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		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
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
…		…
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 C<epoll>, the
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
90	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	112	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	113	(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
…		…
450		592
451	It scales in the same way as the epoll backend, but the interface to the	593	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	594	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	595	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	596	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	597	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	598	might have to leak fd's on fork, but it's more sane than epoll) and it
457	cases	599	drops fds silently in similarly hard-to-detect cases.
458		600
459	This backend usually performs well under most conditions.	601	This backend usually performs well under most conditions.
460		602
461	While nominally embeddable in other event loops, this doesn't work	603	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	604	everywhere, so you might need to test for this. And since it is broken
…		…
479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	621	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
480		622
481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	623	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)).	624	it's really slow, but it still scales very well (O(active_fds)).
483		625
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	626	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	627	file descriptor per loop iteration. For small and medium numbers of file
490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	628	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
491	might perform better.	629	might perform better.
492		630
493	On the positive side, with the exception of the spurious readiness	631	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	632	specification in all tests and is fully embeddable, which is a rare feat
496	OS-specific backends (I vastly prefer correctness over speed hacks).	633	among the OS-specific backends (I vastly prefer correctness over speed
		634	hacks).
		635
		636	On the negative side, the interface is I<bizarre> - so bizarre that
		637	even sun itself gets it wrong in their code examples: The event polling
		638	function sometimes returns events to the caller even though an error
		639	occurred, but with no indication whether it has done so or not (yes, it's
		640	even documented that way) - deadly for edge-triggered interfaces where you
		641	absolutely have to know whether an event occurred or not because you have
		642	to re-arm the watcher.
		643
		644	Fortunately libev seems to be able to work around these idiocies.
497		645
498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	646	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
499	C<EVBACKEND_POLL>.	647	C<EVBACKEND_POLL>.
500		648
501	=item C<EVBACKEND_ALL>	649	=item C<EVBACKEND_ALL>
502		650
503	Try all backends (even potentially broken ones that wouldn't be tried	651	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	652	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	653	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
506		654
507	It is definitely not recommended to use this flag.	655	It is definitely not recommended to use this flag, use whatever
		656	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		657	at all.
		658
		659	=item C<EVBACKEND_MASK>
		660
		661	Not a backend at all, but a mask to select all backend bits from a
		662	C<flags> value, in case you want to mask out any backends from a flags
		663	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
508		664
509	=back	665	=back
510		666
511	If one or more of these are or'ed into the flags value, then only these	667	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	668	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.	669	here). If none are specified, all backends in C<ev_recommended_backends
514		670	()> 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		671
543	Example: Try to create a event loop that uses epoll and nothing else.	672	Example: Try to create a event loop that uses epoll and nothing else.
544		673
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	674	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
546	if (!epoller)	675	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	676	fatal ("no epoll found here, maybe it hides under your chair");
548		677
		678	Example: Use whatever libev has to offer, but make sure that kqueue is
		679	used if available.
		680
		681	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		682
549	=item ev_default_destroy ()	683	=item ev_loop_destroy (loop)
550		684
551	Destroys the default loop again (frees all memory and kernel state	685	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	686	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	687	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>	688	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	689	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	690	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		692
559	Note that certain global state, such as signal state (and installed signal	693	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	694	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	695	as signal and child watchers) would need to be stopped manually.
562		696
563	In general it is not advisable to call this function except in the	697	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	698	C<ev_loop_new>, but it can also be used on the default loop returned by
		699	C<ev_default_loop>, in which case it is not thread-safe.
		700
		701	Note that it is not advisable to call this function on the default loop
		702	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	703	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>).	704	and C<ev_loop_destroy>.
567		705
568	=item ev_loop_destroy (loop)	706	=item ev_loop_fork (loop)
569		707
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	708	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	709	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	710	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	711	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	712	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.	713	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		714
		715	In addition, if you want to reuse a loop (via this function or
		716	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		717
		718	Again, you I<have> to call it on I<any> loop that you want to re-use after
		719	a fork, I<even if you do not plan to use the loop in the parent>. This is
		720	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		721	during fork.
581		722
582	On the other hand, you only need to call this function in the child	723	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	724	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.	725	you just fork+exec or create a new loop in the child, you don't have to
		726	call it at all (in fact, C<epoll> is so badly broken that it makes a
		727	difference, but libev will usually detect this case on its own and do a
		728	costly reset of the backend).
585		729
586	The function itself is quite fast and it's usually not a problem to call	730	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	731	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		732
		733	Example: Automate calling C<ev_loop_fork> on the default loop when
		734	using pthreads.
		735
		736	static void
		737	post_fork_child (void)
		738	{
		739	ev_loop_fork (EV_DEFAULT);
		740	}
		741
		742	...
590	pthread_atfork (0, 0, ev_default_fork);	743	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		744
599	=item int ev_is_default_loop (loop)	745	=item int ev_is_default_loop (loop)
600		746
601	Returns true when the given loop is, in fact, the default loop, and false	747	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	748	otherwise.
603		749
604	=item unsigned int ev_loop_count (loop)	750	=item unsigned int ev_iteration (loop)
605		751
606	Returns the count of loop iterations for the loop, which is identical to	752	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	753	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	754	and happily wraps around with enough iterations.
609		755
610	This value can sometimes be useful as a generation counter of sorts (it	756	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	757	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	758	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		759	prepare and check phases.
		760
		761	=item unsigned int ev_depth (loop)
		762
		763	Returns the number of times C<ev_run> was entered minus the number of
		764	times C<ev_run> was exited normally, in other words, the recursion depth.
		765
		766	Outside C<ev_run>, this number is zero. In a callback, this number is
		767	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		768	in which case it is higher.
		769
		770	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		771	throwing an exception etc.), doesn't count as "exit" - consider this
		772	as a hint to avoid such ungentleman-like behaviour unless it's really
		773	convenient, in which case it is fully supported.
613		774
614	=item unsigned int ev_backend (loop)	775	=item unsigned int ev_backend (loop)
615		776
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	777	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	778	use.
…		…
626		787
627	=item ev_now_update (loop)	788	=item ev_now_update (loop)
628		789
629	Establishes the current time by querying the kernel, updating the time	790	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	791	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	792	is usually done automatically within C<ev_run ()>.
632		793
633	This function is rarely useful, but when some event callback runs for a	794	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	795	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	796	the current time is a good idea.
636		797
637	See also "The special problem of time updates" in the C<ev_timer> section.	798	See also L</The special problem of time updates> in the C<ev_timer> section.
638		799
		800	=item ev_suspend (loop)
		801
		802	=item ev_resume (loop)
		803
		804	These two functions suspend and resume an event loop, for use when the
		805	loop is not used for a while and timeouts should not be processed.
		806
		807	A typical use case would be an interactive program such as a game: When
		808	the user presses C<^Z> to suspend the game and resumes it an hour later it
		809	would be best to handle timeouts as if no time had actually passed while
		810	the program was suspended. This can be achieved by calling C<ev_suspend>
		811	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		812	C<ev_resume> directly afterwards to resume timer processing.
		813
		814	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		815	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		816	will be rescheduled (that is, they will lose any events that would have
		817	occurred while suspended).
		818
		819	After calling C<ev_suspend> you B<must not> call I<any> function on the
		820	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		821	without a previous call to C<ev_suspend>.
		822
		823	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		824	event loop time (see C<ev_now_update>).
		825
639	=item ev_loop (loop, int flags)	826	=item bool ev_run (loop, int flags)
640		827
641	Finally, this is it, the event handler. This function usually is called	828	Finally, this is it, the event handler. This function usually is called
642	after you initialised all your watchers and you want to start handling	829	after you have initialised all your watchers and you want to start
643	events.	830	handling events. It will ask the operating system for any new events, call
		831	the watcher callbacks, and then repeat the whole process indefinitely: This
		832	is why event loops are called I<loops>.
644		833
645	If the flags argument is specified as C<0>, it will not return until	834	If the flags argument is specified as C<0>, it will keep handling events
646	either no event watchers are active anymore or C<ev_unloop> was called.	835	until either no event watchers are active anymore or C<ev_break> was
		836	called.
647		837
		838	The return value is false if there are no more active watchers (which
		839	usually means "all jobs done" or "deadlock"), and true in all other cases
		840	(which usually means " you should call C<ev_run> again").
		841
648	Please note that an explicit C<ev_unloop> is usually better than	842	Please note that an explicit C<ev_break> is usually better than
649	relying on all watchers to be stopped when deciding when a program has	843	relying on all watchers to be stopped when deciding when a program has
650	finished (especially in interactive programs), but having a program	844	finished (especially in interactive programs), but having a program
651	that automatically loops as long as it has to and no longer by virtue	845	that automatically loops as long as it has to and no longer by virtue
652	of relying on its watchers stopping correctly, that is truly a thing of	846	of relying on its watchers stopping correctly, that is truly a thing of
653	beauty.	847	beauty.
654		848
		849	This function is I<mostly> exception-safe - you can break out of a
		850	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		851	exception and so on. This does not decrement the C<ev_depth> value, nor
		852	will it clear any outstanding C<EVBREAK_ONE> breaks.
		853
655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	854	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
656	those events and any already outstanding ones, but will not block your	855	those events and any already outstanding ones, but will not wait and
657	process in case there are no events and will return after one iteration of	856	block your process in case there are no events and will return after one
658	the loop.	857	iteration of the loop. This is sometimes useful to poll and handle new
		858	events while doing lengthy calculations, to keep the program responsive.
659		859
660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	860	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
661	necessary) and will handle those and any already outstanding ones. It	861	necessary) and will handle those and any already outstanding ones. It
662	will block your process until at least one new event arrives (which could	862	will block your process until at least one new event arrives (which could
663	be an event internal to libev itself, so there is no guarantee that a	863	be an event internal to libev itself, so there is no guarantee that a
664	user-registered callback will be called), and will return after one	864	user-registered callback will be called), and will return after one
665	iteration of the loop.	865	iteration of the loop.
666		866
667	This is useful if you are waiting for some external event in conjunction	867	This is useful if you are waiting for some external event in conjunction
668	with something not expressible using other libev watchers (i.e. "roll your	868	with something not expressible using other libev watchers (i.e. "roll your
669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	869	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
670	usually a better approach for this kind of thing.	870	usually a better approach for this kind of thing.
671		871
672	Here are the gory details of what C<ev_loop> does:	872	Here are the gory details of what C<ev_run> does (this is for your
		873	understanding, not a guarantee that things will work exactly like this in
		874	future versions):
673		875
		876	- Increment loop depth.
		877	- Reset the ev_break status.
674	- Before the first iteration, call any pending watchers.	878	- Before the first iteration, call any pending watchers.
		879	LOOP:
675	* If EVFLAG_FORKCHECK was used, check for a fork.	880	- If EVFLAG_FORKCHECK was used, check for a fork.
676	- If a fork was detected (by any means), queue and call all fork watchers.	881	- If a fork was detected (by any means), queue and call all fork watchers.
677	- Queue and call all prepare watchers.	882	- Queue and call all prepare watchers.
		883	- If ev_break was called, goto FINISH.
678	- If we have been forked, detach and recreate the kernel state	884	- If we have been forked, detach and recreate the kernel state
679	as to not disturb the other process.	885	as to not disturb the other process.
680	- Update the kernel state with all outstanding changes.	886	- Update the kernel state with all outstanding changes.
681	- Update the "event loop time" (ev_now ()).	887	- Update the "event loop time" (ev_now ()).
682	- Calculate for how long to sleep or block, if at all	888	- Calculate for how long to sleep or block, if at all
683	(active idle watchers, EVLOOP_NONBLOCK or not having	889	(active idle watchers, EVRUN_NOWAIT or not having
684	any active watchers at all will result in not sleeping).	890	any active watchers at all will result in not sleeping).
685	- Sleep if the I/O and timer collect interval say so.	891	- Sleep if the I/O and timer collect interval say so.
		892	- Increment loop iteration counter.
686	- Block the process, waiting for any events.	893	- Block the process, waiting for any events.
687	- Queue all outstanding I/O (fd) events.	894	- Queue all outstanding I/O (fd) events.
688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	895	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
689	- Queue all expired timers.	896	- Queue all expired timers.
690	- Queue all expired periodics.	897	- Queue all expired periodics.
691	- Unless any events are pending now, queue all idle watchers.	898	- Queue all idle watchers with priority higher than that of pending events.
692	- Queue all check watchers.	899	- Queue all check watchers.
693	- Call all queued watchers in reverse order (i.e. check watchers first).	900	- Call all queued watchers in reverse order (i.e. check watchers first).
694	Signals and child watchers are implemented as I/O watchers, and will	901	Signals and child watchers are implemented as I/O watchers, and will
695	be handled here by queueing them when their watcher gets executed.	902	be handled here by queueing them when their watcher gets executed.
696	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	903	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
697	were used, or there are no active watchers, return, otherwise	904	were used, or there are no active watchers, goto FINISH, otherwise
698	continue with step *.	905	continue with step LOOP.
		906	FINISH:
		907	- Reset the ev_break status iff it was EVBREAK_ONE.
		908	- Decrement the loop depth.
		909	- Return.
699		910
700	Example: Queue some jobs and then loop until no events are outstanding	911	Example: Queue some jobs and then loop until no events are outstanding
701	anymore.	912	anymore.
702		913
703	... queue jobs here, make sure they register event watchers as long	914	... queue jobs here, make sure they register event watchers as long
704	... as they still have work to do (even an idle watcher will do..)	915	... as they still have work to do (even an idle watcher will do..)
705	ev_loop (my_loop, 0);	916	ev_run (my_loop, 0);
706	... jobs done or somebody called unloop. yeah!	917	... jobs done or somebody called break. yeah!
707		918
708	=item ev_unloop (loop, how)	919	=item ev_break (loop, how)
709		920
710	Can be used to make a call to C<ev_loop> return early (but only after it	921	Can be used to make a call to C<ev_run> return early (but only after it
711	has processed all outstanding events). The C<how> argument must be either	922	has processed all outstanding events). The C<how> argument must be either
712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	923	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	924	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
714		925
715	This "unloop state" will be cleared when entering C<ev_loop> again.	926	This "break state" will be cleared on the next call to C<ev_run>.
716		927
717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	928	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		929	which case it will have no effect.
718		930
719	=item ev_ref (loop)	931	=item ev_ref (loop)
720		932
721	=item ev_unref (loop)	933	=item ev_unref (loop)
722		934
723	Ref/unref can be used to add or remove a reference count on the event	935	Ref/unref can be used to add or remove a reference count on the event
724	loop: Every watcher keeps one reference, and as long as the reference	936	loop: Every watcher keeps one reference, and as long as the reference
725	count is nonzero, C<ev_loop> will not return on its own.	937	count is nonzero, C<ev_run> will not return on its own.
726		938
727	If you have a watcher you never unregister that should not keep C<ev_loop>	939	This is useful when you have a watcher that you never intend to
728	from returning, call ev_unref() after starting, and ev_ref() before	940	unregister, but that nevertheless should not keep C<ev_run> from
		941	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
729	stopping it.	942	before stopping it.
730		943
731	As an example, libev itself uses this for its internal signal pipe: It is	944	As an example, libev itself uses this for its internal signal pipe: It
732	not visible to the libev user and should not keep C<ev_loop> from exiting	945	is not visible to the libev user and should not keep C<ev_run> from
733	if no event watchers registered by it are active. It is also an excellent	946	exiting if no event watchers registered by it are active. It is also an
734	way to do this for generic recurring timers or from within third-party	947	excellent way to do this for generic recurring timers or from within
735	libraries. Just remember to I<unref after start> and I<ref before stop>	948	third-party libraries. Just remember to I<unref after start> and I<ref
736	(but only if the watcher wasn't active before, or was active before,	949	before stop> (but only if the watcher wasn't active before, or was active
737	respectively).	950	before, respectively. Note also that libev might stop watchers itself
		951	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		952	in the callback).
738		953
739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	954	Example: Create a signal watcher, but keep it from keeping C<ev_run>
740	running when nothing else is active.	955	running when nothing else is active.
741		956
742	ev_signal exitsig;	957	ev_signal exitsig;
743	ev_signal_init (&exitsig, sig_cb, SIGINT);	958	ev_signal_init (&exitsig, sig_cb, SIGINT);
744	ev_signal_start (loop, &exitsig);	959	ev_signal_start (loop, &exitsig);
745	evf_unref (loop);	960	ev_unref (loop);
746		961
747	Example: For some weird reason, unregister the above signal handler again.	962	Example: For some weird reason, unregister the above signal handler again.
748		963
749	ev_ref (loop);	964	ev_ref (loop);
750	ev_signal_stop (loop, &exitsig);	965	ev_signal_stop (loop, &exitsig);
…		…
770	overhead for the actual polling but can deliver many events at once.	985	overhead for the actual polling but can deliver many events at once.
771		986
772	By setting a higher I<io collect interval> you allow libev to spend more	987	By setting a higher I<io collect interval> you allow libev to spend more
773	time collecting I/O events, so you can handle more events per iteration,	988	time collecting I/O events, so you can handle more events per iteration,
774	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	989	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
775	C<ev_timer>) will be not affected. Setting this to a non-null value will	990	C<ev_timer>) will not be affected. Setting this to a non-null value will
776	introduce an additional C<ev_sleep ()> call into most loop iterations.	991	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		992	sleep time ensures that libev will not poll for I/O events more often then
		993	once per this interval, on average (as long as the host time resolution is
		994	good enough).
777		995
778	Likewise, by setting a higher I<timeout collect interval> you allow libev	996	Likewise, by setting a higher I<timeout collect interval> you allow libev
779	to spend more time collecting timeouts, at the expense of increased	997	to spend more time collecting timeouts, at the expense of increased
780	latency/jitter/inexactness (the watcher callback will be called	998	latency/jitter/inexactness (the watcher callback will be called
781	later). C<ev_io> watchers will not be affected. Setting this to a non-null	999	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
783		1001
784	Many (busy) programs can usually benefit by setting the I/O collect	1002	Many (busy) programs can usually benefit by setting the I/O collect
785	interval to a value near C<0.1> or so, which is often enough for	1003	interval to a value near C<0.1> or so, which is often enough for
786	interactive servers (of course not for games), likewise for timeouts. It	1004	interactive servers (of course not for games), likewise for timeouts. It
787	usually doesn't make much sense to set it to a lower value than C<0.01>,	1005	usually doesn't make much sense to set it to a lower value than C<0.01>,
788	as this approaches the timing granularity of most systems.	1006	as this approaches the timing granularity of most systems. Note that if
		1007	you do transactions with the outside world and you can't increase the
		1008	parallelity, then this setting will limit your transaction rate (if you
		1009	need to poll once per transaction and the I/O collect interval is 0.01,
		1010	then you can't do more than 100 transactions per second).
789		1011
790	Setting the I<timeout collect interval> can improve the opportunity for	1012	Setting the I<timeout collect interval> can improve the opportunity for
791	saving power, as the program will "bundle" timer callback invocations that	1013	saving power, as the program will "bundle" timer callback invocations that
792	are "near" in time together, by delaying some, thus reducing the number of	1014	are "near" in time together, by delaying some, thus reducing the number of
793	times the process sleeps and wakes up again. Another useful technique to	1015	times the process sleeps and wakes up again. Another useful technique to
794	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	1016	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
795	they fire on, say, one-second boundaries only.	1017	they fire on, say, one-second boundaries only.
796		1018
		1019	Example: we only need 0.1s timeout granularity, and we wish not to poll
		1020	more often than 100 times per second:
		1021
		1022	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		1023	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		1024
		1025	=item ev_invoke_pending (loop)
		1026
		1027	This call will simply invoke all pending watchers while resetting their
		1028	pending state. Normally, C<ev_run> does this automatically when required,
		1029	but when overriding the invoke callback this call comes handy. This
		1030	function can be invoked from a watcher - this can be useful for example
		1031	when you want to do some lengthy calculation and want to pass further
		1032	event handling to another thread (you still have to make sure only one
		1033	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1034
		1035	=item int ev_pending_count (loop)
		1036
		1037	Returns the number of pending watchers - zero indicates that no watchers
		1038	are pending.
		1039
		1040	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1041
		1042	This overrides the invoke pending functionality of the loop: Instead of
		1043	invoking all pending watchers when there are any, C<ev_run> will call
		1044	this callback instead. This is useful, for example, when you want to
		1045	invoke the actual watchers inside another context (another thread etc.).
		1046
		1047	If you want to reset the callback, use C<ev_invoke_pending> as new
		1048	callback.
		1049
		1050	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1051
		1052	Sometimes you want to share the same loop between multiple threads. This
		1053	can be done relatively simply by putting mutex_lock/unlock calls around
		1054	each call to a libev function.
		1055
		1056	However, C<ev_run> can run an indefinite time, so it is not feasible
		1057	to wait for it to return. One way around this is to wake up the event
		1058	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1059	I<release> and I<acquire> callbacks on the loop.
		1060
		1061	When set, then C<release> will be called just before the thread is
		1062	suspended waiting for new events, and C<acquire> is called just
		1063	afterwards.
		1064
		1065	Ideally, C<release> will just call your mutex_unlock function, and
		1066	C<acquire> will just call the mutex_lock function again.
		1067
		1068	While event loop modifications are allowed between invocations of
		1069	C<release> and C<acquire> (that's their only purpose after all), no
		1070	modifications done will affect the event loop, i.e. adding watchers will
		1071	have no effect on the set of file descriptors being watched, or the time
		1072	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1073	to take note of any changes you made.
		1074
		1075	In theory, threads executing C<ev_run> will be async-cancel safe between
		1076	invocations of C<release> and C<acquire>.
		1077
		1078	See also the locking example in the C<THREADS> section later in this
		1079	document.
		1080
		1081	=item ev_set_userdata (loop, void *data)
		1082
		1083	=item void *ev_userdata (loop)
		1084
		1085	Set and retrieve a single C<void *> associated with a loop. When
		1086	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1087	C<0>.
		1088
		1089	These two functions can be used to associate arbitrary data with a loop,
		1090	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1091	C<acquire> callbacks described above, but of course can be (ab-)used for
		1092	any other purpose as well.
