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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).	535	fd), epoll scales either O(1) or O(active_fds).
390		536
391	The epoll syscalls are the most misdesigned of the more advanced event	537	The epoll mechanism deserves honorable mention as the most misdesigned
392	mechanisms: problems include silently dropping fds, requiring a system	538	of the more advanced event mechanisms: mere annoyances include silently
		539	dropping file descriptors, requiring a system call per change per file
393	call per change per fd (and unnecessary guessing of parameters), problems	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
394	with dup and so on. The biggest issue is fork races, however - if a	543	0.1ms) and so on. The biggest issue is fork races, however - if a program
395	program forks then I<both> parent and child process have to recreate the	544	forks then I<both> parent and child process have to recreate the epoll
396	epoll set, which can take considerable time (one syscall per fd) and is of	545	set, which can take considerable time (one syscall per file descriptor)
397	course hard to detect.	546	and is of course hard to detect.
398		547
399	Epoll is also notoriously buggy - embedding epoll fds should work, but	548	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
400	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
401	I<different> file descriptors (even already closed ones, so one cannot	550	totally I<different> file descriptors (even already closed ones, so
402	even remove them from the set) than registered in the set (especially	551	one cannot even remove them from the set) than registered in the set
403	on SMP systems). Libev tries to counter these spurious notifications by	552	(especially on SMP systems). Libev tries to counter these spurious
404	employing an additional generation counter and comparing that against the	553	notifications by employing an additional generation counter and comparing
405	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...
406		564
407	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
408	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
409	(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
410	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
411	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.
412		571
413	Best performance from this backend is achieved by not unregistering all	572	Best performance from this backend is achieved by not unregistering all
414	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,
415	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
416	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
417	extra overhead. A fork can both result in spurious notifications as well	576	extra overhead. A fork can both result in spurious notifications as well
418	as in libev having to destroy and recreate the epoll object, which can	577	as in libev having to destroy and recreate the epoll object, which can
419	take considerable time and thus should be avoided.	578	take considerable time and thus should be avoided.
420		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.
		583
421	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
422	all kernel versions tested so far.	585	a lot of kernel revisions, but probably(!) works in current versions.
423		586
424	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
425	C<EVBACKEND_POLL>.	588	C<EVBACKEND_POLL>.
426		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
427	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	634	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
428		635
429	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
430	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
431	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,
432	completely useless). For this reason it's not being "auto-detected" unless	639	where of course it's completely useless). Unlike epoll, however, whose
433	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
434	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	644	known-to-be-good (-enough) system like NetBSD.
435		645
436	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
437	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
438	the target platform). See C<ev_embed> watchers for more info.	648	the target platform). See C<ev_embed> watchers for more info.
439		649
440	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
441	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
442	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
443	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
444	two event changes per incident. Support for C<fork ()> is very bad (but	654	two event changes per incident. Support for C<fork ()> is very bad (you
445	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	655	might have to leak fds on fork, but it's more sane than epoll) and it
446	cases	656	drops fds silently in similarly hard-to-detect cases.
447		657
448	This backend usually performs well under most conditions.	658	This backend usually performs well under most conditions.
449		659
450	While nominally embeddable in other event loops, this doesn't work	660	While nominally embeddable in other event loops, this doesn't work
451	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
452	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
453	(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
454	(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
455	using it only for sockets.	665	also broken on OS X)) and, did I mention it, using it only for sockets.
456		666
457	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
458	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
459	C<NOTE_EOF>.	669	C<NOTE_EOF>.
460		670
…		…
468	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	678	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
469		679
470	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,
471	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)).
472		682
473	Please note that Solaris event ports can deliver a lot of spurious
474	notifications, so you need to use non-blocking I/O or other means to avoid
475	blocking when no data (or space) is available.
476
477	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
478	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
479	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	685	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
480	might perform better.	686	might perform better.
481		687
482	On the positive side, with the exception of the spurious readiness	688	On the positive side, this backend actually performed fully to
483	notifications, this backend actually performed fully to specification
484	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
485	OS-specific backends (I vastly prefer correctness over speed hacks).	690	among the OS-specific backends (I vastly prefer correctness over speed
		691	hacks).
		692
		693	On the negative side, the interface is I<bizarre> - so bizarre that
		694	even sun itself gets it wrong in their code examples: The event polling
		695	function sometimes returns events to the caller even though an error
		696	occurred, but with no indication whether it has done so or not (yes, it's
		697	even documented that way) - deadly for edge-triggered interfaces where you
		698	absolutely have to know whether an event occurred or not because you have
		699	to re-arm the watcher.
		700
		701	Fortunately libev seems to be able to work around these idiocies.
486		702
487	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
488	C<EVBACKEND_POLL>.	704	C<EVBACKEND_POLL>.
489		705
490	=item C<EVBACKEND_ALL>	706	=item C<EVBACKEND_ALL>
491		707
492	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
493	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
494	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	710	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
495		711
496	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).
497		721
498	=back	722	=back
499		723
500	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,
501	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
502	specified, all backends in C<ev_recommended_backends ()> will be tried.	726	here). If none are specified, all backends in C<ev_recommended_backends
503		727	()> will be tried.
504	Example: This is the most typical usage.
505
506	if (!ev_default_loop (0))
507	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
508
509	Example: Restrict libev to the select and poll backends, and do not allow
510	environment settings to be taken into account:
511
512	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
513
514	Example: Use whatever libev has to offer, but make sure that kqueue is
515	used if available (warning, breaks stuff, best use only with your own
516	private event loop and only if you know the OS supports your types of
517	fds):
518
519	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
520
521	=item struct ev_loop *ev_loop_new (unsigned int flags)
522
523	Similar to C<ev_default_loop>, but always creates a new event loop that is
524	always distinct from the default loop. Unlike the default loop, it cannot
525	handle signal and child watchers, and attempts to do so will be greeted by
526	undefined behaviour (or a failed assertion if assertions are enabled).
527
528	Note that this function I<is> thread-safe, and the recommended way to use
529	libev with threads is indeed to create one loop per thread, and using the
530	default loop in the "main" or "initial" thread.
531		728
532	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.
533		730
534	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	731	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
535	if (!epoller)	732	if (!epoller)
536	fatal ("no epoll found here, maybe it hides under your chair");	733	fatal ("no epoll found here, maybe it hides under your chair");
537		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
538	=item ev_default_destroy ()	746	=item ev_loop_destroy (loop)
539		747
540	Destroys the default loop again (frees all memory and kernel state	748	Destroys an event loop object (frees all memory and kernel state
541	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
542	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
543	responsibility to either stop all watchers cleanly yourself I<before>	751	responsibility to either stop all watchers cleanly yourself I<before>
544	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
545	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
…		…
547		755
548	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
549	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
550	as signal and child watchers) would need to be stopped manually.	758	as signal and child watchers) would need to be stopped manually.
551		759
552	In general it is not advisable to call this function except in the	760	This function is normally used on loop objects allocated by
553	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.
554	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>
555	C<ev_loop_new> and C<ev_loop_destroy>).	767	and C<ev_loop_destroy>.
556		768
557	=item ev_loop_destroy (loop)	769	=item ev_loop_fork (loop)
558		770
559	Like C<ev_default_destroy>, but destroys an event loop created by an
560	earlier call to C<ev_loop_new>.
561
562	=item ev_default_fork ()
563
564	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
565	to reinitialise the kernel state for backends that have one. Despite the	772	to reinitialise the kernel state for backends that have one. Despite
566	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
567	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
568	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
569	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.
570		785
571	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
572	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
573	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).
574		792
575	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
576	it just in case after a fork. To make this easy, the function will fit in	794	it just in case after a fork.
577	quite nicely into a call to C<pthread_atfork>:
578		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	...
579	pthread_atfork (0, 0, ev_default_fork);	806	pthread_atfork (0, 0, post_fork_child);
580
581	=item ev_loop_fork (loop)
582
583	Like C<ev_default_fork>, but acts on an event loop created by
584	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
585	after fork that you want to re-use in the child, and how you do this is
586	entirely your own problem.
587		807
588	=item int ev_is_default_loop (loop)	808	=item int ev_is_default_loop (loop)
589		809
590	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
591	otherwise.	811	otherwise.
592		812
593	=item unsigned int ev_loop_count (loop)	813	=item unsigned int ev_iteration (loop)
594		814
595	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
596	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>
597	happily wraps around with enough iterations.	817	and happily wraps around with enough iterations.
598		818
599	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
600	"ticks" the number of loop iterations), as it roughly corresponds with	820	"ticks" the number of loop iterations), as it roughly corresponds with
601	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.
602		837
603	=item unsigned int ev_backend (loop)	838	=item unsigned int ev_backend (loop)
604		839
605	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
606	use.	841	use.
…		…
615		850
616	=item ev_now_update (loop)	851	=item ev_now_update (loop)
617		852
618	Establishes the current time by querying the kernel, updating the time	853	Establishes the current time by querying the kernel, updating the time
619	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
620	is usually done automatically within C<ev_loop ()>.	855	is usually done automatically within C<ev_run ()>.
621		856
622	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
623	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
624	the current time is a good idea.	859	the current time is a good idea.
625		860
626	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.
627		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
628	=item ev_loop (loop, int flags)	889	=item bool ev_run (loop, int flags)
629		890
630	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
631	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
632	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>.
633		896
634	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
635	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.
636		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
637	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
638	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
639	finished (especially in interactive programs), but having a program	907	finished (especially in interactive programs), but having a program
640	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
641	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
642	beauty.	910	beauty.
643		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
644	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
645	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
646	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
647	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.
648		922
649	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
650	necessary) and will handle those and any already outstanding ones. It	924	necessary) and will handle those and any already outstanding ones. It
651	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
652	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
653	user-registered callback will be called), and will return after one	927	user-registered callback will be called), and will return after one
654	iteration of the loop.	928	iteration of the loop.
