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Revision 1.455 by root, Wed Jun 26 00:01:46 2019 UTC

		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
75	While this document tries to be as complete as possible in documenting	77	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	78	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	79	on event-based programming, nor will it introduce event-based programming
78	with libev.	80	with libev.
79		81
80	Familarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	83	throughout this document.
		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
82		92
83	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
84		94
85	Libev is an event loop: you register interest in certain events (such as a	95	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	96	file descriptor being readable or a timeout occurring), and it will manage
…		…
95	details of the event, and then hand it over to libev by I<starting> the	105	details of the event, and then hand it over to libev by I<starting> the
96	watcher.	106	watcher.
97		107
98	=head2 FEATURES	108	=head2 FEATURES
99		109
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	110	Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll>
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	112	mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify>
103	(for C<ev_stat>), 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	This flag's behaviour will become the default in future versions of libev.
382		486
383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	487	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
384		488
385	This is your standard select(2) backend. Not I<completely> standard, as	489	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,	490	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	515	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	516	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
413		517
414	=item C<EVBACKEND_EPOLL> (value 4, Linux)	518	=item C<EVBACKEND_EPOLL> (value 4, Linux)
415		519
		520	Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9
		521	kernels).
		522
416	For few fds, this backend is a bit little slower than poll and select,	523	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	524	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),	525	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).	526	fd), epoll scales either O(1) or O(active_fds).
420		527
421	The epoll mechanism deserves honorable mention as the most misdesigned	528	The epoll mechanism deserves honorable mention as the most misdesigned
422	of the more advanced event mechanisms: mere annoyances include silently	529	of the more advanced event mechanisms: mere annoyances include silently
423	dropping file descriptors, requiring a system call per change per file	530	dropping file descriptors, requiring a system call per change per file
424	descriptor (and unnecessary guessing of parameters), problems with dup and	531	descriptor (and unnecessary guessing of parameters), problems with dup,
		532	returning before the timeout value, resulting in additional iterations
		533	(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	534	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	535	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	536	set, which can take considerable time (one syscall per file descriptor)
428	hard to detect.	537	and is of course hard to detect.
429		538
430	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	539	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	540	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	541	totally I<different> file descriptors (even already closed ones, so
433	even remove them from the set) than registered in the set (especially	542	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	543	(especially on SMP systems). Libev tries to counter these spurious
435	employing an additional generation counter and comparing that against the	544	notifications by employing an additional generation counter and comparing
436	events to filter out spurious ones, recreating the set when required.	545	that against the events to filter out spurious ones, recreating the set
		546	when required. Epoll also erroneously rounds down timeouts, but gives you
		547	no way to know when and by how much, so sometimes you have to busy-wait
		548	because epoll returns immediately despite a nonzero timeout. And last
		549	not least, it also refuses to work with some file descriptors which work
		550	perfectly fine with C<select> (files, many character devices...).
		551
		552	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		553	cobbled together in a hurry, no thought to design or interaction with
		554	others. Oh, the pain, will it ever stop...
437		555
438	While stopping, setting and starting an I/O watcher in the same iteration	556	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	557	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	558	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	559	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	571	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	572	faster than epoll for maybe up to a hundred file descriptors, depending on
455	the usage. So sad.	573	the usage. So sad.
456		574
457	While nominally embeddable in other event loops, this feature is broken in	575	While nominally embeddable in other event loops, this feature is broken in
458	all kernel versions tested so far.	576	a lot of kernel revisions, but probably(!) works in current versions.
459		577
460	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	578	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
461	C<EVBACKEND_POLL>.	579	C<EVBACKEND_POLL>.
462		580
		581	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		582
		583	Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<<
		584	io_submit(2) >>) event interface available in post-4.18 kernels (but libev
		585	only tries to use it in 4.19+).
		586
		587	This is another Linux train wreck of an event interface.
		588
		589	If this backend works for you (as of this writing, it was very
		590	experimental), it is the best event interface available on Linux and might
		591	be well worth enabling it - if it isn't available in your kernel this will
		592	be detected and this backend will be skipped.
		593
		594	This backend can batch oneshot requests and supports a user-space ring
		595	buffer to receive events. It also doesn't suffer from most of the design
		596	problems of epoll (such as not being able to remove event sources from
		597	the epoll set), and generally sounds too good to be true. Because, this
		598	being the Linux kernel, of course it suffers from a whole new set of
		599	limitations, forcing you to fall back to epoll, inheriting all its design
		600	issues.
		601
		602	For one, it is not easily embeddable (but probably could be done using
		603	an event fd at some extra overhead). It also is subject to a system wide
		604	limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO
		605	requests are left, this backend will be skipped during initialisation, and
		606	will switch to epoll when the loop is active.
		607
		608	Most problematic in practice, however, is that not all file descriptors
		609	work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds,
		610	files, F</dev/null> and many others are supported, but ttys do not work
		611	properly (a known bug that the kernel developers don't care about, see
		612	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		613	(yet?) a generic event polling interface.
		614
		615	Overall, it seems the Linux developers just don't want it to have a
		616	generic event handling mechanism other than C<select> or C<poll>.
		617
		618	To work around all these problem, the current version of libev uses its
		619	epoll backend as a fallback for file descriptor types that do not work. Or
		620	falls back completely to epoll if the kernel acts up.
		621
		622	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		623	C<EVBACKEND_POLL>.
		624
463	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	625	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
464		626
465	Kqueue deserves special mention, as at the time of this writing, it	627	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	628	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	629	work reliably with anything but sockets and pipes, except on Darwin,
468	it's completely useless). Unlike epoll, however, whose brokenness	630	where of course it's completely useless). Unlike epoll, however, whose
469	is by design, these kqueue bugs can (and eventually will) be fixed	631	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	632	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	633	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)	634	in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a
473	system like NetBSD.	635	known-to-be-good (-enough) system like NetBSD.
474		636
475	You still can embed kqueue into a normal poll or select backend and use it	637	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	638	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.	639	the target platform). See C<ev_embed> watchers for more info.
478		640
479	It scales in the same way as the epoll backend, but the interface to the	641	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	642	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	643	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	644	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	645	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	646	might have to leak fds on fork, but it's more sane than epoll) and it
485	cases	647	drops fds silently in similarly hard-to-detect cases.
486		648
487	This backend usually performs well under most conditions.	649	This backend usually performs well under most conditions.
488		650
489	While nominally embeddable in other event loops, this doesn't work	651	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	652	everywhere, so you might need to test for this. And since it is broken
…		…
507	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	669	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
508		670
509	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	671	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
510	it's really slow, but it still scales very well (O(active_fds)).	672	it's really slow, but it still scales very well (O(active_fds)).
511		673
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
516	While this backend scales well, it requires one system call per active	674	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	675	file descriptor per loop iteration. For small and medium numbers of file
518	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	676	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
519	might perform better.	677	might perform better.
520		678
521	On the positive side, with the exception of the spurious readiness	679	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	680	specification in all tests and is fully embeddable, which is a rare feat
524	OS-specific backends (I vastly prefer correctness over speed hacks).	681	among the OS-specific backends (I vastly prefer correctness over speed
		682	hacks).
		683
		684	On the negative side, the interface is I<bizarre> - so bizarre that
		685	even sun itself gets it wrong in their code examples: The event polling
		686	function sometimes returns events to the caller even though an error
		687	occurred, but with no indication whether it has done so or not (yes, it's
		688	even documented that way) - deadly for edge-triggered interfaces where you
		689	absolutely have to know whether an event occurred or not because you have
		690	to re-arm the watcher.
		691
		692	Fortunately libev seems to be able to work around these idiocies.
525		693
526	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	694	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
527	C<EVBACKEND_POLL>.	695	C<EVBACKEND_POLL>.
528		696
529	=item C<EVBACKEND_ALL>	697	=item C<EVBACKEND_ALL>
530		698
531	Try all backends (even potentially broken ones that wouldn't be tried	699	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	700	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
533	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	701	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
534		702
535	It is definitely not recommended to use this flag.	703	It is definitely not recommended to use this flag, use whatever
		704	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		705	at all.
		706
		707	=item C<EVBACKEND_MASK>
		708
		709	Not a backend at all, but a mask to select all backend bits from a
		710	C<flags> value, in case you want to mask out any backends from a flags
		711	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
536		712
537	=back	713	=back
538		714
539	If one or more of the backend flags are or'ed into the flags value,	715	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	716	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	717	here). If none are specified, all backends in C<ev_recommended_backends
542	()> will be tried.	718	()> will be tried.
543		719
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.	720	Example: Try to create a event loop that uses epoll and nothing else.
573		721
574	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	722	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
575	if (!epoller)	723	if (!epoller)
576	fatal ("no epoll found here, maybe it hides under your chair");	724	fatal ("no epoll found here, maybe it hides under your chair");
577		725
		726	Example: Use whatever libev has to offer, but make sure that kqueue is
		727	used if available.
		728
		729	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		730
		731	Example: Similarly, on linux, you mgiht want to take advantage of the
		732	linux aio backend if possible, but fall back to something else if that
		733	isn't available.
		734
		735	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		736
578	=item ev_default_destroy ()	737	=item ev_loop_destroy (loop)
579		738
580	Destroys the default loop again (frees all memory and kernel state	739	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	740	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	741	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>	742	responsibility to either stop all watchers cleanly yourself I<before>
584	calling this function, or cope with the fact afterwards (which is usually	743	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	744	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
587		746
588	Note that certain global state, such as signal state (and installed signal	747	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	748	handlers), will not be freed by this function, and related watchers (such
590	as signal and child watchers) would need to be stopped manually.	749	as signal and child watchers) would need to be stopped manually.
591		750
592	In general it is not advisable to call this function except in the	751	This function is normally used on loop objects allocated by
593	rare occasion where you really need to free e.g. the signal handling	752	C<ev_loop_new>, but it can also be used on the default loop returned by
		753	C<ev_default_loop>, in which case it is not thread-safe.
		754
		755	Note that it is not advisable to call this function on the default loop
		756	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	757	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>).	758	and C<ev_loop_destroy>.
596		759
597	=item ev_loop_destroy (loop)	760	=item ev_loop_fork (loop)
598		761
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	762	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	763	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	764	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	765	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	766	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.	767	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		768
		769	In addition, if you want to reuse a loop (via this function or
		770	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		771
		772	Again, you I<have> to call it on I<any> loop that you want to re-use after
		773	a fork, I<even if you do not plan to use the loop in the parent>. This is
		774	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		775	during fork.
610		776
611	On the other hand, you only need to call this function in the child	777	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	778	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.	779	you just fork+exec or create a new loop in the child, you don't have to
		780	call it at all (in fact, C<epoll> is so badly broken that it makes a
		781	difference, but libev will usually detect this case on its own and do a
		782	costly reset of the backend).
614		783
615	The function itself is quite fast and it's usually not a problem to call	784	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	785	it just in case after a fork.
617	quite nicely into a call to C<pthread_atfork>:
618		786
		787	Example: Automate calling C<ev_loop_fork> on the default loop when
		788	using pthreads.
		789
		790	static void
		791	post_fork_child (void)
		792	{
		793	ev_loop_fork (EV_DEFAULT);
		794	}
		795
		796	...
619	pthread_atfork (0, 0, ev_default_fork);	797	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		798
628	=item int ev_is_default_loop (loop)	799	=item int ev_is_default_loop (loop)
629		800
630	Returns true when the given loop is, in fact, the default loop, and false	801	Returns true when the given loop is, in fact, the default loop, and false
631	otherwise.	802	otherwise.
632		803
633	=item unsigned int ev_loop_count (loop)	804	=item unsigned int ev_iteration (loop)
634		805
635	Returns the count of loop iterations for the loop, which is identical to	806	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	807	to the number of times libev did poll for new events. It starts at C<0>
637	happily wraps around with enough iterations.	808	and happily wraps around with enough iterations.
638		809
639	This value can sometimes be useful as a generation counter of sorts (it	810	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	811	"ticks" the number of loop iterations), as it roughly corresponds with
641	C<ev_prepare> and C<ev_check> calls.	812	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		813	prepare and check phases.
642		814
643	=item unsigned int ev_loop_depth (loop)	815	=item unsigned int ev_depth (loop)
644		816
645	Returns the number of times C<ev_loop> was entered minus the number of	817	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.	818	times C<ev_run> was exited normally, in other words, the recursion depth.
647		819
648	Outside C<ev_loop>, this number is zero. In a callback, this number is	820	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),	821	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
650	in which case it is higher.	822	in which case it is higher.
651		823
652	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	824	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
653	etc.), doesn't count as exit.	825	throwing an exception etc.), doesn't count as "exit" - consider this
		826	as a hint to avoid such ungentleman-like behaviour unless it's really
		827	convenient, in which case it is fully supported.
654		828
655	=item unsigned int ev_backend (loop)	829	=item unsigned int ev_backend (loop)
656		830
657	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	831	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
658	use.	832	use.
…		…
667		841
668	=item ev_now_update (loop)	842	=item ev_now_update (loop)
669		843
670	Establishes the current time by querying the kernel, updating the time	844	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	845	returned by C<ev_now ()> in the progress. This is a costly operation and
672	is usually done automatically within C<ev_loop ()>.	846	is usually done automatically within C<ev_run ()>.
673		847
674	This function is rarely useful, but when some event callback runs for a	848	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	849	very long time without entering the event loop, updating libev's idea of
676	the current time is a good idea.	850	the current time is a good idea.
677		851
678	See also L<The special problem of time updates> in the C<ev_timer> section.	852	See also L</The special problem of time updates> in the C<ev_timer> section.
679		853
680	=item ev_suspend (loop)	854	=item ev_suspend (loop)
681		855
682	=item ev_resume (loop)	856	=item ev_resume (loop)
683		857
684	These two functions suspend and resume a loop, for use when the loop is	858	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.	859	loop is not used for a while and timeouts should not be processed.
686		860
687	A typical use case would be an interactive program such as a game: When	861	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	862	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	863	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>	864	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
692	C<ev_resume> directly afterwards to resume timer processing.	866	C<ev_resume> directly afterwards to resume timer processing.
693		867
694	Effectively, all C<ev_timer> watchers will be delayed by the time spend	868	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	869	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	870	will be rescheduled (that is, they will lose any events that would have
697	occured while suspended).	871	occurred while suspended).
698		872
699	After calling C<ev_suspend> you B<must not> call I<any> function on the	873	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>	874	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>.	875	without a previous call to C<ev_suspend>.
702		876
703	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	877	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
704	event loop time (see C<ev_now_update>).	878	event loop time (see C<ev_now_update>).
705		879
706	=item ev_loop (loop, int flags)	880	=item bool ev_run (loop, int flags)
707		881
708	Finally, this is it, the event handler. This function usually is called	882	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	883	after you have initialised all your watchers and you want to start
710	events.	884	handling events. It will ask the operating system for any new events, call
		885	the watcher callbacks, and then repeat the whole process indefinitely: This
		886	is why event loops are called I<loops>.
711		887
712	If the flags argument is specified as C<0>, it will not return until	888	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.	889	until either no event watchers are active anymore or C<ev_break> was
		890	called.
714		891
		892	The return value is false if there are no more active watchers (which
		893	usually means "all jobs done" or "deadlock"), and true in all other cases
		894	(which usually means " you should call C<ev_run> again").
		895
715	Please note that an explicit C<ev_unloop> is usually better than	896	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	897	relying on all watchers to be stopped when deciding when a program has
717	finished (especially in interactive programs), but having a program	898	finished (especially in interactive programs), but having a program
718	that automatically loops as long as it has to and no longer by virtue	899	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	900	of relying on its watchers stopping correctly, that is truly a thing of
720	beauty.	901	beauty.
721		902
		903	This function is I<mostly> exception-safe - you can break out of a
		904	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		905	exception and so on. This does not decrement the C<ev_depth> value, nor
		906	will it clear any outstanding C<EVBREAK_ONE> breaks.
		907
722	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	908	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	909	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	910	block your process in case there are no events and will return after one
725	the loop.	911	iteration of the loop. This is sometimes useful to poll and handle new
		912	events while doing lengthy calculations, to keep the program responsive.
726		913
727	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	914	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	915	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	916	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	917	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	918	user-registered callback will be called), and will return after one
732	iteration of the loop.	919	iteration of the loop.
733		920
734	This is useful if you are waiting for some external event in conjunction	921	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	922	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	923	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.	924	usually a better approach for this kind of thing.
738		925
739	Here are the gory details of what C<ev_loop> does:	926	Here are the gory details of what C<ev_run> does (this is for your
		927	understanding, not a guarantee that things will work exactly like this in
		928	future versions):
740		929
		930	- Increment loop depth.
		931	- Reset the ev_break status.
741	- Before the first iteration, call any pending watchers.	932	- Before the first iteration, call any pending watchers.
		933	LOOP:
742	* If EVFLAG_FORKCHECK was used, check for a fork.	934	- If EVFLAG_FORKCHECK was used, check for a fork.
743	- If a fork was detected (by any means), queue and call all fork watchers.	935	- If a fork was detected (by any means), queue and call all fork watchers.
744	- Queue and call all prepare watchers.	936	- Queue and call all prepare watchers.
		937	- If ev_break was called, goto FINISH.
745	- If we have been forked, detach and recreate the kernel state	938	- If we have been forked, detach and recreate the kernel state
746	as to not disturb the other process.	939	as to not disturb the other process.
747	- Update the kernel state with all outstanding changes.	940	- Update the kernel state with all outstanding changes.
748	- Update the "event loop time" (ev_now ()).	941	- Update the "event loop time" (ev_now ()).
749	- Calculate for how long to sleep or block, if at all	942	- Calculate for how long to sleep or block, if at all
750	(active idle watchers, EVLOOP_NONBLOCK or not having	943	(active idle watchers, EVRUN_NOWAIT or not having
751	any active watchers at all will result in not sleeping).	944	any active watchers at all will result in not sleeping).
752	- Sleep if the I/O and timer collect interval say so.	945	- Sleep if the I/O and timer collect interval say so.
		946	- Increment loop iteration counter.
753	- Block the process, waiting for any events.	947	- Block the process, waiting for any events.
754	- Queue all outstanding I/O (fd) events.	948	- Queue all outstanding I/O (fd) events.
755	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	949	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
756	- Queue all expired timers.	950	- Queue all expired timers.
757	- Queue all expired periodics.	951	- Queue all expired periodics.
758	- Unless any events are pending now, queue all idle watchers.	952	- Queue all idle watchers with priority higher than that of pending events.
759	- Queue all check watchers.	953	- Queue all check watchers.
760	- Call all queued watchers in reverse order (i.e. check watchers first).	954	- 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	955	Signals and child watchers are implemented as I/O watchers, and will
762	be handled here by queueing them when their watcher gets executed.	956	be handled here by queueing them when their watcher gets executed.
763	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	957	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
764	were used, or there are no active watchers, return, otherwise	958	were used, or there are no active watchers, goto FINISH, otherwise
765	continue with step *.	959	continue with step LOOP.
		960	FINISH:
		961	- Reset the ev_break status iff it was EVBREAK_ONE.
		962	- Decrement the loop depth.
		963	- Return.
766		964
767	Example: Queue some jobs and then loop until no events are outstanding	965	Example: Queue some jobs and then loop until no events are outstanding
768	anymore.	966	anymore.
769		967
770	... queue jobs here, make sure they register event watchers as long	968	... 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..)	969	... as they still have work to do (even an idle watcher will do..)
772	ev_loop (my_loop, 0);	970	ev_run (my_loop, 0);
773	... jobs done or somebody called unloop. yeah!	971	... jobs done or somebody called break. yeah!
774		972
775	=item ev_unloop (loop, how)	973	=item ev_break (loop, how)
776		974
777	Can be used to make a call to C<ev_loop> return early (but only after it	975	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	976	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	977	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.	978	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
781		979
782	This "unloop state" will be cleared when entering C<ev_loop> again.	980	This "break state" will be cleared on the next call to C<ev_run>.
