… | |
… | |
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) |
… | |
… | |
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 | |
… | |
… | |
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 C<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 |
… | |
… | |
3921 | |
3966 | |
3922 | ... |
3967 | ... |
3923 | ev_set_syserr_cb (fatal_error); |
3968 | ev_set_syserr_cb (fatal_error); |
3924 | |
3969 | |
3925 | The only API functions that can currently throw exceptions are C<ev_run>, |
3970 | The only API functions that can currently throw exceptions are C<ev_run>, |
3926 | C<ev_inoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
3971 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
3927 | because it runs cleanup watchers). |
3972 | because it runs cleanup watchers). |
3928 | |
3973 | |
3929 | Throwing exceptions in watcher callbacks is only supported if libev itself |
3974 | Throwing exceptions in watcher callbacks is only supported if libev itself |
3930 | is compiled with a C++ compiler or your C and C++ environments allow |
3975 | is compiled with a C++ compiler or your C and C++ environments allow |
3931 | throwing exceptions through C libraries (most do). |
3976 | throwing exceptions through C libraries (most do). |