… | |
… | |
98 | =head2 FEATURES |
98 | =head2 FEATURES |
99 | |
99 | |
100 | 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 |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
102 | 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 |
103 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
104 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
105 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
106 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
107 | 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 |
108 | 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 |
109 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
|
|
110 | limited support for fork events (C<ev_fork>). |
110 | |
111 | |
111 | It also is quite fast (see this |
112 | It also is quite fast (see this |
112 | 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 |
113 | for example). |
114 | for example). |
114 | |
115 | |
… | |
… | |
117 | Libev is very configurable. In this manual the default (and most common) |
118 | Libev is very configurable. In this manual the default (and most common) |
118 | configuration will be described, which supports multiple event loops. For |
119 | configuration will be described, which supports multiple event loops. For |
119 | more info about various configuration options please have a look at |
120 | more info about various configuration options please have a look at |
120 | B<EMBED> section in this manual. If libev was configured without support |
121 | B<EMBED> section in this manual. If libev was configured without support |
121 | for multiple event loops, then all functions taking an initial argument of |
122 | for multiple event loops, then all functions taking an initial argument of |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
123 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
123 | this argument. |
124 | this argument. |
124 | |
125 | |
125 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
126 | |
127 | |
127 | Libev represents time as a single floating point number, representing |
128 | Libev represents time as a single floating point number, representing |
… | |
… | |
362 | flag. |
363 | flag. |
363 | |
364 | |
364 | 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> |
365 | environment variable. |
366 | environment variable. |
366 | |
367 | |
|
|
368 | =item C<EVFLAG_NOINOTIFY> |
|
|
369 | |
|
|
370 | When this flag is specified, then libev will not attempt to use the |
|
|
371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
|
|
372 | testing, this flag can be useful to conserve inotify file descriptors, as |
|
|
373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
|
|
374 | |
|
|
375 | =item C<EVFLAG_SIGNALFD> |
|
|
376 | |
|
|
377 | When this flag is specified, then libev will attempt to use the |
|
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378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
|
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379 | delivers signals synchronously, which makes it both faster and might make |
|
|
380 | it possible to get the queued signal data. It can also simplify signal |
|
|
381 | handling with threads, as long as you properly block signals in your |
|
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382 | threads that are not interested in handling them. |
|
|
383 | |
|
|
384 | Signalfd will not be used by default as this changes your signal mask, and |
|
|
385 | there are a lot of shoddy libraries and programs (glib's threadpool for |
|
|
386 | example) that can't properly initialise their signal masks. |
|
|
387 | |
367 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
368 | |
389 | |
369 | This is your standard select(2) backend. Not I<completely> standard, as |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
370 | libev tries to roll its own fd_set with no limits on the number of fds, |
391 | libev tries to roll its own fd_set with no limits on the number of fds, |
371 | but if that fails, expect a fairly low limit on the number of fds when |
392 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
394 | |
415 | |
395 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
416 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
396 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
417 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
397 | |
418 | |
398 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
419 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
|
|
420 | |
|
|
421 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
|
|
422 | kernels). |
399 | |
423 | |
400 | For few fds, this backend is a bit little slower than poll and select, |
424 | For few fds, this backend is a bit little slower than poll and select, |
401 | but it scales phenomenally better. While poll and select usually scale |
425 | but it scales phenomenally better. While poll and select usually scale |
402 | like O(total_fds) where n is the total number of fds (or the highest fd), |
426 | like O(total_fds) where n is the total number of fds (or the highest fd), |
403 | epoll scales either O(1) or O(active_fds). |
427 | epoll scales either O(1) or O(active_fds). |
… | |
… | |
518 | |
542 | |
519 | It is definitely not recommended to use this flag. |
543 | It is definitely not recommended to use this flag. |
520 | |
544 | |
521 | =back |
545 | =back |
522 | |
546 | |
523 | If one or more of these are or'ed into the flags value, then only these |
547 | If one or more of the backend flags are or'ed into the flags value, |
524 | backends will be tried (in the reverse order as listed here). If none are |
548 | then only these backends will be tried (in the reverse order as listed |
525 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
549 | here). If none are specified, all backends in C<ev_recommended_backends |
|
|
550 | ()> will be tried. |
526 | |
551 | |
527 | Example: This is the most typical usage. |
552 | Example: This is the most typical usage. |
528 | |
553 | |
529 | if (!ev_default_loop (0)) |
554 | if (!ev_default_loop (0)) |
530 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
555 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
… | |
… | |
573 | as signal and child watchers) would need to be stopped manually. |
598 | as signal and child watchers) would need to be stopped manually. |
574 | |
599 | |
575 | In general it is not advisable to call this function except in the |
600 | In general it is not advisable to call this function except in the |
576 | rare occasion where you really need to free e.g. the signal handling |
601 | rare occasion where you really need to free e.g. the signal handling |
577 | pipe fds. If you need dynamically allocated loops it is better to use |
602 | pipe fds. If you need dynamically allocated loops it is better to use |
578 | C<ev_loop_new> and C<ev_loop_destroy>). |
603 | C<ev_loop_new> and C<ev_loop_destroy>. |
579 | |
604 | |
580 | =item ev_loop_destroy (loop) |
605 | =item ev_loop_destroy (loop) |
581 | |
606 | |
582 | Like C<ev_default_destroy>, but destroys an event loop created by an |
607 | Like C<ev_default_destroy>, but destroys an event loop created by an |
583 | earlier call to C<ev_loop_new>. |
608 | earlier call to C<ev_loop_new>. |
… | |
… | |
621 | |
646 | |
622 | This value can sometimes be useful as a generation counter of sorts (it |
647 | This value can sometimes be useful as a generation counter of sorts (it |
623 | "ticks" the number of loop iterations), as it roughly corresponds with |
648 | "ticks" the number of loop iterations), as it roughly corresponds with |
624 | C<ev_prepare> and C<ev_check> calls. |
649 | C<ev_prepare> and C<ev_check> calls. |
625 | |
650 | |
|
|
651 | =item unsigned int ev_loop_depth (loop) |
|
|
652 | |
|
|
653 | Returns the number of times C<ev_loop> was entered minus the number of |
|
|
654 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
655 | |
|
|
656 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
|
|
657 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
|
|
658 | in which case it is higher. |
|
|
659 | |
|
|
660 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
661 | etc.), doesn't count as exit. |
|
|
662 | |
626 | =item unsigned int ev_backend (loop) |
663 | =item unsigned int ev_backend (loop) |
627 | |
664 | |
628 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
665 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
629 | use. |
666 | use. |
630 | |
667 | |
… | |
… | |
644 | |
681 | |
645 | This function is rarely useful, but when some event callback runs for a |
682 | This function is rarely useful, but when some event callback runs for a |
