… | |
… | |
468 | ev_ref (myloop); |
468 | ev_ref (myloop); |
469 | ev_signal_stop (myloop, &exitsig); |
469 | ev_signal_stop (myloop, &exitsig); |
470 | |
470 | |
471 | =back |
471 | =back |
472 | |
472 | |
|
|
473 | |
473 | =head1 ANATOMY OF A WATCHER |
474 | =head1 ANATOMY OF A WATCHER |
474 | |
475 | |
475 | A watcher is a structure that you create and register to record your |
476 | A watcher is a structure that you create and register to record your |
476 | interest in some event. For instance, if you want to wait for STDIN to |
477 | interest in some event. For instance, if you want to wait for STDIN to |
477 | become readable, you would create an C<ev_io> watcher for that: |
478 | become readable, you would create an C<ev_io> watcher for that: |
… | |
… | |
576 | with the error from read() or write(). This will not work in multithreaded |
577 | with the error from read() or write(). This will not work in multithreaded |
577 | programs, though, so beware. |
578 | programs, though, so beware. |
578 | |
579 | |
579 | =back |
580 | =back |
580 | |
581 | |
581 | =head2 SUMMARY OF GENERIC WATCHER FUNCTIONS |
582 | =head2 GENERIC WATCHER FUNCTIONS |
582 | |
583 | |
583 | In the following description, C<TYPE> stands for the watcher type, |
584 | In the following description, C<TYPE> stands for the watcher type, |
584 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
585 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
585 | |
586 | |
586 | =over 4 |
587 | =over 4 |
… | |
… | |
595 | which rolls both calls into one. |
596 | which rolls both calls into one. |
596 | |
597 | |
597 | You can reinitialise a watcher at any time as long as it has been stopped |
598 | You can reinitialise a watcher at any time as long as it has been stopped |
598 | (or never started) and there are no pending events outstanding. |
599 | (or never started) and there are no pending events outstanding. |
599 | |
600 | |
600 | The callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
601 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
601 | int revents)>. |
602 | int revents)>. |
602 | |
603 | |
603 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
604 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
604 | |
605 | |
605 | This macro initialises the type-specific parts of a watcher. You need to |
606 | This macro initialises the type-specific parts of a watcher. You need to |
… | |
… | |
691 | |
692 | |
692 | This section describes each watcher in detail, but will not repeat |
693 | This section describes each watcher in detail, but will not repeat |
693 | information given in the last section. |
694 | information given in the last section. |
694 | |
695 | |
695 | |
696 | |
696 | =head2 C<ev_io> - is this file descriptor readable or writable |
697 | =head2 C<ev_io> - is this file descriptor readable or writable? |
697 | |
698 | |
698 | I/O watchers check whether a file descriptor is readable or writable |
699 | I/O watchers check whether a file descriptor is readable or writable |
699 | in each iteration of the event loop (This behaviour is called |
700 | in each iteration of the event loop, or, more precisely, when reading |
700 | level-triggering because you keep receiving events as long as the |
701 | would not block the process and writing would at least be able to write |
701 | condition persists. Remember you can stop the watcher if you don't want to |
702 | some data. This behaviour is called level-triggering because you keep |
702 | act on the event and neither want to receive future events). |
703 | receiving events as long as the condition persists. Remember you can stop |
|
|
704 | the watcher if you don't want to act on the event and neither want to |
|
|
705 | receive future events. |
703 | |
706 | |
704 | In general you can register as many read and/or write event watchers per |
707 | In general you can register as many read and/or write event watchers per |
705 | fd as you want (as long as you don't confuse yourself). Setting all file |
708 | fd as you want (as long as you don't confuse yourself). Setting all file |
706 | descriptors to non-blocking mode is also usually a good idea (but not |
709 | descriptors to non-blocking mode is also usually a good idea (but not |
707 | required if you know what you are doing). |
710 | required if you know what you are doing). |
708 | |
711 | |
709 | You have to be careful with dup'ed file descriptors, though. Some backends |
712 | You have to be careful with dup'ed file descriptors, though. Some backends |
710 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
713 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
711 | descriptors correctly if you register interest in two or more fds pointing |
714 | descriptors correctly if you register interest in two or more fds pointing |
712 | to the same underlying file/socket etc. description (that is, they share |
