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Revision 1.231 by root, Wed Apr 15 19:35:53 2009 UTC vs.
Revision 1.272 by root, Tue Nov 24 06:39:28 2009 UTC

…		…
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
…		…
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<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_NOSIGFD>
		376
		377	When this flag is specified, then libev will not attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		379	probably only useful to work around any bugs in libev. Consequently, this
		380	flag might go away once the signalfd functionality is considered stable,
		381	so it's useful mostly in environment variables and not in program code.
		382
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		384
357	This is your standard select(2) backend. Not I<completely> standard, as	385	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,	386	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	387	but if that fails, expect a fairly low limit on the number of fds when
…		…
382		410
383	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and	411	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and
384	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.	412	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.
385		413
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	414	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		415
		416	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		417	kernels).
387		418
388	For few fds, this backend is a bit little slower than poll and select,	419	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	420	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),	421	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).	422	epoll scales either O(1) or O(active_fds).
…		…
506		537
507	It is definitely not recommended to use this flag.	538	It is definitely not recommended to use this flag.
508		539
509	=back	540	=back
510		541
511	If one or more of these are or'ed into the flags value, then only these	542	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	543	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.	544	here). If none are specified, all backends in C<ev_recommended_backends
		545	()> will be tried.
514		546
515	Example: This is the most typical usage.	547	Example: This is the most typical usage.
516		548
517	if (!ev_default_loop (0))	549	if (!ev_default_loop (0))
518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
561	as signal and child watchers) would need to be stopped manually.	593	as signal and child watchers) would need to be stopped manually.
562		594
563	In general it is not advisable to call this function except in the	595	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	596	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	597	pipe fds. If you need dynamically allocated loops it is better to use
566	C<ev_loop_new> and C<ev_loop_destroy>).	598	C<ev_loop_new> and C<ev_loop_destroy>.
567		599
568	=item ev_loop_destroy (loop)	600	=item ev_loop_destroy (loop)
569		601
570	Like C<ev_default_destroy>, but destroys an event loop created by an	602	Like C<ev_default_destroy>, but destroys an event loop created by an
571	earlier call to C<ev_loop_new>.	603	earlier call to C<ev_loop_new>.
…		…
609		641
610	This value can sometimes be useful as a generation counter of sorts (it	642	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	643	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	644	C<ev_prepare> and C<ev_check> calls.
613		645
		646	=item unsigned int ev_loop_depth (loop)
		647
		648	Returns the number of times C<ev_loop> was entered minus the number of
		649	times C<ev_loop> was exited, in other words, the recursion depth.
		650
		651	Outside C<ev_loop>, this number is zero. In a callback, this number is
		652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		653	in which case it is higher.
		654
		655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		656	etc.), doesn't count as exit.
		657
614	=item unsigned int ev_backend (loop)	658	=item unsigned int ev_backend (loop)
615		659
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	661	use.
618		662
…		…
632		676
633	This function is rarely useful, but when some event callback runs for a	677	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	678	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	679	the current time is a good idea.
636		680
637	See also "The special problem of time updates" in the C<ev_timer> section.	681	See also L<The special problem of time updates> in the C<ev_timer> section.
638		682
639	=item ev_suspend (loop)	683	=item ev_suspend (loop)
640		684
641	=item ev_resume (loop)	685	=item ev_resume (loop)
642		686
…		…
663	event loop time (see C<ev_now_update>).	707	event loop time (see C<ev_now_update>).
664		708
665	=item ev_loop (loop, int flags)	709	=item ev_loop (loop, int flags)
666		710
667	Finally, this is it, the event handler. This function usually is called	711	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	712	after you have initialised all your watchers and you want to start
669	events.	713	handling events.
670		714
671	If the flags argument is specified as C<0>, it will not return until	715	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.	716	either no event watchers are active anymore or C<ev_unloop> was called.
673		717
674	Please note that an explicit C<ev_unloop> is usually better than	718	Please note that an explicit C<ev_unloop> is usually better than
…		…
799		843
800	By setting a higher I<io collect interval> you allow libev to spend more	844	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,	845	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	846	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	847	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.	848	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		849	sleep time ensures that libev will not poll for I/O events more often then
		850	once per this interval, on average.
805		851
806	Likewise, by setting a higher I<timeout collect interval> you allow libev	852	Likewise, by setting a higher I<timeout collect interval> you allow libev
807	to spend more time collecting timeouts, at the expense of increased	853	to spend more time collecting timeouts, at the expense of increased
808	latency/jitter/inexactness (the watcher callback will be called	854	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	855	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
811		857
812	Many (busy) programs can usually benefit by setting the I/O collect	858	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	859	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	860	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>,	861	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.	862	as this approaches the timing granularity of most systems. Note that if
		863	you do transactions with the outside world and you can't increase the
		864	parallelity, then this setting will limit your transaction rate (if you
		865	need to poll once per transaction and the I/O collect interval is 0.01,
		866	then you can't do more than 100 transations per second).
817		867
818	Setting the I<timeout collect interval> can improve the opportunity for	868	Setting the I<timeout collect interval> can improve the opportunity for
819	saving power, as the program will "bundle" timer callback invocations that	869	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	870	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	871	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	872	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
823	they fire on, say, one-second boundaries only.	873	they fire on, say, one-second boundaries only.
		874
		875	Example: we only need 0.1s timeout granularity, and we wish not to poll
		876	more often than 100 times per second:
		877
		878	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		880
		881	=item ev_invoke_pending (loop)
		882
		883	This call will simply invoke all pending watchers while resetting their
		884	pending state. Normally, C<ev_loop> does this automatically when required,
		885	but when overriding the invoke callback this call comes handy.
		886
		887	=item int ev_pending_count (loop)
		888
		889	Returns the number of pending watchers - zero indicates that no watchers
		890	are pending.
		891
		892	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		893
		894	This overrides the invoke pending functionality of the loop: Instead of
		895	invoking all pending watchers when there are any, C<ev_loop> will call
		896	this callback instead. This is useful, for example, when you want to
		897	invoke the actual watchers inside another context (another thread etc.).
		898
		899	If you want to reset the callback, use C<ev_invoke_pending> as new
		900	callback.
		901
		902	=item ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))
		903
		904	Sometimes you want to share the same loop between multiple threads. This
		905	can be done relatively simply by putting mutex_lock/unlock calls around
		906	each call to a libev function.
