… | |
… | |
82 | |
82 | |
83 | =head1 WHAT TO READ WHEN IN A HURRY |
83 | =head1 WHAT TO READ WHEN IN A HURRY |
84 | |
84 | |
85 | This manual tries to be very detailed, but unfortunately, this also makes |
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 |
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 |
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 |
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>. |
89 | C<ev_timer> sections in L</WATCHER TYPES>. |
90 | |
90 | |
91 | =head1 ABOUT LIBEV |
91 | =head1 ABOUT LIBEV |
92 | |
92 | |
93 | 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 |
94 | 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 |
… | |
… | |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
249 | |
249 | |
250 | See the description of C<ev_embed> watchers for more info. |
250 | See the description of C<ev_embed> watchers for more info. |
251 | |
251 | |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
253 | |
253 | |
254 | Sets the allocation function to use (the prototype is similar - the |
254 | Sets the allocation function to use (the prototype is similar - the |
255 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
255 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
256 | used to allocate and free memory (no surprises here). If it returns zero |
256 | used to allocate and free memory (no surprises here). If it returns zero |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
283 | } |
283 | } |
284 | |
284 | |
285 | ... |
285 | ... |
286 | ev_set_allocator (persistent_realloc); |
286 | ev_set_allocator (persistent_realloc); |
287 | |
287 | |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
289 | |
289 | |
290 | Set the callback function to call on a retryable system call error (such |
290 | Set the callback function to call on a retryable system call error (such |
291 | as failed select, poll, epoll_wait). The message is a printable string |
291 | as failed select, poll, epoll_wait). The message is a printable string |
292 | indicating the system call or subsystem causing the problem. If this |
292 | indicating the system call or subsystem causing the problem. If this |
293 | callback is set, then libev will expect it to remedy the situation, no |
293 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
569 | kernel is more efficient (which says nothing about its actual speed, of |
569 | kernel is more efficient (which says nothing about its actual speed, of |
570 | course). While stopping, setting and starting an I/O watcher does never |
570 | course). While stopping, setting and starting an I/O watcher does never |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
574 | drops fds silently in similarly hard-to-detect cases |
574 | drops fds silently in similarly hard-to-detect cases. |
575 | |
575 | |
576 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
577 | |
577 | |
578 | While nominally embeddable in other event loops, this doesn't work |
578 | While nominally embeddable in other event loops, this doesn't work |
579 | everywhere, so you might need to test for this. And since it is broken |
579 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
764 | |
764 | |
765 | This function is rarely useful, but when some event callback runs for a |
765 | This function is rarely useful, but when some event callback runs for a |
766 | very long time without entering the event loop, updating libev's idea of |
766 | very long time without entering the event loop, updating libev's idea of |
767 | the current time is a good idea. |
767 | the current time is a good idea. |
768 | |
768 | |
769 | See also L<The special problem of time updates> in the C<ev_timer> section. |
769 | See also L</The special problem of time updates> in the C<ev_timer> section. |
770 | |
770 | |
771 | =item ev_suspend (loop) |
771 | =item ev_suspend (loop) |
772 | |
772 | |
773 | =item ev_resume (loop) |
773 | =item ev_resume (loop) |
774 | |
774 | |
… | |
… | |
1016 | invoke the actual watchers inside another context (another thread etc.). |
1016 | invoke the actual watchers inside another context (another thread etc.). |
1017 | |
1017 | |
1018 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1018 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1019 | callback. |
1019 | callback. |
1020 | |
1020 | |
1021 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1021 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
1022 | |
1022 | |
1023 | Sometimes you want to share the same loop between multiple threads. This |
1023 | Sometimes you want to share the same loop between multiple threads. This |
1024 | can be done relatively simply by putting mutex_lock/unlock calls around |
1024 | can be done relatively simply by putting mutex_lock/unlock calls around |
1025 | each call to a libev function. |
1025 | each call to a libev function. |
1026 | |