		1093
797	=item ev_loop_verify (loop)	1094	=item ev_verify (loop)
798		1095
799	This function only does something when C<EV_VERIFY> support has been	1096	This function only does something when C<EV_VERIFY> support has been
800	compiled in, which is the default for non-minimal builds. It tries to go	1097	compiled in, which is the default for non-minimal builds. It tries to go
801	through all internal structures and checks them for validity. If anything	1098	through all internal structures and checks them for validity. If anything
802	is found to be inconsistent, it will print an error message to standard	1099	is found to be inconsistent, it will print an error message to standard
…		…
813		1110
814	In the following description, uppercase C<TYPE> in names stands for the	1111	In the following description, uppercase C<TYPE> in names stands for the
815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1112	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
816	watchers and C<ev_io_start> for I/O watchers.	1113	watchers and C<ev_io_start> for I/O watchers.
817		1114
818	A watcher is a structure that you create and register to record your	1115	A watcher is an opaque structure that you allocate and register to record
819	interest in some event. For instance, if you want to wait for STDIN to	1116	your interest in some event. To make a concrete example, imagine you want
820	become readable, you would create an C<ev_io> watcher for that:	1117	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1118	for that:
821		1119
822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1120	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
823	{	1121	{
824	ev_io_stop (w);	1122	ev_io_stop (w);
825	ev_unloop (loop, EVUNLOOP_ALL);	1123	ev_break (loop, EVBREAK_ALL);
826	}	1124	}
827		1125
828	struct ev_loop *loop = ev_default_loop (0);	1126	struct ev_loop *loop = ev_default_loop (0);
829		1127
830	ev_io stdin_watcher;	1128	ev_io stdin_watcher;
831		1129
832	ev_init (&stdin_watcher, my_cb);	1130	ev_init (&stdin_watcher, my_cb);
833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1131	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
834	ev_io_start (loop, &stdin_watcher);	1132	ev_io_start (loop, &stdin_watcher);
835		1133
836	ev_loop (loop, 0);	1134	ev_run (loop, 0);
837		1135
838	As you can see, you are responsible for allocating the memory for your	1136	As you can see, you are responsible for allocating the memory for your
839	watcher structures (and it is I<usually> a bad idea to do this on the	1137	watcher structures (and it is I<usually> a bad idea to do this on the
840	stack).	1138	stack).
841		1139
842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1140	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1141	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
844		1142
845	Each watcher structure must be initialised by a call to C<ev_init	1143	Each watcher structure must be initialised by a call to C<ev_init (watcher
846	(watcher *, callback)>, which expects a callback to be provided. This	1144	*, callback)>, which expects a callback to be provided. This callback is
847	callback gets invoked each time the event occurs (or, in the case of I/O	1145	invoked each time the event occurs (or, in the case of I/O watchers, each
848	watchers, each time the event loop detects that the file descriptor given	1146	time the event loop detects that the file descriptor given is readable
849	is readable and/or writable).	1147	and/or writable).
850		1148
851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1149	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
852	macro to configure it, with arguments specific to the watcher type. There	1150	macro to configure it, with arguments specific to the watcher type. There
853	is also a macro to combine initialisation and setting in one call: C<<	1151	is also a macro to combine initialisation and setting in one call: C<<
854	ev_TYPE_init (watcher *, callback, ...) >>.	1152	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
877	=item C<EV_WRITE>	1175	=item C<EV_WRITE>
878		1176
879	The file descriptor in the C<ev_io> watcher has become readable and/or	1177	The file descriptor in the C<ev_io> watcher has become readable and/or
880	writable.	1178	writable.
881		1179
882	=item C<EV_TIMEOUT>	1180	=item C<EV_TIMER>
883		1181
884	The C<ev_timer> watcher has timed out.	1182	The C<ev_timer> watcher has timed out.
885		1183
886	=item C<EV_PERIODIC>	1184	=item C<EV_PERIODIC>
887		1185
…		…
905		1203
906	=item C<EV_PREPARE>	1204	=item C<EV_PREPARE>
907		1205
908	=item C<EV_CHECK>	1206	=item C<EV_CHECK>
909		1207
910	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1208	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
911	to gather new events, and all C<ev_check> watchers are invoked just after	1209	gather new events, and all C<ev_check> watchers are queued (not invoked)
912	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1210	just after C<ev_run> has gathered them, but before it queues any callbacks
		1211	for any received events. That means C<ev_prepare> watchers are the last
		1212	watchers invoked before the event loop sleeps or polls for new events, and
		1213	C<ev_check> watchers will be invoked before any other watchers of the same
		1214	or lower priority within an event loop iteration.
		1215
913	received events. Callbacks of both watcher types can start and stop as	1216	Callbacks of both watcher types can start and stop as many watchers as
914	many watchers as they want, and all of them will be taken into account	1217	they want, and all of them will be taken into account (for example, a
915	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1218	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
916	C<ev_loop> from blocking).	1219	blocking).
917		1220
918	=item C<EV_EMBED>	1221	=item C<EV_EMBED>
919		1222
920	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1223	The embedded event loop specified in the C<ev_embed> watcher needs attention.
921		1224
922	=item C<EV_FORK>	1225	=item C<EV_FORK>
923		1226
924	The event loop has been resumed in the child process after fork (see	1227	The event loop has been resumed in the child process after fork (see
925	C<ev_fork>).	1228	C<ev_fork>).
926		1229
		1230	=item C<EV_CLEANUP>
		1231
		1232	The event loop is about to be destroyed (see C<ev_cleanup>).
		1233
927	=item C<EV_ASYNC>	1234	=item C<EV_ASYNC>
928		1235
929	The given async watcher has been asynchronously notified (see C<ev_async>).	1236	The given async watcher has been asynchronously notified (see C<ev_async>).
		1237
		1238	=item C<EV_CUSTOM>
		1239
		1240	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1241	by libev users to signal watchers (e.g. via C<ev_feed_event>).
930		1242
931	=item C<EV_ERROR>	1243	=item C<EV_ERROR>
932		1244
933	An unspecified error has occurred, the watcher has been stopped. This might	1245	An unspecified error has occurred, the watcher has been stopped. This might
934	happen because the watcher could not be properly started because libev	1246	happen because the watcher could not be properly started because libev
…		…
972		1284
973	ev_io w;	1285	ev_io w;
974	ev_init (&w, my_cb);	1286	ev_init (&w, my_cb);
975	ev_io_set (&w, STDIN_FILENO, EV_READ);	1287	ev_io_set (&w, STDIN_FILENO, EV_READ);
976		1288
977	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1289	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
978		1290
979	This macro initialises the type-specific parts of a watcher. You need to	1291	This macro initialises the type-specific parts of a watcher. You need to
980	call C<ev_init> at least once before you call this macro, but you can	1292	call C<ev_init> at least once before you call this macro, but you can
981	call C<ev_TYPE_set> any number of times. You must not, however, call this	1293	call C<ev_TYPE_set> any number of times. You must not, however, call this
982	macro on a watcher that is active (it can be pending, however, which is a	1294	macro on a watcher that is active (it can be pending, however, which is a
…		…
995		1307
996	Example: Initialise and set an C<ev_io> watcher in one step.	1308	Example: Initialise and set an C<ev_io> watcher in one step.
997		1309
998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1310	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
999		1311
1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1312	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1001		1313
1002	Starts (activates) the given watcher. Only active watchers will receive	1314	Starts (activates) the given watcher. Only active watchers will receive
1003	events. If the watcher is already active nothing will happen.	1315	events. If the watcher is already active nothing will happen.
1004		1316
1005	Example: Start the C<ev_io> watcher that is being abused as example in this	1317	Example: Start the C<ev_io> watcher that is being abused as example in this
1006	whole section.	1318	whole section.
1007		1319
1008	ev_io_start (EV_DEFAULT_UC, &w);	1320	ev_io_start (EV_DEFAULT_UC, &w);
1009		1321
1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1322	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1011		1323
1012	Stops the given watcher if active, and clears the pending status (whether	1324	Stops the given watcher if active, and clears the pending status (whether
1013	the watcher was active or not).	1325	the watcher was active or not).
1014		1326
1015	It is possible that stopped watchers are pending - for example,	1327	It is possible that stopped watchers are pending - for example,
…		…
1035		1347
1036	=item callback ev_cb (ev_TYPE *watcher)	1348	=item callback ev_cb (ev_TYPE *watcher)
1037		1349
1038	Returns the callback currently set on the watcher.	1350	Returns the callback currently set on the watcher.
1039		1351
1040	=item ev_cb_set (ev_TYPE *watcher, callback)	1352	=item ev_set_cb (ev_TYPE *watcher, callback)
1041		1353
1042	Change the callback. You can change the callback at virtually any time	1354	Change the callback. You can change the callback at virtually any time
1043	(modulo threads).	1355	(modulo threads).
1044		1356
1045	=item ev_set_priority (ev_TYPE *watcher, priority)	1357	=item ev_set_priority (ev_TYPE *watcher, int priority)
1046		1358
1047	=item int ev_priority (ev_TYPE *watcher)	1359	=item int ev_priority (ev_TYPE *watcher)
1048		1360
1049	Set and query the priority of the watcher. The priority is a small	1361	Set and query the priority of the watcher. The priority is a small
1050	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1362	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1051	(default: C<-2>). Pending watchers with higher priority will be invoked	1363	(default: C<-2>). Pending watchers with higher priority will be invoked
1052	before watchers with lower priority, but priority will not keep watchers	1364	before watchers with lower priority, but priority will not keep watchers
1053	from being executed (except for C<ev_idle> watchers).	1365	from being executed (except for C<ev_idle> watchers).
1054		1366
1055	This means that priorities are I<only> used for ordering callback
1056	invocation after new events have been received. This is useful, for
1057	example, to reduce latency after idling, or more often, to bind two
1058	watchers on the same event and make sure one is called first.
1059
1060	If you need to suppress invocation when higher priority events are pending	1367	If you need to suppress invocation when higher priority events are pending
1061	you need to look at C<ev_idle> watchers, which provide this functionality.	1368	you need to look at C<ev_idle> watchers, which provide this functionality.
1062		1369
1063	You I<must not> change the priority of a watcher as long as it is active or	1370	You I<must not> change the priority of a watcher as long as it is active or
1064	pending.	1371	pending.
1065
1066	The default priority used by watchers when no priority has been set is
1067	always C<0>, which is supposed to not be too high and not be too low :).
1068		1372
1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1373	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1070	fine, as long as you do not mind that the priority value you query might	1374	fine, as long as you do not mind that the priority value you query might
1071	or might not have been clamped to the valid range.	1375	or might not have been clamped to the valid range.
		1376
		1377	The default priority used by watchers when no priority has been set is
		1378	always C<0>, which is supposed to not be too high and not be too low :).
		1379
		1380	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1381	priorities.
1072		1382
1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1383	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1074		1384
1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1385	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1076	C<loop> nor C<revents> need to be valid as long as the watcher callback	1386	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1084	watcher isn't pending it does nothing and returns C<0>.	1394	watcher isn't pending it does nothing and returns C<0>.
1085		1395
1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1396	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1087	callback to be invoked, which can be accomplished with this function.	1397	callback to be invoked, which can be accomplished with this function.
1088		1398
		1399	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1400
		1401	Feeds the given event set into the event loop, as if the specified event
		1402	had happened for the specified watcher (which must be a pointer to an
		1403	initialised but not necessarily started event watcher). Obviously you must
		1404	not free the watcher as long as it has pending events.
		1405
		1406	Stopping the watcher, letting libev invoke it, or calling
		1407	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1408	not started in the first place.
		1409
		1410	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1411	functions that do not need a watcher.
		1412
1089	=back	1413	=back
1090		1414
		1415	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1416	OWN COMPOSITE WATCHERS> idioms.
1091		1417
1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1418	=head2 WATCHER STATES
1093		1419
1094	Each watcher has, by default, a member C<void *data> that you can change	1420	There are various watcher states mentioned throughout this manual -
1095	and read at any time: libev will completely ignore it. This can be used	1421	active, pending and so on. In this section these states and the rules to
1096	to associate arbitrary data with your watcher. If you need more data and	1422	transition between them will be described in more detail - and while these
1097	don't want to allocate memory and store a pointer to it in that data	1423	rules might look complicated, they usually do "the right thing".
1098	member, you can also "subclass" the watcher type and provide your own
1099	data:
1100		1424
1101	struct my_io	1425	=over 4
		1426
		1427	=item initialised
		1428
		1429	Before a watcher can be registered with the event loop it has to be
		1430	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1431	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1432
		1433	In this state it is simply some block of memory that is suitable for
		1434	use in an event loop. It can be moved around, freed, reused etc. at
		1435	will - as long as you either keep the memory contents intact, or call
		1436	C<ev_TYPE_init> again.
		1437
		1438	=item started/running/active
		1439
		1440	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1441	property of the event loop, and is actively waiting for events. While in
		1442	this state it cannot be accessed (except in a few documented ways), moved,
		1443	freed or anything else - the only legal thing is to keep a pointer to it,
		1444	and call libev functions on it that are documented to work on active watchers.
		1445
		1446	=item pending
		1447
		1448	If a watcher is active and libev determines that an event it is interested
		1449	in has occurred (such as a timer expiring), it will become pending. It will
		1450	stay in this pending state until either it is stopped or its callback is
		1451	about to be invoked, so it is not normally pending inside the watcher
		1452	callback.
		1453
		1454	The watcher might or might not be active while it is pending (for example,
		1455	an expired non-repeating timer can be pending but no longer active). If it
		1456	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1457	but it is still property of the event loop at this time, so cannot be
		1458	moved, freed or reused. And if it is active the rules described in the
		1459	previous item still apply.
		1460
		1461	It is also possible to feed an event on a watcher that is not active (e.g.
		1462	via C<ev_feed_event>), in which case it becomes pending without being
		1463	active.
		1464
		1465	=item stopped
		1466
		1467	A watcher can be stopped implicitly by libev (in which case it might still
		1468	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1469	latter will clear any pending state the watcher might be in, regardless
		1470	of whether it was active or not, so stopping a watcher explicitly before
		1471	freeing it is often a good idea.
		1472
		1473	While stopped (and not pending) the watcher is essentially in the
		1474	initialised state, that is, it can be reused, moved, modified in any way
		1475	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1476	it again).
		1477
		1478	=back
		1479
		1480	=head2 WATCHER PRIORITY MODELS
		1481
		1482	Many event loops support I<watcher priorities>, which are usually small
		1483	integers that influence the ordering of event callback invocation
		1484	between watchers in some way, all else being equal.
		1485
		1486	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1487	description for the more technical details such as the actual priority
		1488	range.
		1489
		1490	There are two common ways how these these priorities are being interpreted
		1491	by event loops:
		1492
		1493	In the more common lock-out model, higher priorities "lock out" invocation
		1494	of lower priority watchers, which means as long as higher priority
		1495	watchers receive events, lower priority watchers are not being invoked.
		1496
		1497	The less common only-for-ordering model uses priorities solely to order
		1498	callback invocation within a single event loop iteration: Higher priority
		1499	watchers are invoked before lower priority ones, but they all get invoked
		1500	before polling for new events.
		1501
		1502	Libev uses the second (only-for-ordering) model for all its watchers
		1503	except for idle watchers (which use the lock-out model).
		1504
		1505	The rationale behind this is that implementing the lock-out model for
		1506	watchers is not well supported by most kernel interfaces, and most event
		1507	libraries will just poll for the same events again and again as long as
		1508	their callbacks have not been executed, which is very inefficient in the
		1509	common case of one high-priority watcher locking out a mass of lower
		1510	priority ones.
		1511
		1512	Static (ordering) priorities are most useful when you have two or more
		1513	watchers handling the same resource: a typical usage example is having an
		1514	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1515	timeouts. Under load, data might be received while the program handles
		1516	other jobs, but since timers normally get invoked first, the timeout
		1517	handler will be executed before checking for data. In that case, giving
		1518	the timer a lower priority than the I/O watcher ensures that I/O will be
		1519	handled first even under adverse conditions (which is usually, but not
		1520	always, what you want).
		1521
		1522	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1523	will only be executed when no same or higher priority watchers have
		1524	received events, they can be used to implement the "lock-out" model when
		1525	required.
		1526
		1527	For example, to emulate how many other event libraries handle priorities,
		1528	you can associate an C<ev_idle> watcher to each such watcher, and in
		1529	the normal watcher callback, you just start the idle watcher. The real
		1530	processing is done in the idle watcher callback. This causes libev to
		1531	continuously poll and process kernel event data for the watcher, but when
		1532	the lock-out case is known to be rare (which in turn is rare :), this is
		1533	workable.
		1534
		1535	Usually, however, the lock-out model implemented that way will perform
		1536	miserably under the type of load it was designed to handle. In that case,
		1537	it might be preferable to stop the real watcher before starting the
		1538	idle watcher, so the kernel will not have to process the event in case
		1539	the actual processing will be delayed for considerable time.
		1540
		1541	Here is an example of an I/O watcher that should run at a strictly lower
		1542	priority than the default, and which should only process data when no
		1543	other events are pending:
		1544
		1545	ev_idle idle; // actual processing watcher
		1546	ev_io io; // actual event watcher
		1547
		1548	static void
		1549	io_cb (EV_P_ ev_io *w, int revents)
1102	{	1550	{
1103	ev_io io;	1551	// stop the I/O watcher, we received the event, but
1104	int otherfd;	1552	// are not yet ready to handle it.
1105	void *somedata;	1553	ev_io_stop (EV_A_ w);
1106	struct whatever *mostinteresting;	1554
		1555	// start the idle watcher to handle the actual event.
		1556	// it will not be executed as long as other watchers
		1557	// with the default priority are receiving events.
		1558	ev_idle_start (EV_A_ &idle);
1107	};	1559	}
1108		1560
1109	...	1561	static void
1110	struct my_io w;	1562	idle_cb (EV_P_ ev_idle *w, int revents)
1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
1112
1113	And since your callback will be called with a pointer to the watcher, you
1114	can cast it back to your own type:
1115
1116	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1117	{	1563	{
1118	struct my_io *w = (struct my_io *)w_;	1564	// actual processing
1119	...	1565	read (STDIN_FILENO, ...);
		1566
		1567	// have to start the I/O watcher again, as
		1568	// we have handled the event
		1569	ev_io_start (EV_P_ &io);
1120	}	1570	}
1121		1571
1122	More interesting and less C-conformant ways of casting your callback type	1572	// initialisation
1123	instead have been omitted.	1573	ev_idle_init (&idle, idle_cb);
		1574	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1575	ev_io_start (EV_DEFAULT_ &io);
1124		1576
1125	Another common scenario is to use some data structure with multiple	1577	In the "real" world, it might also be beneficial to start a timer, so that
1126	embedded watchers:	1578	low-priority connections can not be locked out forever under load. This
1127		1579	enables your program to keep a lower latency for important connections
1128	struct my_biggy	1580	during short periods of high load, while not completely locking out less
1129	{	1581	important ones.
1130	int some_data;
1131	ev_timer t1;
1132	ev_timer t2;
1133	}
1134
1135	In this case getting the pointer to C<my_biggy> is a bit more
1136	complicated: Either you store the address of your C<my_biggy> struct
1137	in the C<data> member of the watcher (for woozies), or you need to use
1138	some pointer arithmetic using C<offsetof> inside your watchers (for real
1139	programmers):
1140
1141	#include <stddef.h>
1142
1143	static void
1144	t1_cb (EV_P_ ev_timer *w, int revents)
1145	{
1146	struct my_biggy big = (struct my_biggy *
1147	(((char *)w) - offsetof (struct my_biggy, t1));
1148	}
1149
1150	static void
1151	t2_cb (EV_P_ ev_timer *w, int revents)
1152	{
1153	struct my_biggy big = (struct my_biggy *
1154	(((char *)w) - offsetof (struct my_biggy, t2));
1155	}
1156		1582
1157		1583
1158	=head1 WATCHER TYPES	1584	=head1 WATCHER TYPES
1159		1585
1160	This section describes each watcher in detail, but will not repeat	1586	This section describes each watcher in detail, but will not repeat
…		…
1184	In general you can register as many read and/or write event watchers per	1610	In general you can register as many read and/or write event watchers per
1185	fd as you want (as long as you don't confuse yourself). Setting all file	1611	fd as you want (as long as you don't confuse yourself). Setting all file
1186	descriptors to non-blocking mode is also usually a good idea (but not	1612	descriptors to non-blocking mode is also usually a good idea (but not
1187	required if you know what you are doing).	1613	required if you know what you are doing).
1188		1614
1189	If you cannot use non-blocking mode, then force the use of a
1190	known-to-be-good backend (at the time of this writing, this includes only
1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1192
1193	Another thing you have to watch out for is that it is quite easy to	1615	Another thing you have to watch out for is that it is quite easy to
1194	receive "spurious" readiness notifications, that is your callback might	1616	receive "spurious" readiness notifications, that is, your callback might
1195	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1617	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1196	because there is no data. Not only are some backends known to create a	1618	because there is no data. It is very easy to get into this situation even
1197	lot of those (for example Solaris ports), it is very easy to get into	1619	with a relatively standard program structure. Thus it is best to always
1198	this situation even with a relatively standard program structure. Thus	1620	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1199	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1200	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1621	preferable to a program hanging until some data arrives.
1201		1622
1202	If you cannot run the fd in non-blocking mode (for example you should	1623	If you cannot run the fd in non-blocking mode (for example you should
1203	not play around with an Xlib connection), then you have to separately	1624	not play around with an Xlib connection), then you have to separately
1204	re-test whether a file descriptor is really ready with a known-to-be good	1625	re-test whether a file descriptor is really ready with a known-to-be good
1205	interface such as poll (fortunately in our Xlib example, Xlib already	1626	interface such as poll (fortunately in the case of Xlib, it already does
1206	does this on its own, so its quite safe to use). Some people additionally	1627	this on its own, so its quite safe to use). Some people additionally
1207	use C<SIGALRM> and an interval timer, just to be sure you won't block	1628	use C<SIGALRM> and an interval timer, just to be sure you won't block
1208	indefinitely.	1629	indefinitely.