646 | very long time without entering the event loop, updating libev's idea of |
683 | very long time without entering the event loop, updating libev's idea of |
647 | the current time is a good idea. |
684 | the current time is a good idea. |
648 | |
685 | |
649 | See also "The special problem of time updates" in the C<ev_timer> section. |
686 | See also L<The special problem of time updates> in the C<ev_timer> section. |
650 | |
687 | |
651 | =item ev_suspend (loop) |
688 | =item ev_suspend (loop) |
652 | |
689 | |
653 | =item ev_resume (loop) |
690 | =item ev_resume (loop) |
654 | |
691 | |
… | |
… | |
675 | event loop time (see C<ev_now_update>). |
712 | event loop time (see C<ev_now_update>). |
676 | |
713 | |
677 | =item ev_loop (loop, int flags) |
714 | =item ev_loop (loop, int flags) |
678 | |
715 | |
679 | Finally, this is it, the event handler. This function usually is called |
716 | Finally, this is it, the event handler. This function usually is called |
680 | after you initialised all your watchers and you want to start handling |
717 | after you have initialised all your watchers and you want to start |
681 | events. |
718 | handling events. |
682 | |
719 | |
683 | If the flags argument is specified as C<0>, it will not return until |
720 | If the flags argument is specified as C<0>, it will not return until |
684 | either no event watchers are active anymore or C<ev_unloop> was called. |
721 | either no event watchers are active anymore or C<ev_unloop> was called. |
685 | |
722 | |
686 | Please note that an explicit C<ev_unloop> is usually better than |
723 | Please note that an explicit C<ev_unloop> is usually better than |
… | |
… | |
760 | |
797 | |
761 | Ref/unref can be used to add or remove a reference count on the event |
798 | Ref/unref can be used to add or remove a reference count on the event |
762 | loop: Every watcher keeps one reference, and as long as the reference |
799 | loop: Every watcher keeps one reference, and as long as the reference |
763 | count is nonzero, C<ev_loop> will not return on its own. |
800 | count is nonzero, C<ev_loop> will not return on its own. |
764 | |
801 | |
765 | If you have a watcher you never unregister that should not keep C<ev_loop> |
802 | This is useful when you have a watcher that you never intend to |
766 | from returning, call ev_unref() after starting, and ev_ref() before |
803 | unregister, but that nevertheless should not keep C<ev_loop> from |
|
|
804 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
767 | stopping it. |
805 | before stopping it. |
768 | |
806 | |
769 | As an example, libev itself uses this for its internal signal pipe: It |
807 | As an example, libev itself uses this for its internal signal pipe: It |
770 | is not visible to the libev user and should not keep C<ev_loop> from |
808 | is not visible to the libev user and should not keep C<ev_loop> from |
771 | exiting if no event watchers registered by it are active. It is also an |
809 | exiting if no event watchers registered by it are active. It is also an |
772 | excellent way to do this for generic recurring timers or from within |
810 | excellent way to do this for generic recurring timers or from within |
… | |
… | |
811 | |
849 | |
812 | By setting a higher I<io collect interval> you allow libev to spend more |
850 | By setting a higher I<io collect interval> you allow libev to spend more |
813 | time collecting I/O events, so you can handle more events per iteration, |
851 | time collecting I/O events, so you can handle more events per iteration, |
814 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
852 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
815 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
853 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
816 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
854 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
855 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
856 | once per this interval, on average. |
817 | |
857 | |
818 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
858 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
819 | to spend more time collecting timeouts, at the expense of increased |
859 | to spend more time collecting timeouts, at the expense of increased |
820 | latency/jitter/inexactness (the watcher callback will be called |
860 | latency/jitter/inexactness (the watcher callback will be called |
821 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
861 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
823 | |
863 | |
824 | Many (busy) programs can usually benefit by setting the I/O collect |
864 | Many (busy) programs can usually benefit by setting the I/O collect |
825 | interval to a value near C<0.1> or so, which is often enough for |
865 | interval to a value near C<0.1> or so, which is often enough for |
826 | interactive servers (of course not for games), likewise for timeouts. It |
866 | interactive servers (of course not for games), likewise for timeouts. It |
827 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
867 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
828 | as this approaches the timing granularity of most systems. |
868 | as this approaches the timing granularity of most systems. Note that if |
|
|
869 | you do transactions with the outside world and you can't increase the |
|
|
870 | parallelity, then this setting will limit your transaction rate (if you |
|
|
871 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
872 | then you can't do more than 100 transations per second). |
829 | |
873 | |
830 | Setting the I<timeout collect interval> can improve the opportunity for |
874 | Setting the I<timeout collect interval> can improve the opportunity for |
831 | saving power, as the program will "bundle" timer callback invocations that |
875 | saving power, as the program will "bundle" timer callback invocations that |
832 | are "near" in time together, by delaying some, thus reducing the number of |
876 | are "near" in time together, by delaying some, thus reducing the number of |
833 | times the process sleeps and wakes up again. Another useful technique to |
877 | times the process sleeps and wakes up again. Another useful technique to |
834 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
878 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
835 | they fire on, say, one-second boundaries only. |
879 | they fire on, say, one-second boundaries only. |
|
|
880 | |
|
|
881 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
882 | more often than 100 times per second: |
|
|
883 | |
|
|
884 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
885 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
886 | |
|
|
887 | =item ev_invoke_pending (loop) |
|
|
888 | |
|
|
889 | This call will simply invoke all pending watchers while resetting their |
|
|
890 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
|
891 | but when overriding the invoke callback this call comes handy. |
|
|
892 | |
|
|
893 | =item int ev_pending_count (loop) |
|
|
894 | |
|
|
895 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
896 | are pending. |
|
|
897 | |
|
|
898 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
899 | |
|
|
900 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
901 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
902 | this callback instead. This is useful, for example, when you want to |
|
|
903 | invoke the actual watchers inside another context (another thread etc.). |
|
|
904 | |
|
|
905 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
906 | callback. |
|
|
907 | |
|
|
908 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
909 | |
|
|
910 | Sometimes you want to share the same loop between multiple threads. This |
|
|
911 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
912 | each call to a libev function. |
|
|
913 | |
|
|
914 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
915 | wait for it to return. One way around this is to wake up the loop via |
|
|
916 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
917 | and I<acquire> callbacks on the loop. |
|
|
918 | |
|
|
919 | When set, then C<release> will be called just before the thread is |
|
|
920 | suspended waiting for new events, and C<acquire> is called just |
|
|
921 | afterwards. |
|
|
922 | |
|
|
923 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
924 | C<acquire> will just call the mutex_lock function again. |
|
|
925 | |
|
|
926 | While event loop modifications are allowed between invocations of |
|
|
927 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
928 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
