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Revision 1.453 by root, Tue Jun 25 05:01:22 2019 UTC

		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 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).
…		…
163		175
164	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
165		177
166	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
167	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
168	you actually want to know.	180	you actually want to know. Also interesting is the combination of
		181	C<ev_now_update> and C<ev_now>.
169		182
170	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
171		184
172	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
173	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
174	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
175		194
176	=item int ev_version_major ()	195	=item int ev_version_major ()
177		196
178	=item int ev_version_minor ()	197	=item int ev_version_minor ()
179		198
…		…
190	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
191	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
192	not a problem.	211	not a problem.
193		212
194	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
195	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
196		216
197	assert (("libev version mismatch",	217	assert (("libev version mismatch",
198	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
199	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
200		220
…		…
211	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
212	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
213		233
214	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
215		235
216	Return the set of all backends compiled into this binary of libev and also	236	Return the set of all backends compiled into this binary of libev and
217	recommended for this platform. This set is often smaller than the one	237	also recommended for this platform, meaning it will work for most file
		238	descriptor types. This set is often smaller than the one returned by
218	returned by C<ev_supported_backends>, as for example kqueue is broken on	239	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
219	most BSDs and will not be auto-detected unless you explicitly request it	240	and will not be auto-detected unless you explicitly request it (assuming
220	(assuming you know what you are doing). This is the set of backends that	241	you know what you are doing). This is the set of backends that libev will
221	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
222		243
223	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
224		245
225	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
226	is the theoretical, all-platform, value. To find which backends	247	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	248	current system. To find which embeddable backends might be supported on
228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
229	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
230		251
231	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
232		253
233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
234		255
235	Sets the allocation function to use (the prototype is similar - the	256	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	257	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	258	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	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
244		265
245	You could override this function in high-availability programs to, say,	266	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,	267	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.	268	or even to sleep a while and retry until some memory is available.
248		269
		270	Example: The following is the C<realloc> function that libev itself uses
		271	which should work with C<realloc> and C<free> functions of all kinds and
		272	is probably a good basis for your own implementation.
		273
		274	static void *
		275	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		276	{
		277	if (size)
		278	return realloc (ptr, size);
		279
		280	free (ptr);
		281	return 0;
		282	}
		283
249	Example: Replace the libev allocator with one that waits a bit and then	284	Example: Replace the libev allocator with one that waits a bit and then
250	retries (example requires a standards-compliant C<realloc>).	285	retries.
251		286
252	static void *	287	static void *
253	persistent_realloc (void *ptr, size_t size)	288	persistent_realloc (void *ptr, size_t size)
254	{	289	{
		290	if (!size)
		291	{
		292	free (ptr);
		293	return 0;
		294	}
		295
255	for (;;)	296	for (;;)
256	{	297	{
257	void *newptr = realloc (ptr, size);	298	void *newptr = realloc (ptr, size);
258		299
259	if (newptr)	300	if (newptr)
…		…
264	}	305	}
265		306
266	...	307	...
267	ev_set_allocator (persistent_realloc);	308	ev_set_allocator (persistent_realloc);
268		309
269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	310	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
270		311
271	Set the callback function to call on a retryable system call error (such	312	Set the callback function to call on a retryable system call error (such
272	as failed select, poll, epoll_wait). The message is a printable string	313	as failed select, poll, epoll_wait). The message is a printable string
273	indicating the system call or subsystem causing the problem. If this	314	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	315	callback is set, then libev will expect it to remedy the situation, no
…		…
286	}	327	}
287		328
288	...	329	...
289	ev_set_syserr_cb (fatal_error);	330	ev_set_syserr_cb (fatal_error);
290		331
		332	=item ev_feed_signal (int signum)
		333
		334	This function can be used to "simulate" a signal receive. It is completely
		335	safe to call this function at any time, from any context, including signal
		336	handlers or random threads.
		337
		338	Its main use is to customise signal handling in your process, especially
		339	in the presence of threads. For example, you could block signals
		340	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		341	creating any loops), and in one thread, use C<sigwait> or any other
		342	mechanism to wait for signals, then "deliver" them to libev by calling
		343	C<ev_feed_signal>.
		344
291	=back	345	=back
292		346
293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	347	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
294		348
295	An event loop is described by a C<struct ev_loop *> (the C<struct>	349	An event loop is described by a C<struct ev_loop *> (the C<struct> is
296	is I<not> optional in this case, as there is also an C<ev_loop>	350	I<not> optional in this case unless libev 3 compatibility is disabled, as
297	I<function>).	351	libev 3 had an C<ev_loop> function colliding with the struct name).
298		352
299	The library knows two types of such loops, the I<default> loop, which	353	The library knows two types of such loops, the I<default> loop, which
300	supports signals and child events, and dynamically created loops which do	354	supports child process events, and dynamically created event loops which
301	not.	355	do not.
302		356
303	=over 4	357	=over 4
304		358
305	=item struct ev_loop *ev_default_loop (unsigned int flags)	359	=item struct ev_loop *ev_default_loop (unsigned int flags)
306		360
307	This will initialise the default event loop if it hasn't been initialised	361	This returns the "default" event loop object, which is what you should
308	yet and return it. If the default loop could not be initialised, returns	362	normally use when you just need "the event loop". Event loop objects and
309	false. If it already was initialised it simply returns it (and ignores the	363	the C<flags> parameter are described in more detail in the entry for
310	flags. If that is troubling you, check C<ev_backend ()> afterwards).	364	C<ev_loop_new>.
		365
		366	If the default loop is already initialised then this function simply
		367	returns it (and ignores the flags. If that is troubling you, check
		368	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		369	flags, which should almost always be C<0>, unless the caller is also the
		370	one calling C<ev_run> or otherwise qualifies as "the main program".
311		371
312	If you don't know what event loop to use, use the one returned from this	372	If you don't know what event loop to use, use the one returned from this
313	function.	373	function (or via the C<EV_DEFAULT> macro).
314		374
315	Note that this function is I<not> thread-safe, so if you want to use it	375	Note that this function is I<not> thread-safe, so if you want to use it
316	from multiple threads, you have to lock (note also that this is unlikely,	376	from multiple threads, you have to employ some kind of mutex (note also
317	as loops cannot be shared easily between threads anyway).	377	that this case is unlikely, as loops cannot be shared easily between
		378	threads anyway).
318		379
319	The default loop is the only loop that can handle C<ev_signal> and	380	The default loop is the only loop that can handle C<ev_child> watchers,
320	C<ev_child> watchers, and to do this, it always registers a handler	381	and to do this, it always registers a handler for C<SIGCHLD>. If this is
321	for C<SIGCHLD>. If this is a problem for your application you can either	382	a problem for your application you can either create a dynamic loop with
322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	383	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	384	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
324	C<ev_default_init>.	385
		386	Example: This is the most typical usage.
		387
		388	if (!ev_default_loop (0))
		389	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		390
		391	Example: Restrict libev to the select and poll backends, and do not allow
		392	environment settings to be taken into account:
		393
		394	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		395
		396	=item struct ev_loop *ev_loop_new (unsigned int flags)
		397
		398	This will create and initialise a new event loop object. If the loop
		399	could not be initialised, returns false.
		400
		401	This function is thread-safe, and one common way to use libev with
		402	threads is indeed to create one loop per thread, and using the default
		403	loop in the "main" or "initial" thread.
325		404
326	The flags argument can be used to specify special behaviour or specific	405	The flags argument can be used to specify special behaviour or specific
327	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	406	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
328		407
329	The following flags are supported:	408	The following flags are supported:
…		…
339		418
340	If this flag bit is or'ed into the flag value (or the program runs setuid	419	If this flag bit is or'ed into the flag value (or the program runs setuid
341	or setgid) then libev will I<not> look at the environment variable	420	or setgid) then libev will I<not> look at the environment variable
342	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	421	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
343	override the flags completely if it is found in the environment. This is	422	override the flags completely if it is found in the environment. This is
344	useful to try out specific backends to test their performance, or to work	423	useful to try out specific backends to test their performance, to work
345	around bugs.	424	around bugs, or to make libev threadsafe (accessing environment variables
		425	cannot be done in a threadsafe way, but usually it works if no other
		426	thread modifies them).
346		427
347	=item C<EVFLAG_FORKCHECK>	428	=item C<EVFLAG_FORKCHECK>
348		429
349	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	430	Instead of calling C<ev_loop_fork> manually after a fork, you can also
350	a fork, you can also make libev check for a fork in each iteration by	431	make libev check for a fork in each iteration by enabling this flag.
351	enabling this flag.
352		432
353	This works by calling C<getpid ()> on every iteration of the loop,	433	This works by calling C<getpid ()> on every iteration of the loop,
354	and thus this might slow down your event loop if you do a lot of loop	434	and thus this might slow down your event loop if you do a lot of loop
355	iterations and little real work, but is usually not noticeable (on my	435	iterations and little real work, but is usually not noticeable (on my
356	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	436	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
357	without a system call and thus I<very> fast, but my GNU/Linux system also has	437	sequence without a system call and thus I<very> fast, but my GNU/Linux
358	C<pthread_atfork> which is even faster).	438	system also has C<pthread_atfork> which is even faster). (Update: glibc
		439	versions 2.25 apparently removed the C<getpid> optimisation again).
359		440
360	The big advantage of this flag is that you can forget about fork (and	441	The big advantage of this flag is that you can forget about fork (and
361	forget about forgetting to tell libev about forking) when you use this	442	forget about forgetting to tell libev about forking, although you still
362	flag.	443	have to ignore C<SIGPIPE>) when you use this flag.
363		444
364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	445	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
365	environment variable.	446	environment variable.
366		447
367	=item C<EVFLAG_NOINOTIFY>	448	=item C<EVFLAG_NOINOTIFY>
368		449
369	When this flag is specified, then libev will not attempt to use the	450	When this flag is specified, then libev will not attempt to use the
370	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	451	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
371	testing, this flag can be useful to conserve inotify file descriptors, as	452	testing, this flag can be useful to conserve inotify file descriptors, as
372	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	453	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
373		454
374	=item C<EVFLAG_NOSIGNALFD>	455	=item C<EVFLAG_SIGNALFD>
375		456
376	When this flag is specified, then libev will not attempt to use the	457	When this flag is specified, then libev will attempt to use the
377	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is	458	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
378	probably only useful to work around any bugs in libev. Consequently, this	459	delivers signals synchronously, which makes it both faster and might make
379	flag might go away once the signalfd functionality is considered stable,	460	it possible to get the queued signal data. It can also simplify signal
380	so it's useful mostly in environment variables and not in program code.	461	handling with threads, as long as you properly block signals in your
		462	threads that are not interested in handling them.
		463
		464	Signalfd will not be used by default as this changes your signal mask, and
		465	there are a lot of shoddy libraries and programs (glib's threadpool for
		466	example) that can't properly initialise their signal masks.
		467
		468	=item C<EVFLAG_NOSIGMASK>
		469
		470	When this flag is specified, then libev will avoid to modify the signal
		471	mask. Specifically, this means you have to make sure signals are unblocked
		472	when you want to receive them.
		473
		474	This behaviour is useful when you want to do your own signal handling, or
		475	want to handle signals only in specific threads and want to avoid libev
		476	unblocking the signals.
		477
		478	It's also required by POSIX in a threaded program, as libev calls
		479	C<sigprocmask>, whose behaviour is officially unspecified.
		480
		481	This flag's behaviour will become the default in future versions of libev.
381		482
382	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	483	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
383		484
384	This is your standard select(2) backend. Not I<completely> standard, as	485	This is your standard select(2) backend. Not I<completely> standard, as
385	libev tries to roll its own fd_set with no limits on the number of fds,	486	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
410	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	511	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
411	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	512	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
412		513
413	=item C<EVBACKEND_EPOLL> (value 4, Linux)	514	=item C<EVBACKEND_EPOLL> (value 4, Linux)
414		515
		516	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		517	kernels).
		518
415	For few fds, this backend is a bit little slower than poll and select,	519	For few fds, this backend is a bit little slower than poll and select, but
416	but it scales phenomenally better. While poll and select usually scale	520	it scales phenomenally better. While poll and select usually scale like
417	like O(total_fds) where n is the total number of fds (or the highest fd),	521	O(total_fds) where total_fds is the total number of fds (or the highest
418	epoll scales either O(1) or O(active_fds).	522	fd), epoll scales either O(1) or O(active_fds).
419		523
420	The epoll mechanism deserves honorable mention as the most misdesigned	524	The epoll mechanism deserves honorable mention as the most misdesigned
421	of the more advanced event mechanisms: mere annoyances include silently	525	of the more advanced event mechanisms: mere annoyances include silently
422	dropping file descriptors, requiring a system call per change per file	526	dropping file descriptors, requiring a system call per change per file
423	descriptor (and unnecessary guessing of parameters), problems with dup and	527	descriptor (and unnecessary guessing of parameters), problems with dup,
		528	returning before the timeout value, resulting in additional iterations
		529	(and only giving 5ms accuracy while select on the same platform gives
424	so on. The biggest issue is fork races, however - if a program forks then	530	0.1ms) and so on. The biggest issue is fork races, however - if a program
425	I<both> parent and child process have to recreate the epoll set, which can	531	forks then I<both> parent and child process have to recreate the epoll
426	take considerable time (one syscall per file descriptor) and is of course	532	set, which can take considerable time (one syscall per file descriptor)
427	hard to detect.	533	and is of course hard to detect.
428		534
429	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	535	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
430	of course I<doesn't>, and epoll just loves to report events for totally	536	but of course I<doesn't>, and epoll just loves to report events for
431	I<different> file descriptors (even already closed ones, so one cannot	537	totally I<different> file descriptors (even already closed ones, so
432	even remove them from the set) than registered in the set (especially	538	one cannot even remove them from the set) than registered in the set
433	on SMP systems). Libev tries to counter these spurious notifications by	539	(especially on SMP systems). Libev tries to counter these spurious
434	employing an additional generation counter and comparing that against the	540	notifications by employing an additional generation counter and comparing
435	events to filter out spurious ones, recreating the set when required.	541	that against the events to filter out spurious ones, recreating the set
		542	when required. Epoll also erroneously rounds down timeouts, but gives you
		543	no way to know when and by how much, so sometimes you have to busy-wait
		544	because epoll returns immediately despite a nonzero timeout. And last
		545	not least, it also refuses to work with some file descriptors which work
		546	perfectly fine with C<select> (files, many character devices...).
		547
		548	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		549	cobbled together in a hurry, no thought to design or interaction with
		550	others. Oh, the pain, will it ever stop...
436		551
437	While stopping, setting and starting an I/O watcher in the same iteration	552	While stopping, setting and starting an I/O watcher in the same iteration
438	will result in some caching, there is still a system call per such	553	will result in some caching, there is still a system call per such
439	incident (because the same I<file descriptor> could point to a different	554	incident (because the same I<file descriptor> could point to a different
440	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	555	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
452	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or	567	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
453	faster than epoll for maybe up to a hundred file descriptors, depending on	568	faster than epoll for maybe up to a hundred file descriptors, depending on
454	the usage. So sad.	569	the usage. So sad.
455		570
456	While nominally embeddable in other event loops, this feature is broken in	571	While nominally embeddable in other event loops, this feature is broken in
457	all kernel versions tested so far.	572	a lot of kernel revisions, but probably(!) works in current versions.
458		573
459	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	574	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
460	C<EVBACKEND_POLL>.	575	C<EVBACKEND_POLL>.
461		576
		577	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		578
		579	Use the linux-specific linux aio (I<not> C<< aio(7) >> but C<<
		580	io_submit(2) >>) event interface available in post-4.18 kernels (but libev
		581	only tries to use it in 4.19+).
		582
		583	This is another linux trainwreck of an event interface.
		584
		585	If this backend works for you (as of this writing, it was very
		586	experimental), it is the best event interface available on linux and might
		587	be well worth enabling it - if it isn't available in your kernel this will
		588	be detected and this backend will be skipped.
		589
		590	This backend can batch oneshot requests and supports a user-space ring
		591	buffer to receive events. It also doesn't suffer from most of the design
		592	problems of epoll (such as not being able to remove event sources from
		593	the epoll set), and generally sounds too good to be true. Because, this
		594	being the linux kernel, of course it suffers from a whole new set of
		595	limitations, forcing you to fall back to epoll, inheriting all its design
		596	issues.
		597
		598	For one, it is not easily embeddable (but probably could be done using
		599	an event fd at some extra overhead). It also is subject to a system wide
		600	limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no aio
		601	requests are left, this backend will be skipped during initialisation, and
		602	will switch to epoll when the loop is active.
		603
		604	Most problematic in practice, however, is that not all file descriptors
		605	work with it. For example, in linux 5.1, tcp sockets, pipes, event fds,
		606	files, F</dev/null> and a few others are supported, but ttys do not work
		607	properly (a known bug that the kernel developers don't care about, see
		608	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		609	(yet?) a generic event polling interface.
		610
		611	Overall, it seems the linux developers just don't want it to have a
		612	generic event handling mechanism other than C<select> or C<poll>.
		613
		614	To work around all these problem, the current version of libev uses its
		615	epoll backend as a fallback for file descriptor types that do not work. Or
		616	falls back completely to epoll if the kernel acts up.
		617
		618	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		619	C<EVBACKEND_POLL>.
		620
462	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	621	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
463		622
464	Kqueue deserves special mention, as at the time of this writing, it	623	Kqueue deserves special mention, as at the time this backend was
465	was broken on all BSDs except NetBSD (usually it doesn't work reliably	624	implemented, it was broken on all BSDs except NetBSD (usually it doesn't
466	with anything but sockets and pipes, except on Darwin, where of course	625	work reliably with anything but sockets and pipes, except on Darwin,
467	it's completely useless). Unlike epoll, however, whose brokenness	626	where of course it's completely useless). Unlike epoll, however, whose
468	is by design, these kqueue bugs can (and eventually will) be fixed	627	brokenness is by design, these kqueue bugs can be (and mostly have been)
469	without API changes to existing programs. For this reason it's not being	628	fixed without API changes to existing programs. For this reason it's not
470	"auto-detected" unless you explicitly specify it in the flags (i.e. using	629	being "auto-detected" on all platforms unless you explicitly specify it
471	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	630	in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a
472	system like NetBSD.	631	known-to-be-good (-enough) system like NetBSD.
473		632
474	You still can embed kqueue into a normal poll or select backend and use it	633	You still can embed kqueue into a normal poll or select backend and use it
475	only for sockets (after having made sure that sockets work with kqueue on	634	only for sockets (after having made sure that sockets work with kqueue on
476	the target platform). See C<ev_embed> watchers for more info.	635	the target platform). See C<ev_embed> watchers for more info.
477		636
478	It scales in the same way as the epoll backend, but the interface to the	637	It scales in the same way as the epoll backend, but the interface to the
479	kernel is more efficient (which says nothing about its actual speed, of	638	kernel is more efficient (which says nothing about its actual speed, of
480	course). While stopping, setting and starting an I/O watcher does never	639	course). While stopping, setting and starting an I/O watcher does never
481	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	640	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
482	two event changes per incident. Support for C<fork ()> is very bad (but	641	two event changes per incident. Support for C<fork ()> is very bad (you
483	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	642	might have to leak fd's on fork, but it's more sane than epoll) and it
484	cases	643	drops fds silently in similarly hard-to-detect cases.
485		644
486	This backend usually performs well under most conditions.	645	This backend usually performs well under most conditions.
487		646
488	While nominally embeddable in other event loops, this doesn't work	647	While nominally embeddable in other event loops, this doesn't work
489	everywhere, so you might need to test for this. And since it is broken	648	everywhere, so you might need to test for this. And since it is broken
…		…
506	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	665	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
507		666
508	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	667	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
509	it's really slow, but it still scales very well (O(active_fds)).	668	it's really slow, but it still scales very well (O(active_fds)).
510		669
511	Please note that Solaris event ports can deliver a lot of spurious
512	notifications, so you need to use non-blocking I/O or other means to avoid
513	blocking when no data (or space) is available.
514
515	While this backend scales well, it requires one system call per active	670	While this backend scales well, it requires one system call per active
516	file descriptor per loop iteration. For small and medium numbers of file	671	file descriptor per loop iteration. For small and medium numbers of file
517	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	672	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
518	might perform better.	673	might perform better.
519		674
520	On the positive side, with the exception of the spurious readiness	675	On the positive side, this backend actually performed fully to
521	notifications, this backend actually performed fully to specification
522	in all tests and is fully embeddable, which is a rare feat among the	676	specification in all tests and is fully embeddable, which is a rare feat
523	OS-specific backends (I vastly prefer correctness over speed hacks).	677	among the OS-specific backends (I vastly prefer correctness over speed
		678	hacks).
		679
		680	On the negative side, the interface is I<bizarre> - so bizarre that
		681	even sun itself gets it wrong in their code examples: The event polling
		682	function sometimes returns events to the caller even though an error
		683	occurred, but with no indication whether it has done so or not (yes, it's
		684	even documented that way) - deadly for edge-triggered interfaces where you
		685	absolutely have to know whether an event occurred or not because you have
		686	to re-arm the watcher.
		687
		688	Fortunately libev seems to be able to work around these idiocies.
524		689
525	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	690	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
526	C<EVBACKEND_POLL>.	691	C<EVBACKEND_POLL>.
527		692
528	=item C<EVBACKEND_ALL>	693	=item C<EVBACKEND_ALL>
529		694
530	Try all backends (even potentially broken ones that wouldn't be tried	695	Try all backends (even potentially broken ones that wouldn't be tried
531	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	696	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
532	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	697	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
533		698
534	It is definitely not recommended to use this flag.	699	It is definitely not recommended to use this flag, use whatever
		700	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		701	at all.
		702
		703	=item C<EVBACKEND_MASK>
		704
		705	Not a backend at all, but a mask to select all backend bits from a
		706	C<flags> value, in case you want to mask out any backends from a flags
		707	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
535		708
536	=back	709	=back
537		710
538	If one or more of the backend flags are or'ed into the flags value,	711	If one or more of the backend flags are or'ed into the flags value,
539	then only these backends will be tried (in the reverse order as listed	712	then only these backends will be tried (in the reverse order as listed
540	here). If none are specified, all backends in C<ev_recommended_backends	713	here). If none are specified, all backends in C<ev_recommended_backends
541	()> will be tried.	714	()> will be tried.
542		715
543	Example: This is the most typical usage.
544
545	if (!ev_default_loop (0))
546	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
547
548	Example: Restrict libev to the select and poll backends, and do not allow
549	environment settings to be taken into account:
550
551	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
552
553	Example: Use whatever libev has to offer, but make sure that kqueue is
554	used if available (warning, breaks stuff, best use only with your own
555	private event loop and only if you know the OS supports your types of
556	fds):
557
558	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
559
560	=item struct ev_loop *ev_loop_new (unsigned int flags)
561
562	Similar to C<ev_default_loop>, but always creates a new event loop that is
563	always distinct from the default loop. Unlike the default loop, it cannot
564	handle signal and child watchers, and attempts to do so will be greeted by
565	undefined behaviour (or a failed assertion if assertions are enabled).
566
567	Note that this function I<is> thread-safe, and the recommended way to use
568	libev with threads is indeed to create one loop per thread, and using the
569	default loop in the "main" or "initial" thread.
570
571	Example: Try to create a event loop that uses epoll and nothing else.	716	Example: Try to create a event loop that uses epoll and nothing else.
572		717
573	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	718	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
574	if (!epoller)	719	if (!epoller)
575	fatal ("no epoll found here, maybe it hides under your chair");	720	fatal ("no epoll found here, maybe it hides under your chair");
576		721
		722	Example: Use whatever libev has to offer, but make sure that kqueue is
		723	used if available.
		724
		725	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		726
		727	Example: Similarly, on linux, you mgiht want to take advantage of the
		728	linux aio backend if possible, but fall back to something else if that
		729	isn't available.
		730
		731	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		732
577	=item ev_default_destroy ()	733	=item ev_loop_destroy (loop)
578		734
579	Destroys the default loop again (frees all memory and kernel state	735	Destroys an event loop object (frees all memory and kernel state
580	etc.). None of the active event watchers will be stopped in the normal	736	etc.). None of the active event watchers will be stopped in the normal
581	sense, so e.g. C<ev_is_active> might still return true. It is your	737	sense, so e.g. C<ev_is_active> might still return true. It is your
582	responsibility to either stop all watchers cleanly yourself I<before>	738	responsibility to either stop all watchers cleanly yourself I<before>
583	calling this function, or cope with the fact afterwards (which is usually	739	calling this function, or cope with the fact afterwards (which is usually
584	the easiest thing, you can just ignore the watchers and/or C<free ()> them	740	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
586		742
587	Note that certain global state, such as signal state (and installed signal	743	Note that certain global state, such as signal state (and installed signal
588	handlers), will not be freed by this function, and related watchers (such	744	handlers), will not be freed by this function, and related watchers (such
589	as signal and child watchers) would need to be stopped manually.	745	as signal and child watchers) would need to be stopped manually.
