ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.231 by root, Wed Apr 15 19:35:53 2009 UTC vs.
Revision 1.451 by root, Mon Jun 24 00:19:26 2019 UTC

		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
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	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);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 DESCRIPTION	69	=head1 ABOUT THIS DOCUMENT
		70
		71	This document documents the libev software package.
68		72
69	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
70	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
71	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
72		94
73	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
74	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
75	these event sources and provide your program with events.	97	these event sources and provide your program with events.
76		98
…		…
83	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
84	watcher.	106	watcher.
85		107
86	=head2 FEATURES	108	=head2 FEATURES
87		109
88	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>
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port
90	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>
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
92	with customised rescheduling (C<ev_periodic>), synchronous signals	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
93	(C<ev_signal>), process status change events (C<ev_child>), and event	115	timers (C<ev_timer>), absolute timers with customised rescheduling
94	watchers dealing with the event loop mechanism itself (C<ev_idle>,	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
95	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
96	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
97	(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>).
98		121
99	It also is quite fast (see this	122	It also is quite fast (see this
100	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
101	for example).	124	for example).
102		125
…		…
105	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)
106	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
107	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
108	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
109	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
110	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
111	this argument.	134	this argument.
112		135
113	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
114		137
115	Libev represents time as a single floating point number, representing the	138	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
117	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
118	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
119	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
120	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
121	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
122	throughout libev.	146	time differences (e.g. delays) throughout libev.
123		147
124	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
125		149
126	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
127	and internal errors (bugs).	151	and internal errors (bugs).
…		…
151		175
152	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
153		177
154	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
155	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
156	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>.
157		182
158	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
159		184
160	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
161	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
162	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 >>).
163		194
164	=item int ev_version_major ()	195	=item int ev_version_major ()
165		196
166	=item int ev_version_minor ()	197	=item int ev_version_minor ()
167		198
…		…
178	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
179	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
180	not a problem.	211	not a problem.
181		212
182	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
183	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
184		216
185	assert (("libev version mismatch",	217	assert (("libev version mismatch",
186	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
187	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
188		220
…		…
199	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
200	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
201		233
202	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
203		235
204	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
205	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
206	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
207	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
208	(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
209	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
210		243
211	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
212		245
213	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
214	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
215	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
216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
217	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
218		251
219	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
220		253
221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
222		255
223	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
224	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
225	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
226	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
…		…
232		265
233	You could override this function in high-availability programs to, say,	266	You could override this function in high-availability programs to, say,
234	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,
235	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.
236		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
237	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
238	retries (example requires a standards-compliant C<realloc>).	285	retries.
239		286
240	static void *	287	static void *
241	persistent_realloc (void *ptr, size_t size)	288	persistent_realloc (void *ptr, size_t size)
242	{	289	{
		290	if (!size)
		291	{
		292	free (ptr);
		293	return 0;
		294	}
		295
243	for (;;)	296	for (;;)
244	{	297	{
245	void *newptr = realloc (ptr, size);	298	void *newptr = realloc (ptr, size);
246		299
247	if (newptr)	300	if (newptr)
…		…
252	}	305	}
253		306
254	...	307	...
255	ev_set_allocator (persistent_realloc);	308	ev_set_allocator (persistent_realloc);
256		309
257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	310	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
258		311
259	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
260	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
261	indicating the system call or subsystem causing the problem. If this	314	indicating the system call or subsystem causing the problem. If this
262	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
…		…
274	}	327	}
275		328
276	...	329	...
277	ev_set_syserr_cb (fatal_error);	330	ev_set_syserr_cb (fatal_error);
278		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
279	=back	345	=back
280		346
281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	347	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
282		348
283	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
284	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
285	I<function>).	351	libev 3 had an C<ev_loop> function colliding with the struct name).
286		352
287	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
288	supports signals and child events, and dynamically created loops which do	354	supports child process events, and dynamically created event loops which
289	not.	355	do not.
290		356
291	=over 4	357	=over 4
292		358
293	=item struct ev_loop *ev_default_loop (unsigned int flags)	359	=item struct ev_loop *ev_default_loop (unsigned int flags)
294		360
295	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
296	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
297	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
298	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".
299		371
300	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
301	function.	373	function (or via the C<EV_DEFAULT> macro).
302		374
303	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
304	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
305	as loops cannot be shared easily between threads anyway).	377	that this case is unlikely, as loops cannot be shared easily between
		378	threads anyway).
306		379
307	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,
308	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
309	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
310	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
311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	384	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
312	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.
313		404
314	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
315	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>).
316		407
317	The following flags are supported:	408	The following flags are supported:
…		…
327		418
328	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
329	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
330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	421	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
331	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
332	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
333	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).
334		427
335	=item C<EVFLAG_FORKCHECK>	428	=item C<EVFLAG_FORKCHECK>
336		429
337	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
338	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.
339	enabling this flag.
340		432
341	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,
342	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
343	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
344	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
345	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
346	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).
347		440
348	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
349	forget about forgetting to tell libev about forking) when you use this	442	forget about forgetting to tell libev about forking, although you still
350	flag.	443	have to ignore C<SIGPIPE>) when you use this flag.
351		444
352	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>
353	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.
354		482
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	483	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		484
357	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
358	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,
…		…
383	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
384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	512	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
385		513
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	514	=item C<EVBACKEND_EPOLL> (value 4, Linux)
387		515
		516	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		517	kernels).
		518
388	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
389	but it scales phenomenally better. While poll and select usually scale	520	it scales phenomenally better. While poll and select usually scale like
390	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
391	epoll scales either O(1) or O(active_fds).	522	fd), epoll scales either O(1) or O(active_fds).
392		523
393	The epoll mechanism deserves honorable mention as the most misdesigned	524	The epoll mechanism deserves honorable mention as the most misdesigned
394	of the more advanced event mechanisms: mere annoyances include silently	525	of the more advanced event mechanisms: mere annoyances include silently
395	dropping file descriptors, requiring a system call per change per file	526	dropping file descriptors, requiring a system call per change per file
396	descriptor (and unnecessary guessing of parameters), problems with dup and	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
397	so on. The biggest issue is fork races, however - if a program forks then	530	0.1ms) and so on. The biggest issue is fork races, however - if a program
398	I<both> parent and child process have to recreate the epoll set, which can	531	forks then I<both> parent and child process have to recreate the epoll
399	take considerable time (one syscall per file descriptor) and is of course	532	set, which can take considerable time (one syscall per file descriptor)
400	hard to detect.	533	and is of course hard to detect.
401		534
402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	535	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
403	of course I<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
404	I<different> file descriptors (even already closed ones, so one cannot	537	totally I<different> file descriptors (even already closed ones, so
405	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
406	on SMP systems). Libev tries to counter these spurious notifications by	539	(especially on SMP systems). Libev tries to counter these spurious
407	employing an additional generation counter and comparing that against the	540	notifications by employing an additional generation counter and comparing
408	events to filter out spurious ones, recreating the set when required.	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...
409		551
410	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
411	will result in some caching, there is still a system call per such	553	will result in some caching, there is still a system call per such
412	incident (because the same I<file descriptor> could point to a different	554	incident (because the same I<file descriptor> could point to a different
413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	555	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or	567	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
426	faster than epoll for maybe up to a hundred file descriptors, depending on	568	faster than epoll for maybe up to a hundred file descriptors, depending on
427	the usage. So sad.	569	the usage. So sad.
428		570
429	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
430	all kernel versions tested so far.	572	a lot of kernel revisions, but probably(!) works in current versions.
		573
		574	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		575	C<EVBACKEND_POLL>.
		576
		577	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		578
		579	Use the linux-specific linux aio (I<not> C<< aio(7) >> but C<<
		580	io_submit(2) >>) event interface available in post-4.18 kernels.
		581
		582	If this backend works for you (as of this writing, it was very
		583	experimental), it is the best event interface available on linux and might
		584	be well worth enabling it - if it isn't available in your kernel this will
		585	be detected and this backend will be skipped.
		586
		587	This backend can batch oneshot requests and supports a user-space ring
		588	buffer to receive events. It also doesn't suffer from most of the design
		589	problems of epoll (such as not being able to remove event sources from the
		590	epoll set), and generally sounds too good to be true. Because, this being
		591	the linux kernel, of course it suffers from a whole new set of limitations.
		592
		593	For one, it is not easily embeddable (but probably could be done using
		594	an event fd at some extra overhead). It also is subject to a system wide
		595	limit that can be configured in F</proc/sys/fs/aio-max-nr> - each loop
		596	currently requires C<61> of this number. If no aio requests are left, this
		597	backend will be skipped during initialisation.
		598
		599	Most problematic in practise, however, is that not all file descriptors
		600	work with it. For example, in linux 5.1, tcp sockets, pipes, event fds,
		601	files, F</dev/null> and a few others are supported, but ttys do not work
		602	properly (a known bug that the kernel developers don't care about, see
		603	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		604	(yet?) a generic event polling interface.
		605
		606	Overall, it seems the linux developers just don't want it to have a
		607	generic event handling mechanism other than C<select> or C<poll>.
		608
		609	To work around the fd type problem, the current version of libev uses
		610	epoll as a fallback for file deescriptor types that do not work. Epoll
		611	is used in, kind of, slow mode that hopefully avoids most of its design
		612	problems and requires 1-3 extra syscalls per active fd every iteration.
431		613
432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	614	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
433	C<EVBACKEND_POLL>.	615	C<EVBACKEND_POLL>.
434		616
435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	617	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
…		…
450		632
451	It scales in the same way as the epoll backend, but the interface to the	633	It scales in the same way as the epoll backend, but the interface to the
452	kernel is more efficient (which says nothing about its actual speed, of	634	kernel is more efficient (which says nothing about its actual speed, of
453	course). While stopping, setting and starting an I/O watcher does never	635	course). While stopping, setting and starting an I/O watcher does never
454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	636	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
455	two event changes per incident. Support for C<fork ()> is very bad (but	637	two event changes per incident. Support for C<fork ()> is very bad (you
456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	638	might have to leak fd's on fork, but it's more sane than epoll) and it
457	cases	639	drops fds silently in similarly hard-to-detect cases.
458		640
459	This backend usually performs well under most conditions.	641	This backend usually performs well under most conditions.
460		642
461	While nominally embeddable in other event loops, this doesn't work	643	While nominally embeddable in other event loops, this doesn't work
462	everywhere, so you might need to test for this. And since it is broken	644	everywhere, so you might need to test for this. And since it is broken
…		…
479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	661	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
480		662
481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	663	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
482	it's really slow, but it still scales very well (O(active_fds)).	664	it's really slow, but it still scales very well (O(active_fds)).
483		665
484	Please note that Solaris event ports can deliver a lot of spurious
485	notifications, so you need to use non-blocking I/O or other means to avoid
486	blocking when no data (or space) is available.
487
488	While this backend scales well, it requires one system call per active	666	While this backend scales well, it requires one system call per active
489	file descriptor per loop iteration. For small and medium numbers of file	667	file descriptor per loop iteration. For small and medium numbers of file
490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	668	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
491	might perform better.	669	might perform better.
492		670
493	On the positive side, with the exception of the spurious readiness	671	On the positive side, this backend actually performed fully to
494	notifications, this backend actually performed fully to specification
495	in all tests and is fully embeddable, which is a rare feat among the	672	specification in all tests and is fully embeddable, which is a rare feat
496	OS-specific backends (I vastly prefer correctness over speed hacks).	673	among the OS-specific backends (I vastly prefer correctness over speed
		674	hacks).
		675
		676	On the negative side, the interface is I<bizarre> - so bizarre that
		677	even sun itself gets it wrong in their code examples: The event polling
		678	function sometimes returns events to the caller even though an error
		679	occurred, but with no indication whether it has done so or not (yes, it's
		680	even documented that way) - deadly for edge-triggered interfaces where you
		681	absolutely have to know whether an event occurred or not because you have
		682	to re-arm the watcher.
		683
		684	Fortunately libev seems to be able to work around these idiocies.
497		685
498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	686	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
499	C<EVBACKEND_POLL>.	687	C<EVBACKEND_POLL>.
500		688
501	=item C<EVBACKEND_ALL>	689	=item C<EVBACKEND_ALL>
502		690
503	Try all backends (even potentially broken ones that wouldn't be tried	691	Try all backends (even potentially broken ones that wouldn't be tried
504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	692	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	693	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
506		694
507	It is definitely not recommended to use this flag.	695	It is definitely not recommended to use this flag, use whatever
		696	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		697	at all.
		698
		699	=item C<EVBACKEND_MASK>
		700
		701	Not a backend at all, but a mask to select all backend bits from a
		702	C<flags> value, in case you want to mask out any backends from a flags
		703	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
508		704
509	=back	705	=back
510		706
511	If one or more of these are or'ed into the flags value, then only these	707	If one or more of the backend flags are or'ed into the flags value,
512	backends will be tried (in the reverse order as listed here). If none are	708	then only these backends will be tried (in the reverse order as listed
513	specified, all backends in C<ev_recommended_backends ()> will be tried.	709	here). If none are specified, all backends in C<ev_recommended_backends
514		710	()> will be tried.
515	Example: This is the most typical usage.
516
517	if (!ev_default_loop (0))
518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
519
520	Example: Restrict libev to the select and poll backends, and do not allow
521	environment settings to be taken into account:
522
523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
524
525	Example: Use whatever libev has to offer, but make sure that kqueue is
526	used if available (warning, breaks stuff, best use only with your own
527	private event loop and only if you know the OS supports your types of
528	fds):
529
530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
531
532	=item struct ev_loop *ev_loop_new (unsigned int flags)
533
534	Similar to C<ev_default_loop>, but always creates a new event loop that is
535	always distinct from the default loop. Unlike the default loop, it cannot
536	handle signal and child watchers, and attempts to do so will be greeted by
537	undefined behaviour (or a failed assertion if assertions are enabled).
538
539	Note that this function I<is> thread-safe, and the recommended way to use
540	libev with threads is indeed to create one loop per thread, and using the
541	default loop in the "main" or "initial" thread.
542		711
543	Example: Try to create a event loop that uses epoll and nothing else.	712	Example: Try to create a event loop that uses epoll and nothing else.
544		713
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	714	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
546	if (!epoller)	715	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	716	fatal ("no epoll found here, maybe it hides under your chair");
548		717
		718	Example: Use whatever libev has to offer, but make sure that kqueue is
		719	used if available.
		720
		721	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		722
		723	Example: Similarly, on linux, you mgiht want to take advantage of the
		724	linux aio backend if possible, but fall back to something else if that
		725	isn't available.
		726
		727	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		728
549	=item ev_default_destroy ()	729	=item ev_loop_destroy (loop)
550		730
551	Destroys the default loop again (frees all memory and kernel state	731	Destroys an event loop object (frees all memory and kernel state
552	etc.). None of the active event watchers will be stopped in the normal	732	etc.). None of the active event watchers will be stopped in the normal
553	sense, so e.g. C<ev_is_active> might still return true. It is your	733	sense, so e.g. C<ev_is_active> might still return true. It is your
554	responsibility to either stop all watchers cleanly yourself I<before>	734	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	735	calling this function, or cope with the fact afterwards (which is usually
556	the easiest thing, you can just ignore the watchers and/or C<free ()> them	736	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		738
559	Note that certain global state, such as signal state (and installed signal	739	Note that certain global state, such as signal state (and installed signal
560	handlers), will not be freed by this function, and related watchers (such	740	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	741	as signal and child watchers) would need to be stopped manually.
562		742
563	In general it is not advisable to call this function except in the	743	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	744	C<ev_loop_new>, but it can also be used on the default loop returned by
		745	C<ev_default_loop>, in which case it is not thread-safe.
		746
		747	Note that it is not advisable to call this function on the default loop
		748	except in the rare occasion where you really need to free its resources.
565	pipe fds. If you need dynamically allocated loops it is better to use	749	If you need dynamically allocated loops it is better to use C<ev_loop_new>
566	C<ev_loop_new> and C<ev_loop_destroy>).	750	and C<ev_loop_destroy>.
567		751
568	=item ev_loop_destroy (loop)	752	=item ev_loop_fork (loop)
569		753
570	Like C<ev_default_destroy>, but destroys an event loop created by an
571	earlier call to C<ev_loop_new>.
572
573	=item ev_default_fork ()
574
575	This function sets a flag that causes subsequent C<ev_loop> iterations	754	This function sets a flag that causes subsequent C<ev_run> iterations
576	to reinitialise the kernel state for backends that have one. Despite the	755	to reinitialise the kernel state for backends that have one. Despite
577	name, you can call it anytime, but it makes most sense after forking, in	756	the name, you can call it anytime you are allowed to start or stop
578	the child process (or both child and parent, but that again makes little	757	watchers (except inside an C<ev_prepare> callback), but it makes most
579	sense). You I<must> call it in the child before using any of the libev	758	sense after forking, in the child process. You I<must> call it (or use
580	functions, and it will only take effect at the next C<ev_loop> iteration.	759	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		760
		761	In addition, if you want to reuse a loop (via this function or
		762	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		763
		764	Again, you I<have> to call it on I<any> loop that you want to re-use after
		765	a fork, I<even if you do not plan to use the loop in the parent>. This is
		766	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		767	during fork.
581		768
582	On the other hand, you only need to call this function in the child	769	On the other hand, you only need to call this function in the child
583	process if and only if you want to use the event library in the child. If	770	process if and only if you want to use the event loop in the child. If
584	you just fork+exec, you don't have to call it at all.	771	you just fork+exec or create a new loop in the child, you don't have to
		772	call it at all (in fact, C<epoll> is so badly broken that it makes a
		773	difference, but libev will usually detect this case on its own and do a
		774	costly reset of the backend).
585		775
586	The function itself is quite fast and it's usually not a problem to call	776	The function itself is quite fast and it's usually not a problem to call
587	it just in case after a fork. To make this easy, the function will fit in	777	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		778
		779	Example: Automate calling C<ev_loop_fork> on the default loop when
		780	using pthreads.
		781
		782	static void
		783	post_fork_child (void)
		784	{
		785	ev_loop_fork (EV_DEFAULT);
		786	}
		787
		788	...
590	pthread_atfork (0, 0, ev_default_fork);	789	pthread_atfork (0, 0, post_fork_child);
591
592	=item ev_loop_fork (loop)
593
594	Like C<ev_default_fork>, but acts on an event loop created by
595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
596	after fork that you want to re-use in the child, and how you do this is
597	entirely your own problem.
598		790
599	=item int ev_is_default_loop (loop)	791	=item int ev_is_default_loop (loop)
600		792
601	Returns true when the given loop is, in fact, the default loop, and false	793	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	794	otherwise.
603		795
604	=item unsigned int ev_loop_count (loop)	796	=item unsigned int ev_iteration (loop)
605		797
606	Returns the count of loop iterations for the loop, which is identical to	798	Returns the current iteration count for the event loop, which is identical
607	the number of times libev did poll for new events. It starts at C<0> and	799	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	800	and happily wraps around with enough iterations.
609		801
610	This value can sometimes be useful as a generation counter of sorts (it	802	This value can sometimes be useful as a generation counter of sorts (it
611	"ticks" the number of loop iterations), as it roughly corresponds with	803	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	804	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		805	prepare and check phases.
		806
		807	=item unsigned int ev_depth (loop)
		808
		809	Returns the number of times C<ev_run> was entered minus the number of
		810	times C<ev_run> was exited normally, in other words, the recursion depth.
		811
		812	Outside C<ev_run>, this number is zero. In a callback, this number is
		813	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		814	in which case it is higher.
		815
		816	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		817	throwing an exception etc.), doesn't count as "exit" - consider this
		818	as a hint to avoid such ungentleman-like behaviour unless it's really
		819	convenient, in which case it is fully supported.
613		820
614	=item unsigned int ev_backend (loop)	821	=item unsigned int ev_backend (loop)
615		822
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	823	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	824	use.
…		…
626		833
627	=item ev_now_update (loop)	834	=item ev_now_update (loop)
628		835
629	Establishes the current time by querying the kernel, updating the time	836	Establishes the current time by querying the kernel, updating the time
630	returned by C<ev_now ()> in the progress. This is a costly operation and	837	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	838	is usually done automatically within C<ev_run ()>.
632		839
633	This function is rarely useful, but when some event callback runs for a	840	This function is rarely useful, but when some event callback runs for a
634	very long time without entering the event loop, updating libev's idea of	841	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	842	the current time is a good idea.
636		843
637	See also "The special problem of time updates" in the C<ev_timer> section.	844	See also L</The special problem of time updates> in the C<ev_timer> section.
638		845
639	=item ev_suspend (loop)	846	=item ev_suspend (loop)
640		847
641	=item ev_resume (loop)	848	=item ev_resume (loop)
642		849
643	These two functions suspend and resume a loop, for use when the loop is	850	These two functions suspend and resume an event loop, for use when the
644	not used for a while and timeouts should not be processed.	851	loop is not used for a while and timeouts should not be processed.
645		852
646	A typical use case would be an interactive program such as a game: When	853	A typical use case would be an interactive program such as a game: When
647	the user presses C<^Z> to suspend the game and resumes it an hour later it	854	the user presses C<^Z> to suspend the game and resumes it an hour later it
648	would be best to handle timeouts as if no time had actually passed while	855	would be best to handle timeouts as if no time had actually passed while
649	the program was suspended. This can be achieved by calling C<ev_suspend>	856	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
651	C<ev_resume> directly afterwards to resume timer processing.	858	C<ev_resume> directly afterwards to resume timer processing.
652		859
653	Effectively, all C<ev_timer> watchers will be delayed by the time spend	860	Effectively, all C<ev_timer> watchers will be delayed by the time spend
654	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	861	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
655	will be rescheduled (that is, they will lose any events that would have	862	will be rescheduled (that is, they will lose any events that would have
656	occured while suspended).	863	occurred while suspended).
657		864
658	After calling C<ev_suspend> you B<must not> call I<any> function on the	865	After calling C<ev_suspend> you B<must not> call I<any> function on the
659	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	866	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
660	without a previous call to C<ev_suspend>.	867	without a previous call to C<ev_suspend>.
661		868
662	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	869	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
663	event loop time (see C<ev_now_update>).	870	event loop time (see C<ev_now_update>).
664		871
665	=item ev_loop (loop, int flags)	872	=item bool ev_run (loop, int flags)
666		873
667	Finally, this is it, the event handler. This function usually is called	874	Finally, this is it, the event handler. This function usually is called
668	after you initialised all your watchers and you want to start handling	875	after you have initialised all your watchers and you want to start
669	events.	876	handling events. It will ask the operating system for any new events, call
		877	the watcher callbacks, and then repeat the whole process indefinitely: This
		878	is why event loops are called I<loops>.
670		879
671	If the flags argument is specified as C<0>, it will not return until	880	If the flags argument is specified as C<0>, it will keep handling events
672	either no event watchers are active anymore or C<ev_unloop> was called.	881	until either no event watchers are active anymore or C<ev_break> was
		882	called.
673		883
		884	The return value is false if there are no more active watchers (which
		885	usually means "all jobs done" or "deadlock"), and true in all other cases
		886	(which usually means " you should call C<ev_run> again").
		887
674	Please note that an explicit C<ev_unloop> is usually better than	888	Please note that an explicit C<ev_break> is usually better than
675	relying on all watchers to be stopped when deciding when a program has	889	relying on all watchers to be stopped when deciding when a program has
676	finished (especially in interactive programs), but having a program	890	finished (especially in interactive programs), but having a program
677	that automatically loops as long as it has to and no longer by virtue	891	that automatically loops as long as it has to and no longer by virtue
678	of relying on its watchers stopping correctly, that is truly a thing of	892	of relying on its watchers stopping correctly, that is truly a thing of
679	beauty.	893	beauty.
