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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
…		…
118	Libev is very configurable. In this manual the default (and most common)	128	Libev is very configurable. In this manual the default (and most common)
119	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
120	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
121	B<EMBED> section in this manual. If libev was configured without support	131	B<EMBED> section in this manual. If libev was configured without support
122	for multiple event loops, then all functions taking an initial argument of	132	for multiple event loops, then all functions taking an initial argument of
123	name C<loop> (which is always of type C<ev_loop *>) will not have	133	name C<loop> (which is always of type C<struct ev_loop *>) will not have
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_NOSIGNALFD>	459	=item C<EVFLAG_SIGNALFD>
376		460
377	When this flag is specified, then libev will not 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 is	462	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	probably only useful to work around any bugs in libev. Consequently, this	463	delivers signals synchronously, which makes it both faster and might make
380	flag might go away once the signalfd functionality is considered stable,	464	it possible to get the queued signal data. It can also simplify signal
381	so it's useful mostly in environment variables and not in program code.	465	handling with threads, as long as you properly block signals in your
		466	threads that are not interested in handling them.
		467
		468	Signalfd will not be used by default as this changes your signal mask, and
		469	there are a lot of shoddy libraries and programs (glib's threadpool for
		470	example) that can't properly initialise their signal masks.
		471
		472	=item C<EVFLAG_NOSIGMASK>
		473
		474	When this flag is specified, then libev will avoid to modify the signal
		475	mask. Specifically, this means you have to make sure signals are unblocked
		476	when you want to receive them.
		477
		478	This behaviour is useful when you want to do your own signal handling, or
		479	want to handle signals only in specific threads and want to avoid libev
		480	unblocking the signals.
		481
		482	It's also required by POSIX in a threaded program, as libev calls
		483	C<sigprocmask>, whose behaviour is officially unspecified.
		484
		485	=item C<EVFLAG_NOTIMERFD>
		486
		487	When this flag is specified, the libev will avoid using a C<timerfd> to
		488	detect time jumps. It will still be able to detect time jumps, but takes
		489	longer and has a lower accuracy in doing so, but saves a file descriptor
		490	per loop.
		491
		492	The current implementation only tries to use a C<timerfd> when the first
		493	C<ev_periodic> watcher is started and falls back on other methods if it
		494	cannot be created, but this behaviour might change in the future.
382		495
383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	496	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
384		497
385	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
386	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,
…		…
411	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
412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	525	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
413		526
414	=item C<EVBACKEND_EPOLL> (value 4, Linux)	527	=item C<EVBACKEND_EPOLL> (value 4, Linux)
415		528
		529	Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9
		530	kernels).
		531
416	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
417	but it scales phenomenally better. While poll and select usually scale	533	it scales phenomenally better. While poll and select usually scale like
418	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
419	epoll scales either O(1) or O(active_fds).	535	fd), epoll scales either O(1) or O(active_fds).
420		536
421	The epoll mechanism deserves honorable mention as the most misdesigned	537	The epoll mechanism deserves honorable mention as the most misdesigned
422	of the more advanced event mechanisms: mere annoyances include silently	538	of the more advanced event mechanisms: mere annoyances include silently
423	dropping file descriptors, requiring a system call per change per file	539	dropping file descriptors, requiring a system call per change per file
424	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
425	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
426	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
427	take considerable time (one syscall per file descriptor) and is of course	545	set, which can take considerable time (one syscall per file descriptor)
428	hard to detect.	546	and is of course hard to detect.
429		547
430	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	548	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
431	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
432	I<different> file descriptors (even already closed ones, so one cannot	550	totally I<different> file descriptors (even already closed ones, so
433	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
434	on SMP systems). Libev tries to counter these spurious notifications by	552	(especially on SMP systems). Libev tries to counter these spurious
435	employing an additional generation counter and comparing that against the	553	notifications by employing an additional generation counter and comparing
436	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...
437		564
438	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
439	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
440	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
441	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
…		…
453	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
454	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
455	the usage. So sad.	582	the usage. So sad.
456		583
457	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
458	all kernel versions tested so far.	585	a lot of kernel revisions, but probably(!) works in current versions.
459		586
460	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
461	C<EVBACKEND_POLL>.	588	C<EVBACKEND_POLL>.
462		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
463	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	634	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
464		635
465	Kqueue deserves special mention, as at the time of this writing, it	636	Kqueue deserves special mention, as at the time this backend was
466	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
467	with anything but sockets and pipes, except on Darwin, where of course	638	work reliably with anything but sockets and pipes, except on Darwin,
468	it's completely useless). Unlike epoll, however, whose brokenness	639	where of course it's completely useless). Unlike epoll, however, whose
469	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)
470	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
471	"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
472	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
473	system like NetBSD.	644	known-to-be-good (-enough) system like NetBSD.
474		645
475	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
476	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
477	the target platform). See C<ev_embed> watchers for more info.	648	the target platform). See C<ev_embed> watchers for more info.
478		649
479	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
480	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
481	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
482	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
483	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
484	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
485	cases	656	drops fds silently in similarly hard-to-detect cases.
486		657
487	This backend usually performs well under most conditions.	658	This backend usually performs well under most conditions.
488		659
489	While nominally embeddable in other event loops, this doesn't work	660	While nominally embeddable in other event loops, this doesn't work
490	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
…		…
504	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
505	immensely.	676	immensely.
506		677
507	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	678	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
508		679
509	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
510	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)).
511
512	Please note that Solaris event ports can deliver a lot of spurious
513	notifications, so you need to use non-blocking I/O or other means to avoid
514	blocking when no data (or space) is available.
515		682
516	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
517	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
518	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	685	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
519	might perform better.	686	might perform better.
520		687
521	On the positive side, with the exception of the spurious readiness	688	On the positive side, this backend actually performed fully to
522	notifications, this backend actually performed fully to specification
523	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
524	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.
525		702
526	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
527	C<EVBACKEND_POLL>.	704	C<EVBACKEND_POLL>.
528		705
529	=item C<EVBACKEND_ALL>	706	=item C<EVBACKEND_ALL>
530		707
531	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
532	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
533	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	710	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
534		711
535	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).
536		721
537	=back	722	=back
538		723
539	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,
540	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
541	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
542	()> will be tried.	727	()> will be tried.
543		728
544	Example: This is the most typical usage.
545
546	if (!ev_default_loop (0))
547	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
548
549	Example: Restrict libev to the select and poll backends, and do not allow
550	environment settings to be taken into account:
551
552	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
553
554	Example: Use whatever libev has to offer, but make sure that kqueue is
555	used if available (warning, breaks stuff, best use only with your own
556	private event loop and only if you know the OS supports your types of
557	fds):
558
559	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
560
561	=item struct ev_loop *ev_loop_new (unsigned int flags)
562
563	Similar to C<ev_default_loop>, but always creates a new event loop that is
564	always distinct from the default loop. Unlike the default loop, it cannot
565	handle signal and child watchers, and attempts to do so will be greeted by
566	undefined behaviour (or a failed assertion if assertions are enabled).
567
568	Note that this function I<is> thread-safe, and the recommended way to use
569	libev with threads is indeed to create one loop per thread, and using the
570	default loop in the "main" or "initial" thread.
571
572	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.
573		730
574	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	731	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
575	if (!epoller)	732	if (!epoller)
576	fatal ("no epoll found here, maybe it hides under your chair");	733	fatal ("no epoll found here, maybe it hides under your chair");
577		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
578	=item ev_default_destroy ()	746	=item ev_loop_destroy (loop)
579		747
580	Destroys the default loop again (frees all memory and kernel state	748	Destroys an event loop object (frees all memory and kernel state
581	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
582	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
583	responsibility to either stop all watchers cleanly yourself I<before>	751	responsibility to either stop all watchers cleanly yourself I<before>
584	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
585	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
…		…
587		755
588	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
589	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
590	as signal and child watchers) would need to be stopped manually.	758	as signal and child watchers) would need to be stopped manually.
591		759
592	In general it is not advisable to call this function except in the	760	This function is normally used on loop objects allocated by
593	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.
594	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>
595	C<ev_loop_new> and C<ev_loop_destroy>).	767	and C<ev_loop_destroy>.
596		768
597	=item ev_loop_destroy (loop)	769	=item ev_loop_fork (loop)
598		770
599	Like C<ev_default_destroy>, but destroys an event loop created by an
600	earlier call to C<ev_loop_new>.
601
602	=item ev_default_fork ()
603
604	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
605	to reinitialise the kernel state for backends that have one. Despite the	772	to reinitialise the kernel state for backends that have one. Despite
606	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
607	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
608	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
609	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.
610		785
611	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
612	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
613	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).
614		792
615	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
616	it just in case after a fork. To make this easy, the function will fit in	794	it just in case after a fork.
617	quite nicely into a call to C<pthread_atfork>:
618		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	...
619	pthread_atfork (0, 0, ev_default_fork);	806	pthread_atfork (0, 0, post_fork_child);
620
621	=item ev_loop_fork (loop)
622
623	Like C<ev_default_fork>, but acts on an event loop created by
624	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
625	after fork that you want to re-use in the child, and how you do this is
626	entirely your own problem.
627		807
628	=item int ev_is_default_loop (loop)	808	=item int ev_is_default_loop (loop)
629		809
630	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
631	otherwise.	811	otherwise.
632		812
633	=item unsigned int ev_loop_count (loop)	813	=item unsigned int ev_iteration (loop)
634		814
635	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
636	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>
637	happily wraps around with enough iterations.	817	and happily wraps around with enough iterations.
638		818
639	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
640	"ticks" the number of loop iterations), as it roughly corresponds with	820	"ticks" the number of loop iterations), as it roughly corresponds with
641	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.
642		823
643	=item unsigned int ev_loop_depth (loop)	824	=item unsigned int ev_depth (loop)
644		825
645	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
646	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.
647		828
648	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
649	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),
650	in which case it is higher.	831	in which case it is higher.
651		832
652	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	833	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
653	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.
654		837
655	=item unsigned int ev_backend (loop)	838	=item unsigned int ev_backend (loop)
656		839
657	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
658	use.	841	use.
…		…
667		850
668	=item ev_now_update (loop)	851	=item ev_now_update (loop)
669		852
670	Establishes the current time by querying the kernel, updating the time	853	Establishes the current time by querying the kernel, updating the time
671	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
672	is usually done automatically within C<ev_loop ()>.	855	is usually done automatically within C<ev_run ()>.
673		856
674	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
675	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
676	the current time is a good idea.	859	the current time is a good idea.
677		860
678	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.
679		862
680	=item ev_suspend (loop)	863	=item ev_suspend (loop)
681		864
682	=item ev_resume (loop)	865	=item ev_resume (loop)
683		866
684	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
685	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.
686		869
687	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
688	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
689	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
690	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>
…		…
692	C<ev_resume> directly afterwards to resume timer processing.	875	C<ev_resume> directly afterwards to resume timer processing.
693		876
694	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
695	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
696	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
697	occured while suspended).	880	occurred while suspended).
698		881
699	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
700	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>
701	without a previous call to C<ev_suspend>.	884	without a previous call to C<ev_suspend>.
702		885
703	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
704	event loop time (see C<ev_now_update>).	887	event loop time (see C<ev_now_update>).
705		888
706	=item ev_loop (loop, int flags)	889	=item bool ev_run (loop, int flags)
707		890
708	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
709	after you initialised all your watchers and you want to start handling	892	after you have initialised all your watchers and you want to start
710	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>.
711		896
712	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
713	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.
714		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
715	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
716	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
717	finished (especially in interactive programs), but having a program	907	finished (especially in interactive programs), but having a program
718	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
719	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
720	beauty.	910	beauty.
721		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
722	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
723	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
724	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
725	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.
726		922
727	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
728	necessary) and will handle those and any already outstanding ones. It	924	necessary) and will handle those and any already outstanding ones. It
729	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
730	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
731	user-registered callback will be called), and will return after one	927	user-registered callback will be called), and will return after one
732	iteration of the loop.	928	iteration of the loop.
733		929
734	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
735	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
736	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
737	usually a better approach for this kind of thing.	933	usually a better approach for this kind of thing.
738		934
739	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):
740		938
		939	- Increment loop depth.
		940	- Reset the ev_break status.
741	- Before the first iteration, call any pending watchers.	941	- Before the first iteration, call any pending watchers.
		942	LOOP:
742	* If EVFLAG_FORKCHECK was used, check for a fork.	943	- If EVFLAG_FORKCHECK was used, check for a fork.
743	- 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.
744	- Queue and call all prepare watchers.	945	- Queue and call all prepare watchers.
		946	- If ev_break was called, goto FINISH.
745	- If we have been forked, detach and recreate the kernel state	947	- If we have been forked, detach and recreate the kernel state
746	as to not disturb the other process.	948	as to not disturb the other process.
