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Revision 1.231 by root, Wed Apr 15 19:35:53 2009 UTC vs.
Revision 1.273 by root, Tue Nov 24 14:46:59 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
…		…
1116	returns its C<revents> bitset (as if its callback was invoked). If the	1235	returns its C<revents> bitset (as if its callback was invoked). If the
1117	watcher isn't pending it does nothing and returns C<0>.	1236	watcher isn't pending it does nothing and returns C<0>.
1118		1237
1119	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1238	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1120	callback to be invoked, which can be accomplished with this function.	1239	callback to be invoked, which can be accomplished with this function.
		1240
		1241	=item ev_feed_event (struct ev_loop , watcher , int revents)
		1242
		1243	Feeds the given event set into the event loop, as if the specified event
		1244	had happened for the specified watcher (which must be a pointer to an
		1245	initialised but not necessarily started event watcher). Obviously you must
		1246	not free the watcher as long as it has pending events.
		1247
		1248	Stopping the watcher, letting libev invoke it, or calling
		1249	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1250	not started in the first place.
		1251
		1252	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1253	functions that do not need a watcher.
1121		1254
1122	=back	1255	=back
1123		1256
1124		1257
1125	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1174	#include <stddef.h>	1307	#include <stddef.h>
1175		1308
1176	static void	1309	static void
1177	t1_cb (EV_P_ ev_timer *w, int revents)	1310	t1_cb (EV_P_ ev_timer *w, int revents)
1178	{	1311	{
1179	struct my_biggy big = (struct my_biggy *	1312	struct my_biggy big = (struct my_biggy *)
1180	(((char *)w) - offsetof (struct my_biggy, t1));	1313	(((char *)w) - offsetof (struct my_biggy, t1));
1181	}	1314	}
1182		1315
1183	static void	1316	static void
1184	t2_cb (EV_P_ ev_timer *w, int revents)	1317	t2_cb (EV_P_ ev_timer *w, int revents)
1185	{	1318	{
1186	struct my_biggy big = (struct my_biggy *	1319	struct my_biggy big = (struct my_biggy *)
1187	(((char *)w) - offsetof (struct my_biggy, t2));	1320	(((char *)w) - offsetof (struct my_biggy, t2));
1188	}	1321	}
		1322
		1323	=head2 WATCHER PRIORITY MODELS
		1324
		1325	Many event loops support I<watcher priorities>, which are usually small
		1326	integers that influence the ordering of event callback invocation
		1327	between watchers in some way, all else being equal.
		1328
		1329	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1330	description for the more technical details such as the actual priority
		1331	range.
		1332
		1333	There are two common ways how these these priorities are being interpreted
		1334	by event loops:
		1335
		1336	In the more common lock-out model, higher priorities "lock out" invocation
		1337	of lower priority watchers, which means as long as higher priority
		1338	watchers receive events, lower priority watchers are not being invoked.
		1339
		1340	The less common only-for-ordering model uses priorities solely to order
		1341	callback invocation within a single event loop iteration: Higher priority
		1342	watchers are invoked before lower priority ones, but they all get invoked
		1343	before polling for new events.
		1344
		1345	Libev uses the second (only-for-ordering) model for all its watchers
		1346	except for idle watchers (which use the lock-out model).
		1347
		1348	The rationale behind this is that implementing the lock-out model for
		1349	watchers is not well supported by most kernel interfaces, and most event
		1350	libraries will just poll for the same events again and again as long as
		1351	their callbacks have not been executed, which is very inefficient in the
		1352	common case of one high-priority watcher locking out a mass of lower
		1353	priority ones.
		1354
		1355	Static (ordering) priorities are most useful when you have two or more
		1356	watchers handling the same resource: a typical usage example is having an
		1357	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1358	timeouts. Under load, data might be received while the program handles
		1359	other jobs, but since timers normally get invoked first, the timeout
		1360	handler will be executed before checking for data. In that case, giving
		1361	the timer a lower priority than the I/O watcher ensures that I/O will be
		1362	handled first even under adverse conditions (which is usually, but not
		1363	always, what you want).
		1364
		1365	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1366	will only be executed when no same or higher priority watchers have
		1367	received events, they can be used to implement the "lock-out" model when
		1368	required.
		1369
		1370	For example, to emulate how many other event libraries handle priorities,
		1371	you can associate an C<ev_idle> watcher to each such watcher, and in
		1372	the normal watcher callback, you just start the idle watcher. The real
		1373	processing is done in the idle watcher callback. This causes libev to
		1374	continously poll and process kernel event data for the watcher, but when
		1375	the lock-out case is known to be rare (which in turn is rare :), this is
		1376	workable.
		1377
		1378	Usually, however, the lock-out model implemented that way will perform
		1379	miserably under the type of load it was designed to handle. In that case,
		1380	it might be preferable to stop the real watcher before starting the
		1381	idle watcher, so the kernel will not have to process the event in case
		1382	the actual processing will be delayed for considerable time.
		1383
		1384	Here is an example of an I/O watcher that should run at a strictly lower
		1385	priority than the default, and which should only process data when no
		1386	other events are pending:
		1387
		1388	ev_idle idle; // actual processing watcher
		1389	ev_io io; // actual event watcher
		1390
		1391	static void
		1392	io_cb (EV_P_ ev_io *w, int revents)
		1393	{
		1394	// stop the I/O watcher, we received the event, but
		1395	// are not yet ready to handle it.
		1396	ev_io_stop (EV_A_ w);
		1397
		1398	// start the idle watcher to ahndle the actual event.
		1399	// it will not be executed as long as other watchers
		1400	// with the default priority are receiving events.
		1401	ev_idle_start (EV_A_ &idle);
		1402	}
		1403
		1404	static void
		1405	idle_cb (EV_P_ ev_idle *w, int revents)
		1406	{
		1407	// actual processing
		1408	read (STDIN_FILENO, ...);
		1409
		1410	// have to start the I/O watcher again, as
		1411	// we have handled the event
		1412	ev_io_start (EV_P_ &io);
		1413	}
		1414
		1415	// initialisation
		1416	ev_idle_init (&idle, idle_cb);
		1417	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1418	ev_io_start (EV_DEFAULT_ &io);
		1419
		1420	In the "real" world, it might also be beneficial to start a timer, so that
		1421	low-priority connections can not be locked out forever under load. This
		1422	enables your program to keep a lower latency for important connections
		1423	during short periods of high load, while not completely locking out less
		1424	important ones.
1189		1425
1190		1426
1191	=head1 WATCHER TYPES	1427	=head1 WATCHER TYPES
1192		1428
1193	This section describes each watcher in detail, but will not repeat	1429	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	1455	descriptors to non-blocking mode is also usually a good idea (but not
1220	required if you know what you are doing).	1456	required if you know what you are doing).
1221		1457
1222	If you cannot use non-blocking mode, then force the use of a	1458	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	1459	known-to-be-good backend (at the time of this writing, this includes only
1224	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1460	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1461	descriptors for which non-blocking operation makes no sense (such as
		1462	files) - libev doesn't guarentee any specific behaviour in that case.
1225		1463
1226	Another thing you have to watch out for is that it is quite easy to	1464	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	1465	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	1466	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	1467	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	1588	year, it will still time out after (roughly) one hour. "Roughly" because
1351	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1589	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1352	monotonic clock option helps a lot here).	1590	monotonic clock option helps a lot here).
1353		1591
1354	The callback is guaranteed to be invoked only I<after> its timeout has	1592	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	1593	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	1594	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	1595	same loop iteration then the ones with earlier time-out values are invoked
1358	C<ev_loop> recursively).	1596	before ones of the same priority with later time-out values (but this is
		1597	no longer true when a callback calls C<ev_loop> recursively).
1359		1598
1360	=head3 Be smart about timeouts	1599	=head3 Be smart about timeouts
1361		1600
1362	Many real-world problems involve some kind of timeout, usually for error	1601	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,	1602	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>	1646	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1408	member and C<ev_timer_again>.	1647	member and C<ev_timer_again>.
1409		1648
1410	At start:	1649	At start:
1411		1650
1412	ev_timer_init (timer, callback);	1651	ev_init (timer, callback);
1413	timer->repeat = 60.;	1652	timer->repeat = 60.;
1414	ev_timer_again (loop, timer);	1653	ev_timer_again (loop, timer);
1415		1654
1416	Each time there is some activity:	1655	Each time there is some activity:
1417		1656
…		…
1479		1718
1480	To start the timer, simply initialise the watcher and set C<last_activity>	1719	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	1720	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:	1721	callback, which will "do the right thing" and start the timer:
1483		1722
1484	ev_timer_init (timer, callback);	1723	ev_init (timer, callback);
1485	last_activity = ev_now (loop);	1724	last_activity = ev_now (loop);
1486	callback (loop, timer, EV_TIMEOUT);	1725	callback (loop, timer, EV_TIMEOUT);
1487		1726
1488	And when there is some activity, simply store the current time in	1727	And when there is some activity, simply store the current time in
1489	C<last_activity>, no libev calls at all:	1728	C<last_activity>, no libev calls at all:
…		…
1550		1789
1551	If the event loop is suspended for a long time, you can also force an	1790	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	1791	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1553	()>.	1792	()>.
1554		1793
		1794	=head3 The special problems of suspended animation
		1795
		1796	When you leave the server world it is quite customary to hit machines that
		1797	can suspend/hibernate - what happens to the clocks during such a suspend?
		1798
		1799	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1800	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1801	to run until the system is suspended, but they will not advance while the
		1802	system is suspended. That means, on resume, it will be as if the program
		1803	was frozen for a few seconds, but the suspend time will not be counted
		1804	towards C<ev_timer> when a monotonic clock source is used. The real time
		1805	clock advanced as expected, but if it is used as sole clocksource, then a
		1806	long suspend would be detected as a time jump by libev, and timers would
		1807	be adjusted accordingly.
		1808
		1809	I would not be surprised to see different behaviour in different between
		1810	operating systems, OS versions or even different hardware.
		1811
		1812	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1813	time jump in the monotonic clocks and the realtime clock. If the program
		1814	is suspended for a very long time, and monotonic clock sources are in use,
		1815	then you can expect C<ev_timer>s to expire as the full suspension time
		1816	will be counted towards the timers. When no monotonic clock source is in
		1817	use, then libev will again assume a timejump and adjust accordingly.
		1818
		1819	It might be beneficial for this latter case to call C<ev_suspend>
		1820	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1821	deterministic behaviour in this case (you can do nothing against
		1822	C<SIGSTOP>).
		1823
1555	=head3 Watcher-Specific Functions and Data Members	1824	=head3 Watcher-Specific Functions and Data Members
1556		1825
1557	=over 4	1826	=over 4
1558		1827
1559	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1828	=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).	1851	If the timer is started but non-repeating, stop it (as if it timed out).
1583		1852
1584	If the timer is repeating, either start it if necessary (with the	1853	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.	1854	C<repeat> value), or reset the running timer to the C<repeat> value.
1586		1855
1587	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1856	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1588	usage example.	1857	usage example.
		1858
		1859	=item ev_timer_remaining (loop, ev_timer *)
		1860
		1861	Returns the remaining time until a timer fires. If the timer is active,
		1862	then this time is relative to the current event loop time, otherwise it's
		1863	the timeout value currently configured.
		1864
		1865	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1866	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1867	will return C<4>. When the timer expires and is restarted, it will return
		1868	roughly C<7> (likely slightly less as callback invocation takes some time,
		1869	too), and so on.
1589		1870
1590	=item ev_tstamp repeat [read-write]	1871	=item ev_tstamp repeat [read-write]
1591		1872
1592	The current C<repeat> value. Will be used each time the watcher times out	1873	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),	1874	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	2110	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	2111	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	2112	will try it's best to deliver signals synchronously, i.e. as part of the
1832	normal event processing, like any other event.	2113	normal event processing, like any other event.
1833		2114
1834	If you want signals asynchronously, just use C<sigaction> as you would	2115	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	2116	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.	2117	the signal. You can even use C<ev_async> from a signal handler to
		2118	synchronously wake up an event loop.
1837		2119
1838	You can configure as many watchers as you like per signal. Only when the	2120	You can configure as many watchers as you like for the same signal, but
		2121	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2122	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2123	C<SIGINT> in both the default loop and another loop at the same time. At
		2124	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2125
1839	first watcher gets started will libev actually register a signal handler	2126	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	2127	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	2128	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		2129
1845	If possible and supported, libev will install its handlers with	2130	If possible and supported, libev will install its handlers with
1846	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2131	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1847	interrupted. If you have a problem with system calls getting interrupted by	2132	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	2133	interrupted by signals you can block all signals in an C<ev_check> watcher
1849	them in an C<ev_prepare> watcher.	2134	and unblock them in an C<ev_prepare> watcher.
		2135
		2136	=head3 The special problem of inheritance over execve
		2137
		2138	Both the signal mask (C<sigprocmask>) and the signal disposition
		2139	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2140	stopping it again), that is, libev might or might not block the signal,
		2141	and might or might not set or restore the installed signal handler.
		2142
		2143	While this does not matter for the signal disposition (libev never
		2144	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2145	C<execve>), this matters for the signal mask: many programs do not expect
		2146	certain signals to be blocked.
		2147
		2148	This means that before calling C<exec> (from the child) you should reset
		2149	the signal mask to whatever "default" you expect (all clear is a good
		2150	choice usually).
		2151
		2152	The simplest way to ensure that the signal mask is reset in the child is
		2153	to install a fork handler with C<pthread_atfork> that resets it. That will
		2154	catch fork calls done by libraries (such as the libc) as well.
		2155
		2156	In current versions of libev, you can also ensure that the signal mask is
		2157	not blocking any signals (except temporarily, so thread users watch out)
		2158	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2159	is not guaranteed for future versions, however.
1850		2160
1851	=head3 Watcher-Specific Functions and Data Members	2161	=head3 Watcher-Specific Functions and Data Members
1852		2162
1853	=over 4	2163	=over 4
1854		2164
…		…
1886	some child status changes (most typically when a child of yours dies or	2196	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	2197	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	2198	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.,	2199	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,	2200	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	2201	but forking and registering a watcher a few event loop iterations later or
1892	not.	2202	in the next callback invocation is not.
1893		2203
1894	Only the default event loop is capable of handling signals, and therefore	2204	Only the default event loop is capable of handling signals, and therefore
1895	you can only register child watchers in the default event loop.	2205	you can only register child watchers in the default event loop.
1896		2206
		2207	Due to some design glitches inside libev, child watchers will always be
		2208	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2209	libev)
		2210
1897	=head3 Process Interaction	2211	=head3 Process Interaction
1898		2212
1899	Libev grabs C<SIGCHLD> as soon as the default event loop is	2213	Libev grabs C<SIGCHLD> as soon as the default event loop is
1900	initialised. This is necessary to guarantee proper behaviour even if	2214	initialised. This is necessary to guarantee proper behaviour even if the
1901	the first child watcher is started after the child exits. The occurrence	2215	first child watcher is started after the child exits. The occurrence
1902	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2216	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1903	synchronously as part of the event loop processing. Libev always reaps all	2217	synchronously as part of the event loop processing. Libev always reaps all
1904	children, even ones not watched.	2218	children, even ones not watched.
1905		2219
1906	=head3 Overriding the Built-In Processing	2220	=head3 Overriding the Built-In Processing
…		…
1916	=head3 Stopping the Child Watcher	2230	=head3 Stopping the Child Watcher
1917		2231
1918	Currently, the child watcher never gets stopped, even when the	2232	Currently, the child watcher never gets stopped, even when the
1919	child terminates, so normally one needs to stop the watcher in the	2233	child terminates, so normally one needs to stop the watcher in the
1920	callback. Future versions of libev might stop the watcher automatically	2234	callback. Future versions of libev might stop the watcher automatically
1921	when a child exit is detected.	2235	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2236	problem).
1922		2237
1923	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
1924		2239
1925	=over 4	2240	=over 4
1926		2241
…		…
2252	// no longer anything immediate to do.	2567	// no longer anything immediate to do.
2253	}	2568	}
2254		2569
2255	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2570	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2256	ev_idle_init (idle_watcher, idle_cb);	2571	ev_idle_init (idle_watcher, idle_cb);
2257	ev_idle_start (loop, idle_cb);	2572	ev_idle_start (loop, idle_watcher);
2258		2573
2259		2574
2260	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2575	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2261		2576
2262	Prepare and check watchers are usually (but not always) used in pairs:	2577	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2355	struct pollfd fds [nfd];	2670	struct pollfd fds [nfd];
2356	// actual code will need to loop here and realloc etc.	2671	// actual code will need to loop here and realloc etc.
2357	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2672	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2358		2673
2359	/* the callback is illegal, but won't be called as we stop during check */	2674	/* the callback is illegal, but won't be called as we stop during check */
2360	ev_timer_init (&tw, 0, timeout * 1e-3);	2675	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2361	ev_timer_start (loop, &tw);	2676	ev_timer_start (loop, &tw);
2362		2677
2363	// create one ev_io per pollfd	2678	// create one ev_io per pollfd
2364	for (int i = 0; i < nfd; ++i)	2679	for (int i = 0; i < nfd; ++i)
2365	{	2680	{
…		…
2595	event loop blocks next and before C<ev_check> watchers are being called,	2910	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	2911	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	2912	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2598	handlers will be invoked, too, of course.	2913	handlers will be invoked, too, of course.
2599		2914
		2915	=head3 The special problem of life after fork - how is it possible?
		2916
		2917	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2918	up/change the process environment, followed by a call to C<exec()>. This
		2919	sequence should be handled by libev without any problems.
		2920
		2921	This changes when the application actually wants to do event handling
		2922	in the child, or both parent in child, in effect "continuing" after the
		2923	fork.
		2924
		2925	The default mode of operation (for libev, with application help to detect
		2926	forks) is to duplicate all the state in the child, as would be expected
		2927	when I<either> the parent I<or> the child process continues.
		2928
		2929	When both processes want to continue using libev, then this is usually the
		2930	wrong result. In that case, usually one process (typically the parent) is
		2931	supposed to continue with all watchers in place as before, while the other
		2932	process typically wants to start fresh, i.e. without any active watchers.
		2933
		2934	The cleanest and most efficient way to achieve that with libev is to
		2935	simply create a new event loop, which of course will be "empty", and
		2936	use that for new watchers. This has the advantage of not touching more
		2937	memory than necessary, and thus avoiding the copy-on-write, and the
		2938	disadvantage of having to use multiple event loops (which do not support
		2939	signal watchers).
		2940
		2941	When this is not possible, or you want to use the default loop for
		2942	other reasons, then in the process that wants to start "fresh", call
		2943	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2944	the default loop will "orphan" (not stop) all registered watchers, so you
		2945	have to be careful not to execute code that modifies those watchers. Note
		2946	also that in that case, you have to re-register any signal watchers.
		2947
2600	=head3 Watcher-Specific Functions and Data Members	2948	=head3 Watcher-Specific Functions and Data Members
2601		2949
2602	=over 4	2950	=over 4
2603		2951
2604	=item ev_fork_init (ev_signal *, callback)	2952	=item ev_fork_init (ev_signal *, callback)
…		…
2800	else if (revents & EV_TIMEOUT)	3148	else if (revents & EV_TIMEOUT)
2801	/* doh, nothing entered */;	3149	/* doh, nothing entered */;
2802	}	3150	}
2803		3151
2804	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3152	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2805
2806	=item ev_feed_event (struct ev_loop , watcher , int revents)
2807
2808	Feeds the given event set into the event loop, as if the specified event
2809	had happened for the specified watcher (which must be a pointer to an
2810	initialised but not necessarily started event watcher).
2811		3153
2812	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3154	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2813		3155
2814	Feed an event on the given fd, as if a file descriptor backend detected	3156	Feed an event on the given fd, as if a file descriptor backend detected
2815	the given events it.	3157	the given events it.
…		…
3096	=item Ocaml	3438	=item Ocaml
3097		3439
3098	Erkki Seppala has written Ocaml bindings for libev, to be found at	3440	Erkki Seppala has written Ocaml bindings for libev, to be found at
3099	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3441	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3100		3442
		3443	=item Lua
		3444
		3445	Brian Maher has written a partial interface to libev
		3446	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3447	L<http://github.com/brimworks/lua-ev>.
		3448
3101	=back	3449	=back
3102		3450
3103		3451
3104	=head1 MACRO MAGIC	3452	=head1 MACRO MAGIC
3105		3453
…		…
3271	keeps libev from including F<config.h>, and it also defines dummy	3619	keeps libev from including F<config.h>, and it also defines dummy
3272	implementations for some libevent functions (such as logging, which is not	3620	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	3621	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.	3622	F<event.h> that are not directly supported by the libev core alone.
3275		3623
3276	In stanbdalone mode, libev will still try to automatically deduce the	3624	In standalone mode, libev will still try to automatically deduce the
3277	configuration, but has to be more conservative.	3625	configuration, but has to be more conservative.
3278		3626
3279	=item EV_USE_MONOTONIC	3627	=item EV_USE_MONOTONIC
3280		3628
3281	If defined to be C<1>, libev will try to detect the availability of the	3629	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	3694	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,	3695	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	3696	it is assumed that all these functions actually work on fds, even
3349	on win32. Should not be defined on non-win32 platforms.	3697	on win32. Should not be defined on non-win32 platforms.
3350		3698
3351	=item EV_FD_TO_WIN32_HANDLE	3699	=item EV_FD_TO_WIN32_HANDLE(fd)
3352		3700
3353	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3701	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	3702	file descriptors to socket handles. When not defining this symbol (the
3355	default), then libev will call C<_get_osfhandle>, which is usually	3703	default), then libev will call C<_get_osfhandle>, which is usually
3356	correct. In some cases, programs use their own file descriptor management,	3704	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.	3705	in which case they can provide this function to map fds to socket handles.
		3706
		3707	=item EV_WIN32_HANDLE_TO_FD(handle)
		3708
		3709	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3710	using the standard C<_open_osfhandle> function. For programs implementing
		3711	their own fd to handle mapping, overwriting this function makes it easier
		3712	to do so. This can be done by defining this macro to an appropriate value.
		3713
		3714	=item EV_WIN32_CLOSE_FD(fd)
		3715
		3716	If programs implement their own fd to handle mapping on win32, then this
		3717	macro can be used to override the C<close> function, useful to unregister
		3718	file descriptors again. Note that the replacement function has to close
		3719	the underlying OS handle.
3358		3720
3359	=item EV_USE_POLL	3721	=item EV_USE_POLL
3360		3722
3361	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3723	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	3724	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3494	defined to be C<0>, then they are not.	3856	defined to be C<0>, then they are not.
3495		3857
3496	=item EV_MINIMAL	3858	=item EV_MINIMAL
3497		3859
3498	If you need to shave off some kilobytes of code at the expense of some	3860	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	3861	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	3862	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.	3863	on amd64. It also selects a much smaller 2-heap for timer management over
		3864	the default 4-heap.
		3865
		3866	You can save even more by disabling watcher types you do not need
		3867	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3868	(C<-DNDEBUG>) will usually reduce code size a lot.
		3869
		3870	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3871	provide a bare-bones event library. See C<ev.h> for details on what parts
		3872	of the API are still available, and do not complain if this subset changes
		3873	over time.
		3874
		3875	=item EV_NSIG
		3876
		3877	The highest supported signal number, +1 (or, the number of
		3878	signals): Normally, libev tries to deduce the maximum number of signals
		3879	automatically, but sometimes this fails, in which case it can be
		3880	specified. Also, using a lower number than detected (C<32> should be
		3881	good for about any system in existance) can save some memory, as libev
		3882	statically allocates some 12-24 bytes per signal number.
3502		3883
3503	=item EV_PID_HASHSIZE	3884	=item EV_PID_HASHSIZE
3504		3885
3505	C<ev_child> watchers use a small hash table to distribute workload by	3886	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	3887	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	4073	default loop and triggering an C<ev_async> watcher from the default loop
3693	watcher callback into the event loop interested in the signal.	4074	watcher callback into the event loop interested in the signal.
3694		4075
3695	=back	4076	=back
3696		4077
		4078	=head4 THREAD LOCKING EXAMPLE
		4079
		4080	Here is a fictitious example of how to run an event loop in a different
		4081	thread than where callbacks are being invoked and watchers are
		4082	created/added/removed.
		4083
		4084	For a real-world example, see the C<EV::Loop::Async> perl module,
		4085	which uses exactly this technique (which is suited for many high-level
		4086	languages).
		4087
		4088	The example uses a pthread mutex to protect the loop data, a condition
		4089	variable to wait for callback invocations, an async watcher to notify the
		4090	event loop thread and an unspecified mechanism to wake up the main thread.
		4091
		4092	First, you need to associate some data with the event loop:
		4093
		4094	typedef struct {
		4095	mutex_t lock; /* global loop lock */
		4096	ev_async async_w;
		4097	thread_t tid;
		4098	cond_t invoke_cv;
		4099	} userdata;
		4100
		4101	void prepare_loop (EV_P)
		4102	{
		4103	// for simplicity, we use a static userdata struct.
		4104	static userdata u;
		4105
		4106	ev_async_init (&u->async_w, async_cb);
		4107	ev_async_start (EV_A_ &u->async_w);
		4108
		4109	pthread_mutex_init (&u->lock, 0);
		4110	pthread_cond_init (&u->invoke_cv, 0);
		4111
		4112	// now associate this with the loop
		4113	ev_set_userdata (EV_A_ u);
		4114	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4115	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4116
		4117	// then create the thread running ev_loop
		4118	pthread_create (&u->tid, 0, l_run, EV_A);
		4119	}
		4120
		4121	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4122	solely to wake up the event loop so it takes notice of any new watchers
		4123	that might have been added:
		4124
		4125	static void
		4126	async_cb (EV_P_ ev_async *w, int revents)
		4127	{
		4128	// just used for the side effects
		4129	}
		4130
		4131	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4132	protecting the loop data, respectively.
		4133
		4134	static void
		4135	l_release (EV_P)
		4136	{
		4137	userdata *u = ev_userdata (EV_A);
		4138	pthread_mutex_unlock (&u->lock);
		4139	}
		4140
		4141	static void
		4142	l_acquire (EV_P)
		4143	{
		4144	userdata *u = ev_userdata (EV_A);
		4145	pthread_mutex_lock (&u->lock);
		4146	}
		4147
		4148	The event loop thread first acquires the mutex, and then jumps straight
		4149	into C<ev_loop>:
		4150
		4151	void *
		4152	l_run (void *thr_arg)
		4153	{
		4154	struct ev_loop loop = (struct ev_loop )thr_arg;
		4155
		4156	l_acquire (EV_A);
		4157	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4158	ev_loop (EV_A_ 0);
		4159	l_release (EV_A);
		4160
		4161	return 0;
		4162	}
		4163
		4164	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4165	signal the main thread via some unspecified mechanism (signals? pipe
		4166	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4167	have been called (in a while loop because a) spurious wakeups are possible
		4168	and b) skipping inter-thread-communication when there are no pending
		4169	watchers is very beneficial):
		4170
		4171	static void
		4172	l_invoke (EV_P)
		4173	{
		4174	userdata *u = ev_userdata (EV_A);
		4175
		4176	while (ev_pending_count (EV_A))
		4177	{
		4178	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4179	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4180	}
		4181	}
		4182
		4183	Now, whenever the main thread gets told to invoke pending watchers, it
		4184	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4185	thread to continue:
		4186
		4187	static void
		4188	real_invoke_pending (EV_P)
		4189	{
		4190	userdata *u = ev_userdata (EV_A);
		4191
		4192	pthread_mutex_lock (&u->lock);
		4193	ev_invoke_pending (EV_A);
		4194	pthread_cond_signal (&u->invoke_cv);
		4195	pthread_mutex_unlock (&u->lock);
		4196	}
		4197
		4198	Whenever you want to start/stop a watcher or do other modifications to an
		4199	event loop, you will now have to lock:
		4200
		4201	ev_timer timeout_watcher;
		4202	userdata *u = ev_userdata (EV_A);
		4203
		4204	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4205
		4206	pthread_mutex_lock (&u->lock);
		4207	ev_timer_start (EV_A_ &timeout_watcher);
		4208	ev_async_send (EV_A_ &u->async_w);
		4209	pthread_mutex_unlock (&u->lock);
		4210
		4211	Note that sending the C<ev_async> watcher is required because otherwise
		4212	an event loop currently blocking in the kernel will have no knowledge
		4213	about the newly added timer. By waking up the loop it will pick up any new
		4214	watchers in the next event loop iteration.
		4215
3697	=head3 COROUTINES	4216	=head3 COROUTINES
3698		4217
3699	Libev is very accommodating to coroutines ("cooperative threads"):	4218	Libev is very accommodating to coroutines ("cooperative threads"):
3700	libev fully supports nesting calls to its functions from different	4219	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	4220	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	4221	different coroutines, and switch freely between both coroutines running
3703	loop, as long as you don't confuse yourself). The only exception is that	4222	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.	4223	that you must not do this from C<ev_periodic> reschedule callbacks.
3705		4224
3706	Care has been taken to ensure that libev does not keep local state inside	4225	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	4226	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3708	they do not call any callbacks.	4227	they do not call any callbacks.
3709		4228
…		…
3786	way (note also that glib is the slowest event library known to man).	4305	way (note also that glib is the slowest event library known to man).
3787		4306
3788	There is no supported compilation method available on windows except	4307	There is no supported compilation method available on windows except
3789	embedding it into other applications.	4308	embedding it into other applications.
3790		4309
		4310	Sensible signal handling is officially unsupported by Microsoft - libev
		4311	tries its best, but under most conditions, signals will simply not work.
		4312
3791	Not a libev limitation but worth mentioning: windows apparently doesn't	4313	Not a libev limitation but worth mentioning: windows apparently doesn't
3792	accept large writes: instead of resulting in a partial write, windows will	4314	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,	4315	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	4316	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	4317	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3799	the abysmal performance of winsockets, using a large number of sockets	4321	the abysmal performance of winsockets, using a large number of sockets
3800	is not recommended (and not reasonable). If your program needs to use	4322	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	4323	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	4324	different implementation for windows, as libev offers the POSIX readiness
3803	notification model, which cannot be implemented efficiently on windows	4325	notification model, which cannot be implemented efficiently on windows
3804	(Microsoft monopoly games).	4326	(due to Microsoft monopoly games).
3805		4327
3806	A typical way to use libev under windows is to embed it (see the embedding	4328	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	4329	section for details) and use the following F<evwrap.h> header file instead
3808	of F<ev.h>:	4330	of F<ev.h>:
3809		4331
…		…
3845		4367
3846	Early versions of winsocket's select only supported waiting for a maximum	4368	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	4369	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	4370	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	4371	recommends spawning a chain of threads and wait for 63 handles and the
3850	previous thread in each. Great).	4372	previous thread in each. Sounds great!).
3851		4373
3852	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4374	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	4375	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	4376	call (which might be in libev or elsewhere, for example, perl and many
3855	select emulation on windows).	4377	other interpreters do their own select emulation on windows).
3856		4378
3857	Another limit is the number of file descriptors in the Microsoft runtime	4379	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	4380	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	4381	fetish or something like this inside Microsoft). You can increase this
3860	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4382	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	4383	(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	4384	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	4385	(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	4386	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.	4387	the cost of calling select (O(n²)) will likely make this unworkable.
3868		4388
3869	=back	4389	=back
3870		4390
3871	=head2 PORTABILITY REQUIREMENTS	4391	=head2 PORTABILITY REQUIREMENTS
3872		4392
…		…
3915	=item C<double> must hold a time value in seconds with enough accuracy	4435	=item C<double> must hold a time value in seconds with enough accuracy
3916		4436
3917	The type C<double> is used to represent timestamps. It is required to	4437	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	4438	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	4439	enough for at least into the year 4000. This requirement is fulfilled by
3920	implementations implementing IEEE 754 (basically all existing ones).	4440	implementations implementing IEEE 754, which is basically all existing
		4441	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4442	2200.
3921		4443
3922	=back	4444	=back
3923		4445
3924	If you know of other additional requirements drop me a note.	4446	If you know of other additional requirements drop me a note.
3925		4447
…		…
3993	involves iterating over all running async watchers or all signal numbers.	4515	involves iterating over all running async watchers or all signal numbers.
3994		4516
3995	=back	4517	=back
3996		4518
3997		4519
		4520	=head1 GLOSSARY
		4521
		4522	=over 4
		4523
		4524	=item active
		4525
		4526	A watcher is active as long as it has been started (has been attached to
		4527	an event loop) but not yet stopped (disassociated from the event loop).
		4528
		4529	=item application
		4530
		4531	In this document, an application is whatever is using libev.
		4532
		4533	=item callback
		4534
		4535	The address of a function that is called when some event has been
		4536	detected. Callbacks are being passed the event loop, the watcher that
		4537	received the event, and the actual event bitset.
		4538
		4539	=item callback invocation
		4540
		4541	The act of calling the callback associated with a watcher.
		4542
		4543	=item event
		4544
		4545	A change of state of some external event, such as data now being available
		4546	for reading on a file descriptor, time having passed or simply not having
		4547	any other events happening anymore.
		4548
		4549	In libev, events are represented as single bits (such as C<EV_READ> or
		4550	C<EV_TIMEOUT>).
		4551
		4552	=item event library
		4553
		4554	A software package implementing an event model and loop.
		4555
		4556	=item event loop
		4557
		4558	An entity that handles and processes external events and converts them
		4559	into callback invocations.
		4560
		4561	=item event model
		4562
		4563	The model used to describe how an event loop handles and processes
		4564	watchers and events.
		4565
		4566	=item pending
		4567
		4568	A watcher is pending as soon as the corresponding event has been detected,
		4569	and stops being pending as soon as the watcher will be invoked or its
		4570	pending status is explicitly cleared by the application.
		4571
		4572	A watcher can be pending, but not active. Stopping a watcher also clears
		4573	its pending status.
		4574
		4575	=item real time
		4576
		4577	The physical time that is observed. It is apparently strictly monotonic :)
		4578
		4579	=item wall-clock time
		4580
		4581	The time and date as shown on clocks. Unlike real time, it can actually
		4582	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4583	clock.
		4584
		4585	=item watcher
		4586
		4587	A data structure that describes interest in certain events. Watchers need
		4588	to be started (attached to an event loop) before they can receive events.
		4589
		4590	=item watcher invocation
		4591
		4592	The act of calling the callback associated with a watcher.
		4593
		4594	=back
		4595
3998	=head1 AUTHOR	4596	=head1 AUTHOR
3999		4597
4000	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	4598	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
4001		4599

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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 1.273 by root, Tue Nov 24 14:46:59 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 1.273 by root, Tue Nov 24 14:46:59 2009 UTC