… | |
… | |
8 | |
8 | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
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|
13 | |
|
|
14 | #include <stdio.h> // for puts |
13 | |
15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_TYPE |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
… | |
… | |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // unloop was called, so exit |
62 | return 0; |
64 | return 0; |
63 | } |
65 | } |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
66 | |
70 | |
67 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 ABOUT LIBEV |
70 | |
84 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
74 | |
88 | |
… | |
… | |
108 | name C<loop> (which is always of type C<ev_loop *>) will not have |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
109 | this argument. |
123 | this argument. |
110 | |
124 | |
111 | =head2 TIME REPRESENTATION |
125 | =head2 TIME REPRESENTATION |
112 | |
126 | |
113 | Libev represents time as a single floating point number, representing the |
127 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
129 | near the beginning of 1970, details are complicated, don't ask). This |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
130 | type is called C<ev_tstamp>, which is what you should use too. It usually |
117 | to the C<double> type in C, and when you need to do any calculations on |
131 | aliases to the C<double> type in C. When you need to do any calculations |
118 | it, you should treat it as some floating point value. Unlike the name |
132 | on it, you should treat it as some floating point value. Unlike the name |
119 | component C<stamp> might indicate, it is also used for time differences |
133 | component C<stamp> might indicate, it is also used for time differences |
120 | throughout libev. |
134 | throughout libev. |
121 | |
135 | |
122 | =head1 ERROR HANDLING |
136 | =head1 ERROR HANDLING |
123 | |
137 | |
… | |
… | |
458 | |
472 | |
459 | While nominally embeddable in other event loops, this doesn't work |
473 | While nominally embeddable in other event loops, this doesn't work |
460 | everywhere, so you might need to test for this. And since it is broken |
474 | everywhere, so you might need to test for this. And since it is broken |
461 | almost everywhere, you should only use it when you have a lot of sockets |
475 | almost everywhere, you should only use it when you have a lot of sockets |
462 | (for which it usually works), by embedding it into another event loop |
476 | (for which it usually works), by embedding it into another event loop |
463 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
477 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
464 | using it only for sockets. |
478 | also broken on OS X)) and, did I mention it, using it only for sockets. |
465 | |
479 | |
466 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
480 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
467 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
481 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
468 | C<NOTE_EOF>. |
482 | C<NOTE_EOF>. |
469 | |
483 | |
… | |
… | |
607 | |
621 | |
608 | This value can sometimes be useful as a generation counter of sorts (it |
622 | This value can sometimes be useful as a generation counter of sorts (it |
609 | "ticks" the number of loop iterations), as it roughly corresponds with |
623 | "ticks" the number of loop iterations), as it roughly corresponds with |
610 | C<ev_prepare> and C<ev_check> calls. |
624 | C<ev_prepare> and C<ev_check> calls. |
611 | |
625 | |
|
|
626 | =item unsigned int ev_loop_depth (loop) |
|
|
627 | |
|
|
628 | Returns the number of times C<ev_loop> was entered minus the number of |
|
|
629 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
630 | |
|
|
631 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
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|
632 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
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633 | in which case it is higher. |
|
|
634 | |
|
|
635 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
636 | etc.), doesn't count as exit. |
|
|
637 | |
612 | =item unsigned int ev_backend (loop) |
638 | =item unsigned int ev_backend (loop) |
613 | |
639 | |
614 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
640 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
615 | use. |
641 | use. |
616 | |
642 | |
… | |
… | |
630 | |
656 | |
631 | This function is rarely useful, but when some event callback runs for a |
657 | This function is rarely useful, but when some event callback runs for a |
632 | very long time without entering the event loop, updating libev's idea of |
658 | very long time without entering the event loop, updating libev's idea of |
633 | the current time is a good idea. |
659 | the current time is a good idea. |
634 | |
660 | |
635 | See also "The special problem of time updates" in the C<ev_timer> section. |
661 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
662 | |
|
|
663 | =item ev_suspend (loop) |
|
|
664 | |
|
|
665 | =item ev_resume (loop) |
|
|
666 | |
|
|
667 | These two functions suspend and resume a loop, for use when the loop is |
|
|
668 | not used for a while and timeouts should not be processed. |
|
|
669 | |
|
|
670 | A typical use case would be an interactive program such as a game: When |
|
|
671 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
672 | would be best to handle timeouts as if no time had actually passed while |
|
|
673 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
674 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
675 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
676 | |
|
|
677 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
678 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
679 | will be rescheduled (that is, they will lose any events that would have |
|
|
680 | occured while suspended). |
|
|
681 | |
|
|
682 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
683 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
684 | without a previous call to C<ev_suspend>. |
|
|
685 | |
|
|
686 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
687 | event loop time (see C<ev_now_update>). |
636 | |
688 | |
637 | =item ev_loop (loop, int flags) |
689 | =item ev_loop (loop, int flags) |
638 | |
690 | |
639 | Finally, this is it, the event handler. This function usually is called |
691 | Finally, this is it, the event handler. This function usually is called |
640 | after you initialised all your watchers and you want to start handling |
692 | after you initialised all your watchers and you want to start handling |
… | |
… | |
724 | |
776 | |
725 | If you have a watcher you never unregister that should not keep C<ev_loop> |
777 | If you have a watcher you never unregister that should not keep C<ev_loop> |
726 | from returning, call ev_unref() after starting, and ev_ref() before |
778 | from returning, call ev_unref() after starting, and ev_ref() before |
727 | stopping it. |
779 | stopping it. |
728 | |
780 | |
729 | As an example, libev itself uses this for its internal signal pipe: It is |
781 | As an example, libev itself uses this for its internal signal pipe: It |
730 | not visible to the libev user and should not keep C<ev_loop> from exiting |
782 | is not visible to the libev user and should not keep C<ev_loop> from |
731 | if no event watchers registered by it are active. It is also an excellent |
783 | exiting if no event watchers registered by it are active. It is also an |
732 | way to do this for generic recurring timers or from within third-party |
784 | excellent way to do this for generic recurring timers or from within |
733 | libraries. Just remember to I<unref after start> and I<ref before stop> |
785 | third-party libraries. Just remember to I<unref after start> and I<ref |
734 | (but only if the watcher wasn't active before, or was active before, |
786 | before stop> (but only if the watcher wasn't active before, or was active |
735 | respectively). |
787 | before, respectively. Note also that libev might stop watchers itself |
|
|
788 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
789 | in the callback). |
736 | |
790 | |
737 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
791 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
738 | running when nothing else is active. |
792 | running when nothing else is active. |
739 | |
793 | |
740 | ev_signal exitsig; |
794 | ev_signal exitsig; |
… | |
… | |
769 | |
823 | |
770 | By setting a higher I<io collect interval> you allow libev to spend more |
824 | By setting a higher I<io collect interval> you allow libev to spend more |
771 | time collecting I/O events, so you can handle more events per iteration, |
825 | time collecting I/O events, so you can handle more events per iteration, |
772 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
826 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
773 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
827 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