747	- Update the kernel state with all outstanding changes.	949	- Update the kernel state with all outstanding changes.
748	- Update the "event loop time" (ev_now ()).	950	- Update the "event loop time" (ev_now ()).
749	- Calculate for how long to sleep or block, if at all	951	- Calculate for how long to sleep or block, if at all
750	(active idle watchers, EVLOOP_NONBLOCK or not having	952	(active idle watchers, EVRUN_NOWAIT or not having
751	any active watchers at all will result in not sleeping).	953	any active watchers at all will result in not sleeping).
752	- 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.
753	- Block the process, waiting for any events.	956	- Block the process, waiting for any events.
754	- Queue all outstanding I/O (fd) events.	957	- Queue all outstanding I/O (fd) events.
755	- 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.
756	- Queue all expired timers.	959	- Queue all expired timers.
757	- Queue all expired periodics.	960	- Queue all expired periodics.
758	- Unless any events are pending now, queue all idle watchers.	961	- Queue all idle watchers with priority higher than that of pending events.
759	- Queue all check watchers.	962	- Queue all check watchers.
760	- 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).
761	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
762	be handled here by queueing them when their watcher gets executed.	965	will be handled here by queueing them when their watcher gets executed.
763	- 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
764	were used, or there are no active watchers, return, otherwise	967	were used, or there are no active watchers, goto FINISH, otherwise
765	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.
766		973
767	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
768	anymore.	975	anymore.
769		976
770	... queue jobs here, make sure they register event watchers as long	977	... queue jobs here, make sure they register event watchers as long
771	... 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..)
772	ev_loop (my_loop, 0);	979	ev_run (my_loop, 0);
773	... jobs done or somebody called unloop. yeah!	980	... jobs done or somebody called break. yeah!
774		981
775	=item ev_unloop (loop, how)	982	=item ev_break (loop, how)
776		983
777	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
778	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
779	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
780	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.
781		988
782	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>.
783		990
784	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.
785		993
786	=item ev_ref (loop)	994	=item ev_ref (loop)
787		995
788	=item ev_unref (loop)	996	=item ev_unref (loop)
789		997
790	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
791	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
792	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.
793		1001
794	If you have a watcher you never unregister that should not keep C<ev_loop>	1002	This is useful when you have a watcher that you never intend to
795	from returning, call ev_unref() after starting, and ev_ref() before	1003	unregister, but that nevertheless should not keep C<ev_run> from
		1004	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
796	stopping it.	1005	before stopping it.
797		1006
798	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
799	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
800	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
801	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
802	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
803	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
804	before, respectively. Note also that libev might stop watchers itself	1013	before, respectively. Note also that libev might stop watchers itself
805	(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>
806	in the callback).	1015	in the callback).
807		1016
808	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>
809	running when nothing else is active.	1018	running when nothing else is active.
810		1019
811	ev_signal exitsig;	1020	ev_signal exitsig;
812	ev_signal_init (&exitsig, sig_cb, SIGINT);	1021	ev_signal_init (&exitsig, sig_cb, SIGINT);
813	ev_signal_start (loop, &exitsig);	1022	ev_signal_start (loop, &exitsig);
814	evf_unref (loop);	1023	ev_unref (loop);
815		1024
816	Example: For some weird reason, unregister the above signal handler again.	1025	Example: For some weird reason, unregister the above signal handler again.
817		1026
818	ev_ref (loop);	1027	ev_ref (loop);
819	ev_signal_stop (loop, &exitsig);	1028	ev_signal_stop (loop, &exitsig);
…		…
839	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.
840		1049
841	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
842	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,
843	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
844	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
845	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
846	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
847	once per this interval, on average.	1056	once per this interval, on average (as long as the host time resolution is
		1057	good enough).
848		1058
849	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
850	to spend more time collecting timeouts, at the expense of increased	1060	to spend more time collecting timeouts, at the expense of increased
851	latency/jitter/inexactness (the watcher callback will be called	1061	latency/jitter/inexactness (the watcher callback will be called
852	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
…		…
858	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>,
859	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
860	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
861	parallelity, then this setting will limit your transaction rate (if you	1071	parallelity, then this setting will limit your transaction rate (if you
862	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,
863	then you can't do more than 100 transations per second).	1073	then you can't do more than 100 transactions per second).
864		1074
865	Setting the I<timeout collect interval> can improve the opportunity for	1075	Setting the I<timeout collect interval> can improve the opportunity for
866	saving power, as the program will "bundle" timer callback invocations that	1076	saving power, as the program will "bundle" timer callback invocations that
867	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
868	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
…		…
876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1086	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
877		1087
878	=item ev_invoke_pending (loop)	1088	=item ev_invoke_pending (loop)
879		1089
880	This call will simply invoke all pending watchers while resetting their	1090	This call will simply invoke all pending watchers while resetting their
881	pending state. Normally, C<ev_loop> does this automatically when required,	1091	pending state. Normally, C<ev_run> does this automatically when required,
882	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).
883		1097
884	=item int ev_pending_count (loop)	1098	=item int ev_pending_count (loop)
885		1099
886	Returns the number of pending watchers - zero indicates that no watchers	1100	Returns the number of pending watchers - zero indicates that no watchers
887	are pending.	1101	are pending.
888		1102
889	=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))
890		1104
891	This overrides the invoke pending functionality of the loop: Instead of	1105	This overrides the invoke pending functionality of the loop: Instead of
892	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
893	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
894	invoke the actual watchers inside another context (another thread etc.).	1108	invoke the actual watchers inside another context (another thread etc.).
895		1109
896	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
897	callback.	1111	callback.
898		1112
899	=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 ())
900		1114
901	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
902	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
903	each call to a libev function.	1117	each call to a libev function.
904		1118
905	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
906	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
907	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
908	and I<acquire> callbacks on the loop.	1122	I<release> and I<acquire> callbacks on the loop.
909		1123
910	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
911	suspended waiting for new events, and C<acquire> is called just	1125	suspended waiting for new events, and C<acquire> is called just
912	afterwards.	1126	afterwards.
913		1127
…		…
916		1130
917	While event loop modifications are allowed between invocations of	1131	While event loop modifications are allowed between invocations of
918	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
919	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
920	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
921	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
922	to take note of any changes you made.	1136	to take note of any changes you made.
923		1137
924	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
925	invocations of C<release> and C<acquire>.	1139	invocations of C<release> and C<acquire>.
926		1140
927	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
928	document.	1142	document.
929		1143
930	=item ev_set_userdata (loop, void *data)	1144	=item ev_set_userdata (loop, void *data)
931		1145
932	=item ev_userdata (loop)	1146	=item void *ev_userdata (loop)
933		1147
934	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
935	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
936	C<0.>	1150	C<0>.
937		1151
938	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,
939	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
940	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
941	any other purpose as well.	1155	any other purpose as well.
942		1156
943	=item ev_loop_verify (loop)	1157	=item ev_verify (loop)
944		1158
945	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
946	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
947	through all internal structures and checks them for validity. If anything	1161	through all internal structures and checks them for validity. If anything
948	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
…		…
959		1173
960	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
961	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
962	watchers and C<ev_io_start> for I/O watchers.	1176	watchers and C<ev_io_start> for I/O watchers.
963		1177
964	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
965	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
966	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:
967		1182
968	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)
969	{	1184	{
970	ev_io_stop (w);	1185	ev_io_stop (w);
971	ev_unloop (loop, EVUNLOOP_ALL);	1186	ev_break (loop, EVBREAK_ALL);
972	}	1187	}
973		1188
974	struct ev_loop *loop = ev_default_loop (0);	1189	struct ev_loop *loop = ev_default_loop (0);
975		1190
976	ev_io stdin_watcher;	1191	ev_io stdin_watcher;
977		1192
978	ev_init (&stdin_watcher, my_cb);	1193	ev_init (&stdin_watcher, my_cb);
979	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1194	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
980	ev_io_start (loop, &stdin_watcher);	1195	ev_io_start (loop, &stdin_watcher);
981		1196
982	ev_loop (loop, 0);	1197	ev_run (loop, 0);
983		1198
984	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
985	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
986	stack).	1201	stack).
987		1202
988	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>
989	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).
990		1205
991	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
992	(watcher *, callback)>, which expects a callback to be provided. This	1207	*, callback)>, which expects a callback to be provided. This callback is
993	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
994	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
995	is readable and/or writable).	1210	and/or writable).
996		1211
997	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 *, ...) >>
998	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
999	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<<
1000	ev_TYPE_init (watcher *, callback, ...) >>.	1215	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1003	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
1004	*) >>), 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
1005	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.	1220	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
1006		1221
1007	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
1008	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
1009	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.
1010		1226
1011	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
1012	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
1013	third argument.	1229	third argument.
1014		1230
…		…
1023	=item C<EV_WRITE>	1239	=item C<EV_WRITE>
1024		1240
1025	The file descriptor in the C<ev_io> watcher has become readable and/or	1241	The file descriptor in the C<ev_io> watcher has become readable and/or
1026	writable.	1242	writable.
1027		1243
1028	=item C<EV_TIMEOUT>	1244	=item C<EV_TIMER>
1029		1245
1030	The C<ev_timer> watcher has timed out.	1246	The C<ev_timer> watcher has timed out.
1031		1247
1032	=item C<EV_PERIODIC>	1248	=item C<EV_PERIODIC>
1033		1249
…		…
1051		1267
1052	=item C<EV_PREPARE>	1268	=item C<EV_PREPARE>
1053		1269
1054	=item C<EV_CHECK>	1270	=item C<EV_CHECK>
1055		1271
1056	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
1057	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)
1058	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
1059	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
1060	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
1061	(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
1062	C<ev_loop> from blocking).	1283	blocking).
1063		1284
1064	=item C<EV_EMBED>	1285	=item C<EV_EMBED>
1065		1286
1066	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.
1067		1288
1068	=item C<EV_FORK>	1289	=item C<EV_FORK>
1069		1290
1070	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
1071	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>).
1072		1297
1073	=item C<EV_ASYNC>	1298	=item C<EV_ASYNC>
1074		1299
1075	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>).
1076		1301
…		…
1123		1348
1124	ev_io w;	1349	ev_io w;
1125	ev_init (&w, my_cb);	1350	ev_init (&w, my_cb);
1126	ev_io_set (&w, STDIN_FILENO, EV_READ);	1351	ev_io_set (&w, STDIN_FILENO, EV_READ);
1127		1352
1128	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1353	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1129		1354
1130	This macro initialises the type-specific parts of a watcher. You need to	1355	This macro initialises the type-specific parts of a watcher. You need to
1131	call C<ev_init> at least once before you call this macro, but you can	1356	call C<ev_init> at least once before you call this macro, but you can
1132	call C<ev_TYPE_set> any number of times. You must not, however, call this	1357	call C<ev_TYPE_set> any number of times. You must not, however, call this
1133	macro on a watcher that is active (it can be pending, however, which is a	1358	macro on a watcher that is active (it can be pending, however, which is a
…		…
1146		1371
1147	Example: Initialise and set an C<ev_io> watcher in one step.	1372	Example: Initialise and set an C<ev_io> watcher in one step.
1148		1373
1149	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1374	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1150		1375
1151	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1376	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1152		1377
1153	Starts (activates) the given watcher. Only active watchers will receive	1378	Starts (activates) the given watcher. Only active watchers will receive
1154	events. If the watcher is already active nothing will happen.	1379	events. If the watcher is already active nothing will happen.
1155		1380
1156	Example: Start the C<ev_io> watcher that is being abused as example in this	1381	Example: Start the C<ev_io> watcher that is being abused as example in this
1157	whole section.	1382	whole section.
1158		1383
1159	ev_io_start (EV_DEFAULT_UC, &w);	1384	ev_io_start (EV_DEFAULT_UC, &w);
1160		1385
1161	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1386	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1162		1387
1163	Stops the given watcher if active, and clears the pending status (whether	1388	Stops the given watcher if active, and clears the pending status (whether
1164	the watcher was active or not).	1389	the watcher was active or not).
1165		1390
1166	It is possible that stopped watchers are pending - for example,	1391	It is possible that stopped watchers are pending - for example,
…		…
1171		1396
1172	=item bool ev_is_active (ev_TYPE *watcher)	1397	=item bool ev_is_active (ev_TYPE *watcher)
1173		1398
1174	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
1175	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
1176	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.
1177		1405
1178	=item bool ev_is_pending (ev_TYPE *watcher)	1406	=item bool ev_is_pending (ev_TYPE *watcher)
1179		1407
1180	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
1181	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
1182	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
1183	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
1184	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 ()>
1185	it).	1413	it).
1186		1414
		1415	It is safe to call this on any watcher in any state as long as it is
		1416	initialised.
