… | |
… | |
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> |
|
|
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 |
|
|
68 | |
|
|
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>. |
|
|
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 |
|
|
81 | throughout this document. |
|
|
82 | |
|
|
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 | |
… | |
… | |
417 | i.e. keep at least one watcher active per fd at all times. Stopping and |
431 | i.e. keep at least one watcher active per fd at all times. Stopping and |
418 | starting a watcher (without re-setting it) also usually doesn't cause |
432 | starting a watcher (without re-setting it) also usually doesn't cause |
419 | extra overhead. A fork can both result in spurious notifications as well |
433 | extra overhead. A fork can both result in spurious notifications as well |
420 | as in libev having to destroy and recreate the epoll object, which can |
434 | as in libev having to destroy and recreate the epoll object, which can |
421 | take considerable time and thus should be avoided. |
435 | take considerable time and thus should be avoided. |
|
|
436 | |
|
|
437 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
438 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
439 | the usage. So sad. |
422 | |
440 | |
423 | While nominally embeddable in other event loops, this feature is broken in |
441 | While nominally embeddable in other event loops, this feature is broken in |
424 | all kernel versions tested so far. |
442 | all kernel versions tested so far. |
425 | |
443 | |
426 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
444 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
… | |
… | |
454 | |
472 | |
455 | While nominally embeddable in other event loops, this doesn't work |
473 | While nominally embeddable in other event loops, this doesn't work |
456 | 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 |
457 | 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 |
458 | (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 |
459 | (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 |
460 | using it only for sockets. |
478 | also broken on OS X)) and, did I mention it, using it only for sockets. |
461 | |
479 | |
462 | 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 |
463 | 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 |
464 | C<NOTE_EOF>. |
482 | C<NOTE_EOF>. |
465 | |
483 | |
… | |
… | |
626 | |
644 | |
627 | 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 |
628 | 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 |
629 | the current time is a good idea. |
647 | the current time is a good idea. |
630 | |
648 | |
631 | See also "The special problem of time updates" in the C<ev_timer> section. |
649 | See also L<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>). |
632 | |
676 | |
633 | =item ev_loop (loop, int flags) |
677 | =item ev_loop (loop, int flags) |
634 | |
678 | |
635 | 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 |
636 | 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 |
… | |
… | |
720 | |
764 | |
721 | 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> |
722 | from returning, call ev_unref() after starting, and ev_ref() before |
766 | from returning, call ev_unref() after starting, and ev_ref() before |
723 | stopping it. |
767 | stopping it. |
724 | |
768 | |
725 | 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 |
726 | 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 |
727 | 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 |
728 | 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 |
729 | 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 |
730 | (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 |
731 | 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). |
732 | |
778 | |
733 | 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> |
734 | running when nothing else is active. |
780 | running when nothing else is active. |
735 | |
781 | |
736 | ev_signal exitsig; |
782 | ev_signal exitsig; |
… | |
… | |
920 | |
966 | |
921 | =item C<EV_ASYNC> |
967 | =item C<EV_ASYNC> |
922 | |
968 | |
923 | 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>). |
924 | |
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 | |
925 | =item C<EV_ERROR> |
976 | =item C<EV_ERROR> |
926 | |
977 | |
927 | 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 |
928 | happen because the watcher could not be properly started because libev |
979 | happen because the watcher could not be properly started because libev |
929 | 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 |
… | |
… | |
1044 | 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> |
1045 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1096 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1046 | before watchers with lower priority, but priority will not keep watchers |
1097 | before watchers with lower priority, but priority will not keep watchers |
1047 | from being executed (except for C<ev_idle> watchers). |
1098 | from being executed (except for C<ev_idle> watchers). |
1048 | |
1099 | |
1049 | This means that priorities are I<only> used for ordering callback |
|
|
1050 | invocation after new events have been received. This is useful, for |
|
|
1051 | example, to reduce latency after idling, or more often, to bind two |
|
|
1052 | watchers on the same event and make sure one is called first. |
|
|
1053 | |
|
|
1054 | 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 |
1055 | 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. |
1056 | |
1102 | |
1057 | 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 |
1058 | pending. |
1104 | pending. |
1059 | |
|
|
1060 | The default priority used by watchers when no priority has been set is |
|
|
1061 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1062 | |
1105 | |
1063 | 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 |
1064 | 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 |
1065 | 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. |
1066 | |
1115 | |
1067 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1116 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1068 | |
1117 | |
1069 | 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 |