1026 | |
… | |
… | |
1174 | |
1174 | |
1175 | =item C<EV_PREPARE> |
1175 | =item C<EV_PREPARE> |
1176 | |
1176 | |
1177 | =item C<EV_CHECK> |
1177 | =item C<EV_CHECK> |
1178 | |
1178 | |
1179 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1179 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1180 | to gather new events, and all C<ev_check> watchers are invoked just after |
1180 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1181 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1181 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1182 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1183 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1184 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1185 | or lower priority within an event loop iteration. |
|
|
1186 | |
1182 | received events. Callbacks of both watcher types can start and stop as |
1187 | Callbacks of both watcher types can start and stop as many watchers as |
1183 | many watchers as they want, and all of them will be taken into account |
1188 | they want, and all of them will be taken into account (for example, a |
1184 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1189 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1185 | C<ev_run> from blocking). |
1190 | blocking). |
1186 | |
1191 | |
1187 | =item C<EV_EMBED> |
1192 | =item C<EV_EMBED> |
1188 | |
1193 | |
1189 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1194 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1190 | |
1195 | |
… | |
… | |
1313 | |
1318 | |
1314 | =item callback ev_cb (ev_TYPE *watcher) |
1319 | =item callback ev_cb (ev_TYPE *watcher) |
1315 | |
1320 | |
1316 | Returns the callback currently set on the watcher. |
1321 | Returns the callback currently set on the watcher. |
1317 | |
1322 | |
1318 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1323 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1319 | |
1324 | |
1320 | Change the callback. You can change the callback at virtually any time |
1325 | Change the callback. You can change the callback at virtually any time |
1321 | (modulo threads). |
1326 | (modulo threads). |
1322 | |
1327 | |
1323 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1328 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
… | |
… | |
1341 | or might not have been clamped to the valid range. |
1346 | or might not have been clamped to the valid range. |
1342 | |
1347 | |
1343 | The default priority used by watchers when no priority has been set is |
1348 | The default priority used by watchers when no priority has been set is |
1344 | always C<0>, which is supposed to not be too high and not be too low :). |
1349 | always C<0>, which is supposed to not be too high and not be too low :). |
1345 | |
1350 | |
1346 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1351 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1347 | priorities. |
1352 | priorities. |
1348 | |
1353 | |
1349 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1354 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1350 | |
1355 | |
1351 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1356 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1376 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1381 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1377 | functions that do not need a watcher. |
1382 | functions that do not need a watcher. |
1378 | |
1383 | |
1379 | =back |
1384 | =back |
1380 | |
1385 | |
1381 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
1386 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
1382 | OWN COMPOSITE WATCHERS> idioms. |
1387 | OWN COMPOSITE WATCHERS> idioms. |
1383 | |
1388 | |
1384 | =head2 WATCHER STATES |
1389 | =head2 WATCHER STATES |
1385 | |
1390 | |
1386 | There are various watcher states mentioned throughout this manual - |
1391 | There are various watcher states mentioned throughout this manual - |
… | |
… | |
1388 | transition between them will be described in more detail - and while these |
1393 | transition between them will be described in more detail - and while these |
1389 | rules might look complicated, they usually do "the right thing". |
1394 | rules might look complicated, they usually do "the right thing". |
1390 | |
1395 | |
1391 | =over 4 |
1396 | =over 4 |
1392 | |
1397 | |
1393 | =item initialiased |
1398 | =item initialised |
1394 | |
1399 | |
1395 | Before a watcher can be registered with the event loop it has to be |
1400 | Before a watcher can be registered with the event loop it has to be |
1396 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1401 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1397 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1402 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1398 | |
1403 | |
… | |
… | |
1874 | callback (EV_P_ ev_timer *w, int revents) |