		1417
1187	=item callback ev_cb (ev_TYPE *watcher)	1418	=item callback ev_cb (ev_TYPE *watcher)
1188		1419
1189	Returns the callback currently set on the watcher.	1420	Returns the callback currently set on the watcher.
1190		1421
1191	=item ev_cb_set (ev_TYPE *watcher, callback)	1422	=item ev_set_cb (ev_TYPE *watcher, callback)
1192		1423
1193	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
1194	(modulo threads).	1425	(modulo threads).
1195		1426
1196	=item ev_set_priority (ev_TYPE *watcher, priority)	1427	=item ev_set_priority (ev_TYPE *watcher, int priority)
1197		1428
1198	=item int ev_priority (ev_TYPE *watcher)	1429	=item int ev_priority (ev_TYPE *watcher)
1199		1430
1200	Set and query the priority of the watcher. The priority is a small	1431	Set and query the priority of the watcher. The priority is a small
1201	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1432	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1204	from being executed (except for C<ev_idle> watchers).	1435	from being executed (except for C<ev_idle> watchers).
1205		1436
1206	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
1207	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.
1208		1439
1209	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
1210	pending.	1441	or pending. Reading the priority with C<ev_priority> is fine in any state.
1211		1442
1212	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
1213	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
1214	or might not have been clamped to the valid range.	1445	or might not have been clamped to the valid range.
1215		1446
1216	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
1217	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 :).
1218		1449
1219	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
1220	priorities.	1451	priorities.
1221		1452
1222	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1453	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1223		1454
1224	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
…		…
1233	watcher isn't pending it does nothing and returns C<0>.	1464	watcher isn't pending it does nothing and returns C<0>.
1234		1465
1235	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1466	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1236	callback to be invoked, which can be accomplished with this function.	1467	callback to be invoked, which can be accomplished with this function.
1237		1468
		1469	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1470
		1471	Feeds the given event set into the event loop, as if the specified event
		1472	had happened for the specified watcher (which must be a pointer to an
		1473	initialised but not necessarily started event watcher, though it can be
		1474	active). Obviously you must not free the watcher as long as it has pending
		1475	events.
		1476
		1477	Stopping the watcher, letting libev invoke it, or calling
		1478	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1479	not started in the first place.
		1480
		1481	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1482	functions that do not need a watcher.
		1483
1238	=back	1484	=back
1239		1485
		1486	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1487	OWN COMPOSITE WATCHERS> idioms.
1240		1488
1241	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1489	=head2 WATCHER STATES
1242		1490
1243	Each watcher has, by default, a member C<void *data> that you can change	1491	There are various watcher states mentioned throughout this manual -
1244	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
1245	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
1246	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".
1247	member, you can also "subclass" the watcher type and provide your own
1248	data:
1249		1495
1250	struct my_io	1496	=over 4
1251	{
1252	ev_io io;
1253	int otherfd;
1254	void *somedata;
1255	struct whatever *mostinteresting;
1256	};
1257		1497
1258	...	1498	=item initialised
1259	struct my_io w;
1260	ev_io_init (&w.io, my_cb, fd, EV_READ);
1261		1499
1262	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
1263	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.
1264		1503
1265	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
1266	{	1505	use in an event loop. It can be moved around, freed, reused etc. at
1267	struct my_io *w = (struct my_io *)w_;	1506	will - as long as you either keep the memory contents intact, or call
1268	...	1507	C<ev_TYPE_init> again.
1269	}
1270		1508
1271	More interesting and less C-conformant ways of casting your callback type	1509	=item started/running/active
1272	instead have been omitted.
1273		1510
1274	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
1275	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.
1276		1517
1277	struct my_biggy	1518	As a rule of thumb, before accessing a member or calling any function on
1278	{	1519	a watcher, it should be stopped (or freshly initialised). If that is not
1279	int some_data;	1520	convenient, you can check the documentation for that function or member to
1280	ev_timer t1;	1521	see if it is safe to use on an active watcher.
1281	ev_timer t2;
1282	}
1283		1522
1284	In this case getting the pointer to C<my_biggy> is a bit more	1523	=item pending
1285	complicated: Either you store the address of your C<my_biggy> struct
1286	in the C<data> member of the watcher (for woozies), or you need to use
1287	some pointer arithmetic using C<offsetof> inside your watchers (for real
1288	programmers):
1289		1524
1290	#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.
1291		1530
1292	static void	1531	Generally, the watcher might or might not be active while it is pending
1293	t1_cb (EV_P_ ev_timer *w, int revents)	1532	(for example, an expired non-repeating timer can be pending but no longer
1294	{	1533	active). If it is pending but not active, it can be freely accessed (e.g.
1295	struct my_biggy big = (struct my_biggy *)	1534	by calling C<ev_TYPE_set>), but it is still property of the event loop at
1296	(((char *)w) - offsetof (struct my_biggy, t1));	1535	this time, so cannot be moved, freed or reused. And if it is active the
1297	}	1536	rules described in the previous item still apply.
1298		1537
1299	static void	1538	Explicitly stopping a watcher will also clear the pending state
1300	t2_cb (EV_P_ ev_timer *w, int revents)	1539	unconditionally, so it is safe to stop a watcher and then free it.
1301	{	1540
1302	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.
1303	(((char *)w) - offsetof (struct my_biggy, t2));	1542	via C<ev_feed_event>), in which case it becomes pending without being
1304	}	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
1305		1559
1306	=head2 WATCHER PRIORITY MODELS	1560	=head2 WATCHER PRIORITY MODELS
1307		1561
1308	Many event loops support I<watcher priorities>, which are usually small	1562	Many event loops support I<watcher priorities>, which are usually small
1309	integers that influence the ordering of event callback invocation	1563	integers that influence the ordering of event callback invocation
1310	between watchers in some way, all else being equal.	1564	between watchers in some way, all else being equal.
1311		1565
1312	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
1313	description for the more technical details such as the actual priority	1567	description for the more technical details such as the actual priority
1314	range.	1568	range.
1315		1569
1316	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
1317	by event loops:	1571	by event loops:
…		…
1352		1606
1353	For example, to emulate how many other event libraries handle priorities,	1607	For example, to emulate how many other event libraries handle priorities,
1354	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
1355	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
1356	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
1357	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
1358	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
1359	workable.	1613	workable.
1360		1614
1361	Usually, however, the lock-out model implemented that way will perform	1615	Usually, however, the lock-out model implemented that way will perform
1362	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,
…		…
1376	{	1630	{
1377	// stop the I/O watcher, we received the event, but	1631	// stop the I/O watcher, we received the event, but
1378	// are not yet ready to handle it.	1632	// are not yet ready to handle it.
1379	ev_io_stop (EV_A_ w);	1633	ev_io_stop (EV_A_ w);
1380		1634
1381	// start the idle watcher to ahndle the actual event.	1635	// start the idle watcher to handle the actual event.
1382	// it will not be executed as long as other watchers	1636	// it will not be executed as long as other watchers
1383	// with the default priority are receiving events.	1637	// with the default priority are receiving events.
1384	ev_idle_start (EV_A_ &idle);	1638	ev_idle_start (EV_A_ &idle);
1385	}	1639	}
1386		1640
…		…
1411		1665
1412	This section describes each watcher in detail, but will not repeat	1666	This section describes each watcher in detail, but will not repeat
1413	information given in the last section. Any initialisation/set macros,	1667	information given in the last section. Any initialisation/set macros,
1414	functions and members specific to the watcher type are explained.	1668	functions and members specific to the watcher type are explained.
1415		1669
1416	Members are additionally marked with either I<[read-only]>, meaning that,	1670	Most members are additionally marked with either I<[read-only]>, meaning
1417	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
1418	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
1419	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
1420	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
1421	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
1422	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
1423	not crash or malfunction in any way.	1678	not crash or malfunction in any way.
1424		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.
1425		1682
1426	=head2 C<ev_io> - is this file descriptor readable or writable?	1683	=head2 C<ev_io> - is this file descriptor readable or writable?
1427		1684
1428	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
1429	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
…		…
1436	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
1437	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
1438	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
1439	required if you know what you are doing).	1696	required if you know what you are doing).
1440		1697
1441	If you cannot use non-blocking mode, then force the use of a
1442	known-to-be-good backend (at the time of this writing, this includes only
1443	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1444	descriptors for which non-blocking operation makes no sense (such as
1445	files) - libev doesn't guarentee any specific behaviour in that case.
1446
1447	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
1448	receive "spurious" readiness notifications, that is your callback might	1699	receive "spurious" readiness notifications, that is, your callback might
1449	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
1450	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
1451	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
1452	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
1453	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1454	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1704	preferable to a program hanging until some data arrives.
1455		1705
1456	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
1457	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
1458	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
1459	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
1460	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
1461	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
1462	indefinitely.	1712	indefinitely.
1463		1713
1464	But really, best use non-blocking mode.	1714	But really, best use non-blocking mode.
1465		1715
1466	=head3 The special problem of disappearing file descriptors	1716	=head3 The special problem of disappearing file descriptors
1467		1717
1468	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
1469	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
1470	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
1471	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
1472	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
1473	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,
1474	fact, a different file descriptor.	1724	in fact, a different file descriptor.
1475		1725
1476	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
1477	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
1478	will assume that this is potentially a new file descriptor, otherwise	1728	will assume that this is potentially a new file descriptor, otherwise
1479	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
…		…
1493		1743
1494	There is no workaround possible except not registering events	1744	There is no workaround possible except not registering events
1495	for potentially C<dup ()>'ed file descriptors, or to resort to	1745	for potentially C<dup ()>'ed file descriptors, or to resort to
1496	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1746	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1497		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
1498	=head3 The special problem of fork	1781	=head3 The special problem of fork
1499		1782
1500	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 ()>
1501	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
1502	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.
1503		1787
1504	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
1505	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
1506	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1790	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1507	C<EVBACKEND_POLL>.
1508		1791
1509	=head3 The special problem of SIGPIPE	1792	=head3 The special problem of SIGPIPE
1510		1793
1511	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>:
1512	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
…		…
1515		1798
1516	So when you encounter spurious, unexplained daemon exits, make sure you	1799	So when you encounter spurious, unexplained daemon exits, make sure you
1517	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1800	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1518	somewhere, as that would have given you a big clue).	1801	somewhere, as that would have given you a big clue).
1519		1802
		1803	=head3 The special problem of accept()ing when you can't
		1804
		1805	Many implementations of the POSIX C<accept> function (for example,
		1806	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1807	connection from the pending queue in all error cases.
		1808
		1809	For example, larger servers often run out of file descriptors (because
		1810	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1811	rejecting the connection, leading to libev signalling readiness on
		1812	the next iteration again (the connection still exists after all), and
		1813	typically causing the program to loop at 100% CPU usage.
		1814
		1815	Unfortunately, the set of errors that cause this issue differs between
		1816	operating systems, there is usually little the app can do to remedy the
		1817	situation, and no known thread-safe method of removing the connection to
		1818	cope with overload is known (to me).
		1819
		1820	One of the easiest ways to handle this situation is to just ignore it
		1821	- when the program encounters an overload, it will just loop until the
		1822	situation is over. While this is a form of busy waiting, no OS offers an
		1823	event-based way to handle this situation, so it's the best one can do.
		1824
		1825	A better way to handle the situation is to log any errors other than
		1826	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1827	messages, and continue as usual, which at least gives the user an idea of
		1828	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1829	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1830	usage.
		1831
		1832	If your program is single-threaded, then you could also keep a dummy file
		1833	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1834	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1835	close that fd, and create a new dummy fd. This will gracefully refuse
		1836	clients under typical overload conditions.
		1837
		1838	The last way to handle it is to simply log the error and C<exit>, as
		1839	is often done with C<malloc> failures, but this results in an easy
		1840	opportunity for a DoS attack.
1520		1841
1521	=head3 Watcher-Specific Functions	1842	=head3 Watcher-Specific Functions
1522		1843
1523	=over 4	1844	=over 4
1524		1845
1525	=item ev_io_init (ev_io *, callback, int fd, int events)	1846	=item ev_io_init (ev_io *, callback, int fd, int events)
1526		1847
1527	=item ev_io_set (ev_io *, int fd, int events)	1848	=item ev_io_set (ev_io *, int fd, int events)
1528		1849
1529	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
1530	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
1531	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.
1532		1854
1533	=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.
1534		1859
1535	The file descriptor being watched.	1860	=item ev_io_modify (ev_io *, int events)
1536		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
1537	=item int events [read-only]	1873	=item int events [no-modify]
1538		1874
1539	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.
1540		1881
1541	=back	1882	=back
1542		1883
1543	=head3 Examples	1884	=head3 Examples
1544		1885
…		…
1556	...	1897	...
