… | |
… | |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // unloop was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
68 | |
70 | |
69 | 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 |
70 | 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 |
71 | 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>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 ABOUT LIBEV |
72 | |
84 | |
73 | 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 |
74 | 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 |
75 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
76 | |
88 | |
… | |
… | |
86 | =head2 FEATURES |
98 | =head2 FEATURES |
87 | |
99 | |
88 | 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 |
89 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
90 | 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 |
91 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
92 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
93 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
94 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
95 | 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 |
96 | 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 |
97 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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110 | limited support for fork events (C<ev_fork>). |
98 | |
111 | |
99 | It also is quite fast (see this |
112 | It also is quite fast (see this |
100 | 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 |
101 | for example). |
114 | for example). |
102 | |
115 | |
… | |
… | |
110 | 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 |
111 | this argument. |
124 | this argument. |
112 | |
125 | |
113 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
114 | |
127 | |
115 | Libev represents time as a single floating point number, representing the |
128 | Libev represents time as a single floating point number, representing |
116 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
129 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
117 | 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 |
118 | 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 |
119 | 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 |
120 | 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 |
121 | 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 |
122 | throughout libev. |
135 | throughout libev. |
123 | |
136 | |
124 | =head1 ERROR HANDLING |
137 | =head1 ERROR HANDLING |
125 | |
138 | |
… | |
… | |
349 | 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 |
350 | flag. |
363 | flag. |
351 | |
364 | |
352 | 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> |
353 | environment variable. |
366 | environment variable. |
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367 | |
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368 | =item C<EVFLAG_NOINOTIFY> |
|
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369 | |
|
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370 | When this flag is specified, then libev will not attempt to use the |
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371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
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372 | testing, this flag can be useful to conserve inotify file descriptors, as |
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373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
|
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374 | |
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375 | =item C<EVFLAG_NOSIGNALFD> |
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376 | |
|
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377 | When this flag is specified, then libev will not attempt to use the |
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378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is |
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379 | probably only useful to work around any bugs in libev. Consequently, this |
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380 | flag might go away once the signalfd functionality is considered stable, |
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381 | so it's useful mostly in environment variables and not in program code. |
354 | |
382 | |
355 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
383 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
356 | |
384 | |
357 | 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 |
358 | 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, |
… | |
… | |
506 | |
534 | |
507 | It is definitely not recommended to use this flag. |
535 | It is definitely not recommended to use this flag. |
508 | |
536 | |
509 | =back |
537 | =back |
510 | |
538 | |
511 | 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, |
512 | 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 |
513 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
541 | here). If none are specified, all backends in C<ev_recommended_backends |
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542 | ()> will be tried. |
514 | |
543 | |
515 | Example: This is the most typical usage. |
544 | Example: This is the most typical usage. |
516 | |
545 | |
517 | if (!ev_default_loop (0)) |
546 | if (!ev_default_loop (0)) |
518 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
547 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
… | |
… | |
609 | |
638 | |
610 | 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 |
611 | "ticks" the number of loop iterations), as it roughly corresponds with |
640 | "ticks" the number of loop iterations), as it roughly corresponds with |
612 | C<ev_prepare> and C<ev_check> calls. |
641 | C<ev_prepare> and C<ev_check> calls. |
613 | |
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), |
|
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650 | in which case it is higher. |
|
|
651 | |
|
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652 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