715 | to the same underlying file/socket/etc. description (that is, they share |
713 | the same underlying "file open"). |
716 | the same underlying "file open"). |
714 | |
717 | |
715 | If you must do this, then force the use of a known-to-be-good backend |
718 | If you must do this, then force the use of a known-to-be-good backend |
716 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
719 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
717 | C<EVBACKEND_POLL>). |
720 | C<EVBACKEND_POLL>). |
718 | |
721 | |
|
|
722 | Another thing you have to watch out for is that it is quite easy to |
|
|
723 | receive "spurious" readyness notifications, that is your callback might |
|
|
724 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
|
|
725 | because there is no data. Not only are some backends known to create a |
|
|
726 | lot of those (for example solaris ports), it is very easy to get into |
|
|
727 | this situation even with a relatively standard program structure. Thus |
|
|
728 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
729 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
|
|
730 | |
|
|
731 | If you cannot run the fd in non-blocking mode (for example you should not |
|
|
732 | play around with an Xlib connection), then you have to seperately re-test |
|
|
733 | wether a file descriptor is really ready with a known-to-be good interface |
|
|
734 | such as poll (fortunately in our Xlib example, Xlib already does this on |
|
|
735 | its own, so its quite safe to use). |
|
|
736 | |
719 | =over 4 |
737 | =over 4 |
720 | |
738 | |
721 | =item ev_io_init (ev_io *, callback, int fd, int events) |
739 | =item ev_io_init (ev_io *, callback, int fd, int events) |
722 | |
740 | |
723 | =item ev_io_set (ev_io *, int fd, int events) |
741 | =item ev_io_set (ev_io *, int fd, int events) |
724 | |
742 | |
725 | Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive |
743 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
726 | events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ | |
744 | rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or |
727 | EV_WRITE> to receive the given events. |
745 | C<EV_READ | EV_WRITE> to receive the given events. |
728 | |
|
|
729 | Please note that most of the more scalable backend mechanisms (for example |
|
|
730 | epoll and solaris ports) can result in spurious readyness notifications |
|
|
731 | for file descriptors, so you practically need to use non-blocking I/O (and |
|
|
732 | treat callback invocation as hint only), or retest separately with a safe |
|
|
733 | interface before doing I/O (XLib can do this), or force the use of either |
|
|
734 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this |
|
|
735 | problem. Also note that it is quite easy to have your callback invoked |
|
|
736 | when the readyness condition is no longer valid even when employing |
|
|
737 | typical ways of handling events, so its a good idea to use non-blocking |
|
|
738 | I/O unconditionally. |
|
|
739 | |
746 | |
740 | =back |
747 | =back |
741 | |
748 | |
742 | Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well |
749 | Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well |
743 | readable, but only once. Since it is likely line-buffered, you could |
750 | readable, but only once. Since it is likely line-buffered, you could |
… | |
… | |
756 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
763 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
757 | ev_io_start (loop, &stdin_readable); |
764 | ev_io_start (loop, &stdin_readable); |
758 | ev_loop (loop, 0); |
765 | ev_loop (loop, 0); |
759 | |
766 | |
760 | |
767 | |
761 | =head2 C<ev_timer> - relative and optionally recurring timeouts |
768 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
762 | |
769 | |
763 | Timer watchers are simple relative timers that generate an event after a |
770 | Timer watchers are simple relative timers that generate an event after a |
764 | given time, and optionally repeating in regular intervals after that. |
771 | given time, and optionally repeating in regular intervals after that. |
765 | |
772 | |
766 | The timers are based on real time, that is, if you register an event that |
773 | The timers are based on real time, that is, if you register an event that |
… | |
… | |
848 | // and in some piece of code that gets executed on any "activity": |
855 | // and in some piece of code that gets executed on any "activity": |
849 | // reset the timeout to start ticking again at 10 seconds |
856 | // reset the timeout to start ticking again at 10 seconds |
850 | ev_timer_again (&mytimer); |
857 | ev_timer_again (&mytimer); |
851 | |
858 | |
852 | |
859 | |
853 | =head2 C<ev_periodic> - to cron or not to cron |
860 | =head2 C<ev_periodic> - to cron or not to cron? |
854 | |
861 | |
855 | Periodic watchers are also timers of a kind, but they are very versatile |