655		929
656	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
657	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
658	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
659	usually a better approach for this kind of thing.	933	usually a better approach for this kind of thing.
660		934
661	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):
662		938
		939	- Increment loop depth.
		940	- Reset the ev_break status.
663	- Before the first iteration, call any pending watchers.	941	- Before the first iteration, call any pending watchers.
		942	LOOP:
664	* If EVFLAG_FORKCHECK was used, check for a fork.	943	- If EVFLAG_FORKCHECK was used, check for a fork.
665	- 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.
666	- Queue and call all prepare watchers.	945	- Queue and call all prepare watchers.
		946	- If ev_break was called, goto FINISH.
667	- If we have been forked, detach and recreate the kernel state	947	- If we have been forked, detach and recreate the kernel state
668	as to not disturb the other process.	948	as to not disturb the other process.
669	- Update the kernel state with all outstanding changes.	949	- Update the kernel state with all outstanding changes.
670	- Update the "event loop time" (ev_now ()).	950	- Update the "event loop time" (ev_now ()).
671	- Calculate for how long to sleep or block, if at all	951	- Calculate for how long to sleep or block, if at all
672	(active idle watchers, EVLOOP_NONBLOCK or not having	952	(active idle watchers, EVRUN_NOWAIT or not having
673	any active watchers at all will result in not sleeping).	953	any active watchers at all will result in not sleeping).
674	- 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.
675	- Block the process, waiting for any events.	956	- Block the process, waiting for any events.
676	- Queue all outstanding I/O (fd) events.	957	- Queue all outstanding I/O (fd) events.
677	- 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.
678	- Queue all expired timers.	959	- Queue all expired timers.
679	- Queue all expired periodics.	960	- Queue all expired periodics.
680	- Unless any events are pending now, queue all idle watchers.	961	- Queue all idle watchers with priority higher than that of pending events.
681	- Queue all check watchers.	962	- Queue all check watchers.
682	- 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).
683	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
684	be handled here by queueing them when their watcher gets executed.	965	be handled here by queueing them when their watcher gets executed.
685	- 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
686	were used, or there are no active watchers, return, otherwise	967	were used, or there are no active watchers, goto FINISH, otherwise
687	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.
688		973
689	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
690	anymore.	975	anymore.
691		976
692	... queue jobs here, make sure they register event watchers as long	977	... queue jobs here, make sure they register event watchers as long
693	... 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..)
694	ev_loop (my_loop, 0);	979	ev_run (my_loop, 0);
695	... jobs done or somebody called unloop. yeah!	980	... jobs done or somebody called break. yeah!
696		981
697	=item ev_unloop (loop, how)	982	=item ev_break (loop, how)
698		983
699	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
700	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
701	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
702	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.
703		988
704	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>.
705		990
706	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.
707		993
708	=item ev_ref (loop)	994	=item ev_ref (loop)
709		995
710	=item ev_unref (loop)	996	=item ev_unref (loop)
711		997
712	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
713	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
714	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.
715		1001
716	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
717	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>
718	stopping it.	1005	before stopping it.
719		1006
720	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
721	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
722	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
723	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
724	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
725	(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
726	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).
727		1016
728	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>
729	running when nothing else is active.	1018	running when nothing else is active.
730		1019
731	ev_signal exitsig;	1020	ev_signal exitsig;
732	ev_signal_init (&exitsig, sig_cb, SIGINT);	1021	ev_signal_init (&exitsig, sig_cb, SIGINT);
733	ev_signal_start (loop, &exitsig);	1022	ev_signal_start (loop, &exitsig);
734	evf_unref (loop);	1023	ev_unref (loop);
735		1024
736	Example: For some weird reason, unregister the above signal handler again.	1025	Example: For some weird reason, unregister the above signal handler again.
737		1026
738	ev_ref (loop);	1027	ev_ref (loop);
739	ev_signal_stop (loop, &exitsig);	1028	ev_signal_stop (loop, &exitsig);
…		…
759	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.
760		1049
761	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
762	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,
763	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
764	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
765	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).
766		1058
767	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
768	to spend more time collecting timeouts, at the expense of increased	1060	to spend more time collecting timeouts, at the expense of increased
769	latency/jitter/inexactness (the watcher callback will be called	1061	latency/jitter/inexactness (the watcher callback will be called
770	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
…		…
772		1064
773	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
774	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
775	interactive servers (of course not for games), likewise for timeouts. It	1067	interactive servers (of course not for games), likewise for timeouts. It
776	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>,
777	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).
778		1074
779	Setting the I<timeout collect interval> can improve the opportunity for	1075	Setting the I<timeout collect interval> can improve the opportunity for
780	saving power, as the program will "bundle" timer callback invocations that	1076	saving power, as the program will "bundle" timer callback invocations that
781	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
782	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
783	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
784	they fire on, say, one-second boundaries only.	1080	they fire on, say, one-second boundaries only.
785		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
786	=item ev_loop_verify (loop)	1157	=item ev_verify (loop)
787		1158
788	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
789	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
790	through all internal structures and checks them for validity. If anything	1161	through all internal structures and checks them for validity. If anything
791	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
…		…
802		1173
803	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
804	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
805	watchers and C<ev_io_start> for I/O watchers.	1176	watchers and C<ev_io_start> for I/O watchers.
806		1177
807	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
808	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
809	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:
810		1182
811	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)
812	{	1184	{
813	ev_io_stop (w);	1185	ev_io_stop (w);
814	ev_unloop (loop, EVUNLOOP_ALL);	1186	ev_break (loop, EVBREAK_ALL);
815	}	1187	}
816		1188
817	struct ev_loop *loop = ev_default_loop (0);	1189	struct ev_loop *loop = ev_default_loop (0);
818		1190
819	ev_io stdin_watcher;	1191	ev_io stdin_watcher;
820		1192
821	ev_init (&stdin_watcher, my_cb);	1193	ev_init (&stdin_watcher, my_cb);
822	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1194	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
823	ev_io_start (loop, &stdin_watcher);	1195	ev_io_start (loop, &stdin_watcher);
824		1196
825	ev_loop (loop, 0);	1197	ev_run (loop, 0);
826		1198
827	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
828	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
829	stack).	1201	stack).
830		1202
831	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>
832	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).
833		1205
834	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
835	(watcher *, callback)>, which expects a callback to be provided. This	1207	*, callback)>, which expects a callback to be provided. This callback is
836	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
837	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
838	is readable and/or writable).	1210	and/or writable).
839		1211
840	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 *, ...) >>
841	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
842	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<<
843	ev_TYPE_init (watcher *, callback, ...) >>.	1215	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
846	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
847	*) >>), 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
848	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.	1220	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
849		1221
850	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
851	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
852	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.
853		1226
854	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
855	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
856	third argument.	1229	third argument.
857		1230
…		…
866	=item C<EV_WRITE>	1239	=item C<EV_WRITE>
867		1240
868	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
869	writable.	1242	writable.
870		1243
871	=item C<EV_TIMEOUT>	1244	=item C<EV_TIMER>
872		1245
873	The C<ev_timer> watcher has timed out.	1246	The C<ev_timer> watcher has timed out.
874		1247
875	=item C<EV_PERIODIC>	1248	=item C<EV_PERIODIC>
876		1249
…		…
894		1267
895	=item C<EV_PREPARE>	1268	=item C<EV_PREPARE>
896		1269
897	=item C<EV_CHECK>	1270	=item C<EV_CHECK>
898		1271
899	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
900	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)
901	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
902	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
903	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
904	(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
905	C<ev_loop> from blocking).	1283	blocking).
906		1284
907	=item C<EV_EMBED>	1285	=item C<EV_EMBED>
908		1286
909	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.
910		1288
911	=item C<EV_FORK>	1289	=item C<EV_FORK>
912		1290
913	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
914	C<ev_fork>).	1292	C<ev_fork>).
915		1293
		1294	=item C<EV_CLEANUP>
		1295
		1296	The event loop is about to be destroyed (see C<ev_cleanup>).
		1297
916	=item C<EV_ASYNC>	1298	=item C<EV_ASYNC>
917		1299
918	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>).
919		1306
920	=item C<EV_ERROR>	1307	=item C<EV_ERROR>
921		1308
922	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
923	happen because the watcher could not be properly started because libev	1310	happen because the watcher could not be properly started because libev
…		…
961		1348
962	ev_io w;	1349	ev_io w;
963	ev_init (&w, my_cb);	1350	ev_init (&w, my_cb);
964	ev_io_set (&w, STDIN_FILENO, EV_READ);	1351	ev_io_set (&w, STDIN_FILENO, EV_READ);
965		1352
966	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1353	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
967		1354
968	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
969	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
970	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
971	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
…		…
984		1371
985	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.
986		1373
987	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1374	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
988		1375
989	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1376	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
990		1377
991	Starts (activates) the given watcher. Only active watchers will receive	1378	Starts (activates) the given watcher. Only active watchers will receive
992	events. If the watcher is already active nothing will happen.	1379	events. If the watcher is already active nothing will happen.
993		1380
994	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
995	whole section.	1382	whole section.
996		1383
997	ev_io_start (EV_DEFAULT_UC, &w);	1384	ev_io_start (EV_DEFAULT_UC, &w);
998		1385
999	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1386	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1000		1387
1001	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
1002	the watcher was active or not).	1389	the watcher was active or not).
1003		1390
1004	It is possible that stopped watchers are pending - for example,	1391	It is possible that stopped watchers are pending - for example,
…		…
1024		1411
1025	=item callback ev_cb (ev_TYPE *watcher)	1412	=item callback ev_cb (ev_TYPE *watcher)
1026		1413
1027	Returns the callback currently set on the watcher.	1414	Returns the callback currently set on the watcher.
1028		1415
1029	=item ev_cb_set (ev_TYPE *watcher, callback)	1416	=item ev_set_cb (ev_TYPE *watcher, callback)
1030		1417
1031	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
1032	(modulo threads).	1419	(modulo threads).
