… | |
… | |
77 | on event-based programming, nor will it introduce event-based programming |
77 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
78 | with libev. |
79 | |
79 | |
80 | Familiarity with event based programming techniques in general is assumed |
80 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
81 | throughout this document. |
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82 | |
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83 | =head1 WHAT TO READ WHEN IN A HURRY |
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84 | |
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85 | This manual tries to be very detailed, but unfortunately, this also makes |
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86 | it very long. If you just want to know the basics of libev, I suggest |
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87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
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88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
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89 | C<ev_timer> sections in L<WATCHER TYPES>. |
82 | |
90 | |
83 | =head1 ABOUT LIBEV |
91 | =head1 ABOUT LIBEV |
84 | |
92 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
93 | Libev is an event loop: you register interest in certain events (such as a |
86 | file descriptor being readable or a timeout occurring), and it will manage |
94 | file descriptor being readable or a timeout occurring), and it will manage |
… | |
… | |
455 | epoll scales either O(1) or O(active_fds). |
463 | epoll scales either O(1) or O(active_fds). |
456 | |
464 | |
457 | The epoll mechanism deserves honorable mention as the most misdesigned |
465 | The epoll mechanism deserves honorable mention as the most misdesigned |
458 | of the more advanced event mechanisms: mere annoyances include silently |
466 | of the more advanced event mechanisms: mere annoyances include silently |
459 | dropping file descriptors, requiring a system call per change per file |
467 | dropping file descriptors, requiring a system call per change per file |
460 | descriptor (and unnecessary guessing of parameters), problems with dup and |
468 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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469 | returning before the timeout value requiring additional iterations and so |
461 | so on. The biggest issue is fork races, however - if a program forks then |
470 | on. The biggest issue is fork races, however - if a program forks then |
462 | I<both> parent and child process have to recreate the epoll set, which can |
471 | I<both> parent and child process have to recreate the epoll set, which can |
463 | take considerable time (one syscall per file descriptor) and is of course |
472 | take considerable time (one syscall per file descriptor) and is of course |
464 | hard to detect. |
473 | hard to detect. |
465 | |
474 | |
466 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
475 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
… | |
… | |
815 | Can be used to make a call to C<ev_run> return early (but only after it |
824 | Can be used to make a call to C<ev_run> return early (but only after it |
816 | has processed all outstanding events). The C<how> argument must be either |
825 | has processed all outstanding events). The C<how> argument must be either |
817 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
826 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
818 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
827 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
819 | |
828 | |
820 | This "unloop state" will be cleared when entering C<ev_run> again. |
829 | This "break state" will be cleared when entering C<ev_run> again. |
821 | |
830 | |
822 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
831 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too. |
823 | |
832 | |
824 | =item ev_ref (loop) |
833 | =item ev_ref (loop) |
825 | |
834 | |
826 | =item ev_unref (loop) |
835 | =item ev_unref (loop) |
827 | |
836 | |
… | |
… | |
1146 | programs, though, as the fd could already be closed and reused for another |
1155 | programs, though, as the fd could already be closed and reused for another |
1147 | thing, so beware. |
1156 | thing, so beware. |
1148 | |
1157 | |
1149 | =back |
1158 | =back |
1150 | |
1159 | |
1151 | =head2 WATCHER STATES |
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1152 | |
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1153 | There are various watcher states mentioned throughout this manual - |
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1154 | active, pending and so on. In this section these states and the rules to |
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1155 | transition between them will be described in more detail - and while these |
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1156 | rules might look complicated, they usually do "the right thing". |
|
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1157 | |
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1158 | =over 4 |
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1159 | |
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1160 | =item initialiased |
|
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1161 | |
|
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1162 | Before a watcher can be registered with the event looop it has to be |
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1163 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
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1164 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
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1165 | |
|
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1166 | In this state it is simply some block of memory that is suitable for use |
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1167 | in an event loop. It can be moved around, freed, reused etc. at will. |
|
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1168 | |
|
|
1169 | =item started/running/active |
|
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1170 | |
|
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1171 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
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1172 | property of the event loop, and is actively waiting for events. While in |
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1173 | this state it cannot be accessed (except in a few documented ways), moved, |
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1174 | freed or anything else - the only legal thing is to keep a pointer to it, |
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1175 | and call libev functions on it that are documented to work on active watchers. |
|
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1176 | |
|
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1177 | =item pending |
|
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1178 | |
|
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1179 | If a watcher is active and libev determines that an event it is interested |
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1180 | in has occurred (such as a timer expiring), it will become pending. It will |
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1181 | stay in this pending state until either it is stopped or its callback is |
