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		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
9	=head2 EXAMPLE PROGRAM	11	=head2 EXAMPLE PROGRAM
10		12
11	// a single header file is required	13	// a single header file is required
12	#include <ev.h>	14	#include <ev.h>
13		15
		16	#include <stdio.h> // for puts
		17
14	// every watcher type has its own typedef'd struct	18	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	19	// with the name ev_TYPE
16	ev_io stdin_watcher;	20	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	21	ev_timer timeout_watcher;
18		22
19	// all watcher callbacks have a similar signature	23	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	24	// this callback is called when data is readable on stdin
…		…
24	puts ("stdin ready");	28	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	30	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
28		32
29	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
31	}	35	}
32		36
33	// another callback, this time for a time-out	37	// another callback, this time for a time-out
34	static void	38	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	40	{
37	puts ("timeout");	41	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
40	}	44	}
41		45
42	int	46	int
43	main (void)	47	main (void)
44	{	48	{
45	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
47		51
48	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
57		61
58	// now wait for events to arrive	62	// now wait for events to arrive
59	ev_loop (loop, 0);	63	ev_run (loop, 0);
60		64
61	// unloop was called, so exit	65	// break was called, so exit
62	return 0;	66	return 0;
63	}	67	}
64		68
65	=head1 DESCRIPTION	69	=head1 ABOUT THIS DOCUMENT
		70
		71	This document documents the libev software package.
66		72
67	The newest version of this document is also available as an html-formatted	73	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	74	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>.	75	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		76
		77	While this document tries to be as complete as possible in documenting
		78	libev, its usage and the rationale behind its design, it is not a tutorial
		79	on event-based programming, nor will it introduce event-based programming
		80	with libev.
		81
		82	Familiarity with event based programming techniques in general is assumed
		83	throughout this document.
		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
		92
		93	=head1 ABOUT LIBEV
70		94
71	Libev is an event loop: you register interest in certain events (such as a	95	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	96	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	97	these event sources and provide your program with events.
74		98
…		…
81	details of the event, and then hand it over to libev by I<starting> the	105	details of the event, and then hand it over to libev by I<starting> the
82	watcher.	106	watcher.
83		107
84	=head2 FEATURES	108	=head2 FEATURES
85		109
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	110	Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll>
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	112	mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify>
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	114	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	115	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	116	(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	117	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	118	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	119	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		120	limited support for fork events (C<ev_fork>).
96		121
97	It also is quite fast (see this	122	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	123	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	124	for example).
100		125
…		…
103	Libev is very configurable. In this manual the default (and most common)	128	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	131	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	132	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<ev_loop *>) will not have	133	name C<loop> (which is always of type C<struct ev_loop *>) will not have
109	this argument.	134	this argument.
110		135
111	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
112		137
113	Libev represents time as a single floating point number, representing the	138	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	139	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	140	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	141	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	142	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	143	any calculations on it, you should treat it as some floating point value.
		144
119	component C<stamp> might indicate, it is also used for time differences	145	Unlike the name component C<stamp> might indicate, it is also used for
120	throughout libev.	146	time differences (e.g. delays) throughout libev.
121		147
122	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
123		149
124	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	151	and internal errors (bugs).
…		…
149		175
150	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
151		177
152	Returns the current time as libev would use it. Please note that the	178	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	179	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	180	you actually want to know. Also interesting is the combination of
		181	C<ev_now_update> and C<ev_now>.
155		182
156	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
157		184
158	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
159	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
160	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
161		194
162	=item int ev_version_major ()	195	=item int ev_version_major ()
163		196
164	=item int ev_version_minor ()	197	=item int ev_version_minor ()
165		198
…		…
176	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	211	not a problem.
179		212
180	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
182		216
183	assert (("libev version mismatch",	217	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
186		220
…		…
197	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
199		233
200	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
201		235
202	Return the set of all backends compiled into this binary of libev and also	236	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	237	also recommended for this platform, meaning it will work for most file
		238	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	239	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	240	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	241	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.	242	probe for if you specify no backends explicitly.
208		243
209	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
210		245
211	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	247	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	248	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
216		251
217	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
218		253
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
220		255
221	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
230		265
231	You could override this function in high-availability programs to, say,	266	You could override this function in high-availability programs to, say,
232	free some memory if it cannot allocate memory, to use a special allocator,	267	free some memory if it cannot allocate memory, to use a special allocator,
233	or even to sleep a while and retry until some memory is available.	268	or even to sleep a while and retry until some memory is available.
234		269
		270	Example: The following is the C<realloc> function that libev itself uses
		271	which should work with C<realloc> and C<free> functions of all kinds and
		272	is probably a good basis for your own implementation.
		273
		274	static void *
		275	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		276	{
		277	if (size)
		278	return realloc (ptr, size);
		279
		280	free (ptr);
		281	return 0;
		282	}
		283
235	Example: Replace the libev allocator with one that waits a bit and then	284	Example: Replace the libev allocator with one that waits a bit and then
236	retries (example requires a standards-compliant C<realloc>).	285	retries.
237		286
238	static void *	287	static void *
239	persistent_realloc (void *ptr, size_t size)	288	persistent_realloc (void *ptr, size_t size)
240	{	289	{
		290	if (!size)
		291	{
		292	free (ptr);
		293	return 0;
		294	}
		295
241	for (;;)	296	for (;;)
242	{	297	{
243	void *newptr = realloc (ptr, size);	298	void *newptr = realloc (ptr, size);
244		299
245	if (newptr)	300	if (newptr)
…		…
250	}	305	}
251		306
252	...	307	...
253	ev_set_allocator (persistent_realloc);	308	ev_set_allocator (persistent_realloc);
254		309
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	310	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
256		311
257	Set the callback function to call on a retryable system call error (such	312	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	313	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	314	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	315	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	327	}
273		328
274	...	329	...
275	ev_set_syserr_cb (fatal_error);	330	ev_set_syserr_cb (fatal_error);
276		331
		332	=item ev_feed_signal (int signum)
		333
		334	This function can be used to "simulate" a signal receive. It is completely
		335	safe to call this function at any time, from any context, including signal
		336	handlers or random threads.
		337
		338	Its main use is to customise signal handling in your process, especially
		339	in the presence of threads. For example, you could block signals
		340	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		341	creating any loops), and in one thread, use C<sigwait> or any other
		342	mechanism to wait for signals, then "deliver" them to libev by calling
		343	C<ev_feed_signal>.
		344
277	=back	345	=back
278		346
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	347	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		348
281	An event loop is described by a C<ev_loop *>. The library knows two	349	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	350	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	events, and dynamically created loops which do not.	351	libev 3 had an C<ev_loop> function colliding with the struct name).
		352
		353	The library knows two types of such loops, the I<default> loop, which
		354	supports child process events, and dynamically created event loops which
		355	do not.
284		356
285	=over 4	357	=over 4
286		358
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	359	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		360
289	This will initialise the default event loop if it hasn't been initialised	361	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	362	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	363	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).	364	C<ev_loop_new>.
		365
		366	If the default loop is already initialised then this function simply
		367	returns it (and ignores the flags. If that is troubling you, check
		368	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		369	flags, which should almost always be C<0>, unless the caller is also the
		370	one calling C<ev_run> or otherwise qualifies as "the main program".
293		371
294	If you don't know what event loop to use, use the one returned from this	372	If you don't know what event loop to use, use the one returned from this
295	function.	373	function (or via the C<EV_DEFAULT> macro).
296		374
297	Note that this function is I<not> thread-safe, so if you want to use it	375	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,	376	from multiple threads, you have to employ some kind of mutex (note also
299	as loops cannot bes hared easily between threads anyway).	377	that this case is unlikely, as loops cannot be shared easily between
		378	threads anyway).
300		379
301	The default loop is the only loop that can handle C<ev_signal> and	380	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	381	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	382	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	383	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	384	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
306	C<ev_default_init>.	385
		386	Example: This is the most typical usage.
		387
		388	if (!ev_default_loop (0))
		389	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		390
		391	Example: Restrict libev to the select and poll backends, and do not allow
		392	environment settings to be taken into account:
		393
		394	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		395
		396	=item struct ev_loop *ev_loop_new (unsigned int flags)
		397
		398	This will create and initialise a new event loop object. If the loop
		399	could not be initialised, returns false.
		400
		401	This function is thread-safe, and one common way to use libev with
		402	threads is indeed to create one loop per thread, and using the default
		403	loop in the "main" or "initial" thread.
307		404
308	The flags argument can be used to specify special behaviour or specific	405	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>).	406	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
310		407
311	The following flags are supported:	408	The following flags are supported:
…		…
321		418
322	If this flag bit is or'ed into the flag value (or the program runs setuid	419	If this flag bit is or'ed into the flag value (or the program runs setuid
323	or setgid) then libev will I<not> look at the environment variable	420	or setgid) then libev will I<not> look at the environment variable
324	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	421	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
325	override the flags completely if it is found in the environment. This is	422	override the flags completely if it is found in the environment. This is
326	useful to try out specific backends to test their performance, or to work	423	useful to try out specific backends to test their performance, to work
327	around bugs.	424	around bugs, or to make libev threadsafe (accessing environment variables
		425	cannot be done in a threadsafe way, but usually it works if no other
		426	thread modifies them).
328		427
329	=item C<EVFLAG_FORKCHECK>	428	=item C<EVFLAG_FORKCHECK>
330		429
331	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	430	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	431	make libev check for a fork in each iteration by enabling this flag.
333	enabling this flag.
334		432
335	This works by calling C<getpid ()> on every iteration of the loop,	433	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	434	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	435	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	436	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
339	without a system call and thus I<very> fast, but my GNU/Linux system also has	437	sequence without a system call and thus I<very> fast, but my GNU/Linux
340	C<pthread_atfork> which is even faster).	438	system also has C<pthread_atfork> which is even faster). (Update: glibc
		439	versions 2.25 apparently removed the C<getpid> optimisation again).
341		440
342	The big advantage of this flag is that you can forget about fork (and	441	The big advantage of this flag is that you can forget about fork (and
343	forget about forgetting to tell libev about forking) when you use this	442	forget about forgetting to tell libev about forking, although you still
344	flag.	443	have to ignore C<SIGPIPE>) when you use this flag.
345		444
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	445	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	446	environment variable.
		447
		448	=item C<EVFLAG_NOINOTIFY>
		449
		450	When this flag is specified, then libev will not attempt to use the
		451	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		452	testing, this flag can be useful to conserve inotify file descriptors, as
		453	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		454
		455	=item C<EVFLAG_SIGNALFD>
		456
		457	When this flag is specified, then libev will attempt to use the
		458	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		459	delivers signals synchronously, which makes it both faster and might make
		460	it possible to get the queued signal data. It can also simplify signal
		461	handling with threads, as long as you properly block signals in your
		462	threads that are not interested in handling them.
		463
		464	Signalfd will not be used by default as this changes your signal mask, and
		465	there are a lot of shoddy libraries and programs (glib's threadpool for
		466	example) that can't properly initialise their signal masks.
		467
		468	=item C<EVFLAG_NOSIGMASK>
		469
		470	When this flag is specified, then libev will avoid to modify the signal
		471	mask. Specifically, this means you have to make sure signals are unblocked
		472	when you want to receive them.
		473
		474	This behaviour is useful when you want to do your own signal handling, or
		475	want to handle signals only in specific threads and want to avoid libev
		476	unblocking the signals.
		477
		478	It's also required by POSIX in a threaded program, as libev calls
		479	C<sigprocmask>, whose behaviour is officially unspecified.
		480
		481	This flag's behaviour will become the default in future versions of libev.
348		482
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	483	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		484
351	This is your standard select(2) backend. Not I<completely> standard, as	485	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,	486	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	511	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	512	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		513
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	514	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		515
		516	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		517	kernels).
		518
382	For few fds, this backend is a bit little slower than poll and select,	519	For few fds, this backend is a bit little slower than poll and select, but
383	but it scales phenomenally better. While poll and select usually scale	520	it scales phenomenally better. While poll and select usually scale like
384	like O(total_fds) where n is the total number of fds (or the highest fd),	521	O(total_fds) where total_fds is the total number of fds (or the highest
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	522	fd), epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	523
387	cases and requiring a system call per fd change, no fork support and bad	524	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	525	of the more advanced event mechanisms: mere annoyances include silently
		526	dropping file descriptors, requiring a system call per change per file
		527	descriptor (and unnecessary guessing of parameters), problems with dup,
		528	returning before the timeout value, resulting in additional iterations
		529	(and only giving 5ms accuracy while select on the same platform gives
		530	0.1ms) and so on. The biggest issue is fork races, however - if a program
		531	forks then I<both> parent and child process have to recreate the epoll
		532	set, which can take considerable time (one syscall per file descriptor)
		533	and is of course hard to detect.
		534
		535	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
		536	but of course I<doesn't>, and epoll just loves to report events for
		537	totally I<different> file descriptors (even already closed ones, so
		538	one cannot even remove them from the set) than registered in the set
		539	(especially on SMP systems). Libev tries to counter these spurious
		540	notifications by employing an additional generation counter and comparing
		541	that against the events to filter out spurious ones, recreating the set
		542	when required. Epoll also erroneously rounds down timeouts, but gives you
		543	no way to know when and by how much, so sometimes you have to busy-wait
		544	because epoll returns immediately despite a nonzero timeout. And last
		545	not least, it also refuses to work with some file descriptors which work
		546	perfectly fine with C<select> (files, many character devices...).
		547
		548	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		549	cobbled together in a hurry, no thought to design or interaction with
		550	others. Oh, the pain, will it ever stop...
389		551
390	While stopping, setting and starting an I/O watcher in the same iteration	552	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	553	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	554	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	555	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	556	file descriptors might not work very well if you register events for both
395		557	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		558
400	Best performance from this backend is achieved by not unregistering all	559	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	560	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	561	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	562	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	563	extra overhead. A fork can both result in spurious notifications as well
		564	as in libev having to destroy and recreate the epoll object, which can
		565	take considerable time and thus should be avoided.
		566
		567	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		568	faster than epoll for maybe up to a hundred file descriptors, depending on
		569	the usage. So sad.
405		570
406	While nominally embeddable in other event loops, this feature is broken in	571	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	572	a lot of kernel revisions, but probably(!) works in current versions.
408		573
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	574	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	575	C<EVBACKEND_POLL>.
411		576
		577	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		578
		579	Use the linux-specific linux aio (I<not> C<< aio(7) >> but C<<
		580	io_submit(2) >>) event interface available in post-4.18 kernels.
		581
		582	If this backend works for you (as of this writing, it was very
		583	experimental), it is the best event interface available on linux and might
		584	be well worth enabling it - if it isn't available in your kernel this will
		585	be detected and this backend will be skipped.
		586
		587	This backend can batch oneshot requests and supports a user-space ring
		588	buffer to receive events. It also doesn't suffer from most of the design
		589	problems of epoll (such as not being able to remove event sources from
		590	the epoll set), and generally sounds too good to be true. Because, this
		591	being the linux kernel, of course it suffers from a whole new set of
		592	limitations.
		593
		594	For one, it is not easily embeddable (but probably could be done using
		595	an event fd at some extra overhead). It also is subject to a system wide
		596	limit that can be configured in F</proc/sys/fs/aio-max-nr> - each loop
		597	currently requires C<61> of this number. If no aio requests are left, this
		598	backend will be skipped during initialisation.
		599
		600	Most problematic in practise, however, is that not all file descriptors
		601	work with it. For example, in linux 5.1, tcp sockets, pipes, event fds,
		602	files, F</dev/null> and a few others are supported, but ttys do not work
		603	(probably because of a bug), so this is not (yet?) a generic event polling
		604	interface.
		605
		606	To work around this latter problem, the current version of libev uses
		607	epoll as a fallback for file deescriptor types that do not work. Epoll
		608	is used in, kind of, slow mode that hopefully avoids most of its design
		609	problems.
		610
		611	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		612	C<EVBACKEND_POLL>.
		613
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	614	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		615
414	Kqueue deserves special mention, as at the time of this writing, it was	616	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	617	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	618	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	619	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	620	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.	621	without API changes to existing programs. For this reason it's not being
		622	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		623	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		624	system like NetBSD.
420		625
421	You still can embed kqueue into a normal poll or select backend and use it	626	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	627	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.	628	the target platform). See C<ev_embed> watchers for more info.
424		629
425	It scales in the same way as the epoll backend, but the interface to the	630	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	631	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	632	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	633	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	634	two event changes per incident. Support for C<fork ()> is very bad (you
		635	might have to leak fd's on fork, but it's more sane than epoll) and it
430	drops fds silently in similarly hard-to-detect cases.	636	drops fds silently in similarly hard-to-detect cases.
431		637
432	This backend usually performs well under most conditions.	638	This backend usually performs well under most conditions.
433		639
434	While nominally embeddable in other event loops, this doesn't work	640	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	641	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	642	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	643	(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,	644	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	645	also broken on OS X)) and, did I mention it, using it only for sockets.
440		646
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	647	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	648	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	649	C<NOTE_EOF>.
444		650
…		…
452	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	658	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
453		659
454	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	660	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
455	it's really slow, but it still scales very well (O(active_fds)).	661	it's really slow, but it still scales very well (O(active_fds)).
456		662
457	Please note that Solaris event ports can deliver a lot of spurious
458	notifications, so you need to use non-blocking I/O or other means to avoid
459	blocking when no data (or space) is available.
460
461	While this backend scales well, it requires one system call per active	663	While this backend scales well, it requires one system call per active
462	file descriptor per loop iteration. For small and medium numbers of file	664	file descriptor per loop iteration. For small and medium numbers of file
463	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	665	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
464	might perform better.	666	might perform better.
465		667
466	On the positive side, with the exception of the spurious readiness	668	On the positive side, this backend actually performed fully to
467	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	669	specification in all tests and is fully embeddable, which is a rare feat
469	OS-specific backends.	670	among the OS-specific backends (I vastly prefer correctness over speed
		671	hacks).
		672
		673	On the negative side, the interface is I<bizarre> - so bizarre that
		674	even sun itself gets it wrong in their code examples: The event polling
		675	function sometimes returns events to the caller even though an error
		676	occurred, but with no indication whether it has done so or not (yes, it's
		677	even documented that way) - deadly for edge-triggered interfaces where you
		678	absolutely have to know whether an event occurred or not because you have
		679	to re-arm the watcher.
		680
		681	Fortunately libev seems to be able to work around these idiocies.
470		682
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	683	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	684	C<EVBACKEND_POLL>.
473		685
474	=item C<EVBACKEND_ALL>	686	=item C<EVBACKEND_ALL>
475		687
476	Try all backends (even potentially broken ones that wouldn't be tried	688	Try all backends (even potentially broken ones that wouldn't be tried
477	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	689	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
478	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	690	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
479		691
480	It is definitely not recommended to use this flag.	692	It is definitely not recommended to use this flag, use whatever
		693	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		694	at all.
		695
		696	=item C<EVBACKEND_MASK>
		697
		698	Not a backend at all, but a mask to select all backend bits from a
		699	C<flags> value, in case you want to mask out any backends from a flags
		700	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
481		701
482	=back	702	=back
483		703
484	If one or more of these are or'ed into the flags value, then only these	704	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	705	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.	706	here). If none are specified, all backends in C<ev_recommended_backends
487		707	()> 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		708
516	Example: Try to create a event loop that uses epoll and nothing else.	709	Example: Try to create a event loop that uses epoll and nothing else.
517		710
518	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	711	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
519	if (!epoller)	712	if (!epoller)
520	fatal ("no epoll found here, maybe it hides under your chair");	713	fatal ("no epoll found here, maybe it hides under your chair");
521		714
		715	Example: Use whatever libev has to offer, but make sure that kqueue is
		716	used if available.
		717
		718	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		719
		720	Example: Similarly, on linux, you mgiht want to take advantage of the
		721	linux aio backend if possible, but fall back to something else if that
		722	isn't available.
		723
		724	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		725
522	=item ev_default_destroy ()	726	=item ev_loop_destroy (loop)
523		727
524	Destroys the default loop again (frees all memory and kernel state	728	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	729	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	730	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>	731	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	732	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	733	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	734	for example).
531		735
532	Note that certain global state, such as signal state, will not be freed by	736	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	737	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	738	as signal and child watchers) would need to be stopped manually.
535		739
536	In general it is not advisable to call this function except in the	740	This function is normally used on loop objects allocated by
537	rare occasion where you really need to free e.g. the signal handling	741	C<ev_loop_new>, but it can also be used on the default loop returned by
		742	C<ev_default_loop>, in which case it is not thread-safe.
		743
		744	Note that it is not advisable to call this function on the default loop
		745	except in the rare occasion where you really need to free its resources.
538	pipe fds. If you need dynamically allocated loops it is better to use	746	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>).	747	and C<ev_loop_destroy>.
540		748
541	=item ev_loop_destroy (loop)	749	=item ev_loop_fork (loop)
542		750
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	751	This function sets a flag that causes subsequent C<ev_run> iterations
549	to reinitialise the kernel state for backends that have one. Despite the	752	to reinitialise the kernel state for backends that have one. Despite
550	name, you can call it anytime, but it makes most sense after forking, in	753	the name, you can call it anytime you are allowed to start or stop
551	the child process (or both child and parent, but that again makes little	754	watchers (except inside an C<ev_prepare> callback), but it makes most
552	sense). You I<must> call it in the child before using any of the libev	755	sense after forking, in the child process. You I<must> call it (or use
553	functions, and it will only take effect at the next C<ev_loop> iteration.	756	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		757
		758	In addition, if you want to reuse a loop (via this function or
		759	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		760
		761	Again, you I<have> to call it on I<any> loop that you want to re-use after
		762	a fork, I<even if you do not plan to use the loop in the parent>. This is
		763	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		764	during fork.
554		765
555	On the other hand, you only need to call this function in the child	766	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	767	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.	768	you just fork+exec or create a new loop in the child, you don't have to
		769	call it at all (in fact, C<epoll> is so badly broken that it makes a
		770	difference, but libev will usually detect this case on its own and do a
		771	costly reset of the backend).
558		772
559	The function itself is quite fast and it's usually not a problem to call	773	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	774	it just in case after a fork.
561	quite nicely into a call to C<pthread_atfork>:
562		775
		776	Example: Automate calling C<ev_loop_fork> on the default loop when
		777	using pthreads.
		778
		779	static void
		780	post_fork_child (void)
		781	{
		782	ev_loop_fork (EV_DEFAULT);
		783	}
		784
		785	...
563	pthread_atfork (0, 0, ev_default_fork);	786	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		787
572	=item int ev_is_default_loop (loop)	788	=item int ev_is_default_loop (loop)
573		789
574	Returns true when the given loop is, in fact, the default loop, and false	790	Returns true when the given loop is, in fact, the default loop, and false
575	otherwise.	791	otherwise.
576		792
577	=item unsigned int ev_loop_count (loop)	793	=item unsigned int ev_iteration (loop)
578		794
579	Returns the count of loop iterations for the loop, which is identical to	795	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	796	to the number of times libev did poll for new events. It starts at C<0>
581	happily wraps around with enough iterations.	797	and happily wraps around with enough iterations.
582		798
583	This value can sometimes be useful as a generation counter of sorts (it	799	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	800	"ticks" the number of loop iterations), as it roughly corresponds with
585	C<ev_prepare> and C<ev_check> calls.	801	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		802	prepare and check phases.
		803
		804	=item unsigned int ev_depth (loop)
		805
		806	Returns the number of times C<ev_run> was entered minus the number of
		807	times C<ev_run> was exited normally, in other words, the recursion depth.
		808
		809	Outside C<ev_run>, this number is zero. In a callback, this number is
		810	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		811	in which case it is higher.
		812
		813	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		814	throwing an exception etc.), doesn't count as "exit" - consider this
		815	as a hint to avoid such ungentleman-like behaviour unless it's really
		816	convenient, in which case it is fully supported.
586		817
587	=item unsigned int ev_backend (loop)	818	=item unsigned int ev_backend (loop)
588		819
589	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	820	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
590	use.	821	use.
…		…
599		830
600	=item ev_now_update (loop)	831	=item ev_now_update (loop)
601		832
602	Establishes the current time by querying the kernel, updating the time	833	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	834	returned by C<ev_now ()> in the progress. This is a costly operation and
604	is usually done automatically within C<ev_loop ()>.	835	is usually done automatically within C<ev_run ()>.
605		836
606	This function is rarely useful, but when some event callback runs for a	837	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	838	very long time without entering the event loop, updating libev's idea of
608	the current time is a good idea.	839	the current time is a good idea.
609		840
610	See also "The special problem of time updates" in the C<ev_timer> section.	841	See also L</The special problem of time updates> in the C<ev_timer> section.
611		842
		843	=item ev_suspend (loop)
		844
		845	=item ev_resume (loop)
		846
		847	These two functions suspend and resume an event loop, for use when the
		848	loop is not used for a while and timeouts should not be processed.
		849
		850	A typical use case would be an interactive program such as a game: When
		851	the user presses C<^Z> to suspend the game and resumes it an hour later it
		852	would be best to handle timeouts as if no time had actually passed while
		853	the program was suspended. This can be achieved by calling C<ev_suspend>
		854	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		855	C<ev_resume> directly afterwards to resume timer processing.
		856
		857	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		858	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		859	will be rescheduled (that is, they will lose any events that would have
		860	occurred while suspended).
		861
		862	After calling C<ev_suspend> you B<must not> call I<any> function on the
		863	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		864	without a previous call to C<ev_suspend>.
		865
		866	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		867	event loop time (see C<ev_now_update>).
		868
612	=item ev_loop (loop, int flags)	869	=item bool ev_run (loop, int flags)
613		870
614	Finally, this is it, the event handler. This function usually is called	871	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	872	after you have initialised all your watchers and you want to start
616	events.	873	handling events. It will ask the operating system for any new events, call
		874	the watcher callbacks, and then repeat the whole process indefinitely: This
		875	is why event loops are called I<loops>.
617		876
618	If the flags argument is specified as C<0>, it will not return until	877	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.	878	until either no event watchers are active anymore or C<ev_break> was
		879	called.
620		880
		881	The return value is false if there are no more active watchers (which
		882	usually means "all jobs done" or "deadlock"), and true in all other cases
		883	(which usually means " you should call C<ev_run> again").
		884
621	Please note that an explicit C<ev_unloop> is usually better than	885	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	886	relying on all watchers to be stopped when deciding when a program has
623	finished (especially in interactive programs), but having a program	887	finished (especially in interactive programs), but having a program
624	that automatically loops as long as it has to and no longer by virtue	888	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	889	of relying on its watchers stopping correctly, that is truly a thing of
626	beauty.	890	beauty.
627		891
		892	This function is I<mostly> exception-safe - you can break out of a
		893	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		894	exception and so on. This does not decrement the C<ev_depth> value, nor
		895	will it clear any outstanding C<EVBREAK_ONE> breaks.
		896
628	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	897	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	898	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	899	block your process in case there are no events and will return after one
631	the loop.	900	iteration of the loop. This is sometimes useful to poll and handle new
		901	events while doing lengthy calculations, to keep the program responsive.
632		902
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	903	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	904	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	905	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	906	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	907	user-registered callback will be called), and will return after one
638	iteration of the loop.	908	iteration of the loop.
