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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
…		…
83	details of the event, and then hand it over to libev by I<starting> the	105	details of the event, and then hand it over to libev by I<starting> the
84	watcher.	106	watcher.
85		107
86	=head2 FEATURES	108	=head2 FEATURES
87		109
88	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	110	Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll>
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port
90	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	112	mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify>
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
92	with customised rescheduling (C<ev_periodic>), synchronous signals	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
93	(C<ev_signal>), process status change events (C<ev_child>), and event	115	timers (C<ev_timer>), absolute timers with customised rescheduling
94	watchers dealing with the event loop mechanism itself (C<ev_idle>,	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
95	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	117	change events (C<ev_child>), and event watchers dealing with the event
96	file watchers (C<ev_stat>) and even limited support for fork events	118	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
97	(C<ev_fork>).	119	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		120	limited support for fork events (C<ev_fork>).
98		121
99	It also is quite fast (see this	122	It also is quite fast (see this
100	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	123	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
101	for example).	124	for example).
102		125
…		…
105	Libev is very configurable. In this manual the default (and most common)	128	Libev is very configurable. In this manual the default (and most common)
106	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
107	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
108	B<EMBED> section in this manual. If libev was configured without support	131	B<EMBED> section in this manual. If libev was configured without support
109	for multiple event loops, then all functions taking an initial argument of	132	for multiple event loops, then all functions taking an initial argument of
110	name C<loop> (which is always of type C<ev_loop *>) will not have	133	name C<loop> (which is always of type C<struct ev_loop *>) will not have
111	this argument.	134	this argument.
112		135
113	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
114		137
115	Libev represents time as a single floating point number, representing the	138	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
117	the beginning of 1970, details are complicated, don't ask). This type is	140	somewhere near the beginning of 1970, details are complicated, don't
118	called C<ev_tstamp>, which is what you should use too. It usually aliases	141	ask). This type is called C<ev_tstamp>, which is what you should use
119	to the C<double> type in C, and when you need to do any calculations on	142	too. It usually aliases to the C<double> type in C. When you need to do
120	it, you should treat it as some floating point value. Unlike the name	143	any calculations on it, you should treat it as some floating point value.
		144
121	component C<stamp> might indicate, it is also used for time differences	145	Unlike the name component C<stamp> might indicate, it is also used for
122	throughout libev.	146	time differences (e.g. delays) throughout libev.
123		147
124	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
125		149
126	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
127	and internal errors (bugs).	151	and internal errors (bugs).
…		…
135	When libev detects a usage error such as a negative timer interval, then	159	When libev detects a usage error such as a negative timer interval, then
136	it will print a diagnostic message and abort (via the C<assert> mechanism,	160	it will print a diagnostic message and abort (via the C<assert> mechanism,
137	so C<NDEBUG> will disable this checking): these are programming errors in	161	so C<NDEBUG> will disable this checking): these are programming errors in
138	the libev caller and need to be fixed there.	162	the libev caller and need to be fixed there.
139		163
		164	Via the C<EV_FREQUENT> macro you can compile in and/or enable extensive
		165	consistency checking code inside libev that can be used to check for
		166	internal inconsistencies, suually caused by application bugs.
		167
140	Libev also has a few internal error-checking C<assert>ions, and also has	168	Libev also has a few internal error-checking C<assert>ions. These do not
141	extensive consistency checking code. These do not trigger under normal
142	circumstances, as they indicate either a bug in libev or worse.	169	trigger under normal circumstances, as they indicate either a bug in libev
		170	or worse.
143		171
144		172
145	=head1 GLOBAL FUNCTIONS	173	=head1 GLOBAL FUNCTIONS
146		174
147	These functions can be called anytime, even before initialising the	175	These functions can be called anytime, even before initialising the
…		…
151		179
152	=item ev_tstamp ev_time ()	180	=item ev_tstamp ev_time ()
153		181
154	Returns the current time as libev would use it. Please note that the	182	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	183	C<ev_now> function is usually faster and also often returns the timestamp
156	you actually want to know.	184	you actually want to know. Also interesting is the combination of
		185	C<ev_now_update> and C<ev_now>.
157		186
158	=item ev_sleep (ev_tstamp interval)	187	=item ev_sleep (ev_tstamp interval)
159		188
160	Sleep for the given interval: The current thread will be blocked until	189	Sleep for the given interval: The current thread will be blocked
161	either it is interrupted or the given time interval has passed. Basically	190	until either it is interrupted or the given time interval has
		191	passed (approximately - it might return a bit earlier even if not
		192	interrupted). Returns immediately if C<< interval <= 0 >>.
		193
162	this is a sub-second-resolution C<sleep ()>.	194	Basically this is a sub-second-resolution C<sleep ()>.
		195
		196	The range of the C<interval> is limited - libev only guarantees to work
		197	with sleep times of up to one day (C<< interval <= 86400 >>).
163		198
164	=item int ev_version_major ()	199	=item int ev_version_major ()
165		200
166	=item int ev_version_minor ()	201	=item int ev_version_minor ()
167		202
…		…
178	as this indicates an incompatible change. Minor versions are usually	213	as this indicates an incompatible change. Minor versions are usually
179	compatible to older versions, so a larger minor version alone is usually	214	compatible to older versions, so a larger minor version alone is usually
180	not a problem.	215	not a problem.
181		216
182	Example: Make sure we haven't accidentally been linked against the wrong	217	Example: Make sure we haven't accidentally been linked against the wrong
183	version.	218	version (note, however, that this will not detect other ABI mismatches,
		219	such as LFS or reentrancy).
184		220
185	assert (("libev version mismatch",	221	assert (("libev version mismatch",
186	ev_version_major () == EV_VERSION_MAJOR	222	ev_version_major () == EV_VERSION_MAJOR
187	&& ev_version_minor () >= EV_VERSION_MINOR));	223	&& ev_version_minor () >= EV_VERSION_MINOR));
188		224
…		…
199	assert (("sorry, no epoll, no sex",	235	assert (("sorry, no epoll, no sex",
200	ev_supported_backends () & EVBACKEND_EPOLL));	236	ev_supported_backends () & EVBACKEND_EPOLL));
201		237
202	=item unsigned int ev_recommended_backends ()	238	=item unsigned int ev_recommended_backends ()
203		239
204	Return the set of all backends compiled into this binary of libev and also	240	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	241	also recommended for this platform, meaning it will work for most file
		242	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	243	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	244	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	245	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.	246	probe for if you specify no backends explicitly.
210		247
211	=item unsigned int ev_embeddable_backends ()	248	=item unsigned int ev_embeddable_backends ()
212		249
213	Returns the set of backends that are embeddable in other event loops. This	250	Returns the set of backends that are embeddable in other event loops. This
214	is the theoretical, all-platform, value. To find which backends	251	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	252	current system. To find which embeddable backends might be supported on
216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	253	the current system, you would need to look at C<ev_embeddable_backends ()
217	recommended ones.	254	& ev_supported_backends ()>, likewise for recommended ones.
218		255
219	See the description of C<ev_embed> watchers for more info.	256	See the description of C<ev_embed> watchers for more info.
220		257
221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	258	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
222		259
223	Sets the allocation function to use (the prototype is similar - the	260	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	261	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	262	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	263	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
232		269
233	You could override this function in high-availability programs to, say,	270	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,	271	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.	272	or even to sleep a while and retry until some memory is available.
236		273
		274	Example: The following is the C<realloc> function that libev itself uses
		275	which should work with C<realloc> and C<free> functions of all kinds and
		276	is probably a good basis for your own implementation.
		277
		278	static void *
		279	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		280	{
		281	if (size)
		282	return realloc (ptr, size);
		283
		284	free (ptr);
		285	return 0;
		286	}
		287
237	Example: Replace the libev allocator with one that waits a bit and then	288	Example: Replace the libev allocator with one that waits a bit and then
238	retries (example requires a standards-compliant C<realloc>).	289	retries.
239		290
240	static void *	291	static void *
241	persistent_realloc (void *ptr, size_t size)	292	persistent_realloc (void *ptr, size_t size)
242	{	293	{
		294	if (!size)
		295	{
		296	free (ptr);
		297	return 0;
		298	}
		299
243	for (;;)	300	for (;;)
244	{	301	{
245	void *newptr = realloc (ptr, size);	302	void *newptr = realloc (ptr, size);
246		303
247	if (newptr)	304	if (newptr)
…		…
252	}	309	}
253		310
254	...	311	...
255	ev_set_allocator (persistent_realloc);	312	ev_set_allocator (persistent_realloc);
256		313
257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	314	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
258		315
259	Set the callback function to call on a retryable system call error (such	316	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	317	as failed select, poll, epoll_wait). The message is a printable string
261	indicating the system call or subsystem causing the problem. If this	318	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	319	callback is set, then libev will expect it to remedy the situation, no
…		…
274	}	331	}
275		332
276	...	333	...
277	ev_set_syserr_cb (fatal_error);	334	ev_set_syserr_cb (fatal_error);
278		335
		336	=item ev_feed_signal (int signum)
		337
		338	This function can be used to "simulate" a signal receive. It is completely
		339	safe to call this function at any time, from any context, including signal
		340	handlers or random threads.
		341
		342	Its main use is to customise signal handling in your process, especially
		343	in the presence of threads. For example, you could block signals
		344	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		345	creating any loops), and in one thread, use C<sigwait> or any other
		346	mechanism to wait for signals, then "deliver" them to libev by calling
		347	C<ev_feed_signal>.
		348
279	=back	349	=back
280		350
281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	351	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
282		352
283	An event loop is described by a C<struct ev_loop *> (the C<struct>	353	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>	354	I<not> optional in this case unless libev 3 compatibility is disabled, as
285	I<function>).	355	libev 3 had an C<ev_loop> function colliding with the struct name).
286		356
287	The library knows two types of such loops, the I<default> loop, which	357	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	358	supports child process events, and dynamically created event loops which
289	not.	359	do not.
290		360
291	=over 4	361	=over 4
292		362
293	=item struct ev_loop *ev_default_loop (unsigned int flags)	363	=item struct ev_loop *ev_default_loop (unsigned int flags)
294		364
295	This will initialise the default event loop if it hasn't been initialised	365	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	366	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	367	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).	368	C<ev_loop_new>.
		369
		370	If the default loop is already initialised then this function simply
		371	returns it (and ignores the flags. If that is troubling you, check
		372	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		373	flags, which should almost always be C<0>, unless the caller is also the
		374	one calling C<ev_run> or otherwise qualifies as "the main program".
299		375
300	If you don't know what event loop to use, use the one returned from this	376	If you don't know what event loop to use, use the one returned from this
301	function.	377	function (or via the C<EV_DEFAULT> macro).
302		378
303	Note that this function is I<not> thread-safe, so if you want to use it	379	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,	380	from multiple threads, you have to employ some kind of mutex (note also
305	as loops cannot be shared easily between threads anyway).	381	that this case is unlikely, as loops cannot be shared easily between
		382	threads anyway).
306		383
307	The default loop is the only loop that can handle C<ev_signal> and	384	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	385	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	386	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	387	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	388	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
312	C<ev_default_init>.	389
		390	Example: This is the most typical usage.
		391
		392	if (!ev_default_loop (0))
		393	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		394
		395	Example: Restrict libev to the select and poll backends, and do not allow
		396	environment settings to be taken into account:
		397
		398	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		399
		400	=item struct ev_loop *ev_loop_new (unsigned int flags)
		401
		402	This will create and initialise a new event loop object. If the loop
		403	could not be initialised, returns false.
		404
		405	This function is thread-safe, and one common way to use libev with
		406	threads is indeed to create one loop per thread, and using the default
		407	loop in the "main" or "initial" thread.
313		408
314	The flags argument can be used to specify special behaviour or specific	409	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>).	410	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
316		411
317	The following flags are supported:	412	The following flags are supported:
…		…
327		422
328	If this flag bit is or'ed into the flag value (or the program runs setuid	423	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	424	or setgid) then libev will I<not> look at the environment variable
330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	425	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
331	override the flags completely if it is found in the environment. This is	426	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	427	useful to try out specific backends to test their performance, to work
333	around bugs.	428	around bugs, or to make libev threadsafe (accessing environment variables
		429	cannot be done in a threadsafe way, but usually it works if no other
		430	thread modifies them).
334		431
335	=item C<EVFLAG_FORKCHECK>	432	=item C<EVFLAG_FORKCHECK>
336		433
337	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	434	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	435	make libev check for a fork in each iteration by enabling this flag.
339	enabling this flag.
340		436
341	This works by calling C<getpid ()> on every iteration of the loop,	437	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	438	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	439	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	440	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	441	sequence without a system call and thus I<very> fast, but my GNU/Linux
346	C<pthread_atfork> which is even faster).	442	system also has C<pthread_atfork> which is even faster). (Update: glibc
		443	versions 2.25 apparently removed the C<getpid> optimisation again).
347		444
348	The big advantage of this flag is that you can forget about fork (and	445	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	446	forget about forgetting to tell libev about forking, although you still
350	flag.	447	have to ignore C<SIGPIPE>) when you use this flag.
351		448
352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	449	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
353	environment variable.	450	environment variable.
		451
		452	=item C<EVFLAG_NOINOTIFY>
		453
		454	When this flag is specified, then libev will not attempt to use the
		455	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		456	testing, this flag can be useful to conserve inotify file descriptors, as
		457	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		458
		459	=item C<EVFLAG_SIGNALFD>
		460
		461	When this flag is specified, then libev will attempt to use the
		462	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		463	delivers signals synchronously, which makes it both faster and might make
		464	it possible to get the queued signal data. It can also simplify signal
		465	handling with threads, as long as you properly block signals in your
		466	threads that are not interested in handling them.
		467
		468	Signalfd will not be used by default as this changes your signal mask, and
		469	there are a lot of shoddy libraries and programs (glib's threadpool for
		470	example) that can't properly initialise their signal masks.
		471
		472	=item C<EVFLAG_NOSIGMASK>
		473
		474	When this flag is specified, then libev will avoid to modify the signal
		475	mask. Specifically, this means you have to make sure signals are unblocked
		476	when you want to receive them.
		477
		478	This behaviour is useful when you want to do your own signal handling, or
		479	want to handle signals only in specific threads and want to avoid libev
		480	unblocking the signals.
		481
		482	It's also required by POSIX in a threaded program, as libev calls
		483	C<sigprocmask>, whose behaviour is officially unspecified.
		484
		485	=item C<EVFLAG_NOTIMERFD>
		486
		487	When this flag is specified, the libev will avoid using a C<timerfd> to
		488	detect time jumps. It will still be able to detect time jumps, but takes
		489	longer and has a lower accuracy in doing so, but saves a file descriptor
		490	per loop.
		491
		492	The current implementation only tries to use a C<timerfd> when the first
		493	C<ev_periodic> watcher is started and falls back on other methods if it
		494	cannot be created, but this behaviour might change in the future.
354		495
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	496	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		497
357	This is your standard select(2) backend. Not I<completely> standard, as	498	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,	499	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	524	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	525	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
385		526
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	527	=item C<EVBACKEND_EPOLL> (value 4, Linux)
387		528
		529	Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9
		530	kernels).
		531
388	For few fds, this backend is a bit little slower than poll and select,	532	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	533	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),	534	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).	535	fd), epoll scales either O(1) or O(active_fds).
392		536
393	The epoll mechanism deserves honorable mention as the most misdesigned	537	The epoll mechanism deserves honorable mention as the most misdesigned
394	of the more advanced event mechanisms: mere annoyances include silently	538	of the more advanced event mechanisms: mere annoyances include silently
395	dropping file descriptors, requiring a system call per change per file	539	dropping file descriptors, requiring a system call per change per file
396	descriptor (and unnecessary guessing of parameters), problems with dup and	540	descriptor (and unnecessary guessing of parameters), problems with dup,
		541	returning before the timeout value, resulting in additional iterations
		542	(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	543	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	544	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	545	set, which can take considerable time (one syscall per file descriptor)
400	hard to detect.	546	and is of course hard to detect.
401		547
402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	548	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	549	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	550	totally I<different> file descriptors (even already closed ones, so
405	even remove them from the set) than registered in the set (especially	551	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	552	(especially on SMP systems). Libev tries to counter these spurious
407	employing an additional generation counter and comparing that against the	553	notifications by employing an additional generation counter and comparing
408	events to filter out spurious ones, recreating the set when required.	554	that against the events to filter out spurious ones, recreating the set
		555	when required. Epoll also erroneously rounds down timeouts, but gives you
		556	no way to know when and by how much, so sometimes you have to busy-wait
		557	because epoll returns immediately despite a nonzero timeout. And last
		558	not least, it also refuses to work with some file descriptors which work
		559	perfectly fine with C<select> (files, many character devices...).
		560
		561	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		562	cobbled together in a hurry, no thought to design or interaction with
		563	others. Oh, the pain, will it ever stop...
409		564
410	While stopping, setting and starting an I/O watcher in the same iteration	565	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	566	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	567	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	568	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or	580	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
426	faster than epoll for maybe up to a hundred file descriptors, depending on	581	faster than epoll for maybe up to a hundred file descriptors, depending on
427	the usage. So sad.	582	the usage. So sad.
428		583
429	While nominally embeddable in other event loops, this feature is broken in	584	While nominally embeddable in other event loops, this feature is broken in
430	all kernel versions tested so far.	585	a lot of kernel revisions, but probably(!) works in current versions.
431		586
432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	587	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
433	C<EVBACKEND_POLL>.	588	C<EVBACKEND_POLL>.
434		589
		590	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		591
		592	Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<<
		593	io_submit(2) >>) event interface available in post-4.18 kernels (but libev
		594	only tries to use it in 4.19+).
		595
		596	This is another Linux train wreck of an event interface.
		597
		598	If this backend works for you (as of this writing, it was very
		599	experimental), it is the best event interface available on Linux and might
		600	be well worth enabling it - if it isn't available in your kernel this will
		601	be detected and this backend will be skipped.
		602
		603	This backend can batch oneshot requests and supports a user-space ring
		604	buffer to receive events. It also doesn't suffer from most of the design
		605	problems of epoll (such as not being able to remove event sources from
		606	the epoll set), and generally sounds too good to be true. Because, this
		607	being the Linux kernel, of course it suffers from a whole new set of
		608	limitations, forcing you to fall back to epoll, inheriting all its design
		609	issues.
		610
		611	For one, it is not easily embeddable (but probably could be done using
		612	an event fd at some extra overhead). It also is subject to a system wide
		613	limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO
		614	requests are left, this backend will be skipped during initialisation, and
		615	will switch to epoll when the loop is active.
		616
		617	Most problematic in practice, however, is that not all file descriptors
		618	work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds,
		619	files, F</dev/null> and many others are supported, but ttys do not work
		620	properly (a known bug that the kernel developers don't care about, see
		621	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		622	(yet?) a generic event polling interface.
		623
		624	Overall, it seems the Linux developers just don't want it to have a
		625	generic event handling mechanism other than C<select> or C<poll>.
		626
		627	To work around all these problem, the current version of libev uses its
		628	epoll backend as a fallback for file descriptor types that do not work. Or
		629	falls back completely to epoll if the kernel acts up.
		630
		631	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		632	C<EVBACKEND_POLL>.
		633
435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	634	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
436		635
437	Kqueue deserves special mention, as at the time of this writing, it	636	Kqueue deserves special mention, as at the time this backend was
438	was broken on all BSDs except NetBSD (usually it doesn't work reliably	637	implemented, it was broken on all BSDs except NetBSD (usually it doesn't
439	with anything but sockets and pipes, except on Darwin, where of course	638	work reliably with anything but sockets and pipes, except on Darwin,
440	it's completely useless). Unlike epoll, however, whose brokenness	639	where of course it's completely useless). Unlike epoll, however, whose
441	is by design, these kqueue bugs can (and eventually will) be fixed	640	brokenness is by design, these kqueue bugs can be (and mostly have been)
442	without API changes to existing programs. For this reason it's not being	641	fixed without API changes to existing programs. For this reason it's not
443	"auto-detected" unless you explicitly specify it in the flags (i.e. using	642	being "auto-detected" on all platforms unless you explicitly specify it
444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	643	in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a
445	system like NetBSD.	644	known-to-be-good (-enough) system like NetBSD.
446		645
447	You still can embed kqueue into a normal poll or select backend and use it	646	You still can embed kqueue into a normal poll or select backend and use it
448	only for sockets (after having made sure that sockets work with kqueue on	647	only for sockets (after having made sure that sockets work with kqueue on
449	the target platform). See C<ev_embed> watchers for more info.	648	the target platform). See C<ev_embed> watchers for more info.
450		649
451	It scales in the same way as the epoll backend, but the interface to the	650	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	651	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	652	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	653	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	654	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	655	might have to leak fds on fork, but it's more sane than epoll) and it
457	cases	656	drops fds silently in similarly hard-to-detect cases.
458		657
459	This backend usually performs well under most conditions.	658	This backend usually performs well under most conditions.
460		659
461	While nominally embeddable in other event loops, this doesn't work	660	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	661	everywhere, so you might need to test for this. And since it is broken
…		…
479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	678	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
480		679
481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	680	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)).	681	it's really slow, but it still scales very well (O(active_fds)).
483		682
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	683	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	684	file descriptor per loop iteration. For small and medium numbers of file
490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	685	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
491	might perform better.	686	might perform better.
492		687
493	On the positive side, with the exception of the spurious readiness	688	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	689	specification in all tests and is fully embeddable, which is a rare feat
496	OS-specific backends (I vastly prefer correctness over speed hacks).	690	among the OS-specific backends (I vastly prefer correctness over speed
		691	hacks).
		692
		693	On the negative side, the interface is I<bizarre> - so bizarre that
		694	even sun itself gets it wrong in their code examples: The event polling
		695	function sometimes returns events to the caller even though an error
		696	occurred, but with no indication whether it has done so or not (yes, it's
		697	even documented that way) - deadly for edge-triggered interfaces where you
		698	absolutely have to know whether an event occurred or not because you have
		699	to re-arm the watcher.
		700
		701	Fortunately libev seems to be able to work around these idiocies.
497		702
498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	703	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
499	C<EVBACKEND_POLL>.	704	C<EVBACKEND_POLL>.
500		705
501	=item C<EVBACKEND_ALL>	706	=item C<EVBACKEND_ALL>
502		707
503	Try all backends (even potentially broken ones that wouldn't be tried	708	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	709	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	710	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
506		711
507	It is definitely not recommended to use this flag.	712	It is definitely not recommended to use this flag, use whatever
		713	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		714	at all.
		715
		716	=item C<EVBACKEND_MASK>
		717
		718	Not a backend at all, but a mask to select all backend bits from a
		719	C<flags> value, in case you want to mask out any backends from a flags
		720	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
508		721
509	=back	722	=back
510		723
511	If one or more of these are or'ed into the flags value, then only these	724	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	725	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.	726	here). If none are specified, all backends in C<ev_recommended_backends
514		727	()> 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		728
543	Example: Try to create a event loop that uses epoll and nothing else.	729	Example: Try to create a event loop that uses epoll and nothing else.