929 | have no effect on the set of file descriptors being watched, or the time |
|
|
930 | waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
931 | to take note of any changes you made. |
|
|
932 | |
|
|
933 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
934 | invocations of C<release> and C<acquire>. |
|
|
935 | |
|
|
936 | See also the locking example in the C<THREADS> section later in this |
|
|
937 | document. |
|
|
938 | |
|
|
939 | =item ev_set_userdata (loop, void *data) |
|
|
940 | |
|
|
941 | =item ev_userdata (loop) |
|
|
942 | |
|
|
943 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
944 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
945 | C<0.> |
|
|
946 | |
|
|
947 | These two functions can be used to associate arbitrary data with a loop, |
|
|
948 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
949 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
950 | any other purpose as well. |
836 | |
951 | |
837 | =item ev_loop_verify (loop) |
952 | =item ev_loop_verify (loop) |
838 | |
953 | |
839 | This function only does something when C<EV_VERIFY> support has been |
954 | This function only does something when C<EV_VERIFY> support has been |
840 | compiled in, which is the default for non-minimal builds. It tries to go |
955 | compiled in, which is the default for non-minimal builds. It tries to go |
… | |
… | |
1017 | |
1132 | |
1018 | ev_io w; |
1133 | ev_io w; |
1019 | ev_init (&w, my_cb); |
1134 | ev_init (&w, my_cb); |
1020 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1135 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1021 | |
1136 | |
1022 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1137 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
1023 | |
1138 | |
1024 | This macro initialises the type-specific parts of a watcher. You need to |
1139 | This macro initialises the type-specific parts of a watcher. You need to |
1025 | call C<ev_init> at least once before you call this macro, but you can |
1140 | call C<ev_init> at least once before you call this macro, but you can |
1026 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1141 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1027 | macro on a watcher that is active (it can be pending, however, which is a |
1142 | macro on a watcher that is active (it can be pending, however, which is a |
… | |
… | |
1040 | |
1155 | |
1041 | Example: Initialise and set an C<ev_io> watcher in one step. |
1156 | Example: Initialise and set an C<ev_io> watcher in one step. |
1042 | |
1157 | |
1043 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1158 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1044 | |
1159 | |
1045 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1160 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
1046 | |
1161 | |
1047 | Starts (activates) the given watcher. Only active watchers will receive |
1162 | Starts (activates) the given watcher. Only active watchers will receive |
1048 | events. If the watcher is already active nothing will happen. |
1163 | events. If the watcher is already active nothing will happen. |
1049 | |
1164 | |
1050 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1165 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1051 | whole section. |
1166 | whole section. |
1052 | |
1167 | |
1053 | ev_io_start (EV_DEFAULT_UC, &w); |
1168 | ev_io_start (EV_DEFAULT_UC, &w); |
1054 | |
1169 | |
1055 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1170 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
1056 | |
1171 | |
1057 | Stops the given watcher if active, and clears the pending status (whether |
1172 | Stops the given watcher if active, and clears the pending status (whether |
1058 | the watcher was active or not). |
1173 | the watcher was active or not). |
1059 | |
1174 | |
1060 | It is possible that stopped watchers are pending - for example, |
1175 | It is possible that stopped watchers are pending - for example, |
… | |
… | |
1085 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1200 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1086 | |
1201 | |
1087 | Change the callback. You can change the callback at virtually any time |
1202 | Change the callback. You can change the callback at virtually any time |
1088 | (modulo threads). |
1203 | (modulo threads). |
1089 | |
1204 | |
1090 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1205 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1091 | |
1206 | |
1092 | =item int ev_priority (ev_TYPE *watcher) |
1207 | =item int ev_priority (ev_TYPE *watcher) |
1093 | |
1208 | |
1094 | Set and query the priority of the watcher. The priority is a small |
1209 | Set and query the priority of the watcher. The priority is a small |
1095 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1210 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
… | |
… | |
1126 | returns its C<revents> bitset (as if its callback was invoked). If the |
1241 | returns its C<revents> bitset (as if its callback was invoked). If the |
1127 | watcher isn't pending it does nothing and returns C<0>. |
1242 | watcher isn't pending it does nothing and returns C<0>. |
1128 | |
1243 | |
1129 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1244 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1130 | callback to be invoked, which can be accomplished with this function. |
1245 | callback to be invoked, which can be accomplished with this function. |
|
|
1246 | |
|
|
1247 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1248 | |
|
|
1249 | Feeds the given event set into the event loop, as if the specified event |
|
|
1250 | had happened for the specified watcher (which must be a pointer to an |
|
|
1251 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1252 | not free the watcher as long as it has pending events. |
|
|
1253 | |
|
|
1254 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1255 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1256 | not started in the first place. |
|
|
1257 | |
|
|
1258 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1259 | functions that do not need a watcher. |
1131 | |
1260 | |
1132 | =back |
1261 | =back |
1133 | |
1262 | |
1134 | |
1263 | |
1135 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1264 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
… | |
… | |
1184 | #include <stddef.h> |
1313 | #include <stddef.h> |
1185 | |
1314 | |
1186 | static void |
1315 | static void |
1187 | t1_cb (EV_P_ ev_timer *w, int revents) |
1316 | t1_cb (EV_P_ ev_timer *w, int revents) |
1188 | { |
1317 | { |
1189 | struct my_biggy big = (struct my_biggy * |
1318 | struct my_biggy big = (struct my_biggy *) |
1190 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1319 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1191 | } |
1320 | } |
1192 | |
1321 | |
1193 | static void |
1322 | static void |
1194 | t2_cb (EV_P_ ev_timer *w, int revents) |
1323 | t2_cb (EV_P_ ev_timer *w, int revents) |
1195 | { |
1324 | { |
1196 | struct my_biggy big = (struct my_biggy * |
1325 | struct my_biggy big = (struct my_biggy *) |
1197 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1326 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1198 | } |
1327 | } |
1199 | |
1328 | |
1200 | =head2 WATCHER PRIORITY MODELS |
1329 | =head2 WATCHER PRIORITY MODELS |
1201 | |
1330 | |
… | |
… | |
1277 | // with the default priority are receiving events. |
1406 | // with the default priority are receiving events. |
1278 | ev_idle_start (EV_A_ &idle); |
1407 | ev_idle_start (EV_A_ &idle); |
1279 | } |
1408 | } |
1280 | |
1409 | |
1281 | static void |
1410 | static void |
1282 | idle-cb (EV_P_ ev_idle *w, int revents) |
1411 | idle_cb (EV_P_ ev_idle *w, int revents) |
1283 | { |
1412 | { |
1284 | // actual processing |
1413 | // actual processing |
1285 | read (STDIN_FILENO, ...); |
1414 | read (STDIN_FILENO, ...); |
1286 | |
1415 | |
1287 | // have to start the I/O watcher again, as |
1416 | // have to start the I/O watcher again, as |
… | |
… | |
1332 | descriptors to non-blocking mode is also usually a good idea (but not |
1461 | descriptors to non-blocking mode is also usually a good idea (but not |
1333 | required if you know what you are doing). |
1462 | required if you know what you are doing). |
1334 | |
1463 | |
1335 | If you cannot use non-blocking mode, then force the use of a |
1464 | If you cannot use non-blocking mode, then force the use of a |
1336 | known-to-be-good backend (at the time of this writing, this includes only |
1465 | known-to-be-good backend (at the time of this writing, this includes only |