1557	struct ev_loop *loop = ev_default_init (0);	1898	struct ev_loop *loop = ev_default_init (0);
1558	ev_io stdin_readable;	1899	ev_io stdin_readable;
1559	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);
1560	ev_io_start (loop, &stdin_readable);	1901	ev_io_start (loop, &stdin_readable);
1561	ev_loop (loop, 0);	1902	ev_run (loop, 0);
1562		1903
1563		1904
1564	=head2 C<ev_timer> - relative and optionally repeating timeouts	1905	=head2 C<ev_timer> - relative and optionally repeating timeouts
1565		1906
1566	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
…		…
1572	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1913	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1573	monotonic clock option helps a lot here).	1914	monotonic clock option helps a lot here).
1574		1915
1575	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
1576	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
1577	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
1578	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
1579	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
1580	no longer true when a callback calls C<ev_loop> recursively).	1922	longer true when a callback calls C<ev_run> recursively).
1581		1923
1582	=head3 Be smart about timeouts	1924	=head3 Be smart about timeouts
1583		1925
1584	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
1585	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,
…		…
1660		2002
1661	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,
1662	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
1663	within the callback:	2005	within the callback:
1664		2006
		2007	ev_tstamp timeout = 60.;
1665	ev_tstamp last_activity; // time of last activity	2008	ev_tstamp last_activity; // time of last activity
		2009	ev_timer timer;
1666		2010
1667	static void	2011	static void
1668	callback (EV_P_ ev_timer *w, int revents)	2012	callback (EV_P_ ev_timer *w, int revents)
1669	{	2013	{
1670	ev_tstamp now = ev_now (EV_A);	2014	// calculate when the timeout would happen
1671	ev_tstamp timeout = last_activity + 60.;	2015	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1672		2016
1673	// if last_activity + 60. is older than now, we did time out	2017	// if negative, it means we the timeout already occurred
1674	if (timeout < now)	2018	if (after < 0.)
1675	{	2019	{
1676	// timeout occured, take action	2020	// timeout occurred, take action
1677	}	2021	}
1678	else	2022	else
1679	{	2023	{
1680	// callback was invoked, but there was some activity, re-arm	2024	// callback was invoked, but there was some recent
1681	// the watcher to fire in last_activity + 60, which is	2025	// activity. simply restart the timer to time out
1682	// guaranteed to be in the future, so "again" is positive:	2026	// after "after" seconds, which is the earliest time
1683	w->repeat = timeout - now;	2027	// the timeout can occur.
		2028	ev_timer_set (w, after, 0.);
1684	ev_timer_again (EV_A_ w);	2029	ev_timer_start (EV_A_ w);
1685	}	2030	}
1686	}	2031	}
1687		2032
1688	To summarise the callback: first calculate the real timeout (defined	2033	To summarise the callback: first calculate in how many seconds the
1689	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,
1690	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
1691	the callback was invoked too early (C<timeout> is in the future), so	2036	(EV_A)> from that).
1692	re-schedule the timer to fire at that future time, to see if maybe we have
1693	a timeout then.
1694		2037
1695	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
1696	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.
1697		2047
1698	This scheme causes more callback invocations (about one every 60 seconds	2048	This scheme causes more callback invocations (about one every 60 seconds
1699	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
1700	libev to change the timeout.	2050	libev to change the timeout.
1701		2051
1702	To start the timer, simply initialise the watcher and set C<last_activity>	2052	To start the machinery, simply initialise the watcher and set
1703	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
1704	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:
1705		2056
		2057	last_activity = ev_now (EV_A);
1706	ev_init (timer, callback);	2058	ev_init (&timer, callback);
1707	last_activity = ev_now (loop);	2059	callback (EV_A_ &timer, 0);
1708	callback (loop, timer, EV_TIMEOUT);
1709		2060
1710	And when there is some activity, simply store the current time in	2061	When there is some activity, simply store the current time in
1711	C<last_activity>, no libev calls at all:	2062	C<last_activity>, no libev calls at all:
1712		2063
		2064	if (activity detected)
1713	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);
1714		2074
1715	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
1716	time-out is unlikely to be triggered, much more efficient.	2076	time-out is unlikely to be triggered, much more efficient.
1717
1718	Changing the timeout is trivial as well (if it isn't hard-coded in the
1719	callback :) - just change the timeout and invoke the callback, which will
1720	fix things for you.
1721		2077
1722	=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.
1723		2079
1724	If there is not one request, but many thousands (millions...), all	2080	If there is not one request, but many thousands (millions...), all
1725	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
…		…
1752	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
1753	rather complicated, but extremely efficient, something that really pays	2109	rather complicated, but extremely efficient, something that really pays
1754	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
1755	overkill :)	2111	overkill :)
1756		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
1757	=head3 The special problem of time updates	2150	=head3 The special problem of time updates
1758		2151
1759	Establishing the current time is a costly operation (it usually takes at	2152	Establishing the current time is a costly operation (it usually takes
1760	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
1761	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
1762	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
1763	lots of events in one iteration.	2156	lots of events in one iteration.
1764		2157
1765	The relative timeouts are calculated relative to the C<ev_now ()>	2158	The relative timeouts are calculated relative to the C<ev_now ()>
1766	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
1767	of the event triggering whatever timeout you are modifying/starting. If	2160	of the event triggering whatever timeout you are modifying/starting. If
1768	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
1769	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:
1770		2164
1771	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2165	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1772		2166
1773	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
1774	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
1775	()>.	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.
1776		2204
1777	=head3 The special problems of suspended animation	2205	=head3 The special problems of suspended animation
1778		2206
1779	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
1780	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?
…		…
1810		2238
1811	=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)
1812		2240
1813	=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)
1814		2242
1815	Configure the timer to trigger after C<after> seconds. If C<repeat>	2243	Configure the timer to trigger after C<after> seconds (fractional and
1816	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
1817	reached. If it is positive, then the timer will automatically be	2245	automatically be stopped once the timeout is reached. If it is positive,
1818	configured to trigger again C<repeat> seconds later, again, and again,	2246	then the timer will automatically be configured to trigger again C<repeat>
1819	until stopped manually.	2247	seconds later, again, and again, until stopped manually.
1820		2248
1821	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
1822	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
1823	trigger at exactly 10 second intervals. If, however, your program cannot	2251	trigger at exactly 10 second intervals. If, however, your program cannot
1824	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
1825	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.
1826		2254
1827	=item ev_timer_again (loop, ev_timer *)	2255	=item ev_timer_again (loop, ev_timer *)
1828		2256
1829	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
1830	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>.
1831		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
1832	If the timer is pending, its pending status is cleared.	2266	=item If the timer is pending, the pending status is always cleared.
1833		2267
1834	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).
1835		2270
1836	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
1837	C<repeat> value), or reset the running timer to the C<repeat> value.	2272	and start the timer, if necessary.
1838		2273
		2274	=back
		2275
1839	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
1840	usage example.	2277	usage example.
1841		2278
1842	=item ev_timer_remaining (loop, ev_timer *)	2279	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1843		2280
1844	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,
1845	then this time is relative to the current event loop time, otherwise it's	2282	then this time is relative to the current event loop time, otherwise it's
1846	the timeout value currently configured.	2283	the timeout value currently configured.
1847		2284
1848	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2285	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1849	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2286	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1850	will return C<4>. When the timer expires and is restarted, it will return	2287	will return C<4>. When the timer expires and is restarted, it will return
1851	roughly C<7> (likely slightly less as callback invocation takes some time,	2288	roughly C<7> (likely slightly less as callback invocation takes some time,
1852	too), and so on.	2289	too), and so on.
1853		2290
1854	=item ev_tstamp repeat [read-write]	2291	=item ev_tstamp repeat [read-write]
…		…
1883	}	2320	}
1884		2321
1885	ev_timer mytimer;	2322	ev_timer mytimer;
1886	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 */
1887	ev_timer_again (&mytimer); /* start timer */	2324	ev_timer_again (&mytimer); /* start timer */
1888	ev_loop (loop, 0);	2325	ev_run (loop, 0);
1889		2326
1890	// 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":
1891	// reset the timeout to start ticking again at 10 seconds	2328	// reset the timeout to start ticking again at 10 seconds
1892	ev_timer_again (&mytimer);	2329	ev_timer_again (&mytimer);
1893		2330
…		…
1897	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
1898	(and unfortunately a bit complex).	2335	(and unfortunately a bit complex).
1899		2336
1900	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
1901	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
1902	(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
1903	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
1904	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
1905	wrist-watch).	2342	wrist-watch).
1906		2343
1907	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
…		…
1912	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
1913	it, as it uses a relative timeout).	2350	it, as it uses a relative timeout).
1914		2351
1915	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
1916	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
1917	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>
1918	those cannot react to time jumps.	2355	watchers, as those cannot react to time jumps.
1919		2356
1920	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
1921	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
1922	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
1923	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
1924	(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).
1925		2362
1926	=head3 Watcher-Specific Functions and Data Members	2363	=head3 Watcher-Specific Functions and Data Members
1927		2364
1928	=over 4	2365	=over 4
1929		2366
…		…
1964		2401
1965	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
1966	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
1967	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.
1968		2405
1969	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
1970	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
1971	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.
1972		2412
1973	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
1974	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
1975	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
1976	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).
…		…
2006		2446
2007	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
2008	equal to the passed C<now> value >>.	2448	equal to the passed C<now> value >>.
2009		2449
2010	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
2011	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
2012	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
2013	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
2014	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).
2015		2473
2016	=back	2474	=back
2017		2475
2018	=item ev_periodic_again (loop, ev_periodic *)	2476	=item ev_periodic_again (loop, ev_periodic *)
2019		2477
…		…
2057	Example: Call a callback every hour, or, more precisely, whenever the	2515	Example: Call a callback every hour, or, more precisely, whenever the
2058	system time is divisible by 3600. The callback invocation times have	2516	system time is divisible by 3600. The callback invocation times have
2059	potentially a lot of jitter, but good long-term stability.	2517	potentially a lot of jitter, but good long-term stability.
2060		2518
2061	static void	2519	static void
2062	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2520	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2063	{	2521	{
2064	... 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)
2065	}	2523	}
2066		2524
2067	ev_periodic hourly_tick;	2525	ev_periodic hourly_tick;
…		…
2084		2542
2085	ev_periodic hourly_tick;	2543	ev_periodic hourly_tick;
2086	ev_periodic_init (&hourly_tick, clock_cb,	2544	ev_periodic_init (&hourly_tick, clock_cb,
2087	fmod (ev_now (loop), 3600.), 3600., 0);	2545	fmod (ev_now (loop), 3600.), 3600., 0);
2088	ev_periodic_start (loop, &hourly_tick);	2546	ev_periodic_start (loop, &hourly_tick);
2089		2547
2090		2548
2091	=head2 C<ev_signal> - signal me when a signal gets signalled!	2549	=head2 C<ev_signal> - signal me when a signal gets signalled!
2092		2550
2093	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
2094	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
2095	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
2096	normal event processing, like any other event.	2554	normal event processing, like any other event.
2097		2555
2098	If you want signals to be delivered truly asynchronously, just use	2556	If you want signals to be delivered truly asynchronously, just use
2099	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
2100	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
…		…
2104	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
2105	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
2106	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
2107	the moment, C<SIGCHLD> is permanently tied to the default loop.	2565	the moment, C<SIGCHLD> is permanently tied to the default loop.
2108		2566
2109	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
2110	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
2111	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.
2112
2113	Both the signal mask state (C<sigprocmask>) and the signal handler state
2114	(C<sigaction>) are unspecified after starting a signal watcher (and after
2115	sotpping it again), that is, libev might or might not block the signal,
2116	and might or might not set or restore the installed signal handler.
2117		2570
2118	If possible and supported, libev will install its handlers with	2571	If possible and supported, libev will install its handlers with
2119	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2572	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2120	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
2121	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
2122	and unblock them in an C<ev_prepare> watcher.	2575	and unblock them in an C<ev_prepare> watcher.
2123		2576
		2577	=head3 The special problem of inheritance over fork/execve/pthread_create
		2578
		2579	Both the signal mask (C<sigprocmask>) and the signal disposition
		2580	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2581	stopping it again), that is, libev might or might not block the signal,
		2582	and might or might not set or restore the installed signal handler (but
		2583	see C<EVFLAG_NOSIGMASK>).
		2584
		2585	While this does not matter for the signal disposition (libev never
		2586	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2587	C<execve>), this matters for the signal mask: many programs do not expect
		2588	certain signals to be blocked.
		2589
		2590	This means that before calling C<exec> (from the child) you should reset
		2591	the signal mask to whatever "default" you expect (all clear is a good
		2592	choice usually).