544		730
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	731	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
546	if (!epoller)	732	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	733	fatal ("no epoll found here, maybe it hides under your chair");
548		734
		735	Example: Use whatever libev has to offer, but make sure that kqueue is
		736	used if available.
		737
		738	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		739
		740	Example: Similarly, on linux, you mgiht want to take advantage of the
		741	linux aio backend if possible, but fall back to something else if that
		742	isn't available.
		743
		744	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		745
549	=item ev_default_destroy ()	746	=item ev_loop_destroy (loop)
550		747
551	Destroys the default loop again (frees all memory and kernel state	748	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	749	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	750	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>	751	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	752	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	753	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		755
559	Note that certain global state, such as signal state (and installed signal	756	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	757	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	758	as signal and child watchers) would need to be stopped manually.
562		759
563	In general it is not advisable to call this function except in the	760	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	761	C<ev_loop_new>, but it can also be used on the default loop returned by
		762	C<ev_default_loop>, in which case it is not thread-safe.
		763
		764	Note that it is not advisable to call this function on the default loop
		765	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	766	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>).	767	and C<ev_loop_destroy>.
567		768
568	=item ev_loop_destroy (loop)	769	=item ev_loop_fork (loop)
569		770
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	771	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	772	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	773	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	774	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	775	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.	776	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		777
		778	In addition, if you want to reuse a loop (via this function or
		779	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		780
		781	Again, you I<have> to call it on I<any> loop that you want to re-use after
		782	a fork, I<even if you do not plan to use the loop in the parent>. This is
		783	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		784	during fork.
581		785
582	On the other hand, you only need to call this function in the child	786	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	787	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.	788	you just fork+exec or create a new loop in the child, you don't have to
		789	call it at all (in fact, C<epoll> is so badly broken that it makes a
		790	difference, but libev will usually detect this case on its own and do a
		791	costly reset of the backend).
585		792
586	The function itself is quite fast and it's usually not a problem to call	793	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	794	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		795
		796	Example: Automate calling C<ev_loop_fork> on the default loop when
		797	using pthreads.
		798
		799	static void
		800	post_fork_child (void)
		801	{
		802	ev_loop_fork (EV_DEFAULT);
		803	}
		804
		805	...
590	pthread_atfork (0, 0, ev_default_fork);	806	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		807
599	=item int ev_is_default_loop (loop)	808	=item int ev_is_default_loop (loop)
600		809
601	Returns true when the given loop is, in fact, the default loop, and false	810	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	811	otherwise.
603		812
604	=item unsigned int ev_loop_count (loop)	813	=item unsigned int ev_iteration (loop)
605		814
606	Returns the count of loop iterations for the loop, which is identical to	815	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	816	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	817	and happily wraps around with enough iterations.
609		818
610	This value can sometimes be useful as a generation counter of sorts (it	819	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	820	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	821	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		822	prepare and check phases.
		823
		824	=item unsigned int ev_depth (loop)
		825
		826	Returns the number of times C<ev_run> was entered minus the number of
		827	times C<ev_run> was exited normally, in other words, the recursion depth.
		828
		829	Outside C<ev_run>, this number is zero. In a callback, this number is
		830	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		831	in which case it is higher.
		832
		833	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		834	throwing an exception etc.), doesn't count as "exit" - consider this
		835	as a hint to avoid such ungentleman-like behaviour unless it's really
		836	convenient, in which case it is fully supported.
613		837
614	=item unsigned int ev_backend (loop)	838	=item unsigned int ev_backend (loop)
615		839
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	840	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	841	use.
…		…
626		850
627	=item ev_now_update (loop)	851	=item ev_now_update (loop)
628		852
629	Establishes the current time by querying the kernel, updating the time	853	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	854	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	855	is usually done automatically within C<ev_run ()>.
632		856
633	This function is rarely useful, but when some event callback runs for a	857	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	858	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	859	the current time is a good idea.
636		860
637	See also "The special problem of time updates" in the C<ev_timer> section.	861	See also L</The special problem of time updates> in the C<ev_timer> section.
638		862
		863	=item ev_suspend (loop)
		864
		865	=item ev_resume (loop)
		866
		867	These two functions suspend and resume an event loop, for use when the
		868	loop is not used for a while and timeouts should not be processed.
		869
		870	A typical use case would be an interactive program such as a game: When
		871	the user presses C<^Z> to suspend the game and resumes it an hour later it
		872	would be best to handle timeouts as if no time had actually passed while
		873	the program was suspended. This can be achieved by calling C<ev_suspend>
		874	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		875	C<ev_resume> directly afterwards to resume timer processing.
		876
		877	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		878	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		879	will be rescheduled (that is, they will lose any events that would have
		880	occurred while suspended).
		881
		882	After calling C<ev_suspend> you B<must not> call I<any> function on the
		883	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		884	without a previous call to C<ev_suspend>.
		885
		886	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		887	event loop time (see C<ev_now_update>).
		888
639	=item ev_loop (loop, int flags)	889	=item bool ev_run (loop, int flags)
640		890
641	Finally, this is it, the event handler. This function usually is called	891	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	892	after you have initialised all your watchers and you want to start
643	events.	893	handling events. It will ask the operating system for any new events, call
		894	the watcher callbacks, and then repeat the whole process indefinitely: This
		895	is why event loops are called I<loops>.
644		896
645	If the flags argument is specified as C<0>, it will not return until	897	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.	898	until either no event watchers are active anymore or C<ev_break> was
		899	called.
647		900
		901	The return value is false if there are no more active watchers (which
		902	usually means "all jobs done" or "deadlock"), and true in all other cases
		903	(which usually means " you should call C<ev_run> again").
		904
648	Please note that an explicit C<ev_unloop> is usually better than	905	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	906	relying on all watchers to be stopped when deciding when a program has
650	finished (especially in interactive programs), but having a program	907	finished (especially in interactive programs), but having a program
651	that automatically loops as long as it has to and no longer by virtue	908	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	909	of relying on its watchers stopping correctly, that is truly a thing of
653	beauty.	910	beauty.
654		911
		912	This function is I<mostly> exception-safe - you can break out of a
		913	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		914	exception and so on. This does not decrement the C<ev_depth> value, nor
		915	will it clear any outstanding C<EVBREAK_ONE> breaks.
		916
655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	917	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	918	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	919	block your process in case there are no events and will return after one
658	the loop.	920	iteration of the loop. This is sometimes useful to poll and handle new
		921	events while doing lengthy calculations, to keep the program responsive.
659		922
660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	923	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	924	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	925	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	926	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	927	user-registered callback will be called), and will return after one
665	iteration of the loop.	928	iteration of the loop.
666		929
667	This is useful if you are waiting for some external event in conjunction	930	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	931	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	932	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.	933	usually a better approach for this kind of thing.
671		934
672	Here are the gory details of what C<ev_loop> does:	935	Here are the gory details of what C<ev_run> does (this is for your
		936	understanding, not a guarantee that things will work exactly like this in
		937	future versions):
673		938
		939	- Increment loop depth.
		940	- Reset the ev_break status.
674	- Before the first iteration, call any pending watchers.	941	- Before the first iteration, call any pending watchers.
		942	LOOP:
675	* If EVFLAG_FORKCHECK was used, check for a fork.	943	- If EVFLAG_FORKCHECK was used, check for a fork.
676	- If a fork was detected (by any means), queue and call all fork watchers.	944	- If a fork was detected (by any means), queue and call all fork watchers.
677	- Queue and call all prepare watchers.	945	- Queue and call all prepare watchers.
		946	- If ev_break was called, goto FINISH.
678	- If we have been forked, detach and recreate the kernel state	947	- If we have been forked, detach and recreate the kernel state
679	as to not disturb the other process.	948	as to not disturb the other process.
680	- Update the kernel state with all outstanding changes.	949	- Update the kernel state with all outstanding changes.
681	- Update the "event loop time" (ev_now ()).	950	- Update the "event loop time" (ev_now ()).
682	- Calculate for how long to sleep or block, if at all	951	- Calculate for how long to sleep or block, if at all
683	(active idle watchers, EVLOOP_NONBLOCK or not having	952	(active idle watchers, EVRUN_NOWAIT or not having
684	any active watchers at all will result in not sleeping).	953	any active watchers at all will result in not sleeping).
685	- Sleep if the I/O and timer collect interval say so.	954	- Sleep if the I/O and timer collect interval say so.
		955	- Increment loop iteration counter.
686	- Block the process, waiting for any events.	956	- Block the process, waiting for any events.
687	- Queue all outstanding I/O (fd) events.	957	- Queue all outstanding I/O (fd) events.
688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	958	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
689	- Queue all expired timers.	959	- Queue all expired timers.
690	- Queue all expired periodics.	960	- Queue all expired periodics.
691	- Unless any events are pending now, queue all idle watchers.	961	- Queue all idle watchers with priority higher than that of pending events.
692	- Queue all check watchers.	962	- Queue all check watchers.
693	- Call all queued watchers in reverse order (i.e. check watchers first).	963	- 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	964	Signals and child watchers are implemented as I/O watchers, and will
695	be handled here by queueing them when their watcher gets executed.	965	be handled here by queueing them when their watcher gets executed.
696	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	966	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
697	were used, or there are no active watchers, return, otherwise	967	were used, or there are no active watchers, goto FINISH, otherwise
698	continue with step *.	968	continue with step LOOP.
		969	FINISH:
		970	- Reset the ev_break status iff it was EVBREAK_ONE.
		971	- Decrement the loop depth.
		972	- Return.
699		973
700	Example: Queue some jobs and then loop until no events are outstanding	974	Example: Queue some jobs and then loop until no events are outstanding
701	anymore.	975	anymore.
702		976
703	... queue jobs here, make sure they register event watchers as long	977	... 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..)	978	... as they still have work to do (even an idle watcher will do..)
705	ev_loop (my_loop, 0);	979	ev_run (my_loop, 0);
706	... jobs done or somebody called unloop. yeah!	980	... jobs done or somebody called break. yeah!
707		981
708	=item ev_unloop (loop, how)	982	=item ev_break (loop, how)
709		983
710	Can be used to make a call to C<ev_loop> return early (but only after it	984	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	985	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	986	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.	987	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
714		988
715	This "unloop state" will be cleared when entering C<ev_loop> again.	989	This "break state" will be cleared on the next call to C<ev_run>.
716		990
717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	991	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		992	which case it will have no effect.
718		993
719	=item ev_ref (loop)	994	=item ev_ref (loop)
720		995
721	=item ev_unref (loop)	996	=item ev_unref (loop)
722		997
723	Ref/unref can be used to add or remove a reference count on the event	998	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	999	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.	1000	count is nonzero, C<ev_run> will not return on its own.
726		1001
727	If you have a watcher you never unregister that should not keep C<ev_loop>	1002	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	1003	unregister, but that nevertheless should not keep C<ev_run> from
		1004	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
729	stopping it.	1005	before stopping it.
730		1006
731	As an example, libev itself uses this for its internal signal pipe: It is	1007	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	1008	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	1009	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	1010	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>	1011	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,	1012	before stop> (but only if the watcher wasn't active before, or was active
737	respectively).	1013	before, respectively. Note also that libev might stop watchers itself
		1014	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		1015	in the callback).
738		1016
739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	1017	Example: Create a signal watcher, but keep it from keeping C<ev_run>
740	running when nothing else is active.	1018	running when nothing else is active.
741		1019
742	ev_signal exitsig;	1020	ev_signal exitsig;
743	ev_signal_init (&exitsig, sig_cb, SIGINT);	1021	ev_signal_init (&exitsig, sig_cb, SIGINT);
744	ev_signal_start (loop, &exitsig);	1022	ev_signal_start (loop, &exitsig);
745	evf_unref (loop);	1023	ev_unref (loop);
746		1024
747	Example: For some weird reason, unregister the above signal handler again.	1025	Example: For some weird reason, unregister the above signal handler again.
748		1026
749	ev_ref (loop);	1027	ev_ref (loop);
750	ev_signal_stop (loop, &exitsig);	1028	ev_signal_stop (loop, &exitsig);
…		…
770	overhead for the actual polling but can deliver many events at once.	1048	overhead for the actual polling but can deliver many events at once.
771		1049
772	By setting a higher I<io collect interval> you allow libev to spend more	1050	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,	1051	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	1052	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	1053	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.	1054	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		1055	sleep time ensures that libev will not poll for I/O events more often then
		1056	once per this interval, on average (as long as the host time resolution is
		1057	good enough).
777		1058
778	Likewise, by setting a higher I<timeout collect interval> you allow libev	1059	Likewise, by setting a higher I<timeout collect interval> you allow libev
779	to spend more time collecting timeouts, at the expense of increased	1060	to spend more time collecting timeouts, at the expense of increased
780	latency/jitter/inexactness (the watcher callback will be called	1061	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	1062	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
783		1064
784	Many (busy) programs can usually benefit by setting the I/O collect	1065	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	1066	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	1067	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>,	1068	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.	1069	as this approaches the timing granularity of most systems. Note that if
		1070	you do transactions with the outside world and you can't increase the
		1071	parallelity, then this setting will limit your transaction rate (if you
		1072	need to poll once per transaction and the I/O collect interval is 0.01,
		1073	then you can't do more than 100 transactions per second).
789		1074
790	Setting the I<timeout collect interval> can improve the opportunity for	1075	Setting the I<timeout collect interval> can improve the opportunity for
791	saving power, as the program will "bundle" timer callback invocations that	1076	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	1077	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	1078	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	1079	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
795	they fire on, say, one-second boundaries only.	1080	they fire on, say, one-second boundaries only.
796		1081
		1082	Example: we only need 0.1s timeout granularity, and we wish not to poll
		1083	more often than 100 times per second:
		1084
		1085	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		1086	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		1087
		1088	=item ev_invoke_pending (loop)
		1089
		1090	This call will simply invoke all pending watchers while resetting their
		1091	pending state. Normally, C<ev_run> does this automatically when required,
		1092	but when overriding the invoke callback this call comes handy. This
		1093	function can be invoked from a watcher - this can be useful for example
		1094	when you want to do some lengthy calculation and want to pass further
		1095	event handling to another thread (you still have to make sure only one
		1096	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1097
		1098	=item int ev_pending_count (loop)
		1099
		1100	Returns the number of pending watchers - zero indicates that no watchers
		1101	are pending.
		1102
		1103	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1104
		1105	This overrides the invoke pending functionality of the loop: Instead of
		1106	invoking all pending watchers when there are any, C<ev_run> will call
		1107	this callback instead. This is useful, for example, when you want to
		1108	invoke the actual watchers inside another context (another thread etc.).
		1109
		1110	If you want to reset the callback, use C<ev_invoke_pending> as new
		1111	callback.
		1112
		1113	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1114
		1115	Sometimes you want to share the same loop between multiple threads. This
		1116	can be done relatively simply by putting mutex_lock/unlock calls around
		1117	each call to a libev function.
		1118
		1119	However, C<ev_run> can run an indefinite time, so it is not feasible
		1120	to wait for it to return. One way around this is to wake up the event
		1121	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1122	I<release> and I<acquire> callbacks on the loop.
		1123
		1124	When set, then C<release> will be called just before the thread is
		1125	suspended waiting for new events, and C<acquire> is called just
		1126	afterwards.
		1127
		1128	Ideally, C<release> will just call your mutex_unlock function, and
		1129	C<acquire> will just call the mutex_lock function again.
		1130
		1131	While event loop modifications are allowed between invocations of
		1132	C<release> and C<acquire> (that's their only purpose after all), no
		1133	modifications done will affect the event loop, i.e. adding watchers will
		1134	have no effect on the set of file descriptors being watched, or the time
		1135	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1136	to take note of any changes you made.
		1137
		1138	In theory, threads executing C<ev_run> will be async-cancel safe between
		1139	invocations of C<release> and C<acquire>.
		1140
		1141	See also the locking example in the C<THREADS> section later in this
		1142	document.
		1143
		1144	=item ev_set_userdata (loop, void *data)
		1145
		1146	=item void *ev_userdata (loop)
		1147
		1148	Set and retrieve a single C<void *> associated with a loop. When
		1149	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1150	C<0>.
		1151
		1152	These two functions can be used to associate arbitrary data with a loop,
		1153	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1154	C<acquire> callbacks described above, but of course can be (ab-)used for
		1155	any other purpose as well.
		1156
797	=item ev_loop_verify (loop)	1157	=item ev_verify (loop)
798		1158
799	This function only does something when C<EV_VERIFY> support has been	1159	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	1160	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	1161	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	1162	is found to be inconsistent, it will print an error message to standard
…		…
813		1173
814	In the following description, uppercase C<TYPE> in names stands for the	1174	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	1175	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.	1176	watchers and C<ev_io_start> for I/O watchers.
817		1177
818	A watcher is a structure that you create and register to record your	1178	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	1179	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:	1180	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1181	for that:
821		1182
822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1183	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
823	{	1184	{
824	ev_io_stop (w);	1185	ev_io_stop (w);
825	ev_unloop (loop, EVUNLOOP_ALL);	1186	ev_break (loop, EVBREAK_ALL);
826	}	1187	}
827		1188
828	struct ev_loop *loop = ev_default_loop (0);	1189	struct ev_loop *loop = ev_default_loop (0);
829		1190
830	ev_io stdin_watcher;	1191	ev_io stdin_watcher;
831		1192
832	ev_init (&stdin_watcher, my_cb);	1193	ev_init (&stdin_watcher, my_cb);
833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1194	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
834	ev_io_start (loop, &stdin_watcher);	1195	ev_io_start (loop, &stdin_watcher);
835		1196
836	ev_loop (loop, 0);	1197	ev_run (loop, 0);
837		1198
838	As you can see, you are responsible for allocating the memory for your	1199	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	1200	watcher structures (and it is I<usually> a bad idea to do this on the
840	stack).	1201	stack).
841		1202
842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1203	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).	1204	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
844		1205
845	Each watcher structure must be initialised by a call to C<ev_init	1206	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	1207	*, 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	1208	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	1209	time the event loop detects that the file descriptor given is readable
849	is readable and/or writable).	1210	and/or writable).
850		1211
851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1212	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	1213	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<<	1214	is also a macro to combine initialisation and setting in one call: C<<
854	ev_TYPE_init (watcher *, callback, ...) >>.	1215	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
857	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher	1218	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
858	*) >>), and you can stop watching for events at any time by calling the	1219	*) >>), and you can stop watching for events at any time by calling the
859	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.	1220	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
860		1221
861	As long as your watcher is active (has been started but not stopped) you	1222	As long as your watcher is active (has been started but not stopped) you
862	must not touch the values stored in it. Most specifically you must never	1223	must not touch the values stored in it except when explicitly documented
863	reinitialise it or call its C<ev_TYPE_set> macro.	1224	otherwise. Most specifically you must never reinitialise it or call its
		1225	C<ev_TYPE_set> macro.
864		1226
865	Each and every callback receives the event loop pointer as first, the	1227	Each and every callback receives the event loop pointer as first, the
866	registered watcher structure as second, and a bitset of received events as	1228	registered watcher structure as second, and a bitset of received events as
867	third argument.	1229	third argument.
868		1230
…		…
877	=item C<EV_WRITE>	1239	=item C<EV_WRITE>
878		1240
879	The file descriptor in the C<ev_io> watcher has become readable and/or	1241	The file descriptor in the C<ev_io> watcher has become readable and/or
880	writable.	1242	writable.
881		1243
882	=item C<EV_TIMEOUT>	1244	=item C<EV_TIMER>
883		1245
884	The C<ev_timer> watcher has timed out.	1246	The C<ev_timer> watcher has timed out.
885		1247
886	=item C<EV_PERIODIC>	1248	=item C<EV_PERIODIC>
887		1249
…		…
905		1267
906	=item C<EV_PREPARE>	1268	=item C<EV_PREPARE>
907		1269
908	=item C<EV_CHECK>	1270	=item C<EV_CHECK>
909		1271
910	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1272	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	1273	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	1274	just after C<ev_run> has gathered them, but before it queues any callbacks
		1275	for any received events. That means C<ev_prepare> watchers are the last
		1276	watchers invoked before the event loop sleeps or polls for new events, and
		1277	C<ev_check> watchers will be invoked before any other watchers of the same
		1278	or lower priority within an event loop iteration.
		1279
913	received events. Callbacks of both watcher types can start and stop as	1280	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	1281	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	1282	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
916	C<ev_loop> from blocking).	1283	blocking).
917		1284
918	=item C<EV_EMBED>	1285	=item C<EV_EMBED>
919		1286
920	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1287	The embedded event loop specified in the C<ev_embed> watcher needs attention.
921		1288
922	=item C<EV_FORK>	1289	=item C<EV_FORK>
923		1290
924	The event loop has been resumed in the child process after fork (see	1291	The event loop has been resumed in the child process after fork (see
925	C<ev_fork>).	1292	C<ev_fork>).
926		1293
		1294	=item C<EV_CLEANUP>
		1295
		1296	The event loop is about to be destroyed (see C<ev_cleanup>).
		1297
927	=item C<EV_ASYNC>	1298	=item C<EV_ASYNC>
928		1299
929	The given async watcher has been asynchronously notified (see C<ev_async>).	1300	The given async watcher has been asynchronously notified (see C<ev_async>).
		1301
		1302	=item C<EV_CUSTOM>
		1303
		1304	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1305	by libev users to signal watchers (e.g. via C<ev_feed_event>).
930		1306
931	=item C<EV_ERROR>	1307	=item C<EV_ERROR>
932		1308
933	An unspecified error has occurred, the watcher has been stopped. This might	1309	An unspecified error has occurred, the watcher has been stopped. This might
934	happen because the watcher could not be properly started because libev	1310	happen because the watcher could not be properly started because libev
…		…
972		1348
973	ev_io w;	1349	ev_io w;
974	ev_init (&w, my_cb);	1350	ev_init (&w, my_cb);
975	ev_io_set (&w, STDIN_FILENO, EV_READ);	1351	ev_io_set (&w, STDIN_FILENO, EV_READ);
976		1352
977	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1353	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
978		1354
979	This macro initialises the type-specific parts of a watcher. You need to	1355	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	1356	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	1357	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	1358	macro on a watcher that is active (it can be pending, however, which is a
…		…
995		1371
996	Example: Initialise and set an C<ev_io> watcher in one step.	1372	Example: Initialise and set an C<ev_io> watcher in one step.
997		1373
998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1374	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
999		1375
1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1376	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1001		1377
1002	Starts (activates) the given watcher. Only active watchers will receive	1378	Starts (activates) the given watcher. Only active watchers will receive
1003	events. If the watcher is already active nothing will happen.	1379	events. If the watcher is already active nothing will happen.
