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Revision 1.53 by root, Tue Nov 27 20:15:02 2007 UTC vs.
Revision 1.54 by root, Tue Nov 27 20:26:51 2007 UTC

2 2
3libev - a high performance full-featured event loop written in C 3libev - a high performance full-featured event loop written in C
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 /* this is the only header you need */
8 #include <ev.h> 7 #include <ev.h>
9 8
10 /* what follows is a fully working example program */ 9=head1 EXAMPLE PROGRAM
10
11 #include <ev.h>
12
11 ev_io stdin_watcher; 13 ev_io stdin_watcher;
12 ev_timer timeout_watcher; 14 ev_timer timeout_watcher;
13 15
14 /* called when data readable on stdin */ 16 /* called when data readable on stdin */
15 static void 17 static void
61details of the event, and then hand it over to libev by I<starting> the 63details of the event, and then hand it over to libev by I<starting> the
62watcher. 64watcher.
63 65
64=head1 FEATURES 66=head1 FEATURES
65 67
66Libev supports select, poll, the linux-specific epoll and the bsd-specific 68Libev supports C<select>, C<poll>, the linux-specific C<epoll>, the
67kqueue mechanisms for file descriptor events, relative timers, absolute 69bsd-specific C<kqueue> and the solaris-specific event port mechanisms
68timers with customised rescheduling, signal events, process status change 70for file descriptor events (C<ev_io>), relative timers (C<ev_timer>),
69events (related to SIGCHLD), and event watchers dealing with the event 71absolute timers with customised rescheduling (C<ev_periodic>), synchronous
70loop mechanism itself (idle, prepare and check watchers). It also is quite 72signals (C<ev_signal>), process status change events (C<ev_child>), and
73event watchers dealing with the event loop mechanism itself (C<ev_idle>,
74C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
75file watchers (C<ev_stat>) and even limited support for fork events
76(C<ev_fork>).
77
78It also is quite fast (see this
71fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing 79L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
72it to libevent for example). 80for example).
73 81
74=head1 CONVENTIONS 82=head1 CONVENTIONS
75 83
76Libev is very configurable. In this manual the default configuration 84Libev is very configurable. In this manual the default configuration will
77will be described, which supports multiple event loops. For more info 85be described, which supports multiple event loops. For more info about
78about various configuration options please have a look at the file 86various configuration options please have a look at B<EMBED> section in
79F<README.embed> in the libev distribution. If libev was configured without 87this manual. If libev was configured without support for multiple event
80support for multiple event loops, then all functions taking an initial 88loops, then all functions taking an initial argument of name C<loop>
81argument of name C<loop> (which is always of type C<struct ev_loop *>) 89(which is always of type C<struct ev_loop *>) will not have this argument.
82will not have this argument.
83 90
84=head1 TIME REPRESENTATION 91=head1 TIME REPRESENTATION
85 92
86Libev represents time as a single floating point number, representing the 93Libev represents time as a single floating point number, representing the
87(fractional) number of seconds since the (POSIX) epoch (somewhere near 94(fractional) number of seconds since the (POSIX) epoch (somewhere near
116Usually, it's a good idea to terminate if the major versions mismatch, 123Usually, it's a good idea to terminate if the major versions mismatch,
117as this indicates an incompatible change. Minor versions are usually 124as this indicates an incompatible change. Minor versions are usually
118compatible to older versions, so a larger minor version alone is usually 125compatible to older versions, so a larger minor version alone is usually
119not a problem. 126not a problem.
120 127
121Example: make sure we haven't accidentally been linked against the wrong 128Example: Make sure we haven't accidentally been linked against the wrong
122version: 129version.
123 130
124 assert (("libev version mismatch", 131 assert (("libev version mismatch",
125 ev_version_major () == EV_VERSION_MAJOR 132 ev_version_major () == EV_VERSION_MAJOR
126 && ev_version_minor () >= EV_VERSION_MINOR)); 133 && ev_version_minor () >= EV_VERSION_MINOR));
127 134
167 174
168You could override this function in high-availability programs to, say, 175You could override this function in high-availability programs to, say,
169free some memory if it cannot allocate memory, to use a special allocator, 176free some memory if it cannot allocate memory, to use a special allocator,
170or even to sleep a while and retry until some memory is available. 177or even to sleep a while and retry until some memory is available.
171 178
172Example: replace the libev allocator with one that waits a bit and then 179Example: Replace the libev allocator with one that waits a bit and then
173retries: better than mine). 180retries).