		2593
		2594	The simplest way to ensure that the signal mask is reset in the child is
		2595	to install a fork handler with C<pthread_atfork> that resets it. That will
		2596	catch fork calls done by libraries (such as the libc) as well.
		2597
		2598	In current versions of libev, the signal will not be blocked indefinitely
		2599	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2600	the window of opportunity for problems, it will not go away, as libev
		2601	I<has> to modify the signal mask, at least temporarily.
		2602
		2603	So I can't stress this enough: I<If you do not reset your signal mask when
		2604	you expect it to be empty, you have a race condition in your code>. This
		2605	is not a libev-specific thing, this is true for most event libraries.
		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
2124	=head3 Watcher-Specific Functions and Data Members	2621	=head3 Watcher-Specific Functions and Data Members
2125		2622
2126	=over 4	2623	=over 4
2127		2624
2128	=item ev_signal_init (ev_signal *, callback, int signum)	2625	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2143	Example: Try to exit cleanly on SIGINT.	2640	Example: Try to exit cleanly on SIGINT.
2144		2641
2145	static void	2642	static void
2146	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2643	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2147	{	2644	{
2148	ev_unloop (loop, EVUNLOOP_ALL);	2645	ev_break (loop, EVBREAK_ALL);
2149	}	2646	}
2150		2647
2151	ev_signal signal_watcher;	2648	ev_signal signal_watcher;
2152	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2649	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2153	ev_signal_start (loop, &signal_watcher);	2650	ev_signal_start (loop, &signal_watcher);
…		…
2262		2759
2263	=head2 C<ev_stat> - did the file attributes just change?	2760	=head2 C<ev_stat> - did the file attributes just change?
2264		2761
2265	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
2266	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)
2267	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
2268	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.
2269		2767
2270	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
2271	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
2272	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
2273	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
…		…
2503	Apart from keeping your process non-blocking (which is a useful	3001	Apart from keeping your process non-blocking (which is a useful
2504	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
2505	"pseudo-background processing", or delay processing stuff to after the	3003	"pseudo-background processing", or delay processing stuff to after the
2506	event loop has handled all outstanding events.	3004	event loop has handled all outstanding events.
2507		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
2508	=head3 Watcher-Specific Functions and Data Members	3020	=head3 Watcher-Specific Functions and Data Members
2509		3021
2510	=over 4	3022	=over 4
2511		3023
2512	=item ev_idle_init (ev_idle *, callback)	3024	=item ev_idle_init (ev_idle *, callback)
…		…
2523	callback, free it. Also, use no error checking, as usual.	3035	callback, free it. Also, use no error checking, as usual.
2524		3036
2525	static void	3037	static void
2526	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	3038	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2527	{	3039	{
		3040	// stop the watcher
		3041	ev_idle_stop (loop, w);
		3042
		3043	// now we can free it
2528	free (w);	3044	free (w);
		3045
2529	// now do something you wanted to do when the program has	3046	// now do something you wanted to do when the program has
2530	// no longer anything immediate to do.	3047	// no longer anything immediate to do.
2531	}	3048	}
2532		3049
2533	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3050	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2535	ev_idle_start (loop, idle_watcher);	3052	ev_idle_start (loop, idle_watcher);
2536		3053
2537		3054
2538	=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!
2539		3056
2540	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:
2541	prepare watchers get invoked before the process blocks and check watchers	3058	prepare watchers get invoked before the process blocks and check watchers
2542	afterwards.	3059	afterwards.
2543		3060
2544	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
2545	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
2546	watchers. Other loops than the current one are fine, however. The	3063	C<ev_check> watchers. Other loops than the current one are fine,
2547	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
2548	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
2549	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
2550	called in pairs bracketing the blocking call.	3067	kind they will always be called in pairs bracketing the blocking call.
2551		3068
2552	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
2553	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
2554	variable changes, implement your own watchers, integrate net-snmp or a	3071	variable changes, implement your own watchers, integrate net-snmp or a
2555	coroutine library and lots more. They are also occasionally useful if	3072	coroutine library and lots more. They are also occasionally useful if
…		…
2573	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
2574	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
2575	loop from blocking if lower-priority coroutines are active, thus mapping	3092	loop from blocking if lower-priority coroutines are active, thus mapping
2576	low-priority coroutines to idle/background tasks).	3093	low-priority coroutines to idle/background tasks).
2577		3094
2578	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
2579	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
2580	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).
2581		3099
2582	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
2583	activate ("feed") events into libev. While libev fully supports this, they	3101	activate ("feed") events into libev. While libev fully supports this, they
2584	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
2585	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
2586	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
2587	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
2588	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.
2589		3126
2590	=head3 Watcher-Specific Functions and Data Members	3127	=head3 Watcher-Specific Functions and Data Members
2591		3128
2592	=over 4	3129	=over 4
2593		3130
…		…
2717		3254
2718	if (timeout >= 0)	3255	if (timeout >= 0)
2719	// create/start timer	3256	// create/start timer
2720		3257
2721	// poll	3258	// poll
2722	ev_loop (EV_A_ 0);	3259	ev_run (EV_A_ 0);
2723		3260
2724	// stop timer again	3261	// stop timer again
2725	if (timeout >= 0)	3262	if (timeout >= 0)
2726	ev_timer_stop (EV_A_ &to);	3263	ev_timer_stop (EV_A_ &to);
2727		3264
…		…
2794		3331
2795	=over 4	3332	=over 4
2796		3333
2797	=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)
2798		3335
2799	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3336	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2800		3337
2801	Configures the watcher to embed the given loop, which must be	3338	Configures the watcher to embed the given loop, which must be
2802	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
2803	invoked automatically, otherwise it is the responsibility of the callback	3340	invoked automatically, otherwise it is the responsibility of the callback
2804	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,
2805	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).
2806		3343
2807	=item ev_embed_sweep (loop, ev_embed *)	3344	=item ev_embed_sweep (loop, ev_embed *)
2808		3345
2809	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
2810	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
2811	appropriate way for embedded loops.	3348	appropriate way for embedded loops.
2812		3349
2813	=item struct ev_loop *other [read-only]	3350	=item struct ev_loop *other [read-only]
2814		3351
2815	The embedded event loop.	3352	The embedded event loop.
…		…
2825	used).	3362	used).
2826		3363
2827	struct ev_loop *loop_hi = ev_default_init (0);	3364	struct ev_loop *loop_hi = ev_default_init (0);
2828	struct ev_loop *loop_lo = 0;	3365	struct ev_loop *loop_lo = 0;
2829	ev_embed embed;	3366	ev_embed embed;
2830		3367
2831	// see if there is a chance of getting one that works	3368	// see if there is a chance of getting one that works
2832	// (remember that a flags value of 0 means autodetection)	3369	// (remember that a flags value of 0 means autodetection)
2833	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3370	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2834	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3371	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2835	: 0;	3372	: 0;
…		…
2849	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3386	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2850		3387
2851	struct ev_loop *loop = ev_default_init (0);	3388	struct ev_loop *loop = ev_default_init (0);
2852	struct ev_loop *loop_socket = 0;	3389	struct ev_loop *loop_socket = 0;
2853	ev_embed embed;	3390	ev_embed embed;
2854		3391
2855	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3392	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2856	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3393	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2857	{	3394	{
2858	ev_embed_init (&embed, 0, loop_socket);	3395	ev_embed_init (&embed, 0, loop_socket);
2859	ev_embed_start (loop, &embed);	3396	ev_embed_start (loop, &embed);
…		…
2867		3404
2868	=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
2869		3406
2870	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
2871	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
2872	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
2873	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
2874	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
2875	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,
2876	handlers will be invoked, too, of course.	3413	of course.
2877		3414
2878	=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?
2879		3416
2880	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
2881	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
2882	sequence should be handled by libev without any problems.	3419	sequence should be handled by libev without any problems.
2883		3420
2884	This changes when the application actually wants to do event handling	3421	This changes when the application actually wants to do event handling
2885	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
…		…
2901	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
2902	signal watchers).	3439	signal watchers).
2903		3440
2904	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
2905	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
2906	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3443	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2907	the default loop will "orphan" (not stop) all registered watchers, so you	3444	Destroying the default loop will "orphan" (not stop) all registered
2908	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
2909	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.
2910		3448
2911	=head3 Watcher-Specific Functions and Data Members	3449	=head3 Watcher-Specific Functions and Data Members
2912		3450
2913	=over 4	3451	=over 4
2914		3452
2915	=item ev_fork_init (ev_signal *, callback)	3453	=item ev_fork_init (ev_fork *, callback)
2916		3454
2917	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
2918	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,
2919	believe me.	3457	really.
2920		3458
2921	=back	3459	=back
2922		3460
2923		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
2924	=head2 C<ev_async> - how to wake up another event loop	3502	=head2 C<ev_async> - how to wake up an event loop
2925		3503
2926	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
2927	asynchronous sources such as signal handlers (as opposed to multiple event	3505	asynchronous sources such as signal handlers (as opposed to multiple event
2928	loops - those are of course safe to use in different threads).	3506	loops - those are of course safe to use in different threads).
2929		3507
2930	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,
2931	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>
2932	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
2933	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.
2934	safe.
2935		3512
2936	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,
2937	too, are asynchronous in nature, and signals, too, will be compressed	3514	too, are asynchronous in nature, and signals, too, will be compressed
2938	(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
2939	C<ev_async_sent> calls).	3516	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2940		3517	of "global async watchers" by using a watcher on an otherwise unused
2941	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,
2942	just the default loop.	3519	even without knowing which loop owns the signal.
2943		3520
2944	=head3 Queueing	3521	=head3 Queueing
2945		3522
2946	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
2947	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
2948	multiple-writer-single-reader queue that works in all cases and doesn't	3525	multiple-writer-single-reader queue that works in all cases and doesn't
2949	need elaborate support such as pthreads.	3526	need elaborate support such as pthreads or unportable memory access
		3527	semantics.
2950		3528
2951	That means that if you want to queue data, you have to provide your own	3529	That means that if you want to queue data, you have to provide your own
2952	queue. But at least I can tell you how to implement locking around your	3530	queue. But at least I can tell you how to implement locking around your
2953	queue:	3531	queue:
2954		3532
…		…
3038	trust me.	3616	trust me.
3039		3617
3040	=item ev_async_send (loop, ev_async *)	3618	=item ev_async_send (loop, ev_async *)
3041		3619
3042	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
3043	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
3044	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,
3045	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
3046	section below on what exactly this means).	3626	embedding section below on what exactly this means).
3047		3627
3048	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
3049	compressed into a single callback invocation (another way to look at this	3629	compressed into a single callback invocation (another way to look at
3050	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
3051	reset when the event loop detects that).	3631	C<ev_async_send>, reset when the event loop detects that).
3052		3632
3053	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
3054	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
3055	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.
3056		3639
3057	=item bool = ev_async_pending (ev_async *)	3640	=item bool = ev_async_pending (ev_async *)
3058		3641
3059	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
3060	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
…		…
3077		3660
3078	There are some other functions of possible interest. Described. Here. Now.	3661	There are some other functions of possible interest. Described. Here. Now.
3079		3662
3080	=over 4	3663	=over 4
3081		3664
3082	=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)
3083		3666
3084	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
3085	callback on whichever event happens first and automatically stops both	3668	callback on whichever event happens first and automatically stops both
3086	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
3087	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
…		…
3093		3676
3094	If C<timeout> is less than 0, then no timeout watcher will be	3677	If C<timeout> is less than 0, then no timeout watcher will be
3095	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3678	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3096	repeat = 0) will be started. C<0> is a valid timeout.	3679	repeat = 0) will be started. C<0> is a valid timeout.
3097		3680
3098	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3681	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3099	passed an C<revents> set like normal event callbacks (a combination of	3682	passed an C<revents> set like normal event callbacks (a combination of
3100	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3683	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3101	value passed to C<ev_once>. Note that it is possible to receive I<both>	3684	value passed to C<ev_once>. Note that it is possible to receive I<both>
3102	a timeout and an io event at the same time - you probably should give io	3685	a timeout and an io event at the same time - you probably should give io
3103	events precedence.	3686	events precedence.
3104		3687
3105	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3688	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3106		3689
3107	static void stdin_ready (int revents, void *arg)	3690	static void stdin_ready (int revents, void *arg)
3108	{	3691	{
3109	if (revents & EV_READ)	3692	if (revents & EV_READ)
3110	/* stdin might have data for us, joy! */;	3693	/* stdin might have data for us, joy! */;
3111	else if (revents & EV_TIMEOUT)	3694	else if (revents & EV_TIMER)
3112	/* doh, nothing entered */;	3695	/* doh, nothing entered */;
3113	}	3696	}
3114		3697
3115	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3698	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3116		3699
3117	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3118
3119	Feeds the given event set into the event loop, as if the specified event
3120	had happened for the specified watcher (which must be a pointer to an
3121	initialised but not necessarily started event watcher).
