovery. A typical example is an HTTP request - if the other side hangs, |
1585 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1366 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1629 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1367 | member and C<ev_timer_again>. |
1630 | member and C<ev_timer_again>. |
1368 | |
1631 | |
1369 | At start: |
1632 | At start: |
1370 | |
1633 | |
1371 | ev_timer_init (timer, callback); |
1634 | ev_init (timer, callback); |
1372 | timer->repeat = 60.; |
1635 | timer->repeat = 60.; |
1373 | ev_timer_again (loop, timer); |
1636 | ev_timer_again (loop, timer); |
1374 | |
1637 | |
1375 | Each time there is some activity: |
1638 | Each time there is some activity: |
1376 | |
1639 | |
… | |
… | |
1415 | else |
1678 | else |
1416 | { |
1679 | { |
1417 | // callback was invoked, but there was some activity, re-arm |
1680 | // callback was invoked, but there was some activity, re-arm |
1418 | // the watcher to fire in last_activity + 60, which is |
1681 | // the watcher to fire in last_activity + 60, which is |
1419 | // guaranteed to be in the future, so "again" is positive: |
1682 | // guaranteed to be in the future, so "again" is positive: |
1420 | w->again = timeout - now; |
1683 | w->repeat = timeout - now; |
1421 | ev_timer_again (EV_A_ w); |
1684 | ev_timer_again (EV_A_ w); |
1422 | } |
1685 | } |
1423 | } |
1686 | } |
1424 | |
1687 | |
1425 | To summarise the callback: first calculate the real timeout (defined |
1688 | To summarise the callback: first calculate the real timeout (defined |
… | |
… | |
1438 | |
1701 | |
1439 | To start the timer, simply initialise the watcher and set C<last_activity> |
1702 | To start the timer, simply initialise the watcher and set C<last_activity> |
1440 | to the current time (meaning we just have some activity :), then call the |
1703 | to the current time (meaning we just have some activity :), then call the |
1441 | callback, which will "do the right thing" and start the timer: |
1704 | callback, which will "do the right thing" and start the timer: |
1442 | |
1705 | |
1443 | ev_timer_init (timer, callback); |
1706 | ev_init (timer, callback); |
1444 | last_activity = ev_now (loop); |
1707 | last_activity = ev_now (loop); |
1445 | callback (loop, timer, EV_TIMEOUT); |
1708 | callback (loop, timer, EV_TIMEOUT); |
1446 | |
1709 | |
1447 | And when there is some activity, simply store the current time in |
1710 | And when there is some activity, simply store the current time in |
1448 | C<last_activity>, no libev calls at all: |
1711 | C<last_activity>, no libev calls at all: |
… | |
… | |
1509 | |
1772 | |
1510 | If the event loop is suspended for a long time, you can also force an |
1773 | If the event loop is suspended for a long time, you can also force an |
1511 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1774 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1512 | ()>. |
1775 | ()>. |
1513 | |
1776 | |
|
|
1777 | =head3 The special problems of suspended animation |
|
|
1778 | |
|
|
1779 | When you leave the server world it is quite customary to hit machines that |
|
|
1780 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1781 | |
|
|
1782 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1783 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1784 | to run until the system is suspended, but they will not advance while the |
|
|
1785 | system is suspended. That means, on resume, it will be as if the program |
|
|
1786 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1787 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1788 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1789 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1790 | be adjusted accordingly. |
|
|
1791 | |
|
|
1792 | I would not be surprised to see different behaviour in different between |
|
|
1793 | operating systems, OS versions or even different hardware. |
|
|
1794 | |
|
|
1795 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1796 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1797 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1798 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1799 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1800 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1801 | |
|
|
1802 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1803 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1804 | deterministic behaviour in this case (you can do nothing against |
|
|
1805 | C<SIGSTOP>). |
|
|
1806 | |
1514 | =head3 Watcher-Specific Functions and Data Members |
1807 | =head3 Watcher-Specific Functions and Data Members |
1515 | |
1808 | |
1516 | =over 4 |
1809 | =over 4 |
1517 | |
1810 | |
1518 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1811 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1541 | If the timer is started but non-repeating, stop it (as if it timed out). |
1834 | If the timer is started but non-repeating, stop it (as if it timed out). |
1542 | |
1835 | |
1543 | If the timer is repeating, either start it if necessary (with the |
1836 | If the timer is repeating, either start it if necessary (with the |
1544 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1837 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1545 | |
1838 | |
1546 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1839 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1547 | usage example. |
1840 | usage example. |
|
|
1841 | |
|
|
1842 | =item ev_timer_remaining (loop, ev_timer *) |
|
|
1843 | |
|
|
1844 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
1845 | then this time is relative to the current event loop time, otherwise it's |
|
|
1846 | the timeout value currently configured. |
|
|
1847 | |
|
|
1848 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
1849 | C<5>. When the timer is started and one second passes, C<ev_timer_remain> |
|
|
1850 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1851 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1852 | too), and so on. |
1548 | |
1853 | |
1549 | =item ev_tstamp repeat [read-write] |
1854 | =item ev_tstamp repeat [read-write] |
1550 | |
1855 | |
1551 | The current C<repeat> value. Will be used each time the watcher times out |
1856 | The current C<repeat> value. Will be used each time the watcher times out |
1552 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1857 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1590 | =head2 C<ev_periodic> - to cron or not to cron? |
1895 | =head2 C<ev_periodic> - to cron or not to cron? |
1591 | |
1896 | |
1592 | Periodic watchers are also timers of a kind, but they are very versatile |
1897 | Periodic watchers are also timers of a kind, but they are very versatile |
1593 | (and unfortunately a bit complex). |
1898 | (and unfortunately a bit complex). |
1594 | |
1899 | |
1595 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1900 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1596 | but on wall clock time (absolute time). You can tell a periodic watcher |
1901 | relative time, the physical time that passes) but on wall clock time |
1597 | to trigger after some specific point in time. For example, if you tell a |
1902 | (absolute time, the thing you can read on your calender or clock). The |
1598 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1903 | difference is that wall clock time can run faster or slower than real |
1599 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1904 | time, and time jumps are not uncommon (e.g. when you adjust your |
1600 | clock to January of the previous year, then it will take more than year |
1905 | wrist-watch). |
1601 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1602 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1603 | |
1906 | |
|
|
1907 | You can tell a periodic watcher to trigger after some specific point |
|
|
1908 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1909 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1910 | not a delay) and then reset your system clock to January of the previous |
|
|
1911 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1912 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1913 | it, as it uses a relative timeout). |
|
|
1914 | |
1604 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1915 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1605 | such as triggering an event on each "midnight, local time", or other |
1916 | timers, such as triggering an event on each "midnight, local time", or |
1606 | complicated rules. |
1917 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1918 | those cannot react to time jumps. |
1607 | |
1919 | |
1608 | As with timers, the callback is guaranteed to be invoked only when the |
1920 | As with timers, the callback is guaranteed to be invoked only when the |
1609 | time (C<at>) has passed, but if multiple periodic timers become ready |
1921 | point in time where it is supposed to trigger has passed. If multiple |
1610 | during the same loop iteration, then order of execution is undefined. |
1922 | timers become ready during the same loop iteration then the ones with |
