… | |
… | |
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 | |
… | |
… | |
110 | name C<loop> (which is always of type C<ev_loop *>) will not have |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
111 | this argument. |
123 | this argument. |
112 | |
124 | |
113 | =head2 TIME REPRESENTATION |
125 | =head2 TIME REPRESENTATION |
114 | |
126 | |
115 | Libev represents time as a single floating point number, representing the |
127 | Libev represents time as a single floating point number, representing |
116 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
117 | the beginning of 1970, details are complicated, don't ask). This type is |
129 | 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 |
130 | 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 |
131 | 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 |
132 | 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 |
133 | component C<stamp> might indicate, it is also used for time differences |
122 | throughout libev. |
134 | throughout libev. |
123 | |
135 | |
124 | =head1 ERROR HANDLING |
136 | =head1 ERROR HANDLING |
125 | |
137 | |
… | |
… | |
609 | |
621 | |
610 | This value can sometimes be useful as a generation counter of sorts (it |
622 | 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 |
623 | "ticks" the number of loop iterations), as it roughly corresponds with |
612 | C<ev_prepare> and C<ev_check> calls. |
624 | C<ev_prepare> and C<ev_check> calls. |
613 | |
625 | |
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|
626 | =item unsigned int ev_loop_depth (loop) |
|
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627 | |
|
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628 | Returns the number of times C<ev_loop> was entered minus the number of |
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|
629 | times C<ev_loop> was exited, in other words, the recursion depth. |
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630 | |
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|
631 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
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632 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
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633 | in which case it is higher. |
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634 | |
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635 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
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636 | etc.), doesn't count as exit. |
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637 | |
614 | =item unsigned int ev_backend (loop) |
638 | =item unsigned int ev_backend (loop) |
615 | |
639 | |
616 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
640 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
617 | use. |
641 | use. |
618 | |
642 | |
… | |
… | |
632 | |
656 | |
633 | This function is rarely useful, but when some event callback runs for a |
657 | 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 |
658 | very long time without entering the event loop, updating libev's idea of |
635 | the current time is a good idea. |
659 | the current time is a good idea. |
636 | |
660 | |
637 | See also "The special problem of time updates" in the C<ev_timer> section. |
661 | See also L<The special problem of time updates> in the C<ev_timer> section. |
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662 | |
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663 | =item ev_suspend (loop) |
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664 | |
|
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665 | =item ev_resume (loop) |
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666 | |
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667 | These two functions suspend and resume a loop, for use when the loop is |
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668 | not used for a while and timeouts should not be processed. |
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669 | |
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670 | A typical use case would be an interactive program such as a game: When |
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671 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
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672 | would be best to handle timeouts as if no time had actually passed while |
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673 | the program was suspended. This can be achieved by calling C<ev_suspend> |
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674 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
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675 | C<ev_resume> directly afterwards to resume timer processing. |
|
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676 | |
|
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677 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
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678 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
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679 | will be rescheduled (that is, they will lose any events that would have |
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680 | occured while suspended). |
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681 | |
|
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682 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
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683 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
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684 | without a previous call to C<ev_suspend>. |
|
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685 | |
|
|
686 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
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687 | event loop time (see C<ev_now_update>). |
638 | |
688 | |
639 | =item ev_loop (loop, int flags) |
689 | =item ev_loop (loop, int flags) |
640 | |
690 | |
641 | Finally, this is it, the event handler. This function usually is called |
691 | 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 |
692 | after you initialised all your watchers and you want to start handling |
… | |
… | |
726 | |
776 | |
727 | If you have a watcher you never unregister that should not keep C<ev_loop> |
777 | 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 |