653 | etc.), doesn't count as exit. |
|
|
654 | |
614 | =item unsigned int ev_backend (loop) |
655 | =item unsigned int ev_backend (loop) |
615 | |
656 | |
616 | 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 |
617 | use. |
658 | use. |
618 | |
659 | |
… | |
… | |
632 | |
673 | |
633 | 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 |
634 | 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 |
635 | the current time is a good idea. |
676 | the current time is a good idea. |
636 | |
677 | |
637 | 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>). |
638 | |
705 | |
639 | =item ev_loop (loop, int flags) |
706 | =item ev_loop (loop, int flags) |
640 | |
707 | |
641 | 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 |
642 | 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 |
… | |
… | |
726 | |
793 | |
727 | 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> |
728 | from returning, call ev_unref() after starting, and ev_ref() before |
795 | from returning, call ev_unref() after starting, and ev_ref() before |
729 | stopping it. |
796 | stopping it. |
730 | |
797 | |
731 | 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 |
732 | 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 |
733 | 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 |
734 | 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 |
735 | 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 |
736 | (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 |
737 | 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). |
738 | |
807 | |
739 | 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> |
740 | running when nothing else is active. |
809 | running when nothing else is active. |
741 | |
810 | |
742 | ev_signal exitsig; |
811 | ev_signal exitsig; |
… | |
… | |
771 | |
840 | |
772 | 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 |
773 | 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, |
774 | 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 |
775 | 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 |
776 | 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. |
777 | |
848 | |
778 | 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 |
779 | to spend more time collecting timeouts, at the expense of increased |
850 | to spend more time collecting timeouts, at the expense of increased |
780 | latency/jitter/inexactness (the watcher callback will be called |
851 | latency/jitter/inexactness (the watcher callback will be called |
781 | 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 |
… | |
… | |
783 | |
854 | |
784 | 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 |
785 | 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 |
786 | interactive servers (of course not for games), likewise for timeouts. It |
857 | interactive servers (of course not for games), likewise for timeouts. It |
787 | 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>, |
788 | 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). |
789 | |
864 | |
790 | Setting the I<timeout collect interval> can improve the opportunity for |
865 | Setting the I<timeout collect interval> can improve the opportunity for |
791 | saving power, as the program will "bundle" timer callback invocations that |
866 | saving power, as the program will "bundle" timer callback invocations that |
792 | 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 |
793 | 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 |
794 | 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 |
795 | 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. |
796 | |
942 | |
797 | =item ev_loop_verify (loop) |
943 | =item ev_loop_verify (loop) |
798 | |
944 | |
799 | 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 |
800 | 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 |
… | |
… | |
926 | |
1072 | |
927 | =item C<EV_ASYNC> |
1073 | =item C<EV_ASYNC> |
928 | |
1074 | |
929 | 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>). |
930 | |
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 | |
931 | =item C<EV_ERROR> |
1082 | =item C<EV_ERROR> |
932 | |
1083 | |
933 | 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 |
934 | happen because the watcher could not be properly started because libev |
1085 | happen because the watcher could not be properly started because libev |
935 | 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 |
… | |
… | |
1050 | 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> |
1051 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1202 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1052 | before watchers with lower priority, but priority will not keep watchers |
1203 | before watchers with lower priority, but priority will not keep watchers |
1053 | from being executed (except for C<ev_idle> watchers). |
1204 | from being executed (except for C<ev_idle> watchers). |
1054 | |
1205 | |
1055 | This means that priorities are I<only> used for ordering callback |
|
|
1056 | invocation after new events have been received. This is useful, for |
|
|
1057 | example, to reduce latency after idling, or more often, to bind two |
|
|
1058 | watchers on the same event and make sure one is called first. |
|
|
1059 | |
|
|
1060 | 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 |
1061 | 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. |
1062 | |
1208 | |
1063 | 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 |
1064 | pending. |
1210 | pending. |
1065 | |
|
|
1066 | The default priority used by watchers when no priority has been set is |
|
|
1067 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1068 | |
1211 | |
1069 | 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 |
1070 | 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 |
1071 | 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. |
1072 | |
1221 | |
1073 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1222 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1074 | |
