… | |
… | |
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 |
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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 the |
128 | Libev represents time as a single floating point number, representing |
128 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
129 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
129 | the beginning of 1970, details are complicated, don't ask). This type is |
130 | near the beginning of 1970, details are complicated, don't ask). This |
130 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
131 | type is called C<ev_tstamp>, which is what you should use too. It usually |
131 | to the C<double> type in C, and when you need to do any calculations on |
132 | aliases to the C<double> type in C. When you need to do any calculations |
132 | it, you should treat it as some floating point value. Unlike the name |
133 | on it, you should treat it as some floating point value. Unlike the name |
133 | component C<stamp> might indicate, it is also used for time differences |
134 | component C<stamp> might indicate, it is also used for time differences |
134 | throughout libev. |
135 | throughout libev. |
135 | |
136 | |
136 | =head1 ERROR HANDLING |
137 | =head1 ERROR HANDLING |
137 | |
138 | |
… | |
… | |
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 |
|
|
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 |
|
|
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 |
… | |
… | |
1407 | |
1538 | |
1408 | So when you encounter spurious, unexplained daemon exits, make sure you |
1539 | So when you encounter spurious, unexplained daemon exits, make sure you |
1409 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1540 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1410 | somewhere, as that would have given you a big clue). |
1541 | somewhere, as that would have given you a big clue). |
1411 | |
1542 | |
|
|
1543 | =head3 The special problem of accept()ing when you can't |
|
|
1544 | |
|
|
1545 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1546 | found in port-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1547 | connection from the pending queue in all error cases. |
|
|
1548 | |
|
|
1549 | For example, larger servers often run out of file descriptors (because |
|
|
1550 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1551 | rejecting the connection, leading to libev signalling readiness on |
|
|
1552 | the next iteration again (the connection still exists after all), and |
|
|
1553 | typically causing the program to loop at 100% CPU usage. |
|
|
1554 | |
|
|
1555 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1556 | operating systems, there is usually little the app can do to remedy the |
|
|
1557 | situation, and no known thread-safe method of removing the connection to |
|
|
1558 | cope with overload is known (to me). |
|
|
1559 | |
|
|
1560 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1561 | - when the program encounters an overload, it will just loop until the |
|
|
1562 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1563 | event-based way to handle this situation, so it's the best one can do. |
|
|
1564 | |
|
|
1565 | A better way to handle the situation is to log any errors other than |
|
|
1566 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1567 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1568 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1569 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1570 | usage. |
|
|
1571 | |
|
|
1572 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1573 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1574 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1575 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1576 | clients under typical overload conditions. |
|
|
1577 | |
|
|
1578 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1579 | is often done with C<malloc> failures, but this results in an easy |
|
|
1580 | opportunity for a DoS attack. |
1412 | |
1581 | |
1413 | =head3 Watcher-Specific Functions |
1582 | =head3 Watcher-Specific Functions |
1414 | |
1583 | |
1415 | =over 4 |
1584 | =over 4 |
1416 | |
1585 | |
… | |
… | |
1463 | year, it will still time out after (roughly) one hour. "Roughly" because |
1632 | year, it will still time out after (roughly) one hour. "Roughly" because |
1464 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1633 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1465 | monotonic clock option helps a lot here). |
1634 | monotonic clock option helps a lot here). |
1466 | |
1635 | |
1467 | The callback is guaranteed to be invoked only I<after> its timeout has |
1636 | 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 |
1637 | 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 |
1638 | 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 |
1639 | same loop iteration then the ones with earlier time-out values are invoked |
1471 | C<ev_loop> recursively). |
1640 | before ones of the same priority with later time-out values (but this is |
|
|
1641 | no longer true when a callback calls C<ev_loop> recursively). |
1472 | |
1642 | |
1473 | =head3 Be smart about timeouts |
1643 | =head3 Be smart about timeouts |
1474 | |
1644 | |
1475 | Many real-world problems involve some kind of timeout, usually for error |
1645 | 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, |
1646 | 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> |
1690 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1521 | member and C<ev_timer_again>. |
1691 | member and C<ev_timer_again>. |
1522 | |
1692 | |
1523 | At start: |
1693 | At start: |
1524 | |
1694 | |
1525 | ev_timer_init (timer, callback); |
1695 | ev_init (timer, callback); |
1526 | timer->repeat = 60.; |
1696 | timer->repeat = 60.; |
1527 | ev_timer_again (loop, timer); |
1697 | ev_timer_again (loop, timer); |
1528 | |
1698 | |
1529 | Each time there is some activity: |
1699 | Each time there is some activity: |
1530 | |
1700 | |
… | |
… | |
1592 | |
1762 | |
1593 | To start the timer, simply initialise the watcher and set C<last_activity> |
1763 | 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 |
1764 | 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: |
1765 | callback, which will "do the right thing" and start the timer: |
1596 | |
1766 | |
1597 | ev_timer_init (timer, callback); |
1767 | ev_init (timer, callback); |
1598 | last_activity = ev_now (loop); |
1768 | last_activity = ev_now (loop); |
1599 | callback (loop, timer, EV_TIMEOUT); |
1769 | callback (loop, timer, EV_TIMEOUT); |
1600 | |
1770 | |
1601 | And when there is some activity, simply store the current time in |
1771 | And when there is some activity, simply store the current time in |
1602 | C<last_activity>, no libev calls at all: |
1772 | C<last_activity>, no libev calls at all: |
