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…		…
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		13
		14	#include <stdio.h> // for puts
		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;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
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_ struct 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	struct 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
…		…
108	name C<loop> (which is always of type C<struct 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 library knows two	300	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	types of such loops, the I<default> loop, which supports signals and child	301	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	302	libev 3 had an C<ev_loop> function colliding with the struct name).
		303
		304	The library knows two types of such loops, the I<default> loop, which
		305	supports signals and child events, and dynamically created event loops
		306	which do not.
284		307
285	=over 4	308	=over 4
286		309
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	310	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		311
289	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
290	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
291	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
292	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".
293		322
294	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
295	function.	324	function (or via the C<EV_DEFAULT> macro).
296		325
297	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
298	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
299	as loops cannot bes hared easily between threads anyway).	328	that this case is unlikely, as loops cannot be shared easily between
		329	threads anyway).
300		330
301	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,
302	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
303	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
304	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
305	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	335	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	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.
307		355
308	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
309	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>).
310		358
311	The following flags are supported:	359	The following flags are supported:
…		…
326	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
327	around bugs.	375	around bugs.
328		376
329	=item C<EVFLAG_FORKCHECK>	377	=item C<EVFLAG_FORKCHECK>
330		378
331	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
332	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.
333	enabling this flag.
334		381
335	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,
336	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
337	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
338	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
…		…
344	flag.	391	flag.
345		392
346	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>
347	environment variable.	394	environment variable.
348		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
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	416	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		417
351	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
352	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,
353	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
…		…
377	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
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	445	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		446
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	447	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		448
		449	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		450	kernels).
		451
382	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,
383	but it scales phenomenally better. While poll and select usually scale	453	but it scales phenomenally better. While poll and select usually scale
384	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),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	455	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	456
387	cases and requiring a system call per fd change, no fork support and bad	457	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	458	of the more advanced event mechanisms: mere annoyances include silently
		459	dropping file descriptors, requiring a system call per change per file
		460	descriptor (and unnecessary guessing of parameters), problems with dup and
		461	so on. The biggest issue is fork races, however - if a program forks then
		462	I<both> parent and child process have to recreate the epoll set, which can
		463	take considerable time (one syscall per file descriptor) and is of course
		464	hard to detect.
		465
		466	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		467	of course I<doesn't>, and epoll just loves to report events for totally
		468	I<different> file descriptors (even already closed ones, so one cannot
		469	even remove them from the set) than registered in the set (especially
		470	on SMP systems). Libev tries to counter these spurious notifications by
		471	employing an additional generation counter and comparing that against the
		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...).
389		475
390	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
391	will result in some caching, there is still a system call per such incident	477	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	478	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	479	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	480	file descriptors might not work very well if you register events for both
395		481	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		482
400	Best performance from this backend is achieved by not unregistering all	483	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	484	watchers for a file descriptor until it has been closed, if possible,
402	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
403	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
404	extra overhead.	487	extra overhead. A fork can both result in spurious notifications as well
		488	as in libev having to destroy and recreate the epoll object, which can
		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.
405		494
406	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
407	all kernel versions tested so far.	496	all kernel versions tested so far.
408		497
409	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
410	C<EVBACKEND_POLL>.	499	C<EVBACKEND_POLL>.
411		500
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	501	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		502
414	Kqueue deserves special mention, as at the time of this writing, it was	503	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	504	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	505	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	506	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	507	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	508	without API changes to existing programs. For this reason it's not being
		509	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		510	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		511	system like NetBSD.
420		512
421	You still can embed kqueue into a normal poll or select backend and use it	513	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	514	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	515	the target platform). See C<ev_embed> watchers for more info.
424		516
425	It scales in the same way as the epoll backend, but the interface to the	517	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	518	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	519	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	520	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	521	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	522	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		523	cases
431		524
432	This backend usually performs well under most conditions.	525	This backend usually performs well under most conditions.
433		526
434	While nominally embeddable in other event loops, this doesn't work	527	While nominally embeddable in other event loops, this doesn't work
435	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
436	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
437	(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
438	(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
439	using it only for sockets.	532	also broken on OS X)) and, did I mention it, using it only for sockets.
440		533
441	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
442	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
443	C<NOTE_EOF>.	536	C<NOTE_EOF>.
444		537
…		…
464	might perform better.	557	might perform better.
465		558
466	On the positive side, with the exception of the spurious readiness	559	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	560	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	561	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	562	OS-specific backends (I vastly prefer correctness over speed hacks).
470		563
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	564	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	565	C<EVBACKEND_POLL>.
473		566
474	=item C<EVBACKEND_ALL>	567	=item C<EVBACKEND_ALL>
…		…
479		572
480	It is definitely not recommended to use this flag.	573	It is definitely not recommended to use this flag.
481		574
482	=back	575	=back
483		576
484	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,
485	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
486	specified, all backends in C<ev_recommended_backends ()> will be tried.	579	here). If none are specified, all backends in C<ev_recommended_backends
487		580	()> will be tried.
488	Example: This is the most typical usage.
489
490	if (!ev_default_loop (0))
491	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
492
493	Example: Restrict libev to the select and poll backends, and do not allow
494	environment settings to be taken into account:
495
496	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
497
498	Example: Use whatever libev has to offer, but make sure that kqueue is
499	used if available (warning, breaks stuff, best use only with your own
500	private event loop and only if you know the OS supports your types of
501	fds):
502
503	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
504
505	=item struct ev_loop *ev_loop_new (unsigned int flags)
506
507	Similar to C<ev_default_loop>, but always creates a new event loop that is
508	always distinct from the default loop. Unlike the default loop, it cannot
509	handle signal and child watchers, and attempts to do so will be greeted by
510	undefined behaviour (or a failed assertion if assertions are enabled).
511
512	Note that this function I<is> thread-safe, and the recommended way to use
513	libev with threads is indeed to create one loop per thread, and using the
514	default loop in the "main" or "initial" thread.
515		581
516	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.
517		583
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	584	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	585	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	586	fatal ("no epoll found here, maybe it hides under your chair");
521		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
522	=item ev_default_destroy ()	593	=item ev_loop_destroy (loop)
523		594
524	Destroys the default loop again (frees all memory and kernel state	595	Destroys an event loop object (frees all memory and kernel state
525	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
526	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
527	responsibility to either stop all watchers cleanly yourself I<before>	598	responsibility to either stop all watchers cleanly yourself I<before>
528	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
529	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
530	for example).	601	for example).
531		602
532	Note that certain global state, such as signal state, will not be freed by	603	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	604	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	605	as signal and child watchers) would need to be stopped manually.
535		606
536	In general it is not advisable to call this function except in the	607	This function is normally used on loop objects allocated by
537	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.
538	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>
539	C<ev_loop_new> and C<ev_loop_destroy>).	614	and C<ev_loop_destroy>.
540		615
541	=item ev_loop_destroy (loop)	616	=item ev_loop_fork (loop)
542		617
543	Like C<ev_default_destroy>, but destroys an event loop created by an
544	earlier call to C<ev_loop_new>.
545
546	=item ev_default_fork ()
547
548	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
549	to reinitialise the kernel state for backends that have one. Despite the	619	reinitialise the kernel state for backends that have one. Despite the
550	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
551	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
552	sense). You I<must> call it in the child before using any of the libev	622	child before resuming or calling C<ev_run>.
553	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.
554		628
555	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
556	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
557	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).
558		635
559	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
560	it just in case after a fork. To make this easy, the function will fit in	637	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		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	...
563	pthread_atfork (0, 0, ev_default_fork);	649	pthread_atfork (0, 0, post_fork_child);
564
565	=item ev_loop_fork (loop)
566
567	Like C<ev_default_fork>, but acts on an event loop created by
568	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
569	after fork that you want to re-use in the child, and how you do this is
570	entirely your own problem.
571		650
572	=item int ev_is_default_loop (loop)	651	=item int ev_is_default_loop (loop)
573		652
574	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
575	otherwise.	654	otherwise.
576		655
577	=item unsigned int ev_loop_count (loop)	656	=item unsigned int ev_iteration (loop)
578		657
579	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
580	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>
581	happily wraps around with enough iterations.	660	and happily wraps around with enough iterations.
582		661
583	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
584	"ticks" the number of loop iterations), as it roughly corresponds with	663	"ticks" the number of loop iterations), as it roughly corresponds with
585	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.
586		679
587	=item unsigned int ev_backend (loop)	680	=item unsigned int ev_backend (loop)
588		681
589	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
590	use.	683	use.
…		…
599		692
600	=item ev_now_update (loop)	693	=item ev_now_update (loop)
601		694
602	Establishes the current time by querying the kernel, updating the time	695	Establishes the current time by querying the kernel, updating the time
603	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
604	is usually done automatically within C<ev_loop ()>.	697	is usually done automatically within C<ev_run ()>.
605		698
606	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
607	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
608	the current time is a good idea.	701	the current time is a good idea.
609		702
610	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.
611		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
612	=item ev_loop (loop, int flags)	731	=item ev_run (loop, int flags)
613		732
614	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
615	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
616	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>.
617		738
618	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
619	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.
620		742
621	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
622	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
623	finished (especially in interactive programs), but having a program	745	finished (especially in interactive programs), but having a program
624	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
625	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
626	beauty.	748	beauty.
627		749
628	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
629	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
630	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
631	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.
632		755
633	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
634	necessary) and will handle those and any already outstanding ones. It	757	necessary) and will handle those and any already outstanding ones. It
635	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
636	be an event internal to libev itself, so there is no guarentee that a	759	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	760	user-registered callback will be called), and will return after one
638	iteration of the loop.	761	iteration of the loop.
639		762
640	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
641	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
642	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
643	usually a better approach for this kind of thing.	766	usually a better approach for this kind of thing.
644		767
645	Here are the gory details of what C<ev_loop> does:	768	Here are the gory details of what C<ev_run> does:
646		769
		770	- Increment loop depth.
		771	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	772	- Before the first iteration, call any pending watchers.
		773	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	774	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- 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.
650	- Queue and call all prepare watchers.	776	- Queue and call all prepare watchers.
		777	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	778	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	779	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	780	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	781	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	782	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	783	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	784	any active watchers at all will result in not sleeping).
658	- 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.
659	- Block the process, waiting for any events.	787	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	788	- Queue all outstanding I/O (fd) events.
661	- 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.
662	- Queue all expired timers.	790	- Queue all expired timers.
663	- Queue all expired periodics.	791	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	792	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	793	- Queue all check watchers.
666	- 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).
667	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
668	be handled here by queueing them when their watcher gets executed.	796	be handled here by queueing them when their watcher gets executed.
669	- 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
670	were used, or there are no active watchers, return, otherwise	798	were used, or there are no active watchers, goto FINISH, otherwise
671	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.
672		804
673	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
674	anymore.	806	anymore.
675		807
676	... queue jobs here, make sure they register event watchers as long	808	... queue jobs here, make sure they register event watchers as long
677	... 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..)
678	ev_loop (my_loop, 0);	810	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	811	... jobs done or somebody called unloop. yeah!
680		812
681	=item ev_unloop (loop, how)	813	=item ev_break (loop, how)
682		814
683	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
684	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
685	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
686	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.
687		819
688	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.
		821
		822	It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO##
689		823
690	=item ev_ref (loop)	824	=item ev_ref (loop)
691		825
692	=item ev_unref (loop)	826	=item ev_unref (loop)
693		827
694	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
695	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
696	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.
697		831
698	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
699	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>
700	stopping it.	835	before stopping it.
701		836
702	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
703	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
704	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
705	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
706	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
707	(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
708	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).
709		846
710	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>
711	running when nothing else is active.	848	running when nothing else is active.
712		849
713	struct ev_signal exitsig;	850	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	851	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	852	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	853	evf_unref (loop);
717		854
718	Example: For some weird reason, unregister the above signal handler again.	855	Example: For some weird reason, unregister the above signal handler again.