783		981
784	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	982	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		983	which case it will have no effect.
785		984
786	=item ev_ref (loop)	985	=item ev_ref (loop)
787		986
788	=item ev_unref (loop)	987	=item ev_unref (loop)
789		988
790	Ref/unref can be used to add or remove a reference count on the event	989	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	990	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.	991	count is nonzero, C<ev_run> will not return on its own.
793		992
794	If you have a watcher you never unregister that should not keep C<ev_loop>	993	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	994	unregister, but that nevertheless should not keep C<ev_run> from
		995	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
796	stopping it.	996	before stopping it.
797		997
798	As an example, libev itself uses this for its internal signal pipe: It	998	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	999	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	1000	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	1001	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	1002	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	1003	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	1004	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>	1005	(e.g. non-repeating timers) in which case you have to C<ev_ref>
806	in the callback).	1006	in the callback).
807		1007
808	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	1008	Example: Create a signal watcher, but keep it from keeping C<ev_run>
809	running when nothing else is active.	1009	running when nothing else is active.
810		1010
811	ev_signal exitsig;	1011	ev_signal exitsig;
812	ev_signal_init (&exitsig, sig_cb, SIGINT);	1012	ev_signal_init (&exitsig, sig_cb, SIGINT);
813	ev_signal_start (loop, &exitsig);	1013	ev_signal_start (loop, &exitsig);
814	evf_unref (loop);	1014	ev_unref (loop);
815		1015
816	Example: For some weird reason, unregister the above signal handler again.	1016	Example: For some weird reason, unregister the above signal handler again.
817		1017
818	ev_ref (loop);	1018	ev_ref (loop);
819	ev_signal_stop (loop, &exitsig);	1019	ev_signal_stop (loop, &exitsig);
…		…
839	overhead for the actual polling but can deliver many events at once.	1039	overhead for the actual polling but can deliver many events at once.
840		1040
841	By setting a higher I<io collect interval> you allow libev to spend more	1041	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,	1042	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	1043	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	1044	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	1045	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	1046	sleep time ensures that libev will not poll for I/O events more often then
847	once per this interval, on average.	1047	once per this interval, on average (as long as the host time resolution is
		1048	good enough).
848		1049
849	Likewise, by setting a higher I<timeout collect interval> you allow libev	1050	Likewise, by setting a higher I<timeout collect interval> you allow libev
850	to spend more time collecting timeouts, at the expense of increased	1051	to spend more time collecting timeouts, at the expense of increased
851	latency/jitter/inexactness (the watcher callback will be called	1052	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	1053	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>,	1059	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	1060	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	1061	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	1062	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,	1063	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).	1064	then you can't do more than 100 transactions per second).
864		1065
865	Setting the I<timeout collect interval> can improve the opportunity for	1066	Setting the I<timeout collect interval> can improve the opportunity for
866	saving power, as the program will "bundle" timer callback invocations that	1067	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	1068	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	1069	times the process sleeps and wakes up again. Another useful technique to
…		…
876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1077	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
877		1078
878	=item ev_invoke_pending (loop)	1079	=item ev_invoke_pending (loop)
879		1080
880	This call will simply invoke all pending watchers while resetting their	1081	This call will simply invoke all pending watchers while resetting their
881	pending state. Normally, C<ev_loop> does this automatically when required,	1082	pending state. Normally, C<ev_run> does this automatically when required,
882	but when overriding the invoke callback this call comes handy.	1083	but when overriding the invoke callback this call comes handy. This
		1084	function can be invoked from a watcher - this can be useful for example
		1085	when you want to do some lengthy calculation and want to pass further
		1086	event handling to another thread (you still have to make sure only one
		1087	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
883		1088
884	=item int ev_pending_count (loop)	1089	=item int ev_pending_count (loop)
885		1090
886	Returns the number of pending watchers - zero indicates that no watchers	1091	Returns the number of pending watchers - zero indicates that no watchers
887	are pending.	1092	are pending.
888		1093
889	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1094	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
890		1095
891	This overrides the invoke pending functionality of the loop: Instead of	1096	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	1097	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	1098	this callback instead. This is useful, for example, when you want to
894	invoke the actual watchers inside another context (another thread etc.).	1099	invoke the actual watchers inside another context (another thread etc.).
895		1100
896	If you want to reset the callback, use C<ev_invoke_pending> as new	1101	If you want to reset the callback, use C<ev_invoke_pending> as new
897	callback.	1102	callback.
898		1103
899	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1104	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
900		1105
901	Sometimes you want to share the same loop between multiple threads. This	1106	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	1107	can be done relatively simply by putting mutex_lock/unlock calls around
903	each call to a libev function.	1108	each call to a libev function.
904		1109
905	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1110	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	1111	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>	1112	loop via C<ev_break> and C<ev_async_send>, another way is to set these
908	and I<acquire> callbacks on the loop.	1113	I<release> and I<acquire> callbacks on the loop.
909		1114
910	When set, then C<release> will be called just before the thread is	1115	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	1116	suspended waiting for new events, and C<acquire> is called just
912	afterwards.	1117	afterwards.
913		1118
…		…
916		1121
917	While event loop modifications are allowed between invocations of	1122	While event loop modifications are allowed between invocations of
918	C<release> and C<acquire> (that's their only purpose after all), no	1123	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	1124	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	1125	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	1126	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.	1127	to take note of any changes you made.
923		1128
924	In theory, threads executing C<ev_loop> will be async-cancel safe between	1129	In theory, threads executing C<ev_run> will be async-cancel safe between
925	invocations of C<release> and C<acquire>.	1130	invocations of C<release> and C<acquire>.
926		1131
927	See also the locking example in the C<THREADS> section later in this	1132	See also the locking example in the C<THREADS> section later in this
928	document.	1133	document.
929		1134
930	=item ev_set_userdata (loop, void *data)	1135	=item ev_set_userdata (loop, void *data)
931		1136
932	=item ev_userdata (loop)	1137	=item void *ev_userdata (loop)
933		1138
934	Set and retrieve a single C<void *> associated with a loop. When	1139	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	1140	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
936	C<0.>	1141	C<0>.
937		1142
938	These two functions can be used to associate arbitrary data with a loop,	1143	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	1144	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	1145	C<acquire> callbacks described above, but of course can be (ab-)used for
941	any other purpose as well.	1146	any other purpose as well.
942		1147
943	=item ev_loop_verify (loop)	1148	=item ev_verify (loop)
944		1149
945	This function only does something when C<EV_VERIFY> support has been	1150	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	1151	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	1152	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	1153	is found to be inconsistent, it will print an error message to standard
…		…
959		1164
960	In the following description, uppercase C<TYPE> in names stands for the	1165	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	1166	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.	1167	watchers and C<ev_io_start> for I/O watchers.
963		1168
964	A watcher is a structure that you create and register to record your	1169	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	1170	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:	1171	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1172	for that:
967		1173
968	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1174	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
969	{	1175	{
970	ev_io_stop (w);	1176	ev_io_stop (w);
971	ev_unloop (loop, EVUNLOOP_ALL);	1177	ev_break (loop, EVBREAK_ALL);
972	}	1178	}
973		1179
974	struct ev_loop *loop = ev_default_loop (0);	1180	struct ev_loop *loop = ev_default_loop (0);
975		1181
976	ev_io stdin_watcher;	1182	ev_io stdin_watcher;
977		1183
978	ev_init (&stdin_watcher, my_cb);	1184	ev_init (&stdin_watcher, my_cb);
979	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1185	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
980	ev_io_start (loop, &stdin_watcher);	1186	ev_io_start (loop, &stdin_watcher);
981		1187
982	ev_loop (loop, 0);	1188	ev_run (loop, 0);
983		1189
984	As you can see, you are responsible for allocating the memory for your	1190	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	1191	watcher structures (and it is I<usually> a bad idea to do this on the
986	stack).	1192	stack).
987		1193
988	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1194	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).	1195	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
990		1196
991	Each watcher structure must be initialised by a call to C<ev_init	1197	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	1198	*, 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	1199	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	1200	time the event loop detects that the file descriptor given is readable
995	is readable and/or writable).	1201	and/or writable).
996		1202
997	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1203	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	1204	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<<	1205	is also a macro to combine initialisation and setting in one call: C<<
1000	ev_TYPE_init (watcher *, callback, ...) >>.	1206	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1023	=item C<EV_WRITE>	1229	=item C<EV_WRITE>
1024		1230
1025	The file descriptor in the C<ev_io> watcher has become readable and/or	1231	The file descriptor in the C<ev_io> watcher has become readable and/or
1026	writable.	1232	writable.
1027		1233
1028	=item C<EV_TIMEOUT>	1234	=item C<EV_TIMER>
1029		1235
1030	The C<ev_timer> watcher has timed out.	1236	The C<ev_timer> watcher has timed out.
1031		1237
1032	=item C<EV_PERIODIC>	1238	=item C<EV_PERIODIC>
1033		1239
…		…
1051		1257
1052	=item C<EV_PREPARE>	1258	=item C<EV_PREPARE>
1053		1259
1054	=item C<EV_CHECK>	1260	=item C<EV_CHECK>
1055		1261
1056	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1262	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	1263	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	1264	just after C<ev_run> has gathered them, but before it queues any callbacks
		1265	for any received events. That means C<ev_prepare> watchers are the last
		1266	watchers invoked before the event loop sleeps or polls for new events, and
		1267	C<ev_check> watchers will be invoked before any other watchers of the same
		1268	or lower priority within an event loop iteration.
		1269
1059	received events. Callbacks of both watcher types can start and stop as	1270	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	1271	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	1272	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1062	C<ev_loop> from blocking).	1273	blocking).
1063		1274
1064	=item C<EV_EMBED>	1275	=item C<EV_EMBED>
1065		1276
1066	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1277	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1067		1278
1068	=item C<EV_FORK>	1279	=item C<EV_FORK>
1069		1280
1070	The event loop has been resumed in the child process after fork (see	1281	The event loop has been resumed in the child process after fork (see
1071	C<ev_fork>).	1282	C<ev_fork>).
		1283
		1284	=item C<EV_CLEANUP>
		1285
		1286	The event loop is about to be destroyed (see C<ev_cleanup>).
1072		1287
1073	=item C<EV_ASYNC>	1288	=item C<EV_ASYNC>
1074		1289
1075	The given async watcher has been asynchronously notified (see C<ev_async>).	1290	The given async watcher has been asynchronously notified (see C<ev_async>).
1076		1291
…		…
1123		1338
1124	ev_io w;	1339	ev_io w;
1125	ev_init (&w, my_cb);	1340	ev_init (&w, my_cb);
1126	ev_io_set (&w, STDIN_FILENO, EV_READ);	1341	ev_io_set (&w, STDIN_FILENO, EV_READ);
1127		1342
1128	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1343	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1129		1344
1130	This macro initialises the type-specific parts of a watcher. You need to	1345	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	1346	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	1347	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	1348	macro on a watcher that is active (it can be pending, however, which is a
…		…
1146		1361
1147	Example: Initialise and set an C<ev_io> watcher in one step.	1362	Example: Initialise and set an C<ev_io> watcher in one step.
1148		1363
1149	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1364	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1150		1365
1151	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1366	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1152		1367
1153	Starts (activates) the given watcher. Only active watchers will receive	1368	Starts (activates) the given watcher. Only active watchers will receive
1154	events. If the watcher is already active nothing will happen.	1369	events. If the watcher is already active nothing will happen.
1155		1370
1156	Example: Start the C<ev_io> watcher that is being abused as example in this	1371	Example: Start the C<ev_io> watcher that is being abused as example in this
1157	whole section.	1372	whole section.
1158		1373
1159	ev_io_start (EV_DEFAULT_UC, &w);	1374	ev_io_start (EV_DEFAULT_UC, &w);
1160		1375
1161	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1376	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1162		1377
1163	Stops the given watcher if active, and clears the pending status (whether	1378	Stops the given watcher if active, and clears the pending status (whether
1164	the watcher was active or not).	1379	the watcher was active or not).
1165		1380
1166	It is possible that stopped watchers are pending - for example,	1381	It is possible that stopped watchers are pending - for example,
…		…
1186		1401
1187	=item callback ev_cb (ev_TYPE *watcher)	1402	=item callback ev_cb (ev_TYPE *watcher)
1188		1403
1189	Returns the callback currently set on the watcher.	1404	Returns the callback currently set on the watcher.
1190		1405
1191	=item ev_cb_set (ev_TYPE *watcher, callback)	1406	=item ev_set_cb (ev_TYPE *watcher, callback)
1192		1407
1193	Change the callback. You can change the callback at virtually any time	1408	Change the callback. You can change the callback at virtually any time
1194	(modulo threads).	1409	(modulo threads).
1195		1410
1196	=item ev_set_priority (ev_TYPE *watcher, priority)	1411	=item ev_set_priority (ev_TYPE *watcher, int priority)
1197		1412
1198	=item int ev_priority (ev_TYPE *watcher)	1413	=item int ev_priority (ev_TYPE *watcher)
1199		1414
1200	Set and query the priority of the watcher. The priority is a small	1415	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>	1416	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1214	or might not have been clamped to the valid range.	1429	or might not have been clamped to the valid range.
1215		1430
1216	The default priority used by watchers when no priority has been set is	1431	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 :).	1432	always C<0>, which is supposed to not be too high and not be too low :).
1218		1433
1219	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1434	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1220	priorities.	1435	priorities.
1221		1436
1222	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1437	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1223		1438
1224	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1439	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>.	1448	watcher isn't pending it does nothing and returns C<0>.
1234		1449
1235	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1450	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.	1451	callback to be invoked, which can be accomplished with this function.
1237		1452
		1453	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1454
		1455	Feeds the given event set into the event loop, as if the specified event
		1456	had happened for the specified watcher (which must be a pointer to an
		1457	initialised but not necessarily started event watcher). Obviously you must
		1458	not free the watcher as long as it has pending events.
		1459
		1460	Stopping the watcher, letting libev invoke it, or calling
		1461	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1462	not started in the first place.
		1463
		1464	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1465	functions that do not need a watcher.
		1466
1238	=back	1467	=back
1239		1468
		1469	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1470	OWN COMPOSITE WATCHERS> idioms.
1240		1471
1241	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1472	=head2 WATCHER STATES
1242		1473
1243	Each watcher has, by default, a member C<void *data> that you can change	1474	There are various watcher states mentioned throughout this manual -
1244	and read at any time: libev will completely ignore it. This can be used	1475	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	1476	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	1477	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		1478
1250	struct my_io	1479	=over 4
1251	{
1252	ev_io io;
1253	int otherfd;
1254	void *somedata;
1255	struct whatever *mostinteresting;
1256	};
1257		1480
1258	...	1481	=item initialised
1259	struct my_io w;
1260	ev_io_init (&w.io, my_cb, fd, EV_READ);
1261		1482
1262	And since your callback will be called with a pointer to the watcher, you	1483	Before a watcher can be registered with the event loop it has to be
1263	can cast it back to your own type:	1484	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1485	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1264		1486
1265	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1487	In this state it is simply some block of memory that is suitable for
1266	{	1488	use in an event loop. It can be moved around, freed, reused etc. at
1267	struct my_io *w = (struct my_io *)w_;	1489	will - as long as you either keep the memory contents intact, or call
1268	...	1490	C<ev_TYPE_init> again.
1269	}
1270		1491
1271	More interesting and less C-conformant ways of casting your callback type	1492	=item started/running/active
1272	instead have been omitted.
1273		1493
1274	Another common scenario is to use some data structure with multiple	1494	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1275	embedded watchers:	1495	property of the event loop, and is actively waiting for events. While in
		1496	this state it cannot be accessed (except in a few documented ways), moved,
		1497	freed or anything else - the only legal thing is to keep a pointer to it,
		1498	and call libev functions on it that are documented to work on active watchers.
1276		1499
1277	struct my_biggy	1500	=item pending
1278	{
1279	int some_data;
1280	ev_timer t1;
1281	ev_timer t2;
1282	}
1283		1501
1284	In this case getting the pointer to C<my_biggy> is a bit more	1502	If a watcher is active and libev determines that an event it is interested
1285	complicated: Either you store the address of your C<my_biggy> struct	1503	in has occurred (such as a timer expiring), it will become pending. It will
1286	in the C<data> member of the watcher (for woozies), or you need to use	1504	stay in this pending state until either it is stopped or its callback is
1287	some pointer arithmetic using C<offsetof> inside your watchers (for real	1505	about to be invoked, so it is not normally pending inside the watcher
1288	programmers):	1506	callback.
1289		1507
1290	#include <stddef.h>	1508	The watcher might or might not be active while it is pending (for example,
		1509	an expired non-repeating timer can be pending but no longer active). If it
		1510	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1511	but it is still property of the event loop at this time, so cannot be
		1512	moved, freed or reused. And if it is active the rules described in the
		1513	previous item still apply.
1291		1514
1292	static void	1515	It is also possible to feed an event on a watcher that is not active (e.g.
1293	t1_cb (EV_P_ ev_timer *w, int revents)	1516	via C<ev_feed_event>), in which case it becomes pending without being
1294	{	1517	active.
1295	struct my_biggy big = (struct my_biggy *)
1296	(((char *)w) - offsetof (struct my_biggy, t1));
1297	}
1298		1518
1299	static void	1519	=item stopped
1300	t2_cb (EV_P_ ev_timer *w, int revents)	1520
1301	{	1521	A watcher can be stopped implicitly by libev (in which case it might still
1302	struct my_biggy big = (struct my_biggy *)	1522	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1303	(((char *)w) - offsetof (struct my_biggy, t2));	1523	latter will clear any pending state the watcher might be in, regardless
1304	}	1524	of whether it was active or not, so stopping a watcher explicitly before
		1525	freeing it is often a good idea.
		1526
		1527	While stopped (and not pending) the watcher is essentially in the
		1528	initialised state, that is, it can be reused, moved, modified in any way
		1529	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1530	it again).
		1531
		1532	=back
1305		1533
1306	=head2 WATCHER PRIORITY MODELS	1534	=head2 WATCHER PRIORITY MODELS
1307		1535
1308	Many event loops support I<watcher priorities>, which are usually small	1536	Many event loops support I<watcher priorities>, which are usually small
1309	integers that influence the ordering of event callback invocation	1537	integers that influence the ordering of event callback invocation
…		…
1352		1580
1353	For example, to emulate how many other event libraries handle priorities,	1581	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	1582	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	1583	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	1584	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	1585	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	1586	the lock-out case is known to be rare (which in turn is rare :), this is
1359	workable.	1587	workable.
1360		1588
1361	Usually, however, the lock-out model implemented that way will perform	1589	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,	1590	miserably under the type of load it was designed to handle. In that case,
…		…
1376	{	1604	{
1377	// stop the I/O watcher, we received the event, but	1605	// stop the I/O watcher, we received the event, but
1378	// are not yet ready to handle it.	1606	// are not yet ready to handle it.
1379	ev_io_stop (EV_A_ w);	1607	ev_io_stop (EV_A_ w);
1380		1608
1381	// start the idle watcher to ahndle the actual event.	1609	// start the idle watcher to handle the actual event.
1382	// it will not be executed as long as other watchers	1610	// it will not be executed as long as other watchers
1383	// with the default priority are receiving events.	1611	// with the default priority are receiving events.
1384	ev_idle_start (EV_A_ &idle);	1612	ev_idle_start (EV_A_ &idle);
1385	}	1613	}
1386		1614
…		…
1436	In general you can register as many read and/or write event watchers per	1664	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	1665	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	1666	descriptors to non-blocking mode is also usually a good idea (but not
1439	required if you know what you are doing).	1667	required if you know what you are doing).
1440		1668
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	1669	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	1670	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	1671	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	1672	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	1673	with a relatively standard program structure. Thus it is best to always
1452	this situation even with a relatively standard program structure. Thus	1674	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.	1675	preferable to a program hanging until some data arrives.
1455		1676
1456	If you cannot run the fd in non-blocking mode (for example you should	1677	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	1678	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	1679	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	1680	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	1681	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	1682	use C<SIGALRM> and an interval timer, just to be sure you won't block
1462	indefinitely.	1683	indefinitely.
1463		1684
1464	But really, best use non-blocking mode.	1685	But really, best use non-blocking mode.
1465		1686
1466	=head3 The special problem of disappearing file descriptors	1687	=head3 The special problem of disappearing file descriptors
1467		1688
1468	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1689	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,	1690	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	1691	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	1692	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	1693	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	1694	is registered with libev, there is no efficient way to see that this is,
1474	fact, a different file descriptor.	1695	in fact, a different file descriptor.
1475		1696
1476	To avoid having to explicitly tell libev about such cases, libev follows	1697	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	1698	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	1699	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	1700	it is assumed that the file descriptor stays the same. That means that
…		…
1493		1714
1494	There is no workaround possible except not registering events	1715	There is no workaround possible except not registering events
1495	for potentially C<dup ()>'ed file descriptors, or to resort to	1716	for potentially C<dup ()>'ed file descriptors, or to resort to
1496	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1717	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1497		1718
		1719	=head3 The special problem of files
		1720
		1721	Many people try to use C<select> (or libev) on file descriptors
		1722	representing files, and expect it to become ready when their program
		1723	doesn't block on disk accesses (which can take a long time on their own).
		1724
		1725	However, this cannot ever work in the "expected" way - you get a readiness
		1726	notification as soon as the kernel knows whether and how much data is
		1727	there, and in the case of open files, that's always the case, so you
		1728	always get a readiness notification instantly, and your read (or possibly
		1729	write) will still block on the disk I/O.
		1730
		1731	Another way to view it is that in the case of sockets, pipes, character
		1732	devices and so on, there is another party (the sender) that delivers data
		1733	on its own, but in the case of files, there is no such thing: the disk
		1734	will not send data on its own, simply because it doesn't know what you
		1735	wish to read - you would first have to request some data.
		1736
		1737	Since files are typically not-so-well supported by advanced notification
		1738	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1739	to files, even though you should not use it. The reason for this is
		1740	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1741	usually a tty, often a pipe, but also sometimes files or special devices
		1742	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1743	F</dev/urandom>), and even though the file might better be served with
		1744	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1745	it "just works" instead of freezing.
		1746
		1747	So avoid file descriptors pointing to files when you know it (e.g. use
		1748	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1749	when you rarely read from a file instead of from a socket, and want to
		1750	reuse the same code path.
		1751
1498	=head3 The special problem of fork	1752	=head3 The special problem of fork
1499		1753
1500	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1754	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1501	useless behaviour. Libev fully supports fork, but needs to be told about	1755	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1502	it in the child.	1756	to be told about it in the child if you want to continue to use it in the
		1757	child.
1503		1758
1504	To support fork in your programs, you either have to call	1759	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,	1760	()> 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	1761	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1507	C<EVBACKEND_POLL>.
1508		1762
1509	=head3 The special problem of SIGPIPE	1763	=head3 The special problem of SIGPIPE
1510		1764
1511	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1765	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	1766	when writing to a pipe whose other end has been closed, your program gets
…		…
1515		1769
1516	So when you encounter spurious, unexplained daemon exits, make sure you	1770	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	1771	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).	1772	somewhere, as that would have given you a big clue).
1519		1773
		1774	=head3 The special problem of accept()ing when you can't
		1775
		1776	Many implementations of the POSIX C<accept> function (for example,
		1777	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1778	connection from the pending queue in all error cases.
		1779
		1780	For example, larger servers often run out of file descriptors (because
		1781	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1782	rejecting the connection, leading to libev signalling readiness on
		1783	the next iteration again (the connection still exists after all), and
		1784	typically causing the program to loop at 100% CPU usage.
		1785
		1786	Unfortunately, the set of errors that cause this issue differs between
		1787	operating systems, there is usually little the app can do to remedy the
		1788	situation, and no known thread-safe method of removing the connection to
		1789	cope with overload is known (to me).
		1790
		1791	One of the easiest ways to handle this situation is to just ignore it
		1792	- when the program encounters an overload, it will just loop until the
		1793	situation is over. While this is a form of busy waiting, no OS offers an
		1794	event-based way to handle this situation, so it's the best one can do.
		1795
		1796	A better way to handle the situation is to log any errors other than
		1797	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1798	messages, and continue as usual, which at least gives the user an idea of
		1799	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1800	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1801	usage.
		1802
		1803	If your program is single-threaded, then you could also keep a dummy file
		1804	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1805	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1806	close that fd, and create a new dummy fd. This will gracefully refuse
		1807	clients under typical overload conditions.
		1808
		1809	The last way to handle it is to simply log the error and C<exit>, as
		1810	is often done with C<malloc> failures, but this results in an easy
		1811	opportunity for a DoS attack.
1520		1812
1521	=head3 Watcher-Specific Functions	1813	=head3 Watcher-Specific Functions
1522		1814
1523	=over 4	1815	=over 4
1524		1816
…		…
1556	...	1848	...
1557	struct ev_loop *loop = ev_default_init (0);	1849	struct ev_loop *loop = ev_default_init (0);
1558	ev_io stdin_readable;	1850	ev_io stdin_readable;
1559	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1851	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1560	ev_io_start (loop, &stdin_readable);	1852	ev_io_start (loop, &stdin_readable);
1561	ev_loop (loop, 0);	1853	ev_run (loop, 0);
1562		1854
1563		1855
1564	=head2 C<ev_timer> - relative and optionally repeating timeouts	1856	=head2 C<ev_timer> - relative and optionally repeating timeouts
1565		1857
1566	Timer watchers are simple relative timers that generate an event after a	1858	Timer watchers are simple relative timers that generate an event after a
…		…
1572	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1864	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1573	monotonic clock option helps a lot here).	1865	monotonic clock option helps a lot here).
1574		1866
1575	The callback is guaranteed to be invoked only I<after> its timeout has	1867	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	1868	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	1869	might introduce a small delay, see "the special problem of being too
		1870	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	1871	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	1872	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).	1873	longer true when a callback calls C<ev_run> recursively).
1581		1874
1582	=head3 Be smart about timeouts	1875	=head3 Be smart about timeouts
1583		1876
1584	Many real-world problems involve some kind of timeout, usually for error	1877	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,	1878	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1660		1953
1661	In this case, it would be more efficient to leave the C<ev_timer> alone,	1954	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	1955	but remember the time of last activity, and check for a real timeout only
1663	within the callback:	1956	within the callback:
1664		1957
		1958	ev_tstamp timeout = 60.;
1665	ev_tstamp last_activity; // time of last activity	1959	ev_tstamp last_activity; // time of last activity
		1960	ev_timer timer;
1666		1961
1667	static void	1962	static void
1668	callback (EV_P_ ev_timer *w, int revents)	1963	callback (EV_P_ ev_timer *w, int revents)
1669	{	1964	{
1670	ev_tstamp now = ev_now (EV_A);	1965	// calculate when the timeout would happen
1671	ev_tstamp timeout = last_activity + 60.;	1966	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1672		1967
1673	// if last_activity + 60. is older than now, we did time out	1968	// if negative, it means we the timeout already occurred
1674	if (timeout < now)	1969	if (after < 0.)
1675	{	1970	{
1676	// timeout occured, take action	1971	// timeout occurred, take action
1677	}	1972	}
1678	else	1973	else
1679	{	1974	{
1680	// callback was invoked, but there was some activity, re-arm	1975	// callback was invoked, but there was some recent
1681	// the watcher to fire in last_activity + 60, which is	1976	// activity. simply restart the timer to time out
1682	// guaranteed to be in the future, so "again" is positive:	1977	// after "after" seconds, which is the earliest time
1683	w->repeat = timeout - now;	1978	// the timeout can occur.
		1979	ev_timer_set (w, after, 0.);
1684	ev_timer_again (EV_A_ w);	1980	ev_timer_start (EV_A_ w);
1685	}	1981	}
1686	}	1982	}
1687		1983
1688	To summarise the callback: first calculate the real timeout (defined	1984	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	1985	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	1986	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	1987	(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		1988
1695	Note how C<ev_timer_again> is used, taking advantage of the	1989	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.	1990	timed out, and need to do whatever is needed in this case.
		1991
		1992	Otherwise, we now the earliest time at which the timeout would trigger,
		1993	and simply start the timer with this timeout value.
		1994
		1995	In other words, each time the callback is invoked it will check whether
		1996	the timeout occurred. If not, it will simply reschedule itself to check
		1997	again at the earliest time it could time out. Rinse. Repeat.
1697		1998
1698	This scheme causes more callback invocations (about one every 60 seconds	1999	This scheme causes more callback invocations (about one every 60 seconds
1699	minus half the average time between activity), but virtually no calls to	2000	minus half the average time between activity), but virtually no calls to
1700	libev to change the timeout.	2001	libev to change the timeout.
1701		2002
1702	To start the timer, simply initialise the watcher and set C<last_activity>	2003	To start the machinery, simply initialise the watcher and set
1703	to the current time (meaning we just have some activity :), then call the	2004	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:	2005	now), then call the callback, which will "do the right thing" and start
		2006	the timer:
1705		2007
		2008	last_activity = ev_now (EV_A);
1706	ev_init (timer, callback);	2009	ev_init (&timer, callback);
1707	last_activity = ev_now (loop);	2010	callback (EV_A_ &timer, 0);
1708	callback (loop, timer, EV_TIMEOUT);
1709		2011
1710	And when there is some activity, simply store the current time in	2012	When there is some activity, simply store the current time in
1711	C<last_activity>, no libev calls at all:	2013	C<last_activity>, no libev calls at all:
1712		2014
		2015	if (activity detected)
1713	last_actiivty = ev_now (loop);	2016	last_activity = ev_now (EV_A);
		2017
		2018	When your timeout value changes, then the timeout can be changed by simply
		2019	providing a new value, stopping the timer and calling the callback, which
		2020	will again do the right thing (for example, time out immediately :).
		2021
		2022	timeout = new_value;
		2023	ev_timer_stop (EV_A_ &timer);
		2024	callback (EV_A_ &timer, 0);
1714		2025
1715	This technique is slightly more complex, but in most cases where the	2026	This technique is slightly more complex, but in most cases where the
1716	time-out is unlikely to be triggered, much more efficient.	2027	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		2028
1722	=item 4. Wee, just use a double-linked list for your timeouts.	2029	=item 4. Wee, just use a double-linked list for your timeouts.
1723		2030
1724	If there is not one request, but many thousands (millions...), all	2031	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	2032	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	2059	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	2060	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	2061	off after the first million or so of active timers, i.e. it's usually
1755	overkill :)	2062	overkill :)
1756		2063
		2064	=head3 The special problem of being too early
		2065
		2066	If you ask a timer to call your callback after three seconds, then
		2067	you expect it to be invoked after three seconds - but of course, this
		2068	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2069	guaranteed to any precision by libev - imagine somebody suspending the
		2070	process with a STOP signal for a few hours for example.
		2071
		2072	So, libev tries to invoke your callback as soon as possible I<after> the
		2073	delay has occurred, but cannot guarantee this.
		2074
		2075	A less obvious failure mode is calling your callback too early: many event
		2076	loops compare timestamps with a "elapsed delay >= requested delay", but
		2077	this can cause your callback to be invoked much earlier than you would
		2078	expect.
		2079
		2080	To see why, imagine a system with a clock that only offers full second
		2081	resolution (think windows if you can't come up with a broken enough OS
		2082	yourself). If you schedule a one-second timer at the time 500.9, then the
		2083	event loop will schedule your timeout to elapse at a system time of 500
		2084	(500.9 truncated to the resolution) + 1, or 501.
		2085
		2086	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2087	501" and invoke the callback 0.1s after it was started, even though a
		2088	one-second delay was requested - this is being "too early", despite best
		2089	intentions.
		2090
		2091	This is the reason why libev will never invoke the callback if the elapsed
		2092	delay equals the requested delay, but only when the elapsed delay is
		2093	larger than the requested delay. In the example above, libev would only invoke
		2094	the callback at system time 502, or 1.1s after the timer was started.
		2095
		2096	So, while libev cannot guarantee that your callback will be invoked
		2097	exactly when requested, it I<can> and I<does> guarantee that the requested
		2098	delay has actually elapsed, or in other words, it always errs on the "too
		2099	late" side of things.
		2100
1757	=head3 The special problem of time updates	2101	=head3 The special problem of time updates
1758		2102
1759	Establishing the current time is a costly operation (it usually takes at	2103	Establishing the current time is a costly operation (it usually takes
1760	least two system calls): EV therefore updates its idea of the current	2104	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	2105	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	2106	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1763	lots of events in one iteration.	2107	lots of events in one iteration.
1764		2108
1765	The relative timeouts are calculated relative to the C<ev_now ()>	2109	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	2110	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	2111	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	2112	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:	2113	timeout on the current time, use something like the following to adjust
		2114	for it:
1770		2115
1771	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2116	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1772		2117
1773	If the event loop is suspended for a long time, you can also force an	2118	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	2119	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1775	()>.	2120	()>, although that will push the event time of all outstanding events
		2121	further into the future.
		2122
		2123	=head3 The special problem of unsynchronised clocks
		2124
		2125	Modern systems have a variety of clocks - libev itself uses the normal
		2126	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2127	jumps).
		2128
		2129	Neither of these clocks is synchronised with each other or any other clock
		2130	on the system, so C<ev_time ()> might return a considerably different time
		2131	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2132	a call to C<gettimeofday> might return a second count that is one higher
		2133	than a directly following call to C<time>.
		2134
		2135	The moral of this is to only compare libev-related timestamps with
		2136	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2137	a second or so.
		2138
		2139	One more problem arises due to this lack of synchronisation: if libev uses
		2140	the system monotonic clock and you compare timestamps from C<ev_time>
		2141	or C<ev_now> from when you started your timer and when your callback is
		2142	invoked, you will find that sometimes the callback is a bit "early".
		2143
		2144	This is because C<ev_timer>s work in real time, not wall clock time, so
		2145	libev makes sure your callback is not invoked before the delay happened,
		2146	I<measured according to the real time>, not the system clock.
		2147
		2148	If your timeouts are based on a physical timescale (e.g. "time out this
		2149	connection after 100 seconds") then this shouldn't bother you as it is
		2150	exactly the right behaviour.
		2151
		2152	If you want to compare wall clock/system timestamps to your timers, then
		2153	you need to use C<ev_periodic>s, as these are based on the wall clock
		2154	time, where your comparisons will always generate correct results.
1776		2155
1777	=head3 The special problems of suspended animation	2156	=head3 The special problems of suspended animation
1778		2157
1779	When you leave the server world it is quite customary to hit machines that	2158	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?	2159	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1810		2189
1811	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2190	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1812		2191
1813	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2192	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1814		2193
1815	Configure the timer to trigger after C<after> seconds. If C<repeat>	2194	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	2195	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	2196	automatically be stopped once the timeout is reached. If it is positive,
1818	configured to trigger again C<repeat> seconds later, again, and again,	2197	then the timer will automatically be configured to trigger again C<repeat>
1819	until stopped manually.	2198	seconds later, again, and again, until stopped manually.
1820		2199
1821	The timer itself will do a best-effort at avoiding drift, that is, if	2200	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	2201	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	2202	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	2203	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.	2204	do stuff) the timer will not fire more than once per event loop iteration.
1826		2205
1827	=item ev_timer_again (loop, ev_timer *)	2206	=item ev_timer_again (loop, ev_timer *)
1828		2207
1829	This will act as if the timer timed out and restart it again if it is	2208	This will act as if the timer timed out, and restarts it again if it is
1830	repeating. The exact semantics are:	2209	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2210	timeout to the C<repeat> value and calling C<ev_timer_start>.
1831		2211
		2212	The exact semantics are as in the following rules, all of which will be
		2213	applied to the watcher:
		2214
		2215	=over 4
		2216
1832	If the timer is pending, its pending status is cleared.	2217	=item If the timer is pending, the pending status is always cleared.
1833		2218
1834	If the timer is started but non-repeating, stop it (as if it timed out).	2219	=item If the timer is started but non-repeating, stop it (as if it timed
		2220	out, without invoking it).
1835		2221
1836	If the timer is repeating, either start it if necessary (with the	2222	=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.	2223	and start the timer, if necessary.
1838		2224
		2225	=back
		2226
1839	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2227	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1840	usage example.	2228	usage example.
1841		2229
1842	=item ev_timer_remaining (loop, ev_timer *)	2230	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1843		2231
1844	Returns the remaining time until a timer fires. If the timer is active,	2232	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	2233	then this time is relative to the current event loop time, otherwise it's
1846	the timeout value currently configured.	2234	the timeout value currently configured.
1847		2235
1848	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2236	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>	2237	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	2238	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,	2239	roughly C<7> (likely slightly less as callback invocation takes some time,
1852	too), and so on.	2240	too), and so on.
1853		2241
1854	=item ev_tstamp repeat [read-write]	2242	=item ev_tstamp repeat [read-write]
…		…
1883	}	2271	}
1884		2272
1885	ev_timer mytimer;	2273	ev_timer mytimer;
1886	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2274	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1887	ev_timer_again (&mytimer); /* start timer */	2275	ev_timer_again (&mytimer); /* start timer */
1888	ev_loop (loop, 0);	2276	ev_run (loop, 0);
1889		2277
1890	// and in some piece of code that gets executed on any "activity":	2278	// and in some piece of code that gets executed on any "activity":
1891	// reset the timeout to start ticking again at 10 seconds	2279	// reset the timeout to start ticking again at 10 seconds
1892	ev_timer_again (&mytimer);	2280	ev_timer_again (&mytimer);
1893		2281
…		…
1897	Periodic watchers are also timers of a kind, but they are very versatile	2285	Periodic watchers are also timers of a kind, but they are very versatile
1898	(and unfortunately a bit complex).	2286	(and unfortunately a bit complex).
1899		2287
1900	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2288	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	2289	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	2290	(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	2291	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	2292	time, and time jumps are not uncommon (e.g. when you adjust your
1905	wrist-watch).	2293	wrist-watch).
1906		2294
1907	You can tell a periodic watcher to trigger after some specific point	2295	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	2300	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1913	it, as it uses a relative timeout).	2301	it, as it uses a relative timeout).
1914		2302
1915	C<ev_periodic> watchers can also be used to implement vastly more complex	2303	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	2304	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	2305	other complicated rules. This cannot easily be done with C<ev_timer>
1918	those cannot react to time jumps.	2306	watchers, as those cannot react to time jumps.
1919		2307
1920	As with timers, the callback is guaranteed to be invoked only when the	2308	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	2309	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	2310	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	2311	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).	2312	(but this is no longer true when a callback calls C<ev_run> recursively).
1925		2313
1926	=head3 Watcher-Specific Functions and Data Members	2314	=head3 Watcher-Specific Functions and Data Members
1927		2315
1928	=over 4	2316	=over 4
1929		2317
…		…
1964		2352
1965	Another way to think about it (for the mathematically inclined) is that	2353	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	2354	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.	2355	time where C<time = offset (mod interval)>, regardless of any time jumps.
1968		2356
1969	For numerical stability it is preferable that the C<offset> value is near	2357	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	2358	interval value should be higher than C<1/8192> (which is around 100
1971	this value, and in fact is often specified as zero.	2359	microseconds) and C<offset> should be higher than C<0> and should have
		2360	at most a similar magnitude as the current time (say, within a factor of
		2361	ten). Typical values for offset are, in fact, C<0> or something between
		2362	C<0> and C<interval>, which is also the recommended range.
1972		2363
1973	Note also that there is an upper limit to how often a timer can fire (CPU	2364	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	2365	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	2366	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).	2367	millisecond (if the OS supports it and the machine is fast enough).
…		…
2006		2397
2007	NOTE: I<< This callback must always return a time that is higher than or	2398	NOTE: I<< This callback must always return a time that is higher than or
2008	equal to the passed C<now> value >>.	2399	equal to the passed C<now> value >>.
2009		2400
2010	This can be used to create very complex timers, such as a timer that	2401	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	2402	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	2403	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	2404	this. Here is a (completely untested, no error checking) example on how to
2014	reason I omitted it as an example).	2405	do this:
		2406
		2407	#include <time.h>
		2408
		2409	static ev_tstamp
		2410	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2411	{
		2412	time_t tnow = (time_t)now;
		2413	struct tm tm;
		2414	localtime_r (&tnow, &tm);
		2415
		2416	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2417	++tm.tm_mday; // midnight next day
		2418
		2419	return mktime (&tm);
		2420	}
		2421
		2422	Note: this code might run into trouble on days that have more then two
		2423	midnights (beginning and end).
2015		2424
2016	=back	2425	=back
2017		2426
2018	=item ev_periodic_again (loop, ev_periodic *)	2427	=item ev_periodic_again (loop, ev_periodic *)
2019		2428
…		…
2057	Example: Call a callback every hour, or, more precisely, whenever the	2466	Example: Call a callback every hour, or, more precisely, whenever the
2058	system time is divisible by 3600. The callback invocation times have	2467	system time is divisible by 3600. The callback invocation times have
2059	potentially a lot of jitter, but good long-term stability.	2468	potentially a lot of jitter, but good long-term stability.
2060		2469
2061	static void	2470	static void
2062	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2471	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2063	{	2472	{
2064	... its now a full hour (UTC, or TAI or whatever your clock follows)	2473	... its now a full hour (UTC, or TAI or whatever your clock follows)
2065	}	2474	}
2066		2475
2067	ev_periodic hourly_tick;	2476	ev_periodic hourly_tick;
…		…
2084		2493
2085	ev_periodic hourly_tick;	2494	ev_periodic hourly_tick;
2086	ev_periodic_init (&hourly_tick, clock_cb,	2495	ev_periodic_init (&hourly_tick, clock_cb,
2087	fmod (ev_now (loop), 3600.), 3600., 0);	2496	fmod (ev_now (loop), 3600.), 3600., 0);
2088	ev_periodic_start (loop, &hourly_tick);	2497	ev_periodic_start (loop, &hourly_tick);
2089		2498
2090		2499
2091	=head2 C<ev_signal> - signal me when a signal gets signalled!	2500	=head2 C<ev_signal> - signal me when a signal gets signalled!
2092		2501
2093	Signal watchers will trigger an event when the process receives a specific	2502	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	2503	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	2504	will try its best to deliver signals synchronously, i.e. as part of the
2096	normal event processing, like any other event.	2505	normal event processing, like any other event.
2097		2506
2098	If you want signals to be delivered truly asynchronously, just use	2507	If you want signals to be delivered truly asynchronously, just use
2099	C<sigaction> as you would do without libev and forget about sharing	2508	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	2509	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	2513	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	2514	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	2515	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.	2516	the moment, C<SIGCHLD> is permanently tied to the default loop.
2108		2517
2109	When the first watcher gets started will libev actually register something	2518	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	2519	register something with the kernel. It thus coexists with your own signal
2111	you don't register any with libev for the same signal).	2520	handlers as long as you don't register any with libev for the same signal.
2112		2521
2113	If possible and supported, libev will install its handlers with	2522	If possible and supported, libev will install its handlers with
2114	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2523	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2115	not be unduly interrupted. If you have a problem with system calls getting	2524	not be unduly interrupted. If you have a problem with system calls getting
2116	interrupted by signals you can block all signals in an C<ev_check> watcher	2525	interrupted by signals you can block all signals in an C<ev_check> watcher
2117	and unblock them in an C<ev_prepare> watcher.	2526	and unblock them in an C<ev_prepare> watcher.
2118		2527
2119	=head3 The special problem of inheritance over execve	2528	=head3 The special problem of inheritance over fork/execve/pthread_create
2120		2529
2121	Both the signal mask (C<sigprocmask>) and the signal disposition	2530	Both the signal mask (C<sigprocmask>) and the signal disposition
2122	(C<sigaction>) are unspecified after starting a signal watcher (and after	2531	(C<sigaction>) are unspecified after starting a signal watcher (and after
2123	stopping it again), that is, libev might or might not block the signal,	2532	stopping it again), that is, libev might or might not block the signal,
2124	and might or might not set or restore the installed signal handler.	2533	and might or might not set or restore the installed signal handler (but
		2534	see C<EVFLAG_NOSIGMASK>).
2125		2535
2126	While this does not matter for the signal disposition (libev never	2536	While this does not matter for the signal disposition (libev never
2127	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2537	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2128	C<execve>), this matters for the signal mask: many programs do not expect	2538	C<execve>), this matters for the signal mask: many programs do not expect
2129	many signals to be blocked.	2539	certain signals to be blocked.
2130		2540
2131	This means that before calling C<exec> (from the child) you should reset	2541	This means that before calling C<exec> (from the child) you should reset
2132	the signal mask to whatever "default" you expect (all clear is a good	2542	the signal mask to whatever "default" you expect (all clear is a good
2133	choice usually).	2543	choice usually).
2134		2544
		2545	The simplest way to ensure that the signal mask is reset in the child is
		2546	to install a fork handler with C<pthread_atfork> that resets it. That will
		2547	catch fork calls done by libraries (such as the libc) as well.
		2548
		2549	In current versions of libev, the signal will not be blocked indefinitely
		2550	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2551	the window of opportunity for problems, it will not go away, as libev
		2552	I<has> to modify the signal mask, at least temporarily.
		2553
		2554	So I can't stress this enough: I<If you do not reset your signal mask when
		2555	you expect it to be empty, you have a race condition in your code>. This
		2556	is not a libev-specific thing, this is true for most event libraries.
		2557
		2558	=head3 The special problem of threads signal handling
		2559
		2560	POSIX threads has problematic signal handling semantics, specifically,
		2561	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2562	threads in a process block signals, which is hard to achieve.
		2563
		2564	When you want to use sigwait (or mix libev signal handling with your own
		2565	for the same signals), you can tackle this problem by globally blocking
		2566	all signals before creating any threads (or creating them with a fully set
		2567	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2568	loops. Then designate one thread as "signal receiver thread" which handles
		2569	these signals. You can pass on any signals that libev might be interested
		2570	in by calling C<ev_feed_signal>.
		2571
2135	=head3 Watcher-Specific Functions and Data Members	2572	=head3 Watcher-Specific Functions and Data Members
2136		2573
2137	=over 4	2574	=over 4
2138		2575
2139	=item ev_signal_init (ev_signal *, callback, int signum)	2576	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2154	Example: Try to exit cleanly on SIGINT.	2591	Example: Try to exit cleanly on SIGINT.
2155		2592
2156	static void	2593	static void
2157	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2594	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2158	{	2595	{
2159	ev_unloop (loop, EVUNLOOP_ALL);	2596	ev_break (loop, EVBREAK_ALL);
2160	}	2597	}
2161		2598
2162	ev_signal signal_watcher;	2599	ev_signal signal_watcher;
2163	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2600	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2164	ev_signal_start (loop, &signal_watcher);	2601	ev_signal_start (loop, &signal_watcher);
…		…
2273		2710
2274	=head2 C<ev_stat> - did the file attributes just change?	2711	=head2 C<ev_stat> - did the file attributes just change?
2275		2712
2276	This watches a file system path for attribute changes. That is, it calls	2713	This watches a file system path for attribute changes. That is, it calls
2277	C<stat> on that path in regular intervals (or when the OS says it changed)	2714	C<stat> on that path in regular intervals (or when the OS says it changed)
2278	and sees if it changed compared to the last time, invoking the callback if	2715	and sees if it changed compared to the last time, invoking the callback
2279	it did.	2716	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2717	happen after the watcher has been started will be reported.
2280		2718
2281	The path does not need to exist: changing from "path exists" to "path does	2719	The path does not need to exist: changing from "path exists" to "path does
2282	not exist" is a status change like any other. The condition "path does not	2720	not exist" is a status change like any other. The condition "path does not
2283	exist" (or more correctly "path cannot be stat'ed") is signified by the	2721	exist" (or more correctly "path cannot be stat'ed") is signified by the
2284	C<st_nlink> field being zero (which is otherwise always forced to be at	2722	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2514	Apart from keeping your process non-blocking (which is a useful	2952	Apart from keeping your process non-blocking (which is a useful
2515	effect on its own sometimes), idle watchers are a good place to do	2953	effect on its own sometimes), idle watchers are a good place to do
2516	"pseudo-background processing", or delay processing stuff to after the	2954	"pseudo-background processing", or delay processing stuff to after the
2517	event loop has handled all outstanding events.	2955	event loop has handled all outstanding events.
2518		2956
		2957	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2958
		2959	As long as there is at least one active idle watcher, libev will never
		2960	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2961	For this to work, the idle watcher doesn't need to be invoked at all - the
		2962	lowest priority will do.
		2963
		2964	This mode of operation can be useful together with an C<ev_check> watcher,
		2965	to do something on each event loop iteration - for example to balance load
		2966	between different connections.
		2967
		2968	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2969	example.
		2970
2519	=head3 Watcher-Specific Functions and Data Members	2971	=head3 Watcher-Specific Functions and Data Members
2520		2972
2521	=over 4	2973	=over 4
2522		2974
2523	=item ev_idle_init (ev_idle *, callback)	2975	=item ev_idle_init (ev_idle *, callback)
…		…
2534	callback, free it. Also, use no error checking, as usual.	2986	callback, free it. Also, use no error checking, as usual.
2535		2987
2536	static void	2988	static void
2537	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2989	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2538	{	2990	{
		2991	// stop the watcher
		2992	ev_idle_stop (loop, w);
		2993
		2994	// now we can free it
2539	free (w);	2995	free (w);
		2996
2540	// now do something you wanted to do when the program has	2997	// now do something you wanted to do when the program has
2541	// no longer anything immediate to do.	2998	// no longer anything immediate to do.
2542	}	2999	}
2543		3000
2544	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3001	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2546	ev_idle_start (loop, idle_watcher);	3003	ev_idle_start (loop, idle_watcher);
2547		3004
2548		3005
2549	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3006	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2550		3007
2551	Prepare and check watchers are usually (but not always) used in pairs:	3008	Prepare and check watchers are often (but not always) used in pairs:
2552	prepare watchers get invoked before the process blocks and check watchers	3009	prepare watchers get invoked before the process blocks and check watchers
2553	afterwards.	3010	afterwards.
2554		3011
2555	You I<must not> call C<ev_loop> or similar functions that enter	3012	You I<must not> call C<ev_run> (or similar functions that enter the
2556	the current event loop from either C<ev_prepare> or C<ev_check>	3013	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2557	watchers. Other loops than the current one are fine, however. The	3014	C<ev_check> watchers. Other loops than the current one are fine,
2558	rationale behind this is that you do not need to check for recursion in	3015	however. The rationale behind this is that you do not need to check
2559	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3016	for recursion in those watchers, i.e. the sequence will always be
2560	C<ev_check> so if you have one watcher of each kind they will always be	3017	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2561	called in pairs bracketing the blocking call.	3018	kind they will always be called in pairs bracketing the blocking call.
2562		3019
2563	Their main purpose is to integrate other event mechanisms into libev and	3020	Their main purpose is to integrate other event mechanisms into libev and
2564	their use is somewhat advanced. They could be used, for example, to track	3021	their use is somewhat advanced. They could be used, for example, to track
2565	variable changes, implement your own watchers, integrate net-snmp or a	3022	variable changes, implement your own watchers, integrate net-snmp or a
2566	coroutine library and lots more. They are also occasionally useful if	3023	coroutine library and lots more. They are also occasionally useful if
…		…
2584	with priority higher than or equal to the event loop and one coroutine	3041	with priority higher than or equal to the event loop and one coroutine
2585	of lower priority, but only once, using idle watchers to keep the event	3042	of lower priority, but only once, using idle watchers to keep the event
2586	loop from blocking if lower-priority coroutines are active, thus mapping	3043	loop from blocking if lower-priority coroutines are active, thus mapping
2587	low-priority coroutines to idle/background tasks).	3044	low-priority coroutines to idle/background tasks).
2588		3045
2589	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3046	When used for this purpose, it is recommended to give C<ev_check> watchers
2590	priority, to ensure that they are being run before any other watchers	3047	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2591	after the poll (this doesn't matter for C<ev_prepare> watchers).	3048	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3049	watchers).
2592		3050
2593	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3051	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2594	activate ("feed") events into libev. While libev fully supports this, they	3052	activate ("feed") events into libev. While libev fully supports this, they
2595	might get executed before other C<ev_check> watchers did their job. As	3053	might get executed before other C<ev_check> watchers did their job. As
2596	C<ev_check> watchers are often used to embed other (non-libev) event	3054	C<ev_check> watchers are often used to embed other (non-libev) event
2597	loops those other event loops might be in an unusable state until their	3055	loops those other event loops might be in an unusable state until their
2598	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3056	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2599	others).	3057	others).
		3058
		3059	=head3 Abusing an C<ev_check> watcher for its side-effect
		3060
		3061	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3062	useful because they are called once per event loop iteration. For
		3063	example, if you want to handle a large number of connections fairly, you
		3064	normally only do a bit of work for each active connection, and if there
		3065	is more work to do, you wait for the next event loop iteration, so other
		3066	connections have a chance of making progress.
		3067
		3068	Using an C<ev_check> watcher is almost enough: it will be called on the
		3069	next event loop iteration. However, that isn't as soon as possible -
		3070	without external events, your C<ev_check> watcher will not be invoked.
		3071
		3072	This is where C<ev_idle> watchers come in handy - all you need is a
		3073	single global idle watcher that is active as long as you have one active
		3074	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3075	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3076	invoked. Neither watcher alone can do that.
2600		3077
2601	=head3 Watcher-Specific Functions and Data Members	3078	=head3 Watcher-Specific Functions and Data Members
2602		3079
2603	=over 4	3080	=over 4
2604		3081
…		…
2728		3205
2729	if (timeout >= 0)	3206	if (timeout >= 0)
2730	// create/start timer	3207	// create/start timer
2731		3208
2732	// poll	3209	// poll
2733	ev_loop (EV_A_ 0);	3210	ev_run (EV_A_ 0);
2734		3211
2735	// stop timer again	3212	// stop timer again
2736	if (timeout >= 0)	3213	if (timeout >= 0)
2737	ev_timer_stop (EV_A_ &to);	3214	ev_timer_stop (EV_A_ &to);
2738		3215
…		…
2805		3282
2806	=over 4	3283	=over 4
2807		3284
2808	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3285	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2809		3286
2810	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3287	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2811		3288
2812	Configures the watcher to embed the given loop, which must be	3289	Configures the watcher to embed the given loop, which must be
2813	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3290	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2814	invoked automatically, otherwise it is the responsibility of the callback	3291	invoked automatically, otherwise it is the responsibility of the callback
2815	to invoke it (it will continue to be called until the sweep has been done,	3292	to invoke it (it will continue to be called until the sweep has been done,
2816	if you do not want that, you need to temporarily stop the embed watcher).	3293	if you do not want that, you need to temporarily stop the embed watcher).
2817		3294
2818	=item ev_embed_sweep (loop, ev_embed *)	3295	=item ev_embed_sweep (loop, ev_embed *)
2819		3296
2820	Make a single, non-blocking sweep over the embedded loop. This works	3297	Make a single, non-blocking sweep over the embedded loop. This works
2821	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3298	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2822	appropriate way for embedded loops.	3299	appropriate way for embedded loops.
2823		3300
2824	=item struct ev_loop *other [read-only]	3301	=item struct ev_loop *other [read-only]
2825		3302
2826	The embedded event loop.	3303	The embedded event loop.
…		…
2836	used).	3313	used).
2837		3314
2838	struct ev_loop *loop_hi = ev_default_init (0);	3315	struct ev_loop *loop_hi = ev_default_init (0);
2839	struct ev_loop *loop_lo = 0;	3316	struct ev_loop *loop_lo = 0;
2840	ev_embed embed;	3317	ev_embed embed;
2841		3318
2842	// see if there is a chance of getting one that works	3319	// see if there is a chance of getting one that works
2843	// (remember that a flags value of 0 means autodetection)	3320	// (remember that a flags value of 0 means autodetection)
2844	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3321	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2845	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3322	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2846	: 0;	3323	: 0;
…		…
2860	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3337	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2861		3338
2862	struct ev_loop *loop = ev_default_init (0);	3339	struct ev_loop *loop = ev_default_init (0);
2863	struct ev_loop *loop_socket = 0;	3340	struct ev_loop *loop_socket = 0;
2864	ev_embed embed;	3341	ev_embed embed;
2865		3342
2866	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3343	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2867	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3344	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2868	{	3345	{
2869	ev_embed_init (&embed, 0, loop_socket);	3346	ev_embed_init (&embed, 0, loop_socket);
2870	ev_embed_start (loop, &embed);	3347	ev_embed_start (loop, &embed);
…		…
2878		3355
2879	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3356	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2880		3357
2881	Fork watchers are called when a C<fork ()> was detected (usually because	3358	Fork watchers are called when a C<fork ()> was detected (usually because
2882	whoever is a good citizen cared to tell libev about it by calling	3359	whoever is a good citizen cared to tell libev about it by calling
2883	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3360	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2884	event loop blocks next and before C<ev_check> watchers are being called,	3361	and before C<ev_check> watchers are being called, and only in the child
2885	and only in the child after the fork. If whoever good citizen calling	3362	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2886	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3363	and calls it in the wrong process, the fork handlers will be invoked, too,
2887	handlers will be invoked, too, of course.	3364	of course.
2888		3365
2889	=head3 The special problem of life after fork - how is it possible?	3366	=head3 The special problem of life after fork - how is it possible?
2890		3367
2891	Most uses of C<fork()> consist of forking, then some simple calls to ste	3368	Most uses of C<fork ()> consist of forking, then some simple calls to set
2892	up/change the process environment, followed by a call to C<exec()>. This	3369	up/change the process environment, followed by a call to C<exec()>. This
2893	sequence should be handled by libev without any problems.	3370	sequence should be handled by libev without any problems.
2894		3371
2895	This changes when the application actually wants to do event handling	3372	This changes when the application actually wants to do event handling
2896	in the child, or both parent in child, in effect "continuing" after the	3373	in the child, or both parent in child, in effect "continuing" after the
…		…
2912	disadvantage of having to use multiple event loops (which do not support	3389	disadvantage of having to use multiple event loops (which do not support
2913	signal watchers).	3390	signal watchers).
2914		3391
2915	When this is not possible, or you want to use the default loop for	3392	When this is not possible, or you want to use the default loop for
2916	other reasons, then in the process that wants to start "fresh", call	3393	other reasons, then in the process that wants to start "fresh", call
2917	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3394	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2918	the default loop will "orphan" (not stop) all registered watchers, so you	3395	Destroying the default loop will "orphan" (not stop) all registered
2919	have to be careful not to execute code that modifies those watchers. Note	3396	watchers, so you have to be careful not to execute code that modifies
2920	also that in that case, you have to re-register any signal watchers.	3397	those watchers. Note also that in that case, you have to re-register any
		3398	signal watchers.
2921		3399
2922	=head3 Watcher-Specific Functions and Data Members	3400	=head3 Watcher-Specific Functions and Data Members
2923		3401
2924	=over 4	3402	=over 4
2925		3403
2926	=item ev_fork_init (ev_signal *, callback)	3404	=item ev_fork_init (ev_fork *, callback)
2927		3405
2928	Initialises and configures the fork watcher - it has no parameters of any	3406	Initialises and configures the fork watcher - it has no parameters of any
2929	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3407	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2930	believe me.	3408	really.
2931		3409
2932	=back	3410	=back
2933		3411
2934		3412
		3413	=head2 C<ev_cleanup> - even the best things end
		3414
		3415	Cleanup watchers are called just before the event loop is being destroyed
		3416	by a call to C<ev_loop_destroy>.
		3417
		3418	While there is no guarantee that the event loop gets destroyed, cleanup
		3419	watchers provide a convenient method to install cleanup hooks for your
		3420	program, worker threads and so on - you just to make sure to destroy the
		3421	loop when you want them to be invoked.
		3422
		3423	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3424	all other watchers, they do not keep a reference to the event loop (which
		3425	makes a lot of sense if you think about it). Like all other watchers, you
		3426	can call libev functions in the callback, except C<ev_cleanup_start>.
		3427
		3428	=head3 Watcher-Specific Functions and Data Members
		3429
		3430	=over 4
		3431
		3432	=item ev_cleanup_init (ev_cleanup *, callback)
		3433
		3434	Initialises and configures the cleanup watcher - it has no parameters of
		3435	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3436	pointless, I assure you.
		3437
		3438	=back
		3439
		3440	Example: Register an atexit handler to destroy the default loop, so any
		3441	cleanup functions are called.
		3442
		3443	static void
		3444	program_exits (void)
		3445	{
		3446	ev_loop_destroy (EV_DEFAULT_UC);
		3447	}
		3448
		3449	...
		3450	atexit (program_exits);
		3451
		3452
2935	=head2 C<ev_async> - how to wake up another event loop	3453	=head2 C<ev_async> - how to wake up an event loop
2936		3454
2937	In general, you cannot use an C<ev_loop> from multiple threads or other	3455	In general, you cannot use an C<ev_loop> from multiple threads or other
2938	asynchronous sources such as signal handlers (as opposed to multiple event	3456	asynchronous sources such as signal handlers (as opposed to multiple event
2939	loops - those are of course safe to use in different threads).	3457	loops - those are of course safe to use in different threads).
2940		3458
2941	Sometimes, however, you need to wake up another event loop you do not	3459	Sometimes, however, you need to wake up an event loop you do not control,
2942	control, for example because it belongs to another thread. This is what	3460	for example because it belongs to another thread. This is what C<ev_async>
2943	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3461	watchers do: as long as the C<ev_async> watcher is active, you can signal
2944	can signal it by calling C<ev_async_send>, which is thread- and signal	3462	it by calling C<ev_async_send>, which is thread- and signal safe.
2945	safe.
2946		3463
2947	This functionality is very similar to C<ev_signal> watchers, as signals,	3464	This functionality is very similar to C<ev_signal> watchers, as signals,
2948	too, are asynchronous in nature, and signals, too, will be compressed	3465	too, are asynchronous in nature, and signals, too, will be compressed
2949	(i.e. the number of callback invocations may be less than the number of	3466	(i.e. the number of callback invocations may be less than the number of
2950	C<ev_async_sent> calls).	3467	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2951		3468	of "global async watchers" by using a watcher on an otherwise unused
2952	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3469	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2953	just the default loop.	3470	even without knowing which loop owns the signal.
2954		3471
2955	=head3 Queueing	3472	=head3 Queueing
2956		3473
2957	C<ev_async> does not support queueing of data in any way. The reason	3474	C<ev_async> does not support queueing of data in any way. The reason
2958	is that the author does not know of a simple (or any) algorithm for a	3475	is that the author does not know of a simple (or any) algorithm for a
2959	multiple-writer-single-reader queue that works in all cases and doesn't	3476	multiple-writer-single-reader queue that works in all cases and doesn't
2960	need elaborate support such as pthreads.	3477	need elaborate support such as pthreads or unportable memory access
		3478	semantics.
2961		3479
2962	That means that if you want to queue data, you have to provide your own	3480	That means that if you want to queue data, you have to provide your own
2963	queue. But at least I can tell you how to implement locking around your	3481	queue. But at least I can tell you how to implement locking around your
2964	queue:	3482	queue:
2965		3483
…		…
3049	trust me.	3567	trust me.
3050		3568
3051	=item ev_async_send (loop, ev_async *)	3569	=item ev_async_send (loop, ev_async *)
3052		3570
3053	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3571	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3054	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3572	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3573	returns.
		3574
3055	C<ev_feed_event>, this call is safe to do from other threads, signal or	3575	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3056	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3576	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3057	section below on what exactly this means).	3577	embedding section below on what exactly this means).
3058		3578
3059	Note that, as with other watchers in libev, multiple events might get	3579	Note that, as with other watchers in libev, multiple events might get
3060	compressed into a single callback invocation (another way to look at this	3580	compressed into a single callback invocation (another way to look at
3061	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3581	this is that C<ev_async> watchers are level-triggered: they are set on
3062	reset when the event loop detects that).	3582	C<ev_async_send>, reset when the event loop detects that).
3063		3583
3064	This call incurs the overhead of a system call only once per event loop	3584	This call incurs the overhead of at most one extra system call per event
3065	iteration, so while the overhead might be noticeable, it doesn't apply to	3585	loop iteration, if the event loop is blocked, and no syscall at all if
3066	repeated calls to C<ev_async_send> for the same event loop.	3586	the event loop (or your program) is processing events. That means that
		3587	repeated calls are basically free (there is no need to avoid calls for
		3588	performance reasons) and that the overhead becomes smaller (typically
		3589	zero) under load.
3067		3590
3068	=item bool = ev_async_pending (ev_async *)	3591	=item bool = ev_async_pending (ev_async *)
3069		3592
3070	Returns a non-zero value when C<ev_async_send> has been called on the	3593	Returns a non-zero value when C<ev_async_send> has been called on the
3071	watcher but the event has not yet been processed (or even noted) by the	3594	watcher but the event has not yet been processed (or even noted) by the
…		…
3088		3611
3089	There are some other functions of possible interest. Described. Here. Now.	3612	There are some other functions of possible interest. Described. Here. Now.
3090		3613
3091	=over 4	3614	=over 4
3092		3615
3093	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3616	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3094		3617
3095	This function combines a simple timer and an I/O watcher, calls your	3618	This function combines a simple timer and an I/O watcher, calls your
3096	callback on whichever event happens first and automatically stops both	3619	callback on whichever event happens first and automatically stops both
3097	watchers. This is useful if you want to wait for a single event on an fd	3620	watchers. This is useful if you want to wait for a single event on an fd
3098	or timeout without having to allocate/configure/start/stop/free one or	3621	or timeout without having to allocate/configure/start/stop/free one or
…		…
3104		3627
3105	If C<timeout> is less than 0, then no timeout watcher will be	3628	If C<timeout> is less than 0, then no timeout watcher will be
3106	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3629	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3107	repeat = 0) will be started. C<0> is a valid timeout.	3630	repeat = 0) will be started. C<0> is a valid timeout.
3108		3631
3109	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3632	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3110	passed an C<revents> set like normal event callbacks (a combination of	3633	passed an C<revents> set like normal event callbacks (a combination of
3111	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3634	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3112	value passed to C<ev_once>. Note that it is possible to receive I<both>	3635	value passed to C<ev_once>. Note that it is possible to receive I<both>
3113	a timeout and an io event at the same time - you probably should give io	3636	a timeout and an io event at the same time - you probably should give io
3114	events precedence.	3637	events precedence.
3115		3638
3116	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3639	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3117		3640
3118	static void stdin_ready (int revents, void *arg)	3641	static void stdin_ready (int revents, void *arg)
3119	{	3642	{
3120	if (revents & EV_READ)	3643	if (revents & EV_READ)
3121	/* stdin might have data for us, joy! */;	3644	/* stdin might have data for us, joy! */;
3122	else if (revents & EV_TIMEOUT)	3645	else if (revents & EV_TIMER)
3123	/* doh, nothing entered */;	3646	/* doh, nothing entered */;
3124	}	3647	}
3125		3648
3126	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3649	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3127		3650
3128	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
3129
3130	Feeds the given event set into the event loop, as if the specified event
3131	had happened for the specified watcher (which must be a pointer to an
3132	initialised but not necessarily started event watcher).
3133
3134	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3651	=item ev_feed_fd_event (loop, int fd, int revents)
3135		3652
3136	Feed an event on the given fd, as if a file descriptor backend detected	3653	Feed an event on the given fd, as if a file descriptor backend detected
3137	the given events it.	3654	the given events.
3138		3655
3139	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3656	=item ev_feed_signal_event (loop, int signum)
3140		3657
3141	Feed an event as if the given signal occurred (C<loop> must be the default	3658	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3142	loop!).	3659	which is async-safe.
3143		3660
3144	=back	3661	=back
		3662
		3663
		3664	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3665
		3666	This section explains some common idioms that are not immediately
		3667	obvious. Note that examples are sprinkled over the whole manual, and this
		3668	section only contains stuff that wouldn't fit anywhere else.
		3669
		3670	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3671
		3672	Each watcher has, by default, a C<void *data> member that you can read
		3673	or modify at any time: libev will completely ignore it. This can be used
		3674	to associate arbitrary data with your watcher. If you need more data and
		3675	don't want to allocate memory separately and store a pointer to it in that
		3676	data member, you can also "subclass" the watcher type and provide your own
		3677	data:
		3678
		3679	struct my_io
		3680	{
		3681	ev_io io;
		3682	int otherfd;
		3683	void *somedata;
		3684	struct whatever *mostinteresting;
		3685	};
		3686
		3687	...
		3688	struct my_io w;
		3689	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3690
		3691	And since your callback will be called with a pointer to the watcher, you
		3692	can cast it back to your own type:
		3693
		3694	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3695	{
		3696	struct my_io *w = (struct my_io *)w_;
		3697	...
		3698	}
		3699
		3700	More interesting and less C-conformant ways of casting your callback
		3701	function type instead have been omitted.
		3702
		3703	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3704
		3705	Another common scenario is to use some data structure with multiple
		3706	embedded watchers, in effect creating your own watcher that combines
		3707	multiple libev event sources into one "super-watcher":
		3708
		3709	struct my_biggy
		3710	{
		3711	int some_data;
		3712	ev_timer t1;
		3713	ev_timer t2;
		3714	}
		3715
		3716	In this case getting the pointer to C<my_biggy> is a bit more
		3717	complicated: Either you store the address of your C<my_biggy> struct in
		3718	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3719	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3720	real programmers):
		3721
		3722	#include <stddef.h>
		3723
		3724	static void
		3725	t1_cb (EV_P_ ev_timer *w, int revents)
		3726	{
		3727	struct my_biggy big = (struct my_biggy *)
		3728	(((char *)w) - offsetof (struct my_biggy, t1));
		3729	}
		3730
		3731	static void
		3732	t2_cb (EV_P_ ev_timer *w, int revents)
		3733	{
		3734	struct my_biggy big = (struct my_biggy *)
		3735	(((char *)w) - offsetof (struct my_biggy, t2));
		3736	}
		3737
		3738	=head2 AVOIDING FINISHING BEFORE RETURNING
		3739
		3740	Often you have structures like this in event-based programs:
		3741
		3742	callback ()
		3743	{
		3744	free (request);
		3745	}
		3746
		3747	request = start_new_request (..., callback);
		3748
		3749	The intent is to start some "lengthy" operation. The C<request> could be
		3750	used to cancel the operation, or do other things with it.
		3751
		3752	It's not uncommon to have code paths in C<start_new_request> that
		3753	immediately invoke the callback, for example, to report errors. Or you add
		3754	some caching layer that finds that it can skip the lengthy aspects of the
		3755	operation and simply invoke the callback with the result.
		3756
		3757	The problem here is that this will happen I<before> C<start_new_request>
		3758	has returned, so C<request> is not set.
		3759
		3760	Even if you pass the request by some safer means to the callback, you
		3761	might want to do something to the request after starting it, such as
		3762	canceling it, which probably isn't working so well when the callback has
		3763	already been invoked.
		3764
		3765	A common way around all these issues is to make sure that
		3766	C<start_new_request> I<always> returns before the callback is invoked. If
		3767	C<start_new_request> immediately knows the result, it can artificially
		3768	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3769	example, or more sneakily, by reusing an existing (stopped) watcher and
		3770	pushing it into the pending queue:
		3771
		3772	ev_set_cb (watcher, callback);
		3773	ev_feed_event (EV_A_ watcher, 0);
		3774
		3775	This way, C<start_new_request> can safely return before the callback is
		3776	invoked, while not delaying callback invocation too much.
		3777
		3778	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3779
		3780	Often (especially in GUI toolkits) there are places where you have
		3781	I<modal> interaction, which is most easily implemented by recursively
		3782	invoking C<ev_run>.
		3783
		3784	This brings the problem of exiting - a callback might want to finish the
		3785	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3786	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3787	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3788	other combination: In these cases, a simple C<ev_break> will not work.
		3789
		3790	The solution is to maintain "break this loop" variable for each C<ev_run>
		3791	invocation, and use a loop around C<ev_run> until the condition is
		3792	triggered, using C<EVRUN_ONCE>:
		3793
		3794	// main loop
		3795	int exit_main_loop = 0;
		3796
		3797	while (!exit_main_loop)
		3798	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3799
		3800	// in a modal watcher
		3801	int exit_nested_loop = 0;
		3802
		3803	while (!exit_nested_loop)
		3804	ev_run (EV_A_ EVRUN_ONCE);
		3805
		3806	To exit from any of these loops, just set the corresponding exit variable:
		3807
		3808	// exit modal loop
		3809	exit_nested_loop = 1;
		3810
		3811	// exit main program, after modal loop is finished
		3812	exit_main_loop = 1;
		3813
		3814	// exit both
		3815	exit_main_loop = exit_nested_loop = 1;
		3816
		3817	=head2 THREAD LOCKING EXAMPLE
		3818
		3819	Here is a fictitious example of how to run an event loop in a different
		3820	thread from where callbacks are being invoked and watchers are
		3821	created/added/removed.
		3822
		3823	For a real-world example, see the C<EV::Loop::Async> perl module,
		3824	which uses exactly this technique (which is suited for many high-level
		3825	languages).
		3826
		3827	The example uses a pthread mutex to protect the loop data, a condition
		3828	variable to wait for callback invocations, an async watcher to notify the
		3829	event loop thread and an unspecified mechanism to wake up the main thread.
		3830
		3831	First, you need to associate some data with the event loop:
		3832
		3833	typedef struct {
		3834	mutex_t lock; /* global loop lock */
		3835	ev_async async_w;
		3836	thread_t tid;
		3837	cond_t invoke_cv;
		3838	} userdata;
		3839
		3840	void prepare_loop (EV_P)
		3841	{
		3842	// for simplicity, we use a static userdata struct.
		3843	static userdata u;
		3844
		3845	ev_async_init (&u->async_w, async_cb);
		3846	ev_async_start (EV_A_ &u->async_w);
		3847
		3848	pthread_mutex_init (&u->lock, 0);
		3849	pthread_cond_init (&u->invoke_cv, 0);
		3850
		3851	// now associate this with the loop
		3852	ev_set_userdata (EV_A_ u);
		3853	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3854	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3855
		3856	// then create the thread running ev_run
		3857	pthread_create (&u->tid, 0, l_run, EV_A);
		3858	}
		3859
		3860	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3861	solely to wake up the event loop so it takes notice of any new watchers
		3862	that might have been added:
		3863
		3864	static void
		3865	async_cb (EV_P_ ev_async *w, int revents)
		3866	{
		3867	// just used for the side effects
		3868	}
		3869
		3870	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3871	protecting the loop data, respectively.
		3872
		3873	static void
		3874	l_release (EV_P)
		3875	{
		3876	userdata *u = ev_userdata (EV_A);
		3877	pthread_mutex_unlock (&u->lock);
		3878	}
		3879
		3880	static void
		3881	l_acquire (EV_P)
		3882	{
		3883	userdata *u = ev_userdata (EV_A);
		3884	pthread_mutex_lock (&u->lock);
		3885	}
		3886
		3887	The event loop thread first acquires the mutex, and then jumps straight
		3888	into C<ev_run>:
		3889
		3890	void *
		3891	l_run (void *thr_arg)
		3892	{
		3893	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3894
		3895	l_acquire (EV_A);
		3896	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3897	ev_run (EV_A_ 0);
		3898	l_release (EV_A);
		3899
		3900	return 0;
		3901	}
		3902
		3903	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3904	signal the main thread via some unspecified mechanism (signals? pipe
		3905	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3906	have been called (in a while loop because a) spurious wakeups are possible
		3907	and b) skipping inter-thread-communication when there are no pending
		3908	watchers is very beneficial):
		3909
		3910	static void
		3911	l_invoke (EV_P)
		3912	{
		3913	userdata *u = ev_userdata (EV_A);
		3914
		3915	while (ev_pending_count (EV_A))
		3916	{
		3917	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3918	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3919	}
		3920	}
		3921
		3922	Now, whenever the main thread gets told to invoke pending watchers, it
		3923	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3924	thread to continue:
		3925
		3926	static void
		3927	real_invoke_pending (EV_P)
		3928	{
		3929	userdata *u = ev_userdata (EV_A);
		3930
		3931	pthread_mutex_lock (&u->lock);
		3932	ev_invoke_pending (EV_A);
		3933	pthread_cond_signal (&u->invoke_cv);
		3934	pthread_mutex_unlock (&u->lock);
		3935	}
		3936
		3937	Whenever you want to start/stop a watcher or do other modifications to an
		3938	event loop, you will now have to lock:
		3939
		3940	ev_timer timeout_watcher;
		3941	userdata *u = ev_userdata (EV_A);
		3942
		3943	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3944
		3945	pthread_mutex_lock (&u->lock);
		3946	ev_timer_start (EV_A_ &timeout_watcher);
		3947	ev_async_send (EV_A_ &u->async_w);
		3948	pthread_mutex_unlock (&u->lock);
		3949
		3950	Note that sending the C<ev_async> watcher is required because otherwise
		3951	an event loop currently blocking in the kernel will have no knowledge
		3952	about the newly added timer. By waking up the loop it will pick up any new
		3953	watchers in the next event loop iteration.
		3954
		3955	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3956
		3957	While the overhead of a callback that e.g. schedules a thread is small, it
		3958	is still an overhead. If you embed libev, and your main usage is with some
		3959	kind of threads or coroutines, you might want to customise libev so that
		3960	doesn't need callbacks anymore.
		3961
		3962	Imagine you have coroutines that you can switch to using a function
		3963	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3964	and that due to some magic, the currently active coroutine is stored in a
		3965	global called C<current_coro>. Then you can build your own "wait for libev
		3966	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3967	the differing C<;> conventions):
		3968
		3969	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3970	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3971
		3972	That means instead of having a C callback function, you store the
		3973	coroutine to switch to in each watcher, and instead of having libev call
		3974	your callback, you instead have it switch to that coroutine.
		3975
		3976	A coroutine might now wait for an event with a function called
		3977	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3978	matter when, or whether the watcher is active or not when this function is
		3979	called):
		3980
		3981	void
		3982	wait_for_event (ev_watcher *w)
		3983	{
		3984	ev_set_cb (w, current_coro);
		3985	switch_to (libev_coro);
		3986	}
		3987
		3988	That basically suspends the coroutine inside C<wait_for_event> and
		3989	continues the libev coroutine, which, when appropriate, switches back to
		3990	this or any other coroutine.
		3991
		3992	You can do similar tricks if you have, say, threads with an event queue -
		3993	instead of storing a coroutine, you store the queue object and instead of
		3994	switching to a coroutine, you push the watcher onto the queue and notify
		3995	any waiters.
		3996
		3997	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3998	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3999
		4000	// my_ev.h
		4001	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4002	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4003	#include "../libev/ev.h"
		4004
		4005	// my_ev.c
		4006	#define EV_H "my_ev.h"
		4007	#include "../libev/ev.c"
		4008
		4009	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4010	F<my_ev.c> into your project. When properly specifying include paths, you
		4011	can even use F<ev.h> as header file name directly.
3145		4012
3146		4013
3147	=head1 LIBEVENT EMULATION	4014	=head1 LIBEVENT EMULATION
3148		4015
3149	Libev offers a compatibility emulation layer for libevent. It cannot	4016	Libev offers a compatibility emulation layer for libevent. It cannot
3150	emulate the internals of libevent, so here are some usage hints:	4017	emulate the internals of libevent, so here are some usage hints:
3151		4018
3152	=over 4	4019	=over 4
		4020
		4021	=item * Only the libevent-1.4.1-beta API is being emulated.
		4022
		4023	This was the newest libevent version available when libev was implemented,
		4024	and is still mostly unchanged in 2010.
3153		4025
3154	=item * Use it by including <event.h>, as usual.	4026	=item * Use it by including <event.h>, as usual.
3155		4027
3156	=item * The following members are fully supported: ev_base, ev_callback,	4028	=item * The following members are fully supported: ev_base, ev_callback,
3157	ev_arg, ev_fd, ev_res, ev_events.	4029	ev_arg, ev_fd, ev_res, ev_events.
…		…
3163	=item * Priorities are not currently supported. Initialising priorities	4035	=item * Priorities are not currently supported. Initialising priorities
3164	will fail and all watchers will have the same priority, even though there	4036	will fail and all watchers will have the same priority, even though there
3165	is an ev_pri field.	4037	is an ev_pri field.
3166		4038
3167	=item * In libevent, the last base created gets the signals, in libev, the	4039	=item * In libevent, the last base created gets the signals, in libev, the
3168	first base created (== the default loop) gets the signals.	4040	base that registered the signal gets the signals.
3169		4041
3170	=item * Other members are not supported.	4042	=item * Other members are not supported.
3171		4043
3172	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4044	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3173	to use the libev header file and library.	4045	to use the libev header file and library.
3174		4046
3175	=back	4047	=back
3176		4048
3177	=head1 C++ SUPPORT	4049	=head1 C++ SUPPORT
		4050
		4051	=head2 C API
		4052
		4053	The normal C API should work fine when used from C++: both ev.h and the
		4054	libev sources can be compiled as C++. Therefore, code that uses the C API
		4055	will work fine.
		4056
		4057	Proper exception specifications might have to be added to callbacks passed
		4058	to libev: exceptions may be thrown only from watcher callbacks, all other
		4059	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4060	callbacks) must not throw exceptions, and might need a C<noexcept>
		4061	specification. If you have code that needs to be compiled as both C and
		4062	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4063
		4064	static void
		4065	fatal_error (const char *msg) EV_NOEXCEPT
		4066	{
		4067	perror (msg);
		4068	abort ();
		4069	}
		4070
		4071	...
		4072	ev_set_syserr_cb (fatal_error);
		4073
		4074	The only API functions that can currently throw exceptions are C<ev_run>,
		4075	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4076	because it runs cleanup watchers).
		4077
		4078	Throwing exceptions in watcher callbacks is only supported if libev itself
		4079	is compiled with a C++ compiler or your C and C++ environments allow
		4080	throwing exceptions through C libraries (most do).
		4081
		4082	=head2 C++ API
3178		4083
3179	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4084	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3180	you to use some convenience methods to start/stop watchers and also change	4085	you to use some convenience methods to start/stop watchers and also change
3181	the callback model to a model using method callbacks on objects.	4086	the callback model to a model using method callbacks on objects.
3182		4087
3183	To use it,	4088	To use it,
3184		4089
3185	#include <ev++.h>	4090	#include <ev++.h>
3186		4091
3187	This automatically includes F<ev.h> and puts all of its definitions (many	4092	This automatically includes F<ev.h> and puts all of its definitions (many
3188	of them macros) into the global namespace. All C++ specific things are	4093	of them macros) into the global namespace. All C++ specific things are
3189	put into the C<ev> namespace. It should support all the same embedding	4094	put into the C<ev> namespace. It should support all the same embedding
…		…
3192	Care has been taken to keep the overhead low. The only data member the C++	4097	Care has been taken to keep the overhead low. The only data member the C++
3193	classes add (compared to plain C-style watchers) is the event loop pointer	4098	classes add (compared to plain C-style watchers) is the event loop pointer
3194	that the watcher is associated with (or no additional members at all if	4099	that the watcher is associated with (or no additional members at all if
3195	you disable C<EV_MULTIPLICITY> when embedding libev).	4100	you disable C<EV_MULTIPLICITY> when embedding libev).
3196		4101
3197	Currently, functions, and static and non-static member functions can be	4102	Currently, functions, static and non-static member functions and classes
3198	used as callbacks. Other types should be easy to add as long as they only	4103	with C<operator ()> can be used as callbacks. Other types should be easy
3199	need one additional pointer for context. If you need support for other	4104	to add as long as they only need one additional pointer for context. If
3200	types of functors please contact the author (preferably after implementing	4105	you need support for other types of functors please contact the author
3201	it).	4106	(preferably after implementing it).
		4107
		4108	For all this to work, your C++ compiler either has to use the same calling
		4109	conventions as your C compiler (for static member functions), or you have
		4110	to embed libev and compile libev itself as C++.
3202		4111
3203	Here is a list of things available in the C<ev> namespace:	4112	Here is a list of things available in the C<ev> namespace:
3204		4113
3205	=over 4	4114	=over 4
3206		4115
…		…
3216	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4125	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3217		4126
3218	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4127	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3219	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4128	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3220	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4129	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3221	defines by many implementations.	4130	defined by many implementations.
3222		4131
3223	All of those classes have these methods:	4132	All of those classes have these methods:
3224		4133
3225	=over 4	4134	=over 4
3226		4135
3227	=item ev::TYPE::TYPE ()	4136	=item ev::TYPE::TYPE ()
3228		4137
3229	=item ev::TYPE::TYPE (struct ev_loop *)	4138	=item ev::TYPE::TYPE (loop)
3230		4139
3231	=item ev::TYPE::~TYPE	4140	=item ev::TYPE::~TYPE
3232		4141
3233	The constructor (optionally) takes an event loop to associate the watcher	4142	The constructor (optionally) takes an event loop to associate the watcher
3234	with. If it is omitted, it will use C<EV_DEFAULT>.	4143	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3267	myclass obj;	4176	myclass obj;
3268	ev::io iow;	4177	ev::io iow;
3269	iow.set <myclass, &myclass::io_cb> (&obj);	4178	iow.set <myclass, &myclass::io_cb> (&obj);
3270		4179
3271	=item w->set (object *)	4180	=item w->set (object *)
3272
3273	This is an B<experimental> feature that might go away in a future version.
3274		4181
3275	This is a variation of a method callback - leaving out the method to call	4182	This is a variation of a method callback - leaving out the method to call
3276	will default the method to C<operator ()>, which makes it possible to use	4183	will default the method to C<operator ()>, which makes it possible to use
3277	functor objects without having to manually specify the C<operator ()> all	4184	functor objects without having to manually specify the C<operator ()> all
3278	the time. Incidentally, you can then also leave out the template argument	4185	the time. Incidentally, you can then also leave out the template argument
…		…
3290	void operator() (ev::io &w, int revents)	4197	void operator() (ev::io &w, int revents)
3291	{	4198	{
3292	...	4199	...
3293	}	4200	}
3294	}	4201	}
3295		4202
3296	myfunctor f;	4203	myfunctor f;
3297		4204
3298	ev::io w;	4205	ev::io w;
3299	w.set (&f);	4206	w.set (&f);
3300		4207
…		…
3311	Example: Use a plain function as callback.	4218	Example: Use a plain function as callback.
3312		4219
3313	static void io_cb (ev::io &w, int revents) { }	4220	static void io_cb (ev::io &w, int revents) { }
3314	iow.set <io_cb> ();	4221	iow.set <io_cb> ();
3315		4222
3316	=item w->set (struct ev_loop *)	4223	=item w->set (loop)
3317		4224
3318	Associates a different C<struct ev_loop> with this watcher. You can only	4225	Associates a different C<struct ev_loop> with this watcher. You can only
3319	do this when the watcher is inactive (and not pending either).	4226	do this when the watcher is inactive (and not pending either).
3320		4227
3321	=item w->set ([arguments])	4228	=item w->set ([arguments])
3322		4229
3323	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4230	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4231	with the same arguments. Either this method or a suitable start method
3324	called at least once. Unlike the C counterpart, an active watcher gets	4232	must be called at least once. Unlike the C counterpart, an active watcher
3325	automatically stopped and restarted when reconfiguring it with this	4233	gets automatically stopped and restarted when reconfiguring it with this
3326	method.	4234	method.
		4235
		4236	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4237	clashing with the C<set (loop)> method.
3327		4238
3328	=item w->start ()	4239	=item w->start ()
3329		4240
3330	Starts the watcher. Note that there is no C<loop> argument, as the	4241	Starts the watcher. Note that there is no C<loop> argument, as the
3331	constructor already stores the event loop.	4242	constructor already stores the event loop.
3332		4243
		4244	=item w->start ([arguments])
		4245
		4246	Instead of calling C<set> and C<start> methods separately, it is often
		4247	convenient to wrap them in one call. Uses the same type of arguments as
		4248	the configure C<set> method of the watcher.
		4249
3333	=item w->stop ()	4250	=item w->stop ()
3334		4251
3335	Stops the watcher if it is active. Again, no C<loop> argument.	4252	Stops the watcher if it is active. Again, no C<loop> argument.
3336		4253
3337	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4254	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3349		4266
3350	=back	4267	=back
3351		4268
3352	=back	4269	=back
3353		4270
3354	Example: Define a class with an IO and idle watcher, start one of them in	4271	Example: Define a class with two I/O and idle watchers, start the I/O
3355	the constructor.	4272	watchers in the constructor.
3356		4273
3357	class myclass	4274	class myclass
3358	{	4275	{
3359	ev::io io ; void io_cb (ev::io &w, int revents);	4276	ev::io io ; void io_cb (ev::io &w, int revents);
		4277	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3360	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4278	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3361		4279
3362	myclass (int fd)	4280	myclass (int fd)
3363	{	4281	{
3364	io .set <myclass, &myclass::io_cb > (this);	4282	io .set <myclass, &myclass::io_cb > (this);
		4283	io2 .set <myclass, &myclass::io2_cb > (this);
3365	idle.set <myclass, &myclass::idle_cb> (this);	4284	idle.set <myclass, &myclass::idle_cb> (this);
3366		4285
3367	io.start (fd, ev::READ);	4286	io.set (fd, ev::WRITE); // configure the watcher
		4287	io.start (); // start it whenever convenient
		4288
		4289	io2.start (fd, ev::READ); // set + start in one call
3368	}	4290	}
3369	};	4291	};
3370		4292
3371		4293
3372	=head1 OTHER LANGUAGE BINDINGS	4294	=head1 OTHER LANGUAGE BINDINGS
…		…
3411	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4333	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3412		4334
3413	=item D	4335	=item D
3414		4336
3415	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4337	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3416	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4338	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3417		4339
3418	=item Ocaml	4340	=item Ocaml
3419		4341
3420	Erkki Seppala has written Ocaml bindings for libev, to be found at	4342	Erkki Seppala has written Ocaml bindings for libev, to be found at
3421	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4343	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3422		4344
3423	=item Lua	4345	=item Lua
3424		4346
3425	Brian Maher has written a partial interface to libev	4347	Brian Maher has written a partial interface to libev for lua (at the
3426	for lua (only C<ev_io> and C<ev_timer>), to be found at	4348	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3427	L<http://github.com/brimworks/lua-ev>.	4349	L<http://github.com/brimworks/lua-ev>.
		4350
		4351	=item Javascript
		4352
		4353	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4354
		4355	=item Others
		4356
		4357	There are others, and I stopped counting.
3428		4358
3429	=back	4359	=back
3430		4360
3431		4361
3432	=head1 MACRO MAGIC	4362	=head1 MACRO MAGIC
…		…
3446	loop argument"). The C<EV_A> form is used when this is the sole argument,	4376	loop argument"). The C<EV_A> form is used when this is the sole argument,
3447	C<EV_A_> is used when other arguments are following. Example:	4377	C<EV_A_> is used when other arguments are following. Example:
3448		4378
3449	ev_unref (EV_A);	4379	ev_unref (EV_A);
3450	ev_timer_add (EV_A_ watcher);	4380	ev_timer_add (EV_A_ watcher);
3451	ev_loop (EV_A_ 0);	4381	ev_run (EV_A_ 0);
3452		4382
3453	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4383	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3454	which is often provided by the following macro.	4384	which is often provided by the following macro.
3455		4385
3456	=item C<EV_P>, C<EV_P_>	4386	=item C<EV_P>, C<EV_P_>
…		…
3469	suitable for use with C<EV_A>.	4399	suitable for use with C<EV_A>.
3470		4400
3471	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4401	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3472		4402
3473	Similar to the other two macros, this gives you the value of the default	4403	Similar to the other two macros, this gives you the value of the default
3474	loop, if multiple loops are supported ("ev loop default").	4404	loop, if multiple loops are supported ("ev loop default"). The default loop
		4405	will be initialised if it isn't already initialised.
		4406
		4407	For non-multiplicity builds, these macros do nothing, so you always have
		4408	to initialise the loop somewhere.
3475		4409
3476	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4410	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3477		4411
3478	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4412	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3479	default loop has been initialised (C<UC> == unchecked). Their behaviour	4413	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3496	}	4430	}
3497		4431
3498	ev_check check;	4432	ev_check check;
3499	ev_check_init (&check, check_cb);	4433	ev_check_init (&check, check_cb);
3500	ev_check_start (EV_DEFAULT_ &check);	4434	ev_check_start (EV_DEFAULT_ &check);
3501	ev_loop (EV_DEFAULT_ 0);	4435	ev_run (EV_DEFAULT_ 0);
3502		4436
3503	=head1 EMBEDDING	4437	=head1 EMBEDDING
3504		4438
3505	Libev can (and often is) directly embedded into host	4439	Libev can (and often is) directly embedded into host
3506	applications. Examples of applications that embed it include the Deliantra	4440	applications. Examples of applications that embed it include the Deliantra
…		…
3546	ev_vars.h	4480	ev_vars.h
3547	ev_wrap.h	4481	ev_wrap.h
3548		4482
3549	ev_win32.c required on win32 platforms only	4483	ev_win32.c required on win32 platforms only
3550		4484
3551	ev_select.c only when select backend is enabled (which is enabled by default)	4485	ev_select.c only when select backend is enabled
3552	ev_poll.c only when poll backend is enabled (disabled by default)	4486	ev_poll.c only when poll backend is enabled
3553	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4487	ev_epoll.c only when the epoll backend is enabled
		4488	ev_linuxaio.c only when the linux aio backend is enabled
3554	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4489	ev_kqueue.c only when the kqueue backend is enabled
3555	ev_port.c only when the solaris port backend is enabled (disabled by default)	4490	ev_port.c only when the solaris port backend is enabled
3556		4491
3557	F<ev.c> includes the backend files directly when enabled, so you only need	4492	F<ev.c> includes the backend files directly when enabled, so you only need
3558	to compile this single file.	4493	to compile this single file.
3559		4494
3560	=head3 LIBEVENT COMPATIBILITY API	4495	=head3 LIBEVENT COMPATIBILITY API
…		…
3586	libev.m4	4521	libev.m4
3587		4522
3588	=head2 PREPROCESSOR SYMBOLS/MACROS	4523	=head2 PREPROCESSOR SYMBOLS/MACROS
3589		4524
3590	Libev can be configured via a variety of preprocessor symbols you have to	4525	Libev can be configured via a variety of preprocessor symbols you have to
3591	define before including any of its files. The default in the absence of	4526	define before including (or compiling) any of its files. The default in
3592	autoconf is documented for every option.	4527	the absence of autoconf is documented for every option.
		4528
		4529	Symbols marked with "(h)" do not change the ABI, and can have different
		4530	values when compiling libev vs. including F<ev.h>, so it is permissible
		4531	to redefine them before including F<ev.h> without breaking compatibility
		4532	to a compiled library. All other symbols change the ABI, which means all
		4533	users of libev and the libev code itself must be compiled with compatible
		4534	settings.
3593		4535
3594	=over 4	4536	=over 4
3595		4537
		4538	=item EV_COMPAT3 (h)
		4539
		4540	Backwards compatibility is a major concern for libev. This is why this
		4541	release of libev comes with wrappers for the functions and symbols that
		4542	have been renamed between libev version 3 and 4.
		4543
		4544	You can disable these wrappers (to test compatibility with future
		4545	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4546	sources. This has the additional advantage that you can drop the C<struct>
		4547	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4548	typedef in that case.
		4549
		4550	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4551	and in some even more future version the compatibility code will be
		4552	removed completely.
		4553
3596	=item EV_STANDALONE	4554	=item EV_STANDALONE (h)
3597		4555
3598	Must always be C<1> if you do not use autoconf configuration, which	4556	Must always be C<1> if you do not use autoconf configuration, which
3599	keeps libev from including F<config.h>, and it also defines dummy	4557	keeps libev from including F<config.h>, and it also defines dummy
3600	implementations for some libevent functions (such as logging, which is not	4558	implementations for some libevent functions (such as logging, which is not
3601	supported). It will also not define any of the structs usually found in	4559	supported). It will also not define any of the structs usually found in
3602	F<event.h> that are not directly supported by the libev core alone.	4560	F<event.h> that are not directly supported by the libev core alone.
3603		4561
3604	In standalone mode, libev will still try to automatically deduce the	4562	In standalone mode, libev will still try to automatically deduce the
3605	configuration, but has to be more conservative.	4563	configuration, but has to be more conservative.
		4564
		4565	=item EV_USE_FLOOR
		4566
		4567	If defined to be C<1>, libev will use the C<floor ()> function for its
		4568	periodic reschedule calculations, otherwise libev will fall back on a
		4569	portable (slower) implementation. If you enable this, you usually have to
		4570	link against libm or something equivalent. Enabling this when the C<floor>
		4571	function is not available will fail, so the safe default is to not enable
		4572	this.
3606		4573
3607	=item EV_USE_MONOTONIC	4574	=item EV_USE_MONOTONIC
3608		4575
3609	If defined to be C<1>, libev will try to detect the availability of the	4576	If defined to be C<1>, libev will try to detect the availability of the
3610	monotonic clock option at both compile time and runtime. Otherwise no	4577	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3696	If programs implement their own fd to handle mapping on win32, then this	4663	If programs implement their own fd to handle mapping on win32, then this
3697	macro can be used to override the C<close> function, useful to unregister	4664	macro can be used to override the C<close> function, useful to unregister
3698	file descriptors again. Note that the replacement function has to close	4665	file descriptors again. Note that the replacement function has to close
3699	the underlying OS handle.	4666	the underlying OS handle.
3700		4667
		4668	=item EV_USE_WSASOCKET
		4669
		4670	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4671	communication socket, which works better in some environments. Otherwise,
		4672	the normal C<socket> function will be used, which works better in other
		4673	environments.
		4674
3701	=item EV_USE_POLL	4675	=item EV_USE_POLL
3702		4676
3703	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4677	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3704	backend. Otherwise it will be enabled on non-win32 platforms. It	4678	backend. Otherwise it will be enabled on non-win32 platforms. It
3705	takes precedence over select.	4679	takes precedence over select.
…		…
3709	If defined to be C<1>, libev will compile in support for the Linux	4683	If defined to be C<1>, libev will compile in support for the Linux
3710	C<epoll>(7) backend. Its availability will be detected at runtime,	4684	C<epoll>(7) backend. Its availability will be detected at runtime,
3711	otherwise another method will be used as fallback. This is the preferred	4685	otherwise another method will be used as fallback. This is the preferred
3712	backend for GNU/Linux systems. If undefined, it will be enabled if the	4686	backend for GNU/Linux systems. If undefined, it will be enabled if the
3713	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4687	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4688
		4689	=item EV_USE_LINUXAIO
		4690
		4691	If defined to be C<1>, libev will compile in support for the Linux
		4692	aio backend. Due to it's currenbt limitations it has to be requested
		4693	explicitly. If undefined, it will be enabled on linux, otherwise
		4694	disabled.
3714		4695
3715	=item EV_USE_KQUEUE	4696	=item EV_USE_KQUEUE
3716		4697
3717	If defined to be C<1>, libev will compile in support for the BSD style	4698	If defined to be C<1>, libev will compile in support for the BSD style
3718	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4699	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3740	If defined to be C<1>, libev will compile in support for the Linux inotify	4721	If defined to be C<1>, libev will compile in support for the Linux inotify
3741	interface to speed up C<ev_stat> watchers. Its actual availability will	4722	interface to speed up C<ev_stat> watchers. Its actual availability will
3742	be detected at runtime. If undefined, it will be enabled if the headers	4723	be detected at runtime. If undefined, it will be enabled if the headers
3743	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4724	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3744		4725
		4726	=item EV_NO_SMP
		4727
		4728	If defined to be C<1>, libev will assume that memory is always coherent
		4729	between threads, that is, threads can be used, but threads never run on
		4730	different cpus (or different cpu cores). This reduces dependencies
		4731	and makes libev faster.
		4732
		4733	=item EV_NO_THREADS
		4734
		4735	If defined to be C<1>, libev will assume that it will never be called from
		4736	different threads (that includes signal handlers), which is a stronger
		4737	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4738	libev faster.
		4739
3745	=item EV_ATOMIC_T	4740	=item EV_ATOMIC_T
3746		4741
3747	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4742	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3748	access is atomic with respect to other threads or signal contexts. No such	4743	access is atomic with respect to other threads or signal contexts. No
3749	type is easily found in the C language, so you can provide your own type	4744	such type is easily found in the C language, so you can provide your own
3750	that you know is safe for your purposes. It is used both for signal handler "locking"	4745	type that you know is safe for your purposes. It is used both for signal
3751	as well as for signal and thread safety in C<ev_async> watchers.	4746	handler "locking" as well as for signal and thread safety in C<ev_async>
		4747	watchers.
3752		4748
3753	In the absence of this define, libev will use C<sig_atomic_t volatile>	4749	In the absence of this define, libev will use C<sig_atomic_t volatile>
3754	(from F<signal.h>), which is usually good enough on most platforms.	4750	(from F<signal.h>), which is usually good enough on most platforms.
3755		4751
3756	=item EV_H	4752	=item EV_H (h)
3757		4753
3758	The name of the F<ev.h> header file used to include it. The default if	4754	The name of the F<ev.h> header file used to include it. The default if
3759	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4755	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3760	used to virtually rename the F<ev.h> header file in case of conflicts.	4756	used to virtually rename the F<ev.h> header file in case of conflicts.
3761		4757
3762	=item EV_CONFIG_H	4758	=item EV_CONFIG_H (h)
3763		4759
3764	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4760	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3765	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4761	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3766	C<EV_H>, above.	4762	C<EV_H>, above.
3767		4763
3768	=item EV_EVENT_H	4764	=item EV_EVENT_H (h)
3769		4765
3770	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4766	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3771	of how the F<event.h> header can be found, the default is C<"event.h">.	4767	of how the F<event.h> header can be found, the default is C<"event.h">.
3772		4768
3773	=item EV_PROTOTYPES	4769	=item EV_PROTOTYPES (h)
3774		4770
3775	If defined to be C<0>, then F<ev.h> will not define any function	4771	If defined to be C<0>, then F<ev.h> will not define any function
3776	prototypes, but still define all the structs and other symbols. This is	4772	prototypes, but still define all the structs and other symbols. This is
3777	occasionally useful if you want to provide your own wrapper functions	4773	occasionally useful if you want to provide your own wrapper functions
3778	around libev functions.	4774	around libev functions.
…		…
3783	will have the C<struct ev_loop *> as first argument, and you can create	4779	will have the C<struct ev_loop *> as first argument, and you can create
3784	additional independent event loops. Otherwise there will be no support	4780	additional independent event loops. Otherwise there will be no support
3785	for multiple event loops and there is no first event loop pointer	4781	for multiple event loops and there is no first event loop pointer
3786	argument. Instead, all functions act on the single default loop.	4782	argument. Instead, all functions act on the single default loop.
3787		4783
		4784	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4785	default loop when multiplicity is switched off - you always have to
		4786	initialise the loop manually in this case.
		4787
3788	=item EV_MINPRI	4788	=item EV_MINPRI
3789		4789
3790	=item EV_MAXPRI	4790	=item EV_MAXPRI
3791		4791
3792	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4792	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3800	fine.	4800	fine.
3801		4801
3802	If your embedding application does not need any priorities, defining these	4802	If your embedding application does not need any priorities, defining these
3803	both to C<0> will save some memory and CPU.	4803	both to C<0> will save some memory and CPU.
3804		4804
3805	=item EV_PERIODIC_ENABLE	4805	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4806	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4807	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3806		4808
3807	If undefined or defined to be C<1>, then periodic timers are supported. If	4809	If undefined or defined to be C<1> (and the platform supports it), then
3808	defined to be C<0>, then they are not. Disabling them saves a few kB of	4810	the respective watcher type is supported. If defined to be C<0>, then it
3809	code.	4811	is not. Disabling watcher types mainly saves code size.
3810		4812
3811	=item EV_IDLE_ENABLE	4813	=item EV_FEATURES
3812
3813	If undefined or defined to be C<1>, then idle watchers are supported. If
3814	defined to be C<0>, then they are not. Disabling them saves a few kB of
3815	code.
3816
3817	=item EV_EMBED_ENABLE
3818
3819	If undefined or defined to be C<1>, then embed watchers are supported. If
3820	defined to be C<0>, then they are not. Embed watchers rely on most other
3821	watcher types, which therefore must not be disabled.
3822
3823	=item EV_STAT_ENABLE
3824
3825	If undefined or defined to be C<1>, then stat watchers are supported. If
3826	defined to be C<0>, then they are not.
3827
3828	=item EV_FORK_ENABLE
3829
3830	If undefined or defined to be C<1>, then fork watchers are supported. If
3831	defined to be C<0>, then they are not.
3832
3833	=item EV_ASYNC_ENABLE
3834
3835	If undefined or defined to be C<1>, then async watchers are supported. If
3836	defined to be C<0>, then they are not.
3837
3838	=item EV_MINIMAL
3839		4814
3840	If you need to shave off some kilobytes of code at the expense of some	4815	If you need to shave off some kilobytes of code at the expense of some
3841	speed (but with the full API), define this symbol to C<1>. Currently this	4816	speed (but with the full API), you can define this symbol to request
3842	is used to override some inlining decisions, saves roughly 30% code size	4817	certain subsets of functionality. The default is to enable all features
3843	on amd64. It also selects a much smaller 2-heap for timer management over	4818	that can be enabled on the platform.
3844	the default 4-heap.
3845		4819
3846	You can save even more by disabling watcher types you do not need	4820	A typical way to use this symbol is to define it to C<0> (or to a bitset
3847	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4821	with some broad features you want) and then selectively re-enable
3848	(C<-DNDEBUG>) will usually reduce code size a lot.	4822	additional parts you want, for example if you want everything minimal,
		4823	but multiple event loop support, async and child watchers and the poll
		4824	backend, use this:
3849		4825
3850	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4826	#define EV_FEATURES 0
3851	provide a bare-bones event library. See C<ev.h> for details on what parts	4827	#define EV_MULTIPLICITY 1
3852	of the API are still available, and do not complain if this subset changes	4828	#define EV_USE_POLL 1
3853	over time.	4829	#define EV_CHILD_ENABLE 1
		4830	#define EV_ASYNC_ENABLE 1
		4831
		4832	The actual value is a bitset, it can be a combination of the following
		4833	values (by default, all of these are enabled):
		4834
		4835	=over 4
		4836
		4837	=item C<1> - faster/larger code
		4838
		4839	Use larger code to speed up some operations.
		4840
		4841	Currently this is used to override some inlining decisions (enlarging the
		4842	code size by roughly 30% on amd64).
		4843
		4844	When optimising for size, use of compiler flags such as C<-Os> with
		4845	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4846	assertions.
		4847
		4848	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4849	(e.g. gcc with C<-Os>).
		4850
		4851	=item C<2> - faster/larger data structures
		4852
		4853	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4854	hash table sizes and so on. This will usually further increase code size
		4855	and can additionally have an effect on the size of data structures at
		4856	runtime.
		4857
		4858	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4859	(e.g. gcc with C<-Os>).
		4860
		4861	=item C<4> - full API configuration
		4862
		4863	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4864	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4865
		4866	=item C<8> - full API
		4867
		4868	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4869	details on which parts of the API are still available without this
		4870	feature, and do not complain if this subset changes over time.
		4871
		4872	=item C<16> - enable all optional watcher types
		4873
		4874	Enables all optional watcher types. If you want to selectively enable
		4875	only some watcher types other than I/O and timers (e.g. prepare,
		4876	embed, async, child...) you can enable them manually by defining
		4877	C<EV_watchertype_ENABLE> to C<1> instead.
		4878
		4879	=item C<32> - enable all backends
		4880
		4881	This enables all backends - without this feature, you need to enable at
		4882	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4883
		4884	=item C<64> - enable OS-specific "helper" APIs
		4885
		4886	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4887	default.
		4888
		4889	=back
		4890
		4891	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4892	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4893	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4894	watchers, timers and monotonic clock support.
		4895
		4896	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4897	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4898	your program might be left out as well - a binary starting a timer and an
		4899	I/O watcher then might come out at only 5Kb.
		4900
		4901	=item EV_API_STATIC
		4902
		4903	If this symbol is defined (by default it is not), then all identifiers
		4904	will have static linkage. This means that libev will not export any
		4905	identifiers, and you cannot link against libev anymore. This can be useful
		4906	when you embed libev, only want to use libev functions in a single file,
		4907	and do not want its identifiers to be visible.
		4908
		4909	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4910	wants to use libev.
		4911
		4912	This option only works when libev is compiled with a C compiler, as C++
		4913	doesn't support the required declaration syntax.
		4914
		4915	=item EV_AVOID_STDIO
		4916
		4917	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4918	functions (printf, scanf, perror etc.). This will increase the code size
		4919	somewhat, but if your program doesn't otherwise depend on stdio and your
		4920	libc allows it, this avoids linking in the stdio library which is quite
		4921	big.
		4922
		4923	Note that error messages might become less precise when this option is
		4924	enabled.
3854		4925
3855	=item EV_NSIG	4926	=item EV_NSIG
3856		4927
3857	The highest supported signal number, +1 (or, the number of	4928	The highest supported signal number, +1 (or, the number of
3858	signals): Normally, libev tries to deduce the maximum number of signals	4929	signals): Normally, libev tries to deduce the maximum number of signals
3859	automatically, but sometimes this fails, in which case it can be	4930	automatically, but sometimes this fails, in which case it can be
3860	specified. Also, using a lower number than detected (C<32> should be	4931	specified. Also, using a lower number than detected (C<32> should be
3861	good for about any system in existance) can save some memory, as libev	4932	good for about any system in existence) can save some memory, as libev
3862	statically allocates some 12-24 bytes per signal number.	4933	statically allocates some 12-24 bytes per signal number.
3863		4934
3864	=item EV_PID_HASHSIZE	4935	=item EV_PID_HASHSIZE
3865		4936
3866	C<ev_child> watchers use a small hash table to distribute workload by	4937	C<ev_child> watchers use a small hash table to distribute workload by
3867	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4938	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3868	than enough. If you need to manage thousands of children you might want to	4939	usually more than enough. If you need to manage thousands of children you
3869	increase this value (I<must> be a power of two).	4940	might want to increase this value (I<must> be a power of two).
3870		4941
3871	=item EV_INOTIFY_HASHSIZE	4942	=item EV_INOTIFY_HASHSIZE
3872		4943
3873	C<ev_stat> watchers use a small hash table to distribute workload by	4944	C<ev_stat> watchers use a small hash table to distribute workload by
3874	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4945	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3875	usually more than enough. If you need to manage thousands of C<ev_stat>	4946	disabled), usually more than enough. If you need to manage thousands of
3876	watchers you might want to increase this value (I<must> be a power of	4947	C<ev_stat> watchers you might want to increase this value (I<must> be a
3877	two).	4948	power of two).
3878		4949
3879	=item EV_USE_4HEAP	4950	=item EV_USE_4HEAP
3880		4951
3881	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4952	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3882	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4953	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3883	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4954	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3884	faster performance with many (thousands) of watchers.	4955	faster performance with many (thousands) of watchers.
3885		4956
3886	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4957	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3887	(disabled).	4958	will be C<0>.
3888		4959
3889	=item EV_HEAP_CACHE_AT	4960	=item EV_HEAP_CACHE_AT
3890		4961
3891	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4962	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3892	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4963	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3893	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4964	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3894	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4965	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3895	but avoids random read accesses on heap changes. This improves performance	4966	but avoids random read accesses on heap changes. This improves performance
3896	noticeably with many (hundreds) of watchers.	4967	noticeably with many (hundreds) of watchers.
3897		4968
3898	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4969	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3899	(disabled).	4970	will be C<0>.
3900		4971
3901	=item EV_VERIFY	4972	=item EV_VERIFY
3902		4973
3903	Controls how much internal verification (see C<ev_loop_verify ()>) will	4974	Controls how much internal verification (see C<ev_verify ()>) will
3904	be done: If set to C<0>, no internal verification code will be compiled	4975	be done: If set to C<0>, no internal verification code will be compiled
3905	in. If set to C<1>, then verification code will be compiled in, but not	4976	in. If set to C<1>, then verification code will be compiled in, but not
3906	called. If set to C<2>, then the internal verification code will be	4977	called. If set to C<2>, then the internal verification code will be
3907	called once per loop, which can slow down libev. If set to C<3>, then the	4978	called once per loop, which can slow down libev. If set to C<3>, then the
3908	verification code will be called very frequently, which will slow down	4979	verification code will be called very frequently, which will slow down
3909	libev considerably.	4980	libev considerably.
3910		4981
		4982	Verification errors are reported via C's C<assert> mechanism, so if you
		4983	disable that (e.g. by defining C<NDEBUG>) then no errors will be reported.
		4984
3911	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4985	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3912	C<0>.	4986	will be C<0>.
3913		4987
3914	=item EV_COMMON	4988	=item EV_COMMON
3915		4989
3916	By default, all watchers have a C<void *data> member. By redefining	4990	By default, all watchers have a C<void *data> member. By redefining
3917	this macro to a something else you can include more and other types of	4991	this macro to something else you can include more and other types of
3918	members. You have to define it each time you include one of the files,	4992	members. You have to define it each time you include one of the files,
3919	though, and it must be identical each time.	4993	though, and it must be identical each time.
3920		4994
3921	For example, the perl EV module uses something like this:	4995	For example, the perl EV module uses something like this:
3922		4996
…		…
3975	file.	5049	file.
3976		5050
3977	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5051	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3978	that everybody includes and which overrides some configure choices:	5052	that everybody includes and which overrides some configure choices:
3979		5053
3980	#define EV_MINIMAL 1	5054	#define EV_FEATURES 8
3981	#define EV_USE_POLL 0	5055	#define EV_USE_SELECT 1
3982	#define EV_MULTIPLICITY 0
3983	#define EV_PERIODIC_ENABLE 0	5056	#define EV_PREPARE_ENABLE 1
		5057	#define EV_IDLE_ENABLE 1
3984	#define EV_STAT_ENABLE 0	5058	#define EV_SIGNAL_ENABLE 1
3985	#define EV_FORK_ENABLE 0	5059	#define EV_CHILD_ENABLE 1
		5060	#define EV_USE_STDEXCEPT 0
3986	#define EV_CONFIG_H <config.h>	5061	#define EV_CONFIG_H <config.h>
3987	#define EV_MINPRI 0
3988	#define EV_MAXPRI 0
3989		5062
3990	#include "ev++.h"	5063	#include "ev++.h"
3991		5064
3992	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5065	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3993		5066
3994	#include "ev_cpp.h"	5067	#include "ev_cpp.h"
3995	#include "ev.c"	5068	#include "ev.c"
3996		5069
3997	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5070	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3998		5071
3999	=head2 THREADS AND COROUTINES	5072	=head2 THREADS AND COROUTINES
4000		5073
4001	=head3 THREADS	5074	=head3 THREADS
4002		5075
…		…
4053	default loop and triggering an C<ev_async> watcher from the default loop	5126	default loop and triggering an C<ev_async> watcher from the default loop
4054	watcher callback into the event loop interested in the signal.	5127	watcher callback into the event loop interested in the signal.
4055		5128
4056	=back	5129	=back
4057		5130
4058	=head4 THREAD LOCKING EXAMPLE	5131	See also L</THREAD LOCKING EXAMPLE>.
4059
4060	Here is a fictitious example of how to run an event loop in a different
4061	thread than where callbacks are being invoked and watchers are
4062	created/added/removed.
4063
4064	For a real-world example, see the C<EV::Loop::Async> perl module,
4065	which uses exactly this technique (which is suited for many high-level
4066	languages).
4067
4068	The example uses a pthread mutex to protect the loop data, a condition
4069	variable to wait for callback invocations, an async watcher to notify the
4070	event loop thread and an unspecified mechanism to wake up the main thread.
4071
4072	First, you need to associate some data with the event loop:
4073
4074	typedef struct {
4075	mutex_t lock; /* global loop lock */
4076	ev_async async_w;
4077	thread_t tid;
4078	cond_t invoke_cv;
4079	} userdata;
4080
4081	void prepare_loop (EV_P)
4082	{
4083	// for simplicity, we use a static userdata struct.
4084	static userdata u;
4085
4086	ev_async_init (&u->async_w, async_cb);
4087	ev_async_start (EV_A_ &u->async_w);
4088
4089	pthread_mutex_init (&u->lock, 0);
4090	pthread_cond_init (&u->invoke_cv, 0);
4091
4092	// now associate this with the loop
4093	ev_set_userdata (EV_A_ u);
4094	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4095	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4096
4097	// then create the thread running ev_loop
4098	pthread_create (&u->tid, 0, l_run, EV_A);
4099	}
4100
4101	The callback for the C<ev_async> watcher does nothing: the watcher is used
4102	solely to wake up the event loop so it takes notice of any new watchers
4103	that might have been added:
4104
4105	static void
4106	async_cb (EV_P_ ev_async *w, int revents)
4107	{
4108	// just used for the side effects
4109	}
4110
4111	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4112	protecting the loop data, respectively.
4113
4114	static void
4115	l_release (EV_P)
4116	{
4117	userdata *u = ev_userdata (EV_A);
4118	pthread_mutex_unlock (&u->lock);
4119	}
4120
4121	static void
4122	l_acquire (EV_P)
4123	{
4124	userdata *u = ev_userdata (EV_A);
4125	pthread_mutex_lock (&u->lock);
4126	}
4127
4128	The event loop thread first acquires the mutex, and then jumps straight
4129	into C<ev_loop>:
4130
4131	void *
4132	l_run (void *thr_arg)
4133	{
4134	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4135
4136	l_acquire (EV_A);
4137	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4138	ev_loop (EV_A_ 0);
4139	l_release (EV_A);
4140
4141	return 0;
4142	}
4143
4144	Instead of invoking all pending watchers, the C<l_invoke> callback will
4145	signal the main thread via some unspecified mechanism (signals? pipe
4146	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4147	have been called (in a while loop because a) spurious wakeups are possible
4148	and b) skipping inter-thread-communication when there are no pending
4149	watchers is very beneficial):
4150
4151	static void
4152	l_invoke (EV_P)
4153	{
4154	userdata *u = ev_userdata (EV_A);
4155
4156	while (ev_pending_count (EV_A))
4157	{
4158	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4159	pthread_cond_wait (&u->invoke_cv, &u->lock);
4160	}
4161	}
4162
4163	Now, whenever the main thread gets told to invoke pending watchers, it
4164	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4165	thread to continue:
4166
4167	static void
4168	real_invoke_pending (EV_P)
4169	{
4170	userdata *u = ev_userdata (EV_A);
4171
4172	pthread_mutex_lock (&u->lock);
4173	ev_invoke_pending (EV_A);
4174	pthread_cond_signal (&u->invoke_cv);
4175	pthread_mutex_unlock (&u->lock);
4176	}
4177
4178	Whenever you want to start/stop a watcher or do other modifications to an
4179	event loop, you will now have to lock:
4180
4181	ev_timer timeout_watcher;
4182	userdata *u = ev_userdata (EV_A);
4183
4184	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4185
4186	pthread_mutex_lock (&u->lock);
4187	ev_timer_start (EV_A_ &timeout_watcher);
4188	ev_async_send (EV_A_ &u->async_w);
4189	pthread_mutex_unlock (&u->lock);
4190
4191	Note that sending the C<ev_async> watcher is required because otherwise
4192	an event loop currently blocking in the kernel will have no knowledge
4193	about the newly added timer. By waking up the loop it will pick up any new
4194	watchers in the next event loop iteration.
4195		5132
4196	=head3 COROUTINES	5133	=head3 COROUTINES
4197		5134
4198	Libev is very accommodating to coroutines ("cooperative threads"):	5135	Libev is very accommodating to coroutines ("cooperative threads"):
4199	libev fully supports nesting calls to its functions from different	5136	libev fully supports nesting calls to its functions from different
4200	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5137	coroutines (e.g. you can call C<ev_run> on the same loop from two
4201	different coroutines, and switch freely between both coroutines running	5138	different coroutines, and switch freely between both coroutines running
4202	the loop, as long as you don't confuse yourself). The only exception is	5139	the loop, as long as you don't confuse yourself). The only exception is
4203	that you must not do this from C<ev_periodic> reschedule callbacks.	5140	that you must not do this from C<ev_periodic> reschedule callbacks.
4204		5141
4205	Care has been taken to ensure that libev does not keep local state inside	5142	Care has been taken to ensure that libev does not keep local state inside
4206	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5143	C<ev_run>, and other calls do not usually allow for coroutine switches as
4207	they do not call any callbacks.	5144	they do not call any callbacks.
4208		5145
4209	=head2 COMPILER WARNINGS	5146	=head2 COMPILER WARNINGS
4210		5147
4211	Depending on your compiler and compiler settings, you might get no or a	5148	Depending on your compiler and compiler settings, you might get no or a
…		…
4222	maintainable.	5159	maintainable.
4223		5160
4224	And of course, some compiler warnings are just plain stupid, or simply	5161	And of course, some compiler warnings are just plain stupid, or simply
4225	wrong (because they don't actually warn about the condition their message	5162	wrong (because they don't actually warn about the condition their message
4226	seems to warn about). For example, certain older gcc versions had some	5163	seems to warn about). For example, certain older gcc versions had some
4227	warnings that resulted an extreme number of false positives. These have	5164	warnings that resulted in an extreme number of false positives. These have
4228	been fixed, but some people still insist on making code warn-free with	5165	been fixed, but some people still insist on making code warn-free with
4229	such buggy versions.	5166	such buggy versions.
4230		5167
4231	While libev is written to generate as few warnings as possible,	5168	While libev is written to generate as few warnings as possible,
4232	"warn-free" code is not a goal, and it is recommended not to build libev	5169	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4268	I suggest using suppression lists.	5205	I suggest using suppression lists.
4269		5206
4270		5207
4271	=head1 PORTABILITY NOTES	5208	=head1 PORTABILITY NOTES
4272		5209
		5210	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5211
		5212	GNU/Linux is the only common platform that supports 64 bit file/large file
		5213	interfaces but I<disables> them by default.
		5214
		5215	That means that libev compiled in the default environment doesn't support
		5216	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5217
		5218	Unfortunately, many programs try to work around this GNU/Linux issue
		5219	by enabling the large file API, which makes them incompatible with the
		5220	standard libev compiled for their system.
		5221
		5222	Likewise, libev cannot enable the large file API itself as this would
		5223	suddenly make it incompatible to the default compile time environment,
		5224	i.e. all programs not using special compile switches.
		5225
		5226	=head2 OS/X AND DARWIN BUGS
		5227
		5228	The whole thing is a bug if you ask me - basically any system interface
		5229	you touch is broken, whether it is locales, poll, kqueue or even the
		5230	OpenGL drivers.
		5231
		5232	=head3 C<kqueue> is buggy
		5233
		5234	The kqueue syscall is broken in all known versions - most versions support
		5235	only sockets, many support pipes.
		5236
		5237	Libev tries to work around this by not using C<kqueue> by default on this
		5238	rotten platform, but of course you can still ask for it when creating a
		5239	loop - embedding a socket-only kqueue loop into a select-based one is
		5240	probably going to work well.
		5241
		5242	=head3 C<poll> is buggy
		5243
		5244	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5245	implementation by something calling C<kqueue> internally around the 10.5.6
		5246	release, so now C<kqueue> I<and> C<poll> are broken.
		5247
		5248	Libev tries to work around this by not using C<poll> by default on
		5249	this rotten platform, but of course you can still ask for it when creating
		5250	a loop.
		5251
		5252	=head3 C<select> is buggy
		5253
		5254	All that's left is C<select>, and of course Apple found a way to fuck this
		5255	one up as well: On OS/X, C<select> actively limits the number of file
		5256	descriptors you can pass in to 1024 - your program suddenly crashes when
		5257	you use more.
		5258
		5259	There is an undocumented "workaround" for this - defining
		5260	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5261	work on OS/X.
		5262
		5263	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5264
		5265	=head3 C<errno> reentrancy
		5266
		5267	The default compile environment on Solaris is unfortunately so
		5268	thread-unsafe that you can't even use components/libraries compiled
		5269	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5270	defined by default. A valid, if stupid, implementation choice.
		5271
		5272	If you want to use libev in threaded environments you have to make sure
		5273	it's compiled with C<_REENTRANT> defined.
		5274
		5275	=head3 Event port backend
		5276
		5277	The scalable event interface for Solaris is called "event
		5278	ports". Unfortunately, this mechanism is very buggy in all major
		5279	releases. If you run into high CPU usage, your program freezes or you get
		5280	a large number of spurious wakeups, make sure you have all the relevant
		5281	and latest kernel patches applied. No, I don't know which ones, but there
		5282	are multiple ones to apply, and afterwards, event ports actually work
		5283	great.
		5284
		5285	If you can't get it to work, you can try running the program by setting
		5286	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5287	C<select> backends.
		5288
		5289	=head2 AIX POLL BUG
		5290
		5291	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5292	this by trying to avoid the poll backend altogether (i.e. it's not even
		5293	compiled in), which normally isn't a big problem as C<select> works fine
		5294	with large bitsets on AIX, and AIX is dead anyway.
		5295
4273	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5296	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5297
		5298	=head3 General issues
4274		5299
4275	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5300	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4276	requires, and its I/O model is fundamentally incompatible with the POSIX	5301	requires, and its I/O model is fundamentally incompatible with the POSIX
4277	model. Libev still offers limited functionality on this platform in	5302	model. Libev still offers limited functionality on this platform in
4278	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5303	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4279	descriptors. This only applies when using Win32 natively, not when using	5304	descriptors. This only applies when using Win32 natively, not when using
4280	e.g. cygwin.	5305	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5306	as every compiler comes with a slightly differently broken/incompatible
		5307	environment.
4281		5308
4282	Lifting these limitations would basically require the full	5309	Lifting these limitations would basically require the full
4283	re-implementation of the I/O system. If you are into these kinds of	5310	re-implementation of the I/O system. If you are into this kind of thing,
4284	things, then note that glib does exactly that for you in a very portable	5311	then note that glib does exactly that for you in a very portable way (note
4285	way (note also that glib is the slowest event library known to man).	5312	also that glib is the slowest event library known to man).
4286		5313
4287	There is no supported compilation method available on windows except	5314	There is no supported compilation method available on windows except
4288	embedding it into other applications.	5315	embedding it into other applications.
4289		5316
4290	Sensible signal handling is officially unsupported by Microsoft - libev	5317	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4318	you do I<not> compile the F<ev.c> or any other embedded source files!):	5345	you do I<not> compile the F<ev.c> or any other embedded source files!):
4319		5346
4320	#include "evwrap.h"	5347	#include "evwrap.h"
4321	#include "ev.c"	5348	#include "ev.c"
4322		5349
4323	=over 4
4324
4325	=item The winsocket select function	5350	=head3 The winsocket C<select> function
4326		5351
4327	The winsocket C<select> function doesn't follow POSIX in that it	5352	The winsocket C<select> function doesn't follow POSIX in that it
4328	requires socket I<handles> and not socket I<file descriptors> (it is	5353	requires socket I<handles> and not socket I<file descriptors> (it is
4329	also extremely buggy). This makes select very inefficient, and also	5354	also extremely buggy). This makes select very inefficient, and also
4330	requires a mapping from file descriptors to socket handles (the Microsoft	5355	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4339	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5364	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4340		5365
4341	Note that winsockets handling of fd sets is O(n), so you can easily get a	5366	Note that winsockets handling of fd sets is O(n), so you can easily get a
4342	complexity in the O(n²) range when using win32.	5367	complexity in the O(n²) range when using win32.
4343		5368
4344	=item Limited number of file descriptors	5369	=head3 Limited number of file descriptors
4345		5370
4346	Windows has numerous arbitrary (and low) limits on things.	5371	Windows has numerous arbitrary (and low) limits on things.
4347		5372
4348	Early versions of winsocket's select only supported waiting for a maximum	5373	Early versions of winsocket's select only supported waiting for a maximum
4349	of C<64> handles (probably owning to the fact that all windows kernels	5374	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4364	runtime libraries. This might get you to about C<512> or C<2048> sockets	5389	runtime libraries. This might get you to about C<512> or C<2048> sockets
4365	(depending on windows version and/or the phase of the moon). To get more,	5390	(depending on windows version and/or the phase of the moon). To get more,
4366	you need to wrap all I/O functions and provide your own fd management, but	5391	you need to wrap all I/O functions and provide your own fd management, but
4367	the cost of calling select (O(n²)) will likely make this unworkable.	5392	the cost of calling select (O(n²)) will likely make this unworkable.
4368		5393
4369	=back
4370
4371	=head2 PORTABILITY REQUIREMENTS	5394	=head2 PORTABILITY REQUIREMENTS
4372		5395
4373	In addition to a working ISO-C implementation and of course the	5396	In addition to a working ISO-C implementation and of course the
4374	backend-specific APIs, libev relies on a few additional extensions:	5397	backend-specific APIs, libev relies on a few additional extensions:
4375		5398
…		…
4381	Libev assumes not only that all watcher pointers have the same internal	5404	Libev assumes not only that all watcher pointers have the same internal
4382	structure (guaranteed by POSIX but not by ISO C for example), but it also	5405	structure (guaranteed by POSIX but not by ISO C for example), but it also
4383	assumes that the same (machine) code can be used to call any watcher	5406	assumes that the same (machine) code can be used to call any watcher
4384	callback: The watcher callbacks have different type signatures, but libev	5407	callback: The watcher callbacks have different type signatures, but libev
4385	calls them using an C<ev_watcher *> internally.	5408	calls them using an C<ev_watcher *> internally.
		5409
		5410	=item null pointers and integer zero are represented by 0 bytes
		5411
		5412	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5413	relies on this setting pointers and integers to null.
		5414
		5415	=item pointer accesses must be thread-atomic
		5416
		5417	Accessing a pointer value must be atomic, it must both be readable and
		5418	writable in one piece - this is the case on all current architectures.
4386		5419
4387	=item C<sig_atomic_t volatile> must be thread-atomic as well	5420	=item C<sig_atomic_t volatile> must be thread-atomic as well
4388		5421
4389	The type C<sig_atomic_t volatile> (or whatever is defined as	5422	The type C<sig_atomic_t volatile> (or whatever is defined as
4390	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5423	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4399	thread" or will block signals process-wide, both behaviours would	5432	thread" or will block signals process-wide, both behaviours would
4400	be compatible with libev. Interaction between C<sigprocmask> and	5433	be compatible with libev. Interaction between C<sigprocmask> and
4401	C<pthread_sigmask> could complicate things, however.	5434	C<pthread_sigmask> could complicate things, however.
4402		5435
4403	The most portable way to handle signals is to block signals in all threads	5436	The most portable way to handle signals is to block signals in all threads
4404	except the initial one, and run the default loop in the initial thread as	5437	except the initial one, and run the signal handling loop in the initial
4405	well.	5438	thread as well.
4406		5439
4407	=item C<long> must be large enough for common memory allocation sizes	5440	=item C<long> must be large enough for common memory allocation sizes
4408		5441
4409	To improve portability and simplify its API, libev uses C<long> internally	5442	To improve portability and simplify its API, libev uses C<long> internally
4410	instead of C<size_t> when allocating its data structures. On non-POSIX	5443	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4413	watchers.	5446	watchers.
4414		5447
4415	=item C<double> must hold a time value in seconds with enough accuracy	5448	=item C<double> must hold a time value in seconds with enough accuracy
4416		5449
4417	The type C<double> is used to represent timestamps. It is required to	5450	The type C<double> is used to represent timestamps. It is required to
4418	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5451	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4419	enough for at least into the year 4000. This requirement is fulfilled by	5452	good enough for at least into the year 4000 with millisecond accuracy
		5453	(the design goal for libev). This requirement is overfulfilled by
4420	implementations implementing IEEE 754, which is basically all existing	5454	implementations using IEEE 754, which is basically all existing ones.
		5455
4421	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5456	With IEEE 754 doubles, you get microsecond accuracy until at least the
4422	2200.	5457	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5458	is either obsolete or somebody patched it to use C<long double> or
		5459	something like that, just kidding).
4423		5460
4424	=back	5461	=back
4425		5462
4426	If you know of other additional requirements drop me a note.	5463	If you know of other additional requirements drop me a note.
4427		5464
…		…
4489	=item Processing ev_async_send: O(number_of_async_watchers)	5526	=item Processing ev_async_send: O(number_of_async_watchers)
4490		5527
4491	=item Processing signals: O(max_signal_number)	5528	=item Processing signals: O(max_signal_number)
4492		5529
4493	Sending involves a system call I<iff> there were no other C<ev_async_send>	5530	Sending involves a system call I<iff> there were no other C<ev_async_send>
4494	calls in the current loop iteration. Checking for async and signal events	5531	calls in the current loop iteration and the loop is currently
		5532	blocked. Checking for async and signal events involves iterating over all
4495	involves iterating over all running async watchers or all signal numbers.	5533	running async watchers or all signal numbers.
4496		5534
4497	=back	5535	=back
4498		5536
4499		5537
		5538	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5539
		5540	The major version 4 introduced some incompatible changes to the API.
		5541
		5542	At the moment, the C<ev.h> header file provides compatibility definitions
		5543	for all changes, so most programs should still compile. The compatibility
		5544	layer might be removed in later versions of libev, so better update to the
		5545	new API early than late.
		5546
		5547	=over 4
		5548
		5549	=item C<EV_COMPAT3> backwards compatibility mechanism
		5550
		5551	The backward compatibility mechanism can be controlled by
		5552	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5553	section.
		5554
		5555	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5556
		5557	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5558
		5559	ev_loop_destroy (EV_DEFAULT_UC);
		5560	ev_loop_fork (EV_DEFAULT);
		5561
		5562	=item function/symbol renames
		5563
		5564	A number of functions and symbols have been renamed:
		5565
		5566	ev_loop => ev_run
		5567	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5568	EVLOOP_ONESHOT => EVRUN_ONCE
		5569
		5570	ev_unloop => ev_break
		5571	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5572	EVUNLOOP_ONE => EVBREAK_ONE
		5573	EVUNLOOP_ALL => EVBREAK_ALL
		5574
		5575	EV_TIMEOUT => EV_TIMER
		5576
		5577	ev_loop_count => ev_iteration
		5578	ev_loop_depth => ev_depth
		5579	ev_loop_verify => ev_verify
		5580
		5581	Most functions working on C<struct ev_loop> objects don't have an
		5582	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5583	associated constants have been renamed to not collide with the C<struct
		5584	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5585	as all other watcher types. Note that C<ev_loop_fork> is still called
		5586	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5587	typedef.
		5588
		5589	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5590
		5591	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5592	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5593	and work, but the library code will of course be larger.
		5594
		5595	=back
		5596
		5597
4500	=head1 GLOSSARY	5598	=head1 GLOSSARY
4501		5599
4502	=over 4	5600	=over 4
4503		5601
4504	=item active	5602	=item active
4505		5603
4506	A watcher is active as long as it has been started (has been attached to	5604	A watcher is active as long as it has been started and not yet stopped.
4507	an event loop) but not yet stopped (disassociated from the event loop).	5605	See L</WATCHER STATES> for details.
4508		5606
4509	=item application	5607	=item application
4510		5608
4511	In this document, an application is whatever is using libev.	5609	In this document, an application is whatever is using libev.
		5610
		5611	=item backend
		5612
		5613	The part of the code dealing with the operating system interfaces.
4512		5614
4513	=item callback	5615	=item callback
4514		5616
4515	The address of a function that is called when some event has been	5617	The address of a function that is called when some event has been
4516	detected. Callbacks are being passed the event loop, the watcher that	5618	detected. Callbacks are being passed the event loop, the watcher that
4517	received the event, and the actual event bitset.	5619	received the event, and the actual event bitset.
4518		5620
4519	=item callback invocation	5621	=item callback/watcher invocation
4520		5622
4521	The act of calling the callback associated with a watcher.	5623	The act of calling the callback associated with a watcher.
4522		5624
4523	=item event	5625	=item event
4524		5626
4525	A change of state of some external event, such as data now being available	5627	A change of state of some external event, such as data now being available
4526	for reading on a file descriptor, time having passed or simply not having	5628	for reading on a file descriptor, time having passed or simply not having
4527	any other events happening anymore.	5629	any other events happening anymore.
4528		5630
4529	In libev, events are represented as single bits (such as C<EV_READ> or	5631	In libev, events are represented as single bits (such as C<EV_READ> or
4530	C<EV_TIMEOUT>).	5632	C<EV_TIMER>).
4531		5633
4532	=item event library	5634	=item event library
4533		5635
4534	A software package implementing an event model and loop.	5636	A software package implementing an event model and loop.
4535		5637
…		…
4543	The model used to describe how an event loop handles and processes	5645	The model used to describe how an event loop handles and processes
4544	watchers and events.	5646	watchers and events.
4545		5647
4546	=item pending	5648	=item pending
4547		5649
4548	A watcher is pending as soon as the corresponding event has been detected,	5650	A watcher is pending as soon as the corresponding event has been
4549	and stops being pending as soon as the watcher will be invoked or its	5651	detected. See L</WATCHER STATES> for details.
4550	pending status is explicitly cleared by the application.
4551
4552	A watcher can be pending, but not active. Stopping a watcher also clears
4553	its pending status.
4554		5652
4555	=item real time	5653	=item real time
4556		5654
4557	The physical time that is observed. It is apparently strictly monotonic :)	5655	The physical time that is observed. It is apparently strictly monotonic :)
4558		5656
4559	=item wall-clock time	5657	=item wall-clock time
4560		5658
4561	The time and date as shown on clocks. Unlike real time, it can actually	5659	The time and date as shown on clocks. Unlike real time, it can actually
4562	be wrong and jump forwards and backwards, e.g. when the you adjust your	5660	be wrong and jump forwards and backwards, e.g. when you adjust your
4563	clock.	5661	clock.
4564		5662
4565	=item watcher	5663	=item watcher
4566		5664
4567	A data structure that describes interest in certain events. Watchers need	5665	A data structure that describes interest in certain events. Watchers need
4568	to be started (attached to an event loop) before they can receive events.	5666	to be started (attached to an event loop) before they can receive events.
4569		5667
4570	=item watcher invocation
4571
4572	The act of calling the callback associated with a watcher.
4573
4574	=back	5668	=back
4575		5669
4576	=head1 AUTHOR	5670	=head1 AUTHOR
4577		5671
4578	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5672	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5673	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4579		5674

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