|
|
1923 | earlier time-out values are invoked before ones with later time-out values |
|
|
1924 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1611 | |
1925 | |
1612 | =head3 Watcher-Specific Functions and Data Members |
1926 | =head3 Watcher-Specific Functions and Data Members |
1613 | |
1927 | |
1614 | =over 4 |
1928 | =over 4 |
1615 | |
1929 | |
1616 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1930 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1617 | |
1931 | |
1618 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1932 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1619 | |
1933 | |
1620 | Lots of arguments, lets sort it out... There are basically three modes of |
1934 | Lots of arguments, let's sort it out... There are basically three modes of |
1621 | operation, and we will explain them from simplest to most complex: |
1935 | operation, and we will explain them from simplest to most complex: |
1622 | |
1936 | |
1623 | =over 4 |
1937 | =over 4 |
1624 | |
1938 | |
1625 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1939 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1626 | |
1940 | |
1627 | In this configuration the watcher triggers an event after the wall clock |
1941 | In this configuration the watcher triggers an event after the wall clock |
1628 | time C<at> has passed. It will not repeat and will not adjust when a time |
1942 | time C<offset> has passed. It will not repeat and will not adjust when a |
1629 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1943 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1630 | only run when the system clock reaches or surpasses this time. |
1944 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1945 | this point in time. |
1631 | |
1946 | |
1632 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1947 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1633 | |
1948 | |
1634 | In this mode the watcher will always be scheduled to time out at the next |
1949 | In this mode the watcher will always be scheduled to time out at the next |
1635 | C<at + N * interval> time (for some integer N, which can also be negative) |
1950 | C<offset + N * interval> time (for some integer N, which can also be |
1636 | and then repeat, regardless of any time jumps. |
1951 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1952 | argument is merely an offset into the C<interval> periods. |
1637 | |
1953 | |
1638 | This can be used to create timers that do not drift with respect to the |
1954 | This can be used to create timers that do not drift with respect to the |
1639 | system clock, for example, here is a C<ev_periodic> that triggers each |
1955 | system clock, for example, here is an C<ev_periodic> that triggers each |
1640 | hour, on the hour: |
1956 | hour, on the hour (with respect to UTC): |
1641 | |
1957 | |
1642 | ev_periodic_set (&periodic, 0., 3600., 0); |
1958 | ev_periodic_set (&periodic, 0., 3600., 0); |
1643 | |
1959 | |
1644 | This doesn't mean there will always be 3600 seconds in between triggers, |
1960 | This doesn't mean there will always be 3600 seconds in between triggers, |
1645 | but only that the callback will be called when the system time shows a |
1961 | but only that the callback will be called when the system time shows a |
1646 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1962 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1647 | by 3600. |
1963 | by 3600. |
1648 | |
1964 | |
1649 | Another way to think about it (for the mathematically inclined) is that |
1965 | Another way to think about it (for the mathematically inclined) is that |
1650 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1966 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1651 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1967 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1652 | |
1968 | |
1653 | For numerical stability it is preferable that the C<at> value is near |
1969 | For numerical stability it is preferable that the C<offset> value is near |
1654 | C<ev_now ()> (the current time), but there is no range requirement for |
1970 | C<ev_now ()> (the current time), but there is no range requirement for |
1655 | this value, and in fact is often specified as zero. |
1971 | this value, and in fact is often specified as zero. |
1656 | |
1972 | |
1657 | Note also that there is an upper limit to how often a timer can fire (CPU |
1973 | Note also that there is an upper limit to how often a timer can fire (CPU |
1658 | speed for example), so if C<interval> is very small then timing stability |
1974 | speed for example), so if C<interval> is very small then timing stability |
1659 | will of course deteriorate. Libev itself tries to be exact to be about one |
1975 | will of course deteriorate. Libev itself tries to be exact to be about one |
1660 | millisecond (if the OS supports it and the machine is fast enough). |
1976 | millisecond (if the OS supports it and the machine is fast enough). |
1661 | |
1977 | |
1662 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1978 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1663 | |
1979 | |
1664 | In this mode the values for C<interval> and C<at> are both being |
1980 | In this mode the values for C<interval> and C<offset> are both being |
1665 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1981 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1666 | reschedule callback will be called with the watcher as first, and the |
1982 | reschedule callback will be called with the watcher as first, and the |
1667 | current time as second argument. |
1983 | current time as second argument. |
1668 | |
1984 | |
1669 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1985 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1670 | ever, or make ANY event loop modifications whatsoever>. |
1986 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1987 | allowed by documentation here>. |
1671 | |
1988 | |
1672 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1989 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1673 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1990 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1674 | only event loop modification you are allowed to do). |
1991 | only event loop modification you are allowed to do). |
1675 | |
1992 | |
… | |
… | |
1705 | a different time than the last time it was called (e.g. in a crond like |
2022 | a different time than the last time it was called (e.g. in a crond like |
1706 | program when the crontabs have changed). |
2023 | program when the crontabs have changed). |
1707 | |
2024 | |
1708 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2025 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1709 | |
2026 | |
1710 | When active, returns the absolute time that the watcher is supposed to |
2027 | When active, returns the absolute time that the watcher is supposed |
1711 | trigger next. |
2028 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2029 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2030 | rescheduling modes. |
1712 | |
2031 | |
1713 | =item ev_tstamp offset [read-write] |
2032 | =item ev_tstamp offset [read-write] |
1714 | |
2033 | |
1715 | When repeating, this contains the offset value, otherwise this is the |
2034 | When repeating, this contains the offset value, otherwise this is the |
1716 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2035 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2036 | although libev might modify this value for better numerical stability). |
1717 | |
2037 | |
1718 | Can be modified any time, but changes only take effect when the periodic |
2038 | Can be modified any time, but changes only take effect when the periodic |
1719 | timer fires or C<ev_periodic_again> is being called. |
2039 | timer fires or C<ev_periodic_again> is being called. |
1720 | |
2040 | |
1721 | =item ev_tstamp interval [read-write] |
2041 | =item ev_tstamp interval [read-write] |
… | |
… | |
1773 | Signal watchers will trigger an event when the process receives a specific |
2093 | Signal watchers will trigger an event when the process receives a specific |
1774 | signal one or more times. Even though signals are very asynchronous, libev |
2094 | signal one or more times. Even though signals are very asynchronous, libev |
1775 | will try it's best to deliver signals synchronously, i.e. as part of the |
2095 | will try it's best to deliver signals synchronously, i.e. as part of the |
1776 | normal event processing, like any other event. |
2096 | normal event processing, like any other event. |
1777 | |
2097 | |
1778 | If you want signals asynchronously, just use C<sigaction> as you would |
2098 | If you want signals to be delivered truly asynchronously, just use |
1779 | do without libev and forget about sharing the signal. You can even use |
2099 | C<sigaction> as you would do without libev and forget about sharing |
1780 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
2100 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2101 | synchronously wake up an event loop. |