774 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
828 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
829 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
830 | once per this interval, on average. |
775 | |
831 | |
776 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
832 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
777 | to spend more time collecting timeouts, at the expense of increased |
833 | to spend more time collecting timeouts, at the expense of increased |
778 | latency/jitter/inexactness (the watcher callback will be called |
834 | latency/jitter/inexactness (the watcher callback will be called |
779 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
835 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
781 | |
837 | |
782 | Many (busy) programs can usually benefit by setting the I/O collect |
838 | Many (busy) programs can usually benefit by setting the I/O collect |
783 | interval to a value near C<0.1> or so, which is often enough for |
839 | interval to a value near C<0.1> or so, which is often enough for |
784 | interactive servers (of course not for games), likewise for timeouts. It |
840 | interactive servers (of course not for games), likewise for timeouts. It |
785 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
841 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
786 | as this approaches the timing granularity of most systems. |
842 | as this approaches the timing granularity of most systems. Note that if |
|
|
843 | you do transactions with the outside world and you can't increase the |
|
|
844 | parallelity, then this setting will limit your transaction rate (if you |
|
|
845 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
846 | then you can't do more than 100 transations per second). |
787 | |
847 | |
788 | Setting the I<timeout collect interval> can improve the opportunity for |
848 | Setting the I<timeout collect interval> can improve the opportunity for |
789 | saving power, as the program will "bundle" timer callback invocations that |
849 | saving power, as the program will "bundle" timer callback invocations that |
790 | are "near" in time together, by delaying some, thus reducing the number of |
850 | are "near" in time together, by delaying some, thus reducing the number of |
791 | times the process sleeps and wakes up again. Another useful technique to |
851 | times the process sleeps and wakes up again. Another useful technique to |
792 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
852 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
793 | they fire on, say, one-second boundaries only. |
853 | they fire on, say, one-second boundaries only. |
|
|
854 | |
|
|
855 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
856 | more often than 100 times per second: |
|
|
857 | |
|
|
858 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
859 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
794 | |
860 | |
795 | =item ev_loop_verify (loop) |
861 | =item ev_loop_verify (loop) |
796 | |
862 | |
797 | This function only does something when C<EV_VERIFY> support has been |
863 | This function only does something when C<EV_VERIFY> support has been |
798 | compiled in, which is the default for non-minimal builds. It tries to go |
864 | compiled in, which is the default for non-minimal builds. It tries to go |
… | |
… | |
924 | |
990 | |
925 | =item C<EV_ASYNC> |
991 | =item C<EV_ASYNC> |
926 | |
992 | |
927 | The given async watcher has been asynchronously notified (see C<ev_async>). |
993 | The given async watcher has been asynchronously notified (see C<ev_async>). |
928 | |
994 | |
|
|
995 | =item C<EV_CUSTOM> |
|
|
996 | |
|
|
997 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
998 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
999 | |
929 | =item C<EV_ERROR> |
1000 | =item C<EV_ERROR> |
930 | |
1001 | |
931 | An unspecified error has occurred, the watcher has been stopped. This might |
1002 | An unspecified error has occurred, the watcher has been stopped. This might |
932 | happen because the watcher could not be properly started because libev |
1003 | happen because the watcher could not be properly started because libev |
933 | ran out of memory, a file descriptor was found to be closed or any other |
1004 | ran out of memory, a file descriptor was found to be closed or any other |
… | |
… | |
1048 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1119 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1049 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1120 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1050 | before watchers with lower priority, but priority will not keep watchers |
1121 | before watchers with lower priority, but priority will not keep watchers |
1051 | from being executed (except for C<ev_idle> watchers). |
1122 | from being executed (except for C<ev_idle> watchers). |
1052 | |
1123 | |
1053 | This means that priorities are I<only> used for ordering callback |
|
|
1054 | invocation after new events have been received. This is useful, for |
|
|
1055 | example, to reduce latency after idling, or more often, to bind two |
|
|
1056 | watchers on the same event and make sure one is called first. |
|
|
1057 | |
|
|
1058 | If you need to suppress invocation when higher priority events are pending |
1124 | If you need to suppress invocation when higher priority events are pending |
1059 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1125 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1060 | |
1126 | |
1061 | You I<must not> change the priority of a watcher as long as it is active or |
1127 | You I<must not> change the priority of a watcher as long as it is active or |
1062 | pending. |
1128 | pending. |
1063 | |
|
|
1064 | The default priority used by watchers when no priority has been set is |
|
|
1065 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1066 | |
1129 | |
1067 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1130 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1068 | fine, as long as you do not mind that the priority value you query might |
1131 | fine, as long as you do not mind that the priority value you query might |
1069 | or might not have been clamped to the valid range. |
1132 | or might not have been clamped to the valid range. |
|
|
1133 | |
|
|
1134 | The default priority used by watchers when no priority has been set is |
|
|
1135 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1136 | |
|
|
1137 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1138 | priorities. |
1070 | |
1139 | |
1071 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1140 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1072 | |
1141 | |
1073 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1142 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1074 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1143 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1139 | #include <stddef.h> |
1208 | #include <stddef.h> |
1140 | |
1209 | |
1141 | static void |
1210 | static void |
1142 | t1_cb (EV_P_ ev_timer *w, int revents) |
1211 | t1_cb (EV_P_ ev_timer *w, int revents) |
1143 | { |
1212 | { |
1144 | struct my_biggy big = (struct my_biggy * |
1213 | struct my_biggy big = (struct my_biggy *) |
1145 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1214 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1146 | } |
1215 | } |
1147 | |
1216 | |
1148 | static void |
1217 | static void |
1149 | t2_cb (EV_P_ ev_timer *w, int revents) |
1218 | t2_cb (EV_P_ ev_timer *w, int revents) |
1150 | { |
1219 | { |
1151 | struct my_biggy big = (struct my_biggy * |
1220 | struct my_biggy big = (struct my_biggy *) |
1152 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1221 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1153 | } |
1222 | } |
|
|
1223 | |
|
|
1224 | =head2 WATCHER PRIORITY MODELS |
|
|
1225 | |
|
|
1226 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1227 | integers that influence the ordering of event callback invocation |
|
|
1228 | between watchers in some way, all else being equal. |
|
|
1229 | |
|
|
1230 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1231 | description for the more technical details such as the actual priority |
|
|
1232 | range. |
|
|
1233 | |
|
|
1234 | There are two common ways how these these priorities are being interpreted |
|
|
1235 | by event loops: |
|
|
1236 | |
|
|
1237 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1238 | of lower priority watchers, which means as long as higher priority |
|
|
1239 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1240 | |
|
|
1241 | The less common only-for-ordering model uses priorities solely to order |
|
|
1242 | callback invocation within a single event loop iteration: Higher priority |
|
|
1243 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1244 | before polling for new events. |
|
|
1245 | |
|
|
1246 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1247 | except for idle watchers (which use the lock-out model). |
|
|
1248 | |
|
|