680		894
		895	This function is I<mostly> exception-safe - you can break out of a
		896	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		897	exception and so on. This does not decrement the C<ev_depth> value, nor
		898	will it clear any outstanding C<EVBREAK_ONE> breaks.
		899
681	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	900	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
682	those events and any already outstanding ones, but will not block your	901	those events and any already outstanding ones, but will not wait and
683	process in case there are no events and will return after one iteration of	902	block your process in case there are no events and will return after one
684	the loop.	903	iteration of the loop. This is sometimes useful to poll and handle new
		904	events while doing lengthy calculations, to keep the program responsive.
685		905
686	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	906	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
687	necessary) and will handle those and any already outstanding ones. It	907	necessary) and will handle those and any already outstanding ones. It
688	will block your process until at least one new event arrives (which could	908	will block your process until at least one new event arrives (which could
689	be an event internal to libev itself, so there is no guarantee that a	909	be an event internal to libev itself, so there is no guarantee that a
690	user-registered callback will be called), and will return after one	910	user-registered callback will be called), and will return after one
691	iteration of the loop.	911	iteration of the loop.
692		912
693	This is useful if you are waiting for some external event in conjunction	913	This is useful if you are waiting for some external event in conjunction
694	with something not expressible using other libev watchers (i.e. "roll your	914	with something not expressible using other libev watchers (i.e. "roll your
695	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	915	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
696	usually a better approach for this kind of thing.	916	usually a better approach for this kind of thing.
697		917
698	Here are the gory details of what C<ev_loop> does:	918	Here are the gory details of what C<ev_run> does (this is for your
		919	understanding, not a guarantee that things will work exactly like this in
		920	future versions):
699		921
		922	- Increment loop depth.
		923	- Reset the ev_break status.
700	- Before the first iteration, call any pending watchers.	924	- Before the first iteration, call any pending watchers.
		925	LOOP:
701	* If EVFLAG_FORKCHECK was used, check for a fork.	926	- If EVFLAG_FORKCHECK was used, check for a fork.
702	- If a fork was detected (by any means), queue and call all fork watchers.	927	- If a fork was detected (by any means), queue and call all fork watchers.
703	- Queue and call all prepare watchers.	928	- Queue and call all prepare watchers.
		929	- If ev_break was called, goto FINISH.
704	- If we have been forked, detach and recreate the kernel state	930	- If we have been forked, detach and recreate the kernel state
705	as to not disturb the other process.	931	as to not disturb the other process.
706	- Update the kernel state with all outstanding changes.	932	- Update the kernel state with all outstanding changes.
707	- Update the "event loop time" (ev_now ()).	933	- Update the "event loop time" (ev_now ()).
708	- Calculate for how long to sleep or block, if at all	934	- Calculate for how long to sleep or block, if at all
709	(active idle watchers, EVLOOP_NONBLOCK or not having	935	(active idle watchers, EVRUN_NOWAIT or not having
710	any active watchers at all will result in not sleeping).	936	any active watchers at all will result in not sleeping).
711	- Sleep if the I/O and timer collect interval say so.	937	- Sleep if the I/O and timer collect interval say so.
		938	- Increment loop iteration counter.
712	- Block the process, waiting for any events.	939	- Block the process, waiting for any events.
713	- Queue all outstanding I/O (fd) events.	940	- Queue all outstanding I/O (fd) events.
714	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	941	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
715	- Queue all expired timers.	942	- Queue all expired timers.
716	- Queue all expired periodics.	943	- Queue all expired periodics.
717	- Unless any events are pending now, queue all idle watchers.	944	- Queue all idle watchers with priority higher than that of pending events.
718	- Queue all check watchers.	945	- Queue all check watchers.
719	- Call all queued watchers in reverse order (i.e. check watchers first).	946	- Call all queued watchers in reverse order (i.e. check watchers first).
720	Signals and child watchers are implemented as I/O watchers, and will	947	Signals and child watchers are implemented as I/O watchers, and will
721	be handled here by queueing them when their watcher gets executed.	948	be handled here by queueing them when their watcher gets executed.
722	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	949	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
723	were used, or there are no active watchers, return, otherwise	950	were used, or there are no active watchers, goto FINISH, otherwise
724	continue with step *.	951	continue with step LOOP.
		952	FINISH:
		953	- Reset the ev_break status iff it was EVBREAK_ONE.
		954	- Decrement the loop depth.
		955	- Return.
725		956
726	Example: Queue some jobs and then loop until no events are outstanding	957	Example: Queue some jobs and then loop until no events are outstanding
727	anymore.	958	anymore.
728		959
729	... queue jobs here, make sure they register event watchers as long	960	... queue jobs here, make sure they register event watchers as long
730	... as they still have work to do (even an idle watcher will do..)	961	... as they still have work to do (even an idle watcher will do..)
731	ev_loop (my_loop, 0);	962	ev_run (my_loop, 0);
732	... jobs done or somebody called unloop. yeah!	963	... jobs done or somebody called break. yeah!
733		964
734	=item ev_unloop (loop, how)	965	=item ev_break (loop, how)
735		966
736	Can be used to make a call to C<ev_loop> return early (but only after it	967	Can be used to make a call to C<ev_run> return early (but only after it
737	has processed all outstanding events). The C<how> argument must be either	968	has processed all outstanding events). The C<how> argument must be either
738	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	969	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
739	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	970	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
740		971
741	This "unloop state" will be cleared when entering C<ev_loop> again.	972	This "break state" will be cleared on the next call to C<ev_run>.
742		973
743	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	974	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		975	which case it will have no effect.
744		976
745	=item ev_ref (loop)	977	=item ev_ref (loop)
746		978
747	=item ev_unref (loop)	979	=item ev_unref (loop)
748		980
749	Ref/unref can be used to add or remove a reference count on the event	981	Ref/unref can be used to add or remove a reference count on the event
750	loop: Every watcher keeps one reference, and as long as the reference	982	loop: Every watcher keeps one reference, and as long as the reference
751	count is nonzero, C<ev_loop> will not return on its own.	983	count is nonzero, C<ev_run> will not return on its own.
752		984
753	If you have a watcher you never unregister that should not keep C<ev_loop>	985	This is useful when you have a watcher that you never intend to
754	from returning, call ev_unref() after starting, and ev_ref() before	986	unregister, but that nevertheless should not keep C<ev_run> from
		987	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
755	stopping it.	988	before stopping it.
756		989
757	As an example, libev itself uses this for its internal signal pipe: It	990	As an example, libev itself uses this for its internal signal pipe: It
758	is not visible to the libev user and should not keep C<ev_loop> from	991	is not visible to the libev user and should not keep C<ev_run> from
759	exiting if no event watchers registered by it are active. It is also an	992	exiting if no event watchers registered by it are active. It is also an
760	excellent way to do this for generic recurring timers or from within	993	excellent way to do this for generic recurring timers or from within
761	third-party libraries. Just remember to I<unref after start> and I<ref	994	third-party libraries. Just remember to I<unref after start> and I<ref
762	before stop> (but only if the watcher wasn't active before, or was active	995	before stop> (but only if the watcher wasn't active before, or was active
763	before, respectively. Note also that libev might stop watchers itself	996	before, respectively. Note also that libev might stop watchers itself
764	(e.g. non-repeating timers) in which case you have to C<ev_ref>	997	(e.g. non-repeating timers) in which case you have to C<ev_ref>
765	in the callback).	998	in the callback).
766		999
767	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	1000	Example: Create a signal watcher, but keep it from keeping C<ev_run>
768	running when nothing else is active.	1001	running when nothing else is active.
769		1002
770	ev_signal exitsig;	1003	ev_signal exitsig;
771	ev_signal_init (&exitsig, sig_cb, SIGINT);	1004	ev_signal_init (&exitsig, sig_cb, SIGINT);
772	ev_signal_start (loop, &exitsig);	1005	ev_signal_start (loop, &exitsig);
773	evf_unref (loop);	1006	ev_unref (loop);
774		1007
775	Example: For some weird reason, unregister the above signal handler again.	1008	Example: For some weird reason, unregister the above signal handler again.
776		1009
777	ev_ref (loop);	1010	ev_ref (loop);
778	ev_signal_stop (loop, &exitsig);	1011	ev_signal_stop (loop, &exitsig);
…		…
798	overhead for the actual polling but can deliver many events at once.	1031	overhead for the actual polling but can deliver many events at once.
799		1032
800	By setting a higher I<io collect interval> you allow libev to spend more	1033	By setting a higher I<io collect interval> you allow libev to spend more
801	time collecting I/O events, so you can handle more events per iteration,	1034	time collecting I/O events, so you can handle more events per iteration,
802	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1035	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
803	C<ev_timer>) will be not affected. Setting this to a non-null value will	1036	C<ev_timer>) will not be affected. Setting this to a non-null value will
804	introduce an additional C<ev_sleep ()> call into most loop iterations.	1037	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		1038	sleep time ensures that libev will not poll for I/O events more often then
		1039	once per this interval, on average (as long as the host time resolution is
		1040	good enough).
805		1041
806	Likewise, by setting a higher I<timeout collect interval> you allow libev	1042	Likewise, by setting a higher I<timeout collect interval> you allow libev
807	to spend more time collecting timeouts, at the expense of increased	1043	to spend more time collecting timeouts, at the expense of increased
808	latency/jitter/inexactness (the watcher callback will be called	1044	latency/jitter/inexactness (the watcher callback will be called
809	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1045	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
811		1047
812	Many (busy) programs can usually benefit by setting the I/O collect	1048	Many (busy) programs can usually benefit by setting the I/O collect
813	interval to a value near C<0.1> or so, which is often enough for	1049	interval to a value near C<0.1> or so, which is often enough for
814	interactive servers (of course not for games), likewise for timeouts. It	1050	interactive servers (of course not for games), likewise for timeouts. It
815	usually doesn't make much sense to set it to a lower value than C<0.01>,	1051	usually doesn't make much sense to set it to a lower value than C<0.01>,
816	as this approaches the timing granularity of most systems.	1052	as this approaches the timing granularity of most systems. Note that if
		1053	you do transactions with the outside world and you can't increase the
		1054	parallelity, then this setting will limit your transaction rate (if you
		1055	need to poll once per transaction and the I/O collect interval is 0.01,
		1056	then you can't do more than 100 transactions per second).
817		1057
818	Setting the I<timeout collect interval> can improve the opportunity for	1058	Setting the I<timeout collect interval> can improve the opportunity for
819	saving power, as the program will "bundle" timer callback invocations that	1059	saving power, as the program will "bundle" timer callback invocations that
820	are "near" in time together, by delaying some, thus reducing the number of	1060	are "near" in time together, by delaying some, thus reducing the number of
821	times the process sleeps and wakes up again. Another useful technique to	1061	times the process sleeps and wakes up again. Another useful technique to
822	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	1062	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
823	they fire on, say, one-second boundaries only.	1063	they fire on, say, one-second boundaries only.
824		1064
		1065	Example: we only need 0.1s timeout granularity, and we wish not to poll
		1066	more often than 100 times per second:
		1067
		1068	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		1069	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		1070
		1071	=item ev_invoke_pending (loop)
		1072
		1073	This call will simply invoke all pending watchers while resetting their
		1074	pending state. Normally, C<ev_run> does this automatically when required,
		1075	but when overriding the invoke callback this call comes handy. This
		1076	function can be invoked from a watcher - this can be useful for example
		1077	when you want to do some lengthy calculation and want to pass further
		1078	event handling to another thread (you still have to make sure only one
		1079	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1080
		1081	=item int ev_pending_count (loop)
		1082
		1083	Returns the number of pending watchers - zero indicates that no watchers
		1084	are pending.
		1085
		1086	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1087
		1088	This overrides the invoke pending functionality of the loop: Instead of
		1089	invoking all pending watchers when there are any, C<ev_run> will call
		1090	this callback instead. This is useful, for example, when you want to
		1091	invoke the actual watchers inside another context (another thread etc.).
		1092
		1093	If you want to reset the callback, use C<ev_invoke_pending> as new
		1094	callback.
		1095
		1096	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1097
		1098	Sometimes you want to share the same loop between multiple threads. This
		1099	can be done relatively simply by putting mutex_lock/unlock calls around
		1100	each call to a libev function.
		1101
		1102	However, C<ev_run> can run an indefinite time, so it is not feasible
		1103	to wait for it to return. One way around this is to wake up the event
		1104	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1105	I<release> and I<acquire> callbacks on the loop.
		1106
		1107	When set, then C<release> will be called just before the thread is
		1108	suspended waiting for new events, and C<acquire> is called just
		1109	afterwards.
		1110
		1111	Ideally, C<release> will just call your mutex_unlock function, and
		1112	C<acquire> will just call the mutex_lock function again.
		1113
		1114	While event loop modifications are allowed between invocations of
		1115	C<release> and C<acquire> (that's their only purpose after all), no
		1116	modifications done will affect the event loop, i.e. adding watchers will
		1117	have no effect on the set of file descriptors being watched, or the time
		1118	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1119	to take note of any changes you made.
		1120
		1121	In theory, threads executing C<ev_run> will be async-cancel safe between
		1122	invocations of C<release> and C<acquire>.
		1123
		1124	See also the locking example in the C<THREADS> section later in this
		1125	document.
		1126
		1127	=item ev_set_userdata (loop, void *data)
		1128
		1129	=item void *ev_userdata (loop)
		1130
		1131	Set and retrieve a single C<void *> associated with a loop. When
		1132	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1133	C<0>.
		1134
		1135	These two functions can be used to associate arbitrary data with a loop,
		1136	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1137	C<acquire> callbacks described above, but of course can be (ab-)used for
		1138	any other purpose as well.
		1139
825	=item ev_loop_verify (loop)	1140	=item ev_verify (loop)
826		1141
827	This function only does something when C<EV_VERIFY> support has been	1142	This function only does something when C<EV_VERIFY> support has been
828	compiled in, which is the default for non-minimal builds. It tries to go	1143	compiled in, which is the default for non-minimal builds. It tries to go
829	through all internal structures and checks them for validity. If anything	1144	through all internal structures and checks them for validity. If anything
830	is found to be inconsistent, it will print an error message to standard	1145	is found to be inconsistent, it will print an error message to standard
…		…
841		1156
842	In the following description, uppercase C<TYPE> in names stands for the	1157	In the following description, uppercase C<TYPE> in names stands for the
843	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1158	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
844	watchers and C<ev_io_start> for I/O watchers.	1159	watchers and C<ev_io_start> for I/O watchers.
845		1160
846	A watcher is a structure that you create and register to record your	1161	A watcher is an opaque structure that you allocate and register to record
847	interest in some event. For instance, if you want to wait for STDIN to	1162	your interest in some event. To make a concrete example, imagine you want
848	become readable, you would create an C<ev_io> watcher for that:	1163	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1164	for that:
849		1165
850	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1166	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
851	{	1167	{
852	ev_io_stop (w);	1168	ev_io_stop (w);
853	ev_unloop (loop, EVUNLOOP_ALL);	1169	ev_break (loop, EVBREAK_ALL);
854	}	1170	}
855		1171
856	struct ev_loop *loop = ev_default_loop (0);	1172	struct ev_loop *loop = ev_default_loop (0);
857		1173
858	ev_io stdin_watcher;	1174	ev_io stdin_watcher;
859		1175
860	ev_init (&stdin_watcher, my_cb);	1176	ev_init (&stdin_watcher, my_cb);
861	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1177	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
862	ev_io_start (loop, &stdin_watcher);	1178	ev_io_start (loop, &stdin_watcher);
863		1179
864	ev_loop (loop, 0);	1180	ev_run (loop, 0);
865		1181
866	As you can see, you are responsible for allocating the memory for your	1182	As you can see, you are responsible for allocating the memory for your
867	watcher structures (and it is I<usually> a bad idea to do this on the	1183	watcher structures (and it is I<usually> a bad idea to do this on the
868	stack).	1184	stack).
869		1185
870	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1186	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
871	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1187	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
872		1188
873	Each watcher structure must be initialised by a call to C<ev_init	1189	Each watcher structure must be initialised by a call to C<ev_init (watcher
874	(watcher *, callback)>, which expects a callback to be provided. This	1190	*, callback)>, which expects a callback to be provided. This callback is
875	callback gets invoked each time the event occurs (or, in the case of I/O	1191	invoked each time the event occurs (or, in the case of I/O watchers, each
876	watchers, each time the event loop detects that the file descriptor given	1192	time the event loop detects that the file descriptor given is readable
877	is readable and/or writable).	1193	and/or writable).
878		1194
879	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1195	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
880	macro to configure it, with arguments specific to the watcher type. There	1196	macro to configure it, with arguments specific to the watcher type. There
881	is also a macro to combine initialisation and setting in one call: C<<	1197	is also a macro to combine initialisation and setting in one call: C<<
882	ev_TYPE_init (watcher *, callback, ...) >>.	1198	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
905	=item C<EV_WRITE>	1221	=item C<EV_WRITE>
906		1222
907	The file descriptor in the C<ev_io> watcher has become readable and/or	1223	The file descriptor in the C<ev_io> watcher has become readable and/or
908	writable.	1224	writable.
909		1225
910	=item C<EV_TIMEOUT>	1226	=item C<EV_TIMER>
911		1227
912	The C<ev_timer> watcher has timed out.	1228	The C<ev_timer> watcher has timed out.
913		1229
914	=item C<EV_PERIODIC>	1230	=item C<EV_PERIODIC>
915		1231
…		…
933		1249
934	=item C<EV_PREPARE>	1250	=item C<EV_PREPARE>
935		1251
936	=item C<EV_CHECK>	1252	=item C<EV_CHECK>
937		1253
938	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1254	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
939	to gather new events, and all C<ev_check> watchers are invoked just after	1255	gather new events, and all C<ev_check> watchers are queued (not invoked)
940	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1256	just after C<ev_run> has gathered them, but before it queues any callbacks
		1257	for any received events. That means C<ev_prepare> watchers are the last
		1258	watchers invoked before the event loop sleeps or polls for new events, and
		1259	C<ev_check> watchers will be invoked before any other watchers of the same
		1260	or lower priority within an event loop iteration.
		1261
941	received events. Callbacks of both watcher types can start and stop as	1262	Callbacks of both watcher types can start and stop as many watchers as
942	many watchers as they want, and all of them will be taken into account	1263	they want, and all of them will be taken into account (for example, a
943	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1264	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
944	C<ev_loop> from blocking).	1265	blocking).
945		1266
946	=item C<EV_EMBED>	1267	=item C<EV_EMBED>
947		1268
948	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1269	The embedded event loop specified in the C<ev_embed> watcher needs attention.
949		1270
950	=item C<EV_FORK>	1271	=item C<EV_FORK>
951		1272
952	The event loop has been resumed in the child process after fork (see	1273	The event loop has been resumed in the child process after fork (see
953	C<ev_fork>).	1274	C<ev_fork>).
		1275
		1276	=item C<EV_CLEANUP>
		1277
		1278	The event loop is about to be destroyed (see C<ev_cleanup>).
954		1279
955	=item C<EV_ASYNC>	1280	=item C<EV_ASYNC>
956		1281
957	The given async watcher has been asynchronously notified (see C<ev_async>).	1282	The given async watcher has been asynchronously notified (see C<ev_async>).
958		1283
…		…
1005		1330
1006	ev_io w;	1331	ev_io w;
1007	ev_init (&w, my_cb);	1332	ev_init (&w, my_cb);
1008	ev_io_set (&w, STDIN_FILENO, EV_READ);	1333	ev_io_set (&w, STDIN_FILENO, EV_READ);
1009		1334
1010	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1335	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1011		1336
1012	This macro initialises the type-specific parts of a watcher. You need to	1337	This macro initialises the type-specific parts of a watcher. You need to
1013	call C<ev_init> at least once before you call this macro, but you can	1338	call C<ev_init> at least once before you call this macro, but you can
1014	call C<ev_TYPE_set> any number of times. You must not, however, call this	1339	call C<ev_TYPE_set> any number of times. You must not, however, call this
1015	macro on a watcher that is active (it can be pending, however, which is a	1340	macro on a watcher that is active (it can be pending, however, which is a
…		…
1028		1353
1029	Example: Initialise and set an C<ev_io> watcher in one step.	1354	Example: Initialise and set an C<ev_io> watcher in one step.
1030		1355
1031	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1356	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1032		1357
1033	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1358	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1034		1359
1035	Starts (activates) the given watcher. Only active watchers will receive	1360	Starts (activates) the given watcher. Only active watchers will receive
1036	events. If the watcher is already active nothing will happen.	1361	events. If the watcher is already active nothing will happen.
1037		1362
1038	Example: Start the C<ev_io> watcher that is being abused as example in this	1363	Example: Start the C<ev_io> watcher that is being abused as example in this
1039	whole section.	1364	whole section.
1040		1365
1041	ev_io_start (EV_DEFAULT_UC, &w);	1366	ev_io_start (EV_DEFAULT_UC, &w);
1042		1367
1043	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1368	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1044		1369
1045	Stops the given watcher if active, and clears the pending status (whether	1370	Stops the given watcher if active, and clears the pending status (whether
1046	the watcher was active or not).	1371	the watcher was active or not).
1047		1372
1048	It is possible that stopped watchers are pending - for example,	1373	It is possible that stopped watchers are pending - for example,
…		…
1068		1393
1069	=item callback ev_cb (ev_TYPE *watcher)	1394	=item callback ev_cb (ev_TYPE *watcher)
1070		1395
1071	Returns the callback currently set on the watcher.	1396	Returns the callback currently set on the watcher.
1072		1397
1073	=item ev_cb_set (ev_TYPE *watcher, callback)	1398	=item ev_set_cb (ev_TYPE *watcher, callback)
1074		1399
1075	Change the callback. You can change the callback at virtually any time	1400	Change the callback. You can change the callback at virtually any time
1076	(modulo threads).	1401	(modulo threads).
1077		1402
1078	=item ev_set_priority (ev_TYPE *watcher, priority)	1403	=item ev_set_priority (ev_TYPE *watcher, int priority)
1079		1404
1080	=item int ev_priority (ev_TYPE *watcher)	1405	=item int ev_priority (ev_TYPE *watcher)
1081		1406
1082	Set and query the priority of the watcher. The priority is a small	1407	Set and query the priority of the watcher. The priority is a small
1083	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1408	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1084	(default: C<-2>). Pending watchers with higher priority will be invoked	1409	(default: C<-2>). Pending watchers with higher priority will be invoked
1085	before watchers with lower priority, but priority will not keep watchers	1410	before watchers with lower priority, but priority will not keep watchers
1086	from being executed (except for C<ev_idle> watchers).	1411	from being executed (except for C<ev_idle> watchers).
1087		1412
1088	This means that priorities are I<only> used for ordering callback
1089	invocation after new events have been received. This is useful, for
1090	example, to reduce latency after idling, or more often, to bind two
1091	watchers on the same event and make sure one is called first.
1092
1093	If you need to suppress invocation when higher priority events are pending	1413	If you need to suppress invocation when higher priority events are pending
1094	you need to look at C<ev_idle> watchers, which provide this functionality.	1414	you need to look at C<ev_idle> watchers, which provide this functionality.