… | |
… | |
1663 | |
1833 | |
1664 | If the event loop is suspended for a long time, you can also force an |
1834 | 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 |
1835 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1666 | ()>. |
1836 | ()>. |
1667 | |
1837 | |
|
|
1838 | =head3 The special problems of suspended animation |
|
|
1839 | |
|
|
1840 | When you leave the server world it is quite customary to hit machines that |
|
|
1841 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1842 | |
|
|
1843 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1844 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1845 | to run until the system is suspended, but they will not advance while the |
|
|
1846 | system is suspended. That means, on resume, it will be as if the program |
|
|
1847 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1848 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1849 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1850 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1851 | be adjusted accordingly. |
|
|
1852 | |
|
|
1853 | I would not be surprised to see different behaviour in different between |
|
|
1854 | operating systems, OS versions or even different hardware. |
|
|
1855 | |
|
|
1856 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1857 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1858 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1859 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1860 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1861 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1862 | |
|
|
1863 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1864 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1865 | deterministic behaviour in this case (you can do nothing against |
|
|
1866 | C<SIGSTOP>). |
|
|
1867 | |
1668 | =head3 Watcher-Specific Functions and Data Members |
1868 | =head3 Watcher-Specific Functions and Data Members |
1669 | |
1869 | |
1670 | =over 4 |
1870 | =over 4 |
1671 | |
1871 | |
1672 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1872 | =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 |
1897 | 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. |
1898 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1699 | |
1899 | |
1700 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1900 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1701 | usage example. |
1901 | usage example. |
|
|
1902 | |
|
|
1903 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
|
|
1904 | |
|
|
1905 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
1906 | then this time is relative to the current event loop time, otherwise it's |
|
|
1907 | the timeout value currently configured. |
|
|
1908 | |
|
|
1909 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
1910 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
1911 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1912 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1913 | too), and so on. |
1702 | |
1914 | |
1703 | =item ev_tstamp repeat [read-write] |
1915 | =item ev_tstamp repeat [read-write] |
1704 | |
1916 | |
1705 | The current C<repeat> value. Will be used each time the watcher times out |
1917 | 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), |
1918 | 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 |
2154 | 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 |
2155 | 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 |
2156 | will try it's best to deliver signals synchronously, i.e. as part of the |
1945 | normal event processing, like any other event. |
2157 | normal event processing, like any other event. |
1946 | |
2158 | |
1947 | If you want signals asynchronously, just use C<sigaction> as you would |
2159 | 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 |
2160 | 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. |
2161 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2162 | synchronously wake up an event loop. |
1950 | |
2163 | |
1951 | You can configure as many watchers as you like per signal. Only when the |
2164 | You can configure as many watchers as you like for the same signal, but |
|
|
2165 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2166 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2167 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2168 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2169 | |
1952 | first watcher gets started will libev actually register a signal handler |
2170 | 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 |
2171 | 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 |
2172 | 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 | |
2173 | |
1958 | If possible and supported, libev will install its handlers with |
2174 | If possible and supported, libev will install its handlers with |
1959 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2175 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1960 | interrupted. If you have a problem with system calls getting interrupted by |
2176 | 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 |
2177 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1962 | them in an C<ev_prepare> watcher. |
2178 | and unblock them in an C<ev_prepare> watcher. |
|
|
2179 | |
|
|
2180 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2181 | |
|
|
2182 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2183 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2184 | stopping it again), that is, libev might or might not block the signal, |
|
|
2185 | and might or might not set or restore the installed signal handler. |
|
|
2186 | |
|
|
2187 | While this does not matter for the signal disposition (libev never |
|
|
2188 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2189 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2190 | certain signals to be blocked. |
|
|
2191 | |
|
|
2192 | This means that before calling C<exec> (from the child) you should reset |
|
|
2193 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2194 | choice usually). |
|
|
2195 | |
|
|
2196 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2197 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2198 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2199 | |
|
|
2200 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2201 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2202 | the window of opportunity for problems, it will not go away, as libev |
|
|
2203 | I<has> to modify the signal mask, at least temporarily. |
|
|
2204 | |
|
|
2205 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2206 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2207 | is not a libev-specific thing, this is true for most event libraries. |
1963 | |
2208 | |
1964 | =head3 Watcher-Specific Functions and Data Members |