1249 | The rationale behind this is that implementing the lock-out model for |
|
|
1250 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1251 | libraries will just poll for the same events again and again as long as |
|
|
1252 | their callbacks have not been executed, which is very inefficient in the |
|
|
1253 | common case of one high-priority watcher locking out a mass of lower |
|
|
1254 | priority ones. |
|
|
1255 | |
|
|
1256 | Static (ordering) priorities are most useful when you have two or more |
|
|
1257 | watchers handling the same resource: a typical usage example is having an |
|
|
1258 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1259 | timeouts. Under load, data might be received while the program handles |
|
|
1260 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1261 | handler will be executed before checking for data. In that case, giving |
|
|
1262 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1263 | handled first even under adverse conditions (which is usually, but not |
|
|
1264 | always, what you want). |
|
|
1265 | |
|
|
1266 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1267 | will only be executed when no same or higher priority watchers have |
|
|
1268 | received events, they can be used to implement the "lock-out" model when |
|
|
1269 | required. |
|
|
1270 | |
|
|
1271 | For example, to emulate how many other event libraries handle priorities, |
|
|
1272 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1273 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1274 | processing is done in the idle watcher callback. This causes libev to |
|
|
1275 | continously poll and process kernel event data for the watcher, but when |
|
|
1276 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1277 | workable. |
|
|
1278 | |
|
|
1279 | Usually, however, the lock-out model implemented that way will perform |
|
|
1280 | miserably under the type of load it was designed to handle. In that case, |
|
|
1281 | it might be preferable to stop the real watcher before starting the |
|
|
1282 | idle watcher, so the kernel will not have to process the event in case |
|
|
1283 | the actual processing will be delayed for considerable time. |
|
|
1284 | |
|
|
1285 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1286 | priority than the default, and which should only process data when no |
|
|
1287 | other events are pending: |
|
|
1288 | |
|
|
1289 | ev_idle idle; // actual processing watcher |
|
|
1290 | ev_io io; // actual event watcher |
|
|
1291 | |
|
|
1292 | static void |
|
|
1293 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1294 | { |
|
|
1295 | // stop the I/O watcher, we received the event, but |
|
|
1296 | // are not yet ready to handle it. |
|
|
1297 | ev_io_stop (EV_A_ w); |
|
|
1298 | |
|
|
1299 | // start the idle watcher to ahndle the actual event. |
|
|
1300 | // it will not be executed as long as other watchers |
|
|
1301 | // with the default priority are receiving events. |
|
|
1302 | ev_idle_start (EV_A_ &idle); |
|
|
1303 | } |
|
|
1304 | |
|
|
1305 | static void |
|
|
1306 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1307 | { |
|
|
1308 | // actual processing |
|
|
1309 | read (STDIN_FILENO, ...); |
|
|
1310 | |
|
|
1311 | // have to start the I/O watcher again, as |
|
|
1312 | // we have handled the event |
|
|
1313 | ev_io_start (EV_P_ &io); |
|
|
1314 | } |
|
|
1315 | |
|
|
1316 | // initialisation |
|
|
1317 | ev_idle_init (&idle, idle_cb); |
|
|
1318 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1319 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1320 | |
|
|
1321 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1322 | low-priority connections can not be locked out forever under load. This |
|
|
1323 | enables your program to keep a lower latency for important connections |
|
|
1324 | during short periods of high load, while not completely locking out less |
|
|
1325 | important ones. |
1154 | |
1326 | |
1155 | |
1327 | |
1156 | =head1 WATCHER TYPES |
1328 | =head1 WATCHER TYPES |
1157 | |
1329 | |
1158 | This section describes each watcher in detail, but will not repeat |
1330 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1184 | descriptors to non-blocking mode is also usually a good idea (but not |
1356 | descriptors to non-blocking mode is also usually a good idea (but not |
1185 | required if you know what you are doing). |
1357 | required if you know what you are doing). |
1186 | |
1358 | |
1187 | If you cannot use non-blocking mode, then force the use of a |
1359 | If you cannot use non-blocking mode, then force the use of a |
1188 | known-to-be-good backend (at the time of this writing, this includes only |
1360 | known-to-be-good backend (at the time of this writing, this includes only |
1189 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1361 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1362 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1363 | files) - libev doesn't guarentee any specific behaviour in that case. |
1190 | |
1364 | |
1191 | Another thing you have to watch out for is that it is quite easy to |
1365 | Another thing you have to watch out for is that it is quite easy to |
1192 | receive "spurious" readiness notifications, that is your callback might |
1366 | receive "spurious" readiness notifications, that is your callback might |
1193 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1367 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1194 | because there is no data. Not only are some backends known to create a |
1368 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1315 | year, it will still time out after (roughly) one hour. "Roughly" because |
1489 | year, it will still time out after (roughly) one hour. "Roughly" because |
1316 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1490 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1317 | monotonic clock option helps a lot here). |
1491 | monotonic clock option helps a lot here). |
1318 | |
1492 | |
1319 | The callback is guaranteed to be invoked only I<after> its timeout has |
1493 | The callback is guaranteed to be invoked only I<after> its timeout has |
1320 | passed, but if multiple timers become ready during the same loop iteration |
1494 | passed (not I<at>, so on systems with very low-resolution clocks this |
1321 | then order of execution is undefined. |
1495 | might introduce a small delay). If multiple timers become ready during the |
|
|
1496 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1497 | before ones of the same priority with later time-out values (but this is |
|
|
1498 | no longer true when a callback calls C<ev_loop> recursively). |
1322 | |
1499 | |
1323 | =head3 Be smart about timeouts |
1500 | =head3 Be smart about timeouts |
1324 | |
1501 | |
1325 | Many real-world problems involve some kind of timeout, usually for error |
1502 | Many real-world problems involve some kind of timeout, usually for error |
1326 | recovery. A typical example is an HTTP request - if the other side hangs, |
1503 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1370 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1547 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1371 | member and C<ev_timer_again>. |
1548 | member and C<ev_timer_again>. |
1372 | |
1549 | |
1373 | At start: |
1550 | At start: |
1374 | |
1551 | |
1375 | ev_timer_init (timer, callback); |
1552 | ev_init (timer, callback); |
1376 | timer->repeat = 60.; |
1553 | timer->repeat = 60.; |
1377 | ev_timer_again (loop, timer); |
1554 | ev_timer_again (loop, timer); |
1378 | |
1555 | |
1379 | Each time there is some activity: |
1556 | Each time there is some activity: |
1380 | |
1557 | |
… | |
… | |
1442 | |
1619 | |
1443 | To start the timer, simply initialise the watcher and set C<last_activity> |
1620 | To start the timer, simply initialise the watcher and set C<last_activity> |
1444 | to the current time (meaning we just have some activity :), then call the |
1621 | to the current time (meaning we just have some activity :), then call the |
1445 | callback, which will "do the right thing" and start the timer: |
1622 | callback, which will "do the right thing" and start the timer: |
1446 | |
1623 | |
1447 | ev_timer_init (timer, callback); |
1624 | ev_init (timer, callback); |
1448 | last_activity = ev_now (loop); |
1625 | last_activity = ev_now (loop); |
1449 | callback (loop, timer, EV_TIMEOUT); |
1626 | callback (loop, timer, EV_TIMEOUT); |
1450 | |
1627 | |
1451 | And when there is some activity, simply store the current time in |
1628 | And when there is some activity, simply store the current time in |
1452 | C<last_activity>, no libev calls at all: |
1629 | C<last_activity>, no libev calls at all: |
… | |
… | |
1545 | If the timer is started but non-repeating, stop it (as if it timed out). |
1722 | If the timer is started but non-repeating, stop it (as if it timed out). |
1546 | |
1723 | |
1547 | If the timer is repeating, either start it if necessary (with the |
1724 | If the timer is repeating, either start it if necessary (with the |