1879 | callback (EV_P_ ev_timer *w, int revents) |
1875 | { |
1880 | { |
1876 | // calculate when the timeout would happen |
1881 | // calculate when the timeout would happen |
1877 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1882 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1878 | |
1883 | |
1879 | // if negative, it means we the timeout already occured |
1884 | // if negative, it means we the timeout already occurred |
1880 | if (after < 0.) |
1885 | if (after < 0.) |
1881 | { |
1886 | { |
1882 | // timeout occurred, take action |
1887 | // timeout occurred, take action |
1883 | } |
1888 | } |
1884 | else |
1889 | else |
… | |
… | |
1902 | |
1907 | |
1903 | Otherwise, we now the earliest time at which the timeout would trigger, |
1908 | Otherwise, we now the earliest time at which the timeout would trigger, |
1904 | and simply start the timer with this timeout value. |
1909 | and simply start the timer with this timeout value. |
1905 | |
1910 | |
1906 | In other words, each time the callback is invoked it will check whether |
1911 | In other words, each time the callback is invoked it will check whether |
1907 | the timeout cocured. If not, it will simply reschedule itself to check |
1912 | the timeout occurred. If not, it will simply reschedule itself to check |
1908 | again at the earliest time it could time out. Rinse. Repeat. |
1913 | again at the earliest time it could time out. Rinse. Repeat. |
1909 | |
1914 | |
1910 | This scheme causes more callback invocations (about one every 60 seconds |
1915 | This scheme causes more callback invocations (about one every 60 seconds |
1911 | minus half the average time between activity), but virtually no calls to |
1916 | minus half the average time between activity), but virtually no calls to |
1912 | libev to change the timeout. |
1917 | libev to change the timeout. |
… | |
… | |
1926 | if (activity detected) |
1931 | if (activity detected) |
1927 | last_activity = ev_now (EV_A); |
1932 | last_activity = ev_now (EV_A); |
1928 | |
1933 | |
1929 | When your timeout value changes, then the timeout can be changed by simply |
1934 | When your timeout value changes, then the timeout can be changed by simply |
1930 | providing a new value, stopping the timer and calling the callback, which |
1935 | providing a new value, stopping the timer and calling the callback, which |
1931 | will agaion do the right thing (for example, time out immediately :). |
1936 | will again do the right thing (for example, time out immediately :). |
1932 | |
1937 | |
1933 | timeout = new_value; |
1938 | timeout = new_value; |
1934 | ev_timer_stop (EV_A_ &timer); |
1939 | ev_timer_stop (EV_A_ &timer); |
1935 | callback (EV_A_ &timer, 0); |
1940 | callback (EV_A_ &timer, 0); |
1936 | |
1941 | |
… | |
… | |
2131 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2136 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2132 | and start the timer, if necessary. |
2137 | and start the timer, if necessary. |
2133 | |
2138 | |
2134 | =back |
2139 | =back |
2135 | |
2140 | |
2136 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2141 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
2137 | usage example. |
2142 | usage example. |
2138 | |
2143 | |
2139 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2144 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2140 | |
2145 | |
2141 | Returns the remaining time until a timer fires. If the timer is active, |
2146 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2842 | Apart from keeping your process non-blocking (which is a useful |
2847 | Apart from keeping your process non-blocking (which is a useful |
2843 | effect on its own sometimes), idle watchers are a good place to do |
2848 | effect on its own sometimes), idle watchers are a good place to do |
2844 | "pseudo-background processing", or delay processing stuff to after the |
2849 | "pseudo-background processing", or delay processing stuff to after the |
2845 | event loop has handled all outstanding events. |
2850 | event loop has handled all outstanding events. |
2846 | |
2851 | |
|
|
2852 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2853 | |
|
|
2854 | As long as there is at least one active idle watcher, libev will never |
|
|
2855 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2856 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2857 | lowest priority will do. |
|
|
2858 | |
|
|
2859 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2860 | to do something on each event loop iteration - for example to balance load |
|
|
2861 | between different connections. |
|
|
2862 | |
|
|
2863 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2864 | example. |
|
|
2865 | |
2847 | =head3 Watcher-Specific Functions and Data Members |
2866 | =head3 Watcher-Specific Functions and Data Members |
2848 | |
2867 | |
2849 | =over 4 |
2868 | =over 4 |
2850 | |
