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Revision 1.289 by root, Tue Mar 16 17:11:49 2010 UTC vs.
Revision 1.469 by root, Sat Jun 3 08:53:03 2023 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>), Linux eventfd/signalfd (for faster and cleaner	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	timers (C<ev_timer>), absolute timers with customised rescheduling	115	timers (C<ev_timer>), absolute timers with customised rescheduling
106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	change events (C<ev_child>), and event watchers dealing with the event	117	change events (C<ev_child>), and event watchers dealing with the event
108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and	118	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
…		…
124	this argument.	134	this argument.
125		135
126	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
127		137
128	Libev represents time as a single floating point number, representing	138	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (somewhere	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	140	somewhere near the beginning of 1970, details are complicated, don't
131	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
132	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
133	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
134	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
135	throughout libev.	146	time differences (e.g. delays) throughout libev.
136		147
137	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
138		149
139	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	151	and internal errors (bugs).
…		…
148	When libev detects a usage error such as a negative timer interval, then	159	When libev detects a usage error such as a negative timer interval, then
149	it will print a diagnostic message and abort (via the C<assert> mechanism,	160	it will print a diagnostic message and abort (via the C<assert> mechanism,
150	so C<NDEBUG> will disable this checking): these are programming errors in	161	so C<NDEBUG> will disable this checking): these are programming errors in
151	the libev caller and need to be fixed there.	162	the libev caller and need to be fixed there.
152		163
		164	Via the C<EV_FREQUENT> macro you can compile in and/or enable extensive
		165	consistency checking code inside libev that can be used to check for
		166	internal inconsistencies, suually caused by application bugs.
		167
153	Libev also has a few internal error-checking C<assert>ions, and also has	168	Libev also has a few internal error-checking C<assert>ions. These do not
154	extensive consistency checking code. These do not trigger under normal
155	circumstances, as they indicate either a bug in libev or worse.	169	trigger under normal circumstances, as they indicate either a bug in libev
		170	or worse.
156		171
157		172
158	=head1 GLOBAL FUNCTIONS	173	=head1 GLOBAL FUNCTIONS
159		174
160	These functions can be called anytime, even before initialising the	175	These functions can be called anytime, even before initialising the
…		…
164		179
165	=item ev_tstamp ev_time ()	180	=item ev_tstamp ev_time ()
166		181
167	Returns the current time as libev would use it. Please note that the	182	Returns the current time as libev would use it. Please note that the
168	C<ev_now> function is usually faster and also often returns the timestamp	183	C<ev_now> function is usually faster and also often returns the timestamp
169	you actually want to know.	184	you actually want to know. Also interesting is the combination of
		185	C<ev_now_update> and C<ev_now>.
170		186
171	=item ev_sleep (ev_tstamp interval)	187	=item ev_sleep (ev_tstamp interval)
172		188
173	Sleep for the given interval: The current thread will be blocked until	189	Sleep for the given interval: The current thread will be blocked
174	either it is interrupted or the given time interval has passed. Basically	190	until either it is interrupted or the given time interval has
		191	passed (approximately - it might return a bit earlier even if not
		192	interrupted). Returns immediately if C<< interval <= 0 >>.
		193
175	this is a sub-second-resolution C<sleep ()>.	194	Basically this is a sub-second-resolution C<sleep ()>.
		195
		196	The range of the C<interval> is limited - libev only guarantees to work
		197	with sleep times of up to one day (C<< interval <= 86400 >>).
176		198
177	=item int ev_version_major ()	199	=item int ev_version_major ()
178		200
179	=item int ev_version_minor ()	201	=item int ev_version_minor ()
180		202
…		…
191	as this indicates an incompatible change. Minor versions are usually	213	as this indicates an incompatible change. Minor versions are usually
192	compatible to older versions, so a larger minor version alone is usually	214	compatible to older versions, so a larger minor version alone is usually
193	not a problem.	215	not a problem.
194		216
195	Example: Make sure we haven't accidentally been linked against the wrong	217	Example: Make sure we haven't accidentally been linked against the wrong
196	version.	218	version (note, however, that this will not detect other ABI mismatches,
		219	such as LFS or reentrancy).
197		220
198	assert (("libev version mismatch",	221	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	222	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	223	&& ev_version_minor () >= EV_VERSION_MINOR));
201		224
…		…
212	assert (("sorry, no epoll, no sex",	235	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	236	ev_supported_backends () & EVBACKEND_EPOLL));
214		237
215	=item unsigned int ev_recommended_backends ()	238	=item unsigned int ev_recommended_backends ()
216		239
217	Return the set of all backends compiled into this binary of libev and also	240	Return the set of all backends compiled into this binary of libev and
218	recommended for this platform. This set is often smaller than the one	241	also recommended for this platform, meaning it will work for most file
		242	descriptor types. This set is often smaller than the one returned by
219	returned by C<ev_supported_backends>, as for example kqueue is broken on	243	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
220	most BSDs and will not be auto-detected unless you explicitly request it	244	and will not be auto-detected unless you explicitly request it (assuming
221	(assuming you know what you are doing). This is the set of backends that	245	you know what you are doing). This is the set of backends that libev will
222	libev will probe for if you specify no backends explicitly.	246	probe for if you specify no backends explicitly.
223		247
224	=item unsigned int ev_embeddable_backends ()	248	=item unsigned int ev_embeddable_backends ()
225		249
226	Returns the set of backends that are embeddable in other event loops. This	250	Returns the set of backends that are embeddable in other event loops. This
227	is the theoretical, all-platform, value. To find which backends	251	value is platform-specific but can include backends not available on the
228	might be supported on the current system, you would need to look at	252	current system. To find which embeddable backends might be supported on
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	253	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	254	& ev_supported_backends ()>, likewise for recommended ones.
231		255
232	See the description of C<ev_embed> watchers for more info.	256	See the description of C<ev_embed> watchers for more info.
233		257
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	258	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
235		259
236	Sets the allocation function to use (the prototype is similar - the	260	Sets the allocation function to use (the prototype is similar - the
237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	261	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
238	used to allocate and free memory (no surprises here). If it returns zero	262	used to allocate and free memory (no surprises here). If it returns zero
239	when memory needs to be allocated (C<size != 0>), the library might abort	263	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
245		269
246	You could override this function in high-availability programs to, say,	270	You could override this function in high-availability programs to, say,
247	free some memory if it cannot allocate memory, to use a special allocator,	271	free some memory if it cannot allocate memory, to use a special allocator,
248	or even to sleep a while and retry until some memory is available.	272	or even to sleep a while and retry until some memory is available.
249		273
		274	Example: The following is the C<realloc> function that libev itself uses
		275	which should work with C<realloc> and C<free> functions of all kinds and
		276	is probably a good basis for your own implementation.
		277
		278	static void *
		279	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		280	{
		281	if (size)
		282	return realloc (ptr, size);
		283
		284	free (ptr);
		285	return 0;
		286	}
		287
250	Example: Replace the libev allocator with one that waits a bit and then	288	Example: Replace the libev allocator with one that waits a bit and then
251	retries (example requires a standards-compliant C<realloc>).	289	retries.
252		290
253	static void *	291	static void *
254	persistent_realloc (void *ptr, size_t size)	292	persistent_realloc (void *ptr, size_t size)
255	{	293	{
		294	if (!size)
		295	{
		296	free (ptr);
		297	return 0;
		298	}
		299
256	for (;;)	300	for (;;)
257	{	301	{
258	void *newptr = realloc (ptr, size);	302	void *newptr = realloc (ptr, size);
259		303
260	if (newptr)	304	if (newptr)
…		…
265	}	309	}
266		310
267	...	311	...
268	ev_set_allocator (persistent_realloc);	312	ev_set_allocator (persistent_realloc);
269		313
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	314	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
271		315
272	Set the callback function to call on a retryable system call error (such	316	Set the callback function to call on a retryable system call error (such
273	as failed select, poll, epoll_wait). The message is a printable string	317	as failed select, poll, epoll_wait). The message is a printable string
274	indicating the system call or subsystem causing the problem. If this	318	indicating the system call or subsystem causing the problem. If this
275	callback is set, then libev will expect it to remedy the situation, no	319	callback is set, then libev will expect it to remedy the situation, no
…		…
287	}	331	}
288		332
289	...	333	...
290	ev_set_syserr_cb (fatal_error);	334	ev_set_syserr_cb (fatal_error);
291		335
		336	=item ev_feed_signal (int signum)
		337
		338	This function can be used to "simulate" a signal receive. It is completely
		339	safe to call this function at any time, from any context, including signal
		340	handlers or random threads.
		341
		342	Its main use is to customise signal handling in your process, especially
		343	in the presence of threads. For example, you could block signals
		344	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		345	creating any loops), and in one thread, use C<sigwait> or any other
		346	mechanism to wait for signals, then "deliver" them to libev by calling
		347	C<ev_feed_signal>.
		348
292	=back	349	=back
293		350
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	351	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		352
296	An event loop is described by a C<struct ev_loop *> (the C<struct>	353	An event loop is described by a C<struct ev_loop *> (the C<struct> is
297	is I<not> optional in this case, as there is also an C<ev_loop>	354	I<not> optional in this case unless libev 3 compatibility is disabled, as
298	I<function>).	355	libev 3 had an C<ev_loop> function colliding with the struct name).
299		356
300	The library knows two types of such loops, the I<default> loop, which	357	The library knows two types of such loops, the I<default> loop, which
301	supports signals and child events, and dynamically created loops which do	358	supports child process events, and dynamically created event loops which
302	not.	359	do not.
303		360
304	=over 4	361	=over 4
305		362
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	363	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		364
308	This will initialise the default event loop if it hasn't been initialised	365	This returns the "default" event loop object, which is what you should
309	yet and return it. If the default loop could not be initialised, returns	366	normally use when you just need "the event loop". Event loop objects and
310	false. If it already was initialised it simply returns it (and ignores the	367	the C<flags> parameter are described in more detail in the entry for
311	flags. If that is troubling you, check C<ev_backend ()> afterwards).	368	C<ev_loop_new>.
		369
		370	If the default loop is already initialised then this function simply
		371	returns it (and ignores the flags. If that is troubling you, check
		372	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		373	flags, which should almost always be C<0>, unless the caller is also the
		374	one calling C<ev_run> or otherwise qualifies as "the main program".
312		375
313	If you don't know what event loop to use, use the one returned from this	376	If you don't know what event loop to use, use the one returned from this
314	function.	377	function (or via the C<EV_DEFAULT> macro).
315		378
316	Note that this function is I<not> thread-safe, so if you want to use it	379	Note that this function is I<not> thread-safe, so if you want to use it
317	from multiple threads, you have to lock (note also that this is unlikely,	380	from multiple threads, you have to employ some kind of mutex (note also
318	as loops cannot be shared easily between threads anyway).	381	that this case is unlikely, as loops cannot be shared easily between
		382	threads anyway).
319		383
320	The default loop is the only loop that can handle C<ev_signal> and	384	The default loop is the only loop that can handle C<ev_child> watchers,
321	C<ev_child> watchers, and to do this, it always registers a handler	385	and to do this, it always registers a handler for C<SIGCHLD>. If this is
322	for C<SIGCHLD>. If this is a problem for your application you can either	386	a problem for your application you can either create a dynamic loop with
323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	387	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	388	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	C<ev_default_init>.	389
		390	Example: This is the most typical usage.
		391
		392	if (!ev_default_loop (0))
		393	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		394
		395	Example: Restrict libev to the select and poll backends, and do not allow
		396	environment settings to be taken into account:
		397
		398	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		399
		400	=item struct ev_loop *ev_loop_new (unsigned int flags)
		401
		402	This will create and initialise a new event loop object. If the loop
		403	could not be initialised, returns false.
		404
		405	This function is thread-safe, and one common way to use libev with
		406	threads is indeed to create one loop per thread, and using the default
		407	loop in the "main" or "initial" thread.
326		408
327	The flags argument can be used to specify special behaviour or specific	409	The flags argument can be used to specify special behaviour or specific
328	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	410	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
329		411
330	The following flags are supported:	412	The following flags are supported:
…		…
340		422
341	If this flag bit is or'ed into the flag value (or the program runs setuid	423	If this flag bit is or'ed into the flag value (or the program runs setuid
342	or setgid) then libev will I<not> look at the environment variable	424	or setgid) then libev will I<not> look at the environment variable
343	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	425	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
344	override the flags completely if it is found in the environment. This is	426	override the flags completely if it is found in the environment. This is
345	useful to try out specific backends to test their performance, or to work	427	useful to try out specific backends to test their performance, to work
346	around bugs.	428	around bugs, or to make libev threadsafe (accessing environment variables
		429	cannot be done in a threadsafe way, but usually it works if no other
		430	thread modifies them).
347		431
348	=item C<EVFLAG_FORKCHECK>	432	=item C<EVFLAG_FORKCHECK>
349		433
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	434	Instead of calling C<ev_loop_fork> manually after a fork, you can also
351	a fork, you can also make libev check for a fork in each iteration by	435	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		436
354	This works by calling C<getpid ()> on every iteration of the loop,	437	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	438	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	439	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	440	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
358	without a system call and thus I<very> fast, but my GNU/Linux system also has	441	sequence without a system call and thus I<very> fast, but my GNU/Linux
359	C<pthread_atfork> which is even faster).	442	system also has C<pthread_atfork> which is even faster). (Update: glibc
		443	versions 2.25 apparently removed the C<getpid> optimisation again).
360		444
361	The big advantage of this flag is that you can forget about fork (and	445	The big advantage of this flag is that you can forget about fork (and
362	forget about forgetting to tell libev about forking) when you use this	446	forget about forgetting to tell libev about forking, although you still
363	flag.	447	have to ignore C<SIGPIPE>) when you use this flag.
364		448
365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	449	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
366	environment variable.	450	environment variable.
367		451
368	=item C<EVFLAG_NOINOTIFY>	452	=item C<EVFLAG_NOINOTIFY>
369		453
370	When this flag is specified, then libev will not attempt to use the	454	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	455	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	456	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	457	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		458
375	=item C<EVFLAG_SIGNALFD>	459	=item C<EVFLAG_SIGNALFD>
376		460
377	When this flag is specified, then libev will attempt to use the	461	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	462	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	463	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	464	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	465	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	466	threads that are not interested in handling them.
383		467
384	Signalfd will not be used by default as this changes your signal mask, and	468	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	469	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	470	example) that can't properly initialise their signal masks.
		471
		472	=item C<EVFLAG_NOSIGMASK>
		473
		474	When this flag is specified, then libev will avoid to modify the signal
		475	mask. Specifically, this means you have to make sure signals are unblocked
		476	when you want to receive them.
		477
		478	This behaviour is useful when you want to do your own signal handling, or
		479	want to handle signals only in specific threads and want to avoid libev
		480	unblocking the signals.
		481
		482	It's also required by POSIX in a threaded program, as libev calls
		483	C<sigprocmask>, whose behaviour is officially unspecified.
		484
		485	=item C<EVFLAG_NOTIMERFD>
		486
		487	When this flag is specified, the libev will avoid using a C<timerfd> to
		488	detect time jumps. It will still be able to detect time jumps, but takes
		489	longer and has a lower accuracy in doing so, but saves a file descriptor
		490	per loop.
		491
		492	The current implementation only tries to use a C<timerfd> when the first
		493	C<ev_periodic> watcher is started and falls back on other methods if it
		494	cannot be created, but this behaviour might change in the future.
387		495
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	496	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		497
390	This is your standard select(2) backend. Not I<completely> standard, as	498	This is your standard select(2) backend. Not I<completely> standard, as
391	libev tries to roll its own fd_set with no limits on the number of fds,	499	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
416	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	524	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
417	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	525	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
418		526
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	527	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		528
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	529	Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	530	kernels).
423		531
424	For few fds, this backend is a bit little slower than poll and select,	532	For few fds, this backend is a bit little slower than poll and select, but
425	but it scales phenomenally better. While poll and select usually scale	533	it scales phenomenally better. While poll and select usually scale like
426	like O(total_fds) where n is the total number of fds (or the highest fd),	534	O(total_fds) where total_fds is the total number of fds (or the highest
427	epoll scales either O(1) or O(active_fds).	535	fd), epoll scales either O(1) or O(active_fds).
428		536
429	The epoll mechanism deserves honorable mention as the most misdesigned	537	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	538	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	539	dropping file descriptors, requiring a system call per change per file
432	descriptor (and unnecessary guessing of parameters), problems with dup and	540	descriptor (and unnecessary guessing of parameters), problems with dup,
		541	returning before the timeout value, resulting in additional iterations
		542	(and only giving 5ms accuracy while select on the same platform gives
433	so on. The biggest issue is fork races, however - if a program forks then	543	0.1ms) and so on. The biggest issue is fork races, however - if a program
434	I<both> parent and child process have to recreate the epoll set, which can	544	forks then I<both> parent and child process have to recreate the epoll
435	take considerable time (one syscall per file descriptor) and is of course	545	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	546	and is of course hard to detect.
437		547
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	548	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	of course I<doesn't>, and epoll just loves to report events for totally	549	but of course I<doesn't>, and epoll just loves to report events for
440	I<different> file descriptors (even already closed ones, so one cannot	550	totally I<different> file descriptors (even already closed ones, so
441	even remove them from the set) than registered in the set (especially	551	one cannot even remove them from the set) than registered in the set
442	on SMP systems). Libev tries to counter these spurious notifications by	552	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	553	notifications by employing an additional generation counter and comparing
444	events to filter out spurious ones, recreating the set when required.	554	that against the events to filter out spurious ones, recreating the set
		555	when required. Epoll also erroneously rounds down timeouts, but gives you
		556	no way to know when and by how much, so sometimes you have to busy-wait
		557	because epoll returns immediately despite a nonzero timeout. And last
		558	not least, it also refuses to work with some file descriptors which work
		559	perfectly fine with C<select> (files, many character devices...).
		560
		561	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		562	cobbled together in a hurry, no thought to design or interaction with
		563	others. Oh, the pain, will it ever stop...
445		564
446	While stopping, setting and starting an I/O watcher in the same iteration	565	While stopping, setting and starting an I/O watcher in the same iteration
447	will result in some caching, there is still a system call per such	566	will result in some caching, there is still a system call per such
448	incident (because the same I<file descriptor> could point to a different	567	incident (because the same I<file descriptor> could point to a different
449	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	568	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
461	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or	580	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
462	faster than epoll for maybe up to a hundred file descriptors, depending on	581	faster than epoll for maybe up to a hundred file descriptors, depending on
463	the usage. So sad.	582	the usage. So sad.
464		583
465	While nominally embeddable in other event loops, this feature is broken in	584	While nominally embeddable in other event loops, this feature is broken in
466	all kernel versions tested so far.	585	a lot of kernel revisions, but probably(!) works in current versions.
467		586
468	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	587	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
469	C<EVBACKEND_POLL>.	588	C<EVBACKEND_POLL>.
470		589
		590	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		591
		592	Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<<
		593	io_submit(2) >>) event interface available in post-4.18 kernels (but libev
		594	only tries to use it in 4.19+).
		595
		596	This is another Linux train wreck of an event interface.
		597
		598	If this backend works for you (as of this writing, it was very
		599	experimental), it is the best event interface available on Linux and might
		600	be well worth enabling it - if it isn't available in your kernel this will
		601	be detected and this backend will be skipped.
		602
		603	This backend can batch oneshot requests and supports a user-space ring
		604	buffer to receive events. It also doesn't suffer from most of the design
		605	problems of epoll (such as not being able to remove event sources from
		606	the epoll set), and generally sounds too good to be true. Because, this
		607	being the Linux kernel, of course it suffers from a whole new set of
		608	limitations, forcing you to fall back to epoll, inheriting all its design
		609	issues.
		610
		611	For one, it is not easily embeddable (but probably could be done using
		612	an event fd at some extra overhead). It also is subject to a system wide
		613	limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO
		614	requests are left, this backend will be skipped during initialisation, and
		615	will switch to epoll when the loop is active.
		616
		617	Most problematic in practice, however, is that not all file descriptors
		618	work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds,
		619	files, F</dev/null> and many others are supported, but ttys do not work
		620	properly (a known bug that the kernel developers don't care about, see
		621	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		622	(yet?) a generic event polling interface.
		623
		624	Overall, it seems the Linux developers just don't want it to have a
		625	generic event handling mechanism other than C<select> or C<poll>.
		626
		627	To work around all these problem, the current version of libev uses its
		628	epoll backend as a fallback for file descriptor types that do not work. Or
		629	falls back completely to epoll if the kernel acts up.
		630
		631	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		632	C<EVBACKEND_POLL>.
		633
471	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	634	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
472		635
473	Kqueue deserves special mention, as at the time of this writing, it	636	Kqueue deserves special mention, as at the time this backend was
474	was broken on all BSDs except NetBSD (usually it doesn't work reliably	637	implemented, it was broken on all BSDs except NetBSD (usually it doesn't
475	with anything but sockets and pipes, except on Darwin, where of course	638	work reliably with anything but sockets and pipes, except on Darwin,
476	it's completely useless). Unlike epoll, however, whose brokenness	639	where of course it's completely useless). Unlike epoll, however, whose
477	is by design, these kqueue bugs can (and eventually will) be fixed	640	brokenness is by design, these kqueue bugs can be (and mostly have been)
478	without API changes to existing programs. For this reason it's not being	641	fixed without API changes to existing programs. For this reason it's not
479	"auto-detected" unless you explicitly specify it in the flags (i.e. using	642	being "auto-detected" on all platforms unless you explicitly specify it
480	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	643	in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a
481	system like NetBSD.	644	known-to-be-good (-enough) system like NetBSD.
482		645
483	You still can embed kqueue into a normal poll or select backend and use it	646	You still can embed kqueue into a normal poll or select backend and use it
484	only for sockets (after having made sure that sockets work with kqueue on	647	only for sockets (after having made sure that sockets work with kqueue on
485	the target platform). See C<ev_embed> watchers for more info.	648	the target platform). See C<ev_embed> watchers for more info.
486		649
487	It scales in the same way as the epoll backend, but the interface to the	650	It scales in the same way as the epoll backend, but the interface to the
488	kernel is more efficient (which says nothing about its actual speed, of	651	kernel is more efficient (which says nothing about its actual speed, of
489	course). While stopping, setting and starting an I/O watcher does never	652	course). While stopping, setting and starting an I/O watcher does never
490	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	653	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
491	two event changes per incident. Support for C<fork ()> is very bad (but	654	two event changes per incident. Support for C<fork ()> is very bad (you
492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	655	might have to leak fds on fork, but it's more sane than epoll) and it
493	cases	656	drops fds silently in similarly hard-to-detect cases.
494		657
495	This backend usually performs well under most conditions.	658	This backend usually performs well under most conditions.
496		659
497	While nominally embeddable in other event loops, this doesn't work	660	While nominally embeddable in other event loops, this doesn't work
498	everywhere, so you might need to test for this. And since it is broken	661	everywhere, so you might need to test for this. And since it is broken
…		…
512	and is not embeddable, which would limit the usefulness of this backend	675	and is not embeddable, which would limit the usefulness of this backend
513	immensely.	676	immensely.
514		677
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	678	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		679
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	680	This uses the Solaris 10 event port mechanism. As with everything on
518	it's really slow, but it still scales very well (O(active_fds)).	681	Solaris, it's really slow, but it still scales very well (O(active_fds)).
519
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523		682
524	While this backend scales well, it requires one system call per active	683	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	684	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	685	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	686	might perform better.
528		687
529	On the positive side, with the exception of the spurious readiness	688	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	689	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	690	among the OS-specific backends (I vastly prefer correctness over speed
		691	hacks).
		692
		693	On the negative side, the interface is I<bizarre> - so bizarre that
		694	even sun itself gets it wrong in their code examples: The event polling
		695	function sometimes returns events to the caller even though an error
		696	occurred, but with no indication whether it has done so or not (yes, it's
		697	even documented that way) - deadly for edge-triggered interfaces where you
		698	absolutely have to know whether an event occurred or not because you have
		699	to re-arm the watcher.
		700
		701	Fortunately libev seems to be able to work around these idiocies.
533		702
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	703	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	704	C<EVBACKEND_POLL>.