1004		1380
1005	Example: Start the C<ev_io> watcher that is being abused as example in this	1381	Example: Start the C<ev_io> watcher that is being abused as example in this
1006	whole section.	1382	whole section.
1007		1383
1008	ev_io_start (EV_DEFAULT_UC, &w);	1384	ev_io_start (EV_DEFAULT_UC, &w);
1009		1385
1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1386	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1011		1387
1012	Stops the given watcher if active, and clears the pending status (whether	1388	Stops the given watcher if active, and clears the pending status (whether
1013	the watcher was active or not).	1389	the watcher was active or not).
1014		1390
1015	It is possible that stopped watchers are pending - for example,	1391	It is possible that stopped watchers are pending - for example,
…		…
1035		1411
1036	=item callback ev_cb (ev_TYPE *watcher)	1412	=item callback ev_cb (ev_TYPE *watcher)
1037		1413
1038	Returns the callback currently set on the watcher.	1414	Returns the callback currently set on the watcher.
1039		1415
1040	=item ev_cb_set (ev_TYPE *watcher, callback)	1416	=item ev_set_cb (ev_TYPE *watcher, callback)
1041		1417
1042	Change the callback. You can change the callback at virtually any time	1418	Change the callback. You can change the callback at virtually any time
1043	(modulo threads).	1419	(modulo threads).
1044		1420
1045	=item ev_set_priority (ev_TYPE *watcher, priority)	1421	=item ev_set_priority (ev_TYPE *watcher, int priority)
1046		1422
1047	=item int ev_priority (ev_TYPE *watcher)	1423	=item int ev_priority (ev_TYPE *watcher)
1048		1424
1049	Set and query the priority of the watcher. The priority is a small	1425	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>	1426	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1051	(default: C<-2>). Pending watchers with higher priority will be invoked	1427	(default: C<-2>). Pending watchers with higher priority will be invoked
1052	before watchers with lower priority, but priority will not keep watchers	1428	before watchers with lower priority, but priority will not keep watchers
1053	from being executed (except for C<ev_idle> watchers).	1429	from being executed (except for C<ev_idle> watchers).
1054		1430
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	1431	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.	1432	you need to look at C<ev_idle> watchers, which provide this functionality.
1062		1433
1063	You I<must not> change the priority of a watcher as long as it is active or	1434	You I<must not> change the priority of a watcher as long as it is active or
1064	pending.	1435	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		1436
1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1437	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	1438	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.	1439	or might not have been clamped to the valid range.
		1440
		1441	The default priority used by watchers when no priority has been set is
		1442	always C<0>, which is supposed to not be too high and not be too low :).
		1443
		1444	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1445	priorities.
1072		1446
1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1447	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1074		1448
1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1449	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	1450	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>.	1458	watcher isn't pending it does nothing and returns C<0>.
1085		1459
1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1460	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.	1461	callback to be invoked, which can be accomplished with this function.
1088		1462
		1463	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1464
		1465	Feeds the given event set into the event loop, as if the specified event
		1466	had happened for the specified watcher (which must be a pointer to an
		1467	initialised but not necessarily started event watcher). Obviously you must
		1468	not free the watcher as long as it has pending events.
		1469
		1470	Stopping the watcher, letting libev invoke it, or calling
		1471	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1472	not started in the first place.
		1473
		1474	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1475	functions that do not need a watcher.
		1476
1089	=back	1477	=back
1090		1478
		1479	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1480	OWN COMPOSITE WATCHERS> idioms.
1091		1481
1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1482	=head2 WATCHER STATES
1093		1483
1094	Each watcher has, by default, a member C<void *data> that you can change	1484	There are various watcher states mentioned throughout this manual -
1095	and read at any time: libev will completely ignore it. This can be used	1485	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	1486	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	1487	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		1488
1101	struct my_io	1489	=over 4
		1490
		1491	=item initialised
		1492
		1493	Before a watcher can be registered with the event loop it has to be
		1494	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1495	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1496
		1497	In this state it is simply some block of memory that is suitable for
		1498	use in an event loop. It can be moved around, freed, reused etc. at
		1499	will - as long as you either keep the memory contents intact, or call
		1500	C<ev_TYPE_init> again.
		1501
		1502	=item started/running/active
		1503
		1504	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1505	property of the event loop, and is actively waiting for events. While in
		1506	this state it cannot be accessed (except in a few documented ways), moved,
		1507	freed or anything else - the only legal thing is to keep a pointer to it,
		1508	and call libev functions on it that are documented to work on active watchers.
		1509
		1510	=item pending
		1511
		1512	If a watcher is active and libev determines that an event it is interested
		1513	in has occurred (such as a timer expiring), it will become pending. It will
		1514	stay in this pending state until either it is stopped or its callback is
		1515	about to be invoked, so it is not normally pending inside the watcher
		1516	callback.
		1517
		1518	The watcher might or might not be active while it is pending (for example,
		1519	an expired non-repeating timer can be pending but no longer active). If it
		1520	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1521	but it is still property of the event loop at this time, so cannot be
		1522	moved, freed or reused. And if it is active the rules described in the
		1523	previous item still apply.
		1524
		1525	It is also possible to feed an event on a watcher that is not active (e.g.
		1526	via C<ev_feed_event>), in which case it becomes pending without being
		1527	active.
		1528
		1529	=item stopped
		1530
		1531	A watcher can be stopped implicitly by libev (in which case it might still
		1532	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1533	latter will clear any pending state the watcher might be in, regardless
		1534	of whether it was active or not, so stopping a watcher explicitly before
		1535	freeing it is often a good idea.
		1536
		1537	While stopped (and not pending) the watcher is essentially in the
		1538	initialised state, that is, it can be reused, moved, modified in any way
		1539	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1540	it again).
		1541
		1542	=back
		1543
		1544	=head2 WATCHER PRIORITY MODELS
		1545
		1546	Many event loops support I<watcher priorities>, which are usually small
		1547	integers that influence the ordering of event callback invocation
		1548	between watchers in some way, all else being equal.
		1549
		1550	In libev, watcher priorities can be set using C<ev_set_priority>. See its
		1551	description for the more technical details such as the actual priority
		1552	range.
		1553
		1554	There are two common ways how these these priorities are being interpreted
		1555	by event loops:
		1556
		1557	In the more common lock-out model, higher priorities "lock out" invocation
		1558	of lower priority watchers, which means as long as higher priority
		1559	watchers receive events, lower priority watchers are not being invoked.
		1560
		1561	The less common only-for-ordering model uses priorities solely to order
		1562	callback invocation within a single event loop iteration: Higher priority
		1563	watchers are invoked before lower priority ones, but they all get invoked
		1564	before polling for new events.
		1565
		1566	Libev uses the second (only-for-ordering) model for all its watchers
		1567	except for idle watchers (which use the lock-out model).
		1568
		1569	The rationale behind this is that implementing the lock-out model for
		1570	watchers is not well supported by most kernel interfaces, and most event
		1571	libraries will just poll for the same events again and again as long as
		1572	their callbacks have not been executed, which is very inefficient in the
		1573	common case of one high-priority watcher locking out a mass of lower
		1574	priority ones.
		1575
		1576	Static (ordering) priorities are most useful when you have two or more
		1577	watchers handling the same resource: a typical usage example is having an
		1578	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1579	timeouts. Under load, data might be received while the program handles
		1580	other jobs, but since timers normally get invoked first, the timeout
		1581	handler will be executed before checking for data. In that case, giving
		1582	the timer a lower priority than the I/O watcher ensures that I/O will be
		1583	handled first even under adverse conditions (which is usually, but not
		1584	always, what you want).
		1585
		1586	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1587	will only be executed when no same or higher priority watchers have
		1588	received events, they can be used to implement the "lock-out" model when
		1589	required.
		1590
		1591	For example, to emulate how many other event libraries handle priorities,
		1592	you can associate an C<ev_idle> watcher to each such watcher, and in
		1593	the normal watcher callback, you just start the idle watcher. The real
		1594	processing is done in the idle watcher callback. This causes libev to
		1595	continuously poll and process kernel event data for the watcher, but when
		1596	the lock-out case is known to be rare (which in turn is rare :), this is
		1597	workable.
		1598
		1599	Usually, however, the lock-out model implemented that way will perform
		1600	miserably under the type of load it was designed to handle. In that case,
		1601	it might be preferable to stop the real watcher before starting the
		1602	idle watcher, so the kernel will not have to process the event in case
		1603	the actual processing will be delayed for considerable time.
		1604
		1605	Here is an example of an I/O watcher that should run at a strictly lower
		1606	priority than the default, and which should only process data when no
		1607	other events are pending:
		1608
		1609	ev_idle idle; // actual processing watcher
		1610	ev_io io; // actual event watcher
		1611
		1612	static void
		1613	io_cb (EV_P_ ev_io *w, int revents)
1102	{	1614	{
1103	ev_io io;	1615	// stop the I/O watcher, we received the event, but
1104	int otherfd;	1616	// are not yet ready to handle it.
1105	void *somedata;	1617	ev_io_stop (EV_A_ w);
1106	struct whatever *mostinteresting;	1618
		1619	// start the idle watcher to handle the actual event.
		1620	// it will not be executed as long as other watchers
		1621	// with the default priority are receiving events.
		1622	ev_idle_start (EV_A_ &idle);
1107	};	1623	}
1108		1624
1109	...	1625	static void
1110	struct my_io w;	1626	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	{	1627	{
1118	struct my_io *w = (struct my_io *)w_;	1628	// actual processing
1119	...	1629	read (STDIN_FILENO, ...);
		1630
		1631	// have to start the I/O watcher again, as
		1632	// we have handled the event
		1633	ev_io_start (EV_P_ &io);
1120	}	1634	}
1121		1635
1122	More interesting and less C-conformant ways of casting your callback type	1636	// initialisation
1123	instead have been omitted.	1637	ev_idle_init (&idle, idle_cb);
		1638	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1639	ev_io_start (EV_DEFAULT_ &io);
1124		1640
1125	Another common scenario is to use some data structure with multiple	1641	In the "real" world, it might also be beneficial to start a timer, so that
1126	embedded watchers:	1642	low-priority connections can not be locked out forever under load. This
1127		1643	enables your program to keep a lower latency for important connections
1128	struct my_biggy	1644	during short periods of high load, while not completely locking out less
1129	{	1645	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		1646
1157		1647
1158	=head1 WATCHER TYPES	1648	=head1 WATCHER TYPES
1159		1649
1160	This section describes each watcher in detail, but will not repeat	1650	This section describes each watcher in detail, but will not repeat
1161	information given in the last section. Any initialisation/set macros,	1651	information given in the last section. Any initialisation/set macros,
1162	functions and members specific to the watcher type are explained.	1652	functions and members specific to the watcher type are explained.
1163		1653
1164	Members are additionally marked with either I<[read-only]>, meaning that,	1654	Most members are additionally marked with either I<[read-only]>, meaning
1165	while the watcher is active, you can look at the member and expect some	1655	that, while the watcher is active, you can look at the member and expect
1166	sensible content, but you must not modify it (you can modify it while the	1656	some sensible content, but you must not modify it (you can modify it while
1167	watcher is stopped to your hearts content), or I<[read-write]>, which	1657	the watcher is stopped to your hearts content), or I<[read-write]>, which
1168	means you can expect it to have some sensible content while the watcher	1658	means you can expect it to have some sensible content while the watcher
1169	is active, but you can also modify it. Modifying it may not do something	1659	is active, but you can also modify it. Modifying it may not do something
1170	sensible or take immediate effect (or do anything at all), but libev will	1660	sensible or take immediate effect (or do anything at all), but libev will
1171	not crash or malfunction in any way.	1661	not crash or malfunction in any way.
1172		1662
		1663	In any case, the documentation for each member will explain what the
		1664	effects are, and if there are any additional access restrictions.
1173		1665
1174	=head2 C<ev_io> - is this file descriptor readable or writable?	1666	=head2 C<ev_io> - is this file descriptor readable or writable?
1175		1667
1176	I/O watchers check whether a file descriptor is readable or writable	1668	I/O watchers check whether a file descriptor is readable or writable
1177	in each iteration of the event loop, or, more precisely, when reading	1669	in each iteration of the event loop, or, more precisely, when reading
…		…
1184	In general you can register as many read and/or write event watchers per	1676	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	1677	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	1678	descriptors to non-blocking mode is also usually a good idea (but not
1187	required if you know what you are doing).	1679	required if you know what you are doing).
1188		1680
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	1681	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	1682	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	1683	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	1684	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	1685	with a relatively standard program structure. Thus it is best to always
1198	this situation even with a relatively standard program structure. Thus	1686	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.	1687	preferable to a program hanging until some data arrives.
1201		1688
1202	If you cannot run the fd in non-blocking mode (for example you should	1689	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	1690	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	1691	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	1692	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	1693	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	1694	use C<SIGALRM> and an interval timer, just to be sure you won't block
1208	indefinitely.	1695	indefinitely.
1209		1696
1210	But really, best use non-blocking mode.	1697	But really, best use non-blocking mode.
1211		1698
1212	=head3 The special problem of disappearing file descriptors	1699	=head3 The special problem of disappearing file descriptors
1213		1700
1214	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1701	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1215	descriptor (either due to calling C<close> explicitly or any other means,	1702	a file descriptor (either due to calling C<close> explicitly or any other
1216	such as C<dup2>). The reason is that you register interest in some file	1703	means, such as C<dup2>). The reason is that you register interest in some
1217	descriptor, but when it goes away, the operating system will silently drop	1704	file descriptor, but when it goes away, the operating system will silently
1218	this interest. If another file descriptor with the same number then is	1705	drop this interest. If another file descriptor with the same number then
1219	registered with libev, there is no efficient way to see that this is, in	1706	is registered with libev, there is no efficient way to see that this is,
1220	fact, a different file descriptor.	1707	in fact, a different file descriptor.
1221		1708
1222	To avoid having to explicitly tell libev about such cases, libev follows	1709	To avoid having to explicitly tell libev about such cases, libev follows
1223	the following policy: Each time C<ev_io_set> is being called, libev	1710	the following policy: Each time C<ev_io_set> is being called, libev
1224	will assume that this is potentially a new file descriptor, otherwise	1711	will assume that this is potentially a new file descriptor, otherwise
1225	it is assumed that the file descriptor stays the same. That means that	1712	it is assumed that the file descriptor stays the same. That means that
…		…
1239		1726
1240	There is no workaround possible except not registering events	1727	There is no workaround possible except not registering events
1241	for potentially C<dup ()>'ed file descriptors, or to resort to	1728	for potentially C<dup ()>'ed file descriptors, or to resort to
1242	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1729	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1243		1730
		1731	=head3 The special problem of files
		1732
		1733	Many people try to use C<select> (or libev) on file descriptors
		1734	representing files, and expect it to become ready when their program
		1735	doesn't block on disk accesses (which can take a long time on their own).
		1736
		1737	However, this cannot ever work in the "expected" way - you get a readiness
		1738	notification as soon as the kernel knows whether and how much data is
		1739	there, and in the case of open files, that's always the case, so you
		1740	always get a readiness notification instantly, and your read (or possibly
		1741	write) will still block on the disk I/O.
		1742
		1743	Another way to view it is that in the case of sockets, pipes, character
		1744	devices and so on, there is another party (the sender) that delivers data
		1745	on its own, but in the case of files, there is no such thing: the disk
		1746	will not send data on its own, simply because it doesn't know what you
		1747	wish to read - you would first have to request some data.
		1748
		1749	Since files are typically not-so-well supported by advanced notification
		1750	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1751	to files, even though you should not use it. The reason for this is
		1752	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1753	usually a tty, often a pipe, but also sometimes files or special devices
		1754	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1755	F</dev/urandom>), and even though the file might better be served with
		1756	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1757	it "just works" instead of freezing.
		1758
		1759	So avoid file descriptors pointing to files when you know it (e.g. use
		1760	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1761	when you rarely read from a file instead of from a socket, and want to
		1762	reuse the same code path.
		1763
1244	=head3 The special problem of fork	1764	=head3 The special problem of fork
1245		1765
1246	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1766	Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()>
1247	useless behaviour. Libev fully supports fork, but needs to be told about	1767	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1248	it in the child.	1768	to be told about it in the child if you want to continue to use it in the
		1769	child.
1249		1770
1250	To support fork in your programs, you either have to call	1771	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,	1772	()> 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	1773	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1253	C<EVBACKEND_POLL>.
1254		1774
1255	=head3 The special problem of SIGPIPE	1775	=head3 The special problem of SIGPIPE
1256		1776
1257	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1777	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	1778	when writing to a pipe whose other end has been closed, your program gets
…		…
1261		1781
1262	So when you encounter spurious, unexplained daemon exits, make sure you	1782	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	1783	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).	1784	somewhere, as that would have given you a big clue).
1265		1785
		1786	=head3 The special problem of accept()ing when you can't
		1787
		1788	Many implementations of the POSIX C<accept> function (for example,
		1789	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1790	connection from the pending queue in all error cases.
		1791
		1792	For example, larger servers often run out of file descriptors (because
		1793	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1794	rejecting the connection, leading to libev signalling readiness on
		1795	the next iteration again (the connection still exists after all), and
		1796	typically causing the program to loop at 100% CPU usage.
		1797
		1798	Unfortunately, the set of errors that cause this issue differs between
		1799	operating systems, there is usually little the app can do to remedy the
		1800	situation, and no known thread-safe method of removing the connection to
		1801	cope with overload is known (to me).
		1802
		1803	One of the easiest ways to handle this situation is to just ignore it
		1804	- when the program encounters an overload, it will just loop until the
		1805	situation is over. While this is a form of busy waiting, no OS offers an
		1806	event-based way to handle this situation, so it's the best one can do.
		1807
		1808	A better way to handle the situation is to log any errors other than
		1809	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1810	messages, and continue as usual, which at least gives the user an idea of
		1811	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1812	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1813	usage.
		1814
		1815	If your program is single-threaded, then you could also keep a dummy file
		1816	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1817	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1818	close that fd, and create a new dummy fd. This will gracefully refuse
		1819	clients under typical overload conditions.
		1820
		1821	The last way to handle it is to simply log the error and C<exit>, as
		1822	is often done with C<malloc> failures, but this results in an easy
		1823	opportunity for a DoS attack.
1266		1824
1267	=head3 Watcher-Specific Functions	1825	=head3 Watcher-Specific Functions
1268		1826
1269	=over 4	1827	=over 4
1270		1828
1271	=item ev_io_init (ev_io *, callback, int fd, int events)	1829	=item ev_io_init (ev_io *, callback, int fd, int events)
1272		1830
1273	=item ev_io_set (ev_io *, int fd, int events)	1831	=item ev_io_set (ev_io *, int fd, int events)
1274		1832
1275	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1833	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1276	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or	1834	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE>, both
1277	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.	1835	C<EV_READ | EV_WRITE> or C<0>, to express the desire to receive the given
		1836	events.
1278		1837
1279	=item int fd [read-only]	1838	Note that setting the C<events> to C<0> and starting the watcher is
		1839	supported, but not specially optimized - if your program sometimes happens
		1840	to generate this combination this is fine, but if it is easy to avoid
		1841	starting an io watcher watching for no events you should do so.
1280		1842
1281	The file descriptor being watched.	1843	=item ev_io_modify (ev_io *, int events)
1282		1844
		1845	Similar to C<ev_io_set>, but only changes the event mask. Using this might
		1846	be faster with some backends, as libev can assume that the C<fd> still
		1847	refers to the same underlying file description, something it cannot do
		1848	when using C<ev_io_set>.
		1849
		1850	=item int fd [no-modify]
		1851
		1852	The file descriptor being watched. While it can be read at any time, you
		1853	must not modify this member even when the watcher is stopped - always use
		1854	C<ev_io_set> for that.
		1855
1283	=item int events [read-only]	1856	=item int events [no-modify]
1284		1857
1285	The events being watched.	1858	The set of events the fd is being watched for, among other flags. Remember
		1859	that this is a bit set - to test for C<EV_READ>, use C<< w->events &
		1860	EV_READ >>, and similarly for C<EV_WRITE>.
		1861
		1862	As with C<fd>, you must not modify this member even when the watcher is
		1863	stopped, always use C<ev_io_set> or C<ev_io_modify> for that.
1286		1864
1287	=back	1865	=back
1288		1866
1289	=head3 Examples	1867	=head3 Examples
1290		1868
…		…
1302	...	1880	...
1303	struct ev_loop *loop = ev_default_init (0);	1881	struct ev_loop *loop = ev_default_init (0);
1304	ev_io stdin_readable;	1882	ev_io stdin_readable;
1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1883	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1306	ev_io_start (loop, &stdin_readable);	1884	ev_io_start (loop, &stdin_readable);
1307	ev_loop (loop, 0);	1885	ev_run (loop, 0);
1308		1886
1309		1887
1310	=head2 C<ev_timer> - relative and optionally repeating timeouts	1888	=head2 C<ev_timer> - relative and optionally repeating timeouts
1311		1889
1312	Timer watchers are simple relative timers that generate an event after a	1890	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	1895	year, it will still time out after (roughly) one hour. "Roughly" because
1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1896	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1319	monotonic clock option helps a lot here).	1897	monotonic clock option helps a lot here).
1320		1898
1321	The callback is guaranteed to be invoked only I<after> its timeout has	1899	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	1900	passed (not I<at>, so on systems with very low-resolution clocks this
1323	then order of execution is undefined.	1901	might introduce a small delay, see "the special problem of being too
		1902	early", below). If multiple timers become ready during the same loop
		1903	iteration then the ones with earlier time-out values are invoked before
		1904	ones of the same priority with later time-out values (but this is no
		1905	longer true when a callback calls C<ev_run> recursively).
1324		1906
1325	=head3 Be smart about timeouts	1907	=head3 Be smart about timeouts
1326		1908
1327	Many real-world problems involve some kind of timeout, usually for error	1909	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,	1910	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>	1954	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1373	member and C<ev_timer_again>.	1955	member and C<ev_timer_again>.
1374		1956
1375	At start:	1957	At start:
1376		1958
1377	ev_timer_init (timer, callback);	1959	ev_init (timer, callback);
1378	timer->repeat = 60.;	1960	timer->repeat = 60.;
1379	ev_timer_again (loop, timer);	1961	ev_timer_again (loop, timer);
1380		1962
1381	Each time there is some activity:	1963	Each time there is some activity:
1382		1964
…		…
1403		1985
1404	In this case, it would be more efficient to leave the C<ev_timer> alone,	1986	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	1987	but remember the time of last activity, and check for a real timeout only
1406	within the callback:	1988	within the callback:
1407		1989
		1990	ev_tstamp timeout = 60.;
1408	ev_tstamp last_activity; // time of last activity	1991	ev_tstamp last_activity; // time of last activity
		1992	ev_timer timer;
1409		1993
1410	static void	1994	static void
1411	callback (EV_P_ ev_timer *w, int revents)	1995	callback (EV_P_ ev_timer *w, int revents)
1412	{	1996	{
1413	ev_tstamp now = ev_now (EV_A);	1997	// calculate when the timeout would happen
1414	ev_tstamp timeout = last_activity + 60.;	1998	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1415		1999
1416	// if last_activity + 60. is older than now, we did time out	2000	// if negative, it means we the timeout already occurred
1417	if (timeout < now)	2001	if (after < 0.)