1337 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1466 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1467 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1468 | files) - libev doesn't guarentee any specific behaviour in that case. |
1338 | |
1469 | |
1339 | Another thing you have to watch out for is that it is quite easy to |
1470 | Another thing you have to watch out for is that it is quite easy to |
1340 | receive "spurious" readiness notifications, that is your callback might |
1471 | receive "spurious" readiness notifications, that is your callback might |
1341 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1472 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1342 | because there is no data. Not only are some backends known to create a |
1473 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1463 | year, it will still time out after (roughly) one hour. "Roughly" because |
1594 | year, it will still time out after (roughly) one hour. "Roughly" because |
1464 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1595 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1465 | monotonic clock option helps a lot here). |
1596 | monotonic clock option helps a lot here). |
1466 | |
1597 | |
1467 | The callback is guaranteed to be invoked only I<after> its timeout has |
1598 | The callback is guaranteed to be invoked only I<after> its timeout has |
1468 | passed. If multiple timers become ready during the same loop iteration |
1599 | passed (not I<at>, so on systems with very low-resolution clocks this |
1469 | then the ones with earlier time-out values are invoked before ones with |
1600 | might introduce a small delay). If multiple timers become ready during the |
1470 | later time-out values (but this is no longer true when a callback calls |
1601 | same loop iteration then the ones with earlier time-out values are invoked |
1471 | C<ev_loop> recursively). |
1602 | before ones of the same priority with later time-out values (but this is |
|
|
1603 | no longer true when a callback calls C<ev_loop> recursively). |
1472 | |
1604 | |
1473 | =head3 Be smart about timeouts |
1605 | =head3 Be smart about timeouts |
1474 | |
1606 | |
1475 | Many real-world problems involve some kind of timeout, usually for error |
1607 | Many real-world problems involve some kind of timeout, usually for error |
1476 | recovery. A typical example is an HTTP request - if the other side hangs, |
1608 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1520 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1652 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1521 | member and C<ev_timer_again>. |
1653 | member and C<ev_timer_again>. |
1522 | |
1654 | |
1523 | At start: |
1655 | At start: |
1524 | |
1656 | |
1525 | ev_timer_init (timer, callback); |
1657 | ev_init (timer, callback); |
1526 | timer->repeat = 60.; |
1658 | timer->repeat = 60.; |
1527 | ev_timer_again (loop, timer); |
1659 | ev_timer_again (loop, timer); |
1528 | |
1660 | |
1529 | Each time there is some activity: |
1661 | Each time there is some activity: |
1530 | |
1662 | |
… | |
… | |
1592 | |
1724 | |
1593 | To start the timer, simply initialise the watcher and set C<last_activity> |
1725 | To start the timer, simply initialise the watcher and set C<last_activity> |
1594 | to the current time (meaning we just have some activity :), then call the |
1726 | to the current time (meaning we just have some activity :), then call the |
1595 | callback, which will "do the right thing" and start the timer: |
1727 | callback, which will "do the right thing" and start the timer: |
1596 | |
1728 | |
1597 | ev_timer_init (timer, callback); |
1729 | ev_init (timer, callback); |
1598 | last_activity = ev_now (loop); |
1730 | last_activity = ev_now (loop); |
1599 | callback (loop, timer, EV_TIMEOUT); |
1731 | callback (loop, timer, EV_TIMEOUT); |
1600 | |
1732 | |
1601 | And when there is some activity, simply store the current time in |
1733 | And when there is some activity, simply store the current time in |
1602 | C<last_activity>, no libev calls at all: |
1734 | C<last_activity>, no libev calls at all: |
… | |
… | |
1663 | |
1795 | |
1664 | If the event loop is suspended for a long time, you can also force an |
1796 | If the event loop is suspended for a long time, you can also force an |
1665 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1797 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1666 | ()>. |
1798 | ()>. |
1667 | |
1799 | |
|
|
1800 | =head3 The special problems of suspended animation |
|
|
1801 | |
|
|
1802 | When you leave the server world it is quite customary to hit machines that |
|
|
1803 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1804 | |
|
|
1805 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1806 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1807 | to run until the system is suspended, but they will not advance while the |
|
|
1808 | system is suspended. That means, on resume, it will be as if the program |
|
|
1809 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1810 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1811 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1812 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1813 | be adjusted accordingly. |
|
|
1814 | |
|
|
1815 | I would not be surprised to see different behaviour in different between |
|
|
1816 | operating systems, OS versions or even different hardware. |
|
|
1817 | |
|
|
1818 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1819 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1820 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1821 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1822 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1823 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1824 | |
|
|
1825 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1826 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1827 | deterministic behaviour in this case (you can do nothing against |
|
|
1828 | C<SIGSTOP>). |
|
|
1829 | |
1668 | =head3 Watcher-Specific Functions and Data Members |
1830 | =head3 Watcher-Specific Functions and Data Members |
1669 | |
1831 | |
1670 | =over 4 |
1832 | =over 4 |
1671 | |
1833 | |
1672 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1834 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1697 | If the timer is repeating, either start it if necessary (with the |
1859 | If the timer is repeating, either start it if necessary (with the |
1698 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1860 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1699 | |
1861 | |
1700 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1862 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1701 | usage example. |
1863 | usage example. |
|
|
1864 | |
|
|
1865 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
|
|
1866 | |
|
|
1867 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
1868 | then this time is relative to the current event loop time, otherwise it's |
|
|
1869 | the timeout value currently configured. |
|
|
1870 | |
|
|
1871 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
1872 | C<5>. When the timer is started and one second passes, C<ev_timer_remain> |
|
|
1873 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1874 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1875 | too), and so on. |
1702 | |
1876 | |
1703 | =item ev_tstamp repeat [read-write] |
1877 | =item ev_tstamp repeat [read-write] |
1704 | |
1878 | |
1705 | The current C<repeat> value. Will be used each time the watcher times out |
1879 | The current C<repeat> value. Will be used each time the watcher times out |
1706 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1880 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1942 | Signal watchers will trigger an event when the process receives a specific |
2116 | Signal watchers will trigger an event when the process receives a specific |
1943 | signal one or more times. Even though signals are very asynchronous, libev |
2117 | signal one or more times. Even though signals are very asynchronous, libev |
1944 | will try it's best to deliver signals synchronously, i.e. as part of the |
2118 | will try it's best to deliver signals synchronously, i.e. as part of the |
1945 | normal event processing, like any other event. |
2119 | normal event processing, like any other event. |
1946 | |
2120 | |
1947 | If you want signals asynchronously, just use C<sigaction> as you would |
2121 | If you want signals to be delivered truly asynchronously, just use |
1948 | do without libev and forget about sharing the signal. You can even use |
2122 | C<sigaction> as you would do without libev and forget about sharing |
1949 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