174 181
175 static void * 182 static void *
176 persistent_realloc (void *ptr, size_t size) 183 persistent_realloc (void *ptr, size_t size)
177 { 184 {
178 for (;;) 185 for (;;)
197callback is set, then libev will expect it to remedy the sitution, no 204callback is set, then libev will expect it to remedy the sitution, no
198matter what, when it returns. That is, libev will generally retry the 205matter what, when it returns. That is, libev will generally retry the
199requested operation, or, if the condition doesn't go away, do bad stuff 206requested operation, or, if the condition doesn't go away, do bad stuff
200(such as abort). 207(such as abort).
201 208
202Example: do the same thing as libev does internally: 209Example: This is basically the same thing that libev does internally, too.
203 210
204 static void 211 static void
205 fatal_error (const char *msg) 212 fatal_error (const char *msg)
206 { 213 {
207 perror (msg); 214 perror (msg);
353Similar to C<ev_default_loop>, but always creates a new event loop that is 360Similar to C<ev_default_loop>, but always creates a new event loop that is
354always distinct from the default loop. Unlike the default loop, it cannot 361always distinct from the default loop. Unlike the default loop, it cannot
355handle signal and child watchers, and attempts to do so will be greeted by 362handle signal and child watchers, and attempts to do so will be greeted by
356undefined behaviour (or a failed assertion if assertions are enabled). 363undefined behaviour (or a failed assertion if assertions are enabled).
357 364
358Example: try to create a event loop that uses epoll and nothing else. 365Example: Try to create a event loop that uses epoll and nothing else.
359 366
360 struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 367 struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
361 if (!epoller) 368 if (!epoller)
362 fatal ("no epoll found here, maybe it hides under your chair"); 369 fatal ("no epoll found here, maybe it hides under your chair");
363 370
462 Signals and child watchers are implemented as I/O watchers, and will 469 Signals and child watchers are implemented as I/O watchers, and will
463 be handled here by queueing them when their watcher gets executed. 470 be handled here by queueing them when their watcher gets executed.
464 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 471 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
465 were used, return, otherwise continue with step *. 472 were used, return, otherwise continue with step *.
466 473
467Example: queue some jobs and then loop until no events are outsanding 474Example: Queue some jobs and then loop until no events are outsanding
468anymore. 475anymore.
469 476
470 ... queue jobs here, make sure they register event watchers as long 477 ... queue jobs here, make sure they register event watchers as long
471 ... as they still have work to do (even an idle watcher will do..) 478 ... as they still have work to do (even an idle watcher will do..)
472 ev_loop (my_loop, 0); 479 ev_loop (my_loop, 0);
492visible to the libev user and should not keep C<ev_loop> from exiting if 499visible to the libev user and should not keep C<ev_loop> from exiting if
493no event watchers registered by it are active. It is also an excellent 500no event watchers registered by it are active. It is also an excellent
494way to do this for generic recurring timers or from within third-party 501way to do this for generic recurring timers or from within third-party
495libraries. Just remember to I<unref after start> and I<ref before stop>. 502libraries. Just remember to I<unref after start> and I<ref before stop>.
496 503
497Example: create a signal watcher, but keep it from keeping C<ev_loop> 504Example: Create a signal watcher, but keep it from keeping C<ev_loop>
498running when nothing else is active. 505running when nothing else is active.
499 506
500 struct dv_signal exitsig; 507 struct ev_signal exitsig;
501 ev_signal_init (&exitsig, sig_cb, SIGINT); 508 ev_signal_init (&exitsig, sig_cb, SIGINT);
502 ev_signal_start (myloop, &exitsig); 509 ev_signal_start (loop, &exitsig);
503 evf_unref (myloop); 510 evf_unref (loop);
504 511
505Example: for some weird reason, unregister the above signal handler again. 512Example: For some weird reason, unregister the above signal handler again.
506 513
507 ev_ref (myloop); 514 ev_ref (loop);
508 ev_signal_stop (myloop, &exitsig); 515 ev_signal_stop (loop, &exitsig);
509 516
510=back 517=back
511 518
512 519
513=head1 ANATOMY OF A WATCHER 520=head1 ANATOMY OF A WATCHER
814 821
815The events being watched. 822The events being watched.
816 823
817=back 824=back
818 825
819Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well 826Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
820readable, but only once. Since it is likely line-buffered, you could 827readable, but only once. Since it is likely line-buffered, you could
821attempt to read a whole line in the callback: 828attempt to read a whole line in the callback.
822 829
823 static void 830 static void
824 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 831 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
825 { 832 {
826 ev_io_stop (loop, w); 833 ev_io_stop (loop, w);
916or C<ev_timer_again> is called and determines the next timeout (if any), 923or C<ev_timer_again> is called and determines the next timeout (if any),
917which is also when any modifications are taken into account. 924which is also when any modifications are taken into account.
918 925
919=back 926=back
920 927
921Example: create a timer that fires after 60 seconds. 928Example: Create a timer that fires after 60 seconds.
922 929
923 static void 930 static void
924 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 931 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
925 { 932 {
926 .. one minute over, w is actually stopped right here 933 .. one minute over, w is actually stopped right here
928 935
929 struct ev_timer mytimer; 936 struct ev_timer mytimer;
930 ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 937 ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
931 ev_timer_start (loop, &mytimer); 938 ev_timer_start (loop, &mytimer);
932 939
933Example: create a timeout timer that times out after 10 seconds of 940Example: Create a timeout timer that times out after 10 seconds of
934inactivity. 941inactivity.
935 942
936 static void 943 static void
937 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 944 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
938 { 945 {
1063switched off. Can be changed any time, but changes only take effect when 1070switched off. Can be changed any time, but changes only take effect when
1064the periodic timer fires or C<ev_periodic_again> is being called. 1071the periodic timer fires or C<ev_periodic_again> is being called.
1065 1072
1066=back 1073=back
1067 1074
1068Example: call a callback every hour, or, more precisely, whenever the 1075Example: Call a callback every hour, or, more precisely, whenever the
1069system clock is divisible by 3600. The callback invocation times have 1076system clock is divisible by 3600. The callback invocation times have
1070potentially a lot of jittering, but good long-term stability. 1077potentially a lot of jittering, but good long-term stability.
1071 1078
1072 static void 1079 static void
1073 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1080 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1077 1084
1078 struct ev_periodic hourly_tick; 1085 struct ev_periodic hourly_tick;
1079 ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1086 ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1080 ev_periodic_start (loop, &hourly_tick); 1087 ev_periodic_start (loop, &hourly_tick);
1081 1088
1082Example: the same as above, but use a reschedule callback to do it: 1089Example: The same as above, but use a reschedule callback to do it:
1083 1090
1084 #include <math.h> 1091 #include <math.h>
1085 1092
1086 static ev_tstamp 1093 static ev_tstamp
1087 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1094 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1089 return fmod (now, 3600.) + 3600.; 1096 return fmod (now, 3600.) + 3600.;
1090 } 1097 }
1091 1098
1092 ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1099 ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1093 1100
1094Example: call a callback every hour, starting now: 1101Example: Call a callback every hour, starting now:
1095 1102
1096 struct ev_periodic hourly_tick; 1103 struct ev_periodic hourly_tick;
1097 ev_periodic_init (&hourly_tick, clock_cb, 1104 ev_periodic_init (&hourly_tick, clock_cb,
1098 fmod (ev_now (loop), 3600.), 3600., 0); 1105 fmod (ev_now (loop), 3600.), 3600., 0);
1099 ev_periodic_start (loop, &hourly_tick); 1106 ev_periodic_start (loop, &hourly_tick);
1160The process exit/trace status caused by C<rpid> (see your systems 1167The process exit/trace status caused by C<rpid> (see your systems
1161C<waitpid> and C<sys/wait.h> documentation for details). 1168C<waitpid> and C<sys/wait.h> documentation for details).
1162 1169
1163=back 1170=back
1164 1171
1165Example: try to exit cleanly on SIGINT and SIGTERM. 1172Example: Try to exit cleanly on SIGINT and SIGTERM.
1166 1173
1167 static void 1174 static void
1168 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1175 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1169 { 1176 {
1170 ev_unloop (loop, EVUNLOOP_ALL); 1177 ev_unloop (loop, EVUNLOOP_ALL);
1299kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1306kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1300believe me. 1307believe me.
1301 1308
1302=back 1309=back
1303 1310
1304Example: dynamically allocate an C<ev_idle>, start it, and in the 1311Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1305callback, free it. Alos, use no error checking, as usual. 1312callback, free it. Also, use no error checking, as usual.
1306 1313
1307 static void 1314 static void
1308 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1315 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1309 { 1316 {
1310 free (w); 1317 free (w);

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