1418	{	2002	{
1419	// timeout occured, take action	2003	// timeout occurred, take action
1420	}	2004	}
1421	else	2005	else
1422	{	2006	{
1423	// callback was invoked, but there was some activity, re-arm	2007	// callback was invoked, but there was some recent
1424	// the watcher to fire in last_activity + 60, which is	2008	// activity. simply restart the timer to time out
1425	// guaranteed to be in the future, so "again" is positive:	2009	// after "after" seconds, which is the earliest time
1426	w->repeat = timeout - now;	2010	// the timeout can occur.
		2011	ev_timer_set (w, after, 0.);
1427	ev_timer_again (EV_A_ w);	2012	ev_timer_start (EV_A_ w);
1428	}	2013	}
1429	}	2014	}
1430		2015
1431	To summarise the callback: first calculate the real timeout (defined	2016	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	2017	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	2018	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	2019	(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		2020
1438	Note how C<ev_timer_again> is used, taking advantage of the	2021	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.	2022	timed out, and need to do whatever is needed in this case.
		2023
		2024	Otherwise, we now the earliest time at which the timeout would trigger,
		2025	and simply start the timer with this timeout value.
		2026
		2027	In other words, each time the callback is invoked it will check whether
		2028	the timeout occurred. If not, it will simply reschedule itself to check
		2029	again at the earliest time it could time out. Rinse. Repeat.
1440		2030
1441	This scheme causes more callback invocations (about one every 60 seconds	2031	This scheme causes more callback invocations (about one every 60 seconds
1442	minus half the average time between activity), but virtually no calls to	2032	minus half the average time between activity), but virtually no calls to
1443	libev to change the timeout.	2033	libev to change the timeout.
1444		2034
1445	To start the timer, simply initialise the watcher and set C<last_activity>	2035	To start the machinery, simply initialise the watcher and set
1446	to the current time (meaning we just have some activity :), then call the	2036	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:	2037	now), then call the callback, which will "do the right thing" and start
		2038	the timer:
1448		2039
		2040	last_activity = ev_now (EV_A);
1449	ev_timer_init (timer, callback);	2041	ev_init (&timer, callback);
1450	last_activity = ev_now (loop);	2042	callback (EV_A_ &timer, 0);
1451	callback (loop, timer, EV_TIMEOUT);
1452		2043
1453	And when there is some activity, simply store the current time in	2044	When there is some activity, simply store the current time in
1454	C<last_activity>, no libev calls at all:	2045	C<last_activity>, no libev calls at all:
1455		2046
		2047	if (activity detected)
1456	last_actiivty = ev_now (loop);	2048	last_activity = ev_now (EV_A);
		2049
		2050	When your timeout value changes, then the timeout can be changed by simply
		2051	providing a new value, stopping the timer and calling the callback, which
		2052	will again do the right thing (for example, time out immediately :).
		2053
		2054	timeout = new_value;
		2055	ev_timer_stop (EV_A_ &timer);
		2056	callback (EV_A_ &timer, 0);
1457		2057
1458	This technique is slightly more complex, but in most cases where the	2058	This technique is slightly more complex, but in most cases where the
1459	time-out is unlikely to be triggered, much more efficient.	2059	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		2060
1465	=item 4. Wee, just use a double-linked list for your timeouts.	2061	=item 4. Wee, just use a double-linked list for your timeouts.
1466		2062
1467	If there is not one request, but many thousands (millions...), all	2063	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	2064	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	2091	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	2092	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	2093	off after the first million or so of active timers, i.e. it's usually
1498	overkill :)	2094	overkill :)
1499		2095
		2096	=head3 The special problem of being too early
		2097
		2098	If you ask a timer to call your callback after three seconds, then
		2099	you expect it to be invoked after three seconds - but of course, this
		2100	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2101	guaranteed to any precision by libev - imagine somebody suspending the
		2102	process with a STOP signal for a few hours for example.
		2103
		2104	So, libev tries to invoke your callback as soon as possible I<after> the
		2105	delay has occurred, but cannot guarantee this.
		2106
		2107	A less obvious failure mode is calling your callback too early: many event
		2108	loops compare timestamps with a "elapsed delay >= requested delay", but
		2109	this can cause your callback to be invoked much earlier than you would
		2110	expect.
		2111
		2112	To see why, imagine a system with a clock that only offers full second
		2113	resolution (think windows if you can't come up with a broken enough OS
		2114	yourself). If you schedule a one-second timer at the time 500.9, then the
		2115	event loop will schedule your timeout to elapse at a system time of 500
		2116	(500.9 truncated to the resolution) + 1, or 501.
		2117
		2118	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2119	501" and invoke the callback 0.1s after it was started, even though a
		2120	one-second delay was requested - this is being "too early", despite best
		2121	intentions.
		2122
		2123	This is the reason why libev will never invoke the callback if the elapsed
		2124	delay equals the requested delay, but only when the elapsed delay is
		2125	larger than the requested delay. In the example above, libev would only invoke
		2126	the callback at system time 502, or 1.1s after the timer was started.
		2127
		2128	So, while libev cannot guarantee that your callback will be invoked
		2129	exactly when requested, it I<can> and I<does> guarantee that the requested
		2130	delay has actually elapsed, or in other words, it always errs on the "too
		2131	late" side of things.
		2132
1500	=head3 The special problem of time updates	2133	=head3 The special problem of time updates
1501		2134
1502	Establishing the current time is a costly operation (it usually takes at	2135	Establishing the current time is a costly operation (it usually takes
1503	least two system calls): EV therefore updates its idea of the current	2136	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	2137	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	2138	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1506	lots of events in one iteration.	2139	lots of events in one iteration.
1507		2140
1508	The relative timeouts are calculated relative to the C<ev_now ()>	2141	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	2142	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	2143	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	2144	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:	2145	timeout on the current time, use something like the following to adjust
		2146	for it:
1513		2147
1514	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2148	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1515		2149
1516	If the event loop is suspended for a long time, you can also force an	2150	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	2151	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1518	()>.	2152	()>, although that will push the event time of all outstanding events
		2153	further into the future.
		2154
		2155	=head3 The special problem of unsynchronised clocks
		2156
		2157	Modern systems have a variety of clocks - libev itself uses the normal
		2158	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2159	jumps).
		2160
		2161	Neither of these clocks is synchronised with each other or any other clock
		2162	on the system, so C<ev_time ()> might return a considerably different time
		2163	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2164	a call to C<gettimeofday> might return a second count that is one higher
		2165	than a directly following call to C<time>.
		2166
		2167	The moral of this is to only compare libev-related timestamps with
		2168	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2169	a second or so.
		2170
		2171	One more problem arises due to this lack of synchronisation: if libev uses
		2172	the system monotonic clock and you compare timestamps from C<ev_time>
		2173	or C<ev_now> from when you started your timer and when your callback is
		2174	invoked, you will find that sometimes the callback is a bit "early".
		2175
		2176	This is because C<ev_timer>s work in real time, not wall clock time, so
		2177	libev makes sure your callback is not invoked before the delay happened,
		2178	I<measured according to the real time>, not the system clock.
		2179
		2180	If your timeouts are based on a physical timescale (e.g. "time out this
		2181	connection after 100 seconds") then this shouldn't bother you as it is
		2182	exactly the right behaviour.
		2183
		2184	If you want to compare wall clock/system timestamps to your timers, then
		2185	you need to use C<ev_periodic>s, as these are based on the wall clock
		2186	time, where your comparisons will always generate correct results.
		2187
		2188	=head3 The special problems of suspended animation
		2189
		2190	When you leave the server world it is quite customary to hit machines that
		2191	can suspend/hibernate - what happens to the clocks during such a suspend?
		2192
		2193	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2194	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2195	to run until the system is suspended, but they will not advance while the
		2196	system is suspended. That means, on resume, it will be as if the program
		2197	was frozen for a few seconds, but the suspend time will not be counted
		2198	towards C<ev_timer> when a monotonic clock source is used. The real time
		2199	clock advanced as expected, but if it is used as sole clocksource, then a
		2200	long suspend would be detected as a time jump by libev, and timers would
		2201	be adjusted accordingly.
		2202
		2203	I would not be surprised to see different behaviour in different between
		2204	operating systems, OS versions or even different hardware.
		2205
		2206	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2207	time jump in the monotonic clocks and the realtime clock. If the program
		2208	is suspended for a very long time, and monotonic clock sources are in use,
		2209	then you can expect C<ev_timer>s to expire as the full suspension time
		2210	will be counted towards the timers. When no monotonic clock source is in
		2211	use, then libev will again assume a timejump and adjust accordingly.
		2212
		2213	It might be beneficial for this latter case to call C<ev_suspend>
		2214	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2215	deterministic behaviour in this case (you can do nothing against
		2216	C<SIGSTOP>).
1519		2217
1520	=head3 Watcher-Specific Functions and Data Members	2218	=head3 Watcher-Specific Functions and Data Members
1521		2219
1522	=over 4	2220	=over 4
1523		2221
1524	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2222	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1525		2223
1526	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2224	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1527		2225
1528	Configure the timer to trigger after C<after> seconds. If C<repeat>	2226	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	2227	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	2228	automatically be stopped once the timeout is reached. If it is positive,
1531	configured to trigger again C<repeat> seconds later, again, and again,	2229	then the timer will automatically be configured to trigger again C<repeat>
1532	until stopped manually.	2230	seconds later, again, and again, until stopped manually.
1533		2231
1534	The timer itself will do a best-effort at avoiding drift, that is, if	2232	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	2233	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	2234	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	2235	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.	2236	do stuff) the timer will not fire more than once per event loop iteration.
1539		2237
1540	=item ev_timer_again (loop, ev_timer *)	2238	=item ev_timer_again (loop, ev_timer *)
1541		2239
1542	This will act as if the timer timed out and restart it again if it is	2240	This will act as if the timer timed out, and restarts it again if it is
1543	repeating. The exact semantics are:	2241	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2242	timeout to the C<repeat> value and calling C<ev_timer_start>.
1544		2243
		2244	The exact semantics are as in the following rules, all of which will be
		2245	applied to the watcher:
		2246
		2247	=over 4
		2248
1545	If the timer is pending, its pending status is cleared.	2249	=item If the timer is pending, the pending status is always cleared.
1546		2250
1547	If the timer is started but non-repeating, stop it (as if it timed out).	2251	=item If the timer is started but non-repeating, stop it (as if it timed
		2252	out, without invoking it).
1548		2253
1549	If the timer is repeating, either start it if necessary (with the	2254	=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.	2255	and start the timer, if necessary.
1551		2256
		2257	=back
		2258
1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2259	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1553	usage example.	2260	usage example.
		2261
		2262	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2263
		2264	Returns the remaining time until a timer fires. If the timer is active,
		2265	then this time is relative to the current event loop time, otherwise it's
		2266	the timeout value currently configured.
		2267
		2268	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2269	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2270	will return C<4>. When the timer expires and is restarted, it will return
		2271	roughly C<7> (likely slightly less as callback invocation takes some time,
		2272	too), and so on.
1554		2273
1555	=item ev_tstamp repeat [read-write]	2274	=item ev_tstamp repeat [read-write]
1556		2275
1557	The current C<repeat> value. Will be used each time the watcher times out	2276	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),	2277	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1584	}	2303	}
1585		2304
1586	ev_timer mytimer;	2305	ev_timer mytimer;
1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2306	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1588	ev_timer_again (&mytimer); /* start timer */	2307	ev_timer_again (&mytimer); /* start timer */
1589	ev_loop (loop, 0);	2308	ev_run (loop, 0);
1590		2309
1591	// and in some piece of code that gets executed on any "activity":	2310	// and in some piece of code that gets executed on any "activity":
1592	// reset the timeout to start ticking again at 10 seconds	2311	// reset the timeout to start ticking again at 10 seconds
1593	ev_timer_again (&mytimer);	2312	ev_timer_again (&mytimer);
1594		2313
…		…
1596	=head2 C<ev_periodic> - to cron or not to cron?	2315	=head2 C<ev_periodic> - to cron or not to cron?
1597		2316
1598	Periodic watchers are also timers of a kind, but they are very versatile	2317	Periodic watchers are also timers of a kind, but they are very versatile
1599	(and unfortunately a bit complex).	2318	(and unfortunately a bit complex).
1600		2319
1601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2320	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	2321	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	2322	(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 ()	2323	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	2324	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	2325	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		2326
		2327	You can tell a periodic watcher to trigger after some specific point
		2328	in time: for example, if you tell a periodic watcher to trigger "in 10
		2329	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2330	not a delay) and then reset your system clock to January of the previous
		2331	year, then it will take a year or more to trigger the event (unlike an
		2332	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2333	it, as it uses a relative timeout).
		2334
1610	C<ev_periodic>s can also be used to implement vastly more complex timers,	2335	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	2336	timers, such as triggering an event on each "midnight, local time", or
1612	complicated rules.	2337	other complicated rules. This cannot easily be done with C<ev_timer>
		2338	watchers, as those cannot react to time jumps.
1613		2339
1614	As with timers, the callback is guaranteed to be invoked only when the	2340	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	2341	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.	2342	timers become ready during the same loop iteration then the ones with
		2343	earlier time-out values are invoked before ones with later time-out values
		2344	(but this is no longer true when a callback calls C<ev_run> recursively).
1617		2345
1618	=head3 Watcher-Specific Functions and Data Members	2346	=head3 Watcher-Specific Functions and Data Members
1619		2347
1620	=over 4	2348	=over 4
1621		2349
1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2350	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1623		2351
1624	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2352	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1625		2353
1626	Lots of arguments, lets sort it out... There are basically three modes of	2354	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:	2355	operation, and we will explain them from simplest to most complex:
1628		2356
1629	=over 4	2357	=over 4
1630		2358
1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2359	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1632		2360
1633	In this configuration the watcher triggers an event after the wall clock	2361	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	2362	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	2363	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.	2364	will be stopped and invoked when the system clock reaches or surpasses
		2365	this point in time.
1637		2366
1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2367	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1639		2368
1640	In this mode the watcher will always be scheduled to time out at the next	2369	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)	2370	C<offset + N * interval> time (for some integer N, which can also be
1642	and then repeat, regardless of any time jumps.	2371	negative) and then repeat, regardless of any time jumps. The C<offset>
		2372	argument is merely an offset into the C<interval> periods.
1643		2373
1644	This can be used to create timers that do not drift with respect to the	2374	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	2375	system clock, for example, here is an C<ev_periodic> that triggers each
1646	hour, on the hour:	2376	hour, on the hour (with respect to UTC):
1647		2377
1648	ev_periodic_set (&periodic, 0., 3600., 0);	2378	ev_periodic_set (&periodic, 0., 3600., 0);
1649		2379
1650	This doesn't mean there will always be 3600 seconds in between triggers,	2380	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	2381	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	2382	full hour (UTC), or more correctly, when the system time is evenly divisible
1653	by 3600.	2383	by 3600.
1654		2384
1655	Another way to think about it (for the mathematically inclined) is that	2385	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	2386	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.	2387	time where C<time = offset (mod interval)>, regardless of any time jumps.
1658		2388
1659	For numerical stability it is preferable that the C<at> value is near	2389	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	2390	interval value should be higher than C<1/8192> (which is around 100
1661	this value, and in fact is often specified as zero.	2391	microseconds) and C<offset> should be higher than C<0> and should have
		2392	at most a similar magnitude as the current time (say, within a factor of
		2393	ten). Typical values for offset are, in fact, C<0> or something between
		2394	C<0> and C<interval>, which is also the recommended range.
1662		2395
1663	Note also that there is an upper limit to how often a timer can fire (CPU	2396	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	2397	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	2398	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).	2399	millisecond (if the OS supports it and the machine is fast enough).
1667		2400
1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2401	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1669		2402
1670	In this mode the values for C<interval> and C<at> are both being	2403	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	2404	ignored. Instead, each time the periodic watcher gets scheduled, the
1672	reschedule callback will be called with the watcher as first, and the	2405	reschedule callback will be called with the watcher as first, and the
1673	current time as second argument.	2406	current time as second argument.
1674		2407
1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2408	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1676	ever, or make ANY event loop modifications whatsoever>.	2409	or make ANY other event loop modifications whatsoever, unless explicitly
		2410	allowed by documentation here>.
1677		2411
1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2412	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	2413	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1680	only event loop modification you are allowed to do).	2414	only event loop modification you are allowed to do).
1681		2415
…		…
1695		2429
1696	NOTE: I<< This callback must always return a time that is higher than or	2430	NOTE: I<< This callback must always return a time that is higher than or
1697	equal to the passed C<now> value >>.	2431	equal to the passed C<now> value >>.
1698		2432
1699	This can be used to create very complex timers, such as a timer that	2433	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	2434	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	2435	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	2436	this. Here is a (completely untested, no error checking) example on how to
1703	reason I omitted it as an example).	2437	do this:
		2438
		2439	#include <time.h>
		2440
		2441	static ev_tstamp
		2442	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2443	{
		2444	time_t tnow = (time_t)now;
		2445	struct tm tm;
		2446	localtime_r (&tnow, &tm);
		2447
		2448	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2449	++tm.tm_mday; // midnight next day
		2450
		2451	return mktime (&tm);
		2452	}
		2453
		2454	Note: this code might run into trouble on days that have more then two
		2455	midnights (beginning and end).
1704		2456
1705	=back	2457	=back
1706		2458
1707	=item ev_periodic_again (loop, ev_periodic *)	2459	=item ev_periodic_again (loop, ev_periodic *)
1708		2460
…		…
1711	a different time than the last time it was called (e.g. in a crond like	2463	a different time than the last time it was called (e.g. in a crond like
1712	program when the crontabs have changed).	2464	program when the crontabs have changed).
1713		2465
1714	=item ev_tstamp ev_periodic_at (ev_periodic *)	2466	=item ev_tstamp ev_periodic_at (ev_periodic *)
1715		2467
1716	When active, returns the absolute time that the watcher is supposed to	2468	When active, returns the absolute time that the watcher is supposed
1717	trigger next.	2469	to trigger next. This is not the same as the C<offset> argument to
		2470	C<ev_periodic_set>, but indeed works even in interval and manual
		2471	rescheduling modes.
1718		2472
1719	=item ev_tstamp offset [read-write]	2473	=item ev_tstamp offset [read-write]
1720		2474
1721	When repeating, this contains the offset value, otherwise this is the	2475	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>).	2476	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2477	although libev might modify this value for better numerical stability).
1723		2478
1724	Can be modified any time, but changes only take effect when the periodic	2479	Can be modified any time, but changes only take effect when the periodic
1725	timer fires or C<ev_periodic_again> is being called.	2480	timer fires or C<ev_periodic_again> is being called.
1726		2481
1727	=item ev_tstamp interval [read-write]	2482	=item ev_tstamp interval [read-write]
…		…
1743	Example: Call a callback every hour, or, more precisely, whenever the	2498	Example: Call a callback every hour, or, more precisely, whenever the
1744	system time is divisible by 3600. The callback invocation times have	2499	system time is divisible by 3600. The callback invocation times have
1745	potentially a lot of jitter, but good long-term stability.	2500	potentially a lot of jitter, but good long-term stability.
1746		2501
1747	static void	2502	static void
1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2503	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1749	{	2504	{
1750	... its now a full hour (UTC, or TAI or whatever your clock follows)	2505	... its now a full hour (UTC, or TAI or whatever your clock follows)
1751	}	2506	}
1752		2507
1753	ev_periodic hourly_tick;	2508	ev_periodic hourly_tick;
…		…
1770		2525
1771	ev_periodic hourly_tick;	2526	ev_periodic hourly_tick;
1772	ev_periodic_init (&hourly_tick, clock_cb,	2527	ev_periodic_init (&hourly_tick, clock_cb,
1773	fmod (ev_now (loop), 3600.), 3600., 0);	2528	fmod (ev_now (loop), 3600.), 3600., 0);
1774	ev_periodic_start (loop, &hourly_tick);	2529	ev_periodic_start (loop, &hourly_tick);
1775		2530
1776		2531
1777	=head2 C<ev_signal> - signal me when a signal gets signalled!	2532	=head2 C<ev_signal> - signal me when a signal gets signalled!
1778		2533
1779	Signal watchers will trigger an event when the process receives a specific	2534	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	2535	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	2536	will try its best to deliver signals synchronously, i.e. as part of the
1782	normal event processing, like any other event.	2537	normal event processing, like any other event.
1783		2538
1784	If you want signals asynchronously, just use C<sigaction> as you would	2539	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	2540	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.	2541	the signal. You can even use C<ev_async> from a signal handler to
		2542	synchronously wake up an event loop.
1787		2543
1788	You can configure as many watchers as you like per signal. Only when the	2544	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	2545	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	2546	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	2547	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	2548	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).	2549
		2550	Only after the first watcher for a signal is started will libev actually
		2551	register something with the kernel. It thus coexists with your own signal
		2552	handlers as long as you don't register any with libev for the same signal.
1794		2553
1795	If possible and supported, libev will install its handlers with	2554	If possible and supported, libev will install its handlers with
1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2555	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1797	interrupted. If you have a problem with system calls getting interrupted by	2556	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	2557	interrupted by signals you can block all signals in an C<ev_check> watcher
1799	them in an C<ev_prepare> watcher.	2558	and unblock them in an C<ev_prepare> watcher.
		2559
		2560	=head3 The special problem of inheritance over fork/execve/pthread_create
		2561
		2562	Both the signal mask (C<sigprocmask>) and the signal disposition
		2563	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2564	stopping it again), that is, libev might or might not block the signal,
		2565	and might or might not set or restore the installed signal handler (but
		2566	see C<EVFLAG_NOSIGMASK>).
		2567
		2568	While this does not matter for the signal disposition (libev never
		2569	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2570	C<execve>), this matters for the signal mask: many programs do not expect
		2571	certain signals to be blocked.
		2572
		2573	This means that before calling C<exec> (from the child) you should reset
		2574	the signal mask to whatever "default" you expect (all clear is a good
		2575	choice usually).
		2576
		2577	The simplest way to ensure that the signal mask is reset in the child is
		2578	to install a fork handler with C<pthread_atfork> that resets it. That will
		2579	catch fork calls done by libraries (such as the libc) as well.
		2580
		2581	In current versions of libev, the signal will not be blocked indefinitely
		2582	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2583	the window of opportunity for problems, it will not go away, as libev
		2584	I<has> to modify the signal mask, at least temporarily.
		2585
		2586	So I can't stress this enough: I<If you do not reset your signal mask when
		2587	you expect it to be empty, you have a race condition in your code>. This
		2588	is not a libev-specific thing, this is true for most event libraries.