2123 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2124 | synchronously wake up an event loop. |
1950 | |
2125 | |
1951 | You can configure as many watchers as you like per signal. Only when the |
2126 | You can configure as many watchers as you like for the same signal, but |
|
|
2127 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2128 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2129 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2130 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2131 | |
1952 | first watcher gets started will libev actually register a signal handler |
2132 | When the first watcher gets started will libev actually register something |
1953 | with the kernel (thus it coexists with your own signal handlers as long as |
2133 | with the kernel (thus it coexists with your own signal handlers as long as |
1954 | you don't register any with libev for the same signal). Similarly, when |
2134 | you don't register any with libev for the same signal). |
1955 | the last signal watcher for a signal is stopped, libev will reset the |
|
|
1956 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1957 | |
2135 | |
1958 | If possible and supported, libev will install its handlers with |
2136 | If possible and supported, libev will install its handlers with |
1959 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2137 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1960 | interrupted. If you have a problem with system calls getting interrupted by |
2138 | not be unduly interrupted. If you have a problem with system calls getting |
1961 | signals you can block all signals in an C<ev_check> watcher and unblock |
2139 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1962 | them in an C<ev_prepare> watcher. |
2140 | and unblock them in an C<ev_prepare> watcher. |
|
|
2141 | |
|
|
2142 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2143 | |
|
|
2144 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2145 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2146 | stopping it again), that is, libev might or might not block the signal, |
|
|
2147 | and might or might not set or restore the installed signal handler. |
|
|
2148 | |
|
|
2149 | While this does not matter for the signal disposition (libev never |
|
|
2150 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2151 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2152 | certain signals to be blocked. |
|
|
2153 | |
|
|
2154 | This means that before calling C<exec> (from the child) you should reset |
|
|
2155 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2156 | choice usually). |
|
|
2157 | |
|
|
2158 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2159 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2160 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2161 | |
|
|
2162 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2163 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2164 | the window of opportunity for problems, it will not go away, as libev |
|
|
2165 | I<has> to modify the signal mask, at least temporarily. |
|
|
2166 | |
|
|
2167 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2168 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2169 | is not a libev-specific thing, this is true for most event libraries. |
1963 | |
2170 | |
1964 | =head3 Watcher-Specific Functions and Data Members |
2171 | =head3 Watcher-Specific Functions and Data Members |
1965 | |
2172 | |
1966 | =over 4 |
2173 | =over 4 |
1967 | |
2174 | |
… | |
… | |
1999 | some child status changes (most typically when a child of yours dies or |
2206 | some child status changes (most typically when a child of yours dies or |
2000 | exits). It is permissible to install a child watcher I<after> the child |
2207 | exits). It is permissible to install a child watcher I<after> the child |
2001 | has been forked (which implies it might have already exited), as long |
2208 | has been forked (which implies it might have already exited), as long |
2002 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2209 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2003 | forking and then immediately registering a watcher for the child is fine, |
2210 | forking and then immediately registering a watcher for the child is fine, |
2004 | but forking and registering a watcher a few event loop iterations later is |
2211 | but forking and registering a watcher a few event loop iterations later or |
2005 | not. |
2212 | in the next callback invocation is not. |
2006 | |
2213 | |
2007 | Only the default event loop is capable of handling signals, and therefore |
2214 | Only the default event loop is capable of handling signals, and therefore |
2008 | you can only register child watchers in the default event loop. |
2215 | you can only register child watchers in the default event loop. |
2009 | |
2216 | |
|
|
2217 | Due to some design glitches inside libev, child watchers will always be |
|
|
2218 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2219 | libev) |
|
|
2220 | |
2010 | =head3 Process Interaction |
2221 | =head3 Process Interaction |
2011 | |
2222 | |
2012 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2223 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2013 | initialised. This is necessary to guarantee proper behaviour even if |
2224 | initialised. This is necessary to guarantee proper behaviour even if the |
2014 | the first child watcher is started after the child exits. The occurrence |
2225 | first child watcher is started after the child exits. The occurrence |
2015 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2226 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2016 | synchronously as part of the event loop processing. Libev always reaps all |
2227 | synchronously as part of the event loop processing. Libev always reaps all |
2017 | children, even ones not watched. |
2228 | children, even ones not watched. |
2018 | |
2229 | |
2019 | =head3 Overriding the Built-In Processing |
2230 | =head3 Overriding the Built-In Processing |
… | |
… | |
2029 | =head3 Stopping the Child Watcher |
2240 | =head3 Stopping the Child Watcher |
2030 | |
2241 | |
2031 | Currently, the child watcher never gets stopped, even when the |
2242 | Currently, the child watcher never gets stopped, even when the |
2032 | child terminates, so normally one needs to stop the watcher in the |
2243 | child terminates, so normally one needs to stop the watcher in the |
2033 | callback. Future versions of libev might stop the watcher automatically |
2244 | callback. Future versions of libev might stop the watcher automatically |
2034 | when a child exit is detected. |
2245 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2246 | problem). |
2035 | |
2247 | |
2036 | =head3 Watcher-Specific Functions and Data Members |
2248 | =head3 Watcher-Specific Functions and Data Members |
2037 | |
2249 | |
2038 | =over 4 |
2250 | =over 4 |
2039 | |
2251 | |
… | |
… | |
2365 | // no longer anything immediate to do. |
2577 | // no longer anything immediate to do. |
2366 | } |
2578 | } |
2367 | |
2579 | |
2368 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2580 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2369 | ev_idle_init (idle_watcher, idle_cb); |
2581 | ev_idle_init (idle_watcher, idle_cb); |
2370 | ev_idle_start (loop, idle_cb); |
2582 | ev_idle_start (loop, idle_watcher); |
2371 | |
2583 | |
2372 | |
2584 | |
2373 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2585 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2374 | |
2586 | |
2375 | Prepare and check watchers are usually (but not always) used in pairs: |
2587 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2468 | struct pollfd fds [nfd]; |
2680 | struct pollfd fds [nfd]; |
2469 | // actual code will need to loop here and realloc etc. |
2681 | // actual code will need to loop here and realloc etc. |
2470 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2682 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2471 | |
2683 | |
2472 | /* the callback is illegal, but won't be called as we stop during check */ |
2684 | /* the callback is illegal, but won't be called as we stop during check */ |
2473 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2685 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2474 | ev_timer_start (loop, &tw); |
2686 | ev_timer_start (loop, &tw); |
2475 | |
2687 | |
2476 | // create one ev_io per pollfd |
2688 | // create one ev_io per pollfd |
2477 | for (int i = 0; i < nfd; ++i) |
2689 | for (int i = 0; i < nfd; ++i) |
2478 | { |
2690 | { |
… | |
… | |
2708 | event loop blocks next and before C<ev_check> watchers are being called, |
2920 | event loop blocks next and before C<ev_check> watchers are being called, |
2709 | and only in the child after the fork. If whoever good citizen calling |
2921 | and only in the child after the fork. If whoever good citizen calling |
2710 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2922 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2711 | handlers will be invoked, too, of course. |
2923 | handlers will be invoked, too, of course. |
2712 | |
2924 | |
|
|
2925 | =head3 The special problem of life after fork - how is it possible? |
|
|
2926 | |
|
|
2927 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2928 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2929 | sequence should be handled by libev without any problems. |
|
|
2930 | |
|
|
2931 | This changes when the application actually wants to do event handling |
|
|
2932 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2933 | fork. |
|
|
2934 | |
|
|
2935 | The default mode of operation (for libev, with application help to detect |
|
|
2936 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2937 | when I<either> the parent I<or> the child process continues. |
|
|
2938 | |
|
|
2939 | When both processes want to continue using libev, then this is usually the |
|
|
2940 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2941 | supposed to continue with all watchers in place as before, while the other |
|
|
2942 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2943 | |
|
|
2944 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2945 | simply create a new event loop, which of course will be "empty", and |
|
|
2946 | use that for new watchers. This has the advantage of not touching more |
|
|
2947 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2948 | disadvantage of having to use multiple event loops (which do not support |
|
|
2949 | signal watchers). |
|
|
2950 | |
|
|
2951 | When this is not possible, or you want to use the default loop for |
|
|
2952 | other reasons, then in the process that wants to start "fresh", call |
|
|
2953 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2954 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2955 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2956 | also that in that case, you have to re-register any signal watchers. |
|
|
2957 | |
2713 | =head3 Watcher-Specific Functions and Data Members |
2958 | =head3 Watcher-Specific Functions and Data Members |
2714 | |
2959 | |
2715 | =over 4 |
2960 | =over 4 |
2716 | |
2961 | |
2717 | =item ev_fork_init (ev_signal *, callback) |
2962 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2746 | =head3 Queueing |
2991 | =head3 Queueing |
2747 | |
2992 | |
2748 | C<ev_async> does not support queueing of data in any way. The reason |
2993 | C<ev_async> does not support queueing of data in any way. The reason |
2749 | is that the author does not know of a simple (or any) algorithm for a |
2994 | is that the author does not know of a simple (or any) algorithm for a |
2750 | multiple-writer-single-reader queue that works in all cases and doesn't |
2995 | multiple-writer-single-reader queue that works in all cases and doesn't |
2751 | need elaborate support such as pthreads. |
2996 | need elaborate support such as pthreads or unportable memory access |
|
|
2997 | semantics. |
2752 | |
2998 | |
2753 | That means that if you want to queue data, you have to provide your own |
2999 | That means that if you want to queue data, you have to provide your own |
2754 | queue. But at least I can tell you how to implement locking around your |
3000 | queue. But at least I can tell you how to implement locking around your |
2755 | queue: |
3001 | queue: |
2756 | |
3002 | |
… | |
… | |
2914 | /* doh, nothing entered */; |
3160 | /* doh, nothing entered */; |
2915 | } |
3161 | } |
2916 | |
3162 | |
2917 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3163 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2918 | |
3164 | |
2919 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
|
|
2920 | |
|
|
2921 | Feeds the given event set into the event loop, as if the specified event |
|
|
2922 | had happened for the specified watcher (which must be a pointer to an |
|
|
2923 | initialised but not necessarily started event watcher). |
|
|
2924 | |
|
|
2925 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
3165 | =item ev_feed_fd_event (loop, int fd, int revents) |
2926 | |
3166 | |
2927 | Feed an event on the given fd, as if a file descriptor backend detected |
3167 | Feed an event on the given fd, as if a file descriptor backend detected |
2928 | the given events it. |
3168 | the given events it. |
2929 | |
3169 | |
2930 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
3170 | =item ev_feed_signal_event (loop, int signum) |
2931 | |
3171 | |
2932 | Feed an event as if the given signal occurred (C<loop> must be the default |
3172 | Feed an event as if the given signal occurred (C<loop> must be the default |
2933 | loop!). |
3173 | loop!). |
2934 | |
3174 | |
2935 | =back |
3175 | =back |
… | |
… | |
3015 | |
3255 | |
3016 | =over 4 |
3256 | =over 4 |
3017 | |
3257 | |
3018 | =item ev::TYPE::TYPE () |
3258 | =item ev::TYPE::TYPE () |
3019 | |
3259 | |
3020 | =item ev::TYPE::TYPE (struct ev_loop *) |
3260 | =item ev::TYPE::TYPE (loop) |
3021 | |
3261 | |
3022 | =item ev::TYPE::~TYPE |
3262 | =item ev::TYPE::~TYPE |
3023 | |
3263 | |
3024 | The constructor (optionally) takes an event loop to associate the watcher |
3264 | The constructor (optionally) takes an event loop to associate the watcher |
3025 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3265 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
3102 | Example: Use a plain function as callback. |
3342 | Example: Use a plain function as callback. |
3103 | |
3343 | |
3104 | static void io_cb (ev::io &w, int revents) { } |
3344 | static void io_cb (ev::io &w, int revents) { } |
3105 | iow.set <io_cb> (); |
3345 | iow.set <io_cb> (); |
3106 | |
3346 | |
3107 | =item w->set (struct ev_loop *) |
3347 | =item w->set (loop) |
3108 | |
3348 | |
3109 | Associates a different C<struct ev_loop> with this watcher. You can only |
3349 | Associates a different C<struct ev_loop> with this watcher. You can only |
3110 | do this when the watcher is inactive (and not pending either). |
3350 | do this when the watcher is inactive (and not pending either). |
3111 | |
3351 | |
3112 | =item w->set ([arguments]) |
3352 | =item w->set ([arguments]) |
… | |
… | |
3209 | =item Ocaml |
3449 | =item Ocaml |
3210 | |
3450 | |
3211 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3451 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3212 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3452 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3213 | |
3453 | |
|
|
3454 | =item Lua |
|
|
3455 | |
|
|
3456 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
3457 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
3458 | L<http://github.com/brimworks/lua-ev>. |
|
|
3459 | |
3214 | =back |
3460 | =back |
3215 | |
3461 | |
3216 | |
3462 | |
3217 | =head1 MACRO MAGIC |
3463 | =head1 MACRO MAGIC |
3218 | |
3464 | |
… | |
… | |
3384 | keeps libev from including F<config.h>, and it also defines dummy |
3630 | keeps libev from including F<config.h>, and it also defines dummy |
3385 | implementations for some libevent functions (such as logging, which is not |
3631 | implementations for some libevent functions (such as logging, which is not |
3386 | supported). It will also not define any of the structs usually found in |
3632 | supported). It will also not define any of the structs usually found in |
3387 | F<event.h> that are not directly supported by the libev core alone. |
3633 | F<event.h> that are not directly supported by the libev core alone. |
3388 | |
3634 | |
3389 | In stanbdalone mode, libev will still try to automatically deduce the |
3635 | In standalone mode, libev will still try to automatically deduce the |
3390 | configuration, but has to be more conservative. |
3636 | configuration, but has to be more conservative. |
3391 | |
3637 | |
3392 | =item EV_USE_MONOTONIC |
3638 | =item EV_USE_MONOTONIC |
3393 | |
3639 | |
3394 | If defined to be C<1>, libev will try to detect the availability of the |
3640 | If defined to be C<1>, libev will try to detect the availability of the |
… | |
… | |
3459 | be used is the winsock select). This means that it will call |
3705 | be used is the winsock select). This means that it will call |
3460 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3706 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3461 | it is assumed that all these functions actually work on fds, even |
3707 | it is assumed that all these functions actually work on fds, even |
3462 | on win32. Should not be defined on non-win32 platforms. |
3708 | on win32. Should not be defined on non-win32 platforms. |
3463 | |
3709 | |
3464 | =item EV_FD_TO_WIN32_HANDLE |
3710 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3465 | |
3711 | |
3466 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3712 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3467 | file descriptors to socket handles. When not defining this symbol (the |
3713 | file descriptors to socket handles. When not defining this symbol (the |
3468 | default), then libev will call C<_get_osfhandle>, which is usually |
3714 | default), then libev will call C<_get_osfhandle>, which is usually |
3469 | correct. In some cases, programs use their own file descriptor management, |
3715 | correct. In some cases, programs use their own file descriptor management, |
3470 | in which case they can provide this function to map fds to socket handles. |
3716 | in which case they can provide this function to map fds to socket handles. |
|
|
3717 | |
|
|
3718 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3719 | |
|
|
3720 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3721 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3722 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3723 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3724 | |
|
|
3725 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3726 | |
|
|
3727 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3728 | macro can be used to override the C<close> function, useful to unregister |
|
|
3729 | file descriptors again. Note that the replacement function has to close |
|
|
3730 | the underlying OS handle. |
3471 | |
3731 | |
3472 | =item EV_USE_POLL |
3732 | =item EV_USE_POLL |
3473 | |
3733 | |
3474 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3734 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3475 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3735 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3607 | defined to be C<0>, then they are not. |
3867 | defined to be C<0>, then they are not. |
3608 | |
3868 | |
3609 | =item EV_MINIMAL |
3869 | =item EV_MINIMAL |
3610 | |
3870 | |
3611 | If you need to shave off some kilobytes of code at the expense of some |
3871 | If you need to shave off some kilobytes of code at the expense of some |
3612 | speed, define this symbol to C<1>. Currently this is used to override some |
3872 | speed (but with the full API), define this symbol to C<1>. Currently this |
3613 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3873 | is used to override some inlining decisions, saves roughly 30% code size |
3614 | much smaller 2-heap for timer management over the default 4-heap. |
3874 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3875 | the default 4-heap. |
|
|
3876 | |
|
|
3877 | You can save even more by disabling watcher types you do not need |
|
|
3878 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3879 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3880 | |
|
|
3881 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3882 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3883 | of the API are still available, and do not complain if this subset changes |
|
|
3884 | over time. |
|
|
3885 | |
|
|
3886 | =item EV_NSIG |
|
|
3887 | |
|
|
3888 | The highest supported signal number, +1 (or, the number of |
|
|
3889 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
3890 | automatically, but sometimes this fails, in which case it can be |
|
|
3891 | specified. Also, using a lower number than detected (C<32> should be |
|
|
3892 | good for about any system in existance) can save some memory, as libev |
|
|
3893 | statically allocates some 12-24 bytes per signal number. |
3615 | |
3894 | |
3616 | =item EV_PID_HASHSIZE |
3895 | =item EV_PID_HASHSIZE |
3617 | |
3896 | |
3618 | C<ev_child> watchers use a small hash table to distribute workload by |
3897 | C<ev_child> watchers use a small hash table to distribute workload by |
3619 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3898 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3805 | default loop and triggering an C<ev_async> watcher from the default loop |
4084 | default loop and triggering an C<ev_async> watcher from the default loop |
3806 | watcher callback into the event loop interested in the signal. |
4085 | watcher callback into the event loop interested in the signal. |
3807 | |
4086 | |
3808 | =back |
4087 | =back |
3809 | |
4088 | |
|
|
4089 | =head4 THREAD LOCKING EXAMPLE |
|
|
4090 | |
|
|
4091 | Here is a fictitious example of how to run an event loop in a different |
|
|
4092 | thread than where callbacks are being invoked and watchers are |
|
|
4093 | created/added/removed. |
|
|
4094 | |
|
|
4095 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4096 | which uses exactly this technique (which is suited for many high-level |
|
|
4097 | languages). |
|
|
4098 | |
|
|
4099 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4100 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4101 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4102 | |
|
|
4103 | First, you need to associate some data with the event loop: |
|
|
4104 | |
|
|
4105 | typedef struct { |
|
|
4106 | mutex_t lock; /* global loop lock */ |
|
|
4107 | ev_async async_w; |
|
|
4108 | thread_t tid; |
|
|
4109 | cond_t invoke_cv; |
|
|
4110 | } userdata; |
|
|
4111 | |
|
|
4112 | void prepare_loop (EV_P) |
|
|
4113 | { |
|
|
4114 | // for simplicity, we use a static userdata struct. |
|
|
4115 | static userdata u; |
|
|
4116 | |
|
|
4117 | ev_async_init (&u->async_w, async_cb); |
|
|
4118 | ev_async_start (EV_A_ &u->async_w); |
|
|
4119 | |
|
|
4120 | pthread_mutex_init (&u->lock, 0); |
|
|
4121 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4122 | |
|
|
4123 | // now associate this with the loop |
|
|
4124 | ev_set_userdata (EV_A_ u); |
|
|
4125 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4126 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4127 | |
|
|
4128 | // then create the thread running ev_loop |
|
|
4129 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4130 | } |
|
|
4131 | |
|
|
4132 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4133 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4134 | that might have been added: |
|
|
4135 | |
|
|
4136 | static void |
|
|
4137 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4138 | { |
|
|
4139 | // just used for the side effects |
|
|
4140 | } |
|
|
4141 | |
|
|
4142 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4143 | protecting the loop data, respectively. |
|
|
4144 | |
|
|
4145 | static void |
|
|
4146 | l_release (EV_P) |
|
|
4147 | { |
|
|
4148 | userdata *u = ev_userdata (EV_A); |
|
|
4149 | pthread_mutex_unlock (&u->lock); |
|
|
4150 | } |
|
|
4151 | |
|
|
4152 | static void |
|
|
4153 | l_acquire (EV_P) |
|
|
4154 | { |
|
|
4155 | userdata *u = ev_userdata (EV_A); |
|
|
4156 | pthread_mutex_lock (&u->lock); |
|
|
4157 | } |
|
|
4158 | |
|
|
4159 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4160 | into C<ev_loop>: |
|
|
4161 | |
|
|
4162 | void * |
|
|
4163 | l_run (void *thr_arg) |
|
|
4164 | { |
|
|
4165 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4166 | |
|
|
4167 | l_acquire (EV_A); |
|
|
4168 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4169 | ev_loop (EV_A_ 0); |
|
|
4170 | l_release (EV_A); |
|
|
4171 | |
|
|
4172 | return 0; |
|
|
4173 | } |
|
|
4174 | |
|
|
4175 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4176 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4177 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4178 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4179 | and b) skipping inter-thread-communication when there are no pending |
|
|
4180 | watchers is very beneficial): |
|
|
4181 | |
|
|
4182 | static void |
|
|
4183 | l_invoke (EV_P) |
|
|
4184 | { |
|
|
4185 | userdata *u = ev_userdata (EV_A); |
|
|
4186 | |
|
|
4187 | while (ev_pending_count (EV_A)) |
|
|
4188 | { |
|
|
4189 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4190 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4191 | } |
|
|
4192 | } |
|
|
4193 | |
|
|
4194 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4195 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4196 | thread to continue: |
|
|
4197 | |
|
|
4198 | static void |
|
|
4199 | real_invoke_pending (EV_P) |
|
|
4200 | { |
|
|
4201 | userdata *u = ev_userdata (EV_A); |
|
|
4202 | |
|
|
4203 | pthread_mutex_lock (&u->lock); |
|
|
4204 | ev_invoke_pending (EV_A); |
|
|
4205 | pthread_cond_signal (&u->invoke_cv); |
|
|
4206 | pthread_mutex_unlock (&u->lock); |
|
|
4207 | } |
|
|
4208 | |
|
|
4209 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4210 | event loop, you will now have to lock: |
|
|
4211 | |
|
|
4212 | ev_timer timeout_watcher; |
|
|
4213 | userdata *u = ev_userdata (EV_A); |
|
|
4214 | |
|
|
4215 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4216 | |
|
|
4217 | pthread_mutex_lock (&u->lock); |
|
|
4218 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4219 | ev_async_send (EV_A_ &u->async_w); |
|
|
4220 | pthread_mutex_unlock (&u->lock); |
|
|
4221 | |
|
|
4222 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4223 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4224 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4225 | watchers in the next event loop iteration. |
|
|
4226 | |
3810 | =head3 COROUTINES |
4227 | =head3 COROUTINES |
3811 | |
4228 | |
3812 | Libev is very accommodating to coroutines ("cooperative threads"): |
4229 | Libev is very accommodating to coroutines ("cooperative threads"): |
3813 | libev fully supports nesting calls to its functions from different |
4230 | libev fully supports nesting calls to its functions from different |
3814 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4231 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3815 | different coroutines, and switch freely between both coroutines running the |
4232 | different coroutines, and switch freely between both coroutines running |
3816 | loop, as long as you don't confuse yourself). The only exception is that |
4233 | the loop, as long as you don't confuse yourself). The only exception is |
3817 | you must not do this from C<ev_periodic> reschedule callbacks. |
4234 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3818 | |
4235 | |
3819 | Care has been taken to ensure that libev does not keep local state inside |
4236 | Care has been taken to ensure that libev does not keep local state inside |
3820 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4237 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3821 | they do not call any callbacks. |
4238 | they do not call any callbacks. |
3822 | |
4239 | |
… | |
… | |
3899 | way (note also that glib is the slowest event library known to man). |
4316 | way (note also that glib is the slowest event library known to man). |
3900 | |
4317 | |
3901 | There is no supported compilation method available on windows except |
4318 | There is no supported compilation method available on windows except |
3902 | embedding it into other applications. |
4319 | embedding it into other applications. |
3903 | |
4320 | |
|
|
4321 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4322 | tries its best, but under most conditions, signals will simply not work. |
|
|
4323 | |
3904 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4324 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3905 | accept large writes: instead of resulting in a partial write, windows will |
4325 | accept large writes: instead of resulting in a partial write, windows will |
3906 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4326 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3907 | so make sure you only write small amounts into your sockets (less than a |
4327 | so make sure you only write small amounts into your sockets (less than a |
3908 | megabyte seems safe, but this apparently depends on the amount of memory |
4328 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3912 | the abysmal performance of winsockets, using a large number of sockets |
4332 | the abysmal performance of winsockets, using a large number of sockets |
3913 | is not recommended (and not reasonable). If your program needs to use |
4333 | is not recommended (and not reasonable). If your program needs to use |
3914 | more than a hundred or so sockets, then likely it needs to use a totally |
4334 | more than a hundred or so sockets, then likely it needs to use a totally |
3915 | different implementation for windows, as libev offers the POSIX readiness |
4335 | different implementation for windows, as libev offers the POSIX readiness |
3916 | notification model, which cannot be implemented efficiently on windows |
4336 | notification model, which cannot be implemented efficiently on windows |
3917 | (Microsoft monopoly games). |
4337 | (due to Microsoft monopoly games). |
3918 | |
4338 | |
3919 | A typical way to use libev under windows is to embed it (see the embedding |
4339 | A typical way to use libev under windows is to embed it (see the embedding |
3920 | section for details) and use the following F<evwrap.h> header file instead |
4340 | section for details) and use the following F<evwrap.h> header file instead |
3921 | of F<ev.h>: |
4341 | of F<ev.h>: |
3922 | |
4342 | |
… | |
… | |
3958 | |
4378 | |
3959 | Early versions of winsocket's select only supported waiting for a maximum |
4379 | Early versions of winsocket's select only supported waiting for a maximum |
3960 | of C<64> handles (probably owning to the fact that all windows kernels |
4380 | of C<64> handles (probably owning to the fact that all windows kernels |
3961 | can only wait for C<64> things at the same time internally; Microsoft |
4381 | can only wait for C<64> things at the same time internally; Microsoft |
3962 | recommends spawning a chain of threads and wait for 63 handles and the |
4382 | recommends spawning a chain of threads and wait for 63 handles and the |
3963 | previous thread in each. Great). |
4383 | previous thread in each. Sounds great!). |
3964 | |
4384 | |
3965 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4385 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3966 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4386 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3967 | call (which might be in libev or elsewhere, for example, perl does its own |
4387 | call (which might be in libev or elsewhere, for example, perl and many |
3968 | select emulation on windows). |
4388 | other interpreters do their own select emulation on windows). |
3969 | |
4389 | |
3970 | Another limit is the number of file descriptors in the Microsoft runtime |
4390 | Another limit is the number of file descriptors in the Microsoft runtime |
3971 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4391 | libraries, which by default is C<64> (there must be a hidden I<64> |
3972 | or something like this inside Microsoft). You can increase this by calling |
4392 | fetish or something like this inside Microsoft). You can increase this |
3973 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4393 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3974 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4394 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3975 | libraries. |
|
|
3976 | |
|
|
3977 | This might get you to about C<512> or C<2048> sockets (depending on |
4395 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3978 | windows version and/or the phase of the moon). To get more, you need to |
4396 | (depending on windows version and/or the phase of the moon). To get more, |
3979 | wrap all I/O functions and provide your own fd management, but the cost of |
4397 | you need to wrap all I/O functions and provide your own fd management, but |
3980 | calling select (O(n²)) will likely make this unworkable. |
4398 | the cost of calling select (O(n²)) will likely make this unworkable. |
3981 | |
4399 | |
3982 | =back |
4400 | =back |
3983 | |
4401 | |
3984 | =head2 PORTABILITY REQUIREMENTS |
4402 | =head2 PORTABILITY REQUIREMENTS |
3985 | |
4403 | |
… | |
… | |
4028 | =item C<double> must hold a time value in seconds with enough accuracy |
4446 | =item C<double> must hold a time value in seconds with enough accuracy |
4029 | |
4447 | |
4030 | The type C<double> is used to represent timestamps. It is required to |
4448 | The type C<double> is used to represent timestamps. It is required to |
4031 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4449 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4032 | enough for at least into the year 4000. This requirement is fulfilled by |
4450 | enough for at least into the year 4000. This requirement is fulfilled by |
4033 | implementations implementing IEEE 754 (basically all existing ones). |
4451 | implementations implementing IEEE 754, which is basically all existing |
|
|
4452 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4453 | 2200. |
4034 | |
4454 | |
4035 | =back |
4455 | =back |
4036 | |
4456 | |
4037 | If you know of other additional requirements drop me a note. |
4457 | If you know of other additional requirements drop me a note. |
4038 | |
4458 | |