1095		1415
1096	You I<must not> change the priority of a watcher as long as it is active or	1416	You I<must not> change the priority of a watcher as long as it is active or
1097	pending.	1417	pending.
1098
1099	The default priority used by watchers when no priority has been set is
1100	always C<0>, which is supposed to not be too high and not be too low :).
1101		1418
1102	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1419	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1103	fine, as long as you do not mind that the priority value you query might	1420	fine, as long as you do not mind that the priority value you query might
1104	or might not have been clamped to the valid range.	1421	or might not have been clamped to the valid range.
		1422
		1423	The default priority used by watchers when no priority has been set is
		1424	always C<0>, which is supposed to not be too high and not be too low :).
		1425
		1426	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1427	priorities.
1105		1428
1106	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1429	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1107		1430
1108	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1431	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1109	C<loop> nor C<revents> need to be valid as long as the watcher callback	1432	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1117	watcher isn't pending it does nothing and returns C<0>.	1440	watcher isn't pending it does nothing and returns C<0>.
1118		1441
1119	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1442	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1120	callback to be invoked, which can be accomplished with this function.	1443	callback to be invoked, which can be accomplished with this function.
1121		1444
		1445	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1446
		1447	Feeds the given event set into the event loop, as if the specified event
		1448	had happened for the specified watcher (which must be a pointer to an
		1449	initialised but not necessarily started event watcher). Obviously you must
		1450	not free the watcher as long as it has pending events.
		1451
		1452	Stopping the watcher, letting libev invoke it, or calling
		1453	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1454	not started in the first place.
		1455
		1456	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1457	functions that do not need a watcher.
		1458
1122	=back	1459	=back
1123		1460
		1461	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1462	OWN COMPOSITE WATCHERS> idioms.
1124		1463
1125	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1464	=head2 WATCHER STATES
1126		1465
1127	Each watcher has, by default, a member C<void *data> that you can change	1466	There are various watcher states mentioned throughout this manual -
1128	and read at any time: libev will completely ignore it. This can be used	1467	active, pending and so on. In this section these states and the rules to
1129	to associate arbitrary data with your watcher. If you need more data and	1468	transition between them will be described in more detail - and while these
1130	don't want to allocate memory and store a pointer to it in that data	1469	rules might look complicated, they usually do "the right thing".
1131	member, you can also "subclass" the watcher type and provide your own
1132	data:
1133		1470
1134	struct my_io	1471	=over 4
		1472
		1473	=item initialised
		1474
		1475	Before a watcher can be registered with the event loop it has to be
		1476	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1477	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1478
		1479	In this state it is simply some block of memory that is suitable for
		1480	use in an event loop. It can be moved around, freed, reused etc. at
		1481	will - as long as you either keep the memory contents intact, or call
		1482	C<ev_TYPE_init> again.
		1483
		1484	=item started/running/active
		1485
		1486	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1487	property of the event loop, and is actively waiting for events. While in
		1488	this state it cannot be accessed (except in a few documented ways), moved,
		1489	freed or anything else - the only legal thing is to keep a pointer to it,
		1490	and call libev functions on it that are documented to work on active watchers.
		1491
		1492	=item pending
		1493
		1494	If a watcher is active and libev determines that an event it is interested
		1495	in has occurred (such as a timer expiring), it will become pending. It will
		1496	stay in this pending state until either it is stopped or its callback is
		1497	about to be invoked, so it is not normally pending inside the watcher
		1498	callback.
		1499
		1500	The watcher might or might not be active while it is pending (for example,
		1501	an expired non-repeating timer can be pending but no longer active). If it
		1502	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1503	but it is still property of the event loop at this time, so cannot be
		1504	moved, freed or reused. And if it is active the rules described in the
		1505	previous item still apply.
		1506
		1507	It is also possible to feed an event on a watcher that is not active (e.g.
		1508	via C<ev_feed_event>), in which case it becomes pending without being
		1509	active.
		1510
		1511	=item stopped
		1512
		1513	A watcher can be stopped implicitly by libev (in which case it might still
		1514	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1515	latter will clear any pending state the watcher might be in, regardless
		1516	of whether it was active or not, so stopping a watcher explicitly before
		1517	freeing it is often a good idea.
		1518
		1519	While stopped (and not pending) the watcher is essentially in the
		1520	initialised state, that is, it can be reused, moved, modified in any way
		1521	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1522	it again).
		1523
		1524	=back
		1525
		1526	=head2 WATCHER PRIORITY MODELS
		1527
		1528	Many event loops support I<watcher priorities>, which are usually small
		1529	integers that influence the ordering of event callback invocation
		1530	between watchers in some way, all else being equal.
		1531
		1532	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1533	description for the more technical details such as the actual priority
		1534	range.
		1535
		1536	There are two common ways how these these priorities are being interpreted
		1537	by event loops:
		1538
		1539	In the more common lock-out model, higher priorities "lock out" invocation
		1540	of lower priority watchers, which means as long as higher priority
		1541	watchers receive events, lower priority watchers are not being invoked.
		1542
		1543	The less common only-for-ordering model uses priorities solely to order
		1544	callback invocation within a single event loop iteration: Higher priority
		1545	watchers are invoked before lower priority ones, but they all get invoked
		1546	before polling for new events.
		1547
		1548	Libev uses the second (only-for-ordering) model for all its watchers
		1549	except for idle watchers (which use the lock-out model).
		1550
		1551	The rationale behind this is that implementing the lock-out model for
		1552	watchers is not well supported by most kernel interfaces, and most event
		1553	libraries will just poll for the same events again and again as long as
		1554	their callbacks have not been executed, which is very inefficient in the
		1555	common case of one high-priority watcher locking out a mass of lower
		1556	priority ones.
		1557
		1558	Static (ordering) priorities are most useful when you have two or more
		1559	watchers handling the same resource: a typical usage example is having an
		1560	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1561	timeouts. Under load, data might be received while the program handles
		1562	other jobs, but since timers normally get invoked first, the timeout
		1563	handler will be executed before checking for data. In that case, giving
		1564	the timer a lower priority than the I/O watcher ensures that I/O will be
		1565	handled first even under adverse conditions (which is usually, but not
		1566	always, what you want).
		1567
		1568	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1569	will only be executed when no same or higher priority watchers have
		1570	received events, they can be used to implement the "lock-out" model when
		1571	required.
		1572
		1573	For example, to emulate how many other event libraries handle priorities,
		1574	you can associate an C<ev_idle> watcher to each such watcher, and in
		1575	the normal watcher callback, you just start the idle watcher. The real
		1576	processing is done in the idle watcher callback. This causes libev to
		1577	continuously poll and process kernel event data for the watcher, but when
		1578	the lock-out case is known to be rare (which in turn is rare :), this is
		1579	workable.
		1580
		1581	Usually, however, the lock-out model implemented that way will perform
		1582	miserably under the type of load it was designed to handle. In that case,
		1583	it might be preferable to stop the real watcher before starting the
		1584	idle watcher, so the kernel will not have to process the event in case
		1585	the actual processing will be delayed for considerable time.
		1586
		1587	Here is an example of an I/O watcher that should run at a strictly lower
		1588	priority than the default, and which should only process data when no
		1589	other events are pending:
		1590
		1591	ev_idle idle; // actual processing watcher
		1592	ev_io io; // actual event watcher
		1593
		1594	static void
		1595	io_cb (EV_P_ ev_io *w, int revents)
1135	{	1596	{
1136	ev_io io;	1597	// stop the I/O watcher, we received the event, but
1137	int otherfd;	1598	// are not yet ready to handle it.
1138	void *somedata;	1599	ev_io_stop (EV_A_ w);
1139	struct whatever *mostinteresting;	1600
		1601	// start the idle watcher to handle the actual event.
		1602	// it will not be executed as long as other watchers
		1603	// with the default priority are receiving events.
		1604	ev_idle_start (EV_A_ &idle);
1140	};	1605	}
1141		1606
1142	...	1607	static void
1143	struct my_io w;	1608	idle_cb (EV_P_ ev_idle *w, int revents)
1144	ev_io_init (&w.io, my_cb, fd, EV_READ);
1145
1146	And since your callback will be called with a pointer to the watcher, you
1147	can cast it back to your own type:
1148
1149	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1150	{	1609	{
1151	struct my_io *w = (struct my_io *)w_;	1610	// actual processing
1152	...	1611	read (STDIN_FILENO, ...);
		1612
		1613	// have to start the I/O watcher again, as
		1614	// we have handled the event
		1615	ev_io_start (EV_P_ &io);
1153	}	1616	}
1154		1617
1155	More interesting and less C-conformant ways of casting your callback type	1618	// initialisation
1156	instead have been omitted.	1619	ev_idle_init (&idle, idle_cb);
		1620	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1621	ev_io_start (EV_DEFAULT_ &io);
1157		1622
1158	Another common scenario is to use some data structure with multiple	1623	In the "real" world, it might also be beneficial to start a timer, so that
1159	embedded watchers:	1624	low-priority connections can not be locked out forever under load. This
1160		1625	enables your program to keep a lower latency for important connections
1161	struct my_biggy	1626	during short periods of high load, while not completely locking out less
1162	{	1627	important ones.
1163	int some_data;
1164	ev_timer t1;
1165	ev_timer t2;
1166	}
1167
1168	In this case getting the pointer to C<my_biggy> is a bit more
1169	complicated: Either you store the address of your C<my_biggy> struct
1170	in the C<data> member of the watcher (for woozies), or you need to use
1171	some pointer arithmetic using C<offsetof> inside your watchers (for real
1172	programmers):
1173
1174	#include <stddef.h>
1175
1176	static void
1177	t1_cb (EV_P_ ev_timer *w, int revents)
1178	{
1179	struct my_biggy big = (struct my_biggy *
1180	(((char *)w) - offsetof (struct my_biggy, t1));
1181	}
1182
1183	static void
1184	t2_cb (EV_P_ ev_timer *w, int revents)
1185	{
1186	struct my_biggy big = (struct my_biggy *
1187	(((char *)w) - offsetof (struct my_biggy, t2));
1188	}
1189		1628
1190		1629
1191	=head1 WATCHER TYPES	1630	=head1 WATCHER TYPES
1192		1631
1193	This section describes each watcher in detail, but will not repeat	1632	This section describes each watcher in detail, but will not repeat
…		…
1217	In general you can register as many read and/or write event watchers per	1656	In general you can register as many read and/or write event watchers per
1218	fd as you want (as long as you don't confuse yourself). Setting all file	1657	fd as you want (as long as you don't confuse yourself). Setting all file
1219	descriptors to non-blocking mode is also usually a good idea (but not	1658	descriptors to non-blocking mode is also usually a good idea (but not
1220	required if you know what you are doing).	1659	required if you know what you are doing).
1221		1660
1222	If you cannot use non-blocking mode, then force the use of a
1223	known-to-be-good backend (at the time of this writing, this includes only
1224	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1225
1226	Another thing you have to watch out for is that it is quite easy to	1661	Another thing you have to watch out for is that it is quite easy to
1227	receive "spurious" readiness notifications, that is your callback might	1662	receive "spurious" readiness notifications, that is, your callback might
1228	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1663	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1229	because there is no data. Not only are some backends known to create a	1664	because there is no data. It is very easy to get into this situation even
1230	lot of those (for example Solaris ports), it is very easy to get into	1665	with a relatively standard program structure. Thus it is best to always
1231	this situation even with a relatively standard program structure. Thus	1666	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1232	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1233	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1667	preferable to a program hanging until some data arrives.
1234		1668
1235	If you cannot run the fd in non-blocking mode (for example you should	1669	If you cannot run the fd in non-blocking mode (for example you should
1236	not play around with an Xlib connection), then you have to separately	1670	not play around with an Xlib connection), then you have to separately
1237	re-test whether a file descriptor is really ready with a known-to-be good	1671	re-test whether a file descriptor is really ready with a known-to-be good
1238	interface such as poll (fortunately in our Xlib example, Xlib already	1672	interface such as poll (fortunately in the case of Xlib, it already does
1239	does this on its own, so its quite safe to use). Some people additionally	1673	this on its own, so its quite safe to use). Some people additionally
1240	use C<SIGALRM> and an interval timer, just to be sure you won't block	1674	use C<SIGALRM> and an interval timer, just to be sure you won't block
1241	indefinitely.	1675	indefinitely.
1242		1676
1243	But really, best use non-blocking mode.	1677	But really, best use non-blocking mode.
1244		1678
1245	=head3 The special problem of disappearing file descriptors	1679	=head3 The special problem of disappearing file descriptors
1246		1680
1247	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1681	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1248	descriptor (either due to calling C<close> explicitly or any other means,	1682	a file descriptor (either due to calling C<close> explicitly or any other
1249	such as C<dup2>). The reason is that you register interest in some file	1683	means, such as C<dup2>). The reason is that you register interest in some
1250	descriptor, but when it goes away, the operating system will silently drop	1684	file descriptor, but when it goes away, the operating system will silently
1251	this interest. If another file descriptor with the same number then is	1685	drop this interest. If another file descriptor with the same number then
1252	registered with libev, there is no efficient way to see that this is, in	1686	is registered with libev, there is no efficient way to see that this is,
1253	fact, a different file descriptor.	1687	in fact, a different file descriptor.
1254		1688
1255	To avoid having to explicitly tell libev about such cases, libev follows	1689	To avoid having to explicitly tell libev about such cases, libev follows
1256	the following policy: Each time C<ev_io_set> is being called, libev	1690	the following policy: Each time C<ev_io_set> is being called, libev
1257	will assume that this is potentially a new file descriptor, otherwise	1691	will assume that this is potentially a new file descriptor, otherwise
1258	it is assumed that the file descriptor stays the same. That means that	1692	it is assumed that the file descriptor stays the same. That means that
…		…
1272		1706
1273	There is no workaround possible except not registering events	1707	There is no workaround possible except not registering events
1274	for potentially C<dup ()>'ed file descriptors, or to resort to	1708	for potentially C<dup ()>'ed file descriptors, or to resort to
1275	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1709	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1276		1710
		1711	=head3 The special problem of files
		1712
		1713	Many people try to use C<select> (or libev) on file descriptors
		1714	representing files, and expect it to become ready when their program
		1715	doesn't block on disk accesses (which can take a long time on their own).
		1716
		1717	However, this cannot ever work in the "expected" way - you get a readiness
		1718	notification as soon as the kernel knows whether and how much data is
		1719	there, and in the case of open files, that's always the case, so you
		1720	always get a readiness notification instantly, and your read (or possibly
		1721	write) will still block on the disk I/O.
		1722
		1723	Another way to view it is that in the case of sockets, pipes, character
		1724	devices and so on, there is another party (the sender) that delivers data
		1725	on its own, but in the case of files, there is no such thing: the disk
		1726	will not send data on its own, simply because it doesn't know what you
		1727	wish to read - you would first have to request some data.
		1728
		1729	Since files are typically not-so-well supported by advanced notification
		1730	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1731	to files, even though you should not use it. The reason for this is
		1732	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1733	usually a tty, often a pipe, but also sometimes files or special devices
		1734	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1735	F</dev/urandom>), and even though the file might better be served with
		1736	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1737	it "just works" instead of freezing.
		1738
		1739	So avoid file descriptors pointing to files when you know it (e.g. use
		1740	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1741	when you rarely read from a file instead of from a socket, and want to
		1742	reuse the same code path.
		1743
1277	=head3 The special problem of fork	1744	=head3 The special problem of fork
1278		1745
1279	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1746	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1280	useless behaviour. Libev fully supports fork, but needs to be told about	1747	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1281	it in the child.	1748	to be told about it in the child if you want to continue to use it in the
		1749	child.
1282		1750
1283	To support fork in your programs, you either have to call	1751	To support fork in your child processes, you have to call C<ev_loop_fork
1284	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1752	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1285	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1753	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1286	C<EVBACKEND_POLL>.
1287		1754
1288	=head3 The special problem of SIGPIPE	1755	=head3 The special problem of SIGPIPE
1289		1756
1290	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1757	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1291	when writing to a pipe whose other end has been closed, your program gets	1758	when writing to a pipe whose other end has been closed, your program gets
…		…
1294		1761
1295	So when you encounter spurious, unexplained daemon exits, make sure you	1762	So when you encounter spurious, unexplained daemon exits, make sure you
1296	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1763	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1297	somewhere, as that would have given you a big clue).	1764	somewhere, as that would have given you a big clue).
1298		1765
		1766	=head3 The special problem of accept()ing when you can't
		1767
		1768	Many implementations of the POSIX C<accept> function (for example,
		1769	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1770	connection from the pending queue in all error cases.
		1771
		1772	For example, larger servers often run out of file descriptors (because
		1773	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1774	rejecting the connection, leading to libev signalling readiness on
		1775	the next iteration again (the connection still exists after all), and
		1776	typically causing the program to loop at 100% CPU usage.
		1777
		1778	Unfortunately, the set of errors that cause this issue differs between
		1779	operating systems, there is usually little the app can do to remedy the
		1780	situation, and no known thread-safe method of removing the connection to
		1781	cope with overload is known (to me).
		1782
		1783	One of the easiest ways to handle this situation is to just ignore it
		1784	- when the program encounters an overload, it will just loop until the
		1785	situation is over. While this is a form of busy waiting, no OS offers an
		1786	event-based way to handle this situation, so it's the best one can do.
		1787
		1788	A better way to handle the situation is to log any errors other than
		1789	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1790	messages, and continue as usual, which at least gives the user an idea of
		1791	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1792	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1793	usage.
		1794
		1795	If your program is single-threaded, then you could also keep a dummy file
		1796	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1797	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1798	close that fd, and create a new dummy fd. This will gracefully refuse
		1799	clients under typical overload conditions.
		1800
		1801	The last way to handle it is to simply log the error and C<exit>, as
		1802	is often done with C<malloc> failures, but this results in an easy
		1803	opportunity for a DoS attack.
1299		1804
1300	=head3 Watcher-Specific Functions	1805	=head3 Watcher-Specific Functions
1301		1806
1302	=over 4	1807	=over 4
1303		1808
…		…
1335	...	1840	...
1336	struct ev_loop *loop = ev_default_init (0);	1841	struct ev_loop *loop = ev_default_init (0);
1337	ev_io stdin_readable;	1842	ev_io stdin_readable;
1338	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1843	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1339	ev_io_start (loop, &stdin_readable);	1844	ev_io_start (loop, &stdin_readable);
1340	ev_loop (loop, 0);	1845	ev_run (loop, 0);
1341		1846
1342		1847
1343	=head2 C<ev_timer> - relative and optionally repeating timeouts	1848	=head2 C<ev_timer> - relative and optionally repeating timeouts
1344		1849
1345	Timer watchers are simple relative timers that generate an event after a	1850	Timer watchers are simple relative timers that generate an event after a
…		…
1350	year, it will still time out after (roughly) one hour. "Roughly" because	1855	year, it will still time out after (roughly) one hour. "Roughly" because
1351	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1856	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1352	monotonic clock option helps a lot here).	1857	monotonic clock option helps a lot here).
1353		1858
1354	The callback is guaranteed to be invoked only I<after> its timeout has	1859	The callback is guaranteed to be invoked only I<after> its timeout has
		1860	passed (not I<at>, so on systems with very low-resolution clocks this
		1861	might introduce a small delay, see "the special problem of being too
1355	passed. If multiple timers become ready during the same loop iteration	1862	early", below). If multiple timers become ready during the same loop
1356	then the ones with earlier time-out values are invoked before ones with	1863	iteration then the ones with earlier time-out values are invoked before
1357	later time-out values (but this is no longer true when a callback calls	1864	ones of the same priority with later time-out values (but this is no
1358	C<ev_loop> recursively).	1865	longer true when a callback calls C<ev_run> recursively).
1359		1866
1360	=head3 Be smart about timeouts	1867	=head3 Be smart about timeouts
1361		1868
1362	Many real-world problems involve some kind of timeout, usually for error	1869	Many real-world problems involve some kind of timeout, usually for error
1363	recovery. A typical example is an HTTP request - if the other side hangs,	1870	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1407	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1914	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1408	member and C<ev_timer_again>.	1915	member and C<ev_timer_again>.
1409		1916
1410	At start:	1917	At start:
1411		1918
1412	ev_timer_init (timer, callback);	1919	ev_init (timer, callback);
1413	timer->repeat = 60.;	1920	timer->repeat = 60.;
1414	ev_timer_again (loop, timer);	1921	ev_timer_again (loop, timer);
1415		1922
1416	Each time there is some activity:	1923	Each time there is some activity:
1417		1924
…		…
1438		1945
1439	In this case, it would be more efficient to leave the C<ev_timer> alone,	1946	In this case, it would be more efficient to leave the C<ev_timer> alone,
1440	but remember the time of last activity, and check for a real timeout only	1947	but remember the time of last activity, and check for a real timeout only
1441	within the callback:	1948	within the callback:
1442		1949
		1950	ev_tstamp timeout = 60.;
1443	ev_tstamp last_activity; // time of last activity	1951	ev_tstamp last_activity; // time of last activity
		1952	ev_timer timer;
1444		1953
1445	static void	1954	static void
1446	callback (EV_P_ ev_timer *w, int revents)	1955	callback (EV_P_ ev_timer *w, int revents)
1447	{	1956	{
1448	ev_tstamp now = ev_now (EV_A);	1957	// calculate when the timeout would happen
1449	ev_tstamp timeout = last_activity + 60.;	1958	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1450		1959
1451	// if last_activity + 60. is older than now, we did time out	1960	// if negative, it means we the timeout already occurred
1452	if (timeout < now)	1961	if (after < 0.)
1453	{	1962	{
1454	// timeout occured, take action	1963	// timeout occurred, take action
1455	}	1964	}
1456	else	1965	else
1457	{	1966	{
1458	// callback was invoked, but there was some activity, re-arm	1967	// callback was invoked, but there was some recent
1459	// the watcher to fire in last_activity + 60, which is	1968	// activity. simply restart the timer to time out
1460	// guaranteed to be in the future, so "again" is positive:	1969	// after "after" seconds, which is the earliest time
1461	w->repeat = timeout - now;	1970	// the timeout can occur.
		1971	ev_timer_set (w, after, 0.);
1462	ev_timer_again (EV_A_ w);	1972	ev_timer_start (EV_A_ w);
1463	}	1973	}
1464	}	1974	}
1465		1975
1466	To summarise the callback: first calculate the real timeout (defined	1976	To summarise the callback: first calculate in how many seconds the
1467	as "60 seconds after the last activity"), then check if that time has	1977	timeout will occur (by calculating the absolute time when it would occur,
1468	been reached, which means something I<did>, in fact, time out. Otherwise	1978	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1469	the callback was invoked too early (C<timeout> is in the future), so	1979	(EV_A)> from that).
1470	re-schedule the timer to fire at that future time, to see if maybe we have
1471	a timeout then.
1472		1980
1473	Note how C<ev_timer_again> is used, taking advantage of the	1981	If this value is negative, then we are already past the timeout, i.e. we
1474	C<ev_timer_again> optimisation when the timer is already running.	1982	timed out, and need to do whatever is needed in this case.
		1983
		1984	Otherwise, we now the earliest time at which the timeout would trigger,
		1985	and simply start the timer with this timeout value.
		1986
		1987	In other words, each time the callback is invoked it will check whether
		1988	the timeout occurred. If not, it will simply reschedule itself to check
		1989	again at the earliest time it could time out. Rinse. Repeat.