1781 | |
2102 | |
1782 | You can configure as many watchers as you like per signal. Only when the |
2103 | You can configure as many watchers as you like for the same signal, but |
|
|
2104 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2105 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2106 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2107 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2108 | |
1783 | first watcher gets started will libev actually register a signal handler |
2109 | When the first watcher gets started will libev actually register something |
1784 | with the kernel (thus it coexists with your own signal handlers as long as |
2110 | with the kernel (thus it coexists with your own signal handlers as long as |
1785 | you don't register any with libev for the same signal). Similarly, when |
2111 | you don't register any with libev for the same signal). |
1786 | the last signal watcher for a signal is stopped, libev will reset the |
|
|
1787 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1788 | |
2112 | |
1789 | If possible and supported, libev will install its handlers with |
2113 | If possible and supported, libev will install its handlers with |
1790 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2114 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1791 | interrupted. If you have a problem with system calls getting interrupted by |
2115 | not be unduly interrupted. If you have a problem with system calls getting |
1792 | signals you can block all signals in an C<ev_check> watcher and unblock |
2116 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1793 | them in an C<ev_prepare> watcher. |
2117 | and unblock them in an C<ev_prepare> watcher. |
|
|
2118 | |
|
|
2119 | =head3 The special problem of inheritance over execve |
|
|
2120 | |
|
|
2121 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2122 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2123 | stopping it again), that is, libev might or might not block the signal, |
|
|
2124 | and might or might not set or restore the installed signal handler. |
|
|
2125 | |
|
|
2126 | While this does not matter for the signal disposition (libev never |
|
|
2127 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2128 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2129 | certain signals to be blocked. |
|
|
2130 | |
|
|
2131 | This means that before calling C<exec> (from the child) you should reset |
|
|
2132 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2133 | choice usually). |
|
|
2134 | |
|
|
2135 | In current versions of libev, you can ensure that the signal mask is not |
|
|
2136 | blocking any signals (except temporarily, so thread users watch out) by |
|
|
2137 | specifying the C<EVFLAG_NOSIGNALFD> when creating the event loop. This is |
|
|
2138 | not guaranteed for future versions, however. |
1794 | |
2139 | |
1795 | =head3 Watcher-Specific Functions and Data Members |
2140 | =head3 Watcher-Specific Functions and Data Members |
1796 | |
2141 | |
1797 | =over 4 |
2142 | =over 4 |
1798 | |
2143 | |
… | |
… | |
1830 | some child status changes (most typically when a child of yours dies or |
2175 | some child status changes (most typically when a child of yours dies or |
1831 | exits). It is permissible to install a child watcher I<after> the child |
2176 | exits). It is permissible to install a child watcher I<after> the child |
1832 | has been forked (which implies it might have already exited), as long |
2177 | has been forked (which implies it might have already exited), as long |
1833 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2178 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1834 | forking and then immediately registering a watcher for the child is fine, |
2179 | forking and then immediately registering a watcher for the child is fine, |
1835 | but forking and registering a watcher a few event loop iterations later is |
2180 | but forking and registering a watcher a few event loop iterations later or |
1836 | not. |
2181 | in the next callback invocation is not. |
1837 | |
2182 | |
1838 | Only the default event loop is capable of handling signals, and therefore |
2183 | Only the default event loop is capable of handling signals, and therefore |
1839 | you can only register child watchers in the default event loop. |
2184 | you can only register child watchers in the default event loop. |
1840 | |
2185 | |
|
|
2186 | Due to some design glitches inside libev, child watchers will always be |
|
|
2187 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2188 | libev) |
|
|
2189 | |
1841 | =head3 Process Interaction |
2190 | =head3 Process Interaction |
1842 | |
2191 | |
1843 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2192 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1844 | initialised. This is necessary to guarantee proper behaviour even if |
2193 | initialised. This is necessary to guarantee proper behaviour even if the |
1845 | the first child watcher is started after the child exits. The occurrence |
2194 | first child watcher is started after the child exits. The occurrence |
1846 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2195 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1847 | synchronously as part of the event loop processing. Libev always reaps all |
2196 | synchronously as part of the event loop processing. Libev always reaps all |
1848 | children, even ones not watched. |
2197 | children, even ones not watched. |
1849 | |
2198 | |
1850 | =head3 Overriding the Built-In Processing |
2199 | =head3 Overriding the Built-In Processing |
… | |
… | |
1860 | =head3 Stopping the Child Watcher |
2209 | =head3 Stopping the Child Watcher |
1861 | |
2210 | |
1862 | Currently, the child watcher never gets stopped, even when the |
2211 | Currently, the child watcher never gets stopped, even when the |
1863 | child terminates, so normally one needs to stop the watcher in the |
2212 | child terminates, so normally one needs to stop the watcher in the |
1864 | callback. Future versions of libev might stop the watcher automatically |
2213 | callback. Future versions of libev might stop the watcher automatically |
1865 | when a child exit is detected. |
2214 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2215 | problem). |
1866 | |
2216 | |
1867 | =head3 Watcher-Specific Functions and Data Members |
2217 | =head3 Watcher-Specific Functions and Data Members |
1868 | |
2218 | |
1869 | =over 4 |
2219 | =over 4 |
1870 | |
2220 | |
… | |
… | |
1932 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2282 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1933 | and sees if it changed compared to the last time, invoking the callback if |
2283 | and sees if it changed compared to the last time, invoking the callback if |
1934 | it did. |
2284 | it did. |
1935 | |
2285 | |
1936 | The path does not need to exist: changing from "path exists" to "path does |
2286 | The path does not need to exist: changing from "path exists" to "path does |
1937 | not exist" is a status change like any other. The condition "path does |
2287 | not exist" is a status change like any other. The condition "path does not |
1938 | not exist" is signified by the C<st_nlink> field being zero (which is |
2288 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1939 | otherwise always forced to be at least one) and all the other fields of |
2289 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1940 | the stat buffer having unspecified contents. |
2290 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2291 | contents. |
1941 | |
2292 | |
1942 | The path I<must not> end in a slash or contain special components such as |
2293 | The path I<must not> end in a slash or contain special components such as |
1943 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
2294 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1944 | your working directory changes, then the behaviour is undefined. |
2295 | your working directory changes, then the behaviour is undefined. |
1945 | |
2296 | |
… | |
… | |
1955 | This watcher type is not meant for massive numbers of stat watchers, |
2306 | This watcher type is not meant for massive numbers of stat watchers, |
1956 | as even with OS-supported change notifications, this can be |
2307 | as even with OS-supported change notifications, this can be |
1957 | resource-intensive. |
2308 | resource-intensive. |
1958 | |
2309 | |
1959 | At the time of this writing, the only OS-specific interface implemented |
2310 | At the time of this writing, the only OS-specific interface implemented |
1960 | is the Linux inotify interface (implementing kqueue support is left as |
2311 | is the Linux inotify interface (implementing kqueue support is left as an |
1961 | an exercise for the reader. Note, however, that the author sees no way |
2312 | exercise for the reader. Note, however, that the author sees no way of |
1962 | of implementing C<ev_stat> semantics with kqueue). |
2313 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1963 | |
2314 | |
1964 | =head3 ABI Issues (Largefile Support) |