778 | from returning, call ev_unref() after starting, and ev_ref() before |
729 | stopping it. |
779 | stopping it. |
730 | |
780 | |
731 | As an example, libev itself uses this for its internal signal pipe: It is |
781 | 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 |
782 | 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 |
783 | 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 |
784 | 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> |
785 | 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, |
786 | before stop> (but only if the watcher wasn't active before, or was active |
737 | respectively). |
787 | before, respectively. Note also that libev might stop watchers itself |
|
|
788 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
789 | in the callback). |
738 | |
790 | |
739 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
791 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
740 | running when nothing else is active. |
792 | running when nothing else is active. |
741 | |
793 | |
742 | ev_signal exitsig; |
794 | ev_signal exitsig; |
… | |
… | |
771 | |
823 | |
772 | By setting a higher I<io collect interval> you allow libev to spend more |
824 | 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, |
825 | 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 |
826 | 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 |
827 | 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. |
828 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
829 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
830 | once per this interval, on average. |
777 | |
831 | |
778 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
832 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
779 | to spend more time collecting timeouts, at the expense of increased |
833 | to spend more time collecting timeouts, at the expense of increased |
780 | latency/jitter/inexactness (the watcher callback will be called |
834 | 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 |
835 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
783 | |
837 | |
784 | Many (busy) programs can usually benefit by setting the I/O collect |
838 | 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 |
839 | 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 |
840 | 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>, |
841 | 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. |
842 | as this approaches the timing granularity of most systems. Note that if |
|
|
843 | you do transactions with the outside world and you can't increase the |
|
|
844 | parallelity, then this setting will limit your transaction rate (if you |
|
|
845 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
846 | then you can't do more than 100 transations per second). |
789 | |
847 | |
790 | Setting the I<timeout collect interval> can improve the opportunity for |
848 | Setting the I<timeout collect interval> can improve the opportunity for |
791 | saving power, as the program will "bundle" timer callback invocations that |
849 | 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 |
850 | 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 |
851 | 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 |
852 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
795 | they fire on, say, one-second boundaries only. |
853 | they fire on, say, one-second boundaries only. |
|
|
854 | |
|
|
855 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
856 | more often than 100 times per second: |
|
|
857 | |
|
|
858 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
859 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
860 | |
|
|
861 | =item ev_invoke_pending (loop) |
|
|
862 | |
|
|
863 | This call will simply invoke all pending watchers while resetting their |
|
|
864 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
|
865 | but when overriding the invoke callback this call comes handy. |
|
|
866 | |
|
|
867 | =item int ev_pending_count (loop) |
|
|
868 | |
|
|
869 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
870 | are pending. |
|
|
871 | |
|
|
872 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
873 | |
|
|
874 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
875 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
876 | this callback instead. This is useful, for example, when you want to |
|
|
877 | invoke the actual watchers inside another context (another thread etc.). |
|
|
878 | |
|
|
879 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
880 | callback. |
|
|
881 | |
|
|
882 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
883 | |
|
|
884 | Sometimes you want to share the same loop between multiple threads. This |
|
|
885 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
886 | each call to a libev function. |
|
|
887 | |
|
|
888 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
889 | wait for it to return. One way around this is to wake up the loop via |
|
|
890 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
891 | and I<acquire> callbacks on the loop. |
|
|
892 | |
|
|
893 | When set, then C<release> will be called just before the thread is |
|
|
894 | suspended waiting for new events, and C<acquire> is called just |
|
|
895 | afterwards. |
|
|
896 | |
|
|
897 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
898 | C<acquire> will just call the mutex_lock function again. |
|
|
899 | |
|
|
900 | While event loop modifications are allowed between invocations of |
|
|
901 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
902 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
903 | have no effect on the set of file descriptors being watched, or the time |
|
|
904 | waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
905 | to take note of any changes you made. |
|
|
906 | |
|
|
907 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
908 | invocations of C<release> and C<acquire>. |
|
|
909 | |
|
|
910 | See also the locking example in the C<THREADS> section later in this |
|
|
911 | document. |
|
|
912 | |
|
|
913 | =item ev_set_userdata (loop, void *data) |
|
|
914 | |
|
|
915 | =item ev_userdata (loop) |
|
|
916 | |
|
|
917 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
918 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
919 | C<0.> |
|
|
920 | |
|
|
921 | These two functions can be used to associate arbitrary data with a loop, |
|
|
922 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