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1182 | about to be invoked, so it is not normally pending inside the watcher |
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1183 | callback. |
|
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1184 | |
|
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1185 | The watcher might or might not be active while it is pending (for example, |
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1186 | an expired non-repeating timer can be pending but no longer active). If it |
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1187 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
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1188 | but it is still property of the event loop at this time, so cannot be |
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1189 | moved, freed or reused. And if it is active the rules described in the |
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1190 | previous item still apply. |
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1191 | |
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1192 | It is also possible to feed an event on a watcher that is not active (e.g. |
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1193 | via C<ev_feed_event>), in which case it becomes pending without being |
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1194 | active. |
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1195 | |
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1196 | =item stopped |
|
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1197 | |
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1198 | A watcher can be stopped implicitly by libev (in which case it might still |
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1199 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
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1200 | latter will clear any pending state the watcher might be in, regardless |
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1201 | of whether it was active or not, so stopping a watcher explicitly before |
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1202 | freeing it is often a good idea. |
|
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1203 | |
|
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1204 | While stopped (and not pending) the watcher is essentially in the |
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1205 | initialised state, that is it can be reused, moved, modified in any way |
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1206 | you wish. |
|
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1207 | |
|
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1208 | =back |
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1209 | |
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1210 | =head2 GENERIC WATCHER FUNCTIONS |
1160 | =head2 GENERIC WATCHER FUNCTIONS |
1211 | |
1161 | |
1212 | =over 4 |
1162 | =over 4 |
1213 | |
1163 | |
1214 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1164 | =item C<ev_init> (ev_TYPE *watcher, callback) |
… | |
… | |
1355 | |
1305 | |
1356 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1306 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1357 | functions that do not need a watcher. |
1307 | functions that do not need a watcher. |
1358 | |
1308 | |
1359 | =back |
1309 | =back |
1360 | |
|
|
1361 | |
1310 | |
1362 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1311 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1363 | |
1312 | |
1364 | Each watcher has, by default, a member C<void *data> that you can change |
1313 | Each watcher has, by default, a member C<void *data> that you can change |
1365 | and read at any time: libev will completely ignore it. This can be used |
1314 | and read at any time: libev will completely ignore it. This can be used |
… | |
… | |
1421 | t2_cb (EV_P_ ev_timer *w, int revents) |
1370 | t2_cb (EV_P_ ev_timer *w, int revents) |
1422 | { |
1371 | { |
1423 | struct my_biggy big = (struct my_biggy *) |
1372 | struct my_biggy big = (struct my_biggy *) |
1424 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1373 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1425 | } |
1374 | } |
|
|
1375 | |
|
|
1376 | =head2 WATCHER STATES |
|
|
1377 | |
|
|
1378 | There are various watcher states mentioned throughout this manual - |
|
|
1379 | active, pending and so on. In this section these states and the rules to |
|
|
1380 | transition between them will be described in more detail - and while these |
|
|
1381 | rules might look complicated, they usually do "the right thing". |
|
|
1382 | |
|
|
1383 | =over 4 |
|
|
1384 | |
|
|
1385 | =item initialiased |
|
|
1386 | |
|
|
1387 | Before a watcher can be registered with the event looop it has to be |
|
|
1388 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1389 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1390 | |
|
|
1391 | In this state it is simply some block of memory that is suitable for use |
|
|
1392 | in an event loop. It can be moved around, freed, reused etc. at will. |
|
|
1393 | |
|
|
1394 | =item started/running/active |
|
|
1395 | |
|
|
1396 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1397 | property of the event loop, and is actively waiting for events. While in |
|
|
1398 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1399 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1400 | and call libev functions on it that are documented to work on active watchers. |
|
|
1401 | |
|
|
1402 | =item pending |
|
|
1403 | |
|
|
1404 | If a watcher is active and libev determines that an event it is interested |
|
|
1405 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1406 | stay in this pending state until either it is stopped or its callback is |
|
|
1407 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1408 | callback. |
|
|
1409 | |
|
|
1410 | The watcher might or might not be active while it is pending (for example, |
|
|
1411 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1412 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1413 | but it is still property of the event loop at this time, so cannot be |
|
|
1414 | moved, freed or reused. And if it is active the rules described in the |
|
|
1415 | previous item still apply. |
|
|
1416 | |
|
|
1417 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1418 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1419 | active. |
|
|
1420 | |
|
|
1421 | =item stopped |
|
|
1422 | |
|
|
1423 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1424 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1425 | latter will clear any pending state the watcher might be in, regardless |
|
|
1426 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1427 | freeing it is often a good idea. |
|
|
1428 | |
|
|
1429 | While stopped (and not pending) the watcher is essentially in the |
|
|
1430 | initialised state, that is it can be reused, moved, modified in any way |
|
|
1431 | you wish. |
|
|
1432 | |
|
|
1433 | =back |
1426 | |
1434 | |
1427 | =head2 WATCHER PRIORITY MODELS |
1435 | =head2 WATCHER PRIORITY MODELS |
1428 | |
1436 | |
1429 | Many event loops support I<watcher priorities>, which are usually small |
1437 | Many event loops support I<watcher priorities>, which are usually small |
1430 | integers that influence the ordering of event callback invocation |
1438 | integers that influence the ordering of event callback invocation |