639		909
640	This is useful if you are waiting for some external event in conjunction	910	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	911	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	912	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.	913	usually a better approach for this kind of thing.
644		914
645	Here are the gory details of what C<ev_loop> does:	915	Here are the gory details of what C<ev_run> does (this is for your
		916	understanding, not a guarantee that things will work exactly like this in
		917	future versions):
646		918
		919	- Increment loop depth.
		920	- Reset the ev_break status.
647	- Before the first iteration, call any pending watchers.	921	- Before the first iteration, call any pending watchers.
		922	LOOP:
648	* If EVFLAG_FORKCHECK was used, check for a fork.	923	- If EVFLAG_FORKCHECK was used, check for a fork.
649	- If a fork was detected (by any means), queue and call all fork watchers.	924	- If a fork was detected (by any means), queue and call all fork watchers.
650	- Queue and call all prepare watchers.	925	- Queue and call all prepare watchers.
		926	- If ev_break was called, goto FINISH.
651	- If we have been forked, detach and recreate the kernel state	927	- If we have been forked, detach and recreate the kernel state
652	as to not disturb the other process.	928	as to not disturb the other process.
653	- Update the kernel state with all outstanding changes.	929	- Update the kernel state with all outstanding changes.
654	- Update the "event loop time" (ev_now ()).	930	- Update the "event loop time" (ev_now ()).
655	- Calculate for how long to sleep or block, if at all	931	- Calculate for how long to sleep or block, if at all
656	(active idle watchers, EVLOOP_NONBLOCK or not having	932	(active idle watchers, EVRUN_NOWAIT or not having
657	any active watchers at all will result in not sleeping).	933	any active watchers at all will result in not sleeping).
658	- Sleep if the I/O and timer collect interval say so.	934	- Sleep if the I/O and timer collect interval say so.
		935	- Increment loop iteration counter.
659	- Block the process, waiting for any events.	936	- Block the process, waiting for any events.
660	- Queue all outstanding I/O (fd) events.	937	- Queue all outstanding I/O (fd) events.
661	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	938	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
662	- Queue all expired timers.	939	- Queue all expired timers.
663	- Queue all expired periodics.	940	- Queue all expired periodics.
664	- Unless any events are pending now, queue all idle watchers.	941	- Queue all idle watchers with priority higher than that of pending events.
665	- Queue all check watchers.	942	- Queue all check watchers.
666	- Call all queued watchers in reverse order (i.e. check watchers first).	943	- 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	944	Signals and child watchers are implemented as I/O watchers, and will
668	be handled here by queueing them when their watcher gets executed.	945	be handled here by queueing them when their watcher gets executed.
669	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	946	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
670	were used, or there are no active watchers, return, otherwise	947	were used, or there are no active watchers, goto FINISH, otherwise
671	continue with step *.	948	continue with step LOOP.
		949	FINISH:
		950	- Reset the ev_break status iff it was EVBREAK_ONE.
		951	- Decrement the loop depth.
		952	- Return.
672		953
673	Example: Queue some jobs and then loop until no events are outstanding	954	Example: Queue some jobs and then loop until no events are outstanding
674	anymore.	955	anymore.
675		956
676	... queue jobs here, make sure they register event watchers as long	957	... 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..)	958	... as they still have work to do (even an idle watcher will do..)
678	ev_loop (my_loop, 0);	959	ev_run (my_loop, 0);
679	... jobs done or somebody called unloop. yeah!	960	... jobs done or somebody called break. yeah!
680		961
681	=item ev_unloop (loop, how)	962	=item ev_break (loop, how)
682		963
683	Can be used to make a call to C<ev_loop> return early (but only after it	964	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	965	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	966	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.	967	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
687		968
688	This "unloop state" will be cleared when entering C<ev_loop> again.	969	This "break state" will be cleared on the next call to C<ev_run>.
689		970
690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	971	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		972	which case it will have no effect.
691		973
692	=item ev_ref (loop)	974	=item ev_ref (loop)
693		975
694	=item ev_unref (loop)	976	=item ev_unref (loop)
695		977
696	Ref/unref can be used to add or remove a reference count on the event	978	Ref/unref can be used to add or remove a reference count on the event
697	loop: Every watcher keeps one reference, and as long as the reference	979	loop: Every watcher keeps one reference, and as long as the reference
698	count is nonzero, C<ev_loop> will not return on its own.	980	count is nonzero, C<ev_run> will not return on its own.
699		981
700	If you have a watcher you never unregister that should not keep C<ev_loop>	982	This is useful when you have a watcher that you never intend to
701	from returning, call ev_unref() after starting, and ev_ref() before	983	unregister, but that nevertheless should not keep C<ev_run> from
		984	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
702	stopping it.	985	before stopping it.
703		986
704	As an example, libev itself uses this for its internal signal pipe: It is	987	As an example, libev itself uses this for its internal signal pipe: It
705	not visible to the libev user and should not keep C<ev_loop> from exiting	988	is not visible to the libev user and should not keep C<ev_run> from
706	if no event watchers registered by it are active. It is also an excellent	989	exiting if no event watchers registered by it are active. It is also an
707	way to do this for generic recurring timers or from within third-party	990	excellent way to do this for generic recurring timers or from within
708	libraries. Just remember to I<unref after start> and I<ref before stop>	991	third-party libraries. Just remember to I<unref after start> and I<ref
709	(but only if the watcher wasn't active before, or was active before,	992	before stop> (but only if the watcher wasn't active before, or was active
710	respectively).	993	before, respectively. Note also that libev might stop watchers itself
		994	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		995	in the callback).
711		996
712	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	997	Example: Create a signal watcher, but keep it from keeping C<ev_run>
713	running when nothing else is active.	998	running when nothing else is active.
714		999
715	ev_signal exitsig;	1000	ev_signal exitsig;
716	ev_signal_init (&exitsig, sig_cb, SIGINT);	1001	ev_signal_init (&exitsig, sig_cb, SIGINT);
717	ev_signal_start (loop, &exitsig);	1002	ev_signal_start (loop, &exitsig);
718	evf_unref (loop);	1003	ev_unref (loop);
719		1004
720	Example: For some weird reason, unregister the above signal handler again.	1005	Example: For some weird reason, unregister the above signal handler again.
721		1006
722	ev_ref (loop);	1007	ev_ref (loop);
723	ev_signal_stop (loop, &exitsig);	1008	ev_signal_stop (loop, &exitsig);
…		…
743	overhead for the actual polling but can deliver many events at once.	1028	overhead for the actual polling but can deliver many events at once.
744		1029
745	By setting a higher I<io collect interval> you allow libev to spend more	1030	By setting a higher I<io collect interval> you allow libev to spend more
746	time collecting I/O events, so you can handle more events per iteration,	1031	time collecting I/O events, so you can handle more events per iteration,
747	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1032	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
748	C<ev_timer>) will be not affected. Setting this to a non-null value will	1033	C<ev_timer>) will not be affected. Setting this to a non-null value will
749	introduce an additional C<ev_sleep ()> call into most loop iterations.	1034	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		1035	sleep time ensures that libev will not poll for I/O events more often then
		1036	once per this interval, on average (as long as the host time resolution is
		1037	good enough).
750		1038
751	Likewise, by setting a higher I<timeout collect interval> you allow libev	1039	Likewise, by setting a higher I<timeout collect interval> you allow libev
752	to spend more time collecting timeouts, at the expense of increased	1040	to spend more time collecting timeouts, at the expense of increased
753	latency/jitter/inexactness (the watcher callback will be called	1041	latency/jitter/inexactness (the watcher callback will be called
754	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1042	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
756		1044
757	Many (busy) programs can usually benefit by setting the I/O collect	1045	Many (busy) programs can usually benefit by setting the I/O collect
758	interval to a value near C<0.1> or so, which is often enough for	1046	interval to a value near C<0.1> or so, which is often enough for
759	interactive servers (of course not for games), likewise for timeouts. It	1047	interactive servers (of course not for games), likewise for timeouts. It
760	usually doesn't make much sense to set it to a lower value than C<0.01>,	1048	usually doesn't make much sense to set it to a lower value than C<0.01>,
761	as this approaches the timing granularity of most systems.	1049	as this approaches the timing granularity of most systems. Note that if
		1050	you do transactions with the outside world and you can't increase the
		1051	parallelity, then this setting will limit your transaction rate (if you
		1052	need to poll once per transaction and the I/O collect interval is 0.01,
		1053	then you can't do more than 100 transactions per second).
762		1054
763	Setting the I<timeout collect interval> can improve the opportunity for	1055	Setting the I<timeout collect interval> can improve the opportunity for
764	saving power, as the program will "bundle" timer callback invocations that	1056	saving power, as the program will "bundle" timer callback invocations that
765	are "near" in time together, by delaying some, thus reducing the number of	1057	are "near" in time together, by delaying some, thus reducing the number of
766	times the process sleeps and wakes up again. Another useful technique to	1058	times the process sleeps and wakes up again. Another useful technique to
767	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	1059	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
768	they fire on, say, one-second boundaries only.	1060	they fire on, say, one-second boundaries only.
769		1061
		1062	Example: we only need 0.1s timeout granularity, and we wish not to poll
		1063	more often than 100 times per second:
		1064
		1065	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		1066	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		1067
		1068	=item ev_invoke_pending (loop)
		1069
		1070	This call will simply invoke all pending watchers while resetting their
		1071	pending state. Normally, C<ev_run> does this automatically when required,
		1072	but when overriding the invoke callback this call comes handy. This
		1073	function can be invoked from a watcher - this can be useful for example
		1074	when you want to do some lengthy calculation and want to pass further
		1075	event handling to another thread (you still have to make sure only one
		1076	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1077
		1078	=item int ev_pending_count (loop)
		1079
		1080	Returns the number of pending watchers - zero indicates that no watchers
		1081	are pending.
		1082
		1083	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1084
		1085	This overrides the invoke pending functionality of the loop: Instead of
		1086	invoking all pending watchers when there are any, C<ev_run> will call
		1087	this callback instead. This is useful, for example, when you want to
		1088	invoke the actual watchers inside another context (another thread etc.).
		1089
		1090	If you want to reset the callback, use C<ev_invoke_pending> as new
		1091	callback.
		1092
		1093	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1094
		1095	Sometimes you want to share the same loop between multiple threads. This
		1096	can be done relatively simply by putting mutex_lock/unlock calls around
		1097	each call to a libev function.
		1098
		1099	However, C<ev_run> can run an indefinite time, so it is not feasible
		1100	to wait for it to return. One way around this is to wake up the event
		1101	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1102	I<release> and I<acquire> callbacks on the loop.
		1103
		1104	When set, then C<release> will be called just before the thread is
		1105	suspended waiting for new events, and C<acquire> is called just
		1106	afterwards.
		1107
		1108	Ideally, C<release> will just call your mutex_unlock function, and
		1109	C<acquire> will just call the mutex_lock function again.
		1110
		1111	While event loop modifications are allowed between invocations of
		1112	C<release> and C<acquire> (that's their only purpose after all), no
		1113	modifications done will affect the event loop, i.e. adding watchers will
		1114	have no effect on the set of file descriptors being watched, or the time
		1115	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1116	to take note of any changes you made.
		1117
		1118	In theory, threads executing C<ev_run> will be async-cancel safe between
		1119	invocations of C<release> and C<acquire>.
		1120
		1121	See also the locking example in the C<THREADS> section later in this
		1122	document.
		1123
		1124	=item ev_set_userdata (loop, void *data)
		1125
		1126	=item void *ev_userdata (loop)
		1127
		1128	Set and retrieve a single C<void *> associated with a loop. When
		1129	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1130	C<0>.
		1131
		1132	These two functions can be used to associate arbitrary data with a loop,
		1133	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1134	C<acquire> callbacks described above, but of course can be (ab-)used for
		1135	any other purpose as well.
		1136
770	=item ev_loop_verify (loop)	1137	=item ev_verify (loop)
771		1138
772	This function only does something when C<EV_VERIFY> support has been	1139	This function only does something when C<EV_VERIFY> support has been
773	compiled in. which is the default for non-minimal builds. It tries to go	1140	compiled in, which is the default for non-minimal builds. It tries to go
774	through all internal structures and checks them for validity. If anything	1141	through all internal structures and checks them for validity. If anything
775	is found to be inconsistent, it will print an error message to standard	1142	is found to be inconsistent, it will print an error message to standard
776	error and call C<abort ()>.	1143	error and call C<abort ()>.
777		1144
778	This can be used to catch bugs inside libev itself: under normal	1145	This can be used to catch bugs inside libev itself: under normal
…		…
782	=back	1149	=back
783		1150
784		1151
785	=head1 ANATOMY OF A WATCHER	1152	=head1 ANATOMY OF A WATCHER
786		1153
		1154	In the following description, uppercase C<TYPE> in names stands for the
		1155	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		1156	watchers and C<ev_io_start> for I/O watchers.
		1157
787	A watcher is a structure that you create and register to record your	1158	A watcher is an opaque structure that you allocate and register to record
788	interest in some event. For instance, if you want to wait for STDIN to	1159	your interest in some event. To make a concrete example, imagine you want
789	become readable, you would create an C<ev_io> watcher for that:	1160	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1161	for that:
790		1162
791	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1163	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
792	{	1164	{
793	ev_io_stop (w);	1165	ev_io_stop (w);
794	ev_unloop (loop, EVUNLOOP_ALL);	1166	ev_break (loop, EVBREAK_ALL);
795	}	1167	}
796		1168
797	struct ev_loop *loop = ev_default_loop (0);	1169	struct ev_loop *loop = ev_default_loop (0);
		1170
798	ev_io stdin_watcher;	1171	ev_io stdin_watcher;
		1172
799	ev_init (&stdin_watcher, my_cb);	1173	ev_init (&stdin_watcher, my_cb);
800	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1174	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
801	ev_io_start (loop, &stdin_watcher);	1175	ev_io_start (loop, &stdin_watcher);
		1176
802	ev_loop (loop, 0);	1177	ev_run (loop, 0);
803		1178
804	As you can see, you are responsible for allocating the memory for your	1179	As you can see, you are responsible for allocating the memory for your
805	watcher structures (and it is usually a bad idea to do this on the stack,	1180	watcher structures (and it is I<usually> a bad idea to do this on the
806	although this can sometimes be quite valid).	1181	stack).
807		1182
		1183	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		1184	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
		1185
808	Each watcher structure must be initialised by a call to C<ev_init	1186	Each watcher structure must be initialised by a call to C<ev_init (watcher
809	(watcher *, callback)>, which expects a callback to be provided. This	1187	*, callback)>, which expects a callback to be provided. This callback is
810	callback gets invoked each time the event occurs (or, in the case of I/O	1188	invoked each time the event occurs (or, in the case of I/O watchers, each
811	watchers, each time the event loop detects that the file descriptor given	1189	time the event loop detects that the file descriptor given is readable
812	is readable and/or writable).	1190	and/or writable).
813		1191
814	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1192	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
815	with arguments specific to this watcher type. There is also a macro	1193	macro to configure it, with arguments specific to the watcher type. There
816	to combine initialisation and setting in one call: C<< ev_<type>_init	1194	is also a macro to combine initialisation and setting in one call: C<<
817	(watcher *, callback, ...) >>.	1195	ev_TYPE_init (watcher *, callback, ...) >>.
818		1196
819	To make the watcher actually watch out for events, you have to start it	1197	To make the watcher actually watch out for events, you have to start it
820	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1198	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
821	*) >>), and you can stop watching for events at any time by calling the	1199	*) >>), and you can stop watching for events at any time by calling the
822	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1200	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
823		1201
824	As long as your watcher is active (has been started but not stopped) you	1202	As long as your watcher is active (has been started but not stopped) you
825	must not touch the values stored in it. Most specifically you must never	1203	must not touch the values stored in it. Most specifically you must never
826	reinitialise it or call its C<set> macro.	1204	reinitialise it or call its C<ev_TYPE_set> macro.
827		1205
828	Each and every callback receives the event loop pointer as first, the	1206	Each and every callback receives the event loop pointer as first, the
829	registered watcher structure as second, and a bitset of received events as	1207	registered watcher structure as second, and a bitset of received events as
830	third argument.	1208	third argument.
831		1209
…		…
840	=item C<EV_WRITE>	1218	=item C<EV_WRITE>
841		1219
842	The file descriptor in the C<ev_io> watcher has become readable and/or	1220	The file descriptor in the C<ev_io> watcher has become readable and/or
843	writable.	1221	writable.
844		1222
845	=item C<EV_TIMEOUT>	1223	=item C<EV_TIMER>
846		1224
847	The C<ev_timer> watcher has timed out.	1225	The C<ev_timer> watcher has timed out.
848		1226
849	=item C<EV_PERIODIC>	1227	=item C<EV_PERIODIC>
850		1228
…		…
868		1246
869	=item C<EV_PREPARE>	1247	=item C<EV_PREPARE>
870		1248
871	=item C<EV_CHECK>	1249	=item C<EV_CHECK>
872		1250
873	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1251	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
874	to gather new events, and all C<ev_check> watchers are invoked just after	1252	gather new events, and all C<ev_check> watchers are queued (not invoked)
875	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1253	just after C<ev_run> has gathered them, but before it queues any callbacks
		1254	for any received events. That means C<ev_prepare> watchers are the last
		1255	watchers invoked before the event loop sleeps or polls for new events, and
		1256	C<ev_check> watchers will be invoked before any other watchers of the same
		1257	or lower priority within an event loop iteration.
		1258
876	received events. Callbacks of both watcher types can start and stop as	1259	Callbacks of both watcher types can start and stop as many watchers as
877	many watchers as they want, and all of them will be taken into account	1260	they want, and all of them will be taken into account (for example, a
878	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1261	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
879	C<ev_loop> from blocking).	1262	blocking).
880		1263
881	=item C<EV_EMBED>	1264	=item C<EV_EMBED>
882		1265
883	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1266	The embedded event loop specified in the C<ev_embed> watcher needs attention.
884		1267
885	=item C<EV_FORK>	1268	=item C<EV_FORK>
886		1269
887	The event loop has been resumed in the child process after fork (see	1270	The event loop has been resumed in the child process after fork (see
888	C<ev_fork>).	1271	C<ev_fork>).
889		1272
		1273	=item C<EV_CLEANUP>
		1274
		1275	The event loop is about to be destroyed (see C<ev_cleanup>).
		1276
890	=item C<EV_ASYNC>	1277	=item C<EV_ASYNC>
891		1278
892	The given async watcher has been asynchronously notified (see C<ev_async>).	1279	The given async watcher has been asynchronously notified (see C<ev_async>).
		1280
		1281	=item C<EV_CUSTOM>
		1282
		1283	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1284	by libev users to signal watchers (e.g. via C<ev_feed_event>).
893		1285
894	=item C<EV_ERROR>	1286	=item C<EV_ERROR>
895		1287
896	An unspecified error has occurred, the watcher has been stopped. This might	1288	An unspecified error has occurred, the watcher has been stopped. This might
897	happen because the watcher could not be properly started because libev	1289	happen because the watcher could not be properly started because libev
…		…
912		1304
913	=back	1305	=back
914		1306
915	=head2 GENERIC WATCHER FUNCTIONS	1307	=head2 GENERIC WATCHER FUNCTIONS
916		1308
917	In the following description, C<TYPE> stands for the watcher type,
918	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
919
920	=over 4	1309	=over 4
921		1310
922	=item C<ev_init> (ev_TYPE *watcher, callback)	1311	=item C<ev_init> (ev_TYPE *watcher, callback)
923		1312
924	This macro initialises the generic portion of a watcher. The contents	1313	This macro initialises the generic portion of a watcher. The contents
…		…
938		1327
939	ev_io w;	1328	ev_io w;
940	ev_init (&w, my_cb);	1329	ev_init (&w, my_cb);
941	ev_io_set (&w, STDIN_FILENO, EV_READ);	1330	ev_io_set (&w, STDIN_FILENO, EV_READ);
942		1331
943	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1332	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
944		1333
945	This macro initialises the type-specific parts of a watcher. You need to	1334	This macro initialises the type-specific parts of a watcher. You need to
946	call C<ev_init> at least once before you call this macro, but you can	1335	call C<ev_init> at least once before you call this macro, but you can
947	call C<ev_TYPE_set> any number of times. You must not, however, call this	1336	call C<ev_TYPE_set> any number of times. You must not, however, call this
948	macro on a watcher that is active (it can be pending, however, which is a	1337	macro on a watcher that is active (it can be pending, however, which is a
…		…
961		1350
962	Example: Initialise and set an C<ev_io> watcher in one step.	1351	Example: Initialise and set an C<ev_io> watcher in one step.
963		1352
964	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1353	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
965		1354
966	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1355	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
967		1356
968	Starts (activates) the given watcher. Only active watchers will receive	1357	Starts (activates) the given watcher. Only active watchers will receive
969	events. If the watcher is already active nothing will happen.	1358	events. If the watcher is already active nothing will happen.
970		1359
971	Example: Start the C<ev_io> watcher that is being abused as example in this	1360	Example: Start the C<ev_io> watcher that is being abused as example in this
972	whole section.	1361	whole section.
973		1362
974	ev_io_start (EV_DEFAULT_UC, &w);	1363	ev_io_start (EV_DEFAULT_UC, &w);
975		1364
976	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1365	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
977		1366
978	Stops the given watcher if active, and clears the pending status (whether	1367	Stops the given watcher if active, and clears the pending status (whether
979	the watcher was active or not).	1368	the watcher was active or not).
980		1369
981	It is possible that stopped watchers are pending - for example,	1370	It is possible that stopped watchers are pending - for example,
…		…
1001		1390
1002	=item callback ev_cb (ev_TYPE *watcher)	1391	=item callback ev_cb (ev_TYPE *watcher)
1003		1392
1004	Returns the callback currently set on the watcher.	1393	Returns the callback currently set on the watcher.
1005		1394
1006	=item ev_cb_set (ev_TYPE *watcher, callback)	1395	=item ev_set_cb (ev_TYPE *watcher, callback)
1007		1396
1008	Change the callback. You can change the callback at virtually any time	1397	Change the callback. You can change the callback at virtually any time
1009	(modulo threads).	1398	(modulo threads).
1010		1399
1011	=item ev_set_priority (ev_TYPE *watcher, priority)	1400	=item ev_set_priority (ev_TYPE *watcher, int priority)
1012		1401
1013	=item int ev_priority (ev_TYPE *watcher)	1402	=item int ev_priority (ev_TYPE *watcher)
1014		1403
1015	Set and query the priority of the watcher. The priority is a small	1404	Set and query the priority of the watcher. The priority is a small
1016	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1405	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1017	(default: C<-2>). Pending watchers with higher priority will be invoked	1406	(default: C<-2>). Pending watchers with higher priority will be invoked
1018	before watchers with lower priority, but priority will not keep watchers	1407	before watchers with lower priority, but priority will not keep watchers
1019	from being executed (except for C<ev_idle> watchers).	1408	from being executed (except for C<ev_idle> watchers).
1020		1409
1021	This means that priorities are I<only> used for ordering callback
1022	invocation after new events have been received. This is useful, for
1023	example, to reduce latency after idling, or more often, to bind two
1024	watchers on the same event and make sure one is called first.
1025
1026	If you need to suppress invocation when higher priority events are pending	1410	If you need to suppress invocation when higher priority events are pending
1027	you need to look at C<ev_idle> watchers, which provide this functionality.	1411	you need to look at C<ev_idle> watchers, which provide this functionality.
1028		1412
1029	You I<must not> change the priority of a watcher as long as it is active or	1413	You I<must not> change the priority of a watcher as long as it is active or
1030	pending.	1414	pending.
1031		1415
		1416	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1417	fine, as long as you do not mind that the priority value you query might
		1418	or might not have been clamped to the valid range.
		1419
1032	The default priority used by watchers when no priority has been set is	1420	The default priority used by watchers when no priority has been set is
1033	always C<0>, which is supposed to not be too high and not be too low :).	1421	always C<0>, which is supposed to not be too high and not be too low :).
1034		1422
1035	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1423	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1036	fine, as long as you do not mind that the priority value you query might	1424	priorities.
1037	or might not have been adjusted to be within valid range.
1038		1425
1039	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1426	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1040		1427
1041	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1428	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1042	C<loop> nor C<revents> need to be valid as long as the watcher callback	1429	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1050	watcher isn't pending it does nothing and returns C<0>.	1437	watcher isn't pending it does nothing and returns C<0>.
1051		1438
1052	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1439	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1053	callback to be invoked, which can be accomplished with this function.	1440	callback to be invoked, which can be accomplished with this function.
1054		1441
		1442	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1443
		1444	Feeds the given event set into the event loop, as if the specified event
		1445	had happened for the specified watcher (which must be a pointer to an
		1446	initialised but not necessarily started event watcher). Obviously you must
		1447	not free the watcher as long as it has pending events.
		1448
		1449	Stopping the watcher, letting libev invoke it, or calling
		1450	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1451	not started in the first place.
		1452
		1453	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1454	functions that do not need a watcher.
		1455
1055	=back	1456	=back
1056		1457
		1458	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1459	OWN COMPOSITE WATCHERS> idioms.
1057		1460
1058	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1461	=head2 WATCHER STATES
1059		1462
1060	Each watcher has, by default, a member C<void *data> that you can change	1463	There are various watcher states mentioned throughout this manual -
1061	and read at any time: libev will completely ignore it. This can be used	1464	active, pending and so on. In this section these states and the rules to
1062	to associate arbitrary data with your watcher. If you need more data and	1465	transition between them will be described in more detail - and while these
1063	don't want to allocate memory and store a pointer to it in that data	1466	rules might look complicated, they usually do "the right thing".
1064	member, you can also "subclass" the watcher type and provide your own
1065	data:
1066		1467
1067	struct my_io	1468	=over 4
		1469
		1470	=item initialised
		1471
		1472	Before a watcher can be registered with the event loop it has to be
		1473	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1474	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1475
		1476	In this state it is simply some block of memory that is suitable for
		1477	use in an event loop. It can be moved around, freed, reused etc. at
		1478	will - as long as you either keep the memory contents intact, or call
		1479	C<ev_TYPE_init> again.
		1480
		1481	=item started/running/active
		1482
		1483	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1484	property of the event loop, and is actively waiting for events. While in
		1485	this state it cannot be accessed (except in a few documented ways), moved,
		1486	freed or anything else - the only legal thing is to keep a pointer to it,
		1487	and call libev functions on it that are documented to work on active watchers.
		1488
		1489	=item pending
		1490
		1491	If a watcher is active and libev determines that an event it is interested
		1492	in has occurred (such as a timer expiring), it will become pending. It will
		1493	stay in this pending state until either it is stopped or its callback is
		1494	about to be invoked, so it is not normally pending inside the watcher
		1495	callback.
		1496
		1497	The watcher might or might not be active while it is pending (for example,
		1498	an expired non-repeating timer can be pending but no longer active). If it
		1499	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1500	but it is still property of the event loop at this time, so cannot be
		1501	moved, freed or reused. And if it is active the rules described in the
		1502	previous item still apply.