536		705
537	=item C<EVBACKEND_ALL>	706	=item C<EVBACKEND_ALL>
538		707
539	Try all backends (even potentially broken ones that wouldn't be tried	708	Try all backends (even potentially broken ones that wouldn't be tried
540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	709	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	710	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		711
543	It is definitely not recommended to use this flag.	712	It is definitely not recommended to use this flag, use whatever
		713	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		714	at all.
		715
		716	=item C<EVBACKEND_MASK>
		717
		718	Not a backend at all, but a mask to select all backend bits from a
		719	C<flags> value, in case you want to mask out any backends from a flags
		720	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		721
545	=back	722	=back
546		723
547	If one or more of the backend flags are or'ed into the flags value,	724	If one or more of the backend flags are or'ed into the flags value,
548	then only these backends will be tried (in the reverse order as listed	725	then only these backends will be tried (in the reverse order as listed
549	here). If none are specified, all backends in C<ev_recommended_backends	726	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	727	()> will be tried.
551		728
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop. Unlike the default loop, it cannot
573	handle signal and child watchers, and attempts to do so will be greeted by
574	undefined behaviour (or a failed assertion if assertions are enabled).
575
576	Note that this function I<is> thread-safe, and the recommended way to use
577	libev with threads is indeed to create one loop per thread, and using the
578	default loop in the "main" or "initial" thread.
579
580	Example: Try to create a event loop that uses epoll and nothing else.	729	Example: Try to create a event loop that uses epoll and nothing else.
581		730
582	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	731	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
583	if (!epoller)	732	if (!epoller)
584	fatal ("no epoll found here, maybe it hides under your chair");	733	fatal ("no epoll found here, maybe it hides under your chair");
585		734
		735	Example: Use whatever libev has to offer, but make sure that kqueue is
		736	used if available.
		737
		738	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		739
		740	Example: Similarly, on linux, you mgiht want to take advantage of the
		741	linux aio backend if possible, but fall back to something else if that
		742	isn't available.
		743
		744	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		745
586	=item ev_default_destroy ()	746	=item ev_loop_destroy (loop)
587		747
588	Destroys the default loop again (frees all memory and kernel state	748	Destroys an event loop object (frees all memory and kernel state
589	etc.). None of the active event watchers will be stopped in the normal	749	etc.). None of the active event watchers will be stopped in the normal
590	sense, so e.g. C<ev_is_active> might still return true. It is your	750	sense, so e.g. C<ev_is_active> might still return true. It is your
591	responsibility to either stop all watchers cleanly yourself I<before>	751	responsibility to either stop all watchers cleanly yourself I<before>
592	calling this function, or cope with the fact afterwards (which is usually	752	calling this function, or cope with the fact afterwards (which is usually
593	the easiest thing, you can just ignore the watchers and/or C<free ()> them	753	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
595		755
596	Note that certain global state, such as signal state (and installed signal	756	Note that certain global state, such as signal state (and installed signal
597	handlers), will not be freed by this function, and related watchers (such	757	handlers), will not be freed by this function, and related watchers (such
598	as signal and child watchers) would need to be stopped manually.	758	as signal and child watchers) would need to be stopped manually.
599		759
600	In general it is not advisable to call this function except in the	760	This function is normally used on loop objects allocated by
601	rare occasion where you really need to free e.g. the signal handling	761	C<ev_loop_new>, but it can also be used on the default loop returned by
		762	C<ev_default_loop>, in which case it is not thread-safe.
		763
		764	Note that it is not advisable to call this function on the default loop
		765	except in the rare occasion where you really need to free its resources.
602	pipe fds. If you need dynamically allocated loops it is better to use	766	If you need dynamically allocated loops it is better to use C<ev_loop_new>
603	C<ev_loop_new> and C<ev_loop_destroy>.	767	and C<ev_loop_destroy>.
604		768
605	=item ev_loop_destroy (loop)	769	=item ev_loop_fork (loop)
606		770
607	Like C<ev_default_destroy>, but destroys an event loop created by an
608	earlier call to C<ev_loop_new>.
609
610	=item ev_default_fork ()
611
612	This function sets a flag that causes subsequent C<ev_loop> iterations	771	This function sets a flag that causes subsequent C<ev_run> iterations
613	to reinitialise the kernel state for backends that have one. Despite the	772	to reinitialise the kernel state for backends that have one. Despite
614	name, you can call it anytime, but it makes most sense after forking, in	773	the name, you can call it anytime you are allowed to start or stop
615	the child process (or both child and parent, but that again makes little	774	watchers (except inside an C<ev_prepare> callback), but it makes most
616	sense). You I<must> call it in the child before using any of the libev	775	sense after forking, in the child process. You I<must> call it (or use
617	functions, and it will only take effect at the next C<ev_loop> iteration.	776	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		777
		778	In addition, if you want to reuse a loop (via this function or
		779	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		780
		781	Again, you I<have> to call it on I<any> loop that you want to re-use after
		782	a fork, I<even if you do not plan to use the loop in the parent>. This is
		783	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		784	during fork.
618		785
619	On the other hand, you only need to call this function in the child	786	On the other hand, you only need to call this function in the child
620	process if and only if you want to use the event library in the child. If	787	process if and only if you want to use the event loop in the child. If
621	you just fork+exec, you don't have to call it at all.	788	you just fork+exec or create a new loop in the child, you don't have to
		789	call it at all (in fact, C<epoll> is so badly broken that it makes a
		790	difference, but libev will usually detect this case on its own and do a
		791	costly reset of the backend).
622		792
623	The function itself is quite fast and it's usually not a problem to call	793	The function itself is quite fast and it's usually not a problem to call
624	it just in case after a fork. To make this easy, the function will fit in	794	it just in case after a fork.
625	quite nicely into a call to C<pthread_atfork>:
626		795
		796	Example: Automate calling C<ev_loop_fork> on the default loop when
		797	using pthreads.
		798
		799	static void
		800	post_fork_child (void)
		801	{
		802	ev_loop_fork (EV_DEFAULT);
		803	}
		804
		805	...
627	pthread_atfork (0, 0, ev_default_fork);	806	pthread_atfork (0, 0, post_fork_child);
628
629	=item ev_loop_fork (loop)
630
631	Like C<ev_default_fork>, but acts on an event loop created by
632	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
633	after fork that you want to re-use in the child, and how you do this is
634	entirely your own problem.
635		807
636	=item int ev_is_default_loop (loop)	808	=item int ev_is_default_loop (loop)
637		809
638	Returns true when the given loop is, in fact, the default loop, and false	810	Returns true when the given loop is, in fact, the default loop, and false
639	otherwise.	811	otherwise.
640		812
641	=item unsigned int ev_loop_count (loop)	813	=item unsigned int ev_iteration (loop)
642		814
643	Returns the count of loop iterations for the loop, which is identical to	815	Returns the current iteration count for the event loop, which is identical
644	the number of times libev did poll for new events. It starts at C<0> and	816	to the number of times libev did poll for new events. It starts at C<0>
645	happily wraps around with enough iterations.	817	and happily wraps around with enough iterations.
646		818
647	This value can sometimes be useful as a generation counter of sorts (it	819	This value can sometimes be useful as a generation counter of sorts (it
648	"ticks" the number of loop iterations), as it roughly corresponds with	820	"ticks" the number of loop iterations), as it roughly corresponds with
649	C<ev_prepare> and C<ev_check> calls.	821	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		822	prepare and check phases.
650		823
651	=item unsigned int ev_loop_depth (loop)	824	=item unsigned int ev_depth (loop)
652		825
653	Returns the number of times C<ev_loop> was entered minus the number of	826	Returns the number of times C<ev_run> was entered minus the number of
654	times C<ev_loop> was exited, in other words, the recursion depth.	827	times C<ev_run> was exited normally, in other words, the recursion depth.
655		828
656	Outside C<ev_loop>, this number is zero. In a callback, this number is	829	Outside C<ev_run>, this number is zero. In a callback, this number is
657	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	830	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
658	in which case it is higher.	831	in which case it is higher.
659		832
660	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	833	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
661	etc.), doesn't count as exit.	834	throwing an exception etc.), doesn't count as "exit" - consider this
		835	as a hint to avoid such ungentleman-like behaviour unless it's really
		836	convenient, in which case it is fully supported.
662		837
663	=item unsigned int ev_backend (loop)	838	=item unsigned int ev_backend (loop)
664		839
665	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	840	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
666	use.	841	use.
…		…
675		850
676	=item ev_now_update (loop)	851	=item ev_now_update (loop)
677		852
678	Establishes the current time by querying the kernel, updating the time	853	Establishes the current time by querying the kernel, updating the time
679	returned by C<ev_now ()> in the progress. This is a costly operation and	854	returned by C<ev_now ()> in the progress. This is a costly operation and
680	is usually done automatically within C<ev_loop ()>.	855	is usually done automatically within C<ev_run ()>.
681		856
682	This function is rarely useful, but when some event callback runs for a	857	This function is rarely useful, but when some event callback runs for a
683	very long time without entering the event loop, updating libev's idea of	858	very long time without entering the event loop, updating libev's idea of
684	the current time is a good idea.	859	the current time is a good idea.
685		860
686	See also L<The special problem of time updates> in the C<ev_timer> section.	861	See also L</The special problem of time updates> in the C<ev_timer> section.
687		862
688	=item ev_suspend (loop)	863	=item ev_suspend (loop)
689		864
690	=item ev_resume (loop)	865	=item ev_resume (loop)
691		866
692	These two functions suspend and resume a loop, for use when the loop is	867	These two functions suspend and resume an event loop, for use when the
693	not used for a while and timeouts should not be processed.	868	loop is not used for a while and timeouts should not be processed.
694		869
695	A typical use case would be an interactive program such as a game: When	870	A typical use case would be an interactive program such as a game: When
696	the user presses C<^Z> to suspend the game and resumes it an hour later it	871	the user presses C<^Z> to suspend the game and resumes it an hour later it
697	would be best to handle timeouts as if no time had actually passed while	872	would be best to handle timeouts as if no time had actually passed while
698	the program was suspended. This can be achieved by calling C<ev_suspend>	873	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
700	C<ev_resume> directly afterwards to resume timer processing.	875	C<ev_resume> directly afterwards to resume timer processing.
701		876
702	Effectively, all C<ev_timer> watchers will be delayed by the time spend	877	Effectively, all C<ev_timer> watchers will be delayed by the time spend
703	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	878	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
704	will be rescheduled (that is, they will lose any events that would have	879	will be rescheduled (that is, they will lose any events that would have
705	occured while suspended).	880	occurred while suspended).
706		881
707	After calling C<ev_suspend> you B<must not> call I<any> function on the	882	After calling C<ev_suspend> you B<must not> call I<any> function on the
708	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	883	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
709	without a previous call to C<ev_suspend>.	884	without a previous call to C<ev_suspend>.
710		885
711	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	886	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
712	event loop time (see C<ev_now_update>).	887	event loop time (see C<ev_now_update>).
713		888
714	=item ev_loop (loop, int flags)	889	=item bool ev_run (loop, int flags)
715		890
716	Finally, this is it, the event handler. This function usually is called	891	Finally, this is it, the event handler. This function usually is called
717	after you have initialised all your watchers and you want to start	892	after you have initialised all your watchers and you want to start
718	handling events.	893	handling events. It will ask the operating system for any new events, call
		894	the watcher callbacks, and then repeat the whole process indefinitely: This
		895	is why event loops are called I<loops>.
719		896
720	If the flags argument is specified as C<0>, it will not return until	897	If the flags argument is specified as C<0>, it will keep handling events
721	either no event watchers are active anymore or C<ev_unloop> was called.	898	until either no event watchers are active anymore or C<ev_break> was
		899	called.
722		900
		901	The return value is false if there are no more active watchers (which
		902	usually means "all jobs done" or "deadlock"), and true in all other cases
		903	(which usually means " you should call C<ev_run> again").
		904
723	Please note that an explicit C<ev_unloop> is usually better than	905	Please note that an explicit C<ev_break> is usually better than
724	relying on all watchers to be stopped when deciding when a program has	906	relying on all watchers to be stopped when deciding when a program has
725	finished (especially in interactive programs), but having a program	907	finished (especially in interactive programs), but having a program
726	that automatically loops as long as it has to and no longer by virtue	908	that automatically loops as long as it has to and no longer by virtue
727	of relying on its watchers stopping correctly, that is truly a thing of	909	of relying on its watchers stopping correctly, that is truly a thing of
728	beauty.	910	beauty.
729		911
		912	This function is I<mostly> exception-safe - you can break out of a
		913	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		914	exception and so on. This does not decrement the C<ev_depth> value, nor
		915	will it clear any outstanding C<EVBREAK_ONE> breaks.
		916
730	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	917	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
731	those events and any already outstanding ones, but will not block your	918	those events and any already outstanding ones, but will not wait and
732	process in case there are no events and will return after one iteration of	919	block your process in case there are no events and will return after one
733	the loop.	920	iteration of the loop. This is sometimes useful to poll and handle new
		921	events while doing lengthy calculations, to keep the program responsive.
734		922
735	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	923	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
736	necessary) and will handle those and any already outstanding ones. It	924	necessary) and will handle those and any already outstanding ones. It
737	will block your process until at least one new event arrives (which could	925	will block your process until at least one new event arrives (which could
738	be an event internal to libev itself, so there is no guarantee that a	926	be an event internal to libev itself, so there is no guarantee that a
739	user-registered callback will be called), and will return after one	927	user-registered callback will be called), and will return after one
740	iteration of the loop.	928	iteration of the loop.
741		929
742	This is useful if you are waiting for some external event in conjunction	930	This is useful if you are waiting for some external event in conjunction
743	with something not expressible using other libev watchers (i.e. "roll your	931	with something not expressible using other libev watchers (i.e. "roll your
744	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	932	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
745	usually a better approach for this kind of thing.	933	usually a better approach for this kind of thing.
746		934
747	Here are the gory details of what C<ev_loop> does:	935	Here are the gory details of what C<ev_run> does (this is for your
		936	understanding, not a guarantee that things will work exactly like this in
		937	future versions):
748		938
		939	- Increment loop depth.
		940	- Reset the ev_break status.
749	- Before the first iteration, call any pending watchers.	941	- Before the first iteration, call any pending watchers.
		942	LOOP:
750	* If EVFLAG_FORKCHECK was used, check for a fork.	943	- If EVFLAG_FORKCHECK was used, check for a fork.
751	- If a fork was detected (by any means), queue and call all fork watchers.	944	- If a fork was detected (by any means), queue and call all fork watchers.
752	- Queue and call all prepare watchers.	945	- Queue and call all prepare watchers.
		946	- If ev_break was called, goto FINISH.
753	- If we have been forked, detach and recreate the kernel state	947	- If we have been forked, detach and recreate the kernel state
754	as to not disturb the other process.	948	as to not disturb the other process.
755	- Update the kernel state with all outstanding changes.	949	- Update the kernel state with all outstanding changes.
756	- Update the "event loop time" (ev_now ()).	950	- Update the "event loop time" (ev_now ()).
757	- Calculate for how long to sleep or block, if at all	951	- Calculate for how long to sleep or block, if at all
758	(active idle watchers, EVLOOP_NONBLOCK or not having	952	(active idle watchers, EVRUN_NOWAIT or not having
759	any active watchers at all will result in not sleeping).	953	any active watchers at all will result in not sleeping).
760	- Sleep if the I/O and timer collect interval say so.	954	- Sleep if the I/O and timer collect interval say so.
		955	- Increment loop iteration counter.
761	- Block the process, waiting for any events.	956	- Block the process, waiting for any events.
762	- Queue all outstanding I/O (fd) events.	957	- Queue all outstanding I/O (fd) events.
763	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	958	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
764	- Queue all expired timers.	959	- Queue all expired timers.
765	- Queue all expired periodics.	960	- Queue all expired periodics.
766	- Unless any events are pending now, queue all idle watchers.	961	- Queue all idle watchers with priority higher than that of pending events.
767	- Queue all check watchers.	962	- Queue all check watchers.
768	- Call all queued watchers in reverse order (i.e. check watchers first).	963	- Call all queued watchers in reverse order (i.e. check watchers first).
769	Signals and child watchers are implemented as I/O watchers, and will	964	Signals, async and child watchers are implemented as I/O watchers, and
770	be handled here by queueing them when their watcher gets executed.	965	will be handled here by queueing them when their watcher gets executed.
771	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	966	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
772	were used, or there are no active watchers, return, otherwise	967	were used, or there are no active watchers, goto FINISH, otherwise
773	continue with step *.	968	continue with step LOOP.
		969	FINISH:
		970	- Reset the ev_break status iff it was EVBREAK_ONE.
		971	- Decrement the loop depth.
		972	- Return.
774		973
775	Example: Queue some jobs and then loop until no events are outstanding	974	Example: Queue some jobs and then loop until no events are outstanding
776	anymore.	975	anymore.
777		976
778	... queue jobs here, make sure they register event watchers as long	977	... queue jobs here, make sure they register event watchers as long
779	... as they still have work to do (even an idle watcher will do..)	978	... as they still have work to do (even an idle watcher will do..)
780	ev_loop (my_loop, 0);	979	ev_run (my_loop, 0);
781	... jobs done or somebody called unloop. yeah!	980	... jobs done or somebody called break. yeah!
782		981
783	=item ev_unloop (loop, how)	982	=item ev_break (loop, how)
784		983
785	Can be used to make a call to C<ev_loop> return early (but only after it	984	Can be used to make a call to C<ev_run> return early (but only after it
786	has processed all outstanding events). The C<how> argument must be either	985	has processed all outstanding events). The C<how> argument must be either
787	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	986	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
788	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	987	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
789		988
790	This "unloop state" will be cleared when entering C<ev_loop> again.	989	This "break state" will be cleared on the next call to C<ev_run>.
791		990
792	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	991	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		992	which case it will have no effect.
793		993
794	=item ev_ref (loop)	994	=item ev_ref (loop)
795		995
796	=item ev_unref (loop)	996	=item ev_unref (loop)
797		997
798	Ref/unref can be used to add or remove a reference count on the event	998	Ref/unref can be used to add or remove a reference count on the event
799	loop: Every watcher keeps one reference, and as long as the reference	999	loop: Every watcher keeps one reference, and as long as the reference
800	count is nonzero, C<ev_loop> will not return on its own.	1000	count is nonzero, C<ev_run> will not return on its own.
801		1001
802	This is useful when you have a watcher that you never intend to	1002	This is useful when you have a watcher that you never intend to
803	unregister, but that nevertheless should not keep C<ev_loop> from	1003	unregister, but that nevertheless should not keep C<ev_run> from
804	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	1004	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
805	before stopping it.	1005	before stopping it.
806		1006
807	As an example, libev itself uses this for its internal signal pipe: It	1007	As an example, libev itself uses this for its internal signal pipe: It
808	is not visible to the libev user and should not keep C<ev_loop> from	1008	is not visible to the libev user and should not keep C<ev_run> from
809	exiting if no event watchers registered by it are active. It is also an	1009	exiting if no event watchers registered by it are active. It is also an
810	excellent way to do this for generic recurring timers or from within	1010	excellent way to do this for generic recurring timers or from within
811	third-party libraries. Just remember to I<unref after start> and I<ref	1011	third-party libraries. Just remember to I<unref after start> and I<ref
812	before stop> (but only if the watcher wasn't active before, or was active	1012	before stop> (but only if the watcher wasn't active before, or was active
813	before, respectively. Note also that libev might stop watchers itself	1013	before, respectively. Note also that libev might stop watchers itself
814	(e.g. non-repeating timers) in which case you have to C<ev_ref>	1014	(e.g. non-repeating timers) in which case you have to C<ev_ref>
815	in the callback).	1015	in the callback).
816		1016
817	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	1017	Example: Create a signal watcher, but keep it from keeping C<ev_run>
818	running when nothing else is active.	1018	running when nothing else is active.
819		1019
820	ev_signal exitsig;	1020	ev_signal exitsig;
821	ev_signal_init (&exitsig, sig_cb, SIGINT);	1021	ev_signal_init (&exitsig, sig_cb, SIGINT);
822	ev_signal_start (loop, &exitsig);	1022	ev_signal_start (loop, &exitsig);
823	evf_unref (loop);	1023	ev_unref (loop);
824		1024
825	Example: For some weird reason, unregister the above signal handler again.	1025	Example: For some weird reason, unregister the above signal handler again.
826		1026
827	ev_ref (loop);	1027	ev_ref (loop);
828	ev_signal_stop (loop, &exitsig);	1028	ev_signal_stop (loop, &exitsig);
…		…
848	overhead for the actual polling but can deliver many events at once.	1048	overhead for the actual polling but can deliver many events at once.
849		1049
850	By setting a higher I<io collect interval> you allow libev to spend more	1050	By setting a higher I<io collect interval> you allow libev to spend more
851	time collecting I/O events, so you can handle more events per iteration,	1051	time collecting I/O events, so you can handle more events per iteration,
852	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1052	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
853	C<ev_timer>) will be not affected. Setting this to a non-null value will	1053	C<ev_timer>) will not be affected. Setting this to a non-null value will
854	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1054	introduce an additional C<ev_sleep ()> call into most loop iterations. The
855	sleep time ensures that libev will not poll for I/O events more often then	1055	sleep time ensures that libev will not poll for I/O events more often then
856	once per this interval, on average.	1056	once per this interval, on average (as long as the host time resolution is
		1057	good enough).
857		1058
858	Likewise, by setting a higher I<timeout collect interval> you allow libev	1059	Likewise, by setting a higher I<timeout collect interval> you allow libev
859	to spend more time collecting timeouts, at the expense of increased	1060	to spend more time collecting timeouts, at the expense of increased
860	latency/jitter/inexactness (the watcher callback will be called	1061	latency/jitter/inexactness (the watcher callback will be called
861	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1062	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
867	usually doesn't make much sense to set it to a lower value than C<0.01>,	1068	usually doesn't make much sense to set it to a lower value than C<0.01>,
868	as this approaches the timing granularity of most systems. Note that if	1069	as this approaches the timing granularity of most systems. Note that if
869	you do transactions with the outside world and you can't increase the	1070	you do transactions with the outside world and you can't increase the
870	parallelity, then this setting will limit your transaction rate (if you	1071	parallelity, then this setting will limit your transaction rate (if you
871	need to poll once per transaction and the I/O collect interval is 0.01,	1072	need to poll once per transaction and the I/O collect interval is 0.01,
872	then you can't do more than 100 transations per second).	1073	then you can't do more than 100 transactions per second).
873		1074
874	Setting the I<timeout collect interval> can improve the opportunity for	1075	Setting the I<timeout collect interval> can improve the opportunity for
875	saving power, as the program will "bundle" timer callback invocations that	1076	saving power, as the program will "bundle" timer callback invocations that
876	are "near" in time together, by delaying some, thus reducing the number of	1077	are "near" in time together, by delaying some, thus reducing the number of
877	times the process sleeps and wakes up again. Another useful technique to	1078	times the process sleeps and wakes up again. Another useful technique to
…		…
885	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1086	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
886		1087
887	=item ev_invoke_pending (loop)	1088	=item ev_invoke_pending (loop)
888		1089
889	This call will simply invoke all pending watchers while resetting their	1090	This call will simply invoke all pending watchers while resetting their
890	pending state. Normally, C<ev_loop> does this automatically when required,	1091	pending state. Normally, C<ev_run> does this automatically when required,
891	but when overriding the invoke callback this call comes handy.	1092	but when overriding the invoke callback this call comes handy. This
		1093	function can be invoked from a watcher - this can be useful for example
		1094	when you want to do some lengthy calculation and want to pass further
		1095	event handling to another thread (you still have to make sure only one
		1096	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
892		1097
893	=item int ev_pending_count (loop)	1098	=item int ev_pending_count (loop)
894		1099
895	Returns the number of pending watchers - zero indicates that no watchers	1100	Returns the number of pending watchers - zero indicates that no watchers
896	are pending.	1101	are pending.
897		1102
898	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1103	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
899		1104
900	This overrides the invoke pending functionality of the loop: Instead of	1105	This overrides the invoke pending functionality of the loop: Instead of
901	invoking all pending watchers when there are any, C<ev_loop> will call	1106	invoking all pending watchers when there are any, C<ev_run> will call
902	this callback instead. This is useful, for example, when you want to	1107	this callback instead. This is useful, for example, when you want to
903	invoke the actual watchers inside another context (another thread etc.).	1108	invoke the actual watchers inside another context (another thread etc.).
