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…		…
62		62
63	// unloop was called, so exit	63	// unloop was called, so exit
64	return 0;	64	return 0;
65	}	65	}
66		66
67	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
68		70
69	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
70	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
72		84
73	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
74	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
75	these event sources and provide your program with events.	87	these event sources and provide your program with events.
76		88
…		…
86	=head2 FEATURES	98	=head2 FEATURES
87		99
88	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
90	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
92	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
93	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
94	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
95	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
96	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
97	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
98		111
99	It also is quite fast (see this	112	It also is quite fast (see this
100	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
101	for example).	114	for example).
102		115
…		…
105	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
106	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
107	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
108	B<EMBED> section in this manual. If libev was configured without support	121	B<EMBED> section in this manual. If libev was configured without support
109	for multiple event loops, then all functions taking an initial argument of	122	for multiple event loops, then all functions taking an initial argument of
110	name C<loop> (which is always of type C<ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
111	this argument.	124	this argument.
112		125
113	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
114		127
115	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (somewhere
117	the beginning of 1970, details are complicated, don't ask). This type is	130	near the beginning of 1970, details are complicated, don't ask). This
118	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	type is called C<ev_tstamp>, which is what you should use too. It usually
119	to the C<double> type in C, and when you need to do any calculations on	132	aliases to the C<double> type in C. When you need to do any calculations
120	it, you should treat it as some floating point value. Unlike the name	133	on it, you should treat it as some floating point value. Unlike the name
121	component C<stamp> might indicate, it is also used for time differences	134	component C<stamp> might indicate, it is also used for time differences
122	throughout libev.	135	throughout libev.
123		136
124	=head1 ERROR HANDLING	137	=head1 ERROR HANDLING
125		138
…		…
350	flag.	363	flag.
351		364
352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
353	environment variable.	366	environment variable.
354		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_SIGNALFD>
		376
		377	When this flag is specified, then libev will attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		379	delivers signals synchronously, which makes it both faster and might make
		380	it possible to get the queued signal data. It can also simplify signal
		381	handling with threads, as long as you properly block signals in your
		382	threads that are not interested in handling them.
		383
		384	Signalfd will not be used by default as this changes your signal mask, and
		385	there are a lot of shoddy libraries and programs (glib's threadpool for
		386	example) that can't properly initialise their signal masks.
		387
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		389
357	This is your standard select(2) backend. Not I<completely> standard, as	390	This is your standard select(2) backend. Not I<completely> standard, as
358	libev tries to roll its own fd_set with no limits on the number of fds,	391	libev tries to roll its own fd_set with no limits on the number of fds,
359	but if that fails, expect a fairly low limit on the number of fds when	392	but if that fails, expect a fairly low limit on the number of fds when
…		…
382		415
383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	416	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
385		418
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	419	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		420
		421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		422	kernels).
387		423
388	For few fds, this backend is a bit little slower than poll and select,	424	For few fds, this backend is a bit little slower than poll and select,
389	but it scales phenomenally better. While poll and select usually scale	425	but it scales phenomenally better. While poll and select usually scale
390	like O(total_fds) where n is the total number of fds (or the highest fd),	426	like O(total_fds) where n is the total number of fds (or the highest fd),
391	epoll scales either O(1) or O(active_fds).	427	epoll scales either O(1) or O(active_fds).
…		…
506		542
507	It is definitely not recommended to use this flag.	543	It is definitely not recommended to use this flag.
508		544
509	=back	545	=back
510		546
511	If one or more of these are or'ed into the flags value, then only these	547	If one or more of the backend flags are or'ed into the flags value,
512	backends will be tried (in the reverse order as listed here). If none are	548	then only these backends will be tried (in the reverse order as listed
513	specified, all backends in C<ev_recommended_backends ()> will be tried.	549	here). If none are specified, all backends in C<ev_recommended_backends
		550	()> will be tried.
514		551
515	Example: This is the most typical usage.	552	Example: This is the most typical usage.
516		553
517	if (!ev_default_loop (0))	554	if (!ev_default_loop (0))
518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
561	as signal and child watchers) would need to be stopped manually.	598	as signal and child watchers) would need to be stopped manually.
562		599
563	In general it is not advisable to call this function except in the	600	In general it is not advisable to call this function except in the
564	rare occasion where you really need to free e.g. the signal handling	601	rare occasion where you really need to free e.g. the signal handling
565	pipe fds. If you need dynamically allocated loops it is better to use	602	pipe fds. If you need dynamically allocated loops it is better to use
566	C<ev_loop_new> and C<ev_loop_destroy>).	603	C<ev_loop_new> and C<ev_loop_destroy>.
567		604
568	=item ev_loop_destroy (loop)	605	=item ev_loop_destroy (loop)
569		606
570	Like C<ev_default_destroy>, but destroys an event loop created by an	607	Like C<ev_default_destroy>, but destroys an event loop created by an
571	earlier call to C<ev_loop_new>.	608	earlier call to C<ev_loop_new>.
…		…
609		646
610	This value can sometimes be useful as a generation counter of sorts (it	647	This value can sometimes be useful as a generation counter of sorts (it
611	"ticks" the number of loop iterations), as it roughly corresponds with	648	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	649	C<ev_prepare> and C<ev_check> calls.
613		650
		651	=item unsigned int ev_loop_depth (loop)
		652
		653	Returns the number of times C<ev_loop> was entered minus the number of
		654	times C<ev_loop> was exited, in other words, the recursion depth.
		655
		656	Outside C<ev_loop>, this number is zero. In a callback, this number is
		657	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		658	in which case it is higher.
		659
		660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		661	etc.), doesn't count as exit.
		662
614	=item unsigned int ev_backend (loop)	663	=item unsigned int ev_backend (loop)
615		664
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	665	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	666	use.
618		667
…		…
632		681
633	This function is rarely useful, but when some event callback runs for a	682	This function is rarely useful, but when some event callback runs for a
634	very long time without entering the event loop, updating libev's idea of	683	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	684	the current time is a good idea.
636		685
637	See also "The special problem of time updates" in the C<ev_timer> section.	686	See also L<The special problem of time updates> in the C<ev_timer> section.
638		687
639	=item ev_suspend (loop)	688	=item ev_suspend (loop)
640		689
641	=item ev_resume (loop)	690	=item ev_resume (loop)
642		691
…		…
663	event loop time (see C<ev_now_update>).	712	event loop time (see C<ev_now_update>).
664		713
665	=item ev_loop (loop, int flags)	714	=item ev_loop (loop, int flags)
666		715
667	Finally, this is it, the event handler. This function usually is called	716	Finally, this is it, the event handler. This function usually is called
668	after you initialised all your watchers and you want to start handling	717	after you have initialised all your watchers and you want to start
669	events.	718	handling events.
670		719
671	If the flags argument is specified as C<0>, it will not return until	720	If the flags argument is specified as C<0>, it will not return until
672	either no event watchers are active anymore or C<ev_unloop> was called.	721	either no event watchers are active anymore or C<ev_unloop> was called.
673		722
674	Please note that an explicit C<ev_unloop> is usually better than	723	Please note that an explicit C<ev_unloop> is usually better than
…		…
748		797
749	Ref/unref can be used to add or remove a reference count on the event	798	Ref/unref can be used to add or remove a reference count on the event
750	loop: Every watcher keeps one reference, and as long as the reference	799	loop: Every watcher keeps one reference, and as long as the reference
751	count is nonzero, C<ev_loop> will not return on its own.	800	count is nonzero, C<ev_loop> will not return on its own.
752		801
753	If you have a watcher you never unregister that should not keep C<ev_loop>	802	This is useful when you have a watcher that you never intend to
754	from returning, call ev_unref() after starting, and ev_ref() before	803	unregister, but that nevertheless should not keep C<ev_loop> from
		804	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
755	stopping it.	805	before stopping it.
756		806
757	As an example, libev itself uses this for its internal signal pipe: It	807	As an example, libev itself uses this for its internal signal pipe: It
758	is not visible to the libev user and should not keep C<ev_loop> from	808	is not visible to the libev user and should not keep C<ev_loop> from
759	exiting if no event watchers registered by it are active. It is also an	809	exiting if no event watchers registered by it are active. It is also an
760	excellent way to do this for generic recurring timers or from within	810	excellent way to do this for generic recurring timers or from within
…		…
799		849
800	By setting a higher I<io collect interval> you allow libev to spend more	850	By setting a higher I<io collect interval> you allow libev to spend more
801	time collecting I/O events, so you can handle more events per iteration,	851	time collecting I/O events, so you can handle more events per iteration,
802	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	852	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
803	C<ev_timer>) will be not affected. Setting this to a non-null value will	853	C<ev_timer>) will be not affected. Setting this to a non-null value will
804	introduce an additional C<ev_sleep ()> call into most loop iterations.	854	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		855	sleep time ensures that libev will not poll for I/O events more often then
		856	once per this interval, on average.