923 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
924 | any other purpose as well. |
796 | |
925 | |
797 | =item ev_loop_verify (loop) |
926 | =item ev_loop_verify (loop) |
798 | |
927 | |
799 | This function only does something when C<EV_VERIFY> support has been |
928 | 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 |
929 | compiled in, which is the default for non-minimal builds. It tries to go |
… | |
… | |
926 | |
1055 | |
927 | =item C<EV_ASYNC> |
1056 | =item C<EV_ASYNC> |
928 | |
1057 | |
929 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1058 | The given async watcher has been asynchronously notified (see C<ev_async>). |
930 | |
1059 | |
|
|
1060 | =item C<EV_CUSTOM> |
|
|
1061 | |
|
|
1062 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1063 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
1064 | |
931 | =item C<EV_ERROR> |
1065 | =item C<EV_ERROR> |
932 | |
1066 | |
933 | An unspecified error has occurred, the watcher has been stopped. This might |
1067 | An unspecified error has occurred, the watcher has been stopped. This might |
934 | happen because the watcher could not be properly started because libev |
1068 | 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 |
1069 | 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> |
1184 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1051 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1185 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1052 | before watchers with lower priority, but priority will not keep watchers |
1186 | before watchers with lower priority, but priority will not keep watchers |
1053 | from being executed (except for C<ev_idle> watchers). |
1187 | from being executed (except for C<ev_idle> watchers). |
1054 | |
1188 | |
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 |
1189 | 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. |
1190 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1062 | |
1191 | |
1063 | You I<must not> change the priority of a watcher as long as it is active or |
1192 | You I<must not> change the priority of a watcher as long as it is active or |
1064 | pending. |
1193 | 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 | |
1194 | |
1069 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1195 | 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 |
1196 | 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. |
1197 | or might not have been clamped to the valid range. |
|
|
1198 | |
|
|
1199 | The default priority used by watchers when no priority has been set is |
|
|
1200 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1201 | |
|
|
1202 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1203 | priorities. |
1072 | |
1204 | |
1073 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1205 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1074 | |
1206 | |
1075 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1207 | 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 |
1208 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1141 | #include <stddef.h> |
1273 | #include <stddef.h> |
1142 | |
1274 | |
1143 | static void |
1275 | static void |
1144 | t1_cb (EV_P_ ev_timer *w, int revents) |
1276 | t1_cb (EV_P_ ev_timer *w, int revents) |
1145 | { |
1277 | { |
1146 | struct my_biggy big = (struct my_biggy * |
1278 | struct my_biggy big = (struct my_biggy *) |
1147 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1279 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1148 | } |
1280 | } |
1149 | |
1281 | |
1150 | static void |
1282 | static void |
1151 | t2_cb (EV_P_ ev_timer *w, int revents) |
1283 | t2_cb (EV_P_ ev_timer *w, int revents) |
1152 | { |
1284 | { |
1153 | struct my_biggy big = (struct my_biggy * |
1285 | struct my_biggy big = (struct my_biggy *) |
1154 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1286 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1155 | } |
1287 | } |
|
|
1288 | |
|
|
1289 | =head2 WATCHER PRIORITY MODELS |
|
|
1290 | |
|
|
1291 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1292 | integers that influence the ordering of event callback invocation |
|
|
1293 | between watchers in some way, all else being equal. |
|
|
1294 | |
|
|
1295 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1296 | description for the more technical details such as the actual priority |
|
|
1297 | range. |
|
|
1298 | |
|
|
1299 | There are two common ways how these these priorities are being interpreted |
|
|
1300 | by event loops: |
|
|
1301 | |
|
|
1302 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1303 | of lower priority watchers, which means as long as higher priority |
|
|
1304 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1305 | |
|
|
1306 | The less common only-for-ordering model uses priorities solely to order |
|
|
1307 | callback invocation within a single event loop iteration: Higher priority |
|
|
1308 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1309 | before polling for new events. |
|
|
1310 | |
|
|
1311 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1312 | except for idle watchers (which use the lock-out model). |
|
|
1313 | |
|
|
1314 | The rationale behind this is that implementing the lock-out model for |
|
|
1315 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1316 | libraries will just poll for the same events again and again as long as |
|
|
1317 | their callbacks have not been executed, which is very inefficient in the |
|
|
1318 | common case of one high-priority watcher locking out a mass of lower |
|
|
1319 | priority ones. |
|
|
1320 | |
|
|
1321 | Static (ordering) priorities are most useful when you have two or more |
|
|
1322 | watchers handling the same resource: a typical usage example is having an |
|
|
1323 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1324 | timeouts. Under load, data might be received while the program handles |
|
|
1325 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1326 | handler will be executed before checking for data. In that case, giving |
|
|
1327 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1328 | handled first even under adverse conditions (which is usually, but not |
|
|
1329 | always, what you want). |
|
|
1330 | |
|
|
1331 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1332 | will only be executed when no same or higher priority watchers have |
|
|
