… | |
… | |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // unloop was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
|
|
68 | |
|
|
69 | This document documents the libev software package. |
68 | |
70 | |
69 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
70 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
71 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
|
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74 | |
|
|
75 | While this document tries to be as complete as possible in documenting |
|
|
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
|
|
77 | on event-based programming, nor will it introduce event-based programming |
|
|
78 | with libev. |
|
|
79 | |
|
|
80 | Familarity with event based programming techniques in general is assumed |
|
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81 | throughout this document. |
|
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82 | |
|
|
83 | =head1 ABOUT LIBEV |
72 | |
84 | |
73 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
74 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
75 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
76 | |
88 | |
… | |
… | |
110 | name C<loop> (which is always of type C<ev_loop *>) will not have |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
111 | this argument. |
123 | this argument. |
112 | |
124 | |
113 | =head2 TIME REPRESENTATION |
125 | =head2 TIME REPRESENTATION |
114 | |
126 | |
115 | Libev represents time as a single floating point number, representing the |
127 | Libev represents time as a single floating point number, representing |
116 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
117 | the beginning of 1970, details are complicated, don't ask). This type is |
129 | near the beginning of 1970, details are complicated, don't ask). This |
118 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
130 | type is called C<ev_tstamp>, which is what you should use too. It usually |
119 | to the C<double> type in C, and when you need to do any calculations on |
131 | aliases to the C<double> type in C. When you need to do any calculations |
120 | it, you should treat it as some floating point value. Unlike the name |
132 | on it, you should treat it as some floating point value. Unlike the name |
121 | component C<stamp> might indicate, it is also used for time differences |
133 | component C<stamp> might indicate, it is also used for time differences |
122 | throughout libev. |
134 | throughout libev. |
123 | |
135 | |
124 | =head1 ERROR HANDLING |
136 | =head1 ERROR HANDLING |
125 | |
137 | |
… | |
… | |
460 | |
472 | |
461 | While nominally embeddable in other event loops, this doesn't work |
473 | While nominally embeddable in other event loops, this doesn't work |
462 | 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 |
463 | 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 |
464 | (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 |
465 | (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 |
466 | using it only for sockets. |
478 | also broken on OS X)) and, did I mention it, using it only for sockets. |
467 | |
479 | |
468 | 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 |
469 | 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 |
470 | C<NOTE_EOF>. |
482 | C<NOTE_EOF>. |
471 | |
483 | |
… | |
… | |
633 | This function is rarely useful, but when some event callback runs for a |
645 | This function is rarely useful, but when some event callback runs for a |
634 | very long time without entering the event loop, updating libev's idea of |
646 | very long time without entering the event loop, updating libev's idea of |
635 | the current time is a good idea. |
647 | the current time is a good idea. |
636 | |
648 | |
637 | See also "The special problem of time updates" in the C<ev_timer> section. |
649 | See also "The special problem of time updates" in the C<ev_timer> section. |
|
|
650 | |
|
|
651 | =item ev_suspend (loop) |
|
|
652 | |
|
|
653 | =item ev_resume (loop) |
|
|
654 | |
|
|
655 | These two functions suspend and resume a loop, for use when the loop is |
|
|
656 | not used for a while and timeouts should not be processed. |
|
|
657 | |
|
|
658 | A typical use case would be an interactive program such as a game: When |
|
|
659 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
660 | would be best to handle timeouts as if no time had actually passed while |
|
|
661 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
662 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
663 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
664 | |
|
|
665 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
666 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
667 | will be rescheduled (that is, they will lose any events that would have |
|
|
668 | occured while suspended). |
|
|
669 | |
|
|
670 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
671 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
672 | without a previous call to C<ev_suspend>. |
|
|
673 | |
|
|
674 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
675 | event loop time (see C<ev_now_update>). |
638 | |
676 | |
639 | =item ev_loop (loop, int flags) |
677 | =item ev_loop (loop, int flags) |
640 | |
678 | |
641 | Finally, this is it, the event handler. This function usually is called |