…		…
742		879
743	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
744	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,
745	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
746	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
747	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.
748		887
749	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
750	to spend more time collecting timeouts, at the expense of increased	889	to spend more time collecting timeouts, at the expense of increased
751	latency/jitter/inexactness (the watcher callback will be called	890	latency/jitter/inexactness (the watcher callback will be called
752	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
…		…
754		893
755	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
756	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
757	interactive servers (of course not for games), likewise for timeouts. It	896	interactive servers (of course not for games), likewise for timeouts. It
758	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>,
759	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).
760		903
761	Setting the I<timeout collect interval> can improve the opportunity for	904	Setting the I<timeout collect interval> can improve the opportunity for
762	saving power, as the program will "bundle" timer callback invocations that	905	saving power, as the program will "bundle" timer callback invocations that
763	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
764	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
765	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
766	they fire on, say, one-second boundaries only.	909	they fire on, say, one-second boundaries only.
767		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
768	=item ev_loop_verify (loop)	986	=item ev_verify (loop)
769		987
770	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
771	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
772	through all internal structures and checks them for validity. If anything	990	through all internal structures and checks them for validity. If anything
773	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
774	error and call C<abort ()>.	992	error and call C<abort ()>.
775		993
776	This can be used to catch bugs inside libev itself: under normal	994	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	998	=back
781		999
782		1000
783	=head1 ANATOMY OF A WATCHER	1001	=head1 ANATOMY OF A WATCHER
784		1002
		1003	In the following description, uppercase C<TYPE> in names stands for the
		1004	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1005	watchers and C<ev_io_start> for I/O watchers.
		1006
785	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
786	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
787	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:
788		1011
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1012	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	1013	{
791	ev_io_stop (w);	1014	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	1015	ev_break (loop, EVBREAK_ALL);
793	}	1016	}
794		1017
795	struct ev_loop *loop = ev_default_loop (0);	1018	struct ev_loop *loop = ev_default_loop (0);
		1019
796	struct ev_io stdin_watcher;	1020	ev_io stdin_watcher;
		1021
797	ev_init (&stdin_watcher, my_cb);	1022	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1023	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	1024	ev_io_start (loop, &stdin_watcher);
		1025
800	ev_loop (loop, 0);	1026	ev_run (loop, 0);
801		1027
802	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
803	watcher structures (and it is usually a bad idea to do this on the stack,	1029	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	1030	stack).
805		1031
		1032	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1033	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1034
806	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
807	(watcher *, callback)>, which expects a callback to be provided. This	1036	*, callback)>, which expects a callback to be provided. This callback is
808	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
809	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
810	is readable and/or writable).	1039	and/or writable).
811		1040
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1041	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	1042	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	1043	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	1044	ev_TYPE_init (watcher *, callback, ...) >>.
816		1045
817	To make the watcher actually watch out for events, you have to start it	1046	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1047	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	1048	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1049	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		1050
822	As long as your watcher is active (has been started but not stopped) you	1051	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	1052	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	1053	reinitialise it or call its C<ev_TYPE_set> macro.
825		1054
826	Each and every callback receives the event loop pointer as first, the	1055	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	1056	registered watcher structure as second, and a bitset of received events as
828	third argument.	1057	third argument.
829		1058
…		…
838	=item C<EV_WRITE>	1067	=item C<EV_WRITE>
839		1068
840	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
841	writable.	1070	writable.
842		1071
843	=item C<EV_TIMEOUT>	1072	=item C<EV_TIMER>
844		1073
845	The C<ev_timer> watcher has timed out.	1074	The C<ev_timer> watcher has timed out.
846		1075
847	=item C<EV_PERIODIC>	1076	=item C<EV_PERIODIC>
848		1077
…		…
866		1095
867	=item C<EV_PREPARE>	1096	=item C<EV_PREPARE>
868		1097
869	=item C<EV_CHECK>	1098	=item C<EV_CHECK>
870		1099
871	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
872	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
873	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
874	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
875	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
876	(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
877	C<ev_loop> from blocking).	1106	C<ev_run> from blocking).
878		1107
879	=item C<EV_EMBED>	1108	=item C<EV_EMBED>
880		1109
881	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.
882		1111
883	=item C<EV_FORK>	1112	=item C<EV_FORK>
884		1113
885	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
886	C<ev_fork>).	1115	C<ev_fork>).
887		1116
		1117	=item C<EV_CLEANUP>
		1118
		1119	The event loop is abotu to be destroyed (see C<ev_cleanup>).
		1120
888	=item C<EV_ASYNC>	1121	=item C<EV_ASYNC>
889		1122
890	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>).
891		1129
892	=item C<EV_ERROR>	1130	=item C<EV_ERROR>
893		1131
894	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
895	happen because the watcher could not be properly started because libev	1133	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	1134	ran out of memory, a file descriptor was found to be closed or any other
		1135	problem. Libev considers these application bugs.
		1136
897	problem. You best act on it by reporting the problem and somehow coping	1137	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	1138	watcher being stopped. Note that well-written programs should not receive
		1139	an error ever, so when your watcher receives it, this usually indicates a
		1140	bug in your program.
899		1141
900	Libev will usually signal a few "dummy" events together with an error, for	1142	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	1143	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	1144	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	1145	the error from read() or write(). This will not work in multi-threaded
904	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
905	thing, so beware.	1147	thing, so beware.
906		1148
907	=back	1149	=back
908		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
909	=head2 GENERIC WATCHER FUNCTIONS	1210	=head2 GENERIC WATCHER FUNCTIONS
910
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913		1211
914	=over 4	1212	=over 4
915		1213
916	=item C<ev_init> (ev_TYPE *watcher, callback)	1214	=item C<ev_init> (ev_TYPE *watcher, callback)
917		1215
…		…
923	which rolls both calls into one.	1221	which rolls both calls into one.
924		1222
925	You can reinitialise a watcher at any time as long as it has been stopped	1223	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	1224	(or never started) and there are no pending events outstanding.
927		1225
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1226	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	1227	int revents)>.
930		1228
931	Example: Initialise an C<ev_io> watcher in two steps.	1229	Example: Initialise an C<ev_io> watcher in two steps.
932		1230
933	ev_io w;	1231	ev_io w;
934	ev_init (&w, my_cb);	1232	ev_init (&w, my_cb);
935	ev_io_set (&w, STDIN_FILENO, EV_READ);	1233	ev_io_set (&w, STDIN_FILENO, EV_READ);
936		1234
937	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1235	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
938		1236
939	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
940	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
941	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
942	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
…		…
955		1253
956	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.
957		1255
958	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1256	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
959		1257
960	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1258	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
961		1259
962	Starts (activates) the given watcher. Only active watchers will receive	1260	Starts (activates) the given watcher. Only active watchers will receive
963	events. If the watcher is already active nothing will happen.	1261	events. If the watcher is already active nothing will happen.
964		1262
965	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
966	whole section.	1264	whole section.
967		1265
968	ev_io_start (EV_DEFAULT_UC, &w);	1266	ev_io_start (EV_DEFAULT_UC, &w);
969		1267
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1268	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
971		1269
972	Stops the given watcher again (if active) and clears the pending	1270	Stops the given watcher if active, and clears the pending status (whether
		1271	the watcher was active or not).
		1272
973	status. It is possible that stopped watchers are pending (for example,	1273	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1274	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1275	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1276	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1277	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1278
979	=item bool ev_is_active (ev_TYPE *watcher)	1279	=item bool ev_is_active (ev_TYPE *watcher)
980		1280
981	Returns a true value iff the watcher is active (i.e. it has been started	1281	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1282	and not yet been stopped). As long as a watcher is active you must not modify
…		…
998	=item ev_cb_set (ev_TYPE *watcher, callback)	1298	=item ev_cb_set (ev_TYPE *watcher, callback)
999		1299
1000	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
1001	(modulo threads).	1301	(modulo threads).
1002		1302
1003	=item ev_set_priority (ev_TYPE *watcher, priority)	1303	=item ev_set_priority (ev_TYPE *watcher, int priority)
1004		1304
1005	=item int ev_priority (ev_TYPE *watcher)	1305	=item int ev_priority (ev_TYPE *watcher)
1006		1306
1007	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
1008	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>
1009	(default: C<-2>). Pending watchers with higher priority will be invoked	1309	(default: C<-2>). Pending watchers with higher priority will be invoked
1010	before watchers with lower priority, but priority will not keep watchers	1310	before watchers with lower priority, but priority will not keep watchers
1011	from being executed (except for C<ev_idle> watchers).	1311	from being executed (except for C<ev_idle> watchers).
1012		1312
1013	This means that priorities are I<only> used for ordering callback
1014	invocation after new events have been received. This is useful, for
1015	example, to reduce latency after idling, or more often, to bind two
1016	watchers on the same event and make sure one is called first.
1017
1018	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
1019	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.
1020		1315
1021	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
1022	pending.	1317	pending.
1023		1318
		1319	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1320	fine, as long as you do not mind that the priority value you query might
		1321	or might not have been clamped to the valid range.
		1322
1024	The default priority used by watchers when no priority has been set is	1323	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1324	always C<0>, which is supposed to not be too high and not be too low :).
1026		1325
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1326	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1028	fine, as long as you do not mind that the priority value you query might	1327	priorities.
1029	or might not have been adjusted to be within valid range.
1030		1328
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1329	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1330
1033	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
1034	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
…		…
1041	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
1042	watcher isn't pending it does nothing and returns C<0>.	1340	watcher isn't pending it does nothing and returns C<0>.
1043		1341
1044	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
1045	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.
1046		1358
1047	=back	1359	=back
1048		1360
1049		1361
1050	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1362	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1368	member, you can also "subclass" the watcher type and provide your own
1057	data:	1369	data:
1058		1370
1059	struct my_io	1371	struct my_io
1060	{	1372	{
1061	struct ev_io io;	1373	ev_io io;
1062	int otherfd;	1374	int otherfd;
1063	void *somedata;	1375	void *somedata;
1064	struct whatever *mostinteresting;	1376	struct whatever *mostinteresting;
1065	};	1377	};
1066		1378
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1381	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1382
1071	And since your callback will be called with a pointer to the watcher, you	1383	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1384	can cast it back to your own type:
1073		1385
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1386	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1387	{
1076	struct my_io *w = (struct my_io *)w_;	1388	struct my_io *w = (struct my_io *)w_;
1077	...	1389	...
1078	}	1390	}
1079		1391
…		…
1097	programmers):	1409	programmers):
1098		1410
1099	#include <stddef.h>	1411	#include <stddef.h>
1100		1412
1101	static void	1413	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1414	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1415	{
1104	struct my_biggy big = (struct my_biggy *	1416	struct my_biggy big = (struct my_biggy *)
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1417	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1418	}
1107		1419
1108	static void	1420	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1421	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1422	{
1111	struct my_biggy big = (struct my_biggy *	1423	struct my_biggy big = (struct my_biggy *)
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1424	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	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.
1114		1529
1115		1530
1116	=head1 WATCHER TYPES	1531	=head1 WATCHER TYPES
1117		1532
1118	This section describes each watcher in detail, but will not repeat	1533	This section describes each watcher in detail, but will not repeat
…		…
1144	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
1145	required if you know what you are doing).	1560	required if you know what you are doing).
1146		1561
1147	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
1148	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
1149	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.
1150		1567
1151	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
1152	receive "spurious" readiness notifications, that is your callback might	1569	receive "spurious" readiness notifications, that is your callback might
1153	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
1154	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
…		…
1219		1636
1220	So when you encounter spurious, unexplained daemon exits, make sure you	1637	So when you encounter spurious, unexplained daemon exits, make sure you
1221	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
1222	somewhere, as that would have given you a big clue).	1639	somewhere, as that would have given you a big clue).
1223		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.