1209		1630
1210	But really, best use non-blocking mode.	1631	But really, best use non-blocking mode.
1211		1632
…		…
1239		1660
1240	There is no workaround possible except not registering events	1661	There is no workaround possible except not registering events
1241	for potentially C<dup ()>'ed file descriptors, or to resort to	1662	for potentially C<dup ()>'ed file descriptors, or to resort to
1242	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1663	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1243		1664
		1665	=head3 The special problem of files
		1666
		1667	Many people try to use C<select> (or libev) on file descriptors
		1668	representing files, and expect it to become ready when their program
		1669	doesn't block on disk accesses (which can take a long time on their own).
		1670
		1671	However, this cannot ever work in the "expected" way - you get a readiness
		1672	notification as soon as the kernel knows whether and how much data is
		1673	there, and in the case of open files, that's always the case, so you
		1674	always get a readiness notification instantly, and your read (or possibly
		1675	write) will still block on the disk I/O.
		1676
		1677	Another way to view it is that in the case of sockets, pipes, character
		1678	devices and so on, there is another party (the sender) that delivers data
		1679	on its own, but in the case of files, there is no such thing: the disk
		1680	will not send data on its own, simply because it doesn't know what you
		1681	wish to read - you would first have to request some data.
		1682
		1683	Since files are typically not-so-well supported by advanced notification
		1684	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1685	to files, even though you should not use it. The reason for this is
		1686	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1687	usually a tty, often a pipe, but also sometimes files or special devices
		1688	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1689	F</dev/urandom>), and even though the file might better be served with
		1690	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1691	it "just works" instead of freezing.
		1692
		1693	So avoid file descriptors pointing to files when you know it (e.g. use
		1694	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1695	when you rarely read from a file instead of from a socket, and want to
		1696	reuse the same code path.
		1697
1244	=head3 The special problem of fork	1698	=head3 The special problem of fork
1245		1699
1246	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1700	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1247	useless behaviour. Libev fully supports fork, but needs to be told about	1701	useless behaviour. Libev fully supports fork, but needs to be told about
1248	it in the child.	1702	it in the child if you want to continue to use it in the child.
1249		1703
1250	To support fork in your programs, you either have to call	1704	To support fork in your child processes, you have to call C<ev_loop_fork
1251	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1705	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1706	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1253	C<EVBACKEND_POLL>.
1254		1707
1255	=head3 The special problem of SIGPIPE	1708	=head3 The special problem of SIGPIPE
1256		1709
1257	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1710	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1258	when writing to a pipe whose other end has been closed, your program gets	1711	when writing to a pipe whose other end has been closed, your program gets
…		…
1261		1714
1262	So when you encounter spurious, unexplained daemon exits, make sure you	1715	So when you encounter spurious, unexplained daemon exits, make sure you
1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1716	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1264	somewhere, as that would have given you a big clue).	1717	somewhere, as that would have given you a big clue).
1265		1718
		1719	=head3 The special problem of accept()ing when you can't
		1720
		1721	Many implementations of the POSIX C<accept> function (for example,
		1722	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1723	connection from the pending queue in all error cases.
		1724
		1725	For example, larger servers often run out of file descriptors (because
		1726	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1727	rejecting the connection, leading to libev signalling readiness on
		1728	the next iteration again (the connection still exists after all), and
		1729	typically causing the program to loop at 100% CPU usage.
		1730
		1731	Unfortunately, the set of errors that cause this issue differs between
		1732	operating systems, there is usually little the app can do to remedy the
		1733	situation, and no known thread-safe method of removing the connection to
		1734	cope with overload is known (to me).
		1735
		1736	One of the easiest ways to handle this situation is to just ignore it
		1737	- when the program encounters an overload, it will just loop until the
		1738	situation is over. While this is a form of busy waiting, no OS offers an
		1739	event-based way to handle this situation, so it's the best one can do.
		1740
		1741	A better way to handle the situation is to log any errors other than
		1742	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1743	messages, and continue as usual, which at least gives the user an idea of
		1744	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1745	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1746	usage.
		1747
		1748	If your program is single-threaded, then you could also keep a dummy file
		1749	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1750	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1751	close that fd, and create a new dummy fd. This will gracefully refuse
		1752	clients under typical overload conditions.
		1753
		1754	The last way to handle it is to simply log the error and C<exit>, as
		1755	is often done with C<malloc> failures, but this results in an easy
		1756	opportunity for a DoS attack.
1266		1757
1267	=head3 Watcher-Specific Functions	1758	=head3 Watcher-Specific Functions
1268		1759
1269	=over 4	1760	=over 4
1270		1761
…		…
1302	...	1793	...
1303	struct ev_loop *loop = ev_default_init (0);	1794	struct ev_loop *loop = ev_default_init (0);
1304	ev_io stdin_readable;	1795	ev_io stdin_readable;
1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1796	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1306	ev_io_start (loop, &stdin_readable);	1797	ev_io_start (loop, &stdin_readable);
1307	ev_loop (loop, 0);	1798	ev_run (loop, 0);
1308		1799
1309		1800
1310	=head2 C<ev_timer> - relative and optionally repeating timeouts	1801	=head2 C<ev_timer> - relative and optionally repeating timeouts
1311		1802
1312	Timer watchers are simple relative timers that generate an event after a	1803	Timer watchers are simple relative timers that generate an event after a
…		…
1317	year, it will still time out after (roughly) one hour. "Roughly" because	1808	year, it will still time out after (roughly) one hour. "Roughly" because
1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1809	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1319	monotonic clock option helps a lot here).	1810	monotonic clock option helps a lot here).
1320		1811
1321	The callback is guaranteed to be invoked only I<after> its timeout has	1812	The callback is guaranteed to be invoked only I<after> its timeout has
1322	passed, but if multiple timers become ready during the same loop iteration	1813	passed (not I<at>, so on systems with very low-resolution clocks this
1323	then order of execution is undefined.	1814	might introduce a small delay, see "the special problem of being too
		1815	early", below). If multiple timers become ready during the same loop
		1816	iteration then the ones with earlier time-out values are invoked before
		1817	ones of the same priority with later time-out values (but this is no
		1818	longer true when a callback calls C<ev_run> recursively).
1324		1819
1325	=head3 Be smart about timeouts	1820	=head3 Be smart about timeouts
1326		1821
1327	Many real-world problems involve some kind of timeout, usually for error	1822	Many real-world problems involve some kind of timeout, usually for error
1328	recovery. A typical example is an HTTP request - if the other side hangs,	1823	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1867	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1373	member and C<ev_timer_again>.	1868	member and C<ev_timer_again>.
1374		1869
1375	At start:	1870	At start:
1376		1871
1377	ev_timer_init (timer, callback);	1872	ev_init (timer, callback);
1378	timer->repeat = 60.;	1873	timer->repeat = 60.;
1379	ev_timer_again (loop, timer);	1874	ev_timer_again (loop, timer);
1380		1875
1381	Each time there is some activity:	1876	Each time there is some activity:
1382		1877
…		…
1403		1898
1404	In this case, it would be more efficient to leave the C<ev_timer> alone,	1899	In this case, it would be more efficient to leave the C<ev_timer> alone,
1405	but remember the time of last activity, and check for a real timeout only	1900	but remember the time of last activity, and check for a real timeout only
1406	within the callback:	1901	within the callback:
1407		1902
		1903	ev_tstamp timeout = 60.;
1408	ev_tstamp last_activity; // time of last activity	1904	ev_tstamp last_activity; // time of last activity
		1905	ev_timer timer;
1409		1906
1410	static void	1907	static void
1411	callback (EV_P_ ev_timer *w, int revents)	1908	callback (EV_P_ ev_timer *w, int revents)
1412	{	1909	{
1413	ev_tstamp now = ev_now (EV_A);	1910	// calculate when the timeout would happen
1414	ev_tstamp timeout = last_activity + 60.;	1911	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1415		1912
1416	// if last_activity + 60. is older than now, we did time out	1913	// if negative, it means we the timeout already occurred
1417	if (timeout < now)	1914	if (after < 0.)
1418	{	1915	{
1419	// timeout occured, take action	1916	// timeout occurred, take action
1420	}	1917	}
1421	else	1918	else
1422	{	1919	{
1423	// callback was invoked, but there was some activity, re-arm	1920	// callback was invoked, but there was some recent
1424	// the watcher to fire in last_activity + 60, which is	1921	// activity. simply restart the timer to time out
1425	// guaranteed to be in the future, so "again" is positive:	1922	// after "after" seconds, which is the earliest time
1426	w->repeat = timeout - now;	1923	// the timeout can occur.
		1924	ev_timer_set (w, after, 0.);
1427	ev_timer_again (EV_A_ w);	1925	ev_timer_start (EV_A_ w);
1428	}	1926	}
1429	}	1927	}
1430		1928
1431	To summarise the callback: first calculate the real timeout (defined	1929	To summarise the callback: first calculate in how many seconds the
1432	as "60 seconds after the last activity"), then check if that time has	1930	timeout will occur (by calculating the absolute time when it would occur,
1433	been reached, which means something I<did>, in fact, time out. Otherwise	1931	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1434	the callback was invoked too early (C<timeout> is in the future), so	1932	(EV_A)> from that).
1435	re-schedule the timer to fire at that future time, to see if maybe we have
1436	a timeout then.
1437		1933
1438	Note how C<ev_timer_again> is used, taking advantage of the	1934	If this value is negative, then we are already past the timeout, i.e. we
1439	C<ev_timer_again> optimisation when the timer is already running.	1935	timed out, and need to do whatever is needed in this case.
		1936
		1937	Otherwise, we now the earliest time at which the timeout would trigger,
		1938	and simply start the timer with this timeout value.
		1939
		1940	In other words, each time the callback is invoked it will check whether
		1941	the timeout occurred. If not, it will simply reschedule itself to check
		1942	again at the earliest time it could time out. Rinse. Repeat.
1440		1943
1441	This scheme causes more callback invocations (about one every 60 seconds	1944	This scheme causes more callback invocations (about one every 60 seconds
1442	minus half the average time between activity), but virtually no calls to	1945	minus half the average time between activity), but virtually no calls to
1443	libev to change the timeout.	1946	libev to change the timeout.
1444		1947
1445	To start the timer, simply initialise the watcher and set C<last_activity>	1948	To start the machinery, simply initialise the watcher and set
1446	to the current time (meaning we just have some activity :), then call the	1949	C<last_activity> to the current time (meaning there was some activity just
1447	callback, which will "do the right thing" and start the timer:	1950	now), then call the callback, which will "do the right thing" and start
		1951	the timer:
1448		1952
		1953	last_activity = ev_now (EV_A);
1449	ev_timer_init (timer, callback);	1954	ev_init (&timer, callback);
1450	last_activity = ev_now (loop);	1955	callback (EV_A_ &timer, 0);
1451	callback (loop, timer, EV_TIMEOUT);
1452		1956
1453	And when there is some activity, simply store the current time in	1957	When there is some activity, simply store the current time in
1454	C<last_activity>, no libev calls at all:	1958	C<last_activity>, no libev calls at all:
1455		1959
		1960	if (activity detected)
1456	last_actiivty = ev_now (loop);	1961	last_activity = ev_now (EV_A);
		1962
		1963	When your timeout value changes, then the timeout can be changed by simply
		1964	providing a new value, stopping the timer and calling the callback, which
		1965	will again do the right thing (for example, time out immediately :).
		1966
		1967	timeout = new_value;
		1968	ev_timer_stop (EV_A_ &timer);
		1969	callback (EV_A_ &timer, 0);
1457		1970
1458	This technique is slightly more complex, but in most cases where the	1971	This technique is slightly more complex, but in most cases where the
1459	time-out is unlikely to be triggered, much more efficient.	1972	time-out is unlikely to be triggered, much more efficient.
1460
1461	Changing the timeout is trivial as well (if it isn't hard-coded in the
1462	callback :) - just change the timeout and invoke the callback, which will
1463	fix things for you.
1464		1973
1465	=item 4. Wee, just use a double-linked list for your timeouts.	1974	=item 4. Wee, just use a double-linked list for your timeouts.
1466		1975
1467	If there is not one request, but many thousands (millions...), all	1976	If there is not one request, but many thousands (millions...), all
1468	employing some kind of timeout with the same timeout value, then one can	1977	employing some kind of timeout with the same timeout value, then one can
…		…
1495	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2004	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1496	rather complicated, but extremely efficient, something that really pays	2005	rather complicated, but extremely efficient, something that really pays
1497	off after the first million or so of active timers, i.e. it's usually	2006	off after the first million or so of active timers, i.e. it's usually
1498	overkill :)	2007	overkill :)
1499		2008
		2009	=head3 The special problem of being too early
		2010
		2011	If you ask a timer to call your callback after three seconds, then
		2012	you expect it to be invoked after three seconds - but of course, this
		2013	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2014	guaranteed to any precision by libev - imagine somebody suspending the
		2015	process with a STOP signal for a few hours for example.
		2016
		2017	So, libev tries to invoke your callback as soon as possible I<after> the
		2018	delay has occurred, but cannot guarantee this.
		2019
		2020	A less obvious failure mode is calling your callback too early: many event
		2021	loops compare timestamps with a "elapsed delay >= requested delay", but
		2022	this can cause your callback to be invoked much earlier than you would
		2023	expect.
		2024
		2025	To see why, imagine a system with a clock that only offers full second
		2026	resolution (think windows if you can't come up with a broken enough OS
		2027	yourself). If you schedule a one-second timer at the time 500.9, then the
		2028	event loop will schedule your timeout to elapse at a system time of 500
		2029	(500.9 truncated to the resolution) + 1, or 501.
		2030
		2031	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2032	501" and invoke the callback 0.1s after it was started, even though a
		2033	one-second delay was requested - this is being "too early", despite best
		2034	intentions.
		2035
		2036	This is the reason why libev will never invoke the callback if the elapsed
		2037	delay equals the requested delay, but only when the elapsed delay is
		2038	larger than the requested delay. In the example above, libev would only invoke
		2039	the callback at system time 502, or 1.1s after the timer was started.
		2040
		2041	So, while libev cannot guarantee that your callback will be invoked
		2042	exactly when requested, it I<can> and I<does> guarantee that the requested
		2043	delay has actually elapsed, or in other words, it always errs on the "too
		2044	late" side of things.
		2045
1500	=head3 The special problem of time updates	2046	=head3 The special problem of time updates
1501		2047
1502	Establishing the current time is a costly operation (it usually takes at	2048	Establishing the current time is a costly operation (it usually takes
1503	least two system calls): EV therefore updates its idea of the current	2049	at least one system call): EV therefore updates its idea of the current
1504	time only before and after C<ev_loop> collects new events, which causes a	2050	time only before and after C<ev_run> collects new events, which causes a
1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2051	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1506	lots of events in one iteration.	2052	lots of events in one iteration.
1507		2053
1508	The relative timeouts are calculated relative to the C<ev_now ()>	2054	The relative timeouts are calculated relative to the C<ev_now ()>
1509	time. This is usually the right thing as this timestamp refers to the time	2055	time. This is usually the right thing as this timestamp refers to the time
1510	of the event triggering whatever timeout you are modifying/starting. If	2056	of the event triggering whatever timeout you are modifying/starting. If
1511	you suspect event processing to be delayed and you I<need> to base the	2057	you suspect event processing to be delayed and you I<need> to base the
1512	timeout on the current time, use something like this to adjust for this:	2058	timeout on the current time, use something like the following to adjust
		2059	for it:
1513		2060
1514	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2061	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1515		2062
1516	If the event loop is suspended for a long time, you can also force an	2063	If the event loop is suspended for a long time, you can also force an
1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2064	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1518	()>.	2065	()>, although that will push the event time of all outstanding events
		2066	further into the future.
		2067
		2068	=head3 The special problem of unsynchronised clocks
		2069
		2070	Modern systems have a variety of clocks - libev itself uses the normal
		2071	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2072	jumps).
		2073
		2074	Neither of these clocks is synchronised with each other or any other clock
		2075	on the system, so C<ev_time ()> might return a considerably different time
		2076	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2077	a call to C<gettimeofday> might return a second count that is one higher
		2078	than a directly following call to C<time>.
		2079
		2080	The moral of this is to only compare libev-related timestamps with
		2081	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2082	a second or so.
		2083
		2084	One more problem arises due to this lack of synchronisation: if libev uses
		2085	the system monotonic clock and you compare timestamps from C<ev_time>
		2086	or C<ev_now> from when you started your timer and when your callback is
		2087	invoked, you will find that sometimes the callback is a bit "early".
		2088
		2089	This is because C<ev_timer>s work in real time, not wall clock time, so
		2090	libev makes sure your callback is not invoked before the delay happened,
		2091	I<measured according to the real time>, not the system clock.
		2092
		2093	If your timeouts are based on a physical timescale (e.g. "time out this
		2094	connection after 100 seconds") then this shouldn't bother you as it is
		2095	exactly the right behaviour.
		2096
		2097	If you want to compare wall clock/system timestamps to your timers, then
		2098	you need to use C<ev_periodic>s, as these are based on the wall clock
		2099	time, where your comparisons will always generate correct results.
		2100
		2101	=head3 The special problems of suspended animation
		2102
		2103	When you leave the server world it is quite customary to hit machines that
		2104	can suspend/hibernate - what happens to the clocks during such a suspend?
		2105
		2106	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2107	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2108	to run until the system is suspended, but they will not advance while the
		2109	system is suspended. That means, on resume, it will be as if the program
		2110	was frozen for a few seconds, but the suspend time will not be counted
		2111	towards C<ev_timer> when a monotonic clock source is used. The real time
		2112	clock advanced as expected, but if it is used as sole clocksource, then a
		2113	long suspend would be detected as a time jump by libev, and timers would
		2114	be adjusted accordingly.
		2115
		2116	I would not be surprised to see different behaviour in different between
		2117	operating systems, OS versions or even different hardware.
		2118
		2119	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2120	time jump in the monotonic clocks and the realtime clock. If the program
		2121	is suspended for a very long time, and monotonic clock sources are in use,
		2122	then you can expect C<ev_timer>s to expire as the full suspension time
		2123	will be counted towards the timers. When no monotonic clock source is in
		2124	use, then libev will again assume a timejump and adjust accordingly.
		2125
		2126	It might be beneficial for this latter case to call C<ev_suspend>
		2127	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2128	deterministic behaviour in this case (you can do nothing against
		2129	C<SIGSTOP>).
1519		2130
1520	=head3 Watcher-Specific Functions and Data Members	2131	=head3 Watcher-Specific Functions and Data Members
1521		2132
1522	=over 4	2133	=over 4
1523		2134
1524	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2135	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1525		2136
1526	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2137	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1527		2138
1528	Configure the timer to trigger after C<after> seconds. If C<repeat>	2139	Configure the timer to trigger after C<after> seconds (fractional and
1529	is C<0.>, then it will automatically be stopped once the timeout is	2140	negative values are supported). If C<repeat> is C<0.>, then it will
1530	reached. If it is positive, then the timer will automatically be	2141	automatically be stopped once the timeout is reached. If it is positive,
1531	configured to trigger again C<repeat> seconds later, again, and again,	2142	then the timer will automatically be configured to trigger again C<repeat>
1532	until stopped manually.	2143	seconds later, again, and again, until stopped manually.
1533		2144
1534	The timer itself will do a best-effort at avoiding drift, that is, if	2145	The timer itself will do a best-effort at avoiding drift, that is, if
1535	you configure a timer to trigger every 10 seconds, then it will normally	2146	you configure a timer to trigger every 10 seconds, then it will normally
1536	trigger at exactly 10 second intervals. If, however, your program cannot	2147	trigger at exactly 10 second intervals. If, however, your program cannot
1537	keep up with the timer (because it takes longer than those 10 seconds to	2148	keep up with the timer (because it takes longer than those 10 seconds to
1538	do stuff) the timer will not fire more than once per event loop iteration.	2149	do stuff) the timer will not fire more than once per event loop iteration.
1539		2150
1540	=item ev_timer_again (loop, ev_timer *)	2151	=item ev_timer_again (loop, ev_timer *)
1541		2152
1542	This will act as if the timer timed out and restart it again if it is	2153	This will act as if the timer timed out, and restarts it again if it is
1543	repeating. The exact semantics are:	2154	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2155	timeout to the C<repeat> value and calling C<ev_timer_start>.
1544		2156
		2157	The exact semantics are as in the following rules, all of which will be
		2158	applied to the watcher:
		2159
		2160	=over 4
		2161
1545	If the timer is pending, its pending status is cleared.	2162	=item If the timer is pending, the pending status is always cleared.
1546		2163
1547	If the timer is started but non-repeating, stop it (as if it timed out).	2164	=item If the timer is started but non-repeating, stop it (as if it timed
		2165	out, without invoking it).
1548		2166
1549	If the timer is repeating, either start it if necessary (with the	2167	=item If the timer is repeating, make the C<repeat> value the new timeout
1550	C<repeat> value), or reset the running timer to the C<repeat> value.	2168	and start the timer, if necessary.
1551		2169
		2170	=back
		2171
1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2172	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1553	usage example.	2173	usage example.
		2174
		2175	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2176
		2177	Returns the remaining time until a timer fires. If the timer is active,
		2178	then this time is relative to the current event loop time, otherwise it's
		2179	the timeout value currently configured.
		2180
		2181	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2182	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2183	will return C<4>. When the timer expires and is restarted, it will return
		2184	roughly C<7> (likely slightly less as callback invocation takes some time,
		2185	too), and so on.
