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2 | |
2 | |
3 | libev - a high performance full-featured event loop written in C |
3 | libev - 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 */ |
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8 | #include <ev.h> |
7 | #include <ev.h> |
9 | |
8 | |
10 | /* what follows is a fully working example program */ |
9 | =head1 EXAMPLE PROGRAM |
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10 | |
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11 | #include <ev.h> |
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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 |
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61 | details of the event, and then hand it over to libev by I<starting> the |
63 | details of the event, and then hand it over to libev by I<starting> the |
62 | watcher. |
64 | watcher. |
63 | |
65 | |
64 | =head1 FEATURES |
66 | =head1 FEATURES |
65 | |
67 | |
66 | Libev supports select, poll, the linux-specific epoll and the bsd-specific |
68 | Libev supports C<select>, C<poll>, the linux-specific C<epoll>, the |
67 | kqueue mechanisms for file descriptor events, relative timers, absolute |
69 | bsd-specific C<kqueue> and the solaris-specific event port mechanisms |
68 | timers with customised rescheduling, signal events, process status change |
70 | for file descriptor events (C<ev_io>), relative timers (C<ev_timer>), |
69 | events (related to SIGCHLD), and event watchers dealing with the event |
71 | absolute timers with customised rescheduling (C<ev_periodic>), synchronous |
70 | loop mechanism itself (idle, prepare and check watchers). It also is quite |
72 | signals (C<ev_signal>), process status change events (C<ev_child>), and |
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73 | event watchers dealing with the event loop mechanism itself (C<ev_idle>, |
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74 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
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75 | file watchers (C<ev_stat>) and even limited support for fork events |
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76 | (C<ev_fork>). |
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77 | |
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78 | It also is quite fast (see this |
71 | fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing |
79 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
72 | it to libevent for example). |
80 | for example). |
73 | |
81 | |
74 | =head1 CONVENTIONS |
82 | =head1 CONVENTIONS |
75 | |
83 | |
76 | Libev is very configurable. In this manual the default configuration |
84 | Libev is very configurable. In this manual the default configuration will |
77 | will be described, which supports multiple event loops. For more info |
85 | be described, which supports multiple event loops. For more info about |
78 | about various configuration options please have a look at the file |
86 | various configuration options please have a look at B<EMBED> section in |
79 | F<README.embed> in the libev distribution. If libev was configured without |
87 | this manual. If libev was configured without support for multiple event |
80 | support for multiple event loops, then all functions taking an initial |
88 | loops, then all functions taking an initial argument of name C<loop> |
81 | argument 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. |
82 | will not have this argument. |
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83 | |
90 | |
84 | =head1 TIME REPRESENTATION |
91 | =head1 TIME REPRESENTATION |
85 | |
92 | |
86 | Libev represents time as a single floating point number, representing the |
93 | Libev 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 |
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116 | Usually, it's a good idea to terminate if the major versions mismatch, |
123 | Usually, it's a good idea to terminate if the major versions mismatch, |
117 | as this indicates an incompatible change. Minor versions are usually |
124 | as this indicates an incompatible change. Minor versions are usually |
118 | compatible to older versions, so a larger minor version alone is usually |
125 | compatible to older versions, so a larger minor version alone is usually |
119 | not a problem. |
126 | not a problem. |
120 | |
127 | |
121 | Example: make sure we haven't accidentally been linked against the wrong |
128 | Example: Make sure we haven't accidentally been linked against the wrong |
122 | version: |
129 | version. |
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 | |
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167 | |
174 | |
168 | You could override this function in high-availability programs to, say, |
175 | You could override this function in high-availability programs to, say, |
169 | free some memory if it cannot allocate memory, to use a special allocator, |
176 | free some memory if it cannot allocate memory, to use a special allocator, |
170 | or even to sleep a while and retry until some memory is available. |
177 | or even to sleep a while and retry until some memory is available. |
171 | |
178 | |
172 | Example: replace the libev allocator with one that waits a bit and then |
179 | Example: Replace the libev allocator with one that waits a bit and then |
173 | retries: better than mine). |
180 | retries). |
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 (;;) |
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197 | callback is set, then libev will expect it to remedy the sitution, no |
204 | callback is set, then libev will expect it to remedy the sitution, no |
198 | matter what, when it returns. That is, libev will generally retry the |
205 | matter what, when it returns. That is, libev will generally retry the |
199 | requested operation, or, if the condition doesn't go away, do bad stuff |
206 | requested operation, or, if the condition doesn't go away, do bad stuff |
200 | (such as abort). |
207 | (such as abort). |
201 | |
208 | |
202 | Example: do the same thing as libev does internally: |
209 | Example: 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); |