		1503
		1504	It is also possible to feed an event on a watcher that is not active (e.g.
		1505	via C<ev_feed_event>), in which case it becomes pending without being
		1506	active.
		1507
		1508	=item stopped
		1509
		1510	A watcher can be stopped implicitly by libev (in which case it might still
		1511	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1512	latter will clear any pending state the watcher might be in, regardless
		1513	of whether it was active or not, so stopping a watcher explicitly before
		1514	freeing it is often a good idea.
		1515
		1516	While stopped (and not pending) the watcher is essentially in the
		1517	initialised state, that is, it can be reused, moved, modified in any way
		1518	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1519	it again).
		1520
		1521	=back
		1522
		1523	=head2 WATCHER PRIORITY MODELS
		1524
		1525	Many event loops support I<watcher priorities>, which are usually small
		1526	integers that influence the ordering of event callback invocation
		1527	between watchers in some way, all else being equal.
		1528
		1529	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1530	description for the more technical details such as the actual priority
		1531	range.
		1532
		1533	There are two common ways how these these priorities are being interpreted
		1534	by event loops:
		1535
		1536	In the more common lock-out model, higher priorities "lock out" invocation
		1537	of lower priority watchers, which means as long as higher priority
		1538	watchers receive events, lower priority watchers are not being invoked.
		1539
		1540	The less common only-for-ordering model uses priorities solely to order
		1541	callback invocation within a single event loop iteration: Higher priority
		1542	watchers are invoked before lower priority ones, but they all get invoked
		1543	before polling for new events.
		1544
		1545	Libev uses the second (only-for-ordering) model for all its watchers
		1546	except for idle watchers (which use the lock-out model).
		1547
		1548	The rationale behind this is that implementing the lock-out model for
		1549	watchers is not well supported by most kernel interfaces, and most event
		1550	libraries will just poll for the same events again and again as long as
		1551	their callbacks have not been executed, which is very inefficient in the
		1552	common case of one high-priority watcher locking out a mass of lower
		1553	priority ones.
		1554
		1555	Static (ordering) priorities are most useful when you have two or more
		1556	watchers handling the same resource: a typical usage example is having an
		1557	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1558	timeouts. Under load, data might be received while the program handles
		1559	other jobs, but since timers normally get invoked first, the timeout
		1560	handler will be executed before checking for data. In that case, giving
		1561	the timer a lower priority than the I/O watcher ensures that I/O will be
		1562	handled first even under adverse conditions (which is usually, but not
		1563	always, what you want).
		1564
		1565	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1566	will only be executed when no same or higher priority watchers have
		1567	received events, they can be used to implement the "lock-out" model when
		1568	required.
		1569
		1570	For example, to emulate how many other event libraries handle priorities,
		1571	you can associate an C<ev_idle> watcher to each such watcher, and in
		1572	the normal watcher callback, you just start the idle watcher. The real
		1573	processing is done in the idle watcher callback. This causes libev to
		1574	continuously poll and process kernel event data for the watcher, but when
		1575	the lock-out case is known to be rare (which in turn is rare :), this is
		1576	workable.
		1577
		1578	Usually, however, the lock-out model implemented that way will perform
		1579	miserably under the type of load it was designed to handle. In that case,
		1580	it might be preferable to stop the real watcher before starting the
		1581	idle watcher, so the kernel will not have to process the event in case
		1582	the actual processing will be delayed for considerable time.
		1583
		1584	Here is an example of an I/O watcher that should run at a strictly lower
		1585	priority than the default, and which should only process data when no
		1586	other events are pending:
		1587
		1588	ev_idle idle; // actual processing watcher
		1589	ev_io io; // actual event watcher
		1590
		1591	static void
		1592	io_cb (EV_P_ ev_io *w, int revents)
1068	{	1593	{
1069	ev_io io;	1594	// stop the I/O watcher, we received the event, but
1070	int otherfd;	1595	// are not yet ready to handle it.
1071	void *somedata;	1596	ev_io_stop (EV_A_ w);
1072	struct whatever *mostinteresting;	1597
		1598	// start the idle watcher to handle the actual event.
		1599	// it will not be executed as long as other watchers
		1600	// with the default priority are receiving events.
		1601	ev_idle_start (EV_A_ &idle);
1073	};	1602	}
1074		1603
1075	...	1604	static void
1076	struct my_io w;	1605	idle_cb (EV_P_ ev_idle *w, int revents)
1077	ev_io_init (&w.io, my_cb, fd, EV_READ);
1078
1079	And since your callback will be called with a pointer to the watcher, you
1080	can cast it back to your own type:
1081
1082	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1083	{	1606	{
1084	struct my_io *w = (struct my_io *)w_;	1607	// actual processing
1085	...	1608	read (STDIN_FILENO, ...);
		1609
		1610	// have to start the I/O watcher again, as
		1611	// we have handled the event
		1612	ev_io_start (EV_P_ &io);
1086	}	1613	}
1087		1614
1088	More interesting and less C-conformant ways of casting your callback type	1615	// initialisation
1089	instead have been omitted.	1616	ev_idle_init (&idle, idle_cb);
		1617	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1618	ev_io_start (EV_DEFAULT_ &io);
1090		1619
1091	Another common scenario is to use some data structure with multiple	1620	In the "real" world, it might also be beneficial to start a timer, so that
1092	embedded watchers:	1621	low-priority connections can not be locked out forever under load. This
1093		1622	enables your program to keep a lower latency for important connections
1094	struct my_biggy	1623	during short periods of high load, while not completely locking out less
1095	{	1624	important ones.
1096	int some_data;
1097	ev_timer t1;
1098	ev_timer t2;
1099	}
1100
1101	In this case getting the pointer to C<my_biggy> is a bit more
1102	complicated: Either you store the address of your C<my_biggy> struct
1103	in the C<data> member of the watcher (for woozies), or you need to use
1104	some pointer arithmetic using C<offsetof> inside your watchers (for real
1105	programmers):
1106
1107	#include <stddef.h>
1108
1109	static void
1110	t1_cb (EV_P_ ev_timer *w, int revents)
1111	{
1112	struct my_biggy big = (struct my_biggy *
1113	(((char *)w) - offsetof (struct my_biggy, t1));
1114	}
1115
1116	static void
1117	t2_cb (EV_P_ ev_timer *w, int revents)
1118	{
1119	struct my_biggy big = (struct my_biggy *
1120	(((char *)w) - offsetof (struct my_biggy, t2));
1121	}
1122		1625
1123		1626
1124	=head1 WATCHER TYPES	1627	=head1 WATCHER TYPES
1125		1628
1126	This section describes each watcher in detail, but will not repeat	1629	This section describes each watcher in detail, but will not repeat
…		…
1150	In general you can register as many read and/or write event watchers per	1653	In general you can register as many read and/or write event watchers per
1151	fd as you want (as long as you don't confuse yourself). Setting all file	1654	fd as you want (as long as you don't confuse yourself). Setting all file
1152	descriptors to non-blocking mode is also usually a good idea (but not	1655	descriptors to non-blocking mode is also usually a good idea (but not
1153	required if you know what you are doing).	1656	required if you know what you are doing).
1154		1657
1155	If you cannot use non-blocking mode, then force the use of a
1156	known-to-be-good backend (at the time of this writing, this includes only
1157	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1158
1159	Another thing you have to watch out for is that it is quite easy to	1658	Another thing you have to watch out for is that it is quite easy to
1160	receive "spurious" readiness notifications, that is your callback might	1659	receive "spurious" readiness notifications, that is, your callback might
1161	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1660	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1162	because there is no data. Not only are some backends known to create a	1661	because there is no data. It is very easy to get into this situation even
1163	lot of those (for example Solaris ports), it is very easy to get into	1662	with a relatively standard program structure. Thus it is best to always
1164	this situation even with a relatively standard program structure. Thus	1663	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1165	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1166	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1664	preferable to a program hanging until some data arrives.
1167		1665
1168	If you cannot run the fd in non-blocking mode (for example you should	1666	If you cannot run the fd in non-blocking mode (for example you should
1169	not play around with an Xlib connection), then you have to separately	1667	not play around with an Xlib connection), then you have to separately
1170	re-test whether a file descriptor is really ready with a known-to-be good	1668	re-test whether a file descriptor is really ready with a known-to-be good
1171	interface such as poll (fortunately in our Xlib example, Xlib already	1669	interface such as poll (fortunately in the case of Xlib, it already does
1172	does this on its own, so its quite safe to use). Some people additionally	1670	this on its own, so its quite safe to use). Some people additionally
1173	use C<SIGALRM> and an interval timer, just to be sure you won't block	1671	use C<SIGALRM> and an interval timer, just to be sure you won't block
1174	indefinitely.	1672	indefinitely.
1175		1673
1176	But really, best use non-blocking mode.	1674	But really, best use non-blocking mode.
1177		1675
1178	=head3 The special problem of disappearing file descriptors	1676	=head3 The special problem of disappearing file descriptors
1179		1677
1180	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1678	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1181	descriptor (either due to calling C<close> explicitly or any other means,	1679	a file descriptor (either due to calling C<close> explicitly or any other
1182	such as C<dup2>). The reason is that you register interest in some file	1680	means, such as C<dup2>). The reason is that you register interest in some
1183	descriptor, but when it goes away, the operating system will silently drop	1681	file descriptor, but when it goes away, the operating system will silently
1184	this interest. If another file descriptor with the same number then is	1682	drop this interest. If another file descriptor with the same number then
1185	registered with libev, there is no efficient way to see that this is, in	1683	is registered with libev, there is no efficient way to see that this is,
1186	fact, a different file descriptor.	1684	in fact, a different file descriptor.
1187		1685
1188	To avoid having to explicitly tell libev about such cases, libev follows	1686	To avoid having to explicitly tell libev about such cases, libev follows
1189	the following policy: Each time C<ev_io_set> is being called, libev	1687	the following policy: Each time C<ev_io_set> is being called, libev
1190	will assume that this is potentially a new file descriptor, otherwise	1688	will assume that this is potentially a new file descriptor, otherwise
1191	it is assumed that the file descriptor stays the same. That means that	1689	it is assumed that the file descriptor stays the same. That means that
…		…
1205		1703
1206	There is no workaround possible except not registering events	1704	There is no workaround possible except not registering events
1207	for potentially C<dup ()>'ed file descriptors, or to resort to	1705	for potentially C<dup ()>'ed file descriptors, or to resort to
1208	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1706	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1209		1707
		1708	=head3 The special problem of files
		1709
		1710	Many people try to use C<select> (or libev) on file descriptors
		1711	representing files, and expect it to become ready when their program
		1712	doesn't block on disk accesses (which can take a long time on their own).
		1713
		1714	However, this cannot ever work in the "expected" way - you get a readiness
		1715	notification as soon as the kernel knows whether and how much data is
		1716	there, and in the case of open files, that's always the case, so you
		1717	always get a readiness notification instantly, and your read (or possibly
		1718	write) will still block on the disk I/O.
		1719
		1720	Another way to view it is that in the case of sockets, pipes, character
		1721	devices and so on, there is another party (the sender) that delivers data
		1722	on its own, but in the case of files, there is no such thing: the disk
		1723	will not send data on its own, simply because it doesn't know what you
		1724	wish to read - you would first have to request some data.
		1725
		1726	Since files are typically not-so-well supported by advanced notification
		1727	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1728	to files, even though you should not use it. The reason for this is
		1729	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1730	usually a tty, often a pipe, but also sometimes files or special devices
		1731	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1732	F</dev/urandom>), and even though the file might better be served with
		1733	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1734	it "just works" instead of freezing.
		1735
		1736	So avoid file descriptors pointing to files when you know it (e.g. use
		1737	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1738	when you rarely read from a file instead of from a socket, and want to
		1739	reuse the same code path.
		1740
1210	=head3 The special problem of fork	1741	=head3 The special problem of fork
1211		1742
1212	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1743	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1213	useless behaviour. Libev fully supports fork, but needs to be told about	1744	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1214	it in the child.	1745	to be told about it in the child if you want to continue to use it in the
		1746	child.
1215		1747
1216	To support fork in your programs, you either have to call	1748	To support fork in your child processes, you have to call C<ev_loop_fork
1217	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1749	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1218	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1750	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1219	C<EVBACKEND_POLL>.
1220		1751
1221	=head3 The special problem of SIGPIPE	1752	=head3 The special problem of SIGPIPE
1222		1753
1223	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1754	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1224	when writing to a pipe whose other end has been closed, your program gets	1755	when writing to a pipe whose other end has been closed, your program gets
…		…
1227		1758
1228	So when you encounter spurious, unexplained daemon exits, make sure you	1759	So when you encounter spurious, unexplained daemon exits, make sure you
1229	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1760	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1230	somewhere, as that would have given you a big clue).	1761	somewhere, as that would have given you a big clue).
1231		1762
		1763	=head3 The special problem of accept()ing when you can't
		1764
		1765	Many implementations of the POSIX C<accept> function (for example,
		1766	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1767	connection from the pending queue in all error cases.
		1768
		1769	For example, larger servers often run out of file descriptors (because
		1770	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1771	rejecting the connection, leading to libev signalling readiness on
		1772	the next iteration again (the connection still exists after all), and
		1773	typically causing the program to loop at 100% CPU usage.
		1774
		1775	Unfortunately, the set of errors that cause this issue differs between
		1776	operating systems, there is usually little the app can do to remedy the
		1777	situation, and no known thread-safe method of removing the connection to
		1778	cope with overload is known (to me).
		1779
		1780	One of the easiest ways to handle this situation is to just ignore it
		1781	- when the program encounters an overload, it will just loop until the
		1782	situation is over. While this is a form of busy waiting, no OS offers an
		1783	event-based way to handle this situation, so it's the best one can do.
		1784
		1785	A better way to handle the situation is to log any errors other than
		1786	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1787	messages, and continue as usual, which at least gives the user an idea of
		1788	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1789	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1790	usage.
		1791
		1792	If your program is single-threaded, then you could also keep a dummy file
		1793	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1794	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1795	close that fd, and create a new dummy fd. This will gracefully refuse
		1796	clients under typical overload conditions.
		1797
		1798	The last way to handle it is to simply log the error and C<exit>, as
		1799	is often done with C<malloc> failures, but this results in an easy
		1800	opportunity for a DoS attack.
1232		1801
1233	=head3 Watcher-Specific Functions	1802	=head3 Watcher-Specific Functions
1234		1803
1235	=over 4	1804	=over 4
1236		1805
…		…
1268	...	1837	...
1269	struct ev_loop *loop = ev_default_init (0);	1838	struct ev_loop *loop = ev_default_init (0);
1270	ev_io stdin_readable;	1839	ev_io stdin_readable;
1271	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1840	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1272	ev_io_start (loop, &stdin_readable);	1841	ev_io_start (loop, &stdin_readable);
1273	ev_loop (loop, 0);	1842	ev_run (loop, 0);
1274		1843
1275		1844
1276	=head2 C<ev_timer> - relative and optionally repeating timeouts	1845	=head2 C<ev_timer> - relative and optionally repeating timeouts
1277		1846
1278	Timer watchers are simple relative timers that generate an event after a	1847	Timer watchers are simple relative timers that generate an event after a
…		…
1283	year, it will still time out after (roughly) one hour. "Roughly" because	1852	year, it will still time out after (roughly) one hour. "Roughly" because
1284	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1853	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1285	monotonic clock option helps a lot here).	1854	monotonic clock option helps a lot here).
1286		1855
1287	The callback is guaranteed to be invoked only I<after> its timeout has	1856	The callback is guaranteed to be invoked only I<after> its timeout has
1288	passed, but if multiple timers become ready during the same loop iteration	1857	passed (not I<at>, so on systems with very low-resolution clocks this
1289	then order of execution is undefined.	1858	might introduce a small delay, see "the special problem of being too
		1859	early", below). If multiple timers become ready during the same loop
		1860	iteration then the ones with earlier time-out values are invoked before
		1861	ones of the same priority with later time-out values (but this is no
		1862	longer true when a callback calls C<ev_run> recursively).
1290		1863
1291	=head3 Be smart about timeouts	1864	=head3 Be smart about timeouts
1292		1865
1293	Many real-world problems invole some kind of time-out, usually for error	1866	Many real-world problems involve some kind of timeout, usually for error
1294	recovery. A typical example is an HTTP request - if the other side hangs,	1867	recovery. A typical example is an HTTP request - if the other side hangs,
1295	you want to raise some error after a while.	1868	you want to raise some error after a while.
1296		1869
1297	Here are some ways on how to handle this problem, from simple and	1870	What follows are some ways to handle this problem, from obvious and
1298	inefficient to very efficient.	1871	inefficient to smart and efficient.
1299		1872
1300	In the following examples a 60 second activity timeout is assumed - a	1873	In the following, a 60 second activity timeout is assumed - a timeout that
1301	timeout that gets reset to 60 seconds each time some data ("a lifesign")	1874	gets reset to 60 seconds each time there is activity (e.g. each time some
1302	was received.	1875	data or other life sign was received).
1303		1876
1304	=over 4	1877	=over 4
1305		1878
1306	=item 1. Use a timer and stop, reinitialise, start it on activity.	1879	=item 1. Use a timer and stop, reinitialise and start it on activity.
1307		1880
1308	This is the most obvious, but not the most simple way: In the beginning,	1881	This is the most obvious, but not the most simple way: In the beginning,
1309	start the watcher:	1882	start the watcher:
1310		1883
1311	ev_timer_init (timer, callback, 60., 0.);	1884	ev_timer_init (timer, callback, 60., 0.);
1312	ev_timer_start (loop, timer);	1885	ev_timer_start (loop, timer);
1313		1886
1314	Then, each time there is some activity, C<ev_timer_stop> the timer,	1887	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
1315	initialise it again, and start it:	1888	and start it again:
1316		1889
1317	ev_timer_stop (loop, timer);	1890	ev_timer_stop (loop, timer);
1318	ev_timer_set (timer, 60., 0.);	1891	ev_timer_set (timer, 60., 0.);
1319	ev_timer_start (loop, timer);	1892	ev_timer_start (loop, timer);
1320		1893
1321	This is relatively simple to implement, but means that each time there	1894	This is relatively simple to implement, but means that each time there is
1322	is some activity, libev will first have to remove the timer from it's	1895	some activity, libev will first have to remove the timer from its internal
1323	internal data strcuture and then add it again.	1896	data structure and then add it again. Libev tries to be fast, but it's
		1897	still not a constant-time operation.
1324		1898
1325	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.	1899	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
1326		1900
1327	This is the easiest way, and involves using C<ev_timer_again> instead of	1901	This is the easiest way, and involves using C<ev_timer_again> instead of
1328	C<ev_timer_start>.	1902	C<ev_timer_start>.
1329		1903
1330	For this, configure an C<ev_timer> with a C<repeat> value of C<60> and	1904	To implement this, configure an C<ev_timer> with a C<repeat> value
1331	then call C<ev_timer_again> at start and each time you successfully read	1905	of C<60> and then call C<ev_timer_again> at start and each time you
1332	or write some data. If you go into an idle state where you do not expect	1906	successfully read or write some data. If you go into an idle state where
1333	data to travel on the socket, you can C<ev_timer_stop> the timer, and	1907	you do not expect data to travel on the socket, you can C<ev_timer_stop>
1334	C<ev_timer_again> will automatically restart it if need be.	1908	the timer, and C<ev_timer_again> will automatically restart it if need be.
1335		1909
1336	That means you can ignore the C<after> value and C<ev_timer_start>	1910	That means you can ignore both the C<ev_timer_start> function and the
1337	altogether and only ever use the C<repeat> value and C<ev_timer_again>.	1911	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1912	member and C<ev_timer_again>.
1338		1913
1339	At start:	1914	At start:
1340		1915
1341	ev_timer_init (timer, callback, 0., 60.);	1916	ev_init (timer, callback);
		1917	timer->repeat = 60.;
1342	ev_timer_again (loop, timer);	1918	ev_timer_again (loop, timer);
1343		1919
1344	Each time you receive some data:	1920	Each time there is some activity:
1345		1921
1346	ev_timer_again (loop, timer);	1922	ev_timer_again (loop, timer);
1347		1923
1348	It is even possible to change the time-out on the fly:	1924	It is even possible to change the time-out on the fly, regardless of
		1925	whether the watcher is active or not:
1349		1926
1350	timer->repeat = 30.;	1927	timer->repeat = 30.;
1351	ev_timer_again (loop, timer);	1928	ev_timer_again (loop, timer);
1352		1929
1353	This is slightly more efficient then stopping/starting the timer each time	1930	This is slightly more efficient then stopping/starting the timer each time
1354	you want to modify its timeout value, as libev does not have to completely	1931	you want to modify its timeout value, as libev does not have to completely
1355	remove and re-insert the timer from/into it's internal data structure.	1932	remove and re-insert the timer from/into its internal data structure.
		1933
		1934	It is, however, even simpler than the "obvious" way to do it.
1356		1935
1357	=item 3. Let the timer time out, but then re-arm it as required.	1936	=item 3. Let the timer time out, but then re-arm it as required.
1358		1937
1359	This method is more tricky, but usually most efficient: Most timeouts are	1938	This method is more tricky, but usually most efficient: Most timeouts are
1360	relatively long compared to the loop iteration time - in our example,	1939	relatively long compared to the intervals between other activity - in
1361	within 60 seconds, there are usually many I/O events with associated	1940	our example, within 60 seconds, there are usually many I/O events with
1362	activity resets.	1941	associated activity resets.
1363		1942
1364	In this case, it would be more efficient to leave the C<ev_timer> alone,	1943	In this case, it would be more efficient to leave the C<ev_timer> alone,
1365	but remember the time of last activity, and check for a real timeout only	1944	but remember the time of last activity, and check for a real timeout only
1366	within the callback:	1945	within the callback:
1367		1946
		1947	ev_tstamp timeout = 60.;
1368	ev_tstamp last_activity; // time of last activity	1948	ev_tstamp last_activity; // time of last activity
		1949	ev_timer timer;
1369		1950
1370	static void	1951	static void
1371	callback (EV_P_ ev_timer *w, int revents)	1952	callback (EV_P_ ev_timer *w, int revents)
1372	{	1953	{
1373	ev_tstamp now = ev_now (EV_A);	1954	// calculate when the timeout would happen
1374	ev_tstamp timeout = last_activity + 60.;	1955	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1375		1956
1376	// if last_activity is older than now - timeout, we did time out	1957	// if negative, it means we the timeout already occurred
1377	if (timeout < now)	1958	if (after < 0.)
1378	{	1959	{
1379	// timeout occured, take action	1960	// timeout occurred, take action
1380	}	1961	}
1381	else	1962	else
1382	{	1963	{
1383	// callback was invoked, but there was some activity, re-arm	1964	// callback was invoked, but there was some recent
1384	// to fire in last_activity + 60.	1965	// activity. simply restart the timer to time out
1385	w->again = timeout - now;	1966	// after "after" seconds, which is the earliest time
		1967	// the timeout can occur.
		1968	ev_timer_set (w, after, 0.);
1386	ev_timer_again (EV_A_ w);	1969	ev_timer_start (EV_A_ w);
1387	}	1970	}
1388	}	1971	}
1389		1972
1390	To summarise the callback: first calculate the real time-out (defined as	1973	To summarise the callback: first calculate in how many seconds the
1391	"60 seconds after the last activity"), then check if that time has been	1974	timeout will occur (by calculating the absolute time when it would occur,
1392	reached, which means there was a real timeout. Otherwise the callback was	1975	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1393	invoked too early (timeout is in the future), so re-schedule the timer to	1976	(EV_A)> from that).
1394	fire at that future time.
1395		1977
1396	Note how C<ev_timer_again> is used, taking advantage of the	1978	If this value is negative, then we are already past the timeout, i.e. we
1397	C<ev_timer_again> optimisation when the timer is already running.	1979	timed out, and need to do whatever is needed in this case.
1398		1980
		1981	Otherwise, we now the earliest time at which the timeout would trigger,
		1982	and simply start the timer with this timeout value.
		1983
		1984	In other words, each time the callback is invoked it will check whether
		1985	the timeout occurred. If not, it will simply reschedule itself to check
		1986	again at the earliest time it could time out. Rinse. Repeat.
		1987
1399	This scheme causes more callback invocations (about one every 60 seconds),	1988	This scheme causes more callback invocations (about one every 60 seconds
1400	but virtually no calls to libev to change the timeout.	1989	minus half the average time between activity), but virtually no calls to
		1990	libev to change the timeout.
1401		1991
1402	To start the timer, simply intiialise the watcher and C<last_activity>,	1992	To start the machinery, simply initialise the watcher and set
1403	then call the callback:	1993	C<last_activity> to the current time (meaning there was some activity just
		1994	now), then call the callback, which will "do the right thing" and start
		1995	the timer:
1404		1996
		1997	last_activity = ev_now (EV_A);
1405	ev_timer_init (timer, callback);	1998	ev_init (&timer, callback);
		1999	callback (EV_A_ &timer, 0);
		2000
		2001	When there is some activity, simply store the current time in
		2002	C<last_activity>, no libev calls at all:
		2003
		2004	if (activity detected)
1406	last_activity = ev_now (loop);	2005	last_activity = ev_now (EV_A);
1407	callback (loop, timer, EV_TIMEOUT);
1408		2006
1409	And when there is some activity, simply remember the time in	2007	When your timeout value changes, then the timeout can be changed by simply
1410	C<last_activity>:	2008	providing a new value, stopping the timer and calling the callback, which
		2009	will again do the right thing (for example, time out immediately :).
1411		2010
1412	last_actiivty = ev_now (loop);	2011	timeout = new_value;
		2012	ev_timer_stop (EV_A_ &timer);
		2013	callback (EV_A_ &timer, 0);
1413		2014
1414	This technique is slightly more complex, but in most cases where the	2015	This technique is slightly more complex, but in most cases where the
1415	time-out is unlikely to be triggered, much more efficient.	2016	time-out is unlikely to be triggered, much more efficient.
1416		2017
		2018	=item 4. Wee, just use a double-linked list for your timeouts.
		2019
		2020	If there is not one request, but many thousands (millions...), all
		2021	employing some kind of timeout with the same timeout value, then one can
		2022	do even better:
		2023
		2024	When starting the timeout, calculate the timeout value and put the timeout
		2025	at the I<end> of the list.
		2026
		2027	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		2028	the list is expected to fire (for example, using the technique #3).
		2029
		2030	When there is some activity, remove the timer from the list, recalculate
		2031	the timeout, append it to the end of the list again, and make sure to
		2032	update the C<ev_timer> if it was taken from the beginning of the list.
		2033
		2034	This way, one can manage an unlimited number of timeouts in O(1) time for
		2035	starting, stopping and updating the timers, at the expense of a major
		2036	complication, and having to use a constant timeout. The constant timeout
		2037	ensures that the list stays sorted.
		2038
1417	=back	2039	=back
1418		2040
		2041	So which method the best?
		2042
		2043	Method #2 is a simple no-brain-required solution that is adequate in most
		2044	situations. Method #3 requires a bit more thinking, but handles many cases
		2045	better, and isn't very complicated either. In most case, choosing either
		2046	one is fine, with #3 being better in typical situations.
