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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
…		…
8		10
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>
		15
		16	#include <stdio.h> // for puts
13		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;
…		…
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<struct ev_loop *> (the C<struct>	349	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	350	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	351	libev 3 had an C<ev_loop> function colliding with the struct name).
284		352
285	The library knows two types of such loops, the I<default> loop, which	353	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	354	supports child process events, and dynamically created event loops which
287	not.	355	do not.
288		356
289	=over 4	357	=over 4
290		358
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	359	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		360
293	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
294	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
295	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
296	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".
297		371
298	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
299	function.	373	function (or via the C<EV_DEFAULT> macro).
300		374
301	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
302	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
303	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).
304		379
305	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,
306	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
307	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
308	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
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	384	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	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.
311		404
312	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
313	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>).
314		407
315	The following flags are supported:	408	The following flags are supported:
…		…
325		418
326	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
327	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
328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	421	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
329	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
330	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
331	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).
332		427
333	=item C<EVFLAG_FORKCHECK>	428	=item C<EVFLAG_FORKCHECK>
334		429
335	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
336	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.
337	enabling this flag.
338		432
339	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,
340	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
341	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
342	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
343	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
344	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).
345		440
346	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
347	forget about forgetting to tell libev about forking) when you use this	442	forget about forgetting to tell libev about forking, although you still
348	flag.	443	have to ignore C<SIGPIPE>) when you use this flag.
349		444
350	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>
351	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.
352		482
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	483	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		484
355	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
356	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,
…		…
381	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
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	512	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		513
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	514	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		515
		516	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		517	kernels).
		518
386	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
387	but it scales phenomenally better. While poll and select usually scale	520	it scales phenomenally better. While poll and select usually scale like
388	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
389	epoll scales either O(1) or O(active_fds).	522	fd), epoll scales either O(1) or O(active_fds).
390		523
391	The epoll syscalls are the most misdesigned of the more advanced event	524	The epoll mechanism deserves honorable mention as the most misdesigned
392	mechanisms: problems include silently dropping fds, requiring a system	525	of the more advanced event mechanisms: mere annoyances include silently
		526	dropping file descriptors, requiring a system call per change per file
393	call per change per fd (and unnecessary guessing of parameters), problems	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
394	with dup and so on. The biggest issue is fork races, however - if a	530	0.1ms) and so on. The biggest issue is fork races, however - if a program
395	program forks then I<both> parent and child process have to recreate the	531	forks then I<both> parent and child process have to recreate the epoll
396	epoll set, which can take considerable time (one syscall per fd) and is of	532	set, which can take considerable time (one syscall per file descriptor)
397	course hard to detect.	533	and is of course hard to detect.
398		534
399	Epoll is also notoriously buggy - embedding epoll fds should work, but	535	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
400	of course doesn't, and epoll just loves to report events for totally	536	but of course I<doesn't>, and epoll just loves to report events for
401	I<different> file descriptors (even already closed ones, so one cannot	537	totally I<different> file descriptors (even already closed ones, so
402	even remove them from the set) than registered in the set (especially	538	one cannot even remove them from the set) than registered in the set
403	on SMP systems). Libev tries to counter these spurious notifications by	539	(especially on SMP systems). Libev tries to counter these spurious
404	employing an additional generation counter and comparing that against the	540	notifications by employing an additional generation counter and comparing
405	events to filter out spurious ones.	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...
406		551
407	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
408	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
409	(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
410	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
411	very well if you register events for both fds.	556	file descriptors might not work very well if you register events for both
		557	file descriptors.
412		558
413	Best performance from this backend is achieved by not unregistering all	559	Best performance from this backend is achieved by not unregistering all
414	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,
415	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
416	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
417	extra overhead. A fork can both result in spurious notifications as well	563	extra overhead. A fork can both result in spurious notifications as well
418	as in libev having to destroy and recreate the epoll object, which can	564	as in libev having to destroy and recreate the epoll object, which can
419	take considerable time and thus should be avoided.	565	take considerable time and thus should be avoided.
420		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.
		570
421	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
422	all kernel versions tested so far.	572	a lot of kernel revisions, but probably(!) works in current versions.
423		573
424	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
425	C<EVBACKEND_POLL>.	575	C<EVBACKEND_POLL>.
426		576
		577	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		578
		579	Use the linux-specific linux aio (I<not> C<< aio(7) >>) event interface
		580	available in post-4.18 kernels.
		581
		582	If this backend works for you (as of this writing, it was very
		583	experimental and only supports a subset of file types), it is the best
		584	event interface available on linux and might be well worth it enabling it
		585	- if it isn't available in your kernel this will be detected and another
		586	backend will be chosen.
		587
		588	This backend can batch oneshot requests and uses a user-space ring buffer
		589	to receive events. It also doesn't suffer from most of the design problems
		590	of epoll (such as not being able to remove event sources from the epoll
		591	set), and generally sounds too good to be true. Because, this being the
		592	linux kernel, of course it suffers from a whole new set of 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 various
		596	arbitrary limits that can be configured in F</proc/sys/fs/aio-max-nr>
		597	and F</proc/sys/fs/aio-nr>), which could lead to it being skipped during
		598	initialisation.
		599
		600	Most problematic in practise, however, is that, like kqueue, it requires
		601	special support from drivers, and, not surprisingly, not all drivers
		602	implement it. For example, in linux 4.19, tcp sockets, pipes, event fds,
		603	files, F</dev/null> and a few others are supported, but ttys are not, so
		604	this is not (yet?) a generic event polling interface but is probably still
		605	be very useful in a web server or similar program.
		606
		607	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		608	C<EVBACKEND_POLL>.
		609
427	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	610	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
428		611
429	Kqueue deserves special mention, as at the time of this writing, it was	612	Kqueue deserves special mention, as at the time of this writing, it
430	broken on all BSDs except NetBSD (usually it doesn't work reliably with	613	was broken on all BSDs except NetBSD (usually it doesn't work reliably
431	anything but sockets and pipes, except on Darwin, where of course it's	614	with anything but sockets and pipes, except on Darwin, where of course
432	completely useless). For this reason it's not being "auto-detected" unless	615	it's completely useless). Unlike epoll, however, whose brokenness
433	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	616	is by design, these kqueue bugs can (and eventually will) be fixed
434	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	617	without API changes to existing programs. For this reason it's not being
		618	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		619	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		620	system like NetBSD.
435		621
436	You still can embed kqueue into a normal poll or select backend and use it	622	You still can embed kqueue into a normal poll or select backend and use it
437	only for sockets (after having made sure that sockets work with kqueue on	623	only for sockets (after having made sure that sockets work with kqueue on
438	the target platform). See C<ev_embed> watchers for more info.	624	the target platform). See C<ev_embed> watchers for more info.
439		625
440	It scales in the same way as the epoll backend, but the interface to the	626	It scales in the same way as the epoll backend, but the interface to the
441	kernel is more efficient (which says nothing about its actual speed, of	627	kernel is more efficient (which says nothing about its actual speed, of
442	course). While stopping, setting and starting an I/O watcher does never	628	course). While stopping, setting and starting an I/O watcher does never
443	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	629	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
444	two event changes per incident. Support for C<fork ()> is very bad (but	630	two event changes per incident. Support for C<fork ()> is very bad (you
445	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	631	might have to leak fd's on fork, but it's more sane than epoll) and it
446	cases	632	drops fds silently in similarly hard-to-detect cases.
447		633
448	This backend usually performs well under most conditions.	634	This backend usually performs well under most conditions.
449		635
450	While nominally embeddable in other event loops, this doesn't work	636	While nominally embeddable in other event loops, this doesn't work
451	everywhere, so you might need to test for this. And since it is broken	637	everywhere, so you might need to test for this. And since it is broken
452	almost everywhere, you should only use it when you have a lot of sockets	638	almost everywhere, you should only use it when you have a lot of sockets
453	(for which it usually works), by embedding it into another event loop	639	(for which it usually works), by embedding it into another event loop
454	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	640	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
455	using it only for sockets.	641	also broken on OS X)) and, did I mention it, using it only for sockets.
456		642
457	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	643	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
458	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	644	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
459	C<NOTE_EOF>.	645	C<NOTE_EOF>.
460		646
…		…
468	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	654	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
469		655
470	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	656	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
471	it's really slow, but it still scales very well (O(active_fds)).	657	it's really slow, but it still scales very well (O(active_fds)).
472		658
473	Please note that Solaris event ports can deliver a lot of spurious
474	notifications, so you need to use non-blocking I/O or other means to avoid
475	blocking when no data (or space) is available.
476
477	While this backend scales well, it requires one system call per active	659	While this backend scales well, it requires one system call per active
478	file descriptor per loop iteration. For small and medium numbers of file	660	file descriptor per loop iteration. For small and medium numbers of file
479	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	661	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
480	might perform better.	662	might perform better.
481		663
482	On the positive side, with the exception of the spurious readiness	664	On the positive side, this backend actually performed fully to
483	notifications, this backend actually performed fully to specification
484	in all tests and is fully embeddable, which is a rare feat among the	665	specification in all tests and is fully embeddable, which is a rare feat
485	OS-specific backends (I vastly prefer correctness over speed hacks).	666	among the OS-specific backends (I vastly prefer correctness over speed
		667	hacks).
		668
		669	On the negative side, the interface is I<bizarre> - so bizarre that
		670	even sun itself gets it wrong in their code examples: The event polling
		671	function sometimes returns events to the caller even though an error
		672	occurred, but with no indication whether it has done so or not (yes, it's
		673	even documented that way) - deadly for edge-triggered interfaces where you
		674	absolutely have to know whether an event occurred or not because you have
		675	to re-arm the watcher.
		676
		677	Fortunately libev seems to be able to work around these idiocies.
486		678
487	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	679	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
488	C<EVBACKEND_POLL>.	680	C<EVBACKEND_POLL>.
489		681
490	=item C<EVBACKEND_ALL>	682	=item C<EVBACKEND_ALL>
491		683
492	Try all backends (even potentially broken ones that wouldn't be tried	684	Try all backends (even potentially broken ones that wouldn't be tried
493	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	685	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
494	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	686	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
495		687
496	It is definitely not recommended to use this flag.	688	It is definitely not recommended to use this flag, use whatever
		689	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		690	at all.
		691
		692	=item C<EVBACKEND_MASK>
		693
		694	Not a backend at all, but a mask to select all backend bits from a
		695	C<flags> value, in case you want to mask out any backends from a flags
		696	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
497		697
498	=back	698	=back
499		699
500	If one or more of these are or'ed into the flags value, then only these	700	If one or more of the backend flags are or'ed into the flags value,
501	backends will be tried (in the reverse order as listed here). If none are	701	then only these backends will be tried (in the reverse order as listed
502	specified, all backends in C<ev_recommended_backends ()> will be tried.	702	here). If none are specified, all backends in C<ev_recommended_backends
503		703	()> will be tried.
504	Example: This is the most typical usage.
505
506	if (!ev_default_loop (0))
507	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
508
509	Example: Restrict libev to the select and poll backends, and do not allow
510	environment settings to be taken into account:
511
512	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
513
514	Example: Use whatever libev has to offer, but make sure that kqueue is
515	used if available (warning, breaks stuff, best use only with your own
516	private event loop and only if you know the OS supports your types of
517	fds):
518
519	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
520
521	=item struct ev_loop *ev_loop_new (unsigned int flags)
522
523	Similar to C<ev_default_loop>, but always creates a new event loop that is
524	always distinct from the default loop. Unlike the default loop, it cannot
525	handle signal and child watchers, and attempts to do so will be greeted by
526	undefined behaviour (or a failed assertion if assertions are enabled).
527
528	Note that this function I<is> thread-safe, and the recommended way to use
529	libev with threads is indeed to create one loop per thread, and using the
530	default loop in the "main" or "initial" thread.
531		704
532	Example: Try to create a event loop that uses epoll and nothing else.	705	Example: Try to create a event loop that uses epoll and nothing else.
533		706
534	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	707	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
535	if (!epoller)	708	if (!epoller)
536	fatal ("no epoll found here, maybe it hides under your chair");	709	fatal ("no epoll found here, maybe it hides under your chair");
537		710
		711	Example: Use whatever libev has to offer, but make sure that kqueue is
		712	used if available.
		713
		714	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		715
		716	Example: Similarly, on linux, you mgiht want to take advantage of the
		717	linux aio backend if possible, but fall back to something else if that
		718	isn't available.
		719
		720	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		721
538	=item ev_default_destroy ()	722	=item ev_loop_destroy (loop)
539		723
540	Destroys the default loop again (frees all memory and kernel state	724	Destroys an event loop object (frees all memory and kernel state
541	etc.). None of the active event watchers will be stopped in the normal	725	etc.). None of the active event watchers will be stopped in the normal
542	sense, so e.g. C<ev_is_active> might still return true. It is your	726	sense, so e.g. C<ev_is_active> might still return true. It is your
543	responsibility to either stop all watchers cleanly yourself I<before>	727	responsibility to either stop all watchers cleanly yourself I<before>
544	calling this function, or cope with the fact afterwards (which is usually	728	calling this function, or cope with the fact afterwards (which is usually
545	the easiest thing, you can just ignore the watchers and/or C<free ()> them	729	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
547		731
548	Note that certain global state, such as signal state (and installed signal	732	Note that certain global state, such as signal state (and installed signal
549	handlers), will not be freed by this function, and related watchers (such	733	handlers), will not be freed by this function, and related watchers (such
550	as signal and child watchers) would need to be stopped manually.	734	as signal and child watchers) would need to be stopped manually.
551		735
552	In general it is not advisable to call this function except in the	736	This function is normally used on loop objects allocated by
553	rare occasion where you really need to free e.g. the signal handling	737	C<ev_loop_new>, but it can also be used on the default loop returned by
		738	C<ev_default_loop>, in which case it is not thread-safe.
		739
		740	Note that it is not advisable to call this function on the default loop
		741	except in the rare occasion where you really need to free its resources.
554	pipe fds. If you need dynamically allocated loops it is better to use	742	If you need dynamically allocated loops it is better to use C<ev_loop_new>
555	C<ev_loop_new> and C<ev_loop_destroy>).	743	and C<ev_loop_destroy>.
556		744
557	=item ev_loop_destroy (loop)	745	=item ev_loop_fork (loop)
558		746
559	Like C<ev_default_destroy>, but destroys an event loop created by an
560	earlier call to C<ev_loop_new>.
561
562	=item ev_default_fork ()
563
564	This function sets a flag that causes subsequent C<ev_loop> iterations	747	This function sets a flag that causes subsequent C<ev_run> iterations
565	to reinitialise the kernel state for backends that have one. Despite the	748	to reinitialise the kernel state for backends that have one. Despite
566	name, you can call it anytime, but it makes most sense after forking, in	749	the name, you can call it anytime you are allowed to start or stop
567	the child process (or both child and parent, but that again makes little	750	watchers (except inside an C<ev_prepare> callback), but it makes most
568	sense). You I<must> call it in the child before using any of the libev	751	sense after forking, in the child process. You I<must> call it (or use
569	functions, and it will only take effect at the next C<ev_loop> iteration.	752	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		753
		754	In addition, if you want to reuse a loop (via this function or
		755	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		756
		757	Again, you I<have> to call it on I<any> loop that you want to re-use after
		758	a fork, I<even if you do not plan to use the loop in the parent>. This is
		759	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		760	during fork.
570		761
571	On the other hand, you only need to call this function in the child	762	On the other hand, you only need to call this function in the child
572	process if and only if you want to use the event library in the child. If	763	process if and only if you want to use the event loop in the child. If
573	you just fork+exec, you don't have to call it at all.	764	you just fork+exec or create a new loop in the child, you don't have to
		765	call it at all (in fact, C<epoll> is so badly broken that it makes a
		766	difference, but libev will usually detect this case on its own and do a
		767	costly reset of the backend).
574		768
575	The function itself is quite fast and it's usually not a problem to call	769	The function itself is quite fast and it's usually not a problem to call
576	it just in case after a fork. To make this easy, the function will fit in	770	it just in case after a fork.
577	quite nicely into a call to C<pthread_atfork>:
578		771
		772	Example: Automate calling C<ev_loop_fork> on the default loop when
		773	using pthreads.
		774
		775	static void
		776	post_fork_child (void)
		777	{
		778	ev_loop_fork (EV_DEFAULT);
		779	}
		780
		781	...
579	pthread_atfork (0, 0, ev_default_fork);	782	pthread_atfork (0, 0, post_fork_child);
580
581	=item ev_loop_fork (loop)
582
583	Like C<ev_default_fork>, but acts on an event loop created by
584	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
585	after fork that you want to re-use in the child, and how you do this is
586	entirely your own problem.
587		783
588	=item int ev_is_default_loop (loop)	784	=item int ev_is_default_loop (loop)
589		785
590	Returns true when the given loop is, in fact, the default loop, and false	786	Returns true when the given loop is, in fact, the default loop, and false
591	otherwise.	787	otherwise.
592		788
593	=item unsigned int ev_loop_count (loop)	789	=item unsigned int ev_iteration (loop)
594		790
595	Returns the count of loop iterations for the loop, which is identical to	791	Returns the current iteration count for the event loop, which is identical
596	the number of times libev did poll for new events. It starts at C<0> and	792	to the number of times libev did poll for new events. It starts at C<0>
597	happily wraps around with enough iterations.	793	and happily wraps around with enough iterations.
598		794
599	This value can sometimes be useful as a generation counter of sorts (it	795	This value can sometimes be useful as a generation counter of sorts (it
600	"ticks" the number of loop iterations), as it roughly corresponds with	796	"ticks" the number of loop iterations), as it roughly corresponds with
601	C<ev_prepare> and C<ev_check> calls.	797	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		798	prepare and check phases.
		799
		800	=item unsigned int ev_depth (loop)
		801
		802	Returns the number of times C<ev_run> was entered minus the number of
		803	times C<ev_run> was exited normally, in other words, the recursion depth.
		804
		805	Outside C<ev_run>, this number is zero. In a callback, this number is
		806	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		807	in which case it is higher.
		808
		809	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		810	throwing an exception etc.), doesn't count as "exit" - consider this
		811	as a hint to avoid such ungentleman-like behaviour unless it's really
		812	convenient, in which case it is fully supported.
602		813
603	=item unsigned int ev_backend (loop)	814	=item unsigned int ev_backend (loop)
604		815
605	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	816	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
606	use.	817	use.
…		…
615		826
616	=item ev_now_update (loop)	827	=item ev_now_update (loop)
617		828
618	Establishes the current time by querying the kernel, updating the time	829	Establishes the current time by querying the kernel, updating the time
619	returned by C<ev_now ()> in the progress. This is a costly operation and	830	returned by C<ev_now ()> in the progress. This is a costly operation and
620	is usually done automatically within C<ev_loop ()>.	831	is usually done automatically within C<ev_run ()>.
621		832
622	This function is rarely useful, but when some event callback runs for a	833	This function is rarely useful, but when some event callback runs for a
623	very long time without entering the event loop, updating libev's idea of	834	very long time without entering the event loop, updating libev's idea of
624	the current time is a good idea.	835	the current time is a good idea.
625		836
626	See also "The special problem of time updates" in the C<ev_timer> section.	837	See also L</The special problem of time updates> in the C<ev_timer> section.
627		838
		839	=item ev_suspend (loop)
		840
		841	=item ev_resume (loop)
		842
		843	These two functions suspend and resume an event loop, for use when the
		844	loop is not used for a while and timeouts should not be processed.
		845
		846	A typical use case would be an interactive program such as a game: When
		847	the user presses C<^Z> to suspend the game and resumes it an hour later it
		848	would be best to handle timeouts as if no time had actually passed while
		849	the program was suspended. This can be achieved by calling C<ev_suspend>
		850	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		851	C<ev_resume> directly afterwards to resume timer processing.
		852
		853	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		854	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		855	will be rescheduled (that is, they will lose any events that would have
		856	occurred while suspended).
		857
		858	After calling C<ev_suspend> you B<must not> call I<any> function on the
		859	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		860	without a previous call to C<ev_suspend>.
		861
		862	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		863	event loop time (see C<ev_now_update>).
		864
628	=item ev_loop (loop, int flags)	865	=item bool ev_run (loop, int flags)
629		866
630	Finally, this is it, the event handler. This function usually is called	867	Finally, this is it, the event handler. This function usually is called
631	after you initialised all your watchers and you want to start handling	868	after you have initialised all your watchers and you want to start
632	events.	869	handling events. It will ask the operating system for any new events, call
		870	the watcher callbacks, and then repeat the whole process indefinitely: This
		871	is why event loops are called I<loops>.
633		872
634	If the flags argument is specified as C<0>, it will not return until	873	If the flags argument is specified as C<0>, it will keep handling events
635	either no event watchers are active anymore or C<ev_unloop> was called.	874	until either no event watchers are active anymore or C<ev_break> was
		875	called.
636		876
		877	The return value is false if there are no more active watchers (which
		878	usually means "all jobs done" or "deadlock"), and true in all other cases
		879	(which usually means " you should call C<ev_run> again").
		880
637	Please note that an explicit C<ev_unloop> is usually better than	881	Please note that an explicit C<ev_break> is usually better than
638	relying on all watchers to be stopped when deciding when a program has	882	relying on all watchers to be stopped when deciding when a program has
639	finished (especially in interactive programs), but having a program	883	finished (especially in interactive programs), but having a program
640	that automatically loops as long as it has to and no longer by virtue	884	that automatically loops as long as it has to and no longer by virtue
641	of relying on its watchers stopping correctly, that is truly a thing of	885	of relying on its watchers stopping correctly, that is truly a thing of
642	beauty.	886	beauty.
643		887
		888	This function is I<mostly> exception-safe - you can break out of a
		889	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		890	exception and so on. This does not decrement the C<ev_depth> value, nor
		891	will it clear any outstanding C<EVBREAK_ONE> breaks.
		892
644	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	893	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
645	those events and any already outstanding ones, but will not block your	894	those events and any already outstanding ones, but will not wait and
646	process in case there are no events and will return after one iteration of	895	block your process in case there are no events and will return after one
647	the loop.	896	iteration of the loop. This is sometimes useful to poll and handle new
		897	events while doing lengthy calculations, to keep the program responsive.
648		898
649	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	899	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
650	necessary) and will handle those and any already outstanding ones. It	900	necessary) and will handle those and any already outstanding ones. It
651	will block your process until at least one new event arrives (which could	901	will block your process until at least one new event arrives (which could
652	be an event internal to libev itself, so there is no guarentee that a	902	be an event internal to libev itself, so there is no guarantee that a
653	user-registered callback will be called), and will return after one	903	user-registered callback will be called), and will return after one
654	iteration of the loop.	904	iteration of the loop.
655		905
656	This is useful if you are waiting for some external event in conjunction	906	This is useful if you are waiting for some external event in conjunction
657	with something not expressible using other libev watchers (i.e. "roll your	907	with something not expressible using other libev watchers (i.e. "roll your
658	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	908	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
659	usually a better approach for this kind of thing.	909	usually a better approach for this kind of thing.
660		910
661	Here are the gory details of what C<ev_loop> does:	911	Here are the gory details of what C<ev_run> does (this is for your
		912	understanding, not a guarantee that things will work exactly like this in
		913	future versions):
662		914
		915	- Increment loop depth.
		916	- Reset the ev_break status.
663	- Before the first iteration, call any pending watchers.	917	- Before the first iteration, call any pending watchers.
		918	LOOP:
664	* If EVFLAG_FORKCHECK was used, check for a fork.	919	- If EVFLAG_FORKCHECK was used, check for a fork.
665	- If a fork was detected (by any means), queue and call all fork watchers.	920	- If a fork was detected (by any means), queue and call all fork watchers.
666	- Queue and call all prepare watchers.	921	- Queue and call all prepare watchers.
		922	- If ev_break was called, goto FINISH.
667	- If we have been forked, detach and recreate the kernel state	923	- If we have been forked, detach and recreate the kernel state
668	as to not disturb the other process.	924	as to not disturb the other process.
669	- Update the kernel state with all outstanding changes.	925	- Update the kernel state with all outstanding changes.
670	- Update the "event loop time" (ev_now ()).	926	- Update the "event loop time" (ev_now ()).
671	- Calculate for how long to sleep or block, if at all	927	- Calculate for how long to sleep or block, if at all
672	(active idle watchers, EVLOOP_NONBLOCK or not having	928	(active idle watchers, EVRUN_NOWAIT or not having
673	any active watchers at all will result in not sleeping).	929	any active watchers at all will result in not sleeping).
674	- Sleep if the I/O and timer collect interval say so.	930	- Sleep if the I/O and timer collect interval say so.
		931	- Increment loop iteration counter.
675	- Block the process, waiting for any events.	932	- Block the process, waiting for any events.
676	- Queue all outstanding I/O (fd) events.	933	- Queue all outstanding I/O (fd) events.
677	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	934	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
678	- Queue all expired timers.	935	- Queue all expired timers.
679	- Queue all expired periodics.	936	- Queue all expired periodics.
680	- Unless any events are pending now, queue all idle watchers.	937	- Queue all idle watchers with priority higher than that of pending events.
681	- Queue all check watchers.	938	- Queue all check watchers.
682	- Call all queued watchers in reverse order (i.e. check watchers first).	939	- Call all queued watchers in reverse order (i.e. check watchers first).
683	Signals and child watchers are implemented as I/O watchers, and will	940	Signals and child watchers are implemented as I/O watchers, and will
684	be handled here by queueing them when their watcher gets executed.	941	be handled here by queueing them when their watcher gets executed.
685	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	942	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
686	were used, or there are no active watchers, return, otherwise	943	were used, or there are no active watchers, goto FINISH, otherwise
687	continue with step *.	944	continue with step LOOP.