1554		2186
1555	=item ev_tstamp repeat [read-write]	2187	=item ev_tstamp repeat [read-write]
1556		2188
1557	The current C<repeat> value. Will be used each time the watcher times out	2189	The current C<repeat> value. Will be used each time the watcher times out
1558	or C<ev_timer_again> is called, and determines the next timeout (if any),	2190	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1584	}	2216	}
1585		2217
1586	ev_timer mytimer;	2218	ev_timer mytimer;
1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2219	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1588	ev_timer_again (&mytimer); /* start timer */	2220	ev_timer_again (&mytimer); /* start timer */
1589	ev_loop (loop, 0);	2221	ev_run (loop, 0);
1590		2222
1591	// and in some piece of code that gets executed on any "activity":	2223	// and in some piece of code that gets executed on any "activity":
1592	// reset the timeout to start ticking again at 10 seconds	2224	// reset the timeout to start ticking again at 10 seconds
1593	ev_timer_again (&mytimer);	2225	ev_timer_again (&mytimer);
1594		2226
…		…
1596	=head2 C<ev_periodic> - to cron or not to cron?	2228	=head2 C<ev_periodic> - to cron or not to cron?
1597		2229
1598	Periodic watchers are also timers of a kind, but they are very versatile	2230	Periodic watchers are also timers of a kind, but they are very versatile
1599	(and unfortunately a bit complex).	2231	(and unfortunately a bit complex).
1600		2232
1601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2233	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1602	but on wall clock time (absolute time). You can tell a periodic watcher	2234	relative time, the physical time that passes) but on wall clock time
1603	to trigger after some specific point in time. For example, if you tell a	2235	(absolute time, the thing you can read on your calendar or clock). The
1604	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2236	difference is that wall clock time can run faster or slower than real
1605	+ 10.>, that is, an absolute time not a delay) and then reset your system	2237	time, and time jumps are not uncommon (e.g. when you adjust your
1606	clock to January of the previous year, then it will take more than year	2238	wrist-watch).
1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1608	roughly 10 seconds later as it uses a relative timeout).
1609		2239
		2240	You can tell a periodic watcher to trigger after some specific point
		2241	in time: for example, if you tell a periodic watcher to trigger "in 10
		2242	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2243	not a delay) and then reset your system clock to January of the previous
		2244	year, then it will take a year or more to trigger the event (unlike an
		2245	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2246	it, as it uses a relative timeout).
		2247
1610	C<ev_periodic>s can also be used to implement vastly more complex timers,	2248	C<ev_periodic> watchers can also be used to implement vastly more complex
1611	such as triggering an event on each "midnight, local time", or other	2249	timers, such as triggering an event on each "midnight, local time", or
1612	complicated rules.	2250	other complicated rules. This cannot easily be done with C<ev_timer>
		2251	watchers, as those cannot react to time jumps.
1613		2252
1614	As with timers, the callback is guaranteed to be invoked only when the	2253	As with timers, the callback is guaranteed to be invoked only when the
1615	time (C<at>) has passed, but if multiple periodic timers become ready	2254	point in time where it is supposed to trigger has passed. If multiple
1616	during the same loop iteration, then order of execution is undefined.	2255	timers become ready during the same loop iteration then the ones with
		2256	earlier time-out values are invoked before ones with later time-out values
		2257	(but this is no longer true when a callback calls C<ev_run> recursively).
1617		2258
1618	=head3 Watcher-Specific Functions and Data Members	2259	=head3 Watcher-Specific Functions and Data Members
1619		2260
1620	=over 4	2261	=over 4
1621		2262
1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2263	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1623		2264
1624	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2265	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1625		2266
1626	Lots of arguments, lets sort it out... There are basically three modes of	2267	Lots of arguments, let's sort it out... There are basically three modes of
1627	operation, and we will explain them from simplest to most complex:	2268	operation, and we will explain them from simplest to most complex:
1628		2269
1629	=over 4	2270	=over 4
1630		2271
1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2272	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1632		2273
1633	In this configuration the watcher triggers an event after the wall clock	2274	In this configuration the watcher triggers an event after the wall clock
1634	time C<at> has passed. It will not repeat and will not adjust when a time	2275	time C<offset> has passed. It will not repeat and will not adjust when a
1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2276	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1636	only run when the system clock reaches or surpasses this time.	2277	will be stopped and invoked when the system clock reaches or surpasses
		2278	this point in time.
1637		2279
1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2280	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1639		2281
1640	In this mode the watcher will always be scheduled to time out at the next	2282	In this mode the watcher will always be scheduled to time out at the next
1641	C<at + N * interval> time (for some integer N, which can also be negative)	2283	C<offset + N * interval> time (for some integer N, which can also be
1642	and then repeat, regardless of any time jumps.	2284	negative) and then repeat, regardless of any time jumps. The C<offset>
		2285	argument is merely an offset into the C<interval> periods.
1643		2286
1644	This can be used to create timers that do not drift with respect to the	2287	This can be used to create timers that do not drift with respect to the
1645	system clock, for example, here is a C<ev_periodic> that triggers each	2288	system clock, for example, here is an C<ev_periodic> that triggers each
1646	hour, on the hour:	2289	hour, on the hour (with respect to UTC):
1647		2290
1648	ev_periodic_set (&periodic, 0., 3600., 0);	2291	ev_periodic_set (&periodic, 0., 3600., 0);
1649		2292
1650	This doesn't mean there will always be 3600 seconds in between triggers,	2293	This doesn't mean there will always be 3600 seconds in between triggers,
1651	but only that the callback will be called when the system time shows a	2294	but only that the callback will be called when the system time shows a
1652	full hour (UTC), or more correctly, when the system time is evenly divisible	2295	full hour (UTC), or more correctly, when the system time is evenly divisible
1653	by 3600.	2296	by 3600.
1654		2297
1655	Another way to think about it (for the mathematically inclined) is that	2298	Another way to think about it (for the mathematically inclined) is that
1656	C<ev_periodic> will try to run the callback in this mode at the next possible	2299	C<ev_periodic> will try to run the callback in this mode at the next possible
1657	time where C<time = at (mod interval)>, regardless of any time jumps.	2300	time where C<time = offset (mod interval)>, regardless of any time jumps.
1658		2301
1659	For numerical stability it is preferable that the C<at> value is near	2302	The C<interval> I<MUST> be positive, and for numerical stability, the
1660	C<ev_now ()> (the current time), but there is no range requirement for	2303	interval value should be higher than C<1/8192> (which is around 100
1661	this value, and in fact is often specified as zero.	2304	microseconds) and C<offset> should be higher than C<0> and should have
		2305	at most a similar magnitude as the current time (say, within a factor of
		2306	ten). Typical values for offset are, in fact, C<0> or something between
		2307	C<0> and C<interval>, which is also the recommended range.
1662		2308
1663	Note also that there is an upper limit to how often a timer can fire (CPU	2309	Note also that there is an upper limit to how often a timer can fire (CPU
1664	speed for example), so if C<interval> is very small then timing stability	2310	speed for example), so if C<interval> is very small then timing stability
1665	will of course deteriorate. Libev itself tries to be exact to be about one	2311	will of course deteriorate. Libev itself tries to be exact to be about one
1666	millisecond (if the OS supports it and the machine is fast enough).	2312	millisecond (if the OS supports it and the machine is fast enough).
1667		2313
1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2314	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1669		2315
1670	In this mode the values for C<interval> and C<at> are both being	2316	In this mode the values for C<interval> and C<offset> are both being
1671	ignored. Instead, each time the periodic watcher gets scheduled, the	2317	ignored. Instead, each time the periodic watcher gets scheduled, the
1672	reschedule callback will be called with the watcher as first, and the	2318	reschedule callback will be called with the watcher as first, and the
1673	current time as second argument.	2319	current time as second argument.
1674		2320
1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2321	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1676	ever, or make ANY event loop modifications whatsoever>.	2322	or make ANY other event loop modifications whatsoever, unless explicitly
		2323	allowed by documentation here>.
1677		2324
1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2325	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2326	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1680	only event loop modification you are allowed to do).	2327	only event loop modification you are allowed to do).
1681		2328
…		…
1695		2342
1696	NOTE: I<< This callback must always return a time that is higher than or	2343	NOTE: I<< This callback must always return a time that is higher than or
1697	equal to the passed C<now> value >>.	2344	equal to the passed C<now> value >>.
1698		2345
1699	This can be used to create very complex timers, such as a timer that	2346	This can be used to create very complex timers, such as a timer that
1700	triggers on "next midnight, local time". To do this, you would calculate the	2347	triggers on "next midnight, local time". To do this, you would calculate
1701	next midnight after C<now> and return the timestamp value for this. How	2348	the next midnight after C<now> and return the timestamp value for
1702	you do this is, again, up to you (but it is not trivial, which is the main	2349	this. Here is a (completely untested, no error checking) example on how to
1703	reason I omitted it as an example).	2350	do this:
		2351
		2352	#include <time.h>
		2353
		2354	static ev_tstamp
		2355	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2356	{
		2357	time_t tnow = (time_t)now;
		2358	struct tm tm;
		2359	localtime_r (&tnow, &tm);
		2360
		2361	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2362	++tm.tm_mday; // midnight next day
		2363
		2364	return mktime (&tm);
		2365	}
		2366
		2367	Note: this code might run into trouble on days that have more then two
		2368	midnights (beginning and end).
1704		2369
1705	=back	2370	=back
1706		2371
1707	=item ev_periodic_again (loop, ev_periodic *)	2372	=item ev_periodic_again (loop, ev_periodic *)
1708		2373
…		…
1711	a different time than the last time it was called (e.g. in a crond like	2376	a different time than the last time it was called (e.g. in a crond like
1712	program when the crontabs have changed).	2377	program when the crontabs have changed).
1713		2378
1714	=item ev_tstamp ev_periodic_at (ev_periodic *)	2379	=item ev_tstamp ev_periodic_at (ev_periodic *)
1715		2380
1716	When active, returns the absolute time that the watcher is supposed to	2381	When active, returns the absolute time that the watcher is supposed
1717	trigger next.	2382	to trigger next. This is not the same as the C<offset> argument to
		2383	C<ev_periodic_set>, but indeed works even in interval and manual
		2384	rescheduling modes.
1718		2385
1719	=item ev_tstamp offset [read-write]	2386	=item ev_tstamp offset [read-write]
1720		2387
1721	When repeating, this contains the offset value, otherwise this is the	2388	When repeating, this contains the offset value, otherwise this is the
1722	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2389	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2390	although libev might modify this value for better numerical stability).
1723		2391
1724	Can be modified any time, but changes only take effect when the periodic	2392	Can be modified any time, but changes only take effect when the periodic
1725	timer fires or C<ev_periodic_again> is being called.	2393	timer fires or C<ev_periodic_again> is being called.
1726		2394
1727	=item ev_tstamp interval [read-write]	2395	=item ev_tstamp interval [read-write]
…		…
1743	Example: Call a callback every hour, or, more precisely, whenever the	2411	Example: Call a callback every hour, or, more precisely, whenever the
1744	system time is divisible by 3600. The callback invocation times have	2412	system time is divisible by 3600. The callback invocation times have
1745	potentially a lot of jitter, but good long-term stability.	2413	potentially a lot of jitter, but good long-term stability.
1746		2414
1747	static void	2415	static void
1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2416	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1749	{	2417	{
1750	... its now a full hour (UTC, or TAI or whatever your clock follows)	2418	... its now a full hour (UTC, or TAI or whatever your clock follows)
1751	}	2419	}
1752		2420
1753	ev_periodic hourly_tick;	2421	ev_periodic hourly_tick;
…		…
1770		2438
1771	ev_periodic hourly_tick;	2439	ev_periodic hourly_tick;
1772	ev_periodic_init (&hourly_tick, clock_cb,	2440	ev_periodic_init (&hourly_tick, clock_cb,
1773	fmod (ev_now (loop), 3600.), 3600., 0);	2441	fmod (ev_now (loop), 3600.), 3600., 0);
1774	ev_periodic_start (loop, &hourly_tick);	2442	ev_periodic_start (loop, &hourly_tick);
1775		2443
1776		2444
1777	=head2 C<ev_signal> - signal me when a signal gets signalled!	2445	=head2 C<ev_signal> - signal me when a signal gets signalled!
1778		2446
1779	Signal watchers will trigger an event when the process receives a specific	2447	Signal watchers will trigger an event when the process receives a specific
1780	signal one or more times. Even though signals are very asynchronous, libev	2448	signal one or more times. Even though signals are very asynchronous, libev
1781	will try it's best to deliver signals synchronously, i.e. as part of the	2449	will try its best to deliver signals synchronously, i.e. as part of the
1782	normal event processing, like any other event.	2450	normal event processing, like any other event.
1783		2451
1784	If you want signals asynchronously, just use C<sigaction> as you would	2452	If you want signals to be delivered truly asynchronously, just use
1785	do without libev and forget about sharing the signal. You can even use	2453	C<sigaction> as you would do without libev and forget about sharing
1786	C<ev_async> from a signal handler to synchronously wake up an event loop.	2454	the signal. You can even use C<ev_async> from a signal handler to
		2455	synchronously wake up an event loop.
1787		2456
1788	You can configure as many watchers as you like per signal. Only when the	2457	You can configure as many watchers as you like for the same signal, but
1789	first watcher gets started will libev actually register a signal handler	2458	only within the same loop, i.e. you can watch for C<SIGINT> in your
1790	with the kernel (thus it coexists with your own signal handlers as long as	2459	default loop and for C<SIGIO> in another loop, but you cannot watch for
1791	you don't register any with libev for the same signal). Similarly, when	2460	C<SIGINT> in both the default loop and another loop at the same time. At
1792	the last signal watcher for a signal is stopped, libev will reset the	2461	the moment, C<SIGCHLD> is permanently tied to the default loop.
1793	signal handler to SIG_DFL (regardless of what it was set to before).	2462
		2463	Only after the first watcher for a signal is started will libev actually
		2464	register something with the kernel. It thus coexists with your own signal
		2465	handlers as long as you don't register any with libev for the same signal.
1794		2466
1795	If possible and supported, libev will install its handlers with	2467	If possible and supported, libev will install its handlers with
1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2468	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1797	interrupted. If you have a problem with system calls getting interrupted by	2469	not be unduly interrupted. If you have a problem with system calls getting
1798	signals you can block all signals in an C<ev_check> watcher and unblock	2470	interrupted by signals you can block all signals in an C<ev_check> watcher
1799	them in an C<ev_prepare> watcher.	2471	and unblock them in an C<ev_prepare> watcher.
		2472
		2473	=head3 The special problem of inheritance over fork/execve/pthread_create
		2474
		2475	Both the signal mask (C<sigprocmask>) and the signal disposition
		2476	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2477	stopping it again), that is, libev might or might not block the signal,
		2478	and might or might not set or restore the installed signal handler (but
		2479	see C<EVFLAG_NOSIGMASK>).
		2480
		2481	While this does not matter for the signal disposition (libev never
		2482	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2483	C<execve>), this matters for the signal mask: many programs do not expect
		2484	certain signals to be blocked.
		2485
		2486	This means that before calling C<exec> (from the child) you should reset
		2487	the signal mask to whatever "default" you expect (all clear is a good
		2488	choice usually).
		2489
		2490	The simplest way to ensure that the signal mask is reset in the child is
		2491	to install a fork handler with C<pthread_atfork> that resets it. That will
		2492	catch fork calls done by libraries (such as the libc) as well.
		2493
		2494	In current versions of libev, the signal will not be blocked indefinitely
		2495	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2496	the window of opportunity for problems, it will not go away, as libev
		2497	I<has> to modify the signal mask, at least temporarily.
		2498
		2499	So I can't stress this enough: I<If you do not reset your signal mask when
		2500	you expect it to be empty, you have a race condition in your code>. This
		2501	is not a libev-specific thing, this is true for most event libraries.
		2502
		2503	=head3 The special problem of threads signal handling
		2504
		2505	POSIX threads has problematic signal handling semantics, specifically,
		2506	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2507	threads in a process block signals, which is hard to achieve.
		2508
		2509	When you want to use sigwait (or mix libev signal handling with your own
		2510	for the same signals), you can tackle this problem by globally blocking
		2511	all signals before creating any threads (or creating them with a fully set
		2512	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2513	loops. Then designate one thread as "signal receiver thread" which handles
		2514	these signals. You can pass on any signals that libev might be interested
		2515	in by calling C<ev_feed_signal>.
1800		2516
1801	=head3 Watcher-Specific Functions and Data Members	2517	=head3 Watcher-Specific Functions and Data Members
1802		2518
1803	=over 4	2519	=over 4
1804		2520
…		…
1820	Example: Try to exit cleanly on SIGINT.	2536	Example: Try to exit cleanly on SIGINT.
1821		2537
1822	static void	2538	static void
1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2539	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1824	{	2540	{
1825	ev_unloop (loop, EVUNLOOP_ALL);	2541	ev_break (loop, EVBREAK_ALL);
1826	}	2542	}
1827		2543
1828	ev_signal signal_watcher;	2544	ev_signal signal_watcher;
1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2545	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1830	ev_signal_start (loop, &signal_watcher);	2546	ev_signal_start (loop, &signal_watcher);
…		…
1836	some child status changes (most typically when a child of yours dies or	2552	some child status changes (most typically when a child of yours dies or
1837	exits). It is permissible to install a child watcher I<after> the child	2553	exits). It is permissible to install a child watcher I<after> the child
1838	has been forked (which implies it might have already exited), as long	2554	has been forked (which implies it might have already exited), as long
1839	as the event loop isn't entered (or is continued from a watcher), i.e.,	2555	as the event loop isn't entered (or is continued from a watcher), i.e.,
1840	forking and then immediately registering a watcher for the child is fine,	2556	forking and then immediately registering a watcher for the child is fine,
1841	but forking and registering a watcher a few event loop iterations later is	2557	but forking and registering a watcher a few event loop iterations later or
1842	not.	2558	in the next callback invocation is not.
1843		2559
1844	Only the default event loop is capable of handling signals, and therefore	2560	Only the default event loop is capable of handling signals, and therefore
1845	you can only register child watchers in the default event loop.	2561	you can only register child watchers in the default event loop.
1846		2562
		2563	Due to some design glitches inside libev, child watchers will always be
		2564	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2565	libev)
		2566
1847	=head3 Process Interaction	2567	=head3 Process Interaction
1848		2568
1849	Libev grabs C<SIGCHLD> as soon as the default event loop is	2569	Libev grabs C<SIGCHLD> as soon as the default event loop is
1850	initialised. This is necessary to guarantee proper behaviour even if	2570	initialised. This is necessary to guarantee proper behaviour even if the
1851	the first child watcher is started after the child exits. The occurrence	2571	first child watcher is started after the child exits. The occurrence
1852	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2572	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1853	synchronously as part of the event loop processing. Libev always reaps all	2573	synchronously as part of the event loop processing. Libev always reaps all
1854	children, even ones not watched.	2574	children, even ones not watched.
1855		2575
1856	=head3 Overriding the Built-In Processing	2576	=head3 Overriding the Built-In Processing
…		…
1866	=head3 Stopping the Child Watcher	2586	=head3 Stopping the Child Watcher
1867		2587
1868	Currently, the child watcher never gets stopped, even when the	2588	Currently, the child watcher never gets stopped, even when the
1869	child terminates, so normally one needs to stop the watcher in the	2589	child terminates, so normally one needs to stop the watcher in the
1870	callback. Future versions of libev might stop the watcher automatically	2590	callback. Future versions of libev might stop the watcher automatically
1871	when a child exit is detected.	2591	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2592	problem).
1872		2593
1873	=head3 Watcher-Specific Functions and Data Members	2594	=head3 Watcher-Specific Functions and Data Members
1874		2595
1875	=over 4	2596	=over 4
1876		2597
…		…
1934		2655
1935	=head2 C<ev_stat> - did the file attributes just change?	2656	=head2 C<ev_stat> - did the file attributes just change?
1936		2657
1937	This watches a file system path for attribute changes. That is, it calls	2658	This watches a file system path for attribute changes. That is, it calls
1938	C<stat> on that path in regular intervals (or when the OS says it changed)	2659	C<stat> on that path in regular intervals (or when the OS says it changed)
1939	and sees if it changed compared to the last time, invoking the callback if	2660	and sees if it changed compared to the last time, invoking the callback
1940	it did.	2661	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2662	happen after the watcher has been started will be reported.
1941		2663
1942	The path does not need to exist: changing from "path exists" to "path does	2664	The path does not need to exist: changing from "path exists" to "path does
1943	not exist" is a status change like any other. The condition "path does not	2665	not exist" is a status change like any other. The condition "path does not
1944	exist" (or more correctly "path cannot be stat'ed") is signified by the	2666	exist" (or more correctly "path cannot be stat'ed") is signified by the
1945	C<st_nlink> field being zero (which is otherwise always forced to be at	2667	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2175	Apart from keeping your process non-blocking (which is a useful	2897	Apart from keeping your process non-blocking (which is a useful
2176	effect on its own sometimes), idle watchers are a good place to do	2898	effect on its own sometimes), idle watchers are a good place to do
2177	"pseudo-background processing", or delay processing stuff to after the	2899	"pseudo-background processing", or delay processing stuff to after the
2178	event loop has handled all outstanding events.	2900	event loop has handled all outstanding events.
2179		2901
		2902	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2903
		2904	As long as there is at least one active idle watcher, libev will never
		2905	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2906	For this to work, the idle watcher doesn't need to be invoked at all - the
		2907	lowest priority will do.
		2908
		2909	This mode of operation can be useful together with an C<ev_check> watcher,
		2910	to do something on each event loop iteration - for example to balance load
		2911	between different connections.
		2912
		2913	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2914	example.
		2915
2180	=head3 Watcher-Specific Functions and Data Members	2916	=head3 Watcher-Specific Functions and Data Members
2181		2917
2182	=over 4	2918	=over 4
2183		2919
2184	=item ev_idle_init (ev_signal *, callback)	2920	=item ev_idle_init (ev_idle *, callback)
2185		2921
2186	Initialises and configures the idle watcher - it has no parameters of any	2922	Initialises and configures the idle watcher - it has no parameters of any
2187	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2923	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2188	believe me.	2924	believe me.
2189		2925
…		…
2195	callback, free it. Also, use no error checking, as usual.	2931	callback, free it. Also, use no error checking, as usual.
2196		2932
2197	static void	2933	static void
2198	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2934	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2199	{	2935	{
		2936	// stop the watcher
		2937	ev_idle_stop (loop, w);
		2938
		2939	// now we can free it
2200	free (w);	2940	free (w);
		2941
2201	// now do something you wanted to do when the program has	2942	// now do something you wanted to do when the program has
2202	// no longer anything immediate to do.	2943	// no longer anything immediate to do.
