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…		…
8		8
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
		13
		14	#include <stdio.h> // for puts
13		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_TYPE	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
…		…
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
28		30
29	// this causes all nested ev_loop's to stop iterating	31	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_break (EV_A_ EVBREAK_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_break (EV_A_ EVBREAK_ONE);
40	}	42	}
41		43
42	int	44	int
43	main (void)	45	main (void)
44	{	46	{
45	// use the default event loop unless you have special needs	47	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	48	struct ev_loop *loop = EV_DEFAULT;
47		49
48	// initialise an io watcher, then start it	50	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	51	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	53	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	56	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	58	ev_timer_start (loop, &timeout_watcher);
57		59
58	// now wait for events to arrive	60	// now wait for events to arrive
59	ev_loop (loop, 0);	61	ev_run (loop, 0);
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	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
68	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
69	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	Familiarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	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
72	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
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	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
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	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
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	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
94	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
95	(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>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	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
99	for example).	114	for example).
100		115
…		…
103	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	121	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	122	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	the beginning of 1970, details are complicated, don't ask). This type is	130	somewhere near the beginning of 1970, details are complicated, don't
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	ask). This type is called C<ev_tstamp>, which is what you should use
117	to the C<double> type in C, and when you need to do any calculations on	132	too. It usually aliases to the C<double> type in C. When you need to do
118	it, you should treat it as some floating point value. Unlike the name	133	any calculations on it, you should treat it as some floating point value.
		134
119	component C<stamp> might indicate, it is also used for time differences	135	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	136	time differences (e.g. delays) throughout libev.
121		137
122	=head1 ERROR HANDLING	138	=head1 ERROR HANDLING
123		139
124	Libev knows three classes of errors: operating system errors, usage errors	140	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	141	and internal errors (bugs).
…		…
149		165
150	=item ev_tstamp ev_time ()	166	=item ev_tstamp ev_time ()
151		167
152	Returns the current time as libev would use it. Please note that the	168	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	169	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	170	you actually want to know. Also interesting is the combination of
		171	C<ev_update_now> and C<ev_now>.
155		172
156	=item ev_sleep (ev_tstamp interval)	173	=item ev_sleep (ev_tstamp interval)
157		174
158	Sleep for the given interval: The current thread will be blocked until	175	Sleep for the given interval: The current thread will be blocked until
159	either it is interrupted or the given time interval has passed. Basically	176	either it is interrupted or the given time interval has passed. Basically
…		…
176	as this indicates an incompatible change. Minor versions are usually	193	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	194	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	195	not a problem.
179		196
180	Example: Make sure we haven't accidentally been linked against the wrong	197	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	198	version (note, however, that this will not detect other ABI mismatches,
		199	such as LFS or reentrancy).
182		200
183	assert (("libev version mismatch",	201	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	202	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	203	&& ev_version_minor () >= EV_VERSION_MINOR));
186		204
…		…
197	assert (("sorry, no epoll, no sex",	215	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	216	ev_supported_backends () & EVBACKEND_EPOLL));
199		217
200	=item unsigned int ev_recommended_backends ()	218	=item unsigned int ev_recommended_backends ()
201		219
202	Return the set of all backends compiled into this binary of libev and also	220	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	221	also recommended for this platform, meaning it will work for most file
		222	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	223	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	224	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	225	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	226	probe for if you specify no backends explicitly.
208		227
209	=item unsigned int ev_embeddable_backends ()	228	=item unsigned int ev_embeddable_backends ()
210		229
211	Returns the set of backends that are embeddable in other event loops. This	230	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	231	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	232	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	233	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	234	& ev_supported_backends ()>, likewise for recommended ones.
216		235
217	See the description of C<ev_embed> watchers for more info.	236	See the description of C<ev_embed> watchers for more info.
218		237
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	238	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		239
…		…
274	...	293	...
275	ev_set_syserr_cb (fatal_error);	294	ev_set_syserr_cb (fatal_error);
276		295
277	=back	296	=back
278		297
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	298	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		299
281	An event loop is described by a C<struct ev_loop *> (the C<struct>	300	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	301	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	302	libev 3 had an C<ev_loop> function colliding with the struct name).
284		303
285	The library knows two types of such loops, the I<default> loop, which	304	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	305	supports signals and child events, and dynamically created event loops
287	not.	306	which do not.
288		307
289	=over 4	308	=over 4
290		309
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	310	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		311
293	This will initialise the default event loop if it hasn't been initialised	312	This returns the "default" event loop object, which is what you should
294	yet and return it. If the default loop could not be initialised, returns	313	normally use when you just need "the event loop". Event loop objects and
295	false. If it already was initialised it simply returns it (and ignores the	314	the C<flags> parameter are described in more detail in the entry for
296	flags. If that is troubling you, check C<ev_backend ()> afterwards).	315	C<ev_loop_new>.
		316
		317	If the default loop is already initialised then this function simply
		318	returns it (and ignores the flags. If that is troubling you, check
		319	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		320	flags, which should almost always be C<0>, unless the caller is also the
		321	one calling C<ev_run> or otherwise qualifies as "the main program".
297		322
298	If you don't know what event loop to use, use the one returned from this	323	If you don't know what event loop to use, use the one returned from this
299	function.	324	function (or via the C<EV_DEFAULT> macro).
300		325
301	Note that this function is I<not> thread-safe, so if you want to use it	326	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	327	from multiple threads, you have to employ some kind of mutex (note also
303	as loops cannot be shared easily between threads anyway).	328	that this case is unlikely, as loops cannot be shared easily between
		329	threads anyway).
304		330
305	The default loop is the only loop that can handle C<ev_signal> and	331	The default loop is the only loop that can handle C<ev_child> watchers,
306	C<ev_child> watchers, and to do this, it always registers a handler	332	and to do this, it always registers a handler for C<SIGCHLD>. If this is
307	for C<SIGCHLD>. If this is a problem for your application you can either	333	a problem for your application you can either create a dynamic loop with
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	334	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	335	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	C<ev_default_init>.	336
		337	Example: This is the most typical usage.
		338
		339	if (!ev_default_loop (0))
		340	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		341
		342	Example: Restrict libev to the select and poll backends, and do not allow
		343	environment settings to be taken into account:
		344
		345	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		346
		347	=item struct ev_loop *ev_loop_new (unsigned int flags)
		348
		349	This will create and initialise a new event loop object. If the loop
		350	could not be initialised, returns false.
		351
		352	Note that this function I<is> thread-safe, and one common way to use
		353	libev with threads is indeed to create one loop per thread, and using the
		354	default loop in the "main" or "initial" thread.
311		355
312	The flags argument can be used to specify special behaviour or specific	356	The flags argument can be used to specify special behaviour or specific
313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	357	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
314		358
315	The following flags are supported:	359	The following flags are supported:
…		…
330	useful to try out specific backends to test their performance, or to work	374	useful to try out specific backends to test their performance, or to work
331	around bugs.	375	around bugs.
332		376
333	=item C<EVFLAG_FORKCHECK>	377	=item C<EVFLAG_FORKCHECK>
334		378
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	379	Instead of calling C<ev_loop_fork> manually after a fork, you can also
336	a fork, you can also make libev check for a fork in each iteration by	380	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		381
339	This works by calling C<getpid ()> on every iteration of the loop,	382	This works by calling C<getpid ()> on every iteration of the loop,
340	and thus this might slow down your event loop if you do a lot of loop	383	and thus this might slow down your event loop if you do a lot of loop
341	iterations and little real work, but is usually not noticeable (on my	384	iterations and little real work, but is usually not noticeable (on my
342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	385	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
…		…
348	flag.	391	flag.
349		392
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	393	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	394	environment variable.
352		395
		396	=item C<EVFLAG_NOINOTIFY>
		397
		398	When this flag is specified, then libev will not attempt to use the
		399	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		400	testing, this flag can be useful to conserve inotify file descriptors, as
		401	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		402
		403	=item C<EVFLAG_SIGNALFD>
		404
		405	When this flag is specified, then libev will attempt to use the
		406	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
		407	delivers signals synchronously, which makes it both faster and might make
		408	it possible to get the queued signal data. It can also simplify signal
		409	handling with threads, as long as you properly block signals in your
		410	threads that are not interested in handling them.
		411
		412	Signalfd will not be used by default as this changes your signal mask, and
		413	there are a lot of shoddy libraries and programs (glib's threadpool for
		414	example) that can't properly initialise their signal masks.
		415
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	416	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		417
355	This is your standard select(2) backend. Not I<completely> standard, as	418	This is your standard select(2) backend. Not I<completely> standard, as
356	libev tries to roll its own fd_set with no limits on the number of fds,	419	libev tries to roll its own fd_set with no limits on the number of fds,
357	but if that fails, expect a fairly low limit on the number of fds when	420	but if that fails, expect a fairly low limit on the number of fds when
…		…
380		443
381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	444	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	445	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		446
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	447	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		448
		449	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		450	kernels).
385		451
386	For few fds, this backend is a bit little slower than poll and select,	452	For few fds, this backend is a bit little slower than poll and select,
387	but it scales phenomenally better. While poll and select usually scale	453	but it scales phenomenally better. While poll and select usually scale
388	like O(total_fds) where n is the total number of fds (or the highest fd),	454	like O(total_fds) where n is the total number of fds (or the highest fd),
389	epoll scales either O(1) or O(active_fds).	455	epoll scales either O(1) or O(active_fds).
…		…
401	of course I<doesn't>, and epoll just loves to report events for totally	467	of course I<doesn't>, and epoll just loves to report events for totally
402	I<different> file descriptors (even already closed ones, so one cannot	468	I<different> file descriptors (even already closed ones, so one cannot
403	even remove them from the set) than registered in the set (especially	469	even remove them from the set) than registered in the set (especially
404	on SMP systems). Libev tries to counter these spurious notifications by	470	on SMP systems). Libev tries to counter these spurious notifications by
405	employing an additional generation counter and comparing that against the	471	employing an additional generation counter and comparing that against the
406	events to filter out spurious ones, recreating the set when required.	472	events to filter out spurious ones, recreating the set when required. Last
		473	not least, it also refuses to work with some file descriptors which work
		474	perfectly fine with C<select> (files, many character devices...).
407		475
408	While stopping, setting and starting an I/O watcher in the same iteration	476	While stopping, setting and starting an I/O watcher in the same iteration
409	will result in some caching, there is still a system call per such	477	will result in some caching, there is still a system call per such
410	incident (because the same I<file descriptor> could point to a different	478	incident (because the same I<file descriptor> could point to a different
411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	479	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
458		526
459	While nominally embeddable in other event loops, this doesn't work	527	While nominally embeddable in other event loops, this doesn't work
460	everywhere, so you might need to test for this. And since it is broken	528	everywhere, so you might need to test for this. And since it is broken
461	almost everywhere, you should only use it when you have a lot of sockets	529	almost everywhere, you should only use it when you have a lot of sockets
462	(for which it usually works), by embedding it into another event loop	530	(for which it usually works), by embedding it into another event loop
463	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	531	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
464	using it only for sockets.	532	also broken on OS X)) and, did I mention it, using it only for sockets.
465		533
466	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	534	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
467	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	535	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
468	C<NOTE_EOF>.	536	C<NOTE_EOF>.
469		537
…		…
504		572
505	It is definitely not recommended to use this flag.	573	It is definitely not recommended to use this flag.
506		574
507	=back	575	=back
508		576
509	If one or more of these are or'ed into the flags value, then only these	577	If one or more of the backend flags are or'ed into the flags value,
510	backends will be tried (in the reverse order as listed here). If none are	578	then only these backends will be tried (in the reverse order as listed
511	specified, all backends in C<ev_recommended_backends ()> will be tried.	579	here). If none are specified, all backends in C<ev_recommended_backends
512		580	()> will be tried.
513	Example: This is the most typical usage.
514
515	if (!ev_default_loop (0))
516	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
517
518	Example: Restrict libev to the select and poll backends, and do not allow
519	environment settings to be taken into account:
520
521	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
522
523	Example: Use whatever libev has to offer, but make sure that kqueue is
524	used if available (warning, breaks stuff, best use only with your own
525	private event loop and only if you know the OS supports your types of
526	fds):
527
528	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
529
530	=item struct ev_loop *ev_loop_new (unsigned int flags)
531
532	Similar to C<ev_default_loop>, but always creates a new event loop that is
533	always distinct from the default loop. Unlike the default loop, it cannot
534	handle signal and child watchers, and attempts to do so will be greeted by
535	undefined behaviour (or a failed assertion if assertions are enabled).
536
537	Note that this function I<is> thread-safe, and the recommended way to use
538	libev with threads is indeed to create one loop per thread, and using the
539	default loop in the "main" or "initial" thread.
540		581
541	Example: Try to create a event loop that uses epoll and nothing else.	582	Example: Try to create a event loop that uses epoll and nothing else.
542		583
543	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	584	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
544	if (!epoller)	585	if (!epoller)
545	fatal ("no epoll found here, maybe it hides under your chair");	586	fatal ("no epoll found here, maybe it hides under your chair");
546		587
		588	Example: Use whatever libev has to offer, but make sure that kqueue is
		589	used if available.
		590
		591	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		592
547	=item ev_default_destroy ()	593	=item ev_loop_destroy (loop)
548		594
549	Destroys the default loop again (frees all memory and kernel state	595	Destroys an event loop object (frees all memory and kernel state
550	etc.). None of the active event watchers will be stopped in the normal	596	etc.). None of the active event watchers will be stopped in the normal
551	sense, so e.g. C<ev_is_active> might still return true. It is your	597	sense, so e.g. C<ev_is_active> might still return true. It is your
552	responsibility to either stop all watchers cleanly yourself I<before>	598	responsibility to either stop all watchers cleanly yourself I<before>
553	calling this function, or cope with the fact afterwards (which is usually	599	calling this function, or cope with the fact afterwards (which is usually
554	the easiest thing, you can just ignore the watchers and/or C<free ()> them	600	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
556		602
557	Note that certain global state, such as signal state (and installed signal	603	Note that certain global state, such as signal state (and installed signal
558	handlers), will not be freed by this function, and related watchers (such	604	handlers), will not be freed by this function, and related watchers (such
559	as signal and child watchers) would need to be stopped manually.	605	as signal and child watchers) would need to be stopped manually.
560		606
561	In general it is not advisable to call this function except in the	607	This function is normally used on loop objects allocated by
562	rare occasion where you really need to free e.g. the signal handling	608	C<ev_loop_new>, but it can also be used on the default loop returned by
		609	C<ev_default_loop>, in which case it is not thread-safe.
		610
		611	Note that it is not advisable to call this function on the default loop
		612	except in the rare occasion where you really need to free it's resources.
563	pipe fds. If you need dynamically allocated loops it is better to use	613	If you need dynamically allocated loops it is better to use C<ev_loop_new>
564	C<ev_loop_new> and C<ev_loop_destroy>).	614	and C<ev_loop_destroy>.
565		615
566	=item ev_loop_destroy (loop)	616	=item ev_loop_fork (loop)
567		617
568	Like C<ev_default_destroy>, but destroys an event loop created by an
569	earlier call to C<ev_loop_new>.
570
571	=item ev_default_fork ()
572
573	This function sets a flag that causes subsequent C<ev_loop> iterations	618	This function sets a flag that causes subsequent C<ev_run> iterations to
574	to reinitialise the kernel state for backends that have one. Despite the	619	reinitialise the kernel state for backends that have one. Despite the
575	name, you can call it anytime, but it makes most sense after forking, in	620	name, you can call it anytime, but it makes most sense after forking, in
576	the child process (or both child and parent, but that again makes little	621	the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the
577	sense). You I<must> call it in the child before using any of the libev	622	child before resuming or calling C<ev_run>.
578	functions, and it will only take effect at the next C<ev_loop> iteration.	623
		624	Again, you I<have> to call it on I<any> loop that you want to re-use after
		625	a fork, I<even if you do not plan to use the loop in the parent>. This is
		626	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		627	during fork.
579		628
580	On the other hand, you only need to call this function in the child	629	On the other hand, you only need to call this function in the child
581	process if and only if you want to use the event library in the child. If	630	process if and only if you want to use the event loop in the child. If
582	you just fork+exec, you don't have to call it at all.	631	you just fork+exec or create a new loop in the child, you don't have to
		632	call it at all (in fact, C<epoll> is so badly broken that it makes a
		633	difference, but libev will usually detect this case on its own and do a
		634	costly reset of the backend).
583		635
584	The function itself is quite fast and it's usually not a problem to call	636	The function itself is quite fast and it's usually not a problem to call
585	it just in case after a fork. To make this easy, the function will fit in	637	it just in case after a fork.
586	quite nicely into a call to C<pthread_atfork>:
587		638
		639	Example: Automate calling C<ev_loop_fork> on the default loop when
		640	using pthreads.
		641
		642	static void
		643	post_fork_child (void)
		644	{
		645	ev_loop_fork (EV_DEFAULT);
		646	}
		647
		648	...
588	pthread_atfork (0, 0, ev_default_fork);	649	pthread_atfork (0, 0, post_fork_child);
589
590	=item ev_loop_fork (loop)
591
592	Like C<ev_default_fork>, but acts on an event loop created by
593	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
594	after fork that you want to re-use in the child, and how you do this is
595	entirely your own problem.
596		650
597	=item int ev_is_default_loop (loop)	651	=item int ev_is_default_loop (loop)
598		652
599	Returns true when the given loop is, in fact, the default loop, and false	653	Returns true when the given loop is, in fact, the default loop, and false
600	otherwise.	654	otherwise.
601		655
602	=item unsigned int ev_loop_count (loop)	656	=item unsigned int ev_iteration (loop)
603		657
604	Returns the count of loop iterations for the loop, which is identical to	658	Returns the current iteration count for the event loop, which is identical
605	the number of times libev did poll for new events. It starts at C<0> and	659	to the number of times libev did poll for new events. It starts at C<0>
606	happily wraps around with enough iterations.	660	and happily wraps around with enough iterations.
607		661
608	This value can sometimes be useful as a generation counter of sorts (it	662	This value can sometimes be useful as a generation counter of sorts (it
609	"ticks" the number of loop iterations), as it roughly corresponds with	663	"ticks" the number of loop iterations), as it roughly corresponds with
610	C<ev_prepare> and C<ev_check> calls.	664	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		665	prepare and check phases.
		666
		667	=item unsigned int ev_depth (loop)
		668
		669	Returns the number of times C<ev_run> was entered minus the number of
		670	times C<ev_run> was exited, in other words, the recursion depth.