1223 | |
1075 | 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 |
1076 | 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 |
… | |
… | |
1141 | #include <stddef.h> |
1290 | #include <stddef.h> |
1142 | |
1291 | |
1143 | static void |
1292 | static void |
1144 | t1_cb (EV_P_ ev_timer *w, int revents) |
1293 | t1_cb (EV_P_ ev_timer *w, int revents) |
1145 | { |
1294 | { |
1146 | struct my_biggy big = (struct my_biggy * |
1295 | struct my_biggy big = (struct my_biggy *) |
1147 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1296 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1148 | } |
1297 | } |
1149 | |
1298 | |
1150 | static void |
1299 | static void |
1151 | t2_cb (EV_P_ ev_timer *w, int revents) |
1300 | t2_cb (EV_P_ ev_timer *w, int revents) |
1152 | { |
1301 | { |
1153 | struct my_biggy big = (struct my_biggy * |
1302 | struct my_biggy big = (struct my_biggy *) |
1154 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1303 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1155 | } |
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. |
1156 | |
1408 | |
1157 | |
1409 | |
1158 | =head1 WATCHER TYPES |
1410 | =head1 WATCHER TYPES |
1159 | |
1411 | |
1160 | This section describes each watcher in detail, but will not repeat |
1412 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1186 | 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 |
1187 | required if you know what you are doing). |
1439 | required if you know what you are doing). |
1188 | |
1440 | |
1189 | 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 |
1190 | 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 |
1191 | 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. |
1192 | |
1446 | |
1193 | 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 |
1194 | receive "spurious" readiness notifications, that is your callback might |
1448 | receive "spurious" readiness notifications, that is your callback might |
1195 | 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 |
1196 | 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 |
… | |
… | |
1317 | 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 |
1318 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1572 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1319 | monotonic clock option helps a lot here). |
1573 | monotonic clock option helps a lot here). |
1320 | |
1574 | |
1321 | 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 |
1322 | 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 |
1323 | 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). |
1324 | |
1581 | |
1325 | =head3 Be smart about timeouts |
1582 | =head3 Be smart about timeouts |
1326 | |
1583 | |
1327 | 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 |
1328 | 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, |
… | |
… | |
1372 | 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> |
1373 | member and C<ev_timer_again>. |
1630 | member and C<ev_timer_again>. |
1374 | |
1631 | |
1375 | At start: |
1632 | At start: |
1376 | |
1633 | |
1377 | ev_timer_init (timer, callback); |
1634 | ev_init (timer, callback); |
1378 | timer->repeat = 60.; |
1635 | timer->repeat = 60.; |
1379 | ev_timer_again (loop, timer); |
1636 | ev_timer_again (loop, timer); |
1380 | |
1637 | |
1381 | Each time there is some activity: |
1638 | Each time there is some activity: |
1382 | |
1639 | |
… | |
… | |
1444 | |
1701 | |
1445 | 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> |
1446 | 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 |
1447 | callback, which will "do the right thing" and start the timer: |
1704 | callback, which will "do the right thing" and start the timer: |
1448 | |
1705 | |
1449 | ev_timer_init (timer, callback); |
1706 | ev_init (timer, callback); |
1450 | last_activity = ev_now (loop); |
1707 | last_activity = ev_now (loop); |
1451 | callback (loop, timer, EV_TIMEOUT); |
1708 | callback (loop, timer, EV_TIMEOUT); |
1452 | |
1709 | |
1453 | 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 |
1454 | C<last_activity>, no libev calls at all: |
1711 | C<last_activity>, no libev calls at all: |
… | |
… | |
1515 | |
1772 | |
1516 | 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 |
1517 | 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 |
1518 | ()>. |
1775 | ()>. |
1519 | |
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 | |
1520 | =head3 Watcher-Specific Functions and Data Members |
1807 | =head3 Watcher-Specific Functions and Data Members |
1521 | |
1808 | |
1522 | =over 4 |
1809 | =over 4 |
1523 | |
1810 | |
1524 | =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) |
… | |
… | |
1547 | 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). |
1548 | |
1835 | |
1549 | 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 |
1550 | 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. |
1551 | |
1838 | |
1552 | 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 |
1553 | 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. |
1554 | |
1853 | |
1555 | =item ev_tstamp repeat [read-write] |
1854 | =item ev_tstamp repeat [read-write] |
1556 | |
1855 | |
1557 | 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 |
1558 | 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), |
… | |
… | |
1617 | timers, such as triggering an event on each "midnight, local time", or |
1916 | timers, such as triggering an event on each "midnight, local time", or |
1618 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
1917 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
1619 | those cannot react to time jumps. |
1918 | those cannot react to time jumps. |
1620 | |
1919 | |
1621 | 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 |
1622 | point in time where it is supposed to trigger has passed, but if multiple |
1921 | point in time where it is supposed to trigger has passed. If multiple |
1623 | periodic timers become ready during the same loop iteration, then order of |
1922 | timers become ready during the same loop iteration then the ones with |
1624 | execution is undefined. |
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). |
1625 | |
1925 | |
1626 | =head3 Watcher-Specific Functions and Data Members |
1926 | =head3 Watcher-Specific Functions and Data Members |
1627 | |
1927 | |
1628 | =over 4 |
1928 | =over 4 |
1629 | |
1929 | |
… | |
… | |
1793 | 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 |
1794 | 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 |
1795 | 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 |
1796 | normal event processing, like any other event. |
2096 | normal event processing, like any other event. |
1797 | |
2097 | |
1798 | If you want signals asynchronously, just use C<sigaction> as you would |
2098 | If you want signals to be delivered truly asynchronously, just use |
1799 | 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 |
1800 | 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. |
1801 | |
2102 | |
1802 | 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 | |
1803 | first watcher gets started will libev actually register a signal handler |
2109 | When the first watcher gets started will libev actually register something |
1804 | 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 |
1805 | 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). |
1806 | the last signal watcher for a signal is stopped, libev will reset the |
2112 | |
1807 | signal handler to SIG_DFL (regardless of what it was set to before). |
2113 | Both the signal mask state (C<sigprocmask>) and the signal handler state |
|
|
2114 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2115 | sotpping it again), that is, libev might or might not block the signal, |
|
|
2116 | and might or might not set or restore the installed signal handler. |
1808 | |
2117 | |
1809 | If possible and supported, libev will install its handlers with |
2118 | If possible and supported, libev will install its handlers with |
1810 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2119 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1811 | interrupted. If you have a problem with system calls getting interrupted by |
2120 | not be unduly interrupted. If you have a problem with system calls getting |
1812 | signals you can block all signals in an C<ev_check> watcher and unblock |
2121 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1813 | them in an C<ev_prepare> watcher. |
2122 | and unblock them in an C<ev_prepare> watcher. |
1814 | |
2123 | |
1815 | =head3 Watcher-Specific Functions and Data Members |
2124 | =head3 Watcher-Specific Functions and Data Members |
1816 | |
2125 | |
1817 | =over 4 |
2126 | =over 4 |
1818 | |
2127 | |
… | |
… | |
1850 | some child status changes (most typically when a child of yours dies or |
2159 | some child status changes (most typically when a child of yours dies or |
1851 | exits). It is permissible to install a child watcher I<after> the child |
2160 | exits). It is permissible to install a child watcher I<after> the child |
1852 | has been forked (which implies it might have already exited), as long |
2161 | has been forked (which implies it might have already exited), as long |
1853 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2162 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1854 | forking and then immediately registering a watcher for the child is fine, |
2163 | forking and then immediately registering a watcher for the child is fine, |
1855 | but forking and registering a watcher a few event loop iterations later is |
2164 | but forking and registering a watcher a few event loop iterations later or |
1856 | not. |
2165 | in the next callback invocation is not. |
1857 | |
2166 | |
1858 | Only the default event loop is capable of handling signals, and therefore |
2167 | Only the default event loop is capable of handling signals, and therefore |
1859 | you can only register child watchers in the default event loop. |
2168 | you can only register child watchers in the default event loop. |
1860 | |
2169 | |
|
|
2170 | Due to some design glitches inside libev, child watchers will always be |
|
|
2171 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2172 | libev) |
|
|
2173 | |
1861 | =head3 Process Interaction |
2174 | =head3 Process Interaction |
1862 | |
2175 | |
1863 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2176 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1864 | initialised. This is necessary to guarantee proper behaviour even if |
2177 | initialised. This is necessary to guarantee proper behaviour even if the |
1865 | the first child watcher is started after the child exits. The occurrence |
2178 | first child watcher is started after the child exits. The occurrence |
1866 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2179 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1867 | synchronously as part of the event loop processing. Libev always reaps all |
2180 | synchronously as part of the event loop processing. Libev always reaps all |
1868 | children, even ones not watched. |
2181 | children, even ones not watched. |
1869 | |
2182 | |
1870 | =head3 Overriding the Built-In Processing |
2183 | =head3 Overriding the Built-In Processing |
… | |
… | |
1880 | =head3 Stopping the Child Watcher |
2193 | =head3 Stopping the Child Watcher |
1881 | |
2194 | |
1882 | Currently, the child watcher never gets stopped, even when the |
2195 | Currently, the child watcher never gets stopped, even when the |
1883 | child terminates, so normally one needs to stop the watcher in the |
2196 | child terminates, so normally one needs to stop the watcher in the |
1884 | callback. Future versions of libev might stop the watcher automatically |
2197 | callback. Future versions of libev might stop the watcher automatically |
1885 | when a child exit is detected. |
2198 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2199 | problem). |
1886 | |
2200 | |
1887 | =head3 Watcher-Specific Functions and Data Members |
2201 | =head3 Watcher-Specific Functions and Data Members |