		945	FINISH:
		946	- Reset the ev_break status iff it was EVBREAK_ONE.
		947	- Decrement the loop depth.
		948	- Return.
688		949
689	Example: Queue some jobs and then loop until no events are outstanding	950	Example: Queue some jobs and then loop until no events are outstanding
690	anymore.	951	anymore.
691		952
692	... queue jobs here, make sure they register event watchers as long	953	... queue jobs here, make sure they register event watchers as long
693	... as they still have work to do (even an idle watcher will do..)	954	... as they still have work to do (even an idle watcher will do..)
694	ev_loop (my_loop, 0);	955	ev_run (my_loop, 0);
695	... jobs done or somebody called unloop. yeah!	956	... jobs done or somebody called break. yeah!
696		957
697	=item ev_unloop (loop, how)	958	=item ev_break (loop, how)
698		959
699	Can be used to make a call to C<ev_loop> return early (but only after it	960	Can be used to make a call to C<ev_run> return early (but only after it
700	has processed all outstanding events). The C<how> argument must be either	961	has processed all outstanding events). The C<how> argument must be either
701	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	962	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
702	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	963	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
703		964
704	This "unloop state" will be cleared when entering C<ev_loop> again.	965	This "break state" will be cleared on the next call to C<ev_run>.
705		966
706	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	967	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		968	which case it will have no effect.
707		969
708	=item ev_ref (loop)	970	=item ev_ref (loop)
709		971
710	=item ev_unref (loop)	972	=item ev_unref (loop)
711		973
712	Ref/unref can be used to add or remove a reference count on the event	974	Ref/unref can be used to add or remove a reference count on the event
713	loop: Every watcher keeps one reference, and as long as the reference	975	loop: Every watcher keeps one reference, and as long as the reference
714	count is nonzero, C<ev_loop> will not return on its own.	976	count is nonzero, C<ev_run> will not return on its own.
715		977
716	If you have a watcher you never unregister that should not keep C<ev_loop>	978	This is useful when you have a watcher that you never intend to
717	from returning, call ev_unref() after starting, and ev_ref() before	979	unregister, but that nevertheless should not keep C<ev_run> from
		980	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
718	stopping it.	981	before stopping it.
719		982
720	As an example, libev itself uses this for its internal signal pipe: It is	983	As an example, libev itself uses this for its internal signal pipe: It
721	not visible to the libev user and should not keep C<ev_loop> from exiting	984	is not visible to the libev user and should not keep C<ev_run> from
722	if no event watchers registered by it are active. It is also an excellent	985	exiting if no event watchers registered by it are active. It is also an
723	way to do this for generic recurring timers or from within third-party	986	excellent way to do this for generic recurring timers or from within
724	libraries. Just remember to I<unref after start> and I<ref before stop>	987	third-party libraries. Just remember to I<unref after start> and I<ref
725	(but only if the watcher wasn't active before, or was active before,	988	before stop> (but only if the watcher wasn't active before, or was active
726	respectively).	989	before, respectively. Note also that libev might stop watchers itself
		990	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		991	in the callback).
727		992
728	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	993	Example: Create a signal watcher, but keep it from keeping C<ev_run>
729	running when nothing else is active.	994	running when nothing else is active.
730		995
731	ev_signal exitsig;	996	ev_signal exitsig;
732	ev_signal_init (&exitsig, sig_cb, SIGINT);	997	ev_signal_init (&exitsig, sig_cb, SIGINT);
733	ev_signal_start (loop, &exitsig);	998	ev_signal_start (loop, &exitsig);
734	evf_unref (loop);	999	ev_unref (loop);
735		1000
736	Example: For some weird reason, unregister the above signal handler again.	1001	Example: For some weird reason, unregister the above signal handler again.
737		1002
738	ev_ref (loop);	1003	ev_ref (loop);
739	ev_signal_stop (loop, &exitsig);	1004	ev_signal_stop (loop, &exitsig);
…		…
759	overhead for the actual polling but can deliver many events at once.	1024	overhead for the actual polling but can deliver many events at once.
760		1025
761	By setting a higher I<io collect interval> you allow libev to spend more	1026	By setting a higher I<io collect interval> you allow libev to spend more
762	time collecting I/O events, so you can handle more events per iteration,	1027	time collecting I/O events, so you can handle more events per iteration,
763	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1028	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
764	C<ev_timer>) will be not affected. Setting this to a non-null value will	1029	C<ev_timer>) will not be affected. Setting this to a non-null value will
765	introduce an additional C<ev_sleep ()> call into most loop iterations.	1030	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		1031	sleep time ensures that libev will not poll for I/O events more often then
		1032	once per this interval, on average (as long as the host time resolution is
		1033	good enough).
766		1034
767	Likewise, by setting a higher I<timeout collect interval> you allow libev	1035	Likewise, by setting a higher I<timeout collect interval> you allow libev
768	to spend more time collecting timeouts, at the expense of increased	1036	to spend more time collecting timeouts, at the expense of increased
769	latency/jitter/inexactness (the watcher callback will be called	1037	latency/jitter/inexactness (the watcher callback will be called
770	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1038	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
772		1040
773	Many (busy) programs can usually benefit by setting the I/O collect	1041	Many (busy) programs can usually benefit by setting the I/O collect
774	interval to a value near C<0.1> or so, which is often enough for	1042	interval to a value near C<0.1> or so, which is often enough for
775	interactive servers (of course not for games), likewise for timeouts. It	1043	interactive servers (of course not for games), likewise for timeouts. It
776	usually doesn't make much sense to set it to a lower value than C<0.01>,	1044	usually doesn't make much sense to set it to a lower value than C<0.01>,
777	as this approaches the timing granularity of most systems.	1045	as this approaches the timing granularity of most systems. Note that if
		1046	you do transactions with the outside world and you can't increase the
		1047	parallelity, then this setting will limit your transaction rate (if you
		1048	need to poll once per transaction and the I/O collect interval is 0.01,
		1049	then you can't do more than 100 transactions per second).
778		1050
779	Setting the I<timeout collect interval> can improve the opportunity for	1051	Setting the I<timeout collect interval> can improve the opportunity for
780	saving power, as the program will "bundle" timer callback invocations that	1052	saving power, as the program will "bundle" timer callback invocations that
781	are "near" in time together, by delaying some, thus reducing the number of	1053	are "near" in time together, by delaying some, thus reducing the number of
782	times the process sleeps and wakes up again. Another useful technique to	1054	times the process sleeps and wakes up again. Another useful technique to
783	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	1055	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
784	they fire on, say, one-second boundaries only.	1056	they fire on, say, one-second boundaries only.
785		1057
		1058	Example: we only need 0.1s timeout granularity, and we wish not to poll
		1059	more often than 100 times per second:
		1060
		1061	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		1062	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		1063
		1064	=item ev_invoke_pending (loop)
		1065
		1066	This call will simply invoke all pending watchers while resetting their
		1067	pending state. Normally, C<ev_run> does this automatically when required,
		1068	but when overriding the invoke callback this call comes handy. This
		1069	function can be invoked from a watcher - this can be useful for example
		1070	when you want to do some lengthy calculation and want to pass further
		1071	event handling to another thread (you still have to make sure only one
		1072	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1073
		1074	=item int ev_pending_count (loop)
		1075
		1076	Returns the number of pending watchers - zero indicates that no watchers
		1077	are pending.
		1078
		1079	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1080
		1081	This overrides the invoke pending functionality of the loop: Instead of
		1082	invoking all pending watchers when there are any, C<ev_run> will call
		1083	this callback instead. This is useful, for example, when you want to
		1084	invoke the actual watchers inside another context (another thread etc.).
		1085
		1086	If you want to reset the callback, use C<ev_invoke_pending> as new
		1087	callback.
		1088
		1089	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1090
		1091	Sometimes you want to share the same loop between multiple threads. This
		1092	can be done relatively simply by putting mutex_lock/unlock calls around
		1093	each call to a libev function.
		1094
		1095	However, C<ev_run> can run an indefinite time, so it is not feasible
		1096	to wait for it to return. One way around this is to wake up the event
		1097	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1098	I<release> and I<acquire> callbacks on the loop.
		1099
		1100	When set, then C<release> will be called just before the thread is
		1101	suspended waiting for new events, and C<acquire> is called just
		1102	afterwards.
		1103
		1104	Ideally, C<release> will just call your mutex_unlock function, and
		1105	C<acquire> will just call the mutex_lock function again.
		1106
		1107	While event loop modifications are allowed between invocations of
		1108	C<release> and C<acquire> (that's their only purpose after all), no
		1109	modifications done will affect the event loop, i.e. adding watchers will
		1110	have no effect on the set of file descriptors being watched, or the time
		1111	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1112	to take note of any changes you made.
		1113
		1114	In theory, threads executing C<ev_run> will be async-cancel safe between
		1115	invocations of C<release> and C<acquire>.
		1116
		1117	See also the locking example in the C<THREADS> section later in this
		1118	document.
		1119
		1120	=item ev_set_userdata (loop, void *data)
		1121
		1122	=item void *ev_userdata (loop)
		1123
		1124	Set and retrieve a single C<void *> associated with a loop. When
		1125	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1126	C<0>.
		1127
		1128	These two functions can be used to associate arbitrary data with a loop,
		1129	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1130	C<acquire> callbacks described above, but of course can be (ab-)used for
		1131	any other purpose as well.
		1132
786	=item ev_loop_verify (loop)	1133	=item ev_verify (loop)
787		1134
788	This function only does something when C<EV_VERIFY> support has been	1135	This function only does something when C<EV_VERIFY> support has been
789	compiled in, which is the default for non-minimal builds. It tries to go	1136	compiled in, which is the default for non-minimal builds. It tries to go
790	through all internal structures and checks them for validity. If anything	1137	through all internal structures and checks them for validity. If anything
791	is found to be inconsistent, it will print an error message to standard	1138	is found to be inconsistent, it will print an error message to standard
…		…
802		1149
803	In the following description, uppercase C<TYPE> in names stands for the	1150	In the following description, uppercase C<TYPE> in names stands for the
804	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1151	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
805	watchers and C<ev_io_start> for I/O watchers.	1152	watchers and C<ev_io_start> for I/O watchers.
806		1153
807	A watcher is a structure that you create and register to record your	1154	A watcher is an opaque structure that you allocate and register to record
808	interest in some event. For instance, if you want to wait for STDIN to	1155	your interest in some event. To make a concrete example, imagine you want
809	become readable, you would create an C<ev_io> watcher for that:	1156	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1157	for that:
810		1158
811	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1159	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
812	{	1160	{
813	ev_io_stop (w);	1161	ev_io_stop (w);
814	ev_unloop (loop, EVUNLOOP_ALL);	1162	ev_break (loop, EVBREAK_ALL);
815	}	1163	}
816		1164
817	struct ev_loop *loop = ev_default_loop (0);	1165	struct ev_loop *loop = ev_default_loop (0);
818		1166
819	ev_io stdin_watcher;	1167	ev_io stdin_watcher;
820		1168
821	ev_init (&stdin_watcher, my_cb);	1169	ev_init (&stdin_watcher, my_cb);
822	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1170	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
823	ev_io_start (loop, &stdin_watcher);	1171	ev_io_start (loop, &stdin_watcher);
824		1172
825	ev_loop (loop, 0);	1173	ev_run (loop, 0);
826		1174
827	As you can see, you are responsible for allocating the memory for your	1175	As you can see, you are responsible for allocating the memory for your
828	watcher structures (and it is I<usually> a bad idea to do this on the	1176	watcher structures (and it is I<usually> a bad idea to do this on the
829	stack).	1177	stack).
830		1178
831	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1179	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
832	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1180	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
833		1181
834	Each watcher structure must be initialised by a call to C<ev_init	1182	Each watcher structure must be initialised by a call to C<ev_init (watcher
835	(watcher *, callback)>, which expects a callback to be provided. This	1183	*, callback)>, which expects a callback to be provided. This callback is
836	callback gets invoked each time the event occurs (or, in the case of I/O	1184	invoked each time the event occurs (or, in the case of I/O watchers, each
837	watchers, each time the event loop detects that the file descriptor given	1185	time the event loop detects that the file descriptor given is readable
838	is readable and/or writable).	1186	and/or writable).
839		1187
840	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1188	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
841	macro to configure it, with arguments specific to the watcher type. There	1189	macro to configure it, with arguments specific to the watcher type. There
842	is also a macro to combine initialisation and setting in one call: C<<	1190	is also a macro to combine initialisation and setting in one call: C<<
843	ev_TYPE_init (watcher *, callback, ...) >>.	1191	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
866	=item C<EV_WRITE>	1214	=item C<EV_WRITE>
867		1215
868	The file descriptor in the C<ev_io> watcher has become readable and/or	1216	The file descriptor in the C<ev_io> watcher has become readable and/or
869	writable.	1217	writable.
870		1218
871	=item C<EV_TIMEOUT>	1219	=item C<EV_TIMER>
872		1220
873	The C<ev_timer> watcher has timed out.	1221	The C<ev_timer> watcher has timed out.
874		1222
875	=item C<EV_PERIODIC>	1223	=item C<EV_PERIODIC>
876		1224
…		…
894		1242
895	=item C<EV_PREPARE>	1243	=item C<EV_PREPARE>
896		1244
897	=item C<EV_CHECK>	1245	=item C<EV_CHECK>
898		1246
899	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1247	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
900	to gather new events, and all C<ev_check> watchers are invoked just after	1248	gather new events, and all C<ev_check> watchers are queued (not invoked)
901	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1249	just after C<ev_run> has gathered them, but before it queues any callbacks
		1250	for any received events. That means C<ev_prepare> watchers are the last
		1251	watchers invoked before the event loop sleeps or polls for new events, and
		1252	C<ev_check> watchers will be invoked before any other watchers of the same
		1253	or lower priority within an event loop iteration.
		1254
902	received events. Callbacks of both watcher types can start and stop as	1255	Callbacks of both watcher types can start and stop as many watchers as
903	many watchers as they want, and all of them will be taken into account	1256	they want, and all of them will be taken into account (for example, a
904	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1257	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
905	C<ev_loop> from blocking).	1258	blocking).
906		1259
907	=item C<EV_EMBED>	1260	=item C<EV_EMBED>
908		1261
909	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1262	The embedded event loop specified in the C<ev_embed> watcher needs attention.
910		1263
911	=item C<EV_FORK>	1264	=item C<EV_FORK>
912		1265
913	The event loop has been resumed in the child process after fork (see	1266	The event loop has been resumed in the child process after fork (see
914	C<ev_fork>).	1267	C<ev_fork>).
915		1268
		1269	=item C<EV_CLEANUP>
		1270
		1271	The event loop is about to be destroyed (see C<ev_cleanup>).
		1272
916	=item C<EV_ASYNC>	1273	=item C<EV_ASYNC>
917		1274
918	The given async watcher has been asynchronously notified (see C<ev_async>).	1275	The given async watcher has been asynchronously notified (see C<ev_async>).
		1276
		1277	=item C<EV_CUSTOM>
		1278
		1279	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1280	by libev users to signal watchers (e.g. via C<ev_feed_event>).
919		1281
920	=item C<EV_ERROR>	1282	=item C<EV_ERROR>
921		1283
922	An unspecified error has occurred, the watcher has been stopped. This might	1284	An unspecified error has occurred, the watcher has been stopped. This might
923	happen because the watcher could not be properly started because libev	1285	happen because the watcher could not be properly started because libev
…		…
961		1323
962	ev_io w;	1324	ev_io w;
963	ev_init (&w, my_cb);	1325	ev_init (&w, my_cb);
964	ev_io_set (&w, STDIN_FILENO, EV_READ);	1326	ev_io_set (&w, STDIN_FILENO, EV_READ);
965		1327
966	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1328	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
967		1329
968	This macro initialises the type-specific parts of a watcher. You need to	1330	This macro initialises the type-specific parts of a watcher. You need to
969	call C<ev_init> at least once before you call this macro, but you can	1331	call C<ev_init> at least once before you call this macro, but you can
970	call C<ev_TYPE_set> any number of times. You must not, however, call this	1332	call C<ev_TYPE_set> any number of times. You must not, however, call this
971	macro on a watcher that is active (it can be pending, however, which is a	1333	macro on a watcher that is active (it can be pending, however, which is a
…		…
984		1346
985	Example: Initialise and set an C<ev_io> watcher in one step.	1347	Example: Initialise and set an C<ev_io> watcher in one step.
986		1348
987	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1349	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
988		1350
989	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1351	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
990		1352
991	Starts (activates) the given watcher. Only active watchers will receive	1353	Starts (activates) the given watcher. Only active watchers will receive
992	events. If the watcher is already active nothing will happen.	1354	events. If the watcher is already active nothing will happen.
993		1355
994	Example: Start the C<ev_io> watcher that is being abused as example in this	1356	Example: Start the C<ev_io> watcher that is being abused as example in this
995	whole section.	1357	whole section.
996		1358
997	ev_io_start (EV_DEFAULT_UC, &w);	1359	ev_io_start (EV_DEFAULT_UC, &w);
998		1360
999	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1361	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1000		1362
1001	Stops the given watcher if active, and clears the pending status (whether	1363	Stops the given watcher if active, and clears the pending status (whether
1002	the watcher was active or not).	1364	the watcher was active or not).
1003		1365
1004	It is possible that stopped watchers are pending - for example,	1366	It is possible that stopped watchers are pending - for example,
…		…
1024		1386
1025	=item callback ev_cb (ev_TYPE *watcher)	1387	=item callback ev_cb (ev_TYPE *watcher)
1026		1388
1027	Returns the callback currently set on the watcher.	1389	Returns the callback currently set on the watcher.
1028		1390
1029	=item ev_cb_set (ev_TYPE *watcher, callback)	1391	=item ev_set_cb (ev_TYPE *watcher, callback)
1030		1392
1031	Change the callback. You can change the callback at virtually any time	1393	Change the callback. You can change the callback at virtually any time
1032	(modulo threads).	1394	(modulo threads).
1033		1395
1034	=item ev_set_priority (ev_TYPE *watcher, priority)	1396	=item ev_set_priority (ev_TYPE *watcher, int priority)
1035		1397
1036	=item int ev_priority (ev_TYPE *watcher)	1398	=item int ev_priority (ev_TYPE *watcher)
1037		1399
1038	Set and query the priority of the watcher. The priority is a small	1400	Set and query the priority of the watcher. The priority is a small
1039	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1401	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1040	(default: C<-2>). Pending watchers with higher priority will be invoked	1402	(default: C<-2>). Pending watchers with higher priority will be invoked
1041	before watchers with lower priority, but priority will not keep watchers	1403	before watchers with lower priority, but priority will not keep watchers
1042	from being executed (except for C<ev_idle> watchers).	1404	from being executed (except for C<ev_idle> watchers).
1043		1405
1044	This means that priorities are I<only> used for ordering callback
1045	invocation after new events have been received. This is useful, for
1046	example, to reduce latency after idling, or more often, to bind two
1047	watchers on the same event and make sure one is called first.
1048
1049	If you need to suppress invocation when higher priority events are pending	1406	If you need to suppress invocation when higher priority events are pending
1050	you need to look at C<ev_idle> watchers, which provide this functionality.	1407	you need to look at C<ev_idle> watchers, which provide this functionality.
1051		1408
1052	You I<must not> change the priority of a watcher as long as it is active or	1409	You I<must not> change the priority of a watcher as long as it is active or
1053	pending.	1410	pending.
1054
1055	The default priority used by watchers when no priority has been set is
1056	always C<0>, which is supposed to not be too high and not be too low :).
1057		1411
1058	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1412	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1059	fine, as long as you do not mind that the priority value you query might	1413	fine, as long as you do not mind that the priority value you query might
1060	or might not have been clamped to the valid range.	1414	or might not have been clamped to the valid range.
		1415
		1416	The default priority used by watchers when no priority has been set is
		1417	always C<0>, which is supposed to not be too high and not be too low :).
		1418
		1419	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1420	priorities.
1061		1421
1062	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1422	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1063		1423
1064	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1424	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1065	C<loop> nor C<revents> need to be valid as long as the watcher callback	1425	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1073	watcher isn't pending it does nothing and returns C<0>.	1433	watcher isn't pending it does nothing and returns C<0>.
1074		1434
1075	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1435	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1076	callback to be invoked, which can be accomplished with this function.	1436	callback to be invoked, which can be accomplished with this function.
1077		1437
		1438	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1439
		1440	Feeds the given event set into the event loop, as if the specified event
		1441	had happened for the specified watcher (which must be a pointer to an
		1442	initialised but not necessarily started event watcher). Obviously you must
		1443	not free the watcher as long as it has pending events.
		1444
		1445	Stopping the watcher, letting libev invoke it, or calling
		1446	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1447	not started in the first place.
		1448
		1449	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1450	functions that do not need a watcher.
		1451
1078	=back	1452	=back
1079		1453
		1454	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1455	OWN COMPOSITE WATCHERS> idioms.
1080		1456
1081	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1457	=head2 WATCHER STATES
1082		1458
1083	Each watcher has, by default, a member C<void *data> that you can change	1459	There are various watcher states mentioned throughout this manual -
1084	and read at any time: libev will completely ignore it. This can be used	1460	active, pending and so on. In this section these states and the rules to
1085	to associate arbitrary data with your watcher. If you need more data and	1461	transition between them will be described in more detail - and while these
1086	don't want to allocate memory and store a pointer to it in that data	1462	rules might look complicated, they usually do "the right thing".
1087	member, you can also "subclass" the watcher type and provide your own
1088	data:
1089		1463
1090	struct my_io	1464	=over 4
		1465
		1466	=item initialised
		1467
		1468	Before a watcher can be registered with the event loop it has to be
		1469	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1470	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1471
		1472	In this state it is simply some block of memory that is suitable for
		1473	use in an event loop. It can be moved around, freed, reused etc. at
		1474	will - as long as you either keep the memory contents intact, or call
		1475	C<ev_TYPE_init> again.
		1476
		1477	=item started/running/active
		1478
		1479	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1480	property of the event loop, and is actively waiting for events. While in
		1481	this state it cannot be accessed (except in a few documented ways), moved,
		1482	freed or anything else - the only legal thing is to keep a pointer to it,
		1483	and call libev functions on it that are documented to work on active watchers.
		1484
		1485	=item pending
		1486
		1487	If a watcher is active and libev determines that an event it is interested
		1488	in has occurred (such as a timer expiring), it will become pending. It will
		1489	stay in this pending state until either it is stopped or its callback is
		1490	about to be invoked, so it is not normally pending inside the watcher
		1491	callback.
		1492
		1493	The watcher might or might not be active while it is pending (for example,
		1494	an expired non-repeating timer can be pending but no longer active). If it
		1495	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1496	but it is still property of the event loop at this time, so cannot be
		1497	moved, freed or reused. And if it is active the rules described in the
		1498	previous item still apply.
		1499
		1500	It is also possible to feed an event on a watcher that is not active (e.g.
		1501	via C<ev_feed_event>), in which case it becomes pending without being
		1502	active.
		1503
		1504	=item stopped
		1505
		1506	A watcher can be stopped implicitly by libev (in which case it might still
		1507	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1508	latter will clear any pending state the watcher might be in, regardless
		1509	of whether it was active or not, so stopping a watcher explicitly before
		1510	freeing it is often a good idea.
		1511
		1512	While stopped (and not pending) the watcher is essentially in the
		1513	initialised state, that is, it can be reused, moved, modified in any way
		1514	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1515	it again).
		1516
		1517	=back
		1518
		1519	=head2 WATCHER PRIORITY MODELS
		1520
		1521	Many event loops support I<watcher priorities>, which are usually small
		1522	integers that influence the ordering of event callback invocation
		1523	between watchers in some way, all else being equal.
		1524
		1525	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1526	description for the more technical details such as the actual priority
		1527	range.
		1528
		1529	There are two common ways how these these priorities are being interpreted
		1530	by event loops:
		1531
		1532	In the more common lock-out model, higher priorities "lock out" invocation
		1533	of lower priority watchers, which means as long as higher priority
		1534	watchers receive events, lower priority watchers are not being invoked.
		1535
		1536	The less common only-for-ordering model uses priorities solely to order
		1537	callback invocation within a single event loop iteration: Higher priority
		1538	watchers are invoked before lower priority ones, but they all get invoked
		1539	before polling for new events.
		1540
		1541	Libev uses the second (only-for-ordering) model for all its watchers
		1542	except for idle watchers (which use the lock-out model).
		1543
		1544	The rationale behind this is that implementing the lock-out model for
		1545	watchers is not well supported by most kernel interfaces, and most event
		1546	libraries will just poll for the same events again and again as long as
		1547	their callbacks have not been executed, which is very inefficient in the
		1548	common case of one high-priority watcher locking out a mass of lower
		1549	priority ones.
		1550
		1551	Static (ordering) priorities are most useful when you have two or more
		1552	watchers handling the same resource: a typical usage example is having an
		1553	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1554	timeouts. Under load, data might be received while the program handles
		1555	other jobs, but since timers normally get invoked first, the timeout
		1556	handler will be executed before checking for data. In that case, giving
		1557	the timer a lower priority than the I/O watcher ensures that I/O will be
		1558	handled first even under adverse conditions (which is usually, but not
		1559	always, what you want).
		1560
		1561	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1562	will only be executed when no same or higher priority watchers have
		1563	received events, they can be used to implement the "lock-out" model when
		1564	required.