679 | Finally, this is it, the event handler. This function usually is called |
642 | after you initialised all your watchers and you want to start handling |
680 | after you initialised all your watchers and you want to start handling |
… | |
… | |
726 | |
764 | |
727 | If you have a watcher you never unregister that should not keep C<ev_loop> |
765 | If you have a watcher you never unregister that should not keep C<ev_loop> |
728 | from returning, call ev_unref() after starting, and ev_ref() before |
766 | from returning, call ev_unref() after starting, and ev_ref() before |
729 | stopping it. |
767 | stopping it. |
730 | |
768 | |
731 | As an example, libev itself uses this for its internal signal pipe: It is |
769 | As an example, libev itself uses this for its internal signal pipe: It |
732 | not visible to the libev user and should not keep C<ev_loop> from exiting |
770 | is not visible to the libev user and should not keep C<ev_loop> from |
733 | if no event watchers registered by it are active. It is also an excellent |
771 | exiting if no event watchers registered by it are active. It is also an |
734 | way to do this for generic recurring timers or from within third-party |
772 | excellent way to do this for generic recurring timers or from within |
735 | libraries. Just remember to I<unref after start> and I<ref before stop> |
773 | third-party libraries. Just remember to I<unref after start> and I<ref |
736 | (but only if the watcher wasn't active before, or was active before, |
774 | before stop> (but only if the watcher wasn't active before, or was active |
737 | respectively). |
775 | before, respectively. Note also that libev might stop watchers itself |
|
|
776 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
777 | in the callback). |
738 | |
778 | |
739 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
779 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
740 | running when nothing else is active. |
780 | running when nothing else is active. |
741 | |
781 | |
742 | ev_signal exitsig; |
782 | ev_signal exitsig; |
… | |
… | |
926 | |
966 | |
927 | =item C<EV_ASYNC> |
967 | =item C<EV_ASYNC> |
928 | |
968 | |
929 | The given async watcher has been asynchronously notified (see C<ev_async>). |
969 | The given async watcher has been asynchronously notified (see C<ev_async>). |
930 | |
970 | |
|
|
971 | =item C<EV_CUSTOM> |
|
|
972 | |
|
|
973 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
974 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
975 | |
931 | =item C<EV_ERROR> |
976 | =item C<EV_ERROR> |
932 | |
977 | |
933 | An unspecified error has occurred, the watcher has been stopped. This might |
978 | An unspecified error has occurred, the watcher has been stopped. This might |
934 | happen because the watcher could not be properly started because libev |
979 | happen because the watcher could not be properly started because libev |
935 | ran out of memory, a file descriptor was found to be closed or any other |
980 | ran out of memory, a file descriptor was found to be closed or any other |
… | |
… | |
1050 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1095 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1051 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1096 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1052 | before watchers with lower priority, but priority will not keep watchers |
1097 | before watchers with lower priority, but priority will not keep watchers |
1053 | from being executed (except for C<ev_idle> watchers). |
1098 | from being executed (except for C<ev_idle> watchers). |
1054 | |
1099 | |
1055 | This means that priorities are I<only> used for ordering callback |
|
|
1056 | invocation after new events have been received. This is useful, for |
|
|
1057 | example, to reduce latency after idling, or more often, to bind two |
|
|
1058 | watchers on the same event and make sure one is called first. |
|
|
1059 | |
|
|
1060 | If you need to suppress invocation when higher priority events are pending |
1100 | If you need to suppress invocation when higher priority events are pending |
1061 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1101 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1062 | |
1102 | |
1063 | You I<must not> change the priority of a watcher as long as it is active or |
1103 | You I<must not> change the priority of a watcher as long as it is active or |
1064 | pending. |
1104 | pending. |
1065 | |
|
|
1066 | The default priority used by watchers when no priority has been set is |
|
|
1067 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1068 | |
1105 | |
1069 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1106 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1070 | fine, as long as you do not mind that the priority value you query might |
1107 | fine, as long as you do not mind that the priority value you query might |
1071 | or might not have been clamped to the valid range. |
1108 | or might not have been clamped to the valid range. |
|
|
1109 | |
|
|
1110 | The default priority used by watchers when no priority has been set is |
|
|
1111 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1112 | |
|
|
1113 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1114 | priorities. |
1072 | |
1115 | |
1073 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1116 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1074 | |