1033		1420
1034	=item ev_set_priority (ev_TYPE *watcher, priority)	1421	=item ev_set_priority (ev_TYPE *watcher, int priority)
1035		1422
1036	=item int ev_priority (ev_TYPE *watcher)	1423	=item int ev_priority (ev_TYPE *watcher)
1037		1424
1038	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
1039	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>
1040	(default: C<-2>). Pending watchers with higher priority will be invoked	1427	(default: C<-2>). Pending watchers with higher priority will be invoked
1041	before watchers with lower priority, but priority will not keep watchers	1428	before watchers with lower priority, but priority will not keep watchers
1042	from being executed (except for C<ev_idle> watchers).	1429	from being executed (except for C<ev_idle> watchers).
1043		1430
1044	This means that priorities are I<only> used for ordering callback
1045	invocation after new events have been received. This is useful, for
1046	example, to reduce latency after idling, or more often, to bind two
1047	watchers on the same event and make sure one is called first.
1048
1049	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
1050	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.
1051		1433
1052	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
1053	pending.	1435	pending.
1054
1055	The default priority used by watchers when no priority has been set is
1056	always C<0>, which is supposed to not be too high and not be too low :).
1057		1436
1058	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
1059	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
1060	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.
1061		1446
1062	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1447	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1063		1448
1064	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
1065	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
…		…
1073	watcher isn't pending it does nothing and returns C<0>.	1458	watcher isn't pending it does nothing and returns C<0>.
1074		1459
1075	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
1076	callback to be invoked, which can be accomplished with this function.	1461	callback to be invoked, which can be accomplished with this function.
1077		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
1078	=back	1477	=back
1079		1478
		1479	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1480	OWN COMPOSITE WATCHERS> idioms.
1080		1481
1081	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1482	=head2 WATCHER STATES
1082		1483
1083	Each watcher has, by default, a member C<void *data> that you can change	1484	There are various watcher states mentioned throughout this manual -
1084	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
1085	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
1086	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".
1087	member, you can also "subclass" the watcher type and provide your own
1088	data:
1089		1488
1090	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)
1091	{	1614	{
1092	ev_io io;	1615	// stop the I/O watcher, we received the event, but
1093	int otherfd;	1616	// are not yet ready to handle it.
1094	void *somedata;	1617	ev_io_stop (EV_A_ w);
1095	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);
1096	};	1623	}
1097		1624
1098	...	1625	static void
1099	struct my_io w;	1626	idle_cb (EV_P_ ev_idle *w, int revents)
1100	ev_io_init (&w.io, my_cb, fd, EV_READ);
1101
1102	And since your callback will be called with a pointer to the watcher, you
1103	can cast it back to your own type:
1104
1105	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1106	{	1627	{
1107	struct my_io *w = (struct my_io *)w_;	1628	// actual processing
1108	...	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);
1109	}	1634	}
1110		1635
1111	More interesting and less C-conformant ways of casting your callback type	1636	// initialisation
1112	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);
1113		1640
1114	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
1115	embedded watchers:	1642	low-priority connections can not be locked out forever under load. This
1116		1643	enables your program to keep a lower latency for important connections
1117	struct my_biggy	1644	during short periods of high load, while not completely locking out less
1118	{	1645	important ones.
1119	int some_data;
1120	ev_timer t1;
1121	ev_timer t2;
1122	}
1123
1124	In this case getting the pointer to C<my_biggy> is a bit more
1125	complicated: Either you store the address of your C<my_biggy> struct
1126	in the C<data> member of the watcher (for woozies), or you need to use
1127	some pointer arithmetic using C<offsetof> inside your watchers (for real
1128	programmers):
1129
1130	#include <stddef.h>
1131
1132	static void
1133	t1_cb (EV_P_ ev_timer *w, int revents)
1134	{
1135	struct my_biggy big = (struct my_biggy *
1136	(((char *)w) - offsetof (struct my_biggy, t1));
1137	}
1138
1139	static void
1140	t2_cb (EV_P_ ev_timer *w, int revents)
1141	{
1142	struct my_biggy big = (struct my_biggy *
1143	(((char *)w) - offsetof (struct my_biggy, t2));
1144	}
1145		1646
1146		1647
1147	=head1 WATCHER TYPES	1648	=head1 WATCHER TYPES
1148		1649
1149	This section describes each watcher in detail, but will not repeat	1650	This section describes each watcher in detail, but will not repeat
1150	information given in the last section. Any initialisation/set macros,	1651	information given in the last section. Any initialisation/set macros,
1151	functions and members specific to the watcher type are explained.	1652	functions and members specific to the watcher type are explained.
1152		1653
1153	Members are additionally marked with either I<[read-only]>, meaning that,	1654	Most members are additionally marked with either I<[read-only]>, meaning
1154	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
1155	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
1156	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
1157	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
1158	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
1159	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
1160	not crash or malfunction in any way.	1661	not crash or malfunction in any way.
1161		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.
1162		1665
1163	=head2 C<ev_io> - is this file descriptor readable or writable?	1666	=head2 C<ev_io> - is this file descriptor readable or writable?
1164		1667
1165	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
1166	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
…		…
1173	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
1174	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
1175	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
1176	required if you know what you are doing).	1679	required if you know what you are doing).
1177		1680
1178	If you cannot use non-blocking mode, then force the use of a
1179	known-to-be-good backend (at the time of this writing, this includes only
1180	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1181
1182	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
1183	receive "spurious" readiness notifications, that is your callback might	1682	receive "spurious" readiness notifications, that is, your callback might
1184	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
1185	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
1186	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
1187	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
1188	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1189	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1687	preferable to a program hanging until some data arrives.
1190		1688
1191	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
1192	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
1193	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
1194	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
1195	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
1196	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
1197	indefinitely.	1695	indefinitely.
1198		1696
1199	But really, best use non-blocking mode.	1697	But really, best use non-blocking mode.
1200		1698
1201	=head3 The special problem of disappearing file descriptors	1699	=head3 The special problem of disappearing file descriptors
1202		1700
1203	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
1204	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
1205	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
1206	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
1207	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
1208	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,
1209	fact, a different file descriptor.	1707	in fact, a different file descriptor.
1210		1708
1211	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
1212	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
1213	will assume that this is potentially a new file descriptor, otherwise	1711	will assume that this is potentially a new file descriptor, otherwise
1214	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
…		…
1228		1726
1229	There is no workaround possible except not registering events	1727	There is no workaround possible except not registering events
1230	for potentially C<dup ()>'ed file descriptors, or to resort to	1728	for potentially C<dup ()>'ed file descriptors, or to resort to
1231	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1729	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1232		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
1233	=head3 The special problem of fork	1764	=head3 The special problem of fork
1234		1765
1235	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 ()>
1236	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
1237	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.
1238		1770
1239	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
1240	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
1241	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1773	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1242	C<EVBACKEND_POLL>.
1243		1774
1244	=head3 The special problem of SIGPIPE	1775	=head3 The special problem of SIGPIPE
1245		1776
1246	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>:
1247	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
…		…
1250		1781
1251	So when you encounter spurious, unexplained daemon exits, make sure you	1782	So when you encounter spurious, unexplained daemon exits, make sure you
1252	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
1253	somewhere, as that would have given you a big clue).	1784	somewhere, as that would have given you a big clue).
1254		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.
1255		1824
1256	=head3 Watcher-Specific Functions	1825	=head3 Watcher-Specific Functions
1257		1826
1258	=over 4	1827	=over 4
1259		1828
1260	=item ev_io_init (ev_io *, callback, int fd, int events)	1829	=item ev_io_init (ev_io *, callback, int fd, int events)
1261		1830
1262	=item ev_io_set (ev_io *, int fd, int events)	1831	=item ev_io_set (ev_io *, int fd, int events)
1263		1832
1264	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
1265	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>, both
1266	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.	1835	C<EV_READ | EV_WRITE> or C<0>, to express the desire to receive the given
		1836	events.
1267		1837
1268	=item int fd [read-only]	1838	Note that setting the C<events> to C<0> and starting the watcher is
		1839	supported, but not specially optimized - if your program sometimes happens
		1840	to generate this combination this is fine, but if it is easy to avoid
		1841	starting an io watcher watching for no events you should do so.
1269		1842
1270	The file descriptor being watched.	1843	=item ev_io_modify (ev_io *, int events)
1271		1844
		1845	Similar to C<ev_io_set>, but only changes the event mask. Using this might
		1846	be faster with some backends, as libev can assume that the C<fd> still
		1847	refers to the same underlying file description, something it cannot do
		1848	when using C<ev_io_set>.
		1849
		1850	=item int fd [no-modify]
		1851
		1852	The file descriptor being watched. While it can be read at any time, you
		1853	must not modify this member even when the watcher is stopped - always use
		1854	C<ev_io_set> for that.
		1855
1272	=item int events [read-only]	1856	=item int events [no-modify]
1273		1857
1274	The events being watched.	1858	The set of events the fd is being watched for, among other flags. Remember
		1859	that this is a bit set - to test for C<EV_READ>, use C<< w->events &
		1860	EV_READ >>, and similarly for C<EV_WRITE>.
		1861
		1862	As with C<fd>, you must not modify this member even when the watcher is
		1863	stopped, always use C<ev_io_set> or C<ev_io_modify> for that.
1275		1864
1276	=back	1865	=back
1277		1866
1278	=head3 Examples	1867	=head3 Examples
1279		1868
…		…
1291	...	1880	...
