… | |
… | |
717 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, |
717 | Libev will usually signal a few \*(L"dummy\*(R" events together with an error, |
718 | for example it might indicate that a fd is readable or writable, and if |
718 | for example it might indicate that a fd is readable or writable, and if |
719 | your callbacks is well-written it can just attempt the operation and cope |
719 | your callbacks is well-written it can just attempt the operation and cope |
720 | with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded |
720 | with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded |
721 | programs, though, so beware. |
721 | programs, though, so beware. |
722 | .Sh "\s-1SUMMARY\s0 \s-1OF\s0 \s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
722 | .Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
723 | .IX Subsection "SUMMARY OF GENERIC WATCHER FUNCTIONS" |
723 | .IX Subsection "GENERIC WATCHER FUNCTIONS" |
724 | In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, |
724 | In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, |
725 | e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers. |
725 | e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers. |
726 | .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
726 | .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
727 | .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
727 | .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
728 | .IX Item "ev_init (ev_TYPE *watcher, callback)" |
728 | .IX Item "ev_init (ev_TYPE *watcher, callback)" |
… | |
… | |
734 | which rolls both calls into one. |
734 | which rolls both calls into one. |
735 | .Sp |
735 | .Sp |
736 | You can reinitialise a watcher at any time as long as it has been stopped |
736 | You can reinitialise a watcher at any time as long as it has been stopped |
737 | (or never started) and there are no pending events outstanding. |
737 | (or never started) and there are no pending events outstanding. |
738 | .Sp |
738 | .Sp |
739 | The callbakc is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, |
739 | The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, |
740 | int revents)\*(C'\fR. |
740 | int revents)\*(C'\fR. |
741 | .ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 |
741 | .ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 |
742 | .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 |
742 | .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 |
743 | .IX Item "ev_TYPE_set (ev_TYPE *, [args])" |
743 | .IX Item "ev_TYPE_set (ev_TYPE *, [args])" |
744 | This macro initialises the type-specific parts of a watcher. You need to |
744 | This macro initialises the type-specific parts of a watcher. You need to |
… | |
… | |
822 | have been omitted.... |
822 | have been omitted.... |
823 | .SH "WATCHER TYPES" |
823 | .SH "WATCHER TYPES" |
824 | .IX Header "WATCHER TYPES" |
824 | .IX Header "WATCHER TYPES" |
825 | This section describes each watcher in detail, but will not repeat |
825 | This section describes each watcher in detail, but will not repeat |
826 | information given in the last section. |
826 | information given in the last section. |
827 | .ie n .Sh """ev_io"" \- is this file descriptor readable or writable" |
827 | .ie n .Sh """ev_io"" \- is this file descriptor readable or writable?" |
828 | .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" |
828 | .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
829 | .IX Subsection "ev_io - is this file descriptor readable or writable" |
829 | .IX Subsection "ev_io - is this file descriptor readable or writable?" |
830 | I/O watchers check whether a file descriptor is readable or writable |
830 | I/O watchers check whether a file descriptor is readable or writable |
831 | in each iteration of the event loop (This behaviour is called |
831 | in each iteration of the event loop, or, more precisely, when reading |
832 | level-triggering because you keep receiving events as long as the |
832 | would not block the process and writing would at least be able to write |
833 | condition persists. Remember you can stop the watcher if you don't want to |
833 | some data. This behaviour is called level-triggering because you keep |
834 | act on the event and neither want to receive future events). |
834 | receiving events as long as the condition persists. Remember you can stop |
|
|
835 | the watcher if you don't want to act on the event and neither want to |
|
|
836 | receive future events. |
835 | .PP |
837 | .PP |
836 | In general you can register as many read and/or write event watchers per |
838 | In general you can register as many read and/or write event watchers per |
837 | fd as you want (as long as you don't confuse yourself). Setting all file |
839 | fd as you want (as long as you don't confuse yourself). Setting all file |
838 | descriptors to non-blocking mode is also usually a good idea (but not |