1070 | 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 |
… | |
… | |
1145 | t2_cb (EV_P_ ev_timer *w, int revents) |
1194 | t2_cb (EV_P_ ev_timer *w, int revents) |
1146 | { |
1195 | { |
1147 | struct my_biggy big = (struct my_biggy * |
1196 | struct my_biggy big = (struct my_biggy * |
1148 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1197 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1149 | } |
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. |
1150 | |
1302 | |
1151 | |
1303 | |
1152 | =head1 WATCHER TYPES |
1304 | =head1 WATCHER TYPES |
1153 | |
1305 | |
1154 | This section describes each watcher in detail, but will not repeat |
1306 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1180 | descriptors to non-blocking mode is also usually a good idea (but not |
1332 | descriptors to non-blocking mode is also usually a good idea (but not |
1181 | required if you know what you are doing). |
1333 | required if you know what you are doing). |
1182 | |
1334 | |
1183 | If you cannot use non-blocking mode, then force the use of a |
1335 | If you cannot use non-blocking mode, then force the use of a |
1184 | known-to-be-good backend (at the time of this writing, this includes only |
1336 | known-to-be-good backend (at the time of this writing, this includes only |
1185 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1337 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1338 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1339 | files) - libev doesn't guarentee any specific behaviour in that case. |
1186 | |
1340 | |
1187 | Another thing you have to watch out for is that it is quite easy to |
1341 | Another thing you have to watch out for is that it is quite easy to |
1188 | receive "spurious" readiness notifications, that is your callback might |
1342 | receive "spurious" readiness notifications, that is your callback might |
1189 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1343 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1190 | because there is no data. Not only are some backends known to create a |
1344 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1311 | year, it will still time out after (roughly) one hour. "Roughly" because |
1465 | year, it will still time out after (roughly) one hour. "Roughly" because |
1312 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1466 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1313 | monotonic clock option helps a lot here). |
1467 | monotonic clock option helps a lot here). |
1314 | |
1468 | |
1315 | The callback is guaranteed to be invoked only I<after> its timeout has |
1469 | The callback is guaranteed to be invoked only I<after> its timeout has |
1316 | passed, but if multiple timers become ready during the same loop iteration |
1470 | passed. If multiple timers become ready during the same loop iteration |
1317 | then order of execution is undefined. |
1471 | then the ones with earlier time-out values are invoked before ones with |
|
|
1472 | later time-out values (but this is no longer true when a callback calls |
|
|
1473 | C<ev_loop> recursively). |
1318 | |
1474 | |
1319 | =head3 Be smart about timeouts |
1475 | =head3 Be smart about timeouts |
1320 | |
1476 | |
1321 | Many real-world problems involve some kind of timeout, usually for error |
1477 | Many real-world problems involve some kind of timeout, usually for error |
1322 | recovery. A typical example is an HTTP request - if the other side hangs, |
1478 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1415 | else |
1571 | else |
1416 | { |
1572 | { |
1417 | // callback was invoked, but there was some activity, re-arm |
1573 | // callback was invoked, but there was some activity, re-arm |
1418 | // the watcher to fire in last_activity + 60, which is |
1574 | // the watcher to fire in last_activity + 60, which is |
1419 | // guaranteed to be in the future, so "again" is positive: |
1575 | // guaranteed to be in the future, so "again" is positive: |
1420 | w->again = timeout - now; |
1576 | w->repeat = timeout - now; |
1421 | ev_timer_again (EV_A_ w); |
1577 | ev_timer_again (EV_A_ w); |
1422 | } |
1578 | } |
1423 | } |
1579 | } |
1424 | |
1580 | |
1425 | To summarise the callback: first calculate the real timeout (defined |
1581 | To summarise the callback: first calculate the real timeout (defined |
… | |
… | |
1541 | If the timer is started but non-repeating, stop it (as if it timed out). |
1697 | If the timer is started but non-repeating, stop it (as if it timed out). |
1542 | |
1698 | |
1543 | If the timer is repeating, either start it if necessary (with the |
1699 | If the timer is repeating, either start it if necessary (with the |
1544 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1700 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1545 | |
1701 | |
1546 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1702 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1547 | usage example. |
1703 | usage example. |
1548 | |
1704 | |
1549 | =item ev_tstamp repeat [read-write] |
1705 | =item ev_tstamp repeat [read-write] |
1550 | |
1706 | |
1551 | The current C<repeat> value. Will be used each time the watcher times out |
1707 | The current C<repeat> value. Will be used each time the watcher times out |
… | |
… | |
1590 | =head2 C<ev_periodic> - to cron or not to cron? |
1746 | =head2 C<ev_periodic> - to cron or not to cron? |
1591 | |
1747 | |
1592 | Periodic watchers are also timers of a kind, but they are very versatile |
1748 | Periodic watchers are also timers of a kind, but they are very versatile |
1593 | (and unfortunately a bit complex). |
1749 | (and unfortunately a bit complex). |
1594 | |
1750 | |
1595 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1751 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1596 | but on wall clock time (absolute time). You can tell a periodic watcher |
1752 | relative time, the physical time that passes) but on wall clock time |
1597 | to trigger after some specific point in time. For example, if you tell a |
1753 | (absolute time, the thing you can read on your calender or clock). The |
1598 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1754 | difference is that wall clock time can run faster or slower than real |