		1565
		1566	For example, to emulate how many other event libraries handle priorities,
		1567	you can associate an C<ev_idle> watcher to each such watcher, and in
		1568	the normal watcher callback, you just start the idle watcher. The real
		1569	processing is done in the idle watcher callback. This causes libev to
		1570	continuously poll and process kernel event data for the watcher, but when
		1571	the lock-out case is known to be rare (which in turn is rare :), this is
		1572	workable.
		1573
		1574	Usually, however, the lock-out model implemented that way will perform
		1575	miserably under the type of load it was designed to handle. In that case,
		1576	it might be preferable to stop the real watcher before starting the
		1577	idle watcher, so the kernel will not have to process the event in case
		1578	the actual processing will be delayed for considerable time.
		1579
		1580	Here is an example of an I/O watcher that should run at a strictly lower
		1581	priority than the default, and which should only process data when no
		1582	other events are pending:
		1583
		1584	ev_idle idle; // actual processing watcher
		1585	ev_io io; // actual event watcher
		1586
		1587	static void
		1588	io_cb (EV_P_ ev_io *w, int revents)
1091	{	1589	{
1092	ev_io io;	1590	// stop the I/O watcher, we received the event, but
1093	int otherfd;	1591	// are not yet ready to handle it.
1094	void *somedata;	1592	ev_io_stop (EV_A_ w);
1095	struct whatever *mostinteresting;	1593
		1594	// start the idle watcher to handle the actual event.
		1595	// it will not be executed as long as other watchers
		1596	// with the default priority are receiving events.
		1597	ev_idle_start (EV_A_ &idle);
1096	};	1598	}
1097		1599
1098	...	1600	static void
1099	struct my_io w;	1601	idle_cb (EV_P_ ev_idle *w, int revents)
1100	ev_io_init (&w.io, my_cb, fd, EV_READ);
1101
1102	And since your callback will be called with a pointer to the watcher, you
1103	can cast it back to your own type:
1104
1105	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1106	{	1602	{
1107	struct my_io *w = (struct my_io *)w_;	1603	// actual processing
1108	...	1604	read (STDIN_FILENO, ...);
		1605
		1606	// have to start the I/O watcher again, as
		1607	// we have handled the event
		1608	ev_io_start (EV_P_ &io);
1109	}	1609	}
1110		1610
1111	More interesting and less C-conformant ways of casting your callback type	1611	// initialisation
1112	instead have been omitted.	1612	ev_idle_init (&idle, idle_cb);
		1613	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1614	ev_io_start (EV_DEFAULT_ &io);
1113		1615
1114	Another common scenario is to use some data structure with multiple	1616	In the "real" world, it might also be beneficial to start a timer, so that
1115	embedded watchers:	1617	low-priority connections can not be locked out forever under load. This
1116		1618	enables your program to keep a lower latency for important connections
1117	struct my_biggy	1619	during short periods of high load, while not completely locking out less
1118	{	1620	important ones.
1119	int some_data;
1120	ev_timer t1;
1121	ev_timer t2;
1122	}
1123
1124	In this case getting the pointer to C<my_biggy> is a bit more
1125	complicated: Either you store the address of your C<my_biggy> struct
1126	in the C<data> member of the watcher (for woozies), or you need to use
1127	some pointer arithmetic using C<offsetof> inside your watchers (for real
1128	programmers):
1129
1130	#include <stddef.h>
1131
1132	static void
1133	t1_cb (EV_P_ ev_timer *w, int revents)
1134	{
1135	struct my_biggy big = (struct my_biggy *
1136	(((char *)w) - offsetof (struct my_biggy, t1));
1137	}
1138
1139	static void
1140	t2_cb (EV_P_ ev_timer *w, int revents)
1141	{
1142	struct my_biggy big = (struct my_biggy *
1143	(((char *)w) - offsetof (struct my_biggy, t2));
1144	}
1145		1621
1146		1622
1147	=head1 WATCHER TYPES	1623	=head1 WATCHER TYPES
1148		1624
1149	This section describes each watcher in detail, but will not repeat	1625	This section describes each watcher in detail, but will not repeat
…		…
1173	In general you can register as many read and/or write event watchers per	1649	In general you can register as many read and/or write event watchers per
1174	fd as you want (as long as you don't confuse yourself). Setting all file	1650	fd as you want (as long as you don't confuse yourself). Setting all file
1175	descriptors to non-blocking mode is also usually a good idea (but not	1651	descriptors to non-blocking mode is also usually a good idea (but not
1176	required if you know what you are doing).	1652	required if you know what you are doing).
1177		1653
1178	If you cannot use non-blocking mode, then force the use of a
1179	known-to-be-good backend (at the time of this writing, this includes only
1180	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1181
1182	Another thing you have to watch out for is that it is quite easy to	1654	Another thing you have to watch out for is that it is quite easy to
1183	receive "spurious" readiness notifications, that is your callback might	1655	receive "spurious" readiness notifications, that is, your callback might
1184	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1656	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1185	because there is no data. Not only are some backends known to create a	1657	because there is no data. It is very easy to get into this situation even
1186	lot of those (for example Solaris ports), it is very easy to get into	1658	with a relatively standard program structure. Thus it is best to always
1187	this situation even with a relatively standard program structure. Thus	1659	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1188	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1189	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1660	preferable to a program hanging until some data arrives.
1190		1661
1191	If you cannot run the fd in non-blocking mode (for example you should	1662	If you cannot run the fd in non-blocking mode (for example you should
1192	not play around with an Xlib connection), then you have to separately	1663	not play around with an Xlib connection), then you have to separately
1193	re-test whether a file descriptor is really ready with a known-to-be good	1664	re-test whether a file descriptor is really ready with a known-to-be good
1194	interface such as poll (fortunately in our Xlib example, Xlib already	1665	interface such as poll (fortunately in the case of Xlib, it already does
1195	does this on its own, so its quite safe to use). Some people additionally	1666	this on its own, so its quite safe to use). Some people additionally
1196	use C<SIGALRM> and an interval timer, just to be sure you won't block	1667	use C<SIGALRM> and an interval timer, just to be sure you won't block
1197	indefinitely.	1668	indefinitely.
1198		1669
1199	But really, best use non-blocking mode.	1670	But really, best use non-blocking mode.
1200		1671
1201	=head3 The special problem of disappearing file descriptors	1672	=head3 The special problem of disappearing file descriptors
1202		1673
1203	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1674	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1204	descriptor (either due to calling C<close> explicitly or any other means,	1675	a file descriptor (either due to calling C<close> explicitly or any other
1205	such as C<dup2>). The reason is that you register interest in some file	1676	means, such as C<dup2>). The reason is that you register interest in some
1206	descriptor, but when it goes away, the operating system will silently drop	1677	file descriptor, but when it goes away, the operating system will silently
1207	this interest. If another file descriptor with the same number then is	1678	drop this interest. If another file descriptor with the same number then
1208	registered with libev, there is no efficient way to see that this is, in	1679	is registered with libev, there is no efficient way to see that this is,
1209	fact, a different file descriptor.	1680	in fact, a different file descriptor.
1210		1681
1211	To avoid having to explicitly tell libev about such cases, libev follows	1682	To avoid having to explicitly tell libev about such cases, libev follows
1212	the following policy: Each time C<ev_io_set> is being called, libev	1683	the following policy: Each time C<ev_io_set> is being called, libev
1213	will assume that this is potentially a new file descriptor, otherwise	1684	will assume that this is potentially a new file descriptor, otherwise
1214	it is assumed that the file descriptor stays the same. That means that	1685	it is assumed that the file descriptor stays the same. That means that
…		…
1228		1699
1229	There is no workaround possible except not registering events	1700	There is no workaround possible except not registering events
1230	for potentially C<dup ()>'ed file descriptors, or to resort to	1701	for potentially C<dup ()>'ed file descriptors, or to resort to
1231	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1702	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1232		1703
		1704	=head3 The special problem of files
		1705
		1706	Many people try to use C<select> (or libev) on file descriptors
		1707	representing files, and expect it to become ready when their program
		1708	doesn't block on disk accesses (which can take a long time on their own).
		1709
		1710	However, this cannot ever work in the "expected" way - you get a readiness
		1711	notification as soon as the kernel knows whether and how much data is
		1712	there, and in the case of open files, that's always the case, so you
		1713	always get a readiness notification instantly, and your read (or possibly
		1714	write) will still block on the disk I/O.
		1715
		1716	Another way to view it is that in the case of sockets, pipes, character
		1717	devices and so on, there is another party (the sender) that delivers data
		1718	on its own, but in the case of files, there is no such thing: the disk
		1719	will not send data on its own, simply because it doesn't know what you
		1720	wish to read - you would first have to request some data.
		1721
		1722	Since files are typically not-so-well supported by advanced notification
		1723	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1724	to files, even though you should not use it. The reason for this is
		1725	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1726	usually a tty, often a pipe, but also sometimes files or special devices
		1727	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1728	F</dev/urandom>), and even though the file might better be served with
		1729	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1730	it "just works" instead of freezing.
		1731
		1732	So avoid file descriptors pointing to files when you know it (e.g. use
		1733	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1734	when you rarely read from a file instead of from a socket, and want to
		1735	reuse the same code path.
		1736
1233	=head3 The special problem of fork	1737	=head3 The special problem of fork
1234		1738
1235	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1739	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1236	useless behaviour. Libev fully supports fork, but needs to be told about	1740	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1237	it in the child.	1741	to be told about it in the child if you want to continue to use it in the
		1742	child.
1238		1743
1239	To support fork in your programs, you either have to call	1744	To support fork in your child processes, you have to call C<ev_loop_fork
1240	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1745	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1241	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1746	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1242	C<EVBACKEND_POLL>.
1243		1747
1244	=head3 The special problem of SIGPIPE	1748	=head3 The special problem of SIGPIPE
1245		1749
1246	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1750	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1247	when writing to a pipe whose other end has been closed, your program gets	1751	when writing to a pipe whose other end has been closed, your program gets
…		…
1250		1754
1251	So when you encounter spurious, unexplained daemon exits, make sure you	1755	So when you encounter spurious, unexplained daemon exits, make sure you
1252	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1756	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1253	somewhere, as that would have given you a big clue).	1757	somewhere, as that would have given you a big clue).
1254		1758
		1759	=head3 The special problem of accept()ing when you can't
		1760
		1761	Many implementations of the POSIX C<accept> function (for example,
		1762	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1763	connection from the pending queue in all error cases.
		1764
		1765	For example, larger servers often run out of file descriptors (because
		1766	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1767	rejecting the connection, leading to libev signalling readiness on
		1768	the next iteration again (the connection still exists after all), and
		1769	typically causing the program to loop at 100% CPU usage.
		1770
		1771	Unfortunately, the set of errors that cause this issue differs between
		1772	operating systems, there is usually little the app can do to remedy the
		1773	situation, and no known thread-safe method of removing the connection to
		1774	cope with overload is known (to me).
		1775
		1776	One of the easiest ways to handle this situation is to just ignore it
		1777	- when the program encounters an overload, it will just loop until the
		1778	situation is over. While this is a form of busy waiting, no OS offers an
		1779	event-based way to handle this situation, so it's the best one can do.
		1780
		1781	A better way to handle the situation is to log any errors other than
		1782	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1783	messages, and continue as usual, which at least gives the user an idea of
		1784	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1785	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1786	usage.
		1787
		1788	If your program is single-threaded, then you could also keep a dummy file
		1789	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1790	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1791	close that fd, and create a new dummy fd. This will gracefully refuse
		1792	clients under typical overload conditions.
		1793
		1794	The last way to handle it is to simply log the error and C<exit>, as
		1795	is often done with C<malloc> failures, but this results in an easy
		1796	opportunity for a DoS attack.
1255		1797
1256	=head3 Watcher-Specific Functions	1798	=head3 Watcher-Specific Functions
1257		1799
1258	=over 4	1800	=over 4
1259		1801
…		…
1291	...	1833	...
1292	struct ev_loop *loop = ev_default_init (0);	1834	struct ev_loop *loop = ev_default_init (0);
1293	ev_io stdin_readable;	1835	ev_io stdin_readable;
1294	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1836	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1295	ev_io_start (loop, &stdin_readable);	1837	ev_io_start (loop, &stdin_readable);
1296	ev_loop (loop, 0);	1838	ev_run (loop, 0);
1297		1839
1298		1840
1299	=head2 C<ev_timer> - relative and optionally repeating timeouts	1841	=head2 C<ev_timer> - relative and optionally repeating timeouts
1300		1842
1301	Timer watchers are simple relative timers that generate an event after a	1843	Timer watchers are simple relative timers that generate an event after a
…		…
1306	year, it will still time out after (roughly) one hour. "Roughly" because	1848	year, it will still time out after (roughly) one hour. "Roughly" because
1307	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1849	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1308	monotonic clock option helps a lot here).	1850	monotonic clock option helps a lot here).
1309		1851
1310	The callback is guaranteed to be invoked only I<after> its timeout has	1852	The callback is guaranteed to be invoked only I<after> its timeout has
1311	passed, but if multiple timers become ready during the same loop iteration	1853	passed (not I<at>, so on systems with very low-resolution clocks this
1312	then order of execution is undefined.	1854	might introduce a small delay, see "the special problem of being too
		1855	early", below). If multiple timers become ready during the same loop
		1856	iteration then the ones with earlier time-out values are invoked before
		1857	ones of the same priority with later time-out values (but this is no
		1858	longer true when a callback calls C<ev_run> recursively).
1313		1859
1314	=head3 Be smart about timeouts	1860	=head3 Be smart about timeouts
1315		1861
1316	Many real-world problems involve some kind of timeout, usually for error	1862	Many real-world problems involve some kind of timeout, usually for error
1317	recovery. A typical example is an HTTP request - if the other side hangs,	1863	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1361	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1907	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1362	member and C<ev_timer_again>.	1908	member and C<ev_timer_again>.
1363		1909
1364	At start:	1910	At start:
1365		1911
1366	ev_timer_init (timer, callback);	1912	ev_init (timer, callback);
1367	timer->repeat = 60.;	1913	timer->repeat = 60.;
1368	ev_timer_again (loop, timer);	1914	ev_timer_again (loop, timer);
1369		1915
1370	Each time there is some activity:	1916	Each time there is some activity:
1371		1917
…		…
1392		1938
1393	In this case, it would be more efficient to leave the C<ev_timer> alone,	1939	In this case, it would be more efficient to leave the C<ev_timer> alone,
1394	but remember the time of last activity, and check for a real timeout only	1940	but remember the time of last activity, and check for a real timeout only
1395	within the callback:	1941	within the callback:
1396		1942
		1943	ev_tstamp timeout = 60.;
1397	ev_tstamp last_activity; // time of last activity	1944	ev_tstamp last_activity; // time of last activity
		1945	ev_timer timer;
1398		1946
1399	static void	1947	static void
1400	callback (EV_P_ ev_timer *w, int revents)	1948	callback (EV_P_ ev_timer *w, int revents)
1401	{	1949	{
1402	ev_tstamp now = ev_now (EV_A);	1950	// calculate when the timeout would happen
1403	ev_tstamp timeout = last_activity + 60.;	1951	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1404		1952
1405	// if last_activity + 60. is older than now, we did time out	1953	// if negative, it means we the timeout already occurred
1406	if (timeout < now)	1954	if (after < 0.)
1407	{	1955	{
1408	// timeout occured, take action	1956	// timeout occurred, take action
1409	}	1957	}
1410	else	1958	else
1411	{	1959	{
1412	// callback was invoked, but there was some activity, re-arm	1960	// callback was invoked, but there was some recent
1413	// the watcher to fire in last_activity + 60, which is	1961	// activity. simply restart the timer to time out
1414	// guaranteed to be in the future, so "again" is positive:	1962	// after "after" seconds, which is the earliest time
1415	w->again = timeout - now;	1963	// the timeout can occur.
		1964	ev_timer_set (w, after, 0.);
1416	ev_timer_again (EV_A_ w);	1965	ev_timer_start (EV_A_ w);
1417	}	1966	}
1418	}	1967	}
1419		1968
1420	To summarise the callback: first calculate the real timeout (defined	1969	To summarise the callback: first calculate in how many seconds the
1421	as "60 seconds after the last activity"), then check if that time has	1970	timeout will occur (by calculating the absolute time when it would occur,
1422	been reached, which means something I<did>, in fact, time out. Otherwise	1971	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1423	the callback was invoked too early (C<timeout> is in the future), so	1972	(EV_A)> from that).
1424	re-schedule the timer to fire at that future time, to see if maybe we have
1425	a timeout then.
1426		1973
1427	Note how C<ev_timer_again> is used, taking advantage of the	1974	If this value is negative, then we are already past the timeout, i.e. we
1428	C<ev_timer_again> optimisation when the timer is already running.	1975	timed out, and need to do whatever is needed in this case.
		1976
		1977	Otherwise, we now the earliest time at which the timeout would trigger,
		1978	and simply start the timer with this timeout value.
		1979
		1980	In other words, each time the callback is invoked it will check whether
		1981	the timeout occurred. If not, it will simply reschedule itself to check
		1982	again at the earliest time it could time out. Rinse. Repeat.
1429		1983
1430	This scheme causes more callback invocations (about one every 60 seconds	1984	This scheme causes more callback invocations (about one every 60 seconds
1431	minus half the average time between activity), but virtually no calls to	1985	minus half the average time between activity), but virtually no calls to
1432	libev to change the timeout.	1986	libev to change the timeout.
1433		1987
1434	To start the timer, simply initialise the watcher and set C<last_activity>	1988	To start the machinery, simply initialise the watcher and set
1435	to the current time (meaning we just have some activity :), then call the	1989	C<last_activity> to the current time (meaning there was some activity just
1436	callback, which will "do the right thing" and start the timer:	1990	now), then call the callback, which will "do the right thing" and start
		1991	the timer:
1437		1992
		1993	last_activity = ev_now (EV_A);
1438	ev_timer_init (timer, callback);	1994	ev_init (&timer, callback);
1439	last_activity = ev_now (loop);	1995	callback (EV_A_ &timer, 0);
1440	callback (loop, timer, EV_TIMEOUT);
1441		1996
1442	And when there is some activity, simply store the current time in	1997	When there is some activity, simply store the current time in
1443	C<last_activity>, no libev calls at all:	1998	C<last_activity>, no libev calls at all:
1444		1999
		2000	if (activity detected)
1445	last_actiivty = ev_now (loop);	2001	last_activity = ev_now (EV_A);
		2002
		2003	When your timeout value changes, then the timeout can be changed by simply
		2004	providing a new value, stopping the timer and calling the callback, which
		2005	will again do the right thing (for example, time out immediately :).
		2006
		2007	timeout = new_value;
		2008	ev_timer_stop (EV_A_ &timer);
		2009	callback (EV_A_ &timer, 0);
1446		2010
1447	This technique is slightly more complex, but in most cases where the	2011	This technique is slightly more complex, but in most cases where the
1448	time-out is unlikely to be triggered, much more efficient.	2012	time-out is unlikely to be triggered, much more efficient.
1449
1450	Changing the timeout is trivial as well (if it isn't hard-coded in the
1451	callback :) - just change the timeout and invoke the callback, which will
1452	fix things for you.
1453		2013
1454	=item 4. Wee, just use a double-linked list for your timeouts.	2014	=item 4. Wee, just use a double-linked list for your timeouts.
1455		2015
1456	If there is not one request, but many thousands (millions...), all	2016	If there is not one request, but many thousands (millions...), all
1457	employing some kind of timeout with the same timeout value, then one can	2017	employing some kind of timeout with the same timeout value, then one can
…		…
1484	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2044	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1485	rather complicated, but extremely efficient, something that really pays	2045	rather complicated, but extremely efficient, something that really pays
1486	off after the first million or so of active timers, i.e. it's usually	2046	off after the first million or so of active timers, i.e. it's usually
1487	overkill :)	2047	overkill :)
1488		2048
		2049	=head3 The special problem of being too early
		2050
		2051	If you ask a timer to call your callback after three seconds, then
		2052	you expect it to be invoked after three seconds - but of course, this
		2053	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2054	guaranteed to any precision by libev - imagine somebody suspending the
		2055	process with a STOP signal for a few hours for example.
		2056
		2057	So, libev tries to invoke your callback as soon as possible I<after> the
		2058	delay has occurred, but cannot guarantee this.
		2059
		2060	A less obvious failure mode is calling your callback too early: many event
		2061	loops compare timestamps with a "elapsed delay >= requested delay", but
		2062	this can cause your callback to be invoked much earlier than you would
		2063	expect.
		2064
		2065	To see why, imagine a system with a clock that only offers full second
		2066	resolution (think windows if you can't come up with a broken enough OS
		2067	yourself). If you schedule a one-second timer at the time 500.9, then the
		2068	event loop will schedule your timeout to elapse at a system time of 500
		2069	(500.9 truncated to the resolution) + 1, or 501.
		2070
		2071	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2072	501" and invoke the callback 0.1s after it was started, even though a
		2073	one-second delay was requested - this is being "too early", despite best
		2074	intentions.
		2075
		2076	This is the reason why libev will never invoke the callback if the elapsed
		2077	delay equals the requested delay, but only when the elapsed delay is
		2078	larger than the requested delay. In the example above, libev would only invoke
		2079	the callback at system time 502, or 1.1s after the timer was started.
		2080
		2081	So, while libev cannot guarantee that your callback will be invoked
		2082	exactly when requested, it I<can> and I<does> guarantee that the requested
		2083	delay has actually elapsed, or in other words, it always errs on the "too
		2084	late" side of things.
		2085
1489	=head3 The special problem of time updates	2086	=head3 The special problem of time updates
1490		2087
1491	Establishing the current time is a costly operation (it usually takes at	2088	Establishing the current time is a costly operation (it usually takes
1492	least two system calls): EV therefore updates its idea of the current	2089	at least one system call): EV therefore updates its idea of the current
1493	time only before and after C<ev_loop> collects new events, which causes a	2090	time only before and after C<ev_run> collects new events, which causes a
1494	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2091	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1495	lots of events in one iteration.	2092	lots of events in one iteration.
1496		2093
1497	The relative timeouts are calculated relative to the C<ev_now ()>	2094	The relative timeouts are calculated relative to the C<ev_now ()>
1498	time. This is usually the right thing as this timestamp refers to the time	2095	time. This is usually the right thing as this timestamp refers to the time
1499	of the event triggering whatever timeout you are modifying/starting. If	2096	of the event triggering whatever timeout you are modifying/starting. If
1500	you suspect event processing to be delayed and you I<need> to base the	2097	you suspect event processing to be delayed and you I<need> to base the
1501	timeout on the current time, use something like this to adjust for this:	2098	timeout on the current time, use something like the following to adjust
		2099	for it:
1502		2100
1503	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2101	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1504		2102
1505	If the event loop is suspended for a long time, you can also force an	2103	If the event loop is suspended for a long time, you can also force an
1506	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2104	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1507	()>.	2105	()>, although that will push the event time of all outstanding events
		2106	further into the future.
		2107
		2108	=head3 The special problem of unsynchronised clocks
		2109
		2110	Modern systems have a variety of clocks - libev itself uses the normal
		2111	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2112	jumps).
		2113
		2114	Neither of these clocks is synchronised with each other or any other clock
		2115	on the system, so C<ev_time ()> might return a considerably different time
		2116	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2117	a call to C<gettimeofday> might return a second count that is one higher
		2118	than a directly following call to C<time>.
		2119
		2120	The moral of this is to only compare libev-related timestamps with
		2121	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2122	a second or so.
		2123
		2124	One more problem arises due to this lack of synchronisation: if libev uses
		2125	the system monotonic clock and you compare timestamps from C<ev_time>
		2126	or C<ev_now> from when you started your timer and when your callback is
		2127	invoked, you will find that sometimes the callback is a bit "early".
		2128
		2129	This is because C<ev_timer>s work in real time, not wall clock time, so
		2130	libev makes sure your callback is not invoked before the delay happened,
		2131	I<measured according to the real time>, not the system clock.
		2132
		2133	If your timeouts are based on a physical timescale (e.g. "time out this
		2134	connection after 100 seconds") then this shouldn't bother you as it is
		2135	exactly the right behaviour.
		2136
		2137	If you want to compare wall clock/system timestamps to your timers, then
		2138	you need to use C<ev_periodic>s, as these are based on the wall clock
		2139	time, where your comparisons will always generate correct results.
		2140
		2141	=head3 The special problems of suspended animation
		2142
		2143	When you leave the server world it is quite customary to hit machines that
		2144	can suspend/hibernate - what happens to the clocks during such a suspend?
		2145
		2146	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2147	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2148	to run until the system is suspended, but they will not advance while the
		2149	system is suspended. That means, on resume, it will be as if the program
		2150	was frozen for a few seconds, but the suspend time will not be counted
		2151	towards C<ev_timer> when a monotonic clock source is used. The real time
		2152	clock advanced as expected, but if it is used as sole clocksource, then a
		2153	long suspend would be detected as a time jump by libev, and timers would
		2154	be adjusted accordingly.
		2155
		2156	I would not be surprised to see different behaviour in different between
		2157	operating systems, OS versions or even different hardware.
		2158
		2159	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2160	time jump in the monotonic clocks and the realtime clock. If the program
		2161	is suspended for a very long time, and monotonic clock sources are in use,
		2162	then you can expect C<ev_timer>s to expire as the full suspension time
		2163	will be counted towards the timers. When no monotonic clock source is in
		2164	use, then libev will again assume a timejump and adjust accordingly.