1117 | |
1075 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1118 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1076 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1119 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1151 | t2_cb (EV_P_ ev_timer *w, int revents) |
1194 | t2_cb (EV_P_ ev_timer *w, int revents) |
1152 | { |
1195 | { |
1153 | struct my_biggy big = (struct my_biggy * |
1196 | struct my_biggy big = (struct my_biggy * |
1154 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1197 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1155 | } |
1198 | } |
|
|
1199 | |
|
|
1200 | =head2 WATCHER PRIORITY MODELS |
|
|
1201 | |
|
|
1202 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1203 | integers that influence the ordering of event callback invocation |
|
|
1204 | between watchers in some way, all else being equal. |
|
|
1205 | |
|
|
1206 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1207 | description for the more technical details such as the actual priority |
|
|
1208 | range. |
|
|
1209 | |
|
|
1210 | There are two common ways how these these priorities are being interpreted |
|
|
1211 | by event loops: |
|
|
1212 | |
|
|
1213 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1214 | of lower priority watchers, which means as long as higher priority |
|
|
1215 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1216 | |
|
|
1217 | The less common only-for-ordering model uses priorities solely to order |
|
|
1218 | callback invocation within a single event loop iteration: Higher priority |
|
|
1219 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1220 | before polling for new events. |
|
|
1221 | |
|
|
1222 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1223 | except for idle watchers (which use the lock-out model). |
|
|
1224 | |
|
|
1225 | The rationale behind this is that implementing the lock-out model for |
|
|
1226 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1227 | libraries will just poll for the same events again and again as long as |
|
|
1228 | their callbacks have not been executed, which is very inefficient in the |
|
|
1229 | common case of one high-priority watcher locking out a mass of lower |
|
|
1230 | priority ones. |
|
|
1231 | |
|
|
1232 | Static (ordering) priorities are most useful when you have two or more |
|
|
1233 | watchers handling the same resource: a typical usage example is having an |
|
|
1234 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1235 | timeouts. Under load, data might be received while the program handles |
|
|
1236 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1237 | handler will be executed before checking for data. In that case, giving |
|
|
1238 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1239 | handled first even under adverse conditions (which is usually, but not |
|
|
1240 | always, what you want). |
|
|
1241 | |
|
|
1242 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1243 | will only be executed when no same or higher priority watchers have |
|
|
1244 | received events, they can be used to implement the "lock-out" model when |
|
|
1245 | required. |
|
|
1246 | |
|
|
1247 | For example, to emulate how many other event libraries handle priorities, |
|
|
1248 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1249 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1250 | processing is done in the idle watcher callback. This causes libev to |
|
|
1251 | continously poll and process kernel event data for the watcher, but when |
|
|
1252 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1253 | workable. |
|
|
1254 | |
|
|
1255 | Usually, however, the lock-out model implemented that way will perform |
|
|
1256 | miserably under the type of load it was designed to handle. In that case, |
|
|
1257 | it might be preferable to stop the real watcher before starting the |
|
|
1258 | idle watcher, so the kernel will not have to process the event in case |
|
|
1259 | the actual processing will be delayed for considerable time. |
|
|
1260 | |
|
|
1261 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1262 | priority than the default, and which should only process data when no |
|
|
1263 | other events are pending: |
|
|
1264 | |
|
|
1265 | ev_idle idle; // actual processing watcher |
|
|
1266 | ev_io io; // actual event watcher |
|
|
1267 | |
|
|
1268 | static void |
|
|
1269 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1270 | { |
|
|
1271 | // stop the I/O watcher, we received the event, but |
|
|
1272 | // are not yet ready to handle it. |
|
|
1273 | ev_io_stop (EV_A_ w); |
|
|
1274 | |
|
|
1275 | // start the idle watcher to ahndle the actual event. |
|
|
1276 | // it will not be executed as long as other watchers |
|
|
1277 | // with the default priority are receiving events. |
|
|
1278 | ev_idle_start (EV_A_ &idle); |
|
|
1279 | } |
|
|
1280 | |
|
|
1281 | static void |
|
|
1282 | idle-cb (EV_P_ ev_idle *w, int revents) |
|
|
1283 | { |
|
|
1284 | // actual processing |
|
|
1285 | read (STDIN_FILENO, ...); |
|
|
1286 | |
|
|
1287 | // have to start the I/O watcher again, as |
|
|
1288 | // we have handled the event |
|
|
1289 | ev_io_start (EV_P_ &io); |
|
|
1290 | } |
|
|
1291 | |
|
|
1292 | // initialisation |
|
|
1293 | ev_idle_init (&idle, idle_cb); |
|
|