1599 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1755 | time, and time jumps are not uncommon (e.g. when you adjust your |
1600 | clock to January of the previous year, then it will take more than year |
1756 | wrist-watch). |
1601 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1602 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1603 | |
1757 | |
|
|
1758 | You can tell a periodic watcher to trigger after some specific point |
|
|
1759 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1760 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1761 | not a delay) and then reset your system clock to January of the previous |
|
|
1762 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1763 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1764 | it, as it uses a relative timeout). |
|
|
1765 | |
1604 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1766 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1605 | such as triggering an event on each "midnight, local time", or other |
1767 | timers, such as triggering an event on each "midnight, local time", or |
1606 | complicated rules. |
1768 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1769 | those cannot react to time jumps. |
1607 | |
1770 | |
1608 | As with timers, the callback is guaranteed to be invoked only when the |
1771 | As with timers, the callback is guaranteed to be invoked only when the |
1609 | time (C<at>) has passed, but if multiple periodic timers become ready |
1772 | point in time where it is supposed to trigger has passed. If multiple |
1610 | during the same loop iteration, then order of execution is undefined. |
1773 | timers become ready during the same loop iteration then the ones with |
|
|
1774 | earlier time-out values are invoked before ones with later time-out values |
|
|
1775 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1611 | |
1776 | |
1612 | =head3 Watcher-Specific Functions and Data Members |
1777 | =head3 Watcher-Specific Functions and Data Members |
1613 | |
1778 | |
1614 | =over 4 |
1779 | =over 4 |
1615 | |
1780 | |
1616 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1781 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1617 | |
1782 | |
1618 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1783 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1619 | |
1784 | |
1620 | Lots of arguments, lets sort it out... There are basically three modes of |
1785 | Lots of arguments, let's sort it out... There are basically three modes of |
1621 | operation, and we will explain them from simplest to most complex: |
1786 | operation, and we will explain them from simplest to most complex: |
1622 | |
1787 | |
1623 | =over 4 |
1788 | =over 4 |
1624 | |
1789 | |
1625 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1790 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1626 | |
1791 | |
1627 | In this configuration the watcher triggers an event after the wall clock |
1792 | In this configuration the watcher triggers an event after the wall clock |
1628 | time C<at> has passed. It will not repeat and will not adjust when a time |
1793 | time C<offset> has passed. It will not repeat and will not adjust when a |
1629 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1794 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1630 | only run when the system clock reaches or surpasses this time. |
1795 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1796 | this point in time. |
1631 | |
1797 | |
1632 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1798 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1633 | |
1799 | |
1634 | In this mode the watcher will always be scheduled to time out at the next |
1800 | In this mode the watcher will always be scheduled to time out at the next |
1635 | C<at + N * interval> time (for some integer N, which can also be negative) |
1801 | C<offset + N * interval> time (for some integer N, which can also be |
1636 | and then repeat, regardless of any time jumps. |
1802 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1803 | argument is merely an offset into the C<interval> periods. |
1637 | |
1804 | |
1638 | This can be used to create timers that do not drift with respect to the |
1805 | This can be used to create timers that do not drift with respect to the |
1639 | system clock, for example, here is a C<ev_periodic> that triggers each |
1806 | system clock, for example, here is an C<ev_periodic> that triggers each |
1640 | hour, on the hour: |
1807 | hour, on the hour (with respect to UTC): |
1641 | |
1808 | |
1642 | ev_periodic_set (&periodic, 0., 3600., 0); |
1809 | ev_periodic_set (&periodic, 0., 3600., 0); |
1643 | |
1810 | |
1644 | This doesn't mean there will always be 3600 seconds in between triggers, |
1811 | This doesn't mean there will always be 3600 seconds in between triggers, |
1645 | but only that the callback will be called when the system time shows a |
1812 | but only that the callback will be called when the system time shows a |
1646 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1813 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1647 | by 3600. |
1814 | by 3600. |
1648 | |
1815 | |
1649 | Another way to think about it (for the mathematically inclined) is that |
1816 | Another way to think about it (for the mathematically inclined) is that |
1650 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1817 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1651 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1818 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1652 | |
1819 | |
1653 | For numerical stability it is preferable that the C<at> value is near |
1820 | For numerical stability it is preferable that the C<offset> value is near |
1654 | C<ev_now ()> (the current time), but there is no range requirement for |
1821 | C<ev_now ()> (the current time), but there is no range requirement for |
1655 | this value, and in fact is often specified as zero. |
1822 | this value, and in fact is often specified as zero. |
1656 | |
1823 | |
1657 | Note also that there is an upper limit to how often a timer can fire (CPU |
1824 | Note also that there is an upper limit to how often a timer can fire (CPU |
1658 | speed for example), so if C<interval> is very small then timing stability |