		2165
		2166	It might be beneficial for this latter case to call C<ev_suspend>
		2167	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2168	deterministic behaviour in this case (you can do nothing against
		2169	C<SIGSTOP>).
1508		2170
1509	=head3 Watcher-Specific Functions and Data Members	2171	=head3 Watcher-Specific Functions and Data Members
1510		2172
1511	=over 4	2173	=over 4
1512		2174
1513	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2175	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1514		2176
1515	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2177	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1516		2178
1517	Configure the timer to trigger after C<after> seconds. If C<repeat>	2179	Configure the timer to trigger after C<after> seconds (fractional and
1518	is C<0.>, then it will automatically be stopped once the timeout is	2180	negative values are supported). If C<repeat> is C<0.>, then it will
1519	reached. If it is positive, then the timer will automatically be	2181	automatically be stopped once the timeout is reached. If it is positive,
1520	configured to trigger again C<repeat> seconds later, again, and again,	2182	then the timer will automatically be configured to trigger again C<repeat>
1521	until stopped manually.	2183	seconds later, again, and again, until stopped manually.
1522		2184
1523	The timer itself will do a best-effort at avoiding drift, that is, if	2185	The timer itself will do a best-effort at avoiding drift, that is, if
1524	you configure a timer to trigger every 10 seconds, then it will normally	2186	you configure a timer to trigger every 10 seconds, then it will normally
1525	trigger at exactly 10 second intervals. If, however, your program cannot	2187	trigger at exactly 10 second intervals. If, however, your program cannot
1526	keep up with the timer (because it takes longer than those 10 seconds to	2188	keep up with the timer (because it takes longer than those 10 seconds to
1527	do stuff) the timer will not fire more than once per event loop iteration.	2189	do stuff) the timer will not fire more than once per event loop iteration.
1528		2190
1529	=item ev_timer_again (loop, ev_timer *)	2191	=item ev_timer_again (loop, ev_timer *)
1530		2192
1531	This will act as if the timer timed out and restart it again if it is	2193	This will act as if the timer timed out, and restarts it again if it is
1532	repeating. The exact semantics are:	2194	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2195	timeout to the C<repeat> value and calling C<ev_timer_start>.
1533		2196
		2197	The exact semantics are as in the following rules, all of which will be
		2198	applied to the watcher:
		2199
		2200	=over 4
		2201
1534	If the timer is pending, its pending status is cleared.	2202	=item If the timer is pending, the pending status is always cleared.
1535		2203
1536	If the timer is started but non-repeating, stop it (as if it timed out).	2204	=item If the timer is started but non-repeating, stop it (as if it timed
		2205	out, without invoking it).
1537		2206
1538	If the timer is repeating, either start it if necessary (with the	2207	=item If the timer is repeating, make the C<repeat> value the new timeout
1539	C<repeat> value), or reset the running timer to the C<repeat> value.	2208	and start the timer, if necessary.
1540		2209
		2210	=back
		2211
1541	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2212	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1542	usage example.	2213	usage example.
		2214
		2215	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2216
		2217	Returns the remaining time until a timer fires. If the timer is active,
		2218	then this time is relative to the current event loop time, otherwise it's
		2219	the timeout value currently configured.
		2220
		2221	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2222	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2223	will return C<4>. When the timer expires and is restarted, it will return
		2224	roughly C<7> (likely slightly less as callback invocation takes some time,
		2225	too), and so on.
1543		2226
1544	=item ev_tstamp repeat [read-write]	2227	=item ev_tstamp repeat [read-write]
1545		2228
1546	The current C<repeat> value. Will be used each time the watcher times out	2229	The current C<repeat> value. Will be used each time the watcher times out
1547	or C<ev_timer_again> is called, and determines the next timeout (if any),	2230	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1573	}	2256	}
1574		2257
1575	ev_timer mytimer;	2258	ev_timer mytimer;
1576	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2259	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1577	ev_timer_again (&mytimer); /* start timer */	2260	ev_timer_again (&mytimer); /* start timer */
1578	ev_loop (loop, 0);	2261	ev_run (loop, 0);
1579		2262
1580	// and in some piece of code that gets executed on any "activity":	2263	// and in some piece of code that gets executed on any "activity":
1581	// reset the timeout to start ticking again at 10 seconds	2264	// reset the timeout to start ticking again at 10 seconds
1582	ev_timer_again (&mytimer);	2265	ev_timer_again (&mytimer);
1583		2266
…		…
1585	=head2 C<ev_periodic> - to cron or not to cron?	2268	=head2 C<ev_periodic> - to cron or not to cron?
1586		2269
1587	Periodic watchers are also timers of a kind, but they are very versatile	2270	Periodic watchers are also timers of a kind, but they are very versatile
1588	(and unfortunately a bit complex).	2271	(and unfortunately a bit complex).
1589		2272
1590	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2273	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1591	but on wall clock time (absolute time). You can tell a periodic watcher	2274	relative time, the physical time that passes) but on wall clock time
1592	to trigger after some specific point in time. For example, if you tell a	2275	(absolute time, the thing you can read on your calendar or clock). The
1593	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2276	difference is that wall clock time can run faster or slower than real
1594	+ 10.>, that is, an absolute time not a delay) and then reset your system	2277	time, and time jumps are not uncommon (e.g. when you adjust your
1595	clock to January of the previous year, then it will take more than year	2278	wrist-watch).
1596	to trigger the event (unlike an C<ev_timer>, which would still trigger
1597	roughly 10 seconds later as it uses a relative timeout).
1598		2279
		2280	You can tell a periodic watcher to trigger after some specific point
		2281	in time: for example, if you tell a periodic watcher to trigger "in 10
		2282	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2283	not a delay) and then reset your system clock to January of the previous
		2284	year, then it will take a year or more to trigger the event (unlike an
		2285	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2286	it, as it uses a relative timeout).
		2287
1599	C<ev_periodic>s can also be used to implement vastly more complex timers,	2288	C<ev_periodic> watchers can also be used to implement vastly more complex
1600	such as triggering an event on each "midnight, local time", or other	2289	timers, such as triggering an event on each "midnight, local time", or
1601	complicated rules.	2290	other complicated rules. This cannot easily be done with C<ev_timer>
		2291	watchers, as those cannot react to time jumps.
1602		2292
1603	As with timers, the callback is guaranteed to be invoked only when the	2293	As with timers, the callback is guaranteed to be invoked only when the
1604	time (C<at>) has passed, but if multiple periodic timers become ready	2294	point in time where it is supposed to trigger has passed. If multiple
1605	during the same loop iteration, then order of execution is undefined.	2295	timers become ready during the same loop iteration then the ones with
		2296	earlier time-out values are invoked before ones with later time-out values
		2297	(but this is no longer true when a callback calls C<ev_run> recursively).
1606		2298
1607	=head3 Watcher-Specific Functions and Data Members	2299	=head3 Watcher-Specific Functions and Data Members
1608		2300
1609	=over 4	2301	=over 4
1610		2302
1611	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2303	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1612		2304
1613	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2305	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1614		2306
1615	Lots of arguments, lets sort it out... There are basically three modes of	2307	Lots of arguments, let's sort it out... There are basically three modes of
1616	operation, and we will explain them from simplest to most complex:	2308	operation, and we will explain them from simplest to most complex:
1617		2309
1618	=over 4	2310	=over 4
1619		2311
1620	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2312	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1621		2313
1622	In this configuration the watcher triggers an event after the wall clock	2314	In this configuration the watcher triggers an event after the wall clock
1623	time C<at> has passed. It will not repeat and will not adjust when a time	2315	time C<offset> has passed. It will not repeat and will not adjust when a
1624	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2316	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1625	only run when the system clock reaches or surpasses this time.	2317	will be stopped and invoked when the system clock reaches or surpasses
		2318	this point in time.
1626		2319
1627	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2320	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1628		2321
1629	In this mode the watcher will always be scheduled to time out at the next	2322	In this mode the watcher will always be scheduled to time out at the next
1630	C<at + N * interval> time (for some integer N, which can also be negative)	2323	C<offset + N * interval> time (for some integer N, which can also be
1631	and then repeat, regardless of any time jumps.	2324	negative) and then repeat, regardless of any time jumps. The C<offset>
		2325	argument is merely an offset into the C<interval> periods.
1632		2326
1633	This can be used to create timers that do not drift with respect to the	2327	This can be used to create timers that do not drift with respect to the
1634	system clock, for example, here is a C<ev_periodic> that triggers each	2328	system clock, for example, here is an C<ev_periodic> that triggers each
1635	hour, on the hour:	2329	hour, on the hour (with respect to UTC):
1636		2330
1637	ev_periodic_set (&periodic, 0., 3600., 0);	2331	ev_periodic_set (&periodic, 0., 3600., 0);
1638		2332
1639	This doesn't mean there will always be 3600 seconds in between triggers,	2333	This doesn't mean there will always be 3600 seconds in between triggers,
1640	but only that the callback will be called when the system time shows a	2334	but only that the callback will be called when the system time shows a
1641	full hour (UTC), or more correctly, when the system time is evenly divisible	2335	full hour (UTC), or more correctly, when the system time is evenly divisible
1642	by 3600.	2336	by 3600.
1643		2337
1644	Another way to think about it (for the mathematically inclined) is that	2338	Another way to think about it (for the mathematically inclined) is that
1645	C<ev_periodic> will try to run the callback in this mode at the next possible	2339	C<ev_periodic> will try to run the callback in this mode at the next possible
1646	time where C<time = at (mod interval)>, regardless of any time jumps.	2340	time where C<time = offset (mod interval)>, regardless of any time jumps.
1647		2341
1648	For numerical stability it is preferable that the C<at> value is near	2342	The C<interval> I<MUST> be positive, and for numerical stability, the
1649	C<ev_now ()> (the current time), but there is no range requirement for	2343	interval value should be higher than C<1/8192> (which is around 100
1650	this value, and in fact is often specified as zero.	2344	microseconds) and C<offset> should be higher than C<0> and should have
		2345	at most a similar magnitude as the current time (say, within a factor of
		2346	ten). Typical values for offset are, in fact, C<0> or something between
		2347	C<0> and C<interval>, which is also the recommended range.
1651		2348
1652	Note also that there is an upper limit to how often a timer can fire (CPU	2349	Note also that there is an upper limit to how often a timer can fire (CPU
1653	speed for example), so if C<interval> is very small then timing stability	2350	speed for example), so if C<interval> is very small then timing stability
1654	will of course deteriorate. Libev itself tries to be exact to be about one	2351	will of course deteriorate. Libev itself tries to be exact to be about one
1655	millisecond (if the OS supports it and the machine is fast enough).	2352	millisecond (if the OS supports it and the machine is fast enough).
1656		2353
1657	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2354	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1658		2355
1659	In this mode the values for C<interval> and C<at> are both being	2356	In this mode the values for C<interval> and C<offset> are both being
1660	ignored. Instead, each time the periodic watcher gets scheduled, the	2357	ignored. Instead, each time the periodic watcher gets scheduled, the
1661	reschedule callback will be called with the watcher as first, and the	2358	reschedule callback will be called with the watcher as first, and the
1662	current time as second argument.	2359	current time as second argument.
1663		2360
1664	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2361	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1665	ever, or make ANY event loop modifications whatsoever>.	2362	or make ANY other event loop modifications whatsoever, unless explicitly
		2363	allowed by documentation here>.
1666		2364
1667	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2365	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1668	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2366	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1669	only event loop modification you are allowed to do).	2367	only event loop modification you are allowed to do).
1670		2368
…		…
1684		2382
1685	NOTE: I<< This callback must always return a time that is higher than or	2383	NOTE: I<< This callback must always return a time that is higher than or
1686	equal to the passed C<now> value >>.	2384	equal to the passed C<now> value >>.
1687		2385
1688	This can be used to create very complex timers, such as a timer that	2386	This can be used to create very complex timers, such as a timer that
1689	triggers on "next midnight, local time". To do this, you would calculate the	2387	triggers on "next midnight, local time". To do this, you would calculate
1690	next midnight after C<now> and return the timestamp value for this. How	2388	the next midnight after C<now> and return the timestamp value for
1691	you do this is, again, up to you (but it is not trivial, which is the main	2389	this. Here is a (completely untested, no error checking) example on how to
1692	reason I omitted it as an example).	2390	do this:
		2391
		2392	#include <time.h>
		2393
		2394	static ev_tstamp
		2395	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2396	{
		2397	time_t tnow = (time_t)now;
		2398	struct tm tm;
		2399	localtime_r (&tnow, &tm);
		2400
		2401	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2402	++tm.tm_mday; // midnight next day
		2403
		2404	return mktime (&tm);
		2405	}
		2406
		2407	Note: this code might run into trouble on days that have more then two
		2408	midnights (beginning and end).
1693		2409
1694	=back	2410	=back
1695		2411
1696	=item ev_periodic_again (loop, ev_periodic *)	2412	=item ev_periodic_again (loop, ev_periodic *)
1697		2413
…		…
1700	a different time than the last time it was called (e.g. in a crond like	2416	a different time than the last time it was called (e.g. in a crond like
1701	program when the crontabs have changed).	2417	program when the crontabs have changed).
1702		2418
1703	=item ev_tstamp ev_periodic_at (ev_periodic *)	2419	=item ev_tstamp ev_periodic_at (ev_periodic *)
1704		2420
1705	When active, returns the absolute time that the watcher is supposed to	2421	When active, returns the absolute time that the watcher is supposed
1706	trigger next.	2422	to trigger next. This is not the same as the C<offset> argument to
		2423	C<ev_periodic_set>, but indeed works even in interval and manual
		2424	rescheduling modes.
1707		2425
1708	=item ev_tstamp offset [read-write]	2426	=item ev_tstamp offset [read-write]
1709		2427
1710	When repeating, this contains the offset value, otherwise this is the	2428	When repeating, this contains the offset value, otherwise this is the
1711	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2429	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2430	although libev might modify this value for better numerical stability).
1712		2431
1713	Can be modified any time, but changes only take effect when the periodic	2432	Can be modified any time, but changes only take effect when the periodic
1714	timer fires or C<ev_periodic_again> is being called.	2433	timer fires or C<ev_periodic_again> is being called.
1715		2434
1716	=item ev_tstamp interval [read-write]	2435	=item ev_tstamp interval [read-write]
…		…
1732	Example: Call a callback every hour, or, more precisely, whenever the	2451	Example: Call a callback every hour, or, more precisely, whenever the
1733	system time is divisible by 3600. The callback invocation times have	2452	system time is divisible by 3600. The callback invocation times have
1734	potentially a lot of jitter, but good long-term stability.	2453	potentially a lot of jitter, but good long-term stability.
1735		2454
1736	static void	2455	static void
1737	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2456	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1738	{	2457	{
1739	... its now a full hour (UTC, or TAI or whatever your clock follows)	2458	... its now a full hour (UTC, or TAI or whatever your clock follows)
1740	}	2459	}
1741		2460
1742	ev_periodic hourly_tick;	2461	ev_periodic hourly_tick;
…		…
1759		2478
1760	ev_periodic hourly_tick;	2479	ev_periodic hourly_tick;
1761	ev_periodic_init (&hourly_tick, clock_cb,	2480	ev_periodic_init (&hourly_tick, clock_cb,
1762	fmod (ev_now (loop), 3600.), 3600., 0);	2481	fmod (ev_now (loop), 3600.), 3600., 0);
1763	ev_periodic_start (loop, &hourly_tick);	2482	ev_periodic_start (loop, &hourly_tick);
1764		2483
1765		2484
1766	=head2 C<ev_signal> - signal me when a signal gets signalled!	2485	=head2 C<ev_signal> - signal me when a signal gets signalled!
1767		2486
1768	Signal watchers will trigger an event when the process receives a specific	2487	Signal watchers will trigger an event when the process receives a specific
1769	signal one or more times. Even though signals are very asynchronous, libev	2488	signal one or more times. Even though signals are very asynchronous, libev
1770	will try it's best to deliver signals synchronously, i.e. as part of the	2489	will try its best to deliver signals synchronously, i.e. as part of the
1771	normal event processing, like any other event.	2490	normal event processing, like any other event.
1772		2491
1773	If you want signals asynchronously, just use C<sigaction> as you would	2492	If you want signals to be delivered truly asynchronously, just use
1774	do without libev and forget about sharing the signal. You can even use	2493	C<sigaction> as you would do without libev and forget about sharing
1775	C<ev_async> from a signal handler to synchronously wake up an event loop.	2494	the signal. You can even use C<ev_async> from a signal handler to
		2495	synchronously wake up an event loop.
1776		2496
1777	You can configure as many watchers as you like per signal. Only when the	2497	You can configure as many watchers as you like for the same signal, but
1778	first watcher gets started will libev actually register a signal handler	2498	only within the same loop, i.e. you can watch for C<SIGINT> in your
1779	with the kernel (thus it coexists with your own signal handlers as long as	2499	default loop and for C<SIGIO> in another loop, but you cannot watch for
1780	you don't register any with libev for the same signal). Similarly, when	2500	C<SIGINT> in both the default loop and another loop at the same time. At
1781	the last signal watcher for a signal is stopped, libev will reset the	2501	the moment, C<SIGCHLD> is permanently tied to the default loop.
1782	signal handler to SIG_DFL (regardless of what it was set to before).	2502
		2503	Only after the first watcher for a signal is started will libev actually
		2504	register something with the kernel. It thus coexists with your own signal
		2505	handlers as long as you don't register any with libev for the same signal.
1783		2506
1784	If possible and supported, libev will install its handlers with	2507	If possible and supported, libev will install its handlers with
1785	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2508	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1786	interrupted. If you have a problem with system calls getting interrupted by	2509	not be unduly interrupted. If you have a problem with system calls getting
1787	signals you can block all signals in an C<ev_check> watcher and unblock	2510	interrupted by signals you can block all signals in an C<ev_check> watcher
1788	them in an C<ev_prepare> watcher.	2511	and unblock them in an C<ev_prepare> watcher.
		2512
		2513	=head3 The special problem of inheritance over fork/execve/pthread_create
		2514
		2515	Both the signal mask (C<sigprocmask>) and the signal disposition
		2516	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2517	stopping it again), that is, libev might or might not block the signal,
		2518	and might or might not set or restore the installed signal handler (but
		2519	see C<EVFLAG_NOSIGMASK>).
		2520
		2521	While this does not matter for the signal disposition (libev never
		2522	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2523	C<execve>), this matters for the signal mask: many programs do not expect
		2524	certain signals to be blocked.
		2525
		2526	This means that before calling C<exec> (from the child) you should reset
		2527	the signal mask to whatever "default" you expect (all clear is a good
		2528	choice usually).
		2529
		2530	The simplest way to ensure that the signal mask is reset in the child is
		2531	to install a fork handler with C<pthread_atfork> that resets it. That will
		2532	catch fork calls done by libraries (such as the libc) as well.
		2533
		2534	In current versions of libev, the signal will not be blocked indefinitely
		2535	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2536	the window of opportunity for problems, it will not go away, as libev
		2537	I<has> to modify the signal mask, at least temporarily.
		2538
		2539	So I can't stress this enough: I<If you do not reset your signal mask when
		2540	you expect it to be empty, you have a race condition in your code>. This
		2541	is not a libev-specific thing, this is true for most event libraries.
		2542
		2543	=head3 The special problem of threads signal handling
		2544
		2545	POSIX threads has problematic signal handling semantics, specifically,
		2546	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2547	threads in a process block signals, which is hard to achieve.
		2548
		2549	When you want to use sigwait (or mix libev signal handling with your own
		2550	for the same signals), you can tackle this problem by globally blocking
		2551	all signals before creating any threads (or creating them with a fully set
		2552	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2553	loops. Then designate one thread as "signal receiver thread" which handles
		2554	these signals. You can pass on any signals that libev might be interested
		2555	in by calling C<ev_feed_signal>.
1789		2556
1790	=head3 Watcher-Specific Functions and Data Members	2557	=head3 Watcher-Specific Functions and Data Members
1791		2558
1792	=over 4	2559	=over 4
1793		2560
…		…
1809	Example: Try to exit cleanly on SIGINT.	2576	Example: Try to exit cleanly on SIGINT.
1810		2577
1811	static void	2578	static void
1812	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2579	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1813	{	2580	{
1814	ev_unloop (loop, EVUNLOOP_ALL);	2581	ev_break (loop, EVBREAK_ALL);
1815	}	2582	}
1816		2583
1817	ev_signal signal_watcher;	2584	ev_signal signal_watcher;
1818	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2585	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1819	ev_signal_start (loop, &signal_watcher);	2586	ev_signal_start (loop, &signal_watcher);
…		…
1825	some child status changes (most typically when a child of yours dies or	2592	some child status changes (most typically when a child of yours dies or
1826	exits). It is permissible to install a child watcher I<after> the child	2593	exits). It is permissible to install a child watcher I<after> the child
1827	has been forked (which implies it might have already exited), as long	2594	has been forked (which implies it might have already exited), as long
1828	as the event loop isn't entered (or is continued from a watcher), i.e.,	2595	as the event loop isn't entered (or is continued from a watcher), i.e.,
1829	forking and then immediately registering a watcher for the child is fine,	2596	forking and then immediately registering a watcher for the child is fine,
1830	but forking and registering a watcher a few event loop iterations later is	2597	but forking and registering a watcher a few event loop iterations later or
1831	not.	2598	in the next callback invocation is not.
1832		2599
1833	Only the default event loop is capable of handling signals, and therefore	2600	Only the default event loop is capable of handling signals, and therefore
1834	you can only register child watchers in the default event loop.	2601	you can only register child watchers in the default event loop.
1835		2602
		2603	Due to some design glitches inside libev, child watchers will always be
		2604	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2605	libev)
		2606
1836	=head3 Process Interaction	2607	=head3 Process Interaction
1837		2608
1838	Libev grabs C<SIGCHLD> as soon as the default event loop is	2609	Libev grabs C<SIGCHLD> as soon as the default event loop is
1839	initialised. This is necessary to guarantee proper behaviour even if	2610	initialised. This is necessary to guarantee proper behaviour even if the
1840	the first child watcher is started after the child exits. The occurrence	2611	first child watcher is started after the child exits. The occurrence
1841	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2612	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1842	synchronously as part of the event loop processing. Libev always reaps all	2613	synchronously as part of the event loop processing. Libev always reaps all
1843	children, even ones not watched.	2614	children, even ones not watched.
1844		2615
1845	=head3 Overriding the Built-In Processing	2616	=head3 Overriding the Built-In Processing
…		…
1855	=head3 Stopping the Child Watcher	2626	=head3 Stopping the Child Watcher
1856		2627
1857	Currently, the child watcher never gets stopped, even when the	2628	Currently, the child watcher never gets stopped, even when the
1858	child terminates, so normally one needs to stop the watcher in the	2629	child terminates, so normally one needs to stop the watcher in the
1859	callback. Future versions of libev might stop the watcher automatically	2630	callback. Future versions of libev might stop the watcher automatically
1860	when a child exit is detected.	2631	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2632	problem).
1861		2633
1862	=head3 Watcher-Specific Functions and Data Members	2634	=head3 Watcher-Specific Functions and Data Members
1863		2635
1864	=over 4	2636	=over 4
1865		2637
…		…
1923		2695
1924	=head2 C<ev_stat> - did the file attributes just change?	2696	=head2 C<ev_stat> - did the file attributes just change?
1925		2697
1926	This watches a file system path for attribute changes. That is, it calls	2698	This watches a file system path for attribute changes. That is, it calls
1927	C<stat> on that path in regular intervals (or when the OS says it changed)	2699	C<stat> on that path in regular intervals (or when the OS says it changed)
1928	and sees if it changed compared to the last time, invoking the callback if	2700	and sees if it changed compared to the last time, invoking the callback
1929	it did.	2701	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2702	happen after the watcher has been started will be reported.
1930		2703
1931	The path does not need to exist: changing from "path exists" to "path does	2704	The path does not need to exist: changing from "path exists" to "path does
1932	not exist" is a status change like any other. The condition "path does	2705	not exist" is a status change like any other. The condition "path does not
1933	not exist" is signified by the C<st_nlink> field being zero (which is	2706	exist" (or more correctly "path cannot be stat'ed") is signified by the
1934	otherwise always forced to be at least one) and all the other fields of	2707	C<st_nlink> field being zero (which is otherwise always forced to be at
1935	the stat buffer having unspecified contents.	2708	least one) and all the other fields of the stat buffer having unspecified
		2709	contents.
1936		2710
1937	The path I<must not> end in a slash or contain special components such as	2711	The path I<must not> end in a slash or contain special components such as
1938	C<.> or C<..>. The path I<should> be absolute: If it is relative and	2712	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1939	your working directory changes, then the behaviour is undefined.	2713	your working directory changes, then the behaviour is undefined.
1940		2714
…		…
1943	to see if it changed somehow. You can specify a recommended polling	2717	to see if it changed somehow. You can specify a recommended polling
1944	interval for this case. If you specify a polling interval of C<0> (highly	2718	interval for this case. If you specify a polling interval of C<0> (highly
1945	recommended!) then a I<suitable, unspecified default> value will be used	2719	recommended!) then a I<suitable, unspecified default> value will be used
1946	(which you can expect to be around five seconds, although this might	2720	(which you can expect to be around five seconds, although this might
1947	change dynamically). Libev will also impose a minimum interval which is	2721	change dynamically). Libev will also impose a minimum interval which is
1948	currently around C<0.1>, but thats usually overkill.	2722	currently around C<0.1>, but that's usually overkill.
1949		2723
1950	This watcher type is not meant for massive numbers of stat watchers,	2724	This watcher type is not meant for massive numbers of stat watchers,
1951	as even with OS-supported change notifications, this can be	2725	as even with OS-supported change notifications, this can be
1952	resource-intensive.	2726	resource-intensive.