1224		1679
1225	=head3 Watcher-Specific Functions	1680	=head3 Watcher-Specific Functions
1226		1681
1227	=over 4	1682	=over 4
1228		1683
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1704	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1705	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1706	attempt to read a whole line in the callback.
1252		1707
1253	static void	1708	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1709	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1710	{
1256	ev_io_stop (loop, w);	1711	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1712	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1713	}
1259		1714
1260	...	1715	...
1261	struct ev_loop *loop = ev_default_init (0);	1716	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1717	ev_io stdin_readable;
1263	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);
1264	ev_io_start (loop, &stdin_readable);	1719	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1720	ev_run (loop, 0);
1266		1721
1267		1722
1268	=head2 C<ev_timer> - relative and optionally repeating timeouts	1723	=head2 C<ev_timer> - relative and optionally repeating timeouts
1269		1724
1270	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
…		…
1275	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
1276	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1731	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1277	monotonic clock option helps a lot here).	1732	monotonic clock option helps a lot here).
1278		1733
1279	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
1280	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
1281	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).
		1740
		1741	=head3 Be smart about timeouts
		1742
		1743	Many real-world problems involve some kind of timeout, usually for error
		1744	recovery. A typical example is an HTTP request - if the other side hangs,
		1745	you want to raise some error after a while.
		1746
		1747	What follows are some ways to handle this problem, from obvious and
		1748	inefficient to smart and efficient.
		1749
		1750	In the following, a 60 second activity timeout is assumed - a timeout that
		1751	gets reset to 60 seconds each time there is activity (e.g. each time some
		1752	data or other life sign was received).
		1753
		1754	=over 4
		1755
		1756	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1757
		1758	This is the most obvious, but not the most simple way: In the beginning,
		1759	start the watcher:
		1760
		1761	ev_timer_init (timer, callback, 60., 0.);
		1762	ev_timer_start (loop, timer);
		1763
		1764	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1765	and start it again:
		1766
		1767	ev_timer_stop (loop, timer);
		1768	ev_timer_set (timer, 60., 0.);
		1769	ev_timer_start (loop, timer);
		1770
		1771	This is relatively simple to implement, but means that each time there is
		1772	some activity, libev will first have to remove the timer from its internal
		1773	data structure and then add it again. Libev tries to be fast, but it's
		1774	still not a constant-time operation.
		1775
		1776	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1777
		1778	This is the easiest way, and involves using C<ev_timer_again> instead of
		1779	C<ev_timer_start>.
		1780
		1781	To implement this, configure an C<ev_timer> with a C<repeat> value
		1782	of C<60> and then call C<ev_timer_again> at start and each time you
		1783	successfully read or write some data. If you go into an idle state where
		1784	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1785	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1786
		1787	That means you can ignore both the C<ev_timer_start> function and the
		1788	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1789	member and C<ev_timer_again>.
		1790
		1791	At start:
		1792
		1793	ev_init (timer, callback);
		1794	timer->repeat = 60.;
		1795	ev_timer_again (loop, timer);
		1796
		1797	Each time there is some activity:
		1798
		1799	ev_timer_again (loop, timer);
		1800
		1801	It is even possible to change the time-out on the fly, regardless of
		1802	whether the watcher is active or not:
		1803
		1804	timer->repeat = 30.;
		1805	ev_timer_again (loop, timer);
		1806
		1807	This is slightly more efficient then stopping/starting the timer each time
		1808	you want to modify its timeout value, as libev does not have to completely
		1809	remove and re-insert the timer from/into its internal data structure.
		1810
		1811	It is, however, even simpler than the "obvious" way to do it.
		1812
		1813	=item 3. Let the timer time out, but then re-arm it as required.
		1814
		1815	This method is more tricky, but usually most efficient: Most timeouts are
		1816	relatively long compared to the intervals between other activity - in
		1817	our example, within 60 seconds, there are usually many I/O events with
		1818	associated activity resets.
		1819
		1820	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1821	but remember the time of last activity, and check for a real timeout only
		1822	within the callback:
		1823
		1824	ev_tstamp last_activity; // time of last activity
		1825
		1826	static void
		1827	callback (EV_P_ ev_timer *w, int revents)
		1828	{
		1829	ev_tstamp now = ev_now (EV_A);
		1830	ev_tstamp timeout = last_activity + 60.;
		1831
		1832	// if last_activity + 60. is older than now, we did time out
		1833	if (timeout < now)
		1834	{
		1835	// timeout occurred, take action
		1836	}
		1837	else
		1838	{
		1839	// callback was invoked, but there was some activity, re-arm
		1840	// the watcher to fire in last_activity + 60, which is
		1841	// guaranteed to be in the future, so "again" is positive:
		1842	w->repeat = timeout - now;
		1843	ev_timer_again (EV_A_ w);
		1844	}
		1845	}
		1846
		1847	To summarise the callback: first calculate the real timeout (defined
		1848	as "60 seconds after the last activity"), then check if that time has
		1849	been reached, which means something I<did>, in fact, time out. Otherwise
		1850	the callback was invoked too early (C<timeout> is in the future), so
		1851	re-schedule the timer to fire at that future time, to see if maybe we have
		1852	a timeout then.
		1853
		1854	Note how C<ev_timer_again> is used, taking advantage of the
		1855	C<ev_timer_again> optimisation when the timer is already running.
		1856
		1857	This scheme causes more callback invocations (about one every 60 seconds
		1858	minus half the average time between activity), but virtually no calls to
		1859	libev to change the timeout.
		1860
		1861	To start the timer, simply initialise the watcher and set C<last_activity>
		1862	to the current time (meaning we just have some activity :), then call the
		1863	callback, which will "do the right thing" and start the timer:
		1864
		1865	ev_init (timer, callback);
		1866	last_activity = ev_now (loop);
		1867	callback (loop, timer, EV_TIMER);
		1868
		1869	And when there is some activity, simply store the current time in
		1870	C<last_activity>, no libev calls at all:
		1871
		1872	last_activity = ev_now (loop);
		1873
		1874	This technique is slightly more complex, but in most cases where the
		1875	time-out is unlikely to be triggered, much more efficient.
		1876
		1877	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1878	callback :) - just change the timeout and invoke the callback, which will
		1879	fix things for you.
		1880
		1881	=item 4. Wee, just use a double-linked list for your timeouts.
		1882
		1883	If there is not one request, but many thousands (millions...), all
		1884	employing some kind of timeout with the same timeout value, then one can
		1885	do even better:
		1886
		1887	When starting the timeout, calculate the timeout value and put the timeout
		1888	at the I<end> of the list.
		1889
		1890	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1891	the list is expected to fire (for example, using the technique #3).
		1892
		1893	When there is some activity, remove the timer from the list, recalculate
		1894	the timeout, append it to the end of the list again, and make sure to
		1895	update the C<ev_timer> if it was taken from the beginning of the list.
		1896
		1897	This way, one can manage an unlimited number of timeouts in O(1) time for
		1898	starting, stopping and updating the timers, at the expense of a major
		1899	complication, and having to use a constant timeout. The constant timeout
		1900	ensures that the list stays sorted.
		1901
		1902	=back
		1903
		1904	So which method the best?
		1905
		1906	Method #2 is a simple no-brain-required solution that is adequate in most
		1907	situations. Method #3 requires a bit more thinking, but handles many cases
		1908	better, and isn't very complicated either. In most case, choosing either
		1909	one is fine, with #3 being better in typical situations.
		1910
		1911	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1912	rather complicated, but extremely efficient, something that really pays
		1913	off after the first million or so of active timers, i.e. it's usually
		1914	overkill :)
1282		1915
1283	=head3 The special problem of time updates	1916	=head3 The special problem of time updates
1284		1917
1285	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
1286	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
1287	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
1288	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
1289	lots of events in one iteration.	1922	lots of events in one iteration.
1290		1923
1291	The relative timeouts are calculated relative to the C<ev_now ()>	1924	The relative timeouts are calculated relative to the C<ev_now ()>
1292	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
…		…
1298		1931
1299	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
1300	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
1301	()>.	1934	()>.
1302		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
1303	=head3 Watcher-Specific Functions and Data Members	1966	=head3 Watcher-Specific Functions and Data Members
1304		1967
1305	=over 4	1968	=over 4
1306		1969
1307	=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)
…		…
1330	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).
1331		1994
1332	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
1333	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.
1334		1997
1335	This sounds a bit complicated, but here is a useful and typical	1998	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1999	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344		2000
1345	That means you can ignore the C<after> value and C<ev_timer_start>	2001	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347		2002
1348	ev_timer_init (timer, callback, 0., 5.);	2003	Returns the remaining time until a timer fires. If the timer is active,
1349	ev_timer_again (loop, timer);	2004	then this time is relative to the current event loop time, otherwise it's
1350	...	2005	the timeout value currently configured.
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356		2006
1357	This is more slightly efficient then stopping/starting the timer each time	2007	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1358	you want to modify its timeout value.	2008	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1359		2009	will return C<4>. When the timer expires and is restarted, it will return
1360	Note, however, that it is often even more efficient to remember the	2010	roughly C<7> (likely slightly less as callback invocation takes some time,
1361	time of the last activity and let the timer time-out naturally. In the	2011	too), and so on.
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		2012
1366	=item ev_tstamp repeat [read-write]	2013	=item ev_tstamp repeat [read-write]
1367		2014
1368	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
1369	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),
…		…
1374	=head3 Examples	2021	=head3 Examples
1375		2022
1376	Example: Create a timer that fires after 60 seconds.	2023	Example: Create a timer that fires after 60 seconds.
1377		2024
1378	static void	2025	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2026	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	2027	{
1381	.. one minute over, w is actually stopped right here	2028	.. one minute over, w is actually stopped right here
1382	}	2029	}
1383		2030
1384	struct ev_timer mytimer;	2031	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	2032	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	2033	ev_timer_start (loop, &mytimer);
1387		2034
1388	Example: Create a timeout timer that times out after 10 seconds of	2035	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	2036	inactivity.
1390		2037
1391	static void	2038	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	2039	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	2040	{
1394	.. ten seconds without any activity	2041	.. ten seconds without any activity
1395	}	2042	}
1396		2043
1397	struct ev_timer mytimer;	2044	ev_timer mytimer;
1398	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 */
1399	ev_timer_again (&mytimer); /* start timer */	2046	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	2047	ev_run (loop, 0);
1401		2048
1402	// 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":
1403	// reset the timeout to start ticking again at 10 seconds	2050	// reset the timeout to start ticking again at 10 seconds
1404	ev_timer_again (&mytimer);	2051	ev_timer_again (&mytimer);
1405		2052
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	2054	=head2 C<ev_periodic> - to cron or not to cron?
1408		2055
1409	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
1410	(and unfortunately a bit complex).	2057	(and unfortunately a bit complex).
1411		2058
1412	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
1413	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
1414	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
1415	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
1416	+ 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
1417	clock to January of the previous year, then it will take more than year	2064	wrist-watch).
1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1419	roughly 10 seconds later as it uses a relative timeout).
1420		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
1421	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
1422	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
1423	complicated rules.	2076	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		2077	those cannot react to time jumps.
1424		2078
1425	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
1426	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
1427	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).
1428		2084
1429	=head3 Watcher-Specific Functions and Data Members	2085	=head3 Watcher-Specific Functions and Data Members
1430		2086
1431	=over 4	2087	=over 4
1432		2088
1433	=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)
1434		2090
1435	=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)
1436		2092
1437	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
1438	operation, and we will explain them from simplest to most complex:	2094	operation, and we will explain them from simplest to most complex:
1439		2095
1440	=over 4	2096	=over 4
1441		2097
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2098	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		2099
1444	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
1445	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
1446	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
1447	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.
1448		2105
1449	=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)
1450		2107
1451	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
1452	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
1453	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.