1825 | speed for example), so if C<interval> is very small then timing stability |
1659 | will of course deteriorate. Libev itself tries to be exact to be about one |
1826 | will of course deteriorate. Libev itself tries to be exact to be about one |
1660 | millisecond (if the OS supports it and the machine is fast enough). |
1827 | millisecond (if the OS supports it and the machine is fast enough). |
1661 | |
1828 | |
1662 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1829 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1663 | |
1830 | |
1664 | In this mode the values for C<interval> and C<at> are both being |
1831 | In this mode the values for C<interval> and C<offset> are both being |
1665 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1832 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1666 | reschedule callback will be called with the watcher as first, and the |
1833 | reschedule callback will be called with the watcher as first, and the |
1667 | current time as second argument. |
1834 | current time as second argument. |
1668 | |
1835 | |
1669 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1836 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1670 | ever, or make ANY event loop modifications whatsoever>. |
1837 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1838 | allowed by documentation here>. |
1671 | |
1839 | |
1672 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1840 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1673 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1841 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1674 | only event loop modification you are allowed to do). |
1842 | only event loop modification you are allowed to do). |
1675 | |
1843 | |
… | |
… | |
1705 | a different time than the last time it was called (e.g. in a crond like |
1873 | a different time than the last time it was called (e.g. in a crond like |
1706 | program when the crontabs have changed). |
1874 | program when the crontabs have changed). |
1707 | |
1875 | |
1708 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1876 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1709 | |
1877 | |
1710 | When active, returns the absolute time that the watcher is supposed to |
1878 | When active, returns the absolute time that the watcher is supposed |
1711 | trigger next. |
1879 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1880 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1881 | rescheduling modes. |
1712 | |
1882 | |
1713 | =item ev_tstamp offset [read-write] |
1883 | =item ev_tstamp offset [read-write] |
1714 | |
1884 | |
1715 | When repeating, this contains the offset value, otherwise this is the |
1885 | When repeating, this contains the offset value, otherwise this is the |
1716 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1886 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1887 | although libev might modify this value for better numerical stability). |
1717 | |
1888 | |
1718 | Can be modified any time, but changes only take effect when the periodic |
1889 | Can be modified any time, but changes only take effect when the periodic |
1719 | timer fires or C<ev_periodic_again> is being called. |
1890 | timer fires or C<ev_periodic_again> is being called. |
1720 | |
1891 | |
1721 | =item ev_tstamp interval [read-write] |
1892 | =item ev_tstamp interval [read-write] |
… | |
… | |
1932 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2103 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1933 | and sees if it changed compared to the last time, invoking the callback if |
2104 | and sees if it changed compared to the last time, invoking the callback if |
1934 | it did. |
2105 | it did. |
1935 | |
2106 | |
1936 | The path does not need to exist: changing from "path exists" to "path does |
2107 | The path does not need to exist: changing from "path exists" to "path does |
1937 | not exist" is a status change like any other. The condition "path does |
2108 | not exist" is a status change like any other. The condition "path does not |
1938 | not exist" is signified by the C<st_nlink> field being zero (which is |
2109 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1939 | otherwise always forced to be at least one) and all the other fields of |
2110 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1940 | the stat buffer having unspecified contents. |
2111 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2112 | contents. |
1941 | |
2113 | |
1942 | The path I<must not> end in a slash or contain special components such as |
2114 | The path I<must not> end in a slash or contain special components such as |
1943 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
2115 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1944 | your working directory changes, then the behaviour is undefined. |
2116 | your working directory changes, then the behaviour is undefined. |
1945 | |
2117 | |
… | |
… | |
1955 | This watcher type is not meant for massive numbers of stat watchers, |
2127 | This watcher type is not meant for massive numbers of stat watchers, |
1956 | as even with OS-supported change notifications, this can be |
2128 | as even with OS-supported change notifications, this can be |
1957 | resource-intensive. |
2129 | resource-intensive. |
1958 | |
2130 | |
1959 | At the time of this writing, the only OS-specific interface implemented |
2131 | At the time of this writing, the only OS-specific interface implemented |
1960 | is the Linux inotify interface (implementing kqueue support is left as |
2132 | is the Linux inotify interface (implementing kqueue support is left as an |
1961 | an exercise for the reader. Note, however, that the author sees no way |
2133 | exercise for the reader. Note, however, that the author sees no way of |
1962 | of implementing C<ev_stat> semantics with kqueue). |
2134 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1963 | |
2135 | |
1964 | =head3 ABI Issues (Largefile Support) |
2136 | =head3 ABI Issues (Largefile Support) |
1965 | |
2137 | |
1966 | Libev by default (unless the user overrides this) uses the default |
2138 | Libev by default (unless the user overrides this) uses the default |
1967 | compilation environment, which means that on systems with large file |
2139 | compilation environment, which means that on systems with large file |