		2047
		2048	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		2049	rather complicated, but extremely efficient, something that really pays
		2050	off after the first million or so of active timers, i.e. it's usually
		2051	overkill :)
		2052
		2053	=head3 The special problem of being too early
		2054
		2055	If you ask a timer to call your callback after three seconds, then
		2056	you expect it to be invoked after three seconds - but of course, this
		2057	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2058	guaranteed to any precision by libev - imagine somebody suspending the
		2059	process with a STOP signal for a few hours for example.
		2060
		2061	So, libev tries to invoke your callback as soon as possible I<after> the
		2062	delay has occurred, but cannot guarantee this.
		2063
		2064	A less obvious failure mode is calling your callback too early: many event
		2065	loops compare timestamps with a "elapsed delay >= requested delay", but
		2066	this can cause your callback to be invoked much earlier than you would
		2067	expect.
		2068
		2069	To see why, imagine a system with a clock that only offers full second
		2070	resolution (think windows if you can't come up with a broken enough OS
		2071	yourself). If you schedule a one-second timer at the time 500.9, then the
		2072	event loop will schedule your timeout to elapse at a system time of 500
		2073	(500.9 truncated to the resolution) + 1, or 501.
		2074
		2075	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2076	501" and invoke the callback 0.1s after it was started, even though a
		2077	one-second delay was requested - this is being "too early", despite best
		2078	intentions.
		2079
		2080	This is the reason why libev will never invoke the callback if the elapsed
		2081	delay equals the requested delay, but only when the elapsed delay is
		2082	larger than the requested delay. In the example above, libev would only invoke
		2083	the callback at system time 502, or 1.1s after the timer was started.
		2084
		2085	So, while libev cannot guarantee that your callback will be invoked
		2086	exactly when requested, it I<can> and I<does> guarantee that the requested
		2087	delay has actually elapsed, or in other words, it always errs on the "too
		2088	late" side of things.
		2089
1419	=head3 The special problem of time updates	2090	=head3 The special problem of time updates
1420		2091
1421	Establishing the current time is a costly operation (it usually takes at	2092	Establishing the current time is a costly operation (it usually takes
1422	least two system calls): EV therefore updates its idea of the current	2093	at least one system call): EV therefore updates its idea of the current
1423	time only before and after C<ev_loop> collects new events, which causes a	2094	time only before and after C<ev_run> collects new events, which causes a
1424	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2095	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1425	lots of events in one iteration.	2096	lots of events in one iteration.
1426		2097
1427	The relative timeouts are calculated relative to the C<ev_now ()>	2098	The relative timeouts are calculated relative to the C<ev_now ()>
1428	time. This is usually the right thing as this timestamp refers to the time	2099	time. This is usually the right thing as this timestamp refers to the time
1429	of the event triggering whatever timeout you are modifying/starting. If	2100	of the event triggering whatever timeout you are modifying/starting. If
1430	you suspect event processing to be delayed and you I<need> to base the	2101	you suspect event processing to be delayed and you I<need> to base the
1431	timeout on the current time, use something like this to adjust for this:	2102	timeout on the current time, use something like the following to adjust
		2103	for it:
1432		2104
1433	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2105	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1434		2106
1435	If the event loop is suspended for a long time, you can also force an	2107	If the event loop is suspended for a long time, you can also force an
1436	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2108	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1437	()>.	2109	()>, although that will push the event time of all outstanding events
		2110	further into the future.
		2111
		2112	=head3 The special problem of unsynchronised clocks
		2113
		2114	Modern systems have a variety of clocks - libev itself uses the normal
		2115	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2116	jumps).
		2117
		2118	Neither of these clocks is synchronised with each other or any other clock
		2119	on the system, so C<ev_time ()> might return a considerably different time
		2120	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2121	a call to C<gettimeofday> might return a second count that is one higher
		2122	than a directly following call to C<time>.
		2123
		2124	The moral of this is to only compare libev-related timestamps with
		2125	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2126	a second or so.
		2127
		2128	One more problem arises due to this lack of synchronisation: if libev uses
		2129	the system monotonic clock and you compare timestamps from C<ev_time>
		2130	or C<ev_now> from when you started your timer and when your callback is
		2131	invoked, you will find that sometimes the callback is a bit "early".
		2132
		2133	This is because C<ev_timer>s work in real time, not wall clock time, so
		2134	libev makes sure your callback is not invoked before the delay happened,
		2135	I<measured according to the real time>, not the system clock.
		2136
		2137	If your timeouts are based on a physical timescale (e.g. "time out this
		2138	connection after 100 seconds") then this shouldn't bother you as it is
		2139	exactly the right behaviour.
		2140
		2141	If you want to compare wall clock/system timestamps to your timers, then
		2142	you need to use C<ev_periodic>s, as these are based on the wall clock
		2143	time, where your comparisons will always generate correct results.
		2144
		2145	=head3 The special problems of suspended animation
		2146
		2147	When you leave the server world it is quite customary to hit machines that
		2148	can suspend/hibernate - what happens to the clocks during such a suspend?
		2149
		2150	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2151	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2152	to run until the system is suspended, but they will not advance while the
		2153	system is suspended. That means, on resume, it will be as if the program
		2154	was frozen for a few seconds, but the suspend time will not be counted
		2155	towards C<ev_timer> when a monotonic clock source is used. The real time
		2156	clock advanced as expected, but if it is used as sole clocksource, then a
		2157	long suspend would be detected as a time jump by libev, and timers would
		2158	be adjusted accordingly.
		2159
		2160	I would not be surprised to see different behaviour in different between
		2161	operating systems, OS versions or even different hardware.
		2162
		2163	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2164	time jump in the monotonic clocks and the realtime clock. If the program
		2165	is suspended for a very long time, and monotonic clock sources are in use,
		2166	then you can expect C<ev_timer>s to expire as the full suspension time
		2167	will be counted towards the timers. When no monotonic clock source is in
		2168	use, then libev will again assume a timejump and adjust accordingly.
		2169
		2170	It might be beneficial for this latter case to call C<ev_suspend>
		2171	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2172	deterministic behaviour in this case (you can do nothing against
		2173	C<SIGSTOP>).
1438		2174
1439	=head3 Watcher-Specific Functions and Data Members	2175	=head3 Watcher-Specific Functions and Data Members
1440		2176
1441	=over 4	2177	=over 4
1442		2178
1443	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2179	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1444		2180
1445	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2181	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1446		2182
1447	Configure the timer to trigger after C<after> seconds. If C<repeat>	2183	Configure the timer to trigger after C<after> seconds (fractional and
1448	is C<0.>, then it will automatically be stopped once the timeout is	2184	negative values are supported). If C<repeat> is C<0.>, then it will
1449	reached. If it is positive, then the timer will automatically be	2185	automatically be stopped once the timeout is reached. If it is positive,
1450	configured to trigger again C<repeat> seconds later, again, and again,	2186	then the timer will automatically be configured to trigger again C<repeat>
1451	until stopped manually.	2187	seconds later, again, and again, until stopped manually.
1452		2188
1453	The timer itself will do a best-effort at avoiding drift, that is, if	2189	The timer itself will do a best-effort at avoiding drift, that is, if
1454	you configure a timer to trigger every 10 seconds, then it will normally	2190	you configure a timer to trigger every 10 seconds, then it will normally
1455	trigger at exactly 10 second intervals. If, however, your program cannot	2191	trigger at exactly 10 second intervals. If, however, your program cannot
1456	keep up with the timer (because it takes longer than those 10 seconds to	2192	keep up with the timer (because it takes longer than those 10 seconds to
1457	do stuff) the timer will not fire more than once per event loop iteration.	2193	do stuff) the timer will not fire more than once per event loop iteration.
1458		2194
1459	=item ev_timer_again (loop, ev_timer *)	2195	=item ev_timer_again (loop, ev_timer *)
1460		2196
1461	This will act as if the timer timed out and restart it again if it is	2197	This will act as if the timer timed out, and restarts it again if it is
1462	repeating. The exact semantics are:	2198	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2199	timeout to the C<repeat> value and calling C<ev_timer_start>.
1463		2200
		2201	The exact semantics are as in the following rules, all of which will be
		2202	applied to the watcher:
		2203
		2204	=over 4
		2205
1464	If the timer is pending, its pending status is cleared.	2206	=item If the timer is pending, the pending status is always cleared.
1465		2207
1466	If the timer is started but non-repeating, stop it (as if it timed out).	2208	=item If the timer is started but non-repeating, stop it (as if it timed
		2209	out, without invoking it).
1467		2210
1468	If the timer is repeating, either start it if necessary (with the	2211	=item If the timer is repeating, make the C<repeat> value the new timeout
1469	C<repeat> value), or reset the running timer to the C<repeat> value.	2212	and start the timer, if necessary.
1470		2213
		2214	=back
		2215
1471	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2216	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1472	usage example.	2217	usage example.
		2218
		2219	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2220
		2221	Returns the remaining time until a timer fires. If the timer is active,
		2222	then this time is relative to the current event loop time, otherwise it's
		2223	the timeout value currently configured.
		2224
		2225	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2226	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2227	will return C<4>. When the timer expires and is restarted, it will return
		2228	roughly C<7> (likely slightly less as callback invocation takes some time,
		2229	too), and so on.
1473		2230
1474	=item ev_tstamp repeat [read-write]	2231	=item ev_tstamp repeat [read-write]
1475		2232
1476	The current C<repeat> value. Will be used each time the watcher times out	2233	The current C<repeat> value. Will be used each time the watcher times out
1477	or C<ev_timer_again> is called, and determines the next timeout (if any),	2234	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1503	}	2260	}
1504		2261
1505	ev_timer mytimer;	2262	ev_timer mytimer;
1506	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2263	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1507	ev_timer_again (&mytimer); /* start timer */	2264	ev_timer_again (&mytimer); /* start timer */
1508	ev_loop (loop, 0);	2265	ev_run (loop, 0);
1509		2266
1510	// and in some piece of code that gets executed on any "activity":	2267	// and in some piece of code that gets executed on any "activity":
1511	// reset the timeout to start ticking again at 10 seconds	2268	// reset the timeout to start ticking again at 10 seconds
1512	ev_timer_again (&mytimer);	2269	ev_timer_again (&mytimer);
1513		2270
…		…
1515	=head2 C<ev_periodic> - to cron or not to cron?	2272	=head2 C<ev_periodic> - to cron or not to cron?
1516		2273
1517	Periodic watchers are also timers of a kind, but they are very versatile	2274	Periodic watchers are also timers of a kind, but they are very versatile
1518	(and unfortunately a bit complex).	2275	(and unfortunately a bit complex).
1519		2276
1520	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2277	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1521	but on wall clock time (absolute time). You can tell a periodic watcher	2278	relative time, the physical time that passes) but on wall clock time
1522	to trigger after some specific point in time. For example, if you tell a	2279	(absolute time, the thing you can read on your calendar or clock). The
1523	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2280	difference is that wall clock time can run faster or slower than real
1524	+ 10.>, that is, an absolute time not a delay) and then reset your system	2281	time, and time jumps are not uncommon (e.g. when you adjust your
1525	clock to January of the previous year, then it will take more than year	2282	wrist-watch).
1526	to trigger the event (unlike an C<ev_timer>, which would still trigger
1527	roughly 10 seconds later as it uses a relative timeout).
1528		2283
		2284	You can tell a periodic watcher to trigger after some specific point
		2285	in time: for example, if you tell a periodic watcher to trigger "in 10
		2286	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2287	not a delay) and then reset your system clock to January of the previous
		2288	year, then it will take a year or more to trigger the event (unlike an
		2289	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2290	it, as it uses a relative timeout).
		2291
1529	C<ev_periodic>s can also be used to implement vastly more complex timers,	2292	C<ev_periodic> watchers can also be used to implement vastly more complex
1530	such as triggering an event on each "midnight, local time", or other	2293	timers, such as triggering an event on each "midnight, local time", or
1531	complicated rules.	2294	other complicated rules. This cannot easily be done with C<ev_timer>
		2295	watchers, as those cannot react to time jumps.
1532		2296
1533	As with timers, the callback is guaranteed to be invoked only when the	2297	As with timers, the callback is guaranteed to be invoked only when the
1534	time (C<at>) has passed, but if multiple periodic timers become ready	2298	point in time where it is supposed to trigger has passed. If multiple
1535	during the same loop iteration, then order of execution is undefined.	2299	timers become ready during the same loop iteration then the ones with
		2300	earlier time-out values are invoked before ones with later time-out values
		2301	(but this is no longer true when a callback calls C<ev_run> recursively).
1536		2302
1537	=head3 Watcher-Specific Functions and Data Members	2303	=head3 Watcher-Specific Functions and Data Members
1538		2304
1539	=over 4	2305	=over 4
1540		2306
1541	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2307	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1542		2308
1543	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2309	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1544		2310
1545	Lots of arguments, lets sort it out... There are basically three modes of	2311	Lots of arguments, let's sort it out... There are basically three modes of
1546	operation, and we will explain them from simplest to most complex:	2312	operation, and we will explain them from simplest to most complex:
1547		2313
1548	=over 4	2314	=over 4
1549		2315
1550	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2316	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1551		2317
1552	In this configuration the watcher triggers an event after the wall clock	2318	In this configuration the watcher triggers an event after the wall clock
1553	time C<at> has passed. It will not repeat and will not adjust when a time	2319	time C<offset> has passed. It will not repeat and will not adjust when a
1554	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2320	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1555	only run when the system clock reaches or surpasses this time.	2321	will be stopped and invoked when the system clock reaches or surpasses
		2322	this point in time.
1556		2323
1557	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2324	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1558		2325
1559	In this mode the watcher will always be scheduled to time out at the next	2326	In this mode the watcher will always be scheduled to time out at the next
1560	C<at + N * interval> time (for some integer N, which can also be negative)	2327	C<offset + N * interval> time (for some integer N, which can also be
1561	and then repeat, regardless of any time jumps.	2328	negative) and then repeat, regardless of any time jumps. The C<offset>
		2329	argument is merely an offset into the C<interval> periods.
1562		2330
1563	This can be used to create timers that do not drift with respect to the	2331	This can be used to create timers that do not drift with respect to the
1564	system clock, for example, here is a C<ev_periodic> that triggers each	2332	system clock, for example, here is an C<ev_periodic> that triggers each
1565	hour, on the hour:	2333	hour, on the hour (with respect to UTC):
1566		2334
1567	ev_periodic_set (&periodic, 0., 3600., 0);	2335	ev_periodic_set (&periodic, 0., 3600., 0);
1568		2336
1569	This doesn't mean there will always be 3600 seconds in between triggers,	2337	This doesn't mean there will always be 3600 seconds in between triggers,
1570	but only that the callback will be called when the system time shows a	2338	but only that the callback will be called when the system time shows a
1571	full hour (UTC), or more correctly, when the system time is evenly divisible	2339	full hour (UTC), or more correctly, when the system time is evenly divisible
1572	by 3600.	2340	by 3600.
1573		2341
1574	Another way to think about it (for the mathematically inclined) is that	2342	Another way to think about it (for the mathematically inclined) is that
1575	C<ev_periodic> will try to run the callback in this mode at the next possible	2343	C<ev_periodic> will try to run the callback in this mode at the next possible
1576	time where C<time = at (mod interval)>, regardless of any time jumps.	2344	time where C<time = offset (mod interval)>, regardless of any time jumps.
1577		2345
1578	For numerical stability it is preferable that the C<at> value is near	2346	The C<interval> I<MUST> be positive, and for numerical stability, the
1579	C<ev_now ()> (the current time), but there is no range requirement for	2347	interval value should be higher than C<1/8192> (which is around 100
1580	this value, and in fact is often specified as zero.	2348	microseconds) and C<offset> should be higher than C<0> and should have
		2349	at most a similar magnitude as the current time (say, within a factor of
		2350	ten). Typical values for offset are, in fact, C<0> or something between
		2351	C<0> and C<interval>, which is also the recommended range.
1581		2352
1582	Note also that there is an upper limit to how often a timer can fire (CPU	2353	Note also that there is an upper limit to how often a timer can fire (CPU
1583	speed for example), so if C<interval> is very small then timing stability	2354	speed for example), so if C<interval> is very small then timing stability
1584	will of course deteriorate. Libev itself tries to be exact to be about one	2355	will of course deteriorate. Libev itself tries to be exact to be about one
1585	millisecond (if the OS supports it and the machine is fast enough).	2356	millisecond (if the OS supports it and the machine is fast enough).
1586		2357
1587	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2358	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1588		2359
1589	In this mode the values for C<interval> and C<at> are both being	2360	In this mode the values for C<interval> and C<offset> are both being
1590	ignored. Instead, each time the periodic watcher gets scheduled, the	2361	ignored. Instead, each time the periodic watcher gets scheduled, the
1591	reschedule callback will be called with the watcher as first, and the	2362	reschedule callback will be called with the watcher as first, and the
1592	current time as second argument.	2363	current time as second argument.
1593		2364
1594	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2365	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1595	ever, or make ANY event loop modifications whatsoever>.	2366	or make ANY other event loop modifications whatsoever, unless explicitly
		2367	allowed by documentation here>.
1596		2368
1597	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2369	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1598	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2370	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1599	only event loop modification you are allowed to do).	2371	only event loop modification you are allowed to do).
1600		2372
…		…
1614		2386
1615	NOTE: I<< This callback must always return a time that is higher than or	2387	NOTE: I<< This callback must always return a time that is higher than or
1616	equal to the passed C<now> value >>.	2388	equal to the passed C<now> value >>.
1617		2389
1618	This can be used to create very complex timers, such as a timer that	2390	This can be used to create very complex timers, such as a timer that
1619	triggers on "next midnight, local time". To do this, you would calculate the	2391	triggers on "next midnight, local time". To do this, you would calculate
1620	next midnight after C<now> and return the timestamp value for this. How	2392	the next midnight after C<now> and return the timestamp value for
1621	you do this is, again, up to you (but it is not trivial, which is the main	2393	this. Here is a (completely untested, no error checking) example on how to
1622	reason I omitted it as an example).	2394	do this:
		2395
		2396	#include <time.h>
		2397
		2398	static ev_tstamp
		2399	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2400	{
		2401	time_t tnow = (time_t)now;
		2402	struct tm tm;
		2403	localtime_r (&tnow, &tm);
		2404
		2405	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2406	++tm.tm_mday; // midnight next day
		2407
		2408	return mktime (&tm);
		2409	}
		2410
		2411	Note: this code might run into trouble on days that have more then two
		2412	midnights (beginning and end).
1623		2413
1624	=back	2414	=back
1625		2415
1626	=item ev_periodic_again (loop, ev_periodic *)	2416	=item ev_periodic_again (loop, ev_periodic *)
1627		2417
…		…
1630	a different time than the last time it was called (e.g. in a crond like	2420	a different time than the last time it was called (e.g. in a crond like
1631	program when the crontabs have changed).	2421	program when the crontabs have changed).
1632		2422
1633	=item ev_tstamp ev_periodic_at (ev_periodic *)	2423	=item ev_tstamp ev_periodic_at (ev_periodic *)
1634		2424
1635	When active, returns the absolute time that the watcher is supposed to	2425	When active, returns the absolute time that the watcher is supposed
1636	trigger next.	2426	to trigger next. This is not the same as the C<offset> argument to
		2427	C<ev_periodic_set>, but indeed works even in interval and manual
		2428	rescheduling modes.
1637		2429
1638	=item ev_tstamp offset [read-write]	2430	=item ev_tstamp offset [read-write]
1639		2431
1640	When repeating, this contains the offset value, otherwise this is the	2432	When repeating, this contains the offset value, otherwise this is the
1641	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2433	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2434	although libev might modify this value for better numerical stability).
1642		2435
1643	Can be modified any time, but changes only take effect when the periodic	2436	Can be modified any time, but changes only take effect when the periodic
1644	timer fires or C<ev_periodic_again> is being called.	2437	timer fires or C<ev_periodic_again> is being called.
1645		2438
1646	=item ev_tstamp interval [read-write]	2439	=item ev_tstamp interval [read-write]
…		…
1662	Example: Call a callback every hour, or, more precisely, whenever the	2455	Example: Call a callback every hour, or, more precisely, whenever the
1663	system time is divisible by 3600. The callback invocation times have	2456	system time is divisible by 3600. The callback invocation times have
1664	potentially a lot of jitter, but good long-term stability.	2457	potentially a lot of jitter, but good long-term stability.
1665		2458
1666	static void	2459	static void
1667	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2460	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1668	{	2461	{
1669	... its now a full hour (UTC, or TAI or whatever your clock follows)	2462	... its now a full hour (UTC, or TAI or whatever your clock follows)
1670	}	2463	}
1671		2464
1672	ev_periodic hourly_tick;	2465	ev_periodic hourly_tick;
…		…
1689		2482
1690	ev_periodic hourly_tick;	2483	ev_periodic hourly_tick;
1691	ev_periodic_init (&hourly_tick, clock_cb,	2484	ev_periodic_init (&hourly_tick, clock_cb,
1692	fmod (ev_now (loop), 3600.), 3600., 0);	2485	fmod (ev_now (loop), 3600.), 3600., 0);
1693	ev_periodic_start (loop, &hourly_tick);	2486	ev_periodic_start (loop, &hourly_tick);
1694		2487
1695		2488
1696	=head2 C<ev_signal> - signal me when a signal gets signalled!	2489	=head2 C<ev_signal> - signal me when a signal gets signalled!
1697		2490
1698	Signal watchers will trigger an event when the process receives a specific	2491	Signal watchers will trigger an event when the process receives a specific
1699	signal one or more times. Even though signals are very asynchronous, libev	2492	signal one or more times. Even though signals are very asynchronous, libev
1700	will try it's best to deliver signals synchronously, i.e. as part of the	2493	will try its best to deliver signals synchronously, i.e. as part of the
1701	normal event processing, like any other event.	2494	normal event processing, like any other event.
1702		2495
1703	If you want signals asynchronously, just use C<sigaction> as you would	2496	If you want signals to be delivered truly asynchronously, just use
1704	do without libev and forget about sharing the signal. You can even use	2497	C<sigaction> as you would do without libev and forget about sharing
1705	C<ev_async> from a signal handler to synchronously wake up an event loop.	2498	the signal. You can even use C<ev_async> from a signal handler to
		2499	synchronously wake up an event loop.
1706		2500
1707	You can configure as many watchers as you like per signal. Only when the	2501	You can configure as many watchers as you like for the same signal, but
1708	first watcher gets started will libev actually register a signal handler	2502	only within the same loop, i.e. you can watch for C<SIGINT> in your
1709	with the kernel (thus it coexists with your own signal handlers as long as	2503	default loop and for C<SIGIO> in another loop, but you cannot watch for
1710	you don't register any with libev for the same signal). Similarly, when	2504	C<SIGINT> in both the default loop and another loop at the same time. At
1711	the last signal watcher for a signal is stopped, libev will reset the	2505	the moment, C<SIGCHLD> is permanently tied to the default loop.
1712	signal handler to SIG_DFL (regardless of what it was set to before).	2506
		2507	Only after the first watcher for a signal is started will libev actually
		2508	register something with the kernel. It thus coexists with your own signal
		2509	handlers as long as you don't register any with libev for the same signal.
1713		2510
1714	If possible and supported, libev will install its handlers with	2511	If possible and supported, libev will install its handlers with
1715	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2512	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1716	interrupted. If you have a problem with system calls getting interrupted by	2513	not be unduly interrupted. If you have a problem with system calls getting
1717	signals you can block all signals in an C<ev_check> watcher and unblock	2514	interrupted by signals you can block all signals in an C<ev_check> watcher
1718	them in an C<ev_prepare> watcher.	2515	and unblock them in an C<ev_prepare> watcher.
		2516
		2517	=head3 The special problem of inheritance over fork/execve/pthread_create
		2518
		2519	Both the signal mask (C<sigprocmask>) and the signal disposition
		2520	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2521	stopping it again), that is, libev might or might not block the signal,
		2522	and might or might not set or restore the installed signal handler (but
		2523	see C<EVFLAG_NOSIGMASK>).
		2524
		2525	While this does not matter for the signal disposition (libev never
		2526	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2527	C<execve>), this matters for the signal mask: many programs do not expect
		2528	certain signals to be blocked.
		2529
		2530	This means that before calling C<exec> (from the child) you should reset
		2531	the signal mask to whatever "default" you expect (all clear is a good
		2532	choice usually).
		2533
		2534	The simplest way to ensure that the signal mask is reset in the child is
		2535	to install a fork handler with C<pthread_atfork> that resets it. That will
		2536	catch fork calls done by libraries (such as the libc) as well.
		2537
		2538	In current versions of libev, the signal will not be blocked indefinitely
		2539	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2540	the window of opportunity for problems, it will not go away, as libev
		2541	I<has> to modify the signal mask, at least temporarily.
		2542
		2543	So I can't stress this enough: I<If you do not reset your signal mask when
		2544	you expect it to be empty, you have a race condition in your code>. This
		2545	is not a libev-specific thing, this is true for most event libraries.
		2546
		2547	=head3 The special problem of threads signal handling
		2548
		2549	POSIX threads has problematic signal handling semantics, specifically,
		2550	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2551	threads in a process block signals, which is hard to achieve.
		2552
		2553	When you want to use sigwait (or mix libev signal handling with your own
		2554	for the same signals), you can tackle this problem by globally blocking
		2555	all signals before creating any threads (or creating them with a fully set
		2556	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2557	loops. Then designate one thread as "signal receiver thread" which handles
		2558	these signals. You can pass on any signals that libev might be interested
		2559	in by calling C<ev_feed_signal>.
1719		2560
1720	=head3 Watcher-Specific Functions and Data Members	2561	=head3 Watcher-Specific Functions and Data Members
1721		2562
1722	=over 4	2563	=over 4
1723		2564
…		…
1739	Example: Try to exit cleanly on SIGINT.	2580	Example: Try to exit cleanly on SIGINT.
1740		2581
1741	static void	2582	static void
1742	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2583	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1743	{	2584	{
1744	ev_unloop (loop, EVUNLOOP_ALL);	2585	ev_break (loop, EVBREAK_ALL);
1745	}	2586	}
1746		2587
1747	ev_signal signal_watcher;	2588	ev_signal signal_watcher;
1748	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2589	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1749	ev_signal_start (loop, &signal_watcher);	2590	ev_signal_start (loop, &signal_watcher);
…		…
1755	some child status changes (most typically when a child of yours dies or	2596	some child status changes (most typically when a child of yours dies or
1756	exits). It is permissible to install a child watcher I<after> the child	2597	exits). It is permissible to install a child watcher I<after> the child
1757	has been forked (which implies it might have already exited), as long	2598	has been forked (which implies it might have already exited), as long
1758	as the event loop isn't entered (or is continued from a watcher), i.e.,	2599	as the event loop isn't entered (or is continued from a watcher), i.e.,
1759	forking and then immediately registering a watcher for the child is fine,	2600	forking and then immediately registering a watcher for the child is fine,
1760	but forking and registering a watcher a few event loop iterations later is	2601	but forking and registering a watcher a few event loop iterations later or
1761	not.	2602	in the next callback invocation is not.