		671
		672	Outside C<ev_run>, this number is zero. In a callback, this number is
		673	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		674	in which case it is higher.
		675
		676	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread
		677	etc.), doesn't count as "exit" - consider this as a hint to avoid such
		678	ungentleman-like behaviour unless it's really convenient.
611		679
612	=item unsigned int ev_backend (loop)	680	=item unsigned int ev_backend (loop)
613		681
614	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	682	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
615	use.	683	use.
…		…
624		692
625	=item ev_now_update (loop)	693	=item ev_now_update (loop)
626		694
627	Establishes the current time by querying the kernel, updating the time	695	Establishes the current time by querying the kernel, updating the time
628	returned by C<ev_now ()> in the progress. This is a costly operation and	696	returned by C<ev_now ()> in the progress. This is a costly operation and
629	is usually done automatically within C<ev_loop ()>.	697	is usually done automatically within C<ev_run ()>.
630		698
631	This function is rarely useful, but when some event callback runs for a	699	This function is rarely useful, but when some event callback runs for a
632	very long time without entering the event loop, updating libev's idea of	700	very long time without entering the event loop, updating libev's idea of
633	the current time is a good idea.	701	the current time is a good idea.
634		702
635	See also "The special problem of time updates" in the C<ev_timer> section.	703	See also L<The special problem of time updates> in the C<ev_timer> section.
636		704
		705	=item ev_suspend (loop)
		706
		707	=item ev_resume (loop)
		708
		709	These two functions suspend and resume an event loop, for use when the
		710	loop is not used for a while and timeouts should not be processed.
		711
		712	A typical use case would be an interactive program such as a game: When
		713	the user presses C<^Z> to suspend the game and resumes it an hour later it
		714	would be best to handle timeouts as if no time had actually passed while
		715	the program was suspended. This can be achieved by calling C<ev_suspend>
		716	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		717	C<ev_resume> directly afterwards to resume timer processing.
		718
		719	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		720	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		721	will be rescheduled (that is, they will lose any events that would have
		722	occurred while suspended).
		723
		724	After calling C<ev_suspend> you B<must not> call I<any> function on the
		725	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		726	without a previous call to C<ev_suspend>.
		727
		728	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		729	event loop time (see C<ev_now_update>).
		730
637	=item ev_loop (loop, int flags)	731	=item ev_run (loop, int flags)
638		732
639	Finally, this is it, the event handler. This function usually is called	733	Finally, this is it, the event handler. This function usually is called
640	after you initialised all your watchers and you want to start handling	734	after you have initialised all your watchers and you want to start
641	events.	735	handling events. It will ask the operating system for any new events, call
		736	the watcher callbacks, an then repeat the whole process indefinitely: This
		737	is why event loops are called I<loops>.
642		738
643	If the flags argument is specified as C<0>, it will not return until	739	If the flags argument is specified as C<0>, it will keep handling events
644	either no event watchers are active anymore or C<ev_unloop> was called.	740	until either no event watchers are active anymore or C<ev_break> was
		741	called.
645		742
646	Please note that an explicit C<ev_unloop> is usually better than	743	Please note that an explicit C<ev_break> is usually better than
647	relying on all watchers to be stopped when deciding when a program has	744	relying on all watchers to be stopped when deciding when a program has
648	finished (especially in interactive programs), but having a program	745	finished (especially in interactive programs), but having a program
649	that automatically loops as long as it has to and no longer by virtue	746	that automatically loops as long as it has to and no longer by virtue
650	of relying on its watchers stopping correctly, that is truly a thing of	747	of relying on its watchers stopping correctly, that is truly a thing of
651	beauty.	748	beauty.
652		749
653	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	750	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
654	those events and any already outstanding ones, but will not block your	751	those events and any already outstanding ones, but will not wait and
655	process in case there are no events and will return after one iteration of	752	block your process in case there are no events and will return after one
656	the loop.	753	iteration of the loop. This is sometimes useful to poll and handle new
		754	events while doing lengthy calculations, to keep the program responsive.
657		755
658	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	756	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
659	necessary) and will handle those and any already outstanding ones. It	757	necessary) and will handle those and any already outstanding ones. It
660	will block your process until at least one new event arrives (which could	758	will block your process until at least one new event arrives (which could
661	be an event internal to libev itself, so there is no guarantee that a	759	be an event internal to libev itself, so there is no guarantee that a
662	user-registered callback will be called), and will return after one	760	user-registered callback will be called), and will return after one
663	iteration of the loop.	761	iteration of the loop.
664		762
665	This is useful if you are waiting for some external event in conjunction	763	This is useful if you are waiting for some external event in conjunction
666	with something not expressible using other libev watchers (i.e. "roll your	764	with something not expressible using other libev watchers (i.e. "roll your
667	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	765	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
668	usually a better approach for this kind of thing.	766	usually a better approach for this kind of thing.
669		767
670	Here are the gory details of what C<ev_loop> does:	768	Here are the gory details of what C<ev_run> does:
671		769
		770	- Increment loop depth.
		771	- Reset the ev_break status.
672	- Before the first iteration, call any pending watchers.	772	- Before the first iteration, call any pending watchers.
		773	LOOP:
673	* If EVFLAG_FORKCHECK was used, check for a fork.	774	- If EVFLAG_FORKCHECK was used, check for a fork.
674	- If a fork was detected (by any means), queue and call all fork watchers.	775	- If a fork was detected (by any means), queue and call all fork watchers.
675	- Queue and call all prepare watchers.	776	- Queue and call all prepare watchers.
		777	- If ev_break was called, goto FINISH.
676	- If we have been forked, detach and recreate the kernel state	778	- If we have been forked, detach and recreate the kernel state
677	as to not disturb the other process.	779	as to not disturb the other process.
678	- Update the kernel state with all outstanding changes.	780	- Update the kernel state with all outstanding changes.
679	- Update the "event loop time" (ev_now ()).	781	- Update the "event loop time" (ev_now ()).
680	- Calculate for how long to sleep or block, if at all	782	- Calculate for how long to sleep or block, if at all
681	(active idle watchers, EVLOOP_NONBLOCK or not having	783	(active idle watchers, EVRUN_NOWAIT or not having
682	any active watchers at all will result in not sleeping).	784	any active watchers at all will result in not sleeping).
683	- Sleep if the I/O and timer collect interval say so.	785	- Sleep if the I/O and timer collect interval say so.
		786	- Increment loop iteration counter.
684	- Block the process, waiting for any events.	787	- Block the process, waiting for any events.
685	- Queue all outstanding I/O (fd) events.	788	- Queue all outstanding I/O (fd) events.
686	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	789	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
687	- Queue all expired timers.	790	- Queue all expired timers.
688	- Queue all expired periodics.	791	- Queue all expired periodics.
689	- Unless any events are pending now, queue all idle watchers.	792	- Queue all idle watchers with priority higher than that of pending events.
690	- Queue all check watchers.	793	- Queue all check watchers.
691	- Call all queued watchers in reverse order (i.e. check watchers first).	794	- Call all queued watchers in reverse order (i.e. check watchers first).
692	Signals and child watchers are implemented as I/O watchers, and will	795	Signals and child watchers are implemented as I/O watchers, and will
693	be handled here by queueing them when their watcher gets executed.	796	be handled here by queueing them when their watcher gets executed.
694	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	797	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
695	were used, or there are no active watchers, return, otherwise	798	were used, or there are no active watchers, goto FINISH, otherwise
696	continue with step *.	799	continue with step LOOP.
		800	FINISH:
		801	- Reset the ev_break status iff it was EVBREAK_ONE.
		802	- Decrement the loop depth.
		803	- Return.
697		804
698	Example: Queue some jobs and then loop until no events are outstanding	805	Example: Queue some jobs and then loop until no events are outstanding
699	anymore.	806	anymore.
700		807
701	... queue jobs here, make sure they register event watchers as long	808	... queue jobs here, make sure they register event watchers as long
702	... as they still have work to do (even an idle watcher will do..)	809	... as they still have work to do (even an idle watcher will do..)
703	ev_loop (my_loop, 0);	810	ev_run (my_loop, 0);
704	... jobs done or somebody called unloop. yeah!	811	... jobs done or somebody called unloop. yeah!
705		812
706	=item ev_unloop (loop, how)	813	=item ev_break (loop, how)
707		814
708	Can be used to make a call to C<ev_loop> return early (but only after it	815	Can be used to make a call to C<ev_run> return early (but only after it
709	has processed all outstanding events). The C<how> argument must be either	816	has processed all outstanding events). The C<how> argument must be either
710	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	817	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
711	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	818	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
712		819
713	This "unloop state" will be cleared when entering C<ev_loop> again.	820	This "unloop state" will be cleared when entering C<ev_run> again.
714		821
715	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	822	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##
716		823
717	=item ev_ref (loop)	824	=item ev_ref (loop)
718		825
719	=item ev_unref (loop)	826	=item ev_unref (loop)
720		827
721	Ref/unref can be used to add or remove a reference count on the event	828	Ref/unref can be used to add or remove a reference count on the event
722	loop: Every watcher keeps one reference, and as long as the reference	829	loop: Every watcher keeps one reference, and as long as the reference
723	count is nonzero, C<ev_loop> will not return on its own.	830	count is nonzero, C<ev_run> will not return on its own.
724		831
725	If you have a watcher you never unregister that should not keep C<ev_loop>	832	This is useful when you have a watcher that you never intend to
726	from returning, call ev_unref() after starting, and ev_ref() before	833	unregister, but that nevertheless should not keep C<ev_run> from
		834	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
727	stopping it.	835	before stopping it.
728		836
729	As an example, libev itself uses this for its internal signal pipe: It is	837	As an example, libev itself uses this for its internal signal pipe: It
730	not visible to the libev user and should not keep C<ev_loop> from exiting	838	is not visible to the libev user and should not keep C<ev_run> from
731	if no event watchers registered by it are active. It is also an excellent	839	exiting if no event watchers registered by it are active. It is also an
732	way to do this for generic recurring timers or from within third-party	840	excellent way to do this for generic recurring timers or from within
733	libraries. Just remember to I<unref after start> and I<ref before stop>	841	third-party libraries. Just remember to I<unref after start> and I<ref
734	(but only if the watcher wasn't active before, or was active before,	842	before stop> (but only if the watcher wasn't active before, or was active
735	respectively).	843	before, respectively. Note also that libev might stop watchers itself
		844	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		845	in the callback).
736		846
737	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	847	Example: Create a signal watcher, but keep it from keeping C<ev_run>
738	running when nothing else is active.	848	running when nothing else is active.
739		849
740	ev_signal exitsig;	850	ev_signal exitsig;
741	ev_signal_init (&exitsig, sig_cb, SIGINT);	851	ev_signal_init (&exitsig, sig_cb, SIGINT);
742	ev_signal_start (loop, &exitsig);	852	ev_signal_start (loop, &exitsig);
…		…
769		879
770	By setting a higher I<io collect interval> you allow libev to spend more	880	By setting a higher I<io collect interval> you allow libev to spend more
771	time collecting I/O events, so you can handle more events per iteration,	881	time collecting I/O events, so you can handle more events per iteration,
772	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	882	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
773	C<ev_timer>) will be not affected. Setting this to a non-null value will	883	C<ev_timer>) will be not affected. Setting this to a non-null value will
774	introduce an additional C<ev_sleep ()> call into most loop iterations.	884	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		885	sleep time ensures that libev will not poll for I/O events more often then
		886	once per this interval, on average.
775		887
776	Likewise, by setting a higher I<timeout collect interval> you allow libev	888	Likewise, by setting a higher I<timeout collect interval> you allow libev
777	to spend more time collecting timeouts, at the expense of increased	889	to spend more time collecting timeouts, at the expense of increased
778	latency/jitter/inexactness (the watcher callback will be called	890	latency/jitter/inexactness (the watcher callback will be called
779	later). C<ev_io> watchers will not be affected. Setting this to a non-null	891	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
781		893
782	Many (busy) programs can usually benefit by setting the I/O collect	894	Many (busy) programs can usually benefit by setting the I/O collect
783	interval to a value near C<0.1> or so, which is often enough for	895	interval to a value near C<0.1> or so, which is often enough for
784	interactive servers (of course not for games), likewise for timeouts. It	896	interactive servers (of course not for games), likewise for timeouts. It
785	usually doesn't make much sense to set it to a lower value than C<0.01>,	897	usually doesn't make much sense to set it to a lower value than C<0.01>,
786	as this approaches the timing granularity of most systems.	898	as this approaches the timing granularity of most systems. Note that if
		899	you do transactions with the outside world and you can't increase the
		900	parallelity, then this setting will limit your transaction rate (if you
		901	need to poll once per transaction and the I/O collect interval is 0.01,
		902	then you can't do more than 100 transactions per second).
787		903
788	Setting the I<timeout collect interval> can improve the opportunity for	904	Setting the I<timeout collect interval> can improve the opportunity for
789	saving power, as the program will "bundle" timer callback invocations that	905	saving power, as the program will "bundle" timer callback invocations that
790	are "near" in time together, by delaying some, thus reducing the number of	906	are "near" in time together, by delaying some, thus reducing the number of
791	times the process sleeps and wakes up again. Another useful technique to	907	times the process sleeps and wakes up again. Another useful technique to
792	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	908	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
793	they fire on, say, one-second boundaries only.	909	they fire on, say, one-second boundaries only.
794		910
		911	Example: we only need 0.1s timeout granularity, and we wish not to poll
		912	more often than 100 times per second:
		913
		914	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		915	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		916
		917	=item ev_invoke_pending (loop)
		918
		919	This call will simply invoke all pending watchers while resetting their
		920	pending state. Normally, C<ev_run> does this automatically when required,
		921	but when overriding the invoke callback this call comes handy. This
		922	function can be invoked from a watcher - this can be useful for example
		923	when you want to do some lengthy calculation and want to pass further
		924	event handling to another thread (you still have to make sure only one
		925	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		926
		927	=item int ev_pending_count (loop)
		928
		929	Returns the number of pending watchers - zero indicates that no watchers
		930	are pending.
		931
		932	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		933
		934	This overrides the invoke pending functionality of the loop: Instead of
		935	invoking all pending watchers when there are any, C<ev_run> will call
		936	this callback instead. This is useful, for example, when you want to
		937	invoke the actual watchers inside another context (another thread etc.).
		938
		939	If you want to reset the callback, use C<ev_invoke_pending> as new
		940	callback.
		941
		942	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		943
		944	Sometimes you want to share the same loop between multiple threads. This
		945	can be done relatively simply by putting mutex_lock/unlock calls around
		946	each call to a libev function.
		947
		948	However, C<ev_run> can run an indefinite time, so it is not feasible
		949	to wait for it to return. One way around this is to wake up the event
		950	loop via C<ev_break> and C<av_async_send>, another way is to set these
		951	I<release> and I<acquire> callbacks on the loop.
		952
		953	When set, then C<release> will be called just before the thread is
		954	suspended waiting for new events, and C<acquire> is called just
		955	afterwards.
		956
		957	Ideally, C<release> will just call your mutex_unlock function, and
		958	C<acquire> will just call the mutex_lock function again.
		959
		960	While event loop modifications are allowed between invocations of
		961	C<release> and C<acquire> (that's their only purpose after all), no
		962	modifications done will affect the event loop, i.e. adding watchers will
		963	have no effect on the set of file descriptors being watched, or the time
		964	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		965	to take note of any changes you made.
		966
		967	In theory, threads executing C<ev_run> will be async-cancel safe between
		968	invocations of C<release> and C<acquire>.
		969
		970	See also the locking example in the C<THREADS> section later in this
		971	document.
		972
		973	=item ev_set_userdata (loop, void *data)
		974
		975	=item ev_userdata (loop)
		976
		977	Set and retrieve a single C<void *> associated with a loop. When
		978	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		979	C<0.>
		980
		981	These two functions can be used to associate arbitrary data with a loop,
		982	and are intended solely for the C<invoke_pending_cb>, C<release> and
		983	C<acquire> callbacks described above, but of course can be (ab-)used for
		984	any other purpose as well.
		985
795	=item ev_loop_verify (loop)	986	=item ev_verify (loop)
796		987
797	This function only does something when C<EV_VERIFY> support has been	988	This function only does something when C<EV_VERIFY> support has been
798	compiled in, which is the default for non-minimal builds. It tries to go	989	compiled in, which is the default for non-minimal builds. It tries to go
799	through all internal structures and checks them for validity. If anything	990	through all internal structures and checks them for validity. If anything
800	is found to be inconsistent, it will print an error message to standard	991	is found to be inconsistent, it will print an error message to standard
…		…
811		1002
812	In the following description, uppercase C<TYPE> in names stands for the	1003	In the following description, uppercase C<TYPE> in names stands for the
813	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1004	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
814	watchers and C<ev_io_start> for I/O watchers.	1005	watchers and C<ev_io_start> for I/O watchers.
815		1006
816	A watcher is a structure that you create and register to record your	1007	A watcher is an opaque structure that you allocate and register to record
817	interest in some event. For instance, if you want to wait for STDIN to	1008	your interest in some event. To make a concrete example, imagine you want
818	become readable, you would create an C<ev_io> watcher for that:	1009	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1010	for that:
819		1011
820	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1012	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
821	{	1013	{
822	ev_io_stop (w);	1014	ev_io_stop (w);
823	ev_unloop (loop, EVUNLOOP_ALL);	1015	ev_break (loop, EVBREAK_ALL);
824	}	1016	}
825		1017
826	struct ev_loop *loop = ev_default_loop (0);	1018	struct ev_loop *loop = ev_default_loop (0);
827		1019
828	ev_io stdin_watcher;	1020	ev_io stdin_watcher;
829		1021
830	ev_init (&stdin_watcher, my_cb);	1022	ev_init (&stdin_watcher, my_cb);
831	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1023	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
832	ev_io_start (loop, &stdin_watcher);	1024	ev_io_start (loop, &stdin_watcher);
833		1025
834	ev_loop (loop, 0);	1026	ev_run (loop, 0);
835		1027
836	As you can see, you are responsible for allocating the memory for your	1028	As you can see, you are responsible for allocating the memory for your
837	watcher structures (and it is I<usually> a bad idea to do this on the	1029	watcher structures (and it is I<usually> a bad idea to do this on the
838	stack).	1030	stack).