1475		1990
1476	This scheme causes more callback invocations (about one every 60 seconds	1991	This scheme causes more callback invocations (about one every 60 seconds
1477	minus half the average time between activity), but virtually no calls to	1992	minus half the average time between activity), but virtually no calls to
1478	libev to change the timeout.	1993	libev to change the timeout.
1479		1994
1480	To start the timer, simply initialise the watcher and set C<last_activity>	1995	To start the machinery, simply initialise the watcher and set
1481	to the current time (meaning we just have some activity :), then call the	1996	C<last_activity> to the current time (meaning there was some activity just
1482	callback, which will "do the right thing" and start the timer:	1997	now), then call the callback, which will "do the right thing" and start
		1998	the timer:
1483		1999
		2000	last_activity = ev_now (EV_A);
1484	ev_timer_init (timer, callback);	2001	ev_init (&timer, callback);
1485	last_activity = ev_now (loop);	2002	callback (EV_A_ &timer, 0);
1486	callback (loop, timer, EV_TIMEOUT);
1487		2003
1488	And when there is some activity, simply store the current time in	2004	When there is some activity, simply store the current time in
1489	C<last_activity>, no libev calls at all:	2005	C<last_activity>, no libev calls at all:
1490		2006
		2007	if (activity detected)
1491	last_actiivty = ev_now (loop);	2008	last_activity = ev_now (EV_A);
		2009
		2010	When your timeout value changes, then the timeout can be changed by simply
		2011	providing a new value, stopping the timer and calling the callback, which
		2012	will again do the right thing (for example, time out immediately :).
		2013
		2014	timeout = new_value;
		2015	ev_timer_stop (EV_A_ &timer);
		2016	callback (EV_A_ &timer, 0);
1492		2017
1493	This technique is slightly more complex, but in most cases where the	2018	This technique is slightly more complex, but in most cases where the
1494	time-out is unlikely to be triggered, much more efficient.	2019	time-out is unlikely to be triggered, much more efficient.
1495
1496	Changing the timeout is trivial as well (if it isn't hard-coded in the
1497	callback :) - just change the timeout and invoke the callback, which will
1498	fix things for you.
1499		2020
1500	=item 4. Wee, just use a double-linked list for your timeouts.	2021	=item 4. Wee, just use a double-linked list for your timeouts.
1501		2022
1502	If there is not one request, but many thousands (millions...), all	2023	If there is not one request, but many thousands (millions...), all
1503	employing some kind of timeout with the same timeout value, then one can	2024	employing some kind of timeout with the same timeout value, then one can
…		…
1530	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2051	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1531	rather complicated, but extremely efficient, something that really pays	2052	rather complicated, but extremely efficient, something that really pays
1532	off after the first million or so of active timers, i.e. it's usually	2053	off after the first million or so of active timers, i.e. it's usually
1533	overkill :)	2054	overkill :)
1534		2055
		2056	=head3 The special problem of being too early
		2057
		2058	If you ask a timer to call your callback after three seconds, then
		2059	you expect it to be invoked after three seconds - but of course, this
		2060	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2061	guaranteed to any precision by libev - imagine somebody suspending the
		2062	process with a STOP signal for a few hours for example.
		2063
		2064	So, libev tries to invoke your callback as soon as possible I<after> the
		2065	delay has occurred, but cannot guarantee this.
		2066
		2067	A less obvious failure mode is calling your callback too early: many event
		2068	loops compare timestamps with a "elapsed delay >= requested delay", but
		2069	this can cause your callback to be invoked much earlier than you would
		2070	expect.
		2071
		2072	To see why, imagine a system with a clock that only offers full second
		2073	resolution (think windows if you can't come up with a broken enough OS
		2074	yourself). If you schedule a one-second timer at the time 500.9, then the
		2075	event loop will schedule your timeout to elapse at a system time of 500
		2076	(500.9 truncated to the resolution) + 1, or 501.
		2077
		2078	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2079	501" and invoke the callback 0.1s after it was started, even though a
		2080	one-second delay was requested - this is being "too early", despite best
		2081	intentions.
		2082
		2083	This is the reason why libev will never invoke the callback if the elapsed
		2084	delay equals the requested delay, but only when the elapsed delay is
		2085	larger than the requested delay. In the example above, libev would only invoke
		2086	the callback at system time 502, or 1.1s after the timer was started.
		2087
		2088	So, while libev cannot guarantee that your callback will be invoked
		2089	exactly when requested, it I<can> and I<does> guarantee that the requested
		2090	delay has actually elapsed, or in other words, it always errs on the "too
		2091	late" side of things.
		2092
1535	=head3 The special problem of time updates	2093	=head3 The special problem of time updates
1536		2094
1537	Establishing the current time is a costly operation (it usually takes at	2095	Establishing the current time is a costly operation (it usually takes
1538	least two system calls): EV therefore updates its idea of the current	2096	at least one system call): EV therefore updates its idea of the current
1539	time only before and after C<ev_loop> collects new events, which causes a	2097	time only before and after C<ev_run> collects new events, which causes a
1540	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2098	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1541	lots of events in one iteration.	2099	lots of events in one iteration.
1542		2100
1543	The relative timeouts are calculated relative to the C<ev_now ()>	2101	The relative timeouts are calculated relative to the C<ev_now ()>
1544	time. This is usually the right thing as this timestamp refers to the time	2102	time. This is usually the right thing as this timestamp refers to the time
1545	of the event triggering whatever timeout you are modifying/starting. If	2103	of the event triggering whatever timeout you are modifying/starting. If
1546	you suspect event processing to be delayed and you I<need> to base the	2104	you suspect event processing to be delayed and you I<need> to base the
1547	timeout on the current time, use something like this to adjust for this:	2105	timeout on the current time, use something like the following to adjust
		2106	for it:
1548		2107
1549	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2108	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1550		2109
1551	If the event loop is suspended for a long time, you can also force an	2110	If the event loop is suspended for a long time, you can also force an
1552	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2111	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1553	()>.	2112	()>, although that will push the event time of all outstanding events
		2113	further into the future.
		2114
		2115	=head3 The special problem of unsynchronised clocks
		2116
		2117	Modern systems have a variety of clocks - libev itself uses the normal
		2118	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2119	jumps).
		2120
		2121	Neither of these clocks is synchronised with each other or any other clock
		2122	on the system, so C<ev_time ()> might return a considerably different time
		2123	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2124	a call to C<gettimeofday> might return a second count that is one higher
		2125	than a directly following call to C<time>.
		2126
		2127	The moral of this is to only compare libev-related timestamps with
		2128	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2129	a second or so.
		2130
		2131	One more problem arises due to this lack of synchronisation: if libev uses
		2132	the system monotonic clock and you compare timestamps from C<ev_time>
		2133	or C<ev_now> from when you started your timer and when your callback is
		2134	invoked, you will find that sometimes the callback is a bit "early".
		2135
		2136	This is because C<ev_timer>s work in real time, not wall clock time, so
		2137	libev makes sure your callback is not invoked before the delay happened,
		2138	I<measured according to the real time>, not the system clock.
		2139
		2140	If your timeouts are based on a physical timescale (e.g. "time out this
		2141	connection after 100 seconds") then this shouldn't bother you as it is
		2142	exactly the right behaviour.
		2143
		2144	If you want to compare wall clock/system timestamps to your timers, then
		2145	you need to use C<ev_periodic>s, as these are based on the wall clock
		2146	time, where your comparisons will always generate correct results.
		2147
		2148	=head3 The special problems of suspended animation
		2149
		2150	When you leave the server world it is quite customary to hit machines that
		2151	can suspend/hibernate - what happens to the clocks during such a suspend?
		2152
		2153	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2154	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2155	to run until the system is suspended, but they will not advance while the
		2156	system is suspended. That means, on resume, it will be as if the program
		2157	was frozen for a few seconds, but the suspend time will not be counted
		2158	towards C<ev_timer> when a monotonic clock source is used. The real time
		2159	clock advanced as expected, but if it is used as sole clocksource, then a
		2160	long suspend would be detected as a time jump by libev, and timers would
		2161	be adjusted accordingly.
		2162
		2163	I would not be surprised to see different behaviour in different between
		2164	operating systems, OS versions or even different hardware.
		2165
		2166	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2167	time jump in the monotonic clocks and the realtime clock. If the program
		2168	is suspended for a very long time, and monotonic clock sources are in use,
		2169	then you can expect C<ev_timer>s to expire as the full suspension time
		2170	will be counted towards the timers. When no monotonic clock source is in
		2171	use, then libev will again assume a timejump and adjust accordingly.
		2172
		2173	It might be beneficial for this latter case to call C<ev_suspend>
		2174	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2175	deterministic behaviour in this case (you can do nothing against
		2176	C<SIGSTOP>).
1554		2177
1555	=head3 Watcher-Specific Functions and Data Members	2178	=head3 Watcher-Specific Functions and Data Members
1556		2179
1557	=over 4	2180	=over 4
1558		2181
1559	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2182	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1560		2183
1561	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2184	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1562		2185
1563	Configure the timer to trigger after C<after> seconds. If C<repeat>	2186	Configure the timer to trigger after C<after> seconds (fractional and
1564	is C<0.>, then it will automatically be stopped once the timeout is	2187	negative values are supported). If C<repeat> is C<0.>, then it will
1565	reached. If it is positive, then the timer will automatically be	2188	automatically be stopped once the timeout is reached. If it is positive,
1566	configured to trigger again C<repeat> seconds later, again, and again,	2189	then the timer will automatically be configured to trigger again C<repeat>
1567	until stopped manually.	2190	seconds later, again, and again, until stopped manually.
1568		2191
1569	The timer itself will do a best-effort at avoiding drift, that is, if	2192	The timer itself will do a best-effort at avoiding drift, that is, if
1570	you configure a timer to trigger every 10 seconds, then it will normally	2193	you configure a timer to trigger every 10 seconds, then it will normally
1571	trigger at exactly 10 second intervals. If, however, your program cannot	2194	trigger at exactly 10 second intervals. If, however, your program cannot
1572	keep up with the timer (because it takes longer than those 10 seconds to	2195	keep up with the timer (because it takes longer than those 10 seconds to
1573	do stuff) the timer will not fire more than once per event loop iteration.	2196	do stuff) the timer will not fire more than once per event loop iteration.
1574		2197
1575	=item ev_timer_again (loop, ev_timer *)	2198	=item ev_timer_again (loop, ev_timer *)
1576		2199
1577	This will act as if the timer timed out and restart it again if it is	2200	This will act as if the timer timed out, and restarts it again if it is
1578	repeating. The exact semantics are:	2201	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2202	timeout to the C<repeat> value and calling C<ev_timer_start>.
1579		2203
		2204	The exact semantics are as in the following rules, all of which will be
		2205	applied to the watcher:
		2206
		2207	=over 4
		2208
1580	If the timer is pending, its pending status is cleared.	2209	=item If the timer is pending, the pending status is always cleared.
1581		2210
1582	If the timer is started but non-repeating, stop it (as if it timed out).	2211	=item If the timer is started but non-repeating, stop it (as if it timed
		2212	out, without invoking it).
1583		2213
1584	If the timer is repeating, either start it if necessary (with the	2214	=item If the timer is repeating, make the C<repeat> value the new timeout
1585	C<repeat> value), or reset the running timer to the C<repeat> value.	2215	and start the timer, if necessary.
1586		2216
		2217	=back
		2218
1587	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2219	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1588	usage example.	2220	usage example.
		2221
		2222	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2223
		2224	Returns the remaining time until a timer fires. If the timer is active,
		2225	then this time is relative to the current event loop time, otherwise it's
		2226	the timeout value currently configured.
		2227
		2228	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2229	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2230	will return C<4>. When the timer expires and is restarted, it will return
		2231	roughly C<7> (likely slightly less as callback invocation takes some time,
		2232	too), and so on.
1589		2233
1590	=item ev_tstamp repeat [read-write]	2234	=item ev_tstamp repeat [read-write]
1591		2235
1592	The current C<repeat> value. Will be used each time the watcher times out	2236	The current C<repeat> value. Will be used each time the watcher times out
1593	or C<ev_timer_again> is called, and determines the next timeout (if any),	2237	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1619	}	2263	}
1620		2264
1621	ev_timer mytimer;	2265	ev_timer mytimer;
1622	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2266	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1623	ev_timer_again (&mytimer); /* start timer */	2267	ev_timer_again (&mytimer); /* start timer */
1624	ev_loop (loop, 0);	2268	ev_run (loop, 0);
1625		2269
1626	// and in some piece of code that gets executed on any "activity":	2270	// and in some piece of code that gets executed on any "activity":
1627	// reset the timeout to start ticking again at 10 seconds	2271	// reset the timeout to start ticking again at 10 seconds
1628	ev_timer_again (&mytimer);	2272	ev_timer_again (&mytimer);
1629		2273
…		…
1633	Periodic watchers are also timers of a kind, but they are very versatile	2277	Periodic watchers are also timers of a kind, but they are very versatile
1634	(and unfortunately a bit complex).	2278	(and unfortunately a bit complex).
1635		2279
1636	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2280	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1637	relative time, the physical time that passes) but on wall clock time	2281	relative time, the physical time that passes) but on wall clock time
1638	(absolute time, the thing you can read on your calender or clock). The	2282	(absolute time, the thing you can read on your calendar or clock). The
1639	difference is that wall clock time can run faster or slower than real	2283	difference is that wall clock time can run faster or slower than real
1640	time, and time jumps are not uncommon (e.g. when you adjust your	2284	time, and time jumps are not uncommon (e.g. when you adjust your
1641	wrist-watch).	2285	wrist-watch).
1642		2286
1643	You can tell a periodic watcher to trigger after some specific point	2287	You can tell a periodic watcher to trigger after some specific point
…		…
1648	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2292	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1649	it, as it uses a relative timeout).	2293	it, as it uses a relative timeout).
1650		2294
1651	C<ev_periodic> watchers can also be used to implement vastly more complex	2295	C<ev_periodic> watchers can also be used to implement vastly more complex
1652	timers, such as triggering an event on each "midnight, local time", or	2296	timers, such as triggering an event on each "midnight, local time", or
1653	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2297	other complicated rules. This cannot easily be done with C<ev_timer>
1654	those cannot react to time jumps.	2298	watchers, as those cannot react to time jumps.
1655		2299
1656	As with timers, the callback is guaranteed to be invoked only when the	2300	As with timers, the callback is guaranteed to be invoked only when the
1657	point in time where it is supposed to trigger has passed. If multiple	2301	point in time where it is supposed to trigger has passed. If multiple
1658	timers become ready during the same loop iteration then the ones with	2302	timers become ready during the same loop iteration then the ones with
1659	earlier time-out values are invoked before ones with later time-out values	2303	earlier time-out values are invoked before ones with later time-out values
1660	(but this is no longer true when a callback calls C<ev_loop> recursively).	2304	(but this is no longer true when a callback calls C<ev_run> recursively).
1661		2305
1662	=head3 Watcher-Specific Functions and Data Members	2306	=head3 Watcher-Specific Functions and Data Members
1663		2307
1664	=over 4	2308	=over 4
1665		2309
…		…
1700		2344
1701	Another way to think about it (for the mathematically inclined) is that	2345	Another way to think about it (for the mathematically inclined) is that
1702	C<ev_periodic> will try to run the callback in this mode at the next possible	2346	C<ev_periodic> will try to run the callback in this mode at the next possible
1703	time where C<time = offset (mod interval)>, regardless of any time jumps.	2347	time where C<time = offset (mod interval)>, regardless of any time jumps.
1704		2348
1705	For numerical stability it is preferable that the C<offset> value is near	2349	The C<interval> I<MUST> be positive, and for numerical stability, the
1706	C<ev_now ()> (the current time), but there is no range requirement for	2350	interval value should be higher than C<1/8192> (which is around 100
1707	this value, and in fact is often specified as zero.	2351	microseconds) and C<offset> should be higher than C<0> and should have
		2352	at most a similar magnitude as the current time (say, within a factor of
		2353	ten). Typical values for offset are, in fact, C<0> or something between
		2354	C<0> and C<interval>, which is also the recommended range.
1708		2355
1709	Note also that there is an upper limit to how often a timer can fire (CPU	2356	Note also that there is an upper limit to how often a timer can fire (CPU
1710	speed for example), so if C<interval> is very small then timing stability	2357	speed for example), so if C<interval> is very small then timing stability
1711	will of course deteriorate. Libev itself tries to be exact to be about one	2358	will of course deteriorate. Libev itself tries to be exact to be about one
1712	millisecond (if the OS supports it and the machine is fast enough).	2359	millisecond (if the OS supports it and the machine is fast enough).
…		…
1742		2389
1743	NOTE: I<< This callback must always return a time that is higher than or	2390	NOTE: I<< This callback must always return a time that is higher than or
1744	equal to the passed C<now> value >>.	2391	equal to the passed C<now> value >>.
1745		2392
1746	This can be used to create very complex timers, such as a timer that	2393	This can be used to create very complex timers, such as a timer that
1747	triggers on "next midnight, local time". To do this, you would calculate the	2394	triggers on "next midnight, local time". To do this, you would calculate
1748	next midnight after C<now> and return the timestamp value for this. How	2395	the next midnight after C<now> and return the timestamp value for
1749	you do this is, again, up to you (but it is not trivial, which is the main	2396	this. Here is a (completely untested, no error checking) example on how to
1750	reason I omitted it as an example).	2397	do this:
		2398
		2399	#include <time.h>
		2400
		2401	static ev_tstamp
		2402	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2403	{
		2404	time_t tnow = (time_t)now;
		2405	struct tm tm;
		2406	localtime_r (&tnow, &tm);
		2407
		2408	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2409	++tm.tm_mday; // midnight next day
		2410
		2411	return mktime (&tm);
		2412	}
		2413
		2414	Note: this code might run into trouble on days that have more then two
		2415	midnights (beginning and end).
1751		2416
1752	=back	2417	=back
1753		2418
1754	=item ev_periodic_again (loop, ev_periodic *)	2419	=item ev_periodic_again (loop, ev_periodic *)
1755		2420
…		…
1793	Example: Call a callback every hour, or, more precisely, whenever the	2458	Example: Call a callback every hour, or, more precisely, whenever the
1794	system time is divisible by 3600. The callback invocation times have	2459	system time is divisible by 3600. The callback invocation times have
1795	potentially a lot of jitter, but good long-term stability.	2460	potentially a lot of jitter, but good long-term stability.
1796		2461
1797	static void	2462	static void
1798	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2463	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1799	{	2464	{
1800	... its now a full hour (UTC, or TAI or whatever your clock follows)	2465	... its now a full hour (UTC, or TAI or whatever your clock follows)
1801	}	2466	}
1802		2467
1803	ev_periodic hourly_tick;	2468	ev_periodic hourly_tick;
…		…
1820		2485
1821	ev_periodic hourly_tick;	2486	ev_periodic hourly_tick;
1822	ev_periodic_init (&hourly_tick, clock_cb,	2487	ev_periodic_init (&hourly_tick, clock_cb,
1823	fmod (ev_now (loop), 3600.), 3600., 0);	2488	fmod (ev_now (loop), 3600.), 3600., 0);
1824	ev_periodic_start (loop, &hourly_tick);	2489	ev_periodic_start (loop, &hourly_tick);
1825		2490
1826		2491
1827	=head2 C<ev_signal> - signal me when a signal gets signalled!	2492	=head2 C<ev_signal> - signal me when a signal gets signalled!
1828		2493
1829	Signal watchers will trigger an event when the process receives a specific	2494	Signal watchers will trigger an event when the process receives a specific
1830	signal one or more times. Even though signals are very asynchronous, libev	2495	signal one or more times. Even though signals are very asynchronous, libev
1831	will try it's best to deliver signals synchronously, i.e. as part of the	2496	will try its best to deliver signals synchronously, i.e. as part of the
1832	normal event processing, like any other event.	2497	normal event processing, like any other event.
1833		2498
1834	If you want signals asynchronously, just use C<sigaction> as you would	2499	If you want signals to be delivered truly asynchronously, just use
1835	do without libev and forget about sharing the signal. You can even use	2500	C<sigaction> as you would do without libev and forget about sharing
1836	C<ev_async> from a signal handler to synchronously wake up an event loop.	2501	the signal. You can even use C<ev_async> from a signal handler to
		2502	synchronously wake up an event loop.
1837		2503
1838	You can configure as many watchers as you like per signal. Only when the	2504	You can configure as many watchers as you like for the same signal, but
1839	first watcher gets started will libev actually register a signal handler	2505	only within the same loop, i.e. you can watch for C<SIGINT> in your
1840	with the kernel (thus it coexists with your own signal handlers as long as	2506	default loop and for C<SIGIO> in another loop, but you cannot watch for
1841	you don't register any with libev for the same signal). Similarly, when	2507	C<SIGINT> in both the default loop and another loop at the same time. At
1842	the last signal watcher for a signal is stopped, libev will reset the	2508	the moment, C<SIGCHLD> is permanently tied to the default loop.
1843	signal handler to SIG_DFL (regardless of what it was set to before).	2509
		2510	Only after the first watcher for a signal is started will libev actually
		2511	register something with the kernel. It thus coexists with your own signal
		2512	handlers as long as you don't register any with libev for the same signal.
1844		2513
1845	If possible and supported, libev will install its handlers with	2514	If possible and supported, libev will install its handlers with
1846	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2515	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1847	interrupted. If you have a problem with system calls getting interrupted by	2516	not be unduly interrupted. If you have a problem with system calls getting
1848	signals you can block all signals in an C<ev_check> watcher and unblock	2517	interrupted by signals you can block all signals in an C<ev_check> watcher
1849	them in an C<ev_prepare> watcher.	2518	and unblock them in an C<ev_prepare> watcher.
		2519
		2520	=head3 The special problem of inheritance over fork/execve/pthread_create
		2521
		2522	Both the signal mask (C<sigprocmask>) and the signal disposition
		2523	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2524	stopping it again), that is, libev might or might not block the signal,
		2525	and might or might not set or restore the installed signal handler (but
		2526	see C<EVFLAG_NOSIGMASK>).
		2527
		2528	While this does not matter for the signal disposition (libev never
		2529	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2530	C<execve>), this matters for the signal mask: many programs do not expect
		2531	certain signals to be blocked.
		2532
		2533	This means that before calling C<exec> (from the child) you should reset
		2534	the signal mask to whatever "default" you expect (all clear is a good
		2535	choice usually).
		2536
		2537	The simplest way to ensure that the signal mask is reset in the child is
		2538	to install a fork handler with C<pthread_atfork> that resets it. That will
		2539	catch fork calls done by libraries (such as the libc) as well.
		2540
		2541	In current versions of libev, the signal will not be blocked indefinitely
		2542	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2543	the window of opportunity for problems, it will not go away, as libev
		2544	I<has> to modify the signal mask, at least temporarily.
		2545
		2546	So I can't stress this enough: I<If you do not reset your signal mask when
		2547	you expect it to be empty, you have a race condition in your code>. This
		2548	is not a libev-specific thing, this is true for most event libraries.
		2549
		2550	=head3 The special problem of threads signal handling
		2551
		2552	POSIX threads has problematic signal handling semantics, specifically,
		2553	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2554	threads in a process block signals, which is hard to achieve.
		2555
		2556	When you want to use sigwait (or mix libev signal handling with your own
		2557	for the same signals), you can tackle this problem by globally blocking
		2558	all signals before creating any threads (or creating them with a fully set
		2559	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2560	loops. Then designate one thread as "signal receiver thread" which handles
		2561	these signals. You can pass on any signals that libev might be interested
		2562	in by calling C<ev_feed_signal>.