1762		2603
1763	Only the default event loop is capable of handling signals, and therefore	2604	Only the default event loop is capable of handling signals, and therefore
1764	you can only register child watchers in the default event loop.	2605	you can only register child watchers in the default event loop.
1765		2606
		2607	Due to some design glitches inside libev, child watchers will always be
		2608	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2609	libev)
		2610
1766	=head3 Process Interaction	2611	=head3 Process Interaction
1767		2612
1768	Libev grabs C<SIGCHLD> as soon as the default event loop is	2613	Libev grabs C<SIGCHLD> as soon as the default event loop is
1769	initialised. This is necessary to guarantee proper behaviour even if	2614	initialised. This is necessary to guarantee proper behaviour even if the
1770	the first child watcher is started after the child exits. The occurrence	2615	first child watcher is started after the child exits. The occurrence
1771	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2616	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1772	synchronously as part of the event loop processing. Libev always reaps all	2617	synchronously as part of the event loop processing. Libev always reaps all
1773	children, even ones not watched.	2618	children, even ones not watched.
1774		2619
1775	=head3 Overriding the Built-In Processing	2620	=head3 Overriding the Built-In Processing
…		…
1785	=head3 Stopping the Child Watcher	2630	=head3 Stopping the Child Watcher
1786		2631
1787	Currently, the child watcher never gets stopped, even when the	2632	Currently, the child watcher never gets stopped, even when the
1788	child terminates, so normally one needs to stop the watcher in the	2633	child terminates, so normally one needs to stop the watcher in the
1789	callback. Future versions of libev might stop the watcher automatically	2634	callback. Future versions of libev might stop the watcher automatically
1790	when a child exit is detected.	2635	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2636	problem).
1791		2637
1792	=head3 Watcher-Specific Functions and Data Members	2638	=head3 Watcher-Specific Functions and Data Members
1793		2639
1794	=over 4	2640	=over 4
1795		2641
…		…
1852		2698
1853		2699
1854	=head2 C<ev_stat> - did the file attributes just change?	2700	=head2 C<ev_stat> - did the file attributes just change?
1855		2701
1856	This watches a file system path for attribute changes. That is, it calls	2702	This watches a file system path for attribute changes. That is, it calls
1857	C<stat> regularly (or when the OS says it changed) and sees if it changed	2703	C<stat> on that path in regular intervals (or when the OS says it changed)
1858	compared to the last time, invoking the callback if it did.	2704	and sees if it changed compared to the last time, invoking the callback
		2705	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2706	happen after the watcher has been started will be reported.
1859		2707
1860	The path does not need to exist: changing from "path exists" to "path does	2708	The path does not need to exist: changing from "path exists" to "path does
1861	not exist" is a status change like any other. The condition "path does	2709	not exist" is a status change like any other. The condition "path does not
1862	not exist" is signified by the C<st_nlink> field being zero (which is	2710	exist" (or more correctly "path cannot be stat'ed") is signified by the
1863	otherwise always forced to be at least one) and all the other fields of	2711	C<st_nlink> field being zero (which is otherwise always forced to be at
1864	the stat buffer having unspecified contents.	2712	least one) and all the other fields of the stat buffer having unspecified
		2713	contents.
1865		2714
1866	The path I<should> be absolute and I<must not> end in a slash. If it is	2715	The path I<must not> end in a slash or contain special components such as
		2716	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1867	relative and your working directory changes, the behaviour is undefined.	2717	your working directory changes, then the behaviour is undefined.
1868		2718
1869	Since there is no standard kernel interface to do this, the portable	2719	Since there is no portable change notification interface available, the
1870	implementation simply calls C<stat (2)> regularly on the path to see if	2720	portable implementation simply calls C<stat(2)> regularly on the path
1871	it changed somehow. You can specify a recommended polling interval for	2721	to see if it changed somehow. You can specify a recommended polling
1872	this case. If you specify a polling interval of C<0> (highly recommended!)	2722	interval for this case. If you specify a polling interval of C<0> (highly
1873	then a I<suitable, unspecified default> value will be used (which	2723	recommended!) then a I<suitable, unspecified default> value will be used
1874	you can expect to be around five seconds, although this might change	2724	(which you can expect to be around five seconds, although this might
1875	dynamically). Libev will also impose a minimum interval which is currently	2725	change dynamically). Libev will also impose a minimum interval which is
1876	around C<0.1>, but thats usually overkill.	2726	currently around C<0.1>, but that's usually overkill.
1877		2727
1878	This watcher type is not meant for massive numbers of stat watchers,	2728	This watcher type is not meant for massive numbers of stat watchers,
1879	as even with OS-supported change notifications, this can be	2729	as even with OS-supported change notifications, this can be
1880	resource-intensive.	2730	resource-intensive.
1881		2731
1882	At the time of this writing, the only OS-specific interface implemented	2732	At the time of this writing, the only OS-specific interface implemented
1883	is the Linux inotify interface (implementing kqueue support is left as	2733	is the Linux inotify interface (implementing kqueue support is left as an
1884	an exercise for the reader. Note, however, that the author sees no way	2734	exercise for the reader. Note, however, that the author sees no way of
1885	of implementing C<ev_stat> semantics with kqueue).	2735	implementing C<ev_stat> semantics with kqueue, except as a hint).
1886		2736
1887	=head3 ABI Issues (Largefile Support)	2737	=head3 ABI Issues (Largefile Support)
1888		2738
1889	Libev by default (unless the user overrides this) uses the default	2739	Libev by default (unless the user overrides this) uses the default
1890	compilation environment, which means that on systems with large file	2740	compilation environment, which means that on systems with large file
1891	support disabled by default, you get the 32 bit version of the stat	2741	support disabled by default, you get the 32 bit version of the stat
1892	structure. When using the library from programs that change the ABI to	2742	structure. When using the library from programs that change the ABI to
1893	use 64 bit file offsets the programs will fail. In that case you have to	2743	use 64 bit file offsets the programs will fail. In that case you have to
1894	compile libev with the same flags to get binary compatibility. This is	2744	compile libev with the same flags to get binary compatibility. This is
1895	obviously the case with any flags that change the ABI, but the problem is	2745	obviously the case with any flags that change the ABI, but the problem is
1896	most noticeably disabled with ev_stat and large file support.	2746	most noticeably displayed with ev_stat and large file support.
1897		2747
1898	The solution for this is to lobby your distribution maker to make large	2748	The solution for this is to lobby your distribution maker to make large
1899	file interfaces available by default (as e.g. FreeBSD does) and not	2749	file interfaces available by default (as e.g. FreeBSD does) and not
1900	optional. Libev cannot simply switch on large file support because it has	2750	optional. Libev cannot simply switch on large file support because it has
1901	to exchange stat structures with application programs compiled using the	2751	to exchange stat structures with application programs compiled using the
1902	default compilation environment.	2752	default compilation environment.
1903		2753
1904	=head3 Inotify and Kqueue	2754	=head3 Inotify and Kqueue
1905		2755
1906	When C<inotify (7)> support has been compiled into libev (generally	2756	When C<inotify (7)> support has been compiled into libev and present at
1907	only available with Linux 2.6.25 or above due to bugs in earlier	2757	runtime, it will be used to speed up change detection where possible. The
1908	implementations) and present at runtime, it will be used to speed up	2758	inotify descriptor will be created lazily when the first C<ev_stat>
1909	change detection where possible. The inotify descriptor will be created	2759	watcher is being started.
1910	lazily when the first C<ev_stat> watcher is being started.
1911		2760
1912	Inotify presence does not change the semantics of C<ev_stat> watchers	2761	Inotify presence does not change the semantics of C<ev_stat> watchers
1913	except that changes might be detected earlier, and in some cases, to avoid	2762	except that changes might be detected earlier, and in some cases, to avoid
1914	making regular C<stat> calls. Even in the presence of inotify support	2763	making regular C<stat> calls. Even in the presence of inotify support
1915	there are many cases where libev has to resort to regular C<stat> polling,	2764	there are many cases where libev has to resort to regular C<stat> polling,
1916	but as long as the path exists, libev usually gets away without polling.	2765	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2766	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2767	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2768	xfs are fully working) libev usually gets away without polling.
1917		2769
1918	There is no support for kqueue, as apparently it cannot be used to	2770	There is no support for kqueue, as apparently it cannot be used to
1919	implement this functionality, due to the requirement of having a file	2771	implement this functionality, due to the requirement of having a file
1920	descriptor open on the object at all times, and detecting renames, unlinks	2772	descriptor open on the object at all times, and detecting renames, unlinks
1921	etc. is difficult.	2773	etc. is difficult.
1922		2774
		2775	=head3 C<stat ()> is a synchronous operation
		2776
		2777	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2778	the process. The exception are C<ev_stat> watchers - those call C<stat
		2779	()>, which is a synchronous operation.
		2780
		2781	For local paths, this usually doesn't matter: unless the system is very
		2782	busy or the intervals between stat's are large, a stat call will be fast,
		2783	as the path data is usually in memory already (except when starting the
		2784	watcher).
		2785
		2786	For networked file systems, calling C<stat ()> can block an indefinite
		2787	time due to network issues, and even under good conditions, a stat call
		2788	often takes multiple milliseconds.
		2789
		2790	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2791	paths, although this is fully supported by libev.
		2792
1923	=head3 The special problem of stat time resolution	2793	=head3 The special problem of stat time resolution
1924		2794
1925	The C<stat ()> system call only supports full-second resolution portably, and	2795	The C<stat ()> system call only supports full-second resolution portably,
1926	even on systems where the resolution is higher, most file systems still	2796	and even on systems where the resolution is higher, most file systems
1927	only support whole seconds.	2797	still only support whole seconds.
1928		2798
1929	That means that, if the time is the only thing that changes, you can	2799	That means that, if the time is the only thing that changes, you can
1930	easily miss updates: on the first update, C<ev_stat> detects a change and	2800	easily miss updates: on the first update, C<ev_stat> detects a change and
1931	calls your callback, which does something. When there is another update	2801	calls your callback, which does something. When there is another update
1932	within the same second, C<ev_stat> will be unable to detect unless the	2802	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2071	Apart from keeping your process non-blocking (which is a useful	2941	Apart from keeping your process non-blocking (which is a useful
2072	effect on its own sometimes), idle watchers are a good place to do	2942	effect on its own sometimes), idle watchers are a good place to do
2073	"pseudo-background processing", or delay processing stuff to after the	2943	"pseudo-background processing", or delay processing stuff to after the
2074	event loop has handled all outstanding events.	2944	event loop has handled all outstanding events.
2075		2945
		2946	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2947
		2948	As long as there is at least one active idle watcher, libev will never
		2949	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2950	For this to work, the idle watcher doesn't need to be invoked at all - the
		2951	lowest priority will do.
		2952
		2953	This mode of operation can be useful together with an C<ev_check> watcher,
		2954	to do something on each event loop iteration - for example to balance load
		2955	between different connections.
		2956
		2957	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2958	example.
		2959
2076	=head3 Watcher-Specific Functions and Data Members	2960	=head3 Watcher-Specific Functions and Data Members
2077		2961
2078	=over 4	2962	=over 4
2079		2963
2080	=item ev_idle_init (ev_signal *, callback)	2964	=item ev_idle_init (ev_idle *, callback)
2081		2965
2082	Initialises and configures the idle watcher - it has no parameters of any	2966	Initialises and configures the idle watcher - it has no parameters of any
2083	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2967	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2084	believe me.	2968	believe me.
2085		2969
…		…
2091	callback, free it. Also, use no error checking, as usual.	2975	callback, free it. Also, use no error checking, as usual.
2092		2976
2093	static void	2977	static void
2094	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2978	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2095	{	2979	{
		2980	// stop the watcher
		2981	ev_idle_stop (loop, w);
		2982
		2983	// now we can free it
2096	free (w);	2984	free (w);
		2985
2097	// now do something you wanted to do when the program has	2986	// now do something you wanted to do when the program has
2098	// no longer anything immediate to do.	2987	// no longer anything immediate to do.
2099	}	2988	}
2100		2989
2101	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2990	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2102	ev_idle_init (idle_watcher, idle_cb);	2991	ev_idle_init (idle_watcher, idle_cb);
2103	ev_idle_start (loop, idle_cb);	2992	ev_idle_start (loop, idle_watcher);
2104		2993
2105		2994
2106	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2995	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2107		2996
2108	Prepare and check watchers are usually (but not always) used in pairs:	2997	Prepare and check watchers are often (but not always) used in pairs:
2109	prepare watchers get invoked before the process blocks and check watchers	2998	prepare watchers get invoked before the process blocks and check watchers
2110	afterwards.	2999	afterwards.
2111		3000
2112	You I<must not> call C<ev_loop> or similar functions that enter	3001	You I<must not> call C<ev_run> (or similar functions that enter the
2113	the current event loop from either C<ev_prepare> or C<ev_check>	3002	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2114	watchers. Other loops than the current one are fine, however. The	3003	C<ev_check> watchers. Other loops than the current one are fine,
2115	rationale behind this is that you do not need to check for recursion in	3004	however. The rationale behind this is that you do not need to check
2116	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3005	for recursion in those watchers, i.e. the sequence will always be
2117	C<ev_check> so if you have one watcher of each kind they will always be	3006	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2118	called in pairs bracketing the blocking call.	3007	kind they will always be called in pairs bracketing the blocking call.
2119		3008
2120	Their main purpose is to integrate other event mechanisms into libev and	3009	Their main purpose is to integrate other event mechanisms into libev and
2121	their use is somewhat advanced. They could be used, for example, to track	3010	their use is somewhat advanced. They could be used, for example, to track
2122	variable changes, implement your own watchers, integrate net-snmp or a	3011	variable changes, implement your own watchers, integrate net-snmp or a
2123	coroutine library and lots more. They are also occasionally useful if	3012	coroutine library and lots more. They are also occasionally useful if
…		…
2141	with priority higher than or equal to the event loop and one coroutine	3030	with priority higher than or equal to the event loop and one coroutine
2142	of lower priority, but only once, using idle watchers to keep the event	3031	of lower priority, but only once, using idle watchers to keep the event
2143	loop from blocking if lower-priority coroutines are active, thus mapping	3032	loop from blocking if lower-priority coroutines are active, thus mapping
2144	low-priority coroutines to idle/background tasks).	3033	low-priority coroutines to idle/background tasks).
2145		3034
2146	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3035	When used for this purpose, it is recommended to give C<ev_check> watchers
2147	priority, to ensure that they are being run before any other watchers	3036	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2148	after the poll (this doesn't matter for C<ev_prepare> watchers).	3037	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3038	watchers).
2149		3039
2150	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3040	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2151	activate ("feed") events into libev. While libev fully supports this, they	3041	activate ("feed") events into libev. While libev fully supports this, they
2152	might get executed before other C<ev_check> watchers did their job. As	3042	might get executed before other C<ev_check> watchers did their job. As
2153	C<ev_check> watchers are often used to embed other (non-libev) event	3043	C<ev_check> watchers are often used to embed other (non-libev) event
2154	loops those other event loops might be in an unusable state until their	3044	loops those other event loops might be in an unusable state until their
2155	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3045	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2156	others).	3046	others).
		3047
		3048	=head3 Abusing an C<ev_check> watcher for its side-effect
		3049
		3050	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3051	useful because they are called once per event loop iteration. For
		3052	example, if you want to handle a large number of connections fairly, you
		3053	normally only do a bit of work for each active connection, and if there
		3054	is more work to do, you wait for the next event loop iteration, so other
		3055	connections have a chance of making progress.
		3056
		3057	Using an C<ev_check> watcher is almost enough: it will be called on the
		3058	next event loop iteration. However, that isn't as soon as possible -
		3059	without external events, your C<ev_check> watcher will not be invoked.
		3060
		3061	This is where C<ev_idle> watchers come in handy - all you need is a
		3062	single global idle watcher that is active as long as you have one active
		3063	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3064	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3065	invoked. Neither watcher alone can do that.
2157		3066
2158	=head3 Watcher-Specific Functions and Data Members	3067	=head3 Watcher-Specific Functions and Data Members
2159		3068
2160	=over 4	3069	=over 4
2161		3070
…		…
2201	struct pollfd fds [nfd];	3110	struct pollfd fds [nfd];
2202	// actual code will need to loop here and realloc etc.	3111	// actual code will need to loop here and realloc etc.
2203	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3112	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2204		3113
2205	/* the callback is illegal, but won't be called as we stop during check */	3114	/* the callback is illegal, but won't be called as we stop during check */
2206	ev_timer_init (&tw, 0, timeout * 1e-3);	3115	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2207	ev_timer_start (loop, &tw);	3116	ev_timer_start (loop, &tw);
2208		3117
2209	// create one ev_io per pollfd	3118	// create one ev_io per pollfd
2210	for (int i = 0; i < nfd; ++i)	3119	for (int i = 0; i < nfd; ++i)
2211	{	3120	{
…		…
2285		3194
2286	if (timeout >= 0)	3195	if (timeout >= 0)
2287	// create/start timer	3196	// create/start timer
2288		3197
2289	// poll	3198	// poll
2290	ev_loop (EV_A_ 0);	3199	ev_run (EV_A_ 0);
2291		3200
2292	// stop timer again	3201	// stop timer again
2293	if (timeout >= 0)	3202	if (timeout >= 0)
2294	ev_timer_stop (EV_A_ &to);	3203	ev_timer_stop (EV_A_ &to);
2295		3204
…		…
2324	some fds have to be watched and handled very quickly (with low latency),	3233	some fds have to be watched and handled very quickly (with low latency),
2325	and even priorities and idle watchers might have too much overhead. In	3234	and even priorities and idle watchers might have too much overhead. In
2326	this case you would put all the high priority stuff in one loop and all	3235	this case you would put all the high priority stuff in one loop and all
2327	the rest in a second one, and embed the second one in the first.	3236	the rest in a second one, and embed the second one in the first.
2328		3237
2329	As long as the watcher is active, the callback will be invoked every time	3238	As long as the watcher is active, the callback will be invoked every
2330	there might be events pending in the embedded loop. The callback must then	3239	time there might be events pending in the embedded loop. The callback
2331	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3240	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2332	their callbacks (you could also start an idle watcher to give the embedded	3241	sweep and invoke their callbacks (the callback doesn't need to invoke the
2333	loop strictly lower priority for example). You can also set the callback	3242	C<ev_embed_sweep> function directly, it could also start an idle watcher
2334	to C<0>, in which case the embed watcher will automatically execute the	3243	to give the embedded loop strictly lower priority for example).
2335	embedded loop sweep.
2336		3244
2337	As long as the watcher is started it will automatically handle events. The	3245	You can also set the callback to C<0>, in which case the embed watcher
2338	callback will be invoked whenever some events have been handled. You can	3246	will automatically execute the embedded loop sweep whenever necessary.
2339	set the callback to C<0> to avoid having to specify one if you are not
2340	interested in that.
2341		3247
2342	Also, there have not currently been made special provisions for forking:	3248	Fork detection will be handled transparently while the C<ev_embed> watcher
2343	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3249	is active, i.e., the embedded loop will automatically be forked when the
2344	but you will also have to stop and restart any C<ev_embed> watchers	3250	embedding loop forks. In other cases, the user is responsible for calling
2345	yourself - but you can use a fork watcher to handle this automatically,	3251	C<ev_loop_fork> on the embedded loop.
2346	and future versions of libev might do just that.
2347		3252
2348	Unfortunately, not all backends are embeddable: only the ones returned by	3253	Unfortunately, not all backends are embeddable: only the ones returned by
2349	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3254	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2350	portable one.	3255	portable one.
2351		3256
…		…
2366		3271
2367	=over 4	3272	=over 4
2368		3273
2369	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3274	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2370		3275
2371	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3276	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2372		3277
2373	Configures the watcher to embed the given loop, which must be	3278	Configures the watcher to embed the given loop, which must be
2374	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3279	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2375	invoked automatically, otherwise it is the responsibility of the callback	3280	invoked automatically, otherwise it is the responsibility of the callback
2376	to invoke it (it will continue to be called until the sweep has been done,	3281	to invoke it (it will continue to be called until the sweep has been done,
2377	if you do not want that, you need to temporarily stop the embed watcher).	3282	if you do not want that, you need to temporarily stop the embed watcher).
2378		3283
2379	=item ev_embed_sweep (loop, ev_embed *)	3284	=item ev_embed_sweep (loop, ev_embed *)
2380		3285
2381	Make a single, non-blocking sweep over the embedded loop. This works	3286	Make a single, non-blocking sweep over the embedded loop. This works
2382	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3287	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2383	appropriate way for embedded loops.	3288	appropriate way for embedded loops.
2384		3289
2385	=item struct ev_loop *other [read-only]	3290	=item struct ev_loop *other [read-only]
2386		3291
2387	The embedded event loop.	3292	The embedded event loop.
…		…
2397	used).	3302	used).
2398		3303
2399	struct ev_loop *loop_hi = ev_default_init (0);	3304	struct ev_loop *loop_hi = ev_default_init (0);
2400	struct ev_loop *loop_lo = 0;	3305	struct ev_loop *loop_lo = 0;
2401	ev_embed embed;	3306	ev_embed embed;
2402		3307
2403	// see if there is a chance of getting one that works	3308	// see if there is a chance of getting one that works
2404	// (remember that a flags value of 0 means autodetection)	3309	// (remember that a flags value of 0 means autodetection)
2405	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3310	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2406	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3311	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2407	: 0;	3312	: 0;
…		…
2421	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3326	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2422		3327
2423	struct ev_loop *loop = ev_default_init (0);	3328	struct ev_loop *loop = ev_default_init (0);
2424	struct ev_loop *loop_socket = 0;	3329	struct ev_loop *loop_socket = 0;
2425	ev_embed embed;	3330	ev_embed embed;
2426		3331
2427	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3332	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2428	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3333	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2429	{	3334	{
2430	ev_embed_init (&embed, 0, loop_socket);	3335	ev_embed_init (&embed, 0, loop_socket);
2431	ev_embed_start (loop, &embed);	3336	ev_embed_start (loop, &embed);
…		…
2439		3344
2440	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3345	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2441		3346
2442	Fork watchers are called when a C<fork ()> was detected (usually because	3347	Fork watchers are called when a C<fork ()> was detected (usually because
2443	whoever is a good citizen cared to tell libev about it by calling	3348	whoever is a good citizen cared to tell libev about it by calling
2444	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3349	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2445	event loop blocks next and before C<ev_check> watchers are being called,	3350	and before C<ev_check> watchers are being called, and only in the child
2446	and only in the child after the fork. If whoever good citizen calling	3351	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2447	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3352	and calls it in the wrong process, the fork handlers will be invoked, too,
2448	handlers will be invoked, too, of course.	3353	of course.
		3354
		3355	=head3 The special problem of life after fork - how is it possible?
		3356
		3357	Most uses of C<fork ()> consist of forking, then some simple calls to set
		3358	up/change the process environment, followed by a call to C<exec()>. This
		3359	sequence should be handled by libev without any problems.
		3360
		3361	This changes when the application actually wants to do event handling
		3362	in the child, or both parent in child, in effect "continuing" after the
		3363	fork.
		3364
		3365	The default mode of operation (for libev, with application help to detect
		3366	forks) is to duplicate all the state in the child, as would be expected
		3367	when I<either> the parent I<or> the child process continues.
		3368
		3369	When both processes want to continue using libev, then this is usually the
		3370	wrong result. In that case, usually one process (typically the parent) is
		3371	supposed to continue with all watchers in place as before, while the other
		3372	process typically wants to start fresh, i.e. without any active watchers.
		3373
		3374	The cleanest and most efficient way to achieve that with libev is to
		3375	simply create a new event loop, which of course will be "empty", and
		3376	use that for new watchers. This has the advantage of not touching more
		3377	memory than necessary, and thus avoiding the copy-on-write, and the
		3378	disadvantage of having to use multiple event loops (which do not support
		3379	signal watchers).
		3380
		3381	When this is not possible, or you want to use the default loop for
		3382	other reasons, then in the process that wants to start "fresh", call
		3383	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3384	Destroying the default loop will "orphan" (not stop) all registered
		3385	watchers, so you have to be careful not to execute code that modifies
		3386	those watchers. Note also that in that case, you have to re-register any
		3387	signal watchers.
2449		3388
2450	=head3 Watcher-Specific Functions and Data Members	3389	=head3 Watcher-Specific Functions and Data Members
2451		3390
2452	=over 4	3391	=over 4
2453		3392
2454	=item ev_fork_init (ev_signal *, callback)	3393	=item ev_fork_init (ev_fork *, callback)
2455		3394
2456	Initialises and configures the fork watcher - it has no parameters of any	3395	Initialises and configures the fork watcher - it has no parameters of any
2457	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3396	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2458	believe me.	3397	really.
2459		3398
2460	=back	3399	=back
2461		3400
2462		3401
		3402	=head2 C<ev_cleanup> - even the best things end
		3403
		3404	Cleanup watchers are called just before the event loop is being destroyed
		3405	by a call to C<ev_loop_destroy>.
		3406
		3407	While there is no guarantee that the event loop gets destroyed, cleanup
		3408	watchers provide a convenient method to install cleanup hooks for your
		3409	program, worker threads and so on - you just to make sure to destroy the
		3410	loop when you want them to be invoked.
		3411
		3412	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3413	all other watchers, they do not keep a reference to the event loop (which
		3414	makes a lot of sense if you think about it). Like all other watchers, you
		3415	can call libev functions in the callback, except C<ev_cleanup_start>.
		3416
		3417	=head3 Watcher-Specific Functions and Data Members
		3418
		3419	=over 4
		3420
		3421	=item ev_cleanup_init (ev_cleanup *, callback)
		3422
		3423	Initialises and configures the cleanup watcher - it has no parameters of
		3424	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3425	pointless, I assure you.
		3426
		3427	=back
		3428
		3429	Example: Register an atexit handler to destroy the default loop, so any
		3430	cleanup functions are called.
		3431
		3432	static void
		3433	program_exits (void)
		3434	{
		3435	ev_loop_destroy (EV_DEFAULT_UC);
		3436	}
		3437
		3438	...
		3439	atexit (program_exits);
		3440
		3441
2463	=head2 C<ev_async> - how to wake up another event loop	3442	=head2 C<ev_async> - how to wake up an event loop
2464		3443
2465	In general, you cannot use an C<ev_loop> from multiple threads or other	3444	In general, you cannot use an C<ev_loop> from multiple threads or other
2466	asynchronous sources such as signal handlers (as opposed to multiple event	3445	asynchronous sources such as signal handlers (as opposed to multiple event
2467	loops - those are of course safe to use in different threads).	3446	loops - those are of course safe to use in different threads).
2468		3447
2469	Sometimes, however, you need to wake up another event loop you do not	3448	Sometimes, however, you need to wake up an event loop you do not control,
2470	control, for example because it belongs to another thread. This is what	3449	for example because it belongs to another thread. This is what C<ev_async>
2471	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3450	watchers do: as long as the C<ev_async> watcher is active, you can signal
2472	can signal it by calling C<ev_async_send>, which is thread- and signal	3451	it by calling C<ev_async_send>, which is thread- and signal safe.
2473	safe.