… | |
… | |
1978 | to exchange stat structures with application programs compiled using the |
2150 | to exchange stat structures with application programs compiled using the |
1979 | default compilation environment. |
2151 | default compilation environment. |
1980 | |
2152 | |
1981 | =head3 Inotify and Kqueue |
2153 | =head3 Inotify and Kqueue |
1982 | |
2154 | |
1983 | When C<inotify (7)> support has been compiled into libev (generally |
2155 | When C<inotify (7)> support has been compiled into libev and present at |
1984 | only available with Linux 2.6.25 or above due to bugs in earlier |
2156 | runtime, it will be used to speed up change detection where possible. The |
1985 | implementations) and present at runtime, it will be used to speed up |
2157 | inotify descriptor will be created lazily when the first C<ev_stat> |
1986 | change detection where possible. The inotify descriptor will be created |
2158 | watcher is being started. |
1987 | lazily when the first C<ev_stat> watcher is being started. |
|
|
1988 | |
2159 | |
1989 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2160 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1990 | except that changes might be detected earlier, and in some cases, to avoid |
2161 | except that changes might be detected earlier, and in some cases, to avoid |
1991 | making regular C<stat> calls. Even in the presence of inotify support |
2162 | making regular C<stat> calls. Even in the presence of inotify support |
1992 | there are many cases where libev has to resort to regular C<stat> polling, |
2163 | there are many cases where libev has to resort to regular C<stat> polling, |
1993 | but as long as the path exists, libev usually gets away without polling. |
2164 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2165 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2166 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2167 | xfs are fully working) libev usually gets away without polling. |
1994 | |
2168 | |
1995 | There is no support for kqueue, as apparently it cannot be used to |
2169 | There is no support for kqueue, as apparently it cannot be used to |
1996 | implement this functionality, due to the requirement of having a file |
2170 | implement this functionality, due to the requirement of having a file |
1997 | descriptor open on the object at all times, and detecting renames, unlinks |
2171 | descriptor open on the object at all times, and detecting renames, unlinks |
1998 | etc. is difficult. |
2172 | etc. is difficult. |
|
|
2173 | |
|
|
2174 | =head3 C<stat ()> is a synchronous operation |
|
|
2175 | |
|
|
2176 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2177 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2178 | ()>, which is a synchronous operation. |
|
|
2179 | |
|
|
2180 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2181 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2182 | as the path data is usually in memory already (except when starting the |
|
|
2183 | watcher). |
|
|
2184 | |
|
|
2185 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2186 | time due to network issues, and even under good conditions, a stat call |
|
|
2187 | often takes multiple milliseconds. |
|
|
2188 | |
|
|
2189 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2190 | paths, although this is fully supported by libev. |
1999 | |
2191 | |
2000 | =head3 The special problem of stat time resolution |
2192 | =head3 The special problem of stat time resolution |
2001 | |
2193 | |
2002 | The C<stat ()> system call only supports full-second resolution portably, |
2194 | The C<stat ()> system call only supports full-second resolution portably, |
2003 | and even on systems where the resolution is higher, most file systems |
2195 | and even on systems where the resolution is higher, most file systems |
… | |
… | |
2152 | |
2344 | |
2153 | =head3 Watcher-Specific Functions and Data Members |
2345 | =head3 Watcher-Specific Functions and Data Members |
2154 | |
2346 | |
2155 | =over 4 |
2347 | =over 4 |
2156 | |
2348 | |
2157 | =item ev_idle_init (ev_signal *, callback) |
2349 | =item ev_idle_init (ev_idle *, callback) |
2158 | |
2350 | |
2159 | Initialises and configures the idle watcher - it has no parameters of any |
2351 | Initialises and configures the idle watcher - it has no parameters of any |
2160 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2352 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2161 | believe me. |
2353 | believe me. |
2162 | |
2354 | |
… | |
… | |
2401 | some fds have to be watched and handled very quickly (with low latency), |
2593 | some fds have to be watched and handled very quickly (with low latency), |
2402 | and even priorities and idle watchers might have too much overhead. In |
2594 | and even priorities and idle watchers might have too much overhead. In |
2403 | this case you would put all the high priority stuff in one loop and all |
2595 | this case you would put all the high priority stuff in one loop and all |
2404 | the rest in a second one, and embed the second one in the first. |
2596 | the rest in a second one, and embed the second one in the first. |
2405 | |
2597 | |
2406 | As long as the watcher is active, the callback will be invoked every time |
2598 | As long as the watcher is active, the callback will be invoked every |
2407 | there might be events pending in the embedded loop. The callback must then |
2599 | time there might be events pending in the embedded loop. The callback |
2408 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2600 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2409 | their callbacks (you could also start an idle watcher to give the embedded |
2601 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2410 | loop strictly lower priority for example). You can also set the callback |
2602 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2411 | to C<0>, in which case the embed watcher will automatically execute the |
2603 | to give the embedded loop strictly lower priority for example). |
2412 | embedded loop sweep. |
|
|
2413 | |
2604 | |
2414 | As long as the watcher is started it will automatically handle events. The |
2605 | You can also set the callback to C<0>, in which case the embed watcher |