1294 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1295 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1296 | |
|
|
1297 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1298 | low-priority connections can not be locked out forever under load. This |
|
|
1299 | enables your program to keep a lower latency for important connections |
|
|
1300 | during short periods of high load, while not completely locking out less |
|
|
1301 | important ones. |
1156 | |
1302 | |
1157 | |
1303 | |
1158 | =head1 WATCHER TYPES |
1304 | =head1 WATCHER TYPES |
1159 | |
1305 | |
1160 | This section describes each watcher in detail, but will not repeat |
1306 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1317 | year, it will still time out after (roughly) one hour. "Roughly" because |
1463 | year, it will still time out after (roughly) one hour. "Roughly" because |
1318 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1464 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1319 | monotonic clock option helps a lot here). |
1465 | monotonic clock option helps a lot here). |
1320 | |
1466 | |
1321 | The callback is guaranteed to be invoked only I<after> its timeout has |
1467 | The callback is guaranteed to be invoked only I<after> its timeout has |
1322 | passed, but if multiple timers become ready during the same loop iteration |
1468 | passed. If multiple timers become ready during the same loop iteration |
1323 | then order of execution is undefined. |
1469 | then the ones with earlier time-out values are invoked before ones with |
|
|
1470 | later time-out values (but this is no longer true when a callback calls |
|
|
1471 | C<ev_loop> recursively). |
1324 | |
1472 | |
1325 | =head3 Be smart about timeouts |
1473 | =head3 Be smart about timeouts |
1326 | |
1474 | |
1327 | Many real-world problems involve some kind of timeout, usually for error |
1475 | Many real-world problems involve some kind of timeout, usually for error |
1328 | recovery. A typical example is an HTTP request - if the other side hangs, |
1476 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1547 | If the timer is started but non-repeating, stop it (as if it timed out). |
1695 | If the timer is started but non-repeating, stop it (as if it timed out). |
1548 | |
1696 | |
1549 | If the timer is repeating, either start it if necessary (with the |
1697 | If the timer is repeating, either start it if necessary (with the |
1550 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1698 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1551 | |
1699 | |
1552 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1700 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1553 | usage example. |
1701 | usage example. |
1554 | |
1702 | |
1555 | =item ev_tstamp repeat [read-write] |
1703 | =item ev_tstamp repeat [read-write] |
1556 | |
1704 | |
1557 | The current C<repeat> value. Will be used each time the watcher times out |
1705 | The current C<repeat> value. Will be used each time the watcher times out |
… | |
… | |
1596 | =head2 C<ev_periodic> - to cron or not to cron? |
1744 | =head2 C<ev_periodic> - to cron or not to cron? |
1597 | |
1745 | |
1598 | Periodic watchers are also timers of a kind, but they are very versatile |
1746 | Periodic watchers are also timers of a kind, but they are very versatile |
1599 | (and unfortunately a bit complex). |
1747 | (and unfortunately a bit complex). |
1600 | |
1748 | |
1601 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1749 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1602 | but on wall clock time (absolute time). You can tell a periodic watcher |
1750 | relative time, the physical time that passes) but on wall clock time |
1603 | to trigger after some specific point in time. For example, if you tell a |
1751 | (absolute time, the thing you can read on your calender or clock). The |
1604 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1752 | difference is that wall clock time can run faster or slower than real |
1605 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1753 | time, and time jumps are not uncommon (e.g. when you adjust your |
1606 | clock to January of the previous year, then it will take more than year |
1754 | wrist-watch). |
1607 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1608 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1609 | |
1755 | |
|
|
1756 | You can tell a periodic watcher to trigger after some specific point |
|
|
1757 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1758 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1759 | not a delay) and then reset your system clock to January of the previous |
|
|
1760 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1761 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1762 | it, as it uses a relative timeout). |
|
|
1763 | |
1610 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1764 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1611 | such as triggering an event on each "midnight, local time", or other |
1765 | timers, such as triggering an event on each "midnight, local time", or |
1612 | complicated rules. |
1766 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1767 | those cannot react to time jumps. |
1613 | |
1768 | |
1614 | As with timers, the callback is guaranteed to be invoked only when the |
1769 | As with timers, the callback is guaranteed to be invoked only when the |