1888 | |
2202 | |
1889 | =over 4 |
2203 | =over 4 |
1890 | |
2204 | |
… | |
… | |
2216 | // no longer anything immediate to do. |
2530 | // no longer anything immediate to do. |
2217 | } |
2531 | } |
2218 | |
2532 | |
2219 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2533 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2220 | ev_idle_init (idle_watcher, idle_cb); |
2534 | ev_idle_init (idle_watcher, idle_cb); |
2221 | ev_idle_start (loop, idle_cb); |
2535 | ev_idle_start (loop, idle_watcher); |
2222 | |
2536 | |
2223 | |
2537 | |
2224 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2538 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2225 | |
2539 | |
2226 | Prepare and check watchers are usually (but not always) used in pairs: |
2540 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2319 | struct pollfd fds [nfd]; |
2633 | struct pollfd fds [nfd]; |
2320 | // actual code will need to loop here and realloc etc. |
2634 | // actual code will need to loop here and realloc etc. |
2321 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2635 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2322 | |
2636 | |
2323 | /* the callback is illegal, but won't be called as we stop during check */ |
2637 | /* the callback is illegal, but won't be called as we stop during check */ |
2324 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2638 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2325 | ev_timer_start (loop, &tw); |
2639 | ev_timer_start (loop, &tw); |
2326 | |
2640 | |
2327 | // create one ev_io per pollfd |
2641 | // create one ev_io per pollfd |
2328 | for (int i = 0; i < nfd; ++i) |
2642 | for (int i = 0; i < nfd; ++i) |
2329 | { |
2643 | { |
… | |
… | |
2559 | event loop blocks next and before C<ev_check> watchers are being called, |
2873 | event loop blocks next and before C<ev_check> watchers are being called, |
2560 | and only in the child after the fork. If whoever good citizen calling |
2874 | and only in the child after the fork. If whoever good citizen calling |
2561 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2875 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2562 | handlers will be invoked, too, of course. |
2876 | handlers will be invoked, too, of course. |
2563 | |
2877 | |
|
|
2878 | =head3 The special problem of life after fork - how is it possible? |
|
|
2879 | |
|
|
2880 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2881 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2882 | sequence should be handled by libev without any problems. |
|
|
2883 | |
|
|
2884 | This changes when the application actually wants to do event handling |
|
|
2885 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2886 | fork. |
|
|
2887 | |
|
|
2888 | The default mode of operation (for libev, with application help to detect |
|
|
2889 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2890 | when I<either> the parent I<or> the child process continues. |
|
|
2891 | |
|
|
2892 | When both processes want to continue using libev, then this is usually the |
|
|
2893 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2894 | supposed to continue with all watchers in place as before, while the other |
|
|
2895 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2896 | |
|
|
2897 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2898 | simply create a new event loop, which of course will be "empty", and |
|
|
2899 | use that for new watchers. This has the advantage of not touching more |
|
|
2900 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2901 | disadvantage of having to use multiple event loops (which do not support |
|
|
2902 | signal watchers). |
|
|
2903 | |
|
|
2904 | When this is not possible, or you want to use the default loop for |
|
|
2905 | other reasons, then in the process that wants to start "fresh", call |
|
|
2906 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2907 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2908 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2909 | also that in that case, you have to re-register any signal watchers. |
|
|
2910 | |
2564 | =head3 Watcher-Specific Functions and Data Members |
2911 | =head3 Watcher-Specific Functions and Data Members |
2565 | |
2912 | |
2566 | =over 4 |
2913 | =over 4 |
2567 | |
2914 | |
2568 | =item ev_fork_init (ev_signal *, callback) |
2915 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
3235 | keeps libev from including F<config.h>, and it also defines dummy |
3582 | keeps libev from including F<config.h>, and it also defines dummy |
3236 | implementations for some libevent functions (such as logging, which is not |
3583 | implementations for some libevent functions (such as logging, which is not |
3237 | supported). It will also not define any of the structs usually found in |
3584 | supported). It will also not define any of the structs usually found in |
3238 | F<event.h> that are not directly supported by the libev core alone. |
3585 | F<event.h> that are not directly supported by the libev core alone. |
3239 | |
3586 | |
3240 | In stanbdalone mode, libev will still try to automatically deduce the |
3587 | In standalone mode, libev will still try to automatically deduce the |
3241 | configuration, but has to be more conservative. |
3588 | configuration, but has to be more conservative. |
3242 | |
3589 | |
3243 | =item EV_USE_MONOTONIC |
3590 | =item EV_USE_MONOTONIC |
3244 | |
3591 | |
3245 | If defined to be C<1>, libev will try to detect the availability of the |
3592 | If defined to be C<1>, libev will try to detect the availability of the |
… | |
… | |
3458 | defined to be C<0>, then they are not. |
3805 | defined to be C<0>, then they are not. |
3459 | |
3806 | |
3460 | =item EV_MINIMAL |
3807 | =item EV_MINIMAL |
3461 | |
3808 | |
3462 | If you need to shave off some kilobytes of code at the expense of some |
3809 | If you need to shave off some kilobytes of code at the expense of some |
3463 | speed, define this symbol to C<1>. Currently this is used to override some |
3810 | speed (but with the full API), define this symbol to C<1>. Currently this |
3464 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3811 | is used to override some inlining decisions, saves roughly 30% code size |
3465 | much smaller 2-heap for timer management over the default 4-heap. |
3812 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3813 | the default 4-heap. |
|
|
3814 | |
|
|
3815 | You can save even more by disabling watcher types you do not need |
|
|
3816 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3817 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3818 | |
|
|
3819 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3820 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3821 | of the API are still available, and do not complain if this subset changes |
|
|
3822 | over time. |
|
|
3823 | |
|
|
3824 | =item EV_NSIG |
|
|
3825 | |
|
|
3826 | The highest supported signal number, +1 (or, the number of |
|
|
3827 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
3828 | automatically, but sometimes this fails, in which case it can be |
|
|
3829 | specified. Also, using a lower number than detected (C<32> should be |
|
|
3830 | good for about any system in existance) can save some memory, as libev |
|
|
3831 | statically allocates some 12-24 bytes per signal number. |
3466 | |
3832 | |
3467 | =item EV_PID_HASHSIZE |
3833 | =item EV_PID_HASHSIZE |
3468 | |
3834 | |
3469 | C<ev_child> watchers use a small hash table to distribute workload by |
3835 | C<ev_child> watchers use a small hash table to distribute workload by |
3470 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3836 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3656 | default loop and triggering an C<ev_async> watcher from the default loop |
4022 | default loop and triggering an C<ev_async> watcher from the default loop |
3657 | watcher callback into the event loop interested in the signal. |
4023 | watcher callback into the event loop interested in the signal. |
3658 | |
4024 | |
3659 | =back |
4025 | =back |
3660 | |
4026 | |
|
|
4027 | =head4 THREAD LOCKING EXAMPLE |
|
|
4028 | |
|
|
4029 | Here is a fictitious example of how to run an event loop in a different |
|
|
4030 | thread than where callbacks are being invoked and watchers are |
|
|
4031 | created/added/removed. |
|
|
4032 | |
|
|
4033 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4034 | which uses exactly this technique (which is suited for many high-level |
|
|
4035 | languages). |
|
|
4036 | |
|
|
4037 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4038 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4039 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4040 | |
|
|
4041 | First, you need to associate some data with the event loop: |
|
|
4042 | |
|
|
4043 | typedef struct { |
|
|
4044 | mutex_t lock; /* global loop lock */ |
|
|
4045 | ev_async async_w; |
|
|
4046 | thread_t tid; |
|
|
4047 | cond_t invoke_cv; |
|
|
4048 | } userdata; |
|
|
4049 | |
|
|
4050 | void prepare_loop (EV_P) |
|
|
4051 | { |
|
|
4052 | // for simplicity, we use a static userdata struct. |
|
|
4053 | static userdata u; |
|
|
4054 | |
|
|
4055 | ev_async_init (&u->async_w, async_cb); |
|
|
4056 | ev_async_start (EV_A_ &u->async_w); |
|
|
4057 | |
|
|
4058 | pthread_mutex_init (&u->lock, 0); |
|
|
4059 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4060 | |
|
|
4061 | // now associate this with the loop |
|
|
4062 | ev_set_userdata (EV_A_ u); |
|
|
4063 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4064 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4065 | |
|
|
4066 | // then create the thread running ev_loop |
|
|
4067 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4068 | } |
|
|
4069 | |
|
|
4070 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4071 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4072 | that might have been added: |
|
|
4073 | |
|
|
4074 | static void |
|
|
4075 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4076 | { |
|
|
4077 | // just used for the side effects |
|
|
4078 | } |
|
|
4079 | |
|
|
4080 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4081 | protecting the loop data, respectively. |
|
|
4082 | |
|
|
4083 | static void |
|
|
4084 | l_release (EV_P) |
|
|
4085 | { |
|
|
4086 | userdata *u = ev_userdata (EV_A); |
|
|
4087 | pthread_mutex_unlock (&u->lock); |
|
|
4088 | } |
|
|
4089 | |
|
|
4090 | static void |
|
|
4091 | l_acquire (EV_P) |
|
|
4092 | { |
|
|
4093 | userdata *u = ev_userdata (EV_A); |
|
|
4094 | pthread_mutex_lock (&u->lock); |
|
|
4095 | } |
|
|
4096 | |
|
|
4097 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4098 | into C<ev_loop>: |
|
|
4099 | |
|
|
4100 | void * |
|
|
4101 | l_run (void *thr_arg) |
|
|
4102 | { |
|
|
4103 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4104 | |
|
|
4105 | l_acquire (EV_A); |
|
|
4106 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4107 | ev_loop (EV_A_ 0); |
|
|
4108 | l_release (EV_A); |
|
|
4109 | |
|
|
4110 | return 0; |
|
|
4111 | } |
|
|
4112 | |
|
|
4113 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4114 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4115 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4116 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4117 | and b) skipping inter-thread-communication when there are no pending |
|
|
4118 | watchers is very beneficial): |
|
|
4119 | |
|
|
4120 | static void |
|
|
4121 | l_invoke (EV_P) |
|
|
4122 | { |
|
|
4123 | userdata *u = ev_userdata (EV_A); |
|
|
4124 | |
|
|
4125 | while (ev_pending_count (EV_A)) |
|
|
4126 | { |
|
|
4127 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4128 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4129 | } |
|
|
4130 | } |
|
|
4131 | |
|
|
4132 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4133 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4134 | thread to continue: |
|
|
4135 | |
|
|
4136 | static void |
|
|
4137 | real_invoke_pending (EV_P) |
|
|
4138 | { |
|
|
4139 | userdata *u = ev_userdata (EV_A); |
|
|
4140 | |
|
|
4141 | pthread_mutex_lock (&u->lock); |
|
|
4142 | ev_invoke_pending (EV_A); |
|
|
4143 | pthread_cond_signal (&u->invoke_cv); |
|
|
4144 | pthread_mutex_unlock (&u->lock); |
|
|
4145 | } |
|
|
4146 | |
|
|
4147 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4148 | event loop, you will now have to lock: |
|
|
4149 | |
|
|
4150 | ev_timer timeout_watcher; |
|
|
4151 | userdata *u = ev_userdata (EV_A); |
|
|
4152 | |
|
|
4153 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4154 | |
|
|
4155 | pthread_mutex_lock (&u->lock); |
|
|
4156 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4157 | ev_async_send (EV_A_ &u->async_w); |
|
|
4158 | pthread_mutex_unlock (&u->lock); |
|
|
4159 | |
|
|
4160 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4161 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4162 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4163 | watchers in the next event loop iteration. |
|
|
4164 | |
3661 | =head3 COROUTINES |
4165 | =head3 COROUTINES |
3662 | |
4166 | |
3663 | Libev is very accommodating to coroutines ("cooperative threads"): |
4167 | Libev is very accommodating to coroutines ("cooperative threads"): |
3664 | libev fully supports nesting calls to its functions from different |
4168 | libev fully supports nesting calls to its functions from different |
3665 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4169 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3666 | different coroutines, and switch freely between both coroutines running the |
4170 | different coroutines, and switch freely between both coroutines running |
3667 | loop, as long as you don't confuse yourself). The only exception is that |
4171 | the loop, as long as you don't confuse yourself). The only exception is |
3668 | you must not do this from C<ev_periodic> reschedule callbacks. |
4172 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3669 | |
4173 | |
3670 | Care has been taken to ensure that libev does not keep local state inside |
4174 | Care has been taken to ensure that libev does not keep local state inside |
3671 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4175 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3672 | they do not call any callbacks. |
4176 | they do not call any callbacks. |
3673 | |
4177 | |
… | |
… | |
3750 | way (note also that glib is the slowest event library known to man). |
4254 | way (note also that glib is the slowest event library known to man). |
3751 | |
4255 | |
3752 | There is no supported compilation method available on windows except |
4256 | There is no supported compilation method available on windows except |
3753 | embedding it into other applications. |
4257 | embedding it into other applications. |
3754 | |
4258 | |
|
|
4259 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4260 | tries its best, but under most conditions, signals will simply not work. |
|
|
4261 | |
3755 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4262 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3756 | accept large writes: instead of resulting in a partial write, windows will |
4263 | accept large writes: instead of resulting in a partial write, windows will |
3757 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4264 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3758 | so make sure you only write small amounts into your sockets (less than a |
4265 | so make sure you only write small amounts into your sockets (less than a |
3759 | megabyte seems safe, but this apparently depends on the amount of memory |
4266 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3763 | the abysmal performance of winsockets, using a large number of sockets |
4270 | the abysmal performance of winsockets, using a large number of sockets |
3764 | is not recommended (and not reasonable). If your program needs to use |
4271 | is not recommended (and not reasonable). If your program needs to use |
3765 | more than a hundred or so sockets, then likely it needs to use a totally |
4272 | more than a hundred or so sockets, then likely it needs to use a totally |
3766 | different implementation for windows, as libev offers the POSIX readiness |
4273 | different implementation for windows, as libev offers the POSIX readiness |
3767 | notification model, which cannot be implemented efficiently on windows |
4274 | notification model, which cannot be implemented efficiently on windows |
3768 | (Microsoft monopoly games). |
4275 | (due to Microsoft monopoly games). |
3769 | |
4276 | |
3770 | A typical way to use libev under windows is to embed it (see the embedding |
4277 | A typical way to use libev under windows is to embed it (see the embedding |
3771 | section for details) and use the following F<evwrap.h> header file instead |
4278 | section for details) and use the following F<evwrap.h> header file instead |
3772 | of F<ev.h>: |
4279 | of F<ev.h>: |
3773 | |
4280 | |
… | |
… | |
3809 | |
4316 | |
3810 | Early versions of winsocket's select only supported waiting for a maximum |
4317 | Early versions of winsocket's select only supported waiting for a maximum |
3811 | of C<64> handles (probably owning to the fact that all windows kernels |
4318 | of C<64> handles (probably owning to the fact that all windows kernels |
3812 | can only wait for C<64> things at the same time internally; Microsoft |
4319 | can only wait for C<64> things at the same time internally; Microsoft |
3813 | recommends spawning a chain of threads and wait for 63 handles and the |
4320 | recommends spawning a chain of threads and wait for 63 handles and the |
3814 | previous thread in each. Great). |
4321 | previous thread in each. Sounds great!). |
3815 | |
4322 | |
3816 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4323 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3817 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4324 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3818 | call (which might be in libev or elsewhere, for example, perl does its own |