2415 | callback will be invoked whenever some events have been handled. You can |
2606 | will automatically execute the embedded loop sweep whenever necessary. |
2416 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2417 | interested in that. |
|
|
2418 | |
2607 | |
2419 | Also, there have not currently been made special provisions for forking: |
2608 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2420 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2609 | is active, i.e., the embedded loop will automatically be forked when the |
2421 | but you will also have to stop and restart any C<ev_embed> watchers |
2610 | embedding loop forks. In other cases, the user is responsible for calling |
2422 | yourself - but you can use a fork watcher to handle this automatically, |
2611 | C<ev_loop_fork> on the embedded loop. |
2423 | and future versions of libev might do just that. |
|
|
2424 | |
2612 | |
2425 | Unfortunately, not all backends are embeddable: only the ones returned by |
2613 | Unfortunately, not all backends are embeddable: only the ones returned by |
2426 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2614 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2427 | portable one. |
2615 | portable one. |
2428 | |
2616 | |
… | |
… | |
2522 | event loop blocks next and before C<ev_check> watchers are being called, |
2710 | event loop blocks next and before C<ev_check> watchers are being called, |
2523 | and only in the child after the fork. If whoever good citizen calling |
2711 | and only in the child after the fork. If whoever good citizen calling |
2524 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2712 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2525 | handlers will be invoked, too, of course. |
2713 | handlers will be invoked, too, of course. |
2526 | |
2714 | |
|
|
2715 | =head3 The special problem of life after fork - how is it possible? |
|
|
2716 | |
|
|
2717 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2718 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2719 | sequence should be handled by libev without any problems. |
|
|
2720 | |
|
|
2721 | This changes when the application actually wants to do event handling |
|
|
2722 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2723 | fork. |
|
|
2724 | |
|
|
2725 | The default mode of operation (for libev, with application help to detect |
|
|
2726 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2727 | when I<either> the parent I<or> the child process continues. |
|
|
2728 | |
|
|
2729 | When both processes want to continue using libev, then this is usually the |
|
|
2730 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2731 | supposed to continue with all watchers in place as before, while the other |
|
|
2732 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2733 | |
|
|
2734 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2735 | simply create a new event loop, which of course will be "empty", and |
|
|
2736 | use that for new watchers. This has the advantage of not touching more |
|
|
2737 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2738 | disadvantage of having to use multiple event loops (which do not support |
|
|
2739 | signal watchers). |
|
|
2740 | |
|
|
2741 | When this is not possible, or you want to use the default loop for |
|
|
2742 | other reasons, then in the process that wants to start "fresh", call |
|
|
2743 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2744 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2745 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2746 | also that in that case, you have to re-register any signal watchers. |
|
|
2747 | |
2527 | =head3 Watcher-Specific Functions and Data Members |
2748 | =head3 Watcher-Specific Functions and Data Members |
2528 | |
2749 | |
2529 | =over 4 |
2750 | =over 4 |
2530 | |
2751 | |
2531 | =item ev_fork_init (ev_signal *, callback) |
2752 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2659 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2880 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2660 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2881 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2661 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2882 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2662 | section below on what exactly this means). |
2883 | section below on what exactly this means). |
2663 | |
2884 | |
|
|
2885 | Note that, as with other watchers in libev, multiple events might get |
|
|
2886 | compressed into a single callback invocation (another way to look at this |
|
|
2887 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2888 | reset when the event loop detects that). |
|
|
2889 | |
2664 | This call incurs the overhead of a system call only once per loop iteration, |
2890 | This call incurs the overhead of a system call only once per event loop |
2665 | so while the overhead might be noticeable, it doesn't apply to repeated |
2891 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2666 | calls to C<ev_async_send>. |
2892 | repeated calls to C<ev_async_send> for the same event loop. |
2667 | |
2893 | |
2668 | =item bool = ev_async_pending (ev_async *) |
2894 | =item bool = ev_async_pending (ev_async *) |
2669 | |
2895 | |
2670 | Returns a non-zero value when C<ev_async_send> has been called on the |
2896 | Returns a non-zero value when C<ev_async_send> has been called on the |
2671 | watcher but the event has not yet been processed (or even noted) by the |
2897 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2674 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2900 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2675 | the loop iterates next and checks for the watcher to have become active, |
2901 | the loop iterates next and checks for the watcher to have become active, |
2676 | it will reset the flag again. C<ev_async_pending> can be used to very |
2902 | it will reset the flag again. C<ev_async_pending> can be used to very |
2677 | quickly check whether invoking the loop might be a good idea. |
2903 | quickly check whether invoking the loop might be a good idea. |
2678 | |
2904 | |
2679 | Not that this does I<not> check whether the watcher itself is pending, only |