1615 | time (C<at>) has passed, but if multiple periodic timers become ready |
1770 | point in time where it is supposed to trigger has passed. If multiple |
1616 | during the same loop iteration, then order of execution is undefined. |
1771 | timers become ready during the same loop iteration then the ones with |
|
|
1772 | earlier time-out values are invoked before ones with later time-out values |
|
|
1773 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1617 | |
1774 | |
1618 | =head3 Watcher-Specific Functions and Data Members |
1775 | =head3 Watcher-Specific Functions and Data Members |
1619 | |
1776 | |
1620 | =over 4 |
1777 | =over 4 |
1621 | |
1778 | |
1622 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1779 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1623 | |
1780 | |
1624 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1781 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1625 | |
1782 | |
1626 | Lots of arguments, lets sort it out... There are basically three modes of |
1783 | Lots of arguments, let's sort it out... There are basically three modes of |
1627 | operation, and we will explain them from simplest to most complex: |
1784 | operation, and we will explain them from simplest to most complex: |
1628 | |
1785 | |
1629 | =over 4 |
1786 | =over 4 |
1630 | |
1787 | |
1631 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1788 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1632 | |
1789 | |
1633 | In this configuration the watcher triggers an event after the wall clock |
1790 | In this configuration the watcher triggers an event after the wall clock |
1634 | time C<at> has passed. It will not repeat and will not adjust when a time |
1791 | time C<offset> has passed. It will not repeat and will not adjust when a |
1635 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1792 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1636 | only run when the system clock reaches or surpasses this time. |
1793 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1794 | this point in time. |
1637 | |
1795 | |
1638 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1796 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1639 | |
1797 | |
1640 | In this mode the watcher will always be scheduled to time out at the next |
1798 | In this mode the watcher will always be scheduled to time out at the next |
1641 | C<at + N * interval> time (for some integer N, which can also be negative) |
1799 | C<offset + N * interval> time (for some integer N, which can also be |
1642 | and then repeat, regardless of any time jumps. |
1800 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1801 | argument is merely an offset into the C<interval> periods. |
1643 | |
1802 | |
1644 | This can be used to create timers that do not drift with respect to the |
1803 | This can be used to create timers that do not drift with respect to the |
1645 | system clock, for example, here is a C<ev_periodic> that triggers each |
1804 | system clock, for example, here is an C<ev_periodic> that triggers each |
1646 | hour, on the hour: |
1805 | hour, on the hour (with respect to UTC): |
1647 | |
1806 | |
1648 | ev_periodic_set (&periodic, 0., 3600., 0); |
1807 | ev_periodic_set (&periodic, 0., 3600., 0); |
1649 | |
1808 | |
1650 | This doesn't mean there will always be 3600 seconds in between triggers, |
1809 | This doesn't mean there will always be 3600 seconds in between triggers, |
1651 | but only that the callback will be called when the system time shows a |
1810 | but only that the callback will be called when the system time shows a |
1652 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1811 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1653 | by 3600. |
1812 | by 3600. |
1654 | |
1813 | |
1655 | Another way to think about it (for the mathematically inclined) is that |
1814 | Another way to think about it (for the mathematically inclined) is that |
1656 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1815 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1657 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1816 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1658 | |
1817 | |
1659 | For numerical stability it is preferable that the C<at> value is near |
1818 | For numerical stability it is preferable that the C<offset> value is near |
1660 | C<ev_now ()> (the current time), but there is no range requirement for |
1819 | C<ev_now ()> (the current time), but there is no range requirement for |
1661 | this value, and in fact is often specified as zero. |
1820 | this value, and in fact is often specified as zero. |
1662 | |
1821 | |
1663 | Note also that there is an upper limit to how often a timer can fire (CPU |
1822 | Note also that there is an upper limit to how often a timer can fire (CPU |
1664 | speed for example), so if C<interval> is very small then timing stability |
1823 | speed for example), so if C<interval> is very small then timing stability |
1665 | will of course deteriorate. Libev itself tries to be exact to be about one |
1824 | will of course deteriorate. Libev itself tries to be exact to be about one |
1666 | millisecond (if the OS supports it and the machine is fast enough). |
1825 | millisecond (if the OS supports it and the machine is fast enough). |
1667 | |
1826 | |
1668 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1827 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1669 | |