1953		2727
1954	At the time of this writing, the only OS-specific interface implemented	2728	At the time of this writing, the only OS-specific interface implemented
1955	is the Linux inotify interface (implementing kqueue support is left as	2729	is the Linux inotify interface (implementing kqueue support is left as an
1956	an exercise for the reader. Note, however, that the author sees no way	2730	exercise for the reader. Note, however, that the author sees no way of
1957	of implementing C<ev_stat> semantics with kqueue).	2731	implementing C<ev_stat> semantics with kqueue, except as a hint).
1958		2732
1959	=head3 ABI Issues (Largefile Support)	2733	=head3 ABI Issues (Largefile Support)
1960		2734
1961	Libev by default (unless the user overrides this) uses the default	2735	Libev by default (unless the user overrides this) uses the default
1962	compilation environment, which means that on systems with large file	2736	compilation environment, which means that on systems with large file
…		…
1973	to exchange stat structures with application programs compiled using the	2747	to exchange stat structures with application programs compiled using the
1974	default compilation environment.	2748	default compilation environment.
1975		2749
1976	=head3 Inotify and Kqueue	2750	=head3 Inotify and Kqueue
1977		2751
1978	When C<inotify (7)> support has been compiled into libev (generally	2752	When C<inotify (7)> support has been compiled into libev and present at
1979	only available with Linux 2.6.25 or above due to bugs in earlier	2753	runtime, it will be used to speed up change detection where possible. The
1980	implementations) and present at runtime, it will be used to speed up	2754	inotify descriptor will be created lazily when the first C<ev_stat>
1981	change detection where possible. The inotify descriptor will be created	2755	watcher is being started.
1982	lazily when the first C<ev_stat> watcher is being started.
1983		2756
1984	Inotify presence does not change the semantics of C<ev_stat> watchers	2757	Inotify presence does not change the semantics of C<ev_stat> watchers
1985	except that changes might be detected earlier, and in some cases, to avoid	2758	except that changes might be detected earlier, and in some cases, to avoid
1986	making regular C<stat> calls. Even in the presence of inotify support	2759	making regular C<stat> calls. Even in the presence of inotify support
1987	there are many cases where libev has to resort to regular C<stat> polling,	2760	there are many cases where libev has to resort to regular C<stat> polling,
1988	but as long as the path exists, libev usually gets away without polling.	2761	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2762	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2763	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2764	xfs are fully working) libev usually gets away without polling.
1989		2765
1990	There is no support for kqueue, as apparently it cannot be used to	2766	There is no support for kqueue, as apparently it cannot be used to
1991	implement this functionality, due to the requirement of having a file	2767	implement this functionality, due to the requirement of having a file
1992	descriptor open on the object at all times, and detecting renames, unlinks	2768	descriptor open on the object at all times, and detecting renames, unlinks
1993	etc. is difficult.	2769	etc. is difficult.
		2770
		2771	=head3 C<stat ()> is a synchronous operation
		2772
		2773	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2774	the process. The exception are C<ev_stat> watchers - those call C<stat
		2775	()>, which is a synchronous operation.
		2776
		2777	For local paths, this usually doesn't matter: unless the system is very
		2778	busy or the intervals between stat's are large, a stat call will be fast,
		2779	as the path data is usually in memory already (except when starting the
		2780	watcher).
		2781
		2782	For networked file systems, calling C<stat ()> can block an indefinite
		2783	time due to network issues, and even under good conditions, a stat call
		2784	often takes multiple milliseconds.
		2785
		2786	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2787	paths, although this is fully supported by libev.
1994		2788
1995	=head3 The special problem of stat time resolution	2789	=head3 The special problem of stat time resolution
1996		2790
1997	The C<stat ()> system call only supports full-second resolution portably,	2791	The C<stat ()> system call only supports full-second resolution portably,
1998	and even on systems where the resolution is higher, most file systems	2792	and even on systems where the resolution is higher, most file systems
…		…
2143	Apart from keeping your process non-blocking (which is a useful	2937	Apart from keeping your process non-blocking (which is a useful
2144	effect on its own sometimes), idle watchers are a good place to do	2938	effect on its own sometimes), idle watchers are a good place to do
2145	"pseudo-background processing", or delay processing stuff to after the	2939	"pseudo-background processing", or delay processing stuff to after the
2146	event loop has handled all outstanding events.	2940	event loop has handled all outstanding events.
2147		2941
		2942	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2943
		2944	As long as there is at least one active idle watcher, libev will never
		2945	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2946	For this to work, the idle watcher doesn't need to be invoked at all - the
		2947	lowest priority will do.
		2948
		2949	This mode of operation can be useful together with an C<ev_check> watcher,
		2950	to do something on each event loop iteration - for example to balance load
		2951	between different connections.
		2952
		2953	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2954	example.
		2955
2148	=head3 Watcher-Specific Functions and Data Members	2956	=head3 Watcher-Specific Functions and Data Members
2149		2957
2150	=over 4	2958	=over 4
2151		2959
2152	=item ev_idle_init (ev_signal *, callback)	2960	=item ev_idle_init (ev_idle *, callback)
2153		2961
2154	Initialises and configures the idle watcher - it has no parameters of any	2962	Initialises and configures the idle watcher - it has no parameters of any
2155	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2963	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2156	believe me.	2964	believe me.
2157		2965
…		…
2163	callback, free it. Also, use no error checking, as usual.	2971	callback, free it. Also, use no error checking, as usual.
2164		2972
2165	static void	2973	static void
2166	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2974	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2167	{	2975	{
		2976	// stop the watcher
		2977	ev_idle_stop (loop, w);
		2978
		2979	// now we can free it
2168	free (w);	2980	free (w);
		2981
2169	// now do something you wanted to do when the program has	2982	// now do something you wanted to do when the program has
2170	// no longer anything immediate to do.	2983	// no longer anything immediate to do.
2171	}	2984	}
2172		2985
2173	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2986	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2174	ev_idle_init (idle_watcher, idle_cb);	2987	ev_idle_init (idle_watcher, idle_cb);
2175	ev_idle_start (loop, idle_cb);	2988	ev_idle_start (loop, idle_watcher);
2176		2989
2177		2990
2178	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2991	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2179		2992
2180	Prepare and check watchers are usually (but not always) used in pairs:	2993	Prepare and check watchers are often (but not always) used in pairs:
2181	prepare watchers get invoked before the process blocks and check watchers	2994	prepare watchers get invoked before the process blocks and check watchers
2182	afterwards.	2995	afterwards.
2183		2996
2184	You I<must not> call C<ev_loop> or similar functions that enter	2997	You I<must not> call C<ev_run> (or similar functions that enter the
2185	the current event loop from either C<ev_prepare> or C<ev_check>	2998	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2186	watchers. Other loops than the current one are fine, however. The	2999	C<ev_check> watchers. Other loops than the current one are fine,
2187	rationale behind this is that you do not need to check for recursion in	3000	however. The rationale behind this is that you do not need to check
2188	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3001	for recursion in those watchers, i.e. the sequence will always be
2189	C<ev_check> so if you have one watcher of each kind they will always be	3002	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2190	called in pairs bracketing the blocking call.	3003	kind they will always be called in pairs bracketing the blocking call.
2191		3004
2192	Their main purpose is to integrate other event mechanisms into libev and	3005	Their main purpose is to integrate other event mechanisms into libev and
2193	their use is somewhat advanced. They could be used, for example, to track	3006	their use is somewhat advanced. They could be used, for example, to track
2194	variable changes, implement your own watchers, integrate net-snmp or a	3007	variable changes, implement your own watchers, integrate net-snmp or a
2195	coroutine library and lots more. They are also occasionally useful if	3008	coroutine library and lots more. They are also occasionally useful if
…		…
2213	with priority higher than or equal to the event loop and one coroutine	3026	with priority higher than or equal to the event loop and one coroutine
2214	of lower priority, but only once, using idle watchers to keep the event	3027	of lower priority, but only once, using idle watchers to keep the event
2215	loop from blocking if lower-priority coroutines are active, thus mapping	3028	loop from blocking if lower-priority coroutines are active, thus mapping
2216	low-priority coroutines to idle/background tasks).	3029	low-priority coroutines to idle/background tasks).
2217		3030
2218	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3031	When used for this purpose, it is recommended to give C<ev_check> watchers
2219	priority, to ensure that they are being run before any other watchers	3032	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2220	after the poll (this doesn't matter for C<ev_prepare> watchers).	3033	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3034	watchers).
2221		3035
2222	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3036	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2223	activate ("feed") events into libev. While libev fully supports this, they	3037	activate ("feed") events into libev. While libev fully supports this, they
2224	might get executed before other C<ev_check> watchers did their job. As	3038	might get executed before other C<ev_check> watchers did their job. As
2225	C<ev_check> watchers are often used to embed other (non-libev) event	3039	C<ev_check> watchers are often used to embed other (non-libev) event
2226	loops those other event loops might be in an unusable state until their	3040	loops those other event loops might be in an unusable state until their
2227	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3041	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2228	others).	3042	others).
		3043
		3044	=head3 Abusing an C<ev_check> watcher for its side-effect
		3045
		3046	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3047	useful because they are called once per event loop iteration. For
		3048	example, if you want to handle a large number of connections fairly, you
		3049	normally only do a bit of work for each active connection, and if there
		3050	is more work to do, you wait for the next event loop iteration, so other
		3051	connections have a chance of making progress.
		3052
		3053	Using an C<ev_check> watcher is almost enough: it will be called on the
		3054	next event loop iteration. However, that isn't as soon as possible -
		3055	without external events, your C<ev_check> watcher will not be invoked.
		3056
		3057	This is where C<ev_idle> watchers come in handy - all you need is a
		3058	single global idle watcher that is active as long as you have one active
		3059	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3060	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3061	invoked. Neither watcher alone can do that.
2229		3062
2230	=head3 Watcher-Specific Functions and Data Members	3063	=head3 Watcher-Specific Functions and Data Members
2231		3064
2232	=over 4	3065	=over 4
2233		3066
…		…
2273	struct pollfd fds [nfd];	3106	struct pollfd fds [nfd];
2274	// actual code will need to loop here and realloc etc.	3107	// actual code will need to loop here and realloc etc.
2275	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3108	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2276		3109
2277	/* the callback is illegal, but won't be called as we stop during check */	3110	/* the callback is illegal, but won't be called as we stop during check */
2278	ev_timer_init (&tw, 0, timeout * 1e-3);	3111	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2279	ev_timer_start (loop, &tw);	3112	ev_timer_start (loop, &tw);
2280		3113
2281	// create one ev_io per pollfd	3114	// create one ev_io per pollfd
2282	for (int i = 0; i < nfd; ++i)	3115	for (int i = 0; i < nfd; ++i)
2283	{	3116	{
…		…
2357		3190
2358	if (timeout >= 0)	3191	if (timeout >= 0)
2359	// create/start timer	3192	// create/start timer
2360		3193
2361	// poll	3194	// poll
2362	ev_loop (EV_A_ 0);	3195	ev_run (EV_A_ 0);
2363		3196
2364	// stop timer again	3197	// stop timer again
2365	if (timeout >= 0)	3198	if (timeout >= 0)
2366	ev_timer_stop (EV_A_ &to);	3199	ev_timer_stop (EV_A_ &to);
2367		3200
…		…
2396	some fds have to be watched and handled very quickly (with low latency),	3229	some fds have to be watched and handled very quickly (with low latency),
2397	and even priorities and idle watchers might have too much overhead. In	3230	and even priorities and idle watchers might have too much overhead. In
2398	this case you would put all the high priority stuff in one loop and all	3231	this case you would put all the high priority stuff in one loop and all
2399	the rest in a second one, and embed the second one in the first.	3232	the rest in a second one, and embed the second one in the first.
2400		3233
2401	As long as the watcher is active, the callback will be invoked every time	3234	As long as the watcher is active, the callback will be invoked every
2402	there might be events pending in the embedded loop. The callback must then	3235	time there might be events pending in the embedded loop. The callback
2403	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3236	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2404	their callbacks (you could also start an idle watcher to give the embedded	3237	sweep and invoke their callbacks (the callback doesn't need to invoke the
2405	loop strictly lower priority for example). You can also set the callback	3238	C<ev_embed_sweep> function directly, it could also start an idle watcher
2406	to C<0>, in which case the embed watcher will automatically execute the	3239	to give the embedded loop strictly lower priority for example).
2407	embedded loop sweep.
2408		3240
2409	As long as the watcher is started it will automatically handle events. The	3241	You can also set the callback to C<0>, in which case the embed watcher
2410	callback will be invoked whenever some events have been handled. You can	3242	will automatically execute the embedded loop sweep whenever necessary.
2411	set the callback to C<0> to avoid having to specify one if you are not
2412	interested in that.
2413		3243
2414	Also, there have not currently been made special provisions for forking:	3244	Fork detection will be handled transparently while the C<ev_embed> watcher
2415	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3245	is active, i.e., the embedded loop will automatically be forked when the
2416	but you will also have to stop and restart any C<ev_embed> watchers	3246	embedding loop forks. In other cases, the user is responsible for calling
2417	yourself - but you can use a fork watcher to handle this automatically,	3247	C<ev_loop_fork> on the embedded loop.
2418	and future versions of libev might do just that.
2419		3248
2420	Unfortunately, not all backends are embeddable: only the ones returned by	3249	Unfortunately, not all backends are embeddable: only the ones returned by
2421	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3250	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2422	portable one.	3251	portable one.
2423		3252
…		…
2438		3267
2439	=over 4	3268	=over 4
2440		3269
2441	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3270	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2442		3271
2443	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3272	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2444		3273
2445	Configures the watcher to embed the given loop, which must be	3274	Configures the watcher to embed the given loop, which must be
2446	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3275	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2447	invoked automatically, otherwise it is the responsibility of the callback	3276	invoked automatically, otherwise it is the responsibility of the callback
2448	to invoke it (it will continue to be called until the sweep has been done,	3277	to invoke it (it will continue to be called until the sweep has been done,
2449	if you do not want that, you need to temporarily stop the embed watcher).	3278	if you do not want that, you need to temporarily stop the embed watcher).
2450		3279
2451	=item ev_embed_sweep (loop, ev_embed *)	3280	=item ev_embed_sweep (loop, ev_embed *)
2452		3281
2453	Make a single, non-blocking sweep over the embedded loop. This works	3282	Make a single, non-blocking sweep over the embedded loop. This works
2454	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3283	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2455	appropriate way for embedded loops.	3284	appropriate way for embedded loops.
2456		3285
2457	=item struct ev_loop *other [read-only]	3286	=item struct ev_loop *other [read-only]
2458		3287
2459	The embedded event loop.	3288	The embedded event loop.
…		…
2469	used).	3298	used).
2470		3299
2471	struct ev_loop *loop_hi = ev_default_init (0);	3300	struct ev_loop *loop_hi = ev_default_init (0);
2472	struct ev_loop *loop_lo = 0;	3301	struct ev_loop *loop_lo = 0;
2473	ev_embed embed;	3302	ev_embed embed;
2474		3303
2475	// see if there is a chance of getting one that works	3304	// see if there is a chance of getting one that works
2476	// (remember that a flags value of 0 means autodetection)	3305	// (remember that a flags value of 0 means autodetection)
2477	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3306	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2478	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3307	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2479	: 0;	3308	: 0;
…		…
2493	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3322	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2494		3323
2495	struct ev_loop *loop = ev_default_init (0);	3324	struct ev_loop *loop = ev_default_init (0);
2496	struct ev_loop *loop_socket = 0;	3325	struct ev_loop *loop_socket = 0;
2497	ev_embed embed;	3326	ev_embed embed;
2498		3327
2499	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3328	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2500	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3329	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2501	{	3330	{
2502	ev_embed_init (&embed, 0, loop_socket);	3331	ev_embed_init (&embed, 0, loop_socket);
2503	ev_embed_start (loop, &embed);	3332	ev_embed_start (loop, &embed);
…		…
2511		3340
2512	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3341	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2513		3342
2514	Fork watchers are called when a C<fork ()> was detected (usually because	3343	Fork watchers are called when a C<fork ()> was detected (usually because
2515	whoever is a good citizen cared to tell libev about it by calling	3344	whoever is a good citizen cared to tell libev about it by calling
2516	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3345	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2517	event loop blocks next and before C<ev_check> watchers are being called,	3346	and before C<ev_check> watchers are being called, and only in the child
2518	and only in the child after the fork. If whoever good citizen calling	3347	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2519	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3348	and calls it in the wrong process, the fork handlers will be invoked, too,
2520	handlers will be invoked, too, of course.	3349	of course.
		3350
		3351	=head3 The special problem of life after fork - how is it possible?
		3352
		3353	Most uses of C<fork ()> consist of forking, then some simple calls to set
		3354	up/change the process environment, followed by a call to C<exec()>. This
		3355	sequence should be handled by libev without any problems.
		3356
		3357	This changes when the application actually wants to do event handling
		3358	in the child, or both parent in child, in effect "continuing" after the
		3359	fork.
		3360
		3361	The default mode of operation (for libev, with application help to detect
		3362	forks) is to duplicate all the state in the child, as would be expected
		3363	when I<either> the parent I<or> the child process continues.
		3364
		3365	When both processes want to continue using libev, then this is usually the
		3366	wrong result. In that case, usually one process (typically the parent) is
		3367	supposed to continue with all watchers in place as before, while the other
		3368	process typically wants to start fresh, i.e. without any active watchers.
		3369
		3370	The cleanest and most efficient way to achieve that with libev is to
		3371	simply create a new event loop, which of course will be "empty", and
		3372	use that for new watchers. This has the advantage of not touching more
		3373	memory than necessary, and thus avoiding the copy-on-write, and the
		3374	disadvantage of having to use multiple event loops (which do not support
		3375	signal watchers).
		3376
		3377	When this is not possible, or you want to use the default loop for
		3378	other reasons, then in the process that wants to start "fresh", call
		3379	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3380	Destroying the default loop will "orphan" (not stop) all registered
		3381	watchers, so you have to be careful not to execute code that modifies
		3382	those watchers. Note also that in that case, you have to re-register any
		3383	signal watchers.
2521		3384
2522	=head3 Watcher-Specific Functions and Data Members	3385	=head3 Watcher-Specific Functions and Data Members
2523		3386
2524	=over 4	3387	=over 4
2525		3388
2526	=item ev_fork_init (ev_signal *, callback)	3389	=item ev_fork_init (ev_fork *, callback)
2527		3390
2528	Initialises and configures the fork watcher - it has no parameters of any	3391	Initialises and configures the fork watcher - it has no parameters of any
2529	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3392	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2530	believe me.	3393	really.
2531		3394
2532	=back	3395	=back
2533		3396
2534		3397
		3398	=head2 C<ev_cleanup> - even the best things end
		3399
		3400	Cleanup watchers are called just before the event loop is being destroyed
		3401	by a call to C<ev_loop_destroy>.
		3402
		3403	While there is no guarantee that the event loop gets destroyed, cleanup
		3404	watchers provide a convenient method to install cleanup hooks for your
		3405	program, worker threads and so on - you just to make sure to destroy the
		3406	loop when you want them to be invoked.
		3407
		3408	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3409	all other watchers, they do not keep a reference to the event loop (which
		3410	makes a lot of sense if you think about it). Like all other watchers, you
		3411	can call libev functions in the callback, except C<ev_cleanup_start>.
		3412
		3413	=head3 Watcher-Specific Functions and Data Members
		3414
		3415	=over 4
		3416
		3417	=item ev_cleanup_init (ev_cleanup *, callback)
		3418
		3419	Initialises and configures the cleanup watcher - it has no parameters of
		3420	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3421	pointless, I assure you.
		3422
		3423	=back
		3424
		3425	Example: Register an atexit handler to destroy the default loop, so any
		3426	cleanup functions are called.
		3427
		3428	static void
		3429	program_exits (void)
		3430	{
		3431	ev_loop_destroy (EV_DEFAULT_UC);
		3432	}
		3433
		3434	...
		3435	atexit (program_exits);
		3436
		3437
2535	=head2 C<ev_async> - how to wake up another event loop	3438	=head2 C<ev_async> - how to wake up an event loop
2536		3439
2537	In general, you cannot use an C<ev_loop> from multiple threads or other	3440	In general, you cannot use an C<ev_loop> from multiple threads or other
2538	asynchronous sources such as signal handlers (as opposed to multiple event	3441	asynchronous sources such as signal handlers (as opposed to multiple event
2539	loops - those are of course safe to use in different threads).	3442	loops - those are of course safe to use in different threads).
2540		3443
2541	Sometimes, however, you need to wake up another event loop you do not	3444	Sometimes, however, you need to wake up an event loop you do not control,
2542	control, for example because it belongs to another thread. This is what	3445	for example because it belongs to another thread. This is what C<ev_async>
2543	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3446	watchers do: as long as the C<ev_async> watcher is active, you can signal
2544	can signal it by calling C<ev_async_send>, which is thread- and signal	3447	it by calling C<ev_async_send>, which is thread- and signal safe.
2545	safe.
2546		3448
2547	This functionality is very similar to C<ev_signal> watchers, as signals,	3449	This functionality is very similar to C<ev_signal> watchers, as signals,
2548	too, are asynchronous in nature, and signals, too, will be compressed	3450	too, are asynchronous in nature, and signals, too, will be compressed
2549	(i.e. the number of callback invocations may be less than the number of	3451	(i.e. the number of callback invocations may be less than the number of
2550	C<ev_async_sent> calls).	3452	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2551		3453	of "global async watchers" by using a watcher on an otherwise unused
2552	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3454	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2553	just the default loop.	3455	even without knowing which loop owns the signal.
2554		3456
2555	=head3 Queueing	3457	=head3 Queueing
2556		3458
2557	C<ev_async> does not support queueing of data in any way. The reason	3459	C<ev_async> does not support queueing of data in any way. The reason
2558	is that the author does not know of a simple (or any) algorithm for a	3460	is that the author does not know of a simple (or any) algorithm for a
2559	multiple-writer-single-reader queue that works in all cases and doesn't	3461	multiple-writer-single-reader queue that works in all cases and doesn't
2560	need elaborate support such as pthreads.	3462	need elaborate support such as pthreads or unportable memory access
		3463	semantics.
2561		3464
2562	That means that if you want to queue data, you have to provide your own	3465	That means that if you want to queue data, you have to provide your own
2563	queue. But at least I can tell you how to implement locking around your	3466	queue. But at least I can tell you how to implement locking around your
2564	queue:	3467	queue:
2565		3468
…		…
2643	=over 4	3546	=over 4
2644		3547
2645	=item ev_async_init (ev_async *, callback)	3548	=item ev_async_init (ev_async *, callback)
2646		3549
2647	Initialises and configures the async watcher - it has no parameters of any	3550	Initialises and configures the async watcher - it has no parameters of any
2648	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3551	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2649	trust me.	3552	trust me.
2650		3553
2651	=item ev_async_send (loop, ev_async *)	3554	=item ev_async_send (loop, ev_async *)
2652		3555
2653	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3556	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2654	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3557	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3558	returns.
		3559
2655	C<ev_feed_event>, this call is safe to do from other threads, signal or	3560	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2656	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3561	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2657	section below on what exactly this means).	3562	embedding section below on what exactly this means).
2658		3563
2659	This call incurs the overhead of a system call only once per loop iteration,	3564	Note that, as with other watchers in libev, multiple events might get
2660	so while the overhead might be noticeable, it doesn't apply to repeated	3565	compressed into a single callback invocation (another way to look at
2661	calls to C<ev_async_send>.	3566	this is that C<ev_async> watchers are level-triggered: they are set on
		3567	C<ev_async_send>, reset when the event loop detects that).
		3568
		3569	This call incurs the overhead of at most one extra system call per event
		3570	loop iteration, if the event loop is blocked, and no syscall at all if
		3571	the event loop (or your program) is processing events. That means that
		3572	repeated calls are basically free (there is no need to avoid calls for
		3573	performance reasons) and that the overhead becomes smaller (typically
		3574	zero) under load.
2662		3575
2663	=item bool = ev_async_pending (ev_async *)	3576	=item bool = ev_async_pending (ev_async *)
2664		3577
2665	Returns a non-zero value when C<ev_async_send> has been called on the	3578	Returns a non-zero value when C<ev_async_send> has been called on the
2666	watcher but the event has not yet been processed (or even noted) by the	3579	watcher but the event has not yet been processed (or even noted) by the
…		…
2669	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3582	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2670	the loop iterates next and checks for the watcher to have become active,	3583	the loop iterates next and checks for the watcher to have become active,
2671	it will reset the flag again. C<ev_async_pending> can be used to very	3584	it will reset the flag again. C<ev_async_pending> can be used to very
2672	quickly check whether invoking the loop might be a good idea.	3585	quickly check whether invoking the loop might be a good idea.
2673		3586
2674	Not that this does I<not> check whether the watcher itself is pending, only	3587	Not that this does I<not> check whether the watcher itself is pending,
2675	whether it has been requested to make this watcher pending.	3588	only whether it has been requested to make this watcher pending: there
		3589	is a time window between the event loop checking and resetting the async
		3590	notification, and the callback being invoked.
2676		3591
2677	=back	3592	=back
2678		3593
2679		3594
2680	=head1 OTHER FUNCTIONS	3595	=head1 OTHER FUNCTIONS
2681		3596
2682	There are some other functions of possible interest. Described. Here. Now.	3597	There are some other functions of possible interest. Described. Here. Now.
