… | |
… | |
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. |
|
|
82 | |
|
|
83 | =head1 WHAT TO READ WHEN IN A HURRY |
|
|
84 | |
|
|
85 | This manual tries to be very detailed, but unfortunately, this also makes |
|
|
86 | it very long. If you just want to know the basics of libev, I suggest |
|
|
87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
|
|
88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
|
|
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 |
… | |
… | |
300 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
308 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
301 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
309 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
302 | libev 3 had an C<ev_loop> function colliding with the struct name). |
310 | libev 3 had an C<ev_loop> function colliding with the struct name). |
303 | |
311 | |
304 | The library knows two types of such loops, the I<default> loop, which |
312 | The library knows two types of such loops, the I<default> loop, which |
305 | supports signals and child events, and dynamically created event loops |
313 | supports child process events, and dynamically created event loops which |
306 | which do not. |
314 | do not. |
307 | |
315 | |
308 | =over 4 |
316 | =over 4 |
309 | |
317 | |
310 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
318 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
311 | |
319 | |
… | |
… | |
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, |
|
|
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 |
|
|
1152 | |
|
|
1153 | There are various watcher states mentioned throughout this manual - |
|
|
1154 | active, pending and so on. In this section these states and the rules to |
|
|
1155 | transition between them will be described in more detail - and while these |
|
|
1156 | rules might look complicated, they usually do "the right thing". |
|
|
1157 | |
|
|
1158 | =over 4 |
|
|
1159 | |
|
|
1160 | =item initialiased |
|
|
1161 | |
|
|
1162 | Before a watcher can be registered with the event looop it has to be |
|
|
1163 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1164 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1165 | |
|
|
1166 | In this state it is simply some block of memory that is suitable for use |
|
|
1167 | in an event loop. It can be moved around, freed, reused etc. at will. |
|
|
1168 | |
|
|
1169 | =item started/running/active |
|
|
1170 | |
|
|
1171 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1172 | property of the event loop, and is actively waiting for events. While in |
|
|
1173 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1174 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1175 | and call libev functions on it that are documented to work on active watchers. |
|
|
1176 | |
|
|
1177 | =item pending |
|
|
1178 | |
|
|
1179 | If a watcher is active and libev determines that an event it is interested |
|
|
1180 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1181 | stay in this pending state until either it is stopped or its callback is |
|
|
1182 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1183 | callback. |
|
|
1184 | |
|
|
1185 | The watcher might or might not be active while it is pending (for example, |
|
|
1186 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1187 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1188 | but it is still property of the event loop at this time, so cannot be |
|
|
1189 | moved, freed or reused. And if it is active the rules described in the |
|
|
1190 | previous item still apply. |
|
|
1191 | |
|
|
1192 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1193 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1194 | active. |
|
|
1195 | |
|
|
1196 | =item stopped |
|
|
1197 | |
|
|
1198 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1199 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1200 | latter will clear any pending state the watcher might be in, regardless |
|
|
1201 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1202 | freeing it is often a good idea. |
|
|
1203 | |
|
|
1204 | While stopped (and not pending) the watcher is essentially in the |
|
|
1205 | initialised state, that is it can be reused, moved, modified in any way |
|
|
1206 | you wish. |
|
|
1207 | |
|
|
1208 | =back |
|
|
1209 | |
|
|
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 |
… | |
… | |
4757 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4765 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4758 | assumes that the same (machine) code can be used to call any watcher |
4766 | assumes that the same (machine) code can be used to call any watcher |
4759 | callback: The watcher callbacks have different type signatures, but libev |
4767 | callback: The watcher callbacks have different type signatures, but libev |
4760 | calls them using an C<ev_watcher *> internally. |
4768 | calls them using an C<ev_watcher *> internally. |
4761 | |
4769 | |
|
|
4770 | =item pointer accesses must be thread-atomic |
|
|
4771 | |
|
|
4772 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
4773 | writable in one piece - this is the case on all current architectures. |
|
|
4774 | |
4762 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4775 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4763 | |
4776 | |
4764 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4777 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4765 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4778 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4766 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
4779 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
… | |
… | |
4872 | =back |
4885 | =back |
4873 | |
4886 | |
4874 | |
4887 | |
4875 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4888 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4876 | |
4889 | |
4877 | The major version 4 introduced some minor incompatible changes to the API. |
4890 | The major version 4 introduced some incompatible changes to the API. |
4878 | |
4891 | |
4879 | At the moment, the C<ev.h> header file tries to implement superficial |
4892 | At the moment, the C<ev.h> header file provides compatibility definitions |
4880 | compatibility, so most programs should still compile. Those might be |
4893 | for all changes, so most programs should still compile. The compatibility |
4881 | removed in later versions of libev, so better update early than late. |
4894 | layer might be removed in later versions of libev, so better update to the |
|
|
4895 | new API early than late. |
4882 | |
4896 | |
4883 | =over 4 |
4897 | =over 4 |
|
|
4898 | |
|
|
4899 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4900 | |
|
|
4901 | The backward compatibility mechanism can be controlled by |
|
|
4902 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4903 | section. |
4884 | |
4904 | |
4885 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
4905 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
4886 | |
4906 | |
4887 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
4907 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
4888 | |
4908 | |
… | |
… | |
4914 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
4934 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
4915 | as all other watcher types. Note that C<ev_loop_fork> is still called |
4935 | as all other watcher types. Note that C<ev_loop_fork> is still called |
4916 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
4936 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
4917 | typedef. |
4937 | typedef. |
4918 | |
4938 | |
4919 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4920 | |
|
|
4921 | The backward compatibility mechanism can be controlled by |
|
|
4922 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4923 | section. |
|
|
4924 | |
|
|
4925 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4939 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4926 | |
4940 | |
4927 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4941 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4928 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
4942 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
4929 | and work, but the library code will of course be larger. |
4943 | and work, but the library code will of course be larger. |
… | |
… | |
5003 | |
5017 | |
5004 | =back |
5018 | =back |
5005 | |
5019 | |
5006 | =head1 AUTHOR |
5020 | =head1 AUTHOR |
5007 | |
5021 | |
5008 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5022 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5023 | Magnusson and Emanuele Giaquinta. |
5009 | |
5024 | |