1828 | |
1670 | In this mode the values for C<interval> and C<at> are both being |
1829 | In this mode the values for C<interval> and C<offset> are both being |
1671 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1830 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1672 | reschedule callback will be called with the watcher as first, and the |
1831 | reschedule callback will be called with the watcher as first, and the |
1673 | current time as second argument. |
1832 | current time as second argument. |
1674 | |
1833 | |
1675 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1834 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1676 | ever, or make ANY event loop modifications whatsoever>. |
1835 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1836 | allowed by documentation here>. |
1677 | |
1837 | |
1678 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1838 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1679 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1839 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1680 | only event loop modification you are allowed to do). |
1840 | only event loop modification you are allowed to do). |
1681 | |
1841 | |
… | |
… | |
1711 | a different time than the last time it was called (e.g. in a crond like |
1871 | a different time than the last time it was called (e.g. in a crond like |
1712 | program when the crontabs have changed). |
1872 | program when the crontabs have changed). |
1713 | |
1873 | |
1714 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1874 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1715 | |
1875 | |
1716 | When active, returns the absolute time that the watcher is supposed to |
1876 | When active, returns the absolute time that the watcher is supposed |
1717 | trigger next. |
1877 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1878 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1879 | rescheduling modes. |
1718 | |
1880 | |
1719 | =item ev_tstamp offset [read-write] |
1881 | =item ev_tstamp offset [read-write] |
1720 | |
1882 | |
1721 | When repeating, this contains the offset value, otherwise this is the |
1883 | When repeating, this contains the offset value, otherwise this is the |
1722 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1884 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1885 | although libev might modify this value for better numerical stability). |
1723 | |
1886 | |
1724 | Can be modified any time, but changes only take effect when the periodic |
1887 | Can be modified any time, but changes only take effect when the periodic |
1725 | timer fires or C<ev_periodic_again> is being called. |
1888 | timer fires or C<ev_periodic_again> is being called. |
1726 | |
1889 | |
1727 | =item ev_tstamp interval [read-write] |
1890 | =item ev_tstamp interval [read-write] |
… | |
… | |
2179 | |
2342 | |
2180 | =head3 Watcher-Specific Functions and Data Members |
2343 | =head3 Watcher-Specific Functions and Data Members |
2181 | |
2344 | |
2182 | =over 4 |
2345 | =over 4 |
2183 | |
2346 | |
2184 | =item ev_idle_init (ev_signal *, callback) |
2347 | =item ev_idle_init (ev_idle *, callback) |
2185 | |
2348 | |
2186 | Initialises and configures the idle watcher - it has no parameters of any |
2349 | Initialises and configures the idle watcher - it has no parameters of any |
2187 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2350 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2188 | believe me. |
2351 | believe me. |
2189 | |
2352 | |
… | |
… | |
2428 | some fds have to be watched and handled very quickly (with low latency), |
2591 | some fds have to be watched and handled very quickly (with low latency), |
2429 | and even priorities and idle watchers might have too much overhead. In |
2592 | and even priorities and idle watchers might have too much overhead. In |
2430 | this case you would put all the high priority stuff in one loop and all |
2593 | this case you would put all the high priority stuff in one loop and all |
2431 | the rest in a second one, and embed the second one in the first. |
2594 | the rest in a second one, and embed the second one in the first. |
2432 | |
2595 | |
2433 | As long as the watcher is active, the callback will be invoked every time |
2596 | As long as the watcher is active, the callback will be invoked every |
2434 | there might be events pending in the embedded loop. The callback must then |
2597 | time there might be events pending in the embedded loop. The callback |
2435 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2598 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2436 | their callbacks (you could also start an idle watcher to give the embedded |
2599 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2437 | loop strictly lower priority for example). You can also set the callback |
2600 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2438 | to C<0>, in which case the embed watcher will automatically execute the |
2601 | to give the embedded loop strictly lower priority for example). |
2439 | embedded loop sweep. |
|
|
2440 | |
2602 | |
2441 | As long as the watcher is started it will automatically handle events. The |
2603 | You can also set the callback to C<0>, in which case the embed watcher |