		2589
		2590	=head3 The special problem of threads signal handling
		2591
		2592	POSIX threads has problematic signal handling semantics, specifically,
		2593	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2594	threads in a process block signals, which is hard to achieve.
		2595
		2596	When you want to use sigwait (or mix libev signal handling with your own
		2597	for the same signals), you can tackle this problem by globally blocking
		2598	all signals before creating any threads (or creating them with a fully set
		2599	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2600	loops. Then designate one thread as "signal receiver thread" which handles
		2601	these signals. You can pass on any signals that libev might be interested
		2602	in by calling C<ev_feed_signal>.
1800		2603
1801	=head3 Watcher-Specific Functions and Data Members	2604	=head3 Watcher-Specific Functions and Data Members
1802		2605
1803	=over 4	2606	=over 4
1804		2607
…		…
1820	Example: Try to exit cleanly on SIGINT.	2623	Example: Try to exit cleanly on SIGINT.
1821		2624
1822	static void	2625	static void
1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2626	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1824	{	2627	{
1825	ev_unloop (loop, EVUNLOOP_ALL);	2628	ev_break (loop, EVBREAK_ALL);
1826	}	2629	}
1827		2630
1828	ev_signal signal_watcher;	2631	ev_signal signal_watcher;
1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2632	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1830	ev_signal_start (loop, &signal_watcher);	2633	ev_signal_start (loop, &signal_watcher);
…		…
1836	some child status changes (most typically when a child of yours dies or	2639	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	2640	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	2641	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.,	2642	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,	2643	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	2644	but forking and registering a watcher a few event loop iterations later or
1842	not.	2645	in the next callback invocation is not.
1843		2646
1844	Only the default event loop is capable of handling signals, and therefore	2647	Only the default event loop is capable of handling signals, and therefore
1845	you can only register child watchers in the default event loop.	2648	you can only register child watchers in the default event loop.
1846		2649
		2650	Due to some design glitches inside libev, child watchers will always be
		2651	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2652	libev)
		2653
1847	=head3 Process Interaction	2654	=head3 Process Interaction
1848		2655
1849	Libev grabs C<SIGCHLD> as soon as the default event loop is	2656	Libev grabs C<SIGCHLD> as soon as the default event loop is
1850	initialised. This is necessary to guarantee proper behaviour even if	2657	initialised. This is necessary to guarantee proper behaviour even if the
1851	the first child watcher is started after the child exits. The occurrence	2658	first child watcher is started after the child exits. The occurrence
1852	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2659	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1853	synchronously as part of the event loop processing. Libev always reaps all	2660	synchronously as part of the event loop processing. Libev always reaps all
1854	children, even ones not watched.	2661	children, even ones not watched.
1855		2662
1856	=head3 Overriding the Built-In Processing	2663	=head3 Overriding the Built-In Processing
…		…
1866	=head3 Stopping the Child Watcher	2673	=head3 Stopping the Child Watcher
1867		2674
1868	Currently, the child watcher never gets stopped, even when the	2675	Currently, the child watcher never gets stopped, even when the
1869	child terminates, so normally one needs to stop the watcher in the	2676	child terminates, so normally one needs to stop the watcher in the
1870	callback. Future versions of libev might stop the watcher automatically	2677	callback. Future versions of libev might stop the watcher automatically
1871	when a child exit is detected.	2678	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2679	problem).
1872		2680
1873	=head3 Watcher-Specific Functions and Data Members	2681	=head3 Watcher-Specific Functions and Data Members
1874		2682
1875	=over 4	2683	=over 4
1876		2684
…		…
1934		2742
1935	=head2 C<ev_stat> - did the file attributes just change?	2743	=head2 C<ev_stat> - did the file attributes just change?
1936		2744
1937	This watches a file system path for attribute changes. That is, it calls	2745	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)	2746	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	2747	and sees if it changed compared to the last time, invoking the callback
1940	it did.	2748	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2749	happen after the watcher has been started will be reported.
1941		2750
1942	The path does not need to exist: changing from "path exists" to "path does	2751	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	2752	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	2753	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	2754	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	2984	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	2985	effect on its own sometimes), idle watchers are a good place to do
2177	"pseudo-background processing", or delay processing stuff to after the	2986	"pseudo-background processing", or delay processing stuff to after the
2178	event loop has handled all outstanding events.	2987	event loop has handled all outstanding events.
2179		2988
		2989	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2990
		2991	As long as there is at least one active idle watcher, libev will never
		2992	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2993	For this to work, the idle watcher doesn't need to be invoked at all - the
		2994	lowest priority will do.
		2995
		2996	This mode of operation can be useful together with an C<ev_check> watcher,
		2997	to do something on each event loop iteration - for example to balance load
		2998	between different connections.
		2999
		3000	See L</Abusing an ev_check watcher for its side-effect> for a longer
		3001	example.
		3002
2180	=head3 Watcher-Specific Functions and Data Members	3003	=head3 Watcher-Specific Functions and Data Members
2181		3004
2182	=over 4	3005	=over 4
2183		3006
2184	=item ev_idle_init (ev_signal *, callback)	3007	=item ev_idle_init (ev_idle *, callback)
2185		3008
2186	Initialises and configures the idle watcher - it has no parameters of any	3009	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,	3010	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2188	believe me.	3011	believe me.
2189		3012
…		…
2195	callback, free it. Also, use no error checking, as usual.	3018	callback, free it. Also, use no error checking, as usual.
2196		3019
2197	static void	3020	static void
2198	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	3021	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2199	{	3022	{
		3023	// stop the watcher
		3024	ev_idle_stop (loop, w);
		3025
		3026	// now we can free it
2200	free (w);	3027	free (w);
		3028
2201	// now do something you wanted to do when the program has	3029	// now do something you wanted to do when the program has
2202	// no longer anything immediate to do.	3030	// no longer anything immediate to do.
2203	}	3031	}
2204		3032
2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3033	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2206	ev_idle_init (idle_watcher, idle_cb);	3034	ev_idle_init (idle_watcher, idle_cb);
2207	ev_idle_start (loop, idle_cb);	3035	ev_idle_start (loop, idle_watcher);
2208		3036
2209		3037
2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3038	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2211		3039
2212	Prepare and check watchers are usually (but not always) used in pairs:	3040	Prepare and check watchers are often (but not always) used in pairs:
2213	prepare watchers get invoked before the process blocks and check watchers	3041	prepare watchers get invoked before the process blocks and check watchers
2214	afterwards.	3042	afterwards.
2215		3043
2216	You I<must not> call C<ev_loop> or similar functions that enter	3044	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>	3045	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	3046	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	3047	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,	3048	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	3049	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2222	called in pairs bracketing the blocking call.	3050	kind they will always be called in pairs bracketing the blocking call.
2223		3051
2224	Their main purpose is to integrate other event mechanisms into libev and	3052	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	3053	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	3054	variable changes, implement your own watchers, integrate net-snmp or a
2227	coroutine library and lots more. They are also occasionally useful if	3055	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	3073	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	3074	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	3075	loop from blocking if lower-priority coroutines are active, thus mapping
2248	low-priority coroutines to idle/background tasks).	3076	low-priority coroutines to idle/background tasks).
2249		3077
2250	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3078	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	3079	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).	3080	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3081	watchers).
2253		3082
2254	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3083	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	3084	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	3085	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	3086	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	3087	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	3088	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2260	others).	3089	others).
		3090
		3091	=head3 Abusing an C<ev_check> watcher for its side-effect
		3092
		3093	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3094	useful because they are called once per event loop iteration. For
		3095	example, if you want to handle a large number of connections fairly, you
		3096	normally only do a bit of work for each active connection, and if there
		3097	is more work to do, you wait for the next event loop iteration, so other
		3098	connections have a chance of making progress.
		3099
		3100	Using an C<ev_check> watcher is almost enough: it will be called on the
		3101	next event loop iteration. However, that isn't as soon as possible -
		3102	without external events, your C<ev_check> watcher will not be invoked.
		3103
		3104	This is where C<ev_idle> watchers come in handy - all you need is a
		3105	single global idle watcher that is active as long as you have one active
		3106	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3107	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3108	invoked. Neither watcher alone can do that.
2261		3109
2262	=head3 Watcher-Specific Functions and Data Members	3110	=head3 Watcher-Specific Functions and Data Members
2263		3111
2264	=over 4	3112	=over 4
2265		3113
…		…
2305	struct pollfd fds [nfd];	3153	struct pollfd fds [nfd];
2306	// actual code will need to loop here and realloc etc.	3154	// actual code will need to loop here and realloc etc.
2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3155	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2308		3156
2309	/* the callback is illegal, but won't be called as we stop during check */	3157	/* the callback is illegal, but won't be called as we stop during check */
2310	ev_timer_init (&tw, 0, timeout * 1e-3);	3158	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2311	ev_timer_start (loop, &tw);	3159	ev_timer_start (loop, &tw);
2312		3160
2313	// create one ev_io per pollfd	3161	// create one ev_io per pollfd
2314	for (int i = 0; i < nfd; ++i)	3162	for (int i = 0; i < nfd; ++i)
2315	{	3163	{
…		…
2389		3237
2390	if (timeout >= 0)	3238	if (timeout >= 0)
2391	// create/start timer	3239	// create/start timer
2392		3240
2393	// poll	3241	// poll
2394	ev_loop (EV_A_ 0);	3242	ev_run (EV_A_ 0);
2395		3243
2396	// stop timer again	3244	// stop timer again
2397	if (timeout >= 0)	3245	if (timeout >= 0)
2398	ev_timer_stop (EV_A_ &to);	3246	ev_timer_stop (EV_A_ &to);
2399		3247
…		…
2466		3314
2467	=over 4	3315	=over 4
2468		3316
2469	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3317	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2470		3318
2471	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3319	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2472		3320
2473	Configures the watcher to embed the given loop, which must be	3321	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	3322	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	3323	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,	3324	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).	3325	if you do not want that, you need to temporarily stop the embed watcher).
2478		3326
2479	=item ev_embed_sweep (loop, ev_embed *)	3327	=item ev_embed_sweep (loop, ev_embed *)
2480		3328
2481	Make a single, non-blocking sweep over the embedded loop. This works	3329	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	3330	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2483	appropriate way for embedded loops.	3331	appropriate way for embedded loops.
2484		3332
2485	=item struct ev_loop *other [read-only]	3333	=item struct ev_loop *other [read-only]
2486		3334
2487	The embedded event loop.	3335	The embedded event loop.
…		…
2497	used).	3345	used).
2498		3346
2499	struct ev_loop *loop_hi = ev_default_init (0);	3347	struct ev_loop *loop_hi = ev_default_init (0);
2500	struct ev_loop *loop_lo = 0;	3348	struct ev_loop *loop_lo = 0;
2501	ev_embed embed;	3349	ev_embed embed;
2502		3350
2503	// see if there is a chance of getting one that works	3351	// see if there is a chance of getting one that works
2504	// (remember that a flags value of 0 means autodetection)	3352	// (remember that a flags value of 0 means autodetection)
2505	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3353	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2506	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3354	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2507	: 0;	3355	: 0;
…		…
2521	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3369	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2522		3370
2523	struct ev_loop *loop = ev_default_init (0);	3371	struct ev_loop *loop = ev_default_init (0);
2524	struct ev_loop *loop_socket = 0;	3372	struct ev_loop *loop_socket = 0;
2525	ev_embed embed;	3373	ev_embed embed;
2526		3374
2527	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3375	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2528	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3376	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2529	{	3377	{
2530	ev_embed_init (&embed, 0, loop_socket);	3378	ev_embed_init (&embed, 0, loop_socket);
2531	ev_embed_start (loop, &embed);	3379	ev_embed_start (loop, &embed);
…		…
2539		3387
2540	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3388	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2541		3389
2542	Fork watchers are called when a C<fork ()> was detected (usually because	3390	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	3391	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	3392	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,	3393	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	3394	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	3395	and calls it in the wrong process, the fork handlers will be invoked, too,
2548	handlers will be invoked, too, of course.	3396	of course.
		3397
		3398	=head3 The special problem of life after fork - how is it possible?
		3399
		3400	Most uses of C<fork ()> consist of forking, then some simple calls to set
		3401	up/change the process environment, followed by a call to C<exec()>. This
		3402	sequence should be handled by libev without any problems.
		3403
		3404	This changes when the application actually wants to do event handling
		3405	in the child, or both parent in child, in effect "continuing" after the
		3406	fork.
		3407
		3408	The default mode of operation (for libev, with application help to detect
		3409	forks) is to duplicate all the state in the child, as would be expected
		3410	when I<either> the parent I<or> the child process continues.
		3411
		3412	When both processes want to continue using libev, then this is usually the
		3413	wrong result. In that case, usually one process (typically the parent) is
		3414	supposed to continue with all watchers in place as before, while the other
		3415	process typically wants to start fresh, i.e. without any active watchers.
		3416
		3417	The cleanest and most efficient way to achieve that with libev is to
		3418	simply create a new event loop, which of course will be "empty", and
		3419	use that for new watchers. This has the advantage of not touching more
		3420	memory than necessary, and thus avoiding the copy-on-write, and the
		3421	disadvantage of having to use multiple event loops (which do not support
		3422	signal watchers).
		3423
		3424	When this is not possible, or you want to use the default loop for
		3425	other reasons, then in the process that wants to start "fresh", call
		3426	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3427	Destroying the default loop will "orphan" (not stop) all registered
		3428	watchers, so you have to be careful not to execute code that modifies
		3429	those watchers. Note also that in that case, you have to re-register any
		3430	signal watchers.
2549		3431
2550	=head3 Watcher-Specific Functions and Data Members	3432	=head3 Watcher-Specific Functions and Data Members
2551		3433
2552	=over 4	3434	=over 4
2553		3435
2554	=item ev_fork_init (ev_signal *, callback)	3436	=item ev_fork_init (ev_fork *, callback)
2555		3437
2556	Initialises and configures the fork watcher - it has no parameters of any	3438	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,	3439	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2558	believe me.	3440	really.
2559		3441
2560	=back	3442	=back
2561		3443
2562		3444
		3445	=head2 C<ev_cleanup> - even the best things end
		3446
		3447	Cleanup watchers are called just before the event loop is being destroyed
		3448	by a call to C<ev_loop_destroy>.
		3449
		3450	While there is no guarantee that the event loop gets destroyed, cleanup
		3451	watchers provide a convenient method to install cleanup hooks for your
		3452	program, worker threads and so on - you just to make sure to destroy the
		3453	loop when you want them to be invoked.
		3454
		3455	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3456	all other watchers, they do not keep a reference to the event loop (which
		3457	makes a lot of sense if you think about it). Like all other watchers, you
		3458	can call libev functions in the callback, except C<ev_cleanup_start>.
		3459
		3460	=head3 Watcher-Specific Functions and Data Members
		3461
		3462	=over 4
		3463
		3464	=item ev_cleanup_init (ev_cleanup *, callback)
		3465
		3466	Initialises and configures the cleanup watcher - it has no parameters of
		3467	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3468	pointless, I assure you.
		3469
		3470	=back
		3471
		3472	Example: Register an atexit handler to destroy the default loop, so any
		3473	cleanup functions are called.
		3474
		3475	static void
		3476	program_exits (void)
		3477	{
		3478	ev_loop_destroy (EV_DEFAULT_UC);
		3479	}
		3480
		3481	...
		3482	atexit (program_exits);
		3483
		3484
2563	=head2 C<ev_async> - how to wake up another event loop	3485	=head2 C<ev_async> - how to wake up an event loop
2564		3486
2565	In general, you cannot use an C<ev_loop> from multiple threads or other	3487	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	3488	asynchronous sources such as signal handlers (as opposed to multiple event
2567	loops - those are of course safe to use in different threads).	3489	loops - those are of course safe to use in different threads).
2568		3490
2569	Sometimes, however, you need to wake up another event loop you do not	3491	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	3492	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	3493	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	3494	it by calling C<ev_async_send>, which is thread- and signal safe.
2573	safe.
2574		3495
2575	This functionality is very similar to C<ev_signal> watchers, as signals,	3496	This functionality is very similar to C<ev_signal> watchers, as signals,
2576	too, are asynchronous in nature, and signals, too, will be compressed	3497	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	3498	(i.e. the number of callback invocations may be less than the number of
2578	C<ev_async_sent> calls).	3499	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2579		3500	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	3501	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2581	just the default loop.	3502	even without knowing which loop owns the signal.
2582		3503
2583	=head3 Queueing	3504	=head3 Queueing
2584		3505
2585	C<ev_async> does not support queueing of data in any way. The reason	3506	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	3507	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	3508	multiple-writer-single-reader queue that works in all cases and doesn't
2588	need elaborate support such as pthreads.	3509	need elaborate support such as pthreads or unportable memory access
		3510	semantics.
2589		3511
2590	That means that if you want to queue data, you have to provide your own	3512	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	3513	queue. But at least I can tell you how to implement locking around your
2592	queue:	3514	queue:
2593		3515
…		…
2677	trust me.	3599	trust me.
2678		3600
2679	=item ev_async_send (loop, ev_async *)	3601	=item ev_async_send (loop, ev_async *)
2680		3602
2681	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3603	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	3604	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3605	returns.
		3606
2683	C<ev_feed_event>, this call is safe to do from other threads, signal or	3607	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	3608	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2685	section below on what exactly this means).	3609	embedding section below on what exactly this means).
2686		3610
2687	This call incurs the overhead of a system call only once per loop iteration,	3611	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	3612	compressed into a single callback invocation (another way to look at
2689	calls to C<ev_async_send>.	3613	this is that C<ev_async> watchers are level-triggered: they are set on
		3614	C<ev_async_send>, reset when the event loop detects that).
		3615
		3616	This call incurs the overhead of at most one extra system call per event
		3617	loop iteration, if the event loop is blocked, and no syscall at all if
		3618	the event loop (or your program) is processing events. That means that
		3619	repeated calls are basically free (there is no need to avoid calls for
		3620	performance reasons) and that the overhead becomes smaller (typically
		3621	zero) under load.
2690		3622
2691	=item bool = ev_async_pending (ev_async *)	3623	=item bool = ev_async_pending (ev_async *)
2692		3624
2693	Returns a non-zero value when C<ev_async_send> has been called on the	3625	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	3626	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	3629	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,	3630	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	3631	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.	3632	quickly check whether invoking the loop might be a good idea.
2701		3633
2702	Not that this does I<not> check whether the watcher itself is pending, only	3634	Not that this does I<not> check whether the watcher itself is pending,
2703	whether it has been requested to make this watcher pending.	3635	only whether it has been requested to make this watcher pending: there
		3636	is a time window between the event loop checking and resetting the async
		3637	notification, and the callback being invoked.
2704		3638
2705	=back	3639	=back
2706		3640
2707		3641
2708	=head1 OTHER FUNCTIONS	3642	=head1 OTHER FUNCTIONS
2709		3643
2710	There are some other functions of possible interest. Described. Here. Now.	3644	There are some other functions of possible interest. Described. Here. Now.
2711		3645
2712	=over 4	3646	=over 4
2713		3647
2714	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3648	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
2715		3649
2716	This function combines a simple timer and an I/O watcher, calls your	3650	This function combines a simple timer and an I/O watcher, calls your
2717	callback on whichever event happens first and automatically stops both	3651	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	3652	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	3653	or timeout without having to allocate/configure/start/stop/free one or
…		…
2725		3659
2726	If C<timeout> is less than 0, then no timeout watcher will be	3660	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	3661	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2728	repeat = 0) will be started. C<0> is a valid timeout.	3662	repeat = 0) will be started. C<0> is a valid timeout.
2729		3663
2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3664	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	3665	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>	3666	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>	3667	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	3668	a timeout and an io event at the same time - you probably should give io
2735	events precedence.	3669	events precedence.
2736		3670
2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3671	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2738		3672
2739	static void stdin_ready (int revents, void *arg)	3673	static void stdin_ready (int revents, void *arg)
2740	{	3674	{
2741	if (revents & EV_READ)	3675	if (revents & EV_READ)
2742	/* stdin might have data for us, joy! */;	3676	/* stdin might have data for us, joy! */;
2743	else if (revents & EV_TIMEOUT)	3677	else if (revents & EV_TIMER)
2744	/* doh, nothing entered */;	3678	/* doh, nothing entered */;
2745	}	3679	}
2746		3680
2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3681	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2748		3682
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)	3683	=item ev_feed_fd_event (loop, int fd, int revents)
2756		3684
2757	Feed an event on the given fd, as if a file descriptor backend detected	3685	Feed an event on the given fd, as if a file descriptor backend detected
2758	the given events it.	3686	the given events.
2759		3687
2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3688	=item ev_feed_signal_event (loop, int signum)
2761		3689
2762	Feed an event as if the given signal occurred (C<loop> must be the default	3690	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2763	loop!).	3691	which is async-safe.
2764		3692
2765	=back	3693	=back
		3694
		3695
		3696	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3697
		3698	This section explains some common idioms that are not immediately
		3699	obvious. Note that examples are sprinkled over the whole manual, and this
		3700	section only contains stuff that wouldn't fit anywhere else.
		3701
		3702	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3703
		3704	Each watcher has, by default, a C<void *data> member that you can read
		3705	or modify at any time: libev will completely ignore it. This can be used
		3706	to associate arbitrary data with your watcher. If you need more data and
		3707	don't want to allocate memory separately and store a pointer to it in that
		3708	data member, you can also "subclass" the watcher type and provide your own
		3709	data:
		3710
		3711	struct my_io
		3712	{
		3713	ev_io io;
		3714	int otherfd;
		3715	void *somedata;
		3716	struct whatever *mostinteresting;
		3717	};
		3718
		3719	...
		3720	struct my_io w;
		3721	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3722
		3723	And since your callback will be called with a pointer to the watcher, you
		3724	can cast it back to your own type:
		3725
		3726	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3727	{
		3728	struct my_io *w = (struct my_io *)w_;
		3729	...
		3730	}
		3731
		3732	More interesting and less C-conformant ways of casting your callback
		3733	function type instead have been omitted.
		3734
		3735	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3736
		3737	Another common scenario is to use some data structure with multiple
		3738	embedded watchers, in effect creating your own watcher that combines
		3739	multiple libev event sources into one "super-watcher":
		3740
		3741	struct my_biggy
		3742	{
		3743	int some_data;
		3744	ev_timer t1;
		3745	ev_timer t2;
		3746	}
		3747
		3748	In this case getting the pointer to C<my_biggy> is a bit more
		3749	complicated: Either you store the address of your C<my_biggy> struct in
		3750	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3751	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3752	real programmers):
		3753
		3754	#include <stddef.h>
		3755
		3756	static void
		3757	t1_cb (EV_P_ ev_timer *w, int revents)
		3758	{
		3759	struct my_biggy big = (struct my_biggy *)
		3760	(((char *)w) - offsetof (struct my_biggy, t1));
		3761	}
		3762
		3763	static void
		3764	t2_cb (EV_P_ ev_timer *w, int revents)
		3765	{
		3766	struct my_biggy big = (struct my_biggy *)
		3767	(((char *)w) - offsetof (struct my_biggy, t2));
		3768	}
		3769
		3770	=head2 AVOIDING FINISHING BEFORE RETURNING
		3771
		3772	Often you have structures like this in event-based programs:
		3773
		3774	callback ()
		3775	{
		3776	free (request);
		3777	}
		3778
		3779	request = start_new_request (..., callback);
		3780
		3781	The intent is to start some "lengthy" operation. The C<request> could be
		3782	used to cancel the operation, or do other things with it.
		3783
		3784	It's not uncommon to have code paths in C<start_new_request> that
		3785	immediately invoke the callback, for example, to report errors. Or you add
		3786	some caching layer that finds that it can skip the lengthy aspects of the
		3787	operation and simply invoke the callback with the result.
		3788
		3789	The problem here is that this will happen I<before> C<start_new_request>
		3790	has returned, so C<request> is not set.
		3791
		3792	Even if you pass the request by some safer means to the callback, you
		3793	might want to do something to the request after starting it, such as
		3794	canceling it, which probably isn't working so well when the callback has
		3795	already been invoked.
		3796
		3797	A common way around all these issues is to make sure that
		3798	C<start_new_request> I<always> returns before the callback is invoked. If
		3799	C<start_new_request> immediately knows the result, it can artificially
		3800	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3801	example, or more sneakily, by reusing an existing (stopped) watcher and
		3802	pushing it into the pending queue:
		3803
		3804	ev_set_cb (watcher, callback);
		3805	ev_feed_event (EV_A_ watcher, 0);
		3806
		3807	This way, C<start_new_request> can safely return before the callback is
		3808	invoked, while not delaying callback invocation too much.
		3809
		3810	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3811
		3812	Often (especially in GUI toolkits) there are places where you have
		3813	I<modal> interaction, which is most easily implemented by recursively
		3814	invoking C<ev_run>.
		3815
		3816	This brings the problem of exiting - a callback might want to finish the
		3817	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3818	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3819	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3820	other combination: In these cases, a simple C<ev_break> will not work.
		3821
		3822	The solution is to maintain "break this loop" variable for each C<ev_run>
		3823	invocation, and use a loop around C<ev_run> until the condition is
		3824	triggered, using C<EVRUN_ONCE>:
		3825
		3826	// main loop
		3827	int exit_main_loop = 0;
		3828
		3829	while (!exit_main_loop)
		3830	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3831
		3832	// in a modal watcher
		3833	int exit_nested_loop = 0;
		3834
		3835	while (!exit_nested_loop)
		3836	ev_run (EV_A_ EVRUN_ONCE);
		3837
		3838	To exit from any of these loops, just set the corresponding exit variable:
		3839
		3840	// exit modal loop
		3841	exit_nested_loop = 1;
		3842
		3843	// exit main program, after modal loop is finished
		3844	exit_main_loop = 1;
		3845
		3846	// exit both
		3847	exit_main_loop = exit_nested_loop = 1;
		3848
		3849	=head2 THREAD LOCKING EXAMPLE
		3850
		3851	Here is a fictitious example of how to run an event loop in a different
		3852	thread from where callbacks are being invoked and watchers are
		3853	created/added/removed.
		3854
		3855	For a real-world example, see the C<EV::Loop::Async> perl module,
		3856	which uses exactly this technique (which is suited for many high-level
		3857	languages).
		3858
		3859	The example uses a pthread mutex to protect the loop data, a condition
		3860	variable to wait for callback invocations, an async watcher to notify the
		3861	event loop thread and an unspecified mechanism to wake up the main thread.
		3862
		3863	First, you need to associate some data with the event loop:
		3864
		3865	typedef struct {
		3866	mutex_t lock; /* global loop lock */
		3867	ev_async async_w;
		3868	thread_t tid;
		3869	cond_t invoke_cv;
		3870	} userdata;
		3871
		3872	void prepare_loop (EV_P)
		3873	{
		3874	// for simplicity, we use a static userdata struct.
		3875	static userdata u;
		3876
		3877	ev_async_init (&u->async_w, async_cb);
		3878	ev_async_start (EV_A_ &u->async_w);
		3879
		3880	pthread_mutex_init (&u->lock, 0);
		3881	pthread_cond_init (&u->invoke_cv, 0);
		3882
		3883	// now associate this with the loop
		3884	ev_set_userdata (EV_A_ u);
		3885	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3886	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3887
		3888	// then create the thread running ev_run
		3889	pthread_create (&u->tid, 0, l_run, EV_A);
		3890	}
		3891
		3892	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3893	solely to wake up the event loop so it takes notice of any new watchers
		3894	that might have been added:
		3895
		3896	static void
		3897	async_cb (EV_P_ ev_async *w, int revents)
		3898	{
		3899	// just used for the side effects
		3900	}
		3901
		3902	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3903	protecting the loop data, respectively.
		3904
		3905	static void
		3906	l_release (EV_P)
		3907	{
		3908	userdata *u = ev_userdata (EV_A);
		3909	pthread_mutex_unlock (&u->lock);
		3910	}
		3911
		3912	static void
		3913	l_acquire (EV_P)
		3914	{
		3915	userdata *u = ev_userdata (EV_A);
		3916	pthread_mutex_lock (&u->lock);
		3917	}
		3918
		3919	The event loop thread first acquires the mutex, and then jumps straight
		3920	into C<ev_run>:
		3921
		3922	void *
		3923	l_run (void *thr_arg)
		3924	{
		3925	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3926
		3927	l_acquire (EV_A);
		3928	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3929	ev_run (EV_A_ 0);
		3930	l_release (EV_A);
		3931
		3932	return 0;
		3933	}
		3934
		3935	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3936	signal the main thread via some unspecified mechanism (signals? pipe
		3937	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3938	have been called (in a while loop because a) spurious wakeups are possible
		3939	and b) skipping inter-thread-communication when there are no pending
		3940	watchers is very beneficial):
		3941
		3942	static void
		3943	l_invoke (EV_P)
		3944	{
		3945	userdata *u = ev_userdata (EV_A);
		3946
		3947	while (ev_pending_count (EV_A))
		3948	{
		3949	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3950	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3951	}
		3952	}
		3953
		3954	Now, whenever the main thread gets told to invoke pending watchers, it
		3955	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3956	thread to continue:
		3957
		3958	static void
		3959	real_invoke_pending (EV_P)
		3960	{
		3961	userdata *u = ev_userdata (EV_A);
		3962
		3963	pthread_mutex_lock (&u->lock);
		3964	ev_invoke_pending (EV_A);
		3965	pthread_cond_signal (&u->invoke_cv);
		3966	pthread_mutex_unlock (&u->lock);
		3967	}
		3968
		3969	Whenever you want to start/stop a watcher or do other modifications to an
		3970	event loop, you will now have to lock:
		3971
		3972	ev_timer timeout_watcher;
		3973	userdata *u = ev_userdata (EV_A);
		3974
		3975	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3976
		3977	pthread_mutex_lock (&u->lock);
		3978	ev_timer_start (EV_A_ &timeout_watcher);
		3979	ev_async_send (EV_A_ &u->async_w);
		3980	pthread_mutex_unlock (&u->lock);
		3981
		3982	Note that sending the C<ev_async> watcher is required because otherwise
		3983	an event loop currently blocking in the kernel will have no knowledge
		3984	about the newly added timer. By waking up the loop it will pick up any new
		3985	watchers in the next event loop iteration.
		3986
		3987	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3988
		3989	While the overhead of a callback that e.g. schedules a thread is small, it
		3990	is still an overhead. If you embed libev, and your main usage is with some
		3991	kind of threads or coroutines, you might want to customise libev so that
		3992	doesn't need callbacks anymore.
		3993
		3994	Imagine you have coroutines that you can switch to using a function
		3995	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3996	and that due to some magic, the currently active coroutine is stored in a
		3997	global called C<current_coro>. Then you can build your own "wait for libev
		3998	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3999	the differing C<;> conventions):
		4000
		4001	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4002	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4003
		4004	That means instead of having a C callback function, you store the
		4005	coroutine to switch to in each watcher, and instead of having libev call
		4006	your callback, you instead have it switch to that coroutine.
		4007
		4008	A coroutine might now wait for an event with a function called
		4009	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		4010	matter when, or whether the watcher is active or not when this function is
		4011	called):
		4012
		4013	void
		4014	wait_for_event (ev_watcher *w)
		4015	{
		4016	ev_set_cb (w, current_coro);
		4017	switch_to (libev_coro);
		4018	}
		4019
		4020	That basically suspends the coroutine inside C<wait_for_event> and
		4021	continues the libev coroutine, which, when appropriate, switches back to
		4022	this or any other coroutine.
		4023
		4024	You can do similar tricks if you have, say, threads with an event queue -
		4025	instead of storing a coroutine, you store the queue object and instead of
		4026	switching to a coroutine, you push the watcher onto the queue and notify
		4027	any waiters.
		4028
		4029	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		4030	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		4031
		4032	// my_ev.h
		4033	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4034	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4035	#include "../libev/ev.h"
		4036
		4037	// my_ev.c
		4038	#define EV_H "my_ev.h"
		4039	#include "../libev/ev.c"
		4040
		4041	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4042	F<my_ev.c> into your project. When properly specifying include paths, you
		4043	can even use F<ev.h> as header file name directly.
2766		4044
2767		4045
2768	=head1 LIBEVENT EMULATION	4046	=head1 LIBEVENT EMULATION
2769		4047
2770	Libev offers a compatibility emulation layer for libevent. It cannot	4048	Libev offers a compatibility emulation layer for libevent. It cannot
2771	emulate the internals of libevent, so here are some usage hints:	4049	emulate the internals of libevent, so here are some usage hints:
2772		4050
2773	=over 4	4051	=over 4
		4052
		4053	=item * Only the libevent-1.4.1-beta API is being emulated.
		4054
		4055	This was the newest libevent version available when libev was implemented,
		4056	and is still mostly unchanged in 2010.
2774		4057
2775	=item * Use it by including <event.h>, as usual.	4058	=item * Use it by including <event.h>, as usual.
2776		4059
2777	=item * The following members are fully supported: ev_base, ev_callback,	4060	=item * The following members are fully supported: ev_base, ev_callback,
2778	ev_arg, ev_fd, ev_res, ev_events.	4061	ev_arg, ev_fd, ev_res, ev_events.
…		…
2784	=item * Priorities are not currently supported. Initialising priorities	4067	=item * Priorities are not currently supported. Initialising priorities
2785	will fail and all watchers will have the same priority, even though there	4068	will fail and all watchers will have the same priority, even though there
2786	is an ev_pri field.	4069	is an ev_pri field.
2787		4070
2788	=item * In libevent, the last base created gets the signals, in libev, the	4071	=item * In libevent, the last base created gets the signals, in libev, the
2789	first base created (== the default loop) gets the signals.	4072	base that registered the signal gets the signals.
2790		4073
2791	=item * Other members are not supported.	4074	=item * Other members are not supported.
2792		4075
2793	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4076	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2794	to use the libev header file and library.	4077	to use the libev header file and library.
2795		4078
2796	=back	4079	=back
2797		4080
2798	=head1 C++ SUPPORT	4081	=head1 C++ SUPPORT
		4082
		4083	=head2 C API
		4084
		4085	The normal C API should work fine when used from C++: both ev.h and the
		4086	libev sources can be compiled as C++. Therefore, code that uses the C API
		4087	will work fine.
		4088
		4089	Proper exception specifications might have to be added to callbacks passed
		4090	to libev: exceptions may be thrown only from watcher callbacks, all other
		4091	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4092	callbacks) must not throw exceptions, and might need a C<noexcept>
		4093	specification. If you have code that needs to be compiled as both C and
		4094	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4095
		4096	static void
		4097	fatal_error (const char *msg) EV_NOEXCEPT
		4098	{
		4099	perror (msg);
		4100	abort ();
		4101	}
		4102
		4103	...
		4104	ev_set_syserr_cb (fatal_error);
		4105
		4106	The only API functions that can currently throw exceptions are C<ev_run>,
		4107	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4108	because it runs cleanup watchers).
		4109
		4110	Throwing exceptions in watcher callbacks is only supported if libev itself
		4111	is compiled with a C++ compiler or your C and C++ environments allow
		4112	throwing exceptions through C libraries (most do).
		4113
		4114	=head2 C++ API
2799		4115
2800	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4116	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	4117	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.	4118	the callback model to a model using method callbacks on objects.
2803		4119
2804	To use it,	4120	To use it,
2805		4121
2806	#include <ev++.h>	4122	#include <ev++.h>
2807		4123
2808	This automatically includes F<ev.h> and puts all of its definitions (many	4124	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	4125	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	4126	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++	4129	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	4130	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	4131	that the watcher is associated with (or no additional members at all if
2816	you disable C<EV_MULTIPLICITY> when embedding libev).	4132	you disable C<EV_MULTIPLICITY> when embedding libev).
2817		4133
2818	Currently, functions, and static and non-static member functions can be	4134	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	4135	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	4136	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	4137	you need support for other types of functors please contact the author
2822	it).	4138	(preferably after implementing it).
		4139
		4140	For all this to work, your C++ compiler either has to use the same calling
		4141	conventions as your C compiler (for static member functions), or you have
		4142	to embed libev and compile libev itself as C++.
2823		4143
2824	Here is a list of things available in the C<ev> namespace:	4144	Here is a list of things available in the C<ev> namespace:
2825		4145
2826	=over 4	4146	=over 4
2827		4147
…		…
2837	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4157	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2838		4158
2839	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4159	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>	4160	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	4161	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2842	defines by many implementations.	4162	defined by many implementations.
2843		4163
2844	All of those classes have these methods:	4164	All of those classes have these methods:
2845		4165
2846	=over 4	4166	=over 4
2847		4167
2848	=item ev::TYPE::TYPE ()	4168	=item ev::TYPE::TYPE ()
2849		4169
2850	=item ev::TYPE::TYPE (struct ev_loop *)	4170	=item ev::TYPE::TYPE (loop)
2851		4171
2852	=item ev::TYPE::~TYPE	4172	=item ev::TYPE::~TYPE
2853		4173
2854	The constructor (optionally) takes an event loop to associate the watcher	4174	The constructor (optionally) takes an event loop to associate the watcher
2855	with. If it is omitted, it will use C<EV_DEFAULT>.	4175	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2888	myclass obj;	4208	myclass obj;
2889	ev::io iow;	4209	ev::io iow;
2890	iow.set <myclass, &myclass::io_cb> (&obj);	4210	iow.set <myclass, &myclass::io_cb> (&obj);
2891		4211
2892	=item w->set (object *)	4212	=item w->set (object *)
2893
2894	This is an B<experimental> feature that might go away in a future version.
2895		4213
2896	This is a variation of a method callback - leaving out the method to call	4214	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	4215	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	4216	functor objects without having to manually specify the C<operator ()> all
2899	the time. Incidentally, you can then also leave out the template argument	4217	the time. Incidentally, you can then also leave out the template argument
…		…
2911	void operator() (ev::io &w, int revents)	4229	void operator() (ev::io &w, int revents)
2912	{	4230	{
2913	...	4231	...
2914	}	4232	}
2915	}	4233	}
2916		4234
2917	myfunctor f;	4235	myfunctor f;
2918		4236
2919	ev::io w;	4237	ev::io w;
2920	w.set (&f);	4238	w.set (&f);
2921		4239
…		…
2932	Example: Use a plain function as callback.	4250	Example: Use a plain function as callback.
2933		4251
2934	static void io_cb (ev::io &w, int revents) { }	4252	static void io_cb (ev::io &w, int revents) { }
2935	iow.set <io_cb> ();	4253	iow.set <io_cb> ();
2936		4254
2937	=item w->set (struct ev_loop *)	4255	=item w->set (loop)
2938		4256
2939	Associates a different C<struct ev_loop> with this watcher. You can only	4257	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).	4258	do this when the watcher is inactive (and not pending either).
2941		4259
2942	=item w->set ([arguments])	4260	=item w->set ([arguments])
2943		4261
2944	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4262	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4263	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	4264	must be called at least once. Unlike the C counterpart, an active watcher
2946	automatically stopped and restarted when reconfiguring it with this	4265	gets automatically stopped and restarted when reconfiguring it with this
2947	method.	4266	method.
		4267
		4268	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4269	clashing with the C<set (loop)> method.
		4270
		4271	For C<ev::io> watchers there is an additional C<set> method that acepts a
		4272	new event mask only, and internally calls C<ev_io_modfify>.
2948		4273
2949	=item w->start ()	4274	=item w->start ()
2950		4275
2951	Starts the watcher. Note that there is no C<loop> argument, as the	4276	Starts the watcher. Note that there is no C<loop> argument, as the
2952	constructor already stores the event loop.	4277	constructor already stores the event loop.
2953		4278
		4279	=item w->start ([arguments])
		4280
		4281	Instead of calling C<set> and C<start> methods separately, it is often
		4282	convenient to wrap them in one call. Uses the same type of arguments as
		4283	the configure C<set> method of the watcher.
		4284
2954	=item w->stop ()	4285	=item w->stop ()
2955		4286
2956	Stops the watcher if it is active. Again, no C<loop> argument.	4287	Stops the watcher if it is active. Again, no C<loop> argument.
2957		4288
2958	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4289	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2970		4301
2971	=back	4302	=back
2972		4303
2973	=back	4304	=back
2974		4305
2975	Example: Define a class with an IO and idle watcher, start one of them in	4306	Example: Define a class with two I/O and idle watchers, start the I/O
2976	the constructor.	4307	watchers in the constructor.
2977		4308
2978	class myclass	4309	class myclass
2979	{	4310	{
2980	ev::io io ; void io_cb (ev::io &w, int revents);	4311	ev::io io ; void io_cb (ev::io &w, int revents);
		4312	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4313	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2982		4314
2983	myclass (int fd)	4315	myclass (int fd)
2984	{	4316	{
2985	io .set <myclass, &myclass::io_cb > (this);	4317	io .set <myclass, &myclass::io_cb > (this);
		4318	io2 .set <myclass, &myclass::io2_cb > (this);
2986	idle.set <myclass, &myclass::idle_cb> (this);	4319	idle.set <myclass, &myclass::idle_cb> (this);
2987		4320
2988	io.start (fd, ev::READ);	4321	io.set (fd, ev::WRITE); // configure the watcher
		4322	io.start (); // start it whenever convenient
		4323
		4324	io2.start (fd, ev::READ); // set + start in one call
2989	}	4325	}
2990	};	4326	};
2991		4327
2992		4328
2993	=head1 OTHER LANGUAGE BINDINGS	4329	=head1 OTHER LANGUAGE BINDINGS
…		…
3012	L<http://software.schmorp.de/pkg/EV>.	4348	L<http://software.schmorp.de/pkg/EV>.
3013		4349
3014	=item Python	4350	=item Python
3015		4351
3016	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4352	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	4353	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		4354
3023	=item Ruby	4355	=item Ruby
3024		4356
3025	Tony Arcieri has written a ruby extension that offers access to a subset	4357	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	4358	of the libev API and adds file handle abstractions, asynchronous DNS and
…		…
3028	L<http://rev.rubyforge.org/>.	4360	L<http://rev.rubyforge.org/>.
3029		4361
3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>	4362	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
3031	makes rev work even on mingw.	4363	makes rev work even on mingw.
3032		4364
		4365	=item Haskell
		4366
		4367	A haskell binding to libev is available at
		4368	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4369
3033	=item D	4370	=item D
3034		4371
3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4372	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>.	4373	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3037		4374
3038	=item Ocaml	4375	=item Ocaml
3039		4376
3040	Erkki Seppala has written Ocaml bindings for libev, to be found at	4377	Erkki Seppala has written Ocaml bindings for libev, to be found at
3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4378	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4379
		4380	=item Lua
		4381
		4382	Brian Maher has written a partial interface to libev for lua (at the
		4383	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4384	L<http://github.com/brimworks/lua-ev>.
		4385
		4386	=item Javascript
		4387
		4388	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4389
		4390	=item Others
		4391
		4392	There are others, and I stopped counting.
3042		4393
3043	=back	4394	=back
3044		4395
3045		4396
3046	=head1 MACRO MAGIC	4397	=head1 MACRO MAGIC
…		…
3060	loop argument"). The C<EV_A> form is used when this is the sole argument,	4411	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:	4412	C<EV_A_> is used when other arguments are following. Example:
3062		4413
3063	ev_unref (EV_A);	4414	ev_unref (EV_A);
3064	ev_timer_add (EV_A_ watcher);	4415	ev_timer_add (EV_A_ watcher);
3065	ev_loop (EV_A_ 0);	4416	ev_run (EV_A_ 0);
3066		4417
3067	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4418	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3068	which is often provided by the following macro.	4419	which is often provided by the following macro.
3069		4420
3070	=item C<EV_P>, C<EV_P_>	4421	=item C<EV_P>, C<EV_P_>
…		…
3083	suitable for use with C<EV_A>.	4434	suitable for use with C<EV_A>.
3084		4435
3085	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4436	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3086		4437
3087	Similar to the other two macros, this gives you the value of the default	4438	Similar to the other two macros, this gives you the value of the default
3088	loop, if multiple loops are supported ("ev loop default").	4439	loop, if multiple loops are supported ("ev loop default"). The default loop
		4440	will be initialised if it isn't already initialised.
		4441
		4442	For non-multiplicity builds, these macros do nothing, so you always have
		4443	to initialise the loop somewhere.
3089		4444
3090	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4445	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3091		4446
3092	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4447	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	4448	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3110	}	4465	}
3111		4466
3112	ev_check check;	4467	ev_check check;
3113	ev_check_init (&check, check_cb);	4468	ev_check_init (&check, check_cb);
3114	ev_check_start (EV_DEFAULT_ &check);	4469	ev_check_start (EV_DEFAULT_ &check);
3115	ev_loop (EV_DEFAULT_ 0);	4470	ev_run (EV_DEFAULT_ 0);
3116		4471
3117	=head1 EMBEDDING	4472	=head1 EMBEDDING
3118		4473
3119	Libev can (and often is) directly embedded into host	4474	Libev can (and often is) directly embedded into host
3120	applications. Examples of applications that embed it include the Deliantra	4475	applications. Examples of applications that embed it include the Deliantra
…		…
3160	ev_vars.h	4515	ev_vars.h
3161	ev_wrap.h	4516	ev_wrap.h
3162		4517
3163	ev_win32.c required on win32 platforms only	4518	ev_win32.c required on win32 platforms only
3164		4519
3165	ev_select.c only when select backend is enabled (which is enabled by default)	4520	ev_select.c only when select backend is enabled
3166	ev_poll.c only when poll backend is enabled (disabled by default)	4521	ev_poll.c only when poll backend is enabled
3167	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4522	ev_epoll.c only when the epoll backend is enabled
		4523	ev_linuxaio.c only when the linux aio backend is enabled
		4524	ev_iouring.c only when the linux io_uring backend is enabled
3168	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4525	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)	4526	ev_port.c only when the solaris port backend is enabled
3170		4527
3171	F<ev.c> includes the backend files directly when enabled, so you only need	4528	F<ev.c> includes the backend files directly when enabled, so you only need
3172	to compile this single file.	4529	to compile this single file.
3173		4530
3174	=head3 LIBEVENT COMPATIBILITY API	4531	=head3 LIBEVENT COMPATIBILITY API
…		…
3200	libev.m4	4557	libev.m4
3201		4558
3202	=head2 PREPROCESSOR SYMBOLS/MACROS	4559	=head2 PREPROCESSOR SYMBOLS/MACROS
3203		4560
3204	Libev can be configured via a variety of preprocessor symbols you have to	4561	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	4562	define before including (or compiling) any of its files. The default in
3206	autoconf is documented for every option.	4563	the absence of autoconf is documented for every option.
		4564
		4565	Symbols marked with "(h)" do not change the ABI, and can have different
		4566	values when compiling libev vs. including F<ev.h>, so it is permissible
		4567	to redefine them before including F<ev.h> without breaking compatibility
		4568	to a compiled library. All other symbols change the ABI, which means all
		4569	users of libev and the libev code itself must be compiled with compatible
		4570	settings.
3207		4571
3208	=over 4	4572	=over 4
3209		4573
		4574	=item EV_COMPAT3 (h)
		4575
		4576	Backwards compatibility is a major concern for libev. This is why this
		4577	release of libev comes with wrappers for the functions and symbols that
		4578	have been renamed between libev version 3 and 4.
		4579
		4580	You can disable these wrappers (to test compatibility with future
		4581	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4582	sources. This has the additional advantage that you can drop the C<struct>
		4583	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4584	typedef in that case.
		4585
		4586	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4587	and in some even more future version the compatibility code will be
		4588	removed completely.
		4589
3210	=item EV_STANDALONE	4590	=item EV_STANDALONE (h)
3211		4591
3212	Must always be C<1> if you do not use autoconf configuration, which	4592	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	4593	keeps libev from including F<config.h>, and it also defines dummy
3214	implementations for some libevent functions (such as logging, which is not	4594	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	4595	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.	4596	F<event.h> that are not directly supported by the libev core alone.
3217		4597
3218	In stanbdalone mode, libev will still try to automatically deduce the	4598	In standalone mode, libev will still try to automatically deduce the
3219	configuration, but has to be more conservative.	4599	configuration, but has to be more conservative.
		4600
		4601	=item EV_USE_FLOOR
		4602
		4603	If defined to be C<1>, libev will use the C<floor ()> function for its
		4604	periodic reschedule calculations, otherwise libev will fall back on a
		4605	portable (slower) implementation. If you enable this, you usually have to
		4606	link against libm or something equivalent. Enabling this when the C<floor>
		4607	function is not available will fail, so the safe default is to not enable
		4608	this.
3220		4609
3221	=item EV_USE_MONOTONIC	4610	=item EV_USE_MONOTONIC
3222		4611
3223	If defined to be C<1>, libev will try to detect the availability of the	4612	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	4613	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3229	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.	4618	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3230		4619
3231	=item EV_USE_REALTIME	4620	=item EV_USE_REALTIME
3232		4621
3233	If defined to be C<1>, libev will try to detect the availability of the	4622	If defined to be C<1>, libev will try to detect the availability of the
3234	real-time clock option at compile time (and assume its availability at	4623	real-time clock option at compile time (and assume its availability
3235	runtime if successful). Otherwise no use of the real-time clock option will	4624	at runtime if successful). Otherwise no use of the real-time clock
3236	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4625	option will be attempted. This effectively replaces C<gettimeofday>
3237	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4626	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3238	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4627	correctness. See the note about libraries in the description of
		4628	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4629	C<EV_USE_CLOCK_SYSCALL>.
3239		4630
3240	=item EV_USE_CLOCK_SYSCALL	4631	=item EV_USE_CLOCK_SYSCALL
3241		4632
3242	If defined to be C<1>, libev will try to use a direct syscall instead	4633	If defined to be C<1>, libev will try to use a direct syscall instead
3243	of calling the system-provided C<clock_gettime> function. This option	4634	of calling the system-provided C<clock_gettime> function. This option
…		…
3259	available and will probe for kernel support at runtime. This will improve	4650	available and will probe for kernel support at runtime. This will improve
3260	C<ev_signal> and C<ev_async> performance and reduce resource consumption.	4651	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
3261	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc	4652	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
3262	2.7 or newer, otherwise disabled.	4653	2.7 or newer, otherwise disabled.
3263		4654
		4655	=item EV_USE_SIGNALFD
		4656
		4657	If defined to be C<1>, then libev will assume that C<signalfd ()> is
		4658	available and will probe for kernel support at runtime. This enables
		4659	the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If
		4660	undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4661	2.7 or newer, otherwise disabled.
		4662
		4663	=item EV_USE_TIMERFD
		4664
		4665	If defined to be C<1>, then libev will assume that C<timerfd ()> is
		4666	available and will probe for kernel support at runtime. This allows
		4667	libev to detect time jumps accurately. If undefined, it will be enabled
		4668	if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
		4669	C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled.
		4670
		4671	=item EV_USE_EVENTFD
		4672
		4673	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		4674	available and will probe for kernel support at runtime. This will improve
		4675	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		4676	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4677	2.7 or newer, otherwise disabled.
		4678
3264	=item EV_USE_SELECT	4679	=item EV_USE_SELECT
3265		4680
3266	If undefined or defined to be C<1>, libev will compile in support for the	4681	If undefined or defined to be C<1>, libev will compile in support for the
3267	C<select>(2) backend. No attempt at auto-detection will be done: if no	4682	C<select>(2) backend. No attempt at auto-detection will be done: if no
3268	other method takes over, select will be it. Otherwise the select backend	4683	other method takes over, select will be it. Otherwise the select backend
…		…
3286	be used is the winsock select). This means that it will call	4701	be used is the winsock select). This means that it will call
3287	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4702	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3288	it is assumed that all these functions actually work on fds, even	4703	it is assumed that all these functions actually work on fds, even
3289	on win32. Should not be defined on non-win32 platforms.	4704	on win32. Should not be defined on non-win32 platforms.
3290		4705
3291	=item EV_FD_TO_WIN32_HANDLE	4706	=item EV_FD_TO_WIN32_HANDLE(fd)
3292		4707
3293	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4708	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3294	file descriptors to socket handles. When not defining this symbol (the	4709	file descriptors to socket handles. When not defining this symbol (the
3295	default), then libev will call C<_get_osfhandle>, which is usually	4710	default), then libev will call C<_get_osfhandle>, which is usually
3296	correct. In some cases, programs use their own file descriptor management,	4711	correct. In some cases, programs use their own file descriptor management,
3297	in which case they can provide this function to map fds to socket handles.	4712	in which case they can provide this function to map fds to socket handles.
3298		4713
		4714	=item EV_WIN32_HANDLE_TO_FD(handle)
		4715
		4716	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4717	using the standard C<_open_osfhandle> function. For programs implementing
		4718	their own fd to handle mapping, overwriting this function makes it easier
		4719	to do so. This can be done by defining this macro to an appropriate value.
		4720
		4721	=item EV_WIN32_CLOSE_FD(fd)
		4722
		4723	If programs implement their own fd to handle mapping on win32, then this
		4724	macro can be used to override the C<close> function, useful to unregister
		4725	file descriptors again. Note that the replacement function has to close
		4726	the underlying OS handle.
		4727
		4728	=item EV_USE_WSASOCKET
		4729
		4730	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4731	communication socket, which works better in some environments. Otherwise,
		4732	the normal C<socket> function will be used, which works better in other
		4733	environments.
		4734
3299	=item EV_USE_POLL	4735	=item EV_USE_POLL
3300		4736
3301	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4737	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3302	backend. Otherwise it will be enabled on non-win32 platforms. It	4738	backend. Otherwise it will be enabled on non-win32 platforms. It
3303	takes precedence over select.	4739	takes precedence over select.
…		…
3307	If defined to be C<1>, libev will compile in support for the Linux	4743	If defined to be C<1>, libev will compile in support for the Linux
3308	C<epoll>(7) backend. Its availability will be detected at runtime,	4744	C<epoll>(7) backend. Its availability will be detected at runtime,
3309	otherwise another method will be used as fallback. This is the preferred	4745	otherwise another method will be used as fallback. This is the preferred
3310	backend for GNU/Linux systems. If undefined, it will be enabled if the	4746	backend for GNU/Linux systems. If undefined, it will be enabled if the
3311	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4747	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4748
		4749	=item EV_USE_LINUXAIO
		4750
		4751	If defined to be C<1>, libev will compile in support for the Linux aio
		4752	backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be
		4753	enabled on linux, otherwise disabled.
		4754
		4755	=item EV_USE_IOURING
		4756
		4757	If defined to be C<1>, libev will compile in support for the Linux
		4758	io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's
		4759	current limitations it has to be requested explicitly. If undefined, it
		4760	will be enabled on linux, otherwise disabled.
3312		4761
3313	=item EV_USE_KQUEUE	4762	=item EV_USE_KQUEUE
3314		4763
3315	If defined to be C<1>, libev will compile in support for the BSD style	4764	If defined to be C<1>, libev will compile in support for the BSD style
3316	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4765	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3338	If defined to be C<1>, libev will compile in support for the Linux inotify	4787	If defined to be C<1>, libev will compile in support for the Linux inotify
3339	interface to speed up C<ev_stat> watchers. Its actual availability will	4788	interface to speed up C<ev_stat> watchers. Its actual availability will
3340	be detected at runtime. If undefined, it will be enabled if the headers	4789	be detected at runtime. If undefined, it will be enabled if the headers
3341	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4790	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3342		4791
		4792	=item EV_NO_SMP
		4793
		4794	If defined to be C<1>, libev will assume that memory is always coherent
		4795	between threads, that is, threads can be used, but threads never run on
		4796	different cpus (or different cpu cores). This reduces dependencies
		4797	and makes libev faster.
		4798
		4799	=item EV_NO_THREADS
		4800
		4801	If defined to be C<1>, libev will assume that it will never be called from
		4802	different threads (that includes signal handlers), which is a stronger
		4803	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4804	libev faster.
		4805
3343	=item EV_ATOMIC_T	4806	=item EV_ATOMIC_T
3344		4807
3345	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4808	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3346	access is atomic with respect to other threads or signal contexts. No such	4809	access is atomic with respect to other threads or signal contexts. No
3347	type is easily found in the C language, so you can provide your own type	4810	such type is easily found in the C language, so you can provide your own
3348	that you know is safe for your purposes. It is used both for signal handler "locking"	4811	type that you know is safe for your purposes. It is used both for signal
3349	as well as for signal and thread safety in C<ev_async> watchers.	4812	handler "locking" as well as for signal and thread safety in C<ev_async>
		4813	watchers.
3350		4814
3351	In the absence of this define, libev will use C<sig_atomic_t volatile>	4815	In the absence of this define, libev will use C<sig_atomic_t volatile>
3352	(from F<signal.h>), which is usually good enough on most platforms.	4816	(from F<signal.h>), which is usually good enough on most platforms.
3353		4817
3354	=item EV_H	4818	=item EV_H (h)
3355		4819
3356	The name of the F<ev.h> header file used to include it. The default if	4820	The name of the F<ev.h> header file used to include it. The default if
3357	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4821	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3358	used to virtually rename the F<ev.h> header file in case of conflicts.	4822	used to virtually rename the F<ev.h> header file in case of conflicts.
3359		4823
3360	=item EV_CONFIG_H	4824	=item EV_CONFIG_H (h)
3361		4825
3362	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4826	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3363	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4827	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3364	C<EV_H>, above.	4828	C<EV_H>, above.
3365		4829
3366	=item EV_EVENT_H	4830	=item EV_EVENT_H (h)
3367		4831
3368	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4832	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3369	of how the F<event.h> header can be found, the default is C<"event.h">.	4833	of how the F<event.h> header can be found, the default is C<"event.h">.
3370		4834
3371	=item EV_PROTOTYPES	4835	=item EV_PROTOTYPES (h)
3372		4836
3373	If defined to be C<0>, then F<ev.h> will not define any function	4837	If defined to be C<0>, then F<ev.h> will not define any function
3374	prototypes, but still define all the structs and other symbols. This is	4838	prototypes, but still define all the structs and other symbols. This is
3375	occasionally useful if you want to provide your own wrapper functions	4839	occasionally useful if you want to provide your own wrapper functions
3376	around libev functions.	4840	around libev functions.
…		…
3381	will have the C<struct ev_loop *> as first argument, and you can create	4845	will have the C<struct ev_loop *> as first argument, and you can create
3382	additional independent event loops. Otherwise there will be no support	4846	additional independent event loops. Otherwise there will be no support
3383	for multiple event loops and there is no first event loop pointer	4847	for multiple event loops and there is no first event loop pointer
3384	argument. Instead, all functions act on the single default loop.	4848	argument. Instead, all functions act on the single default loop.
3385		4849
		4850	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4851	default loop when multiplicity is switched off - you always have to
		4852	initialise the loop manually in this case.
		4853
3386	=item EV_MINPRI	4854	=item EV_MINPRI
3387		4855
3388	=item EV_MAXPRI	4856	=item EV_MAXPRI
3389		4857
3390	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4858	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3398	fine.	4866	fine.
3399		4867
3400	If your embedding application does not need any priorities, defining these	4868	If your embedding application does not need any priorities, defining these
3401	both to C<0> will save some memory and CPU.	4869	both to C<0> will save some memory and CPU.
3402		4870
3403	=item EV_PERIODIC_ENABLE	4871	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4872	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4873	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3404		4874
3405	If undefined or defined to be C<1>, then periodic timers are supported. If	4875	If undefined or defined to be C<1> (and the platform supports it), then
3406	defined to be C<0>, then they are not. Disabling them saves a few kB of	4876	the respective watcher type is supported. If defined to be C<0>, then it
3407	code.	4877	is not. Disabling watcher types mainly saves code size.
3408		4878
3409	=item EV_IDLE_ENABLE	4879	=item EV_FEATURES
3410
3411	If undefined or defined to be C<1>, then idle watchers are supported. If
3412	defined to be C<0>, then they are not. Disabling them saves a few kB of
3413	code.
3414
3415	=item EV_EMBED_ENABLE
3416
3417	If undefined or defined to be C<1>, then embed watchers are supported. If
3418	defined to be C<0>, then they are not. Embed watchers rely on most other
3419	watcher types, which therefore must not be disabled.
3420
3421	=item EV_STAT_ENABLE
3422
3423	If undefined or defined to be C<1>, then stat watchers are supported. If
3424	defined to be C<0>, then they are not.
3425
3426	=item EV_FORK_ENABLE
3427
3428	If undefined or defined to be C<1>, then fork watchers are supported. If
3429	defined to be C<0>, then they are not.
3430
3431	=item EV_ASYNC_ENABLE
3432
3433	If undefined or defined to be C<1>, then async watchers are supported. If
3434	defined to be C<0>, then they are not.
3435
3436	=item EV_MINIMAL
3437		4880
3438	If you need to shave off some kilobytes of code at the expense of some	4881	If you need to shave off some kilobytes of code at the expense of some
3439	speed, define this symbol to C<1>. Currently this is used to override some	4882	speed (but with the full API), you can define this symbol to request
3440	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4883	certain subsets of functionality. The default is to enable all features
3441	much smaller 2-heap for timer management over the default 4-heap.	4884	that can be enabled on the platform.
		4885
		4886	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4887	with some broad features you want) and then selectively re-enable
		4888	additional parts you want, for example if you want everything minimal,
		4889	but multiple event loop support, async and child watchers and the poll
		4890	backend, use this:
		4891
		4892	#define EV_FEATURES 0
		4893	#define EV_MULTIPLICITY 1
		4894	#define EV_USE_POLL 1
		4895	#define EV_CHILD_ENABLE 1
		4896	#define EV_ASYNC_ENABLE 1
		4897
		4898	The actual value is a bitset, it can be a combination of the following
		4899	values (by default, all of these are enabled):
		4900
		4901	=over 4
		4902
		4903	=item C<1> - faster/larger code
		4904
		4905	Use larger code to speed up some operations.
		4906
		4907	Currently this is used to override some inlining decisions (enlarging the
		4908	code size by roughly 30% on amd64).
		4909
		4910	When optimising for size, use of compiler flags such as C<-Os> with
		4911	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4912	assertions.
		4913
		4914	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4915	(e.g. gcc with C<-Os>).
		4916
		4917	=item C<2> - faster/larger data structures
		4918
		4919	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4920	hash table sizes and so on. This will usually further increase code size
		4921	and can additionally have an effect on the size of data structures at
		4922	runtime.
		4923
		4924	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4925	(e.g. gcc with C<-Os>).
		4926
		4927	=item C<4> - full API configuration
		4928
		4929	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4930	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4931
		4932	=item C<8> - full API
		4933
		4934	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4935	details on which parts of the API are still available without this
		4936	feature, and do not complain if this subset changes over time.
		4937
		4938	=item C<16> - enable all optional watcher types
		4939
		4940	Enables all optional watcher types. If you want to selectively enable
		4941	only some watcher types other than I/O and timers (e.g. prepare,
		4942	embed, async, child...) you can enable them manually by defining
		4943	C<EV_watchertype_ENABLE> to C<1> instead.
		4944
		4945	=item C<32> - enable all backends
		4946
		4947	This enables all backends - without this feature, you need to enable at
		4948	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4949
		4950	=item C<64> - enable OS-specific "helper" APIs
		4951
		4952	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4953	default.
		4954
		4955	=back
		4956
		4957	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4958	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4959	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4960	watchers, timers and monotonic clock support.
		4961
		4962	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4963	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4964	your program might be left out as well - a binary starting a timer and an
		4965	I/O watcher then might come out at only 5Kb.
		4966
		4967	=item EV_API_STATIC
		4968
		4969	If this symbol is defined (by default it is not), then all identifiers
		4970	will have static linkage. This means that libev will not export any
		4971	identifiers, and you cannot link against libev anymore. This can be useful
		4972	when you embed libev, only want to use libev functions in a single file,
		4973	and do not want its identifiers to be visible.
		4974
		4975	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4976	wants to use libev.
		4977
		4978	This option only works when libev is compiled with a C compiler, as C++
		4979	doesn't support the required declaration syntax.
		4980
		4981	=item EV_AVOID_STDIO
		4982
		4983	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4984	functions (printf, scanf, perror etc.). This will increase the code size
		4985	somewhat, but if your program doesn't otherwise depend on stdio and your
		4986	libc allows it, this avoids linking in the stdio library which is quite
		4987	big.
		4988
		4989	Note that error messages might become less precise when this option is
		4990	enabled.
		4991
		4992	=item EV_NSIG
		4993
		4994	The highest supported signal number, +1 (or, the number of
		4995	signals): Normally, libev tries to deduce the maximum number of signals
		4996	automatically, but sometimes this fails, in which case it can be
		4997	specified. Also, using a lower number than detected (C<32> should be
		4998	good for about any system in existence) can save some memory, as libev
		4999	statically allocates some 12-24 bytes per signal number.
3442		5000
3443	=item EV_PID_HASHSIZE	5001	=item EV_PID_HASHSIZE
3444		5002
3445	C<ev_child> watchers use a small hash table to distribute workload by	5003	C<ev_child> watchers use a small hash table to distribute workload by
3446	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	5004	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3447	than enough. If you need to manage thousands of children you might want to	5005	usually more than enough. If you need to manage thousands of children you
3448	increase this value (I<must> be a power of two).	5006	might want to increase this value (I<must> be a power of two).
3449		5007
3450	=item EV_INOTIFY_HASHSIZE	5008	=item EV_INOTIFY_HASHSIZE
3451		5009
3452	C<ev_stat> watchers use a small hash table to distribute workload by	5010	C<ev_stat> watchers use a small hash table to distribute workload by
3453	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	5011	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3454	usually more than enough. If you need to manage thousands of C<ev_stat>	5012	disabled), usually more than enough. If you need to manage thousands of
3455	watchers you might want to increase this value (I<must> be a power of	5013	C<ev_stat> watchers you might want to increase this value (I<must> be a
3456	two).	5014	power of two).
3457		5015
3458	=item EV_USE_4HEAP	5016	=item EV_USE_4HEAP
3459		5017
3460	Heaps are not very cache-efficient. To improve the cache-efficiency of the	5018	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3461	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	5019	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3462	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	5020	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3463	faster performance with many (thousands) of watchers.	5021	faster performance with many (thousands) of watchers.
3464		5022
3465	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	5023	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3466	(disabled).	5024	will be C<0>.
3467		5025
3468	=item EV_HEAP_CACHE_AT	5026	=item EV_HEAP_CACHE_AT
3469		5027
3470	Heaps are not very cache-efficient. To improve the cache-efficiency of the	5028	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3471	timer and periodics heaps, libev can cache the timestamp (I<at>) within	5029	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3472	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	5030	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3473	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	5031	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3474	but avoids random read accesses on heap changes. This improves performance	5032	but avoids random read accesses on heap changes. This improves performance
3475	noticeably with many (hundreds) of watchers.	5033	noticeably with many (hundreds) of watchers.
3476		5034
3477	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	5035	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3478	(disabled).	5036	will be C<0>.
3479		5037
3480	=item EV_VERIFY	5038	=item EV_VERIFY
3481		5039
3482	Controls how much internal verification (see C<ev_loop_verify ()>) will	5040	Controls how much internal verification (see C<ev_verify ()>) will
3483	be done: If set to C<0>, no internal verification code will be compiled	5041	be done: If set to C<0>, no internal verification code will be compiled
3484	in. If set to C<1>, then verification code will be compiled in, but not	5042	in. If set to C<1>, then verification code will be compiled in, but not
3485	called. If set to C<2>, then the internal verification code will be	5043	called. If set to C<2>, then the internal verification code will be
3486	called once per loop, which can slow down libev. If set to C<3>, then the	5044	called once per loop, which can slow down libev. If set to C<3>, then the
3487	verification code will be called very frequently, which will slow down	5045	verification code will be called very frequently, which will slow down
3488	libev considerably.	5046	libev considerably.
3489		5047
		5048	Verification errors are reported via C's C<assert> mechanism, so if you
		5049	disable that (e.g. by defining C<NDEBUG>) then no errors will be reported.
		5050
3490	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	5051	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3491	C<0>.	5052	will be C<0>.
3492		5053
3493	=item EV_COMMON	5054	=item EV_COMMON
3494		5055
3495	By default, all watchers have a C<void *data> member. By redefining	5056	By default, all watchers have a C<void *data> member. By redefining
3496	this macro to a something else you can include more and other types of	5057	this macro to something else you can include more and other types of
3497	members. You have to define it each time you include one of the files,	5058	members. You have to define it each time you include one of the files,
3498	though, and it must be identical each time.	5059	though, and it must be identical each time.
3499		5060
3500	For example, the perl EV module uses something like this:	5061	For example, the perl EV module uses something like this:
3501		5062
…		…
3554	file.	5115	file.
3555		5116
3556	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5117	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3557	that everybody includes and which overrides some configure choices:	5118	that everybody includes and which overrides some configure choices:
3558		5119
3559	#define EV_MINIMAL 1	5120	#define EV_FEATURES 8
3560	#define EV_USE_POLL 0	5121	#define EV_USE_SELECT 1
3561	#define EV_MULTIPLICITY 0
3562	#define EV_PERIODIC_ENABLE 0	5122	#define EV_PREPARE_ENABLE 1
		5123	#define EV_IDLE_ENABLE 1
3563	#define EV_STAT_ENABLE 0	5124	#define EV_SIGNAL_ENABLE 1
3564	#define EV_FORK_ENABLE 0	5125	#define EV_CHILD_ENABLE 1
		5126	#define EV_USE_STDEXCEPT 0
3565	#define EV_CONFIG_H <config.h>	5127	#define EV_CONFIG_H <config.h>
3566	#define EV_MINPRI 0
3567	#define EV_MAXPRI 0
3568		5128
3569	#include "ev++.h"	5129	#include "ev++.h"
3570		5130
3571	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5131	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3572		5132
3573	#include "ev_cpp.h"	5133	#include "ev_cpp.h"
3574	#include "ev.c"	5134	#include "ev.c"
3575		5135
3576	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5136	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3577		5137
3578	=head2 THREADS AND COROUTINES	5138	=head2 THREADS AND COROUTINES
3579		5139
3580	=head3 THREADS	5140	=head3 THREADS
3581		5141
…		…
3632	default loop and triggering an C<ev_async> watcher from the default loop	5192	default loop and triggering an C<ev_async> watcher from the default loop
3633	watcher callback into the event loop interested in the signal.	5193	watcher callback into the event loop interested in the signal.
3634		5194
3635	=back	5195	=back
3636		5196
		5197	See also L</THREAD LOCKING EXAMPLE>.
		5198
3637	=head3 COROUTINES	5199	=head3 COROUTINES
3638		5200
3639	Libev is very accommodating to coroutines ("cooperative threads"):	5201	Libev is very accommodating to coroutines ("cooperative threads"):
3640	libev fully supports nesting calls to its functions from different	5202	libev fully supports nesting calls to its functions from different
3641	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5203	coroutines (e.g. you can call C<ev_run> on the same loop from two
3642	different coroutines, and switch freely between both coroutines running the	5204	different coroutines, and switch freely between both coroutines running
3643	loop, as long as you don't confuse yourself). The only exception is that	5205	the loop, as long as you don't confuse yourself). The only exception is
3644	you must not do this from C<ev_periodic> reschedule callbacks.	5206	that you must not do this from C<ev_periodic> reschedule callbacks.
3645		5207
3646	Care has been taken to ensure that libev does not keep local state inside	5208	Care has been taken to ensure that libev does not keep local state inside
3647	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5209	C<ev_run>, and other calls do not usually allow for coroutine switches as
3648	they do not call any callbacks.	5210	they do not call any callbacks.
3649		5211
3650	=head2 COMPILER WARNINGS	5212	=head2 COMPILER WARNINGS
3651		5213
3652	Depending on your compiler and compiler settings, you might get no or a	5214	Depending on your compiler and compiler settings, you might get no or a
…		…
3663	maintainable.	5225	maintainable.
3664		5226
3665	And of course, some compiler warnings are just plain stupid, or simply	5227	And of course, some compiler warnings are just plain stupid, or simply
3666	wrong (because they don't actually warn about the condition their message	5228	wrong (because they don't actually warn about the condition their message
3667	seems to warn about). For example, certain older gcc versions had some	5229	seems to warn about). For example, certain older gcc versions had some
3668	warnings that resulted an extreme number of false positives. These have	5230	warnings that resulted in an extreme number of false positives. These have
3669	been fixed, but some people still insist on making code warn-free with	5231	been fixed, but some people still insist on making code warn-free with
3670	such buggy versions.	5232	such buggy versions.
3671		5233
3672	While libev is written to generate as few warnings as possible,	5234	While libev is written to generate as few warnings as possible,
3673	"warn-free" code is not a goal, and it is recommended not to build libev	5235	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3709	I suggest using suppression lists.	5271	I suggest using suppression lists.
3710		5272
3711		5273
3712	=head1 PORTABILITY NOTES	5274	=head1 PORTABILITY NOTES
3713		5275
		5276	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5277
		5278	GNU/Linux is the only common platform that supports 64 bit file/large file
		5279	interfaces but I<disables> them by default.
		5280
		5281	That means that libev compiled in the default environment doesn't support
		5282	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5283
		5284	Unfortunately, many programs try to work around this GNU/Linux issue
		5285	by enabling the large file API, which makes them incompatible with the
		5286	standard libev compiled for their system.
		5287
		5288	Likewise, libev cannot enable the large file API itself as this would
		5289	suddenly make it incompatible to the default compile time environment,
		5290	i.e. all programs not using special compile switches.
		5291
		5292	=head2 OS/X AND DARWIN BUGS
		5293
		5294	The whole thing is a bug if you ask me - basically any system interface
		5295	you touch is broken, whether it is locales, poll, kqueue or even the
		5296	OpenGL drivers.
		5297
		5298	=head3 C<kqueue> is buggy
		5299
		5300	The kqueue syscall is broken in all known versions - most versions support
		5301	only sockets, many support pipes.
		5302
		5303	Libev tries to work around this by not using C<kqueue> by default on this
		5304	rotten platform, but of course you can still ask for it when creating a
		5305	loop - embedding a socket-only kqueue loop into a select-based one is
		5306	probably going to work well.
		5307
		5308	=head3 C<poll> is buggy
		5309
		5310	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5311	implementation by something calling C<kqueue> internally around the 10.5.6
		5312	release, so now C<kqueue> I<and> C<poll> are broken.
		5313
		5314	Libev tries to work around this by not using C<poll> by default on
		5315	this rotten platform, but of course you can still ask for it when creating
		5316	a loop.
		5317
		5318	=head3 C<select> is buggy
		5319
		5320	All that's left is C<select>, and of course Apple found a way to fuck this
		5321	one up as well: On OS/X, C<select> actively limits the number of file
		5322	descriptors you can pass in to 1024 - your program suddenly crashes when
		5323	you use more.
		5324
		5325	There is an undocumented "workaround" for this - defining
		5326	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5327	work on OS/X.
		5328
		5329	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5330
		5331	=head3 C<errno> reentrancy
		5332
		5333	The default compile environment on Solaris is unfortunately so
		5334	thread-unsafe that you can't even use components/libraries compiled
		5335	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5336	defined by default. A valid, if stupid, implementation choice.
		5337
		5338	If you want to use libev in threaded environments you have to make sure
		5339	it's compiled with C<_REENTRANT> defined.
		5340
		5341	=head3 Event port backend
		5342
		5343	The scalable event interface for Solaris is called "event
		5344	ports". Unfortunately, this mechanism is very buggy in all major
		5345	releases. If you run into high CPU usage, your program freezes or you get
		5346	a large number of spurious wakeups, make sure you have all the relevant
		5347	and latest kernel patches applied. No, I don't know which ones, but there
		5348	are multiple ones to apply, and afterwards, event ports actually work
		5349	great.
		5350
		5351	If you can't get it to work, you can try running the program by setting
		5352	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5353	C<select> backends.
		5354
		5355	=head2 AIX POLL BUG
		5356
		5357	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5358	this by trying to avoid the poll backend altogether (i.e. it's not even
		5359	compiled in), which normally isn't a big problem as C<select> works fine
		5360	with large bitsets on AIX, and AIX is dead anyway.
		5361
3714	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5362	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5363
		5364	=head3 General issues
3715		5365
3716	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5366	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3717	requires, and its I/O model is fundamentally incompatible with the POSIX	5367	requires, and its I/O model is fundamentally incompatible with the POSIX
3718	model. Libev still offers limited functionality on this platform in	5368	model. Libev still offers limited functionality on this platform in
3719	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5369	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3720	descriptors. This only applies when using Win32 natively, not when using	5370	descriptors. This only applies when using Win32 natively, not when using
3721	e.g. cygwin.	5371	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5372	as every compiler comes with a slightly differently broken/incompatible
		5373	environment.
3722		5374
3723	Lifting these limitations would basically require the full	5375	Lifting these limitations would basically require the full
3724	re-implementation of the I/O system. If you are into these kinds of	5376	re-implementation of the I/O system. If you are into this kind of thing,
3725	things, then note that glib does exactly that for you in a very portable	5377	then note that glib does exactly that for you in a very portable way (note
3726	way (note also that glib is the slowest event library known to man).	5378	also that glib is the slowest event library known to man).
3727		5379
3728	There is no supported compilation method available on windows except	5380	There is no supported compilation method available on windows except
3729	embedding it into other applications.	5381	embedding it into other applications.
		5382
		5383	Sensible signal handling is officially unsupported by Microsoft - libev
		5384	tries its best, but under most conditions, signals will simply not work.
3730		5385
3731	Not a libev limitation but worth mentioning: windows apparently doesn't	5386	Not a libev limitation but worth mentioning: windows apparently doesn't
3732	accept large writes: instead of resulting in a partial write, windows will	5387	accept large writes: instead of resulting in a partial write, windows will
3733	either accept everything or return C<ENOBUFS> if the buffer is too large,	5388	either accept everything or return C<ENOBUFS> if the buffer is too large,
3734	so make sure you only write small amounts into your sockets (less than a	5389	so make sure you only write small amounts into your sockets (less than a
…		…
3739	the abysmal performance of winsockets, using a large number of sockets	5394	the abysmal performance of winsockets, using a large number of sockets
3740	is not recommended (and not reasonable). If your program needs to use	5395	is not recommended (and not reasonable). If your program needs to use
3741	more than a hundred or so sockets, then likely it needs to use a totally	5396	more than a hundred or so sockets, then likely it needs to use a totally
3742	different implementation for windows, as libev offers the POSIX readiness	5397	different implementation for windows, as libev offers the POSIX readiness
3743	notification model, which cannot be implemented efficiently on windows	5398	notification model, which cannot be implemented efficiently on windows
3744	(Microsoft monopoly games).	5399	(due to Microsoft monopoly games).
3745		5400
3746	A typical way to use libev under windows is to embed it (see the embedding	5401	A typical way to use libev under windows is to embed it (see the embedding
3747	section for details) and use the following F<evwrap.h> header file instead	5402	section for details) and use the following F<evwrap.h> header file instead
3748	of F<ev.h>:	5403	of F<ev.h>:
3749		5404
…		…
3756	you do I<not> compile the F<ev.c> or any other embedded source files!):	5411	you do I<not> compile the F<ev.c> or any other embedded source files!):
3757		5412
3758	#include "evwrap.h"	5413	#include "evwrap.h"
3759	#include "ev.c"	5414	#include "ev.c"
3760		5415
3761	=over 4
3762
3763	=item The winsocket select function	5416	=head3 The winsocket C<select> function
3764		5417
3765	The winsocket C<select> function doesn't follow POSIX in that it	5418	The winsocket C<select> function doesn't follow POSIX in that it
3766	requires socket I<handles> and not socket I<file descriptors> (it is	5419	requires socket I<handles> and not socket I<file descriptors> (it is
3767	also extremely buggy). This makes select very inefficient, and also	5420	also extremely buggy). This makes select very inefficient, and also
3768	requires a mapping from file descriptors to socket handles (the Microsoft	5421	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3777	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5430	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3778		5431
3779	Note that winsockets handling of fd sets is O(n), so you can easily get a	5432	Note that winsockets handling of fd sets is O(n), so you can easily get a
3780	complexity in the O(n²) range when using win32.	5433	complexity in the O(n²) range when using win32.
3781		5434
3782	=item Limited number of file descriptors	5435	=head3 Limited number of file descriptors
3783		5436
3784	Windows has numerous arbitrary (and low) limits on things.	5437	Windows has numerous arbitrary (and low) limits on things.
3785		5438
3786	Early versions of winsocket's select only supported waiting for a maximum	5439	Early versions of winsocket's select only supported waiting for a maximum
3787	of C<64> handles (probably owning to the fact that all windows kernels	5440	of C<64> handles (probably owning to the fact that all windows kernels
3788	can only wait for C<64> things at the same time internally; Microsoft	5441	can only wait for C<64> things at the same time internally; Microsoft
3789	recommends spawning a chain of threads and wait for 63 handles and the	5442	recommends spawning a chain of threads and wait for 63 handles and the
3790	previous thread in each. Great).	5443	previous thread in each. Sounds great!).
3791		5444
3792	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5445	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3793	to some high number (e.g. C<2048>) before compiling the winsocket select	5446	to some high number (e.g. C<2048>) before compiling the winsocket select
3794	call (which might be in libev or elsewhere, for example, perl does its own	5447	call (which might be in libev or elsewhere, for example, perl and many
3795	select emulation on windows).	5448	other interpreters do their own select emulation on windows).
3796		5449
3797	Another limit is the number of file descriptors in the Microsoft runtime	5450	Another limit is the number of file descriptors in the Microsoft runtime
3798	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5451	libraries, which by default is C<64> (there must be a hidden I<64>
3799	or something like this inside Microsoft). You can increase this by calling	5452	fetish or something like this inside Microsoft). You can increase this
3800	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5453	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3801	arbitrary limit), but is broken in many versions of the Microsoft runtime	5454	(another arbitrary limit), but is broken in many versions of the Microsoft
3802	libraries.
3803
3804	This might get you to about C<512> or C<2048> sockets (depending on	5455	runtime libraries. This might get you to about C<512> or C<2048> sockets
3805	windows version and/or the phase of the moon). To get more, you need to	5456	(depending on windows version and/or the phase of the moon). To get more,
3806	wrap all I/O functions and provide your own fd management, but the cost of	5457	you need to wrap all I/O functions and provide your own fd management, but
3807	calling select (O(n²)) will likely make this unworkable.	5458	the cost of calling select (O(n²)) will likely make this unworkable.
3808
3809	=back
3810		5459
3811	=head2 PORTABILITY REQUIREMENTS	5460	=head2 PORTABILITY REQUIREMENTS
3812		5461
3813	In addition to a working ISO-C implementation and of course the	5462	In addition to a working ISO-C implementation and of course the
3814	backend-specific APIs, libev relies on a few additional extensions:	5463	backend-specific APIs, libev relies on a few additional extensions:
…		…
3821	Libev assumes not only that all watcher pointers have the same internal	5470	Libev assumes not only that all watcher pointers have the same internal
3822	structure (guaranteed by POSIX but not by ISO C for example), but it also	5471	structure (guaranteed by POSIX but not by ISO C for example), but it also
3823	assumes that the same (machine) code can be used to call any watcher	5472	assumes that the same (machine) code can be used to call any watcher
3824	callback: The watcher callbacks have different type signatures, but libev	5473	callback: The watcher callbacks have different type signatures, but libev
3825	calls them using an C<ev_watcher *> internally.	5474	calls them using an C<ev_watcher *> internally.
		5475
		5476	=item null pointers and integer zero are represented by 0 bytes
		5477
		5478	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5479	relies on this setting pointers and integers to null.
		5480
		5481	=item pointer accesses must be thread-atomic
		5482
		5483	Accessing a pointer value must be atomic, it must both be readable and
		5484	writable in one piece - this is the case on all current architectures.
3826		5485
3827	=item C<sig_atomic_t volatile> must be thread-atomic as well	5486	=item C<sig_atomic_t volatile> must be thread-atomic as well
3828		5487
3829	The type C<sig_atomic_t volatile> (or whatever is defined as	5488	The type C<sig_atomic_t volatile> (or whatever is defined as
3830	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5489	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3839	thread" or will block signals process-wide, both behaviours would	5498	thread" or will block signals process-wide, both behaviours would
3840	be compatible with libev. Interaction between C<sigprocmask> and	5499	be compatible with libev. Interaction between C<sigprocmask> and
3841	C<pthread_sigmask> could complicate things, however.	5500	C<pthread_sigmask> could complicate things, however.
3842		5501
3843	The most portable way to handle signals is to block signals in all threads	5502	The most portable way to handle signals is to block signals in all threads
3844	except the initial one, and run the default loop in the initial thread as	5503	except the initial one, and run the signal handling loop in the initial
3845	well.	5504	thread as well.
3846		5505
3847	=item C<long> must be large enough for common memory allocation sizes	5506	=item C<long> must be large enough for common memory allocation sizes
3848		5507
3849	To improve portability and simplify its API, libev uses C<long> internally	5508	To improve portability and simplify its API, libev uses C<long> internally
3850	instead of C<size_t> when allocating its data structures. On non-POSIX	5509	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3853	watchers.	5512	watchers.
3854		5513
3855	=item C<double> must hold a time value in seconds with enough accuracy	5514	=item C<double> must hold a time value in seconds with enough accuracy
3856		5515
3857	The type C<double> is used to represent timestamps. It is required to	5516	The type C<double> is used to represent timestamps. It is required to
3858	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5517	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3859	enough for at least into the year 4000. This requirement is fulfilled by	5518	good enough for at least into the year 4000 with millisecond accuracy
		5519	(the design goal for libev). This requirement is overfulfilled by
3860	implementations implementing IEEE 754 (basically all existing ones).	5520	implementations using IEEE 754, which is basically all existing ones.
		5521
		5522	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5523	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5524	is either obsolete or somebody patched it to use C<long double> or
		5525	something like that, just kidding).
3861		5526
3862	=back	5527	=back
3863		5528
3864	If you know of other additional requirements drop me a note.	5529	If you know of other additional requirements drop me a note.
3865		5530
…		…
3927	=item Processing ev_async_send: O(number_of_async_watchers)	5592	=item Processing ev_async_send: O(number_of_async_watchers)
3928		5593
3929	=item Processing signals: O(max_signal_number)	5594	=item Processing signals: O(max_signal_number)
3930		5595
3931	Sending involves a system call I<iff> there were no other C<ev_async_send>	5596	Sending involves a system call I<iff> there were no other C<ev_async_send>
3932	calls in the current loop iteration. Checking for async and signal events	5597	calls in the current loop iteration and the loop is currently
		5598	blocked. Checking for async and signal events involves iterating over all
3933	involves iterating over all running async watchers or all signal numbers.	5599	running async watchers or all signal numbers.
3934		5600
3935	=back	5601	=back
3936		5602
3937		5603
		5604	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5605
		5606	The major version 4 introduced some incompatible changes to the API.
		5607
		5608	At the moment, the C<ev.h> header file provides compatibility definitions
		5609	for all changes, so most programs should still compile. The compatibility
		5610	layer might be removed in later versions of libev, so better update to the
		5611	new API early than late.
		5612
		5613	=over 4
		5614
		5615	=item C<EV_COMPAT3> backwards compatibility mechanism
		5616
		5617	The backward compatibility mechanism can be controlled by
		5618	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5619	section.
		5620
		5621	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5622
		5623	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5624
		5625	ev_loop_destroy (EV_DEFAULT_UC);
		5626	ev_loop_fork (EV_DEFAULT);
		5627
		5628	=item function/symbol renames
		5629
		5630	A number of functions and symbols have been renamed:
		5631
		5632	ev_loop => ev_run
		5633	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5634	EVLOOP_ONESHOT => EVRUN_ONCE
		5635
		5636	ev_unloop => ev_break
		5637	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5638	EVUNLOOP_ONE => EVBREAK_ONE
		5639	EVUNLOOP_ALL => EVBREAK_ALL
		5640
		5641	EV_TIMEOUT => EV_TIMER
		5642
		5643	ev_loop_count => ev_iteration
		5644	ev_loop_depth => ev_depth
		5645	ev_loop_verify => ev_verify
		5646
		5647	Most functions working on C<struct ev_loop> objects don't have an
		5648	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5649	associated constants have been renamed to not collide with the C<struct
		5650	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5651	as all other watcher types. Note that C<ev_loop_fork> is still called
		5652	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5653	typedef.
		5654
		5655	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5656
		5657	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5658	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5659	and work, but the library code will of course be larger.
		5660
		5661	=back
		5662
		5663
		5664	=head1 GLOSSARY
		5665
		5666	=over 4
		5667
		5668	=item active
		5669
		5670	A watcher is active as long as it has been started and not yet stopped.
		5671	See L</WATCHER STATES> for details.
		5672
		5673	=item application
		5674
		5675	In this document, an application is whatever is using libev.
		5676
		5677	=item backend
		5678
		5679	The part of the code dealing with the operating system interfaces.
		5680
		5681	=item callback
		5682
		5683	The address of a function that is called when some event has been
		5684	detected. Callbacks are being passed the event loop, the watcher that
		5685	received the event, and the actual event bitset.
		5686
		5687	=item callback/watcher invocation
		5688
		5689	The act of calling the callback associated with a watcher.
		5690
		5691	=item event
		5692
		5693	A change of state of some external event, such as data now being available
		5694	for reading on a file descriptor, time having passed or simply not having
		5695	any other events happening anymore.
		5696
		5697	In libev, events are represented as single bits (such as C<EV_READ> or
		5698	C<EV_TIMER>).
		5699
		5700	=item event library
		5701
		5702	A software package implementing an event model and loop.
		5703
		5704	=item event loop
		5705
		5706	An entity that handles and processes external events and converts them
		5707	into callback invocations.
		5708
		5709	=item event model
		5710
		5711	The model used to describe how an event loop handles and processes
		5712	watchers and events.
		5713
		5714	=item pending
		5715
		5716	A watcher is pending as soon as the corresponding event has been
		5717	detected. See L</WATCHER STATES> for details.
		5718
		5719	=item real time
		5720
		5721	The physical time that is observed. It is apparently strictly monotonic :)
		5722
		5723	=item wall-clock time
		5724
		5725	The time and date as shown on clocks. Unlike real time, it can actually
		5726	be wrong and jump forwards and backwards, e.g. when you adjust your
		5727	clock.
		5728
		5729	=item watcher
		5730
		5731	A data structure that describes interest in certain events. Watchers need
		5732	to be started (attached to an event loop) before they can receive events.
		5733
		5734	=back
		5735
3938	=head1 AUTHOR	5736	=head1 AUTHOR
3939		5737
3940	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5738	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5739	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3941		5740

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