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		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
…		…
8		10
9	=head2 EXAMPLE PROGRAM	11	=head2 EXAMPLE PROGRAM
10		12
11	// a single header file is required	13	// a single header file is required
12	#include <ev.h>	14	#include <ev.h>
		15
		16	#include <stdio.h> // for puts
13		17
14	// every watcher type has its own typedef'd struct	18	// every watcher type has its own typedef'd struct
15	// with the name ev_TYPE	19	// with the name ev_TYPE
16	ev_io stdin_watcher;	20	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	21	ev_timer timeout_watcher;
…		…
24	puts ("stdin ready");	28	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	30	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
28		32
29	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
31	}	35	}
32		36
33	// another callback, this time for a time-out	37	// another callback, this time for a time-out
34	static void	38	static void
35	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	40	{
37	puts ("timeout");	41	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
40	}	44	}
41		45
42	int	46	int
43	main (void)	47	main (void)
44	{	48	{
45	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
46	ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
47		51
48	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
50	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);
51	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
54	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
55	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
56	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
57		61
58	// now wait for events to arrive	62	// now wait for events to arrive
59	ev_loop (loop, 0);	63	ev_run (loop, 0);
60		64
61	// unloop was called, so exit	65	// break was called, so exit
62	return 0;	66	return 0;
63	}	67	}
64		68
65	=head1 DESCRIPTION	69	=head1 ABOUT THIS DOCUMENT
		70
		71	This document documents the libev software package.
66		72
67	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
68	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
69	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
70		94
71	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
72	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
73	these event sources and provide your program with events.	97	these event sources and provide your program with events.
74		98
…		…
81	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
82	watcher.	106	watcher.
83		107
84	=head2 FEATURES	108	=head2 FEATURES
85		109
86	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>
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port
88	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>
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	115	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	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
94	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
95	(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>).
96		121
97	It also is quite fast (see this	122	It also is quite fast (see this
98	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
99	for example).	124	for example).
100		125
…		…
103	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)
104	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
106	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
107	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
108	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
109	this argument.	134	this argument.
110		135
111	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
112		137
113	Libev represents time as a single floating point number, representing the	138	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
115	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
116	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
117	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
118	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
119	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
120	throughout libev.	146	time differences (e.g. delays) throughout libev.
121		147
122	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
123		149
124	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
125	and internal errors (bugs).	151	and internal errors (bugs).
…		…
133	When libev detects a usage error such as a negative timer interval, then	159	When libev detects a usage error such as a negative timer interval, then
134	it will print a diagnostic message and abort (via the C<assert> mechanism,	160	it will print a diagnostic message and abort (via the C<assert> mechanism,
135	so C<NDEBUG> will disable this checking): these are programming errors in	161	so C<NDEBUG> will disable this checking): these are programming errors in
136	the libev caller and need to be fixed there.	162	the libev caller and need to be fixed there.
137		163
		164	Via the C<EV_FREQUENT> macro you can compile in and/or enable extensive
		165	consistency checking code inside libev that can be used to check for
		166	internal inconsistencies, suually caused by application bugs.
		167
138	Libev also has a few internal error-checking C<assert>ions, and also has	168	Libev also has a few internal error-checking C<assert>ions. These do not
139	extensive consistency checking code. These do not trigger under normal
140	circumstances, as they indicate either a bug in libev or worse.	169	trigger under normal circumstances, as they indicate either a bug in libev
		170	or worse.
141		171
142		172
143	=head1 GLOBAL FUNCTIONS	173	=head1 GLOBAL FUNCTIONS
144		174
145	These functions can be called anytime, even before initialising the	175	These functions can be called anytime, even before initialising the
…		…
149		179
150	=item ev_tstamp ev_time ()	180	=item ev_tstamp ev_time ()
151		181
152	Returns the current time as libev would use it. Please note that the	182	Returns the current time as libev would use it. Please note that the
153	C<ev_now> function is usually faster and also often returns the timestamp	183	C<ev_now> function is usually faster and also often returns the timestamp
154	you actually want to know.	184	you actually want to know. Also interesting is the combination of
		185	C<ev_now_update> and C<ev_now>.
155		186
156	=item ev_sleep (ev_tstamp interval)	187	=item ev_sleep (ev_tstamp interval)
157		188
158	Sleep for the given interval: The current thread will be blocked until	189	Sleep for the given interval: The current thread will be blocked
159	either it is interrupted or the given time interval has passed. Basically	190	until either it is interrupted or the given time interval has
		191	passed (approximately - it might return a bit earlier even if not
		192	interrupted). Returns immediately if C<< interval <= 0 >>.
		193
160	this is a sub-second-resolution C<sleep ()>.	194	Basically this is a sub-second-resolution C<sleep ()>.
		195
		196	The range of the C<interval> is limited - libev only guarantees to work
		197	with sleep times of up to one day (C<< interval <= 86400 >>).
161		198
162	=item int ev_version_major ()	199	=item int ev_version_major ()
163		200
164	=item int ev_version_minor ()	201	=item int ev_version_minor ()
165		202
…		…
176	as this indicates an incompatible change. Minor versions are usually	213	as this indicates an incompatible change. Minor versions are usually
177	compatible to older versions, so a larger minor version alone is usually	214	compatible to older versions, so a larger minor version alone is usually
178	not a problem.	215	not a problem.
179		216
180	Example: Make sure we haven't accidentally been linked against the wrong	217	Example: Make sure we haven't accidentally been linked against the wrong
181	version.	218	version (note, however, that this will not detect other ABI mismatches,
		219	such as LFS or reentrancy).
182		220
183	assert (("libev version mismatch",	221	assert (("libev version mismatch",
184	ev_version_major () == EV_VERSION_MAJOR	222	ev_version_major () == EV_VERSION_MAJOR
185	&& ev_version_minor () >= EV_VERSION_MINOR));	223	&& ev_version_minor () >= EV_VERSION_MINOR));
186		224
…		…
197	assert (("sorry, no epoll, no sex",	235	assert (("sorry, no epoll, no sex",
198	ev_supported_backends () & EVBACKEND_EPOLL));	236	ev_supported_backends () & EVBACKEND_EPOLL));
199		237
200	=item unsigned int ev_recommended_backends ()	238	=item unsigned int ev_recommended_backends ()
201		239
202	Return the set of all backends compiled into this binary of libev and also	240	Return the set of all backends compiled into this binary of libev and
203	recommended for this platform. This set is often smaller than the one	241	also recommended for this platform, meaning it will work for most file
		242	descriptor types. This set is often smaller than the one returned by
204	returned by C<ev_supported_backends>, as for example kqueue is broken on	243	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
205	most BSDs and will not be auto-detected unless you explicitly request it	244	and will not be auto-detected unless you explicitly request it (assuming
206	(assuming you know what you are doing). This is the set of backends that	245	you know what you are doing). This is the set of backends that libev will
207	libev will probe for if you specify no backends explicitly.	246	probe for if you specify no backends explicitly.
208		247
209	=item unsigned int ev_embeddable_backends ()	248	=item unsigned int ev_embeddable_backends ()
210		249
211	Returns the set of backends that are embeddable in other event loops. This	250	Returns the set of backends that are embeddable in other event loops. This
212	is the theoretical, all-platform, value. To find which backends	251	value is platform-specific but can include backends not available on the
213	might be supported on the current system, you would need to look at	252	current system. To find which embeddable backends might be supported on
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	253	the current system, you would need to look at C<ev_embeddable_backends ()
215	recommended ones.	254	& ev_supported_backends ()>, likewise for recommended ones.
216		255
217	See the description of C<ev_embed> watchers for more info.	256	See the description of C<ev_embed> watchers for more info.
218		257
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	258	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
220		259
221	Sets the allocation function to use (the prototype is similar - the	260	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	261	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	262	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	263	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
230		269
231	You could override this function in high-availability programs to, say,	270	You could override this function in high-availability programs to, say,
232	free some memory if it cannot allocate memory, to use a special allocator,	271	free some memory if it cannot allocate memory, to use a special allocator,
233	or even to sleep a while and retry until some memory is available.	272	or even to sleep a while and retry until some memory is available.
234		273
		274	Example: The following is the C<realloc> function that libev itself uses
		275	which should work with C<realloc> and C<free> functions of all kinds and
		276	is probably a good basis for your own implementation.
		277
		278	static void *
		279	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		280	{
		281	if (size)
		282	return realloc (ptr, size);
		283
		284	free (ptr);
		285	return 0;
		286	}
		287
235	Example: Replace the libev allocator with one that waits a bit and then	288	Example: Replace the libev allocator with one that waits a bit and then
236	retries (example requires a standards-compliant C<realloc>).	289	retries.
237		290
238	static void *	291	static void *
239	persistent_realloc (void *ptr, size_t size)	292	persistent_realloc (void *ptr, size_t size)
240	{	293	{
		294	if (!size)
		295	{
		296	free (ptr);
		297	return 0;
		298	}
		299
241	for (;;)	300	for (;;)
242	{	301	{
243	void *newptr = realloc (ptr, size);	302	void *newptr = realloc (ptr, size);
244		303
245	if (newptr)	304	if (newptr)
…		…
250	}	309	}
251		310
252	...	311	...
253	ev_set_allocator (persistent_realloc);	312	ev_set_allocator (persistent_realloc);
254		313
255	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	314	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
256		315
257	Set the callback function to call on a retryable system call error (such	316	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	317	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	318	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	319	callback is set, then libev will expect it to remedy the situation, no
…		…
272	}	331	}
273		332
274	...	333	...
275	ev_set_syserr_cb (fatal_error);	334	ev_set_syserr_cb (fatal_error);
276		335
		336	=item ev_feed_signal (int signum)
		337
		338	This function can be used to "simulate" a signal receive. It is completely
		339	safe to call this function at any time, from any context, including signal
		340	handlers or random threads.
		341
		342	Its main use is to customise signal handling in your process, especially
		343	in the presence of threads. For example, you could block signals
		344	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		345	creating any loops), and in one thread, use C<sigwait> or any other
		346	mechanism to wait for signals, then "deliver" them to libev by calling
		347	C<ev_feed_signal>.
		348
277	=back	349	=back
278		350
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	351	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
280		352
281	An event loop is described by a C<struct ev_loop *> (the C<struct>	353	An event loop is described by a C<struct ev_loop *> (the C<struct> is
282	is I<not> optional in this case, as there is also an C<ev_loop>	354	I<not> optional in this case unless libev 3 compatibility is disabled, as
283	I<function>).	355	libev 3 had an C<ev_loop> function colliding with the struct name).
284		356
285	The library knows two types of such loops, the I<default> loop, which	357	The library knows two types of such loops, the I<default> loop, which
286	supports signals and child events, and dynamically created loops which do	358	supports child process events, and dynamically created event loops which
287	not.	359	do not.
288		360
289	=over 4	361	=over 4
290		362
291	=item struct ev_loop *ev_default_loop (unsigned int flags)	363	=item struct ev_loop *ev_default_loop (unsigned int flags)
292		364
293	This will initialise the default event loop if it hasn't been initialised	365	This returns the "default" event loop object, which is what you should
294	yet and return it. If the default loop could not be initialised, returns	366	normally use when you just need "the event loop". Event loop objects and
295	false. If it already was initialised it simply returns it (and ignores the	367	the C<flags> parameter are described in more detail in the entry for
296	flags. If that is troubling you, check C<ev_backend ()> afterwards).	368	C<ev_loop_new>.
		369
		370	If the default loop is already initialised then this function simply
		371	returns it (and ignores the flags. If that is troubling you, check
		372	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		373	flags, which should almost always be C<0>, unless the caller is also the
		374	one calling C<ev_run> or otherwise qualifies as "the main program".
297		375
298	If you don't know what event loop to use, use the one returned from this	376	If you don't know what event loop to use, use the one returned from this
299	function.	377	function (or via the C<EV_DEFAULT> macro).
300		378
301	Note that this function is I<not> thread-safe, so if you want to use it	379	Note that this function is I<not> thread-safe, so if you want to use it
302	from multiple threads, you have to lock (note also that this is unlikely,	380	from multiple threads, you have to employ some kind of mutex (note also
303	as loops cannot bes hared easily between threads anyway).	381	that this case is unlikely, as loops cannot be shared easily between
		382	threads anyway).
304		383
305	The default loop is the only loop that can handle C<ev_signal> and	384	The default loop is the only loop that can handle C<ev_child> watchers,
306	C<ev_child> watchers, and to do this, it always registers a handler	385	and to do this, it always registers a handler for C<SIGCHLD>. If this is
307	for C<SIGCHLD>. If this is a problem for your application you can either	386	a problem for your application you can either create a dynamic loop with
308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	387	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
309	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	388	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
310	C<ev_default_init>.	389
		390	Example: This is the most typical usage.
		391
		392	if (!ev_default_loop (0))
		393	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		394
		395	Example: Restrict libev to the select and poll backends, and do not allow
		396	environment settings to be taken into account:
		397
		398	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		399
		400	=item struct ev_loop *ev_loop_new (unsigned int flags)
		401
		402	This will create and initialise a new event loop object. If the loop
		403	could not be initialised, returns false.
		404
		405	This function is thread-safe, and one common way to use libev with
		406	threads is indeed to create one loop per thread, and using the default
		407	loop in the "main" or "initial" thread.
311		408
312	The flags argument can be used to specify special behaviour or specific	409	The flags argument can be used to specify special behaviour or specific
313	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	410	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
314		411
315	The following flags are supported:	412	The following flags are supported:
…		…
325		422
326	If this flag bit is or'ed into the flag value (or the program runs setuid	423	If this flag bit is or'ed into the flag value (or the program runs setuid
327	or setgid) then libev will I<not> look at the environment variable	424	or setgid) then libev will I<not> look at the environment variable
328	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	425	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
329	override the flags completely if it is found in the environment. This is	426	override the flags completely if it is found in the environment. This is
330	useful to try out specific backends to test their performance, or to work	427	useful to try out specific backends to test their performance, to work
331	around bugs.	428	around bugs, or to make libev threadsafe (accessing environment variables
		429	cannot be done in a threadsafe way, but usually it works if no other
		430	thread modifies them).
332		431
333	=item C<EVFLAG_FORKCHECK>	432	=item C<EVFLAG_FORKCHECK>
334		433
335	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	434	Instead of calling C<ev_loop_fork> manually after a fork, you can also
336	a fork, you can also make libev check for a fork in each iteration by	435	make libev check for a fork in each iteration by enabling this flag.
337	enabling this flag.
338		436
339	This works by calling C<getpid ()> on every iteration of the loop,	437	This works by calling C<getpid ()> on every iteration of the loop,
340	and thus this might slow down your event loop if you do a lot of loop	438	and thus this might slow down your event loop if you do a lot of loop
341	iterations and little real work, but is usually not noticeable (on my	439	iterations and little real work, but is usually not noticeable (on my
342	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	440	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
343	without a system call and thus I<very> fast, but my GNU/Linux system also has	441	sequence without a system call and thus I<very> fast, but my GNU/Linux
344	C<pthread_atfork> which is even faster).	442	system also has C<pthread_atfork> which is even faster). (Update: glibc
		443	versions 2.25 apparently removed the C<getpid> optimisation again).
345		444
346	The big advantage of this flag is that you can forget about fork (and	445	The big advantage of this flag is that you can forget about fork (and
347	forget about forgetting to tell libev about forking) when you use this	446	forget about forgetting to tell libev about forking, although you still
348	flag.	447	have to ignore C<SIGPIPE>) when you use this flag.
349		448
350	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	449	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
351	environment variable.	450	environment variable.
		451
		452	=item C<EVFLAG_NOINOTIFY>
		453
		454	When this flag is specified, then libev will not attempt to use the
		455	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		456	testing, this flag can be useful to conserve inotify file descriptors, as
		457	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		458
		459	=item C<EVFLAG_SIGNALFD>
		460
		461	When this flag is specified, then libev will attempt to use the
		462	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		463	delivers signals synchronously, which makes it both faster and might make
		464	it possible to get the queued signal data. It can also simplify signal
		465	handling with threads, as long as you properly block signals in your
		466	threads that are not interested in handling them.
		467
		468	Signalfd will not be used by default as this changes your signal mask, and
		469	there are a lot of shoddy libraries and programs (glib's threadpool for
		470	example) that can't properly initialise their signal masks.
		471
		472	=item C<EVFLAG_NOSIGMASK>
		473
		474	When this flag is specified, then libev will avoid to modify the signal
		475	mask. Specifically, this means you have to make sure signals are unblocked
		476	when you want to receive them.
		477
		478	This behaviour is useful when you want to do your own signal handling, or
		479	want to handle signals only in specific threads and want to avoid libev
		480	unblocking the signals.
		481
		482	It's also required by POSIX in a threaded program, as libev calls
		483	C<sigprocmask>, whose behaviour is officially unspecified.
		484
		485	=item C<EVFLAG_NOTIMERFD>
		486
		487	When this flag is specified, the libev will avoid using a C<timerfd> to
		488	detect time jumps. It will still be able to detect time jumps, but takes
		489	longer and has a lower accuracy in doing so, but saves a file descriptor
		490	per loop.
		491
		492	The current implementation only tries to use a C<timerfd> when the first
		493	C<ev_periodic> watcher is started and falls back on other methods if it
		494	cannot be created, but this behaviour might change in the future.
352		495
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	496	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		497
355	This is your standard select(2) backend. Not I<completely> standard, as	498	This is your standard select(2) backend. Not I<completely> standard, as
356	libev tries to roll its own fd_set with no limits on the number of fds,	499	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	524	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	525	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		526
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	527	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		528
		529	Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9
		530	kernels).
		531
386	For few fds, this backend is a bit little slower than poll and select,	532	For few fds, this backend is a bit little slower than poll and select, but
387	but it scales phenomenally better. While poll and select usually scale	533	it scales phenomenally better. While poll and select usually scale like
388	like O(total_fds) where n is the total number of fds (or the highest fd),	534	O(total_fds) where total_fds is the total number of fds (or the highest
389	epoll scales either O(1) or O(active_fds). The epoll design has a number	535	fd), epoll scales either O(1) or O(active_fds).
390	of shortcomings, such as silently dropping events in some hard-to-detect
391	cases and requiring a system call per fd change, no fork support and bad
392	support for dup.
393		536
		537	The epoll mechanism deserves honorable mention as the most misdesigned
		538	of the more advanced event mechanisms: mere annoyances include silently
		539	dropping file descriptors, requiring a system call per change per file
		540	descriptor (and unnecessary guessing of parameters), problems with dup,
		541	returning before the timeout value, resulting in additional iterations
		542	(and only giving 5ms accuracy while select on the same platform gives
		543	0.1ms) and so on. The biggest issue is fork races, however - if a program
		544	forks then I<both> parent and child process have to recreate the epoll
		545	set, which can take considerable time (one syscall per file descriptor)
		546	and is of course hard to detect.
		547
394	Epoll is also notoriously buggy - embedding epoll fds should work, but	548	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
395	of course doesn't, and epoll just loves to report events for totally	549	but of course I<doesn't>, and epoll just loves to report events for
396	I<different> file descriptors (even already closed ones) than registered	550	totally I<different> file descriptors (even already closed ones, so
		551	one cannot even remove them from the set) than registered in the set
397	in the set (especially on SMP systems). Libev tries to counter these	552	(especially on SMP systems). Libev tries to counter these spurious
398	spurious notifications by employing an additional generation counter and	553	notifications by employing an additional generation counter and comparing
399	comparing that against the events to filter out spurious ones.	554	that against the events to filter out spurious ones, recreating the set
		555	when required. Epoll also erroneously rounds down timeouts, but gives you
		556	no way to know when and by how much, so sometimes you have to busy-wait
		557	because epoll returns immediately despite a nonzero timeout. And last
		558	not least, it also refuses to work with some file descriptors which work
		559	perfectly fine with C<select> (files, many character devices...).
		560
		561	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		562	cobbled together in a hurry, no thought to design or interaction with
		563	others. Oh, the pain, will it ever stop...
400		564
401	While stopping, setting and starting an I/O watcher in the same iteration	565	While stopping, setting and starting an I/O watcher in the same iteration
402	will result in some caching, there is still a system call per such incident	566	will result in some caching, there is still a system call per such
403	(because the fd could point to a different file description now), so its	567	incident (because the same I<file descriptor> could point to a different
404	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	568	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
405	very well if you register events for both fds.	569	file descriptors might not work very well if you register events for both
		570	file descriptors.
406		571
407	Best performance from this backend is achieved by not unregistering all	572	Best performance from this backend is achieved by not unregistering all
408	watchers for a file descriptor until it has been closed, if possible,	573	watchers for a file descriptor until it has been closed, if possible,
409	i.e. keep at least one watcher active per fd at all times. Stopping and	574	i.e. keep at least one watcher active per fd at all times. Stopping and
410	starting a watcher (without re-setting it) also usually doesn't cause	575	starting a watcher (without re-setting it) also usually doesn't cause
411	extra overhead.	576	extra overhead. A fork can both result in spurious notifications as well
		577	as in libev having to destroy and recreate the epoll object, which can
		578	take considerable time and thus should be avoided.
		579
		580	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		581	faster than epoll for maybe up to a hundred file descriptors, depending on
		582	the usage. So sad.
412		583
413	While nominally embeddable in other event loops, this feature is broken in	584	While nominally embeddable in other event loops, this feature is broken in
414	all kernel versions tested so far.	585	a lot of kernel revisions, but probably(!) works in current versions.
415		586
416	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	587	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
417	C<EVBACKEND_POLL>.	588	C<EVBACKEND_POLL>.
418		589
		590	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		591
		592	Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<<
		593	io_submit(2) >>) event interface available in post-4.18 kernels (but libev
		594	only tries to use it in 4.19+).
		595
		596	This is another Linux train wreck of an event interface.
		597
		598	If this backend works for you (as of this writing, it was very
		599	experimental), it is the best event interface available on Linux and might
		600	be well worth enabling it - if it isn't available in your kernel this will
		601	be detected and this backend will be skipped.
		602
		603	This backend can batch oneshot requests and supports a user-space ring
		604	buffer to receive events. It also doesn't suffer from most of the design
		605	problems of epoll (such as not being able to remove event sources from
		606	the epoll set), and generally sounds too good to be true. Because, this
		607	being the Linux kernel, of course it suffers from a whole new set of
		608	limitations, forcing you to fall back to epoll, inheriting all its design
		609	issues.
		610
		611	For one, it is not easily embeddable (but probably could be done using
		612	an event fd at some extra overhead). It also is subject to a system wide
		613	limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO
		614	requests are left, this backend will be skipped during initialisation, and
		615	will switch to epoll when the loop is active.
		616
		617	Most problematic in practice, however, is that not all file descriptors
		618	work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds,
		619	files, F</dev/null> and many others are supported, but ttys do not work
		620	properly (a known bug that the kernel developers don't care about, see
		621	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		622	(yet?) a generic event polling interface.
		623
		624	Overall, it seems the Linux developers just don't want it to have a
		625	generic event handling mechanism other than C<select> or C<poll>.
		626
		627	To work around all these problem, the current version of libev uses its
		628	epoll backend as a fallback for file descriptor types that do not work. Or
		629	falls back completely to epoll if the kernel acts up.
		630
		631	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		632	C<EVBACKEND_POLL>.
		633
419	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	634	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
420		635
421	Kqueue deserves special mention, as at the time of this writing, it was	636	Kqueue deserves special mention, as at the time this backend was
422	broken on all BSDs except NetBSD (usually it doesn't work reliably with	637	implemented, it was broken on all BSDs except NetBSD (usually it doesn't
423	anything but sockets and pipes, except on Darwin, where of course it's	638	work reliably with anything but sockets and pipes, except on Darwin,
424	completely useless). For this reason it's not being "auto-detected" unless	639	where of course it's completely useless). Unlike epoll, however, whose
425	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	640	brokenness is by design, these kqueue bugs can be (and mostly have been)
		641	fixed without API changes to existing programs. For this reason it's not
		642	being "auto-detected" on all platforms unless you explicitly specify it
		643	in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a
426	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	644	known-to-be-good (-enough) system like NetBSD.
427		645
428	You still can embed kqueue into a normal poll or select backend and use it	646	You still can embed kqueue into a normal poll or select backend and use it
429	only for sockets (after having made sure that sockets work with kqueue on	647	only for sockets (after having made sure that sockets work with kqueue on
430	the target platform). See C<ev_embed> watchers for more info.	648	the target platform). See C<ev_embed> watchers for more info.
431		649
432	It scales in the same way as the epoll backend, but the interface to the	650	It scales in the same way as the epoll backend, but the interface to the
433	kernel is more efficient (which says nothing about its actual speed, of	651	kernel is more efficient (which says nothing about its actual speed, of
434	course). While stopping, setting and starting an I/O watcher does never	652	course). While stopping, setting and starting an I/O watcher does never
435	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	653	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
436	two event changes per incident. Support for C<fork ()> is very bad and it	654	two event changes per incident. Support for C<fork ()> is very bad (you
		655	might have to leak fds on fork, but it's more sane than epoll) and it
437	drops fds silently in similarly hard-to-detect cases.	656	drops fds silently in similarly hard-to-detect cases.
438		657
439	This backend usually performs well under most conditions.	658	This backend usually performs well under most conditions.
440		659
441	While nominally embeddable in other event loops, this doesn't work	660	While nominally embeddable in other event loops, this doesn't work
442	everywhere, so you might need to test for this. And since it is broken	661	everywhere, so you might need to test for this. And since it is broken
443	almost everywhere, you should only use it when you have a lot of sockets	662	almost everywhere, you should only use it when you have a lot of sockets
444	(for which it usually works), by embedding it into another event loop	663	(for which it usually works), by embedding it into another event loop
445	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	664	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
446	using it only for sockets.	665	also broken on OS X)) and, did I mention it, using it only for sockets.
447		666
448	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	667	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
449	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	668	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
450	C<NOTE_EOF>.	669	C<NOTE_EOF>.
451		670
…		…
459	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	678	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
460		679
461	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	680	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
462	it's really slow, but it still scales very well (O(active_fds)).	681	it's really slow, but it still scales very well (O(active_fds)).
463		682
464	Please note that Solaris event ports can deliver a lot of spurious
465	notifications, so you need to use non-blocking I/O or other means to avoid
466	blocking when no data (or space) is available.
467
468	While this backend scales well, it requires one system call per active	683	While this backend scales well, it requires one system call per active
469	file descriptor per loop iteration. For small and medium numbers of file	684	file descriptor per loop iteration. For small and medium numbers of file
470	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	685	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
471	might perform better.	686	might perform better.
472		687
473	On the positive side, with the exception of the spurious readiness	688	On the positive side, this backend actually performed fully to
474	notifications, this backend actually performed fully to specification
475	in all tests and is fully embeddable, which is a rare feat among the	689	specification in all tests and is fully embeddable, which is a rare feat
476	OS-specific backends.	690	among the OS-specific backends (I vastly prefer correctness over speed
		691	hacks).
		692
		693	On the negative side, the interface is I<bizarre> - so bizarre that
		694	even sun itself gets it wrong in their code examples: The event polling
		695	function sometimes returns events to the caller even though an error
		696	occurred, but with no indication whether it has done so or not (yes, it's
		697	even documented that way) - deadly for edge-triggered interfaces where you
		698	absolutely have to know whether an event occurred or not because you have
		699	to re-arm the watcher.
		700
		701	Fortunately libev seems to be able to work around these idiocies.
477		702
478	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	703	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
479	C<EVBACKEND_POLL>.	704	C<EVBACKEND_POLL>.
480		705
481	=item C<EVBACKEND_ALL>	706	=item C<EVBACKEND_ALL>
482		707
483	Try all backends (even potentially broken ones that wouldn't be tried	708	Try all backends (even potentially broken ones that wouldn't be tried
484	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	709	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
485	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	710	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
486		711
487	It is definitely not recommended to use this flag.	712	It is definitely not recommended to use this flag, use whatever
		713	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		714	at all.
		715
		716	=item C<EVBACKEND_MASK>
		717
		718	Not a backend at all, but a mask to select all backend bits from a
		719	C<flags> value, in case you want to mask out any backends from a flags
		720	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
488		721
489	=back	722	=back
490		723
491	If one or more of these are or'ed into the flags value, then only these	724	If one or more of the backend flags are or'ed into the flags value,
492	backends will be tried (in the reverse order as listed here). If none are	725	then only these backends will be tried (in the reverse order as listed
493	specified, all backends in C<ev_recommended_backends ()> will be tried.	726	here). If none are specified, all backends in C<ev_recommended_backends
494		727	()> will be tried.
