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… …
122.\} 122.\}
123.rm #[ #] #H #V #F C 123.rm #[ #] #H #V #F C
124.\" ======================================================================== 124.\" ========================================================================
125.\" 125.\"
126.IX Title "LIBEV 3" 126.IX Title "LIBEV 3"
127.TH LIBEV 3 "2009-07-15" "libev-3.7" "libev - high performance full featured event loop" 127.TH LIBEV 3 "2009-12-31" "libev-3.9" "libev - high performance full featured event loop"
128.\" For nroff, turn off justification. Always turn off hyphenation; it makes 128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents. 129.\" way too many mistakes in technical documents.
130.if n .ad l 130.if n .ad l
131.nh 131.nh
132.SH "NAME" 132.SH "NAME"
… …
227.SS "\s-1FEATURES\s0" 227.SS "\s-1FEATURES\s0"
228.IX Subsection "FEATURES" 228.IX Subsection "FEATURES"
229Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the 229Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
230BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms 230BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
231for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface 231for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
232(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers 232(for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner
233with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals 233inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative
234(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event 234timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling
235watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, 235(\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status
236\&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as 236change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event
237file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events 237loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and
238(\f(CW\*(C`ev_fork\*(C'\fR). 238\&\f(CW\*(C`ev_check\*(C'\fR watchers) as well as file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even
239limited support for fork events (\f(CW\*(C`ev_fork\*(C'\fR).
239.PP 240.PP
240It also is quite fast (see this 241It also is quite fast (see this
241<benchmark> comparing it to libevent 242<benchmark> comparing it to libevent
242for example). 243for example).
243.SS "\s-1CONVENTIONS\s0" 244.SS "\s-1CONVENTIONS\s0"
… …
245Libev is very configurable. In this manual the default (and most common) 246Libev is very configurable. In this manual the default (and most common)
246configuration will be described, which supports multiple event loops. For 247configuration will be described, which supports multiple event loops. For
247more info about various configuration options please have a look at 248more info about various configuration options please have a look at
248\&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support 249\&\fB\s-1EMBED\s0\fR section in this manual. If libev was configured without support
249for multiple event loops, then all functions taking an initial argument of 250for multiple event loops, then all functions taking an initial argument of
250name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`ev_loop *\*(C'\fR) will not have 251name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have
251this argument. 252this argument.
252.SS "\s-1TIME\s0 \s-1REPRESENTATION\s0" 253.SS "\s-1TIME\s0 \s-1REPRESENTATION\s0"
253.IX Subsection "TIME REPRESENTATION" 254.IX Subsection "TIME REPRESENTATION"
254Libev represents time as a single floating point number, representing 255Libev represents time as a single floating point number, representing
255the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere 256the (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere
… …
478forget about forgetting to tell libev about forking) when you use this 479forget about forgetting to tell libev about forking) when you use this
479flag. 480flag.
480.Sp 481.Sp
481This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR 482This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
482environment variable. 483environment variable.
484.ie n .IP """EVFLAG_NOINOTIFY""" 4
485.el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4
486.IX Item "EVFLAG_NOINOTIFY"
487When this flag is specified, then libev will not attempt to use the
488\&\fIinotify\fR \s-1API\s0 for it's \f(CW\*(C`ev_stat\*(C'\fR watchers. Apart from debugging and
489testing, this flag can be useful to conserve inotify file descriptors, as
490otherwise each loop using \f(CW\*(C`ev_stat\*(C'\fR watchers consumes one inotify handle.
491.ie n .IP """EVFLAG_SIGNALFD""" 4
492.el .IP "\f(CWEVFLAG_SIGNALFD\fR" 4
493.IX Item "EVFLAG_SIGNALFD"
494When this flag is specified, then libev will attempt to use the
495\&\fIsignalfd\fR \s-1API\s0 for it's \f(CW\*(C`ev_signal\*(C'\fR (and \f(CW\*(C`ev_child\*(C'\fR) watchers. This \s-1API\s0
496delivers signals synchronously, which makes it both faster and might make
497it possible to get the queued signal data. It can also simplify signal
498handling with threads, as long as you properly block signals in your
499threads that are not interested in handling them.
500.Sp
501Signalfd will not be used by default as this changes your signal mask, and
502there are a lot of shoddy libraries and programs (glib's threadpool for
503example) that can't properly initialise their signal masks.
483.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 504.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
484.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 505.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
485.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 506.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
486This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 507This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
487libev tries to roll its own fd_set with no limits on the number of fds, 508libev tries to roll its own fd_set with no limits on the number of fds,
… …
512This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and 533This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and
513\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR. 534\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR.