840 | descriptors to non-blocking mode is also usually a good idea (but not |
839 | required if you know what you are doing). |
841 | required if you know what you are doing). |
840 | .PP |
842 | .PP |
841 | You have to be careful with dup'ed file descriptors, though. Some backends |
843 | You have to be careful with dup'ed file descriptors, though. Some backends |
842 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
844 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
843 | descriptors correctly if you register interest in two or more fds pointing |
845 | descriptors correctly if you register interest in two or more fds pointing |
844 | to the same underlying file/socket etc. description (that is, they share |
846 | to the same underlying file/socket/etc. description (that is, they share |
845 | the same underlying \*(L"file open\*(R"). |
847 | the same underlying \*(L"file open\*(R"). |
846 | .PP |
848 | .PP |
847 | If you must do this, then force the use of a known-to-be-good backend |
849 | If you must do this, then force the use of a known-to-be-good backend |
848 | (at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and |
850 | (at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and |
849 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). |
851 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). |
|
|
852 | .PP |
|
|
853 | Another thing you have to watch out for is that it is quite easy to |
|
|
854 | receive \*(L"spurious\*(R" readyness notifications, that is your callback might |
|
|
855 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
|
|
856 | because there is no data. Not only are some backends known to create a |
|
|
857 | lot of those (for example solaris ports), it is very easy to get into |
|
|
858 | this situation even with a relatively standard program structure. Thus |
|
|
859 | it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning |
|
|
860 | \&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. |
|
|
861 | .PP |
|
|
862 | If you cannot run the fd in non-blocking mode (for example you should not |
|
|
863 | play around with an Xlib connection), then you have to seperately re-test |
|
|
864 | wether a file descriptor is really ready with a known-to-be good interface |
|
|
865 | such as poll (fortunately in our Xlib example, Xlib already does this on |
|
|
866 | its own, so its quite safe to use). |
850 | .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
867 | .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
851 | .IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
868 | .IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
852 | .PD 0 |
869 | .PD 0 |
853 | .IP "ev_io_set (ev_io *, int fd, int events)" 4 |
870 | .IP "ev_io_set (ev_io *, int fd, int events)" 4 |
854 | .IX Item "ev_io_set (ev_io *, int fd, int events)" |
871 | .IX Item "ev_io_set (ev_io *, int fd, int events)" |
855 | .PD |
872 | .PD |
856 | Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive |
873 | Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to |
857 | events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ | |
874 | rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or |
858 | EV_WRITE\*(C'\fR to receive the given events. |
875 | \&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events. |
859 | .Sp |
|
|
860 | Please note that most of the more scalable backend mechanisms (for example |
|
|
861 | epoll and solaris ports) can result in spurious readyness notifications |
|
|
862 | for file descriptors, so you practically need to use non-blocking I/O (and |
|
|
863 | treat callback invocation as hint only), or retest separately with a safe |
|
|
864 | interface before doing I/O (XLib can do this), or force the use of either |
|
|
865 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this |
|
|
866 | problem. Also note that it is quite easy to have your callback invoked |
|
|
867 | when the readyness condition is no longer valid even when employing |
|
|
868 | typical ways of handling events, so its a good idea to use non-blocking |
|
|
869 | I/O unconditionally. |
|
|
870 | .PP |
876 | .PP |
871 | Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well |
877 | Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well |
872 | readable, but only once. Since it is likely line\-buffered, you could |
878 | readable, but only once. Since it is likely line\-buffered, you could |
873 | attempt to read a whole line in the callback: |
879 | attempt to read a whole line in the callback: |
874 | .PP |
880 | .PP |
… | |
… | |
887 | \& struct ev_io stdin_readable; |
893 | \& struct ev_io stdin_readable; |
888 | \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
894 | \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
889 | \& ev_io_start (loop, &stdin_readable); |
895 | \& ev_io_start (loop, &stdin_readable); |
890 | \& ev_loop (loop, 0); |
896 | \& ev_loop (loop, 0); |
891 | .Ve |
897 | .Ve |
892 | .ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" |
898 | .ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" |
893 | .el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" |
899 | .el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts" |
894 | .IX Subsection "ev_timer - relative and optionally recurring timeouts" |
900 | .IX Subsection "ev_timer - relative and optionally repeating timeouts" |
895 | Timer watchers are simple relative timers that generate an event after a |
901 | Timer watchers are simple relative timers that generate an event after a |
896 | given time, and optionally repeating in regular intervals after that. |
902 | given time, and optionally repeating in regular intervals after that. |
897 | .PP |
903 | .PP |
898 | The timers are based on real time, that is, if you register an event that |
904 | The timers are based on real time, that is, if you register an event that |
899 | times out after an hour and you reset your system clock to last years |
905 | times out after an hour and you reset your system clock to last years |
… | |
… | |
986 | .Vb 3 |
992 | .Vb 3 |
987 | \& // and in some piece of code that gets executed on any "activity": |
993 | \& // and in some piece of code that gets executed on any "activity": |
988 | \& // reset the timeout to start ticking again at 10 seconds |
994 | \& // reset the timeout to start ticking again at 10 seconds |
989 | \& ev_timer_again (&mytimer); |
995 | \& ev_timer_again (&mytimer); |
990 | .Ve |
996 | .Ve |
991 | .ie n .Sh """ev_periodic"" \- to cron or not to cron" |
997 | .ie n .Sh """ev_periodic"" \- to cron or not to cron?" |
992 | .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" |
998 | .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" |
993 | .IX Subsection "ev_periodic - to cron or not to cron" |
999 | .IX Subsection "ev_periodic - to cron or not to cron?" |
994 | Periodic watchers are also timers of a kind, but they are very versatile |
1000 | Periodic watchers are also timers of a kind, but they are very versatile |
995 | (and unfortunately a bit complex). |
1001 | (and unfortunately a bit complex). |
996 | .PP |
1002 | .PP |
997 | Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) |
1003 | Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) |
998 | but on wallclock time (absolute time). You can tell a periodic watcher |
1004 | but on wallclock time (absolute time). You can tell a periodic watcher |
… | |
… | |
1132 | \& struct ev_periodic hourly_tick; |
1138 | \& struct ev_periodic hourly_tick; |
1133 | \& ev_periodic_init (&hourly_tick, clock_cb, |
1139 | \& ev_periodic_init (&hourly_tick, clock_cb, |
1134 | \& fmod (ev_now (loop), 3600.), 3600., 0); |
1140 | \& fmod (ev_now (loop), 3600.), 3600., 0); |
1135 | \& ev_periodic_start (loop, &hourly_tick); |
1141 | \& ev_periodic_start (loop, &hourly_tick); |
1136 | .Ve |
1142 | .Ve |
1137 | .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" |
1143 | .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" |
1138 | .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" |
1144 | .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
1139 | .IX Subsection "ev_signal - signal me when a signal gets signalled" |
1145 | .IX Subsection "ev_signal - signal me when a signal gets signalled!" |
1140 | Signal watchers will trigger an event when the process receives a specific |
1146 | Signal watchers will trigger an event when the process receives a specific |
1141 | signal one or more times. Even though signals are very asynchronous, libev |
1147 | signal one or more times. Even though signals are very asynchronous, libev |
1142 | will try it's best to deliver signals synchronously, i.e. as part of the |
1148 | will try it's best to deliver signals synchronously, i.e. as part of the |
1143 | normal event processing, like any other event. |
1149 | normal event processing, like any other event. |
1144 | .PP |
1150 | .PP |
… | |
… | |
1154 | .IP "ev_signal_set (ev_signal *, int signum)" 4 |
1160 | .IP "ev_signal_set (ev_signal *, int signum)" 4 |
1155 | .IX Item "ev_signal_set (ev_signal *, int signum)" |
1161 | .IX Item "ev_signal_set (ev_signal *, int signum)" |
1156 | .PD |
1162 | .PD |
1157 | Configures the watcher to trigger on the given signal number (usually one |
1163 | Configures the watcher to trigger on the given signal number (usually one |
1158 | of the \f(CW\*(C`SIGxxx\*(C'\fR constants). |
1164 | of the \f(CW\*(C`SIGxxx\*(C'\fR constants). |
1159 | .ie n .Sh """ev_child"" \- wait for pid status changes" |
1165 | .ie n .Sh """ev_child"" \- watch out for process status changes" |
1160 | .el .Sh "\f(CWev_child\fP \- wait for pid status changes" |
1166 | .el .Sh "\f(CWev_child\fP \- watch out for process status changes" |
1161 | .IX Subsection "ev_child - wait for pid status changes" |
1167 | .IX Subsection "ev_child - watch out for process status changes" |
1162 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
1168 | Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