805		857
806	Likewise, by setting a higher I<timeout collect interval> you allow libev	858	Likewise, by setting a higher I<timeout collect interval> you allow libev
807	to spend more time collecting timeouts, at the expense of increased	859	to spend more time collecting timeouts, at the expense of increased
808	latency/jitter/inexactness (the watcher callback will be called	860	latency/jitter/inexactness (the watcher callback will be called
809	later). C<ev_io> watchers will not be affected. Setting this to a non-null	861	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
811		863
812	Many (busy) programs can usually benefit by setting the I/O collect	864	Many (busy) programs can usually benefit by setting the I/O collect
813	interval to a value near C<0.1> or so, which is often enough for	865	interval to a value near C<0.1> or so, which is often enough for
814	interactive servers (of course not for games), likewise for timeouts. It	866	interactive servers (of course not for games), likewise for timeouts. It
815	usually doesn't make much sense to set it to a lower value than C<0.01>,	867	usually doesn't make much sense to set it to a lower value than C<0.01>,
816	as this approaches the timing granularity of most systems.	868	as this approaches the timing granularity of most systems. Note that if
		869	you do transactions with the outside world and you can't increase the
		870	parallelity, then this setting will limit your transaction rate (if you
		871	need to poll once per transaction and the I/O collect interval is 0.01,
		872	then you can't do more than 100 transations per second).
817		873
818	Setting the I<timeout collect interval> can improve the opportunity for	874	Setting the I<timeout collect interval> can improve the opportunity for
819	saving power, as the program will "bundle" timer callback invocations that	875	saving power, as the program will "bundle" timer callback invocations that
820	are "near" in time together, by delaying some, thus reducing the number of	876	are "near" in time together, by delaying some, thus reducing the number of
821	times the process sleeps and wakes up again. Another useful technique to	877	times the process sleeps and wakes up again. Another useful technique to
822	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	878	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
823	they fire on, say, one-second boundaries only.	879	they fire on, say, one-second boundaries only.
		880
		881	Example: we only need 0.1s timeout granularity, and we wish not to poll
		882	more often than 100 times per second:
		883
		884	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		886
		887	=item ev_invoke_pending (loop)
		888
		889	This call will simply invoke all pending watchers while resetting their
		890	pending state. Normally, C<ev_loop> does this automatically when required,
		891	but when overriding the invoke callback this call comes handy.
		892
		893	=item int ev_pending_count (loop)
		894
		895	Returns the number of pending watchers - zero indicates that no watchers
		896	are pending.
		897
		898	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		899
		900	This overrides the invoke pending functionality of the loop: Instead of
		901	invoking all pending watchers when there are any, C<ev_loop> will call
		902	this callback instead. This is useful, for example, when you want to
		903	invoke the actual watchers inside another context (another thread etc.).
		904
		905	If you want to reset the callback, use C<ev_invoke_pending> as new
		906	callback.
		907
		908	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		909
		910	Sometimes you want to share the same loop between multiple threads. This
		911	can be done relatively simply by putting mutex_lock/unlock calls around
		912	each call to a libev function.
		913
		914	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		915	wait for it to return. One way around this is to wake up the loop via
		916	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		917	and I<acquire> callbacks on the loop.
		918
		919	When set, then C<release> will be called just before the thread is
		920	suspended waiting for new events, and C<acquire> is called just
		921	afterwards.
		922
		923	Ideally, C<release> will just call your mutex_unlock function, and
		924	C<acquire> will just call the mutex_lock function again.
		925
		926	While event loop modifications are allowed between invocations of
		927	C<release> and C<acquire> (that's their only purpose after all), no
		928	modifications done will affect the event loop, i.e. adding watchers will
		929	have no effect on the set of file descriptors being watched, or the time
		930	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it
		931	to take note of any changes you made.
		932
		933	In theory, threads executing C<ev_loop> will be async-cancel safe between
		934	invocations of C<release> and C<acquire>.
		935
		936	See also the locking example in the C<THREADS> section later in this
		937	document.
		938
		939	=item ev_set_userdata (loop, void *data)
		940
		941	=item ev_userdata (loop)
		942
		943	Set and retrieve a single C<void *> associated with a loop. When
		944	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		945	C<0.>
		946
		947	These two functions can be used to associate arbitrary data with a loop,
		948	and are intended solely for the C<invoke_pending_cb>, C<release> and
		949	C<acquire> callbacks described above, but of course can be (ab-)used for
		950	any other purpose as well.
824		951
825	=item ev_loop_verify (loop)	952	=item ev_loop_verify (loop)
826		953
827	This function only does something when C<EV_VERIFY> support has been	954	This function only does something when C<EV_VERIFY> support has been
828	compiled in, which is the default for non-minimal builds. It tries to go	955	compiled in, which is the default for non-minimal builds. It tries to go
…		…
1005		1132
1006	ev_io w;	1133	ev_io w;
1007	ev_init (&w, my_cb);	1134	ev_init (&w, my_cb);
1008	ev_io_set (&w, STDIN_FILENO, EV_READ);	1135	ev_io_set (&w, STDIN_FILENO, EV_READ);
1009		1136
1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1137	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1011		1138
1012	This macro initialises the type-specific parts of a watcher. You need to	1139	This macro initialises the type-specific parts of a watcher. You need to
1013	call C<ev_init> at least once before you call this macro, but you can	1140	call C<ev_init> at least once before you call this macro, but you can
1014	call C<ev_TYPE_set> any number of times. You must not, however, call this	1141	call C<ev_TYPE_set> any number of times. You must not, however, call this
1015	macro on a watcher that is active (it can be pending, however, which is a	1142	macro on a watcher that is active (it can be pending, however, which is a
…		…
1028		1155
1029	Example: Initialise and set an C<ev_io> watcher in one step.	1156	Example: Initialise and set an C<ev_io> watcher in one step.
1030		1157
1031	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1158	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1032		1159
1033	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1160	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1034		1161
1035	Starts (activates) the given watcher. Only active watchers will receive	1162	Starts (activates) the given watcher. Only active watchers will receive
1036	events. If the watcher is already active nothing will happen.	1163	events. If the watcher is already active nothing will happen.
1037		1164
1038	Example: Start the C<ev_io> watcher that is being abused as example in this	1165	Example: Start the C<ev_io> watcher that is being abused as example in this
1039	whole section.	1166	whole section.
1040		1167
1041	ev_io_start (EV_DEFAULT_UC, &w);	1168	ev_io_start (EV_DEFAULT_UC, &w);
1042		1169
1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1170	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1044		1171
1045	Stops the given watcher if active, and clears the pending status (whether	1172	Stops the given watcher if active, and clears the pending status (whether
1046	the watcher was active or not).	1173	the watcher was active or not).
1047		1174
1048	It is possible that stopped watchers are pending - for example,	1175	It is possible that stopped watchers are pending - for example,
…		…
1073	=item ev_cb_set (ev_TYPE *watcher, callback)	1200	=item ev_cb_set (ev_TYPE *watcher, callback)
1074		1201
1075	Change the callback. You can change the callback at virtually any time	1202	Change the callback. You can change the callback at virtually any time
1076	(modulo threads).	1203	(modulo threads).
1077		1204
1078	=item ev_set_priority (ev_TYPE *watcher, priority)	1205	=item ev_set_priority (ev_TYPE *watcher, int priority)
1079		1206
1080	=item int ev_priority (ev_TYPE *watcher)	1207	=item int ev_priority (ev_TYPE *watcher)
1081		1208
1082	Set and query the priority of the watcher. The priority is a small	1209	Set and query the priority of the watcher. The priority is a small
1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1210	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1084	(default: C<-2>). Pending watchers with higher priority will be invoked	1211	(default: C<-2>). Pending watchers with higher priority will be invoked
1085	before watchers with lower priority, but priority will not keep watchers	1212	before watchers with lower priority, but priority will not keep watchers
1086	from being executed (except for C<ev_idle> watchers).	1213	from being executed (except for C<ev_idle> watchers).
1087		1214
1088	See L<
1089
1090	This means that priorities are I<only> used for ordering callback
1091	invocation after new events have been received. This is useful, for
1092	example, to reduce latency after idling, or more often, to bind two
1093	watchers on the same event and make sure one is called first.
1094
1095	If you need to suppress invocation when higher priority events are pending	1215	If you need to suppress invocation when higher priority events are pending
1096	you need to look at C<ev_idle> watchers, which provide this functionality.	1216	you need to look at C<ev_idle> watchers, which provide this functionality.
1097		1217
1098	You I<must not> change the priority of a watcher as long as it is active or	1218	You I<must not> change the priority of a watcher as long as it is active or
1099	pending.	1219	pending.
1100
1101	The default priority used by watchers when no priority has been set is
1102	always C<0>, which is supposed to not be too high and not be too low :).
1103		1220
1104	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1221	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1105	fine, as long as you do not mind that the priority value you query might	1222	fine, as long as you do not mind that the priority value you query might
1106	or might not have been clamped to the valid range.	1223	or might not have been clamped to the valid range.
		1224
		1225	The default priority used by watchers when no priority has been set is
		1226	always C<0>, which is supposed to not be too high and not be too low :).
		1227
		1228	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1229	priorities.
1107		1230
1108	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1231	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1109		1232
1110	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1233	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1111	C<loop> nor C<revents> need to be valid as long as the watcher callback	1234	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1118	returns its C<revents> bitset (as if its callback was invoked). If the	1241	returns its C<revents> bitset (as if its callback was invoked). If the
1119	watcher isn't pending it does nothing and returns C<0>.	1242	watcher isn't pending it does nothing and returns C<0>.
1120		1243
1121	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1244	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1122	callback to be invoked, which can be accomplished with this function.	1245	callback to be invoked, which can be accomplished with this function.
		1246
		1247	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1248
		1249	Feeds the given event set into the event loop, as if the specified event
		1250	had happened for the specified watcher (which must be a pointer to an
		1251	initialised but not necessarily started event watcher). Obviously you must
		1252	not free the watcher as long as it has pending events.
		1253
		1254	Stopping the watcher, letting libev invoke it, or calling
		1255	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1256	not started in the first place.
		1257
		1258	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1259	functions that do not need a watcher.
1123		1260
1124	=back	1261	=back
1125		1262
1126		1263
1127	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1176	#include <stddef.h>	1313	#include <stddef.h>
1177		1314
1178	static void	1315	static void
1179	t1_cb (EV_P_ ev_timer *w, int revents)	1316	t1_cb (EV_P_ ev_timer *w, int revents)
1180	{	1317	{
1181	struct my_biggy big = (struct my_biggy *	1318	struct my_biggy big = (struct my_biggy *)
1182	(((char *)w) - offsetof (struct my_biggy, t1));	1319	(((char *)w) - offsetof (struct my_biggy, t1));
1183	}	1320	}
1184		1321
1185	static void	1322	static void
1186	t2_cb (EV_P_ ev_timer *w, int revents)	1323	t2_cb (EV_P_ ev_timer *w, int revents)
1187	{	1324	{
1188	struct my_biggy big = (struct my_biggy *	1325	struct my_biggy big = (struct my_biggy *)
1189	(((char *)w) - offsetof (struct my_biggy, t2));	1326	(((char *)w) - offsetof (struct my_biggy, t2));
1190	}	1327	}
		1328
		1329	=head2 WATCHER PRIORITY MODELS
		1330
		1331	Many event loops support I<watcher priorities>, which are usually small
		1332	integers that influence the ordering of event callback invocation
		1333	between watchers in some way, all else being equal.
		1334
		1335	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1336	description for the more technical details such as the actual priority
		1337	range.
		1338
		1339	There are two common ways how these these priorities are being interpreted
		1340	by event loops:
		1341
		1342	In the more common lock-out model, higher priorities "lock out" invocation
		1343	of lower priority watchers, which means as long as higher priority
		1344	watchers receive events, lower priority watchers are not being invoked.
		1345
		1346	The less common only-for-ordering model uses priorities solely to order
		1347	callback invocation within a single event loop iteration: Higher priority
		1348	watchers are invoked before lower priority ones, but they all get invoked
		1349	before polling for new events.
		1350
		1351	Libev uses the second (only-for-ordering) model for all its watchers
		1352	except for idle watchers (which use the lock-out model).
		1353
		1354	The rationale behind this is that implementing the lock-out model for
		1355	watchers is not well supported by most kernel interfaces, and most event
		1356	libraries will just poll for the same events again and again as long as
		1357	their callbacks have not been executed, which is very inefficient in the
		1358	common case of one high-priority watcher locking out a mass of lower
		1359	priority ones.
		1360
		1361	Static (ordering) priorities are most useful when you have two or more
		1362	watchers handling the same resource: a typical usage example is having an
		1363	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1364	timeouts. Under load, data might be received while the program handles
		1365	other jobs, but since timers normally get invoked first, the timeout
		1366	handler will be executed before checking for data. In that case, giving
		1367	the timer a lower priority than the I/O watcher ensures that I/O will be
		1368	handled first even under adverse conditions (which is usually, but not
		1369	always, what you want).
		1370
		1371	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1372	will only be executed when no same or higher priority watchers have
		1373	received events, they can be used to implement the "lock-out" model when
		1374	required.
		1375
		1376	For example, to emulate how many other event libraries handle priorities,
		1377	you can associate an C<ev_idle> watcher to each such watcher, and in
		1378	the normal watcher callback, you just start the idle watcher. The real
		1379	processing is done in the idle watcher callback. This causes libev to
		1380	continously poll and process kernel event data for the watcher, but when
		1381	the lock-out case is known to be rare (which in turn is rare :), this is
		1382	workable.
		1383
		1384	Usually, however, the lock-out model implemented that way will perform
		1385	miserably under the type of load it was designed to handle. In that case,
		1386	it might be preferable to stop the real watcher before starting the
		1387	idle watcher, so the kernel will not have to process the event in case
		1388	the actual processing will be delayed for considerable time.
		1389
		1390	Here is an example of an I/O watcher that should run at a strictly lower
		1391	priority than the default, and which should only process data when no
		1392	other events are pending:
		1393
		1394	ev_idle idle; // actual processing watcher
		1395	ev_io io; // actual event watcher
		1396
		1397	static void
		1398	io_cb (EV_P_ ev_io *w, int revents)
		1399	{
		1400	// stop the I/O watcher, we received the event, but
		1401	// are not yet ready to handle it.
		1402	ev_io_stop (EV_A_ w);
		1403
		1404	// start the idle watcher to ahndle the actual event.
		1405	// it will not be executed as long as other watchers
		1406	// with the default priority are receiving events.
		1407	ev_idle_start (EV_A_ &idle);
		1408	}
		1409
		1410	static void
		1411	idle_cb (EV_P_ ev_idle *w, int revents)
		1412	{
		1413	// actual processing
		1414	read (STDIN_FILENO, ...);
		1415
		1416	// have to start the I/O watcher again, as
		1417	// we have handled the event
		1418	ev_io_start (EV_P_ &io);
		1419	}
		1420
		1421	// initialisation
		1422	ev_idle_init (&idle, idle_cb);
		1423	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1424	ev_io_start (EV_DEFAULT_ &io);
		1425
		1426	In the "real" world, it might also be beneficial to start a timer, so that
		1427	low-priority connections can not be locked out forever under load. This
		1428	enables your program to keep a lower latency for important connections
		1429	during short periods of high load, while not completely locking out less
		1430	important ones.
1191		1431
1192		1432
1193	=head1 WATCHER TYPES	1433	=head1 WATCHER TYPES
1194		1434
1195	This section describes each watcher in detail, but will not repeat	1435	This section describes each watcher in detail, but will not repeat
…		…
1221	descriptors to non-blocking mode is also usually a good idea (but not	1461	descriptors to non-blocking mode is also usually a good idea (but not
1222	required if you know what you are doing).	1462	required if you know what you are doing).
1223		1463
1224	If you cannot use non-blocking mode, then force the use of a	1464	If you cannot use non-blocking mode, then force the use of a
1225	known-to-be-good backend (at the time of this writing, this includes only	1465	known-to-be-good backend (at the time of this writing, this includes only
1226	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1466	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1467	descriptors for which non-blocking operation makes no sense (such as
		1468	files) - libev doesn't guarentee any specific behaviour in that case.
1227		1469
1228	Another thing you have to watch out for is that it is quite easy to	1470	Another thing you have to watch out for is that it is quite easy to
1229	receive "spurious" readiness notifications, that is your callback might	1471	receive "spurious" readiness notifications, that is your callback might
1230	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1472	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1231	because there is no data. Not only are some backends known to create a	1473	because there is no data. Not only are some backends known to create a
…		…
1296		1538
1297	So when you encounter spurious, unexplained daemon exits, make sure you	1539	So when you encounter spurious, unexplained daemon exits, make sure you
1298	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1540	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1299	somewhere, as that would have given you a big clue).	1541	somewhere, as that would have given you a big clue).
1300		1542
		1543	=head3 The special problem of accept()ing when you can't
		1544
		1545	Many implementations of the POSIX C<accept> function (for example,
		1546	found in port-2004 Linux) have the peculiar behaviour of not removing a
		1547	connection from the pending queue in all error cases.
		1548
		1549	For example, larger servers often run out of file descriptors (because
		1550	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1551	rejecting the connection, leading to libev signalling readiness on
		1552	the next iteration again (the connection still exists after all), and
		1553	typically causing the program to loop at 100% CPU usage.
		1554
		1555	Unfortunately, the set of errors that cause this issue differs between
		1556	operating systems, there is usually little the app can do to remedy the
		1557	situation, and no known thread-safe method of removing the connection to
		1558	cope with overload is known (to me).
		1559
		1560	One of the easiest ways to handle this situation is to just ignore it
		1561	- when the program encounters an overload, it will just loop until the
		1562	situation is over. While this is a form of busy waiting, no OS offers an
		1563	event-based way to handle this situation, so it's the best one can do.
		1564
		1565	A better way to handle the situation is to log any errors other than
		1566	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1567	messages, and continue as usual, which at least gives the user an idea of
		1568	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1569	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1570	usage.
		1571
		1572	If your program is single-threaded, then you could also keep a dummy file
		1573	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1574	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1575	close that fd, and create a new dummy fd. This will gracefully refuse
		1576	clients under typical overload conditions.
		1577
		1578	The last way to handle it is to simply log the error and C<exit>, as
		1579	is often done with C<malloc> failures, but this results in an easy
		1580	opportunity for a DoS attack.
1301		1581
1302	=head3 Watcher-Specific Functions	1582	=head3 Watcher-Specific Functions
1303		1583
1304	=over 4	1584	=over 4
1305		1585
…		…
1352	year, it will still time out after (roughly) one hour. "Roughly" because	1632	year, it will still time out after (roughly) one hour. "Roughly" because
1353	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1633	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1354	monotonic clock option helps a lot here).	1634	monotonic clock option helps a lot here).
1355		1635
1356	The callback is guaranteed to be invoked only I<after> its timeout has	1636	The callback is guaranteed to be invoked only I<after> its timeout has
1357	passed. If multiple timers become ready during the same loop iteration	1637	passed (not I<at>, so on systems with very low-resolution clocks this
1358	then the ones with earlier time-out values are invoked before ones with	1638	might introduce a small delay). If multiple timers become ready during the
1359	later time-out values (but this is no longer true when a callback calls	1639	same loop iteration then the ones with earlier time-out values are invoked
1360	C<ev_loop> recursively).	1640	before ones of the same priority with later time-out values (but this is
		1641	no longer true when a callback calls C<ev_loop> recursively).
1361		1642
1362	=head3 Be smart about timeouts	1643	=head3 Be smart about timeouts
1363		1644
1364	Many real-world problems involve some kind of timeout, usually for error	1645	Many real-world problems involve some kind of timeout, usually for error
1365	recovery. A typical example is an HTTP request - if the other side hangs,	1646	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1409	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1690	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1410	member and C<ev_timer_again>.	1691	member and C<ev_timer_again>.
1411		1692
1412	At start:	1693	At start:
1413		1694
1414	ev_timer_init (timer, callback);	1695	ev_init (timer, callback);
1415	timer->repeat = 60.;	1696	timer->repeat = 60.;
1416	ev_timer_again (loop, timer);	1697	ev_timer_again (loop, timer);
1417		1698
1418	Each time there is some activity:	1699	Each time there is some activity:
1419		1700
…		…
1481		1762
1482	To start the timer, simply initialise the watcher and set C<last_activity>	1763	To start the timer, simply initialise the watcher and set C<last_activity>
1483	to the current time (meaning we just have some activity :), then call the	1764	to the current time (meaning we just have some activity :), then call the
1484	callback, which will "do the right thing" and start the timer:	1765	callback, which will "do the right thing" and start the timer:
1485		1766
1486	ev_timer_init (timer, callback);	1767	ev_init (timer, callback);
1487	last_activity = ev_now (loop);	1768	last_activity = ev_now (loop);
1488	callback (loop, timer, EV_TIMEOUT);	1769	callback (loop, timer, EV_TIMEOUT);
1489		1770
1490	And when there is some activity, simply store the current time in	1771	And when there is some activity, simply store the current time in
1491	C<last_activity>, no libev calls at all:	1772	C<last_activity>, no libev calls at all:
…		…
1552		1833
1553	If the event loop is suspended for a long time, you can also force an	1834	If the event loop is suspended for a long time, you can also force an
1554	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1835	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1555	()>.	1836	()>.
1556		1837
		1838	=head3 The special problems of suspended animation
		1839
		1840	When you leave the server world it is quite customary to hit machines that
		1841	can suspend/hibernate - what happens to the clocks during such a suspend?
		1842
		1843	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1844	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1845	to run until the system is suspended, but they will not advance while the
		1846	system is suspended. That means, on resume, it will be as if the program
		1847	was frozen for a few seconds, but the suspend time will not be counted
		1848	towards C<ev_timer> when a monotonic clock source is used. The real time
		1849	clock advanced as expected, but if it is used as sole clocksource, then a
		1850	long suspend would be detected as a time jump by libev, and timers would
		1851	be adjusted accordingly.
		1852
		1853	I would not be surprised to see different behaviour in different between
		1854	operating systems, OS versions or even different hardware.
		1855
		1856	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1857	time jump in the monotonic clocks and the realtime clock. If the program
		1858	is suspended for a very long time, and monotonic clock sources are in use,
		1859	then you can expect C<ev_timer>s to expire as the full suspension time
		1860	will be counted towards the timers. When no monotonic clock source is in
		1861	use, then libev will again assume a timejump and adjust accordingly.
		1862
		1863	It might be beneficial for this latter case to call C<ev_suspend>
		1864	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1865	deterministic behaviour in this case (you can do nothing against
		1866	C<SIGSTOP>).
		1867
1557	=head3 Watcher-Specific Functions and Data Members	1868	=head3 Watcher-Specific Functions and Data Members
1558		1869
1559	=over 4	1870	=over 4
1560		1871
1561	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1872	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1586	If the timer is repeating, either start it if necessary (with the	1897	If the timer is repeating, either start it if necessary (with the
1587	C<repeat> value), or reset the running timer to the C<repeat> value.	1898	C<repeat> value), or reset the running timer to the C<repeat> value.
1588		1899
1589	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	1900	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1590	usage example.	1901	usage example.
		1902
		1903	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		1904
		1905	Returns the remaining time until a timer fires. If the timer is active,
		1906	then this time is relative to the current event loop time, otherwise it's
		1907	the timeout value currently configured.
		1908
		1909	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1910	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		1911	will return C<4>. When the timer expires and is restarted, it will return
		1912	roughly C<7> (likely slightly less as callback invocation takes some time,
		1913	too), and so on.
1591		1914
1592	=item ev_tstamp repeat [read-write]	1915	=item ev_tstamp repeat [read-write]
1593		1916
1594	The current C<repeat> value. Will be used each time the watcher times out	1917	The current C<repeat> value. Will be used each time the watcher times out
1595	or C<ev_timer_again> is called, and determines the next timeout (if any),	1918	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1831	Signal watchers will trigger an event when the process receives a specific	2154	Signal watchers will trigger an event when the process receives a specific
1832	signal one or more times. Even though signals are very asynchronous, libev	2155	signal one or more times. Even though signals are very asynchronous, libev
1833	will try it's best to deliver signals synchronously, i.e. as part of the	2156	will try it's best to deliver signals synchronously, i.e. as part of the
1834	normal event processing, like any other event.	2157	normal event processing, like any other event.
1835		2158
1836	If you want signals asynchronously, just use C<sigaction> as you would	2159	If you want signals to be delivered truly asynchronously, just use
1837	do without libev and forget about sharing the signal. You can even use	2160	C<sigaction> as you would do without libev and forget about sharing
1838	C<ev_async> from a signal handler to synchronously wake up an event loop.	2161	the signal. You can even use C<ev_async> from a signal handler to
		2162	synchronously wake up an event loop.
1839		2163
1840	You can configure as many watchers as you like per signal. Only when the	2164	You can configure as many watchers as you like for the same signal, but
		2165	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2166	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2167	C<SIGINT> in both the default loop and another loop at the same time. At
		2168	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2169
1841	first watcher gets started will libev actually register a signal handler	2170	When the first watcher gets started will libev actually register something
1842	with the kernel (thus it coexists with your own signal handlers as long as	2171	with the kernel (thus it coexists with your own signal handlers as long as
1843	you don't register any with libev for the same signal). Similarly, when	2172	you don't register any with libev for the same signal).
1844	the last signal watcher for a signal is stopped, libev will reset the
1845	signal handler to SIG_DFL (regardless of what it was set to before).
1846		2173
1847	If possible and supported, libev will install its handlers with	2174	If possible and supported, libev will install its handlers with
1848	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2175	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1849	interrupted. If you have a problem with system calls getting interrupted by	2176	not be unduly interrupted. If you have a problem with system calls getting
1850	signals you can block all signals in an C<ev_check> watcher and unblock	2177	interrupted by signals you can block all signals in an C<ev_check> watcher
1851	them in an C<ev_prepare> watcher.	2178	and unblock them in an C<ev_prepare> watcher.
		2179
		2180	=head3 The special problem of inheritance over fork/execve/pthread_create
		2181
		2182	Both the signal mask (C<sigprocmask>) and the signal disposition
		2183	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2184	stopping it again), that is, libev might or might not block the signal,
		2185	and might or might not set or restore the installed signal handler.
		2186
		2187	While this does not matter for the signal disposition (libev never
		2188	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2189	C<execve>), this matters for the signal mask: many programs do not expect
		2190	certain signals to be blocked.
		2191
		2192	This means that before calling C<exec> (from the child) you should reset
		2193	the signal mask to whatever "default" you expect (all clear is a good
		2194	choice usually).
		2195
		2196	The simplest way to ensure that the signal mask is reset in the child is
		2197	to install a fork handler with C<pthread_atfork> that resets it. That will
		2198	catch fork calls done by libraries (such as the libc) as well.
		2199
		2200	In current versions of libev, the signal will not be blocked indefinitely
		2201	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2202	the window of opportunity for problems, it will not go away, as libev
		2203	I<has> to modify the signal mask, at least temporarily.
		2204
		2205	So I can't stress this enough: I<If you do not reset your signal mask when
		2206	you expect it to be empty, you have a race condition in your code>. This
		2207	is not a libev-specific thing, this is true for most event libraries.
1852		2208
1853	=head3 Watcher-Specific Functions and Data Members	2209	=head3 Watcher-Specific Functions and Data Members
1854		2210
1855	=over 4	2211	=over 4
1856		2212
…		…
1888	some child status changes (most typically when a child of yours dies or	2244	some child status changes (most typically when a child of yours dies or
1889	exits). It is permissible to install a child watcher I<after> the child	2245	exits). It is permissible to install a child watcher I<after> the child
1890	has been forked (which implies it might have already exited), as long	2246	has been forked (which implies it might have already exited), as long
1891	as the event loop isn't entered (or is continued from a watcher), i.e.,	2247	as the event loop isn't entered (or is continued from a watcher), i.e.,
1892	forking and then immediately registering a watcher for the child is fine,	2248	forking and then immediately registering a watcher for the child is fine,
1893	but forking and registering a watcher a few event loop iterations later is	2249	but forking and registering a watcher a few event loop iterations later or
1894	not.	2250	in the next callback invocation is not.
1895		2251
1896	Only the default event loop is capable of handling signals, and therefore	2252	Only the default event loop is capable of handling signals, and therefore
1897	you can only register child watchers in the default event loop.	2253	you can only register child watchers in the default event loop.
1898		2254
		2255	Due to some design glitches inside libev, child watchers will always be
		2256	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2257	libev)
		2258
1899	=head3 Process Interaction	2259	=head3 Process Interaction
1900		2260
1901	Libev grabs C<SIGCHLD> as soon as the default event loop is	2261	Libev grabs C<SIGCHLD> as soon as the default event loop is
1902	initialised. This is necessary to guarantee proper behaviour even if	2262	initialised. This is necessary to guarantee proper behaviour even if the
1903	the first child watcher is started after the child exits. The occurrence	2263	first child watcher is started after the child exits. The occurrence
1904	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2264	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1905	synchronously as part of the event loop processing. Libev always reaps all	2265	synchronously as part of the event loop processing. Libev always reaps all
1906	children, even ones not watched.	2266	children, even ones not watched.
1907		2267
1908	=head3 Overriding the Built-In Processing	2268	=head3 Overriding the Built-In Processing
…		…
1918	=head3 Stopping the Child Watcher	2278	=head3 Stopping the Child Watcher
1919		2279
1920	Currently, the child watcher never gets stopped, even when the	2280	Currently, the child watcher never gets stopped, even when the
1921	child terminates, so normally one needs to stop the watcher in the	2281	child terminates, so normally one needs to stop the watcher in the
1922	callback. Future versions of libev might stop the watcher automatically	2282	callback. Future versions of libev might stop the watcher automatically
1923	when a child exit is detected.	2283	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2284	problem).
1924		2285
1925	=head3 Watcher-Specific Functions and Data Members	2286	=head3 Watcher-Specific Functions and Data Members
1926		2287
1927	=over 4	2288	=over 4
1928		2289
…		…
2254	// no longer anything immediate to do.	2615	// no longer anything immediate to do.
2255	}	2616	}
2256		2617
2257	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2618	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2258	ev_idle_init (idle_watcher, idle_cb);	2619	ev_idle_init (idle_watcher, idle_cb);
2259	ev_idle_start (loop, idle_cb);	2620	ev_idle_start (loop, idle_watcher);
2260		2621
2261		2622
2262	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2623	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2263		2624
2264	Prepare and check watchers are usually (but not always) used in pairs:	2625	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2357	struct pollfd fds [nfd];	2718	struct pollfd fds [nfd];
2358	// actual code will need to loop here and realloc etc.	2719	// actual code will need to loop here and realloc etc.
2359	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2720	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2360		2721
2361	/* the callback is illegal, but won't be called as we stop during check */	2722	/* the callback is illegal, but won't be called as we stop during check */
2362	ev_timer_init (&tw, 0, timeout * 1e-3);	2723	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2363	ev_timer_start (loop, &tw);	2724	ev_timer_start (loop, &tw);
2364		2725
2365	// create one ev_io per pollfd	2726	// create one ev_io per pollfd
2366	for (int i = 0; i < nfd; ++i)	2727	for (int i = 0; i < nfd; ++i)
2367	{	2728	{
…		…
2597	event loop blocks next and before C<ev_check> watchers are being called,	2958	event loop blocks next and before C<ev_check> watchers are being called,
2598	and only in the child after the fork. If whoever good citizen calling	2959	and only in the child after the fork. If whoever good citizen calling
2599	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2960	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2600	handlers will be invoked, too, of course.	2961	handlers will be invoked, too, of course.
2601		2962
		2963	=head3 The special problem of life after fork - how is it possible?
		2964
		2965	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2966	up/change the process environment, followed by a call to C<exec()>. This
		2967	sequence should be handled by libev without any problems.
		2968
		2969	This changes when the application actually wants to do event handling
		2970	in the child, or both parent in child, in effect "continuing" after the
		2971	fork.
		2972
		2973	The default mode of operation (for libev, with application help to detect
		2974	forks) is to duplicate all the state in the child, as would be expected
		2975	when I<either> the parent I<or> the child process continues.
		2976
		2977	When both processes want to continue using libev, then this is usually the
		2978	wrong result. In that case, usually one process (typically the parent) is
		2979	supposed to continue with all watchers in place as before, while the other
		2980	process typically wants to start fresh, i.e. without any active watchers.
		2981
		2982	The cleanest and most efficient way to achieve that with libev is to
		2983	simply create a new event loop, which of course will be "empty", and
		2984	use that for new watchers. This has the advantage of not touching more
		2985	memory than necessary, and thus avoiding the copy-on-write, and the
		2986	disadvantage of having to use multiple event loops (which do not support
		2987	signal watchers).
		2988
		2989	When this is not possible, or you want to use the default loop for
		2990	other reasons, then in the process that wants to start "fresh", call
		2991	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2992	the default loop will "orphan" (not stop) all registered watchers, so you
		2993	have to be careful not to execute code that modifies those watchers. Note
		2994	also that in that case, you have to re-register any signal watchers.
		2995
2602	=head3 Watcher-Specific Functions and Data Members	2996	=head3 Watcher-Specific Functions and Data Members
2603		2997
2604	=over 4	2998	=over 4
2605		2999
2606	=item ev_fork_init (ev_signal *, callback)	3000	=item ev_fork_init (ev_signal *, callback)
…		…
2635	=head3 Queueing	3029	=head3 Queueing
2636		3030
2637	C<ev_async> does not support queueing of data in any way. The reason	3031	C<ev_async> does not support queueing of data in any way. The reason
2638	is that the author does not know of a simple (or any) algorithm for a	3032	is that the author does not know of a simple (or any) algorithm for a
2639	multiple-writer-single-reader queue that works in all cases and doesn't	3033	multiple-writer-single-reader queue that works in all cases and doesn't
2640	need elaborate support such as pthreads.	3034	need elaborate support such as pthreads or unportable memory access
		3035	semantics.
2641		3036
2642	That means that if you want to queue data, you have to provide your own	3037	That means that if you want to queue data, you have to provide your own
2643	queue. But at least I can tell you how to implement locking around your	3038	queue. But at least I can tell you how to implement locking around your
2644	queue:	3039	queue:
2645		3040
…		…
2803	/* doh, nothing entered */;	3198	/* doh, nothing entered */;
2804	}	3199	}
2805		3200
2806	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3201	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2807		3202
2808	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2809
2810	Feeds the given event set into the event loop, as if the specified event
2811	had happened for the specified watcher (which must be a pointer to an
2812	initialised but not necessarily started event watcher).
2813
2814	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3203	=item ev_feed_fd_event (loop, int fd, int revents)
2815		3204
2816	Feed an event on the given fd, as if a file descriptor backend detected	3205	Feed an event on the given fd, as if a file descriptor backend detected
2817	the given events it.	3206	the given events it.
2818		3207
2819	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3208	=item ev_feed_signal_event (loop, int signum)
2820		3209
2821	Feed an event as if the given signal occurred (C<loop> must be the default	3210	Feed an event as if the given signal occurred (C<loop> must be the default
2822	loop!).	3211	loop!).
2823		3212
2824	=back	3213	=back
…		…
2904		3293
2905	=over 4	3294	=over 4
2906		3295
2907	=item ev::TYPE::TYPE ()	3296	=item ev::TYPE::TYPE ()
2908		3297
2909	=item ev::TYPE::TYPE (struct ev_loop *)	3298	=item ev::TYPE::TYPE (loop)
2910		3299
2911	=item ev::TYPE::~TYPE	3300	=item ev::TYPE::~TYPE
2912		3301
2913	The constructor (optionally) takes an event loop to associate the watcher	3302	The constructor (optionally) takes an event loop to associate the watcher
2914	with. If it is omitted, it will use C<EV_DEFAULT>.	3303	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2991	Example: Use a plain function as callback.	3380	Example: Use a plain function as callback.
2992		3381
2993	static void io_cb (ev::io &w, int revents) { }	3382	static void io_cb (ev::io &w, int revents) { }
2994	iow.set <io_cb> ();	3383	iow.set <io_cb> ();
2995		3384
2996	=item w->set (struct ev_loop *)	3385	=item w->set (loop)
2997		3386
2998	Associates a different C<struct ev_loop> with this watcher. You can only	3387	Associates a different C<struct ev_loop> with this watcher. You can only
2999	do this when the watcher is inactive (and not pending either).	3388	do this when the watcher is inactive (and not pending either).
3000		3389
3001	=item w->set ([arguments])	3390	=item w->set ([arguments])
…		…
3098	=item Ocaml	3487	=item Ocaml
3099		3488
3100	Erkki Seppala has written Ocaml bindings for libev, to be found at	3489	Erkki Seppala has written Ocaml bindings for libev, to be found at
3101	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3490	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3102		3491
		3492	=item Lua
		3493
		3494	Brian Maher has written a partial interface to libev for lua (at the
		3495	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3496	L<http://github.com/brimworks/lua-ev>.
		3497
3103	=back	3498	=back
3104		3499
3105		3500
3106	=head1 MACRO MAGIC	3501	=head1 MACRO MAGIC
3107		3502
…		…
3260	libev.m4	3655	libev.m4
3261		3656
3262	=head2 PREPROCESSOR SYMBOLS/MACROS	3657	=head2 PREPROCESSOR SYMBOLS/MACROS
3263		3658
3264	Libev can be configured via a variety of preprocessor symbols you have to	3659	Libev can be configured via a variety of preprocessor symbols you have to
3265	define before including any of its files. The default in the absence of	3660	define before including (or compiling) any of its files. The default in
3266	autoconf is documented for every option.	3661	the absence of autoconf is documented for every option.
		3662
		3663	Symbols marked with "(h)" do not change the ABI, and can have different
		3664	values when compiling libev vs. including F<ev.h>, so it is permissible
		3665	to redefine them before including F<ev.h> without breakign compatibility
		3666	to a compiled library. All other symbols change the ABI, which means all
		3667	users of libev and the libev code itself must be compiled with compatible
		3668	settings.
3267		3669
3268	=over 4	3670	=over 4
3269		3671
3270	=item EV_STANDALONE	3672	=item EV_STANDALONE (h)
3271		3673
3272	Must always be C<1> if you do not use autoconf configuration, which	3674	Must always be C<1> if you do not use autoconf configuration, which
3273	keeps libev from including F<config.h>, and it also defines dummy	3675	keeps libev from including F<config.h>, and it also defines dummy
3274	implementations for some libevent functions (such as logging, which is not	3676	implementations for some libevent functions (such as logging, which is not
3275	supported). It will also not define any of the structs usually found in	3677	supported). It will also not define any of the structs usually found in
3276	F<event.h> that are not directly supported by the libev core alone.	3678	F<event.h> that are not directly supported by the libev core alone.
3277		3679
3278	In stanbdalone mode, libev will still try to automatically deduce the	3680	In standalone mode, libev will still try to automatically deduce the
3279	configuration, but has to be more conservative.	3681	configuration, but has to be more conservative.
3280		3682
3281	=item EV_USE_MONOTONIC	3683	=item EV_USE_MONOTONIC
3282		3684
3283	If defined to be C<1>, libev will try to detect the availability of the	3685	If defined to be C<1>, libev will try to detect the availability of the
…		…
3348	be used is the winsock select). This means that it will call	3750	be used is the winsock select). This means that it will call
3349	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3751	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3350	it is assumed that all these functions actually work on fds, even	3752	it is assumed that all these functions actually work on fds, even
3351	on win32. Should not be defined on non-win32 platforms.	3753	on win32. Should not be defined on non-win32 platforms.
3352		3754
3353	=item EV_FD_TO_WIN32_HANDLE	3755	=item EV_FD_TO_WIN32_HANDLE(fd)
3354		3756
3355	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3757	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3356	file descriptors to socket handles. When not defining this symbol (the	3758	file descriptors to socket handles. When not defining this symbol (the
3357	default), then libev will call C<_get_osfhandle>, which is usually	3759	default), then libev will call C<_get_osfhandle>, which is usually
3358	correct. In some cases, programs use their own file descriptor management,	3760	correct. In some cases, programs use their own file descriptor management,
3359	in which case they can provide this function to map fds to socket handles.	3761	in which case they can provide this function to map fds to socket handles.
		3762
		3763	=item EV_WIN32_HANDLE_TO_FD(handle)
		3764
		3765	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3766	using the standard C<_open_osfhandle> function. For programs implementing
		3767	their own fd to handle mapping, overwriting this function makes it easier
		3768	to do so. This can be done by defining this macro to an appropriate value.
		3769
		3770	=item EV_WIN32_CLOSE_FD(fd)
		3771
		3772	If programs implement their own fd to handle mapping on win32, then this
		3773	macro can be used to override the C<close> function, useful to unregister
		3774	file descriptors again. Note that the replacement function has to close
		3775	the underlying OS handle.
3360		3776
3361	=item EV_USE_POLL	3777	=item EV_USE_POLL
3362		3778
3363	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3779	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3364	backend. Otherwise it will be enabled on non-win32 platforms. It	3780	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3411	as well as for signal and thread safety in C<ev_async> watchers.	3827	as well as for signal and thread safety in C<ev_async> watchers.
3412		3828
3413	In the absence of this define, libev will use C<sig_atomic_t volatile>	3829	In the absence of this define, libev will use C<sig_atomic_t volatile>
3414	(from F<signal.h>), which is usually good enough on most platforms.	3830	(from F<signal.h>), which is usually good enough on most platforms.
3415		3831
3416	=item EV_H	3832	=item EV_H (h)
3417		3833
3418	The name of the F<ev.h> header file used to include it. The default if	3834	The name of the F<ev.h> header file used to include it. The default if
3419	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3835	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3420	used to virtually rename the F<ev.h> header file in case of conflicts.	3836	used to virtually rename the F<ev.h> header file in case of conflicts.
3421		3837
3422	=item EV_CONFIG_H	3838	=item EV_CONFIG_H (h)
3423		3839
3424	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3840	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3425	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3841	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3426	C<EV_H>, above.	3842	C<EV_H>, above.
3427		3843
3428	=item EV_EVENT_H	3844	=item EV_EVENT_H (h)
3429		3845
3430	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3846	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3431	of how the F<event.h> header can be found, the default is C<"event.h">.	3847	of how the F<event.h> header can be found, the default is C<"event.h">.
3432		3848
3433	=item EV_PROTOTYPES	3849	=item EV_PROTOTYPES (h)
3434		3850
3435	If defined to be C<0>, then F<ev.h> will not define any function	3851	If defined to be C<0>, then F<ev.h> will not define any function
3436	prototypes, but still define all the structs and other symbols. This is	3852	prototypes, but still define all the structs and other symbols. This is
3437	occasionally useful if you want to provide your own wrapper functions	3853	occasionally useful if you want to provide your own wrapper functions
3438	around libev functions.	3854	around libev functions.
…		…
3460	fine.	3876	fine.
3461		3877
3462	If your embedding application does not need any priorities, defining these	3878	If your embedding application does not need any priorities, defining these
3463	both to C<0> will save some memory and CPU.	3879	both to C<0> will save some memory and CPU.
3464		3880
3465	=item EV_PERIODIC_ENABLE	3881	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		3882	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		3883	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3466		3884
3467	If undefined or defined to be C<1>, then periodic timers are supported. If	3885	If undefined or defined to be C<1> (and the platform supports it), then
3468	defined to be C<0>, then they are not. Disabling them saves a few kB of	3886	the respective watcher type is supported. If defined to be C<0>, then it
3469	code.	3887	is not. Disabling watcher types mainly saves codesize.
3470
3471	=item EV_IDLE_ENABLE
3472
3473	If undefined or defined to be C<1>, then idle watchers are supported. If
3474	defined to be C<0>, then they are not. Disabling them saves a few kB of
3475	code.
3476
3477	=item EV_EMBED_ENABLE
3478
3479	If undefined or defined to be C<1>, then embed watchers are supported. If
3480	defined to be C<0>, then they are not. Embed watchers rely on most other
3481	watcher types, which therefore must not be disabled.
3482
3483	=item EV_STAT_ENABLE
3484
3485	If undefined or defined to be C<1>, then stat watchers are supported. If
3486	defined to be C<0>, then they are not.
3487
3488	=item EV_FORK_ENABLE
3489
3490	If undefined or defined to be C<1>, then fork watchers are supported. If
3491	defined to be C<0>, then they are not.
3492
3493	=item EV_ASYNC_ENABLE
3494
3495	If undefined or defined to be C<1>, then async watchers are supported. If
3496	defined to be C<0>, then they are not.
3497		3888
3498	=item EV_MINIMAL	3889	=item EV_MINIMAL
3499		3890
3500	If you need to shave off some kilobytes of code at the expense of some	3891	If you need to shave off some kilobytes of code at the expense of some
3501	speed, define this symbol to C<1>. Currently this is used to override some	3892	speed (but with the full API), define this symbol to C<1>. Currently this
3502	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3893	is used to override some inlining decisions, saves roughly 30% code size
3503	much smaller 2-heap for timer management over the default 4-heap.	3894	on amd64. It also selects a much smaller 2-heap for timer management over
		3895	the default 4-heap.
		3896
		3897	You can save even more by disabling watcher types you do not need
		3898	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3899	(C<-DNDEBUG>) will usually reduce code size a lot. Disabling inotify,
		3900	eventfd and signalfd will further help, and disabling backends one doesn't
		3901	need (e.g. poll, epoll, kqueue, ports) will help further.
		3902
		3903	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3904	provide a bare-bones event library. See C<ev.h> for details on what parts
		3905	of the API are still available, and do not complain if this subset changes
		3906	over time.
		3907
		3908	This example set of settings reduces the compiled size of libev from
		3909	23.9Kb to 7.7Kb on my GNU/Linux amd64 system (and leaves little
		3910	in - there is also an effect on the amount of memory used). With
		3911	an intelligent-enough linker (gcc+binutils do this when you use
		3912	C<-Wl,--gc-sections -ffunction-sections>) further unused functions might
		3913	be left out as well automatically - a binary starting a timer and an I/O
		3914	watcher then might come out at only 5Kb.
		3915
		3916	// tuning and API changes
		3917	#define EV_MINIMAL 2
		3918	#define EV_MULTIPLICITY 0
		3919	#define EV_MINPRI 0
		3920	#define EV_MAXPRI 0
		3921
		3922	// OS-specific backends
		3923	#define EV_USE_INOTIFY 0
		3924	#define EV_USE_EVENTFD 0
		3925	#define EV_USE_SIGNALFD 0
		3926	#define EV_USE_REALTIME 0
		3927	#define EV_USE_MONOTONIC 0
		3928	#define EV_USE_CLOCK_SYSCALL 0
		3929
		3930	// disable all backends except select
		3931	#define EV_USE_POLL 0
		3932	#define EV_USE_PORT 0
		3933	#define EV_USE_KQUEUE 0
		3934	#define EV_USE_EPOLL 0
		3935
		3936	// disable all watcher types that cna be disabled
		3937	#define EV_STAT_ENABLE 0
		3938	#define EV_PERIODIC_ENABLE 0
		3939	#define EV_IDLE_ENABLE 0
		3940	#define EV_CHECK_ENABLE 0
		3941	#define EV_PREPARE_ENABLE 0
		3942	#define EV_FORK_ENABLE 0
		3943	#define EV_SIGNAL_ENABLE 0
		3944	#define EV_CHILD_ENABLE 0
		3945	#define EV_ASYNC_ENABLE 0
		3946	#define EV_EMBED_ENABLE 0
		3947
		3948	=item EV_AVOID_STDIO
		3949
		3950	If this is set to C<1> at compiletime, then libev will avoid using stdio
		3951	functions (printf, scanf, perror etc.). This will increase the codesize
		3952	somewhat, but if your program doesn't otherwise depend on stdio and your
		3953	libc allows it, this avoids linking in the stdio library which is quite
		3954	big.
		3955
		3956	Note that error messages might become less precise when this option is
		3957	enabled.
		3958
		3959	=item EV_NSIG
		3960
		3961	The highest supported signal number, +1 (or, the number of
		3962	signals): Normally, libev tries to deduce the maximum number of signals
		3963	automatically, but sometimes this fails, in which case it can be
		3964	specified. Also, using a lower number than detected (C<32> should be
		3965	good for about any system in existance) can save some memory, as libev
		3966	statically allocates some 12-24 bytes per signal number.
3504		3967
3505	=item EV_PID_HASHSIZE	3968	=item EV_PID_HASHSIZE
3506		3969
3507	C<ev_child> watchers use a small hash table to distribute workload by	3970	C<ev_child> watchers use a small hash table to distribute workload by
3508	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3971	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3694	default loop and triggering an C<ev_async> watcher from the default loop	4157	default loop and triggering an C<ev_async> watcher from the default loop
3695	watcher callback into the event loop interested in the signal.	4158	watcher callback into the event loop interested in the signal.
3696		4159
3697	=back	4160	=back
3698		4161
		4162	=head4 THREAD LOCKING EXAMPLE
		4163
		4164	Here is a fictitious example of how to run an event loop in a different
		4165	thread than where callbacks are being invoked and watchers are
		4166	created/added/removed.
		4167
		4168	For a real-world example, see the C<EV::Loop::Async> perl module,
		4169	which uses exactly this technique (which is suited for many high-level
		4170	languages).
		4171
		4172	The example uses a pthread mutex to protect the loop data, a condition
		4173	variable to wait for callback invocations, an async watcher to notify the
		4174	event loop thread and an unspecified mechanism to wake up the main thread.
		4175
		4176	First, you need to associate some data with the event loop:
		4177
		4178	typedef struct {
		4179	mutex_t lock; /* global loop lock */
		4180	ev_async async_w;
		4181	thread_t tid;
		4182	cond_t invoke_cv;
		4183	} userdata;
		4184
		4185	void prepare_loop (EV_P)
		4186	{
		4187	// for simplicity, we use a static userdata struct.
		4188	static userdata u;
		4189
		4190	ev_async_init (&u->async_w, async_cb);
		4191	ev_async_start (EV_A_ &u->async_w);
		4192
		4193	pthread_mutex_init (&u->lock, 0);
		4194	pthread_cond_init (&u->invoke_cv, 0);
		4195
		4196	// now associate this with the loop
		4197	ev_set_userdata (EV_A_ u);
		4198	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4199	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4200
		4201	// then create the thread running ev_loop
		4202	pthread_create (&u->tid, 0, l_run, EV_A);
		4203	}
		4204
		4205	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4206	solely to wake up the event loop so it takes notice of any new watchers
		4207	that might have been added:
		4208
		4209	static void
		4210	async_cb (EV_P_ ev_async *w, int revents)
		4211	{
		4212	// just used for the side effects
		4213	}
		4214
		4215	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4216	protecting the loop data, respectively.
		4217
		4218	static void
		4219	l_release (EV_P)
		4220	{
		4221	userdata *u = ev_userdata (EV_A);
		4222	pthread_mutex_unlock (&u->lock);
		4223	}
		4224
		4225	static void
		4226	l_acquire (EV_P)
		4227	{
		4228	userdata *u = ev_userdata (EV_A);
		4229	pthread_mutex_lock (&u->lock);
		4230	}
		4231
		4232	The event loop thread first acquires the mutex, and then jumps straight
		4233	into C<ev_loop>:
		4234
		4235	void *
		4236	l_run (void *thr_arg)
		4237	{
		4238	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4239
		4240	l_acquire (EV_A);
		4241	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4242	ev_loop (EV_A_ 0);
		4243	l_release (EV_A);
		4244
		4245	return 0;
		4246	}
		4247
		4248	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4249	signal the main thread via some unspecified mechanism (signals? pipe
		4250	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4251	have been called (in a while loop because a) spurious wakeups are possible
		4252	and b) skipping inter-thread-communication when there are no pending
		4253	watchers is very beneficial):
		4254
		4255	static void
		4256	l_invoke (EV_P)
		4257	{
		4258	userdata *u = ev_userdata (EV_A);
		4259
		4260	while (ev_pending_count (EV_A))
		4261	{
		4262	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4263	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4264	}
		4265	}
		4266
		4267	Now, whenever the main thread gets told to invoke pending watchers, it
		4268	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4269	thread to continue:
		4270
		4271	static void
		4272	real_invoke_pending (EV_P)
		4273	{
		4274	userdata *u = ev_userdata (EV_A);
		4275
		4276	pthread_mutex_lock (&u->lock);
		4277	ev_invoke_pending (EV_A);
		4278	pthread_cond_signal (&u->invoke_cv);
		4279	pthread_mutex_unlock (&u->lock);
		4280	}
		4281
		4282	Whenever you want to start/stop a watcher or do other modifications to an
		4283	event loop, you will now have to lock:
		4284
		4285	ev_timer timeout_watcher;
		4286	userdata *u = ev_userdata (EV_A);
		4287
		4288	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4289
		4290	pthread_mutex_lock (&u->lock);
		4291	ev_timer_start (EV_A_ &timeout_watcher);
		4292	ev_async_send (EV_A_ &u->async_w);
		4293	pthread_mutex_unlock (&u->lock);
		4294
		4295	Note that sending the C<ev_async> watcher is required because otherwise
		4296	an event loop currently blocking in the kernel will have no knowledge
		4297	about the newly added timer. By waking up the loop it will pick up any new
		4298	watchers in the next event loop iteration.
		4299
3699	=head3 COROUTINES	4300	=head3 COROUTINES
3700		4301
3701	Libev is very accommodating to coroutines ("cooperative threads"):	4302	Libev is very accommodating to coroutines ("cooperative threads"):
3702	libev fully supports nesting calls to its functions from different	4303	libev fully supports nesting calls to its functions from different
3703	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4304	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3704	different coroutines, and switch freely between both coroutines running the	4305	different coroutines, and switch freely between both coroutines running
3705	loop, as long as you don't confuse yourself). The only exception is that	4306	the loop, as long as you don't confuse yourself). The only exception is
3706	you must not do this from C<ev_periodic> reschedule callbacks.	4307	that you must not do this from C<ev_periodic> reschedule callbacks.
3707		4308
3708	Care has been taken to ensure that libev does not keep local state inside	4309	Care has been taken to ensure that libev does not keep local state inside
3709	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4310	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3710	they do not call any callbacks.	4311	they do not call any callbacks.
3711		4312
…		…
3788	way (note also that glib is the slowest event library known to man).	4389	way (note also that glib is the slowest event library known to man).
3789		4390
3790	There is no supported compilation method available on windows except	4391	There is no supported compilation method available on windows except
3791	embedding it into other applications.	4392	embedding it into other applications.
3792		4393
		4394	Sensible signal handling is officially unsupported by Microsoft - libev
		4395	tries its best, but under most conditions, signals will simply not work.
		4396
3793	Not a libev limitation but worth mentioning: windows apparently doesn't	4397	Not a libev limitation but worth mentioning: windows apparently doesn't
3794	accept large writes: instead of resulting in a partial write, windows will	4398	accept large writes: instead of resulting in a partial write, windows will
3795	either accept everything or return C<ENOBUFS> if the buffer is too large,	4399	either accept everything or return C<ENOBUFS> if the buffer is too large,
3796	so make sure you only write small amounts into your sockets (less than a	4400	so make sure you only write small amounts into your sockets (less than a
3797	megabyte seems safe, but this apparently depends on the amount of memory	4401	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3801	the abysmal performance of winsockets, using a large number of sockets	4405	the abysmal performance of winsockets, using a large number of sockets
3802	is not recommended (and not reasonable). If your program needs to use	4406	is not recommended (and not reasonable). If your program needs to use
3803	more than a hundred or so sockets, then likely it needs to use a totally	4407	more than a hundred or so sockets, then likely it needs to use a totally
3804	different implementation for windows, as libev offers the POSIX readiness	4408	different implementation for windows, as libev offers the POSIX readiness
3805	notification model, which cannot be implemented efficiently on windows	4409	notification model, which cannot be implemented efficiently on windows
3806	(Microsoft monopoly games).	4410	(due to Microsoft monopoly games).
3807		4411
3808	A typical way to use libev under windows is to embed it (see the embedding	4412	A typical way to use libev under windows is to embed it (see the embedding
3809	section for details) and use the following F<evwrap.h> header file instead	4413	section for details) and use the following F<evwrap.h> header file instead
3810	of F<ev.h>:	4414	of F<ev.h>:
3811		4415
…		…
3847		4451
3848	Early versions of winsocket's select only supported waiting for a maximum	4452	Early versions of winsocket's select only supported waiting for a maximum
3849	of C<64> handles (probably owning to the fact that all windows kernels	4453	of C<64> handles (probably owning to the fact that all windows kernels
3850	can only wait for C<64> things at the same time internally; Microsoft	4454	can only wait for C<64> things at the same time internally; Microsoft
3851	recommends spawning a chain of threads and wait for 63 handles and the	4455	recommends spawning a chain of threads and wait for 63 handles and the
3852	previous thread in each. Great).	4456	previous thread in each. Sounds great!).
3853		4457
3854	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4458	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3855	to some high number (e.g. C<2048>) before compiling the winsocket select	4459	to some high number (e.g. C<2048>) before compiling the winsocket select
3856	call (which might be in libev or elsewhere, for example, perl does its own	4460	call (which might be in libev or elsewhere, for example, perl and many
3857	select emulation on windows).	4461	other interpreters do their own select emulation on windows).
3858		4462
3859	Another limit is the number of file descriptors in the Microsoft runtime	4463	Another limit is the number of file descriptors in the Microsoft runtime
3860	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4464	libraries, which by default is C<64> (there must be a hidden I<64>
3861	or something like this inside Microsoft). You can increase this by calling	4465	fetish or something like this inside Microsoft). You can increase this
3862	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4466	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3863	arbitrary limit), but is broken in many versions of the Microsoft runtime	4467	(another arbitrary limit), but is broken in many versions of the Microsoft
3864	libraries.
3865
3866	This might get you to about C<512> or C<2048> sockets (depending on	4468	runtime libraries. This might get you to about C<512> or C<2048> sockets
3867	windows version and/or the phase of the moon). To get more, you need to	4469	(depending on windows version and/or the phase of the moon). To get more,
3868	wrap all I/O functions and provide your own fd management, but the cost of	4470	you need to wrap all I/O functions and provide your own fd management, but
3869	calling select (O(n²)) will likely make this unworkable.	4471	the cost of calling select (O(n²)) will likely make this unworkable.
3870		4472
3871	=back	4473	=back
3872		4474
3873	=head2 PORTABILITY REQUIREMENTS	4475	=head2 PORTABILITY REQUIREMENTS
3874		4476
…		…
3917	=item C<double> must hold a time value in seconds with enough accuracy	4519	=item C<double> must hold a time value in seconds with enough accuracy
3918		4520
3919	The type C<double> is used to represent timestamps. It is required to	4521	The type C<double> is used to represent timestamps. It is required to
3920	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4522	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3921	enough for at least into the year 4000. This requirement is fulfilled by	4523	enough for at least into the year 4000. This requirement is fulfilled by
3922	implementations implementing IEEE 754 (basically all existing ones).	4524	implementations implementing IEEE 754, which is basically all existing
		4525	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4526	2200.
3923		4527
3924	=back	4528	=back
3925		4529
3926	If you know of other additional requirements drop me a note.	4530	If you know of other additional requirements drop me a note.
3927		4531
…		…
3995	involves iterating over all running async watchers or all signal numbers.	4599	involves iterating over all running async watchers or all signal numbers.
3996		4600
3997	=back	4601	=back
3998		4602
3999		4603
		4604	=head1 GLOSSARY
		4605
		4606	=over 4
		4607
		4608	=item active
		4609
		4610	A watcher is active as long as it has been started (has been attached to
		4611	an event loop) but not yet stopped (disassociated from the event loop).
		4612
		4613	=item application
		4614
		4615	In this document, an application is whatever is using libev.
		4616
		4617	=item callback
		4618
		4619	The address of a function that is called when some event has been
		4620	detected. Callbacks are being passed the event loop, the watcher that
		4621	received the event, and the actual event bitset.
		4622
		4623	=item callback invocation
		4624
		4625	The act of calling the callback associated with a watcher.
		4626
		4627	=item event
		4628
		4629	A change of state of some external event, such as data now being available
		4630	for reading on a file descriptor, time having passed or simply not having
		4631	any other events happening anymore.
		4632
		4633	In libev, events are represented as single bits (such as C<EV_READ> or
		4634	C<EV_TIMEOUT>).
		4635
		4636	=item event library
		4637
		4638	A software package implementing an event model and loop.
		4639
		4640	=item event loop
		4641
		4642	An entity that handles and processes external events and converts them
		4643	into callback invocations.
		4644
		4645	=item event model
		4646
		4647	The model used to describe how an event loop handles and processes
		4648	watchers and events.
		4649
		4650	=item pending
		4651
		4652	A watcher is pending as soon as the corresponding event has been detected,
		4653	and stops being pending as soon as the watcher will be invoked or its
		4654	pending status is explicitly cleared by the application.
		4655
		4656	A watcher can be pending, but not active. Stopping a watcher also clears
		4657	its pending status.
		4658
		4659	=item real time
		4660
		4661	The physical time that is observed. It is apparently strictly monotonic :)
		4662
		4663	=item wall-clock time
		4664
		4665	The time and date as shown on clocks. Unlike real time, it can actually
		4666	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4667	clock.
		4668
		4669	=item watcher
		4670
		4671	A data structure that describes interest in certain events. Watchers need
		4672	to be started (attached to an event loop) before they can receive events.
		4673
		4674	=item watcher invocation
		4675
		4676	The act of calling the callback associated with a watcher.
		4677
		4678	=back
		4679
4000	=head1 AUTHOR	4680	=head1 AUTHOR
4001		4681
4002	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	4682	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
4003		4683

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