2315 | =head3 ABI Issues (Largefile Support) |
1965 | |
2316 | |
1966 | Libev by default (unless the user overrides this) uses the default |
2317 | Libev by default (unless the user overrides this) uses the default |
1967 | compilation environment, which means that on systems with large file |
2318 | compilation environment, which means that on systems with large file |
… | |
… | |
1978 | to exchange stat structures with application programs compiled using the |
2329 | to exchange stat structures with application programs compiled using the |
1979 | default compilation environment. |
2330 | default compilation environment. |
1980 | |
2331 | |
1981 | =head3 Inotify and Kqueue |
2332 | =head3 Inotify and Kqueue |
1982 | |
2333 | |
1983 | When C<inotify (7)> support has been compiled into libev (generally |
2334 | When C<inotify (7)> support has been compiled into libev and present at |
1984 | only available with Linux 2.6.25 or above due to bugs in earlier |
2335 | runtime, it will be used to speed up change detection where possible. The |
1985 | implementations) and present at runtime, it will be used to speed up |
2336 | inotify descriptor will be created lazily when the first C<ev_stat> |
1986 | change detection where possible. The inotify descriptor will be created |
2337 | watcher is being started. |
1987 | lazily when the first C<ev_stat> watcher is being started. |
|
|
1988 | |
2338 | |
1989 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2339 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1990 | except that changes might be detected earlier, and in some cases, to avoid |
2340 | except that changes might be detected earlier, and in some cases, to avoid |
1991 | making regular C<stat> calls. Even in the presence of inotify support |
2341 | making regular C<stat> calls. Even in the presence of inotify support |
1992 | there are many cases where libev has to resort to regular C<stat> polling, |
2342 | there are many cases where libev has to resort to regular C<stat> polling, |
1993 | but as long as the path exists, libev usually gets away without polling. |
2343 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2344 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2345 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2346 | xfs are fully working) libev usually gets away without polling. |
1994 | |
2347 | |
1995 | There is no support for kqueue, as apparently it cannot be used to |
2348 | There is no support for kqueue, as apparently it cannot be used to |
1996 | implement this functionality, due to the requirement of having a file |
2349 | implement this functionality, due to the requirement of having a file |
1997 | descriptor open on the object at all times, and detecting renames, unlinks |
2350 | descriptor open on the object at all times, and detecting renames, unlinks |
1998 | etc. is difficult. |
2351 | etc. is difficult. |
|
|
2352 | |
|
|
2353 | =head3 C<stat ()> is a synchronous operation |
|
|
2354 | |
|
|
2355 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2356 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2357 | ()>, which is a synchronous operation. |
|
|
2358 | |
|
|
2359 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2360 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2361 | as the path data is usually in memory already (except when starting the |
|
|
2362 | watcher). |
|
|
2363 | |
|
|
2364 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2365 | time due to network issues, and even under good conditions, a stat call |
|
|
2366 | often takes multiple milliseconds. |
|
|
2367 | |
|
|
2368 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2369 | paths, although this is fully supported by libev. |
1999 | |
2370 | |
2000 | =head3 The special problem of stat time resolution |
2371 | =head3 The special problem of stat time resolution |
2001 | |
2372 | |
2002 | The C<stat ()> system call only supports full-second resolution portably, |
2373 | The C<stat ()> system call only supports full-second resolution portably, |
2003 | and even on systems where the resolution is higher, most file systems |
2374 | and even on systems where the resolution is higher, most file systems |
… | |
… | |
2152 | |
2523 | |
2153 | =head3 Watcher-Specific Functions and Data Members |
2524 | =head3 Watcher-Specific Functions and Data Members |
2154 | |
2525 | |
2155 | =over 4 |
2526 | =over 4 |
2156 | |
2527 | |
2157 | =item ev_idle_init (ev_signal *, callback) |
2528 | =item ev_idle_init (ev_idle *, callback) |
2158 | |
2529 | |
2159 | Initialises and configures the idle watcher - it has no parameters of any |
2530 | Initialises and configures the idle watcher - it has no parameters of any |
2160 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2531 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2161 | believe me. |
2532 | believe me. |
2162 | |
2533 | |
… | |
… | |
2175 | // no longer anything immediate to do. |
2546 | // no longer anything immediate to do. |
2176 | } |
2547 | } |
2177 | |
2548 | |
2178 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2549 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2179 | ev_idle_init (idle_watcher, idle_cb); |
2550 | ev_idle_init (idle_watcher, idle_cb); |
2180 | ev_idle_start (loop, idle_cb); |
2551 | ev_idle_start (loop, idle_watcher); |
2181 | |
2552 | |
2182 | |
2553 | |
2183 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2554 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2184 | |
2555 | |
2185 | Prepare and check watchers are usually (but not always) used in pairs: |
2556 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2278 | struct pollfd fds [nfd]; |
2649 | struct pollfd fds [nfd]; |
2279 | // actual code will need to loop here and realloc etc. |
2650 | // actual code will need to loop here and realloc etc. |
2280 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2651 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2281 | |
2652 | |
2282 | /* the callback is illegal, but won't be called as we stop during check */ |
2653 | /* the callback is illegal, but won't be called as we stop during check */ |
2283 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2654 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2284 | ev_timer_start (loop, &tw); |
2655 | ev_timer_start (loop, &tw); |
2285 | |
2656 | |
2286 | // create one ev_io per pollfd |
2657 | // create one ev_io per pollfd |
2287 | for (int i = 0; i < nfd; ++i) |
2658 | for (int i = 0; i < nfd; ++i) |
2288 | { |
2659 | { |
… | |
… | |
2401 | some fds have to be watched and handled very quickly (with low latency), |
2772 | some fds have to be watched and handled very quickly (with low latency), |
2402 | and even priorities and idle watchers might have too much overhead. In |
2773 | and even priorities and idle watchers might have too much overhead. In |
2403 | this case you would put all the high priority stuff in one loop and all |
2774 | this case you would put all the high priority stuff in one loop and all |
2404 | the rest in a second one, and embed the second one in the first. |
2775 | the rest in a second one, and embed the second one in the first. |
2405 | |
2776 | |
2406 | As long as the watcher is active, the callback will be invoked every time |
2777 | As long as the watcher is active, the callback will be invoked every |
2407 | there might be events pending in the embedded loop. The callback must then |
2778 | time there might be events pending in the embedded loop. The callback |
2408 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2779 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2409 | their callbacks (you could also start an idle watcher to give the embedded |
2780 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2410 | loop strictly lower priority for example). You can also set the callback |
2781 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2411 | to C<0>, in which case the embed watcher will automatically execute the |
2782 | to give the embedded loop strictly lower priority for example). |
2412 | embedded loop sweep. |
|
|
2413 | |
2783 | |
2414 | As long as the watcher is started it will automatically handle events. The |
2784 | You can also set the callback to C<0>, in which case the embed watcher |
2415 | callback will be invoked whenever some events have been handled. You can |
2785 | will automatically execute the embedded loop sweep whenever necessary. |
2416 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2417 | interested in that. |
|
|
2418 | |
2786 | |
2419 | Also, there have not currently been made special provisions for forking: |
2787 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2420 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2788 | is active, i.e., the embedded loop will automatically be forked when the |
2421 | but you will also have to stop and restart any C<ev_embed> watchers |
2789 | embedding loop forks. In other cases, the user is responsible for calling |
2422 | yourself - but you can use a fork watcher to handle this automatically, |
2790 | C<ev_loop_fork> on the embedded loop. |
