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Revision 1.461 by root, Wed Jan 22 12:15:52 2020 UTC

		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
75	While this document tries to be as complete as possible in documenting	77	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	78	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	79	on event-based programming, nor will it introduce event-based programming
78	with libev.	80	with libev.
79		81
80	Familarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	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>.
82		92
83	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
84		94
85	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
86	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
…		…
95	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
96	watcher.	106	watcher.
97		107
98	=head2 FEATURES	108	=head2 FEATURES
99		109
100	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>
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port
102	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>
103	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	with customised rescheduling (C<ev_periodic>), synchronous signals	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	(C<ev_signal>), process status change events (C<ev_child>), and event	115	timers (C<ev_timer>), absolute timers with customised rescheduling
106	watchers dealing with the event loop mechanism itself (C<ev_idle>,	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	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
108	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
109	(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>).
110		121
111	It also is quite fast (see this	122	It also is quite fast (see this
112	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
113	for example).	124	for example).
114		125
…		…
117	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)
118	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
119	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
120	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
121	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
122	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
123	this argument.	134	this argument.
124		135
125	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
126		137
127	Libev represents time as a single floating point number, representing	138	Libev represents time as a single floating point number, representing
128	the (fractional) number of seconds since the (POSIX) epoch (somewhere	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
129	near the beginning of 1970, details are complicated, don't ask). This	140	somewhere near the beginning of 1970, details are complicated, don't
130	type is called C<ev_tstamp>, which is what you should use too. It usually	141	ask). This type is called C<ev_tstamp>, which is what you should use
131	aliases to the C<double> type in C. When you need to do any calculations	142	too. It usually aliases to the C<double> type in C. When you need to do
132	on 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
133	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
134	throughout libev.	146	time differences (e.g. delays) throughout libev.
135		147
136	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
137		149
138	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
139	and internal errors (bugs).	151	and internal errors (bugs).
…		…
147	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
148	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,
149	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
150	the libev caller and need to be fixed there.	162	the libev caller and need to be fixed there.
151		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
152	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
153	extensive consistency checking code. These do not trigger under normal
154	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.
155		171
156		172
157	=head1 GLOBAL FUNCTIONS	173	=head1 GLOBAL FUNCTIONS
158		174
159	These functions can be called anytime, even before initialising the	175	These functions can be called anytime, even before initialising the
…		…
163		179
164	=item ev_tstamp ev_time ()	180	=item ev_tstamp ev_time ()
165		181
166	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
167	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
168	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>.
169		186
170	=item ev_sleep (ev_tstamp interval)	187	=item ev_sleep (ev_tstamp interval)
171		188
172	Sleep for the given interval: The current thread will be blocked until	189	Sleep for the given interval: The current thread will be blocked
173	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
174	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 >>).
175		198
176	=item int ev_version_major ()	199	=item int ev_version_major ()
177		200
178	=item int ev_version_minor ()	201	=item int ev_version_minor ()
179		202
…		…
190	as this indicates an incompatible change. Minor versions are usually	213	as this indicates an incompatible change. Minor versions are usually
191	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
192	not a problem.	215	not a problem.
193		216
194	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
195	version.	218	version (note, however, that this will not detect other ABI mismatches,
		219	such as LFS or reentrancy).
196		220
197	assert (("libev version mismatch",	221	assert (("libev version mismatch",
198	ev_version_major () == EV_VERSION_MAJOR	222	ev_version_major () == EV_VERSION_MAJOR
199	&& ev_version_minor () >= EV_VERSION_MINOR));	223	&& ev_version_minor () >= EV_VERSION_MINOR));
200		224
…		…
211	assert (("sorry, no epoll, no sex",	235	assert (("sorry, no epoll, no sex",
212	ev_supported_backends () & EVBACKEND_EPOLL));	236	ev_supported_backends () & EVBACKEND_EPOLL));
213		237
214	=item unsigned int ev_recommended_backends ()	238	=item unsigned int ev_recommended_backends ()
215		239
216	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
217	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
218	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
219	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
220	(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
221	libev will probe for if you specify no backends explicitly.	246	probe for if you specify no backends explicitly.
222		247
223	=item unsigned int ev_embeddable_backends ()	248	=item unsigned int ev_embeddable_backends ()
224		249
225	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
226	is the theoretical, all-platform, value. To find which backends	251	value is platform-specific but can include backends not available on the
227	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
228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	253	the current system, you would need to look at C<ev_embeddable_backends ()
229	recommended ones.	254	& ev_supported_backends ()>, likewise for recommended ones.
230		255
231	See the description of C<ev_embed> watchers for more info.	256	See the description of C<ev_embed> watchers for more info.
232		257
233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	258	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
234		259
235	Sets the allocation function to use (the prototype is similar - the	260	Sets the allocation function to use (the prototype is similar - the
236	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
237	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
238	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
…		…
244		269
245	You could override this function in high-availability programs to, say,	270	You could override this function in high-availability programs to, say,
246	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,
247	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.
248		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
249	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
250	retries (example requires a standards-compliant C<realloc>).	289	retries.
251		290
252	static void *	291	static void *
253	persistent_realloc (void *ptr, size_t size)	292	persistent_realloc (void *ptr, size_t size)
254	{	293	{
		294	if (!size)
		295	{
		296	free (ptr);
		297	return 0;
		298	}
		299
255	for (;;)	300	for (;;)
256	{	301	{
257	void *newptr = realloc (ptr, size);	302	void *newptr = realloc (ptr, size);
258		303
259	if (newptr)	304	if (newptr)
…		…
264	}	309	}
265		310
266	...	311	...
267	ev_set_allocator (persistent_realloc);	312	ev_set_allocator (persistent_realloc);
268		313
269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	314	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
270		315
271	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
272	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
273	indicating the system call or subsystem causing the problem. If this	318	indicating the system call or subsystem causing the problem. If this
274	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
…		…
286	}	331	}
287		332
288	...	333	...
289	ev_set_syserr_cb (fatal_error);	334	ev_set_syserr_cb (fatal_error);
290		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
291	=back	349	=back
292		350
293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	351	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
294		352
295	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
296	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
297	I<function>).	355	libev 3 had an C<ev_loop> function colliding with the struct name).
298		356
299	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
300	supports signals and child events, and dynamically created loops which do	358	supports child process events, and dynamically created event loops which
301	not.	359	do not.
302		360
303	=over 4	361	=over 4
304		362
305	=item struct ev_loop *ev_default_loop (unsigned int flags)	363	=item struct ev_loop *ev_default_loop (unsigned int flags)
306		364
307	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
308	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
309	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
310	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".
311		375
312	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
313	function.	377	function (or via the C<EV_DEFAULT> macro).
314		378
315	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
316	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
317	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).
318		383
319	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,
320	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
321	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
322	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
323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	388	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
324	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.
325		408
326	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
327	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>).
328		411
329	The following flags are supported:	412	The following flags are supported:
…		…
339		422
340	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
341	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
342	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	425	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
343	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
344	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
345	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).
346		431
347	=item C<EVFLAG_FORKCHECK>	432	=item C<EVFLAG_FORKCHECK>
348		433
349	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
350	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.
351	enabling this flag.
352		436
353	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,
354	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
355	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
356	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
357	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
358	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).
359		444
360	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
361	forget about forgetting to tell libev about forking) when you use this	446	forget about forgetting to tell libev about forking, although you still
362	flag.	447	have to ignore C<SIGPIPE>) when you use this flag.
363		448
364	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>
365	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.
366		495
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	496	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		497
369	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
370	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,
…		…
395	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
396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	525	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
397		526
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	527	=item C<EVBACKEND_EPOLL> (value 4, Linux)
399		528
		529	Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9
		530	kernels).
		531
400	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
401	but it scales phenomenally better. While poll and select usually scale	533	it scales phenomenally better. While poll and select usually scale like
402	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
403	epoll scales either O(1) or O(active_fds).	535	fd), epoll scales either O(1) or O(active_fds).
404		536
405	The epoll mechanism deserves honorable mention as the most misdesigned	537	The epoll mechanism deserves honorable mention as the most misdesigned
406	of the more advanced event mechanisms: mere annoyances include silently	538	of the more advanced event mechanisms: mere annoyances include silently
407	dropping file descriptors, requiring a system call per change per file	539	dropping file descriptors, requiring a system call per change per file
408	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
409	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
410	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
411	take considerable time (one syscall per file descriptor) and is of course	545	set, which can take considerable time (one syscall per file descriptor)
412	hard to detect.	546	and is of course hard to detect.
413		547
414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	548	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
415	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
416	I<different> file descriptors (even already closed ones, so one cannot	550	totally I<different> file descriptors (even already closed ones, so
417	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
418	on SMP systems). Libev tries to counter these spurious notifications by	552	(especially on SMP systems). Libev tries to counter these spurious
419	employing an additional generation counter and comparing that against the	553	notifications by employing an additional generation counter and comparing
420	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...
421		564
422	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
423	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
424	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
425	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
…		…
437	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
438	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
439	the usage. So sad.	582	the usage. So sad.
440		583
441	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
442	all kernel versions tested so far.	585	a lot of kernel revisions, but probably(!) works in current versions.
443		586
444	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
445	C<EVBACKEND_POLL>.	588	C<EVBACKEND_POLL>.
446		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
447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	634	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
448		635
449	Kqueue deserves special mention, as at the time of this writing, it	636	Kqueue deserves special mention, as at the time this backend was
450	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
451	with anything but sockets and pipes, except on Darwin, where of course	638	work reliably with anything but sockets and pipes, except on Darwin,
452	it's completely useless). Unlike epoll, however, whose brokenness	639	where of course it's completely useless). Unlike epoll, however, whose
453	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)
454	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
455	"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
456	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
457	system like NetBSD.	644	known-to-be-good (-enough) system like NetBSD.
458		645
459	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
460	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
461	the target platform). See C<ev_embed> watchers for more info.	648	the target platform). See C<ev_embed> watchers for more info.
462		649
463	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
464	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
465	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
466	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
467	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
468	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
469	cases	656	drops fds silently in similarly hard-to-detect cases.
470		657
471	This backend usually performs well under most conditions.	658	This backend usually performs well under most conditions.
472		659
473	While nominally embeddable in other event loops, this doesn't work	660	While nominally embeddable in other event loops, this doesn't work
474	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
…		…
491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	678	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
492		679
493	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,
494	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)).
495		682
496	Please note that Solaris event ports can deliver a lot of spurious
497	notifications, so you need to use non-blocking I/O or other means to avoid
498	blocking when no data (or space) is available.
499
500	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
501	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
502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	685	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
503	might perform better.	686	might perform better.
504		687
505	On the positive side, with the exception of the spurious readiness	688	On the positive side, this backend actually performed fully to
506	notifications, this backend actually performed fully to specification
507	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
508	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.
509		702
510	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
511	C<EVBACKEND_POLL>.	704	C<EVBACKEND_POLL>.
512		705
513	=item C<EVBACKEND_ALL>	706	=item C<EVBACKEND_ALL>
514		707
515	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
516	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
517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	710	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
518		711
519	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).
520		721
521	=back	722	=back
522		723
523	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,
524	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
525	specified, all backends in C<ev_recommended_backends ()> will be tried.	726	here). If none are specified, all backends in C<ev_recommended_backends
526		727	()> will be tried.
527	Example: This is the most typical usage.
528
529	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
531
532	Example: Restrict libev to the select and poll backends, and do not allow
533	environment settings to be taken into account:
534
535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
536
537	Example: Use whatever libev has to offer, but make sure that kqueue is
538	used if available (warning, breaks stuff, best use only with your own
539	private event loop and only if you know the OS supports your types of
540	fds):
541
542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
543
544	=item struct ev_loop *ev_loop_new (unsigned int flags)
545
546	Similar to C<ev_default_loop>, but always creates a new event loop that is
547	always distinct from the default loop. Unlike the default loop, it cannot
548	handle signal and child watchers, and attempts to do so will be greeted by
549	undefined behaviour (or a failed assertion if assertions are enabled).
550
551	Note that this function I<is> thread-safe, and the recommended way to use
552	libev with threads is indeed to create one loop per thread, and using the
553	default loop in the "main" or "initial" thread.
554		728
555	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.
556		730
557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	731	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
558	if (!epoller)	732	if (!epoller)
559	fatal ("no epoll found here, maybe it hides under your chair");	733	fatal ("no epoll found here, maybe it hides under your chair");
560		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
561	=item ev_default_destroy ()	746	=item ev_loop_destroy (loop)
562		747
563	Destroys the default loop again (frees all memory and kernel state	748	Destroys an event loop object (frees all memory and kernel state
564	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
565	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
566	responsibility to either stop all watchers cleanly yourself I<before>	751	responsibility to either stop all watchers cleanly yourself I<before>
567	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
568	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
…		…
570		755
571	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
572	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
573	as signal and child watchers) would need to be stopped manually.	758	as signal and child watchers) would need to be stopped manually.
574		759
575	In general it is not advisable to call this function except in the	760	This function is normally used on loop objects allocated by
576	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.
577	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>
578	C<ev_loop_new> and C<ev_loop_destroy>).	767	and C<ev_loop_destroy>.
579		768
580	=item ev_loop_destroy (loop)	769	=item ev_loop_fork (loop)
581		770
582	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.
584
585	=item ev_default_fork ()
586
587	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
588	to reinitialise the kernel state for backends that have one. Despite the	772	to reinitialise the kernel state for backends that have one. Despite
589	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
590	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
591	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
592	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.
593		785
594	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
595	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
596	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).
597		792
598	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
599	it just in case after a fork. To make this easy, the function will fit in	794	it just in case after a fork.
600	quite nicely into a call to C<pthread_atfork>:
601		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	...
602	pthread_atfork (0, 0, ev_default_fork);	806	pthread_atfork (0, 0, post_fork_child);
603
604	=item ev_loop_fork (loop)
605
606	Like C<ev_default_fork>, but acts on an event loop created by
607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
608	after fork that you want to re-use in the child, and how you do this is
609	entirely your own problem.
610		807
611	=item int ev_is_default_loop (loop)	808	=item int ev_is_default_loop (loop)
612		809
613	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
614	otherwise.	811	otherwise.
615		812
616	=item unsigned int ev_loop_count (loop)	813	=item unsigned int ev_iteration (loop)
617		814
618	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
619	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>
620	happily wraps around with enough iterations.	817	and happily wraps around with enough iterations.
621		818
622	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
623	"ticks" the number of loop iterations), as it roughly corresponds with	820	"ticks" the number of loop iterations), as it roughly corresponds with
624	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.
625		823
626	=item unsigned int ev_loop_depth (loop)	824	=item unsigned int ev_depth (loop)
627		825
628	Returns the number of times C<ev_loop> was entered minus the number of	826	Returns the number of times C<ev_run> was entered minus the number of
629	times C<ev_loop> was exited, in other words, the recursion depth.	827	times C<ev_run> was exited normally, in other words, the recursion depth.
630		828
631	Outside C<ev_loop>, this number is zero. In a callback, this number is	829	Outside C<ev_run>, this number is zero. In a callback, this number is
632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	830	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
633	in which case it is higher.	831	in which case it is higher.
634		832
635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	833	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
636	etc.), doesn't count as exit.	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.
637		837
638	=item unsigned int ev_backend (loop)	838	=item unsigned int ev_backend (loop)
639		839
640	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
641	use.	841	use.
…		…
650		850
651	=item ev_now_update (loop)	851	=item ev_now_update (loop)
652		852
653	Establishes the current time by querying the kernel, updating the time	853	Establishes the current time by querying the kernel, updating the time
654	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
655	is usually done automatically within C<ev_loop ()>.	855	is usually done automatically within C<ev_run ()>.
656		856
657	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
658	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
659	the current time is a good idea.	859	the current time is a good idea.
660		860
661	See also L<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.
662		862
663	=item ev_suspend (loop)	863	=item ev_suspend (loop)
664		864
665	=item ev_resume (loop)	865	=item ev_resume (loop)
666		866
667	These two functions suspend and resume a loop, for use when the loop is	867	These two functions suspend and resume an event loop, for use when the
668	not used for a while and timeouts should not be processed.	868	loop is not used for a while and timeouts should not be processed.
669		869
670	A typical use case would be an interactive program such as a game: When	870	A typical use case would be an interactive program such as a game: When
671	the user presses C<^Z> to suspend the game and resumes it an hour later it	871	the user presses C<^Z> to suspend the game and resumes it an hour later it
672	would be best to handle timeouts as if no time had actually passed while	872	would be best to handle timeouts as if no time had actually passed while
673	the program was suspended. This can be achieved by calling C<ev_suspend>	873	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
675	C<ev_resume> directly afterwards to resume timer processing.	875	C<ev_resume> directly afterwards to resume timer processing.
676		876
677	Effectively, all C<ev_timer> watchers will be delayed by the time spend	877	Effectively, all C<ev_timer> watchers will be delayed by the time spend
678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	878	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
679	will be rescheduled (that is, they will lose any events that would have	879	will be rescheduled (that is, they will lose any events that would have
680	occured while suspended).	880	occurred while suspended).
681		881
682	After calling C<ev_suspend> you B<must not> call I<any> function on the	882	After calling C<ev_suspend> you B<must not> call I<any> function on the
683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	883	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
684	without a previous call to C<ev_suspend>.	884	without a previous call to C<ev_suspend>.
685		885
686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	886	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
687	event loop time (see C<ev_now_update>).	887	event loop time (see C<ev_now_update>).
688		888
689	=item ev_loop (loop, int flags)	889	=item bool ev_run (loop, int flags)
690		890
691	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
692	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
693	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>.
694		896
695	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
696	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.
697		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
698	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
699	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
700	finished (especially in interactive programs), but having a program	907	finished (especially in interactive programs), but having a program
701	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
702	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
703	beauty.	910	beauty.
704		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
705	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
706	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
707	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
708	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.
709		922
710	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
711	necessary) and will handle those and any already outstanding ones. It	924	necessary) and will handle those and any already outstanding ones. It
712	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
713	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
714	user-registered callback will be called), and will return after one	927	user-registered callback will be called), and will return after one
715	iteration of the loop.	928	iteration of the loop.
716		929
717	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
718	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
719	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
720	usually a better approach for this kind of thing.	933	usually a better approach for this kind of thing.
721		934
722	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):
723		938
		939	- Increment loop depth.
		940	- Reset the ev_break status.
724	- Before the first iteration, call any pending watchers.	941	- Before the first iteration, call any pending watchers.
		942	LOOP:
725	* If EVFLAG_FORKCHECK was used, check for a fork.	943	- If EVFLAG_FORKCHECK was used, check for a fork.
726	- 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.
727	- Queue and call all prepare watchers.	945	- Queue and call all prepare watchers.
		946	- If ev_break was called, goto FINISH.
728	- If we have been forked, detach and recreate the kernel state	947	- If we have been forked, detach and recreate the kernel state
729	as to not disturb the other process.	948	as to not disturb the other process.
730	- Update the kernel state with all outstanding changes.	949	- Update the kernel state with all outstanding changes.
731	- Update the "event loop time" (ev_now ()).	950	- Update the "event loop time" (ev_now ()).
732	- Calculate for how long to sleep or block, if at all	951	- Calculate for how long to sleep or block, if at all
733	(active idle watchers, EVLOOP_NONBLOCK or not having	952	(active idle watchers, EVRUN_NOWAIT or not having
734	any active watchers at all will result in not sleeping).	953	any active watchers at all will result in not sleeping).
735	- 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.
736	- Block the process, waiting for any events.	956	- Block the process, waiting for any events.
737	- Queue all outstanding I/O (fd) events.	957	- Queue all outstanding I/O (fd) events.
738	- 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.
739	- Queue all expired timers.	959	- Queue all expired timers.
740	- Queue all expired periodics.	960	- Queue all expired periodics.
741	- Unless any events are pending now, queue all idle watchers.	961	- Queue all idle watchers with priority higher than that of pending events.
742	- Queue all check watchers.	962	- Queue all check watchers.
743	- 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).
744	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
745	be handled here by queueing them when their watcher gets executed.	965	be handled here by queueing them when their watcher gets executed.
746	- 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
747	were used, or there are no active watchers, return, otherwise	967	were used, or there are no active watchers, goto FINISH, otherwise
748	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.
749		973
750	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
751	anymore.	975	anymore.
752		976
753	... queue jobs here, make sure they register event watchers as long	977	... queue jobs here, make sure they register event watchers as long
754	... 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..)