1454		2112
1455	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
1456	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
1457	hour, on the hour:	2115	hour, on the hour (with respect to UTC):
1458		2116
1459	ev_periodic_set (&periodic, 0., 3600., 0);	2117	ev_periodic_set (&periodic, 0., 3600., 0);
1460		2118
1461	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,
1462	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
1463	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
1464	by 3600.	2122	by 3600.
1465		2123
1466	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
1467	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
1468	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.
1469		2127
1470	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
1471	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
1472	this value, and in fact is often specified as zero.	2130	this value, and in fact is often specified as zero.
1473		2131
1474	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
1475	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
1476	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
1477	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).
1478		2136
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2137	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		2138
1481	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
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	2140	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	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
1484	current time as second argument.	2142	current time as second argument.
1485		2143
1486	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,
1487	ever, or make ANY event loop modifications whatsoever>.	2145	or make ANY other event loop modifications whatsoever, unless explicitly
		2146	allowed by documentation here>.
1488		2147
1489	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
1490	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
1491	only event loop modification you are allowed to do).	2150	only event loop modification you are allowed to do).
1492		2151
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2152	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	2153	*w, ev_tstamp now)>, e.g.:
1495		2154
		2155	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2156	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	2157	{
1498	return now + 60.;	2158	return now + 60.;
1499	}	2159	}
1500		2160
1501	It must return the next time to trigger, based on the passed time value	2161	It must return the next time to trigger, based on the passed time value
…		…
1521	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
1522	program when the crontabs have changed).	2182	program when the crontabs have changed).
1523		2183
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	2184	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		2185
1526	When active, returns the absolute time that the watcher is supposed to	2186	When active, returns the absolute time that the watcher is supposed
1527	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.
1528		2190
1529	=item ev_tstamp offset [read-write]	2191	=item ev_tstamp offset [read-write]
1530		2192
1531	When repeating, this contains the offset value, otherwise this is the	2193	When repeating, this contains the offset value, otherwise this is the
1532	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).
1533		2196
1534	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
1535	timer fires or C<ev_periodic_again> is being called.	2198	timer fires or C<ev_periodic_again> is being called.
1536		2199
1537	=item ev_tstamp interval [read-write]	2200	=item ev_tstamp interval [read-write]
1538		2201
1539	The current interval value. Can be modified any time, but changes only	2202	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	2203	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	2204	called.
1542		2205
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2206	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		2207
1545	The current reschedule callback, or C<0>, if this functionality is	2208	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	2209	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	2210	the periodic timer fires or C<ev_periodic_again> is being called.
1548		2211
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	2216	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	2217	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	2218	potentially a lot of jitter, but good long-term stability.
1556		2219
1557	static void	2220	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2221	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1559	{	2222	{
1560	... 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)
1561	}	2224	}
1562		2225
1563	struct ev_periodic hourly_tick;	2226	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2227	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	2228	ev_periodic_start (loop, &hourly_tick);
1566		2229
1567	Example: The same as above, but use a reschedule callback to do it:	2230	Example: The same as above, but use a reschedule callback to do it:
1568		2231
1569	#include <math.h>	2232	#include <math.h>
1570		2233
1571	static ev_tstamp	2234	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2235	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	2236	{
1574	return now + (3600. - fmod (now, 3600.));	2237	return now + (3600. - fmod (now, 3600.));
1575	}	2238	}
1576		2239
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2240	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		2241
1579	Example: Call a callback every hour, starting now:	2242	Example: Call a callback every hour, starting now:
1580		2243
1581	struct ev_periodic hourly_tick;	2244	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	2245	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	2246	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	2247	ev_periodic_start (loop, &hourly_tick);
1585		2248
1586		2249
…		…
1589	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
1590	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
1591	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
1592	normal event processing, like any other event.	2255	normal event processing, like any other event.
1593		2256
1594	If you want signals asynchronously, just use C<sigaction> as you would	2257	If you want signals to be delivered truly asynchronously, just use
1595	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
1596	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.
1597		2261
1598	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
1599	first watcher gets started will libev actually register a signal handler	2268	When the first watcher gets started will libev actually register something
1600	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
1601	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).
1602	the last signal watcher for a signal is stopped, libev will reset the
1603	signal handler to SIG_DFL (regardless of what it was set to before).
1604		2271
1605	If possible and supported, libev will install its handlers with	2272	If possible and supported, libev will install its handlers with
1606	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2273	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1607	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
1608	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
1609	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.
1610		2306
1611	=head3 Watcher-Specific Functions and Data Members	2307	=head3 Watcher-Specific Functions and Data Members
1612		2308
1613	=over 4	2309	=over 4
1614		2310
…		…
1625		2321
1626	=back	2322	=back
1627		2323
1628	=head3 Examples	2324	=head3 Examples
1629		2325
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	2326	Example: Try to exit cleanly on SIGINT.
1631		2327
1632	static void	2328	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2329	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	2330	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	2331	ev_break (loop, EVBREAK_ALL);
1636	}	2332	}
1637		2333
1638	struct ev_signal signal_watcher;	2334	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2335	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	2336	ev_signal_start (loop, &signal_watcher);
1641		2337
1642		2338
1643	=head2 C<ev_child> - watch out for process status changes	2339	=head2 C<ev_child> - watch out for process status changes
1644		2340
1645	Child watchers trigger when your process receives a SIGCHLD in response to	2341	Child watchers trigger when your process receives a SIGCHLD in response to
1646	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
1647	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
1648	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
1649	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.,
1650	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,
1651	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
1652	not.	2348	in the next callback invocation is not.
1653		2349
1654	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
1655	you can only register child watchers in the default event loop.	2351	you can only register child watchers in the default event loop.
1656		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
1657	=head3 Process Interaction	2357	=head3 Process Interaction
1658		2358
1659	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
1660	initialised. This is necessary to guarantee proper behaviour even if	2360	initialised. This is necessary to guarantee proper behaviour even if the
1661	the first child watcher is started after the child exits. The occurrence	2361	first child watcher is started after the child exits. The occurrence
1662	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2362	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1663	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
1664	children, even ones not watched.	2364	children, even ones not watched.
1665		2365
1666	=head3 Overriding the Built-In Processing	2366	=head3 Overriding the Built-In Processing
…		…
1676	=head3 Stopping the Child Watcher	2376	=head3 Stopping the Child Watcher
1677		2377
1678	Currently, the child watcher never gets stopped, even when the	2378	Currently, the child watcher never gets stopped, even when the
1679	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
1680	callback. Future versions of libev might stop the watcher automatically	2380	callback. Future versions of libev might stop the watcher automatically
1681	when a child exit is detected.	2381	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2382	problem).
1682		2383
1683	=head3 Watcher-Specific Functions and Data Members	2384	=head3 Watcher-Specific Functions and Data Members
1684		2385
1685	=over 4	2386	=over 4
1686		2387
…		…
1718	its completion.	2419	its completion.
1719		2420
1720	ev_child cw;	2421	ev_child cw;
1721		2422
1722	static void	2423	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	2424	child_cb (EV_P_ ev_child *w, int revents)
1724	{	2425	{
1725	ev_child_stop (EV_A_ w);	2426	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2427	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	2428	}
1728		2429
…		…
1743		2444
1744		2445
1745	=head2 C<ev_stat> - did the file attributes just change?	2446	=head2 C<ev_stat> - did the file attributes just change?
1746		2447
1747	This watches a file system path for attribute changes. That is, it calls	2448	This watches a file system path for attribute changes. That is, it calls
1748	C<stat> regularly (or when the OS says it changed) and sees if it changed	2449	C<stat> on that path in regular intervals (or when the OS says it changed)
1749	compared to the last time, invoking the callback if it did.	2450	and sees if it changed compared to the last time, invoking the callback if
		2451	it did.
1750		2452
1751	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
1752	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
1753	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
1754	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
1755	the stat buffer having unspecified contents.	2457	least one) and all the other fields of the stat buffer having unspecified
		2458	contents.
1756		2459
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	2460	The path I<must not> end in a slash or contain special components such as
		2461	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1758	relative and your working directory changes, the behaviour is undefined.	2462	your working directory changes, then the behaviour is undefined.
1759		2463
1760	Since there is no standard kernel interface to do this, the portable	2464	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	2465	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	2466	to see if it changed somehow. You can specify a recommended polling
1763	this case. If you specify a polling interval of C<0> (highly recommended!)	2467	interval for this case. If you specify a polling interval of C<0> (highly
1764	then a I<suitable, unspecified default> value will be used (which	2468	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	2469	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	2470	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	2471	currently around C<0.1>, but that's usually overkill.
1768		2472
1769	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,
1770	as even with OS-supported change notifications, this can be	2474	as even with OS-supported change notifications, this can be
1771	resource-intensive.	2475	resource-intensive.
1772		2476
1773	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
1774	is the Linux inotify interface (implementing kqueue support is left as	2478	is the Linux inotify interface (implementing kqueue support is left as an
1775	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
1776	of implementing C<ev_stat> semantics with kqueue).	2480	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		2481
1778	=head3 ABI Issues (Largefile Support)	2482	=head3 ABI Issues (Largefile Support)
1779		2483
1780	Libev by default (unless the user overrides this) uses the default	2484	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	2485	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	2486	support disabled by default, you get the 32 bit version of the stat
1783	structure. When using the library from programs that change the ABI to	2487	structure. When using the library from programs that change the ABI to
1784	use 64 bit file offsets the programs will fail. In that case you have to	2488	use 64 bit file offsets the programs will fail. In that case you have to
1785	compile libev with the same flags to get binary compatibility. This is	2489	compile libev with the same flags to get binary compatibility. This is
1786	obviously the case with any flags that change the ABI, but the problem is	2490	obviously the case with any flags that change the ABI, but the problem is
1787	most noticeably disabled with ev_stat and large file support.	2491	most noticeably displayed with ev_stat and large file support.
1788		2492
1789	The solution for this is to lobby your distribution maker to make large	2493	The solution for this is to lobby your distribution maker to make large
1790	file interfaces available by default (as e.g. FreeBSD does) and not	2494	file interfaces available by default (as e.g. FreeBSD does) and not
1791	optional. Libev cannot simply switch on large file support because it has	2495	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2496	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2497	default compilation environment.
1794		2498
1795	=head3 Inotify and Kqueue	2499	=head3 Inotify and Kqueue
1796		2500
1797	When C<inotify (7)> support has been compiled into libev (generally only	2501	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2502	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2503	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2504	watcher is being started.
1801		2505
1802	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
1803	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
1804	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
1805	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,
1806	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.
1807		2514
1808	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
1809	implement this functionality, due to the requirement of having a file	2516	implement this functionality, due to the requirement of having a file
1810	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
1811	etc. is difficult.	2518	etc. is difficult.
1812		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.
		2537
1813	=head3 The special problem of stat time resolution	2538	=head3 The special problem of stat time resolution
1814		2539
1815	The C<stat ()> system call only supports full-second resolution portably, and	2540	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2541	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2542	still only support whole seconds.
1818		2543
1819	That means that, if the time is the only thing that changes, you can	2544	That means that, if the time is the only thing that changes, you can
1820	easily miss updates: on the first update, C<ev_stat> detects a change and	2545	easily miss updates: on the first update, C<ev_stat> detects a change and
1821	calls your callback, which does something. When there is another update	2546	calls your callback, which does something. When there is another update
1822	within the same second, C<ev_stat> will be unable to detect unless the	2547	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2690
1966	=head3 Watcher-Specific Functions and Data Members	2691	=head3 Watcher-Specific Functions and Data Members
1967		2692
1968	=over 4	2693	=over 4
1969		2694
1970	=item ev_idle_init (ev_signal *, callback)	2695	=item ev_idle_init (ev_idle *, callback)
1971		2696
1972	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
1973	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,
1974	believe me.	2699	believe me.
1975		2700
…		…
1979		2704
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2705	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2706	callback, free it. Also, use no error checking, as usual.
