… | |
… | |
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 |
… | |
… | |
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 | |
… | |
… | |
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 - |
… | |
… | |
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 | |
|
|
2968 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2969 | single global idle watcher that is active as long as you have one active |
|
|
2970 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
2971 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
2972 | invoked. Neither watcher alone can do that. |
2928 | |
2973 | |
2929 | =head3 Watcher-Specific Functions and Data Members |
2974 | =head3 Watcher-Specific Functions and Data Members |
2930 | |
2975 | |
2931 | =over 4 |
2976 | =over 4 |
2932 | |
2977 | |
… | |
… | |
3313 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3358 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3314 | |
3359 | |
3315 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3360 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3316 | too, are asynchronous in nature, and signals, too, will be compressed |
3361 | 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 |
3362 | (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 |
3363 | 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 |
3364 | 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, |
3365 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3321 | even without knowing which loop owns the signal. |
3366 | even without knowing which loop owns the signal. |
3322 | |
3367 | |
3323 | =head3 Queueing |
3368 | =head3 Queueing |
… | |
… | |
3830 | called): |
3875 | called): |
3831 | |
3876 | |
3832 | void |
3877 | void |
3833 | wait_for_event (ev_watcher *w) |
3878 | wait_for_event (ev_watcher *w) |
3834 | { |
3879 | { |
3835 | ev_cb_set (w) = current_coro; |
3880 | ev_set_cb (w, current_coro); |
3836 | switch_to (libev_coro); |
3881 | switch_to (libev_coro); |
3837 | } |
3882 | } |
3838 | |
3883 | |
3839 | That basically suspends the coroutine inside C<wait_for_event> and |
3884 | That basically suspends the coroutine inside C<wait_for_event> and |
3840 | continues the libev coroutine, which, when appropriate, switches back to |
3885 | 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 - |
3888 | 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 |
3889 | 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 |
3890 | switching to a coroutine, you push the watcher onto the queue and notify |
3846 | any waiters. |
3891 | any waiters. |
3847 | |
3892 | |
3848 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
3893 | 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: |
3894 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3850 | |
3895 | |
3851 | // my_ev.h |
3896 | // my_ev.h |
3852 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3897 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3853 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
3898 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
… | |
… | |
4193 | |
4238 | |
4194 | Brian Maher has written a partial interface to libev for lua (at the |
4239 | Brian Maher has written a partial interface to libev for lua (at the |
4195 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4240 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4196 | L<http://github.com/brimworks/lua-ev>. |
4241 | L<http://github.com/brimworks/lua-ev>. |
4197 | |
4242 | |
|
|
4243 | =item Javascript |
|
|
4244 | |
|
|
4245 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4246 | |
|
|
4247 | =item Others |
|
|
4248 | |
|
|
4249 | There are others, and I stopped counting. |
|
|
4250 | |
4198 | =back |
4251 | =back |
4199 | |
4252 | |
4200 | |
4253 | |
4201 | =head1 MACRO MAGIC |
4254 | =head1 MACRO MAGIC |
4202 | |
4255 | |
… | |
… | |
4948 | default loop and triggering an C<ev_async> watcher from the default loop |
5001 | default loop and triggering an C<ev_async> watcher from the default loop |
4949 | watcher callback into the event loop interested in the signal. |
5002 | watcher callback into the event loop interested in the signal. |
4950 | |
5003 | |
4951 | =back |
5004 | =back |
4952 | |
5005 | |
4953 | See also L<THREAD LOCKING EXAMPLE>. |
5006 | See also L</THREAD LOCKING EXAMPLE>. |
4954 | |
5007 | |
4955 | =head3 COROUTINES |
5008 | =head3 COROUTINES |
4956 | |
5009 | |
4957 | Libev is very accommodating to coroutines ("cooperative threads"): |
5010 | Libev is very accommodating to coroutines ("cooperative threads"): |
4958 | libev fully supports nesting calls to its functions from different |
5011 | libev fully supports nesting calls to its functions from different |
… | |
… | |
5364 | =over 4 |
5417 | =over 4 |
5365 | |
5418 | |
5366 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5419 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5367 | |
5420 | |
5368 | The backward compatibility mechanism can be controlled by |
5421 | The backward compatibility mechanism can be controlled by |
5369 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
5422 | C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING> |
5370 | section. |
5423 | section. |
5371 | |
5424 | |
5372 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5425 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5373 | |
5426 | |
5374 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5427 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
… | |
… | |
5417 | =over 4 |
5470 | =over 4 |
5418 | |
5471 | |
5419 | =item active |
5472 | =item active |
5420 | |
5473 | |
5421 | A watcher is active as long as it has been started and not yet stopped. |
5474 | A watcher is active as long as it has been started and not yet stopped. |
5422 | See L<WATCHER STATES> for details. |
5475 | See L</WATCHER STATES> for details. |
5423 | |
5476 | |
5424 | =item application |
5477 | =item application |
5425 | |
5478 | |
5426 | In this document, an application is whatever is using libev. |
5479 | In this document, an application is whatever is using libev. |
5427 | |
5480 | |
… | |
… | |
5463 | watchers and events. |
5516 | watchers and events. |
5464 | |
5517 | |
5465 | =item pending |
5518 | =item pending |
5466 | |
5519 | |
5467 | A watcher is pending as soon as the corresponding event has been |
5520 | A watcher is pending as soon as the corresponding event has been |
5468 | detected. See L<WATCHER STATES> for details. |
5521 | detected. See L</WATCHER STATES> for details. |
5469 | |
5522 | |
5470 | =item real time |
5523 | =item real time |
5471 | |
5524 | |
5472 | The physical time that is observed. It is apparently strictly monotonic :) |
5525 | The physical time that is observed. It is apparently strictly monotonic :) |
5473 | |
5526 | |