514.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 535.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
515.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 536.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
516.IX Item "EVBACKEND_EPOLL (value 4, Linux)" 537.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
538Use the linux-specific \fIepoll\fR\|(7) interface (for both pre\- and post\-2.6.9
539kernels).
540.Sp
517For few fds, this backend is a bit little slower than poll and select, 541For few fds, this backend is a bit little slower than poll and select,
518but it scales phenomenally better. While poll and select usually scale 542but it scales phenomenally better. While poll and select usually scale
519like O(total_fds) where n is the total number of fds (or the highest fd), 543like O(total_fds) where n is the total number of fds (or the highest fd),
520epoll scales either O(1) or O(active_fds). 544epoll scales either O(1) or O(active_fds).
521.Sp 545.Sp
… …
635.Sp 659.Sp
636It is definitely not recommended to use this flag. 660It is definitely not recommended to use this flag.
637.RE 661.RE
638.RS 4 662.RS 4
639.Sp 663.Sp
640If one or more of these are or'ed into the flags value, then only these 664If one or more of the backend flags are or'ed into the flags value,
641backends will be tried (in the reverse order as listed here). If none are 665then only these backends will be tried (in the reverse order as listed
642specified, all backends in \f(CW\*(C`ev_recommended_backends ()\*(C'\fR will be tried. 666here). If none are specified, all backends in \f(CW\*(C`ev_recommended_backends
667()\*(C'\fR will be tried.
643.Sp 668.Sp
644Example: This is the most typical usage. 669Example: This is the most typical usage.
645.Sp 670.Sp
646.Vb 2 671.Vb 2
647\& if (!ev_default_loop (0)) 672\& if (!ev_default_loop (0))
… …
697as signal and child watchers) would need to be stopped manually. 722as signal and child watchers) would need to be stopped manually.
698.Sp 723.Sp
699In general it is not advisable to call this function except in the 724In general it is not advisable to call this function except in the
700rare occasion where you really need to free e.g. the signal handling 725rare occasion where you really need to free e.g. the signal handling
701pipe fds. If you need dynamically allocated loops it is better to use 726pipe fds. If you need dynamically allocated loops it is better to use
702\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR). 727\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR.
703.IP "ev_loop_destroy (loop)" 4 728.IP "ev_loop_destroy (loop)" 4
704.IX Item "ev_loop_destroy (loop)" 729.IX Item "ev_loop_destroy (loop)"
705Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 730Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
706earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 731earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
707.IP "ev_default_fork ()" 4 732.IP "ev_default_fork ()" 4
… …
804Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the 829Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the
805event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR). 830event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR).
806.IP "ev_loop (loop, int flags)" 4 831.IP "ev_loop (loop, int flags)" 4
807.IX Item "ev_loop (loop, int flags)" 832.IX Item "ev_loop (loop, int flags)"
808Finally, this is it, the event handler. This function usually is called 833Finally, this is it, the event handler. This function usually is called
809after you initialised all your watchers and you want to start handling 834after you have initialised all your watchers and you want to start
810events. 835handling events.
811.Sp 836.Sp
812If the flags argument is specified as \f(CW0\fR, it will not return until 837If the flags argument is specified as \f(CW0\fR, it will not return until
813either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. 838either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
814.Sp 839.Sp
815Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than 840Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
… …
893.PD 918.PD
894Ref/unref can be used to add or remove a reference count on the event 919Ref/unref can be used to add or remove a reference count on the event
895loop: Every watcher keeps one reference, and as long as the reference 920loop: Every watcher keeps one reference, and as long as the reference
896count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. 921count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own.
897.Sp 922.Sp
898If you have a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR 923This is useful when you have a watcher that you never intend to
899from returning, call \fIev_unref()\fR after starting, and \fIev_ref()\fR before 924unregister, but that nevertheless should not keep \f(CW\*(C`ev_loop\*(C'\fR from
925returning. In such a case, call \f(CW\*(C`ev_unref\*(C'\fR after starting, and \f(CW\*(C`ev_ref\*(C'\fR
900stopping it. 926before stopping it.
901.Sp 927.Sp
902As an example, libev itself uses this for its internal signal pipe: It 928As an example, libev itself uses this for its internal signal pipe: It
903is not visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from 929is not visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from
904exiting if no event watchers registered by it are active. It is also an 930exiting if no event watchers registered by it are active. It is also an
905excellent way to do this for generic recurring timers or from within 931excellent way to do this for generic recurring timers or from within
… …
1023.Sp 1049.Sp
1024While event loop modifications are allowed between invocations of 1050While event loop modifications are allowed between invocations of
1025\&\f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR (that's their only purpose after all), no 1051\&\f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR (that's their only purpose after all), no
1026modifications done will affect the event loop, i.e. adding watchers will 1052modifications done will affect the event loop, i.e. adding watchers will
1027have no effect on the set of file descriptors being watched, or the time 1053have no effect on the set of file descriptors being watched, or the time
1028waited. USe an \f(CW\*(C`ev_async\*(C'\fR watcher to wake up \f(CW\*(C`ev_loop\*(C'\fR when you want it 1054waited. Use an \f(CW\*(C`ev_async\*(C'\fR watcher to wake up \f(CW\*(C`ev_loop\*(C'\fR when you want it
1029to take note of any changes you made. 1055to take note of any changes you made.
1030.Sp 1056.Sp
1031In theory, threads executing \f(CW\*(C`ev_loop\*(C'\fR will be async-cancel safe between 1057In theory, threads executing \f(CW\*(C`ev_loop\*(C'\fR will be async-cancel safe between
1032invocations of \f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR. 1058invocations of \f(CW\*(C`release\*(C'\fR and \f(CW\*(C`acquire\*(C'\fR.
1033.Sp 1059.Sp
… …
1228.Vb 3 1254.Vb 3
1229\& ev_io w; 1255\& ev_io w;
1230\& ev_init (&w, my_cb); 1256\& ev_init (&w, my_cb);
1231\& ev_io_set (&w, STDIN_FILENO, EV_READ); 1257\& ev_io_set (&w, STDIN_FILENO, EV_READ);
1232.Ve 1258.Ve
1233.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 1259.ie n .IP """ev_TYPE_set"" (ev_TYPE *watcher, [args])" 4
1234.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 1260.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *watcher, [args])" 4
1235.IX Item "ev_TYPE_set (ev_TYPE *, [args])" 1261.IX Item "ev_TYPE_set (ev_TYPE *watcher, [args])"
1236This macro initialises the type-specific parts of a watcher. You need to 1262This macro initialises the type-specific parts of a watcher. You need to
1237call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can 1263call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
1238call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this 1264call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
1239macro on a watcher that is active (it can be pending, however, which is a 1265macro on a watcher that is active (it can be pending, however, which is a
1240difference to the \f(CW\*(C`ev_init\*(C'\fR macro). 1266difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
… …
1253Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step. 1279Example: Initialise and set an \f(CW\*(C`ev_io\*(C'\fR watcher in one step.
1254.Sp 1280.Sp
1255.Vb 1 1281.Vb 1
1256\& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); 1282\& ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1257.Ve 1283.Ve
1258.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 1284.ie n .IP """ev_TYPE_start"" (loop, ev_TYPE *watcher)" 4
1259.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 1285.el .IP "\f(CWev_TYPE_start\fR (loop, ev_TYPE *watcher)" 4
1260.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" 1286.IX Item "ev_TYPE_start (loop, ev_TYPE *watcher)"
1261Starts (activates) the given watcher. Only active watchers will receive 1287Starts (activates) the given watcher. Only active watchers will receive
1262events. If the watcher is already active nothing will happen. 1288events. If the watcher is already active nothing will happen.
1263.Sp 1289.Sp
1264Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this 1290Example: Start the \f(CW\*(C`ev_io\*(C'\fR watcher that is being abused as example in this
1265whole section. 1291whole section.
1266.Sp 1292.Sp
1267.Vb 1 1293.Vb 1
1268\& ev_io_start (EV_DEFAULT_UC, &w); 1294\& ev_io_start (EV_DEFAULT_UC, &w);
1269.Ve 1295.Ve
1270.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 1296.ie n .IP """ev_TYPE_stop"" (loop, ev_TYPE *watcher)" 4
1271.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 1297.el .IP "\f(CWev_TYPE_stop\fR (loop, ev_TYPE *watcher)" 4
1272.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" 1298.IX Item "ev_TYPE_stop (loop, ev_TYPE *watcher)"
1273Stops the given watcher if active, and clears the pending status (whether 1299Stops the given watcher if active, and clears the pending status (whether
1274the watcher was active or not). 1300the watcher was active or not).
1275.Sp 1301.Sp
1276It is possible that stopped watchers are pending \- for example, 1302It is possible that stopped watchers are pending \- for example,
1277non-repeating timers are being stopped when they become pending \- but 1303non-repeating timers are being stopped when they become pending \- but
… …
1296Returns the callback currently set on the watcher. 1322Returns the callback currently set on the watcher.
1297.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 1323.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
1298.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" 1324.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
1299Change the callback. You can change the callback at virtually any time 1325Change the callback. You can change the callback at virtually any time
1300(modulo threads). 1326(modulo threads).
1301.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4 1327.IP "ev_set_priority (ev_TYPE *watcher, int priority)" 4
1302.IX Item "ev_set_priority (ev_TYPE *watcher, priority)" 1328.IX Item "ev_set_priority (ev_TYPE *watcher, int priority)"
1303.PD 0 1329.PD 0
1304.IP "int ev_priority (ev_TYPE *watcher)" 4 1330.IP "int ev_priority (ev_TYPE *watcher)" 4
1305.IX Item "int ev_priority (ev_TYPE *watcher)" 1331.IX Item "int ev_priority (ev_TYPE *watcher)"
1306.PD 1332.PD
1307Set and query the priority of the watcher. The priority is a small 1333Set and query the priority of the watcher. The priority is a small
… …
1337returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the 1363returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
1338watcher isn't pending it does nothing and returns \f(CW0\fR. 1364watcher isn't pending it does nothing and returns \f(CW0\fR.
1339.Sp 1365.Sp
1340Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its 1366Sometimes it can be useful to \*(L"poll\*(R" a watcher instead of waiting for its
1341callback to be invoked, which can be accomplished with this function. 1367callback to be invoked, which can be accomplished with this function.
1368.IP "ev_feed_event (loop, ev_TYPE *watcher, int revents)" 4
1369.IX Item "ev_feed_event (loop, ev_TYPE *watcher, int revents)"
1370Feeds the given event set into the event loop, as if the specified event
1371had happened for the specified watcher (which must be a pointer to an
1372initialised but not necessarily started event watcher). Obviously you must
1373not free the watcher as long as it has pending events.
1374.Sp
1375Stopping the watcher, letting libev invoke it, or calling
1376\&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was
1377not started in the first place.
1378.Sp
1379See also \f(CW\*(C`ev_feed_fd_event\*(C'\fR and \f(CW\*(C`ev_feed_signal_event\*(C'\fR for related
1380functions that do not need a watcher.
1342.SS "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 1381.SS "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
1343.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 1382.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
1344Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 1383Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
1345and read at any time: libev will completely ignore it. This can be used 1384and read at any time: libev will completely ignore it. This can be used
1346to associate arbitrary data with your watcher. If you need more data and 1385to associate arbitrary data with your watcher. If you need more data and
… …
1957If the timer is repeating, either start it if necessary (with the 1996If the timer is repeating, either start it if necessary (with the
1958\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. 1997\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
1959.Sp 1998.Sp
1960This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a 1999This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a
1961usage example. 2000usage example.
1962.IP "ev_timer_remaining (loop, ev_timer *)" 4 2001.IP "ev_tstamp ev_timer_remaining (loop, ev_timer *)" 4
1963.IX Item "ev_timer_remaining (loop, ev_timer *)" 2002.IX Item "ev_tstamp ev_timer_remaining (loop, ev_timer *)"
1964Returns the remaining time until a timer fires. If the timer is active, 2003Returns the remaining time until a timer fires. If the timer is active,
1965then this time is relative to the current event loop time, otherwise it's 2004then this time is relative to the current event loop time, otherwise it's
1966the timeout value currently configured. 2005the timeout value currently configured.
1967.Sp 2006.Sp
1968That is, after an \f(CW\*(C`ev_timer_set (w, 5, 7)\*(C'\fR, \f(CW\*(C`ev_timer_remaining\*(C'\fR returns 2007That is, after an \f(CW\*(C`ev_timer_set (w, 5, 7)\*(C'\fR, \f(CW\*(C`ev_timer_remaining\*(C'\fR returns
… …
2217Signal watchers will trigger an event when the process receives a specific 2256Signal watchers will trigger an event when the process receives a specific
2218signal one or more times. Even though signals are very asynchronous, libev 2257signal one or more times. Even though signals are very asynchronous, libev
2219will try it's best to deliver signals synchronously, i.e. as part of the 2258will try it's best to deliver signals synchronously, i.e. as part of the
2220normal event processing, like any other event. 2259normal event processing, like any other event.
2221.PP 2260.PP
2222If you want signals asynchronously, just use \f(CW\*(C`sigaction\*(C'\fR as you would 2261If you want signals to be delivered truly asynchronously, just use
2223do without libev and forget about sharing the signal. You can even use 2262\&\f(CW\*(C`sigaction\*(C'\fR as you would do without libev and forget about sharing
2224\&\f(CW\*(C`ev_async\*(C'\fR from a signal handler to synchronously wake up an event loop. 2263the signal. You can even use \f(CW\*(C`ev_async\*(C'\fR from a signal handler to
2264synchronously wake up an event loop.
2225.PP 2265.PP
2226You can configure as many watchers as you like per signal. Only when the 2266You can configure as many watchers as you like for the same signal, but
2267only within the same loop, i.e. you can watch for \f(CW\*(C`SIGINT\*(C'\fR in your
2268default loop and for \f(CW\*(C`SIGIO\*(C'\fR in another loop, but you cannot watch for
2269\&\f(CW\*(C`SIGINT\*(C'\fR in both the default loop and another loop at the same time. At
2270the moment, \f(CW\*(C`SIGCHLD\*(C'\fR is permanently tied to the default loop.
2271.PP
2227first watcher gets started will libev actually register a signal handler 2272When the first watcher gets started will libev actually register something
2228with the kernel (thus it coexists with your own signal handlers as long as 2273with the kernel (thus it coexists with your own signal handlers as long as
2229you don't register any with libev for the same signal). Similarly, when 2274you don't register any with libev for the same signal).
2230the last signal watcher for a signal is stopped, libev will reset the
2231signal handler to \s-1SIG_DFL\s0 (regardless of what it was set to before).
2232.PP 2275.PP
2233If possible and supported, libev will install its handlers with 2276If possible and supported, libev will install its handlers with
2234\&\f(CW\*(C`SA_RESTART\*(C'\fR behaviour enabled, so system calls should not be unduly 2277\&\f(CW\*(C`SA_RESTART\*(C'\fR (or equivalent) behaviour enabled, so system calls should
2235interrupted. If you have a problem with system calls getting interrupted by 2278not be unduly interrupted. If you have a problem with system calls getting
2236signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher and unblock 2279interrupted by signals you can block all signals in an \f(CW\*(C`ev_check\*(C'\fR watcher
2237them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher. 2280and unblock them in an \f(CW\*(C`ev_prepare\*(C'\fR watcher.
2281.PP
2282\fIThe special problem of inheritance over fork/execve/pthread_create\fR
2283.IX Subsection "The special problem of inheritance over fork/execve/pthread_create"
2284.PP
2285Both the signal mask (\f(CW\*(C`sigprocmask\*(C'\fR) and the signal disposition
2286(\f(CW\*(C`sigaction\*(C'\fR) are unspecified after starting a signal watcher (and after
2287stopping it again), that is, libev might or might not block the signal,
2288and might or might not set or restore the installed signal handler.
2289.PP
2290While this does not matter for the signal disposition (libev never
2291sets signals to \f(CW\*(C`SIG_IGN\*(C'\fR, so handlers will be reset to \f(CW\*(C`SIG_DFL\*(C'\fR on
2292\&\f(CW\*(C`execve\*(C'\fR), this matters for the signal mask: many programs do not expect
2293certain signals to be blocked.
2294.PP
2295This means that before calling \f(CW\*(C`exec\*(C'\fR (from the child) you should reset
2296the signal mask to whatever \*(L"default\*(R" you expect (all clear is a good
2297choice usually).
2298.PP
2299The simplest way to ensure that the signal mask is reset in the child is
2300to install a fork handler with \f(CW\*(C`pthread_atfork\*(C'\fR that resets it. That will
2301catch fork calls done by libraries (such as the libc) as well.
2302.PP
2303In current versions of libev, the signal will not be blocked indefinitely
2304unless you use the \f(CW\*(C`signalfd\*(C'\fR \s-1API\s0 (\f(CW\*(C`EV_SIGNALFD\*(C'\fR). While this reduces
2305the window of opportunity for problems, it will not go away, as libev
2306\&\fIhas\fR to modify the signal mask, at least temporarily.
2307.PP
2308So I can't stress this enough: \fIIf you do not reset your signal mask when
2309you expect it to be empty, you have a race condition in your code\fR. This
2310is not a libev-specific thing, this is true for most event libraries.
2238.PP 2311.PP
2239\fIWatcher-Specific Functions and Data Members\fR 2312\fIWatcher-Specific Functions and Data Members\fR
2240.IX Subsection "Watcher-Specific Functions and Data Members" 2313.IX Subsection "Watcher-Specific Functions and Data Members"
2241.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 2314.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
2242.IX Item "ev_signal_init (ev_signal *, callback, int signum)" 2315.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
… …
2287.PP 2360.PP
2288\fIProcess Interaction\fR 2361\fIProcess Interaction\fR
2289.IX Subsection "Process Interaction" 2362.IX Subsection "Process Interaction"
2290.PP 2363.PP
2291Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is 2364Libev grabs \f(CW\*(C`SIGCHLD\*(C'\fR as soon as the default event loop is
2292initialised. This is necessary to guarantee proper behaviour even if 2365initialised. This is necessary to guarantee proper behaviour even if the
2293the first child watcher is started after the child exits. The occurrence 2366first child watcher is started after the child exits. The occurrence
2294of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done 2367of \f(CW\*(C`SIGCHLD\*(C'\fR is recorded asynchronously, but child reaping is done
2295synchronously as part of the event loop processing. Libev always reaps all 2368synchronously as part of the event loop processing. Libev always reaps all
2296children, even ones not watched. 2369children, even ones not watched.
2297.PP 2370.PP
2298\fIOverriding the Built-In Processing\fR 2371\fIOverriding the Built-In Processing\fR
… …
2310.IX Subsection "Stopping the Child Watcher" 2383.IX Subsection "Stopping the Child Watcher"
2311.PP 2384.PP
2312Currently, the child watcher never gets stopped, even when the 2385Currently, the child watcher never gets stopped, even when the
2313child terminates, so normally one needs to stop the watcher in the 2386child terminates, so normally one needs to stop the watcher in the
2314callback. Future versions of libev might stop the watcher automatically 2387callback. Future versions of libev might stop the watcher automatically
2315when a child exit is detected. 2388when a child exit is detected (calling \f(CW\*(C`ev_child_stop\*(C'\fR twice is not a
2389problem).
2316.PP 2390.PP
2317\fIWatcher-Specific Functions and Data Members\fR 2391\fIWatcher-Specific Functions and Data Members\fR
2318.IX Subsection "Watcher-Specific Functions and Data Members" 2392.IX Subsection "Watcher-Specific Functions and Data Members"
2319.IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4 2393.IP "ev_child_init (ev_child *, callback, int pid, int trace)" 4
2320.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)" 2394.IX Item "ev_child_init (ev_child *, callback, int pid, int trace)"
… …
3058.IX Subsection "Queueing" 3132.IX Subsection "Queueing"
3059.PP 3133.PP
3060\&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason 3134\&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason
3061is that the author does not know of a simple (or any) algorithm for a 3135is that the author does not know of a simple (or any) algorithm for a
3062multiple-writer-single-reader queue that works in all cases and doesn't 3136multiple-writer-single-reader queue that works in all cases and doesn't
3063need elaborate support such as pthreads. 3137need elaborate support such as pthreads or unportable memory access
3138semantics.
3064.PP 3139.PP
3065That means that if you want to queue data, you have to provide your own 3140That means that if you want to queue data, you have to provide your own
3066queue. But at least I can tell you how to implement locking around your 3141queue. But at least I can tell you how to implement locking around your
3067queue: 3142queue:
3068.IP "queueing from a signal handler context" 4 3143.IP "queueing from a signal handler context" 4
… …
3213\& /* doh, nothing entered */; 3288\& /* doh, nothing entered */;
3214\& } 3289\& }
3215\& 3290\&
3216\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 3291\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3217.Ve 3292.Ve
3218.IP "ev_feed_event (struct ev_loop *, watcher *, int revents)" 4
3219.IX Item "ev_feed_event (struct ev_loop *, watcher *, int revents)"
3220Feeds the given event set into the event loop, as if the specified event
3221had happened for the specified watcher (which must be a pointer to an
3222initialised but not necessarily started event watcher).
3223.IP "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" 4 3293.IP "ev_feed_fd_event (loop, int fd, int revents)" 4
3224.IX Item "ev_feed_fd_event (struct ev_loop *, int fd, int revents)" 3294.IX Item "ev_feed_fd_event (loop, int fd, int revents)"
3225Feed an event on the given fd, as if a file descriptor backend detected 3295Feed an event on the given fd, as if a file descriptor backend detected
3226the given events it. 3296the given events it.
3227.IP "ev_feed_signal_event (struct ev_loop *loop, int signum)" 4 3297.IP "ev_feed_signal_event (loop, int signum)" 4
3228.IX Item "ev_feed_signal_event (struct ev_loop *loop, int signum)" 3298.IX Item "ev_feed_signal_event (loop, int signum)"
3229Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default 3299Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default
3230loop!). 3300loop!).
3231.SH "LIBEVENT EMULATION" 3301.SH "LIBEVENT EMULATION"
3232.IX Header "LIBEVENT EMULATION" 3302.IX Header "LIBEVENT EMULATION"
3233Libev offers a compatibility emulation layer for libevent. It cannot 3303Libev offers a compatibility emulation layer for libevent. It cannot
… …
3302All of those classes have these methods: 3372All of those classes have these methods:
3303.RS 4 3373.RS 4
3304.IP "ev::TYPE::TYPE ()" 4 3374.IP "ev::TYPE::TYPE ()" 4
3305.IX Item "ev::TYPE::TYPE ()" 3375.IX Item "ev::TYPE::TYPE ()"
3306.PD 0 3376.PD 0
3307.IP "ev::TYPE::TYPE (struct ev_loop *)" 4 3377.IP "ev::TYPE::TYPE (loop)" 4
3308.IX Item "ev::TYPE::TYPE (struct ev_loop *)" 3378.IX Item "ev::TYPE::TYPE (loop)"
3309.IP "ev::TYPE::~TYPE" 4 3379.IP "ev::TYPE::~TYPE" 4
3310.IX Item "ev::TYPE::~TYPE" 3380.IX Item "ev::TYPE::~TYPE"
3311.PD 3381.PD
3312The constructor (optionally) takes an event loop to associate the watcher 3382The constructor (optionally) takes an event loop to associate the watcher
3313with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR. 3383with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
… …
3392.Sp 3462.Sp
3393.Vb 2 3463.Vb 2
3394\& static void io_cb (ev::io &w, int revents) { } 3464\& static void io_cb (ev::io &w, int revents) { }
3395\& iow.set <io_cb> (); 3465\& iow.set <io_cb> ();
3396.Ve 3466.Ve
3397.IP "w\->set (struct ev_loop *)" 4 3467.IP "w\->set (loop)" 4
3398.IX Item "w->set (struct ev_loop *)" 3468.IX Item "w->set (loop)"
3399Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only 3469Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
3400do this when the watcher is inactive (and not pending either). 3470do this when the watcher is inactive (and not pending either).
3401.IP "w\->set ([arguments])" 4 3471.IP "w\->set ([arguments])" 4
3402.IX Item "w->set ([arguments])" 3472.IX Item "w->set ([arguments])"
3403Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same arguments. Must be 3473Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same arguments. Must be
… …
3486be found at <http://proj.llucax.com.ar/wiki/evd>. 3556be found at <http://proj.llucax.com.ar/wiki/evd>.
3487.IP "Ocaml" 4 3557.IP "Ocaml" 4
3488.IX Item "Ocaml" 3558.IX Item "Ocaml"
3489Erkki Seppala has written Ocaml bindings for libev, to be found at 3559Erkki Seppala has written Ocaml bindings for libev, to be found at
3490<http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>. 3560<http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>.
3561.IP "Lua" 4
3562.IX Item "Lua"
3563Brian Maher has written a partial interface to libev
3564for lua (only \f(CW\*(C`ev_io\*(C'\fR and \f(CW\*(C`ev_timer\*(C'\fR), to be found at
3565<http://github.com/brimworks/lua\-ev>.
3491.SH "MACRO MAGIC" 3566.SH "MACRO MAGIC"
3492.IX Header "MACRO MAGIC" 3567.IX Header "MACRO MAGIC"
3493Libev can be compiled with a variety of options, the most fundamental 3568Libev can be compiled with a variety of options, the most fundamental
3494of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) 3569of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
3495functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. 3570functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
… …
3671keeps libev from including \fIconfig.h\fR, and it also defines dummy 3746keeps libev from including \fIconfig.h\fR, and it also defines dummy
3672implementations for some libevent functions (such as logging, which is not 3747implementations for some libevent functions (such as logging, which is not
3673supported). It will also not define any of the structs usually found in 3748supported). It will also not define any of the structs usually found in
3674\&\fIevent.h\fR that are not directly supported by the libev core alone. 3749\&\fIevent.h\fR that are not directly supported by the libev core alone.
3675.Sp 3750.Sp
3676In stanbdalone mode, libev will still try to automatically deduce the 3751In standalone mode, libev will still try to automatically deduce the
3677configuration, but has to be more conservative. 3752configuration, but has to be more conservative.
3678.IP "\s-1EV_USE_MONOTONIC\s0" 4 3753.IP "\s-1EV_USE_MONOTONIC\s0" 4
3679.IX Item "EV_USE_MONOTONIC" 3754.IX Item "EV_USE_MONOTONIC"
3680If defined to be \f(CW1\fR, libev will try to detect the availability of the 3755If defined to be \f(CW1\fR, libev will try to detect the availability of the
3681monotonic clock option at both compile time and runtime. Otherwise no 3756monotonic clock option at both compile time and runtime. Otherwise no
… …
3737wants osf handles on win32 (this is the case when the select to 3812wants osf handles on win32 (this is the case when the select to
3738be used is the winsock select). This means that it will call 3813be used is the winsock select). This means that it will call
3739\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, 3814\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
3740it is assumed that all these functions actually work on fds, even 3815it is assumed that all these functions actually work on fds, even
3741on win32. Should not be defined on non\-win32 platforms. 3816on win32. Should not be defined on non\-win32 platforms.
3742.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0" 4 3817.IP "\s-1EV_FD_TO_WIN32_HANDLE\s0(fd)" 4
3743.IX Item "EV_FD_TO_WIN32_HANDLE" 3818.IX Item "EV_FD_TO_WIN32_HANDLE(fd)"
3744If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map 3819If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR is enabled, then libev needs a way to map
3745file descriptors to socket handles. When not defining this symbol (the 3820file descriptors to socket handles. When not defining this symbol (the
3746default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually 3821default), then libev will call \f(CW\*(C`_get_osfhandle\*(C'\fR, which is usually
3747correct. In some cases, programs use their own file descriptor management, 3822correct. In some cases, programs use their own file descriptor management,
3748in which case they can provide this function to map fds to socket handles. 3823in which case they can provide this function to map fds to socket handles.
3824.IP "\s-1EV_WIN32_HANDLE_TO_FD\s0(handle)" 4
3825.IX Item "EV_WIN32_HANDLE_TO_FD(handle)"
3826If \f(CW\*(C`EV_SELECT_IS_WINSOCKET\*(C'\fR then libev maps handles to file descriptors
3827using the standard \f(CW\*(C`_open_osfhandle\*(C'\fR function. For programs implementing
3828their own fd to handle mapping, overwriting this function makes it easier
3829to do so. This can be done by defining this macro to an appropriate value.
3830.IP "\s-1EV_WIN32_CLOSE_FD\s0(fd)" 4
3831.IX Item "EV_WIN32_CLOSE_FD(fd)"
3832If programs implement their own fd to handle mapping on win32, then this
3833macro can be used to override the \f(CW\*(C`close\*(C'\fR function, useful to unregister
3834file descriptors again. Note that the replacement function has to close
3835the underlying \s-1OS\s0 handle.
3749.IP "\s-1EV_USE_POLL\s0" 4 3836.IP "\s-1EV_USE_POLL\s0" 4
3750.IX Item "EV_USE_POLL" 3837.IX Item "EV_USE_POLL"
3751If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) 3838If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
3752backend. Otherwise it will be enabled on non\-win32 platforms. It 3839backend. Otherwise it will be enabled on non\-win32 platforms. It
3753takes precedence over select. 3840takes precedence over select.
… …
3880.Sp 3967.Sp
3881Defining \f(CW\*(C`EV_MINIMAL\*(C'\fR to \f(CW2\fR will additionally reduce the core \s-1API\s0 to 3968Defining \f(CW\*(C`EV_MINIMAL\*(C'\fR to \f(CW2\fR will additionally reduce the core \s-1API\s0 to
3882provide a bare-bones event library. See \f(CW\*(C`ev.h\*(C'\fR for details on what parts 3969provide a bare-bones event library. See \f(CW\*(C`ev.h\*(C'\fR for details on what parts
3883of the \s-1API\s0 are still available, and do not complain if this subset changes 3970of the \s-1API\s0 are still available, and do not complain if this subset changes
3884over time. 3971over time.
3972.IP "\s-1EV_NSIG\s0" 4
3973.IX Item "EV_NSIG"
3974The highest supported signal number, +1 (or, the number of
3975signals): Normally, libev tries to deduce the maximum number of signals
3976automatically, but sometimes this fails, in which case it can be
3977specified. Also, using a lower number than detected (\f(CW32\fR should be
3978good for about any system in existance) can save some memory, as libev
3979statically allocates some 12\-24 bytes per signal number.
3885.IP "\s-1EV_PID_HASHSIZE\s0" 4 3980.IP "\s-1EV_PID_HASHSIZE\s0" 4
3886.IX Item "EV_PID_HASHSIZE" 3981.IX Item "EV_PID_HASHSIZE"
3887\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by 3982\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
3888pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more 3983pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
3889than enough. If you need to manage thousands of children you might want to 3984than enough. If you need to manage thousands of children you might want to

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