1982		2707
1983	static void	2708	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2709	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2710	{
1986	free (w);	2711	free (w);
1987	// now do something you wanted to do when the program has	2712	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2713	// no longer anything immediate to do.
1989	}	2714	}
1990		2715
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2716	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2717	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2718	ev_idle_start (loop, idle_watcher);
1994		2719
1995		2720
1996	=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!
1997		2722
1998	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:
1999	prepare watchers get invoked before the process blocks and check watchers	2724	prepare watchers get invoked before the process blocks and check watchers
2000	afterwards.	2725	afterwards.
2001		2726
2002	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
2003	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>
2004	watchers. Other loops than the current one are fine, however. The	2729	watchers. Other loops than the current one are fine, however. The
2005	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
2006	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,
2007	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
…		…
2077		2802
2078	static ev_io iow [nfd];	2803	static ev_io iow [nfd];
2079	static ev_timer tw;	2804	static ev_timer tw;
2080		2805
2081	static void	2806	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2807	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2808	{
2084	}	2809	}
2085		2810
2086	// create io watchers for each fd and a timer before blocking	2811	// create io watchers for each fd and a timer before blocking
2087	static void	2812	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2813	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2814	{
2090	int timeout = 3600000;	2815	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2816	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2817	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2818	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2094		2819
2095	/* 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 */
2096	ev_timer_init (&tw, 0, timeout * 1e-3);	2821	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2097	ev_timer_start (loop, &tw);	2822	ev_timer_start (loop, &tw);
2098		2823
2099	// create one ev_io per pollfd	2824	// create one ev_io per pollfd
2100	for (int i = 0; i < nfd; ++i)	2825	for (int i = 0; i < nfd; ++i)
2101	{	2826	{
…		…
2108	}	2833	}
2109	}	2834	}
2110		2835
2111	// stop all watchers after blocking	2836	// stop all watchers after blocking
2112	static void	2837	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2838	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2839	{
2115	ev_timer_stop (loop, &tw);	2840	ev_timer_stop (loop, &tw);
2116		2841
2117	for (int i = 0; i < nfd; ++i)	2842	for (int i = 0; i < nfd; ++i)
2118	{	2843	{
…		…
2175		2900
2176	if (timeout >= 0)	2901	if (timeout >= 0)
2177	// create/start timer	2902	// create/start timer
2178		2903
2179	// poll	2904	// poll
2180	ev_loop (EV_A_ 0);	2905	ev_run (EV_A_ 0);
2181		2906
2182	// stop timer again	2907	// stop timer again
2183	if (timeout >= 0)	2908	if (timeout >= 0)
2184	ev_timer_stop (EV_A_ &to);	2909	ev_timer_stop (EV_A_ &to);
2185		2910
…		…
2214	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),
2215	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
2216	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
2217	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.
2218		2943
2219	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
2220	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
2221	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
2222	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
2223	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
2224	to C<0>, in which case the embed watcher will automatically execute the	2949	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2950
2227	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
2228	callback will be invoked whenever some events have been handled. You can	2952	will automatically execute the embedded loop sweep whenever necessary.
2229	set the callback to C<0> to avoid having to specify one if you are not
2230	interested in that.
2231		2953
2232	Also, there have not currently been made special provisions for forking:	2954	Fork detection will be handled transparently while the C<ev_embed> watcher
2233	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
2234	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
2235	yourself - but you can use a fork watcher to handle this automatically,	2957	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2958
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2959	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2960	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2961	portable one.
2241		2962
2242	So when you want to use this feature you will always have to be prepared	2963	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2964	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2965	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2966	create it, and if that fails, use the normal loop for everything.
		2967
		2968	=head3 C<ev_embed> and fork
		2969
		2970	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2971	automatically be applied to the embedded loop as well, so no special
		2972	fork handling is required in that case. When the watcher is not running,
		2973	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2974	as applicable.
2246		2975
2247	=head3 Watcher-Specific Functions and Data Members	2976	=head3 Watcher-Specific Functions and Data Members
2248		2977
2249	=over 4	2978	=over 4
2250		2979
…		…
2259	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).
2260		2989
2261	=item ev_embed_sweep (loop, ev_embed *)	2990	=item ev_embed_sweep (loop, ev_embed *)
2262		2991
2263	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
2264	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
2265	appropriate way for embedded loops.	2994	appropriate way for embedded loops.
2266		2995
2267	=item struct ev_loop *other [read-only]	2996	=item struct ev_loop *other [read-only]
2268		2997
2269	The embedded event loop.	2998	The embedded event loop.
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	3007	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	3008	used).
2280		3009
2281	struct ev_loop *loop_hi = ev_default_init (0);	3010	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	3011	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	3012	ev_embed embed;
2284		3013
2285	// see if there is a chance of getting one that works	3014	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	3015	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3016	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3017	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	3031	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3032	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		3033
2305	struct ev_loop *loop = ev_default_init (0);	3034	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	3035	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	3036	ev_embed embed;
2308		3037
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3038	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3039	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	3040	{
2312	ev_embed_init (&embed, 0, loop_socket);	3041	ev_embed_init (&embed, 0, loop_socket);
…		…
2327	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,
2328	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
2329	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
2330	handlers will be invoked, too, of course.	3059	handlers will be invoked, too, of course.
2331		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
2332	=head3 Watcher-Specific Functions and Data Members	3095	=head3 Watcher-Specific Functions and Data Members
2333		3096
2334	=over 4	3097	=over 4
2335		3098
2336	=item ev_fork_init (ev_signal *, callback)	3099	=item ev_fork_init (ev_fork *, callback)
2337		3100
2338	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
2339	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,
2340	believe me.	3103	believe me.
2341		3104
2342	=back	3105	=back
2343		3106
2344		3107
		3108	=head2 C<ev_cleanup> - even the best things end
		3109
		3110	Cleanup watchers are called just before the event loop they are registered
		3111	with is being destroyed.
		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, believe me.
		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
2345	=head2 C<ev_async> - how to wake up another event loop	3148	=head2 C<ev_async> - how to wake up an event loop
2346		3149
2347	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
2348	asynchronous sources such as signal handlers (as opposed to multiple event	3151	asynchronous sources such as signal handlers (as opposed to multiple event
2349	loops - those are of course safe to use in different threads).	3152	loops - those are of course safe to use in different threads).
2350		3153
2351	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,
2352	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>
2353	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
2354	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.
2355	safe.
2356		3158
2357	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,
2358	too, are asynchronous in nature, and signals, too, will be compressed	3160	too, are asynchronous in nature, and signals, too, will be compressed
2359	(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
2360	C<ev_async_sent> calls).	3162	C<ev_async_sent> calls).
…		…
2365	=head3 Queueing	3167	=head3 Queueing
2366		3168
2367	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
2368	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
2369	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
2370	need elaborate support such as pthreads.	3172	need elaborate support such as pthreads or unportable memory access
		3173	semantics.
2371		3174
2372	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
2373	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
2374	queue:	3177	queue:
2375		3178
2376	=over 4	3179	=over 4
2377		3180
2378	=item queueing from a signal handler context	3181	=item queueing from a signal handler context
2379		3182
2380	To implement race-free queueing, you simply add to the queue in the signal	3183	To implement race-free queueing, you simply add to the queue in the signal
2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for	3184	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	3185	an example that does that for some fictitious SIGUSR1 handler:
2383		3186
2384	static ev_async mysig;	3187	static ev_async mysig;
2385		3188
2386	static void	3189	static void
2387	sigusr1_handler (void)	3190	sigusr1_handler (void)
…		…
2453	=over 4	3256	=over 4
2454		3257
2455	=item ev_async_init (ev_async *, callback)	3258	=item ev_async_init (ev_async *, callback)
2456		3259
2457	Initialises and configures the async watcher - it has no parameters of any	3260	Initialises and configures the async watcher - it has no parameters of any
2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3261	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2459	trust me.	3262	trust me.
2460		3263
2461	=item ev_async_send (loop, ev_async *)	3264	=item ev_async_send (loop, ev_async *)
2462		3265
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3266	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	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
2465	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
2466	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
2467	section below on what exactly this means).	3270	section below on what exactly this means).
2468		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
2469	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
2470	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
2471	calls to C<ev_async_send>.	3279	repeated calls to C<ev_async_send> for the same event loop.
2472		3280
2473	=item bool = ev_async_pending (ev_async *)	3281	=item bool = ev_async_pending (ev_async *)
2474		3282
2475	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
2476	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
…		…
2479	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
2480	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,
2481	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
2482	quickly check whether invoking the loop might be a good idea.	3290	quickly check whether invoking the loop might be a good idea.
2483		3291
2484	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,
2485	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.
2486		3296
2487	=back	3297	=back
2488		3298
2489		3299
2490	=head1 OTHER FUNCTIONS	3300	=head1 OTHER FUNCTIONS
…		…
2494	=over 4	3304	=over 4
2495		3305
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3306	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		3307
2498	This function combines a simple timer and an I/O watcher, calls your	3308	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	3309	callback on whichever event happens first and automatically stops both
2500	watchers. This is useful if you want to wait for a single event on an fd	3310	watchers. This is useful if you want to wait for a single event on an fd
2501	or timeout without having to allocate/configure/start/stop/free one or	3311	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	3312	more watchers yourself.
2503		3313
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	3314	If C<fd> is less than 0, then no I/O watcher will be started and the
2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3315	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	3316	the given C<fd> and C<events> set will be created and started.
2507		3317
2508	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
2509	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
2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3320	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		3321
2513	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
2514	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
2515	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>
2516	value passed to C<ev_once>:	3325	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3326	a timeout and an io event at the same time - you probably should give io
		3327	events precedence.
		3328
		3329	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		3330
2518	static void stdin_ready (int revents, void *arg)	3331	static void stdin_ready (int revents, void *arg)
2519	{	3332	{
		3333	if (revents & EV_READ)
		3334	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	3335	else if (revents & EV_TIMER)
2521	/* doh, nothing entered */;	3336	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	3337	}
2525		3338
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3339	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		3340
2528	=item ev_feed_event (ev_loop *, watcher *, int revents)
2529
2530	Feeds the given event set into the event loop, as if the specified event
2531	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).
2533
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3341	=item ev_feed_fd_event (loop, int fd, int revents)
2535		3342
2536	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
2537	the given events it.	3344	the given events it.
2538		3345
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	3346	=item ev_feed_signal_event (loop, int signum)
2540		3347
2541	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
2542	loop!).	3349	loop!).
2543		3350
2544	=back	3351	=back
…		…
2624		3431
2625	=over 4	3432	=over 4
2626		3433
2627	=item ev::TYPE::TYPE ()	3434	=item ev::TYPE::TYPE ()
2628		3435
2629	=item ev::TYPE::TYPE (struct ev_loop *)	3436	=item ev::TYPE::TYPE (loop)
2630		3437
2631	=item ev::TYPE::~TYPE	3438	=item ev::TYPE::~TYPE
2632		3439
2633	The constructor (optionally) takes an event loop to associate the watcher	3440	The constructor (optionally) takes an event loop to associate the watcher
2634	with. If it is omitted, it will use C<EV_DEFAULT>.	3441	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2666		3473
2667	myclass obj;	3474	myclass obj;
2668	ev::io iow;	3475	ev::io iow;
2669	iow.set <myclass, &myclass::io_cb> (&obj);	3476	iow.set <myclass, &myclass::io_cb> (&obj);
2670		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
2671	=item w->set<function> (void *data = 0)	3506	=item w->set<function> (void *data = 0)
2672		3507
2673	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
2674	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
2675	C<data> member and is free for you to use.	3510	C<data> member and is free for you to use.
…		…
2681	Example: Use a plain function as callback.	3516	Example: Use a plain function as callback.
2682		3517
2683	static void io_cb (ev::io &w, int revents) { }	3518	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	3519	iow.set <io_cb> ();
2685		3520
2686	=item w->set (struct ev_loop *)	3521	=item w->set (loop)
2687		3522
2688	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
2689	do this when the watcher is inactive (and not pending either).	3524	do this when the watcher is inactive (and not pending either).
2690		3525
2691	=item w->set ([arguments])	3526	=item w->set ([arguments])
2692		3527
2693	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
2694	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
2695	automatically stopped and restarted when reconfiguring it with this	3530	C counterpart, an active watcher gets automatically stopped and restarted
2696	method.	3531	when reconfiguring it with this method.
2697		3532
2698	=item w->start ()	3533	=item w->start ()
2699		3534
2700	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
2701	constructor already stores the event loop.	3536	constructor already stores the event loop.
2702		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
2703	=item w->stop ()	3544	=item w->stop ()
2704		3545
2705	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.
2706		3547
2707	=item w->again () (C<ev::timer>, C<ev::periodic> only)	3548	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2719		3560
2720	=back	3561	=back
2721		3562
2722	=back	3563	=back
2723		3564
2724	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
2725	the constructor.	3566	watchers in the constructor.
2726		3567
2727	class myclass	3568	class myclass
2728	{	3569	{
2729	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);
2730	ev::idle idle; void idle_cb (ev::idle &w, int revents);	3572	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2731		3573
2732	myclass (int fd)	3574	myclass (int fd)
2733	{	3575	{
2734	io .set <myclass, &myclass::io_cb > (this);	3576	io .set <myclass, &myclass::io_cb > (this);
		3577	io2 .set <myclass, &myclass::io2_cb > (this);
2735	idle.set <myclass, &myclass::idle_cb> (this);	3578	idle.set <myclass, &myclass::idle_cb> (this);
2736		3579
2737	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
2738	}	3584	}
2739	};	3585	};
2740		3586
2741		3587
2742	=head1 OTHER LANGUAGE BINDINGS	3588	=head1 OTHER LANGUAGE BINDINGS
…		…
2761	L<http://software.schmorp.de/pkg/EV>.	3607	L<http://software.schmorp.de/pkg/EV>.
2762		3608
2763	=item Python	3609	=item Python
2764		3610
2765	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
2766	seems to be quite complete and well-documented. Note, however, that the	3612	seems to be quite complete and well-documented.
2767	patch they require for libev is outright dangerous as it breaks the ABI
2768	for everybody else, and therefore, should never be applied in an installed
2769	libev (if python requires an incompatible ABI then it needs to embed
2770	libev).
2771		3613
2772	=item Ruby	3614	=item Ruby
2773		3615
2774	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
2775	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
2776	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
2777	L<http://rev.rubyforge.org/>.	3619	L<http://rev.rubyforge.org/>.
2778		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
2779	=item D	3629	=item D
2780		3630
2781	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
2782	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3632	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3633
		3634	=item Ocaml
		3635
		3636	Erkki Seppala has written Ocaml bindings for libev, to be found at
		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>.
2783		3644
2784	=back	3645	=back
2785		3646
2786		3647
2787	=head1 MACRO MAGIC	3648	=head1 MACRO MAGIC
…		…
2801	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,
2802	C<EV_A_> is used when other arguments are following. Example:	3663	C<EV_A_> is used when other arguments are following. Example:
2803		3664
2804	ev_unref (EV_A);	3665	ev_unref (EV_A);
2805	ev_timer_add (EV_A_ watcher);	3666	ev_timer_add (EV_A_ watcher);
2806	ev_loop (EV_A_ 0);	3667	ev_run (EV_A_ 0);
2807		3668
2808	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,
2809	which is often provided by the following macro.	3670	which is often provided by the following macro.
2810		3671
2811	=item C<EV_P>, C<EV_P_>	3672	=item C<EV_P>, C<EV_P_>
…		…
2851	}	3712	}
2852		3713
2853	ev_check check;	3714	ev_check check;
2854	ev_check_init (&check, check_cb);	3715	ev_check_init (&check, check_cb);
2855	ev_check_start (EV_DEFAULT_ &check);	3716	ev_check_start (EV_DEFAULT_ &check);
2856	ev_loop (EV_DEFAULT_ 0);	3717	ev_run (EV_DEFAULT_ 0);
2857		3718
2858	=head1 EMBEDDING	3719	=head1 EMBEDDING
2859		3720
2860	Libev can (and often is) directly embedded into host	3721	Libev can (and often is) directly embedded into host
2861	applications. Examples of applications that embed it include the Deliantra	3722	applications. Examples of applications that embed it include the Deliantra
…		…
2888		3749
2889	#define EV_STANDALONE 1	3750	#define EV_STANDALONE 1
2890	#include "ev.h"	3751	#include "ev.h"
2891		3752
2892	Both header files and implementation files can be compiled with a C++	3753	Both header files and implementation files can be compiled with a C++
2893	compiler (at least, thats a stated goal, and breakage will be treated	3754	compiler (at least, that's a stated goal, and breakage will be treated
2894	as a bug).	3755	as a bug).
2895		3756
2896	You need the following files in your source tree, or in a directory	3757	You need the following files in your source tree, or in a directory
2897	in your include path (e.g. in libev/ when using -Ilibev):	3758	in your include path (e.g. in libev/ when using -Ilibev):
2898		3759
…		…
2941	libev.m4	3802	libev.m4
2942		3803
2943	=head2 PREPROCESSOR SYMBOLS/MACROS	3804	=head2 PREPROCESSOR SYMBOLS/MACROS
2944		3805
2945	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
2946	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
2947	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.
2948		3816
2949	=over 4	3817	=over 4
2950		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
2951	=item EV_STANDALONE	3835	=item EV_STANDALONE (h)
2952		3836
2953	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
2954	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
2955	implementations for some libevent functions (such as logging, which is not	3839	implementations for some libevent functions (such as logging, which is not
2956	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
2957	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.
2958		3842
		3843	In standalone mode, libev will still try to automatically deduce the
		3844	configuration, but has to be more conservative.
		3845
2959	=item EV_USE_MONOTONIC	3846	=item EV_USE_MONOTONIC
2960		3847
2961	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
2962	monotonic clock option at both compile time and runtime. Otherwise no use	3849	monotonic clock option at both compile time and runtime. Otherwise no
2963	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,
2964	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
2965	the functionality isn't available is safe, though, although you have	3852	when the functionality isn't available is safe, though, although you have
2966	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>
2967	function is hiding in (often F<-lrt>).	3854	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2968		3855
2969	=item EV_USE_REALTIME	3856	=item EV_USE_REALTIME
2970		3857
2971	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
2972	real-time clock option at compile time (and assume its availability at	3859	real-time clock option at compile time (and assume its availability
2973	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
2974	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3861	option will be attempted. This effectively replaces C<gettimeofday>
2975	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3862	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2976	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>).
2977		3877
2978	=item EV_USE_NANOSLEEP	3878	=item EV_USE_NANOSLEEP
2979		3879
2980	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
2981	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 ()>.
…		…
2997		3897
2998	=item EV_SELECT_USE_FD_SET	3898	=item EV_SELECT_USE_FD_SET
2999		3899
3000	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>
3001	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
3002	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
3003	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
3004	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
3005	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,
3006	influence the size of the C<fd_set> used.	3906	configures the maximum size of the C<fd_set>.
3007		3907
3008	=item EV_SELECT_IS_WINSOCKET	3908	=item EV_SELECT_IS_WINSOCKET
3009		3909
3010	When defined to C<1>, the select backend will assume that	3910	When defined to C<1>, the select backend will assume that
3011	select/socket/connect etc. don't understand file descriptors but	3911	select/socket/connect etc. don't understand file descriptors but
…		…
3013	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
3014	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,
3015	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
3016	on win32. Should not be defined on non-win32 platforms.	3916	on win32. Should not be defined on non-win32 platforms.
3017		3917
3018	=item EV_FD_TO_WIN32_HANDLE	3918	=item EV_FD_TO_WIN32_HANDLE(fd)
3019		3919
3020	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
3021	file descriptors to socket handles. When not defining this symbol (the	3921	file descriptors to socket handles. When not defining this symbol (the
3022	default), then libev will call C<_get_osfhandle>, which is usually	3922	default), then libev will call C<_get_osfhandle>, which is usually
3023	correct. In some cases, programs use their own file descriptor management,	3923	correct. In some cases, programs use their own file descriptor management,
3024	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.
3025		3939
3026	=item EV_USE_POLL	3940	=item EV_USE_POLL
3027		3941
3028	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)
3029	backend. Otherwise it will be enabled on non-win32 platforms. It	3943	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3076	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.
3077		3991
3078	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>
3079	(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.
3080		3994
3081	=item EV_H	3995	=item EV_H (h)
3082		3996
3083	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
3084	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
3085	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.
3086		4000
3087	=item EV_CONFIG_H	4001	=item EV_CONFIG_H (h)
3088		4002
3089	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
3090	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
3091	C<EV_H>, above.	4005	C<EV_H>, above.
3092		4006
3093	=item EV_EVENT_H	4007	=item EV_EVENT_H (h)
3094		4008
3095	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
3096	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">.
3097		4011
3098	=item EV_PROTOTYPES	4012	=item EV_PROTOTYPES (h)
3099		4013
3100	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
3101	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
3102	occasionally useful if you want to provide your own wrapper functions	4016	occasionally useful if you want to provide your own wrapper functions
3103	around libev functions.	4017	around libev functions.
…		…
3125	fine.	4039	fine.
3126		4040
3127	If your embedding application does not need any priorities, defining these	4041	If your embedding application does not need any priorities, defining these
3128	both to C<0> will save some memory and CPU.	4042	both to C<0> will save some memory and CPU.
3129		4043
3130	=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.
3131		4047
3132	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
3133	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
3134	code.	4050	is not. Disabling watcher types mainly saves code size.
3135		4051
3136	=item EV_IDLE_ENABLE	4052	=item EV_FEATURES
3137
3138	If undefined or defined to be C<1>, then idle watchers are supported. If
3139	defined to be C<0>, then they are not. Disabling them saves a few kB of
3140	code.
3141
3142	=item EV_EMBED_ENABLE
3143
3144	If undefined or defined to be C<1>, then embed watchers are supported. If
3145	defined to be C<0>, then they are not. Embed watchers rely on most other
3146	watcher types, which therefore must not be disabled.
3147
3148	=item EV_STAT_ENABLE
3149
3150	If undefined or defined to be C<1>, then stat watchers are supported. If
3151	defined to be C<0>, then they are not.
3152
3153	=item EV_FORK_ENABLE
3154
3155	If undefined or defined to be C<1>, then fork watchers are supported. If
3156	defined to be C<0>, then they are not.
3157
3158	=item EV_ASYNC_ENABLE
3159
3160	If undefined or defined to be C<1>, then async watchers are supported. If
3161	defined to be C<0>, then they are not.
3162
3163	=item EV_MINIMAL
3164		4053
3165	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
3166	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
3167	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
3168	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.
3169		4153
3170	=item EV_PID_HASHSIZE	4154	=item EV_PID_HASHSIZE
3171		4155
3172	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
3173	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),
3174	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
3175	increase this value (I<must> be a power of two).	4159	might want to increase this value (I<must> be a power of two).
3176		4160
3177	=item EV_INOTIFY_HASHSIZE	4161	=item EV_INOTIFY_HASHSIZE
3178		4162
3179	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
3180	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>
3181	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
3182	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
3183	two).	4167	power of two).
3184		4168
3185	=item EV_USE_4HEAP	4169	=item EV_USE_4HEAP
3186		4170
3187	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
3188	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
3189	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
3190	faster performance with many (thousands) of watchers.	4174	faster performance with many (thousands) of watchers.
3191		4175
3192	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
3193	(disabled).	4177	will be C<0>.