1292	struct ev_loop *loop = ev_default_init (0);	1881	struct ev_loop *loop = ev_default_init (0);
1293	ev_io stdin_readable;	1882	ev_io stdin_readable;
1294	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1883	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1295	ev_io_start (loop, &stdin_readable);	1884	ev_io_start (loop, &stdin_readable);
1296	ev_loop (loop, 0);	1885	ev_run (loop, 0);
1297		1886
1298		1887
1299	=head2 C<ev_timer> - relative and optionally repeating timeouts	1888	=head2 C<ev_timer> - relative and optionally repeating timeouts
1300		1889
1301	Timer watchers are simple relative timers that generate an event after a	1890	Timer watchers are simple relative timers that generate an event after a
…		…
1306	year, it will still time out after (roughly) one hour. "Roughly" because	1895	year, it will still time out after (roughly) one hour. "Roughly" because
1307	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1896	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1308	monotonic clock option helps a lot here).	1897	monotonic clock option helps a lot here).
1309		1898
1310	The callback is guaranteed to be invoked only I<after> its timeout has	1899	The callback is guaranteed to be invoked only I<after> its timeout has
1311	passed, but if multiple timers become ready during the same loop iteration	1900	passed (not I<at>, so on systems with very low-resolution clocks this
1312	then order of execution is undefined.	1901	might introduce a small delay, see "the special problem of being too
		1902	early", below). If multiple timers become ready during the same loop
		1903	iteration then the ones with earlier time-out values are invoked before
		1904	ones of the same priority with later time-out values (but this is no
		1905	longer true when a callback calls C<ev_run> recursively).
1313		1906
1314	=head3 Be smart about timeouts	1907	=head3 Be smart about timeouts
1315		1908
1316	Many real-world problems involve some kind of timeout, usually for error	1909	Many real-world problems involve some kind of timeout, usually for error
1317	recovery. A typical example is an HTTP request - if the other side hangs,	1910	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1361	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1954	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1362	member and C<ev_timer_again>.	1955	member and C<ev_timer_again>.
1363		1956
1364	At start:	1957	At start:
1365		1958
1366	ev_timer_init (timer, callback);	1959	ev_init (timer, callback);
1367	timer->repeat = 60.;	1960	timer->repeat = 60.;
1368	ev_timer_again (loop, timer);	1961	ev_timer_again (loop, timer);
1369		1962
1370	Each time there is some activity:	1963	Each time there is some activity:
1371		1964
…		…
1392		1985
1393	In this case, it would be more efficient to leave the C<ev_timer> alone,	1986	In this case, it would be more efficient to leave the C<ev_timer> alone,
1394	but remember the time of last activity, and check for a real timeout only	1987	but remember the time of last activity, and check for a real timeout only
1395	within the callback:	1988	within the callback:
1396		1989
		1990	ev_tstamp timeout = 60.;
1397	ev_tstamp last_activity; // time of last activity	1991	ev_tstamp last_activity; // time of last activity
		1992	ev_timer timer;
1398		1993
1399	static void	1994	static void
1400	callback (EV_P_ ev_timer *w, int revents)	1995	callback (EV_P_ ev_timer *w, int revents)
1401	{	1996	{
1402	ev_tstamp now = ev_now (EV_A);	1997	// calculate when the timeout would happen
1403	ev_tstamp timeout = last_activity + 60.;	1998	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1404		1999
1405	// if last_activity + 60. is older than now, we did time out	2000	// if negative, it means we the timeout already occurred
1406	if (timeout < now)	2001	if (after < 0.)
1407	{	2002	{
1408	// timeout occured, take action	2003	// timeout occurred, take action
1409	}	2004	}
1410	else	2005	else
1411	{	2006	{
1412	// callback was invoked, but there was some activity, re-arm	2007	// callback was invoked, but there was some recent
1413	// the watcher to fire in last_activity + 60, which is	2008	// activity. simply restart the timer to time out
1414	// guaranteed to be in the future, so "again" is positive:	2009	// after "after" seconds, which is the earliest time
1415	w->again = timeout - now;	2010	// the timeout can occur.
		2011	ev_timer_set (w, after, 0.);
1416	ev_timer_again (EV_A_ w);	2012	ev_timer_start (EV_A_ w);
1417	}	2013	}
1418	}	2014	}
1419		2015
1420	To summarise the callback: first calculate the real timeout (defined	2016	To summarise the callback: first calculate in how many seconds the
1421	as "60 seconds after the last activity"), then check if that time has	2017	timeout will occur (by calculating the absolute time when it would occur,
1422	been reached, which means something I<did>, in fact, time out. Otherwise	2018	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1423	the callback was invoked too early (C<timeout> is in the future), so	2019	(EV_A)> from that).
1424	re-schedule the timer to fire at that future time, to see if maybe we have
1425	a timeout then.
1426		2020
1427	Note how C<ev_timer_again> is used, taking advantage of the	2021	If this value is negative, then we are already past the timeout, i.e. we
1428	C<ev_timer_again> optimisation when the timer is already running.	2022	timed out, and need to do whatever is needed in this case.
		2023
		2024	Otherwise, we now the earliest time at which the timeout would trigger,
		2025	and simply start the timer with this timeout value.
		2026
		2027	In other words, each time the callback is invoked it will check whether
		2028	the timeout occurred. If not, it will simply reschedule itself to check
		2029	again at the earliest time it could time out. Rinse. Repeat.
1429		2030
1430	This scheme causes more callback invocations (about one every 60 seconds	2031	This scheme causes more callback invocations (about one every 60 seconds
1431	minus half the average time between activity), but virtually no calls to	2032	minus half the average time between activity), but virtually no calls to
1432	libev to change the timeout.	2033	libev to change the timeout.
1433		2034
1434	To start the timer, simply initialise the watcher and set C<last_activity>	2035	To start the machinery, simply initialise the watcher and set
1435	to the current time (meaning we just have some activity :), then call the	2036	C<last_activity> to the current time (meaning there was some activity just
1436	callback, which will "do the right thing" and start the timer:	2037	now), then call the callback, which will "do the right thing" and start
		2038	the timer:
1437		2039
		2040	last_activity = ev_now (EV_A);
1438	ev_timer_init (timer, callback);	2041	ev_init (&timer, callback);
1439	last_activity = ev_now (loop);	2042	callback (EV_A_ &timer, 0);
1440	callback (loop, timer, EV_TIMEOUT);
1441		2043
1442	And when there is some activity, simply store the current time in	2044	When there is some activity, simply store the current time in
1443	C<last_activity>, no libev calls at all:	2045	C<last_activity>, no libev calls at all:
1444		2046
		2047	if (activity detected)
1445	last_actiivty = ev_now (loop);	2048	last_activity = ev_now (EV_A);
		2049
		2050	When your timeout value changes, then the timeout can be changed by simply
		2051	providing a new value, stopping the timer and calling the callback, which
		2052	will again do the right thing (for example, time out immediately :).
		2053
		2054	timeout = new_value;
		2055	ev_timer_stop (EV_A_ &timer);
		2056	callback (EV_A_ &timer, 0);
1446		2057
1447	This technique is slightly more complex, but in most cases where the	2058	This technique is slightly more complex, but in most cases where the
1448	time-out is unlikely to be triggered, much more efficient.	2059	time-out is unlikely to be triggered, much more efficient.
1449
1450	Changing the timeout is trivial as well (if it isn't hard-coded in the
1451	callback :) - just change the timeout and invoke the callback, which will
1452	fix things for you.
1453		2060
1454	=item 4. Wee, just use a double-linked list for your timeouts.	2061	=item 4. Wee, just use a double-linked list for your timeouts.
1455		2062
1456	If there is not one request, but many thousands (millions...), all	2063	If there is not one request, but many thousands (millions...), all
1457	employing some kind of timeout with the same timeout value, then one can	2064	employing some kind of timeout with the same timeout value, then one can
…		…
1484	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2091	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1485	rather complicated, but extremely efficient, something that really pays	2092	rather complicated, but extremely efficient, something that really pays
1486	off after the first million or so of active timers, i.e. it's usually	2093	off after the first million or so of active timers, i.e. it's usually
1487	overkill :)	2094	overkill :)
1488		2095
		2096	=head3 The special problem of being too early
		2097
		2098	If you ask a timer to call your callback after three seconds, then
		2099	you expect it to be invoked after three seconds - but of course, this
		2100	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2101	guaranteed to any precision by libev - imagine somebody suspending the
		2102	process with a STOP signal for a few hours for example.
		2103
		2104	So, libev tries to invoke your callback as soon as possible I<after> the
		2105	delay has occurred, but cannot guarantee this.
		2106
		2107	A less obvious failure mode is calling your callback too early: many event
		2108	loops compare timestamps with a "elapsed delay >= requested delay", but
		2109	this can cause your callback to be invoked much earlier than you would
		2110	expect.
		2111
		2112	To see why, imagine a system with a clock that only offers full second
		2113	resolution (think windows if you can't come up with a broken enough OS
		2114	yourself). If you schedule a one-second timer at the time 500.9, then the
		2115	event loop will schedule your timeout to elapse at a system time of 500
		2116	(500.9 truncated to the resolution) + 1, or 501.
		2117
		2118	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2119	501" and invoke the callback 0.1s after it was started, even though a
		2120	one-second delay was requested - this is being "too early", despite best
		2121	intentions.
		2122
		2123	This is the reason why libev will never invoke the callback if the elapsed
		2124	delay equals the requested delay, but only when the elapsed delay is
		2125	larger than the requested delay. In the example above, libev would only invoke
		2126	the callback at system time 502, or 1.1s after the timer was started.
		2127
		2128	So, while libev cannot guarantee that your callback will be invoked
		2129	exactly when requested, it I<can> and I<does> guarantee that the requested
		2130	delay has actually elapsed, or in other words, it always errs on the "too
		2131	late" side of things.
		2132
1489	=head3 The special problem of time updates	2133	=head3 The special problem of time updates
1490		2134
1491	Establishing the current time is a costly operation (it usually takes at	2135	Establishing the current time is a costly operation (it usually takes
1492	least two system calls): EV therefore updates its idea of the current	2136	at least one system call): EV therefore updates its idea of the current
1493	time only before and after C<ev_loop> collects new events, which causes a	2137	time only before and after C<ev_run> collects new events, which causes a
1494	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2138	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1495	lots of events in one iteration.	2139	lots of events in one iteration.
1496		2140
1497	The relative timeouts are calculated relative to the C<ev_now ()>	2141	The relative timeouts are calculated relative to the C<ev_now ()>
1498	time. This is usually the right thing as this timestamp refers to the time	2142	time. This is usually the right thing as this timestamp refers to the time
1499	of the event triggering whatever timeout you are modifying/starting. If	2143	of the event triggering whatever timeout you are modifying/starting. If
1500	you suspect event processing to be delayed and you I<need> to base the	2144	you suspect event processing to be delayed and you I<need> to base the
1501	timeout on the current time, use something like this to adjust for this:	2145	timeout on the current time, use something like the following to adjust
		2146	for it:
1502		2147
1503	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2148	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1504		2149
1505	If the event loop is suspended for a long time, you can also force an	2150	If the event loop is suspended for a long time, you can also force an
1506	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2151	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1507	()>.	2152	()>, although that will push the event time of all outstanding events
		2153	further into the future.
		2154
		2155	=head3 The special problem of unsynchronised clocks
		2156
		2157	Modern systems have a variety of clocks - libev itself uses the normal
		2158	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2159	jumps).
		2160
		2161	Neither of these clocks is synchronised with each other or any other clock
		2162	on the system, so C<ev_time ()> might return a considerably different time
		2163	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2164	a call to C<gettimeofday> might return a second count that is one higher
		2165	than a directly following call to C<time>.
		2166
		2167	The moral of this is to only compare libev-related timestamps with
		2168	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2169	a second or so.
		2170
		2171	One more problem arises due to this lack of synchronisation: if libev uses
		2172	the system monotonic clock and you compare timestamps from C<ev_time>
		2173	or C<ev_now> from when you started your timer and when your callback is
		2174	invoked, you will find that sometimes the callback is a bit "early".
		2175
		2176	This is because C<ev_timer>s work in real time, not wall clock time, so
		2177	libev makes sure your callback is not invoked before the delay happened,
		2178	I<measured according to the real time>, not the system clock.
		2179
		2180	If your timeouts are based on a physical timescale (e.g. "time out this
		2181	connection after 100 seconds") then this shouldn't bother you as it is
		2182	exactly the right behaviour.
		2183
		2184	If you want to compare wall clock/system timestamps to your timers, then
		2185	you need to use C<ev_periodic>s, as these are based on the wall clock
		2186	time, where your comparisons will always generate correct results.
		2187
		2188	=head3 The special problems of suspended animation
		2189
		2190	When you leave the server world it is quite customary to hit machines that
		2191	can suspend/hibernate - what happens to the clocks during such a suspend?
		2192
		2193	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2194	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2195	to run until the system is suspended, but they will not advance while the
		2196	system is suspended. That means, on resume, it will be as if the program
		2197	was frozen for a few seconds, but the suspend time will not be counted
		2198	towards C<ev_timer> when a monotonic clock source is used. The real time
		2199	clock advanced as expected, but if it is used as sole clocksource, then a
		2200	long suspend would be detected as a time jump by libev, and timers would
		2201	be adjusted accordingly.
		2202
		2203	I would not be surprised to see different behaviour in different between
		2204	operating systems, OS versions or even different hardware.
		2205
		2206	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2207	time jump in the monotonic clocks and the realtime clock. If the program
		2208	is suspended for a very long time, and monotonic clock sources are in use,
		2209	then you can expect C<ev_timer>s to expire as the full suspension time
		2210	will be counted towards the timers. When no monotonic clock source is in
		2211	use, then libev will again assume a timejump and adjust accordingly.
		2212
		2213	It might be beneficial for this latter case to call C<ev_suspend>
		2214	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2215	deterministic behaviour in this case (you can do nothing against
		2216	C<SIGSTOP>).
1508		2217
1509	=head3 Watcher-Specific Functions and Data Members	2218	=head3 Watcher-Specific Functions and Data Members
1510		2219
1511	=over 4	2220	=over 4
1512		2221
1513	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2222	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1514		2223
1515	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2224	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1516		2225
1517	Configure the timer to trigger after C<after> seconds. If C<repeat>	2226	Configure the timer to trigger after C<after> seconds (fractional and
1518	is C<0.>, then it will automatically be stopped once the timeout is	2227	negative values are supported). If C<repeat> is C<0.>, then it will
1519	reached. If it is positive, then the timer will automatically be	2228	automatically be stopped once the timeout is reached. If it is positive,
1520	configured to trigger again C<repeat> seconds later, again, and again,	2229	then the timer will automatically be configured to trigger again C<repeat>
1521	until stopped manually.	2230	seconds later, again, and again, until stopped manually.
1522		2231
1523	The timer itself will do a best-effort at avoiding drift, that is, if	2232	The timer itself will do a best-effort at avoiding drift, that is, if
1524	you configure a timer to trigger every 10 seconds, then it will normally	2233	you configure a timer to trigger every 10 seconds, then it will normally
1525	trigger at exactly 10 second intervals. If, however, your program cannot	2234	trigger at exactly 10 second intervals. If, however, your program cannot
1526	keep up with the timer (because it takes longer than those 10 seconds to	2235	keep up with the timer (because it takes longer than those 10 seconds to
1527	do stuff) the timer will not fire more than once per event loop iteration.	2236	do stuff) the timer will not fire more than once per event loop iteration.
1528		2237
1529	=item ev_timer_again (loop, ev_timer *)	2238	=item ev_timer_again (loop, ev_timer *)
1530		2239
1531	This will act as if the timer timed out and restart it again if it is	2240	This will act as if the timer timed out, and restarts it again if it is
1532	repeating. The exact semantics are:	2241	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2242	timeout to the C<repeat> value and calling C<ev_timer_start>.
1533		2243
		2244	The exact semantics are as in the following rules, all of which will be
		2245	applied to the watcher:
		2246
		2247	=over 4
		2248
1534	If the timer is pending, its pending status is cleared.	2249	=item If the timer is pending, the pending status is always cleared.
1535		2250
1536	If the timer is started but non-repeating, stop it (as if it timed out).	2251	=item If the timer is started but non-repeating, stop it (as if it timed
		2252	out, without invoking it).
1537		2253
1538	If the timer is repeating, either start it if necessary (with the	2254	=item If the timer is repeating, make the C<repeat> value the new timeout
1539	C<repeat> value), or reset the running timer to the C<repeat> value.	2255	and start the timer, if necessary.
1540		2256
		2257	=back
		2258
1541	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2259	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1542	usage example.	2260	usage example.
		2261
		2262	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2263
		2264	Returns the remaining time until a timer fires. If the timer is active,
		2265	then this time is relative to the current event loop time, otherwise it's
		2266	the timeout value currently configured.
		2267
		2268	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2269	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2270	will return C<4>. When the timer expires and is restarted, it will return
		2271	roughly C<7> (likely slightly less as callback invocation takes some time,
		2272	too), and so on.
1543		2273
1544	=item ev_tstamp repeat [read-write]	2274	=item ev_tstamp repeat [read-write]
1545		2275
1546	The current C<repeat> value. Will be used each time the watcher times out	2276	The current C<repeat> value. Will be used each time the watcher times out
1547	or C<ev_timer_again> is called, and determines the next timeout (if any),	2277	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1573	}	2303	}
1574		2304
1575	ev_timer mytimer;	2305	ev_timer mytimer;
1576	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2306	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1577	ev_timer_again (&mytimer); /* start timer */	2307	ev_timer_again (&mytimer); /* start timer */
1578	ev_loop (loop, 0);	2308	ev_run (loop, 0);
1579		2309
1580	// and in some piece of code that gets executed on any "activity":	2310	// and in some piece of code that gets executed on any "activity":
1581	// reset the timeout to start ticking again at 10 seconds	2311	// reset the timeout to start ticking again at 10 seconds
1582	ev_timer_again (&mytimer);	2312	ev_timer_again (&mytimer);
1583		2313
…		…
1585	=head2 C<ev_periodic> - to cron or not to cron?	2315	=head2 C<ev_periodic> - to cron or not to cron?
1586		2316
1587	Periodic watchers are also timers of a kind, but they are very versatile	2317	Periodic watchers are also timers of a kind, but they are very versatile
1588	(and unfortunately a bit complex).	2318	(and unfortunately a bit complex).
1589		2319
1590	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2320	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1591	but on wall clock time (absolute time). You can tell a periodic watcher	2321	relative time, the physical time that passes) but on wall clock time
1592	to trigger after some specific point in time. For example, if you tell a	2322	(absolute time, the thing you can read on your calendar or clock). The
1593	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	2323	difference is that wall clock time can run faster or slower than real
1594	+ 10.>, that is, an absolute time not a delay) and then reset your system	2324	time, and time jumps are not uncommon (e.g. when you adjust your
1595	clock to January of the previous year, then it will take more than year	2325	wrist-watch).
1596	to trigger the event (unlike an C<ev_timer>, which would still trigger
1597	roughly 10 seconds later as it uses a relative timeout).
1598		2326
		2327	You can tell a periodic watcher to trigger after some specific point
		2328	in time: for example, if you tell a periodic watcher to trigger "in 10
		2329	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2330	not a delay) and then reset your system clock to January of the previous
		2331	year, then it will take a year or more to trigger the event (unlike an
		2332	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2333	it, as it uses a relative timeout).
		2334
1599	C<ev_periodic>s can also be used to implement vastly more complex timers,	2335	C<ev_periodic> watchers can also be used to implement vastly more complex
1600	such as triggering an event on each "midnight, local time", or other	2336	timers, such as triggering an event on each "midnight, local time", or
1601	complicated rules.	2337	other complicated rules. This cannot easily be done with C<ev_timer>
		2338	watchers, as those cannot react to time jumps.
1602		2339
1603	As with timers, the callback is guaranteed to be invoked only when the	2340	As with timers, the callback is guaranteed to be invoked only when the
1604	time (C<at>) has passed, but if multiple periodic timers become ready	2341	point in time where it is supposed to trigger has passed. If multiple
1605	during the same loop iteration, then order of execution is undefined.	2342	timers become ready during the same loop iteration then the ones with
		2343	earlier time-out values are invoked before ones with later time-out values
		2344	(but this is no longer true when a callback calls C<ev_run> recursively).
1606		2345
1607	=head3 Watcher-Specific Functions and Data Members	2346	=head3 Watcher-Specific Functions and Data Members
1608		2347
1609	=over 4	2348	=over 4
1610		2349
1611	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2350	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1612		2351
1613	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2352	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1614		2353
1615	Lots of arguments, lets sort it out... There are basically three modes of	2354	Lots of arguments, let's sort it out... There are basically three modes of
1616	operation, and we will explain them from simplest to most complex:	2355	operation, and we will explain them from simplest to most complex:
1617		2356
1618	=over 4	2357	=over 4
1619		2358
1620	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2359	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1621		2360
1622	In this configuration the watcher triggers an event after the wall clock	2361	In this configuration the watcher triggers an event after the wall clock
1623	time C<at> has passed. It will not repeat and will not adjust when a time	2362	time C<offset> has passed. It will not repeat and will not adjust when a
1624	jump occurs, that is, if it is to be run at January 1st 2011 then it will	2363	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1625	only run when the system clock reaches or surpasses this time.	2364	will be stopped and invoked when the system clock reaches or surpasses
		2365	this point in time.
1626		2366
1627	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2367	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1628		2368
1629	In this mode the watcher will always be scheduled to time out at the next	2369	In this mode the watcher will always be scheduled to time out at the next
1630	C<at + N * interval> time (for some integer N, which can also be negative)	2370	C<offset + N * interval> time (for some integer N, which can also be
1631	and then repeat, regardless of any time jumps.	2371	negative) and then repeat, regardless of any time jumps. The C<offset>
		2372	argument is merely an offset into the C<interval> periods.
1632		2373
1633	This can be used to create timers that do not drift with respect to the	2374	This can be used to create timers that do not drift with respect to the
1634	system clock, for example, here is a C<ev_periodic> that triggers each	2375	system clock, for example, here is an C<ev_periodic> that triggers each
1635	hour, on the hour:	2376	hour, on the hour (with respect to UTC):
1636		2377
1637	ev_periodic_set (&periodic, 0., 3600., 0);	2378	ev_periodic_set (&periodic, 0., 3600., 0);
1638		2379
1639	This doesn't mean there will always be 3600 seconds in between triggers,	2380	This doesn't mean there will always be 3600 seconds in between triggers,
1640	but only that the callback will be called when the system time shows a	2381	but only that the callback will be called when the system time shows a
1641	full hour (UTC), or more correctly, when the system time is evenly divisible	2382	full hour (UTC), or more correctly, when the system time is evenly divisible
1642	by 3600.	2383	by 3600.
1643		2384
1644	Another way to think about it (for the mathematically inclined) is that	2385	Another way to think about it (for the mathematically inclined) is that
1645	C<ev_periodic> will try to run the callback in this mode at the next possible	2386	C<ev_periodic> will try to run the callback in this mode at the next possible
1646	time where C<time = at (mod interval)>, regardless of any time jumps.	2387	time where C<time = offset (mod interval)>, regardless of any time jumps.
1647		2388
1648	For numerical stability it is preferable that the C<at> value is near	2389	The C<interval> I<MUST> be positive, and for numerical stability, the
1649	C<ev_now ()> (the current time), but there is no range requirement for	2390	interval value should be higher than C<1/8192> (which is around 100
1650	this value, and in fact is often specified as zero.	2391	microseconds) and C<offset> should be higher than C<0> and should have
		2392	at most a similar magnitude as the current time (say, within a factor of
		2393	ten). Typical values for offset are, in fact, C<0> or something between
		2394	C<0> and C<interval>, which is also the recommended range.
1651		2395
1652	Note also that there is an upper limit to how often a timer can fire (CPU	2396	Note also that there is an upper limit to how often a timer can fire (CPU
1653	speed for example), so if C<interval> is very small then timing stability	2397	speed for example), so if C<interval> is very small then timing stability
1654	will of course deteriorate. Libev itself tries to be exact to be about one	2398	will of course deteriorate. Libev itself tries to be exact to be about one
1655	millisecond (if the OS supports it and the machine is fast enough).	2399	millisecond (if the OS supports it and the machine is fast enough).
1656		2400
1657	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2401	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1658		2402
1659	In this mode the values for C<interval> and C<at> are both being	2403	In this mode the values for C<interval> and C<offset> are both being
1660	ignored. Instead, each time the periodic watcher gets scheduled, the	2404	ignored. Instead, each time the periodic watcher gets scheduled, the
1661	reschedule callback will be called with the watcher as first, and the	2405	reschedule callback will be called with the watcher as first, and the
1662	current time as second argument.	2406	current time as second argument.
1663		2407
1664	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2408	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1665	ever, or make ANY event loop modifications whatsoever>.	2409	or make ANY other event loop modifications whatsoever, unless explicitly
		2410	allowed by documentation here>.
1666		2411
1667	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2412	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1668	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2413	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1669	only event loop modification you are allowed to do).	2414	only event loop modification you are allowed to do).
1670		2415
…		…
1684		2429
1685	NOTE: I<< This callback must always return a time that is higher than or	2430	NOTE: I<< This callback must always return a time that is higher than or
1686	equal to the passed C<now> value >>.	2431	equal to the passed C<now> value >>.
1687		2432
1688	This can be used to create very complex timers, such as a timer that	2433	This can be used to create very complex timers, such as a timer that
1689	triggers on "next midnight, local time". To do this, you would calculate the	2434	triggers on "next midnight, local time". To do this, you would calculate
1690	next midnight after C<now> and return the timestamp value for this. How	2435	the next midnight after C<now> and return the timestamp value for
1691	you do this is, again, up to you (but it is not trivial, which is the main	2436	this. Here is a (completely untested, no error checking) example on how to
1692	reason I omitted it as an example).	2437	do this:
		2438
		2439	#include <time.h>
		2440
		2441	static ev_tstamp
		2442	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2443	{
		2444	time_t tnow = (time_t)now;
		2445	struct tm tm;
		2446	localtime_r (&tnow, &tm);
		2447
		2448	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2449	++tm.tm_mday; // midnight next day
		2450
		2451	return mktime (&tm);
		2452	}
		2453
		2454	Note: this code might run into trouble on days that have more then two
		2455	midnights (beginning and end).
1693		2456
1694	=back	2457	=back
1695		2458
1696	=item ev_periodic_again (loop, ev_periodic *)	2459	=item ev_periodic_again (loop, ev_periodic *)
1697		2460
…		…
1700	a different time than the last time it was called (e.g. in a crond like	2463	a different time than the last time it was called (e.g. in a crond like
1701	program when the crontabs have changed).	2464	program when the crontabs have changed).
1702		2465
1703	=item ev_tstamp ev_periodic_at (ev_periodic *)	2466	=item ev_tstamp ev_periodic_at (ev_periodic *)
1704		2467
1705	When active, returns the absolute time that the watcher is supposed to	2468	When active, returns the absolute time that the watcher is supposed
1706	trigger next.	2469	to trigger next. This is not the same as the C<offset> argument to
		2470	C<ev_periodic_set>, but indeed works even in interval and manual
		2471	rescheduling modes.
1707		2472
1708	=item ev_tstamp offset [read-write]	2473	=item ev_tstamp offset [read-write]
1709		2474
1710	When repeating, this contains the offset value, otherwise this is the	2475	When repeating, this contains the offset value, otherwise this is the
1711	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2476	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2477	although libev might modify this value for better numerical stability).
1712		2478
1713	Can be modified any time, but changes only take effect when the periodic	2479	Can be modified any time, but changes only take effect when the periodic
1714	timer fires or C<ev_periodic_again> is being called.	2480	timer fires or C<ev_periodic_again> is being called.
1715		2481
1716	=item ev_tstamp interval [read-write]	2482	=item ev_tstamp interval [read-write]
…		…
1732	Example: Call a callback every hour, or, more precisely, whenever the	2498	Example: Call a callback every hour, or, more precisely, whenever the
1733	system time is divisible by 3600. The callback invocation times have	2499	system time is divisible by 3600. The callback invocation times have
1734	potentially a lot of jitter, but good long-term stability.	2500	potentially a lot of jitter, but good long-term stability.
1735		2501
1736	static void	2502	static void
1737	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2503	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1738	{	2504	{
1739	... its now a full hour (UTC, or TAI or whatever your clock follows)	2505	... its now a full hour (UTC, or TAI or whatever your clock follows)
1740	}	2506	}
1741		2507
1742	ev_periodic hourly_tick;	2508	ev_periodic hourly_tick;
…		…
1759		2525
1760	ev_periodic hourly_tick;	2526	ev_periodic hourly_tick;
1761	ev_periodic_init (&hourly_tick, clock_cb,	2527	ev_periodic_init (&hourly_tick, clock_cb,
1762	fmod (ev_now (loop), 3600.), 3600., 0);	2528	fmod (ev_now (loop), 3600.), 3600., 0);
1763	ev_periodic_start (loop, &hourly_tick);	2529	ev_periodic_start (loop, &hourly_tick);
1764		2530
1765		2531
1766	=head2 C<ev_signal> - signal me when a signal gets signalled!	2532	=head2 C<ev_signal> - signal me when a signal gets signalled!
1767		2533
1768	Signal watchers will trigger an event when the process receives a specific	2534	Signal watchers will trigger an event when the process receives a specific
1769	signal one or more times. Even though signals are very asynchronous, libev	2535	signal one or more times. Even though signals are very asynchronous, libev
1770	will try it's best to deliver signals synchronously, i.e. as part of the	2536	will try its best to deliver signals synchronously, i.e. as part of the
1771	normal event processing, like any other event.	2537	normal event processing, like any other event.
1772		2538
1773	If you want signals asynchronously, just use C<sigaction> as you would	2539	If you want signals to be delivered truly asynchronously, just use
1774	do without libev and forget about sharing the signal. You can even use	2540	C<sigaction> as you would do without libev and forget about sharing
1775	C<ev_async> from a signal handler to synchronously wake up an event loop.	2541	the signal. You can even use C<ev_async> from a signal handler to
		2542	synchronously wake up an event loop.
1776		2543
1777	You can configure as many watchers as you like per signal. Only when the	2544	You can configure as many watchers as you like for the same signal, but
1778	first watcher gets started will libev actually register a signal handler	2545	only within the same loop, i.e. you can watch for C<SIGINT> in your
1779	with the kernel (thus it coexists with your own signal handlers as long as	2546	default loop and for C<SIGIO> in another loop, but you cannot watch for
1780	you don't register any with libev for the same signal). Similarly, when	2547	C<SIGINT> in both the default loop and another loop at the same time. At
1781	the last signal watcher for a signal is stopped, libev will reset the	2548	the moment, C<SIGCHLD> is permanently tied to the default loop.
1782	signal handler to SIG_DFL (regardless of what it was set to before).	2549
		2550	Only after the first watcher for a signal is started will libev actually
		2551	register something with the kernel. It thus coexists with your own signal
		2552	handlers as long as you don't register any with libev for the same signal.
1783		2553
1784	If possible and supported, libev will install its handlers with	2554	If possible and supported, libev will install its handlers with
1785	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2555	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1786	interrupted. If you have a problem with system calls getting interrupted by	2556	not be unduly interrupted. If you have a problem with system calls getting
1787	signals you can block all signals in an C<ev_check> watcher and unblock	2557	interrupted by signals you can block all signals in an C<ev_check> watcher
1788	them in an C<ev_prepare> watcher.	2558	and unblock them in an C<ev_prepare> watcher.
		2559
		2560	=head3 The special problem of inheritance over fork/execve/pthread_create
		2561
		2562	Both the signal mask (C<sigprocmask>) and the signal disposition
		2563	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2564	stopping it again), that is, libev might or might not block the signal,
		2565	and might or might not set or restore the installed signal handler (but
		2566	see C<EVFLAG_NOSIGMASK>).
		2567
		2568	While this does not matter for the signal disposition (libev never
		2569	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2570	C<execve>), this matters for the signal mask: many programs do not expect
		2571	certain signals to be blocked.
		2572
		2573	This means that before calling C<exec> (from the child) you should reset
		2574	the signal mask to whatever "default" you expect (all clear is a good
		2575	choice usually).
		2576
		2577	The simplest way to ensure that the signal mask is reset in the child is
		2578	to install a fork handler with C<pthread_atfork> that resets it. That will
		2579	catch fork calls done by libraries (such as the libc) as well.
		2580
		2581	In current versions of libev, the signal will not be blocked indefinitely
		2582	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2583	the window of opportunity for problems, it will not go away, as libev
		2584	I<has> to modify the signal mask, at least temporarily.
		2585
		2586	So I can't stress this enough: I<If you do not reset your signal mask when
		2587	you expect it to be empty, you have a race condition in your code>. This
		2588	is not a libev-specific thing, this is true for most event libraries.
		2589
		2590	=head3 The special problem of threads signal handling
		2591
		2592	POSIX threads has problematic signal handling semantics, specifically,
		2593	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2594	threads in a process block signals, which is hard to achieve.
		2595
		2596	When you want to use sigwait (or mix libev signal handling with your own
		2597	for the same signals), you can tackle this problem by globally blocking
		2598	all signals before creating any threads (or creating them with a fully set
		2599	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2600	loops. Then designate one thread as "signal receiver thread" which handles
		2601	these signals. You can pass on any signals that libev might be interested
		2602	in by calling C<ev_feed_signal>.
1789		2603
1790	=head3 Watcher-Specific Functions and Data Members	2604	=head3 Watcher-Specific Functions and Data Members
1791		2605
1792	=over 4	2606	=over 4
1793		2607
…		…
1809	Example: Try to exit cleanly on SIGINT.	2623	Example: Try to exit cleanly on SIGINT.
1810		2624
1811	static void	2625	static void
1812	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2626	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1813	{	2627	{
1814	ev_unloop (loop, EVUNLOOP_ALL);	2628	ev_break (loop, EVBREAK_ALL);
1815	}	2629	}
1816		2630
1817	ev_signal signal_watcher;	2631	ev_signal signal_watcher;
1818	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2632	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1819	ev_signal_start (loop, &signal_watcher);	2633	ev_signal_start (loop, &signal_watcher);
…		…
1825	some child status changes (most typically when a child of yours dies or	2639	some child status changes (most typically when a child of yours dies or
1826	exits). It is permissible to install a child watcher I<after> the child	2640	exits). It is permissible to install a child watcher I<after> the child
1827	has been forked (which implies it might have already exited), as long	2641	has been forked (which implies it might have already exited), as long
1828	as the event loop isn't entered (or is continued from a watcher), i.e.,	2642	as the event loop isn't entered (or is continued from a watcher), i.e.,
1829	forking and then immediately registering a watcher for the child is fine,	2643	forking and then immediately registering a watcher for the child is fine,
1830	but forking and registering a watcher a few event loop iterations later is	2644	but forking and registering a watcher a few event loop iterations later or
1831	not.	2645	in the next callback invocation is not.
1832		2646
1833	Only the default event loop is capable of handling signals, and therefore	2647	Only the default event loop is capable of handling signals, and therefore
1834	you can only register child watchers in the default event loop.	2648	you can only register child watchers in the default event loop.
1835		2649
		2650	Due to some design glitches inside libev, child watchers will always be
		2651	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2652	libev)
		2653
1836	=head3 Process Interaction	2654	=head3 Process Interaction
1837		2655
1838	Libev grabs C<SIGCHLD> as soon as the default event loop is	2656	Libev grabs C<SIGCHLD> as soon as the default event loop is
1839	initialised. This is necessary to guarantee proper behaviour even if	2657	initialised. This is necessary to guarantee proper behaviour even if the
1840	the first child watcher is started after the child exits. The occurrence	2658	first child watcher is started after the child exits. The occurrence
1841	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2659	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1842	synchronously as part of the event loop processing. Libev always reaps all	2660	synchronously as part of the event loop processing. Libev always reaps all
1843	children, even ones not watched.	2661	children, even ones not watched.
1844		2662
1845	=head3 Overriding the Built-In Processing	2663	=head3 Overriding the Built-In Processing
…		…
1855	=head3 Stopping the Child Watcher	2673	=head3 Stopping the Child Watcher
1856		2674
1857	Currently, the child watcher never gets stopped, even when the	2675	Currently, the child watcher never gets stopped, even when the
1858	child terminates, so normally one needs to stop the watcher in the	2676	child terminates, so normally one needs to stop the watcher in the
1859	callback. Future versions of libev might stop the watcher automatically	2677	callback. Future versions of libev might stop the watcher automatically
1860	when a child exit is detected.	2678	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2679	problem).
1861		2680
1862	=head3 Watcher-Specific Functions and Data Members	2681	=head3 Watcher-Specific Functions and Data Members
1863		2682
1864	=over 4	2683	=over 4
1865		2684
…		…
1923		2742
1924	=head2 C<ev_stat> - did the file attributes just change?	2743	=head2 C<ev_stat> - did the file attributes just change?
1925		2744
1926	This watches a file system path for attribute changes. That is, it calls	2745	This watches a file system path for attribute changes. That is, it calls
1927	C<stat> on that path in regular intervals (or when the OS says it changed)	2746	C<stat> on that path in regular intervals (or when the OS says it changed)
1928	and sees if it changed compared to the last time, invoking the callback if	2747	and sees if it changed compared to the last time, invoking the callback
1929	it did.	2748	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2749	happen after the watcher has been started will be reported.
1930		2750
1931	The path does not need to exist: changing from "path exists" to "path does	2751	The path does not need to exist: changing from "path exists" to "path does
1932	not exist" is a status change like any other. The condition "path does	2752	not exist" is a status change like any other. The condition "path does not
1933	not exist" is signified by the C<st_nlink> field being zero (which is	2753	exist" (or more correctly "path cannot be stat'ed") is signified by the
1934	otherwise always forced to be at least one) and all the other fields of	2754	C<st_nlink> field being zero (which is otherwise always forced to be at
1935	the stat buffer having unspecified contents.	2755	least one) and all the other fields of the stat buffer having unspecified
		2756	contents.
1936		2757
1937	The path I<must not> end in a slash or contain special components such as	2758	The path I<must not> end in a slash or contain special components such as
1938	C<.> or C<..>. The path I<should> be absolute: If it is relative and	2759	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1939	your working directory changes, then the behaviour is undefined.	2760	your working directory changes, then the behaviour is undefined.