862 | Periodic watchers are also timers of a kind, but they are very versatile |
856 | (and unfortunately a bit complex). |
863 | (and unfortunately a bit complex). |
857 | |
864 | |
858 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
865 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
… | |
… | |
986 | ev_periodic_init (&hourly_tick, clock_cb, |
993 | ev_periodic_init (&hourly_tick, clock_cb, |
987 | fmod (ev_now (loop), 3600.), 3600., 0); |
994 | fmod (ev_now (loop), 3600.), 3600., 0); |
988 | ev_periodic_start (loop, &hourly_tick); |
995 | ev_periodic_start (loop, &hourly_tick); |
989 | |
996 | |
990 | |
997 | |
991 | =head2 C<ev_signal> - signal me when a signal gets signalled |
998 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
992 | |
999 | |
993 | Signal watchers will trigger an event when the process receives a specific |
1000 | Signal watchers will trigger an event when the process receives a specific |
994 | signal one or more times. Even though signals are very asynchronous, libev |
1001 | signal one or more times. Even though signals are very asynchronous, libev |
995 | will try it's best to deliver signals synchronously, i.e. as part of the |
1002 | will try it's best to deliver signals synchronously, i.e. as part of the |
996 | normal event processing, like any other event. |
1003 | normal event processing, like any other event. |
… | |
… | |
1012 | of the C<SIGxxx> constants). |
1019 | of the C<SIGxxx> constants). |
1013 | |
1020 | |
1014 | =back |
1021 | =back |
1015 | |
1022 | |
1016 | |
1023 | |
1017 | =head2 C<ev_child> - wait for pid status changes |
1024 | =head2 C<ev_child> - watch out for process status changes |
1018 | |
1025 | |
1019 | Child watchers trigger when your process receives a SIGCHLD in response to |
1026 | Child watchers trigger when your process receives a SIGCHLD in response to |
1020 | some child status changes (most typically when a child of yours dies). |
1027 | some child status changes (most typically when a child of yours dies). |
1021 | |
1028 | |
1022 | =over 4 |
1029 | =over 4 |
… | |
… | |
1045 | struct ev_signal signal_watcher; |
1052 | struct ev_signal signal_watcher; |
1046 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1053 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1047 | ev_signal_start (loop, &sigint_cb); |
1054 | ev_signal_start (loop, &sigint_cb); |
1048 | |
1055 | |
1049 | |
1056 | |
1050 | =head2 C<ev_idle> - when you've got nothing better to do |
1057 | =head2 C<ev_idle> - when you've got nothing better to do... |
1051 | |
1058 | |
1052 | Idle watchers trigger events when there are no other events are pending |
1059 | Idle watchers trigger events when there are no other events are pending |
1053 | (prepare, check and other idle watchers do not count). That is, as long |
1060 | (prepare, check and other idle watchers do not count). That is, as long |
1054 | as your process is busy handling sockets or timeouts (or even signals, |
1061 | as your process is busy handling sockets or timeouts (or even signals, |
1055 | imagine) it will not be triggered. But when your process is idle all idle |
1062 | imagine) it will not be triggered. But when your process is idle all idle |
… | |
… | |
1089 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1096 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1090 | ev_idle_init (idle_watcher, idle_cb); |
1097 | ev_idle_init (idle_watcher, idle_cb); |
1091 | ev_idle_start (loop, idle_cb); |
1098 | ev_idle_start (loop, idle_cb); |
1092 | |
1099 | |
1093 | |
1100 | |
1094 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop |
1101 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1095 | |
1102 | |
1096 | Prepare and check watchers are usually (but not always) used in tandem: |
1103 | Prepare and check watchers are usually (but not always) used in tandem: |
1097 | prepare watchers get invoked before the process blocks and check watchers |
1104 | prepare watchers get invoked before the process blocks and check watchers |
1098 | afterwards. |
1105 | afterwards. |
1099 | |
1106 | |
… | |
… | |
1133 | =back |
1140 | =back |
1134 | |
1141 | |
1135 | Example: *TODO*. |
1142 | Example: *TODO*. |
1136 | |
1143 | |
1137 | |
1144 | |
1138 | =head2 C<ev_embed> - when one backend isn't enough |
1145 | =head2 C<ev_embed> - when one backend isn't enough... |
1139 | |
1146 | |
1140 | This is a rather advanced watcher type that lets you embed one event loop |
1147 | This is a rather advanced watcher type that lets you embed one event loop |
1141 | into another (currently only C<ev_io> events are supported in the embedded |
1148 | into another (currently only C<ev_io> events are supported in the embedded |
1142 | loop, other types of watchers might be handled in a delayed or incorrect |
1149 | loop, other types of watchers might be handled in a delayed or incorrect |
1143 | fashion and must not be used). |
1150 | fashion and must not be used). |