2209 | =head3 Watcher-Specific Functions and Data Members |
1965 | |
2210 | |
1966 | =over 4 |
2211 | =over 4 |
1967 | |
2212 | |
… | |
… | |
1999 | some child status changes (most typically when a child of yours dies or |
2244 | 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 |
2245 | 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 |
2246 | 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., |
2247 | 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, |
2248 | 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 |
2249 | but forking and registering a watcher a few event loop iterations later or |
2005 | not. |
2250 | in the next callback invocation is not. |
2006 | |
2251 | |
2007 | Only the default event loop is capable of handling signals, and therefore |
2252 | Only the default event loop is capable of handling signals, and therefore |
2008 | you can only register child watchers in the default event loop. |
2253 | you can only register child watchers in the default event loop. |
2009 | |
2254 | |
|
|
2255 | Due to some design glitches inside libev, child watchers will always be |
|
|
2256 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2257 | libev) |
|
|
2258 | |
2010 | =head3 Process Interaction |
2259 | =head3 Process Interaction |
2011 | |
2260 | |
2012 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2261 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2013 | initialised. This is necessary to guarantee proper behaviour even if |
2262 | initialised. This is necessary to guarantee proper behaviour even if the |
2014 | the first child watcher is started after the child exits. The occurrence |
2263 | first child watcher is started after the child exits. The occurrence |
2015 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2264 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2016 | synchronously as part of the event loop processing. Libev always reaps all |
2265 | synchronously as part of the event loop processing. Libev always reaps all |
2017 | children, even ones not watched. |
2266 | children, even ones not watched. |
2018 | |
2267 | |
2019 | =head3 Overriding the Built-In Processing |
2268 | =head3 Overriding the Built-In Processing |
… | |
… | |
2029 | =head3 Stopping the Child Watcher |
2278 | =head3 Stopping the Child Watcher |
2030 | |
2279 | |
2031 | Currently, the child watcher never gets stopped, even when the |
2280 | Currently, the child watcher never gets stopped, even when the |
2032 | child terminates, so normally one needs to stop the watcher in the |
2281 | child terminates, so normally one needs to stop the watcher in the |
2033 | callback. Future versions of libev might stop the watcher automatically |
2282 | callback. Future versions of libev might stop the watcher automatically |
2034 | when a child exit is detected. |
2283 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2284 | problem). |
2035 | |
2285 | |
2036 | =head3 Watcher-Specific Functions and Data Members |
2286 | =head3 Watcher-Specific Functions and Data Members |
2037 | |
2287 | |
2038 | =over 4 |
2288 | =over 4 |
2039 | |
2289 | |
… | |
… | |
2365 | // no longer anything immediate to do. |
2615 | // no longer anything immediate to do. |
2366 | } |
2616 | } |
2367 | |
2617 | |
2368 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2618 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2369 | ev_idle_init (idle_watcher, idle_cb); |
2619 | ev_idle_init (idle_watcher, idle_cb); |
2370 | ev_idle_start (loop, idle_cb); |
2620 | ev_idle_start (loop, idle_watcher); |
2371 | |
2621 | |
2372 | |
2622 | |
2373 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2623 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2374 | |
2624 | |
2375 | Prepare and check watchers are usually (but not always) used in pairs: |
2625 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2468 | struct pollfd fds [nfd]; |
2718 | struct pollfd fds [nfd]; |
2469 | // actual code will need to loop here and realloc etc. |
2719 | // actual code will need to loop here and realloc etc. |
2470 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2720 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2471 | |
2721 | |
2472 | /* the callback is illegal, but won't be called as we stop during check */ |
2722 | /* the callback is illegal, but won't be called as we stop during check */ |
2473 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2723 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2474 | ev_timer_start (loop, &tw); |
2724 | ev_timer_start (loop, &tw); |
2475 | |
2725 | |
2476 | // create one ev_io per pollfd |
2726 | // create one ev_io per pollfd |
2477 | for (int i = 0; i < nfd; ++i) |
2727 | for (int i = 0; i < nfd; ++i) |
2478 | { |
2728 | { |
… | |
… | |
2708 | event loop blocks next and before C<ev_check> watchers are being called, |
2958 | 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 |
2959 | 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 |
2960 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2711 | handlers will be invoked, too, of course. |
2961 | handlers will be invoked, too, of course. |
2712 | |
2962 | |
|
|
2963 | =head3 The special problem of life after fork - how is it possible? |
|
|
2964 | |
|
|
2965 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2966 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2967 | sequence should be handled by libev without any problems. |
|
|
2968 | |
|
|
2969 | This changes when the application actually wants to do event handling |
|
|
2970 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2971 | fork. |
|
|
2972 | |
|
|
2973 | The default mode of operation (for libev, with application help to detect |
|
|
2974 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2975 | when I<either> the parent I<or> the child process continues. |
|
|
2976 | |
|
|
2977 | When both processes want to continue using libev, then this is usually the |
|
|
2978 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2979 | supposed to continue with all watchers in place as before, while the other |
|
|
2980 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2981 | |
|
|
2982 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2983 | simply create a new event loop, which of course will be "empty", and |
|
|
2984 | use that for new watchers. This has the advantage of not touching more |
|
|
2985 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2986 | disadvantage of having to use multiple event loops (which do not support |
|
|
2987 | signal watchers). |
|
|
2988 | |
|
|
2989 | When this is not possible, or you want to use the default loop for |
|
|
2990 | other reasons, then in the process that wants to start "fresh", call |
|
|