1333 | received events, they can be used to implement the "lock-out" model when |
|
|
1334 | required. |
|
|
1335 | |
|
|
1336 | For example, to emulate how many other event libraries handle priorities, |
|
|
1337 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1338 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1339 | processing is done in the idle watcher callback. This causes libev to |
|
|
1340 | continously poll and process kernel event data for the watcher, but when |
|
|
1341 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1342 | workable. |
|
|
1343 | |
|
|
1344 | Usually, however, the lock-out model implemented that way will perform |
|
|
1345 | miserably under the type of load it was designed to handle. In that case, |
|
|
1346 | it might be preferable to stop the real watcher before starting the |
|
|
1347 | idle watcher, so the kernel will not have to process the event in case |
|
|
1348 | the actual processing will be delayed for considerable time. |
|
|
1349 | |
|
|
1350 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1351 | priority than the default, and which should only process data when no |
|
|
1352 | other events are pending: |
|
|
1353 | |
|
|
1354 | ev_idle idle; // actual processing watcher |
|
|
1355 | ev_io io; // actual event watcher |
|
|
1356 | |
|
|
1357 | static void |
|
|
1358 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1359 | { |
|
|
1360 | // stop the I/O watcher, we received the event, but |
|
|
1361 | // are not yet ready to handle it. |
|
|
1362 | ev_io_stop (EV_A_ w); |
|
|
1363 | |
|
|
1364 | // start the idle watcher to ahndle the actual event. |
|
|
1365 | // it will not be executed as long as other watchers |
|
|
1366 | // with the default priority are receiving events. |
|
|
1367 | ev_idle_start (EV_A_ &idle); |
|
|
1368 | } |
|
|
1369 | |
|
|
1370 | static void |
|
|
1371 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1372 | { |
|
|
1373 | // actual processing |
|
|
1374 | read (STDIN_FILENO, ...); |
|
|
1375 | |
|
|
1376 | // have to start the I/O watcher again, as |
|
|
1377 | // we have handled the event |
|
|
1378 | ev_io_start (EV_P_ &io); |
|
|
1379 | } |
|
|
1380 | |
|
|
1381 | // initialisation |
|
|
1382 | ev_idle_init (&idle, idle_cb); |
|
|
1383 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1384 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1385 | |
|
|
1386 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1387 | low-priority connections can not be locked out forever under load. This |
|
|
1388 | enables your program to keep a lower latency for important connections |
|
|
1389 | during short periods of high load, while not completely locking out less |
|
|
1390 | important ones. |
1156 | |
1391 | |
1157 | |
1392 | |
1158 | =head1 WATCHER TYPES |
1393 | =head1 WATCHER TYPES |
1159 | |
1394 | |
1160 | This section describes each watcher in detail, but will not repeat |
1395 | 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 |
1421 | descriptors to non-blocking mode is also usually a good idea (but not |
1187 | required if you know what you are doing). |
1422 | required if you know what you are doing). |
1188 | |
1423 | |
1189 | If you cannot use non-blocking mode, then force the use of a |
1424 | 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 |
1425 | known-to-be-good backend (at the time of this writing, this includes only |
1191 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1426 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1427 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1428 | files) - libev doesn't guarentee any specific behaviour in that case. |
1192 | |
1429 | |
1193 | Another thing you have to watch out for is that it is quite easy to |
1430 | 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 |
1431 | 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 |
1432 | 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 |
1433 | 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 |
1554 | year, it will still time out after (roughly) one hour. "Roughly" because |
1318 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1555 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1319 | monotonic clock option helps a lot here). |
1556 | monotonic clock option helps a lot here). |
1320 | |
1557 | |
1321 | The callback is guaranteed to be invoked only I<after> its timeout has |
1558 | 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 |
1559 | passed (not I<at>, so on systems with very low-resolution clocks this |
1323 | then order of execution is undefined. |
1560 | might introduce a small delay). If multiple timers become ready during the |
|
|
1561 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1562 | before ones of the same priority with later time-out values (but this is |
|
|
1563 | no longer true when a callback calls C<ev_loop> recursively). |
1324 | |
1564 | |
1325 | =head3 Be smart about timeouts |
1565 | =head3 Be smart about timeouts |
1326 | |
1566 | |
1327 | Many real-world problems involve some kind of timeout, usually for error |
1567 | 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, |
1568 | 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> |
1612 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1373 | member and C<ev_timer_again>. |
1613 | member and C<ev_timer_again>. |
1374 | |
1614 | |
1375 | At start: |
1615 | At start: |
1376 | |
1616 | |
1377 | ev_timer_init (timer, callback); |
1617 | ev_init (timer, callback); |
1378 | timer->repeat = 60.; |
1618 | timer->repeat = 60.; |
1379 | ev_timer_again (loop, timer); |
1619 | ev_timer_again (loop, timer); |
1380 | |
1620 | |
1381 | Each time there is some activity: |
1621 | Each time there is some activity: |
1382 | |
1622 | |
… | |
… | |
1444 | |
1684 | |
1445 | To start the timer, simply initialise the watcher and set C<last_activity> |
1685 | 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 |
1686 | 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: |
1687 | callback, which will "do the right thing" and start the timer: |
1448 | |
1688 | |
1449 | ev_timer_init (timer, callback); |
1689 | ev_init (timer, callback); |
1450 | last_activity = ev_now (loop); |
1690 | last_activity = ev_now (loop); |
1451 | callback (loop, timer, EV_TIMEOUT); |
1691 | callback (loop, timer, EV_TIMEOUT); |
1452 | |
1692 | |
1453 | And when there is some activity, simply store the current time in |