839		1031
840	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1032	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
841	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1033	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
842		1034
843	Each watcher structure must be initialised by a call to C<ev_init	1035	Each watcher structure must be initialised by a call to C<ev_init (watcher
844	(watcher *, callback)>, which expects a callback to be provided. This	1036	*, callback)>, which expects a callback to be provided. This callback is
845	callback gets invoked each time the event occurs (or, in the case of I/O	1037	invoked each time the event occurs (or, in the case of I/O watchers, each
846	watchers, each time the event loop detects that the file descriptor given	1038	time the event loop detects that the file descriptor given is readable
847	is readable and/or writable).	1039	and/or writable).
848		1040
849	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1041	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
850	macro to configure it, with arguments specific to the watcher type. There	1042	macro to configure it, with arguments specific to the watcher type. There
851	is also a macro to combine initialisation and setting in one call: C<<	1043	is also a macro to combine initialisation and setting in one call: C<<
852	ev_TYPE_init (watcher *, callback, ...) >>.	1044	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
875	=item C<EV_WRITE>	1067	=item C<EV_WRITE>
876		1068
877	The file descriptor in the C<ev_io> watcher has become readable and/or	1069	The file descriptor in the C<ev_io> watcher has become readable and/or
878	writable.	1070	writable.
879		1071
880	=item C<EV_TIMEOUT>	1072	=item C<EV_TIMER>
881		1073
882	The C<ev_timer> watcher has timed out.	1074	The C<ev_timer> watcher has timed out.
883		1075
884	=item C<EV_PERIODIC>	1076	=item C<EV_PERIODIC>
885		1077
…		…
903		1095
904	=item C<EV_PREPARE>	1096	=item C<EV_PREPARE>
905		1097
906	=item C<EV_CHECK>	1098	=item C<EV_CHECK>
907		1099
908	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1100	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts
909	to gather new events, and all C<ev_check> watchers are invoked just after	1101	to gather new events, and all C<ev_check> watchers are invoked just after
910	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1102	C<ev_run> has gathered them, but before it invokes any callbacks for any
911	received events. Callbacks of both watcher types can start and stop as	1103	received events. Callbacks of both watcher types can start and stop as
912	many watchers as they want, and all of them will be taken into account	1104	many watchers as they want, and all of them will be taken into account
913	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1105	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
914	C<ev_loop> from blocking).	1106	C<ev_run> from blocking).
915		1107
916	=item C<EV_EMBED>	1108	=item C<EV_EMBED>
917		1109
918	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1110	The embedded event loop specified in the C<ev_embed> watcher needs attention.
919		1111
…		…
923	C<ev_fork>).	1115	C<ev_fork>).
924		1116
925	=item C<EV_ASYNC>	1117	=item C<EV_ASYNC>
926		1118
927	The given async watcher has been asynchronously notified (see C<ev_async>).	1119	The given async watcher has been asynchronously notified (see C<ev_async>).
		1120
		1121	=item C<EV_CUSTOM>
		1122
		1123	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1124	by libev users to signal watchers (e.g. via C<ev_feed_event>).
928		1125
929	=item C<EV_ERROR>	1126	=item C<EV_ERROR>
930		1127
931	An unspecified error has occurred, the watcher has been stopped. This might	1128	An unspecified error has occurred, the watcher has been stopped. This might
932	happen because the watcher could not be properly started because libev	1129	happen because the watcher could not be properly started because libev
…		…
945	programs, though, as the fd could already be closed and reused for another	1142	programs, though, as the fd could already be closed and reused for another
946	thing, so beware.	1143	thing, so beware.
947		1144
948	=back	1145	=back
949		1146
		1147	=head2 WATCHER STATES
		1148
		1149	There are various watcher states mentioned throughout this manual -
		1150	active, pending and so on. In this section these states and the rules to
		1151	transition between them will be described in more detail - and while these
		1152	rules might look complicated, they usually do "the right thing".
		1153
		1154	=over 4
		1155
		1156	=item initialiased
		1157
		1158	Before a watcher can be registered with the event looop it has to be
		1159	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1160	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1161
		1162	In this state it is simply some block of memory that is suitable for use
		1163	in an event loop. It can be moved around, freed, reused etc. at will.
		1164
		1165	=item started/running/active
		1166
		1167	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1168	property of the event loop, and is actively waiting for events. While in
		1169	this state it cannot be accessed (except in a few documented ways), moved,
		1170	freed or anything else - the only legal thing is to keep a pointer to it,
		1171	and call libev functions on it that are documented to work on active watchers.
		1172
		1173	=item pending
		1174
		1175	If a watcher is active and libev determines that an event it is interested
		1176	in has occurred (such as a timer expiring), it will become pending. It will
		1177	stay in this pending state until either it is stopped or its callback is
		1178	about to be invoked, so it is not normally pending inside the watcher
		1179	callback.
		1180
		1181	The watcher might or might not be active while it is pending (for example,
		1182	an expired non-repeating timer can be pending but no longer active). If it
		1183	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1184	but it is still property of the event loop at this time, so cannot be
		1185	moved, freed or reused. And if it is active the rules described in the
		1186	previous item still apply.
		1187
		1188	It is also possible to feed an event on a watcher that is not active (e.g.
		1189	via C<ev_feed_event>), in which case it becomes pending without being
		1190	active.
		1191
		1192	=item stopped
		1193
		1194	A watcher can be stopped implicitly by libev (in which case it might still
		1195	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1196	latter will clear any pending state the watcher might be in, regardless
		1197	of whether it was active or not, so stopping a watcher explicitly before
		1198	freeing it is often a good idea.
		1199
		1200	While stopped (and not pending) the watcher is essentially in the
		1201	initialised state, that is it can be reused, moved, modified in any way
		1202	you wish.
		1203
		1204	=back
		1205
950	=head2 GENERIC WATCHER FUNCTIONS	1206	=head2 GENERIC WATCHER FUNCTIONS
951		1207
952	=over 4	1208	=over 4
953		1209
954	=item C<ev_init> (ev_TYPE *watcher, callback)	1210	=item C<ev_init> (ev_TYPE *watcher, callback)
…		…
970		1226
971	ev_io w;	1227	ev_io w;
972	ev_init (&w, my_cb);	1228	ev_init (&w, my_cb);
973	ev_io_set (&w, STDIN_FILENO, EV_READ);	1229	ev_io_set (&w, STDIN_FILENO, EV_READ);
974		1230
975	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1231	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
976		1232
977	This macro initialises the type-specific parts of a watcher. You need to	1233	This macro initialises the type-specific parts of a watcher. You need to
978	call C<ev_init> at least once before you call this macro, but you can	1234	call C<ev_init> at least once before you call this macro, but you can
979	call C<ev_TYPE_set> any number of times. You must not, however, call this	1235	call C<ev_TYPE_set> any number of times. You must not, however, call this
980	macro on a watcher that is active (it can be pending, however, which is a	1236	macro on a watcher that is active (it can be pending, however, which is a
…		…
993		1249
994	Example: Initialise and set an C<ev_io> watcher in one step.	1250	Example: Initialise and set an C<ev_io> watcher in one step.
995		1251
996	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1252	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
997		1253
998	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1254	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
999		1255
1000	Starts (activates) the given watcher. Only active watchers will receive	1256	Starts (activates) the given watcher. Only active watchers will receive
1001	events. If the watcher is already active nothing will happen.	1257	events. If the watcher is already active nothing will happen.
1002		1258
1003	Example: Start the C<ev_io> watcher that is being abused as example in this	1259	Example: Start the C<ev_io> watcher that is being abused as example in this
1004	whole section.	1260	whole section.
1005		1261
1006	ev_io_start (EV_DEFAULT_UC, &w);	1262	ev_io_start (EV_DEFAULT_UC, &w);
1007		1263
1008	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1264	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1009		1265
1010	Stops the given watcher if active, and clears the pending status (whether	1266	Stops the given watcher if active, and clears the pending status (whether
1011	the watcher was active or not).	1267	the watcher was active or not).
1012		1268
1013	It is possible that stopped watchers are pending - for example,	1269	It is possible that stopped watchers are pending - for example,
…		…
1038	=item ev_cb_set (ev_TYPE *watcher, callback)	1294	=item ev_cb_set (ev_TYPE *watcher, callback)
1039		1295
1040	Change the callback. You can change the callback at virtually any time	1296	Change the callback. You can change the callback at virtually any time
1041	(modulo threads).	1297	(modulo threads).
1042		1298
1043	=item ev_set_priority (ev_TYPE *watcher, priority)	1299	=item ev_set_priority (ev_TYPE *watcher, int priority)
1044		1300
1045	=item int ev_priority (ev_TYPE *watcher)	1301	=item int ev_priority (ev_TYPE *watcher)
1046		1302
1047	Set and query the priority of the watcher. The priority is a small	1303	Set and query the priority of the watcher. The priority is a small
1048	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1304	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1049	(default: C<-2>). Pending watchers with higher priority will be invoked	1305	(default: C<-2>). Pending watchers with higher priority will be invoked
1050	before watchers with lower priority, but priority will not keep watchers	1306	before watchers with lower priority, but priority will not keep watchers
1051	from being executed (except for C<ev_idle> watchers).	1307	from being executed (except for C<ev_idle> watchers).
1052		1308
1053	This means that priorities are I<only> used for ordering callback
1054	invocation after new events have been received. This is useful, for
1055	example, to reduce latency after idling, or more often, to bind two
1056	watchers on the same event and make sure one is called first.
1057
1058	If you need to suppress invocation when higher priority events are pending	1309	If you need to suppress invocation when higher priority events are pending
1059	you need to look at C<ev_idle> watchers, which provide this functionality.	1310	you need to look at C<ev_idle> watchers, which provide this functionality.
1060		1311
1061	You I<must not> change the priority of a watcher as long as it is active or	1312	You I<must not> change the priority of a watcher as long as it is active or
1062	pending.	1313	pending.
1063
1064	The default priority used by watchers when no priority has been set is
1065	always C<0>, which is supposed to not be too high and not be too low :).
1066		1314
1067	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1315	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1068	fine, as long as you do not mind that the priority value you query might	1316	fine, as long as you do not mind that the priority value you query might
1069	or might not have been clamped to the valid range.	1317	or might not have been clamped to the valid range.
		1318
		1319	The default priority used by watchers when no priority has been set is
		1320	always C<0>, which is supposed to not be too high and not be too low :).
		1321
		1322	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1323	priorities.
1070		1324
1071	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1325	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1072		1326
1073	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1327	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1074	C<loop> nor C<revents> need to be valid as long as the watcher callback	1328	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1081	returns its C<revents> bitset (as if its callback was invoked). If the	1335	returns its C<revents> bitset (as if its callback was invoked). If the
1082	watcher isn't pending it does nothing and returns C<0>.	1336	watcher isn't pending it does nothing and returns C<0>.
1083		1337
1084	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1338	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1085	callback to be invoked, which can be accomplished with this function.	1339	callback to be invoked, which can be accomplished with this function.
		1340
		1341	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1342
		1343	Feeds the given event set into the event loop, as if the specified event
		1344	had happened for the specified watcher (which must be a pointer to an
		1345	initialised but not necessarily started event watcher). Obviously you must
		1346	not free the watcher as long as it has pending events.
		1347
		1348	Stopping the watcher, letting libev invoke it, or calling
		1349	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1350	not started in the first place.
		1351
		1352	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1353	functions that do not need a watcher.
1086		1354
1087	=back	1355	=back
1088		1356
1089		1357
1090	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1358	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1139	#include <stddef.h>	1407	#include <stddef.h>
1140		1408
1141	static void	1409	static void
1142	t1_cb (EV_P_ ev_timer *w, int revents)	1410	t1_cb (EV_P_ ev_timer *w, int revents)
1143	{	1411	{
1144	struct my_biggy big = (struct my_biggy *	1412	struct my_biggy big = (struct my_biggy *)
1145	(((char *)w) - offsetof (struct my_biggy, t1));	1413	(((char *)w) - offsetof (struct my_biggy, t1));
1146	}	1414	}
1147		1415
1148	static void	1416	static void
1149	t2_cb (EV_P_ ev_timer *w, int revents)	1417	t2_cb (EV_P_ ev_timer *w, int revents)
1150	{	1418	{
1151	struct my_biggy big = (struct my_biggy *	1419	struct my_biggy big = (struct my_biggy *)
1152	(((char *)w) - offsetof (struct my_biggy, t2));	1420	(((char *)w) - offsetof (struct my_biggy, t2));
1153	}	1421	}
		1422
		1423	=head2 WATCHER PRIORITY MODELS
		1424
		1425	Many event loops support I<watcher priorities>, which are usually small
		1426	integers that influence the ordering of event callback invocation
		1427	between watchers in some way, all else being equal.
		1428
		1429	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1430	description for the more technical details such as the actual priority
		1431	range.
		1432
		1433	There are two common ways how these these priorities are being interpreted
		1434	by event loops:
		1435
		1436	In the more common lock-out model, higher priorities "lock out" invocation
		1437	of lower priority watchers, which means as long as higher priority
		1438	watchers receive events, lower priority watchers are not being invoked.
		1439
		1440	The less common only-for-ordering model uses priorities solely to order
		1441	callback invocation within a single event loop iteration: Higher priority
		1442	watchers are invoked before lower priority ones, but they all get invoked
		1443	before polling for new events.
		1444
		1445	Libev uses the second (only-for-ordering) model for all its watchers
		1446	except for idle watchers (which use the lock-out model).
		1447
		1448	The rationale behind this is that implementing the lock-out model for
		1449	watchers is not well supported by most kernel interfaces, and most event
		1450	libraries will just poll for the same events again and again as long as
		1451	their callbacks have not been executed, which is very inefficient in the
		1452	common case of one high-priority watcher locking out a mass of lower
		1453	priority ones.
		1454
		1455	Static (ordering) priorities are most useful when you have two or more
		1456	watchers handling the same resource: a typical usage example is having an
		1457	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1458	timeouts. Under load, data might be received while the program handles
		1459	other jobs, but since timers normally get invoked first, the timeout
		1460	handler will be executed before checking for data. In that case, giving
		1461	the timer a lower priority than the I/O watcher ensures that I/O will be
		1462	handled first even under adverse conditions (which is usually, but not
		1463	always, what you want).
		1464
		1465	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1466	will only be executed when no same or higher priority watchers have
		1467	received events, they can be used to implement the "lock-out" model when
		1468	required.
		1469
		1470	For example, to emulate how many other event libraries handle priorities,
		1471	you can associate an C<ev_idle> watcher to each such watcher, and in
		1472	the normal watcher callback, you just start the idle watcher. The real
		1473	processing is done in the idle watcher callback. This causes libev to
		1474	continuously poll and process kernel event data for the watcher, but when
		1475	the lock-out case is known to be rare (which in turn is rare :), this is
		1476	workable.
		1477
		1478	Usually, however, the lock-out model implemented that way will perform
		1479	miserably under the type of load it was designed to handle. In that case,
		1480	it might be preferable to stop the real watcher before starting the
		1481	idle watcher, so the kernel will not have to process the event in case
		1482	the actual processing will be delayed for considerable time.
		1483
		1484	Here is an example of an I/O watcher that should run at a strictly lower
		1485	priority than the default, and which should only process data when no
		1486	other events are pending:
		1487
		1488	ev_idle idle; // actual processing watcher
		1489	ev_io io; // actual event watcher
		1490
		1491	static void
		1492	io_cb (EV_P_ ev_io *w, int revents)
		1493	{
		1494	// stop the I/O watcher, we received the event, but
		1495	// are not yet ready to handle it.
		1496	ev_io_stop (EV_A_ w);
		1497
		1498	// start the idle watcher to handle the actual event.
		1499	// it will not be executed as long as other watchers
		1500	// with the default priority are receiving events.
		1501	ev_idle_start (EV_A_ &idle);
		1502	}
		1503
		1504	static void
		1505	idle_cb (EV_P_ ev_idle *w, int revents)
		1506	{
		1507	// actual processing
		1508	read (STDIN_FILENO, ...);
		1509
		1510	// have to start the I/O watcher again, as
		1511	// we have handled the event
		1512	ev_io_start (EV_P_ &io);
		1513	}
		1514
		1515	// initialisation
		1516	ev_idle_init (&idle, idle_cb);
		1517	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1518	ev_io_start (EV_DEFAULT_ &io);
		1519
		1520	In the "real" world, it might also be beneficial to start a timer, so that
		1521	low-priority connections can not be locked out forever under load. This
		1522	enables your program to keep a lower latency for important connections
		1523	during short periods of high load, while not completely locking out less
		1524	important ones.
1154		1525
1155		1526
1156	=head1 WATCHER TYPES	1527	=head1 WATCHER TYPES
1157		1528
1158	This section describes each watcher in detail, but will not repeat	1529	This section describes each watcher in detail, but will not repeat
…		…
1184	descriptors to non-blocking mode is also usually a good idea (but not	1555	descriptors to non-blocking mode is also usually a good idea (but not
1185	required if you know what you are doing).	1556	required if you know what you are doing).
1186		1557
1187	If you cannot use non-blocking mode, then force the use of a	1558	If you cannot use non-blocking mode, then force the use of a
1188	known-to-be-good backend (at the time of this writing, this includes only	1559	known-to-be-good backend (at the time of this writing, this includes only
1189	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1560	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1561	descriptors for which non-blocking operation makes no sense (such as
		1562	files) - libev doesn't guarantee any specific behaviour in that case.
1190		1563
1191	Another thing you have to watch out for is that it is quite easy to	1564	Another thing you have to watch out for is that it is quite easy to
1192	receive "spurious" readiness notifications, that is your callback might	1565	receive "spurious" readiness notifications, that is your callback might
1193	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1566	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1194	because there is no data. Not only are some backends known to create a	1567	because there is no data. Not only are some backends known to create a
…		…
1259		1632
1260	So when you encounter spurious, unexplained daemon exits, make sure you	1633	So when you encounter spurious, unexplained daemon exits, make sure you
1261	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1634	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1262	somewhere, as that would have given you a big clue).	1635	somewhere, as that would have given you a big clue).
1263		1636
		1637	=head3 The special problem of accept()ing when you can't
		1638
		1639	Many implementations of the POSIX C<accept> function (for example,
		1640	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1641	connection from the pending queue in all error cases.
		1642
		1643	For example, larger servers often run out of file descriptors (because
		1644	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1645	rejecting the connection, leading to libev signalling readiness on
		1646	the next iteration again (the connection still exists after all), and
		1647	typically causing the program to loop at 100% CPU usage.
		1648
		1649	Unfortunately, the set of errors that cause this issue differs between
		1650	operating systems, there is usually little the app can do to remedy the
		1651	situation, and no known thread-safe method of removing the connection to
		1652	cope with overload is known (to me).
		1653
		1654	One of the easiest ways to handle this situation is to just ignore it
		1655	- when the program encounters an overload, it will just loop until the
		1656	situation is over. While this is a form of busy waiting, no OS offers an
		1657	event-based way to handle this situation, so it's the best one can do.
		1658
		1659	A better way to handle the situation is to log any errors other than
		1660	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1661	messages, and continue as usual, which at least gives the user an idea of
		1662	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1663	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1664	usage.
		1665
		1666	If your program is single-threaded, then you could also keep a dummy file
		1667	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1668	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1669	close that fd, and create a new dummy fd. This will gracefully refuse
		1670	clients under typical overload conditions.
		1671
		1672	The last way to handle it is to simply log the error and C<exit>, as
		1673	is often done with C<malloc> failures, but this results in an easy
		1674	opportunity for a DoS attack.
1264		1675
1265	=head3 Watcher-Specific Functions	1676	=head3 Watcher-Specific Functions
1266		1677
1267	=over 4	1678	=over 4
1268		1679
…		…
1300	...	1711	...
1301	struct ev_loop *loop = ev_default_init (0);	1712	struct ev_loop *loop = ev_default_init (0);
1302	ev_io stdin_readable;	1713	ev_io stdin_readable;
1303	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1714	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1304	ev_io_start (loop, &stdin_readable);	1715	ev_io_start (loop, &stdin_readable);
1305	ev_loop (loop, 0);	1716	ev_run (loop, 0);
1306		1717
1307		1718
1308	=head2 C<ev_timer> - relative and optionally repeating timeouts	1719	=head2 C<ev_timer> - relative and optionally repeating timeouts
1309		1720
1310	Timer watchers are simple relative timers that generate an event after a	1721	Timer watchers are simple relative timers that generate an event after a
…		…
1315	year, it will still time out after (roughly) one hour. "Roughly" because	1726	year, it will still time out after (roughly) one hour. "Roughly" because
1316	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1727	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1317	monotonic clock option helps a lot here).	1728	monotonic clock option helps a lot here).
1318		1729
1319	The callback is guaranteed to be invoked only I<after> its timeout has	1730	The callback is guaranteed to be invoked only I<after> its timeout has
1320	passed, but if multiple timers become ready during the same loop iteration	1731	passed (not I<at>, so on systems with very low-resolution clocks this
1321	then order of execution is undefined.	1732	might introduce a small delay). If multiple timers become ready during the
		1733	same loop iteration then the ones with earlier time-out values are invoked
		1734	before ones of the same priority with later time-out values (but this is
		1735	no longer true when a callback calls C<ev_run> recursively).
1322		1736
1323	=head3 Be smart about timeouts	1737	=head3 Be smart about timeouts
1324		1738
1325	Many real-world problems involve some kind of timeout, usually for error	1739	Many real-world problems involve some kind of timeout, usually for error
1326	recovery. A typical example is an HTTP request - if the other side hangs,	1740	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1370	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1784	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1371	member and C<ev_timer_again>.	1785	member and C<ev_timer_again>.
1372		1786
1373	At start:	1787	At start:
1374		1788
1375	ev_timer_init (timer, callback);	1789	ev_init (timer, callback);
1376	timer->repeat = 60.;	1790	timer->repeat = 60.;
1377	ev_timer_again (loop, timer);	1791	ev_timer_again (loop, timer);
1378		1792
1379	Each time there is some activity:	1793	Each time there is some activity:
1380		1794
…		…
1412	ev_tstamp timeout = last_activity + 60.;	1826	ev_tstamp timeout = last_activity + 60.;
1413		1827
1414	// if last_activity + 60. is older than now, we did time out	1828	// if last_activity + 60. is older than now, we did time out
1415	if (timeout < now)	1829	if (timeout < now)
1416	{	1830	{
1417	// timeout occured, take action	1831	// timeout occurred, take action
1418	}	1832	}
1419	else	1833	else
1420	{	1834	{
1421	// callback was invoked, but there was some activity, re-arm	1835	// callback was invoked, but there was some activity, re-arm
1422	// the watcher to fire in last_activity + 60, which is	1836	// the watcher to fire in last_activity + 60, which is
1423	// guaranteed to be in the future, so "again" is positive:	1837	// guaranteed to be in the future, so "again" is positive:
1424	w->again = timeout - now;	1838	w->repeat = timeout - now;
1425	ev_timer_again (EV_A_ w);	1839	ev_timer_again (EV_A_ w);
1426	}	1840	}
1427	}	1841	}
1428		1842
1429	To summarise the callback: first calculate the real timeout (defined	1843	To summarise the callback: first calculate the real timeout (defined
…		…
1442		1856
1443	To start the timer, simply initialise the watcher and set C<last_activity>	1857	To start the timer, simply initialise the watcher and set C<last_activity>
1444	to the current time (meaning we just have some activity :), then call the	1858	to the current time (meaning we just have some activity :), then call the
1445	callback, which will "do the right thing" and start the timer:	1859	callback, which will "do the right thing" and start the timer:
1446		1860
1447	ev_timer_init (timer, callback);	1861	ev_init (timer, callback);
1448	last_activity = ev_now (loop);	1862	last_activity = ev_now (loop);
1449	callback (loop, timer, EV_TIMEOUT);	1863	callback (loop, timer, EV_TIMER);
1450		1864
1451	And when there is some activity, simply store the current time in	1865	And when there is some activity, simply store the current time in
1452	C<last_activity>, no libev calls at all:	1866	C<last_activity>, no libev calls at all:
1453		1867
1454	last_actiivty = ev_now (loop);	1868	last_activity = ev_now (loop);
1455		1869
1456	This technique is slightly more complex, but in most cases where the	1870	This technique is slightly more complex, but in most cases where the
1457	time-out is unlikely to be triggered, much more efficient.	1871	time-out is unlikely to be triggered, much more efficient.
1458		1872
1459	Changing the timeout is trivial as well (if it isn't hard-coded in the	1873	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1497		1911
1498	=head3 The special problem of time updates	1912	=head3 The special problem of time updates
1499		1913
1500	Establishing the current time is a costly operation (it usually takes at	1914	Establishing the current time is a costly operation (it usually takes at
1501	least two system calls): EV therefore updates its idea of the current	1915	least two system calls): EV therefore updates its idea of the current
1502	time only before and after C<ev_loop> collects new events, which causes a	1916	time only before and after C<ev_run> collects new events, which causes a
1503	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1917	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1504	lots of events in one iteration.	1918	lots of events in one iteration.
1505		1919
1506	The relative timeouts are calculated relative to the C<ev_now ()>	1920	The relative timeouts are calculated relative to the C<ev_now ()>
1507	time. This is usually the right thing as this timestamp refers to the time	1921	time. This is usually the right thing as this timestamp refers to the time
…		…
1513		1927
1514	If the event loop is suspended for a long time, you can also force an	1928	If the event loop is suspended for a long time, you can also force an
1515	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1929	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1516	()>.	1930	()>.
1517		1931
		1932	=head3 The special problems of suspended animation
		1933
		1934	When you leave the server world it is quite customary to hit machines that
		1935	can suspend/hibernate - what happens to the clocks during such a suspend?
		1936
		1937	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1938	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1939	to run until the system is suspended, but they will not advance while the
		1940	system is suspended. That means, on resume, it will be as if the program
		1941	was frozen for a few seconds, but the suspend time will not be counted
		1942	towards C<ev_timer> when a monotonic clock source is used. The real time
		1943	clock advanced as expected, but if it is used as sole clocksource, then a
		1944	long suspend would be detected as a time jump by libev, and timers would
		1945	be adjusted accordingly.
		1946
		1947	I would not be surprised to see different behaviour in different between
		1948	operating systems, OS versions or even different hardware.
		1949
		1950	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1951	time jump in the monotonic clocks and the realtime clock. If the program
		1952	is suspended for a very long time, and monotonic clock sources are in use,
		1953	then you can expect C<ev_timer>s to expire as the full suspension time
		1954	will be counted towards the timers. When no monotonic clock source is in
		1955	use, then libev will again assume a timejump and adjust accordingly.
		1956
		1957	It might be beneficial for this latter case to call C<ev_suspend>
		1958	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1959	deterministic behaviour in this case (you can do nothing against
		1960	C<SIGSTOP>).
		1961
1518	=head3 Watcher-Specific Functions and Data Members	1962	=head3 Watcher-Specific Functions and Data Members
1519		1963
1520	=over 4	1964	=over 4
1521		1965
1522	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1966	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1545	If the timer is started but non-repeating, stop it (as if it timed out).	1989	If the timer is started but non-repeating, stop it (as if it timed out).
1546		1990
1547	If the timer is repeating, either start it if necessary (with the	1991	If the timer is repeating, either start it if necessary (with the
1548	C<repeat> value), or reset the running timer to the C<repeat> value.	1992	C<repeat> value), or reset the running timer to the C<repeat> value.
1549		1993
1550	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1994	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1551	usage example.	1995	usage example.
		1996
		1997	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		1998
		1999	Returns the remaining time until a timer fires. If the timer is active,
		2000	then this time is relative to the current event loop time, otherwise it's
		2001	the timeout value currently configured.
		2002
		2003	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2004	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2005	will return C<4>. When the timer expires and is restarted, it will return
		2006	roughly C<7> (likely slightly less as callback invocation takes some time,
		2007	too), and so on.
1552		2008
1553	=item ev_tstamp repeat [read-write]	2009	=item ev_tstamp repeat [read-write]
1554		2010
1555	The current C<repeat> value. Will be used each time the watcher times out	2011	The current C<repeat> value. Will be used each time the watcher times out
1556	or C<ev_timer_again> is called, and determines the next timeout (if any),	2012	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1582	}	2038	}
1583		2039
1584	ev_timer mytimer;	2040	ev_timer mytimer;
1585	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2041	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1586	ev_timer_again (&mytimer); /* start timer */	2042	ev_timer_again (&mytimer); /* start timer */
1587	ev_loop (loop, 0);	2043	ev_run (loop, 0);
1588		2044
1589	// and in some piece of code that gets executed on any "activity":	2045	// and in some piece of code that gets executed on any "activity":
1590	// reset the timeout to start ticking again at 10 seconds	2046	// reset the timeout to start ticking again at 10 seconds
1591	ev_timer_again (&mytimer);	2047	ev_timer_again (&mytimer);
1592		2048
…		…
1594	=head2 C<ev_periodic> - to cron or not to cron?	2050	=head2 C<ev_periodic> - to cron or not to cron?
1595		2051
1596	Periodic watchers are also timers of a kind, but they are very versatile	2052	Periodic watchers are also timers of a kind, but they are very versatile
1597	(and unfortunately a bit complex).	2053	(and unfortunately a bit complex).
1598		2054
1599	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2055	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1600	but on wall clock time (absolute time). You can tell a periodic watcher	2056	relative time, the physical time that passes) but on wall clock time
1601	to trigger after some specific point in time. For example, if you tell a	2057	(absolute time, the thing you can read on your calender or clock). The
1602	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2058	difference is that wall clock time can run faster or slower than real
1603	+ 10.>, that is, an absolute time not a delay) and then reset your system	2059	time, and time jumps are not uncommon (e.g. when you adjust your
1604	clock to January of the previous year, then it will take more than year	2060	wrist-watch).
1605	to trigger the event (unlike an C<ev_timer>, which would still trigger
1606	roughly 10 seconds later as it uses a relative timeout).
1607		2061
		2062	You can tell a periodic watcher to trigger after some specific point
		2063	in time: for example, if you tell a periodic watcher to trigger "in 10
		2064	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2065	not a delay) and then reset your system clock to January of the previous
		2066	year, then it will take a year or more to trigger the event (unlike an
		2067	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2068	it, as it uses a relative timeout).
		2069
1608	C<ev_periodic>s can also be used to implement vastly more complex timers,	2070	C<ev_periodic> watchers can also be used to implement vastly more complex
1609	such as triggering an event on each "midnight, local time", or other	2071	timers, such as triggering an event on each "midnight, local time", or
1610	complicated rules.	2072	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2073	those cannot react to time jumps.
1611		2074
1612	As with timers, the callback is guaranteed to be invoked only when the	2075	As with timers, the callback is guaranteed to be invoked only when the
1613	time (C<at>) has passed, but if multiple periodic timers become ready	2076	point in time where it is supposed to trigger has passed. If multiple
1614	during the same loop iteration, then order of execution is undefined.	2077	timers become ready during the same loop iteration then the ones with
		2078	earlier time-out values are invoked before ones with later time-out values
		2079	(but this is no longer true when a callback calls C<ev_run> recursively).
1615		2080
1616	=head3 Watcher-Specific Functions and Data Members	2081	=head3 Watcher-Specific Functions and Data Members
1617		2082
1618	=over 4	2083	=over 4
1619		2084
1620	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2085	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1621		2086
1622	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2087	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1623		2088
1624	Lots of arguments, lets sort it out... There are basically three modes of	2089	Lots of arguments, let's sort it out... There are basically three modes of
1625	operation, and we will explain them from simplest to most complex:	2090	operation, and we will explain them from simplest to most complex:
1626		2091
1627	=over 4	2092	=over 4
1628		2093
1629	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2094	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1630		2095
1631	In this configuration the watcher triggers an event after the wall clock	2096	In this configuration the watcher triggers an event after the wall clock
1632	time C<at> has passed. It will not repeat and will not adjust when a time	2097	time C<offset> has passed. It will not repeat and will not adjust when a
1633	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2098	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1634	only run when the system clock reaches or surpasses this time.	2099	will be stopped and invoked when the system clock reaches or surpasses
		2100	this point in time.
1635		2101
1636	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2102	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1637		2103
1638	In this mode the watcher will always be scheduled to time out at the next	2104	In this mode the watcher will always be scheduled to time out at the next
1639	C<at + N * interval> time (for some integer N, which can also be negative)	2105	C<offset + N * interval> time (for some integer N, which can also be
1640	and then repeat, regardless of any time jumps.	2106	negative) and then repeat, regardless of any time jumps. The C<offset>
		2107	argument is merely an offset into the C<interval> periods.
1641		2108
1642	This can be used to create timers that do not drift with respect to the	2109	This can be used to create timers that do not drift with respect to the
1643	system clock, for example, here is a C<ev_periodic> that triggers each	2110	system clock, for example, here is an C<ev_periodic> that triggers each
1644	hour, on the hour:	2111	hour, on the hour (with respect to UTC):
1645		2112
1646	ev_periodic_set (&periodic, 0., 3600., 0);	2113	ev_periodic_set (&periodic, 0., 3600., 0);
1647		2114
1648	This doesn't mean there will always be 3600 seconds in between triggers,	2115	This doesn't mean there will always be 3600 seconds in between triggers,
1649	but only that the callback will be called when the system time shows a	2116	but only that the callback will be called when the system time shows a
1650	full hour (UTC), or more correctly, when the system time is evenly divisible	2117	full hour (UTC), or more correctly, when the system time is evenly divisible
1651	by 3600.	2118	by 3600.
1652		2119
1653	Another way to think about it (for the mathematically inclined) is that	2120	Another way to think about it (for the mathematically inclined) is that
1654	C<ev_periodic> will try to run the callback in this mode at the next possible	2121	C<ev_periodic> will try to run the callback in this mode at the next possible
1655	time where C<time = at (mod interval)>, regardless of any time jumps.	2122	time where C<time = offset (mod interval)>, regardless of any time jumps.
1656		2123
1657	For numerical stability it is preferable that the C<at> value is near	2124	For numerical stability it is preferable that the C<offset> value is near
1658	C<ev_now ()> (the current time), but there is no range requirement for	2125	C<ev_now ()> (the current time), but there is no range requirement for
1659	this value, and in fact is often specified as zero.	2126	this value, and in fact is often specified as zero.
1660		2127
1661	Note also that there is an upper limit to how often a timer can fire (CPU	2128	Note also that there is an upper limit to how often a timer can fire (CPU
1662	speed for example), so if C<interval> is very small then timing stability	2129	speed for example), so if C<interval> is very small then timing stability
1663	will of course deteriorate. Libev itself tries to be exact to be about one	2130	will of course deteriorate. Libev itself tries to be exact to be about one
1664	millisecond (if the OS supports it and the machine is fast enough).	2131	millisecond (if the OS supports it and the machine is fast enough).
1665		2132
1666	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2133	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1667		2134
1668	In this mode the values for C<interval> and C<at> are both being	2135	In this mode the values for C<interval> and C<offset> are both being
1669	ignored. Instead, each time the periodic watcher gets scheduled, the	2136	ignored. Instead, each time the periodic watcher gets scheduled, the
1670	reschedule callback will be called with the watcher as first, and the	2137	reschedule callback will be called with the watcher as first, and the
1671	current time as second argument.	2138	current time as second argument.
1672		2139
1673	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2140	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1674	ever, or make ANY event loop modifications whatsoever>.	2141	or make ANY other event loop modifications whatsoever, unless explicitly
		2142	allowed by documentation here>.
1675		2143
1676	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2144	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1677	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2145	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1678	only event loop modification you are allowed to do).	2146	only event loop modification you are allowed to do).
1679		2147
…		…
1709	a different time than the last time it was called (e.g. in a crond like	2177	a different time than the last time it was called (e.g. in a crond like
1710	program when the crontabs have changed).	2178	program when the crontabs have changed).
1711		2179
1712	=item ev_tstamp ev_periodic_at (ev_periodic *)	2180	=item ev_tstamp ev_periodic_at (ev_periodic *)
1713		2181
1714	When active, returns the absolute time that the watcher is supposed to	2182	When active, returns the absolute time that the watcher is supposed
1715	trigger next.	2183	to trigger next. This is not the same as the C<offset> argument to
		2184	C<ev_periodic_set>, but indeed works even in interval and manual
		2185	rescheduling modes.
1716		2186
1717	=item ev_tstamp offset [read-write]	2187	=item ev_tstamp offset [read-write]
1718		2188
1719	When repeating, this contains the offset value, otherwise this is the	2189	When repeating, this contains the offset value, otherwise this is the
1720	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2190	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2191	although libev might modify this value for better numerical stability).
1721		2192
1722	Can be modified any time, but changes only take effect when the periodic	2193	Can be modified any time, but changes only take effect when the periodic
1723	timer fires or C<ev_periodic_again> is being called.	2194	timer fires or C<ev_periodic_again> is being called.
1724		2195
1725	=item ev_tstamp interval [read-write]	2196	=item ev_tstamp interval [read-write]
…		…
1741	Example: Call a callback every hour, or, more precisely, whenever the	2212	Example: Call a callback every hour, or, more precisely, whenever the
1742	system time is divisible by 3600. The callback invocation times have	2213	system time is divisible by 3600. The callback invocation times have
1743	potentially a lot of jitter, but good long-term stability.	2214	potentially a lot of jitter, but good long-term stability.
1744		2215
1745	static void	2216	static void
1746	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2217	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1747	{	2218	{
1748	... its now a full hour (UTC, or TAI or whatever your clock follows)	2219	... its now a full hour (UTC, or TAI or whatever your clock follows)
1749	}	2220	}
1750		2221
1751	ev_periodic hourly_tick;	2222	ev_periodic hourly_tick;
…		…
1777	Signal watchers will trigger an event when the process receives a specific	2248	Signal watchers will trigger an event when the process receives a specific
1778	signal one or more times. Even though signals are very asynchronous, libev	2249	signal one or more times. Even though signals are very asynchronous, libev
1779	will try it's best to deliver signals synchronously, i.e. as part of the	2250	will try it's best to deliver signals synchronously, i.e. as part of the
1780	normal event processing, like any other event.	2251	normal event processing, like any other event.
1781		2252
1782	If you want signals asynchronously, just use C<sigaction> as you would	2253	If you want signals to be delivered truly asynchronously, just use
1783	do without libev and forget about sharing the signal. You can even use	2254	C<sigaction> as you would do without libev and forget about sharing
1784	C<ev_async> from a signal handler to synchronously wake up an event loop.	2255	the signal. You can even use C<ev_async> from a signal handler to
		2256	synchronously wake up an event loop.
1785		2257
1786	You can configure as many watchers as you like per signal. Only when the	2258	You can configure as many watchers as you like for the same signal, but
		2259	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2260	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2261	C<SIGINT> in both the default loop and another loop at the same time. At
		2262	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2263
1787	first watcher gets started will libev actually register a signal handler	2264	When the first watcher gets started will libev actually register something
1788	with the kernel (thus it coexists with your own signal handlers as long as	2265	with the kernel (thus it coexists with your own signal handlers as long as
1789	you don't register any with libev for the same signal). Similarly, when	2266	you don't register any with libev for the same signal).
1790	the last signal watcher for a signal is stopped, libev will reset the
1791	signal handler to SIG_DFL (regardless of what it was set to before).
1792		2267
1793	If possible and supported, libev will install its handlers with	2268	If possible and supported, libev will install its handlers with
1794	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2269	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1795	interrupted. If you have a problem with system calls getting interrupted by	2270	not be unduly interrupted. If you have a problem with system calls getting
1796	signals you can block all signals in an C<ev_check> watcher and unblock	2271	interrupted by signals you can block all signals in an C<ev_check> watcher
1797	them in an C<ev_prepare> watcher.	2272	and unblock them in an C<ev_prepare> watcher.
		2273
		2274	=head3 The special problem of inheritance over fork/execve/pthread_create
		2275
		2276	Both the signal mask (C<sigprocmask>) and the signal disposition
		2277	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2278	stopping it again), that is, libev might or might not block the signal,
		2279	and might or might not set or restore the installed signal handler.
		2280
		2281	While this does not matter for the signal disposition (libev never
		2282	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2283	C<execve>), this matters for the signal mask: many programs do not expect
		2284	certain signals to be blocked.
		2285
		2286	This means that before calling C<exec> (from the child) you should reset
		2287	the signal mask to whatever "default" you expect (all clear is a good
		2288	choice usually).
		2289
		2290	The simplest way to ensure that the signal mask is reset in the child is
		2291	to install a fork handler with C<pthread_atfork> that resets it. That will
		2292	catch fork calls done by libraries (such as the libc) as well.
		2293
		2294	In current versions of libev, the signal will not be blocked indefinitely
		2295	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2296	the window of opportunity for problems, it will not go away, as libev
		2297	I<has> to modify the signal mask, at least temporarily.
		2298
		2299	So I can't stress this enough: I<If you do not reset your signal mask when
		2300	you expect it to be empty, you have a race condition in your code>. This
		2301	is not a libev-specific thing, this is true for most event libraries.
1798		2302
1799	=head3 Watcher-Specific Functions and Data Members	2303	=head3 Watcher-Specific Functions and Data Members
1800		2304
1801	=over 4	2305	=over 4
1802		2306
…		…
1818	Example: Try to exit cleanly on SIGINT.	2322	Example: Try to exit cleanly on SIGINT.
1819		2323
1820	static void	2324	static void
1821	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2325	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1822	{	2326	{
1823	ev_unloop (loop, EVUNLOOP_ALL);	2327	ev_break (loop, EVBREAK_ALL);
1824	}	2328	}
1825		2329
1826	ev_signal signal_watcher;	2330	ev_signal signal_watcher;
1827	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2331	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1828	ev_signal_start (loop, &signal_watcher);	2332	ev_signal_start (loop, &signal_watcher);
…		…
1834	some child status changes (most typically when a child of yours dies or	2338	some child status changes (most typically when a child of yours dies or
1835	exits). It is permissible to install a child watcher I<after> the child	2339	exits). It is permissible to install a child watcher I<after> the child
1836	has been forked (which implies it might have already exited), as long	2340	has been forked (which implies it might have already exited), as long
1837	as the event loop isn't entered (or is continued from a watcher), i.e.,	2341	as the event loop isn't entered (or is continued from a watcher), i.e.,
1838	forking and then immediately registering a watcher for the child is fine,	2342	forking and then immediately registering a watcher for the child is fine,
1839	but forking and registering a watcher a few event loop iterations later is	2343	but forking and registering a watcher a few event loop iterations later or
1840	not.	2344	in the next callback invocation is not.
1841		2345
1842	Only the default event loop is capable of handling signals, and therefore	2346	Only the default event loop is capable of handling signals, and therefore
1843	you can only register child watchers in the default event loop.	2347	you can only register child watchers in the default event loop.
1844		2348
		2349	Due to some design glitches inside libev, child watchers will always be
		2350	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2351	libev)
		2352
1845	=head3 Process Interaction	2353	=head3 Process Interaction
1846		2354
1847	Libev grabs C<SIGCHLD> as soon as the default event loop is	2355	Libev grabs C<SIGCHLD> as soon as the default event loop is
1848	initialised. This is necessary to guarantee proper behaviour even if	2356	initialised. This is necessary to guarantee proper behaviour even if the
1849	the first child watcher is started after the child exits. The occurrence	2357	first child watcher is started after the child exits. The occurrence
1850	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2358	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1851	synchronously as part of the event loop processing. Libev always reaps all	2359	synchronously as part of the event loop processing. Libev always reaps all
1852	children, even ones not watched.	2360	children, even ones not watched.
1853		2361
1854	=head3 Overriding the Built-In Processing	2362	=head3 Overriding the Built-In Processing
…		…
1864	=head3 Stopping the Child Watcher	2372	=head3 Stopping the Child Watcher
1865		2373
1866	Currently, the child watcher never gets stopped, even when the	2374	Currently, the child watcher never gets stopped, even when the
1867	child terminates, so normally one needs to stop the watcher in the	2375	child terminates, so normally one needs to stop the watcher in the
1868	callback. Future versions of libev might stop the watcher automatically	2376	callback. Future versions of libev might stop the watcher automatically
1869	when a child exit is detected.	2377	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2378	problem).
1870		2379
1871	=head3 Watcher-Specific Functions and Data Members	2380	=head3 Watcher-Specific Functions and Data Members
1872		2381
1873	=over 4	2382	=over 4
1874		2383
…		…
2010	the process. The exception are C<ev_stat> watchers - those call C<stat	2519	the process. The exception are C<ev_stat> watchers - those call C<stat
2011	()>, which is a synchronous operation.	2520	()>, which is a synchronous operation.
2012		2521
2013	For local paths, this usually doesn't matter: unless the system is very	2522	For local paths, this usually doesn't matter: unless the system is very
2014	busy or the intervals between stat's are large, a stat call will be fast,	2523	busy or the intervals between stat's are large, a stat call will be fast,
2015	as the path data is suually in memory already (except when starting the	2524	as the path data is usually in memory already (except when starting the
2016	watcher).	2525	watcher).
2017		2526
2018	For networked file systems, calling C<stat ()> can block an indefinite	2527	For networked file systems, calling C<stat ()> can block an indefinite
2019	time due to network issues, and even under good conditions, a stat call	2528	time due to network issues, and even under good conditions, a stat call
2020	often takes multiple milliseconds.	2529	often takes multiple milliseconds.
…		…
2177		2686
2178	=head3 Watcher-Specific Functions and Data Members	2687	=head3 Watcher-Specific Functions and Data Members
2179		2688
2180	=over 4	2689	=over 4
2181		2690
2182	=item ev_idle_init (ev_signal *, callback)	2691	=item ev_idle_init (ev_idle *, callback)
2183		2692
2184	Initialises and configures the idle watcher - it has no parameters of any	2693	Initialises and configures the idle watcher - it has no parameters of any
2185	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2694	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2186	believe me.	2695	believe me.
2187		2696
…		…
2200	// no longer anything immediate to do.	2709	// no longer anything immediate to do.
2201	}	2710	}
2202		2711
2203	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2712	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2204	ev_idle_init (idle_watcher, idle_cb);	2713	ev_idle_init (idle_watcher, idle_cb);
2205	ev_idle_start (loop, idle_cb);	2714	ev_idle_start (loop, idle_watcher);
2206		2715
2207		2716
2208	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2717	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2209		2718
2210	Prepare and check watchers are usually (but not always) used in pairs:	2719	Prepare and check watchers are usually (but not always) used in pairs:
2211	prepare watchers get invoked before the process blocks and check watchers	2720	prepare watchers get invoked before the process blocks and check watchers
2212	afterwards.	2721	afterwards.
2213		2722
2214	You I<must not> call C<ev_loop> or similar functions that enter	2723	You I<must not> call C<ev_run> or similar functions that enter
2215	the current event loop from either C<ev_prepare> or C<ev_check>	2724	the current event loop from either C<ev_prepare> or C<ev_check>
2216	watchers. Other loops than the current one are fine, however. The	2725	watchers. Other loops than the current one are fine, however. The
2217	rationale behind this is that you do not need to check for recursion in	2726	rationale behind this is that you do not need to check for recursion in
2218	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2727	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2219	C<ev_check> so if you have one watcher of each kind they will always be	2728	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2303	struct pollfd fds [nfd];	2812	struct pollfd fds [nfd];
2304	// actual code will need to loop here and realloc etc.	2813	// actual code will need to loop here and realloc etc.
2305	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2814	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2306		2815
2307	/* the callback is illegal, but won't be called as we stop during check */	2816	/* the callback is illegal, but won't be called as we stop during check */
2308	ev_timer_init (&tw, 0, timeout * 1e-3);	2817	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2309	ev_timer_start (loop, &tw);	2818	ev_timer_start (loop, &tw);
2310		2819
2311	// create one ev_io per pollfd	2820	// create one ev_io per pollfd
2312	for (int i = 0; i < nfd; ++i)	2821	for (int i = 0; i < nfd; ++i)
2313	{	2822	{
…		…
2387		2896
2388	if (timeout >= 0)	2897	if (timeout >= 0)
2389	// create/start timer	2898	// create/start timer
2390		2899
2391	// poll	2900	// poll
2392	ev_loop (EV_A_ 0);	2901	ev_run (EV_A_ 0);
2393		2902
2394	// stop timer again	2903	// stop timer again
2395	if (timeout >= 0)	2904	if (timeout >= 0)
2396	ev_timer_stop (EV_A_ &to);	2905	ev_timer_stop (EV_A_ &to);
2397		2906
…		…
2426	some fds have to be watched and handled very quickly (with low latency),	2935	some fds have to be watched and handled very quickly (with low latency),
2427	and even priorities and idle watchers might have too much overhead. In	2936	and even priorities and idle watchers might have too much overhead. In
2428	this case you would put all the high priority stuff in one loop and all	2937	this case you would put all the high priority stuff in one loop and all
2429	the rest in a second one, and embed the second one in the first.	2938	the rest in a second one, and embed the second one in the first.
2430		2939
2431	As long as the watcher is active, the callback will be invoked every time	2940	As long as the watcher is active, the callback will be invoked every
2432	there might be events pending in the embedded loop. The callback must then	2941	time there might be events pending in the embedded loop. The callback
2433	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2942	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2434	their callbacks (you could also start an idle watcher to give the embedded	2943	sweep and invoke their callbacks (the callback doesn't need to invoke the
2435	loop strictly lower priority for example). You can also set the callback	2944	C<ev_embed_sweep> function directly, it could also start an idle watcher
2436	to C<0>, in which case the embed watcher will automatically execute the	2945	to give the embedded loop strictly lower priority for example).
2437	embedded loop sweep.
2438		2946
2439	As long as the watcher is started it will automatically handle events. The	2947	You can also set the callback to C<0>, in which case the embed watcher
2440	callback will be invoked whenever some events have been handled. You can	2948	will automatically execute the embedded loop sweep whenever necessary.
2441	set the callback to C<0> to avoid having to specify one if you are not
2442	interested in that.
2443		2949
2444	Also, there have not currently been made special provisions for forking:	2950	Fork detection will be handled transparently while the C<ev_embed> watcher
2445	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2951	is active, i.e., the embedded loop will automatically be forked when the
2446	but you will also have to stop and restart any C<ev_embed> watchers	2952	embedding loop forks. In other cases, the user is responsible for calling
2447	yourself - but you can use a fork watcher to handle this automatically,	2953	C<ev_loop_fork> on the embedded loop.
2448	and future versions of libev might do just that.
2449		2954
2450	Unfortunately, not all backends are embeddable: only the ones returned by	2955	Unfortunately, not all backends are embeddable: only the ones returned by
2451	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2956	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2452	portable one.	2957	portable one.
2453		2958
…		…
2479	if you do not want that, you need to temporarily stop the embed watcher).	2984	if you do not want that, you need to temporarily stop the embed watcher).
2480		2985
2481	=item ev_embed_sweep (loop, ev_embed *)	2986	=item ev_embed_sweep (loop, ev_embed *)
2482		2987
2483	Make a single, non-blocking sweep over the embedded loop. This works	2988	Make a single, non-blocking sweep over the embedded loop. This works
2484	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2989	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2485	appropriate way for embedded loops.	2990	appropriate way for embedded loops.
2486		2991
2487	=item struct ev_loop *other [read-only]	2992	=item struct ev_loop *other [read-only]
2488		2993
2489	The embedded event loop.	2994	The embedded event loop.
…		…
2547	event loop blocks next and before C<ev_check> watchers are being called,	3052	event loop blocks next and before C<ev_check> watchers are being called,
2548	and only in the child after the fork. If whoever good citizen calling	3053	and only in the child after the fork. If whoever good citizen calling
2549	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3054	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2550	handlers will be invoked, too, of course.	3055	handlers will be invoked, too, of course.
2551		3056
		3057	=head3 The special problem of life after fork - how is it possible?
		3058
		3059	Most uses of C<fork()> consist of forking, then some simple calls to set
		3060	up/change the process environment, followed by a call to C<exec()>. This
		3061	sequence should be handled by libev without any problems.
		3062
		3063	This changes when the application actually wants to do event handling
		3064	in the child, or both parent in child, in effect "continuing" after the
		3065	fork.
		3066
		3067	The default mode of operation (for libev, with application help to detect
		3068	forks) is to duplicate all the state in the child, as would be expected
		3069	when I<either> the parent I<or> the child process continues.
		3070
		3071	When both processes want to continue using libev, then this is usually the
		3072	wrong result. In that case, usually one process (typically the parent) is
		3073	supposed to continue with all watchers in place as before, while the other
		3074	process typically wants to start fresh, i.e. without any active watchers.
		3075
		3076	The cleanest and most efficient way to achieve that with libev is to
		3077	simply create a new event loop, which of course will be "empty", and
		3078	use that for new watchers. This has the advantage of not touching more
		3079	memory than necessary, and thus avoiding the copy-on-write, and the
		3080	disadvantage of having to use multiple event loops (which do not support
		3081	signal watchers).
		3082
		3083	When this is not possible, or you want to use the default loop for
		3084	other reasons, then in the process that wants to start "fresh", call
		3085	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3086	Destroying the default loop will "orphan" (not stop) all registered
		3087	watchers, so you have to be careful not to execute code that modifies
		3088	those watchers. Note also that in that case, you have to re-register any
		3089	signal watchers.
		3090
2552	=head3 Watcher-Specific Functions and Data Members	3091	=head3 Watcher-Specific Functions and Data Members
2553		3092
2554	=over 4	3093	=over 4
2555		3094
2556	=item ev_fork_init (ev_signal *, callback)	3095	=item ev_fork_init (ev_signal *, callback)
…		…
2560	believe me.	3099	believe me.
2561		3100
2562	=back	3101	=back
2563		3102
2564		3103
2565	=head2 C<ev_async> - how to wake up another event loop	3104	=head2 C<ev_async> - how to wake up an event loop
2566		3105
2567	In general, you cannot use an C<ev_loop> from multiple threads or other	3106	In general, you cannot use an C<ev_run> from multiple threads or other
2568	asynchronous sources such as signal handlers (as opposed to multiple event	3107	asynchronous sources such as signal handlers (as opposed to multiple event
2569	loops - those are of course safe to use in different threads).	3108	loops - those are of course safe to use in different threads).
2570		3109
2571	Sometimes, however, you need to wake up another event loop you do not	3110	Sometimes, however, you need to wake up an event loop you do not control,
2572	control, for example because it belongs to another thread. This is what	3111	for example because it belongs to another thread. This is what C<ev_async>
2573	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3112	watchers do: as long as the C<ev_async> watcher is active, you can signal
2574	can signal it by calling C<ev_async_send>, which is thread- and signal	3113	it by calling C<ev_async_send>, which is thread- and signal safe.
2575	safe.
2576		3114
2577	This functionality is very similar to C<ev_signal> watchers, as signals,	3115	This functionality is very similar to C<ev_signal> watchers, as signals,
2578	too, are asynchronous in nature, and signals, too, will be compressed	3116	too, are asynchronous in nature, and signals, too, will be compressed
2579	(i.e. the number of callback invocations may be less than the number of	3117	(i.e. the number of callback invocations may be less than the number of
2580	C<ev_async_sent> calls).	3118	C<ev_async_sent> calls).
…		…
2585	=head3 Queueing	3123	=head3 Queueing
2586		3124
2587	C<ev_async> does not support queueing of data in any way. The reason	3125	C<ev_async> does not support queueing of data in any way. The reason
2588	is that the author does not know of a simple (or any) algorithm for a	3126	is that the author does not know of a simple (or any) algorithm for a
2589	multiple-writer-single-reader queue that works in all cases and doesn't	3127	multiple-writer-single-reader queue that works in all cases and doesn't
2590	need elaborate support such as pthreads.	3128	need elaborate support such as pthreads or unportable memory access
		3129	semantics.
2591		3130
2592	That means that if you want to queue data, you have to provide your own	3131	That means that if you want to queue data, you have to provide your own
2593	queue. But at least I can tell you how to implement locking around your	3132	queue. But at least I can tell you how to implement locking around your
2594	queue:	3133	queue:
2595		3134
…		…
2684	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3223	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2685	C<ev_feed_event>, this call is safe to do from other threads, signal or	3224	C<ev_feed_event>, this call is safe to do from other threads, signal or
2686	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3225	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2687	section below on what exactly this means).	3226	section below on what exactly this means).
2688		3227
		3228	Note that, as with other watchers in libev, multiple events might get
		3229	compressed into a single callback invocation (another way to look at this
		3230	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3231	reset when the event loop detects that).
		3232
2689	This call incurs the overhead of a system call only once per loop iteration,	3233	This call incurs the overhead of a system call only once per event loop
2690	so while the overhead might be noticeable, it doesn't apply to repeated	3234	iteration, so while the overhead might be noticeable, it doesn't apply to
2691	calls to C<ev_async_send>.	3235	repeated calls to C<ev_async_send> for the same event loop.
2692		3236
2693	=item bool = ev_async_pending (ev_async *)	3237	=item bool = ev_async_pending (ev_async *)
2694		3238
2695	Returns a non-zero value when C<ev_async_send> has been called on the	3239	Returns a non-zero value when C<ev_async_send> has been called on the
2696	watcher but the event has not yet been processed (or even noted) by the	3240	watcher but the event has not yet been processed (or even noted) by the
…		…
2699	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3243	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2700	the loop iterates next and checks for the watcher to have become active,	3244	the loop iterates next and checks for the watcher to have become active,
2701	it will reset the flag again. C<ev_async_pending> can be used to very	3245	it will reset the flag again. C<ev_async_pending> can be used to very
2702	quickly check whether invoking the loop might be a good idea.	3246	quickly check whether invoking the loop might be a good idea.
2703		3247
2704	Not that this does I<not> check whether the watcher itself is pending, only	3248	Not that this does I<not> check whether the watcher itself is pending,
2705	whether it has been requested to make this watcher pending.	3249	only whether it has been requested to make this watcher pending: there
		3250	is a time window between the event loop checking and resetting the async
		3251	notification, and the callback being invoked.
2706		3252
2707	=back	3253	=back
2708		3254
2709		3255
2710	=head1 OTHER FUNCTIONS	3256	=head1 OTHER FUNCTIONS
…		…
2727		3273
2728	If C<timeout> is less than 0, then no timeout watcher will be	3274	If C<timeout> is less than 0, then no timeout watcher will be
2729	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3275	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2730	repeat = 0) will be started. C<0> is a valid timeout.	3276	repeat = 0) will be started. C<0> is a valid timeout.
2731		3277
2732	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3278	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2733	passed an C<revents> set like normal event callbacks (a combination of	3279	passed an C<revents> set like normal event callbacks (a combination of
2734	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3280	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2735	value passed to C<ev_once>. Note that it is possible to receive I<both>	3281	value passed to C<ev_once>. Note that it is possible to receive I<both>
2736	a timeout and an io event at the same time - you probably should give io	3282	a timeout and an io event at the same time - you probably should give io
2737	events precedence.	3283	events precedence.
2738		3284
2739	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3285	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2740		3286
2741	static void stdin_ready (int revents, void *arg)	3287	static void stdin_ready (int revents, void *arg)
2742	{	3288	{
2743	if (revents & EV_READ)	3289	if (revents & EV_READ)
2744	/* stdin might have data for us, joy! */;	3290	/* stdin might have data for us, joy! */;
2745	else if (revents & EV_TIMEOUT)	3291	else if (revents & EV_TIMER)
2746	/* doh, nothing entered */;	3292	/* doh, nothing entered */;
2747	}	3293	}
2748		3294
2749	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3295	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2750		3296
2751	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2752
2753	Feeds the given event set into the event loop, as if the specified event
2754	had happened for the specified watcher (which must be a pointer to an
2755	initialised but not necessarily started event watcher).
2756
2757	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3297	=item ev_feed_fd_event (loop, int fd, int revents)
2758		3298
2759	Feed an event on the given fd, as if a file descriptor backend detected	3299	Feed an event on the given fd, as if a file descriptor backend detected
2760	the given events it.	3300	the given events it.
2761		3301
2762	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3302	=item ev_feed_signal_event (loop, int signum)
2763		3303
2764	Feed an event as if the given signal occurred (C<loop> must be the default	3304	Feed an event as if the given signal occurred (C<loop> must be the default
2765	loop!).	3305	loop!).
2766		3306
2767	=back	3307	=back
…		…
2847		3387
2848	=over 4	3388	=over 4
2849		3389
2850	=item ev::TYPE::TYPE ()	3390	=item ev::TYPE::TYPE ()
2851		3391
2852	=item ev::TYPE::TYPE (struct ev_loop *)	3392	=item ev::TYPE::TYPE (loop)
2853		3393
2854	=item ev::TYPE::~TYPE	3394	=item ev::TYPE::~TYPE
2855		3395
2856	The constructor (optionally) takes an event loop to associate the watcher	3396	The constructor (optionally) takes an event loop to associate the watcher
2857	with. If it is omitted, it will use C<EV_DEFAULT>.	3397	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2889		3429
2890	myclass obj;	3430	myclass obj;
2891	ev::io iow;	3431	ev::io iow;
2892	iow.set <myclass, &myclass::io_cb> (&obj);	3432	iow.set <myclass, &myclass::io_cb> (&obj);
2893		3433
		3434	=item w->set (object *)
		3435
		3436	This is a variation of a method callback - leaving out the method to call
		3437	will default the method to C<operator ()>, which makes it possible to use
		3438	functor objects without having to manually specify the C<operator ()> all
		3439	the time. Incidentally, you can then also leave out the template argument
		3440	list.
		3441
		3442	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3443	int revents)>.
		3444
		3445	See the method-C<set> above for more details.
		3446
		3447	Example: use a functor object as callback.
		3448
		3449	struct myfunctor
		3450	{
		3451	void operator() (ev::io &w, int revents)
		3452	{
		3453	...
		3454	}
		3455	}
		3456
		3457	myfunctor f;
		3458
		3459	ev::io w;
		3460	w.set (&f);
		3461
2894	=item w->set<function> (void *data = 0)	3462	=item w->set<function> (void *data = 0)
2895		3463
2896	Also sets a callback, but uses a static method or plain function as	3464	Also sets a callback, but uses a static method or plain function as
2897	callback. The optional C<data> argument will be stored in the watcher's	3465	callback. The optional C<data> argument will be stored in the watcher's
2898	C<data> member and is free for you to use.	3466	C<data> member and is free for you to use.
…		…
2904	Example: Use a plain function as callback.	3472	Example: Use a plain function as callback.
2905		3473
2906	static void io_cb (ev::io &w, int revents) { }	3474	static void io_cb (ev::io &w, int revents) { }
2907	iow.set <io_cb> ();	3475	iow.set <io_cb> ();
2908		3476
2909	=item w->set (struct ev_loop *)	3477	=item w->set (loop)
2910		3478
2911	Associates a different C<struct ev_loop> with this watcher. You can only	3479	Associates a different C<struct ev_loop> with this watcher. You can only
2912	do this when the watcher is inactive (and not pending either).	3480	do this when the watcher is inactive (and not pending either).
2913		3481
2914	=item w->set ([arguments])	3482	=item w->set ([arguments])
2915		3483
2916	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3484	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2917	called at least once. Unlike the C counterpart, an active watcher gets	3485	method or a suitable start method must be called at least once. Unlike the
2918	automatically stopped and restarted when reconfiguring it with this	3486	C counterpart, an active watcher gets automatically stopped and restarted
2919	method.	3487	when reconfiguring it with this method.
2920		3488
2921	=item w->start ()	3489	=item w->start ()
2922		3490
2923	Starts the watcher. Note that there is no C<loop> argument, as the	3491	Starts the watcher. Note that there is no C<loop> argument, as the
2924	constructor already stores the event loop.	3492	constructor already stores the event loop.
2925		3493
		3494	=item w->start ([arguments])
		3495
		3496	Instead of calling C<set> and C<start> methods separately, it is often
		3497	convenient to wrap them in one call. Uses the same type of arguments as
		3498	the configure C<set> method of the watcher.
		3499
2926	=item w->stop ()	3500	=item w->stop ()
2927		3501
2928	Stops the watcher if it is active. Again, no C<loop> argument.	3502	Stops the watcher if it is active. Again, no C<loop> argument.
2929		3503
2930	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3504	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2942		3516
2943	=back	3517	=back
2944		3518
2945	=back	3519	=back
2946		3520
2947	Example: Define a class with an IO and idle watcher, start one of them in	3521	Example: Define a class with two I/O and idle watchers, start the I/O
2948	the constructor.	3522	watchers in the constructor.
2949		3523
2950	class myclass	3524	class myclass
2951	{	3525	{
2952	ev::io io ; void io_cb (ev::io &w, int revents);	3526	ev::io io ; void io_cb (ev::io &w, int revents);
		3527	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2953	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3528	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2954		3529
2955	myclass (int fd)	3530	myclass (int fd)
2956	{	3531	{
2957	io .set <myclass, &myclass::io_cb > (this);	3532	io .set <myclass, &myclass::io_cb > (this);
		3533	io2 .set <myclass, &myclass::io2_cb > (this);
2958	idle.set <myclass, &myclass::idle_cb> (this);	3534	idle.set <myclass, &myclass::idle_cb> (this);
2959		3535
2960	io.start (fd, ev::READ);	3536	io.set (fd, ev::WRITE); // configure the watcher
		3537	io.start (); // start it whenever convenient
		3538
		3539	io2.start (fd, ev::READ); // set + start in one call
2961	}	3540	}
2962	};	3541	};
2963		3542
2964		3543
2965	=head1 OTHER LANGUAGE BINDINGS	3544	=head1 OTHER LANGUAGE BINDINGS
…		…
2984	L<http://software.schmorp.de/pkg/EV>.	3563	L<http://software.schmorp.de/pkg/EV>.
2985		3564
2986	=item Python	3565	=item Python
2987		3566
2988	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3567	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2989	seems to be quite complete and well-documented. Note, however, that the	3568	seems to be quite complete and well-documented.
2990	patch they require for libev is outright dangerous as it breaks the ABI
2991	for everybody else, and therefore, should never be applied in an installed
2992	libev (if python requires an incompatible ABI then it needs to embed
2993	libev).
2994		3569
2995	=item Ruby	3570	=item Ruby
2996		3571
2997	Tony Arcieri has written a ruby extension that offers access to a subset	3572	Tony Arcieri has written a ruby extension that offers access to a subset
2998	of the libev API and adds file handle abstractions, asynchronous DNS and	3573	of the libev API and adds file handle abstractions, asynchronous DNS and
2999	more on top of it. It can be found via gem servers. Its homepage is at	3574	more on top of it. It can be found via gem servers. Its homepage is at
3000	L<http://rev.rubyforge.org/>.	3575	L<http://rev.rubyforge.org/>.
3001		3576
		3577	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3578	makes rev work even on mingw.
		3579
		3580	=item Haskell
		3581
		3582	A haskell binding to libev is available at
		3583	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3584
3002	=item D	3585	=item D
3003		3586
3004	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3587	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3005	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3588	be found at L<http://proj.llucax.com.ar/wiki/evd>.
3006		3589
3007	=item Ocaml	3590	=item Ocaml
3008		3591
3009	Erkki Seppala has written Ocaml bindings for libev, to be found at	3592	Erkki Seppala has written Ocaml bindings for libev, to be found at
3010	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3593	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3594
		3595	=item Lua
		3596
		3597	Brian Maher has written a partial interface to libev for lua (at the
		3598	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3599	L<http://github.com/brimworks/lua-ev>.
3011		3600
3012	=back	3601	=back
3013		3602
3014		3603
3015	=head1 MACRO MAGIC	3604	=head1 MACRO MAGIC
…		…
3029	loop argument"). The C<EV_A> form is used when this is the sole argument,	3618	loop argument"). The C<EV_A> form is used when this is the sole argument,
3030	C<EV_A_> is used when other arguments are following. Example:	3619	C<EV_A_> is used when other arguments are following. Example:
3031		3620
3032	ev_unref (EV_A);	3621	ev_unref (EV_A);
3033	ev_timer_add (EV_A_ watcher);	3622	ev_timer_add (EV_A_ watcher);
3034	ev_loop (EV_A_ 0);	3623	ev_run (EV_A_ 0);
3035		3624
3036	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3625	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3037	which is often provided by the following macro.	3626	which is often provided by the following macro.
3038		3627
3039	=item C<EV_P>, C<EV_P_>	3628	=item C<EV_P>, C<EV_P_>
…		…
3079	}	3668	}
3080		3669
3081	ev_check check;	3670	ev_check check;
3082	ev_check_init (&check, check_cb);	3671	ev_check_init (&check, check_cb);
3083	ev_check_start (EV_DEFAULT_ &check);	3672	ev_check_start (EV_DEFAULT_ &check);
3084	ev_loop (EV_DEFAULT_ 0);	3673	ev_run (EV_DEFAULT_ 0);
3085		3674
3086	=head1 EMBEDDING	3675	=head1 EMBEDDING
3087		3676
3088	Libev can (and often is) directly embedded into host	3677	Libev can (and often is) directly embedded into host
3089	applications. Examples of applications that embed it include the Deliantra	3678	applications. Examples of applications that embed it include the Deliantra
…		…
3169	libev.m4	3758	libev.m4
3170		3759
3171	=head2 PREPROCESSOR SYMBOLS/MACROS	3760	=head2 PREPROCESSOR SYMBOLS/MACROS
3172		3761
3173	Libev can be configured via a variety of preprocessor symbols you have to	3762	Libev can be configured via a variety of preprocessor symbols you have to
3174	define before including any of its files. The default in the absence of	3763	define before including (or compiling) any of its files. The default in
3175	autoconf is documented for every option.	3764	the absence of autoconf is documented for every option.
		3765
		3766	Symbols marked with "(h)" do not change the ABI, and can have different
		3767	values when compiling libev vs. including F<ev.h>, so it is permissible
		3768	to redefine them before including F<ev.h> without breaking compatibility
		3769	to a compiled library. All other symbols change the ABI, which means all
		3770	users of libev and the libev code itself must be compiled with compatible
		3771	settings.
3176		3772
3177	=over 4	3773	=over 4
3178		3774
		3775	=item EV_COMPAT3 (h)
		3776
		3777	Backwards compatibility is a major concern for libev. This is why this
		3778	release of libev comes with wrappers for the functions and symbols that
		3779	have been renamed between libev version 3 and 4.
		3780
		3781	You can disable these wrappers (to test compatibility with future
		3782	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3783	sources. This has the additional advantage that you can drop the C<struct>
		3784	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3785	typedef in that case.
		3786
		3787	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3788	and in some even more future version the compatibility code will be
		3789	removed completely.
		3790
3179	=item EV_STANDALONE	3791	=item EV_STANDALONE (h)
3180		3792
3181	Must always be C<1> if you do not use autoconf configuration, which	3793	Must always be C<1> if you do not use autoconf configuration, which
3182	keeps libev from including F<config.h>, and it also defines dummy	3794	keeps libev from including F<config.h>, and it also defines dummy
3183	implementations for some libevent functions (such as logging, which is not	3795	implementations for some libevent functions (such as logging, which is not
3184	supported). It will also not define any of the structs usually found in	3796	supported). It will also not define any of the structs usually found in
3185	F<event.h> that are not directly supported by the libev core alone.	3797	F<event.h> that are not directly supported by the libev core alone.
3186		3798
		3799	In standalone mode, libev will still try to automatically deduce the
		3800	configuration, but has to be more conservative.
		3801
3187	=item EV_USE_MONOTONIC	3802	=item EV_USE_MONOTONIC
3188		3803
3189	If defined to be C<1>, libev will try to detect the availability of the	3804	If defined to be C<1>, libev will try to detect the availability of the
3190	monotonic clock option at both compile time and runtime. Otherwise no use	3805	monotonic clock option at both compile time and runtime. Otherwise no
3191	of the monotonic clock option will be attempted. If you enable this, you	3806	use of the monotonic clock option will be attempted. If you enable this,
3192	usually have to link against librt or something similar. Enabling it when	3807	you usually have to link against librt or something similar. Enabling it
3193	the functionality isn't available is safe, though, although you have	3808	when the functionality isn't available is safe, though, although you have
3194	to make sure you link against any libraries where the C<clock_gettime>	3809	to make sure you link against any libraries where the C<clock_gettime>
3195	function is hiding in (often F<-lrt>).	3810	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3196		3811
3197	=item EV_USE_REALTIME	3812	=item EV_USE_REALTIME
3198		3813
3199	If defined to be C<1>, libev will try to detect the availability of the	3814	If defined to be C<1>, libev will try to detect the availability of the
3200	real-time clock option at compile time (and assume its availability at	3815	real-time clock option at compile time (and assume its availability
3201	runtime if successful). Otherwise no use of the real-time clock option will	3816	at runtime if successful). Otherwise no use of the real-time clock
3202	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3817	option will be attempted. This effectively replaces C<gettimeofday>
3203	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3818	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3204	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3819	correctness. See the note about libraries in the description of
		3820	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3821	C<EV_USE_CLOCK_SYSCALL>.
		3822
		3823	=item EV_USE_CLOCK_SYSCALL
		3824
		3825	If defined to be C<1>, libev will try to use a direct syscall instead
		3826	of calling the system-provided C<clock_gettime> function. This option
		3827	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3828	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3829	programs needlessly. Using a direct syscall is slightly slower (in
		3830	theory), because no optimised vdso implementation can be used, but avoids
		3831	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3832	higher, as it simplifies linking (no need for C<-lrt>).
3205		3833
3206	=item EV_USE_NANOSLEEP	3834	=item EV_USE_NANOSLEEP
3207		3835
3208	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3836	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3209	and will use it for delays. Otherwise it will use C<select ()>.	3837	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3225		3853
3226	=item EV_SELECT_USE_FD_SET	3854	=item EV_SELECT_USE_FD_SET
3227		3855
3228	If defined to C<1>, then the select backend will use the system C<fd_set>	3856	If defined to C<1>, then the select backend will use the system C<fd_set>
3229	structure. This is useful if libev doesn't compile due to a missing	3857	structure. This is useful if libev doesn't compile due to a missing
3230	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3858	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3231	exotic systems. This usually limits the range of file descriptors to some	3859	on exotic systems. This usually limits the range of file descriptors to
3232	low limit such as 1024 or might have other limitations (winsocket only	3860	some low limit such as 1024 or might have other limitations (winsocket
3233	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3861	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3234	influence the size of the C<fd_set> used.	3862	configures the maximum size of the C<fd_set>.
3235		3863
3236	=item EV_SELECT_IS_WINSOCKET	3864	=item EV_SELECT_IS_WINSOCKET
3237		3865
3238	When defined to C<1>, the select backend will assume that	3866	When defined to C<1>, the select backend will assume that
3239	select/socket/connect etc. don't understand file descriptors but	3867	select/socket/connect etc. don't understand file descriptors but
…		…
3241	be used is the winsock select). This means that it will call	3869	be used is the winsock select). This means that it will call
3242	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3870	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3243	it is assumed that all these functions actually work on fds, even	3871	it is assumed that all these functions actually work on fds, even
3244	on win32. Should not be defined on non-win32 platforms.	3872	on win32. Should not be defined on non-win32 platforms.
3245		3873
3246	=item EV_FD_TO_WIN32_HANDLE	3874	=item EV_FD_TO_WIN32_HANDLE(fd)
3247		3875
3248	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3876	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3249	file descriptors to socket handles. When not defining this symbol (the	3877	file descriptors to socket handles. When not defining this symbol (the
3250	default), then libev will call C<_get_osfhandle>, which is usually	3878	default), then libev will call C<_get_osfhandle>, which is usually
3251	correct. In some cases, programs use their own file descriptor management,	3879	correct. In some cases, programs use their own file descriptor management,
3252	in which case they can provide this function to map fds to socket handles.	3880	in which case they can provide this function to map fds to socket handles.
		3881
		3882	=item EV_WIN32_HANDLE_TO_FD(handle)
		3883
		3884	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3885	using the standard C<_open_osfhandle> function. For programs implementing
		3886	their own fd to handle mapping, overwriting this function makes it easier
		3887	to do so. This can be done by defining this macro to an appropriate value.
		3888
		3889	=item EV_WIN32_CLOSE_FD(fd)
		3890
		3891	If programs implement their own fd to handle mapping on win32, then this
		3892	macro can be used to override the C<close> function, useful to unregister
		3893	file descriptors again. Note that the replacement function has to close
		3894	the underlying OS handle.
3253		3895
3254	=item EV_USE_POLL	3896	=item EV_USE_POLL
3255		3897
3256	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3898	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3257	backend. Otherwise it will be enabled on non-win32 platforms. It	3899	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3304	as well as for signal and thread safety in C<ev_async> watchers.	3946	as well as for signal and thread safety in C<ev_async> watchers.
3305		3947
3306	In the absence of this define, libev will use C<sig_atomic_t volatile>	3948	In the absence of this define, libev will use C<sig_atomic_t volatile>
3307	(from F<signal.h>), which is usually good enough on most platforms.	3949	(from F<signal.h>), which is usually good enough on most platforms.
3308		3950
3309	=item EV_H	3951	=item EV_H (h)
3310		3952
3311	The name of the F<ev.h> header file used to include it. The default if	3953	The name of the F<ev.h> header file used to include it. The default if
3312	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3954	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3313	used to virtually rename the F<ev.h> header file in case of conflicts.	3955	used to virtually rename the F<ev.h> header file in case of conflicts.
3314		3956
3315	=item EV_CONFIG_H	3957	=item EV_CONFIG_H (h)
3316		3958
3317	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	3959	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3318	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	3960	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3319	C<EV_H>, above.	3961	C<EV_H>, above.
3320		3962
3321	=item EV_EVENT_H	3963	=item EV_EVENT_H (h)
3322		3964
3323	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	3965	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3324	of how the F<event.h> header can be found, the default is C<"event.h">.	3966	of how the F<event.h> header can be found, the default is C<"event.h">.
3325		3967
3326	=item EV_PROTOTYPES	3968	=item EV_PROTOTYPES (h)
3327		3969
3328	If defined to be C<0>, then F<ev.h> will not define any function	3970	If defined to be C<0>, then F<ev.h> will not define any function
3329	prototypes, but still define all the structs and other symbols. This is	3971	prototypes, but still define all the structs and other symbols. This is
3330	occasionally useful if you want to provide your own wrapper functions	3972	occasionally useful if you want to provide your own wrapper functions
3331	around libev functions.	3973	around libev functions.
…		…
3353	fine.	3995	fine.
3354		3996
3355	If your embedding application does not need any priorities, defining these	3997	If your embedding application does not need any priorities, defining these
3356	both to C<0> will save some memory and CPU.	3998	both to C<0> will save some memory and CPU.
3357		3999
3358	=item EV_PERIODIC_ENABLE	4000	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4001	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4002	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3359		4003
3360	If undefined or defined to be C<1>, then periodic timers are supported. If	4004	If undefined or defined to be C<1> (and the platform supports it), then
3361	defined to be C<0>, then they are not. Disabling them saves a few kB of	4005	the respective watcher type is supported. If defined to be C<0>, then it
3362	code.	4006	is not. Disabling watcher types mainly saves code size.
3363		4007
3364	=item EV_IDLE_ENABLE	4008	=item EV_FEATURES
3365
3366	If undefined or defined to be C<1>, then idle watchers are supported. If
3367	defined to be C<0>, then they are not. Disabling them saves a few kB of
3368	code.
3369
3370	=item EV_EMBED_ENABLE
3371
3372	If undefined or defined to be C<1>, then embed watchers are supported. If
3373	defined to be C<0>, then they are not. Embed watchers rely on most other
3374	watcher types, which therefore must not be disabled.
3375
3376	=item EV_STAT_ENABLE
3377
3378	If undefined or defined to be C<1>, then stat watchers are supported. If
3379	defined to be C<0>, then they are not.
3380
3381	=item EV_FORK_ENABLE
3382
3383	If undefined or defined to be C<1>, then fork watchers are supported. If
3384	defined to be C<0>, then they are not.
3385
3386	=item EV_ASYNC_ENABLE
3387
3388	If undefined or defined to be C<1>, then async watchers are supported. If
3389	defined to be C<0>, then they are not.
3390
3391	=item EV_MINIMAL
3392		4009
3393	If you need to shave off some kilobytes of code at the expense of some	4010	If you need to shave off some kilobytes of code at the expense of some
3394	speed, define this symbol to C<1>. Currently this is used to override some	4011	speed (but with the full API), you can define this symbol to request
3395	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4012	certain subsets of functionality. The default is to enable all features
3396	much smaller 2-heap for timer management over the default 4-heap.	4013	that can be enabled on the platform.
		4014
		4015	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4016	with some broad features you want) and then selectively re-enable
		4017	additional parts you want, for example if you want everything minimal,
		4018	but multiple event loop support, async and child watchers and the poll
		4019	backend, use this:
		4020
		4021	#define EV_FEATURES 0
		4022	#define EV_MULTIPLICITY 1
		4023	#define EV_USE_POLL 1
		4024	#define EV_CHILD_ENABLE 1
		4025	#define EV_ASYNC_ENABLE 1
		4026
		4027	The actual value is a bitset, it can be a combination of the following
		4028	values:
		4029
		4030	=over 4
		4031
		4032	=item C<1> - faster/larger code
		4033
		4034	Use larger code to speed up some operations.
		4035
		4036	Currently this is used to override some inlining decisions (enlarging the
		4037	code size by roughly 30% on amd64).
		4038
		4039	When optimising for size, use of compiler flags such as C<-Os> with
		4040	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4041	assertions.
		4042
		4043	=item C<2> - faster/larger data structures
		4044
		4045	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4046	hash table sizes and so on. This will usually further increase code size
		4047	and can additionally have an effect on the size of data structures at
		4048	runtime.
		4049
		4050	=item C<4> - full API configuration
		4051
		4052	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4053	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4054
		4055	=item C<8> - full API
		4056
		4057	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4058	details on which parts of the API are still available without this
		4059	feature, and do not complain if this subset changes over time.
		4060
		4061	=item C<16> - enable all optional watcher types
		4062
		4063	Enables all optional watcher types. If you want to selectively enable
		4064	only some watcher types other than I/O and timers (e.g. prepare,
		4065	embed, async, child...) you can enable them manually by defining
		4066	C<EV_watchertype_ENABLE> to C<1> instead.
		4067
		4068	=item C<32> - enable all backends
		4069
		4070	This enables all backends - without this feature, you need to enable at
		4071	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4072
		4073	=item C<64> - enable OS-specific "helper" APIs
		4074
		4075	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4076	default.
		4077
		4078	=back
		4079
		4080	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4081	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4082	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4083	watchers, timers and monotonic clock support.
		4084
		4085	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4086	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4087	your program might be left out as well - a binary starting a timer and an
		4088	I/O watcher then might come out at only 5Kb.
		4089
		4090	=item EV_AVOID_STDIO
		4091
		4092	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4093	functions (printf, scanf, perror etc.). This will increase the code size
		4094	somewhat, but if your program doesn't otherwise depend on stdio and your
		4095	libc allows it, this avoids linking in the stdio library which is quite
		4096	big.
		4097
		4098	Note that error messages might become less precise when this option is
		4099	enabled.
		4100
		4101	=item EV_NSIG
		4102
		4103	The highest supported signal number, +1 (or, the number of
		4104	signals): Normally, libev tries to deduce the maximum number of signals
		4105	automatically, but sometimes this fails, in which case it can be
		4106	specified. Also, using a lower number than detected (C<32> should be
		4107	good for about any system in existence) can save some memory, as libev
		4108	statically allocates some 12-24 bytes per signal number.
3397		4109
3398	=item EV_PID_HASHSIZE	4110	=item EV_PID_HASHSIZE
3399		4111
3400	C<ev_child> watchers use a small hash table to distribute workload by	4112	C<ev_child> watchers use a small hash table to distribute workload by
3401	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4113	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3402	than enough. If you need to manage thousands of children you might want to	4114	usually more than enough. If you need to manage thousands of children you
3403	increase this value (I<must> be a power of two).	4115	might want to increase this value (I<must> be a power of two).
3404		4116
3405	=item EV_INOTIFY_HASHSIZE	4117	=item EV_INOTIFY_HASHSIZE
3406		4118
3407	C<ev_stat> watchers use a small hash table to distribute workload by	4119	C<ev_stat> watchers use a small hash table to distribute workload by
3408	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4120	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3409	usually more than enough. If you need to manage thousands of C<ev_stat>	4121	disabled), usually more than enough. If you need to manage thousands of
3410	watchers you might want to increase this value (I<must> be a power of	4122	C<ev_stat> watchers you might want to increase this value (I<must> be a
3411	two).	4123	power of two).
3412		4124
3413	=item EV_USE_4HEAP	4125	=item EV_USE_4HEAP
3414		4126
3415	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4127	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3416	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4128	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3417	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4129	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3418	faster performance with many (thousands) of watchers.	4130	faster performance with many (thousands) of watchers.
3419		4131
3420	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4132	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3421	(disabled).	4133	will be C<0>.
3422		4134
3423	=item EV_HEAP_CACHE_AT	4135	=item EV_HEAP_CACHE_AT
3424		4136
3425	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4137	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3426	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4138	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3427	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4139	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3428	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4140	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3429	but avoids random read accesses on heap changes. This improves performance	4141	but avoids random read accesses on heap changes. This improves performance
3430	noticeably with many (hundreds) of watchers.	4142	noticeably with many (hundreds) of watchers.
3431		4143
3432	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4144	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3433	(disabled).	4145	will be C<0>.
3434		4146
3435	=item EV_VERIFY	4147	=item EV_VERIFY
3436		4148
3437	Controls how much internal verification (see C<ev_loop_verify ()>) will	4149	Controls how much internal verification (see C<ev_verify ()>) will
3438	be done: If set to C<0>, no internal verification code will be compiled	4150	be done: If set to C<0>, no internal verification code will be compiled
3439	in. If set to C<1>, then verification code will be compiled in, but not	4151	in. If set to C<1>, then verification code will be compiled in, but not
3440	called. If set to C<2>, then the internal verification code will be	4152	called. If set to C<2>, then the internal verification code will be
3441	called once per loop, which can slow down libev. If set to C<3>, then the	4153	called once per loop, which can slow down libev. If set to C<3>, then the
3442	verification code will be called very frequently, which will slow down	4154	verification code will be called very frequently, which will slow down
3443	libev considerably.	4155	libev considerably.
3444		4156
3445	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4157	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3446	C<0>.	4158	will be C<0>.
3447		4159
3448	=item EV_COMMON	4160	=item EV_COMMON
3449		4161
3450	By default, all watchers have a C<void *data> member. By redefining	4162	By default, all watchers have a C<void *data> member. By redefining
3451	this macro to a something else you can include more and other types of	4163	this macro to something else you can include more and other types of
3452	members. You have to define it each time you include one of the files,	4164	members. You have to define it each time you include one of the files,
3453	though, and it must be identical each time.	4165	though, and it must be identical each time.
3454		4166
3455	For example, the perl EV module uses something like this:	4167	For example, the perl EV module uses something like this:
3456		4168
…		…
3509	file.	4221	file.
3510		4222
3511	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4223	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3512	that everybody includes and which overrides some configure choices:	4224	that everybody includes and which overrides some configure choices:
3513		4225
3514	#define EV_MINIMAL 1	4226	#define EV_FEATURES 8
3515	#define EV_USE_POLL 0	4227	#define EV_USE_SELECT 1
3516	#define EV_MULTIPLICITY 0
3517	#define EV_PERIODIC_ENABLE 0	4228	#define EV_PREPARE_ENABLE 1
		4229	#define EV_IDLE_ENABLE 1
3518	#define EV_STAT_ENABLE 0	4230	#define EV_SIGNAL_ENABLE 1
3519	#define EV_FORK_ENABLE 0	4231	#define EV_CHILD_ENABLE 1
		4232	#define EV_USE_STDEXCEPT 0
3520	#define EV_CONFIG_H <config.h>	4233	#define EV_CONFIG_H <config.h>
3521	#define EV_MINPRI 0
3522	#define EV_MAXPRI 0
3523		4234
3524	#include "ev++.h"	4235	#include "ev++.h"
3525		4236
3526	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4237	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3527		4238
…		…
3587	default loop and triggering an C<ev_async> watcher from the default loop	4298	default loop and triggering an C<ev_async> watcher from the default loop
3588	watcher callback into the event loop interested in the signal.	4299	watcher callback into the event loop interested in the signal.
3589		4300
3590	=back	4301	=back
3591		4302
		4303	=head4 THREAD LOCKING EXAMPLE
		4304
		4305	Here is a fictitious example of how to run an event loop in a different
		4306	thread than where callbacks are being invoked and watchers are
		4307	created/added/removed.
		4308
		4309	For a real-world example, see the C<EV::Loop::Async> perl module,
		4310	which uses exactly this technique (which is suited for many high-level
		4311	languages).
		4312
		4313	The example uses a pthread mutex to protect the loop data, a condition
		4314	variable to wait for callback invocations, an async watcher to notify the
		4315	event loop thread and an unspecified mechanism to wake up the main thread.
		4316
		4317	First, you need to associate some data with the event loop:
		4318
		4319	typedef struct {
		4320	mutex_t lock; /* global loop lock */
		4321	ev_async async_w;
		4322	thread_t tid;
		4323	cond_t invoke_cv;
		4324	} userdata;
		4325
		4326	void prepare_loop (EV_P)
		4327	{
		4328	// for simplicity, we use a static userdata struct.
		4329	static userdata u;
		4330
		4331	ev_async_init (&u->async_w, async_cb);
		4332	ev_async_start (EV_A_ &u->async_w);
		4333
		4334	pthread_mutex_init (&u->lock, 0);
		4335	pthread_cond_init (&u->invoke_cv, 0);
		4336
		4337	// now associate this with the loop
		4338	ev_set_userdata (EV_A_ u);
		4339	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4340	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4341
		4342	// then create the thread running ev_loop
		4343	pthread_create (&u->tid, 0, l_run, EV_A);
		4344	}
		4345
		4346	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4347	solely to wake up the event loop so it takes notice of any new watchers
		4348	that might have been added:
		4349
		4350	static void
		4351	async_cb (EV_P_ ev_async *w, int revents)
		4352	{
		4353	// just used for the side effects
		4354	}
		4355
		4356	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4357	protecting the loop data, respectively.
		4358
		4359	static void
		4360	l_release (EV_P)
		4361	{
		4362	userdata *u = ev_userdata (EV_A);
		4363	pthread_mutex_unlock (&u->lock);
		4364	}
		4365
		4366	static void
		4367	l_acquire (EV_P)
		4368	{
		4369	userdata *u = ev_userdata (EV_A);
		4370	pthread_mutex_lock (&u->lock);
		4371	}
		4372
		4373	The event loop thread first acquires the mutex, and then jumps straight
		4374	into C<ev_run>:
		4375
		4376	void *
		4377	l_run (void *thr_arg)
		4378	{
		4379	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4380
		4381	l_acquire (EV_A);
		4382	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4383	ev_run (EV_A_ 0);
		4384	l_release (EV_A);
		4385
		4386	return 0;
		4387	}
		4388
		4389	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4390	signal the main thread via some unspecified mechanism (signals? pipe
		4391	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4392	have been called (in a while loop because a) spurious wakeups are possible
		4393	and b) skipping inter-thread-communication when there are no pending
		4394	watchers is very beneficial):
		4395
		4396	static void
		4397	l_invoke (EV_P)
		4398	{
		4399	userdata *u = ev_userdata (EV_A);
		4400
		4401	while (ev_pending_count (EV_A))
		4402	{
		4403	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4404	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4405	}
		4406	}
		4407
		4408	Now, whenever the main thread gets told to invoke pending watchers, it
		4409	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4410	thread to continue:
		4411
		4412	static void
		4413	real_invoke_pending (EV_P)
		4414	{
		4415	userdata *u = ev_userdata (EV_A);
		4416
		4417	pthread_mutex_lock (&u->lock);
		4418	ev_invoke_pending (EV_A);
		4419	pthread_cond_signal (&u->invoke_cv);
		4420	pthread_mutex_unlock (&u->lock);
		4421	}
		4422
		4423	Whenever you want to start/stop a watcher or do other modifications to an
		4424	event loop, you will now have to lock:
		4425
		4426	ev_timer timeout_watcher;
		4427	userdata *u = ev_userdata (EV_A);
		4428
		4429	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4430
		4431	pthread_mutex_lock (&u->lock);
		4432	ev_timer_start (EV_A_ &timeout_watcher);
		4433	ev_async_send (EV_A_ &u->async_w);
		4434	pthread_mutex_unlock (&u->lock);
		4435
		4436	Note that sending the C<ev_async> watcher is required because otherwise
		4437	an event loop currently blocking in the kernel will have no knowledge
		4438	about the newly added timer. By waking up the loop it will pick up any new
		4439	watchers in the next event loop iteration.
		4440
3592	=head3 COROUTINES	4441	=head3 COROUTINES
3593		4442
3594	Libev is very accommodating to coroutines ("cooperative threads"):	4443	Libev is very accommodating to coroutines ("cooperative threads"):
3595	libev fully supports nesting calls to its functions from different	4444	libev fully supports nesting calls to its functions from different
3596	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4445	coroutines (e.g. you can call C<ev_run> on the same loop from two
3597	different coroutines, and switch freely between both coroutines running the	4446	different coroutines, and switch freely between both coroutines running
3598	loop, as long as you don't confuse yourself). The only exception is that	4447	the loop, as long as you don't confuse yourself). The only exception is
3599	you must not do this from C<ev_periodic> reschedule callbacks.	4448	that you must not do this from C<ev_periodic> reschedule callbacks.
3600		4449
3601	Care has been taken to ensure that libev does not keep local state inside	4450	Care has been taken to ensure that libev does not keep local state inside
3602	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4451	C<ev_run>, and other calls do not usually allow for coroutine switches as
3603	they do not call any callbacks.	4452	they do not call any callbacks.
3604		4453
3605	=head2 COMPILER WARNINGS	4454	=head2 COMPILER WARNINGS
3606		4455
3607	Depending on your compiler and compiler settings, you might get no or a	4456	Depending on your compiler and compiler settings, you might get no or a
…		…
3618	maintainable.	4467	maintainable.
3619		4468
3620	And of course, some compiler warnings are just plain stupid, or simply	4469	And of course, some compiler warnings are just plain stupid, or simply
3621	wrong (because they don't actually warn about the condition their message	4470	wrong (because they don't actually warn about the condition their message
3622	seems to warn about). For example, certain older gcc versions had some	4471	seems to warn about). For example, certain older gcc versions had some
3623	warnings that resulted an extreme number of false positives. These have	4472	warnings that resulted in an extreme number of false positives. These have
3624	been fixed, but some people still insist on making code warn-free with	4473	been fixed, but some people still insist on making code warn-free with
3625	such buggy versions.	4474	such buggy versions.
3626		4475
3627	While libev is written to generate as few warnings as possible,	4476	While libev is written to generate as few warnings as possible,
3628	"warn-free" code is not a goal, and it is recommended not to build libev	4477	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3664	I suggest using suppression lists.	4513	I suggest using suppression lists.
3665		4514
3666		4515
3667	=head1 PORTABILITY NOTES	4516	=head1 PORTABILITY NOTES
3668		4517
		4518	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4519
		4520	GNU/Linux is the only common platform that supports 64 bit file/large file
		4521	interfaces but I<disables> them by default.
		4522
		4523	That means that libev compiled in the default environment doesn't support
		4524	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4525
		4526	Unfortunately, many programs try to work around this GNU/Linux issue
		4527	by enabling the large file API, which makes them incompatible with the
		4528	standard libev compiled for their system.
		4529
		4530	Likewise, libev cannot enable the large file API itself as this would
		4531	suddenly make it incompatible to the default compile time environment,
		4532	i.e. all programs not using special compile switches.
		4533
		4534	=head2 OS/X AND DARWIN BUGS
		4535
		4536	The whole thing is a bug if you ask me - basically any system interface
		4537	you touch is broken, whether it is locales, poll, kqueue or even the
		4538	OpenGL drivers.
		4539
		4540	=head3 C<kqueue> is buggy
		4541
		4542	The kqueue syscall is broken in all known versions - most versions support
		4543	only sockets, many support pipes.
		4544
		4545	Libev tries to work around this by not using C<kqueue> by default on this
		4546	rotten platform, but of course you can still ask for it when creating a
		4547	loop - embedding a socket-only kqueue loop into a select-based one is
		4548	probably going to work well.
		4549
		4550	=head3 C<poll> is buggy
		4551
		4552	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4553	implementation by something calling C<kqueue> internally around the 10.5.6
		4554	release, so now C<kqueue> I<and> C<poll> are broken.
		4555
		4556	Libev tries to work around this by not using C<poll> by default on
		4557	this rotten platform, but of course you can still ask for it when creating
		4558	a loop.
		4559
		4560	=head3 C<select> is buggy
		4561
		4562	All that's left is C<select>, and of course Apple found a way to fuck this
		4563	one up as well: On OS/X, C<select> actively limits the number of file
		4564	descriptors you can pass in to 1024 - your program suddenly crashes when
		4565	you use more.
		4566
		4567	There is an undocumented "workaround" for this - defining
		4568	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4569	work on OS/X.
		4570
		4571	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4572
		4573	=head3 C<errno> reentrancy
		4574
		4575	The default compile environment on Solaris is unfortunately so
		4576	thread-unsafe that you can't even use components/libraries compiled
		4577	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4578	defined by default. A valid, if stupid, implementation choice.
		4579
		4580	If you want to use libev in threaded environments you have to make sure
		4581	it's compiled with C<_REENTRANT> defined.
		4582
		4583	=head3 Event port backend
		4584
		4585	The scalable event interface for Solaris is called "event
		4586	ports". Unfortunately, this mechanism is very buggy in all major
		4587	releases. If you run into high CPU usage, your program freezes or you get
		4588	a large number of spurious wakeups, make sure you have all the relevant
		4589	and latest kernel patches applied. No, I don't know which ones, but there
		4590	are multiple ones to apply, and afterwards, event ports actually work
		4591	great.
		4592
		4593	If you can't get it to work, you can try running the program by setting
		4594	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4595	C<select> backends.
		4596
		4597	=head2 AIX POLL BUG
		4598
		4599	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4600	this by trying to avoid the poll backend altogether (i.e. it's not even
		4601	compiled in), which normally isn't a big problem as C<select> works fine
		4602	with large bitsets on AIX, and AIX is dead anyway.
		4603
3669	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4604	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4605
		4606	=head3 General issues
3670		4607
3671	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4608	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3672	requires, and its I/O model is fundamentally incompatible with the POSIX	4609	requires, and its I/O model is fundamentally incompatible with the POSIX
3673	model. Libev still offers limited functionality on this platform in	4610	model. Libev still offers limited functionality on this platform in
3674	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4611	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3675	descriptors. This only applies when using Win32 natively, not when using	4612	descriptors. This only applies when using Win32 natively, not when using
3676	e.g. cygwin.	4613	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4614	as every compielr comes with a slightly differently broken/incompatible
		4615	environment.
3677		4616
3678	Lifting these limitations would basically require the full	4617	Lifting these limitations would basically require the full
3679	re-implementation of the I/O system. If you are into these kinds of	4618	re-implementation of the I/O system. If you are into this kind of thing,
3680	things, then note that glib does exactly that for you in a very portable	4619	then note that glib does exactly that for you in a very portable way (note
3681	way (note also that glib is the slowest event library known to man).	4620	also that glib is the slowest event library known to man).
3682		4621
3683	There is no supported compilation method available on windows except	4622	There is no supported compilation method available on windows except
3684	embedding it into other applications.	4623	embedding it into other applications.
		4624
		4625	Sensible signal handling is officially unsupported by Microsoft - libev
		4626	tries its best, but under most conditions, signals will simply not work.
3685		4627
3686	Not a libev limitation but worth mentioning: windows apparently doesn't	4628	Not a libev limitation but worth mentioning: windows apparently doesn't
3687	accept large writes: instead of resulting in a partial write, windows will	4629	accept large writes: instead of resulting in a partial write, windows will
3688	either accept everything or return C<ENOBUFS> if the buffer is too large,	4630	either accept everything or return C<ENOBUFS> if the buffer is too large,
3689	so make sure you only write small amounts into your sockets (less than a	4631	so make sure you only write small amounts into your sockets (less than a
…		…
3694	the abysmal performance of winsockets, using a large number of sockets	4636	the abysmal performance of winsockets, using a large number of sockets
3695	is not recommended (and not reasonable). If your program needs to use	4637	is not recommended (and not reasonable). If your program needs to use
3696	more than a hundred or so sockets, then likely it needs to use a totally	4638	more than a hundred or so sockets, then likely it needs to use a totally
3697	different implementation for windows, as libev offers the POSIX readiness	4639	different implementation for windows, as libev offers the POSIX readiness
3698	notification model, which cannot be implemented efficiently on windows	4640	notification model, which cannot be implemented efficiently on windows
3699	(Microsoft monopoly games).	4641	(due to Microsoft monopoly games).
3700		4642
3701	A typical way to use libev under windows is to embed it (see the embedding	4643	A typical way to use libev under windows is to embed it (see the embedding
3702	section for details) and use the following F<evwrap.h> header file instead	4644	section for details) and use the following F<evwrap.h> header file instead
3703	of F<ev.h>:	4645	of F<ev.h>:
3704		4646
…		…
3711	you do I<not> compile the F<ev.c> or any other embedded source files!):	4653	you do I<not> compile the F<ev.c> or any other embedded source files!):
3712		4654
3713	#include "evwrap.h"	4655	#include "evwrap.h"
3714	#include "ev.c"	4656	#include "ev.c"
3715		4657
3716	=over 4
3717
3718	=item The winsocket select function	4658	=head3 The winsocket C<select> function
3719		4659
3720	The winsocket C<select> function doesn't follow POSIX in that it	4660	The winsocket C<select> function doesn't follow POSIX in that it
3721	requires socket I<handles> and not socket I<file descriptors> (it is	4661	requires socket I<handles> and not socket I<file descriptors> (it is
3722	also extremely buggy). This makes select very inefficient, and also	4662	also extremely buggy). This makes select very inefficient, and also
3723	requires a mapping from file descriptors to socket handles (the Microsoft	4663	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3732	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4672	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3733		4673
3734	Note that winsockets handling of fd sets is O(n), so you can easily get a	4674	Note that winsockets handling of fd sets is O(n), so you can easily get a
3735	complexity in the O(n²) range when using win32.	4675	complexity in the O(n²) range when using win32.
3736		4676
3737	=item Limited number of file descriptors	4677	=head3 Limited number of file descriptors
3738		4678
3739	Windows has numerous arbitrary (and low) limits on things.	4679	Windows has numerous arbitrary (and low) limits on things.
3740		4680
3741	Early versions of winsocket's select only supported waiting for a maximum	4681	Early versions of winsocket's select only supported waiting for a maximum
3742	of C<64> handles (probably owning to the fact that all windows kernels	4682	of C<64> handles (probably owning to the fact that all windows kernels
3743	can only wait for C<64> things at the same time internally; Microsoft	4683	can only wait for C<64> things at the same time internally; Microsoft
3744	recommends spawning a chain of threads and wait for 63 handles and the	4684	recommends spawning a chain of threads and wait for 63 handles and the
3745	previous thread in each. Great).	4685	previous thread in each. Sounds great!).
3746		4686
3747	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4687	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3748	to some high number (e.g. C<2048>) before compiling the winsocket select	4688	to some high number (e.g. C<2048>) before compiling the winsocket select
3749	call (which might be in libev or elsewhere, for example, perl does its own	4689	call (which might be in libev or elsewhere, for example, perl and many
3750	select emulation on windows).	4690	other interpreters do their own select emulation on windows).
3751		4691
3752	Another limit is the number of file descriptors in the Microsoft runtime	4692	Another limit is the number of file descriptors in the Microsoft runtime
3753	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4693	libraries, which by default is C<64> (there must be a hidden I<64>
3754	or something like this inside Microsoft). You can increase this by calling	4694	fetish or something like this inside Microsoft). You can increase this
3755	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4695	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3756	arbitrary limit), but is broken in many versions of the Microsoft runtime	4696	(another arbitrary limit), but is broken in many versions of the Microsoft
3757	libraries.
3758
3759	This might get you to about C<512> or C<2048> sockets (depending on	4697	runtime libraries. This might get you to about C<512> or C<2048> sockets
3760	windows version and/or the phase of the moon). To get more, you need to	4698	(depending on windows version and/or the phase of the moon). To get more,
3761	wrap all I/O functions and provide your own fd management, but the cost of	4699	you need to wrap all I/O functions and provide your own fd management, but
3762	calling select (O(n²)) will likely make this unworkable.	4700	the cost of calling select (O(n²)) will likely make this unworkable.
3763
3764	=back
3765		4701
3766	=head2 PORTABILITY REQUIREMENTS	4702	=head2 PORTABILITY REQUIREMENTS
3767		4703
3768	In addition to a working ISO-C implementation and of course the	4704	In addition to a working ISO-C implementation and of course the
3769	backend-specific APIs, libev relies on a few additional extensions:	4705	backend-specific APIs, libev relies on a few additional extensions:
…		…
3808	watchers.	4744	watchers.
3809		4745
3810	=item C<double> must hold a time value in seconds with enough accuracy	4746	=item C<double> must hold a time value in seconds with enough accuracy
3811		4747
3812	The type C<double> is used to represent timestamps. It is required to	4748	The type C<double> is used to represent timestamps. It is required to
3813	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4749	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3814	enough for at least into the year 4000. This requirement is fulfilled by	4750	good enough for at least into the year 4000 with millisecond accuracy
		4751	(the design goal for libev). This requirement is overfulfilled by
3815	implementations implementing IEEE 754 (basically all existing ones).	4752	implementations using IEEE 754, which is basically all existing ones. With
		4753	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3816		4754
3817	=back	4755	=back
3818		4756
3819	If you know of other additional requirements drop me a note.	4757	If you know of other additional requirements drop me a note.
3820		4758
…		…
3888	involves iterating over all running async watchers or all signal numbers.	4826	involves iterating over all running async watchers or all signal numbers.
3889		4827
3890	=back	4828	=back
3891		4829
3892		4830
		4831	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4832
		4833	The major version 4 introduced some minor incompatible changes to the API.
		4834
		4835	At the moment, the C<ev.h> header file tries to implement superficial
		4836	compatibility, so most programs should still compile. Those might be
		4837	removed in later versions of libev, so better update early than late.
		4838
		4839	=over 4
		4840
		4841	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4842
		4843	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4844
		4845	ev_loop_destroy (EV_DEFAULT);
		4846	ev_loop_fork (EV_DEFAULT);
		4847
		4848	=item function/symbol renames
		4849
		4850	A number of functions and symbols have been renamed:
		4851
		4852	ev_loop => ev_run
		4853	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4854	EVLOOP_ONESHOT => EVRUN_ONCE
		4855
		4856	ev_unloop => ev_break
		4857	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4858	EVUNLOOP_ONE => EVBREAK_ONE
		4859	EVUNLOOP_ALL => EVBREAK_ALL
		4860
		4861	EV_TIMEOUT => EV_TIMER
		4862
		4863	ev_loop_count => ev_iteration
		4864	ev_loop_depth => ev_depth
		4865	ev_loop_verify => ev_verify
		4866
		4867	Most functions working on C<struct ev_loop> objects don't have an
		4868	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4869	associated constants have been renamed to not collide with the C<struct
		4870	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4871	as all other watcher types. Note that C<ev_loop_fork> is still called
		4872	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4873	typedef.
		4874
		4875	=item C<EV_COMPAT3> backwards compatibility mechanism
		4876
		4877	The backward compatibility mechanism can be controlled by
		4878	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4879	section.
		4880
		4881	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4882
		4883	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4884	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4885	and work, but the library code will of course be larger.
		4886
		4887	=back
		4888
		4889
		4890	=head1 GLOSSARY
		4891
		4892	=over 4
		4893
		4894	=item active
		4895
		4896	A watcher is active as long as it has been started and not yet stopped.
		4897	See L<WATCHER STATES> for details.
		4898
		4899	=item application
		4900
		4901	In this document, an application is whatever is using libev.
		4902
		4903	=item backend
		4904
		4905	The part of the code dealing with the operating system interfaces.
		4906
		4907	=item callback
		4908
		4909	The address of a function that is called when some event has been
		4910	detected. Callbacks are being passed the event loop, the watcher that
		4911	received the event, and the actual event bitset.
		4912
		4913	=item callback/watcher invocation
		4914
		4915	The act of calling the callback associated with a watcher.
		4916
		4917	=item event
		4918
		4919	A change of state of some external event, such as data now being available
		4920	for reading on a file descriptor, time having passed or simply not having
		4921	any other events happening anymore.
		4922
		4923	In libev, events are represented as single bits (such as C<EV_READ> or
		4924	C<EV_TIMER>).
		4925
		4926	=item event library
		4927
		4928	A software package implementing an event model and loop.
		4929
		4930	=item event loop
		4931
		4932	An entity that handles and processes external events and converts them
		4933	into callback invocations.
		4934
		4935	=item event model
		4936
		4937	The model used to describe how an event loop handles and processes
		4938	watchers and events.
		4939
		4940	=item pending
		4941
		4942	A watcher is pending as soon as the corresponding event has been
		4943	detected. See L<WATCHER STATES> for details.
		4944
		4945	=item real time
		4946
		4947	The physical time that is observed. It is apparently strictly monotonic :)
		4948
		4949	=item wall-clock time
		4950
		4951	The time and date as shown on clocks. Unlike real time, it can actually
		4952	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4953	clock.
		4954
		4955	=item watcher
		4956
		4957	A data structure that describes interest in certain events. Watchers need
		4958	to be started (attached to an event loop) before they can receive events.
		4959
		4960	=back
		4961
3893	=head1 AUTHOR	4962	=head1 AUTHOR
3894		4963
3895	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	4964	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3896		4965

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