2423 | and future versions of libev might do just that. |
|
|
2424 | |
2791 | |
2425 | Unfortunately, not all backends are embeddable: only the ones returned by |
2792 | Unfortunately, not all backends are embeddable: only the ones returned by |
2426 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2793 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2427 | portable one. |
2794 | portable one. |
2428 | |
2795 | |
… | |
… | |
2522 | event loop blocks next and before C<ev_check> watchers are being called, |
2889 | event loop blocks next and before C<ev_check> watchers are being called, |
2523 | and only in the child after the fork. If whoever good citizen calling |
2890 | and only in the child after the fork. If whoever good citizen calling |
2524 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2891 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2525 | handlers will be invoked, too, of course. |
2892 | handlers will be invoked, too, of course. |
2526 | |
2893 | |
|
|
2894 | =head3 The special problem of life after fork - how is it possible? |
|
|
2895 | |
|
|
2896 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2897 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2898 | sequence should be handled by libev without any problems. |
|
|
2899 | |
|
|
2900 | This changes when the application actually wants to do event handling |
|
|
2901 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2902 | fork. |
|
|
2903 | |
|
|
2904 | The default mode of operation (for libev, with application help to detect |
|
|
2905 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2906 | when I<either> the parent I<or> the child process continues. |
|
|
2907 | |
|
|
2908 | When both processes want to continue using libev, then this is usually the |
|
|
2909 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2910 | supposed to continue with all watchers in place as before, while the other |
|
|
2911 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2912 | |
|
|
2913 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2914 | simply create a new event loop, which of course will be "empty", and |
|
|
2915 | use that for new watchers. This has the advantage of not touching more |
|
|
2916 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2917 | disadvantage of having to use multiple event loops (which do not support |
|
|
2918 | signal watchers). |
|
|
2919 | |
|
|
2920 | When this is not possible, or you want to use the default loop for |
|
|
2921 | other reasons, then in the process that wants to start "fresh", call |
|
|
2922 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2923 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2924 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2925 | also that in that case, you have to re-register any signal watchers. |
|
|
2926 | |
2527 | =head3 Watcher-Specific Functions and Data Members |
2927 | =head3 Watcher-Specific Functions and Data Members |
2528 | |
2928 | |
2529 | =over 4 |
2929 | =over 4 |
2530 | |
2930 | |
2531 | =item ev_fork_init (ev_signal *, callback) |
2931 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2659 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3059 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2660 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3060 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2661 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3061 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2662 | section below on what exactly this means). |
3062 | section below on what exactly this means). |
2663 | |
3063 | |
|
|
3064 | Note that, as with other watchers in libev, multiple events might get |
|
|
3065 | compressed into a single callback invocation (another way to look at this |
|
|
3066 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3067 | reset when the event loop detects that). |
|
|
3068 | |
2664 | This call incurs the overhead of a system call only once per loop iteration, |
3069 | This call incurs the overhead of a system call only once per event loop |
2665 | so while the overhead might be noticeable, it doesn't apply to repeated |
3070 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2666 | calls to C<ev_async_send>. |
3071 | repeated calls to C<ev_async_send> for the same event loop. |
2667 | |
3072 | |
2668 | =item bool = ev_async_pending (ev_async *) |
3073 | =item bool = ev_async_pending (ev_async *) |
2669 | |
3074 | |
2670 | Returns a non-zero value when C<ev_async_send> has been called on the |
3075 | Returns a non-zero value when C<ev_async_send> has been called on the |
2671 | watcher but the event has not yet been processed (or even noted) by the |
3076 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2674 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3079 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2675 | the loop iterates next and checks for the watcher to have become active, |
3080 | the loop iterates next and checks for the watcher to have become active, |
2676 | it will reset the flag again. C<ev_async_pending> can be used to very |
3081 | it will reset the flag again. C<ev_async_pending> can be used to very |
2677 | quickly check whether invoking the loop might be a good idea. |
3082 | quickly check whether invoking the loop might be a good idea. |
2678 | |
3083 | |
2679 | Not that this does I<not> check whether the watcher itself is pending, only |
3084 | Not that this does I<not> check whether the watcher itself is pending, |
2680 | whether it has been requested to make this watcher pending. |
3085 | only whether it has been requested to make this watcher pending: there |
|
|
3086 | is a time window between the event loop checking and resetting the async |
|
|
3087 | notification, and the callback being invoked. |
2681 | |
3088 | |
2682 | =back |
3089 | =back |
2683 | |
3090 | |
2684 | |
3091 | |
2685 | =head1 OTHER FUNCTIONS |
3092 | =head1 OTHER FUNCTIONS |
… | |
… | |
2864 | |
3271 | |
2865 | myclass obj; |
3272 | myclass obj; |
2866 | ev::io iow; |
3273 | ev::io iow; |
2867 | iow.set <myclass, &myclass::io_cb> (&obj); |
3274 | iow.set <myclass, &myclass::io_cb> (&obj); |
2868 | |
3275 | |
|
|
3276 | =item w->set (object *) |
|
|
3277 | |
|
|
3278 | This is an B<experimental> feature that might go away in a future version. |
|
|
3279 | |
|
|
3280 | This is a variation of a method callback - leaving out the method to call |
|
|
3281 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3282 | functor objects without having to manually specify the C<operator ()> all |
|
|
3283 | the time. Incidentally, you can then also leave out the template argument |
|
|
3284 | list. |
|
|
3285 | |
|
|
3286 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3287 | int revents)>. |
|
|
3288 | |
|
|
3289 | See the method-C<set> above for more details. |
|
|
3290 | |
|
|
3291 | Example: use a functor object as callback. |
|
|
3292 | |
|
|
3293 | struct myfunctor |
|
|
3294 | { |
|
|
3295 | void operator() (ev::io &w, int revents) |
|
|
3296 | { |
|
|
3297 | ... |
|
|
3298 | } |
|
|
3299 | } |
|
|
3300 | |
|
|
3301 | myfunctor f; |
|
|
3302 | |
|
|
3303 | ev::io w; |
|
|
3304 | w.set (&f); |
|
|
3305 | |
2869 | =item w->set<function> (void *data = 0) |
3306 | =item w->set<function> (void *data = 0) |
2870 | |
3307 | |
2871 | Also sets a callback, but uses a static method or plain function as |
3308 | Also sets a callback, but uses a static method or plain function as |
2872 | callback. The optional C<data> argument will be stored in the watcher's |
3309 | callback. The optional C<data> argument will be stored in the watcher's |
2873 | C<data> member and is free for you to use. |
3310 | C<data> member and is free for you to use. |
… | |
… | |
2959 | L<http://software.schmorp.de/pkg/EV>. |
3396 | L<http://software.schmorp.de/pkg/EV>. |
2960 | |
3397 | |
2961 | =item Python |
3398 | =item Python |
2962 | |
3399 | |
2963 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3400 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2964 | seems to be quite complete and well-documented. Note, however, that the |
3401 | seems to be quite complete and well-documented. |
2965 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2966 | for everybody else, and therefore, should never be applied in an installed |
|
|
2967 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2968 | libev). |
|
|
2969 | |
3402 | |
2970 | =item Ruby |
3403 | =item Ruby |
2971 | |
3404 | |
2972 | Tony Arcieri has written a ruby extension that offers access to a subset |
3405 | Tony Arcieri has written a ruby extension that offers access to a subset |
2973 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3406 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2974 | more on top of it. It can be found via gem servers. Its homepage is at |
3407 | more on top of it. It can be found via gem servers. Its homepage is at |
2975 | L<http://rev.rubyforge.org/>. |
3408 | L<http://rev.rubyforge.org/>. |
2976 | |
3409 | |
|
|
3410 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3411 | makes rev work even on mingw. |
|
|
3412 | |
|