1693 | And when there is some activity, simply store the current time in |
1454 | C<last_activity>, no libev calls at all: |
1694 | C<last_activity>, no libev calls at all: |
… | |
… | |
1515 | |
1755 | |
1516 | If the event loop is suspended for a long time, you can also force an |
1756 | 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 |
1757 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1518 | ()>. |
1758 | ()>. |
1519 | |
1759 | |
|
|
1760 | =head3 The special problems of suspended animation |
|
|
1761 | |
|
|
1762 | When you leave the server world it is quite customary to hit machines that |
|
|
1763 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1764 | |
|
|
1765 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1766 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1767 | to run until the system is suspended, but they will not advance while the |
|
|
1768 | system is suspended. That means, on resume, it will be as if the program |
|
|
1769 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1770 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1771 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1772 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1773 | be adjusted accordingly. |
|
|
1774 | |
|
|
1775 | I would not be surprised to see different behaviour in different between |
|
|
1776 | operating systems, OS versions or even different hardware. |
|
|
1777 | |
|
|
1778 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1779 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1780 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1781 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1782 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1783 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1784 | |
|
|
1785 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1786 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1787 | deterministic behaviour in this case (you can do nothing against |
|
|
1788 | C<SIGSTOP>). |
|
|
1789 | |
1520 | =head3 Watcher-Specific Functions and Data Members |
1790 | =head3 Watcher-Specific Functions and Data Members |
1521 | |
1791 | |
1522 | =over 4 |
1792 | =over 4 |
1523 | |
1793 | |
1524 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1794 | =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). |
1817 | If the timer is started but non-repeating, stop it (as if it timed out). |
1548 | |
1818 | |
1549 | If the timer is repeating, either start it if necessary (with the |
1819 | 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. |
1820 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1551 | |
1821 | |
1552 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1822 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1553 | usage example. |
1823 | usage example. |
|
|
1824 | |
|
|
1825 | =item ev_timer_remaining (loop, ev_timer *) |
|
|
1826 | |
|
|
1827 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
1828 | then this time is relative to the current event loop time, otherwise it's |
|
|
1829 | the timeout value currently configured. |
|
|
1830 | |
|
|
1831 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
1832 | C<5>. When the timer is started and one second passes, C<ev_timer_remain> |
|
|
1833 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1834 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1835 | too), and so on. |
1554 | |
1836 | |
1555 | =item ev_tstamp repeat [read-write] |
1837 | =item ev_tstamp repeat [read-write] |
1556 | |
1838 | |
1557 | The current C<repeat> value. Will be used each time the watcher times out |
1839 | 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), |
1840 | 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 |
1899 | 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 |
1900 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
1619 | those cannot react to time jumps. |
1901 | those cannot react to time jumps. |
1620 | |
1902 | |
1621 | As with timers, the callback is guaranteed to be invoked only when the |
1903 | 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 |
1904 | 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 |
1905 | timers become ready during the same loop iteration then the ones with |
1624 | execution is undefined. |
1906 | earlier time-out values are invoked before ones with later time-out values |
|
|
1907 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1625 | |
1908 | |
1626 | =head3 Watcher-Specific Functions and Data Members |
1909 | =head3 Watcher-Specific Functions and Data Members |
1627 | |
1910 | |
1628 | =over 4 |
1911 | =over 4 |
1629 | |
1912 | |
… | |
… | |
1850 | some child status changes (most typically when a child of yours dies or |
2133 | 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 |
2134 | 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 |
2135 | 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., |
2136 | 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, |
2137 | 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 |
2138 | but forking and registering a watcher a few event loop iterations later or |
1856 | not. |
2139 | in the next callback invocation is not. |
1857 | |
2140 | |
1858 | Only the default event loop is capable of handling signals, and therefore |
2141 | Only the default event loop is capable of handling signals, and therefore |
1859 | you can only register child watchers in the default event loop. |
2142 | you can only register child watchers in the default event loop. |
|
|
2143 | |
|
|
2144 | Due to some design glitches inside libev, child watchers will always be |
|
|
2145 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2146 | libev) |
1860 | |
2147 | |
1861 | =head3 Process Interaction |
2148 | =head3 Process Interaction |
1862 | |
2149 | |
1863 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2150 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1864 | initialised. This is necessary to guarantee proper behaviour even if |
2151 | initialised. This is necessary to guarantee proper behaviour even if |
… | |
… | |
2216 | // no longer anything immediate to do. |
2503 | // no longer anything immediate to do. |
2217 | } |
2504 | } |
2218 | |
2505 | |
2219 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2506 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2220 | ev_idle_init (idle_watcher, idle_cb); |
2507 | ev_idle_init (idle_watcher, idle_cb); |