1850		2563
1851	=head3 Watcher-Specific Functions and Data Members	2564	=head3 Watcher-Specific Functions and Data Members
1852		2565
1853	=over 4	2566	=over 4
1854		2567
…		…
1870	Example: Try to exit cleanly on SIGINT.	2583	Example: Try to exit cleanly on SIGINT.
1871		2584
1872	static void	2585	static void
1873	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2586	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1874	{	2587	{
1875	ev_unloop (loop, EVUNLOOP_ALL);	2588	ev_break (loop, EVBREAK_ALL);
1876	}	2589	}
1877		2590
1878	ev_signal signal_watcher;	2591	ev_signal signal_watcher;
1879	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2592	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1880	ev_signal_start (loop, &signal_watcher);	2593	ev_signal_start (loop, &signal_watcher);
…		…
1886	some child status changes (most typically when a child of yours dies or	2599	some child status changes (most typically when a child of yours dies or
1887	exits). It is permissible to install a child watcher I<after> the child	2600	exits). It is permissible to install a child watcher I<after> the child
1888	has been forked (which implies it might have already exited), as long	2601	has been forked (which implies it might have already exited), as long
1889	as the event loop isn't entered (or is continued from a watcher), i.e.,	2602	as the event loop isn't entered (or is continued from a watcher), i.e.,
1890	forking and then immediately registering a watcher for the child is fine,	2603	forking and then immediately registering a watcher for the child is fine,
1891	but forking and registering a watcher a few event loop iterations later is	2604	but forking and registering a watcher a few event loop iterations later or
1892	not.	2605	in the next callback invocation is not.
1893		2606
1894	Only the default event loop is capable of handling signals, and therefore	2607	Only the default event loop is capable of handling signals, and therefore
1895	you can only register child watchers in the default event loop.	2608	you can only register child watchers in the default event loop.
1896		2609
		2610	Due to some design glitches inside libev, child watchers will always be
		2611	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2612	libev)
		2613
1897	=head3 Process Interaction	2614	=head3 Process Interaction
1898		2615
1899	Libev grabs C<SIGCHLD> as soon as the default event loop is	2616	Libev grabs C<SIGCHLD> as soon as the default event loop is
1900	initialised. This is necessary to guarantee proper behaviour even if	2617	initialised. This is necessary to guarantee proper behaviour even if the
1901	the first child watcher is started after the child exits. The occurrence	2618	first child watcher is started after the child exits. The occurrence
1902	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2619	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1903	synchronously as part of the event loop processing. Libev always reaps all	2620	synchronously as part of the event loop processing. Libev always reaps all
1904	children, even ones not watched.	2621	children, even ones not watched.
1905		2622
1906	=head3 Overriding the Built-In Processing	2623	=head3 Overriding the Built-In Processing
…		…
1916	=head3 Stopping the Child Watcher	2633	=head3 Stopping the Child Watcher
1917		2634
1918	Currently, the child watcher never gets stopped, even when the	2635	Currently, the child watcher never gets stopped, even when the
1919	child terminates, so normally one needs to stop the watcher in the	2636	child terminates, so normally one needs to stop the watcher in the
1920	callback. Future versions of libev might stop the watcher automatically	2637	callback. Future versions of libev might stop the watcher automatically
1921	when a child exit is detected.	2638	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2639	problem).
1922		2640
1923	=head3 Watcher-Specific Functions and Data Members	2641	=head3 Watcher-Specific Functions and Data Members
1924		2642
1925	=over 4	2643	=over 4
1926		2644
…		…
1984		2702
1985	=head2 C<ev_stat> - did the file attributes just change?	2703	=head2 C<ev_stat> - did the file attributes just change?
1986		2704
1987	This watches a file system path for attribute changes. That is, it calls	2705	This watches a file system path for attribute changes. That is, it calls
1988	C<stat> on that path in regular intervals (or when the OS says it changed)	2706	C<stat> on that path in regular intervals (or when the OS says it changed)
1989	and sees if it changed compared to the last time, invoking the callback if	2707	and sees if it changed compared to the last time, invoking the callback
1990	it did.	2708	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2709	happen after the watcher has been started will be reported.
1991		2710
1992	The path does not need to exist: changing from "path exists" to "path does	2711	The path does not need to exist: changing from "path exists" to "path does
1993	not exist" is a status change like any other. The condition "path does not	2712	not exist" is a status change like any other. The condition "path does not
1994	exist" (or more correctly "path cannot be stat'ed") is signified by the	2713	exist" (or more correctly "path cannot be stat'ed") is signified by the
1995	C<st_nlink> field being zero (which is otherwise always forced to be at	2714	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2225	Apart from keeping your process non-blocking (which is a useful	2944	Apart from keeping your process non-blocking (which is a useful
2226	effect on its own sometimes), idle watchers are a good place to do	2945	effect on its own sometimes), idle watchers are a good place to do
2227	"pseudo-background processing", or delay processing stuff to after the	2946	"pseudo-background processing", or delay processing stuff to after the
2228	event loop has handled all outstanding events.	2947	event loop has handled all outstanding events.
2229		2948
		2949	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2950
		2951	As long as there is at least one active idle watcher, libev will never
		2952	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2953	For this to work, the idle watcher doesn't need to be invoked at all - the
		2954	lowest priority will do.
		2955
		2956	This mode of operation can be useful together with an C<ev_check> watcher,
		2957	to do something on each event loop iteration - for example to balance load
		2958	between different connections.
		2959
		2960	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2961	example.
		2962
2230	=head3 Watcher-Specific Functions and Data Members	2963	=head3 Watcher-Specific Functions and Data Members
2231		2964
2232	=over 4	2965	=over 4
2233		2966
2234	=item ev_idle_init (ev_idle *, callback)	2967	=item ev_idle_init (ev_idle *, callback)
…		…
2245	callback, free it. Also, use no error checking, as usual.	2978	callback, free it. Also, use no error checking, as usual.
2246		2979
2247	static void	2980	static void
2248	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2981	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2249	{	2982	{
		2983	// stop the watcher
		2984	ev_idle_stop (loop, w);
		2985
		2986	// now we can free it
2250	free (w);	2987	free (w);
		2988
2251	// now do something you wanted to do when the program has	2989	// now do something you wanted to do when the program has
2252	// no longer anything immediate to do.	2990	// no longer anything immediate to do.
2253	}	2991	}
2254		2992
2255	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2993	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2256	ev_idle_init (idle_watcher, idle_cb);	2994	ev_idle_init (idle_watcher, idle_cb);
2257	ev_idle_start (loop, idle_cb);	2995	ev_idle_start (loop, idle_watcher);
2258		2996
2259		2997
2260	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2261		2999
2262	Prepare and check watchers are usually (but not always) used in pairs:	3000	Prepare and check watchers are often (but not always) used in pairs:
2263	prepare watchers get invoked before the process blocks and check watchers	3001	prepare watchers get invoked before the process blocks and check watchers
2264	afterwards.	3002	afterwards.
2265		3003
2266	You I<must not> call C<ev_loop> or similar functions that enter	3004	You I<must not> call C<ev_run> (or similar functions that enter the
2267	the current event loop from either C<ev_prepare> or C<ev_check>	3005	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2268	watchers. Other loops than the current one are fine, however. The	3006	C<ev_check> watchers. Other loops than the current one are fine,
2269	rationale behind this is that you do not need to check for recursion in	3007	however. The rationale behind this is that you do not need to check
2270	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3008	for recursion in those watchers, i.e. the sequence will always be
2271	C<ev_check> so if you have one watcher of each kind they will always be	3009	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2272	called in pairs bracketing the blocking call.	3010	kind they will always be called in pairs bracketing the blocking call.
2273		3011
2274	Their main purpose is to integrate other event mechanisms into libev and	3012	Their main purpose is to integrate other event mechanisms into libev and
2275	their use is somewhat advanced. They could be used, for example, to track	3013	their use is somewhat advanced. They could be used, for example, to track
2276	variable changes, implement your own watchers, integrate net-snmp or a	3014	variable changes, implement your own watchers, integrate net-snmp or a
2277	coroutine library and lots more. They are also occasionally useful if	3015	coroutine library and lots more. They are also occasionally useful if
…		…
2295	with priority higher than or equal to the event loop and one coroutine	3033	with priority higher than or equal to the event loop and one coroutine
2296	of lower priority, but only once, using idle watchers to keep the event	3034	of lower priority, but only once, using idle watchers to keep the event
2297	loop from blocking if lower-priority coroutines are active, thus mapping	3035	loop from blocking if lower-priority coroutines are active, thus mapping
2298	low-priority coroutines to idle/background tasks).	3036	low-priority coroutines to idle/background tasks).
2299		3037
2300	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3038	When used for this purpose, it is recommended to give C<ev_check> watchers
2301	priority, to ensure that they are being run before any other watchers	3039	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2302	after the poll (this doesn't matter for C<ev_prepare> watchers).	3040	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3041	watchers).
2303		3042
2304	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3043	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2305	activate ("feed") events into libev. While libev fully supports this, they	3044	activate ("feed") events into libev. While libev fully supports this, they
2306	might get executed before other C<ev_check> watchers did their job. As	3045	might get executed before other C<ev_check> watchers did their job. As
2307	C<ev_check> watchers are often used to embed other (non-libev) event	3046	C<ev_check> watchers are often used to embed other (non-libev) event
2308	loops those other event loops might be in an unusable state until their	3047	loops those other event loops might be in an unusable state until their
2309	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3048	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2310	others).	3049	others).
		3050
		3051	=head3 Abusing an C<ev_check> watcher for its side-effect
		3052
		3053	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3054	useful because they are called once per event loop iteration. For
		3055	example, if you want to handle a large number of connections fairly, you
		3056	normally only do a bit of work for each active connection, and if there
		3057	is more work to do, you wait for the next event loop iteration, so other
		3058	connections have a chance of making progress.
		3059
		3060	Using an C<ev_check> watcher is almost enough: it will be called on the
		3061	next event loop iteration. However, that isn't as soon as possible -
		3062	without external events, your C<ev_check> watcher will not be invoked.
		3063
		3064	This is where C<ev_idle> watchers come in handy - all you need is a
		3065	single global idle watcher that is active as long as you have one active
		3066	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3067	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3068	invoked. Neither watcher alone can do that.
2311		3069
2312	=head3 Watcher-Specific Functions and Data Members	3070	=head3 Watcher-Specific Functions and Data Members
2313		3071
2314	=over 4	3072	=over 4
2315		3073
…		…
2355	struct pollfd fds [nfd];	3113	struct pollfd fds [nfd];
2356	// actual code will need to loop here and realloc etc.	3114	// actual code will need to loop here and realloc etc.
2357	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3115	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2358		3116
2359	/* the callback is illegal, but won't be called as we stop during check */	3117	/* the callback is illegal, but won't be called as we stop during check */
2360	ev_timer_init (&tw, 0, timeout * 1e-3);	3118	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2361	ev_timer_start (loop, &tw);	3119	ev_timer_start (loop, &tw);
2362		3120
2363	// create one ev_io per pollfd	3121	// create one ev_io per pollfd
2364	for (int i = 0; i < nfd; ++i)	3122	for (int i = 0; i < nfd; ++i)
2365	{	3123	{
…		…
2439		3197
2440	if (timeout >= 0)	3198	if (timeout >= 0)
2441	// create/start timer	3199	// create/start timer
2442		3200
2443	// poll	3201	// poll
2444	ev_loop (EV_A_ 0);	3202	ev_run (EV_A_ 0);
2445		3203
2446	// stop timer again	3204	// stop timer again
2447	if (timeout >= 0)	3205	if (timeout >= 0)
2448	ev_timer_stop (EV_A_ &to);	3206	ev_timer_stop (EV_A_ &to);
2449		3207
…		…
2516		3274
2517	=over 4	3275	=over 4
2518		3276
2519	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3277	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2520		3278
2521	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3279	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2522		3280
2523	Configures the watcher to embed the given loop, which must be	3281	Configures the watcher to embed the given loop, which must be
2524	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3282	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2525	invoked automatically, otherwise it is the responsibility of the callback	3283	invoked automatically, otherwise it is the responsibility of the callback
2526	to invoke it (it will continue to be called until the sweep has been done,	3284	to invoke it (it will continue to be called until the sweep has been done,
2527	if you do not want that, you need to temporarily stop the embed watcher).	3285	if you do not want that, you need to temporarily stop the embed watcher).
2528		3286
2529	=item ev_embed_sweep (loop, ev_embed *)	3287	=item ev_embed_sweep (loop, ev_embed *)
2530		3288
2531	Make a single, non-blocking sweep over the embedded loop. This works	3289	Make a single, non-blocking sweep over the embedded loop. This works
2532	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3290	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2533	appropriate way for embedded loops.	3291	appropriate way for embedded loops.
2534		3292
2535	=item struct ev_loop *other [read-only]	3293	=item struct ev_loop *other [read-only]
2536		3294
2537	The embedded event loop.	3295	The embedded event loop.
…		…
2547	used).	3305	used).
2548		3306
2549	struct ev_loop *loop_hi = ev_default_init (0);	3307	struct ev_loop *loop_hi = ev_default_init (0);
2550	struct ev_loop *loop_lo = 0;	3308	struct ev_loop *loop_lo = 0;
2551	ev_embed embed;	3309	ev_embed embed;
2552		3310
2553	// see if there is a chance of getting one that works	3311	// see if there is a chance of getting one that works
2554	// (remember that a flags value of 0 means autodetection)	3312	// (remember that a flags value of 0 means autodetection)
2555	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3313	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2556	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3314	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2557	: 0;	3315	: 0;
…		…
2571	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3329	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2572		3330
2573	struct ev_loop *loop = ev_default_init (0);	3331	struct ev_loop *loop = ev_default_init (0);
2574	struct ev_loop *loop_socket = 0;	3332	struct ev_loop *loop_socket = 0;
2575	ev_embed embed;	3333	ev_embed embed;
2576		3334
2577	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3335	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2578	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3336	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2579	{	3337	{
2580	ev_embed_init (&embed, 0, loop_socket);	3338	ev_embed_init (&embed, 0, loop_socket);
2581	ev_embed_start (loop, &embed);	3339	ev_embed_start (loop, &embed);
…		…
2589		3347
2590	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3348	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2591		3349
2592	Fork watchers are called when a C<fork ()> was detected (usually because	3350	Fork watchers are called when a C<fork ()> was detected (usually because
2593	whoever is a good citizen cared to tell libev about it by calling	3351	whoever is a good citizen cared to tell libev about it by calling
2594	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3352	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2595	event loop blocks next and before C<ev_check> watchers are being called,	3353	and before C<ev_check> watchers are being called, and only in the child
2596	and only in the child after the fork. If whoever good citizen calling	3354	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2597	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3355	and calls it in the wrong process, the fork handlers will be invoked, too,
2598	handlers will be invoked, too, of course.	3356	of course.
		3357
		3358	=head3 The special problem of life after fork - how is it possible?
		3359
		3360	Most uses of C<fork ()> consist of forking, then some simple calls to set
		3361	up/change the process environment, followed by a call to C<exec()>. This
		3362	sequence should be handled by libev without any problems.
		3363
		3364	This changes when the application actually wants to do event handling
		3365	in the child, or both parent in child, in effect "continuing" after the
		3366	fork.
		3367
		3368	The default mode of operation (for libev, with application help to detect
		3369	forks) is to duplicate all the state in the child, as would be expected
		3370	when I<either> the parent I<or> the child process continues.
		3371
		3372	When both processes want to continue using libev, then this is usually the
		3373	wrong result. In that case, usually one process (typically the parent) is
		3374	supposed to continue with all watchers in place as before, while the other
		3375	process typically wants to start fresh, i.e. without any active watchers.
		3376
		3377	The cleanest and most efficient way to achieve that with libev is to
		3378	simply create a new event loop, which of course will be "empty", and
		3379	use that for new watchers. This has the advantage of not touching more
		3380	memory than necessary, and thus avoiding the copy-on-write, and the
		3381	disadvantage of having to use multiple event loops (which do not support
		3382	signal watchers).
		3383
		3384	When this is not possible, or you want to use the default loop for
		3385	other reasons, then in the process that wants to start "fresh", call
		3386	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3387	Destroying the default loop will "orphan" (not stop) all registered
		3388	watchers, so you have to be careful not to execute code that modifies
		3389	those watchers. Note also that in that case, you have to re-register any
		3390	signal watchers.
2599		3391
2600	=head3 Watcher-Specific Functions and Data Members	3392	=head3 Watcher-Specific Functions and Data Members
2601		3393
2602	=over 4	3394	=over 4
2603		3395
2604	=item ev_fork_init (ev_signal *, callback)	3396	=item ev_fork_init (ev_fork *, callback)
2605		3397
2606	Initialises and configures the fork watcher - it has no parameters of any	3398	Initialises and configures the fork watcher - it has no parameters of any
2607	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3399	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2608	believe me.	3400	really.
2609		3401
2610	=back	3402	=back
2611		3403
2612		3404
		3405	=head2 C<ev_cleanup> - even the best things end
		3406
		3407	Cleanup watchers are called just before the event loop is being destroyed
		3408	by a call to C<ev_loop_destroy>.
		3409
		3410	While there is no guarantee that the event loop gets destroyed, cleanup
		3411	watchers provide a convenient method to install cleanup hooks for your
		3412	program, worker threads and so on - you just to make sure to destroy the
		3413	loop when you want them to be invoked.
		3414
		3415	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3416	all other watchers, they do not keep a reference to the event loop (which
		3417	makes a lot of sense if you think about it). Like all other watchers, you
		3418	can call libev functions in the callback, except C<ev_cleanup_start>.
		3419
		3420	=head3 Watcher-Specific Functions and Data Members
		3421
		3422	=over 4
		3423
		3424	=item ev_cleanup_init (ev_cleanup *, callback)
		3425
		3426	Initialises and configures the cleanup watcher - it has no parameters of
		3427	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3428	pointless, I assure you.
		3429
		3430	=back
		3431
		3432	Example: Register an atexit handler to destroy the default loop, so any
		3433	cleanup functions are called.
		3434
		3435	static void
		3436	program_exits (void)
		3437	{
		3438	ev_loop_destroy (EV_DEFAULT_UC);
		3439	}
		3440
		3441	...
		3442	atexit (program_exits);
		3443
		3444
2613	=head2 C<ev_async> - how to wake up another event loop	3445	=head2 C<ev_async> - how to wake up an event loop
2614		3446
2615	In general, you cannot use an C<ev_loop> from multiple threads or other	3447	In general, you cannot use an C<ev_loop> from multiple threads or other
2616	asynchronous sources such as signal handlers (as opposed to multiple event	3448	asynchronous sources such as signal handlers (as opposed to multiple event
2617	loops - those are of course safe to use in different threads).	3449	loops - those are of course safe to use in different threads).
2618		3450
2619	Sometimes, however, you need to wake up another event loop you do not	3451	Sometimes, however, you need to wake up an event loop you do not control,
2620	control, for example because it belongs to another thread. This is what	3452	for example because it belongs to another thread. This is what C<ev_async>
2621	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3453	watchers do: as long as the C<ev_async> watcher is active, you can signal
2622	can signal it by calling C<ev_async_send>, which is thread- and signal	3454	it by calling C<ev_async_send>, which is thread- and signal safe.
2623	safe.
2624		3455
2625	This functionality is very similar to C<ev_signal> watchers, as signals,	3456	This functionality is very similar to C<ev_signal> watchers, as signals,
2626	too, are asynchronous in nature, and signals, too, will be compressed	3457	too, are asynchronous in nature, and signals, too, will be compressed
2627	(i.e. the number of callback invocations may be less than the number of	3458	(i.e. the number of callback invocations may be less than the number of
2628	C<ev_async_sent> calls).	3459	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2629		3460	of "global async watchers" by using a watcher on an otherwise unused
2630	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3461	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2631	just the default loop.	3462	even without knowing which loop owns the signal.
2632		3463
2633	=head3 Queueing	3464	=head3 Queueing
2634		3465
2635	C<ev_async> does not support queueing of data in any way. The reason	3466	C<ev_async> does not support queueing of data in any way. The reason
2636	is that the author does not know of a simple (or any) algorithm for a	3467	is that the author does not know of a simple (or any) algorithm for a
2637	multiple-writer-single-reader queue that works in all cases and doesn't	3468	multiple-writer-single-reader queue that works in all cases and doesn't
2638	need elaborate support such as pthreads.	3469	need elaborate support such as pthreads or unportable memory access
		3470	semantics.
2639		3471
2640	That means that if you want to queue data, you have to provide your own	3472	That means that if you want to queue data, you have to provide your own
2641	queue. But at least I can tell you how to implement locking around your	3473	queue. But at least I can tell you how to implement locking around your
2642	queue:	3474	queue:
2643		3475
…		…
2727	trust me.	3559	trust me.
2728		3560
2729	=item ev_async_send (loop, ev_async *)	3561	=item ev_async_send (loop, ev_async *)
2730		3562
2731	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3563	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2732	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3564	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3565	returns.
		3566
2733	C<ev_feed_event>, this call is safe to do from other threads, signal or	3567	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2734	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3568	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2735	section below on what exactly this means).	3569	embedding section below on what exactly this means).
2736		3570
2737	Note that, as with other watchers in libev, multiple events might get	3571	Note that, as with other watchers in libev, multiple events might get
2738	compressed into a single callback invocation (another way to look at this	3572	compressed into a single callback invocation (another way to look at
2739	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3573	this is that C<ev_async> watchers are level-triggered: they are set on
2740	reset when the event loop detects that).	3574	C<ev_async_send>, reset when the event loop detects that).
2741		3575
2742	This call incurs the overhead of a system call only once per event loop	3576	This call incurs the overhead of at most one extra system call per event
2743	iteration, so while the overhead might be noticeable, it doesn't apply to	3577	loop iteration, if the event loop is blocked, and no syscall at all if
2744	repeated calls to C<ev_async_send> for the same event loop.	3578	the event loop (or your program) is processing events. That means that
		3579	repeated calls are basically free (there is no need to avoid calls for
		3580	performance reasons) and that the overhead becomes smaller (typically
		3581	zero) under load.
2745		3582
2746	=item bool = ev_async_pending (ev_async *)	3583	=item bool = ev_async_pending (ev_async *)
2747		3584
2748	Returns a non-zero value when C<ev_async_send> has been called on the	3585	Returns a non-zero value when C<ev_async_send> has been called on the
2749	watcher but the event has not yet been processed (or even noted) by the	3586	watcher but the event has not yet been processed (or even noted) by the
…		…
2766		3603
2767	There are some other functions of possible interest. Described. Here. Now.	3604	There are some other functions of possible interest. Described. Here. Now.
2768		3605
2769	=over 4	3606	=over 4
2770		3607
2771	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3608	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
2772		3609
2773	This function combines a simple timer and an I/O watcher, calls your	3610	This function combines a simple timer and an I/O watcher, calls your
2774	callback on whichever event happens first and automatically stops both	3611	callback on whichever event happens first and automatically stops both
2775	watchers. This is useful if you want to wait for a single event on an fd	3612	watchers. This is useful if you want to wait for a single event on an fd
2776	or timeout without having to allocate/configure/start/stop/free one or	3613	or timeout without having to allocate/configure/start/stop/free one or
…		…
2782		3619
2783	If C<timeout> is less than 0, then no timeout watcher will be	3620	If C<timeout> is less than 0, then no timeout watcher will be
2784	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3621	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2785	repeat = 0) will be started. C<0> is a valid timeout.	3622	repeat = 0) will be started. C<0> is a valid timeout.