2869 | |
2851 | =item ev_idle_init (ev_idle *, callback) |
2870 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2862 | callback, free it. Also, use no error checking, as usual. |
2881 | callback, free it. Also, use no error checking, as usual. |
2863 | |
2882 | |
2864 | static void |
2883 | static void |
2865 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2884 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2866 | { |
2885 | { |
|
|
2886 | // stop the watcher |
|
|
2887 | ev_idle_stop (loop, w); |
|
|
2888 | |
|
|
2889 | // now we can free it |
2867 | free (w); |
2890 | free (w); |
|
|
2891 | |
2868 | // now do something you wanted to do when the program has |
2892 | // now do something you wanted to do when the program has |
2869 | // no longer anything immediate to do. |
2893 | // no longer anything immediate to do. |
2870 | } |
2894 | } |
2871 | |
2895 | |
2872 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2896 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2874 | ev_idle_start (loop, idle_watcher); |
2898 | ev_idle_start (loop, idle_watcher); |
2875 | |
2899 | |
2876 | |
2900 | |
2877 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2901 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2878 | |
2902 | |
2879 | Prepare and check watchers are usually (but not always) used in pairs: |
2903 | Prepare and check watchers are often (but not always) used in pairs: |
2880 | prepare watchers get invoked before the process blocks and check watchers |
2904 | prepare watchers get invoked before the process blocks and check watchers |
2881 | afterwards. |
2905 | afterwards. |
2882 | |
2906 | |
2883 | You I<must not> call C<ev_run> or similar functions that enter |
2907 | You I<must not> call C<ev_run> or similar functions that enter |
2884 | the current event loop from either C<ev_prepare> or C<ev_check> |
2908 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
2912 | with priority higher than or equal to the event loop and one coroutine |
2936 | with priority higher than or equal to the event loop and one coroutine |
2913 | of lower priority, but only once, using idle watchers to keep the event |
2937 | of lower priority, but only once, using idle watchers to keep the event |
2914 | loop from blocking if lower-priority coroutines are active, thus mapping |
2938 | loop from blocking if lower-priority coroutines are active, thus mapping |
2915 | low-priority coroutines to idle/background tasks). |
2939 | low-priority coroutines to idle/background tasks). |
2916 | |
2940 | |
2917 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2941 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2918 | priority, to ensure that they are being run before any other watchers |
2942 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2919 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
2943 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
2944 | watchers). |
2920 | |
2945 | |
2921 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2946 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2922 | activate ("feed") events into libev. While libev fully supports this, they |
2947 | activate ("feed") events into libev. While libev fully supports this, they |
2923 | might get executed before other C<ev_check> watchers did their job. As |
2948 | might get executed before other C<ev_check> watchers did their job. As |
2924 | C<ev_check> watchers are often used to embed other (non-libev) event |
2949 | C<ev_check> watchers are often used to embed other (non-libev) event |
2925 | loops those other event loops might be in an unusable state until their |
2950 | loops those other event loops might be in an unusable state until their |
2926 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2951 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2927 | others). |
2952 | others). |
|
|
2953 | |
|
|
2954 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
2955 | |
|
|
2956 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
2957 | useful because they are called once per event loop iteration. For |
|
|
2958 | example, if you want to handle a large number of connections fairly, you |
|
|
2959 | normally only do a bit of work for each active connection, and if there |
|
|
2960 | is more work to do, you wait for the next event loop iteration, so other |
|
|
2961 | connections have a chance of making progress. |
|
|
2962 | |
|
|
2963 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
2964 | next event loop iteration. However, that isn't as soon as possible - |
|
|
2965 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
2966 | |
|
|
2967 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2968 | single global idle watcher that is active as long as you have one active |
|
|
2969 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
2970 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
2971 | invoked. Neither watcher alone can do that. |
2928 | |
2972 | |
2929 | =head3 Watcher-Specific Functions and Data Members |
2973 | =head3 Watcher-Specific Functions and Data Members |
2930 | |
2974 | |
2931 | =over 4 |
2975 | =over 4 |
2932 | |
2976 | |
… | |
… | |
3133 | |
3177 | |
3134 | =over 4 |
3178 | =over 4 |
3135 | |
3179 | |
3136 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3180 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3137 | |
3181 | |
3138 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3182 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
3139 | |
3183 | |
3140 | Configures the watcher to embed the given loop, which must be |
3184 | Configures the watcher to embed the given loop, which must be |
3141 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3185 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3142 | invoked automatically, otherwise it is the responsibility of the callback |
3186 | invoked automatically, otherwise it is the responsibility of the callback |
3143 | to invoke it (it will continue to be called until the sweep has been done, |
3187 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3206 | |
3250 | |
3207 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3251 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3208 | |
3252 | |
3209 | Fork watchers are called when a C<fork ()> was detected (usually because |
3253 | Fork watchers are called when a C<fork ()> was detected (usually because |
3210 | whoever is a good citizen cared to tell libev about it by calling |
3254 | whoever is a good citizen cared to tell libev about it by calling |
3211 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3255 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3212 | event loop blocks next and before C<ev_check> watchers are being called, |
3256 | and before C<ev_check> watchers are being called, and only in the child |
3213 | and only in the child after the fork. If whoever good citizen calling |
3257 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3214 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3258 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3215 | handlers will be invoked, too, of course. |
3259 | of course. |
3216 | |
3260 | |
3217 | =head3 The special problem of life after fork - how is it possible? |
3261 | =head3 The special problem of life after fork - how is it possible? |
3218 | |
3262 | |
3219 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3263 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3220 | up/change the process environment, followed by a call to C<exec()>. This |
3264 | up/change the process environment, followed by a call to C<exec()>. This |
… | |
… | |
3313 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3357 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3314 | |
3358 | |
3315 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3359 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3316 | too, are asynchronous in nature, and signals, too, will be compressed |
3360 | too, are asynchronous in nature, and signals, too, will be compressed |
3317 | (i.e. the number of callback invocations may be less than the number of |
3361 | (i.e. the number of callback invocations may be less than the number of |
3318 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3362 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3319 | of "global async watchers" by using a watcher on an otherwise unused |
3363 | of "global async watchers" by using a watcher on an otherwise unused |
3320 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3364 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3321 | even without knowing which loop owns the signal. |
3365 | even without knowing which loop owns the signal. |
3322 | |
3366 | |
3323 | =head3 Queueing |
3367 | =head3 Queueing |
… | |
… | |
3614 | already been invoked. |
3658 | already been invoked. |
3615 | |
3659 | |
3616 | A common way around all these issues is to make sure that |
3660 | A common way around all these issues is to make sure that |
3617 | C<start_new_request> I<always> returns before the callback is invoked. If |
3661 | C<start_new_request> I<always> returns before the callback is invoked. If |
3618 | C<start_new_request> immediately knows the result, it can artificially |
3662 | C<start_new_request> immediately knows the result, it can artificially |
3619 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
3663 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
3620 | for example, or more sneakily, by reusing an existing (stopped) watcher |
3664 | example, or more sneakily, by reusing an existing (stopped) watcher and |
3621 | and pushing it into the pending queue: |
3665 | pushing it into the pending queue: |
3622 | |
3666 | |
3623 | ev_set_cb (watcher, callback); |
3667 | ev_set_cb (watcher, callback); |
3624 | ev_feed_event (EV_A_ watcher, 0); |
3668 | ev_feed_event (EV_A_ watcher, 0); |
3625 | |
3669 | |
3626 | This way, C<start_new_request> can safely return before the callback is |
3670 | This way, C<start_new_request> can safely return before the callback is |
… | |
… | |
3634 | |
3678 | |
3635 | This brings the problem of exiting - a callback might want to finish the |
3679 | This brings the problem of exiting - a callback might want to finish the |
3636 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3680 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3637 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3681 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3638 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3682 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3639 | other combination: In these cases, C<ev_break> will not work alone. |
3683 | other combination: In these cases, a simple C<ev_break> will not work. |
3640 | |
3684 | |
3641 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3685 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3642 | invocation, and use a loop around C<ev_run> until the condition is |
3686 | invocation, and use a loop around C<ev_run> until the condition is |
3643 | triggered, using C<EVRUN_ONCE>: |
3687 | triggered, using C<EVRUN_ONCE>: |
3644 | |
3688 | |
… | |
… | |
3830 | called): |
3874 | called): |
3831 | |
3875 | |
3832 | void |
3876 | void |
3833 | wait_for_event (ev_watcher *w) |
3877 | wait_for_event (ev_watcher *w) |
3834 | { |
3878 | { |
3835 | ev_cb_set (w) = current_coro; |
3879 | ev_set_cb (w, current_coro); |
3836 | switch_to (libev_coro); |
3880 | switch_to (libev_coro); |
3837 | } |
3881 | } |
3838 | |
3882 | |
3839 | That basically suspends the coroutine inside C<wait_for_event> and |
3883 | That basically suspends the coroutine inside C<wait_for_event> and |
3840 | continues the libev coroutine, which, when appropriate, switches back to |
3884 | continues the libev coroutine, which, when appropriate, switches back to |
… | |
… | |
3843 | You can do similar tricks if you have, say, threads with an event queue - |
3887 | You can do similar tricks if you have, say, threads with an event queue - |
3844 | instead of storing a coroutine, you store the queue object and instead of |
3888 | instead of storing a coroutine, you store the queue object and instead of |
3845 | switching to a coroutine, you push the watcher onto the queue and notify |
3889 | switching to a coroutine, you push the watcher onto the queue and notify |
3846 | any waiters. |
3890 | any waiters. |
3847 | |
3891 | |
3848 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
3892 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3849 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3893 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3850 | |
3894 | |
3851 | // my_ev.h |
3895 | // my_ev.h |
3852 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3896 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3853 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
3897 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
… | |
… | |
3896 | to use the libev header file and library. |
3940 | to use the libev header file and library. |
3897 | |
3941 | |
3898 | =back |
3942 | =back |
3899 | |
3943 | |
3900 | =head1 C++ SUPPORT |
3944 | =head1 C++ SUPPORT |
|
|
3945 | |
|
|
3946 | =head2 C API |
|
|
3947 | |
|
|
3948 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3949 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3950 | will work fine. |
|
|
3951 | |
|
|
3952 | Proper exception specifications might have to be added to callbacks passed |
|
|
3953 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3954 | other callbacks (allocator, syserr, loop acquire/release and periodic |
|
|
3955 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3956 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3957 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3958 | |
|
|
3959 | static void |
|
|
3960 | fatal_error (const char *msg) EV_THROW |
|
|
3961 | { |
|
|
3962 | perror (msg); |
|
|
3963 | abort (); |
|
|
3964 | } |
|
|
3965 | |
|
|
3966 | ... |
|
|
3967 | ev_set_syserr_cb (fatal_error); |
|
|
3968 | |
|
|
3969 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3970 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
3971 | because it runs cleanup watchers). |
|
|
3972 | |
|
|
3973 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3974 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3975 | throwing exceptions through C libraries (most do). |
|
|
3976 | |
|
|
3977 | =head2 C++ API |
3901 | |
3978 | |
3902 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3979 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3903 | you to use some convenience methods to start/stop watchers and also change |
3980 | you to use some convenience methods to start/stop watchers and also change |
3904 | the callback model to a model using method callbacks on objects. |
3981 | the callback model to a model using method callbacks on objects. |
3905 | |
3982 | |
… | |
… | |
4043 | Associates a different C<struct ev_loop> with this watcher. You can only |
4120 | Associates a different C<struct ev_loop> with this watcher. You can only |
4044 | do this when the watcher is inactive (and not pending either). |
4121 | do this when the watcher is inactive (and not pending either). |
4045 | |
4122 | |
4046 | =item w->set ([arguments]) |
4123 | =item w->set ([arguments]) |
4047 | |
4124 | |
4048 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4125 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
4049 | method or a suitable start method must be called at least once. Unlike the |
4126 | with the same arguments. Either this method or a suitable start method |
4050 | C counterpart, an active watcher gets automatically stopped and restarted |
4127 | must be called at least once. Unlike the C counterpart, an active watcher |
4051 | when reconfiguring it with this method. |
4128 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4129 | method. |
|
|
4130 | |
|
|
4131 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4132 | clashing with the C<set (loop)> method. |
4052 | |
4133 | |
4053 | =item w->start () |
4134 | =item w->start () |
4054 | |
4135 | |
4055 | Starts the watcher. Note that there is no C<loop> argument, as the |
4136 | Starts the watcher. Note that there is no C<loop> argument, as the |
4056 | constructor already stores the event loop. |
4137 | constructor already stores the event loop. |
… | |
… | |
4159 | =item Lua |
4240 | =item Lua |
4160 | |
4241 | |
4161 | Brian Maher has written a partial interface to libev for lua (at the |
4242 | Brian Maher has written a partial interface to libev for lua (at the |
4162 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4243 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4163 | L<http://github.com/brimworks/lua-ev>. |
4244 | L<http://github.com/brimworks/lua-ev>. |
|
|
4245 | |
|
|
4246 | =item Javascript |
|
|
4247 | |
|
|
4248 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4249 | |
|
|
4250 | =item Others |
|
|
4251 | |
|
|
4252 | There are others, and I stopped counting. |
4164 | |
4253 | |
4165 | =back |
4254 | =back |
4166 | |
4255 | |
4167 | |
4256 | |
4168 | =head1 MACRO MAGIC |
4257 | =head1 MACRO MAGIC |
… | |
… | |
4467 | |
4556 | |
4468 | If programs implement their own fd to handle mapping on win32, then this |
4557 | If programs implement their own fd to handle mapping on win32, then this |
4469 | macro can be used to override the C<close> function, useful to unregister |
4558 | macro can be used to override the C<close> function, useful to unregister |
4470 | file descriptors again. Note that the replacement function has to close |
4559 | file descriptors again. Note that the replacement function has to close |
4471 | the underlying OS handle. |
4560 | the underlying OS handle. |
|
|
4561 | |
|
|
4562 | =item EV_USE_WSASOCKET |
|
|
4563 | |
|
|
4564 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4565 | communication socket, which works better in some environments. Otherwise, |
|
|
4566 | the normal C<socket> function will be used, which works better in other |
|
|
4567 | environments. |
4472 | |
4568 | |
4473 | =item EV_USE_POLL |
4569 | =item EV_USE_POLL |
4474 | |
4570 | |
4475 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4571 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4476 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4572 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
4528 | above. This reduces dependencies and makes libev faster. |
4624 | above. This reduces dependencies and makes libev faster. |
4529 | |
4625 | |
4530 | =item EV_ATOMIC_T |
4626 | =item EV_ATOMIC_T |
4531 | |
4627 | |
4532 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4628 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4533 | access is atomic and serialised with respect to other threads or signal |
4629 | access is atomic with respect to other threads or signal contexts. No |
4534 | contexts. No such type is easily found in the C language, so you can |
4630 | such type is easily found in the C language, so you can provide your own |
4535 | provide your own type that you know is safe for your purposes. It is used |
4631 | type that you know is safe for your purposes. It is used both for signal |
4536 | both for signal handler "locking" as well as for signal and thread safety |
4632 | handler "locking" as well as for signal and thread safety in C<ev_async> |
4537 | in C<ev_async> watchers. |
4633 | watchers. |
4538 | |
4634 | |
4539 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4635 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4540 | (from F<signal.h>), which is usually good enough on most platforms, |
4636 | (from F<signal.h>), which is usually good enough on most platforms. |
4541 | although strictly speaking using a type that also implies a memory fence |
|
|
4542 | is required. |
|
|
4543 | |
4637 | |
4544 | =item EV_H (h) |
4638 | =item EV_H (h) |
4545 | |
4639 | |
4546 | The name of the F<ev.h> header file used to include it. The default if |
4640 | The name of the F<ev.h> header file used to include it. The default if |
4547 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4641 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
4915 | default loop and triggering an C<ev_async> watcher from the default loop |
5009 | default loop and triggering an C<ev_async> watcher from the default loop |
4916 | watcher callback into the event loop interested in the signal. |
5010 | watcher callback into the event loop interested in the signal. |
4917 | |
5011 | |
4918 | =back |
5012 | =back |
4919 | |
5013 | |
4920 | See also L<THREAD LOCKING EXAMPLE>. |
5014 | See also L</THREAD LOCKING EXAMPLE>. |
4921 | |
5015 | |
4922 | =head3 COROUTINES |
5016 | =head3 COROUTINES |
4923 | |
5017 | |
4924 | Libev is very accommodating to coroutines ("cooperative threads"): |
5018 | Libev is very accommodating to coroutines ("cooperative threads"): |
4925 | libev fully supports nesting calls to its functions from different |
5019 | libev fully supports nesting calls to its functions from different |
… | |
… | |
5216 | thread" or will block signals process-wide, both behaviours would |
5310 | thread" or will block signals process-wide, both behaviours would |
5217 | be compatible with libev. Interaction between C<sigprocmask> and |
5311 | be compatible with libev. Interaction between C<sigprocmask> and |
5218 | C<pthread_sigmask> could complicate things, however. |
5312 | C<pthread_sigmask> could complicate things, however. |
5219 | |
5313 | |
5220 | The most portable way to handle signals is to block signals in all threads |
5314 | The most portable way to handle signals is to block signals in all threads |
5221 | except the initial one, and run the default loop in the initial thread as |
5315 | except the initial one, and run the signal handling loop in the initial |
5222 | well. |
5316 | thread as well. |
5223 | |
5317 | |
5224 | =item C<long> must be large enough for common memory allocation sizes |
5318 | =item C<long> must be large enough for common memory allocation sizes |
5225 | |
5319 | |
5226 | To improve portability and simplify its API, libev uses C<long> internally |
5320 | To improve portability and simplify its API, libev uses C<long> internally |
5227 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5321 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
5331 | =over 4 |
5425 | =over 4 |
5332 | |
5426 | |
5333 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5427 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5334 | |
5428 | |
5335 | The backward compatibility mechanism can be controlled by |
5429 | The backward compatibility mechanism can be controlled by |
5336 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
5430 | C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING> |
5337 | section. |
5431 | section. |
5338 | |
5432 | |
5339 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5433 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5340 | |
5434 | |
5341 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5435 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
… | |
… | |
5384 | =over 4 |
5478 | =over 4 |
5385 | |
5479 | |
5386 | =item active |
5480 | =item active |
5387 | |
5481 | |
5388 | A watcher is active as long as it has been started and not yet stopped. |
5482 | A watcher is active as long as it has been started and not yet stopped. |
5389 | See L<WATCHER STATES> for details. |
5483 | See L</WATCHER STATES> for details. |
5390 | |
5484 | |
5391 | =item application |
5485 | =item application |
5392 | |
5486 | |
5393 | In this document, an application is whatever is using libev. |
5487 | In this document, an application is whatever is using libev. |
5394 | |
5488 | |
… | |
… | |
5430 | watchers and events. |
5524 | watchers and events. |
5431 | |
5525 | |
5432 | =item pending |
5526 | =item pending |
5433 | |
5527 | |
5434 | A watcher is pending as soon as the corresponding event has been |
5528 | A watcher is pending as soon as the corresponding event has been |
5435 | detected. See L<WATCHER STATES> for details. |
5529 | detected. See L</WATCHER STATES> for details. |
5436 | |
5530 | |
5437 | =item real time |
5531 | =item real time |
5438 | |
5532 | |
5439 | The physical time that is observed. It is apparently strictly monotonic :) |
5533 | The physical time that is observed. It is apparently strictly monotonic :) |
5440 | |
5534 | |