2474		3452
2475	This functionality is very similar to C<ev_signal> watchers, as signals,	3453	This functionality is very similar to C<ev_signal> watchers, as signals,
2476	too, are asynchronous in nature, and signals, too, will be compressed	3454	too, are asynchronous in nature, and signals, too, will be compressed
2477	(i.e. the number of callback invocations may be less than the number of	3455	(i.e. the number of callback invocations may be less than the number of
2478	C<ev_async_sent> calls).	3456	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2479		3457	of "global async watchers" by using a watcher on an otherwise unused
2480	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3458	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2481	just the default loop.	3459	even without knowing which loop owns the signal.
2482		3460
2483	=head3 Queueing	3461	=head3 Queueing
2484		3462
2485	C<ev_async> does not support queueing of data in any way. The reason	3463	C<ev_async> does not support queueing of data in any way. The reason
2486	is that the author does not know of a simple (or any) algorithm for a	3464	is that the author does not know of a simple (or any) algorithm for a
2487	multiple-writer-single-reader queue that works in all cases and doesn't	3465	multiple-writer-single-reader queue that works in all cases and doesn't
2488	need elaborate support such as pthreads.	3466	need elaborate support such as pthreads or unportable memory access
		3467	semantics.
2489		3468
2490	That means that if you want to queue data, you have to provide your own	3469	That means that if you want to queue data, you have to provide your own
2491	queue. But at least I can tell you how to implement locking around your	3470	queue. But at least I can tell you how to implement locking around your
2492	queue:	3471	queue:
2493		3472
…		…
2571	=over 4	3550	=over 4
2572		3551
2573	=item ev_async_init (ev_async *, callback)	3552	=item ev_async_init (ev_async *, callback)
2574		3553
2575	Initialises and configures the async watcher - it has no parameters of any	3554	Initialises and configures the async watcher - it has no parameters of any
2576	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3555	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2577	trust me.	3556	trust me.
2578		3557
2579	=item ev_async_send (loop, ev_async *)	3558	=item ev_async_send (loop, ev_async *)
2580		3559
2581	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3560	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2582	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3561	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3562	returns.
		3563
2583	C<ev_feed_event>, this call is safe to do from other threads, signal or	3564	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2584	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3565	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2585	section below on what exactly this means).	3566	embedding section below on what exactly this means).
2586		3567
2587	This call incurs the overhead of a system call only once per loop iteration,	3568	Note that, as with other watchers in libev, multiple events might get
2588	so while the overhead might be noticeable, it doesn't apply to repeated	3569	compressed into a single callback invocation (another way to look at
2589	calls to C<ev_async_send>.	3570	this is that C<ev_async> watchers are level-triggered: they are set on
		3571	C<ev_async_send>, reset when the event loop detects that).
		3572
		3573	This call incurs the overhead of at most one extra system call per event
		3574	loop iteration, if the event loop is blocked, and no syscall at all if
		3575	the event loop (or your program) is processing events. That means that
		3576	repeated calls are basically free (there is no need to avoid calls for
		3577	performance reasons) and that the overhead becomes smaller (typically
		3578	zero) under load.
2590		3579
2591	=item bool = ev_async_pending (ev_async *)	3580	=item bool = ev_async_pending (ev_async *)
2592		3581
2593	Returns a non-zero value when C<ev_async_send> has been called on the	3582	Returns a non-zero value when C<ev_async_send> has been called on the
2594	watcher but the event has not yet been processed (or even noted) by the	3583	watcher but the event has not yet been processed (or even noted) by the
…		…
2597	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3586	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2598	the loop iterates next and checks for the watcher to have become active,	3587	the loop iterates next and checks for the watcher to have become active,
2599	it will reset the flag again. C<ev_async_pending> can be used to very	3588	it will reset the flag again. C<ev_async_pending> can be used to very
2600	quickly check whether invoking the loop might be a good idea.	3589	quickly check whether invoking the loop might be a good idea.
2601		3590
2602	Not that this does I<not> check whether the watcher itself is pending, only	3591	Not that this does I<not> check whether the watcher itself is pending,
2603	whether it has been requested to make this watcher pending.	3592	only whether it has been requested to make this watcher pending: there
		3593	is a time window between the event loop checking and resetting the async
		3594	notification, and the callback being invoked.
2604		3595
2605	=back	3596	=back
2606		3597
2607		3598
2608	=head1 OTHER FUNCTIONS	3599	=head1 OTHER FUNCTIONS
2609		3600
2610	There are some other functions of possible interest. Described. Here. Now.	3601	There are some other functions of possible interest. Described. Here. Now.
2611		3602
2612	=over 4	3603	=over 4
2613		3604
2614	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3605	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
2615		3606
2616	This function combines a simple timer and an I/O watcher, calls your	3607	This function combines a simple timer and an I/O watcher, calls your
2617	callback on whichever event happens first and automatically stops both	3608	callback on whichever event happens first and automatically stops both
2618	watchers. This is useful if you want to wait for a single event on an fd	3609	watchers. This is useful if you want to wait for a single event on an fd
2619	or timeout without having to allocate/configure/start/stop/free one or	3610	or timeout without having to allocate/configure/start/stop/free one or
…		…
2625		3616
2626	If C<timeout> is less than 0, then no timeout watcher will be	3617	If C<timeout> is less than 0, then no timeout watcher will be
2627	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3618	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2628	repeat = 0) will be started. C<0> is a valid timeout.	3619	repeat = 0) will be started. C<0> is a valid timeout.
2629		3620
2630	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3621	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2631	passed an C<revents> set like normal event callbacks (a combination of	3622	passed an C<revents> set like normal event callbacks (a combination of
2632	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3623	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2633	value passed to C<ev_once>. Note that it is possible to receive I<both>	3624	value passed to C<ev_once>. Note that it is possible to receive I<both>
2634	a timeout and an io event at the same time - you probably should give io	3625	a timeout and an io event at the same time - you probably should give io
2635	events precedence.	3626	events precedence.
2636		3627
2637	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3628	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2638		3629
2639	static void stdin_ready (int revents, void *arg)	3630	static void stdin_ready (int revents, void *arg)
2640	{	3631	{
2641	if (revents & EV_READ)	3632	if (revents & EV_READ)
2642	/* stdin might have data for us, joy! */;	3633	/* stdin might have data for us, joy! */;
2643	else if (revents & EV_TIMEOUT)	3634	else if (revents & EV_TIMER)
2644	/* doh, nothing entered */;	3635	/* doh, nothing entered */;
2645	}	3636	}
2646		3637
2647	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3638	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2648		3639
2649	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2650
2651	Feeds the given event set into the event loop, as if the specified event
2652	had happened for the specified watcher (which must be a pointer to an
2653	initialised but not necessarily started event watcher).
2654
2655	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3640	=item ev_feed_fd_event (loop, int fd, int revents)
2656		3641
2657	Feed an event on the given fd, as if a file descriptor backend detected	3642	Feed an event on the given fd, as if a file descriptor backend detected
2658	the given events it.	3643	the given events.
2659		3644
2660	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3645	=item ev_feed_signal_event (loop, int signum)
2661		3646
2662	Feed an event as if the given signal occurred (C<loop> must be the default	3647	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2663	loop!).	3648	which is async-safe.
2664		3649
2665	=back	3650	=back
		3651
		3652
		3653	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3654
		3655	This section explains some common idioms that are not immediately
		3656	obvious. Note that examples are sprinkled over the whole manual, and this
		3657	section only contains stuff that wouldn't fit anywhere else.
		3658
		3659	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3660
		3661	Each watcher has, by default, a C<void *data> member that you can read
		3662	or modify at any time: libev will completely ignore it. This can be used
		3663	to associate arbitrary data with your watcher. If you need more data and
		3664	don't want to allocate memory separately and store a pointer to it in that
		3665	data member, you can also "subclass" the watcher type and provide your own
		3666	data:
		3667
		3668	struct my_io
		3669	{
		3670	ev_io io;
		3671	int otherfd;
		3672	void *somedata;
		3673	struct whatever *mostinteresting;
		3674	};
		3675
		3676	...
		3677	struct my_io w;
		3678	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3679
		3680	And since your callback will be called with a pointer to the watcher, you
		3681	can cast it back to your own type:
		3682
		3683	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3684	{
		3685	struct my_io *w = (struct my_io *)w_;
		3686	...
		3687	}
		3688
		3689	More interesting and less C-conformant ways of casting your callback
		3690	function type instead have been omitted.
		3691
		3692	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3693
		3694	Another common scenario is to use some data structure with multiple
		3695	embedded watchers, in effect creating your own watcher that combines
		3696	multiple libev event sources into one "super-watcher":
		3697
		3698	struct my_biggy
		3699	{
		3700	int some_data;
		3701	ev_timer t1;
		3702	ev_timer t2;
		3703	}
		3704
		3705	In this case getting the pointer to C<my_biggy> is a bit more
		3706	complicated: Either you store the address of your C<my_biggy> struct in
		3707	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3708	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3709	real programmers):
		3710
		3711	#include <stddef.h>
		3712
		3713	static void
		3714	t1_cb (EV_P_ ev_timer *w, int revents)
		3715	{
		3716	struct my_biggy big = (struct my_biggy *)
		3717	(((char *)w) - offsetof (struct my_biggy, t1));
		3718	}
		3719
		3720	static void
		3721	t2_cb (EV_P_ ev_timer *w, int revents)
		3722	{
		3723	struct my_biggy big = (struct my_biggy *)
		3724	(((char *)w) - offsetof (struct my_biggy, t2));
		3725	}
		3726
		3727	=head2 AVOIDING FINISHING BEFORE RETURNING
		3728
		3729	Often you have structures like this in event-based programs:
		3730
		3731	callback ()
		3732	{
		3733	free (request);
		3734	}
		3735
		3736	request = start_new_request (..., callback);
		3737
		3738	The intent is to start some "lengthy" operation. The C<request> could be
		3739	used to cancel the operation, or do other things with it.
		3740
		3741	It's not uncommon to have code paths in C<start_new_request> that
		3742	immediately invoke the callback, for example, to report errors. Or you add
		3743	some caching layer that finds that it can skip the lengthy aspects of the
		3744	operation and simply invoke the callback with the result.
		3745
		3746	The problem here is that this will happen I<before> C<start_new_request>
		3747	has returned, so C<request> is not set.
		3748
		3749	Even if you pass the request by some safer means to the callback, you
		3750	might want to do something to the request after starting it, such as
		3751	canceling it, which probably isn't working so well when the callback has
		3752	already been invoked.
		3753
		3754	A common way around all these issues is to make sure that
		3755	C<start_new_request> I<always> returns before the callback is invoked. If
		3756	C<start_new_request> immediately knows the result, it can artificially
		3757	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3758	example, or more sneakily, by reusing an existing (stopped) watcher and
		3759	pushing it into the pending queue:
		3760
		3761	ev_set_cb (watcher, callback);
		3762	ev_feed_event (EV_A_ watcher, 0);
		3763
		3764	This way, C<start_new_request> can safely return before the callback is
		3765	invoked, while not delaying callback invocation too much.
		3766
		3767	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3768
		3769	Often (especially in GUI toolkits) there are places where you have
		3770	I<modal> interaction, which is most easily implemented by recursively
		3771	invoking C<ev_run>.
		3772
		3773	This brings the problem of exiting - a callback might want to finish the
		3774	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3775	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3776	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3777	other combination: In these cases, a simple C<ev_break> will not work.
		3778
		3779	The solution is to maintain "break this loop" variable for each C<ev_run>
		3780	invocation, and use a loop around C<ev_run> until the condition is
		3781	triggered, using C<EVRUN_ONCE>:
		3782
		3783	// main loop
		3784	int exit_main_loop = 0;
		3785
		3786	while (!exit_main_loop)
		3787	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3788
		3789	// in a modal watcher
		3790	int exit_nested_loop = 0;
		3791
		3792	while (!exit_nested_loop)
		3793	ev_run (EV_A_ EVRUN_ONCE);
		3794
		3795	To exit from any of these loops, just set the corresponding exit variable:
		3796
		3797	// exit modal loop
		3798	exit_nested_loop = 1;
		3799
		3800	// exit main program, after modal loop is finished
		3801	exit_main_loop = 1;
		3802
		3803	// exit both
		3804	exit_main_loop = exit_nested_loop = 1;
		3805
		3806	=head2 THREAD LOCKING EXAMPLE
		3807
		3808	Here is a fictitious example of how to run an event loop in a different
		3809	thread from where callbacks are being invoked and watchers are
		3810	created/added/removed.
		3811
		3812	For a real-world example, see the C<EV::Loop::Async> perl module,
		3813	which uses exactly this technique (which is suited for many high-level
		3814	languages).
		3815
		3816	The example uses a pthread mutex to protect the loop data, a condition
		3817	variable to wait for callback invocations, an async watcher to notify the
		3818	event loop thread and an unspecified mechanism to wake up the main thread.
		3819
		3820	First, you need to associate some data with the event loop:
		3821
		3822	typedef struct {
		3823	mutex_t lock; /* global loop lock */
		3824	ev_async async_w;
		3825	thread_t tid;
		3826	cond_t invoke_cv;
		3827	} userdata;
		3828
		3829	void prepare_loop (EV_P)
		3830	{
		3831	// for simplicity, we use a static userdata struct.
		3832	static userdata u;
		3833
		3834	ev_async_init (&u->async_w, async_cb);
		3835	ev_async_start (EV_A_ &u->async_w);
		3836
		3837	pthread_mutex_init (&u->lock, 0);
		3838	pthread_cond_init (&u->invoke_cv, 0);
		3839
		3840	// now associate this with the loop
		3841	ev_set_userdata (EV_A_ u);
		3842	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3843	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3844
		3845	// then create the thread running ev_run
		3846	pthread_create (&u->tid, 0, l_run, EV_A);
		3847	}
		3848
		3849	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3850	solely to wake up the event loop so it takes notice of any new watchers
		3851	that might have been added:
		3852
		3853	static void
		3854	async_cb (EV_P_ ev_async *w, int revents)
		3855	{
		3856	// just used for the side effects
		3857	}
		3858
		3859	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3860	protecting the loop data, respectively.
		3861
		3862	static void
		3863	l_release (EV_P)
		3864	{
		3865	userdata *u = ev_userdata (EV_A);
		3866	pthread_mutex_unlock (&u->lock);
		3867	}
		3868
		3869	static void
		3870	l_acquire (EV_P)
		3871	{
		3872	userdata *u = ev_userdata (EV_A);
		3873	pthread_mutex_lock (&u->lock);
		3874	}
		3875
		3876	The event loop thread first acquires the mutex, and then jumps straight
		3877	into C<ev_run>:
		3878
		3879	void *
		3880	l_run (void *thr_arg)
		3881	{
		3882	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3883
		3884	l_acquire (EV_A);
		3885	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3886	ev_run (EV_A_ 0);
		3887	l_release (EV_A);
		3888
		3889	return 0;
		3890	}
		3891
		3892	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3893	signal the main thread via some unspecified mechanism (signals? pipe
		3894	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3895	have been called (in a while loop because a) spurious wakeups are possible
		3896	and b) skipping inter-thread-communication when there are no pending
		3897	watchers is very beneficial):
		3898
		3899	static void
		3900	l_invoke (EV_P)
		3901	{
		3902	userdata *u = ev_userdata (EV_A);
		3903
		3904	while (ev_pending_count (EV_A))
		3905	{
		3906	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3907	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3908	}
		3909	}
		3910
		3911	Now, whenever the main thread gets told to invoke pending watchers, it
		3912	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3913	thread to continue:
		3914
		3915	static void
		3916	real_invoke_pending (EV_P)
		3917	{
		3918	userdata *u = ev_userdata (EV_A);
		3919
		3920	pthread_mutex_lock (&u->lock);
		3921	ev_invoke_pending (EV_A);
		3922	pthread_cond_signal (&u->invoke_cv);
		3923	pthread_mutex_unlock (&u->lock);
		3924	}
		3925
		3926	Whenever you want to start/stop a watcher or do other modifications to an
		3927	event loop, you will now have to lock:
		3928
		3929	ev_timer timeout_watcher;
		3930	userdata *u = ev_userdata (EV_A);
		3931
		3932	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3933
		3934	pthread_mutex_lock (&u->lock);
		3935	ev_timer_start (EV_A_ &timeout_watcher);
		3936	ev_async_send (EV_A_ &u->async_w);
		3937	pthread_mutex_unlock (&u->lock);
		3938
		3939	Note that sending the C<ev_async> watcher is required because otherwise
		3940	an event loop currently blocking in the kernel will have no knowledge
		3941	about the newly added timer. By waking up the loop it will pick up any new
		3942	watchers in the next event loop iteration.
		3943
		3944	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3945
		3946	While the overhead of a callback that e.g. schedules a thread is small, it
		3947	is still an overhead. If you embed libev, and your main usage is with some
		3948	kind of threads or coroutines, you might want to customise libev so that
		3949	doesn't need callbacks anymore.
		3950
		3951	Imagine you have coroutines that you can switch to using a function
		3952	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3953	and that due to some magic, the currently active coroutine is stored in a
		3954	global called C<current_coro>. Then you can build your own "wait for libev
		3955	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3956	the differing C<;> conventions):
		3957
		3958	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3959	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3960
		3961	That means instead of having a C callback function, you store the
		3962	coroutine to switch to in each watcher, and instead of having libev call
		3963	your callback, you instead have it switch to that coroutine.
		3964
		3965	A coroutine might now wait for an event with a function called
		3966	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3967	matter when, or whether the watcher is active or not when this function is
		3968	called):
		3969
		3970	void
		3971	wait_for_event (ev_watcher *w)
		3972	{
		3973	ev_set_cb (w, current_coro);
		3974	switch_to (libev_coro);
		3975	}
		3976
		3977	That basically suspends the coroutine inside C<wait_for_event> and
		3978	continues the libev coroutine, which, when appropriate, switches back to
		3979	this or any other coroutine.
		3980
		3981	You can do similar tricks if you have, say, threads with an event queue -
		3982	instead of storing a coroutine, you store the queue object and instead of
		3983	switching to a coroutine, you push the watcher onto the queue and notify
		3984	any waiters.
		3985
		3986	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3987	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3988
		3989	// my_ev.h
		3990	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3991	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3992	#include "../libev/ev.h"
		3993
		3994	// my_ev.c
		3995	#define EV_H "my_ev.h"
		3996	#include "../libev/ev.c"
		3997
		3998	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3999	F<my_ev.c> into your project. When properly specifying include paths, you
		4000	can even use F<ev.h> as header file name directly.
2666		4001
2667		4002
2668	=head1 LIBEVENT EMULATION	4003	=head1 LIBEVENT EMULATION
2669		4004
2670	Libev offers a compatibility emulation layer for libevent. It cannot	4005	Libev offers a compatibility emulation layer for libevent. It cannot
2671	emulate the internals of libevent, so here are some usage hints:	4006	emulate the internals of libevent, so here are some usage hints:
2672		4007
2673	=over 4	4008	=over 4
		4009
		4010	=item * Only the libevent-1.4.1-beta API is being emulated.
		4011
		4012	This was the newest libevent version available when libev was implemented,
		4013	and is still mostly unchanged in 2010.
2674		4014
2675	=item * Use it by including <event.h>, as usual.	4015	=item * Use it by including <event.h>, as usual.
2676		4016
2677	=item * The following members are fully supported: ev_base, ev_callback,	4017	=item * The following members are fully supported: ev_base, ev_callback,
2678	ev_arg, ev_fd, ev_res, ev_events.	4018	ev_arg, ev_fd, ev_res, ev_events.
…		…
2684	=item * Priorities are not currently supported. Initialising priorities	4024	=item * Priorities are not currently supported. Initialising priorities
2685	will fail and all watchers will have the same priority, even though there	4025	will fail and all watchers will have the same priority, even though there
2686	is an ev_pri field.	4026	is an ev_pri field.
2687		4027
2688	=item * In libevent, the last base created gets the signals, in libev, the	4028	=item * In libevent, the last base created gets the signals, in libev, the
2689	first base created (== the default loop) gets the signals.	4029	base that registered the signal gets the signals.
2690		4030
2691	=item * Other members are not supported.	4031	=item * Other members are not supported.
2692		4032
2693	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4033	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2694	to use the libev header file and library.	4034	to use the libev header file and library.
2695		4035
2696	=back	4036	=back
2697		4037
2698	=head1 C++ SUPPORT	4038	=head1 C++ SUPPORT
		4039
		4040	=head2 C API
		4041
		4042	The normal C API should work fine when used from C++: both ev.h and the
		4043	libev sources can be compiled as C++. Therefore, code that uses the C API
		4044	will work fine.
		4045
		4046	Proper exception specifications might have to be added to callbacks passed
		4047	to libev: exceptions may be thrown only from watcher callbacks, all other
		4048	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4049	callbacks) must not throw exceptions, and might need a C<noexcept>
		4050	specification. If you have code that needs to be compiled as both C and
		4051	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4052
		4053	static void
		4054	fatal_error (const char *msg) EV_NOEXCEPT
		4055	{
		4056	perror (msg);
		4057	abort ();
		4058	}
		4059
		4060	...
		4061	ev_set_syserr_cb (fatal_error);
		4062
		4063	The only API functions that can currently throw exceptions are C<ev_run>,
		4064	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4065	because it runs cleanup watchers).
		4066
		4067	Throwing exceptions in watcher callbacks is only supported if libev itself
		4068	is compiled with a C++ compiler or your C and C++ environments allow
		4069	throwing exceptions through C libraries (most do).
		4070
		4071	=head2 C++ API
2699		4072
2700	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4073	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2701	you to use some convenience methods to start/stop watchers and also change	4074	you to use some convenience methods to start/stop watchers and also change
2702	the callback model to a model using method callbacks on objects.	4075	the callback model to a model using method callbacks on objects.
2703		4076
2704	To use it,	4077	To use it,
2705		4078
2706	#include <ev++.h>	4079	#include <ev++.h>
2707		4080
2708	This automatically includes F<ev.h> and puts all of its definitions (many	4081	This automatically includes F<ev.h> and puts all of its definitions (many
2709	of them macros) into the global namespace. All C++ specific things are	4082	of them macros) into the global namespace. All C++ specific things are
2710	put into the C<ev> namespace. It should support all the same embedding	4083	put into the C<ev> namespace. It should support all the same embedding
…		…
2713	Care has been taken to keep the overhead low. The only data member the C++	4086	Care has been taken to keep the overhead low. The only data member the C++
2714	classes add (compared to plain C-style watchers) is the event loop pointer	4087	classes add (compared to plain C-style watchers) is the event loop pointer
2715	that the watcher is associated with (or no additional members at all if	4088	that the watcher is associated with (or no additional members at all if
2716	you disable C<EV_MULTIPLICITY> when embedding libev).	4089	you disable C<EV_MULTIPLICITY> when embedding libev).
2717		4090
2718	Currently, functions, and static and non-static member functions can be	4091	Currently, functions, static and non-static member functions and classes
2719	used as callbacks. Other types should be easy to add as long as they only	4092	with C<operator ()> can be used as callbacks. Other types should be easy
2720	need one additional pointer for context. If you need support for other	4093	to add as long as they only need one additional pointer for context. If
2721	types of functors please contact the author (preferably after implementing	4094	you need support for other types of functors please contact the author
2722	it).	4095	(preferably after implementing it).
		4096
		4097	For all this to work, your C++ compiler either has to use the same calling
		4098	conventions as your C compiler (for static member functions), or you have
		4099	to embed libev and compile libev itself as C++.
2723		4100
2724	Here is a list of things available in the C<ev> namespace:	4101	Here is a list of things available in the C<ev> namespace:
2725		4102
2726	=over 4	4103	=over 4
2727		4104
…		…
2737	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4114	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2738		4115
2739	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4116	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2740	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4117	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2741	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4118	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2742	defines by many implementations.	4119	defined by many implementations.
2743		4120
2744	All of those classes have these methods:	4121	All of those classes have these methods:
2745		4122
2746	=over 4	4123	=over 4
2747		4124
2748	=item ev::TYPE::TYPE ()	4125	=item ev::TYPE::TYPE ()
2749		4126
2750	=item ev::TYPE::TYPE (struct ev_loop *)	4127	=item ev::TYPE::TYPE (loop)
2751		4128
2752	=item ev::TYPE::~TYPE	4129	=item ev::TYPE::~TYPE
2753		4130
2754	The constructor (optionally) takes an event loop to associate the watcher	4131	The constructor (optionally) takes an event loop to associate the watcher
2755	with. If it is omitted, it will use C<EV_DEFAULT>.	4132	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2787		4164
2788	myclass obj;	4165	myclass obj;
2789	ev::io iow;	4166	ev::io iow;
2790	iow.set <myclass, &myclass::io_cb> (&obj);	4167	iow.set <myclass, &myclass::io_cb> (&obj);
2791		4168
		4169	=item w->set (object *)
		4170
		4171	This is a variation of a method callback - leaving out the method to call
		4172	will default the method to C<operator ()>, which makes it possible to use
		4173	functor objects without having to manually specify the C<operator ()> all
		4174	the time. Incidentally, you can then also leave out the template argument
		4175	list.
		4176
		4177	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		4178	int revents)>.
		4179
		4180	See the method-C<set> above for more details.
		4181
		4182	Example: use a functor object as callback.
		4183
		4184	struct myfunctor
		4185	{
		4186	void operator() (ev::io &w, int revents)
		4187	{
		4188	...
		4189	}
		4190	}
		4191
		4192	myfunctor f;
		4193
		4194	ev::io w;
		4195	w.set (&f);
		4196
2792	=item w->set<function> (void *data = 0)	4197	=item w->set<function> (void *data = 0)
2793		4198
2794	Also sets a callback, but uses a static method or plain function as	4199	Also sets a callback, but uses a static method or plain function as
2795	callback. The optional C<data> argument will be stored in the watcher's	4200	callback. The optional C<data> argument will be stored in the watcher's
2796	C<data> member and is free for you to use.	4201	C<data> member and is free for you to use.
…		…
2802	Example: Use a plain function as callback.	4207	Example: Use a plain function as callback.
2803		4208
2804	static void io_cb (ev::io &w, int revents) { }	4209	static void io_cb (ev::io &w, int revents) { }
2805	iow.set <io_cb> ();	4210	iow.set <io_cb> ();
2806		4211
2807	=item w->set (struct ev_loop *)	4212	=item w->set (loop)
2808		4213
2809	Associates a different C<struct ev_loop> with this watcher. You can only	4214	Associates a different C<struct ev_loop> with this watcher. You can only
2810	do this when the watcher is inactive (and not pending either).	4215	do this when the watcher is inactive (and not pending either).
2811		4216
2812	=item w->set ([arguments])	4217	=item w->set ([arguments])
2813		4218
2814	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4219	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4220	with the same arguments. Either this method or a suitable start method
2815	called at least once. Unlike the C counterpart, an active watcher gets	4221	must be called at least once. Unlike the C counterpart, an active watcher
2816	automatically stopped and restarted when reconfiguring it with this	4222	gets automatically stopped and restarted when reconfiguring it with this
2817	method.	4223	method.
		4224
		4225	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4226	clashing with the C<set (loop)> method.