2786		3623
2787	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3624	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2788	passed an C<revents> set like normal event callbacks (a combination of	3625	passed an C<revents> set like normal event callbacks (a combination of
2789	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3626	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2790	value passed to C<ev_once>. Note that it is possible to receive I<both>	3627	value passed to C<ev_once>. Note that it is possible to receive I<both>
2791	a timeout and an io event at the same time - you probably should give io	3628	a timeout and an io event at the same time - you probably should give io
2792	events precedence.	3629	events precedence.
2793		3630
2794	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3631	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2795		3632
2796	static void stdin_ready (int revents, void *arg)	3633	static void stdin_ready (int revents, void *arg)
2797	{	3634	{
2798	if (revents & EV_READ)	3635	if (revents & EV_READ)
2799	/* stdin might have data for us, joy! */;	3636	/* stdin might have data for us, joy! */;
2800	else if (revents & EV_TIMEOUT)	3637	else if (revents & EV_TIMER)
2801	/* doh, nothing entered */;	3638	/* doh, nothing entered */;
2802	}	3639	}
2803		3640
2804	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3641	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2805		3642
2806	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2807
2808	Feeds the given event set into the event loop, as if the specified event
2809	had happened for the specified watcher (which must be a pointer to an
2810	initialised but not necessarily started event watcher).
2811
2812	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3643	=item ev_feed_fd_event (loop, int fd, int revents)
2813		3644
2814	Feed an event on the given fd, as if a file descriptor backend detected	3645	Feed an event on the given fd, as if a file descriptor backend detected
2815	the given events it.	3646	the given events.
2816		3647
2817	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3648	=item ev_feed_signal_event (loop, int signum)
2818		3649
2819	Feed an event as if the given signal occurred (C<loop> must be the default	3650	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2820	loop!).	3651	which is async-safe.
2821		3652
2822	=back	3653	=back
		3654
		3655
		3656	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3657
		3658	This section explains some common idioms that are not immediately
		3659	obvious. Note that examples are sprinkled over the whole manual, and this
		3660	section only contains stuff that wouldn't fit anywhere else.
		3661
		3662	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3663
		3664	Each watcher has, by default, a C<void *data> member that you can read
		3665	or modify at any time: libev will completely ignore it. This can be used
		3666	to associate arbitrary data with your watcher. If you need more data and
		3667	don't want to allocate memory separately and store a pointer to it in that
		3668	data member, you can also "subclass" the watcher type and provide your own
		3669	data:
		3670
		3671	struct my_io
		3672	{
		3673	ev_io io;
		3674	int otherfd;
		3675	void *somedata;
		3676	struct whatever *mostinteresting;
		3677	};
		3678
		3679	...
		3680	struct my_io w;
		3681	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3682
		3683	And since your callback will be called with a pointer to the watcher, you
		3684	can cast it back to your own type:
		3685
		3686	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3687	{
		3688	struct my_io *w = (struct my_io *)w_;
		3689	...
		3690	}
		3691
		3692	More interesting and less C-conformant ways of casting your callback
		3693	function type instead have been omitted.
		3694
		3695	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3696
		3697	Another common scenario is to use some data structure with multiple
		3698	embedded watchers, in effect creating your own watcher that combines
		3699	multiple libev event sources into one "super-watcher":
		3700
		3701	struct my_biggy
		3702	{
		3703	int some_data;
		3704	ev_timer t1;
		3705	ev_timer t2;
		3706	}
		3707
		3708	In this case getting the pointer to C<my_biggy> is a bit more
		3709	complicated: Either you store the address of your C<my_biggy> struct in
		3710	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3711	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3712	real programmers):
		3713
		3714	#include <stddef.h>
		3715
		3716	static void
		3717	t1_cb (EV_P_ ev_timer *w, int revents)
		3718	{
		3719	struct my_biggy big = (struct my_biggy *)
		3720	(((char *)w) - offsetof (struct my_biggy, t1));
		3721	}
		3722
		3723	static void
		3724	t2_cb (EV_P_ ev_timer *w, int revents)
		3725	{
		3726	struct my_biggy big = (struct my_biggy *)
		3727	(((char *)w) - offsetof (struct my_biggy, t2));
		3728	}
		3729
		3730	=head2 AVOIDING FINISHING BEFORE RETURNING
		3731
		3732	Often you have structures like this in event-based programs:
		3733
		3734	callback ()
		3735	{
		3736	free (request);
		3737	}
		3738
		3739	request = start_new_request (..., callback);
		3740
		3741	The intent is to start some "lengthy" operation. The C<request> could be
		3742	used to cancel the operation, or do other things with it.
		3743
		3744	It's not uncommon to have code paths in C<start_new_request> that
		3745	immediately invoke the callback, for example, to report errors. Or you add
		3746	some caching layer that finds that it can skip the lengthy aspects of the
		3747	operation and simply invoke the callback with the result.
		3748
		3749	The problem here is that this will happen I<before> C<start_new_request>
		3750	has returned, so C<request> is not set.
		3751
		3752	Even if you pass the request by some safer means to the callback, you
		3753	might want to do something to the request after starting it, such as
		3754	canceling it, which probably isn't working so well when the callback has
		3755	already been invoked.
		3756
		3757	A common way around all these issues is to make sure that
		3758	C<start_new_request> I<always> returns before the callback is invoked. If
		3759	C<start_new_request> immediately knows the result, it can artificially
		3760	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3761	example, or more sneakily, by reusing an existing (stopped) watcher and
		3762	pushing it into the pending queue:
		3763
		3764	ev_set_cb (watcher, callback);
		3765	ev_feed_event (EV_A_ watcher, 0);
		3766
		3767	This way, C<start_new_request> can safely return before the callback is
		3768	invoked, while not delaying callback invocation too much.
		3769
		3770	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3771
		3772	Often (especially in GUI toolkits) there are places where you have
		3773	I<modal> interaction, which is most easily implemented by recursively
		3774	invoking C<ev_run>.
		3775
		3776	This brings the problem of exiting - a callback might want to finish the
		3777	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3778	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3779	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3780	other combination: In these cases, a simple C<ev_break> will not work.
		3781
		3782	The solution is to maintain "break this loop" variable for each C<ev_run>
		3783	invocation, and use a loop around C<ev_run> until the condition is
		3784	triggered, using C<EVRUN_ONCE>:
		3785
		3786	// main loop
		3787	int exit_main_loop = 0;
		3788
		3789	while (!exit_main_loop)
		3790	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3791
		3792	// in a modal watcher
		3793	int exit_nested_loop = 0;
		3794
		3795	while (!exit_nested_loop)
		3796	ev_run (EV_A_ EVRUN_ONCE);
		3797
		3798	To exit from any of these loops, just set the corresponding exit variable:
		3799
		3800	// exit modal loop
		3801	exit_nested_loop = 1;
		3802
		3803	// exit main program, after modal loop is finished
		3804	exit_main_loop = 1;
		3805
		3806	// exit both
		3807	exit_main_loop = exit_nested_loop = 1;
		3808
		3809	=head2 THREAD LOCKING EXAMPLE
		3810
		3811	Here is a fictitious example of how to run an event loop in a different
		3812	thread from where callbacks are being invoked and watchers are
		3813	created/added/removed.
		3814
		3815	For a real-world example, see the C<EV::Loop::Async> perl module,
		3816	which uses exactly this technique (which is suited for many high-level
		3817	languages).
		3818
		3819	The example uses a pthread mutex to protect the loop data, a condition
		3820	variable to wait for callback invocations, an async watcher to notify the
		3821	event loop thread and an unspecified mechanism to wake up the main thread.
		3822
		3823	First, you need to associate some data with the event loop:
		3824
		3825	typedef struct {
		3826	mutex_t lock; /* global loop lock */
		3827	ev_async async_w;
		3828	thread_t tid;
		3829	cond_t invoke_cv;
		3830	} userdata;
		3831
		3832	void prepare_loop (EV_P)
		3833	{
		3834	// for simplicity, we use a static userdata struct.
		3835	static userdata u;
		3836
		3837	ev_async_init (&u->async_w, async_cb);
		3838	ev_async_start (EV_A_ &u->async_w);
		3839
		3840	pthread_mutex_init (&u->lock, 0);
		3841	pthread_cond_init (&u->invoke_cv, 0);
		3842
		3843	// now associate this with the loop
		3844	ev_set_userdata (EV_A_ u);
		3845	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3846	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3847
		3848	// then create the thread running ev_run
		3849	pthread_create (&u->tid, 0, l_run, EV_A);
		3850	}
		3851
		3852	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3853	solely to wake up the event loop so it takes notice of any new watchers
		3854	that might have been added:
		3855
		3856	static void
		3857	async_cb (EV_P_ ev_async *w, int revents)
		3858	{
		3859	// just used for the side effects
		3860	}
		3861
		3862	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3863	protecting the loop data, respectively.
		3864
		3865	static void
		3866	l_release (EV_P)
		3867	{
		3868	userdata *u = ev_userdata (EV_A);
		3869	pthread_mutex_unlock (&u->lock);
		3870	}
		3871
		3872	static void
		3873	l_acquire (EV_P)
		3874	{
		3875	userdata *u = ev_userdata (EV_A);
		3876	pthread_mutex_lock (&u->lock);
		3877	}
		3878
		3879	The event loop thread first acquires the mutex, and then jumps straight
		3880	into C<ev_run>:
		3881
		3882	void *
		3883	l_run (void *thr_arg)
		3884	{
		3885	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3886
		3887	l_acquire (EV_A);
		3888	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3889	ev_run (EV_A_ 0);
		3890	l_release (EV_A);
		3891
		3892	return 0;
		3893	}
		3894
		3895	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3896	signal the main thread via some unspecified mechanism (signals? pipe
		3897	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3898	have been called (in a while loop because a) spurious wakeups are possible
		3899	and b) skipping inter-thread-communication when there are no pending
		3900	watchers is very beneficial):
		3901
		3902	static void
		3903	l_invoke (EV_P)
		3904	{
		3905	userdata *u = ev_userdata (EV_A);
		3906
		3907	while (ev_pending_count (EV_A))
		3908	{
		3909	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3910	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3911	}
		3912	}
		3913
		3914	Now, whenever the main thread gets told to invoke pending watchers, it
		3915	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3916	thread to continue:
		3917
		3918	static void
		3919	real_invoke_pending (EV_P)
		3920	{
		3921	userdata *u = ev_userdata (EV_A);
		3922
		3923	pthread_mutex_lock (&u->lock);
		3924	ev_invoke_pending (EV_A);
		3925	pthread_cond_signal (&u->invoke_cv);
		3926	pthread_mutex_unlock (&u->lock);
		3927	}
		3928
		3929	Whenever you want to start/stop a watcher or do other modifications to an
		3930	event loop, you will now have to lock:
		3931
		3932	ev_timer timeout_watcher;
		3933	userdata *u = ev_userdata (EV_A);
		3934
		3935	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3936
		3937	pthread_mutex_lock (&u->lock);
		3938	ev_timer_start (EV_A_ &timeout_watcher);
		3939	ev_async_send (EV_A_ &u->async_w);
		3940	pthread_mutex_unlock (&u->lock);
		3941
		3942	Note that sending the C<ev_async> watcher is required because otherwise
		3943	an event loop currently blocking in the kernel will have no knowledge
		3944	about the newly added timer. By waking up the loop it will pick up any new
		3945	watchers in the next event loop iteration.
		3946
		3947	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3948
		3949	While the overhead of a callback that e.g. schedules a thread is small, it
		3950	is still an overhead. If you embed libev, and your main usage is with some
		3951	kind of threads or coroutines, you might want to customise libev so that
		3952	doesn't need callbacks anymore.
		3953
		3954	Imagine you have coroutines that you can switch to using a function
		3955	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3956	and that due to some magic, the currently active coroutine is stored in a
		3957	global called C<current_coro>. Then you can build your own "wait for libev
		3958	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3959	the differing C<;> conventions):
		3960
		3961	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3962	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3963
		3964	That means instead of having a C callback function, you store the
		3965	coroutine to switch to in each watcher, and instead of having libev call
		3966	your callback, you instead have it switch to that coroutine.
		3967
		3968	A coroutine might now wait for an event with a function called
		3969	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3970	matter when, or whether the watcher is active or not when this function is
		3971	called):
		3972
		3973	void
		3974	wait_for_event (ev_watcher *w)
		3975	{
		3976	ev_set_cb (w, current_coro);
		3977	switch_to (libev_coro);
		3978	}
		3979
		3980	That basically suspends the coroutine inside C<wait_for_event> and
		3981	continues the libev coroutine, which, when appropriate, switches back to
		3982	this or any other coroutine.
		3983
		3984	You can do similar tricks if you have, say, threads with an event queue -
		3985	instead of storing a coroutine, you store the queue object and instead of
		3986	switching to a coroutine, you push the watcher onto the queue and notify
		3987	any waiters.
		3988
		3989	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3990	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3991
		3992	// my_ev.h
		3993	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3994	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3995	#include "../libev/ev.h"
		3996
		3997	// my_ev.c
		3998	#define EV_H "my_ev.h"
		3999	#include "../libev/ev.c"
		4000
		4001	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4002	F<my_ev.c> into your project. When properly specifying include paths, you
		4003	can even use F<ev.h> as header file name directly.
2823		4004
2824		4005
2825	=head1 LIBEVENT EMULATION	4006	=head1 LIBEVENT EMULATION
2826		4007
2827	Libev offers a compatibility emulation layer for libevent. It cannot	4008	Libev offers a compatibility emulation layer for libevent. It cannot
2828	emulate the internals of libevent, so here are some usage hints:	4009	emulate the internals of libevent, so here are some usage hints:
2829		4010
2830	=over 4	4011	=over 4
		4012
		4013	=item * Only the libevent-1.4.1-beta API is being emulated.
		4014
		4015	This was the newest libevent version available when libev was implemented,
		4016	and is still mostly unchanged in 2010.
2831		4017
2832	=item * Use it by including <event.h>, as usual.	4018	=item * Use it by including <event.h>, as usual.
2833		4019
2834	=item * The following members are fully supported: ev_base, ev_callback,	4020	=item * The following members are fully supported: ev_base, ev_callback,
2835	ev_arg, ev_fd, ev_res, ev_events.	4021	ev_arg, ev_fd, ev_res, ev_events.
…		…
2841	=item * Priorities are not currently supported. Initialising priorities	4027	=item * Priorities are not currently supported. Initialising priorities
2842	will fail and all watchers will have the same priority, even though there	4028	will fail and all watchers will have the same priority, even though there
2843	is an ev_pri field.	4029	is an ev_pri field.
2844		4030
2845	=item * In libevent, the last base created gets the signals, in libev, the	4031	=item * In libevent, the last base created gets the signals, in libev, the
2846	first base created (== the default loop) gets the signals.	4032	base that registered the signal gets the signals.
2847		4033
2848	=item * Other members are not supported.	4034	=item * Other members are not supported.
2849		4035
2850	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4036	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2851	to use the libev header file and library.	4037	to use the libev header file and library.
2852		4038
2853	=back	4039	=back
2854		4040
2855	=head1 C++ SUPPORT	4041	=head1 C++ SUPPORT
		4042
		4043	=head2 C API
		4044
		4045	The normal C API should work fine when used from C++: both ev.h and the
		4046	libev sources can be compiled as C++. Therefore, code that uses the C API
		4047	will work fine.
		4048
		4049	Proper exception specifications might have to be added to callbacks passed
		4050	to libev: exceptions may be thrown only from watcher callbacks, all other
		4051	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4052	callbacks) must not throw exceptions, and might need a C<noexcept>
		4053	specification. If you have code that needs to be compiled as both C and
		4054	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4055
		4056	static void
		4057	fatal_error (const char *msg) EV_NOEXCEPT
		4058	{
		4059	perror (msg);
		4060	abort ();
		4061	}
		4062
		4063	...
		4064	ev_set_syserr_cb (fatal_error);
		4065
		4066	The only API functions that can currently throw exceptions are C<ev_run>,
		4067	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4068	because it runs cleanup watchers).
		4069
		4070	Throwing exceptions in watcher callbacks is only supported if libev itself
		4071	is compiled with a C++ compiler or your C and C++ environments allow
		4072	throwing exceptions through C libraries (most do).
		4073
		4074	=head2 C++ API
2856		4075
2857	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4076	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2858	you to use some convenience methods to start/stop watchers and also change	4077	you to use some convenience methods to start/stop watchers and also change
2859	the callback model to a model using method callbacks on objects.	4078	the callback model to a model using method callbacks on objects.
2860		4079
2861	To use it,	4080	To use it,
2862		4081
2863	#include <ev++.h>	4082	#include <ev++.h>
2864		4083
2865	This automatically includes F<ev.h> and puts all of its definitions (many	4084	This automatically includes F<ev.h> and puts all of its definitions (many
2866	of them macros) into the global namespace. All C++ specific things are	4085	of them macros) into the global namespace. All C++ specific things are
2867	put into the C<ev> namespace. It should support all the same embedding	4086	put into the C<ev> namespace. It should support all the same embedding
…		…
2870	Care has been taken to keep the overhead low. The only data member the C++	4089	Care has been taken to keep the overhead low. The only data member the C++
2871	classes add (compared to plain C-style watchers) is the event loop pointer	4090	classes add (compared to plain C-style watchers) is the event loop pointer
2872	that the watcher is associated with (or no additional members at all if	4091	that the watcher is associated with (or no additional members at all if
2873	you disable C<EV_MULTIPLICITY> when embedding libev).	4092	you disable C<EV_MULTIPLICITY> when embedding libev).
2874		4093
2875	Currently, functions, and static and non-static member functions can be	4094	Currently, functions, static and non-static member functions and classes
2876	used as callbacks. Other types should be easy to add as long as they only	4095	with C<operator ()> can be used as callbacks. Other types should be easy
2877	need one additional pointer for context. If you need support for other	4096	to add as long as they only need one additional pointer for context. If
2878	types of functors please contact the author (preferably after implementing	4097	you need support for other types of functors please contact the author
2879	it).	4098	(preferably after implementing it).
		4099
		4100	For all this to work, your C++ compiler either has to use the same calling
		4101	conventions as your C compiler (for static member functions), or you have
		4102	to embed libev and compile libev itself as C++.
2880		4103
2881	Here is a list of things available in the C<ev> namespace:	4104	Here is a list of things available in the C<ev> namespace:
2882		4105
2883	=over 4	4106	=over 4
2884		4107
…		…
2894	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4117	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2895		4118
2896	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4119	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2897	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4120	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2898	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4121	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2899	defines by many implementations.	4122	defined by many implementations.
2900		4123
2901	All of those classes have these methods:	4124	All of those classes have these methods:
2902		4125
2903	=over 4	4126	=over 4
2904		4127
2905	=item ev::TYPE::TYPE ()	4128	=item ev::TYPE::TYPE ()
2906		4129
2907	=item ev::TYPE::TYPE (struct ev_loop *)	4130	=item ev::TYPE::TYPE (loop)
2908		4131
2909	=item ev::TYPE::~TYPE	4132	=item ev::TYPE::~TYPE
2910		4133
2911	The constructor (optionally) takes an event loop to associate the watcher	4134	The constructor (optionally) takes an event loop to associate the watcher
2912	with. If it is omitted, it will use C<EV_DEFAULT>.	4135	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2945	myclass obj;	4168	myclass obj;
2946	ev::io iow;	4169	ev::io iow;
2947	iow.set <myclass, &myclass::io_cb> (&obj);	4170	iow.set <myclass, &myclass::io_cb> (&obj);
2948		4171
2949	=item w->set (object *)	4172	=item w->set (object *)
2950
2951	This is an B<experimental> feature that might go away in a future version.
2952		4173
2953	This is a variation of a method callback - leaving out the method to call	4174	This is a variation of a method callback - leaving out the method to call
2954	will default the method to C<operator ()>, which makes it possible to use	4175	will default the method to C<operator ()>, which makes it possible to use
2955	functor objects without having to manually specify the C<operator ()> all	4176	functor objects without having to manually specify the C<operator ()> all
2956	the time. Incidentally, you can then also leave out the template argument	4177	the time. Incidentally, you can then also leave out the template argument
…		…
2968	void operator() (ev::io &w, int revents)	4189	void operator() (ev::io &w, int revents)
2969	{	4190	{
2970	...	4191	...
2971	}	4192	}
2972	}	4193	}
2973		4194
2974	myfunctor f;	4195	myfunctor f;
2975		4196
2976	ev::io w;	4197	ev::io w;
2977	w.set (&f);	4198	w.set (&f);
2978		4199
…		…
2989	Example: Use a plain function as callback.	4210	Example: Use a plain function as callback.
2990		4211
2991	static void io_cb (ev::io &w, int revents) { }	4212	static void io_cb (ev::io &w, int revents) { }
2992	iow.set <io_cb> ();	4213	iow.set <io_cb> ();
2993		4214
2994	=item w->set (struct ev_loop *)	4215	=item w->set (loop)
2995		4216
2996	Associates a different C<struct ev_loop> with this watcher. You can only	4217	Associates a different C<struct ev_loop> with this watcher. You can only
2997	do this when the watcher is inactive (and not pending either).	4218	do this when the watcher is inactive (and not pending either).
2998		4219
2999	=item w->set ([arguments])	4220	=item w->set ([arguments])
3000		4221
3001	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4222	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4223	with the same arguments. Either this method or a suitable start method
3002	called at least once. Unlike the C counterpart, an active watcher gets	4224	must be called at least once. Unlike the C counterpart, an active watcher
3003	automatically stopped and restarted when reconfiguring it with this	4225	gets automatically stopped and restarted when reconfiguring it with this
3004	method.	4226	method.
		4227
		4228	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4229	clashing with the C<set (loop)> method.
3005		4230
3006	=item w->start ()	4231	=item w->start ()
3007		4232
3008	Starts the watcher. Note that there is no C<loop> argument, as the	4233	Starts the watcher. Note that there is no C<loop> argument, as the
3009	constructor already stores the event loop.	4234	constructor already stores the event loop.
3010		4235
		4236	=item w->start ([arguments])
		4237
		4238	Instead of calling C<set> and C<start> methods separately, it is often
		4239	convenient to wrap them in one call. Uses the same type of arguments as
		4240	the configure C<set> method of the watcher.
		4241
3011	=item w->stop ()	4242	=item w->stop ()
3012		4243
3013	Stops the watcher if it is active. Again, no C<loop> argument.	4244	Stops the watcher if it is active. Again, no C<loop> argument.
3014		4245
3015	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4246	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3027		4258
3028	=back	4259	=back
3029		4260
3030	=back	4261	=back
3031		4262
3032	Example: Define a class with an IO and idle watcher, start one of them in	4263	Example: Define a class with two I/O and idle watchers, start the I/O
3033	the constructor.	4264	watchers in the constructor.
3034		4265
3035	class myclass	4266	class myclass
3036	{	4267	{
3037	ev::io io ; void io_cb (ev::io &w, int revents);	4268	ev::io io ; void io_cb (ev::io &w, int revents);
		4269	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3038	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4270	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3039		4271
3040	myclass (int fd)	4272	myclass (int fd)
3041	{	4273	{
3042	io .set <myclass, &myclass::io_cb > (this);	4274	io .set <myclass, &myclass::io_cb > (this);
		4275	io2 .set <myclass, &myclass::io2_cb > (this);
3043	idle.set <myclass, &myclass::idle_cb> (this);	4276	idle.set <myclass, &myclass::idle_cb> (this);
3044		4277
3045	io.start (fd, ev::READ);	4278	io.set (fd, ev::WRITE); // configure the watcher
		4279	io.start (); // start it whenever convenient
		4280
		4281	io2.start (fd, ev::READ); // set + start in one call
3046	}	4282	}
3047	};	4283	};
3048		4284
3049		4285
3050	=head1 OTHER LANGUAGE BINDINGS	4286	=head1 OTHER LANGUAGE BINDINGS
…		…
3089	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4325	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3090		4326
3091	=item D	4327	=item D
3092		4328
3093	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4329	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3094	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4330	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3095		4331
3096	=item Ocaml	4332	=item Ocaml
3097		4333
3098	Erkki Seppala has written Ocaml bindings for libev, to be found at	4334	Erkki Seppala has written Ocaml bindings for libev, to be found at
3099	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4335	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4336
		4337	=item Lua
		4338
		4339	Brian Maher has written a partial interface to libev for lua (at the
		4340	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4341	L<http://github.com/brimworks/lua-ev>.
		4342
		4343	=item Javascript
		4344
		4345	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4346
		4347	=item Others
		4348
		4349	There are others, and I stopped counting.
3100		4350
3101	=back	4351	=back
3102		4352
3103		4353
3104	=head1 MACRO MAGIC	4354	=head1 MACRO MAGIC
…		…
3118	loop argument"). The C<EV_A> form is used when this is the sole argument,	4368	loop argument"). The C<EV_A> form is used when this is the sole argument,
3119	C<EV_A_> is used when other arguments are following. Example:	4369	C<EV_A_> is used when other arguments are following. Example:
3120		4370
3121	ev_unref (EV_A);	4371	ev_unref (EV_A);
3122	ev_timer_add (EV_A_ watcher);	4372	ev_timer_add (EV_A_ watcher);
3123	ev_loop (EV_A_ 0);	4373	ev_run (EV_A_ 0);
3124		4374
3125	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4375	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3126	which is often provided by the following macro.	4376	which is often provided by the following macro.
3127		4377
3128	=item C<EV_P>, C<EV_P_>	4378	=item C<EV_P>, C<EV_P_>
…		…
3141	suitable for use with C<EV_A>.	4391	suitable for use with C<EV_A>.
3142		4392
3143	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4393	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3144		4394
3145	Similar to the other two macros, this gives you the value of the default	4395	Similar to the other two macros, this gives you the value of the default
3146	loop, if multiple loops are supported ("ev loop default").	4396	loop, if multiple loops are supported ("ev loop default"). The default loop
		4397	will be initialised if it isn't already initialised.
		4398
		4399	For non-multiplicity builds, these macros do nothing, so you always have
		4400	to initialise the loop somewhere.
3147		4401
3148	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4402	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3149		4403
3150	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4404	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3151	default loop has been initialised (C<UC> == unchecked). Their behaviour	4405	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3168	}	4422	}
3169		4423
3170	ev_check check;	4424	ev_check check;
3171	ev_check_init (&check, check_cb);	4425	ev_check_init (&check, check_cb);
3172	ev_check_start (EV_DEFAULT_ &check);	4426	ev_check_start (EV_DEFAULT_ &check);
3173	ev_loop (EV_DEFAULT_ 0);	4427	ev_run (EV_DEFAULT_ 0);
3174		4428
3175	=head1 EMBEDDING	4429	=head1 EMBEDDING
3176		4430
3177	Libev can (and often is) directly embedded into host	4431	Libev can (and often is) directly embedded into host
3178	applications. Examples of applications that embed it include the Deliantra	4432	applications. Examples of applications that embed it include the Deliantra
…		…
3218	ev_vars.h	4472	ev_vars.h
3219	ev_wrap.h	4473	ev_wrap.h
3220		4474
3221	ev_win32.c required on win32 platforms only	4475	ev_win32.c required on win32 platforms only
3222		4476
3223	ev_select.c only when select backend is enabled (which is enabled by default)	4477	ev_select.c only when select backend is enabled
3224	ev_poll.c only when poll backend is enabled (disabled by default)	4478	ev_poll.c only when poll backend is enabled
3225	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4479	ev_epoll.c only when the epoll backend is enabled
		4480	ev_linuxaio.c only when the linux aio backend is enabled
3226	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4481	ev_kqueue.c only when the kqueue backend is enabled
3227	ev_port.c only when the solaris port backend is enabled (disabled by default)	4482	ev_port.c only when the solaris port backend is enabled
3228		4483
3229	F<ev.c> includes the backend files directly when enabled, so you only need	4484	F<ev.c> includes the backend files directly when enabled, so you only need
3230	to compile this single file.	4485	to compile this single file.
3231		4486
3232	=head3 LIBEVENT COMPATIBILITY API	4487	=head3 LIBEVENT COMPATIBILITY API
…		…
3258	libev.m4	4513	libev.m4
3259		4514
3260	=head2 PREPROCESSOR SYMBOLS/MACROS	4515	=head2 PREPROCESSOR SYMBOLS/MACROS
3261		4516
3262	Libev can be configured via a variety of preprocessor symbols you have to	4517	Libev can be configured via a variety of preprocessor symbols you have to
3263	define before including any of its files. The default in the absence of	4518	define before including (or compiling) any of its files. The default in
3264	autoconf is documented for every option.	4519	the absence of autoconf is documented for every option.
		4520
		4521	Symbols marked with "(h)" do not change the ABI, and can have different
		4522	values when compiling libev vs. including F<ev.h>, so it is permissible
		4523	to redefine them before including F<ev.h> without breaking compatibility
		4524	to a compiled library. All other symbols change the ABI, which means all
		4525	users of libev and the libev code itself must be compiled with compatible
		4526	settings.
3265		4527
3266	=over 4	4528	=over 4
3267		4529
		4530	=item EV_COMPAT3 (h)
		4531
		4532	Backwards compatibility is a major concern for libev. This is why this
		4533	release of libev comes with wrappers for the functions and symbols that
		4534	have been renamed between libev version 3 and 4.
		4535
		4536	You can disable these wrappers (to test compatibility with future
		4537	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4538	sources. This has the additional advantage that you can drop the C<struct>
		4539	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4540	typedef in that case.
		4541
		4542	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4543	and in some even more future version the compatibility code will be
		4544	removed completely.
		4545
3268	=item EV_STANDALONE	4546	=item EV_STANDALONE (h)
3269		4547
3270	Must always be C<1> if you do not use autoconf configuration, which	4548	Must always be C<1> if you do not use autoconf configuration, which
3271	keeps libev from including F<config.h>, and it also defines dummy	4549	keeps libev from including F<config.h>, and it also defines dummy
3272	implementations for some libevent functions (such as logging, which is not	4550	implementations for some libevent functions (such as logging, which is not
3273	supported). It will also not define any of the structs usually found in	4551	supported). It will also not define any of the structs usually found in
3274	F<event.h> that are not directly supported by the libev core alone.	4552	F<event.h> that are not directly supported by the libev core alone.
3275		4553
3276	In stanbdalone mode, libev will still try to automatically deduce the	4554	In standalone mode, libev will still try to automatically deduce the
3277	configuration, but has to be more conservative.	4555	configuration, but has to be more conservative.
		4556
		4557	=item EV_USE_FLOOR
		4558
		4559	If defined to be C<1>, libev will use the C<floor ()> function for its
		4560	periodic reschedule calculations, otherwise libev will fall back on a
		4561	portable (slower) implementation. If you enable this, you usually have to
		4562	link against libm or something equivalent. Enabling this when the C<floor>
		4563	function is not available will fail, so the safe default is to not enable
		4564	this.
3278		4565
3279	=item EV_USE_MONOTONIC	4566	=item EV_USE_MONOTONIC
3280		4567
3281	If defined to be C<1>, libev will try to detect the availability of the	4568	If defined to be C<1>, libev will try to detect the availability of the
3282	monotonic clock option at both compile time and runtime. Otherwise no	4569	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3346	be used is the winsock select). This means that it will call	4633	be used is the winsock select). This means that it will call
3347	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4634	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3348	it is assumed that all these functions actually work on fds, even	4635	it is assumed that all these functions actually work on fds, even
3349	on win32. Should not be defined on non-win32 platforms.	4636	on win32. Should not be defined on non-win32 platforms.
3350		4637
3351	=item EV_FD_TO_WIN32_HANDLE	4638	=item EV_FD_TO_WIN32_HANDLE(fd)
3352		4639
3353	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4640	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3354	file descriptors to socket handles. When not defining this symbol (the	4641	file descriptors to socket handles. When not defining this symbol (the
3355	default), then libev will call C<_get_osfhandle>, which is usually	4642	default), then libev will call C<_get_osfhandle>, which is usually
3356	correct. In some cases, programs use their own file descriptor management,	4643	correct. In some cases, programs use their own file descriptor management,
3357	in which case they can provide this function to map fds to socket handles.	4644	in which case they can provide this function to map fds to socket handles.
3358		4645
		4646	=item EV_WIN32_HANDLE_TO_FD(handle)
		4647
		4648	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4649	using the standard C<_open_osfhandle> function. For programs implementing
		4650	their own fd to handle mapping, overwriting this function makes it easier
		4651	to do so. This can be done by defining this macro to an appropriate value.
		4652
		4653	=item EV_WIN32_CLOSE_FD(fd)
		4654
		4655	If programs implement their own fd to handle mapping on win32, then this
		4656	macro can be used to override the C<close> function, useful to unregister
		4657	file descriptors again. Note that the replacement function has to close
		4658	the underlying OS handle.
		4659
		4660	=item EV_USE_WSASOCKET
		4661
		4662	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4663	communication socket, which works better in some environments. Otherwise,
		4664	the normal C<socket> function will be used, which works better in other
		4665	environments.
		4666
3359	=item EV_USE_POLL	4667	=item EV_USE_POLL
3360		4668
3361	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4669	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3362	backend. Otherwise it will be enabled on non-win32 platforms. It	4670	backend. Otherwise it will be enabled on non-win32 platforms. It
3363	takes precedence over select.	4671	takes precedence over select.
…		…
3367	If defined to be C<1>, libev will compile in support for the Linux	4675	If defined to be C<1>, libev will compile in support for the Linux
3368	C<epoll>(7) backend. Its availability will be detected at runtime,	4676	C<epoll>(7) backend. Its availability will be detected at runtime,
3369	otherwise another method will be used as fallback. This is the preferred	4677	otherwise another method will be used as fallback. This is the preferred
3370	backend for GNU/Linux systems. If undefined, it will be enabled if the	4678	backend for GNU/Linux systems. If undefined, it will be enabled if the
3371	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4679	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4680
		4681	=item EV_USE_LINUXAIO
		4682
		4683	If defined to be C<1>, libev will compile in support for the Linux
		4684	aio backend. Due to it's currenbt limitations it has to be requested
		4685	explicitly. If undefined, it will be enabled on linux, otherwise
		4686	disabled.
3372		4687
3373	=item EV_USE_KQUEUE	4688	=item EV_USE_KQUEUE
3374		4689
3375	If defined to be C<1>, libev will compile in support for the BSD style	4690	If defined to be C<1>, libev will compile in support for the BSD style
3376	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4691	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3398	If defined to be C<1>, libev will compile in support for the Linux inotify	4713	If defined to be C<1>, libev will compile in support for the Linux inotify
3399	interface to speed up C<ev_stat> watchers. Its actual availability will	4714	interface to speed up C<ev_stat> watchers. Its actual availability will
3400	be detected at runtime. If undefined, it will be enabled if the headers	4715	be detected at runtime. If undefined, it will be enabled if the headers
3401	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4716	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3402		4717
		4718	=item EV_NO_SMP
		4719
		4720	If defined to be C<1>, libev will assume that memory is always coherent
		4721	between threads, that is, threads can be used, but threads never run on
		4722	different cpus (or different cpu cores). This reduces dependencies
		4723	and makes libev faster.
		4724
		4725	=item EV_NO_THREADS
		4726
		4727	If defined to be C<1>, libev will assume that it will never be called from
		4728	different threads (that includes signal handlers), which is a stronger
		4729	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4730	libev faster.
		4731
3403	=item EV_ATOMIC_T	4732	=item EV_ATOMIC_T
3404		4733
3405	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4734	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3406	access is atomic with respect to other threads or signal contexts. No such	4735	access is atomic with respect to other threads or signal contexts. No
3407	type is easily found in the C language, so you can provide your own type	4736	such type is easily found in the C language, so you can provide your own
3408	that you know is safe for your purposes. It is used both for signal handler "locking"	4737	type that you know is safe for your purposes. It is used both for signal
3409	as well as for signal and thread safety in C<ev_async> watchers.	4738	handler "locking" as well as for signal and thread safety in C<ev_async>
		4739	watchers.
3410		4740
3411	In the absence of this define, libev will use C<sig_atomic_t volatile>	4741	In the absence of this define, libev will use C<sig_atomic_t volatile>
3412	(from F<signal.h>), which is usually good enough on most platforms.	4742	(from F<signal.h>), which is usually good enough on most platforms.
3413		4743
3414	=item EV_H	4744	=item EV_H (h)
3415		4745
3416	The name of the F<ev.h> header file used to include it. The default if	4746	The name of the F<ev.h> header file used to include it. The default if
3417	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4747	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3418	used to virtually rename the F<ev.h> header file in case of conflicts.	4748	used to virtually rename the F<ev.h> header file in case of conflicts.
3419		4749
3420	=item EV_CONFIG_H	4750	=item EV_CONFIG_H (h)
3421		4751
3422	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4752	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3423	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4753	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3424	C<EV_H>, above.	4754	C<EV_H>, above.
3425		4755
3426	=item EV_EVENT_H	4756	=item EV_EVENT_H (h)
3427		4757
3428	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4758	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3429	of how the F<event.h> header can be found, the default is C<"event.h">.	4759	of how the F<event.h> header can be found, the default is C<"event.h">.
3430		4760
3431	=item EV_PROTOTYPES	4761	=item EV_PROTOTYPES (h)
3432		4762
3433	If defined to be C<0>, then F<ev.h> will not define any function	4763	If defined to be C<0>, then F<ev.h> will not define any function
3434	prototypes, but still define all the structs and other symbols. This is	4764	prototypes, but still define all the structs and other symbols. This is
3435	occasionally useful if you want to provide your own wrapper functions	4765	occasionally useful if you want to provide your own wrapper functions
3436	around libev functions.	4766	around libev functions.
…		…
3441	will have the C<struct ev_loop *> as first argument, and you can create	4771	will have the C<struct ev_loop *> as first argument, and you can create
3442	additional independent event loops. Otherwise there will be no support	4772	additional independent event loops. Otherwise there will be no support
3443	for multiple event loops and there is no first event loop pointer	4773	for multiple event loops and there is no first event loop pointer
3444	argument. Instead, all functions act on the single default loop.	4774	argument. Instead, all functions act on the single default loop.
3445		4775
		4776	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4777	default loop when multiplicity is switched off - you always have to
		4778	initialise the loop manually in this case.
		4779
3446	=item EV_MINPRI	4780	=item EV_MINPRI
3447		4781
3448	=item EV_MAXPRI	4782	=item EV_MAXPRI
3449		4783
3450	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4784	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3458	fine.	4792	fine.
3459		4793
3460	If your embedding application does not need any priorities, defining these	4794	If your embedding application does not need any priorities, defining these
3461	both to C<0> will save some memory and CPU.	4795	both to C<0> will save some memory and CPU.
3462		4796
3463	=item EV_PERIODIC_ENABLE	4797	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4798	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4799	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3464		4800
3465	If undefined or defined to be C<1>, then periodic timers are supported. If	4801	If undefined or defined to be C<1> (and the platform supports it), then
3466	defined to be C<0>, then they are not. Disabling them saves a few kB of	4802	the respective watcher type is supported. If defined to be C<0>, then it
3467	code.	4803	is not. Disabling watcher types mainly saves code size.
3468		4804
3469	=item EV_IDLE_ENABLE	4805	=item EV_FEATURES
3470
3471	If undefined or defined to be C<1>, then idle watchers are supported. If
3472	defined to be C<0>, then they are not. Disabling them saves a few kB of
3473	code.
3474
3475	=item EV_EMBED_ENABLE
3476
3477	If undefined or defined to be C<1>, then embed watchers are supported. If
3478	defined to be C<0>, then they are not. Embed watchers rely on most other
3479	watcher types, which therefore must not be disabled.
3480
3481	=item EV_STAT_ENABLE
3482
3483	If undefined or defined to be C<1>, then stat watchers are supported. If
3484	defined to be C<0>, then they are not.
3485
3486	=item EV_FORK_ENABLE
3487
3488	If undefined or defined to be C<1>, then fork watchers are supported. If
3489	defined to be C<0>, then they are not.
3490
3491	=item EV_ASYNC_ENABLE
3492
3493	If undefined or defined to be C<1>, then async watchers are supported. If
3494	defined to be C<0>, then they are not.
3495
3496	=item EV_MINIMAL
3497		4806
3498	If you need to shave off some kilobytes of code at the expense of some	4807	If you need to shave off some kilobytes of code at the expense of some
3499	speed, define this symbol to C<1>. Currently this is used to override some	4808	speed (but with the full API), you can define this symbol to request
3500	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4809	certain subsets of functionality. The default is to enable all features
3501	much smaller 2-heap for timer management over the default 4-heap.	4810	that can be enabled on the platform.
		4811
		4812	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4813	with some broad features you want) and then selectively re-enable
		4814	additional parts you want, for example if you want everything minimal,
		4815	but multiple event loop support, async and child watchers and the poll
		4816	backend, use this:
		4817
		4818	#define EV_FEATURES 0
		4819	#define EV_MULTIPLICITY 1
		4820	#define EV_USE_POLL 1
		4821	#define EV_CHILD_ENABLE 1
		4822	#define EV_ASYNC_ENABLE 1
		4823
		4824	The actual value is a bitset, it can be a combination of the following
		4825	values (by default, all of these are enabled):
		4826
		4827	=over 4
		4828
		4829	=item C<1> - faster/larger code
		4830
		4831	Use larger code to speed up some operations.
		4832
		4833	Currently this is used to override some inlining decisions (enlarging the
		4834	code size by roughly 30% on amd64).
		4835
		4836	When optimising for size, use of compiler flags such as C<-Os> with
		4837	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4838	assertions.
		4839
		4840	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4841	(e.g. gcc with C<-Os>).
		4842
		4843	=item C<2> - faster/larger data structures
		4844
		4845	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4846	hash table sizes and so on. This will usually further increase code size
		4847	and can additionally have an effect on the size of data structures at
		4848	runtime.
		4849
		4850	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4851	(e.g. gcc with C<-Os>).
		4852
		4853	=item C<4> - full API configuration
		4854
		4855	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4856	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4857
		4858	=item C<8> - full API
		4859
		4860	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4861	details on which parts of the API are still available without this
		4862	feature, and do not complain if this subset changes over time.
		4863
		4864	=item C<16> - enable all optional watcher types
		4865
		4866	Enables all optional watcher types. If you want to selectively enable
		4867	only some watcher types other than I/O and timers (e.g. prepare,
		4868	embed, async, child...) you can enable them manually by defining
		4869	C<EV_watchertype_ENABLE> to C<1> instead.
		4870
		4871	=item C<32> - enable all backends
		4872
		4873	This enables all backends - without this feature, you need to enable at
		4874	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4875
		4876	=item C<64> - enable OS-specific "helper" APIs
		4877
		4878	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4879	default.
		4880
		4881	=back
		4882
		4883	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4884	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4885	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4886	watchers, timers and monotonic clock support.
		4887
		4888	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4889	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4890	your program might be left out as well - a binary starting a timer and an
		4891	I/O watcher then might come out at only 5Kb.
		4892
		4893	=item EV_API_STATIC
		4894
		4895	If this symbol is defined (by default it is not), then all identifiers
		4896	will have static linkage. This means that libev will not export any
		4897	identifiers, and you cannot link against libev anymore. This can be useful
		4898	when you embed libev, only want to use libev functions in a single file,
		4899	and do not want its identifiers to be visible.
		4900
		4901	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4902	wants to use libev.
		4903
		4904	This option only works when libev is compiled with a C compiler, as C++
		4905	doesn't support the required declaration syntax.
		4906
		4907	=item EV_AVOID_STDIO
		4908
		4909	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4910	functions (printf, scanf, perror etc.). This will increase the code size
		4911	somewhat, but if your program doesn't otherwise depend on stdio and your
		4912	libc allows it, this avoids linking in the stdio library which is quite
		4913	big.
		4914
		4915	Note that error messages might become less precise when this option is
		4916	enabled.
		4917
		4918	=item EV_NSIG
		4919
		4920	The highest supported signal number, +1 (or, the number of
		4921	signals): Normally, libev tries to deduce the maximum number of signals
		4922	automatically, but sometimes this fails, in which case it can be
		4923	specified. Also, using a lower number than detected (C<32> should be
		4924	good for about any system in existence) can save some memory, as libev
		4925	statically allocates some 12-24 bytes per signal number.
3502		4926
3503	=item EV_PID_HASHSIZE	4927	=item EV_PID_HASHSIZE
3504		4928
3505	C<ev_child> watchers use a small hash table to distribute workload by	4929	C<ev_child> watchers use a small hash table to distribute workload by
3506	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4930	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3507	than enough. If you need to manage thousands of children you might want to	4931	usually more than enough. If you need to manage thousands of children you
3508	increase this value (I<must> be a power of two).	4932	might want to increase this value (I<must> be a power of two).
3509		4933
3510	=item EV_INOTIFY_HASHSIZE	4934	=item EV_INOTIFY_HASHSIZE
3511		4935
3512	C<ev_stat> watchers use a small hash table to distribute workload by	4936	C<ev_stat> watchers use a small hash table to distribute workload by
3513	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4937	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3514	usually more than enough. If you need to manage thousands of C<ev_stat>	4938	disabled), usually more than enough. If you need to manage thousands of
3515	watchers you might want to increase this value (I<must> be a power of	4939	C<ev_stat> watchers you might want to increase this value (I<must> be a
3516	two).	4940	power of two).
3517		4941
3518	=item EV_USE_4HEAP	4942	=item EV_USE_4HEAP
3519		4943
3520	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4944	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3521	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4945	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3522	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4946	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3523	faster performance with many (thousands) of watchers.	4947	faster performance with many (thousands) of watchers.
3524		4948
3525	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4949	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3526	(disabled).	4950	will be C<0>.
3527		4951
3528	=item EV_HEAP_CACHE_AT	4952	=item EV_HEAP_CACHE_AT
3529		4953
3530	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4954	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3531	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4955	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3532	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4956	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3533	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4957	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3534	but avoids random read accesses on heap changes. This improves performance	4958	but avoids random read accesses on heap changes. This improves performance
3535	noticeably with many (hundreds) of watchers.	4959	noticeably with many (hundreds) of watchers.
3536		4960
3537	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4961	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3538	(disabled).	4962	will be C<0>.
3539		4963
3540	=item EV_VERIFY	4964	=item EV_VERIFY
3541		4965
3542	Controls how much internal verification (see C<ev_loop_verify ()>) will	4966	Controls how much internal verification (see C<ev_verify ()>) will
3543	be done: If set to C<0>, no internal verification code will be compiled	4967	be done: If set to C<0>, no internal verification code will be compiled
3544	in. If set to C<1>, then verification code will be compiled in, but not	4968	in. If set to C<1>, then verification code will be compiled in, but not
3545	called. If set to C<2>, then the internal verification code will be	4969	called. If set to C<2>, then the internal verification code will be
3546	called once per loop, which can slow down libev. If set to C<3>, then the	4970	called once per loop, which can slow down libev. If set to C<3>, then the
3547	verification code will be called very frequently, which will slow down	4971	verification code will be called very frequently, which will slow down
3548	libev considerably.	4972	libev considerably.
3549		4973
3550	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4974	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3551	C<0>.	4975	will be C<0>.
3552		4976
3553	=item EV_COMMON	4977	=item EV_COMMON
3554		4978
3555	By default, all watchers have a C<void *data> member. By redefining	4979	By default, all watchers have a C<void *data> member. By redefining
3556	this macro to a something else you can include more and other types of	4980	this macro to something else you can include more and other types of
3557	members. You have to define it each time you include one of the files,	4981	members. You have to define it each time you include one of the files,
3558	though, and it must be identical each time.	4982	though, and it must be identical each time.
3559		4983
3560	For example, the perl EV module uses something like this:	4984	For example, the perl EV module uses something like this:
3561		4985
…		…
3614	file.	5038	file.
3615		5039
3616	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5040	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3617	that everybody includes and which overrides some configure choices:	5041	that everybody includes and which overrides some configure choices:
3618		5042
3619	#define EV_MINIMAL 1	5043	#define EV_FEATURES 8
3620	#define EV_USE_POLL 0	5044	#define EV_USE_SELECT 1
3621	#define EV_MULTIPLICITY 0
3622	#define EV_PERIODIC_ENABLE 0	5045	#define EV_PREPARE_ENABLE 1
		5046	#define EV_IDLE_ENABLE 1
3623	#define EV_STAT_ENABLE 0	5047	#define EV_SIGNAL_ENABLE 1
3624	#define EV_FORK_ENABLE 0	5048	#define EV_CHILD_ENABLE 1
		5049	#define EV_USE_STDEXCEPT 0
3625	#define EV_CONFIG_H <config.h>	5050	#define EV_CONFIG_H <config.h>
3626	#define EV_MINPRI 0
3627	#define EV_MAXPRI 0
3628		5051
3629	#include "ev++.h"	5052	#include "ev++.h"
3630		5053
3631	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5054	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3632		5055
3633	#include "ev_cpp.h"	5056	#include "ev_cpp.h"
3634	#include "ev.c"	5057	#include "ev.c"
3635		5058
3636	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5059	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3637		5060
3638	=head2 THREADS AND COROUTINES	5061	=head2 THREADS AND COROUTINES
3639		5062
3640	=head3 THREADS	5063	=head3 THREADS
3641		5064
…		…
3692	default loop and triggering an C<ev_async> watcher from the default loop	5115	default loop and triggering an C<ev_async> watcher from the default loop
3693	watcher callback into the event loop interested in the signal.	5116	watcher callback into the event loop interested in the signal.
3694		5117
3695	=back	5118	=back
3696		5119
		5120	See also L</THREAD LOCKING EXAMPLE>.
		5121
3697	=head3 COROUTINES	5122	=head3 COROUTINES
3698		5123
3699	Libev is very accommodating to coroutines ("cooperative threads"):	5124	Libev is very accommodating to coroutines ("cooperative threads"):
3700	libev fully supports nesting calls to its functions from different	5125	libev fully supports nesting calls to its functions from different
3701	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5126	coroutines (e.g. you can call C<ev_run> on the same loop from two
3702	different coroutines, and switch freely between both coroutines running the	5127	different coroutines, and switch freely between both coroutines running
3703	loop, as long as you don't confuse yourself). The only exception is that	5128	the loop, as long as you don't confuse yourself). The only exception is
3704	you must not do this from C<ev_periodic> reschedule callbacks.	5129	that you must not do this from C<ev_periodic> reschedule callbacks.
3705		5130
3706	Care has been taken to ensure that libev does not keep local state inside	5131	Care has been taken to ensure that libev does not keep local state inside
3707	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5132	C<ev_run>, and other calls do not usually allow for coroutine switches as
3708	they do not call any callbacks.	5133	they do not call any callbacks.
3709		5134
3710	=head2 COMPILER WARNINGS	5135	=head2 COMPILER WARNINGS
3711		5136
3712	Depending on your compiler and compiler settings, you might get no or a	5137	Depending on your compiler and compiler settings, you might get no or a
…		…
3723	maintainable.	5148	maintainable.
3724		5149
3725	And of course, some compiler warnings are just plain stupid, or simply	5150	And of course, some compiler warnings are just plain stupid, or simply
3726	wrong (because they don't actually warn about the condition their message	5151	wrong (because they don't actually warn about the condition their message
3727	seems to warn about). For example, certain older gcc versions had some	5152	seems to warn about). For example, certain older gcc versions had some
3728	warnings that resulted an extreme number of false positives. These have	5153	warnings that resulted in an extreme number of false positives. These have
3729	been fixed, but some people still insist on making code warn-free with	5154	been fixed, but some people still insist on making code warn-free with
3730	such buggy versions.	5155	such buggy versions.
3731		5156
3732	While libev is written to generate as few warnings as possible,	5157	While libev is written to generate as few warnings as possible,
3733	"warn-free" code is not a goal, and it is recommended not to build libev	5158	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3769	I suggest using suppression lists.	5194	I suggest using suppression lists.
3770		5195
3771		5196
3772	=head1 PORTABILITY NOTES	5197	=head1 PORTABILITY NOTES
3773		5198
		5199	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5200
		5201	GNU/Linux is the only common platform that supports 64 bit file/large file
		5202	interfaces but I<disables> them by default.
		5203
		5204	That means that libev compiled in the default environment doesn't support
		5205	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5206
		5207	Unfortunately, many programs try to work around this GNU/Linux issue
		5208	by enabling the large file API, which makes them incompatible with the
		5209	standard libev compiled for their system.
		5210
		5211	Likewise, libev cannot enable the large file API itself as this would
		5212	suddenly make it incompatible to the default compile time environment,
		5213	i.e. all programs not using special compile switches.
		5214
		5215	=head2 OS/X AND DARWIN BUGS
		5216
		5217	The whole thing is a bug if you ask me - basically any system interface
		5218	you touch is broken, whether it is locales, poll, kqueue or even the
		5219	OpenGL drivers.
		5220
		5221	=head3 C<kqueue> is buggy
		5222
		5223	The kqueue syscall is broken in all known versions - most versions support
		5224	only sockets, many support pipes.
		5225
		5226	Libev tries to work around this by not using C<kqueue> by default on this
		5227	rotten platform, but of course you can still ask for it when creating a
		5228	loop - embedding a socket-only kqueue loop into a select-based one is
		5229	probably going to work well.
		5230
		5231	=head3 C<poll> is buggy
		5232
		5233	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5234	implementation by something calling C<kqueue> internally around the 10.5.6
		5235	release, so now C<kqueue> I<and> C<poll> are broken.
		5236
		5237	Libev tries to work around this by not using C<poll> by default on
		5238	this rotten platform, but of course you can still ask for it when creating
		5239	a loop.
		5240
		5241	=head3 C<select> is buggy
		5242
		5243	All that's left is C<select>, and of course Apple found a way to fuck this
		5244	one up as well: On OS/X, C<select> actively limits the number of file
		5245	descriptors you can pass in to 1024 - your program suddenly crashes when
		5246	you use more.
		5247
		5248	There is an undocumented "workaround" for this - defining
		5249	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5250	work on OS/X.
		5251
		5252	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5253
		5254	=head3 C<errno> reentrancy
		5255
		5256	The default compile environment on Solaris is unfortunately so
		5257	thread-unsafe that you can't even use components/libraries compiled
		5258	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5259	defined by default. A valid, if stupid, implementation choice.
		5260
		5261	If you want to use libev in threaded environments you have to make sure
		5262	it's compiled with C<_REENTRANT> defined.
		5263
		5264	=head3 Event port backend
		5265
		5266	The scalable event interface for Solaris is called "event
		5267	ports". Unfortunately, this mechanism is very buggy in all major
		5268	releases. If you run into high CPU usage, your program freezes or you get
		5269	a large number of spurious wakeups, make sure you have all the relevant
		5270	and latest kernel patches applied. No, I don't know which ones, but there
		5271	are multiple ones to apply, and afterwards, event ports actually work
		5272	great.
		5273
		5274	If you can't get it to work, you can try running the program by setting
		5275	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5276	C<select> backends.
		5277
		5278	=head2 AIX POLL BUG
		5279
		5280	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5281	this by trying to avoid the poll backend altogether (i.e. it's not even
		5282	compiled in), which normally isn't a big problem as C<select> works fine
		5283	with large bitsets on AIX, and AIX is dead anyway.
		5284
3774	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5285	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5286
		5287	=head3 General issues
3775		5288
3776	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5289	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3777	requires, and its I/O model is fundamentally incompatible with the POSIX	5290	requires, and its I/O model is fundamentally incompatible with the POSIX
3778	model. Libev still offers limited functionality on this platform in	5291	model. Libev still offers limited functionality on this platform in
3779	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5292	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3780	descriptors. This only applies when using Win32 natively, not when using	5293	descriptors. This only applies when using Win32 natively, not when using
3781	e.g. cygwin.	5294	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5295	as every compiler comes with a slightly differently broken/incompatible
		5296	environment.
3782		5297
3783	Lifting these limitations would basically require the full	5298	Lifting these limitations would basically require the full
3784	re-implementation of the I/O system. If you are into these kinds of	5299	re-implementation of the I/O system. If you are into this kind of thing,
3785	things, then note that glib does exactly that for you in a very portable	5300	then note that glib does exactly that for you in a very portable way (note
3786	way (note also that glib is the slowest event library known to man).	5301	also that glib is the slowest event library known to man).
3787		5302
3788	There is no supported compilation method available on windows except	5303	There is no supported compilation method available on windows except
3789	embedding it into other applications.	5304	embedding it into other applications.
		5305
		5306	Sensible signal handling is officially unsupported by Microsoft - libev
		5307	tries its best, but under most conditions, signals will simply not work.
3790		5308
3791	Not a libev limitation but worth mentioning: windows apparently doesn't	5309	Not a libev limitation but worth mentioning: windows apparently doesn't
3792	accept large writes: instead of resulting in a partial write, windows will	5310	accept large writes: instead of resulting in a partial write, windows will
3793	either accept everything or return C<ENOBUFS> if the buffer is too large,	5311	either accept everything or return C<ENOBUFS> if the buffer is too large,
3794	so make sure you only write small amounts into your sockets (less than a	5312	so make sure you only write small amounts into your sockets (less than a
…		…
3799	the abysmal performance of winsockets, using a large number of sockets	5317	the abysmal performance of winsockets, using a large number of sockets
3800	is not recommended (and not reasonable). If your program needs to use	5318	is not recommended (and not reasonable). If your program needs to use
3801	more than a hundred or so sockets, then likely it needs to use a totally	5319	more than a hundred or so sockets, then likely it needs to use a totally
3802	different implementation for windows, as libev offers the POSIX readiness	5320	different implementation for windows, as libev offers the POSIX readiness
3803	notification model, which cannot be implemented efficiently on windows	5321	notification model, which cannot be implemented efficiently on windows
3804	(Microsoft monopoly games).	5322	(due to Microsoft monopoly games).
3805		5323
3806	A typical way to use libev under windows is to embed it (see the embedding	5324	A typical way to use libev under windows is to embed it (see the embedding
3807	section for details) and use the following F<evwrap.h> header file instead	5325	section for details) and use the following F<evwrap.h> header file instead
3808	of F<ev.h>:	5326	of F<ev.h>:
3809		5327
…		…
3816	you do I<not> compile the F<ev.c> or any other embedded source files!):	5334	you do I<not> compile the F<ev.c> or any other embedded source files!):
3817		5335
3818	#include "evwrap.h"	5336	#include "evwrap.h"
3819	#include "ev.c"	5337	#include "ev.c"
3820		5338
3821	=over 4
3822
3823	=item The winsocket select function	5339	=head3 The winsocket C<select> function
3824		5340
3825	The winsocket C<select> function doesn't follow POSIX in that it	5341	The winsocket C<select> function doesn't follow POSIX in that it
3826	requires socket I<handles> and not socket I<file descriptors> (it is	5342	requires socket I<handles> and not socket I<file descriptors> (it is
3827	also extremely buggy). This makes select very inefficient, and also	5343	also extremely buggy). This makes select very inefficient, and also
3828	requires a mapping from file descriptors to socket handles (the Microsoft	5344	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3837	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5353	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3838		5354
3839	Note that winsockets handling of fd sets is O(n), so you can easily get a	5355	Note that winsockets handling of fd sets is O(n), so you can easily get a
3840	complexity in the O(n²) range when using win32.	5356	complexity in the O(n²) range when using win32.
3841		5357
3842	=item Limited number of file descriptors	5358	=head3 Limited number of file descriptors
3843		5359
3844	Windows has numerous arbitrary (and low) limits on things.	5360	Windows has numerous arbitrary (and low) limits on things.
3845		5361
3846	Early versions of winsocket's select only supported waiting for a maximum	5362	Early versions of winsocket's select only supported waiting for a maximum
3847	of C<64> handles (probably owning to the fact that all windows kernels	5363	of C<64> handles (probably owning to the fact that all windows kernels
3848	can only wait for C<64> things at the same time internally; Microsoft	5364	can only wait for C<64> things at the same time internally; Microsoft
3849	recommends spawning a chain of threads and wait for 63 handles and the	5365	recommends spawning a chain of threads and wait for 63 handles and the
3850	previous thread in each. Great).	5366	previous thread in each. Sounds great!).
3851		5367
3852	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5368	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3853	to some high number (e.g. C<2048>) before compiling the winsocket select	5369	to some high number (e.g. C<2048>) before compiling the winsocket select
3854	call (which might be in libev or elsewhere, for example, perl does its own	5370	call (which might be in libev or elsewhere, for example, perl and many
3855	select emulation on windows).	5371	other interpreters do their own select emulation on windows).
3856		5372
3857	Another limit is the number of file descriptors in the Microsoft runtime	5373	Another limit is the number of file descriptors in the Microsoft runtime
3858	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5374	libraries, which by default is C<64> (there must be a hidden I<64>
3859	or something like this inside Microsoft). You can increase this by calling	5375	fetish or something like this inside Microsoft). You can increase this
3860	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5376	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3861	arbitrary limit), but is broken in many versions of the Microsoft runtime	5377	(another arbitrary limit), but is broken in many versions of the Microsoft
3862	libraries.
3863
3864	This might get you to about C<512> or C<2048> sockets (depending on	5378	runtime libraries. This might get you to about C<512> or C<2048> sockets
3865	windows version and/or the phase of the moon). To get more, you need to	5379	(depending on windows version and/or the phase of the moon). To get more,
3866	wrap all I/O functions and provide your own fd management, but the cost of	5380	you need to wrap all I/O functions and provide your own fd management, but
3867	calling select (O(n²)) will likely make this unworkable.	5381	the cost of calling select (O(n²)) will likely make this unworkable.
3868
3869	=back
3870		5382
3871	=head2 PORTABILITY REQUIREMENTS	5383	=head2 PORTABILITY REQUIREMENTS
3872		5384
3873	In addition to a working ISO-C implementation and of course the	5385	In addition to a working ISO-C implementation and of course the
3874	backend-specific APIs, libev relies on a few additional extensions:	5386	backend-specific APIs, libev relies on a few additional extensions:
…		…
3881	Libev assumes not only that all watcher pointers have the same internal	5393	Libev assumes not only that all watcher pointers have the same internal
3882	structure (guaranteed by POSIX but not by ISO C for example), but it also	5394	structure (guaranteed by POSIX but not by ISO C for example), but it also
3883	assumes that the same (machine) code can be used to call any watcher	5395	assumes that the same (machine) code can be used to call any watcher
3884	callback: The watcher callbacks have different type signatures, but libev	5396	callback: The watcher callbacks have different type signatures, but libev
3885	calls them using an C<ev_watcher *> internally.	5397	calls them using an C<ev_watcher *> internally.
		5398
		5399	=item null pointers and integer zero are represented by 0 bytes
		5400
		5401	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5402	relies on this setting pointers and integers to null.
		5403
		5404	=item pointer accesses must be thread-atomic
		5405
		5406	Accessing a pointer value must be atomic, it must both be readable and
		5407	writable in one piece - this is the case on all current architectures.
3886		5408
3887	=item C<sig_atomic_t volatile> must be thread-atomic as well	5409	=item C<sig_atomic_t volatile> must be thread-atomic as well
3888		5410
3889	The type C<sig_atomic_t volatile> (or whatever is defined as	5411	The type C<sig_atomic_t volatile> (or whatever is defined as
3890	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5412	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3899	thread" or will block signals process-wide, both behaviours would	5421	thread" or will block signals process-wide, both behaviours would
3900	be compatible with libev. Interaction between C<sigprocmask> and	5422	be compatible with libev. Interaction between C<sigprocmask> and
3901	C<pthread_sigmask> could complicate things, however.	5423	C<pthread_sigmask> could complicate things, however.
3902		5424
3903	The most portable way to handle signals is to block signals in all threads	5425	The most portable way to handle signals is to block signals in all threads
3904	except the initial one, and run the default loop in the initial thread as	5426	except the initial one, and run the signal handling loop in the initial
3905	well.	5427	thread as well.
3906		5428
3907	=item C<long> must be large enough for common memory allocation sizes	5429	=item C<long> must be large enough for common memory allocation sizes
3908		5430
3909	To improve portability and simplify its API, libev uses C<long> internally	5431	To improve portability and simplify its API, libev uses C<long> internally
3910	instead of C<size_t> when allocating its data structures. On non-POSIX	5432	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3913	watchers.	5435	watchers.
3914		5436
3915	=item C<double> must hold a time value in seconds with enough accuracy	5437	=item C<double> must hold a time value in seconds with enough accuracy
3916		5438
3917	The type C<double> is used to represent timestamps. It is required to	5439	The type C<double> is used to represent timestamps. It is required to
3918	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5440	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3919	enough for at least into the year 4000. This requirement is fulfilled by	5441	good enough for at least into the year 4000 with millisecond accuracy
		5442	(the design goal for libev). This requirement is overfulfilled by
3920	implementations implementing IEEE 754 (basically all existing ones).	5443	implementations using IEEE 754, which is basically all existing ones.
		5444
		5445	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5446	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5447	is either obsolete or somebody patched it to use C<long double> or
		5448	something like that, just kidding).
3921		5449
3922	=back	5450	=back
3923		5451
3924	If you know of other additional requirements drop me a note.	5452	If you know of other additional requirements drop me a note.
3925		5453
…		…
3987	=item Processing ev_async_send: O(number_of_async_watchers)	5515	=item Processing ev_async_send: O(number_of_async_watchers)
3988		5516
3989	=item Processing signals: O(max_signal_number)	5517	=item Processing signals: O(max_signal_number)
3990		5518
3991	Sending involves a system call I<iff> there were no other C<ev_async_send>	5519	Sending involves a system call I<iff> there were no other C<ev_async_send>
3992	calls in the current loop iteration. Checking for async and signal events	5520	calls in the current loop iteration and the loop is currently
		5521	blocked. Checking for async and signal events involves iterating over all
3993	involves iterating over all running async watchers or all signal numbers.	5522	running async watchers or all signal numbers.
3994		5523
3995	=back	5524	=back
3996		5525
3997		5526
		5527	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5528
		5529	The major version 4 introduced some incompatible changes to the API.
		5530
		5531	At the moment, the C<ev.h> header file provides compatibility definitions
		5532	for all changes, so most programs should still compile. The compatibility
		5533	layer might be removed in later versions of libev, so better update to the
		5534	new API early than late.
		5535
		5536	=over 4
		5537
		5538	=item C<EV_COMPAT3> backwards compatibility mechanism
		5539
		5540	The backward compatibility mechanism can be controlled by
		5541	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5542	section.
		5543
		5544	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5545
		5546	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5547
		5548	ev_loop_destroy (EV_DEFAULT_UC);
		5549	ev_loop_fork (EV_DEFAULT);
		5550
		5551	=item function/symbol renames
		5552
		5553	A number of functions and symbols have been renamed:
		5554
		5555	ev_loop => ev_run
		5556	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5557	EVLOOP_ONESHOT => EVRUN_ONCE
		5558
		5559	ev_unloop => ev_break
		5560	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5561	EVUNLOOP_ONE => EVBREAK_ONE
		5562	EVUNLOOP_ALL => EVBREAK_ALL
		5563
		5564	EV_TIMEOUT => EV_TIMER
		5565
		5566	ev_loop_count => ev_iteration
		5567	ev_loop_depth => ev_depth
		5568	ev_loop_verify => ev_verify
		5569
		5570	Most functions working on C<struct ev_loop> objects don't have an
		5571	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5572	associated constants have been renamed to not collide with the C<struct
		5573	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5574	as all other watcher types. Note that C<ev_loop_fork> is still called
		5575	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5576	typedef.
		5577
		5578	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5579
		5580	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5581	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5582	and work, but the library code will of course be larger.
		5583
		5584	=back
		5585
		5586
		5587	=head1 GLOSSARY
		5588
		5589	=over 4
		5590
		5591	=item active
		5592
		5593	A watcher is active as long as it has been started and not yet stopped.
		5594	See L</WATCHER STATES> for details.
		5595
		5596	=item application
		5597
		5598	In this document, an application is whatever is using libev.
		5599
		5600	=item backend
		5601
		5602	The part of the code dealing with the operating system interfaces.
		5603
		5604	=item callback
		5605
		5606	The address of a function that is called when some event has been
		5607	detected. Callbacks are being passed the event loop, the watcher that
		5608	received the event, and the actual event bitset.
		5609
		5610	=item callback/watcher invocation
		5611
		5612	The act of calling the callback associated with a watcher.
		5613
		5614	=item event
		5615
		5616	A change of state of some external event, such as data now being available
		5617	for reading on a file descriptor, time having passed or simply not having
		5618	any other events happening anymore.
		5619
		5620	In libev, events are represented as single bits (such as C<EV_READ> or
		5621	C<EV_TIMER>).
		5622
		5623	=item event library
		5624
		5625	A software package implementing an event model and loop.
		5626
		5627	=item event loop
		5628
		5629	An entity that handles and processes external events and converts them
		5630	into callback invocations.
		5631
		5632	=item event model
		5633
		5634	The model used to describe how an event loop handles and processes
		5635	watchers and events.
		5636
		5637	=item pending
		5638
		5639	A watcher is pending as soon as the corresponding event has been
		5640	detected. See L</WATCHER STATES> for details.
		5641
		5642	=item real time
		5643
		5644	The physical time that is observed. It is apparently strictly monotonic :)
		5645
		5646	=item wall-clock time
		5647
		5648	The time and date as shown on clocks. Unlike real time, it can actually
		5649	be wrong and jump forwards and backwards, e.g. when you adjust your
		5650	clock.
		5651
		5652	=item watcher
		5653
		5654	A data structure that describes interest in certain events. Watchers need
		5655	to be started (attached to an event loop) before they can receive events.
		5656
		5657	=back
		5658
3998	=head1 AUTHOR	5659	=head1 AUTHOR
3999		5660
4000	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5661	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5662	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4001		5663

Diff Legend

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