1548 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1725 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1549 | |
1726 | |
1550 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1727 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1551 | usage example. |
1728 | usage example. |
1552 | |
1729 | |
1553 | =item ev_tstamp repeat [read-write] |
1730 | =item ev_tstamp repeat [read-write] |
1554 | |
1731 | |
1555 | The current C<repeat> value. Will be used each time the watcher times out |
1732 | The current C<repeat> value. Will be used each time the watcher times out |
… | |
… | |
1594 | =head2 C<ev_periodic> - to cron or not to cron? |
1771 | =head2 C<ev_periodic> - to cron or not to cron? |
1595 | |
1772 | |
1596 | Periodic watchers are also timers of a kind, but they are very versatile |
1773 | Periodic watchers are also timers of a kind, but they are very versatile |
1597 | (and unfortunately a bit complex). |
1774 | (and unfortunately a bit complex). |
1598 | |
1775 | |
1599 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1776 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1600 | but on wall clock time (absolute time). You can tell a periodic watcher |
1777 | relative time, the physical time that passes) but on wall clock time |
1601 | to trigger after some specific point in time. For example, if you tell a |
1778 | (absolute time, the thing you can read on your calender or clock). The |
1602 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1779 | difference is that wall clock time can run faster or slower than real |
1603 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1780 | time, and time jumps are not uncommon (e.g. when you adjust your |
1604 | clock to January of the previous year, then it will take more than year |
1781 | wrist-watch). |
1605 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1606 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1607 | |
1782 | |
|
|
1783 | You can tell a periodic watcher to trigger after some specific point |
|
|
1784 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1785 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1786 | not a delay) and then reset your system clock to January of the previous |
|
|
1787 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1788 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1789 | it, as it uses a relative timeout). |
|
|
1790 | |
1608 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1791 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1609 | such as triggering an event on each "midnight, local time", or other |
1792 | timers, such as triggering an event on each "midnight, local time", or |
1610 | complicated rules. |
1793 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1794 | those cannot react to time jumps. |
1611 | |
1795 | |
1612 | As with timers, the callback is guaranteed to be invoked only when the |
1796 | As with timers, the callback is guaranteed to be invoked only when the |
1613 | time (C<at>) has passed, but if multiple periodic timers become ready |
1797 | point in time where it is supposed to trigger has passed. If multiple |
1614 | during the same loop iteration, then order of execution is undefined. |
1798 | timers become ready during the same loop iteration then the ones with |
|
|
1799 | earlier time-out values are invoked before ones with later time-out values |
|
|
1800 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1615 | |
1801 | |
1616 | =head3 Watcher-Specific Functions and Data Members |
1802 | =head3 Watcher-Specific Functions and Data Members |
1617 | |
1803 | |
1618 | =over 4 |
1804 | =over 4 |
1619 | |
1805 | |
1620 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1806 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1621 | |
1807 | |
1622 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1808 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1623 | |
1809 | |
1624 | Lots of arguments, lets sort it out... There are basically three modes of |
1810 | Lots of arguments, let's sort it out... There are basically three modes of |
1625 | operation, and we will explain them from simplest to most complex: |
1811 | operation, and we will explain them from simplest to most complex: |
1626 | |
1812 | |
1627 | =over 4 |
1813 | =over 4 |
1628 | |
1814 | |
1629 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1815 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1630 | |
1816 | |
1631 | In this configuration the watcher triggers an event after the wall clock |
1817 | In this configuration the watcher triggers an event after the wall clock |
1632 | time C<at> has passed. It will not repeat and will not adjust when a time |
1818 | time C<offset> has passed. It will not repeat and will not adjust when a |
1633 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1819 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1634 | only run when the system clock reaches or surpasses this time. |
1820 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1821 | this point in time. |
1635 | |
1822 | |
1636 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1823 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1637 | |
1824 | |
1638 | In this mode the watcher will always be scheduled to time out at the next |
1825 | In this mode the watcher will always be scheduled to time out at the next |
1639 | C<at + N * interval> time (for some integer N, which can also be negative) |
1826 | C<offset + N * interval> time (for some integer N, which can also be |
1640 | and then repeat, regardless of any time jumps. |
1827 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1828 | argument is merely an offset into the C<interval> periods. |
1641 | |
1829 | |
1642 | This can be used to create timers that do not drift with respect to the |
1830 | This can be used to create timers that do not drift with respect to the |
1643 | system clock, for example, here is a C<ev_periodic> that triggers each |
1831 | system clock, for example, here is an C<ev_periodic> that triggers each |
1644 | hour, on the hour: |
1832 | hour, on the hour (with respect to UTC): |
1645 | |
1833 | |
1646 | ev_periodic_set (&periodic, 0., 3600., 0); |
1834 | ev_periodic_set (&periodic, 0., 3600., 0); |
1647 | |
1835 | |
1648 | This doesn't mean there will always be 3600 seconds in between triggers, |
1836 | This doesn't mean there will always be 3600 seconds in between triggers, |
1649 | but only that the callback will be called when the system time shows a |
1837 | but only that the callback will be called when the system time shows a |
1650 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1838 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1651 | by 3600. |
1839 | by 3600. |
1652 | |
1840 | |
1653 | Another way to think about it (for the mathematically inclined) is that |
1841 | Another way to think about it (for the mathematically inclined) is that |
1654 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1842 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1655 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1843 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1656 | |
1844 | |
1657 | For numerical stability it is preferable that the C<at> value is near |
1845 | For numerical stability it is preferable that the C<offset> value is near |
1658 | C<ev_now ()> (the current time), but there is no range requirement for |
1846 | C<ev_now ()> (the current time), but there is no range requirement for |
1659 | this value, and in fact is often specified as zero. |
1847 | this value, and in fact is often specified as zero. |
1660 | |
1848 | |
1661 | Note also that there is an upper limit to how often a timer can fire (CPU |
1849 | Note also that there is an upper limit to how often a timer can fire (CPU |
1662 | speed for example), so if C<interval> is very small then timing stability |
1850 | speed for example), so if C<interval> is very small then timing stability |
1663 | will of course deteriorate. Libev itself tries to be exact to be about one |
1851 | will of course deteriorate. Libev itself tries to be exact to be about one |
1664 | millisecond (if the OS supports it and the machine is fast enough). |
1852 | millisecond (if the OS supports it and the machine is fast enough). |
1665 | |
1853 | |
1666 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1854 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1667 | |
1855 | |
1668 | In this mode the values for C<interval> and C<at> are both being |
1856 | In this mode the values for C<interval> and C<offset> are both being |
1669 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1857 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1670 | reschedule callback will be called with the watcher as first, and the |
1858 | reschedule callback will be called with the watcher as first, and the |
1671 | current time as second argument. |
1859 | current time as second argument. |
1672 | |
1860 | |
1673 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1861 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1674 | ever, or make ANY event loop modifications whatsoever>. |