2442 | callback will be invoked whenever some events have been handled. You can |
2604 | will automatically execute the embedded loop sweep whenever necessary. |
2443 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2444 | interested in that. |
|
|
2445 | |
2605 | |
2446 | Also, there have not currently been made special provisions for forking: |
2606 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2447 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2607 | is active, i.e., the embedded loop will automatically be forked when the |
2448 | but you will also have to stop and restart any C<ev_embed> watchers |
2608 | embedding loop forks. In other cases, the user is responsible for calling |
2449 | yourself - but you can use a fork watcher to handle this automatically, |
2609 | C<ev_loop_fork> on the embedded loop. |
2450 | and future versions of libev might do just that. |
|
|
2451 | |
2610 | |
2452 | Unfortunately, not all backends are embeddable: only the ones returned by |
2611 | Unfortunately, not all backends are embeddable: only the ones returned by |
2453 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2612 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2454 | portable one. |
2613 | portable one. |
2455 | |
2614 | |
… | |
… | |
2686 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2845 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2687 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2846 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2688 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2847 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2689 | section below on what exactly this means). |
2848 | section below on what exactly this means). |
2690 | |
2849 | |
|
|
2850 | Note that, as with other watchers in libev, multiple events might get |
|
|
2851 | compressed into a single callback invocation (another way to look at this |
|
|
2852 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2853 | reset when the event loop detects that). |
|
|
2854 | |
2691 | This call incurs the overhead of a system call only once per loop iteration, |
2855 | This call incurs the overhead of a system call only once per event loop |
2692 | so while the overhead might be noticeable, it doesn't apply to repeated |
2856 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2693 | calls to C<ev_async_send>. |
2857 | repeated calls to C<ev_async_send> for the same event loop. |
2694 | |
2858 | |
2695 | =item bool = ev_async_pending (ev_async *) |
2859 | =item bool = ev_async_pending (ev_async *) |
2696 | |
2860 | |
2697 | Returns a non-zero value when C<ev_async_send> has been called on the |
2861 | Returns a non-zero value when C<ev_async_send> has been called on the |
2698 | watcher but the event has not yet been processed (or even noted) by the |
2862 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2701 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2865 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2702 | the loop iterates next and checks for the watcher to have become active, |
2866 | the loop iterates next and checks for the watcher to have become active, |
2703 | it will reset the flag again. C<ev_async_pending> can be used to very |
2867 | it will reset the flag again. C<ev_async_pending> can be used to very |
2704 | quickly check whether invoking the loop might be a good idea. |
2868 | quickly check whether invoking the loop might be a good idea. |
2705 | |
2869 | |
2706 | Not that this does I<not> check whether the watcher itself is pending, only |
2870 | Not that this does I<not> check whether the watcher itself is pending, |
2707 | whether it has been requested to make this watcher pending. |
2871 | only whether it has been requested to make this watcher pending: there |
|
|
2872 | is a time window between the event loop checking and resetting the async |
|
|
2873 | notification, and the callback being invoked. |
2708 | |
2874 | |
2709 | =back |
2875 | =back |
2710 | |
2876 | |
2711 | |
2877 | |
2712 | =head1 OTHER FUNCTIONS |
2878 | =head1 OTHER FUNCTIONS |
… | |
… | |
3016 | L<http://software.schmorp.de/pkg/EV>. |
3182 | L<http://software.schmorp.de/pkg/EV>. |
3017 | |
3183 | |
3018 | =item Python |
3184 | =item Python |
3019 | |
3185 | |
3020 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3186 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3021 | seems to be quite complete and well-documented. Note, however, that the |
3187 | seems to be quite complete and well-documented. |
3022 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
3023 | for everybody else, and therefore, should never be applied in an installed |
|
|
3024 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
3025 | libev). |
|
|
3026 | |
3188 | |
3027 | =item Ruby |
3189 | =item Ruby |
3028 | |
3190 | |
3029 | Tony Arcieri has written a ruby extension that offers access to a subset |
3191 | Tony Arcieri has written a ruby extension that offers access to a subset |
3030 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3192 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3031 | more on top of it. It can be found via gem servers. Its homepage is at |
3193 | more on top of it. It can be found via gem servers. Its homepage is at |
3032 | L<http://rev.rubyforge.org/>. |
3194 | L<http://rev.rubyforge.org/>. |
3033 | |
3195 | |
3034 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