2683		3598
2684	=over 4	3599	=over 4
2685		3600
2686	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3601	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
2687		3602
2688	This function combines a simple timer and an I/O watcher, calls your	3603	This function combines a simple timer and an I/O watcher, calls your
2689	callback on whichever event happens first and automatically stops both	3604	callback on whichever event happens first and automatically stops both
2690	watchers. This is useful if you want to wait for a single event on an fd	3605	watchers. This is useful if you want to wait for a single event on an fd
2691	or timeout without having to allocate/configure/start/stop/free one or	3606	or timeout without having to allocate/configure/start/stop/free one or
…		…
2697		3612
2698	If C<timeout> is less than 0, then no timeout watcher will be	3613	If C<timeout> is less than 0, then no timeout watcher will be
2699	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3614	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2700	repeat = 0) will be started. C<0> is a valid timeout.	3615	repeat = 0) will be started. C<0> is a valid timeout.
2701		3616
2702	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3617	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2703	passed an C<revents> set like normal event callbacks (a combination of	3618	passed an C<revents> set like normal event callbacks (a combination of
2704	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3619	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2705	value passed to C<ev_once>. Note that it is possible to receive I<both>	3620	value passed to C<ev_once>. Note that it is possible to receive I<both>
2706	a timeout and an io event at the same time - you probably should give io	3621	a timeout and an io event at the same time - you probably should give io
2707	events precedence.	3622	events precedence.
2708		3623
2709	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3624	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2710		3625
2711	static void stdin_ready (int revents, void *arg)	3626	static void stdin_ready (int revents, void *arg)
2712	{	3627	{
2713	if (revents & EV_READ)	3628	if (revents & EV_READ)
2714	/* stdin might have data for us, joy! */;	3629	/* stdin might have data for us, joy! */;
2715	else if (revents & EV_TIMEOUT)	3630	else if (revents & EV_TIMER)
2716	/* doh, nothing entered */;	3631	/* doh, nothing entered */;
2717	}	3632	}
2718		3633
2719	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3634	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2720		3635
2721	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2722
2723	Feeds the given event set into the event loop, as if the specified event
2724	had happened for the specified watcher (which must be a pointer to an
2725	initialised but not necessarily started event watcher).
2726
2727	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3636	=item ev_feed_fd_event (loop, int fd, int revents)
2728		3637
2729	Feed an event on the given fd, as if a file descriptor backend detected	3638	Feed an event on the given fd, as if a file descriptor backend detected
2730	the given events it.	3639	the given events.
2731		3640
2732	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3641	=item ev_feed_signal_event (loop, int signum)
2733		3642
2734	Feed an event as if the given signal occurred (C<loop> must be the default	3643	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2735	loop!).	3644	which is async-safe.
2736		3645
2737	=back	3646	=back
		3647
		3648
		3649	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3650
		3651	This section explains some common idioms that are not immediately
		3652	obvious. Note that examples are sprinkled over the whole manual, and this
		3653	section only contains stuff that wouldn't fit anywhere else.
		3654
		3655	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3656
		3657	Each watcher has, by default, a C<void *data> member that you can read
		3658	or modify at any time: libev will completely ignore it. This can be used
		3659	to associate arbitrary data with your watcher. If you need more data and
		3660	don't want to allocate memory separately and store a pointer to it in that
		3661	data member, you can also "subclass" the watcher type and provide your own
		3662	data:
		3663
		3664	struct my_io
		3665	{
		3666	ev_io io;
		3667	int otherfd;
		3668	void *somedata;
		3669	struct whatever *mostinteresting;
		3670	};
		3671
		3672	...
		3673	struct my_io w;
		3674	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3675
		3676	And since your callback will be called with a pointer to the watcher, you
		3677	can cast it back to your own type:
		3678
		3679	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3680	{
		3681	struct my_io *w = (struct my_io *)w_;
		3682	...
		3683	}
		3684
		3685	More interesting and less C-conformant ways of casting your callback
		3686	function type instead have been omitted.
		3687
		3688	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3689
		3690	Another common scenario is to use some data structure with multiple
		3691	embedded watchers, in effect creating your own watcher that combines
		3692	multiple libev event sources into one "super-watcher":
		3693
		3694	struct my_biggy
		3695	{
		3696	int some_data;
		3697	ev_timer t1;
		3698	ev_timer t2;
		3699	}
		3700
		3701	In this case getting the pointer to C<my_biggy> is a bit more
		3702	complicated: Either you store the address of your C<my_biggy> struct in
		3703	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3704	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3705	real programmers):
		3706
		3707	#include <stddef.h>
		3708
		3709	static void
		3710	t1_cb (EV_P_ ev_timer *w, int revents)
		3711	{
		3712	struct my_biggy big = (struct my_biggy *)
		3713	(((char *)w) - offsetof (struct my_biggy, t1));
		3714	}
		3715
		3716	static void
		3717	t2_cb (EV_P_ ev_timer *w, int revents)
		3718	{
		3719	struct my_biggy big = (struct my_biggy *)
		3720	(((char *)w) - offsetof (struct my_biggy, t2));
		3721	}
		3722
		3723	=head2 AVOIDING FINISHING BEFORE RETURNING
		3724
		3725	Often you have structures like this in event-based programs:
		3726
		3727	callback ()
		3728	{
		3729	free (request);
		3730	}
		3731
		3732	request = start_new_request (..., callback);
		3733
		3734	The intent is to start some "lengthy" operation. The C<request> could be
		3735	used to cancel the operation, or do other things with it.
		3736
		3737	It's not uncommon to have code paths in C<start_new_request> that
		3738	immediately invoke the callback, for example, to report errors. Or you add
		3739	some caching layer that finds that it can skip the lengthy aspects of the
		3740	operation and simply invoke the callback with the result.
		3741
		3742	The problem here is that this will happen I<before> C<start_new_request>
		3743	has returned, so C<request> is not set.
		3744
		3745	Even if you pass the request by some safer means to the callback, you
		3746	might want to do something to the request after starting it, such as
		3747	canceling it, which probably isn't working so well when the callback has
		3748	already been invoked.
		3749
		3750	A common way around all these issues is to make sure that
		3751	C<start_new_request> I<always> returns before the callback is invoked. If
		3752	C<start_new_request> immediately knows the result, it can artificially
		3753	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3754	example, or more sneakily, by reusing an existing (stopped) watcher and
		3755	pushing it into the pending queue:
		3756
		3757	ev_set_cb (watcher, callback);
		3758	ev_feed_event (EV_A_ watcher, 0);
		3759
		3760	This way, C<start_new_request> can safely return before the callback is
		3761	invoked, while not delaying callback invocation too much.
		3762
		3763	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3764
		3765	Often (especially in GUI toolkits) there are places where you have
		3766	I<modal> interaction, which is most easily implemented by recursively
		3767	invoking C<ev_run>.
		3768
		3769	This brings the problem of exiting - a callback might want to finish the
		3770	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3771	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3772	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3773	other combination: In these cases, a simple C<ev_break> will not work.
		3774
		3775	The solution is to maintain "break this loop" variable for each C<ev_run>
		3776	invocation, and use a loop around C<ev_run> until the condition is
		3777	triggered, using C<EVRUN_ONCE>:
		3778
		3779	// main loop
		3780	int exit_main_loop = 0;
		3781
		3782	while (!exit_main_loop)
		3783	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3784
		3785	// in a modal watcher
		3786	int exit_nested_loop = 0;
		3787
		3788	while (!exit_nested_loop)
		3789	ev_run (EV_A_ EVRUN_ONCE);
		3790
		3791	To exit from any of these loops, just set the corresponding exit variable:
		3792
		3793	// exit modal loop
		3794	exit_nested_loop = 1;
		3795
		3796	// exit main program, after modal loop is finished
		3797	exit_main_loop = 1;
		3798
		3799	// exit both
		3800	exit_main_loop = exit_nested_loop = 1;
		3801
		3802	=head2 THREAD LOCKING EXAMPLE
		3803
		3804	Here is a fictitious example of how to run an event loop in a different
		3805	thread from where callbacks are being invoked and watchers are
		3806	created/added/removed.
		3807
		3808	For a real-world example, see the C<EV::Loop::Async> perl module,
		3809	which uses exactly this technique (which is suited for many high-level
		3810	languages).
		3811
		3812	The example uses a pthread mutex to protect the loop data, a condition
		3813	variable to wait for callback invocations, an async watcher to notify the
		3814	event loop thread and an unspecified mechanism to wake up the main thread.
		3815
		3816	First, you need to associate some data with the event loop:
		3817
		3818	typedef struct {
		3819	mutex_t lock; /* global loop lock */
		3820	ev_async async_w;
		3821	thread_t tid;
		3822	cond_t invoke_cv;
		3823	} userdata;
		3824
		3825	void prepare_loop (EV_P)
		3826	{
		3827	// for simplicity, we use a static userdata struct.
		3828	static userdata u;
		3829
		3830	ev_async_init (&u->async_w, async_cb);
		3831	ev_async_start (EV_A_ &u->async_w);
		3832
		3833	pthread_mutex_init (&u->lock, 0);
		3834	pthread_cond_init (&u->invoke_cv, 0);
		3835
		3836	// now associate this with the loop
		3837	ev_set_userdata (EV_A_ u);
		3838	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3839	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3840
		3841	// then create the thread running ev_run
		3842	pthread_create (&u->tid, 0, l_run, EV_A);
		3843	}
		3844
		3845	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3846	solely to wake up the event loop so it takes notice of any new watchers
		3847	that might have been added:
		3848
		3849	static void
		3850	async_cb (EV_P_ ev_async *w, int revents)
		3851	{
		3852	// just used for the side effects
		3853	}
		3854
		3855	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3856	protecting the loop data, respectively.
		3857
		3858	static void
		3859	l_release (EV_P)
		3860	{
		3861	userdata *u = ev_userdata (EV_A);
		3862	pthread_mutex_unlock (&u->lock);
		3863	}
		3864
		3865	static void
		3866	l_acquire (EV_P)
		3867	{
		3868	userdata *u = ev_userdata (EV_A);
		3869	pthread_mutex_lock (&u->lock);
		3870	}
		3871
		3872	The event loop thread first acquires the mutex, and then jumps straight
		3873	into C<ev_run>:
		3874
		3875	void *
		3876	l_run (void *thr_arg)
		3877	{
		3878	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3879
		3880	l_acquire (EV_A);
		3881	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3882	ev_run (EV_A_ 0);
		3883	l_release (EV_A);
		3884
		3885	return 0;
		3886	}
		3887
		3888	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3889	signal the main thread via some unspecified mechanism (signals? pipe
		3890	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3891	have been called (in a while loop because a) spurious wakeups are possible
		3892	and b) skipping inter-thread-communication when there are no pending
		3893	watchers is very beneficial):
		3894
		3895	static void
		3896	l_invoke (EV_P)
		3897	{
		3898	userdata *u = ev_userdata (EV_A);
		3899
		3900	while (ev_pending_count (EV_A))
		3901	{
		3902	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3903	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3904	}
		3905	}
		3906
		3907	Now, whenever the main thread gets told to invoke pending watchers, it
		3908	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3909	thread to continue:
		3910
		3911	static void
		3912	real_invoke_pending (EV_P)
		3913	{
		3914	userdata *u = ev_userdata (EV_A);
		3915
		3916	pthread_mutex_lock (&u->lock);
		3917	ev_invoke_pending (EV_A);
		3918	pthread_cond_signal (&u->invoke_cv);
		3919	pthread_mutex_unlock (&u->lock);
		3920	}
		3921
		3922	Whenever you want to start/stop a watcher or do other modifications to an
		3923	event loop, you will now have to lock:
		3924
		3925	ev_timer timeout_watcher;
		3926	userdata *u = ev_userdata (EV_A);
		3927
		3928	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3929
		3930	pthread_mutex_lock (&u->lock);
		3931	ev_timer_start (EV_A_ &timeout_watcher);
		3932	ev_async_send (EV_A_ &u->async_w);
		3933	pthread_mutex_unlock (&u->lock);
		3934
		3935	Note that sending the C<ev_async> watcher is required because otherwise
		3936	an event loop currently blocking in the kernel will have no knowledge
		3937	about the newly added timer. By waking up the loop it will pick up any new
		3938	watchers in the next event loop iteration.
		3939
		3940	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3941
		3942	While the overhead of a callback that e.g. schedules a thread is small, it
		3943	is still an overhead. If you embed libev, and your main usage is with some
		3944	kind of threads or coroutines, you might want to customise libev so that
		3945	doesn't need callbacks anymore.
		3946
		3947	Imagine you have coroutines that you can switch to using a function
		3948	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3949	and that due to some magic, the currently active coroutine is stored in a
		3950	global called C<current_coro>. Then you can build your own "wait for libev
		3951	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3952	the differing C<;> conventions):
		3953
		3954	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3955	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3956
		3957	That means instead of having a C callback function, you store the
		3958	coroutine to switch to in each watcher, and instead of having libev call
		3959	your callback, you instead have it switch to that coroutine.
		3960
		3961	A coroutine might now wait for an event with a function called
		3962	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3963	matter when, or whether the watcher is active or not when this function is
		3964	called):
		3965
		3966	void
		3967	wait_for_event (ev_watcher *w)
		3968	{
		3969	ev_set_cb (w, current_coro);
		3970	switch_to (libev_coro);
		3971	}
		3972
		3973	That basically suspends the coroutine inside C<wait_for_event> and
		3974	continues the libev coroutine, which, when appropriate, switches back to
		3975	this or any other coroutine.
		3976
		3977	You can do similar tricks if you have, say, threads with an event queue -
		3978	instead of storing a coroutine, you store the queue object and instead of
		3979	switching to a coroutine, you push the watcher onto the queue and notify
		3980	any waiters.
		3981
		3982	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3983	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3984
		3985	// my_ev.h
		3986	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3987	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3988	#include "../libev/ev.h"
		3989
		3990	// my_ev.c
		3991	#define EV_H "my_ev.h"
		3992	#include "../libev/ev.c"
		3993
		3994	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3995	F<my_ev.c> into your project. When properly specifying include paths, you
		3996	can even use F<ev.h> as header file name directly.
2738		3997
2739		3998
2740	=head1 LIBEVENT EMULATION	3999	=head1 LIBEVENT EMULATION
2741		4000
2742	Libev offers a compatibility emulation layer for libevent. It cannot	4001	Libev offers a compatibility emulation layer for libevent. It cannot
2743	emulate the internals of libevent, so here are some usage hints:	4002	emulate the internals of libevent, so here are some usage hints:
2744		4003
2745	=over 4	4004	=over 4
		4005
		4006	=item * Only the libevent-1.4.1-beta API is being emulated.
		4007
		4008	This was the newest libevent version available when libev was implemented,
		4009	and is still mostly unchanged in 2010.
2746		4010
2747	=item * Use it by including <event.h>, as usual.	4011	=item * Use it by including <event.h>, as usual.
2748		4012
2749	=item * The following members are fully supported: ev_base, ev_callback,	4013	=item * The following members are fully supported: ev_base, ev_callback,
2750	ev_arg, ev_fd, ev_res, ev_events.	4014	ev_arg, ev_fd, ev_res, ev_events.
…		…
2756	=item * Priorities are not currently supported. Initialising priorities	4020	=item * Priorities are not currently supported. Initialising priorities
2757	will fail and all watchers will have the same priority, even though there	4021	will fail and all watchers will have the same priority, even though there
2758	is an ev_pri field.	4022	is an ev_pri field.
2759		4023
2760	=item * In libevent, the last base created gets the signals, in libev, the	4024	=item * In libevent, the last base created gets the signals, in libev, the
2761	first base created (== the default loop) gets the signals.	4025	base that registered the signal gets the signals.
2762		4026
2763	=item * Other members are not supported.	4027	=item * Other members are not supported.
2764		4028
2765	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4029	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2766	to use the libev header file and library.	4030	to use the libev header file and library.
2767		4031
2768	=back	4032	=back
2769		4033
2770	=head1 C++ SUPPORT	4034	=head1 C++ SUPPORT
		4035
		4036	=head2 C API
		4037
		4038	The normal C API should work fine when used from C++: both ev.h and the
		4039	libev sources can be compiled as C++. Therefore, code that uses the C API
		4040	will work fine.
		4041
		4042	Proper exception specifications might have to be added to callbacks passed
		4043	to libev: exceptions may be thrown only from watcher callbacks, all other
		4044	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4045	callbacks) must not throw exceptions, and might need a C<noexcept>
		4046	specification. If you have code that needs to be compiled as both C and
		4047	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4048
		4049	static void
		4050	fatal_error (const char *msg) EV_NOEXCEPT
		4051	{
		4052	perror (msg);
		4053	abort ();
		4054	}
		4055
		4056	...
		4057	ev_set_syserr_cb (fatal_error);
		4058
		4059	The only API functions that can currently throw exceptions are C<ev_run>,
		4060	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4061	because it runs cleanup watchers).
		4062
		4063	Throwing exceptions in watcher callbacks is only supported if libev itself
		4064	is compiled with a C++ compiler or your C and C++ environments allow
		4065	throwing exceptions through C libraries (most do).
		4066
		4067	=head2 C++ API
2771		4068
2772	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4069	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2773	you to use some convenience methods to start/stop watchers and also change	4070	you to use some convenience methods to start/stop watchers and also change
2774	the callback model to a model using method callbacks on objects.	4071	the callback model to a model using method callbacks on objects.
2775		4072
2776	To use it,	4073	To use it,
2777		4074
2778	#include <ev++.h>	4075	#include <ev++.h>
2779		4076
2780	This automatically includes F<ev.h> and puts all of its definitions (many	4077	This automatically includes F<ev.h> and puts all of its definitions (many
2781	of them macros) into the global namespace. All C++ specific things are	4078	of them macros) into the global namespace. All C++ specific things are
2782	put into the C<ev> namespace. It should support all the same embedding	4079	put into the C<ev> namespace. It should support all the same embedding
…		…
2785	Care has been taken to keep the overhead low. The only data member the C++	4082	Care has been taken to keep the overhead low. The only data member the C++
2786	classes add (compared to plain C-style watchers) is the event loop pointer	4083	classes add (compared to plain C-style watchers) is the event loop pointer
2787	that the watcher is associated with (or no additional members at all if	4084	that the watcher is associated with (or no additional members at all if
2788	you disable C<EV_MULTIPLICITY> when embedding libev).	4085	you disable C<EV_MULTIPLICITY> when embedding libev).
2789		4086
2790	Currently, functions, and static and non-static member functions can be	4087	Currently, functions, static and non-static member functions and classes
2791	used as callbacks. Other types should be easy to add as long as they only	4088	with C<operator ()> can be used as callbacks. Other types should be easy
2792	need one additional pointer for context. If you need support for other	4089	to add as long as they only need one additional pointer for context. If
2793	types of functors please contact the author (preferably after implementing	4090	you need support for other types of functors please contact the author
2794	it).	4091	(preferably after implementing it).
		4092
		4093	For all this to work, your C++ compiler either has to use the same calling
		4094	conventions as your C compiler (for static member functions), or you have
		4095	to embed libev and compile libev itself as C++.
2795		4096
2796	Here is a list of things available in the C<ev> namespace:	4097	Here is a list of things available in the C<ev> namespace:
2797		4098
2798	=over 4	4099	=over 4
2799		4100
…		…
2809	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4110	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2810		4111
2811	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4112	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2812	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4113	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2813	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4114	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2814	defines by many implementations.	4115	defined by many implementations.
2815		4116
2816	All of those classes have these methods:	4117	All of those classes have these methods:
2817		4118
2818	=over 4	4119	=over 4
2819		4120
2820	=item ev::TYPE::TYPE ()	4121	=item ev::TYPE::TYPE ()
2821		4122
2822	=item ev::TYPE::TYPE (struct ev_loop *)	4123	=item ev::TYPE::TYPE (loop)
2823		4124
2824	=item ev::TYPE::~TYPE	4125	=item ev::TYPE::~TYPE
2825		4126
2826	The constructor (optionally) takes an event loop to associate the watcher	4127	The constructor (optionally) takes an event loop to associate the watcher
2827	with. If it is omitted, it will use C<EV_DEFAULT>.	4128	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2859		4160
2860	myclass obj;	4161	myclass obj;
2861	ev::io iow;	4162	ev::io iow;
2862	iow.set <myclass, &myclass::io_cb> (&obj);	4163	iow.set <myclass, &myclass::io_cb> (&obj);
2863		4164
		4165	=item w->set (object *)
		4166
		4167	This is a variation of a method callback - leaving out the method to call
		4168	will default the method to C<operator ()>, which makes it possible to use
		4169	functor objects without having to manually specify the C<operator ()> all
		4170	the time. Incidentally, you can then also leave out the template argument
		4171	list.
		4172
		4173	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		4174	int revents)>.
		4175
		4176	See the method-C<set> above for more details.
		4177
		4178	Example: use a functor object as callback.
		4179
		4180	struct myfunctor
		4181	{
		4182	void operator() (ev::io &w, int revents)
		4183	{
		4184	...
		4185	}
		4186	}
		4187
		4188	myfunctor f;
		4189
		4190	ev::io w;
		4191	w.set (&f);
		4192
2864	=item w->set<function> (void *data = 0)	4193	=item w->set<function> (void *data = 0)
2865		4194
2866	Also sets a callback, but uses a static method or plain function as	4195	Also sets a callback, but uses a static method or plain function as
2867	callback. The optional C<data> argument will be stored in the watcher's	4196	callback. The optional C<data> argument will be stored in the watcher's
2868	C<data> member and is free for you to use.	4197	C<data> member and is free for you to use.
…		…
2874	Example: Use a plain function as callback.	4203	Example: Use a plain function as callback.
2875		4204
2876	static void io_cb (ev::io &w, int revents) { }	4205	static void io_cb (ev::io &w, int revents) { }
2877	iow.set <io_cb> ();	4206	iow.set <io_cb> ();
2878		4207
2879	=item w->set (struct ev_loop *)	4208	=item w->set (loop)
2880		4209
2881	Associates a different C<struct ev_loop> with this watcher. You can only	4210	Associates a different C<struct ev_loop> with this watcher. You can only
2882	do this when the watcher is inactive (and not pending either).	4211	do this when the watcher is inactive (and not pending either).
2883		4212
2884	=item w->set ([arguments])	4213	=item w->set ([arguments])
2885		4214
2886	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4215	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4216	with the same arguments. Either this method or a suitable start method
2887	called at least once. Unlike the C counterpart, an active watcher gets	4217	must be called at least once. Unlike the C counterpart, an active watcher
2888	automatically stopped and restarted when reconfiguring it with this	4218	gets automatically stopped and restarted when reconfiguring it with this
2889	method.	4219	method.
		4220
		4221	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4222	clashing with the C<set (loop)> method.
2890		4223
2891	=item w->start ()	4224	=item w->start ()
2892		4225
2893	Starts the watcher. Note that there is no C<loop> argument, as the	4226	Starts the watcher. Note that there is no C<loop> argument, as the
2894	constructor already stores the event loop.	4227	constructor already stores the event loop.
2895		4228
		4229	=item w->start ([arguments])
		4230
		4231	Instead of calling C<set> and C<start> methods separately, it is often
		4232	convenient to wrap them in one call. Uses the same type of arguments as
		4233	the configure C<set> method of the watcher.
		4234
2896	=item w->stop ()	4235	=item w->stop ()
2897		4236
2898	Stops the watcher if it is active. Again, no C<loop> argument.	4237	Stops the watcher if it is active. Again, no C<loop> argument.
2899		4238
2900	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4239	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2912		4251
2913	=back	4252	=back
2914		4253
2915	=back	4254	=back
2916		4255
2917	Example: Define a class with an IO and idle watcher, start one of them in	4256	Example: Define a class with two I/O and idle watchers, start the I/O
2918	the constructor.	4257	watchers in the constructor.
2919		4258
2920	class myclass	4259	class myclass
2921	{	4260	{
2922	ev::io io ; void io_cb (ev::io &w, int revents);	4261	ev::io io ; void io_cb (ev::io &w, int revents);
		4262	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2923	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4263	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2924		4264
2925	myclass (int fd)	4265	myclass (int fd)
2926	{	4266	{
2927	io .set <myclass, &myclass::io_cb > (this);	4267	io .set <myclass, &myclass::io_cb > (this);
		4268	io2 .set <myclass, &myclass::io2_cb > (this);
2928	idle.set <myclass, &myclass::idle_cb> (this);	4269	idle.set <myclass, &myclass::idle_cb> (this);
2929		4270
2930	io.start (fd, ev::READ);	4271	io.set (fd, ev::WRITE); // configure the watcher
		4272	io.start (); // start it whenever convenient
		4273
		4274	io2.start (fd, ev::READ); // set + start in one call
2931	}	4275	}
2932	};	4276	};
2933		4277
2934		4278
2935	=head1 OTHER LANGUAGE BINDINGS	4279	=head1 OTHER LANGUAGE BINDINGS
…		…
2954	L<http://software.schmorp.de/pkg/EV>.	4298	L<http://software.schmorp.de/pkg/EV>.
2955		4299
2956	=item Python	4300	=item Python
2957		4301
2958	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4302	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2959	seems to be quite complete and well-documented. Note, however, that the	4303	seems to be quite complete and well-documented.
2960	patch they require for libev is outright dangerous as it breaks the ABI
2961	for everybody else, and therefore, should never be applied in an installed
2962	libev (if python requires an incompatible ABI then it needs to embed
2963	libev).
2964		4304
2965	=item Ruby	4305	=item Ruby
2966		4306
2967	Tony Arcieri has written a ruby extension that offers access to a subset	4307	Tony Arcieri has written a ruby extension that offers access to a subset
2968	of the libev API and adds file handle abstractions, asynchronous DNS and	4308	of the libev API and adds file handle abstractions, asynchronous DNS and
2969	more on top of it. It can be found via gem servers. Its homepage is at	4309	more on top of it. It can be found via gem servers. Its homepage is at
2970	L<http://rev.rubyforge.org/>.	4310	L<http://rev.rubyforge.org/>.
2971		4311
		4312	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4313	makes rev work even on mingw.