4325 | call (which might be in libev or elsewhere, for example, perl and many |
3819 | select emulation on windows). |
4326 | other interpreters do their own select emulation on windows). |
3820 | |
4327 | |
3821 | Another limit is the number of file descriptors in the Microsoft runtime |
4328 | Another limit is the number of file descriptors in the Microsoft runtime |
3822 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4329 | libraries, which by default is C<64> (there must be a hidden I<64> |
3823 | or something like this inside Microsoft). You can increase this by calling |
4330 | fetish or something like this inside Microsoft). You can increase this |
3824 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4331 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3825 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4332 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3826 | libraries. |
|
|
3827 | |
|
|
3828 | This might get you to about C<512> or C<2048> sockets (depending on |
4333 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3829 | windows version and/or the phase of the moon). To get more, you need to |
4334 | (depending on windows version and/or the phase of the moon). To get more, |
3830 | wrap all I/O functions and provide your own fd management, but the cost of |
4335 | you need to wrap all I/O functions and provide your own fd management, but |
3831 | calling select (O(n²)) will likely make this unworkable. |
4336 | the cost of calling select (O(n²)) will likely make this unworkable. |
3832 | |
4337 | |
3833 | =back |
4338 | =back |
3834 | |
4339 | |
3835 | =head2 PORTABILITY REQUIREMENTS |
4340 | =head2 PORTABILITY REQUIREMENTS |
3836 | |
4341 | |
… | |
… | |
3879 | =item C<double> must hold a time value in seconds with enough accuracy |
4384 | =item C<double> must hold a time value in seconds with enough accuracy |
3880 | |
4385 | |
3881 | The type C<double> is used to represent timestamps. It is required to |
4386 | The type C<double> is used to represent timestamps. It is required to |
3882 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4387 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3883 | enough for at least into the year 4000. This requirement is fulfilled by |
4388 | enough for at least into the year 4000. This requirement is fulfilled by |
3884 | implementations implementing IEEE 754 (basically all existing ones). |
4389 | implementations implementing IEEE 754, which is basically all existing |
|
|
4390 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4391 | 2200. |
3885 | |
4392 | |
3886 | =back |
4393 | =back |
3887 | |
4394 | |
3888 | If you know of other additional requirements drop me a note. |
4395 | If you know of other additional requirements drop me a note. |
3889 | |
4396 | |
… | |
… | |
3957 | involves iterating over all running async watchers or all signal numbers. |
4464 | involves iterating over all running async watchers or all signal numbers. |
3958 | |
4465 | |
3959 | =back |
4466 | =back |
3960 | |
4467 | |
3961 | |
4468 | |
|
|
4469 | =head1 GLOSSARY |
|
|
4470 | |
|
|
4471 | =over 4 |
|
|
4472 | |
|
|
4473 | =item active |
|
|
4474 | |
|
|
4475 | A watcher is active as long as it has been started (has been attached to |
|
|
4476 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4477 | |
|
|
4478 | =item application |
|
|
4479 | |
|
|
4480 | In this document, an application is whatever is using libev. |
|
|
4481 | |
|
|
4482 | =item callback |
|
|
4483 | |
|
|
4484 | The address of a function that is called when some event has been |
|
|
4485 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4486 | received the event, and the actual event bitset. |
|
|
4487 | |
|
|
4488 | =item callback invocation |
|
|
4489 | |
|
|
4490 | The act of calling the callback associated with a watcher. |
|
|
4491 | |
|
|
4492 | =item event |
|
|
4493 | |
|
|
4494 | A change of state of some external event, such as data now being available |
|
|
4495 | for reading on a file descriptor, time having passed or simply not having |
|
|
4496 | any other events happening anymore. |
|
|
4497 | |
|
|
4498 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4499 | C<EV_TIMEOUT>). |
|
|
4500 | |
|
|
4501 | =item event library |
|
|
4502 | |
|
|
4503 | A software package implementing an event model and loop. |
|
|
4504 | |
|
|
4505 | =item event loop |
|
|
4506 | |
|
|
4507 | An entity that handles and processes external events and converts them |
|
|
4508 | into callback invocations. |
|
|
4509 | |
|
|
4510 | =item event model |
|
|
4511 | |
|
|
4512 | The model used to describe how an event loop handles and processes |
|
|
4513 | watchers and events. |
|
|
4514 | |
|
|
4515 | =item pending |
|
|
4516 | |
|
|
4517 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4518 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4519 | pending status is explicitly cleared by the application. |
|
|
4520 | |
|
|
4521 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4522 | its pending status. |
|
|
4523 | |
|
|
4524 | =item real time |
|
|
4525 | |
|
|
4526 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4527 | |
|
|
4528 | =item wall-clock time |
|
|
4529 | |
|
|
4530 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4531 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4532 | clock. |
|
|
4533 | |
|
|
4534 | =item watcher |
|
|
4535 | |
|
|
4536 | A data structure that describes interest in certain events. Watchers need |
|
|
4537 | to be started (attached to an event loop) before they can receive events. |
|
|
4538 | |
|
|
4539 | =item watcher invocation |
|
|
4540 | |
|
|
4541 | The act of calling the callback associated with a watcher. |
|
|
4542 | |
|
|
4543 | =back |
|
|
4544 | |
3962 | =head1 AUTHOR |
4545 | =head1 AUTHOR |
3963 | |
4546 | |
3964 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
4547 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3965 | |
4548 | |