1163 | some child status changes (most typically when a child of yours dies). |
1169 | some child status changes (most typically when a child of yours dies). |
1164 | .IP "ev_child_init (ev_child *, callback, int pid)" 4 |
1170 | .IP "ev_child_init (ev_child *, callback, int pid)" 4 |
1165 | .IX Item "ev_child_init (ev_child *, callback, int pid)" |
1171 | .IX Item "ev_child_init (ev_child *, callback, int pid)" |
1166 | .PD 0 |
1172 | .PD 0 |
… | |
… | |
1187 | .Vb 3 |
1193 | .Vb 3 |
1188 | \& struct ev_signal signal_watcher; |
1194 | \& struct ev_signal signal_watcher; |
1189 | \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1195 | \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1190 | \& ev_signal_start (loop, &sigint_cb); |
1196 | \& ev_signal_start (loop, &sigint_cb); |
1191 | .Ve |
1197 | .Ve |
1192 | .ie n .Sh """ev_idle"" \- when you've got nothing better to do" |
1198 | .ie n .Sh """ev_idle"" \- when you've got nothing better to do..." |
1193 | .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" |
1199 | .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." |
1194 | .IX Subsection "ev_idle - when you've got nothing better to do" |
1200 | .IX Subsection "ev_idle - when you've got nothing better to do..." |
1195 | Idle watchers trigger events when there are no other events are pending |
1201 | Idle watchers trigger events when there are no other events are pending |
1196 | (prepare, check and other idle watchers do not count). That is, as long |
1202 | (prepare, check and other idle watchers do not count). That is, as long |
1197 | as your process is busy handling sockets or timeouts (or even signals, |
1203 | as your process is busy handling sockets or timeouts (or even signals, |
1198 | imagine) it will not be triggered. But when your process is idle all idle |
1204 | imagine) it will not be triggered. But when your process is idle all idle |
1199 | watchers are being called again and again, once per event loop iteration \- |
1205 | watchers are being called again and again, once per event loop iteration \- |
… | |
… | |
1229 | .Vb 3 |
1235 | .Vb 3 |
1230 | \& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1236 | \& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1231 | \& ev_idle_init (idle_watcher, idle_cb); |
1237 | \& ev_idle_init (idle_watcher, idle_cb); |
1232 | \& ev_idle_start (loop, idle_cb); |
1238 | \& ev_idle_start (loop, idle_cb); |
1233 | .Ve |
1239 | .Ve |
1234 | .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" |
1240 | .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" |
1235 | .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" |
1241 | .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
1236 | .IX Subsection "ev_prepare and ev_check - customise your event loop" |
1242 | .IX Subsection "ev_prepare and ev_check - customise your event loop!" |
1237 | Prepare and check watchers are usually (but not always) used in tandem: |
1243 | Prepare and check watchers are usually (but not always) used in tandem: |
1238 | prepare watchers get invoked before the process blocks and check watchers |
1244 | prepare watchers get invoked before the process blocks and check watchers |
1239 | afterwards. |
1245 | afterwards. |
1240 | .PP |
1246 | .PP |
1241 | Their main purpose is to integrate other event mechanisms into libev and |
1247 | Their main purpose is to integrate other event mechanisms into libev and |
… | |
… | |
1269 | Initialises and configures the prepare or check watcher \- they have no |
1275 | Initialises and configures the prepare or check watcher \- they have no |
1270 | parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
1276 | parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
1271 | macros, but using them is utterly, utterly and completely pointless. |
1277 | macros, but using them is utterly, utterly and completely pointless. |
1272 | .PP |
1278 | .PP |
1273 | Example: *TODO*. |
1279 | Example: *TODO*. |
1274 | .ie n .Sh """ev_embed"" \- when one backend isn't enough" |
1280 | .ie n .Sh """ev_embed"" \- when one backend isn't enough..." |
1275 | .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough" |
1281 | .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." |
1276 | .IX Subsection "ev_embed - when one backend isn't enough" |
1282 | .IX Subsection "ev_embed - when one backend isn't enough..." |
1277 | This is a rather advanced watcher type that lets you embed one event loop |
1283 | This is a rather advanced watcher type that lets you embed one event loop |
1278 | into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
1284 | into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
1279 | loop, other types of watchers might be handled in a delayed or incorrect |
1285 | loop, other types of watchers might be handled in a delayed or incorrect |
1280 | fashion and must not be used). |
1286 | fashion and must not be used). |
1281 | .PP |
1287 | .PP |