590		746
591	In general it is not advisable to call this function except in the	747	This function is normally used on loop objects allocated by
592	rare occasion where you really need to free e.g. the signal handling	748	C<ev_loop_new>, but it can also be used on the default loop returned by
		749	C<ev_default_loop>, in which case it is not thread-safe.
		750
		751	Note that it is not advisable to call this function on the default loop
		752	except in the rare occasion where you really need to free its resources.
593	pipe fds. If you need dynamically allocated loops it is better to use	753	If you need dynamically allocated loops it is better to use C<ev_loop_new>
594	C<ev_loop_new> and C<ev_loop_destroy>).	754	and C<ev_loop_destroy>.
595		755
596	=item ev_loop_destroy (loop)	756	=item ev_loop_fork (loop)
597		757
598	Like C<ev_default_destroy>, but destroys an event loop created by an
599	earlier call to C<ev_loop_new>.
600
601	=item ev_default_fork ()
602
603	This function sets a flag that causes subsequent C<ev_loop> iterations	758	This function sets a flag that causes subsequent C<ev_run> iterations
604	to reinitialise the kernel state for backends that have one. Despite the	759	to reinitialise the kernel state for backends that have one. Despite
605	name, you can call it anytime, but it makes most sense after forking, in	760	the name, you can call it anytime you are allowed to start or stop
606	the child process (or both child and parent, but that again makes little	761	watchers (except inside an C<ev_prepare> callback), but it makes most
607	sense). You I<must> call it in the child before using any of the libev	762	sense after forking, in the child process. You I<must> call it (or use
608	functions, and it will only take effect at the next C<ev_loop> iteration.	763	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		764
		765	In addition, if you want to reuse a loop (via this function or
		766	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		767
		768	Again, you I<have> to call it on I<any> loop that you want to re-use after
		769	a fork, I<even if you do not plan to use the loop in the parent>. This is
		770	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		771	during fork.
609		772
610	On the other hand, you only need to call this function in the child	773	On the other hand, you only need to call this function in the child
611	process if and only if you want to use the event library in the child. If	774	process if and only if you want to use the event loop in the child. If
612	you just fork+exec, you don't have to call it at all.	775	you just fork+exec or create a new loop in the child, you don't have to
		776	call it at all (in fact, C<epoll> is so badly broken that it makes a
		777	difference, but libev will usually detect this case on its own and do a
		778	costly reset of the backend).
613		779
614	The function itself is quite fast and it's usually not a problem to call	780	The function itself is quite fast and it's usually not a problem to call
615	it just in case after a fork. To make this easy, the function will fit in	781	it just in case after a fork.
616	quite nicely into a call to C<pthread_atfork>:
617		782
		783	Example: Automate calling C<ev_loop_fork> on the default loop when
		784	using pthreads.
		785
		786	static void
		787	post_fork_child (void)
		788	{
		789	ev_loop_fork (EV_DEFAULT);
		790	}
		791
		792	...
618	pthread_atfork (0, 0, ev_default_fork);	793	pthread_atfork (0, 0, post_fork_child);
619
620	=item ev_loop_fork (loop)
621
622	Like C<ev_default_fork>, but acts on an event loop created by
623	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
624	after fork that you want to re-use in the child, and how you do this is
625	entirely your own problem.
626		794
627	=item int ev_is_default_loop (loop)	795	=item int ev_is_default_loop (loop)
628		796
629	Returns true when the given loop is, in fact, the default loop, and false	797	Returns true when the given loop is, in fact, the default loop, and false
630	otherwise.	798	otherwise.
631		799
632	=item unsigned int ev_loop_count (loop)	800	=item unsigned int ev_iteration (loop)
633		801
634	Returns the count of loop iterations for the loop, which is identical to	802	Returns the current iteration count for the event loop, which is identical
635	the number of times libev did poll for new events. It starts at C<0> and	803	to the number of times libev did poll for new events. It starts at C<0>
636	happily wraps around with enough iterations.	804	and happily wraps around with enough iterations.
637		805
638	This value can sometimes be useful as a generation counter of sorts (it	806	This value can sometimes be useful as a generation counter of sorts (it
639	"ticks" the number of loop iterations), as it roughly corresponds with	807	"ticks" the number of loop iterations), as it roughly corresponds with
640	C<ev_prepare> and C<ev_check> calls.	808	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		809	prepare and check phases.
641		810
642	=item unsigned int ev_loop_depth (loop)	811	=item unsigned int ev_depth (loop)
643		812
644	Returns the number of times C<ev_loop> was entered minus the number of	813	Returns the number of times C<ev_run> was entered minus the number of
645	times C<ev_loop> was exited, in other words, the recursion depth.	814	times C<ev_run> was exited normally, in other words, the recursion depth.
646		815
647	Outside C<ev_loop>, this number is zero. In a callback, this number is	816	Outside C<ev_run>, this number is zero. In a callback, this number is
648	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	817	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
649	in which case it is higher.	818	in which case it is higher.
650		819
651	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	820	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
652	etc.), doesn't count as exit.	821	throwing an exception etc.), doesn't count as "exit" - consider this
		822	as a hint to avoid such ungentleman-like behaviour unless it's really
		823	convenient, in which case it is fully supported.
653		824
654	=item unsigned int ev_backend (loop)	825	=item unsigned int ev_backend (loop)
655		826
656	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	827	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
657	use.	828	use.
…		…
666		837
667	=item ev_now_update (loop)	838	=item ev_now_update (loop)
668		839
669	Establishes the current time by querying the kernel, updating the time	840	Establishes the current time by querying the kernel, updating the time
670	returned by C<ev_now ()> in the progress. This is a costly operation and	841	returned by C<ev_now ()> in the progress. This is a costly operation and
671	is usually done automatically within C<ev_loop ()>.	842	is usually done automatically within C<ev_run ()>.
672		843
673	This function is rarely useful, but when some event callback runs for a	844	This function is rarely useful, but when some event callback runs for a
674	very long time without entering the event loop, updating libev's idea of	845	very long time without entering the event loop, updating libev's idea of
675	the current time is a good idea.	846	the current time is a good idea.
676		847
677	See also L<The special problem of time updates> in the C<ev_timer> section.	848	See also L</The special problem of time updates> in the C<ev_timer> section.
678		849
679	=item ev_suspend (loop)	850	=item ev_suspend (loop)
680		851
681	=item ev_resume (loop)	852	=item ev_resume (loop)
682		853
683	These two functions suspend and resume a loop, for use when the loop is	854	These two functions suspend and resume an event loop, for use when the
684	not used for a while and timeouts should not be processed.	855	loop is not used for a while and timeouts should not be processed.
685		856
686	A typical use case would be an interactive program such as a game: When	857	A typical use case would be an interactive program such as a game: When
687	the user presses C<^Z> to suspend the game and resumes it an hour later it	858	the user presses C<^Z> to suspend the game and resumes it an hour later it
688	would be best to handle timeouts as if no time had actually passed while	859	would be best to handle timeouts as if no time had actually passed while
689	the program was suspended. This can be achieved by calling C<ev_suspend>	860	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
691	C<ev_resume> directly afterwards to resume timer processing.	862	C<ev_resume> directly afterwards to resume timer processing.
692		863
693	Effectively, all C<ev_timer> watchers will be delayed by the time spend	864	Effectively, all C<ev_timer> watchers will be delayed by the time spend
694	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	865	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
695	will be rescheduled (that is, they will lose any events that would have	866	will be rescheduled (that is, they will lose any events that would have
696	occured while suspended).	867	occurred while suspended).
697		868
698	After calling C<ev_suspend> you B<must not> call I<any> function on the	869	After calling C<ev_suspend> you B<must not> call I<any> function on the
699	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	870	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
700	without a previous call to C<ev_suspend>.	871	without a previous call to C<ev_suspend>.
701		872
702	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	873	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
703	event loop time (see C<ev_now_update>).	874	event loop time (see C<ev_now_update>).
704		875
705	=item ev_loop (loop, int flags)	876	=item bool ev_run (loop, int flags)
706		877
707	Finally, this is it, the event handler. This function usually is called	878	Finally, this is it, the event handler. This function usually is called
708	after you initialised all your watchers and you want to start handling	879	after you have initialised all your watchers and you want to start
709	events.	880	handling events. It will ask the operating system for any new events, call
		881	the watcher callbacks, and then repeat the whole process indefinitely: This
		882	is why event loops are called I<loops>.
710		883
711	If the flags argument is specified as C<0>, it will not return until	884	If the flags argument is specified as C<0>, it will keep handling events
712	either no event watchers are active anymore or C<ev_unloop> was called.	885	until either no event watchers are active anymore or C<ev_break> was
		886	called.
713		887
		888	The return value is false if there are no more active watchers (which
		889	usually means "all jobs done" or "deadlock"), and true in all other cases
		890	(which usually means " you should call C<ev_run> again").
		891
714	Please note that an explicit C<ev_unloop> is usually better than	892	Please note that an explicit C<ev_break> is usually better than
715	relying on all watchers to be stopped when deciding when a program has	893	relying on all watchers to be stopped when deciding when a program has
716	finished (especially in interactive programs), but having a program	894	finished (especially in interactive programs), but having a program
717	that automatically loops as long as it has to and no longer by virtue	895	that automatically loops as long as it has to and no longer by virtue
718	of relying on its watchers stopping correctly, that is truly a thing of	896	of relying on its watchers stopping correctly, that is truly a thing of
719	beauty.	897	beauty.
720		898
		899	This function is I<mostly> exception-safe - you can break out of a
		900	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		901	exception and so on. This does not decrement the C<ev_depth> value, nor
		902	will it clear any outstanding C<EVBREAK_ONE> breaks.
		903
721	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	904	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
722	those events and any already outstanding ones, but will not block your	905	those events and any already outstanding ones, but will not wait and
723	process in case there are no events and will return after one iteration of	906	block your process in case there are no events and will return after one
724	the loop.	907	iteration of the loop. This is sometimes useful to poll and handle new
		908	events while doing lengthy calculations, to keep the program responsive.
725		909
726	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	910	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
727	necessary) and will handle those and any already outstanding ones. It	911	necessary) and will handle those and any already outstanding ones. It
728	will block your process until at least one new event arrives (which could	912	will block your process until at least one new event arrives (which could
729	be an event internal to libev itself, so there is no guarantee that a	913	be an event internal to libev itself, so there is no guarantee that a
730	user-registered callback will be called), and will return after one	914	user-registered callback will be called), and will return after one
731	iteration of the loop.	915	iteration of the loop.
732		916
733	This is useful if you are waiting for some external event in conjunction	917	This is useful if you are waiting for some external event in conjunction
734	with something not expressible using other libev watchers (i.e. "roll your	918	with something not expressible using other libev watchers (i.e. "roll your
735	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	919	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
736	usually a better approach for this kind of thing.	920	usually a better approach for this kind of thing.
737		921
738	Here are the gory details of what C<ev_loop> does:	922	Here are the gory details of what C<ev_run> does (this is for your
		923	understanding, not a guarantee that things will work exactly like this in
		924	future versions):
739		925
		926	- Increment loop depth.
		927	- Reset the ev_break status.
740	- Before the first iteration, call any pending watchers.	928	- Before the first iteration, call any pending watchers.
		929	LOOP:
741	* If EVFLAG_FORKCHECK was used, check for a fork.	930	- If EVFLAG_FORKCHECK was used, check for a fork.
742	- If a fork was detected (by any means), queue and call all fork watchers.	931	- If a fork was detected (by any means), queue and call all fork watchers.
743	- Queue and call all prepare watchers.	932	- Queue and call all prepare watchers.
		933	- If ev_break was called, goto FINISH.
744	- If we have been forked, detach and recreate the kernel state	934	- If we have been forked, detach and recreate the kernel state
745	as to not disturb the other process.	935	as to not disturb the other process.
746	- Update the kernel state with all outstanding changes.	936	- Update the kernel state with all outstanding changes.
747	- Update the "event loop time" (ev_now ()).	937	- Update the "event loop time" (ev_now ()).
748	- Calculate for how long to sleep or block, if at all	938	- Calculate for how long to sleep or block, if at all
749	(active idle watchers, EVLOOP_NONBLOCK or not having	939	(active idle watchers, EVRUN_NOWAIT or not having
750	any active watchers at all will result in not sleeping).	940	any active watchers at all will result in not sleeping).
751	- Sleep if the I/O and timer collect interval say so.	941	- Sleep if the I/O and timer collect interval say so.
		942	- Increment loop iteration counter.
752	- Block the process, waiting for any events.	943	- Block the process, waiting for any events.
753	- Queue all outstanding I/O (fd) events.	944	- Queue all outstanding I/O (fd) events.
754	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	945	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
755	- Queue all expired timers.	946	- Queue all expired timers.
756	- Queue all expired periodics.	947	- Queue all expired periodics.
757	- Unless any events are pending now, queue all idle watchers.	948	- Queue all idle watchers with priority higher than that of pending events.
758	- Queue all check watchers.	949	- Queue all check watchers.
759	- Call all queued watchers in reverse order (i.e. check watchers first).	950	- Call all queued watchers in reverse order (i.e. check watchers first).
760	Signals and child watchers are implemented as I/O watchers, and will	951	Signals and child watchers are implemented as I/O watchers, and will
761	be handled here by queueing them when their watcher gets executed.	952	be handled here by queueing them when their watcher gets executed.
762	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	953	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
763	were used, or there are no active watchers, return, otherwise	954	were used, or there are no active watchers, goto FINISH, otherwise
764	continue with step *.	955	continue with step LOOP.
		956	FINISH:
		957	- Reset the ev_break status iff it was EVBREAK_ONE.
		958	- Decrement the loop depth.
		959	- Return.
765		960
766	Example: Queue some jobs and then loop until no events are outstanding	961	Example: Queue some jobs and then loop until no events are outstanding
767	anymore.	962	anymore.
768		963
769	... queue jobs here, make sure they register event watchers as long	964	... queue jobs here, make sure they register event watchers as long
770	... as they still have work to do (even an idle watcher will do..)	965	... as they still have work to do (even an idle watcher will do..)
771	ev_loop (my_loop, 0);	966	ev_run (my_loop, 0);
772	... jobs done or somebody called unloop. yeah!	967	... jobs done or somebody called break. yeah!
773		968
774	=item ev_unloop (loop, how)	969	=item ev_break (loop, how)
775		970
776	Can be used to make a call to C<ev_loop> return early (but only after it	971	Can be used to make a call to C<ev_run> return early (but only after it
777	has processed all outstanding events). The C<how> argument must be either	972	has processed all outstanding events). The C<how> argument must be either
778	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	973	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
779	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	974	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
780		975
781	This "unloop state" will be cleared when entering C<ev_loop> again.	976	This "break state" will be cleared on the next call to C<ev_run>.
782		977
783	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	978	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		979	which case it will have no effect.
784		980
785	=item ev_ref (loop)	981	=item ev_ref (loop)
786		982
787	=item ev_unref (loop)	983	=item ev_unref (loop)
788		984
789	Ref/unref can be used to add or remove a reference count on the event	985	Ref/unref can be used to add or remove a reference count on the event
790	loop: Every watcher keeps one reference, and as long as the reference	986	loop: Every watcher keeps one reference, and as long as the reference
791	count is nonzero, C<ev_loop> will not return on its own.	987	count is nonzero, C<ev_run> will not return on its own.
792		988
793	If you have a watcher you never unregister that should not keep C<ev_loop>	989	This is useful when you have a watcher that you never intend to
794	from returning, call ev_unref() after starting, and ev_ref() before	990	unregister, but that nevertheless should not keep C<ev_run> from
		991	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
795	stopping it.	992	before stopping it.
796		993
797	As an example, libev itself uses this for its internal signal pipe: It	994	As an example, libev itself uses this for its internal signal pipe: It
798	is not visible to the libev user and should not keep C<ev_loop> from	995	is not visible to the libev user and should not keep C<ev_run> from
799	exiting if no event watchers registered by it are active. It is also an	996	exiting if no event watchers registered by it are active. It is also an
800	excellent way to do this for generic recurring timers or from within	997	excellent way to do this for generic recurring timers or from within
801	third-party libraries. Just remember to I<unref after start> and I<ref	998	third-party libraries. Just remember to I<unref after start> and I<ref
802	before stop> (but only if the watcher wasn't active before, or was active	999	before stop> (but only if the watcher wasn't active before, or was active
803	before, respectively. Note also that libev might stop watchers itself	1000	before, respectively. Note also that libev might stop watchers itself
804	(e.g. non-repeating timers) in which case you have to C<ev_ref>	1001	(e.g. non-repeating timers) in which case you have to C<ev_ref>
805	in the callback).	1002	in the callback).
806		1003
807	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	1004	Example: Create a signal watcher, but keep it from keeping C<ev_run>
808	running when nothing else is active.	1005	running when nothing else is active.
809		1006
810	ev_signal exitsig;	1007	ev_signal exitsig;
811	ev_signal_init (&exitsig, sig_cb, SIGINT);	1008	ev_signal_init (&exitsig, sig_cb, SIGINT);
812	ev_signal_start (loop, &exitsig);	1009	ev_signal_start (loop, &exitsig);
813	evf_unref (loop);	1010	ev_unref (loop);
814		1011
815	Example: For some weird reason, unregister the above signal handler again.	1012	Example: For some weird reason, unregister the above signal handler again.
816		1013
817	ev_ref (loop);	1014	ev_ref (loop);
818	ev_signal_stop (loop, &exitsig);	1015	ev_signal_stop (loop, &exitsig);
…		…
838	overhead for the actual polling but can deliver many events at once.	1035	overhead for the actual polling but can deliver many events at once.
839		1036
840	By setting a higher I<io collect interval> you allow libev to spend more	1037	By setting a higher I<io collect interval> you allow libev to spend more
841	time collecting I/O events, so you can handle more events per iteration,	1038	time collecting I/O events, so you can handle more events per iteration,
842	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1039	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
843	C<ev_timer>) will be not affected. Setting this to a non-null value will	1040	C<ev_timer>) will not be affected. Setting this to a non-null value will
844	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1041	introduce an additional C<ev_sleep ()> call into most loop iterations. The
845	sleep time ensures that libev will not poll for I/O events more often then	1042	sleep time ensures that libev will not poll for I/O events more often then
846	once per this interval, on average.	1043	once per this interval, on average (as long as the host time resolution is
		1044	good enough).
847		1045
848	Likewise, by setting a higher I<timeout collect interval> you allow libev	1046	Likewise, by setting a higher I<timeout collect interval> you allow libev
849	to spend more time collecting timeouts, at the expense of increased	1047	to spend more time collecting timeouts, at the expense of increased
850	latency/jitter/inexactness (the watcher callback will be called	1048	latency/jitter/inexactness (the watcher callback will be called
851	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1049	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
857	usually doesn't make much sense to set it to a lower value than C<0.01>,	1055	usually doesn't make much sense to set it to a lower value than C<0.01>,
858	as this approaches the timing granularity of most systems. Note that if	1056	as this approaches the timing granularity of most systems. Note that if
859	you do transactions with the outside world and you can't increase the	1057	you do transactions with the outside world and you can't increase the
860	parallelity, then this setting will limit your transaction rate (if you	1058	parallelity, then this setting will limit your transaction rate (if you
861	need to poll once per transaction and the I/O collect interval is 0.01,	1059	need to poll once per transaction and the I/O collect interval is 0.01,
862	then you can't do more than 100 transations per second).	1060	then you can't do more than 100 transactions per second).
863		1061
864	Setting the I<timeout collect interval> can improve the opportunity for	1062	Setting the I<timeout collect interval> can improve the opportunity for
865	saving power, as the program will "bundle" timer callback invocations that	1063	saving power, as the program will "bundle" timer callback invocations that
866	are "near" in time together, by delaying some, thus reducing the number of	1064	are "near" in time together, by delaying some, thus reducing the number of
867	times the process sleeps and wakes up again. Another useful technique to	1065	times the process sleeps and wakes up again. Another useful technique to
…		…
875	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1073	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
876		1074
877	=item ev_invoke_pending (loop)	1075	=item ev_invoke_pending (loop)
878		1076
879	This call will simply invoke all pending watchers while resetting their	1077	This call will simply invoke all pending watchers while resetting their
880	pending state. Normally, C<ev_loop> does this automatically when required,	1078	pending state. Normally, C<ev_run> does this automatically when required,
881	but when overriding the invoke callback this call comes handy.	1079	but when overriding the invoke callback this call comes handy. This
		1080	function can be invoked from a watcher - this can be useful for example
		1081	when you want to do some lengthy calculation and want to pass further
		1082	event handling to another thread (you still have to make sure only one
		1083	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
882		1084
883	=item int ev_pending_count (loop)	1085	=item int ev_pending_count (loop)
884		1086
885	Returns the number of pending watchers - zero indicates that no watchers	1087	Returns the number of pending watchers - zero indicates that no watchers
886	are pending.	1088	are pending.
887		1089
888	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1090	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
889		1091
890	This overrides the invoke pending functionality of the loop: Instead of	1092	This overrides the invoke pending functionality of the loop: Instead of
891	invoking all pending watchers when there are any, C<ev_loop> will call	1093	invoking all pending watchers when there are any, C<ev_run> will call
892	this callback instead. This is useful, for example, when you want to	1094	this callback instead. This is useful, for example, when you want to
893	invoke the actual watchers inside another context (another thread etc.).	1095	invoke the actual watchers inside another context (another thread etc.).
894		1096
895	If you want to reset the callback, use C<ev_invoke_pending> as new	1097	If you want to reset the callback, use C<ev_invoke_pending> as new
896	callback.	1098	callback.
897		1099
898	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1100	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
899		1101
900	Sometimes you want to share the same loop between multiple threads. This	1102	Sometimes you want to share the same loop between multiple threads. This
901	can be done relatively simply by putting mutex_lock/unlock calls around	1103	can be done relatively simply by putting mutex_lock/unlock calls around
902	each call to a libev function.	1104	each call to a libev function.
903		1105
904	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1106	However, C<ev_run> can run an indefinite time, so it is not feasible
905	wait for it to return. One way around this is to wake up the loop via	1107	to wait for it to return. One way around this is to wake up the event
906	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1108	loop via C<ev_break> and C<ev_async_send>, another way is to set these
907	and I<acquire> callbacks on the loop.	1109	I<release> and I<acquire> callbacks on the loop.
908		1110
909	When set, then C<release> will be called just before the thread is	1111	When set, then C<release> will be called just before the thread is
910	suspended waiting for new events, and C<acquire> is called just	1112	suspended waiting for new events, and C<acquire> is called just
911	afterwards.	1113	afterwards.
912		1114
…		…
915		1117
916	While event loop modifications are allowed between invocations of	1118	While event loop modifications are allowed between invocations of
917	C<release> and C<acquire> (that's their only purpose after all), no	1119	C<release> and C<acquire> (that's their only purpose after all), no
918	modifications done will affect the event loop, i.e. adding watchers will	1120	modifications done will affect the event loop, i.e. adding watchers will
919	have no effect on the set of file descriptors being watched, or the time	1121	have no effect on the set of file descriptors being watched, or the time
920	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it	1122	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
921	to take note of any changes you made.	1123	to take note of any changes you made.
922		1124
923	In theory, threads executing C<ev_loop> will be async-cancel safe between	1125	In theory, threads executing C<ev_run> will be async-cancel safe between
924	invocations of C<release> and C<acquire>.	1126	invocations of C<release> and C<acquire>.
925		1127
926	See also the locking example in the C<THREADS> section later in this	1128	See also the locking example in the C<THREADS> section later in this
927	document.	1129	document.
928		1130
929	=item ev_set_userdata (loop, void *data)	1131	=item ev_set_userdata (loop, void *data)
930		1132
931	=item ev_userdata (loop)	1133	=item void *ev_userdata (loop)
932		1134
933	Set and retrieve a single C<void *> associated with a loop. When	1135	Set and retrieve a single C<void *> associated with a loop. When
934	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1136	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
935	C<0.>	1137	C<0>.
936		1138
937	These two functions can be used to associate arbitrary data with a loop,	1139	These two functions can be used to associate arbitrary data with a loop,
938	and are intended solely for the C<invoke_pending_cb>, C<release> and	1140	and are intended solely for the C<invoke_pending_cb>, C<release> and
939	C<acquire> callbacks described above, but of course can be (ab-)used for	1141	C<acquire> callbacks described above, but of course can be (ab-)used for
940	any other purpose as well.	1142	any other purpose as well.
941		1143
942	=item ev_loop_verify (loop)	1144	=item ev_verify (loop)
943		1145
944	This function only does something when C<EV_VERIFY> support has been	1146	This function only does something when C<EV_VERIFY> support has been
945	compiled in, which is the default for non-minimal builds. It tries to go	1147	compiled in, which is the default for non-minimal builds. It tries to go
946	through all internal structures and checks them for validity. If anything	1148	through all internal structures and checks them for validity. If anything
947	is found to be inconsistent, it will print an error message to standard	1149	is found to be inconsistent, it will print an error message to standard
…		…
958		1160
959	In the following description, uppercase C<TYPE> in names stands for the	1161	In the following description, uppercase C<TYPE> in names stands for the
960	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1162	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
961	watchers and C<ev_io_start> for I/O watchers.	1163	watchers and C<ev_io_start> for I/O watchers.
962		1164
963	A watcher is a structure that you create and register to record your	1165	A watcher is an opaque structure that you allocate and register to record
964	interest in some event. For instance, if you want to wait for STDIN to	1166	your interest in some event. To make a concrete example, imagine you want
965	become readable, you would create an C<ev_io> watcher for that:	1167	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1168	for that:
966		1169
967	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1170	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
968	{	1171	{
969	ev_io_stop (w);	1172	ev_io_stop (w);
970	ev_unloop (loop, EVUNLOOP_ALL);	1173	ev_break (loop, EVBREAK_ALL);
971	}	1174	}
972		1175
973	struct ev_loop *loop = ev_default_loop (0);	1176	struct ev_loop *loop = ev_default_loop (0);
974		1177
975	ev_io stdin_watcher;	1178	ev_io stdin_watcher;
976		1179
977	ev_init (&stdin_watcher, my_cb);	1180	ev_init (&stdin_watcher, my_cb);
978	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1181	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
979	ev_io_start (loop, &stdin_watcher);	1182	ev_io_start (loop, &stdin_watcher);
980		1183
981	ev_loop (loop, 0);	1184	ev_run (loop, 0);
982		1185
983	As you can see, you are responsible for allocating the memory for your	1186	As you can see, you are responsible for allocating the memory for your
984	watcher structures (and it is I<usually> a bad idea to do this on the	1187	watcher structures (and it is I<usually> a bad idea to do this on the
985	stack).	1188	stack).
986		1189
987	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1190	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
988	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1191	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
989		1192
990	Each watcher structure must be initialised by a call to C<ev_init	1193	Each watcher structure must be initialised by a call to C<ev_init (watcher
991	(watcher *, callback)>, which expects a callback to be provided. This	1194	*, callback)>, which expects a callback to be provided. This callback is
992	callback gets invoked each time the event occurs (or, in the case of I/O	1195	invoked each time the event occurs (or, in the case of I/O watchers, each
993	watchers, each time the event loop detects that the file descriptor given	1196	time the event loop detects that the file descriptor given is readable
994	is readable and/or writable).	1197	and/or writable).
995		1198
996	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1199	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
997	macro to configure it, with arguments specific to the watcher type. There	1200	macro to configure it, with arguments specific to the watcher type. There
998	is also a macro to combine initialisation and setting in one call: C<<	1201	is also a macro to combine initialisation and setting in one call: C<<
999	ev_TYPE_init (watcher *, callback, ...) >>.	1202	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1022	=item C<EV_WRITE>	1225	=item C<EV_WRITE>
1023		1226
1024	The file descriptor in the C<ev_io> watcher has become readable and/or	1227	The file descriptor in the C<ev_io> watcher has become readable and/or
1025	writable.	1228	writable.
1026		1229
1027	=item C<EV_TIMEOUT>	1230	=item C<EV_TIMER>
1028		1231
1029	The C<ev_timer> watcher has timed out.	1232	The C<ev_timer> watcher has timed out.
1030		1233
1031	=item C<EV_PERIODIC>	1234	=item C<EV_PERIODIC>
1032		1235
…		…
1050		1253
1051	=item C<EV_PREPARE>	1254	=item C<EV_PREPARE>
1052		1255
1053	=item C<EV_CHECK>	1256	=item C<EV_CHECK>
1054		1257
1055	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1258	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1056	to gather new events, and all C<ev_check> watchers are invoked just after	1259	gather new events, and all C<ev_check> watchers are queued (not invoked)
1057	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1260	just after C<ev_run> has gathered them, but before it queues any callbacks
		1261	for any received events. That means C<ev_prepare> watchers are the last
		1262	watchers invoked before the event loop sleeps or polls for new events, and
		1263	C<ev_check> watchers will be invoked before any other watchers of the same
		1264	or lower priority within an event loop iteration.
		1265
1058	received events. Callbacks of both watcher types can start and stop as	1266	Callbacks of both watcher types can start and stop as many watchers as
1059	many watchers as they want, and all of them will be taken into account	1267	they want, and all of them will be taken into account (for example, a
1060	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1268	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1061	C<ev_loop> from blocking).	1269	blocking).
1062		1270
1063	=item C<EV_EMBED>	1271	=item C<EV_EMBED>
1064		1272
1065	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1273	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1066		1274
1067	=item C<EV_FORK>	1275	=item C<EV_FORK>
1068		1276
1069	The event loop has been resumed in the child process after fork (see	1277	The event loop has been resumed in the child process after fork (see
1070	C<ev_fork>).	1278	C<ev_fork>).
		1279
		1280	=item C<EV_CLEANUP>
		1281
		1282	The event loop is about to be destroyed (see C<ev_cleanup>).
1071		1283
1072	=item C<EV_ASYNC>	1284	=item C<EV_ASYNC>
1073		1285
1074	The given async watcher has been asynchronously notified (see C<ev_async>).	1286	The given async watcher has been asynchronously notified (see C<ev_async>).
1075		1287
…		…
1122		1334
1123	ev_io w;	1335	ev_io w;
1124	ev_init (&w, my_cb);	1336	ev_init (&w, my_cb);
1125	ev_io_set (&w, STDIN_FILENO, EV_READ);	1337	ev_io_set (&w, STDIN_FILENO, EV_READ);
1126		1338
1127	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1339	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1128		1340
1129	This macro initialises the type-specific parts of a watcher. You need to	1341	This macro initialises the type-specific parts of a watcher. You need to
1130	call C<ev_init> at least once before you call this macro, but you can	1342	call C<ev_init> at least once before you call this macro, but you can
1131	call C<ev_TYPE_set> any number of times. You must not, however, call this	1343	call C<ev_TYPE_set> any number of times. You must not, however, call this
1132	macro on a watcher that is active (it can be pending, however, which is a	1344	macro on a watcher that is active (it can be pending, however, which is a
…		…
1145		1357
1146	Example: Initialise and set an C<ev_io> watcher in one step.	1358	Example: Initialise and set an C<ev_io> watcher in one step.
1147		1359
1148	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1360	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1149		1361
1150	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1362	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1151		1363
1152	Starts (activates) the given watcher. Only active watchers will receive	1364	Starts (activates) the given watcher. Only active watchers will receive
1153	events. If the watcher is already active nothing will happen.	1365	events. If the watcher is already active nothing will happen.
1154		1366
1155	Example: Start the C<ev_io> watcher that is being abused as example in this	1367	Example: Start the C<ev_io> watcher that is being abused as example in this
1156	whole section.	1368	whole section.
1157		1369
1158	ev_io_start (EV_DEFAULT_UC, &w);	1370	ev_io_start (EV_DEFAULT_UC, &w);
1159		1371
1160	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1372	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1161		1373
1162	Stops the given watcher if active, and clears the pending status (whether	1374	Stops the given watcher if active, and clears the pending status (whether
1163	the watcher was active or not).	1375	the watcher was active or not).
1164		1376
1165	It is possible that stopped watchers are pending - for example,	1377	It is possible that stopped watchers are pending - for example,
…		…
1185		1397
1186	=item callback ev_cb (ev_TYPE *watcher)	1398	=item callback ev_cb (ev_TYPE *watcher)
1187		1399
1188	Returns the callback currently set on the watcher.	1400	Returns the callback currently set on the watcher.
1189		1401
1190	=item ev_cb_set (ev_TYPE *watcher, callback)	1402	=item ev_set_cb (ev_TYPE *watcher, callback)
1191		1403
1192	Change the callback. You can change the callback at virtually any time	1404	Change the callback. You can change the callback at virtually any time
1193	(modulo threads).	1405	(modulo threads).
1194		1406
1195	=item ev_set_priority (ev_TYPE *watcher, priority)	1407	=item ev_set_priority (ev_TYPE *watcher, int priority)
1196		1408
1197	=item int ev_priority (ev_TYPE *watcher)	1409	=item int ev_priority (ev_TYPE *watcher)
1198		1410
1199	Set and query the priority of the watcher. The priority is a small	1411	Set and query the priority of the watcher. The priority is a small
1200	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1412	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1213	or might not have been clamped to the valid range.	1425	or might not have been clamped to the valid range.
1214		1426
1215	The default priority used by watchers when no priority has been set is	1427	The default priority used by watchers when no priority has been set is
1216	always C<0>, which is supposed to not be too high and not be too low :).	1428	always C<0>, which is supposed to not be too high and not be too low :).
1217		1429
1218	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1430	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1219	priorities.	1431	priorities.
1220		1432
1221	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1433	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1222		1434
1223	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1435	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1232	watcher isn't pending it does nothing and returns C<0>.	1444	watcher isn't pending it does nothing and returns C<0>.
1233		1445
1234	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1446	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1235	callback to be invoked, which can be accomplished with this function.	1447	callback to be invoked, which can be accomplished with this function.
1236		1448
		1449	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1450
		1451	Feeds the given event set into the event loop, as if the specified event
		1452	had happened for the specified watcher (which must be a pointer to an
		1453	initialised but not necessarily started event watcher). Obviously you must
		1454	not free the watcher as long as it has pending events.
		1455
		1456	Stopping the watcher, letting libev invoke it, or calling
		1457	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1458	not started in the first place.
		1459
		1460	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1461	functions that do not need a watcher.
		1462
1237	=back	1463	=back
1238		1464
		1465	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1466	OWN COMPOSITE WATCHERS> idioms.
1239		1467
1240	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1468	=head2 WATCHER STATES
1241		1469
1242	Each watcher has, by default, a member C<void *data> that you can change	1470	There are various watcher states mentioned throughout this manual -
1243	and read at any time: libev will completely ignore it. This can be used	1471	active, pending and so on. In this section these states and the rules to
1244	to associate arbitrary data with your watcher. If you need more data and	1472	transition between them will be described in more detail - and while these
1245	don't want to allocate memory and store a pointer to it in that data	1473	rules might look complicated, they usually do "the right thing".
1246	member, you can also "subclass" the watcher type and provide your own
1247	data:
1248		1474
1249	struct my_io	1475	=over 4
1250	{
1251	ev_io io;
1252	int otherfd;
1253	void *somedata;
1254	struct whatever *mostinteresting;
1255	};
1256		1476
1257	...	1477	=item initialised
1258	struct my_io w;
1259	ev_io_init (&w.io, my_cb, fd, EV_READ);
1260		1478
1261	And since your callback will be called with a pointer to the watcher, you	1479	Before a watcher can be registered with the event loop it has to be
1262	can cast it back to your own type:	1480	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1481	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1263		1482
1264	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1483	In this state it is simply some block of memory that is suitable for
1265	{	1484	use in an event loop. It can be moved around, freed, reused etc. at
1266	struct my_io *w = (struct my_io *)w_;	1485	will - as long as you either keep the memory contents intact, or call
1267	...	1486	C<ev_TYPE_init> again.
1268	}
1269		1487
1270	More interesting and less C-conformant ways of casting your callback type	1488	=item started/running/active
1271	instead have been omitted.
1272		1489
1273	Another common scenario is to use some data structure with multiple	1490	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1274	embedded watchers:	1491	property of the event loop, and is actively waiting for events. While in
		1492	this state it cannot be accessed (except in a few documented ways), moved,
		1493	freed or anything else - the only legal thing is to keep a pointer to it,
		1494	and call libev functions on it that are documented to work on active watchers.
1275		1495
1276	struct my_biggy	1496	=item pending
1277	{
1278	int some_data;
1279	ev_timer t1;
1280	ev_timer t2;
1281	}
1282		1497
1283	In this case getting the pointer to C<my_biggy> is a bit more	1498	If a watcher is active and libev determines that an event it is interested
1284	complicated: Either you store the address of your C<my_biggy> struct	1499	in has occurred (such as a timer expiring), it will become pending. It will
1285	in the C<data> member of the watcher (for woozies), or you need to use	1500	stay in this pending state until either it is stopped or its callback is
1286	some pointer arithmetic using C<offsetof> inside your watchers (for real	1501	about to be invoked, so it is not normally pending inside the watcher
1287	programmers):	1502	callback.
1288		1503
1289	#include <stddef.h>	1504	The watcher might or might not be active while it is pending (for example,
		1505	an expired non-repeating timer can be pending but no longer active). If it
		1506	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1507	but it is still property of the event loop at this time, so cannot be
		1508	moved, freed or reused. And if it is active the rules described in the
		1509	previous item still apply.
1290		1510
1291	static void	1511	It is also possible to feed an event on a watcher that is not active (e.g.
1292	t1_cb (EV_P_ ev_timer *w, int revents)	1512	via C<ev_feed_event>), in which case it becomes pending without being
1293	{	1513	active.
1294	struct my_biggy big = (struct my_biggy *)
1295	(((char *)w) - offsetof (struct my_biggy, t1));
1296	}
1297		1514
1298	static void	1515	=item stopped
1299	t2_cb (EV_P_ ev_timer *w, int revents)	1516
1300	{	1517	A watcher can be stopped implicitly by libev (in which case it might still
1301	struct my_biggy big = (struct my_biggy *)	1518	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1302	(((char *)w) - offsetof (struct my_biggy, t2));	1519	latter will clear any pending state the watcher might be in, regardless
1303	}	1520	of whether it was active or not, so stopping a watcher explicitly before
		1521	freeing it is often a good idea.
		1522
		1523	While stopped (and not pending) the watcher is essentially in the
		1524	initialised state, that is, it can be reused, moved, modified in any way
		1525	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1526	it again).
		1527
		1528	=back
1304		1529
1305	=head2 WATCHER PRIORITY MODELS	1530	=head2 WATCHER PRIORITY MODELS
1306		1531
1307	Many event loops support I<watcher priorities>, which are usually small	1532	Many event loops support I<watcher priorities>, which are usually small
1308	integers that influence the ordering of event callback invocation	1533	integers that influence the ordering of event callback invocation
…		…
1351		1576
1352	For example, to emulate how many other event libraries handle priorities,	1577	For example, to emulate how many other event libraries handle priorities,
1353	you can associate an C<ev_idle> watcher to each such watcher, and in	1578	you can associate an C<ev_idle> watcher to each such watcher, and in
1354	the normal watcher callback, you just start the idle watcher. The real	1579	the normal watcher callback, you just start the idle watcher. The real
1355	processing is done in the idle watcher callback. This causes libev to	1580	processing is done in the idle watcher callback. This causes libev to
1356	continously poll and process kernel event data for the watcher, but when	1581	continuously poll and process kernel event data for the watcher, but when
1357	the lock-out case is known to be rare (which in turn is rare :), this is	1582	the lock-out case is known to be rare (which in turn is rare :), this is
1358	workable.	1583	workable.
1359		1584
1360	Usually, however, the lock-out model implemented that way will perform	1585	Usually, however, the lock-out model implemented that way will perform
1361	miserably under the type of load it was designed to handle. In that case,	1586	miserably under the type of load it was designed to handle. In that case,
…		…
1375	{	1600	{
1376	// stop the I/O watcher, we received the event, but	1601	// stop the I/O watcher, we received the event, but
1377	// are not yet ready to handle it.	1602	// are not yet ready to handle it.
1378	ev_io_stop (EV_A_ w);	1603	ev_io_stop (EV_A_ w);
1379		1604
1380	// start the idle watcher to ahndle the actual event.	1605	// start the idle watcher to handle the actual event.
1381	// it will not be executed as long as other watchers	1606	// it will not be executed as long as other watchers
1382	// with the default priority are receiving events.	1607	// with the default priority are receiving events.
1383	ev_idle_start (EV_A_ &idle);	1608	ev_idle_start (EV_A_ &idle);
1384	}	1609	}
1385		1610
…		…
1435	In general you can register as many read and/or write event watchers per	1660	In general you can register as many read and/or write event watchers per
1436	fd as you want (as long as you don't confuse yourself). Setting all file	1661	fd as you want (as long as you don't confuse yourself). Setting all file
1437	descriptors to non-blocking mode is also usually a good idea (but not	1662	descriptors to non-blocking mode is also usually a good idea (but not
1438	required if you know what you are doing).	1663	required if you know what you are doing).
1439		1664
1440	If you cannot use non-blocking mode, then force the use of a
1441	known-to-be-good backend (at the time of this writing, this includes only
1442	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1443	descriptors for which non-blocking operation makes no sense (such as
1444	files) - libev doesn't guarentee any specific behaviour in that case.
1445
1446	Another thing you have to watch out for is that it is quite easy to	1665	Another thing you have to watch out for is that it is quite easy to
1447	receive "spurious" readiness notifications, that is your callback might	1666	receive "spurious" readiness notifications, that is, your callback might
1448	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1667	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1449	because there is no data. Not only are some backends known to create a	1668	because there is no data. It is very easy to get into this situation even
1450	lot of those (for example Solaris ports), it is very easy to get into	1669	with a relatively standard program structure. Thus it is best to always
1451	this situation even with a relatively standard program structure. Thus	1670	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1452	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1453	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1671	preferable to a program hanging until some data arrives.
1454		1672
1455	If you cannot run the fd in non-blocking mode (for example you should	1673	If you cannot run the fd in non-blocking mode (for example you should
1456	not play around with an Xlib connection), then you have to separately	1674	not play around with an Xlib connection), then you have to separately
1457	re-test whether a file descriptor is really ready with a known-to-be good	1675	re-test whether a file descriptor is really ready with a known-to-be good
1458	interface such as poll (fortunately in our Xlib example, Xlib already	1676	interface such as poll (fortunately in the case of Xlib, it already does
1459	does this on its own, so its quite safe to use). Some people additionally	1677	this on its own, so its quite safe to use). Some people additionally
1460	use C<SIGALRM> and an interval timer, just to be sure you won't block	1678	use C<SIGALRM> and an interval timer, just to be sure you won't block
1461	indefinitely.	1679	indefinitely.
1462		1680
1463	But really, best use non-blocking mode.	1681	But really, best use non-blocking mode.
1464		1682
1465	=head3 The special problem of disappearing file descriptors	1683	=head3 The special problem of disappearing file descriptors
1466		1684
1467	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1685	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1468	descriptor (either due to calling C<close> explicitly or any other means,	1686	a file descriptor (either due to calling C<close> explicitly or any other
1469	such as C<dup2>). The reason is that you register interest in some file	1687	means, such as C<dup2>). The reason is that you register interest in some
1470	descriptor, but when it goes away, the operating system will silently drop	1688	file descriptor, but when it goes away, the operating system will silently
1471	this interest. If another file descriptor with the same number then is	1689	drop this interest. If another file descriptor with the same number then
1472	registered with libev, there is no efficient way to see that this is, in	1690	is registered with libev, there is no efficient way to see that this is,
1473	fact, a different file descriptor.	1691	in fact, a different file descriptor.
1474		1692
1475	To avoid having to explicitly tell libev about such cases, libev follows	1693	To avoid having to explicitly tell libev about such cases, libev follows
1476	the following policy: Each time C<ev_io_set> is being called, libev	1694	the following policy: Each time C<ev_io_set> is being called, libev
1477	will assume that this is potentially a new file descriptor, otherwise	1695	will assume that this is potentially a new file descriptor, otherwise
1478	it is assumed that the file descriptor stays the same. That means that	1696	it is assumed that the file descriptor stays the same. That means that
…		…
1492		1710
1493	There is no workaround possible except not registering events	1711	There is no workaround possible except not registering events
1494	for potentially C<dup ()>'ed file descriptors, or to resort to	1712	for potentially C<dup ()>'ed file descriptors, or to resort to
1495	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1713	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1496		1714
		1715	=head3 The special problem of files
		1716
		1717	Many people try to use C<select> (or libev) on file descriptors
		1718	representing files, and expect it to become ready when their program
		1719	doesn't block on disk accesses (which can take a long time on their own).
		1720
		1721	However, this cannot ever work in the "expected" way - you get a readiness
		1722	notification as soon as the kernel knows whether and how much data is
		1723	there, and in the case of open files, that's always the case, so you
		1724	always get a readiness notification instantly, and your read (or possibly
		1725	write) will still block on the disk I/O.
		1726
		1727	Another way to view it is that in the case of sockets, pipes, character
		1728	devices and so on, there is another party (the sender) that delivers data
		1729	on its own, but in the case of files, there is no such thing: the disk
		1730	will not send data on its own, simply because it doesn't know what you
		1731	wish to read - you would first have to request some data.
		1732
		1733	Since files are typically not-so-well supported by advanced notification
		1734	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1735	to files, even though you should not use it. The reason for this is
		1736	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1737	usually a tty, often a pipe, but also sometimes files or special devices
		1738	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1739	F</dev/urandom>), and even though the file might better be served with
		1740	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1741	it "just works" instead of freezing.
		1742
		1743	So avoid file descriptors pointing to files when you know it (e.g. use
		1744	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1745	when you rarely read from a file instead of from a socket, and want to
		1746	reuse the same code path.
		1747
1497	=head3 The special problem of fork	1748	=head3 The special problem of fork
1498		1749
1499	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1750	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1500	useless behaviour. Libev fully supports fork, but needs to be told about	1751	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1501	it in the child.	1752	to be told about it in the child if you want to continue to use it in the
		1753	child.
1502		1754
1503	To support fork in your programs, you either have to call	1755	To support fork in your child processes, you have to call C<ev_loop_fork
1504	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1756	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1505	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1757	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1506	C<EVBACKEND_POLL>.
1507		1758
1508	=head3 The special problem of SIGPIPE	1759	=head3 The special problem of SIGPIPE
1509		1760
1510	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1761	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1511	when writing to a pipe whose other end has been closed, your program gets	1762	when writing to a pipe whose other end has been closed, your program gets
…		…
1514		1765
1515	So when you encounter spurious, unexplained daemon exits, make sure you	1766	So when you encounter spurious, unexplained daemon exits, make sure you
1516	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1767	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1517	somewhere, as that would have given you a big clue).	1768	somewhere, as that would have given you a big clue).
1518		1769
		1770	=head3 The special problem of accept()ing when you can't
		1771
		1772	Many implementations of the POSIX C<accept> function (for example,
		1773	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1774	connection from the pending queue in all error cases.
		1775
		1776	For example, larger servers often run out of file descriptors (because
		1777	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1778	rejecting the connection, leading to libev signalling readiness on
		1779	the next iteration again (the connection still exists after all), and
		1780	typically causing the program to loop at 100% CPU usage.
		1781
		1782	Unfortunately, the set of errors that cause this issue differs between
		1783	operating systems, there is usually little the app can do to remedy the
		1784	situation, and no known thread-safe method of removing the connection to
		1785	cope with overload is known (to me).
		1786
		1787	One of the easiest ways to handle this situation is to just ignore it
		1788	- when the program encounters an overload, it will just loop until the
		1789	situation is over. While this is a form of busy waiting, no OS offers an
		1790	event-based way to handle this situation, so it's the best one can do.
		1791
		1792	A better way to handle the situation is to log any errors other than
		1793	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1794	messages, and continue as usual, which at least gives the user an idea of
		1795	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1796	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1797	usage.
		1798
		1799	If your program is single-threaded, then you could also keep a dummy file
		1800	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1801	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1802	close that fd, and create a new dummy fd. This will gracefully refuse
		1803	clients under typical overload conditions.
		1804
		1805	The last way to handle it is to simply log the error and C<exit>, as
		1806	is often done with C<malloc> failures, but this results in an easy
		1807	opportunity for a DoS attack.
1519		1808
1520	=head3 Watcher-Specific Functions	1809	=head3 Watcher-Specific Functions
1521		1810
1522	=over 4	1811	=over 4
1523		1812
…		…
1555	...	1844	...
1556	struct ev_loop *loop = ev_default_init (0);	1845	struct ev_loop *loop = ev_default_init (0);
1557	ev_io stdin_readable;	1846	ev_io stdin_readable;
1558	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1847	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1559	ev_io_start (loop, &stdin_readable);	1848	ev_io_start (loop, &stdin_readable);
1560	ev_loop (loop, 0);	1849	ev_run (loop, 0);
1561		1850
1562		1851
1563	=head2 C<ev_timer> - relative and optionally repeating timeouts	1852	=head2 C<ev_timer> - relative and optionally repeating timeouts
1564		1853
1565	Timer watchers are simple relative timers that generate an event after a	1854	Timer watchers are simple relative timers that generate an event after a
…		…
1571	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1860	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1572	monotonic clock option helps a lot here).	1861	monotonic clock option helps a lot here).
1573		1862
1574	The callback is guaranteed to be invoked only I<after> its timeout has	1863	The callback is guaranteed to be invoked only I<after> its timeout has
1575	passed (not I<at>, so on systems with very low-resolution clocks this	1864	passed (not I<at>, so on systems with very low-resolution clocks this
1576	might introduce a small delay). If multiple timers become ready during the	1865	might introduce a small delay, see "the special problem of being too
		1866	early", below). If multiple timers become ready during the same loop
1577	same loop iteration then the ones with earlier time-out values are invoked	1867	iteration then the ones with earlier time-out values are invoked before
1578	before ones of the same priority with later time-out values (but this is	1868	ones of the same priority with later time-out values (but this is no
1579	no longer true when a callback calls C<ev_loop> recursively).	1869	longer true when a callback calls C<ev_run> recursively).
1580		1870
1581	=head3 Be smart about timeouts	1871	=head3 Be smart about timeouts
1582		1872
1583	Many real-world problems involve some kind of timeout, usually for error	1873	Many real-world problems involve some kind of timeout, usually for error
1584	recovery. A typical example is an HTTP request - if the other side hangs,	1874	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1659		1949
1660	In this case, it would be more efficient to leave the C<ev_timer> alone,	1950	In this case, it would be more efficient to leave the C<ev_timer> alone,
1661	but remember the time of last activity, and check for a real timeout only	1951	but remember the time of last activity, and check for a real timeout only
1662	within the callback:	1952	within the callback:
1663		1953
		1954	ev_tstamp timeout = 60.;
1664	ev_tstamp last_activity; // time of last activity	1955	ev_tstamp last_activity; // time of last activity
		1956	ev_timer timer;
1665		1957
1666	static void	1958	static void
1667	callback (EV_P_ ev_timer *w, int revents)	1959	callback (EV_P_ ev_timer *w, int revents)
1668	{	1960	{
1669	ev_tstamp now = ev_now (EV_A);	1961	// calculate when the timeout would happen
1670	ev_tstamp timeout = last_activity + 60.;	1962	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1671		1963
1672	// if last_activity + 60. is older than now, we did time out	1964	// if negative, it means we the timeout already occurred
1673	if (timeout < now)	1965	if (after < 0.)
1674	{	1966	{
1675	// timeout occured, take action	1967	// timeout occurred, take action
1676	}	1968	}
1677	else	1969	else
1678	{	1970	{
1679	// callback was invoked, but there was some activity, re-arm	1971	// callback was invoked, but there was some recent
1680	// the watcher to fire in last_activity + 60, which is	1972	// activity. simply restart the timer to time out
1681	// guaranteed to be in the future, so "again" is positive:	1973	// after "after" seconds, which is the earliest time
1682	w->repeat = timeout - now;	1974	// the timeout can occur.
		1975	ev_timer_set (w, after, 0.);
1683	ev_timer_again (EV_A_ w);	1976	ev_timer_start (EV_A_ w);
1684	}	1977	}
1685	}	1978	}
1686		1979
1687	To summarise the callback: first calculate the real timeout (defined	1980	To summarise the callback: first calculate in how many seconds the
1688	as "60 seconds after the last activity"), then check if that time has	1981	timeout will occur (by calculating the absolute time when it would occur,
1689	been reached, which means something I<did>, in fact, time out. Otherwise	1982	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1690	the callback was invoked too early (C<timeout> is in the future), so	1983	(EV_A)> from that).
1691	re-schedule the timer to fire at that future time, to see if maybe we have
1692	a timeout then.
1693		1984
1694	Note how C<ev_timer_again> is used, taking advantage of the	1985	If this value is negative, then we are already past the timeout, i.e. we
1695	C<ev_timer_again> optimisation when the timer is already running.	1986	timed out, and need to do whatever is needed in this case.
		1987
		1988	Otherwise, we now the earliest time at which the timeout would trigger,
		1989	and simply start the timer with this timeout value.
		1990
		1991	In other words, each time the callback is invoked it will check whether
		1992	the timeout occurred. If not, it will simply reschedule itself to check
		1993	again at the earliest time it could time out. Rinse. Repeat.
1696		1994
1697	This scheme causes more callback invocations (about one every 60 seconds	1995	This scheme causes more callback invocations (about one every 60 seconds
1698	minus half the average time between activity), but virtually no calls to	1996	minus half the average time between activity), but virtually no calls to
1699	libev to change the timeout.	1997	libev to change the timeout.
1700		1998
1701	To start the timer, simply initialise the watcher and set C<last_activity>	1999	To start the machinery, simply initialise the watcher and set
1702	to the current time (meaning we just have some activity :), then call the	2000	C<last_activity> to the current time (meaning there was some activity just
1703	callback, which will "do the right thing" and start the timer:	2001	now), then call the callback, which will "do the right thing" and start
		2002	the timer:
1704		2003
		2004	last_activity = ev_now (EV_A);
1705	ev_init (timer, callback);	2005	ev_init (&timer, callback);
1706	last_activity = ev_now (loop);	2006	callback (EV_A_ &timer, 0);
1707	callback (loop, timer, EV_TIMEOUT);
1708		2007
1709	And when there is some activity, simply store the current time in	2008	When there is some activity, simply store the current time in
1710	C<last_activity>, no libev calls at all:	2009	C<last_activity>, no libev calls at all:
1711		2010
		2011	if (activity detected)
1712	last_actiivty = ev_now (loop);	2012	last_activity = ev_now (EV_A);
		2013
		2014	When your timeout value changes, then the timeout can be changed by simply
		2015	providing a new value, stopping the timer and calling the callback, which
		2016	will again do the right thing (for example, time out immediately :).
		2017
		2018	timeout = new_value;
		2019	ev_timer_stop (EV_A_ &timer);
		2020	callback (EV_A_ &timer, 0);
1713		2021
1714	This technique is slightly more complex, but in most cases where the	2022	This technique is slightly more complex, but in most cases where the
1715	time-out is unlikely to be triggered, much more efficient.	2023	time-out is unlikely to be triggered, much more efficient.
1716
1717	Changing the timeout is trivial as well (if it isn't hard-coded in the
1718	callback :) - just change the timeout and invoke the callback, which will
1719	fix things for you.
1720		2024
1721	=item 4. Wee, just use a double-linked list for your timeouts.	2025	=item 4. Wee, just use a double-linked list for your timeouts.
1722		2026
1723	If there is not one request, but many thousands (millions...), all	2027	If there is not one request, but many thousands (millions...), all
1724	employing some kind of timeout with the same timeout value, then one can	2028	employing some kind of timeout with the same timeout value, then one can
…		…
1751	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2055	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1752	rather complicated, but extremely efficient, something that really pays	2056	rather complicated, but extremely efficient, something that really pays
1753	off after the first million or so of active timers, i.e. it's usually	2057	off after the first million or so of active timers, i.e. it's usually
1754	overkill :)	2058	overkill :)
1755		2059
		2060	=head3 The special problem of being too early
		2061
		2062	If you ask a timer to call your callback after three seconds, then
		2063	you expect it to be invoked after three seconds - but of course, this
		2064	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2065	guaranteed to any precision by libev - imagine somebody suspending the
		2066	process with a STOP signal for a few hours for example.
		2067
		2068	So, libev tries to invoke your callback as soon as possible I<after> the
		2069	delay has occurred, but cannot guarantee this.
		2070
		2071	A less obvious failure mode is calling your callback too early: many event
		2072	loops compare timestamps with a "elapsed delay >= requested delay", but
		2073	this can cause your callback to be invoked much earlier than you would
		2074	expect.
		2075
		2076	To see why, imagine a system with a clock that only offers full second
		2077	resolution (think windows if you can't come up with a broken enough OS
		2078	yourself). If you schedule a one-second timer at the time 500.9, then the
		2079	event loop will schedule your timeout to elapse at a system time of 500
		2080	(500.9 truncated to the resolution) + 1, or 501.
		2081
		2082	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2083	501" and invoke the callback 0.1s after it was started, even though a
		2084	one-second delay was requested - this is being "too early", despite best
		2085	intentions.
		2086
		2087	This is the reason why libev will never invoke the callback if the elapsed
		2088	delay equals the requested delay, but only when the elapsed delay is
		2089	larger than the requested delay. In the example above, libev would only invoke
		2090	the callback at system time 502, or 1.1s after the timer was started.
		2091
		2092	So, while libev cannot guarantee that your callback will be invoked
		2093	exactly when requested, it I<can> and I<does> guarantee that the requested
		2094	delay has actually elapsed, or in other words, it always errs on the "too
		2095	late" side of things.
		2096
1756	=head3 The special problem of time updates	2097	=head3 The special problem of time updates
1757		2098
1758	Establishing the current time is a costly operation (it usually takes at	2099	Establishing the current time is a costly operation (it usually takes
1759	least two system calls): EV therefore updates its idea of the current	2100	at least one system call): EV therefore updates its idea of the current
1760	time only before and after C<ev_loop> collects new events, which causes a	2101	time only before and after C<ev_run> collects new events, which causes a
1761	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2102	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1762	lots of events in one iteration.	2103	lots of events in one iteration.
1763		2104
1764	The relative timeouts are calculated relative to the C<ev_now ()>	2105	The relative timeouts are calculated relative to the C<ev_now ()>
1765	time. This is usually the right thing as this timestamp refers to the time	2106	time. This is usually the right thing as this timestamp refers to the time
1766	of the event triggering whatever timeout you are modifying/starting. If	2107	of the event triggering whatever timeout you are modifying/starting. If
1767	you suspect event processing to be delayed and you I<need> to base the	2108	you suspect event processing to be delayed and you I<need> to base the
1768	timeout on the current time, use something like this to adjust for this:	2109	timeout on the current time, use something like the following to adjust
		2110	for it:
1769		2111
1770	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2112	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1771		2113
1772	If the event loop is suspended for a long time, you can also force an	2114	If the event loop is suspended for a long time, you can also force an
1773	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2115	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1774	()>.	2116	()>, although that will push the event time of all outstanding events
		2117	further into the future.
		2118
		2119	=head3 The special problem of unsynchronised clocks
		2120
		2121	Modern systems have a variety of clocks - libev itself uses the normal
		2122	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2123	jumps).
		2124
		2125	Neither of these clocks is synchronised with each other or any other clock
		2126	on the system, so C<ev_time ()> might return a considerably different time
		2127	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2128	a call to C<gettimeofday> might return a second count that is one higher
		2129	than a directly following call to C<time>.
		2130
		2131	The moral of this is to only compare libev-related timestamps with
		2132	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2133	a second or so.
		2134
		2135	One more problem arises due to this lack of synchronisation: if libev uses
		2136	the system monotonic clock and you compare timestamps from C<ev_time>
		2137	or C<ev_now> from when you started your timer and when your callback is
		2138	invoked, you will find that sometimes the callback is a bit "early".
		2139
		2140	This is because C<ev_timer>s work in real time, not wall clock time, so
		2141	libev makes sure your callback is not invoked before the delay happened,
		2142	I<measured according to the real time>, not the system clock.
		2143
		2144	If your timeouts are based on a physical timescale (e.g. "time out this
		2145	connection after 100 seconds") then this shouldn't bother you as it is
		2146	exactly the right behaviour.
		2147
		2148	If you want to compare wall clock/system timestamps to your timers, then
		2149	you need to use C<ev_periodic>s, as these are based on the wall clock
		2150	time, where your comparisons will always generate correct results.
1775		2151
1776	=head3 The special problems of suspended animation	2152	=head3 The special problems of suspended animation
1777		2153
1778	When you leave the server world it is quite customary to hit machines that	2154	When you leave the server world it is quite customary to hit machines that
1779	can suspend/hibernate - what happens to the clocks during such a suspend?	2155	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1809		2185
1810	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2186	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1811		2187
1812	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2188	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1813		2189
1814	Configure the timer to trigger after C<after> seconds. If C<repeat>	2190	Configure the timer to trigger after C<after> seconds (fractional and
1815	is C<0.>, then it will automatically be stopped once the timeout is	2191	negative values are supported). If C<repeat> is C<0.>, then it will
1816	reached. If it is positive, then the timer will automatically be	2192	automatically be stopped once the timeout is reached. If it is positive,
1817	configured to trigger again C<repeat> seconds later, again, and again,	2193	then the timer will automatically be configured to trigger again C<repeat>
1818	until stopped manually.	2194	seconds later, again, and again, until stopped manually.
1819		2195
1820	The timer itself will do a best-effort at avoiding drift, that is, if	2196	The timer itself will do a best-effort at avoiding drift, that is, if
1821	you configure a timer to trigger every 10 seconds, then it will normally	2197	you configure a timer to trigger every 10 seconds, then it will normally
1822	trigger at exactly 10 second intervals. If, however, your program cannot	2198	trigger at exactly 10 second intervals. If, however, your program cannot
1823	keep up with the timer (because it takes longer than those 10 seconds to	2199	keep up with the timer (because it takes longer than those 10 seconds to
1824	do stuff) the timer will not fire more than once per event loop iteration.	2200	do stuff) the timer will not fire more than once per event loop iteration.
1825		2201
1826	=item ev_timer_again (loop, ev_timer *)	2202	=item ev_timer_again (loop, ev_timer *)
1827		2203
1828	This will act as if the timer timed out and restart it again if it is	2204	This will act as if the timer timed out, and restarts it again if it is
1829	repeating. The exact semantics are:	2205	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2206	timeout to the C<repeat> value and calling C<ev_timer_start>.
1830		2207
		2208	The exact semantics are as in the following rules, all of which will be
		2209	applied to the watcher:
		2210
		2211	=over 4
		2212
1831	If the timer is pending, its pending status is cleared.	2213	=item If the timer is pending, the pending status is always cleared.
1832		2214
1833	If the timer is started but non-repeating, stop it (as if it timed out).	2215	=item If the timer is started but non-repeating, stop it (as if it timed
		2216	out, without invoking it).
1834		2217
1835	If the timer is repeating, either start it if necessary (with the	2218	=item If the timer is repeating, make the C<repeat> value the new timeout
1836	C<repeat> value), or reset the running timer to the C<repeat> value.	2219	and start the timer, if necessary.
1837		2220
		2221	=back
		2222
1838	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2223	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1839	usage example.	2224	usage example.
1840		2225
1841	=item ev_timer_remaining (loop, ev_timer *)	2226	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1842		2227
1843	Returns the remaining time until a timer fires. If the timer is active,	2228	Returns the remaining time until a timer fires. If the timer is active,
1844	then this time is relative to the current event loop time, otherwise it's	2229	then this time is relative to the current event loop time, otherwise it's
1845	the timeout value currently configured.	2230	the timeout value currently configured.
1846		2231
1847	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2232	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1848	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2233	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1849	will return C<4>. When the timer expires and is restarted, it will return	2234	will return C<4>. When the timer expires and is restarted, it will return
1850	roughly C<7> (likely slightly less as callback invocation takes some time,	2235	roughly C<7> (likely slightly less as callback invocation takes some time,
1851	too), and so on.	2236	too), and so on.
1852		2237
1853	=item ev_tstamp repeat [read-write]	2238	=item ev_tstamp repeat [read-write]
…		…
1882	}	2267	}
1883		2268
1884	ev_timer mytimer;	2269	ev_timer mytimer;
1885	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2270	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1886	ev_timer_again (&mytimer); /* start timer */	2271	ev_timer_again (&mytimer); /* start timer */
1887	ev_loop (loop, 0);	2272	ev_run (loop, 0);
1888		2273
1889	// and in some piece of code that gets executed on any "activity":	2274	// and in some piece of code that gets executed on any "activity":
1890	// reset the timeout to start ticking again at 10 seconds	2275	// reset the timeout to start ticking again at 10 seconds
1891	ev_timer_again (&mytimer);	2276	ev_timer_again (&mytimer);
1892		2277
…		…
1896	Periodic watchers are also timers of a kind, but they are very versatile	2281	Periodic watchers are also timers of a kind, but they are very versatile
1897	(and unfortunately a bit complex).	2282	(and unfortunately a bit complex).
1898		2283
1899	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2284	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1900	relative time, the physical time that passes) but on wall clock time	2285	relative time, the physical time that passes) but on wall clock time
1901	(absolute time, the thing you can read on your calender or clock). The	2286	(absolute time, the thing you can read on your calendar or clock). The
1902	difference is that wall clock time can run faster or slower than real	2287	difference is that wall clock time can run faster or slower than real
1903	time, and time jumps are not uncommon (e.g. when you adjust your	2288	time, and time jumps are not uncommon (e.g. when you adjust your
1904	wrist-watch).	2289	wrist-watch).
1905		2290
1906	You can tell a periodic watcher to trigger after some specific point	2291	You can tell a periodic watcher to trigger after some specific point
…		…
1911	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2296	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1912	it, as it uses a relative timeout).	2297	it, as it uses a relative timeout).
1913		2298
1914	C<ev_periodic> watchers can also be used to implement vastly more complex	2299	C<ev_periodic> watchers can also be used to implement vastly more complex
1915	timers, such as triggering an event on each "midnight, local time", or	2300	timers, such as triggering an event on each "midnight, local time", or
1916	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2301	other complicated rules. This cannot easily be done with C<ev_timer>
1917	those cannot react to time jumps.	2302	watchers, as those cannot react to time jumps.
1918		2303
1919	As with timers, the callback is guaranteed to be invoked only when the	2304	As with timers, the callback is guaranteed to be invoked only when the
1920	point in time where it is supposed to trigger has passed. If multiple	2305	point in time where it is supposed to trigger has passed. If multiple
1921	timers become ready during the same loop iteration then the ones with	2306	timers become ready during the same loop iteration then the ones with
1922	earlier time-out values are invoked before ones with later time-out values	2307	earlier time-out values are invoked before ones with later time-out values
1923	(but this is no longer true when a callback calls C<ev_loop> recursively).	2308	(but this is no longer true when a callback calls C<ev_run> recursively).
1924		2309
1925	=head3 Watcher-Specific Functions and Data Members	2310	=head3 Watcher-Specific Functions and Data Members
1926		2311
1927	=over 4	2312	=over 4
1928		2313
…		…
1963		2348
1964	Another way to think about it (for the mathematically inclined) is that	2349	Another way to think about it (for the mathematically inclined) is that
1965	C<ev_periodic> will try to run the callback in this mode at the next possible	2350	C<ev_periodic> will try to run the callback in this mode at the next possible
1966	time where C<time = offset (mod interval)>, regardless of any time jumps.	2351	time where C<time = offset (mod interval)>, regardless of any time jumps.
1967		2352
1968	For numerical stability it is preferable that the C<offset> value is near	2353	The C<interval> I<MUST> be positive, and for numerical stability, the
1969	C<ev_now ()> (the current time), but there is no range requirement for	2354	interval value should be higher than C<1/8192> (which is around 100
1970	this value, and in fact is often specified as zero.	2355	microseconds) and C<offset> should be higher than C<0> and should have
		2356	at most a similar magnitude as the current time (say, within a factor of
		2357	ten). Typical values for offset are, in fact, C<0> or something between
		2358	C<0> and C<interval>, which is also the recommended range.
1971		2359
1972	Note also that there is an upper limit to how often a timer can fire (CPU	2360	Note also that there is an upper limit to how often a timer can fire (CPU
1973	speed for example), so if C<interval> is very small then timing stability	2361	speed for example), so if C<interval> is very small then timing stability
1974	will of course deteriorate. Libev itself tries to be exact to be about one	2362	will of course deteriorate. Libev itself tries to be exact to be about one
1975	millisecond (if the OS supports it and the machine is fast enough).	2363	millisecond (if the OS supports it and the machine is fast enough).
…		…
2005		2393
2006	NOTE: I<< This callback must always return a time that is higher than or	2394	NOTE: I<< This callback must always return a time that is higher than or
2007	equal to the passed C<now> value >>.	2395	equal to the passed C<now> value >>.
2008		2396
2009	This can be used to create very complex timers, such as a timer that	2397	This can be used to create very complex timers, such as a timer that
2010	triggers on "next midnight, local time". To do this, you would calculate the	2398	triggers on "next midnight, local time". To do this, you would calculate
2011	next midnight after C<now> and return the timestamp value for this. How	2399	the next midnight after C<now> and return the timestamp value for
2012	you do this is, again, up to you (but it is not trivial, which is the main	2400	this. Here is a (completely untested, no error checking) example on how to
2013	reason I omitted it as an example).	2401	do this:
		2402
		2403	#include <time.h>
		2404
		2405	static ev_tstamp
		2406	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2407	{
		2408	time_t tnow = (time_t)now;
		2409	struct tm tm;
		2410	localtime_r (&tnow, &tm);
		2411
		2412	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2413	++tm.tm_mday; // midnight next day
		2414
		2415	return mktime (&tm);
		2416	}
		2417
		2418	Note: this code might run into trouble on days that have more then two
		2419	midnights (beginning and end).
2014		2420
2015	=back	2421	=back
2016		2422
2017	=item ev_periodic_again (loop, ev_periodic *)	2423	=item ev_periodic_again (loop, ev_periodic *)
2018		2424
…		…
2056	Example: Call a callback every hour, or, more precisely, whenever the	2462	Example: Call a callback every hour, or, more precisely, whenever the
2057	system time is divisible by 3600. The callback invocation times have	2463	system time is divisible by 3600. The callback invocation times have
2058	potentially a lot of jitter, but good long-term stability.	2464	potentially a lot of jitter, but good long-term stability.
2059		2465
2060	static void	2466	static void
2061	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2467	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2062	{	2468	{
2063	... its now a full hour (UTC, or TAI or whatever your clock follows)	2469	... its now a full hour (UTC, or TAI or whatever your clock follows)
2064	}	2470	}
2065		2471
2066	ev_periodic hourly_tick;	2472	ev_periodic hourly_tick;
…		…
2083		2489
2084	ev_periodic hourly_tick;	2490	ev_periodic hourly_tick;
2085	ev_periodic_init (&hourly_tick, clock_cb,	2491	ev_periodic_init (&hourly_tick, clock_cb,
2086	fmod (ev_now (loop), 3600.), 3600., 0);	2492	fmod (ev_now (loop), 3600.), 3600., 0);
2087	ev_periodic_start (loop, &hourly_tick);	2493	ev_periodic_start (loop, &hourly_tick);
2088		2494
2089		2495
2090	=head2 C<ev_signal> - signal me when a signal gets signalled!	2496	=head2 C<ev_signal> - signal me when a signal gets signalled!
2091		2497
2092	Signal watchers will trigger an event when the process receives a specific	2498	Signal watchers will trigger an event when the process receives a specific
2093	signal one or more times. Even though signals are very asynchronous, libev	2499	signal one or more times. Even though signals are very asynchronous, libev
2094	will try it's best to deliver signals synchronously, i.e. as part of the	2500	will try its best to deliver signals synchronously, i.e. as part of the
2095	normal event processing, like any other event.	2501	normal event processing, like any other event.
2096		2502
2097	If you want signals to be delivered truly asynchronously, just use	2503	If you want signals to be delivered truly asynchronously, just use
2098	C<sigaction> as you would do without libev and forget about sharing	2504	C<sigaction> as you would do without libev and forget about sharing
2099	the signal. You can even use C<ev_async> from a signal handler to	2505	the signal. You can even use C<ev_async> from a signal handler to
…		…
2103	only within the same loop, i.e. you can watch for C<SIGINT> in your	2509	only within the same loop, i.e. you can watch for C<SIGINT> in your
2104	default loop and for C<SIGIO> in another loop, but you cannot watch for	2510	default loop and for C<SIGIO> in another loop, but you cannot watch for
2105	C<SIGINT> in both the default loop and another loop at the same time. At	2511	C<SIGINT> in both the default loop and another loop at the same time. At
2106	the moment, C<SIGCHLD> is permanently tied to the default loop.	2512	the moment, C<SIGCHLD> is permanently tied to the default loop.
2107		2513
2108	When the first watcher gets started will libev actually register something	2514	Only after the first watcher for a signal is started will libev actually
2109	with the kernel (thus it coexists with your own signal handlers as long as	2515	register something with the kernel. It thus coexists with your own signal
2110	you don't register any with libev for the same signal).	2516	handlers as long as you don't register any with libev for the same signal.
2111
2112	Both the signal mask state (C<sigprocmask>) and the signal handler state
2113	(C<sigaction>) are unspecified after starting a signal watcher (and after
2114	sotpping it again), that is, libev might or might not block the signal,
2115	and might or might not set or restore the installed signal handler.
2116		2517
2117	If possible and supported, libev will install its handlers with	2518	If possible and supported, libev will install its handlers with
2118	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2519	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2119	not be unduly interrupted. If you have a problem with system calls getting	2520	not be unduly interrupted. If you have a problem with system calls getting
2120	interrupted by signals you can block all signals in an C<ev_check> watcher	2521	interrupted by signals you can block all signals in an C<ev_check> watcher
2121	and unblock them in an C<ev_prepare> watcher.	2522	and unblock them in an C<ev_prepare> watcher.
2122		2523
		2524	=head3 The special problem of inheritance over fork/execve/pthread_create
		2525
		2526	Both the signal mask (C<sigprocmask>) and the signal disposition
		2527	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2528	stopping it again), that is, libev might or might not block the signal,
		2529	and might or might not set or restore the installed signal handler (but
		2530	see C<EVFLAG_NOSIGMASK>).
		2531
		2532	While this does not matter for the signal disposition (libev never
		2533	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2534	C<execve>), this matters for the signal mask: many programs do not expect
		2535	certain signals to be blocked.
		2536
		2537	This means that before calling C<exec> (from the child) you should reset
		2538	the signal mask to whatever "default" you expect (all clear is a good
		2539	choice usually).
		2540
		2541	The simplest way to ensure that the signal mask is reset in the child is
		2542	to install a fork handler with C<pthread_atfork> that resets it. That will
		2543	catch fork calls done by libraries (such as the libc) as well.
		2544
		2545	In current versions of libev, the signal will not be blocked indefinitely
		2546	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2547	the window of opportunity for problems, it will not go away, as libev
		2548	I<has> to modify the signal mask, at least temporarily.
		2549
		2550	So I can't stress this enough: I<If you do not reset your signal mask when
		2551	you expect it to be empty, you have a race condition in your code>. This
		2552	is not a libev-specific thing, this is true for most event libraries.
		2553
		2554	=head3 The special problem of threads signal handling
		2555
		2556	POSIX threads has problematic signal handling semantics, specifically,
		2557	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2558	threads in a process block signals, which is hard to achieve.
		2559
		2560	When you want to use sigwait (or mix libev signal handling with your own
		2561	for the same signals), you can tackle this problem by globally blocking
		2562	all signals before creating any threads (or creating them with a fully set
		2563	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2564	loops. Then designate one thread as "signal receiver thread" which handles
		2565	these signals. You can pass on any signals that libev might be interested
		2566	in by calling C<ev_feed_signal>.
		2567
2123	=head3 Watcher-Specific Functions and Data Members	2568	=head3 Watcher-Specific Functions and Data Members
2124		2569
2125	=over 4	2570	=over 4
2126		2571
2127	=item ev_signal_init (ev_signal *, callback, int signum)	2572	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2142	Example: Try to exit cleanly on SIGINT.	2587	Example: Try to exit cleanly on SIGINT.
2143		2588
2144	static void	2589	static void
2145	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2590	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2146	{	2591	{
2147	ev_unloop (loop, EVUNLOOP_ALL);	2592	ev_break (loop, EVBREAK_ALL);
2148	}	2593	}
2149		2594
2150	ev_signal signal_watcher;	2595	ev_signal signal_watcher;
2151	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2596	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2152	ev_signal_start (loop, &signal_watcher);	2597	ev_signal_start (loop, &signal_watcher);
…		…
2261		2706
2262	=head2 C<ev_stat> - did the file attributes just change?	2707	=head2 C<ev_stat> - did the file attributes just change?
2263		2708
2264	This watches a file system path for attribute changes. That is, it calls	2709	This watches a file system path for attribute changes. That is, it calls
2265	C<stat> on that path in regular intervals (or when the OS says it changed)	2710	C<stat> on that path in regular intervals (or when the OS says it changed)
2266	and sees if it changed compared to the last time, invoking the callback if	2711	and sees if it changed compared to the last time, invoking the callback
2267	it did.	2712	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2713	happen after the watcher has been started will be reported.
2268		2714
2269	The path does not need to exist: changing from "path exists" to "path does	2715	The path does not need to exist: changing from "path exists" to "path does
2270	not exist" is a status change like any other. The condition "path does not	2716	not exist" is a status change like any other. The condition "path does not
2271	exist" (or more correctly "path cannot be stat'ed") is signified by the	2717	exist" (or more correctly "path cannot be stat'ed") is signified by the
2272	C<st_nlink> field being zero (which is otherwise always forced to be at	2718	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2502	Apart from keeping your process non-blocking (which is a useful	2948	Apart from keeping your process non-blocking (which is a useful
2503	effect on its own sometimes), idle watchers are a good place to do	2949	effect on its own sometimes), idle watchers are a good place to do
2504	"pseudo-background processing", or delay processing stuff to after the	2950	"pseudo-background processing", or delay processing stuff to after the
2505	event loop has handled all outstanding events.	2951	event loop has handled all outstanding events.
2506		2952
		2953	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2954
		2955	As long as there is at least one active idle watcher, libev will never
		2956	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2957	For this to work, the idle watcher doesn't need to be invoked at all - the
		2958	lowest priority will do.
		2959
		2960	This mode of operation can be useful together with an C<ev_check> watcher,
		2961	to do something on each event loop iteration - for example to balance load
		2962	between different connections.
		2963
		2964	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2965	example.
		2966
2507	=head3 Watcher-Specific Functions and Data Members	2967	=head3 Watcher-Specific Functions and Data Members
2508		2968
2509	=over 4	2969	=over 4
2510		2970
2511	=item ev_idle_init (ev_idle *, callback)	2971	=item ev_idle_init (ev_idle *, callback)
…		…
2522	callback, free it. Also, use no error checking, as usual.	2982	callback, free it. Also, use no error checking, as usual.
2523		2983
2524	static void	2984	static void
2525	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2985	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2526	{	2986	{
		2987	// stop the watcher
		2988	ev_idle_stop (loop, w);
		2989
		2990	// now we can free it
2527	free (w);	2991	free (w);
		2992
2528	// now do something you wanted to do when the program has	2993	// now do something you wanted to do when the program has
2529	// no longer anything immediate to do.	2994	// no longer anything immediate to do.
2530	}	2995	}
2531		2996
2532	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2997	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2534	ev_idle_start (loop, idle_watcher);	2999	ev_idle_start (loop, idle_watcher);
2535		3000
2536		3001
2537	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3002	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2538		3003
2539	Prepare and check watchers are usually (but not always) used in pairs:	3004	Prepare and check watchers are often (but not always) used in pairs:
2540	prepare watchers get invoked before the process blocks and check watchers	3005	prepare watchers get invoked before the process blocks and check watchers
2541	afterwards.	3006	afterwards.
2542		3007
2543	You I<must not> call C<ev_loop> or similar functions that enter	3008	You I<must not> call C<ev_run> (or similar functions that enter the
2544	the current event loop from either C<ev_prepare> or C<ev_check>	3009	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2545	watchers. Other loops than the current one are fine, however. The	3010	C<ev_check> watchers. Other loops than the current one are fine,
2546	rationale behind this is that you do not need to check for recursion in	3011	however. The rationale behind this is that you do not need to check
2547	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3012	for recursion in those watchers, i.e. the sequence will always be
2548	C<ev_check> so if you have one watcher of each kind they will always be	3013	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2549	called in pairs bracketing the blocking call.	3014	kind they will always be called in pairs bracketing the blocking call.
2550		3015
2551	Their main purpose is to integrate other event mechanisms into libev and	3016	Their main purpose is to integrate other event mechanisms into libev and
2552	their use is somewhat advanced. They could be used, for example, to track	3017	their use is somewhat advanced. They could be used, for example, to track
2553	variable changes, implement your own watchers, integrate net-snmp or a	3018	variable changes, implement your own watchers, integrate net-snmp or a
2554	coroutine library and lots more. They are also occasionally useful if	3019	coroutine library and lots more. They are also occasionally useful if
…		…
2572	with priority higher than or equal to the event loop and one coroutine	3037	with priority higher than or equal to the event loop and one coroutine
2573	of lower priority, but only once, using idle watchers to keep the event	3038	of lower priority, but only once, using idle watchers to keep the event
2574	loop from blocking if lower-priority coroutines are active, thus mapping	3039	loop from blocking if lower-priority coroutines are active, thus mapping
2575	low-priority coroutines to idle/background tasks).	3040	low-priority coroutines to idle/background tasks).
2576		3041
2577	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3042	When used for this purpose, it is recommended to give C<ev_check> watchers
2578	priority, to ensure that they are being run before any other watchers	3043	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2579	after the poll (this doesn't matter for C<ev_prepare> watchers).	3044	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3045	watchers).
2580		3046
2581	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3047	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2582	activate ("feed") events into libev. While libev fully supports this, they	3048	activate ("feed") events into libev. While libev fully supports this, they
2583	might get executed before other C<ev_check> watchers did their job. As	3049	might get executed before other C<ev_check> watchers did their job. As
2584	C<ev_check> watchers are often used to embed other (non-libev) event	3050	C<ev_check> watchers are often used to embed other (non-libev) event
2585	loops those other event loops might be in an unusable state until their	3051	loops those other event loops might be in an unusable state until their
2586	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3052	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2587	others).	3053	others).
		3054
		3055	=head3 Abusing an C<ev_check> watcher for its side-effect
		3056
		3057	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3058	useful because they are called once per event loop iteration. For
		3059	example, if you want to handle a large number of connections fairly, you
		3060	normally only do a bit of work for each active connection, and if there
		3061	is more work to do, you wait for the next event loop iteration, so other
		3062	connections have a chance of making progress.
		3063
		3064	Using an C<ev_check> watcher is almost enough: it will be called on the
		3065	next event loop iteration. However, that isn't as soon as possible -
		3066	without external events, your C<ev_check> watcher will not be invoked.
		3067
		3068	This is where C<ev_idle> watchers come in handy - all you need is a
		3069	single global idle watcher that is active as long as you have one active
		3070	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3071	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3072	invoked. Neither watcher alone can do that.
2588		3073
2589	=head3 Watcher-Specific Functions and Data Members	3074	=head3 Watcher-Specific Functions and Data Members
2590		3075
2591	=over 4	3076	=over 4
2592		3077
…		…
2716		3201
2717	if (timeout >= 0)	3202	if (timeout >= 0)
2718	// create/start timer	3203	// create/start timer
2719		3204
2720	// poll	3205	// poll
2721	ev_loop (EV_A_ 0);	3206	ev_run (EV_A_ 0);
2722		3207
2723	// stop timer again	3208	// stop timer again
2724	if (timeout >= 0)	3209	if (timeout >= 0)
2725	ev_timer_stop (EV_A_ &to);	3210	ev_timer_stop (EV_A_ &to);
2726		3211
…		…
2793		3278
2794	=over 4	3279	=over 4
2795		3280
2796	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3281	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2797		3282
2798	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3283	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2799		3284
2800	Configures the watcher to embed the given loop, which must be	3285	Configures the watcher to embed the given loop, which must be
2801	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3286	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2802	invoked automatically, otherwise it is the responsibility of the callback	3287	invoked automatically, otherwise it is the responsibility of the callback
2803	to invoke it (it will continue to be called until the sweep has been done,	3288	to invoke it (it will continue to be called until the sweep has been done,
2804	if you do not want that, you need to temporarily stop the embed watcher).	3289	if you do not want that, you need to temporarily stop the embed watcher).
2805		3290
2806	=item ev_embed_sweep (loop, ev_embed *)	3291	=item ev_embed_sweep (loop, ev_embed *)
2807		3292
2808	Make a single, non-blocking sweep over the embedded loop. This works	3293	Make a single, non-blocking sweep over the embedded loop. This works
2809	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3294	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2810	appropriate way for embedded loops.	3295	appropriate way for embedded loops.
2811		3296
2812	=item struct ev_loop *other [read-only]	3297	=item struct ev_loop *other [read-only]
2813		3298
2814	The embedded event loop.	3299	The embedded event loop.
…		…
2824	used).	3309	used).
2825		3310
2826	struct ev_loop *loop_hi = ev_default_init (0);	3311	struct ev_loop *loop_hi = ev_default_init (0);
2827	struct ev_loop *loop_lo = 0;	3312	struct ev_loop *loop_lo = 0;
2828	ev_embed embed;	3313	ev_embed embed;
2829		3314
2830	// see if there is a chance of getting one that works	3315	// see if there is a chance of getting one that works
2831	// (remember that a flags value of 0 means autodetection)	3316	// (remember that a flags value of 0 means autodetection)
2832	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3317	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2833	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3318	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2834	: 0;	3319	: 0;
…		…
2848	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3333	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2849		3334
2850	struct ev_loop *loop = ev_default_init (0);	3335	struct ev_loop *loop = ev_default_init (0);
2851	struct ev_loop *loop_socket = 0;	3336	struct ev_loop *loop_socket = 0;
2852	ev_embed embed;	3337	ev_embed embed;
2853		3338
2854	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3339	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2855	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3340	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2856	{	3341	{
2857	ev_embed_init (&embed, 0, loop_socket);	3342	ev_embed_init (&embed, 0, loop_socket);
2858	ev_embed_start (loop, &embed);	3343	ev_embed_start (loop, &embed);
…		…
2866		3351
2867	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3352	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2868		3353
2869	Fork watchers are called when a C<fork ()> was detected (usually because	3354	Fork watchers are called when a C<fork ()> was detected (usually because
2870	whoever is a good citizen cared to tell libev about it by calling	3355	whoever is a good citizen cared to tell libev about it by calling
2871	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3356	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2872	event loop blocks next and before C<ev_check> watchers are being called,	3357	and before C<ev_check> watchers are being called, and only in the child
2873	and only in the child after the fork. If whoever good citizen calling	3358	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2874	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3359	and calls it in the wrong process, the fork handlers will be invoked, too,
2875	handlers will be invoked, too, of course.	3360	of course.
2876		3361
2877	=head3 The special problem of life after fork - how is it possible?	3362	=head3 The special problem of life after fork - how is it possible?
2878		3363
2879	Most uses of C<fork()> consist of forking, then some simple calls to ste	3364	Most uses of C<fork ()> consist of forking, then some simple calls to set
2880	up/change the process environment, followed by a call to C<exec()>. This	3365	up/change the process environment, followed by a call to C<exec()>. This
2881	sequence should be handled by libev without any problems.	3366	sequence should be handled by libev without any problems.
2882		3367
2883	This changes when the application actually wants to do event handling	3368	This changes when the application actually wants to do event handling
2884	in the child, or both parent in child, in effect "continuing" after the	3369	in the child, or both parent in child, in effect "continuing" after the
…		…
2900	disadvantage of having to use multiple event loops (which do not support	3385	disadvantage of having to use multiple event loops (which do not support
2901	signal watchers).	3386	signal watchers).
2902		3387
2903	When this is not possible, or you want to use the default loop for	3388	When this is not possible, or you want to use the default loop for
2904	other reasons, then in the process that wants to start "fresh", call	3389	other reasons, then in the process that wants to start "fresh", call
2905	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3390	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2906	the default loop will "orphan" (not stop) all registered watchers, so you	3391	Destroying the default loop will "orphan" (not stop) all registered
2907	have to be careful not to execute code that modifies those watchers. Note	3392	watchers, so you have to be careful not to execute code that modifies
2908	also that in that case, you have to re-register any signal watchers.	3393	those watchers. Note also that in that case, you have to re-register any
		3394	signal watchers.
2909		3395
2910	=head3 Watcher-Specific Functions and Data Members	3396	=head3 Watcher-Specific Functions and Data Members
2911		3397
2912	=over 4	3398	=over 4
2913		3399
2914	=item ev_fork_init (ev_signal *, callback)	3400	=item ev_fork_init (ev_fork *, callback)
2915		3401
2916	Initialises and configures the fork watcher - it has no parameters of any	3402	Initialises and configures the fork watcher - it has no parameters of any
2917	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3403	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2918	believe me.	3404	really.
2919		3405
2920	=back	3406	=back
2921		3407
2922		3408
		3409	=head2 C<ev_cleanup> - even the best things end
		3410
		3411	Cleanup watchers are called just before the event loop is being destroyed
		3412	by a call to C<ev_loop_destroy>.
		3413
		3414	While there is no guarantee that the event loop gets destroyed, cleanup
		3415	watchers provide a convenient method to install cleanup hooks for your
		3416	program, worker threads and so on - you just to make sure to destroy the
		3417	loop when you want them to be invoked.
		3418
		3419	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3420	all other watchers, they do not keep a reference to the event loop (which
		3421	makes a lot of sense if you think about it). Like all other watchers, you
		3422	can call libev functions in the callback, except C<ev_cleanup_start>.
		3423
		3424	=head3 Watcher-Specific Functions and Data Members
		3425
		3426	=over 4
		3427
		3428	=item ev_cleanup_init (ev_cleanup *, callback)
		3429
		3430	Initialises and configures the cleanup watcher - it has no parameters of
		3431	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3432	pointless, I assure you.
		3433
		3434	=back
		3435
		3436	Example: Register an atexit handler to destroy the default loop, so any
		3437	cleanup functions are called.
		3438
		3439	static void
		3440	program_exits (void)
		3441	{
		3442	ev_loop_destroy (EV_DEFAULT_UC);
		3443	}
		3444
		3445	...
		3446	atexit (program_exits);
		3447
		3448
2923	=head2 C<ev_async> - how to wake up another event loop	3449	=head2 C<ev_async> - how to wake up an event loop
2924		3450
2925	In general, you cannot use an C<ev_loop> from multiple threads or other	3451	In general, you cannot use an C<ev_loop> from multiple threads or other
2926	asynchronous sources such as signal handlers (as opposed to multiple event	3452	asynchronous sources such as signal handlers (as opposed to multiple event
2927	loops - those are of course safe to use in different threads).	3453	loops - those are of course safe to use in different threads).
2928		3454
2929	Sometimes, however, you need to wake up another event loop you do not	3455	Sometimes, however, you need to wake up an event loop you do not control,
2930	control, for example because it belongs to another thread. This is what	3456	for example because it belongs to another thread. This is what C<ev_async>
2931	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3457	watchers do: as long as the C<ev_async> watcher is active, you can signal
2932	can signal it by calling C<ev_async_send>, which is thread- and signal	3458	it by calling C<ev_async_send>, which is thread- and signal safe.
2933	safe.
2934		3459
2935	This functionality is very similar to C<ev_signal> watchers, as signals,	3460	This functionality is very similar to C<ev_signal> watchers, as signals,
2936	too, are asynchronous in nature, and signals, too, will be compressed	3461	too, are asynchronous in nature, and signals, too, will be compressed
2937	(i.e. the number of callback invocations may be less than the number of	3462	(i.e. the number of callback invocations may be less than the number of
2938	C<ev_async_sent> calls).	3463	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2939		3464	of "global async watchers" by using a watcher on an otherwise unused
2940	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3465	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2941	just the default loop.	3466	even without knowing which loop owns the signal.
2942		3467
2943	=head3 Queueing	3468	=head3 Queueing
2944		3469
2945	C<ev_async> does not support queueing of data in any way. The reason	3470	C<ev_async> does not support queueing of data in any way. The reason
2946	is that the author does not know of a simple (or any) algorithm for a	3471	is that the author does not know of a simple (or any) algorithm for a
2947	multiple-writer-single-reader queue that works in all cases and doesn't	3472	multiple-writer-single-reader queue that works in all cases and doesn't
2948	need elaborate support such as pthreads.	3473	need elaborate support such as pthreads or unportable memory access
		3474	semantics.
2949		3475
2950	That means that if you want to queue data, you have to provide your own	3476	That means that if you want to queue data, you have to provide your own
2951	queue. But at least I can tell you how to implement locking around your	3477	queue. But at least I can tell you how to implement locking around your
2952	queue:	3478	queue:
2953		3479
…		…
3037	trust me.	3563	trust me.
3038		3564
3039	=item ev_async_send (loop, ev_async *)	3565	=item ev_async_send (loop, ev_async *)
3040		3566
3041	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3567	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3042	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3568	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3569	returns.
		3570
3043	C<ev_feed_event>, this call is safe to do from other threads, signal or	3571	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3044	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3572	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3045	section below on what exactly this means).	3573	embedding section below on what exactly this means).
3046		3574
3047	Note that, as with other watchers in libev, multiple events might get	3575	Note that, as with other watchers in libev, multiple events might get
3048	compressed into a single callback invocation (another way to look at this	3576	compressed into a single callback invocation (another way to look at
3049	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3577	this is that C<ev_async> watchers are level-triggered: they are set on
3050	reset when the event loop detects that).	3578	C<ev_async_send>, reset when the event loop detects that).
3051		3579
3052	This call incurs the overhead of a system call only once per event loop	3580	This call incurs the overhead of at most one extra system call per event
3053	iteration, so while the overhead might be noticeable, it doesn't apply to	3581	loop iteration, if the event loop is blocked, and no syscall at all if
3054	repeated calls to C<ev_async_send> for the same event loop.	3582	the event loop (or your program) is processing events. That means that
		3583	repeated calls are basically free (there is no need to avoid calls for
		3584	performance reasons) and that the overhead becomes smaller (typically
		3585	zero) under load.
3055		3586
3056	=item bool = ev_async_pending (ev_async *)	3587	=item bool = ev_async_pending (ev_async *)
3057		3588
3058	Returns a non-zero value when C<ev_async_send> has been called on the	3589	Returns a non-zero value when C<ev_async_send> has been called on the
3059	watcher but the event has not yet been processed (or even noted) by the	3590	watcher but the event has not yet been processed (or even noted) by the
…		…
3076		3607
3077	There are some other functions of possible interest. Described. Here. Now.	3608	There are some other functions of possible interest. Described. Here. Now.
3078		3609
3079	=over 4	3610	=over 4
3080		3611
3081	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3612	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3082		3613
3083	This function combines a simple timer and an I/O watcher, calls your	3614	This function combines a simple timer and an I/O watcher, calls your
3084	callback on whichever event happens first and automatically stops both	3615	callback on whichever event happens first and automatically stops both
3085	watchers. This is useful if you want to wait for a single event on an fd	3616	watchers. This is useful if you want to wait for a single event on an fd
3086	or timeout without having to allocate/configure/start/stop/free one or	3617	or timeout without having to allocate/configure/start/stop/free one or
…		…
3092		3623
3093	If C<timeout> is less than 0, then no timeout watcher will be	3624	If C<timeout> is less than 0, then no timeout watcher will be
3094	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3625	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3095	repeat = 0) will be started. C<0> is a valid timeout.	3626	repeat = 0) will be started. C<0> is a valid timeout.
3096		3627
3097	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3628	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3098	passed an C<revents> set like normal event callbacks (a combination of	3629	passed an C<revents> set like normal event callbacks (a combination of
3099	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3630	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3100	value passed to C<ev_once>. Note that it is possible to receive I<both>	3631	value passed to C<ev_once>. Note that it is possible to receive I<both>
3101	a timeout and an io event at the same time - you probably should give io	3632	a timeout and an io event at the same time - you probably should give io
3102	events precedence.	3633	events precedence.
3103		3634
3104	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3635	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3105		3636
3106	static void stdin_ready (int revents, void *arg)	3637	static void stdin_ready (int revents, void *arg)
3107	{	3638	{
3108	if (revents & EV_READ)	3639	if (revents & EV_READ)
3109	/* stdin might have data for us, joy! */;	3640	/* stdin might have data for us, joy! */;
3110	else if (revents & EV_TIMEOUT)	3641	else if (revents & EV_TIMER)
3111	/* doh, nothing entered */;	3642	/* doh, nothing entered */;
3112	}	3643	}
3113		3644
3114	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3645	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3115		3646
3116	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3117
3118	Feeds the given event set into the event loop, as if the specified event
3119	had happened for the specified watcher (which must be a pointer to an
3120	initialised but not necessarily started event watcher).
3121
3122	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3647	=item ev_feed_fd_event (loop, int fd, int revents)
3123		3648
3124	Feed an event on the given fd, as if a file descriptor backend detected	3649	Feed an event on the given fd, as if a file descriptor backend detected
3125	the given events it.	3650	the given events.
3126		3651
3127	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3652	=item ev_feed_signal_event (loop, int signum)
3128		3653
3129	Feed an event as if the given signal occurred (C<loop> must be the default	3654	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3130	loop!).	3655	which is async-safe.
3131		3656
3132	=back	3657	=back
		3658
		3659
		3660	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3661
		3662	This section explains some common idioms that are not immediately
		3663	obvious. Note that examples are sprinkled over the whole manual, and this
		3664	section only contains stuff that wouldn't fit anywhere else.
		3665
		3666	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3667
		3668	Each watcher has, by default, a C<void *data> member that you can read
		3669	or modify at any time: libev will completely ignore it. This can be used
		3670	to associate arbitrary data with your watcher. If you need more data and
		3671	don't want to allocate memory separately and store a pointer to it in that
		3672	data member, you can also "subclass" the watcher type and provide your own
		3673	data:
		3674
		3675	struct my_io
		3676	{
		3677	ev_io io;
		3678	int otherfd;
		3679	void *somedata;
		3680	struct whatever *mostinteresting;
		3681	};
		3682
		3683	...
		3684	struct my_io w;
		3685	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3686
		3687	And since your callback will be called with a pointer to the watcher, you
		3688	can cast it back to your own type:
		3689
		3690	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3691	{
		3692	struct my_io *w = (struct my_io *)w_;
		3693	...
		3694	}
		3695
		3696	More interesting and less C-conformant ways of casting your callback
		3697	function type instead have been omitted.
		3698
		3699	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3700
		3701	Another common scenario is to use some data structure with multiple
		3702	embedded watchers, in effect creating your own watcher that combines
		3703	multiple libev event sources into one "super-watcher":
		3704
		3705	struct my_biggy
		3706	{
		3707	int some_data;
		3708	ev_timer t1;
		3709	ev_timer t2;
		3710	}
		3711
		3712	In this case getting the pointer to C<my_biggy> is a bit more
		3713	complicated: Either you store the address of your C<my_biggy> struct in
		3714	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3715	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3716	real programmers):
		3717
		3718	#include <stddef.h>
		3719
		3720	static void
		3721	t1_cb (EV_P_ ev_timer *w, int revents)
		3722	{
		3723	struct my_biggy big = (struct my_biggy *)
		3724	(((char *)w) - offsetof (struct my_biggy, t1));
		3725	}
		3726
		3727	static void
		3728	t2_cb (EV_P_ ev_timer *w, int revents)
		3729	{
		3730	struct my_biggy big = (struct my_biggy *)
		3731	(((char *)w) - offsetof (struct my_biggy, t2));
		3732	}
		3733
		3734	=head2 AVOIDING FINISHING BEFORE RETURNING
		3735
		3736	Often you have structures like this in event-based programs:
		3737
		3738	callback ()
		3739	{
		3740	free (request);
		3741	}
		3742
		3743	request = start_new_request (..., callback);
		3744
		3745	The intent is to start some "lengthy" operation. The C<request> could be
		3746	used to cancel the operation, or do other things with it.
		3747
		3748	It's not uncommon to have code paths in C<start_new_request> that
		3749	immediately invoke the callback, for example, to report errors. Or you add
		3750	some caching layer that finds that it can skip the lengthy aspects of the
		3751	operation and simply invoke the callback with the result.
		3752
		3753	The problem here is that this will happen I<before> C<start_new_request>
		3754	has returned, so C<request> is not set.
		3755
		3756	Even if you pass the request by some safer means to the callback, you
		3757	might want to do something to the request after starting it, such as
		3758	canceling it, which probably isn't working so well when the callback has
		3759	already been invoked.
		3760
		3761	A common way around all these issues is to make sure that
		3762	C<start_new_request> I<always> returns before the callback is invoked. If
		3763	C<start_new_request> immediately knows the result, it can artificially
		3764	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3765	example, or more sneakily, by reusing an existing (stopped) watcher and
		3766	pushing it into the pending queue:
		3767
		3768	ev_set_cb (watcher, callback);
		3769	ev_feed_event (EV_A_ watcher, 0);
		3770
		3771	This way, C<start_new_request> can safely return before the callback is
		3772	invoked, while not delaying callback invocation too much.
		3773
		3774	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3775
		3776	Often (especially in GUI toolkits) there are places where you have
		3777	I<modal> interaction, which is most easily implemented by recursively
		3778	invoking C<ev_run>.
		3779
		3780	This brings the problem of exiting - a callback might want to finish the
		3781	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3782	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3783	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3784	other combination: In these cases, a simple C<ev_break> will not work.
		3785
		3786	The solution is to maintain "break this loop" variable for each C<ev_run>
		3787	invocation, and use a loop around C<ev_run> until the condition is
		3788	triggered, using C<EVRUN_ONCE>:
		3789
		3790	// main loop
		3791	int exit_main_loop = 0;
		3792
		3793	while (!exit_main_loop)
		3794	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3795
		3796	// in a modal watcher
		3797	int exit_nested_loop = 0;
		3798
		3799	while (!exit_nested_loop)
		3800	ev_run (EV_A_ EVRUN_ONCE);
		3801
		3802	To exit from any of these loops, just set the corresponding exit variable:
		3803
		3804	// exit modal loop
		3805	exit_nested_loop = 1;
		3806
		3807	// exit main program, after modal loop is finished
		3808	exit_main_loop = 1;
		3809
		3810	// exit both
		3811	exit_main_loop = exit_nested_loop = 1;
		3812
		3813	=head2 THREAD LOCKING EXAMPLE
		3814
		3815	Here is a fictitious example of how to run an event loop in a different
		3816	thread from where callbacks are being invoked and watchers are
		3817	created/added/removed.
		3818
		3819	For a real-world example, see the C<EV::Loop::Async> perl module,
		3820	which uses exactly this technique (which is suited for many high-level
		3821	languages).
		3822
		3823	The example uses a pthread mutex to protect the loop data, a condition
		3824	variable to wait for callback invocations, an async watcher to notify the
		3825	event loop thread and an unspecified mechanism to wake up the main thread.
		3826
		3827	First, you need to associate some data with the event loop:
		3828
		3829	typedef struct {
		3830	mutex_t lock; /* global loop lock */
		3831	ev_async async_w;
		3832	thread_t tid;
		3833	cond_t invoke_cv;
		3834	} userdata;
		3835
		3836	void prepare_loop (EV_P)
		3837	{
		3838	// for simplicity, we use a static userdata struct.
		3839	static userdata u;
		3840
		3841	ev_async_init (&u->async_w, async_cb);
		3842	ev_async_start (EV_A_ &u->async_w);
		3843
		3844	pthread_mutex_init (&u->lock, 0);
		3845	pthread_cond_init (&u->invoke_cv, 0);
		3846
		3847	// now associate this with the loop
		3848	ev_set_userdata (EV_A_ u);
		3849	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3850	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3851
		3852	// then create the thread running ev_run
		3853	pthread_create (&u->tid, 0, l_run, EV_A);
		3854	}
		3855
		3856	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3857	solely to wake up the event loop so it takes notice of any new watchers
		3858	that might have been added:
		3859
		3860	static void
		3861	async_cb (EV_P_ ev_async *w, int revents)
		3862	{
		3863	// just used for the side effects
		3864	}
		3865
		3866	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3867	protecting the loop data, respectively.
		3868
		3869	static void
		3870	l_release (EV_P)
		3871	{
		3872	userdata *u = ev_userdata (EV_A);
		3873	pthread_mutex_unlock (&u->lock);
		3874	}
		3875
		3876	static void
		3877	l_acquire (EV_P)
		3878	{
		3879	userdata *u = ev_userdata (EV_A);
		3880	pthread_mutex_lock (&u->lock);
		3881	}
		3882
		3883	The event loop thread first acquires the mutex, and then jumps straight
		3884	into C<ev_run>:
		3885
		3886	void *
		3887	l_run (void *thr_arg)
		3888	{
		3889	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3890
		3891	l_acquire (EV_A);
		3892	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3893	ev_run (EV_A_ 0);
		3894	l_release (EV_A);
		3895
		3896	return 0;
		3897	}
		3898
		3899	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3900	signal the main thread via some unspecified mechanism (signals? pipe
		3901	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3902	have been called (in a while loop because a) spurious wakeups are possible
		3903	and b) skipping inter-thread-communication when there are no pending
		3904	watchers is very beneficial):
		3905
		3906	static void
		3907	l_invoke (EV_P)
		3908	{
		3909	userdata *u = ev_userdata (EV_A);
		3910
		3911	while (ev_pending_count (EV_A))
		3912	{
		3913	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3914	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3915	}
		3916	}
		3917
		3918	Now, whenever the main thread gets told to invoke pending watchers, it
		3919	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3920	thread to continue:
		3921
		3922	static void
		3923	real_invoke_pending (EV_P)
		3924	{
		3925	userdata *u = ev_userdata (EV_A);
		3926
		3927	pthread_mutex_lock (&u->lock);
		3928	ev_invoke_pending (EV_A);
		3929	pthread_cond_signal (&u->invoke_cv);
		3930	pthread_mutex_unlock (&u->lock);
		3931	}
		3932
		3933	Whenever you want to start/stop a watcher or do other modifications to an
		3934	event loop, you will now have to lock:
		3935
		3936	ev_timer timeout_watcher;
		3937	userdata *u = ev_userdata (EV_A);
		3938
		3939	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3940
		3941	pthread_mutex_lock (&u->lock);
		3942	ev_timer_start (EV_A_ &timeout_watcher);
		3943	ev_async_send (EV_A_ &u->async_w);
		3944	pthread_mutex_unlock (&u->lock);
		3945
		3946	Note that sending the C<ev_async> watcher is required because otherwise
		3947	an event loop currently blocking in the kernel will have no knowledge
		3948	about the newly added timer. By waking up the loop it will pick up any new
		3949	watchers in the next event loop iteration.
		3950
		3951	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3952
		3953	While the overhead of a callback that e.g. schedules a thread is small, it
		3954	is still an overhead. If you embed libev, and your main usage is with some
		3955	kind of threads or coroutines, you might want to customise libev so that
		3956	doesn't need callbacks anymore.
		3957
		3958	Imagine you have coroutines that you can switch to using a function
		3959	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3960	and that due to some magic, the currently active coroutine is stored in a
		3961	global called C<current_coro>. Then you can build your own "wait for libev
		3962	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3963	the differing C<;> conventions):
		3964
		3965	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3966	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3967
		3968	That means instead of having a C callback function, you store the
		3969	coroutine to switch to in each watcher, and instead of having libev call
		3970	your callback, you instead have it switch to that coroutine.
		3971
		3972	A coroutine might now wait for an event with a function called
		3973	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3974	matter when, or whether the watcher is active or not when this function is
		3975	called):
		3976
		3977	void
		3978	wait_for_event (ev_watcher *w)
		3979	{
		3980	ev_set_cb (w, current_coro);
		3981	switch_to (libev_coro);
		3982	}
		3983
		3984	That basically suspends the coroutine inside C<wait_for_event> and
		3985	continues the libev coroutine, which, when appropriate, switches back to
		3986	this or any other coroutine.
		3987
		3988	You can do similar tricks if you have, say, threads with an event queue -
		3989	instead of storing a coroutine, you store the queue object and instead of
		3990	switching to a coroutine, you push the watcher onto the queue and notify
		3991	any waiters.
		3992
		3993	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3994	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3995
		3996	// my_ev.h
		3997	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3998	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3999	#include "../libev/ev.h"
		4000
		4001	// my_ev.c
		4002	#define EV_H "my_ev.h"
		4003	#include "../libev/ev.c"
		4004
		4005	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4006	F<my_ev.c> into your project. When properly specifying include paths, you
		4007	can even use F<ev.h> as header file name directly.
3133		4008
3134		4009
3135	=head1 LIBEVENT EMULATION	4010	=head1 LIBEVENT EMULATION
3136		4011
3137	Libev offers a compatibility emulation layer for libevent. It cannot	4012	Libev offers a compatibility emulation layer for libevent. It cannot
3138	emulate the internals of libevent, so here are some usage hints:	4013	emulate the internals of libevent, so here are some usage hints:
3139		4014
3140	=over 4	4015	=over 4
		4016
		4017	=item * Only the libevent-1.4.1-beta API is being emulated.
		4018
		4019	This was the newest libevent version available when libev was implemented,
		4020	and is still mostly unchanged in 2010.
3141		4021
3142	=item * Use it by including <event.h>, as usual.	4022	=item * Use it by including <event.h>, as usual.
3143		4023
3144	=item * The following members are fully supported: ev_base, ev_callback,	4024	=item * The following members are fully supported: ev_base, ev_callback,
3145	ev_arg, ev_fd, ev_res, ev_events.	4025	ev_arg, ev_fd, ev_res, ev_events.
…		…
3151	=item * Priorities are not currently supported. Initialising priorities	4031	=item * Priorities are not currently supported. Initialising priorities
3152	will fail and all watchers will have the same priority, even though there	4032	will fail and all watchers will have the same priority, even though there
3153	is an ev_pri field.	4033	is an ev_pri field.
3154		4034
3155	=item * In libevent, the last base created gets the signals, in libev, the	4035	=item * In libevent, the last base created gets the signals, in libev, the
3156	first base created (== the default loop) gets the signals.	4036	base that registered the signal gets the signals.
3157		4037
3158	=item * Other members are not supported.	4038	=item * Other members are not supported.
3159		4039
3160	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4040	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3161	to use the libev header file and library.	4041	to use the libev header file and library.
3162		4042
3163	=back	4043	=back
3164		4044
3165	=head1 C++ SUPPORT	4045	=head1 C++ SUPPORT
		4046
		4047	=head2 C API
		4048
		4049	The normal C API should work fine when used from C++: both ev.h and the
		4050	libev sources can be compiled as C++. Therefore, code that uses the C API
		4051	will work fine.
		4052
		4053	Proper exception specifications might have to be added to callbacks passed
		4054	to libev: exceptions may be thrown only from watcher callbacks, all other
		4055	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4056	callbacks) must not throw exceptions, and might need a C<noexcept>
		4057	specification. If you have code that needs to be compiled as both C and
		4058	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4059
		4060	static void
		4061	fatal_error (const char *msg) EV_NOEXCEPT
		4062	{
		4063	perror (msg);
		4064	abort ();
		4065	}
		4066
		4067	...
		4068	ev_set_syserr_cb (fatal_error);
		4069
		4070	The only API functions that can currently throw exceptions are C<ev_run>,
		4071	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4072	because it runs cleanup watchers).
		4073
		4074	Throwing exceptions in watcher callbacks is only supported if libev itself
		4075	is compiled with a C++ compiler or your C and C++ environments allow
		4076	throwing exceptions through C libraries (most do).
		4077
		4078	=head2 C++ API
3166		4079
3167	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4080	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3168	you to use some convenience methods to start/stop watchers and also change	4081	you to use some convenience methods to start/stop watchers and also change
3169	the callback model to a model using method callbacks on objects.	4082	the callback model to a model using method callbacks on objects.
3170		4083
3171	To use it,	4084	To use it,
3172		4085
3173	#include <ev++.h>	4086	#include <ev++.h>
3174		4087
3175	This automatically includes F<ev.h> and puts all of its definitions (many	4088	This automatically includes F<ev.h> and puts all of its definitions (many
3176	of them macros) into the global namespace. All C++ specific things are	4089	of them macros) into the global namespace. All C++ specific things are
3177	put into the C<ev> namespace. It should support all the same embedding	4090	put into the C<ev> namespace. It should support all the same embedding
…		…
3180	Care has been taken to keep the overhead low. The only data member the C++	4093	Care has been taken to keep the overhead low. The only data member the C++
3181	classes add (compared to plain C-style watchers) is the event loop pointer	4094	classes add (compared to plain C-style watchers) is the event loop pointer
3182	that the watcher is associated with (or no additional members at all if	4095	that the watcher is associated with (or no additional members at all if
3183	you disable C<EV_MULTIPLICITY> when embedding libev).	4096	you disable C<EV_MULTIPLICITY> when embedding libev).
3184		4097
3185	Currently, functions, and static and non-static member functions can be	4098	Currently, functions, static and non-static member functions and classes
3186	used as callbacks. Other types should be easy to add as long as they only	4099	with C<operator ()> can be used as callbacks. Other types should be easy
3187	need one additional pointer for context. If you need support for other	4100	to add as long as they only need one additional pointer for context. If
3188	types of functors please contact the author (preferably after implementing	4101	you need support for other types of functors please contact the author
3189	it).	4102	(preferably after implementing it).
		4103
		4104	For all this to work, your C++ compiler either has to use the same calling
		4105	conventions as your C compiler (for static member functions), or you have
		4106	to embed libev and compile libev itself as C++.
3190		4107
3191	Here is a list of things available in the C<ev> namespace:	4108	Here is a list of things available in the C<ev> namespace:
3192		4109
3193	=over 4	4110	=over 4
3194		4111
…		…
3204	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4121	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3205		4122
3206	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4123	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3207	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4124	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3208	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4125	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3209	defines by many implementations.	4126	defined by many implementations.
3210		4127
3211	All of those classes have these methods:	4128	All of those classes have these methods:
3212		4129
3213	=over 4	4130	=over 4
3214		4131
3215	=item ev::TYPE::TYPE ()	4132	=item ev::TYPE::TYPE ()
3216		4133
3217	=item ev::TYPE::TYPE (struct ev_loop *)	4134	=item ev::TYPE::TYPE (loop)
3218		4135
3219	=item ev::TYPE::~TYPE	4136	=item ev::TYPE::~TYPE
3220		4137
3221	The constructor (optionally) takes an event loop to associate the watcher	4138	The constructor (optionally) takes an event loop to associate the watcher
3222	with. If it is omitted, it will use C<EV_DEFAULT>.	4139	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3255	myclass obj;	4172	myclass obj;
3256	ev::io iow;	4173	ev::io iow;
3257	iow.set <myclass, &myclass::io_cb> (&obj);	4174	iow.set <myclass, &myclass::io_cb> (&obj);
3258		4175
3259	=item w->set (object *)	4176	=item w->set (object *)
3260
3261	This is an B<experimental> feature that might go away in a future version.
3262		4177
3263	This is a variation of a method callback - leaving out the method to call	4178	This is a variation of a method callback - leaving out the method to call
3264	will default the method to C<operator ()>, which makes it possible to use	4179	will default the method to C<operator ()>, which makes it possible to use
3265	functor objects without having to manually specify the C<operator ()> all	4180	functor objects without having to manually specify the C<operator ()> all
3266	the time. Incidentally, you can then also leave out the template argument	4181	the time. Incidentally, you can then also leave out the template argument
…		…
3278	void operator() (ev::io &w, int revents)	4193	void operator() (ev::io &w, int revents)
3279	{	4194	{
3280	...	4195	...
3281	}	4196	}
3282	}	4197	}
3283		4198
3284	myfunctor f;	4199	myfunctor f;
3285		4200
3286	ev::io w;	4201	ev::io w;
3287	w.set (&f);	4202	w.set (&f);
3288		4203
…		…
3299	Example: Use a plain function as callback.	4214	Example: Use a plain function as callback.
3300		4215
3301	static void io_cb (ev::io &w, int revents) { }	4216	static void io_cb (ev::io &w, int revents) { }
3302	iow.set <io_cb> ();	4217	iow.set <io_cb> ();
3303		4218
3304	=item w->set (struct ev_loop *)	4219	=item w->set (loop)
3305		4220
3306	Associates a different C<struct ev_loop> with this watcher. You can only	4221	Associates a different C<struct ev_loop> with this watcher. You can only
3307	do this when the watcher is inactive (and not pending either).	4222	do this when the watcher is inactive (and not pending either).
3308		4223
3309	=item w->set ([arguments])	4224	=item w->set ([arguments])
3310		4225
3311	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4226	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4227	with the same arguments. Either this method or a suitable start method
3312	called at least once. Unlike the C counterpart, an active watcher gets	4228	must be called at least once. Unlike the C counterpart, an active watcher
3313	automatically stopped and restarted when reconfiguring it with this	4229	gets automatically stopped and restarted when reconfiguring it with this
3314	method.	4230	method.
		4231
		4232	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4233	clashing with the C<set (loop)> method.
3315		4234
3316	=item w->start ()	4235	=item w->start ()
3317		4236
3318	Starts the watcher. Note that there is no C<loop> argument, as the	4237	Starts the watcher. Note that there is no C<loop> argument, as the
3319	constructor already stores the event loop.	4238	constructor already stores the event loop.
3320		4239
		4240	=item w->start ([arguments])
		4241
		4242	Instead of calling C<set> and C<start> methods separately, it is often
		4243	convenient to wrap them in one call. Uses the same type of arguments as
		4244	the configure C<set> method of the watcher.
		4245
3321	=item w->stop ()	4246	=item w->stop ()
3322		4247
3323	Stops the watcher if it is active. Again, no C<loop> argument.	4248	Stops the watcher if it is active. Again, no C<loop> argument.
3324		4249
3325	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4250	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3337		4262
3338	=back	4263	=back
3339		4264
3340	=back	4265	=back
3341		4266
3342	Example: Define a class with an IO and idle watcher, start one of them in	4267	Example: Define a class with two I/O and idle watchers, start the I/O
3343	the constructor.	4268	watchers in the constructor.
3344		4269
3345	class myclass	4270	class myclass
3346	{	4271	{
3347	ev::io io ; void io_cb (ev::io &w, int revents);	4272	ev::io io ; void io_cb (ev::io &w, int revents);
		4273	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3348	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4274	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3349		4275
3350	myclass (int fd)	4276	myclass (int fd)
3351	{	4277	{
3352	io .set <myclass, &myclass::io_cb > (this);	4278	io .set <myclass, &myclass::io_cb > (this);
		4279	io2 .set <myclass, &myclass::io2_cb > (this);
3353	idle.set <myclass, &myclass::idle_cb> (this);	4280	idle.set <myclass, &myclass::idle_cb> (this);
3354		4281
3355	io.start (fd, ev::READ);	4282	io.set (fd, ev::WRITE); // configure the watcher
		4283	io.start (); // start it whenever convenient
		4284
		4285	io2.start (fd, ev::READ); // set + start in one call
3356	}	4286	}
3357	};	4287	};
3358		4288
3359		4289
3360	=head1 OTHER LANGUAGE BINDINGS	4290	=head1 OTHER LANGUAGE BINDINGS
…		…
3399	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4329	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3400		4330
3401	=item D	4331	=item D
3402		4332
3403	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4333	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3404	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4334	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3405		4335
3406	=item Ocaml	4336	=item Ocaml
3407		4337
3408	Erkki Seppala has written Ocaml bindings for libev, to be found at	4338	Erkki Seppala has written Ocaml bindings for libev, to be found at
3409	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4339	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4340
		4341	=item Lua
		4342
		4343	Brian Maher has written a partial interface to libev for lua (at the
		4344	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4345	L<http://github.com/brimworks/lua-ev>.
		4346
		4347	=item Javascript
		4348
		4349	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4350
		4351	=item Others
		4352
		4353	There are others, and I stopped counting.
3410		4354
3411	=back	4355	=back
3412		4356
3413		4357
3414	=head1 MACRO MAGIC	4358	=head1 MACRO MAGIC
…		…
3428	loop argument"). The C<EV_A> form is used when this is the sole argument,	4372	loop argument"). The C<EV_A> form is used when this is the sole argument,
3429	C<EV_A_> is used when other arguments are following. Example:	4373	C<EV_A_> is used when other arguments are following. Example:
3430		4374
3431	ev_unref (EV_A);	4375	ev_unref (EV_A);
3432	ev_timer_add (EV_A_ watcher);	4376	ev_timer_add (EV_A_ watcher);
3433	ev_loop (EV_A_ 0);	4377	ev_run (EV_A_ 0);
3434		4378
3435	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4379	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3436	which is often provided by the following macro.	4380	which is often provided by the following macro.
3437		4381
3438	=item C<EV_P>, C<EV_P_>	4382	=item C<EV_P>, C<EV_P_>
…		…
3451	suitable for use with C<EV_A>.	4395	suitable for use with C<EV_A>.
3452		4396
3453	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4397	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3454		4398
3455	Similar to the other two macros, this gives you the value of the default	4399	Similar to the other two macros, this gives you the value of the default
3456	loop, if multiple loops are supported ("ev loop default").	4400	loop, if multiple loops are supported ("ev loop default"). The default loop
		4401	will be initialised if it isn't already initialised.
		4402
		4403	For non-multiplicity builds, these macros do nothing, so you always have
		4404	to initialise the loop somewhere.
3457		4405
3458	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4406	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3459		4407
3460	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4408	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3461	default loop has been initialised (C<UC> == unchecked). Their behaviour	4409	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3478	}	4426	}
3479		4427
3480	ev_check check;	4428	ev_check check;
3481	ev_check_init (&check, check_cb);	4429	ev_check_init (&check, check_cb);
3482	ev_check_start (EV_DEFAULT_ &check);	4430	ev_check_start (EV_DEFAULT_ &check);
3483	ev_loop (EV_DEFAULT_ 0);	4431	ev_run (EV_DEFAULT_ 0);
3484		4432
3485	=head1 EMBEDDING	4433	=head1 EMBEDDING
3486		4434
3487	Libev can (and often is) directly embedded into host	4435	Libev can (and often is) directly embedded into host
3488	applications. Examples of applications that embed it include the Deliantra	4436	applications. Examples of applications that embed it include the Deliantra
…		…
3528	ev_vars.h	4476	ev_vars.h
3529	ev_wrap.h	4477	ev_wrap.h
3530		4478
3531	ev_win32.c required on win32 platforms only	4479	ev_win32.c required on win32 platforms only
3532		4480
3533	ev_select.c only when select backend is enabled (which is enabled by default)	4481	ev_select.c only when select backend is enabled
3534	ev_poll.c only when poll backend is enabled (disabled by default)	4482	ev_poll.c only when poll backend is enabled
3535	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4483	ev_epoll.c only when the epoll backend is enabled
		4484	ev_linuxaio.c only when the linux aio backend is enabled
3536	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4485	ev_kqueue.c only when the kqueue backend is enabled
3537	ev_port.c only when the solaris port backend is enabled (disabled by default)	4486	ev_port.c only when the solaris port backend is enabled
3538		4487
3539	F<ev.c> includes the backend files directly when enabled, so you only need	4488	F<ev.c> includes the backend files directly when enabled, so you only need
3540	to compile this single file.	4489	to compile this single file.
3541		4490
3542	=head3 LIBEVENT COMPATIBILITY API	4491	=head3 LIBEVENT COMPATIBILITY API
…		…
3568	libev.m4	4517	libev.m4
3569		4518
3570	=head2 PREPROCESSOR SYMBOLS/MACROS	4519	=head2 PREPROCESSOR SYMBOLS/MACROS
3571		4520
3572	Libev can be configured via a variety of preprocessor symbols you have to	4521	Libev can be configured via a variety of preprocessor symbols you have to
3573	define before including any of its files. The default in the absence of	4522	define before including (or compiling) any of its files. The default in
3574	autoconf is documented for every option.	4523	the absence of autoconf is documented for every option.
		4524
		4525	Symbols marked with "(h)" do not change the ABI, and can have different
		4526	values when compiling libev vs. including F<ev.h>, so it is permissible
		4527	to redefine them before including F<ev.h> without breaking compatibility
		4528	to a compiled library. All other symbols change the ABI, which means all
		4529	users of libev and the libev code itself must be compiled with compatible
		4530	settings.
3575		4531
3576	=over 4	4532	=over 4
3577		4533
		4534	=item EV_COMPAT3 (h)
		4535
		4536	Backwards compatibility is a major concern for libev. This is why this
		4537	release of libev comes with wrappers for the functions and symbols that
		4538	have been renamed between libev version 3 and 4.
		4539
		4540	You can disable these wrappers (to test compatibility with future
		4541	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4542	sources. This has the additional advantage that you can drop the C<struct>
		4543	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4544	typedef in that case.
		4545
		4546	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4547	and in some even more future version the compatibility code will be
		4548	removed completely.
		4549
3578	=item EV_STANDALONE	4550	=item EV_STANDALONE (h)
3579		4551
3580	Must always be C<1> if you do not use autoconf configuration, which	4552	Must always be C<1> if you do not use autoconf configuration, which
3581	keeps libev from including F<config.h>, and it also defines dummy	4553	keeps libev from including F<config.h>, and it also defines dummy
3582	implementations for some libevent functions (such as logging, which is not	4554	implementations for some libevent functions (such as logging, which is not
3583	supported). It will also not define any of the structs usually found in	4555	supported). It will also not define any of the structs usually found in
3584	F<event.h> that are not directly supported by the libev core alone.	4556	F<event.h> that are not directly supported by the libev core alone.
3585		4557
3586	In stanbdalone mode, libev will still try to automatically deduce the	4558	In standalone mode, libev will still try to automatically deduce the
3587	configuration, but has to be more conservative.	4559	configuration, but has to be more conservative.
		4560
		4561	=item EV_USE_FLOOR
		4562
		4563	If defined to be C<1>, libev will use the C<floor ()> function for its
		4564	periodic reschedule calculations, otherwise libev will fall back on a
		4565	portable (slower) implementation. If you enable this, you usually have to
		4566	link against libm or something equivalent. Enabling this when the C<floor>
		4567	function is not available will fail, so the safe default is to not enable
		4568	this.
3588		4569
3589	=item EV_USE_MONOTONIC	4570	=item EV_USE_MONOTONIC
3590		4571
3591	If defined to be C<1>, libev will try to detect the availability of the	4572	If defined to be C<1>, libev will try to detect the availability of the
3592	monotonic clock option at both compile time and runtime. Otherwise no	4573	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3656	be used is the winsock select). This means that it will call	4637	be used is the winsock select). This means that it will call
3657	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4638	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3658	it is assumed that all these functions actually work on fds, even	4639	it is assumed that all these functions actually work on fds, even
3659	on win32. Should not be defined on non-win32 platforms.	4640	on win32. Should not be defined on non-win32 platforms.
3660		4641
3661	=item EV_FD_TO_WIN32_HANDLE	4642	=item EV_FD_TO_WIN32_HANDLE(fd)
3662		4643
3663	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4644	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3664	file descriptors to socket handles. When not defining this symbol (the	4645	file descriptors to socket handles. When not defining this symbol (the
3665	default), then libev will call C<_get_osfhandle>, which is usually	4646	default), then libev will call C<_get_osfhandle>, which is usually
3666	correct. In some cases, programs use their own file descriptor management,	4647	correct. In some cases, programs use their own file descriptor management,
3667	in which case they can provide this function to map fds to socket handles.	4648	in which case they can provide this function to map fds to socket handles.
3668		4649
		4650	=item EV_WIN32_HANDLE_TO_FD(handle)
		4651
		4652	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4653	using the standard C<_open_osfhandle> function. For programs implementing
		4654	their own fd to handle mapping, overwriting this function makes it easier
		4655	to do so. This can be done by defining this macro to an appropriate value.
		4656
		4657	=item EV_WIN32_CLOSE_FD(fd)
		4658
		4659	If programs implement their own fd to handle mapping on win32, then this
		4660	macro can be used to override the C<close> function, useful to unregister
		4661	file descriptors again. Note that the replacement function has to close
		4662	the underlying OS handle.
		4663
		4664	=item EV_USE_WSASOCKET
		4665
		4666	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4667	communication socket, which works better in some environments. Otherwise,
		4668	the normal C<socket> function will be used, which works better in other
		4669	environments.
		4670
3669	=item EV_USE_POLL	4671	=item EV_USE_POLL
3670		4672
3671	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4673	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3672	backend. Otherwise it will be enabled on non-win32 platforms. It	4674	backend. Otherwise it will be enabled on non-win32 platforms. It
3673	takes precedence over select.	4675	takes precedence over select.
…		…
3677	If defined to be C<1>, libev will compile in support for the Linux	4679	If defined to be C<1>, libev will compile in support for the Linux
3678	C<epoll>(7) backend. Its availability will be detected at runtime,	4680	C<epoll>(7) backend. Its availability will be detected at runtime,
3679	otherwise another method will be used as fallback. This is the preferred	4681	otherwise another method will be used as fallback. This is the preferred
3680	backend for GNU/Linux systems. If undefined, it will be enabled if the	4682	backend for GNU/Linux systems. If undefined, it will be enabled if the
3681	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4683	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4684
		4685	=item EV_USE_LINUXAIO
		4686
		4687	If defined to be C<1>, libev will compile in support for the Linux
		4688	aio backend. Due to it's currenbt limitations it has to be requested
		4689	explicitly. If undefined, it will be enabled on linux, otherwise
		4690	disabled.
3682		4691
3683	=item EV_USE_KQUEUE	4692	=item EV_USE_KQUEUE
3684		4693
3685	If defined to be C<1>, libev will compile in support for the BSD style	4694	If defined to be C<1>, libev will compile in support for the BSD style
3686	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4695	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3708	If defined to be C<1>, libev will compile in support for the Linux inotify	4717	If defined to be C<1>, libev will compile in support for the Linux inotify
3709	interface to speed up C<ev_stat> watchers. Its actual availability will	4718	interface to speed up C<ev_stat> watchers. Its actual availability will
3710	be detected at runtime. If undefined, it will be enabled if the headers	4719	be detected at runtime. If undefined, it will be enabled if the headers
3711	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4720	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3712		4721
		4722	=item EV_NO_SMP
		4723
		4724	If defined to be C<1>, libev will assume that memory is always coherent
		4725	between threads, that is, threads can be used, but threads never run on
		4726	different cpus (or different cpu cores). This reduces dependencies
		4727	and makes libev faster.
		4728
		4729	=item EV_NO_THREADS
		4730
		4731	If defined to be C<1>, libev will assume that it will never be called from
		4732	different threads (that includes signal handlers), which is a stronger
		4733	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4734	libev faster.
		4735
3713	=item EV_ATOMIC_T	4736	=item EV_ATOMIC_T
3714		4737
3715	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4738	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3716	access is atomic with respect to other threads or signal contexts. No such	4739	access is atomic with respect to other threads or signal contexts. No
3717	type is easily found in the C language, so you can provide your own type	4740	such type is easily found in the C language, so you can provide your own
3718	that you know is safe for your purposes. It is used both for signal handler "locking"	4741	type that you know is safe for your purposes. It is used both for signal
3719	as well as for signal and thread safety in C<ev_async> watchers.	4742	handler "locking" as well as for signal and thread safety in C<ev_async>
		4743	watchers.
3720		4744
3721	In the absence of this define, libev will use C<sig_atomic_t volatile>	4745	In the absence of this define, libev will use C<sig_atomic_t volatile>
3722	(from F<signal.h>), which is usually good enough on most platforms.	4746	(from F<signal.h>), which is usually good enough on most platforms.
3723		4747
3724	=item EV_H	4748	=item EV_H (h)
3725		4749
3726	The name of the F<ev.h> header file used to include it. The default if	4750	The name of the F<ev.h> header file used to include it. The default if
3727	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4751	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3728	used to virtually rename the F<ev.h> header file in case of conflicts.	4752	used to virtually rename the F<ev.h> header file in case of conflicts.
3729		4753
3730	=item EV_CONFIG_H	4754	=item EV_CONFIG_H (h)
3731		4755
3732	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4756	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3733	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4757	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3734	C<EV_H>, above.	4758	C<EV_H>, above.
3735		4759
3736	=item EV_EVENT_H	4760	=item EV_EVENT_H (h)
3737		4761
3738	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4762	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3739	of how the F<event.h> header can be found, the default is C<"event.h">.	4763	of how the F<event.h> header can be found, the default is C<"event.h">.
3740		4764
3741	=item EV_PROTOTYPES	4765	=item EV_PROTOTYPES (h)
3742		4766
3743	If defined to be C<0>, then F<ev.h> will not define any function	4767	If defined to be C<0>, then F<ev.h> will not define any function
3744	prototypes, but still define all the structs and other symbols. This is	4768	prototypes, but still define all the structs and other symbols. This is
3745	occasionally useful if you want to provide your own wrapper functions	4769	occasionally useful if you want to provide your own wrapper functions
3746	around libev functions.	4770	around libev functions.
…		…
3751	will have the C<struct ev_loop *> as first argument, and you can create	4775	will have the C<struct ev_loop *> as first argument, and you can create
3752	additional independent event loops. Otherwise there will be no support	4776	additional independent event loops. Otherwise there will be no support
3753	for multiple event loops and there is no first event loop pointer	4777	for multiple event loops and there is no first event loop pointer
3754	argument. Instead, all functions act on the single default loop.	4778	argument. Instead, all functions act on the single default loop.
3755		4779
		4780	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4781	default loop when multiplicity is switched off - you always have to
		4782	initialise the loop manually in this case.
		4783
3756	=item EV_MINPRI	4784	=item EV_MINPRI
3757		4785
3758	=item EV_MAXPRI	4786	=item EV_MAXPRI
3759		4787
3760	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4788	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3768	fine.	4796	fine.
3769		4797
3770	If your embedding application does not need any priorities, defining these	4798	If your embedding application does not need any priorities, defining these
3771	both to C<0> will save some memory and CPU.	4799	both to C<0> will save some memory and CPU.
3772		4800
3773	=item EV_PERIODIC_ENABLE	4801	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4802	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4803	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3774		4804
3775	If undefined or defined to be C<1>, then periodic timers are supported. If	4805	If undefined or defined to be C<1> (and the platform supports it), then
3776	defined to be C<0>, then they are not. Disabling them saves a few kB of	4806	the respective watcher type is supported. If defined to be C<0>, then it
3777	code.	4807	is not. Disabling watcher types mainly saves code size.
3778		4808
3779	=item EV_IDLE_ENABLE	4809	=item EV_FEATURES
3780
3781	If undefined or defined to be C<1>, then idle watchers are supported. If
3782	defined to be C<0>, then they are not. Disabling them saves a few kB of
3783	code.
3784
3785	=item EV_EMBED_ENABLE
3786
3787	If undefined or defined to be C<1>, then embed watchers are supported. If
3788	defined to be C<0>, then they are not. Embed watchers rely on most other
3789	watcher types, which therefore must not be disabled.
3790
3791	=item EV_STAT_ENABLE
3792
3793	If undefined or defined to be C<1>, then stat watchers are supported. If
3794	defined to be C<0>, then they are not.
3795
3796	=item EV_FORK_ENABLE
3797
3798	If undefined or defined to be C<1>, then fork watchers are supported. If
3799	defined to be C<0>, then they are not.
3800
3801	=item EV_ASYNC_ENABLE
3802
3803	If undefined or defined to be C<1>, then async watchers are supported. If
3804	defined to be C<0>, then they are not.
3805
3806	=item EV_MINIMAL
3807		4810
3808	If you need to shave off some kilobytes of code at the expense of some	4811	If you need to shave off some kilobytes of code at the expense of some
3809	speed (but with the full API), define this symbol to C<1>. Currently this	4812	speed (but with the full API), you can define this symbol to request
3810	is used to override some inlining decisions, saves roughly 30% code size	4813	certain subsets of functionality. The default is to enable all features
3811	on amd64. It also selects a much smaller 2-heap for timer management over	4814	that can be enabled on the platform.
3812	the default 4-heap.
3813		4815
3814	You can save even more by disabling watcher types you do not need	4816	A typical way to use this symbol is to define it to C<0> (or to a bitset
3815	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4817	with some broad features you want) and then selectively re-enable
3816	(C<-DNDEBUG>) will usually reduce code size a lot.	4818	additional parts you want, for example if you want everything minimal,
		4819	but multiple event loop support, async and child watchers and the poll
		4820	backend, use this:
3817		4821
3818	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4822	#define EV_FEATURES 0
3819	provide a bare-bones event library. See C<ev.h> for details on what parts	4823	#define EV_MULTIPLICITY 1
3820	of the API are still available, and do not complain if this subset changes	4824	#define EV_USE_POLL 1
3821	over time.	4825	#define EV_CHILD_ENABLE 1
		4826	#define EV_ASYNC_ENABLE 1
		4827
		4828	The actual value is a bitset, it can be a combination of the following
		4829	values (by default, all of these are enabled):
		4830
		4831	=over 4
		4832
		4833	=item C<1> - faster/larger code
		4834
		4835	Use larger code to speed up some operations.
		4836
		4837	Currently this is used to override some inlining decisions (enlarging the
		4838	code size by roughly 30% on amd64).
		4839
		4840	When optimising for size, use of compiler flags such as C<-Os> with
		4841	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4842	assertions.
		4843
		4844	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4845	(e.g. gcc with C<-Os>).
		4846
		4847	=item C<2> - faster/larger data structures
		4848
		4849	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4850	hash table sizes and so on. This will usually further increase code size
		4851	and can additionally have an effect on the size of data structures at
		4852	runtime.
		4853
		4854	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4855	(e.g. gcc with C<-Os>).
		4856
		4857	=item C<4> - full API configuration
		4858
		4859	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4860	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4861
		4862	=item C<8> - full API
		4863
		4864	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4865	details on which parts of the API are still available without this
		4866	feature, and do not complain if this subset changes over time.
		4867
		4868	=item C<16> - enable all optional watcher types
		4869
		4870	Enables all optional watcher types. If you want to selectively enable
		4871	only some watcher types other than I/O and timers (e.g. prepare,
		4872	embed, async, child...) you can enable them manually by defining
		4873	C<EV_watchertype_ENABLE> to C<1> instead.
		4874
		4875	=item C<32> - enable all backends
		4876
		4877	This enables all backends - without this feature, you need to enable at
		4878	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4879
		4880	=item C<64> - enable OS-specific "helper" APIs
		4881
		4882	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4883	default.
		4884
		4885	=back
		4886
		4887	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4888	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4889	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4890	watchers, timers and monotonic clock support.
		4891
		4892	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4893	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4894	your program might be left out as well - a binary starting a timer and an
		4895	I/O watcher then might come out at only 5Kb.
		4896
		4897	=item EV_API_STATIC
		4898
		4899	If this symbol is defined (by default it is not), then all identifiers
		4900	will have static linkage. This means that libev will not export any
		4901	identifiers, and you cannot link against libev anymore. This can be useful
		4902	when you embed libev, only want to use libev functions in a single file,
		4903	and do not want its identifiers to be visible.
		4904
		4905	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4906	wants to use libev.
		4907
		4908	This option only works when libev is compiled with a C compiler, as C++
		4909	doesn't support the required declaration syntax.
		4910
		4911	=item EV_AVOID_STDIO
		4912
		4913	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4914	functions (printf, scanf, perror etc.). This will increase the code size
		4915	somewhat, but if your program doesn't otherwise depend on stdio and your
		4916	libc allows it, this avoids linking in the stdio library which is quite
		4917	big.
		4918
		4919	Note that error messages might become less precise when this option is
		4920	enabled.
3822		4921
3823	=item EV_NSIG	4922	=item EV_NSIG
3824		4923
3825	The highest supported signal number, +1 (or, the number of	4924	The highest supported signal number, +1 (or, the number of
3826	signals): Normally, libev tries to deduce the maximum number of signals	4925	signals): Normally, libev tries to deduce the maximum number of signals
3827	automatically, but sometimes this fails, in which case it can be	4926	automatically, but sometimes this fails, in which case it can be
3828	specified. Also, using a lower number than detected (C<32> should be	4927	specified. Also, using a lower number than detected (C<32> should be
3829	good for about any system in existance) can save some memory, as libev	4928	good for about any system in existence) can save some memory, as libev
3830	statically allocates some 12-24 bytes per signal number.	4929	statically allocates some 12-24 bytes per signal number.
3831		4930
3832	=item EV_PID_HASHSIZE	4931	=item EV_PID_HASHSIZE
3833		4932
3834	C<ev_child> watchers use a small hash table to distribute workload by	4933	C<ev_child> watchers use a small hash table to distribute workload by
3835	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4934	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3836	than enough. If you need to manage thousands of children you might want to	4935	usually more than enough. If you need to manage thousands of children you
3837	increase this value (I<must> be a power of two).	4936	might want to increase this value (I<must> be a power of two).
3838		4937
3839	=item EV_INOTIFY_HASHSIZE	4938	=item EV_INOTIFY_HASHSIZE
3840		4939
3841	C<ev_stat> watchers use a small hash table to distribute workload by	4940	C<ev_stat> watchers use a small hash table to distribute workload by
3842	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4941	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3843	usually more than enough. If you need to manage thousands of C<ev_stat>	4942	disabled), usually more than enough. If you need to manage thousands of
3844	watchers you might want to increase this value (I<must> be a power of	4943	C<ev_stat> watchers you might want to increase this value (I<must> be a
3845	two).	4944	power of two).
3846		4945
3847	=item EV_USE_4HEAP	4946	=item EV_USE_4HEAP
3848		4947
3849	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4948	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3850	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4949	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3851	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4950	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3852	faster performance with many (thousands) of watchers.	4951	faster performance with many (thousands) of watchers.
3853		4952
3854	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4953	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3855	(disabled).	4954	will be C<0>.
3856		4955
3857	=item EV_HEAP_CACHE_AT	4956	=item EV_HEAP_CACHE_AT
3858		4957
3859	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4958	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3860	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4959	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3861	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4960	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3862	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4961	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3863	but avoids random read accesses on heap changes. This improves performance	4962	but avoids random read accesses on heap changes. This improves performance
3864	noticeably with many (hundreds) of watchers.	4963	noticeably with many (hundreds) of watchers.
3865		4964
3866	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4965	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3867	(disabled).	4966	will be C<0>.
3868		4967
3869	=item EV_VERIFY	4968	=item EV_VERIFY
3870		4969
3871	Controls how much internal verification (see C<ev_loop_verify ()>) will	4970	Controls how much internal verification (see C<ev_verify ()>) will
3872	be done: If set to C<0>, no internal verification code will be compiled	4971	be done: If set to C<0>, no internal verification code will be compiled
3873	in. If set to C<1>, then verification code will be compiled in, but not	4972	in. If set to C<1>, then verification code will be compiled in, but not
3874	called. If set to C<2>, then the internal verification code will be	4973	called. If set to C<2>, then the internal verification code will be
3875	called once per loop, which can slow down libev. If set to C<3>, then the	4974	called once per loop, which can slow down libev. If set to C<3>, then the
3876	verification code will be called very frequently, which will slow down	4975	verification code will be called very frequently, which will slow down
3877	libev considerably.	4976	libev considerably.
3878		4977
3879	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4978	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3880	C<0>.	4979	will be C<0>.
3881		4980
3882	=item EV_COMMON	4981	=item EV_COMMON
3883		4982
3884	By default, all watchers have a C<void *data> member. By redefining	4983	By default, all watchers have a C<void *data> member. By redefining
3885	this macro to a something else you can include more and other types of	4984	this macro to something else you can include more and other types of
3886	members. You have to define it each time you include one of the files,	4985	members. You have to define it each time you include one of the files,
3887	though, and it must be identical each time.	4986	though, and it must be identical each time.
3888		4987
3889	For example, the perl EV module uses something like this:	4988	For example, the perl EV module uses something like this:
3890		4989
…		…
3943	file.	5042	file.
3944		5043
3945	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5044	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3946	that everybody includes and which overrides some configure choices:	5045	that everybody includes and which overrides some configure choices:
3947		5046
3948	#define EV_MINIMAL 1	5047	#define EV_FEATURES 8
3949	#define EV_USE_POLL 0	5048	#define EV_USE_SELECT 1
3950	#define EV_MULTIPLICITY 0
3951	#define EV_PERIODIC_ENABLE 0	5049	#define EV_PREPARE_ENABLE 1
		5050	#define EV_IDLE_ENABLE 1
3952	#define EV_STAT_ENABLE 0	5051	#define EV_SIGNAL_ENABLE 1
3953	#define EV_FORK_ENABLE 0	5052	#define EV_CHILD_ENABLE 1
		5053	#define EV_USE_STDEXCEPT 0
3954	#define EV_CONFIG_H <config.h>	5054	#define EV_CONFIG_H <config.h>
3955	#define EV_MINPRI 0
3956	#define EV_MAXPRI 0
3957		5055
3958	#include "ev++.h"	5056	#include "ev++.h"
3959		5057
3960	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5058	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3961		5059
3962	#include "ev_cpp.h"	5060	#include "ev_cpp.h"
3963	#include "ev.c"	5061	#include "ev.c"
3964		5062
3965	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5063	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3966		5064
3967	=head2 THREADS AND COROUTINES	5065	=head2 THREADS AND COROUTINES
3968		5066
3969	=head3 THREADS	5067	=head3 THREADS
3970		5068
…		…
4021	default loop and triggering an C<ev_async> watcher from the default loop	5119	default loop and triggering an C<ev_async> watcher from the default loop
4022	watcher callback into the event loop interested in the signal.	5120	watcher callback into the event loop interested in the signal.
4023		5121
4024	=back	5122	=back
4025		5123
4026	=head4 THREAD LOCKING EXAMPLE	5124	See also L</THREAD LOCKING EXAMPLE>.
4027
4028	Here is a fictitious example of how to run an event loop in a different
4029	thread than where callbacks are being invoked and watchers are
4030	created/added/removed.
4031
4032	For a real-world example, see the C<EV::Loop::Async> perl module,
4033	which uses exactly this technique (which is suited for many high-level
4034	languages).
4035
4036	The example uses a pthread mutex to protect the loop data, a condition
4037	variable to wait for callback invocations, an async watcher to notify the
4038	event loop thread and an unspecified mechanism to wake up the main thread.
4039
4040	First, you need to associate some data with the event loop:
4041
4042	typedef struct {
4043	mutex_t lock; /* global loop lock */
4044	ev_async async_w;
4045	thread_t tid;
4046	cond_t invoke_cv;
4047	} userdata;
4048
4049	void prepare_loop (EV_P)
4050	{
4051	// for simplicity, we use a static userdata struct.
4052	static userdata u;
4053
4054	ev_async_init (&u->async_w, async_cb);
4055	ev_async_start (EV_A_ &u->async_w);
4056
4057	pthread_mutex_init (&u->lock, 0);
4058	pthread_cond_init (&u->invoke_cv, 0);
4059
4060	// now associate this with the loop
4061	ev_set_userdata (EV_A_ u);
4062	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4063	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4064
4065	// then create the thread running ev_loop
4066	pthread_create (&u->tid, 0, l_run, EV_A);
4067	}
4068
4069	The callback for the C<ev_async> watcher does nothing: the watcher is used
4070	solely to wake up the event loop so it takes notice of any new watchers
4071	that might have been added:
4072
4073	static void
4074	async_cb (EV_P_ ev_async *w, int revents)
4075	{
4076	// just used for the side effects
4077	}
4078
4079	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4080	protecting the loop data, respectively.
4081
4082	static void
4083	l_release (EV_P)
4084	{
4085	userdata *u = ev_userdata (EV_A);
4086	pthread_mutex_unlock (&u->lock);
4087	}
4088
4089	static void
4090	l_acquire (EV_P)
4091	{
4092	userdata *u = ev_userdata (EV_A);
4093	pthread_mutex_lock (&u->lock);
4094	}
4095
4096	The event loop thread first acquires the mutex, and then jumps straight
4097	into C<ev_loop>:
4098
4099	void *
4100	l_run (void *thr_arg)
4101	{
4102	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4103
4104	l_acquire (EV_A);
4105	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4106	ev_loop (EV_A_ 0);
4107	l_release (EV_A);
4108
4109	return 0;
4110	}
4111
4112	Instead of invoking all pending watchers, the C<l_invoke> callback will
4113	signal the main thread via some unspecified mechanism (signals? pipe
4114	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4115	have been called (in a while loop because a) spurious wakeups are possible
4116	and b) skipping inter-thread-communication when there are no pending
4117	watchers is very beneficial):
4118
4119	static void
4120	l_invoke (EV_P)
4121	{
4122	userdata *u = ev_userdata (EV_A);
4123
4124	while (ev_pending_count (EV_A))
4125	{
4126	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4127	pthread_cond_wait (&u->invoke_cv, &u->lock);
4128	}
4129	}
4130
4131	Now, whenever the main thread gets told to invoke pending watchers, it
4132	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4133	thread to continue:
4134
4135	static void
4136	real_invoke_pending (EV_P)
4137	{
4138	userdata *u = ev_userdata (EV_A);
4139
4140	pthread_mutex_lock (&u->lock);
4141	ev_invoke_pending (EV_A);
4142	pthread_cond_signal (&u->invoke_cv);
4143	pthread_mutex_unlock (&u->lock);
4144	}
4145
4146	Whenever you want to start/stop a watcher or do other modifications to an
4147	event loop, you will now have to lock:
4148
4149	ev_timer timeout_watcher;
4150	userdata *u = ev_userdata (EV_A);
4151
4152	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4153
4154	pthread_mutex_lock (&u->lock);
4155	ev_timer_start (EV_A_ &timeout_watcher);
4156	ev_async_send (EV_A_ &u->async_w);
4157	pthread_mutex_unlock (&u->lock);
4158
4159	Note that sending the C<ev_async> watcher is required because otherwise
4160	an event loop currently blocking in the kernel will have no knowledge
4161	about the newly added timer. By waking up the loop it will pick up any new
4162	watchers in the next event loop iteration.
4163		5125
4164	=head3 COROUTINES	5126	=head3 COROUTINES
4165		5127
4166	Libev is very accommodating to coroutines ("cooperative threads"):	5128	Libev is very accommodating to coroutines ("cooperative threads"):
4167	libev fully supports nesting calls to its functions from different	5129	libev fully supports nesting calls to its functions from different
4168	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5130	coroutines (e.g. you can call C<ev_run> on the same loop from two
4169	different coroutines, and switch freely between both coroutines running	5131	different coroutines, and switch freely between both coroutines running
4170	the loop, as long as you don't confuse yourself). The only exception is	5132	the loop, as long as you don't confuse yourself). The only exception is
4171	that you must not do this from C<ev_periodic> reschedule callbacks.	5133	that you must not do this from C<ev_periodic> reschedule callbacks.
4172		5134
4173	Care has been taken to ensure that libev does not keep local state inside	5135	Care has been taken to ensure that libev does not keep local state inside
4174	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5136	C<ev_run>, and other calls do not usually allow for coroutine switches as
4175	they do not call any callbacks.	5137	they do not call any callbacks.
4176		5138
4177	=head2 COMPILER WARNINGS	5139	=head2 COMPILER WARNINGS
4178		5140
4179	Depending on your compiler and compiler settings, you might get no or a	5141	Depending on your compiler and compiler settings, you might get no or a
…		…
4190	maintainable.	5152	maintainable.
4191		5153
4192	And of course, some compiler warnings are just plain stupid, or simply	5154	And of course, some compiler warnings are just plain stupid, or simply
4193	wrong (because they don't actually warn about the condition their message	5155	wrong (because they don't actually warn about the condition their message
4194	seems to warn about). For example, certain older gcc versions had some	5156	seems to warn about). For example, certain older gcc versions had some
4195	warnings that resulted an extreme number of false positives. These have	5157	warnings that resulted in an extreme number of false positives. These have
4196	been fixed, but some people still insist on making code warn-free with	5158	been fixed, but some people still insist on making code warn-free with
4197	such buggy versions.	5159	such buggy versions.
4198		5160
4199	While libev is written to generate as few warnings as possible,	5161	While libev is written to generate as few warnings as possible,
4200	"warn-free" code is not a goal, and it is recommended not to build libev	5162	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4236	I suggest using suppression lists.	5198	I suggest using suppression lists.
4237		5199
4238		5200
4239	=head1 PORTABILITY NOTES	5201	=head1 PORTABILITY NOTES
4240		5202
		5203	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5204
		5205	GNU/Linux is the only common platform that supports 64 bit file/large file
		5206	interfaces but I<disables> them by default.
		5207
		5208	That means that libev compiled in the default environment doesn't support
		5209	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5210
		5211	Unfortunately, many programs try to work around this GNU/Linux issue
		5212	by enabling the large file API, which makes them incompatible with the
		5213	standard libev compiled for their system.
		5214
		5215	Likewise, libev cannot enable the large file API itself as this would
		5216	suddenly make it incompatible to the default compile time environment,
		5217	i.e. all programs not using special compile switches.
		5218
		5219	=head2 OS/X AND DARWIN BUGS
		5220
		5221	The whole thing is a bug if you ask me - basically any system interface
		5222	you touch is broken, whether it is locales, poll, kqueue or even the
		5223	OpenGL drivers.
		5224
		5225	=head3 C<kqueue> is buggy
		5226
		5227	The kqueue syscall is broken in all known versions - most versions support
		5228	only sockets, many support pipes.
		5229
		5230	Libev tries to work around this by not using C<kqueue> by default on this
		5231	rotten platform, but of course you can still ask for it when creating a
		5232	loop - embedding a socket-only kqueue loop into a select-based one is
		5233	probably going to work well.
		5234
		5235	=head3 C<poll> is buggy
		5236
		5237	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5238	implementation by something calling C<kqueue> internally around the 10.5.6
		5239	release, so now C<kqueue> I<and> C<poll> are broken.
		5240
		5241	Libev tries to work around this by not using C<poll> by default on
		5242	this rotten platform, but of course you can still ask for it when creating
		5243	a loop.
		5244
		5245	=head3 C<select> is buggy
		5246
		5247	All that's left is C<select>, and of course Apple found a way to fuck this
		5248	one up as well: On OS/X, C<select> actively limits the number of file
		5249	descriptors you can pass in to 1024 - your program suddenly crashes when
		5250	you use more.
		5251
		5252	There is an undocumented "workaround" for this - defining
		5253	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5254	work on OS/X.
		5255
		5256	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5257
		5258	=head3 C<errno> reentrancy
		5259
		5260	The default compile environment on Solaris is unfortunately so
		5261	thread-unsafe that you can't even use components/libraries compiled
		5262	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5263	defined by default. A valid, if stupid, implementation choice.
		5264
		5265	If you want to use libev in threaded environments you have to make sure
		5266	it's compiled with C<_REENTRANT> defined.
		5267
		5268	=head3 Event port backend
		5269
		5270	The scalable event interface for Solaris is called "event
		5271	ports". Unfortunately, this mechanism is very buggy in all major
		5272	releases. If you run into high CPU usage, your program freezes or you get
		5273	a large number of spurious wakeups, make sure you have all the relevant
		5274	and latest kernel patches applied. No, I don't know which ones, but there
		5275	are multiple ones to apply, and afterwards, event ports actually work
		5276	great.
		5277
		5278	If you can't get it to work, you can try running the program by setting
		5279	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5280	C<select> backends.
		5281
		5282	=head2 AIX POLL BUG
		5283
		5284	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5285	this by trying to avoid the poll backend altogether (i.e. it's not even
		5286	compiled in), which normally isn't a big problem as C<select> works fine
		5287	with large bitsets on AIX, and AIX is dead anyway.
		5288
4241	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5289	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5290
		5291	=head3 General issues
4242		5292
4243	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5293	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4244	requires, and its I/O model is fundamentally incompatible with the POSIX	5294	requires, and its I/O model is fundamentally incompatible with the POSIX
4245	model. Libev still offers limited functionality on this platform in	5295	model. Libev still offers limited functionality on this platform in
4246	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5296	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4247	descriptors. This only applies when using Win32 natively, not when using	5297	descriptors. This only applies when using Win32 natively, not when using
4248	e.g. cygwin.	5298	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5299	as every compiler comes with a slightly differently broken/incompatible
		5300	environment.
4249		5301
4250	Lifting these limitations would basically require the full	5302	Lifting these limitations would basically require the full
4251	re-implementation of the I/O system. If you are into these kinds of	5303	re-implementation of the I/O system. If you are into this kind of thing,
4252	things, then note that glib does exactly that for you in a very portable	5304	then note that glib does exactly that for you in a very portable way (note
4253	way (note also that glib is the slowest event library known to man).	5305	also that glib is the slowest event library known to man).
4254		5306
4255	There is no supported compilation method available on windows except	5307	There is no supported compilation method available on windows except
4256	embedding it into other applications.	5308	embedding it into other applications.
4257		5309
4258	Sensible signal handling is officially unsupported by Microsoft - libev	5310	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4286	you do I<not> compile the F<ev.c> or any other embedded source files!):	5338	you do I<not> compile the F<ev.c> or any other embedded source files!):
4287		5339
4288	#include "evwrap.h"	5340	#include "evwrap.h"
4289	#include "ev.c"	5341	#include "ev.c"
4290		5342
4291	=over 4
4292
4293	=item The winsocket select function	5343	=head3 The winsocket C<select> function
4294		5344
4295	The winsocket C<select> function doesn't follow POSIX in that it	5345	The winsocket C<select> function doesn't follow POSIX in that it
4296	requires socket I<handles> and not socket I<file descriptors> (it is	5346	requires socket I<handles> and not socket I<file descriptors> (it is
4297	also extremely buggy). This makes select very inefficient, and also	5347	also extremely buggy). This makes select very inefficient, and also
4298	requires a mapping from file descriptors to socket handles (the Microsoft	5348	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4307	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5357	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4308		5358
4309	Note that winsockets handling of fd sets is O(n), so you can easily get a	5359	Note that winsockets handling of fd sets is O(n), so you can easily get a
4310	complexity in the O(n²) range when using win32.	5360	complexity in the O(n²) range when using win32.
4311		5361
4312	=item Limited number of file descriptors	5362	=head3 Limited number of file descriptors
4313		5363
4314	Windows has numerous arbitrary (and low) limits on things.	5364	Windows has numerous arbitrary (and low) limits on things.
4315		5365
4316	Early versions of winsocket's select only supported waiting for a maximum	5366	Early versions of winsocket's select only supported waiting for a maximum
4317	of C<64> handles (probably owning to the fact that all windows kernels	5367	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4332	runtime libraries. This might get you to about C<512> or C<2048> sockets	5382	runtime libraries. This might get you to about C<512> or C<2048> sockets
4333	(depending on windows version and/or the phase of the moon). To get more,	5383	(depending on windows version and/or the phase of the moon). To get more,
4334	you need to wrap all I/O functions and provide your own fd management, but	5384	you need to wrap all I/O functions and provide your own fd management, but
4335	the cost of calling select (O(n²)) will likely make this unworkable.	5385	the cost of calling select (O(n²)) will likely make this unworkable.
4336		5386
4337	=back
4338
4339	=head2 PORTABILITY REQUIREMENTS	5387	=head2 PORTABILITY REQUIREMENTS
4340		5388
4341	In addition to a working ISO-C implementation and of course the	5389	In addition to a working ISO-C implementation and of course the
4342	backend-specific APIs, libev relies on a few additional extensions:	5390	backend-specific APIs, libev relies on a few additional extensions:
4343		5391
…		…
4349	Libev assumes not only that all watcher pointers have the same internal	5397	Libev assumes not only that all watcher pointers have the same internal
4350	structure (guaranteed by POSIX but not by ISO C for example), but it also	5398	structure (guaranteed by POSIX but not by ISO C for example), but it also
4351	assumes that the same (machine) code can be used to call any watcher	5399	assumes that the same (machine) code can be used to call any watcher
4352	callback: The watcher callbacks have different type signatures, but libev	5400	callback: The watcher callbacks have different type signatures, but libev
4353	calls them using an C<ev_watcher *> internally.	5401	calls them using an C<ev_watcher *> internally.
		5402
		5403	=item null pointers and integer zero are represented by 0 bytes
		5404
		5405	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5406	relies on this setting pointers and integers to null.
		5407
		5408	=item pointer accesses must be thread-atomic
		5409
		5410	Accessing a pointer value must be atomic, it must both be readable and
		5411	writable in one piece - this is the case on all current architectures.
4354		5412
4355	=item C<sig_atomic_t volatile> must be thread-atomic as well	5413	=item C<sig_atomic_t volatile> must be thread-atomic as well
4356		5414
4357	The type C<sig_atomic_t volatile> (or whatever is defined as	5415	The type C<sig_atomic_t volatile> (or whatever is defined as
4358	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5416	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4367	thread" or will block signals process-wide, both behaviours would	5425	thread" or will block signals process-wide, both behaviours would
4368	be compatible with libev. Interaction between C<sigprocmask> and	5426	be compatible with libev. Interaction between C<sigprocmask> and
4369	C<pthread_sigmask> could complicate things, however.	5427	C<pthread_sigmask> could complicate things, however.
4370		5428
4371	The most portable way to handle signals is to block signals in all threads	5429	The most portable way to handle signals is to block signals in all threads
4372	except the initial one, and run the default loop in the initial thread as	5430	except the initial one, and run the signal handling loop in the initial
4373	well.	5431	thread as well.
4374		5432
4375	=item C<long> must be large enough for common memory allocation sizes	5433	=item C<long> must be large enough for common memory allocation sizes
4376		5434
4377	To improve portability and simplify its API, libev uses C<long> internally	5435	To improve portability and simplify its API, libev uses C<long> internally
4378	instead of C<size_t> when allocating its data structures. On non-POSIX	5436	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4381	watchers.	5439	watchers.
4382		5440
4383	=item C<double> must hold a time value in seconds with enough accuracy	5441	=item C<double> must hold a time value in seconds with enough accuracy
4384		5442
4385	The type C<double> is used to represent timestamps. It is required to	5443	The type C<double> is used to represent timestamps. It is required to
4386	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5444	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4387	enough for at least into the year 4000. This requirement is fulfilled by	5445	good enough for at least into the year 4000 with millisecond accuracy
		5446	(the design goal for libev). This requirement is overfulfilled by
4388	implementations implementing IEEE 754, which is basically all existing	5447	implementations using IEEE 754, which is basically all existing ones.
		5448
4389	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5449	With IEEE 754 doubles, you get microsecond accuracy until at least the
4390	2200.	5450	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5451	is either obsolete or somebody patched it to use C<long double> or
		5452	something like that, just kidding).
4391		5453
4392	=back	5454	=back
4393		5455
4394	If you know of other additional requirements drop me a note.	5456	If you know of other additional requirements drop me a note.
4395		5457
…		…
4457	=item Processing ev_async_send: O(number_of_async_watchers)	5519	=item Processing ev_async_send: O(number_of_async_watchers)
4458		5520
4459	=item Processing signals: O(max_signal_number)	5521	=item Processing signals: O(max_signal_number)
4460		5522
4461	Sending involves a system call I<iff> there were no other C<ev_async_send>	5523	Sending involves a system call I<iff> there were no other C<ev_async_send>
4462	calls in the current loop iteration. Checking for async and signal events	5524	calls in the current loop iteration and the loop is currently
		5525	blocked. Checking for async and signal events involves iterating over all
4463	involves iterating over all running async watchers or all signal numbers.	5526	running async watchers or all signal numbers.
4464		5527
4465	=back	5528	=back
4466		5529
4467		5530
		5531	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5532
		5533	The major version 4 introduced some incompatible changes to the API.
		5534
		5535	At the moment, the C<ev.h> header file provides compatibility definitions
		5536	for all changes, so most programs should still compile. The compatibility
		5537	layer might be removed in later versions of libev, so better update to the
		5538	new API early than late.
		5539
		5540	=over 4
		5541
		5542	=item C<EV_COMPAT3> backwards compatibility mechanism
		5543
		5544	The backward compatibility mechanism can be controlled by
		5545	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5546	section.
		5547
		5548	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5549
		5550	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5551
		5552	ev_loop_destroy (EV_DEFAULT_UC);
		5553	ev_loop_fork (EV_DEFAULT);
		5554
		5555	=item function/symbol renames
		5556
		5557	A number of functions and symbols have been renamed:
		5558
		5559	ev_loop => ev_run
		5560	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5561	EVLOOP_ONESHOT => EVRUN_ONCE
		5562
		5563	ev_unloop => ev_break
		5564	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5565	EVUNLOOP_ONE => EVBREAK_ONE
		5566	EVUNLOOP_ALL => EVBREAK_ALL
		5567
		5568	EV_TIMEOUT => EV_TIMER
		5569
		5570	ev_loop_count => ev_iteration
		5571	ev_loop_depth => ev_depth
		5572	ev_loop_verify => ev_verify
		5573
		5574	Most functions working on C<struct ev_loop> objects don't have an
		5575	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5576	associated constants have been renamed to not collide with the C<struct
		5577	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5578	as all other watcher types. Note that C<ev_loop_fork> is still called
		5579	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5580	typedef.
		5581
		5582	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5583
		5584	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5585	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5586	and work, but the library code will of course be larger.
		5587
		5588	=back
		5589
		5590
4468	=head1 GLOSSARY	5591	=head1 GLOSSARY
4469		5592
4470	=over 4	5593	=over 4
4471		5594
4472	=item active	5595	=item active
4473		5596
4474	A watcher is active as long as it has been started (has been attached to	5597	A watcher is active as long as it has been started and not yet stopped.
4475	an event loop) but not yet stopped (disassociated from the event loop).	5598	See L</WATCHER STATES> for details.
4476		5599
4477	=item application	5600	=item application
4478		5601
4479	In this document, an application is whatever is using libev.	5602	In this document, an application is whatever is using libev.
		5603
		5604	=item backend
		5605
		5606	The part of the code dealing with the operating system interfaces.
4480		5607
4481	=item callback	5608	=item callback
4482		5609
4483	The address of a function that is called when some event has been	5610	The address of a function that is called when some event has been
4484	detected. Callbacks are being passed the event loop, the watcher that	5611	detected. Callbacks are being passed the event loop, the watcher that
4485	received the event, and the actual event bitset.	5612	received the event, and the actual event bitset.
4486		5613
4487	=item callback invocation	5614	=item callback/watcher invocation
4488		5615
4489	The act of calling the callback associated with a watcher.	5616	The act of calling the callback associated with a watcher.
4490		5617
4491	=item event	5618	=item event
4492		5619
4493	A change of state of some external event, such as data now being available	5620	A change of state of some external event, such as data now being available
4494	for reading on a file descriptor, time having passed or simply not having	5621	for reading on a file descriptor, time having passed or simply not having
4495	any other events happening anymore.	5622	any other events happening anymore.
4496		5623
4497	In libev, events are represented as single bits (such as C<EV_READ> or	5624	In libev, events are represented as single bits (such as C<EV_READ> or
4498	C<EV_TIMEOUT>).	5625	C<EV_TIMER>).
4499		5626
4500	=item event library	5627	=item event library
4501		5628
4502	A software package implementing an event model and loop.	5629	A software package implementing an event model and loop.
4503		5630
…		…
4511	The model used to describe how an event loop handles and processes	5638	The model used to describe how an event loop handles and processes
4512	watchers and events.	5639	watchers and events.
4513		5640
4514	=item pending	5641	=item pending
4515		5642
4516	A watcher is pending as soon as the corresponding event has been detected,	5643	A watcher is pending as soon as the corresponding event has been
4517	and stops being pending as soon as the watcher will be invoked or its	5644	detected. See L</WATCHER STATES> for details.
4518	pending status is explicitly cleared by the application.
4519
4520	A watcher can be pending, but not active. Stopping a watcher also clears
4521	its pending status.
4522		5645
4523	=item real time	5646	=item real time
4524		5647
4525	The physical time that is observed. It is apparently strictly monotonic :)	5648	The physical time that is observed. It is apparently strictly monotonic :)
4526		5649
4527	=item wall-clock time	5650	=item wall-clock time
4528		5651
4529	The time and date as shown on clocks. Unlike real time, it can actually	5652	The time and date as shown on clocks. Unlike real time, it can actually
4530	be wrong and jump forwards and backwards, e.g. when the you adjust your	5653	be wrong and jump forwards and backwards, e.g. when you adjust your
4531	clock.	5654	clock.
4532		5655
4533	=item watcher	5656	=item watcher
4534		5657
4535	A data structure that describes interest in certain events. Watchers need	5658	A data structure that describes interest in certain events. Watchers need
4536	to be started (attached to an event loop) before they can receive events.	5659	to be started (attached to an event loop) before they can receive events.
4537		5660
4538	=item watcher invocation
4539
4540	The act of calling the callback associated with a watcher.
4541
4542	=back	5661	=back
4543		5662
4544	=head1 AUTHOR	5663	=head1 AUTHOR
4545		5664
4546	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5665	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5666	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4547		5667

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