ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.210 by root, Thu Oct 30 08:09:30 2008 UTC vs.
Revision 1.332 by root, Sun Oct 24 23:30:23 2010 UTC

…		…
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 child process events, and dynamically created event loops which
287	not.	306	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
…		…
417	i.e. keep at least one watcher active per fd at all times. Stopping and	485	i.e. keep at least one watcher active per fd at all times. Stopping and
418	starting a watcher (without re-setting it) also usually doesn't cause	486	starting a watcher (without re-setting it) also usually doesn't cause
419	extra overhead. A fork can both result in spurious notifications as well	487	extra overhead. A fork can both result in spurious notifications as well
420	as in libev having to destroy and recreate the epoll object, which can	488	as in libev having to destroy and recreate the epoll object, which can
421	take considerable time and thus should be avoided.	489	take considerable time and thus should be avoided.
		490
		491	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		492	faster than epoll for maybe up to a hundred file descriptors, depending on
		493	the usage. So sad.
422		494
423	While nominally embeddable in other event loops, this feature is broken in	495	While nominally embeddable in other event loops, this feature is broken in
424	all kernel versions tested so far.	496	all kernel versions tested so far.
425		497
426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
454		526
455	While nominally embeddable in other event loops, this doesn't work	527	While nominally embeddable in other event loops, this doesn't work
456	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
457	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
458	(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
459	(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
460	using it only for sockets.	532	also broken on OS X)) and, did I mention it, using it only for sockets.
461		533
462	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
463	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
464	C<NOTE_EOF>.	536	C<NOTE_EOF>.
465		537
…		…
500		572
501	It is definitely not recommended to use this flag.	573	It is definitely not recommended to use this flag.
502		574
503	=back	575	=back
504		576
505	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,
506	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
507	specified, all backends in C<ev_recommended_backends ()> will be tried.	579	here). If none are specified, all backends in C<ev_recommended_backends
508		580	()> will be tried.
509	Example: This is the most typical usage.
510
511	if (!ev_default_loop (0))
512	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
513
514	Example: Restrict libev to the select and poll backends, and do not allow
515	environment settings to be taken into account:
516
517	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
518
519	Example: Use whatever libev has to offer, but make sure that kqueue is
520	used if available (warning, breaks stuff, best use only with your own
521	private event loop and only if you know the OS supports your types of
522	fds):
523
524	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
525
526	=item struct ev_loop *ev_loop_new (unsigned int flags)
527
528	Similar to C<ev_default_loop>, but always creates a new event loop that is
529	always distinct from the default loop. Unlike the default loop, it cannot
530	handle signal and child watchers, and attempts to do so will be greeted by
531	undefined behaviour (or a failed assertion if assertions are enabled).
532
533	Note that this function I<is> thread-safe, and the recommended way to use
534	libev with threads is indeed to create one loop per thread, and using the
535	default loop in the "main" or "initial" thread.
536		581
537	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.
538		583
539	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	584	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
540	if (!epoller)	585	if (!epoller)
541	fatal ("no epoll found here, maybe it hides under your chair");	586	fatal ("no epoll found here, maybe it hides under your chair");
542		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
543	=item ev_default_destroy ()	593	=item ev_loop_destroy (loop)
544		594
545	Destroys the default loop again (frees all memory and kernel state	595	Destroys an event loop object (frees all memory and kernel state
546	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
547	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
548	responsibility to either stop all watchers cleanly yourself I<before>	598	responsibility to either stop all watchers cleanly yourself I<before>
549	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
550	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
…		…
552		602
553	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
554	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
555	as signal and child watchers) would need to be stopped manually.	605	as signal and child watchers) would need to be stopped manually.
556		606
557	In general it is not advisable to call this function except in the	607	This function is normally used on loop objects allocated by
558	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.
559	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>
560	C<ev_loop_new> and C<ev_loop_destroy>).	614	and C<ev_loop_destroy>.
561		615
562	=item ev_loop_destroy (loop)	616	=item ev_loop_fork (loop)
563		617
564	Like C<ev_default_destroy>, but destroys an event loop created by an
565	earlier call to C<ev_loop_new>.
566
567	=item ev_default_fork ()
568
569	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
570	to reinitialise the kernel state for backends that have one. Despite the	619	reinitialise the kernel state for backends that have one. Despite the
571	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
572	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
573	sense). You I<must> call it in the child before using any of the libev	622	child before resuming or calling C<ev_run>.
574	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.
575		628
576	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
577	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
578	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).
579		635
580	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
581	it just in case after a fork. To make this easy, the function will fit in	637	it just in case after a fork.
582	quite nicely into a call to C<pthread_atfork>:
583		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	...
584	pthread_atfork (0, 0, ev_default_fork);	649	pthread_atfork (0, 0, post_fork_child);
585
586	=item ev_loop_fork (loop)
587
588	Like C<ev_default_fork>, but acts on an event loop created by
589	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
590	after fork that you want to re-use in the child, and how you do this is
591	entirely your own problem.
592		650
593	=item int ev_is_default_loop (loop)	651	=item int ev_is_default_loop (loop)
594		652
595	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
596	otherwise.	654	otherwise.
597		655
598	=item unsigned int ev_loop_count (loop)	656	=item unsigned int ev_iteration (loop)
599		657
600	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
601	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>
602	happily wraps around with enough iterations.	660	and happily wraps around with enough iterations.
603		661
604	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
605	"ticks" the number of loop iterations), as it roughly corresponds with	663	"ticks" the number of loop iterations), as it roughly corresponds with
606	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.
607		679
608	=item unsigned int ev_backend (loop)	680	=item unsigned int ev_backend (loop)
609		681
610	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
611	use.	683	use.
…		…
620		692
621	=item ev_now_update (loop)	693	=item ev_now_update (loop)
622		694
623	Establishes the current time by querying the kernel, updating the time	695	Establishes the current time by querying the kernel, updating the time
624	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
625	is usually done automatically within C<ev_loop ()>.	697	is usually done automatically within C<ev_run ()>.
626		698
627	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
628	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
629	the current time is a good idea.	701	the current time is a good idea.
630		702
631	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.
632		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
633	=item ev_loop (loop, int flags)	731	=item ev_run (loop, int flags)
634		732
635	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
636	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
637	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>.
638		738
639	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
640	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.
641		742
642	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
643	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
644	finished (especially in interactive programs), but having a program	745	finished (especially in interactive programs), but having a program
645	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
646	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
647	beauty.	748	beauty.
648		749
649	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
650	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
651	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
652	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.
653		755
654	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
655	necessary) and will handle those and any already outstanding ones. It	757	necessary) and will handle those and any already outstanding ones. It
656	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
657	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
658	user-registered callback will be called), and will return after one	760	user-registered callback will be called), and will return after one
659	iteration of the loop.	761	iteration of the loop.
660		762
661	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
662	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
663	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
664	usually a better approach for this kind of thing.	766	usually a better approach for this kind of thing.
665		767
666	Here are the gory details of what C<ev_loop> does:	768	Here are the gory details of what C<ev_run> does:
667		769
		770	- Increment loop depth.
		771	- Reset the ev_break status.
668	- Before the first iteration, call any pending watchers.	772	- Before the first iteration, call any pending watchers.
		773	LOOP:
669	* If EVFLAG_FORKCHECK was used, check for a fork.	774	- If EVFLAG_FORKCHECK was used, check for a fork.
670	- 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.
671	- Queue and call all prepare watchers.	776	- Queue and call all prepare watchers.
		777	- If ev_break was called, goto FINISH.
672	- If we have been forked, detach and recreate the kernel state	778	- If we have been forked, detach and recreate the kernel state
673	as to not disturb the other process.	779	as to not disturb the other process.
674	- Update the kernel state with all outstanding changes.	780	- Update the kernel state with all outstanding changes.
675	- Update the "event loop time" (ev_now ()).	781	- Update the "event loop time" (ev_now ()).
676	- Calculate for how long to sleep or block, if at all	782	- Calculate for how long to sleep or block, if at all
677	(active idle watchers, EVLOOP_NONBLOCK or not having	783	(active idle watchers, EVRUN_NOWAIT or not having
678	any active watchers at all will result in not sleeping).	784	any active watchers at all will result in not sleeping).
679	- 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.
680	- Block the process, waiting for any events.	787	- Block the process, waiting for any events.
681	- Queue all outstanding I/O (fd) events.	788	- Queue all outstanding I/O (fd) events.
682	- 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.
683	- Queue all expired timers.	790	- Queue all expired timers.
684	- Queue all expired periodics.	791	- Queue all expired periodics.
685	- Unless any events are pending now, queue all idle watchers.	792	- Queue all idle watchers with priority higher than that of pending events.
686	- Queue all check watchers.	793	- Queue all check watchers.
687	- 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).
688	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
689	be handled here by queueing them when their watcher gets executed.	796	be handled here by queueing them when their watcher gets executed.
690	- 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
691	were used, or there are no active watchers, return, otherwise	798	were used, or there are no active watchers, goto FINISH, otherwise
692	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.
693		804
694	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
695	anymore.	806	anymore.
696		807
697	... queue jobs here, make sure they register event watchers as long	808	... queue jobs here, make sure they register event watchers as long
698	... 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..)
699	ev_loop (my_loop, 0);	810	ev_run (my_loop, 0);
700	... jobs done or somebody called unloop. yeah!	811	... jobs done or somebody called unloop. yeah!
701		812
702	=item ev_unloop (loop, how)	813	=item ev_break (loop, how)
703		814
704	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
705	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
706	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
707	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.
708		819
709	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.
710		821
711	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##
712		823
713	=item ev_ref (loop)	824	=item ev_ref (loop)
714		825
715	=item ev_unref (loop)	826	=item ev_unref (loop)
716		827
717	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
718	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
719	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.
720		831
721	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
722	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>
723	stopping it.	835	before stopping it.
724		836
725	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
726	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
727	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
728	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
729	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
730	(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
731	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).
732		846
733	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>
734	running when nothing else is active.	848	running when nothing else is active.
735		849
736	ev_signal exitsig;	850	ev_signal exitsig;
737	ev_signal_init (&exitsig, sig_cb, SIGINT);	851	ev_signal_init (&exitsig, sig_cb, SIGINT);
738	ev_signal_start (loop, &exitsig);	852	ev_signal_start (loop, &exitsig);
…		…
765		879
766	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
767	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,
768	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
769	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
770	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.
771		887
772	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
773	to spend more time collecting timeouts, at the expense of increased	889	to spend more time collecting timeouts, at the expense of increased
774	latency/jitter/inexactness (the watcher callback will be called	890	latency/jitter/inexactness (the watcher callback will be called
775	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
…		…
777		893
778	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
779	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
780	interactive servers (of course not for games), likewise for timeouts. It	896	interactive servers (of course not for games), likewise for timeouts. It
781	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>,
782	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).
783		903
784	Setting the I<timeout collect interval> can improve the opportunity for	904	Setting the I<timeout collect interval> can improve the opportunity for
785	saving power, as the program will "bundle" timer callback invocations that	905	saving power, as the program will "bundle" timer callback invocations that
786	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
787	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
788	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
789	they fire on, say, one-second boundaries only.	909	they fire on, say, one-second boundaries only.
790		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
791	=item ev_loop_verify (loop)	986	=item ev_verify (loop)
792		987
793	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
794	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
795	through all internal structures and checks them for validity. If anything	990	through all internal structures and checks them for validity. If anything
796	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
…		…
807		1002
808	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
809	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
810	watchers and C<ev_io_start> for I/O watchers.	1005	watchers and C<ev_io_start> for I/O watchers.
811		1006
812	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
813	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
814	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:
815		1011
816	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)
817	{	1013	{
818	ev_io_stop (w);	1014	ev_io_stop (w);
819	ev_unloop (loop, EVUNLOOP_ALL);	1015	ev_break (loop, EVBREAK_ALL);
820	}	1016	}
821		1017
822	struct ev_loop *loop = ev_default_loop (0);	1018	struct ev_loop *loop = ev_default_loop (0);
823		1019
824	ev_io stdin_watcher;	1020	ev_io stdin_watcher;
825		1021
826	ev_init (&stdin_watcher, my_cb);	1022	ev_init (&stdin_watcher, my_cb);
827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1023	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
828	ev_io_start (loop, &stdin_watcher);	1024	ev_io_start (loop, &stdin_watcher);
829		1025
830	ev_loop (loop, 0);	1026	ev_run (loop, 0);
831		1027
832	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
833	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
834	stack).	1030	stack).
835		1031
836	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>
837	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).
838		1034
839	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
840	(watcher *, callback)>, which expects a callback to be provided. This	1036	*, callback)>, which expects a callback to be provided. This callback is
841	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
842	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
843	is readable and/or writable).	1039	and/or writable).
844		1040
845	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 *, ...) >>
846	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
847	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<<
848	ev_TYPE_init (watcher *, callback, ...) >>.	1044	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
871	=item C<EV_WRITE>	1067	=item C<EV_WRITE>
872		1068
873	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
874	writable.	1070	writable.
875		1071
876	=item C<EV_TIMEOUT>	1072	=item C<EV_TIMER>
877		1073
878	The C<ev_timer> watcher has timed out.	1074	The C<ev_timer> watcher has timed out.
879		1075
880	=item C<EV_PERIODIC>	1076	=item C<EV_PERIODIC>
881		1077
…		…
899		1095
900	=item C<EV_PREPARE>	1096	=item C<EV_PREPARE>
901		1097
902	=item C<EV_CHECK>	1098	=item C<EV_CHECK>
903		1099
904	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
905	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
906	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
907	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
908	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
909	(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
910	C<ev_loop> from blocking).	1106	C<ev_run> from blocking).
911		1107
912	=item C<EV_EMBED>	1108	=item C<EV_EMBED>
913		1109
914	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.
915		1111
916	=item C<EV_FORK>	1112	=item C<EV_FORK>
917		1113
918	The event loop has been resumed in the child process after fork (see	1114	The event loop has been resumed in the child process after fork (see
919	C<ev_fork>).	1115	C<ev_fork>).
920		1116
		1117	=item C<EV_CLEANUP>
		1118
		1119	The event loop is about to be destroyed (see C<ev_cleanup>).
		1120
921	=item C<EV_ASYNC>	1121	=item C<EV_ASYNC>
922		1122
923	The given async watcher has been asynchronously notified (see C<ev_async>).	1123	The given async watcher has been asynchronously notified (see C<ev_async>).
		1124
		1125	=item C<EV_CUSTOM>
		1126
		1127	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1128	by libev users to signal watchers (e.g. via C<ev_feed_event>).
924		1129
925	=item C<EV_ERROR>	1130	=item C<EV_ERROR>
926		1131
927	An unspecified error has occurred, the watcher has been stopped. This might	1132	An unspecified error has occurred, the watcher has been stopped. This might
928	happen because the watcher could not be properly started because libev	1133	happen because the watcher could not be properly started because libev
…		…
941	programs, though, as the fd could already be closed and reused for another	1146	programs, though, as the fd could already be closed and reused for another
942	thing, so beware.	1147	thing, so beware.
943		1148
944	=back	1149	=back
945		1150
		1151	=head2 WATCHER STATES
		1152
		1153	There are various watcher states mentioned throughout this manual -
		1154	active, pending and so on. In this section these states and the rules to
		1155	transition between them will be described in more detail - and while these
		1156	rules might look complicated, they usually do "the right thing".
		1157
		1158	=over 4
		1159
		1160	=item initialiased
		1161
		1162	Before a watcher can be registered with the event looop it has to be
		1163	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1164	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1165
		1166	In this state it is simply some block of memory that is suitable for use
		1167	in an event loop. It can be moved around, freed, reused etc. at will.
		1168
		1169	=item started/running/active
		1170
		1171	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1172	property of the event loop, and is actively waiting for events. While in
		1173	this state it cannot be accessed (except in a few documented ways), moved,
		1174	freed or anything else - the only legal thing is to keep a pointer to it,
		1175	and call libev functions on it that are documented to work on active watchers.
		1176
		1177	=item pending
		1178
		1179	If a watcher is active and libev determines that an event it is interested
		1180	in has occurred (such as a timer expiring), it will become pending. It will
		1181	stay in this pending state until either it is stopped or its callback is
		1182	about to be invoked, so it is not normally pending inside the watcher
		1183	callback.
		1184
		1185	The watcher might or might not be active while it is pending (for example,
		1186	an expired non-repeating timer can be pending but no longer active). If it
		1187	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1188	but it is still property of the event loop at this time, so cannot be
		1189	moved, freed or reused. And if it is active the rules described in the
		1190	previous item still apply.
		1191
		1192	It is also possible to feed an event on a watcher that is not active (e.g.
		1193	via C<ev_feed_event>), in which case it becomes pending without being
		1194	active.
		1195
		1196	=item stopped
		1197
		1198	A watcher can be stopped implicitly by libev (in which case it might still
		1199	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1200	latter will clear any pending state the watcher might be in, regardless
		1201	of whether it was active or not, so stopping a watcher explicitly before
		1202	freeing it is often a good idea.
		1203
		1204	While stopped (and not pending) the watcher is essentially in the
		1205	initialised state, that is it can be reused, moved, modified in any way
		1206	you wish.
		1207
		1208	=back
		1209
946	=head2 GENERIC WATCHER FUNCTIONS	1210	=head2 GENERIC WATCHER FUNCTIONS
947		1211
948	=over 4	1212	=over 4
949		1213
950	=item C<ev_init> (ev_TYPE *watcher, callback)	1214	=item C<ev_init> (ev_TYPE *watcher, callback)
…		…
966		1230
967	ev_io w;	1231	ev_io w;
968	ev_init (&w, my_cb);	1232	ev_init (&w, my_cb);
969	ev_io_set (&w, STDIN_FILENO, EV_READ);	1233	ev_io_set (&w, STDIN_FILENO, EV_READ);
970		1234
971	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1235	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
972		1236
973	This macro initialises the type-specific parts of a watcher. You need to	1237	This macro initialises the type-specific parts of a watcher. You need to
974	call C<ev_init> at least once before you call this macro, but you can	1238	call C<ev_init> at least once before you call this macro, but you can
975	call C<ev_TYPE_set> any number of times. You must not, however, call this	1239	call C<ev_TYPE_set> any number of times. You must not, however, call this
976	macro on a watcher that is active (it can be pending, however, which is a	1240	macro on a watcher that is active (it can be pending, however, which is a
…		…
989		1253
990	Example: Initialise and set an C<ev_io> watcher in one step.	1254	Example: Initialise and set an C<ev_io> watcher in one step.
991		1255
992	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1256	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
993		1257
994	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1258	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
995		1259
996	Starts (activates) the given watcher. Only active watchers will receive	1260	Starts (activates) the given watcher. Only active watchers will receive
997	events. If the watcher is already active nothing will happen.	1261	events. If the watcher is already active nothing will happen.
998		1262
999	Example: Start the C<ev_io> watcher that is being abused as example in this	1263	Example: Start the C<ev_io> watcher that is being abused as example in this
1000	whole section.	1264	whole section.
1001		1265
1002	ev_io_start (EV_DEFAULT_UC, &w);	1266	ev_io_start (EV_DEFAULT_UC, &w);
1003		1267
1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1268	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1005		1269
1006	Stops the given watcher if active, and clears the pending status (whether	1270	Stops the given watcher if active, and clears the pending status (whether
1007	the watcher was active or not).	1271	the watcher was active or not).
1008		1272
1009	It is possible that stopped watchers are pending - for example,	1273	It is possible that stopped watchers are pending - for example,
…		…
1034	=item ev_cb_set (ev_TYPE *watcher, callback)	1298	=item ev_cb_set (ev_TYPE *watcher, callback)
1035		1299
1036	Change the callback. You can change the callback at virtually any time	1300	Change the callback. You can change the callback at virtually any time
1037	(modulo threads).	1301	(modulo threads).
1038		1302
1039	=item ev_set_priority (ev_TYPE *watcher, priority)	1303	=item ev_set_priority (ev_TYPE *watcher, int priority)
1040		1304
1041	=item int ev_priority (ev_TYPE *watcher)	1305	=item int ev_priority (ev_TYPE *watcher)
1042		1306
1043	Set and query the priority of the watcher. The priority is a small	1307	Set and query the priority of the watcher. The priority is a small
1044	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1308	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1045	(default: C<-2>). Pending watchers with higher priority will be invoked	1309	(default: C<-2>). Pending watchers with higher priority will be invoked
1046	before watchers with lower priority, but priority will not keep watchers	1310	before watchers with lower priority, but priority will not keep watchers
1047	from being executed (except for C<ev_idle> watchers).	1311	from being executed (except for C<ev_idle> watchers).
1048		1312
1049	This means that priorities are I<only> used for ordering callback
1050	invocation after new events have been received. This is useful, for
1051	example, to reduce latency after idling, or more often, to bind two
1052	watchers on the same event and make sure one is called first.
1053
1054	If you need to suppress invocation when higher priority events are pending	1313	If you need to suppress invocation when higher priority events are pending
1055	you need to look at C<ev_idle> watchers, which provide this functionality.	1314	you need to look at C<ev_idle> watchers, which provide this functionality.
1056		1315
1057	You I<must not> change the priority of a watcher as long as it is active or	1316	You I<must not> change the priority of a watcher as long as it is active or
1058	pending.	1317	pending.
1059
1060	The default priority used by watchers when no priority has been set is
1061	always C<0>, which is supposed to not be too high and not be too low :).
1062		1318
1063	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1319	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1064	fine, as long as you do not mind that the priority value you query might	1320	fine, as long as you do not mind that the priority value you query might
1065	or might not have been clamped to the valid range.	1321	or might not have been clamped to the valid range.
		1322
		1323	The default priority used by watchers when no priority has been set is
		1324	always C<0>, which is supposed to not be too high and not be too low :).
		1325
		1326	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1327	priorities.
1066		1328
1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1329	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1068		1330
1069	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1331	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1070	C<loop> nor C<revents> need to be valid as long as the watcher callback	1332	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1077	returns its C<revents> bitset (as if its callback was invoked). If the	1339	returns its C<revents> bitset (as if its callback was invoked). If the
1078	watcher isn't pending it does nothing and returns C<0>.	1340	watcher isn't pending it does nothing and returns C<0>.
1079		1341
1080	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1342	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1081	callback to be invoked, which can be accomplished with this function.	1343	callback to be invoked, which can be accomplished with this function.
		1344
		1345	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1346
		1347	Feeds the given event set into the event loop, as if the specified event
		1348	had happened for the specified watcher (which must be a pointer to an
		1349	initialised but not necessarily started event watcher). Obviously you must
		1350	not free the watcher as long as it has pending events.
		1351
		1352	Stopping the watcher, letting libev invoke it, or calling
		1353	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1354	not started in the first place.
		1355
		1356	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1357	functions that do not need a watcher.
1082		1358
1083	=back	1359	=back
1084		1360
1085		1361
1086	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1135	#include <stddef.h>	1411	#include <stddef.h>
1136		1412
1137	static void	1413	static void
1138	t1_cb (EV_P_ ev_timer *w, int revents)	1414	t1_cb (EV_P_ ev_timer *w, int revents)
1139	{	1415	{
1140	struct my_biggy big = (struct my_biggy *	1416	struct my_biggy big = (struct my_biggy *)
1141	(((char *)w) - offsetof (struct my_biggy, t1));	1417	(((char *)w) - offsetof (struct my_biggy, t1));
1142	}	1418	}
1143		1419
1144	static void	1420	static void
1145	t2_cb (EV_P_ ev_timer *w, int revents)	1421	t2_cb (EV_P_ ev_timer *w, int revents)
1146	{	1422	{
1147	struct my_biggy big = (struct my_biggy *	1423	struct my_biggy big = (struct my_biggy *)
1148	(((char *)w) - offsetof (struct my_biggy, t2));	1424	(((char *)w) - offsetof (struct my_biggy, t2));
1149	}	1425	}
		1426
		1427	=head2 WATCHER PRIORITY MODELS
		1428
		1429	Many event loops support I<watcher priorities>, which are usually small
		1430	integers that influence the ordering of event callback invocation
		1431	between watchers in some way, all else being equal.
		1432
		1433	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1434	description for the more technical details such as the actual priority
		1435	range.
		1436
		1437	There are two common ways how these these priorities are being interpreted
		1438	by event loops:
		1439
		1440	In the more common lock-out model, higher priorities "lock out" invocation
		1441	of lower priority watchers, which means as long as higher priority
		1442	watchers receive events, lower priority watchers are not being invoked.
		1443
		1444	The less common only-for-ordering model uses priorities solely to order
		1445	callback invocation within a single event loop iteration: Higher priority
		1446	watchers are invoked before lower priority ones, but they all get invoked
		1447	before polling for new events.
		1448
		1449	Libev uses the second (only-for-ordering) model for all its watchers
		1450	except for idle watchers (which use the lock-out model).
		1451
		1452	The rationale behind this is that implementing the lock-out model for
		1453	watchers is not well supported by most kernel interfaces, and most event
		1454	libraries will just poll for the same events again and again as long as
		1455	their callbacks have not been executed, which is very inefficient in the
		1456	common case of one high-priority watcher locking out a mass of lower
		1457	priority ones.
		1458
		1459	Static (ordering) priorities are most useful when you have two or more
		1460	watchers handling the same resource: a typical usage example is having an
		1461	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1462	timeouts. Under load, data might be received while the program handles
		1463	other jobs, but since timers normally get invoked first, the timeout
		1464	handler will be executed before checking for data. In that case, giving
		1465	the timer a lower priority than the I/O watcher ensures that I/O will be
		1466	handled first even under adverse conditions (which is usually, but not
		1467	always, what you want).
		1468
		1469	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1470	will only be executed when no same or higher priority watchers have
		1471	received events, they can be used to implement the "lock-out" model when
		1472	required.
		1473
		1474	For example, to emulate how many other event libraries handle priorities,
		1475	you can associate an C<ev_idle> watcher to each such watcher, and in
		1476	the normal watcher callback, you just start the idle watcher. The real
		1477	processing is done in the idle watcher callback. This causes libev to
		1478	continuously poll and process kernel event data for the watcher, but when
		1479	the lock-out case is known to be rare (which in turn is rare :), this is
		1480	workable.
		1481
		1482	Usually, however, the lock-out model implemented that way will perform
		1483	miserably under the type of load it was designed to handle. In that case,
		1484	it might be preferable to stop the real watcher before starting the
		1485	idle watcher, so the kernel will not have to process the event in case
		1486	the actual processing will be delayed for considerable time.
		1487
		1488	Here is an example of an I/O watcher that should run at a strictly lower
		1489	priority than the default, and which should only process data when no
		1490	other events are pending:
		1491
		1492	ev_idle idle; // actual processing watcher
		1493	ev_io io; // actual event watcher
		1494
		1495	static void
		1496	io_cb (EV_P_ ev_io *w, int revents)
		1497	{
		1498	// stop the I/O watcher, we received the event, but
		1499	// are not yet ready to handle it.
		1500	ev_io_stop (EV_A_ w);
		1501
		1502	// start the idle watcher to handle the actual event.
		1503	// it will not be executed as long as other watchers
		1504	// with the default priority are receiving events.
		1505	ev_idle_start (EV_A_ &idle);
		1506	}
		1507
		1508	static void
		1509	idle_cb (EV_P_ ev_idle *w, int revents)
		1510	{
		1511	// actual processing
		1512	read (STDIN_FILENO, ...);
		1513
		1514	// have to start the I/O watcher again, as
		1515	// we have handled the event
		1516	ev_io_start (EV_P_ &io);
		1517	}
		1518
		1519	// initialisation
		1520	ev_idle_init (&idle, idle_cb);
		1521	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1522	ev_io_start (EV_DEFAULT_ &io);
		1523
		1524	In the "real" world, it might also be beneficial to start a timer, so that
		1525	low-priority connections can not be locked out forever under load. This
		1526	enables your program to keep a lower latency for important connections
		1527	during short periods of high load, while not completely locking out less
		1528	important ones.
1150		1529
1151		1530
1152	=head1 WATCHER TYPES	1531	=head1 WATCHER TYPES
1153		1532
1154	This section describes each watcher in detail, but will not repeat	1533	This section describes each watcher in detail, but will not repeat
…		…
1180	descriptors to non-blocking mode is also usually a good idea (but not	1559	descriptors to non-blocking mode is also usually a good idea (but not
1181	required if you know what you are doing).	1560	required if you know what you are doing).
1182		1561
1183	If you cannot use non-blocking mode, then force the use of a	1562	If you cannot use non-blocking mode, then force the use of a
1184	known-to-be-good backend (at the time of this writing, this includes only	1563	known-to-be-good backend (at the time of this writing, this includes only
1185	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).	1564	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1565	descriptors for which non-blocking operation makes no sense (such as
		1566	files) - libev doesn't guarantee any specific behaviour in that case.
1186		1567
1187	Another thing you have to watch out for is that it is quite easy to	1568	Another thing you have to watch out for is that it is quite easy to
1188	receive "spurious" readiness notifications, that is your callback might	1569	receive "spurious" readiness notifications, that is your callback might
1189	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1570	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1190	because there is no data. Not only are some backends known to create a	1571	because there is no data. Not only are some backends known to create a
…		…
1255		1636
1256	So when you encounter spurious, unexplained daemon exits, make sure you	1637	So when you encounter spurious, unexplained daemon exits, make sure you
1257	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1638	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1258	somewhere, as that would have given you a big clue).	1639	somewhere, as that would have given you a big clue).
1259		1640
		1641	=head3 The special problem of accept()ing when you can't
		1642
		1643	Many implementations of the POSIX C<accept> function (for example,
		1644	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1645	connection from the pending queue in all error cases.
		1646
		1647	For example, larger servers often run out of file descriptors (because
		1648	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1649	rejecting the connection, leading to libev signalling readiness on
		1650	the next iteration again (the connection still exists after all), and
		1651	typically causing the program to loop at 100% CPU usage.
		1652
		1653	Unfortunately, the set of errors that cause this issue differs between
		1654	operating systems, there is usually little the app can do to remedy the
		1655	situation, and no known thread-safe method of removing the connection to
		1656	cope with overload is known (to me).
		1657
		1658	One of the easiest ways to handle this situation is to just ignore it
		1659	- when the program encounters an overload, it will just loop until the
		1660	situation is over. While this is a form of busy waiting, no OS offers an
		1661	event-based way to handle this situation, so it's the best one can do.
		1662
		1663	A better way to handle the situation is to log any errors other than
		1664	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1665	messages, and continue as usual, which at least gives the user an idea of
		1666	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1667	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1668	usage.
		1669
		1670	If your program is single-threaded, then you could also keep a dummy file
		1671	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1672	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1673	close that fd, and create a new dummy fd. This will gracefully refuse
		1674	clients under typical overload conditions.
		1675
		1676	The last way to handle it is to simply log the error and C<exit>, as
		1677	is often done with C<malloc> failures, but this results in an easy
		1678	opportunity for a DoS attack.
1260		1679
1261	=head3 Watcher-Specific Functions	1680	=head3 Watcher-Specific Functions
1262		1681
1263	=over 4	1682	=over 4
1264		1683
…		…
1296	...	1715	...
1297	struct ev_loop *loop = ev_default_init (0);	1716	struct ev_loop *loop = ev_default_init (0);
1298	ev_io stdin_readable;	1717	ev_io stdin_readable;
1299	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1718	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1300	ev_io_start (loop, &stdin_readable);	1719	ev_io_start (loop, &stdin_readable);
1301	ev_loop (loop, 0);	1720	ev_run (loop, 0);
1302		1721
1303		1722
1304	=head2 C<ev_timer> - relative and optionally repeating timeouts	1723	=head2 C<ev_timer> - relative and optionally repeating timeouts
1305		1724
1306	Timer watchers are simple relative timers that generate an event after a	1725	Timer watchers are simple relative timers that generate an event after a
…		…
1311	year, it will still time out after (roughly) one hour. "Roughly" because	1730	year, it will still time out after (roughly) one hour. "Roughly" because
1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1731	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1313	monotonic clock option helps a lot here).	1732	monotonic clock option helps a lot here).
1314		1733
1315	The callback is guaranteed to be invoked only I<after> its timeout has	1734	The callback is guaranteed to be invoked only I<after> its timeout has
1316	passed, but if multiple timers become ready during the same loop iteration	1735	passed (not I<at>, so on systems with very low-resolution clocks this
1317	then order of execution is undefined.	1736	might introduce a small delay). If multiple timers become ready during the
		1737	same loop iteration then the ones with earlier time-out values are invoked
		1738	before ones of the same priority with later time-out values (but this is
		1739	no longer true when a callback calls C<ev_run> recursively).
1318		1740
1319	=head3 Be smart about timeouts	1741	=head3 Be smart about timeouts
1320		1742
1321	Many real-world problems involve some kind of timeout, usually for error	1743	Many real-world problems involve some kind of timeout, usually for error
1322	recovery. A typical example is an HTTP request - if the other side hangs,	1744	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1366	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1788	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1367	member and C<ev_timer_again>.	1789	member and C<ev_timer_again>.
1368		1790
1369	At start:	1791	At start:
1370		1792
1371	ev_timer_init (timer, callback);	1793	ev_init (timer, callback);
1372	timer->repeat = 60.;	1794	timer->repeat = 60.;
1373	ev_timer_again (loop, timer);	1795	ev_timer_again (loop, timer);
1374		1796
1375	Each time there is some activity:	1797	Each time there is some activity:
1376		1798
…		…
1408	ev_tstamp timeout = last_activity + 60.;	1830	ev_tstamp timeout = last_activity + 60.;
1409		1831
1410	// if last_activity + 60. is older than now, we did time out	1832	// if last_activity + 60. is older than now, we did time out
1411	if (timeout < now)	1833	if (timeout < now)
1412	{	1834	{
1413	// timeout occured, take action	1835	// timeout occurred, take action
1414	}	1836	}
1415	else	1837	else
1416	{	1838	{
1417	// callback was invoked, but there was some activity, re-arm	1839	// callback was invoked, but there was some activity, re-arm
1418	// the watcher to fire in last_activity + 60, which is	1840	// the watcher to fire in last_activity + 60, which is
1419	// guaranteed to be in the future, so "again" is positive:	1841	// guaranteed to be in the future, so "again" is positive:
1420	w->again = timeout - now;	1842	w->repeat = timeout - now;
1421	ev_timer_again (EV_A_ w);	1843	ev_timer_again (EV_A_ w);
1422	}	1844	}
1423	}	1845	}
1424		1846
1425	To summarise the callback: first calculate the real timeout (defined	1847	To summarise the callback: first calculate the real timeout (defined
…		…
1438		1860
1439	To start the timer, simply initialise the watcher and set C<last_activity>	1861	To start the timer, simply initialise the watcher and set C<last_activity>
1440	to the current time (meaning we just have some activity :), then call the	1862	to the current time (meaning we just have some activity :), then call the
1441	callback, which will "do the right thing" and start the timer:	1863	callback, which will "do the right thing" and start the timer:
1442		1864
1443	ev_timer_init (timer, callback);	1865	ev_init (timer, callback);
1444	last_activity = ev_now (loop);	1866	last_activity = ev_now (loop);
1445	callback (loop, timer, EV_TIMEOUT);	1867	callback (loop, timer, EV_TIMER);
1446		1868
1447	And when there is some activity, simply store the current time in	1869	And when there is some activity, simply store the current time in
1448	C<last_activity>, no libev calls at all:	1870	C<last_activity>, no libev calls at all:
1449		1871
1450	last_actiivty = ev_now (loop);	1872	last_activity = ev_now (loop);
1451		1873
1452	This technique is slightly more complex, but in most cases where the	1874	This technique is slightly more complex, but in most cases where the
1453	time-out is unlikely to be triggered, much more efficient.	1875	time-out is unlikely to be triggered, much more efficient.
1454		1876
1455	Changing the timeout is trivial as well (if it isn't hard-coded in the	1877	Changing the timeout is trivial as well (if it isn't hard-coded in the
…		…
1493		1915
1494	=head3 The special problem of time updates	1916	=head3 The special problem of time updates
1495		1917
1496	Establishing the current time is a costly operation (it usually takes at	1918	Establishing the current time is a costly operation (it usually takes at
1497	least two system calls): EV therefore updates its idea of the current	1919	least two system calls): EV therefore updates its idea of the current
1498	time only before and after C<ev_loop> collects new events, which causes a	1920	time only before and after C<ev_run> collects new events, which causes a
1499	growing difference between C<ev_now ()> and C<ev_time ()> when handling	1921	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1500	lots of events in one iteration.	1922	lots of events in one iteration.
1501		1923
1502	The relative timeouts are calculated relative to the C<ev_now ()>	1924	The relative timeouts are calculated relative to the C<ev_now ()>
1503	time. This is usually the right thing as this timestamp refers to the time	1925	time. This is usually the right thing as this timestamp refers to the time
…		…
1509		1931
1510	If the event loop is suspended for a long time, you can also force an	1932	If the event loop is suspended for a long time, you can also force an
1511	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1933	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1512	()>.	1934	()>.
1513		1935
		1936	=head3 The special problems of suspended animation
		1937
		1938	When you leave the server world it is quite customary to hit machines that
		1939	can suspend/hibernate - what happens to the clocks during such a suspend?
		1940
		1941	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1942	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1943	to run until the system is suspended, but they will not advance while the
		1944	system is suspended. That means, on resume, it will be as if the program
		1945	was frozen for a few seconds, but the suspend time will not be counted
		1946	towards C<ev_timer> when a monotonic clock source is used. The real time
		1947	clock advanced as expected, but if it is used as sole clocksource, then a
		1948	long suspend would be detected as a time jump by libev, and timers would
		1949	be adjusted accordingly.
		1950
		1951	I would not be surprised to see different behaviour in different between
		1952	operating systems, OS versions or even different hardware.
		1953
		1954	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1955	time jump in the monotonic clocks and the realtime clock. If the program
		1956	is suspended for a very long time, and monotonic clock sources are in use,
		1957	then you can expect C<ev_timer>s to expire as the full suspension time
		1958	will be counted towards the timers. When no monotonic clock source is in
		1959	use, then libev will again assume a timejump and adjust accordingly.
		1960
		1961	It might be beneficial for this latter case to call C<ev_suspend>
		1962	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1963	deterministic behaviour in this case (you can do nothing against
		1964	C<SIGSTOP>).
		1965
1514	=head3 Watcher-Specific Functions and Data Members	1966	=head3 Watcher-Specific Functions and Data Members
1515		1967
1516	=over 4	1968	=over 4
1517		1969
1518	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1970	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1541	If the timer is started but non-repeating, stop it (as if it timed out).	1993	If the timer is started but non-repeating, stop it (as if it timed out).
1542		1994
1543	If the timer is repeating, either start it if necessary (with the	1995	If the timer is repeating, either start it if necessary (with the
1544	C<repeat> value), or reset the running timer to the C<repeat> value.	1996	C<repeat> value), or reset the running timer to the C<repeat> value.
1545		1997
1546	This sounds a bit complicated, see "Be smart about timeouts", above, for a	1998	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1547	usage example.	1999	usage example.
		2000
		2001	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2002
		2003	Returns the remaining time until a timer fires. If the timer is active,
		2004	then this time is relative to the current event loop time, otherwise it's
		2005	the timeout value currently configured.
		2006
		2007	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2008	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2009	will return C<4>. When the timer expires and is restarted, it will return
		2010	roughly C<7> (likely slightly less as callback invocation takes some time,
		2011	too), and so on.
1548		2012
1549	=item ev_tstamp repeat [read-write]	2013	=item ev_tstamp repeat [read-write]
1550		2014
1551	The current C<repeat> value. Will be used each time the watcher times out	2015	The current C<repeat> value. Will be used each time the watcher times out
1552	or C<ev_timer_again> is called, and determines the next timeout (if any),	2016	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1578	}	2042	}
1579		2043
1580	ev_timer mytimer;	2044	ev_timer mytimer;
1581	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2045	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1582	ev_timer_again (&mytimer); /* start timer */	2046	ev_timer_again (&mytimer); /* start timer */
1583	ev_loop (loop, 0);	2047	ev_run (loop, 0);
1584		2048
1585	// and in some piece of code that gets executed on any "activity":	2049	// and in some piece of code that gets executed on any "activity":
1586	// reset the timeout to start ticking again at 10 seconds	2050	// reset the timeout to start ticking again at 10 seconds
1587	ev_timer_again (&mytimer);	2051	ev_timer_again (&mytimer);
1588		2052
…		…
1590	=head2 C<ev_periodic> - to cron or not to cron?	2054	=head2 C<ev_periodic> - to cron or not to cron?
1591		2055
1592	Periodic watchers are also timers of a kind, but they are very versatile	2056	Periodic watchers are also timers of a kind, but they are very versatile
1593	(and unfortunately a bit complex).	2057	(and unfortunately a bit complex).
1594		2058
1595	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2059	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1596	but on wall clock time (absolute time). You can tell a periodic watcher	2060	relative time, the physical time that passes) but on wall clock time
1597	to trigger after some specific point in time. For example, if you tell a	2061	(absolute time, the thing you can read on your calender or clock). The
1598	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2062	difference is that wall clock time can run faster or slower than real
1599	+ 10.>, that is, an absolute time not a delay) and then reset your system	2063	time, and time jumps are not uncommon (e.g. when you adjust your
1600	clock to January of the previous year, then it will take more than year	2064	wrist-watch).
1601	to trigger the event (unlike an C<ev_timer>, which would still trigger
1602	roughly 10 seconds later as it uses a relative timeout).
1603		2065
		2066	You can tell a periodic watcher to trigger after some specific point
		2067	in time: for example, if you tell a periodic watcher to trigger "in 10
		2068	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2069	not a delay) and then reset your system clock to January of the previous
		2070	year, then it will take a year or more to trigger the event (unlike an
		2071	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2072	it, as it uses a relative timeout).
		2073
1604	C<ev_periodic>s can also be used to implement vastly more complex timers,	2074	C<ev_periodic> watchers can also be used to implement vastly more complex
1605	such as triggering an event on each "midnight, local time", or other	2075	timers, such as triggering an event on each "midnight, local time", or
1606	complicated rules.	2076	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2077	those cannot react to time jumps.
1607		2078
1608	As with timers, the callback is guaranteed to be invoked only when the	2079	As with timers, the callback is guaranteed to be invoked only when the
1609	time (C<at>) has passed, but if multiple periodic timers become ready	2080	point in time where it is supposed to trigger has passed. If multiple
1610	during the same loop iteration, then order of execution is undefined.	2081	timers become ready during the same loop iteration then the ones with
		2082	earlier time-out values are invoked before ones with later time-out values
		2083	(but this is no longer true when a callback calls C<ev_run> recursively).
1611		2084
1612	=head3 Watcher-Specific Functions and Data Members	2085	=head3 Watcher-Specific Functions and Data Members
1613		2086
1614	=over 4	2087	=over 4
1615		2088
1616	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2089	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1617		2090
1618	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2091	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1619		2092
1620	Lots of arguments, lets sort it out... There are basically three modes of	2093	Lots of arguments, let's sort it out... There are basically three modes of
1621	operation, and we will explain them from simplest to most complex:	2094	operation, and we will explain them from simplest to most complex:
1622		2095
1623	=over 4	2096	=over 4
1624		2097
1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2098	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1626		2099
1627	In this configuration the watcher triggers an event after the wall clock	2100	In this configuration the watcher triggers an event after the wall clock
1628	time C<at> has passed. It will not repeat and will not adjust when a time	2101	time C<offset> has passed. It will not repeat and will not adjust when a
1629	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2102	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1630	only run when the system clock reaches or surpasses this time.	2103	will be stopped and invoked when the system clock reaches or surpasses
		2104	this point in time.
1631		2105
1632	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2106	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1633		2107
1634	In this mode the watcher will always be scheduled to time out at the next	2108	In this mode the watcher will always be scheduled to time out at the next
1635	C<at + N * interval> time (for some integer N, which can also be negative)	2109	C<offset + N * interval> time (for some integer N, which can also be
1636	and then repeat, regardless of any time jumps.	2110	negative) and then repeat, regardless of any time jumps. The C<offset>
		2111	argument is merely an offset into the C<interval> periods.
1637		2112
1638	This can be used to create timers that do not drift with respect to the	2113	This can be used to create timers that do not drift with respect to the
1639	system clock, for example, here is a C<ev_periodic> that triggers each	2114	system clock, for example, here is an C<ev_periodic> that triggers each
1640	hour, on the hour:	2115	hour, on the hour (with respect to UTC):
1641		2116
1642	ev_periodic_set (&periodic, 0., 3600., 0);	2117	ev_periodic_set (&periodic, 0., 3600., 0);
1643		2118
1644	This doesn't mean there will always be 3600 seconds in between triggers,	2119	This doesn't mean there will always be 3600 seconds in between triggers,
1645	but only that the callback will be called when the system time shows a	2120	but only that the callback will be called when the system time shows a
1646	full hour (UTC), or more correctly, when the system time is evenly divisible	2121	full hour (UTC), or more correctly, when the system time is evenly divisible
1647	by 3600.	2122	by 3600.
1648		2123
1649	Another way to think about it (for the mathematically inclined) is that	2124	Another way to think about it (for the mathematically inclined) is that
1650	C<ev_periodic> will try to run the callback in this mode at the next possible	2125	C<ev_periodic> will try to run the callback in this mode at the next possible
1651	time where C<time = at (mod interval)>, regardless of any time jumps.	2126	time where C<time = offset (mod interval)>, regardless of any time jumps.
1652		2127
1653	For numerical stability it is preferable that the C<at> value is near	2128	For numerical stability it is preferable that the C<offset> value is near
1654	C<ev_now ()> (the current time), but there is no range requirement for	2129	C<ev_now ()> (the current time), but there is no range requirement for
1655	this value, and in fact is often specified as zero.	2130	this value, and in fact is often specified as zero.
1656		2131
1657	Note also that there is an upper limit to how often a timer can fire (CPU	2132	Note also that there is an upper limit to how often a timer can fire (CPU
1658	speed for example), so if C<interval> is very small then timing stability	2133	speed for example), so if C<interval> is very small then timing stability
1659	will of course deteriorate. Libev itself tries to be exact to be about one	2134	will of course deteriorate. Libev itself tries to be exact to be about one
1660	millisecond (if the OS supports it and the machine is fast enough).	2135	millisecond (if the OS supports it and the machine is fast enough).
1661		2136
1662	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2137	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1663		2138
1664	In this mode the values for C<interval> and C<at> are both being	2139	In this mode the values for C<interval> and C<offset> are both being
1665	ignored. Instead, each time the periodic watcher gets scheduled, the	2140	ignored. Instead, each time the periodic watcher gets scheduled, the
1666	reschedule callback will be called with the watcher as first, and the	2141	reschedule callback will be called with the watcher as first, and the
1667	current time as second argument.	2142	current time as second argument.
1668		2143
1669	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2144	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1670	ever, or make ANY event loop modifications whatsoever>.	2145	or make ANY other event loop modifications whatsoever, unless explicitly
		2146	allowed by documentation here>.
1671		2147
1672	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2148	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1673	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2149	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1674	only event loop modification you are allowed to do).	2150	only event loop modification you are allowed to do).
1675		2151
…		…
1705	a different time than the last time it was called (e.g. in a crond like	2181	a different time than the last time it was called (e.g. in a crond like
1706	program when the crontabs have changed).	2182	program when the crontabs have changed).
1707		2183
1708	=item ev_tstamp ev_periodic_at (ev_periodic *)	2184	=item ev_tstamp ev_periodic_at (ev_periodic *)
1709		2185
1710	When active, returns the absolute time that the watcher is supposed to	2186	When active, returns the absolute time that the watcher is supposed
1711	trigger next.	2187	to trigger next. This is not the same as the C<offset> argument to
		2188	C<ev_periodic_set>, but indeed works even in interval and manual
		2189	rescheduling modes.
1712		2190
1713	=item ev_tstamp offset [read-write]	2191	=item ev_tstamp offset [read-write]
1714		2192
1715	When repeating, this contains the offset value, otherwise this is the	2193	When repeating, this contains the offset value, otherwise this is the
1716	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2194	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2195	although libev might modify this value for better numerical stability).
1717		2196
1718	Can be modified any time, but changes only take effect when the periodic	2197	Can be modified any time, but changes only take effect when the periodic
1719	timer fires or C<ev_periodic_again> is being called.	2198	timer fires or C<ev_periodic_again> is being called.
1720		2199
1721	=item ev_tstamp interval [read-write]	2200	=item ev_tstamp interval [read-write]
…		…
1737	Example: Call a callback every hour, or, more precisely, whenever the	2216	Example: Call a callback every hour, or, more precisely, whenever the
1738	system time is divisible by 3600. The callback invocation times have	2217	system time is divisible by 3600. The callback invocation times have
1739	potentially a lot of jitter, but good long-term stability.	2218	potentially a lot of jitter, but good long-term stability.
1740		2219
1741	static void	2220	static void
1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2221	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1743	{	2222	{
1744	... its now a full hour (UTC, or TAI or whatever your clock follows)	2223	... its now a full hour (UTC, or TAI or whatever your clock follows)
1745	}	2224	}
1746		2225
1747	ev_periodic hourly_tick;	2226	ev_periodic hourly_tick;
…		…
1773	Signal watchers will trigger an event when the process receives a specific	2252	Signal watchers will trigger an event when the process receives a specific
1774	signal one or more times. Even though signals are very asynchronous, libev	2253	signal one or more times. Even though signals are very asynchronous, libev
1775	will try it's best to deliver signals synchronously, i.e. as part of the	2254	will try it's best to deliver signals synchronously, i.e. as part of the
1776	normal event processing, like any other event.	2255	normal event processing, like any other event.
1777		2256
1778	If you want signals asynchronously, just use C<sigaction> as you would	2257	If you want signals to be delivered truly asynchronously, just use
1779	do without libev and forget about sharing the signal. You can even use	2258	C<sigaction> as you would do without libev and forget about sharing
1780	C<ev_async> from a signal handler to synchronously wake up an event loop.	2259	the signal. You can even use C<ev_async> from a signal handler to
		2260	synchronously wake up an event loop.
1781		2261
1782	You can configure as many watchers as you like per signal. Only when the	2262	You can configure as many watchers as you like for the same signal, but
		2263	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2264	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2265	C<SIGINT> in both the default loop and another loop at the same time. At
		2266	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2267
1783	first watcher gets started will libev actually register a signal handler	2268	When the first watcher gets started will libev actually register something
1784	with the kernel (thus it coexists with your own signal handlers as long as	2269	with the kernel (thus it coexists with your own signal handlers as long as
1785	you don't register any with libev for the same signal). Similarly, when	2270	you don't register any with libev for the same signal).
1786	the last signal watcher for a signal is stopped, libev will reset the
1787	signal handler to SIG_DFL (regardless of what it was set to before).
1788		2271
1789	If possible and supported, libev will install its handlers with	2272	If possible and supported, libev will install its handlers with
1790	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2273	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1791	interrupted. If you have a problem with system calls getting interrupted by	2274	not be unduly interrupted. If you have a problem with system calls getting
1792	signals you can block all signals in an C<ev_check> watcher and unblock	2275	interrupted by signals you can block all signals in an C<ev_check> watcher
1793	them in an C<ev_prepare> watcher.	2276	and unblock them in an C<ev_prepare> watcher.
		2277
		2278	=head3 The special problem of inheritance over fork/execve/pthread_create
		2279
		2280	Both the signal mask (C<sigprocmask>) and the signal disposition
		2281	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2282	stopping it again), that is, libev might or might not block the signal,
		2283	and might or might not set or restore the installed signal handler.
		2284
		2285	While this does not matter for the signal disposition (libev never
		2286	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2287	C<execve>), this matters for the signal mask: many programs do not expect
		2288	certain signals to be blocked.
		2289
		2290	This means that before calling C<exec> (from the child) you should reset
		2291	the signal mask to whatever "default" you expect (all clear is a good
		2292	choice usually).
		2293
		2294	The simplest way to ensure that the signal mask is reset in the child is
		2295	to install a fork handler with C<pthread_atfork> that resets it. That will
		2296	catch fork calls done by libraries (such as the libc) as well.
		2297
		2298	In current versions of libev, the signal will not be blocked indefinitely
		2299	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2300	the window of opportunity for problems, it will not go away, as libev
		2301	I<has> to modify the signal mask, at least temporarily.
		2302
		2303	So I can't stress this enough: I<If you do not reset your signal mask when
		2304	you expect it to be empty, you have a race condition in your code>. This
		2305	is not a libev-specific thing, this is true for most event libraries.
1794		2306
1795	=head3 Watcher-Specific Functions and Data Members	2307	=head3 Watcher-Specific Functions and Data Members
1796		2308
1797	=over 4	2309	=over 4
1798		2310
…		…
1814	Example: Try to exit cleanly on SIGINT.	2326	Example: Try to exit cleanly on SIGINT.
1815		2327
1816	static void	2328	static void
1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2329	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1818	{	2330	{
1819	ev_unloop (loop, EVUNLOOP_ALL);	2331	ev_break (loop, EVBREAK_ALL);
1820	}	2332	}
1821		2333
1822	ev_signal signal_watcher;	2334	ev_signal signal_watcher;
1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2335	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1824	ev_signal_start (loop, &signal_watcher);	2336	ev_signal_start (loop, &signal_watcher);
…		…
1830	some child status changes (most typically when a child of yours dies or	2342	some child status changes (most typically when a child of yours dies or
1831	exits). It is permissible to install a child watcher I<after> the child	2343	exits). It is permissible to install a child watcher I<after> the child
1832	has been forked (which implies it might have already exited), as long	2344	has been forked (which implies it might have already exited), as long
1833	as the event loop isn't entered (or is continued from a watcher), i.e.,	2345	as the event loop isn't entered (or is continued from a watcher), i.e.,
1834	forking and then immediately registering a watcher for the child is fine,	2346	forking and then immediately registering a watcher for the child is fine,
1835	but forking and registering a watcher a few event loop iterations later is	2347	but forking and registering a watcher a few event loop iterations later or
1836	not.	2348	in the next callback invocation is not.
1837		2349
1838	Only the default event loop is capable of handling signals, and therefore	2350	Only the default event loop is capable of handling signals, and therefore
1839	you can only register child watchers in the default event loop.	2351	you can only register child watchers in the default event loop.
1840		2352
		2353	Due to some design glitches inside libev, child watchers will always be
		2354	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2355	libev)
		2356
1841	=head3 Process Interaction	2357	=head3 Process Interaction
1842		2358
1843	Libev grabs C<SIGCHLD> as soon as the default event loop is	2359	Libev grabs C<SIGCHLD> as soon as the default event loop is
1844	initialised. This is necessary to guarantee proper behaviour even if	2360	initialised. This is necessary to guarantee proper behaviour even if the
1845	the first child watcher is started after the child exits. The occurrence	2361	first child watcher is started after the child exits. The occurrence
1846	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2362	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1847	synchronously as part of the event loop processing. Libev always reaps all	2363	synchronously as part of the event loop processing. Libev always reaps all
1848	children, even ones not watched.	2364	children, even ones not watched.
1849		2365
1850	=head3 Overriding the Built-In Processing	2366	=head3 Overriding the Built-In Processing
…		…
1860	=head3 Stopping the Child Watcher	2376	=head3 Stopping the Child Watcher
1861		2377
1862	Currently, the child watcher never gets stopped, even when the	2378	Currently, the child watcher never gets stopped, even when the
1863	child terminates, so normally one needs to stop the watcher in the	2379	child terminates, so normally one needs to stop the watcher in the
1864	callback. Future versions of libev might stop the watcher automatically	2380	callback. Future versions of libev might stop the watcher automatically
1865	when a child exit is detected.	2381	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2382	problem).
1866		2383
1867	=head3 Watcher-Specific Functions and Data Members	2384	=head3 Watcher-Specific Functions and Data Members
1868		2385
1869	=over 4	2386	=over 4
1870		2387
…		…
1932	C<stat> on that path in regular intervals (or when the OS says it changed)	2449	C<stat> on that path in regular intervals (or when the OS says it changed)
1933	and sees if it changed compared to the last time, invoking the callback if	2450	and sees if it changed compared to the last time, invoking the callback if
1934	it did.	2451	it did.
1935		2452
1936	The path does not need to exist: changing from "path exists" to "path does	2453	The path does not need to exist: changing from "path exists" to "path does
1937	not exist" is a status change like any other. The condition "path does	2454	not exist" is a status change like any other. The condition "path does not
1938	not exist" is signified by the C<st_nlink> field being zero (which is	2455	exist" (or more correctly "path cannot be stat'ed") is signified by the
1939	otherwise always forced to be at least one) and all the other fields of	2456	C<st_nlink> field being zero (which is otherwise always forced to be at
1940	the stat buffer having unspecified contents.	2457	least one) and all the other fields of the stat buffer having unspecified
		2458	contents.
1941		2459
1942	The path I<must not> end in a slash or contain special components such as	2460	The path I<must not> end in a slash or contain special components such as
1943	C<.> or C<..>. The path I<should> be absolute: If it is relative and	2461	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1944	your working directory changes, then the behaviour is undefined.	2462	your working directory changes, then the behaviour is undefined.
1945		2463
…		…
1955	This watcher type is not meant for massive numbers of stat watchers,	2473	This watcher type is not meant for massive numbers of stat watchers,
1956	as even with OS-supported change notifications, this can be	2474	as even with OS-supported change notifications, this can be
1957	resource-intensive.	2475	resource-intensive.
1958		2476
1959	At the time of this writing, the only OS-specific interface implemented	2477	At the time of this writing, the only OS-specific interface implemented
1960	is the Linux inotify interface (implementing kqueue support is left as	2478	is the Linux inotify interface (implementing kqueue support is left as an
1961	an exercise for the reader. Note, however, that the author sees no way	2479	exercise for the reader. Note, however, that the author sees no way of
1962	of implementing C<ev_stat> semantics with kqueue).	2480	implementing C<ev_stat> semantics with kqueue, except as a hint).
1963		2481
1964	=head3 ABI Issues (Largefile Support)	2482	=head3 ABI Issues (Largefile Support)
1965		2483
1966	Libev by default (unless the user overrides this) uses the default	2484	Libev by default (unless the user overrides this) uses the default
1967	compilation environment, which means that on systems with large file	2485	compilation environment, which means that on systems with large file
…		…
1978	to exchange stat structures with application programs compiled using the	2496	to exchange stat structures with application programs compiled using the
1979	default compilation environment.	2497	default compilation environment.
1980		2498
1981	=head3 Inotify and Kqueue	2499	=head3 Inotify and Kqueue
1982		2500
1983	When C<inotify (7)> support has been compiled into libev (generally	2501	When C<inotify (7)> support has been compiled into libev and present at
1984	only available with Linux 2.6.25 or above due to bugs in earlier	2502	runtime, it will be used to speed up change detection where possible. The
1985	implementations) and present at runtime, it will be used to speed up	2503	inotify descriptor will be created lazily when the first C<ev_stat>
1986	change detection where possible. The inotify descriptor will be created	2504	watcher is being started.
1987	lazily when the first C<ev_stat> watcher is being started.
1988		2505
1989	Inotify presence does not change the semantics of C<ev_stat> watchers	2506	Inotify presence does not change the semantics of C<ev_stat> watchers
1990	except that changes might be detected earlier, and in some cases, to avoid	2507	except that changes might be detected earlier, and in some cases, to avoid
1991	making regular C<stat> calls. Even in the presence of inotify support	2508	making regular C<stat> calls. Even in the presence of inotify support
1992	there are many cases where libev has to resort to regular C<stat> polling,	2509	there are many cases where libev has to resort to regular C<stat> polling,
1993	but as long as the path exists, libev usually gets away without polling.	2510	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2511	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2512	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2513	xfs are fully working) libev usually gets away without polling.
1994		2514
1995	There is no support for kqueue, as apparently it cannot be used to	2515	There is no support for kqueue, as apparently it cannot be used to
1996	implement this functionality, due to the requirement of having a file	2516	implement this functionality, due to the requirement of having a file
1997	descriptor open on the object at all times, and detecting renames, unlinks	2517	descriptor open on the object at all times, and detecting renames, unlinks
1998	etc. is difficult.	2518	etc. is difficult.
		2519
		2520	=head3 C<stat ()> is a synchronous operation
		2521
		2522	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2523	the process. The exception are C<ev_stat> watchers - those call C<stat
		2524	()>, which is a synchronous operation.
		2525
		2526	For local paths, this usually doesn't matter: unless the system is very
		2527	busy or the intervals between stat's are large, a stat call will be fast,
		2528	as the path data is usually in memory already (except when starting the
		2529	watcher).
		2530
		2531	For networked file systems, calling C<stat ()> can block an indefinite
		2532	time due to network issues, and even under good conditions, a stat call
		2533	often takes multiple milliseconds.
		2534
		2535	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2536	paths, although this is fully supported by libev.
1999		2537
2000	=head3 The special problem of stat time resolution	2538	=head3 The special problem of stat time resolution
2001		2539
2002	The C<stat ()> system call only supports full-second resolution portably,	2540	The C<stat ()> system call only supports full-second resolution portably,
2003	and even on systems where the resolution is higher, most file systems	2541	and even on systems where the resolution is higher, most file systems
…		…
2152		2690
2153	=head3 Watcher-Specific Functions and Data Members	2691	=head3 Watcher-Specific Functions and Data Members
2154		2692
2155	=over 4	2693	=over 4
2156		2694
2157	=item ev_idle_init (ev_signal *, callback)	2695	=item ev_idle_init (ev_idle *, callback)
2158		2696
2159	Initialises and configures the idle watcher - it has no parameters of any	2697	Initialises and configures the idle watcher - it has no parameters of any
2160	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2698	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2161	believe me.	2699	believe me.
2162		2700
…		…
2175	// no longer anything immediate to do.	2713	// no longer anything immediate to do.
2176	}	2714	}
2177		2715
2178	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2716	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2179	ev_idle_init (idle_watcher, idle_cb);	2717	ev_idle_init (idle_watcher, idle_cb);
2180	ev_idle_start (loop, idle_cb);	2718	ev_idle_start (loop, idle_watcher);
2181		2719
2182		2720
2183	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2721	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2184		2722
2185	Prepare and check watchers are usually (but not always) used in pairs:	2723	Prepare and check watchers are usually (but not always) used in pairs:
2186	prepare watchers get invoked before the process blocks and check watchers	2724	prepare watchers get invoked before the process blocks and check watchers
2187	afterwards.	2725	afterwards.
2188		2726
2189	You I<must not> call C<ev_loop> or similar functions that enter	2727	You I<must not> call C<ev_run> or similar functions that enter
2190	the current event loop from either C<ev_prepare> or C<ev_check>	2728	the current event loop from either C<ev_prepare> or C<ev_check>
2191	watchers. Other loops than the current one are fine, however. The	2729	watchers. Other loops than the current one are fine, however. The
2192	rationale behind this is that you do not need to check for recursion in	2730	rationale behind this is that you do not need to check for recursion in
2193	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2731	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
2194	C<ev_check> so if you have one watcher of each kind they will always be	2732	C<ev_check> so if you have one watcher of each kind they will always be
…		…
2278	struct pollfd fds [nfd];	2816	struct pollfd fds [nfd];
2279	// actual code will need to loop here and realloc etc.	2817	// actual code will need to loop here and realloc etc.
2280	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2818	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2281		2819
2282	/* the callback is illegal, but won't be called as we stop during check */	2820	/* the callback is illegal, but won't be called as we stop during check */
2283	ev_timer_init (&tw, 0, timeout * 1e-3);	2821	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2284	ev_timer_start (loop, &tw);	2822	ev_timer_start (loop, &tw);
2285		2823
2286	// create one ev_io per pollfd	2824	// create one ev_io per pollfd
2287	for (int i = 0; i < nfd; ++i)	2825	for (int i = 0; i < nfd; ++i)
2288	{	2826	{
…		…
2362		2900
2363	if (timeout >= 0)	2901	if (timeout >= 0)
2364	// create/start timer	2902	// create/start timer
2365		2903
2366	// poll	2904	// poll
2367	ev_loop (EV_A_ 0);	2905	ev_run (EV_A_ 0);
2368		2906
2369	// stop timer again	2907	// stop timer again
2370	if (timeout >= 0)	2908	if (timeout >= 0)
2371	ev_timer_stop (EV_A_ &to);	2909	ev_timer_stop (EV_A_ &to);
2372		2910
…		…
2401	some fds have to be watched and handled very quickly (with low latency),	2939	some fds have to be watched and handled very quickly (with low latency),
2402	and even priorities and idle watchers might have too much overhead. In	2940	and even priorities and idle watchers might have too much overhead. In
2403	this case you would put all the high priority stuff in one loop and all	2941	this case you would put all the high priority stuff in one loop and all
2404	the rest in a second one, and embed the second one in the first.	2942	the rest in a second one, and embed the second one in the first.
2405		2943
2406	As long as the watcher is active, the callback will be invoked every time	2944	As long as the watcher is active, the callback will be invoked every
2407	there might be events pending in the embedded loop. The callback must then	2945	time there might be events pending in the embedded loop. The callback
2408	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2946	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2409	their callbacks (you could also start an idle watcher to give the embedded	2947	sweep and invoke their callbacks (the callback doesn't need to invoke the
2410	loop strictly lower priority for example). You can also set the callback	2948	C<ev_embed_sweep> function directly, it could also start an idle watcher
2411	to C<0>, in which case the embed watcher will automatically execute the	2949	to give the embedded loop strictly lower priority for example).
2412	embedded loop sweep.
2413		2950
2414	As long as the watcher is started it will automatically handle events. The	2951	You can also set the callback to C<0>, in which case the embed watcher
2415	callback will be invoked whenever some events have been handled. You can	2952	will automatically execute the embedded loop sweep whenever necessary.
2416	set the callback to C<0> to avoid having to specify one if you are not
2417	interested in that.
2418		2953
2419	Also, there have not currently been made special provisions for forking:	2954	Fork detection will be handled transparently while the C<ev_embed> watcher
2420	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2955	is active, i.e., the embedded loop will automatically be forked when the
2421	but you will also have to stop and restart any C<ev_embed> watchers	2956	embedding loop forks. In other cases, the user is responsible for calling
2422	yourself - but you can use a fork watcher to handle this automatically,	2957	C<ev_loop_fork> on the embedded loop.
2423	and future versions of libev might do just that.
2424		2958
2425	Unfortunately, not all backends are embeddable: only the ones returned by	2959	Unfortunately, not all backends are embeddable: only the ones returned by
2426	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2960	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2427	portable one.	2961	portable one.
2428		2962
…		…
2454	if you do not want that, you need to temporarily stop the embed watcher).	2988	if you do not want that, you need to temporarily stop the embed watcher).
2455		2989
2456	=item ev_embed_sweep (loop, ev_embed *)	2990	=item ev_embed_sweep (loop, ev_embed *)
2457		2991
2458	Make a single, non-blocking sweep over the embedded loop. This works	2992	Make a single, non-blocking sweep over the embedded loop. This works
2459	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	2993	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2460	appropriate way for embedded loops.	2994	appropriate way for embedded loops.
2461		2995
2462	=item struct ev_loop *other [read-only]	2996	=item struct ev_loop *other [read-only]
2463		2997
2464	The embedded event loop.	2998	The embedded event loop.
…		…
2522	event loop blocks next and before C<ev_check> watchers are being called,	3056	event loop blocks next and before C<ev_check> watchers are being called,
2523	and only in the child after the fork. If whoever good citizen calling	3057	and only in the child after the fork. If whoever good citizen calling
2524	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3058	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2525	handlers will be invoked, too, of course.	3059	handlers will be invoked, too, of course.
2526		3060
		3061	=head3 The special problem of life after fork - how is it possible?
		3062
		3063	Most uses of C<fork()> consist of forking, then some simple calls to set
		3064	up/change the process environment, followed by a call to C<exec()>. This
		3065	sequence should be handled by libev without any problems.
		3066
		3067	This changes when the application actually wants to do event handling
		3068	in the child, or both parent in child, in effect "continuing" after the
		3069	fork.
		3070
		3071	The default mode of operation (for libev, with application help to detect
		3072	forks) is to duplicate all the state in the child, as would be expected
		3073	when I<either> the parent I<or> the child process continues.
		3074
		3075	When both processes want to continue using libev, then this is usually the
		3076	wrong result. In that case, usually one process (typically the parent) is
		3077	supposed to continue with all watchers in place as before, while the other
		3078	process typically wants to start fresh, i.e. without any active watchers.
		3079
		3080	The cleanest and most efficient way to achieve that with libev is to
		3081	simply create a new event loop, which of course will be "empty", and
		3082	use that for new watchers. This has the advantage of not touching more
		3083	memory than necessary, and thus avoiding the copy-on-write, and the
		3084	disadvantage of having to use multiple event loops (which do not support
		3085	signal watchers).
		3086
		3087	When this is not possible, or you want to use the default loop for
		3088	other reasons, then in the process that wants to start "fresh", call
		3089	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3090	Destroying the default loop will "orphan" (not stop) all registered
		3091	watchers, so you have to be careful not to execute code that modifies
		3092	those watchers. Note also that in that case, you have to re-register any
		3093	signal watchers.
		3094
2527	=head3 Watcher-Specific Functions and Data Members	3095	=head3 Watcher-Specific Functions and Data Members
2528		3096
2529	=over 4	3097	=over 4
2530		3098
2531	=item ev_fork_init (ev_signal *, callback)	3099	=item ev_fork_init (ev_fork *, callback)
2532		3100
2533	Initialises and configures the fork watcher - it has no parameters of any	3101	Initialises and configures the fork watcher - it has no parameters of any
2534	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3102	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2535	believe me.	3103	really.
2536		3104
2537	=back	3105	=back
2538		3106
2539		3107
		3108	=head2 C<ev_cleanup> - even the best things end
		3109
		3110	Cleanup watchers are called just before the event loop is being destroyed
		3111	by a call to C<ev_loop_destroy>.
		3112
		3113	While there is no guarantee that the event loop gets destroyed, cleanup
		3114	watchers provide a convenient method to install cleanup hooks for your
		3115	program, worker threads and so on - you just to make sure to destroy the
		3116	loop when you want them to be invoked.
		3117
		3118	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3119	all other watchers, they do not keep a reference to the event loop (which
		3120	makes a lot of sense if you think about it). Like all other watchers, you
		3121	can call libev functions in the callback, except C<ev_cleanup_start>.
		3122
		3123	=head3 Watcher-Specific Functions and Data Members
		3124
		3125	=over 4
		3126
		3127	=item ev_cleanup_init (ev_cleanup *, callback)
		3128
		3129	Initialises and configures the cleanup watcher - it has no parameters of
		3130	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3131	pointless, I assure you.
		3132
		3133	=back
		3134
		3135	Example: Register an atexit handler to destroy the default loop, so any
		3136	cleanup functions are called.
		3137
		3138	static void
		3139	program_exits (void)
		3140	{
		3141	ev_loop_destroy (EV_DEFAULT_UC);
		3142	}
		3143
		3144	...
		3145	atexit (program_exits);
		3146
		3147
2540	=head2 C<ev_async> - how to wake up another event loop	3148	=head2 C<ev_async> - how to wake up an event loop
2541		3149
2542	In general, you cannot use an C<ev_loop> from multiple threads or other	3150	In general, you cannot use an C<ev_run> from multiple threads or other
2543	asynchronous sources such as signal handlers (as opposed to multiple event	3151	asynchronous sources such as signal handlers (as opposed to multiple event
2544	loops - those are of course safe to use in different threads).	3152	loops - those are of course safe to use in different threads).
2545		3153
2546	Sometimes, however, you need to wake up another event loop you do not	3154	Sometimes, however, you need to wake up an event loop you do not control,
2547	control, for example because it belongs to another thread. This is what	3155	for example because it belongs to another thread. This is what C<ev_async>
2548	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3156	watchers do: as long as the C<ev_async> watcher is active, you can signal
2549	can signal it by calling C<ev_async_send>, which is thread- and signal	3157	it by calling C<ev_async_send>, which is thread- and signal safe.
2550	safe.
2551		3158
2552	This functionality is very similar to C<ev_signal> watchers, as signals,	3159	This functionality is very similar to C<ev_signal> watchers, as signals,
2553	too, are asynchronous in nature, and signals, too, will be compressed	3160	too, are asynchronous in nature, and signals, too, will be compressed
2554	(i.e. the number of callback invocations may be less than the number of	3161	(i.e. the number of callback invocations may be less than the number of
2555	C<ev_async_sent> calls).	3162	C<ev_async_sent> calls).
…		…
2560	=head3 Queueing	3167	=head3 Queueing
2561		3168
2562	C<ev_async> does not support queueing of data in any way. The reason	3169	C<ev_async> does not support queueing of data in any way. The reason
2563	is that the author does not know of a simple (or any) algorithm for a	3170	is that the author does not know of a simple (or any) algorithm for a
2564	multiple-writer-single-reader queue that works in all cases and doesn't	3171	multiple-writer-single-reader queue that works in all cases and doesn't
2565	need elaborate support such as pthreads.	3172	need elaborate support such as pthreads or unportable memory access
		3173	semantics.
2566		3174
2567	That means that if you want to queue data, you have to provide your own	3175	That means that if you want to queue data, you have to provide your own
2568	queue. But at least I can tell you how to implement locking around your	3176	queue. But at least I can tell you how to implement locking around your
2569	queue:	3177	queue:
2570		3178
…		…
2659	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3267	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2660	C<ev_feed_event>, this call is safe to do from other threads, signal or	3268	C<ev_feed_event>, this call is safe to do from other threads, signal or
2661	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3269	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2662	section below on what exactly this means).	3270	section below on what exactly this means).
2663		3271
		3272	Note that, as with other watchers in libev, multiple events might get
		3273	compressed into a single callback invocation (another way to look at this
		3274	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3275	reset when the event loop detects that).
		3276
2664	This call incurs the overhead of a system call only once per loop iteration,	3277	This call incurs the overhead of a system call only once per event loop
2665	so while the overhead might be noticeable, it doesn't apply to repeated	3278	iteration, so while the overhead might be noticeable, it doesn't apply to
2666	calls to C<ev_async_send>.	3279	repeated calls to C<ev_async_send> for the same event loop.
2667		3280
2668	=item bool = ev_async_pending (ev_async *)	3281	=item bool = ev_async_pending (ev_async *)
2669		3282
2670	Returns a non-zero value when C<ev_async_send> has been called on the	3283	Returns a non-zero value when C<ev_async_send> has been called on the
2671	watcher but the event has not yet been processed (or even noted) by the	3284	watcher but the event has not yet been processed (or even noted) by the
…		…
2674	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3287	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2675	the loop iterates next and checks for the watcher to have become active,	3288	the loop iterates next and checks for the watcher to have become active,
2676	it will reset the flag again. C<ev_async_pending> can be used to very	3289	it will reset the flag again. C<ev_async_pending> can be used to very
2677	quickly check whether invoking the loop might be a good idea.	3290	quickly check whether invoking the loop might be a good idea.
2678		3291
2679	Not that this does I<not> check whether the watcher itself is pending, only	3292	Not that this does I<not> check whether the watcher itself is pending,
2680	whether it has been requested to make this watcher pending.	3293	only whether it has been requested to make this watcher pending: there
		3294	is a time window between the event loop checking and resetting the async
		3295	notification, and the callback being invoked.
2681		3296
2682	=back	3297	=back
2683		3298
2684		3299
2685	=head1 OTHER FUNCTIONS	3300	=head1 OTHER FUNCTIONS
…		…
2702		3317
2703	If C<timeout> is less than 0, then no timeout watcher will be	3318	If C<timeout> is less than 0, then no timeout watcher will be
2704	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3319	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2705	repeat = 0) will be started. C<0> is a valid timeout.	3320	repeat = 0) will be started. C<0> is a valid timeout.
2706		3321
2707	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3322	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2708	passed an C<revents> set like normal event callbacks (a combination of	3323	passed an C<revents> set like normal event callbacks (a combination of
2709	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3324	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2710	value passed to C<ev_once>. Note that it is possible to receive I<both>	3325	value passed to C<ev_once>. Note that it is possible to receive I<both>
2711	a timeout and an io event at the same time - you probably should give io	3326	a timeout and an io event at the same time - you probably should give io
2712	events precedence.	3327	events precedence.
2713		3328
2714	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3329	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2715		3330
2716	static void stdin_ready (int revents, void *arg)	3331	static void stdin_ready (int revents, void *arg)
2717	{	3332	{
2718	if (revents & EV_READ)	3333	if (revents & EV_READ)
2719	/* stdin might have data for us, joy! */;	3334	/* stdin might have data for us, joy! */;
2720	else if (revents & EV_TIMEOUT)	3335	else if (revents & EV_TIMER)
2721	/* doh, nothing entered */;	3336	/* doh, nothing entered */;
2722	}	3337	}
2723		3338
2724	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3339	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2725		3340
2726	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2727
2728	Feeds the given event set into the event loop, as if the specified event
2729	had happened for the specified watcher (which must be a pointer to an
2730	initialised but not necessarily started event watcher).
2731
2732	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3341	=item ev_feed_fd_event (loop, int fd, int revents)
2733		3342
2734	Feed an event on the given fd, as if a file descriptor backend detected	3343	Feed an event on the given fd, as if a file descriptor backend detected
2735	the given events it.	3344	the given events it.
2736		3345
2737	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3346	=item ev_feed_signal_event (loop, int signum)
2738		3347
2739	Feed an event as if the given signal occurred (C<loop> must be the default	3348	Feed an event as if the given signal occurred (C<loop> must be the default
2740	loop!).	3349	loop!).
2741		3350
2742	=back	3351	=back
…		…
2822		3431
2823	=over 4	3432	=over 4
2824		3433
2825	=item ev::TYPE::TYPE ()	3434	=item ev::TYPE::TYPE ()
2826		3435
2827	=item ev::TYPE::TYPE (struct ev_loop *)	3436	=item ev::TYPE::TYPE (loop)
2828		3437
2829	=item ev::TYPE::~TYPE	3438	=item ev::TYPE::~TYPE
2830		3439
2831	The constructor (optionally) takes an event loop to associate the watcher	3440	The constructor (optionally) takes an event loop to associate the watcher
2832	with. If it is omitted, it will use C<EV_DEFAULT>.	3441	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2864		3473
2865	myclass obj;	3474	myclass obj;
2866	ev::io iow;	3475	ev::io iow;
2867	iow.set <myclass, &myclass::io_cb> (&obj);	3476	iow.set <myclass, &myclass::io_cb> (&obj);
2868		3477
		3478	=item w->set (object *)
		3479
		3480	This is a variation of a method callback - leaving out the method to call
		3481	will default the method to C<operator ()>, which makes it possible to use
		3482	functor objects without having to manually specify the C<operator ()> all
		3483	the time. Incidentally, you can then also leave out the template argument
		3484	list.
		3485
		3486	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3487	int revents)>.
		3488
		3489	See the method-C<set> above for more details.
		3490
		3491	Example: use a functor object as callback.
		3492
		3493	struct myfunctor
		3494	{
		3495	void operator() (ev::io &w, int revents)
		3496	{
		3497	...
		3498	}
		3499	}
		3500
		3501	myfunctor f;
		3502
		3503	ev::io w;
		3504	w.set (&f);
		3505
2869	=item w->set<function> (void *data = 0)	3506	=item w->set<function> (void *data = 0)
2870		3507
2871	Also sets a callback, but uses a static method or plain function as	3508	Also sets a callback, but uses a static method or plain function as
2872	callback. The optional C<data> argument will be stored in the watcher's	3509	callback. The optional C<data> argument will be stored in the watcher's
2873	C<data> member and is free for you to use.	3510	C<data> member and is free for you to use.
…		…
2879	Example: Use a plain function as callback.	3516	Example: Use a plain function as callback.
2880		3517
2881	static void io_cb (ev::io &w, int revents) { }	3518	static void io_cb (ev::io &w, int revents) { }
2882	iow.set <io_cb> ();	3519	iow.set <io_cb> ();
2883		3520
2884	=item w->set (struct ev_loop *)	3521	=item w->set (loop)
2885		3522
2886	Associates a different C<struct ev_loop> with this watcher. You can only	3523	Associates a different C<struct ev_loop> with this watcher. You can only
2887	do this when the watcher is inactive (and not pending either).	3524	do this when the watcher is inactive (and not pending either).
2888		3525
2889	=item w->set ([arguments])	3526	=item w->set ([arguments])
2890		3527
2891	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	3528	Basically the same as C<ev_TYPE_set>, with the same arguments. Either this
2892	called at least once. Unlike the C counterpart, an active watcher gets	3529	method or a suitable start method must be called at least once. Unlike the
2893	automatically stopped and restarted when reconfiguring it with this	3530	C counterpart, an active watcher gets automatically stopped and restarted
2894	method.	3531	when reconfiguring it with this method.
2895		3532
2896	=item w->start ()	3533	=item w->start ()
2897		3534
2898	Starts the watcher. Note that there is no C<loop> argument, as the	3535	Starts the watcher. Note that there is no C<loop> argument, as the
2899	constructor already stores the event loop.	3536	constructor already stores the event loop.
2900		3537
		3538	=item w->start ([arguments])
		3539
		3540	Instead of calling C<set> and C<start> methods separately, it is often
		3541	convenient to wrap them in one call. Uses the same type of arguments as
		3542	the configure C<set> method of the watcher.
		3543
2901	=item w->stop ()	3544	=item w->stop ()
2902		3545
2903	Stops the watcher if it is active. Again, no C<loop> argument.	3546	Stops the watcher if it is active. Again, no C<loop> argument.
2904		3547
2905	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3548	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2917		3560
2918	=back	3561	=back
2919		3562
2920	=back	3563	=back
2921		3564
2922	Example: Define a class with an IO and idle watcher, start one of them in	3565	Example: Define a class with two I/O and idle watchers, start the I/O
2923	the constructor.	3566	watchers in the constructor.
2924		3567
2925	class myclass	3568	class myclass
2926	{	3569	{
2927	ev::io io ; void io_cb (ev::io &w, int revents);	3570	ev::io io ; void io_cb (ev::io &w, int revents);
		3571	ev::io2 io2 ; void io2_cb (ev::io &w, int revents);
2928	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3572	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2929		3573
2930	myclass (int fd)	3574	myclass (int fd)
2931	{	3575	{
2932	io .set <myclass, &myclass::io_cb > (this);	3576	io .set <myclass, &myclass::io_cb > (this);
		3577	io2 .set <myclass, &myclass::io2_cb > (this);
2933	idle.set <myclass, &myclass::idle_cb> (this);	3578	idle.set <myclass, &myclass::idle_cb> (this);
2934		3579
2935	io.start (fd, ev::READ);	3580	io.set (fd, ev::WRITE); // configure the watcher
		3581	io.start (); // start it whenever convenient
		3582
		3583	io2.start (fd, ev::READ); // set + start in one call
2936	}	3584	}
2937	};	3585	};
2938		3586
2939		3587
2940	=head1 OTHER LANGUAGE BINDINGS	3588	=head1 OTHER LANGUAGE BINDINGS
…		…
2959	L<http://software.schmorp.de/pkg/EV>.	3607	L<http://software.schmorp.de/pkg/EV>.
2960		3608
2961	=item Python	3609	=item Python
2962		3610
2963	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3611	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2964	seems to be quite complete and well-documented. Note, however, that the	3612	seems to be quite complete and well-documented.
2965	patch they require for libev is outright dangerous as it breaks the ABI
2966	for everybody else, and therefore, should never be applied in an installed
2967	libev (if python requires an incompatible ABI then it needs to embed
2968	libev).
2969		3613
2970	=item Ruby	3614	=item Ruby
2971		3615
2972	Tony Arcieri has written a ruby extension that offers access to a subset	3616	Tony Arcieri has written a ruby extension that offers access to a subset
2973	of the libev API and adds file handle abstractions, asynchronous DNS and	3617	of the libev API and adds file handle abstractions, asynchronous DNS and
2974	more on top of it. It can be found via gem servers. Its homepage is at	3618	more on top of it. It can be found via gem servers. Its homepage is at
2975	L<http://rev.rubyforge.org/>.	3619	L<http://rev.rubyforge.org/>.
2976		3620
		3621	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3622	makes rev work even on mingw.
		3623
		3624	=item Haskell
		3625
		3626	A haskell binding to libev is available at
		3627	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3628
2977	=item D	3629	=item D
2978		3630
2979	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3631	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2980	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3632	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2981		3633
2982	=item Ocaml	3634	=item Ocaml
2983		3635
2984	Erkki Seppala has written Ocaml bindings for libev, to be found at	3636	Erkki Seppala has written Ocaml bindings for libev, to be found at
2985	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3637	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3638
		3639	=item Lua
		3640
		3641	Brian Maher has written a partial interface to libev for lua (at the
		3642	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		3643	L<http://github.com/brimworks/lua-ev>.
2986		3644
2987	=back	3645	=back
2988		3646
2989		3647
2990	=head1 MACRO MAGIC	3648	=head1 MACRO MAGIC
…		…
3004	loop argument"). The C<EV_A> form is used when this is the sole argument,	3662	loop argument"). The C<EV_A> form is used when this is the sole argument,
3005	C<EV_A_> is used when other arguments are following. Example:	3663	C<EV_A_> is used when other arguments are following. Example:
3006		3664
3007	ev_unref (EV_A);	3665	ev_unref (EV_A);
3008	ev_timer_add (EV_A_ watcher);	3666	ev_timer_add (EV_A_ watcher);
3009	ev_loop (EV_A_ 0);	3667	ev_run (EV_A_ 0);
3010		3668
3011	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	3669	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3012	which is often provided by the following macro.	3670	which is often provided by the following macro.
3013		3671
3014	=item C<EV_P>, C<EV_P_>	3672	=item C<EV_P>, C<EV_P_>
…		…
3054	}	3712	}
3055		3713
3056	ev_check check;	3714	ev_check check;
3057	ev_check_init (&check, check_cb);	3715	ev_check_init (&check, check_cb);
3058	ev_check_start (EV_DEFAULT_ &check);	3716	ev_check_start (EV_DEFAULT_ &check);
3059	ev_loop (EV_DEFAULT_ 0);	3717	ev_run (EV_DEFAULT_ 0);
3060		3718
3061	=head1 EMBEDDING	3719	=head1 EMBEDDING
3062		3720
3063	Libev can (and often is) directly embedded into host	3721	Libev can (and often is) directly embedded into host
3064	applications. Examples of applications that embed it include the Deliantra	3722	applications. Examples of applications that embed it include the Deliantra
…		…
3144	libev.m4	3802	libev.m4
3145		3803
3146	=head2 PREPROCESSOR SYMBOLS/MACROS	3804	=head2 PREPROCESSOR SYMBOLS/MACROS
3147		3805
3148	Libev can be configured via a variety of preprocessor symbols you have to	3806	Libev can be configured via a variety of preprocessor symbols you have to
3149	define before including any of its files. The default in the absence of	3807	define before including (or compiling) any of its files. The default in
3150	autoconf is documented for every option.	3808	the absence of autoconf is documented for every option.
		3809
		3810	Symbols marked with "(h)" do not change the ABI, and can have different
		3811	values when compiling libev vs. including F<ev.h>, so it is permissible
		3812	to redefine them before including F<ev.h> without breaking compatibility
		3813	to a compiled library. All other symbols change the ABI, which means all
		3814	users of libev and the libev code itself must be compiled with compatible
		3815	settings.
3151		3816
3152	=over 4	3817	=over 4
3153		3818
		3819	=item EV_COMPAT3 (h)
		3820
		3821	Backwards compatibility is a major concern for libev. This is why this
		3822	release of libev comes with wrappers for the functions and symbols that
		3823	have been renamed between libev version 3 and 4.
		3824
		3825	You can disable these wrappers (to test compatibility with future
		3826	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		3827	sources. This has the additional advantage that you can drop the C<struct>
		3828	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		3829	typedef in that case.
		3830
		3831	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		3832	and in some even more future version the compatibility code will be
		3833	removed completely.
		3834
3154	=item EV_STANDALONE	3835	=item EV_STANDALONE (h)
3155		3836
3156	Must always be C<1> if you do not use autoconf configuration, which	3837	Must always be C<1> if you do not use autoconf configuration, which
3157	keeps libev from including F<config.h>, and it also defines dummy	3838	keeps libev from including F<config.h>, and it also defines dummy
3158	implementations for some libevent functions (such as logging, which is not	3839	implementations for some libevent functions (such as logging, which is not
3159	supported). It will also not define any of the structs usually found in	3840	supported). It will also not define any of the structs usually found in
3160	F<event.h> that are not directly supported by the libev core alone.	3841	F<event.h> that are not directly supported by the libev core alone.
3161		3842
		3843	In standalone mode, libev will still try to automatically deduce the
		3844	configuration, but has to be more conservative.
		3845
3162	=item EV_USE_MONOTONIC	3846	=item EV_USE_MONOTONIC
3163		3847
3164	If defined to be C<1>, libev will try to detect the availability of the	3848	If defined to be C<1>, libev will try to detect the availability of the
3165	monotonic clock option at both compile time and runtime. Otherwise no use	3849	monotonic clock option at both compile time and runtime. Otherwise no
3166	of the monotonic clock option will be attempted. If you enable this, you	3850	use of the monotonic clock option will be attempted. If you enable this,
3167	usually have to link against librt or something similar. Enabling it when	3851	you usually have to link against librt or something similar. Enabling it
3168	the functionality isn't available is safe, though, although you have	3852	when the functionality isn't available is safe, though, although you have
3169	to make sure you link against any libraries where the C<clock_gettime>	3853	to make sure you link against any libraries where the C<clock_gettime>
3170	function is hiding in (often F<-lrt>).	3854	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3171		3855
3172	=item EV_USE_REALTIME	3856	=item EV_USE_REALTIME
3173		3857
3174	If defined to be C<1>, libev will try to detect the availability of the	3858	If defined to be C<1>, libev will try to detect the availability of the
3175	real-time clock option at compile time (and assume its availability at	3859	real-time clock option at compile time (and assume its availability
3176	runtime if successful). Otherwise no use of the real-time clock option will	3860	at runtime if successful). Otherwise no use of the real-time clock
3177	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3861	option will be attempted. This effectively replaces C<gettimeofday>
3178	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3862	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3179	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3863	correctness. See the note about libraries in the description of
		3864	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3865	C<EV_USE_CLOCK_SYSCALL>.
		3866
		3867	=item EV_USE_CLOCK_SYSCALL
		3868
		3869	If defined to be C<1>, libev will try to use a direct syscall instead
		3870	of calling the system-provided C<clock_gettime> function. This option
		3871	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3872	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3873	programs needlessly. Using a direct syscall is slightly slower (in
		3874	theory), because no optimised vdso implementation can be used, but avoids
		3875	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3876	higher, as it simplifies linking (no need for C<-lrt>).
3180		3877
3181	=item EV_USE_NANOSLEEP	3878	=item EV_USE_NANOSLEEP
3182		3879
3183	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3880	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3184	and will use it for delays. Otherwise it will use C<select ()>.	3881	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3200		3897
3201	=item EV_SELECT_USE_FD_SET	3898	=item EV_SELECT_USE_FD_SET
3202		3899
3203	If defined to C<1>, then the select backend will use the system C<fd_set>	3900	If defined to C<1>, then the select backend will use the system C<fd_set>
3204	structure. This is useful if libev doesn't compile due to a missing	3901	structure. This is useful if libev doesn't compile due to a missing
3205	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3902	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3206	exotic systems. This usually limits the range of file descriptors to some	3903	on exotic systems. This usually limits the range of file descriptors to
3207	low limit such as 1024 or might have other limitations (winsocket only	3904	some low limit such as 1024 or might have other limitations (winsocket
3208	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3905	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3209	influence the size of the C<fd_set> used.	3906	configures the maximum size of the C<fd_set>.
3210		3907
3211	=item EV_SELECT_IS_WINSOCKET	3908	=item EV_SELECT_IS_WINSOCKET
3212		3909
3213	When defined to C<1>, the select backend will assume that	3910	When defined to C<1>, the select backend will assume that
3214	select/socket/connect etc. don't understand file descriptors but	3911	select/socket/connect etc. don't understand file descriptors but
…		…
3216	be used is the winsock select). This means that it will call	3913	be used is the winsock select). This means that it will call
3217	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3914	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3218	it is assumed that all these functions actually work on fds, even	3915	it is assumed that all these functions actually work on fds, even
3219	on win32. Should not be defined on non-win32 platforms.	3916	on win32. Should not be defined on non-win32 platforms.
3220		3917
3221	=item EV_FD_TO_WIN32_HANDLE	3918	=item EV_FD_TO_WIN32_HANDLE(fd)
3222		3919
3223	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3920	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3224	file descriptors to socket handles. When not defining this symbol (the	3921	file descriptors to socket handles. When not defining this symbol (the
3225	default), then libev will call C<_get_osfhandle>, which is usually	3922	default), then libev will call C<_get_osfhandle>, which is usually
3226	correct. In some cases, programs use their own file descriptor management,	3923	correct. In some cases, programs use their own file descriptor management,
3227	in which case they can provide this function to map fds to socket handles.	3924	in which case they can provide this function to map fds to socket handles.
		3925
		3926	=item EV_WIN32_HANDLE_TO_FD(handle)
		3927
		3928	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3929	using the standard C<_open_osfhandle> function. For programs implementing
		3930	their own fd to handle mapping, overwriting this function makes it easier
		3931	to do so. This can be done by defining this macro to an appropriate value.
		3932
		3933	=item EV_WIN32_CLOSE_FD(fd)
		3934
		3935	If programs implement their own fd to handle mapping on win32, then this
		3936	macro can be used to override the C<close> function, useful to unregister
		3937	file descriptors again. Note that the replacement function has to close
		3938	the underlying OS handle.
3228		3939
3229	=item EV_USE_POLL	3940	=item EV_USE_POLL
3230		3941
3231	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3942	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3232	backend. Otherwise it will be enabled on non-win32 platforms. It	3943	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3279	as well as for signal and thread safety in C<ev_async> watchers.	3990	as well as for signal and thread safety in C<ev_async> watchers.
3280		3991
3281	In the absence of this define, libev will use C<sig_atomic_t volatile>	3992	In the absence of this define, libev will use C<sig_atomic_t volatile>
3282	(from F<signal.h>), which is usually good enough on most platforms.	3993	(from F<signal.h>), which is usually good enough on most platforms.
3283		3994
3284	=item EV_H	3995	=item EV_H (h)
3285		3996
3286	The name of the F<ev.h> header file used to include it. The default if	3997	The name of the F<ev.h> header file used to include it. The default if
3287	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	3998	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3288	used to virtually rename the F<ev.h> header file in case of conflicts.	3999	used to virtually rename the F<ev.h> header file in case of conflicts.
3289		4000
3290	=item EV_CONFIG_H	4001	=item EV_CONFIG_H (h)
3291		4002
3292	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4003	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3293	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4004	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3294	C<EV_H>, above.	4005	C<EV_H>, above.
3295		4006
3296	=item EV_EVENT_H	4007	=item EV_EVENT_H (h)
3297		4008
3298	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4009	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3299	of how the F<event.h> header can be found, the default is C<"event.h">.	4010	of how the F<event.h> header can be found, the default is C<"event.h">.
3300		4011
3301	=item EV_PROTOTYPES	4012	=item EV_PROTOTYPES (h)
3302		4013
3303	If defined to be C<0>, then F<ev.h> will not define any function	4014	If defined to be C<0>, then F<ev.h> will not define any function
3304	prototypes, but still define all the structs and other symbols. This is	4015	prototypes, but still define all the structs and other symbols. This is
3305	occasionally useful if you want to provide your own wrapper functions	4016	occasionally useful if you want to provide your own wrapper functions
3306	around libev functions.	4017	around libev functions.
…		…
3328	fine.	4039	fine.
3329		4040
3330	If your embedding application does not need any priorities, defining these	4041	If your embedding application does not need any priorities, defining these
3331	both to C<0> will save some memory and CPU.	4042	both to C<0> will save some memory and CPU.
3332		4043
3333	=item EV_PERIODIC_ENABLE	4044	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4045	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4046	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3334		4047
3335	If undefined or defined to be C<1>, then periodic timers are supported. If	4048	If undefined or defined to be C<1> (and the platform supports it), then
3336	defined to be C<0>, then they are not. Disabling them saves a few kB of	4049	the respective watcher type is supported. If defined to be C<0>, then it
3337	code.	4050	is not. Disabling watcher types mainly saves code size.
3338		4051
3339	=item EV_IDLE_ENABLE	4052	=item EV_FEATURES
3340
3341	If undefined or defined to be C<1>, then idle watchers are supported. If
3342	defined to be C<0>, then they are not. Disabling them saves a few kB of
3343	code.
3344
3345	=item EV_EMBED_ENABLE
3346
3347	If undefined or defined to be C<1>, then embed watchers are supported. If
3348	defined to be C<0>, then they are not. Embed watchers rely on most other
3349	watcher types, which therefore must not be disabled.
3350
3351	=item EV_STAT_ENABLE
3352
3353	If undefined or defined to be C<1>, then stat watchers are supported. If
3354	defined to be C<0>, then they are not.
3355
3356	=item EV_FORK_ENABLE
3357
3358	If undefined or defined to be C<1>, then fork watchers are supported. If
3359	defined to be C<0>, then they are not.
3360
3361	=item EV_ASYNC_ENABLE
3362
3363	If undefined or defined to be C<1>, then async watchers are supported. If
3364	defined to be C<0>, then they are not.
3365
3366	=item EV_MINIMAL
3367		4053
3368	If you need to shave off some kilobytes of code at the expense of some	4054	If you need to shave off some kilobytes of code at the expense of some
3369	speed, define this symbol to C<1>. Currently this is used to override some	4055	speed (but with the full API), you can define this symbol to request
3370	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4056	certain subsets of functionality. The default is to enable all features
3371	much smaller 2-heap for timer management over the default 4-heap.	4057	that can be enabled on the platform.
		4058
		4059	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4060	with some broad features you want) and then selectively re-enable
		4061	additional parts you want, for example if you want everything minimal,
		4062	but multiple event loop support, async and child watchers and the poll
		4063	backend, use this:
		4064
		4065	#define EV_FEATURES 0
		4066	#define EV_MULTIPLICITY 1
		4067	#define EV_USE_POLL 1
		4068	#define EV_CHILD_ENABLE 1
		4069	#define EV_ASYNC_ENABLE 1
		4070
		4071	The actual value is a bitset, it can be a combination of the following
		4072	values:
		4073
		4074	=over 4
		4075
		4076	=item C<1> - faster/larger code
		4077
		4078	Use larger code to speed up some operations.
		4079
		4080	Currently this is used to override some inlining decisions (enlarging the
		4081	code size by roughly 30% on amd64).
		4082
		4083	When optimising for size, use of compiler flags such as C<-Os> with
		4084	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4085	assertions.
		4086
		4087	=item C<2> - faster/larger data structures
		4088
		4089	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4090	hash table sizes and so on. This will usually further increase code size
		4091	and can additionally have an effect on the size of data structures at
		4092	runtime.
		4093
		4094	=item C<4> - full API configuration
		4095
		4096	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4097	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4098
		4099	=item C<8> - full API
		4100
		4101	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4102	details on which parts of the API are still available without this
		4103	feature, and do not complain if this subset changes over time.
		4104
		4105	=item C<16> - enable all optional watcher types
		4106
		4107	Enables all optional watcher types. If you want to selectively enable
		4108	only some watcher types other than I/O and timers (e.g. prepare,
		4109	embed, async, child...) you can enable them manually by defining
		4110	C<EV_watchertype_ENABLE> to C<1> instead.
		4111
		4112	=item C<32> - enable all backends
		4113
		4114	This enables all backends - without this feature, you need to enable at
		4115	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4116
		4117	=item C<64> - enable OS-specific "helper" APIs
		4118
		4119	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4120	default.
		4121
		4122	=back
		4123
		4124	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4125	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4126	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4127	watchers, timers and monotonic clock support.
		4128
		4129	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4130	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4131	your program might be left out as well - a binary starting a timer and an
		4132	I/O watcher then might come out at only 5Kb.
		4133
		4134	=item EV_AVOID_STDIO
		4135
		4136	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4137	functions (printf, scanf, perror etc.). This will increase the code size
		4138	somewhat, but if your program doesn't otherwise depend on stdio and your
		4139	libc allows it, this avoids linking in the stdio library which is quite
		4140	big.
		4141
		4142	Note that error messages might become less precise when this option is
		4143	enabled.
		4144
		4145	=item EV_NSIG
		4146
		4147	The highest supported signal number, +1 (or, the number of
		4148	signals): Normally, libev tries to deduce the maximum number of signals
		4149	automatically, but sometimes this fails, in which case it can be
		4150	specified. Also, using a lower number than detected (C<32> should be
		4151	good for about any system in existence) can save some memory, as libev
		4152	statically allocates some 12-24 bytes per signal number.
3372		4153
3373	=item EV_PID_HASHSIZE	4154	=item EV_PID_HASHSIZE
3374		4155
3375	C<ev_child> watchers use a small hash table to distribute workload by	4156	C<ev_child> watchers use a small hash table to distribute workload by
3376	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4157	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3377	than enough. If you need to manage thousands of children you might want to	4158	usually more than enough. If you need to manage thousands of children you
3378	increase this value (I<must> be a power of two).	4159	might want to increase this value (I<must> be a power of two).
3379		4160
3380	=item EV_INOTIFY_HASHSIZE	4161	=item EV_INOTIFY_HASHSIZE
3381		4162
3382	C<ev_stat> watchers use a small hash table to distribute workload by	4163	C<ev_stat> watchers use a small hash table to distribute workload by
3383	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4164	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3384	usually more than enough. If you need to manage thousands of C<ev_stat>	4165	disabled), usually more than enough. If you need to manage thousands of
3385	watchers you might want to increase this value (I<must> be a power of	4166	C<ev_stat> watchers you might want to increase this value (I<must> be a
3386	two).	4167	power of two).
3387		4168
3388	=item EV_USE_4HEAP	4169	=item EV_USE_4HEAP
3389		4170
3390	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4171	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3391	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4172	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3392	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4173	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3393	faster performance with many (thousands) of watchers.	4174	faster performance with many (thousands) of watchers.
3394		4175
3395	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4176	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3396	(disabled).	4177	will be C<0>.
3397		4178
3398	=item EV_HEAP_CACHE_AT	4179	=item EV_HEAP_CACHE_AT
3399		4180
3400	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4181	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3401	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4182	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3402	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4183	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3403	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4184	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3404	but avoids random read accesses on heap changes. This improves performance	4185	but avoids random read accesses on heap changes. This improves performance
3405	noticeably with many (hundreds) of watchers.	4186	noticeably with many (hundreds) of watchers.
3406		4187
3407	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4188	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3408	(disabled).	4189	will be C<0>.
3409		4190
3410	=item EV_VERIFY	4191	=item EV_VERIFY
3411		4192
3412	Controls how much internal verification (see C<ev_loop_verify ()>) will	4193	Controls how much internal verification (see C<ev_verify ()>) will
3413	be done: If set to C<0>, no internal verification code will be compiled	4194	be done: If set to C<0>, no internal verification code will be compiled
3414	in. If set to C<1>, then verification code will be compiled in, but not	4195	in. If set to C<1>, then verification code will be compiled in, but not
3415	called. If set to C<2>, then the internal verification code will be	4196	called. If set to C<2>, then the internal verification code will be
3416	called once per loop, which can slow down libev. If set to C<3>, then the	4197	called once per loop, which can slow down libev. If set to C<3>, then the
3417	verification code will be called very frequently, which will slow down	4198	verification code will be called very frequently, which will slow down
3418	libev considerably.	4199	libev considerably.
3419		4200
3420	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4201	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3421	C<0>.	4202	will be C<0>.
3422		4203
3423	=item EV_COMMON	4204	=item EV_COMMON
3424		4205
3425	By default, all watchers have a C<void *data> member. By redefining	4206	By default, all watchers have a C<void *data> member. By redefining
3426	this macro to a something else you can include more and other types of	4207	this macro to something else you can include more and other types of
3427	members. You have to define it each time you include one of the files,	4208	members. You have to define it each time you include one of the files,
3428	though, and it must be identical each time.	4209	though, and it must be identical each time.
3429		4210
3430	For example, the perl EV module uses something like this:	4211	For example, the perl EV module uses something like this:
3431		4212
…		…
3484	file.	4265	file.
3485		4266
3486	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4267	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3487	that everybody includes and which overrides some configure choices:	4268	that everybody includes and which overrides some configure choices:
3488		4269
3489	#define EV_MINIMAL 1	4270	#define EV_FEATURES 8
3490	#define EV_USE_POLL 0	4271	#define EV_USE_SELECT 1
3491	#define EV_MULTIPLICITY 0
3492	#define EV_PERIODIC_ENABLE 0	4272	#define EV_PREPARE_ENABLE 1
		4273	#define EV_IDLE_ENABLE 1
3493	#define EV_STAT_ENABLE 0	4274	#define EV_SIGNAL_ENABLE 1
3494	#define EV_FORK_ENABLE 0	4275	#define EV_CHILD_ENABLE 1
		4276	#define EV_USE_STDEXCEPT 0
3495	#define EV_CONFIG_H <config.h>	4277	#define EV_CONFIG_H <config.h>
3496	#define EV_MINPRI 0
3497	#define EV_MAXPRI 0
3498		4278
3499	#include "ev++.h"	4279	#include "ev++.h"
3500		4280
3501	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4281	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3502		4282
…		…
3562	default loop and triggering an C<ev_async> watcher from the default loop	4342	default loop and triggering an C<ev_async> watcher from the default loop
3563	watcher callback into the event loop interested in the signal.	4343	watcher callback into the event loop interested in the signal.
3564		4344
3565	=back	4345	=back
3566		4346
		4347	=head4 THREAD LOCKING EXAMPLE
		4348
		4349	Here is a fictitious example of how to run an event loop in a different
		4350	thread than where callbacks are being invoked and watchers are
		4351	created/added/removed.
		4352
		4353	For a real-world example, see the C<EV::Loop::Async> perl module,
		4354	which uses exactly this technique (which is suited for many high-level
		4355	languages).
		4356
		4357	The example uses a pthread mutex to protect the loop data, a condition
		4358	variable to wait for callback invocations, an async watcher to notify the
		4359	event loop thread and an unspecified mechanism to wake up the main thread.
		4360
		4361	First, you need to associate some data with the event loop:
		4362
		4363	typedef struct {
		4364	mutex_t lock; /* global loop lock */
		4365	ev_async async_w;
		4366	thread_t tid;
		4367	cond_t invoke_cv;
		4368	} userdata;
		4369
		4370	void prepare_loop (EV_P)
		4371	{
		4372	// for simplicity, we use a static userdata struct.
		4373	static userdata u;
		4374
		4375	ev_async_init (&u->async_w, async_cb);
		4376	ev_async_start (EV_A_ &u->async_w);
		4377
		4378	pthread_mutex_init (&u->lock, 0);
		4379	pthread_cond_init (&u->invoke_cv, 0);
		4380
		4381	// now associate this with the loop
		4382	ev_set_userdata (EV_A_ u);
		4383	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4384	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4385
		4386	// then create the thread running ev_loop
		4387	pthread_create (&u->tid, 0, l_run, EV_A);
		4388	}
		4389
		4390	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4391	solely to wake up the event loop so it takes notice of any new watchers
		4392	that might have been added:
		4393
		4394	static void
		4395	async_cb (EV_P_ ev_async *w, int revents)
		4396	{
		4397	// just used for the side effects
		4398	}
		4399
		4400	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4401	protecting the loop data, respectively.
		4402
		4403	static void
		4404	l_release (EV_P)
		4405	{
		4406	userdata *u = ev_userdata (EV_A);
		4407	pthread_mutex_unlock (&u->lock);
		4408	}
		4409
		4410	static void
		4411	l_acquire (EV_P)
		4412	{
		4413	userdata *u = ev_userdata (EV_A);
		4414	pthread_mutex_lock (&u->lock);
		4415	}
		4416
		4417	The event loop thread first acquires the mutex, and then jumps straight
		4418	into C<ev_run>:
		4419
		4420	void *
		4421	l_run (void *thr_arg)
		4422	{
		4423	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4424
		4425	l_acquire (EV_A);
		4426	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4427	ev_run (EV_A_ 0);
		4428	l_release (EV_A);
		4429
		4430	return 0;
		4431	}
		4432
		4433	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4434	signal the main thread via some unspecified mechanism (signals? pipe
		4435	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4436	have been called (in a while loop because a) spurious wakeups are possible
		4437	and b) skipping inter-thread-communication when there are no pending
		4438	watchers is very beneficial):
		4439
		4440	static void
		4441	l_invoke (EV_P)
		4442	{
		4443	userdata *u = ev_userdata (EV_A);
		4444
		4445	while (ev_pending_count (EV_A))
		4446	{
		4447	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4448	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4449	}
		4450	}
		4451
		4452	Now, whenever the main thread gets told to invoke pending watchers, it
		4453	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4454	thread to continue:
		4455
		4456	static void
		4457	real_invoke_pending (EV_P)
		4458	{
		4459	userdata *u = ev_userdata (EV_A);
		4460
		4461	pthread_mutex_lock (&u->lock);
		4462	ev_invoke_pending (EV_A);
		4463	pthread_cond_signal (&u->invoke_cv);
		4464	pthread_mutex_unlock (&u->lock);
		4465	}
		4466
		4467	Whenever you want to start/stop a watcher or do other modifications to an
		4468	event loop, you will now have to lock:
		4469
		4470	ev_timer timeout_watcher;
		4471	userdata *u = ev_userdata (EV_A);
		4472
		4473	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4474
		4475	pthread_mutex_lock (&u->lock);
		4476	ev_timer_start (EV_A_ &timeout_watcher);
		4477	ev_async_send (EV_A_ &u->async_w);
		4478	pthread_mutex_unlock (&u->lock);
		4479
		4480	Note that sending the C<ev_async> watcher is required because otherwise
		4481	an event loop currently blocking in the kernel will have no knowledge
		4482	about the newly added timer. By waking up the loop it will pick up any new
		4483	watchers in the next event loop iteration.
		4484
3567	=head3 COROUTINES	4485	=head3 COROUTINES
3568		4486
3569	Libev is very accommodating to coroutines ("cooperative threads"):	4487	Libev is very accommodating to coroutines ("cooperative threads"):
3570	libev fully supports nesting calls to its functions from different	4488	libev fully supports nesting calls to its functions from different
3571	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4489	coroutines (e.g. you can call C<ev_run> on the same loop from two
3572	different coroutines, and switch freely between both coroutines running the	4490	different coroutines, and switch freely between both coroutines running
3573	loop, as long as you don't confuse yourself). The only exception is that	4491	the loop, as long as you don't confuse yourself). The only exception is
3574	you must not do this from C<ev_periodic> reschedule callbacks.	4492	that you must not do this from C<ev_periodic> reschedule callbacks.
3575		4493
3576	Care has been taken to ensure that libev does not keep local state inside	4494	Care has been taken to ensure that libev does not keep local state inside
3577	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4495	C<ev_run>, and other calls do not usually allow for coroutine switches as
3578	they do not call any callbacks.	4496	they do not call any callbacks.
3579		4497
3580	=head2 COMPILER WARNINGS	4498	=head2 COMPILER WARNINGS
3581		4499
3582	Depending on your compiler and compiler settings, you might get no or a	4500	Depending on your compiler and compiler settings, you might get no or a
…		…
3593	maintainable.	4511	maintainable.
3594		4512
3595	And of course, some compiler warnings are just plain stupid, or simply	4513	And of course, some compiler warnings are just plain stupid, or simply
3596	wrong (because they don't actually warn about the condition their message	4514	wrong (because they don't actually warn about the condition their message
3597	seems to warn about). For example, certain older gcc versions had some	4515	seems to warn about). For example, certain older gcc versions had some
3598	warnings that resulted an extreme number of false positives. These have	4516	warnings that resulted in an extreme number of false positives. These have
3599	been fixed, but some people still insist on making code warn-free with	4517	been fixed, but some people still insist on making code warn-free with
3600	such buggy versions.	4518	such buggy versions.
3601		4519
3602	While libev is written to generate as few warnings as possible,	4520	While libev is written to generate as few warnings as possible,
3603	"warn-free" code is not a goal, and it is recommended not to build libev	4521	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3639	I suggest using suppression lists.	4557	I suggest using suppression lists.
3640		4558
3641		4559
3642	=head1 PORTABILITY NOTES	4560	=head1 PORTABILITY NOTES
3643		4561
		4562	=head2 GNU/LINUX 32 BIT LIMITATIONS
		4563
		4564	GNU/Linux is the only common platform that supports 64 bit file/large file
		4565	interfaces but I<disables> them by default.
		4566
		4567	That means that libev compiled in the default environment doesn't support
		4568	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		4569
		4570	Unfortunately, many programs try to work around this GNU/Linux issue
		4571	by enabling the large file API, which makes them incompatible with the
		4572	standard libev compiled for their system.
		4573
		4574	Likewise, libev cannot enable the large file API itself as this would
		4575	suddenly make it incompatible to the default compile time environment,
		4576	i.e. all programs not using special compile switches.
		4577
		4578	=head2 OS/X AND DARWIN BUGS
		4579
		4580	The whole thing is a bug if you ask me - basically any system interface
		4581	you touch is broken, whether it is locales, poll, kqueue or even the
		4582	OpenGL drivers.
		4583
		4584	=head3 C<kqueue> is buggy
		4585
		4586	The kqueue syscall is broken in all known versions - most versions support
		4587	only sockets, many support pipes.
		4588
		4589	Libev tries to work around this by not using C<kqueue> by default on this
		4590	rotten platform, but of course you can still ask for it when creating a
		4591	loop - embedding a socket-only kqueue loop into a select-based one is
		4592	probably going to work well.
		4593
		4594	=head3 C<poll> is buggy
		4595
		4596	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		4597	implementation by something calling C<kqueue> internally around the 10.5.6
		4598	release, so now C<kqueue> I<and> C<poll> are broken.
		4599
		4600	Libev tries to work around this by not using C<poll> by default on
		4601	this rotten platform, but of course you can still ask for it when creating
		4602	a loop.
		4603
		4604	=head3 C<select> is buggy
		4605
		4606	All that's left is C<select>, and of course Apple found a way to fuck this
		4607	one up as well: On OS/X, C<select> actively limits the number of file
		4608	descriptors you can pass in to 1024 - your program suddenly crashes when
		4609	you use more.
		4610
		4611	There is an undocumented "workaround" for this - defining
		4612	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		4613	work on OS/X.
		4614
		4615	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		4616
		4617	=head3 C<errno> reentrancy
		4618
		4619	The default compile environment on Solaris is unfortunately so
		4620	thread-unsafe that you can't even use components/libraries compiled
		4621	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		4622	defined by default. A valid, if stupid, implementation choice.
		4623
		4624	If you want to use libev in threaded environments you have to make sure
		4625	it's compiled with C<_REENTRANT> defined.
		4626
		4627	=head3 Event port backend
		4628
		4629	The scalable event interface for Solaris is called "event
		4630	ports". Unfortunately, this mechanism is very buggy in all major
		4631	releases. If you run into high CPU usage, your program freezes or you get
		4632	a large number of spurious wakeups, make sure you have all the relevant
		4633	and latest kernel patches applied. No, I don't know which ones, but there
		4634	are multiple ones to apply, and afterwards, event ports actually work
		4635	great.
		4636
		4637	If you can't get it to work, you can try running the program by setting
		4638	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		4639	C<select> backends.
		4640
		4641	=head2 AIX POLL BUG
		4642
		4643	AIX unfortunately has a broken C<poll.h> header. Libev works around
		4644	this by trying to avoid the poll backend altogether (i.e. it's not even
		4645	compiled in), which normally isn't a big problem as C<select> works fine
		4646	with large bitsets on AIX, and AIX is dead anyway.
		4647
3644	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4648	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4649
		4650	=head3 General issues
3645		4651
3646	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4652	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3647	requires, and its I/O model is fundamentally incompatible with the POSIX	4653	requires, and its I/O model is fundamentally incompatible with the POSIX
3648	model. Libev still offers limited functionality on this platform in	4654	model. Libev still offers limited functionality on this platform in
3649	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4655	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3650	descriptors. This only applies when using Win32 natively, not when using	4656	descriptors. This only applies when using Win32 natively, not when using
3651	e.g. cygwin.	4657	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		4658	as every compielr comes with a slightly differently broken/incompatible
		4659	environment.
3652		4660
3653	Lifting these limitations would basically require the full	4661	Lifting these limitations would basically require the full
3654	re-implementation of the I/O system. If you are into these kinds of	4662	re-implementation of the I/O system. If you are into this kind of thing,
3655	things, then note that glib does exactly that for you in a very portable	4663	then note that glib does exactly that for you in a very portable way (note
3656	way (note also that glib is the slowest event library known to man).	4664	also that glib is the slowest event library known to man).
3657		4665
3658	There is no supported compilation method available on windows except	4666	There is no supported compilation method available on windows except
3659	embedding it into other applications.	4667	embedding it into other applications.
		4668
		4669	Sensible signal handling is officially unsupported by Microsoft - libev
		4670	tries its best, but under most conditions, signals will simply not work.
3660		4671
3661	Not a libev limitation but worth mentioning: windows apparently doesn't	4672	Not a libev limitation but worth mentioning: windows apparently doesn't
3662	accept large writes: instead of resulting in a partial write, windows will	4673	accept large writes: instead of resulting in a partial write, windows will
3663	either accept everything or return C<ENOBUFS> if the buffer is too large,	4674	either accept everything or return C<ENOBUFS> if the buffer is too large,
3664	so make sure you only write small amounts into your sockets (less than a	4675	so make sure you only write small amounts into your sockets (less than a
…		…
3669	the abysmal performance of winsockets, using a large number of sockets	4680	the abysmal performance of winsockets, using a large number of sockets
3670	is not recommended (and not reasonable). If your program needs to use	4681	is not recommended (and not reasonable). If your program needs to use
3671	more than a hundred or so sockets, then likely it needs to use a totally	4682	more than a hundred or so sockets, then likely it needs to use a totally
3672	different implementation for windows, as libev offers the POSIX readiness	4683	different implementation for windows, as libev offers the POSIX readiness
3673	notification model, which cannot be implemented efficiently on windows	4684	notification model, which cannot be implemented efficiently on windows
3674	(Microsoft monopoly games).	4685	(due to Microsoft monopoly games).
3675		4686
3676	A typical way to use libev under windows is to embed it (see the embedding	4687	A typical way to use libev under windows is to embed it (see the embedding
3677	section for details) and use the following F<evwrap.h> header file instead	4688	section for details) and use the following F<evwrap.h> header file instead
3678	of F<ev.h>:	4689	of F<ev.h>:
3679		4690
…		…
3686	you do I<not> compile the F<ev.c> or any other embedded source files!):	4697	you do I<not> compile the F<ev.c> or any other embedded source files!):
3687		4698
3688	#include "evwrap.h"	4699	#include "evwrap.h"
3689	#include "ev.c"	4700	#include "ev.c"
3690		4701
3691	=over 4
3692
3693	=item The winsocket select function	4702	=head3 The winsocket C<select> function
3694		4703
3695	The winsocket C<select> function doesn't follow POSIX in that it	4704	The winsocket C<select> function doesn't follow POSIX in that it
3696	requires socket I<handles> and not socket I<file descriptors> (it is	4705	requires socket I<handles> and not socket I<file descriptors> (it is
3697	also extremely buggy). This makes select very inefficient, and also	4706	also extremely buggy). This makes select very inefficient, and also
3698	requires a mapping from file descriptors to socket handles (the Microsoft	4707	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3707	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	4716	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3708		4717
3709	Note that winsockets handling of fd sets is O(n), so you can easily get a	4718	Note that winsockets handling of fd sets is O(n), so you can easily get a
3710	complexity in the O(n²) range when using win32.	4719	complexity in the O(n²) range when using win32.
3711		4720
3712	=item Limited number of file descriptors	4721	=head3 Limited number of file descriptors
3713		4722
3714	Windows has numerous arbitrary (and low) limits on things.	4723	Windows has numerous arbitrary (and low) limits on things.
3715		4724
3716	Early versions of winsocket's select only supported waiting for a maximum	4725	Early versions of winsocket's select only supported waiting for a maximum
3717	of C<64> handles (probably owning to the fact that all windows kernels	4726	of C<64> handles (probably owning to the fact that all windows kernels
3718	can only wait for C<64> things at the same time internally; Microsoft	4727	can only wait for C<64> things at the same time internally; Microsoft
3719	recommends spawning a chain of threads and wait for 63 handles and the	4728	recommends spawning a chain of threads and wait for 63 handles and the
3720	previous thread in each. Great).	4729	previous thread in each. Sounds great!).
3721		4730
3722	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4731	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3723	to some high number (e.g. C<2048>) before compiling the winsocket select	4732	to some high number (e.g. C<2048>) before compiling the winsocket select
3724	call (which might be in libev or elsewhere, for example, perl does its own	4733	call (which might be in libev or elsewhere, for example, perl and many
3725	select emulation on windows).	4734	other interpreters do their own select emulation on windows).
3726		4735
3727	Another limit is the number of file descriptors in the Microsoft runtime	4736	Another limit is the number of file descriptors in the Microsoft runtime
3728	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4737	libraries, which by default is C<64> (there must be a hidden I<64>
3729	or something like this inside Microsoft). You can increase this by calling	4738	fetish or something like this inside Microsoft). You can increase this
3730	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4739	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3731	arbitrary limit), but is broken in many versions of the Microsoft runtime	4740	(another arbitrary limit), but is broken in many versions of the Microsoft
3732	libraries.
3733
3734	This might get you to about C<512> or C<2048> sockets (depending on	4741	runtime libraries. This might get you to about C<512> or C<2048> sockets
3735	windows version and/or the phase of the moon). To get more, you need to	4742	(depending on windows version and/or the phase of the moon). To get more,
3736	wrap all I/O functions and provide your own fd management, but the cost of	4743	you need to wrap all I/O functions and provide your own fd management, but
3737	calling select (O(n²)) will likely make this unworkable.	4744	the cost of calling select (O(n²)) will likely make this unworkable.
3738
3739	=back
3740		4745
3741	=head2 PORTABILITY REQUIREMENTS	4746	=head2 PORTABILITY REQUIREMENTS
3742		4747
3743	In addition to a working ISO-C implementation and of course the	4748	In addition to a working ISO-C implementation and of course the
3744	backend-specific APIs, libev relies on a few additional extensions:	4749	backend-specific APIs, libev relies on a few additional extensions:
…		…
3783	watchers.	4788	watchers.
3784		4789
3785	=item C<double> must hold a time value in seconds with enough accuracy	4790	=item C<double> must hold a time value in seconds with enough accuracy
3786		4791
3787	The type C<double> is used to represent timestamps. It is required to	4792	The type C<double> is used to represent timestamps. It is required to
3788	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4793	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3789	enough for at least into the year 4000. This requirement is fulfilled by	4794	good enough for at least into the year 4000 with millisecond accuracy
		4795	(the design goal for libev). This requirement is overfulfilled by
3790	implementations implementing IEEE 754 (basically all existing ones).	4796	implementations using IEEE 754, which is basically all existing ones. With
		4797	IEEE 754 doubles, you get microsecond accuracy until at least 2200.
3791		4798
3792	=back	4799	=back
3793		4800
3794	If you know of other additional requirements drop me a note.	4801	If you know of other additional requirements drop me a note.
3795		4802
…		…
3863	involves iterating over all running async watchers or all signal numbers.	4870	involves iterating over all running async watchers or all signal numbers.
3864		4871
3865	=back	4872	=back
3866		4873
3867		4874
		4875	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4876
		4877	The major version 4 introduced some incompatible changes to the API.
		4878
		4879	At the moment, the C<ev.h> header file provides compatibility definitions
		4880	for all changes, so most programs should still compile. The compatibility
		4881	layer might be removed in later versions of libev, so better update to the
		4882	new API early than late.
		4883
		4884	=over 4
		4885
		4886	=item C<EV_COMPAT3> backwards compatibility mechanism
		4887
		4888	The backward compatibility mechanism can be controlled by
		4889	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4890	section.
		4891
		4892	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4893
		4894	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4895
		4896	ev_loop_destroy (EV_DEFAULT_UC);
		4897	ev_loop_fork (EV_DEFAULT);
		4898
		4899	=item function/symbol renames
		4900
		4901	A number of functions and symbols have been renamed:
		4902
		4903	ev_loop => ev_run
		4904	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4905	EVLOOP_ONESHOT => EVRUN_ONCE
		4906
		4907	ev_unloop => ev_break
		4908	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4909	EVUNLOOP_ONE => EVBREAK_ONE
		4910	EVUNLOOP_ALL => EVBREAK_ALL
		4911
		4912	EV_TIMEOUT => EV_TIMER
		4913
		4914	ev_loop_count => ev_iteration
		4915	ev_loop_depth => ev_depth
		4916	ev_loop_verify => ev_verify
		4917
		4918	Most functions working on C<struct ev_loop> objects don't have an
		4919	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4920	associated constants have been renamed to not collide with the C<struct
		4921	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4922	as all other watcher types. Note that C<ev_loop_fork> is still called
		4923	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4924	typedef.
		4925
		4926	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4927
		4928	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4929	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4930	and work, but the library code will of course be larger.
		4931
		4932	=back
		4933
		4934
		4935	=head1 GLOSSARY
		4936
		4937	=over 4
		4938
		4939	=item active
		4940
		4941	A watcher is active as long as it has been started and not yet stopped.
		4942	See L<WATCHER STATES> for details.
		4943
		4944	=item application
		4945
		4946	In this document, an application is whatever is using libev.
		4947
		4948	=item backend
		4949
		4950	The part of the code dealing with the operating system interfaces.
		4951
		4952	=item callback
		4953
		4954	The address of a function that is called when some event has been
		4955	detected. Callbacks are being passed the event loop, the watcher that
		4956	received the event, and the actual event bitset.
		4957
		4958	=item callback/watcher invocation
		4959
		4960	The act of calling the callback associated with a watcher.
		4961
		4962	=item event
		4963
		4964	A change of state of some external event, such as data now being available
		4965	for reading on a file descriptor, time having passed or simply not having
		4966	any other events happening anymore.
		4967
		4968	In libev, events are represented as single bits (such as C<EV_READ> or
		4969	C<EV_TIMER>).
		4970
		4971	=item event library
		4972
		4973	A software package implementing an event model and loop.
		4974
		4975	=item event loop
		4976
		4977	An entity that handles and processes external events and converts them
		4978	into callback invocations.
		4979
		4980	=item event model
		4981
		4982	The model used to describe how an event loop handles and processes
		4983	watchers and events.
		4984
		4985	=item pending
		4986
		4987	A watcher is pending as soon as the corresponding event has been
		4988	detected. See L<WATCHER STATES> for details.
		4989
		4990	=item real time
		4991
		4992	The physical time that is observed. It is apparently strictly monotonic :)
		4993
		4994	=item wall-clock time
		4995
		4996	The time and date as shown on clocks. Unlike real time, it can actually
		4997	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4998	clock.
		4999
		5000	=item watcher
		5001
		5002	A data structure that describes interest in certain events. Watchers need
		5003	to be started (attached to an event loop) before they can receive events.
		5004
		5005	=back
		5006
3868	=head1 AUTHOR	5007	=head1 AUTHOR
3869		5008
3870	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5009	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3871		5010

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines