ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.226 by root, Wed Mar 4 12:51:37 2009 UTC vs.
Revision 1.450 by root, Mon Jun 24 00:04:26 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 DESCRIPTION	69	=head1 ABOUT THIS DOCUMENT
		70
		71	This document documents the libev software package.
68		72
69	The newest version of this document is also available as an html-formatted	73	The newest version of this document is also available as an html-formatted
70	web page you might find easier to navigate when reading it for the first	74	web page you might find easier to navigate when reading it for the first
71	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	75	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		76
		77	While this document tries to be as complete as possible in documenting
		78	libev, its usage and the rationale behind its design, it is not a tutorial
		79	on event-based programming, nor will it introduce event-based programming
		80	with libev.
		81
		82	Familiarity with event based programming techniques in general is assumed
		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>.
		92
		93	=head1 ABOUT LIBEV
72		94
73	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
74	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
75	these event sources and provide your program with events.	97	these event sources and provide your program with events.
76		98
…		…
83	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
84	watcher.	106	watcher.
85		107
86	=head2 FEATURES	108	=head2 FEATURES
87		109
88	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>
89	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port
90	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>
91	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
92	with customised rescheduling (C<ev_periodic>), synchronous signals	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
93	(C<ev_signal>), process status change events (C<ev_child>), and event	115	timers (C<ev_timer>), absolute timers with customised rescheduling
94	watchers dealing with the event loop mechanism itself (C<ev_idle>,	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
95	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	117	change events (C<ev_child>), and event watchers dealing with the event
96	file watchers (C<ev_stat>) and even limited support for fork events	118	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
97	(C<ev_fork>).	119	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		120	limited support for fork events (C<ev_fork>).
98		121
99	It also is quite fast (see this	122	It also is quite fast (see this
100	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	123	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
101	for example).	124	for example).
102		125
…		…
105	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)
106	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
107	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
108	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
109	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
110	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
111	this argument.	134	this argument.
112		135
113	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
114		137
115	Libev represents time as a single floating point number, representing the	138	Libev represents time as a single floating point number, representing
116	(fractional) number of seconds since the (POSIX) epoch (somewhere near	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
117	the beginning of 1970, details are complicated, don't ask). This type is	140	somewhere near the beginning of 1970, details are complicated, don't
118	called C<ev_tstamp>, which is what you should use too. It usually aliases	141	ask). This type is called C<ev_tstamp>, which is what you should use
119	to the C<double> type in C, and when you need to do any calculations on	142	too. It usually aliases to the C<double> type in C. When you need to do
120	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
121	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
122	throughout libev.	146	time differences (e.g. delays) throughout libev.
123		147
124	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
125		149
126	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
127	and internal errors (bugs).	151	and internal errors (bugs).
…		…
151		175
152	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
153		177
154	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
155	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
156	you actually want to know.	180	you actually want to know. Also interesting is the combination of
		181	C<ev_now_update> and C<ev_now>.
157		182
158	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
159		184
160	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
161	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
162	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
163		194
164	=item int ev_version_major ()	195	=item int ev_version_major ()
165		196
166	=item int ev_version_minor ()	197	=item int ev_version_minor ()
167		198
…		…
178	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
179	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
180	not a problem.	211	not a problem.
181		212
182	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
183	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
184		216
185	assert (("libev version mismatch",	217	assert (("libev version mismatch",
186	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
187	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
188		220
…		…
199	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
200	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
201		233
202	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
203		235
204	Return the set of all backends compiled into this binary of libev and also	236	Return the set of all backends compiled into this binary of libev and
205	recommended for this platform. This set is often smaller than the one	237	also recommended for this platform, meaning it will work for most file
		238	descriptor types. This set is often smaller than the one returned by
206	returned by C<ev_supported_backends>, as for example kqueue is broken on	239	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
207	most BSDs and will not be auto-detected unless you explicitly request it	240	and will not be auto-detected unless you explicitly request it (assuming
208	(assuming you know what you are doing). This is the set of backends that	241	you know what you are doing). This is the set of backends that libev will
209	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
210		243
211	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
212		245
213	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
214	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
215	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
217	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
218		251
219	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
220		253
221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
222		255
223	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
225	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
226	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
232		265
233	You could override this function in high-availability programs to, say,	266	You could override this function in high-availability programs to, say,
234	free some memory if it cannot allocate memory, to use a special allocator,	267	free some memory if it cannot allocate memory, to use a special allocator,
235	or even to sleep a while and retry until some memory is available.	268	or even to sleep a while and retry until some memory is available.
236		269
		270	Example: The following is the C<realloc> function that libev itself uses
		271	which should work with C<realloc> and C<free> functions of all kinds and
		272	is probably a good basis for your own implementation.
		273
		274	static void *
		275	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		276	{
		277	if (size)
		278	return realloc (ptr, size);
		279
		280	free (ptr);
		281	return 0;
		282	}
		283
237	Example: Replace the libev allocator with one that waits a bit and then	284	Example: Replace the libev allocator with one that waits a bit and then
238	retries (example requires a standards-compliant C<realloc>).	285	retries.
239		286
240	static void *	287	static void *
241	persistent_realloc (void *ptr, size_t size)	288	persistent_realloc (void *ptr, size_t size)
242	{	289	{
		290	if (!size)
		291	{
		292	free (ptr);
		293	return 0;
		294	}
		295
243	for (;;)	296	for (;;)
244	{	297	{
245	void *newptr = realloc (ptr, size);	298	void *newptr = realloc (ptr, size);
246		299
247	if (newptr)	300	if (newptr)
…		…
252	}	305	}
253		306
254	...	307	...
255	ev_set_allocator (persistent_realloc);	308	ev_set_allocator (persistent_realloc);
256		309
257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	310	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
258		311
259	Set the callback function to call on a retryable system call error (such	312	Set the callback function to call on a retryable system call error (such
260	as failed select, poll, epoll_wait). The message is a printable string	313	as failed select, poll, epoll_wait). The message is a printable string
261	indicating the system call or subsystem causing the problem. If this	314	indicating the system call or subsystem causing the problem. If this
262	callback is set, then libev will expect it to remedy the situation, no	315	callback is set, then libev will expect it to remedy the situation, no
…		…
274	}	327	}
275		328
276	...	329	...
277	ev_set_syserr_cb (fatal_error);	330	ev_set_syserr_cb (fatal_error);
278		331
		332	=item ev_feed_signal (int signum)
		333
		334	This function can be used to "simulate" a signal receive. It is completely
		335	safe to call this function at any time, from any context, including signal
		336	handlers or random threads.
		337
		338	Its main use is to customise signal handling in your process, especially
		339	in the presence of threads. For example, you could block signals
		340	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		341	creating any loops), and in one thread, use C<sigwait> or any other
		342	mechanism to wait for signals, then "deliver" them to libev by calling
		343	C<ev_feed_signal>.
		344
279	=back	345	=back
280		346
281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	347	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
282		348
283	An event loop is described by a C<struct ev_loop *> (the C<struct>	349	An event loop is described by a C<struct ev_loop *> (the C<struct> is
284	is I<not> optional in this case, as there is also an C<ev_loop>	350	I<not> optional in this case unless libev 3 compatibility is disabled, as
285	I<function>).	351	libev 3 had an C<ev_loop> function colliding with the struct name).
286		352
287	The library knows two types of such loops, the I<default> loop, which	353	The library knows two types of such loops, the I<default> loop, which
288	supports signals and child events, and dynamically created loops which do	354	supports child process events, and dynamically created event loops which
289	not.	355	do not.
290		356
291	=over 4	357	=over 4
292		358
293	=item struct ev_loop *ev_default_loop (unsigned int flags)	359	=item struct ev_loop *ev_default_loop (unsigned int flags)
294		360
295	This will initialise the default event loop if it hasn't been initialised	361	This returns the "default" event loop object, which is what you should
296	yet and return it. If the default loop could not be initialised, returns	362	normally use when you just need "the event loop". Event loop objects and
297	false. If it already was initialised it simply returns it (and ignores the	363	the C<flags> parameter are described in more detail in the entry for
298	flags. If that is troubling you, check C<ev_backend ()> afterwards).	364	C<ev_loop_new>.
		365
		366	If the default loop is already initialised then this function simply
		367	returns it (and ignores the flags. If that is troubling you, check
		368	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		369	flags, which should almost always be C<0>, unless the caller is also the
		370	one calling C<ev_run> or otherwise qualifies as "the main program".
299		371
300	If you don't know what event loop to use, use the one returned from this	372	If you don't know what event loop to use, use the one returned from this
301	function.	373	function (or via the C<EV_DEFAULT> macro).
302		374
303	Note that this function is I<not> thread-safe, so if you want to use it	375	Note that this function is I<not> thread-safe, so if you want to use it
304	from multiple threads, you have to lock (note also that this is unlikely,	376	from multiple threads, you have to employ some kind of mutex (note also
305	as loops cannot be shared easily between threads anyway).	377	that this case is unlikely, as loops cannot be shared easily between
		378	threads anyway).
306		379
307	The default loop is the only loop that can handle C<ev_signal> and	380	The default loop is the only loop that can handle C<ev_child> watchers,
308	C<ev_child> watchers, and to do this, it always registers a handler	381	and to do this, it always registers a handler for C<SIGCHLD>. If this is
309	for C<SIGCHLD>. If this is a problem for your application you can either	382	a problem for your application you can either create a dynamic loop with
310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	383	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
311	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	384	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
312	C<ev_default_init>.	385
		386	Example: This is the most typical usage.
		387
		388	if (!ev_default_loop (0))
		389	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		390
		391	Example: Restrict libev to the select and poll backends, and do not allow
		392	environment settings to be taken into account:
		393
		394	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		395
		396	=item struct ev_loop *ev_loop_new (unsigned int flags)
		397
		398	This will create and initialise a new event loop object. If the loop
		399	could not be initialised, returns false.
		400
		401	This function is thread-safe, and one common way to use libev with
		402	threads is indeed to create one loop per thread, and using the default
		403	loop in the "main" or "initial" thread.
313		404
314	The flags argument can be used to specify special behaviour or specific	405	The flags argument can be used to specify special behaviour or specific
315	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	406	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
316		407
317	The following flags are supported:	408	The following flags are supported:
…		…
327		418
328	If this flag bit is or'ed into the flag value (or the program runs setuid	419	If this flag bit is or'ed into the flag value (or the program runs setuid
329	or setgid) then libev will I<not> look at the environment variable	420	or setgid) then libev will I<not> look at the environment variable
330	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	421	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
331	override the flags completely if it is found in the environment. This is	422	override the flags completely if it is found in the environment. This is
332	useful to try out specific backends to test their performance, or to work	423	useful to try out specific backends to test their performance, to work
333	around bugs.	424	around bugs, or to make libev threadsafe (accessing environment variables
		425	cannot be done in a threadsafe way, but usually it works if no other
		426	thread modifies them).
334		427
335	=item C<EVFLAG_FORKCHECK>	428	=item C<EVFLAG_FORKCHECK>
336		429
337	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	430	Instead of calling C<ev_loop_fork> manually after a fork, you can also
338	a fork, you can also make libev check for a fork in each iteration by	431	make libev check for a fork in each iteration by enabling this flag.
339	enabling this flag.
340		432
341	This works by calling C<getpid ()> on every iteration of the loop,	433	This works by calling C<getpid ()> on every iteration of the loop,
342	and thus this might slow down your event loop if you do a lot of loop	434	and thus this might slow down your event loop if you do a lot of loop
343	iterations and little real work, but is usually not noticeable (on my	435	iterations and little real work, but is usually not noticeable (on my
344	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	436	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
345	without a system call and thus I<very> fast, but my GNU/Linux system also has	437	sequence without a system call and thus I<very> fast, but my GNU/Linux
346	C<pthread_atfork> which is even faster).	438	system also has C<pthread_atfork> which is even faster). (Update: glibc
		439	versions 2.25 apparently removed the C<getpid> optimisation again).
347		440
348	The big advantage of this flag is that you can forget about fork (and	441	The big advantage of this flag is that you can forget about fork (and
349	forget about forgetting to tell libev about forking) when you use this	442	forget about forgetting to tell libev about forking, although you still
350	flag.	443	have to ignore C<SIGPIPE>) when you use this flag.
351		444
352	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	445	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
353	environment variable.	446	environment variable.
		447
		448	=item C<EVFLAG_NOINOTIFY>
		449
		450	When this flag is specified, then libev will not attempt to use the
		451	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		452	testing, this flag can be useful to conserve inotify file descriptors, as
		453	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		454
		455	=item C<EVFLAG_SIGNALFD>
		456
		457	When this flag is specified, then libev will attempt to use the
		458	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		459	delivers signals synchronously, which makes it both faster and might make
		460	it possible to get the queued signal data. It can also simplify signal
		461	handling with threads, as long as you properly block signals in your
		462	threads that are not interested in handling them.
		463
		464	Signalfd will not be used by default as this changes your signal mask, and
		465	there are a lot of shoddy libraries and programs (glib's threadpool for
		466	example) that can't properly initialise their signal masks.
		467
		468	=item C<EVFLAG_NOSIGMASK>
		469
		470	When this flag is specified, then libev will avoid to modify the signal
		471	mask. Specifically, this means you have to make sure signals are unblocked
		472	when you want to receive them.
		473
		474	This behaviour is useful when you want to do your own signal handling, or
		475	want to handle signals only in specific threads and want to avoid libev
		476	unblocking the signals.
		477
		478	It's also required by POSIX in a threaded program, as libev calls
		479	C<sigprocmask>, whose behaviour is officially unspecified.
		480
		481	This flag's behaviour will become the default in future versions of libev.
354		482
355	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	483	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
356		484
357	This is your standard select(2) backend. Not I<completely> standard, as	485	This is your standard select(2) backend. Not I<completely> standard, as
358	libev tries to roll its own fd_set with no limits on the number of fds,	486	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
383	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	511	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
384	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	512	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
385		513
386	=item C<EVBACKEND_EPOLL> (value 4, Linux)	514	=item C<EVBACKEND_EPOLL> (value 4, Linux)
387		515
		516	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		517	kernels).
		518
388	For few fds, this backend is a bit little slower than poll and select,	519	For few fds, this backend is a bit little slower than poll and select, but
389	but it scales phenomenally better. While poll and select usually scale	520	it scales phenomenally better. While poll and select usually scale like
390	like O(total_fds) where n is the total number of fds (or the highest fd),	521	O(total_fds) where total_fds is the total number of fds (or the highest
391	epoll scales either O(1) or O(active_fds).	522	fd), epoll scales either O(1) or O(active_fds).
392		523
393	The epoll mechanism deserves honorable mention as the most misdesigned	524	The epoll mechanism deserves honorable mention as the most misdesigned
394	of the more advanced event mechanisms: mere annoyances include silently	525	of the more advanced event mechanisms: mere annoyances include silently
395	dropping file descriptors, requiring a system call per change per file	526	dropping file descriptors, requiring a system call per change per file
396	descriptor (and unnecessary guessing of parameters), problems with dup and	527	descriptor (and unnecessary guessing of parameters), problems with dup,
		528	returning before the timeout value, resulting in additional iterations
		529	(and only giving 5ms accuracy while select on the same platform gives
397	so on. The biggest issue is fork races, however - if a program forks then	530	0.1ms) and so on. The biggest issue is fork races, however - if a program
398	I<both> parent and child process have to recreate the epoll set, which can	531	forks then I<both> parent and child process have to recreate the epoll
399	take considerable time (one syscall per file descriptor) and is of course	532	set, which can take considerable time (one syscall per file descriptor)
400	hard to detect.	533	and is of course hard to detect.
401		534
402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	535	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
403	of course I<doesn't>, and epoll just loves to report events for totally	536	but of course I<doesn't>, and epoll just loves to report events for
404	I<different> file descriptors (even already closed ones, so one cannot	537	totally I<different> file descriptors (even already closed ones, so
405	even remove them from the set) than registered in the set (especially	538	one cannot even remove them from the set) than registered in the set
406	on SMP systems). Libev tries to counter these spurious notifications by	539	(especially on SMP systems). Libev tries to counter these spurious
407	employing an additional generation counter and comparing that against the	540	notifications by employing an additional generation counter and comparing
408	events to filter out spurious ones, recreating the set when required.	541	that against the events to filter out spurious ones, recreating the set
		542	when required. Epoll also erroneously rounds down timeouts, but gives you
		543	no way to know when and by how much, so sometimes you have to busy-wait
		544	because epoll returns immediately despite a nonzero timeout. And last
		545	not least, it also refuses to work with some file descriptors which work
		546	perfectly fine with C<select> (files, many character devices...).
		547
		548	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		549	cobbled together in a hurry, no thought to design or interaction with
		550	others. Oh, the pain, will it ever stop...
409		551
410	While stopping, setting and starting an I/O watcher in the same iteration	552	While stopping, setting and starting an I/O watcher in the same iteration
411	will result in some caching, there is still a system call per such	553	will result in some caching, there is still a system call per such
412	incident (because the same I<file descriptor> could point to a different	554	incident (because the same I<file descriptor> could point to a different
413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	555	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or	567	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
426	faster than epoll for maybe up to a hundred file descriptors, depending on	568	faster than epoll for maybe up to a hundred file descriptors, depending on
427	the usage. So sad.	569	the usage. So sad.
428		570
429	While nominally embeddable in other event loops, this feature is broken in	571	While nominally embeddable in other event loops, this feature is broken in
430	all kernel versions tested so far.	572	a lot of kernel revisions, but probably(!) works in current versions.
		573
		574	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		575	C<EVBACKEND_POLL>.
		576
		577	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		578
		579	Use the linux-specific linux aio (I<not> C<< aio(7) >> but C<<
		580	io_submit(2) >>) event interface available in post-4.18 kernels.
		581
		582	If this backend works for you (as of this writing, it was very
		583	experimental), it is the best event interface available on linux and might
		584	be well worth enabling it - if it isn't available in your kernel this will
		585	be detected and this backend will be skipped.
		586
		587	This backend can batch oneshot requests and supports a user-space ring
		588	buffer to receive events. It also doesn't suffer from most of the design
		589	problems of epoll (such as not being able to remove event sources from
		590	the epoll set), and generally sounds too good to be true. Because, this
		591	being the linux kernel, of course it suffers from a whole new set of
		592	limitations.
		593
		594	For one, it is not easily embeddable (but probably could be done using
		595	an event fd at some extra overhead). It also is subject to a system wide
		596	limit that can be configured in F</proc/sys/fs/aio-max-nr> - each loop
		597	currently requires C<61> of this number. If no aio requests are left, this
		598	backend will be skipped during initialisation.
		599
		600	Most problematic in practise, however, is that not all file descriptors
		601	work with it. For example, in linux 5.1, tcp sockets, pipes, event fds,
		602	files, F</dev/null> and a few others are supported, but ttys do not work
		603	properly (a known bug that the kernel developers don't care about, see
		604	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		605	(yet?) a generic event polling interface.
		606
		607	To work around this latter problem, the current version of libev uses
		608	epoll as a fallback for file deescriptor types that do not work. Epoll
		609	is used in, kind of, slow mode that hopefully avoids most of its design
		610	problems and requires 1-3 extra syscalls per active fd every iteration.
431		611
432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	612	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
433	C<EVBACKEND_POLL>.	613	C<EVBACKEND_POLL>.
434		614
435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	615	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
…		…
450		630
451	It scales in the same way as the epoll backend, but the interface to the	631	It scales in the same way as the epoll backend, but the interface to the
452	kernel is more efficient (which says nothing about its actual speed, of	632	kernel is more efficient (which says nothing about its actual speed, of
453	course). While stopping, setting and starting an I/O watcher does never	633	course). While stopping, setting and starting an I/O watcher does never
454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	634	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
455	two event changes per incident. Support for C<fork ()> is very bad (but	635	two event changes per incident. Support for C<fork ()> is very bad (you
456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	636	might have to leak fd's on fork, but it's more sane than epoll) and it
457	cases	637	drops fds silently in similarly hard-to-detect cases.
458		638
459	This backend usually performs well under most conditions.	639	This backend usually performs well under most conditions.
460		640
461	While nominally embeddable in other event loops, this doesn't work	641	While nominally embeddable in other event loops, this doesn't work
462	everywhere, so you might need to test for this. And since it is broken	642	everywhere, so you might need to test for this. And since it is broken
…		…
479	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	659	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
480		660
481	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	661	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
482	it's really slow, but it still scales very well (O(active_fds)).	662	it's really slow, but it still scales very well (O(active_fds)).
483		663
484	Please note that Solaris event ports can deliver a lot of spurious
485	notifications, so you need to use non-blocking I/O or other means to avoid
486	blocking when no data (or space) is available.
487
488	While this backend scales well, it requires one system call per active	664	While this backend scales well, it requires one system call per active
489	file descriptor per loop iteration. For small and medium numbers of file	665	file descriptor per loop iteration. For small and medium numbers of file
490	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	666	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
491	might perform better.	667	might perform better.
492		668
493	On the positive side, with the exception of the spurious readiness	669	On the positive side, this backend actually performed fully to
494	notifications, this backend actually performed fully to specification
495	in all tests and is fully embeddable, which is a rare feat among the	670	specification in all tests and is fully embeddable, which is a rare feat
496	OS-specific backends (I vastly prefer correctness over speed hacks).	671	among the OS-specific backends (I vastly prefer correctness over speed
		672	hacks).
		673
		674	On the negative side, the interface is I<bizarre> - so bizarre that
		675	even sun itself gets it wrong in their code examples: The event polling
		676	function sometimes returns events to the caller even though an error
		677	occurred, but with no indication whether it has done so or not (yes, it's
		678	even documented that way) - deadly for edge-triggered interfaces where you
		679	absolutely have to know whether an event occurred or not because you have
		680	to re-arm the watcher.
		681
		682	Fortunately libev seems to be able to work around these idiocies.
497		683
498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	684	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
499	C<EVBACKEND_POLL>.	685	C<EVBACKEND_POLL>.
500		686
501	=item C<EVBACKEND_ALL>	687	=item C<EVBACKEND_ALL>
502		688
503	Try all backends (even potentially broken ones that wouldn't be tried	689	Try all backends (even potentially broken ones that wouldn't be tried
504	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	690	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
505	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	691	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
506		692
507	It is definitely not recommended to use this flag.	693	It is definitely not recommended to use this flag, use whatever
		694	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		695	at all.
		696
		697	=item C<EVBACKEND_MASK>
		698
		699	Not a backend at all, but a mask to select all backend bits from a
		700	C<flags> value, in case you want to mask out any backends from a flags
		701	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
508		702
509	=back	703	=back
510		704
511	If one or more of these are or'ed into the flags value, then only these	705	If one or more of the backend flags are or'ed into the flags value,
512	backends will be tried (in the reverse order as listed here). If none are	706	then only these backends will be tried (in the reverse order as listed
513	specified, all backends in C<ev_recommended_backends ()> will be tried.	707	here). If none are specified, all backends in C<ev_recommended_backends
514		708	()> will be tried.
515	Example: This is the most typical usage.
516
517	if (!ev_default_loop (0))
518	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
519
520	Example: Restrict libev to the select and poll backends, and do not allow
521	environment settings to be taken into account:
522
523	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
524
525	Example: Use whatever libev has to offer, but make sure that kqueue is
526	used if available (warning, breaks stuff, best use only with your own
527	private event loop and only if you know the OS supports your types of
528	fds):
529
530	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
531
532	=item struct ev_loop *ev_loop_new (unsigned int flags)
533
534	Similar to C<ev_default_loop>, but always creates a new event loop that is
535	always distinct from the default loop. Unlike the default loop, it cannot
536	handle signal and child watchers, and attempts to do so will be greeted by
537	undefined behaviour (or a failed assertion if assertions are enabled).
538
539	Note that this function I<is> thread-safe, and the recommended way to use
540	libev with threads is indeed to create one loop per thread, and using the
541	default loop in the "main" or "initial" thread.
542		709
543	Example: Try to create a event loop that uses epoll and nothing else.	710	Example: Try to create a event loop that uses epoll and nothing else.
544		711
545	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	712	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
546	if (!epoller)	713	if (!epoller)
547	fatal ("no epoll found here, maybe it hides under your chair");	714	fatal ("no epoll found here, maybe it hides under your chair");
548		715
		716	Example: Use whatever libev has to offer, but make sure that kqueue is
		717	used if available.
		718
		719	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		720
		721	Example: Similarly, on linux, you mgiht want to take advantage of the
		722	linux aio backend if possible, but fall back to something else if that
		723	isn't available.
		724
		725	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		726
549	=item ev_default_destroy ()	727	=item ev_loop_destroy (loop)
550		728
551	Destroys the default loop again (frees all memory and kernel state	729	Destroys an event loop object (frees all memory and kernel state
552	etc.). None of the active event watchers will be stopped in the normal	730	etc.). None of the active event watchers will be stopped in the normal
553	sense, so e.g. C<ev_is_active> might still return true. It is your	731	sense, so e.g. C<ev_is_active> might still return true. It is your
554	responsibility to either stop all watchers cleanly yourself I<before>	732	responsibility to either stop all watchers cleanly yourself I<before>
555	calling this function, or cope with the fact afterwards (which is usually	733	calling this function, or cope with the fact afterwards (which is usually
556	the easiest thing, you can just ignore the watchers and/or C<free ()> them	734	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
558		736
559	Note that certain global state, such as signal state (and installed signal	737	Note that certain global state, such as signal state (and installed signal
560	handlers), will not be freed by this function, and related watchers (such	738	handlers), will not be freed by this function, and related watchers (such
561	as signal and child watchers) would need to be stopped manually.	739	as signal and child watchers) would need to be stopped manually.