1862 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1863 | allowed by documentation here>. |
1675 | |
1864 | |
1676 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1865 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1677 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1866 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1678 | only event loop modification you are allowed to do). |
1867 | only event loop modification you are allowed to do). |
1679 | |
1868 | |
… | |
… | |
1709 | a different time than the last time it was called (e.g. in a crond like |
1898 | a different time than the last time it was called (e.g. in a crond like |
1710 | program when the crontabs have changed). |
1899 | program when the crontabs have changed). |
1711 | |
1900 | |
1712 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1901 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1713 | |
1902 | |
1714 | When active, returns the absolute time that the watcher is supposed to |
1903 | When active, returns the absolute time that the watcher is supposed |
1715 | trigger next. |
1904 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1905 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1906 | rescheduling modes. |
1716 | |
1907 | |
1717 | =item ev_tstamp offset [read-write] |
1908 | =item ev_tstamp offset [read-write] |
1718 | |
1909 | |
1719 | When repeating, this contains the offset value, otherwise this is the |
1910 | When repeating, this contains the offset value, otherwise this is the |
1720 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1911 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1912 | although libev might modify this value for better numerical stability). |
1721 | |
1913 | |
1722 | Can be modified any time, but changes only take effect when the periodic |
1914 | Can be modified any time, but changes only take effect when the periodic |
1723 | timer fires or C<ev_periodic_again> is being called. |
1915 | timer fires or C<ev_periodic_again> is being called. |
1724 | |
1916 | |
1725 | =item ev_tstamp interval [read-write] |
1917 | =item ev_tstamp interval [read-write] |
… | |
… | |
1834 | some child status changes (most typically when a child of yours dies or |
2026 | some child status changes (most typically when a child of yours dies or |
1835 | exits). It is permissible to install a child watcher I<after> the child |
2027 | exits). It is permissible to install a child watcher I<after> the child |
1836 | has been forked (which implies it might have already exited), as long |
2028 | has been forked (which implies it might have already exited), as long |
1837 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2029 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1838 | forking and then immediately registering a watcher for the child is fine, |
2030 | forking and then immediately registering a watcher for the child is fine, |
1839 | but forking and registering a watcher a few event loop iterations later is |
2031 | but forking and registering a watcher a few event loop iterations later or |
1840 | not. |
2032 | in the next callback invocation is not. |
1841 | |
2033 | |
1842 | Only the default event loop is capable of handling signals, and therefore |
2034 | Only the default event loop is capable of handling signals, and therefore |
1843 | you can only register child watchers in the default event loop. |
2035 | you can only register child watchers in the default event loop. |
|
|
2036 | |
|
|
2037 | Due to some design glitches inside libev, child watchers will always be |
|
|
2038 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2039 | libev) |
1844 | |
2040 | |
1845 | =head3 Process Interaction |
2041 | =head3 Process Interaction |
1846 | |
2042 | |
1847 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2043 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1848 | initialised. This is necessary to guarantee proper behaviour even if |
2044 | initialised. This is necessary to guarantee proper behaviour even if |
… | |
… | |
2010 | the process. The exception are C<ev_stat> watchers - those call C<stat |
2206 | the process. The exception are C<ev_stat> watchers - those call C<stat |
2011 | ()>, which is a synchronous operation. |
2207 | ()>, which is a synchronous operation. |
2012 | |
2208 | |
2013 | For local paths, this usually doesn't matter: unless the system is very |
2209 | For local paths, this usually doesn't matter: unless the system is very |
2014 | busy or the intervals between stat's are large, a stat call will be fast, |
2210 | busy or the intervals between stat's are large, a stat call will be fast, |
2015 | as the path data is suually in memory already (except when starting the |
2211 | as the path data is usually in memory already (except when starting the |
2016 | watcher). |
2212 | watcher). |
2017 | |
2213 | |
2018 | For networked file systems, calling C<stat ()> can block an indefinite |
2214 | For networked file systems, calling C<stat ()> can block an indefinite |
2019 | time due to network issues, and even under good conditions, a stat call |
2215 | time due to network issues, and even under good conditions, a stat call |
2020 | often takes multiple milliseconds. |
2216 | often takes multiple milliseconds. |
… | |
… | |
2177 | |
2373 | |
2178 | =head3 Watcher-Specific Functions and Data Members |
2374 | =head3 Watcher-Specific Functions and Data Members |
2179 | |
2375 | |
2180 | =over 4 |
2376 | =over 4 |
2181 | |
2377 | |
2182 | =item ev_idle_init (ev_signal *, callback) |
2378 | =item ev_idle_init (ev_idle *, callback) |
2183 | |
2379 | |
2184 | Initialises and configures the idle watcher - it has no parameters of any |
2380 | Initialises and configures the idle watcher - it has no parameters of any |
2185 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2381 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2186 | believe me. |
2382 | believe me. |
2187 | |
2383 | |
… | |
… | |
2200 | // no longer anything immediate to do. |
2396 | // no longer anything immediate to do. |
2201 | } |
2397 | } |
2202 | |
2398 | |
2203 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2399 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2204 | ev_idle_init (idle_watcher, idle_cb); |
2400 | ev_idle_init (idle_watcher, idle_cb); |
2205 | ev_idle_start (loop, idle_cb); |
2401 | ev_idle_start (loop, idle_watcher); |
2206 | |
2402 | |
2207 | |
2403 | |
2208 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2404 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2209 | |
2405 | |
2210 | Prepare and check watchers are usually (but not always) used in pairs: |
2406 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2303 | struct pollfd fds [nfd]; |
2499 | struct pollfd fds [nfd]; |
2304 | // actual code will need to loop here and realloc etc. |
2500 | // actual code will need to loop here and realloc etc. |
2305 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2501 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2306 | |
2502 | |
2307 | /* the callback is illegal, but won't be called as we stop during check */ |
2503 | /* the callback is illegal, but won't be called as we stop during check */ |
2308 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2504 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2309 | ev_timer_start (loop, &tw); |
2505 | ev_timer_start (loop, &tw); |
2310 | |
2506 | |
2311 | // create one ev_io per pollfd |
2507 | // create one ev_io per pollfd |
2312 | for (int i = 0; i < nfd; ++i) |
2508 | for (int i = 0; i < nfd; ++i) |
2313 | { |
2509 | { |
… | |
… | |
2426 | some fds have to be watched and handled very quickly (with low latency), |
2622 | some fds have to be watched and handled very quickly (with low latency), |
2427 | and even priorities and idle watchers might have too much overhead. In |
2623 | and even priorities and idle watchers might have too much overhead. In |
2428 | this case you would put all the high priority stuff in one loop and all |
2624 | this case you would put all the high priority stuff in one loop and all |
2429 | the rest in a second one, and embed the second one in the first. |
2625 | the rest in a second one, and embed the second one in the first. |
2430 | |
2626 | |
2431 | As long as the watcher is active, the callback will be invoked every time |
2627 | As long as the watcher is active, the callback will be invoked every |
2432 | there might be events pending in the embedded loop. The callback must then |
2628 | time there might be events pending in the embedded loop. The callback |
2433 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2629 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2434 | their callbacks (you could also start an idle watcher to give the embedded |
2630 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2435 | loop strictly lower priority for example). You can also set the callback |
2631 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2436 | to C<0>, in which case the embed watcher will automatically execute the |