904		1109
905	If you want to reset the callback, use C<ev_invoke_pending> as new	1110	If you want to reset the callback, use C<ev_invoke_pending> as new
906	callback.	1111	callback.
907		1112
908	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1113	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
909		1114
910	Sometimes you want to share the same loop between multiple threads. This	1115	Sometimes you want to share the same loop between multiple threads. This
911	can be done relatively simply by putting mutex_lock/unlock calls around	1116	can be done relatively simply by putting mutex_lock/unlock calls around
912	each call to a libev function.	1117	each call to a libev function.
913		1118
914	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1119	However, C<ev_run> can run an indefinite time, so it is not feasible
915	wait for it to return. One way around this is to wake up the loop via	1120	to wait for it to return. One way around this is to wake up the event
916	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1121	loop via C<ev_break> and C<ev_async_send>, another way is to set these
917	and I<acquire> callbacks on the loop.	1122	I<release> and I<acquire> callbacks on the loop.
918		1123
919	When set, then C<release> will be called just before the thread is	1124	When set, then C<release> will be called just before the thread is
920	suspended waiting for new events, and C<acquire> is called just	1125	suspended waiting for new events, and C<acquire> is called just
921	afterwards.	1126	afterwards.
922		1127
…		…
925		1130
926	While event loop modifications are allowed between invocations of	1131	While event loop modifications are allowed between invocations of
927	C<release> and C<acquire> (that's their only purpose after all), no	1132	C<release> and C<acquire> (that's their only purpose after all), no
928	modifications done will affect the event loop, i.e. adding watchers will	1133	modifications done will affect the event loop, i.e. adding watchers will
929	have no effect on the set of file descriptors being watched, or the time	1134	have no effect on the set of file descriptors being watched, or the time
930	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1135	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
931	to take note of any changes you made.	1136	to take note of any changes you made.
932		1137
933	In theory, threads executing C<ev_loop> will be async-cancel safe between	1138	In theory, threads executing C<ev_run> will be async-cancel safe between
934	invocations of C<release> and C<acquire>.	1139	invocations of C<release> and C<acquire>.
935		1140
936	See also the locking example in the C<THREADS> section later in this	1141	See also the locking example in the C<THREADS> section later in this
937	document.	1142	document.
938		1143
939	=item ev_set_userdata (loop, void *data)	1144	=item ev_set_userdata (loop, void *data)
940		1145
941	=item ev_userdata (loop)	1146	=item void *ev_userdata (loop)
942		1147
943	Set and retrieve a single C<void *> associated with a loop. When	1148	Set and retrieve a single C<void *> associated with a loop. When
944	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1149	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
945	C<0.>	1150	C<0>.
946		1151
947	These two functions can be used to associate arbitrary data with a loop,	1152	These two functions can be used to associate arbitrary data with a loop,
948	and are intended solely for the C<invoke_pending_cb>, C<release> and	1153	and are intended solely for the C<invoke_pending_cb>, C<release> and
949	C<acquire> callbacks described above, but of course can be (ab-)used for	1154	C<acquire> callbacks described above, but of course can be (ab-)used for
950	any other purpose as well.	1155	any other purpose as well.
951		1156
952	=item ev_loop_verify (loop)	1157	=item ev_verify (loop)
953		1158
954	This function only does something when C<EV_VERIFY> support has been	1159	This function only does something when C<EV_VERIFY> support has been
955	compiled in, which is the default for non-minimal builds. It tries to go	1160	compiled in, which is the default for non-minimal builds. It tries to go
956	through all internal structures and checks them for validity. If anything	1161	through all internal structures and checks them for validity. If anything
957	is found to be inconsistent, it will print an error message to standard	1162	is found to be inconsistent, it will print an error message to standard
…		…
968		1173
969	In the following description, uppercase C<TYPE> in names stands for the	1174	In the following description, uppercase C<TYPE> in names stands for the
970	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1175	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
971	watchers and C<ev_io_start> for I/O watchers.	1176	watchers and C<ev_io_start> for I/O watchers.
972		1177
973	A watcher is a structure that you create and register to record your	1178	A watcher is an opaque structure that you allocate and register to record
974	interest in some event. For instance, if you want to wait for STDIN to	1179	your interest in some event. To make a concrete example, imagine you want
975	become readable, you would create an C<ev_io> watcher for that:	1180	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1181	for that:
976		1182
977	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1183	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
978	{	1184	{
979	ev_io_stop (w);	1185	ev_io_stop (w);
980	ev_unloop (loop, EVUNLOOP_ALL);	1186	ev_break (loop, EVBREAK_ALL);
981	}	1187	}
982		1188
983	struct ev_loop *loop = ev_default_loop (0);	1189	struct ev_loop *loop = ev_default_loop (0);
984		1190
985	ev_io stdin_watcher;	1191	ev_io stdin_watcher;
986		1192
987	ev_init (&stdin_watcher, my_cb);	1193	ev_init (&stdin_watcher, my_cb);
988	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1194	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
989	ev_io_start (loop, &stdin_watcher);	1195	ev_io_start (loop, &stdin_watcher);
990		1196
991	ev_loop (loop, 0);	1197	ev_run (loop, 0);
992		1198
993	As you can see, you are responsible for allocating the memory for your	1199	As you can see, you are responsible for allocating the memory for your
994	watcher structures (and it is I<usually> a bad idea to do this on the	1200	watcher structures (and it is I<usually> a bad idea to do this on the
995	stack).	1201	stack).
996		1202
997	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1203	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
998	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1204	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
999		1205
1000	Each watcher structure must be initialised by a call to C<ev_init	1206	Each watcher structure must be initialised by a call to C<ev_init (watcher
1001	(watcher *, callback)>, which expects a callback to be provided. This	1207	*, callback)>, which expects a callback to be provided. This callback is
1002	callback gets invoked each time the event occurs (or, in the case of I/O	1208	invoked each time the event occurs (or, in the case of I/O watchers, each
1003	watchers, each time the event loop detects that the file descriptor given	1209	time the event loop detects that the file descriptor given is readable
1004	is readable and/or writable).	1210	and/or writable).
1005		1211
1006	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1212	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1007	macro to configure it, with arguments specific to the watcher type. There	1213	macro to configure it, with arguments specific to the watcher type. There
1008	is also a macro to combine initialisation and setting in one call: C<<	1214	is also a macro to combine initialisation and setting in one call: C<<
1009	ev_TYPE_init (watcher *, callback, ...) >>.	1215	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1012	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher	1218	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
1013	*) >>), and you can stop watching for events at any time by calling the	1219	*) >>), and you can stop watching for events at any time by calling the
1014	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.	1220	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
1015		1221
1016	As long as your watcher is active (has been started but not stopped) you	1222	As long as your watcher is active (has been started but not stopped) you
1017	must not touch the values stored in it. Most specifically you must never	1223	must not touch the values stored in it except when explicitly documented
1018	reinitialise it or call its C<ev_TYPE_set> macro.	1224	otherwise. Most specifically you must never reinitialise it or call its
		1225	C<ev_TYPE_set> macro.
1019		1226
1020	Each and every callback receives the event loop pointer as first, the	1227	Each and every callback receives the event loop pointer as first, the
1021	registered watcher structure as second, and a bitset of received events as	1228	registered watcher structure as second, and a bitset of received events as
1022	third argument.	1229	third argument.
1023		1230
…		…
1060		1267
1061	=item C<EV_PREPARE>	1268	=item C<EV_PREPARE>
1062		1269
1063	=item C<EV_CHECK>	1270	=item C<EV_CHECK>
1064		1271
1065	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1272	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1066	to gather new events, and all C<ev_check> watchers are invoked just after	1273	gather new events, and all C<ev_check> watchers are queued (not invoked)
1067	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1274	just after C<ev_run> has gathered them, but before it queues any callbacks
		1275	for any received events. That means C<ev_prepare> watchers are the last
		1276	watchers invoked before the event loop sleeps or polls for new events, and
		1277	C<ev_check> watchers will be invoked before any other watchers of the same
		1278	or lower priority within an event loop iteration.
		1279
1068	received events. Callbacks of both watcher types can start and stop as	1280	Callbacks of both watcher types can start and stop as many watchers as
1069	many watchers as they want, and all of them will be taken into account	1281	they want, and all of them will be taken into account (for example, a
1070	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1282	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1071	C<ev_loop> from blocking).	1283	blocking).
1072		1284
1073	=item C<EV_EMBED>	1285	=item C<EV_EMBED>
1074		1286
1075	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1287	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1076		1288
1077	=item C<EV_FORK>	1289	=item C<EV_FORK>
1078		1290
1079	The event loop has been resumed in the child process after fork (see	1291	The event loop has been resumed in the child process after fork (see
1080	C<ev_fork>).	1292	C<ev_fork>).
		1293
		1294	=item C<EV_CLEANUP>
		1295
		1296	The event loop is about to be destroyed (see C<ev_cleanup>).
1081		1297
1082	=item C<EV_ASYNC>	1298	=item C<EV_ASYNC>
1083		1299
1084	The given async watcher has been asynchronously notified (see C<ev_async>).	1300	The given async watcher has been asynchronously notified (see C<ev_async>).
1085		1301
…		…
1180		1396
1181	=item bool ev_is_active (ev_TYPE *watcher)	1397	=item bool ev_is_active (ev_TYPE *watcher)
1182		1398
1183	Returns a true value iff the watcher is active (i.e. it has been started	1399	Returns a true value iff the watcher is active (i.e. it has been started
1184	and not yet been stopped). As long as a watcher is active you must not modify	1400	and not yet been stopped). As long as a watcher is active you must not modify
1185	it.	1401	it unless documented otherwise.
		1402
		1403	Obviously, it is safe to call this on an active watcher, or actually any
		1404	watcher that is initialised.
1186		1405
1187	=item bool ev_is_pending (ev_TYPE *watcher)	1406	=item bool ev_is_pending (ev_TYPE *watcher)
1188		1407
1189	Returns a true value iff the watcher is pending, (i.e. it has outstanding	1408	Returns a true value iff the watcher is pending, (i.e. it has outstanding
1190	events but its callback has not yet been invoked). As long as a watcher	1409	events but its callback has not yet been invoked). As long as a watcher
1191	is pending (but not active) you must not call an init function on it (but	1410	is pending (but not active) you must not call an init function on it (but
1192	C<ev_TYPE_set> is safe), you must not change its priority, and you must	1411	C<ev_TYPE_set> is safe), you must not change its priority, and you must
1193	make sure the watcher is available to libev (e.g. you cannot C<free ()>	1412	make sure the watcher is available to libev (e.g. you cannot C<free ()>
1194	it).	1413	it).
1195		1414
		1415	It is safe to call this on any watcher in any state as long as it is
		1416	initialised.
		1417
1196	=item callback ev_cb (ev_TYPE *watcher)	1418	=item callback ev_cb (ev_TYPE *watcher)
1197		1419
1198	Returns the callback currently set on the watcher.	1420	Returns the callback currently set on the watcher.
1199		1421
1200	=item ev_cb_set (ev_TYPE *watcher, callback)	1422	=item ev_set_cb (ev_TYPE *watcher, callback)
1201		1423
1202	Change the callback. You can change the callback at virtually any time	1424	Change the callback. You can change the callback at virtually any time
1203	(modulo threads).	1425	(modulo threads).
1204		1426
1205	=item ev_set_priority (ev_TYPE *watcher, int priority)	1427	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1213	from being executed (except for C<ev_idle> watchers).	1435	from being executed (except for C<ev_idle> watchers).
1214		1436
1215	If you need to suppress invocation when higher priority events are pending	1437	If you need to suppress invocation when higher priority events are pending
1216	you need to look at C<ev_idle> watchers, which provide this functionality.	1438	you need to look at C<ev_idle> watchers, which provide this functionality.
1217		1439
1218	You I<must not> change the priority of a watcher as long as it is active or	1440	You I<must not> change the priority of a watcher as long as it is active
1219	pending.	1441	or pending. Reading the priority with C<ev_priority> is fine in any state.
1220		1442
1221	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1443	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1222	fine, as long as you do not mind that the priority value you query might	1444	fine, as long as you do not mind that the priority value you query might
1223	or might not have been clamped to the valid range.	1445	or might not have been clamped to the valid range.
1224		1446
1225	The default priority used by watchers when no priority has been set is	1447	The default priority used by watchers when no priority has been set is
1226	always C<0>, which is supposed to not be too high and not be too low :).	1448	always C<0>, which is supposed to not be too high and not be too low :).
1227		1449
1228	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1450	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1229	priorities.	1451	priorities.
1230		1452
1231	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1453	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1232		1454
1233	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1455	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1246		1468
1247	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)	1469	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
1248		1470
1249	Feeds the given event set into the event loop, as if the specified event	1471	Feeds the given event set into the event loop, as if the specified event
1250	had happened for the specified watcher (which must be a pointer to an	1472	had happened for the specified watcher (which must be a pointer to an
1251	initialised but not necessarily started event watcher). Obviously you must	1473	initialised but not necessarily started event watcher, though it can be
1252	not free the watcher as long as it has pending events.	1474	active). Obviously you must not free the watcher as long as it has pending
		1475	events.
1253		1476
1254	Stopping the watcher, letting libev invoke it, or calling	1477	Stopping the watcher, letting libev invoke it, or calling
1255	C<ev_clear_pending> will clear the pending event, even if the watcher was	1478	C<ev_clear_pending> will clear the pending event, even if the watcher was
1256	not started in the first place.	1479	not started in the first place.
1257		1480
1258	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1481	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1259	functions that do not need a watcher.	1482	functions that do not need a watcher.
1260		1483
1261	=back	1484	=back
1262		1485
		1486	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1487	OWN COMPOSITE WATCHERS> idioms.
1263		1488
1264	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1489	=head2 WATCHER STATES
1265		1490
1266	Each watcher has, by default, a member C<void *data> that you can change	1491	There are various watcher states mentioned throughout this manual -
1267	and read at any time: libev will completely ignore it. This can be used	1492	active, pending and so on. In this section these states and the rules to
1268	to associate arbitrary data with your watcher. If you need more data and	1493	transition between them will be described in more detail - and while these
1269	don't want to allocate memory and store a pointer to it in that data	1494	rules might look complicated, they usually do "the right thing".
1270	member, you can also "subclass" the watcher type and provide your own
1271	data:
1272		1495
1273	struct my_io	1496	=over 4
1274	{
1275	ev_io io;
1276	int otherfd;
1277	void *somedata;
1278	struct whatever *mostinteresting;
1279	};
1280		1497
1281	...	1498	=item initialised
1282	struct my_io w;
1283	ev_io_init (&w.io, my_cb, fd, EV_READ);
1284		1499
1285	And since your callback will be called with a pointer to the watcher, you	1500	Before a watcher can be registered with the event loop it has to be
1286	can cast it back to your own type:	1501	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1502	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1287		1503
1288	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1504	In this state it is simply some block of memory that is suitable for
1289	{	1505	use in an event loop. It can be moved around, freed, reused etc. at
1290	struct my_io *w = (struct my_io *)w_;	1506	will - as long as you either keep the memory contents intact, or call
1291	...	1507	C<ev_TYPE_init> again.
1292	}
1293		1508
1294	More interesting and less C-conformant ways of casting your callback type	1509	=item started/running/active
1295	instead have been omitted.
1296		1510
1297	Another common scenario is to use some data structure with multiple	1511	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1298	embedded watchers:	1512	property of the event loop, and is actively waiting for events. While in
		1513	this state it cannot be accessed (except in a few documented ways, such as
		1514	stoping it), moved, freed or anything else - the only legal thing is to
		1515	keep a pointer to it, and call libev functions on it that are documented
		1516	to work on active watchers.
1299		1517
1300	struct my_biggy	1518	As a rule of thumb, before accessing a member or calling any function on
1301	{	1519	a watcher, it should be stopped (or freshly initialised). If that is not
1302	int some_data;	1520	convenient, you can check the documentation for that function or member to
1303	ev_timer t1;	1521	see if it is safe to use on an active watcher.
1304	ev_timer t2;
1305	}
1306		1522
1307	In this case getting the pointer to C<my_biggy> is a bit more	1523	=item pending
1308	complicated: Either you store the address of your C<my_biggy> struct
1309	in the C<data> member of the watcher (for woozies), or you need to use
1310	some pointer arithmetic using C<offsetof> inside your watchers (for real
1311	programmers):
1312		1524
1313	#include <stddef.h>	1525	If a watcher is active and libev determines that an event it is interested
		1526	in has occurred (such as a timer expiring), it will become pending. It
		1527	will stay in this pending state until either it is explicitly stopped or
		1528	its callback is about to be invoked, so it is not normally pending inside
		1529	the watcher callback.
1314		1530
1315	static void	1531	Generally, the watcher might or might not be active while it is pending
1316	t1_cb (EV_P_ ev_timer *w, int revents)	1532	(for example, an expired non-repeating timer can be pending but no longer
1317	{	1533	active). If it is pending but not active, it can be freely accessed (e.g.
1318	struct my_biggy big = (struct my_biggy *)	1534	by calling C<ev_TYPE_set>), but it is still property of the event loop at
1319	(((char *)w) - offsetof (struct my_biggy, t1));	1535	this time, so cannot be moved, freed or reused. And if it is active the
1320	}	1536	rules described in the previous item still apply.
1321		1537
1322	static void	1538	Explicitly stopping a watcher will also clear the pending state
1323	t2_cb (EV_P_ ev_timer *w, int revents)	1539	unconditionally, so it is safe to stop a watcher and then free it.
1324	{	1540
1325	struct my_biggy big = (struct my_biggy *)	1541	It is also possible to feed an event on a watcher that is not active (e.g.
1326	(((char *)w) - offsetof (struct my_biggy, t2));	1542	via C<ev_feed_event>), in which case it becomes pending without being
1327	}	1543	active.
		1544
		1545	=item stopped
		1546
		1547	A watcher can be stopped implicitly by libev (in which case it might still
		1548	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1549	latter will clear any pending state the watcher might be in, regardless
		1550	of whether it was active or not, so stopping a watcher explicitly before
		1551	freeing it is often a good idea.
		1552
		1553	While stopped (and not pending) the watcher is essentially in the
		1554	initialised state, that is, it can be reused, moved, modified in any way
		1555	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1556	it again).
		1557
		1558	=back
1328		1559
1329	=head2 WATCHER PRIORITY MODELS	1560	=head2 WATCHER PRIORITY MODELS
1330		1561
1331	Many event loops support I<watcher priorities>, which are usually small	1562	Many event loops support I<watcher priorities>, which are usually small
1332	integers that influence the ordering of event callback invocation	1563	integers that influence the ordering of event callback invocation
1333	between watchers in some way, all else being equal.	1564	between watchers in some way, all else being equal.
1334		1565
1335	In libev, Watcher priorities can be set using C<ev_set_priority>. See its	1566	In libev, watcher priorities can be set using C<ev_set_priority>. See its
1336	description for the more technical details such as the actual priority	1567	description for the more technical details such as the actual priority
1337	range.	1568	range.
1338		1569
1339	There are two common ways how these these priorities are being interpreted	1570	There are two common ways how these these priorities are being interpreted
1340	by event loops:	1571	by event loops:
…		…
1375		1606
1376	For example, to emulate how many other event libraries handle priorities,	1607	For example, to emulate how many other event libraries handle priorities,
1377	you can associate an C<ev_idle> watcher to each such watcher, and in	1608	you can associate an C<ev_idle> watcher to each such watcher, and in
1378	the normal watcher callback, you just start the idle watcher. The real	1609	the normal watcher callback, you just start the idle watcher. The real
1379	processing is done in the idle watcher callback. This causes libev to	1610	processing is done in the idle watcher callback. This causes libev to
1380	continously poll and process kernel event data for the watcher, but when	1611	continuously poll and process kernel event data for the watcher, but when
1381	the lock-out case is known to be rare (which in turn is rare :), this is	1612	the lock-out case is known to be rare (which in turn is rare :), this is
1382	workable.	1613	workable.
1383		1614
1384	Usually, however, the lock-out model implemented that way will perform	1615	Usually, however, the lock-out model implemented that way will perform
1385	miserably under the type of load it was designed to handle. In that case,	1616	miserably under the type of load it was designed to handle. In that case,
…		…
1399	{	1630	{
1400	// stop the I/O watcher, we received the event, but	1631	// stop the I/O watcher, we received the event, but
1401	// are not yet ready to handle it.	1632	// are not yet ready to handle it.
1402	ev_io_stop (EV_A_ w);	1633	ev_io_stop (EV_A_ w);
1403		1634
1404	// start the idle watcher to ahndle the actual event.	1635	// start the idle watcher to handle the actual event.
1405	// it will not be executed as long as other watchers	1636	// it will not be executed as long as other watchers
1406	// with the default priority are receiving events.	1637	// with the default priority are receiving events.
1407	ev_idle_start (EV_A_ &idle);	1638	ev_idle_start (EV_A_ &idle);
1408	}	1639	}
1409		1640
…		…
1434		1665
1435	This section describes each watcher in detail, but will not repeat	1666	This section describes each watcher in detail, but will not repeat
1436	information given in the last section. Any initialisation/set macros,	1667	information given in the last section. Any initialisation/set macros,
1437	functions and members specific to the watcher type are explained.	1668	functions and members specific to the watcher type are explained.
1438		1669
1439	Members are additionally marked with either I<[read-only]>, meaning that,	1670	Most members are additionally marked with either I<[read-only]>, meaning
1440	while the watcher is active, you can look at the member and expect some	1671	that, while the watcher is active, you can look at the member and expect
1441	sensible content, but you must not modify it (you can modify it while the	1672	some sensible content, but you must not modify it (you can modify it while
1442	watcher is stopped to your hearts content), or I<[read-write]>, which	1673	the watcher is stopped to your hearts content), or I<[read-write]>, which
1443	means you can expect it to have some sensible content while the watcher	1674	means you can expect it to have some sensible content while the watcher is
1444	is active, but you can also modify it. Modifying it may not do something	1675	active, but you can also modify it (within the same thread as the event
		1676	loop, i.e. without creating data races). Modifying it may not do something
1445	sensible or take immediate effect (or do anything at all), but libev will	1677	sensible or take immediate effect (or do anything at all), but libev will
1446	not crash or malfunction in any way.	1678	not crash or malfunction in any way.
1447		1679
		1680	In any case, the documentation for each member will explain what the
		1681	effects are, and if there are any additional access restrictions.
1448		1682
1449	=head2 C<ev_io> - is this file descriptor readable or writable?	1683	=head2 C<ev_io> - is this file descriptor readable or writable?
1450		1684
1451	I/O watchers check whether a file descriptor is readable or writable	1685	I/O watchers check whether a file descriptor is readable or writable
1452	in each iteration of the event loop, or, more precisely, when reading	1686	in each iteration of the event loop, or, more precisely, when reading
…		…
1459	In general you can register as many read and/or write event watchers per	1693	In general you can register as many read and/or write event watchers per
1460	fd as you want (as long as you don't confuse yourself). Setting all file	1694	fd as you want (as long as you don't confuse yourself). Setting all file
1461	descriptors to non-blocking mode is also usually a good idea (but not	1695	descriptors to non-blocking mode is also usually a good idea (but not
1462	required if you know what you are doing).	1696	required if you know what you are doing).
1463		1697
1464	If you cannot use non-blocking mode, then force the use of a
1465	known-to-be-good backend (at the time of this writing, this includes only
1466	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1467	descriptors for which non-blocking operation makes no sense (such as
1468	files) - libev doesn't guarentee any specific behaviour in that case.
1469
1470	Another thing you have to watch out for is that it is quite easy to	1698	Another thing you have to watch out for is that it is quite easy to
1471	receive "spurious" readiness notifications, that is your callback might	1699	receive "spurious" readiness notifications, that is, your callback might
1472	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1700	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1473	because there is no data. Not only are some backends known to create a	1701	because there is no data. It is very easy to get into this situation even
1474	lot of those (for example Solaris ports), it is very easy to get into	1702	with a relatively standard program structure. Thus it is best to always
1475	this situation even with a relatively standard program structure. Thus	1703	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1476	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1477	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1704	preferable to a program hanging until some data arrives.
1478		1705
1479	If you cannot run the fd in non-blocking mode (for example you should	1706	If you cannot run the fd in non-blocking mode (for example you should
1480	not play around with an Xlib connection), then you have to separately	1707	not play around with an Xlib connection), then you have to separately
1481	re-test whether a file descriptor is really ready with a known-to-be good	1708	re-test whether a file descriptor is really ready with a known-to-be good
1482	interface such as poll (fortunately in our Xlib example, Xlib already	1709	interface such as poll (fortunately in the case of Xlib, it already does
1483	does this on its own, so its quite safe to use). Some people additionally	1710	this on its own, so its quite safe to use). Some people additionally
1484	use C<SIGALRM> and an interval timer, just to be sure you won't block	1711	use C<SIGALRM> and an interval timer, just to be sure you won't block
1485	indefinitely.	1712	indefinitely.
1486		1713
1487	But really, best use non-blocking mode.	1714	But really, best use non-blocking mode.
1488		1715
1489	=head3 The special problem of disappearing file descriptors	1716	=head3 The special problem of disappearing file descriptors
1490		1717
1491	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1718	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1492	descriptor (either due to calling C<close> explicitly or any other means,	1719	a file descriptor (either due to calling C<close> explicitly or any other
1493	such as C<dup2>). The reason is that you register interest in some file	1720	means, such as C<dup2>). The reason is that you register interest in some
1494	descriptor, but when it goes away, the operating system will silently drop	1721	file descriptor, but when it goes away, the operating system will silently
1495	this interest. If another file descriptor with the same number then is	1722	drop this interest. If another file descriptor with the same number then
1496	registered with libev, there is no efficient way to see that this is, in	1723	is registered with libev, there is no efficient way to see that this is,
1497	fact, a different file descriptor.	1724	in fact, a different file descriptor.
1498		1725
1499	To avoid having to explicitly tell libev about such cases, libev follows	1726	To avoid having to explicitly tell libev about such cases, libev follows
1500	the following policy: Each time C<ev_io_set> is being called, libev	1727	the following policy: Each time C<ev_io_set> is being called, libev
1501	will assume that this is potentially a new file descriptor, otherwise	1728	will assume that this is potentially a new file descriptor, otherwise
1502	it is assumed that the file descriptor stays the same. That means that	1729	it is assumed that the file descriptor stays the same. That means that
…		…
1516		1743
1517	There is no workaround possible except not registering events	1744	There is no workaround possible except not registering events
1518	for potentially C<dup ()>'ed file descriptors, or to resort to	1745	for potentially C<dup ()>'ed file descriptors, or to resort to
1519	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1746	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1520		1747
		1748	=head3 The special problem of files
		1749
		1750	Many people try to use C<select> (or libev) on file descriptors
		1751	representing files, and expect it to become ready when their program
		1752	doesn't block on disk accesses (which can take a long time on their own).
		1753
		1754	However, this cannot ever work in the "expected" way - you get a readiness
		1755	notification as soon as the kernel knows whether and how much data is
		1756	there, and in the case of open files, that's always the case, so you
		1757	always get a readiness notification instantly, and your read (or possibly
		1758	write) will still block on the disk I/O.
		1759
		1760	Another way to view it is that in the case of sockets, pipes, character
		1761	devices and so on, there is another party (the sender) that delivers data
		1762	on its own, but in the case of files, there is no such thing: the disk
		1763	will not send data on its own, simply because it doesn't know what you
		1764	wish to read - you would first have to request some data.
		1765
		1766	Since files are typically not-so-well supported by advanced notification
		1767	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1768	to files, even though you should not use it. The reason for this is
		1769	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1770	usually a tty, often a pipe, but also sometimes files or special devices
		1771	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1772	F</dev/urandom>), and even though the file might better be served with
		1773	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1774	it "just works" instead of freezing.
		1775
		1776	So avoid file descriptors pointing to files when you know it (e.g. use
		1777	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1778	when you rarely read from a file instead of from a socket, and want to
		1779	reuse the same code path.
		1780
1521	=head3 The special problem of fork	1781	=head3 The special problem of fork
1522		1782
1523	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1783	Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()>
1524	useless behaviour. Libev fully supports fork, but needs to be told about	1784	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1525	it in the child.	1785	to be told about it in the child if you want to continue to use it in the
		1786	child.
1526		1787
1527	To support fork in your programs, you either have to call	1788	To support fork in your child processes, you have to call C<ev_loop_fork
1528	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1789	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1529	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1790	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1530	C<EVBACKEND_POLL>.
1531		1791
1532	=head3 The special problem of SIGPIPE	1792	=head3 The special problem of SIGPIPE
1533		1793
1534	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1794	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1535	when writing to a pipe whose other end has been closed, your program gets	1795	when writing to a pipe whose other end has been closed, your program gets
…		…
1541	somewhere, as that would have given you a big clue).	1801	somewhere, as that would have given you a big clue).
1542		1802
1543	=head3 The special problem of accept()ing when you can't	1803	=head3 The special problem of accept()ing when you can't
1544		1804
1545	Many implementations of the POSIX C<accept> function (for example,	1805	Many implementations of the POSIX C<accept> function (for example,
1546	found in port-2004 Linux) have the peculiar behaviour of not removing a	1806	found in post-2004 Linux) have the peculiar behaviour of not removing a
1547	connection from the pending queue in all error cases.	1807	connection from the pending queue in all error cases.
1548		1808
1549	For example, larger servers often run out of file descriptors (because	1809	For example, larger servers often run out of file descriptors (because
1550	of resource limits), causing C<accept> to fail with C<ENFILE> but not	1810	of resource limits), causing C<accept> to fail with C<ENFILE> but not
1551	rejecting the connection, leading to libev signalling readiness on	1811	rejecting the connection, leading to libev signalling readiness on
…		…
1586	=item ev_io_init (ev_io *, callback, int fd, int events)	1846	=item ev_io_init (ev_io *, callback, int fd, int events)
1587		1847
1588	=item ev_io_set (ev_io *, int fd, int events)	1848	=item ev_io_set (ev_io *, int fd, int events)
1589		1849
1590	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1850	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1591	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or	1851	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE>, both
1592	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.	1852	C<EV_READ | EV_WRITE> or C<0>, to express the desire to receive the given
		1853	events.
1593		1854
1594	=item int fd [read-only]	1855	Note that setting the C<events> to C<0> and starting the watcher is
		1856	supported, but not specially optimized - if your program sometimes happens
		1857	to generate this combination this is fine, but if it is easy to avoid
		1858	starting an io watcher watching for no events you should do so.
1595		1859
1596	The file descriptor being watched.	1860	=item ev_io_modify (ev_io *, int events)
1597		1861
		1862	Similar to C<ev_io_set>, but only changes the requested events. Using this
		1863	might be faster with some backends, as libev can assume that the C<fd>
		1864	still refers to the same underlying file description, something it cannot
		1865	do when using C<ev_io_set>.
		1866
		1867	=item int fd [no-modify]
		1868
		1869	The file descriptor being watched. While it can be read at any time, you
		1870	must not modify this member even when the watcher is stopped - always use
		1871	C<ev_io_set> for that.
		1872
1598	=item int events [read-only]	1873	=item int events [no-modify]
1599		1874
1600	The events being watched.	1875	The set of events the fd is being watched for, among other flags. Remember
		1876	that this is a bit set - to test for C<EV_READ>, use C<< w->events &
		1877	EV_READ >>, and similarly for C<EV_WRITE>.
		1878
		1879	As with C<fd>, you must not modify this member even when the watcher is
		1880	stopped, always use C<ev_io_set> or C<ev_io_modify> for that.
1601		1881
1602	=back	1882	=back
1603		1883
1604	=head3 Examples	1884	=head3 Examples
1605		1885
…		…
1617	...	1897	...
1618	struct ev_loop *loop = ev_default_init (0);	1898	struct ev_loop *loop = ev_default_init (0);
1619	ev_io stdin_readable;	1899	ev_io stdin_readable;
1620	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1900	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1621	ev_io_start (loop, &stdin_readable);	1901	ev_io_start (loop, &stdin_readable);
1622	ev_loop (loop, 0);	1902	ev_run (loop, 0);
1623		1903
1624		1904
1625	=head2 C<ev_timer> - relative and optionally repeating timeouts	1905	=head2 C<ev_timer> - relative and optionally repeating timeouts
1626		1906
1627	Timer watchers are simple relative timers that generate an event after a	1907	Timer watchers are simple relative timers that generate an event after a
…		…
1633	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1913	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1634	monotonic clock option helps a lot here).	1914	monotonic clock option helps a lot here).
1635		1915
1636	The callback is guaranteed to be invoked only I<after> its timeout has	1916	The callback is guaranteed to be invoked only I<after> its timeout has
1637	passed (not I<at>, so on systems with very low-resolution clocks this	1917	passed (not I<at>, so on systems with very low-resolution clocks this
1638	might introduce a small delay). If multiple timers become ready during the	1918	might introduce a small delay, see "the special problem of being too
		1919	early", below). If multiple timers become ready during the same loop
1639	same loop iteration then the ones with earlier time-out values are invoked	1920	iteration then the ones with earlier time-out values are invoked before
1640	before ones of the same priority with later time-out values (but this is	1921	ones of the same priority with later time-out values (but this is no
1641	no longer true when a callback calls C<ev_loop> recursively).	1922	longer true when a callback calls C<ev_run> recursively).
1642		1923
1643	=head3 Be smart about timeouts	1924	=head3 Be smart about timeouts
1644		1925
1645	Many real-world problems involve some kind of timeout, usually for error	1926	Many real-world problems involve some kind of timeout, usually for error
1646	recovery. A typical example is an HTTP request - if the other side hangs,	1927	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1721		2002
1722	In this case, it would be more efficient to leave the C<ev_timer> alone,	2003	In this case, it would be more efficient to leave the C<ev_timer> alone,
1723	but remember the time of last activity, and check for a real timeout only	2004	but remember the time of last activity, and check for a real timeout only
1724	within the callback:	2005	within the callback:
1725		2006
		2007	ev_tstamp timeout = 60.;
1726	ev_tstamp last_activity; // time of last activity	2008	ev_tstamp last_activity; // time of last activity
		2009	ev_timer timer;
1727		2010
1728	static void	2011	static void
1729	callback (EV_P_ ev_timer *w, int revents)	2012	callback (EV_P_ ev_timer *w, int revents)
1730	{	2013	{
1731	ev_tstamp now = ev_now (EV_A);	2014	// calculate when the timeout would happen
1732	ev_tstamp timeout = last_activity + 60.;	2015	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1733		2016
1734	// if last_activity + 60. is older than now, we did time out	2017	// if negative, it means we the timeout already occurred
1735	if (timeout < now)	2018	if (after < 0.)
1736	{	2019	{
1737	// timeout occured, take action	2020	// timeout occurred, take action
1738	}	2021	}
1739	else	2022	else
1740	{	2023	{
1741	// callback was invoked, but there was some activity, re-arm	2024	// callback was invoked, but there was some recent
1742	// the watcher to fire in last_activity + 60, which is	2025	// activity. simply restart the timer to time out
1743	// guaranteed to be in the future, so "again" is positive:	2026	// after "after" seconds, which is the earliest time
1744	w->repeat = timeout - now;	2027	// the timeout can occur.
		2028	ev_timer_set (w, after, 0.);
1745	ev_timer_again (EV_A_ w);	2029	ev_timer_start (EV_A_ w);
1746	}	2030	}
1747	}	2031	}
1748		2032
1749	To summarise the callback: first calculate the real timeout (defined	2033	To summarise the callback: first calculate in how many seconds the
1750	as "60 seconds after the last activity"), then check if that time has	2034	timeout will occur (by calculating the absolute time when it would occur,
1751	been reached, which means something I<did>, in fact, time out. Otherwise	2035	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1752	the callback was invoked too early (C<timeout> is in the future), so	2036	(EV_A)> from that).
1753	re-schedule the timer to fire at that future time, to see if maybe we have
1754	a timeout then.
1755		2037
1756	Note how C<ev_timer_again> is used, taking advantage of the	2038	If this value is negative, then we are already past the timeout, i.e. we
1757	C<ev_timer_again> optimisation when the timer is already running.	2039	timed out, and need to do whatever is needed in this case.
		2040
		2041	Otherwise, we now the earliest time at which the timeout would trigger,
		2042	and simply start the timer with this timeout value.
		2043
		2044	In other words, each time the callback is invoked it will check whether
		2045	the timeout occurred. If not, it will simply reschedule itself to check
		2046	again at the earliest time it could time out. Rinse. Repeat.
1758		2047
1759	This scheme causes more callback invocations (about one every 60 seconds	2048	This scheme causes more callback invocations (about one every 60 seconds
1760	minus half the average time between activity), but virtually no calls to	2049	minus half the average time between activity), but virtually no calls to
1761	libev to change the timeout.	2050	libev to change the timeout.
1762		2051
1763	To start the timer, simply initialise the watcher and set C<last_activity>	2052	To start the machinery, simply initialise the watcher and set
1764	to the current time (meaning we just have some activity :), then call the	2053	C<last_activity> to the current time (meaning there was some activity just
1765	callback, which will "do the right thing" and start the timer:	2054	now), then call the callback, which will "do the right thing" and start
		2055	the timer:
1766		2056
		2057	last_activity = ev_now (EV_A);
1767	ev_init (timer, callback);	2058	ev_init (&timer, callback);
1768	last_activity = ev_now (loop);	2059	callback (EV_A_ &timer, 0);
1769	callback (loop, timer, EV_TIMER);
1770		2060
1771	And when there is some activity, simply store the current time in	2061	When there is some activity, simply store the current time in
1772	C<last_activity>, no libev calls at all:	2062	C<last_activity>, no libev calls at all:
1773		2063
		2064	if (activity detected)
1774	last_actiivty = ev_now (loop);	2065	last_activity = ev_now (EV_A);
		2066
		2067	When your timeout value changes, then the timeout can be changed by simply
		2068	providing a new value, stopping the timer and calling the callback, which
		2069	will again do the right thing (for example, time out immediately :).
		2070
		2071	timeout = new_value;
		2072	ev_timer_stop (EV_A_ &timer);
		2073	callback (EV_A_ &timer, 0);
1775		2074
1776	This technique is slightly more complex, but in most cases where the	2075	This technique is slightly more complex, but in most cases where the
1777	time-out is unlikely to be triggered, much more efficient.	2076	time-out is unlikely to be triggered, much more efficient.
1778
1779	Changing the timeout is trivial as well (if it isn't hard-coded in the
1780	callback :) - just change the timeout and invoke the callback, which will
1781	fix things for you.
1782		2077
1783	=item 4. Wee, just use a double-linked list for your timeouts.	2078	=item 4. Wee, just use a double-linked list for your timeouts.
1784		2079
1785	If there is not one request, but many thousands (millions...), all	2080	If there is not one request, but many thousands (millions...), all
1786	employing some kind of timeout with the same timeout value, then one can	2081	employing some kind of timeout with the same timeout value, then one can
…		…
1813	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2108	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1814	rather complicated, but extremely efficient, something that really pays	2109	rather complicated, but extremely efficient, something that really pays
1815	off after the first million or so of active timers, i.e. it's usually	2110	off after the first million or so of active timers, i.e. it's usually
1816	overkill :)	2111	overkill :)
1817		2112
		2113	=head3 The special problem of being too early
		2114
		2115	If you ask a timer to call your callback after three seconds, then
		2116	you expect it to be invoked after three seconds - but of course, this
		2117	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2118	guaranteed to any precision by libev - imagine somebody suspending the
		2119	process with a STOP signal for a few hours for example.
		2120
		2121	So, libev tries to invoke your callback as soon as possible I<after> the
		2122	delay has occurred, but cannot guarantee this.
		2123
		2124	A less obvious failure mode is calling your callback too early: many event
		2125	loops compare timestamps with a "elapsed delay >= requested delay", but
		2126	this can cause your callback to be invoked much earlier than you would
		2127	expect.
		2128
		2129	To see why, imagine a system with a clock that only offers full second
		2130	resolution (think windows if you can't come up with a broken enough OS
		2131	yourself). If you schedule a one-second timer at the time 500.9, then the
		2132	event loop will schedule your timeout to elapse at a system time of 500
		2133	(500.9 truncated to the resolution) + 1, or 501.
		2134
		2135	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2136	501" and invoke the callback 0.1s after it was started, even though a
		2137	one-second delay was requested - this is being "too early", despite best
		2138	intentions.
		2139
		2140	This is the reason why libev will never invoke the callback if the elapsed
		2141	delay equals the requested delay, but only when the elapsed delay is
		2142	larger than the requested delay. In the example above, libev would only invoke
		2143	the callback at system time 502, or 1.1s after the timer was started.
		2144
		2145	So, while libev cannot guarantee that your callback will be invoked
		2146	exactly when requested, it I<can> and I<does> guarantee that the requested
		2147	delay has actually elapsed, or in other words, it always errs on the "too
		2148	late" side of things.
		2149
1818	=head3 The special problem of time updates	2150	=head3 The special problem of time updates
1819		2151
1820	Establishing the current time is a costly operation (it usually takes at	2152	Establishing the current time is a costly operation (it usually takes
1821	least two system calls): EV therefore updates its idea of the current	2153	at least one system call): EV therefore updates its idea of the current
1822	time only before and after C<ev_loop> collects new events, which causes a	2154	time only before and after C<ev_run> collects new events, which causes a
1823	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2155	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1824	lots of events in one iteration.	2156	lots of events in one iteration.
1825		2157
1826	The relative timeouts are calculated relative to the C<ev_now ()>	2158	The relative timeouts are calculated relative to the C<ev_now ()>
1827	time. This is usually the right thing as this timestamp refers to the time	2159	time. This is usually the right thing as this timestamp refers to the time
1828	of the event triggering whatever timeout you are modifying/starting. If	2160	of the event triggering whatever timeout you are modifying/starting. If
1829	you suspect event processing to be delayed and you I<need> to base the	2161	you suspect event processing to be delayed and you I<need> to base the
1830	timeout on the current time, use something like this to adjust for this:	2162	timeout on the current time, use something like the following to adjust
		2163	for it:
1831		2164
1832	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2165	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1833		2166
1834	If the event loop is suspended for a long time, you can also force an	2167	If the event loop is suspended for a long time, you can also force an
1835	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2168	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1836	()>.	2169	()>, although that will push the event time of all outstanding events
		2170	further into the future.
		2171
		2172	=head3 The special problem of unsynchronised clocks
		2173
		2174	Modern systems have a variety of clocks - libev itself uses the normal
		2175	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2176	jumps).
		2177
		2178	Neither of these clocks is synchronised with each other or any other clock
		2179	on the system, so C<ev_time ()> might return a considerably different time
		2180	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2181	a call to C<gettimeofday> might return a second count that is one higher
		2182	than a directly following call to C<time>.
		2183
		2184	The moral of this is to only compare libev-related timestamps with
		2185	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2186	a second or so.
		2187
		2188	One more problem arises due to this lack of synchronisation: if libev uses
		2189	the system monotonic clock and you compare timestamps from C<ev_time>
		2190	or C<ev_now> from when you started your timer and when your callback is
		2191	invoked, you will find that sometimes the callback is a bit "early".
		2192
		2193	This is because C<ev_timer>s work in real time, not wall clock time, so
		2194	libev makes sure your callback is not invoked before the delay happened,
		2195	I<measured according to the real time>, not the system clock.
		2196
		2197	If your timeouts are based on a physical timescale (e.g. "time out this
		2198	connection after 100 seconds") then this shouldn't bother you as it is
		2199	exactly the right behaviour.
		2200
		2201	If you want to compare wall clock/system timestamps to your timers, then
		2202	you need to use C<ev_periodic>s, as these are based on the wall clock
		2203	time, where your comparisons will always generate correct results.
1837		2204
1838	=head3 The special problems of suspended animation	2205	=head3 The special problems of suspended animation
1839		2206
1840	When you leave the server world it is quite customary to hit machines that	2207	When you leave the server world it is quite customary to hit machines that
1841	can suspend/hibernate - what happens to the clocks during such a suspend?	2208	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1871		2238
1872	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2239	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1873		2240
1874	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2241	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1875		2242
1876	Configure the timer to trigger after C<after> seconds. If C<repeat>	2243	Configure the timer to trigger after C<after> seconds (fractional and
1877	is C<0.>, then it will automatically be stopped once the timeout is	2244	negative values are supported). If C<repeat> is C<0.>, then it will
1878	reached. If it is positive, then the timer will automatically be	2245	automatically be stopped once the timeout is reached. If it is positive,
1879	configured to trigger again C<repeat> seconds later, again, and again,	2246	then the timer will automatically be configured to trigger again C<repeat>
1880	until stopped manually.	2247	seconds later, again, and again, until stopped manually.
1881		2248
1882	The timer itself will do a best-effort at avoiding drift, that is, if	2249	The timer itself will do a best-effort at avoiding drift, that is, if
1883	you configure a timer to trigger every 10 seconds, then it will normally	2250	you configure a timer to trigger every 10 seconds, then it will normally
1884	trigger at exactly 10 second intervals. If, however, your program cannot	2251	trigger at exactly 10 second intervals. If, however, your program cannot
1885	keep up with the timer (because it takes longer than those 10 seconds to	2252	keep up with the timer (because it takes longer than those 10 seconds to
1886	do stuff) the timer will not fire more than once per event loop iteration.	2253	do stuff) the timer will not fire more than once per event loop iteration.
1887		2254
1888	=item ev_timer_again (loop, ev_timer *)	2255	=item ev_timer_again (loop, ev_timer *)
1889		2256
1890	This will act as if the timer timed out and restart it again if it is	2257	This will act as if the timer timed out, and restarts it again if it is
1891	repeating. The exact semantics are:	2258	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2259	timeout to the C<repeat> value and calling C<ev_timer_start>.
1892		2260
		2261	The exact semantics are as in the following rules, all of which will be
		2262	applied to the watcher:
		2263
		2264	=over 4
		2265
1893	If the timer is pending, its pending status is cleared.	2266	=item If the timer is pending, the pending status is always cleared.
1894		2267
1895	If the timer is started but non-repeating, stop it (as if it timed out).	2268	=item If the timer is started but non-repeating, stop it (as if it timed
		2269	out, without invoking it).
1896		2270
1897	If the timer is repeating, either start it if necessary (with the	2271	=item If the timer is repeating, make the C<repeat> value the new timeout
1898	C<repeat> value), or reset the running timer to the C<repeat> value.	2272	and start the timer, if necessary.
1899		2273
		2274	=back
		2275
1900	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2276	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1901	usage example.	2277	usage example.
1902		2278
1903	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2279	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1904		2280
1905	Returns the remaining time until a timer fires. If the timer is active,	2281	Returns the remaining time until a timer fires. If the timer is active,
…		…
1944	}	2320	}
1945		2321
1946	ev_timer mytimer;	2322	ev_timer mytimer;
1947	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2323	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1948	ev_timer_again (&mytimer); /* start timer */	2324	ev_timer_again (&mytimer); /* start timer */
1949	ev_loop (loop, 0);	2325	ev_run (loop, 0);
1950		2326
1951	// and in some piece of code that gets executed on any "activity":	2327	// and in some piece of code that gets executed on any "activity":
1952	// reset the timeout to start ticking again at 10 seconds	2328	// reset the timeout to start ticking again at 10 seconds
1953	ev_timer_again (&mytimer);	2329	ev_timer_again (&mytimer);
1954		2330
…		…
1958	Periodic watchers are also timers of a kind, but they are very versatile	2334	Periodic watchers are also timers of a kind, but they are very versatile
1959	(and unfortunately a bit complex).	2335	(and unfortunately a bit complex).
1960		2336
1961	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2337	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1962	relative time, the physical time that passes) but on wall clock time	2338	relative time, the physical time that passes) but on wall clock time
1963	(absolute time, the thing you can read on your calender or clock). The	2339	(absolute time, the thing you can read on your calendar or clock). The
1964	difference is that wall clock time can run faster or slower than real	2340	difference is that wall clock time can run faster or slower than real
1965	time, and time jumps are not uncommon (e.g. when you adjust your	2341	time, and time jumps are not uncommon (e.g. when you adjust your
1966	wrist-watch).	2342	wrist-watch).
1967		2343
1968	You can tell a periodic watcher to trigger after some specific point	2344	You can tell a periodic watcher to trigger after some specific point
…		…
1973	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2349	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1974	it, as it uses a relative timeout).	2350	it, as it uses a relative timeout).
1975		2351
1976	C<ev_periodic> watchers can also be used to implement vastly more complex	2352	C<ev_periodic> watchers can also be used to implement vastly more complex
1977	timers, such as triggering an event on each "midnight, local time", or	2353	timers, such as triggering an event on each "midnight, local time", or
1978	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2354	other complicated rules. This cannot easily be done with C<ev_timer>
1979	those cannot react to time jumps.	2355	watchers, as those cannot react to time jumps.
1980		2356
1981	As with timers, the callback is guaranteed to be invoked only when the	2357	As with timers, the callback is guaranteed to be invoked only when the
1982	point in time where it is supposed to trigger has passed. If multiple	2358	point in time where it is supposed to trigger has passed. If multiple
1983	timers become ready during the same loop iteration then the ones with	2359	timers become ready during the same loop iteration then the ones with
1984	earlier time-out values are invoked before ones with later time-out values	2360	earlier time-out values are invoked before ones with later time-out values
1985	(but this is no longer true when a callback calls C<ev_loop> recursively).	2361	(but this is no longer true when a callback calls C<ev_run> recursively).
1986		2362
1987	=head3 Watcher-Specific Functions and Data Members	2363	=head3 Watcher-Specific Functions and Data Members
1988		2364
1989	=over 4	2365	=over 4
1990		2366
…		…
2025		2401
2026	Another way to think about it (for the mathematically inclined) is that	2402	Another way to think about it (for the mathematically inclined) is that
2027	C<ev_periodic> will try to run the callback in this mode at the next possible	2403	C<ev_periodic> will try to run the callback in this mode at the next possible
2028	time where C<time = offset (mod interval)>, regardless of any time jumps.	2404	time where C<time = offset (mod interval)>, regardless of any time jumps.
2029		2405
2030	For numerical stability it is preferable that the C<offset> value is near	2406	The C<interval> I<MUST> be positive, and for numerical stability, the
2031	C<ev_now ()> (the current time), but there is no range requirement for	2407	interval value should be higher than C<1/8192> (which is around 100
2032	this value, and in fact is often specified as zero.	2408	microseconds) and C<offset> should be higher than C<0> and should have
		2409	at most a similar magnitude as the current time (say, within a factor of
		2410	ten). Typical values for offset are, in fact, C<0> or something between
		2411	C<0> and C<interval>, which is also the recommended range.
2033		2412
2034	Note also that there is an upper limit to how often a timer can fire (CPU	2413	Note also that there is an upper limit to how often a timer can fire (CPU
2035	speed for example), so if C<interval> is very small then timing stability	2414	speed for example), so if C<interval> is very small then timing stability
2036	will of course deteriorate. Libev itself tries to be exact to be about one	2415	will of course deteriorate. Libev itself tries to be exact to be about one
2037	millisecond (if the OS supports it and the machine is fast enough).	2416	millisecond (if the OS supports it and the machine is fast enough).
…		…
2067		2446
2068	NOTE: I<< This callback must always return a time that is higher than or	2447	NOTE: I<< This callback must always return a time that is higher than or
2069	equal to the passed C<now> value >>.	2448	equal to the passed C<now> value >>.
2070		2449
2071	This can be used to create very complex timers, such as a timer that	2450	This can be used to create very complex timers, such as a timer that
2072	triggers on "next midnight, local time". To do this, you would calculate the	2451	triggers on "next midnight, local time". To do this, you would calculate
2073	next midnight after C<now> and return the timestamp value for this. How	2452	the next midnight after C<now> and return the timestamp value for
2074	you do this is, again, up to you (but it is not trivial, which is the main	2453	this. Here is a (completely untested, no error checking) example on how to
2075	reason I omitted it as an example).	2454	do this:
		2455
		2456	#include <time.h>
		2457
		2458	static ev_tstamp
		2459	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2460	{
		2461	time_t tnow = (time_t)now;
		2462	struct tm tm;
		2463	localtime_r (&tnow, &tm);
		2464
		2465	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2466	++tm.tm_mday; // midnight next day
		2467
		2468	return mktime (&tm);
		2469	}
		2470
		2471	Note: this code might run into trouble on days that have more then two
		2472	midnights (beginning and end).
2076		2473
2077	=back	2474	=back
2078		2475
2079	=item ev_periodic_again (loop, ev_periodic *)	2476	=item ev_periodic_again (loop, ev_periodic *)
2080		2477
…		…
2118	Example: Call a callback every hour, or, more precisely, whenever the	2515	Example: Call a callback every hour, or, more precisely, whenever the
2119	system time is divisible by 3600. The callback invocation times have	2516	system time is divisible by 3600. The callback invocation times have
2120	potentially a lot of jitter, but good long-term stability.	2517	potentially a lot of jitter, but good long-term stability.
2121		2518
2122	static void	2519	static void
2123	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2520	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2124	{	2521	{
2125	... its now a full hour (UTC, or TAI or whatever your clock follows)	2522	... its now a full hour (UTC, or TAI or whatever your clock follows)
2126	}	2523	}
2127		2524
2128	ev_periodic hourly_tick;	2525	ev_periodic hourly_tick;
…		…
2145		2542
2146	ev_periodic hourly_tick;	2543	ev_periodic hourly_tick;
2147	ev_periodic_init (&hourly_tick, clock_cb,	2544	ev_periodic_init (&hourly_tick, clock_cb,
2148	fmod (ev_now (loop), 3600.), 3600., 0);	2545	fmod (ev_now (loop), 3600.), 3600., 0);
2149	ev_periodic_start (loop, &hourly_tick);	2546	ev_periodic_start (loop, &hourly_tick);
2150		2547
2151		2548
2152	=head2 C<ev_signal> - signal me when a signal gets signalled!	2549	=head2 C<ev_signal> - signal me when a signal gets signalled!
2153		2550
2154	Signal watchers will trigger an event when the process receives a specific	2551	Signal watchers will trigger an event when the process receives a specific
2155	signal one or more times. Even though signals are very asynchronous, libev	2552	signal one or more times. Even though signals are very asynchronous, libev
2156	will try it's best to deliver signals synchronously, i.e. as part of the	2553	will try its best to deliver signals synchronously, i.e. as part of the
2157	normal event processing, like any other event.	2554	normal event processing, like any other event.
2158		2555
2159	If you want signals to be delivered truly asynchronously, just use	2556	If you want signals to be delivered truly asynchronously, just use
2160	C<sigaction> as you would do without libev and forget about sharing	2557	C<sigaction> as you would do without libev and forget about sharing
2161	the signal. You can even use C<ev_async> from a signal handler to	2558	the signal. You can even use C<ev_async> from a signal handler to
…		…
2165	only within the same loop, i.e. you can watch for C<SIGINT> in your	2562	only within the same loop, i.e. you can watch for C<SIGINT> in your
2166	default loop and for C<SIGIO> in another loop, but you cannot watch for	2563	default loop and for C<SIGIO> in another loop, but you cannot watch for
2167	C<SIGINT> in both the default loop and another loop at the same time. At	2564	C<SIGINT> in both the default loop and another loop at the same time. At
2168	the moment, C<SIGCHLD> is permanently tied to the default loop.	2565	the moment, C<SIGCHLD> is permanently tied to the default loop.
2169		2566
2170	When the first watcher gets started will libev actually register something	2567	Only after the first watcher for a signal is started will libev actually
2171	with the kernel (thus it coexists with your own signal handlers as long as	2568	register something with the kernel. It thus coexists with your own signal
2172	you don't register any with libev for the same signal).	2569	handlers as long as you don't register any with libev for the same signal.
2173		2570
2174	If possible and supported, libev will install its handlers with	2571	If possible and supported, libev will install its handlers with
2175	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2572	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2176	not be unduly interrupted. If you have a problem with system calls getting	2573	not be unduly interrupted. If you have a problem with system calls getting
2177	interrupted by signals you can block all signals in an C<ev_check> watcher	2574	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2180	=head3 The special problem of inheritance over fork/execve/pthread_create	2577	=head3 The special problem of inheritance over fork/execve/pthread_create
2181		2578
2182	Both the signal mask (C<sigprocmask>) and the signal disposition	2579	Both the signal mask (C<sigprocmask>) and the signal disposition
2183	(C<sigaction>) are unspecified after starting a signal watcher (and after	2580	(C<sigaction>) are unspecified after starting a signal watcher (and after
2184	stopping it again), that is, libev might or might not block the signal,	2581	stopping it again), that is, libev might or might not block the signal,
2185	and might or might not set or restore the installed signal handler.	2582	and might or might not set or restore the installed signal handler (but
		2583	see C<EVFLAG_NOSIGMASK>).
2186		2584
2187	While this does not matter for the signal disposition (libev never	2585	While this does not matter for the signal disposition (libev never
2188	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2586	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2189	C<execve>), this matters for the signal mask: many programs do not expect	2587	C<execve>), this matters for the signal mask: many programs do not expect
2190	certain signals to be blocked.	2588	certain signals to be blocked.
…		…
2204		2602
2205	So I can't stress this enough: I<If you do not reset your signal mask when	2603	So I can't stress this enough: I<If you do not reset your signal mask when
2206	you expect it to be empty, you have a race condition in your code>. This	2604	you expect it to be empty, you have a race condition in your code>. This
2207	is not a libev-specific thing, this is true for most event libraries.	2605	is not a libev-specific thing, this is true for most event libraries.
2208		2606
		2607	=head3 The special problem of threads signal handling
		2608
		2609	POSIX threads has problematic signal handling semantics, specifically,
		2610	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2611	threads in a process block signals, which is hard to achieve.
		2612
		2613	When you want to use sigwait (or mix libev signal handling with your own
		2614	for the same signals), you can tackle this problem by globally blocking
		2615	all signals before creating any threads (or creating them with a fully set
		2616	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2617	loops. Then designate one thread as "signal receiver thread" which handles
		2618	these signals. You can pass on any signals that libev might be interested
		2619	in by calling C<ev_feed_signal>.
		2620
2209	=head3 Watcher-Specific Functions and Data Members	2621	=head3 Watcher-Specific Functions and Data Members
2210		2622
2211	=over 4	2623	=over 4
2212		2624
2213	=item ev_signal_init (ev_signal *, callback, int signum)	2625	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2228	Example: Try to exit cleanly on SIGINT.	2640	Example: Try to exit cleanly on SIGINT.
2229		2641
2230	static void	2642	static void
2231	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2643	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2232	{	2644	{
2233	ev_unloop (loop, EVUNLOOP_ALL);	2645	ev_break (loop, EVBREAK_ALL);
2234	}	2646	}
2235		2647
2236	ev_signal signal_watcher;	2648	ev_signal signal_watcher;
2237	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2649	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2238	ev_signal_start (loop, &signal_watcher);	2650	ev_signal_start (loop, &signal_watcher);
…		…
2347		2759
2348	=head2 C<ev_stat> - did the file attributes just change?	2760	=head2 C<ev_stat> - did the file attributes just change?
2349		2761
2350	This watches a file system path for attribute changes. That is, it calls	2762	This watches a file system path for attribute changes. That is, it calls
2351	C<stat> on that path in regular intervals (or when the OS says it changed)	2763	C<stat> on that path in regular intervals (or when the OS says it changed)
2352	and sees if it changed compared to the last time, invoking the callback if	2764	and sees if it changed compared to the last time, invoking the callback
2353	it did.	2765	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2766	happen after the watcher has been started will be reported.
2354		2767
2355	The path does not need to exist: changing from "path exists" to "path does	2768	The path does not need to exist: changing from "path exists" to "path does
2356	not exist" is a status change like any other. The condition "path does not	2769	not exist" is a status change like any other. The condition "path does not
2357	exist" (or more correctly "path cannot be stat'ed") is signified by the	2770	exist" (or more correctly "path cannot be stat'ed") is signified by the
2358	C<st_nlink> field being zero (which is otherwise always forced to be at	2771	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2588	Apart from keeping your process non-blocking (which is a useful	3001	Apart from keeping your process non-blocking (which is a useful
2589	effect on its own sometimes), idle watchers are a good place to do	3002	effect on its own sometimes), idle watchers are a good place to do
2590	"pseudo-background processing", or delay processing stuff to after the	3003	"pseudo-background processing", or delay processing stuff to after the
2591	event loop has handled all outstanding events.	3004	event loop has handled all outstanding events.
2592		3005
		3006	=head3 Abusing an C<ev_idle> watcher for its side-effect
		3007
		3008	As long as there is at least one active idle watcher, libev will never
		3009	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		3010	For this to work, the idle watcher doesn't need to be invoked at all - the
		3011	lowest priority will do.
		3012
		3013	This mode of operation can be useful together with an C<ev_check> watcher,
		3014	to do something on each event loop iteration - for example to balance load
		3015	between different connections.
		3016
		3017	See L</Abusing an ev_check watcher for its side-effect> for a longer
		3018	example.
		3019
2593	=head3 Watcher-Specific Functions and Data Members	3020	=head3 Watcher-Specific Functions and Data Members
2594		3021
2595	=over 4	3022	=over 4
2596		3023
2597	=item ev_idle_init (ev_idle *, callback)	3024	=item ev_idle_init (ev_idle *, callback)
…		…
2608	callback, free it. Also, use no error checking, as usual.	3035	callback, free it. Also, use no error checking, as usual.
2609		3036
2610	static void	3037	static void
2611	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	3038	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2612	{	3039	{
		3040	// stop the watcher
		3041	ev_idle_stop (loop, w);
		3042
		3043	// now we can free it
2613	free (w);	3044	free (w);
		3045
2614	// now do something you wanted to do when the program has	3046	// now do something you wanted to do when the program has
2615	// no longer anything immediate to do.	3047	// no longer anything immediate to do.
2616	}	3048	}
2617		3049
2618	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3050	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2620	ev_idle_start (loop, idle_watcher);	3052	ev_idle_start (loop, idle_watcher);
2621		3053
2622		3054
2623	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3055	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2624		3056
2625	Prepare and check watchers are usually (but not always) used in pairs:	3057	Prepare and check watchers are often (but not always) used in pairs:
2626	prepare watchers get invoked before the process blocks and check watchers	3058	prepare watchers get invoked before the process blocks and check watchers
2627	afterwards.	3059	afterwards.
2628		3060
2629	You I<must not> call C<ev_loop> or similar functions that enter	3061	You I<must not> call C<ev_run> (or similar functions that enter the
2630	the current event loop from either C<ev_prepare> or C<ev_check>	3062	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2631	watchers. Other loops than the current one are fine, however. The	3063	C<ev_check> watchers. Other loops than the current one are fine,
2632	rationale behind this is that you do not need to check for recursion in	3064	however. The rationale behind this is that you do not need to check
2633	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3065	for recursion in those watchers, i.e. the sequence will always be
2634	C<ev_check> so if you have one watcher of each kind they will always be	3066	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2635	called in pairs bracketing the blocking call.	3067	kind they will always be called in pairs bracketing the blocking call.
2636		3068
2637	Their main purpose is to integrate other event mechanisms into libev and	3069	Their main purpose is to integrate other event mechanisms into libev and
2638	their use is somewhat advanced. They could be used, for example, to track	3070	their use is somewhat advanced. They could be used, for example, to track
2639	variable changes, implement your own watchers, integrate net-snmp or a	3071	variable changes, implement your own watchers, integrate net-snmp or a
2640	coroutine library and lots more. They are also occasionally useful if	3072	coroutine library and lots more. They are also occasionally useful if
…		…
2658	with priority higher than or equal to the event loop and one coroutine	3090	with priority higher than or equal to the event loop and one coroutine
2659	of lower priority, but only once, using idle watchers to keep the event	3091	of lower priority, but only once, using idle watchers to keep the event
2660	loop from blocking if lower-priority coroutines are active, thus mapping	3092	loop from blocking if lower-priority coroutines are active, thus mapping
2661	low-priority coroutines to idle/background tasks).	3093	low-priority coroutines to idle/background tasks).
2662		3094
2663	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3095	When used for this purpose, it is recommended to give C<ev_check> watchers
2664	priority, to ensure that they are being run before any other watchers	3096	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2665	after the poll (this doesn't matter for C<ev_prepare> watchers).	3097	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3098	watchers).
2666		3099
2667	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3100	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2668	activate ("feed") events into libev. While libev fully supports this, they	3101	activate ("feed") events into libev. While libev fully supports this, they
2669	might get executed before other C<ev_check> watchers did their job. As	3102	might get executed before other C<ev_check> watchers did their job. As
2670	C<ev_check> watchers are often used to embed other (non-libev) event	3103	C<ev_check> watchers are often used to embed other (non-libev) event
2671	loops those other event loops might be in an unusable state until their	3104	loops those other event loops might be in an unusable state until their
2672	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3105	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2673	others).	3106	others).
		3107
		3108	=head3 Abusing an C<ev_check> watcher for its side-effect
		3109
		3110	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3111	useful because they are called once per event loop iteration. For
		3112	example, if you want to handle a large number of connections fairly, you
		3113	normally only do a bit of work for each active connection, and if there
		3114	is more work to do, you wait for the next event loop iteration, so other
		3115	connections have a chance of making progress.
		3116
		3117	Using an C<ev_check> watcher is almost enough: it will be called on the
		3118	next event loop iteration. However, that isn't as soon as possible -
		3119	without external events, your C<ev_check> watcher will not be invoked.
		3120
		3121	This is where C<ev_idle> watchers come in handy - all you need is a
		3122	single global idle watcher that is active as long as you have one active
		3123	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3124	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3125	invoked. Neither watcher alone can do that.
2674		3126
2675	=head3 Watcher-Specific Functions and Data Members	3127	=head3 Watcher-Specific Functions and Data Members
2676		3128
2677	=over 4	3129	=over 4
2678		3130
…		…
2802		3254
2803	if (timeout >= 0)	3255	if (timeout >= 0)
2804	// create/start timer	3256	// create/start timer
2805		3257
2806	// poll	3258	// poll
2807	ev_loop (EV_A_ 0);	3259	ev_run (EV_A_ 0);
2808		3260
2809	// stop timer again	3261	// stop timer again
2810	if (timeout >= 0)	3262	if (timeout >= 0)
2811	ev_timer_stop (EV_A_ &to);	3263	ev_timer_stop (EV_A_ &to);
2812		3264
…		…
2879		3331
2880	=over 4	3332	=over 4
2881		3333
2882	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3334	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2883		3335
2884	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3336	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2885		3337
2886	Configures the watcher to embed the given loop, which must be	3338	Configures the watcher to embed the given loop, which must be
2887	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3339	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2888	invoked automatically, otherwise it is the responsibility of the callback	3340	invoked automatically, otherwise it is the responsibility of the callback
2889	to invoke it (it will continue to be called until the sweep has been done,	3341	to invoke it (it will continue to be called until the sweep has been done,
2890	if you do not want that, you need to temporarily stop the embed watcher).	3342	if you do not want that, you need to temporarily stop the embed watcher).
2891		3343
2892	=item ev_embed_sweep (loop, ev_embed *)	3344	=item ev_embed_sweep (loop, ev_embed *)
2893		3345
2894	Make a single, non-blocking sweep over the embedded loop. This works	3346	Make a single, non-blocking sweep over the embedded loop. This works
2895	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3347	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2896	appropriate way for embedded loops.	3348	appropriate way for embedded loops.
2897		3349
2898	=item struct ev_loop *other [read-only]	3350	=item struct ev_loop *other [read-only]
2899		3351
2900	The embedded event loop.	3352	The embedded event loop.
…		…
2910	used).	3362	used).
2911		3363
2912	struct ev_loop *loop_hi = ev_default_init (0);	3364	struct ev_loop *loop_hi = ev_default_init (0);
2913	struct ev_loop *loop_lo = 0;	3365	struct ev_loop *loop_lo = 0;
2914	ev_embed embed;	3366	ev_embed embed;
2915		3367
2916	// see if there is a chance of getting one that works	3368	// see if there is a chance of getting one that works
2917	// (remember that a flags value of 0 means autodetection)	3369	// (remember that a flags value of 0 means autodetection)
2918	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3370	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2919	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3371	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2920	: 0;	3372	: 0;
…		…
2934	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3386	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2935		3387
2936	struct ev_loop *loop = ev_default_init (0);	3388	struct ev_loop *loop = ev_default_init (0);
2937	struct ev_loop *loop_socket = 0;	3389	struct ev_loop *loop_socket = 0;
2938	ev_embed embed;	3390	ev_embed embed;
2939		3391
2940	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3392	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2941	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3393	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2942	{	3394	{
2943	ev_embed_init (&embed, 0, loop_socket);	3395	ev_embed_init (&embed, 0, loop_socket);
2944	ev_embed_start (loop, &embed);	3396	ev_embed_start (loop, &embed);
…		…
2952		3404
2953	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3405	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2954		3406
2955	Fork watchers are called when a C<fork ()> was detected (usually because	3407	Fork watchers are called when a C<fork ()> was detected (usually because
2956	whoever is a good citizen cared to tell libev about it by calling	3408	whoever is a good citizen cared to tell libev about it by calling
2957	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3409	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2958	event loop blocks next and before C<ev_check> watchers are being called,	3410	and before C<ev_check> watchers are being called, and only in the child
2959	and only in the child after the fork. If whoever good citizen calling	3411	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2960	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3412	and calls it in the wrong process, the fork handlers will be invoked, too,
2961	handlers will be invoked, too, of course.	3413	of course.
2962		3414
2963	=head3 The special problem of life after fork - how is it possible?	3415	=head3 The special problem of life after fork - how is it possible?
2964		3416
2965	Most uses of C<fork()> consist of forking, then some simple calls to ste	3417	Most uses of C<fork ()> consist of forking, then some simple calls to set
2966	up/change the process environment, followed by a call to C<exec()>. This	3418	up/change the process environment, followed by a call to C<exec()>. This
2967	sequence should be handled by libev without any problems.	3419	sequence should be handled by libev without any problems.
2968		3420
2969	This changes when the application actually wants to do event handling	3421	This changes when the application actually wants to do event handling
2970	in the child, or both parent in child, in effect "continuing" after the	3422	in the child, or both parent in child, in effect "continuing" after the
…		…
2986	disadvantage of having to use multiple event loops (which do not support	3438	disadvantage of having to use multiple event loops (which do not support
2987	signal watchers).	3439	signal watchers).
2988		3440
2989	When this is not possible, or you want to use the default loop for	3441	When this is not possible, or you want to use the default loop for
2990	other reasons, then in the process that wants to start "fresh", call	3442	other reasons, then in the process that wants to start "fresh", call
2991	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3443	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2992	the default loop will "orphan" (not stop) all registered watchers, so you	3444	Destroying the default loop will "orphan" (not stop) all registered
2993	have to be careful not to execute code that modifies those watchers. Note	3445	watchers, so you have to be careful not to execute code that modifies
2994	also that in that case, you have to re-register any signal watchers.	3446	those watchers. Note also that in that case, you have to re-register any
		3447	signal watchers.
2995		3448
2996	=head3 Watcher-Specific Functions and Data Members	3449	=head3 Watcher-Specific Functions and Data Members
2997		3450
2998	=over 4	3451	=over 4
2999		3452
3000	=item ev_fork_init (ev_signal *, callback)	3453	=item ev_fork_init (ev_fork *, callback)
3001		3454
3002	Initialises and configures the fork watcher - it has no parameters of any	3455	Initialises and configures the fork watcher - it has no parameters of any
3003	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3456	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3004	believe me.	3457	really.
3005		3458
3006	=back	3459	=back
3007		3460
3008		3461
		3462	=head2 C<ev_cleanup> - even the best things end
		3463
		3464	Cleanup watchers are called just before the event loop is being destroyed
		3465	by a call to C<ev_loop_destroy>.
		3466
		3467	While there is no guarantee that the event loop gets destroyed, cleanup
		3468	watchers provide a convenient method to install cleanup hooks for your
		3469	program, worker threads and so on - you just to make sure to destroy the
		3470	loop when you want them to be invoked.
		3471
		3472	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3473	all other watchers, they do not keep a reference to the event loop (which
		3474	makes a lot of sense if you think about it). Like all other watchers, you
		3475	can call libev functions in the callback, except C<ev_cleanup_start>.
		3476
		3477	=head3 Watcher-Specific Functions and Data Members
		3478
		3479	=over 4
		3480
		3481	=item ev_cleanup_init (ev_cleanup *, callback)
		3482
		3483	Initialises and configures the cleanup watcher - it has no parameters of
		3484	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3485	pointless, I assure you.
		3486
		3487	=back
		3488
		3489	Example: Register an atexit handler to destroy the default loop, so any
		3490	cleanup functions are called.
		3491
		3492	static void
		3493	program_exits (void)
		3494	{
		3495	ev_loop_destroy (EV_DEFAULT_UC);
		3496	}
		3497
		3498	...
		3499	atexit (program_exits);
		3500
		3501
3009	=head2 C<ev_async> - how to wake up another event loop	3502	=head2 C<ev_async> - how to wake up an event loop
3010		3503
3011	In general, you cannot use an C<ev_loop> from multiple threads or other	3504	In general, you cannot use an C<ev_loop> from multiple threads or other
3012	asynchronous sources such as signal handlers (as opposed to multiple event	3505	asynchronous sources such as signal handlers (as opposed to multiple event
3013	loops - those are of course safe to use in different threads).	3506	loops - those are of course safe to use in different threads).
3014		3507
3015	Sometimes, however, you need to wake up another event loop you do not	3508	Sometimes, however, you need to wake up an event loop you do not control,
3016	control, for example because it belongs to another thread. This is what	3509	for example because it belongs to another thread. This is what C<ev_async>
3017	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3510	watchers do: as long as the C<ev_async> watcher is active, you can signal
3018	can signal it by calling C<ev_async_send>, which is thread- and signal	3511	it by calling C<ev_async_send>, which is thread- and signal safe.
3019	safe.
3020		3512
3021	This functionality is very similar to C<ev_signal> watchers, as signals,	3513	This functionality is very similar to C<ev_signal> watchers, as signals,
3022	too, are asynchronous in nature, and signals, too, will be compressed	3514	too, are asynchronous in nature, and signals, too, will be compressed
3023	(i.e. the number of callback invocations may be less than the number of	3515	(i.e. the number of callback invocations may be less than the number of
3024	C<ev_async_sent> calls).	3516	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3025		3517	of "global async watchers" by using a watcher on an otherwise unused
3026	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3518	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3027	just the default loop.	3519	even without knowing which loop owns the signal.
3028		3520
3029	=head3 Queueing	3521	=head3 Queueing
3030		3522
3031	C<ev_async> does not support queueing of data in any way. The reason	3523	C<ev_async> does not support queueing of data in any way. The reason
3032	is that the author does not know of a simple (or any) algorithm for a	3524	is that the author does not know of a simple (or any) algorithm for a
…		…
3124	trust me.	3616	trust me.
3125		3617
3126	=item ev_async_send (loop, ev_async *)	3618	=item ev_async_send (loop, ev_async *)
3127		3619
3128	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3620	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3129	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3621	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3622	returns.
		3623
3130	C<ev_feed_event>, this call is safe to do from other threads, signal or	3624	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3131	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3625	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3132	section below on what exactly this means).	3626	embedding section below on what exactly this means).
3133		3627
3134	Note that, as with other watchers in libev, multiple events might get	3628	Note that, as with other watchers in libev, multiple events might get
3135	compressed into a single callback invocation (another way to look at this	3629	compressed into a single callback invocation (another way to look at
3136	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3630	this is that C<ev_async> watchers are level-triggered: they are set on
3137	reset when the event loop detects that).	3631	C<ev_async_send>, reset when the event loop detects that).
3138		3632
3139	This call incurs the overhead of a system call only once per event loop	3633	This call incurs the overhead of at most one extra system call per event
3140	iteration, so while the overhead might be noticeable, it doesn't apply to	3634	loop iteration, if the event loop is blocked, and no syscall at all if
3141	repeated calls to C<ev_async_send> for the same event loop.	3635	the event loop (or your program) is processing events. That means that
		3636	repeated calls are basically free (there is no need to avoid calls for
		3637	performance reasons) and that the overhead becomes smaller (typically
		3638	zero) under load.
3142		3639
3143	=item bool = ev_async_pending (ev_async *)	3640	=item bool = ev_async_pending (ev_async *)
3144		3641
3145	Returns a non-zero value when C<ev_async_send> has been called on the	3642	Returns a non-zero value when C<ev_async_send> has been called on the
3146	watcher but the event has not yet been processed (or even noted) by the	3643	watcher but the event has not yet been processed (or even noted) by the
…		…
3163		3660
3164	There are some other functions of possible interest. Described. Here. Now.	3661	There are some other functions of possible interest. Described. Here. Now.
3165		3662
3166	=over 4	3663	=over 4
3167		3664
3168	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3665	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3169		3666
3170	This function combines a simple timer and an I/O watcher, calls your	3667	This function combines a simple timer and an I/O watcher, calls your
3171	callback on whichever event happens first and automatically stops both	3668	callback on whichever event happens first and automatically stops both
3172	watchers. This is useful if you want to wait for a single event on an fd	3669	watchers. This is useful if you want to wait for a single event on an fd
3173	or timeout without having to allocate/configure/start/stop/free one or	3670	or timeout without having to allocate/configure/start/stop/free one or
…		…
3201	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3698	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3202		3699
3203	=item ev_feed_fd_event (loop, int fd, int revents)	3700	=item ev_feed_fd_event (loop, int fd, int revents)
3204		3701
3205	Feed an event on the given fd, as if a file descriptor backend detected	3702	Feed an event on the given fd, as if a file descriptor backend detected
3206	the given events it.	3703	the given events.
3207		3704
3208	=item ev_feed_signal_event (loop, int signum)	3705	=item ev_feed_signal_event (loop, int signum)
3209		3706
3210	Feed an event as if the given signal occurred (C<loop> must be the default	3707	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3211	loop!).	3708	which is async-safe.
3212		3709
3213	=back	3710	=back
		3711
		3712
		3713	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3714
		3715	This section explains some common idioms that are not immediately
		3716	obvious. Note that examples are sprinkled over the whole manual, and this
		3717	section only contains stuff that wouldn't fit anywhere else.
		3718
		3719	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3720
		3721	Each watcher has, by default, a C<void *data> member that you can read
		3722	or modify at any time: libev will completely ignore it. This can be used
		3723	to associate arbitrary data with your watcher. If you need more data and
		3724	don't want to allocate memory separately and store a pointer to it in that
		3725	data member, you can also "subclass" the watcher type and provide your own
		3726	data:
		3727
		3728	struct my_io
		3729	{
		3730	ev_io io;
		3731	int otherfd;
		3732	void *somedata;
		3733	struct whatever *mostinteresting;
		3734	};
		3735
		3736	...
		3737	struct my_io w;
		3738	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3739
		3740	And since your callback will be called with a pointer to the watcher, you
		3741	can cast it back to your own type:
		3742
		3743	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3744	{
		3745	struct my_io *w = (struct my_io *)w_;
		3746	...
		3747	}
		3748
		3749	More interesting and less C-conformant ways of casting your callback
		3750	function type instead have been omitted.
		3751
		3752	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3753
		3754	Another common scenario is to use some data structure with multiple
		3755	embedded watchers, in effect creating your own watcher that combines
		3756	multiple libev event sources into one "super-watcher":
		3757
		3758	struct my_biggy
		3759	{
		3760	int some_data;
		3761	ev_timer t1;
		3762	ev_timer t2;
		3763	}
		3764
		3765	In this case getting the pointer to C<my_biggy> is a bit more
		3766	complicated: Either you store the address of your C<my_biggy> struct in
		3767	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3768	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3769	real programmers):
		3770
		3771	#include <stddef.h>
		3772
		3773	static void
		3774	t1_cb (EV_P_ ev_timer *w, int revents)
		3775	{
		3776	struct my_biggy big = (struct my_biggy *)
		3777	(((char *)w) - offsetof (struct my_biggy, t1));
		3778	}
		3779
		3780	static void
		3781	t2_cb (EV_P_ ev_timer *w, int revents)
		3782	{
		3783	struct my_biggy big = (struct my_biggy *)
		3784	(((char *)w) - offsetof (struct my_biggy, t2));
		3785	}
		3786
		3787	=head2 AVOIDING FINISHING BEFORE RETURNING
		3788
		3789	Often you have structures like this in event-based programs:
		3790
		3791	callback ()
		3792	{
		3793	free (request);
		3794	}
		3795
		3796	request = start_new_request (..., callback);
		3797
		3798	The intent is to start some "lengthy" operation. The C<request> could be
		3799	used to cancel the operation, or do other things with it.
		3800
		3801	It's not uncommon to have code paths in C<start_new_request> that
		3802	immediately invoke the callback, for example, to report errors. Or you add
		3803	some caching layer that finds that it can skip the lengthy aspects of the
		3804	operation and simply invoke the callback with the result.
		3805
		3806	The problem here is that this will happen I<before> C<start_new_request>
		3807	has returned, so C<request> is not set.
		3808
		3809	Even if you pass the request by some safer means to the callback, you
		3810	might want to do something to the request after starting it, such as
		3811	canceling it, which probably isn't working so well when the callback has
		3812	already been invoked.
		3813
		3814	A common way around all these issues is to make sure that
		3815	C<start_new_request> I<always> returns before the callback is invoked. If
		3816	C<start_new_request> immediately knows the result, it can artificially
		3817	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3818	example, or more sneakily, by reusing an existing (stopped) watcher and
		3819	pushing it into the pending queue:
		3820
		3821	ev_set_cb (watcher, callback);
		3822	ev_feed_event (EV_A_ watcher, 0);
		3823
		3824	This way, C<start_new_request> can safely return before the callback is
		3825	invoked, while not delaying callback invocation too much.
		3826
		3827	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3828
		3829	Often (especially in GUI toolkits) there are places where you have
		3830	I<modal> interaction, which is most easily implemented by recursively
		3831	invoking C<ev_run>.
		3832
		3833	This brings the problem of exiting - a callback might want to finish the
		3834	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3835	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3836	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3837	other combination: In these cases, a simple C<ev_break> will not work.
		3838
		3839	The solution is to maintain "break this loop" variable for each C<ev_run>
		3840	invocation, and use a loop around C<ev_run> until the condition is
		3841	triggered, using C<EVRUN_ONCE>:
		3842
		3843	// main loop
		3844	int exit_main_loop = 0;
		3845
		3846	while (!exit_main_loop)
		3847	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3848
		3849	// in a modal watcher
		3850	int exit_nested_loop = 0;
		3851
		3852	while (!exit_nested_loop)
		3853	ev_run (EV_A_ EVRUN_ONCE);
		3854
		3855	To exit from any of these loops, just set the corresponding exit variable:
		3856
		3857	// exit modal loop
		3858	exit_nested_loop = 1;
		3859
		3860	// exit main program, after modal loop is finished
		3861	exit_main_loop = 1;
		3862
		3863	// exit both
		3864	exit_main_loop = exit_nested_loop = 1;
		3865
		3866	=head2 THREAD LOCKING EXAMPLE
		3867
		3868	Here is a fictitious example of how to run an event loop in a different
		3869	thread from where callbacks are being invoked and watchers are
		3870	created/added/removed.
		3871
		3872	For a real-world example, see the C<EV::Loop::Async> perl module,
		3873	which uses exactly this technique (which is suited for many high-level
		3874	languages).
		3875
		3876	The example uses a pthread mutex to protect the loop data, a condition
		3877	variable to wait for callback invocations, an async watcher to notify the
		3878	event loop thread and an unspecified mechanism to wake up the main thread.
		3879
		3880	First, you need to associate some data with the event loop:
		3881
		3882	typedef struct {
		3883	pthread_mutex_t lock; /* global loop lock */
		3884	pthread_t tid;
		3885	pthread_cond_t invoke_cv;
		3886	ev_async async_w;
		3887	} userdata;
		3888
		3889	void prepare_loop (EV_P)
		3890	{
		3891	// for simplicity, we use a static userdata struct.
		3892	static userdata u;
		3893
		3894	ev_async_init (&u.async_w, async_cb);
		3895	ev_async_start (EV_A_ &u.async_w);
		3896
		3897	pthread_mutex_init (&u.lock, 0);
		3898	pthread_cond_init (&u.invoke_cv, 0);
		3899
		3900	// now associate this with the loop
		3901	ev_set_userdata (EV_A_ &u);
		3902	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3903	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3904
		3905	// then create the thread running ev_run
		3906	pthread_create (&u.tid, 0, l_run, EV_A);
		3907	}
		3908
		3909	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3910	solely to wake up the event loop so it takes notice of any new watchers
		3911	that might have been added:
		3912
		3913	static void
		3914	async_cb (EV_P_ ev_async *w, int revents)
		3915	{
		3916	// just used for the side effects
		3917	}
		3918
		3919	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3920	protecting the loop data, respectively.
		3921
		3922	static void
		3923	l_release (EV_P)
		3924	{
		3925	userdata *u = ev_userdata (EV_A);
		3926	pthread_mutex_unlock (&u->lock);
		3927	}
		3928
		3929	static void
		3930	l_acquire (EV_P)
		3931	{
		3932	userdata *u = ev_userdata (EV_A);
		3933	pthread_mutex_lock (&u->lock);
		3934	}
		3935
		3936	The event loop thread first acquires the mutex, and then jumps straight
		3937	into C<ev_run>:
		3938
		3939	void *
		3940	l_run (void *thr_arg)
		3941	{
		3942	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3943
		3944	l_acquire (EV_A);
		3945	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3946	ev_run (EV_A_ 0);
		3947	l_release (EV_A);
		3948
		3949	return 0;
		3950	}
		3951
		3952	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3953	signal the main thread via some unspecified mechanism (signals? pipe
		3954	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3955	have been called (in a while loop because a) spurious wakeups are possible
		3956	and b) skipping inter-thread-communication when there are no pending
		3957	watchers is very beneficial):
		3958
		3959	static void
		3960	l_invoke (EV_P)
		3961	{
		3962	userdata *u = ev_userdata (EV_A);
		3963
		3964	while (ev_pending_count (EV_A))
		3965	{
		3966	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3967	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3968	}
		3969	}
		3970
		3971	Now, whenever the main thread gets told to invoke pending watchers, it
		3972	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3973	thread to continue:
		3974
		3975	static void
		3976	real_invoke_pending (EV_P)
		3977	{
		3978	userdata *u = ev_userdata (EV_A);
		3979
		3980	pthread_mutex_lock (&u->lock);
		3981	ev_invoke_pending (EV_A);
		3982	pthread_cond_signal (&u->invoke_cv);
		3983	pthread_mutex_unlock (&u->lock);
		3984	}
		3985
		3986	Whenever you want to start/stop a watcher or do other modifications to an
		3987	event loop, you will now have to lock:
		3988
		3989	ev_timer timeout_watcher;
		3990	userdata *u = ev_userdata (EV_A);
		3991
		3992	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3993
		3994	pthread_mutex_lock (&u->lock);
		3995	ev_timer_start (EV_A_ &timeout_watcher);
		3996	ev_async_send (EV_A_ &u->async_w);
		3997	pthread_mutex_unlock (&u->lock);
		3998
		3999	Note that sending the C<ev_async> watcher is required because otherwise
		4000	an event loop currently blocking in the kernel will have no knowledge
		4001	about the newly added timer. By waking up the loop it will pick up any new
		4002	watchers in the next event loop iteration.
		4003
		4004	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		4005
		4006	While the overhead of a callback that e.g. schedules a thread is small, it
		4007	is still an overhead. If you embed libev, and your main usage is with some
		4008	kind of threads or coroutines, you might want to customise libev so that
		4009	doesn't need callbacks anymore.
		4010
		4011	Imagine you have coroutines that you can switch to using a function
		4012	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		4013	and that due to some magic, the currently active coroutine is stored in a
		4014	global called C<current_coro>. Then you can build your own "wait for libev
		4015	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		4016	the differing C<;> conventions):
		4017
		4018	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4019	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4020
		4021	That means instead of having a C callback function, you store the
		4022	coroutine to switch to in each watcher, and instead of having libev call
		4023	your callback, you instead have it switch to that coroutine.
		4024
		4025	A coroutine might now wait for an event with a function called
		4026	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		4027	matter when, or whether the watcher is active or not when this function is
		4028	called):
		4029
		4030	void
		4031	wait_for_event (ev_watcher *w)
		4032	{
		4033	ev_set_cb (w, current_coro);
		4034	switch_to (libev_coro);
		4035	}
		4036
		4037	That basically suspends the coroutine inside C<wait_for_event> and
		4038	continues the libev coroutine, which, when appropriate, switches back to
		4039	this or any other coroutine.
		4040
		4041	You can do similar tricks if you have, say, threads with an event queue -
		4042	instead of storing a coroutine, you store the queue object and instead of
		4043	switching to a coroutine, you push the watcher onto the queue and notify
		4044	any waiters.
		4045
		4046	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		4047	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		4048
		4049	// my_ev.h
		4050	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4051	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4052	#include "../libev/ev.h"
		4053
		4054	// my_ev.c
		4055	#define EV_H "my_ev.h"
		4056	#include "../libev/ev.c"
		4057
		4058	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4059	F<my_ev.c> into your project. When properly specifying include paths, you
		4060	can even use F<ev.h> as header file name directly.
3214		4061
3215		4062
3216	=head1 LIBEVENT EMULATION	4063	=head1 LIBEVENT EMULATION
3217		4064
3218	Libev offers a compatibility emulation layer for libevent. It cannot	4065	Libev offers a compatibility emulation layer for libevent. It cannot
3219	emulate the internals of libevent, so here are some usage hints:	4066	emulate the internals of libevent, so here are some usage hints:
3220		4067
3221	=over 4	4068	=over 4
		4069
		4070	=item * Only the libevent-1.4.1-beta API is being emulated.
		4071
		4072	This was the newest libevent version available when libev was implemented,
		4073	and is still mostly unchanged in 2010.
3222		4074
3223	=item * Use it by including <event.h>, as usual.	4075	=item * Use it by including <event.h>, as usual.
3224		4076
3225	=item * The following members are fully supported: ev_base, ev_callback,	4077	=item * The following members are fully supported: ev_base, ev_callback,
3226	ev_arg, ev_fd, ev_res, ev_events.	4078	ev_arg, ev_fd, ev_res, ev_events.
…		…
3232	=item * Priorities are not currently supported. Initialising priorities	4084	=item * Priorities are not currently supported. Initialising priorities
3233	will fail and all watchers will have the same priority, even though there	4085	will fail and all watchers will have the same priority, even though there
3234	is an ev_pri field.	4086	is an ev_pri field.
3235		4087
3236	=item * In libevent, the last base created gets the signals, in libev, the	4088	=item * In libevent, the last base created gets the signals, in libev, the
3237	first base created (== the default loop) gets the signals.	4089	base that registered the signal gets the signals.
3238		4090
3239	=item * Other members are not supported.	4091	=item * Other members are not supported.
3240		4092
3241	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4093	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3242	to use the libev header file and library.	4094	to use the libev header file and library.
3243		4095
3244	=back	4096	=back
3245		4097
3246	=head1 C++ SUPPORT	4098	=head1 C++ SUPPORT
		4099
		4100	=head2 C API
		4101
		4102	The normal C API should work fine when used from C++: both ev.h and the
		4103	libev sources can be compiled as C++. Therefore, code that uses the C API
		4104	will work fine.
		4105
		4106	Proper exception specifications might have to be added to callbacks passed
		4107	to libev: exceptions may be thrown only from watcher callbacks, all other
		4108	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4109	callbacks) must not throw exceptions, and might need a C<noexcept>
		4110	specification. If you have code that needs to be compiled as both C and
		4111	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4112
		4113	static void
		4114	fatal_error (const char *msg) EV_NOEXCEPT
		4115	{
		4116	perror (msg);
		4117	abort ();
		4118	}
		4119
		4120	...
		4121	ev_set_syserr_cb (fatal_error);
		4122
		4123	The only API functions that can currently throw exceptions are C<ev_run>,
		4124	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4125	because it runs cleanup watchers).
		4126
		4127	Throwing exceptions in watcher callbacks is only supported if libev itself
		4128	is compiled with a C++ compiler or your C and C++ environments allow
		4129	throwing exceptions through C libraries (most do).
		4130
		4131	=head2 C++ API
3247		4132
3248	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4133	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3249	you to use some convenience methods to start/stop watchers and also change	4134	you to use some convenience methods to start/stop watchers and also change
3250	the callback model to a model using method callbacks on objects.	4135	the callback model to a model using method callbacks on objects.
3251		4136
3252	To use it,	4137	To use it,
3253		4138
3254	#include <ev++.h>	4139	#include <ev++.h>
3255		4140
3256	This automatically includes F<ev.h> and puts all of its definitions (many	4141	This automatically includes F<ev.h> and puts all of its definitions (many
3257	of them macros) into the global namespace. All C++ specific things are	4142	of them macros) into the global namespace. All C++ specific things are
3258	put into the C<ev> namespace. It should support all the same embedding	4143	put into the C<ev> namespace. It should support all the same embedding
…		…
3261	Care has been taken to keep the overhead low. The only data member the C++	4146	Care has been taken to keep the overhead low. The only data member the C++
3262	classes add (compared to plain C-style watchers) is the event loop pointer	4147	classes add (compared to plain C-style watchers) is the event loop pointer
3263	that the watcher is associated with (or no additional members at all if	4148	that the watcher is associated with (or no additional members at all if
3264	you disable C<EV_MULTIPLICITY> when embedding libev).	4149	you disable C<EV_MULTIPLICITY> when embedding libev).
3265		4150
3266	Currently, functions, and static and non-static member functions can be	4151	Currently, functions, static and non-static member functions and classes
3267	used as callbacks. Other types should be easy to add as long as they only	4152	with C<operator ()> can be used as callbacks. Other types should be easy
3268	need one additional pointer for context. If you need support for other	4153	to add as long as they only need one additional pointer for context. If
3269	types of functors please contact the author (preferably after implementing	4154	you need support for other types of functors please contact the author
3270	it).	4155	(preferably after implementing it).
		4156
		4157	For all this to work, your C++ compiler either has to use the same calling
		4158	conventions as your C compiler (for static member functions), or you have
		4159	to embed libev and compile libev itself as C++.
3271		4160
3272	Here is a list of things available in the C<ev> namespace:	4161	Here is a list of things available in the C<ev> namespace:
3273		4162
3274	=over 4	4163	=over 4
3275		4164
…		…
3285	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4174	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3286		4175
3287	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4176	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3288	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4177	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3289	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4178	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3290	defines by many implementations.	4179	defined by many implementations.
3291		4180
3292	All of those classes have these methods:	4181	All of those classes have these methods:
3293		4182
3294	=over 4	4183	=over 4
3295		4184
…		…
3336	myclass obj;	4225	myclass obj;
3337	ev::io iow;	4226	ev::io iow;
3338	iow.set <myclass, &myclass::io_cb> (&obj);	4227	iow.set <myclass, &myclass::io_cb> (&obj);
3339		4228
3340	=item w->set (object *)	4229	=item w->set (object *)
3341
3342	This is an B<experimental> feature that might go away in a future version.
3343		4230
3344	This is a variation of a method callback - leaving out the method to call	4231	This is a variation of a method callback - leaving out the method to call
3345	will default the method to C<operator ()>, which makes it possible to use	4232	will default the method to C<operator ()>, which makes it possible to use
3346	functor objects without having to manually specify the C<operator ()> all	4233	functor objects without having to manually specify the C<operator ()> all
3347	the time. Incidentally, you can then also leave out the template argument	4234	the time. Incidentally, you can then also leave out the template argument
…		…
3359	void operator() (ev::io &w, int revents)	4246	void operator() (ev::io &w, int revents)
3360	{	4247	{
3361	...	4248	...
3362	}	4249	}
3363	}	4250	}
3364		4251
3365	myfunctor f;	4252	myfunctor f;
3366		4253
3367	ev::io w;	4254	ev::io w;
3368	w.set (&f);	4255	w.set (&f);
3369		4256
…		…
3387	Associates a different C<struct ev_loop> with this watcher. You can only	4274	Associates a different C<struct ev_loop> with this watcher. You can only
3388	do this when the watcher is inactive (and not pending either).	4275	do this when the watcher is inactive (and not pending either).
3389		4276
3390	=item w->set ([arguments])	4277	=item w->set ([arguments])
3391		4278
3392	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4279	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4280	with the same arguments. Either this method or a suitable start method
3393	called at least once. Unlike the C counterpart, an active watcher gets	4281	must be called at least once. Unlike the C counterpart, an active watcher
3394	automatically stopped and restarted when reconfiguring it with this	4282	gets automatically stopped and restarted when reconfiguring it with this
3395	method.	4283	method.
		4284
		4285	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4286	clashing with the C<set (loop)> method.
		4287
		4288	For C<ev::io> watchers there is an additional C<set> method that acepts a
		4289	new event mask only, and internally calls C<ev_io_modify>.
3396		4290
3397	=item w->start ()	4291	=item w->start ()
3398		4292
3399	Starts the watcher. Note that there is no C<loop> argument, as the	4293	Starts the watcher. Note that there is no C<loop> argument, as the
3400	constructor already stores the event loop.	4294	constructor already stores the event loop.
3401		4295
		4296	=item w->start ([arguments])
		4297
		4298	Instead of calling C<set> and C<start> methods separately, it is often
		4299	convenient to wrap them in one call. Uses the same type of arguments as
		4300	the configure C<set> method of the watcher.
		4301
3402	=item w->stop ()	4302	=item w->stop ()
3403		4303
3404	Stops the watcher if it is active. Again, no C<loop> argument.	4304	Stops the watcher if it is active. Again, no C<loop> argument.
3405		4305
3406	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4306	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3418		4318
3419	=back	4319	=back
3420		4320
3421	=back	4321	=back
3422		4322
3423	Example: Define a class with an IO and idle watcher, start one of them in	4323	Example: Define a class with two I/O and idle watchers, start the I/O
3424	the constructor.	4324	watchers in the constructor.
3425		4325
3426	class myclass	4326	class myclass
3427	{	4327	{
3428	ev::io io ; void io_cb (ev::io &w, int revents);	4328	ev::io io ; void io_cb (ev::io &w, int revents);
		4329	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3429	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4330	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3430		4331
3431	myclass (int fd)	4332	myclass (int fd)
3432	{	4333	{
3433	io .set <myclass, &myclass::io_cb > (this);	4334	io .set <myclass, &myclass::io_cb > (this);
		4335	io2 .set <myclass, &myclass::io2_cb > (this);
3434	idle.set <myclass, &myclass::idle_cb> (this);	4336	idle.set <myclass, &myclass::idle_cb> (this);
3435		4337
3436	io.start (fd, ev::READ);	4338	io.set (fd, ev::WRITE); // configure the watcher
		4339	io.start (); // start it whenever convenient
		4340
		4341	io2.start (fd, ev::READ); // set + start in one call
3437	}	4342	}
3438	};	4343	};
3439		4344
3440		4345
3441	=head1 OTHER LANGUAGE BINDINGS	4346	=head1 OTHER LANGUAGE BINDINGS
…		…
3480	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4385	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3481		4386
3482	=item D	4387	=item D
3483		4388
3484	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4389	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3485	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4390	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3486		4391
3487	=item Ocaml	4392	=item Ocaml
3488		4393
3489	Erkki Seppala has written Ocaml bindings for libev, to be found at	4394	Erkki Seppala has written Ocaml bindings for libev, to be found at
3490	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4395	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3493		4398
3494	Brian Maher has written a partial interface to libev for lua (at the	4399	Brian Maher has written a partial interface to libev for lua (at the
3495	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4400	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3496	L<http://github.com/brimworks/lua-ev>.	4401	L<http://github.com/brimworks/lua-ev>.
3497		4402
		4403	=item Javascript
		4404
		4405	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4406
		4407	=item Others
		4408
		4409	There are others, and I stopped counting.
		4410
3498	=back	4411	=back
3499		4412
3500		4413
3501	=head1 MACRO MAGIC	4414	=head1 MACRO MAGIC
3502		4415
…		…
3515	loop argument"). The C<EV_A> form is used when this is the sole argument,	4428	loop argument"). The C<EV_A> form is used when this is the sole argument,
3516	C<EV_A_> is used when other arguments are following. Example:	4429	C<EV_A_> is used when other arguments are following. Example:
3517		4430
3518	ev_unref (EV_A);	4431	ev_unref (EV_A);
3519	ev_timer_add (EV_A_ watcher);	4432	ev_timer_add (EV_A_ watcher);
3520	ev_loop (EV_A_ 0);	4433	ev_run (EV_A_ 0);
3521		4434
3522	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4435	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3523	which is often provided by the following macro.	4436	which is often provided by the following macro.
3524		4437
3525	=item C<EV_P>, C<EV_P_>	4438	=item C<EV_P>, C<EV_P_>
…		…
3538	suitable for use with C<EV_A>.	4451	suitable for use with C<EV_A>.
3539		4452
3540	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4453	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3541		4454
3542	Similar to the other two macros, this gives you the value of the default	4455	Similar to the other two macros, this gives you the value of the default
3543	loop, if multiple loops are supported ("ev loop default").	4456	loop, if multiple loops are supported ("ev loop default"). The default loop
		4457	will be initialised if it isn't already initialised.
		4458
		4459	For non-multiplicity builds, these macros do nothing, so you always have
		4460	to initialise the loop somewhere.
3544		4461
3545	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4462	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3546		4463
3547	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4464	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3548	default loop has been initialised (C<UC> == unchecked). Their behaviour	4465	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3565	}	4482	}
3566		4483
3567	ev_check check;	4484	ev_check check;
3568	ev_check_init (&check, check_cb);	4485	ev_check_init (&check, check_cb);
3569	ev_check_start (EV_DEFAULT_ &check);	4486	ev_check_start (EV_DEFAULT_ &check);
3570	ev_loop (EV_DEFAULT_ 0);	4487	ev_run (EV_DEFAULT_ 0);
3571		4488
3572	=head1 EMBEDDING	4489	=head1 EMBEDDING
3573		4490
3574	Libev can (and often is) directly embedded into host	4491	Libev can (and often is) directly embedded into host
3575	applications. Examples of applications that embed it include the Deliantra	4492	applications. Examples of applications that embed it include the Deliantra
…		…
3615	ev_vars.h	4532	ev_vars.h
3616	ev_wrap.h	4533	ev_wrap.h
3617		4534
3618	ev_win32.c required on win32 platforms only	4535	ev_win32.c required on win32 platforms only
3619		4536
3620	ev_select.c only when select backend is enabled (which is enabled by default)	4537	ev_select.c only when select backend is enabled
3621	ev_poll.c only when poll backend is enabled (disabled by default)	4538	ev_poll.c only when poll backend is enabled
3622	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4539	ev_epoll.c only when the epoll backend is enabled
		4540	ev_linuxaio.c only when the linux aio backend is enabled
		4541	ev_iouring.c only when the linux io_uring backend is enabled
3623	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4542	ev_kqueue.c only when the kqueue backend is enabled
3624	ev_port.c only when the solaris port backend is enabled (disabled by default)	4543	ev_port.c only when the solaris port backend is enabled
3625		4544
3626	F<ev.c> includes the backend files directly when enabled, so you only need	4545	F<ev.c> includes the backend files directly when enabled, so you only need
3627	to compile this single file.	4546	to compile this single file.
3628		4547
3629	=head3 LIBEVENT COMPATIBILITY API	4548	=head3 LIBEVENT COMPATIBILITY API
…		…
3660	define before including (or compiling) any of its files. The default in	4579	define before including (or compiling) any of its files. The default in
3661	the absence of autoconf is documented for every option.	4580	the absence of autoconf is documented for every option.
3662		4581
3663	Symbols marked with "(h)" do not change the ABI, and can have different	4582	Symbols marked with "(h)" do not change the ABI, and can have different
3664	values when compiling libev vs. including F<ev.h>, so it is permissible	4583	values when compiling libev vs. including F<ev.h>, so it is permissible
3665	to redefine them before including F<ev.h> without breakign compatibility	4584	to redefine them before including F<ev.h> without breaking compatibility
3666	to a compiled library. All other symbols change the ABI, which means all	4585	to a compiled library. All other symbols change the ABI, which means all
3667	users of libev and the libev code itself must be compiled with compatible	4586	users of libev and the libev code itself must be compiled with compatible
3668	settings.	4587	settings.
3669		4588
3670	=over 4	4589	=over 4
		4590
		4591	=item EV_COMPAT3 (h)
		4592
		4593	Backwards compatibility is a major concern for libev. This is why this
		4594	release of libev comes with wrappers for the functions and symbols that
		4595	have been renamed between libev version 3 and 4.
		4596
		4597	You can disable these wrappers (to test compatibility with future
		4598	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4599	sources. This has the additional advantage that you can drop the C<struct>
		4600	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4601	typedef in that case.
		4602
		4603	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4604	and in some even more future version the compatibility code will be
		4605	removed completely.
3671		4606
3672	=item EV_STANDALONE (h)	4607	=item EV_STANDALONE (h)
3673		4608
3674	Must always be C<1> if you do not use autoconf configuration, which	4609	Must always be C<1> if you do not use autoconf configuration, which
3675	keeps libev from including F<config.h>, and it also defines dummy	4610	keeps libev from including F<config.h>, and it also defines dummy
…		…
3677	supported). It will also not define any of the structs usually found in	4612	supported). It will also not define any of the structs usually found in
3678	F<event.h> that are not directly supported by the libev core alone.	4613	F<event.h> that are not directly supported by the libev core alone.
3679		4614
3680	In standalone mode, libev will still try to automatically deduce the	4615	In standalone mode, libev will still try to automatically deduce the
3681	configuration, but has to be more conservative.	4616	configuration, but has to be more conservative.
		4617
		4618	=item EV_USE_FLOOR
		4619
		4620	If defined to be C<1>, libev will use the C<floor ()> function for its
		4621	periodic reschedule calculations, otherwise libev will fall back on a
		4622	portable (slower) implementation. If you enable this, you usually have to
		4623	link against libm or something equivalent. Enabling this when the C<floor>
		4624	function is not available will fail, so the safe default is to not enable
		4625	this.
3682		4626
3683	=item EV_USE_MONOTONIC	4627	=item EV_USE_MONOTONIC
3684		4628
3685	If defined to be C<1>, libev will try to detect the availability of the	4629	If defined to be C<1>, libev will try to detect the availability of the
3686	monotonic clock option at both compile time and runtime. Otherwise no	4630	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3723	available and will probe for kernel support at runtime. This will improve	4667	available and will probe for kernel support at runtime. This will improve
3724	C<ev_signal> and C<ev_async> performance and reduce resource consumption.	4668	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
3725	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc	4669	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
3726	2.7 or newer, otherwise disabled.	4670	2.7 or newer, otherwise disabled.
3727		4671
		4672	=item EV_USE_SIGNALFD
		4673
		4674	If defined to be C<1>, then libev will assume that C<signalfd ()> is
		4675	available and will probe for kernel support at runtime. This enables
		4676	the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If
		4677	undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4678	2.7 or newer, otherwise disabled.
		4679
		4680	=item EV_USE_TIMERFD
		4681
		4682	If defined to be C<1>, then libev will assume that C<timerfd ()> is
		4683	available and will probe for kernel support at runtime. This allows
		4684	libev to detect time jumps accurately. If undefined, it will be enabled
		4685	if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
		4686	C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled.
		4687
		4688	=item EV_USE_EVENTFD
		4689
		4690	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		4691	available and will probe for kernel support at runtime. This will improve
		4692	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		4693	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4694	2.7 or newer, otherwise disabled.
		4695
3728	=item EV_USE_SELECT	4696	=item EV_USE_SELECT
3729		4697
3730	If undefined or defined to be C<1>, libev will compile in support for the	4698	If undefined or defined to be C<1>, libev will compile in support for the
3731	C<select>(2) backend. No attempt at auto-detection will be done: if no	4699	C<select>(2) backend. No attempt at auto-detection will be done: if no
3732	other method takes over, select will be it. Otherwise the select backend	4700	other method takes over, select will be it. Otherwise the select backend
…		…
3772	If programs implement their own fd to handle mapping on win32, then this	4740	If programs implement their own fd to handle mapping on win32, then this
3773	macro can be used to override the C<close> function, useful to unregister	4741	macro can be used to override the C<close> function, useful to unregister
3774	file descriptors again. Note that the replacement function has to close	4742	file descriptors again. Note that the replacement function has to close
3775	the underlying OS handle.	4743	the underlying OS handle.
3776		4744
		4745	=item EV_USE_WSASOCKET
		4746
		4747	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4748	communication socket, which works better in some environments. Otherwise,
		4749	the normal C<socket> function will be used, which works better in other
		4750	environments.
		4751
3777	=item EV_USE_POLL	4752	=item EV_USE_POLL
3778		4753
3779	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4754	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3780	backend. Otherwise it will be enabled on non-win32 platforms. It	4755	backend. Otherwise it will be enabled on non-win32 platforms. It
3781	takes precedence over select.	4756	takes precedence over select.
…		…
3785	If defined to be C<1>, libev will compile in support for the Linux	4760	If defined to be C<1>, libev will compile in support for the Linux
3786	C<epoll>(7) backend. Its availability will be detected at runtime,	4761	C<epoll>(7) backend. Its availability will be detected at runtime,
3787	otherwise another method will be used as fallback. This is the preferred	4762	otherwise another method will be used as fallback. This is the preferred
3788	backend for GNU/Linux systems. If undefined, it will be enabled if the	4763	backend for GNU/Linux systems. If undefined, it will be enabled if the
3789	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4764	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4765
		4766	=item EV_USE_LINUXAIO
		4767
		4768	If defined to be C<1>, libev will compile in support for the Linux aio
		4769	backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be
		4770	enabled on linux, otherwise disabled.
		4771
		4772	=item EV_USE_IOURING
		4773
		4774	If defined to be C<1>, libev will compile in support for the Linux
		4775	io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's
		4776	current limitations it has to be requested explicitly. If undefined, it
		4777	will be enabled on linux, otherwise disabled.
3790		4778
3791	=item EV_USE_KQUEUE	4779	=item EV_USE_KQUEUE
3792		4780
3793	If defined to be C<1>, libev will compile in support for the BSD style	4781	If defined to be C<1>, libev will compile in support for the BSD style
3794	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4782	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3816	If defined to be C<1>, libev will compile in support for the Linux inotify	4804	If defined to be C<1>, libev will compile in support for the Linux inotify
3817	interface to speed up C<ev_stat> watchers. Its actual availability will	4805	interface to speed up C<ev_stat> watchers. Its actual availability will
3818	be detected at runtime. If undefined, it will be enabled if the headers	4806	be detected at runtime. If undefined, it will be enabled if the headers
3819	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4807	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3820		4808
		4809	=item EV_NO_SMP
		4810
		4811	If defined to be C<1>, libev will assume that memory is always coherent
		4812	between threads, that is, threads can be used, but threads never run on
		4813	different cpus (or different cpu cores). This reduces dependencies
		4814	and makes libev faster.
		4815
		4816	=item EV_NO_THREADS
		4817
		4818	If defined to be C<1>, libev will assume that it will never be called from
		4819	different threads (that includes signal handlers), which is a stronger
		4820	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4821	libev faster.
		4822
3821	=item EV_ATOMIC_T	4823	=item EV_ATOMIC_T
3822		4824
3823	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4825	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3824	access is atomic with respect to other threads or signal contexts. No such	4826	access is atomic with respect to other threads or signal contexts. No
3825	type is easily found in the C language, so you can provide your own type	4827	such type is easily found in the C language, so you can provide your own
3826	that you know is safe for your purposes. It is used both for signal handler "locking"	4828	type that you know is safe for your purposes. It is used both for signal
3827	as well as for signal and thread safety in C<ev_async> watchers.	4829	handler "locking" as well as for signal and thread safety in C<ev_async>
		4830	watchers.
3828		4831
3829	In the absence of this define, libev will use C<sig_atomic_t volatile>	4832	In the absence of this define, libev will use C<sig_atomic_t volatile>
3830	(from F<signal.h>), which is usually good enough on most platforms.	4833	(from F<signal.h>), which is usually good enough on most platforms.
3831		4834
3832	=item EV_H (h)	4835	=item EV_H (h)
…		…
3859	will have the C<struct ev_loop *> as first argument, and you can create	4862	will have the C<struct ev_loop *> as first argument, and you can create
3860	additional independent event loops. Otherwise there will be no support	4863	additional independent event loops. Otherwise there will be no support
3861	for multiple event loops and there is no first event loop pointer	4864	for multiple event loops and there is no first event loop pointer
3862	argument. Instead, all functions act on the single default loop.	4865	argument. Instead, all functions act on the single default loop.
3863		4866
		4867	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4868	default loop when multiplicity is switched off - you always have to
		4869	initialise the loop manually in this case.
		4870
3864	=item EV_MINPRI	4871	=item EV_MINPRI
3865		4872
3866	=item EV_MAXPRI	4873	=item EV_MAXPRI
3867		4874
3868	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4875	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3882	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,	4889	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3883	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.	4890	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3884		4891
3885	If undefined or defined to be C<1> (and the platform supports it), then	4892	If undefined or defined to be C<1> (and the platform supports it), then
3886	the respective watcher type is supported. If defined to be C<0>, then it	4893	the respective watcher type is supported. If defined to be C<0>, then it
3887	is not. Disabling watcher types mainly saves codesize.	4894	is not. Disabling watcher types mainly saves code size.
3888		4895
3889	=item EV_FEATURES	4896	=item EV_FEATURES
3890		4897
3891	If you need to shave off some kilobytes of code at the expense of some	4898	If you need to shave off some kilobytes of code at the expense of some
3892	speed (but with the full API), you can define this symbol to request	4899	speed (but with the full API), you can define this symbol to request
…		…
3904	#define EV_USE_POLL 1	4911	#define EV_USE_POLL 1
3905	#define EV_CHILD_ENABLE 1	4912	#define EV_CHILD_ENABLE 1
3906	#define EV_ASYNC_ENABLE 1	4913	#define EV_ASYNC_ENABLE 1
3907		4914
3908	The actual value is a bitset, it can be a combination of the following	4915	The actual value is a bitset, it can be a combination of the following
3909	values:	4916	values (by default, all of these are enabled):
3910		4917
3911	=over 4	4918	=over 4
3912		4919
3913	=item C<1> - faster/larger code	4920	=item C<1> - faster/larger code
3914		4921
3915	Use larger code to speed up some operations.	4922	Use larger code to speed up some operations.
3916		4923
3917	Currently this is used to override some inlining decisions (enlarging the roughly	4924	Currently this is used to override some inlining decisions (enlarging the
3918	30% code size on amd64.	4925	code size by roughly 30% on amd64).
3919		4926
3920	When optimising for size, use of compiler flags such as C<-Os> with	4927	When optimising for size, use of compiler flags such as C<-Os> with
3921	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of	4928	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3922	assertions.	4929	assertions.
3923		4930
		4931	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4932	(e.g. gcc with C<-Os>).
		4933
3924	=item C<2> - faster/larger data structures	4934	=item C<2> - faster/larger data structures
3925		4935
3926	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4936	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3927	hash table sizes and so on. This will usually further increase codesize	4937	hash table sizes and so on. This will usually further increase code size
3928	and can additionally have an effect on the size of data structures at	4938	and can additionally have an effect on the size of data structures at
3929	runtime.	4939	runtime.
		4940
		4941	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4942	(e.g. gcc with C<-Os>).
3930		4943
3931	=item C<4> - full API configuration	4944	=item C<4> - full API configuration
3932		4945
3933	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4946	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3934	enables multiplicity (C<EV_MULTIPLICITY>=1).	4947	enables multiplicity (C<EV_MULTIPLICITY>=1).
…		…
3966	With an intelligent-enough linker (gcc+binutils are intelligent enough	4979	With an intelligent-enough linker (gcc+binutils are intelligent enough
3967	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4980	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3968	your program might be left out as well - a binary starting a timer and an	4981	your program might be left out as well - a binary starting a timer and an
3969	I/O watcher then might come out at only 5Kb.	4982	I/O watcher then might come out at only 5Kb.
3970		4983
		4984	=item EV_API_STATIC
		4985
		4986	If this symbol is defined (by default it is not), then all identifiers
		4987	will have static linkage. This means that libev will not export any
		4988	identifiers, and you cannot link against libev anymore. This can be useful
		4989	when you embed libev, only want to use libev functions in a single file,
		4990	and do not want its identifiers to be visible.
		4991
		4992	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4993	wants to use libev.
		4994
		4995	This option only works when libev is compiled with a C compiler, as C++
		4996	doesn't support the required declaration syntax.
		4997
3971	=item EV_AVOID_STDIO	4998	=item EV_AVOID_STDIO
3972		4999
3973	If this is set to C<1> at compiletime, then libev will avoid using stdio	5000	If this is set to C<1> at compiletime, then libev will avoid using stdio
3974	functions (printf, scanf, perror etc.). This will increase the codesize	5001	functions (printf, scanf, perror etc.). This will increase the code size
3975	somewhat, but if your program doesn't otherwise depend on stdio and your	5002	somewhat, but if your program doesn't otherwise depend on stdio and your
3976	libc allows it, this avoids linking in the stdio library which is quite	5003	libc allows it, this avoids linking in the stdio library which is quite
3977	big.	5004	big.
3978		5005
3979	Note that error messages might become less precise when this option is	5006	Note that error messages might become less precise when this option is
…		…
3983		5010
3984	The highest supported signal number, +1 (or, the number of	5011	The highest supported signal number, +1 (or, the number of
3985	signals): Normally, libev tries to deduce the maximum number of signals	5012	signals): Normally, libev tries to deduce the maximum number of signals
3986	automatically, but sometimes this fails, in which case it can be	5013	automatically, but sometimes this fails, in which case it can be
3987	specified. Also, using a lower number than detected (C<32> should be	5014	specified. Also, using a lower number than detected (C<32> should be
3988	good for about any system in existance) can save some memory, as libev	5015	good for about any system in existence) can save some memory, as libev
3989	statically allocates some 12-24 bytes per signal number.	5016	statically allocates some 12-24 bytes per signal number.
3990		5017
3991	=item EV_PID_HASHSIZE	5018	=item EV_PID_HASHSIZE
3992		5019
3993	C<ev_child> watchers use a small hash table to distribute workload by	5020	C<ev_child> watchers use a small hash table to distribute workload by
…		…
4025	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	5052	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4026	will be C<0>.	5053	will be C<0>.
4027		5054
4028	=item EV_VERIFY	5055	=item EV_VERIFY
4029		5056
4030	Controls how much internal verification (see C<ev_loop_verify ()>) will	5057	Controls how much internal verification (see C<ev_verify ()>) will
4031	be done: If set to C<0>, no internal verification code will be compiled	5058	be done: If set to C<0>, no internal verification code will be compiled
4032	in. If set to C<1>, then verification code will be compiled in, but not	5059	in. If set to C<1>, then verification code will be compiled in, but not
4033	called. If set to C<2>, then the internal verification code will be	5060	called. If set to C<2>, then the internal verification code will be
4034	called once per loop, which can slow down libev. If set to C<3>, then the	5061	called once per loop, which can slow down libev. If set to C<3>, then the
4035	verification code will be called very frequently, which will slow down	5062	verification code will be called very frequently, which will slow down
4036	libev considerably.	5063	libev considerably.
4037		5064
		5065	Verification errors are reported via C's C<assert> mechanism, so if you
		5066	disable that (e.g. by defining C<NDEBUG>) then no errors will be reported.
		5067
4038	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	5068	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4039	will be C<0>.	5069	will be C<0>.
4040		5070
4041	=item EV_COMMON	5071	=item EV_COMMON
4042		5072
4043	By default, all watchers have a C<void *data> member. By redefining	5073	By default, all watchers have a C<void *data> member. By redefining
4044	this macro to a something else you can include more and other types of	5074	this macro to something else you can include more and other types of
4045	members. You have to define it each time you include one of the files,	5075	members. You have to define it each time you include one of the files,
4046	though, and it must be identical each time.	5076	though, and it must be identical each time.
4047		5077
4048	For example, the perl EV module uses something like this:	5078	For example, the perl EV module uses something like this:
4049		5079
…		…
4118	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5148	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4119		5149
4120	#include "ev_cpp.h"	5150	#include "ev_cpp.h"
4121	#include "ev.c"	5151	#include "ev.c"
4122		5152
4123	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5153	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4124		5154
4125	=head2 THREADS AND COROUTINES	5155	=head2 THREADS AND COROUTINES
4126		5156
4127	=head3 THREADS	5157	=head3 THREADS
4128		5158
…		…
4179	default loop and triggering an C<ev_async> watcher from the default loop	5209	default loop and triggering an C<ev_async> watcher from the default loop
4180	watcher callback into the event loop interested in the signal.	5210	watcher callback into the event loop interested in the signal.
4181		5211
4182	=back	5212	=back
4183		5213
4184	=head4 THREAD LOCKING EXAMPLE	5214	See also L</THREAD LOCKING EXAMPLE>.
4185
4186	Here is a fictitious example of how to run an event loop in a different
4187	thread than where callbacks are being invoked and watchers are
4188	created/added/removed.
4189
4190	For a real-world example, see the C<EV::Loop::Async> perl module,
4191	which uses exactly this technique (which is suited for many high-level
4192	languages).
4193
4194	The example uses a pthread mutex to protect the loop data, a condition
4195	variable to wait for callback invocations, an async watcher to notify the
4196	event loop thread and an unspecified mechanism to wake up the main thread.
4197
4198	First, you need to associate some data with the event loop:
4199
4200	typedef struct {
4201	mutex_t lock; /* global loop lock */
4202	ev_async async_w;
4203	thread_t tid;
4204	cond_t invoke_cv;
4205	} userdata;
4206
4207	void prepare_loop (EV_P)
4208	{
4209	// for simplicity, we use a static userdata struct.
4210	static userdata u;
4211
4212	ev_async_init (&u->async_w, async_cb);
4213	ev_async_start (EV_A_ &u->async_w);
4214
4215	pthread_mutex_init (&u->lock, 0);
4216	pthread_cond_init (&u->invoke_cv, 0);
4217
4218	// now associate this with the loop
4219	ev_set_userdata (EV_A_ u);
4220	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4221	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4222
4223	// then create the thread running ev_loop
4224	pthread_create (&u->tid, 0, l_run, EV_A);
4225	}
4226
4227	The callback for the C<ev_async> watcher does nothing: the watcher is used
4228	solely to wake up the event loop so it takes notice of any new watchers
4229	that might have been added:
4230
4231	static void
4232	async_cb (EV_P_ ev_async *w, int revents)
4233	{
4234	// just used for the side effects
4235	}
4236
4237	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4238	protecting the loop data, respectively.
4239
4240	static void
4241	l_release (EV_P)
4242	{
4243	userdata *u = ev_userdata (EV_A);
4244	pthread_mutex_unlock (&u->lock);
4245	}
4246
4247	static void
4248	l_acquire (EV_P)
4249	{
4250	userdata *u = ev_userdata (EV_A);
4251	pthread_mutex_lock (&u->lock);
4252	}
4253
4254	The event loop thread first acquires the mutex, and then jumps straight
4255	into C<ev_loop>:
4256
4257	void *
4258	l_run (void *thr_arg)
4259	{
4260	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4261
4262	l_acquire (EV_A);
4263	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4264	ev_loop (EV_A_ 0);
4265	l_release (EV_A);
4266
4267	return 0;
4268	}
4269
4270	Instead of invoking all pending watchers, the C<l_invoke> callback will
4271	signal the main thread via some unspecified mechanism (signals? pipe
4272	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4273	have been called (in a while loop because a) spurious wakeups are possible
4274	and b) skipping inter-thread-communication when there are no pending
4275	watchers is very beneficial):
4276
4277	static void
4278	l_invoke (EV_P)
4279	{
4280	userdata *u = ev_userdata (EV_A);
4281
4282	while (ev_pending_count (EV_A))
4283	{
4284	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4285	pthread_cond_wait (&u->invoke_cv, &u->lock);
4286	}
4287	}
4288
4289	Now, whenever the main thread gets told to invoke pending watchers, it
4290	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4291	thread to continue:
4292
4293	static void
4294	real_invoke_pending (EV_P)
4295	{
4296	userdata *u = ev_userdata (EV_A);
4297
4298	pthread_mutex_lock (&u->lock);
4299	ev_invoke_pending (EV_A);
4300	pthread_cond_signal (&u->invoke_cv);
4301	pthread_mutex_unlock (&u->lock);
4302	}
4303
4304	Whenever you want to start/stop a watcher or do other modifications to an
4305	event loop, you will now have to lock:
4306
4307	ev_timer timeout_watcher;
4308	userdata *u = ev_userdata (EV_A);
4309
4310	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4311
4312	pthread_mutex_lock (&u->lock);
4313	ev_timer_start (EV_A_ &timeout_watcher);
4314	ev_async_send (EV_A_ &u->async_w);
4315	pthread_mutex_unlock (&u->lock);
4316
4317	Note that sending the C<ev_async> watcher is required because otherwise
4318	an event loop currently blocking in the kernel will have no knowledge
4319	about the newly added timer. By waking up the loop it will pick up any new
4320	watchers in the next event loop iteration.
4321		5215
4322	=head3 COROUTINES	5216	=head3 COROUTINES
4323		5217
4324	Libev is very accommodating to coroutines ("cooperative threads"):	5218	Libev is very accommodating to coroutines ("cooperative threads"):
4325	libev fully supports nesting calls to its functions from different	5219	libev fully supports nesting calls to its functions from different
4326	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5220	coroutines (e.g. you can call C<ev_run> on the same loop from two
4327	different coroutines, and switch freely between both coroutines running	5221	different coroutines, and switch freely between both coroutines running
4328	the loop, as long as you don't confuse yourself). The only exception is	5222	the loop, as long as you don't confuse yourself). The only exception is
4329	that you must not do this from C<ev_periodic> reschedule callbacks.	5223	that you must not do this from C<ev_periodic> reschedule callbacks.
4330		5224
4331	Care has been taken to ensure that libev does not keep local state inside	5225	Care has been taken to ensure that libev does not keep local state inside
4332	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5226	C<ev_run>, and other calls do not usually allow for coroutine switches as
4333	they do not call any callbacks.	5227	they do not call any callbacks.
4334		5228
4335	=head2 COMPILER WARNINGS	5229	=head2 COMPILER WARNINGS
4336		5230
4337	Depending on your compiler and compiler settings, you might get no or a	5231	Depending on your compiler and compiler settings, you might get no or a
…		…
4348	maintainable.	5242	maintainable.
4349		5243
4350	And of course, some compiler warnings are just plain stupid, or simply	5244	And of course, some compiler warnings are just plain stupid, or simply
4351	wrong (because they don't actually warn about the condition their message	5245	wrong (because they don't actually warn about the condition their message
4352	seems to warn about). For example, certain older gcc versions had some	5246	seems to warn about). For example, certain older gcc versions had some
4353	warnings that resulted an extreme number of false positives. These have	5247	warnings that resulted in an extreme number of false positives. These have
4354	been fixed, but some people still insist on making code warn-free with	5248	been fixed, but some people still insist on making code warn-free with
4355	such buggy versions.	5249	such buggy versions.
4356		5250
4357	While libev is written to generate as few warnings as possible,	5251	While libev is written to generate as few warnings as possible,
4358	"warn-free" code is not a goal, and it is recommended not to build libev	5252	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4394	I suggest using suppression lists.	5288	I suggest using suppression lists.
4395		5289
4396		5290
4397	=head1 PORTABILITY NOTES	5291	=head1 PORTABILITY NOTES
4398		5292
		5293	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5294
		5295	GNU/Linux is the only common platform that supports 64 bit file/large file
		5296	interfaces but I<disables> them by default.
		5297
		5298	That means that libev compiled in the default environment doesn't support
		5299	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5300
		5301	Unfortunately, many programs try to work around this GNU/Linux issue
		5302	by enabling the large file API, which makes them incompatible with the
		5303	standard libev compiled for their system.
		5304
		5305	Likewise, libev cannot enable the large file API itself as this would
		5306	suddenly make it incompatible to the default compile time environment,
		5307	i.e. all programs not using special compile switches.
		5308
		5309	=head2 OS/X AND DARWIN BUGS
		5310
		5311	The whole thing is a bug if you ask me - basically any system interface
		5312	you touch is broken, whether it is locales, poll, kqueue or even the
		5313	OpenGL drivers.
		5314
		5315	=head3 C<kqueue> is buggy
		5316
		5317	The kqueue syscall is broken in all known versions - most versions support
		5318	only sockets, many support pipes.
		5319
		5320	Libev tries to work around this by not using C<kqueue> by default on this
		5321	rotten platform, but of course you can still ask for it when creating a
		5322	loop - embedding a socket-only kqueue loop into a select-based one is
		5323	probably going to work well.
		5324
		5325	=head3 C<poll> is buggy
		5326
		5327	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5328	implementation by something calling C<kqueue> internally around the 10.5.6
		5329	release, so now C<kqueue> I<and> C<poll> are broken.
		5330
		5331	Libev tries to work around this by not using C<poll> by default on
		5332	this rotten platform, but of course you can still ask for it when creating
		5333	a loop.
		5334
		5335	=head3 C<select> is buggy
		5336
		5337	All that's left is C<select>, and of course Apple found a way to fuck this
		5338	one up as well: On OS/X, C<select> actively limits the number of file
		5339	descriptors you can pass in to 1024 - your program suddenly crashes when
		5340	you use more.
		5341
		5342	There is an undocumented "workaround" for this - defining
		5343	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5344	work on OS/X.
		5345
		5346	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5347
		5348	=head3 C<errno> reentrancy
		5349
		5350	The default compile environment on Solaris is unfortunately so
		5351	thread-unsafe that you can't even use components/libraries compiled
		5352	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5353	defined by default. A valid, if stupid, implementation choice.
		5354
		5355	If you want to use libev in threaded environments you have to make sure
		5356	it's compiled with C<_REENTRANT> defined.
		5357
		5358	=head3 Event port backend
		5359
		5360	The scalable event interface for Solaris is called "event
		5361	ports". Unfortunately, this mechanism is very buggy in all major
		5362	releases. If you run into high CPU usage, your program freezes or you get
		5363	a large number of spurious wakeups, make sure you have all the relevant
		5364	and latest kernel patches applied. No, I don't know which ones, but there
		5365	are multiple ones to apply, and afterwards, event ports actually work
		5366	great.
		5367
		5368	If you can't get it to work, you can try running the program by setting
		5369	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5370	C<select> backends.
		5371
		5372	=head2 AIX POLL BUG
		5373
		5374	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5375	this by trying to avoid the poll backend altogether (i.e. it's not even
		5376	compiled in), which normally isn't a big problem as C<select> works fine
		5377	with large bitsets on AIX, and AIX is dead anyway.
		5378
4399	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5379	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5380
		5381	=head3 General issues
4400		5382
4401	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5383	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4402	requires, and its I/O model is fundamentally incompatible with the POSIX	5384	requires, and its I/O model is fundamentally incompatible with the POSIX
4403	model. Libev still offers limited functionality on this platform in	5385	model. Libev still offers limited functionality on this platform in
4404	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5386	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4405	descriptors. This only applies when using Win32 natively, not when using	5387	descriptors. This only applies when using Win32 natively, not when using
4406	e.g. cygwin.	5388	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5389	as every compiler comes with a slightly differently broken/incompatible
		5390	environment.
4407		5391
4408	Lifting these limitations would basically require the full	5392	Lifting these limitations would basically require the full
4409	re-implementation of the I/O system. If you are into these kinds of	5393	re-implementation of the I/O system. If you are into this kind of thing,
4410	things, then note that glib does exactly that for you in a very portable	5394	then note that glib does exactly that for you in a very portable way (note
4411	way (note also that glib is the slowest event library known to man).	5395	also that glib is the slowest event library known to man).
4412		5396
4413	There is no supported compilation method available on windows except	5397	There is no supported compilation method available on windows except
4414	embedding it into other applications.	5398	embedding it into other applications.
4415		5399
4416	Sensible signal handling is officially unsupported by Microsoft - libev	5400	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4444	you do I<not> compile the F<ev.c> or any other embedded source files!):	5428	you do I<not> compile the F<ev.c> or any other embedded source files!):
4445		5429
4446	#include "evwrap.h"	5430	#include "evwrap.h"
4447	#include "ev.c"	5431	#include "ev.c"
4448		5432
4449	=over 4
4450
4451	=item The winsocket select function	5433	=head3 The winsocket C<select> function
4452		5434
4453	The winsocket C<select> function doesn't follow POSIX in that it	5435	The winsocket C<select> function doesn't follow POSIX in that it
4454	requires socket I<handles> and not socket I<file descriptors> (it is	5436	requires socket I<handles> and not socket I<file descriptors> (it is
4455	also extremely buggy). This makes select very inefficient, and also	5437	also extremely buggy). This makes select very inefficient, and also
4456	requires a mapping from file descriptors to socket handles (the Microsoft	5438	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4465	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5447	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4466		5448
4467	Note that winsockets handling of fd sets is O(n), so you can easily get a	5449	Note that winsockets handling of fd sets is O(n), so you can easily get a
4468	complexity in the O(n²) range when using win32.	5450	complexity in the O(n²) range when using win32.
4469		5451
4470	=item Limited number of file descriptors	5452	=head3 Limited number of file descriptors
4471		5453
4472	Windows has numerous arbitrary (and low) limits on things.	5454	Windows has numerous arbitrary (and low) limits on things.
4473		5455
4474	Early versions of winsocket's select only supported waiting for a maximum	5456	Early versions of winsocket's select only supported waiting for a maximum
4475	of C<64> handles (probably owning to the fact that all windows kernels	5457	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4490	runtime libraries. This might get you to about C<512> or C<2048> sockets	5472	runtime libraries. This might get you to about C<512> or C<2048> sockets
4491	(depending on windows version and/or the phase of the moon). To get more,	5473	(depending on windows version and/or the phase of the moon). To get more,
4492	you need to wrap all I/O functions and provide your own fd management, but	5474	you need to wrap all I/O functions and provide your own fd management, but
4493	the cost of calling select (O(n²)) will likely make this unworkable.	5475	the cost of calling select (O(n²)) will likely make this unworkable.
4494		5476
4495	=back
4496
4497	=head2 PORTABILITY REQUIREMENTS	5477	=head2 PORTABILITY REQUIREMENTS
4498		5478
4499	In addition to a working ISO-C implementation and of course the	5479	In addition to a working ISO-C implementation and of course the
4500	backend-specific APIs, libev relies on a few additional extensions:	5480	backend-specific APIs, libev relies on a few additional extensions:
4501		5481
…		…
4507	Libev assumes not only that all watcher pointers have the same internal	5487	Libev assumes not only that all watcher pointers have the same internal
4508	structure (guaranteed by POSIX but not by ISO C for example), but it also	5488	structure (guaranteed by POSIX but not by ISO C for example), but it also
4509	assumes that the same (machine) code can be used to call any watcher	5489	assumes that the same (machine) code can be used to call any watcher
4510	callback: The watcher callbacks have different type signatures, but libev	5490	callback: The watcher callbacks have different type signatures, but libev
4511	calls them using an C<ev_watcher *> internally.	5491	calls them using an C<ev_watcher *> internally.
		5492
		5493	=item null pointers and integer zero are represented by 0 bytes
		5494
		5495	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5496	relies on this setting pointers and integers to null.
		5497
		5498	=item pointer accesses must be thread-atomic
		5499
		5500	Accessing a pointer value must be atomic, it must both be readable and
		5501	writable in one piece - this is the case on all current architectures.
4512		5502
4513	=item C<sig_atomic_t volatile> must be thread-atomic as well	5503	=item C<sig_atomic_t volatile> must be thread-atomic as well
4514		5504
4515	The type C<sig_atomic_t volatile> (or whatever is defined as	5505	The type C<sig_atomic_t volatile> (or whatever is defined as
4516	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5506	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4525	thread" or will block signals process-wide, both behaviours would	5515	thread" or will block signals process-wide, both behaviours would
4526	be compatible with libev. Interaction between C<sigprocmask> and	5516	be compatible with libev. Interaction between C<sigprocmask> and
4527	C<pthread_sigmask> could complicate things, however.	5517	C<pthread_sigmask> could complicate things, however.
4528		5518
4529	The most portable way to handle signals is to block signals in all threads	5519	The most portable way to handle signals is to block signals in all threads
4530	except the initial one, and run the default loop in the initial thread as	5520	except the initial one, and run the signal handling loop in the initial
4531	well.	5521	thread as well.
4532		5522
4533	=item C<long> must be large enough for common memory allocation sizes	5523	=item C<long> must be large enough for common memory allocation sizes
4534		5524
4535	To improve portability and simplify its API, libev uses C<long> internally	5525	To improve portability and simplify its API, libev uses C<long> internally
4536	instead of C<size_t> when allocating its data structures. On non-POSIX	5526	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4539	watchers.	5529	watchers.
4540		5530
4541	=item C<double> must hold a time value in seconds with enough accuracy	5531	=item C<double> must hold a time value in seconds with enough accuracy
4542		5532
4543	The type C<double> is used to represent timestamps. It is required to	5533	The type C<double> is used to represent timestamps. It is required to
4544	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5534	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4545	enough for at least into the year 4000. This requirement is fulfilled by	5535	good enough for at least into the year 4000 with millisecond accuracy
		5536	(the design goal for libev). This requirement is overfulfilled by
4546	implementations implementing IEEE 754, which is basically all existing	5537	implementations using IEEE 754, which is basically all existing ones.
		5538
4547	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5539	With IEEE 754 doubles, you get microsecond accuracy until at least the
4548	2200.	5540	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5541	is either obsolete or somebody patched it to use C<long double> or
		5542	something like that, just kidding).
4549		5543
4550	=back	5544	=back
4551		5545
4552	If you know of other additional requirements drop me a note.	5546	If you know of other additional requirements drop me a note.
4553		5547
…		…
4615	=item Processing ev_async_send: O(number_of_async_watchers)	5609	=item Processing ev_async_send: O(number_of_async_watchers)
4616		5610
4617	=item Processing signals: O(max_signal_number)	5611	=item Processing signals: O(max_signal_number)
4618		5612
4619	Sending involves a system call I<iff> there were no other C<ev_async_send>	5613	Sending involves a system call I<iff> there were no other C<ev_async_send>
4620	calls in the current loop iteration. Checking for async and signal events	5614	calls in the current loop iteration and the loop is currently
		5615	blocked. Checking for async and signal events involves iterating over all
4621	involves iterating over all running async watchers or all signal numbers.	5616	running async watchers or all signal numbers.
4622		5617
4623	=back	5618	=back
4624		5619
4625		5620
4626	=head1 PORTING FROM 3.X TO 4.X	5621	=head1 PORTING FROM LIBEV 3.X TO 4.X
4627		5622
4628	The major version 4 introduced some minor incompatible changes to the API.	5623	The major version 4 introduced some incompatible changes to the API.
		5624
		5625	At the moment, the C<ev.h> header file provides compatibility definitions
		5626	for all changes, so most programs should still compile. The compatibility
		5627	layer might be removed in later versions of libev, so better update to the
		5628	new API early than late.
4629		5629
4630	=over 4	5630	=over 4
4631		5631
4632	=item C<EV_TIMEOUT> replaced by C<EV_TIMER> in C<revents>	5632	=item C<EV_COMPAT3> backwards compatibility mechanism
4633		5633
4634	This is a simple rename - all other watcher types use their name	5634	The backward compatibility mechanism can be controlled by
4635	as revents flag, and now C<ev_timer> does, too.	5635	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5636	section.
4636		5637
4637	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions	5638	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
4638	and continue to be present for the forseeable future, so this is mostly a	5639
4639	documentation change.	5640	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5641
		5642	ev_loop_destroy (EV_DEFAULT_UC);
		5643	ev_loop_fork (EV_DEFAULT);
		5644
		5645	=item function/symbol renames
		5646
		5647	A number of functions and symbols have been renamed:
		5648
		5649	ev_loop => ev_run
		5650	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5651	EVLOOP_ONESHOT => EVRUN_ONCE
		5652
		5653	ev_unloop => ev_break
		5654	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5655	EVUNLOOP_ONE => EVBREAK_ONE
		5656	EVUNLOOP_ALL => EVBREAK_ALL
		5657
		5658	EV_TIMEOUT => EV_TIMER
		5659
		5660	ev_loop_count => ev_iteration
		5661	ev_loop_depth => ev_depth
		5662	ev_loop_verify => ev_verify
		5663
		5664	Most functions working on C<struct ev_loop> objects don't have an
		5665	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5666	associated constants have been renamed to not collide with the C<struct
		5667	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5668	as all other watcher types. Note that C<ev_loop_fork> is still called
		5669	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5670	typedef.
4640		5671
4641	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5672	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4642		5673
4643	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5674	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4644	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5675	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4651		5682
4652	=over 4	5683	=over 4
4653		5684
4654	=item active	5685	=item active
4655		5686
4656	A watcher is active as long as it has been started (has been attached to	5687	A watcher is active as long as it has been started and not yet stopped.
4657	an event loop) but not yet stopped (disassociated from the event loop).	5688	See L</WATCHER STATES> for details.
4658		5689
4659	=item application	5690	=item application
4660		5691
4661	In this document, an application is whatever is using libev.	5692	In this document, an application is whatever is using libev.
		5693
		5694	=item backend
		5695
		5696	The part of the code dealing with the operating system interfaces.
4662		5697
4663	=item callback	5698	=item callback
4664		5699
4665	The address of a function that is called when some event has been	5700	The address of a function that is called when some event has been
4666	detected. Callbacks are being passed the event loop, the watcher that	5701	detected. Callbacks are being passed the event loop, the watcher that
4667	received the event, and the actual event bitset.	5702	received the event, and the actual event bitset.
4668		5703
4669	=item callback invocation	5704	=item callback/watcher invocation
4670		5705
4671	The act of calling the callback associated with a watcher.	5706	The act of calling the callback associated with a watcher.
4672		5707
4673	=item event	5708	=item event
4674		5709
…		…
4693	The model used to describe how an event loop handles and processes	5728	The model used to describe how an event loop handles and processes
4694	watchers and events.	5729	watchers and events.
4695		5730
4696	=item pending	5731	=item pending
4697		5732
4698	A watcher is pending as soon as the corresponding event has been detected,	5733	A watcher is pending as soon as the corresponding event has been
4699	and stops being pending as soon as the watcher will be invoked or its	5734	detected. See L</WATCHER STATES> for details.
4700	pending status is explicitly cleared by the application.
4701
4702	A watcher can be pending, but not active. Stopping a watcher also clears
4703	its pending status.
4704		5735
4705	=item real time	5736	=item real time
4706		5737
4707	The physical time that is observed. It is apparently strictly monotonic :)	5738	The physical time that is observed. It is apparently strictly monotonic :)
4708		5739
4709	=item wall-clock time	5740	=item wall-clock time
4710		5741
4711	The time and date as shown on clocks. Unlike real time, it can actually	5742	The time and date as shown on clocks. Unlike real time, it can actually
4712	be wrong and jump forwards and backwards, e.g. when the you adjust your	5743	be wrong and jump forwards and backwards, e.g. when you adjust your
4713	clock.	5744	clock.
4714		5745
4715	=item watcher	5746	=item watcher
4716		5747
4717	A data structure that describes interest in certain events. Watchers need	5748	A data structure that describes interest in certain events. Watchers need
4718	to be started (attached to an event loop) before they can receive events.	5749	to be started (attached to an event loop) before they can receive events.
4719		5750
4720	=item watcher invocation
4721
4722	The act of calling the callback associated with a watcher.
4723
4724	=back	5751	=back
4725		5752
4726	=head1 AUTHOR	5753	=head1 AUTHOR
4727		5754
4728	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5755	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5756	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4729		5757

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