2905 | Not that this does I<not> check whether the watcher itself is pending, |
2680 | whether it has been requested to make this watcher pending. |
2906 | only whether it has been requested to make this watcher pending: there |
|
|
2907 | is a time window between the event loop checking and resetting the async |
|
|
2908 | notification, and the callback being invoked. |
2681 | |
2909 | |
2682 | =back |
2910 | =back |
2683 | |
2911 | |
2684 | |
2912 | |
2685 | =head1 OTHER FUNCTIONS |
2913 | =head1 OTHER FUNCTIONS |
… | |
… | |
2864 | |
3092 | |
2865 | myclass obj; |
3093 | myclass obj; |
2866 | ev::io iow; |
3094 | ev::io iow; |
2867 | iow.set <myclass, &myclass::io_cb> (&obj); |
3095 | iow.set <myclass, &myclass::io_cb> (&obj); |
2868 | |
3096 | |
|
|
3097 | =item w->set (object *) |
|
|
3098 | |
|
|
3099 | This is an B<experimental> feature that might go away in a future version. |
|
|
3100 | |
|
|
3101 | This is a variation of a method callback - leaving out the method to call |
|
|
3102 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3103 | functor objects without having to manually specify the C<operator ()> all |
|
|
3104 | the time. Incidentally, you can then also leave out the template argument |
|
|
3105 | list. |
|
|
3106 | |
|
|
3107 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3108 | int revents)>. |
|
|
3109 | |
|
|
3110 | See the method-C<set> above for more details. |
|
|
3111 | |
|
|
3112 | Example: use a functor object as callback. |
|
|
3113 | |
|
|
3114 | struct myfunctor |
|
|
3115 | { |
|
|
3116 | void operator() (ev::io &w, int revents) |
|
|
3117 | { |
|
|
3118 | ... |
|
|
3119 | } |
|
|
3120 | } |
|
|
3121 | |
|
|
3122 | myfunctor f; |
|
|
3123 | |
|
|
3124 | ev::io w; |
|
|
3125 | w.set (&f); |
|
|
3126 | |
2869 | =item w->set<function> (void *data = 0) |
3127 | =item w->set<function> (void *data = 0) |
2870 | |
3128 | |
2871 | Also sets a callback, but uses a static method or plain function as |
3129 | Also sets a callback, but uses a static method or plain function as |
2872 | callback. The optional C<data> argument will be stored in the watcher's |
3130 | callback. The optional C<data> argument will be stored in the watcher's |
2873 | C<data> member and is free for you to use. |
3131 | C<data> member and is free for you to use. |
… | |
… | |
2959 | L<http://software.schmorp.de/pkg/EV>. |
3217 | L<http://software.schmorp.de/pkg/EV>. |
2960 | |
3218 | |
2961 | =item Python |
3219 | =item Python |
2962 | |
3220 | |
2963 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3221 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2964 | seems to be quite complete and well-documented. Note, however, that the |
3222 | seems to be quite complete and well-documented. |
2965 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2966 | for everybody else, and therefore, should never be applied in an installed |
|
|
2967 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2968 | libev). |
|
|
2969 | |
3223 | |
2970 | =item Ruby |
3224 | =item Ruby |
2971 | |
3225 | |
2972 | Tony Arcieri has written a ruby extension that offers access to a subset |
3226 | Tony Arcieri has written a ruby extension that offers access to a subset |
2973 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3227 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2974 | more on top of it. It can be found via gem servers. Its homepage is at |
3228 | more on top of it. It can be found via gem servers. Its homepage is at |
2975 | L<http://rev.rubyforge.org/>. |
3229 | L<http://rev.rubyforge.org/>. |
|
|
3230 | |
|
|
3231 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3232 | makes rev work even on mingw. |
|
|
3233 | |
|
|
3234 | =item Haskell |
|
|
3235 | |
|
|
3236 | A haskell binding to libev is available at |
|
|
3237 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
2976 | |
3238 | |
2977 | =item D |
3239 | =item D |
2978 | |
3240 | |
2979 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3241 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2980 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3242 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
… | |
… | |
3157 | keeps libev from including F<config.h>, and it also defines dummy |
3419 | keeps libev from including F<config.h>, and it also defines dummy |
3158 | implementations for some libevent functions (such as logging, which is not |
3420 | implementations for some libevent functions (such as logging, which is not |
3159 | supported). It will also not define any of the structs usually found in |
3421 | supported). It will also not define any of the structs usually found in |
3160 | F<event.h> that are not directly supported by the libev core alone. |
3422 | F<event.h> that are not directly supported by the libev core alone. |
3161 | |
3423 | |
|
|
3424 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3425 | configuration, but has to be more conservative. |
|
|
3426 | |
3162 | =item EV_USE_MONOTONIC |
3427 | =item EV_USE_MONOTONIC |
3163 | |
3428 | |
3164 | If defined to be C<1>, libev will try to detect the availability of the |
3429 | If defined to be C<1>, libev will try to detect the availability of the |
3165 | monotonic clock option at both compile time and runtime. Otherwise no use |
3430 | monotonic clock option at both compile time and runtime. Otherwise no |
3166 | of the monotonic clock option will be attempted. If you enable this, you |
3431 | use of the monotonic clock option will be attempted. If you enable this, |
3167 | usually have to link against librt or something similar. Enabling it when |
3432 | you usually have to link against librt or something similar. Enabling it |
3168 | the functionality isn't available is safe, though, although you have |
3433 | when the functionality isn't available is safe, though, although you have |
3169 | to make sure you link against any libraries where the C<clock_gettime> |
3434 | to make sure you link against any libraries where the C<clock_gettime> |
3170 | function is hiding in (often F<-lrt>). |
3435 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3171 | |
3436 | |
3172 | =item EV_USE_REALTIME |
3437 | =item EV_USE_REALTIME |
3173 | |
3438 | |
3174 | If defined to be C<1>, libev will try to detect the availability of the |