|
3413 | =item Haskell |
|
|
3414 | |
|
|
3415 | A haskell binding to libev is available at |
|
|
3416 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3417 | |
2977 | =item D |
3418 | =item D |
2978 | |
3419 | |
2979 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3420 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2980 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3421 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
2981 | |
3422 | |
2982 | =item Ocaml |
3423 | =item Ocaml |
2983 | |
3424 | |
2984 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3425 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
2985 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3426 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3427 | |
|
|
3428 | =item Lua |
|
|
3429 | |
|
|
3430 | Brian Maher has written a partial interface to libev |
|
|
3431 | for lua (only C<ev_io> and C<ev_timer>), to be found at |
|
|
3432 | L<http://github.com/brimworks/lua-ev>. |
2986 | |
3433 | |
2987 | =back |
3434 | =back |
2988 | |
3435 | |
2989 | |
3436 | |
2990 | =head1 MACRO MAGIC |
3437 | =head1 MACRO MAGIC |
… | |
… | |
3157 | keeps libev from including F<config.h>, and it also defines dummy |
3604 | keeps libev from including F<config.h>, and it also defines dummy |
3158 | implementations for some libevent functions (such as logging, which is not |
3605 | implementations for some libevent functions (such as logging, which is not |
3159 | supported). It will also not define any of the structs usually found in |
3606 | supported). It will also not define any of the structs usually found in |
3160 | F<event.h> that are not directly supported by the libev core alone. |
3607 | F<event.h> that are not directly supported by the libev core alone. |
3161 | |
3608 | |
|
|
3609 | In standalone mode, libev will still try to automatically deduce the |
|
|
3610 | configuration, but has to be more conservative. |
|
|
3611 | |
3162 | =item EV_USE_MONOTONIC |
3612 | =item EV_USE_MONOTONIC |
3163 | |
3613 | |
3164 | If defined to be C<1>, libev will try to detect the availability of the |
3614 | If defined to be C<1>, libev will try to detect the availability of the |
3165 | monotonic clock option at both compile time and runtime. Otherwise no use |
3615 | monotonic clock option at both compile time and runtime. Otherwise no |
3166 | of the monotonic clock option will be attempted. If you enable this, you |
3616 | use of the monotonic clock option will be attempted. If you enable this, |
3167 | usually have to link against librt or something similar. Enabling it when |
3617 | you usually have to link against librt or something similar. Enabling it |
3168 | the functionality isn't available is safe, though, although you have |
3618 | when the functionality isn't available is safe, though, although you have |
3169 | to make sure you link against any libraries where the C<clock_gettime> |
3619 | to make sure you link against any libraries where the C<clock_gettime> |
3170 | function is hiding in (often F<-lrt>). |
3620 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3171 | |
3621 | |
3172 | =item EV_USE_REALTIME |
3622 | =item EV_USE_REALTIME |
3173 | |
3623 | |
3174 | If defined to be C<1>, libev will try to detect the availability of the |
3624 | If defined to be C<1>, libev will try to detect the availability of the |
3175 | real-time clock option at compile time (and assume its availability at |
3625 | real-time clock option at compile time (and assume its availability |
3176 | runtime if successful). Otherwise no use of the real-time clock option will |
3626 | at runtime if successful). Otherwise no use of the real-time clock |
3177 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3627 | option will be attempted. This effectively replaces C<gettimeofday> |
3178 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3628 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3179 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3629 | correctness. See the note about libraries in the description of |
|
|
3630 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3631 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3632 | |
|
|
3633 | =item EV_USE_CLOCK_SYSCALL |
|
|
3634 | |
|
|
3635 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3636 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3637 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3638 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3639 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3640 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3641 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3642 | higher, as it simplifies linking (no need for C<-lrt>). |
3180 | |
3643 | |
3181 | =item EV_USE_NANOSLEEP |
3644 | =item EV_USE_NANOSLEEP |
3182 | |
3645 | |
3183 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3646 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3184 | and will use it for delays. Otherwise it will use C<select ()>. |
3647 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3200 | |
3663 | |
3201 | =item EV_SELECT_USE_FD_SET |
3664 | =item EV_SELECT_USE_FD_SET |
3202 | |
3665 | |
3203 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3666 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3204 | structure. This is useful if libev doesn't compile due to a missing |
3667 | structure. This is useful if libev doesn't compile due to a missing |
3205 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3668 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3206 | exotic systems. This usually limits the range of file descriptors to some |
3669 | on exotic systems. This usually limits the range of file descriptors to |
3207 | low limit such as 1024 or might have other limitations (winsocket only |
3670 | some low limit such as 1024 or might have other limitations (winsocket |
3208 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3671 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3209 | influence the size of the C<fd_set> used. |
3672 | configures the maximum size of the C<fd_set>. |
3210 | |
3673 | |
3211 | =item EV_SELECT_IS_WINSOCKET |
3674 | =item EV_SELECT_IS_WINSOCKET |
3212 | |
3675 | |
3213 | When defined to C<1>, the select backend will assume that |
3676 | When defined to C<1>, the select backend will assume that |
3214 | select/socket/connect etc. don't understand file descriptors but |
3677 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3216 | be used is the winsock select). This means that it will call |
3679 | be used is the winsock select). This means that it will call |
3217 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3680 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3218 | it is assumed that all these functions actually work on fds, even |
3681 | it is assumed that all these functions actually work on fds, even |
3219 | on win32. Should not be defined on non-win32 platforms. |
3682 | on win32. Should not be defined on non-win32 platforms. |
3220 | |
3683 | |
3221 | =item EV_FD_TO_WIN32_HANDLE |
3684 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3222 | |
3685 | |
3223 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3686 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3224 | file descriptors to socket handles. When not defining this symbol (the |
3687 | file descriptors to socket handles. When not defining this symbol (the |
3225 | default), then libev will call C<_get_osfhandle>, which is usually |
3688 | default), then libev will call C<_get_osfhandle>, which is usually |
3226 | correct. In some cases, programs use their own file descriptor management, |
3689 | correct. In some cases, programs use their own file descriptor management, |
3227 | in which case they can provide this function to map fds to socket handles. |
3690 | in which case they can provide this function to map fds to socket handles. |
|
|
3691 | |
|
|
3692 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3693 | |
|
|
3694 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3695 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3696 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3697 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3698 | |
|
|
3699 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3700 | |
|
|
3701 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3702 | macro can be used to override the C<close> function, useful to unregister |
|
|
3703 | file descriptors again. Note that the replacement function has to close |
|
|
3704 | the underlying OS handle. |
3228 | |
3705 | |
3229 | =item EV_USE_POLL |
3706 | =item EV_USE_POLL |
3230 | |
3707 | |
3231 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3708 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3232 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3709 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3364 | defined to be C<0>, then they are not. |
3841 | defined to be C<0>, then they are not. |
3365 | |
3842 | |
3366 | =item EV_MINIMAL |
3843 | =item EV_MINIMAL |
3367 | |
3844 | |