2203	}	2944	}
2204		2945
2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2946	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2206	ev_idle_init (idle_watcher, idle_cb);	2947	ev_idle_init (idle_watcher, idle_cb);
2207	ev_idle_start (loop, idle_cb);	2948	ev_idle_start (loop, idle_watcher);
2208		2949
2209		2950
2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2951	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2211		2952
2212	Prepare and check watchers are usually (but not always) used in pairs:	2953	Prepare and check watchers are often (but not always) used in pairs:
2213	prepare watchers get invoked before the process blocks and check watchers	2954	prepare watchers get invoked before the process blocks and check watchers
2214	afterwards.	2955	afterwards.
2215		2956
2216	You I<must not> call C<ev_loop> or similar functions that enter	2957	You I<must not> call C<ev_run> (or similar functions that enter the
2217	the current event loop from either C<ev_prepare> or C<ev_check>	2958	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2218	watchers. Other loops than the current one are fine, however. The	2959	C<ev_check> watchers. Other loops than the current one are fine,
2219	rationale behind this is that you do not need to check for recursion in	2960	however. The rationale behind this is that you do not need to check
2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2961	for recursion in those watchers, i.e. the sequence will always be
2221	C<ev_check> so if you have one watcher of each kind they will always be	2962	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2222	called in pairs bracketing the blocking call.	2963	kind they will always be called in pairs bracketing the blocking call.
2223		2964
2224	Their main purpose is to integrate other event mechanisms into libev and	2965	Their main purpose is to integrate other event mechanisms into libev and
2225	their use is somewhat advanced. They could be used, for example, to track	2966	their use is somewhat advanced. They could be used, for example, to track
2226	variable changes, implement your own watchers, integrate net-snmp or a	2967	variable changes, implement your own watchers, integrate net-snmp or a
2227	coroutine library and lots more. They are also occasionally useful if	2968	coroutine library and lots more. They are also occasionally useful if
…		…
2245	with priority higher than or equal to the event loop and one coroutine	2986	with priority higher than or equal to the event loop and one coroutine
2246	of lower priority, but only once, using idle watchers to keep the event	2987	of lower priority, but only once, using idle watchers to keep the event
2247	loop from blocking if lower-priority coroutines are active, thus mapping	2988	loop from blocking if lower-priority coroutines are active, thus mapping
2248	low-priority coroutines to idle/background tasks).	2989	low-priority coroutines to idle/background tasks).
2249		2990
2250	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2991	When used for this purpose, it is recommended to give C<ev_check> watchers
2251	priority, to ensure that they are being run before any other watchers	2992	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2252	after the poll (this doesn't matter for C<ev_prepare> watchers).	2993	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		2994	watchers).
2253		2995
2254	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	2996	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2255	activate ("feed") events into libev. While libev fully supports this, they	2997	activate ("feed") events into libev. While libev fully supports this, they
2256	might get executed before other C<ev_check> watchers did their job. As	2998	might get executed before other C<ev_check> watchers did their job. As
2257	C<ev_check> watchers are often used to embed other (non-libev) event	2999	C<ev_check> watchers are often used to embed other (non-libev) event
2258	loops those other event loops might be in an unusable state until their	3000	loops those other event loops might be in an unusable state until their
2259	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3001	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2260	others).	3002	others).
		3003
		3004	=head3 Abusing an C<ev_check> watcher for its side-effect
		3005
		3006	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3007	useful because they are called once per event loop iteration. For
		3008	example, if you want to handle a large number of connections fairly, you
		3009	normally only do a bit of work for each active connection, and if there
		3010	is more work to do, you wait for the next event loop iteration, so other
		3011	connections have a chance of making progress.
		3012
		3013	Using an C<ev_check> watcher is almost enough: it will be called on the
		3014	next event loop iteration. However, that isn't as soon as possible -
		3015	without external events, your C<ev_check> watcher will not be invoked.
		3016
		3017	This is where C<ev_idle> watchers come in handy - all you need is a
		3018	single global idle watcher that is active as long as you have one active
		3019	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3020	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3021	invoked. Neither watcher alone can do that.
2261		3022
2262	=head3 Watcher-Specific Functions and Data Members	3023	=head3 Watcher-Specific Functions and Data Members
2263		3024
2264	=over 4	3025	=over 4
2265		3026
…		…
2305	struct pollfd fds [nfd];	3066	struct pollfd fds [nfd];
2306	// actual code will need to loop here and realloc etc.	3067	// actual code will need to loop here and realloc etc.
2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3068	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2308		3069
2309	/* the callback is illegal, but won't be called as we stop during check */	3070	/* the callback is illegal, but won't be called as we stop during check */
2310	ev_timer_init (&tw, 0, timeout * 1e-3);	3071	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2311	ev_timer_start (loop, &tw);	3072	ev_timer_start (loop, &tw);
2312		3073
2313	// create one ev_io per pollfd	3074	// create one ev_io per pollfd
2314	for (int i = 0; i < nfd; ++i)	3075	for (int i = 0; i < nfd; ++i)
2315	{	3076	{
…		…
2389		3150
2390	if (timeout >= 0)	3151	if (timeout >= 0)
2391	// create/start timer	3152	// create/start timer
2392		3153
2393	// poll	3154	// poll
2394	ev_loop (EV_A_ 0);	3155	ev_run (EV_A_ 0);
2395		3156
2396	// stop timer again	3157	// stop timer again
2397	if (timeout >= 0)	3158	if (timeout >= 0)
2398	ev_timer_stop (EV_A_ &to);	3159	ev_timer_stop (EV_A_ &to);
2399		3160
…		…
2466		3227
2467	=over 4	3228	=over 4
2468		3229
2469	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3230	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2470		3231
2471	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3232	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2472		3233
2473	Configures the watcher to embed the given loop, which must be	3234	Configures the watcher to embed the given loop, which must be
2474	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3235	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2475	invoked automatically, otherwise it is the responsibility of the callback	3236	invoked automatically, otherwise it is the responsibility of the callback
2476	to invoke it (it will continue to be called until the sweep has been done,	3237	to invoke it (it will continue to be called until the sweep has been done,
2477	if you do not want that, you need to temporarily stop the embed watcher).	3238	if you do not want that, you need to temporarily stop the embed watcher).
2478		3239
2479	=item ev_embed_sweep (loop, ev_embed *)	3240	=item ev_embed_sweep (loop, ev_embed *)
2480		3241
2481	Make a single, non-blocking sweep over the embedded loop. This works	3242	Make a single, non-blocking sweep over the embedded loop. This works
2482	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3243	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2483	appropriate way for embedded loops.	3244	appropriate way for embedded loops.
2484		3245
2485	=item struct ev_loop *other [read-only]	3246	=item struct ev_loop *other [read-only]
2486		3247
2487	The embedded event loop.	3248	The embedded event loop.
…		…
2497	used).	3258	used).
2498		3259
2499	struct ev_loop *loop_hi = ev_default_init (0);	3260	struct ev_loop *loop_hi = ev_default_init (0);
2500	struct ev_loop *loop_lo = 0;	3261	struct ev_loop *loop_lo = 0;
2501	ev_embed embed;	3262	ev_embed embed;
2502		3263
2503	// see if there is a chance of getting one that works	3264	// see if there is a chance of getting one that works
2504	// (remember that a flags value of 0 means autodetection)	3265	// (remember that a flags value of 0 means autodetection)
2505	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3266	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2506	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3267	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2507	: 0;	3268	: 0;
…		…
2521	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3282	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2522		3283
2523	struct ev_loop *loop = ev_default_init (0);	3284	struct ev_loop *loop = ev_default_init (0);
2524	struct ev_loop *loop_socket = 0;	3285	struct ev_loop *loop_socket = 0;
2525	ev_embed embed;	3286	ev_embed embed;
2526		3287
2527	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3288	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2528	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3289	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2529	{	3290	{
2530	ev_embed_init (&embed, 0, loop_socket);	3291	ev_embed_init (&embed, 0, loop_socket);
2531	ev_embed_start (loop, &embed);	3292	ev_embed_start (loop, &embed);
…		…
2539		3300
2540	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3301	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2541		3302
2542	Fork watchers are called when a C<fork ()> was detected (usually because	3303	Fork watchers are called when a C<fork ()> was detected (usually because
2543	whoever is a good citizen cared to tell libev about it by calling	3304	whoever is a good citizen cared to tell libev about it by calling
2544	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3305	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2545	event loop blocks next and before C<ev_check> watchers are being called,	3306	and before C<ev_check> watchers are being called, and only in the child
2546	and only in the child after the fork. If whoever good citizen calling	3307	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2547	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3308	and calls it in the wrong process, the fork handlers will be invoked, too,
2548	handlers will be invoked, too, of course.	3309	of course.
		3310
		3311	=head3 The special problem of life after fork - how is it possible?
		3312
		3313	Most uses of C<fork ()> consist of forking, then some simple calls to set
		3314	up/change the process environment, followed by a call to C<exec()>. This
		3315	sequence should be handled by libev without any problems.
		3316
		3317	This changes when the application actually wants to do event handling
		3318	in the child, or both parent in child, in effect "continuing" after the
		3319	fork.
		3320
		3321	The default mode of operation (for libev, with application help to detect
		3322	forks) is to duplicate all the state in the child, as would be expected
		3323	when I<either> the parent I<or> the child process continues.
		3324
		3325	When both processes want to continue using libev, then this is usually the
		3326	wrong result. In that case, usually one process (typically the parent) is
		3327	supposed to continue with all watchers in place as before, while the other
		3328	process typically wants to start fresh, i.e. without any active watchers.
		3329
		3330	The cleanest and most efficient way to achieve that with libev is to
		3331	simply create a new event loop, which of course will be "empty", and
		3332	use that for new watchers. This has the advantage of not touching more
		3333	memory than necessary, and thus avoiding the copy-on-write, and the
		3334	disadvantage of having to use multiple event loops (which do not support
		3335	signal watchers).
		3336
		3337	When this is not possible, or you want to use the default loop for
		3338	other reasons, then in the process that wants to start "fresh", call
		3339	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3340	Destroying the default loop will "orphan" (not stop) all registered
		3341	watchers, so you have to be careful not to execute code that modifies
		3342	those watchers. Note also that in that case, you have to re-register any
		3343	signal watchers.
2549		3344
2550	=head3 Watcher-Specific Functions and Data Members	3345	=head3 Watcher-Specific Functions and Data Members
2551		3346
2552	=over 4	3347	=over 4
2553		3348
2554	=item ev_fork_init (ev_signal *, callback)	3349	=item ev_fork_init (ev_fork *, callback)
2555		3350
2556	Initialises and configures the fork watcher - it has no parameters of any	3351	Initialises and configures the fork watcher - it has no parameters of any
2557	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3352	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2558	believe me.	3353	really.
2559		3354
2560	=back	3355	=back
2561		3356
2562		3357
		3358	=head2 C<ev_cleanup> - even the best things end
		3359
		3360	Cleanup watchers are called just before the event loop is being destroyed
		3361	by a call to C<ev_loop_destroy>.
		3362
		3363	While there is no guarantee that the event loop gets destroyed, cleanup
		3364	watchers provide a convenient method to install cleanup hooks for your
		3365	program, worker threads and so on - you just to make sure to destroy the
		3366	loop when you want them to be invoked.
		3367
		3368	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3369	all other watchers, they do not keep a reference to the event loop (which
		3370	makes a lot of sense if you think about it). Like all other watchers, you
		3371	can call libev functions in the callback, except C<ev_cleanup_start>.
		3372
		3373	=head3 Watcher-Specific Functions and Data Members
		3374
		3375	=over 4
		3376
		3377	=item ev_cleanup_init (ev_cleanup *, callback)
		3378
		3379	Initialises and configures the cleanup watcher - it has no parameters of
		3380	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3381	pointless, I assure you.
		3382
		3383	=back
		3384
		3385	Example: Register an atexit handler to destroy the default loop, so any
		3386	cleanup functions are called.
		3387
		3388	static void
		3389	program_exits (void)
		3390	{
		3391	ev_loop_destroy (EV_DEFAULT_UC);
		3392	}
		3393
		3394	...
		3395	atexit (program_exits);
		3396
		3397
2563	=head2 C<ev_async> - how to wake up another event loop	3398	=head2 C<ev_async> - how to wake up an event loop
2564		3399
2565	In general, you cannot use an C<ev_loop> from multiple threads or other	3400	In general, you cannot use an C<ev_loop> from multiple threads or other
2566	asynchronous sources such as signal handlers (as opposed to multiple event	3401	asynchronous sources such as signal handlers (as opposed to multiple event
2567	loops - those are of course safe to use in different threads).	3402	loops - those are of course safe to use in different threads).
2568		3403
2569	Sometimes, however, you need to wake up another event loop you do not	3404	Sometimes, however, you need to wake up an event loop you do not control,
2570	control, for example because it belongs to another thread. This is what	3405	for example because it belongs to another thread. This is what C<ev_async>
2571	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3406	watchers do: as long as the C<ev_async> watcher is active, you can signal
2572	can signal it by calling C<ev_async_send>, which is thread- and signal	3407	it by calling C<ev_async_send>, which is thread- and signal safe.
2573	safe.
2574		3408
2575	This functionality is very similar to C<ev_signal> watchers, as signals,	3409	This functionality is very similar to C<ev_signal> watchers, as signals,
2576	too, are asynchronous in nature, and signals, too, will be compressed	3410	too, are asynchronous in nature, and signals, too, will be compressed
2577	(i.e. the number of callback invocations may be less than the number of	3411	(i.e. the number of callback invocations may be less than the number of
2578	C<ev_async_sent> calls).	3412	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2579		3413	of "global async watchers" by using a watcher on an otherwise unused
2580	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3414	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2581	just the default loop.	3415	even without knowing which loop owns the signal.
2582		3416
2583	=head3 Queueing	3417	=head3 Queueing
2584		3418
2585	C<ev_async> does not support queueing of data in any way. The reason	3419	C<ev_async> does not support queueing of data in any way. The reason
2586	is that the author does not know of a simple (or any) algorithm for a	3420	is that the author does not know of a simple (or any) algorithm for a
2587	multiple-writer-single-reader queue that works in all cases and doesn't	3421	multiple-writer-single-reader queue that works in all cases and doesn't
2588	need elaborate support such as pthreads.	3422	need elaborate support such as pthreads or unportable memory access
		3423	semantics.
2589		3424
2590	That means that if you want to queue data, you have to provide your own	3425	That means that if you want to queue data, you have to provide your own
2591	queue. But at least I can tell you how to implement locking around your	3426	queue. But at least I can tell you how to implement locking around your
2592	queue:	3427	queue:
2593		3428
…		…
2677	trust me.	3512	trust me.
2678		3513
2679	=item ev_async_send (loop, ev_async *)	3514	=item ev_async_send (loop, ev_async *)
2680		3515
2681	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3516	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2682	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3517	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3518	returns.
		3519
2683	C<ev_feed_event>, this call is safe to do from other threads, signal or	3520	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2684	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3521	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2685	section below on what exactly this means).	3522	embedding section below on what exactly this means).
2686		3523
2687	This call incurs the overhead of a system call only once per loop iteration,	3524	Note that, as with other watchers in libev, multiple events might get
2688	so while the overhead might be noticeable, it doesn't apply to repeated	3525	compressed into a single callback invocation (another way to look at
2689	calls to C<ev_async_send>.	3526	this is that C<ev_async> watchers are level-triggered: they are set on
		3527	C<ev_async_send>, reset when the event loop detects that).
		3528
		3529	This call incurs the overhead of at most one extra system call per event
		3530	loop iteration, if the event loop is blocked, and no syscall at all if
		3531	the event loop (or your program) is processing events. That means that
		3532	repeated calls are basically free (there is no need to avoid calls for
		3533	performance reasons) and that the overhead becomes smaller (typically
		3534	zero) under load.
2690		3535
2691	=item bool = ev_async_pending (ev_async *)	3536	=item bool = ev_async_pending (ev_async *)
2692		3537
2693	Returns a non-zero value when C<ev_async_send> has been called on the	3538	Returns a non-zero value when C<ev_async_send> has been called on the
2694	watcher but the event has not yet been processed (or even noted) by the	3539	watcher but the event has not yet been processed (or even noted) by the
…		…
2697	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3542	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2698	the loop iterates next and checks for the watcher to have become active,	3543	the loop iterates next and checks for the watcher to have become active,
2699	it will reset the flag again. C<ev_async_pending> can be used to very	3544	it will reset the flag again. C<ev_async_pending> can be used to very
2700	quickly check whether invoking the loop might be a good idea.	3545	quickly check whether invoking the loop might be a good idea.
2701		3546
2702	Not that this does I<not> check whether the watcher itself is pending, only	3547	Not that this does I<not> check whether the watcher itself is pending,
2703	whether it has been requested to make this watcher pending.	3548	only whether it has been requested to make this watcher pending: there
		3549	is a time window between the event loop checking and resetting the async
		3550	notification, and the callback being invoked.
2704		3551
2705	=back	3552	=back
2706		3553
2707		3554
2708	=head1 OTHER FUNCTIONS	3555	=head1 OTHER FUNCTIONS
2709		3556
2710	There are some other functions of possible interest. Described. Here. Now.	3557	There are some other functions of possible interest. Described. Here. Now.
2711		3558
2712	=over 4	3559	=over 4
2713		3560
2714	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3561	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
2715		3562
2716	This function combines a simple timer and an I/O watcher, calls your	3563	This function combines a simple timer and an I/O watcher, calls your
2717	callback on whichever event happens first and automatically stops both	3564	callback on whichever event happens first and automatically stops both
2718	watchers. This is useful if you want to wait for a single event on an fd	3565	watchers. This is useful if you want to wait for a single event on an fd
2719	or timeout without having to allocate/configure/start/stop/free one or	3566	or timeout without having to allocate/configure/start/stop/free one or
…		…
2725		3572
2726	If C<timeout> is less than 0, then no timeout watcher will be	3573	If C<timeout> is less than 0, then no timeout watcher will be
2727	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3574	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2728	repeat = 0) will be started. C<0> is a valid timeout.	3575	repeat = 0) will be started. C<0> is a valid timeout.
2729		3576
2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3577	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2731	passed an C<revents> set like normal event callbacks (a combination of	3578	passed an C<revents> set like normal event callbacks (a combination of
2732	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3579	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2733	value passed to C<ev_once>. Note that it is possible to receive I<both>	3580	value passed to C<ev_once>. Note that it is possible to receive I<both>
2734	a timeout and an io event at the same time - you probably should give io	3581	a timeout and an io event at the same time - you probably should give io
2735	events precedence.	3582	events precedence.
2736		3583
2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3584	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2738		3585
2739	static void stdin_ready (int revents, void *arg)	3586	static void stdin_ready (int revents, void *arg)
2740	{	3587	{
2741	if (revents & EV_READ)	3588	if (revents & EV_READ)
2742	/* stdin might have data for us, joy! */;	3589	/* stdin might have data for us, joy! */;
2743	else if (revents & EV_TIMEOUT)	3590	else if (revents & EV_TIMER)
2744	/* doh, nothing entered */;	3591	/* doh, nothing entered */;
2745	}	3592	}
2746		3593
2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3594	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2748		3595
2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2750
2751	Feeds the given event set into the event loop, as if the specified event
2752	had happened for the specified watcher (which must be a pointer to an
2753	initialised but not necessarily started event watcher).
2754
2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3596	=item ev_feed_fd_event (loop, int fd, int revents)
2756		3597
2757	Feed an event on the given fd, as if a file descriptor backend detected	3598	Feed an event on the given fd, as if a file descriptor backend detected
2758	the given events it.	3599	the given events.
2759		3600
2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3601	=item ev_feed_signal_event (loop, int signum)
2761		3602
2762	Feed an event as if the given signal occurred (C<loop> must be the default	3603	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2763	loop!).	3604	which is async-safe.
2764		3605
2765	=back	3606	=back
		3607
		3608
		3609	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3610
		3611	This section explains some common idioms that are not immediately
		3612	obvious. Note that examples are sprinkled over the whole manual, and this
		3613	section only contains stuff that wouldn't fit anywhere else.
		3614
		3615	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3616
		3617	Each watcher has, by default, a C<void *data> member that you can read
		3618	or modify at any time: libev will completely ignore it. This can be used
		3619	to associate arbitrary data with your watcher. If you need more data and
		3620	don't want to allocate memory separately and store a pointer to it in that
		3621	data member, you can also "subclass" the watcher type and provide your own
		3622	data:
		3623
		3624	struct my_io
		3625	{
		3626	ev_io io;
		3627	int otherfd;
		3628	void *somedata;
		3629	struct whatever *mostinteresting;
		3630	};
		3631
		3632	...
		3633	struct my_io w;
		3634	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3635
		3636	And since your callback will be called with a pointer to the watcher, you
		3637	can cast it back to your own type:
		3638
		3639	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3640	{
		3641	struct my_io *w = (struct my_io *)w_;
		3642	...
		3643	}
		3644
		3645	More interesting and less C-conformant ways of casting your callback
		3646	function type instead have been omitted.
		3647
		3648	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3649
		3650	Another common scenario is to use some data structure with multiple
		3651	embedded watchers, in effect creating your own watcher that combines
		3652	multiple libev event sources into one "super-watcher":
		3653
		3654	struct my_biggy
		3655	{
		3656	int some_data;
		3657	ev_timer t1;
		3658	ev_timer t2;
		3659	}
		3660
		3661	In this case getting the pointer to C<my_biggy> is a bit more
		3662	complicated: Either you store the address of your C<my_biggy> struct in
		3663	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3664	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3665	real programmers):
		3666
		3667	#include <stddef.h>
		3668
		3669	static void
		3670	t1_cb (EV_P_ ev_timer *w, int revents)
		3671	{
		3672	struct my_biggy big = (struct my_biggy *)
		3673	(((char *)w) - offsetof (struct my_biggy, t1));
		3674	}
		3675
		3676	static void
		3677	t2_cb (EV_P_ ev_timer *w, int revents)
		3678	{
		3679	struct my_biggy big = (struct my_biggy *)
		3680	(((char *)w) - offsetof (struct my_biggy, t2));
		3681	}
		3682
		3683	=head2 AVOIDING FINISHING BEFORE RETURNING
		3684
		3685	Often you have structures like this in event-based programs:
		3686
		3687	callback ()
		3688	{
		3689	free (request);
		3690	}
		3691
		3692	request = start_new_request (..., callback);
		3693
		3694	The intent is to start some "lengthy" operation. The C<request> could be
		3695	used to cancel the operation, or do other things with it.