2221 | ev_idle_start (loop, idle_cb); |
2508 | ev_idle_start (loop, idle_watcher); |
2222 | |
2509 | |
2223 | |
2510 | |
2224 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2511 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2225 | |
2512 | |
2226 | Prepare and check watchers are usually (but not always) used in pairs: |
2513 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2319 | struct pollfd fds [nfd]; |
2606 | struct pollfd fds [nfd]; |
2320 | // actual code will need to loop here and realloc etc. |
2607 | // actual code will need to loop here and realloc etc. |
2321 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2608 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2322 | |
2609 | |
2323 | /* the callback is illegal, but won't be called as we stop during check */ |
2610 | /* the callback is illegal, but won't be called as we stop during check */ |
2324 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2611 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2325 | ev_timer_start (loop, &tw); |
2612 | ev_timer_start (loop, &tw); |
2326 | |
2613 | |
2327 | // create one ev_io per pollfd |
2614 | // create one ev_io per pollfd |
2328 | for (int i = 0; i < nfd; ++i) |
2615 | for (int i = 0; i < nfd; ++i) |
2329 | { |
2616 | { |
… | |
… | |
2559 | event loop blocks next and before C<ev_check> watchers are being called, |
2846 | 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 |
2847 | 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 |
2848 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2562 | handlers will be invoked, too, of course. |
2849 | handlers will be invoked, too, of course. |
2563 | |
2850 | |
|
|
2851 | =head3 The special problem of life after fork - how is it possible? |
|
|
2852 | |
|
|
2853 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2854 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2855 | sequence should be handled by libev without any problems. |
|
|
2856 | |
|
|
2857 | This changes when the application actually wants to do event handling |
|
|
2858 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2859 | fork. |
|
|
2860 | |
|
|
2861 | The default mode of operation (for libev, with application help to detect |
|
|
2862 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2863 | when I<either> the parent I<or> the child process continues. |
|
|
2864 | |
|
|
2865 | When both processes want to continue using libev, then this is usually the |
|
|
2866 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2867 | supposed to continue with all watchers in place as before, while the other |
|
|
2868 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2869 | |
|
|
2870 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2871 | simply create a new event loop, which of course will be "empty", and |
|
|
2872 | use that for new watchers. This has the advantage of not touching more |
|
|
2873 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2874 | disadvantage of having to use multiple event loops (which do not support |
|
|
2875 | signal watchers). |
|
|
2876 | |
|
|
2877 | When this is not possible, or you want to use the default loop for |
|
|
2878 | other reasons, then in the process that wants to start "fresh", call |
|
|
2879 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2880 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2881 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2882 | also that in that case, you have to re-register any signal watchers. |
|
|
2883 | |
2564 | =head3 Watcher-Specific Functions and Data Members |
2884 | =head3 Watcher-Specific Functions and Data Members |
2565 | |
2885 | |
2566 | =over 4 |
2886 | =over 4 |
2567 | |
2887 | |
2568 | =item ev_fork_init (ev_signal *, callback) |
2888 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
3458 | defined to be C<0>, then they are not. |
3778 | defined to be C<0>, then they are not. |
3459 | |
3779 | |
3460 | =item EV_MINIMAL |
3780 | =item EV_MINIMAL |
3461 | |
3781 | |
3462 | If you need to shave off some kilobytes of code at the expense of some |
3782 | 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 |
3783 | 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 |
3784 | 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. |
3785 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3786 | the default 4-heap. |
|
|
3787 | |
|
|
3788 | You can save even more by disabling watcher types you do not need |
|
|
3789 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3790 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3791 | |
|
|
3792 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3793 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3794 | of the API are still available, and do not complain if this subset changes |
|
|
3795 | over time. |
3466 | |
3796 | |
3467 | =item EV_PID_HASHSIZE |
3797 | =item EV_PID_HASHSIZE |
3468 | |
3798 | |
3469 | C<ev_child> watchers use a small hash table to distribute workload by |
3799 | 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 |
3800 | 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 |
3986 | default loop and triggering an C<ev_async> watcher from the default loop |
3657 | watcher callback into the event loop interested in the signal. |
3987 | watcher callback into the event loop interested in the signal. |
3658 | |
3988 | |
3659 | =back |
3989 | =back |
3660 | |
3990 | |
|
|
3991 | =head4 THREAD LOCKING EXAMPLE |
|
|
3992 | |
|
|
3993 | Here is a fictitious example of how to run an event loop in a different |
|
|
3994 | thread than where callbacks are being invoked and watchers are |
|
|
3995 | created/added/removed. |
|
|
3996 | |
|
|
3997 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3998 | which uses exactly this technique (which is suited for many high-level |
|
|
3999 | languages). |
|
|
4000 | |
|
|
4001 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4002 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4003 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4004 | |
|
|
4005 | First, you need to associate some data with the event loop: |
|
|
4006 | |
|
|
4007 | typedef struct { |
|
|
4008 | mutex_t lock; /* global loop lock */ |
|
|
4009 | ev_async async_w; |
|
|
4010 | thread_t tid; |
|
|
4011 | cond_t invoke_cv; |
|
|
4012 | } userdata; |
|
|
4013 | |
|
|
4014 | void prepare_loop (EV_P) |
|
|
4015 | { |
|
|
4016 | // for simplicity, we use a static userdata struct. |
|