3368 | If you need to shave off some kilobytes of code at the expense of some |
3845 | If you need to shave off some kilobytes of code at the expense of some |
3369 | speed, define this symbol to C<1>. Currently this is used to override some |
3846 | speed (but with the full API), define this symbol to C<1>. Currently this |
3370 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3847 | is used to override some inlining decisions, saves roughly 30% code size |
3371 | much smaller 2-heap for timer management over the default 4-heap. |
3848 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3849 | the default 4-heap. |
|
|
3850 | |
|
|
3851 | You can save even more by disabling watcher types you do not need |
|
|
3852 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3853 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3854 | |
|
|
3855 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3856 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3857 | of the API are still available, and do not complain if this subset changes |
|
|
3858 | over time. |
|
|
3859 | |
|
|
3860 | =item EV_NSIG |
|
|
3861 | |
|
|
3862 | The highest supported signal number, +1 (or, the number of |
|
|
3863 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
3864 | automatically, but sometimes this fails, in which case it can be |
|
|
3865 | specified. Also, using a lower number than detected (C<32> should be |
|
|
3866 | good for about any system in existance) can save some memory, as libev |
|
|
3867 | statically allocates some 12-24 bytes per signal number. |
3372 | |
3868 | |
3373 | =item EV_PID_HASHSIZE |
3869 | =item EV_PID_HASHSIZE |
3374 | |
3870 | |
3375 | C<ev_child> watchers use a small hash table to distribute workload by |
3871 | C<ev_child> watchers use a small hash table to distribute workload by |
3376 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3872 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3562 | default loop and triggering an C<ev_async> watcher from the default loop |
4058 | default loop and triggering an C<ev_async> watcher from the default loop |
3563 | watcher callback into the event loop interested in the signal. |
4059 | watcher callback into the event loop interested in the signal. |
3564 | |
4060 | |
3565 | =back |
4061 | =back |
3566 | |
4062 | |
|
|
4063 | =head4 THREAD LOCKING EXAMPLE |
|
|
4064 | |
|
|
4065 | Here is a fictitious example of how to run an event loop in a different |
|
|
4066 | thread than where callbacks are being invoked and watchers are |
|
|
4067 | created/added/removed. |
|
|
4068 | |
|
|
4069 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4070 | which uses exactly this technique (which is suited for many high-level |
|
|
4071 | languages). |
|
|
4072 | |
|
|
4073 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4074 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4075 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4076 | |
|
|
4077 | First, you need to associate some data with the event loop: |
|
|
4078 | |
|
|
4079 | typedef struct { |
|
|
4080 | mutex_t lock; /* global loop lock */ |
|
|
4081 | ev_async async_w; |
|
|
4082 | thread_t tid; |
|
|
4083 | cond_t invoke_cv; |
|
|
4084 | } userdata; |
|
|
4085 | |
|
|
4086 | void prepare_loop (EV_P) |
|
|
4087 | { |
|
|
4088 | // for simplicity, we use a static userdata struct. |
|
|
4089 | static userdata u; |
|
|
4090 | |
|
|
4091 | ev_async_init (&u->async_w, async_cb); |
|
|
4092 | ev_async_start (EV_A_ &u->async_w); |
|
|
4093 | |
|
|
4094 | pthread_mutex_init (&u->lock, 0); |
|
|
4095 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4096 | |
|
|
4097 | // now associate this with the loop |
|
|
4098 | ev_set_userdata (EV_A_ u); |
|
|
4099 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4100 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4101 | |
|
|
4102 | // then create the thread running ev_loop |
|
|
4103 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4104 | } |
|
|
4105 | |
|
|
4106 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4107 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4108 | that might have been added: |
|
|
4109 | |
|
|
4110 | static void |
|
|
4111 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4112 | { |
|
|
4113 | // just used for the side effects |
|
|
4114 | } |
|
|
4115 | |
|
|
4116 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4117 | protecting the loop data, respectively. |
|
|
4118 | |
|
|
4119 | static void |
|
|
4120 | l_release (EV_P) |
|
|
4121 | { |
|
|
4122 | userdata *u = ev_userdata (EV_A); |
|
|
4123 | pthread_mutex_unlock (&u->lock); |
|
|
4124 | } |
|
|
4125 | |
|
|
4126 | static void |
|
|
4127 | l_acquire (EV_P) |
|
|
4128 | { |
|
|
4129 | userdata *u = ev_userdata (EV_A); |
|
|
4130 | pthread_mutex_lock (&u->lock); |
|
|
4131 | } |
|
|
4132 | |
|
|
4133 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4134 | into C<ev_loop>: |
|
|
4135 | |
|
|
4136 | void * |
|
|
4137 | l_run (void *thr_arg) |
|
|
4138 | { |
|
|
4139 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4140 | |
|
|
4141 | l_acquire (EV_A); |
|
|
4142 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4143 | ev_loop (EV_A_ 0); |
|
|
4144 | l_release (EV_A); |
|
|
4145 | |
|
|
4146 | return 0; |
|
|
4147 | } |
|
|
4148 | |
|
|
4149 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4150 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4151 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4152 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4153 | and b) skipping inter-thread-communication when there are no pending |
|
|
4154 | watchers is very beneficial): |
|
|
4155 | |
|
|
4156 | static void |
|
|
4157 | l_invoke (EV_P) |
|
|
4158 | { |
|
|
4159 | userdata *u = ev_userdata (EV_A); |
|
|
4160 | |
|
|
4161 | while (ev_pending_count (EV_A)) |
|
|
4162 | { |
|
|
4163 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4164 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4165 | } |
|
|
4166 | } |
|
|
4167 | |
|
|
4168 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4169 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4170 | thread to continue: |
|
|
4171 | |
|
|
4172 | static void |
|
|
4173 | real_invoke_pending (EV_P) |
|
|
4174 | { |
|
|
4175 | userdata *u = ev_userdata (EV_A); |
|
|
4176 | |
|
|
4177 | pthread_mutex_lock (&u->lock); |
|
|
4178 | ev_invoke_pending (EV_A); |
|
|
4179 | pthread_cond_signal (&u->invoke_cv); |
|
|
4180 | pthread_mutex_unlock (&u->lock); |
|
|
4181 | } |
|
|
4182 | |
|
|
4183 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4184 | event loop, you will now have to lock: |
|
|
4185 | |
|
|
4186 | ev_timer timeout_watcher; |
|
|
4187 | userdata *u = ev_userdata (EV_A); |
|
|
4188 | |
|
|
4189 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4190 | |
|
|
4191 | pthread_mutex_lock (&u->lock); |
|
|
4192 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4193 | ev_async_send (EV_A_ &u->async_w); |
|
|
4194 | pthread_mutex_unlock (&u->lock); |
|
|
4195 | |
|
|
4196 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4197 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4198 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4199 | watchers in the next event loop iteration. |
|
|
4200 | |
3567 | =head3 COROUTINES |
4201 | =head3 COROUTINES |
3568 | |
4202 | |
3569 | Libev is very accommodating to coroutines ("cooperative threads"): |
4203 | Libev is very accommodating to coroutines ("cooperative threads"): |
3570 | libev fully supports nesting calls to its functions from different |
4204 | libev fully supports nesting calls to its functions from different |
3571 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4205 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3572 | different coroutines, and switch freely between both coroutines running the |
4206 | different coroutines, and switch freely between both coroutines running |
3573 | loop, as long as you don't confuse yourself). The only exception is that |
4207 | the loop, as long as you don't confuse yourself). The only exception is |
3574 | you must not do this from C<ev_periodic> reschedule callbacks. |
4208 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3575 | |
4209 | |
3576 | Care has been taken to ensure that libev does not keep local state inside |
4210 | Care has been taken to ensure that libev does not keep local state inside |
3577 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4211 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3578 | they do not call any callbacks. |
4212 | they do not call any callbacks. |
3579 | |
4213 | |
… | |
… | |
3656 | way (note also that glib is the slowest event library known to man). |
4290 | way (note also that glib is the slowest event library known to man). |
3657 | |
4291 | |
3658 | There is no supported compilation method available on windows except |
4292 | There is no supported compilation method available on windows except |
3659 | embedding it into other applications. |
4293 | embedding it into other applications. |
3660 | |
4294 | |
|
|
4295 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4296 | tries its best, but under most conditions, signals will simply not work. |