3122
3123	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3700	=item ev_feed_fd_event (loop, int fd, int revents)
3124		3701
3125	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
3126	the given events it.	3703	the given events.
3127		3704
3128	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3705	=item ev_feed_signal_event (loop, int signum)
3129		3706
3130	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>,
3131	loop!).	3708	which is async-safe.
3132		3709
3133	=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.
3134		4061
3135		4062
3136	=head1 LIBEVENT EMULATION	4063	=head1 LIBEVENT EMULATION
3137		4064
3138	Libev offers a compatibility emulation layer for libevent. It cannot	4065	Libev offers a compatibility emulation layer for libevent. It cannot
3139	emulate the internals of libevent, so here are some usage hints:	4066	emulate the internals of libevent, so here are some usage hints:
3140		4067
3141	=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.
3142		4074
3143	=item * Use it by including <event.h>, as usual.	4075	=item * Use it by including <event.h>, as usual.
3144		4076
3145	=item * The following members are fully supported: ev_base, ev_callback,	4077	=item * The following members are fully supported: ev_base, ev_callback,
3146	ev_arg, ev_fd, ev_res, ev_events.	4078	ev_arg, ev_fd, ev_res, ev_events.
…		…
3152	=item * Priorities are not currently supported. Initialising priorities	4084	=item * Priorities are not currently supported. Initialising priorities
3153	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
3154	is an ev_pri field.	4086	is an ev_pri field.
3155		4087
3156	=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
3157	first base created (== the default loop) gets the signals.	4089	base that registered the signal gets the signals.
3158		4090
3159	=item * Other members are not supported.	4091	=item * Other members are not supported.
3160		4092
3161	=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
3162	to use the libev header file and library.	4094	to use the libev header file and library.
3163		4095
3164	=back	4096	=back
3165		4097
3166	=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
3167		4132
3168	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
3169	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
3170	the callback model to a model using method callbacks on objects.	4135	the callback model to a model using method callbacks on objects.
3171		4136
3172	To use it,	4137	To use it,
3173		4138
3174	#include <ev++.h>	4139	#include <ev++.h>
3175		4140
3176	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
3177	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
3178	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
…		…
3181	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++
3182	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
3183	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
3184	you disable C<EV_MULTIPLICITY> when embedding libev).	4149	you disable C<EV_MULTIPLICITY> when embedding libev).
3185		4150
3186	Currently, functions, and static and non-static member functions can be	4151	Currently, functions, static and non-static member functions and classes
3187	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
3188	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
3189	types of functors please contact the author (preferably after implementing	4154	you need support for other types of functors please contact the author
3190	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++.
3191		4160
3192	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:
3193		4162
3194	=over 4	4163	=over 4
3195		4164
…		…
3205	=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.
3206		4175
3207	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
3208	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>
3209	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
3210	defines by many implementations.	4179	defined by many implementations.
3211		4180
3212	All of those classes have these methods:	4181	All of those classes have these methods:
3213		4182
3214	=over 4	4183	=over 4
3215		4184
3216	=item ev::TYPE::TYPE ()	4185	=item ev::TYPE::TYPE ()
3217		4186
3218	=item ev::TYPE::TYPE (struct ev_loop *)	4187	=item ev::TYPE::TYPE (loop)
3219		4188
3220	=item ev::TYPE::~TYPE	4189	=item ev::TYPE::~TYPE
3221		4190
3222	The constructor (optionally) takes an event loop to associate the watcher	4191	The constructor (optionally) takes an event loop to associate the watcher
3223	with. If it is omitted, it will use C<EV_DEFAULT>.	4192	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3256	myclass obj;	4225	myclass obj;
3257	ev::io iow;	4226	ev::io iow;
3258	iow.set <myclass, &myclass::io_cb> (&obj);	4227	iow.set <myclass, &myclass::io_cb> (&obj);
3259		4228
3260	=item w->set (object *)	4229	=item w->set (object *)
3261
3262	This is an B<experimental> feature that might go away in a future version.
3263		4230
3264	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
3265	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
3266	functor objects without having to manually specify the C<operator ()> all	4233	functor objects without having to manually specify the C<operator ()> all
3267	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
…		…
3279	void operator() (ev::io &w, int revents)	4246	void operator() (ev::io &w, int revents)
3280	{	4247	{
3281	...	4248	...
3282	}	4249	}
3283	}	4250	}
3284		4251
3285	myfunctor f;	4252	myfunctor f;
3286		4253
3287	ev::io w;	4254	ev::io w;
3288	w.set (&f);	4255	w.set (&f);
3289		4256
…		…
3300	Example: Use a plain function as callback.	4267	Example: Use a plain function as callback.
3301		4268
3302	static void io_cb (ev::io &w, int revents) { }	4269	static void io_cb (ev::io &w, int revents) { }
3303	iow.set <io_cb> ();	4270	iow.set <io_cb> ();
3304		4271
3305	=item w->set (struct ev_loop *)	4272	=item w->set (loop)
3306		4273
3307	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
3308	do this when the watcher is inactive (and not pending either).	4275	do this when the watcher is inactive (and not pending either).
3309		4276
3310	=item w->set ([arguments])	4277	=item w->set ([arguments])
3311		4278
3312	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
3313	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
3314	automatically stopped and restarted when reconfiguring it with this	4282	gets automatically stopped and restarted when reconfiguring it with this
3315	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>.
3316		4290
3317	=item w->start ()	4291	=item w->start ()
3318		4292
3319	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
3320	constructor already stores the event loop.	4294	constructor already stores the event loop.
3321		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
3322	=item w->stop ()	4302	=item w->stop ()
3323		4303
3324	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.
3325		4305
3326	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4306	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3338		4318
3339	=back	4319	=back
3340		4320
3341	=back	4321	=back
3342		4322
3343	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
3344	the constructor.	4324	watchers in the constructor.
3345		4325
3346	class myclass	4326	class myclass
3347	{	4327	{
3348	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);
3349	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4330	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3350		4331
3351	myclass (int fd)	4332	myclass (int fd)
3352	{	4333	{
3353	io .set <myclass, &myclass::io_cb > (this);	4334	io .set <myclass, &myclass::io_cb > (this);
		4335	io2 .set <myclass, &myclass::io2_cb > (this);
3354	idle.set <myclass, &myclass::idle_cb> (this);	4336	idle.set <myclass, &myclass::idle_cb> (this);
3355		4337
3356	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
3357	}	4342	}
3358	};	4343	};
3359		4344
3360		4345
3361	=head1 OTHER LANGUAGE BINDINGS	4346	=head1 OTHER LANGUAGE BINDINGS
…		…
3400	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4385	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3401		4386
3402	=item D	4387	=item D
3403		4388
3404	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
3405	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>.
3406		4391
3407	=item Ocaml	4392	=item Ocaml
3408		4393
3409	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
3410	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4395	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3411		4396
3412	=item Lua	4397	=item Lua
3413		4398
3414	Brian Maher has written a partial interface to libev	4399	Brian Maher has written a partial interface to libev for lua (at the
3415	for lua (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
3416	L<http://github.com/brimworks/lua-ev>.	4401	L<http://github.com/brimworks/lua-ev>.
		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.
3417		4410
3418	=back	4411	=back
3419		4412
3420		4413
3421	=head1 MACRO MAGIC	4414	=head1 MACRO MAGIC
…		…
3435	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,
3436	C<EV_A_> is used when other arguments are following. Example:	4429	C<EV_A_> is used when other arguments are following. Example:
3437		4430
3438	ev_unref (EV_A);	4431	ev_unref (EV_A);
3439	ev_timer_add (EV_A_ watcher);	4432	ev_timer_add (EV_A_ watcher);
3440	ev_loop (EV_A_ 0);	4433	ev_run (EV_A_ 0);
3441		4434
3442	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,
3443	which is often provided by the following macro.	4436	which is often provided by the following macro.
3444		4437
3445	=item C<EV_P>, C<EV_P_>	4438	=item C<EV_P>, C<EV_P_>
…		…
3458	suitable for use with C<EV_A>.	4451	suitable for use with C<EV_A>.
3459		4452
3460	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4453	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3461		4454
3462	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
3463	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.
3464		4461
3465	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4462	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3466		4463
3467	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
3468	default loop has been initialised (C<UC> == unchecked). Their behaviour	4465	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3485	}	4482	}
3486		4483
3487	ev_check check;	4484	ev_check check;
3488	ev_check_init (&check, check_cb);	4485	ev_check_init (&check, check_cb);
3489	ev_check_start (EV_DEFAULT_ &check);	4486	ev_check_start (EV_DEFAULT_ &check);
3490	ev_loop (EV_DEFAULT_ 0);	4487	ev_run (EV_DEFAULT_ 0);
3491		4488
3492	=head1 EMBEDDING	4489	=head1 EMBEDDING
3493		4490
3494	Libev can (and often is) directly embedded into host	4491	Libev can (and often is) directly embedded into host
3495	applications. Examples of applications that embed it include the Deliantra	4492	applications. Examples of applications that embed it include the Deliantra
…		…
3535	ev_vars.h	4532	ev_vars.h
3536	ev_wrap.h	4533	ev_wrap.h
3537		4534
3538	ev_win32.c required on win32 platforms only	4535	ev_win32.c required on win32 platforms only
3539		4536
3540	ev_select.c only when select backend is enabled (which is enabled by default)	4537	ev_select.c only when select backend is enabled
3541	ev_poll.c only when poll backend is enabled (disabled by default)	4538	ev_poll.c only when poll backend is enabled
3542	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
3543	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4542	ev_kqueue.c only when the kqueue backend is enabled
3544	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
3545		4544
3546	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
3547	to compile this single file.	4546	to compile this single file.
3548		4547
3549	=head3 LIBEVENT COMPATIBILITY API	4548	=head3 LIBEVENT COMPATIBILITY API
…		…
3575	libev.m4	4574	libev.m4
3576		4575
3577	=head2 PREPROCESSOR SYMBOLS/MACROS	4576	=head2 PREPROCESSOR SYMBOLS/MACROS
3578		4577
3579	Libev can be configured via a variety of preprocessor symbols you have to	4578	Libev can be configured via a variety of preprocessor symbols you have to
3580	define before including any of its files. The default in the absence of	4579	define before including (or compiling) any of its files. The default in
3581	autoconf is documented for every option.	4580	the absence of autoconf is documented for every option.
		4581
		4582	Symbols marked with "(h)" do not change the ABI, and can have different
		4583	values when compiling libev vs. including F<ev.h>, so it is permissible
		4584	to redefine them before including F<ev.h> without breaking compatibility
		4585	to a compiled library. All other symbols change the ABI, which means all
		4586	users of libev and the libev code itself must be compiled with compatible
		4587	settings.
3582		4588
3583	=over 4	4589	=over 4
3584		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.
		4606
3585	=item EV_STANDALONE	4607	=item EV_STANDALONE (h)
3586		4608
3587	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
3588	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
3589	implementations for some libevent functions (such as logging, which is not	4611	implementations for some libevent functions (such as logging, which is not
3590	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
3591	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.
3592		4614
3593	In standalone mode, libev will still try to automatically deduce the	4615	In standalone mode, libev will still try to automatically deduce the
3594	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.
3595		4626
3596	=item EV_USE_MONOTONIC	4627	=item EV_USE_MONOTONIC
3597		4628
3598	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
3599	monotonic clock option at both compile time and runtime. Otherwise no	4630	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3636	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
3637	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.
3638	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
3639	2.7 or newer, otherwise disabled.	4670	2.7 or newer, otherwise disabled.
3640		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
3641	=item EV_USE_SELECT	4696	=item EV_USE_SELECT
3642		4697
3643	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
3644	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
3645	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
…		…
3685	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
3686	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
3687	file descriptors again. Note that the replacement function has to close	4742	file descriptors again. Note that the replacement function has to close
3688	the underlying OS handle.	4743	the underlying OS handle.
3689		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
3690	=item EV_USE_POLL	4752	=item EV_USE_POLL
3691		4753
3692	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)
3693	backend. Otherwise it will be enabled on non-win32 platforms. It	4755	backend. Otherwise it will be enabled on non-win32 platforms. It
3694	takes precedence over select.	4756	takes precedence over select.
…		…
3698	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
3699	C<epoll>(7) backend. Its availability will be detected at runtime,	4761	C<epoll>(7) backend. Its availability will be detected at runtime,
3700	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
3701	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
3702	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.
3703		4778
3704	=item EV_USE_KQUEUE	4779	=item EV_USE_KQUEUE
3705		4780
3706	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
3707	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,
…		…
3729	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
3730	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
3731	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
3732	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4807	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3733		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
3734	=item EV_ATOMIC_T	4823	=item EV_ATOMIC_T
3735		4824
3736	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
3737	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
3738	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
3739	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
3740	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.