3439 | If defined to be C<1>, libev will try to detect the availability of the |
3175 | real-time clock option at compile time (and assume its availability at |
3440 | real-time clock option at compile time (and assume its availability |
3176 | runtime if successful). Otherwise no use of the real-time clock option will |
3441 | at runtime if successful). Otherwise no use of the real-time clock |
3177 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3442 | option will be attempted. This effectively replaces C<gettimeofday> |
3178 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3443 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3179 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3444 | correctness. See the note about libraries in the description of |
|
|
3445 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3446 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3447 | |
|
|
3448 | =item EV_USE_CLOCK_SYSCALL |
|
|
3449 | |
|
|
3450 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3451 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3452 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3453 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3454 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3455 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3456 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3457 | higher, as it simplifies linking (no need for C<-lrt>). |
3180 | |
3458 | |
3181 | =item EV_USE_NANOSLEEP |
3459 | =item EV_USE_NANOSLEEP |
3182 | |
3460 | |
3183 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3461 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3184 | and will use it for delays. Otherwise it will use C<select ()>. |
3462 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3200 | |
3478 | |
3201 | =item EV_SELECT_USE_FD_SET |
3479 | =item EV_SELECT_USE_FD_SET |
3202 | |
3480 | |
3203 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3481 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3204 | structure. This is useful if libev doesn't compile due to a missing |
3482 | structure. This is useful if libev doesn't compile due to a missing |
3205 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3483 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3206 | exotic systems. This usually limits the range of file descriptors to some |
3484 | on exotic systems. This usually limits the range of file descriptors to |
3207 | low limit such as 1024 or might have other limitations (winsocket only |
3485 | some low limit such as 1024 or might have other limitations (winsocket |
3208 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3486 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3209 | influence the size of the C<fd_set> used. |
3487 | configures the maximum size of the C<fd_set>. |
3210 | |
3488 | |
3211 | =item EV_SELECT_IS_WINSOCKET |
3489 | =item EV_SELECT_IS_WINSOCKET |
3212 | |
3490 | |
3213 | When defined to C<1>, the select backend will assume that |
3491 | When defined to C<1>, the select backend will assume that |
3214 | select/socket/connect etc. don't understand file descriptors but |
3492 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3863 | involves iterating over all running async watchers or all signal numbers. |
4141 | involves iterating over all running async watchers or all signal numbers. |
3864 | |
4142 | |
3865 | =back |
4143 | =back |
3866 | |
4144 | |
3867 | |
4145 | |
|
|
4146 | =head1 GLOSSARY |
|
|
4147 | |
|
|
4148 | =over 4 |
|
|
4149 | |
|
|
4150 | =item active |
|
|
4151 | |
|
|
4152 | A watcher is active as long as it has been started (has been attached to |
|
|
4153 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4154 | |
|
|
4155 | =item application |
|
|
4156 | |
|
|
4157 | In this document, an application is whatever is using libev. |
|
|
4158 | |
|
|
4159 | =item callback |
|
|
4160 | |
|
|
4161 | The address of a function that is called when some event has been |
|
|
4162 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4163 | received the event, and the actual event bitset. |
|
|
4164 | |
|
|
4165 | =item callback invocation |
|
|
4166 | |
|
|
4167 | The act of calling the callback associated with a watcher. |
|
|
4168 | |
|
|
4169 | =item event |
|
|
4170 | |
|
|
4171 | A change of state of some external event, such as data now being available |
|
|
4172 | for reading on a file descriptor, time having passed or simply not having |
|
|
4173 | any other events happening anymore. |
|
|
4174 | |
|
|
4175 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4176 | C<EV_TIMEOUT>). |
|
|
4177 | |
|
|
4178 | =item event library |
|
|
4179 | |
|
|
4180 | A software package implementing an event model and loop. |
|
|
4181 | |
|
|
4182 | =item event loop |
|
|
4183 | |
|
|
4184 | An entity that handles and processes external events and converts them |
|
|
4185 | into callback invocations. |
|
|
4186 | |
|
|
4187 | =item event model |
|
|
4188 | |
|
|
4189 | The model used to describe how an event loop handles and processes |
|
|
4190 | watchers and events. |
|
|
4191 | |
|
|
4192 | =item pending |
|
|
4193 | |
|
|
4194 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4195 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4196 | pending status is explicitly cleared by the application. |
|
|
4197 | |
|
|
4198 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4199 | its pending status. |
|
|
4200 | |
|
|
4201 | =item real time |
|
|
4202 | |
|
|
4203 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4204 | |
|
|
4205 | =item wall-clock time |
|
|
4206 | |
|
|
4207 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4208 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4209 | clock. |
|
|
4210 | |
|
|
4211 | =item watcher |
|
|
4212 | |
|
|
4213 | A data structure that describes interest in certain events. Watchers need |
|
|
4214 | to be started (attached to an event loop) before they can receive events. |
|
|
4215 | |
|
|
4216 | =item watcher invocation |
|
|
4217 | |
|
|
4218 | The act of calling the callback associated with a watcher. |
|
|
4219 | |
|
|
4220 | =back |
|
|
4221 | |
3868 | =head1 AUTHOR |
4222 | =head1 AUTHOR |
3869 | |
4223 | |
3870 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
4224 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3871 | |
4225 | |