|
|
4297 | |
3661 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4298 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3662 | accept large writes: instead of resulting in a partial write, windows will |
4299 | accept large writes: instead of resulting in a partial write, windows will |
3663 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4300 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3664 | so make sure you only write small amounts into your sockets (less than a |
4301 | so make sure you only write small amounts into your sockets (less than a |
3665 | megabyte seems safe, but this apparently depends on the amount of memory |
4302 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3669 | the abysmal performance of winsockets, using a large number of sockets |
4306 | the abysmal performance of winsockets, using a large number of sockets |
3670 | is not recommended (and not reasonable). If your program needs to use |
4307 | is not recommended (and not reasonable). If your program needs to use |
3671 | more than a hundred or so sockets, then likely it needs to use a totally |
4308 | more than a hundred or so sockets, then likely it needs to use a totally |
3672 | different implementation for windows, as libev offers the POSIX readiness |
4309 | different implementation for windows, as libev offers the POSIX readiness |
3673 | notification model, which cannot be implemented efficiently on windows |
4310 | notification model, which cannot be implemented efficiently on windows |
3674 | (Microsoft monopoly games). |
4311 | (due to Microsoft monopoly games). |
3675 | |
4312 | |
3676 | A typical way to use libev under windows is to embed it (see the embedding |
4313 | A typical way to use libev under windows is to embed it (see the embedding |
3677 | section for details) and use the following F<evwrap.h> header file instead |
4314 | section for details) and use the following F<evwrap.h> header file instead |
3678 | of F<ev.h>: |
4315 | of F<ev.h>: |
3679 | |
4316 | |
… | |
… | |
3715 | |
4352 | |
3716 | Early versions of winsocket's select only supported waiting for a maximum |
4353 | Early versions of winsocket's select only supported waiting for a maximum |
3717 | of C<64> handles (probably owning to the fact that all windows kernels |
4354 | of C<64> handles (probably owning to the fact that all windows kernels |
3718 | can only wait for C<64> things at the same time internally; Microsoft |
4355 | can only wait for C<64> things at the same time internally; Microsoft |
3719 | recommends spawning a chain of threads and wait for 63 handles and the |
4356 | recommends spawning a chain of threads and wait for 63 handles and the |
3720 | previous thread in each. Great). |
4357 | previous thread in each. Sounds great!). |
3721 | |
4358 | |
3722 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4359 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3723 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4360 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3724 | call (which might be in libev or elsewhere, for example, perl does its own |
4361 | call (which might be in libev or elsewhere, for example, perl and many |
3725 | select emulation on windows). |
4362 | other interpreters do their own select emulation on windows). |
3726 | |
4363 | |
3727 | Another limit is the number of file descriptors in the Microsoft runtime |
4364 | Another limit is the number of file descriptors in the Microsoft runtime |
3728 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4365 | libraries, which by default is C<64> (there must be a hidden I<64> |
3729 | or something like this inside Microsoft). You can increase this by calling |
4366 | fetish or something like this inside Microsoft). You can increase this |
3730 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4367 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3731 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4368 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3732 | libraries. |
|
|
3733 | |
|
|
3734 | This might get you to about C<512> or C<2048> sockets (depending on |
4369 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3735 | windows version and/or the phase of the moon). To get more, you need to |
4370 | (depending on windows version and/or the phase of the moon). To get more, |
3736 | wrap all I/O functions and provide your own fd management, but the cost of |
4371 | you need to wrap all I/O functions and provide your own fd management, but |
3737 | calling select (O(n²)) will likely make this unworkable. |
4372 | the cost of calling select (O(n²)) will likely make this unworkable. |
3738 | |
4373 | |
3739 | =back |
4374 | =back |
3740 | |
4375 | |
3741 | =head2 PORTABILITY REQUIREMENTS |
4376 | =head2 PORTABILITY REQUIREMENTS |
3742 | |
4377 | |
… | |
… | |
3785 | =item C<double> must hold a time value in seconds with enough accuracy |
4420 | =item C<double> must hold a time value in seconds with enough accuracy |
3786 | |
4421 | |
3787 | The type C<double> is used to represent timestamps. It is required to |
4422 | The type C<double> is used to represent timestamps. It is required to |
3788 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4423 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3789 | enough for at least into the year 4000. This requirement is fulfilled by |
4424 | enough for at least into the year 4000. This requirement is fulfilled by |
3790 | implementations implementing IEEE 754 (basically all existing ones). |
4425 | implementations implementing IEEE 754, which is basically all existing |
|
|
4426 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4427 | 2200. |
3791 | |
4428 | |
3792 | =back |
4429 | =back |
3793 | |
4430 | |
3794 | If you know of other additional requirements drop me a note. |
4431 | If you know of other additional requirements drop me a note. |
3795 | |
4432 | |
… | |
… | |
3863 | involves iterating over all running async watchers or all signal numbers. |
4500 | involves iterating over all running async watchers or all signal numbers. |
3864 | |
4501 | |
3865 | =back |
4502 | =back |
3866 | |
4503 | |
3867 | |
4504 | |
|
|
4505 | =head1 GLOSSARY |
|
|
4506 | |
|
|
4507 | =over 4 |
|
|
4508 | |
|
|
4509 | =item active |
|
|
4510 | |
|
|
4511 | A watcher is active as long as it has been started (has been attached to |
|
|
4512 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4513 | |
|
|
4514 | =item application |
|
|
4515 | |
|
|
4516 | In this document, an application is whatever is using libev. |
|
|
4517 | |
|
|
4518 | =item callback |
|
|
4519 | |
|
|
4520 | The address of a function that is called when some event has been |
|
|
4521 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4522 | received the event, and the actual event bitset. |
|
|
4523 | |
|
|
4524 | =item callback invocation |
|
|
4525 | |
|
|
4526 | The act of calling the callback associated with a watcher. |
|
|
4527 | |
|
|
4528 | =item event |
|
|
4529 | |
|
|
4530 | A change of state of some external event, such as data now being available |
|
|
4531 | for reading on a file descriptor, time having passed or simply not having |
|
|
4532 | any other events happening anymore. |
|
|
4533 | |
|
|
4534 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4535 | C<EV_TIMEOUT>). |
|
|
4536 | |
|
|
4537 | =item event library |
|
|
4538 | |
|
|
4539 | A software package implementing an event model and loop. |
|
|
4540 | |
|
|
4541 | =item event loop |
|
|
4542 | |
|
|
4543 | An entity that handles and processes external events and converts them |
|
|
4544 | into callback invocations. |
|
|
4545 | |
|
|
4546 | =item event model |
|
|
4547 | |
|
|
4548 | The model used to describe how an event loop handles and processes |
|
|
4549 | watchers and events. |
|
|
4550 | |
|
|
4551 | =item pending |
|
|
4552 | |
|
|
4553 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4554 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4555 | pending status is explicitly cleared by the application. |
|
|
4556 | |
|
|
4557 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4558 | its pending status. |
|
|
4559 | |
|
|
4560 | =item real time |
|
|
4561 | |
|
|
4562 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4563 | |
|
|
4564 | =item wall-clock time |
|
|
4565 | |
|
|
4566 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4567 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4568 | clock. |
|
|
4569 | |
|
|
4570 | =item watcher |
|
|
4571 | |
|
|
4572 | A data structure that describes interest in certain events. Watchers need |
|
|
4573 | to be started (attached to an event loop) before they can receive events. |
|
|
4574 | |
|
|
4575 | =item watcher invocation |
|
|
4576 | |
|
|
4577 | The act of calling the callback associated with a watcher. |
|
|
4578 | |
|
|
4579 | =back |
|
|
4580 | |
3868 | =head1 AUTHOR |
4581 | =head1 AUTHOR |
3869 | |
4582 | |
3870 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
4583 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3871 | |
4584 | |