		907
		908	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		909	wait for it to return. One way around this is to wake up the loop via
		910	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		911	and I<acquire> callbacks on the loop.
		912
		913	When set, then C<release> will be called just before the thread is
		914	suspended waiting for new events, and C<acquire> is called just
		915	afterwards.
		916
		917	Ideally, C<release> will just call your mutex_unlock function, and
		918	C<acquire> will just call the mutex_lock function again.
		919
		920	While event loop modifications are allowed between invocations of
		921	C<release> and C<acquire> (that's their only purpose after all), no
		922	modifications done will affect the event loop, i.e. adding watchers will
		923	have no effect on the set of file descriptors being watched, or the time
		924	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		925	to take note of any changes you made.
		926
		927	In theory, threads executing C<ev_loop> will be async-cancel safe between
		928	invocations of C<release> and C<acquire>.
		929
		930	See also the locking example in the C<THREADS> section later in this
		931	document.
		932
		933	=item ev_set_userdata (loop, void *data)
		934
		935	=item ev_userdata (loop)
		936
		937	Set and retrieve a single C<void *> associated with a loop. When
		938	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		939	C<0.>
		940
		941	These two functions can be used to associate arbitrary data with a loop,
		942	and are intended solely for the C<invoke_pending_cb>, C<release> and
		943	C<acquire> callbacks described above, but of course can be (ab-)used for
		944	any other purpose as well.
824		945
825	=item ev_loop_verify (loop)	946	=item ev_loop_verify (loop)
826		947
827	This function only does something when C<EV_VERIFY> support has been	948	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	949	compiled in, which is the default for non-minimal builds. It tries to go
…		…
1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1204	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1084	(default: C<-2>). Pending watchers with higher priority will be invoked	1205	(default: C<-2>). Pending watchers with higher priority will be invoked
1085	before watchers with lower priority, but priority will not keep watchers	1206	before watchers with lower priority, but priority will not keep watchers
1086	from being executed (except for C<ev_idle> watchers).	1207	from being executed (except for C<ev_idle> watchers).
1087		1208
1088	This means that priorities are I<only> used for ordering callback
1089	invocation after new events have been received. This is useful, for
1090	example, to reduce latency after idling, or more often, to bind two
1091	watchers on the same event and make sure one is called first.
1092
1093	If you need to suppress invocation when higher priority events are pending	1209	If you need to suppress invocation when higher priority events are pending
1094	you need to look at C<ev_idle> watchers, which provide this functionality.	1210	you need to look at C<ev_idle> watchers, which provide this functionality.
1095		1211
1096	You I<must not> change the priority of a watcher as long as it is active or	1212	You I<must not> change the priority of a watcher as long as it is active or
1097	pending.	1213	pending.
1098
1099	The default priority used by watchers when no priority has been set is
1100	always C<0>, which is supposed to not be too high and not be too low :).
1101		1214
1102	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1215	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1103	fine, as long as you do not mind that the priority value you query might	1216	fine, as long as you do not mind that the priority value you query might
1104	or might not have been clamped to the valid range.	1217	or might not have been clamped to the valid range.
		1218
		1219	The default priority used by watchers when no priority has been set is
		1220	always C<0>, which is supposed to not be too high and not be too low :).
		1221
		1222	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1223	priorities.
1105		1224
1106	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1225	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1107		1226
1108	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1227	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1109	C<loop> nor C<revents> need to be valid as long as the watcher callback	1228	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1174	#include <stddef.h>	1293	#include <stddef.h>
1175		1294
1176	static void	1295	static void
1177	t1_cb (EV_P_ ev_timer *w, int revents)	1296	t1_cb (EV_P_ ev_timer *w, int revents)
1178	{	1297	{
1179	struct my_biggy big = (struct my_biggy *	1298	struct my_biggy big = (struct my_biggy *)
1180	(((char *)w) - offsetof (struct my_biggy, t1));	1299	(((char *)w) - offsetof (struct my_biggy, t1));
1181	}	1300	}
1182		1301
1183	static void	1302	static void
1184	t2_cb (EV_P_ ev_timer *w, int revents)	1303	t2_cb (EV_P_ ev_timer *w, int revents)
1185	{	1304	{
1186	struct my_biggy big = (struct my_biggy *	1305	struct my_biggy big = (struct my_biggy *)
1187	(((char *)w) - offsetof (struct my_biggy, t2));	1306	(((char *)w) - offsetof (struct my_biggy, t2));
1188	}	1307	}
		1308
		1309	=head2 WATCHER PRIORITY MODELS
		1310
		1311	Many event loops support I<watcher priorities>, which are usually small
		1312	integers that influence the ordering of event callback invocation
		1313	between watchers in some way, all else being equal.
		1314
		1315	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1316	description for the more technical details such as the actual priority
		1317	range.
		1318
		1319	There are two common ways how these these priorities are being interpreted
		1320	by event loops:
		1321
		1322	In the more common lock-out model, higher priorities "lock out" invocation
		1323	of lower priority watchers, which means as long as higher priority
		1324	watchers receive events, lower priority watchers are not being invoked.
		1325
		1326	The less common only-for-ordering model uses priorities solely to order
		1327	callback invocation within a single event loop iteration: Higher priority
		1328	watchers are invoked before lower priority ones, but they all get invoked
		1329	before polling for new events.
		1330
		1331	Libev uses the second (only-for-ordering) model for all its watchers
		1332	except for idle watchers (which use the lock-out model).
		1333
		1334	The rationale behind this is that implementing the lock-out model for
		1335	watchers is not well supported by most kernel interfaces, and most event
		1336	libraries will just poll for the same events again and again as long as
		1337	their callbacks have not been executed, which is very inefficient in the
		1338	common case of one high-priority watcher locking out a mass of lower
		1339	priority ones.
		1340
		1341	Static (ordering) priorities are most useful when you have two or more
		1342	watchers handling the same resource: a typical usage example is having an
		1343	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1344	timeouts. Under load, data might be received while the program handles
		1345	other jobs, but since timers normally get invoked first, the timeout
		1346	handler will be executed before checking for data. In that case, giving
		1347	the timer a lower priority than the I/O watcher ensures that I/O will be
		1348	handled first even under adverse conditions (which is usually, but not
		1349	always, what you want).
		1350
		1351	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1352	will only be executed when no same or higher priority watchers have
		1353	received events, they can be used to implement the "lock-out" model when
		1354	required.
		1355
		1356	For example, to emulate how many other event libraries handle priorities,
		1357	you can associate an C<ev_idle> watcher to each such watcher, and in
		1358	the normal watcher callback, you just start the idle watcher. The real
		1359	processing is done in the idle watcher callback. This causes libev to
		1360	continously poll and process kernel event data for the watcher, but when
		1361	the lock-out case is known to be rare (which in turn is rare :), this is
		1362	workable.
		1363
		1364	Usually, however, the lock-out model implemented that way will perform
		1365	miserably under the type of load it was designed to handle. In that case,
		1366	it might be preferable to stop the real watcher before starting the
		1367	idle watcher, so the kernel will not have to process the event in case
		1368	the actual processing will be delayed for considerable time.
		1369
		1370	Here is an example of an I/O watcher that should run at a strictly lower
		1371	priority than the default, and which should only process data when no
		1372	other events are pending:
		1373
		1374	ev_idle idle; // actual processing watcher
		1375	ev_io io; // actual event watcher
		1376
		1377	static void
		1378	io_cb (EV_P_ ev_io *w, int revents)
		1379	{
		1380	// stop the I/O watcher, we received the event, but
		1381	// are not yet ready to handle it.
		1382	ev_io_stop (EV_A_ w);
		1383
		1384	// start the idle watcher to ahndle the actual event.
		1385	// it will not be executed as long as other watchers
		1386	// with the default priority are receiving events.
		1387	ev_idle_start (EV_A_ &idle);
		1388	}
		1389
		1390	static void
		1391	idle_cb (EV_P_ ev_idle *w, int revents)
		1392	{
		1393	// actual processing
		1394	read (STDIN_FILENO, ...);
		1395
		1396	// have to start the I/O watcher again, as
		1397	// we have handled the event
		1398	ev_io_start (EV_P_ &io);
		1399	}
		1400
		1401	// initialisation
		1402	ev_idle_init (&idle, idle_cb);
		1403	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1404	ev_io_start (EV_DEFAULT_ &io);
		1405
		1406	In the "real" world, it might also be beneficial to start a timer, so that
		1407	low-priority connections can not be locked out forever under load. This
		1408	enables your program to keep a lower latency for important connections
		1409	during short periods of high load, while not completely locking out less
		1410	important ones.
1189		1411
1190		1412
1191	=head1 WATCHER TYPES	1413	=head1 WATCHER TYPES
1192		1414
1193	This section describes each watcher in detail, but will not repeat	1415	This section describes each watcher in detail, but will not repeat
…		…
1219	descriptors to non-blocking mode is also usually a good idea (but not	1441	descriptors to non-blocking mode is also usually a good idea (but not
1220	required if you know what you are doing).	1442	required if you know what you are doing).
1221		1443
1222	If you cannot use non-blocking mode, then force the use of a	1444	If you cannot use non-blocking mode, then force the use of a
1223	known-to-be-good backend (at the time of this writing, this includes only	1445	known-to-be-good backend (at the time of this writing, this includes only
1224	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1446	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1447	descriptors for which non-blocking operation makes no sense (such as
		1448	files) - libev doesn't guarentee any specific behaviour in that case.
1225		1449
1226	Another thing you have to watch out for is that it is quite easy to	1450	Another thing you have to watch out for is that it is quite easy to
1227	receive "spurious" readiness notifications, that is your callback might	1451	receive "spurious" readiness notifications, that is your callback might
1228	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1452	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1229	because there is no data. Not only are some backends known to create a	1453	because there is no data. Not only are some backends known to create a
…		…
1350	year, it will still time out after (roughly) one hour. "Roughly" because	1574	year, it will still time out after (roughly) one hour. "Roughly" because
1351	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1575	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1352	monotonic clock option helps a lot here).	1576	monotonic clock option helps a lot here).
1353		1577
1354	The callback is guaranteed to be invoked only I<after> its timeout has	1578	The callback is guaranteed to be invoked only I<after> its timeout has
1355	passed. If multiple timers become ready during the same loop iteration	1579	passed (not I<at>, so on systems with very low-resolution clocks this
1356	then the ones with earlier time-out values are invoked before ones with	1580	might introduce a small delay). If multiple timers become ready during the
1357	later time-out values (but this is no longer true when a callback calls	1581	same loop iteration then the ones with earlier time-out values are invoked
1358	C<ev_loop> recursively).	1582	before ones of the same priority with later time-out values (but this is
		1583	no longer true when a callback calls C<ev_loop> recursively).
1359		1584
1360	=head3 Be smart about timeouts	1585	=head3 Be smart about timeouts
1361		1586
1362	Many real-world problems involve some kind of timeout, usually for error	1587	Many real-world problems involve some kind of timeout, usually for error
1363	recovery. A typical example is an HTTP request - if the other side hangs,	1588	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1407	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1632	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1408	member and C<ev_timer_again>.	1633	member and C<ev_timer_again>.
1409		1634
1410	At start:	1635	At start:
1411		1636
1412	ev_timer_init (timer, callback);	1637	ev_init (timer, callback);
1413	timer->repeat = 60.;	1638	timer->repeat = 60.;
1414	ev_timer_again (loop, timer);	1639	ev_timer_again (loop, timer);
1415		1640
1416	Each time there is some activity:	1641	Each time there is some activity:
1417		1642
…		…
1479		1704
1480	To start the timer, simply initialise the watcher and set C<last_activity>	1705	To start the timer, simply initialise the watcher and set C<last_activity>
1481	to the current time (meaning we just have some activity :), then call the	1706	to the current time (meaning we just have some activity :), then call the
1482	callback, which will "do the right thing" and start the timer:	1707	callback, which will "do the right thing" and start the timer:
1483		1708
1484	ev_timer_init (timer, callback);	1709	ev_init (timer, callback);
1485	last_activity = ev_now (loop);	1710	last_activity = ev_now (loop);
1486	callback (loop, timer, EV_TIMEOUT);	1711	callback (loop, timer, EV_TIMEOUT);
1487		1712
1488	And when there is some activity, simply store the current time in	1713	And when there is some activity, simply store the current time in
1489	C<last_activity>, no libev calls at all:	1714	C<last_activity>, no libev calls at all:
…		…
1550		1775
1551	If the event loop is suspended for a long time, you can also force an	1776	If the event loop is suspended for a long time, you can also force an
1552	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1777	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1553	()>.	1778	()>.
1554		1779
		1780	=head3 The special problems of suspended animation
		1781
		1782	When you leave the server world it is quite customary to hit machines that
		1783	can suspend/hibernate - what happens to the clocks during such a suspend?
		1784
		1785	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1786	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1787	to run until the system is suspended, but they will not advance while the
		1788	system is suspended. That means, on resume, it will be as if the program
		1789	was frozen for a few seconds, but the suspend time will not be counted
		1790	towards C<ev_timer> when a monotonic clock source is used. The real time
		1791	clock advanced as expected, but if it is used as sole clocksource, then a
		1792	long suspend would be detected as a time jump by libev, and timers would
		1793	be adjusted accordingly.
		1794
		1795	I would not be surprised to see different behaviour in different between
		1796	operating systems, OS versions or even different hardware.
		1797
		1798	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1799	time jump in the monotonic clocks and the realtime clock. If the program
		1800	is suspended for a very long time, and monotonic clock sources are in use,
		1801	then you can expect C<ev_timer>s to expire as the full suspension time
		1802	will be counted towards the timers. When no monotonic clock source is in
		1803	use, then libev will again assume a timejump and adjust accordingly.
		1804
		1805	It might be beneficial for this latter case to call C<ev_suspend>
		1806	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1807	deterministic behaviour in this case (you can do nothing against
		1808	C<SIGSTOP>).
		1809
1555	=head3 Watcher-Specific Functions and Data Members	1810	=head3 Watcher-Specific Functions and Data Members
1556		1811
1557	=over 4	1812	=over 4
1558		1813
1559	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1814	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1582	If the timer is started but non-repeating, stop it (as if it timed out).	1837	If the timer is started but non-repeating, stop it (as if it timed out).
1583		1838
1584	If the timer is repeating, either start it if necessary (with the	1839	If the timer is repeating, either start it if necessary (with the
1585	C<repeat> value), or reset the running timer to the C<repeat> value.	1840	C<repeat> value), or reset the running timer to the C<repeat> value.
1586		1841
1587	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1842	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1588	usage example.	1843	usage example.
		1844
		1845	=item ev_timer_remaining (loop, ev_timer *)
		1846
		1847	Returns the remaining time until a timer fires. If the timer is active,
		1848	then this time is relative to the current event loop time, otherwise it's
		1849	the timeout value currently configured.
		1850
		1851	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1852	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1853	will return C<4>. When the timer expires and is restarted, it will return
		1854	roughly C<7> (likely slightly less as callback invocation takes some time,
		1855	too), and so on.
1589		1856
1590	=item ev_tstamp repeat [read-write]	1857	=item ev_tstamp repeat [read-write]
1591		1858
1592	The current C<repeat> value. Will be used each time the watcher times out	1859	The current C<repeat> value. Will be used each time the watcher times out
1593	or C<ev_timer_again> is called, and determines the next timeout (if any),	1860	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1829	Signal watchers will trigger an event when the process receives a specific	2096	Signal watchers will trigger an event when the process receives a specific
1830	signal one or more times. Even though signals are very asynchronous, libev	2097	signal one or more times. Even though signals are very asynchronous, libev
1831	will try it's best to deliver signals synchronously, i.e. as part of the	2098	will try it's best to deliver signals synchronously, i.e. as part of the
1832	normal event processing, like any other event.	2099	normal event processing, like any other event.
1833		2100
1834	If you want signals asynchronously, just use C<sigaction> as you would	2101	If you want signals to be delivered truly asynchronously, just use
1835	do without libev and forget about sharing the signal. You can even use	2102	C<sigaction> as you would do without libev and forget about sharing
1836	C<ev_async> from a signal handler to synchronously wake up an event loop.	2103	the signal. You can even use C<ev_async> from a signal handler to
		2104	synchronously wake up an event loop.
1837		2105
1838	You can configure as many watchers as you like per signal. Only when the	2106	You can configure as many watchers as you like for the same signal, but
		2107	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2108	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2109	C<SIGINT> in both the default loop and another loop at the same time. At
		2110	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2111
1839	first watcher gets started will libev actually register a signal handler	2112	When the first watcher gets started will libev actually register something
1840	with the kernel (thus it coexists with your own signal handlers as long as	2113	with the kernel (thus it coexists with your own signal handlers as long as
1841	you don't register any with libev for the same signal). Similarly, when	2114	you don't register any with libev for the same signal).
1842	the last signal watcher for a signal is stopped, libev will reset the
1843	signal handler to SIG_DFL (regardless of what it was set to before).
1844		2115
1845	If possible and supported, libev will install its handlers with	2116	If possible and supported, libev will install its handlers with
1846	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2117	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1847	interrupted. If you have a problem with system calls getting interrupted by	2118	not be unduly interrupted. If you have a problem with system calls getting
1848	signals you can block all signals in an C<ev_check> watcher and unblock	2119	interrupted by signals you can block all signals in an C<ev_check> watcher
1849	them in an C<ev_prepare> watcher.	2120	and unblock them in an C<ev_prepare> watcher.
		2121
		2122	=head3 The special problem of inheritance over execve
		2123
		2124	Both the signal mask (C<sigprocmask>) and the signal disposition
		2125	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2126	stopping it again), that is, libev might or might not block the signal,
		2127	and might or might not set or restore the installed signal handler.
		2128
		2129	While this does not matter for the signal disposition (libev never
		2130	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2131	C<execve>), this matters for the signal mask: many programs do not expect
		2132	certain signals to be blocked.
		2133
		2134	This means that before calling C<exec> (from the child) you should reset
		2135	the signal mask to whatever "default" you expect (all clear is a good
		2136	choice usually).
		2137
		2138	The simplest way to ensure that the signal mask is reset in the child is
		2139	to install a fork handler with C<pthread_atfork> that resets it. That will
		2140	catch fork calls done by libraries (such as the libc) as well.
		2141
		2142	In current versions of libev, you can also ensure that the signal mask is
		2143	not blocking any signals (except temporarily, so thread users watch out)
		2144	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2145	is not guaranteed for future versions, however.
1850		2146
1851	=head3 Watcher-Specific Functions and Data Members	2147	=head3 Watcher-Specific Functions and Data Members
1852		2148
1853	=over 4	2149	=over 4
1854		2150
…		…
1886	some child status changes (most typically when a child of yours dies or	2182	some child status changes (most typically when a child of yours dies or
1887	exits). It is permissible to install a child watcher I<after> the child	2183	exits). It is permissible to install a child watcher I<after> the child
1888	has been forked (which implies it might have already exited), as long	2184	has been forked (which implies it might have already exited), as long
1889	as the event loop isn't entered (or is continued from a watcher), i.e.,	2185	as the event loop isn't entered (or is continued from a watcher), i.e.,
1890	forking and then immediately registering a watcher for the child is fine,	2186	forking and then immediately registering a watcher for the child is fine,
1891	but forking and registering a watcher a few event loop iterations later is	2187	but forking and registering a watcher a few event loop iterations later or
1892	not.	2188	in the next callback invocation is not.
1893		2189
1894	Only the default event loop is capable of handling signals, and therefore	2190	Only the default event loop is capable of handling signals, and therefore
1895	you can only register child watchers in the default event loop.	2191	you can only register child watchers in the default event loop.
1896		2192
		2193	Due to some design glitches inside libev, child watchers will always be
		2194	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2195	libev)
		2196
1897	=head3 Process Interaction	2197	=head3 Process Interaction
1898		2198
1899	Libev grabs C<SIGCHLD> as soon as the default event loop is	2199	Libev grabs C<SIGCHLD> as soon as the default event loop is
1900	initialised. This is necessary to guarantee proper behaviour even if	2200	initialised. This is necessary to guarantee proper behaviour even if the
1901	the first child watcher is started after the child exits. The occurrence	2201	first child watcher is started after the child exits. The occurrence
1902	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2202	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1903	synchronously as part of the event loop processing. Libev always reaps all	2203	synchronously as part of the event loop processing. Libev always reaps all
1904	children, even ones not watched.	2204	children, even ones not watched.
1905		2205
1906	=head3 Overriding the Built-In Processing	2206	=head3 Overriding the Built-In Processing
…		…
1916	=head3 Stopping the Child Watcher	2216	=head3 Stopping the Child Watcher
1917		2217
1918	Currently, the child watcher never gets stopped, even when the	2218	Currently, the child watcher never gets stopped, even when the
1919	child terminates, so normally one needs to stop the watcher in the	2219	child terminates, so normally one needs to stop the watcher in the
1920	callback. Future versions of libev might stop the watcher automatically	2220	callback. Future versions of libev might stop the watcher automatically
1921	when a child exit is detected.	2221	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2222	problem).
1922		2223
1923	=head3 Watcher-Specific Functions and Data Members	2224	=head3 Watcher-Specific Functions and Data Members
1924		2225
1925	=over 4	2226	=over 4
1926		2227
…		…
2252	// no longer anything immediate to do.	2553	// no longer anything immediate to do.
2253	}	2554	}
2254		2555
2255	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2556	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2256	ev_idle_init (idle_watcher, idle_cb);	2557	ev_idle_init (idle_watcher, idle_cb);
2257	ev_idle_start (loop, idle_cb);	2558	ev_idle_start (loop, idle_watcher);
2258		2559
2259		2560
2260	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2561	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2261		2562
2262	Prepare and check watchers are usually (but not always) used in pairs:	2563	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2355	struct pollfd fds [nfd];	2656	struct pollfd fds [nfd];
2356	// actual code will need to loop here and realloc etc.	2657	// actual code will need to loop here and realloc etc.
2357	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2658	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2358		2659
2359	/* the callback is illegal, but won't be called as we stop during check */	2660	/* the callback is illegal, but won't be called as we stop during check */
2360	ev_timer_init (&tw, 0, timeout * 1e-3);	2661	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2361	ev_timer_start (loop, &tw);	2662	ev_timer_start (loop, &tw);
2362		2663
2363	// create one ev_io per pollfd	2664	// create one ev_io per pollfd
2364	for (int i = 0; i < nfd; ++i)	2665	for (int i = 0; i < nfd; ++i)
2365	{	2666	{
…		…
2595	event loop blocks next and before C<ev_check> watchers are being called,	2896	event loop blocks next and before C<ev_check> watchers are being called,
2596	and only in the child after the fork. If whoever good citizen calling	2897	and only in the child after the fork. If whoever good citizen calling
2597	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2898	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2598	handlers will be invoked, too, of course.	2899	handlers will be invoked, too, of course.
2599		2900
		2901	=head3 The special problem of life after fork - how is it possible?
		2902
		2903	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2904	up/change the process environment, followed by a call to C<exec()>. This
		2905	sequence should be handled by libev without any problems.
		2906
		2907	This changes when the application actually wants to do event handling
		2908	in the child, or both parent in child, in effect "continuing" after the
		2909	fork.
		2910
		2911	The default mode of operation (for libev, with application help to detect
		2912	forks) is to duplicate all the state in the child, as would be expected
		2913	when I<either> the parent I<or> the child process continues.
		2914
		2915	When both processes want to continue using libev, then this is usually the
		2916	wrong result. In that case, usually one process (typically the parent) is
		2917	supposed to continue with all watchers in place as before, while the other
		2918	process typically wants to start fresh, i.e. without any active watchers.
		2919
		2920	The cleanest and most efficient way to achieve that with libev is to
		2921	simply create a new event loop, which of course will be "empty", and
		2922	use that for new watchers. This has the advantage of not touching more
		2923	memory than necessary, and thus avoiding the copy-on-write, and the
		2924	disadvantage of having to use multiple event loops (which do not support
		2925	signal watchers).
		2926
		2927	When this is not possible, or you want to use the default loop for
		2928	other reasons, then in the process that wants to start "fresh", call
		2929	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2930	the default loop will "orphan" (not stop) all registered watchers, so you
		2931	have to be careful not to execute code that modifies those watchers. Note
		2932	also that in that case, you have to re-register any signal watchers.
		2933
2600	=head3 Watcher-Specific Functions and Data Members	2934	=head3 Watcher-Specific Functions and Data Members
2601		2935
2602	=over 4	2936	=over 4
2603		2937
2604	=item ev_fork_init (ev_signal *, callback)	2938	=item ev_fork_init (ev_signal *, callback)
…		…
3096	=item Ocaml	3430	=item Ocaml
3097		3431
3098	Erkki Seppala has written Ocaml bindings for libev, to be found at	3432	Erkki Seppala has written Ocaml bindings for libev, to be found at
3099	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3433	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3100		3434
		3435	=item Lua
		3436
		3437	Brian Maher has written a partial interface to libev
		3438	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3439	L<http://github.com/brimworks/lua-ev>.
		3440
3101	=back	3441	=back
3102		3442
3103		3443
3104	=head1 MACRO MAGIC	3444	=head1 MACRO MAGIC
3105		3445
…		…
3271	keeps libev from including F<config.h>, and it also defines dummy	3611	keeps libev from including F<config.h>, and it also defines dummy
3272	implementations for some libevent functions (such as logging, which is not	3612	implementations for some libevent functions (such as logging, which is not
3273	supported). It will also not define any of the structs usually found in	3613	supported). It will also not define any of the structs usually found in
3274	F<event.h> that are not directly supported by the libev core alone.	3614	F<event.h> that are not directly supported by the libev core alone.
3275		3615
3276	In stanbdalone mode, libev will still try to automatically deduce the	3616	In standalone mode, libev will still try to automatically deduce the
3277	configuration, but has to be more conservative.	3617	configuration, but has to be more conservative.
3278		3618
3279	=item EV_USE_MONOTONIC	3619	=item EV_USE_MONOTONIC
3280		3620
3281	If defined to be C<1>, libev will try to detect the availability of the	3621	If defined to be C<1>, libev will try to detect the availability of the
…		…
3346	be used is the winsock select). This means that it will call	3686	be used is the winsock select). This means that it will call
3347	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3687	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3348	it is assumed that all these functions actually work on fds, even	3688	it is assumed that all these functions actually work on fds, even
3349	on win32. Should not be defined on non-win32 platforms.	3689	on win32. Should not be defined on non-win32 platforms.
3350		3690
3351	=item EV_FD_TO_WIN32_HANDLE	3691	=item EV_FD_TO_WIN32_HANDLE(fd)
3352		3692
3353	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3693	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3354	file descriptors to socket handles. When not defining this symbol (the	3694	file descriptors to socket handles. When not defining this symbol (the
3355	default), then libev will call C<_get_osfhandle>, which is usually	3695	default), then libev will call C<_get_osfhandle>, which is usually
3356	correct. In some cases, programs use their own file descriptor management,	3696	correct. In some cases, programs use their own file descriptor management,
3357	in which case they can provide this function to map fds to socket handles.	3697	in which case they can provide this function to map fds to socket handles.
		3698
		3699	=item EV_WIN32_HANDLE_TO_FD(handle)
		3700
		3701	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3702	using the standard C<_open_osfhandle> function. For programs implementing
		3703	their own fd to handle mapping, overwriting this function makes it easier
		3704	to do so. This can be done by defining this macro to an appropriate value.
		3705
		3706	=item EV_WIN32_CLOSE_FD(fd)
		3707
		3708	If programs implement their own fd to handle mapping on win32, then this
		3709	macro can be used to override the C<close> function, useful to unregister
		3710	file descriptors again. Note that the replacement function has to close
		3711	the underlying OS handle.
3358		3712
3359	=item EV_USE_POLL	3713	=item EV_USE_POLL
3360		3714
3361	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3715	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3362	backend. Otherwise it will be enabled on non-win32 platforms. It	3716	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3494	defined to be C<0>, then they are not.	3848	defined to be C<0>, then they are not.
3495		3849
3496	=item EV_MINIMAL	3850	=item EV_MINIMAL
3497		3851
3498	If you need to shave off some kilobytes of code at the expense of some	3852	If you need to shave off some kilobytes of code at the expense of some
3499	speed, define this symbol to C<1>. Currently this is used to override some	3853	speed (but with the full API), define this symbol to C<1>. Currently this
3500	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3854	is used to override some inlining decisions, saves roughly 30% code size
3501	much smaller 2-heap for timer management over the default 4-heap.	3855	on amd64. It also selects a much smaller 2-heap for timer management over
		3856	the default 4-heap.
		3857
		3858	You can save even more by disabling watcher types you do not need
		3859	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3860	(C<-DNDEBUG>) will usually reduce code size a lot.
		3861
		3862	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3863	provide a bare-bones event library. See C<ev.h> for details on what parts
		3864	of the API are still available, and do not complain if this subset changes
		3865	over time.
		3866
		3867	=item EV_NSIG
		3868
		3869	The highest supported signal number, +1 (or, the number of
		3870	signals): Normally, libev tries to deduce the maximum number of signals
		3871	automatically, but sometimes this fails, in which case it can be
		3872	specified. Also, using a lower number than detected (C<32> should be
		3873	good for about any system in existance) can save some memory, as libev
		3874	statically allocates some 12-24 bytes per signal number.
3502		3875
3503	=item EV_PID_HASHSIZE	3876	=item EV_PID_HASHSIZE
3504		3877
3505	C<ev_child> watchers use a small hash table to distribute workload by	3878	C<ev_child> watchers use a small hash table to distribute workload by
3506	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3879	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3692	default loop and triggering an C<ev_async> watcher from the default loop	4065	default loop and triggering an C<ev_async> watcher from the default loop
3693	watcher callback into the event loop interested in the signal.	4066	watcher callback into the event loop interested in the signal.
3694		4067
3695	=back	4068	=back
3696		4069
		4070	=head4 THREAD LOCKING EXAMPLE
		4071
		4072	Here is a fictitious example of how to run an event loop in a different
		4073	thread than where callbacks are being invoked and watchers are
		4074	created/added/removed.
		4075
		4076	For a real-world example, see the C<EV::Loop::Async> perl module,
		4077	which uses exactly this technique (which is suited for many high-level
		4078	languages).
		4079
		4080	The example uses a pthread mutex to protect the loop data, a condition
		4081	variable to wait for callback invocations, an async watcher to notify the
		4082	event loop thread and an unspecified mechanism to wake up the main thread.
		4083
		4084	First, you need to associate some data with the event loop:
		4085
		4086	typedef struct {
		4087	mutex_t lock; /* global loop lock */
		4088	ev_async async_w;
		4089	thread_t tid;
		4090	cond_t invoke_cv;
		4091	} userdata;
		4092
		4093	void prepare_loop (EV_P)
		4094	{
		4095	// for simplicity, we use a static userdata struct.
		4096	static userdata u;
		4097
		4098	ev_async_init (&u->async_w, async_cb);
		4099	ev_async_start (EV_A_ &u->async_w);
		4100
		4101	pthread_mutex_init (&u->lock, 0);
		4102	pthread_cond_init (&u->invoke_cv, 0);
		4103
		4104	// now associate this with the loop
		4105	ev_set_userdata (EV_A_ u);
		4106	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4107	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4108
		4109	// then create the thread running ev_loop
		4110	pthread_create (&u->tid, 0, l_run, EV_A);
		4111	}
		4112
		4113	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4114	solely to wake up the event loop so it takes notice of any new watchers
		4115	that might have been added:
		4116
		4117	static void
		4118	async_cb (EV_P_ ev_async *w, int revents)
		4119	{
		4120	// just used for the side effects
		4121	}
		4122
		4123	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4124	protecting the loop data, respectively.
		4125
		4126	static void
		4127	l_release (EV_P)
		4128	{
		4129	userdata *u = ev_userdata (EV_A);
		4130	pthread_mutex_unlock (&u->lock);
		4131	}
		4132
		4133	static void
		4134	l_acquire (EV_P)
		4135	{
		4136	userdata *u = ev_userdata (EV_A);
		4137	pthread_mutex_lock (&u->lock);
		4138	}
		4139
		4140	The event loop thread first acquires the mutex, and then jumps straight
		4141	into C<ev_loop>:
		4142
		4143	void *
		4144	l_run (void *thr_arg)
		4145	{
		4146	struct ev_loop loop = (struct ev_loop )thr_arg;
		4147
		4148	l_acquire (EV_A);
		4149	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4150	ev_loop (EV_A_ 0);
		4151	l_release (EV_A);
		4152
		4153	return 0;
		4154	}
		4155
		4156	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4157	signal the main thread via some unspecified mechanism (signals? pipe
		4158	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4159	have been called (in a while loop because a) spurious wakeups are possible
		4160	and b) skipping inter-thread-communication when there are no pending
		4161	watchers is very beneficial):
		4162
		4163	static void
		4164	l_invoke (EV_P)
		4165	{
		4166	userdata *u = ev_userdata (EV_A);
		4167
		4168	while (ev_pending_count (EV_A))
		4169	{
		4170	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4171	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4172	}
		4173	}
		4174
		4175	Now, whenever the main thread gets told to invoke pending watchers, it
		4176	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4177	thread to continue:
		4178
		4179	static void
		4180	real_invoke_pending (EV_P)
		4181	{
		4182	userdata *u = ev_userdata (EV_A);
		4183
		4184	pthread_mutex_lock (&u->lock);
		4185	ev_invoke_pending (EV_A);
		4186	pthread_cond_signal (&u->invoke_cv);
		4187	pthread_mutex_unlock (&u->lock);
		4188	}
		4189
		4190	Whenever you want to start/stop a watcher or do other modifications to an
		4191	event loop, you will now have to lock:
		4192
		4193	ev_timer timeout_watcher;
		4194	userdata *u = ev_userdata (EV_A);
		4195
		4196	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4197
		4198	pthread_mutex_lock (&u->lock);
		4199	ev_timer_start (EV_A_ &timeout_watcher);
		4200	ev_async_send (EV_A_ &u->async_w);
		4201	pthread_mutex_unlock (&u->lock);
		4202
		4203	Note that sending the C<ev_async> watcher is required because otherwise
		4204	an event loop currently blocking in the kernel will have no knowledge
		4205	about the newly added timer. By waking up the loop it will pick up any new
		4206	watchers in the next event loop iteration.
		4207
3697	=head3 COROUTINES	4208	=head3 COROUTINES
3698		4209
3699	Libev is very accommodating to coroutines ("cooperative threads"):	4210	Libev is very accommodating to coroutines ("cooperative threads"):
3700	libev fully supports nesting calls to its functions from different	4211	libev fully supports nesting calls to its functions from different
3701	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4212	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3702	different coroutines, and switch freely between both coroutines running the	4213	different coroutines, and switch freely between both coroutines running
3703	loop, as long as you don't confuse yourself). The only exception is that	4214	the loop, as long as you don't confuse yourself). The only exception is
3704	you must not do this from C<ev_periodic> reschedule callbacks.	4215	that you must not do this from C<ev_periodic> reschedule callbacks.
3705		4216
3706	Care has been taken to ensure that libev does not keep local state inside	4217	Care has been taken to ensure that libev does not keep local state inside
3707	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4218	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3708	they do not call any callbacks.	4219	they do not call any callbacks.
3709		4220
…		…
3786	way (note also that glib is the slowest event library known to man).	4297	way (note also that glib is the slowest event library known to man).
3787		4298
3788	There is no supported compilation method available on windows except	4299	There is no supported compilation method available on windows except
3789	embedding it into other applications.	4300	embedding it into other applications.
3790		4301
		4302	Sensible signal handling is officially unsupported by Microsoft - libev
		4303	tries its best, but under most conditions, signals will simply not work.
		4304
3791	Not a libev limitation but worth mentioning: windows apparently doesn't	4305	Not a libev limitation but worth mentioning: windows apparently doesn't
3792	accept large writes: instead of resulting in a partial write, windows will	4306	accept large writes: instead of resulting in a partial write, windows will
3793	either accept everything or return C<ENOBUFS> if the buffer is too large,	4307	either accept everything or return C<ENOBUFS> if the buffer is too large,
3794	so make sure you only write small amounts into your sockets (less than a	4308	so make sure you only write small amounts into your sockets (less than a
3795	megabyte seems safe, but this apparently depends on the amount of memory	4309	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3799	the abysmal performance of winsockets, using a large number of sockets	4313	the abysmal performance of winsockets, using a large number of sockets
3800	is not recommended (and not reasonable). If your program needs to use	4314	is not recommended (and not reasonable). If your program needs to use
3801	more than a hundred or so sockets, then likely it needs to use a totally	4315	more than a hundred or so sockets, then likely it needs to use a totally
3802	different implementation for windows, as libev offers the POSIX readiness	4316	different implementation for windows, as libev offers the POSIX readiness
3803	notification model, which cannot be implemented efficiently on windows	4317	notification model, which cannot be implemented efficiently on windows
3804	(Microsoft monopoly games).	4318	(due to Microsoft monopoly games).
3805		4319
3806	A typical way to use libev under windows is to embed it (see the embedding	4320	A typical way to use libev under windows is to embed it (see the embedding
3807	section for details) and use the following F<evwrap.h> header file instead	4321	section for details) and use the following F<evwrap.h> header file instead
3808	of F<ev.h>:	4322	of F<ev.h>:
3809		4323
…		…
3845		4359
3846	Early versions of winsocket's select only supported waiting for a maximum	4360	Early versions of winsocket's select only supported waiting for a maximum
3847	of C<64> handles (probably owning to the fact that all windows kernels	4361	of C<64> handles (probably owning to the fact that all windows kernels
3848	can only wait for C<64> things at the same time internally; Microsoft	4362	can only wait for C<64> things at the same time internally; Microsoft
3849	recommends spawning a chain of threads and wait for 63 handles and the	4363	recommends spawning a chain of threads and wait for 63 handles and the
3850	previous thread in each. Great).	4364	previous thread in each. Sounds great!).
3851		4365
3852	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4366	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3853	to some high number (e.g. C<2048>) before compiling the winsocket select	4367	to some high number (e.g. C<2048>) before compiling the winsocket select
3854	call (which might be in libev or elsewhere, for example, perl does its own	4368	call (which might be in libev or elsewhere, for example, perl and many
3855	select emulation on windows).	4369	other interpreters do their own select emulation on windows).
3856		4370
3857	Another limit is the number of file descriptors in the Microsoft runtime	4371	Another limit is the number of file descriptors in the Microsoft runtime
3858	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4372	libraries, which by default is C<64> (there must be a hidden I<64>
3859	or something like this inside Microsoft). You can increase this by calling	4373	fetish or something like this inside Microsoft). You can increase this
3860	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4374	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3861	arbitrary limit), but is broken in many versions of the Microsoft runtime	4375	(another arbitrary limit), but is broken in many versions of the Microsoft
3862	libraries.
3863
3864	This might get you to about C<512> or C<2048> sockets (depending on	4376	runtime libraries. This might get you to about C<512> or C<2048> sockets
3865	windows version and/or the phase of the moon). To get more, you need to	4377	(depending on windows version and/or the phase of the moon). To get more,
3866	wrap all I/O functions and provide your own fd management, but the cost of	4378	you need to wrap all I/O functions and provide your own fd management, but
3867	calling select (O(n²)) will likely make this unworkable.	4379	the cost of calling select (O(n²)) will likely make this unworkable.
3868		4380
3869	=back	4381	=back
3870		4382
3871	=head2 PORTABILITY REQUIREMENTS	4383	=head2 PORTABILITY REQUIREMENTS
3872		4384
…		…
3915	=item C<double> must hold a time value in seconds with enough accuracy	4427	=item C<double> must hold a time value in seconds with enough accuracy
3916		4428
3917	The type C<double> is used to represent timestamps. It is required to	4429	The type C<double> is used to represent timestamps. It is required to
3918	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4430	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3919	enough for at least into the year 4000. This requirement is fulfilled by	4431	enough for at least into the year 4000. This requirement is fulfilled by
3920	implementations implementing IEEE 754 (basically all existing ones).	4432	implementations implementing IEEE 754, which is basically all existing
		4433	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4434	2200.
3921		4435
3922	=back	4436	=back
3923		4437
3924	If you know of other additional requirements drop me a note.	4438	If you know of other additional requirements drop me a note.
3925		4439
…		…
3993	involves iterating over all running async watchers or all signal numbers.	4507	involves iterating over all running async watchers or all signal numbers.
3994		4508
3995	=back	4509	=back
3996		4510
3997		4511
		4512	=head1 GLOSSARY
		4513
		4514	=over 4
		4515
		4516	=item active
		4517
		4518	A watcher is active as long as it has been started (has been attached to
		4519	an event loop) but not yet stopped (disassociated from the event loop).
		4520
		4521	=item application
		4522
		4523	In this document, an application is whatever is using libev.
		4524
		4525	=item callback
		4526
		4527	The address of a function that is called when some event has been
		4528	detected. Callbacks are being passed the event loop, the watcher that
		4529	received the event, and the actual event bitset.
		4530
		4531	=item callback invocation
		4532
		4533	The act of calling the callback associated with a watcher.
		4534
		4535	=item event
		4536
		4537	A change of state of some external event, such as data now being available
		4538	for reading on a file descriptor, time having passed or simply not having
		4539	any other events happening anymore.
		4540
		4541	In libev, events are represented as single bits (such as C<EV_READ> or
		4542	C<EV_TIMEOUT>).
		4543
		4544	=item event library
		4545
		4546	A software package implementing an event model and loop.
		4547
		4548	=item event loop
		4549
		4550	An entity that handles and processes external events and converts them
		4551	into callback invocations.
		4552
		4553	=item event model
		4554
		4555	The model used to describe how an event loop handles and processes
		4556	watchers and events.
		4557
		4558	=item pending
		4559
		4560	A watcher is pending as soon as the corresponding event has been detected,
		4561	and stops being pending as soon as the watcher will be invoked or its
		4562	pending status is explicitly cleared by the application.
		4563
		4564	A watcher can be pending, but not active. Stopping a watcher also clears
		4565	its pending status.
		4566
		4567	=item real time
		4568
		4569	The physical time that is observed. It is apparently strictly monotonic :)
		4570
		4571	=item wall-clock time
		4572
		4573	The time and date as shown on clocks. Unlike real time, it can actually
		4574	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4575	clock.
		4576
		4577	=item watcher
		4578
		4579	A data structure that describes interest in certain events. Watchers need
		4580	to be started (attached to an event loop) before they can receive events.
		4581
		4582	=item watcher invocation
		4583
		4584	The act of calling the callback associated with a watcher.
		4585
		4586	=back
		4587
3998	=head1 AUTHOR	4588	=head1 AUTHOR
3999		4589
4000	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	4590	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
4001		4591

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Comparing libev/ev.pod (file contents): Revision 1.231 by root, Wed Apr 15 19:35:53 2009 UTC vs. Revision 1.272 by root, Tue Nov 24 06:39:28 2009 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.231 by root, Wed Apr 15 19:35:53 2009 UTC vs.
Revision 1.272 by root, Tue Nov 24 06:39:28 2009 UTC