		3696
		3697	It's not uncommon to have code paths in C<start_new_request> that
		3698	immediately invoke the callback, for example, to report errors. Or you add
		3699	some caching layer that finds that it can skip the lengthy aspects of the
		3700	operation and simply invoke the callback with the result.
		3701
		3702	The problem here is that this will happen I<before> C<start_new_request>
		3703	has returned, so C<request> is not set.
		3704
		3705	Even if you pass the request by some safer means to the callback, you
		3706	might want to do something to the request after starting it, such as
		3707	canceling it, which probably isn't working so well when the callback has
		3708	already been invoked.
		3709
		3710	A common way around all these issues is to make sure that
		3711	C<start_new_request> I<always> returns before the callback is invoked. If
		3712	C<start_new_request> immediately knows the result, it can artificially
		3713	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3714	example, or more sneakily, by reusing an existing (stopped) watcher and
		3715	pushing it into the pending queue:
		3716
		3717	ev_set_cb (watcher, callback);
		3718	ev_feed_event (EV_A_ watcher, 0);
		3719
		3720	This way, C<start_new_request> can safely return before the callback is
		3721	invoked, while not delaying callback invocation too much.
		3722
		3723	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3724
		3725	Often (especially in GUI toolkits) there are places where you have
		3726	I<modal> interaction, which is most easily implemented by recursively
		3727	invoking C<ev_run>.
		3728
		3729	This brings the problem of exiting - a callback might want to finish the
		3730	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3731	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3732	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3733	other combination: In these cases, a simple C<ev_break> will not work.
		3734
		3735	The solution is to maintain "break this loop" variable for each C<ev_run>
		3736	invocation, and use a loop around C<ev_run> until the condition is
		3737	triggered, using C<EVRUN_ONCE>:
		3738
		3739	// main loop
		3740	int exit_main_loop = 0;
		3741
		3742	while (!exit_main_loop)
		3743	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3744
		3745	// in a modal watcher
		3746	int exit_nested_loop = 0;
		3747
		3748	while (!exit_nested_loop)
		3749	ev_run (EV_A_ EVRUN_ONCE);
		3750
		3751	To exit from any of these loops, just set the corresponding exit variable:
		3752
		3753	// exit modal loop
		3754	exit_nested_loop = 1;
		3755
		3756	// exit main program, after modal loop is finished
		3757	exit_main_loop = 1;
		3758
		3759	// exit both
		3760	exit_main_loop = exit_nested_loop = 1;
		3761
		3762	=head2 THREAD LOCKING EXAMPLE
		3763
		3764	Here is a fictitious example of how to run an event loop in a different
		3765	thread from where callbacks are being invoked and watchers are
		3766	created/added/removed.
		3767
		3768	For a real-world example, see the C<EV::Loop::Async> perl module,
		3769	which uses exactly this technique (which is suited for many high-level
		3770	languages).
		3771
		3772	The example uses a pthread mutex to protect the loop data, a condition
		3773	variable to wait for callback invocations, an async watcher to notify the
		3774	event loop thread and an unspecified mechanism to wake up the main thread.
		3775
		3776	First, you need to associate some data with the event loop:
		3777
		3778	typedef struct {
		3779	mutex_t lock; /* global loop lock */
		3780	ev_async async_w;
		3781	thread_t tid;
		3782	cond_t invoke_cv;
		3783	} userdata;
		3784
		3785	void prepare_loop (EV_P)
		3786	{
		3787	// for simplicity, we use a static userdata struct.
		3788	static userdata u;
		3789
		3790	ev_async_init (&u->async_w, async_cb);
		3791	ev_async_start (EV_A_ &u->async_w);
		3792
		3793	pthread_mutex_init (&u->lock, 0);
		3794	pthread_cond_init (&u->invoke_cv, 0);
		3795
		3796	// now associate this with the loop
		3797	ev_set_userdata (EV_A_ u);
		3798	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3799	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3800
		3801	// then create the thread running ev_run
		3802	pthread_create (&u->tid, 0, l_run, EV_A);
		3803	}
		3804
		3805	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3806	solely to wake up the event loop so it takes notice of any new watchers
		3807	that might have been added:
		3808
		3809	static void
		3810	async_cb (EV_P_ ev_async *w, int revents)
		3811	{
		3812	// just used for the side effects
		3813	}
		3814
		3815	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3816	protecting the loop data, respectively.
		3817
		3818	static void
		3819	l_release (EV_P)
		3820	{
		3821	userdata *u = ev_userdata (EV_A);
		3822	pthread_mutex_unlock (&u->lock);
		3823	}
		3824
		3825	static void
		3826	l_acquire (EV_P)
		3827	{
		3828	userdata *u = ev_userdata (EV_A);
		3829	pthread_mutex_lock (&u->lock);
		3830	}
		3831
		3832	The event loop thread first acquires the mutex, and then jumps straight
		3833	into C<ev_run>:
		3834
		3835	void *
		3836	l_run (void *thr_arg)
		3837	{
		3838	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3839
		3840	l_acquire (EV_A);
		3841	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3842	ev_run (EV_A_ 0);
		3843	l_release (EV_A);
		3844
		3845	return 0;
		3846	}
		3847
		3848	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3849	signal the main thread via some unspecified mechanism (signals? pipe
		3850	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3851	have been called (in a while loop because a) spurious wakeups are possible
		3852	and b) skipping inter-thread-communication when there are no pending
		3853	watchers is very beneficial):
		3854
		3855	static void
		3856	l_invoke (EV_P)
		3857	{
		3858	userdata *u = ev_userdata (EV_A);
		3859
		3860	while (ev_pending_count (EV_A))
		3861	{
		3862	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3863	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3864	}
		3865	}
		3866
		3867	Now, whenever the main thread gets told to invoke pending watchers, it
		3868	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3869	thread to continue:
		3870
		3871	static void
		3872	real_invoke_pending (EV_P)
		3873	{
		3874	userdata *u = ev_userdata (EV_A);
		3875
		3876	pthread_mutex_lock (&u->lock);
		3877	ev_invoke_pending (EV_A);
		3878	pthread_cond_signal (&u->invoke_cv);
		3879	pthread_mutex_unlock (&u->lock);
		3880	}
		3881
		3882	Whenever you want to start/stop a watcher or do other modifications to an
		3883	event loop, you will now have to lock:
		3884
		3885	ev_timer timeout_watcher;
		3886	userdata *u = ev_userdata (EV_A);
		3887
		3888	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3889
		3890	pthread_mutex_lock (&u->lock);
		3891	ev_timer_start (EV_A_ &timeout_watcher);
		3892	ev_async_send (EV_A_ &u->async_w);
		3893	pthread_mutex_unlock (&u->lock);
		3894
		3895	Note that sending the C<ev_async> watcher is required because otherwise
		3896	an event loop currently blocking in the kernel will have no knowledge
		3897	about the newly added timer. By waking up the loop it will pick up any new
		3898	watchers in the next event loop iteration.
		3899
		3900	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3901
		3902	While the overhead of a callback that e.g. schedules a thread is small, it
		3903	is still an overhead. If you embed libev, and your main usage is with some
		3904	kind of threads or coroutines, you might want to customise libev so that
		3905	doesn't need callbacks anymore.
		3906
		3907	Imagine you have coroutines that you can switch to using a function
		3908	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3909	and that due to some magic, the currently active coroutine is stored in a
		3910	global called C<current_coro>. Then you can build your own "wait for libev
		3911	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3912	the differing C<;> conventions):
		3913
		3914	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3915	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3916
		3917	That means instead of having a C callback function, you store the
		3918	coroutine to switch to in each watcher, and instead of having libev call
		3919	your callback, you instead have it switch to that coroutine.
		3920
		3921	A coroutine might now wait for an event with a function called
		3922	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3923	matter when, or whether the watcher is active or not when this function is
		3924	called):
		3925
		3926	void
		3927	wait_for_event (ev_watcher *w)
		3928	{
		3929	ev_set_cb (w, current_coro);
		3930	switch_to (libev_coro);
		3931	}
		3932
		3933	That basically suspends the coroutine inside C<wait_for_event> and
		3934	continues the libev coroutine, which, when appropriate, switches back to
		3935	this or any other coroutine.
		3936
		3937	You can do similar tricks if you have, say, threads with an event queue -
		3938	instead of storing a coroutine, you store the queue object and instead of
		3939	switching to a coroutine, you push the watcher onto the queue and notify
		3940	any waiters.
		3941
		3942	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3943	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3944
		3945	// my_ev.h
		3946	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3947	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3948	#include "../libev/ev.h"
		3949
		3950	// my_ev.c
		3951	#define EV_H "my_ev.h"
		3952	#include "../libev/ev.c"
		3953
		3954	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3955	F<my_ev.c> into your project. When properly specifying include paths, you
		3956	can even use F<ev.h> as header file name directly.
2766		3957
2767		3958
2768	=head1 LIBEVENT EMULATION	3959	=head1 LIBEVENT EMULATION
2769		3960
2770	Libev offers a compatibility emulation layer for libevent. It cannot	3961	Libev offers a compatibility emulation layer for libevent. It cannot
2771	emulate the internals of libevent, so here are some usage hints:	3962	emulate the internals of libevent, so here are some usage hints:
2772		3963
2773	=over 4	3964	=over 4
		3965
		3966	=item * Only the libevent-1.4.1-beta API is being emulated.
		3967
		3968	This was the newest libevent version available when libev was implemented,
		3969	and is still mostly unchanged in 2010.
2774		3970
2775	=item * Use it by including <event.h>, as usual.	3971	=item * Use it by including <event.h>, as usual.
2776		3972
2777	=item * The following members are fully supported: ev_base, ev_callback,	3973	=item * The following members are fully supported: ev_base, ev_callback,
2778	ev_arg, ev_fd, ev_res, ev_events.	3974	ev_arg, ev_fd, ev_res, ev_events.
…		…
2784	=item * Priorities are not currently supported. Initialising priorities	3980	=item * Priorities are not currently supported. Initialising priorities
2785	will fail and all watchers will have the same priority, even though there	3981	will fail and all watchers will have the same priority, even though there
2786	is an ev_pri field.	3982	is an ev_pri field.
2787		3983
2788	=item * In libevent, the last base created gets the signals, in libev, the	3984	=item * In libevent, the last base created gets the signals, in libev, the
2789	first base created (== the default loop) gets the signals.	3985	base that registered the signal gets the signals.
2790		3986
2791	=item * Other members are not supported.	3987	=item * Other members are not supported.
2792		3988
2793	=item * The libev emulation is I<not> ABI compatible to libevent, you need	3989	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2794	to use the libev header file and library.	3990	to use the libev header file and library.
2795		3991
2796	=back	3992	=back
2797		3993
2798	=head1 C++ SUPPORT	3994	=head1 C++ SUPPORT
		3995
		3996	=head2 C API
		3997
		3998	The normal C API should work fine when used from C++: both ev.h and the
		3999	libev sources can be compiled as C++. Therefore, code that uses the C API
		4000	will work fine.
		4001
		4002	Proper exception specifications might have to be added to callbacks passed
		4003	to libev: exceptions may be thrown only from watcher callbacks, all other
		4004	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4005	callbacks) must not throw exceptions, and might need a C<noexcept>
		4006	specification. If you have code that needs to be compiled as both C and
		4007	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4008
		4009	static void
		4010	fatal_error (const char *msg) EV_NOEXCEPT
		4011	{
		4012	perror (msg);
		4013	abort ();
		4014	}
		4015
		4016	...
		4017	ev_set_syserr_cb (fatal_error);
		4018
		4019	The only API functions that can currently throw exceptions are C<ev_run>,
		4020	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4021	because it runs cleanup watchers).
		4022
		4023	Throwing exceptions in watcher callbacks is only supported if libev itself
		4024	is compiled with a C++ compiler or your C and C++ environments allow
		4025	throwing exceptions through C libraries (most do).
		4026
		4027	=head2 C++ API
2799		4028
2800	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4029	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2801	you to use some convenience methods to start/stop watchers and also change	4030	you to use some convenience methods to start/stop watchers and also change
2802	the callback model to a model using method callbacks on objects.	4031	the callback model to a model using method callbacks on objects.
2803		4032
2804	To use it,	4033	To use it,
2805		4034
2806	#include <ev++.h>	4035	#include <ev++.h>
2807		4036
2808	This automatically includes F<ev.h> and puts all of its definitions (many	4037	This automatically includes F<ev.h> and puts all of its definitions (many
2809	of them macros) into the global namespace. All C++ specific things are	4038	of them macros) into the global namespace. All C++ specific things are
2810	put into the C<ev> namespace. It should support all the same embedding	4039	put into the C<ev> namespace. It should support all the same embedding
…		…
2813	Care has been taken to keep the overhead low. The only data member the C++	4042	Care has been taken to keep the overhead low. The only data member the C++
2814	classes add (compared to plain C-style watchers) is the event loop pointer	4043	classes add (compared to plain C-style watchers) is the event loop pointer
2815	that the watcher is associated with (or no additional members at all if	4044	that the watcher is associated with (or no additional members at all if
2816	you disable C<EV_MULTIPLICITY> when embedding libev).	4045	you disable C<EV_MULTIPLICITY> when embedding libev).
2817		4046
2818	Currently, functions, and static and non-static member functions can be	4047	Currently, functions, static and non-static member functions and classes
2819	used as callbacks. Other types should be easy to add as long as they only	4048	with C<operator ()> can be used as callbacks. Other types should be easy
2820	need one additional pointer for context. If you need support for other	4049	to add as long as they only need one additional pointer for context. If
2821	types of functors please contact the author (preferably after implementing	4050	you need support for other types of functors please contact the author
2822	it).	4051	(preferably after implementing it).
		4052
		4053	For all this to work, your C++ compiler either has to use the same calling
		4054	conventions as your C compiler (for static member functions), or you have
		4055	to embed libev and compile libev itself as C++.
2823		4056
2824	Here is a list of things available in the C<ev> namespace:	4057	Here is a list of things available in the C<ev> namespace:
2825		4058
2826	=over 4	4059	=over 4
2827		4060
…		…
2837	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4070	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2838		4071
2839	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4072	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2840	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4073	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2841	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4074	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2842	defines by many implementations.	4075	defined by many implementations.
2843		4076
2844	All of those classes have these methods:	4077	All of those classes have these methods:
2845		4078
2846	=over 4	4079	=over 4
2847		4080
2848	=item ev::TYPE::TYPE ()	4081	=item ev::TYPE::TYPE ()
2849		4082
2850	=item ev::TYPE::TYPE (struct ev_loop *)	4083	=item ev::TYPE::TYPE (loop)
2851		4084
2852	=item ev::TYPE::~TYPE	4085	=item ev::TYPE::~TYPE
2853		4086
2854	The constructor (optionally) takes an event loop to associate the watcher	4087	The constructor (optionally) takes an event loop to associate the watcher
2855	with. If it is omitted, it will use C<EV_DEFAULT>.	4088	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2888	myclass obj;	4121	myclass obj;
2889	ev::io iow;	4122	ev::io iow;
2890	iow.set <myclass, &myclass::io_cb> (&obj);	4123	iow.set <myclass, &myclass::io_cb> (&obj);
2891		4124
2892	=item w->set (object *)	4125	=item w->set (object *)
2893
2894	This is an B<experimental> feature that might go away in a future version.
2895		4126
2896	This is a variation of a method callback - leaving out the method to call	4127	This is a variation of a method callback - leaving out the method to call
2897	will default the method to C<operator ()>, which makes it possible to use	4128	will default the method to C<operator ()>, which makes it possible to use
2898	functor objects without having to manually specify the C<operator ()> all	4129	functor objects without having to manually specify the C<operator ()> all
2899	the time. Incidentally, you can then also leave out the template argument	4130	the time. Incidentally, you can then also leave out the template argument
…		…
2911	void operator() (ev::io &w, int revents)	4142	void operator() (ev::io &w, int revents)
2912	{	4143	{
2913	...	4144	...
2914	}	4145	}
2915	}	4146	}
2916		4147
2917	myfunctor f;	4148	myfunctor f;
2918		4149
2919	ev::io w;	4150	ev::io w;
2920	w.set (&f);	4151	w.set (&f);
2921		4152
…		…
2932	Example: Use a plain function as callback.	4163	Example: Use a plain function as callback.
2933		4164
2934	static void io_cb (ev::io &w, int revents) { }	4165	static void io_cb (ev::io &w, int revents) { }
2935	iow.set <io_cb> ();	4166	iow.set <io_cb> ();
2936		4167
2937	=item w->set (struct ev_loop *)	4168	=item w->set (loop)
2938		4169
2939	Associates a different C<struct ev_loop> with this watcher. You can only	4170	Associates a different C<struct ev_loop> with this watcher. You can only
2940	do this when the watcher is inactive (and not pending either).	4171	do this when the watcher is inactive (and not pending either).
2941		4172
2942	=item w->set ([arguments])	4173	=item w->set ([arguments])
2943		4174
2944	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4175	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4176	with the same arguments. Either this method or a suitable start method
2945	called at least once. Unlike the C counterpart, an active watcher gets	4177	must be called at least once. Unlike the C counterpart, an active watcher
2946	automatically stopped and restarted when reconfiguring it with this	4178	gets automatically stopped and restarted when reconfiguring it with this
2947	method.	4179	method.
		4180
		4181	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4182	clashing with the C<set (loop)> method.
2948		4183
2949	=item w->start ()	4184	=item w->start ()
2950		4185
2951	Starts the watcher. Note that there is no C<loop> argument, as the	4186	Starts the watcher. Note that there is no C<loop> argument, as the
2952	constructor already stores the event loop.	4187	constructor already stores the event loop.
2953		4188
		4189	=item w->start ([arguments])
		4190
		4191	Instead of calling C<set> and C<start> methods separately, it is often
		4192	convenient to wrap them in one call. Uses the same type of arguments as
		4193	the configure C<set> method of the watcher.
		4194
2954	=item w->stop ()	4195	=item w->stop ()
2955		4196
2956	Stops the watcher if it is active. Again, no C<loop> argument.	4197	Stops the watcher if it is active. Again, no C<loop> argument.
2957		4198
2958	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4199	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2970		4211
2971	=back	4212	=back
2972		4213
2973	=back	4214	=back
2974		4215
2975	Example: Define a class with an IO and idle watcher, start one of them in	4216	Example: Define a class with two I/O and idle watchers, start the I/O
2976	the constructor.	4217	watchers in the constructor.
2977		4218
2978	class myclass	4219	class myclass
2979	{	4220	{
2980	ev::io io ; void io_cb (ev::io &w, int revents);	4221	ev::io io ; void io_cb (ev::io &w, int revents);
		4222	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4223	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2982		4224
2983	myclass (int fd)	4225	myclass (int fd)
2984	{	4226	{
2985	io .set <myclass, &myclass::io_cb > (this);	4227	io .set <myclass, &myclass::io_cb > (this);
		4228	io2 .set <myclass, &myclass::io2_cb > (this);
2986	idle.set <myclass, &myclass::idle_cb> (this);	4229	idle.set <myclass, &myclass::idle_cb> (this);
2987		4230
2988	io.start (fd, ev::READ);	4231	io.set (fd, ev::WRITE); // configure the watcher
		4232	io.start (); // start it whenever convenient
		4233
		4234	io2.start (fd, ev::READ); // set + start in one call
2989	}	4235	}
2990	};	4236	};
2991		4237
2992		4238
2993	=head1 OTHER LANGUAGE BINDINGS	4239	=head1 OTHER LANGUAGE BINDINGS
…		…
3012	L<http://software.schmorp.de/pkg/EV>.	4258	L<http://software.schmorp.de/pkg/EV>.
3013		4259
3014	=item Python	4260	=item Python
3015		4261
3016	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4262	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
3017	seems to be quite complete and well-documented. Note, however, that the	4263	seems to be quite complete and well-documented.
3018	patch they require for libev is outright dangerous as it breaks the ABI
3019	for everybody else, and therefore, should never be applied in an installed
3020	libev (if python requires an incompatible ABI then it needs to embed
3021	libev).
3022		4264
3023	=item Ruby	4265	=item Ruby
3024		4266
3025	Tony Arcieri has written a ruby extension that offers access to a subset	4267	Tony Arcieri has written a ruby extension that offers access to a subset
3026	of the libev API and adds file handle abstractions, asynchronous DNS and	4268	of the libev API and adds file handle abstractions, asynchronous DNS and
…		…
3028	L<http://rev.rubyforge.org/>.	4270	L<http://rev.rubyforge.org/>.
3029		4271
3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>	4272	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
3031	makes rev work even on mingw.	4273	makes rev work even on mingw.
3032		4274
		4275	=item Haskell
		4276
		4277	A haskell binding to libev is available at
		4278	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4279
3033	=item D	4280	=item D
3034		4281
3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4282	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3036	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4283	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3037		4284
3038	=item Ocaml	4285	=item Ocaml
3039		4286
3040	Erkki Seppala has written Ocaml bindings for libev, to be found at	4287	Erkki Seppala has written Ocaml bindings for libev, to be found at
3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4288	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4289
		4290	=item Lua
		4291
		4292	Brian Maher has written a partial interface to libev for lua (at the
		4293	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4294	L<http://github.com/brimworks/lua-ev>.
		4295
		4296	=item Javascript
		4297
		4298	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4299
		4300	=item Others
		4301
		4302	There are others, and I stopped counting.
3042		4303
3043	=back	4304	=back
3044		4305
3045		4306
3046	=head1 MACRO MAGIC	4307	=head1 MACRO MAGIC
…		…
3060	loop argument"). The C<EV_A> form is used when this is the sole argument,	4321	loop argument"). The C<EV_A> form is used when this is the sole argument,
3061	C<EV_A_> is used when other arguments are following. Example:	4322	C<EV_A_> is used when other arguments are following. Example:
3062		4323
3063	ev_unref (EV_A);	4324	ev_unref (EV_A);
3064	ev_timer_add (EV_A_ watcher);	4325	ev_timer_add (EV_A_ watcher);
3065	ev_loop (EV_A_ 0);	4326	ev_run (EV_A_ 0);
3066		4327
3067	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4328	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3068	which is often provided by the following macro.	4329	which is often provided by the following macro.
3069		4330
3070	=item C<EV_P>, C<EV_P_>	4331	=item C<EV_P>, C<EV_P_>
…		…
3083	suitable for use with C<EV_A>.	4344	suitable for use with C<EV_A>.
3084		4345
3085	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4346	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3086		4347
3087	Similar to the other two macros, this gives you the value of the default	4348	Similar to the other two macros, this gives you the value of the default
3088	loop, if multiple loops are supported ("ev loop default").	4349	loop, if multiple loops are supported ("ev loop default"). The default loop
		4350	will be initialised if it isn't already initialised.
		4351
		4352	For non-multiplicity builds, these macros do nothing, so you always have
		4353	to initialise the loop somewhere.
3089		4354
3090	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4355	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3091		4356
3092	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4357	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3093	default loop has been initialised (C<UC> == unchecked). Their behaviour	4358	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3110	}	4375	}
3111		4376
3112	ev_check check;	4377	ev_check check;
3113	ev_check_init (&check, check_cb);	4378	ev_check_init (&check, check_cb);
3114	ev_check_start (EV_DEFAULT_ &check);	4379	ev_check_start (EV_DEFAULT_ &check);
3115	ev_loop (EV_DEFAULT_ 0);	4380	ev_run (EV_DEFAULT_ 0);
3116		4381
3117	=head1 EMBEDDING	4382	=head1 EMBEDDING
3118		4383
3119	Libev can (and often is) directly embedded into host	4384	Libev can (and often is) directly embedded into host
3120	applications. Examples of applications that embed it include the Deliantra	4385	applications. Examples of applications that embed it include the Deliantra
…		…
3160	ev_vars.h	4425	ev_vars.h
3161	ev_wrap.h	4426	ev_wrap.h
3162		4427
3163	ev_win32.c required on win32 platforms only	4428	ev_win32.c required on win32 platforms only
3164		4429
3165	ev_select.c only when select backend is enabled (which is enabled by default)	4430	ev_select.c only when select backend is enabled
3166	ev_poll.c only when poll backend is enabled (disabled by default)	4431	ev_poll.c only when poll backend is enabled
3167	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4432	ev_epoll.c only when the epoll backend is enabled
3168	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4433	ev_kqueue.c only when the kqueue backend is enabled
3169	ev_port.c only when the solaris port backend is enabled (disabled by default)	4434	ev_port.c only when the solaris port backend is enabled
3170		4435
3171	F<ev.c> includes the backend files directly when enabled, so you only need	4436	F<ev.c> includes the backend files directly when enabled, so you only need
3172	to compile this single file.	4437	to compile this single file.
3173		4438
3174	=head3 LIBEVENT COMPATIBILITY API	4439	=head3 LIBEVENT COMPATIBILITY API
…		…
3200	libev.m4	4465	libev.m4
3201		4466
3202	=head2 PREPROCESSOR SYMBOLS/MACROS	4467	=head2 PREPROCESSOR SYMBOLS/MACROS
3203		4468
3204	Libev can be configured via a variety of preprocessor symbols you have to	4469	Libev can be configured via a variety of preprocessor symbols you have to
3205	define before including any of its files. The default in the absence of	4470	define before including (or compiling) any of its files. The default in
3206	autoconf is documented for every option.	4471	the absence of autoconf is documented for every option.
		4472
		4473	Symbols marked with "(h)" do not change the ABI, and can have different
		4474	values when compiling libev vs. including F<ev.h>, so it is permissible
		4475	to redefine them before including F<ev.h> without breaking compatibility
		4476	to a compiled library. All other symbols change the ABI, which means all
		4477	users of libev and the libev code itself must be compiled with compatible
		4478	settings.
3207		4479
3208	=over 4	4480	=over 4
3209		4481
		4482	=item EV_COMPAT3 (h)
		4483
		4484	Backwards compatibility is a major concern for libev. This is why this
		4485	release of libev comes with wrappers for the functions and symbols that
		4486	have been renamed between libev version 3 and 4.
		4487
		4488	You can disable these wrappers (to test compatibility with future
		4489	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4490	sources. This has the additional advantage that you can drop the C<struct>
		4491	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4492	typedef in that case.
		4493
		4494	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4495	and in some even more future version the compatibility code will be
		4496	removed completely.
		4497
3210	=item EV_STANDALONE	4498	=item EV_STANDALONE (h)
3211		4499
3212	Must always be C<1> if you do not use autoconf configuration, which	4500	Must always be C<1> if you do not use autoconf configuration, which
3213	keeps libev from including F<config.h>, and it also defines dummy	4501	keeps libev from including F<config.h>, and it also defines dummy
3214	implementations for some libevent functions (such as logging, which is not	4502	implementations for some libevent functions (such as logging, which is not
3215	supported). It will also not define any of the structs usually found in	4503	supported). It will also not define any of the structs usually found in
3216	F<event.h> that are not directly supported by the libev core alone.	4504	F<event.h> that are not directly supported by the libev core alone.
3217		4505
3218	In stanbdalone mode, libev will still try to automatically deduce the	4506	In standalone mode, libev will still try to automatically deduce the
3219	configuration, but has to be more conservative.	4507	configuration, but has to be more conservative.
		4508
		4509	=item EV_USE_FLOOR
		4510
		4511	If defined to be C<1>, libev will use the C<floor ()> function for its
		4512	periodic reschedule calculations, otherwise libev will fall back on a
		4513	portable (slower) implementation. If you enable this, you usually have to
		4514	link against libm or something equivalent. Enabling this when the C<floor>
		4515	function is not available will fail, so the safe default is to not enable
		4516	this.
3220		4517
3221	=item EV_USE_MONOTONIC	4518	=item EV_USE_MONOTONIC
3222		4519
3223	If defined to be C<1>, libev will try to detect the availability of the	4520	If defined to be C<1>, libev will try to detect the availability of the
3224	monotonic clock option at both compile time and runtime. Otherwise no	4521	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3288	be used is the winsock select). This means that it will call	4585	be used is the winsock select). This means that it will call
3289	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4586	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3290	it is assumed that all these functions actually work on fds, even	4587	it is assumed that all these functions actually work on fds, even
3291	on win32. Should not be defined on non-win32 platforms.	4588	on win32. Should not be defined on non-win32 platforms.
3292		4589
3293	=item EV_FD_TO_WIN32_HANDLE	4590	=item EV_FD_TO_WIN32_HANDLE(fd)
3294		4591
3295	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4592	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3296	file descriptors to socket handles. When not defining this symbol (the	4593	file descriptors to socket handles. When not defining this symbol (the
3297	default), then libev will call C<_get_osfhandle>, which is usually	4594	default), then libev will call C<_get_osfhandle>, which is usually
3298	correct. In some cases, programs use their own file descriptor management,	4595	correct. In some cases, programs use their own file descriptor management,
3299	in which case they can provide this function to map fds to socket handles.	4596	in which case they can provide this function to map fds to socket handles.
		4597
		4598	=item EV_WIN32_HANDLE_TO_FD(handle)
		4599
		4600	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4601	using the standard C<_open_osfhandle> function. For programs implementing
		4602	their own fd to handle mapping, overwriting this function makes it easier
		4603	to do so. This can be done by defining this macro to an appropriate value.
		4604
		4605	=item EV_WIN32_CLOSE_FD(fd)
		4606
		4607	If programs implement their own fd to handle mapping on win32, then this
		4608	macro can be used to override the C<close> function, useful to unregister
		4609	file descriptors again. Note that the replacement function has to close
		4610	the underlying OS handle.
		4611
		4612	=item EV_USE_WSASOCKET
		4613
		4614	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4615	communication socket, which works better in some environments. Otherwise,
		4616	the normal C<socket> function will be used, which works better in other
		4617	environments.
3300		4618
3301	=item EV_USE_POLL	4619	=item EV_USE_POLL
3302		4620
3303	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4621	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3304	backend. Otherwise it will be enabled on non-win32 platforms. It	4622	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3340	If defined to be C<1>, libev will compile in support for the Linux inotify	4658	If defined to be C<1>, libev will compile in support for the Linux inotify
3341	interface to speed up C<ev_stat> watchers. Its actual availability will	4659	interface to speed up C<ev_stat> watchers. Its actual availability will
3342	be detected at runtime. If undefined, it will be enabled if the headers	4660	be detected at runtime. If undefined, it will be enabled if the headers
3343	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4661	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3344		4662
		4663	=item EV_NO_SMP
		4664
		4665	If defined to be C<1>, libev will assume that memory is always coherent
		4666	between threads, that is, threads can be used, but threads never run on
		4667	different cpus (or different cpu cores). This reduces dependencies
		4668	and makes libev faster.
		4669
		4670	=item EV_NO_THREADS
		4671
		4672	If defined to be C<1>, libev will assume that it will never be called from
		4673	different threads (that includes signal handlers), which is a stronger
		4674	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4675	libev faster.
		4676
3345	=item EV_ATOMIC_T	4677	=item EV_ATOMIC_T
3346		4678
3347	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4679	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3348	access is atomic with respect to other threads or signal contexts. No such	4680	access is atomic with respect to other threads or signal contexts. No
3349	type is easily found in the C language, so you can provide your own type	4681	such type is easily found in the C language, so you can provide your own
3350	that you know is safe for your purposes. It is used both for signal handler "locking"	4682	type that you know is safe for your purposes. It is used both for signal
3351	as well as for signal and thread safety in C<ev_async> watchers.	4683	handler "locking" as well as for signal and thread safety in C<ev_async>
		4684	watchers.
3352		4685
3353	In the absence of this define, libev will use C<sig_atomic_t volatile>	4686	In the absence of this define, libev will use C<sig_atomic_t volatile>
3354	(from F<signal.h>), which is usually good enough on most platforms.	4687	(from F<signal.h>), which is usually good enough on most platforms.
3355		4688
3356	=item EV_H	4689	=item EV_H (h)
3357		4690
3358	The name of the F<ev.h> header file used to include it. The default if	4691	The name of the F<ev.h> header file used to include it. The default if
3359	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4692	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3360	used to virtually rename the F<ev.h> header file in case of conflicts.	4693	used to virtually rename the F<ev.h> header file in case of conflicts.
3361		4694
3362	=item EV_CONFIG_H	4695	=item EV_CONFIG_H (h)
3363		4696
3364	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4697	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3365	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4698	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3366	C<EV_H>, above.	4699	C<EV_H>, above.
3367		4700
3368	=item EV_EVENT_H	4701	=item EV_EVENT_H (h)
3369		4702
3370	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4703	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3371	of how the F<event.h> header can be found, the default is C<"event.h">.	4704	of how the F<event.h> header can be found, the default is C<"event.h">.
3372		4705
3373	=item EV_PROTOTYPES	4706	=item EV_PROTOTYPES (h)
3374		4707
3375	If defined to be C<0>, then F<ev.h> will not define any function	4708	If defined to be C<0>, then F<ev.h> will not define any function
3376	prototypes, but still define all the structs and other symbols. This is	4709	prototypes, but still define all the structs and other symbols. This is
3377	occasionally useful if you want to provide your own wrapper functions	4710	occasionally useful if you want to provide your own wrapper functions
3378	around libev functions.	4711	around libev functions.
…		…
3383	will have the C<struct ev_loop *> as first argument, and you can create	4716	will have the C<struct ev_loop *> as first argument, and you can create
3384	additional independent event loops. Otherwise there will be no support	4717	additional independent event loops. Otherwise there will be no support
3385	for multiple event loops and there is no first event loop pointer	4718	for multiple event loops and there is no first event loop pointer
3386	argument. Instead, all functions act on the single default loop.	4719	argument. Instead, all functions act on the single default loop.
3387		4720
		4721	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4722	default loop when multiplicity is switched off - you always have to
		4723	initialise the loop manually in this case.
		4724
3388	=item EV_MINPRI	4725	=item EV_MINPRI
3389		4726
3390	=item EV_MAXPRI	4727	=item EV_MAXPRI
3391		4728
3392	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4729	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3400	fine.	4737	fine.
3401		4738
3402	If your embedding application does not need any priorities, defining these	4739	If your embedding application does not need any priorities, defining these
3403	both to C<0> will save some memory and CPU.	4740	both to C<0> will save some memory and CPU.
3404		4741
3405	=item EV_PERIODIC_ENABLE	4742	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4743	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4744	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3406		4745
3407	If undefined or defined to be C<1>, then periodic timers are supported. If	4746	If undefined or defined to be C<1> (and the platform supports it), then
3408	defined to be C<0>, then they are not. Disabling them saves a few kB of	4747	the respective watcher type is supported. If defined to be C<0>, then it
3409	code.	4748	is not. Disabling watcher types mainly saves code size.
3410		4749
3411	=item EV_IDLE_ENABLE	4750	=item EV_FEATURES
3412
3413	If undefined or defined to be C<1>, then idle watchers are supported. If
3414	defined to be C<0>, then they are not. Disabling them saves a few kB of
3415	code.
3416
3417	=item EV_EMBED_ENABLE
3418
3419	If undefined or defined to be C<1>, then embed watchers are supported. If
3420	defined to be C<0>, then they are not. Embed watchers rely on most other
3421	watcher types, which therefore must not be disabled.
3422
3423	=item EV_STAT_ENABLE
3424
3425	If undefined or defined to be C<1>, then stat watchers are supported. If
3426	defined to be C<0>, then they are not.
3427
3428	=item EV_FORK_ENABLE
3429
3430	If undefined or defined to be C<1>, then fork watchers are supported. If
3431	defined to be C<0>, then they are not.
3432
3433	=item EV_ASYNC_ENABLE
3434
3435	If undefined or defined to be C<1>, then async watchers are supported. If
3436	defined to be C<0>, then they are not.
3437
3438	=item EV_MINIMAL
3439		4751
3440	If you need to shave off some kilobytes of code at the expense of some	4752	If you need to shave off some kilobytes of code at the expense of some
3441	speed, define this symbol to C<1>. Currently this is used to override some	4753	speed (but with the full API), you can define this symbol to request
3442	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4754	certain subsets of functionality. The default is to enable all features
3443	much smaller 2-heap for timer management over the default 4-heap.	4755	that can be enabled on the platform.
		4756
		4757	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4758	with some broad features you want) and then selectively re-enable
		4759	additional parts you want, for example if you want everything minimal,
		4760	but multiple event loop support, async and child watchers and the poll
		4761	backend, use this:
		4762
		4763	#define EV_FEATURES 0
		4764	#define EV_MULTIPLICITY 1
		4765	#define EV_USE_POLL 1
		4766	#define EV_CHILD_ENABLE 1
		4767	#define EV_ASYNC_ENABLE 1
		4768
		4769	The actual value is a bitset, it can be a combination of the following
		4770	values (by default, all of these are enabled):
		4771
		4772	=over 4
		4773
		4774	=item C<1> - faster/larger code
		4775
		4776	Use larger code to speed up some operations.
		4777
		4778	Currently this is used to override some inlining decisions (enlarging the
		4779	code size by roughly 30% on amd64).
		4780
		4781	When optimising for size, use of compiler flags such as C<-Os> with
		4782	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4783	assertions.
		4784
		4785	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4786	(e.g. gcc with C<-Os>).
		4787
		4788	=item C<2> - faster/larger data structures
		4789
		4790	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4791	hash table sizes and so on. This will usually further increase code size
		4792	and can additionally have an effect on the size of data structures at
		4793	runtime.
		4794
		4795	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4796	(e.g. gcc with C<-Os>).
		4797
		4798	=item C<4> - full API configuration
		4799
		4800	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4801	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4802
		4803	=item C<8> - full API
		4804
		4805	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4806	details on which parts of the API are still available without this
		4807	feature, and do not complain if this subset changes over time.
		4808
		4809	=item C<16> - enable all optional watcher types
		4810
		4811	Enables all optional watcher types. If you want to selectively enable
		4812	only some watcher types other than I/O and timers (e.g. prepare,
		4813	embed, async, child...) you can enable them manually by defining
		4814	C<EV_watchertype_ENABLE> to C<1> instead.
		4815
		4816	=item C<32> - enable all backends
		4817
		4818	This enables all backends - without this feature, you need to enable at
		4819	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4820
		4821	=item C<64> - enable OS-specific "helper" APIs
		4822
		4823	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4824	default.
		4825
		4826	=back
		4827
		4828	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4829	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4830	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4831	watchers, timers and monotonic clock support.
		4832
		4833	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4834	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4835	your program might be left out as well - a binary starting a timer and an
		4836	I/O watcher then might come out at only 5Kb.
		4837
		4838	=item EV_API_STATIC
		4839
		4840	If this symbol is defined (by default it is not), then all identifiers
		4841	will have static linkage. This means that libev will not export any
		4842	identifiers, and you cannot link against libev anymore. This can be useful
		4843	when you embed libev, only want to use libev functions in a single file,
		4844	and do not want its identifiers to be visible.
		4845
		4846	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4847	wants to use libev.
		4848
		4849	This option only works when libev is compiled with a C compiler, as C++
		4850	doesn't support the required declaration syntax.
		4851
		4852	=item EV_AVOID_STDIO
		4853
		4854	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4855	functions (printf, scanf, perror etc.). This will increase the code size
		4856	somewhat, but if your program doesn't otherwise depend on stdio and your
		4857	libc allows it, this avoids linking in the stdio library which is quite
		4858	big.
		4859
		4860	Note that error messages might become less precise when this option is
		4861	enabled.
		4862
		4863	=item EV_NSIG
		4864
		4865	The highest supported signal number, +1 (or, the number of
		4866	signals): Normally, libev tries to deduce the maximum number of signals
		4867	automatically, but sometimes this fails, in which case it can be
		4868	specified. Also, using a lower number than detected (C<32> should be
		4869	good for about any system in existence) can save some memory, as libev
		4870	statically allocates some 12-24 bytes per signal number.
3444		4871
3445	=item EV_PID_HASHSIZE	4872	=item EV_PID_HASHSIZE
3446		4873
3447	C<ev_child> watchers use a small hash table to distribute workload by	4874	C<ev_child> watchers use a small hash table to distribute workload by
3448	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4875	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3449	than enough. If you need to manage thousands of children you might want to	4876	usually more than enough. If you need to manage thousands of children you
3450	increase this value (I<must> be a power of two).	4877	might want to increase this value (I<must> be a power of two).
3451		4878
3452	=item EV_INOTIFY_HASHSIZE	4879	=item EV_INOTIFY_HASHSIZE
3453		4880
3454	C<ev_stat> watchers use a small hash table to distribute workload by	4881	C<ev_stat> watchers use a small hash table to distribute workload by
3455	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4882	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3456	usually more than enough. If you need to manage thousands of C<ev_stat>	4883	disabled), usually more than enough. If you need to manage thousands of
3457	watchers you might want to increase this value (I<must> be a power of	4884	C<ev_stat> watchers you might want to increase this value (I<must> be a
3458	two).	4885	power of two).
3459		4886
3460	=item EV_USE_4HEAP	4887	=item EV_USE_4HEAP
3461		4888
3462	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4889	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3463	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4890	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3464	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4891	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3465	faster performance with many (thousands) of watchers.	4892	faster performance with many (thousands) of watchers.
3466		4893
3467	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4894	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3468	(disabled).	4895	will be C<0>.
3469		4896
3470	=item EV_HEAP_CACHE_AT	4897	=item EV_HEAP_CACHE_AT
3471		4898
3472	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4899	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3473	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4900	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3474	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4901	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3475	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4902	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3476	but avoids random read accesses on heap changes. This improves performance	4903	but avoids random read accesses on heap changes. This improves performance
3477	noticeably with many (hundreds) of watchers.	4904	noticeably with many (hundreds) of watchers.
3478		4905
3479	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4906	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3480	(disabled).	4907	will be C<0>.
3481		4908
3482	=item EV_VERIFY	4909	=item EV_VERIFY
3483		4910
3484	Controls how much internal verification (see C<ev_loop_verify ()>) will	4911	Controls how much internal verification (see C<ev_verify ()>) will
3485	be done: If set to C<0>, no internal verification code will be compiled	4912	be done: If set to C<0>, no internal verification code will be compiled
3486	in. If set to C<1>, then verification code will be compiled in, but not	4913	in. If set to C<1>, then verification code will be compiled in, but not
3487	called. If set to C<2>, then the internal verification code will be	4914	called. If set to C<2>, then the internal verification code will be
3488	called once per loop, which can slow down libev. If set to C<3>, then the	4915	called once per loop, which can slow down libev. If set to C<3>, then the
3489	verification code will be called very frequently, which will slow down	4916	verification code will be called very frequently, which will slow down
3490	libev considerably.	4917	libev considerably.
3491		4918
3492	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4919	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3493	C<0>.	4920	will be C<0>.
3494		4921
3495	=item EV_COMMON	4922	=item EV_COMMON
3496		4923
3497	By default, all watchers have a C<void *data> member. By redefining	4924	By default, all watchers have a C<void *data> member. By redefining
3498	this macro to a something else you can include more and other types of	4925	this macro to something else you can include more and other types of
3499	members. You have to define it each time you include one of the files,	4926	members. You have to define it each time you include one of the files,
3500	though, and it must be identical each time.	4927	though, and it must be identical each time.
3501		4928
3502	For example, the perl EV module uses something like this:	4929	For example, the perl EV module uses something like this:
3503		4930
…		…
3556	file.	4983	file.
3557		4984
3558	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	4985	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3559	that everybody includes and which overrides some configure choices:	4986	that everybody includes and which overrides some configure choices:
3560		4987
3561	#define EV_MINIMAL 1	4988	#define EV_FEATURES 8
3562	#define EV_USE_POLL 0	4989	#define EV_USE_SELECT 1
3563	#define EV_MULTIPLICITY 0
3564	#define EV_PERIODIC_ENABLE 0	4990	#define EV_PREPARE_ENABLE 1
		4991	#define EV_IDLE_ENABLE 1
3565	#define EV_STAT_ENABLE 0	4992	#define EV_SIGNAL_ENABLE 1
3566	#define EV_FORK_ENABLE 0	4993	#define EV_CHILD_ENABLE 1
		4994	#define EV_USE_STDEXCEPT 0
3567	#define EV_CONFIG_H <config.h>	4995	#define EV_CONFIG_H <config.h>
3568	#define EV_MINPRI 0
3569	#define EV_MAXPRI 0
3570		4996
3571	#include "ev++.h"	4997	#include "ev++.h"
3572		4998
3573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4999	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3574		5000
3575	#include "ev_cpp.h"	5001	#include "ev_cpp.h"
3576	#include "ev.c"	5002	#include "ev.c"
3577		5003
3578	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5004	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3579		5005
3580	=head2 THREADS AND COROUTINES	5006	=head2 THREADS AND COROUTINES
3581		5007
3582	=head3 THREADS	5008	=head3 THREADS
3583		5009
…		…
3634	default loop and triggering an C<ev_async> watcher from the default loop	5060	default loop and triggering an C<ev_async> watcher from the default loop
3635	watcher callback into the event loop interested in the signal.	5061	watcher callback into the event loop interested in the signal.
3636		5062
3637	=back	5063	=back
3638		5064
		5065	See also L</THREAD LOCKING EXAMPLE>.
		5066
3639	=head3 COROUTINES	5067	=head3 COROUTINES
3640		5068
3641	Libev is very accommodating to coroutines ("cooperative threads"):	5069	Libev is very accommodating to coroutines ("cooperative threads"):
3642	libev fully supports nesting calls to its functions from different	5070	libev fully supports nesting calls to its functions from different
3643	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5071	coroutines (e.g. you can call C<ev_run> on the same loop from two
3644	different coroutines, and switch freely between both coroutines running the	5072	different coroutines, and switch freely between both coroutines running
3645	loop, as long as you don't confuse yourself). The only exception is that	5073	the loop, as long as you don't confuse yourself). The only exception is
3646	you must not do this from C<ev_periodic> reschedule callbacks.	5074	that you must not do this from C<ev_periodic> reschedule callbacks.
3647		5075
3648	Care has been taken to ensure that libev does not keep local state inside	5076	Care has been taken to ensure that libev does not keep local state inside
3649	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5077	C<ev_run>, and other calls do not usually allow for coroutine switches as
3650	they do not call any callbacks.	5078	they do not call any callbacks.
3651		5079
3652	=head2 COMPILER WARNINGS	5080	=head2 COMPILER WARNINGS
3653		5081
3654	Depending on your compiler and compiler settings, you might get no or a	5082	Depending on your compiler and compiler settings, you might get no or a
…		…
3665	maintainable.	5093	maintainable.
3666		5094
3667	And of course, some compiler warnings are just plain stupid, or simply	5095	And of course, some compiler warnings are just plain stupid, or simply
3668	wrong (because they don't actually warn about the condition their message	5096	wrong (because they don't actually warn about the condition their message
3669	seems to warn about). For example, certain older gcc versions had some	5097	seems to warn about). For example, certain older gcc versions had some
3670	warnings that resulted an extreme number of false positives. These have	5098	warnings that resulted in an extreme number of false positives. These have
3671	been fixed, but some people still insist on making code warn-free with	5099	been fixed, but some people still insist on making code warn-free with
3672	such buggy versions.	5100	such buggy versions.
3673		5101
3674	While libev is written to generate as few warnings as possible,	5102	While libev is written to generate as few warnings as possible,
3675	"warn-free" code is not a goal, and it is recommended not to build libev	5103	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3711	I suggest using suppression lists.	5139	I suggest using suppression lists.
3712		5140
3713		5141
3714	=head1 PORTABILITY NOTES	5142	=head1 PORTABILITY NOTES
3715		5143
		5144	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5145
		5146	GNU/Linux is the only common platform that supports 64 bit file/large file
		5147	interfaces but I<disables> them by default.
		5148
		5149	That means that libev compiled in the default environment doesn't support
		5150	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5151
		5152	Unfortunately, many programs try to work around this GNU/Linux issue
		5153	by enabling the large file API, which makes them incompatible with the
		5154	standard libev compiled for their system.
		5155
		5156	Likewise, libev cannot enable the large file API itself as this would
		5157	suddenly make it incompatible to the default compile time environment,
		5158	i.e. all programs not using special compile switches.
		5159
		5160	=head2 OS/X AND DARWIN BUGS
		5161
		5162	The whole thing is a bug if you ask me - basically any system interface
		5163	you touch is broken, whether it is locales, poll, kqueue or even the
		5164	OpenGL drivers.
		5165
		5166	=head3 C<kqueue> is buggy
		5167
		5168	The kqueue syscall is broken in all known versions - most versions support
		5169	only sockets, many support pipes.
		5170
		5171	Libev tries to work around this by not using C<kqueue> by default on this
		5172	rotten platform, but of course you can still ask for it when creating a
		5173	loop - embedding a socket-only kqueue loop into a select-based one is
		5174	probably going to work well.
		5175
		5176	=head3 C<poll> is buggy
		5177
		5178	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5179	implementation by something calling C<kqueue> internally around the 10.5.6
		5180	release, so now C<kqueue> I<and> C<poll> are broken.
		5181
		5182	Libev tries to work around this by not using C<poll> by default on
		5183	this rotten platform, but of course you can still ask for it when creating
		5184	a loop.
		5185
		5186	=head3 C<select> is buggy
		5187
		5188	All that's left is C<select>, and of course Apple found a way to fuck this
		5189	one up as well: On OS/X, C<select> actively limits the number of file
		5190	descriptors you can pass in to 1024 - your program suddenly crashes when
		5191	you use more.
		5192
		5193	There is an undocumented "workaround" for this - defining
		5194	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5195	work on OS/X.
		5196
		5197	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5198
		5199	=head3 C<errno> reentrancy
		5200
		5201	The default compile environment on Solaris is unfortunately so
		5202	thread-unsafe that you can't even use components/libraries compiled
		5203	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5204	defined by default. A valid, if stupid, implementation choice.
		5205
		5206	If you want to use libev in threaded environments you have to make sure
		5207	it's compiled with C<_REENTRANT> defined.
		5208
		5209	=head3 Event port backend
		5210
		5211	The scalable event interface for Solaris is called "event
		5212	ports". Unfortunately, this mechanism is very buggy in all major
		5213	releases. If you run into high CPU usage, your program freezes or you get
		5214	a large number of spurious wakeups, make sure you have all the relevant
		5215	and latest kernel patches applied. No, I don't know which ones, but there
		5216	are multiple ones to apply, and afterwards, event ports actually work
		5217	great.
		5218
		5219	If you can't get it to work, you can try running the program by setting
		5220	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5221	C<select> backends.
		5222
		5223	=head2 AIX POLL BUG
		5224
		5225	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5226	this by trying to avoid the poll backend altogether (i.e. it's not even
		5227	compiled in), which normally isn't a big problem as C<select> works fine
		5228	with large bitsets on AIX, and AIX is dead anyway.
		5229
3716	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5230	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5231
		5232	=head3 General issues
3717		5233
3718	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5234	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3719	requires, and its I/O model is fundamentally incompatible with the POSIX	5235	requires, and its I/O model is fundamentally incompatible with the POSIX
3720	model. Libev still offers limited functionality on this platform in	5236	model. Libev still offers limited functionality on this platform in
3721	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5237	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3722	descriptors. This only applies when using Win32 natively, not when using	5238	descriptors. This only applies when using Win32 natively, not when using
3723	e.g. cygwin.	5239	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5240	as every compiler comes with a slightly differently broken/incompatible
		5241	environment.
3724		5242
3725	Lifting these limitations would basically require the full	5243	Lifting these limitations would basically require the full
3726	re-implementation of the I/O system. If you are into these kinds of	5244	re-implementation of the I/O system. If you are into this kind of thing,
3727	things, then note that glib does exactly that for you in a very portable	5245	then note that glib does exactly that for you in a very portable way (note
3728	way (note also that glib is the slowest event library known to man).	5246	also that glib is the slowest event library known to man).
3729		5247
3730	There is no supported compilation method available on windows except	5248	There is no supported compilation method available on windows except
3731	embedding it into other applications.	5249	embedding it into other applications.
		5250
		5251	Sensible signal handling is officially unsupported by Microsoft - libev
		5252	tries its best, but under most conditions, signals will simply not work.
3732		5253
3733	Not a libev limitation but worth mentioning: windows apparently doesn't	5254	Not a libev limitation but worth mentioning: windows apparently doesn't
3734	accept large writes: instead of resulting in a partial write, windows will	5255	accept large writes: instead of resulting in a partial write, windows will
3735	either accept everything or return C<ENOBUFS> if the buffer is too large,	5256	either accept everything or return C<ENOBUFS> if the buffer is too large,
3736	so make sure you only write small amounts into your sockets (less than a	5257	so make sure you only write small amounts into your sockets (less than a
…		…
3741	the abysmal performance of winsockets, using a large number of sockets	5262	the abysmal performance of winsockets, using a large number of sockets
3742	is not recommended (and not reasonable). If your program needs to use	5263	is not recommended (and not reasonable). If your program needs to use
3743	more than a hundred or so sockets, then likely it needs to use a totally	5264	more than a hundred or so sockets, then likely it needs to use a totally
3744	different implementation for windows, as libev offers the POSIX readiness	5265	different implementation for windows, as libev offers the POSIX readiness
3745	notification model, which cannot be implemented efficiently on windows	5266	notification model, which cannot be implemented efficiently on windows
3746	(Microsoft monopoly games).	5267	(due to Microsoft monopoly games).
3747		5268
3748	A typical way to use libev under windows is to embed it (see the embedding	5269	A typical way to use libev under windows is to embed it (see the embedding
3749	section for details) and use the following F<evwrap.h> header file instead	5270	section for details) and use the following F<evwrap.h> header file instead
3750	of F<ev.h>:	5271	of F<ev.h>:
3751		5272
…		…
3758	you do I<not> compile the F<ev.c> or any other embedded source files!):	5279	you do I<not> compile the F<ev.c> or any other embedded source files!):
3759		5280
3760	#include "evwrap.h"	5281	#include "evwrap.h"
3761	#include "ev.c"	5282	#include "ev.c"
3762		5283
3763	=over 4
3764
3765	=item The winsocket select function	5284	=head3 The winsocket C<select> function
3766		5285
3767	The winsocket C<select> function doesn't follow POSIX in that it	5286	The winsocket C<select> function doesn't follow POSIX in that it
3768	requires socket I<handles> and not socket I<file descriptors> (it is	5287	requires socket I<handles> and not socket I<file descriptors> (it is
3769	also extremely buggy). This makes select very inefficient, and also	5288	also extremely buggy). This makes select very inefficient, and also
3770	requires a mapping from file descriptors to socket handles (the Microsoft	5289	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3779	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5298	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3780		5299
3781	Note that winsockets handling of fd sets is O(n), so you can easily get a	5300	Note that winsockets handling of fd sets is O(n), so you can easily get a
3782	complexity in the O(n²) range when using win32.	5301	complexity in the O(n²) range when using win32.
3783		5302
3784	=item Limited number of file descriptors	5303	=head3 Limited number of file descriptors
3785		5304
3786	Windows has numerous arbitrary (and low) limits on things.	5305	Windows has numerous arbitrary (and low) limits on things.
3787		5306
3788	Early versions of winsocket's select only supported waiting for a maximum	5307	Early versions of winsocket's select only supported waiting for a maximum
3789	of C<64> handles (probably owning to the fact that all windows kernels	5308	of C<64> handles (probably owning to the fact that all windows kernels
3790	can only wait for C<64> things at the same time internally; Microsoft	5309	can only wait for C<64> things at the same time internally; Microsoft
3791	recommends spawning a chain of threads and wait for 63 handles and the	5310	recommends spawning a chain of threads and wait for 63 handles and the
3792	previous thread in each. Great).	5311	previous thread in each. Sounds great!).
3793		5312
3794	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5313	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3795	to some high number (e.g. C<2048>) before compiling the winsocket select	5314	to some high number (e.g. C<2048>) before compiling the winsocket select
3796	call (which might be in libev or elsewhere, for example, perl does its own	5315	call (which might be in libev or elsewhere, for example, perl and many
3797	select emulation on windows).	5316	other interpreters do their own select emulation on windows).
3798		5317
3799	Another limit is the number of file descriptors in the Microsoft runtime	5318	Another limit is the number of file descriptors in the Microsoft runtime
3800	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5319	libraries, which by default is C<64> (there must be a hidden I<64>
3801	or something like this inside Microsoft). You can increase this by calling	5320	fetish or something like this inside Microsoft). You can increase this
3802	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5321	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3803	arbitrary limit), but is broken in many versions of the Microsoft runtime	5322	(another arbitrary limit), but is broken in many versions of the Microsoft
3804	libraries.
3805
3806	This might get you to about C<512> or C<2048> sockets (depending on	5323	runtime libraries. This might get you to about C<512> or C<2048> sockets
3807	windows version and/or the phase of the moon). To get more, you need to	5324	(depending on windows version and/or the phase of the moon). To get more,
3808	wrap all I/O functions and provide your own fd management, but the cost of	5325	you need to wrap all I/O functions and provide your own fd management, but
3809	calling select (O(n²)) will likely make this unworkable.	5326	the cost of calling select (O(n²)) will likely make this unworkable.
3810
3811	=back
3812		5327
3813	=head2 PORTABILITY REQUIREMENTS	5328	=head2 PORTABILITY REQUIREMENTS
3814		5329
3815	In addition to a working ISO-C implementation and of course the	5330	In addition to a working ISO-C implementation and of course the
3816	backend-specific APIs, libev relies on a few additional extensions:	5331	backend-specific APIs, libev relies on a few additional extensions:
…		…
3823	Libev assumes not only that all watcher pointers have the same internal	5338	Libev assumes not only that all watcher pointers have the same internal
3824	structure (guaranteed by POSIX but not by ISO C for example), but it also	5339	structure (guaranteed by POSIX but not by ISO C for example), but it also
3825	assumes that the same (machine) code can be used to call any watcher	5340	assumes that the same (machine) code can be used to call any watcher
3826	callback: The watcher callbacks have different type signatures, but libev	5341	callback: The watcher callbacks have different type signatures, but libev
3827	calls them using an C<ev_watcher *> internally.	5342	calls them using an C<ev_watcher *> internally.
		5343
		5344	=item null pointers and integer zero are represented by 0 bytes
		5345
		5346	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5347	relies on this setting pointers and integers to null.
		5348
		5349	=item pointer accesses must be thread-atomic
		5350
		5351	Accessing a pointer value must be atomic, it must both be readable and
		5352	writable in one piece - this is the case on all current architectures.
3828		5353
3829	=item C<sig_atomic_t volatile> must be thread-atomic as well	5354	=item C<sig_atomic_t volatile> must be thread-atomic as well
3830		5355
3831	The type C<sig_atomic_t volatile> (or whatever is defined as	5356	The type C<sig_atomic_t volatile> (or whatever is defined as
3832	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5357	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3841	thread" or will block signals process-wide, both behaviours would	5366	thread" or will block signals process-wide, both behaviours would
3842	be compatible with libev. Interaction between C<sigprocmask> and	5367	be compatible with libev. Interaction between C<sigprocmask> and
3843	C<pthread_sigmask> could complicate things, however.	5368	C<pthread_sigmask> could complicate things, however.
3844		5369
3845	The most portable way to handle signals is to block signals in all threads	5370	The most portable way to handle signals is to block signals in all threads
3846	except the initial one, and run the default loop in the initial thread as	5371	except the initial one, and run the signal handling loop in the initial
3847	well.	5372	thread as well.
3848		5373
3849	=item C<long> must be large enough for common memory allocation sizes	5374	=item C<long> must be large enough for common memory allocation sizes
3850		5375
3851	To improve portability and simplify its API, libev uses C<long> internally	5376	To improve portability and simplify its API, libev uses C<long> internally
3852	instead of C<size_t> when allocating its data structures. On non-POSIX	5377	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3855	watchers.	5380	watchers.
3856		5381
3857	=item C<double> must hold a time value in seconds with enough accuracy	5382	=item C<double> must hold a time value in seconds with enough accuracy
3858		5383
3859	The type C<double> is used to represent timestamps. It is required to	5384	The type C<double> is used to represent timestamps. It is required to
3860	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5385	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3861	enough for at least into the year 4000. This requirement is fulfilled by	5386	good enough for at least into the year 4000 with millisecond accuracy
		5387	(the design goal for libev). This requirement is overfulfilled by
3862	implementations implementing IEEE 754 (basically all existing ones).	5388	implementations using IEEE 754, which is basically all existing ones.
		5389
		5390	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5391	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5392	is either obsolete or somebody patched it to use C<long double> or
		5393	something like that, just kidding).
3863		5394
3864	=back	5395	=back
3865		5396
3866	If you know of other additional requirements drop me a note.	5397	If you know of other additional requirements drop me a note.
3867		5398
…		…
3929	=item Processing ev_async_send: O(number_of_async_watchers)	5460	=item Processing ev_async_send: O(number_of_async_watchers)
3930		5461
3931	=item Processing signals: O(max_signal_number)	5462	=item Processing signals: O(max_signal_number)
3932		5463
3933	Sending involves a system call I<iff> there were no other C<ev_async_send>	5464	Sending involves a system call I<iff> there were no other C<ev_async_send>
3934	calls in the current loop iteration. Checking for async and signal events	5465	calls in the current loop iteration and the loop is currently
		5466	blocked. Checking for async and signal events involves iterating over all
3935	involves iterating over all running async watchers or all signal numbers.	5467	running async watchers or all signal numbers.
3936		5468
3937	=back	5469	=back
3938		5470
3939		5471
		5472	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5473
		5474	The major version 4 introduced some incompatible changes to the API.
		5475
		5476	At the moment, the C<ev.h> header file provides compatibility definitions
		5477	for all changes, so most programs should still compile. The compatibility
		5478	layer might be removed in later versions of libev, so better update to the
		5479	new API early than late.
		5480
		5481	=over 4
		5482
		5483	=item C<EV_COMPAT3> backwards compatibility mechanism
		5484
		5485	The backward compatibility mechanism can be controlled by
		5486	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5487	section.
		5488
		5489	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5490
		5491	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5492
		5493	ev_loop_destroy (EV_DEFAULT_UC);
		5494	ev_loop_fork (EV_DEFAULT);
		5495
		5496	=item function/symbol renames
		5497
		5498	A number of functions and symbols have been renamed:
		5499
		5500	ev_loop => ev_run
		5501	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5502	EVLOOP_ONESHOT => EVRUN_ONCE
		5503
		5504	ev_unloop => ev_break
		5505	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5506	EVUNLOOP_ONE => EVBREAK_ONE
		5507	EVUNLOOP_ALL => EVBREAK_ALL
		5508
		5509	EV_TIMEOUT => EV_TIMER
		5510
		5511	ev_loop_count => ev_iteration
		5512	ev_loop_depth => ev_depth
		5513	ev_loop_verify => ev_verify
		5514
		5515	Most functions working on C<struct ev_loop> objects don't have an
		5516	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5517	associated constants have been renamed to not collide with the C<struct
		5518	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5519	as all other watcher types. Note that C<ev_loop_fork> is still called
		5520	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5521	typedef.
		5522
		5523	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5524
		5525	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5526	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5527	and work, but the library code will of course be larger.
		5528
		5529	=back
		5530
		5531
		5532	=head1 GLOSSARY
		5533
		5534	=over 4
		5535
		5536	=item active
		5537
		5538	A watcher is active as long as it has been started and not yet stopped.
		5539	See L</WATCHER STATES> for details.
		5540
		5541	=item application
		5542
		5543	In this document, an application is whatever is using libev.
		5544
		5545	=item backend
		5546
		5547	The part of the code dealing with the operating system interfaces.
		5548
		5549	=item callback
		5550
		5551	The address of a function that is called when some event has been
		5552	detected. Callbacks are being passed the event loop, the watcher that
		5553	received the event, and the actual event bitset.
		5554
		5555	=item callback/watcher invocation
		5556
		5557	The act of calling the callback associated with a watcher.
		5558
		5559	=item event
		5560
		5561	A change of state of some external event, such as data now being available
		5562	for reading on a file descriptor, time having passed or simply not having
		5563	any other events happening anymore.
		5564
		5565	In libev, events are represented as single bits (such as C<EV_READ> or
		5566	C<EV_TIMER>).
		5567
		5568	=item event library
		5569
		5570	A software package implementing an event model and loop.
		5571
		5572	=item event loop
		5573
		5574	An entity that handles and processes external events and converts them
		5575	into callback invocations.
		5576
		5577	=item event model
		5578
		5579	The model used to describe how an event loop handles and processes
		5580	watchers and events.
		5581
		5582	=item pending
		5583
		5584	A watcher is pending as soon as the corresponding event has been
		5585	detected. See L</WATCHER STATES> for details.
		5586
		5587	=item real time
		5588
		5589	The physical time that is observed. It is apparently strictly monotonic :)
		5590
		5591	=item wall-clock time
		5592
		5593	The time and date as shown on clocks. Unlike real time, it can actually
		5594	be wrong and jump forwards and backwards, e.g. when you adjust your
		5595	clock.
		5596
		5597	=item watcher
		5598
		5599	A data structure that describes interest in certain events. Watchers need
		5600	to be started (attached to an event loop) before they can receive events.
		5601
		5602	=back
		5603
3940	=head1 AUTHOR	5604	=head1 AUTHOR
3941		5605
3942	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5606	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5607	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3943		5608

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