2632 | to give the embedded loop strictly lower priority for example). |
2437 | embedded loop sweep. |
|
|
2438 | |
2633 | |
2439 | As long as the watcher is started it will automatically handle events. The |
2634 | You can also set the callback to C<0>, in which case the embed watcher |
2440 | callback will be invoked whenever some events have been handled. You can |
2635 | will automatically execute the embedded loop sweep whenever necessary. |
2441 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2442 | interested in that. |
|
|
2443 | |
2636 | |
2444 | Also, there have not currently been made special provisions for forking: |
2637 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2445 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2638 | is active, i.e., the embedded loop will automatically be forked when the |
2446 | but you will also have to stop and restart any C<ev_embed> watchers |
2639 | embedding loop forks. In other cases, the user is responsible for calling |
2447 | yourself - but you can use a fork watcher to handle this automatically, |
2640 | C<ev_loop_fork> on the embedded loop. |
2448 | and future versions of libev might do just that. |
|
|
2449 | |
2641 | |
2450 | Unfortunately, not all backends are embeddable: only the ones returned by |
2642 | Unfortunately, not all backends are embeddable: only the ones returned by |
2451 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2643 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2452 | portable one. |
2644 | portable one. |
2453 | |
2645 | |
… | |
… | |
2547 | event loop blocks next and before C<ev_check> watchers are being called, |
2739 | event loop blocks next and before C<ev_check> watchers are being called, |
2548 | and only in the child after the fork. If whoever good citizen calling |
2740 | and only in the child after the fork. If whoever good citizen calling |
2549 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2741 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2550 | handlers will be invoked, too, of course. |
2742 | handlers will be invoked, too, of course. |
2551 | |
2743 | |
|
|
2744 | =head3 The special problem of life after fork - how is it possible? |
|
|
2745 | |
|
|
2746 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2747 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2748 | sequence should be handled by libev without any problems. |
|
|
2749 | |
|
|
2750 | This changes when the application actually wants to do event handling |
|
|
2751 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2752 | fork. |
|
|
2753 | |
|
|
2754 | The default mode of operation (for libev, with application help to detect |
|
|
2755 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2756 | when I<either> the parent I<or> the child process continues. |
|
|
2757 | |
|
|
2758 | When both processes want to continue using libev, then this is usually the |
|
|
2759 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2760 | supposed to continue with all watchers in place as before, while the other |
|
|
2761 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2762 | |
|
|
2763 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2764 | simply create a new event loop, which of course will be "empty", and |
|
|
2765 | use that for new watchers. This has the advantage of not touching more |
|
|
2766 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2767 | disadvantage of having to use multiple event loops (which do not support |
|
|
2768 | signal watchers). |
|
|
2769 | |
|
|
2770 | When this is not possible, or you want to use the default loop for |
|
|
2771 | other reasons, then in the process that wants to start "fresh", call |
|
|
2772 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2773 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2774 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2775 | also that in that case, you have to re-register any signal watchers. |
|
|
2776 | |
2552 | =head3 Watcher-Specific Functions and Data Members |
2777 | =head3 Watcher-Specific Functions and Data Members |
2553 | |
2778 | |
2554 | =over 4 |
2779 | =over 4 |
2555 | |
2780 | |
2556 | =item ev_fork_init (ev_signal *, callback) |
2781 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2684 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2909 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2685 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2910 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2686 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2911 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2687 | section below on what exactly this means). |
2912 | section below on what exactly this means). |
2688 | |
2913 | |
|
|
2914 | Note that, as with other watchers in libev, multiple events might get |
|
|
2915 | compressed into a single callback invocation (another way to look at this |
|
|
2916 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2917 | reset when the event loop detects that). |
|
|
2918 | |
2689 | This call incurs the overhead of a system call only once per loop iteration, |
2919 | This call incurs the overhead of a system call only once per event loop |
2690 | so while the overhead might be noticeable, it doesn't apply to repeated |
2920 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2691 | calls to C<ev_async_send>. |
2921 | repeated calls to C<ev_async_send> for the same event loop. |
2692 | |
2922 | |
2693 | =item bool = ev_async_pending (ev_async *) |
2923 | =item bool = ev_async_pending (ev_async *) |
2694 | |
2924 | |
2695 | Returns a non-zero value when C<ev_async_send> has been called on the |
2925 | Returns a non-zero value when C<ev_async_send> has been called on the |
2696 | watcher but the event has not yet been processed (or even noted) by the |
2926 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2699 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2929 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2700 | the loop iterates next and checks for the watcher to have become active, |
2930 | the loop iterates next and checks for the watcher to have become active, |
2701 | it will reset the flag again. C<ev_async_pending> can be used to very |
2931 | it will reset the flag again. C<ev_async_pending> can be used to very |
2702 | quickly check whether invoking the loop might be a good idea. |
2932 | quickly check whether invoking the loop might be a good idea. |
2703 | |
2933 | |
2704 | Not that this does I<not> check whether the watcher itself is pending, only |
2934 | Not that this does I<not> check whether the watcher itself is pending, |
2705 | whether it has been requested to make this watcher pending. |
2935 | only whether it has been requested to make this watcher pending: there |
|
|
2936 | is a time window between the event loop checking and resetting the async |
|
|
2937 | notification, and the callback being invoked. |
2706 | |
2938 | |
2707 | =back |
2939 | =back |
2708 | |
2940 | |
2709 | |
2941 | |
2710 | =head1 OTHER FUNCTIONS |
2942 | =head1 OTHER FUNCTIONS |
… | |
… | |
2889 | |
3121 | |
2890 | myclass obj; |
3122 | myclass obj; |
2891 | ev::io iow; |
3123 | ev::io iow; |
2892 | iow.set <myclass, &myclass::io_cb> (&obj); |
3124 | iow.set <myclass, &myclass::io_cb> (&obj); |
2893 | |
3125 | |
|
|
3126 | =item w->set (object *) |
|
|
3127 | |
|
|
3128 | This is an B<experimental> feature that might go away in a future version. |
|
|
3129 | |
|
|
3130 | This is a variation of a method callback - leaving out the method to call |
|
|
3131 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3132 | functor objects without having to manually specify the C<operator ()> all |
|
|
3133 | the time. Incidentally, you can then also leave out the template argument |
|
|
3134 | list. |
|
|
3135 | |
|
|
3136 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3137 | int revents)>. |
|
|
3138 | |
|
|
3139 | See the method-C<set> above for more details. |
|
|
3140 | |
|
|
3141 | Example: use a functor object as callback. |
|
|
3142 | |
|
|
3143 | struct myfunctor |
|
|
3144 | { |
|
|
3145 | void operator() (ev::io &w, int revents) |
|
|
3146 | { |
|
|
3147 | ... |
|
|
3148 | } |
|
|
3149 | } |
|
|
3150 | |
|
|
3151 | myfunctor f; |
|
|
3152 | |
|
|
3153 | ev::io w; |
|
|
3154 | w.set (&f); |
|
|
3155 | |
2894 | =item w->set<function> (void *data = 0) |
3156 | =item w->set<function> (void *data = 0) |
2895 | |
3157 | |
2896 | Also sets a callback, but uses a static method or plain function as |
3158 | Also sets a callback, but uses a static method or plain function as |
2897 | callback. The optional C<data> argument will be stored in the watcher's |
3159 | callback. The optional C<data> argument will be stored in the watcher's |
2898 | C<data> member and is free for you to use. |
3160 | C<data> member and is free for you to use. |
… | |
… | |
2984 | L<http://software.schmorp.de/pkg/EV>. |
3246 | L<http://software.schmorp.de/pkg/EV>. |
2985 | |
3247 | |
2986 | =item Python |
3248 | =item Python |
2987 | |
3249 | |
2988 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3250 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2989 | seems to be quite complete and well-documented. Note, however, that the |
3251 | seems to be quite complete and well-documented. |
2990 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2991 | for everybody else, and therefore, should never be applied in an installed |
|
|
2992 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2993 | libev). |
|
|
2994 | |
3252 | |
2995 | =item Ruby |
3253 | =item Ruby |
2996 | |
3254 | |
2997 | Tony Arcieri has written a ruby extension that offers access to a subset |
3255 | Tony Arcieri has written a ruby extension that offers access to a subset |
2998 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3256 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2999 | more on top of it. It can be found via gem servers. Its homepage is at |
3257 | more on top of it. It can be found via gem servers. Its homepage is at |
3000 | L<http://rev.rubyforge.org/>. |
3258 | L<http://rev.rubyforge.org/>. |
|
|
3259 | |
|
|
3260 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3261 | makes rev work even on mingw. |
|
|
3262 | |
|
|
3263 | =item Haskell |
|
|
3264 | |
|
|
3265 | A haskell binding to libev is available at |
|
|
3266 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3001 | |
3267 | |
3002 | =item D |
3268 | =item D |
3003 | |
3269 | |
3004 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3270 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3005 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3271 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
… | |
… | |
3182 | keeps libev from including F<config.h>, and it also defines dummy |
3448 | keeps libev from including F<config.h>, and it also defines dummy |
3183 | implementations for some libevent functions (such as logging, which is not |
3449 | implementations for some libevent functions (such as logging, which is not |
3184 | supported). It will also not define any of the structs usually found in |
3450 | supported). It will also not define any of the structs usually found in |
3185 | F<event.h> that are not directly supported by the libev core alone. |
3451 | F<event.h> that are not directly supported by the libev core alone. |
3186 | |
3452 | |
|
|
3453 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3454 | configuration, but has to be more conservative. |
|
|
3455 | |
3187 | =item EV_USE_MONOTONIC |
3456 | =item EV_USE_MONOTONIC |
3188 | |
3457 | |
3189 | If defined to be C<1>, libev will try to detect the availability of the |
3458 | If defined to be C<1>, libev will try to detect the availability of the |
3190 | monotonic clock option at both compile time and runtime. Otherwise no use |
3459 | monotonic clock option at both compile time and runtime. Otherwise no |
3191 | of the monotonic clock option will be attempted. If you enable this, you |
3460 | use of the monotonic clock option will be attempted. If you enable this, |
3192 | usually have to link against librt or something similar. Enabling it when |
3461 | you usually have to link against librt or something similar. Enabling it |
3193 | the functionality isn't available is safe, though, although you have |
3462 | when the functionality isn't available is safe, though, although you have |
3194 | to make sure you link against any libraries where the C<clock_gettime> |
3463 | to make sure you link against any libraries where the C<clock_gettime> |
3195 | function is hiding in (often F<-lrt>). |
3464 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3196 | |
3465 | |
3197 | =item EV_USE_REALTIME |
3466 | =item EV_USE_REALTIME |
3198 | |
3467 | |
3199 | If defined to be C<1>, libev will try to detect the availability of the |
3468 | If defined to be C<1>, libev will try to detect the availability of the |
3200 | real-time clock option at compile time (and assume its availability at |
3469 | real-time clock option at compile time (and assume its availability |
3201 | runtime if successful). Otherwise no use of the real-time clock option will |
3470 | at runtime if successful). Otherwise no use of the real-time clock |
3202 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3471 | option will be attempted. This effectively replaces C<gettimeofday> |
3203 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3472 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3204 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3473 | correctness. See the note about libraries in the description of |
|
|
3474 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3475 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3476 | |
|
|
3477 | =item EV_USE_CLOCK_SYSCALL |
|
|
3478 | |
|
|
3479 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3480 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3481 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3482 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3483 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3484 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3485 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3486 | higher, as it simplifies linking (no need for C<-lrt>). |
3205 | |
3487 | |
3206 | =item EV_USE_NANOSLEEP |
3488 | =item EV_USE_NANOSLEEP |
3207 | |
3489 | |
3208 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3490 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3209 | and will use it for delays. Otherwise it will use C<select ()>. |
3491 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3225 | |
3507 | |
3226 | =item EV_SELECT_USE_FD_SET |
3508 | =item EV_SELECT_USE_FD_SET |
3227 | |
3509 | |
3228 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3510 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3229 | structure. This is useful if libev doesn't compile due to a missing |
3511 | structure. This is useful if libev doesn't compile due to a missing |
3230 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3512 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3231 | exotic systems. This usually limits the range of file descriptors to some |
3513 | on exotic systems. This usually limits the range of file descriptors to |
3232 | low limit such as 1024 or might have other limitations (winsocket only |
3514 | some low limit such as 1024 or might have other limitations (winsocket |
3233 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3515 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3234 | influence the size of the C<fd_set> used. |
3516 | configures the maximum size of the C<fd_set>. |
3235 | |
3517 | |
3236 | =item EV_SELECT_IS_WINSOCKET |
3518 | =item EV_SELECT_IS_WINSOCKET |
3237 | |
3519 | |
3238 | When defined to C<1>, the select backend will assume that |
3520 | When defined to C<1>, the select backend will assume that |
3239 | select/socket/connect etc. don't understand file descriptors but |
3521 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3389 | defined to be C<0>, then they are not. |
3671 | defined to be C<0>, then they are not. |
3390 | |
3672 | |
3391 | =item EV_MINIMAL |
3673 | =item EV_MINIMAL |
3392 | |
3674 | |
3393 | If you need to shave off some kilobytes of code at the expense of some |
3675 | If you need to shave off some kilobytes of code at the expense of some |
3394 | speed, define this symbol to C<1>. Currently this is used to override some |
3676 | speed (but with the full API), define this symbol to C<1>. Currently this |
3395 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3677 | is used to override some inlining decisions, saves roughly 30% code size |
3396 | much smaller 2-heap for timer management over the default 4-heap. |
3678 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3679 | the default 4-heap. |
|
|
3680 | |
|
|
3681 | You can save even more by disabling watcher types you do not need |
|
|
3682 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3683 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3684 | |
|
|
3685 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3686 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3687 | of the API are still available, and do not complain if this subset changes |
|
|
3688 | over time. |
3397 | |
3689 | |
3398 | =item EV_PID_HASHSIZE |
3690 | =item EV_PID_HASHSIZE |
3399 | |
3691 | |
3400 | C<ev_child> watchers use a small hash table to distribute workload by |
3692 | C<ev_child> watchers use a small hash table to distribute workload by |
3401 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3693 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3681 | way (note also that glib is the slowest event library known to man). |
3973 | way (note also that glib is the slowest event library known to man). |
3682 | |
3974 | |
3683 | There is no supported compilation method available on windows except |
3975 | There is no supported compilation method available on windows except |
3684 | embedding it into other applications. |
3976 | embedding it into other applications. |
3685 | |
3977 | |
|
|
3978 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
3979 | tries its best, but under most conditions, signals will simply not work. |
|
|
3980 | |
3686 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3981 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3687 | accept large writes: instead of resulting in a partial write, windows will |
3982 | accept large writes: instead of resulting in a partial write, windows will |
3688 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3983 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3689 | so make sure you only write small amounts into your sockets (less than a |
3984 | so make sure you only write small amounts into your sockets (less than a |
3690 | megabyte seems safe, but this apparently depends on the amount of memory |
3985 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3694 | the abysmal performance of winsockets, using a large number of sockets |
3989 | the abysmal performance of winsockets, using a large number of sockets |
3695 | is not recommended (and not reasonable). If your program needs to use |
3990 | is not recommended (and not reasonable). If your program needs to use |
3696 | more than a hundred or so sockets, then likely it needs to use a totally |
3991 | more than a hundred or so sockets, then likely it needs to use a totally |
3697 | different implementation for windows, as libev offers the POSIX readiness |
3992 | different implementation for windows, as libev offers the POSIX readiness |
3698 | notification model, which cannot be implemented efficiently on windows |
3993 | notification model, which cannot be implemented efficiently on windows |
3699 | (Microsoft monopoly games). |
3994 | (due to Microsoft monopoly games). |
3700 | |
3995 | |
3701 | A typical way to use libev under windows is to embed it (see the embedding |
3996 | A typical way to use libev under windows is to embed it (see the embedding |
3702 | section for details) and use the following F<evwrap.h> header file instead |
3997 | section for details) and use the following F<evwrap.h> header file instead |
3703 | of F<ev.h>: |
3998 | of F<ev.h>: |
3704 | |
3999 | |
… | |
… | |
3740 | |
4035 | |
3741 | Early versions of winsocket's select only supported waiting for a maximum |
4036 | Early versions of winsocket's select only supported waiting for a maximum |
3742 | of C<64> handles (probably owning to the fact that all windows kernels |
4037 | of C<64> handles (probably owning to the fact that all windows kernels |
3743 | can only wait for C<64> things at the same time internally; Microsoft |
4038 | can only wait for C<64> things at the same time internally; Microsoft |
3744 | recommends spawning a chain of threads and wait for 63 handles and the |
4039 | recommends spawning a chain of threads and wait for 63 handles and the |
3745 | previous thread in each. Great). |
4040 | previous thread in each. Sounds great!). |
3746 | |
4041 | |
3747 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4042 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3748 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4043 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3749 | call (which might be in libev or elsewhere, for example, perl does its own |
4044 | call (which might be in libev or elsewhere, for example, perl and many |
3750 | select emulation on windows). |
4045 | other interpreters do their own select emulation on windows). |
3751 | |
4046 | |
3752 | Another limit is the number of file descriptors in the Microsoft runtime |
4047 | Another limit is the number of file descriptors in the Microsoft runtime |
3753 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4048 | libraries, which by default is C<64> (there must be a hidden I<64> |
3754 | or something like this inside Microsoft). You can increase this by calling |
4049 | fetish or something like this inside Microsoft). You can increase this |
3755 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4050 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3756 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4051 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3757 | libraries. |
|
|
3758 | |
|
|
3759 | This might get you to about C<512> or C<2048> sockets (depending on |
4052 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3760 | windows version and/or the phase of the moon). To get more, you need to |
4053 | (depending on windows version and/or the phase of the moon). To get more, |
3761 | wrap all I/O functions and provide your own fd management, but the cost of |
4054 | you need to wrap all I/O functions and provide your own fd management, but |
3762 | calling select (O(n²)) will likely make this unworkable. |
4055 | the cost of calling select (O(n²)) will likely make this unworkable. |
3763 | |
4056 | |
3764 | =back |
4057 | =back |
3765 | |
4058 | |
3766 | =head2 PORTABILITY REQUIREMENTS |
4059 | =head2 PORTABILITY REQUIREMENTS |
3767 | |
4060 | |
… | |
… | |
3810 | =item C<double> must hold a time value in seconds with enough accuracy |
4103 | =item C<double> must hold a time value in seconds with enough accuracy |
3811 | |
4104 | |
3812 | The type C<double> is used to represent timestamps. It is required to |
4105 | The type C<double> is used to represent timestamps. It is required to |
3813 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4106 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3814 | enough for at least into the year 4000. This requirement is fulfilled by |
4107 | enough for at least into the year 4000. This requirement is fulfilled by |
3815 | implementations implementing IEEE 754 (basically all existing ones). |
4108 | implementations implementing IEEE 754, which is basically all existing |
|
|
4109 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4110 | 2200. |
3816 | |
4111 | |
3817 | =back |
4112 | =back |
3818 | |
4113 | |
3819 | If you know of other additional requirements drop me a note. |
4114 | If you know of other additional requirements drop me a note. |
3820 | |
4115 | |
… | |
… | |
3888 | involves iterating over all running async watchers or all signal numbers. |
4183 | involves iterating over all running async watchers or all signal numbers. |
3889 | |
4184 | |
3890 | =back |
4185 | =back |
3891 | |
4186 | |
3892 | |
4187 | |
|
|
4188 | =head1 GLOSSARY |
|
|
4189 | |
|
|
4190 | =over 4 |
|
|
4191 | |
|
|
4192 | =item active |
|
|
4193 | |
|
|
4194 | A watcher is active as long as it has been started (has been attached to |
|
|
4195 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4196 | |
|
|
4197 | =item application |
|
|
4198 | |
|
|
4199 | In this document, an application is whatever is using libev. |
|
|
4200 | |
|
|
4201 | =item callback |
|
|
4202 | |
|
|
4203 | The address of a function that is called when some event has been |
|
|
4204 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4205 | received the event, and the actual event bitset. |
|
|
4206 | |
|
|
4207 | =item callback invocation |
|
|
4208 | |
|
|
4209 | The act of calling the callback associated with a watcher. |
|
|
4210 | |
|
|
4211 | =item event |
|
|
4212 | |
|
|
4213 | A change of state of some external event, such as data now being available |
|
|
4214 | for reading on a file descriptor, time having passed or simply not having |
|
|
4215 | any other events happening anymore. |
|
|
4216 | |
|
|
4217 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4218 | C<EV_TIMEOUT>). |
|
|
4219 | |
|
|
4220 | =item event library |
|
|
4221 | |
|
|
4222 | A software package implementing an event model and loop. |
|
|
4223 | |
|
|
4224 | =item event loop |
|
|
4225 | |
|
|
4226 | An entity that handles and processes external events and converts them |
|
|
4227 | into callback invocations. |
|
|
4228 | |
|
|
4229 | =item event model |
|
|
4230 | |
|
|
4231 | The model used to describe how an event loop handles and processes |
|
|
4232 | watchers and events. |
|
|
4233 | |
|
|
4234 | =item pending |
|
|
4235 | |
|
|
4236 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4237 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4238 | pending status is explicitly cleared by the application. |
|
|
4239 | |
|
|
4240 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4241 | its pending status. |
|
|
4242 | |
|
|
4243 | =item real time |
|
|
4244 | |
|
|
4245 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4246 | |
|
|
4247 | =item wall-clock time |
|
|
4248 | |
|
|
4249 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4250 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4251 | clock. |
|
|
4252 | |
|
|
4253 | =item watcher |
|
|
4254 | |
|
|
4255 | A data structure that describes interest in certain events. Watchers need |
|
|
4256 | to be started (attached to an event loop) before they can receive events. |
|
|
4257 | |
|
|
4258 | =item watcher invocation |
|
|
4259 | |
|
|
4260 | The act of calling the callback associated with a watcher. |
|
|
4261 | |
|
|
4262 | =back |
|
|
4263 | |
3893 | =head1 AUTHOR |
4264 | =head1 AUTHOR |
3894 | |
4265 | |
3895 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
4266 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3896 | |
4267 | |