562		740
563	In general it is not advisable to call this function except in the	741	This function is normally used on loop objects allocated by
564	rare occasion where you really need to free e.g. the signal handling	742	C<ev_loop_new>, but it can also be used on the default loop returned by
		743	C<ev_default_loop>, in which case it is not thread-safe.
		744
		745	Note that it is not advisable to call this function on the default loop
		746	except in the rare occasion where you really need to free its resources.
565	pipe fds. If you need dynamically allocated loops it is better to use	747	If you need dynamically allocated loops it is better to use C<ev_loop_new>
566	C<ev_loop_new> and C<ev_loop_destroy>).	748	and C<ev_loop_destroy>.
567		749
568	=item ev_loop_destroy (loop)	750	=item ev_loop_fork (loop)
569		751
570	Like C<ev_default_destroy>, but destroys an event loop created by an
571	earlier call to C<ev_loop_new>.
572
573	=item ev_default_fork ()
574
575	This function sets a flag that causes subsequent C<ev_loop> iterations	752	This function sets a flag that causes subsequent C<ev_run> iterations
576	to reinitialise the kernel state for backends that have one. Despite the	753	to reinitialise the kernel state for backends that have one. Despite
577	name, you can call it anytime, but it makes most sense after forking, in	754	the name, you can call it anytime you are allowed to start or stop
578	the child process (or both child and parent, but that again makes little	755	watchers (except inside an C<ev_prepare> callback), but it makes most
579	sense). You I<must> call it in the child before using any of the libev	756	sense after forking, in the child process. You I<must> call it (or use
580	functions, and it will only take effect at the next C<ev_loop> iteration.	757	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		758
		759	In addition, if you want to reuse a loop (via this function or
		760	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		761
		762	Again, you I<have> to call it on I<any> loop that you want to re-use after
		763	a fork, I<even if you do not plan to use the loop in the parent>. This is
		764	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		765	during fork.
581		766
582	On the other hand, you only need to call this function in the child	767	On the other hand, you only need to call this function in the child
583	process if and only if you want to use the event library in the child. If	768	process if and only if you want to use the event loop in the child. If
584	you just fork+exec, you don't have to call it at all.	769	you just fork+exec or create a new loop in the child, you don't have to
		770	call it at all (in fact, C<epoll> is so badly broken that it makes a
		771	difference, but libev will usually detect this case on its own and do a
		772	costly reset of the backend).
585		773
586	The function itself is quite fast and it's usually not a problem to call	774	The function itself is quite fast and it's usually not a problem to call
587	it just in case after a fork. To make this easy, the function will fit in	775	it just in case after a fork.
588	quite nicely into a call to C<pthread_atfork>:
589		776
		777	Example: Automate calling C<ev_loop_fork> on the default loop when
		778	using pthreads.
		779
		780	static void
		781	post_fork_child (void)
		782	{
		783	ev_loop_fork (EV_DEFAULT);
		784	}
		785
		786	...
590	pthread_atfork (0, 0, ev_default_fork);	787	pthread_atfork (0, 0, post_fork_child);
591
592	=item ev_loop_fork (loop)
593
594	Like C<ev_default_fork>, but acts on an event loop created by
595	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
596	after fork that you want to re-use in the child, and how you do this is
597	entirely your own problem.
598		788
599	=item int ev_is_default_loop (loop)	789	=item int ev_is_default_loop (loop)
600		790
601	Returns true when the given loop is, in fact, the default loop, and false	791	Returns true when the given loop is, in fact, the default loop, and false
602	otherwise.	792	otherwise.
603		793
604	=item unsigned int ev_loop_count (loop)	794	=item unsigned int ev_iteration (loop)
605		795
606	Returns the count of loop iterations for the loop, which is identical to	796	Returns the current iteration count for the event loop, which is identical
607	the number of times libev did poll for new events. It starts at C<0> and	797	to the number of times libev did poll for new events. It starts at C<0>
608	happily wraps around with enough iterations.	798	and happily wraps around with enough iterations.
609		799
610	This value can sometimes be useful as a generation counter of sorts (it	800	This value can sometimes be useful as a generation counter of sorts (it
611	"ticks" the number of loop iterations), as it roughly corresponds with	801	"ticks" the number of loop iterations), as it roughly corresponds with
612	C<ev_prepare> and C<ev_check> calls.	802	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		803	prepare and check phases.
		804
		805	=item unsigned int ev_depth (loop)
		806
		807	Returns the number of times C<ev_run> was entered minus the number of
		808	times C<ev_run> was exited normally, in other words, the recursion depth.
		809
		810	Outside C<ev_run>, this number is zero. In a callback, this number is
		811	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		812	in which case it is higher.
		813
		814	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		815	throwing an exception etc.), doesn't count as "exit" - consider this
		816	as a hint to avoid such ungentleman-like behaviour unless it's really
		817	convenient, in which case it is fully supported.
613		818
614	=item unsigned int ev_backend (loop)	819	=item unsigned int ev_backend (loop)
615		820
616	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	821	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
617	use.	822	use.
…		…
626		831
627	=item ev_now_update (loop)	832	=item ev_now_update (loop)
628		833
629	Establishes the current time by querying the kernel, updating the time	834	Establishes the current time by querying the kernel, updating the time
630	returned by C<ev_now ()> in the progress. This is a costly operation and	835	returned by C<ev_now ()> in the progress. This is a costly operation and
631	is usually done automatically within C<ev_loop ()>.	836	is usually done automatically within C<ev_run ()>.
632		837
633	This function is rarely useful, but when some event callback runs for a	838	This function is rarely useful, but when some event callback runs for a
634	very long time without entering the event loop, updating libev's idea of	839	very long time without entering the event loop, updating libev's idea of
635	the current time is a good idea.	840	the current time is a good idea.
636		841
637	See also "The special problem of time updates" in the C<ev_timer> section.	842	See also L</The special problem of time updates> in the C<ev_timer> section.
638		843
		844	=item ev_suspend (loop)
		845
		846	=item ev_resume (loop)
		847
		848	These two functions suspend and resume an event loop, for use when the
		849	loop is not used for a while and timeouts should not be processed.
		850
		851	A typical use case would be an interactive program such as a game: When
		852	the user presses C<^Z> to suspend the game and resumes it an hour later it
		853	would be best to handle timeouts as if no time had actually passed while
		854	the program was suspended. This can be achieved by calling C<ev_suspend>
		855	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		856	C<ev_resume> directly afterwards to resume timer processing.
		857
		858	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		859	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		860	will be rescheduled (that is, they will lose any events that would have
		861	occurred while suspended).
		862
		863	After calling C<ev_suspend> you B<must not> call I<any> function on the
		864	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		865	without a previous call to C<ev_suspend>.
		866
		867	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		868	event loop time (see C<ev_now_update>).
		869
639	=item ev_loop (loop, int flags)	870	=item bool ev_run (loop, int flags)
640		871
641	Finally, this is it, the event handler. This function usually is called	872	Finally, this is it, the event handler. This function usually is called
642	after you initialised all your watchers and you want to start handling	873	after you have initialised all your watchers and you want to start
643	events.	874	handling events. It will ask the operating system for any new events, call
		875	the watcher callbacks, and then repeat the whole process indefinitely: This
		876	is why event loops are called I<loops>.
644		877
645	If the flags argument is specified as C<0>, it will not return until	878	If the flags argument is specified as C<0>, it will keep handling events
646	either no event watchers are active anymore or C<ev_unloop> was called.	879	until either no event watchers are active anymore or C<ev_break> was
		880	called.
647		881
		882	The return value is false if there are no more active watchers (which
		883	usually means "all jobs done" or "deadlock"), and true in all other cases
		884	(which usually means " you should call C<ev_run> again").
		885
648	Please note that an explicit C<ev_unloop> is usually better than	886	Please note that an explicit C<ev_break> is usually better than
649	relying on all watchers to be stopped when deciding when a program has	887	relying on all watchers to be stopped when deciding when a program has
650	finished (especially in interactive programs), but having a program	888	finished (especially in interactive programs), but having a program
651	that automatically loops as long as it has to and no longer by virtue	889	that automatically loops as long as it has to and no longer by virtue
652	of relying on its watchers stopping correctly, that is truly a thing of	890	of relying on its watchers stopping correctly, that is truly a thing of
653	beauty.	891	beauty.
654		892
		893	This function is I<mostly> exception-safe - you can break out of a
		894	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		895	exception and so on. This does not decrement the C<ev_depth> value, nor
		896	will it clear any outstanding C<EVBREAK_ONE> breaks.
		897
655	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	898	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
656	those events and any already outstanding ones, but will not block your	899	those events and any already outstanding ones, but will not wait and
657	process in case there are no events and will return after one iteration of	900	block your process in case there are no events and will return after one
658	the loop.	901	iteration of the loop. This is sometimes useful to poll and handle new
		902	events while doing lengthy calculations, to keep the program responsive.
659		903
660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	904	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
661	necessary) and will handle those and any already outstanding ones. It	905	necessary) and will handle those and any already outstanding ones. It
662	will block your process until at least one new event arrives (which could	906	will block your process until at least one new event arrives (which could
663	be an event internal to libev itself, so there is no guarantee that a	907	be an event internal to libev itself, so there is no guarantee that a
664	user-registered callback will be called), and will return after one	908	user-registered callback will be called), and will return after one
665	iteration of the loop.	909	iteration of the loop.
666		910
667	This is useful if you are waiting for some external event in conjunction	911	This is useful if you are waiting for some external event in conjunction
668	with something not expressible using other libev watchers (i.e. "roll your	912	with something not expressible using other libev watchers (i.e. "roll your
669	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	913	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
670	usually a better approach for this kind of thing.	914	usually a better approach for this kind of thing.
671		915
672	Here are the gory details of what C<ev_loop> does:	916	Here are the gory details of what C<ev_run> does (this is for your
		917	understanding, not a guarantee that things will work exactly like this in
		918	future versions):
673		919
		920	- Increment loop depth.
		921	- Reset the ev_break status.
674	- Before the first iteration, call any pending watchers.	922	- Before the first iteration, call any pending watchers.
		923	LOOP:
675	* If EVFLAG_FORKCHECK was used, check for a fork.	924	- If EVFLAG_FORKCHECK was used, check for a fork.
676	- If a fork was detected (by any means), queue and call all fork watchers.	925	- If a fork was detected (by any means), queue and call all fork watchers.
677	- Queue and call all prepare watchers.	926	- Queue and call all prepare watchers.
		927	- If ev_break was called, goto FINISH.
678	- If we have been forked, detach and recreate the kernel state	928	- If we have been forked, detach and recreate the kernel state
679	as to not disturb the other process.	929	as to not disturb the other process.
680	- Update the kernel state with all outstanding changes.	930	- Update the kernel state with all outstanding changes.
681	- Update the "event loop time" (ev_now ()).	931	- Update the "event loop time" (ev_now ()).
682	- Calculate for how long to sleep or block, if at all	932	- Calculate for how long to sleep or block, if at all
683	(active idle watchers, EVLOOP_NONBLOCK or not having	933	(active idle watchers, EVRUN_NOWAIT or not having
684	any active watchers at all will result in not sleeping).	934	any active watchers at all will result in not sleeping).
685	- Sleep if the I/O and timer collect interval say so.	935	- Sleep if the I/O and timer collect interval say so.
		936	- Increment loop iteration counter.
686	- Block the process, waiting for any events.	937	- Block the process, waiting for any events.
687	- Queue all outstanding I/O (fd) events.	938	- Queue all outstanding I/O (fd) events.
688	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	939	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
689	- Queue all expired timers.	940	- Queue all expired timers.
690	- Queue all expired periodics.	941	- Queue all expired periodics.
691	- Unless any events are pending now, queue all idle watchers.	942	- Queue all idle watchers with priority higher than that of pending events.
692	- Queue all check watchers.	943	- Queue all check watchers.
693	- Call all queued watchers in reverse order (i.e. check watchers first).	944	- Call all queued watchers in reverse order (i.e. check watchers first).
694	Signals and child watchers are implemented as I/O watchers, and will	945	Signals and child watchers are implemented as I/O watchers, and will
695	be handled here by queueing them when their watcher gets executed.	946	be handled here by queueing them when their watcher gets executed.
696	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	947	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
697	were used, or there are no active watchers, return, otherwise	948	were used, or there are no active watchers, goto FINISH, otherwise
698	continue with step *.	949	continue with step LOOP.
		950	FINISH:
		951	- Reset the ev_break status iff it was EVBREAK_ONE.
		952	- Decrement the loop depth.
		953	- Return.
699		954
700	Example: Queue some jobs and then loop until no events are outstanding	955	Example: Queue some jobs and then loop until no events are outstanding
701	anymore.	956	anymore.
702		957
703	... queue jobs here, make sure they register event watchers as long	958	... queue jobs here, make sure they register event watchers as long
704	... as they still have work to do (even an idle watcher will do..)	959	... as they still have work to do (even an idle watcher will do..)
705	ev_loop (my_loop, 0);	960	ev_run (my_loop, 0);
706	... jobs done or somebody called unloop. yeah!	961	... jobs done or somebody called break. yeah!
707		962
708	=item ev_unloop (loop, how)	963	=item ev_break (loop, how)
709		964
710	Can be used to make a call to C<ev_loop> return early (but only after it	965	Can be used to make a call to C<ev_run> return early (but only after it
711	has processed all outstanding events). The C<how> argument must be either	966	has processed all outstanding events). The C<how> argument must be either
712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	967	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	968	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
714		969
715	This "unloop state" will be cleared when entering C<ev_loop> again.	970	This "break state" will be cleared on the next call to C<ev_run>.
716		971
717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	972	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		973	which case it will have no effect.
718		974
719	=item ev_ref (loop)	975	=item ev_ref (loop)
720		976
721	=item ev_unref (loop)	977	=item ev_unref (loop)
722		978
723	Ref/unref can be used to add or remove a reference count on the event	979	Ref/unref can be used to add or remove a reference count on the event
724	loop: Every watcher keeps one reference, and as long as the reference	980	loop: Every watcher keeps one reference, and as long as the reference
725	count is nonzero, C<ev_loop> will not return on its own.	981	count is nonzero, C<ev_run> will not return on its own.
726		982
727	If you have a watcher you never unregister that should not keep C<ev_loop>	983	This is useful when you have a watcher that you never intend to
728	from returning, call ev_unref() after starting, and ev_ref() before	984	unregister, but that nevertheless should not keep C<ev_run> from
		985	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
729	stopping it.	986	before stopping it.
730		987
731	As an example, libev itself uses this for its internal signal pipe: It is	988	As an example, libev itself uses this for its internal signal pipe: It
732	not visible to the libev user and should not keep C<ev_loop> from exiting	989	is not visible to the libev user and should not keep C<ev_run> from
733	if no event watchers registered by it are active. It is also an excellent	990	exiting if no event watchers registered by it are active. It is also an
734	way to do this for generic recurring timers or from within third-party	991	excellent way to do this for generic recurring timers or from within
735	libraries. Just remember to I<unref after start> and I<ref before stop>	992	third-party libraries. Just remember to I<unref after start> and I<ref
736	(but only if the watcher wasn't active before, or was active before,	993	before stop> (but only if the watcher wasn't active before, or was active
737	respectively).	994	before, respectively. Note also that libev might stop watchers itself
		995	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		996	in the callback).
738		997
739	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	998	Example: Create a signal watcher, but keep it from keeping C<ev_run>
740	running when nothing else is active.	999	running when nothing else is active.
741		1000
742	ev_signal exitsig;	1001	ev_signal exitsig;
743	ev_signal_init (&exitsig, sig_cb, SIGINT);	1002	ev_signal_init (&exitsig, sig_cb, SIGINT);
744	ev_signal_start (loop, &exitsig);	1003	ev_signal_start (loop, &exitsig);
745	evf_unref (loop);	1004	ev_unref (loop);
746		1005
747	Example: For some weird reason, unregister the above signal handler again.	1006	Example: For some weird reason, unregister the above signal handler again.
748		1007
749	ev_ref (loop);	1008	ev_ref (loop);
750	ev_signal_stop (loop, &exitsig);	1009	ev_signal_stop (loop, &exitsig);
…		…
770	overhead for the actual polling but can deliver many events at once.	1029	overhead for the actual polling but can deliver many events at once.
771		1030
772	By setting a higher I<io collect interval> you allow libev to spend more	1031	By setting a higher I<io collect interval> you allow libev to spend more
773	time collecting I/O events, so you can handle more events per iteration,	1032	time collecting I/O events, so you can handle more events per iteration,
774	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1033	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
775	C<ev_timer>) will be not affected. Setting this to a non-null value will	1034	C<ev_timer>) will not be affected. Setting this to a non-null value will
776	introduce an additional C<ev_sleep ()> call into most loop iterations.	1035	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		1036	sleep time ensures that libev will not poll for I/O events more often then
		1037	once per this interval, on average (as long as the host time resolution is
		1038	good enough).
777		1039
778	Likewise, by setting a higher I<timeout collect interval> you allow libev	1040	Likewise, by setting a higher I<timeout collect interval> you allow libev
779	to spend more time collecting timeouts, at the expense of increased	1041	to spend more time collecting timeouts, at the expense of increased
780	latency/jitter/inexactness (the watcher callback will be called	1042	latency/jitter/inexactness (the watcher callback will be called
781	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1043	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
783		1045
784	Many (busy) programs can usually benefit by setting the I/O collect	1046	Many (busy) programs can usually benefit by setting the I/O collect
785	interval to a value near C<0.1> or so, which is often enough for	1047	interval to a value near C<0.1> or so, which is often enough for
786	interactive servers (of course not for games), likewise for timeouts. It	1048	interactive servers (of course not for games), likewise for timeouts. It
787	usually doesn't make much sense to set it to a lower value than C<0.01>,	1049	usually doesn't make much sense to set it to a lower value than C<0.01>,
788	as this approaches the timing granularity of most systems.	1050	as this approaches the timing granularity of most systems. Note that if
		1051	you do transactions with the outside world and you can't increase the
		1052	parallelity, then this setting will limit your transaction rate (if you
		1053	need to poll once per transaction and the I/O collect interval is 0.01,
		1054	then you can't do more than 100 transactions per second).
789		1055
790	Setting the I<timeout collect interval> can improve the opportunity for	1056	Setting the I<timeout collect interval> can improve the opportunity for
791	saving power, as the program will "bundle" timer callback invocations that	1057	saving power, as the program will "bundle" timer callback invocations that
792	are "near" in time together, by delaying some, thus reducing the number of	1058	are "near" in time together, by delaying some, thus reducing the number of
793	times the process sleeps and wakes up again. Another useful technique to	1059	times the process sleeps and wakes up again. Another useful technique to
794	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	1060	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
795	they fire on, say, one-second boundaries only.	1061	they fire on, say, one-second boundaries only.
796		1062
		1063	Example: we only need 0.1s timeout granularity, and we wish not to poll
		1064	more often than 100 times per second:
		1065
		1066	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		1067	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		1068
		1069	=item ev_invoke_pending (loop)
		1070
		1071	This call will simply invoke all pending watchers while resetting their
		1072	pending state. Normally, C<ev_run> does this automatically when required,
		1073	but when overriding the invoke callback this call comes handy. This
		1074	function can be invoked from a watcher - this can be useful for example
		1075	when you want to do some lengthy calculation and want to pass further
		1076	event handling to another thread (you still have to make sure only one
		1077	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1078
		1079	=item int ev_pending_count (loop)
		1080
		1081	Returns the number of pending watchers - zero indicates that no watchers
		1082	are pending.
		1083
		1084	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1085
		1086	This overrides the invoke pending functionality of the loop: Instead of
		1087	invoking all pending watchers when there are any, C<ev_run> will call
		1088	this callback instead. This is useful, for example, when you want to
		1089	invoke the actual watchers inside another context (another thread etc.).
		1090
		1091	If you want to reset the callback, use C<ev_invoke_pending> as new
		1092	callback.
		1093
		1094	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1095
		1096	Sometimes you want to share the same loop between multiple threads. This
		1097	can be done relatively simply by putting mutex_lock/unlock calls around
		1098	each call to a libev function.
		1099
		1100	However, C<ev_run> can run an indefinite time, so it is not feasible
		1101	to wait for it to return. One way around this is to wake up the event
		1102	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1103	I<release> and I<acquire> callbacks on the loop.
		1104
		1105	When set, then C<release> will be called just before the thread is
		1106	suspended waiting for new events, and C<acquire> is called just
		1107	afterwards.
		1108
		1109	Ideally, C<release> will just call your mutex_unlock function, and
		1110	C<acquire> will just call the mutex_lock function again.
		1111
		1112	While event loop modifications are allowed between invocations of
		1113	C<release> and C<acquire> (that's their only purpose after all), no
		1114	modifications done will affect the event loop, i.e. adding watchers will
		1115	have no effect on the set of file descriptors being watched, or the time
		1116	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1117	to take note of any changes you made.
		1118
		1119	In theory, threads executing C<ev_run> will be async-cancel safe between
		1120	invocations of C<release> and C<acquire>.
		1121
		1122	See also the locking example in the C<THREADS> section later in this
		1123	document.
		1124
		1125	=item ev_set_userdata (loop, void *data)
		1126
		1127	=item void *ev_userdata (loop)
		1128
		1129	Set and retrieve a single C<void *> associated with a loop. When
		1130	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1131	C<0>.
		1132
		1133	These two functions can be used to associate arbitrary data with a loop,
		1134	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1135	C<acquire> callbacks described above, but of course can be (ab-)used for
		1136	any other purpose as well.
		1137
797	=item ev_loop_verify (loop)	1138	=item ev_verify (loop)
798		1139
799	This function only does something when C<EV_VERIFY> support has been	1140	This function only does something when C<EV_VERIFY> support has been
800	compiled in, which is the default for non-minimal builds. It tries to go	1141	compiled in, which is the default for non-minimal builds. It tries to go
801	through all internal structures and checks them for validity. If anything	1142	through all internal structures and checks them for validity. If anything
802	is found to be inconsistent, it will print an error message to standard	1143	is found to be inconsistent, it will print an error message to standard
…		…
813		1154
814	In the following description, uppercase C<TYPE> in names stands for the	1155	In the following description, uppercase C<TYPE> in names stands for the
815	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1156	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
816	watchers and C<ev_io_start> for I/O watchers.	1157	watchers and C<ev_io_start> for I/O watchers.
817		1158
818	A watcher is a structure that you create and register to record your	1159	A watcher is an opaque structure that you allocate and register to record
819	interest in some event. For instance, if you want to wait for STDIN to	1160	your interest in some event. To make a concrete example, imagine you want
820	become readable, you would create an C<ev_io> watcher for that:	1161	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1162	for that:
821		1163
822	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1164	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
823	{	1165	{
824	ev_io_stop (w);	1166	ev_io_stop (w);
825	ev_unloop (loop, EVUNLOOP_ALL);	1167	ev_break (loop, EVBREAK_ALL);
826	}	1168	}
827		1169
828	struct ev_loop *loop = ev_default_loop (0);	1170	struct ev_loop *loop = ev_default_loop (0);
829		1171
830	ev_io stdin_watcher;	1172	ev_io stdin_watcher;
831		1173
832	ev_init (&stdin_watcher, my_cb);	1174	ev_init (&stdin_watcher, my_cb);
833	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1175	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
834	ev_io_start (loop, &stdin_watcher);	1176	ev_io_start (loop, &stdin_watcher);
835		1177
836	ev_loop (loop, 0);	1178	ev_run (loop, 0);
837		1179
838	As you can see, you are responsible for allocating the memory for your	1180	As you can see, you are responsible for allocating the memory for your
839	watcher structures (and it is I<usually> a bad idea to do this on the	1181	watcher structures (and it is I<usually> a bad idea to do this on the
840	stack).	1182	stack).
841		1183
842	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1184	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
843	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1185	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
844		1186
845	Each watcher structure must be initialised by a call to C<ev_init	1187	Each watcher structure must be initialised by a call to C<ev_init (watcher
846	(watcher *, callback)>, which expects a callback to be provided. This	1188	*, callback)>, which expects a callback to be provided. This callback is
847	callback gets invoked each time the event occurs (or, in the case of I/O	1189	invoked each time the event occurs (or, in the case of I/O watchers, each
848	watchers, each time the event loop detects that the file descriptor given	1190	time the event loop detects that the file descriptor given is readable
849	is readable and/or writable).	1191	and/or writable).
850		1192
851	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1193	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
852	macro to configure it, with arguments specific to the watcher type. There	1194	macro to configure it, with arguments specific to the watcher type. There
853	is also a macro to combine initialisation and setting in one call: C<<	1195	is also a macro to combine initialisation and setting in one call: C<<
854	ev_TYPE_init (watcher *, callback, ...) >>.	1196	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
877	=item C<EV_WRITE>	1219	=item C<EV_WRITE>
878		1220
879	The file descriptor in the C<ev_io> watcher has become readable and/or	1221	The file descriptor in the C<ev_io> watcher has become readable and/or
880	writable.	1222	writable.