3741		4831
3742	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>
3743	(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.
3744		4834
3745	=item EV_H	4835	=item EV_H (h)
3746		4836
3747	The name of the F<ev.h> header file used to include it. The default if	4837	The name of the F<ev.h> header file used to include it. The default if
3748	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4838	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3749	used to virtually rename the F<ev.h> header file in case of conflicts.	4839	used to virtually rename the F<ev.h> header file in case of conflicts.
3750		4840
3751	=item EV_CONFIG_H	4841	=item EV_CONFIG_H (h)
3752		4842
3753	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4843	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3754	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4844	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3755	C<EV_H>, above.	4845	C<EV_H>, above.
3756		4846
3757	=item EV_EVENT_H	4847	=item EV_EVENT_H (h)
3758		4848
3759	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4849	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3760	of how the F<event.h> header can be found, the default is C<"event.h">.	4850	of how the F<event.h> header can be found, the default is C<"event.h">.
3761		4851
3762	=item EV_PROTOTYPES	4852	=item EV_PROTOTYPES (h)
3763		4853
3764	If defined to be C<0>, then F<ev.h> will not define any function	4854	If defined to be C<0>, then F<ev.h> will not define any function
3765	prototypes, but still define all the structs and other symbols. This is	4855	prototypes, but still define all the structs and other symbols. This is
3766	occasionally useful if you want to provide your own wrapper functions	4856	occasionally useful if you want to provide your own wrapper functions
3767	around libev functions.	4857	around libev functions.
…		…
3772	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
3773	additional independent event loops. Otherwise there will be no support	4863	additional independent event loops. Otherwise there will be no support
3774	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
3775	argument. Instead, all functions act on the single default loop.	4865	argument. Instead, all functions act on the single default loop.
3776		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
3777	=item EV_MINPRI	4871	=item EV_MINPRI
3778		4872
3779	=item EV_MAXPRI	4873	=item EV_MAXPRI
3780		4874
3781	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
…		…
3789	fine.	4883	fine.
3790		4884
3791	If your embedding application does not need any priorities, defining these	4885	If your embedding application does not need any priorities, defining these
3792	both to C<0> will save some memory and CPU.	4886	both to C<0> will save some memory and CPU.
3793		4887
3794	=item EV_PERIODIC_ENABLE	4888	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4889	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4890	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3795		4891
3796	If undefined or defined to be C<1>, then periodic timers are supported. If	4892	If undefined or defined to be C<1> (and the platform supports it), then
3797	defined to be C<0>, then they are not. Disabling them saves a few kB of	4893	the respective watcher type is supported. If defined to be C<0>, then it
3798	code.	4894	is not. Disabling watcher types mainly saves code size.
3799		4895
3800	=item EV_IDLE_ENABLE	4896	=item EV_FEATURES
3801
3802	If undefined or defined to be C<1>, then idle watchers are supported. If
3803	defined to be C<0>, then they are not. Disabling them saves a few kB of
3804	code.
3805
3806	=item EV_EMBED_ENABLE
3807
3808	If undefined or defined to be C<1>, then embed watchers are supported. If
3809	defined to be C<0>, then they are not. Embed watchers rely on most other
3810	watcher types, which therefore must not be disabled.
3811
3812	=item EV_STAT_ENABLE
3813
3814	If undefined or defined to be C<1>, then stat watchers are supported. If
3815	defined to be C<0>, then they are not.
3816
3817	=item EV_FORK_ENABLE
3818
3819	If undefined or defined to be C<1>, then fork watchers are supported. If
3820	defined to be C<0>, then they are not.
3821
3822	=item EV_ASYNC_ENABLE
3823
3824	If undefined or defined to be C<1>, then async watchers are supported. If
3825	defined to be C<0>, then they are not.
3826
3827	=item EV_MINIMAL
3828		4897
3829	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
3830	speed (but with the full API), define this symbol to C<1>. Currently this	4899	speed (but with the full API), you can define this symbol to request
3831	is used to override some inlining decisions, saves roughly 30% code size	4900	certain subsets of functionality. The default is to enable all features
3832	on amd64. It also selects a much smaller 2-heap for timer management over	4901	that can be enabled on the platform.
3833	the default 4-heap.
3834		4902
3835	You can save even more by disabling watcher types you do not need	4903	A typical way to use this symbol is to define it to C<0> (or to a bitset
3836	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4904	with some broad features you want) and then selectively re-enable
3837	(C<-DNDEBUG>) will usually reduce code size a lot.	4905	additional parts you want, for example if you want everything minimal,
		4906	but multiple event loop support, async and child watchers and the poll
		4907	backend, use this:
3838		4908
3839	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4909	#define EV_FEATURES 0
3840	provide a bare-bones event library. See C<ev.h> for details on what parts	4910	#define EV_MULTIPLICITY 1
3841	of the API are still available, and do not complain if this subset changes	4911	#define EV_USE_POLL 1
3842	over time.	4912	#define EV_CHILD_ENABLE 1
		4913	#define EV_ASYNC_ENABLE 1
		4914
		4915	The actual value is a bitset, it can be a combination of the following
		4916	values (by default, all of these are enabled):
		4917
		4918	=over 4
		4919
		4920	=item C<1> - faster/larger code
		4921
		4922	Use larger code to speed up some operations.
		4923
		4924	Currently this is used to override some inlining decisions (enlarging the
		4925	code size by roughly 30% on amd64).
		4926
		4927	When optimising for size, use of compiler flags such as C<-Os> with
		4928	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4929	assertions.
		4930
		4931	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4932	(e.g. gcc with C<-Os>).
		4933
		4934	=item C<2> - faster/larger data structures
		4935
		4936	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4937	hash table sizes and so on. This will usually further increase code size
		4938	and can additionally have an effect on the size of data structures at
		4939	runtime.
		4940
		4941	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4942	(e.g. gcc with C<-Os>).
		4943
		4944	=item C<4> - full API configuration
		4945
		4946	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4947	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4948
		4949	=item C<8> - full API
		4950
		4951	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4952	details on which parts of the API are still available without this
		4953	feature, and do not complain if this subset changes over time.
		4954
		4955	=item C<16> - enable all optional watcher types
		4956
		4957	Enables all optional watcher types. If you want to selectively enable
		4958	only some watcher types other than I/O and timers (e.g. prepare,
		4959	embed, async, child...) you can enable them manually by defining
		4960	C<EV_watchertype_ENABLE> to C<1> instead.
		4961
		4962	=item C<32> - enable all backends
		4963
		4964	This enables all backends - without this feature, you need to enable at
		4965	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4966
		4967	=item C<64> - enable OS-specific "helper" APIs
		4968
		4969	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4970	default.
		4971
		4972	=back
		4973
		4974	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4975	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4976	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4977	watchers, timers and monotonic clock support.
		4978
		4979	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4980	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4981	your program might be left out as well - a binary starting a timer and an
		4982	I/O watcher then might come out at only 5Kb.
		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
		4998	=item EV_AVOID_STDIO
		4999
		5000	If this is set to C<1> at compiletime, then libev will avoid using stdio
		5001	functions (printf, scanf, perror etc.). This will increase the code size
		5002	somewhat, but if your program doesn't otherwise depend on stdio and your
		5003	libc allows it, this avoids linking in the stdio library which is quite
		5004	big.
		5005
		5006	Note that error messages might become less precise when this option is
		5007	enabled.
3843		5008
3844	=item EV_NSIG	5009	=item EV_NSIG
3845		5010
3846	The highest supported signal number, +1 (or, the number of	5011	The highest supported signal number, +1 (or, the number of
3847	signals): Normally, libev tries to deduce the maximum number of signals	5012	signals): Normally, libev tries to deduce the maximum number of signals
3848	automatically, but sometimes this fails, in which case it can be	5013	automatically, but sometimes this fails, in which case it can be
3849	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
3850	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
3851	statically allocates some 12-24 bytes per signal number.	5016	statically allocates some 12-24 bytes per signal number.
3852		5017
3853	=item EV_PID_HASHSIZE	5018	=item EV_PID_HASHSIZE
3854		5019
3855	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
3856	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	5021	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3857	than enough. If you need to manage thousands of children you might want to	5022	usually more than enough. If you need to manage thousands of children you
3858	increase this value (I<must> be a power of two).	5023	might want to increase this value (I<must> be a power of two).
3859		5024
3860	=item EV_INOTIFY_HASHSIZE	5025	=item EV_INOTIFY_HASHSIZE
3861		5026
3862	C<ev_stat> watchers use a small hash table to distribute workload by	5027	C<ev_stat> watchers use a small hash table to distribute workload by
3863	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	5028	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3864	usually more than enough. If you need to manage thousands of C<ev_stat>	5029	disabled), usually more than enough. If you need to manage thousands of
3865	watchers you might want to increase this value (I<must> be a power of	5030	C<ev_stat> watchers you might want to increase this value (I<must> be a
3866	two).	5031	power of two).
3867		5032
3868	=item EV_USE_4HEAP	5033	=item EV_USE_4HEAP
3869		5034
3870	Heaps are not very cache-efficient. To improve the cache-efficiency of the	5035	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3871	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	5036	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3872	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	5037	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3873	faster performance with many (thousands) of watchers.	5038	faster performance with many (thousands) of watchers.
3874		5039
3875	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	5040	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3876	(disabled).	5041	will be C<0>.
3877		5042
3878	=item EV_HEAP_CACHE_AT	5043	=item EV_HEAP_CACHE_AT
3879		5044
3880	Heaps are not very cache-efficient. To improve the cache-efficiency of the	5045	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3881	timer and periodics heaps, libev can cache the timestamp (I<at>) within	5046	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3882	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	5047	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3883	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	5048	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3884	but avoids random read accesses on heap changes. This improves performance	5049	but avoids random read accesses on heap changes. This improves performance
3885	noticeably with many (hundreds) of watchers.	5050	noticeably with many (hundreds) of watchers.
3886		5051
3887	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	5052	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3888	(disabled).	5053	will be C<0>.
3889		5054
3890	=item EV_VERIFY	5055	=item EV_VERIFY
3891		5056
3892	Controls how much internal verification (see C<ev_loop_verify ()>) will	5057	Controls how much internal verification (see C<ev_verify ()>) will
3893	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
3894	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
3895	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
3896	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
3897	verification code will be called very frequently, which will slow down	5062	verification code will be called very frequently, which will slow down
3898	libev considerably.	5063	libev considerably.
3899		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
3900	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	5068	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3901	C<0>.	5069	will be C<0>.
3902		5070
3903	=item EV_COMMON	5071	=item EV_COMMON
3904		5072
3905	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
3906	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
3907	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,
3908	though, and it must be identical each time.	5076	though, and it must be identical each time.
3909		5077
3910	For example, the perl EV module uses something like this:	5078	For example, the perl EV module uses something like this:
3911		5079
…		…
3964	file.	5132	file.
3965		5133
3966	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5134	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3967	that everybody includes and which overrides some configure choices:	5135	that everybody includes and which overrides some configure choices:
3968		5136
3969	#define EV_MINIMAL 1	5137	#define EV_FEATURES 8
3970	#define EV_USE_POLL 0	5138	#define EV_USE_SELECT 1
3971	#define EV_MULTIPLICITY 0
3972	#define EV_PERIODIC_ENABLE 0	5139	#define EV_PREPARE_ENABLE 1
		5140	#define EV_IDLE_ENABLE 1
3973	#define EV_STAT_ENABLE 0	5141	#define EV_SIGNAL_ENABLE 1
3974	#define EV_FORK_ENABLE 0	5142	#define EV_CHILD_ENABLE 1
		5143	#define EV_USE_STDEXCEPT 0
3975	#define EV_CONFIG_H <config.h>	5144	#define EV_CONFIG_H <config.h>
3976	#define EV_MINPRI 0
3977	#define EV_MAXPRI 0
3978		5145
3979	#include "ev++.h"	5146	#include "ev++.h"
3980		5147
3981	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:
3982		5149
3983	#include "ev_cpp.h"	5150	#include "ev_cpp.h"
3984	#include "ev.c"	5151	#include "ev.c"
3985		5152
3986	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5153	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3987		5154
3988	=head2 THREADS AND COROUTINES	5155	=head2 THREADS AND COROUTINES
3989		5156
3990	=head3 THREADS	5157	=head3 THREADS
3991		5158
…		…
4042	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
4043	watcher callback into the event loop interested in the signal.	5210	watcher callback into the event loop interested in the signal.
4044		5211
4045	=back	5212	=back
4046		5213
4047	=head4 THREAD LOCKING EXAMPLE	5214	See also L</THREAD LOCKING EXAMPLE>.
4048
4049	Here is a fictitious example of how to run an event loop in a different
4050	thread than where callbacks are being invoked and watchers are
4051	created/added/removed.
4052
4053	For a real-world example, see the C<EV::Loop::Async> perl module,
4054	which uses exactly this technique (which is suited for many high-level
4055	languages).
4056
4057	The example uses a pthread mutex to protect the loop data, a condition
4058	variable to wait for callback invocations, an async watcher to notify the
4059	event loop thread and an unspecified mechanism to wake up the main thread.
4060
4061	First, you need to associate some data with the event loop:
4062
4063	typedef struct {
4064	mutex_t lock; /* global loop lock */
4065	ev_async async_w;
4066	thread_t tid;
4067	cond_t invoke_cv;
4068	} userdata;
4069
4070	void prepare_loop (EV_P)
4071	{
4072	// for simplicity, we use a static userdata struct.
4073	static userdata u;
4074
4075	ev_async_init (&u->async_w, async_cb);
4076	ev_async_start (EV_A_ &u->async_w);
4077
4078	pthread_mutex_init (&u->lock, 0);
4079	pthread_cond_init (&u->invoke_cv, 0);
4080
4081	// now associate this with the loop
4082	ev_set_userdata (EV_A_ u);
4083	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4084	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4085
4086	// then create the thread running ev_loop
4087	pthread_create (&u->tid, 0, l_run, EV_A);
4088	}
4089
4090	The callback for the C<ev_async> watcher does nothing: the watcher is used
4091	solely to wake up the event loop so it takes notice of any new watchers
4092	that might have been added:
4093
4094	static void
4095	async_cb (EV_P_ ev_async *w, int revents)
4096	{
4097	// just used for the side effects
4098	}
4099
4100	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4101	protecting the loop data, respectively.
4102
4103	static void
4104	l_release (EV_P)
4105	{
4106	userdata *u = ev_userdata (EV_A);
4107	pthread_mutex_unlock (&u->lock);
4108	}
4109
4110	static void
4111	l_acquire (EV_P)
4112	{
4113	userdata *u = ev_userdata (EV_A);
4114	pthread_mutex_lock (&u->lock);
4115	}
4116
4117	The event loop thread first acquires the mutex, and then jumps straight
4118	into C<ev_loop>:
4119
4120	void *
4121	l_run (void *thr_arg)
4122	{
4123	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4124
4125	l_acquire (EV_A);
4126	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4127	ev_loop (EV_A_ 0);
4128	l_release (EV_A);
4129
4130	return 0;
4131	}
4132
4133	Instead of invoking all pending watchers, the C<l_invoke> callback will
4134	signal the main thread via some unspecified mechanism (signals? pipe
4135	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4136	have been called (in a while loop because a) spurious wakeups are possible
4137	and b) skipping inter-thread-communication when there are no pending
4138	watchers is very beneficial):
4139
4140	static void
4141	l_invoke (EV_P)
4142	{
4143	userdata *u = ev_userdata (EV_A);
4144
4145	while (ev_pending_count (EV_A))
4146	{
4147	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4148	pthread_cond_wait (&u->invoke_cv, &u->lock);
4149	}
4150	}
4151
4152	Now, whenever the main thread gets told to invoke pending watchers, it
4153	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4154	thread to continue:
4155
4156	static void
4157	real_invoke_pending (EV_P)
4158	{
4159	userdata *u = ev_userdata (EV_A);
4160
4161	pthread_mutex_lock (&u->lock);
4162	ev_invoke_pending (EV_A);
4163	pthread_cond_signal (&u->invoke_cv);
4164	pthread_mutex_unlock (&u->lock);
4165	}
4166
4167	Whenever you want to start/stop a watcher or do other modifications to an
4168	event loop, you will now have to lock:
4169
4170	ev_timer timeout_watcher;
4171	userdata *u = ev_userdata (EV_A);
4172
4173	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4174
4175	pthread_mutex_lock (&u->lock);
4176	ev_timer_start (EV_A_ &timeout_watcher);
4177	ev_async_send (EV_A_ &u->async_w);
4178	pthread_mutex_unlock (&u->lock);
4179
4180	Note that sending the C<ev_async> watcher is required because otherwise
4181	an event loop currently blocking in the kernel will have no knowledge
4182	about the newly added timer. By waking up the loop it will pick up any new
4183	watchers in the next event loop iteration.
4184		5215
4185	=head3 COROUTINES	5216	=head3 COROUTINES
4186		5217
4187	Libev is very accommodating to coroutines ("cooperative threads"):	5218	Libev is very accommodating to coroutines ("cooperative threads"):
4188	libev fully supports nesting calls to its functions from different	5219	libev fully supports nesting calls to its functions from different
4189	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
4190	different coroutines, and switch freely between both coroutines running	5221	different coroutines, and switch freely between both coroutines running
4191	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
4192	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.
4193		5224
4194	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
4195	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
4196	they do not call any callbacks.	5227	they do not call any callbacks.
4197		5228
4198	=head2 COMPILER WARNINGS	5229	=head2 COMPILER WARNINGS
4199		5230
4200	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
…		…
4211	maintainable.	5242	maintainable.
4212		5243
4213	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
4214	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
4215	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
4216	warnings that resulted an extreme number of false positives. These have	5247	warnings that resulted in an extreme number of false positives. These have
4217	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
4218	such buggy versions.	5249	such buggy versions.
4219		5250
4220	While libev is written to generate as few warnings as possible,	5251	While libev is written to generate as few warnings as possible,
4221	"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
…		…
4257	I suggest using suppression lists.	5288	I suggest using suppression lists.
4258		5289
4259		5290
4260	=head1 PORTABILITY NOTES	5291	=head1 PORTABILITY NOTES
4261		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
4262	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5379	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5380
		5381	=head3 General issues
4263		5382
4264	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
4265	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
4266	model. Libev still offers limited functionality on this platform in	5385	model. Libev still offers limited functionality on this platform in
4267	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
4268	descriptors. This only applies when using Win32 natively, not when using	5387	descriptors. This only applies when using Win32 natively, not when using
4269	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.
4270		5391
4271	Lifting these limitations would basically require the full	5392	Lifting these limitations would basically require the full
4272	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,
4273	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
4274	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).
4275		5396
4276	There is no supported compilation method available on windows except	5397	There is no supported compilation method available on windows except
4277	embedding it into other applications.	5398	embedding it into other applications.
4278		5399
4279	Sensible signal handling is officially unsupported by Microsoft - libev	5400	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4307	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!):
4308		5429
4309	#include "evwrap.h"	5430	#include "evwrap.h"
4310	#include "ev.c"	5431	#include "ev.c"
4311		5432
4312	=over 4
4313
4314	=item The winsocket select function	5433	=head3 The winsocket C<select> function
4315		5434
4316	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
4317	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
4318	also extremely buggy). This makes select very inefficient, and also	5437	also extremely buggy). This makes select very inefficient, and also
4319	requires a mapping from file descriptors to socket handles (the Microsoft	5438	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4328	#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 */
4329		5448
4330	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
4331	complexity in the O(n²) range when using win32.	5450	complexity in the O(n²) range when using win32.
4332		5451
4333	=item Limited number of file descriptors	5452	=head3 Limited number of file descriptors
4334		5453
4335	Windows has numerous arbitrary (and low) limits on things.	5454	Windows has numerous arbitrary (and low) limits on things.
4336		5455
4337	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
4338	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
…		…
4353	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
4354	(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,
4355	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
4356	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.
4357		5476
4358	=back
4359
4360	=head2 PORTABILITY REQUIREMENTS	5477	=head2 PORTABILITY REQUIREMENTS
4361		5478
4362	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
4363	backend-specific APIs, libev relies on a few additional extensions:	5480	backend-specific APIs, libev relies on a few additional extensions:
4364		5481
…		…
4370	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
4371	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
4372	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
4373	callback: The watcher callbacks have different type signatures, but libev	5490	callback: The watcher callbacks have different type signatures, but libev
4374	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.
4375		5502
4376	=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
4377		5504
4378	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
4379	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
…		…
4388	thread" or will block signals process-wide, both behaviours would	5515	thread" or will block signals process-wide, both behaviours would
4389	be compatible with libev. Interaction between C<sigprocmask> and	5516	be compatible with libev. Interaction between C<sigprocmask> and
4390	C<pthread_sigmask> could complicate things, however.	5517	C<pthread_sigmask> could complicate things, however.
4391		5518
4392	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
4393	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
4394	well.	5521	thread as well.
4395		5522
4396	=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
4397		5524
4398	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
4399	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
…		…
4402	watchers.	5529	watchers.
4403		5530
4404	=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
4405		5532
4406	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
4407	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
4408	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
4409	implementations implementing IEEE 754, which is basically all existing	5537	implementations using IEEE 754, which is basically all existing ones.
		5538
4410	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
4411	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).
4412		5543
4413	=back	5544	=back
4414		5545
4415	If you know of other additional requirements drop me a note.	5546	If you know of other additional requirements drop me a note.
4416		5547
…		…
4478	=item Processing ev_async_send: O(number_of_async_watchers)	5609	=item Processing ev_async_send: O(number_of_async_watchers)
4479		5610
4480	=item Processing signals: O(max_signal_number)	5611	=item Processing signals: O(max_signal_number)
4481		5612
4482	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>
4483	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
4484	involves iterating over all running async watchers or all signal numbers.	5616	running async watchers or all signal numbers.
4485		5617
4486	=back	5618	=back
4487		5619
4488		5620
		5621	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5622
		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.
		5629
		5630	=over 4
		5631
		5632	=item C<EV_COMPAT3> backwards compatibility mechanism
		5633
		5634	The backward compatibility mechanism can be controlled by
		5635	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5636	section.
		5637
		5638	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5639
		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.
		5671
		5672	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5673
		5674	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5675	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5676	and work, but the library code will of course be larger.
		5677
		5678	=back
		5679
		5680
4489	=head1 GLOSSARY	5681	=head1 GLOSSARY
4490		5682
4491	=over 4	5683	=over 4
4492		5684
4493	=item active	5685	=item active
4494		5686
4495	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.
4496	an event loop) but not yet stopped (disassociated from the event loop).	5688	See L</WATCHER STATES> for details.
4497		5689
4498	=item application	5690	=item application
4499		5691
4500	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.
4501		5697
4502	=item callback	5698	=item callback
4503		5699
4504	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
4505	detected. Callbacks are being passed the event loop, the watcher that	5701	detected. Callbacks are being passed the event loop, the watcher that
4506	received the event, and the actual event bitset.	5702	received the event, and the actual event bitset.
4507		5703
4508	=item callback invocation	5704	=item callback/watcher invocation
4509		5705
4510	The act of calling the callback associated with a watcher.	5706	The act of calling the callback associated with a watcher.
4511		5707
4512	=item event	5708	=item event
4513		5709
4514	A change of state of some external event, such as data now being available	5710	A change of state of some external event, such as data now being available
4515	for reading on a file descriptor, time having passed or simply not having	5711	for reading on a file descriptor, time having passed or simply not having
4516	any other events happening anymore.	5712	any other events happening anymore.
4517		5713
4518	In libev, events are represented as single bits (such as C<EV_READ> or	5714	In libev, events are represented as single bits (such as C<EV_READ> or
4519	C<EV_TIMEOUT>).	5715	C<EV_TIMER>).
4520		5716
4521	=item event library	5717	=item event library
4522		5718
4523	A software package implementing an event model and loop.	5719	A software package implementing an event model and loop.
4524		5720
…		…
4532	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
4533	watchers and events.	5729	watchers and events.
4534		5730
4535	=item pending	5731	=item pending
4536		5732
4537	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
4538	and stops being pending as soon as the watcher will be invoked or its	5734	detected. See L</WATCHER STATES> for details.
4539	pending status is explicitly cleared by the application.
4540
4541	A watcher can be pending, but not active. Stopping a watcher also clears
4542	its pending status.
4543		5735
4544	=item real time	5736	=item real time
4545		5737
4546	The physical time that is observed. It is apparently strictly monotonic :)	5738	The physical time that is observed. It is apparently strictly monotonic :)
4547		5739
4548	=item wall-clock time	5740	=item wall-clock time
4549		5741
4550	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
4551	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
4552	clock.	5744	clock.
4553		5745
4554	=item watcher	5746	=item watcher
4555		5747
4556	A data structure that describes interest in certain events. Watchers need	5748	A data structure that describes interest in certain events. Watchers need
4557	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.
4558		5750
4559	=item watcher invocation
4560
4561	The act of calling the callback associated with a watcher.
4562
4563	=back	5751	=back
4564		5752
4565	=head1 AUTHOR	5753	=head1 AUTHOR
4566		5754
4567	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.
4568		5757

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