		4314
		4315	=item Haskell
		4316
		4317	A haskell binding to libev is available at
		4318	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4319
2972	=item D	4320	=item D
2973		4321
2974	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4322	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2975	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4323	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
2976		4324
2977	=item Ocaml	4325	=item Ocaml
2978		4326
2979	Erkki Seppala has written Ocaml bindings for libev, to be found at	4327	Erkki Seppala has written Ocaml bindings for libev, to be found at
2980	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4328	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4329
		4330	=item Lua
		4331
		4332	Brian Maher has written a partial interface to libev for lua (at the
		4333	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4334	L<http://github.com/brimworks/lua-ev>.
		4335
		4336	=item Javascript
		4337
		4338	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4339
		4340	=item Others
		4341
		4342	There are others, and I stopped counting.
2981		4343
2982	=back	4344	=back
2983		4345
2984		4346
2985	=head1 MACRO MAGIC	4347	=head1 MACRO MAGIC
…		…
2999	loop argument"). The C<EV_A> form is used when this is the sole argument,	4361	loop argument"). The C<EV_A> form is used when this is the sole argument,
3000	C<EV_A_> is used when other arguments are following. Example:	4362	C<EV_A_> is used when other arguments are following. Example:
3001		4363
3002	ev_unref (EV_A);	4364	ev_unref (EV_A);
3003	ev_timer_add (EV_A_ watcher);	4365	ev_timer_add (EV_A_ watcher);
3004	ev_loop (EV_A_ 0);	4366	ev_run (EV_A_ 0);
3005		4367
3006	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4368	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3007	which is often provided by the following macro.	4369	which is often provided by the following macro.
3008		4370
3009	=item C<EV_P>, C<EV_P_>	4371	=item C<EV_P>, C<EV_P_>
…		…
3022	suitable for use with C<EV_A>.	4384	suitable for use with C<EV_A>.
3023		4385
3024	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4386	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3025		4387
3026	Similar to the other two macros, this gives you the value of the default	4388	Similar to the other two macros, this gives you the value of the default
3027	loop, if multiple loops are supported ("ev loop default").	4389	loop, if multiple loops are supported ("ev loop default"). The default loop
		4390	will be initialised if it isn't already initialised.
		4391
		4392	For non-multiplicity builds, these macros do nothing, so you always have
		4393	to initialise the loop somewhere.
3028		4394
3029	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4395	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3030		4396
3031	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4397	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3032	default loop has been initialised (C<UC> == unchecked). Their behaviour	4398	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3049	}	4415	}
3050		4416
3051	ev_check check;	4417	ev_check check;
3052	ev_check_init (&check, check_cb);	4418	ev_check_init (&check, check_cb);
3053	ev_check_start (EV_DEFAULT_ &check);	4419	ev_check_start (EV_DEFAULT_ &check);
3054	ev_loop (EV_DEFAULT_ 0);	4420	ev_run (EV_DEFAULT_ 0);
3055		4421
3056	=head1 EMBEDDING	4422	=head1 EMBEDDING
3057		4423
3058	Libev can (and often is) directly embedded into host	4424	Libev can (and often is) directly embedded into host
3059	applications. Examples of applications that embed it include the Deliantra	4425	applications. Examples of applications that embed it include the Deliantra
…		…
3086		4452
3087	#define EV_STANDALONE 1	4453	#define EV_STANDALONE 1
3088	#include "ev.h"	4454	#include "ev.h"
3089		4455
3090	Both header files and implementation files can be compiled with a C++	4456	Both header files and implementation files can be compiled with a C++
3091	compiler (at least, thats a stated goal, and breakage will be treated	4457	compiler (at least, that's a stated goal, and breakage will be treated
3092	as a bug).	4458	as a bug).
3093		4459
3094	You need the following files in your source tree, or in a directory	4460	You need the following files in your source tree, or in a directory
3095	in your include path (e.g. in libev/ when using -Ilibev):	4461	in your include path (e.g. in libev/ when using -Ilibev):
3096		4462
…		…
3099	ev_vars.h	4465	ev_vars.h
3100	ev_wrap.h	4466	ev_wrap.h
3101		4467
3102	ev_win32.c required on win32 platforms only	4468	ev_win32.c required on win32 platforms only
3103		4469
3104	ev_select.c only when select backend is enabled (which is enabled by default)	4470	ev_select.c only when select backend is enabled
3105	ev_poll.c only when poll backend is enabled (disabled by default)	4471	ev_poll.c only when poll backend is enabled
3106	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4472	ev_epoll.c only when the epoll backend is enabled
		4473	ev_linuxaio.c only when the linux aio backend is enabled
3107	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4474	ev_kqueue.c only when the kqueue backend is enabled
3108	ev_port.c only when the solaris port backend is enabled (disabled by default)	4475	ev_port.c only when the solaris port backend is enabled
3109		4476
3110	F<ev.c> includes the backend files directly when enabled, so you only need	4477	F<ev.c> includes the backend files directly when enabled, so you only need
3111	to compile this single file.	4478	to compile this single file.
3112		4479
3113	=head3 LIBEVENT COMPATIBILITY API	4480	=head3 LIBEVENT COMPATIBILITY API
…		…
3139	libev.m4	4506	libev.m4
3140		4507
3141	=head2 PREPROCESSOR SYMBOLS/MACROS	4508	=head2 PREPROCESSOR SYMBOLS/MACROS
3142		4509
3143	Libev can be configured via a variety of preprocessor symbols you have to	4510	Libev can be configured via a variety of preprocessor symbols you have to
3144	define before including any of its files. The default in the absence of	4511	define before including (or compiling) any of its files. The default in
3145	autoconf is documented for every option.	4512	the absence of autoconf is documented for every option.
		4513
		4514	Symbols marked with "(h)" do not change the ABI, and can have different
		4515	values when compiling libev vs. including F<ev.h>, so it is permissible
		4516	to redefine them before including F<ev.h> without breaking compatibility
		4517	to a compiled library. All other symbols change the ABI, which means all
		4518	users of libev and the libev code itself must be compiled with compatible
		4519	settings.
3146		4520
3147	=over 4	4521	=over 4
3148		4522
		4523	=item EV_COMPAT3 (h)
		4524
		4525	Backwards compatibility is a major concern for libev. This is why this
		4526	release of libev comes with wrappers for the functions and symbols that
		4527	have been renamed between libev version 3 and 4.
		4528
		4529	You can disable these wrappers (to test compatibility with future
		4530	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4531	sources. This has the additional advantage that you can drop the C<struct>
		4532	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4533	typedef in that case.
		4534
		4535	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4536	and in some even more future version the compatibility code will be
		4537	removed completely.
		4538
3149	=item EV_STANDALONE	4539	=item EV_STANDALONE (h)
3150		4540
3151	Must always be C<1> if you do not use autoconf configuration, which	4541	Must always be C<1> if you do not use autoconf configuration, which
3152	keeps libev from including F<config.h>, and it also defines dummy	4542	keeps libev from including F<config.h>, and it also defines dummy
3153	implementations for some libevent functions (such as logging, which is not	4543	implementations for some libevent functions (such as logging, which is not
3154	supported). It will also not define any of the structs usually found in	4544	supported). It will also not define any of the structs usually found in
3155	F<event.h> that are not directly supported by the libev core alone.	4545	F<event.h> that are not directly supported by the libev core alone.
3156		4546
		4547	In standalone mode, libev will still try to automatically deduce the
		4548	configuration, but has to be more conservative.
		4549
		4550	=item EV_USE_FLOOR
		4551
		4552	If defined to be C<1>, libev will use the C<floor ()> function for its
		4553	periodic reschedule calculations, otherwise libev will fall back on a
		4554	portable (slower) implementation. If you enable this, you usually have to
		4555	link against libm or something equivalent. Enabling this when the C<floor>
		4556	function is not available will fail, so the safe default is to not enable
		4557	this.
		4558
3157	=item EV_USE_MONOTONIC	4559	=item EV_USE_MONOTONIC
3158		4560
3159	If defined to be C<1>, libev will try to detect the availability of the	4561	If defined to be C<1>, libev will try to detect the availability of the
3160	monotonic clock option at both compile time and runtime. Otherwise no use	4562	monotonic clock option at both compile time and runtime. Otherwise no
3161	of the monotonic clock option will be attempted. If you enable this, you	4563	use of the monotonic clock option will be attempted. If you enable this,
3162	usually have to link against librt or something similar. Enabling it when	4564	you usually have to link against librt or something similar. Enabling it
3163	the functionality isn't available is safe, though, although you have	4565	when the functionality isn't available is safe, though, although you have
3164	to make sure you link against any libraries where the C<clock_gettime>	4566	to make sure you link against any libraries where the C<clock_gettime>
3165	function is hiding in (often F<-lrt>).	4567	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3166		4568
3167	=item EV_USE_REALTIME	4569	=item EV_USE_REALTIME
3168		4570
3169	If defined to be C<1>, libev will try to detect the availability of the	4571	If defined to be C<1>, libev will try to detect the availability of the
3170	real-time clock option at compile time (and assume its availability at	4572	real-time clock option at compile time (and assume its availability
3171	runtime if successful). Otherwise no use of the real-time clock option will	4573	at runtime if successful). Otherwise no use of the real-time clock
3172	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4574	option will be attempted. This effectively replaces C<gettimeofday>
3173	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4575	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3174	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4576	correctness. See the note about libraries in the description of
		4577	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4578	C<EV_USE_CLOCK_SYSCALL>.
		4579
		4580	=item EV_USE_CLOCK_SYSCALL
		4581
		4582	If defined to be C<1>, libev will try to use a direct syscall instead
		4583	of calling the system-provided C<clock_gettime> function. This option
		4584	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4585	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4586	programs needlessly. Using a direct syscall is slightly slower (in
		4587	theory), because no optimised vdso implementation can be used, but avoids
		4588	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4589	higher, as it simplifies linking (no need for C<-lrt>).
3175		4590
3176	=item EV_USE_NANOSLEEP	4591	=item EV_USE_NANOSLEEP
3177		4592
3178	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4593	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3179	and will use it for delays. Otherwise it will use C<select ()>.	4594	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3195		4610
3196	=item EV_SELECT_USE_FD_SET	4611	=item EV_SELECT_USE_FD_SET
3197		4612
3198	If defined to C<1>, then the select backend will use the system C<fd_set>	4613	If defined to C<1>, then the select backend will use the system C<fd_set>
3199	structure. This is useful if libev doesn't compile due to a missing	4614	structure. This is useful if libev doesn't compile due to a missing
3200	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4615	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3201	exotic systems. This usually limits the range of file descriptors to some	4616	on exotic systems. This usually limits the range of file descriptors to
3202	low limit such as 1024 or might have other limitations (winsocket only	4617	some low limit such as 1024 or might have other limitations (winsocket
3203	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4618	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3204	influence the size of the C<fd_set> used.	4619	configures the maximum size of the C<fd_set>.
3205		4620
3206	=item EV_SELECT_IS_WINSOCKET	4621	=item EV_SELECT_IS_WINSOCKET
3207		4622
3208	When defined to C<1>, the select backend will assume that	4623	When defined to C<1>, the select backend will assume that
3209	select/socket/connect etc. don't understand file descriptors but	4624	select/socket/connect etc. don't understand file descriptors but
…		…
3211	be used is the winsock select). This means that it will call	4626	be used is the winsock select). This means that it will call
3212	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4627	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3213	it is assumed that all these functions actually work on fds, even	4628	it is assumed that all these functions actually work on fds, even
3214	on win32. Should not be defined on non-win32 platforms.	4629	on win32. Should not be defined on non-win32 platforms.
3215		4630
3216	=item EV_FD_TO_WIN32_HANDLE	4631	=item EV_FD_TO_WIN32_HANDLE(fd)
3217		4632
3218	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4633	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3219	file descriptors to socket handles. When not defining this symbol (the	4634	file descriptors to socket handles. When not defining this symbol (the
3220	default), then libev will call C<_get_osfhandle>, which is usually	4635	default), then libev will call C<_get_osfhandle>, which is usually
3221	correct. In some cases, programs use their own file descriptor management,	4636	correct. In some cases, programs use their own file descriptor management,
3222	in which case they can provide this function to map fds to socket handles.	4637	in which case they can provide this function to map fds to socket handles.
3223		4638
		4639	=item EV_WIN32_HANDLE_TO_FD(handle)
		4640
		4641	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4642	using the standard C<_open_osfhandle> function. For programs implementing
		4643	their own fd to handle mapping, overwriting this function makes it easier
		4644	to do so. This can be done by defining this macro to an appropriate value.
		4645
		4646	=item EV_WIN32_CLOSE_FD(fd)
		4647
		4648	If programs implement their own fd to handle mapping on win32, then this
		4649	macro can be used to override the C<close> function, useful to unregister
		4650	file descriptors again. Note that the replacement function has to close
		4651	the underlying OS handle.
		4652
		4653	=item EV_USE_WSASOCKET
		4654
		4655	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4656	communication socket, which works better in some environments. Otherwise,
		4657	the normal C<socket> function will be used, which works better in other
		4658	environments.
		4659
3224	=item EV_USE_POLL	4660	=item EV_USE_POLL
3225		4661
3226	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4662	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3227	backend. Otherwise it will be enabled on non-win32 platforms. It	4663	backend. Otherwise it will be enabled on non-win32 platforms. It
3228	takes precedence over select.	4664	takes precedence over select.
…		…
3232	If defined to be C<1>, libev will compile in support for the Linux	4668	If defined to be C<1>, libev will compile in support for the Linux
3233	C<epoll>(7) backend. Its availability will be detected at runtime,	4669	C<epoll>(7) backend. Its availability will be detected at runtime,
3234	otherwise another method will be used as fallback. This is the preferred	4670	otherwise another method will be used as fallback. This is the preferred
3235	backend for GNU/Linux systems. If undefined, it will be enabled if the	4671	backend for GNU/Linux systems. If undefined, it will be enabled if the
3236	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4672	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4673
		4674	=item EV_USE_LINUXAIO
		4675
		4676	If defined to be C<1>, libev will compile in support for the Linux
		4677	aio backend. Due to it's currenbt limitations it has to be requested
		4678	explicitly. If undefined, it will be enabled on linux, otherwise
		4679	disabled.
3237		4680
3238	=item EV_USE_KQUEUE	4681	=item EV_USE_KQUEUE
3239		4682
3240	If defined to be C<1>, libev will compile in support for the BSD style	4683	If defined to be C<1>, libev will compile in support for the BSD style
3241	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4684	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3263	If defined to be C<1>, libev will compile in support for the Linux inotify	4706	If defined to be C<1>, libev will compile in support for the Linux inotify
3264	interface to speed up C<ev_stat> watchers. Its actual availability will	4707	interface to speed up C<ev_stat> watchers. Its actual availability will
3265	be detected at runtime. If undefined, it will be enabled if the headers	4708	be detected at runtime. If undefined, it will be enabled if the headers
3266	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4709	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3267		4710
		4711	=item EV_NO_SMP
		4712
		4713	If defined to be C<1>, libev will assume that memory is always coherent
		4714	between threads, that is, threads can be used, but threads never run on
		4715	different cpus (or different cpu cores). This reduces dependencies
		4716	and makes libev faster.
		4717
		4718	=item EV_NO_THREADS
		4719
		4720	If defined to be C<1>, libev will assume that it will never be called from
		4721	different threads (that includes signal handlers), which is a stronger
		4722	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4723	libev faster.
		4724
3268	=item EV_ATOMIC_T	4725	=item EV_ATOMIC_T
3269		4726
3270	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4727	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3271	access is atomic with respect to other threads or signal contexts. No such	4728	access is atomic with respect to other threads or signal contexts. No
3272	type is easily found in the C language, so you can provide your own type	4729	such type is easily found in the C language, so you can provide your own
3273	that you know is safe for your purposes. It is used both for signal handler "locking"	4730	type that you know is safe for your purposes. It is used both for signal
3274	as well as for signal and thread safety in C<ev_async> watchers.	4731	handler "locking" as well as for signal and thread safety in C<ev_async>
		4732	watchers.
3275		4733
3276	In the absence of this define, libev will use C<sig_atomic_t volatile>	4734	In the absence of this define, libev will use C<sig_atomic_t volatile>
3277	(from F<signal.h>), which is usually good enough on most platforms.	4735	(from F<signal.h>), which is usually good enough on most platforms.
3278		4736
3279	=item EV_H	4737	=item EV_H (h)
3280		4738
3281	The name of the F<ev.h> header file used to include it. The default if	4739	The name of the F<ev.h> header file used to include it. The default if
3282	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4740	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3283	used to virtually rename the F<ev.h> header file in case of conflicts.	4741	used to virtually rename the F<ev.h> header file in case of conflicts.
3284		4742
3285	=item EV_CONFIG_H	4743	=item EV_CONFIG_H (h)
3286		4744
3287	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4745	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3288	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4746	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3289	C<EV_H>, above.	4747	C<EV_H>, above.
3290		4748
3291	=item EV_EVENT_H	4749	=item EV_EVENT_H (h)
3292		4750
3293	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4751	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3294	of how the F<event.h> header can be found, the default is C<"event.h">.	4752	of how the F<event.h> header can be found, the default is C<"event.h">.
3295		4753
3296	=item EV_PROTOTYPES	4754	=item EV_PROTOTYPES (h)
3297		4755
3298	If defined to be C<0>, then F<ev.h> will not define any function	4756	If defined to be C<0>, then F<ev.h> will not define any function
3299	prototypes, but still define all the structs and other symbols. This is	4757	prototypes, but still define all the structs and other symbols. This is
3300	occasionally useful if you want to provide your own wrapper functions	4758	occasionally useful if you want to provide your own wrapper functions
3301	around libev functions.	4759	around libev functions.
…		…
3306	will have the C<struct ev_loop *> as first argument, and you can create	4764	will have the C<struct ev_loop *> as first argument, and you can create
3307	additional independent event loops. Otherwise there will be no support	4765	additional independent event loops. Otherwise there will be no support
3308	for multiple event loops and there is no first event loop pointer	4766	for multiple event loops and there is no first event loop pointer
3309	argument. Instead, all functions act on the single default loop.	4767	argument. Instead, all functions act on the single default loop.
3310		4768
		4769	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4770	default loop when multiplicity is switched off - you always have to
		4771	initialise the loop manually in this case.
		4772
3311	=item EV_MINPRI	4773	=item EV_MINPRI
3312		4774
3313	=item EV_MAXPRI	4775	=item EV_MAXPRI
3314		4776
3315	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4777	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3323	fine.	4785	fine.
3324		4786
3325	If your embedding application does not need any priorities, defining these	4787	If your embedding application does not need any priorities, defining these
3326	both to C<0> will save some memory and CPU.	4788	both to C<0> will save some memory and CPU.
3327		4789
3328	=item EV_PERIODIC_ENABLE	4790	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4791	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4792	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3329		4793
3330	If undefined or defined to be C<1>, then periodic timers are supported. If	4794	If undefined or defined to be C<1> (and the platform supports it), then
3331	defined to be C<0>, then they are not. Disabling them saves a few kB of	4795	the respective watcher type is supported. If defined to be C<0>, then it
3332	code.	4796	is not. Disabling watcher types mainly saves code size.
3333		4797
3334	=item EV_IDLE_ENABLE	4798	=item EV_FEATURES
3335
3336	If undefined or defined to be C<1>, then idle watchers are supported. If
3337	defined to be C<0>, then they are not. Disabling them saves a few kB of
3338	code.
3339
3340	=item EV_EMBED_ENABLE
3341
3342	If undefined or defined to be C<1>, then embed watchers are supported. If
3343	defined to be C<0>, then they are not. Embed watchers rely on most other
3344	watcher types, which therefore must not be disabled.
3345
3346	=item EV_STAT_ENABLE
3347
3348	If undefined or defined to be C<1>, then stat watchers are supported. If
3349	defined to be C<0>, then they are not.
3350
3351	=item EV_FORK_ENABLE
3352
3353	If undefined or defined to be C<1>, then fork watchers are supported. If
3354	defined to be C<0>, then they are not.
3355
3356	=item EV_ASYNC_ENABLE
3357
3358	If undefined or defined to be C<1>, then async watchers are supported. If
3359	defined to be C<0>, then they are not.
3360
3361	=item EV_MINIMAL
3362		4799
3363	If you need to shave off some kilobytes of code at the expense of some	4800	If you need to shave off some kilobytes of code at the expense of some
3364	speed, define this symbol to C<1>. Currently this is used to override some	4801	speed (but with the full API), you can define this symbol to request
3365	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4802	certain subsets of functionality. The default is to enable all features
3366	much smaller 2-heap for timer management over the default 4-heap.	4803	that can be enabled on the platform.
		4804
		4805	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4806	with some broad features you want) and then selectively re-enable
		4807	additional parts you want, for example if you want everything minimal,
		4808	but multiple event loop support, async and child watchers and the poll
		4809	backend, use this:
		4810
		4811	#define EV_FEATURES 0
		4812	#define EV_MULTIPLICITY 1
		4813	#define EV_USE_POLL 1
		4814	#define EV_CHILD_ENABLE 1
		4815	#define EV_ASYNC_ENABLE 1
		4816
		4817	The actual value is a bitset, it can be a combination of the following
		4818	values (by default, all of these are enabled):
		4819
		4820	=over 4
		4821
		4822	=item C<1> - faster/larger code
		4823
		4824	Use larger code to speed up some operations.
		4825
		4826	Currently this is used to override some inlining decisions (enlarging the
		4827	code size by roughly 30% on amd64).
		4828
		4829	When optimising for size, use of compiler flags such as C<-Os> with
		4830	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4831	assertions.
		4832
		4833	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4834	(e.g. gcc with C<-Os>).
		4835
		4836	=item C<2> - faster/larger data structures
		4837
		4838	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4839	hash table sizes and so on. This will usually further increase code size
		4840	and can additionally have an effect on the size of data structures at
		4841	runtime.
		4842
		4843	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4844	(e.g. gcc with C<-Os>).
		4845
		4846	=item C<4> - full API configuration
		4847
		4848	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4849	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4850
		4851	=item C<8> - full API
		4852
		4853	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4854	details on which parts of the API are still available without this
		4855	feature, and do not complain if this subset changes over time.
		4856
		4857	=item C<16> - enable all optional watcher types
		4858
		4859	Enables all optional watcher types. If you want to selectively enable
		4860	only some watcher types other than I/O and timers (e.g. prepare,
		4861	embed, async, child...) you can enable them manually by defining
		4862	C<EV_watchertype_ENABLE> to C<1> instead.
		4863
		4864	=item C<32> - enable all backends
		4865
		4866	This enables all backends - without this feature, you need to enable at
		4867	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4868
		4869	=item C<64> - enable OS-specific "helper" APIs
		4870
		4871	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4872	default.
		4873
		4874	=back
		4875
		4876	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4877	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4878	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4879	watchers, timers and monotonic clock support.
		4880
		4881	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4882	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4883	your program might be left out as well - a binary starting a timer and an
		4884	I/O watcher then might come out at only 5Kb.
		4885
		4886	=item EV_API_STATIC
		4887
		4888	If this symbol is defined (by default it is not), then all identifiers
		4889	will have static linkage. This means that libev will not export any
		4890	identifiers, and you cannot link against libev anymore. This can be useful
		4891	when you embed libev, only want to use libev functions in a single file,
		4892	and do not want its identifiers to be visible.
		4893
		4894	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4895	wants to use libev.
		4896
		4897	This option only works when libev is compiled with a C compiler, as C++
		4898	doesn't support the required declaration syntax.
		4899
		4900	=item EV_AVOID_STDIO
		4901
		4902	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4903	functions (printf, scanf, perror etc.). This will increase the code size
		4904	somewhat, but if your program doesn't otherwise depend on stdio and your
		4905	libc allows it, this avoids linking in the stdio library which is quite
		4906	big.
		4907
		4908	Note that error messages might become less precise when this option is
		4909	enabled.
		4910
		4911	=item EV_NSIG
		4912
		4913	The highest supported signal number, +1 (or, the number of
		4914	signals): Normally, libev tries to deduce the maximum number of signals
		4915	automatically, but sometimes this fails, in which case it can be
		4916	specified. Also, using a lower number than detected (C<32> should be
		4917	good for about any system in existence) can save some memory, as libev
		4918	statically allocates some 12-24 bytes per signal number.
3367		4919
3368	=item EV_PID_HASHSIZE	4920	=item EV_PID_HASHSIZE
3369		4921
3370	C<ev_child> watchers use a small hash table to distribute workload by	4922	C<ev_child> watchers use a small hash table to distribute workload by
3371	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4923	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3372	than enough. If you need to manage thousands of children you might want to	4924	usually more than enough. If you need to manage thousands of children you
3373	increase this value (I<must> be a power of two).	4925	might want to increase this value (I<must> be a power of two).
3374		4926
3375	=item EV_INOTIFY_HASHSIZE	4927	=item EV_INOTIFY_HASHSIZE
3376		4928
3377	C<ev_stat> watchers use a small hash table to distribute workload by	4929	C<ev_stat> watchers use a small hash table to distribute workload by
3378	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4930	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3379	usually more than enough. If you need to manage thousands of C<ev_stat>	4931	disabled), usually more than enough. If you need to manage thousands of
3380	watchers you might want to increase this value (I<must> be a power of	4932	C<ev_stat> watchers you might want to increase this value (I<must> be a
3381	two).	4933	power of two).
3382		4934
3383	=item EV_USE_4HEAP	4935	=item EV_USE_4HEAP
3384		4936
3385	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4937	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3386	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4938	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3387	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4939	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3388	faster performance with many (thousands) of watchers.	4940	faster performance with many (thousands) of watchers.