2991 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2992 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2993 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2994 | also that in that case, you have to re-register any signal watchers. |
|
|
2995 | |
2713 | =head3 Watcher-Specific Functions and Data Members |
2996 | =head3 Watcher-Specific Functions and Data Members |
2714 | |
2997 | |
2715 | =over 4 |
2998 | =over 4 |
2716 | |
2999 | |
2717 | =item ev_fork_init (ev_signal *, callback) |
3000 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2746 | =head3 Queueing |
3029 | =head3 Queueing |
2747 | |
3030 | |
2748 | C<ev_async> does not support queueing of data in any way. The reason |
3031 | 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 |
3032 | 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 |
3033 | multiple-writer-single-reader queue that works in all cases and doesn't |
2751 | need elaborate support such as pthreads. |
3034 | need elaborate support such as pthreads or unportable memory access |
|
|
3035 | semantics. |
2752 | |
3036 | |
2753 | That means that if you want to queue data, you have to provide your own |
3037 | 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 |
3038 | queue. But at least I can tell you how to implement locking around your |
2755 | queue: |
3039 | queue: |
2756 | |
3040 | |
… | |
… | |
2914 | /* doh, nothing entered */; |
3198 | /* doh, nothing entered */; |
2915 | } |
3199 | } |
2916 | |
3200 | |
2917 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3201 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2918 | |
3202 | |
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) |
3203 | =item ev_feed_fd_event (loop, int fd, int revents) |
2926 | |
3204 | |
2927 | Feed an event on the given fd, as if a file descriptor backend detected |
3205 | Feed an event on the given fd, as if a file descriptor backend detected |
2928 | the given events it. |
3206 | the given events it. |
2929 | |
3207 | |
2930 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
3208 | =item ev_feed_signal_event (loop, int signum) |
2931 | |
3209 | |
2932 | Feed an event as if the given signal occurred (C<loop> must be the default |
3210 | Feed an event as if the given signal occurred (C<loop> must be the default |
2933 | loop!). |
3211 | loop!). |
2934 | |
3212 | |
2935 | =back |
3213 | =back |
… | |
… | |
3015 | |
3293 | |
3016 | =over 4 |
3294 | =over 4 |
3017 | |
3295 | |
3018 | =item ev::TYPE::TYPE () |
3296 | =item ev::TYPE::TYPE () |
3019 | |
3297 | |
3020 | =item ev::TYPE::TYPE (struct ev_loop *) |
3298 | =item ev::TYPE::TYPE (loop) |
3021 | |
3299 | |
3022 | =item ev::TYPE::~TYPE |
3300 | =item ev::TYPE::~TYPE |
3023 | |
3301 | |
3024 | The constructor (optionally) takes an event loop to associate the watcher |
3302 | The constructor (optionally) takes an event loop to associate the watcher |
3025 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3303 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
3102 | Example: Use a plain function as callback. |
3380 | Example: Use a plain function as callback. |
3103 | |
3381 | |
3104 | static void io_cb (ev::io &w, int revents) { } |
3382 | static void io_cb (ev::io &w, int revents) { } |
3105 | iow.set <io_cb> (); |
3383 | iow.set <io_cb> (); |
3106 | |
3384 | |
3107 | =item w->set (struct ev_loop *) |
3385 | =item w->set (loop) |
3108 | |
3386 | |
3109 | Associates a different C<struct ev_loop> with this watcher. You can only |
3387 | 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). |
3388 | do this when the watcher is inactive (and not pending either). |
3111 | |
3389 | |
3112 | =item w->set ([arguments]) |
3390 | =item w->set ([arguments]) |
… | |
… | |
3209 | =item Ocaml |
3487 | =item Ocaml |
3210 | |
3488 | |
3211 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3489 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3212 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3490 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3213 | |
3491 | |
|
|
3492 | =item Lua |
|
|
3493 | |
|
|
3494 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
3495 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
3496 | L<http://github.com/brimworks/lua-ev>. |
|
|
3497 | |
3214 | =back |
3498 | =back |
3215 | |
3499 | |
3216 | |
3500 | |
3217 | =head1 MACRO MAGIC |
3501 | =head1 MACRO MAGIC |
3218 | |
3502 | |
… | |
… | |
3371 | libev.m4 |
3655 | libev.m4 |
3372 | |
3656 | |
3373 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3657 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3374 | |
3658 | |
3375 | Libev can be configured via a variety of preprocessor symbols you have to |
3659 | Libev can be configured via a variety of preprocessor symbols you have to |
3376 | define before including any of its files. The default in the absence of |
3660 | define before including (or compiling) any of its files. The default in |
3377 | autoconf is documented for every option. |
3661 | the absence of autoconf is documented for every option. |
|
|
3662 | |
|
|
3663 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3664 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3665 | to redefine them before including F<ev.h> without breakign compatibility |
|
|
3666 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3667 | users of libev and the libev code itself must be compiled with compatible |
|
|
3668 | settings. |
3378 | |
3669 | |
3379 | =over 4 |
3670 | =over 4 |
3380 | |
3671 | |
3381 | =item EV_STANDALONE |
3672 | =item EV_STANDALONE (h) |
3382 | |
3673 | |
3383 | Must always be C<1> if you do not use autoconf configuration, which |
3674 | Must always be C<1> if you do not use autoconf configuration, which |
3384 | keeps libev from including F<config.h>, and it also defines dummy |
3675 | keeps libev from including F<config.h>, and it also defines dummy |
3385 | implementations for some libevent functions (such as logging, which is not |
3676 | 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 |
3677 | 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. |
3678 | F<event.h> that are not directly supported by the libev core alone. |
3388 | |
3679 | |
3389 | In stanbdalone mode, libev will still try to automatically deduce the |
3680 | In standalone mode, libev will still try to automatically deduce the |
3390 | configuration, but has to be more conservative. |
3681 | configuration, but has to be more conservative. |
3391 | |
3682 | |
3392 | =item EV_USE_MONOTONIC |
3683 | =item EV_USE_MONOTONIC |
3393 | |
3684 | |
3394 | If defined to be C<1>, libev will try to detect the availability of the |
3685 | 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 |
3750 | 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, |
3751 | 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 |
3752 | it is assumed that all these functions actually work on fds, even |
3462 | on win32. Should not be defined on non-win32 platforms. |
3753 | on win32. Should not be defined on non-win32 platforms. |
3463 | |
3754 | |
3464 | =item EV_FD_TO_WIN32_HANDLE |
3755 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3465 | |
3756 | |
3466 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3757 | 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 |
3758 | file descriptors to socket handles. When not defining this symbol (the |
3468 | default), then libev will call C<_get_osfhandle>, which is usually |
3759 | default), then libev will call C<_get_osfhandle>, which is usually |
3469 | correct. In some cases, programs use their own file descriptor management, |
3760 | 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. |
3761 | in which case they can provide this function to map fds to socket handles. |
|
|
3762 | |
|
|
3763 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3764 | |
|
|
3765 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3766 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3767 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3768 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3769 | |
|
|
3770 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3771 | |
|
|
3772 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3773 | macro can be used to override the C<close> function, useful to unregister |
|
|
3774 | file descriptors again. Note that the replacement function has to close |
|
|
3775 | the underlying OS handle. |
3471 | |
3776 | |
3472 | =item EV_USE_POLL |
3777 | =item EV_USE_POLL |
3473 | |
3778 | |
3474 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3779 | 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 |
3780 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3522 | as well as for signal and thread safety in C<ev_async> watchers. |
3827 | as well as for signal and thread safety in C<ev_async> watchers. |
3523 | |
3828 | |
3524 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3829 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3525 | (from F<signal.h>), which is usually good enough on most platforms. |
3830 | (from F<signal.h>), which is usually good enough on most platforms. |
3526 | |
3831 | |
3527 | =item EV_H |
3832 | =item EV_H (h) |
3528 | |
3833 | |
3529 | The name of the F<ev.h> header file used to include it. The default if |
3834 | The name of the F<ev.h> header file used to include it. The default if |
3530 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3835 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3531 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3836 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3532 | |
3837 | |
3533 | =item EV_CONFIG_H |
3838 | =item EV_CONFIG_H (h) |
3534 | |
3839 | |
3535 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3840 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3536 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3841 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3537 | C<EV_H>, above. |
3842 | C<EV_H>, above. |
3538 | |
3843 | |
3539 | =item EV_EVENT_H |
3844 | =item EV_EVENT_H (h) |
3540 | |
3845 | |
3541 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3846 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3542 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3847 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3543 | |
3848 | |
3544 | =item EV_PROTOTYPES |
3849 | =item EV_PROTOTYPES (h) |
3545 | |
3850 | |
3546 | If defined to be C<0>, then F<ev.h> will not define any function |
3851 | If defined to be C<0>, then F<ev.h> will not define any function |
3547 | prototypes, but still define all the structs and other symbols. This is |
3852 | prototypes, but still define all the structs and other symbols. This is |
3548 | occasionally useful if you want to provide your own wrapper functions |
3853 | occasionally useful if you want to provide your own wrapper functions |
3549 | around libev functions. |
3854 | around libev functions. |
… | |
… | |
3571 | fine. |
3876 | fine. |
3572 | |
3877 | |
3573 | If your embedding application does not need any priorities, defining these |
3878 | If your embedding application does not need any priorities, defining these |
3574 | both to C<0> will save some memory and CPU. |
3879 | both to C<0> will save some memory and CPU. |
3575 | |
3880 | |
3576 | =item EV_PERIODIC_ENABLE |
3881 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
3882 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
3883 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3577 | |
3884 | |
3578 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3885 | If undefined or defined to be C<1> (and the platform supports it), then |
3579 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3886 | the respective watcher type is supported. If defined to be C<0>, then it |
3580 | code. |
3887 | is not. Disabling watcher types mainly saves codesize. |
3581 | |
3888 | |
3582 | =item EV_IDLE_ENABLE |
3889 | =item EV_FEATURES |
3583 | |
|
|
3584 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3585 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3586 | code. |
|
|
3587 | |
|
|
3588 | =item EV_EMBED_ENABLE |
|
|
3589 | |
|
|
3590 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3591 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3592 | watcher types, which therefore must not be disabled. |
|
|
3593 | |
|
|
3594 | =item EV_STAT_ENABLE |
|
|
3595 | |
|
|
3596 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3597 | defined to be C<0>, then they are not. |
|
|
3598 | |
|
|
3599 | =item EV_FORK_ENABLE |
|
|
3600 | |
|
|
3601 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3602 | defined to be C<0>, then they are not. |
|
|
3603 | |
|
|
3604 | =item EV_ASYNC_ENABLE |
|
|
3605 | |
|
|
3606 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3607 | defined to be C<0>, then they are not. |
|
|
3608 | |
|
|
3609 | =item EV_MINIMAL |
|
|
3610 | |
3890 | |
3611 | If you need to shave off some kilobytes of code at the expense of some |
3891 | 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 |
3892 | speed (but with the full API), you can define this symbol to request |
3613 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3893 | certain subsets of functionality. The default is to enable all features |
3614 | much smaller 2-heap for timer management over the default 4-heap. |
3894 | that can be enabled on the platform. |
|
|
3895 | |
|
|
3896 | Note that using autoconf will usually override most of the features, so |
|
|
3897 | using this symbol makes sense mostly when embedding libev. |
|
|
3898 | |
|
|
3899 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
3900 | with some broad features you want) and then selectively re-enable |
|
|
3901 | additional parts you want, for example if you want everything minimal, |
|
|
3902 | but multiple event loop support, async and child watchers and the poll |
|
|
3903 | backend, use this: |
|
|
3904 | |
|
|
3905 | #define EV_FEATURES 0 |
|
|
3906 | #define EV_MULTIPLICITY 1 |
|
|
3907 | #define EV_USE_POLL 1 |
|
|
3908 | #define EV_CHILD_ENABLE 1 |
|
|
3909 | #define EV_ASYNC_ENABLE 1 |
|
|
3910 | |
|
|
3911 | The actual value is a bitset, it can be a combination of the following |
|
|
3912 | values: |
|
|
3913 | |
|
|
3914 | =over 4 |
|
|
3915 | |
|
|
3916 | =item C<1> - faster/larger code |
|
|
3917 | |
|
|
3918 | Use larger code to speed up some operations. |
|
|
3919 | |
|
|
3920 | Currently this is used to override some inlining decisions (enlarging the roughly |
|
|
3921 | 30% code size on amd64. |
|
|
3922 | |
|
|
3923 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
3924 | gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
3925 | assertions. |
|
|
3926 | |
|
|
3927 | =item C<2> - faster/larger data structures |
|
|
3928 | |
|
|
3929 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
3930 | hash table sizes and so on. This will usually further increase codesize |
|
|
3931 | and can additionally have an effect on the size of data structures at |
|
|
3932 | runtime. |
|
|
3933 | |
|
|
3934 | =item C<4> - full API configuration |
|
|
3935 | |
|
|
3936 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
3937 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
3938 | |
|
|
3939 | It also enables a lot of the "lesser used" core API functions. See C<ev.h> |
|
|
3940 | for details on which parts of the API are still available without this |
|
|
3941 | feature, and do not complain if this subset changes over time. |
|
|
3942 | |
|
|
3943 | =item C<8> - enable all optional watcher types |
|
|
3944 | |
|
|
3945 | Enables all optional watcher types. If you want to selectively enable |
|
|
3946 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
3947 | embed, async, child...) you can enable them manually by defining |
|
|
3948 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
3949 | |
|
|
3950 | =item C<16> - enable all backends |
|
|
3951 | |
|
|
3952 | This enables all backends - without this feature, you need to enable at |
|
|
3953 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
3954 | |
|
|
3955 | =item C<32> - enable OS-specific "helper" APIs |
|
|
3956 | |
|
|
3957 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
3958 | default. |
|
|
3959 | |
|
|
3960 | =back |
|
|
3961 | |
|
|
3962 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
3963 | reduces the compiled size of libev from 24.7Kb to 6.5Kb on my GNU/Linux |
|
|
3964 | amd64 system, while still giving you I/O watchers, timers and monotonic |
|
|
3965 | clock support. |
|
|
3966 | |
|
|
3967 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
3968 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
3969 | your program might be left out as well - a binary starting a timer and an |
|
|
3970 | I/O watcher then might come out at only 5Kb. |
|
|
3971 | |
|
|
3972 | =item EV_AVOID_STDIO |
|
|
3973 | |
|
|
3974 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
3975 | functions (printf, scanf, perror etc.). This will increase the codesize |
|
|
3976 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
3977 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
3978 | big. |
|
|
3979 | |
|
|
3980 | Note that error messages might become less precise when this option is |
|
|
3981 | enabled. |
|
|
3982 | |
|
|
3983 | =item EV_NSIG |
|
|
3984 | |
|
|
3985 | The highest supported signal number, +1 (or, the number of |
|
|
3986 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
3987 | automatically, but sometimes this fails, in which case it can be |
|
|
3988 | specified. Also, using a lower number than detected (C<32> should be |
|
|
3989 | good for about any system in existance) can save some memory, as libev |
|
|
3990 | statically allocates some 12-24 bytes per signal number. |
3615 | |
3991 | |
3616 | =item EV_PID_HASHSIZE |
3992 | =item EV_PID_HASHSIZE |
3617 | |
3993 | |
3618 | C<ev_child> watchers use a small hash table to distribute workload by |
3994 | 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 |
3995 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3620 | than enough. If you need to manage thousands of children you might want to |
3996 | usually more than enough. If you need to manage thousands of children you |
3621 | increase this value (I<must> be a power of two). |
3997 | might want to increase this value (I<must> be a power of two). |
3622 | |
3998 | |
3623 | =item EV_INOTIFY_HASHSIZE |
3999 | =item EV_INOTIFY_HASHSIZE |
3624 | |
4000 | |
3625 | C<ev_stat> watchers use a small hash table to distribute workload by |
4001 | C<ev_stat> watchers use a small hash table to distribute workload by |
3626 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4002 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3627 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4003 | disabled), usually more than enough. If you need to manage thousands of |
3628 | watchers you might want to increase this value (I<must> be a power of |
4004 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3629 | two). |
4005 | power of two). |
3630 | |
4006 | |
3631 | =item EV_USE_4HEAP |
4007 | =item EV_USE_4HEAP |
3632 | |
4008 | |
3633 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4009 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3634 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4010 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3635 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4011 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3636 | faster performance with many (thousands) of watchers. |
4012 | faster performance with many (thousands) of watchers. |
3637 | |
4013 | |
3638 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4014 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3639 | (disabled). |
4015 | will be C<0>. |
3640 | |
4016 | |
3641 | =item EV_HEAP_CACHE_AT |
4017 | =item EV_HEAP_CACHE_AT |
3642 | |
4018 | |
3643 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4019 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3644 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4020 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3645 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4021 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3646 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4022 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3647 | but avoids random read accesses on heap changes. This improves performance |
4023 | but avoids random read accesses on heap changes. This improves performance |
3648 | noticeably with many (hundreds) of watchers. |
4024 | noticeably with many (hundreds) of watchers. |
3649 | |
4025 | |
3650 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4026 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3651 | (disabled). |
4027 | will be C<0>. |
3652 | |
4028 | |
3653 | =item EV_VERIFY |
4029 | =item EV_VERIFY |
3654 | |
4030 | |
3655 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4031 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
3656 | be done: If set to C<0>, no internal verification code will be compiled |
4032 | be done: If set to C<0>, no internal verification code will be compiled |
… | |
… | |
3658 | called. If set to C<2>, then the internal verification code will be |
4034 | called. If set to C<2>, then the internal verification code will be |
3659 | called once per loop, which can slow down libev. If set to C<3>, then the |
4035 | called once per loop, which can slow down libev. If set to C<3>, then the |
3660 | verification code will be called very frequently, which will slow down |
4036 | verification code will be called very frequently, which will slow down |
3661 | libev considerably. |
4037 | libev considerably. |
3662 | |
4038 | |
3663 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4039 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3664 | C<0>. |
4040 | will be C<0>. |
3665 | |
4041 | |
3666 | =item EV_COMMON |
4042 | =item EV_COMMON |
3667 | |
4043 | |
3668 | By default, all watchers have a C<void *data> member. By redefining |
4044 | By default, all watchers have a C<void *data> member. By redefining |
3669 | this macro to a something else you can include more and other types of |
4045 | this macro to a something else you can include more and other types of |
… | |
… | |
3727 | file. |
4103 | file. |
3728 | |
4104 | |
3729 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4105 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3730 | that everybody includes and which overrides some configure choices: |
4106 | that everybody includes and which overrides some configure choices: |
3731 | |
4107 | |
3732 | #define EV_MINIMAL 1 |
4108 | #define EV_FEATURES 0 |
3733 | #define EV_USE_POLL 0 |
4109 | #define EV_USE_SELECT 1 |
3734 | #define EV_MULTIPLICITY 0 |
|
|
3735 | #define EV_PERIODIC_ENABLE 0 |
|
|
3736 | #define EV_STAT_ENABLE 0 |
|
|
3737 | #define EV_FORK_ENABLE 0 |
|
|
3738 | #define EV_CONFIG_H <config.h> |
4110 | #define EV_CONFIG_H <config.h> |
3739 | #define EV_MINPRI 0 |
|
|
3740 | #define EV_MAXPRI 0 |
|
|
3741 | |
4111 | |
3742 | #include "ev++.h" |
4112 | #include "ev++.h" |
3743 | |
4113 | |
3744 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4114 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3745 | |
4115 | |
… | |
… | |
3805 | default loop and triggering an C<ev_async> watcher from the default loop |
4175 | default loop and triggering an C<ev_async> watcher from the default loop |
3806 | watcher callback into the event loop interested in the signal. |
4176 | watcher callback into the event loop interested in the signal. |
3807 | |
4177 | |
3808 | =back |
4178 | =back |
3809 | |
4179 | |
|
|
4180 | =head4 THREAD LOCKING EXAMPLE |
|
|
4181 | |
|
|
4182 | Here is a fictitious example of how to run an event loop in a different |
|
|
4183 | thread than where callbacks are being invoked and watchers are |
|
|
4184 | created/added/removed. |
|
|
4185 | |
|
|
4186 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4187 | which uses exactly this technique (which is suited for many high-level |
|
|
4188 | languages). |
|
|
4189 | |
|
|
4190 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4191 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4192 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4193 | |
|
|
4194 | First, you need to associate some data with the event loop: |
|
|
4195 | |
|
|
4196 | typedef struct { |
|
|
4197 | mutex_t lock; /* global loop lock */ |
|
|
4198 | ev_async async_w; |
|
|
4199 | thread_t tid; |
|
|
4200 | cond_t invoke_cv; |
|
|
4201 | } userdata; |
|
|
4202 | |
|
|
4203 | void prepare_loop (EV_P) |
|
|
4204 | { |
|
|
4205 | // for simplicity, we use a static userdata struct. |
|
|
4206 | static userdata u; |
|
|
4207 | |
|
|
4208 | ev_async_init (&u->async_w, async_cb); |
|
|
4209 | ev_async_start (EV_A_ &u->async_w); |
|
|
4210 | |
|
|
4211 | pthread_mutex_init (&u->lock, 0); |
|
|
4212 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4213 | |
|
|
4214 | // now associate this with the loop |
|
|
4215 | ev_set_userdata (EV_A_ u); |
|
|
4216 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4217 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4218 | |
|
|
4219 | // then create the thread running ev_loop |
|
|
4220 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4221 | } |
|
|
4222 | |
|
|
4223 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4224 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4225 | that might have been added: |
|
|
4226 | |
|
|
4227 | static void |
|
|
4228 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4229 | { |
|
|
4230 | // just used for the side effects |
|
|
4231 | } |
|
|
4232 | |
|
|
4233 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4234 | protecting the loop data, respectively. |
|
|
4235 | |
|
|
4236 | static void |
|
|
4237 | l_release (EV_P) |
|
|
4238 | { |
|
|
4239 | userdata *u = ev_userdata (EV_A); |
|
|
4240 | pthread_mutex_unlock (&u->lock); |
|
|
4241 | } |
|
|
4242 | |
|
|
4243 | static void |
|
|
4244 | l_acquire (EV_P) |
|
|
4245 | { |
|
|
4246 | userdata *u = ev_userdata (EV_A); |
|
|
4247 | pthread_mutex_lock (&u->lock); |
|
|
4248 | } |
|
|
4249 | |
|
|
4250 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4251 | into C<ev_loop>: |
|
|
4252 | |
|
|
4253 | void * |
|
|
4254 | l_run (void *thr_arg) |
|
|
4255 | { |
|
|
4256 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4257 | |
|
|
4258 | l_acquire (EV_A); |
|
|
4259 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4260 | ev_loop (EV_A_ 0); |
|
|
4261 | l_release (EV_A); |
|
|
4262 | |
|
|
4263 | return 0; |
|
|
4264 | } |
|
|
4265 | |
|
|
4266 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4267 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4268 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4269 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4270 | and b) skipping inter-thread-communication when there are no pending |
|
|
4271 | watchers is very beneficial): |
|
|
4272 | |
|
|
4273 | static void |
|
|
4274 | l_invoke (EV_P) |
|
|
4275 | { |
|
|
4276 | userdata *u = ev_userdata (EV_A); |
|
|
4277 | |
|
|
4278 | while (ev_pending_count (EV_A)) |
|
|
4279 | { |
|
|
4280 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4281 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4282 | } |
|
|
4283 | } |
|
|
4284 | |
|
|
4285 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4286 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4287 | thread to continue: |
|
|
4288 | |
|
|
4289 | static void |
|
|
4290 | real_invoke_pending (EV_P) |
|
|
4291 | { |
|
|
4292 | userdata *u = ev_userdata (EV_A); |
|
|
4293 | |
|
|
4294 | pthread_mutex_lock (&u->lock); |
|
|
4295 | ev_invoke_pending (EV_A); |
|
|
4296 | pthread_cond_signal (&u->invoke_cv); |
|
|
4297 | pthread_mutex_unlock (&u->lock); |
|
|
4298 | } |
|
|
4299 | |
|
|
4300 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4301 | event loop, you will now have to lock: |
|
|
4302 | |
|
|
4303 | ev_timer timeout_watcher; |
|
|
4304 | userdata *u = ev_userdata (EV_A); |
|
|
4305 | |
|
|
4306 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4307 | |
|
|
4308 | pthread_mutex_lock (&u->lock); |
|
|
4309 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4310 | ev_async_send (EV_A_ &u->async_w); |
|
|
4311 | pthread_mutex_unlock (&u->lock); |
|
|
4312 | |
|
|
4313 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4314 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4315 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4316 | watchers in the next event loop iteration. |
|
|
4317 | |
3810 | =head3 COROUTINES |
4318 | =head3 COROUTINES |
3811 | |
4319 | |
3812 | Libev is very accommodating to coroutines ("cooperative threads"): |
4320 | Libev is very accommodating to coroutines ("cooperative threads"): |
3813 | libev fully supports nesting calls to its functions from different |
4321 | 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 |
4322 | 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 |
4323 | different coroutines, and switch freely between both coroutines running |
3816 | loop, as long as you don't confuse yourself). The only exception is that |
4324 | 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. |
4325 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3818 | |
4326 | |
3819 | Care has been taken to ensure that libev does not keep local state inside |
4327 | 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 |
4328 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3821 | they do not call any callbacks. |
4329 | they do not call any callbacks. |
3822 | |
4330 | |
… | |
… | |
3899 | way (note also that glib is the slowest event library known to man). |
4407 | way (note also that glib is the slowest event library known to man). |
3900 | |
4408 | |
3901 | There is no supported compilation method available on windows except |
4409 | There is no supported compilation method available on windows except |
3902 | embedding it into other applications. |
4410 | embedding it into other applications. |
3903 | |
4411 | |
|
|
4412 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4413 | tries its best, but under most conditions, signals will simply not work. |
|
|
4414 | |
3904 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4415 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3905 | accept large writes: instead of resulting in a partial write, windows will |
4416 | 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, |
4417 | 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 |
4418 | 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 |
4419 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3912 | the abysmal performance of winsockets, using a large number of sockets |
4423 | the abysmal performance of winsockets, using a large number of sockets |
3913 | is not recommended (and not reasonable). If your program needs to use |
4424 | 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 |
4425 | 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 |
4426 | different implementation for windows, as libev offers the POSIX readiness |
3916 | notification model, which cannot be implemented efficiently on windows |
4427 | notification model, which cannot be implemented efficiently on windows |
3917 | (Microsoft monopoly games). |
4428 | (due to Microsoft monopoly games). |
3918 | |
4429 | |
3919 | A typical way to use libev under windows is to embed it (see the embedding |
4430 | 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 |
4431 | section for details) and use the following F<evwrap.h> header file instead |
3921 | of F<ev.h>: |
4432 | of F<ev.h>: |
3922 | |
4433 | |
… | |
… | |
3958 | |
4469 | |
3959 | Early versions of winsocket's select only supported waiting for a maximum |
4470 | 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 |
4471 | 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 |
4472 | 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 |
4473 | recommends spawning a chain of threads and wait for 63 handles and the |
3963 | previous thread in each. Great). |
4474 | previous thread in each. Sounds great!). |
3964 | |
4475 | |
3965 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4476 | 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 |
4477 | 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 |
4478 | call (which might be in libev or elsewhere, for example, perl and many |
3968 | select emulation on windows). |
4479 | other interpreters do their own select emulation on windows). |
3969 | |
4480 | |
3970 | Another limit is the number of file descriptors in the Microsoft runtime |
4481 | 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 |
4482 | 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 |
4483 | fetish or something like this inside Microsoft). You can increase this |
3973 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4484 | 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 |
4485 | (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 |
4486 | 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 |
4487 | (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 |
4488 | 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. |
4489 | the cost of calling select (O(n²)) will likely make this unworkable. |
3981 | |
4490 | |
3982 | =back |
4491 | =back |
3983 | |
4492 | |
3984 | =head2 PORTABILITY REQUIREMENTS |
4493 | =head2 PORTABILITY REQUIREMENTS |
3985 | |
4494 | |
… | |
… | |
4028 | =item C<double> must hold a time value in seconds with enough accuracy |
4537 | =item C<double> must hold a time value in seconds with enough accuracy |
4029 | |
4538 | |
4030 | The type C<double> is used to represent timestamps. It is required to |
4539 | 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 |
4540 | 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 |
4541 | enough for at least into the year 4000. This requirement is fulfilled by |
4033 | implementations implementing IEEE 754 (basically all existing ones). |
4542 | implementations implementing IEEE 754, which is basically all existing |
|
|
4543 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4544 | 2200. |
4034 | |
4545 | |
4035 | =back |
4546 | =back |
4036 | |
4547 | |
4037 | If you know of other additional requirements drop me a note. |
4548 | If you know of other additional requirements drop me a note. |
4038 | |
4549 | |