495	Example: This is the most typical usage.
496
497	if (!ev_default_loop (0))
498	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
499
500	Example: Restrict libev to the select and poll backends, and do not allow
501	environment settings to be taken into account:
502
503	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
504
505	Example: Use whatever libev has to offer, but make sure that kqueue is
506	used if available (warning, breaks stuff, best use only with your own
507	private event loop and only if you know the OS supports your types of
508	fds):
509
510	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
511
512	=item struct ev_loop *ev_loop_new (unsigned int flags)
513
514	Similar to C<ev_default_loop>, but always creates a new event loop that is
515	always distinct from the default loop. Unlike the default loop, it cannot
516	handle signal and child watchers, and attempts to do so will be greeted by
517	undefined behaviour (or a failed assertion if assertions are enabled).
518
519	Note that this function I<is> thread-safe, and the recommended way to use
520	libev with threads is indeed to create one loop per thread, and using the
521	default loop in the "main" or "initial" thread.
522		728
523	Example: Try to create a event loop that uses epoll and nothing else.	729	Example: Try to create a event loop that uses epoll and nothing else.
524		730
525	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	731	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
526	if (!epoller)	732	if (!epoller)
527	fatal ("no epoll found here, maybe it hides under your chair");	733	fatal ("no epoll found here, maybe it hides under your chair");
528		734
		735	Example: Use whatever libev has to offer, but make sure that kqueue is
		736	used if available.
		737
		738	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		739
		740	Example: Similarly, on linux, you mgiht want to take advantage of the
		741	linux aio backend if possible, but fall back to something else if that
		742	isn't available.
		743
		744	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		745
529	=item ev_default_destroy ()	746	=item ev_loop_destroy (loop)
530		747
531	Destroys the default loop again (frees all memory and kernel state	748	Destroys an event loop object (frees all memory and kernel state
532	etc.). None of the active event watchers will be stopped in the normal	749	etc.). None of the active event watchers will be stopped in the normal
533	sense, so e.g. C<ev_is_active> might still return true. It is your	750	sense, so e.g. C<ev_is_active> might still return true. It is your
534	responsibility to either stop all watchers cleanly yourself I<before>	751	responsibility to either stop all watchers cleanly yourself I<before>
535	calling this function, or cope with the fact afterwards (which is usually	752	calling this function, or cope with the fact afterwards (which is usually
536	the easiest thing, you can just ignore the watchers and/or C<free ()> them	753	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
538		755
539	Note that certain global state, such as signal state (and installed signal	756	Note that certain global state, such as signal state (and installed signal
540	handlers), will not be freed by this function, and related watchers (such	757	handlers), will not be freed by this function, and related watchers (such
541	as signal and child watchers) would need to be stopped manually.	758	as signal and child watchers) would need to be stopped manually.
542		759
543	In general it is not advisable to call this function except in the	760	This function is normally used on loop objects allocated by
544	rare occasion where you really need to free e.g. the signal handling	761	C<ev_loop_new>, but it can also be used on the default loop returned by
		762	C<ev_default_loop>, in which case it is not thread-safe.
		763
		764	Note that it is not advisable to call this function on the default loop
		765	except in the rare occasion where you really need to free its resources.
545	pipe fds. If you need dynamically allocated loops it is better to use	766	If you need dynamically allocated loops it is better to use C<ev_loop_new>
546	C<ev_loop_new> and C<ev_loop_destroy>).	767	and C<ev_loop_destroy>.
547		768
548	=item ev_loop_destroy (loop)	769	=item ev_loop_fork (loop)
549		770
550	Like C<ev_default_destroy>, but destroys an event loop created by an
551	earlier call to C<ev_loop_new>.
552
553	=item ev_default_fork ()
554
555	This function sets a flag that causes subsequent C<ev_loop> iterations	771	This function sets a flag that causes subsequent C<ev_run> iterations
556	to reinitialise the kernel state for backends that have one. Despite the	772	to reinitialise the kernel state for backends that have one. Despite
557	name, you can call it anytime, but it makes most sense after forking, in	773	the name, you can call it anytime you are allowed to start or stop
558	the child process (or both child and parent, but that again makes little	774	watchers (except inside an C<ev_prepare> callback), but it makes most
559	sense). You I<must> call it in the child before using any of the libev	775	sense after forking, in the child process. You I<must> call it (or use
560	functions, and it will only take effect at the next C<ev_loop> iteration.	776	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		777
		778	In addition, if you want to reuse a loop (via this function or
		779	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		780
		781	Again, you I<have> to call it on I<any> loop that you want to re-use after
		782	a fork, I<even if you do not plan to use the loop in the parent>. This is
		783	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		784	during fork.
561		785
562	On the other hand, you only need to call this function in the child	786	On the other hand, you only need to call this function in the child
563	process if and only if you want to use the event library in the child. If	787	process if and only if you want to use the event loop in the child. If
564	you just fork+exec, you don't have to call it at all.	788	you just fork+exec or create a new loop in the child, you don't have to
		789	call it at all (in fact, C<epoll> is so badly broken that it makes a
		790	difference, but libev will usually detect this case on its own and do a
		791	costly reset of the backend).
565		792
566	The function itself is quite fast and it's usually not a problem to call	793	The function itself is quite fast and it's usually not a problem to call
567	it just in case after a fork. To make this easy, the function will fit in	794	it just in case after a fork.
568	quite nicely into a call to C<pthread_atfork>:
569		795
		796	Example: Automate calling C<ev_loop_fork> on the default loop when
		797	using pthreads.
		798
		799	static void
		800	post_fork_child (void)
		801	{
		802	ev_loop_fork (EV_DEFAULT);
		803	}
		804
		805	...
570	pthread_atfork (0, 0, ev_default_fork);	806	pthread_atfork (0, 0, post_fork_child);
571
572	=item ev_loop_fork (loop)
573
574	Like C<ev_default_fork>, but acts on an event loop created by
575	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
576	after fork that you want to re-use in the child, and how you do this is
577	entirely your own problem.
578		807
579	=item int ev_is_default_loop (loop)	808	=item int ev_is_default_loop (loop)
580		809
581	Returns true when the given loop is, in fact, the default loop, and false	810	Returns true when the given loop is, in fact, the default loop, and false
582	otherwise.	811	otherwise.
583		812
584	=item unsigned int ev_loop_count (loop)	813	=item unsigned int ev_iteration (loop)
585		814
586	Returns the count of loop iterations for the loop, which is identical to	815	Returns the current iteration count for the event loop, which is identical
587	the number of times libev did poll for new events. It starts at C<0> and	816	to the number of times libev did poll for new events. It starts at C<0>
588	happily wraps around with enough iterations.	817	and happily wraps around with enough iterations.
589		818
590	This value can sometimes be useful as a generation counter of sorts (it	819	This value can sometimes be useful as a generation counter of sorts (it
591	"ticks" the number of loop iterations), as it roughly corresponds with	820	"ticks" the number of loop iterations), as it roughly corresponds with
592	C<ev_prepare> and C<ev_check> calls.	821	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		822	prepare and check phases.
		823
		824	=item unsigned int ev_depth (loop)
		825
		826	Returns the number of times C<ev_run> was entered minus the number of
		827	times C<ev_run> was exited normally, in other words, the recursion depth.
		828
		829	Outside C<ev_run>, this number is zero. In a callback, this number is
		830	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		831	in which case it is higher.
		832
		833	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		834	throwing an exception etc.), doesn't count as "exit" - consider this
		835	as a hint to avoid such ungentleman-like behaviour unless it's really
		836	convenient, in which case it is fully supported.
593		837
594	=item unsigned int ev_backend (loop)	838	=item unsigned int ev_backend (loop)
595		839
596	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	840	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
597	use.	841	use.
…		…
606		850
607	=item ev_now_update (loop)	851	=item ev_now_update (loop)
608		852
609	Establishes the current time by querying the kernel, updating the time	853	Establishes the current time by querying the kernel, updating the time
610	returned by C<ev_now ()> in the progress. This is a costly operation and	854	returned by C<ev_now ()> in the progress. This is a costly operation and
611	is usually done automatically within C<ev_loop ()>.	855	is usually done automatically within C<ev_run ()>.
612		856
613	This function is rarely useful, but when some event callback runs for a	857	This function is rarely useful, but when some event callback runs for a
614	very long time without entering the event loop, updating libev's idea of	858	very long time without entering the event loop, updating libev's idea of
615	the current time is a good idea.	859	the current time is a good idea.
616		860
617	See also "The special problem of time updates" in the C<ev_timer> section.	861	See also L</The special problem of time updates> in the C<ev_timer> section.
618		862
		863	=item ev_suspend (loop)
		864
		865	=item ev_resume (loop)
		866
		867	These two functions suspend and resume an event loop, for use when the
		868	loop is not used for a while and timeouts should not be processed.
		869
		870	A typical use case would be an interactive program such as a game: When
		871	the user presses C<^Z> to suspend the game and resumes it an hour later it
		872	would be best to handle timeouts as if no time had actually passed while
		873	the program was suspended. This can be achieved by calling C<ev_suspend>
		874	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		875	C<ev_resume> directly afterwards to resume timer processing.
		876
		877	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		878	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		879	will be rescheduled (that is, they will lose any events that would have
		880	occurred while suspended).
		881
		882	After calling C<ev_suspend> you B<must not> call I<any> function on the
		883	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		884	without a previous call to C<ev_suspend>.
		885
		886	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		887	event loop time (see C<ev_now_update>).
		888
619	=item ev_loop (loop, int flags)	889	=item bool ev_run (loop, int flags)
620		890
621	Finally, this is it, the event handler. This function usually is called	891	Finally, this is it, the event handler. This function usually is called
622	after you initialised all your watchers and you want to start handling	892	after you have initialised all your watchers and you want to start
623	events.	893	handling events. It will ask the operating system for any new events, call
		894	the watcher callbacks, and then repeat the whole process indefinitely: This
		895	is why event loops are called I<loops>.
624		896
625	If the flags argument is specified as C<0>, it will not return until	897	If the flags argument is specified as C<0>, it will keep handling events
626	either no event watchers are active anymore or C<ev_unloop> was called.	898	until either no event watchers are active anymore or C<ev_break> was
		899	called.
627		900
		901	The return value is false if there are no more active watchers (which
		902	usually means "all jobs done" or "deadlock"), and true in all other cases
		903	(which usually means " you should call C<ev_run> again").
		904
628	Please note that an explicit C<ev_unloop> is usually better than	905	Please note that an explicit C<ev_break> is usually better than
629	relying on all watchers to be stopped when deciding when a program has	906	relying on all watchers to be stopped when deciding when a program has
630	finished (especially in interactive programs), but having a program	907	finished (especially in interactive programs), but having a program
631	that automatically loops as long as it has to and no longer by virtue	908	that automatically loops as long as it has to and no longer by virtue
632	of relying on its watchers stopping correctly, that is truly a thing of	909	of relying on its watchers stopping correctly, that is truly a thing of
633	beauty.	910	beauty.
634		911
		912	This function is I<mostly> exception-safe - you can break out of a
		913	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		914	exception and so on. This does not decrement the C<ev_depth> value, nor
		915	will it clear any outstanding C<EVBREAK_ONE> breaks.
		916
635	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	917	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
636	those events and any already outstanding ones, but will not block your	918	those events and any already outstanding ones, but will not wait and
637	process in case there are no events and will return after one iteration of	919	block your process in case there are no events and will return after one
638	the loop.	920	iteration of the loop. This is sometimes useful to poll and handle new
		921	events while doing lengthy calculations, to keep the program responsive.
639		922
640	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	923	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
641	necessary) and will handle those and any already outstanding ones. It	924	necessary) and will handle those and any already outstanding ones. It
642	will block your process until at least one new event arrives (which could	925	will block your process until at least one new event arrives (which could
643	be an event internal to libev itself, so there is no guarentee that a	926	be an event internal to libev itself, so there is no guarantee that a
644	user-registered callback will be called), and will return after one	927	user-registered callback will be called), and will return after one
645	iteration of the loop.	928	iteration of the loop.
646		929
647	This is useful if you are waiting for some external event in conjunction	930	This is useful if you are waiting for some external event in conjunction
648	with something not expressible using other libev watchers (i.e. "roll your	931	with something not expressible using other libev watchers (i.e. "roll your
649	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	932	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
650	usually a better approach for this kind of thing.	933	usually a better approach for this kind of thing.
651		934
652	Here are the gory details of what C<ev_loop> does:	935	Here are the gory details of what C<ev_run> does (this is for your
		936	understanding, not a guarantee that things will work exactly like this in
		937	future versions):
653		938
		939	- Increment loop depth.
		940	- Reset the ev_break status.
654	- Before the first iteration, call any pending watchers.	941	- Before the first iteration, call any pending watchers.
		942	LOOP:
655	* If EVFLAG_FORKCHECK was used, check for a fork.	943	- If EVFLAG_FORKCHECK was used, check for a fork.
656	- If a fork was detected (by any means), queue and call all fork watchers.	944	- If a fork was detected (by any means), queue and call all fork watchers.
657	- Queue and call all prepare watchers.	945	- Queue and call all prepare watchers.
		946	- If ev_break was called, goto FINISH.
658	- If we have been forked, detach and recreate the kernel state	947	- If we have been forked, detach and recreate the kernel state
659	as to not disturb the other process.	948	as to not disturb the other process.
660	- Update the kernel state with all outstanding changes.	949	- Update the kernel state with all outstanding changes.
661	- Update the "event loop time" (ev_now ()).	950	- Update the "event loop time" (ev_now ()).
662	- Calculate for how long to sleep or block, if at all	951	- Calculate for how long to sleep or block, if at all
663	(active idle watchers, EVLOOP_NONBLOCK or not having	952	(active idle watchers, EVRUN_NOWAIT or not having
664	any active watchers at all will result in not sleeping).	953	any active watchers at all will result in not sleeping).
665	- Sleep if the I/O and timer collect interval say so.	954	- Sleep if the I/O and timer collect interval say so.
		955	- Increment loop iteration counter.
666	- Block the process, waiting for any events.	956	- Block the process, waiting for any events.
667	- Queue all outstanding I/O (fd) events.	957	- Queue all outstanding I/O (fd) events.
668	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	958	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
669	- Queue all expired timers.	959	- Queue all expired timers.
670	- Queue all expired periodics.	960	- Queue all expired periodics.
671	- Unless any events are pending now, queue all idle watchers.	961	- Queue all idle watchers with priority higher than that of pending events.
672	- Queue all check watchers.	962	- Queue all check watchers.
673	- Call all queued watchers in reverse order (i.e. check watchers first).	963	- Call all queued watchers in reverse order (i.e. check watchers first).
674	Signals and child watchers are implemented as I/O watchers, and will	964	Signals and child watchers are implemented as I/O watchers, and will
675	be handled here by queueing them when their watcher gets executed.	965	be handled here by queueing them when their watcher gets executed.
676	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	966	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
677	were used, or there are no active watchers, return, otherwise	967	were used, or there are no active watchers, goto FINISH, otherwise
678	continue with step *.	968	continue with step LOOP.
		969	FINISH:
		970	- Reset the ev_break status iff it was EVBREAK_ONE.
		971	- Decrement the loop depth.
		972	- Return.
679		973
680	Example: Queue some jobs and then loop until no events are outstanding	974	Example: Queue some jobs and then loop until no events are outstanding
681	anymore.	975	anymore.
682		976
683	... queue jobs here, make sure they register event watchers as long	977	... queue jobs here, make sure they register event watchers as long
684	... as they still have work to do (even an idle watcher will do..)	978	... as they still have work to do (even an idle watcher will do..)
685	ev_loop (my_loop, 0);	979	ev_run (my_loop, 0);
686	... jobs done or somebody called unloop. yeah!	980	... jobs done or somebody called break. yeah!
687		981
688	=item ev_unloop (loop, how)	982	=item ev_break (loop, how)
689		983
690	Can be used to make a call to C<ev_loop> return early (but only after it	984	Can be used to make a call to C<ev_run> return early (but only after it
691	has processed all outstanding events). The C<how> argument must be either	985	has processed all outstanding events). The C<how> argument must be either
692	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	986	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
693	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	987	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
694		988
695	This "unloop state" will be cleared when entering C<ev_loop> again.	989	This "break state" will be cleared on the next call to C<ev_run>.
696		990
697	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	991	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		992	which case it will have no effect.
698		993
699	=item ev_ref (loop)	994	=item ev_ref (loop)
700		995
701	=item ev_unref (loop)	996	=item ev_unref (loop)
702		997
703	Ref/unref can be used to add or remove a reference count on the event	998	Ref/unref can be used to add or remove a reference count on the event
704	loop: Every watcher keeps one reference, and as long as the reference	999	loop: Every watcher keeps one reference, and as long as the reference
705	count is nonzero, C<ev_loop> will not return on its own.	1000	count is nonzero, C<ev_run> will not return on its own.
706		1001
707	If you have a watcher you never unregister that should not keep C<ev_loop>	1002	This is useful when you have a watcher that you never intend to
708	from returning, call ev_unref() after starting, and ev_ref() before	1003	unregister, but that nevertheless should not keep C<ev_run> from
		1004	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
709	stopping it.	1005	before stopping it.
710		1006
711	As an example, libev itself uses this for its internal signal pipe: It is	1007	As an example, libev itself uses this for its internal signal pipe: It
712	not visible to the libev user and should not keep C<ev_loop> from exiting	1008	is not visible to the libev user and should not keep C<ev_run> from
713	if no event watchers registered by it are active. It is also an excellent	1009	exiting if no event watchers registered by it are active. It is also an
714	way to do this for generic recurring timers or from within third-party	1010	excellent way to do this for generic recurring timers or from within
715	libraries. Just remember to I<unref after start> and I<ref before stop>	1011	third-party libraries. Just remember to I<unref after start> and I<ref
716	(but only if the watcher wasn't active before, or was active before,	1012	before stop> (but only if the watcher wasn't active before, or was active
717	respectively).	1013	before, respectively. Note also that libev might stop watchers itself
		1014	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		1015	in the callback).
718		1016
719	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	1017	Example: Create a signal watcher, but keep it from keeping C<ev_run>
720	running when nothing else is active.	1018	running when nothing else is active.
721		1019
722	ev_signal exitsig;	1020	ev_signal exitsig;
723	ev_signal_init (&exitsig, sig_cb, SIGINT);	1021	ev_signal_init (&exitsig, sig_cb, SIGINT);
724	ev_signal_start (loop, &exitsig);	1022	ev_signal_start (loop, &exitsig);
725	evf_unref (loop);	1023	ev_unref (loop);
726		1024
727	Example: For some weird reason, unregister the above signal handler again.	1025	Example: For some weird reason, unregister the above signal handler again.
728		1026
729	ev_ref (loop);	1027	ev_ref (loop);
730	ev_signal_stop (loop, &exitsig);	1028	ev_signal_stop (loop, &exitsig);
…		…
750	overhead for the actual polling but can deliver many events at once.	1048	overhead for the actual polling but can deliver many events at once.
751		1049
752	By setting a higher I<io collect interval> you allow libev to spend more	1050	By setting a higher I<io collect interval> you allow libev to spend more
753	time collecting I/O events, so you can handle more events per iteration,	1051	time collecting I/O events, so you can handle more events per iteration,
754	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1052	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
755	C<ev_timer>) will be not affected. Setting this to a non-null value will	1053	C<ev_timer>) will not be affected. Setting this to a non-null value will
756	introduce an additional C<ev_sleep ()> call into most loop iterations.	1054	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		1055	sleep time ensures that libev will not poll for I/O events more often then
		1056	once per this interval, on average (as long as the host time resolution is
		1057	good enough).
757		1058
758	Likewise, by setting a higher I<timeout collect interval> you allow libev	1059	Likewise, by setting a higher I<timeout collect interval> you allow libev
759	to spend more time collecting timeouts, at the expense of increased	1060	to spend more time collecting timeouts, at the expense of increased
760	latency/jitter/inexactness (the watcher callback will be called	1061	latency/jitter/inexactness (the watcher callback will be called
761	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1062	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
763		1064
764	Many (busy) programs can usually benefit by setting the I/O collect	1065	Many (busy) programs can usually benefit by setting the I/O collect
765	interval to a value near C<0.1> or so, which is often enough for	1066	interval to a value near C<0.1> or so, which is often enough for
766	interactive servers (of course not for games), likewise for timeouts. It	1067	interactive servers (of course not for games), likewise for timeouts. It
767	usually doesn't make much sense to set it to a lower value than C<0.01>,	1068	usually doesn't make much sense to set it to a lower value than C<0.01>,
768	as this approaches the timing granularity of most systems.	1069	as this approaches the timing granularity of most systems. Note that if
		1070	you do transactions with the outside world and you can't increase the
		1071	parallelity, then this setting will limit your transaction rate (if you
		1072	need to poll once per transaction and the I/O collect interval is 0.01,
		1073	then you can't do more than 100 transactions per second).
769		1074
770	Setting the I<timeout collect interval> can improve the opportunity for	1075	Setting the I<timeout collect interval> can improve the opportunity for
771	saving power, as the program will "bundle" timer callback invocations that	1076	saving power, as the program will "bundle" timer callback invocations that
772	are "near" in time together, by delaying some, thus reducing the number of	1077	are "near" in time together, by delaying some, thus reducing the number of
773	times the process sleeps and wakes up again. Another useful technique to	1078	times the process sleeps and wakes up again. Another useful technique to
774	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	1079	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
775	they fire on, say, one-second boundaries only.	1080	they fire on, say, one-second boundaries only.
776		1081
		1082	Example: we only need 0.1s timeout granularity, and we wish not to poll
		1083	more often than 100 times per second:
		1084
		1085	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		1086	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		1087
		1088	=item ev_invoke_pending (loop)
		1089
		1090	This call will simply invoke all pending watchers while resetting their
		1091	pending state. Normally, C<ev_run> does this automatically when required,
		1092	but when overriding the invoke callback this call comes handy. This
		1093	function can be invoked from a watcher - this can be useful for example
		1094	when you want to do some lengthy calculation and want to pass further
		1095	event handling to another thread (you still have to make sure only one
		1096	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1097
		1098	=item int ev_pending_count (loop)
		1099
		1100	Returns the number of pending watchers - zero indicates that no watchers
		1101	are pending.
		1102
		1103	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1104
		1105	This overrides the invoke pending functionality of the loop: Instead of
		1106	invoking all pending watchers when there are any, C<ev_run> will call
		1107	this callback instead. This is useful, for example, when you want to
		1108	invoke the actual watchers inside another context (another thread etc.).
		1109
		1110	If you want to reset the callback, use C<ev_invoke_pending> as new
		1111	callback.
		1112
		1113	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1114
		1115	Sometimes you want to share the same loop between multiple threads. This
		1116	can be done relatively simply by putting mutex_lock/unlock calls around
		1117	each call to a libev function.
		1118
		1119	However, C<ev_run> can run an indefinite time, so it is not feasible
		1120	to wait for it to return. One way around this is to wake up the event
		1121	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1122	I<release> and I<acquire> callbacks on the loop.
		1123
		1124	When set, then C<release> will be called just before the thread is
		1125	suspended waiting for new events, and C<acquire> is called just
		1126	afterwards.
		1127
		1128	Ideally, C<release> will just call your mutex_unlock function, and
		1129	C<acquire> will just call the mutex_lock function again.
		1130
		1131	While event loop modifications are allowed between invocations of
		1132	C<release> and C<acquire> (that's their only purpose after all), no
		1133	modifications done will affect the event loop, i.e. adding watchers will
		1134	have no effect on the set of file descriptors being watched, or the time
		1135	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1136	to take note of any changes you made.
		1137
		1138	In theory, threads executing C<ev_run> will be async-cancel safe between
		1139	invocations of C<release> and C<acquire>.
		1140
		1141	See also the locking example in the C<THREADS> section later in this
		1142	document.
		1143
		1144	=item ev_set_userdata (loop, void *data)
		1145
		1146	=item void *ev_userdata (loop)
		1147
		1148	Set and retrieve a single C<void *> associated with a loop. When
		1149	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1150	C<0>.
		1151
		1152	These two functions can be used to associate arbitrary data with a loop,
		1153	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1154	C<acquire> callbacks described above, but of course can be (ab-)used for
		1155	any other purpose as well.
		1156
777	=item ev_loop_verify (loop)	1157	=item ev_verify (loop)
778		1158
779	This function only does something when C<EV_VERIFY> support has been	1159	This function only does something when C<EV_VERIFY> support has been
780	compiled in, which is the default for non-minimal builds. It tries to go	1160	compiled in, which is the default for non-minimal builds. It tries to go
781	through all internal structures and checks them for validity. If anything	1161	through all internal structures and checks them for validity. If anything
782	is found to be inconsistent, it will print an error message to standard	1162	is found to be inconsistent, it will print an error message to standard
…		…
793		1173
794	In the following description, uppercase C<TYPE> in names stands for the	1174	In the following description, uppercase C<TYPE> in names stands for the
795	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1175	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
796	watchers and C<ev_io_start> for I/O watchers.	1176	watchers and C<ev_io_start> for I/O watchers.
797		1177
798	A watcher is a structure that you create and register to record your	1178	A watcher is an opaque structure that you allocate and register to record
799	interest in some event. For instance, if you want to wait for STDIN to	1179	your interest in some event. To make a concrete example, imagine you want
800	become readable, you would create an C<ev_io> watcher for that:	1180	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1181	for that:
801		1182
802	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1183	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
803	{	1184	{
804	ev_io_stop (w);	1185	ev_io_stop (w);
805	ev_unloop (loop, EVUNLOOP_ALL);	1186	ev_break (loop, EVBREAK_ALL);
806	}	1187	}
807		1188
808	struct ev_loop *loop = ev_default_loop (0);	1189	struct ev_loop *loop = ev_default_loop (0);
809		1190
810	ev_io stdin_watcher;	1191	ev_io stdin_watcher;
811		1192
812	ev_init (&stdin_watcher, my_cb);	1193	ev_init (&stdin_watcher, my_cb);
813	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1194	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
814	ev_io_start (loop, &stdin_watcher);	1195	ev_io_start (loop, &stdin_watcher);
815		1196
816	ev_loop (loop, 0);	1197	ev_run (loop, 0);
817		1198
818	As you can see, you are responsible for allocating the memory for your	1199	As you can see, you are responsible for allocating the memory for your
819	watcher structures (and it is I<usually> a bad idea to do this on the	1200	watcher structures (and it is I<usually> a bad idea to do this on the
820	stack).	1201	stack).
821		1202
822	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1203	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
823	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1204	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
824		1205
825	Each watcher structure must be initialised by a call to C<ev_init	1206	Each watcher structure must be initialised by a call to C<ev_init (watcher
826	(watcher *, callback)>, which expects a callback to be provided. This	1207	*, callback)>, which expects a callback to be provided. This callback is
827	callback gets invoked each time the event occurs (or, in the case of I/O	1208	invoked each time the event occurs (or, in the case of I/O watchers, each
828	watchers, each time the event loop detects that the file descriptor given	1209	time the event loop detects that the file descriptor given is readable
829	is readable and/or writable).	1210	and/or writable).
830		1211
831	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1212	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
832	macro to configure it, with arguments specific to the watcher type. There	1213	macro to configure it, with arguments specific to the watcher type. There
833	is also a macro to combine initialisation and setting in one call: C<<	1214	is also a macro to combine initialisation and setting in one call: C<<
834	ev_TYPE_init (watcher *, callback, ...) >>.	1215	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
837	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher	1218	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
838	*) >>), and you can stop watching for events at any time by calling the	1219	*) >>), and you can stop watching for events at any time by calling the
839	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.	1220	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
840		1221
841	As long as your watcher is active (has been started but not stopped) you	1222	As long as your watcher is active (has been started but not stopped) you
842	must not touch the values stored in it. Most specifically you must never	1223	must not touch the values stored in it except when explicitly documented
843	reinitialise it or call its C<ev_TYPE_set> macro.	1224	otherwise. Most specifically you must never reinitialise it or call its
		1225	C<ev_TYPE_set> macro.
844		1226
845	Each and every callback receives the event loop pointer as first, the	1227	Each and every callback receives the event loop pointer as first, the
846	registered watcher structure as second, and a bitset of received events as	1228	registered watcher structure as second, and a bitset of received events as
847	third argument.	1229	third argument.
848		1230
…		…
857	=item C<EV_WRITE>	1239	=item C<EV_WRITE>
858		1240
859	The file descriptor in the C<ev_io> watcher has become readable and/or	1241	The file descriptor in the C<ev_io> watcher has become readable and/or
860	writable.	1242	writable.
861		1243
862	=item C<EV_TIMEOUT>	1244	=item C<EV_TIMER>
863		1245
864	The C<ev_timer> watcher has timed out.	1246	The C<ev_timer> watcher has timed out.
865		1247
866	=item C<EV_PERIODIC>	1248	=item C<EV_PERIODIC>
867		1249
…		…
885		1267
886	=item C<EV_PREPARE>	1268	=item C<EV_PREPARE>
887		1269
888	=item C<EV_CHECK>	1270	=item C<EV_CHECK>
889		1271
890	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1272	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
891	to gather new events, and all C<ev_check> watchers are invoked just after	1273	gather new events, and all C<ev_check> watchers are queued (not invoked)
892	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1274	just after C<ev_run> has gathered them, but before it queues any callbacks
		1275	for any received events. That means C<ev_prepare> watchers are the last
		1276	watchers invoked before the event loop sleeps or polls for new events, and
		1277	C<ev_check> watchers will be invoked before any other watchers of the same
		1278	or lower priority within an event loop iteration.
		1279
893	received events. Callbacks of both watcher types can start and stop as	1280	Callbacks of both watcher types can start and stop as many watchers as
894	many watchers as they want, and all of them will be taken into account	1281	they want, and all of them will be taken into account (for example, a
895	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1282	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
896	C<ev_loop> from blocking).	1283	blocking).
897		1284
898	=item C<EV_EMBED>	1285	=item C<EV_EMBED>
899		1286
900	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1287	The embedded event loop specified in the C<ev_embed> watcher needs attention.
901		1288
902	=item C<EV_FORK>	1289	=item C<EV_FORK>
903		1290
904	The event loop has been resumed in the child process after fork (see	1291	The event loop has been resumed in the child process after fork (see
905	C<ev_fork>).	1292	C<ev_fork>).
906		1293
		1294	=item C<EV_CLEANUP>
		1295
		1296	The event loop is about to be destroyed (see C<ev_cleanup>).
		1297
907	=item C<EV_ASYNC>	1298	=item C<EV_ASYNC>
908		1299
909	The given async watcher has been asynchronously notified (see C<ev_async>).	1300	The given async watcher has been asynchronously notified (see C<ev_async>).
		1301
		1302	=item C<EV_CUSTOM>
		1303
		1304	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1305	by libev users to signal watchers (e.g. via C<ev_feed_event>).
910		1306
911	=item C<EV_ERROR>	1307	=item C<EV_ERROR>
912		1308
913	An unspecified error has occurred, the watcher has been stopped. This might	1309	An unspecified error has occurred, the watcher has been stopped. This might
914	happen because the watcher could not be properly started because libev	1310	happen because the watcher could not be properly started because libev
…		…
952		1348
953	ev_io w;	1349	ev_io w;
954	ev_init (&w, my_cb);	1350	ev_init (&w, my_cb);
955	ev_io_set (&w, STDIN_FILENO, EV_READ);	1351	ev_io_set (&w, STDIN_FILENO, EV_READ);
956		1352
957	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1353	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
958		1354
959	This macro initialises the type-specific parts of a watcher. You need to	1355	This macro initialises the type-specific parts of a watcher. You need to
960	call C<ev_init> at least once before you call this macro, but you can	1356	call C<ev_init> at least once before you call this macro, but you can
961	call C<ev_TYPE_set> any number of times. You must not, however, call this	1357	call C<ev_TYPE_set> any number of times. You must not, however, call this
962	macro on a watcher that is active (it can be pending, however, which is a	1358	macro on a watcher that is active (it can be pending, however, which is a
…		…
975		1371
976	Example: Initialise and set an C<ev_io> watcher in one step.	1372	Example: Initialise and set an C<ev_io> watcher in one step.
977		1373
978	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1374	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
979		1375
980	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1376	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
981		1377
982	Starts (activates) the given watcher. Only active watchers will receive	1378	Starts (activates) the given watcher. Only active watchers will receive
983	events. If the watcher is already active nothing will happen.	1379	events. If the watcher is already active nothing will happen.
984		1380
985	Example: Start the C<ev_io> watcher that is being abused as example in this	1381	Example: Start the C<ev_io> watcher that is being abused as example in this
986	whole section.	1382	whole section.
987		1383
988	ev_io_start (EV_DEFAULT_UC, &w);	1384	ev_io_start (EV_DEFAULT_UC, &w);
989		1385
990	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1386	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
991		1387
992	Stops the given watcher if active, and clears the pending status (whether	1388	Stops the given watcher if active, and clears the pending status (whether
993	the watcher was active or not).	1389	the watcher was active or not).
994		1390
995	It is possible that stopped watchers are pending - for example,	1391	It is possible that stopped watchers are pending - for example,
…		…
1015		1411
1016	=item callback ev_cb (ev_TYPE *watcher)	1412	=item callback ev_cb (ev_TYPE *watcher)
1017		1413
1018	Returns the callback currently set on the watcher.	1414	Returns the callback currently set on the watcher.
1019		1415
1020	=item ev_cb_set (ev_TYPE *watcher, callback)	1416	=item ev_set_cb (ev_TYPE *watcher, callback)
1021		1417
1022	Change the callback. You can change the callback at virtually any time	1418	Change the callback. You can change the callback at virtually any time
1023	(modulo threads).	1419	(modulo threads).
1024		1420
1025	=item ev_set_priority (ev_TYPE *watcher, priority)	1421	=item ev_set_priority (ev_TYPE *watcher, int priority)
1026		1422
1027	=item int ev_priority (ev_TYPE *watcher)	1423	=item int ev_priority (ev_TYPE *watcher)
1028		1424
1029	Set and query the priority of the watcher. The priority is a small	1425	Set and query the priority of the watcher. The priority is a small
1030	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1426	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1031	(default: C<-2>). Pending watchers with higher priority will be invoked	1427	(default: C<-2>). Pending watchers with higher priority will be invoked
1032	before watchers with lower priority, but priority will not keep watchers	1428	before watchers with lower priority, but priority will not keep watchers
1033	from being executed (except for C<ev_idle> watchers).	1429	from being executed (except for C<ev_idle> watchers).
1034		1430
1035	This means that priorities are I<only> used for ordering callback
1036	invocation after new events have been received. This is useful, for
1037	example, to reduce latency after idling, or more often, to bind two
1038	watchers on the same event and make sure one is called first.
1039
1040	If you need to suppress invocation when higher priority events are pending	1431	If you need to suppress invocation when higher priority events are pending
1041	you need to look at C<ev_idle> watchers, which provide this functionality.	1432	you need to look at C<ev_idle> watchers, which provide this functionality.
1042		1433
1043	You I<must not> change the priority of a watcher as long as it is active or	1434	You I<must not> change the priority of a watcher as long as it is active or
1044	pending.	1435	pending.
1045
1046	The default priority used by watchers when no priority has been set is
1047	always C<0>, which is supposed to not be too high and not be too low :).
1048		1436
1049	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1437	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1050	fine, as long as you do not mind that the priority value you query might	1438	fine, as long as you do not mind that the priority value you query might
1051	or might not have been clamped to the valid range.	1439	or might not have been clamped to the valid range.
		1440
		1441	The default priority used by watchers when no priority has been set is
		1442	always C<0>, which is supposed to not be too high and not be too low :).
		1443
		1444	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1445	priorities.
1052		1446
1053	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1447	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1054		1448
1055	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1449	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1056	C<loop> nor C<revents> need to be valid as long as the watcher callback	1450	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1064	watcher isn't pending it does nothing and returns C<0>.	1458	watcher isn't pending it does nothing and returns C<0>.
1065		1459
1066	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1460	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1067	callback to be invoked, which can be accomplished with this function.	1461	callback to be invoked, which can be accomplished with this function.
1068		1462
		1463	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1464
		1465	Feeds the given event set into the event loop, as if the specified event
		1466	had happened for the specified watcher (which must be a pointer to an
		1467	initialised but not necessarily started event watcher). Obviously you must
		1468	not free the watcher as long as it has pending events.
		1469
		1470	Stopping the watcher, letting libev invoke it, or calling
		1471	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1472	not started in the first place.
		1473
		1474	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1475	functions that do not need a watcher.
		1476
1069	=back	1477	=back
1070		1478
		1479	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1480	OWN COMPOSITE WATCHERS> idioms.
1071		1481
1072	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1482	=head2 WATCHER STATES
1073		1483
1074	Each watcher has, by default, a member C<void *data> that you can change	1484	There are various watcher states mentioned throughout this manual -
1075	and read at any time: libev will completely ignore it. This can be used	1485	active, pending and so on. In this section these states and the rules to
1076	to associate arbitrary data with your watcher. If you need more data and	1486	transition between them will be described in more detail - and while these
1077	don't want to allocate memory and store a pointer to it in that data	1487	rules might look complicated, they usually do "the right thing".
1078	member, you can also "subclass" the watcher type and provide your own
1079	data:
1080		1488
1081	struct my_io	1489	=over 4
		1490
		1491	=item initialised
		1492
		1493	Before a watcher can be registered with the event loop it has to be
		1494	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1495	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1496
		1497	In this state it is simply some block of memory that is suitable for
		1498	use in an event loop. It can be moved around, freed, reused etc. at
		1499	will - as long as you either keep the memory contents intact, or call
		1500	C<ev_TYPE_init> again.
		1501
		1502	=item started/running/active
		1503
		1504	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1505	property of the event loop, and is actively waiting for events. While in
		1506	this state it cannot be accessed (except in a few documented ways), moved,
		1507	freed or anything else - the only legal thing is to keep a pointer to it,
		1508	and call libev functions on it that are documented to work on active watchers.
		1509
		1510	=item pending
		1511
		1512	If a watcher is active and libev determines that an event it is interested
		1513	in has occurred (such as a timer expiring), it will become pending. It will
		1514	stay in this pending state until either it is stopped or its callback is
		1515	about to be invoked, so it is not normally pending inside the watcher
		1516	callback.
		1517
		1518	The watcher might or might not be active while it is pending (for example,
		1519	an expired non-repeating timer can be pending but no longer active). If it
		1520	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1521	but it is still property of the event loop at this time, so cannot be
		1522	moved, freed or reused. And if it is active the rules described in the
		1523	previous item still apply.
		1524
		1525	It is also possible to feed an event on a watcher that is not active (e.g.
		1526	via C<ev_feed_event>), in which case it becomes pending without being
		1527	active.
		1528
		1529	=item stopped
		1530
		1531	A watcher can be stopped implicitly by libev (in which case it might still
		1532	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1533	latter will clear any pending state the watcher might be in, regardless
		1534	of whether it was active or not, so stopping a watcher explicitly before
		1535	freeing it is often a good idea.
		1536
		1537	While stopped (and not pending) the watcher is essentially in the
		1538	initialised state, that is, it can be reused, moved, modified in any way
		1539	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1540	it again).
		1541
		1542	=back
		1543
		1544	=head2 WATCHER PRIORITY MODELS
		1545
		1546	Many event loops support I<watcher priorities>, which are usually small
		1547	integers that influence the ordering of event callback invocation
		1548	between watchers in some way, all else being equal.
		1549
		1550	In libev, watcher priorities can be set using C<ev_set_priority>. See its
		1551	description for the more technical details such as the actual priority
		1552	range.
		1553
		1554	There are two common ways how these these priorities are being interpreted
		1555	by event loops:
		1556
		1557	In the more common lock-out model, higher priorities "lock out" invocation
		1558	of lower priority watchers, which means as long as higher priority
		1559	watchers receive events, lower priority watchers are not being invoked.
		1560
		1561	The less common only-for-ordering model uses priorities solely to order
		1562	callback invocation within a single event loop iteration: Higher priority
		1563	watchers are invoked before lower priority ones, but they all get invoked
		1564	before polling for new events.
		1565
		1566	Libev uses the second (only-for-ordering) model for all its watchers
		1567	except for idle watchers (which use the lock-out model).
		1568
		1569	The rationale behind this is that implementing the lock-out model for
		1570	watchers is not well supported by most kernel interfaces, and most event
		1571	libraries will just poll for the same events again and again as long as
		1572	their callbacks have not been executed, which is very inefficient in the
		1573	common case of one high-priority watcher locking out a mass of lower
		1574	priority ones.
		1575
		1576	Static (ordering) priorities are most useful when you have two or more
		1577	watchers handling the same resource: a typical usage example is having an
		1578	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1579	timeouts. Under load, data might be received while the program handles
		1580	other jobs, but since timers normally get invoked first, the timeout
		1581	handler will be executed before checking for data. In that case, giving
		1582	the timer a lower priority than the I/O watcher ensures that I/O will be
		1583	handled first even under adverse conditions (which is usually, but not
		1584	always, what you want).
		1585
		1586	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1587	will only be executed when no same or higher priority watchers have
		1588	received events, they can be used to implement the "lock-out" model when
		1589	required.
		1590
		1591	For example, to emulate how many other event libraries handle priorities,
		1592	you can associate an C<ev_idle> watcher to each such watcher, and in
		1593	the normal watcher callback, you just start the idle watcher. The real
		1594	processing is done in the idle watcher callback. This causes libev to
		1595	continuously poll and process kernel event data for the watcher, but when
		1596	the lock-out case is known to be rare (which in turn is rare :), this is
		1597	workable.
		1598
		1599	Usually, however, the lock-out model implemented that way will perform
		1600	miserably under the type of load it was designed to handle. In that case,
		1601	it might be preferable to stop the real watcher before starting the
		1602	idle watcher, so the kernel will not have to process the event in case
		1603	the actual processing will be delayed for considerable time.
		1604
		1605	Here is an example of an I/O watcher that should run at a strictly lower
		1606	priority than the default, and which should only process data when no
		1607	other events are pending:
		1608
		1609	ev_idle idle; // actual processing watcher
		1610	ev_io io; // actual event watcher
		1611
		1612	static void
		1613	io_cb (EV_P_ ev_io *w, int revents)
1082	{	1614	{
1083	ev_io io;	1615	// stop the I/O watcher, we received the event, but
1084	int otherfd;	1616	// are not yet ready to handle it.
1085	void *somedata;	1617	ev_io_stop (EV_A_ w);
1086	struct whatever *mostinteresting;	1618
		1619	// start the idle watcher to handle the actual event.
		1620	// it will not be executed as long as other watchers
		1621	// with the default priority are receiving events.
		1622	ev_idle_start (EV_A_ &idle);
1087	};	1623	}
1088		1624
1089	...	1625	static void
1090	struct my_io w;	1626	idle_cb (EV_P_ ev_idle *w, int revents)
1091	ev_io_init (&w.io, my_cb, fd, EV_READ);
1092
1093	And since your callback will be called with a pointer to the watcher, you
1094	can cast it back to your own type:
1095
1096	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1097	{	1627	{
1098	struct my_io *w = (struct my_io *)w_;	1628	// actual processing
1099	...	1629	read (STDIN_FILENO, ...);
		1630
		1631	// have to start the I/O watcher again, as
		1632	// we have handled the event
		1633	ev_io_start (EV_P_ &io);
1100	}	1634	}
1101		1635
1102	More interesting and less C-conformant ways of casting your callback type	1636	// initialisation
1103	instead have been omitted.	1637	ev_idle_init (&idle, idle_cb);
		1638	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1639	ev_io_start (EV_DEFAULT_ &io);
1104		1640
1105	Another common scenario is to use some data structure with multiple	1641	In the "real" world, it might also be beneficial to start a timer, so that
1106	embedded watchers:	1642	low-priority connections can not be locked out forever under load. This
1107		1643	enables your program to keep a lower latency for important connections
1108	struct my_biggy	1644	during short periods of high load, while not completely locking out less
1109	{	1645	important ones.
1110	int some_data;
1111	ev_timer t1;
1112	ev_timer t2;
1113	}
1114
1115	In this case getting the pointer to C<my_biggy> is a bit more
1116	complicated: Either you store the address of your C<my_biggy> struct
1117	in the C<data> member of the watcher (for woozies), or you need to use
1118	some pointer arithmetic using C<offsetof> inside your watchers (for real
1119	programmers):
1120
1121	#include <stddef.h>
1122
1123	static void
1124	t1_cb (EV_P_ ev_timer *w, int revents)
1125	{
1126	struct my_biggy big = (struct my_biggy *
1127	(((char *)w) - offsetof (struct my_biggy, t1));
1128	}
1129
1130	static void
1131	t2_cb (EV_P_ ev_timer *w, int revents)
1132	{
1133	struct my_biggy big = (struct my_biggy *
1134	(((char *)w) - offsetof (struct my_biggy, t2));
1135	}
1136		1646
1137		1647
1138	=head1 WATCHER TYPES	1648	=head1 WATCHER TYPES
1139		1649
1140	This section describes each watcher in detail, but will not repeat	1650	This section describes each watcher in detail, but will not repeat
1141	information given in the last section. Any initialisation/set macros,	1651	information given in the last section. Any initialisation/set macros,
1142	functions and members specific to the watcher type are explained.	1652	functions and members specific to the watcher type are explained.
1143		1653
1144	Members are additionally marked with either I<[read-only]>, meaning that,	1654	Most members are additionally marked with either I<[read-only]>, meaning
1145	while the watcher is active, you can look at the member and expect some	1655	that, while the watcher is active, you can look at the member and expect
1146	sensible content, but you must not modify it (you can modify it while the	1656	some sensible content, but you must not modify it (you can modify it while
1147	watcher is stopped to your hearts content), or I<[read-write]>, which	1657	the watcher is stopped to your hearts content), or I<[read-write]>, which
1148	means you can expect it to have some sensible content while the watcher	1658	means you can expect it to have some sensible content while the watcher
1149	is active, but you can also modify it. Modifying it may not do something	1659	is active, but you can also modify it. Modifying it may not do something
1150	sensible or take immediate effect (or do anything at all), but libev will	1660	sensible or take immediate effect (or do anything at all), but libev will
1151	not crash or malfunction in any way.	1661	not crash or malfunction in any way.
1152		1662
		1663	In any case, the documentation for each member will explain what the
		1664	effects are, and if there are any additional access restrictions.
1153		1665
1154	=head2 C<ev_io> - is this file descriptor readable or writable?	1666	=head2 C<ev_io> - is this file descriptor readable or writable?
1155		1667
1156	I/O watchers check whether a file descriptor is readable or writable	1668	I/O watchers check whether a file descriptor is readable or writable
1157	in each iteration of the event loop, or, more precisely, when reading	1669	in each iteration of the event loop, or, more precisely, when reading
…		…
1164	In general you can register as many read and/or write event watchers per	1676	In general you can register as many read and/or write event watchers per
1165	fd as you want (as long as you don't confuse yourself). Setting all file	1677	fd as you want (as long as you don't confuse yourself). Setting all file
1166	descriptors to non-blocking mode is also usually a good idea (but not	1678	descriptors to non-blocking mode is also usually a good idea (but not
1167	required if you know what you are doing).	1679	required if you know what you are doing).
1168		1680
1169	If you cannot use non-blocking mode, then force the use of a
1170	known-to-be-good backend (at the time of this writing, this includes only
1171	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1172
1173	Another thing you have to watch out for is that it is quite easy to	1681	Another thing you have to watch out for is that it is quite easy to
1174	receive "spurious" readiness notifications, that is your callback might	1682	receive "spurious" readiness notifications, that is, your callback might
1175	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1683	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1176	because there is no data. Not only are some backends known to create a	1684	because there is no data. It is very easy to get into this situation even
1177	lot of those (for example Solaris ports), it is very easy to get into	1685	with a relatively standard program structure. Thus it is best to always
1178	this situation even with a relatively standard program structure. Thus	1686	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1179	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1180	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1687	preferable to a program hanging until some data arrives.
1181		1688
1182	If you cannot run the fd in non-blocking mode (for example you should	1689	If you cannot run the fd in non-blocking mode (for example you should
1183	not play around with an Xlib connection), then you have to separately	1690	not play around with an Xlib connection), then you have to separately
1184	re-test whether a file descriptor is really ready with a known-to-be good	1691	re-test whether a file descriptor is really ready with a known-to-be good
1185	interface such as poll (fortunately in our Xlib example, Xlib already	1692	interface such as poll (fortunately in the case of Xlib, it already does
1186	does this on its own, so its quite safe to use). Some people additionally	1693	this on its own, so its quite safe to use). Some people additionally
1187	use C<SIGALRM> and an interval timer, just to be sure you won't block	1694	use C<SIGALRM> and an interval timer, just to be sure you won't block
1188	indefinitely.	1695	indefinitely.
1189		1696
1190	But really, best use non-blocking mode.	1697	But really, best use non-blocking mode.
1191		1698
1192	=head3 The special problem of disappearing file descriptors	1699	=head3 The special problem of disappearing file descriptors
1193		1700
1194	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1701	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1195	descriptor (either due to calling C<close> explicitly or any other means,	1702	a file descriptor (either due to calling C<close> explicitly or any other
1196	such as C<dup2>). The reason is that you register interest in some file	1703	means, such as C<dup2>). The reason is that you register interest in some
1197	descriptor, but when it goes away, the operating system will silently drop	1704	file descriptor, but when it goes away, the operating system will silently
1198	this interest. If another file descriptor with the same number then is	1705	drop this interest. If another file descriptor with the same number then
1199	registered with libev, there is no efficient way to see that this is, in	1706	is registered with libev, there is no efficient way to see that this is,
1200	fact, a different file descriptor.	1707	in fact, a different file descriptor.
1201		1708
1202	To avoid having to explicitly tell libev about such cases, libev follows	1709	To avoid having to explicitly tell libev about such cases, libev follows
1203	the following policy: Each time C<ev_io_set> is being called, libev	1710	the following policy: Each time C<ev_io_set> is being called, libev
1204	will assume that this is potentially a new file descriptor, otherwise	1711	will assume that this is potentially a new file descriptor, otherwise
1205	it is assumed that the file descriptor stays the same. That means that	1712	it is assumed that the file descriptor stays the same. That means that
…		…
1219		1726
1220	There is no workaround possible except not registering events	1727	There is no workaround possible except not registering events
1221	for potentially C<dup ()>'ed file descriptors, or to resort to	1728	for potentially C<dup ()>'ed file descriptors, or to resort to
1222	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1729	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1223		1730
		1731	=head3 The special problem of files
		1732
		1733	Many people try to use C<select> (or libev) on file descriptors
		1734	representing files, and expect it to become ready when their program
		1735	doesn't block on disk accesses (which can take a long time on their own).
		1736
		1737	However, this cannot ever work in the "expected" way - you get a readiness
		1738	notification as soon as the kernel knows whether and how much data is
		1739	there, and in the case of open files, that's always the case, so you
		1740	always get a readiness notification instantly, and your read (or possibly
		1741	write) will still block on the disk I/O.
		1742
		1743	Another way to view it is that in the case of sockets, pipes, character
		1744	devices and so on, there is another party (the sender) that delivers data
		1745	on its own, but in the case of files, there is no such thing: the disk
		1746	will not send data on its own, simply because it doesn't know what you
		1747	wish to read - you would first have to request some data.
		1748
		1749	Since files are typically not-so-well supported by advanced notification
		1750	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1751	to files, even though you should not use it. The reason for this is
		1752	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1753	usually a tty, often a pipe, but also sometimes files or special devices
		1754	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1755	F</dev/urandom>), and even though the file might better be served with
		1756	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1757	it "just works" instead of freezing.
		1758
		1759	So avoid file descriptors pointing to files when you know it (e.g. use
		1760	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1761	when you rarely read from a file instead of from a socket, and want to
		1762	reuse the same code path.
		1763
1224	=head3 The special problem of fork	1764	=head3 The special problem of fork
1225		1765
1226	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1766	Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()>
1227	useless behaviour. Libev fully supports fork, but needs to be told about	1767	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1228	it in the child.	1768	to be told about it in the child if you want to continue to use it in the
		1769	child.
1229		1770
1230	To support fork in your programs, you either have to call	1771	To support fork in your child processes, you have to call C<ev_loop_fork
1231	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1772	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1232	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1773	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1233	C<EVBACKEND_POLL>.
1234		1774
1235	=head3 The special problem of SIGPIPE	1775	=head3 The special problem of SIGPIPE
1236		1776
1237	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1777	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1238	when writing to a pipe whose other end has been closed, your program gets	1778	when writing to a pipe whose other end has been closed, your program gets
…		…
1241		1781
1242	So when you encounter spurious, unexplained daemon exits, make sure you	1782	So when you encounter spurious, unexplained daemon exits, make sure you
1243	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1783	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1244	somewhere, as that would have given you a big clue).	1784	somewhere, as that would have given you a big clue).
1245		1785
		1786	=head3 The special problem of accept()ing when you can't
		1787
		1788	Many implementations of the POSIX C<accept> function (for example,
		1789	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1790	connection from the pending queue in all error cases.
		1791
		1792	For example, larger servers often run out of file descriptors (because
		1793	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1794	rejecting the connection, leading to libev signalling readiness on
		1795	the next iteration again (the connection still exists after all), and
		1796	typically causing the program to loop at 100% CPU usage.
		1797
		1798	Unfortunately, the set of errors that cause this issue differs between
		1799	operating systems, there is usually little the app can do to remedy the
		1800	situation, and no known thread-safe method of removing the connection to
		1801	cope with overload is known (to me).
		1802
		1803	One of the easiest ways to handle this situation is to just ignore it
		1804	- when the program encounters an overload, it will just loop until the
		1805	situation is over. While this is a form of busy waiting, no OS offers an
		1806	event-based way to handle this situation, so it's the best one can do.
		1807
		1808	A better way to handle the situation is to log any errors other than
		1809	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1810	messages, and continue as usual, which at least gives the user an idea of
		1811	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1812	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1813	usage.
		1814
		1815	If your program is single-threaded, then you could also keep a dummy file
		1816	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1817	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1818	close that fd, and create a new dummy fd. This will gracefully refuse
		1819	clients under typical overload conditions.
		1820
		1821	The last way to handle it is to simply log the error and C<exit>, as
		1822	is often done with C<malloc> failures, but this results in an easy
		1823	opportunity for a DoS attack.
1246		1824
1247	=head3 Watcher-Specific Functions	1825	=head3 Watcher-Specific Functions
1248		1826
1249	=over 4	1827	=over 4
1250		1828
…		…
1254		1832
1255	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1833	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1256	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or	1834	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1257	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.	1835	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1258		1836
1259	=item int fd [read-only]	1837	=item ev_io_modify (ev_io *, int events)
1260		1838
1261	The file descriptor being watched.	1839	Similar to C<ev_io_set>, but only changes the event mask. Using this might
		1840	be faster with some backends, as libev can assume that the C<fd> still
		1841	refers to the same underlying file description, something it cannot do
		1842	when using C<ev_io_set>.
1262		1843
		1844	=item int fd [no-modify]
		1845
		1846	The file descriptor being watched. While it can be read at any time, you
		1847	must not modify this member even when the watcher is stopped - always use
		1848	C<ev_io_set> for that.
		1849
1263	=item int events [read-only]	1850	=item int events [no-modify]
1264		1851
1265	The events being watched.	1852	The set of events the fd is being watched for, among other flags. Remember
		1853	that this is a bit set - to test for C<EV_READ>, use C<< w->events &
		1854	EV_READ >>, and similarly for C<EV_WRITE>.
		1855
		1856	As with C<fd>, you must not modify this member even when the watcher is
		1857	stopped, always use C<ev_io_set> or C<ev_io_modify> for that.
1266		1858
1267	=back	1859	=back
1268		1860
1269	=head3 Examples	1861	=head3 Examples
1270		1862
…		…
1282	...	1874	...
1283	struct ev_loop *loop = ev_default_init (0);	1875	struct ev_loop *loop = ev_default_init (0);
1284	ev_io stdin_readable;	1876	ev_io stdin_readable;
1285	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1877	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1286	ev_io_start (loop, &stdin_readable);	1878	ev_io_start (loop, &stdin_readable);
1287	ev_loop (loop, 0);	1879	ev_run (loop, 0);
1288		1880
1289		1881
1290	=head2 C<ev_timer> - relative and optionally repeating timeouts	1882	=head2 C<ev_timer> - relative and optionally repeating timeouts
1291		1883
1292	Timer watchers are simple relative timers that generate an event after a	1884	Timer watchers are simple relative timers that generate an event after a
…		…
1297	year, it will still time out after (roughly) one hour. "Roughly" because	1889	year, it will still time out after (roughly) one hour. "Roughly" because
1298	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1890	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1299	monotonic clock option helps a lot here).	1891	monotonic clock option helps a lot here).
1300		1892
1301	The callback is guaranteed to be invoked only I<after> its timeout has	1893	The callback is guaranteed to be invoked only I<after> its timeout has
1302	passed, but if multiple timers become ready during the same loop iteration	1894	passed (not I<at>, so on systems with very low-resolution clocks this
1303	then order of execution is undefined.	1895	might introduce a small delay, see "the special problem of being too
		1896	early", below). If multiple timers become ready during the same loop
		1897	iteration then the ones with earlier time-out values are invoked before
		1898	ones of the same priority with later time-out values (but this is no
		1899	longer true when a callback calls C<ev_run> recursively).
1304		1900
1305	=head3 Be smart about timeouts	1901	=head3 Be smart about timeouts
1306		1902
1307	Many real-world problems involve some kind of timeout, usually for error	1903	Many real-world problems involve some kind of timeout, usually for error
1308	recovery. A typical example is an HTTP request - if the other side hangs,	1904	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1352	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1948	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1353	member and C<ev_timer_again>.	1949	member and C<ev_timer_again>.
1354		1950
1355	At start:	1951	At start:
1356		1952
1357	ev_timer_init (timer, callback);	1953	ev_init (timer, callback);
1358	timer->repeat = 60.;	1954	timer->repeat = 60.;
1359	ev_timer_again (loop, timer);	1955	ev_timer_again (loop, timer);
1360		1956
1361	Each time there is some activity:	1957	Each time there is some activity:
1362		1958
…		…
1383		1979
1384	In this case, it would be more efficient to leave the C<ev_timer> alone,	1980	In this case, it would be more efficient to leave the C<ev_timer> alone,
1385	but remember the time of last activity, and check for a real timeout only	1981	but remember the time of last activity, and check for a real timeout only
1386	within the callback:	1982	within the callback:
1387		1983
		1984	ev_tstamp timeout = 60.;
1388	ev_tstamp last_activity; // time of last activity	1985	ev_tstamp last_activity; // time of last activity
		1986	ev_timer timer;
1389		1987
1390	static void	1988	static void
1391	callback (EV_P_ ev_timer *w, int revents)	1989	callback (EV_P_ ev_timer *w, int revents)
1392	{	1990	{
1393	ev_tstamp now = ev_now (EV_A);	1991	// calculate when the timeout would happen
1394	ev_tstamp timeout = last_activity + 60.;	1992	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1395		1993
1396	// if last_activity + 60. is older than now, we did time out	1994	// if negative, it means we the timeout already occurred
1397	if (timeout < now)	1995	if (after < 0.)
1398	{	1996	{
1399	// timeout occured, take action	1997	// timeout occurred, take action
1400	}	1998	}
1401	else	1999	else
1402	{	2000	{
1403	// callback was invoked, but there was some activity, re-arm	2001	// callback was invoked, but there was some recent
1404	// the watcher to fire in last_activity + 60, which is	2002	// activity. simply restart the timer to time out
1405	// guaranteed to be in the future, so "again" is positive:	2003	// after "after" seconds, which is the earliest time
1406	w->again = timeout - now;	2004	// the timeout can occur.
		2005	ev_timer_set (w, after, 0.);
1407	ev_timer_again (EV_A_ w);	2006	ev_timer_start (EV_A_ w);
1408	}	2007	}
1409	}	2008	}
1410		2009
1411	To summarise the callback: first calculate the real timeout (defined	2010	To summarise the callback: first calculate in how many seconds the
1412	as "60 seconds after the last activity"), then check if that time has	2011	timeout will occur (by calculating the absolute time when it would occur,
1413	been reached, which means something I<did>, in fact, time out. Otherwise	2012	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1414	the callback was invoked too early (C<timeout> is in the future), so	2013	(EV_A)> from that).
1415	re-schedule the timer to fire at that future time, to see if maybe we have
1416	a timeout then.
1417		2014
1418	Note how C<ev_timer_again> is used, taking advantage of the	2015	If this value is negative, then we are already past the timeout, i.e. we
1419	C<ev_timer_again> optimisation when the timer is already running.	2016	timed out, and need to do whatever is needed in this case.
		2017
		2018	Otherwise, we now the earliest time at which the timeout would trigger,
		2019	and simply start the timer with this timeout value.
		2020
		2021	In other words, each time the callback is invoked it will check whether
		2022	the timeout occurred. If not, it will simply reschedule itself to check
		2023	again at the earliest time it could time out. Rinse. Repeat.
1420		2024
1421	This scheme causes more callback invocations (about one every 60 seconds	2025	This scheme causes more callback invocations (about one every 60 seconds
1422	minus half the average time between activity), but virtually no calls to	2026	minus half the average time between activity), but virtually no calls to
1423	libev to change the timeout.	2027	libev to change the timeout.
1424		2028
1425	To start the timer, simply initialise the watcher and set C<last_activity>	2029	To start the machinery, simply initialise the watcher and set
1426	to the current time (meaning we just have some activity :), then call the	2030	C<last_activity> to the current time (meaning there was some activity just
1427	callback, which will "do the right thing" and start the timer:	2031	now), then call the callback, which will "do the right thing" and start
		2032	the timer:
1428		2033
		2034	last_activity = ev_now (EV_A);
1429	ev_timer_init (timer, callback);	2035	ev_init (&timer, callback);
1430	last_activity = ev_now (loop);	2036	callback (EV_A_ &timer, 0);
1431	callback (loop, timer, EV_TIMEOUT);
1432		2037
1433	And when there is some activity, simply store the current time in	2038	When there is some activity, simply store the current time in
1434	C<last_activity>, no libev calls at all:	2039	C<last_activity>, no libev calls at all:
1435		2040
		2041	if (activity detected)
1436	last_actiivty = ev_now (loop);	2042	last_activity = ev_now (EV_A);
		2043
		2044	When your timeout value changes, then the timeout can be changed by simply
		2045	providing a new value, stopping the timer and calling the callback, which
		2046	will again do the right thing (for example, time out immediately :).
		2047
		2048	timeout = new_value;
		2049	ev_timer_stop (EV_A_ &timer);
		2050	callback (EV_A_ &timer, 0);
1437		2051
1438	This technique is slightly more complex, but in most cases where the	2052	This technique is slightly more complex, but in most cases where the
1439	time-out is unlikely to be triggered, much more efficient.	2053	time-out is unlikely to be triggered, much more efficient.
1440
1441	Changing the timeout is trivial as well (if it isn't hard-coded in the
1442	callback :) - just change the timeout and invoke the callback, which will
1443	fix things for you.
1444		2054
1445	=item 4. Wee, just use a double-linked list for your timeouts.	2055	=item 4. Wee, just use a double-linked list for your timeouts.
1446		2056
1447	If there is not one request, but many thousands (millions...), all	2057	If there is not one request, but many thousands (millions...), all
1448	employing some kind of timeout with the same timeout value, then one can	2058	employing some kind of timeout with the same timeout value, then one can
…		…
1475	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2085	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1476	rather complicated, but extremely efficient, something that really pays	2086	rather complicated, but extremely efficient, something that really pays
1477	off after the first million or so of active timers, i.e. it's usually	2087	off after the first million or so of active timers, i.e. it's usually
1478	overkill :)	2088	overkill :)
1479		2089
		2090	=head3 The special problem of being too early
		2091
		2092	If you ask a timer to call your callback after three seconds, then
		2093	you expect it to be invoked after three seconds - but of course, this
		2094	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2095	guaranteed to any precision by libev - imagine somebody suspending the
		2096	process with a STOP signal for a few hours for example.
		2097
		2098	So, libev tries to invoke your callback as soon as possible I<after> the
		2099	delay has occurred, but cannot guarantee this.
		2100
		2101	A less obvious failure mode is calling your callback too early: many event
		2102	loops compare timestamps with a "elapsed delay >= requested delay", but
		2103	this can cause your callback to be invoked much earlier than you would
		2104	expect.
		2105
		2106	To see why, imagine a system with a clock that only offers full second
		2107	resolution (think windows if you can't come up with a broken enough OS
		2108	yourself). If you schedule a one-second timer at the time 500.9, then the
		2109	event loop will schedule your timeout to elapse at a system time of 500
		2110	(500.9 truncated to the resolution) + 1, or 501.
		2111
		2112	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2113	501" and invoke the callback 0.1s after it was started, even though a
		2114	one-second delay was requested - this is being "too early", despite best
		2115	intentions.
		2116
		2117	This is the reason why libev will never invoke the callback if the elapsed
		2118	delay equals the requested delay, but only when the elapsed delay is
		2119	larger than the requested delay. In the example above, libev would only invoke
		2120	the callback at system time 502, or 1.1s after the timer was started.
		2121
		2122	So, while libev cannot guarantee that your callback will be invoked
		2123	exactly when requested, it I<can> and I<does> guarantee that the requested
		2124	delay has actually elapsed, or in other words, it always errs on the "too
		2125	late" side of things.
		2126
1480	=head3 The special problem of time updates	2127	=head3 The special problem of time updates
1481		2128
1482	Establishing the current time is a costly operation (it usually takes at	2129	Establishing the current time is a costly operation (it usually takes
1483	least two system calls): EV therefore updates its idea of the current	2130	at least one system call): EV therefore updates its idea of the current
1484	time only before and after C<ev_loop> collects new events, which causes a	2131	time only before and after C<ev_run> collects new events, which causes a
1485	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2132	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1486	lots of events in one iteration.	2133	lots of events in one iteration.
1487		2134
1488	The relative timeouts are calculated relative to the C<ev_now ()>	2135	The relative timeouts are calculated relative to the C<ev_now ()>
1489	time. This is usually the right thing as this timestamp refers to the time	2136	time. This is usually the right thing as this timestamp refers to the time
1490	of the event triggering whatever timeout you are modifying/starting. If	2137	of the event triggering whatever timeout you are modifying/starting. If
1491	you suspect event processing to be delayed and you I<need> to base the	2138	you suspect event processing to be delayed and you I<need> to base the
1492	timeout on the current time, use something like this to adjust for this:	2139	timeout on the current time, use something like the following to adjust
		2140	for it:
1493		2141
1494	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2142	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1495		2143
1496	If the event loop is suspended for a long time, you can also force an	2144	If the event loop is suspended for a long time, you can also force an
1497	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2145	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1498	()>.	2146	()>, although that will push the event time of all outstanding events
		2147	further into the future.
		2148
		2149	=head3 The special problem of unsynchronised clocks
		2150
		2151	Modern systems have a variety of clocks - libev itself uses the normal
		2152	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2153	jumps).
		2154
		2155	Neither of these clocks is synchronised with each other or any other clock
		2156	on the system, so C<ev_time ()> might return a considerably different time
		2157	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2158	a call to C<gettimeofday> might return a second count that is one higher
		2159	than a directly following call to C<time>.
		2160
		2161	The moral of this is to only compare libev-related timestamps with
		2162	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2163	a second or so.
		2164
		2165	One more problem arises due to this lack of synchronisation: if libev uses
		2166	the system monotonic clock and you compare timestamps from C<ev_time>
		2167	or C<ev_now> from when you started your timer and when your callback is
		2168	invoked, you will find that sometimes the callback is a bit "early".
		2169
		2170	This is because C<ev_timer>s work in real time, not wall clock time, so
		2171	libev makes sure your callback is not invoked before the delay happened,
		2172	I<measured according to the real time>, not the system clock.
		2173
		2174	If your timeouts are based on a physical timescale (e.g. "time out this
		2175	connection after 100 seconds") then this shouldn't bother you as it is
		2176	exactly the right behaviour.
		2177
		2178	If you want to compare wall clock/system timestamps to your timers, then
		2179	you need to use C<ev_periodic>s, as these are based on the wall clock
		2180	time, where your comparisons will always generate correct results.
		2181
		2182	=head3 The special problems of suspended animation
		2183
		2184	When you leave the server world it is quite customary to hit machines that
		2185	can suspend/hibernate - what happens to the clocks during such a suspend?
		2186
		2187	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2188	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2189	to run until the system is suspended, but they will not advance while the
		2190	system is suspended. That means, on resume, it will be as if the program
		2191	was frozen for a few seconds, but the suspend time will not be counted
		2192	towards C<ev_timer> when a monotonic clock source is used. The real time
		2193	clock advanced as expected, but if it is used as sole clocksource, then a
		2194	long suspend would be detected as a time jump by libev, and timers would
		2195	be adjusted accordingly.
		2196
		2197	I would not be surprised to see different behaviour in different between
		2198	operating systems, OS versions or even different hardware.
		2199
		2200	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2201	time jump in the monotonic clocks and the realtime clock. If the program
		2202	is suspended for a very long time, and monotonic clock sources are in use,
		2203	then you can expect C<ev_timer>s to expire as the full suspension time
		2204	will be counted towards the timers. When no monotonic clock source is in
		2205	use, then libev will again assume a timejump and adjust accordingly.
		2206
		2207	It might be beneficial for this latter case to call C<ev_suspend>
		2208	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2209	deterministic behaviour in this case (you can do nothing against
		2210	C<SIGSTOP>).
1499		2211
1500	=head3 Watcher-Specific Functions and Data Members	2212	=head3 Watcher-Specific Functions and Data Members
1501		2213
1502	=over 4	2214	=over 4
1503		2215
1504	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2216	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1505		2217
1506	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2218	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1507		2219
1508	Configure the timer to trigger after C<after> seconds. If C<repeat>	2220	Configure the timer to trigger after C<after> seconds (fractional and
1509	is C<0.>, then it will automatically be stopped once the timeout is	2221	negative values are supported). If C<repeat> is C<0.>, then it will
1510	reached. If it is positive, then the timer will automatically be	2222	automatically be stopped once the timeout is reached. If it is positive,
1511	configured to trigger again C<repeat> seconds later, again, and again,	2223	then the timer will automatically be configured to trigger again C<repeat>
1512	until stopped manually.	2224	seconds later, again, and again, until stopped manually.
1513		2225
1514	The timer itself will do a best-effort at avoiding drift, that is, if	2226	The timer itself will do a best-effort at avoiding drift, that is, if
1515	you configure a timer to trigger every 10 seconds, then it will normally	2227	you configure a timer to trigger every 10 seconds, then it will normally
1516	trigger at exactly 10 second intervals. If, however, your program cannot	2228	trigger at exactly 10 second intervals. If, however, your program cannot
1517	keep up with the timer (because it takes longer than those 10 seconds to	2229	keep up with the timer (because it takes longer than those 10 seconds to
1518	do stuff) the timer will not fire more than once per event loop iteration.	2230	do stuff) the timer will not fire more than once per event loop iteration.
1519		2231
1520	=item ev_timer_again (loop, ev_timer *)	2232	=item ev_timer_again (loop, ev_timer *)
1521		2233
1522	This will act as if the timer timed out and restart it again if it is	2234	This will act as if the timer timed out, and restarts it again if it is
1523	repeating. The exact semantics are:	2235	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2236	timeout to the C<repeat> value and calling C<ev_timer_start>.
1524		2237
		2238	The exact semantics are as in the following rules, all of which will be
		2239	applied to the watcher:
		2240
		2241	=over 4
		2242
1525	If the timer is pending, its pending status is cleared.	2243	=item If the timer is pending, the pending status is always cleared.
1526		2244
1527	If the timer is started but non-repeating, stop it (as if it timed out).	2245	=item If the timer is started but non-repeating, stop it (as if it timed
		2246	out, without invoking it).
1528		2247
1529	If the timer is repeating, either start it if necessary (with the	2248	=item If the timer is repeating, make the C<repeat> value the new timeout
1530	C<repeat> value), or reset the running timer to the C<repeat> value.	2249	and start the timer, if necessary.
1531		2250
		2251	=back
		2252
1532	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2253	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1533	usage example.	2254	usage example.
		2255
		2256	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2257
		2258	Returns the remaining time until a timer fires. If the timer is active,
		2259	then this time is relative to the current event loop time, otherwise it's
		2260	the timeout value currently configured.
		2261
		2262	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2263	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2264	will return C<4>. When the timer expires and is restarted, it will return
		2265	roughly C<7> (likely slightly less as callback invocation takes some time,
		2266	too), and so on.
1534		2267
1535	=item ev_tstamp repeat [read-write]	2268	=item ev_tstamp repeat [read-write]
1536		2269
1537	The current C<repeat> value. Will be used each time the watcher times out	2270	The current C<repeat> value. Will be used each time the watcher times out
1538	or C<ev_timer_again> is called, and determines the next timeout (if any),	2271	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1564	}	2297	}
1565		2298
1566	ev_timer mytimer;	2299	ev_timer mytimer;
1567	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2300	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1568	ev_timer_again (&mytimer); /* start timer */	2301	ev_timer_again (&mytimer); /* start timer */
1569	ev_loop (loop, 0);	2302	ev_run (loop, 0);
1570		2303
1571	// and in some piece of code that gets executed on any "activity":	2304	// and in some piece of code that gets executed on any "activity":
1572	// reset the timeout to start ticking again at 10 seconds	2305	// reset the timeout to start ticking again at 10 seconds
1573	ev_timer_again (&mytimer);	2306	ev_timer_again (&mytimer);
1574		2307
…		…
1576	=head2 C<ev_periodic> - to cron or not to cron?	2309	=head2 C<ev_periodic> - to cron or not to cron?
1577		2310
1578	Periodic watchers are also timers of a kind, but they are very versatile	2311	Periodic watchers are also timers of a kind, but they are very versatile
1579	(and unfortunately a bit complex).	2312	(and unfortunately a bit complex).
1580		2313
1581	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2314	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1582	but on wall clock time (absolute time). You can tell a periodic watcher	2315	relative time, the physical time that passes) but on wall clock time
1583	to trigger after some specific point in time. For example, if you tell a	2316	(absolute time, the thing you can read on your calendar or clock). The
1584	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2317	difference is that wall clock time can run faster or slower than real
1585	+ 10.>, that is, an absolute time not a delay) and then reset your system	2318	time, and time jumps are not uncommon (e.g. when you adjust your
1586	clock to January of the previous year, then it will take more than year	2319	wrist-watch).
1587	to trigger the event (unlike an C<ev_timer>, which would still trigger
1588	roughly 10 seconds later as it uses a relative timeout).
1589		2320
		2321	You can tell a periodic watcher to trigger after some specific point
		2322	in time: for example, if you tell a periodic watcher to trigger "in 10
		2323	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2324	not a delay) and then reset your system clock to January of the previous
		2325	year, then it will take a year or more to trigger the event (unlike an
		2326	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2327	it, as it uses a relative timeout).
		2328
1590	C<ev_periodic>s can also be used to implement vastly more complex timers,	2329	C<ev_periodic> watchers can also be used to implement vastly more complex
1591	such as triggering an event on each "midnight, local time", or other	2330	timers, such as triggering an event on each "midnight, local time", or
1592	complicated rules.	2331	other complicated rules. This cannot easily be done with C<ev_timer>
		2332	watchers, as those cannot react to time jumps.
1593		2333
1594	As with timers, the callback is guaranteed to be invoked only when the	2334	As with timers, the callback is guaranteed to be invoked only when the
1595	time (C<at>) has passed, but if multiple periodic timers become ready	2335	point in time where it is supposed to trigger has passed. If multiple
1596	during the same loop iteration, then order of execution is undefined.	2336	timers become ready during the same loop iteration then the ones with
		2337	earlier time-out values are invoked before ones with later time-out values
		2338	(but this is no longer true when a callback calls C<ev_run> recursively).
1597		2339
1598	=head3 Watcher-Specific Functions and Data Members	2340	=head3 Watcher-Specific Functions and Data Members
1599		2341
1600	=over 4	2342	=over 4
1601		2343
1602	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2344	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1603		2345
1604	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2346	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1605		2347
1606	Lots of arguments, lets sort it out... There are basically three modes of	2348	Lots of arguments, let's sort it out... There are basically three modes of
1607	operation, and we will explain them from simplest to most complex:	2349	operation, and we will explain them from simplest to most complex:
1608		2350
1609	=over 4	2351	=over 4
1610		2352
1611	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2353	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1612		2354
1613	In this configuration the watcher triggers an event after the wall clock	2355	In this configuration the watcher triggers an event after the wall clock
1614	time C<at> has passed. It will not repeat and will not adjust when a time	2356	time C<offset> has passed. It will not repeat and will not adjust when a
1615	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2357	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1616	only run when the system clock reaches or surpasses this time.	2358	will be stopped and invoked when the system clock reaches or surpasses
		2359	this point in time.
1617		2360
1618	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2361	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1619		2362
1620	In this mode the watcher will always be scheduled to time out at the next	2363	In this mode the watcher will always be scheduled to time out at the next
1621	C<at + N * interval> time (for some integer N, which can also be negative)	2364	C<offset + N * interval> time (for some integer N, which can also be
1622	and then repeat, regardless of any time jumps.	2365	negative) and then repeat, regardless of any time jumps. The C<offset>
		2366	argument is merely an offset into the C<interval> periods.
1623		2367
1624	This can be used to create timers that do not drift with respect to the	2368	This can be used to create timers that do not drift with respect to the
1625	system clock, for example, here is a C<ev_periodic> that triggers each	2369	system clock, for example, here is an C<ev_periodic> that triggers each
1626	hour, on the hour:	2370	hour, on the hour (with respect to UTC):
1627		2371
1628	ev_periodic_set (&periodic, 0., 3600., 0);	2372	ev_periodic_set (&periodic, 0., 3600., 0);
1629		2373
1630	This doesn't mean there will always be 3600 seconds in between triggers,	2374	This doesn't mean there will always be 3600 seconds in between triggers,
1631	but only that the callback will be called when the system time shows a	2375	but only that the callback will be called when the system time shows a
1632	full hour (UTC), or more correctly, when the system time is evenly divisible	2376	full hour (UTC), or more correctly, when the system time is evenly divisible
1633	by 3600.	2377	by 3600.
1634		2378
1635	Another way to think about it (for the mathematically inclined) is that	2379	Another way to think about it (for the mathematically inclined) is that
1636	C<ev_periodic> will try to run the callback in this mode at the next possible	2380	C<ev_periodic> will try to run the callback in this mode at the next possible
1637	time where C<time = at (mod interval)>, regardless of any time jumps.	2381	time where C<time = offset (mod interval)>, regardless of any time jumps.
1638		2382
1639	For numerical stability it is preferable that the C<at> value is near	2383	The C<interval> I<MUST> be positive, and for numerical stability, the
1640	C<ev_now ()> (the current time), but there is no range requirement for	2384	interval value should be higher than C<1/8192> (which is around 100
1641	this value, and in fact is often specified as zero.	2385	microseconds) and C<offset> should be higher than C<0> and should have
		2386	at most a similar magnitude as the current time (say, within a factor of
		2387	ten). Typical values for offset are, in fact, C<0> or something between
		2388	C<0> and C<interval>, which is also the recommended range.
1642		2389
1643	Note also that there is an upper limit to how often a timer can fire (CPU	2390	Note also that there is an upper limit to how often a timer can fire (CPU
1644	speed for example), so if C<interval> is very small then timing stability	2391	speed for example), so if C<interval> is very small then timing stability
1645	will of course deteriorate. Libev itself tries to be exact to be about one	2392	will of course deteriorate. Libev itself tries to be exact to be about one
1646	millisecond (if the OS supports it and the machine is fast enough).	2393	millisecond (if the OS supports it and the machine is fast enough).
1647		2394
1648	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2395	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1649		2396
1650	In this mode the values for C<interval> and C<at> are both being	2397	In this mode the values for C<interval> and C<offset> are both being
1651	ignored. Instead, each time the periodic watcher gets scheduled, the	2398	ignored. Instead, each time the periodic watcher gets scheduled, the
1652	reschedule callback will be called with the watcher as first, and the	2399	reschedule callback will be called with the watcher as first, and the
1653	current time as second argument.	2400	current time as second argument.
1654		2401
1655	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2402	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1656	ever, or make ANY event loop modifications whatsoever>.	2403	or make ANY other event loop modifications whatsoever, unless explicitly
		2404	allowed by documentation here>.
1657		2405
1658	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2406	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1659	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2407	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1660	only event loop modification you are allowed to do).	2408	only event loop modification you are allowed to do).
1661		2409
…		…
1675		2423
1676	NOTE: I<< This callback must always return a time that is higher than or	2424	NOTE: I<< This callback must always return a time that is higher than or
1677	equal to the passed C<now> value >>.	2425	equal to the passed C<now> value >>.
1678		2426
1679	This can be used to create very complex timers, such as a timer that	2427	This can be used to create very complex timers, such as a timer that
1680	triggers on "next midnight, local time". To do this, you would calculate the	2428	triggers on "next midnight, local time". To do this, you would calculate
1681	next midnight after C<now> and return the timestamp value for this. How	2429	the next midnight after C<now> and return the timestamp value for
1682	you do this is, again, up to you (but it is not trivial, which is the main	2430	this. Here is a (completely untested, no error checking) example on how to
1683	reason I omitted it as an example).	2431	do this:
		2432
		2433	#include <time.h>
		2434
		2435	static ev_tstamp
		2436	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2437	{
		2438	time_t tnow = (time_t)now;
		2439	struct tm tm;
		2440	localtime_r (&tnow, &tm);
		2441
		2442	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2443	++tm.tm_mday; // midnight next day
		2444
		2445	return mktime (&tm);
		2446	}
		2447
		2448	Note: this code might run into trouble on days that have more then two
		2449	midnights (beginning and end).
1684		2450
1685	=back	2451	=back
1686		2452
1687	=item ev_periodic_again (loop, ev_periodic *)	2453	=item ev_periodic_again (loop, ev_periodic *)
1688		2454
…		…
1691	a different time than the last time it was called (e.g. in a crond like	2457	a different time than the last time it was called (e.g. in a crond like
1692	program when the crontabs have changed).	2458	program when the crontabs have changed).
1693		2459
1694	=item ev_tstamp ev_periodic_at (ev_periodic *)	2460	=item ev_tstamp ev_periodic_at (ev_periodic *)
1695		2461
1696	When active, returns the absolute time that the watcher is supposed to	2462	When active, returns the absolute time that the watcher is supposed
1697	trigger next.	2463	to trigger next. This is not the same as the C<offset> argument to
		2464	C<ev_periodic_set>, but indeed works even in interval and manual
		2465	rescheduling modes.
1698		2466
1699	=item ev_tstamp offset [read-write]	2467	=item ev_tstamp offset [read-write]
1700		2468
1701	When repeating, this contains the offset value, otherwise this is the	2469	When repeating, this contains the offset value, otherwise this is the
1702	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2470	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2471	although libev might modify this value for better numerical stability).
1703		2472
1704	Can be modified any time, but changes only take effect when the periodic	2473	Can be modified any time, but changes only take effect when the periodic
1705	timer fires or C<ev_periodic_again> is being called.	2474	timer fires or C<ev_periodic_again> is being called.
1706		2475
1707	=item ev_tstamp interval [read-write]	2476	=item ev_tstamp interval [read-write]
…		…
1723	Example: Call a callback every hour, or, more precisely, whenever the	2492	Example: Call a callback every hour, or, more precisely, whenever the
1724	system time is divisible by 3600. The callback invocation times have	2493	system time is divisible by 3600. The callback invocation times have
1725	potentially a lot of jitter, but good long-term stability.	2494	potentially a lot of jitter, but good long-term stability.
1726		2495
1727	static void	2496	static void
1728	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2497	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1729	{	2498	{
1730	... its now a full hour (UTC, or TAI or whatever your clock follows)	2499	... its now a full hour (UTC, or TAI or whatever your clock follows)
1731	}	2500	}
1732		2501
1733	ev_periodic hourly_tick;	2502	ev_periodic hourly_tick;
…		…
1750		2519
1751	ev_periodic hourly_tick;	2520	ev_periodic hourly_tick;
1752	ev_periodic_init (&hourly_tick, clock_cb,	2521	ev_periodic_init (&hourly_tick, clock_cb,
1753	fmod (ev_now (loop), 3600.), 3600., 0);	2522	fmod (ev_now (loop), 3600.), 3600., 0);
1754	ev_periodic_start (loop, &hourly_tick);	2523	ev_periodic_start (loop, &hourly_tick);
1755		2524
1756		2525
1757	=head2 C<ev_signal> - signal me when a signal gets signalled!	2526	=head2 C<ev_signal> - signal me when a signal gets signalled!
1758		2527
1759	Signal watchers will trigger an event when the process receives a specific	2528	Signal watchers will trigger an event when the process receives a specific
1760	signal one or more times. Even though signals are very asynchronous, libev	2529	signal one or more times. Even though signals are very asynchronous, libev
1761	will try it's best to deliver signals synchronously, i.e. as part of the	2530	will try its best to deliver signals synchronously, i.e. as part of the
1762	normal event processing, like any other event.	2531	normal event processing, like any other event.
1763		2532
1764	If you want signals asynchronously, just use C<sigaction> as you would	2533	If you want signals to be delivered truly asynchronously, just use
1765	do without libev and forget about sharing the signal. You can even use	2534	C<sigaction> as you would do without libev and forget about sharing
1766	C<ev_async> from a signal handler to synchronously wake up an event loop.	2535	the signal. You can even use C<ev_async> from a signal handler to
		2536	synchronously wake up an event loop.
1767		2537
1768	You can configure as many watchers as you like per signal. Only when the	2538	You can configure as many watchers as you like for the same signal, but
1769	first watcher gets started will libev actually register a signal handler	2539	only within the same loop, i.e. you can watch for C<SIGINT> in your
1770	with the kernel (thus it coexists with your own signal handlers as long as	2540	default loop and for C<SIGIO> in another loop, but you cannot watch for
1771	you don't register any with libev for the same signal). Similarly, when	2541	C<SIGINT> in both the default loop and another loop at the same time. At
1772	the last signal watcher for a signal is stopped, libev will reset the	2542	the moment, C<SIGCHLD> is permanently tied to the default loop.
1773	signal handler to SIG_DFL (regardless of what it was set to before).	2543
		2544	Only after the first watcher for a signal is started will libev actually
		2545	register something with the kernel. It thus coexists with your own signal
		2546	handlers as long as you don't register any with libev for the same signal.
1774		2547
1775	If possible and supported, libev will install its handlers with	2548	If possible and supported, libev will install its handlers with
1776	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2549	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1777	interrupted. If you have a problem with system calls getting interrupted by	2550	not be unduly interrupted. If you have a problem with system calls getting
1778	signals you can block all signals in an C<ev_check> watcher and unblock	2551	interrupted by signals you can block all signals in an C<ev_check> watcher
1779	them in an C<ev_prepare> watcher.	2552	and unblock them in an C<ev_prepare> watcher.
		2553
		2554	=head3 The special problem of inheritance over fork/execve/pthread_create
		2555
		2556	Both the signal mask (C<sigprocmask>) and the signal disposition
		2557	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2558	stopping it again), that is, libev might or might not block the signal,
		2559	and might or might not set or restore the installed signal handler (but
		2560	see C<EVFLAG_NOSIGMASK>).
		2561
		2562	While this does not matter for the signal disposition (libev never
		2563	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2564	C<execve>), this matters for the signal mask: many programs do not expect
		2565	certain signals to be blocked.
		2566
		2567	This means that before calling C<exec> (from the child) you should reset
		2568	the signal mask to whatever "default" you expect (all clear is a good
		2569	choice usually).
		2570
		2571	The simplest way to ensure that the signal mask is reset in the child is
		2572	to install a fork handler with C<pthread_atfork> that resets it. That will
		2573	catch fork calls done by libraries (such as the libc) as well.
		2574
		2575	In current versions of libev, the signal will not be blocked indefinitely
		2576	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2577	the window of opportunity for problems, it will not go away, as libev
		2578	I<has> to modify the signal mask, at least temporarily.
		2579
		2580	So I can't stress this enough: I<If you do not reset your signal mask when
		2581	you expect it to be empty, you have a race condition in your code>. This
		2582	is not a libev-specific thing, this is true for most event libraries.
		2583
		2584	=head3 The special problem of threads signal handling
		2585
		2586	POSIX threads has problematic signal handling semantics, specifically,
		2587	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2588	threads in a process block signals, which is hard to achieve.
		2589
		2590	When you want to use sigwait (or mix libev signal handling with your own
		2591	for the same signals), you can tackle this problem by globally blocking
		2592	all signals before creating any threads (or creating them with a fully set
		2593	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2594	loops. Then designate one thread as "signal receiver thread" which handles
		2595	these signals. You can pass on any signals that libev might be interested
		2596	in by calling C<ev_feed_signal>.
1780		2597
1781	=head3 Watcher-Specific Functions and Data Members	2598	=head3 Watcher-Specific Functions and Data Members
1782		2599
1783	=over 4	2600	=over 4
1784		2601
…		…
1800	Example: Try to exit cleanly on SIGINT.	2617	Example: Try to exit cleanly on SIGINT.
1801		2618
1802	static void	2619	static void
1803	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2620	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1804	{	2621	{
1805	ev_unloop (loop, EVUNLOOP_ALL);	2622	ev_break (loop, EVBREAK_ALL);
1806	}	2623	}
1807		2624
1808	ev_signal signal_watcher;	2625	ev_signal signal_watcher;
1809	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2626	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1810	ev_signal_start (loop, &signal_watcher);	2627	ev_signal_start (loop, &signal_watcher);
…		…
1816	some child status changes (most typically when a child of yours dies or	2633	some child status changes (most typically when a child of yours dies or
1817	exits). It is permissible to install a child watcher I<after> the child	2634	exits). It is permissible to install a child watcher I<after> the child
1818	has been forked (which implies it might have already exited), as long	2635	has been forked (which implies it might have already exited), as long
1819	as the event loop isn't entered (or is continued from a watcher), i.e.,	2636	as the event loop isn't entered (or is continued from a watcher), i.e.,
1820	forking and then immediately registering a watcher for the child is fine,	2637	forking and then immediately registering a watcher for the child is fine,
1821	but forking and registering a watcher a few event loop iterations later is	2638	but forking and registering a watcher a few event loop iterations later or
1822	not.	2639	in the next callback invocation is not.
1823		2640
1824	Only the default event loop is capable of handling signals, and therefore	2641	Only the default event loop is capable of handling signals, and therefore
1825	you can only register child watchers in the default event loop.	2642	you can only register child watchers in the default event loop.
1826		2643
		2644	Due to some design glitches inside libev, child watchers will always be
		2645	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2646	libev)
		2647
1827	=head3 Process Interaction	2648	=head3 Process Interaction
1828		2649
1829	Libev grabs C<SIGCHLD> as soon as the default event loop is	2650	Libev grabs C<SIGCHLD> as soon as the default event loop is
1830	initialised. This is necessary to guarantee proper behaviour even if	2651	initialised. This is necessary to guarantee proper behaviour even if the
1831	the first child watcher is started after the child exits. The occurrence	2652	first child watcher is started after the child exits. The occurrence
1832	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2653	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1833	synchronously as part of the event loop processing. Libev always reaps all	2654	synchronously as part of the event loop processing. Libev always reaps all
1834	children, even ones not watched.	2655	children, even ones not watched.
1835		2656
1836	=head3 Overriding the Built-In Processing	2657	=head3 Overriding the Built-In Processing
…		…
1846	=head3 Stopping the Child Watcher	2667	=head3 Stopping the Child Watcher
1847		2668
1848	Currently, the child watcher never gets stopped, even when the	2669	Currently, the child watcher never gets stopped, even when the
1849	child terminates, so normally one needs to stop the watcher in the	2670	child terminates, so normally one needs to stop the watcher in the
1850	callback. Future versions of libev might stop the watcher automatically	2671	callback. Future versions of libev might stop the watcher automatically
1851	when a child exit is detected.	2672	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2673	problem).
1852		2674
1853	=head3 Watcher-Specific Functions and Data Members	2675	=head3 Watcher-Specific Functions and Data Members
1854		2676
1855	=over 4	2677	=over 4
1856		2678
…		…
1913		2735
1914		2736
1915	=head2 C<ev_stat> - did the file attributes just change?	2737	=head2 C<ev_stat> - did the file attributes just change?
1916		2738
1917	This watches a file system path for attribute changes. That is, it calls	2739	This watches a file system path for attribute changes. That is, it calls
1918	C<stat> regularly (or when the OS says it changed) and sees if it changed	2740	C<stat> on that path in regular intervals (or when the OS says it changed)
1919	compared to the last time, invoking the callback if it did.	2741	and sees if it changed compared to the last time, invoking the callback
		2742	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2743	happen after the watcher has been started will be reported.
1920		2744
1921	The path does not need to exist: changing from "path exists" to "path does	2745	The path does not need to exist: changing from "path exists" to "path does
1922	not exist" is a status change like any other. The condition "path does	2746	not exist" is a status change like any other. The condition "path does not
1923	not exist" is signified by the C<st_nlink> field being zero (which is	2747	exist" (or more correctly "path cannot be stat'ed") is signified by the
1924	otherwise always forced to be at least one) and all the other fields of	2748	C<st_nlink> field being zero (which is otherwise always forced to be at
1925	the stat buffer having unspecified contents.	2749	least one) and all the other fields of the stat buffer having unspecified
		2750	contents.
1926		2751
1927	The path I<should> be absolute and I<must not> end in a slash. If it is	2752	The path I<must not> end in a slash or contain special components such as
		2753	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1928	relative and your working directory changes, the behaviour is undefined.	2754	your working directory changes, then the behaviour is undefined.
1929		2755
1930	Since there is no standard kernel interface to do this, the portable	2756	Since there is no portable change notification interface available, the
1931	implementation simply calls C<stat (2)> regularly on the path to see if	2757	portable implementation simply calls C<stat(2)> regularly on the path
1932	it changed somehow. You can specify a recommended polling interval for	2758	to see if it changed somehow. You can specify a recommended polling
1933	this case. If you specify a polling interval of C<0> (highly recommended!)	2759	interval for this case. If you specify a polling interval of C<0> (highly
1934	then a I<suitable, unspecified default> value will be used (which	2760	recommended!) then a I<suitable, unspecified default> value will be used
1935	you can expect to be around five seconds, although this might change	2761	(which you can expect to be around five seconds, although this might
1936	dynamically). Libev will also impose a minimum interval which is currently	2762	change dynamically). Libev will also impose a minimum interval which is
1937	around C<0.1>, but thats usually overkill.	2763	currently around C<0.1>, but that's usually overkill.
1938		2764
1939	This watcher type is not meant for massive numbers of stat watchers,	2765	This watcher type is not meant for massive numbers of stat watchers,
1940	as even with OS-supported change notifications, this can be	2766	as even with OS-supported change notifications, this can be
1941	resource-intensive.	2767	resource-intensive.
1942		2768
1943	At the time of this writing, the only OS-specific interface implemented	2769	At the time of this writing, the only OS-specific interface implemented
1944	is the Linux inotify interface (implementing kqueue support is left as	2770	is the Linux inotify interface (implementing kqueue support is left as an
1945	an exercise for the reader. Note, however, that the author sees no way	2771	exercise for the reader. Note, however, that the author sees no way of
1946	of implementing C<ev_stat> semantics with kqueue).	2772	implementing C<ev_stat> semantics with kqueue, except as a hint).
1947		2773
1948	=head3 ABI Issues (Largefile Support)	2774	=head3 ABI Issues (Largefile Support)
1949		2775
1950	Libev by default (unless the user overrides this) uses the default	2776	Libev by default (unless the user overrides this) uses the default
1951	compilation environment, which means that on systems with large file	2777	compilation environment, which means that on systems with large file
1952	support disabled by default, you get the 32 bit version of the stat	2778	support disabled by default, you get the 32 bit version of the stat
1953	structure. When using the library from programs that change the ABI to	2779	structure. When using the library from programs that change the ABI to
1954	use 64 bit file offsets the programs will fail. In that case you have to	2780	use 64 bit file offsets the programs will fail. In that case you have to
1955	compile libev with the same flags to get binary compatibility. This is	2781	compile libev with the same flags to get binary compatibility. This is
1956	obviously the case with any flags that change the ABI, but the problem is	2782	obviously the case with any flags that change the ABI, but the problem is
1957	most noticeably disabled with ev_stat and large file support.	2783	most noticeably displayed with ev_stat and large file support.
1958		2784
1959	The solution for this is to lobby your distribution maker to make large	2785	The solution for this is to lobby your distribution maker to make large
1960	file interfaces available by default (as e.g. FreeBSD does) and not	2786	file interfaces available by default (as e.g. FreeBSD does) and not
1961	optional. Libev cannot simply switch on large file support because it has	2787	optional. Libev cannot simply switch on large file support because it has
1962	to exchange stat structures with application programs compiled using the	2788	to exchange stat structures with application programs compiled using the
1963	default compilation environment.	2789	default compilation environment.
1964		2790
1965	=head3 Inotify and Kqueue	2791	=head3 Inotify and Kqueue
1966		2792
1967	When C<inotify (7)> support has been compiled into libev (generally	2793	When C<inotify (7)> support has been compiled into libev and present at
1968	only available with Linux 2.6.25 or above due to bugs in earlier	2794	runtime, it will be used to speed up change detection where possible. The
1969	implementations) and present at runtime, it will be used to speed up	2795	inotify descriptor will be created lazily when the first C<ev_stat>
1970	change detection where possible. The inotify descriptor will be created	2796	watcher is being started.
1971	lazily when the first C<ev_stat> watcher is being started.
1972		2797
1973	Inotify presence does not change the semantics of C<ev_stat> watchers	2798	Inotify presence does not change the semantics of C<ev_stat> watchers
1974	except that changes might be detected earlier, and in some cases, to avoid	2799	except that changes might be detected earlier, and in some cases, to avoid
1975	making regular C<stat> calls. Even in the presence of inotify support	2800	making regular C<stat> calls. Even in the presence of inotify support
1976	there are many cases where libev has to resort to regular C<stat> polling,	2801	there are many cases where libev has to resort to regular C<stat> polling,
1977	but as long as the path exists, libev usually gets away without polling.	2802	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2803	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2804	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2805	xfs are fully working) libev usually gets away without polling.
1978		2806
1979	There is no support for kqueue, as apparently it cannot be used to	2807	There is no support for kqueue, as apparently it cannot be used to
1980	implement this functionality, due to the requirement of having a file	2808	implement this functionality, due to the requirement of having a file
1981	descriptor open on the object at all times, and detecting renames, unlinks	2809	descriptor open on the object at all times, and detecting renames, unlinks
1982	etc. is difficult.	2810	etc. is difficult.
1983		2811
		2812	=head3 C<stat ()> is a synchronous operation
		2813
		2814	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2815	the process. The exception are C<ev_stat> watchers - those call C<stat
		2816	()>, which is a synchronous operation.
		2817
		2818	For local paths, this usually doesn't matter: unless the system is very
		2819	busy or the intervals between stat's are large, a stat call will be fast,
		2820	as the path data is usually in memory already (except when starting the
		2821	watcher).
		2822
		2823	For networked file systems, calling C<stat ()> can block an indefinite
		2824	time due to network issues, and even under good conditions, a stat call
		2825	often takes multiple milliseconds.
		2826
		2827	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2828	paths, although this is fully supported by libev.
		2829
1984	=head3 The special problem of stat time resolution	2830	=head3 The special problem of stat time resolution
1985		2831
1986	The C<stat ()> system call only supports full-second resolution portably, and	2832	The C<stat ()> system call only supports full-second resolution portably,
1987	even on systems where the resolution is higher, most file systems still	2833	and even on systems where the resolution is higher, most file systems
1988	only support whole seconds.	2834	still only support whole seconds.
1989		2835
1990	That means that, if the time is the only thing that changes, you can	2836	That means that, if the time is the only thing that changes, you can
1991	easily miss updates: on the first update, C<ev_stat> detects a change and	2837	easily miss updates: on the first update, C<ev_stat> detects a change and
1992	calls your callback, which does something. When there is another update	2838	calls your callback, which does something. When there is another update
1993	within the same second, C<ev_stat> will be unable to detect unless the	2839	within the same second, C<ev_stat> will be unable to detect unless the
…		…
2132	Apart from keeping your process non-blocking (which is a useful	2978	Apart from keeping your process non-blocking (which is a useful
2133	effect on its own sometimes), idle watchers are a good place to do	2979	effect on its own sometimes), idle watchers are a good place to do
2134	"pseudo-background processing", or delay processing stuff to after the	2980	"pseudo-background processing", or delay processing stuff to after the
2135	event loop has handled all outstanding events.	2981	event loop has handled all outstanding events.
2136		2982
		2983	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2984
		2985	As long as there is at least one active idle watcher, libev will never
		2986	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2987	For this to work, the idle watcher doesn't need to be invoked at all - the
		2988	lowest priority will do.
		2989
		2990	This mode of operation can be useful together with an C<ev_check> watcher,
		2991	to do something on each event loop iteration - for example to balance load
		2992	between different connections.
		2993
		2994	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2995	example.
		2996
2137	=head3 Watcher-Specific Functions and Data Members	2997	=head3 Watcher-Specific Functions and Data Members
2138		2998
2139	=over 4	2999	=over 4
2140		3000
2141	=item ev_idle_init (ev_signal *, callback)	3001	=item ev_idle_init (ev_idle *, callback)
2142		3002
2143	Initialises and configures the idle watcher - it has no parameters of any	3003	Initialises and configures the idle watcher - it has no parameters of any
2144	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	3004	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2145	believe me.	3005	believe me.
2146		3006
…		…
2152	callback, free it. Also, use no error checking, as usual.	3012	callback, free it. Also, use no error checking, as usual.
2153		3013
2154	static void	3014	static void
2155	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	3015	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2156	{	3016	{
		3017	// stop the watcher
		3018	ev_idle_stop (loop, w);
		3019
		3020	// now we can free it
2157	free (w);	3021	free (w);
		3022
2158	// now do something you wanted to do when the program has	3023	// now do something you wanted to do when the program has
2159	// no longer anything immediate to do.	3024	// no longer anything immediate to do.
2160	}	3025	}
2161		3026
2162	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3027	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2163	ev_idle_init (idle_watcher, idle_cb);	3028	ev_idle_init (idle_watcher, idle_cb);
2164	ev_idle_start (loop, idle_cb);	3029	ev_idle_start (loop, idle_watcher);
2165		3030
2166		3031
2167	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3032	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2168		3033
2169	Prepare and check watchers are usually (but not always) used in pairs:	3034	Prepare and check watchers are often (but not always) used in pairs:
2170	prepare watchers get invoked before the process blocks and check watchers	3035	prepare watchers get invoked before the process blocks and check watchers
2171	afterwards.	3036	afterwards.
2172		3037
2173	You I<must not> call C<ev_loop> or similar functions that enter	3038	You I<must not> call C<ev_run> (or similar functions that enter the
2174	the current event loop from either C<ev_prepare> or C<ev_check>	3039	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2175	watchers. Other loops than the current one are fine, however. The	3040	C<ev_check> watchers. Other loops than the current one are fine,
2176	rationale behind this is that you do not need to check for recursion in	3041	however. The rationale behind this is that you do not need to check
2177	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3042	for recursion in those watchers, i.e. the sequence will always be
2178	C<ev_check> so if you have one watcher of each kind they will always be	3043	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2179	called in pairs bracketing the blocking call.	3044	kind they will always be called in pairs bracketing the blocking call.
2180		3045
2181	Their main purpose is to integrate other event mechanisms into libev and	3046	Their main purpose is to integrate other event mechanisms into libev and
2182	their use is somewhat advanced. They could be used, for example, to track	3047	their use is somewhat advanced. They could be used, for example, to track
2183	variable changes, implement your own watchers, integrate net-snmp or a	3048	variable changes, implement your own watchers, integrate net-snmp or a
2184	coroutine library and lots more. They are also occasionally useful if	3049	coroutine library and lots more. They are also occasionally useful if
…		…
2202	with priority higher than or equal to the event loop and one coroutine	3067	with priority higher than or equal to the event loop and one coroutine
2203	of lower priority, but only once, using idle watchers to keep the event	3068	of lower priority, but only once, using idle watchers to keep the event
2204	loop from blocking if lower-priority coroutines are active, thus mapping	3069	loop from blocking if lower-priority coroutines are active, thus mapping
2205	low-priority coroutines to idle/background tasks).	3070	low-priority coroutines to idle/background tasks).
2206		3071
2207	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3072	When used for this purpose, it is recommended to give C<ev_check> watchers
2208	priority, to ensure that they are being run before any other watchers	3073	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2209	after the poll (this doesn't matter for C<ev_prepare> watchers).	3074	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3075	watchers).
2210		3076
2211	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3077	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2212	activate ("feed") events into libev. While libev fully supports this, they	3078	activate ("feed") events into libev. While libev fully supports this, they
2213	might get executed before other C<ev_check> watchers did their job. As	3079	might get executed before other C<ev_check> watchers did their job. As
2214	C<ev_check> watchers are often used to embed other (non-libev) event	3080	C<ev_check> watchers are often used to embed other (non-libev) event
2215	loops those other event loops might be in an unusable state until their	3081	loops those other event loops might be in an unusable state until their
2216	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3082	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2217	others).	3083	others).
		3084
		3085	=head3 Abusing an C<ev_check> watcher for its side-effect
		3086
		3087	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3088	useful because they are called once per event loop iteration. For
		3089	example, if you want to handle a large number of connections fairly, you
		3090	normally only do a bit of work for each active connection, and if there
		3091	is more work to do, you wait for the next event loop iteration, so other
		3092	connections have a chance of making progress.
		3093
		3094	Using an C<ev_check> watcher is almost enough: it will be called on the
		3095	next event loop iteration. However, that isn't as soon as possible -
		3096	without external events, your C<ev_check> watcher will not be invoked.
		3097
		3098	This is where C<ev_idle> watchers come in handy - all you need is a
		3099	single global idle watcher that is active as long as you have one active
		3100	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3101	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3102	invoked. Neither watcher alone can do that.
2218		3103
2219	=head3 Watcher-Specific Functions and Data Members	3104	=head3 Watcher-Specific Functions and Data Members
2220		3105
2221	=over 4	3106	=over 4
2222		3107
…		…
2262	struct pollfd fds [nfd];	3147	struct pollfd fds [nfd];
2263	// actual code will need to loop here and realloc etc.	3148	// actual code will need to loop here and realloc etc.
2264	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3149	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2265		3150
2266	/* the callback is illegal, but won't be called as we stop during check */	3151	/* the callback is illegal, but won't be called as we stop during check */
2267	ev_timer_init (&tw, 0, timeout * 1e-3);	3152	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2268	ev_timer_start (loop, &tw);	3153	ev_timer_start (loop, &tw);
2269		3154
2270	// create one ev_io per pollfd	3155	// create one ev_io per pollfd
2271	for (int i = 0; i < nfd; ++i)	3156	for (int i = 0; i < nfd; ++i)
2272	{	3157	{
…		…
2346		3231
2347	if (timeout >= 0)	3232	if (timeout >= 0)
2348	// create/start timer	3233	// create/start timer
2349		3234
2350	// poll	3235	// poll
2351	ev_loop (EV_A_ 0);	3236	ev_run (EV_A_ 0);
2352		3237
2353	// stop timer again	3238	// stop timer again
2354	if (timeout >= 0)	3239	if (timeout >= 0)
2355	ev_timer_stop (EV_A_ &to);	3240	ev_timer_stop (EV_A_ &to);
2356		3241
…		…
2385	some fds have to be watched and handled very quickly (with low latency),	3270	some fds have to be watched and handled very quickly (with low latency),
2386	and even priorities and idle watchers might have too much overhead. In	3271	and even priorities and idle watchers might have too much overhead. In
2387	this case you would put all the high priority stuff in one loop and all	3272	this case you would put all the high priority stuff in one loop and all
2388	the rest in a second one, and embed the second one in the first.	3273	the rest in a second one, and embed the second one in the first.
2389		3274
2390	As long as the watcher is active, the callback will be invoked every time	3275	As long as the watcher is active, the callback will be invoked every
2391	there might be events pending in the embedded loop. The callback must then	3276	time there might be events pending in the embedded loop. The callback
2392	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3277	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2393	their callbacks (you could also start an idle watcher to give the embedded	3278	sweep and invoke their callbacks (the callback doesn't need to invoke the
2394	loop strictly lower priority for example). You can also set the callback	3279	C<ev_embed_sweep> function directly, it could also start an idle watcher
2395	to C<0>, in which case the embed watcher will automatically execute the	3280	to give the embedded loop strictly lower priority for example).
2396	embedded loop sweep.
2397		3281
2398	As long as the watcher is started it will automatically handle events. The	3282	You can also set the callback to C<0>, in which case the embed watcher
2399	callback will be invoked whenever some events have been handled. You can	3283	will automatically execute the embedded loop sweep whenever necessary.
2400	set the callback to C<0> to avoid having to specify one if you are not
2401	interested in that.
2402		3284
2403	Also, there have not currently been made special provisions for forking:	3285	Fork detection will be handled transparently while the C<ev_embed> watcher
2404	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3286	is active, i.e., the embedded loop will automatically be forked when the
2405	but you will also have to stop and restart any C<ev_embed> watchers	3287	embedding loop forks. In other cases, the user is responsible for calling
2406	yourself - but you can use a fork watcher to handle this automatically,	3288	C<ev_loop_fork> on the embedded loop.
2407	and future versions of libev might do just that.
2408		3289
2409	Unfortunately, not all backends are embeddable: only the ones returned by	3290	Unfortunately, not all backends are embeddable: only the ones returned by
2410	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3291	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2411	portable one.	3292	portable one.
2412		3293
…		…
2427		3308
2428	=over 4	3309	=over 4
2429		3310
2430	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3311	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2431		3312
2432	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3313	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2433		3314
2434	Configures the watcher to embed the given loop, which must be	3315	Configures the watcher to embed the given loop, which must be
2435	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3316	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2436	invoked automatically, otherwise it is the responsibility of the callback	3317	invoked automatically, otherwise it is the responsibility of the callback
2437	to invoke it (it will continue to be called until the sweep has been done,	3318	to invoke it (it will continue to be called until the sweep has been done,
2438	if you do not want that, you need to temporarily stop the embed watcher).	3319	if you do not want that, you need to temporarily stop the embed watcher).
2439		3320
2440	=item ev_embed_sweep (loop, ev_embed *)	3321	=item ev_embed_sweep (loop, ev_embed *)
2441		3322
2442	Make a single, non-blocking sweep over the embedded loop. This works	3323	Make a single, non-blocking sweep over the embedded loop. This works
2443	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3324	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2444	appropriate way for embedded loops.	3325	appropriate way for embedded loops.
2445		3326
2446	=item struct ev_loop *other [read-only]	3327	=item struct ev_loop *other [read-only]
2447		3328
2448	The embedded event loop.	3329	The embedded event loop.
…		…
2458	used).	3339	used).
2459		3340
2460	struct ev_loop *loop_hi = ev_default_init (0);	3341	struct ev_loop *loop_hi = ev_default_init (0);
2461	struct ev_loop *loop_lo = 0;	3342	struct ev_loop *loop_lo = 0;
2462	ev_embed embed;	3343	ev_embed embed;
2463		3344
2464	// see if there is a chance of getting one that works	3345	// see if there is a chance of getting one that works
2465	// (remember that a flags value of 0 means autodetection)	3346	// (remember that a flags value of 0 means autodetection)
2466	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3347	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2467	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3348	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2468	: 0;	3349	: 0;
…		…
2482	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3363	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2483		3364
2484	struct ev_loop *loop = ev_default_init (0);	3365	struct ev_loop *loop = ev_default_init (0);
2485	struct ev_loop *loop_socket = 0;	3366	struct ev_loop *loop_socket = 0;
2486	ev_embed embed;	3367	ev_embed embed;
2487		3368
2488	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3369	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2489	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3370	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2490	{	3371	{
2491	ev_embed_init (&embed, 0, loop_socket);	3372	ev_embed_init (&embed, 0, loop_socket);
2492	ev_embed_start (loop, &embed);	3373	ev_embed_start (loop, &embed);
…		…
2500		3381
2501	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3382	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2502		3383
2503	Fork watchers are called when a C<fork ()> was detected (usually because	3384	Fork watchers are called when a C<fork ()> was detected (usually because
2504	whoever is a good citizen cared to tell libev about it by calling	3385	whoever is a good citizen cared to tell libev about it by calling
2505	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3386	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2506	event loop blocks next and before C<ev_check> watchers are being called,	3387	and before C<ev_check> watchers are being called, and only in the child
2507	and only in the child after the fork. If whoever good citizen calling	3388	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2508	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3389	and calls it in the wrong process, the fork handlers will be invoked, too,
2509	handlers will be invoked, too, of course.	3390	of course.
		3391
		3392	=head3 The special problem of life after fork - how is it possible?
		3393
		3394	Most uses of C<fork ()> consist of forking, then some simple calls to set
		3395	up/change the process environment, followed by a call to C<exec()>. This
		3396	sequence should be handled by libev without any problems.
		3397
		3398	This changes when the application actually wants to do event handling
		3399	in the child, or both parent in child, in effect "continuing" after the
		3400	fork.
		3401
		3402	The default mode of operation (for libev, with application help to detect
		3403	forks) is to duplicate all the state in the child, as would be expected
		3404	when I<either> the parent I<or> the child process continues.
		3405
		3406	When both processes want to continue using libev, then this is usually the
		3407	wrong result. In that case, usually one process (typically the parent) is
		3408	supposed to continue with all watchers in place as before, while the other
		3409	process typically wants to start fresh, i.e. without any active watchers.
		3410
		3411	The cleanest and most efficient way to achieve that with libev is to
		3412	simply create a new event loop, which of course will be "empty", and
		3413	use that for new watchers. This has the advantage of not touching more
		3414	memory than necessary, and thus avoiding the copy-on-write, and the
		3415	disadvantage of having to use multiple event loops (which do not support
		3416	signal watchers).
		3417
		3418	When this is not possible, or you want to use the default loop for
		3419	other reasons, then in the process that wants to start "fresh", call
		3420	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3421	Destroying the default loop will "orphan" (not stop) all registered
		3422	watchers, so you have to be careful not to execute code that modifies
		3423	those watchers. Note also that in that case, you have to re-register any
		3424	signal watchers.
2510		3425
2511	=head3 Watcher-Specific Functions and Data Members	3426	=head3 Watcher-Specific Functions and Data Members
2512		3427
2513	=over 4	3428	=over 4
2514		3429
2515	=item ev_fork_init (ev_signal *, callback)	3430	=item ev_fork_init (ev_fork *, callback)
2516		3431
2517	Initialises and configures the fork watcher - it has no parameters of any	3432	Initialises and configures the fork watcher - it has no parameters of any
2518	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3433	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2519	believe me.	3434	really.
2520		3435
2521	=back	3436	=back
2522		3437
2523		3438
		3439	=head2 C<ev_cleanup> - even the best things end
		3440
		3441	Cleanup watchers are called just before the event loop is being destroyed
		3442	by a call to C<ev_loop_destroy>.
		3443
		3444	While there is no guarantee that the event loop gets destroyed, cleanup
		3445	watchers provide a convenient method to install cleanup hooks for your
		3446	program, worker threads and so on - you just to make sure to destroy the
		3447	loop when you want them to be invoked.
		3448
		3449	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3450	all other watchers, they do not keep a reference to the event loop (which
		3451	makes a lot of sense if you think about it). Like all other watchers, you
		3452	can call libev functions in the callback, except C<ev_cleanup_start>.
		3453
		3454	=head3 Watcher-Specific Functions and Data Members
		3455
		3456	=over 4
		3457
		3458	=item ev_cleanup_init (ev_cleanup *, callback)
		3459
		3460	Initialises and configures the cleanup watcher - it has no parameters of
		3461	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3462	pointless, I assure you.
		3463
		3464	=back
		3465
		3466	Example: Register an atexit handler to destroy the default loop, so any
		3467	cleanup functions are called.
		3468
		3469	static void
		3470	program_exits (void)
		3471	{
		3472	ev_loop_destroy (EV_DEFAULT_UC);
		3473	}
		3474
		3475	...
		3476	atexit (program_exits);
		3477
		3478
2524	=head2 C<ev_async> - how to wake up another event loop	3479	=head2 C<ev_async> - how to wake up an event loop
2525		3480
2526	In general, you cannot use an C<ev_loop> from multiple threads or other	3481	In general, you cannot use an C<ev_loop> from multiple threads or other
2527	asynchronous sources such as signal handlers (as opposed to multiple event	3482	asynchronous sources such as signal handlers (as opposed to multiple event
2528	loops - those are of course safe to use in different threads).	3483	loops - those are of course safe to use in different threads).
2529		3484
2530	Sometimes, however, you need to wake up another event loop you do not	3485	Sometimes, however, you need to wake up an event loop you do not control,
2531	control, for example because it belongs to another thread. This is what	3486	for example because it belongs to another thread. This is what C<ev_async>
2532	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3487	watchers do: as long as the C<ev_async> watcher is active, you can signal
2533	can signal it by calling C<ev_async_send>, which is thread- and signal	3488	it by calling C<ev_async_send>, which is thread- and signal safe.
2534	safe.
2535		3489
2536	This functionality is very similar to C<ev_signal> watchers, as signals,	3490	This functionality is very similar to C<ev_signal> watchers, as signals,
2537	too, are asynchronous in nature, and signals, too, will be compressed	3491	too, are asynchronous in nature, and signals, too, will be compressed
2538	(i.e. the number of callback invocations may be less than the number of	3492	(i.e. the number of callback invocations may be less than the number of
2539	C<ev_async_sent> calls).	3493	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2540		3494	of "global async watchers" by using a watcher on an otherwise unused
2541	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3495	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2542	just the default loop.	3496	even without knowing which loop owns the signal.
2543		3497
2544	=head3 Queueing	3498	=head3 Queueing
2545		3499
2546	C<ev_async> does not support queueing of data in any way. The reason	3500	C<ev_async> does not support queueing of data in any way. The reason
2547	is that the author does not know of a simple (or any) algorithm for a	3501	is that the author does not know of a simple (or any) algorithm for a
2548	multiple-writer-single-reader queue that works in all cases and doesn't	3502	multiple-writer-single-reader queue that works in all cases and doesn't
2549	need elaborate support such as pthreads.	3503	need elaborate support such as pthreads or unportable memory access
		3504	semantics.
2550		3505
2551	That means that if you want to queue data, you have to provide your own	3506	That means that if you want to queue data, you have to provide your own
2552	queue. But at least I can tell you how to implement locking around your	3507	queue. But at least I can tell you how to implement locking around your
2553	queue:	3508	queue:
2554		3509
…		…
2632	=over 4	3587	=over 4
2633		3588
2634	=item ev_async_init (ev_async *, callback)	3589	=item ev_async_init (ev_async *, callback)
2635		3590
2636	Initialises and configures the async watcher - it has no parameters of any	3591	Initialises and configures the async watcher - it has no parameters of any
2637	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3592	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2638	trust me.	3593	trust me.
2639		3594
2640	=item ev_async_send (loop, ev_async *)	3595	=item ev_async_send (loop, ev_async *)
2641		3596
2642	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3597	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2643	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3598	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3599	returns.
		3600
2644	C<ev_feed_event>, this call is safe to do from other threads, signal or	3601	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2645	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3602	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2646	section below on what exactly this means).	3603	embedding section below on what exactly this means).
2647		3604
2648	This call incurs the overhead of a system call only once per loop iteration,	3605	Note that, as with other watchers in libev, multiple events might get
2649	so while the overhead might be noticeable, it doesn't apply to repeated	3606	compressed into a single callback invocation (another way to look at
2650	calls to C<ev_async_send>.	3607	this is that C<ev_async> watchers are level-triggered: they are set on
		3608	C<ev_async_send>, reset when the event loop detects that).
		3609
		3610	This call incurs the overhead of at most one extra system call per event
		3611	loop iteration, if the event loop is blocked, and no syscall at all if
		3612	the event loop (or your program) is processing events. That means that
		3613	repeated calls are basically free (there is no need to avoid calls for
		3614	performance reasons) and that the overhead becomes smaller (typically
		3615	zero) under load.
2651		3616
2652	=item bool = ev_async_pending (ev_async *)	3617	=item bool = ev_async_pending (ev_async *)
2653		3618
2654	Returns a non-zero value when C<ev_async_send> has been called on the	3619	Returns a non-zero value when C<ev_async_send> has been called on the
2655	watcher but the event has not yet been processed (or even noted) by the	3620	watcher but the event has not yet been processed (or even noted) by the
…		…
2658	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3623	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2659	the loop iterates next and checks for the watcher to have become active,	3624	the loop iterates next and checks for the watcher to have become active,
2660	it will reset the flag again. C<ev_async_pending> can be used to very	3625	it will reset the flag again. C<ev_async_pending> can be used to very
2661	quickly check whether invoking the loop might be a good idea.	3626	quickly check whether invoking the loop might be a good idea.
2662		3627
2663	Not that this does I<not> check whether the watcher itself is pending, only	3628	Not that this does I<not> check whether the watcher itself is pending,
2664	whether it has been requested to make this watcher pending.	3629	only whether it has been requested to make this watcher pending: there
		3630	is a time window between the event loop checking and resetting the async
		3631	notification, and the callback being invoked.
2665		3632
2666	=back	3633	=back
2667		3634
2668		3635
2669	=head1 OTHER FUNCTIONS	3636	=head1 OTHER FUNCTIONS
2670		3637
2671	There are some other functions of possible interest. Described. Here. Now.	3638	There are some other functions of possible interest. Described. Here. Now.
2672		3639
2673	=over 4	3640	=over 4
2674		3641
2675	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3642	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
2676		3643
2677	This function combines a simple timer and an I/O watcher, calls your	3644	This function combines a simple timer and an I/O watcher, calls your
2678	callback on whichever event happens first and automatically stops both	3645	callback on whichever event happens first and automatically stops both
2679	watchers. This is useful if you want to wait for a single event on an fd	3646	watchers. This is useful if you want to wait for a single event on an fd
2680	or timeout without having to allocate/configure/start/stop/free one or	3647	or timeout without having to allocate/configure/start/stop/free one or
…		…
2686		3653
2687	If C<timeout> is less than 0, then no timeout watcher will be	3654	If C<timeout> is less than 0, then no timeout watcher will be
2688	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3655	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2689	repeat = 0) will be started. C<0> is a valid timeout.	3656	repeat = 0) will be started. C<0> is a valid timeout.
2690		3657
2691	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3658	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2692	passed an C<revents> set like normal event callbacks (a combination of	3659	passed an C<revents> set like normal event callbacks (a combination of
2693	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3660	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2694	value passed to C<ev_once>. Note that it is possible to receive I<both>	3661	value passed to C<ev_once>. Note that it is possible to receive I<both>
2695	a timeout and an io event at the same time - you probably should give io	3662	a timeout and an io event at the same time - you probably should give io
2696	events precedence.	3663	events precedence.
2697		3664
2698	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3665	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2699		3666
2700	static void stdin_ready (int revents, void *arg)	3667	static void stdin_ready (int revents, void *arg)
2701	{	3668	{
2702	if (revents & EV_READ)	3669	if (revents & EV_READ)
2703	/* stdin might have data for us, joy! */;	3670	/* stdin might have data for us, joy! */;
2704	else if (revents & EV_TIMEOUT)	3671	else if (revents & EV_TIMER)
2705	/* doh, nothing entered */;	3672	/* doh, nothing entered */;
2706	}	3673	}
2707		3674
2708	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3675	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2709		3676
2710	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2711
2712	Feeds the given event set into the event loop, as if the specified event
2713	had happened for the specified watcher (which must be a pointer to an
2714	initialised but not necessarily started event watcher).
2715
2716	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3677	=item ev_feed_fd_event (loop, int fd, int revents)
2717		3678
2718	Feed an event on the given fd, as if a file descriptor backend detected	3679	Feed an event on the given fd, as if a file descriptor backend detected
2719	the given events it.	3680	the given events.
2720		3681
2721	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3682	=item ev_feed_signal_event (loop, int signum)
2722		3683
2723	Feed an event as if the given signal occurred (C<loop> must be the default	3684	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2724	loop!).	3685	which is async-safe.
2725		3686
2726	=back	3687	=back
		3688
		3689
		3690	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3691
		3692	This section explains some common idioms that are not immediately
		3693	obvious. Note that examples are sprinkled over the whole manual, and this
		3694	section only contains stuff that wouldn't fit anywhere else.
		3695
		3696	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3697
		3698	Each watcher has, by default, a C<void *data> member that you can read
		3699	or modify at any time: libev will completely ignore it. This can be used
		3700	to associate arbitrary data with your watcher. If you need more data and
		3701	don't want to allocate memory separately and store a pointer to it in that
		3702	data member, you can also "subclass" the watcher type and provide your own
		3703	data:
		3704
		3705	struct my_io
		3706	{
		3707	ev_io io;
		3708	int otherfd;
		3709	void *somedata;
		3710	struct whatever *mostinteresting;
		3711	};
		3712
		3713	...
		3714	struct my_io w;
		3715	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3716
		3717	And since your callback will be called with a pointer to the watcher, you
		3718	can cast it back to your own type:
		3719
		3720	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3721	{
		3722	struct my_io *w = (struct my_io *)w_;
		3723	...
		3724	}
		3725
		3726	More interesting and less C-conformant ways of casting your callback
		3727	function type instead have been omitted.
		3728
		3729	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3730
		3731	Another common scenario is to use some data structure with multiple
		3732	embedded watchers, in effect creating your own watcher that combines
		3733	multiple libev event sources into one "super-watcher":
		3734
		3735	struct my_biggy
		3736	{
		3737	int some_data;
		3738	ev_timer t1;
		3739	ev_timer t2;
		3740	}
		3741
		3742	In this case getting the pointer to C<my_biggy> is a bit more
		3743	complicated: Either you store the address of your C<my_biggy> struct in
		3744	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3745	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3746	real programmers):
		3747
		3748	#include <stddef.h>
		3749
		3750	static void
		3751	t1_cb (EV_P_ ev_timer *w, int revents)
		3752	{
		3753	struct my_biggy big = (struct my_biggy *)
		3754	(((char *)w) - offsetof (struct my_biggy, t1));
		3755	}
		3756
		3757	static void
		3758	t2_cb (EV_P_ ev_timer *w, int revents)
		3759	{
		3760	struct my_biggy big = (struct my_biggy *)
		3761	(((char *)w) - offsetof (struct my_biggy, t2));
		3762	}
		3763
		3764	=head2 AVOIDING FINISHING BEFORE RETURNING
		3765
		3766	Often you have structures like this in event-based programs:
		3767
		3768	callback ()
		3769	{
		3770	free (request);
		3771	}
		3772
		3773	request = start_new_request (..., callback);
		3774
		3775	The intent is to start some "lengthy" operation. The C<request> could be
		3776	used to cancel the operation, or do other things with it.
		3777
		3778	It's not uncommon to have code paths in C<start_new_request> that
		3779	immediately invoke the callback, for example, to report errors. Or you add
		3780	some caching layer that finds that it can skip the lengthy aspects of the
		3781	operation and simply invoke the callback with the result.
		3782
		3783	The problem here is that this will happen I<before> C<start_new_request>
		3784	has returned, so C<request> is not set.
		3785
		3786	Even if you pass the request by some safer means to the callback, you
		3787	might want to do something to the request after starting it, such as
		3788	canceling it, which probably isn't working so well when the callback has
		3789	already been invoked.
		3790
		3791	A common way around all these issues is to make sure that
		3792	C<start_new_request> I<always> returns before the callback is invoked. If
		3793	C<start_new_request> immediately knows the result, it can artificially
		3794	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3795	example, or more sneakily, by reusing an existing (stopped) watcher and
		3796	pushing it into the pending queue:
		3797
		3798	ev_set_cb (watcher, callback);
		3799	ev_feed_event (EV_A_ watcher, 0);
		3800
		3801	This way, C<start_new_request> can safely return before the callback is
		3802	invoked, while not delaying callback invocation too much.
		3803
		3804	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3805
		3806	Often (especially in GUI toolkits) there are places where you have
		3807	I<modal> interaction, which is most easily implemented by recursively
		3808	invoking C<ev_run>.
		3809
		3810	This brings the problem of exiting - a callback might want to finish the
		3811	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3812	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3813	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3814	other combination: In these cases, a simple C<ev_break> will not work.
		3815
		3816	The solution is to maintain "break this loop" variable for each C<ev_run>
		3817	invocation, and use a loop around C<ev_run> until the condition is
		3818	triggered, using C<EVRUN_ONCE>:
		3819
		3820	// main loop
		3821	int exit_main_loop = 0;
		3822
		3823	while (!exit_main_loop)
		3824	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3825
		3826	// in a modal watcher
		3827	int exit_nested_loop = 0;
		3828
		3829	while (!exit_nested_loop)
		3830	ev_run (EV_A_ EVRUN_ONCE);
		3831
		3832	To exit from any of these loops, just set the corresponding exit variable:
		3833
		3834	// exit modal loop
		3835	exit_nested_loop = 1;
		3836
		3837	// exit main program, after modal loop is finished
		3838	exit_main_loop = 1;
		3839
		3840	// exit both
		3841	exit_main_loop = exit_nested_loop = 1;
		3842
		3843	=head2 THREAD LOCKING EXAMPLE
		3844
		3845	Here is a fictitious example of how to run an event loop in a different
		3846	thread from where callbacks are being invoked and watchers are
		3847	created/added/removed.
		3848
		3849	For a real-world example, see the C<EV::Loop::Async> perl module,
		3850	which uses exactly this technique (which is suited for many high-level
		3851	languages).
		3852
		3853	The example uses a pthread mutex to protect the loop data, a condition
		3854	variable to wait for callback invocations, an async watcher to notify the
		3855	event loop thread and an unspecified mechanism to wake up the main thread.
		3856
		3857	First, you need to associate some data with the event loop:
		3858
		3859	typedef struct {
		3860	mutex_t lock; /* global loop lock */
		3861	ev_async async_w;
		3862	thread_t tid;
		3863	cond_t invoke_cv;
		3864	} userdata;
		3865
		3866	void prepare_loop (EV_P)
		3867	{
		3868	// for simplicity, we use a static userdata struct.
		3869	static userdata u;
		3870
		3871	ev_async_init (&u->async_w, async_cb);
		3872	ev_async_start (EV_A_ &u->async_w);
		3873
		3874	pthread_mutex_init (&u->lock, 0);
		3875	pthread_cond_init (&u->invoke_cv, 0);
		3876
		3877	// now associate this with the loop
		3878	ev_set_userdata (EV_A_ u);
		3879	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3880	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3881
		3882	// then create the thread running ev_run
		3883	pthread_create (&u->tid, 0, l_run, EV_A);
		3884	}
		3885
		3886	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3887	solely to wake up the event loop so it takes notice of any new watchers
		3888	that might have been added:
		3889
		3890	static void
		3891	async_cb (EV_P_ ev_async *w, int revents)
		3892	{
		3893	// just used for the side effects
		3894	}
		3895
		3896	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3897	protecting the loop data, respectively.
		3898
		3899	static void
		3900	l_release (EV_P)
		3901	{
		3902	userdata *u = ev_userdata (EV_A);
		3903	pthread_mutex_unlock (&u->lock);
		3904	}
		3905
		3906	static void
		3907	l_acquire (EV_P)
		3908	{
		3909	userdata *u = ev_userdata (EV_A);
		3910	pthread_mutex_lock (&u->lock);
		3911	}
		3912
		3913	The event loop thread first acquires the mutex, and then jumps straight
		3914	into C<ev_run>:
		3915
		3916	void *
		3917	l_run (void *thr_arg)
		3918	{
		3919	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3920
		3921	l_acquire (EV_A);
		3922	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3923	ev_run (EV_A_ 0);
		3924	l_release (EV_A);
		3925
		3926	return 0;
		3927	}
		3928
		3929	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3930	signal the main thread via some unspecified mechanism (signals? pipe
		3931	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3932	have been called (in a while loop because a) spurious wakeups are possible
		3933	and b) skipping inter-thread-communication when there are no pending
		3934	watchers is very beneficial):
		3935
		3936	static void
		3937	l_invoke (EV_P)
		3938	{
		3939	userdata *u = ev_userdata (EV_A);
		3940
		3941	while (ev_pending_count (EV_A))
		3942	{
		3943	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3944	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3945	}
		3946	}
		3947
		3948	Now, whenever the main thread gets told to invoke pending watchers, it
		3949	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3950	thread to continue:
		3951
		3952	static void
		3953	real_invoke_pending (EV_P)
		3954	{
		3955	userdata *u = ev_userdata (EV_A);
		3956
		3957	pthread_mutex_lock (&u->lock);
		3958	ev_invoke_pending (EV_A);
		3959	pthread_cond_signal (&u->invoke_cv);
		3960	pthread_mutex_unlock (&u->lock);
		3961	}
		3962
		3963	Whenever you want to start/stop a watcher or do other modifications to an
		3964	event loop, you will now have to lock:
		3965
		3966	ev_timer timeout_watcher;
		3967	userdata *u = ev_userdata (EV_A);
		3968
		3969	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3970
		3971	pthread_mutex_lock (&u->lock);
		3972	ev_timer_start (EV_A_ &timeout_watcher);
		3973	ev_async_send (EV_A_ &u->async_w);
		3974	pthread_mutex_unlock (&u->lock);
		3975
		3976	Note that sending the C<ev_async> watcher is required because otherwise
		3977	an event loop currently blocking in the kernel will have no knowledge
		3978	about the newly added timer. By waking up the loop it will pick up any new
		3979	watchers in the next event loop iteration.
		3980
		3981	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3982
		3983	While the overhead of a callback that e.g. schedules a thread is small, it
		3984	is still an overhead. If you embed libev, and your main usage is with some
		3985	kind of threads or coroutines, you might want to customise libev so that
		3986	doesn't need callbacks anymore.
		3987
		3988	Imagine you have coroutines that you can switch to using a function
		3989	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3990	and that due to some magic, the currently active coroutine is stored in a
		3991	global called C<current_coro>. Then you can build your own "wait for libev
		3992	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3993	the differing C<;> conventions):
		3994
		3995	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3996	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3997
		3998	That means instead of having a C callback function, you store the
		3999	coroutine to switch to in each watcher, and instead of having libev call
		4000	your callback, you instead have it switch to that coroutine.
		4001
		4002	A coroutine might now wait for an event with a function called
		4003	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		4004	matter when, or whether the watcher is active or not when this function is
		4005	called):
		4006
		4007	void
		4008	wait_for_event (ev_watcher *w)
		4009	{
		4010	ev_set_cb (w, current_coro);
		4011	switch_to (libev_coro);
		4012	}
		4013
		4014	That basically suspends the coroutine inside C<wait_for_event> and
		4015	continues the libev coroutine, which, when appropriate, switches back to
		4016	this or any other coroutine.
		4017
		4018	You can do similar tricks if you have, say, threads with an event queue -
		4019	instead of storing a coroutine, you store the queue object and instead of
		4020	switching to a coroutine, you push the watcher onto the queue and notify
		4021	any waiters.
		4022
		4023	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		4024	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		4025
		4026	// my_ev.h
		4027	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4028	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4029	#include "../libev/ev.h"
		4030
		4031	// my_ev.c
		4032	#define EV_H "my_ev.h"
		4033	#include "../libev/ev.c"
		4034
		4035	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4036	F<my_ev.c> into your project. When properly specifying include paths, you
		4037	can even use F<ev.h> as header file name directly.
2727		4038
2728		4039
2729	=head1 LIBEVENT EMULATION	4040	=head1 LIBEVENT EMULATION
2730		4041
2731	Libev offers a compatibility emulation layer for libevent. It cannot	4042	Libev offers a compatibility emulation layer for libevent. It cannot
2732	emulate the internals of libevent, so here are some usage hints:	4043	emulate the internals of libevent, so here are some usage hints:
2733		4044
2734	=over 4	4045	=over 4
		4046
		4047	=item * Only the libevent-1.4.1-beta API is being emulated.
		4048
		4049	This was the newest libevent version available when libev was implemented,
		4050	and is still mostly unchanged in 2010.
2735		4051
2736	=item * Use it by including <event.h>, as usual.	4052	=item * Use it by including <event.h>, as usual.
2737		4053
2738	=item * The following members are fully supported: ev_base, ev_callback,	4054	=item * The following members are fully supported: ev_base, ev_callback,
2739	ev_arg, ev_fd, ev_res, ev_events.	4055	ev_arg, ev_fd, ev_res, ev_events.
…		…
2745	=item * Priorities are not currently supported. Initialising priorities	4061	=item * Priorities are not currently supported. Initialising priorities
2746	will fail and all watchers will have the same priority, even though there	4062	will fail and all watchers will have the same priority, even though there
2747	is an ev_pri field.	4063	is an ev_pri field.
2748		4064
2749	=item * In libevent, the last base created gets the signals, in libev, the	4065	=item * In libevent, the last base created gets the signals, in libev, the
2750	first base created (== the default loop) gets the signals.	4066	base that registered the signal gets the signals.
2751		4067
2752	=item * Other members are not supported.	4068	=item * Other members are not supported.
2753		4069
2754	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4070	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2755	to use the libev header file and library.	4071	to use the libev header file and library.
2756		4072
2757	=back	4073	=back
2758		4074
2759	=head1 C++ SUPPORT	4075	=head1 C++ SUPPORT
		4076
		4077	=head2 C API
		4078
		4079	The normal C API should work fine when used from C++: both ev.h and the
		4080	libev sources can be compiled as C++. Therefore, code that uses the C API
		4081	will work fine.
		4082
		4083	Proper exception specifications might have to be added to callbacks passed
		4084	to libev: exceptions may be thrown only from watcher callbacks, all other
		4085	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4086	callbacks) must not throw exceptions, and might need a C<noexcept>
		4087	specification. If you have code that needs to be compiled as both C and
		4088	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4089
		4090	static void
		4091	fatal_error (const char *msg) EV_NOEXCEPT
		4092	{
		4093	perror (msg);
		4094	abort ();
		4095	}
		4096
		4097	...
		4098	ev_set_syserr_cb (fatal_error);
		4099
		4100	The only API functions that can currently throw exceptions are C<ev_run>,
		4101	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4102	because it runs cleanup watchers).
		4103
		4104	Throwing exceptions in watcher callbacks is only supported if libev itself
		4105	is compiled with a C++ compiler or your C and C++ environments allow
		4106	throwing exceptions through C libraries (most do).
		4107
		4108	=head2 C++ API
2760		4109
2761	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4110	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2762	you to use some convenience methods to start/stop watchers and also change	4111	you to use some convenience methods to start/stop watchers and also change
2763	the callback model to a model using method callbacks on objects.	4112	the callback model to a model using method callbacks on objects.
2764		4113
2765	To use it,	4114	To use it,
2766		4115
2767	#include <ev++.h>	4116	#include <ev++.h>
2768		4117
2769	This automatically includes F<ev.h> and puts all of its definitions (many	4118	This automatically includes F<ev.h> and puts all of its definitions (many
2770	of them macros) into the global namespace. All C++ specific things are	4119	of them macros) into the global namespace. All C++ specific things are
2771	put into the C<ev> namespace. It should support all the same embedding	4120	put into the C<ev> namespace. It should support all the same embedding
…		…
2774	Care has been taken to keep the overhead low. The only data member the C++	4123	Care has been taken to keep the overhead low. The only data member the C++
2775	classes add (compared to plain C-style watchers) is the event loop pointer	4124	classes add (compared to plain C-style watchers) is the event loop pointer
2776	that the watcher is associated with (or no additional members at all if	4125	that the watcher is associated with (or no additional members at all if
2777	you disable C<EV_MULTIPLICITY> when embedding libev).	4126	you disable C<EV_MULTIPLICITY> when embedding libev).
2778		4127
2779	Currently, functions, and static and non-static member functions can be	4128	Currently, functions, static and non-static member functions and classes
2780	used as callbacks. Other types should be easy to add as long as they only	4129	with C<operator ()> can be used as callbacks. Other types should be easy
2781	need one additional pointer for context. If you need support for other	4130	to add as long as they only need one additional pointer for context. If
2782	types of functors please contact the author (preferably after implementing	4131	you need support for other types of functors please contact the author
2783	it).	4132	(preferably after implementing it).
		4133
		4134	For all this to work, your C++ compiler either has to use the same calling
		4135	conventions as your C compiler (for static member functions), or you have
		4136	to embed libev and compile libev itself as C++.
2784		4137
2785	Here is a list of things available in the C<ev> namespace:	4138	Here is a list of things available in the C<ev> namespace:
2786		4139
2787	=over 4	4140	=over 4
2788		4141
…		…
2798	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4151	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2799		4152
2800	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4153	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2801	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4154	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2802	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4155	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2803	defines by many implementations.	4156	defined by many implementations.
2804		4157
2805	All of those classes have these methods:	4158	All of those classes have these methods:
2806		4159
2807	=over 4	4160	=over 4
2808		4161
2809	=item ev::TYPE::TYPE ()	4162	=item ev::TYPE::TYPE ()
2810		4163
2811	=item ev::TYPE::TYPE (struct ev_loop *)	4164	=item ev::TYPE::TYPE (loop)
2812		4165
2813	=item ev::TYPE::~TYPE	4166	=item ev::TYPE::~TYPE
2814		4167
2815	The constructor (optionally) takes an event loop to associate the watcher	4168	The constructor (optionally) takes an event loop to associate the watcher
2816	with. If it is omitted, it will use C<EV_DEFAULT>.	4169	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2848		4201
2849	myclass obj;	4202	myclass obj;
2850	ev::io iow;	4203	ev::io iow;
2851	iow.set <myclass, &myclass::io_cb> (&obj);	4204	iow.set <myclass, &myclass::io_cb> (&obj);
2852		4205
		4206	=item w->set (object *)
		4207
		4208	This is a variation of a method callback - leaving out the method to call
		4209	will default the method to C<operator ()>, which makes it possible to use
		4210	functor objects without having to manually specify the C<operator ()> all
		4211	the time. Incidentally, you can then also leave out the template argument
		4212	list.
		4213
		4214	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		4215	int revents)>.
		4216
		4217	See the method-C<set> above for more details.
		4218
		4219	Example: use a functor object as callback.
		4220
		4221	struct myfunctor
		4222	{
		4223	void operator() (ev::io &w, int revents)
		4224	{
		4225	...
		4226	}
		4227	}
		4228
		4229	myfunctor f;
		4230
		4231	ev::io w;
		4232	w.set (&f);
		4233
2853	=item w->set<function> (void *data = 0)	4234	=item w->set<function> (void *data = 0)
2854		4235
2855	Also sets a callback, but uses a static method or plain function as	4236	Also sets a callback, but uses a static method or plain function as
2856	callback. The optional C<data> argument will be stored in the watcher's	4237	callback. The optional C<data> argument will be stored in the watcher's
2857	C<data> member and is free for you to use.	4238	C<data> member and is free for you to use.
…		…
2863	Example: Use a plain function as callback.	4244	Example: Use a plain function as callback.
2864		4245
2865	static void io_cb (ev::io &w, int revents) { }	4246	static void io_cb (ev::io &w, int revents) { }
2866	iow.set <io_cb> ();	4247	iow.set <io_cb> ();
2867		4248
2868	=item w->set (struct ev_loop *)	4249	=item w->set (loop)
2869		4250
2870	Associates a different C<struct ev_loop> with this watcher. You can only	4251	Associates a different C<struct ev_loop> with this watcher. You can only
2871	do this when the watcher is inactive (and not pending either).	4252	do this when the watcher is inactive (and not pending either).
2872		4253
2873	=item w->set ([arguments])	4254	=item w->set ([arguments])
2874		4255
2875	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4256	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4257	with the same arguments. Either this method or a suitable start method
2876	called at least once. Unlike the C counterpart, an active watcher gets	4258	must be called at least once. Unlike the C counterpart, an active watcher
2877	automatically stopped and restarted when reconfiguring it with this	4259	gets automatically stopped and restarted when reconfiguring it with this
2878	method.	4260	method.
		4261
		4262	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4263	clashing with the C<set (loop)> method.
2879		4264
2880	=item w->start ()	4265	=item w->start ()
2881		4266
2882	Starts the watcher. Note that there is no C<loop> argument, as the	4267	Starts the watcher. Note that there is no C<loop> argument, as the
2883	constructor already stores the event loop.	4268	constructor already stores the event loop.
2884		4269
		4270	=item w->start ([arguments])
		4271
		4272	Instead of calling C<set> and C<start> methods separately, it is often
		4273	convenient to wrap them in one call. Uses the same type of arguments as
		4274	the configure C<set> method of the watcher.
		4275
2885	=item w->stop ()	4276	=item w->stop ()
2886		4277
2887	Stops the watcher if it is active. Again, no C<loop> argument.	4278	Stops the watcher if it is active. Again, no C<loop> argument.
2888		4279
2889	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4280	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2901		4292
2902	=back	4293	=back
2903		4294
2904	=back	4295	=back
2905		4296
2906	Example: Define a class with an IO and idle watcher, start one of them in	4297	Example: Define a class with two I/O and idle watchers, start the I/O
2907	the constructor.	4298	watchers in the constructor.
2908		4299
2909	class myclass	4300	class myclass
2910	{	4301	{
2911	ev::io io ; void io_cb (ev::io &w, int revents);	4302	ev::io io ; void io_cb (ev::io &w, int revents);
		4303	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2912	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4304	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2913		4305
2914	myclass (int fd)	4306	myclass (int fd)
2915	{	4307	{
2916	io .set <myclass, &myclass::io_cb > (this);	4308	io .set <myclass, &myclass::io_cb > (this);
		4309	io2 .set <myclass, &myclass::io2_cb > (this);
2917	idle.set <myclass, &myclass::idle_cb> (this);	4310	idle.set <myclass, &myclass::idle_cb> (this);
2918		4311
2919	io.start (fd, ev::READ);	4312	io.set (fd, ev::WRITE); // configure the watcher
		4313	io.start (); // start it whenever convenient
		4314
		4315	io2.start (fd, ev::READ); // set + start in one call
2920	}	4316	}
2921	};	4317	};
2922		4318
2923		4319
2924	=head1 OTHER LANGUAGE BINDINGS	4320	=head1 OTHER LANGUAGE BINDINGS
…		…
2943	L<http://software.schmorp.de/pkg/EV>.	4339	L<http://software.schmorp.de/pkg/EV>.
2944		4340
2945	=item Python	4341	=item Python
2946		4342
2947	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4343	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2948	seems to be quite complete and well-documented. Note, however, that the	4344	seems to be quite complete and well-documented.
2949	patch they require for libev is outright dangerous as it breaks the ABI
2950	for everybody else, and therefore, should never be applied in an installed
2951	libev (if python requires an incompatible ABI then it needs to embed
2952	libev).
2953		4345
2954	=item Ruby	4346	=item Ruby
2955		4347
2956	Tony Arcieri has written a ruby extension that offers access to a subset	4348	Tony Arcieri has written a ruby extension that offers access to a subset
2957	of the libev API and adds file handle abstractions, asynchronous DNS and	4349	of the libev API and adds file handle abstractions, asynchronous DNS and
2958	more on top of it. It can be found via gem servers. Its homepage is at	4350	more on top of it. It can be found via gem servers. Its homepage is at
2959	L<http://rev.rubyforge.org/>.	4351	L<http://rev.rubyforge.org/>.
2960		4352
		4353	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4354	makes rev work even on mingw.
		4355
		4356	=item Haskell
		4357
		4358	A haskell binding to libev is available at
		4359	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4360
2961	=item D	4361	=item D
2962		4362
2963	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4363	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2964	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4364	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
2965		4365
2966	=item Ocaml	4366	=item Ocaml
2967		4367
2968	Erkki Seppala has written Ocaml bindings for libev, to be found at	4368	Erkki Seppala has written Ocaml bindings for libev, to be found at
2969	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4369	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4370
		4371	=item Lua
		4372
		4373	Brian Maher has written a partial interface to libev for lua (at the
		4374	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4375	L<http://github.com/brimworks/lua-ev>.
		4376
		4377	=item Javascript
		4378
		4379	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4380
		4381	=item Others
		4382
		4383	There are others, and I stopped counting.
2970		4384
2971	=back	4385	=back
2972		4386
2973		4387
2974	=head1 MACRO MAGIC	4388	=head1 MACRO MAGIC
…		…
2988	loop argument"). The C<EV_A> form is used when this is the sole argument,	4402	loop argument"). The C<EV_A> form is used when this is the sole argument,
2989	C<EV_A_> is used when other arguments are following. Example:	4403	C<EV_A_> is used when other arguments are following. Example:
2990		4404
2991	ev_unref (EV_A);	4405	ev_unref (EV_A);
2992	ev_timer_add (EV_A_ watcher);	4406	ev_timer_add (EV_A_ watcher);
2993	ev_loop (EV_A_ 0);	4407	ev_run (EV_A_ 0);
2994		4408
2995	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4409	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
2996	which is often provided by the following macro.	4410	which is often provided by the following macro.
2997		4411
2998	=item C<EV_P>, C<EV_P_>	4412	=item C<EV_P>, C<EV_P_>
…		…
3011	suitable for use with C<EV_A>.	4425	suitable for use with C<EV_A>.
3012		4426
3013	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4427	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3014		4428
3015	Similar to the other two macros, this gives you the value of the default	4429	Similar to the other two macros, this gives you the value of the default
3016	loop, if multiple loops are supported ("ev loop default").	4430	loop, if multiple loops are supported ("ev loop default"). The default loop
		4431	will be initialised if it isn't already initialised.
		4432
		4433	For non-multiplicity builds, these macros do nothing, so you always have
		4434	to initialise the loop somewhere.
3017		4435
3018	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4436	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3019		4437
3020	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4438	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3021	default loop has been initialised (C<UC> == unchecked). Their behaviour	4439	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3038	}	4456	}
3039		4457
3040	ev_check check;	4458	ev_check check;
3041	ev_check_init (&check, check_cb);	4459	ev_check_init (&check, check_cb);
3042	ev_check_start (EV_DEFAULT_ &check);	4460	ev_check_start (EV_DEFAULT_ &check);
3043	ev_loop (EV_DEFAULT_ 0);	4461	ev_run (EV_DEFAULT_ 0);
3044		4462
3045	=head1 EMBEDDING	4463	=head1 EMBEDDING
3046		4464
3047	Libev can (and often is) directly embedded into host	4465	Libev can (and often is) directly embedded into host
3048	applications. Examples of applications that embed it include the Deliantra	4466	applications. Examples of applications that embed it include the Deliantra
…		…
3075		4493
3076	#define EV_STANDALONE 1	4494	#define EV_STANDALONE 1
3077	#include "ev.h"	4495	#include "ev.h"
3078		4496
3079	Both header files and implementation files can be compiled with a C++	4497	Both header files and implementation files can be compiled with a C++
3080	compiler (at least, thats a stated goal, and breakage will be treated	4498	compiler (at least, that's a stated goal, and breakage will be treated
3081	as a bug).	4499	as a bug).
3082		4500
3083	You need the following files in your source tree, or in a directory	4501	You need the following files in your source tree, or in a directory
3084	in your include path (e.g. in libev/ when using -Ilibev):	4502	in your include path (e.g. in libev/ when using -Ilibev):
3085		4503
…		…
3088	ev_vars.h	4506	ev_vars.h
3089	ev_wrap.h	4507	ev_wrap.h
3090		4508
3091	ev_win32.c required on win32 platforms only	4509	ev_win32.c required on win32 platforms only
3092		4510
3093	ev_select.c only when select backend is enabled (which is enabled by default)	4511	ev_select.c only when select backend is enabled
3094	ev_poll.c only when poll backend is enabled (disabled by default)	4512	ev_poll.c only when poll backend is enabled
3095	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4513	ev_epoll.c only when the epoll backend is enabled
		4514	ev_linuxaio.c only when the linux aio backend is enabled
		4515	ev_iouring.c only when the linux io_uring backend is enabled
3096	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4516	ev_kqueue.c only when the kqueue backend is enabled
3097	ev_port.c only when the solaris port backend is enabled (disabled by default)	4517	ev_port.c only when the solaris port backend is enabled
3098		4518
3099	F<ev.c> includes the backend files directly when enabled, so you only need	4519	F<ev.c> includes the backend files directly when enabled, so you only need
3100	to compile this single file.	4520	to compile this single file.
3101		4521
3102	=head3 LIBEVENT COMPATIBILITY API	4522	=head3 LIBEVENT COMPATIBILITY API
…		…
3128	libev.m4	4548	libev.m4
3129		4549
3130	=head2 PREPROCESSOR SYMBOLS/MACROS	4550	=head2 PREPROCESSOR SYMBOLS/MACROS
3131		4551
3132	Libev can be configured via a variety of preprocessor symbols you have to	4552	Libev can be configured via a variety of preprocessor symbols you have to
3133	define before including any of its files. The default in the absence of	4553	define before including (or compiling) any of its files. The default in
3134	autoconf is documented for every option.	4554	the absence of autoconf is documented for every option.
		4555
		4556	Symbols marked with "(h)" do not change the ABI, and can have different
		4557	values when compiling libev vs. including F<ev.h>, so it is permissible
		4558	to redefine them before including F<ev.h> without breaking compatibility
		4559	to a compiled library. All other symbols change the ABI, which means all
		4560	users of libev and the libev code itself must be compiled with compatible
		4561	settings.
3135		4562
3136	=over 4	4563	=over 4
3137		4564
		4565	=item EV_COMPAT3 (h)
		4566
		4567	Backwards compatibility is a major concern for libev. This is why this
		4568	release of libev comes with wrappers for the functions and symbols that
		4569	have been renamed between libev version 3 and 4.
		4570
		4571	You can disable these wrappers (to test compatibility with future
		4572	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4573	sources. This has the additional advantage that you can drop the C<struct>
		4574	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4575	typedef in that case.
		4576
		4577	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4578	and in some even more future version the compatibility code will be
		4579	removed completely.
		4580
3138	=item EV_STANDALONE	4581	=item EV_STANDALONE (h)
3139		4582
3140	Must always be C<1> if you do not use autoconf configuration, which	4583	Must always be C<1> if you do not use autoconf configuration, which
3141	keeps libev from including F<config.h>, and it also defines dummy	4584	keeps libev from including F<config.h>, and it also defines dummy
3142	implementations for some libevent functions (such as logging, which is not	4585	implementations for some libevent functions (such as logging, which is not
3143	supported). It will also not define any of the structs usually found in	4586	supported). It will also not define any of the structs usually found in
3144	F<event.h> that are not directly supported by the libev core alone.	4587	F<event.h> that are not directly supported by the libev core alone.
3145		4588
		4589	In standalone mode, libev will still try to automatically deduce the
		4590	configuration, but has to be more conservative.
		4591
		4592	=item EV_USE_FLOOR
		4593
		4594	If defined to be C<1>, libev will use the C<floor ()> function for its
		4595	periodic reschedule calculations, otherwise libev will fall back on a
		4596	portable (slower) implementation. If you enable this, you usually have to
		4597	link against libm or something equivalent. Enabling this when the C<floor>
		4598	function is not available will fail, so the safe default is to not enable
		4599	this.
		4600
3146	=item EV_USE_MONOTONIC	4601	=item EV_USE_MONOTONIC
3147		4602
3148	If defined to be C<1>, libev will try to detect the availability of the	4603	If defined to be C<1>, libev will try to detect the availability of the
3149	monotonic clock option at both compile time and runtime. Otherwise no use	4604	monotonic clock option at both compile time and runtime. Otherwise no
3150	of the monotonic clock option will be attempted. If you enable this, you	4605	use of the monotonic clock option will be attempted. If you enable this,
3151	usually have to link against librt or something similar. Enabling it when	4606	you usually have to link against librt or something similar. Enabling it
3152	the functionality isn't available is safe, though, although you have	4607	when the functionality isn't available is safe, though, although you have
3153	to make sure you link against any libraries where the C<clock_gettime>	4608	to make sure you link against any libraries where the C<clock_gettime>
3154	function is hiding in (often F<-lrt>).	4609	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3155		4610
3156	=item EV_USE_REALTIME	4611	=item EV_USE_REALTIME
3157		4612
3158	If defined to be C<1>, libev will try to detect the availability of the	4613	If defined to be C<1>, libev will try to detect the availability of the
3159	real-time clock option at compile time (and assume its availability at	4614	real-time clock option at compile time (and assume its availability
3160	runtime if successful). Otherwise no use of the real-time clock option will	4615	at runtime if successful). Otherwise no use of the real-time clock
3161	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4616	option will be attempted. This effectively replaces C<gettimeofday>
3162	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4617	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3163	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4618	correctness. See the note about libraries in the description of
		4619	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4620	C<EV_USE_CLOCK_SYSCALL>.
		4621
		4622	=item EV_USE_CLOCK_SYSCALL
		4623
		4624	If defined to be C<1>, libev will try to use a direct syscall instead
		4625	of calling the system-provided C<clock_gettime> function. This option
		4626	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4627	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4628	programs needlessly. Using a direct syscall is slightly slower (in
		4629	theory), because no optimised vdso implementation can be used, but avoids
		4630	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4631	higher, as it simplifies linking (no need for C<-lrt>).
3164		4632
3165	=item EV_USE_NANOSLEEP	4633	=item EV_USE_NANOSLEEP
3166		4634
3167	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4635	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3168	and will use it for delays. Otherwise it will use C<select ()>.	4636	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3173	available and will probe for kernel support at runtime. This will improve	4641	available and will probe for kernel support at runtime. This will improve
3174	C<ev_signal> and C<ev_async> performance and reduce resource consumption.	4642	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
3175	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc	4643	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
3176	2.7 or newer, otherwise disabled.	4644	2.7 or newer, otherwise disabled.
3177		4645
		4646	=item EV_USE_SIGNALFD
		4647
		4648	If defined to be C<1>, then libev will assume that C<signalfd ()> is
		4649	available and will probe for kernel support at runtime. This enables
		4650	the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If
		4651	undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4652	2.7 or newer, otherwise disabled.
		4653
		4654	=item EV_USE_TIMERFD
		4655
		4656	If defined to be C<1>, then libev will assume that C<timerfd ()> is
		4657	available and will probe for kernel support at runtime. This allows
		4658	libev to detect time jumps accurately. If undefined, it will be enabled
		4659	if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
		4660	C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled.
		4661
		4662	=item EV_USE_EVENTFD
		4663
		4664	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		4665	available and will probe for kernel support at runtime. This will improve
		4666	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		4667	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4668	2.7 or newer, otherwise disabled.
		4669
3178	=item EV_USE_SELECT	4670	=item EV_USE_SELECT
3179		4671
3180	If undefined or defined to be C<1>, libev will compile in support for the	4672	If undefined or defined to be C<1>, libev will compile in support for the
3181	C<select>(2) backend. No attempt at auto-detection will be done: if no	4673	C<select>(2) backend. No attempt at auto-detection will be done: if no
3182	other method takes over, select will be it. Otherwise the select backend	4674	other method takes over, select will be it. Otherwise the select backend
…		…
3184		4676
3185	=item EV_SELECT_USE_FD_SET	4677	=item EV_SELECT_USE_FD_SET
3186		4678
3187	If defined to C<1>, then the select backend will use the system C<fd_set>	4679	If defined to C<1>, then the select backend will use the system C<fd_set>
3188	structure. This is useful if libev doesn't compile due to a missing	4680	structure. This is useful if libev doesn't compile due to a missing
3189	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4681	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3190	exotic systems. This usually limits the range of file descriptors to some	4682	on exotic systems. This usually limits the range of file descriptors to
3191	low limit such as 1024 or might have other limitations (winsocket only	4683	some low limit such as 1024 or might have other limitations (winsocket
3192	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4684	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3193	influence the size of the C<fd_set> used.	4685	configures the maximum size of the C<fd_set>.
3194		4686
3195	=item EV_SELECT_IS_WINSOCKET	4687	=item EV_SELECT_IS_WINSOCKET
3196		4688
3197	When defined to C<1>, the select backend will assume that	4689	When defined to C<1>, the select backend will assume that
3198	select/socket/connect etc. don't understand file descriptors but	4690	select/socket/connect etc. don't understand file descriptors but
…		…
3200	be used is the winsock select). This means that it will call	4692	be used is the winsock select). This means that it will call
3201	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4693	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3202	it is assumed that all these functions actually work on fds, even	4694	it is assumed that all these functions actually work on fds, even
3203	on win32. Should not be defined on non-win32 platforms.	4695	on win32. Should not be defined on non-win32 platforms.
3204		4696
3205	=item EV_FD_TO_WIN32_HANDLE	4697	=item EV_FD_TO_WIN32_HANDLE(fd)
3206		4698
3207	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4699	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3208	file descriptors to socket handles. When not defining this symbol (the	4700	file descriptors to socket handles. When not defining this symbol (the
3209	default), then libev will call C<_get_osfhandle>, which is usually	4701	default), then libev will call C<_get_osfhandle>, which is usually
3210	correct. In some cases, programs use their own file descriptor management,	4702	correct. In some cases, programs use their own file descriptor management,
3211	in which case they can provide this function to map fds to socket handles.	4703	in which case they can provide this function to map fds to socket handles.
3212		4704
		4705	=item EV_WIN32_HANDLE_TO_FD(handle)
		4706
		4707	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4708	using the standard C<_open_osfhandle> function. For programs implementing
		4709	their own fd to handle mapping, overwriting this function makes it easier
		4710	to do so. This can be done by defining this macro to an appropriate value.
		4711
		4712	=item EV_WIN32_CLOSE_FD(fd)
		4713
		4714	If programs implement their own fd to handle mapping on win32, then this
		4715	macro can be used to override the C<close> function, useful to unregister
		4716	file descriptors again. Note that the replacement function has to close
		4717	the underlying OS handle.
		4718
		4719	=item EV_USE_WSASOCKET
		4720
		4721	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4722	communication socket, which works better in some environments. Otherwise,
		4723	the normal C<socket> function will be used, which works better in other
		4724	environments.
		4725
3213	=item EV_USE_POLL	4726	=item EV_USE_POLL
3214		4727
3215	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4728	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3216	backend. Otherwise it will be enabled on non-win32 platforms. It	4729	backend. Otherwise it will be enabled on non-win32 platforms. It
3217	takes precedence over select.	4730	takes precedence over select.
…		…
3221	If defined to be C<1>, libev will compile in support for the Linux	4734	If defined to be C<1>, libev will compile in support for the Linux
3222	C<epoll>(7) backend. Its availability will be detected at runtime,	4735	C<epoll>(7) backend. Its availability will be detected at runtime,
3223	otherwise another method will be used as fallback. This is the preferred	4736	otherwise another method will be used as fallback. This is the preferred
3224	backend for GNU/Linux systems. If undefined, it will be enabled if the	4737	backend for GNU/Linux systems. If undefined, it will be enabled if the
3225	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4738	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4739
		4740	=item EV_USE_LINUXAIO
		4741
		4742	If defined to be C<1>, libev will compile in support for the Linux aio
		4743	backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be
		4744	enabled on linux, otherwise disabled.
		4745
		4746	=item EV_USE_IOURING
		4747
		4748	If defined to be C<1>, libev will compile in support for the Linux
		4749	io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's
		4750	current limitations it has to be requested explicitly. If undefined, it
		4751	will be enabled on linux, otherwise disabled.
3226		4752
3227	=item EV_USE_KQUEUE	4753	=item EV_USE_KQUEUE
3228		4754
3229	If defined to be C<1>, libev will compile in support for the BSD style	4755	If defined to be C<1>, libev will compile in support for the BSD style
3230	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4756	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3252	If defined to be C<1>, libev will compile in support for the Linux inotify	4778	If defined to be C<1>, libev will compile in support for the Linux inotify
3253	interface to speed up C<ev_stat> watchers. Its actual availability will	4779	interface to speed up C<ev_stat> watchers. Its actual availability will
3254	be detected at runtime. If undefined, it will be enabled if the headers	4780	be detected at runtime. If undefined, it will be enabled if the headers
3255	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4781	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3256		4782
		4783	=item EV_NO_SMP
		4784
		4785	If defined to be C<1>, libev will assume that memory is always coherent
		4786	between threads, that is, threads can be used, but threads never run on
		4787	different cpus (or different cpu cores). This reduces dependencies
		4788	and makes libev faster.
		4789
		4790	=item EV_NO_THREADS
		4791
		4792	If defined to be C<1>, libev will assume that it will never be called from
		4793	different threads (that includes signal handlers), which is a stronger
		4794	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4795	libev faster.
		4796
3257	=item EV_ATOMIC_T	4797	=item EV_ATOMIC_T
3258		4798
3259	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4799	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3260	access is atomic with respect to other threads or signal contexts. No such	4800	access is atomic with respect to other threads or signal contexts. No
3261	type is easily found in the C language, so you can provide your own type	4801	such type is easily found in the C language, so you can provide your own
3262	that you know is safe for your purposes. It is used both for signal handler "locking"	4802	type that you know is safe for your purposes. It is used both for signal
3263	as well as for signal and thread safety in C<ev_async> watchers.	4803	handler "locking" as well as for signal and thread safety in C<ev_async>
		4804	watchers.
3264		4805
3265	In the absence of this define, libev will use C<sig_atomic_t volatile>	4806	In the absence of this define, libev will use C<sig_atomic_t volatile>
3266	(from F<signal.h>), which is usually good enough on most platforms.	4807	(from F<signal.h>), which is usually good enough on most platforms.
3267		4808
3268	=item EV_H	4809	=item EV_H (h)
3269		4810
3270	The name of the F<ev.h> header file used to include it. The default if	4811	The name of the F<ev.h> header file used to include it. The default if
3271	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4812	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3272	used to virtually rename the F<ev.h> header file in case of conflicts.	4813	used to virtually rename the F<ev.h> header file in case of conflicts.
3273		4814
3274	=item EV_CONFIG_H	4815	=item EV_CONFIG_H (h)
3275		4816
3276	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4817	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3277	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4818	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3278	C<EV_H>, above.	4819	C<EV_H>, above.
3279		4820
3280	=item EV_EVENT_H	4821	=item EV_EVENT_H (h)
3281		4822
3282	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4823	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3283	of how the F<event.h> header can be found, the default is C<"event.h">.	4824	of how the F<event.h> header can be found, the default is C<"event.h">.
3284		4825
3285	=item EV_PROTOTYPES	4826	=item EV_PROTOTYPES (h)
3286		4827
3287	If defined to be C<0>, then F<ev.h> will not define any function	4828	If defined to be C<0>, then F<ev.h> will not define any function
3288	prototypes, but still define all the structs and other symbols. This is	4829	prototypes, but still define all the structs and other symbols. This is
3289	occasionally useful if you want to provide your own wrapper functions	4830	occasionally useful if you want to provide your own wrapper functions
3290	around libev functions.	4831	around libev functions.
…		…
3295	will have the C<struct ev_loop *> as first argument, and you can create	4836	will have the C<struct ev_loop *> as first argument, and you can create
3296	additional independent event loops. Otherwise there will be no support	4837	additional independent event loops. Otherwise there will be no support
3297	for multiple event loops and there is no first event loop pointer	4838	for multiple event loops and there is no first event loop pointer
3298	argument. Instead, all functions act on the single default loop.	4839	argument. Instead, all functions act on the single default loop.
3299		4840
		4841	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4842	default loop when multiplicity is switched off - you always have to
		4843	initialise the loop manually in this case.
		4844
3300	=item EV_MINPRI	4845	=item EV_MINPRI
3301		4846
3302	=item EV_MAXPRI	4847	=item EV_MAXPRI
3303		4848
3304	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4849	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3312	fine.	4857	fine.
3313		4858
3314	If your embedding application does not need any priorities, defining these	4859	If your embedding application does not need any priorities, defining these
3315	both to C<0> will save some memory and CPU.	4860	both to C<0> will save some memory and CPU.
3316		4861
3317	=item EV_PERIODIC_ENABLE	4862	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4863	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4864	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3318		4865
3319	If undefined or defined to be C<1>, then periodic timers are supported. If	4866	If undefined or defined to be C<1> (and the platform supports it), then
3320	defined to be C<0>, then they are not. Disabling them saves a few kB of	4867	the respective watcher type is supported. If defined to be C<0>, then it
3321	code.	4868	is not. Disabling watcher types mainly saves code size.
3322		4869
3323	=item EV_IDLE_ENABLE	4870	=item EV_FEATURES
3324
3325	If undefined or defined to be C<1>, then idle watchers are supported. If
3326	defined to be C<0>, then they are not. Disabling them saves a few kB of
3327	code.
3328
3329	=item EV_EMBED_ENABLE
3330
3331	If undefined or defined to be C<1>, then embed watchers are supported. If
3332	defined to be C<0>, then they are not. Embed watchers rely on most other
3333	watcher types, which therefore must not be disabled.
3334
3335	=item EV_STAT_ENABLE
3336
3337	If undefined or defined to be C<1>, then stat watchers are supported. If
3338	defined to be C<0>, then they are not.
3339
3340	=item EV_FORK_ENABLE
3341
3342	If undefined or defined to be C<1>, then fork watchers are supported. If
3343	defined to be C<0>, then they are not.
3344
3345	=item EV_ASYNC_ENABLE
3346
3347	If undefined or defined to be C<1>, then async watchers are supported. If
3348	defined to be C<0>, then they are not.
3349
3350	=item EV_MINIMAL
3351		4871
3352	If you need to shave off some kilobytes of code at the expense of some	4872	If you need to shave off some kilobytes of code at the expense of some
3353	speed, define this symbol to C<1>. Currently this is used to override some	4873	speed (but with the full API), you can define this symbol to request
3354	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4874	certain subsets of functionality. The default is to enable all features
3355	much smaller 2-heap for timer management over the default 4-heap.	4875	that can be enabled on the platform.
		4876
		4877	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4878	with some broad features you want) and then selectively re-enable
		4879	additional parts you want, for example if you want everything minimal,
		4880	but multiple event loop support, async and child watchers and the poll
		4881	backend, use this:
		4882
		4883	#define EV_FEATURES 0
		4884	#define EV_MULTIPLICITY 1
		4885	#define EV_USE_POLL 1
		4886	#define EV_CHILD_ENABLE 1
		4887	#define EV_ASYNC_ENABLE 1
		4888
		4889	The actual value is a bitset, it can be a combination of the following
		4890	values (by default, all of these are enabled):
		4891
		4892	=over 4
		4893
		4894	=item C<1> - faster/larger code
		4895
		4896	Use larger code to speed up some operations.
		4897
		4898	Currently this is used to override some inlining decisions (enlarging the
		4899	code size by roughly 30% on amd64).
		4900
		4901	When optimising for size, use of compiler flags such as C<-Os> with
		4902	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4903	assertions.
		4904
		4905	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4906	(e.g. gcc with C<-Os>).
		4907
		4908	=item C<2> - faster/larger data structures
		4909
		4910	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4911	hash table sizes and so on. This will usually further increase code size
		4912	and can additionally have an effect on the size of data structures at
		4913	runtime.
		4914
		4915	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4916	(e.g. gcc with C<-Os>).
		4917
		4918	=item C<4> - full API configuration
		4919
		4920	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4921	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4922
		4923	=item C<8> - full API
		4924
		4925	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4926	details on which parts of the API are still available without this
		4927	feature, and do not complain if this subset changes over time.
		4928
		4929	=item C<16> - enable all optional watcher types
		4930
		4931	Enables all optional watcher types. If you want to selectively enable
		4932	only some watcher types other than I/O and timers (e.g. prepare,
		4933	embed, async, child...) you can enable them manually by defining
		4934	C<EV_watchertype_ENABLE> to C<1> instead.
		4935
		4936	=item C<32> - enable all backends
		4937
		4938	This enables all backends - without this feature, you need to enable at
		4939	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4940
		4941	=item C<64> - enable OS-specific "helper" APIs
		4942
		4943	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4944	default.
		4945
		4946	=back
		4947
		4948	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4949	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4950	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4951	watchers, timers and monotonic clock support.
		4952
		4953	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4954	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4955	your program might be left out as well - a binary starting a timer and an
		4956	I/O watcher then might come out at only 5Kb.
		4957
		4958	=item EV_API_STATIC
		4959
		4960	If this symbol is defined (by default it is not), then all identifiers
		4961	will have static linkage. This means that libev will not export any
		4962	identifiers, and you cannot link against libev anymore. This can be useful
		4963	when you embed libev, only want to use libev functions in a single file,
		4964	and do not want its identifiers to be visible.
		4965
		4966	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4967	wants to use libev.
		4968
		4969	This option only works when libev is compiled with a C compiler, as C++
		4970	doesn't support the required declaration syntax.
		4971
		4972	=item EV_AVOID_STDIO
		4973
		4974	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4975	functions (printf, scanf, perror etc.). This will increase the code size
		4976	somewhat, but if your program doesn't otherwise depend on stdio and your
		4977	libc allows it, this avoids linking in the stdio library which is quite
		4978	big.
		4979
		4980	Note that error messages might become less precise when this option is
		4981	enabled.
		4982
		4983	=item EV_NSIG
		4984
		4985	The highest supported signal number, +1 (or, the number of
		4986	signals): Normally, libev tries to deduce the maximum number of signals
		4987	automatically, but sometimes this fails, in which case it can be
		4988	specified. Also, using a lower number than detected (C<32> should be
		4989	good for about any system in existence) can save some memory, as libev
		4990	statically allocates some 12-24 bytes per signal number.
3356		4991
3357	=item EV_PID_HASHSIZE	4992	=item EV_PID_HASHSIZE
3358		4993
3359	C<ev_child> watchers use a small hash table to distribute workload by	4994	C<ev_child> watchers use a small hash table to distribute workload by
3360	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4995	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3361	than enough. If you need to manage thousands of children you might want to	4996	usually more than enough. If you need to manage thousands of children you
3362	increase this value (I<must> be a power of two).	4997	might want to increase this value (I<must> be a power of two).
3363		4998
3364	=item EV_INOTIFY_HASHSIZE	4999	=item EV_INOTIFY_HASHSIZE
3365		5000
3366	C<ev_stat> watchers use a small hash table to distribute workload by	5001	C<ev_stat> watchers use a small hash table to distribute workload by
3367	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	5002	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3368	usually more than enough. If you need to manage thousands of C<ev_stat>	5003	disabled), usually more than enough. If you need to manage thousands of
3369	watchers you might want to increase this value (I<must> be a power of	5004	C<ev_stat> watchers you might want to increase this value (I<must> be a
3370	two).	5005	power of two).
3371		5006
3372	=item EV_USE_4HEAP	5007	=item EV_USE_4HEAP
3373		5008
3374	Heaps are not very cache-efficient. To improve the cache-efficiency of the	5009	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3375	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	5010	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3376	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	5011	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3377	faster performance with many (thousands) of watchers.	5012	faster performance with many (thousands) of watchers.
3378		5013
3379	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	5014	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3380	(disabled).	5015	will be C<0>.
3381		5016
3382	=item EV_HEAP_CACHE_AT	5017	=item EV_HEAP_CACHE_AT
3383		5018
3384	Heaps are not very cache-efficient. To improve the cache-efficiency of the	5019	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3385	timer and periodics heaps, libev can cache the timestamp (I<at>) within	5020	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3386	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	5021	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3387	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	5022	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3388	but avoids random read accesses on heap changes. This improves performance	5023	but avoids random read accesses on heap changes. This improves performance
3389	noticeably with many (hundreds) of watchers.	5024	noticeably with many (hundreds) of watchers.
3390		5025
3391	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	5026	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3392	(disabled).	5027	will be C<0>.
3393		5028
3394	=item EV_VERIFY	5029	=item EV_VERIFY
3395		5030
3396	Controls how much internal verification (see C<ev_loop_verify ()>) will	5031	Controls how much internal verification (see C<ev_verify ()>) will
3397	be done: If set to C<0>, no internal verification code will be compiled	5032	be done: If set to C<0>, no internal verification code will be compiled
3398	in. If set to C<1>, then verification code will be compiled in, but not	5033	in. If set to C<1>, then verification code will be compiled in, but not
3399	called. If set to C<2>, then the internal verification code will be	5034	called. If set to C<2>, then the internal verification code will be
3400	called once per loop, which can slow down libev. If set to C<3>, then the	5035	called once per loop, which can slow down libev. If set to C<3>, then the
3401	verification code will be called very frequently, which will slow down	5036	verification code will be called very frequently, which will slow down
3402	libev considerably.	5037	libev considerably.
3403		5038
		5039	Verification errors are reported via C's C<assert> mechanism, so if you
		5040	disable that (e.g. by defining C<NDEBUG>) then no errors will be reported.
		5041
3404	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	5042	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3405	C<0>.	5043	will be C<0>.
3406		5044
3407	=item EV_COMMON	5045	=item EV_COMMON
3408		5046
3409	By default, all watchers have a C<void *data> member. By redefining	5047	By default, all watchers have a C<void *data> member. By redefining
3410	this macro to a something else you can include more and other types of	5048	this macro to something else you can include more and other types of
3411	members. You have to define it each time you include one of the files,	5049	members. You have to define it each time you include one of the files,
3412	though, and it must be identical each time.	5050	though, and it must be identical each time.
3413		5051
3414	For example, the perl EV module uses something like this:	5052	For example, the perl EV module uses something like this:
3415		5053
…		…
3468	file.	5106	file.
3469		5107
3470	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5108	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3471	that everybody includes and which overrides some configure choices:	5109	that everybody includes and which overrides some configure choices:
3472		5110
3473	#define EV_MINIMAL 1	5111	#define EV_FEATURES 8
3474	#define EV_USE_POLL 0	5112	#define EV_USE_SELECT 1
3475	#define EV_MULTIPLICITY 0
3476	#define EV_PERIODIC_ENABLE 0	5113	#define EV_PREPARE_ENABLE 1
		5114	#define EV_IDLE_ENABLE 1
3477	#define EV_STAT_ENABLE 0	5115	#define EV_SIGNAL_ENABLE 1
3478	#define EV_FORK_ENABLE 0	5116	#define EV_CHILD_ENABLE 1
		5117	#define EV_USE_STDEXCEPT 0
3479	#define EV_CONFIG_H <config.h>	5118	#define EV_CONFIG_H <config.h>
3480	#define EV_MINPRI 0
3481	#define EV_MAXPRI 0
3482		5119
3483	#include "ev++.h"	5120	#include "ev++.h"
3484		5121
3485	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5122	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3486		5123
3487	#include "ev_cpp.h"	5124	#include "ev_cpp.h"
3488	#include "ev.c"	5125	#include "ev.c"
3489		5126
3490	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5127	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3491		5128
3492	=head2 THREADS AND COROUTINES	5129	=head2 THREADS AND COROUTINES
3493		5130
3494	=head3 THREADS	5131	=head3 THREADS
3495		5132
…		…
3546	default loop and triggering an C<ev_async> watcher from the default loop	5183	default loop and triggering an C<ev_async> watcher from the default loop
3547	watcher callback into the event loop interested in the signal.	5184	watcher callback into the event loop interested in the signal.
3548		5185
3549	=back	5186	=back
3550		5187
		5188	See also L</THREAD LOCKING EXAMPLE>.
		5189
3551	=head3 COROUTINES	5190	=head3 COROUTINES
3552		5191
3553	Libev is very accommodating to coroutines ("cooperative threads"):	5192	Libev is very accommodating to coroutines ("cooperative threads"):
3554	libev fully supports nesting calls to its functions from different	5193	libev fully supports nesting calls to its functions from different
3555	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5194	coroutines (e.g. you can call C<ev_run> on the same loop from two
3556	different coroutines, and switch freely between both coroutines running the	5195	different coroutines, and switch freely between both coroutines running
3557	loop, as long as you don't confuse yourself). The only exception is that	5196	the loop, as long as you don't confuse yourself). The only exception is
3558	you must not do this from C<ev_periodic> reschedule callbacks.	5197	that you must not do this from C<ev_periodic> reschedule callbacks.
3559		5198
3560	Care has been taken to ensure that libev does not keep local state inside	5199	Care has been taken to ensure that libev does not keep local state inside
3561	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5200	C<ev_run>, and other calls do not usually allow for coroutine switches as
3562	they do not clal any callbacks.	5201	they do not call any callbacks.
3563		5202
3564	=head2 COMPILER WARNINGS	5203	=head2 COMPILER WARNINGS
3565		5204
3566	Depending on your compiler and compiler settings, you might get no or a	5205	Depending on your compiler and compiler settings, you might get no or a
3567	lot of warnings when compiling libev code. Some people are apparently	5206	lot of warnings when compiling libev code. Some people are apparently
…		…
3577	maintainable.	5216	maintainable.
3578		5217
3579	And of course, some compiler warnings are just plain stupid, or simply	5218	And of course, some compiler warnings are just plain stupid, or simply
3580	wrong (because they don't actually warn about the condition their message	5219	wrong (because they don't actually warn about the condition their message
3581	seems to warn about). For example, certain older gcc versions had some	5220	seems to warn about). For example, certain older gcc versions had some
3582	warnings that resulted an extreme number of false positives. These have	5221	warnings that resulted in an extreme number of false positives. These have
3583	been fixed, but some people still insist on making code warn-free with	5222	been fixed, but some people still insist on making code warn-free with
3584	such buggy versions.	5223	such buggy versions.
3585		5224
3586	While libev is written to generate as few warnings as possible,	5225	While libev is written to generate as few warnings as possible,
3587	"warn-free" code is not a goal, and it is recommended not to build libev	5226	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3601	==2274== definitely lost: 0 bytes in 0 blocks.	5240	==2274== definitely lost: 0 bytes in 0 blocks.
3602	==2274== possibly lost: 0 bytes in 0 blocks.	5241	==2274== possibly lost: 0 bytes in 0 blocks.
3603	==2274== still reachable: 256 bytes in 1 blocks.	5242	==2274== still reachable: 256 bytes in 1 blocks.
3604		5243
3605	Then there is no memory leak, just as memory accounted to global variables	5244	Then there is no memory leak, just as memory accounted to global variables
3606	is not a memleak - the memory is still being refernced, and didn't leak.	5245	is not a memleak - the memory is still being referenced, and didn't leak.
3607		5246
3608	Similarly, under some circumstances, valgrind might report kernel bugs	5247	Similarly, under some circumstances, valgrind might report kernel bugs
3609	as if it were a bug in libev (e.g. in realloc or in the poll backend,	5248	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3610	although an acceptable workaround has been found here), or it might be	5249	although an acceptable workaround has been found here), or it might be
3611	confused.	5250	confused.
…		…
3623	I suggest using suppression lists.	5262	I suggest using suppression lists.
3624		5263
3625		5264
3626	=head1 PORTABILITY NOTES	5265	=head1 PORTABILITY NOTES
3627		5266
		5267	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5268
		5269	GNU/Linux is the only common platform that supports 64 bit file/large file
		5270	interfaces but I<disables> them by default.
		5271
		5272	That means that libev compiled in the default environment doesn't support
		5273	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5274
		5275	Unfortunately, many programs try to work around this GNU/Linux issue
		5276	by enabling the large file API, which makes them incompatible with the
		5277	standard libev compiled for their system.
		5278
		5279	Likewise, libev cannot enable the large file API itself as this would
		5280	suddenly make it incompatible to the default compile time environment,
		5281	i.e. all programs not using special compile switches.
		5282
		5283	=head2 OS/X AND DARWIN BUGS
		5284
		5285	The whole thing is a bug if you ask me - basically any system interface
		5286	you touch is broken, whether it is locales, poll, kqueue or even the
		5287	OpenGL drivers.
		5288
		5289	=head3 C<kqueue> is buggy
		5290
		5291	The kqueue syscall is broken in all known versions - most versions support
		5292	only sockets, many support pipes.
		5293
		5294	Libev tries to work around this by not using C<kqueue> by default on this
		5295	rotten platform, but of course you can still ask for it when creating a
		5296	loop - embedding a socket-only kqueue loop into a select-based one is
		5297	probably going to work well.
		5298
		5299	=head3 C<poll> is buggy
		5300
		5301	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5302	implementation by something calling C<kqueue> internally around the 10.5.6
		5303	release, so now C<kqueue> I<and> C<poll> are broken.
		5304
		5305	Libev tries to work around this by not using C<poll> by default on
		5306	this rotten platform, but of course you can still ask for it when creating
		5307	a loop.
		5308
		5309	=head3 C<select> is buggy
		5310
		5311	All that's left is C<select>, and of course Apple found a way to fuck this
		5312	one up as well: On OS/X, C<select> actively limits the number of file
		5313	descriptors you can pass in to 1024 - your program suddenly crashes when
		5314	you use more.
		5315
		5316	There is an undocumented "workaround" for this - defining
		5317	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5318	work on OS/X.
		5319
		5320	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5321
		5322	=head3 C<errno> reentrancy
		5323
		5324	The default compile environment on Solaris is unfortunately so
		5325	thread-unsafe that you can't even use components/libraries compiled
		5326	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5327	defined by default. A valid, if stupid, implementation choice.
		5328
		5329	If you want to use libev in threaded environments you have to make sure
		5330	it's compiled with C<_REENTRANT> defined.
		5331
		5332	=head3 Event port backend
		5333
		5334	The scalable event interface for Solaris is called "event
		5335	ports". Unfortunately, this mechanism is very buggy in all major
		5336	releases. If you run into high CPU usage, your program freezes or you get
		5337	a large number of spurious wakeups, make sure you have all the relevant
		5338	and latest kernel patches applied. No, I don't know which ones, but there
		5339	are multiple ones to apply, and afterwards, event ports actually work
		5340	great.
		5341
		5342	If you can't get it to work, you can try running the program by setting
		5343	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5344	C<select> backends.
		5345
		5346	=head2 AIX POLL BUG
		5347
		5348	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5349	this by trying to avoid the poll backend altogether (i.e. it's not even
		5350	compiled in), which normally isn't a big problem as C<select> works fine
		5351	with large bitsets on AIX, and AIX is dead anyway.
		5352
3628	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5353	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5354
		5355	=head3 General issues
3629		5356
3630	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5357	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3631	requires, and its I/O model is fundamentally incompatible with the POSIX	5358	requires, and its I/O model is fundamentally incompatible with the POSIX
3632	model. Libev still offers limited functionality on this platform in	5359	model. Libev still offers limited functionality on this platform in
3633	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5360	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3634	descriptors. This only applies when using Win32 natively, not when using	5361	descriptors. This only applies when using Win32 natively, not when using
3635	e.g. cygwin.	5362	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5363	as every compiler comes with a slightly differently broken/incompatible
		5364	environment.
3636		5365
3637	Lifting these limitations would basically require the full	5366	Lifting these limitations would basically require the full
3638	re-implementation of the I/O system. If you are into these kinds of	5367	re-implementation of the I/O system. If you are into this kind of thing,
3639	things, then note that glib does exactly that for you in a very portable	5368	then note that glib does exactly that for you in a very portable way (note
3640	way (note also that glib is the slowest event library known to man).	5369	also that glib is the slowest event library known to man).
3641		5370
3642	There is no supported compilation method available on windows except	5371	There is no supported compilation method available on windows except
3643	embedding it into other applications.	5372	embedding it into other applications.
		5373
		5374	Sensible signal handling is officially unsupported by Microsoft - libev
		5375	tries its best, but under most conditions, signals will simply not work.
3644		5376
3645	Not a libev limitation but worth mentioning: windows apparently doesn't	5377	Not a libev limitation but worth mentioning: windows apparently doesn't
3646	accept large writes: instead of resulting in a partial write, windows will	5378	accept large writes: instead of resulting in a partial write, windows will
3647	either accept everything or return C<ENOBUFS> if the buffer is too large,	5379	either accept everything or return C<ENOBUFS> if the buffer is too large,
3648	so make sure you only write small amounts into your sockets (less than a	5380	so make sure you only write small amounts into your sockets (less than a
…		…
3653	the abysmal performance of winsockets, using a large number of sockets	5385	the abysmal performance of winsockets, using a large number of sockets
3654	is not recommended (and not reasonable). If your program needs to use	5386	is not recommended (and not reasonable). If your program needs to use
3655	more than a hundred or so sockets, then likely it needs to use a totally	5387	more than a hundred or so sockets, then likely it needs to use a totally
3656	different implementation for windows, as libev offers the POSIX readiness	5388	different implementation for windows, as libev offers the POSIX readiness
3657	notification model, which cannot be implemented efficiently on windows	5389	notification model, which cannot be implemented efficiently on windows
3658	(Microsoft monopoly games).	5390	(due to Microsoft monopoly games).
3659		5391
3660	A typical way to use libev under windows is to embed it (see the embedding	5392	A typical way to use libev under windows is to embed it (see the embedding
3661	section for details) and use the following F<evwrap.h> header file instead	5393	section for details) and use the following F<evwrap.h> header file instead
3662	of F<ev.h>:	5394	of F<ev.h>:
3663		5395
…		…
3670	you do I<not> compile the F<ev.c> or any other embedded source files!):	5402	you do I<not> compile the F<ev.c> or any other embedded source files!):
3671		5403
3672	#include "evwrap.h"	5404	#include "evwrap.h"
3673	#include "ev.c"	5405	#include "ev.c"
3674		5406
3675	=over 4
3676
3677	=item The winsocket select function	5407	=head3 The winsocket C<select> function
3678		5408
3679	The winsocket C<select> function doesn't follow POSIX in that it	5409	The winsocket C<select> function doesn't follow POSIX in that it
3680	requires socket I<handles> and not socket I<file descriptors> (it is	5410	requires socket I<handles> and not socket I<file descriptors> (it is
3681	also extremely buggy). This makes select very inefficient, and also	5411	also extremely buggy). This makes select very inefficient, and also
3682	requires a mapping from file descriptors to socket handles (the Microsoft	5412	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3691	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5421	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3692		5422
3693	Note that winsockets handling of fd sets is O(n), so you can easily get a	5423	Note that winsockets handling of fd sets is O(n), so you can easily get a
3694	complexity in the O(n²) range when using win32.	5424	complexity in the O(n²) range when using win32.
3695		5425
3696	=item Limited number of file descriptors	5426	=head3 Limited number of file descriptors
3697		5427
3698	Windows has numerous arbitrary (and low) limits on things.	5428	Windows has numerous arbitrary (and low) limits on things.
3699		5429
3700	Early versions of winsocket's select only supported waiting for a maximum	5430	Early versions of winsocket's select only supported waiting for a maximum
3701	of C<64> handles (probably owning to the fact that all windows kernels	5431	of C<64> handles (probably owning to the fact that all windows kernels
3702	can only wait for C<64> things at the same time internally; Microsoft	5432	can only wait for C<64> things at the same time internally; Microsoft
3703	recommends spawning a chain of threads and wait for 63 handles and the	5433	recommends spawning a chain of threads and wait for 63 handles and the
3704	previous thread in each. Great).	5434	previous thread in each. Sounds great!).
3705		5435
3706	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5436	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3707	to some high number (e.g. C<2048>) before compiling the winsocket select	5437	to some high number (e.g. C<2048>) before compiling the winsocket select
3708	call (which might be in libev or elsewhere, for example, perl does its own	5438	call (which might be in libev or elsewhere, for example, perl and many
3709	select emulation on windows).	5439	other interpreters do their own select emulation on windows).
3710		5440
3711	Another limit is the number of file descriptors in the Microsoft runtime	5441	Another limit is the number of file descriptors in the Microsoft runtime
3712	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5442	libraries, which by default is C<64> (there must be a hidden I<64>
3713	or something like this inside Microsoft). You can increase this by calling	5443	fetish or something like this inside Microsoft). You can increase this
3714	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5444	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3715	arbitrary limit), but is broken in many versions of the Microsoft runtime	5445	(another arbitrary limit), but is broken in many versions of the Microsoft
3716	libraries.
3717
3718	This might get you to about C<512> or C<2048> sockets (depending on	5446	runtime libraries. This might get you to about C<512> or C<2048> sockets
3719	windows version and/or the phase of the moon). To get more, you need to	5447	(depending on windows version and/or the phase of the moon). To get more,
3720	wrap all I/O functions and provide your own fd management, but the cost of	5448	you need to wrap all I/O functions and provide your own fd management, but
3721	calling select (O(n²)) will likely make this unworkable.	5449	the cost of calling select (O(n²)) will likely make this unworkable.
3722
3723	=back
3724		5450
3725	=head2 PORTABILITY REQUIREMENTS	5451	=head2 PORTABILITY REQUIREMENTS
3726		5452
3727	In addition to a working ISO-C implementation and of course the	5453	In addition to a working ISO-C implementation and of course the
3728	backend-specific APIs, libev relies on a few additional extensions:	5454	backend-specific APIs, libev relies on a few additional extensions:
…		…
3735	Libev assumes not only that all watcher pointers have the same internal	5461	Libev assumes not only that all watcher pointers have the same internal
3736	structure (guaranteed by POSIX but not by ISO C for example), but it also	5462	structure (guaranteed by POSIX but not by ISO C for example), but it also
3737	assumes that the same (machine) code can be used to call any watcher	5463	assumes that the same (machine) code can be used to call any watcher
3738	callback: The watcher callbacks have different type signatures, but libev	5464	callback: The watcher callbacks have different type signatures, but libev
3739	calls them using an C<ev_watcher *> internally.	5465	calls them using an C<ev_watcher *> internally.
		5466
		5467	=item null pointers and integer zero are represented by 0 bytes
		5468
		5469	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5470	relies on this setting pointers and integers to null.
		5471
		5472	=item pointer accesses must be thread-atomic
		5473
		5474	Accessing a pointer value must be atomic, it must both be readable and
		5475	writable in one piece - this is the case on all current architectures.
3740		5476
3741	=item C<sig_atomic_t volatile> must be thread-atomic as well	5477	=item C<sig_atomic_t volatile> must be thread-atomic as well
3742		5478
3743	The type C<sig_atomic_t volatile> (or whatever is defined as	5479	The type C<sig_atomic_t volatile> (or whatever is defined as
3744	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5480	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3753	thread" or will block signals process-wide, both behaviours would	5489	thread" or will block signals process-wide, both behaviours would
3754	be compatible with libev. Interaction between C<sigprocmask> and	5490	be compatible with libev. Interaction between C<sigprocmask> and
3755	C<pthread_sigmask> could complicate things, however.	5491	C<pthread_sigmask> could complicate things, however.
3756		5492
3757	The most portable way to handle signals is to block signals in all threads	5493	The most portable way to handle signals is to block signals in all threads
3758	except the initial one, and run the default loop in the initial thread as	5494	except the initial one, and run the signal handling loop in the initial
3759	well.	5495	thread as well.
3760		5496
3761	=item C<long> must be large enough for common memory allocation sizes	5497	=item C<long> must be large enough for common memory allocation sizes
3762		5498
3763	To improve portability and simplify its API, libev uses C<long> internally	5499	To improve portability and simplify its API, libev uses C<long> internally
3764	instead of C<size_t> when allocating its data structures. On non-POSIX	5500	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3767	watchers.	5503	watchers.
3768		5504
3769	=item C<double> must hold a time value in seconds with enough accuracy	5505	=item C<double> must hold a time value in seconds with enough accuracy
3770		5506
3771	The type C<double> is used to represent timestamps. It is required to	5507	The type C<double> is used to represent timestamps. It is required to
3772	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5508	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3773	enough for at least into the year 4000. This requirement is fulfilled by	5509	good enough for at least into the year 4000 with millisecond accuracy
		5510	(the design goal for libev). This requirement is overfulfilled by
3774	implementations implementing IEEE 754 (basically all existing ones).	5511	implementations using IEEE 754, which is basically all existing ones.
		5512
		5513	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5514	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5515	is either obsolete or somebody patched it to use C<long double> or
		5516	something like that, just kidding).
3775		5517
3776	=back	5518	=back
3777		5519
3778	If you know of other additional requirements drop me a note.	5520	If you know of other additional requirements drop me a note.
3779		5521
…		…
3841	=item Processing ev_async_send: O(number_of_async_watchers)	5583	=item Processing ev_async_send: O(number_of_async_watchers)
3842		5584
3843	=item Processing signals: O(max_signal_number)	5585	=item Processing signals: O(max_signal_number)
3844		5586
3845	Sending involves a system call I<iff> there were no other C<ev_async_send>	5587	Sending involves a system call I<iff> there were no other C<ev_async_send>
3846	calls in the current loop iteration. Checking for async and signal events	5588	calls in the current loop iteration and the loop is currently
		5589	blocked. Checking for async and signal events involves iterating over all
3847	involves iterating over all running async watchers or all signal numbers.	5590	running async watchers or all signal numbers.
3848		5591
3849	=back	5592	=back
3850		5593
3851		5594
		5595	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5596
		5597	The major version 4 introduced some incompatible changes to the API.
		5598
		5599	At the moment, the C<ev.h> header file provides compatibility definitions
		5600	for all changes, so most programs should still compile. The compatibility
		5601	layer might be removed in later versions of libev, so better update to the
		5602	new API early than late.
		5603
		5604	=over 4
		5605
		5606	=item C<EV_COMPAT3> backwards compatibility mechanism
		5607
		5608	The backward compatibility mechanism can be controlled by
		5609	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5610	section.
		5611
		5612	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5613
		5614	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5615
		5616	ev_loop_destroy (EV_DEFAULT_UC);
		5617	ev_loop_fork (EV_DEFAULT);
		5618
		5619	=item function/symbol renames
		5620
		5621	A number of functions and symbols have been renamed:
		5622
		5623	ev_loop => ev_run
		5624	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5625	EVLOOP_ONESHOT => EVRUN_ONCE
		5626
		5627	ev_unloop => ev_break
		5628	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5629	EVUNLOOP_ONE => EVBREAK_ONE
		5630	EVUNLOOP_ALL => EVBREAK_ALL
		5631
		5632	EV_TIMEOUT => EV_TIMER
		5633
		5634	ev_loop_count => ev_iteration
		5635	ev_loop_depth => ev_depth
		5636	ev_loop_verify => ev_verify
		5637
		5638	Most functions working on C<struct ev_loop> objects don't have an
		5639	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5640	associated constants have been renamed to not collide with the C<struct
		5641	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5642	as all other watcher types. Note that C<ev_loop_fork> is still called
		5643	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5644	typedef.
		5645
		5646	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5647
		5648	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5649	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5650	and work, but the library code will of course be larger.
		5651
		5652	=back
		5653
		5654
		5655	=head1 GLOSSARY
		5656
		5657	=over 4
		5658
		5659	=item active
		5660
		5661	A watcher is active as long as it has been started and not yet stopped.
		5662	See L</WATCHER STATES> for details.
		5663
		5664	=item application
		5665
		5666	In this document, an application is whatever is using libev.
		5667
		5668	=item backend
		5669
		5670	The part of the code dealing with the operating system interfaces.
		5671
		5672	=item callback
		5673
		5674	The address of a function that is called when some event has been
		5675	detected. Callbacks are being passed the event loop, the watcher that
		5676	received the event, and the actual event bitset.
		5677
		5678	=item callback/watcher invocation
		5679
		5680	The act of calling the callback associated with a watcher.
		5681
		5682	=item event
		5683
		5684	A change of state of some external event, such as data now being available
		5685	for reading on a file descriptor, time having passed or simply not having
		5686	any other events happening anymore.
		5687
		5688	In libev, events are represented as single bits (such as C<EV_READ> or
		5689	C<EV_TIMER>).
		5690
		5691	=item event library
		5692
		5693	A software package implementing an event model and loop.
		5694
		5695	=item event loop
		5696
		5697	An entity that handles and processes external events and converts them
		5698	into callback invocations.
		5699
		5700	=item event model
		5701
		5702	The model used to describe how an event loop handles and processes
		5703	watchers and events.
		5704
		5705	=item pending
		5706
		5707	A watcher is pending as soon as the corresponding event has been
		5708	detected. See L</WATCHER STATES> for details.
		5709
		5710	=item real time
		5711
		5712	The physical time that is observed. It is apparently strictly monotonic :)
		5713
		5714	=item wall-clock time
		5715
		5716	The time and date as shown on clocks. Unlike real time, it can actually
		5717	be wrong and jump forwards and backwards, e.g. when you adjust your
		5718	clock.
		5719
		5720	=item watcher
		5721
		5722	A data structure that describes interest in certain events. Watchers need
		5723	to be started (attached to an event loop) before they can receive events.
		5724
		5725	=back
		5726
3852	=head1 AUTHOR	5727	=head1 AUTHOR
3853		5728
3854	Marc Lehmann <libev@schmorp.de>.	5729	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5730	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3855		5731

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