3194		4178
3195	=item EV_HEAP_CACHE_AT	4179	=item EV_HEAP_CACHE_AT
3196		4180
3197	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
3198	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
3199	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>),
3200	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,
3201	but avoids random read accesses on heap changes. This improves performance	4185	but avoids random read accesses on heap changes. This improves performance
3202	noticeably with many (hundreds) of watchers.	4186	noticeably with many (hundreds) of watchers.
3203		4187
3204	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
3205	(disabled).	4189	will be C<0>.
3206		4190
3207	=item EV_VERIFY	4191	=item EV_VERIFY
3208		4192
3209	Controls how much internal verification (see C<ev_loop_verify ()>) will	4193	Controls how much internal verification (see C<ev_verify ()>) will
3210	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
3211	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
3212	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
3213	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
3214	verification code will be called very frequently, which will slow down	4198	verification code will be called very frequently, which will slow down
3215	libev considerably.	4199	libev considerably.
3216		4200
3217	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
3218	C<0>.	4202	will be C<0>.
3219		4203
3220	=item EV_COMMON	4204	=item EV_COMMON
3221		4205
3222	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
3223	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
3224	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,
3225	though, and it must be identical each time.	4209	though, and it must be identical each time.
3226		4210
3227	For example, the perl EV module uses something like this:	4211	For example, the perl EV module uses something like this:
3228		4212
…		…
3281	file.	4265	file.
3282		4266
3283	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
3284	that everybody includes and which overrides some configure choices:	4268	that everybody includes and which overrides some configure choices:
3285		4269
3286	#define EV_MINIMAL 1	4270	#define EV_FEATURES 8
3287	#define EV_USE_POLL 0	4271	#define EV_USE_SELECT 1
3288	#define EV_MULTIPLICITY 0
3289	#define EV_PERIODIC_ENABLE 0	4272	#define EV_PREPARE_ENABLE 1
		4273	#define EV_IDLE_ENABLE 1
3290	#define EV_STAT_ENABLE 0	4274	#define EV_SIGNAL_ENABLE 1
3291	#define EV_FORK_ENABLE 0	4275	#define EV_CHILD_ENABLE 1
		4276	#define EV_USE_STDEXCEPT 0
3292	#define EV_CONFIG_H <config.h>	4277	#define EV_CONFIG_H <config.h>
3293	#define EV_MINPRI 0
3294	#define EV_MAXPRI 0
3295		4278
3296	#include "ev++.h"	4279	#include "ev++.h"
3297		4280
3298	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:
3299		4282
3300	#include "ev_cpp.h"	4283	#include "ev_cpp.h"
3301	#include "ev.c"	4284	#include "ev.c"
3302		4285
		4286	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3303		4287
3304	=head1 THREADS AND COROUTINES	4288	=head2 THREADS AND COROUTINES
3305		4289
3306	=head2 THREADS	4290	=head3 THREADS
3307		4291
3308	All libev functions are reentrant and thread-safe unless explicitly	4292	All libev functions are reentrant and thread-safe unless explicitly
3309	documented otherwise, but it uses no locking itself. This means that you	4293	documented otherwise, but libev implements no locking itself. This means
3310	can use as many loops as you want in parallel, as long as there are no	4294	that you can use as many loops as you want in parallel, as long as there
3311	concurrent calls into any libev function with the same loop parameter	4295	are no concurrent calls into any libev function with the same loop
3312	(C<ev_default_*> calls have an implicit default loop parameter, of	4296	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3313	course): libev guarantees that different event loops share no data	4297	of course): libev guarantees that different event loops share no data
3314	structures that need any locking.	4298	structures that need any locking.
3315		4299
3316	Or to put it differently: calls with different loop parameters can be done	4300	Or to put it differently: calls with different loop parameters can be done
3317	concurrently from multiple threads, calls with the same loop parameter	4301	concurrently from multiple threads, calls with the same loop parameter
3318	must be done serially (but can be done from different threads, as long as	4302	must be done serially (but can be done from different threads, as long as
…		…
3358	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
3359	watcher callback into the event loop interested in the signal.	4343	watcher callback into the event loop interested in the signal.
3360		4344
3361	=back	4345	=back
3362		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
3363	=head2 COROUTINES	4485	=head3 COROUTINES
3364		4486
3365	Libev is much more accommodating to coroutines ("cooperative threads"):	4487	Libev is very accommodating to coroutines ("cooperative threads"):
3366	libev fully supports nesting calls to it's functions from different	4488	libev fully supports nesting calls to its functions from different
3367	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
3368	different coroutines and switch freely between both coroutines running the	4490	different coroutines, and switch freely between both coroutines running
3369	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
3370	you must not do this from C<ev_periodic> reschedule callbacks.	4492	that you must not do this from C<ev_periodic> reschedule callbacks.
3371		4493
3372	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
3373	C<ev_loop>, and other calls do not usually allow coroutine switches.	4495	C<ev_run>, and other calls do not usually allow for coroutine switches as
		4496	they do not call any callbacks.
3374		4497
		4498	=head2 COMPILER WARNINGS
3375		4499
3376	=head1 COMPLEXITIES	4500	Depending on your compiler and compiler settings, you might get no or a
		4501	lot of warnings when compiling libev code. Some people are apparently
		4502	scared by this.
3377		4503
3378	In this section the complexities of (many of) the algorithms used inside	4504	However, these are unavoidable for many reasons. For one, each compiler
3379	libev will be explained. For complexity discussions about backends see the	4505	has different warnings, and each user has different tastes regarding
3380	documentation for C<ev_default_init>.	4506	warning options. "Warn-free" code therefore cannot be a goal except when
		4507	targeting a specific compiler and compiler-version.
3381		4508
3382	All of the following are about amortised time: If an array needs to be	4509	Another reason is that some compiler warnings require elaborate
3383	extended, libev needs to realloc and move the whole array, but this	4510	workarounds, or other changes to the code that make it less clear and less
3384	happens asymptotically never with higher number of elements, so O(1) might	4511	maintainable.
3385	mean it might do a lengthy realloc operation in rare cases, but on average
3386	it is much faster and asymptotically approaches constant time.
3387		4512
3388	=over 4	4513	And of course, some compiler warnings are just plain stupid, or simply
		4514	wrong (because they don't actually warn about the condition their message
		4515	seems to warn about). For example, certain older gcc versions had some
		4516	warnings that resulted in an extreme number of false positives. These have
		4517	been fixed, but some people still insist on making code warn-free with
		4518	such buggy versions.
3389		4519
3390	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4520	While libev is written to generate as few warnings as possible,
		4521	"warn-free" code is not a goal, and it is recommended not to build libev
		4522	with any compiler warnings enabled unless you are prepared to cope with
		4523	them (e.g. by ignoring them). Remember that warnings are just that:
		4524	warnings, not errors, or proof of bugs.
3391		4525
3392	This means that, when you have a watcher that triggers in one hour and
3393	there are 100 watchers that would trigger before that then inserting will
3394	have to skip roughly seven (C<ld 100>) of these watchers.
3395		4526
3396	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4527	=head2 VALGRIND
3397		4528
3398	That means that changing a timer costs less than removing/adding them	4529	Valgrind has a special section here because it is a popular tool that is
3399	as only the relative motion in the event queue has to be paid for.	4530	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3400		4531
3401	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4532	If you think you found a bug (memory leak, uninitialised data access etc.)
		4533	in libev, then check twice: If valgrind reports something like:
3402		4534
3403	These just add the watcher into an array or at the head of a list.	4535	==2274== definitely lost: 0 bytes in 0 blocks.
		4536	==2274== possibly lost: 0 bytes in 0 blocks.
		4537	==2274== still reachable: 256 bytes in 1 blocks.
3404		4538
3405	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4539	Then there is no memory leak, just as memory accounted to global variables
		4540	is not a memleak - the memory is still being referenced, and didn't leak.
3406		4541
3407	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4542	Similarly, under some circumstances, valgrind might report kernel bugs
		4543	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4544	although an acceptable workaround has been found here), or it might be
		4545	confused.
3408		4546
3409	These watchers are stored in lists then need to be walked to find the	4547	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3410	correct watcher to remove. The lists are usually short (you don't usually	4548	make it into some kind of religion.
3411	have many watchers waiting for the same fd or signal).
3412		4549
3413	=item Finding the next timer in each loop iteration: O(1)	4550	If you are unsure about something, feel free to contact the mailing list
		4551	with the full valgrind report and an explanation on why you think this
		4552	is a bug in libev (best check the archives, too :). However, don't be
		4553	annoyed when you get a brisk "this is no bug" answer and take the chance
		4554	of learning how to interpret valgrind properly.
3414		4555
3415	By virtue of using a binary or 4-heap, the next timer is always found at a	4556	If you need, for some reason, empty reports from valgrind for your project
3416	fixed position in the storage array.	4557	I suggest using suppression lists.
3417		4558
3418	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3419		4559
3420	A change means an I/O watcher gets started or stopped, which requires	4560	=head1 PORTABILITY NOTES
3421	libev to recalculate its status (and possibly tell the kernel, depending
3422	on backend and whether C<ev_io_set> was used).
3423		4561
3424	=item Activating one watcher (putting it into the pending state): O(1)	4562	=head2 GNU/LINUX 32 BIT LIMITATIONS
3425		4563
3426	=item Priority handling: O(number_of_priorities)	4564	GNU/Linux is the only common platform that supports 64 bit file/large file
		4565	interfaces but I<disables> them by default.
3427		4566
3428	Priorities are implemented by allocating some space for each	4567	That means that libev compiled in the default environment doesn't support
3429	priority. When doing priority-based operations, libev usually has to	4568	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
3430	linearly search all the priorities, but starting/stopping and activating
3431	watchers becomes O(1) with respect to priority handling.
3432		4569
3433	=item Sending an ev_async: O(1)	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.
3434		4573
3435	=item Processing ev_async_send: O(number_of_async_watchers)	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.
3436		4577
3437	=item Processing signals: O(max_signal_number)	4578	=head2 OS/X AND DARWIN BUGS
3438		4579
3439	Sending involves a system call I<iff> there were no other C<ev_async_send>	4580	The whole thing is a bug if you ask me - basically any system interface
3440	calls in the current loop iteration. Checking for async and signal events	4581	you touch is broken, whether it is locales, poll, kqueue or even the
3441	involves iterating over all running async watchers or all signal numbers.	4582	OpenGL drivers.
3442		4583
3443	=back	4584	=head3 C<kqueue> is buggy
3444		4585
		4586	The kqueue syscall is broken in all known versions - most versions support
		4587	only sockets, many support pipes.
3445		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
3446	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4648	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		4649
		4650	=head3 General issues
3447		4651
3448	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
3449	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
3450	model. Libev still offers limited functionality on this platform in	4654	model. Libev still offers limited functionality on this platform in
3451	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
3452	descriptors. This only applies when using Win32 natively, not when using	4656	descriptors. This only applies when using Win32 natively, not when using
3453	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.
3454		4660
3455	Lifting these limitations would basically require the full	4661	Lifting these limitations would basically require the full
3456	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,
3457	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
3458	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).
3459		4665
3460	There is no supported compilation method available on windows except	4666	There is no supported compilation method available on windows except
3461	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.
3462		4671
3463	Not a libev limitation but worth mentioning: windows apparently doesn't	4672	Not a libev limitation but worth mentioning: windows apparently doesn't
3464	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
3465	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,
3466	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
…		…
3471	the abysmal performance of winsockets, using a large number of sockets	4680	the abysmal performance of winsockets, using a large number of sockets
3472	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
3473	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
3474	different implementation for windows, as libev offers the POSIX readiness	4683	different implementation for windows, as libev offers the POSIX readiness
3475	notification model, which cannot be implemented efficiently on windows	4684	notification model, which cannot be implemented efficiently on windows
3476	(Microsoft monopoly games).	4685	(due to Microsoft monopoly games).
3477		4686
3478	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
3479	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
3480	of F<ev.h>:	4689	of F<ev.h>:
3481		4690
…		…
3488	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!):
3489		4698
3490	#include "evwrap.h"	4699	#include "evwrap.h"
3491	#include "ev.c"	4700	#include "ev.c"
3492		4701
3493	=over 4
3494
3495	=item The winsocket select function	4702	=head3 The winsocket C<select> function
3496		4703
3497	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
3498	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
3499	also extremely buggy). This makes select very inefficient, and also	4706	also extremely buggy). This makes select very inefficient, and also
3500	requires a mapping from file descriptors to socket handles (the Microsoft	4707	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3509	#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 */
3510		4717
3511	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
3512	complexity in the O(n²) range when using win32.	4719	complexity in the O(n²) range when using win32.
3513		4720
3514	=item Limited number of file descriptors	4721	=head3 Limited number of file descriptors
3515		4722
3516	Windows has numerous arbitrary (and low) limits on things.	4723	Windows has numerous arbitrary (and low) limits on things.
3517		4724
3518	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
3519	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
3520	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
3521	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
3522	previous thread in each. Great).	4729	previous thread in each. Sounds great!).
3523		4730
3524	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>
3525	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
3526	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
3527	select emulation on windows).	4734	other interpreters do their own select emulation on windows).
3528		4735
3529	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
3530	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>
3531	or something like this inside Microsoft). You can increase this by calling	4738	fetish or something like this inside Microsoft). You can increase this
3532	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4739	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3533	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
3534	libraries.
3535
3536	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
3537	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,
3538	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
3539	calling select (O(n²)) will likely make this unworkable.	4744	the cost of calling select (O(n²)) will likely make this unworkable.
3540		4745
3541	=back
3542
3543
3544	=head1 PORTABILITY REQUIREMENTS	4746	=head2 PORTABILITY REQUIREMENTS
3545		4747
3546	In addition to a working ISO-C implementation, libev relies on a few	4748	In addition to a working ISO-C implementation and of course the
3547	additional extensions:	4749	backend-specific APIs, libev relies on a few additional extensions:
3548		4750
3549	=over 4	4751	=over 4
3550		4752
3551	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4753	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3552	calling conventions regardless of C<ev_watcher_type *>.	4754	calling conventions regardless of C<ev_watcher_type *>.
…		…
3577	except the initial one, and run the default loop in the initial thread as	4779	except the initial one, and run the default loop in the initial thread as
3578	well.	4780	well.
3579		4781
3580	=item C<long> must be large enough for common memory allocation sizes	4782	=item C<long> must be large enough for common memory allocation sizes
3581		4783
3582	To improve portability and simplify using libev, libev uses C<long>	4784	To improve portability and simplify its API, libev uses C<long> internally
3583	internally instead of C<size_t> when allocating its data structures. On	4785	instead of C<size_t> when allocating its data structures. On non-POSIX
3584	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4786	systems (Microsoft...) this might be unexpectedly low, but is still at
3585	is still at least 31 bits everywhere, which is enough for hundreds of	4787	least 31 bits everywhere, which is enough for hundreds of millions of
3586	millions of watchers.	4788	watchers.
3587		4789
3588	=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
3589		4791
3590	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
3591	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
3592	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
3593	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.
3594		4798
3595	=back	4799	=back
3596		4800
3597	If you know of other additional requirements drop me a note.	4801	If you know of other additional requirements drop me a note.
3598		4802
3599		4803
3600	=head1 COMPILER WARNINGS	4804	=head1 ALGORITHMIC COMPLEXITIES
3601		4805
3602	Depending on your compiler and compiler settings, you might get no or a	4806	In this section the complexities of (many of) the algorithms used inside
3603	lot of warnings when compiling libev code. Some people are apparently	4807	libev will be documented. For complexity discussions about backends see
3604	scared by this.	4808	the documentation for C<ev_default_init>.
3605		4809
3606	However, these are unavoidable for many reasons. For one, each compiler	4810	All of the following are about amortised time: If an array needs to be
3607	has different warnings, and each user has different tastes regarding	4811	extended, libev needs to realloc and move the whole array, but this
3608	warning options. "Warn-free" code therefore cannot be a goal except when	4812	happens asymptotically rarer with higher number of elements, so O(1) might
3609	targeting a specific compiler and compiler-version.	4813	mean that libev does a lengthy realloc operation in rare cases, but on
		4814	average it is much faster and asymptotically approaches constant time.
3610		4815
3611	Another reason is that some compiler warnings require elaborate	4816	=over 4
3612	workarounds, or other changes to the code that make it less clear and less
3613	maintainable.
3614		4817
3615	And of course, some compiler warnings are just plain stupid, or simply	4818	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3616	wrong (because they don't actually warn about the condition their message
3617	seems to warn about).
3618		4819
3619	While libev is written to generate as few warnings as possible,	4820	This means that, when you have a watcher that triggers in one hour and
3620	"warn-free" code is not a goal, and it is recommended not to build libev	4821	there are 100 watchers that would trigger before that, then inserting will
3621	with any compiler warnings enabled unless you are prepared to cope with	4822	have to skip roughly seven (C<ld 100>) of these watchers.
3622	them (e.g. by ignoring them). Remember that warnings are just that:
3623	warnings, not errors, or proof of bugs.
3624		4823
		4824	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3625		4825
3626	=head1 VALGRIND	4826	That means that changing a timer costs less than removing/adding them,
		4827	as only the relative motion in the event queue has to be paid for.
3627		4828
3628	Valgrind has a special section here because it is a popular tool that is	4829	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3629	highly useful, but valgrind reports are very hard to interpret.
3630		4830
3631	If you think you found a bug (memory leak, uninitialised data access etc.)	4831	These just add the watcher into an array or at the head of a list.
3632	in libev, then check twice: If valgrind reports something like:
3633		4832
3634	==2274== definitely lost: 0 bytes in 0 blocks.	4833	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3635	==2274== possibly lost: 0 bytes in 0 blocks.
3636	==2274== still reachable: 256 bytes in 1 blocks.
3637		4834
3638	Then there is no memory leak. Similarly, under some circumstances,	4835	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3639	valgrind might report kernel bugs as if it were a bug in libev, or it
3640	might be confused (it is a very good tool, but only a tool).
3641		4836
3642	If you are unsure about something, feel free to contact the mailing list	4837	These watchers are stored in lists, so they need to be walked to find the
3643	with the full valgrind report and an explanation on why you think this is	4838	correct watcher to remove. The lists are usually short (you don't usually
3644	a bug in libev. However, don't be annoyed when you get a brisk "this is	4839	have many watchers waiting for the same fd or signal: one is typical, two
3645	no bug" answer and take the chance of learning how to interpret valgrind	4840	is rare).
3646	properly.
3647		4841
3648	If you need, for some reason, empty reports from valgrind for your project	4842	=item Finding the next timer in each loop iteration: O(1)
3649	I suggest using suppression lists.
3650		4843
		4844	By virtue of using a binary or 4-heap, the next timer is always found at a
		4845	fixed position in the storage array.
		4846
		4847	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4848
		4849	A change means an I/O watcher gets started or stopped, which requires
		4850	libev to recalculate its status (and possibly tell the kernel, depending
		4851	on backend and whether C<ev_io_set> was used).
		4852
		4853	=item Activating one watcher (putting it into the pending state): O(1)
		4854
		4855	=item Priority handling: O(number_of_priorities)
		4856
		4857	Priorities are implemented by allocating some space for each
		4858	priority. When doing priority-based operations, libev usually has to
		4859	linearly search all the priorities, but starting/stopping and activating
		4860	watchers becomes O(1) with respect to priority handling.
		4861
		4862	=item Sending an ev_async: O(1)
		4863
		4864	=item Processing ev_async_send: O(number_of_async_watchers)
		4865
		4866	=item Processing signals: O(max_signal_number)
		4867
		4868	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4869	calls in the current loop iteration. Checking for async and signal events
		4870	involves iterating over all running async watchers or all signal numbers.
		4871
		4872	=back
		4873
		4874
		4875	=head1 PORTING FROM LIBEV 3.X TO 4.X
		4876
		4877	The major version 4 introduced some minor incompatible changes to the API.
		4878
		4879	At the moment, the C<ev.h> header file tries to implement superficial
		4880	compatibility, so most programs should still compile. Those might be
		4881	removed in later versions of libev, so better update early than late.
		4882
		4883	=over 4
		4884
		4885	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		4886
		4887	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		4888
		4889	ev_loop_destroy (EV_DEFAULT_UC);
		4890	ev_loop_fork (EV_DEFAULT);
		4891
		4892	=item function/symbol renames
		4893
		4894	A number of functions and symbols have been renamed:
		4895
		4896	ev_loop => ev_run
		4897	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		4898	EVLOOP_ONESHOT => EVRUN_ONCE
		4899
		4900	ev_unloop => ev_break
		4901	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		4902	EVUNLOOP_ONE => EVBREAK_ONE
		4903	EVUNLOOP_ALL => EVBREAK_ALL
		4904
		4905	EV_TIMEOUT => EV_TIMER
		4906
		4907	ev_loop_count => ev_iteration
		4908	ev_loop_depth => ev_depth
		4909	ev_loop_verify => ev_verify
		4910
		4911	Most functions working on C<struct ev_loop> objects don't have an
		4912	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		4913	associated constants have been renamed to not collide with the C<struct
		4914	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		4915	as all other watcher types. Note that C<ev_loop_fork> is still called
		4916	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		4917	typedef.
		4918
		4919	=item C<EV_COMPAT3> backwards compatibility mechanism
		4920
		4921	The backward compatibility mechanism can be controlled by
		4922	C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING>
		4923	section.
		4924
		4925	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		4926
		4927	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		4928	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		4929	and work, but the library code will of course be larger.
		4930
		4931	=back
		4932
		4933
		4934	=head1 GLOSSARY
		4935
		4936	=over 4
		4937
		4938	=item active
		4939
		4940	A watcher is active as long as it has been started and not yet stopped.
		4941	See L<WATCHER STATES> for details.
		4942
		4943	=item application
		4944
		4945	In this document, an application is whatever is using libev.
		4946
		4947	=item backend
		4948
		4949	The part of the code dealing with the operating system interfaces.
		4950
		4951	=item callback
		4952
		4953	The address of a function that is called when some event has been
		4954	detected. Callbacks are being passed the event loop, the watcher that
		4955	received the event, and the actual event bitset.
		4956
		4957	=item callback/watcher invocation
		4958
		4959	The act of calling the callback associated with a watcher.
		4960
		4961	=item event
		4962
		4963	A change of state of some external event, such as data now being available
		4964	for reading on a file descriptor, time having passed or simply not having
		4965	any other events happening anymore.
		4966
		4967	In libev, events are represented as single bits (such as C<EV_READ> or
		4968	C<EV_TIMER>).
		4969
		4970	=item event library
		4971
		4972	A software package implementing an event model and loop.
		4973
		4974	=item event loop
		4975
		4976	An entity that handles and processes external events and converts them
		4977	into callback invocations.
		4978
		4979	=item event model
		4980
		4981	The model used to describe how an event loop handles and processes
		4982	watchers and events.
		4983
		4984	=item pending
		4985
		4986	A watcher is pending as soon as the corresponding event has been
		4987	detected. See L<WATCHER STATES> for details.
		4988
		4989	=item real time
		4990
		4991	The physical time that is observed. It is apparently strictly monotonic :)
		4992
		4993	=item wall-clock time
		4994
		4995	The time and date as shown on clocks. Unlike real time, it can actually
		4996	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4997	clock.
		4998
		4999	=item watcher
		5000
		5001	A data structure that describes interest in certain events. Watchers need
		5002	to be started (attached to an event loop) before they can receive events.
		5003
		5004	=back
3651		5005
3652	=head1 AUTHOR	5006	=head1 AUTHOR
3653		5007
3654	Marc Lehmann <libev@schmorp.de>.	5008	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3655		5009

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