3196 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
3035 | makes rev work even on mingw. |
3197 | makes rev work even on mingw. |
|
|
3198 | |
|
|
3199 | =item Haskell |
|
|
3200 | |
|
|
3201 | A haskell binding to libev is available at |
|
|
3202 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3036 | |
3203 | |
3037 | =item D |
3204 | =item D |
3038 | |
3205 | |
3039 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3206 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3040 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3207 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
… | |
… | |
3233 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3400 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3234 | |
3401 | |
3235 | =item EV_USE_REALTIME |
3402 | =item EV_USE_REALTIME |
3236 | |
3403 | |
3237 | If defined to be C<1>, libev will try to detect the availability of the |
3404 | If defined to be C<1>, libev will try to detect the availability of the |
3238 | real-time clock option at compile time (and assume its availability at |
3405 | real-time clock option at compile time (and assume its availability |
3239 | runtime if successful). Otherwise no use of the real-time clock option will |
3406 | at runtime if successful). Otherwise no use of the real-time clock |
3240 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3407 | option will be attempted. This effectively replaces C<gettimeofday> |
3241 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3408 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3242 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3409 | correctness. See the note about libraries in the description of |
|
|
3410 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3411 | C<EV_USE_CLOCK_SYSCALL>. |
3243 | |
3412 | |
3244 | =item EV_USE_CLOCK_SYSCALL |
3413 | =item EV_USE_CLOCK_SYSCALL |
3245 | |
3414 | |
3246 | If defined to be C<1>, libev will try to use a direct syscall instead |
3415 | If defined to be C<1>, libev will try to use a direct syscall instead |
3247 | of calling the system-provided C<clock_gettime> function. This option |
3416 | of calling the system-provided C<clock_gettime> function. This option |
… | |
… | |
3937 | involves iterating over all running async watchers or all signal numbers. |
4106 | involves iterating over all running async watchers or all signal numbers. |
3938 | |
4107 | |
3939 | =back |
4108 | =back |
3940 | |
4109 | |
3941 | |
4110 | |
|
|
4111 | =head1 GLOSSARY |
|
|
4112 | |
|
|
4113 | =over 4 |
|
|
4114 | |
|
|
4115 | =item active |
|
|
4116 | |
|
|
4117 | A watcher is active as long as it has been started (has been attached to |
|
|
4118 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4119 | |
|
|
4120 | =item application |
|
|
4121 | |
|
|
4122 | In this document, an application is whatever is using libev. |
|
|
4123 | |
|
|
4124 | =item callback |
|
|
4125 | |
|
|
4126 | The address of a function that is called when some event has been |
|
|
4127 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4128 | received the event, and the actual event bitset. |
|
|
4129 | |
|
|
4130 | =item callback invocation |
|
|
4131 | |
|
|
4132 | The act of calling the callback associated with a watcher. |
|
|
4133 | |
|
|
4134 | =item event |
|
|
4135 | |
|
|
4136 | A change of state of some external event, such as data now being available |
|
|
4137 | for reading on a file descriptor, time having passed or simply not having |
|
|
4138 | any other events happening anymore. |
|
|
4139 | |
|
|
4140 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4141 | C<EV_TIMEOUT>). |
|
|
4142 | |
|
|
4143 | =item event library |
|
|
4144 | |
|
|
4145 | A software package implementing an event model and loop. |
|
|
4146 | |
|
|
4147 | =item event loop |
|
|
4148 | |
|
|
4149 | An entity that handles and processes external events and converts them |
|
|
4150 | into callback invocations. |
|
|
4151 | |
|
|
4152 | =item event model |
|
|
4153 | |
|
|
4154 | The model used to describe how an event loop handles and processes |
|
|
4155 | watchers and events. |
|
|
4156 | |
|
|
4157 | =item pending |
|
|
4158 | |
|
|
4159 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4160 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4161 | pending status is explicitly cleared by the application. |
|
|
4162 | |
|
|
4163 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4164 | its pending status. |
|
|
4165 | |
|
|
4166 | =item real time |
|
|
4167 | |
|
|
4168 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4169 | |
|
|
4170 | =item wall-clock time |
|
|
4171 | |
|
|
4172 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4173 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4174 | clock. |
|
|
4175 | |
|
|
4176 | =item watcher |
|
|
4177 | |
|
|
4178 | A data structure that describes interest in certain events. Watchers need |
|
|
4179 | to be started (attached to an event loop) before they can receive events. |
|
|
4180 | |
|
|
4181 | =item watcher invocation |
|
|
4182 | |
|
|
4183 | The act of calling the callback associated with a watcher. |
|
|
4184 | |
|
|
4185 | =back |
|
|
4186 | |
3942 | =head1 AUTHOR |
4187 | =head1 AUTHOR |
3943 | |
4188 | |
3944 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
4189 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3945 | |
4190 | |