|
4017 | static userdata u; |
|
|
4018 | |
|
|
4019 | ev_async_init (&u->async_w, async_cb); |
|
|
4020 | ev_async_start (EV_A_ &u->async_w); |
|
|
4021 | |
|
|
4022 | pthread_mutex_init (&u->lock, 0); |
|
|
4023 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4024 | |
|
|
4025 | // now associate this with the loop |
|
|
4026 | ev_set_userdata (EV_A_ u); |
|
|
4027 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4028 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4029 | |
|
|
4030 | // then create the thread running ev_loop |
|
|
4031 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4032 | } |
|
|
4033 | |
|
|
4034 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4035 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4036 | that might have been added: |
|
|
4037 | |
|
|
4038 | static void |
|
|
4039 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4040 | { |
|
|
4041 | // just used for the side effects |
|
|
4042 | } |
|
|
4043 | |
|
|
4044 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4045 | protecting the loop data, respectively. |
|
|
4046 | |
|
|
4047 | static void |
|
|
4048 | l_release (EV_P) |
|
|
4049 | { |
|
|
4050 | userdata *u = ev_userdata (EV_A); |
|
|
4051 | pthread_mutex_unlock (&u->lock); |
|
|
4052 | } |
|
|
4053 | |
|
|
4054 | static void |
|
|
4055 | l_acquire (EV_P) |
|
|
4056 | { |
|
|
4057 | userdata *u = ev_userdata (EV_A); |
|
|
4058 | pthread_mutex_lock (&u->lock); |
|
|
4059 | } |
|
|
4060 | |
|
|
4061 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4062 | into C<ev_loop>: |
|
|
4063 | |
|
|
4064 | void * |
|
|
4065 | l_run (void *thr_arg) |
|
|
4066 | { |
|
|
4067 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4068 | |
|
|
4069 | l_acquire (EV_A); |
|
|
4070 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4071 | ev_loop (EV_A_ 0); |
|
|
4072 | l_release (EV_A); |
|
|
4073 | |
|
|
4074 | return 0; |
|
|
4075 | } |
|
|
4076 | |
|
|
4077 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4078 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4079 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4080 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4081 | and b) skipping inter-thread-communication when there are no pending |
|
|
4082 | watchers is very beneficial): |
|
|
4083 | |
|
|
4084 | static void |
|
|
4085 | l_invoke (EV_P) |
|
|
4086 | { |
|
|
4087 | userdata *u = ev_userdata (EV_A); |
|
|
4088 | |
|
|
4089 | while (ev_pending_count (EV_A)) |
|
|
4090 | { |
|
|
4091 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4092 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4093 | } |
|
|
4094 | } |
|
|
4095 | |
|
|
4096 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4097 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4098 | thread to continue: |
|
|
4099 | |
|
|
4100 | static void |
|
|
4101 | real_invoke_pending (EV_P) |
|
|
4102 | { |
|
|
4103 | userdata *u = ev_userdata (EV_A); |
|
|
4104 | |
|
|
4105 | pthread_mutex_lock (&u->lock); |
|
|
4106 | ev_invoke_pending (EV_A); |
|
|
4107 | pthread_cond_signal (&u->invoke_cv); |
|
|
4108 | pthread_mutex_unlock (&u->lock); |
|
|
4109 | } |
|
|
4110 | |
|
|
4111 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4112 | event loop, you will now have to lock: |
|
|
4113 | |
|
|
4114 | ev_timer timeout_watcher; |
|
|
4115 | userdata *u = ev_userdata (EV_A); |
|
|
4116 | |
|
|
4117 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4118 | |
|
|
4119 | pthread_mutex_lock (&u->lock); |
|
|
4120 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4121 | ev_async_send (EV_A_ &u->async_w); |
|
|
4122 | pthread_mutex_unlock (&u->lock); |
|
|
4123 | |
|
|
4124 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4125 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4126 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4127 | watchers in the next event loop iteration. |
|
|
4128 | |
3661 | =head3 COROUTINES |
4129 | =head3 COROUTINES |
3662 | |
4130 | |
3663 | Libev is very accommodating to coroutines ("cooperative threads"): |
4131 | Libev is very accommodating to coroutines ("cooperative threads"): |
3664 | libev fully supports nesting calls to its functions from different |
4132 | 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 |
4133 | 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 |
4134 | different coroutines, and switch freely between both coroutines running |
3667 | loop, as long as you don't confuse yourself). The only exception is that |
4135 | 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. |
4136 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3669 | |
4137 | |
3670 | Care has been taken to ensure that libev does not keep local state inside |
4138 | 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 |
4139 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3672 | they do not call any callbacks. |
4140 | they do not call any callbacks. |
3673 | |
4141 | |
… | |
… | |
3750 | way (note also that glib is the slowest event library known to man). |
4218 | way (note also that glib is the slowest event library known to man). |
3751 | |
4219 | |
3752 | There is no supported compilation method available on windows except |
4220 | There is no supported compilation method available on windows except |
3753 | embedding it into other applications. |
4221 | embedding it into other applications. |
3754 | |
4222 | |
|
|
4223 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4224 | tries its best, but under most conditions, signals will simply not work. |
|
|
4225 | |
3755 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4226 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3756 | accept large writes: instead of resulting in a partial write, windows will |
4227 | 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, |
4228 | 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 |
4229 | 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 |
4230 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3763 | the abysmal performance of winsockets, using a large number of sockets |
4234 | the abysmal performance of winsockets, using a large number of sockets |
3764 | is not recommended (and not reasonable). If your program needs to use |
4235 | 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 |
4236 | 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 |
4237 | different implementation for windows, as libev offers the POSIX readiness |
3767 | notification model, which cannot be implemented efficiently on windows |
4238 | notification model, which cannot be implemented efficiently on windows |
3768 | (Microsoft monopoly games). |
4239 | (due to Microsoft monopoly games). |
3769 | |
4240 | |
3770 | A typical way to use libev under windows is to embed it (see the embedding |
4241 | 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 |
4242 | section for details) and use the following F<evwrap.h> header file instead |
3772 | of F<ev.h>: |
4243 | of F<ev.h>: |
3773 | |
4244 | |
… | |
… | |
3809 | |
4280 | |
3810 | Early versions of winsocket's select only supported waiting for a maximum |
4281 | 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 |
4282 | 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 |
4283 | 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 |
4284 | recommends spawning a chain of threads and wait for 63 handles and the |
3814 | previous thread in each. Great). |
4285 | previous thread in each. Sounds great!). |
3815 | |
4286 | |
3816 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4287 | 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 |
4288 | 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 |
4289 | call (which might be in libev or elsewhere, for example, perl and many |
3819 | select emulation on windows). |
4290 | other interpreters do their own select emulation on windows). |
3820 | |
4291 | |
3821 | Another limit is the number of file descriptors in the Microsoft runtime |
4292 | 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 |
4293 | 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 |
4294 | fetish or something like this inside Microsoft). You can increase this |
3824 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4295 | 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 |
4296 | (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 |
4297 | 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 |
4298 | (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 |
4299 | 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. |
4300 | the cost of calling select (O(n²)) will likely make this unworkable. |
3832 | |
4301 | |
3833 | =back |
4302 | =back |
3834 | |
4303 | |
3835 | =head2 PORTABILITY REQUIREMENTS |
4304 | =head2 PORTABILITY REQUIREMENTS |
3836 | |
4305 | |
… | |
… | |
3879 | =item C<double> must hold a time value in seconds with enough accuracy |
4348 | =item C<double> must hold a time value in seconds with enough accuracy |
3880 | |
4349 | |
3881 | The type C<double> is used to represent timestamps. It is required to |
4350 | 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 |
4351 | 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 |
4352 | enough for at least into the year 4000. This requirement is fulfilled by |
3884 | implementations implementing IEEE 754 (basically all existing ones). |
4353 | implementations implementing IEEE 754, which is basically all existing |
|
|
4354 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4355 | 2200. |
3885 | |
4356 | |
3886 | =back |
4357 | =back |
3887 | |
4358 | |
3888 | If you know of other additional requirements drop me a note. |
4359 | If you know of other additional requirements drop me a note. |
3889 | |
4360 | |
… | |
… | |
3957 | involves iterating over all running async watchers or all signal numbers. |
4428 | involves iterating over all running async watchers or all signal numbers. |
3958 | |
4429 | |
3959 | =back |
4430 | =back |
3960 | |
4431 | |
3961 | |
4432 | |
|
|
4433 | =head1 GLOSSARY |
|
|
4434 | |
|
|
4435 | =over 4 |
|
|
4436 | |
|
|
4437 | =item active |
|
|
4438 | |
|
|
4439 | A watcher is active as long as it has been started (has been attached to |
|
|
4440 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4441 | |
|
|
4442 | =item application |
|
|
4443 | |
|
|
4444 | In this document, an application is whatever is using libev. |
|
|
4445 | |
|
|
4446 | =item callback |
|
|
4447 | |
|
|
4448 | The address of a function that is called when some event has been |
|
|
4449 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4450 | received the event, and the actual event bitset. |
|
|
4451 | |
|
|
4452 | =item callback invocation |
|
|
4453 | |
|
|
4454 | The act of calling the callback associated with a watcher. |
|
|
4455 | |
|
|
4456 | =item event |
|
|
4457 | |
|
|
4458 | A change of state of some external event, such as data now being available |
|
|
4459 | for reading on a file descriptor, time having passed or simply not having |
|
|
4460 | any other events happening anymore. |
|
|
4461 | |
|
|
4462 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4463 | C<EV_TIMEOUT>). |
|
|
4464 | |
|
|
4465 | =item event library |
|
|
4466 | |
|
|
4467 | A software package implementing an event model and loop. |
|
|
4468 | |
|
|
4469 | =item event loop |
|
|
4470 | |
|
|
4471 | An entity that handles and processes external events and converts them |
|
|
4472 | into callback invocations. |
|
|
4473 | |
|
|
4474 | =item event model |
|
|
4475 | |
|
|
4476 | The model used to describe how an event loop handles and processes |
|
|
4477 | watchers and events. |
|
|
4478 | |
|
|
4479 | =item pending |
|
|
4480 | |
|
|
4481 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4482 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4483 | pending status is explicitly cleared by the application. |
|
|
4484 | |
|
|
4485 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4486 | its pending status. |
|
|
4487 | |
|
|
4488 | =item real time |
|
|
4489 | |
|
|
4490 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4491 | |
|
|
4492 | =item wall-clock time |
|
|
4493 | |
|
|
4494 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4495 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4496 | clock. |
|
|
4497 | |
|
|
4498 | =item watcher |
|
|
4499 | |
|
|
4500 | A data structure that describes interest in certain events. Watchers need |
|
|
4501 | to be started (attached to an event loop) before they can receive events. |
|
|
4502 | |
|
|
4503 | =item watcher invocation |
|
|
4504 | |
|
|
4505 | The act of calling the callback associated with a watcher. |
|
|
4506 | |
|
|
4507 | =back |
|
|
4508 | |
3962 | =head1 AUTHOR |
4509 | =head1 AUTHOR |
3963 | |
4510 | |
3964 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
4511 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3965 | |
4512 | |