755	ev_loop (my_loop, 0);	979	ev_run (my_loop, 0);
756	... jobs done or somebody called unloop. yeah!	980	... jobs done or somebody called break. yeah!
757		981
758	=item ev_unloop (loop, how)	982	=item ev_break (loop, how)
759		983
760	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
761	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
762	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
763	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.
764		988
765	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>.
766		990
767	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.
768		993
769	=item ev_ref (loop)	994	=item ev_ref (loop)
770		995
771	=item ev_unref (loop)	996	=item ev_unref (loop)
772		997
773	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
774	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
775	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.
776		1001
777	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
778	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>
779	stopping it.	1005	before stopping it.
780		1006
781	As an example, libev itself uses this for its internal signal pipe: It	1007	As an example, libev itself uses this for its internal signal pipe: It
782	is not visible to the libev user and should not keep C<ev_loop> from	1008	is not visible to the libev user and should not keep C<ev_run> from
783	exiting if no event watchers registered by it are active. It is also an	1009	exiting if no event watchers registered by it are active. It is also an
784	excellent way to do this for generic recurring timers or from within	1010	excellent way to do this for generic recurring timers or from within
785	third-party libraries. Just remember to I<unref after start> and I<ref	1011	third-party libraries. Just remember to I<unref after start> and I<ref
786	before stop> (but only if the watcher wasn't active before, or was active	1012	before stop> (but only if the watcher wasn't active before, or was active
787	before, respectively. Note also that libev might stop watchers itself	1013	before, respectively. Note also that libev might stop watchers itself
788	(e.g. non-repeating timers) in which case you have to C<ev_ref>	1014	(e.g. non-repeating timers) in which case you have to C<ev_ref>
789	in the callback).	1015	in the callback).
790		1016
791	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>
792	running when nothing else is active.	1018	running when nothing else is active.
793		1019
794	ev_signal exitsig;	1020	ev_signal exitsig;
795	ev_signal_init (&exitsig, sig_cb, SIGINT);	1021	ev_signal_init (&exitsig, sig_cb, SIGINT);
796	ev_signal_start (loop, &exitsig);	1022	ev_signal_start (loop, &exitsig);
797	evf_unref (loop);	1023	ev_unref (loop);
798		1024
799	Example: For some weird reason, unregister the above signal handler again.	1025	Example: For some weird reason, unregister the above signal handler again.
800		1026
801	ev_ref (loop);	1027	ev_ref (loop);
802	ev_signal_stop (loop, &exitsig);	1028	ev_signal_stop (loop, &exitsig);
…		…
822	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.
823		1049
824	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
825	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,
826	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
827	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
828	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1054	introduce an additional C<ev_sleep ()> call into most loop iterations. The
829	sleep time ensures that libev will not poll for I/O events more often then	1055	sleep time ensures that libev will not poll for I/O events more often then
830	once per this interval, on average.	1056	once per this interval, on average (as long as the host time resolution is
		1057	good enough).
831		1058
832	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
833	to spend more time collecting timeouts, at the expense of increased	1060	to spend more time collecting timeouts, at the expense of increased
834	latency/jitter/inexactness (the watcher callback will be called	1061	latency/jitter/inexactness (the watcher callback will be called
835	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
…		…
841	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>,
842	as this approaches the timing granularity of most systems. Note that if	1069	as this approaches the timing granularity of most systems. Note that if
843	you do transactions with the outside world and you can't increase the	1070	you do transactions with the outside world and you can't increase the
844	parallelity, then this setting will limit your transaction rate (if you	1071	parallelity, then this setting will limit your transaction rate (if you
845	need to poll once per transaction and the I/O collect interval is 0.01,	1072	need to poll once per transaction and the I/O collect interval is 0.01,
846	then you can't do more than 100 transations per second).	1073	then you can't do more than 100 transactions per second).
847		1074
848	Setting the I<timeout collect interval> can improve the opportunity for	1075	Setting the I<timeout collect interval> can improve the opportunity for
849	saving power, as the program will "bundle" timer callback invocations that	1076	saving power, as the program will "bundle" timer callback invocations that
850	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
851	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
…		…
856	more often than 100 times per second:	1083	more often than 100 times per second:
857		1084
858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	1085	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1086	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		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
861	=item ev_loop_verify (loop)	1157	=item ev_verify (loop)
862		1158
863	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
864	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
865	through all internal structures and checks them for validity. If anything	1161	through all internal structures and checks them for validity. If anything
866	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
…		…
877		1173
878	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
879	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
880	watchers and C<ev_io_start> for I/O watchers.	1176	watchers and C<ev_io_start> for I/O watchers.
881		1177
882	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
883	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
884	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:
885		1182
886	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)
887	{	1184	{
888	ev_io_stop (w);	1185	ev_io_stop (w);
889	ev_unloop (loop, EVUNLOOP_ALL);	1186	ev_break (loop, EVBREAK_ALL);
890	}	1187	}
891		1188
892	struct ev_loop *loop = ev_default_loop (0);	1189	struct ev_loop *loop = ev_default_loop (0);
893		1190
894	ev_io stdin_watcher;	1191	ev_io stdin_watcher;
895		1192
896	ev_init (&stdin_watcher, my_cb);	1193	ev_init (&stdin_watcher, my_cb);
897	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1194	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
898	ev_io_start (loop, &stdin_watcher);	1195	ev_io_start (loop, &stdin_watcher);
899		1196
900	ev_loop (loop, 0);	1197	ev_run (loop, 0);
901		1198
902	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
903	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
904	stack).	1201	stack).
905		1202
906	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>
907	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).
908		1205
909	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
910	(watcher *, callback)>, which expects a callback to be provided. This	1207	*, callback)>, which expects a callback to be provided. This callback is
911	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
912	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
913	is readable and/or writable).	1210	and/or writable).
914		1211
915	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 *, ...) >>
916	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
917	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<<
918	ev_TYPE_init (watcher *, callback, ...) >>.	1215	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
921	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
922	*) >>), 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
923	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.	1220	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
924		1221
925	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
926	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
927	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.
928		1226
929	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
930	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
931	third argument.	1229	third argument.
932		1230
…		…
941	=item C<EV_WRITE>	1239	=item C<EV_WRITE>
942		1240
943	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
944	writable.	1242	writable.
945		1243
946	=item C<EV_TIMEOUT>	1244	=item C<EV_TIMER>
947		1245
948	The C<ev_timer> watcher has timed out.	1246	The C<ev_timer> watcher has timed out.
949		1247
950	=item C<EV_PERIODIC>	1248	=item C<EV_PERIODIC>
951		1249
…		…
969		1267
970	=item C<EV_PREPARE>	1268	=item C<EV_PREPARE>
971		1269
972	=item C<EV_CHECK>	1270	=item C<EV_CHECK>
973		1271
974	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
975	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)
976	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
977	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
978	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
979	(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
980	C<ev_loop> from blocking).	1283	blocking).
981		1284
982	=item C<EV_EMBED>	1285	=item C<EV_EMBED>
983		1286
984	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.
985		1288
986	=item C<EV_FORK>	1289	=item C<EV_FORK>
987		1290
988	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
989	C<ev_fork>).	1292	C<ev_fork>).
		1293
		1294	=item C<EV_CLEANUP>
		1295
		1296	The event loop is about to be destroyed (see C<ev_cleanup>).
990		1297
991	=item C<EV_ASYNC>	1298	=item C<EV_ASYNC>
992		1299
993	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>).
994		1301
…		…
1041		1348
1042	ev_io w;	1349	ev_io w;
1043	ev_init (&w, my_cb);	1350	ev_init (&w, my_cb);
1044	ev_io_set (&w, STDIN_FILENO, EV_READ);	1351	ev_io_set (&w, STDIN_FILENO, EV_READ);
1045		1352
1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1353	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1047		1354
1048	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
1049	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
1050	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
1051	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
…		…
1064		1371
1065	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.
1066		1373
1067	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1374	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1068		1375
1069	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1376	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1070		1377
1071	Starts (activates) the given watcher. Only active watchers will receive	1378	Starts (activates) the given watcher. Only active watchers will receive
1072	events. If the watcher is already active nothing will happen.	1379	events. If the watcher is already active nothing will happen.
1073		1380
1074	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
1075	whole section.	1382	whole section.
1076		1383
1077	ev_io_start (EV_DEFAULT_UC, &w);	1384	ev_io_start (EV_DEFAULT_UC, &w);
1078		1385
1079	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1386	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1080		1387
1081	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
1082	the watcher was active or not).	1389	the watcher was active or not).
1083		1390
1084	It is possible that stopped watchers are pending - for example,	1391	It is possible that stopped watchers are pending - for example,
…		…
1104		1411
1105	=item callback ev_cb (ev_TYPE *watcher)	1412	=item callback ev_cb (ev_TYPE *watcher)
1106		1413
1107	Returns the callback currently set on the watcher.	1414	Returns the callback currently set on the watcher.
1108		1415
1109	=item ev_cb_set (ev_TYPE *watcher, callback)	1416	=item ev_set_cb (ev_TYPE *watcher, callback)
1110		1417
1111	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
1112	(modulo threads).	1419	(modulo threads).
1113		1420
1114	=item ev_set_priority (ev_TYPE *watcher, priority)	1421	=item ev_set_priority (ev_TYPE *watcher, int priority)
1115		1422
1116	=item int ev_priority (ev_TYPE *watcher)	1423	=item int ev_priority (ev_TYPE *watcher)
1117		1424
1118	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
1119	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>
…		…
1132	or might not have been clamped to the valid range.	1439	or might not have been clamped to the valid range.
1133		1440
1134	The default priority used by watchers when no priority has been set is	1441	The default priority used by watchers when no priority has been set is
1135	always C<0>, which is supposed to not be too high and not be too low :).	1442	always C<0>, which is supposed to not be too high and not be too low :).
1136		1443
1137	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1444	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1138	priorities.	1445	priorities.
1139		1446
1140	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1447	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1141		1448
1142	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
…		…
1151	watcher isn't pending it does nothing and returns C<0>.	1458	watcher isn't pending it does nothing and returns C<0>.
1152		1459
1153	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
1154	callback to be invoked, which can be accomplished with this function.	1461	callback to be invoked, which can be accomplished with this function.
1155		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
1156	=back	1477	=back
1157		1478
		1479	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1480	OWN COMPOSITE WATCHERS> idioms.
1158		1481
1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1482	=head2 WATCHER STATES
1160		1483
1161	Each watcher has, by default, a member C<void *data> that you can change	1484	There are various watcher states mentioned throughout this manual -
1162	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
1163	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
1164	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".
1165	member, you can also "subclass" the watcher type and provide your own
1166	data:
1167		1488
1168	struct my_io	1489	=over 4
1169	{
1170	ev_io io;
1171	int otherfd;
1172	void *somedata;
1173	struct whatever *mostinteresting;
1174	};
1175		1490
1176	...	1491	=item initialised
1177	struct my_io w;
1178	ev_io_init (&w.io, my_cb, fd, EV_READ);
1179		1492
1180	And since your callback will be called with a pointer to the watcher, you	1493	Before a watcher can be registered with the event loop it has to be
1181	can cast it back to your own type:	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.
1182		1496
1183	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1497	In this state it is simply some block of memory that is suitable for
1184	{	1498	use in an event loop. It can be moved around, freed, reused etc. at
1185	struct my_io *w = (struct my_io *)w_;	1499	will - as long as you either keep the memory contents intact, or call
1186	...	1500	C<ev_TYPE_init> again.
1187	}
1188		1501
1189	More interesting and less C-conformant ways of casting your callback type	1502	=item started/running/active
1190	instead have been omitted.
1191		1503
1192	Another common scenario is to use some data structure with multiple	1504	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1193	embedded watchers:	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.
1194		1509
1195	struct my_biggy	1510	=item pending
1196	{
1197	int some_data;
1198	ev_timer t1;
1199	ev_timer t2;
1200	}
1201		1511
1202	In this case getting the pointer to C<my_biggy> is a bit more	1512	If a watcher is active and libev determines that an event it is interested
1203	complicated: Either you store the address of your C<my_biggy> struct	1513	in has occurred (such as a timer expiring), it will become pending. It will
1204	in the C<data> member of the watcher (for woozies), or you need to use	1514	stay in this pending state until either it is stopped or its callback is
1205	some pointer arithmetic using C<offsetof> inside your watchers (for real	1515	about to be invoked, so it is not normally pending inside the watcher
1206	programmers):	1516	callback.
1207		1517
1208	#include <stddef.h>	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.
1209		1524
1210	static void	1525	It is also possible to feed an event on a watcher that is not active (e.g.
1211	t1_cb (EV_P_ ev_timer *w, int revents)	1526	via C<ev_feed_event>), in which case it becomes pending without being
1212	{	1527	active.
1213	struct my_biggy big = (struct my_biggy *)
1214	(((char *)w) - offsetof (struct my_biggy, t1));
1215	}
1216		1528
1217	static void	1529	=item stopped
1218	t2_cb (EV_P_ ev_timer *w, int revents)	1530
1219	{	1531	A watcher can be stopped implicitly by libev (in which case it might still
1220	struct my_biggy big = (struct my_biggy *)	1532	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1221	(((char *)w) - offsetof (struct my_biggy, t2));	1533	latter will clear any pending state the watcher might be in, regardless
1222	}	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
1223		1543
1224	=head2 WATCHER PRIORITY MODELS	1544	=head2 WATCHER PRIORITY MODELS
1225		1545
1226	Many event loops support I<watcher priorities>, which are usually small	1546	Many event loops support I<watcher priorities>, which are usually small
1227	integers that influence the ordering of event callback invocation	1547	integers that influence the ordering of event callback invocation
1228	between watchers in some way, all else being equal.	1548	between watchers in some way, all else being equal.
1229		1549
1230	In libev, Watcher priorities can be set using C<ev_set_priority>. See its	1550	In libev, watcher priorities can be set using C<ev_set_priority>. See its
1231	description for the more technical details such as the actual priority	1551	description for the more technical details such as the actual priority
1232	range.	1552	range.
1233		1553
1234	There are two common ways how these these priorities are being interpreted	1554	There are two common ways how these these priorities are being interpreted
1235	by event loops:	1555	by event loops:
…		…
1270		1590
1271	For example, to emulate how many other event libraries handle priorities,	1591	For example, to emulate how many other event libraries handle priorities,
1272	you can associate an C<ev_idle> watcher to each such watcher, and in	1592	you can associate an C<ev_idle> watcher to each such watcher, and in
1273	the normal watcher callback, you just start the idle watcher. The real	1593	the normal watcher callback, you just start the idle watcher. The real
1274	processing is done in the idle watcher callback. This causes libev to	1594	processing is done in the idle watcher callback. This causes libev to
1275	continously poll and process kernel event data for the watcher, but when	1595	continuously poll and process kernel event data for the watcher, but when
1276	the lock-out case is known to be rare (which in turn is rare :), this is	1596	the lock-out case is known to be rare (which in turn is rare :), this is
1277	workable.	1597	workable.
1278		1598
1279	Usually, however, the lock-out model implemented that way will perform	1599	Usually, however, the lock-out model implemented that way will perform
1280	miserably under the type of load it was designed to handle. In that case,	1600	miserably under the type of load it was designed to handle. In that case,
…		…
1294	{	1614	{
1295	// stop the I/O watcher, we received the event, but	1615	// stop the I/O watcher, we received the event, but
1296	// are not yet ready to handle it.	1616	// are not yet ready to handle it.
1297	ev_io_stop (EV_A_ w);	1617	ev_io_stop (EV_A_ w);
1298		1618
1299	// start the idle watcher to ahndle the actual event.	1619	// start the idle watcher to handle the actual event.
1300	// it will not be executed as long as other watchers	1620	// it will not be executed as long as other watchers
1301	// with the default priority are receiving events.	1621	// with the default priority are receiving events.
1302	ev_idle_start (EV_A_ &idle);	1622	ev_idle_start (EV_A_ &idle);
1303	}	1623	}
1304		1624
…		…
1329		1649
1330	This section describes each watcher in detail, but will not repeat	1650	This section describes each watcher in detail, but will not repeat
1331	information given in the last section. Any initialisation/set macros,	1651	information given in the last section. Any initialisation/set macros,
1332	functions and members specific to the watcher type are explained.	1652	functions and members specific to the watcher type are explained.
1333		1653
1334	Members are additionally marked with either I<[read-only]>, meaning that,	1654	Most members are additionally marked with either I<[read-only]>, meaning
1335	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
1336	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
1337	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
1338	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
1339	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
1340	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
1341	not crash or malfunction in any way.	1661	not crash or malfunction in any way.
1342		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.
1343		1665
1344	=head2 C<ev_io> - is this file descriptor readable or writable?	1666	=head2 C<ev_io> - is this file descriptor readable or writable?
1345		1667
1346	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
1347	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
…		…
1354	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
1355	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
1356	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
1357	required if you know what you are doing).	1679	required if you know what you are doing).
1358		1680
1359	If you cannot use non-blocking mode, then force the use of a
1360	known-to-be-good backend (at the time of this writing, this includes only
1361	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1362	descriptors for which non-blocking operation makes no sense (such as
1363	files) - libev doesn't guarentee any specific behaviour in that case.
1364
1365	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
1366	receive "spurious" readiness notifications, that is your callback might	1682	receive "spurious" readiness notifications, that is, your callback might
1367	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
1368	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
1369	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
1370	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
1371	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1372	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1687	preferable to a program hanging until some data arrives.
1373		1688
1374	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
1375	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
1376	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
1377	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
1378	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
1379	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
1380	indefinitely.	1695	indefinitely.
1381		1696
1382	But really, best use non-blocking mode.	1697	But really, best use non-blocking mode.
1383		1698
1384	=head3 The special problem of disappearing file descriptors	1699	=head3 The special problem of disappearing file descriptors
1385		1700
1386	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
1387	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
1388	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
1389	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
1390	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
1391	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,
1392	fact, a different file descriptor.	1707	in fact, a different file descriptor.
1393		1708
1394	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
1395	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
1396	will assume that this is potentially a new file descriptor, otherwise	1711	will assume that this is potentially a new file descriptor, otherwise
1397	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
…		…
1411		1726
1412	There is no workaround possible except not registering events	1727	There is no workaround possible except not registering events
1413	for potentially C<dup ()>'ed file descriptors, or to resort to	1728	for potentially C<dup ()>'ed file descriptors, or to resort to
1414	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1729	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1415		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
1416	=head3 The special problem of fork	1764	=head3 The special problem of fork
1417		1765
1418	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 ()>
1419	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
1420	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.
1421		1770
1422	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
1423	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
1424	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1773	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1425	C<EVBACKEND_POLL>.
1426		1774
1427	=head3 The special problem of SIGPIPE	1775	=head3 The special problem of SIGPIPE
1428		1776
1429	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>:
1430	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
…		…
1433		1781
1434	So when you encounter spurious, unexplained daemon exits, make sure you	1782	So when you encounter spurious, unexplained daemon exits, make sure you
1435	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
1436	somewhere, as that would have given you a big clue).	1784	somewhere, as that would have given you a big clue).
1437		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.
1438		1824
1439	=head3 Watcher-Specific Functions	1825	=head3 Watcher-Specific Functions
1440		1826
1441	=over 4	1827	=over 4
1442		1828
…		…
1446		1832
1447	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
1448	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> or
1449	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.	1835	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1450		1836
1451	=item int fd [read-only]	1837	=item ev_io_modify (ev_io *, int events)
1452		1838
1453	The file descriptor being watched.	1839	Similar to C<ev_io_set>, but only changes the event mask. Using this might
		1840	be faster with some backends, as libev can assume that the C<fd> still
		1841	refers to the same underlying file description, something it cannot do
		1842	when using C<ev_io_set>.
1454		1843
		1844	=item int fd [no-modify]
		1845
		1846	The file descriptor being watched. While it can be read at any time, you
		1847	must not modify this member even when the watcher is stopped - always use
		1848	C<ev_io_set> for that.
		1849
1455	=item int events [read-only]	1850	=item int events [no-modify]
1456		1851
1457	The events being watched.	1852	The set of events the fd is being watched for, among other flags. Remember
		1853	that this is a bit set - to test for C<EV_READ>, use C<< w->events &
		1854	EV_READ >>, and similarly for C<EV_WRITE>.
		1855
		1856	As with C<fd>, you must not modify this member even when the watcher is
		1857	stopped, always use C<ev_io_set> or C<ev_io_modify> for that.
1458		1858
1459	=back	1859	=back
1460		1860
1461	=head3 Examples	1861	=head3 Examples
1462		1862
…		…
1474	...	1874	...
1475	struct ev_loop *loop = ev_default_init (0);	1875	struct ev_loop *loop = ev_default_init (0);
1476	ev_io stdin_readable;	1876	ev_io stdin_readable;
1477	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1877	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1478	ev_io_start (loop, &stdin_readable);	1878	ev_io_start (loop, &stdin_readable);
1479	ev_loop (loop, 0);	1879	ev_run (loop, 0);
1480		1880
1481		1881
1482	=head2 C<ev_timer> - relative and optionally repeating timeouts	1882	=head2 C<ev_timer> - relative and optionally repeating timeouts
1483		1883
1484	Timer watchers are simple relative timers that generate an event after a	1884	Timer watchers are simple relative timers that generate an event after a
…		…
1490	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1890	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1491	monotonic clock option helps a lot here).	1891	monotonic clock option helps a lot here).
1492		1892
1493	The callback is guaranteed to be invoked only I<after> its timeout has	1893	The callback is guaranteed to be invoked only I<after> its timeout has
1494	passed (not I<at>, so on systems with very low-resolution clocks this	1894	passed (not I<at>, so on systems with very low-resolution clocks this
1495	might introduce a small delay). If multiple timers become ready during the	1895	might introduce a small delay, see "the special problem of being too
		1896	early", below). If multiple timers become ready during the same loop
1496	same loop iteration then the ones with earlier time-out values are invoked	1897	iteration then the ones with earlier time-out values are invoked before
1497	before ones of the same priority with later time-out values (but this is	1898	ones of the same priority with later time-out values (but this is no
1498	no longer true when a callback calls C<ev_loop> recursively).	1899	longer true when a callback calls C<ev_run> recursively).
1499		1900
1500	=head3 Be smart about timeouts	1901	=head3 Be smart about timeouts
1501		1902
1502	Many real-world problems involve some kind of timeout, usually for error	1903	Many real-world problems involve some kind of timeout, usually for error
1503	recovery. A typical example is an HTTP request - if the other side hangs,	1904	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1578		1979
1579	In this case, it would be more efficient to leave the C<ev_timer> alone,	1980	In this case, it would be more efficient to leave the C<ev_timer> alone,
1580	but remember the time of last activity, and check for a real timeout only	1981	but remember the time of last activity, and check for a real timeout only
1581	within the callback:	1982	within the callback:
1582		1983
		1984	ev_tstamp timeout = 60.;
1583	ev_tstamp last_activity; // time of last activity	1985	ev_tstamp last_activity; // time of last activity
		1986	ev_timer timer;
1584		1987
1585	static void	1988	static void
1586	callback (EV_P_ ev_timer *w, int revents)	1989	callback (EV_P_ ev_timer *w, int revents)
1587	{	1990	{
1588	ev_tstamp now = ev_now (EV_A);	1991	// calculate when the timeout would happen
1589	ev_tstamp timeout = last_activity + 60.;	1992	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1590		1993
1591	// if last_activity + 60. is older than now, we did time out	1994	// if negative, it means we the timeout already occurred
1592	if (timeout < now)	1995	if (after < 0.)
1593	{	1996	{
1594	// timeout occured, take action	1997	// timeout occurred, take action
1595	}	1998	}
1596	else	1999	else
1597	{	2000	{
1598	// callback was invoked, but there was some activity, re-arm	2001	// callback was invoked, but there was some recent
1599	// the watcher to fire in last_activity + 60, which is	2002	// activity. simply restart the timer to time out
1600	// guaranteed to be in the future, so "again" is positive:	2003	// after "after" seconds, which is the earliest time
1601	w->repeat = timeout - now;	2004	// the timeout can occur.
		2005	ev_timer_set (w, after, 0.);
1602	ev_timer_again (EV_A_ w);	2006	ev_timer_start (EV_A_ w);
1603	}	2007	}
1604	}	2008	}
1605		2009
1606	To summarise the callback: first calculate the real timeout (defined	2010	To summarise the callback: first calculate in how many seconds the
1607	as "60 seconds after the last activity"), then check if that time has	2011	timeout will occur (by calculating the absolute time when it would occur,
1608	been reached, which means something I<did>, in fact, time out. Otherwise	2012	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1609	the callback was invoked too early (C<timeout> is in the future), so	2013	(EV_A)> from that).
1610	re-schedule the timer to fire at that future time, to see if maybe we have
1611	a timeout then.
1612		2014
1613	Note how C<ev_timer_again> is used, taking advantage of the	2015	If this value is negative, then we are already past the timeout, i.e. we
1614	C<ev_timer_again> optimisation when the timer is already running.	2016	timed out, and need to do whatever is needed in this case.
		2017
		2018	Otherwise, we now the earliest time at which the timeout would trigger,
		2019	and simply start the timer with this timeout value.
		2020
		2021	In other words, each time the callback is invoked it will check whether
		2022	the timeout occurred. If not, it will simply reschedule itself to check
		2023	again at the earliest time it could time out. Rinse. Repeat.
1615		2024
1616	This scheme causes more callback invocations (about one every 60 seconds	2025	This scheme causes more callback invocations (about one every 60 seconds
1617	minus half the average time between activity), but virtually no calls to	2026	minus half the average time between activity), but virtually no calls to
1618	libev to change the timeout.	2027	libev to change the timeout.
1619		2028
1620	To start the timer, simply initialise the watcher and set C<last_activity>	2029	To start the machinery, simply initialise the watcher and set
1621	to the current time (meaning we just have some activity :), then call the	2030	C<last_activity> to the current time (meaning there was some activity just
1622	callback, which will "do the right thing" and start the timer:	2031	now), then call the callback, which will "do the right thing" and start
		2032	the timer:
1623		2033
		2034	last_activity = ev_now (EV_A);
1624	ev_init (timer, callback);	2035	ev_init (&timer, callback);
1625	last_activity = ev_now (loop);	2036	callback (EV_A_ &timer, 0);
1626	callback (loop, timer, EV_TIMEOUT);
1627		2037
1628	And when there is some activity, simply store the current time in	2038	When there is some activity, simply store the current time in
1629	C<last_activity>, no libev calls at all:	2039	C<last_activity>, no libev calls at all:
1630		2040
		2041	if (activity detected)
1631	last_actiivty = ev_now (loop);	2042	last_activity = ev_now (EV_A);
		2043
		2044	When your timeout value changes, then the timeout can be changed by simply
		2045	providing a new value, stopping the timer and calling the callback, which
		2046	will again do the right thing (for example, time out immediately :).
		2047
		2048	timeout = new_value;
		2049	ev_timer_stop (EV_A_ &timer);
		2050	callback (EV_A_ &timer, 0);
1632		2051
1633	This technique is slightly more complex, but in most cases where the	2052	This technique is slightly more complex, but in most cases where the
1634	time-out is unlikely to be triggered, much more efficient.	2053	time-out is unlikely to be triggered, much more efficient.
1635
1636	Changing the timeout is trivial as well (if it isn't hard-coded in the
1637	callback :) - just change the timeout and invoke the callback, which will
1638	fix things for you.
1639		2054
1640	=item 4. Wee, just use a double-linked list for your timeouts.	2055	=item 4. Wee, just use a double-linked list for your timeouts.
1641		2056
1642	If there is not one request, but many thousands (millions...), all	2057	If there is not one request, but many thousands (millions...), all
1643	employing some kind of timeout with the same timeout value, then one can	2058	employing some kind of timeout with the same timeout value, then one can
…		…
1670	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2085	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1671	rather complicated, but extremely efficient, something that really pays	2086	rather complicated, but extremely efficient, something that really pays
1672	off after the first million or so of active timers, i.e. it's usually	2087	off after the first million or so of active timers, i.e. it's usually
1673	overkill :)	2088	overkill :)
1674		2089
		2090	=head3 The special problem of being too early
		2091
		2092	If you ask a timer to call your callback after three seconds, then
		2093	you expect it to be invoked after three seconds - but of course, this
		2094	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2095	guaranteed to any precision by libev - imagine somebody suspending the
		2096	process with a STOP signal for a few hours for example.
		2097
		2098	So, libev tries to invoke your callback as soon as possible I<after> the
		2099	delay has occurred, but cannot guarantee this.
		2100
		2101	A less obvious failure mode is calling your callback too early: many event
		2102	loops compare timestamps with a "elapsed delay >= requested delay", but
		2103	this can cause your callback to be invoked much earlier than you would
		2104	expect.
		2105
		2106	To see why, imagine a system with a clock that only offers full second
		2107	resolution (think windows if you can't come up with a broken enough OS
		2108	yourself). If you schedule a one-second timer at the time 500.9, then the
		2109	event loop will schedule your timeout to elapse at a system time of 500
		2110	(500.9 truncated to the resolution) + 1, or 501.
		2111
		2112	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2113	501" and invoke the callback 0.1s after it was started, even though a
		2114	one-second delay was requested - this is being "too early", despite best
		2115	intentions.
		2116
		2117	This is the reason why libev will never invoke the callback if the elapsed
		2118	delay equals the requested delay, but only when the elapsed delay is
		2119	larger than the requested delay. In the example above, libev would only invoke
		2120	the callback at system time 502, or 1.1s after the timer was started.
		2121
		2122	So, while libev cannot guarantee that your callback will be invoked
		2123	exactly when requested, it I<can> and I<does> guarantee that the requested
		2124	delay has actually elapsed, or in other words, it always errs on the "too
		2125	late" side of things.
		2126
1675	=head3 The special problem of time updates	2127	=head3 The special problem of time updates
1676		2128
1677	Establishing the current time is a costly operation (it usually takes at	2129	Establishing the current time is a costly operation (it usually takes
1678	least two system calls): EV therefore updates its idea of the current	2130	at least one system call): EV therefore updates its idea of the current
1679	time only before and after C<ev_loop> collects new events, which causes a	2131	time only before and after C<ev_run> collects new events, which causes a
1680	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2132	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1681	lots of events in one iteration.	2133	lots of events in one iteration.
1682		2134
1683	The relative timeouts are calculated relative to the C<ev_now ()>	2135	The relative timeouts are calculated relative to the C<ev_now ()>
1684	time. This is usually the right thing as this timestamp refers to the time	2136	time. This is usually the right thing as this timestamp refers to the time
1685	of the event triggering whatever timeout you are modifying/starting. If	2137	of the event triggering whatever timeout you are modifying/starting. If
1686	you suspect event processing to be delayed and you I<need> to base the	2138	you suspect event processing to be delayed and you I<need> to base the
1687	timeout on the current time, use something like this to adjust for this:	2139	timeout on the current time, use something like the following to adjust
		2140	for it:
1688		2141
1689	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2142	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1690		2143
1691	If the event loop is suspended for a long time, you can also force an	2144	If the event loop is suspended for a long time, you can also force an
1692	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2145	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1693	()>.	2146	()>, although that will push the event time of all outstanding events
		2147	further into the future.
		2148
		2149	=head3 The special problem of unsynchronised clocks
		2150
		2151	Modern systems have a variety of clocks - libev itself uses the normal
		2152	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2153	jumps).
		2154
		2155	Neither of these clocks is synchronised with each other or any other clock
		2156	on the system, so C<ev_time ()> might return a considerably different time
		2157	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2158	a call to C<gettimeofday> might return a second count that is one higher
		2159	than a directly following call to C<time>.
		2160
		2161	The moral of this is to only compare libev-related timestamps with
		2162	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2163	a second or so.
		2164
		2165	One more problem arises due to this lack of synchronisation: if libev uses
		2166	the system monotonic clock and you compare timestamps from C<ev_time>
		2167	or C<ev_now> from when you started your timer and when your callback is
		2168	invoked, you will find that sometimes the callback is a bit "early".
		2169
		2170	This is because C<ev_timer>s work in real time, not wall clock time, so
		2171	libev makes sure your callback is not invoked before the delay happened,
		2172	I<measured according to the real time>, not the system clock.
		2173
		2174	If your timeouts are based on a physical timescale (e.g. "time out this
		2175	connection after 100 seconds") then this shouldn't bother you as it is
		2176	exactly the right behaviour.
		2177
		2178	If you want to compare wall clock/system timestamps to your timers, then
		2179	you need to use C<ev_periodic>s, as these are based on the wall clock
		2180	time, where your comparisons will always generate correct results.
		2181
		2182	=head3 The special problems of suspended animation
		2183
		2184	When you leave the server world it is quite customary to hit machines that
		2185	can suspend/hibernate - what happens to the clocks during such a suspend?
		2186
		2187	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2188	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2189	to run until the system is suspended, but they will not advance while the
		2190	system is suspended. That means, on resume, it will be as if the program
		2191	was frozen for a few seconds, but the suspend time will not be counted
		2192	towards C<ev_timer> when a monotonic clock source is used. The real time
		2193	clock advanced as expected, but if it is used as sole clocksource, then a
		2194	long suspend would be detected as a time jump by libev, and timers would
		2195	be adjusted accordingly.
		2196
		2197	I would not be surprised to see different behaviour in different between
		2198	operating systems, OS versions or even different hardware.
		2199
		2200	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2201	time jump in the monotonic clocks and the realtime clock. If the program
		2202	is suspended for a very long time, and monotonic clock sources are in use,
		2203	then you can expect C<ev_timer>s to expire as the full suspension time
		2204	will be counted towards the timers. When no monotonic clock source is in
		2205	use, then libev will again assume a timejump and adjust accordingly.
		2206
		2207	It might be beneficial for this latter case to call C<ev_suspend>
		2208	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2209	deterministic behaviour in this case (you can do nothing against
		2210	C<SIGSTOP>).
1694		2211
1695	=head3 Watcher-Specific Functions and Data Members	2212	=head3 Watcher-Specific Functions and Data Members
1696		2213
1697	=over 4	2214	=over 4
1698		2215
1699	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2216	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1700		2217
1701	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2218	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1702		2219
1703	Configure the timer to trigger after C<after> seconds. If C<repeat>	2220	Configure the timer to trigger after C<after> seconds (fractional and
1704	is C<0.>, then it will automatically be stopped once the timeout is	2221	negative values are supported). If C<repeat> is C<0.>, then it will
1705	reached. If it is positive, then the timer will automatically be	2222	automatically be stopped once the timeout is reached. If it is positive,
1706	configured to trigger again C<repeat> seconds later, again, and again,	2223	then the timer will automatically be configured to trigger again C<repeat>
1707	until stopped manually.	2224	seconds later, again, and again, until stopped manually.
1708		2225
1709	The timer itself will do a best-effort at avoiding drift, that is, if	2226	The timer itself will do a best-effort at avoiding drift, that is, if
1710	you configure a timer to trigger every 10 seconds, then it will normally	2227	you configure a timer to trigger every 10 seconds, then it will normally
1711	trigger at exactly 10 second intervals. If, however, your program cannot	2228	trigger at exactly 10 second intervals. If, however, your program cannot
1712	keep up with the timer (because it takes longer than those 10 seconds to	2229	keep up with the timer (because it takes longer than those 10 seconds to
1713	do stuff) the timer will not fire more than once per event loop iteration.	2230	do stuff) the timer will not fire more than once per event loop iteration.
1714		2231
1715	=item ev_timer_again (loop, ev_timer *)	2232	=item ev_timer_again (loop, ev_timer *)
1716		2233
1717	This will act as if the timer timed out and restart it again if it is	2234	This will act as if the timer timed out, and restarts it again if it is
1718	repeating. The exact semantics are:	2235	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2236	timeout to the C<repeat> value and calling C<ev_timer_start>.
1719		2237
		2238	The exact semantics are as in the following rules, all of which will be
		2239	applied to the watcher:
		2240
		2241	=over 4
		2242
1720	If the timer is pending, its pending status is cleared.	2243	=item If the timer is pending, the pending status is always cleared.
1721		2244
1722	If the timer is started but non-repeating, stop it (as if it timed out).	2245	=item If the timer is started but non-repeating, stop it (as if it timed
		2246	out, without invoking it).
1723		2247
1724	If the timer is repeating, either start it if necessary (with the	2248	=item If the timer is repeating, make the C<repeat> value the new timeout
1725	C<repeat> value), or reset the running timer to the C<repeat> value.	2249	and start the timer, if necessary.
1726		2250
		2251	=back
		2252
1727	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2253	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1728	usage example.	2254	usage example.
		2255
		2256	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2257
		2258	Returns the remaining time until a timer fires. If the timer is active,
		2259	then this time is relative to the current event loop time, otherwise it's
		2260	the timeout value currently configured.
		2261
		2262	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2263	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2264	will return C<4>. When the timer expires and is restarted, it will return
		2265	roughly C<7> (likely slightly less as callback invocation takes some time,
		2266	too), and so on.
1729		2267
1730	=item ev_tstamp repeat [read-write]	2268	=item ev_tstamp repeat [read-write]
1731		2269
1732	The current C<repeat> value. Will be used each time the watcher times out	2270	The current C<repeat> value. Will be used each time the watcher times out
1733	or C<ev_timer_again> is called, and determines the next timeout (if any),	2271	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1759	}	2297	}
1760		2298
1761	ev_timer mytimer;	2299	ev_timer mytimer;
1762	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2300	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1763	ev_timer_again (&mytimer); /* start timer */	2301	ev_timer_again (&mytimer); /* start timer */
1764	ev_loop (loop, 0);	2302	ev_run (loop, 0);
1765		2303
1766	// and in some piece of code that gets executed on any "activity":	2304	// and in some piece of code that gets executed on any "activity":
1767	// reset the timeout to start ticking again at 10 seconds	2305	// reset the timeout to start ticking again at 10 seconds
1768	ev_timer_again (&mytimer);	2306	ev_timer_again (&mytimer);
1769		2307
…		…
1773	Periodic watchers are also timers of a kind, but they are very versatile	2311	Periodic watchers are also timers of a kind, but they are very versatile
1774	(and unfortunately a bit complex).	2312	(and unfortunately a bit complex).
1775		2313
1776	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2314	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1777	relative time, the physical time that passes) but on wall clock time	2315	relative time, the physical time that passes) but on wall clock time
1778	(absolute time, the thing you can read on your calender or clock). The	2316	(absolute time, the thing you can read on your calendar or clock). The
1779	difference is that wall clock time can run faster or slower than real	2317	difference is that wall clock time can run faster or slower than real
1780	time, and time jumps are not uncommon (e.g. when you adjust your	2318	time, and time jumps are not uncommon (e.g. when you adjust your
1781	wrist-watch).	2319	wrist-watch).
1782		2320
1783	You can tell a periodic watcher to trigger after some specific point	2321	You can tell a periodic watcher to trigger after some specific point
…		…
1788	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2326	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1789	it, as it uses a relative timeout).	2327	it, as it uses a relative timeout).
1790		2328
1791	C<ev_periodic> watchers can also be used to implement vastly more complex	2329	C<ev_periodic> watchers can also be used to implement vastly more complex
1792	timers, such as triggering an event on each "midnight, local time", or	2330	timers, such as triggering an event on each "midnight, local time", or
1793	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2331	other complicated rules. This cannot easily be done with C<ev_timer>
1794	those cannot react to time jumps.	2332	watchers, as those cannot react to time jumps.
1795		2333
1796	As with timers, the callback is guaranteed to be invoked only when the	2334	As with timers, the callback is guaranteed to be invoked only when the
1797	point in time where it is supposed to trigger has passed. If multiple	2335	point in time where it is supposed to trigger has passed. If multiple
1798	timers become ready during the same loop iteration then the ones with	2336	timers become ready during the same loop iteration then the ones with
1799	earlier time-out values are invoked before ones with later time-out values	2337	earlier time-out values are invoked before ones with later time-out values
1800	(but this is no longer true when a callback calls C<ev_loop> recursively).	2338	(but this is no longer true when a callback calls C<ev_run> recursively).
1801		2339
1802	=head3 Watcher-Specific Functions and Data Members	2340	=head3 Watcher-Specific Functions and Data Members
1803		2341
1804	=over 4	2342	=over 4
1805		2343
…		…
1840		2378
1841	Another way to think about it (for the mathematically inclined) is that	2379	Another way to think about it (for the mathematically inclined) is that
1842	C<ev_periodic> will try to run the callback in this mode at the next possible	2380	C<ev_periodic> will try to run the callback in this mode at the next possible
1843	time where C<time = offset (mod interval)>, regardless of any time jumps.	2381	time where C<time = offset (mod interval)>, regardless of any time jumps.
1844		2382
1845	For numerical stability it is preferable that the C<offset> value is near	2383	The C<interval> I<MUST> be positive, and for numerical stability, the
1846	C<ev_now ()> (the current time), but there is no range requirement for	2384	interval value should be higher than C<1/8192> (which is around 100
1847	this value, and in fact is often specified as zero.	2385	microseconds) and C<offset> should be higher than C<0> and should have
		2386	at most a similar magnitude as the current time (say, within a factor of
		2387	ten). Typical values for offset are, in fact, C<0> or something between
		2388	C<0> and C<interval>, which is also the recommended range.
1848		2389
1849	Note also that there is an upper limit to how often a timer can fire (CPU	2390	Note also that there is an upper limit to how often a timer can fire (CPU
1850	speed for example), so if C<interval> is very small then timing stability	2391	speed for example), so if C<interval> is very small then timing stability
1851	will of course deteriorate. Libev itself tries to be exact to be about one	2392	will of course deteriorate. Libev itself tries to be exact to be about one
1852	millisecond (if the OS supports it and the machine is fast enough).	2393	millisecond (if the OS supports it and the machine is fast enough).
…		…
1882		2423
1883	NOTE: I<< This callback must always return a time that is higher than or	2424	NOTE: I<< This callback must always return a time that is higher than or
1884	equal to the passed C<now> value >>.	2425	equal to the passed C<now> value >>.
1885		2426
1886	This can be used to create very complex timers, such as a timer that	2427	This can be used to create very complex timers, such as a timer that
1887	triggers on "next midnight, local time". To do this, you would calculate the	2428	triggers on "next midnight, local time". To do this, you would calculate
1888	next midnight after C<now> and return the timestamp value for this. How	2429	the next midnight after C<now> and return the timestamp value for
1889	you do this is, again, up to you (but it is not trivial, which is the main	2430	this. Here is a (completely untested, no error checking) example on how to
1890	reason I omitted it as an example).	2431	do this:
		2432
		2433	#include <time.h>
		2434
		2435	static ev_tstamp
		2436	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2437	{
		2438	time_t tnow = (time_t)now;
		2439	struct tm tm;
		2440	localtime_r (&tnow, &tm);
		2441
		2442	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2443	++tm.tm_mday; // midnight next day
		2444
		2445	return mktime (&tm);
		2446	}
		2447
		2448	Note: this code might run into trouble on days that have more then two
		2449	midnights (beginning and end).
1891		2450
1892	=back	2451	=back
1893		2452
1894	=item ev_periodic_again (loop, ev_periodic *)	2453	=item ev_periodic_again (loop, ev_periodic *)
1895		2454
…		…
1933	Example: Call a callback every hour, or, more precisely, whenever the	2492	Example: Call a callback every hour, or, more precisely, whenever the
1934	system time is divisible by 3600. The callback invocation times have	2493	system time is divisible by 3600. The callback invocation times have
1935	potentially a lot of jitter, but good long-term stability.	2494	potentially a lot of jitter, but good long-term stability.
1936		2495
1937	static void	2496	static void
1938	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2497	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1939	{	2498	{
1940	... its now a full hour (UTC, or TAI or whatever your clock follows)	2499	... its now a full hour (UTC, or TAI or whatever your clock follows)
1941	}	2500	}
1942		2501
1943	ev_periodic hourly_tick;	2502	ev_periodic hourly_tick;
…		…
1960		2519
1961	ev_periodic hourly_tick;	2520	ev_periodic hourly_tick;
1962	ev_periodic_init (&hourly_tick, clock_cb,	2521	ev_periodic_init (&hourly_tick, clock_cb,
1963	fmod (ev_now (loop), 3600.), 3600., 0);	2522	fmod (ev_now (loop), 3600.), 3600., 0);
1964	ev_periodic_start (loop, &hourly_tick);	2523	ev_periodic_start (loop, &hourly_tick);
1965		2524
1966		2525
1967	=head2 C<ev_signal> - signal me when a signal gets signalled!	2526	=head2 C<ev_signal> - signal me when a signal gets signalled!
1968		2527
1969	Signal watchers will trigger an event when the process receives a specific	2528	Signal watchers will trigger an event when the process receives a specific
1970	signal one or more times. Even though signals are very asynchronous, libev	2529	signal one or more times. Even though signals are very asynchronous, libev
1971	will try it's best to deliver signals synchronously, i.e. as part of the	2530	will try its best to deliver signals synchronously, i.e. as part of the
1972	normal event processing, like any other event.	2531	normal event processing, like any other event.
1973		2532
1974	If you want signals asynchronously, just use C<sigaction> as you would	2533	If you want signals to be delivered truly asynchronously, just use
1975	do without libev and forget about sharing the signal. You can even use	2534	C<sigaction> as you would do without libev and forget about sharing
1976	C<ev_async> from a signal handler to synchronously wake up an event loop.	2535	the signal. You can even use C<ev_async> from a signal handler to
		2536	synchronously wake up an event loop.
1977		2537
1978	You can configure as many watchers as you like per signal. Only when the	2538	You can configure as many watchers as you like for the same signal, but
1979	first watcher gets started will libev actually register a signal handler	2539	only within the same loop, i.e. you can watch for C<SIGINT> in your
1980	with the kernel (thus it coexists with your own signal handlers as long as	2540	default loop and for C<SIGIO> in another loop, but you cannot watch for
1981	you don't register any with libev for the same signal). Similarly, when	2541	C<SIGINT> in both the default loop and another loop at the same time. At
1982	the last signal watcher for a signal is stopped, libev will reset the	2542	the moment, C<SIGCHLD> is permanently tied to the default loop.
1983	signal handler to SIG_DFL (regardless of what it was set to before).	2543
		2544	Only after the first watcher for a signal is started will libev actually
		2545	register something with the kernel. It thus coexists with your own signal
		2546	handlers as long as you don't register any with libev for the same signal.
1984		2547
1985	If possible and supported, libev will install its handlers with	2548	If possible and supported, libev will install its handlers with
1986	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2549	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1987	interrupted. If you have a problem with system calls getting interrupted by	2550	not be unduly interrupted. If you have a problem with system calls getting
1988	signals you can block all signals in an C<ev_check> watcher and unblock	2551	interrupted by signals you can block all signals in an C<ev_check> watcher
1989	them in an C<ev_prepare> watcher.	2552	and unblock them in an C<ev_prepare> watcher.
		2553
		2554	=head3 The special problem of inheritance over fork/execve/pthread_create
		2555
		2556	Both the signal mask (C<sigprocmask>) and the signal disposition
		2557	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2558	stopping it again), that is, libev might or might not block the signal,
		2559	and might or might not set or restore the installed signal handler (but
		2560	see C<EVFLAG_NOSIGMASK>).
		2561
		2562	While this does not matter for the signal disposition (libev never
		2563	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2564	C<execve>), this matters for the signal mask: many programs do not expect
		2565	certain signals to be blocked.
		2566
		2567	This means that before calling C<exec> (from the child) you should reset
		2568	the signal mask to whatever "default" you expect (all clear is a good
		2569	choice usually).
		2570
		2571	The simplest way to ensure that the signal mask is reset in the child is
		2572	to install a fork handler with C<pthread_atfork> that resets it. That will
		2573	catch fork calls done by libraries (such as the libc) as well.
		2574
		2575	In current versions of libev, the signal will not be blocked indefinitely
		2576	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2577	the window of opportunity for problems, it will not go away, as libev
		2578	I<has> to modify the signal mask, at least temporarily.
		2579
		2580	So I can't stress this enough: I<If you do not reset your signal mask when
		2581	you expect it to be empty, you have a race condition in your code>. This
		2582	is not a libev-specific thing, this is true for most event libraries.
		2583
		2584	=head3 The special problem of threads signal handling
		2585
		2586	POSIX threads has problematic signal handling semantics, specifically,
		2587	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2588	threads in a process block signals, which is hard to achieve.
		2589
		2590	When you want to use sigwait (or mix libev signal handling with your own
		2591	for the same signals), you can tackle this problem by globally blocking
		2592	all signals before creating any threads (or creating them with a fully set
		2593	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2594	loops. Then designate one thread as "signal receiver thread" which handles
		2595	these signals. You can pass on any signals that libev might be interested
		2596	in by calling C<ev_feed_signal>.
1990		2597
1991	=head3 Watcher-Specific Functions and Data Members	2598	=head3 Watcher-Specific Functions and Data Members
1992		2599
1993	=over 4	2600	=over 4
1994		2601
…		…
2010	Example: Try to exit cleanly on SIGINT.	2617	Example: Try to exit cleanly on SIGINT.
2011		2618
2012	static void	2619	static void
2013	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2620	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2014	{	2621	{
2015	ev_unloop (loop, EVUNLOOP_ALL);	2622	ev_break (loop, EVBREAK_ALL);
2016	}	2623	}
2017		2624
2018	ev_signal signal_watcher;	2625	ev_signal signal_watcher;
2019	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2626	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2020	ev_signal_start (loop, &signal_watcher);	2627	ev_signal_start (loop, &signal_watcher);
…		…
2033		2640
2034	Only the default event loop is capable of handling signals, and therefore	2641	Only the default event loop is capable of handling signals, and therefore
2035	you can only register child watchers in the default event loop.	2642	you can only register child watchers in the default event loop.
2036		2643
2037	Due to some design glitches inside libev, child watchers will always be	2644	Due to some design glitches inside libev, child watchers will always be
2038	handled at maximum priority (their priority is set to EV_MAXPRI by libev)	2645	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2646	libev)
2039		2647
2040	=head3 Process Interaction	2648	=head3 Process Interaction
2041		2649
2042	Libev grabs C<SIGCHLD> as soon as the default event loop is	2650	Libev grabs C<SIGCHLD> as soon as the default event loop is
2043	initialised. This is necessary to guarantee proper behaviour even if	2651	initialised. This is necessary to guarantee proper behaviour even if the
2044	the first child watcher is started after the child exits. The occurrence	2652	first child watcher is started after the child exits. The occurrence
2045	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2653	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2046	synchronously as part of the event loop processing. Libev always reaps all	2654	synchronously as part of the event loop processing. Libev always reaps all
2047	children, even ones not watched.	2655	children, even ones not watched.
2048		2656
2049	=head3 Overriding the Built-In Processing	2657	=head3 Overriding the Built-In Processing
…		…
2059	=head3 Stopping the Child Watcher	2667	=head3 Stopping the Child Watcher
2060		2668
2061	Currently, the child watcher never gets stopped, even when the	2669	Currently, the child watcher never gets stopped, even when the
2062	child terminates, so normally one needs to stop the watcher in the	2670	child terminates, so normally one needs to stop the watcher in the
2063	callback. Future versions of libev might stop the watcher automatically	2671	callback. Future versions of libev might stop the watcher automatically
2064	when a child exit is detected.	2672	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2673	problem).
2065		2674
2066	=head3 Watcher-Specific Functions and Data Members	2675	=head3 Watcher-Specific Functions and Data Members
2067		2676
2068	=over 4	2677	=over 4
2069		2678
…		…
2127		2736
2128	=head2 C<ev_stat> - did the file attributes just change?	2737	=head2 C<ev_stat> - did the file attributes just change?
2129		2738
2130	This watches a file system path for attribute changes. That is, it calls	2739	This watches a file system path for attribute changes. That is, it calls
2131	C<stat> on that path in regular intervals (or when the OS says it changed)	2740	C<stat> on that path in regular intervals (or when the OS says it changed)
2132	and sees if it changed compared to the last time, invoking the callback if	2741	and sees if it changed compared to the last time, invoking the callback
2133	it did.	2742	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2743	happen after the watcher has been started will be reported.
2134		2744
2135	The path does not need to exist: changing from "path exists" to "path does	2745	The path does not need to exist: changing from "path exists" to "path does
2136	not exist" is a status change like any other. The condition "path does not	2746	not exist" is a status change like any other. The condition "path does not
2137	exist" (or more correctly "path cannot be stat'ed") is signified by the	2747	exist" (or more correctly "path cannot be stat'ed") is signified by the
2138	C<st_nlink> field being zero (which is otherwise always forced to be at	2748	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2368	Apart from keeping your process non-blocking (which is a useful	2978	Apart from keeping your process non-blocking (which is a useful
2369	effect on its own sometimes), idle watchers are a good place to do	2979	effect on its own sometimes), idle watchers are a good place to do
2370	"pseudo-background processing", or delay processing stuff to after the	2980	"pseudo-background processing", or delay processing stuff to after the
2371	event loop has handled all outstanding events.	2981	event loop has handled all outstanding events.
2372		2982
		2983	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2984
		2985	As long as there is at least one active idle watcher, libev will never
		2986	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2987	For this to work, the idle watcher doesn't need to be invoked at all - the
		2988	lowest priority will do.
		2989
		2990	This mode of operation can be useful together with an C<ev_check> watcher,
		2991	to do something on each event loop iteration - for example to balance load
		2992	between different connections.
		2993
		2994	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2995	example.
		2996
2373	=head3 Watcher-Specific Functions and Data Members	2997	=head3 Watcher-Specific Functions and Data Members
2374		2998
2375	=over 4	2999	=over 4
2376		3000
2377	=item ev_idle_init (ev_idle *, callback)	3001	=item ev_idle_init (ev_idle *, callback)
…		…
2388	callback, free it. Also, use no error checking, as usual.	3012	callback, free it. Also, use no error checking, as usual.
2389		3013
2390	static void	3014	static void
2391	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	3015	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2392	{	3016	{
		3017	// stop the watcher
		3018	ev_idle_stop (loop, w);
		3019
		3020	// now we can free it
2393	free (w);	3021	free (w);
		3022
2394	// now do something you wanted to do when the program has	3023	// now do something you wanted to do when the program has
2395	// no longer anything immediate to do.	3024	// no longer anything immediate to do.
2396	}	3025	}
2397		3026
2398	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3027	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2400	ev_idle_start (loop, idle_watcher);	3029	ev_idle_start (loop, idle_watcher);
2401		3030
2402		3031
2403	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3032	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2404		3033
2405	Prepare and check watchers are usually (but not always) used in pairs:	3034	Prepare and check watchers are often (but not always) used in pairs:
2406	prepare watchers get invoked before the process blocks and check watchers	3035	prepare watchers get invoked before the process blocks and check watchers
2407	afterwards.	3036	afterwards.
2408		3037
2409	You I<must not> call C<ev_loop> or similar functions that enter	3038	You I<must not> call C<ev_run> (or similar functions that enter the
2410	the current event loop from either C<ev_prepare> or C<ev_check>	3039	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2411	watchers. Other loops than the current one are fine, however. The	3040	C<ev_check> watchers. Other loops than the current one are fine,
2412	rationale behind this is that you do not need to check for recursion in	3041	however. The rationale behind this is that you do not need to check
2413	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3042	for recursion in those watchers, i.e. the sequence will always be
2414	C<ev_check> so if you have one watcher of each kind they will always be	3043	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2415	called in pairs bracketing the blocking call.	3044	kind they will always be called in pairs bracketing the blocking call.
2416		3045
2417	Their main purpose is to integrate other event mechanisms into libev and	3046	Their main purpose is to integrate other event mechanisms into libev and
2418	their use is somewhat advanced. They could be used, for example, to track	3047	their use is somewhat advanced. They could be used, for example, to track
2419	variable changes, implement your own watchers, integrate net-snmp or a	3048	variable changes, implement your own watchers, integrate net-snmp or a
2420	coroutine library and lots more. They are also occasionally useful if	3049	coroutine library and lots more. They are also occasionally useful if
…		…
2438	with priority higher than or equal to the event loop and one coroutine	3067	with priority higher than or equal to the event loop and one coroutine
2439	of lower priority, but only once, using idle watchers to keep the event	3068	of lower priority, but only once, using idle watchers to keep the event
2440	loop from blocking if lower-priority coroutines are active, thus mapping	3069	loop from blocking if lower-priority coroutines are active, thus mapping
2441	low-priority coroutines to idle/background tasks).	3070	low-priority coroutines to idle/background tasks).
2442		3071
2443	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3072	When used for this purpose, it is recommended to give C<ev_check> watchers
2444	priority, to ensure that they are being run before any other watchers	3073	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2445	after the poll (this doesn't matter for C<ev_prepare> watchers).	3074	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3075	watchers).
2446		3076
2447	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3077	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2448	activate ("feed") events into libev. While libev fully supports this, they	3078	activate ("feed") events into libev. While libev fully supports this, they
2449	might get executed before other C<ev_check> watchers did their job. As	3079	might get executed before other C<ev_check> watchers did their job. As
2450	C<ev_check> watchers are often used to embed other (non-libev) event	3080	C<ev_check> watchers are often used to embed other (non-libev) event
2451	loops those other event loops might be in an unusable state until their	3081	loops those other event loops might be in an unusable state until their
2452	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3082	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2453	others).	3083	others).
		3084
		3085	=head3 Abusing an C<ev_check> watcher for its side-effect
		3086
		3087	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3088	useful because they are called once per event loop iteration. For
		3089	example, if you want to handle a large number of connections fairly, you
		3090	normally only do a bit of work for each active connection, and if there
		3091	is more work to do, you wait for the next event loop iteration, so other
		3092	connections have a chance of making progress.
		3093
		3094	Using an C<ev_check> watcher is almost enough: it will be called on the
		3095	next event loop iteration. However, that isn't as soon as possible -
		3096	without external events, your C<ev_check> watcher will not be invoked.
		3097
		3098	This is where C<ev_idle> watchers come in handy - all you need is a
		3099	single global idle watcher that is active as long as you have one active
		3100	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3101	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3102	invoked. Neither watcher alone can do that.
2454		3103
2455	=head3 Watcher-Specific Functions and Data Members	3104	=head3 Watcher-Specific Functions and Data Members
2456		3105
2457	=over 4	3106	=over 4
2458		3107
…		…
2582		3231
2583	if (timeout >= 0)	3232	if (timeout >= 0)
2584	// create/start timer	3233	// create/start timer
2585		3234
2586	// poll	3235	// poll
2587	ev_loop (EV_A_ 0);	3236	ev_run (EV_A_ 0);
2588		3237
2589	// stop timer again	3238	// stop timer again
2590	if (timeout >= 0)	3239	if (timeout >= 0)
2591	ev_timer_stop (EV_A_ &to);	3240	ev_timer_stop (EV_A_ &to);
2592		3241
…		…
2659		3308
2660	=over 4	3309	=over 4
2661		3310
2662	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3311	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2663		3312
2664	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3313	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2665		3314
2666	Configures the watcher to embed the given loop, which must be	3315	Configures the watcher to embed the given loop, which must be
2667	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3316	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2668	invoked automatically, otherwise it is the responsibility of the callback	3317	invoked automatically, otherwise it is the responsibility of the callback
2669	to invoke it (it will continue to be called until the sweep has been done,	3318	to invoke it (it will continue to be called until the sweep has been done,
2670	if you do not want that, you need to temporarily stop the embed watcher).	3319	if you do not want that, you need to temporarily stop the embed watcher).
2671		3320
2672	=item ev_embed_sweep (loop, ev_embed *)	3321	=item ev_embed_sweep (loop, ev_embed *)
2673		3322
2674	Make a single, non-blocking sweep over the embedded loop. This works	3323	Make a single, non-blocking sweep over the embedded loop. This works
2675	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3324	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2676	appropriate way for embedded loops.	3325	appropriate way for embedded loops.
2677		3326
2678	=item struct ev_loop *other [read-only]	3327	=item struct ev_loop *other [read-only]
2679		3328
2680	The embedded event loop.	3329	The embedded event loop.
…		…
2690	used).	3339	used).
2691		3340
2692	struct ev_loop *loop_hi = ev_default_init (0);	3341	struct ev_loop *loop_hi = ev_default_init (0);
2693	struct ev_loop *loop_lo = 0;	3342	struct ev_loop *loop_lo = 0;
2694	ev_embed embed;	3343	ev_embed embed;
2695		3344
2696	// see if there is a chance of getting one that works	3345	// see if there is a chance of getting one that works
2697	// (remember that a flags value of 0 means autodetection)	3346	// (remember that a flags value of 0 means autodetection)
2698	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3347	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2699	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3348	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2700	: 0;	3349	: 0;
…		…
2714	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3363	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2715		3364
2716	struct ev_loop *loop = ev_default_init (0);	3365	struct ev_loop *loop = ev_default_init (0);
2717	struct ev_loop *loop_socket = 0;	3366	struct ev_loop *loop_socket = 0;
2718	ev_embed embed;	3367	ev_embed embed;
2719		3368
2720	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3369	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2721	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3370	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2722	{	3371	{
2723	ev_embed_init (&embed, 0, loop_socket);	3372	ev_embed_init (&embed, 0, loop_socket);
2724	ev_embed_start (loop, &embed);	3373	ev_embed_start (loop, &embed);
…		…
2732		3381
2733	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3382	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2734		3383
2735	Fork watchers are called when a C<fork ()> was detected (usually because	3384	Fork watchers are called when a C<fork ()> was detected (usually because
2736	whoever is a good citizen cared to tell libev about it by calling	3385	whoever is a good citizen cared to tell libev about it by calling
2737	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3386	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2738	event loop blocks next and before C<ev_check> watchers are being called,	3387	and before C<ev_check> watchers are being called, and only in the child
2739	and only in the child after the fork. If whoever good citizen calling	3388	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2740	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3389	and calls it in the wrong process, the fork handlers will be invoked, too,
2741	handlers will be invoked, too, of course.	3390	of course.
2742		3391
2743	=head3 The special problem of life after fork - how is it possible?	3392	=head3 The special problem of life after fork - how is it possible?
2744		3393
2745	Most uses of C<fork()> consist of forking, then some simple calls to ste	3394	Most uses of C<fork ()> consist of forking, then some simple calls to set
2746	up/change the process environment, followed by a call to C<exec()>. This	3395	up/change the process environment, followed by a call to C<exec()>. This
2747	sequence should be handled by libev without any problems.	3396	sequence should be handled by libev without any problems.
2748		3397
2749	This changes when the application actually wants to do event handling	3398	This changes when the application actually wants to do event handling
2750	in the child, or both parent in child, in effect "continuing" after the	3399	in the child, or both parent in child, in effect "continuing" after the
…		…
2766	disadvantage of having to use multiple event loops (which do not support	3415	disadvantage of having to use multiple event loops (which do not support
2767	signal watchers).	3416	signal watchers).
2768		3417
2769	When this is not possible, or you want to use the default loop for	3418	When this is not possible, or you want to use the default loop for
2770	other reasons, then in the process that wants to start "fresh", call	3419	other reasons, then in the process that wants to start "fresh", call
2771	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3420	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2772	the default loop will "orphan" (not stop) all registered watchers, so you	3421	Destroying the default loop will "orphan" (not stop) all registered
2773	have to be careful not to execute code that modifies those watchers. Note	3422	watchers, so you have to be careful not to execute code that modifies
2774	also that in that case, you have to re-register any signal watchers.	3423	those watchers. Note also that in that case, you have to re-register any
		3424	signal watchers.
2775		3425
2776	=head3 Watcher-Specific Functions and Data Members	3426	=head3 Watcher-Specific Functions and Data Members
2777		3427
2778	=over 4	3428	=over 4
2779		3429
2780	=item ev_fork_init (ev_signal *, callback)	3430	=item ev_fork_init (ev_fork *, callback)
2781		3431
2782	Initialises and configures the fork watcher - it has no parameters of any	3432	Initialises and configures the fork watcher - it has no parameters of any
2783	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3433	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2784	believe me.	3434	really.
2785		3435
2786	=back	3436	=back
2787		3437
2788		3438
		3439	=head2 C<ev_cleanup> - even the best things end
		3440
		3441	Cleanup watchers are called just before the event loop is being destroyed
		3442	by a call to C<ev_loop_destroy>.
		3443
		3444	While there is no guarantee that the event loop gets destroyed, cleanup
		3445	watchers provide a convenient method to install cleanup hooks for your
		3446	program, worker threads and so on - you just to make sure to destroy the
		3447	loop when you want them to be invoked.
		3448
		3449	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3450	all other watchers, they do not keep a reference to the event loop (which
		3451	makes a lot of sense if you think about it). Like all other watchers, you
		3452	can call libev functions in the callback, except C<ev_cleanup_start>.
		3453
		3454	=head3 Watcher-Specific Functions and Data Members
		3455
		3456	=over 4
		3457
		3458	=item ev_cleanup_init (ev_cleanup *, callback)
		3459
		3460	Initialises and configures the cleanup watcher - it has no parameters of
		3461	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3462	pointless, I assure you.
		3463
		3464	=back
		3465
		3466	Example: Register an atexit handler to destroy the default loop, so any
		3467	cleanup functions are called.
		3468
		3469	static void
		3470	program_exits (void)
		3471	{
		3472	ev_loop_destroy (EV_DEFAULT_UC);
		3473	}
		3474
		3475	...
		3476	atexit (program_exits);
		3477
		3478
2789	=head2 C<ev_async> - how to wake up another event loop	3479	=head2 C<ev_async> - how to wake up an event loop
2790		3480
2791	In general, you cannot use an C<ev_loop> from multiple threads or other	3481	In general, you cannot use an C<ev_loop> from multiple threads or other
2792	asynchronous sources such as signal handlers (as opposed to multiple event	3482	asynchronous sources such as signal handlers (as opposed to multiple event
2793	loops - those are of course safe to use in different threads).	3483	loops - those are of course safe to use in different threads).
2794		3484
2795	Sometimes, however, you need to wake up another event loop you do not	3485	Sometimes, however, you need to wake up an event loop you do not control,
2796	control, for example because it belongs to another thread. This is what	3486	for example because it belongs to another thread. This is what C<ev_async>
2797	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3487	watchers do: as long as the C<ev_async> watcher is active, you can signal
2798	can signal it by calling C<ev_async_send>, which is thread- and signal	3488	it by calling C<ev_async_send>, which is thread- and signal safe.
2799	safe.
2800		3489
2801	This functionality is very similar to C<ev_signal> watchers, as signals,	3490	This functionality is very similar to C<ev_signal> watchers, as signals,
2802	too, are asynchronous in nature, and signals, too, will be compressed	3491	too, are asynchronous in nature, and signals, too, will be compressed
2803	(i.e. the number of callback invocations may be less than the number of	3492	(i.e. the number of callback invocations may be less than the number of
2804	C<ev_async_sent> calls).	3493	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2805		3494	of "global async watchers" by using a watcher on an otherwise unused
2806	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3495	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2807	just the default loop.	3496	even without knowing which loop owns the signal.
2808		3497
2809	=head3 Queueing	3498	=head3 Queueing
2810		3499
2811	C<ev_async> does not support queueing of data in any way. The reason	3500	C<ev_async> does not support queueing of data in any way. The reason
2812	is that the author does not know of a simple (or any) algorithm for a	3501	is that the author does not know of a simple (or any) algorithm for a
2813	multiple-writer-single-reader queue that works in all cases and doesn't	3502	multiple-writer-single-reader queue that works in all cases and doesn't
2814	need elaborate support such as pthreads.	3503	need elaborate support such as pthreads or unportable memory access
		3504	semantics.
2815		3505
2816	That means that if you want to queue data, you have to provide your own	3506	That means that if you want to queue data, you have to provide your own
2817	queue. But at least I can tell you how to implement locking around your	3507	queue. But at least I can tell you how to implement locking around your
2818	queue:	3508	queue:
2819		3509
…		…
2903	trust me.	3593	trust me.
2904		3594
2905	=item ev_async_send (loop, ev_async *)	3595	=item ev_async_send (loop, ev_async *)
2906		3596
2907	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3597	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2908	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3598	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3599	returns.
		3600
2909	C<ev_feed_event>, this call is safe to do from other threads, signal or	3601	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2910	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3602	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2911	section below on what exactly this means).	3603	embedding section below on what exactly this means).
2912		3604
2913	Note that, as with other watchers in libev, multiple events might get	3605	Note that, as with other watchers in libev, multiple events might get
2914	compressed into a single callback invocation (another way to look at this	3606	compressed into a single callback invocation (another way to look at
2915	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3607	this is that C<ev_async> watchers are level-triggered: they are set on
2916	reset when the event loop detects that).	3608	C<ev_async_send>, reset when the event loop detects that).
2917		3609
2918	This call incurs the overhead of a system call only once per event loop	3610	This call incurs the overhead of at most one extra system call per event
2919	iteration, so while the overhead might be noticeable, it doesn't apply to	3611	loop iteration, if the event loop is blocked, and no syscall at all if
2920	repeated calls to C<ev_async_send> for the same event loop.	3612	the event loop (or your program) is processing events. That means that
		3613	repeated calls are basically free (there is no need to avoid calls for
		3614	performance reasons) and that the overhead becomes smaller (typically
		3615	zero) under load.
2921		3616
2922	=item bool = ev_async_pending (ev_async *)	3617	=item bool = ev_async_pending (ev_async *)
2923		3618
2924	Returns a non-zero value when C<ev_async_send> has been called on the	3619	Returns a non-zero value when C<ev_async_send> has been called on the
2925	watcher but the event has not yet been processed (or even noted) by the	3620	watcher but the event has not yet been processed (or even noted) by the
…		…
2942		3637
2943	There are some other functions of possible interest. Described. Here. Now.	3638	There are some other functions of possible interest. Described. Here. Now.
2944		3639
2945	=over 4	3640	=over 4
2946		3641
2947	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3642	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
2948		3643
2949	This function combines a simple timer and an I/O watcher, calls your	3644	This function combines a simple timer and an I/O watcher, calls your
2950	callback on whichever event happens first and automatically stops both	3645	callback on whichever event happens first and automatically stops both
2951	watchers. This is useful if you want to wait for a single event on an fd	3646	watchers. This is useful if you want to wait for a single event on an fd
2952	or timeout without having to allocate/configure/start/stop/free one or	3647	or timeout without having to allocate/configure/start/stop/free one or
…		…
2958		3653
2959	If C<timeout> is less than 0, then no timeout watcher will be	3654	If C<timeout> is less than 0, then no timeout watcher will be
2960	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3655	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2961	repeat = 0) will be started. C<0> is a valid timeout.	3656	repeat = 0) will be started. C<0> is a valid timeout.
2962		3657
2963	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3658	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2964	passed an C<revents> set like normal event callbacks (a combination of	3659	passed an C<revents> set like normal event callbacks (a combination of
2965	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3660	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2966	value passed to C<ev_once>. Note that it is possible to receive I<both>	3661	value passed to C<ev_once>. Note that it is possible to receive I<both>
2967	a timeout and an io event at the same time - you probably should give io	3662	a timeout and an io event at the same time - you probably should give io
2968	events precedence.	3663	events precedence.
2969		3664
2970	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3665	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2971		3666
2972	static void stdin_ready (int revents, void *arg)	3667	static void stdin_ready (int revents, void *arg)
2973	{	3668	{
2974	if (revents & EV_READ)	3669	if (revents & EV_READ)
2975	/* stdin might have data for us, joy! */;	3670	/* stdin might have data for us, joy! */;
2976	else if (revents & EV_TIMEOUT)	3671	else if (revents & EV_TIMER)
2977	/* doh, nothing entered */;	3672	/* doh, nothing entered */;
2978	}	3673	}
2979		3674
2980	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3675	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2981		3676
2982	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2983
2984	Feeds the given event set into the event loop, as if the specified event
2985	had happened for the specified watcher (which must be a pointer to an
2986	initialised but not necessarily started event watcher).
2987
2988	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3677	=item ev_feed_fd_event (loop, int fd, int revents)
2989		3678
2990	Feed an event on the given fd, as if a file descriptor backend detected	3679	Feed an event on the given fd, as if a file descriptor backend detected
2991	the given events it.	3680	the given events.
2992		3681
2993	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3682	=item ev_feed_signal_event (loop, int signum)
2994		3683
2995	Feed an event as if the given signal occurred (C<loop> must be the default	3684	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2996	loop!).	3685	which is async-safe.
2997		3686
2998	=back	3687	=back
		3688
		3689
		3690	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3691
		3692	This section explains some common idioms that are not immediately
		3693	obvious. Note that examples are sprinkled over the whole manual, and this
		3694	section only contains stuff that wouldn't fit anywhere else.
		3695
		3696	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3697
		3698	Each watcher has, by default, a C<void *data> member that you can read
		3699	or modify at any time: libev will completely ignore it. This can be used
		3700	to associate arbitrary data with your watcher. If you need more data and
		3701	don't want to allocate memory separately and store a pointer to it in that
		3702	data member, you can also "subclass" the watcher type and provide your own
		3703	data:
		3704
		3705	struct my_io
		3706	{
		3707	ev_io io;
		3708	int otherfd;
		3709	void *somedata;
		3710	struct whatever *mostinteresting;
		3711	};
		3712
		3713	...
		3714	struct my_io w;
		3715	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3716
		3717	And since your callback will be called with a pointer to the watcher, you
		3718	can cast it back to your own type:
		3719
		3720	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3721	{
		3722	struct my_io *w = (struct my_io *)w_;
		3723	...
		3724	}
		3725
		3726	More interesting and less C-conformant ways of casting your callback
		3727	function type instead have been omitted.
		3728
		3729	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3730
		3731	Another common scenario is to use some data structure with multiple
		3732	embedded watchers, in effect creating your own watcher that combines
		3733	multiple libev event sources into one "super-watcher":
		3734
		3735	struct my_biggy
		3736	{
		3737	int some_data;
		3738	ev_timer t1;
		3739	ev_timer t2;
		3740	}
		3741
		3742	In this case getting the pointer to C<my_biggy> is a bit more
		3743	complicated: Either you store the address of your C<my_biggy> struct in
		3744	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3745	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3746	real programmers):
		3747
		3748	#include <stddef.h>
		3749
		3750	static void
		3751	t1_cb (EV_P_ ev_timer *w, int revents)
		3752	{
		3753	struct my_biggy big = (struct my_biggy *)
		3754	(((char *)w) - offsetof (struct my_biggy, t1));
		3755	}
		3756
		3757	static void
		3758	t2_cb (EV_P_ ev_timer *w, int revents)
		3759	{
		3760	struct my_biggy big = (struct my_biggy *)
		3761	(((char *)w) - offsetof (struct my_biggy, t2));
		3762	}
		3763
		3764	=head2 AVOIDING FINISHING BEFORE RETURNING
		3765
		3766	Often you have structures like this in event-based programs:
		3767
		3768	callback ()
		3769	{
		3770	free (request);
		3771	}
		3772
		3773	request = start_new_request (..., callback);
		3774
		3775	The intent is to start some "lengthy" operation. The C<request> could be
		3776	used to cancel the operation, or do other things with it.
		3777
		3778	It's not uncommon to have code paths in C<start_new_request> that
		3779	immediately invoke the callback, for example, to report errors. Or you add
		3780	some caching layer that finds that it can skip the lengthy aspects of the
		3781	operation and simply invoke the callback with the result.
		3782
		3783	The problem here is that this will happen I<before> C<start_new_request>
		3784	has returned, so C<request> is not set.
		3785
		3786	Even if you pass the request by some safer means to the callback, you
		3787	might want to do something to the request after starting it, such as
		3788	canceling it, which probably isn't working so well when the callback has
		3789	already been invoked.
		3790
		3791	A common way around all these issues is to make sure that
		3792	C<start_new_request> I<always> returns before the callback is invoked. If
		3793	C<start_new_request> immediately knows the result, it can artificially
		3794	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3795	example, or more sneakily, by reusing an existing (stopped) watcher and
		3796	pushing it into the pending queue:
		3797
		3798	ev_set_cb (watcher, callback);
		3799	ev_feed_event (EV_A_ watcher, 0);
		3800
		3801	This way, C<start_new_request> can safely return before the callback is
		3802	invoked, while not delaying callback invocation too much.
		3803
		3804	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3805
		3806	Often (especially in GUI toolkits) there are places where you have
		3807	I<modal> interaction, which is most easily implemented by recursively
		3808	invoking C<ev_run>.
		3809
		3810	This brings the problem of exiting - a callback might want to finish the
		3811	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3812	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3813	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3814	other combination: In these cases, a simple C<ev_break> will not work.
		3815
		3816	The solution is to maintain "break this loop" variable for each C<ev_run>
		3817	invocation, and use a loop around C<ev_run> until the condition is
		3818	triggered, using C<EVRUN_ONCE>:
		3819
		3820	// main loop
		3821	int exit_main_loop = 0;
		3822
		3823	while (!exit_main_loop)
		3824	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3825
		3826	// in a modal watcher
		3827	int exit_nested_loop = 0;
		3828
		3829	while (!exit_nested_loop)
		3830	ev_run (EV_A_ EVRUN_ONCE);
		3831
		3832	To exit from any of these loops, just set the corresponding exit variable:
		3833
		3834	// exit modal loop
		3835	exit_nested_loop = 1;
		3836
		3837	// exit main program, after modal loop is finished
		3838	exit_main_loop = 1;
		3839
		3840	// exit both
		3841	exit_main_loop = exit_nested_loop = 1;
		3842
		3843	=head2 THREAD LOCKING EXAMPLE
		3844
		3845	Here is a fictitious example of how to run an event loop in a different
		3846	thread from where callbacks are being invoked and watchers are
		3847	created/added/removed.
		3848
		3849	For a real-world example, see the C<EV::Loop::Async> perl module,
		3850	which uses exactly this technique (which is suited for many high-level
		3851	languages).
		3852
		3853	The example uses a pthread mutex to protect the loop data, a condition
		3854	variable to wait for callback invocations, an async watcher to notify the
		3855	event loop thread and an unspecified mechanism to wake up the main thread.
		3856
		3857	First, you need to associate some data with the event loop:
		3858
		3859	typedef struct {
		3860	mutex_t lock; /* global loop lock */
		3861	ev_async async_w;
		3862	thread_t tid;
		3863	cond_t invoke_cv;
		3864	} userdata;
		3865
		3866	void prepare_loop (EV_P)
		3867	{
		3868	// for simplicity, we use a static userdata struct.
		3869	static userdata u;
		3870
		3871	ev_async_init (&u->async_w, async_cb);
		3872	ev_async_start (EV_A_ &u->async_w);
		3873
		3874	pthread_mutex_init (&u->lock, 0);
		3875	pthread_cond_init (&u->invoke_cv, 0);
		3876
		3877	// now associate this with the loop
		3878	ev_set_userdata (EV_A_ u);
		3879	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3880	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3881
		3882	// then create the thread running ev_run
		3883	pthread_create (&u->tid, 0, l_run, EV_A);
		3884	}
		3885
		3886	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3887	solely to wake up the event loop so it takes notice of any new watchers
		3888	that might have been added:
		3889
		3890	static void
		3891	async_cb (EV_P_ ev_async *w, int revents)
		3892	{
		3893	// just used for the side effects
		3894	}
		3895
		3896	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3897	protecting the loop data, respectively.
		3898
		3899	static void
		3900	l_release (EV_P)
		3901	{
		3902	userdata *u = ev_userdata (EV_A);
		3903	pthread_mutex_unlock (&u->lock);
		3904	}
		3905
		3906	static void
		3907	l_acquire (EV_P)
		3908	{
		3909	userdata *u = ev_userdata (EV_A);
		3910	pthread_mutex_lock (&u->lock);
		3911	}
		3912
		3913	The event loop thread first acquires the mutex, and then jumps straight
		3914	into C<ev_run>:
		3915
		3916	void *
		3917	l_run (void *thr_arg)
		3918	{
		3919	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3920
		3921	l_acquire (EV_A);
		3922	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3923	ev_run (EV_A_ 0);
		3924	l_release (EV_A);
		3925
		3926	return 0;
		3927	}
		3928
		3929	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3930	signal the main thread via some unspecified mechanism (signals? pipe
		3931	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3932	have been called (in a while loop because a) spurious wakeups are possible
		3933	and b) skipping inter-thread-communication when there are no pending
		3934	watchers is very beneficial):
		3935
		3936	static void
		3937	l_invoke (EV_P)
		3938	{
		3939	userdata *u = ev_userdata (EV_A);
		3940
		3941	while (ev_pending_count (EV_A))
		3942	{
		3943	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3944	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3945	}
		3946	}
		3947
		3948	Now, whenever the main thread gets told to invoke pending watchers, it
		3949	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3950	thread to continue:
		3951
		3952	static void
		3953	real_invoke_pending (EV_P)
		3954	{
		3955	userdata *u = ev_userdata (EV_A);
		3956
		3957	pthread_mutex_lock (&u->lock);
		3958	ev_invoke_pending (EV_A);
		3959	pthread_cond_signal (&u->invoke_cv);
		3960	pthread_mutex_unlock (&u->lock);
		3961	}
		3962
		3963	Whenever you want to start/stop a watcher or do other modifications to an
		3964	event loop, you will now have to lock:
		3965
		3966	ev_timer timeout_watcher;
		3967	userdata *u = ev_userdata (EV_A);
		3968
		3969	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3970
		3971	pthread_mutex_lock (&u->lock);
		3972	ev_timer_start (EV_A_ &timeout_watcher);
		3973	ev_async_send (EV_A_ &u->async_w);
		3974	pthread_mutex_unlock (&u->lock);
		3975
		3976	Note that sending the C<ev_async> watcher is required because otherwise
		3977	an event loop currently blocking in the kernel will have no knowledge
		3978	about the newly added timer. By waking up the loop it will pick up any new
		3979	watchers in the next event loop iteration.
		3980
		3981	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3982
		3983	While the overhead of a callback that e.g. schedules a thread is small, it
		3984	is still an overhead. If you embed libev, and your main usage is with some
		3985	kind of threads or coroutines, you might want to customise libev so that
		3986	doesn't need callbacks anymore.
		3987
		3988	Imagine you have coroutines that you can switch to using a function
		3989	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3990	and that due to some magic, the currently active coroutine is stored in a
		3991	global called C<current_coro>. Then you can build your own "wait for libev
		3992	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3993	the differing C<;> conventions):
		3994
		3995	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3996	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3997
		3998	That means instead of having a C callback function, you store the
		3999	coroutine to switch to in each watcher, and instead of having libev call
		4000	your callback, you instead have it switch to that coroutine.
		4001
		4002	A coroutine might now wait for an event with a function called
		4003	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		4004	matter when, or whether the watcher is active or not when this function is
		4005	called):
		4006
		4007	void
		4008	wait_for_event (ev_watcher *w)
		4009	{
		4010	ev_set_cb (w, current_coro);
		4011	switch_to (libev_coro);
		4012	}
		4013
		4014	That basically suspends the coroutine inside C<wait_for_event> and
		4015	continues the libev coroutine, which, when appropriate, switches back to
		4016	this or any other coroutine.
		4017
		4018	You can do similar tricks if you have, say, threads with an event queue -
		4019	instead of storing a coroutine, you store the queue object and instead of
		4020	switching to a coroutine, you push the watcher onto the queue and notify
		4021	any waiters.
		4022
		4023	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		4024	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		4025
		4026	// my_ev.h
		4027	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4028	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4029	#include "../libev/ev.h"
		4030
		4031	// my_ev.c
		4032	#define EV_H "my_ev.h"
		4033	#include "../libev/ev.c"
		4034
		4035	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4036	F<my_ev.c> into your project. When properly specifying include paths, you
		4037	can even use F<ev.h> as header file name directly.
2999		4038
3000		4039
3001	=head1 LIBEVENT EMULATION	4040	=head1 LIBEVENT EMULATION
3002		4041
3003	Libev offers a compatibility emulation layer for libevent. It cannot	4042	Libev offers a compatibility emulation layer for libevent. It cannot
3004	emulate the internals of libevent, so here are some usage hints:	4043	emulate the internals of libevent, so here are some usage hints:
3005		4044
3006	=over 4	4045	=over 4
		4046
		4047	=item * Only the libevent-1.4.1-beta API is being emulated.
		4048
		4049	This was the newest libevent version available when libev was implemented,
		4050	and is still mostly unchanged in 2010.
3007		4051
3008	=item * Use it by including <event.h>, as usual.	4052	=item * Use it by including <event.h>, as usual.
3009		4053
3010	=item * The following members are fully supported: ev_base, ev_callback,	4054	=item * The following members are fully supported: ev_base, ev_callback,
3011	ev_arg, ev_fd, ev_res, ev_events.	4055	ev_arg, ev_fd, ev_res, ev_events.
…		…
3017	=item * Priorities are not currently supported. Initialising priorities	4061	=item * Priorities are not currently supported. Initialising priorities
3018	will fail and all watchers will have the same priority, even though there	4062	will fail and all watchers will have the same priority, even though there
3019	is an ev_pri field.	4063	is an ev_pri field.
3020		4064
3021	=item * In libevent, the last base created gets the signals, in libev, the	4065	=item * In libevent, the last base created gets the signals, in libev, the
3022	first base created (== the default loop) gets the signals.	4066	base that registered the signal gets the signals.
3023		4067
3024	=item * Other members are not supported.	4068	=item * Other members are not supported.
3025		4069
3026	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4070	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3027	to use the libev header file and library.	4071	to use the libev header file and library.
3028		4072
3029	=back	4073	=back
3030		4074
3031	=head1 C++ SUPPORT	4075	=head1 C++ SUPPORT
		4076
		4077	=head2 C API
		4078
		4079	The normal C API should work fine when used from C++: both ev.h and the
		4080	libev sources can be compiled as C++. Therefore, code that uses the C API
		4081	will work fine.
		4082
		4083	Proper exception specifications might have to be added to callbacks passed
		4084	to libev: exceptions may be thrown only from watcher callbacks, all other
		4085	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4086	callbacks) must not throw exceptions, and might need a C<noexcept>
		4087	specification. If you have code that needs to be compiled as both C and
		4088	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4089
		4090	static void
		4091	fatal_error (const char *msg) EV_NOEXCEPT
		4092	{
		4093	perror (msg);
		4094	abort ();
		4095	}
		4096
		4097	...
		4098	ev_set_syserr_cb (fatal_error);
		4099
		4100	The only API functions that can currently throw exceptions are C<ev_run>,
		4101	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4102	because it runs cleanup watchers).
		4103
		4104	Throwing exceptions in watcher callbacks is only supported if libev itself
		4105	is compiled with a C++ compiler or your C and C++ environments allow
		4106	throwing exceptions through C libraries (most do).
		4107
		4108	=head2 C++ API
3032		4109
3033	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4110	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3034	you to use some convenience methods to start/stop watchers and also change	4111	you to use some convenience methods to start/stop watchers and also change
3035	the callback model to a model using method callbacks on objects.	4112	the callback model to a model using method callbacks on objects.
3036		4113
3037	To use it,	4114	To use it,
3038		4115
3039	#include <ev++.h>	4116	#include <ev++.h>
3040		4117
3041	This automatically includes F<ev.h> and puts all of its definitions (many	4118	This automatically includes F<ev.h> and puts all of its definitions (many
3042	of them macros) into the global namespace. All C++ specific things are	4119	of them macros) into the global namespace. All C++ specific things are
3043	put into the C<ev> namespace. It should support all the same embedding	4120	put into the C<ev> namespace. It should support all the same embedding
…		…
3046	Care has been taken to keep the overhead low. The only data member the C++	4123	Care has been taken to keep the overhead low. The only data member the C++
3047	classes add (compared to plain C-style watchers) is the event loop pointer	4124	classes add (compared to plain C-style watchers) is the event loop pointer
3048	that the watcher is associated with (or no additional members at all if	4125	that the watcher is associated with (or no additional members at all if
3049	you disable C<EV_MULTIPLICITY> when embedding libev).	4126	you disable C<EV_MULTIPLICITY> when embedding libev).
3050		4127
3051	Currently, functions, and static and non-static member functions can be	4128	Currently, functions, static and non-static member functions and classes
3052	used as callbacks. Other types should be easy to add as long as they only	4129	with C<operator ()> can be used as callbacks. Other types should be easy
3053	need one additional pointer for context. If you need support for other	4130	to add as long as they only need one additional pointer for context. If
3054	types of functors please contact the author (preferably after implementing	4131	you need support for other types of functors please contact the author
3055	it).	4132	(preferably after implementing it).
		4133
		4134	For all this to work, your C++ compiler either has to use the same calling
		4135	conventions as your C compiler (for static member functions), or you have
		4136	to embed libev and compile libev itself as C++.
3056		4137
3057	Here is a list of things available in the C<ev> namespace:	4138	Here is a list of things available in the C<ev> namespace:
3058		4139
3059	=over 4	4140	=over 4
3060		4141
…		…
3070	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4151	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3071		4152
3072	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4153	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3073	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4154	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3074	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4155	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3075	defines by many implementations.	4156	defined by many implementations.
3076		4157
3077	All of those classes have these methods:	4158	All of those classes have these methods:
3078		4159
3079	=over 4	4160	=over 4
3080		4161
3081	=item ev::TYPE::TYPE ()	4162	=item ev::TYPE::TYPE ()
3082		4163
3083	=item ev::TYPE::TYPE (struct ev_loop *)	4164	=item ev::TYPE::TYPE (loop)
3084		4165
3085	=item ev::TYPE::~TYPE	4166	=item ev::TYPE::~TYPE
3086		4167
3087	The constructor (optionally) takes an event loop to associate the watcher	4168	The constructor (optionally) takes an event loop to associate the watcher
3088	with. If it is omitted, it will use C<EV_DEFAULT>.	4169	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3121	myclass obj;	4202	myclass obj;
3122	ev::io iow;	4203	ev::io iow;
3123	iow.set <myclass, &myclass::io_cb> (&obj);	4204	iow.set <myclass, &myclass::io_cb> (&obj);
3124		4205
3125	=item w->set (object *)	4206	=item w->set (object *)
3126
3127	This is an B<experimental> feature that might go away in a future version.
3128		4207
3129	This is a variation of a method callback - leaving out the method to call	4208	This is a variation of a method callback - leaving out the method to call
3130	will default the method to C<operator ()>, which makes it possible to use	4209	will default the method to C<operator ()>, which makes it possible to use
3131	functor objects without having to manually specify the C<operator ()> all	4210	functor objects without having to manually specify the C<operator ()> all
3132	the time. Incidentally, you can then also leave out the template argument	4211	the time. Incidentally, you can then also leave out the template argument
…		…
3144	void operator() (ev::io &w, int revents)	4223	void operator() (ev::io &w, int revents)
3145	{	4224	{
3146	...	4225	...
3147	}	4226	}
3148	}	4227	}
3149		4228
3150	myfunctor f;	4229	myfunctor f;
3151		4230
3152	ev::io w;	4231	ev::io w;
3153	w.set (&f);	4232	w.set (&f);
3154		4233
…		…
3165	Example: Use a plain function as callback.	4244	Example: Use a plain function as callback.
3166		4245
3167	static void io_cb (ev::io &w, int revents) { }	4246	static void io_cb (ev::io &w, int revents) { }
3168	iow.set <io_cb> ();	4247	iow.set <io_cb> ();
3169		4248
3170	=item w->set (struct ev_loop *)	4249	=item w->set (loop)
3171		4250
3172	Associates a different C<struct ev_loop> with this watcher. You can only	4251	Associates a different C<struct ev_loop> with this watcher. You can only
3173	do this when the watcher is inactive (and not pending either).	4252	do this when the watcher is inactive (and not pending either).
3174		4253
3175	=item w->set ([arguments])	4254	=item w->set ([arguments])
3176		4255
3177	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4256	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4257	with the same arguments. Either this method or a suitable start method
3178	called at least once. Unlike the C counterpart, an active watcher gets	4258	must be called at least once. Unlike the C counterpart, an active watcher
3179	automatically stopped and restarted when reconfiguring it with this	4259	gets automatically stopped and restarted when reconfiguring it with this
3180	method.	4260	method.
		4261
		4262	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4263	clashing with the C<set (loop)> method.
		4264
		4265	For C<ev::io> watchers there is an additional C<set> method that acepts a
		4266	new event mask only, and internally calls C<ev_io_modfify>.
3181		4267
3182	=item w->start ()	4268	=item w->start ()
3183		4269
3184	Starts the watcher. Note that there is no C<loop> argument, as the	4270	Starts the watcher. Note that there is no C<loop> argument, as the
3185	constructor already stores the event loop.	4271	constructor already stores the event loop.
3186		4272
		4273	=item w->start ([arguments])
		4274
		4275	Instead of calling C<set> and C<start> methods separately, it is often
		4276	convenient to wrap them in one call. Uses the same type of arguments as
		4277	the configure C<set> method of the watcher.
		4278
3187	=item w->stop ()	4279	=item w->stop ()
3188		4280
3189	Stops the watcher if it is active. Again, no C<loop> argument.	4281	Stops the watcher if it is active. Again, no C<loop> argument.
3190		4282
3191	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4283	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3203		4295
3204	=back	4296	=back
3205		4297
3206	=back	4298	=back
3207		4299
3208	Example: Define a class with an IO and idle watcher, start one of them in	4300	Example: Define a class with two I/O and idle watchers, start the I/O
3209	the constructor.	4301	watchers in the constructor.
3210		4302
3211	class myclass	4303	class myclass
3212	{	4304	{
3213	ev::io io ; void io_cb (ev::io &w, int revents);	4305	ev::io io ; void io_cb (ev::io &w, int revents);
		4306	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3214	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4307	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3215		4308
3216	myclass (int fd)	4309	myclass (int fd)
3217	{	4310	{
3218	io .set <myclass, &myclass::io_cb > (this);	4311	io .set <myclass, &myclass::io_cb > (this);
		4312	io2 .set <myclass, &myclass::io2_cb > (this);
3219	idle.set <myclass, &myclass::idle_cb> (this);	4313	idle.set <myclass, &myclass::idle_cb> (this);
3220		4314
3221	io.start (fd, ev::READ);	4315	io.set (fd, ev::WRITE); // configure the watcher
		4316	io.start (); // start it whenever convenient
		4317
		4318	io2.start (fd, ev::READ); // set + start in one call
3222	}	4319	}
3223	};	4320	};
3224		4321
3225		4322
3226	=head1 OTHER LANGUAGE BINDINGS	4323	=head1 OTHER LANGUAGE BINDINGS
…		…
3265	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4362	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3266		4363
3267	=item D	4364	=item D
3268		4365
3269	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4366	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3270	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4367	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3271		4368
3272	=item Ocaml	4369	=item Ocaml
3273		4370
3274	Erkki Seppala has written Ocaml bindings for libev, to be found at	4371	Erkki Seppala has written Ocaml bindings for libev, to be found at
3275	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4372	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4373
		4374	=item Lua
		4375
		4376	Brian Maher has written a partial interface to libev for lua (at the
		4377	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4378	L<http://github.com/brimworks/lua-ev>.
		4379
		4380	=item Javascript
		4381
		4382	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4383
		4384	=item Others
		4385
		4386	There are others, and I stopped counting.
3276		4387
3277	=back	4388	=back
3278		4389
3279		4390
3280	=head1 MACRO MAGIC	4391	=head1 MACRO MAGIC
…		…
3294	loop argument"). The C<EV_A> form is used when this is the sole argument,	4405	loop argument"). The C<EV_A> form is used when this is the sole argument,
3295	C<EV_A_> is used when other arguments are following. Example:	4406	C<EV_A_> is used when other arguments are following. Example:
3296		4407
3297	ev_unref (EV_A);	4408	ev_unref (EV_A);
3298	ev_timer_add (EV_A_ watcher);	4409	ev_timer_add (EV_A_ watcher);
3299	ev_loop (EV_A_ 0);	4410	ev_run (EV_A_ 0);
3300		4411
3301	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4412	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3302	which is often provided by the following macro.	4413	which is often provided by the following macro.
3303		4414
3304	=item C<EV_P>, C<EV_P_>	4415	=item C<EV_P>, C<EV_P_>
…		…
3317	suitable for use with C<EV_A>.	4428	suitable for use with C<EV_A>.
3318		4429
3319	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4430	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3320		4431
3321	Similar to the other two macros, this gives you the value of the default	4432	Similar to the other two macros, this gives you the value of the default
3322	loop, if multiple loops are supported ("ev loop default").	4433	loop, if multiple loops are supported ("ev loop default"). The default loop
		4434	will be initialised if it isn't already initialised.
		4435
		4436	For non-multiplicity builds, these macros do nothing, so you always have
		4437	to initialise the loop somewhere.
3323		4438
3324	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4439	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3325		4440
3326	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4441	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3327	default loop has been initialised (C<UC> == unchecked). Their behaviour	4442	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3344	}	4459	}
3345		4460
3346	ev_check check;	4461	ev_check check;
3347	ev_check_init (&check, check_cb);	4462	ev_check_init (&check, check_cb);
3348	ev_check_start (EV_DEFAULT_ &check);	4463	ev_check_start (EV_DEFAULT_ &check);
3349	ev_loop (EV_DEFAULT_ 0);	4464	ev_run (EV_DEFAULT_ 0);
3350		4465
3351	=head1 EMBEDDING	4466	=head1 EMBEDDING
3352		4467
3353	Libev can (and often is) directly embedded into host	4468	Libev can (and often is) directly embedded into host
3354	applications. Examples of applications that embed it include the Deliantra	4469	applications. Examples of applications that embed it include the Deliantra
…		…
3394	ev_vars.h	4509	ev_vars.h
3395	ev_wrap.h	4510	ev_wrap.h
3396		4511
3397	ev_win32.c required on win32 platforms only	4512	ev_win32.c required on win32 platforms only
3398		4513
3399	ev_select.c only when select backend is enabled (which is enabled by default)	4514	ev_select.c only when select backend is enabled
3400	ev_poll.c only when poll backend is enabled (disabled by default)	4515	ev_poll.c only when poll backend is enabled
3401	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4516	ev_epoll.c only when the epoll backend is enabled
		4517	ev_linuxaio.c only when the linux aio backend is enabled
		4518	ev_iouring.c only when the linux io_uring backend is enabled
3402	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4519	ev_kqueue.c only when the kqueue backend is enabled
3403	ev_port.c only when the solaris port backend is enabled (disabled by default)	4520	ev_port.c only when the solaris port backend is enabled
3404		4521
3405	F<ev.c> includes the backend files directly when enabled, so you only need	4522	F<ev.c> includes the backend files directly when enabled, so you only need
3406	to compile this single file.	4523	to compile this single file.
3407		4524
3408	=head3 LIBEVENT COMPATIBILITY API	4525	=head3 LIBEVENT COMPATIBILITY API
…		…
3434	libev.m4	4551	libev.m4
3435		4552
3436	=head2 PREPROCESSOR SYMBOLS/MACROS	4553	=head2 PREPROCESSOR SYMBOLS/MACROS
3437		4554
3438	Libev can be configured via a variety of preprocessor symbols you have to	4555	Libev can be configured via a variety of preprocessor symbols you have to
3439	define before including any of its files. The default in the absence of	4556	define before including (or compiling) any of its files. The default in
3440	autoconf is documented for every option.	4557	the absence of autoconf is documented for every option.
		4558
		4559	Symbols marked with "(h)" do not change the ABI, and can have different
		4560	values when compiling libev vs. including F<ev.h>, so it is permissible
		4561	to redefine them before including F<ev.h> without breaking compatibility
		4562	to a compiled library. All other symbols change the ABI, which means all
		4563	users of libev and the libev code itself must be compiled with compatible
		4564	settings.
3441		4565
3442	=over 4	4566	=over 4
3443		4567
		4568	=item EV_COMPAT3 (h)
		4569
		4570	Backwards compatibility is a major concern for libev. This is why this
		4571	release of libev comes with wrappers for the functions and symbols that
		4572	have been renamed between libev version 3 and 4.
		4573
		4574	You can disable these wrappers (to test compatibility with future
		4575	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4576	sources. This has the additional advantage that you can drop the C<struct>
		4577	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4578	typedef in that case.
		4579
		4580	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4581	and in some even more future version the compatibility code will be
		4582	removed completely.
		4583
3444	=item EV_STANDALONE	4584	=item EV_STANDALONE (h)
3445		4585
3446	Must always be C<1> if you do not use autoconf configuration, which	4586	Must always be C<1> if you do not use autoconf configuration, which
3447	keeps libev from including F<config.h>, and it also defines dummy	4587	keeps libev from including F<config.h>, and it also defines dummy
3448	implementations for some libevent functions (such as logging, which is not	4588	implementations for some libevent functions (such as logging, which is not
3449	supported). It will also not define any of the structs usually found in	4589	supported). It will also not define any of the structs usually found in
3450	F<event.h> that are not directly supported by the libev core alone.	4590	F<event.h> that are not directly supported by the libev core alone.
3451		4591
3452	In stanbdalone mode, libev will still try to automatically deduce the	4592	In standalone mode, libev will still try to automatically deduce the
3453	configuration, but has to be more conservative.	4593	configuration, but has to be more conservative.
		4594
		4595	=item EV_USE_FLOOR
		4596
		4597	If defined to be C<1>, libev will use the C<floor ()> function for its
		4598	periodic reschedule calculations, otherwise libev will fall back on a
		4599	portable (slower) implementation. If you enable this, you usually have to
		4600	link against libm or something equivalent. Enabling this when the C<floor>
		4601	function is not available will fail, so the safe default is to not enable
		4602	this.
3454		4603
3455	=item EV_USE_MONOTONIC	4604	=item EV_USE_MONOTONIC
3456		4605
3457	If defined to be C<1>, libev will try to detect the availability of the	4606	If defined to be C<1>, libev will try to detect the availability of the
3458	monotonic clock option at both compile time and runtime. Otherwise no	4607	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3495	available and will probe for kernel support at runtime. This will improve	4644	available and will probe for kernel support at runtime. This will improve
3496	C<ev_signal> and C<ev_async> performance and reduce resource consumption.	4645	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
3497	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc	4646	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
3498	2.7 or newer, otherwise disabled.	4647	2.7 or newer, otherwise disabled.
3499		4648
		4649	=item EV_USE_SIGNALFD
		4650
		4651	If defined to be C<1>, then libev will assume that C<signalfd ()> is
		4652	available and will probe for kernel support at runtime. This enables
		4653	the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If
		4654	undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4655	2.7 or newer, otherwise disabled.
		4656
		4657	=item EV_USE_TIMERFD
		4658
		4659	If defined to be C<1>, then libev will assume that C<timerfd ()> is
		4660	available and will probe for kernel support at runtime. This allows
		4661	libev to detect time jumps accurately. If undefined, it will be enabled
		4662	if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
		4663	C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled.
		4664
		4665	=item EV_USE_EVENTFD
		4666
		4667	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		4668	available and will probe for kernel support at runtime. This will improve
		4669	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		4670	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4671	2.7 or newer, otherwise disabled.
		4672
3500	=item EV_USE_SELECT	4673	=item EV_USE_SELECT
3501		4674
3502	If undefined or defined to be C<1>, libev will compile in support for the	4675	If undefined or defined to be C<1>, libev will compile in support for the
3503	C<select>(2) backend. No attempt at auto-detection will be done: if no	4676	C<select>(2) backend. No attempt at auto-detection will be done: if no
3504	other method takes over, select will be it. Otherwise the select backend	4677	other method takes over, select will be it. Otherwise the select backend
…		…
3522	be used is the winsock select). This means that it will call	4695	be used is the winsock select). This means that it will call
3523	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4696	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3524	it is assumed that all these functions actually work on fds, even	4697	it is assumed that all these functions actually work on fds, even
3525	on win32. Should not be defined on non-win32 platforms.	4698	on win32. Should not be defined on non-win32 platforms.
3526		4699
3527	=item EV_FD_TO_WIN32_HANDLE	4700	=item EV_FD_TO_WIN32_HANDLE(fd)
3528		4701
3529	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4702	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3530	file descriptors to socket handles. When not defining this symbol (the	4703	file descriptors to socket handles. When not defining this symbol (the
3531	default), then libev will call C<_get_osfhandle>, which is usually	4704	default), then libev will call C<_get_osfhandle>, which is usually
3532	correct. In some cases, programs use their own file descriptor management,	4705	correct. In some cases, programs use their own file descriptor management,
3533	in which case they can provide this function to map fds to socket handles.	4706	in which case they can provide this function to map fds to socket handles.
3534		4707
		4708	=item EV_WIN32_HANDLE_TO_FD(handle)
		4709
		4710	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4711	using the standard C<_open_osfhandle> function. For programs implementing
		4712	their own fd to handle mapping, overwriting this function makes it easier
		4713	to do so. This can be done by defining this macro to an appropriate value.
		4714
		4715	=item EV_WIN32_CLOSE_FD(fd)
		4716
		4717	If programs implement their own fd to handle mapping on win32, then this
		4718	macro can be used to override the C<close> function, useful to unregister
		4719	file descriptors again. Note that the replacement function has to close
		4720	the underlying OS handle.
		4721
		4722	=item EV_USE_WSASOCKET
		4723
		4724	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4725	communication socket, which works better in some environments. Otherwise,
		4726	the normal C<socket> function will be used, which works better in other
		4727	environments.
		4728
3535	=item EV_USE_POLL	4729	=item EV_USE_POLL
3536		4730
3537	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4731	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3538	backend. Otherwise it will be enabled on non-win32 platforms. It	4732	backend. Otherwise it will be enabled on non-win32 platforms. It
3539	takes precedence over select.	4733	takes precedence over select.
…		…
3543	If defined to be C<1>, libev will compile in support for the Linux	4737	If defined to be C<1>, libev will compile in support for the Linux
3544	C<epoll>(7) backend. Its availability will be detected at runtime,	4738	C<epoll>(7) backend. Its availability will be detected at runtime,
3545	otherwise another method will be used as fallback. This is the preferred	4739	otherwise another method will be used as fallback. This is the preferred
3546	backend for GNU/Linux systems. If undefined, it will be enabled if the	4740	backend for GNU/Linux systems. If undefined, it will be enabled if the
3547	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4741	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4742
		4743	=item EV_USE_LINUXAIO
		4744
		4745	If defined to be C<1>, libev will compile in support for the Linux aio
		4746	backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be
		4747	enabled on linux, otherwise disabled.
		4748
		4749	=item EV_USE_IOURING
		4750
		4751	If defined to be C<1>, libev will compile in support for the Linux
		4752	io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's
		4753	current limitations it has to be requested explicitly. If undefined, it
		4754	will be enabled on linux, otherwise disabled.
3548		4755
3549	=item EV_USE_KQUEUE	4756	=item EV_USE_KQUEUE
3550		4757
3551	If defined to be C<1>, libev will compile in support for the BSD style	4758	If defined to be C<1>, libev will compile in support for the BSD style
3552	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4759	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3574	If defined to be C<1>, libev will compile in support for the Linux inotify	4781	If defined to be C<1>, libev will compile in support for the Linux inotify
3575	interface to speed up C<ev_stat> watchers. Its actual availability will	4782	interface to speed up C<ev_stat> watchers. Its actual availability will
3576	be detected at runtime. If undefined, it will be enabled if the headers	4783	be detected at runtime. If undefined, it will be enabled if the headers
3577	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4784	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3578		4785
		4786	=item EV_NO_SMP
		4787
		4788	If defined to be C<1>, libev will assume that memory is always coherent
		4789	between threads, that is, threads can be used, but threads never run on
		4790	different cpus (or different cpu cores). This reduces dependencies
		4791	and makes libev faster.
		4792
		4793	=item EV_NO_THREADS
		4794
		4795	If defined to be C<1>, libev will assume that it will never be called from
		4796	different threads (that includes signal handlers), which is a stronger
		4797	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4798	libev faster.
		4799
3579	=item EV_ATOMIC_T	4800	=item EV_ATOMIC_T
3580		4801
3581	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4802	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3582	access is atomic with respect to other threads or signal contexts. No such	4803	access is atomic with respect to other threads or signal contexts. No
3583	type is easily found in the C language, so you can provide your own type	4804	such type is easily found in the C language, so you can provide your own
3584	that you know is safe for your purposes. It is used both for signal handler "locking"	4805	type that you know is safe for your purposes. It is used both for signal
3585	as well as for signal and thread safety in C<ev_async> watchers.	4806	handler "locking" as well as for signal and thread safety in C<ev_async>
		4807	watchers.
3586		4808
3587	In the absence of this define, libev will use C<sig_atomic_t volatile>	4809	In the absence of this define, libev will use C<sig_atomic_t volatile>
3588	(from F<signal.h>), which is usually good enough on most platforms.	4810	(from F<signal.h>), which is usually good enough on most platforms.
3589		4811
3590	=item EV_H	4812	=item EV_H (h)
3591		4813
3592	The name of the F<ev.h> header file used to include it. The default if	4814	The name of the F<ev.h> header file used to include it. The default if
3593	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4815	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3594	used to virtually rename the F<ev.h> header file in case of conflicts.	4816	used to virtually rename the F<ev.h> header file in case of conflicts.
3595		4817
3596	=item EV_CONFIG_H	4818	=item EV_CONFIG_H (h)
3597		4819
3598	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4820	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3599	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4821	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3600	C<EV_H>, above.	4822	C<EV_H>, above.
3601		4823
3602	=item EV_EVENT_H	4824	=item EV_EVENT_H (h)
3603		4825
3604	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4826	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3605	of how the F<event.h> header can be found, the default is C<"event.h">.	4827	of how the F<event.h> header can be found, the default is C<"event.h">.
3606		4828
3607	=item EV_PROTOTYPES	4829	=item EV_PROTOTYPES (h)
3608		4830
3609	If defined to be C<0>, then F<ev.h> will not define any function	4831	If defined to be C<0>, then F<ev.h> will not define any function
3610	prototypes, but still define all the structs and other symbols. This is	4832	prototypes, but still define all the structs and other symbols. This is
3611	occasionally useful if you want to provide your own wrapper functions	4833	occasionally useful if you want to provide your own wrapper functions
3612	around libev functions.	4834	around libev functions.
…		…
3617	will have the C<struct ev_loop *> as first argument, and you can create	4839	will have the C<struct ev_loop *> as first argument, and you can create
3618	additional independent event loops. Otherwise there will be no support	4840	additional independent event loops. Otherwise there will be no support
3619	for multiple event loops and there is no first event loop pointer	4841	for multiple event loops and there is no first event loop pointer
3620	argument. Instead, all functions act on the single default loop.	4842	argument. Instead, all functions act on the single default loop.
3621		4843
		4844	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4845	default loop when multiplicity is switched off - you always have to
		4846	initialise the loop manually in this case.
		4847
3622	=item EV_MINPRI	4848	=item EV_MINPRI
3623		4849
3624	=item EV_MAXPRI	4850	=item EV_MAXPRI
3625		4851
3626	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4852	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3634	fine.	4860	fine.
3635		4861
3636	If your embedding application does not need any priorities, defining these	4862	If your embedding application does not need any priorities, defining these
3637	both to C<0> will save some memory and CPU.	4863	both to C<0> will save some memory and CPU.
3638		4864
3639	=item EV_PERIODIC_ENABLE	4865	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4866	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4867	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3640		4868
3641	If undefined or defined to be C<1>, then periodic timers are supported. If	4869	If undefined or defined to be C<1> (and the platform supports it), then
3642	defined to be C<0>, then they are not. Disabling them saves a few kB of	4870	the respective watcher type is supported. If defined to be C<0>, then it
3643	code.	4871	is not. Disabling watcher types mainly saves code size.
3644		4872
3645	=item EV_IDLE_ENABLE	4873	=item EV_FEATURES
3646
3647	If undefined or defined to be C<1>, then idle watchers are supported. If
3648	defined to be C<0>, then they are not. Disabling them saves a few kB of
3649	code.
3650
3651	=item EV_EMBED_ENABLE
3652
3653	If undefined or defined to be C<1>, then embed watchers are supported. If
3654	defined to be C<0>, then they are not. Embed watchers rely on most other
3655	watcher types, which therefore must not be disabled.
3656
3657	=item EV_STAT_ENABLE
3658
3659	If undefined or defined to be C<1>, then stat watchers are supported. If
3660	defined to be C<0>, then they are not.
3661
3662	=item EV_FORK_ENABLE
3663
3664	If undefined or defined to be C<1>, then fork watchers are supported. If
3665	defined to be C<0>, then they are not.
3666
3667	=item EV_ASYNC_ENABLE
3668
3669	If undefined or defined to be C<1>, then async watchers are supported. If
3670	defined to be C<0>, then they are not.
3671
3672	=item EV_MINIMAL
3673		4874
3674	If you need to shave off some kilobytes of code at the expense of some	4875	If you need to shave off some kilobytes of code at the expense of some
3675	speed, define this symbol to C<1>. Currently this is used to override some	4876	speed (but with the full API), you can define this symbol to request
3676	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4877	certain subsets of functionality. The default is to enable all features
3677	much smaller 2-heap for timer management over the default 4-heap.	4878	that can be enabled on the platform.
		4879
		4880	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4881	with some broad features you want) and then selectively re-enable
		4882	additional parts you want, for example if you want everything minimal,
		4883	but multiple event loop support, async and child watchers and the poll
		4884	backend, use this:
		4885
		4886	#define EV_FEATURES 0
		4887	#define EV_MULTIPLICITY 1
		4888	#define EV_USE_POLL 1
		4889	#define EV_CHILD_ENABLE 1
		4890	#define EV_ASYNC_ENABLE 1
		4891
		4892	The actual value is a bitset, it can be a combination of the following
		4893	values (by default, all of these are enabled):
		4894
		4895	=over 4
		4896
		4897	=item C<1> - faster/larger code
		4898
		4899	Use larger code to speed up some operations.
		4900
		4901	Currently this is used to override some inlining decisions (enlarging the
		4902	code size by roughly 30% on amd64).
		4903
		4904	When optimising for size, use of compiler flags such as C<-Os> with
		4905	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4906	assertions.
		4907
		4908	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4909	(e.g. gcc with C<-Os>).
		4910
		4911	=item C<2> - faster/larger data structures
		4912
		4913	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4914	hash table sizes and so on. This will usually further increase code size
		4915	and can additionally have an effect on the size of data structures at
		4916	runtime.
		4917
		4918	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4919	(e.g. gcc with C<-Os>).
		4920
		4921	=item C<4> - full API configuration
		4922
		4923	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4924	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4925
		4926	=item C<8> - full API
		4927
		4928	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4929	details on which parts of the API are still available without this
		4930	feature, and do not complain if this subset changes over time.
		4931
		4932	=item C<16> - enable all optional watcher types
		4933
		4934	Enables all optional watcher types. If you want to selectively enable
		4935	only some watcher types other than I/O and timers (e.g. prepare,
		4936	embed, async, child...) you can enable them manually by defining
		4937	C<EV_watchertype_ENABLE> to C<1> instead.
		4938
		4939	=item C<32> - enable all backends
		4940
		4941	This enables all backends - without this feature, you need to enable at
		4942	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4943
		4944	=item C<64> - enable OS-specific "helper" APIs
		4945
		4946	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4947	default.
		4948
		4949	=back
		4950
		4951	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4952	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4953	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4954	watchers, timers and monotonic clock support.
		4955
		4956	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4957	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4958	your program might be left out as well - a binary starting a timer and an
		4959	I/O watcher then might come out at only 5Kb.
		4960
		4961	=item EV_API_STATIC
		4962
		4963	If this symbol is defined (by default it is not), then all identifiers
		4964	will have static linkage. This means that libev will not export any
		4965	identifiers, and you cannot link against libev anymore. This can be useful
		4966	when you embed libev, only want to use libev functions in a single file,
		4967	and do not want its identifiers to be visible.
		4968
		4969	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4970	wants to use libev.
		4971
		4972	This option only works when libev is compiled with a C compiler, as C++
		4973	doesn't support the required declaration syntax.
		4974
		4975	=item EV_AVOID_STDIO
		4976
		4977	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4978	functions (printf, scanf, perror etc.). This will increase the code size
		4979	somewhat, but if your program doesn't otherwise depend on stdio and your
		4980	libc allows it, this avoids linking in the stdio library which is quite
		4981	big.
		4982
		4983	Note that error messages might become less precise when this option is
		4984	enabled.
		4985
		4986	=item EV_NSIG
		4987
		4988	The highest supported signal number, +1 (or, the number of
		4989	signals): Normally, libev tries to deduce the maximum number of signals
		4990	automatically, but sometimes this fails, in which case it can be
		4991	specified. Also, using a lower number than detected (C<32> should be
		4992	good for about any system in existence) can save some memory, as libev
		4993	statically allocates some 12-24 bytes per signal number.
3678		4994
3679	=item EV_PID_HASHSIZE	4995	=item EV_PID_HASHSIZE
3680		4996
3681	C<ev_child> watchers use a small hash table to distribute workload by	4997	C<ev_child> watchers use a small hash table to distribute workload by
3682	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4998	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3683	than enough. If you need to manage thousands of children you might want to	4999	usually more than enough. If you need to manage thousands of children you
3684	increase this value (I<must> be a power of two).	5000	might want to increase this value (I<must> be a power of two).
3685		5001
3686	=item EV_INOTIFY_HASHSIZE	5002	=item EV_INOTIFY_HASHSIZE
3687		5003
3688	C<ev_stat> watchers use a small hash table to distribute workload by	5004	C<ev_stat> watchers use a small hash table to distribute workload by
3689	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	5005	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3690	usually more than enough. If you need to manage thousands of C<ev_stat>	5006	disabled), usually more than enough. If you need to manage thousands of
3691	watchers you might want to increase this value (I<must> be a power of	5007	C<ev_stat> watchers you might want to increase this value (I<must> be a
3692	two).	5008	power of two).
3693		5009
3694	=item EV_USE_4HEAP	5010	=item EV_USE_4HEAP
3695		5011
3696	Heaps are not very cache-efficient. To improve the cache-efficiency of the	5012	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3697	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	5013	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3698	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	5014	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3699	faster performance with many (thousands) of watchers.	5015	faster performance with many (thousands) of watchers.
3700		5016
3701	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	5017	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3702	(disabled).	5018	will be C<0>.
3703		5019
3704	=item EV_HEAP_CACHE_AT	5020	=item EV_HEAP_CACHE_AT
3705		5021
3706	Heaps are not very cache-efficient. To improve the cache-efficiency of the	5022	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3707	timer and periodics heaps, libev can cache the timestamp (I<at>) within	5023	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3708	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	5024	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3709	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	5025	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3710	but avoids random read accesses on heap changes. This improves performance	5026	but avoids random read accesses on heap changes. This improves performance
3711	noticeably with many (hundreds) of watchers.	5027	noticeably with many (hundreds) of watchers.
3712		5028
3713	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	5029	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3714	(disabled).	5030	will be C<0>.
3715		5031
3716	=item EV_VERIFY	5032	=item EV_VERIFY
3717		5033
3718	Controls how much internal verification (see C<ev_loop_verify ()>) will	5034	Controls how much internal verification (see C<ev_verify ()>) will
3719	be done: If set to C<0>, no internal verification code will be compiled	5035	be done: If set to C<0>, no internal verification code will be compiled
3720	in. If set to C<1>, then verification code will be compiled in, but not	5036	in. If set to C<1>, then verification code will be compiled in, but not
3721	called. If set to C<2>, then the internal verification code will be	5037	called. If set to C<2>, then the internal verification code will be
3722	called once per loop, which can slow down libev. If set to C<3>, then the	5038	called once per loop, which can slow down libev. If set to C<3>, then the
3723	verification code will be called very frequently, which will slow down	5039	verification code will be called very frequently, which will slow down
3724	libev considerably.	5040	libev considerably.
3725		5041
		5042	Verification errors are reported via C's C<assert> mechanism, so if you
		5043	disable that (e.g. by defining C<NDEBUG>) then no errors will be reported.
		5044
3726	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	5045	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3727	C<0>.	5046	will be C<0>.
3728		5047
3729	=item EV_COMMON	5048	=item EV_COMMON
3730		5049
3731	By default, all watchers have a C<void *data> member. By redefining	5050	By default, all watchers have a C<void *data> member. By redefining
3732	this macro to a something else you can include more and other types of	5051	this macro to something else you can include more and other types of
3733	members. You have to define it each time you include one of the files,	5052	members. You have to define it each time you include one of the files,
3734	though, and it must be identical each time.	5053	though, and it must be identical each time.
3735		5054
3736	For example, the perl EV module uses something like this:	5055	For example, the perl EV module uses something like this:
3737		5056
…		…
3790	file.	5109	file.
3791		5110
3792	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5111	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3793	that everybody includes and which overrides some configure choices:	5112	that everybody includes and which overrides some configure choices:
3794		5113
3795	#define EV_MINIMAL 1	5114	#define EV_FEATURES 8
3796	#define EV_USE_POLL 0	5115	#define EV_USE_SELECT 1
3797	#define EV_MULTIPLICITY 0
3798	#define EV_PERIODIC_ENABLE 0	5116	#define EV_PREPARE_ENABLE 1
		5117	#define EV_IDLE_ENABLE 1
3799	#define EV_STAT_ENABLE 0	5118	#define EV_SIGNAL_ENABLE 1
3800	#define EV_FORK_ENABLE 0	5119	#define EV_CHILD_ENABLE 1
		5120	#define EV_USE_STDEXCEPT 0
3801	#define EV_CONFIG_H <config.h>	5121	#define EV_CONFIG_H <config.h>
3802	#define EV_MINPRI 0
3803	#define EV_MAXPRI 0
3804		5122
3805	#include "ev++.h"	5123	#include "ev++.h"
3806		5124
3807	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5125	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3808		5126
3809	#include "ev_cpp.h"	5127	#include "ev_cpp.h"
3810	#include "ev.c"	5128	#include "ev.c"
3811		5129
3812	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5130	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3813		5131
3814	=head2 THREADS AND COROUTINES	5132	=head2 THREADS AND COROUTINES
3815		5133
3816	=head3 THREADS	5134	=head3 THREADS
3817		5135
…		…
3868	default loop and triggering an C<ev_async> watcher from the default loop	5186	default loop and triggering an C<ev_async> watcher from the default loop
3869	watcher callback into the event loop interested in the signal.	5187	watcher callback into the event loop interested in the signal.
3870		5188
3871	=back	5189	=back
3872		5190
		5191	See also L</THREAD LOCKING EXAMPLE>.
		5192
3873	=head3 COROUTINES	5193	=head3 COROUTINES
3874		5194
3875	Libev is very accommodating to coroutines ("cooperative threads"):	5195	Libev is very accommodating to coroutines ("cooperative threads"):
3876	libev fully supports nesting calls to its functions from different	5196	libev fully supports nesting calls to its functions from different
3877	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5197	coroutines (e.g. you can call C<ev_run> on the same loop from two
3878	different coroutines, and switch freely between both coroutines running the	5198	different coroutines, and switch freely between both coroutines running
3879	loop, as long as you don't confuse yourself). The only exception is that	5199	the loop, as long as you don't confuse yourself). The only exception is
3880	you must not do this from C<ev_periodic> reschedule callbacks.	5200	that you must not do this from C<ev_periodic> reschedule callbacks.
3881		5201
3882	Care has been taken to ensure that libev does not keep local state inside	5202	Care has been taken to ensure that libev does not keep local state inside
3883	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5203	C<ev_run>, and other calls do not usually allow for coroutine switches as
3884	they do not call any callbacks.	5204	they do not call any callbacks.
3885		5205
3886	=head2 COMPILER WARNINGS	5206	=head2 COMPILER WARNINGS
3887		5207
3888	Depending on your compiler and compiler settings, you might get no or a	5208	Depending on your compiler and compiler settings, you might get no or a
…		…
3899	maintainable.	5219	maintainable.
3900		5220
3901	And of course, some compiler warnings are just plain stupid, or simply	5221	And of course, some compiler warnings are just plain stupid, or simply
3902	wrong (because they don't actually warn about the condition their message	5222	wrong (because they don't actually warn about the condition their message
3903	seems to warn about). For example, certain older gcc versions had some	5223	seems to warn about). For example, certain older gcc versions had some
3904	warnings that resulted an extreme number of false positives. These have	5224	warnings that resulted in an extreme number of false positives. These have
3905	been fixed, but some people still insist on making code warn-free with	5225	been fixed, but some people still insist on making code warn-free with
3906	such buggy versions.	5226	such buggy versions.
3907		5227
3908	While libev is written to generate as few warnings as possible,	5228	While libev is written to generate as few warnings as possible,
3909	"warn-free" code is not a goal, and it is recommended not to build libev	5229	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3945	I suggest using suppression lists.	5265	I suggest using suppression lists.
3946		5266
3947		5267
3948	=head1 PORTABILITY NOTES	5268	=head1 PORTABILITY NOTES
3949		5269
		5270	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5271
		5272	GNU/Linux is the only common platform that supports 64 bit file/large file
		5273	interfaces but I<disables> them by default.
		5274
		5275	That means that libev compiled in the default environment doesn't support
		5276	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5277
		5278	Unfortunately, many programs try to work around this GNU/Linux issue
		5279	by enabling the large file API, which makes them incompatible with the
		5280	standard libev compiled for their system.
		5281
		5282	Likewise, libev cannot enable the large file API itself as this would
		5283	suddenly make it incompatible to the default compile time environment,
		5284	i.e. all programs not using special compile switches.
		5285
		5286	=head2 OS/X AND DARWIN BUGS
		5287
		5288	The whole thing is a bug if you ask me - basically any system interface
		5289	you touch is broken, whether it is locales, poll, kqueue or even the
		5290	OpenGL drivers.
		5291
		5292	=head3 C<kqueue> is buggy
		5293
		5294	The kqueue syscall is broken in all known versions - most versions support
		5295	only sockets, many support pipes.
		5296
		5297	Libev tries to work around this by not using C<kqueue> by default on this
		5298	rotten platform, but of course you can still ask for it when creating a
		5299	loop - embedding a socket-only kqueue loop into a select-based one is
		5300	probably going to work well.
		5301
		5302	=head3 C<poll> is buggy
		5303
		5304	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5305	implementation by something calling C<kqueue> internally around the 10.5.6
		5306	release, so now C<kqueue> I<and> C<poll> are broken.
		5307
		5308	Libev tries to work around this by not using C<poll> by default on
		5309	this rotten platform, but of course you can still ask for it when creating
		5310	a loop.
		5311
		5312	=head3 C<select> is buggy
		5313
		5314	All that's left is C<select>, and of course Apple found a way to fuck this
		5315	one up as well: On OS/X, C<select> actively limits the number of file
		5316	descriptors you can pass in to 1024 - your program suddenly crashes when
		5317	you use more.
		5318
		5319	There is an undocumented "workaround" for this - defining
		5320	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5321	work on OS/X.
		5322
		5323	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5324
		5325	=head3 C<errno> reentrancy
		5326
		5327	The default compile environment on Solaris is unfortunately so
		5328	thread-unsafe that you can't even use components/libraries compiled
		5329	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5330	defined by default. A valid, if stupid, implementation choice.
		5331
		5332	If you want to use libev in threaded environments you have to make sure
		5333	it's compiled with C<_REENTRANT> defined.
		5334
		5335	=head3 Event port backend
		5336
		5337	The scalable event interface for Solaris is called "event
		5338	ports". Unfortunately, this mechanism is very buggy in all major
		5339	releases. If you run into high CPU usage, your program freezes or you get
		5340	a large number of spurious wakeups, make sure you have all the relevant
		5341	and latest kernel patches applied. No, I don't know which ones, but there
		5342	are multiple ones to apply, and afterwards, event ports actually work
		5343	great.
		5344
		5345	If you can't get it to work, you can try running the program by setting
		5346	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5347	C<select> backends.
		5348
		5349	=head2 AIX POLL BUG
		5350
		5351	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5352	this by trying to avoid the poll backend altogether (i.e. it's not even
		5353	compiled in), which normally isn't a big problem as C<select> works fine
		5354	with large bitsets on AIX, and AIX is dead anyway.
		5355
3950	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5356	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5357
		5358	=head3 General issues
3951		5359
3952	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5360	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3953	requires, and its I/O model is fundamentally incompatible with the POSIX	5361	requires, and its I/O model is fundamentally incompatible with the POSIX
3954	model. Libev still offers limited functionality on this platform in	5362	model. Libev still offers limited functionality on this platform in
3955	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5363	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3956	descriptors. This only applies when using Win32 natively, not when using	5364	descriptors. This only applies when using Win32 natively, not when using
3957	e.g. cygwin.	5365	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5366	as every compiler comes with a slightly differently broken/incompatible
		5367	environment.
3958		5368
3959	Lifting these limitations would basically require the full	5369	Lifting these limitations would basically require the full
3960	re-implementation of the I/O system. If you are into these kinds of	5370	re-implementation of the I/O system. If you are into this kind of thing,
3961	things, then note that glib does exactly that for you in a very portable	5371	then note that glib does exactly that for you in a very portable way (note
3962	way (note also that glib is the slowest event library known to man).	5372	also that glib is the slowest event library known to man).
3963		5373
3964	There is no supported compilation method available on windows except	5374	There is no supported compilation method available on windows except
3965	embedding it into other applications.	5375	embedding it into other applications.
3966		5376
3967	Sensible signal handling is officially unsupported by Microsoft - libev	5377	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
3995	you do I<not> compile the F<ev.c> or any other embedded source files!):	5405	you do I<not> compile the F<ev.c> or any other embedded source files!):
3996		5406
3997	#include "evwrap.h"	5407	#include "evwrap.h"
3998	#include "ev.c"	5408	#include "ev.c"
3999		5409
4000	=over 4
4001
4002	=item The winsocket select function	5410	=head3 The winsocket C<select> function
4003		5411
4004	The winsocket C<select> function doesn't follow POSIX in that it	5412	The winsocket C<select> function doesn't follow POSIX in that it
4005	requires socket I<handles> and not socket I<file descriptors> (it is	5413	requires socket I<handles> and not socket I<file descriptors> (it is
4006	also extremely buggy). This makes select very inefficient, and also	5414	also extremely buggy). This makes select very inefficient, and also
4007	requires a mapping from file descriptors to socket handles (the Microsoft	5415	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4016	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5424	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4017		5425
4018	Note that winsockets handling of fd sets is O(n), so you can easily get a	5426	Note that winsockets handling of fd sets is O(n), so you can easily get a
4019	complexity in the O(n²) range when using win32.	5427	complexity in the O(n²) range when using win32.
4020		5428
4021	=item Limited number of file descriptors	5429	=head3 Limited number of file descriptors
4022		5430
4023	Windows has numerous arbitrary (and low) limits on things.	5431	Windows has numerous arbitrary (and low) limits on things.
4024		5432
4025	Early versions of winsocket's select only supported waiting for a maximum	5433	Early versions of winsocket's select only supported waiting for a maximum
4026	of C<64> handles (probably owning to the fact that all windows kernels	5434	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4041	runtime libraries. This might get you to about C<512> or C<2048> sockets	5449	runtime libraries. This might get you to about C<512> or C<2048> sockets
4042	(depending on windows version and/or the phase of the moon). To get more,	5450	(depending on windows version and/or the phase of the moon). To get more,
4043	you need to wrap all I/O functions and provide your own fd management, but	5451	you need to wrap all I/O functions and provide your own fd management, but
4044	the cost of calling select (O(n²)) will likely make this unworkable.	5452	the cost of calling select (O(n²)) will likely make this unworkable.
4045		5453
4046	=back
4047
4048	=head2 PORTABILITY REQUIREMENTS	5454	=head2 PORTABILITY REQUIREMENTS
4049		5455
4050	In addition to a working ISO-C implementation and of course the	5456	In addition to a working ISO-C implementation and of course the
4051	backend-specific APIs, libev relies on a few additional extensions:	5457	backend-specific APIs, libev relies on a few additional extensions:
4052		5458
…		…
4058	Libev assumes not only that all watcher pointers have the same internal	5464	Libev assumes not only that all watcher pointers have the same internal
4059	structure (guaranteed by POSIX but not by ISO C for example), but it also	5465	structure (guaranteed by POSIX but not by ISO C for example), but it also
4060	assumes that the same (machine) code can be used to call any watcher	5466	assumes that the same (machine) code can be used to call any watcher
4061	callback: The watcher callbacks have different type signatures, but libev	5467	callback: The watcher callbacks have different type signatures, but libev
4062	calls them using an C<ev_watcher *> internally.	5468	calls them using an C<ev_watcher *> internally.
		5469
		5470	=item null pointers and integer zero are represented by 0 bytes
		5471
		5472	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5473	relies on this setting pointers and integers to null.
		5474
		5475	=item pointer accesses must be thread-atomic
		5476
		5477	Accessing a pointer value must be atomic, it must both be readable and
		5478	writable in one piece - this is the case on all current architectures.
4063		5479
4064	=item C<sig_atomic_t volatile> must be thread-atomic as well	5480	=item C<sig_atomic_t volatile> must be thread-atomic as well
4065		5481
4066	The type C<sig_atomic_t volatile> (or whatever is defined as	5482	The type C<sig_atomic_t volatile> (or whatever is defined as
4067	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5483	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4076	thread" or will block signals process-wide, both behaviours would	5492	thread" or will block signals process-wide, both behaviours would
4077	be compatible with libev. Interaction between C<sigprocmask> and	5493	be compatible with libev. Interaction between C<sigprocmask> and
4078	C<pthread_sigmask> could complicate things, however.	5494	C<pthread_sigmask> could complicate things, however.
4079		5495
4080	The most portable way to handle signals is to block signals in all threads	5496	The most portable way to handle signals is to block signals in all threads
4081	except the initial one, and run the default loop in the initial thread as	5497	except the initial one, and run the signal handling loop in the initial
4082	well.	5498	thread as well.
4083		5499
4084	=item C<long> must be large enough for common memory allocation sizes	5500	=item C<long> must be large enough for common memory allocation sizes
4085		5501
4086	To improve portability and simplify its API, libev uses C<long> internally	5502	To improve portability and simplify its API, libev uses C<long> internally
4087	instead of C<size_t> when allocating its data structures. On non-POSIX	5503	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4090	watchers.	5506	watchers.
4091		5507
4092	=item C<double> must hold a time value in seconds with enough accuracy	5508	=item C<double> must hold a time value in seconds with enough accuracy
4093		5509
4094	The type C<double> is used to represent timestamps. It is required to	5510	The type C<double> is used to represent timestamps. It is required to
4095	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5511	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4096	enough for at least into the year 4000. This requirement is fulfilled by	5512	good enough for at least into the year 4000 with millisecond accuracy
		5513	(the design goal for libev). This requirement is overfulfilled by
4097	implementations implementing IEEE 754, which is basically all existing	5514	implementations using IEEE 754, which is basically all existing ones.
		5515
4098	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5516	With IEEE 754 doubles, you get microsecond accuracy until at least the
4099	2200.	5517	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5518	is either obsolete or somebody patched it to use C<long double> or
		5519	something like that, just kidding).
4100		5520
4101	=back	5521	=back
4102		5522
4103	If you know of other additional requirements drop me a note.	5523	If you know of other additional requirements drop me a note.
4104		5524
…		…
4166	=item Processing ev_async_send: O(number_of_async_watchers)	5586	=item Processing ev_async_send: O(number_of_async_watchers)
4167		5587
4168	=item Processing signals: O(max_signal_number)	5588	=item Processing signals: O(max_signal_number)
4169		5589
4170	Sending involves a system call I<iff> there were no other C<ev_async_send>	5590	Sending involves a system call I<iff> there were no other C<ev_async_send>
4171	calls in the current loop iteration. Checking for async and signal events	5591	calls in the current loop iteration and the loop is currently
		5592	blocked. Checking for async and signal events involves iterating over all
4172	involves iterating over all running async watchers or all signal numbers.	5593	running async watchers or all signal numbers.
4173		5594
4174	=back	5595	=back
4175		5596
4176		5597
		5598	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5599
		5600	The major version 4 introduced some incompatible changes to the API.
		5601
		5602	At the moment, the C<ev.h> header file provides compatibility definitions
		5603	for all changes, so most programs should still compile. The compatibility
		5604	layer might be removed in later versions of libev, so better update to the
		5605	new API early than late.
		5606
		5607	=over 4
		5608
		5609	=item C<EV_COMPAT3> backwards compatibility mechanism
		5610
		5611	The backward compatibility mechanism can be controlled by
		5612	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5613	section.
		5614
		5615	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5616
		5617	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5618
		5619	ev_loop_destroy (EV_DEFAULT_UC);
		5620	ev_loop_fork (EV_DEFAULT);
		5621
		5622	=item function/symbol renames
		5623
		5624	A number of functions and symbols have been renamed:
		5625
		5626	ev_loop => ev_run
		5627	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5628	EVLOOP_ONESHOT => EVRUN_ONCE
		5629
		5630	ev_unloop => ev_break
		5631	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5632	EVUNLOOP_ONE => EVBREAK_ONE
		5633	EVUNLOOP_ALL => EVBREAK_ALL
		5634
		5635	EV_TIMEOUT => EV_TIMER
		5636
		5637	ev_loop_count => ev_iteration
		5638	ev_loop_depth => ev_depth
		5639	ev_loop_verify => ev_verify
		5640
		5641	Most functions working on C<struct ev_loop> objects don't have an
		5642	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5643	associated constants have been renamed to not collide with the C<struct
		5644	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5645	as all other watcher types. Note that C<ev_loop_fork> is still called
		5646	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5647	typedef.
		5648
		5649	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5650
		5651	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5652	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5653	and work, but the library code will of course be larger.
		5654
		5655	=back
		5656
		5657
4177	=head1 GLOSSARY	5658	=head1 GLOSSARY
4178		5659
4179	=over 4	5660	=over 4
4180		5661
4181	=item active	5662	=item active
4182		5663
4183	A watcher is active as long as it has been started (has been attached to	5664	A watcher is active as long as it has been started and not yet stopped.
4184	an event loop) but not yet stopped (disassociated from the event loop).	5665	See L</WATCHER STATES> for details.
4185		5666
4186	=item application	5667	=item application
4187		5668
4188	In this document, an application is whatever is using libev.	5669	In this document, an application is whatever is using libev.
		5670
		5671	=item backend
		5672
		5673	The part of the code dealing with the operating system interfaces.
4189		5674
4190	=item callback	5675	=item callback
4191		5676
4192	The address of a function that is called when some event has been	5677	The address of a function that is called when some event has been
4193	detected. Callbacks are being passed the event loop, the watcher that	5678	detected. Callbacks are being passed the event loop, the watcher that
4194	received the event, and the actual event bitset.	5679	received the event, and the actual event bitset.
4195		5680
4196	=item callback invocation	5681	=item callback/watcher invocation
4197		5682
4198	The act of calling the callback associated with a watcher.	5683	The act of calling the callback associated with a watcher.
4199		5684
4200	=item event	5685	=item event
4201		5686
4202	A change of state of some external event, such as data now being available	5687	A change of state of some external event, such as data now being available
4203	for reading on a file descriptor, time having passed or simply not having	5688	for reading on a file descriptor, time having passed or simply not having
4204	any other events happening anymore.	5689	any other events happening anymore.
4205		5690
4206	In libev, events are represented as single bits (such as C<EV_READ> or	5691	In libev, events are represented as single bits (such as C<EV_READ> or
4207	C<EV_TIMEOUT>).	5692	C<EV_TIMER>).
4208		5693
4209	=item event library	5694	=item event library
4210		5695
4211	A software package implementing an event model and loop.	5696	A software package implementing an event model and loop.
4212		5697
…		…
4220	The model used to describe how an event loop handles and processes	5705	The model used to describe how an event loop handles and processes
4221	watchers and events.	5706	watchers and events.
4222		5707
4223	=item pending	5708	=item pending
4224		5709
4225	A watcher is pending as soon as the corresponding event has been detected,	5710	A watcher is pending as soon as the corresponding event has been
4226	and stops being pending as soon as the watcher will be invoked or its	5711	detected. See L</WATCHER STATES> for details.
4227	pending status is explicitly cleared by the application.
4228
4229	A watcher can be pending, but not active. Stopping a watcher also clears
4230	its pending status.
4231		5712
4232	=item real time	5713	=item real time
4233		5714
4234	The physical time that is observed. It is apparently strictly monotonic :)	5715	The physical time that is observed. It is apparently strictly monotonic :)
4235		5716
4236	=item wall-clock time	5717	=item wall-clock time
4237		5718
4238	The time and date as shown on clocks. Unlike real time, it can actually	5719	The time and date as shown on clocks. Unlike real time, it can actually
4239	be wrong and jump forwards and backwards, e.g. when the you adjust your	5720	be wrong and jump forwards and backwards, e.g. when you adjust your
4240	clock.	5721	clock.
4241		5722
4242	=item watcher	5723	=item watcher
4243		5724
4244	A data structure that describes interest in certain events. Watchers need	5725	A data structure that describes interest in certain events. Watchers need
4245	to be started (attached to an event loop) before they can receive events.	5726	to be started (attached to an event loop) before they can receive events.
4246		5727
4247	=item watcher invocation
4248
4249	The act of calling the callback associated with a watcher.
4250
4251	=back	5728	=back
4252		5729
4253	=head1 AUTHOR	5730	=head1 AUTHOR
4254		5731
4255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5732	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5733	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4256		5734

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