3389		4941
3390	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4942	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3391	(disabled).	4943	will be C<0>.
3392		4944
3393	=item EV_HEAP_CACHE_AT	4945	=item EV_HEAP_CACHE_AT
3394		4946
3395	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4947	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3396	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4948	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3397	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4949	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3398	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4950	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3399	but avoids random read accesses on heap changes. This improves performance	4951	but avoids random read accesses on heap changes. This improves performance
3400	noticeably with many (hundreds) of watchers.	4952	noticeably with many (hundreds) of watchers.
3401		4953
3402	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4954	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3403	(disabled).	4955	will be C<0>.
3404		4956
3405	=item EV_VERIFY	4957	=item EV_VERIFY
3406		4958
3407	Controls how much internal verification (see C<ev_loop_verify ()>) will	4959	Controls how much internal verification (see C<ev_verify ()>) will
3408	be done: If set to C<0>, no internal verification code will be compiled	4960	be done: If set to C<0>, no internal verification code will be compiled
3409	in. If set to C<1>, then verification code will be compiled in, but not	4961	in. If set to C<1>, then verification code will be compiled in, but not
3410	called. If set to C<2>, then the internal verification code will be	4962	called. If set to C<2>, then the internal verification code will be
3411	called once per loop, which can slow down libev. If set to C<3>, then the	4963	called once per loop, which can slow down libev. If set to C<3>, then the
3412	verification code will be called very frequently, which will slow down	4964	verification code will be called very frequently, which will slow down
3413	libev considerably.	4965	libev considerably.
3414		4966
3415	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4967	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3416	C<0>.	4968	will be C<0>.
3417		4969
3418	=item EV_COMMON	4970	=item EV_COMMON
3419		4971
3420	By default, all watchers have a C<void *data> member. By redefining	4972	By default, all watchers have a C<void *data> member. By redefining
3421	this macro to a something else you can include more and other types of	4973	this macro to something else you can include more and other types of
3422	members. You have to define it each time you include one of the files,	4974	members. You have to define it each time you include one of the files,
3423	though, and it must be identical each time.	4975	though, and it must be identical each time.
3424		4976
3425	For example, the perl EV module uses something like this:	4977	For example, the perl EV module uses something like this:
3426		4978
…		…
3479	file.	5031	file.
3480		5032
3481	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5033	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3482	that everybody includes and which overrides some configure choices:	5034	that everybody includes and which overrides some configure choices:
3483		5035
3484	#define EV_MINIMAL 1	5036	#define EV_FEATURES 8
3485	#define EV_USE_POLL 0	5037	#define EV_USE_SELECT 1
3486	#define EV_MULTIPLICITY 0
3487	#define EV_PERIODIC_ENABLE 0	5038	#define EV_PREPARE_ENABLE 1
		5039	#define EV_IDLE_ENABLE 1
3488	#define EV_STAT_ENABLE 0	5040	#define EV_SIGNAL_ENABLE 1
3489	#define EV_FORK_ENABLE 0	5041	#define EV_CHILD_ENABLE 1
		5042	#define EV_USE_STDEXCEPT 0
3490	#define EV_CONFIG_H <config.h>	5043	#define EV_CONFIG_H <config.h>
3491	#define EV_MINPRI 0
3492	#define EV_MAXPRI 0
3493		5044
3494	#include "ev++.h"	5045	#include "ev++.h"
3495		5046
3496	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5047	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3497		5048
3498	#include "ev_cpp.h"	5049	#include "ev_cpp.h"
3499	#include "ev.c"	5050	#include "ev.c"
3500		5051
3501	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5052	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3502		5053
3503	=head2 THREADS AND COROUTINES	5054	=head2 THREADS AND COROUTINES
3504		5055
3505	=head3 THREADS	5056	=head3 THREADS
3506		5057
…		…
3557	default loop and triggering an C<ev_async> watcher from the default loop	5108	default loop and triggering an C<ev_async> watcher from the default loop
3558	watcher callback into the event loop interested in the signal.	5109	watcher callback into the event loop interested in the signal.
3559		5110
3560	=back	5111	=back
3561		5112
		5113	See also L</THREAD LOCKING EXAMPLE>.
		5114
3562	=head3 COROUTINES	5115	=head3 COROUTINES
3563		5116
3564	Libev is very accommodating to coroutines ("cooperative threads"):	5117	Libev is very accommodating to coroutines ("cooperative threads"):
3565	libev fully supports nesting calls to its functions from different	5118	libev fully supports nesting calls to its functions from different
3566	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5119	coroutines (e.g. you can call C<ev_run> on the same loop from two
3567	different coroutines, and switch freely between both coroutines running the	5120	different coroutines, and switch freely between both coroutines running
3568	loop, as long as you don't confuse yourself). The only exception is that	5121	the loop, as long as you don't confuse yourself). The only exception is
3569	you must not do this from C<ev_periodic> reschedule callbacks.	5122	that you must not do this from C<ev_periodic> reschedule callbacks.
3570		5123
3571	Care has been taken to ensure that libev does not keep local state inside	5124	Care has been taken to ensure that libev does not keep local state inside
3572	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5125	C<ev_run>, and other calls do not usually allow for coroutine switches as
3573	they do not clal any callbacks.	5126	they do not call any callbacks.
3574		5127
3575	=head2 COMPILER WARNINGS	5128	=head2 COMPILER WARNINGS
3576		5129
3577	Depending on your compiler and compiler settings, you might get no or a	5130	Depending on your compiler and compiler settings, you might get no or a
3578	lot of warnings when compiling libev code. Some people are apparently	5131	lot of warnings when compiling libev code. Some people are apparently
…		…
3588	maintainable.	5141	maintainable.
3589		5142
3590	And of course, some compiler warnings are just plain stupid, or simply	5143	And of course, some compiler warnings are just plain stupid, or simply
3591	wrong (because they don't actually warn about the condition their message	5144	wrong (because they don't actually warn about the condition their message
3592	seems to warn about). For example, certain older gcc versions had some	5145	seems to warn about). For example, certain older gcc versions had some
3593	warnings that resulted an extreme number of false positives. These have	5146	warnings that resulted in an extreme number of false positives. These have
3594	been fixed, but some people still insist on making code warn-free with	5147	been fixed, but some people still insist on making code warn-free with
3595	such buggy versions.	5148	such buggy versions.
3596		5149
3597	While libev is written to generate as few warnings as possible,	5150	While libev is written to generate as few warnings as possible,
3598	"warn-free" code is not a goal, and it is recommended not to build libev	5151	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3612	==2274== definitely lost: 0 bytes in 0 blocks.	5165	==2274== definitely lost: 0 bytes in 0 blocks.
3613	==2274== possibly lost: 0 bytes in 0 blocks.	5166	==2274== possibly lost: 0 bytes in 0 blocks.
3614	==2274== still reachable: 256 bytes in 1 blocks.	5167	==2274== still reachable: 256 bytes in 1 blocks.
3615		5168
3616	Then there is no memory leak, just as memory accounted to global variables	5169	Then there is no memory leak, just as memory accounted to global variables
3617	is not a memleak - the memory is still being refernced, and didn't leak.	5170	is not a memleak - the memory is still being referenced, and didn't leak.
3618		5171
3619	Similarly, under some circumstances, valgrind might report kernel bugs	5172	Similarly, under some circumstances, valgrind might report kernel bugs
3620	as if it were a bug in libev (e.g. in realloc or in the poll backend,	5173	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3621	although an acceptable workaround has been found here), or it might be	5174	although an acceptable workaround has been found here), or it might be
3622	confused.	5175	confused.
…		…
3634	I suggest using suppression lists.	5187	I suggest using suppression lists.
3635		5188
3636		5189
3637	=head1 PORTABILITY NOTES	5190	=head1 PORTABILITY NOTES
3638		5191
		5192	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5193
		5194	GNU/Linux is the only common platform that supports 64 bit file/large file
		5195	interfaces but I<disables> them by default.
		5196
		5197	That means that libev compiled in the default environment doesn't support
		5198	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5199
		5200	Unfortunately, many programs try to work around this GNU/Linux issue
		5201	by enabling the large file API, which makes them incompatible with the
		5202	standard libev compiled for their system.
		5203
		5204	Likewise, libev cannot enable the large file API itself as this would
		5205	suddenly make it incompatible to the default compile time environment,
		5206	i.e. all programs not using special compile switches.
		5207
		5208	=head2 OS/X AND DARWIN BUGS
		5209
		5210	The whole thing is a bug if you ask me - basically any system interface
		5211	you touch is broken, whether it is locales, poll, kqueue or even the
		5212	OpenGL drivers.
		5213
		5214	=head3 C<kqueue> is buggy
		5215
		5216	The kqueue syscall is broken in all known versions - most versions support
		5217	only sockets, many support pipes.
		5218
		5219	Libev tries to work around this by not using C<kqueue> by default on this
		5220	rotten platform, but of course you can still ask for it when creating a
		5221	loop - embedding a socket-only kqueue loop into a select-based one is
		5222	probably going to work well.
		5223
		5224	=head3 C<poll> is buggy
		5225
		5226	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5227	implementation by something calling C<kqueue> internally around the 10.5.6
		5228	release, so now C<kqueue> I<and> C<poll> are broken.
		5229
		5230	Libev tries to work around this by not using C<poll> by default on
		5231	this rotten platform, but of course you can still ask for it when creating
		5232	a loop.
		5233
		5234	=head3 C<select> is buggy
		5235
		5236	All that's left is C<select>, and of course Apple found a way to fuck this
		5237	one up as well: On OS/X, C<select> actively limits the number of file
		5238	descriptors you can pass in to 1024 - your program suddenly crashes when
		5239	you use more.
		5240
		5241	There is an undocumented "workaround" for this - defining
		5242	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5243	work on OS/X.
		5244
		5245	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5246
		5247	=head3 C<errno> reentrancy
		5248
		5249	The default compile environment on Solaris is unfortunately so
		5250	thread-unsafe that you can't even use components/libraries compiled
		5251	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5252	defined by default. A valid, if stupid, implementation choice.
		5253
		5254	If you want to use libev in threaded environments you have to make sure
		5255	it's compiled with C<_REENTRANT> defined.
		5256
		5257	=head3 Event port backend
		5258
		5259	The scalable event interface for Solaris is called "event
		5260	ports". Unfortunately, this mechanism is very buggy in all major
		5261	releases. If you run into high CPU usage, your program freezes or you get
		5262	a large number of spurious wakeups, make sure you have all the relevant
		5263	and latest kernel patches applied. No, I don't know which ones, but there
		5264	are multiple ones to apply, and afterwards, event ports actually work
		5265	great.
		5266
		5267	If you can't get it to work, you can try running the program by setting
		5268	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5269	C<select> backends.
		5270
		5271	=head2 AIX POLL BUG
		5272
		5273	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5274	this by trying to avoid the poll backend altogether (i.e. it's not even
		5275	compiled in), which normally isn't a big problem as C<select> works fine
		5276	with large bitsets on AIX, and AIX is dead anyway.
		5277
3639	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5278	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5279
		5280	=head3 General issues
3640		5281
3641	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5282	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3642	requires, and its I/O model is fundamentally incompatible with the POSIX	5283	requires, and its I/O model is fundamentally incompatible with the POSIX
3643	model. Libev still offers limited functionality on this platform in	5284	model. Libev still offers limited functionality on this platform in
3644	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5285	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3645	descriptors. This only applies when using Win32 natively, not when using	5286	descriptors. This only applies when using Win32 natively, not when using
3646	e.g. cygwin.	5287	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5288	as every compiler comes with a slightly differently broken/incompatible
		5289	environment.
3647		5290
3648	Lifting these limitations would basically require the full	5291	Lifting these limitations would basically require the full
3649	re-implementation of the I/O system. If you are into these kinds of	5292	re-implementation of the I/O system. If you are into this kind of thing,
3650	things, then note that glib does exactly that for you in a very portable	5293	then note that glib does exactly that for you in a very portable way (note
3651	way (note also that glib is the slowest event library known to man).	5294	also that glib is the slowest event library known to man).
3652		5295
3653	There is no supported compilation method available on windows except	5296	There is no supported compilation method available on windows except
3654	embedding it into other applications.	5297	embedding it into other applications.
		5298
		5299	Sensible signal handling is officially unsupported by Microsoft - libev
		5300	tries its best, but under most conditions, signals will simply not work.
3655		5301
3656	Not a libev limitation but worth mentioning: windows apparently doesn't	5302	Not a libev limitation but worth mentioning: windows apparently doesn't
3657	accept large writes: instead of resulting in a partial write, windows will	5303	accept large writes: instead of resulting in a partial write, windows will
3658	either accept everything or return C<ENOBUFS> if the buffer is too large,	5304	either accept everything or return C<ENOBUFS> if the buffer is too large,
3659	so make sure you only write small amounts into your sockets (less than a	5305	so make sure you only write small amounts into your sockets (less than a
…		…
3664	the abysmal performance of winsockets, using a large number of sockets	5310	the abysmal performance of winsockets, using a large number of sockets
3665	is not recommended (and not reasonable). If your program needs to use	5311	is not recommended (and not reasonable). If your program needs to use
3666	more than a hundred or so sockets, then likely it needs to use a totally	5312	more than a hundred or so sockets, then likely it needs to use a totally
3667	different implementation for windows, as libev offers the POSIX readiness	5313	different implementation for windows, as libev offers the POSIX readiness
3668	notification model, which cannot be implemented efficiently on windows	5314	notification model, which cannot be implemented efficiently on windows
3669	(Microsoft monopoly games).	5315	(due to Microsoft monopoly games).
3670		5316
3671	A typical way to use libev under windows is to embed it (see the embedding	5317	A typical way to use libev under windows is to embed it (see the embedding
3672	section for details) and use the following F<evwrap.h> header file instead	5318	section for details) and use the following F<evwrap.h> header file instead
3673	of F<ev.h>:	5319	of F<ev.h>:
3674		5320
…		…
3681	you do I<not> compile the F<ev.c> or any other embedded source files!):	5327	you do I<not> compile the F<ev.c> or any other embedded source files!):
3682		5328
3683	#include "evwrap.h"	5329	#include "evwrap.h"
3684	#include "ev.c"	5330	#include "ev.c"
3685		5331
3686	=over 4
3687
3688	=item The winsocket select function	5332	=head3 The winsocket C<select> function
3689		5333
3690	The winsocket C<select> function doesn't follow POSIX in that it	5334	The winsocket C<select> function doesn't follow POSIX in that it
3691	requires socket I<handles> and not socket I<file descriptors> (it is	5335	requires socket I<handles> and not socket I<file descriptors> (it is
3692	also extremely buggy). This makes select very inefficient, and also	5336	also extremely buggy). This makes select very inefficient, and also
3693	requires a mapping from file descriptors to socket handles (the Microsoft	5337	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3702	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5346	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3703		5347
3704	Note that winsockets handling of fd sets is O(n), so you can easily get a	5348	Note that winsockets handling of fd sets is O(n), so you can easily get a
3705	complexity in the O(n²) range when using win32.	5349	complexity in the O(n²) range when using win32.
3706		5350
3707	=item Limited number of file descriptors	5351	=head3 Limited number of file descriptors
3708		5352
3709	Windows has numerous arbitrary (and low) limits on things.	5353	Windows has numerous arbitrary (and low) limits on things.
3710		5354
3711	Early versions of winsocket's select only supported waiting for a maximum	5355	Early versions of winsocket's select only supported waiting for a maximum
3712	of C<64> handles (probably owning to the fact that all windows kernels	5356	of C<64> handles (probably owning to the fact that all windows kernels
3713	can only wait for C<64> things at the same time internally; Microsoft	5357	can only wait for C<64> things at the same time internally; Microsoft
3714	recommends spawning a chain of threads and wait for 63 handles and the	5358	recommends spawning a chain of threads and wait for 63 handles and the
3715	previous thread in each. Great).	5359	previous thread in each. Sounds great!).
3716		5360
3717	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5361	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3718	to some high number (e.g. C<2048>) before compiling the winsocket select	5362	to some high number (e.g. C<2048>) before compiling the winsocket select
3719	call (which might be in libev or elsewhere, for example, perl does its own	5363	call (which might be in libev or elsewhere, for example, perl and many
3720	select emulation on windows).	5364	other interpreters do their own select emulation on windows).
3721		5365
3722	Another limit is the number of file descriptors in the Microsoft runtime	5366	Another limit is the number of file descriptors in the Microsoft runtime
3723	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5367	libraries, which by default is C<64> (there must be a hidden I<64>
3724	or something like this inside Microsoft). You can increase this by calling	5368	fetish or something like this inside Microsoft). You can increase this
3725	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5369	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3726	arbitrary limit), but is broken in many versions of the Microsoft runtime	5370	(another arbitrary limit), but is broken in many versions of the Microsoft
3727	libraries.
3728
3729	This might get you to about C<512> or C<2048> sockets (depending on	5371	runtime libraries. This might get you to about C<512> or C<2048> sockets
3730	windows version and/or the phase of the moon). To get more, you need to	5372	(depending on windows version and/or the phase of the moon). To get more,
3731	wrap all I/O functions and provide your own fd management, but the cost of	5373	you need to wrap all I/O functions and provide your own fd management, but
3732	calling select (O(n²)) will likely make this unworkable.	5374	the cost of calling select (O(n²)) will likely make this unworkable.
3733
3734	=back
3735		5375
3736	=head2 PORTABILITY REQUIREMENTS	5376	=head2 PORTABILITY REQUIREMENTS
3737		5377
3738	In addition to a working ISO-C implementation and of course the	5378	In addition to a working ISO-C implementation and of course the
3739	backend-specific APIs, libev relies on a few additional extensions:	5379	backend-specific APIs, libev relies on a few additional extensions:
…		…
3746	Libev assumes not only that all watcher pointers have the same internal	5386	Libev assumes not only that all watcher pointers have the same internal
3747	structure (guaranteed by POSIX but not by ISO C for example), but it also	5387	structure (guaranteed by POSIX but not by ISO C for example), but it also
3748	assumes that the same (machine) code can be used to call any watcher	5388	assumes that the same (machine) code can be used to call any watcher
3749	callback: The watcher callbacks have different type signatures, but libev	5389	callback: The watcher callbacks have different type signatures, but libev
3750	calls them using an C<ev_watcher *> internally.	5390	calls them using an C<ev_watcher *> internally.
		5391
		5392	=item null pointers and integer zero are represented by 0 bytes
		5393
		5394	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5395	relies on this setting pointers and integers to null.
		5396
		5397	=item pointer accesses must be thread-atomic
		5398
		5399	Accessing a pointer value must be atomic, it must both be readable and
		5400	writable in one piece - this is the case on all current architectures.
3751		5401
3752	=item C<sig_atomic_t volatile> must be thread-atomic as well	5402	=item C<sig_atomic_t volatile> must be thread-atomic as well
3753		5403
3754	The type C<sig_atomic_t volatile> (or whatever is defined as	5404	The type C<sig_atomic_t volatile> (or whatever is defined as
3755	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5405	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3764	thread" or will block signals process-wide, both behaviours would	5414	thread" or will block signals process-wide, both behaviours would
3765	be compatible with libev. Interaction between C<sigprocmask> and	5415	be compatible with libev. Interaction between C<sigprocmask> and
3766	C<pthread_sigmask> could complicate things, however.	5416	C<pthread_sigmask> could complicate things, however.
3767		5417
3768	The most portable way to handle signals is to block signals in all threads	5418	The most portable way to handle signals is to block signals in all threads
3769	except the initial one, and run the default loop in the initial thread as	5419	except the initial one, and run the signal handling loop in the initial
3770	well.	5420	thread as well.
3771		5421
3772	=item C<long> must be large enough for common memory allocation sizes	5422	=item C<long> must be large enough for common memory allocation sizes
3773		5423
3774	To improve portability and simplify its API, libev uses C<long> internally	5424	To improve portability and simplify its API, libev uses C<long> internally
3775	instead of C<size_t> when allocating its data structures. On non-POSIX	5425	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3778	watchers.	5428	watchers.
3779		5429
3780	=item C<double> must hold a time value in seconds with enough accuracy	5430	=item C<double> must hold a time value in seconds with enough accuracy
3781		5431
3782	The type C<double> is used to represent timestamps. It is required to	5432	The type C<double> is used to represent timestamps. It is required to
3783	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5433	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3784	enough for at least into the year 4000. This requirement is fulfilled by	5434	good enough for at least into the year 4000 with millisecond accuracy
		5435	(the design goal for libev). This requirement is overfulfilled by
3785	implementations implementing IEEE 754 (basically all existing ones).	5436	implementations using IEEE 754, which is basically all existing ones.
		5437
		5438	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5439	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5440	is either obsolete or somebody patched it to use C<long double> or
		5441	something like that, just kidding).
3786		5442
3787	=back	5443	=back
3788		5444
3789	If you know of other additional requirements drop me a note.	5445	If you know of other additional requirements drop me a note.
3790		5446
…		…
3852	=item Processing ev_async_send: O(number_of_async_watchers)	5508	=item Processing ev_async_send: O(number_of_async_watchers)
3853		5509
3854	=item Processing signals: O(max_signal_number)	5510	=item Processing signals: O(max_signal_number)
3855		5511
3856	Sending involves a system call I<iff> there were no other C<ev_async_send>	5512	Sending involves a system call I<iff> there were no other C<ev_async_send>
3857	calls in the current loop iteration. Checking for async and signal events	5513	calls in the current loop iteration and the loop is currently
		5514	blocked. Checking for async and signal events involves iterating over all
3858	involves iterating over all running async watchers or all signal numbers.	5515	running async watchers or all signal numbers.
3859		5516
3860	=back	5517	=back
3861		5518
3862		5519
		5520	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5521
		5522	The major version 4 introduced some incompatible changes to the API.
		5523
		5524	At the moment, the C<ev.h> header file provides compatibility definitions
		5525	for all changes, so most programs should still compile. The compatibility
		5526	layer might be removed in later versions of libev, so better update to the
		5527	new API early than late.
		5528
		5529	=over 4
		5530
		5531	=item C<EV_COMPAT3> backwards compatibility mechanism
		5532
		5533	The backward compatibility mechanism can be controlled by
		5534	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5535	section.
		5536
		5537	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5538
		5539	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5540
		5541	ev_loop_destroy (EV_DEFAULT_UC);
		5542	ev_loop_fork (EV_DEFAULT);
		5543
		5544	=item function/symbol renames
		5545
		5546	A number of functions and symbols have been renamed:
		5547
		5548	ev_loop => ev_run
		5549	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5550	EVLOOP_ONESHOT => EVRUN_ONCE
		5551
		5552	ev_unloop => ev_break
		5553	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5554	EVUNLOOP_ONE => EVBREAK_ONE
		5555	EVUNLOOP_ALL => EVBREAK_ALL
		5556
		5557	EV_TIMEOUT => EV_TIMER
		5558
		5559	ev_loop_count => ev_iteration
		5560	ev_loop_depth => ev_depth
		5561	ev_loop_verify => ev_verify
		5562
		5563	Most functions working on C<struct ev_loop> objects don't have an
		5564	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5565	associated constants have been renamed to not collide with the C<struct
		5566	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5567	as all other watcher types. Note that C<ev_loop_fork> is still called
		5568	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5569	typedef.
		5570
		5571	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5572
		5573	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5574	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5575	and work, but the library code will of course be larger.
		5576
		5577	=back
		5578
		5579
		5580	=head1 GLOSSARY
		5581
		5582	=over 4
		5583
		5584	=item active
		5585
		5586	A watcher is active as long as it has been started and not yet stopped.
		5587	See L</WATCHER STATES> for details.
		5588
		5589	=item application
		5590
		5591	In this document, an application is whatever is using libev.
		5592
		5593	=item backend
		5594
		5595	The part of the code dealing with the operating system interfaces.
		5596
		5597	=item callback
		5598
		5599	The address of a function that is called when some event has been
		5600	detected. Callbacks are being passed the event loop, the watcher that
		5601	received the event, and the actual event bitset.
		5602
		5603	=item callback/watcher invocation
		5604
		5605	The act of calling the callback associated with a watcher.
		5606
		5607	=item event
		5608
		5609	A change of state of some external event, such as data now being available
		5610	for reading on a file descriptor, time having passed or simply not having
		5611	any other events happening anymore.
		5612
		5613	In libev, events are represented as single bits (such as C<EV_READ> or
		5614	C<EV_TIMER>).
		5615
		5616	=item event library
		5617
		5618	A software package implementing an event model and loop.
		5619
		5620	=item event loop
		5621
		5622	An entity that handles and processes external events and converts them
		5623	into callback invocations.
		5624
		5625	=item event model
		5626
		5627	The model used to describe how an event loop handles and processes
		5628	watchers and events.
		5629
		5630	=item pending
		5631
		5632	A watcher is pending as soon as the corresponding event has been
		5633	detected. See L</WATCHER STATES> for details.
		5634
		5635	=item real time
		5636
		5637	The physical time that is observed. It is apparently strictly monotonic :)
		5638
		5639	=item wall-clock time
		5640
		5641	The time and date as shown on clocks. Unlike real time, it can actually
		5642	be wrong and jump forwards and backwards, e.g. when you adjust your
		5643	clock.
		5644
		5645	=item watcher
		5646
		5647	A data structure that describes interest in certain events. Watchers need
		5648	to be started (attached to an event loop) before they can receive events.
		5649
		5650	=back
		5651
3863	=head1 AUTHOR	5652	=head1 AUTHOR
3864		5653
3865	Marc Lehmann <libev@schmorp.de>.	5654	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5655	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3866		5656

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