2818		4227
2819	=item w->start ()	4228	=item w->start ()
2820		4229
2821	Starts the watcher. Note that there is no C<loop> argument, as the	4230	Starts the watcher. Note that there is no C<loop> argument, as the
2822	constructor already stores the event loop.	4231	constructor already stores the event loop.
2823		4232
		4233	=item w->start ([arguments])
		4234
		4235	Instead of calling C<set> and C<start> methods separately, it is often
		4236	convenient to wrap them in one call. Uses the same type of arguments as
		4237	the configure C<set> method of the watcher.
		4238
2824	=item w->stop ()	4239	=item w->stop ()
2825		4240
2826	Stops the watcher if it is active. Again, no C<loop> argument.	4241	Stops the watcher if it is active. Again, no C<loop> argument.
2827		4242
2828	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4243	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2840		4255
2841	=back	4256	=back
2842		4257
2843	=back	4258	=back
2844		4259
2845	Example: Define a class with an IO and idle watcher, start one of them in	4260	Example: Define a class with two I/O and idle watchers, start the I/O
2846	the constructor.	4261	watchers in the constructor.
2847		4262
2848	class myclass	4263	class myclass
2849	{	4264	{
2850	ev::io io ; void io_cb (ev::io &w, int revents);	4265	ev::io io ; void io_cb (ev::io &w, int revents);
		4266	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2851	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4267	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2852		4268
2853	myclass (int fd)	4269	myclass (int fd)
2854	{	4270	{
2855	io .set <myclass, &myclass::io_cb > (this);	4271	io .set <myclass, &myclass::io_cb > (this);
		4272	io2 .set <myclass, &myclass::io2_cb > (this);
2856	idle.set <myclass, &myclass::idle_cb> (this);	4273	idle.set <myclass, &myclass::idle_cb> (this);
2857		4274
2858	io.start (fd, ev::READ);	4275	io.set (fd, ev::WRITE); // configure the watcher
		4276	io.start (); // start it whenever convenient
		4277
		4278	io2.start (fd, ev::READ); // set + start in one call
2859	}	4279	}
2860	};	4280	};
2861		4281
2862		4282
2863	=head1 OTHER LANGUAGE BINDINGS	4283	=head1 OTHER LANGUAGE BINDINGS
…		…
2882	L<http://software.schmorp.de/pkg/EV>.	4302	L<http://software.schmorp.de/pkg/EV>.
2883		4303
2884	=item Python	4304	=item Python
2885		4305
2886	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4306	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2887	seems to be quite complete and well-documented. Note, however, that the	4307	seems to be quite complete and well-documented.
2888	patch they require for libev is outright dangerous as it breaks the ABI
2889	for everybody else, and therefore, should never be applied in an installed
2890	libev (if python requires an incompatible ABI then it needs to embed
2891	libev).
2892		4308
2893	=item Ruby	4309	=item Ruby
2894		4310
2895	Tony Arcieri has written a ruby extension that offers access to a subset	4311	Tony Arcieri has written a ruby extension that offers access to a subset
2896	of the libev API and adds file handle abstractions, asynchronous DNS and	4312	of the libev API and adds file handle abstractions, asynchronous DNS and
2897	more on top of it. It can be found via gem servers. Its homepage is at	4313	more on top of it. It can be found via gem servers. Its homepage is at
2898	L<http://rev.rubyforge.org/>.	4314	L<http://rev.rubyforge.org/>.
2899		4315
		4316	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4317	makes rev work even on mingw.
		4318
		4319	=item Haskell
		4320
		4321	A haskell binding to libev is available at
		4322	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4323
2900	=item D	4324	=item D
2901		4325
2902	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4326	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2903	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4327	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
		4328
		4329	=item Ocaml
		4330
		4331	Erkki Seppala has written Ocaml bindings for libev, to be found at
		4332	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4333
		4334	=item Lua
		4335
		4336	Brian Maher has written a partial interface to libev for lua (at the
		4337	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4338	L<http://github.com/brimworks/lua-ev>.
		4339
		4340	=item Javascript
		4341
		4342	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4343
		4344	=item Others
		4345
		4346	There are others, and I stopped counting.
2904		4347
2905	=back	4348	=back
2906		4349
2907		4350
2908	=head1 MACRO MAGIC	4351	=head1 MACRO MAGIC
…		…
2922	loop argument"). The C<EV_A> form is used when this is the sole argument,	4365	loop argument"). The C<EV_A> form is used when this is the sole argument,
2923	C<EV_A_> is used when other arguments are following. Example:	4366	C<EV_A_> is used when other arguments are following. Example:
2924		4367
2925	ev_unref (EV_A);	4368	ev_unref (EV_A);
2926	ev_timer_add (EV_A_ watcher);	4369	ev_timer_add (EV_A_ watcher);
2927	ev_loop (EV_A_ 0);	4370	ev_run (EV_A_ 0);
2928		4371
2929	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4372	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2930	which is often provided by the following macro.	4373	which is often provided by the following macro.
2931		4374
2932	=item C<EV_P>, C<EV_P_>	4375	=item C<EV_P>, C<EV_P_>
…		…
2945	suitable for use with C<EV_A>.	4388	suitable for use with C<EV_A>.
2946		4389
2947	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4390	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
2948		4391
2949	Similar to the other two macros, this gives you the value of the default	4392	Similar to the other two macros, this gives you the value of the default
2950	loop, if multiple loops are supported ("ev loop default").	4393	loop, if multiple loops are supported ("ev loop default"). The default loop
		4394	will be initialised if it isn't already initialised.
		4395
		4396	For non-multiplicity builds, these macros do nothing, so you always have
		4397	to initialise the loop somewhere.
2951		4398
2952	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4399	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
2953		4400
2954	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4401	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
2955	default loop has been initialised (C<UC> == unchecked). Their behaviour	4402	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
2972	}	4419	}
2973		4420
2974	ev_check check;	4421	ev_check check;
2975	ev_check_init (&check, check_cb);	4422	ev_check_init (&check, check_cb);
2976	ev_check_start (EV_DEFAULT_ &check);	4423	ev_check_start (EV_DEFAULT_ &check);
2977	ev_loop (EV_DEFAULT_ 0);	4424	ev_run (EV_DEFAULT_ 0);
2978		4425
2979	=head1 EMBEDDING	4426	=head1 EMBEDDING
2980		4427
2981	Libev can (and often is) directly embedded into host	4428	Libev can (and often is) directly embedded into host
2982	applications. Examples of applications that embed it include the Deliantra	4429	applications. Examples of applications that embed it include the Deliantra
…		…
3009		4456
3010	#define EV_STANDALONE 1	4457	#define EV_STANDALONE 1
3011	#include "ev.h"	4458	#include "ev.h"
3012		4459
3013	Both header files and implementation files can be compiled with a C++	4460	Both header files and implementation files can be compiled with a C++
3014	compiler (at least, thats a stated goal, and breakage will be treated	4461	compiler (at least, that's a stated goal, and breakage will be treated
3015	as a bug).	4462	as a bug).
3016		4463
3017	You need the following files in your source tree, or in a directory	4464	You need the following files in your source tree, or in a directory
3018	in your include path (e.g. in libev/ when using -Ilibev):	4465	in your include path (e.g. in libev/ when using -Ilibev):
3019		4466
…		…
3022	ev_vars.h	4469	ev_vars.h
3023	ev_wrap.h	4470	ev_wrap.h
3024		4471
3025	ev_win32.c required on win32 platforms only	4472	ev_win32.c required on win32 platforms only
3026		4473
3027	ev_select.c only when select backend is enabled (which is enabled by default)	4474	ev_select.c only when select backend is enabled
3028	ev_poll.c only when poll backend is enabled (disabled by default)	4475	ev_poll.c only when poll backend is enabled
3029	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4476	ev_epoll.c only when the epoll backend is enabled
		4477	ev_linuxaio.c only when the linux aio backend is enabled
3030	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4478	ev_kqueue.c only when the kqueue backend is enabled
3031	ev_port.c only when the solaris port backend is enabled (disabled by default)	4479	ev_port.c only when the solaris port backend is enabled
3032		4480
3033	F<ev.c> includes the backend files directly when enabled, so you only need	4481	F<ev.c> includes the backend files directly when enabled, so you only need
3034	to compile this single file.	4482	to compile this single file.
3035		4483
3036	=head3 LIBEVENT COMPATIBILITY API	4484	=head3 LIBEVENT COMPATIBILITY API
…		…
3062	libev.m4	4510	libev.m4
3063		4511
3064	=head2 PREPROCESSOR SYMBOLS/MACROS	4512	=head2 PREPROCESSOR SYMBOLS/MACROS
3065		4513
3066	Libev can be configured via a variety of preprocessor symbols you have to	4514	Libev can be configured via a variety of preprocessor symbols you have to
3067	define before including any of its files. The default in the absence of	4515	define before including (or compiling) any of its files. The default in
3068	autoconf is documented for every option.	4516	the absence of autoconf is documented for every option.
		4517
		4518	Symbols marked with "(h)" do not change the ABI, and can have different
		4519	values when compiling libev vs. including F<ev.h>, so it is permissible
		4520	to redefine them before including F<ev.h> without breaking compatibility
		4521	to a compiled library. All other symbols change the ABI, which means all
		4522	users of libev and the libev code itself must be compiled with compatible
		4523	settings.
3069		4524
3070	=over 4	4525	=over 4
3071		4526
		4527	=item EV_COMPAT3 (h)
		4528
		4529	Backwards compatibility is a major concern for libev. This is why this
		4530	release of libev comes with wrappers for the functions and symbols that
		4531	have been renamed between libev version 3 and 4.
		4532
		4533	You can disable these wrappers (to test compatibility with future
		4534	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4535	sources. This has the additional advantage that you can drop the C<struct>
		4536	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4537	typedef in that case.
		4538
		4539	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4540	and in some even more future version the compatibility code will be
		4541	removed completely.
		4542
3072	=item EV_STANDALONE	4543	=item EV_STANDALONE (h)
3073		4544
3074	Must always be C<1> if you do not use autoconf configuration, which	4545	Must always be C<1> if you do not use autoconf configuration, which
3075	keeps libev from including F<config.h>, and it also defines dummy	4546	keeps libev from including F<config.h>, and it also defines dummy
3076	implementations for some libevent functions (such as logging, which is not	4547	implementations for some libevent functions (such as logging, which is not
3077	supported). It will also not define any of the structs usually found in	4548	supported). It will also not define any of the structs usually found in
3078	F<event.h> that are not directly supported by the libev core alone.	4549	F<event.h> that are not directly supported by the libev core alone.
3079		4550
		4551	In standalone mode, libev will still try to automatically deduce the
		4552	configuration, but has to be more conservative.
		4553
		4554	=item EV_USE_FLOOR
		4555
		4556	If defined to be C<1>, libev will use the C<floor ()> function for its
		4557	periodic reschedule calculations, otherwise libev will fall back on a
		4558	portable (slower) implementation. If you enable this, you usually have to
		4559	link against libm or something equivalent. Enabling this when the C<floor>
		4560	function is not available will fail, so the safe default is to not enable
		4561	this.
		4562
3080	=item EV_USE_MONOTONIC	4563	=item EV_USE_MONOTONIC
3081		4564
3082	If defined to be C<1>, libev will try to detect the availability of the	4565	If defined to be C<1>, libev will try to detect the availability of the
3083	monotonic clock option at both compile time and runtime. Otherwise no use	4566	monotonic clock option at both compile time and runtime. Otherwise no
3084	of the monotonic clock option will be attempted. If you enable this, you	4567	use of the monotonic clock option will be attempted. If you enable this,
3085	usually have to link against librt or something similar. Enabling it when	4568	you usually have to link against librt or something similar. Enabling it
3086	the functionality isn't available is safe, though, although you have	4569	when the functionality isn't available is safe, though, although you have
3087	to make sure you link against any libraries where the C<clock_gettime>	4570	to make sure you link against any libraries where the C<clock_gettime>
3088	function is hiding in (often F<-lrt>).	4571	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3089		4572
3090	=item EV_USE_REALTIME	4573	=item EV_USE_REALTIME
3091		4574
3092	If defined to be C<1>, libev will try to detect the availability of the	4575	If defined to be C<1>, libev will try to detect the availability of the
3093	real-time clock option at compile time (and assume its availability at	4576	real-time clock option at compile time (and assume its availability
3094	runtime if successful). Otherwise no use of the real-time clock option will	4577	at runtime if successful). Otherwise no use of the real-time clock
3095	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4578	option will be attempted. This effectively replaces C<gettimeofday>
3096	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4579	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3097	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4580	correctness. See the note about libraries in the description of
		4581	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4582	C<EV_USE_CLOCK_SYSCALL>.
		4583
		4584	=item EV_USE_CLOCK_SYSCALL
		4585
		4586	If defined to be C<1>, libev will try to use a direct syscall instead
		4587	of calling the system-provided C<clock_gettime> function. This option
		4588	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4589	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4590	programs needlessly. Using a direct syscall is slightly slower (in
		4591	theory), because no optimised vdso implementation can be used, but avoids
		4592	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4593	higher, as it simplifies linking (no need for C<-lrt>).
3098		4594
3099	=item EV_USE_NANOSLEEP	4595	=item EV_USE_NANOSLEEP
3100		4596
3101	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4597	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3102	and will use it for delays. Otherwise it will use C<select ()>.	4598	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3118		4614
3119	=item EV_SELECT_USE_FD_SET	4615	=item EV_SELECT_USE_FD_SET
3120		4616
3121	If defined to C<1>, then the select backend will use the system C<fd_set>	4617	If defined to C<1>, then the select backend will use the system C<fd_set>
3122	structure. This is useful if libev doesn't compile due to a missing	4618	structure. This is useful if libev doesn't compile due to a missing
3123	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4619	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3124	exotic systems. This usually limits the range of file descriptors to some	4620	on exotic systems. This usually limits the range of file descriptors to
3125	low limit such as 1024 or might have other limitations (winsocket only	4621	some low limit such as 1024 or might have other limitations (winsocket
3126	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4622	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3127	influence the size of the C<fd_set> used.	4623	configures the maximum size of the C<fd_set>.
3128		4624
3129	=item EV_SELECT_IS_WINSOCKET	4625	=item EV_SELECT_IS_WINSOCKET
3130		4626
3131	When defined to C<1>, the select backend will assume that	4627	When defined to C<1>, the select backend will assume that
3132	select/socket/connect etc. don't understand file descriptors but	4628	select/socket/connect etc. don't understand file descriptors but
…		…
3134	be used is the winsock select). This means that it will call	4630	be used is the winsock select). This means that it will call
3135	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4631	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3136	it is assumed that all these functions actually work on fds, even	4632	it is assumed that all these functions actually work on fds, even
3137	on win32. Should not be defined on non-win32 platforms.	4633	on win32. Should not be defined on non-win32 platforms.
3138		4634
3139	=item EV_FD_TO_WIN32_HANDLE	4635	=item EV_FD_TO_WIN32_HANDLE(fd)
3140		4636
3141	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4637	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3142	file descriptors to socket handles. When not defining this symbol (the	4638	file descriptors to socket handles. When not defining this symbol (the
3143	default), then libev will call C<_get_osfhandle>, which is usually	4639	default), then libev will call C<_get_osfhandle>, which is usually
3144	correct. In some cases, programs use their own file descriptor management,	4640	correct. In some cases, programs use their own file descriptor management,
3145	in which case they can provide this function to map fds to socket handles.	4641	in which case they can provide this function to map fds to socket handles.
3146		4642
		4643	=item EV_WIN32_HANDLE_TO_FD(handle)
		4644
		4645	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4646	using the standard C<_open_osfhandle> function. For programs implementing
		4647	their own fd to handle mapping, overwriting this function makes it easier
		4648	to do so. This can be done by defining this macro to an appropriate value.
		4649
		4650	=item EV_WIN32_CLOSE_FD(fd)
		4651
		4652	If programs implement their own fd to handle mapping on win32, then this
		4653	macro can be used to override the C<close> function, useful to unregister
		4654	file descriptors again. Note that the replacement function has to close
		4655	the underlying OS handle.
		4656
		4657	=item EV_USE_WSASOCKET
		4658
		4659	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4660	communication socket, which works better in some environments. Otherwise,
		4661	the normal C<socket> function will be used, which works better in other
		4662	environments.
		4663
3147	=item EV_USE_POLL	4664	=item EV_USE_POLL
3148		4665
3149	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4666	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3150	backend. Otherwise it will be enabled on non-win32 platforms. It	4667	backend. Otherwise it will be enabled on non-win32 platforms. It
3151	takes precedence over select.	4668	takes precedence over select.
…		…
3155	If defined to be C<1>, libev will compile in support for the Linux	4672	If defined to be C<1>, libev will compile in support for the Linux
3156	C<epoll>(7) backend. Its availability will be detected at runtime,	4673	C<epoll>(7) backend. Its availability will be detected at runtime,
3157	otherwise another method will be used as fallback. This is the preferred	4674	otherwise another method will be used as fallback. This is the preferred
3158	backend for GNU/Linux systems. If undefined, it will be enabled if the	4675	backend for GNU/Linux systems. If undefined, it will be enabled if the
3159	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4676	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4677
		4678	=item EV_USE_LINUXAIO
		4679
		4680	If defined to be C<1>, libev will compile in support for the Linux
		4681	aio backend. Due to it's currenbt limitations it has to be requested
		4682	explicitly. If undefined, it will be enabled on linux, otherwise
		4683	disabled.
3160		4684
3161	=item EV_USE_KQUEUE	4685	=item EV_USE_KQUEUE
3162		4686
3163	If defined to be C<1>, libev will compile in support for the BSD style	4687	If defined to be C<1>, libev will compile in support for the BSD style
3164	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4688	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3186	If defined to be C<1>, libev will compile in support for the Linux inotify	4710	If defined to be C<1>, libev will compile in support for the Linux inotify
3187	interface to speed up C<ev_stat> watchers. Its actual availability will	4711	interface to speed up C<ev_stat> watchers. Its actual availability will
3188	be detected at runtime. If undefined, it will be enabled if the headers	4712	be detected at runtime. If undefined, it will be enabled if the headers
3189	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4713	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3190		4714
		4715	=item EV_NO_SMP
		4716
		4717	If defined to be C<1>, libev will assume that memory is always coherent
		4718	between threads, that is, threads can be used, but threads never run on
		4719	different cpus (or different cpu cores). This reduces dependencies
		4720	and makes libev faster.
		4721
		4722	=item EV_NO_THREADS
		4723
		4724	If defined to be C<1>, libev will assume that it will never be called from
		4725	different threads (that includes signal handlers), which is a stronger
		4726	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4727	libev faster.
		4728
3191	=item EV_ATOMIC_T	4729	=item EV_ATOMIC_T
3192		4730
3193	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4731	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3194	access is atomic with respect to other threads or signal contexts. No such	4732	access is atomic with respect to other threads or signal contexts. No
3195	type is easily found in the C language, so you can provide your own type	4733	such type is easily found in the C language, so you can provide your own
3196	that you know is safe for your purposes. It is used both for signal handler "locking"	4734	type that you know is safe for your purposes. It is used both for signal
3197	as well as for signal and thread safety in C<ev_async> watchers.	4735	handler "locking" as well as for signal and thread safety in C<ev_async>
		4736	watchers.
3198		4737
3199	In the absence of this define, libev will use C<sig_atomic_t volatile>	4738	In the absence of this define, libev will use C<sig_atomic_t volatile>
3200	(from F<signal.h>), which is usually good enough on most platforms.	4739	(from F<signal.h>), which is usually good enough on most platforms.
3201		4740
3202	=item EV_H	4741	=item EV_H (h)
3203		4742
3204	The name of the F<ev.h> header file used to include it. The default if	4743	The name of the F<ev.h> header file used to include it. The default if
3205	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4744	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3206	used to virtually rename the F<ev.h> header file in case of conflicts.	4745	used to virtually rename the F<ev.h> header file in case of conflicts.
3207		4746
3208	=item EV_CONFIG_H	4747	=item EV_CONFIG_H (h)
3209		4748
3210	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4749	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3211	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4750	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3212	C<EV_H>, above.	4751	C<EV_H>, above.
3213		4752
3214	=item EV_EVENT_H	4753	=item EV_EVENT_H (h)
3215		4754
3216	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4755	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3217	of how the F<event.h> header can be found, the default is C<"event.h">.	4756	of how the F<event.h> header can be found, the default is C<"event.h">.
3218		4757
3219	=item EV_PROTOTYPES	4758	=item EV_PROTOTYPES (h)
3220		4759
3221	If defined to be C<0>, then F<ev.h> will not define any function	4760	If defined to be C<0>, then F<ev.h> will not define any function
3222	prototypes, but still define all the structs and other symbols. This is	4761	prototypes, but still define all the structs and other symbols. This is
3223	occasionally useful if you want to provide your own wrapper functions	4762	occasionally useful if you want to provide your own wrapper functions
3224	around libev functions.	4763	around libev functions.
…		…
3229	will have the C<struct ev_loop *> as first argument, and you can create	4768	will have the C<struct ev_loop *> as first argument, and you can create
3230	additional independent event loops. Otherwise there will be no support	4769	additional independent event loops. Otherwise there will be no support
3231	for multiple event loops and there is no first event loop pointer	4770	for multiple event loops and there is no first event loop pointer
3232	argument. Instead, all functions act on the single default loop.	4771	argument. Instead, all functions act on the single default loop.
3233		4772
		4773	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4774	default loop when multiplicity is switched off - you always have to
		4775	initialise the loop manually in this case.
		4776
3234	=item EV_MINPRI	4777	=item EV_MINPRI
3235		4778
3236	=item EV_MAXPRI	4779	=item EV_MAXPRI
3237		4780
3238	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4781	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3246	fine.	4789	fine.
3247		4790
3248	If your embedding application does not need any priorities, defining these	4791	If your embedding application does not need any priorities, defining these
3249	both to C<0> will save some memory and CPU.	4792	both to C<0> will save some memory and CPU.
3250		4793
3251	=item EV_PERIODIC_ENABLE	4794	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4795	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4796	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3252		4797
3253	If undefined or defined to be C<1>, then periodic timers are supported. If	4798	If undefined or defined to be C<1> (and the platform supports it), then
3254	defined to be C<0>, then they are not. Disabling them saves a few kB of	4799	the respective watcher type is supported. If defined to be C<0>, then it
3255	code.	4800	is not. Disabling watcher types mainly saves code size.
3256		4801
3257	=item EV_IDLE_ENABLE	4802	=item EV_FEATURES
3258
3259	If undefined or defined to be C<1>, then idle watchers are supported. If
3260	defined to be C<0>, then they are not. Disabling them saves a few kB of
3261	code.
3262
3263	=item EV_EMBED_ENABLE
3264
3265	If undefined or defined to be C<1>, then embed watchers are supported. If
3266	defined to be C<0>, then they are not. Embed watchers rely on most other
3267	watcher types, which therefore must not be disabled.
3268
3269	=item EV_STAT_ENABLE
3270
3271	If undefined or defined to be C<1>, then stat watchers are supported. If
3272	defined to be C<0>, then they are not.
3273
3274	=item EV_FORK_ENABLE
3275
3276	If undefined or defined to be C<1>, then fork watchers are supported. If
3277	defined to be C<0>, then they are not.
3278
3279	=item EV_ASYNC_ENABLE
3280
3281	If undefined or defined to be C<1>, then async watchers are supported. If
3282	defined to be C<0>, then they are not.
3283
3284	=item EV_MINIMAL
3285		4803
3286	If you need to shave off some kilobytes of code at the expense of some	4804	If you need to shave off some kilobytes of code at the expense of some
3287	speed, define this symbol to C<1>. Currently this is used to override some	4805	speed (but with the full API), you can define this symbol to request
3288	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4806	certain subsets of functionality. The default is to enable all features
3289	much smaller 2-heap for timer management over the default 4-heap.	4807	that can be enabled on the platform.
		4808
		4809	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4810	with some broad features you want) and then selectively re-enable
		4811	additional parts you want, for example if you want everything minimal,
		4812	but multiple event loop support, async and child watchers and the poll
		4813	backend, use this:
		4814
		4815	#define EV_FEATURES 0
		4816	#define EV_MULTIPLICITY 1
		4817	#define EV_USE_POLL 1
		4818	#define EV_CHILD_ENABLE 1
		4819	#define EV_ASYNC_ENABLE 1
		4820
		4821	The actual value is a bitset, it can be a combination of the following
		4822	values (by default, all of these are enabled):
		4823
		4824	=over 4
		4825
		4826	=item C<1> - faster/larger code
		4827
		4828	Use larger code to speed up some operations.
		4829
		4830	Currently this is used to override some inlining decisions (enlarging the
		4831	code size by roughly 30% on amd64).
		4832
		4833	When optimising for size, use of compiler flags such as C<-Os> with
		4834	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4835	assertions.
		4836
		4837	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4838	(e.g. gcc with C<-Os>).
		4839
		4840	=item C<2> - faster/larger data structures
		4841
		4842	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4843	hash table sizes and so on. This will usually further increase code size
		4844	and can additionally have an effect on the size of data structures at
		4845	runtime.
		4846
		4847	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4848	(e.g. gcc with C<-Os>).
		4849
		4850	=item C<4> - full API configuration
		4851
		4852	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4853	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4854
		4855	=item C<8> - full API
		4856
		4857	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4858	details on which parts of the API are still available without this
		4859	feature, and do not complain if this subset changes over time.
		4860
		4861	=item C<16> - enable all optional watcher types
		4862
		4863	Enables all optional watcher types. If you want to selectively enable
		4864	only some watcher types other than I/O and timers (e.g. prepare,
		4865	embed, async, child...) you can enable them manually by defining
		4866	C<EV_watchertype_ENABLE> to C<1> instead.
		4867
		4868	=item C<32> - enable all backends
		4869
		4870	This enables all backends - without this feature, you need to enable at
		4871	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4872
		4873	=item C<64> - enable OS-specific "helper" APIs
		4874
		4875	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4876	default.
		4877
		4878	=back
		4879
		4880	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4881	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4882	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4883	watchers, timers and monotonic clock support.
		4884
		4885	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4886	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4887	your program might be left out as well - a binary starting a timer and an
		4888	I/O watcher then might come out at only 5Kb.
		4889
		4890	=item EV_API_STATIC
		4891
		4892	If this symbol is defined (by default it is not), then all identifiers
		4893	will have static linkage. This means that libev will not export any
		4894	identifiers, and you cannot link against libev anymore. This can be useful
		4895	when you embed libev, only want to use libev functions in a single file,
		4896	and do not want its identifiers to be visible.
		4897
		4898	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4899	wants to use libev.
		4900
		4901	This option only works when libev is compiled with a C compiler, as C++
		4902	doesn't support the required declaration syntax.
		4903
		4904	=item EV_AVOID_STDIO
		4905
		4906	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4907	functions (printf, scanf, perror etc.). This will increase the code size
		4908	somewhat, but if your program doesn't otherwise depend on stdio and your
		4909	libc allows it, this avoids linking in the stdio library which is quite
		4910	big.
		4911
		4912	Note that error messages might become less precise when this option is
		4913	enabled.
		4914
		4915	=item EV_NSIG
		4916
		4917	The highest supported signal number, +1 (or, the number of
		4918	signals): Normally, libev tries to deduce the maximum number of signals
		4919	automatically, but sometimes this fails, in which case it can be
		4920	specified. Also, using a lower number than detected (C<32> should be
		4921	good for about any system in existence) can save some memory, as libev
		4922	statically allocates some 12-24 bytes per signal number.
3290		4923
3291	=item EV_PID_HASHSIZE	4924	=item EV_PID_HASHSIZE
3292		4925
3293	C<ev_child> watchers use a small hash table to distribute workload by	4926	C<ev_child> watchers use a small hash table to distribute workload by
3294	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4927	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3295	than enough. If you need to manage thousands of children you might want to	4928	usually more than enough. If you need to manage thousands of children you
3296	increase this value (I<must> be a power of two).	4929	might want to increase this value (I<must> be a power of two).
3297		4930
3298	=item EV_INOTIFY_HASHSIZE	4931	=item EV_INOTIFY_HASHSIZE
3299		4932
3300	C<ev_stat> watchers use a small hash table to distribute workload by	4933	C<ev_stat> watchers use a small hash table to distribute workload by
3301	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4934	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3302	usually more than enough. If you need to manage thousands of C<ev_stat>	4935	disabled), usually more than enough. If you need to manage thousands of
3303	watchers you might want to increase this value (I<must> be a power of	4936	C<ev_stat> watchers you might want to increase this value (I<must> be a
3304	two).	4937	power of two).
3305		4938
3306	=item EV_USE_4HEAP	4939	=item EV_USE_4HEAP
3307		4940
3308	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4941	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3309	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4942	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3310	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4943	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3311	faster performance with many (thousands) of watchers.	4944	faster performance with many (thousands) of watchers.
3312		4945
3313	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4946	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3314	(disabled).	4947	will be C<0>.
3315		4948
3316	=item EV_HEAP_CACHE_AT	4949	=item EV_HEAP_CACHE_AT
3317		4950
3318	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4951	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3319	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4952	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3320	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4953	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3321	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4954	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3322	but avoids random read accesses on heap changes. This improves performance	4955	but avoids random read accesses on heap changes. This improves performance
3323	noticeably with many (hundreds) of watchers.	4956	noticeably with many (hundreds) of watchers.
3324		4957
3325	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4958	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3326	(disabled).	4959	will be C<0>.
3327		4960
3328	=item EV_VERIFY	4961	=item EV_VERIFY
3329		4962
3330	Controls how much internal verification (see C<ev_loop_verify ()>) will	4963	Controls how much internal verification (see C<ev_verify ()>) will
3331	be done: If set to C<0>, no internal verification code will be compiled	4964	be done: If set to C<0>, no internal verification code will be compiled
3332	in. If set to C<1>, then verification code will be compiled in, but not	4965	in. If set to C<1>, then verification code will be compiled in, but not
3333	called. If set to C<2>, then the internal verification code will be	4966	called. If set to C<2>, then the internal verification code will be
3334	called once per loop, which can slow down libev. If set to C<3>, then the	4967	called once per loop, which can slow down libev. If set to C<3>, then the
3335	verification code will be called very frequently, which will slow down	4968	verification code will be called very frequently, which will slow down
3336	libev considerably.	4969	libev considerably.
3337		4970
3338	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4971	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3339	C<0>.	4972	will be C<0>.
3340		4973
3341	=item EV_COMMON	4974	=item EV_COMMON
3342		4975
3343	By default, all watchers have a C<void *data> member. By redefining	4976	By default, all watchers have a C<void *data> member. By redefining
3344	this macro to a something else you can include more and other types of	4977	this macro to something else you can include more and other types of
3345	members. You have to define it each time you include one of the files,	4978	members. You have to define it each time you include one of the files,
3346	though, and it must be identical each time.	4979	though, and it must be identical each time.
3347		4980
3348	For example, the perl EV module uses something like this:	4981	For example, the perl EV module uses something like this:
3349		4982
…		…
3402	file.	5035	file.
3403		5036
3404	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5037	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3405	that everybody includes and which overrides some configure choices:	5038	that everybody includes and which overrides some configure choices:
3406		5039
3407	#define EV_MINIMAL 1	5040	#define EV_FEATURES 8
3408	#define EV_USE_POLL 0	5041	#define EV_USE_SELECT 1
3409	#define EV_MULTIPLICITY 0
3410	#define EV_PERIODIC_ENABLE 0	5042	#define EV_PREPARE_ENABLE 1
		5043	#define EV_IDLE_ENABLE 1
3411	#define EV_STAT_ENABLE 0	5044	#define EV_SIGNAL_ENABLE 1
3412	#define EV_FORK_ENABLE 0	5045	#define EV_CHILD_ENABLE 1
		5046	#define EV_USE_STDEXCEPT 0
3413	#define EV_CONFIG_H <config.h>	5047	#define EV_CONFIG_H <config.h>
3414	#define EV_MINPRI 0
3415	#define EV_MAXPRI 0
3416		5048
3417	#include "ev++.h"	5049	#include "ev++.h"
3418		5050
3419	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5051	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3420		5052
3421	#include "ev_cpp.h"	5053	#include "ev_cpp.h"
3422	#include "ev.c"	5054	#include "ev.c"
3423		5055
3424	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5056	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3425		5057
3426	=head2 THREADS AND COROUTINES	5058	=head2 THREADS AND COROUTINES
3427		5059
3428	=head3 THREADS	5060	=head3 THREADS
3429		5061
…		…
3480	default loop and triggering an C<ev_async> watcher from the default loop	5112	default loop and triggering an C<ev_async> watcher from the default loop
3481	watcher callback into the event loop interested in the signal.	5113	watcher callback into the event loop interested in the signal.
3482		5114
3483	=back	5115	=back
3484		5116
		5117	See also L</THREAD LOCKING EXAMPLE>.
		5118
3485	=head3 COROUTINES	5119	=head3 COROUTINES
3486		5120
3487	Libev is very accommodating to coroutines ("cooperative threads"):	5121	Libev is very accommodating to coroutines ("cooperative threads"):
3488	libev fully supports nesting calls to its functions from different	5122	libev fully supports nesting calls to its functions from different
3489	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5123	coroutines (e.g. you can call C<ev_run> on the same loop from two
3490	different coroutines, and switch freely between both coroutines running the	5124	different coroutines, and switch freely between both coroutines running
3491	loop, as long as you don't confuse yourself). The only exception is that	5125	the loop, as long as you don't confuse yourself). The only exception is
3492	you must not do this from C<ev_periodic> reschedule callbacks.	5126	that you must not do this from C<ev_periodic> reschedule callbacks.
3493		5127
3494	Care has been taken to ensure that libev does not keep local state inside	5128	Care has been taken to ensure that libev does not keep local state inside
3495	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5129	C<ev_run>, and other calls do not usually allow for coroutine switches as
3496	they do not clal any callbacks.	5130	they do not call any callbacks.
3497		5131
3498	=head2 COMPILER WARNINGS	5132	=head2 COMPILER WARNINGS
3499		5133
3500	Depending on your compiler and compiler settings, you might get no or a	5134	Depending on your compiler and compiler settings, you might get no or a
3501	lot of warnings when compiling libev code. Some people are apparently	5135	lot of warnings when compiling libev code. Some people are apparently
…		…
3511	maintainable.	5145	maintainable.
3512		5146
3513	And of course, some compiler warnings are just plain stupid, or simply	5147	And of course, some compiler warnings are just plain stupid, or simply
3514	wrong (because they don't actually warn about the condition their message	5148	wrong (because they don't actually warn about the condition their message
3515	seems to warn about). For example, certain older gcc versions had some	5149	seems to warn about). For example, certain older gcc versions had some
3516	warnings that resulted an extreme number of false positives. These have	5150	warnings that resulted in an extreme number of false positives. These have
3517	been fixed, but some people still insist on making code warn-free with	5151	been fixed, but some people still insist on making code warn-free with
3518	such buggy versions.	5152	such buggy versions.
3519		5153
3520	While libev is written to generate as few warnings as possible,	5154	While libev is written to generate as few warnings as possible,
3521	"warn-free" code is not a goal, and it is recommended not to build libev	5155	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3535	==2274== definitely lost: 0 bytes in 0 blocks.	5169	==2274== definitely lost: 0 bytes in 0 blocks.
3536	==2274== possibly lost: 0 bytes in 0 blocks.	5170	==2274== possibly lost: 0 bytes in 0 blocks.
3537	==2274== still reachable: 256 bytes in 1 blocks.	5171	==2274== still reachable: 256 bytes in 1 blocks.
3538		5172
3539	Then there is no memory leak, just as memory accounted to global variables	5173	Then there is no memory leak, just as memory accounted to global variables
3540	is not a memleak - the memory is still being refernced, and didn't leak.	5174	is not a memleak - the memory is still being referenced, and didn't leak.
3541		5175
3542	Similarly, under some circumstances, valgrind might report kernel bugs	5176	Similarly, under some circumstances, valgrind might report kernel bugs
3543	as if it were a bug in libev (e.g. in realloc or in the poll backend,	5177	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3544	although an acceptable workaround has been found here), or it might be	5178	although an acceptable workaround has been found here), or it might be
3545	confused.	5179	confused.
…		…
3557	I suggest using suppression lists.	5191	I suggest using suppression lists.
3558		5192
3559		5193
3560	=head1 PORTABILITY NOTES	5194	=head1 PORTABILITY NOTES
3561		5195
		5196	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5197
		5198	GNU/Linux is the only common platform that supports 64 bit file/large file
		5199	interfaces but I<disables> them by default.
		5200
		5201	That means that libev compiled in the default environment doesn't support
		5202	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5203
		5204	Unfortunately, many programs try to work around this GNU/Linux issue
		5205	by enabling the large file API, which makes them incompatible with the
		5206	standard libev compiled for their system.
		5207
		5208	Likewise, libev cannot enable the large file API itself as this would
		5209	suddenly make it incompatible to the default compile time environment,
		5210	i.e. all programs not using special compile switches.
		5211
		5212	=head2 OS/X AND DARWIN BUGS
		5213
		5214	The whole thing is a bug if you ask me - basically any system interface
		5215	you touch is broken, whether it is locales, poll, kqueue or even the
		5216	OpenGL drivers.
		5217
		5218	=head3 C<kqueue> is buggy
		5219
		5220	The kqueue syscall is broken in all known versions - most versions support
		5221	only sockets, many support pipes.
		5222
		5223	Libev tries to work around this by not using C<kqueue> by default on this
		5224	rotten platform, but of course you can still ask for it when creating a
		5225	loop - embedding a socket-only kqueue loop into a select-based one is
		5226	probably going to work well.
		5227
		5228	=head3 C<poll> is buggy
		5229
		5230	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5231	implementation by something calling C<kqueue> internally around the 10.5.6
		5232	release, so now C<kqueue> I<and> C<poll> are broken.
		5233
		5234	Libev tries to work around this by not using C<poll> by default on
		5235	this rotten platform, but of course you can still ask for it when creating
		5236	a loop.
		5237
		5238	=head3 C<select> is buggy
		5239
		5240	All that's left is C<select>, and of course Apple found a way to fuck this
		5241	one up as well: On OS/X, C<select> actively limits the number of file
		5242	descriptors you can pass in to 1024 - your program suddenly crashes when
		5243	you use more.
		5244
		5245	There is an undocumented "workaround" for this - defining
		5246	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5247	work on OS/X.
		5248
		5249	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5250
		5251	=head3 C<errno> reentrancy
		5252
		5253	The default compile environment on Solaris is unfortunately so
		5254	thread-unsafe that you can't even use components/libraries compiled
		5255	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5256	defined by default. A valid, if stupid, implementation choice.
		5257
		5258	If you want to use libev in threaded environments you have to make sure
		5259	it's compiled with C<_REENTRANT> defined.
		5260
		5261	=head3 Event port backend
		5262
		5263	The scalable event interface for Solaris is called "event
		5264	ports". Unfortunately, this mechanism is very buggy in all major
		5265	releases. If you run into high CPU usage, your program freezes or you get
		5266	a large number of spurious wakeups, make sure you have all the relevant
		5267	and latest kernel patches applied. No, I don't know which ones, but there
		5268	are multiple ones to apply, and afterwards, event ports actually work
		5269	great.
		5270
		5271	If you can't get it to work, you can try running the program by setting
		5272	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5273	C<select> backends.
		5274
		5275	=head2 AIX POLL BUG
		5276
		5277	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5278	this by trying to avoid the poll backend altogether (i.e. it's not even
		5279	compiled in), which normally isn't a big problem as C<select> works fine
		5280	with large bitsets on AIX, and AIX is dead anyway.
		5281
3562	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5282	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5283
		5284	=head3 General issues
3563		5285
3564	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5286	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3565	requires, and its I/O model is fundamentally incompatible with the POSIX	5287	requires, and its I/O model is fundamentally incompatible with the POSIX
3566	model. Libev still offers limited functionality on this platform in	5288	model. Libev still offers limited functionality on this platform in
3567	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5289	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3568	descriptors. This only applies when using Win32 natively, not when using	5290	descriptors. This only applies when using Win32 natively, not when using
3569	e.g. cygwin.	5291	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5292	as every compiler comes with a slightly differently broken/incompatible
		5293	environment.
3570		5294
3571	Lifting these limitations would basically require the full	5295	Lifting these limitations would basically require the full
3572	re-implementation of the I/O system. If you are into these kinds of	5296	re-implementation of the I/O system. If you are into this kind of thing,
3573	things, then note that glib does exactly that for you in a very portable	5297	then note that glib does exactly that for you in a very portable way (note
3574	way (note also that glib is the slowest event library known to man).	5298	also that glib is the slowest event library known to man).
3575		5299
3576	There is no supported compilation method available on windows except	5300	There is no supported compilation method available on windows except
3577	embedding it into other applications.	5301	embedding it into other applications.
		5302
		5303	Sensible signal handling is officially unsupported by Microsoft - libev
		5304	tries its best, but under most conditions, signals will simply not work.
3578		5305
3579	Not a libev limitation but worth mentioning: windows apparently doesn't	5306	Not a libev limitation but worth mentioning: windows apparently doesn't
3580	accept large writes: instead of resulting in a partial write, windows will	5307	accept large writes: instead of resulting in a partial write, windows will
3581	either accept everything or return C<ENOBUFS> if the buffer is too large,	5308	either accept everything or return C<ENOBUFS> if the buffer is too large,
3582	so make sure you only write small amounts into your sockets (less than a	5309	so make sure you only write small amounts into your sockets (less than a
…		…
3587	the abysmal performance of winsockets, using a large number of sockets	5314	the abysmal performance of winsockets, using a large number of sockets
3588	is not recommended (and not reasonable). If your program needs to use	5315	is not recommended (and not reasonable). If your program needs to use
3589	more than a hundred or so sockets, then likely it needs to use a totally	5316	more than a hundred or so sockets, then likely it needs to use a totally
3590	different implementation for windows, as libev offers the POSIX readiness	5317	different implementation for windows, as libev offers the POSIX readiness
3591	notification model, which cannot be implemented efficiently on windows	5318	notification model, which cannot be implemented efficiently on windows
3592	(Microsoft monopoly games).	5319	(due to Microsoft monopoly games).
3593		5320
3594	A typical way to use libev under windows is to embed it (see the embedding	5321	A typical way to use libev under windows is to embed it (see the embedding
3595	section for details) and use the following F<evwrap.h> header file instead	5322	section for details) and use the following F<evwrap.h> header file instead
3596	of F<ev.h>:	5323	of F<ev.h>:
3597		5324
…		…
3604	you do I<not> compile the F<ev.c> or any other embedded source files!):	5331	you do I<not> compile the F<ev.c> or any other embedded source files!):
3605		5332
3606	#include "evwrap.h"	5333	#include "evwrap.h"
3607	#include "ev.c"	5334	#include "ev.c"
3608		5335
3609	=over 4
3610
3611	=item The winsocket select function	5336	=head3 The winsocket C<select> function
3612		5337
3613	The winsocket C<select> function doesn't follow POSIX in that it	5338	The winsocket C<select> function doesn't follow POSIX in that it
3614	requires socket I<handles> and not socket I<file descriptors> (it is	5339	requires socket I<handles> and not socket I<file descriptors> (it is
3615	also extremely buggy). This makes select very inefficient, and also	5340	also extremely buggy). This makes select very inefficient, and also
3616	requires a mapping from file descriptors to socket handles (the Microsoft	5341	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3625	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5350	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3626		5351
3627	Note that winsockets handling of fd sets is O(n), so you can easily get a	5352	Note that winsockets handling of fd sets is O(n), so you can easily get a
3628	complexity in the O(n²) range when using win32.	5353	complexity in the O(n²) range when using win32.
3629		5354
3630	=item Limited number of file descriptors	5355	=head3 Limited number of file descriptors
3631		5356
3632	Windows has numerous arbitrary (and low) limits on things.	5357	Windows has numerous arbitrary (and low) limits on things.
3633		5358
3634	Early versions of winsocket's select only supported waiting for a maximum	5359	Early versions of winsocket's select only supported waiting for a maximum
3635	of C<64> handles (probably owning to the fact that all windows kernels	5360	of C<64> handles (probably owning to the fact that all windows kernels
3636	can only wait for C<64> things at the same time internally; Microsoft	5361	can only wait for C<64> things at the same time internally; Microsoft
3637	recommends spawning a chain of threads and wait for 63 handles and the	5362	recommends spawning a chain of threads and wait for 63 handles and the
3638	previous thread in each. Great).	5363	previous thread in each. Sounds great!).
3639		5364
3640	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5365	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3641	to some high number (e.g. C<2048>) before compiling the winsocket select	5366	to some high number (e.g. C<2048>) before compiling the winsocket select
3642	call (which might be in libev or elsewhere, for example, perl does its own	5367	call (which might be in libev or elsewhere, for example, perl and many
3643	select emulation on windows).	5368	other interpreters do their own select emulation on windows).
3644		5369
3645	Another limit is the number of file descriptors in the Microsoft runtime	5370	Another limit is the number of file descriptors in the Microsoft runtime
3646	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5371	libraries, which by default is C<64> (there must be a hidden I<64>
3647	or something like this inside Microsoft). You can increase this by calling	5372	fetish or something like this inside Microsoft). You can increase this
3648	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5373	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3649	arbitrary limit), but is broken in many versions of the Microsoft runtime	5374	(another arbitrary limit), but is broken in many versions of the Microsoft
3650	libraries.
3651
3652	This might get you to about C<512> or C<2048> sockets (depending on	5375	runtime libraries. This might get you to about C<512> or C<2048> sockets
3653	windows version and/or the phase of the moon). To get more, you need to	5376	(depending on windows version and/or the phase of the moon). To get more,
3654	wrap all I/O functions and provide your own fd management, but the cost of	5377	you need to wrap all I/O functions and provide your own fd management, but
3655	calling select (O(n²)) will likely make this unworkable.	5378	the cost of calling select (O(n²)) will likely make this unworkable.
3656
3657	=back
3658		5379
3659	=head2 PORTABILITY REQUIREMENTS	5380	=head2 PORTABILITY REQUIREMENTS
3660		5381
3661	In addition to a working ISO-C implementation and of course the	5382	In addition to a working ISO-C implementation and of course the
3662	backend-specific APIs, libev relies on a few additional extensions:	5383	backend-specific APIs, libev relies on a few additional extensions:
…		…
3669	Libev assumes not only that all watcher pointers have the same internal	5390	Libev assumes not only that all watcher pointers have the same internal
3670	structure (guaranteed by POSIX but not by ISO C for example), but it also	5391	structure (guaranteed by POSIX but not by ISO C for example), but it also
3671	assumes that the same (machine) code can be used to call any watcher	5392	assumes that the same (machine) code can be used to call any watcher
3672	callback: The watcher callbacks have different type signatures, but libev	5393	callback: The watcher callbacks have different type signatures, but libev
3673	calls them using an C<ev_watcher *> internally.	5394	calls them using an C<ev_watcher *> internally.
		5395
		5396	=item null pointers and integer zero are represented by 0 bytes
		5397
		5398	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5399	relies on this setting pointers and integers to null.
		5400
		5401	=item pointer accesses must be thread-atomic
		5402
		5403	Accessing a pointer value must be atomic, it must both be readable and
		5404	writable in one piece - this is the case on all current architectures.
3674		5405
3675	=item C<sig_atomic_t volatile> must be thread-atomic as well	5406	=item C<sig_atomic_t volatile> must be thread-atomic as well
3676		5407
3677	The type C<sig_atomic_t volatile> (or whatever is defined as	5408	The type C<sig_atomic_t volatile> (or whatever is defined as
3678	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5409	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3687	thread" or will block signals process-wide, both behaviours would	5418	thread" or will block signals process-wide, both behaviours would
3688	be compatible with libev. Interaction between C<sigprocmask> and	5419	be compatible with libev. Interaction between C<sigprocmask> and
3689	C<pthread_sigmask> could complicate things, however.	5420	C<pthread_sigmask> could complicate things, however.
3690		5421
3691	The most portable way to handle signals is to block signals in all threads	5422	The most portable way to handle signals is to block signals in all threads
3692	except the initial one, and run the default loop in the initial thread as	5423	except the initial one, and run the signal handling loop in the initial
3693	well.	5424	thread as well.
3694		5425
3695	=item C<long> must be large enough for common memory allocation sizes	5426	=item C<long> must be large enough for common memory allocation sizes
3696		5427
3697	To improve portability and simplify its API, libev uses C<long> internally	5428	To improve portability and simplify its API, libev uses C<long> internally
3698	instead of C<size_t> when allocating its data structures. On non-POSIX	5429	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3701	watchers.	5432	watchers.
3702		5433
3703	=item C<double> must hold a time value in seconds with enough accuracy	5434	=item C<double> must hold a time value in seconds with enough accuracy
3704		5435
3705	The type C<double> is used to represent timestamps. It is required to	5436	The type C<double> is used to represent timestamps. It is required to
3706	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5437	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3707	enough for at least into the year 4000. This requirement is fulfilled by	5438	good enough for at least into the year 4000 with millisecond accuracy
		5439	(the design goal for libev). This requirement is overfulfilled by
3708	implementations implementing IEEE 754 (basically all existing ones).	5440	implementations using IEEE 754, which is basically all existing ones.
		5441
		5442	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5443	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5444	is either obsolete or somebody patched it to use C<long double> or
		5445	something like that, just kidding).
3709		5446
3710	=back	5447	=back
3711		5448
3712	If you know of other additional requirements drop me a note.	5449	If you know of other additional requirements drop me a note.
3713		5450
…		…
3775	=item Processing ev_async_send: O(number_of_async_watchers)	5512	=item Processing ev_async_send: O(number_of_async_watchers)
3776		5513
3777	=item Processing signals: O(max_signal_number)	5514	=item Processing signals: O(max_signal_number)
3778		5515
3779	Sending involves a system call I<iff> there were no other C<ev_async_send>	5516	Sending involves a system call I<iff> there were no other C<ev_async_send>
3780	calls in the current loop iteration. Checking for async and signal events	5517	calls in the current loop iteration and the loop is currently
		5518	blocked. Checking for async and signal events involves iterating over all
3781	involves iterating over all running async watchers or all signal numbers.	5519	running async watchers or all signal numbers.
3782		5520
3783	=back	5521	=back
3784		5522
3785		5523
		5524	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5525
		5526	The major version 4 introduced some incompatible changes to the API.
		5527
		5528	At the moment, the C<ev.h> header file provides compatibility definitions
		5529	for all changes, so most programs should still compile. The compatibility
		5530	layer might be removed in later versions of libev, so better update to the
		5531	new API early than late.
		5532
		5533	=over 4
		5534
		5535	=item C<EV_COMPAT3> backwards compatibility mechanism
		5536
		5537	The backward compatibility mechanism can be controlled by
		5538	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5539	section.
		5540
		5541	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5542
		5543	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5544
		5545	ev_loop_destroy (EV_DEFAULT_UC);
		5546	ev_loop_fork (EV_DEFAULT);
		5547
		5548	=item function/symbol renames
		5549
		5550	A number of functions and symbols have been renamed:
		5551
		5552	ev_loop => ev_run
		5553	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5554	EVLOOP_ONESHOT => EVRUN_ONCE
		5555
		5556	ev_unloop => ev_break
		5557	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5558	EVUNLOOP_ONE => EVBREAK_ONE
		5559	EVUNLOOP_ALL => EVBREAK_ALL
		5560
		5561	EV_TIMEOUT => EV_TIMER
		5562
		5563	ev_loop_count => ev_iteration
		5564	ev_loop_depth => ev_depth
		5565	ev_loop_verify => ev_verify
		5566
		5567	Most functions working on C<struct ev_loop> objects don't have an
		5568	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5569	associated constants have been renamed to not collide with the C<struct
		5570	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5571	as all other watcher types. Note that C<ev_loop_fork> is still called
		5572	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5573	typedef.
		5574
		5575	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5576
		5577	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5578	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5579	and work, but the library code will of course be larger.
		5580
		5581	=back
		5582
		5583
		5584	=head1 GLOSSARY
		5585
		5586	=over 4
		5587
		5588	=item active
		5589
		5590	A watcher is active as long as it has been started and not yet stopped.
		5591	See L</WATCHER STATES> for details.
		5592
		5593	=item application
		5594
		5595	In this document, an application is whatever is using libev.
		5596
		5597	=item backend
		5598
		5599	The part of the code dealing with the operating system interfaces.
		5600
		5601	=item callback
		5602
		5603	The address of a function that is called when some event has been
		5604	detected. Callbacks are being passed the event loop, the watcher that
		5605	received the event, and the actual event bitset.
		5606
		5607	=item callback/watcher invocation
		5608
		5609	The act of calling the callback associated with a watcher.
		5610
		5611	=item event
		5612
		5613	A change of state of some external event, such as data now being available
		5614	for reading on a file descriptor, time having passed or simply not having
		5615	any other events happening anymore.
		5616
		5617	In libev, events are represented as single bits (such as C<EV_READ> or
		5618	C<EV_TIMER>).
		5619
		5620	=item event library
		5621
		5622	A software package implementing an event model and loop.
		5623
		5624	=item event loop
		5625
		5626	An entity that handles and processes external events and converts them
		5627	into callback invocations.
		5628
		5629	=item event model
		5630
		5631	The model used to describe how an event loop handles and processes
		5632	watchers and events.
		5633
		5634	=item pending
		5635
		5636	A watcher is pending as soon as the corresponding event has been
		5637	detected. See L</WATCHER STATES> for details.
		5638
		5639	=item real time
		5640
		5641	The physical time that is observed. It is apparently strictly monotonic :)
		5642
		5643	=item wall-clock time
		5644
		5645	The time and date as shown on clocks. Unlike real time, it can actually
		5646	be wrong and jump forwards and backwards, e.g. when you adjust your
		5647	clock.
		5648
		5649	=item watcher
		5650
		5651	A data structure that describes interest in certain events. Watchers need
		5652	to be started (attached to an event loop) before they can receive events.
		5653
		5654	=back
		5655
3786	=head1 AUTHOR	5656	=head1 AUTHOR
3787		5657
3788	Marc Lehmann <libev@schmorp.de>.	5658	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5659	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3789		5660

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