881		1223
882	=item C<EV_TIMEOUT>	1224	=item C<EV_TIMER>
883		1225
884	The C<ev_timer> watcher has timed out.	1226	The C<ev_timer> watcher has timed out.
885		1227
886	=item C<EV_PERIODIC>	1228	=item C<EV_PERIODIC>
887		1229
…		…
905		1247
906	=item C<EV_PREPARE>	1248	=item C<EV_PREPARE>
907		1249
908	=item C<EV_CHECK>	1250	=item C<EV_CHECK>
909		1251
910	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1252	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
911	to gather new events, and all C<ev_check> watchers are invoked just after	1253	gather new events, and all C<ev_check> watchers are queued (not invoked)
912	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1254	just after C<ev_run> has gathered them, but before it queues any callbacks
		1255	for any received events. That means C<ev_prepare> watchers are the last
		1256	watchers invoked before the event loop sleeps or polls for new events, and
		1257	C<ev_check> watchers will be invoked before any other watchers of the same
		1258	or lower priority within an event loop iteration.
		1259
913	received events. Callbacks of both watcher types can start and stop as	1260	Callbacks of both watcher types can start and stop as many watchers as
914	many watchers as they want, and all of them will be taken into account	1261	they want, and all of them will be taken into account (for example, a
915	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1262	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
916	C<ev_loop> from blocking).	1263	blocking).
917		1264
918	=item C<EV_EMBED>	1265	=item C<EV_EMBED>
919		1266
920	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1267	The embedded event loop specified in the C<ev_embed> watcher needs attention.
921		1268
922	=item C<EV_FORK>	1269	=item C<EV_FORK>
923		1270
924	The event loop has been resumed in the child process after fork (see	1271	The event loop has been resumed in the child process after fork (see
925	C<ev_fork>).	1272	C<ev_fork>).
926		1273
		1274	=item C<EV_CLEANUP>
		1275
		1276	The event loop is about to be destroyed (see C<ev_cleanup>).
		1277
927	=item C<EV_ASYNC>	1278	=item C<EV_ASYNC>
928		1279
929	The given async watcher has been asynchronously notified (see C<ev_async>).	1280	The given async watcher has been asynchronously notified (see C<ev_async>).
		1281
		1282	=item C<EV_CUSTOM>
		1283
		1284	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1285	by libev users to signal watchers (e.g. via C<ev_feed_event>).
930		1286
931	=item C<EV_ERROR>	1287	=item C<EV_ERROR>
932		1288
933	An unspecified error has occurred, the watcher has been stopped. This might	1289	An unspecified error has occurred, the watcher has been stopped. This might
934	happen because the watcher could not be properly started because libev	1290	happen because the watcher could not be properly started because libev
…		…
972		1328
973	ev_io w;	1329	ev_io w;
974	ev_init (&w, my_cb);	1330	ev_init (&w, my_cb);
975	ev_io_set (&w, STDIN_FILENO, EV_READ);	1331	ev_io_set (&w, STDIN_FILENO, EV_READ);
976		1332
977	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1333	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
978		1334
979	This macro initialises the type-specific parts of a watcher. You need to	1335	This macro initialises the type-specific parts of a watcher. You need to
980	call C<ev_init> at least once before you call this macro, but you can	1336	call C<ev_init> at least once before you call this macro, but you can
981	call C<ev_TYPE_set> any number of times. You must not, however, call this	1337	call C<ev_TYPE_set> any number of times. You must not, however, call this
982	macro on a watcher that is active (it can be pending, however, which is a	1338	macro on a watcher that is active (it can be pending, however, which is a
…		…
995		1351
996	Example: Initialise and set an C<ev_io> watcher in one step.	1352	Example: Initialise and set an C<ev_io> watcher in one step.
997		1353
998	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1354	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
999		1355
1000	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1356	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1001		1357
1002	Starts (activates) the given watcher. Only active watchers will receive	1358	Starts (activates) the given watcher. Only active watchers will receive
1003	events. If the watcher is already active nothing will happen.	1359	events. If the watcher is already active nothing will happen.
1004		1360
1005	Example: Start the C<ev_io> watcher that is being abused as example in this	1361	Example: Start the C<ev_io> watcher that is being abused as example in this
1006	whole section.	1362	whole section.
1007		1363
1008	ev_io_start (EV_DEFAULT_UC, &w);	1364	ev_io_start (EV_DEFAULT_UC, &w);
1009		1365
1010	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1366	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1011		1367
1012	Stops the given watcher if active, and clears the pending status (whether	1368	Stops the given watcher if active, and clears the pending status (whether
1013	the watcher was active or not).	1369	the watcher was active or not).
1014		1370
1015	It is possible that stopped watchers are pending - for example,	1371	It is possible that stopped watchers are pending - for example,
…		…
1035		1391
1036	=item callback ev_cb (ev_TYPE *watcher)	1392	=item callback ev_cb (ev_TYPE *watcher)
1037		1393
1038	Returns the callback currently set on the watcher.	1394	Returns the callback currently set on the watcher.
1039		1395
1040	=item ev_cb_set (ev_TYPE *watcher, callback)	1396	=item ev_set_cb (ev_TYPE *watcher, callback)
1041		1397
1042	Change the callback. You can change the callback at virtually any time	1398	Change the callback. You can change the callback at virtually any time
1043	(modulo threads).	1399	(modulo threads).
1044		1400
1045	=item ev_set_priority (ev_TYPE *watcher, priority)	1401	=item ev_set_priority (ev_TYPE *watcher, int priority)
1046		1402
1047	=item int ev_priority (ev_TYPE *watcher)	1403	=item int ev_priority (ev_TYPE *watcher)
1048		1404
1049	Set and query the priority of the watcher. The priority is a small	1405	Set and query the priority of the watcher. The priority is a small
1050	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1406	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1051	(default: C<-2>). Pending watchers with higher priority will be invoked	1407	(default: C<-2>). Pending watchers with higher priority will be invoked
1052	before watchers with lower priority, but priority will not keep watchers	1408	before watchers with lower priority, but priority will not keep watchers
1053	from being executed (except for C<ev_idle> watchers).	1409	from being executed (except for C<ev_idle> watchers).
1054		1410
1055	This means that priorities are I<only> used for ordering callback
1056	invocation after new events have been received. This is useful, for
1057	example, to reduce latency after idling, or more often, to bind two
1058	watchers on the same event and make sure one is called first.
1059
1060	If you need to suppress invocation when higher priority events are pending	1411	If you need to suppress invocation when higher priority events are pending
1061	you need to look at C<ev_idle> watchers, which provide this functionality.	1412	you need to look at C<ev_idle> watchers, which provide this functionality.
1062		1413
1063	You I<must not> change the priority of a watcher as long as it is active or	1414	You I<must not> change the priority of a watcher as long as it is active or
1064	pending.	1415	pending.
1065
1066	The default priority used by watchers when no priority has been set is
1067	always C<0>, which is supposed to not be too high and not be too low :).
1068		1416
1069	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1417	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1070	fine, as long as you do not mind that the priority value you query might	1418	fine, as long as you do not mind that the priority value you query might
1071	or might not have been clamped to the valid range.	1419	or might not have been clamped to the valid range.
		1420
		1421	The default priority used by watchers when no priority has been set is
		1422	always C<0>, which is supposed to not be too high and not be too low :).
		1423
		1424	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1425	priorities.
1072		1426
1073	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1427	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1074		1428
1075	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1429	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1076	C<loop> nor C<revents> need to be valid as long as the watcher callback	1430	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1084	watcher isn't pending it does nothing and returns C<0>.	1438	watcher isn't pending it does nothing and returns C<0>.
1085		1439
1086	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1440	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1087	callback to be invoked, which can be accomplished with this function.	1441	callback to be invoked, which can be accomplished with this function.
1088		1442
		1443	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1444
		1445	Feeds the given event set into the event loop, as if the specified event
		1446	had happened for the specified watcher (which must be a pointer to an
		1447	initialised but not necessarily started event watcher). Obviously you must
		1448	not free the watcher as long as it has pending events.
		1449
		1450	Stopping the watcher, letting libev invoke it, or calling
		1451	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1452	not started in the first place.
		1453
		1454	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1455	functions that do not need a watcher.
		1456
1089	=back	1457	=back
1090		1458
		1459	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1460	OWN COMPOSITE WATCHERS> idioms.
1091		1461
1092	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1462	=head2 WATCHER STATES
1093		1463
1094	Each watcher has, by default, a member C<void *data> that you can change	1464	There are various watcher states mentioned throughout this manual -
1095	and read at any time: libev will completely ignore it. This can be used	1465	active, pending and so on. In this section these states and the rules to
1096	to associate arbitrary data with your watcher. If you need more data and	1466	transition between them will be described in more detail - and while these
1097	don't want to allocate memory and store a pointer to it in that data	1467	rules might look complicated, they usually do "the right thing".
1098	member, you can also "subclass" the watcher type and provide your own
1099	data:
1100		1468
1101	struct my_io	1469	=over 4
		1470
		1471	=item initialised
		1472
		1473	Before a watcher can be registered with the event loop it has to be
		1474	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1475	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1476
		1477	In this state it is simply some block of memory that is suitable for
		1478	use in an event loop. It can be moved around, freed, reused etc. at
		1479	will - as long as you either keep the memory contents intact, or call
		1480	C<ev_TYPE_init> again.
		1481
		1482	=item started/running/active
		1483
		1484	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1485	property of the event loop, and is actively waiting for events. While in
		1486	this state it cannot be accessed (except in a few documented ways), moved,
		1487	freed or anything else - the only legal thing is to keep a pointer to it,
		1488	and call libev functions on it that are documented to work on active watchers.
		1489
		1490	=item pending
		1491
		1492	If a watcher is active and libev determines that an event it is interested
		1493	in has occurred (such as a timer expiring), it will become pending. It will
		1494	stay in this pending state until either it is stopped or its callback is
		1495	about to be invoked, so it is not normally pending inside the watcher
		1496	callback.
		1497
		1498	The watcher might or might not be active while it is pending (for example,
		1499	an expired non-repeating timer can be pending but no longer active). If it
		1500	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1501	but it is still property of the event loop at this time, so cannot be
		1502	moved, freed or reused. And if it is active the rules described in the
		1503	previous item still apply.
		1504
		1505	It is also possible to feed an event on a watcher that is not active (e.g.
		1506	via C<ev_feed_event>), in which case it becomes pending without being
		1507	active.
		1508
		1509	=item stopped
		1510
		1511	A watcher can be stopped implicitly by libev (in which case it might still
		1512	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1513	latter will clear any pending state the watcher might be in, regardless
		1514	of whether it was active or not, so stopping a watcher explicitly before
		1515	freeing it is often a good idea.
		1516
		1517	While stopped (and not pending) the watcher is essentially in the
		1518	initialised state, that is, it can be reused, moved, modified in any way
		1519	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1520	it again).
		1521
		1522	=back
		1523
		1524	=head2 WATCHER PRIORITY MODELS
		1525
		1526	Many event loops support I<watcher priorities>, which are usually small
		1527	integers that influence the ordering of event callback invocation
		1528	between watchers in some way, all else being equal.
		1529
		1530	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1531	description for the more technical details such as the actual priority
		1532	range.
		1533
		1534	There are two common ways how these these priorities are being interpreted
		1535	by event loops:
		1536
		1537	In the more common lock-out model, higher priorities "lock out" invocation
		1538	of lower priority watchers, which means as long as higher priority
		1539	watchers receive events, lower priority watchers are not being invoked.
		1540
		1541	The less common only-for-ordering model uses priorities solely to order
		1542	callback invocation within a single event loop iteration: Higher priority
		1543	watchers are invoked before lower priority ones, but they all get invoked
		1544	before polling for new events.
		1545
		1546	Libev uses the second (only-for-ordering) model for all its watchers
		1547	except for idle watchers (which use the lock-out model).
		1548
		1549	The rationale behind this is that implementing the lock-out model for
		1550	watchers is not well supported by most kernel interfaces, and most event
		1551	libraries will just poll for the same events again and again as long as
		1552	their callbacks have not been executed, which is very inefficient in the
		1553	common case of one high-priority watcher locking out a mass of lower
		1554	priority ones.
		1555
		1556	Static (ordering) priorities are most useful when you have two or more
		1557	watchers handling the same resource: a typical usage example is having an
		1558	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1559	timeouts. Under load, data might be received while the program handles
		1560	other jobs, but since timers normally get invoked first, the timeout
		1561	handler will be executed before checking for data. In that case, giving
		1562	the timer a lower priority than the I/O watcher ensures that I/O will be
		1563	handled first even under adverse conditions (which is usually, but not
		1564	always, what you want).
		1565
		1566	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1567	will only be executed when no same or higher priority watchers have
		1568	received events, they can be used to implement the "lock-out" model when
		1569	required.
		1570
		1571	For example, to emulate how many other event libraries handle priorities,
		1572	you can associate an C<ev_idle> watcher to each such watcher, and in
		1573	the normal watcher callback, you just start the idle watcher. The real
		1574	processing is done in the idle watcher callback. This causes libev to
		1575	continuously poll and process kernel event data for the watcher, but when
		1576	the lock-out case is known to be rare (which in turn is rare :), this is
		1577	workable.
		1578
		1579	Usually, however, the lock-out model implemented that way will perform
		1580	miserably under the type of load it was designed to handle. In that case,
		1581	it might be preferable to stop the real watcher before starting the
		1582	idle watcher, so the kernel will not have to process the event in case
		1583	the actual processing will be delayed for considerable time.
		1584
		1585	Here is an example of an I/O watcher that should run at a strictly lower
		1586	priority than the default, and which should only process data when no
		1587	other events are pending:
		1588
		1589	ev_idle idle; // actual processing watcher
		1590	ev_io io; // actual event watcher
		1591
		1592	static void
		1593	io_cb (EV_P_ ev_io *w, int revents)
1102	{	1594	{
1103	ev_io io;	1595	// stop the I/O watcher, we received the event, but
1104	int otherfd;	1596	// are not yet ready to handle it.
1105	void *somedata;	1597	ev_io_stop (EV_A_ w);
1106	struct whatever *mostinteresting;	1598
		1599	// start the idle watcher to handle the actual event.
		1600	// it will not be executed as long as other watchers
		1601	// with the default priority are receiving events.
		1602	ev_idle_start (EV_A_ &idle);
1107	};	1603	}
1108		1604
1109	...	1605	static void
1110	struct my_io w;	1606	idle_cb (EV_P_ ev_idle *w, int revents)
1111	ev_io_init (&w.io, my_cb, fd, EV_READ);
1112
1113	And since your callback will be called with a pointer to the watcher, you
1114	can cast it back to your own type:
1115
1116	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1117	{	1607	{
1118	struct my_io *w = (struct my_io *)w_;	1608	// actual processing
1119	...	1609	read (STDIN_FILENO, ...);
		1610
		1611	// have to start the I/O watcher again, as
		1612	// we have handled the event
		1613	ev_io_start (EV_P_ &io);
1120	}	1614	}
1121		1615
1122	More interesting and less C-conformant ways of casting your callback type	1616	// initialisation
1123	instead have been omitted.	1617	ev_idle_init (&idle, idle_cb);
		1618	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1619	ev_io_start (EV_DEFAULT_ &io);
1124		1620
1125	Another common scenario is to use some data structure with multiple	1621	In the "real" world, it might also be beneficial to start a timer, so that
1126	embedded watchers:	1622	low-priority connections can not be locked out forever under load. This
1127		1623	enables your program to keep a lower latency for important connections
1128	struct my_biggy	1624	during short periods of high load, while not completely locking out less
1129	{	1625	important ones.
1130	int some_data;
1131	ev_timer t1;
1132	ev_timer t2;
1133	}
1134
1135	In this case getting the pointer to C<my_biggy> is a bit more
1136	complicated: Either you store the address of your C<my_biggy> struct
1137	in the C<data> member of the watcher (for woozies), or you need to use
1138	some pointer arithmetic using C<offsetof> inside your watchers (for real
1139	programmers):
1140
1141	#include <stddef.h>
1142
1143	static void
1144	t1_cb (EV_P_ ev_timer *w, int revents)
1145	{
1146	struct my_biggy big = (struct my_biggy *
1147	(((char *)w) - offsetof (struct my_biggy, t1));
1148	}
1149
1150	static void
1151	t2_cb (EV_P_ ev_timer *w, int revents)
1152	{
1153	struct my_biggy big = (struct my_biggy *
1154	(((char *)w) - offsetof (struct my_biggy, t2));
1155	}
1156		1626
1157		1627
1158	=head1 WATCHER TYPES	1628	=head1 WATCHER TYPES
1159		1629
1160	This section describes each watcher in detail, but will not repeat	1630	This section describes each watcher in detail, but will not repeat
…		…
1184	In general you can register as many read and/or write event watchers per	1654	In general you can register as many read and/or write event watchers per
1185	fd as you want (as long as you don't confuse yourself). Setting all file	1655	fd as you want (as long as you don't confuse yourself). Setting all file
1186	descriptors to non-blocking mode is also usually a good idea (but not	1656	descriptors to non-blocking mode is also usually a good idea (but not
1187	required if you know what you are doing).	1657	required if you know what you are doing).
1188		1658
1189	If you cannot use non-blocking mode, then force the use of a
1190	known-to-be-good backend (at the time of this writing, this includes only
1191	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1192
1193	Another thing you have to watch out for is that it is quite easy to	1659	Another thing you have to watch out for is that it is quite easy to
1194	receive "spurious" readiness notifications, that is your callback might	1660	receive "spurious" readiness notifications, that is, your callback might
1195	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1661	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1196	because there is no data. Not only are some backends known to create a	1662	because there is no data. It is very easy to get into this situation even
1197	lot of those (for example Solaris ports), it is very easy to get into	1663	with a relatively standard program structure. Thus it is best to always
1198	this situation even with a relatively standard program structure. Thus	1664	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1199	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1200	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1665	preferable to a program hanging until some data arrives.
1201		1666
1202	If you cannot run the fd in non-blocking mode (for example you should	1667	If you cannot run the fd in non-blocking mode (for example you should
1203	not play around with an Xlib connection), then you have to separately	1668	not play around with an Xlib connection), then you have to separately
1204	re-test whether a file descriptor is really ready with a known-to-be good	1669	re-test whether a file descriptor is really ready with a known-to-be good
1205	interface such as poll (fortunately in our Xlib example, Xlib already	1670	interface such as poll (fortunately in the case of Xlib, it already does
1206	does this on its own, so its quite safe to use). Some people additionally	1671	this on its own, so its quite safe to use). Some people additionally
1207	use C<SIGALRM> and an interval timer, just to be sure you won't block	1672	use C<SIGALRM> and an interval timer, just to be sure you won't block
1208	indefinitely.	1673	indefinitely.
1209		1674
1210	But really, best use non-blocking mode.	1675	But really, best use non-blocking mode.
1211		1676
1212	=head3 The special problem of disappearing file descriptors	1677	=head3 The special problem of disappearing file descriptors
1213		1678
1214	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1679	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1215	descriptor (either due to calling C<close> explicitly or any other means,	1680	a file descriptor (either due to calling C<close> explicitly or any other
1216	such as C<dup2>). The reason is that you register interest in some file	1681	means, such as C<dup2>). The reason is that you register interest in some
1217	descriptor, but when it goes away, the operating system will silently drop	1682	file descriptor, but when it goes away, the operating system will silently
1218	this interest. If another file descriptor with the same number then is	1683	drop this interest. If another file descriptor with the same number then
1219	registered with libev, there is no efficient way to see that this is, in	1684	is registered with libev, there is no efficient way to see that this is,
1220	fact, a different file descriptor.	1685	in fact, a different file descriptor.
1221		1686
1222	To avoid having to explicitly tell libev about such cases, libev follows	1687	To avoid having to explicitly tell libev about such cases, libev follows
1223	the following policy: Each time C<ev_io_set> is being called, libev	1688	the following policy: Each time C<ev_io_set> is being called, libev
1224	will assume that this is potentially a new file descriptor, otherwise	1689	will assume that this is potentially a new file descriptor, otherwise
1225	it is assumed that the file descriptor stays the same. That means that	1690	it is assumed that the file descriptor stays the same. That means that
…		…
1239		1704
1240	There is no workaround possible except not registering events	1705	There is no workaround possible except not registering events
1241	for potentially C<dup ()>'ed file descriptors, or to resort to	1706	for potentially C<dup ()>'ed file descriptors, or to resort to
1242	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1707	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1243		1708
		1709	=head3 The special problem of files
		1710
		1711	Many people try to use C<select> (or libev) on file descriptors
		1712	representing files, and expect it to become ready when their program
		1713	doesn't block on disk accesses (which can take a long time on their own).
		1714
		1715	However, this cannot ever work in the "expected" way - you get a readiness
		1716	notification as soon as the kernel knows whether and how much data is
		1717	there, and in the case of open files, that's always the case, so you
		1718	always get a readiness notification instantly, and your read (or possibly
		1719	write) will still block on the disk I/O.
		1720
		1721	Another way to view it is that in the case of sockets, pipes, character
		1722	devices and so on, there is another party (the sender) that delivers data
		1723	on its own, but in the case of files, there is no such thing: the disk
		1724	will not send data on its own, simply because it doesn't know what you
		1725	wish to read - you would first have to request some data.
		1726
		1727	Since files are typically not-so-well supported by advanced notification
		1728	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1729	to files, even though you should not use it. The reason for this is
		1730	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1731	usually a tty, often a pipe, but also sometimes files or special devices
		1732	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1733	F</dev/urandom>), and even though the file might better be served with
		1734	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1735	it "just works" instead of freezing.
		1736
		1737	So avoid file descriptors pointing to files when you know it (e.g. use
		1738	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1739	when you rarely read from a file instead of from a socket, and want to
		1740	reuse the same code path.
		1741
1244	=head3 The special problem of fork	1742	=head3 The special problem of fork
1245		1743
1246	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1744	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1247	useless behaviour. Libev fully supports fork, but needs to be told about	1745	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1248	it in the child.	1746	to be told about it in the child if you want to continue to use it in the
		1747	child.
1249		1748
1250	To support fork in your programs, you either have to call	1749	To support fork in your child processes, you have to call C<ev_loop_fork
1251	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1750	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1252	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1751	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1253	C<EVBACKEND_POLL>.
1254		1752
1255	=head3 The special problem of SIGPIPE	1753	=head3 The special problem of SIGPIPE
1256		1754
1257	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1755	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1258	when writing to a pipe whose other end has been closed, your program gets	1756	when writing to a pipe whose other end has been closed, your program gets
…		…
1261		1759
1262	So when you encounter spurious, unexplained daemon exits, make sure you	1760	So when you encounter spurious, unexplained daemon exits, make sure you
1263	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1761	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1264	somewhere, as that would have given you a big clue).	1762	somewhere, as that would have given you a big clue).
1265		1763
		1764	=head3 The special problem of accept()ing when you can't
		1765
		1766	Many implementations of the POSIX C<accept> function (for example,
		1767	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1768	connection from the pending queue in all error cases.
		1769
		1770	For example, larger servers often run out of file descriptors (because
		1771	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1772	rejecting the connection, leading to libev signalling readiness on
		1773	the next iteration again (the connection still exists after all), and
		1774	typically causing the program to loop at 100% CPU usage.
		1775
		1776	Unfortunately, the set of errors that cause this issue differs between
		1777	operating systems, there is usually little the app can do to remedy the
		1778	situation, and no known thread-safe method of removing the connection to
		1779	cope with overload is known (to me).
		1780
		1781	One of the easiest ways to handle this situation is to just ignore it
		1782	- when the program encounters an overload, it will just loop until the
		1783	situation is over. While this is a form of busy waiting, no OS offers an
		1784	event-based way to handle this situation, so it's the best one can do.
		1785
		1786	A better way to handle the situation is to log any errors other than
		1787	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1788	messages, and continue as usual, which at least gives the user an idea of
		1789	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1790	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1791	usage.
		1792
		1793	If your program is single-threaded, then you could also keep a dummy file
		1794	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1795	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1796	close that fd, and create a new dummy fd. This will gracefully refuse
		1797	clients under typical overload conditions.
		1798
		1799	The last way to handle it is to simply log the error and C<exit>, as
		1800	is often done with C<malloc> failures, but this results in an easy
		1801	opportunity for a DoS attack.
1266		1802
1267	=head3 Watcher-Specific Functions	1803	=head3 Watcher-Specific Functions
1268		1804
1269	=over 4	1805	=over 4
1270		1806
…		…
1302	...	1838	...
1303	struct ev_loop *loop = ev_default_init (0);	1839	struct ev_loop *loop = ev_default_init (0);
1304	ev_io stdin_readable;	1840	ev_io stdin_readable;
1305	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1841	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1306	ev_io_start (loop, &stdin_readable);	1842	ev_io_start (loop, &stdin_readable);
1307	ev_loop (loop, 0);	1843	ev_run (loop, 0);
1308		1844
1309		1845
1310	=head2 C<ev_timer> - relative and optionally repeating timeouts	1846	=head2 C<ev_timer> - relative and optionally repeating timeouts
1311		1847
1312	Timer watchers are simple relative timers that generate an event after a	1848	Timer watchers are simple relative timers that generate an event after a
…		…
1317	year, it will still time out after (roughly) one hour. "Roughly" because	1853	year, it will still time out after (roughly) one hour. "Roughly" because
1318	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1854	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1319	monotonic clock option helps a lot here).	1855	monotonic clock option helps a lot here).
1320		1856
1321	The callback is guaranteed to be invoked only I<after> its timeout has	1857	The callback is guaranteed to be invoked only I<after> its timeout has
1322	passed, but if multiple timers become ready during the same loop iteration	1858	passed (not I<at>, so on systems with very low-resolution clocks this
1323	then order of execution is undefined.	1859	might introduce a small delay, see "the special problem of being too
		1860	early", below). If multiple timers become ready during the same loop
		1861	iteration then the ones with earlier time-out values are invoked before
		1862	ones of the same priority with later time-out values (but this is no
		1863	longer true when a callback calls C<ev_run> recursively).
1324		1864
1325	=head3 Be smart about timeouts	1865	=head3 Be smart about timeouts
1326		1866
1327	Many real-world problems involve some kind of timeout, usually for error	1867	Many real-world problems involve some kind of timeout, usually for error
1328	recovery. A typical example is an HTTP request - if the other side hangs,	1868	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1372	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1912	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1373	member and C<ev_timer_again>.	1913	member and C<ev_timer_again>.
1374		1914
1375	At start:	1915	At start:
1376		1916
1377	ev_timer_init (timer, callback);	1917	ev_init (timer, callback);
1378	timer->repeat = 60.;	1918	timer->repeat = 60.;
1379	ev_timer_again (loop, timer);	1919	ev_timer_again (loop, timer);
1380		1920
1381	Each time there is some activity:	1921	Each time there is some activity:
1382		1922
…		…
1403		1943
1404	In this case, it would be more efficient to leave the C<ev_timer> alone,	1944	In this case, it would be more efficient to leave the C<ev_timer> alone,
1405	but remember the time of last activity, and check for a real timeout only	1945	but remember the time of last activity, and check for a real timeout only
1406	within the callback:	1946	within the callback:
1407		1947
		1948	ev_tstamp timeout = 60.;
1408	ev_tstamp last_activity; // time of last activity	1949	ev_tstamp last_activity; // time of last activity
		1950	ev_timer timer;
1409		1951
1410	static void	1952	static void
1411	callback (EV_P_ ev_timer *w, int revents)	1953	callback (EV_P_ ev_timer *w, int revents)
1412	{	1954	{
1413	ev_tstamp now = ev_now (EV_A);	1955	// calculate when the timeout would happen
1414	ev_tstamp timeout = last_activity + 60.;	1956	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1415		1957
1416	// if last_activity + 60. is older than now, we did time out	1958	// if negative, it means we the timeout already occurred
1417	if (timeout < now)	1959	if (after < 0.)
1418	{	1960	{
1419	// timeout occured, take action	1961	// timeout occurred, take action
1420	}	1962	}
1421	else	1963	else
1422	{	1964	{
1423	// callback was invoked, but there was some activity, re-arm	1965	// callback was invoked, but there was some recent
1424	// the watcher to fire in last_activity + 60, which is	1966	// activity. simply restart the timer to time out
1425	// guaranteed to be in the future, so "again" is positive:	1967	// after "after" seconds, which is the earliest time
1426	w->repeat = timeout - now;	1968	// the timeout can occur.
		1969	ev_timer_set (w, after, 0.);
1427	ev_timer_again (EV_A_ w);	1970	ev_timer_start (EV_A_ w);
1428	}	1971	}
1429	}	1972	}
1430		1973
1431	To summarise the callback: first calculate the real timeout (defined	1974	To summarise the callback: first calculate in how many seconds the
1432	as "60 seconds after the last activity"), then check if that time has	1975	timeout will occur (by calculating the absolute time when it would occur,
1433	been reached, which means something I<did>, in fact, time out. Otherwise	1976	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1434	the callback was invoked too early (C<timeout> is in the future), so	1977	(EV_A)> from that).
1435	re-schedule the timer to fire at that future time, to see if maybe we have
1436	a timeout then.
1437		1978
1438	Note how C<ev_timer_again> is used, taking advantage of the	1979	If this value is negative, then we are already past the timeout, i.e. we
1439	C<ev_timer_again> optimisation when the timer is already running.	1980	timed out, and need to do whatever is needed in this case.
		1981
		1982	Otherwise, we now the earliest time at which the timeout would trigger,
		1983	and simply start the timer with this timeout value.
		1984
		1985	In other words, each time the callback is invoked it will check whether
		1986	the timeout occurred. If not, it will simply reschedule itself to check
		1987	again at the earliest time it could time out. Rinse. Repeat.
1440		1988
1441	This scheme causes more callback invocations (about one every 60 seconds	1989	This scheme causes more callback invocations (about one every 60 seconds
1442	minus half the average time between activity), but virtually no calls to	1990	minus half the average time between activity), but virtually no calls to
1443	libev to change the timeout.	1991	libev to change the timeout.
1444		1992
1445	To start the timer, simply initialise the watcher and set C<last_activity>	1993	To start the machinery, simply initialise the watcher and set
1446	to the current time (meaning we just have some activity :), then call the	1994	C<last_activity> to the current time (meaning there was some activity just
1447	callback, which will "do the right thing" and start the timer:	1995	now), then call the callback, which will "do the right thing" and start
		1996	the timer:
1448		1997
		1998	last_activity = ev_now (EV_A);
1449	ev_timer_init (timer, callback);	1999	ev_init (&timer, callback);
1450	last_activity = ev_now (loop);	2000	callback (EV_A_ &timer, 0);
1451	callback (loop, timer, EV_TIMEOUT);
1452		2001
1453	And when there is some activity, simply store the current time in	2002	When there is some activity, simply store the current time in
1454	C<last_activity>, no libev calls at all:	2003	C<last_activity>, no libev calls at all:
1455		2004
		2005	if (activity detected)
1456	last_actiivty = ev_now (loop);	2006	last_activity = ev_now (EV_A);
		2007
		2008	When your timeout value changes, then the timeout can be changed by simply
		2009	providing a new value, stopping the timer and calling the callback, which
		2010	will again do the right thing (for example, time out immediately :).
		2011
		2012	timeout = new_value;
		2013	ev_timer_stop (EV_A_ &timer);
		2014	callback (EV_A_ &timer, 0);
1457		2015
1458	This technique is slightly more complex, but in most cases where the	2016	This technique is slightly more complex, but in most cases where the
1459	time-out is unlikely to be triggered, much more efficient.	2017	time-out is unlikely to be triggered, much more efficient.
1460
1461	Changing the timeout is trivial as well (if it isn't hard-coded in the
1462	callback :) - just change the timeout and invoke the callback, which will
1463	fix things for you.
1464		2018
1465	=item 4. Wee, just use a double-linked list for your timeouts.	2019	=item 4. Wee, just use a double-linked list for your timeouts.
1466		2020
1467	If there is not one request, but many thousands (millions...), all	2021	If there is not one request, but many thousands (millions...), all
1468	employing some kind of timeout with the same timeout value, then one can	2022	employing some kind of timeout with the same timeout value, then one can
…		…
1495	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2049	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1496	rather complicated, but extremely efficient, something that really pays	2050	rather complicated, but extremely efficient, something that really pays
1497	off after the first million or so of active timers, i.e. it's usually	2051	off after the first million or so of active timers, i.e. it's usually
1498	overkill :)	2052	overkill :)
1499		2053
		2054	=head3 The special problem of being too early
		2055
		2056	If you ask a timer to call your callback after three seconds, then
		2057	you expect it to be invoked after three seconds - but of course, this
		2058	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2059	guaranteed to any precision by libev - imagine somebody suspending the
		2060	process with a STOP signal for a few hours for example.
		2061
		2062	So, libev tries to invoke your callback as soon as possible I<after> the
		2063	delay has occurred, but cannot guarantee this.
		2064
		2065	A less obvious failure mode is calling your callback too early: many event
		2066	loops compare timestamps with a "elapsed delay >= requested delay", but
		2067	this can cause your callback to be invoked much earlier than you would
		2068	expect.
		2069
		2070	To see why, imagine a system with a clock that only offers full second
		2071	resolution (think windows if you can't come up with a broken enough OS
		2072	yourself). If you schedule a one-second timer at the time 500.9, then the
		2073	event loop will schedule your timeout to elapse at a system time of 500
		2074	(500.9 truncated to the resolution) + 1, or 501.
		2075
		2076	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2077	501" and invoke the callback 0.1s after it was started, even though a
		2078	one-second delay was requested - this is being "too early", despite best
		2079	intentions.
		2080
		2081	This is the reason why libev will never invoke the callback if the elapsed
		2082	delay equals the requested delay, but only when the elapsed delay is
		2083	larger than the requested delay. In the example above, libev would only invoke
		2084	the callback at system time 502, or 1.1s after the timer was started.
		2085
		2086	So, while libev cannot guarantee that your callback will be invoked
		2087	exactly when requested, it I<can> and I<does> guarantee that the requested
		2088	delay has actually elapsed, or in other words, it always errs on the "too
		2089	late" side of things.
		2090
1500	=head3 The special problem of time updates	2091	=head3 The special problem of time updates
1501		2092
1502	Establishing the current time is a costly operation (it usually takes at	2093	Establishing the current time is a costly operation (it usually takes
1503	least two system calls): EV therefore updates its idea of the current	2094	at least one system call): EV therefore updates its idea of the current
1504	time only before and after C<ev_loop> collects new events, which causes a	2095	time only before and after C<ev_run> collects new events, which causes a
1505	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2096	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1506	lots of events in one iteration.	2097	lots of events in one iteration.
1507		2098
1508	The relative timeouts are calculated relative to the C<ev_now ()>	2099	The relative timeouts are calculated relative to the C<ev_now ()>
1509	time. This is usually the right thing as this timestamp refers to the time	2100	time. This is usually the right thing as this timestamp refers to the time
1510	of the event triggering whatever timeout you are modifying/starting. If	2101	of the event triggering whatever timeout you are modifying/starting. If
1511	you suspect event processing to be delayed and you I<need> to base the	2102	you suspect event processing to be delayed and you I<need> to base the
1512	timeout on the current time, use something like this to adjust for this:	2103	timeout on the current time, use something like the following to adjust
		2104	for it:
1513		2105
1514	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2106	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1515		2107
1516	If the event loop is suspended for a long time, you can also force an	2108	If the event loop is suspended for a long time, you can also force an
1517	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2109	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1518	()>.	2110	()>, although that will push the event time of all outstanding events
		2111	further into the future.
		2112
		2113	=head3 The special problem of unsynchronised clocks
		2114
		2115	Modern systems have a variety of clocks - libev itself uses the normal
		2116	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2117	jumps).
		2118
		2119	Neither of these clocks is synchronised with each other or any other clock
		2120	on the system, so C<ev_time ()> might return a considerably different time
		2121	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2122	a call to C<gettimeofday> might return a second count that is one higher
		2123	than a directly following call to C<time>.
		2124
		2125	The moral of this is to only compare libev-related timestamps with
		2126	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2127	a second or so.
		2128
		2129	One more problem arises due to this lack of synchronisation: if libev uses
		2130	the system monotonic clock and you compare timestamps from C<ev_time>
		2131	or C<ev_now> from when you started your timer and when your callback is
		2132	invoked, you will find that sometimes the callback is a bit "early".
		2133
		2134	This is because C<ev_timer>s work in real time, not wall clock time, so
		2135	libev makes sure your callback is not invoked before the delay happened,
		2136	I<measured according to the real time>, not the system clock.
		2137
		2138	If your timeouts are based on a physical timescale (e.g. "time out this
		2139	connection after 100 seconds") then this shouldn't bother you as it is
		2140	exactly the right behaviour.
		2141
		2142	If you want to compare wall clock/system timestamps to your timers, then
		2143	you need to use C<ev_periodic>s, as these are based on the wall clock
		2144	time, where your comparisons will always generate correct results.
		2145
		2146	=head3 The special problems of suspended animation
		2147
		2148	When you leave the server world it is quite customary to hit machines that
		2149	can suspend/hibernate - what happens to the clocks during such a suspend?
		2150
		2151	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2152	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2153	to run until the system is suspended, but they will not advance while the
		2154	system is suspended. That means, on resume, it will be as if the program
		2155	was frozen for a few seconds, but the suspend time will not be counted
		2156	towards C<ev_timer> when a monotonic clock source is used. The real time
		2157	clock advanced as expected, but if it is used as sole clocksource, then a
		2158	long suspend would be detected as a time jump by libev, and timers would
		2159	be adjusted accordingly.
		2160
		2161	I would not be surprised to see different behaviour in different between
		2162	operating systems, OS versions or even different hardware.
		2163
		2164	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2165	time jump in the monotonic clocks and the realtime clock. If the program
		2166	is suspended for a very long time, and monotonic clock sources are in use,
		2167	then you can expect C<ev_timer>s to expire as the full suspension time
		2168	will be counted towards the timers. When no monotonic clock source is in
		2169	use, then libev will again assume a timejump and adjust accordingly.
		2170
		2171	It might be beneficial for this latter case to call C<ev_suspend>
		2172	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2173	deterministic behaviour in this case (you can do nothing against
		2174	C<SIGSTOP>).
1519		2175
1520	=head3 Watcher-Specific Functions and Data Members	2176	=head3 Watcher-Specific Functions and Data Members
1521		2177
1522	=over 4	2178	=over 4
1523		2179
1524	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2180	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1525		2181
1526	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2182	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1527		2183
1528	Configure the timer to trigger after C<after> seconds. If C<repeat>	2184	Configure the timer to trigger after C<after> seconds (fractional and
1529	is C<0.>, then it will automatically be stopped once the timeout is	2185	negative values are supported). If C<repeat> is C<0.>, then it will
1530	reached. If it is positive, then the timer will automatically be	2186	automatically be stopped once the timeout is reached. If it is positive,
1531	configured to trigger again C<repeat> seconds later, again, and again,	2187	then the timer will automatically be configured to trigger again C<repeat>
1532	until stopped manually.	2188	seconds later, again, and again, until stopped manually.
1533		2189
1534	The timer itself will do a best-effort at avoiding drift, that is, if	2190	The timer itself will do a best-effort at avoiding drift, that is, if
1535	you configure a timer to trigger every 10 seconds, then it will normally	2191	you configure a timer to trigger every 10 seconds, then it will normally
1536	trigger at exactly 10 second intervals. If, however, your program cannot	2192	trigger at exactly 10 second intervals. If, however, your program cannot
1537	keep up with the timer (because it takes longer than those 10 seconds to	2193	keep up with the timer (because it takes longer than those 10 seconds to
1538	do stuff) the timer will not fire more than once per event loop iteration.	2194	do stuff) the timer will not fire more than once per event loop iteration.
1539		2195
1540	=item ev_timer_again (loop, ev_timer *)	2196	=item ev_timer_again (loop, ev_timer *)
1541		2197
1542	This will act as if the timer timed out and restart it again if it is	2198	This will act as if the timer timed out, and restarts it again if it is
1543	repeating. The exact semantics are:	2199	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2200	timeout to the C<repeat> value and calling C<ev_timer_start>.
1544		2201
		2202	The exact semantics are as in the following rules, all of which will be
		2203	applied to the watcher:
		2204
		2205	=over 4
		2206
1545	If the timer is pending, its pending status is cleared.	2207	=item If the timer is pending, the pending status is always cleared.
1546		2208
1547	If the timer is started but non-repeating, stop it (as if it timed out).	2209	=item If the timer is started but non-repeating, stop it (as if it timed
		2210	out, without invoking it).
1548		2211
1549	If the timer is repeating, either start it if necessary (with the	2212	=item If the timer is repeating, make the C<repeat> value the new timeout
1550	C<repeat> value), or reset the running timer to the C<repeat> value.	2213	and start the timer, if necessary.
1551		2214
		2215	=back
		2216
1552	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2217	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1553	usage example.	2218	usage example.
		2219
		2220	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2221
		2222	Returns the remaining time until a timer fires. If the timer is active,
		2223	then this time is relative to the current event loop time, otherwise it's
		2224	the timeout value currently configured.
		2225
		2226	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2227	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2228	will return C<4>. When the timer expires and is restarted, it will return
		2229	roughly C<7> (likely slightly less as callback invocation takes some time,
		2230	too), and so on.
1554		2231
1555	=item ev_tstamp repeat [read-write]	2232	=item ev_tstamp repeat [read-write]
1556		2233
1557	The current C<repeat> value. Will be used each time the watcher times out	2234	The current C<repeat> value. Will be used each time the watcher times out
1558	or C<ev_timer_again> is called, and determines the next timeout (if any),	2235	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1584	}	2261	}
1585		2262
1586	ev_timer mytimer;	2263	ev_timer mytimer;
1587	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2264	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1588	ev_timer_again (&mytimer); /* start timer */	2265	ev_timer_again (&mytimer); /* start timer */
1589	ev_loop (loop, 0);	2266	ev_run (loop, 0);
1590		2267
1591	// and in some piece of code that gets executed on any "activity":	2268	// and in some piece of code that gets executed on any "activity":
1592	// reset the timeout to start ticking again at 10 seconds	2269	// reset the timeout to start ticking again at 10 seconds
1593	ev_timer_again (&mytimer);	2270	ev_timer_again (&mytimer);
1594		2271
…		…
1596	=head2 C<ev_periodic> - to cron or not to cron?	2273	=head2 C<ev_periodic> - to cron or not to cron?
1597		2274
1598	Periodic watchers are also timers of a kind, but they are very versatile	2275	Periodic watchers are also timers of a kind, but they are very versatile
1599	(and unfortunately a bit complex).	2276	(and unfortunately a bit complex).
1600		2277
1601	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2278	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1602	but on wall clock time (absolute time). You can tell a periodic watcher	2279	relative time, the physical time that passes) but on wall clock time
1603	to trigger after some specific point in time. For example, if you tell a	2280	(absolute time, the thing you can read on your calendar or clock). The
1604	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2281	difference is that wall clock time can run faster or slower than real
1605	+ 10.>, that is, an absolute time not a delay) and then reset your system	2282	time, and time jumps are not uncommon (e.g. when you adjust your
1606	clock to January of the previous year, then it will take more than year	2283	wrist-watch).
1607	to trigger the event (unlike an C<ev_timer>, which would still trigger
1608	roughly 10 seconds later as it uses a relative timeout).
1609		2284
		2285	You can tell a periodic watcher to trigger after some specific point
		2286	in time: for example, if you tell a periodic watcher to trigger "in 10
		2287	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2288	not a delay) and then reset your system clock to January of the previous
		2289	year, then it will take a year or more to trigger the event (unlike an
		2290	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2291	it, as it uses a relative timeout).
		2292
1610	C<ev_periodic>s can also be used to implement vastly more complex timers,	2293	C<ev_periodic> watchers can also be used to implement vastly more complex
1611	such as triggering an event on each "midnight, local time", or other	2294	timers, such as triggering an event on each "midnight, local time", or
1612	complicated rules.	2295	other complicated rules. This cannot easily be done with C<ev_timer>
		2296	watchers, as those cannot react to time jumps.
1613		2297
1614	As with timers, the callback is guaranteed to be invoked only when the	2298	As with timers, the callback is guaranteed to be invoked only when the
1615	time (C<at>) has passed, but if multiple periodic timers become ready	2299	point in time where it is supposed to trigger has passed. If multiple
1616	during the same loop iteration, then order of execution is undefined.	2300	timers become ready during the same loop iteration then the ones with
		2301	earlier time-out values are invoked before ones with later time-out values
		2302	(but this is no longer true when a callback calls C<ev_run> recursively).
1617		2303
1618	=head3 Watcher-Specific Functions and Data Members	2304	=head3 Watcher-Specific Functions and Data Members
1619		2305
1620	=over 4	2306	=over 4
1621		2307
1622	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2308	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1623		2309
1624	=item ev_periodic_set (ev_periodic *, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2310	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1625		2311
1626	Lots of arguments, lets sort it out... There are basically three modes of	2312	Lots of arguments, let's sort it out... There are basically three modes of
1627	operation, and we will explain them from simplest to most complex:	2313	operation, and we will explain them from simplest to most complex:
1628		2314
1629	=over 4	2315	=over 4
1630		2316
1631	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2317	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1632		2318
1633	In this configuration the watcher triggers an event after the wall clock	2319	In this configuration the watcher triggers an event after the wall clock
1634	time C<at> has passed. It will not repeat and will not adjust when a time	2320	time C<offset> has passed. It will not repeat and will not adjust when a
1635	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2321	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1636	only run when the system clock reaches or surpasses this time.	2322	will be stopped and invoked when the system clock reaches or surpasses
		2323	this point in time.
1637		2324
1638	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2325	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1639		2326
1640	In this mode the watcher will always be scheduled to time out at the next	2327	In this mode the watcher will always be scheduled to time out at the next
1641	C<at + N * interval> time (for some integer N, which can also be negative)	2328	C<offset + N * interval> time (for some integer N, which can also be
1642	and then repeat, regardless of any time jumps.	2329	negative) and then repeat, regardless of any time jumps. The C<offset>
		2330	argument is merely an offset into the C<interval> periods.
1643		2331
1644	This can be used to create timers that do not drift with respect to the	2332	This can be used to create timers that do not drift with respect to the
1645	system clock, for example, here is a C<ev_periodic> that triggers each	2333	system clock, for example, here is an C<ev_periodic> that triggers each
1646	hour, on the hour:	2334	hour, on the hour (with respect to UTC):
1647		2335
1648	ev_periodic_set (&periodic, 0., 3600., 0);	2336	ev_periodic_set (&periodic, 0., 3600., 0);
1649		2337
1650	This doesn't mean there will always be 3600 seconds in between triggers,	2338	This doesn't mean there will always be 3600 seconds in between triggers,
1651	but only that the callback will be called when the system time shows a	2339	but only that the callback will be called when the system time shows a
1652	full hour (UTC), or more correctly, when the system time is evenly divisible	2340	full hour (UTC), or more correctly, when the system time is evenly divisible
1653	by 3600.	2341	by 3600.
1654		2342
1655	Another way to think about it (for the mathematically inclined) is that	2343	Another way to think about it (for the mathematically inclined) is that
1656	C<ev_periodic> will try to run the callback in this mode at the next possible	2344	C<ev_periodic> will try to run the callback in this mode at the next possible
1657	time where C<time = at (mod interval)>, regardless of any time jumps.	2345	time where C<time = offset (mod interval)>, regardless of any time jumps.
1658		2346
1659	For numerical stability it is preferable that the C<at> value is near	2347	The C<interval> I<MUST> be positive, and for numerical stability, the
1660	C<ev_now ()> (the current time), but there is no range requirement for	2348	interval value should be higher than C<1/8192> (which is around 100
1661	this value, and in fact is often specified as zero.	2349	microseconds) and C<offset> should be higher than C<0> and should have
		2350	at most a similar magnitude as the current time (say, within a factor of
		2351	ten). Typical values for offset are, in fact, C<0> or something between
		2352	C<0> and C<interval>, which is also the recommended range.
1662		2353
1663	Note also that there is an upper limit to how often a timer can fire (CPU	2354	Note also that there is an upper limit to how often a timer can fire (CPU
1664	speed for example), so if C<interval> is very small then timing stability	2355	speed for example), so if C<interval> is very small then timing stability
1665	will of course deteriorate. Libev itself tries to be exact to be about one	2356	will of course deteriorate. Libev itself tries to be exact to be about one
1666	millisecond (if the OS supports it and the machine is fast enough).	2357	millisecond (if the OS supports it and the machine is fast enough).
1667		2358
1668	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2359	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1669		2360
1670	In this mode the values for C<interval> and C<at> are both being	2361	In this mode the values for C<interval> and C<offset> are both being
1671	ignored. Instead, each time the periodic watcher gets scheduled, the	2362	ignored. Instead, each time the periodic watcher gets scheduled, the
1672	reschedule callback will be called with the watcher as first, and the	2363	reschedule callback will be called with the watcher as first, and the
1673	current time as second argument.	2364	current time as second argument.
1674		2365
1675	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2366	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1676	ever, or make ANY other event loop modifications whatsoever>.	2367	or make ANY other event loop modifications whatsoever, unless explicitly
		2368	allowed by documentation here>.
1677		2369
1678	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2370	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1679	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2371	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1680	only event loop modification you are allowed to do).	2372	only event loop modification you are allowed to do).
1681		2373
…		…
1695		2387
1696	NOTE: I<< This callback must always return a time that is higher than or	2388	NOTE: I<< This callback must always return a time that is higher than or
1697	equal to the passed C<now> value >>.	2389	equal to the passed C<now> value >>.
1698		2390
1699	This can be used to create very complex timers, such as a timer that	2391	This can be used to create very complex timers, such as a timer that
1700	triggers on "next midnight, local time". To do this, you would calculate the	2392	triggers on "next midnight, local time". To do this, you would calculate
1701	next midnight after C<now> and return the timestamp value for this. How	2393	the next midnight after C<now> and return the timestamp value for
1702	you do this is, again, up to you (but it is not trivial, which is the main	2394	this. Here is a (completely untested, no error checking) example on how to
1703	reason I omitted it as an example).	2395	do this:
		2396
		2397	#include <time.h>
		2398
		2399	static ev_tstamp
		2400	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2401	{
		2402	time_t tnow = (time_t)now;
		2403	struct tm tm;
		2404	localtime_r (&tnow, &tm);
		2405
		2406	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2407	++tm.tm_mday; // midnight next day
		2408
		2409	return mktime (&tm);
		2410	}
		2411
		2412	Note: this code might run into trouble on days that have more then two
		2413	midnights (beginning and end).
1704		2414
1705	=back	2415	=back
1706		2416
1707	=item ev_periodic_again (loop, ev_periodic *)	2417	=item ev_periodic_again (loop, ev_periodic *)
1708		2418
…		…
1711	a different time than the last time it was called (e.g. in a crond like	2421	a different time than the last time it was called (e.g. in a crond like
1712	program when the crontabs have changed).	2422	program when the crontabs have changed).
1713		2423
1714	=item ev_tstamp ev_periodic_at (ev_periodic *)	2424	=item ev_tstamp ev_periodic_at (ev_periodic *)
1715		2425
1716	When active, returns the absolute time that the watcher is supposed to	2426	When active, returns the absolute time that the watcher is supposed
1717	trigger next.	2427	to trigger next. This is not the same as the C<offset> argument to
		2428	C<ev_periodic_set>, but indeed works even in interval and manual
		2429	rescheduling modes.
1718		2430
1719	=item ev_tstamp offset [read-write]	2431	=item ev_tstamp offset [read-write]
1720		2432
1721	When repeating, this contains the offset value, otherwise this is the	2433	When repeating, this contains the offset value, otherwise this is the
1722	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2434	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2435	although libev might modify this value for better numerical stability).
1723		2436
1724	Can be modified any time, but changes only take effect when the periodic	2437	Can be modified any time, but changes only take effect when the periodic
1725	timer fires or C<ev_periodic_again> is being called.	2438	timer fires or C<ev_periodic_again> is being called.
1726		2439
1727	=item ev_tstamp interval [read-write]	2440	=item ev_tstamp interval [read-write]
…		…
1743	Example: Call a callback every hour, or, more precisely, whenever the	2456	Example: Call a callback every hour, or, more precisely, whenever the
1744	system time is divisible by 3600. The callback invocation times have	2457	system time is divisible by 3600. The callback invocation times have
1745	potentially a lot of jitter, but good long-term stability.	2458	potentially a lot of jitter, but good long-term stability.
1746		2459
1747	static void	2460	static void
1748	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2461	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1749	{	2462	{
1750	... its now a full hour (UTC, or TAI or whatever your clock follows)	2463	... its now a full hour (UTC, or TAI or whatever your clock follows)
1751	}	2464	}
1752		2465
1753	ev_periodic hourly_tick;	2466	ev_periodic hourly_tick;
…		…
1770		2483
1771	ev_periodic hourly_tick;	2484	ev_periodic hourly_tick;
1772	ev_periodic_init (&hourly_tick, clock_cb,	2485	ev_periodic_init (&hourly_tick, clock_cb,
1773	fmod (ev_now (loop), 3600.), 3600., 0);	2486	fmod (ev_now (loop), 3600.), 3600., 0);
1774	ev_periodic_start (loop, &hourly_tick);	2487	ev_periodic_start (loop, &hourly_tick);
1775		2488
1776		2489
1777	=head2 C<ev_signal> - signal me when a signal gets signalled!	2490	=head2 C<ev_signal> - signal me when a signal gets signalled!
1778		2491
1779	Signal watchers will trigger an event when the process receives a specific	2492	Signal watchers will trigger an event when the process receives a specific
1780	signal one or more times. Even though signals are very asynchronous, libev	2493	signal one or more times. Even though signals are very asynchronous, libev
1781	will try it's best to deliver signals synchronously, i.e. as part of the	2494	will try its best to deliver signals synchronously, i.e. as part of the
1782	normal event processing, like any other event.	2495	normal event processing, like any other event.
1783		2496
1784	If you want signals asynchronously, just use C<sigaction> as you would	2497	If you want signals to be delivered truly asynchronously, just use
1785	do without libev and forget about sharing the signal. You can even use	2498	C<sigaction> as you would do without libev and forget about sharing
1786	C<ev_async> from a signal handler to synchronously wake up an event loop.	2499	the signal. You can even use C<ev_async> from a signal handler to
		2500	synchronously wake up an event loop.
1787		2501
1788	You can configure as many watchers as you like per signal. Only when the	2502	You can configure as many watchers as you like for the same signal, but
1789	first watcher gets started will libev actually register a signal handler	2503	only within the same loop, i.e. you can watch for C<SIGINT> in your
1790	with the kernel (thus it coexists with your own signal handlers as long as	2504	default loop and for C<SIGIO> in another loop, but you cannot watch for
1791	you don't register any with libev for the same signal). Similarly, when	2505	C<SIGINT> in both the default loop and another loop at the same time. At
1792	the last signal watcher for a signal is stopped, libev will reset the	2506	the moment, C<SIGCHLD> is permanently tied to the default loop.
1793	signal handler to SIG_DFL (regardless of what it was set to before).	2507
		2508	Only after the first watcher for a signal is started will libev actually
		2509	register something with the kernel. It thus coexists with your own signal
		2510	handlers as long as you don't register any with libev for the same signal.
1794		2511
1795	If possible and supported, libev will install its handlers with	2512	If possible and supported, libev will install its handlers with
1796	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2513	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1797	interrupted. If you have a problem with system calls getting interrupted by	2514	not be unduly interrupted. If you have a problem with system calls getting
1798	signals you can block all signals in an C<ev_check> watcher and unblock	2515	interrupted by signals you can block all signals in an C<ev_check> watcher
1799	them in an C<ev_prepare> watcher.	2516	and unblock them in an C<ev_prepare> watcher.
		2517
		2518	=head3 The special problem of inheritance over fork/execve/pthread_create
		2519
		2520	Both the signal mask (C<sigprocmask>) and the signal disposition
		2521	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2522	stopping it again), that is, libev might or might not block the signal,
		2523	and might or might not set or restore the installed signal handler (but
		2524	see C<EVFLAG_NOSIGMASK>).
		2525
		2526	While this does not matter for the signal disposition (libev never
		2527	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2528	C<execve>), this matters for the signal mask: many programs do not expect
		2529	certain signals to be blocked.
		2530
		2531	This means that before calling C<exec> (from the child) you should reset
		2532	the signal mask to whatever "default" you expect (all clear is a good
		2533	choice usually).
		2534
		2535	The simplest way to ensure that the signal mask is reset in the child is
		2536	to install a fork handler with C<pthread_atfork> that resets it. That will
		2537	catch fork calls done by libraries (such as the libc) as well.
		2538
		2539	In current versions of libev, the signal will not be blocked indefinitely
		2540	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2541	the window of opportunity for problems, it will not go away, as libev
		2542	I<has> to modify the signal mask, at least temporarily.
		2543
		2544	So I can't stress this enough: I<If you do not reset your signal mask when
		2545	you expect it to be empty, you have a race condition in your code>. This
		2546	is not a libev-specific thing, this is true for most event libraries.
		2547
		2548	=head3 The special problem of threads signal handling
		2549
		2550	POSIX threads has problematic signal handling semantics, specifically,
		2551	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2552	threads in a process block signals, which is hard to achieve.
		2553
		2554	When you want to use sigwait (or mix libev signal handling with your own
		2555	for the same signals), you can tackle this problem by globally blocking
		2556	all signals before creating any threads (or creating them with a fully set
		2557	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2558	loops. Then designate one thread as "signal receiver thread" which handles
		2559	these signals. You can pass on any signals that libev might be interested
		2560	in by calling C<ev_feed_signal>.
1800		2561
1801	=head3 Watcher-Specific Functions and Data Members	2562	=head3 Watcher-Specific Functions and Data Members
1802		2563
1803	=over 4	2564	=over 4
1804		2565
…		…
1820	Example: Try to exit cleanly on SIGINT.	2581	Example: Try to exit cleanly on SIGINT.
1821		2582
1822	static void	2583	static void
1823	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2584	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1824	{	2585	{
1825	ev_unloop (loop, EVUNLOOP_ALL);	2586	ev_break (loop, EVBREAK_ALL);
1826	}	2587	}
1827		2588
1828	ev_signal signal_watcher;	2589	ev_signal signal_watcher;
1829	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2590	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1830	ev_signal_start (loop, &signal_watcher);	2591	ev_signal_start (loop, &signal_watcher);
…		…
1836	some child status changes (most typically when a child of yours dies or	2597	some child status changes (most typically when a child of yours dies or
1837	exits). It is permissible to install a child watcher I<after> the child	2598	exits). It is permissible to install a child watcher I<after> the child
1838	has been forked (which implies it might have already exited), as long	2599	has been forked (which implies it might have already exited), as long
1839	as the event loop isn't entered (or is continued from a watcher), i.e.,	2600	as the event loop isn't entered (or is continued from a watcher), i.e.,
1840	forking and then immediately registering a watcher for the child is fine,	2601	forking and then immediately registering a watcher for the child is fine,
1841	but forking and registering a watcher a few event loop iterations later is	2602	but forking and registering a watcher a few event loop iterations later or
1842	not.	2603	in the next callback invocation is not.
1843		2604
1844	Only the default event loop is capable of handling signals, and therefore	2605	Only the default event loop is capable of handling signals, and therefore
1845	you can only register child watchers in the default event loop.	2606	you can only register child watchers in the default event loop.
1846		2607
		2608	Due to some design glitches inside libev, child watchers will always be
		2609	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2610	libev)
		2611
1847	=head3 Process Interaction	2612	=head3 Process Interaction
1848		2613
1849	Libev grabs C<SIGCHLD> as soon as the default event loop is	2614	Libev grabs C<SIGCHLD> as soon as the default event loop is
1850	initialised. This is necessary to guarantee proper behaviour even if	2615	initialised. This is necessary to guarantee proper behaviour even if the
1851	the first child watcher is started after the child exits. The occurrence	2616	first child watcher is started after the child exits. The occurrence
1852	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2617	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1853	synchronously as part of the event loop processing. Libev always reaps all	2618	synchronously as part of the event loop processing. Libev always reaps all
1854	children, even ones not watched.	2619	children, even ones not watched.
1855		2620
1856	=head3 Overriding the Built-In Processing	2621	=head3 Overriding the Built-In Processing
…		…
1866	=head3 Stopping the Child Watcher	2631	=head3 Stopping the Child Watcher
1867		2632
1868	Currently, the child watcher never gets stopped, even when the	2633	Currently, the child watcher never gets stopped, even when the
1869	child terminates, so normally one needs to stop the watcher in the	2634	child terminates, so normally one needs to stop the watcher in the
1870	callback. Future versions of libev might stop the watcher automatically	2635	callback. Future versions of libev might stop the watcher automatically
1871	when a child exit is detected.	2636	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2637	problem).
1872		2638
1873	=head3 Watcher-Specific Functions and Data Members	2639	=head3 Watcher-Specific Functions and Data Members
1874		2640
1875	=over 4	2641	=over 4
1876		2642
…		…
1934		2700
1935	=head2 C<ev_stat> - did the file attributes just change?	2701	=head2 C<ev_stat> - did the file attributes just change?
1936		2702
1937	This watches a file system path for attribute changes. That is, it calls	2703	This watches a file system path for attribute changes. That is, it calls
1938	C<stat> on that path in regular intervals (or when the OS says it changed)	2704	C<stat> on that path in regular intervals (or when the OS says it changed)
1939	and sees if it changed compared to the last time, invoking the callback if	2705	and sees if it changed compared to the last time, invoking the callback
1940	it did.	2706	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2707	happen after the watcher has been started will be reported.
1941		2708
1942	The path does not need to exist: changing from "path exists" to "path does	2709	The path does not need to exist: changing from "path exists" to "path does
1943	not exist" is a status change like any other. The condition "path does not	2710	not exist" is a status change like any other. The condition "path does not
1944	exist" (or more correctly "path cannot be stat'ed") is signified by the	2711	exist" (or more correctly "path cannot be stat'ed") is signified by the
1945	C<st_nlink> field being zero (which is otherwise always forced to be at	2712	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2175	Apart from keeping your process non-blocking (which is a useful	2942	Apart from keeping your process non-blocking (which is a useful
2176	effect on its own sometimes), idle watchers are a good place to do	2943	effect on its own sometimes), idle watchers are a good place to do
2177	"pseudo-background processing", or delay processing stuff to after the	2944	"pseudo-background processing", or delay processing stuff to after the
2178	event loop has handled all outstanding events.	2945	event loop has handled all outstanding events.
2179		2946
		2947	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2948
		2949	As long as there is at least one active idle watcher, libev will never
		2950	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2951	For this to work, the idle watcher doesn't need to be invoked at all - the
		2952	lowest priority will do.
		2953
		2954	This mode of operation can be useful together with an C<ev_check> watcher,
		2955	to do something on each event loop iteration - for example to balance load
		2956	between different connections.
		2957
		2958	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2959	example.
		2960
2180	=head3 Watcher-Specific Functions and Data Members	2961	=head3 Watcher-Specific Functions and Data Members
2181		2962
2182	=over 4	2963	=over 4
2183		2964
2184	=item ev_idle_init (ev_idle *, callback)	2965	=item ev_idle_init (ev_idle *, callback)
…		…
2195	callback, free it. Also, use no error checking, as usual.	2976	callback, free it. Also, use no error checking, as usual.
2196		2977
2197	static void	2978	static void
2198	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2979	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2199	{	2980	{
		2981	// stop the watcher
		2982	ev_idle_stop (loop, w);
		2983
		2984	// now we can free it
2200	free (w);	2985	free (w);
		2986
2201	// now do something you wanted to do when the program has	2987	// now do something you wanted to do when the program has
2202	// no longer anything immediate to do.	2988	// no longer anything immediate to do.
2203	}	2989	}
2204		2990
2205	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2991	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2206	ev_idle_init (idle_watcher, idle_cb);	2992	ev_idle_init (idle_watcher, idle_cb);
2207	ev_idle_start (loop, idle_cb);	2993	ev_idle_start (loop, idle_watcher);
2208		2994
2209		2995
2210	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2211		2997
2212	Prepare and check watchers are usually (but not always) used in pairs:	2998	Prepare and check watchers are often (but not always) used in pairs:
2213	prepare watchers get invoked before the process blocks and check watchers	2999	prepare watchers get invoked before the process blocks and check watchers
2214	afterwards.	3000	afterwards.
2215		3001
2216	You I<must not> call C<ev_loop> or similar functions that enter	3002	You I<must not> call C<ev_run> (or similar functions that enter the
2217	the current event loop from either C<ev_prepare> or C<ev_check>	3003	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2218	watchers. Other loops than the current one are fine, however. The	3004	C<ev_check> watchers. Other loops than the current one are fine,
2219	rationale behind this is that you do not need to check for recursion in	3005	however. The rationale behind this is that you do not need to check
2220	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3006	for recursion in those watchers, i.e. the sequence will always be
2221	C<ev_check> so if you have one watcher of each kind they will always be	3007	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2222	called in pairs bracketing the blocking call.	3008	kind they will always be called in pairs bracketing the blocking call.
2223		3009
2224	Their main purpose is to integrate other event mechanisms into libev and	3010	Their main purpose is to integrate other event mechanisms into libev and
2225	their use is somewhat advanced. They could be used, for example, to track	3011	their use is somewhat advanced. They could be used, for example, to track
2226	variable changes, implement your own watchers, integrate net-snmp or a	3012	variable changes, implement your own watchers, integrate net-snmp or a
2227	coroutine library and lots more. They are also occasionally useful if	3013	coroutine library and lots more. They are also occasionally useful if
…		…
2245	with priority higher than or equal to the event loop and one coroutine	3031	with priority higher than or equal to the event loop and one coroutine
2246	of lower priority, but only once, using idle watchers to keep the event	3032	of lower priority, but only once, using idle watchers to keep the event
2247	loop from blocking if lower-priority coroutines are active, thus mapping	3033	loop from blocking if lower-priority coroutines are active, thus mapping
2248	low-priority coroutines to idle/background tasks).	3034	low-priority coroutines to idle/background tasks).
2249		3035
2250	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3036	When used for this purpose, it is recommended to give C<ev_check> watchers
2251	priority, to ensure that they are being run before any other watchers	3037	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2252	after the poll (this doesn't matter for C<ev_prepare> watchers).	3038	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3039	watchers).
2253		3040
2254	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3041	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2255	activate ("feed") events into libev. While libev fully supports this, they	3042	activate ("feed") events into libev. While libev fully supports this, they
2256	might get executed before other C<ev_check> watchers did their job. As	3043	might get executed before other C<ev_check> watchers did their job. As
2257	C<ev_check> watchers are often used to embed other (non-libev) event	3044	C<ev_check> watchers are often used to embed other (non-libev) event
2258	loops those other event loops might be in an unusable state until their	3045	loops those other event loops might be in an unusable state until their
2259	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3046	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2260	others).	3047	others).
		3048
		3049	=head3 Abusing an C<ev_check> watcher for its side-effect
		3050
		3051	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3052	useful because they are called once per event loop iteration. For
		3053	example, if you want to handle a large number of connections fairly, you
		3054	normally only do a bit of work for each active connection, and if there
		3055	is more work to do, you wait for the next event loop iteration, so other
		3056	connections have a chance of making progress.
		3057
		3058	Using an C<ev_check> watcher is almost enough: it will be called on the
		3059	next event loop iteration. However, that isn't as soon as possible -
		3060	without external events, your C<ev_check> watcher will not be invoked.
		3061
		3062	This is where C<ev_idle> watchers come in handy - all you need is a
		3063	single global idle watcher that is active as long as you have one active
		3064	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3065	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3066	invoked. Neither watcher alone can do that.
2261		3067
2262	=head3 Watcher-Specific Functions and Data Members	3068	=head3 Watcher-Specific Functions and Data Members
2263		3069
2264	=over 4	3070	=over 4
2265		3071
…		…
2305	struct pollfd fds [nfd];	3111	struct pollfd fds [nfd];
2306	// actual code will need to loop here and realloc etc.	3112	// actual code will need to loop here and realloc etc.
2307	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3113	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2308		3114
2309	/* the callback is illegal, but won't be called as we stop during check */	3115	/* the callback is illegal, but won't be called as we stop during check */
2310	ev_timer_init (&tw, 0, timeout * 1e-3);	3116	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2311	ev_timer_start (loop, &tw);	3117	ev_timer_start (loop, &tw);
2312		3118
2313	// create one ev_io per pollfd	3119	// create one ev_io per pollfd
2314	for (int i = 0; i < nfd; ++i)	3120	for (int i = 0; i < nfd; ++i)
2315	{	3121	{
…		…
2389		3195
2390	if (timeout >= 0)	3196	if (timeout >= 0)
2391	// create/start timer	3197	// create/start timer
2392		3198
2393	// poll	3199	// poll
2394	ev_loop (EV_A_ 0);	3200	ev_run (EV_A_ 0);
2395		3201
2396	// stop timer again	3202	// stop timer again
2397	if (timeout >= 0)	3203	if (timeout >= 0)
2398	ev_timer_stop (EV_A_ &to);	3204	ev_timer_stop (EV_A_ &to);
2399		3205
…		…
2466		3272
2467	=over 4	3273	=over 4
2468		3274
2469	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3275	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2470		3276
2471	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3277	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2472		3278
2473	Configures the watcher to embed the given loop, which must be	3279	Configures the watcher to embed the given loop, which must be
2474	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3280	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2475	invoked automatically, otherwise it is the responsibility of the callback	3281	invoked automatically, otherwise it is the responsibility of the callback
2476	to invoke it (it will continue to be called until the sweep has been done,	3282	to invoke it (it will continue to be called until the sweep has been done,
2477	if you do not want that, you need to temporarily stop the embed watcher).	3283	if you do not want that, you need to temporarily stop the embed watcher).
2478		3284
2479	=item ev_embed_sweep (loop, ev_embed *)	3285	=item ev_embed_sweep (loop, ev_embed *)
2480		3286
2481	Make a single, non-blocking sweep over the embedded loop. This works	3287	Make a single, non-blocking sweep over the embedded loop. This works
2482	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3288	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2483	appropriate way for embedded loops.	3289	appropriate way for embedded loops.
2484		3290
2485	=item struct ev_loop *other [read-only]	3291	=item struct ev_loop *other [read-only]
2486		3292
2487	The embedded event loop.	3293	The embedded event loop.
…		…
2497	used).	3303	used).
2498		3304
2499	struct ev_loop *loop_hi = ev_default_init (0);	3305	struct ev_loop *loop_hi = ev_default_init (0);
2500	struct ev_loop *loop_lo = 0;	3306	struct ev_loop *loop_lo = 0;
2501	ev_embed embed;	3307	ev_embed embed;
2502		3308
2503	// see if there is a chance of getting one that works	3309	// see if there is a chance of getting one that works
2504	// (remember that a flags value of 0 means autodetection)	3310	// (remember that a flags value of 0 means autodetection)
2505	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3311	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2506	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3312	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2507	: 0;	3313	: 0;
…		…
2521	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3327	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2522		3328
2523	struct ev_loop *loop = ev_default_init (0);	3329	struct ev_loop *loop = ev_default_init (0);
2524	struct ev_loop *loop_socket = 0;	3330	struct ev_loop *loop_socket = 0;
2525	ev_embed embed;	3331	ev_embed embed;
2526		3332
2527	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3333	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2528	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3334	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2529	{	3335	{
2530	ev_embed_init (&embed, 0, loop_socket);	3336	ev_embed_init (&embed, 0, loop_socket);
2531	ev_embed_start (loop, &embed);	3337	ev_embed_start (loop, &embed);
…		…
2539		3345
2540	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3346	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2541		3347
2542	Fork watchers are called when a C<fork ()> was detected (usually because	3348	Fork watchers are called when a C<fork ()> was detected (usually because
2543	whoever is a good citizen cared to tell libev about it by calling	3349	whoever is a good citizen cared to tell libev about it by calling
2544	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3350	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2545	event loop blocks next and before C<ev_check> watchers are being called,	3351	and before C<ev_check> watchers are being called, and only in the child
2546	and only in the child after the fork. If whoever good citizen calling	3352	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2547	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3353	and calls it in the wrong process, the fork handlers will be invoked, too,
2548	handlers will be invoked, too, of course.	3354	of course.
		3355
		3356	=head3 The special problem of life after fork - how is it possible?
		3357
		3358	Most uses of C<fork ()> consist of forking, then some simple calls to set
		3359	up/change the process environment, followed by a call to C<exec()>. This
		3360	sequence should be handled by libev without any problems.
		3361
		3362	This changes when the application actually wants to do event handling
		3363	in the child, or both parent in child, in effect "continuing" after the
		3364	fork.
		3365
		3366	The default mode of operation (for libev, with application help to detect
		3367	forks) is to duplicate all the state in the child, as would be expected
		3368	when I<either> the parent I<or> the child process continues.
		3369
		3370	When both processes want to continue using libev, then this is usually the
		3371	wrong result. In that case, usually one process (typically the parent) is
		3372	supposed to continue with all watchers in place as before, while the other
		3373	process typically wants to start fresh, i.e. without any active watchers.
		3374
		3375	The cleanest and most efficient way to achieve that with libev is to
		3376	simply create a new event loop, which of course will be "empty", and
		3377	use that for new watchers. This has the advantage of not touching more
		3378	memory than necessary, and thus avoiding the copy-on-write, and the
		3379	disadvantage of having to use multiple event loops (which do not support
		3380	signal watchers).
		3381
		3382	When this is not possible, or you want to use the default loop for
		3383	other reasons, then in the process that wants to start "fresh", call
		3384	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3385	Destroying the default loop will "orphan" (not stop) all registered
		3386	watchers, so you have to be careful not to execute code that modifies
		3387	those watchers. Note also that in that case, you have to re-register any
		3388	signal watchers.
2549		3389
2550	=head3 Watcher-Specific Functions and Data Members	3390	=head3 Watcher-Specific Functions and Data Members
2551		3391
2552	=over 4	3392	=over 4
2553		3393
2554	=item ev_fork_init (ev_signal *, callback)	3394	=item ev_fork_init (ev_fork *, callback)
2555		3395
2556	Initialises and configures the fork watcher - it has no parameters of any	3396	Initialises and configures the fork watcher - it has no parameters of any
2557	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3397	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2558	believe me.	3398	really.
2559		3399
2560	=back	3400	=back
2561		3401
2562		3402
		3403	=head2 C<ev_cleanup> - even the best things end
		3404
		3405	Cleanup watchers are called just before the event loop is being destroyed
		3406	by a call to C<ev_loop_destroy>.
		3407
		3408	While there is no guarantee that the event loop gets destroyed, cleanup
		3409	watchers provide a convenient method to install cleanup hooks for your
		3410	program, worker threads and so on - you just to make sure to destroy the
		3411	loop when you want them to be invoked.
		3412
		3413	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3414	all other watchers, they do not keep a reference to the event loop (which
		3415	makes a lot of sense if you think about it). Like all other watchers, you
		3416	can call libev functions in the callback, except C<ev_cleanup_start>.
		3417
		3418	=head3 Watcher-Specific Functions and Data Members
		3419
		3420	=over 4
		3421
		3422	=item ev_cleanup_init (ev_cleanup *, callback)
		3423
		3424	Initialises and configures the cleanup watcher - it has no parameters of
		3425	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3426	pointless, I assure you.
		3427
		3428	=back
		3429
		3430	Example: Register an atexit handler to destroy the default loop, so any
		3431	cleanup functions are called.
		3432
		3433	static void
		3434	program_exits (void)
		3435	{
		3436	ev_loop_destroy (EV_DEFAULT_UC);
		3437	}
		3438
		3439	...
		3440	atexit (program_exits);
		3441
		3442
2563	=head2 C<ev_async> - how to wake up another event loop	3443	=head2 C<ev_async> - how to wake up an event loop
2564		3444
2565	In general, you cannot use an C<ev_loop> from multiple threads or other	3445	In general, you cannot use an C<ev_loop> from multiple threads or other
2566	asynchronous sources such as signal handlers (as opposed to multiple event	3446	asynchronous sources such as signal handlers (as opposed to multiple event
2567	loops - those are of course safe to use in different threads).	3447	loops - those are of course safe to use in different threads).
2568		3448
2569	Sometimes, however, you need to wake up another event loop you do not	3449	Sometimes, however, you need to wake up an event loop you do not control,
2570	control, for example because it belongs to another thread. This is what	3450	for example because it belongs to another thread. This is what C<ev_async>
2571	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3451	watchers do: as long as the C<ev_async> watcher is active, you can signal
2572	can signal it by calling C<ev_async_send>, which is thread- and signal	3452	it by calling C<ev_async_send>, which is thread- and signal safe.
2573	safe.
2574		3453
2575	This functionality is very similar to C<ev_signal> watchers, as signals,	3454	This functionality is very similar to C<ev_signal> watchers, as signals,
2576	too, are asynchronous in nature, and signals, too, will be compressed	3455	too, are asynchronous in nature, and signals, too, will be compressed
2577	(i.e. the number of callback invocations may be less than the number of	3456	(i.e. the number of callback invocations may be less than the number of
2578	C<ev_async_sent> calls).	3457	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2579		3458	of "global async watchers" by using a watcher on an otherwise unused
2580	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3459	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2581	just the default loop.	3460	even without knowing which loop owns the signal.
2582		3461
2583	=head3 Queueing	3462	=head3 Queueing
2584		3463
2585	C<ev_async> does not support queueing of data in any way. The reason	3464	C<ev_async> does not support queueing of data in any way. The reason
2586	is that the author does not know of a simple (or any) algorithm for a	3465	is that the author does not know of a simple (or any) algorithm for a
2587	multiple-writer-single-reader queue that works in all cases and doesn't	3466	multiple-writer-single-reader queue that works in all cases and doesn't
2588	need elaborate support such as pthreads.	3467	need elaborate support such as pthreads or unportable memory access
		3468	semantics.
2589		3469
2590	That means that if you want to queue data, you have to provide your own	3470	That means that if you want to queue data, you have to provide your own
2591	queue. But at least I can tell you how to implement locking around your	3471	queue. But at least I can tell you how to implement locking around your
2592	queue:	3472	queue:
2593		3473
…		…
2677	trust me.	3557	trust me.
2678		3558
2679	=item ev_async_send (loop, ev_async *)	3559	=item ev_async_send (loop, ev_async *)
2680		3560
2681	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3561	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2682	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3562	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3563	returns.
		3564
2683	C<ev_feed_event>, this call is safe to do from other threads, signal or	3565	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2684	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3566	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2685	section below on what exactly this means).	3567	embedding section below on what exactly this means).
2686		3568
2687	This call incurs the overhead of a system call only once per loop iteration,	3569	Note that, as with other watchers in libev, multiple events might get
2688	so while the overhead might be noticeable, it doesn't apply to repeated	3570	compressed into a single callback invocation (another way to look at
2689	calls to C<ev_async_send>.	3571	this is that C<ev_async> watchers are level-triggered: they are set on
		3572	C<ev_async_send>, reset when the event loop detects that).
		3573
		3574	This call incurs the overhead of at most one extra system call per event
		3575	loop iteration, if the event loop is blocked, and no syscall at all if
		3576	the event loop (or your program) is processing events. That means that
		3577	repeated calls are basically free (there is no need to avoid calls for
		3578	performance reasons) and that the overhead becomes smaller (typically
		3579	zero) under load.
2690		3580
2691	=item bool = ev_async_pending (ev_async *)	3581	=item bool = ev_async_pending (ev_async *)
2692		3582
2693	Returns a non-zero value when C<ev_async_send> has been called on the	3583	Returns a non-zero value when C<ev_async_send> has been called on the
2694	watcher but the event has not yet been processed (or even noted) by the	3584	watcher but the event has not yet been processed (or even noted) by the
…		…
2697	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3587	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2698	the loop iterates next and checks for the watcher to have become active,	3588	the loop iterates next and checks for the watcher to have become active,
2699	it will reset the flag again. C<ev_async_pending> can be used to very	3589	it will reset the flag again. C<ev_async_pending> can be used to very
2700	quickly check whether invoking the loop might be a good idea.	3590	quickly check whether invoking the loop might be a good idea.
2701		3591
2702	Not that this does I<not> check whether the watcher itself is pending, only	3592	Not that this does I<not> check whether the watcher itself is pending,
2703	whether it has been requested to make this watcher pending.	3593	only whether it has been requested to make this watcher pending: there
		3594	is a time window between the event loop checking and resetting the async
		3595	notification, and the callback being invoked.
2704		3596
2705	=back	3597	=back
2706		3598
2707		3599
2708	=head1 OTHER FUNCTIONS	3600	=head1 OTHER FUNCTIONS
2709		3601
2710	There are some other functions of possible interest. Described. Here. Now.	3602	There are some other functions of possible interest. Described. Here. Now.
2711		3603
2712	=over 4	3604	=over 4
2713		3605
2714	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3606	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
2715		3607
2716	This function combines a simple timer and an I/O watcher, calls your	3608	This function combines a simple timer and an I/O watcher, calls your
2717	callback on whichever event happens first and automatically stops both	3609	callback on whichever event happens first and automatically stops both
2718	watchers. This is useful if you want to wait for a single event on an fd	3610	watchers. This is useful if you want to wait for a single event on an fd
2719	or timeout without having to allocate/configure/start/stop/free one or	3611	or timeout without having to allocate/configure/start/stop/free one or
…		…
2725		3617
2726	If C<timeout> is less than 0, then no timeout watcher will be	3618	If C<timeout> is less than 0, then no timeout watcher will be
2727	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3619	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2728	repeat = 0) will be started. C<0> is a valid timeout.	3620	repeat = 0) will be started. C<0> is a valid timeout.
2729		3621
2730	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3622	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2731	passed an C<revents> set like normal event callbacks (a combination of	3623	passed an C<revents> set like normal event callbacks (a combination of
2732	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3624	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2733	value passed to C<ev_once>. Note that it is possible to receive I<both>	3625	value passed to C<ev_once>. Note that it is possible to receive I<both>
2734	a timeout and an io event at the same time - you probably should give io	3626	a timeout and an io event at the same time - you probably should give io
2735	events precedence.	3627	events precedence.
2736		3628
2737	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3629	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2738		3630
2739	static void stdin_ready (int revents, void *arg)	3631	static void stdin_ready (int revents, void *arg)
2740	{	3632	{
2741	if (revents & EV_READ)	3633	if (revents & EV_READ)
2742	/* stdin might have data for us, joy! */;	3634	/* stdin might have data for us, joy! */;
2743	else if (revents & EV_TIMEOUT)	3635	else if (revents & EV_TIMER)
2744	/* doh, nothing entered */;	3636	/* doh, nothing entered */;
2745	}	3637	}
2746		3638
2747	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3639	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2748		3640
2749	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2750
2751	Feeds the given event set into the event loop, as if the specified event
2752	had happened for the specified watcher (which must be a pointer to an
2753	initialised but not necessarily started event watcher).
2754
2755	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3641	=item ev_feed_fd_event (loop, int fd, int revents)
2756		3642
2757	Feed an event on the given fd, as if a file descriptor backend detected	3643	Feed an event on the given fd, as if a file descriptor backend detected
2758	the given events it.	3644	the given events.
2759		3645
2760	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3646	=item ev_feed_signal_event (loop, int signum)
2761		3647
2762	Feed an event as if the given signal occurred (C<loop> must be the default	3648	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2763	loop!).	3649	which is async-safe.
2764		3650
2765	=back	3651	=back
		3652
		3653
		3654	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3655
		3656	This section explains some common idioms that are not immediately
		3657	obvious. Note that examples are sprinkled over the whole manual, and this
		3658	section only contains stuff that wouldn't fit anywhere else.
		3659
		3660	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3661
		3662	Each watcher has, by default, a C<void *data> member that you can read
		3663	or modify at any time: libev will completely ignore it. This can be used
		3664	to associate arbitrary data with your watcher. If you need more data and
		3665	don't want to allocate memory separately and store a pointer to it in that
		3666	data member, you can also "subclass" the watcher type and provide your own
		3667	data:
		3668
		3669	struct my_io
		3670	{
		3671	ev_io io;
		3672	int otherfd;
		3673	void *somedata;
		3674	struct whatever *mostinteresting;
		3675	};
		3676
		3677	...
		3678	struct my_io w;
		3679	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3680
		3681	And since your callback will be called with a pointer to the watcher, you
		3682	can cast it back to your own type:
		3683
		3684	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3685	{
		3686	struct my_io *w = (struct my_io *)w_;
		3687	...
		3688	}
		3689
		3690	More interesting and less C-conformant ways of casting your callback
		3691	function type instead have been omitted.
		3692
		3693	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3694
		3695	Another common scenario is to use some data structure with multiple
		3696	embedded watchers, in effect creating your own watcher that combines
		3697	multiple libev event sources into one "super-watcher":
		3698
		3699	struct my_biggy
		3700	{
		3701	int some_data;
		3702	ev_timer t1;
		3703	ev_timer t2;
		3704	}
		3705
		3706	In this case getting the pointer to C<my_biggy> is a bit more
		3707	complicated: Either you store the address of your C<my_biggy> struct in
		3708	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3709	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3710	real programmers):
		3711
		3712	#include <stddef.h>
		3713
		3714	static void
		3715	t1_cb (EV_P_ ev_timer *w, int revents)
		3716	{
		3717	struct my_biggy big = (struct my_biggy *)
		3718	(((char *)w) - offsetof (struct my_biggy, t1));
		3719	}
		3720
		3721	static void
		3722	t2_cb (EV_P_ ev_timer *w, int revents)
		3723	{
		3724	struct my_biggy big = (struct my_biggy *)
		3725	(((char *)w) - offsetof (struct my_biggy, t2));
		3726	}
		3727
		3728	=head2 AVOIDING FINISHING BEFORE RETURNING
		3729
		3730	Often you have structures like this in event-based programs:
		3731
		3732	callback ()
		3733	{
		3734	free (request);
		3735	}
		3736
		3737	request = start_new_request (..., callback);
		3738
		3739	The intent is to start some "lengthy" operation. The C<request> could be
		3740	used to cancel the operation, or do other things with it.
		3741
		3742	It's not uncommon to have code paths in C<start_new_request> that
		3743	immediately invoke the callback, for example, to report errors. Or you add
		3744	some caching layer that finds that it can skip the lengthy aspects of the
		3745	operation and simply invoke the callback with the result.
		3746
		3747	The problem here is that this will happen I<before> C<start_new_request>
		3748	has returned, so C<request> is not set.
		3749
		3750	Even if you pass the request by some safer means to the callback, you
		3751	might want to do something to the request after starting it, such as
		3752	canceling it, which probably isn't working so well when the callback has
		3753	already been invoked.
		3754
		3755	A common way around all these issues is to make sure that
		3756	C<start_new_request> I<always> returns before the callback is invoked. If
		3757	C<start_new_request> immediately knows the result, it can artificially
		3758	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3759	example, or more sneakily, by reusing an existing (stopped) watcher and
		3760	pushing it into the pending queue:
		3761
		3762	ev_set_cb (watcher, callback);
		3763	ev_feed_event (EV_A_ watcher, 0);
		3764
		3765	This way, C<start_new_request> can safely return before the callback is
		3766	invoked, while not delaying callback invocation too much.
		3767
		3768	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3769
		3770	Often (especially in GUI toolkits) there are places where you have
		3771	I<modal> interaction, which is most easily implemented by recursively
		3772	invoking C<ev_run>.
		3773
		3774	This brings the problem of exiting - a callback might want to finish the
		3775	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3776	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3777	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3778	other combination: In these cases, a simple C<ev_break> will not work.
		3779
		3780	The solution is to maintain "break this loop" variable for each C<ev_run>
		3781	invocation, and use a loop around C<ev_run> until the condition is
		3782	triggered, using C<EVRUN_ONCE>:
		3783
		3784	// main loop
		3785	int exit_main_loop = 0;
		3786
		3787	while (!exit_main_loop)
		3788	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3789
		3790	// in a modal watcher
		3791	int exit_nested_loop = 0;
		3792
		3793	while (!exit_nested_loop)
		3794	ev_run (EV_A_ EVRUN_ONCE);
		3795
		3796	To exit from any of these loops, just set the corresponding exit variable:
		3797
		3798	// exit modal loop
		3799	exit_nested_loop = 1;
		3800
		3801	// exit main program, after modal loop is finished
		3802	exit_main_loop = 1;
		3803
		3804	// exit both
		3805	exit_main_loop = exit_nested_loop = 1;
		3806
		3807	=head2 THREAD LOCKING EXAMPLE
		3808
		3809	Here is a fictitious example of how to run an event loop in a different
		3810	thread from where callbacks are being invoked and watchers are
		3811	created/added/removed.
		3812
		3813	For a real-world example, see the C<EV::Loop::Async> perl module,
		3814	which uses exactly this technique (which is suited for many high-level
		3815	languages).
		3816
		3817	The example uses a pthread mutex to protect the loop data, a condition
		3818	variable to wait for callback invocations, an async watcher to notify the
		3819	event loop thread and an unspecified mechanism to wake up the main thread.
		3820
		3821	First, you need to associate some data with the event loop:
		3822
		3823	typedef struct {
		3824	mutex_t lock; /* global loop lock */
		3825	ev_async async_w;
		3826	thread_t tid;
		3827	cond_t invoke_cv;
		3828	} userdata;
		3829
		3830	void prepare_loop (EV_P)
		3831	{
		3832	// for simplicity, we use a static userdata struct.
		3833	static userdata u;
		3834
		3835	ev_async_init (&u->async_w, async_cb);
		3836	ev_async_start (EV_A_ &u->async_w);
		3837
		3838	pthread_mutex_init (&u->lock, 0);
		3839	pthread_cond_init (&u->invoke_cv, 0);
		3840
		3841	// now associate this with the loop
		3842	ev_set_userdata (EV_A_ u);
		3843	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3844	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3845
		3846	// then create the thread running ev_run
		3847	pthread_create (&u->tid, 0, l_run, EV_A);
		3848	}
		3849
		3850	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3851	solely to wake up the event loop so it takes notice of any new watchers
		3852	that might have been added:
		3853
		3854	static void
		3855	async_cb (EV_P_ ev_async *w, int revents)
		3856	{
		3857	// just used for the side effects
		3858	}
		3859
		3860	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3861	protecting the loop data, respectively.
		3862
		3863	static void
		3864	l_release (EV_P)
		3865	{
		3866	userdata *u = ev_userdata (EV_A);
		3867	pthread_mutex_unlock (&u->lock);
		3868	}
		3869
		3870	static void
		3871	l_acquire (EV_P)
		3872	{
		3873	userdata *u = ev_userdata (EV_A);
		3874	pthread_mutex_lock (&u->lock);
		3875	}
		3876
		3877	The event loop thread first acquires the mutex, and then jumps straight
		3878	into C<ev_run>:
		3879
		3880	void *
		3881	l_run (void *thr_arg)
		3882	{
		3883	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3884
		3885	l_acquire (EV_A);
		3886	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3887	ev_run (EV_A_ 0);
		3888	l_release (EV_A);
		3889
		3890	return 0;
		3891	}
		3892
		3893	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3894	signal the main thread via some unspecified mechanism (signals? pipe
		3895	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3896	have been called (in a while loop because a) spurious wakeups are possible
		3897	and b) skipping inter-thread-communication when there are no pending
		3898	watchers is very beneficial):
		3899
		3900	static void
		3901	l_invoke (EV_P)
		3902	{
		3903	userdata *u = ev_userdata (EV_A);
		3904
		3905	while (ev_pending_count (EV_A))
		3906	{
		3907	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3908	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3909	}
		3910	}
		3911
		3912	Now, whenever the main thread gets told to invoke pending watchers, it
		3913	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3914	thread to continue:
		3915
		3916	static void
		3917	real_invoke_pending (EV_P)
		3918	{
		3919	userdata *u = ev_userdata (EV_A);
		3920
		3921	pthread_mutex_lock (&u->lock);
		3922	ev_invoke_pending (EV_A);
		3923	pthread_cond_signal (&u->invoke_cv);
		3924	pthread_mutex_unlock (&u->lock);
		3925	}
		3926
		3927	Whenever you want to start/stop a watcher or do other modifications to an
		3928	event loop, you will now have to lock:
		3929
		3930	ev_timer timeout_watcher;
		3931	userdata *u = ev_userdata (EV_A);
		3932
		3933	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3934
		3935	pthread_mutex_lock (&u->lock);
		3936	ev_timer_start (EV_A_ &timeout_watcher);
		3937	ev_async_send (EV_A_ &u->async_w);
		3938	pthread_mutex_unlock (&u->lock);
		3939
		3940	Note that sending the C<ev_async> watcher is required because otherwise
		3941	an event loop currently blocking in the kernel will have no knowledge
		3942	about the newly added timer. By waking up the loop it will pick up any new
		3943	watchers in the next event loop iteration.
		3944
		3945	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3946
		3947	While the overhead of a callback that e.g. schedules a thread is small, it
		3948	is still an overhead. If you embed libev, and your main usage is with some
		3949	kind of threads or coroutines, you might want to customise libev so that
		3950	doesn't need callbacks anymore.
		3951
		3952	Imagine you have coroutines that you can switch to using a function
		3953	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3954	and that due to some magic, the currently active coroutine is stored in a
		3955	global called C<current_coro>. Then you can build your own "wait for libev
		3956	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3957	the differing C<;> conventions):
		3958
		3959	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3960	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3961
		3962	That means instead of having a C callback function, you store the
		3963	coroutine to switch to in each watcher, and instead of having libev call
		3964	your callback, you instead have it switch to that coroutine.
		3965
		3966	A coroutine might now wait for an event with a function called
		3967	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3968	matter when, or whether the watcher is active or not when this function is
		3969	called):
		3970
		3971	void
		3972	wait_for_event (ev_watcher *w)
		3973	{
		3974	ev_set_cb (w, current_coro);
		3975	switch_to (libev_coro);
		3976	}
		3977
		3978	That basically suspends the coroutine inside C<wait_for_event> and
		3979	continues the libev coroutine, which, when appropriate, switches back to
		3980	this or any other coroutine.
		3981
		3982	You can do similar tricks if you have, say, threads with an event queue -
		3983	instead of storing a coroutine, you store the queue object and instead of
		3984	switching to a coroutine, you push the watcher onto the queue and notify
		3985	any waiters.
		3986
		3987	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3988	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3989
		3990	// my_ev.h
		3991	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3992	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3993	#include "../libev/ev.h"
		3994
		3995	// my_ev.c
		3996	#define EV_H "my_ev.h"
		3997	#include "../libev/ev.c"
		3998
		3999	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4000	F<my_ev.c> into your project. When properly specifying include paths, you
		4001	can even use F<ev.h> as header file name directly.
2766		4002
2767		4003
2768	=head1 LIBEVENT EMULATION	4004	=head1 LIBEVENT EMULATION
2769		4005
2770	Libev offers a compatibility emulation layer for libevent. It cannot	4006	Libev offers a compatibility emulation layer for libevent. It cannot
2771	emulate the internals of libevent, so here are some usage hints:	4007	emulate the internals of libevent, so here are some usage hints:
2772		4008
2773	=over 4	4009	=over 4
		4010
		4011	=item * Only the libevent-1.4.1-beta API is being emulated.
		4012
		4013	This was the newest libevent version available when libev was implemented,
		4014	and is still mostly unchanged in 2010.
2774		4015
2775	=item * Use it by including <event.h>, as usual.	4016	=item * Use it by including <event.h>, as usual.
2776		4017
2777	=item * The following members are fully supported: ev_base, ev_callback,	4018	=item * The following members are fully supported: ev_base, ev_callback,
2778	ev_arg, ev_fd, ev_res, ev_events.	4019	ev_arg, ev_fd, ev_res, ev_events.
…		…
2784	=item * Priorities are not currently supported. Initialising priorities	4025	=item * Priorities are not currently supported. Initialising priorities
2785	will fail and all watchers will have the same priority, even though there	4026	will fail and all watchers will have the same priority, even though there
2786	is an ev_pri field.	4027	is an ev_pri field.
2787		4028
2788	=item * In libevent, the last base created gets the signals, in libev, the	4029	=item * In libevent, the last base created gets the signals, in libev, the
2789	first base created (== the default loop) gets the signals.	4030	base that registered the signal gets the signals.
2790		4031
2791	=item * Other members are not supported.	4032	=item * Other members are not supported.
2792		4033
2793	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4034	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2794	to use the libev header file and library.	4035	to use the libev header file and library.
2795		4036
2796	=back	4037	=back
2797		4038
2798	=head1 C++ SUPPORT	4039	=head1 C++ SUPPORT
		4040
		4041	=head2 C API
		4042
		4043	The normal C API should work fine when used from C++: both ev.h and the
		4044	libev sources can be compiled as C++. Therefore, code that uses the C API
		4045	will work fine.
		4046
		4047	Proper exception specifications might have to be added to callbacks passed
		4048	to libev: exceptions may be thrown only from watcher callbacks, all other
		4049	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4050	callbacks) must not throw exceptions, and might need a C<noexcept>
		4051	specification. If you have code that needs to be compiled as both C and
		4052	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4053
		4054	static void
		4055	fatal_error (const char *msg) EV_NOEXCEPT
		4056	{
		4057	perror (msg);
		4058	abort ();
		4059	}
		4060
		4061	...
		4062	ev_set_syserr_cb (fatal_error);
		4063
		4064	The only API functions that can currently throw exceptions are C<ev_run>,
		4065	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4066	because it runs cleanup watchers).
		4067
		4068	Throwing exceptions in watcher callbacks is only supported if libev itself
		4069	is compiled with a C++ compiler or your C and C++ environments allow
		4070	throwing exceptions through C libraries (most do).
		4071
		4072	=head2 C++ API
2799		4073
2800	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4074	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2801	you to use some convenience methods to start/stop watchers and also change	4075	you to use some convenience methods to start/stop watchers and also change
2802	the callback model to a model using method callbacks on objects.	4076	the callback model to a model using method callbacks on objects.
2803		4077
2804	To use it,	4078	To use it,
2805		4079
2806	#include <ev++.h>	4080	#include <ev++.h>
2807		4081
2808	This automatically includes F<ev.h> and puts all of its definitions (many	4082	This automatically includes F<ev.h> and puts all of its definitions (many
2809	of them macros) into the global namespace. All C++ specific things are	4083	of them macros) into the global namespace. All C++ specific things are
2810	put into the C<ev> namespace. It should support all the same embedding	4084	put into the C<ev> namespace. It should support all the same embedding
…		…
2813	Care has been taken to keep the overhead low. The only data member the C++	4087	Care has been taken to keep the overhead low. The only data member the C++
2814	classes add (compared to plain C-style watchers) is the event loop pointer	4088	classes add (compared to plain C-style watchers) is the event loop pointer
2815	that the watcher is associated with (or no additional members at all if	4089	that the watcher is associated with (or no additional members at all if
2816	you disable C<EV_MULTIPLICITY> when embedding libev).	4090	you disable C<EV_MULTIPLICITY> when embedding libev).
2817		4091
2818	Currently, functions, and static and non-static member functions can be	4092	Currently, functions, static and non-static member functions and classes
2819	used as callbacks. Other types should be easy to add as long as they only	4093	with C<operator ()> can be used as callbacks. Other types should be easy
2820	need one additional pointer for context. If you need support for other	4094	to add as long as they only need one additional pointer for context. If
2821	types of functors please contact the author (preferably after implementing	4095	you need support for other types of functors please contact the author
2822	it).	4096	(preferably after implementing it).
		4097
		4098	For all this to work, your C++ compiler either has to use the same calling
		4099	conventions as your C compiler (for static member functions), or you have
		4100	to embed libev and compile libev itself as C++.
2823		4101
2824	Here is a list of things available in the C<ev> namespace:	4102	Here is a list of things available in the C<ev> namespace:
2825		4103
2826	=over 4	4104	=over 4
2827		4105
…		…
2837	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4115	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2838		4116
2839	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4117	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2840	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4118	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2841	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4119	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2842	defines by many implementations.	4120	defined by many implementations.
2843		4121
2844	All of those classes have these methods:	4122	All of those classes have these methods:
2845		4123
2846	=over 4	4124	=over 4
2847		4125
2848	=item ev::TYPE::TYPE ()	4126	=item ev::TYPE::TYPE ()
2849		4127
2850	=item ev::TYPE::TYPE (struct ev_loop *)	4128	=item ev::TYPE::TYPE (loop)
2851		4129
2852	=item ev::TYPE::~TYPE	4130	=item ev::TYPE::~TYPE
2853		4131
2854	The constructor (optionally) takes an event loop to associate the watcher	4132	The constructor (optionally) takes an event loop to associate the watcher
2855	with. If it is omitted, it will use C<EV_DEFAULT>.	4133	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2888	myclass obj;	4166	myclass obj;
2889	ev::io iow;	4167	ev::io iow;
2890	iow.set <myclass, &myclass::io_cb> (&obj);	4168	iow.set <myclass, &myclass::io_cb> (&obj);
2891		4169
2892	=item w->set (object *)	4170	=item w->set (object *)
2893
2894	This is an B<experimental> feature that might go away in a future version.
2895		4171
2896	This is a variation of a method callback - leaving out the method to call	4172	This is a variation of a method callback - leaving out the method to call
2897	will default the method to C<operator ()>, which makes it possible to use	4173	will default the method to C<operator ()>, which makes it possible to use
2898	functor objects without having to manually specify the C<operator ()> all	4174	functor objects without having to manually specify the C<operator ()> all
2899	the time. Incidentally, you can then also leave out the template argument	4175	the time. Incidentally, you can then also leave out the template argument
…		…
2911	void operator() (ev::io &w, int revents)	4187	void operator() (ev::io &w, int revents)
2912	{	4188	{
2913	...	4189	...
2914	}	4190	}
2915	}	4191	}
2916		4192
2917	myfunctor f;	4193	myfunctor f;
2918		4194
2919	ev::io w;	4195	ev::io w;
2920	w.set (&f);	4196	w.set (&f);
2921		4197
…		…
2932	Example: Use a plain function as callback.	4208	Example: Use a plain function as callback.
2933		4209
2934	static void io_cb (ev::io &w, int revents) { }	4210	static void io_cb (ev::io &w, int revents) { }
2935	iow.set <io_cb> ();	4211	iow.set <io_cb> ();
2936		4212
2937	=item w->set (struct ev_loop *)	4213	=item w->set (loop)
2938		4214
2939	Associates a different C<struct ev_loop> with this watcher. You can only	4215	Associates a different C<struct ev_loop> with this watcher. You can only
2940	do this when the watcher is inactive (and not pending either).	4216	do this when the watcher is inactive (and not pending either).
2941		4217
2942	=item w->set ([arguments])	4218	=item w->set ([arguments])
2943		4219
2944	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4220	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4221	with the same arguments. Either this method or a suitable start method
2945	called at least once. Unlike the C counterpart, an active watcher gets	4222	must be called at least once. Unlike the C counterpart, an active watcher
2946	automatically stopped and restarted when reconfiguring it with this	4223	gets automatically stopped and restarted when reconfiguring it with this
2947	method.	4224	method.
		4225
		4226	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4227	clashing with the C<set (loop)> method.
2948		4228
2949	=item w->start ()	4229	=item w->start ()
2950		4230
2951	Starts the watcher. Note that there is no C<loop> argument, as the	4231	Starts the watcher. Note that there is no C<loop> argument, as the
2952	constructor already stores the event loop.	4232	constructor already stores the event loop.
2953		4233
		4234	=item w->start ([arguments])
		4235
		4236	Instead of calling C<set> and C<start> methods separately, it is often
		4237	convenient to wrap them in one call. Uses the same type of arguments as
		4238	the configure C<set> method of the watcher.
		4239
2954	=item w->stop ()	4240	=item w->stop ()
2955		4241
2956	Stops the watcher if it is active. Again, no C<loop> argument.	4242	Stops the watcher if it is active. Again, no C<loop> argument.
2957		4243
2958	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4244	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2970		4256
2971	=back	4257	=back
2972		4258
2973	=back	4259	=back
2974		4260
2975	Example: Define a class with an IO and idle watcher, start one of them in	4261	Example: Define a class with two I/O and idle watchers, start the I/O
2976	the constructor.	4262	watchers in the constructor.
2977		4263
2978	class myclass	4264	class myclass
2979	{	4265	{
2980	ev::io io ; void io_cb (ev::io &w, int revents);	4266	ev::io io ; void io_cb (ev::io &w, int revents);
		4267	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2981	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4268	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2982		4269
2983	myclass (int fd)	4270	myclass (int fd)
2984	{	4271	{
2985	io .set <myclass, &myclass::io_cb > (this);	4272	io .set <myclass, &myclass::io_cb > (this);
		4273	io2 .set <myclass, &myclass::io2_cb > (this);
2986	idle.set <myclass, &myclass::idle_cb> (this);	4274	idle.set <myclass, &myclass::idle_cb> (this);
2987		4275
2988	io.start (fd, ev::READ);	4276	io.set (fd, ev::WRITE); // configure the watcher
		4277	io.start (); // start it whenever convenient
		4278
		4279	io2.start (fd, ev::READ); // set + start in one call
2989	}	4280	}
2990	};	4281	};
2991		4282
2992		4283
2993	=head1 OTHER LANGUAGE BINDINGS	4284	=head1 OTHER LANGUAGE BINDINGS
…		…
3012	L<http://software.schmorp.de/pkg/EV>.	4303	L<http://software.schmorp.de/pkg/EV>.
3013		4304
3014	=item Python	4305	=item Python
3015		4306
3016	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4307	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
3017	seems to be quite complete and well-documented. Note, however, that the	4308	seems to be quite complete and well-documented.
3018	patch they require for libev is outright dangerous as it breaks the ABI
3019	for everybody else, and therefore, should never be applied in an installed
3020	libev (if python requires an incompatible ABI then it needs to embed
3021	libev).
3022		4309
3023	=item Ruby	4310	=item Ruby
3024		4311
3025	Tony Arcieri has written a ruby extension that offers access to a subset	4312	Tony Arcieri has written a ruby extension that offers access to a subset
3026	of the libev API and adds file handle abstractions, asynchronous DNS and	4313	of the libev API and adds file handle abstractions, asynchronous DNS and
…		…
3028	L<http://rev.rubyforge.org/>.	4315	L<http://rev.rubyforge.org/>.
3029		4316
3030	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>	4317	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
3031	makes rev work even on mingw.	4318	makes rev work even on mingw.
3032		4319
		4320	=item Haskell
		4321
		4322	A haskell binding to libev is available at
		4323	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4324
3033	=item D	4325	=item D
3034		4326
3035	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4327	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3036	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4328	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3037		4329
3038	=item Ocaml	4330	=item Ocaml
3039		4331
3040	Erkki Seppala has written Ocaml bindings for libev, to be found at	4332	Erkki Seppala has written Ocaml bindings for libev, to be found at
3041	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4333	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4334
		4335	=item Lua
		4336
		4337	Brian Maher has written a partial interface to libev for lua (at the
		4338	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4339	L<http://github.com/brimworks/lua-ev>.
		4340
		4341	=item Javascript
		4342
		4343	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4344
		4345	=item Others
		4346
		4347	There are others, and I stopped counting.
3042		4348
3043	=back	4349	=back
3044		4350
3045		4351
3046	=head1 MACRO MAGIC	4352	=head1 MACRO MAGIC
…		…
3060	loop argument"). The C<EV_A> form is used when this is the sole argument,	4366	loop argument"). The C<EV_A> form is used when this is the sole argument,
3061	C<EV_A_> is used when other arguments are following. Example:	4367	C<EV_A_> is used when other arguments are following. Example:
3062		4368
3063	ev_unref (EV_A);	4369	ev_unref (EV_A);
3064	ev_timer_add (EV_A_ watcher);	4370	ev_timer_add (EV_A_ watcher);
3065	ev_loop (EV_A_ 0);	4371	ev_run (EV_A_ 0);
3066		4372
3067	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4373	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3068	which is often provided by the following macro.	4374	which is often provided by the following macro.
3069		4375
3070	=item C<EV_P>, C<EV_P_>	4376	=item C<EV_P>, C<EV_P_>
…		…
3083	suitable for use with C<EV_A>.	4389	suitable for use with C<EV_A>.
3084		4390
3085	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4391	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3086		4392
3087	Similar to the other two macros, this gives you the value of the default	4393	Similar to the other two macros, this gives you the value of the default
3088	loop, if multiple loops are supported ("ev loop default").	4394	loop, if multiple loops are supported ("ev loop default"). The default loop
		4395	will be initialised if it isn't already initialised.
		4396
		4397	For non-multiplicity builds, these macros do nothing, so you always have
		4398	to initialise the loop somewhere.
3089		4399
3090	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4400	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3091		4401
3092	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4402	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3093	default loop has been initialised (C<UC> == unchecked). Their behaviour	4403	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3110	}	4420	}
3111		4421
3112	ev_check check;	4422	ev_check check;
3113	ev_check_init (&check, check_cb);	4423	ev_check_init (&check, check_cb);
3114	ev_check_start (EV_DEFAULT_ &check);	4424	ev_check_start (EV_DEFAULT_ &check);
3115	ev_loop (EV_DEFAULT_ 0);	4425	ev_run (EV_DEFAULT_ 0);
3116		4426
3117	=head1 EMBEDDING	4427	=head1 EMBEDDING
3118		4428
3119	Libev can (and often is) directly embedded into host	4429	Libev can (and often is) directly embedded into host
3120	applications. Examples of applications that embed it include the Deliantra	4430	applications. Examples of applications that embed it include the Deliantra
…		…
3160	ev_vars.h	4470	ev_vars.h
3161	ev_wrap.h	4471	ev_wrap.h
3162		4472
3163	ev_win32.c required on win32 platforms only	4473	ev_win32.c required on win32 platforms only
3164		4474
3165	ev_select.c only when select backend is enabled (which is enabled by default)	4475	ev_select.c only when select backend is enabled
3166	ev_poll.c only when poll backend is enabled (disabled by default)	4476	ev_poll.c only when poll backend is enabled
3167	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4477	ev_epoll.c only when the epoll backend is enabled
		4478	ev_linuxaio.c only when the linux aio backend is enabled
3168	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4479	ev_kqueue.c only when the kqueue backend is enabled
3169	ev_port.c only when the solaris port backend is enabled (disabled by default)	4480	ev_port.c only when the solaris port backend is enabled
3170		4481
3171	F<ev.c> includes the backend files directly when enabled, so you only need	4482	F<ev.c> includes the backend files directly when enabled, so you only need
3172	to compile this single file.	4483	to compile this single file.
3173		4484
3174	=head3 LIBEVENT COMPATIBILITY API	4485	=head3 LIBEVENT COMPATIBILITY API
…		…
3200	libev.m4	4511	libev.m4
3201		4512
3202	=head2 PREPROCESSOR SYMBOLS/MACROS	4513	=head2 PREPROCESSOR SYMBOLS/MACROS
3203		4514
3204	Libev can be configured via a variety of preprocessor symbols you have to	4515	Libev can be configured via a variety of preprocessor symbols you have to
3205	define before including any of its files. The default in the absence of	4516	define before including (or compiling) any of its files. The default in
3206	autoconf is documented for every option.	4517	the absence of autoconf is documented for every option.
		4518
		4519	Symbols marked with "(h)" do not change the ABI, and can have different
		4520	values when compiling libev vs. including F<ev.h>, so it is permissible
		4521	to redefine them before including F<ev.h> without breaking compatibility
		4522	to a compiled library. All other symbols change the ABI, which means all
		4523	users of libev and the libev code itself must be compiled with compatible
		4524	settings.
3207		4525
3208	=over 4	4526	=over 4
3209		4527
		4528	=item EV_COMPAT3 (h)
		4529
		4530	Backwards compatibility is a major concern for libev. This is why this
		4531	release of libev comes with wrappers for the functions and symbols that
		4532	have been renamed between libev version 3 and 4.
		4533
		4534	You can disable these wrappers (to test compatibility with future
		4535	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4536	sources. This has the additional advantage that you can drop the C<struct>
		4537	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4538	typedef in that case.
		4539
		4540	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4541	and in some even more future version the compatibility code will be
		4542	removed completely.
		4543
3210	=item EV_STANDALONE	4544	=item EV_STANDALONE (h)
3211		4545
3212	Must always be C<1> if you do not use autoconf configuration, which	4546	Must always be C<1> if you do not use autoconf configuration, which
3213	keeps libev from including F<config.h>, and it also defines dummy	4547	keeps libev from including F<config.h>, and it also defines dummy
3214	implementations for some libevent functions (such as logging, which is not	4548	implementations for some libevent functions (such as logging, which is not
3215	supported). It will also not define any of the structs usually found in	4549	supported). It will also not define any of the structs usually found in
3216	F<event.h> that are not directly supported by the libev core alone.	4550	F<event.h> that are not directly supported by the libev core alone.
3217		4551
3218	In stanbdalone mode, libev will still try to automatically deduce the	4552	In standalone mode, libev will still try to automatically deduce the
3219	configuration, but has to be more conservative.	4553	configuration, but has to be more conservative.
		4554
		4555	=item EV_USE_FLOOR
		4556
		4557	If defined to be C<1>, libev will use the C<floor ()> function for its
		4558	periodic reschedule calculations, otherwise libev will fall back on a
		4559	portable (slower) implementation. If you enable this, you usually have to
		4560	link against libm or something equivalent. Enabling this when the C<floor>
		4561	function is not available will fail, so the safe default is to not enable
		4562	this.
3220		4563
3221	=item EV_USE_MONOTONIC	4564	=item EV_USE_MONOTONIC
3222		4565
3223	If defined to be C<1>, libev will try to detect the availability of the	4566	If defined to be C<1>, libev will try to detect the availability of the
3224	monotonic clock option at both compile time and runtime. Otherwise no	4567	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3288	be used is the winsock select). This means that it will call	4631	be used is the winsock select). This means that it will call
3289	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4632	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3290	it is assumed that all these functions actually work on fds, even	4633	it is assumed that all these functions actually work on fds, even
3291	on win32. Should not be defined on non-win32 platforms.	4634	on win32. Should not be defined on non-win32 platforms.
3292		4635
3293	=item EV_FD_TO_WIN32_HANDLE	4636	=item EV_FD_TO_WIN32_HANDLE(fd)
3294		4637
3295	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4638	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3296	file descriptors to socket handles. When not defining this symbol (the	4639	file descriptors to socket handles. When not defining this symbol (the
3297	default), then libev will call C<_get_osfhandle>, which is usually	4640	default), then libev will call C<_get_osfhandle>, which is usually
3298	correct. In some cases, programs use their own file descriptor management,	4641	correct. In some cases, programs use their own file descriptor management,
3299	in which case they can provide this function to map fds to socket handles.	4642	in which case they can provide this function to map fds to socket handles.
3300		4643
		4644	=item EV_WIN32_HANDLE_TO_FD(handle)
		4645
		4646	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4647	using the standard C<_open_osfhandle> function. For programs implementing
		4648	their own fd to handle mapping, overwriting this function makes it easier
		4649	to do so. This can be done by defining this macro to an appropriate value.
		4650
		4651	=item EV_WIN32_CLOSE_FD(fd)
		4652
		4653	If programs implement their own fd to handle mapping on win32, then this
		4654	macro can be used to override the C<close> function, useful to unregister
		4655	file descriptors again. Note that the replacement function has to close
		4656	the underlying OS handle.
		4657
		4658	=item EV_USE_WSASOCKET
		4659
		4660	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4661	communication socket, which works better in some environments. Otherwise,
		4662	the normal C<socket> function will be used, which works better in other
		4663	environments.
		4664
3301	=item EV_USE_POLL	4665	=item EV_USE_POLL
3302		4666
3303	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4667	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3304	backend. Otherwise it will be enabled on non-win32 platforms. It	4668	backend. Otherwise it will be enabled on non-win32 platforms. It
3305	takes precedence over select.	4669	takes precedence over select.
…		…
3309	If defined to be C<1>, libev will compile in support for the Linux	4673	If defined to be C<1>, libev will compile in support for the Linux
3310	C<epoll>(7) backend. Its availability will be detected at runtime,	4674	C<epoll>(7) backend. Its availability will be detected at runtime,
3311	otherwise another method will be used as fallback. This is the preferred	4675	otherwise another method will be used as fallback. This is the preferred
3312	backend for GNU/Linux systems. If undefined, it will be enabled if the	4676	backend for GNU/Linux systems. If undefined, it will be enabled if the
3313	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4677	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4678
		4679	=item EV_USE_LINUXAIO
		4680
		4681	If defined to be C<1>, libev will compile in support for the Linux
		4682	aio backend. Due to it's currenbt limitations it has to be requested
		4683	explicitly. If undefined, it will be enabled on linux, otherwise
		4684	disabled.
3314		4685
3315	=item EV_USE_KQUEUE	4686	=item EV_USE_KQUEUE
3316		4687
3317	If defined to be C<1>, libev will compile in support for the BSD style	4688	If defined to be C<1>, libev will compile in support for the BSD style
3318	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4689	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3340	If defined to be C<1>, libev will compile in support for the Linux inotify	4711	If defined to be C<1>, libev will compile in support for the Linux inotify
3341	interface to speed up C<ev_stat> watchers. Its actual availability will	4712	interface to speed up C<ev_stat> watchers. Its actual availability will
3342	be detected at runtime. If undefined, it will be enabled if the headers	4713	be detected at runtime. If undefined, it will be enabled if the headers
3343	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4714	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3344		4715
		4716	=item EV_NO_SMP
		4717
		4718	If defined to be C<1>, libev will assume that memory is always coherent
		4719	between threads, that is, threads can be used, but threads never run on
		4720	different cpus (or different cpu cores). This reduces dependencies
		4721	and makes libev faster.
		4722
		4723	=item EV_NO_THREADS
		4724
		4725	If defined to be C<1>, libev will assume that it will never be called from
		4726	different threads (that includes signal handlers), which is a stronger
		4727	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4728	libev faster.
		4729
3345	=item EV_ATOMIC_T	4730	=item EV_ATOMIC_T
3346		4731
3347	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4732	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3348	access is atomic with respect to other threads or signal contexts. No such	4733	access is atomic with respect to other threads or signal contexts. No
3349	type is easily found in the C language, so you can provide your own type	4734	such type is easily found in the C language, so you can provide your own
3350	that you know is safe for your purposes. It is used both for signal handler "locking"	4735	type that you know is safe for your purposes. It is used both for signal
3351	as well as for signal and thread safety in C<ev_async> watchers.	4736	handler "locking" as well as for signal and thread safety in C<ev_async>
		4737	watchers.
3352		4738
3353	In the absence of this define, libev will use C<sig_atomic_t volatile>	4739	In the absence of this define, libev will use C<sig_atomic_t volatile>
3354	(from F<signal.h>), which is usually good enough on most platforms.	4740	(from F<signal.h>), which is usually good enough on most platforms.
3355		4741
3356	=item EV_H	4742	=item EV_H (h)
3357		4743
3358	The name of the F<ev.h> header file used to include it. The default if	4744	The name of the F<ev.h> header file used to include it. The default if
3359	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4745	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3360	used to virtually rename the F<ev.h> header file in case of conflicts.	4746	used to virtually rename the F<ev.h> header file in case of conflicts.
3361		4747
3362	=item EV_CONFIG_H	4748	=item EV_CONFIG_H (h)
3363		4749
3364	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4750	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3365	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4751	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3366	C<EV_H>, above.	4752	C<EV_H>, above.
3367		4753
3368	=item EV_EVENT_H	4754	=item EV_EVENT_H (h)
3369		4755
3370	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4756	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3371	of how the F<event.h> header can be found, the default is C<"event.h">.	4757	of how the F<event.h> header can be found, the default is C<"event.h">.
3372		4758
3373	=item EV_PROTOTYPES	4759	=item EV_PROTOTYPES (h)
3374		4760
3375	If defined to be C<0>, then F<ev.h> will not define any function	4761	If defined to be C<0>, then F<ev.h> will not define any function
3376	prototypes, but still define all the structs and other symbols. This is	4762	prototypes, but still define all the structs and other symbols. This is
3377	occasionally useful if you want to provide your own wrapper functions	4763	occasionally useful if you want to provide your own wrapper functions
3378	around libev functions.	4764	around libev functions.
…		…
3383	will have the C<struct ev_loop *> as first argument, and you can create	4769	will have the C<struct ev_loop *> as first argument, and you can create
3384	additional independent event loops. Otherwise there will be no support	4770	additional independent event loops. Otherwise there will be no support
3385	for multiple event loops and there is no first event loop pointer	4771	for multiple event loops and there is no first event loop pointer
3386	argument. Instead, all functions act on the single default loop.	4772	argument. Instead, all functions act on the single default loop.
3387		4773
		4774	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4775	default loop when multiplicity is switched off - you always have to
		4776	initialise the loop manually in this case.
		4777
3388	=item EV_MINPRI	4778	=item EV_MINPRI
3389		4779
3390	=item EV_MAXPRI	4780	=item EV_MAXPRI
3391		4781
3392	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4782	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3400	fine.	4790	fine.
3401		4791
3402	If your embedding application does not need any priorities, defining these	4792	If your embedding application does not need any priorities, defining these
3403	both to C<0> will save some memory and CPU.	4793	both to C<0> will save some memory and CPU.
3404		4794
3405	=item EV_PERIODIC_ENABLE	4795	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4796	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4797	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3406		4798
3407	If undefined or defined to be C<1>, then periodic timers are supported. If	4799	If undefined or defined to be C<1> (and the platform supports it), then
3408	defined to be C<0>, then they are not. Disabling them saves a few kB of	4800	the respective watcher type is supported. If defined to be C<0>, then it
3409	code.	4801	is not. Disabling watcher types mainly saves code size.
3410		4802
3411	=item EV_IDLE_ENABLE	4803	=item EV_FEATURES
3412
3413	If undefined or defined to be C<1>, then idle watchers are supported. If
3414	defined to be C<0>, then they are not. Disabling them saves a few kB of
3415	code.
3416
3417	=item EV_EMBED_ENABLE
3418
3419	If undefined or defined to be C<1>, then embed watchers are supported. If
3420	defined to be C<0>, then they are not. Embed watchers rely on most other
3421	watcher types, which therefore must not be disabled.
3422
3423	=item EV_STAT_ENABLE
3424
3425	If undefined or defined to be C<1>, then stat watchers are supported. If
3426	defined to be C<0>, then they are not.
3427
3428	=item EV_FORK_ENABLE
3429
3430	If undefined or defined to be C<1>, then fork watchers are supported. If
3431	defined to be C<0>, then they are not.
3432
3433	=item EV_ASYNC_ENABLE
3434
3435	If undefined or defined to be C<1>, then async watchers are supported. If
3436	defined to be C<0>, then they are not.
3437
3438	=item EV_MINIMAL
3439		4804
3440	If you need to shave off some kilobytes of code at the expense of some	4805	If you need to shave off some kilobytes of code at the expense of some
3441	speed, define this symbol to C<1>. Currently this is used to override some	4806	speed (but with the full API), you can define this symbol to request
3442	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4807	certain subsets of functionality. The default is to enable all features
3443	much smaller 2-heap for timer management over the default 4-heap.	4808	that can be enabled on the platform.
		4809
		4810	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4811	with some broad features you want) and then selectively re-enable
		4812	additional parts you want, for example if you want everything minimal,
		4813	but multiple event loop support, async and child watchers and the poll
		4814	backend, use this:
		4815
		4816	#define EV_FEATURES 0
		4817	#define EV_MULTIPLICITY 1
		4818	#define EV_USE_POLL 1
		4819	#define EV_CHILD_ENABLE 1
		4820	#define EV_ASYNC_ENABLE 1
		4821
		4822	The actual value is a bitset, it can be a combination of the following
		4823	values (by default, all of these are enabled):
		4824
		4825	=over 4
		4826
		4827	=item C<1> - faster/larger code
		4828
		4829	Use larger code to speed up some operations.
		4830
		4831	Currently this is used to override some inlining decisions (enlarging the
		4832	code size by roughly 30% on amd64).
		4833
		4834	When optimising for size, use of compiler flags such as C<-Os> with
		4835	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4836	assertions.
		4837
		4838	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4839	(e.g. gcc with C<-Os>).
		4840
		4841	=item C<2> - faster/larger data structures
		4842
		4843	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4844	hash table sizes and so on. This will usually further increase code size
		4845	and can additionally have an effect on the size of data structures at
		4846	runtime.
		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<4> - full API configuration
		4852
		4853	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4854	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4855
		4856	=item C<8> - full API
		4857
		4858	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4859	details on which parts of the API are still available without this
		4860	feature, and do not complain if this subset changes over time.
		4861
		4862	=item C<16> - enable all optional watcher types
		4863
		4864	Enables all optional watcher types. If you want to selectively enable
		4865	only some watcher types other than I/O and timers (e.g. prepare,
		4866	embed, async, child...) you can enable them manually by defining
		4867	C<EV_watchertype_ENABLE> to C<1> instead.
		4868
		4869	=item C<32> - enable all backends
		4870
		4871	This enables all backends - without this feature, you need to enable at
		4872	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4873
		4874	=item C<64> - enable OS-specific "helper" APIs
		4875
		4876	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4877	default.
		4878
		4879	=back
		4880
		4881	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4882	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4883	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4884	watchers, timers and monotonic clock support.
		4885
		4886	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4887	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4888	your program might be left out as well - a binary starting a timer and an
		4889	I/O watcher then might come out at only 5Kb.
		4890
		4891	=item EV_API_STATIC
		4892
		4893	If this symbol is defined (by default it is not), then all identifiers
		4894	will have static linkage. This means that libev will not export any
		4895	identifiers, and you cannot link against libev anymore. This can be useful
		4896	when you embed libev, only want to use libev functions in a single file,
		4897	and do not want its identifiers to be visible.
		4898
		4899	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4900	wants to use libev.
		4901
		4902	This option only works when libev is compiled with a C compiler, as C++
		4903	doesn't support the required declaration syntax.
		4904
		4905	=item EV_AVOID_STDIO
		4906
		4907	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4908	functions (printf, scanf, perror etc.). This will increase the code size
		4909	somewhat, but if your program doesn't otherwise depend on stdio and your
		4910	libc allows it, this avoids linking in the stdio library which is quite
		4911	big.
		4912
		4913	Note that error messages might become less precise when this option is
		4914	enabled.
		4915
		4916	=item EV_NSIG
		4917
		4918	The highest supported signal number, +1 (or, the number of
		4919	signals): Normally, libev tries to deduce the maximum number of signals
		4920	automatically, but sometimes this fails, in which case it can be
		4921	specified. Also, using a lower number than detected (C<32> should be
		4922	good for about any system in existence) can save some memory, as libev
		4923	statically allocates some 12-24 bytes per signal number.
3444		4924
3445	=item EV_PID_HASHSIZE	4925	=item EV_PID_HASHSIZE
3446		4926
3447	C<ev_child> watchers use a small hash table to distribute workload by	4927	C<ev_child> watchers use a small hash table to distribute workload by
3448	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4928	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3449	than enough. If you need to manage thousands of children you might want to	4929	usually more than enough. If you need to manage thousands of children you
3450	increase this value (I<must> be a power of two).	4930	might want to increase this value (I<must> be a power of two).
3451		4931
3452	=item EV_INOTIFY_HASHSIZE	4932	=item EV_INOTIFY_HASHSIZE
3453		4933
3454	C<ev_stat> watchers use a small hash table to distribute workload by	4934	C<ev_stat> watchers use a small hash table to distribute workload by
3455	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4935	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3456	usually more than enough. If you need to manage thousands of C<ev_stat>	4936	disabled), usually more than enough. If you need to manage thousands of
3457	watchers you might want to increase this value (I<must> be a power of	4937	C<ev_stat> watchers you might want to increase this value (I<must> be a
3458	two).	4938	power of two).
3459		4939
3460	=item EV_USE_4HEAP	4940	=item EV_USE_4HEAP
3461		4941
3462	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4942	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3463	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4943	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3464	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4944	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3465	faster performance with many (thousands) of watchers.	4945	faster performance with many (thousands) of watchers.
3466		4946
3467	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4947	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3468	(disabled).	4948	will be C<0>.
3469		4949
3470	=item EV_HEAP_CACHE_AT	4950	=item EV_HEAP_CACHE_AT
3471		4951
3472	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
3473	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4953	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3474	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4954	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3475	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4955	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3476	but avoids random read accesses on heap changes. This improves performance	4956	but avoids random read accesses on heap changes. This improves performance
3477	noticeably with many (hundreds) of watchers.	4957	noticeably with many (hundreds) of watchers.
3478		4958
3479	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4959	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3480	(disabled).	4960	will be C<0>.
3481		4961
3482	=item EV_VERIFY	4962	=item EV_VERIFY
3483		4963
3484	Controls how much internal verification (see C<ev_loop_verify ()>) will	4964	Controls how much internal verification (see C<ev_verify ()>) will
3485	be done: If set to C<0>, no internal verification code will be compiled	4965	be done: If set to C<0>, no internal verification code will be compiled
3486	in. If set to C<1>, then verification code will be compiled in, but not	4966	in. If set to C<1>, then verification code will be compiled in, but not
3487	called. If set to C<2>, then the internal verification code will be	4967	called. If set to C<2>, then the internal verification code will be
3488	called once per loop, which can slow down libev. If set to C<3>, then the	4968	called once per loop, which can slow down libev. If set to C<3>, then the
3489	verification code will be called very frequently, which will slow down	4969	verification code will be called very frequently, which will slow down
3490	libev considerably.	4970	libev considerably.
3491		4971
3492	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4972	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3493	C<0>.	4973	will be C<0>.
3494		4974
3495	=item EV_COMMON	4975	=item EV_COMMON
3496		4976
3497	By default, all watchers have a C<void *data> member. By redefining	4977	By default, all watchers have a C<void *data> member. By redefining
3498	this macro to a something else you can include more and other types of	4978	this macro to something else you can include more and other types of
3499	members. You have to define it each time you include one of the files,	4979	members. You have to define it each time you include one of the files,
3500	though, and it must be identical each time.	4980	though, and it must be identical each time.
3501		4981
3502	For example, the perl EV module uses something like this:	4982	For example, the perl EV module uses something like this:
3503		4983
…		…
3556	file.	5036	file.
3557		5037
3558	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5038	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3559	that everybody includes and which overrides some configure choices:	5039	that everybody includes and which overrides some configure choices:
3560		5040
3561	#define EV_MINIMAL 1	5041	#define EV_FEATURES 8
3562	#define EV_USE_POLL 0	5042	#define EV_USE_SELECT 1
3563	#define EV_MULTIPLICITY 0
3564	#define EV_PERIODIC_ENABLE 0	5043	#define EV_PREPARE_ENABLE 1
		5044	#define EV_IDLE_ENABLE 1
3565	#define EV_STAT_ENABLE 0	5045	#define EV_SIGNAL_ENABLE 1
3566	#define EV_FORK_ENABLE 0	5046	#define EV_CHILD_ENABLE 1
		5047	#define EV_USE_STDEXCEPT 0
3567	#define EV_CONFIG_H <config.h>	5048	#define EV_CONFIG_H <config.h>
3568	#define EV_MINPRI 0
3569	#define EV_MAXPRI 0
3570		5049
3571	#include "ev++.h"	5050	#include "ev++.h"
3572		5051
3573	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5052	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3574		5053
3575	#include "ev_cpp.h"	5054	#include "ev_cpp.h"
3576	#include "ev.c"	5055	#include "ev.c"
3577		5056
3578	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5057	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3579		5058
3580	=head2 THREADS AND COROUTINES	5059	=head2 THREADS AND COROUTINES
3581		5060
3582	=head3 THREADS	5061	=head3 THREADS
3583		5062
…		…
3634	default loop and triggering an C<ev_async> watcher from the default loop	5113	default loop and triggering an C<ev_async> watcher from the default loop
3635	watcher callback into the event loop interested in the signal.	5114	watcher callback into the event loop interested in the signal.
3636		5115
3637	=back	5116	=back
3638		5117
		5118	See also L</THREAD LOCKING EXAMPLE>.
		5119
3639	=head3 COROUTINES	5120	=head3 COROUTINES
3640		5121
3641	Libev is very accommodating to coroutines ("cooperative threads"):	5122	Libev is very accommodating to coroutines ("cooperative threads"):
3642	libev fully supports nesting calls to its functions from different	5123	libev fully supports nesting calls to its functions from different
3643	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5124	coroutines (e.g. you can call C<ev_run> on the same loop from two
3644	different coroutines, and switch freely between both coroutines running the	5125	different coroutines, and switch freely between both coroutines running
3645	loop, as long as you don't confuse yourself). The only exception is that	5126	the loop, as long as you don't confuse yourself). The only exception is
3646	you must not do this from C<ev_periodic> reschedule callbacks.	5127	that you must not do this from C<ev_periodic> reschedule callbacks.
3647		5128
3648	Care has been taken to ensure that libev does not keep local state inside	5129	Care has been taken to ensure that libev does not keep local state inside
3649	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5130	C<ev_run>, and other calls do not usually allow for coroutine switches as
3650	they do not call any callbacks.	5131	they do not call any callbacks.
3651		5132
3652	=head2 COMPILER WARNINGS	5133	=head2 COMPILER WARNINGS
3653		5134
3654	Depending on your compiler and compiler settings, you might get no or a	5135	Depending on your compiler and compiler settings, you might get no or a
…		…
3665	maintainable.	5146	maintainable.
3666		5147
3667	And of course, some compiler warnings are just plain stupid, or simply	5148	And of course, some compiler warnings are just plain stupid, or simply
3668	wrong (because they don't actually warn about the condition their message	5149	wrong (because they don't actually warn about the condition their message
3669	seems to warn about). For example, certain older gcc versions had some	5150	seems to warn about). For example, certain older gcc versions had some
3670	warnings that resulted an extreme number of false positives. These have	5151	warnings that resulted in an extreme number of false positives. These have
3671	been fixed, but some people still insist on making code warn-free with	5152	been fixed, but some people still insist on making code warn-free with
3672	such buggy versions.	5153	such buggy versions.
3673		5154
3674	While libev is written to generate as few warnings as possible,	5155	While libev is written to generate as few warnings as possible,
3675	"warn-free" code is not a goal, and it is recommended not to build libev	5156	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3711	I suggest using suppression lists.	5192	I suggest using suppression lists.
3712		5193
3713		5194
3714	=head1 PORTABILITY NOTES	5195	=head1 PORTABILITY NOTES
3715		5196
		5197	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5198
		5199	GNU/Linux is the only common platform that supports 64 bit file/large file
		5200	interfaces but I<disables> them by default.
		5201
		5202	That means that libev compiled in the default environment doesn't support
		5203	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5204
		5205	Unfortunately, many programs try to work around this GNU/Linux issue
		5206	by enabling the large file API, which makes them incompatible with the
		5207	standard libev compiled for their system.
		5208
		5209	Likewise, libev cannot enable the large file API itself as this would
		5210	suddenly make it incompatible to the default compile time environment,
		5211	i.e. all programs not using special compile switches.
		5212
		5213	=head2 OS/X AND DARWIN BUGS
		5214
		5215	The whole thing is a bug if you ask me - basically any system interface
		5216	you touch is broken, whether it is locales, poll, kqueue or even the
		5217	OpenGL drivers.
		5218
		5219	=head3 C<kqueue> is buggy
		5220
		5221	The kqueue syscall is broken in all known versions - most versions support
		5222	only sockets, many support pipes.
		5223
		5224	Libev tries to work around this by not using C<kqueue> by default on this
		5225	rotten platform, but of course you can still ask for it when creating a
		5226	loop - embedding a socket-only kqueue loop into a select-based one is
		5227	probably going to work well.
		5228
		5229	=head3 C<poll> is buggy
		5230
		5231	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5232	implementation by something calling C<kqueue> internally around the 10.5.6
		5233	release, so now C<kqueue> I<and> C<poll> are broken.
		5234
		5235	Libev tries to work around this by not using C<poll> by default on
		5236	this rotten platform, but of course you can still ask for it when creating
		5237	a loop.
		5238
		5239	=head3 C<select> is buggy
		5240
		5241	All that's left is C<select>, and of course Apple found a way to fuck this
		5242	one up as well: On OS/X, C<select> actively limits the number of file
		5243	descriptors you can pass in to 1024 - your program suddenly crashes when
		5244	you use more.
		5245
		5246	There is an undocumented "workaround" for this - defining
		5247	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5248	work on OS/X.
		5249
		5250	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5251
		5252	=head3 C<errno> reentrancy
		5253
		5254	The default compile environment on Solaris is unfortunately so
		5255	thread-unsafe that you can't even use components/libraries compiled
		5256	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5257	defined by default. A valid, if stupid, implementation choice.
		5258
		5259	If you want to use libev in threaded environments you have to make sure
		5260	it's compiled with C<_REENTRANT> defined.
		5261
		5262	=head3 Event port backend
		5263
		5264	The scalable event interface for Solaris is called "event
		5265	ports". Unfortunately, this mechanism is very buggy in all major
		5266	releases. If you run into high CPU usage, your program freezes or you get
		5267	a large number of spurious wakeups, make sure you have all the relevant
		5268	and latest kernel patches applied. No, I don't know which ones, but there
		5269	are multiple ones to apply, and afterwards, event ports actually work
		5270	great.
		5271
		5272	If you can't get it to work, you can try running the program by setting
		5273	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5274	C<select> backends.
		5275
		5276	=head2 AIX POLL BUG
		5277
		5278	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5279	this by trying to avoid the poll backend altogether (i.e. it's not even
		5280	compiled in), which normally isn't a big problem as C<select> works fine
		5281	with large bitsets on AIX, and AIX is dead anyway.
		5282
3716	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5283	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5284
		5285	=head3 General issues
3717		5286
3718	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5287	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3719	requires, and its I/O model is fundamentally incompatible with the POSIX	5288	requires, and its I/O model is fundamentally incompatible with the POSIX
3720	model. Libev still offers limited functionality on this platform in	5289	model. Libev still offers limited functionality on this platform in
3721	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5290	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3722	descriptors. This only applies when using Win32 natively, not when using	5291	descriptors. This only applies when using Win32 natively, not when using
3723	e.g. cygwin.	5292	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5293	as every compiler comes with a slightly differently broken/incompatible
		5294	environment.
3724		5295
3725	Lifting these limitations would basically require the full	5296	Lifting these limitations would basically require the full
3726	re-implementation of the I/O system. If you are into these kinds of	5297	re-implementation of the I/O system. If you are into this kind of thing,
3727	things, then note that glib does exactly that for you in a very portable	5298	then note that glib does exactly that for you in a very portable way (note
3728	way (note also that glib is the slowest event library known to man).	5299	also that glib is the slowest event library known to man).
3729		5300
3730	There is no supported compilation method available on windows except	5301	There is no supported compilation method available on windows except
3731	embedding it into other applications.	5302	embedding it into other applications.
		5303
		5304	Sensible signal handling is officially unsupported by Microsoft - libev
		5305	tries its best, but under most conditions, signals will simply not work.
3732		5306
3733	Not a libev limitation but worth mentioning: windows apparently doesn't	5307	Not a libev limitation but worth mentioning: windows apparently doesn't
3734	accept large writes: instead of resulting in a partial write, windows will	5308	accept large writes: instead of resulting in a partial write, windows will
3735	either accept everything or return C<ENOBUFS> if the buffer is too large,	5309	either accept everything or return C<ENOBUFS> if the buffer is too large,
3736	so make sure you only write small amounts into your sockets (less than a	5310	so make sure you only write small amounts into your sockets (less than a
…		…
3741	the abysmal performance of winsockets, using a large number of sockets	5315	the abysmal performance of winsockets, using a large number of sockets
3742	is not recommended (and not reasonable). If your program needs to use	5316	is not recommended (and not reasonable). If your program needs to use
3743	more than a hundred or so sockets, then likely it needs to use a totally	5317	more than a hundred or so sockets, then likely it needs to use a totally
3744	different implementation for windows, as libev offers the POSIX readiness	5318	different implementation for windows, as libev offers the POSIX readiness
3745	notification model, which cannot be implemented efficiently on windows	5319	notification model, which cannot be implemented efficiently on windows
3746	(Microsoft monopoly games).	5320	(due to Microsoft monopoly games).
3747		5321
3748	A typical way to use libev under windows is to embed it (see the embedding	5322	A typical way to use libev under windows is to embed it (see the embedding
3749	section for details) and use the following F<evwrap.h> header file instead	5323	section for details) and use the following F<evwrap.h> header file instead
3750	of F<ev.h>:	5324	of F<ev.h>:
3751		5325
…		…
3758	you do I<not> compile the F<ev.c> or any other embedded source files!):	5332	you do I<not> compile the F<ev.c> or any other embedded source files!):
3759		5333
3760	#include "evwrap.h"	5334	#include "evwrap.h"
3761	#include "ev.c"	5335	#include "ev.c"
3762		5336
3763	=over 4
3764
3765	=item The winsocket select function	5337	=head3 The winsocket C<select> function
3766		5338
3767	The winsocket C<select> function doesn't follow POSIX in that it	5339	The winsocket C<select> function doesn't follow POSIX in that it
3768	requires socket I<handles> and not socket I<file descriptors> (it is	5340	requires socket I<handles> and not socket I<file descriptors> (it is
3769	also extremely buggy). This makes select very inefficient, and also	5341	also extremely buggy). This makes select very inefficient, and also
3770	requires a mapping from file descriptors to socket handles (the Microsoft	5342	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3779	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5351	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3780		5352
3781	Note that winsockets handling of fd sets is O(n), so you can easily get a	5353	Note that winsockets handling of fd sets is O(n), so you can easily get a
3782	complexity in the O(n²) range when using win32.	5354	complexity in the O(n²) range when using win32.
3783		5355
3784	=item Limited number of file descriptors	5356	=head3 Limited number of file descriptors
3785		5357
3786	Windows has numerous arbitrary (and low) limits on things.	5358	Windows has numerous arbitrary (and low) limits on things.
3787		5359
3788	Early versions of winsocket's select only supported waiting for a maximum	5360	Early versions of winsocket's select only supported waiting for a maximum
3789	of C<64> handles (probably owning to the fact that all windows kernels	5361	of C<64> handles (probably owning to the fact that all windows kernels
3790	can only wait for C<64> things at the same time internally; Microsoft	5362	can only wait for C<64> things at the same time internally; Microsoft
3791	recommends spawning a chain of threads and wait for 63 handles and the	5363	recommends spawning a chain of threads and wait for 63 handles and the
3792	previous thread in each. Great).	5364	previous thread in each. Sounds great!).
3793		5365
3794	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5366	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3795	to some high number (e.g. C<2048>) before compiling the winsocket select	5367	to some high number (e.g. C<2048>) before compiling the winsocket select
3796	call (which might be in libev or elsewhere, for example, perl does its own	5368	call (which might be in libev or elsewhere, for example, perl and many
3797	select emulation on windows).	5369	other interpreters do their own select emulation on windows).
3798		5370
3799	Another limit is the number of file descriptors in the Microsoft runtime	5371	Another limit is the number of file descriptors in the Microsoft runtime
3800	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5372	libraries, which by default is C<64> (there must be a hidden I<64>
3801	or something like this inside Microsoft). You can increase this by calling	5373	fetish or something like this inside Microsoft). You can increase this
3802	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5374	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3803	arbitrary limit), but is broken in many versions of the Microsoft runtime	5375	(another arbitrary limit), but is broken in many versions of the Microsoft
3804	libraries.
3805
3806	This might get you to about C<512> or C<2048> sockets (depending on	5376	runtime libraries. This might get you to about C<512> or C<2048> sockets
3807	windows version and/or the phase of the moon). To get more, you need to	5377	(depending on windows version and/or the phase of the moon). To get more,
3808	wrap all I/O functions and provide your own fd management, but the cost of	5378	you need to wrap all I/O functions and provide your own fd management, but
3809	calling select (O(n²)) will likely make this unworkable.	5379	the cost of calling select (O(n²)) will likely make this unworkable.
3810
3811	=back
3812		5380
3813	=head2 PORTABILITY REQUIREMENTS	5381	=head2 PORTABILITY REQUIREMENTS
3814		5382
3815	In addition to a working ISO-C implementation and of course the	5383	In addition to a working ISO-C implementation and of course the
3816	backend-specific APIs, libev relies on a few additional extensions:	5384	backend-specific APIs, libev relies on a few additional extensions:
…		…
3823	Libev assumes not only that all watcher pointers have the same internal	5391	Libev assumes not only that all watcher pointers have the same internal
3824	structure (guaranteed by POSIX but not by ISO C for example), but it also	5392	structure (guaranteed by POSIX but not by ISO C for example), but it also
3825	assumes that the same (machine) code can be used to call any watcher	5393	assumes that the same (machine) code can be used to call any watcher
3826	callback: The watcher callbacks have different type signatures, but libev	5394	callback: The watcher callbacks have different type signatures, but libev
3827	calls them using an C<ev_watcher *> internally.	5395	calls them using an C<ev_watcher *> internally.
		5396
		5397	=item null pointers and integer zero are represented by 0 bytes
		5398
		5399	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5400	relies on this setting pointers and integers to null.
		5401
		5402	=item pointer accesses must be thread-atomic
		5403
		5404	Accessing a pointer value must be atomic, it must both be readable and
		5405	writable in one piece - this is the case on all current architectures.
3828		5406
3829	=item C<sig_atomic_t volatile> must be thread-atomic as well	5407	=item C<sig_atomic_t volatile> must be thread-atomic as well
3830		5408
3831	The type C<sig_atomic_t volatile> (or whatever is defined as	5409	The type C<sig_atomic_t volatile> (or whatever is defined as
3832	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5410	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3841	thread" or will block signals process-wide, both behaviours would	5419	thread" or will block signals process-wide, both behaviours would
3842	be compatible with libev. Interaction between C<sigprocmask> and	5420	be compatible with libev. Interaction between C<sigprocmask> and
3843	C<pthread_sigmask> could complicate things, however.	5421	C<pthread_sigmask> could complicate things, however.
3844		5422
3845	The most portable way to handle signals is to block signals in all threads	5423	The most portable way to handle signals is to block signals in all threads
3846	except the initial one, and run the default loop in the initial thread as	5424	except the initial one, and run the signal handling loop in the initial
3847	well.	5425	thread as well.
3848		5426
3849	=item C<long> must be large enough for common memory allocation sizes	5427	=item C<long> must be large enough for common memory allocation sizes
3850		5428
3851	To improve portability and simplify its API, libev uses C<long> internally	5429	To improve portability and simplify its API, libev uses C<long> internally
3852	instead of C<size_t> when allocating its data structures. On non-POSIX	5430	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3855	watchers.	5433	watchers.
3856		5434
3857	=item C<double> must hold a time value in seconds with enough accuracy	5435	=item C<double> must hold a time value in seconds with enough accuracy
3858		5436
3859	The type C<double> is used to represent timestamps. It is required to	5437	The type C<double> is used to represent timestamps. It is required to
3860	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5438	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3861	enough for at least into the year 4000. This requirement is fulfilled by	5439	good enough for at least into the year 4000 with millisecond accuracy
		5440	(the design goal for libev). This requirement is overfulfilled by
3862	implementations implementing IEEE 754 (basically all existing ones).	5441	implementations using IEEE 754, which is basically all existing ones.
		5442
		5443	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5444	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5445	is either obsolete or somebody patched it to use C<long double> or
		5446	something like that, just kidding).
3863		5447
3864	=back	5448	=back
3865		5449
3866	If you know of other additional requirements drop me a note.	5450	If you know of other additional requirements drop me a note.
3867		5451
…		…
3929	=item Processing ev_async_send: O(number_of_async_watchers)	5513	=item Processing ev_async_send: O(number_of_async_watchers)
3930		5514
3931	=item Processing signals: O(max_signal_number)	5515	=item Processing signals: O(max_signal_number)
3932		5516
3933	Sending involves a system call I<iff> there were no other C<ev_async_send>	5517	Sending involves a system call I<iff> there were no other C<ev_async_send>
3934	calls in the current loop iteration. Checking for async and signal events	5518	calls in the current loop iteration and the loop is currently
		5519	blocked. Checking for async and signal events involves iterating over all
3935	involves iterating over all running async watchers or all signal numbers.	5520	running async watchers or all signal numbers.
3936		5521
3937	=back	5522	=back
3938		5523
3939		5524
		5525	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5526
		5527	The major version 4 introduced some incompatible changes to the API.
		5528
		5529	At the moment, the C<ev.h> header file provides compatibility definitions
		5530	for all changes, so most programs should still compile. The compatibility
		5531	layer might be removed in later versions of libev, so better update to the
		5532	new API early than late.
		5533
		5534	=over 4
		5535
		5536	=item C<EV_COMPAT3> backwards compatibility mechanism
		5537
		5538	The backward compatibility mechanism can be controlled by
		5539	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5540	section.
		5541
		5542	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5543
		5544	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5545
		5546	ev_loop_destroy (EV_DEFAULT_UC);
		5547	ev_loop_fork (EV_DEFAULT);
		5548
		5549	=item function/symbol renames
		5550
		5551	A number of functions and symbols have been renamed:
		5552
		5553	ev_loop => ev_run
		5554	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5555	EVLOOP_ONESHOT => EVRUN_ONCE
		5556
		5557	ev_unloop => ev_break
		5558	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5559	EVUNLOOP_ONE => EVBREAK_ONE
		5560	EVUNLOOP_ALL => EVBREAK_ALL
		5561
		5562	EV_TIMEOUT => EV_TIMER
		5563
		5564	ev_loop_count => ev_iteration
		5565	ev_loop_depth => ev_depth
		5566	ev_loop_verify => ev_verify
		5567
		5568	Most functions working on C<struct ev_loop> objects don't have an
		5569	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5570	associated constants have been renamed to not collide with the C<struct
		5571	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5572	as all other watcher types. Note that C<ev_loop_fork> is still called
		5573	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5574	typedef.
		5575
		5576	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5577
		5578	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5579	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5580	and work, but the library code will of course be larger.
		5581
		5582	=back
		5583
		5584
		5585	=head1 GLOSSARY
		5586
		5587	=over 4
		5588
		5589	=item active
		5590
		5591	A watcher is active as long as it has been started and not yet stopped.
		5592	See L</WATCHER STATES> for details.
		5593
		5594	=item application
		5595
		5596	In this document, an application is whatever is using libev.
		5597
		5598	=item backend
		5599
		5600	The part of the code dealing with the operating system interfaces.
		5601
		5602	=item callback
		5603
		5604	The address of a function that is called when some event has been
		5605	detected. Callbacks are being passed the event loop, the watcher that
		5606	received the event, and the actual event bitset.
		5607
		5608	=item callback/watcher invocation
		5609
		5610	The act of calling the callback associated with a watcher.
		5611
		5612	=item event
		5613
		5614	A change of state of some external event, such as data now being available
		5615	for reading on a file descriptor, time having passed or simply not having
		5616	any other events happening anymore.
		5617
		5618	In libev, events are represented as single bits (such as C<EV_READ> or
		5619	C<EV_TIMER>).
		5620
		5621	=item event library
		5622
		5623	A software package implementing an event model and loop.
		5624
		5625	=item event loop
		5626
		5627	An entity that handles and processes external events and converts them
		5628	into callback invocations.
		5629
		5630	=item event model
		5631
		5632	The model used to describe how an event loop handles and processes
		5633	watchers and events.
		5634
		5635	=item pending
		5636
		5637	A watcher is pending as soon as the corresponding event has been
		5638	detected. See L</WATCHER STATES> for details.
		5639
		5640	=item real time
		5641
		5642	The physical time that is observed. It is apparently strictly monotonic :)
		5643
		5644	=item wall-clock time
		5645
		5646	The time and date as shown on clocks. Unlike real time, it can actually
		5647	be wrong and jump forwards and backwards, e.g. when you adjust your
		5648	clock.
		5649
		5650	=item watcher
		5651
		5652	A data structure that describes interest in certain events. Watchers need
		5653	to be started (attached to an event loop) before they can receive events.
		5654
		5655	=back
		5656
3940	=head1 AUTHOR	5657	=head1 AUTHOR
3941		5658
3942	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5659	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5660	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3943		5661

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines