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Comparing libev/ev.pod (file contents):
Revision 1.232 by root, Thu Apr 16 06:17:26 2009 UTC vs.
Revision 1.259 by root, Sun Jul 19 01:36:34 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
…		…
110	name C<loop> (which is always of type C<ev_loop *>) will not have	122	name C<loop> (which is always of type C<ev_loop *>) will not have
111	this argument.	123	this argument.
112		124
113	=head2 TIME REPRESENTATION	125	=head2 TIME REPRESENTATION
114		126
115	Libev represents time as a single floating point number, representing the	127	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	128	the (fractional) number of seconds since the (POSIX) epoch (somewhere
117	the beginning of 1970, details are complicated, don't ask). This type is	129	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	130	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	131	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	132	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	133	component C<stamp> might indicate, it is also used for time differences
122	throughout libev.	134	throughout libev.
123		135
124	=head1 ERROR HANDLING	136	=head1 ERROR HANDLING
125		137
…		…
609		621
610	This value can sometimes be useful as a generation counter of sorts (it	622	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	623	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	624	C<ev_prepare> and C<ev_check> calls.
613		625
		626	=item unsigned int ev_loop_depth (loop)
		627
		628	Returns the number of times C<ev_loop> was entered minus the number of
		629	times C<ev_loop> was exited, in other words, the recursion depth.
		630
		631	Outside C<ev_loop>, this number is zero. In a callback, this number is
		632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		633	in which case it is higher.
		634
		635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		636	etc.), doesn't count as exit.
		637
614	=item unsigned int ev_backend (loop)	638	=item unsigned int ev_backend (loop)
615		639
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	641	use.
618		642
…		…
632		656
633	This function is rarely useful, but when some event callback runs for a	657	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	658	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	659	the current time is a good idea.
636		660
637	See also "The special problem of time updates" in the C<ev_timer> section.	661	See also L<The special problem of time updates> in the C<ev_timer> section.
638		662
639	=item ev_suspend (loop)	663	=item ev_suspend (loop)
640		664
641	=item ev_resume (loop)	665	=item ev_resume (loop)
642		666
…		…
799		823
800	By setting a higher I<io collect interval> you allow libev to spend more	824	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,	825	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	826	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	827	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.	828	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		829	sleep time ensures that libev will not poll for I/O events more often then
		830	once per this interval, on average.
805		831
806	Likewise, by setting a higher I<timeout collect interval> you allow libev	832	Likewise, by setting a higher I<timeout collect interval> you allow libev
807	to spend more time collecting timeouts, at the expense of increased	833	to spend more time collecting timeouts, at the expense of increased
808	latency/jitter/inexactness (the watcher callback will be called	834	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	835	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
811		837
812	Many (busy) programs can usually benefit by setting the I/O collect	838	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	839	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	840	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>,	841	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.	842	as this approaches the timing granularity of most systems. Note that if
		843	you do transactions with the outside world and you can't increase the
		844	parallelity, then this setting will limit your transaction rate (if you
		845	need to poll once per transaction and the I/O collect interval is 0.01,
		846	then you can't do more than 100 transations per second).
817		847
818	Setting the I<timeout collect interval> can improve the opportunity for	848	Setting the I<timeout collect interval> can improve the opportunity for
819	saving power, as the program will "bundle" timer callback invocations that	849	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	850	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	851	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	852	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
823	they fire on, say, one-second boundaries only.	853	they fire on, say, one-second boundaries only.
		854
		855	Example: we only need 0.1s timeout granularity, and we wish not to poll
		856	more often than 100 times per second:
		857
		858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		860
		861	=item ev_invoke_pending (loop)
		862
		863	This call will simply invoke all pending watchers while resetting their
		864	pending state. Normally, C<ev_loop> does this automatically when required,
		865	but when overriding the invoke callback this call comes handy.
		866
		867	=item int ev_pending_count (loop)
		868
		869	Returns the number of pending watchers - zero indicates that no watchers
		870	are pending.
		871
		872	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		873
		874	This overrides the invoke pending functionality of the loop: Instead of
		875	invoking all pending watchers when there are any, C<ev_loop> will call
		876	this callback instead. This is useful, for example, when you want to
		877	invoke the actual watchers inside another context (another thread etc.).
		878
		879	If you want to reset the callback, use C<ev_invoke_pending> as new
		880	callback.
		881
		882	=item ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))
		883
		884	Sometimes you want to share the same loop between multiple threads. This
		885	can be done relatively simply by putting mutex_lock/unlock calls around
		886	each call to a libev function.
		887
		888	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		889	wait for it to return. One way around this is to wake up the loop via
		890	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		891	and I<acquire> callbacks on the loop.
		892
		893	When set, then C<release> will be called just before the thread is
		894	suspended waiting for new events, and C<acquire> is called just
		895	afterwards.
		896
		897	Ideally, C<release> will just call your mutex_unlock function, and
		898	C<acquire> will just call the mutex_lock function again.
		899
		900	While event loop modifications are allowed between invocations of
		901	C<release> and C<acquire> (that's their only purpose after all), no
		902	modifications done will affect the event loop, i.e. adding watchers will
		903	have no effect on the set of file descriptors being watched, or the time
		904	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		905	to take note of any changes you made.
		906
		907	In theory, threads executing C<ev_loop> will be async-cancel safe between
		908	invocations of C<release> and C<acquire>.
		909
		910	See also the locking example in the C<THREADS> section later in this
		911	document.
		912
		913	=item ev_set_userdata (loop, void *data)
		914
		915	=item ev_userdata (loop)
		916
		917	Set and retrieve a single C<void *> associated with a loop. When
		918	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		919	C<0.>
		920
		921	These two functions can be used to associate arbitrary data with a loop,
		922	and are intended solely for the C<invoke_pending_cb>, C<release> and
		923	C<acquire> callbacks described above, but of course can be (ab-)used for
		924	any other purpose as well.
824		925
825	=item ev_loop_verify (loop)	926	=item ev_loop_verify (loop)
826		927
827	This function only does something when C<EV_VERIFY> support has been	928	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	929	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>	1184	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1084	(default: C<-2>). Pending watchers with higher priority will be invoked	1185	(default: C<-2>). Pending watchers with higher priority will be invoked
1085	before watchers with lower priority, but priority will not keep watchers	1186	before watchers with lower priority, but priority will not keep watchers
1086	from being executed (except for C<ev_idle> watchers).	1187	from being executed (except for C<ev_idle> watchers).
1087		1188
1088	See L<
1089
1090	This means that priorities are I<only> used for ordering callback
1091	invocation after new events have been received. This is useful, for
1092	example, to reduce latency after idling, or more often, to bind two
1093	watchers on the same event and make sure one is called first.
1094
1095	If you need to suppress invocation when higher priority events are pending	1189	If you need to suppress invocation when higher priority events are pending
1096	you need to look at C<ev_idle> watchers, which provide this functionality.	1190	you need to look at C<ev_idle> watchers, which provide this functionality.
1097		1191
1098	You I<must not> change the priority of a watcher as long as it is active or	1192	You I<must not> change the priority of a watcher as long as it is active or
1099	pending.	1193	pending.
1100
1101	The default priority used by watchers when no priority has been set is
1102	always C<0>, which is supposed to not be too high and not be too low :).
1103		1194
1104	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1195	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1105	fine, as long as you do not mind that the priority value you query might	1196	fine, as long as you do not mind that the priority value you query might
1106	or might not have been clamped to the valid range.	1197	or might not have been clamped to the valid range.
		1198
		1199	The default priority used by watchers when no priority has been set is
		1200	always C<0>, which is supposed to not be too high and not be too low :).
		1201
		1202	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1203	priorities.
1107		1204
1108	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1205	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1109		1206
1110	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1207	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1111	C<loop> nor C<revents> need to be valid as long as the watcher callback	1208	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1176	#include <stddef.h>	1273	#include <stddef.h>
1177		1274
1178	static void	1275	static void
1179	t1_cb (EV_P_ ev_timer *w, int revents)	1276	t1_cb (EV_P_ ev_timer *w, int revents)
1180	{	1277	{
1181	struct my_biggy big = (struct my_biggy *	1278	struct my_biggy big = (struct my_biggy *)
1182	(((char *)w) - offsetof (struct my_biggy, t1));	1279	(((char *)w) - offsetof (struct my_biggy, t1));
1183	}	1280	}
1184		1281
1185	static void	1282	static void
1186	t2_cb (EV_P_ ev_timer *w, int revents)	1283	t2_cb (EV_P_ ev_timer *w, int revents)
1187	{	1284	{
1188	struct my_biggy big = (struct my_biggy *	1285	struct my_biggy big = (struct my_biggy *)
1189	(((char *)w) - offsetof (struct my_biggy, t2));	1286	(((char *)w) - offsetof (struct my_biggy, t2));
1190	}	1287	}
		1288
		1289	=head2 WATCHER PRIORITY MODELS
		1290
		1291	Many event loops support I<watcher priorities>, which are usually small
		1292	integers that influence the ordering of event callback invocation
		1293	between watchers in some way, all else being equal.
		1294
		1295	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1296	description for the more technical details such as the actual priority
		1297	range.
		1298
		1299	There are two common ways how these these priorities are being interpreted
		1300	by event loops:
		1301
		1302	In the more common lock-out model, higher priorities "lock out" invocation
		1303	of lower priority watchers, which means as long as higher priority
		1304	watchers receive events, lower priority watchers are not being invoked.
		1305
		1306	The less common only-for-ordering model uses priorities solely to order
		1307	callback invocation within a single event loop iteration: Higher priority
		1308	watchers are invoked before lower priority ones, but they all get invoked
		1309	before polling for new events.
		1310
		1311	Libev uses the second (only-for-ordering) model for all its watchers
		1312	except for idle watchers (which use the lock-out model).
		1313
		1314	The rationale behind this is that implementing the lock-out model for
		1315	watchers is not well supported by most kernel interfaces, and most event
		1316	libraries will just poll for the same events again and again as long as
		1317	their callbacks have not been executed, which is very inefficient in the
		1318	common case of one high-priority watcher locking out a mass of lower
		1319	priority ones.
		1320
		1321	Static (ordering) priorities are most useful when you have two or more
		1322	watchers handling the same resource: a typical usage example is having an
		1323	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1324	timeouts. Under load, data might be received while the program handles
		1325	other jobs, but since timers normally get invoked first, the timeout
		1326	handler will be executed before checking for data. In that case, giving
		1327	the timer a lower priority than the I/O watcher ensures that I/O will be
		1328	handled first even under adverse conditions (which is usually, but not
		1329	always, what you want).
		1330
		1331	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1332	will only be executed when no same or higher priority watchers have
		1333	received events, they can be used to implement the "lock-out" model when
		1334	required.
		1335
		1336	For example, to emulate how many other event libraries handle priorities,
		1337	you can associate an C<ev_idle> watcher to each such watcher, and in
		1338	the normal watcher callback, you just start the idle watcher. The real
		1339	processing is done in the idle watcher callback. This causes libev to
		1340	continously poll and process kernel event data for the watcher, but when
		1341	the lock-out case is known to be rare (which in turn is rare :), this is
		1342	workable.
		1343
		1344	Usually, however, the lock-out model implemented that way will perform
		1345	miserably under the type of load it was designed to handle. In that case,
		1346	it might be preferable to stop the real watcher before starting the
		1347	idle watcher, so the kernel will not have to process the event in case
		1348	the actual processing will be delayed for considerable time.
		1349
		1350	Here is an example of an I/O watcher that should run at a strictly lower
		1351	priority than the default, and which should only process data when no
		1352	other events are pending:
		1353
		1354	ev_idle idle; // actual processing watcher
		1355	ev_io io; // actual event watcher
		1356
		1357	static void
		1358	io_cb (EV_P_ ev_io *w, int revents)
		1359	{
		1360	// stop the I/O watcher, we received the event, but
		1361	// are not yet ready to handle it.
		1362	ev_io_stop (EV_A_ w);
		1363
		1364	// start the idle watcher to ahndle the actual event.
		1365	// it will not be executed as long as other watchers
		1366	// with the default priority are receiving events.
		1367	ev_idle_start (EV_A_ &idle);
		1368	}
		1369
		1370	static void
		1371	idle_cb (EV_P_ ev_idle *w, int revents)
		1372	{
		1373	// actual processing
		1374	read (STDIN_FILENO, ...);
		1375
		1376	// have to start the I/O watcher again, as
		1377	// we have handled the event
		1378	ev_io_start (EV_P_ &io);
		1379	}
		1380
		1381	// initialisation
		1382	ev_idle_init (&idle, idle_cb);
		1383	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1384	ev_io_start (EV_DEFAULT_ &io);
		1385
		1386	In the "real" world, it might also be beneficial to start a timer, so that
		1387	low-priority connections can not be locked out forever under load. This
		1388	enables your program to keep a lower latency for important connections
		1389	during short periods of high load, while not completely locking out less
		1390	important ones.
1191		1391
1192		1392
1193	=head1 WATCHER TYPES	1393	=head1 WATCHER TYPES
1194		1394
1195	This section describes each watcher in detail, but will not repeat	1395	This section describes each watcher in detail, but will not repeat
…		…
1221	descriptors to non-blocking mode is also usually a good idea (but not	1421	descriptors to non-blocking mode is also usually a good idea (but not
1222	required if you know what you are doing).	1422	required if you know what you are doing).
1223		1423
1224	If you cannot use non-blocking mode, then force the use of a	1424	If you cannot use non-blocking mode, then force the use of a
1225	known-to-be-good backend (at the time of this writing, this includes only	1425	known-to-be-good backend (at the time of this writing, this includes only
1226	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1426	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1427	descriptors for which non-blocking operation makes no sense (such as
		1428	files) - libev doesn't guarentee any specific behaviour in that case.
1227		1429
1228	Another thing you have to watch out for is that it is quite easy to	1430	Another thing you have to watch out for is that it is quite easy to
1229	receive "spurious" readiness notifications, that is your callback might	1431	receive "spurious" readiness notifications, that is your callback might
1230	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1432	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1231	because there is no data. Not only are some backends known to create a	1433	because there is no data. Not only are some backends known to create a
…		…
1352	year, it will still time out after (roughly) one hour. "Roughly" because	1554	year, it will still time out after (roughly) one hour. "Roughly" because
1353	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1555	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1354	monotonic clock option helps a lot here).	1556	monotonic clock option helps a lot here).
1355		1557
1356	The callback is guaranteed to be invoked only I<after> its timeout has	1558	The callback is guaranteed to be invoked only I<after> its timeout has
1357	passed. If multiple timers become ready during the same loop iteration	1559	passed (not I<at>, so on systems with very low-resolution clocks this
1358	then the ones with earlier time-out values are invoked before ones with	1560	might introduce a small delay). If multiple timers become ready during the
1359	later time-out values (but this is no longer true when a callback calls	1561	same loop iteration then the ones with earlier time-out values are invoked
1360	C<ev_loop> recursively).	1562	before ones of the same priority with later time-out values (but this is
		1563	no longer true when a callback calls C<ev_loop> recursively).
1361		1564
1362	=head3 Be smart about timeouts	1565	=head3 Be smart about timeouts
1363		1566
1364	Many real-world problems involve some kind of timeout, usually for error	1567	Many real-world problems involve some kind of timeout, usually for error
1365	recovery. A typical example is an HTTP request - if the other side hangs,	1568	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1409	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1612	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1410	member and C<ev_timer_again>.	1613	member and C<ev_timer_again>.
1411		1614
1412	At start:	1615	At start:
1413		1616
1414	ev_timer_init (timer, callback);	1617	ev_init (timer, callback);
1415	timer->repeat = 60.;	1618	timer->repeat = 60.;
1416	ev_timer_again (loop, timer);	1619	ev_timer_again (loop, timer);
1417		1620
1418	Each time there is some activity:	1621	Each time there is some activity:
1419		1622
…		…
1481		1684
1482	To start the timer, simply initialise the watcher and set C<last_activity>	1685	To start the timer, simply initialise the watcher and set C<last_activity>
1483	to the current time (meaning we just have some activity :), then call the	1686	to the current time (meaning we just have some activity :), then call the
1484	callback, which will "do the right thing" and start the timer:	1687	callback, which will "do the right thing" and start the timer:
1485		1688
1486	ev_timer_init (timer, callback);	1689	ev_init (timer, callback);
1487	last_activity = ev_now (loop);	1690	last_activity = ev_now (loop);
1488	callback (loop, timer, EV_TIMEOUT);	1691	callback (loop, timer, EV_TIMEOUT);
1489		1692
1490	And when there is some activity, simply store the current time in	1693	And when there is some activity, simply store the current time in
1491	C<last_activity>, no libev calls at all:	1694	C<last_activity>, no libev calls at all:
…		…
1552		1755
1553	If the event loop is suspended for a long time, you can also force an	1756	If the event loop is suspended for a long time, you can also force an
1554	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1757	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1555	()>.	1758	()>.
1556		1759
		1760	=head3 The special problems of suspended animation
		1761
		1762	When you leave the server world it is quite customary to hit machines that
		1763	can suspend/hibernate - what happens to the clocks during such a suspend?
		1764
		1765	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1766	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1767	to run until the system is suspended, but they will not advance while the
		1768	system is suspended. That means, on resume, it will be as if the program
		1769	was frozen for a few seconds, but the suspend time will not be counted
		1770	towards C<ev_timer> when a monotonic clock source is used. The real time
		1771	clock advanced as expected, but if it is used as sole clocksource, then a
		1772	long suspend would be detected as a time jump by libev, and timers would
		1773	be adjusted accordingly.
		1774
		1775	I would not be surprised to see different behaviour in different between
		1776	operating systems, OS versions or even different hardware.
		1777
		1778	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1779	time jump in the monotonic clocks and the realtime clock. If the program
		1780	is suspended for a very long time, and monotonic clock sources are in use,
		1781	then you can expect C<ev_timer>s to expire as the full suspension time
		1782	will be counted towards the timers. When no monotonic clock source is in
		1783	use, then libev will again assume a timejump and adjust accordingly.
		1784
		1785	It might be beneficial for this latter case to call C<ev_suspend>
		1786	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1787	deterministic behaviour in this case (you can do nothing against
		1788	C<SIGSTOP>).
		1789
1557	=head3 Watcher-Specific Functions and Data Members	1790	=head3 Watcher-Specific Functions and Data Members
1558		1791
1559	=over 4	1792	=over 4
1560		1793
1561	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1794	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1586	If the timer is repeating, either start it if necessary (with the	1819	If the timer is repeating, either start it if necessary (with the
1587	C<repeat> value), or reset the running timer to the C<repeat> value.	1820	C<repeat> value), or reset the running timer to the C<repeat> value.
1588		1821
1589	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	1822	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1590	usage example.	1823	usage example.
		1824
		1825	=item ev_timer_remaining (loop, ev_timer *)
		1826
		1827	Returns the remaining time until a timer fires. If the timer is active,
		1828	then this time is relative to the current event loop time, otherwise it's
		1829	the timeout value currently configured.
		1830
		1831	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1832	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1833	will return C<4>. When the timer expires and is restarted, it will return
		1834	roughly C<7> (likely slightly less as callback invocation takes some time,
		1835	too), and so on.
1591		1836
1592	=item ev_tstamp repeat [read-write]	1837	=item ev_tstamp repeat [read-write]
1593		1838
1594	The current C<repeat> value. Will be used each time the watcher times out	1839	The current C<repeat> value. Will be used each time the watcher times out
1595	or C<ev_timer_again> is called, and determines the next timeout (if any),	1840	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1831	Signal watchers will trigger an event when the process receives a specific	2076	Signal watchers will trigger an event when the process receives a specific
1832	signal one or more times. Even though signals are very asynchronous, libev	2077	signal one or more times. Even though signals are very asynchronous, libev
1833	will try it's best to deliver signals synchronously, i.e. as part of the	2078	will try it's best to deliver signals synchronously, i.e. as part of the
1834	normal event processing, like any other event.	2079	normal event processing, like any other event.
1835		2080
		2081	Note that only the default loop supports registering signal watchers
		2082	currently.
		2083
1836	If you want signals asynchronously, just use C<sigaction> as you would	2084	If you want signals asynchronously, just use C<sigaction> as you would
1837	do without libev and forget about sharing the signal. You can even use	2085	do without libev and forget about sharing the signal. You can even use
1838	C<ev_async> from a signal handler to synchronously wake up an event loop.	2086	C<ev_async> from a signal handler to synchronously wake up an event loop.
1839		2087
1840	You can configure as many watchers as you like per signal. Only when the	2088	You can configure as many watchers as you like per signal. Only when the
1841	first watcher gets started will libev actually register a signal handler	2089	first watcher gets started will libev actually register something with
1842	with the kernel (thus it coexists with your own signal handlers as long as	2090	the kernel (thus it coexists with your own signal handlers as long as you
1843	you don't register any with libev for the same signal). Similarly, when	2091	don't register any with libev for the same signal).
1844	the last signal watcher for a signal is stopped, libev will reset the	2092
1845	signal handler to SIG_DFL (regardless of what it was set to before).	2093	Both the signal mask state (C<sigprocmask>) and the signal handler state
		2094	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2095	sotpping it again), that is, libev might or might not block the signal,
		2096	and might or might not set or restore the installed signal handler.
1846		2097
1847	If possible and supported, libev will install its handlers with	2098	If possible and supported, libev will install its handlers with
1848	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2099	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1849	interrupted. If you have a problem with system calls getting interrupted by	2100	not be unduly interrupted. If you have a problem with system calls getting
1850	signals you can block all signals in an C<ev_check> watcher and unblock	2101	interrupted by signals you can block all signals in an C<ev_check> watcher
1851	them in an C<ev_prepare> watcher.	2102	and unblock them in an C<ev_prepare> watcher.
1852		2103
1853	=head3 Watcher-Specific Functions and Data Members	2104	=head3 Watcher-Specific Functions and Data Members
1854		2105
1855	=over 4	2106	=over 4
1856		2107
…		…
1888	some child status changes (most typically when a child of yours dies or	2139	some child status changes (most typically when a child of yours dies or
1889	exits). It is permissible to install a child watcher I<after> the child	2140	exits). It is permissible to install a child watcher I<after> the child
1890	has been forked (which implies it might have already exited), as long	2141	has been forked (which implies it might have already exited), as long
1891	as the event loop isn't entered (or is continued from a watcher), i.e.,	2142	as the event loop isn't entered (or is continued from a watcher), i.e.,
1892	forking and then immediately registering a watcher for the child is fine,	2143	forking and then immediately registering a watcher for the child is fine,
1893	but forking and registering a watcher a few event loop iterations later is	2144	but forking and registering a watcher a few event loop iterations later or
1894	not.	2145	in the next callback invocation is not.
1895		2146
1896	Only the default event loop is capable of handling signals, and therefore	2147	Only the default event loop is capable of handling signals, and therefore
1897	you can only register child watchers in the default event loop.	2148	you can only register child watchers in the default event loop.
1898		2149
		2150	Due to some design glitches inside libev, child watchers will always be
		2151	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2152	libev)
		2153
1899	=head3 Process Interaction	2154	=head3 Process Interaction
1900		2155
1901	Libev grabs C<SIGCHLD> as soon as the default event loop is	2156	Libev grabs C<SIGCHLD> as soon as the default event loop is
1902	initialised. This is necessary to guarantee proper behaviour even if	2157	initialised. This is necessary to guarantee proper behaviour even if the
1903	the first child watcher is started after the child exits. The occurrence	2158	first child watcher is started after the child exits. The occurrence
1904	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2159	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1905	synchronously as part of the event loop processing. Libev always reaps all	2160	synchronously as part of the event loop processing. Libev always reaps all
1906	children, even ones not watched.	2161	children, even ones not watched.
1907		2162
1908	=head3 Overriding the Built-In Processing	2163	=head3 Overriding the Built-In Processing
…		…
1918	=head3 Stopping the Child Watcher	2173	=head3 Stopping the Child Watcher
1919		2174
1920	Currently, the child watcher never gets stopped, even when the	2175	Currently, the child watcher never gets stopped, even when the
1921	child terminates, so normally one needs to stop the watcher in the	2176	child terminates, so normally one needs to stop the watcher in the
1922	callback. Future versions of libev might stop the watcher automatically	2177	callback. Future versions of libev might stop the watcher automatically
1923	when a child exit is detected.	2178	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2179	problem).
1924		2180
1925	=head3 Watcher-Specific Functions and Data Members	2181	=head3 Watcher-Specific Functions and Data Members
1926		2182
1927	=over 4	2183	=over 4
1928		2184
…		…
2254	// no longer anything immediate to do.	2510	// no longer anything immediate to do.
2255	}	2511	}
2256		2512
2257	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2513	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2258	ev_idle_init (idle_watcher, idle_cb);	2514	ev_idle_init (idle_watcher, idle_cb);
2259	ev_idle_start (loop, idle_cb);	2515	ev_idle_start (loop, idle_watcher);
2260		2516
2261		2517
2262	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2518	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2263		2519
2264	Prepare and check watchers are usually (but not always) used in pairs:	2520	Prepare and check watchers are usually (but not always) used in pairs:
…		…
2357	struct pollfd fds [nfd];	2613	struct pollfd fds [nfd];
2358	// actual code will need to loop here and realloc etc.	2614	// actual code will need to loop here and realloc etc.
2359	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2615	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2360		2616
2361	/* the callback is illegal, but won't be called as we stop during check */	2617	/* the callback is illegal, but won't be called as we stop during check */
2362	ev_timer_init (&tw, 0, timeout * 1e-3);	2618	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2363	ev_timer_start (loop, &tw);	2619	ev_timer_start (loop, &tw);
2364		2620
2365	// create one ev_io per pollfd	2621	// create one ev_io per pollfd
2366	for (int i = 0; i < nfd; ++i)	2622	for (int i = 0; i < nfd; ++i)
2367	{	2623	{
…		…
2597	event loop blocks next and before C<ev_check> watchers are being called,	2853	event loop blocks next and before C<ev_check> watchers are being called,
2598	and only in the child after the fork. If whoever good citizen calling	2854	and only in the child after the fork. If whoever good citizen calling
2599	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2855	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2600	handlers will be invoked, too, of course.	2856	handlers will be invoked, too, of course.
2601		2857
		2858	=head3 The special problem of life after fork - how is it possible?
		2859
		2860	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2861	up/change the process environment, followed by a call to C<exec()>. This
		2862	sequence should be handled by libev without any problems.
		2863
		2864	This changes when the application actually wants to do event handling
		2865	in the child, or both parent in child, in effect "continuing" after the
		2866	fork.
		2867
		2868	The default mode of operation (for libev, with application help to detect
		2869	forks) is to duplicate all the state in the child, as would be expected
		2870	when I<either> the parent I<or> the child process continues.
		2871
		2872	When both processes want to continue using libev, then this is usually the
		2873	wrong result. In that case, usually one process (typically the parent) is
		2874	supposed to continue with all watchers in place as before, while the other
		2875	process typically wants to start fresh, i.e. without any active watchers.
		2876
		2877	The cleanest and most efficient way to achieve that with libev is to
		2878	simply create a new event loop, which of course will be "empty", and
		2879	use that for new watchers. This has the advantage of not touching more
		2880	memory than necessary, and thus avoiding the copy-on-write, and the
		2881	disadvantage of having to use multiple event loops (which do not support
		2882	signal watchers).
		2883
		2884	When this is not possible, or you want to use the default loop for
		2885	other reasons, then in the process that wants to start "fresh", call
		2886	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2887	the default loop will "orphan" (not stop) all registered watchers, so you
		2888	have to be careful not to execute code that modifies those watchers. Note
		2889	also that in that case, you have to re-register any signal watchers.
		2890
2602	=head3 Watcher-Specific Functions and Data Members	2891	=head3 Watcher-Specific Functions and Data Members
2603		2892
2604	=over 4	2893	=over 4
2605		2894
2606	=item ev_fork_init (ev_signal *, callback)	2895	=item ev_fork_init (ev_signal *, callback)
…		…
3496	defined to be C<0>, then they are not.	3785	defined to be C<0>, then they are not.
3497		3786
3498	=item EV_MINIMAL	3787	=item EV_MINIMAL
3499		3788
3500	If you need to shave off some kilobytes of code at the expense of some	3789	If you need to shave off some kilobytes of code at the expense of some
3501	speed, define this symbol to C<1>. Currently this is used to override some	3790	speed (but with the full API), define this symbol to C<1>. Currently this
3502	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3791	is used to override some inlining decisions, saves roughly 30% code size
3503	much smaller 2-heap for timer management over the default 4-heap.	3792	on amd64. It also selects a much smaller 2-heap for timer management over
		3793	the default 4-heap.
		3794
		3795	You can save even more by disabling watcher types you do not need
		3796	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3797	(C<-DNDEBUG>) will usually reduce code size a lot.
		3798
		3799	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3800	provide a bare-bones event library. See C<ev.h> for details on what parts
		3801	of the API are still available, and do not complain if this subset changes
		3802	over time.
3504		3803
3505	=item EV_PID_HASHSIZE	3804	=item EV_PID_HASHSIZE
3506		3805
3507	C<ev_child> watchers use a small hash table to distribute workload by	3806	C<ev_child> watchers use a small hash table to distribute workload by
3508	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3807	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3694	default loop and triggering an C<ev_async> watcher from the default loop	3993	default loop and triggering an C<ev_async> watcher from the default loop
3695	watcher callback into the event loop interested in the signal.	3994	watcher callback into the event loop interested in the signal.
3696		3995
3697	=back	3996	=back
3698		3997
		3998	=head4 THREAD LOCKING EXAMPLE
		3999
		4000	Here is a fictitious example of how to run an event loop in a different
		4001	thread than where callbacks are being invoked and watchers are
		4002	created/added/removed.
		4003
		4004	For a real-world example, see the C<EV::Loop::Async> perl module,
		4005	which uses exactly this technique (which is suited for many high-level
		4006	languages).
		4007
		4008	The example uses a pthread mutex to protect the loop data, a condition
		4009	variable to wait for callback invocations, an async watcher to notify the
		4010	event loop thread and an unspecified mechanism to wake up the main thread.
		4011
		4012	First, you need to associate some data with the event loop:
		4013
		4014	typedef struct {
		4015	mutex_t lock; /* global loop lock */
		4016	ev_async async_w;
		4017	thread_t tid;
		4018	cond_t invoke_cv;
		4019	} userdata;
		4020
		4021	void prepare_loop (EV_P)
		4022	{
		4023	// for simplicity, we use a static userdata struct.
		4024	static userdata u;
		4025
		4026	ev_async_init (&u->async_w, async_cb);
		4027	ev_async_start (EV_A_ &u->async_w);
		4028
		4029	pthread_mutex_init (&u->lock, 0);
		4030	pthread_cond_init (&u->invoke_cv, 0);
		4031
		4032	// now associate this with the loop
		4033	ev_set_userdata (EV_A_ u);
		4034	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4035	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4036
		4037	// then create the thread running ev_loop
		4038	pthread_create (&u->tid, 0, l_run, EV_A);
		4039	}
		4040
		4041	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4042	solely to wake up the event loop so it takes notice of any new watchers
		4043	that might have been added:
		4044
		4045	static void
		4046	async_cb (EV_P_ ev_async *w, int revents)
		4047	{
		4048	// just used for the side effects
		4049	}
		4050
		4051	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4052	protecting the loop data, respectively.
		4053
		4054	static void
		4055	l_release (EV_P)
		4056	{
		4057	userdata *u = ev_userdata (EV_A);
		4058	pthread_mutex_unlock (&u->lock);
		4059	}
		4060
		4061	static void
		4062	l_acquire (EV_P)
		4063	{
		4064	userdata *u = ev_userdata (EV_A);
		4065	pthread_mutex_lock (&u->lock);
		4066	}
		4067
		4068	The event loop thread first acquires the mutex, and then jumps straight
		4069	into C<ev_loop>:
		4070
		4071	void *
		4072	l_run (void *thr_arg)
		4073	{
		4074	struct ev_loop loop = (struct ev_loop )thr_arg;
		4075
		4076	l_acquire (EV_A);
		4077	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4078	ev_loop (EV_A_ 0);
		4079	l_release (EV_A);
		4080
		4081	return 0;
		4082	}
		4083
		4084	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4085	signal the main thread via some unspecified mechanism (signals? pipe
		4086	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4087	have been called (in a while loop because a) spurious wakeups are possible
		4088	and b) skipping inter-thread-communication when there are no pending
		4089	watchers is very beneficial):
		4090
		4091	static void
		4092	l_invoke (EV_P)
		4093	{
		4094	userdata *u = ev_userdata (EV_A);
		4095
		4096	while (ev_pending_count (EV_A))
		4097	{
		4098	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4099	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4100	}
		4101	}
		4102
		4103	Now, whenever the main thread gets told to invoke pending watchers, it
		4104	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4105	thread to continue:
		4106
		4107	static void
		4108	real_invoke_pending (EV_P)
		4109	{
		4110	userdata *u = ev_userdata (EV_A);
		4111
		4112	pthread_mutex_lock (&u->lock);
		4113	ev_invoke_pending (EV_A);
		4114	pthread_cond_signal (&u->invoke_cv);
		4115	pthread_mutex_unlock (&u->lock);
		4116	}
		4117
		4118	Whenever you want to start/stop a watcher or do other modifications to an
		4119	event loop, you will now have to lock:
		4120
		4121	ev_timer timeout_watcher;
		4122	userdata *u = ev_userdata (EV_A);
		4123
		4124	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4125
		4126	pthread_mutex_lock (&u->lock);
		4127	ev_timer_start (EV_A_ &timeout_watcher);
		4128	ev_async_send (EV_A_ &u->async_w);
		4129	pthread_mutex_unlock (&u->lock);
		4130
		4131	Note that sending the C<ev_async> watcher is required because otherwise
		4132	an event loop currently blocking in the kernel will have no knowledge
		4133	about the newly added timer. By waking up the loop it will pick up any new
		4134	watchers in the next event loop iteration.
		4135
3699	=head3 COROUTINES	4136	=head3 COROUTINES
3700		4137
3701	Libev is very accommodating to coroutines ("cooperative threads"):	4138	Libev is very accommodating to coroutines ("cooperative threads"):
3702	libev fully supports nesting calls to its functions from different	4139	libev fully supports nesting calls to its functions from different
3703	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4140	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3704	different coroutines, and switch freely between both coroutines running the	4141	different coroutines, and switch freely between both coroutines running
3705	loop, as long as you don't confuse yourself). The only exception is that	4142	the loop, as long as you don't confuse yourself). The only exception is
3706	you must not do this from C<ev_periodic> reschedule callbacks.	4143	that you must not do this from C<ev_periodic> reschedule callbacks.
3707		4144
3708	Care has been taken to ensure that libev does not keep local state inside	4145	Care has been taken to ensure that libev does not keep local state inside
3709	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4146	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3710	they do not call any callbacks.	4147	they do not call any callbacks.
3711		4148
…		…
3788	way (note also that glib is the slowest event library known to man).	4225	way (note also that glib is the slowest event library known to man).
3789		4226
3790	There is no supported compilation method available on windows except	4227	There is no supported compilation method available on windows except
3791	embedding it into other applications.	4228	embedding it into other applications.
3792		4229
		4230	Sensible signal handling is officially unsupported by Microsoft - libev
		4231	tries its best, but under most conditions, signals will simply not work.
		4232
3793	Not a libev limitation but worth mentioning: windows apparently doesn't	4233	Not a libev limitation but worth mentioning: windows apparently doesn't
3794	accept large writes: instead of resulting in a partial write, windows will	4234	accept large writes: instead of resulting in a partial write, windows will
3795	either accept everything or return C<ENOBUFS> if the buffer is too large,	4235	either accept everything or return C<ENOBUFS> if the buffer is too large,
3796	so make sure you only write small amounts into your sockets (less than a	4236	so make sure you only write small amounts into your sockets (less than a
3797	megabyte seems safe, but this apparently depends on the amount of memory	4237	megabyte seems safe, but this apparently depends on the amount of memory
…		…
3801	the abysmal performance of winsockets, using a large number of sockets	4241	the abysmal performance of winsockets, using a large number of sockets
3802	is not recommended (and not reasonable). If your program needs to use	4242	is not recommended (and not reasonable). If your program needs to use
3803	more than a hundred or so sockets, then likely it needs to use a totally	4243	more than a hundred or so sockets, then likely it needs to use a totally
3804	different implementation for windows, as libev offers the POSIX readiness	4244	different implementation for windows, as libev offers the POSIX readiness
3805	notification model, which cannot be implemented efficiently on windows	4245	notification model, which cannot be implemented efficiently on windows
3806	(Microsoft monopoly games).	4246	(due to Microsoft monopoly games).
3807		4247
3808	A typical way to use libev under windows is to embed it (see the embedding	4248	A typical way to use libev under windows is to embed it (see the embedding
3809	section for details) and use the following F<evwrap.h> header file instead	4249	section for details) and use the following F<evwrap.h> header file instead
3810	of F<ev.h>:	4250	of F<ev.h>:
3811		4251
…		…
3847		4287
3848	Early versions of winsocket's select only supported waiting for a maximum	4288	Early versions of winsocket's select only supported waiting for a maximum
3849	of C<64> handles (probably owning to the fact that all windows kernels	4289	of C<64> handles (probably owning to the fact that all windows kernels
3850	can only wait for C<64> things at the same time internally; Microsoft	4290	can only wait for C<64> things at the same time internally; Microsoft
3851	recommends spawning a chain of threads and wait for 63 handles and the	4291	recommends spawning a chain of threads and wait for 63 handles and the
3852	previous thread in each. Great).	4292	previous thread in each. Sounds great!).
3853		4293
3854	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4294	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3855	to some high number (e.g. C<2048>) before compiling the winsocket select	4295	to some high number (e.g. C<2048>) before compiling the winsocket select
3856	call (which might be in libev or elsewhere, for example, perl does its own	4296	call (which might be in libev or elsewhere, for example, perl and many
3857	select emulation on windows).	4297	other interpreters do their own select emulation on windows).
3858		4298
3859	Another limit is the number of file descriptors in the Microsoft runtime	4299	Another limit is the number of file descriptors in the Microsoft runtime
3860	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4300	libraries, which by default is C<64> (there must be a hidden I<64>
3861	or something like this inside Microsoft). You can increase this by calling	4301	fetish or something like this inside Microsoft). You can increase this
3862	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4302	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3863	arbitrary limit), but is broken in many versions of the Microsoft runtime	4303	(another arbitrary limit), but is broken in many versions of the Microsoft
3864	libraries.
3865
3866	This might get you to about C<512> or C<2048> sockets (depending on	4304	runtime libraries. This might get you to about C<512> or C<2048> sockets
3867	windows version and/or the phase of the moon). To get more, you need to	4305	(depending on windows version and/or the phase of the moon). To get more,
3868	wrap all I/O functions and provide your own fd management, but the cost of	4306	you need to wrap all I/O functions and provide your own fd management, but
3869	calling select (O(n²)) will likely make this unworkable.	4307	the cost of calling select (O(n²)) will likely make this unworkable.
3870		4308
3871	=back	4309	=back
3872		4310
3873	=head2 PORTABILITY REQUIREMENTS	4311	=head2 PORTABILITY REQUIREMENTS
3874		4312
…		…
3917	=item C<double> must hold a time value in seconds with enough accuracy	4355	=item C<double> must hold a time value in seconds with enough accuracy
3918		4356
3919	The type C<double> is used to represent timestamps. It is required to	4357	The type C<double> is used to represent timestamps. It is required to
3920	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4358	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3921	enough for at least into the year 4000. This requirement is fulfilled by	4359	enough for at least into the year 4000. This requirement is fulfilled by
3922	implementations implementing IEEE 754 (basically all existing ones).	4360	implementations implementing IEEE 754, which is basically all existing
		4361	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4362	2200.
3923		4363
3924	=back	4364	=back
3925		4365
3926	If you know of other additional requirements drop me a note.	4366	If you know of other additional requirements drop me a note.
3927		4367
…		…
3995	involves iterating over all running async watchers or all signal numbers.	4435	involves iterating over all running async watchers or all signal numbers.
3996		4436
3997	=back	4437	=back
3998		4438
3999		4439
		4440	=head1 GLOSSARY
		4441
		4442	=over 4
		4443
		4444	=item active
		4445
		4446	A watcher is active as long as it has been started (has been attached to
		4447	an event loop) but not yet stopped (disassociated from the event loop).
		4448
		4449	=item application
		4450
		4451	In this document, an application is whatever is using libev.
		4452
		4453	=item callback
		4454
		4455	The address of a function that is called when some event has been
		4456	detected. Callbacks are being passed the event loop, the watcher that
		4457	received the event, and the actual event bitset.
		4458
		4459	=item callback invocation
		4460
		4461	The act of calling the callback associated with a watcher.
		4462
		4463	=item event
		4464
		4465	A change of state of some external event, such as data now being available
		4466	for reading on a file descriptor, time having passed or simply not having
		4467	any other events happening anymore.
		4468
		4469	In libev, events are represented as single bits (such as C<EV_READ> or
		4470	C<EV_TIMEOUT>).
		4471
		4472	=item event library
		4473
		4474	A software package implementing an event model and loop.
		4475
		4476	=item event loop
		4477
		4478	An entity that handles and processes external events and converts them
		4479	into callback invocations.
		4480
		4481	=item event model
		4482
		4483	The model used to describe how an event loop handles and processes
		4484	watchers and events.
		4485
		4486	=item pending
		4487
		4488	A watcher is pending as soon as the corresponding event has been detected,
		4489	and stops being pending as soon as the watcher will be invoked or its
		4490	pending status is explicitly cleared by the application.
		4491
		4492	A watcher can be pending, but not active. Stopping a watcher also clears
		4493	its pending status.
		4494
		4495	=item real time
		4496
		4497	The physical time that is observed. It is apparently strictly monotonic :)
		4498
		4499	=item wall-clock time
		4500
		4501	The time and date as shown on clocks. Unlike real time, it can actually
		4502	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4503	clock.
		4504
		4505	=item watcher
		4506
		4507	A data structure that describes interest in certain events. Watchers need
		4508	to be started (attached to an event loop) before they can receive events.
		4509
		4510	=item watcher invocation
		4511
		4512	The act of calling the callback associated with a watcher.
		4513
		4514	=back
		4515
4000	=head1 AUTHOR	4516	=head1 AUTHOR
4001		4517
4002	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	4518	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
4003		4519

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Comparing libev/ev.pod (file contents):
Revision 1.232 by root, Thu Apr 16 06:17:26 2009 UTC vs.
Revision 1.259 by root, Sun Jul 19 01:36:34 2009 UTC