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353 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
360 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
354 | always distinct from the default loop. Unlike the default loop, it cannot |
361 | always distinct from the default loop. Unlike the default loop, it cannot |
355 | handle signal and child watchers, and attempts to do so will be greeted by |
362 | handle signal and child watchers, and attempts to do so will be greeted by |
356 | undefined behaviour (or a failed assertion if assertions are enabled). |
363 | undefined behaviour (or a failed assertion if assertions are enabled). |
357 | |
364 | |
358 | Example: try to create a event loop that uses epoll and nothing else. |
365 | Example: 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 | |
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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 | |
467 | Example: queue some jobs and then loop until no events are outsanding |
474 | Example: Queue some jobs and then loop until no events are outsanding |
468 | anymore. |
475 | anymore. |
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); |
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492 | visible to the libev user and should not keep C<ev_loop> from exiting if |
499 | visible to the libev user and should not keep C<ev_loop> from exiting if |
493 | no event watchers registered by it are active. It is also an excellent |
500 | no event watchers registered by it are active. It is also an excellent |
494 | way to do this for generic recurring timers or from within third-party |
501 | way to do this for generic recurring timers or from within third-party |
495 | libraries. Just remember to I<unref after start> and I<ref before stop>. |
502 | libraries. Just remember to I<unref after start> and I<ref before stop>. |
496 | |
503 | |
497 | Example: create a signal watcher, but keep it from keeping C<ev_loop> |
504 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
498 | running when nothing else is active. |
505 | running 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 | |
505 | Example: for some weird reason, unregister the above signal handler again. |
512 | Example: 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 |
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814 | |
821 | |
815 | The events being watched. |
822 | The events being watched. |
816 | |
823 | |
817 | =back |
824 | =back |
818 | |
825 | |
819 | Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well |
826 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
820 | readable, but only once. Since it is likely line-buffered, you could |
827 | readable, but only once. Since it is likely line-buffered, you could |
821 | attempt to read a whole line in the callback: |
828 | attempt 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); |
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916 | or C<ev_timer_again> is called and determines the next timeout (if any), |
923 | or C<ev_timer_again> is called and determines the next timeout (if any), |
917 | which is also when any modifications are taken into account. |
924 | which is also when any modifications are taken into account. |
918 | |
925 | |
919 | =back |
926 | =back |
920 | |
927 | |
921 | Example: create a timer that fires after 60 seconds. |
928 | Example: 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 |
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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 | |
933 | Example: create a timeout timer that times out after 10 seconds of |
940 | Example: Create a timeout timer that times out after 10 seconds of |
934 | inactivity. |
941 | inactivity. |
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 | { |
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1063 | switched off. Can be changed any time, but changes only take effect when |
1070 | switched off. Can be changed any time, but changes only take effect when |
1064 | the periodic timer fires or C<ev_periodic_again> is being called. |
1071 | the periodic timer fires or C<ev_periodic_again> is being called. |
1065 | |
1072 | |
1066 | =back |
1073 | =back |
1067 | |
1074 | |
1068 | Example: call a callback every hour, or, more precisely, whenever the |
1075 | Example: Call a callback every hour, or, more precisely, whenever the |
1069 | system clock is divisible by 3600. The callback invocation times have |
1076 | system clock is divisible by 3600. The callback invocation times have |
1070 | potentially a lot of jittering, but good long-term stability. |
1077 | potentially 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) |
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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 | |
1082 | Example: the same as above, but use a reschedule callback to do it: |
1089 | Example: 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) |
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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 | |
1094 | Example: call a callback every hour, starting now: |
1101 | Example: 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); |
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1160 | The process exit/trace status caused by C<rpid> (see your systems |
1167 | The process exit/trace status caused by C<rpid> (see your systems |
1161 | C<waitpid> and C<sys/wait.h> documentation for details). |
1168 | C<waitpid> and C<sys/wait.h> documentation for details). |
1162 | |
1169 | |
1163 | =back |
1170 | =back |
1164 | |
1171 | |
1165 | Example: try to exit cleanly on SIGINT and SIGTERM. |
1172 | Example: 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); |
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1299 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1306 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1300 | believe me. |
1307 | believe me. |
1301 | |
1308 | |
1302 | =back |
1309 | =back |
1303 | |
1310 | |
1304 | Example: dynamically allocate an C<ev_idle>, start it, and in the |
1311 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1305 | callback, free it. Alos, use no error checking, as usual. |
1312 | callback, 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); |