1940		2761
…		…
1943	to see if it changed somehow. You can specify a recommended polling	2764	to see if it changed somehow. You can specify a recommended polling
1944	interval for this case. If you specify a polling interval of C<0> (highly	2765	interval for this case. If you specify a polling interval of C<0> (highly
1945	recommended!) then a I<suitable, unspecified default> value will be used	2766	recommended!) then a I<suitable, unspecified default> value will be used
1946	(which you can expect to be around five seconds, although this might	2767	(which you can expect to be around five seconds, although this might
1947	change dynamically). Libev will also impose a minimum interval which is	2768	change dynamically). Libev will also impose a minimum interval which is
1948	currently around C<0.1>, but thats usually overkill.	2769	currently around C<0.1>, but that's usually overkill.
1949		2770
1950	This watcher type is not meant for massive numbers of stat watchers,	2771	This watcher type is not meant for massive numbers of stat watchers,
1951	as even with OS-supported change notifications, this can be	2772	as even with OS-supported change notifications, this can be
1952	resource-intensive.	2773	resource-intensive.
1953		2774
1954	At the time of this writing, the only OS-specific interface implemented	2775	At the time of this writing, the only OS-specific interface implemented
1955	is the Linux inotify interface (implementing kqueue support is left as	2776	is the Linux inotify interface (implementing kqueue support is left as an
1956	an exercise for the reader. Note, however, that the author sees no way	2777	exercise for the reader. Note, however, that the author sees no way of
1957	of implementing C<ev_stat> semantics with kqueue).	2778	implementing C<ev_stat> semantics with kqueue, except as a hint).
1958		2779
1959	=head3 ABI Issues (Largefile Support)	2780	=head3 ABI Issues (Largefile Support)
1960		2781
1961	Libev by default (unless the user overrides this) uses the default	2782	Libev by default (unless the user overrides this) uses the default
1962	compilation environment, which means that on systems with large file	2783	compilation environment, which means that on systems with large file
…		…
1973	to exchange stat structures with application programs compiled using the	2794	to exchange stat structures with application programs compiled using the
1974	default compilation environment.	2795	default compilation environment.
1975		2796
1976	=head3 Inotify and Kqueue	2797	=head3 Inotify and Kqueue
1977		2798
1978	When C<inotify (7)> support has been compiled into libev (generally	2799	When C<inotify (7)> support has been compiled into libev and present at
1979	only available with Linux 2.6.25 or above due to bugs in earlier	2800	runtime, it will be used to speed up change detection where possible. The
1980	implementations) and present at runtime, it will be used to speed up	2801	inotify descriptor will be created lazily when the first C<ev_stat>
1981	change detection where possible. The inotify descriptor will be created	2802	watcher is being started.
1982	lazily when the first C<ev_stat> watcher is being started.
1983		2803
1984	Inotify presence does not change the semantics of C<ev_stat> watchers	2804	Inotify presence does not change the semantics of C<ev_stat> watchers
1985	except that changes might be detected earlier, and in some cases, to avoid	2805	except that changes might be detected earlier, and in some cases, to avoid
1986	making regular C<stat> calls. Even in the presence of inotify support	2806	making regular C<stat> calls. Even in the presence of inotify support
1987	there are many cases where libev has to resort to regular C<stat> polling,	2807	there are many cases where libev has to resort to regular C<stat> polling,
1988	but as long as the path exists, libev usually gets away without polling.	2808	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2809	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2810	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2811	xfs are fully working) libev usually gets away without polling.
1989		2812
1990	There is no support for kqueue, as apparently it cannot be used to	2813	There is no support for kqueue, as apparently it cannot be used to
1991	implement this functionality, due to the requirement of having a file	2814	implement this functionality, due to the requirement of having a file
1992	descriptor open on the object at all times, and detecting renames, unlinks	2815	descriptor open on the object at all times, and detecting renames, unlinks
1993	etc. is difficult.	2816	etc. is difficult.
		2817
		2818	=head3 C<stat ()> is a synchronous operation
		2819
		2820	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2821	the process. The exception are C<ev_stat> watchers - those call C<stat
		2822	()>, which is a synchronous operation.
		2823
		2824	For local paths, this usually doesn't matter: unless the system is very
		2825	busy or the intervals between stat's are large, a stat call will be fast,
		2826	as the path data is usually in memory already (except when starting the
		2827	watcher).
		2828
		2829	For networked file systems, calling C<stat ()> can block an indefinite
		2830	time due to network issues, and even under good conditions, a stat call
		2831	often takes multiple milliseconds.
		2832
		2833	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2834	paths, although this is fully supported by libev.
1994		2835
1995	=head3 The special problem of stat time resolution	2836	=head3 The special problem of stat time resolution
1996		2837
1997	The C<stat ()> system call only supports full-second resolution portably,	2838	The C<stat ()> system call only supports full-second resolution portably,
1998	and even on systems where the resolution is higher, most file systems	2839	and even on systems where the resolution is higher, most file systems
…		…
2143	Apart from keeping your process non-blocking (which is a useful	2984	Apart from keeping your process non-blocking (which is a useful
2144	effect on its own sometimes), idle watchers are a good place to do	2985	effect on its own sometimes), idle watchers are a good place to do
2145	"pseudo-background processing", or delay processing stuff to after the	2986	"pseudo-background processing", or delay processing stuff to after the
2146	event loop has handled all outstanding events.	2987	event loop has handled all outstanding events.
2147		2988
		2989	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2990
		2991	As long as there is at least one active idle watcher, libev will never
		2992	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2993	For this to work, the idle watcher doesn't need to be invoked at all - the
		2994	lowest priority will do.
		2995
		2996	This mode of operation can be useful together with an C<ev_check> watcher,
		2997	to do something on each event loop iteration - for example to balance load
		2998	between different connections.
		2999
		3000	See L</Abusing an ev_check watcher for its side-effect> for a longer
		3001	example.
		3002
2148	=head3 Watcher-Specific Functions and Data Members	3003	=head3 Watcher-Specific Functions and Data Members
2149		3004
2150	=over 4	3005	=over 4
2151		3006
2152	=item ev_idle_init (ev_signal *, callback)	3007	=item ev_idle_init (ev_idle *, callback)
2153		3008
2154	Initialises and configures the idle watcher - it has no parameters of any	3009	Initialises and configures the idle watcher - it has no parameters of any
2155	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	3010	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2156	believe me.	3011	believe me.
2157		3012
…		…
2163	callback, free it. Also, use no error checking, as usual.	3018	callback, free it. Also, use no error checking, as usual.
2164		3019
2165	static void	3020	static void
2166	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	3021	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2167	{	3022	{
		3023	// stop the watcher
		3024	ev_idle_stop (loop, w);
		3025
		3026	// now we can free it
2168	free (w);	3027	free (w);
		3028
2169	// now do something you wanted to do when the program has	3029	// now do something you wanted to do when the program has
2170	// no longer anything immediate to do.	3030	// no longer anything immediate to do.
2171	}	3031	}
2172		3032
2173	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3033	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2174	ev_idle_init (idle_watcher, idle_cb);	3034	ev_idle_init (idle_watcher, idle_cb);
2175	ev_idle_start (loop, idle_cb);	3035	ev_idle_start (loop, idle_watcher);
2176		3036
2177		3037
2178	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3038	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2179		3039
2180	Prepare and check watchers are usually (but not always) used in pairs:	3040	Prepare and check watchers are often (but not always) used in pairs:
2181	prepare watchers get invoked before the process blocks and check watchers	3041	prepare watchers get invoked before the process blocks and check watchers
2182	afterwards.	3042	afterwards.
2183		3043
2184	You I<must not> call C<ev_loop> or similar functions that enter	3044	You I<must not> call C<ev_run> (or similar functions that enter the
2185	the current event loop from either C<ev_prepare> or C<ev_check>	3045	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2186	watchers. Other loops than the current one are fine, however. The	3046	C<ev_check> watchers. Other loops than the current one are fine,
2187	rationale behind this is that you do not need to check for recursion in	3047	however. The rationale behind this is that you do not need to check
2188	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3048	for recursion in those watchers, i.e. the sequence will always be
2189	C<ev_check> so if you have one watcher of each kind they will always be	3049	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2190	called in pairs bracketing the blocking call.	3050	kind they will always be called in pairs bracketing the blocking call.
2191		3051
2192	Their main purpose is to integrate other event mechanisms into libev and	3052	Their main purpose is to integrate other event mechanisms into libev and
2193	their use is somewhat advanced. They could be used, for example, to track	3053	their use is somewhat advanced. They could be used, for example, to track
2194	variable changes, implement your own watchers, integrate net-snmp or a	3054	variable changes, implement your own watchers, integrate net-snmp or a
2195	coroutine library and lots more. They are also occasionally useful if	3055	coroutine library and lots more. They are also occasionally useful if
…		…
2213	with priority higher than or equal to the event loop and one coroutine	3073	with priority higher than or equal to the event loop and one coroutine
2214	of lower priority, but only once, using idle watchers to keep the event	3074	of lower priority, but only once, using idle watchers to keep the event
2215	loop from blocking if lower-priority coroutines are active, thus mapping	3075	loop from blocking if lower-priority coroutines are active, thus mapping
2216	low-priority coroutines to idle/background tasks).	3076	low-priority coroutines to idle/background tasks).
2217		3077
2218	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3078	When used for this purpose, it is recommended to give C<ev_check> watchers
2219	priority, to ensure that they are being run before any other watchers	3079	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2220	after the poll (this doesn't matter for C<ev_prepare> watchers).	3080	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3081	watchers).
2221		3082
2222	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3083	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2223	activate ("feed") events into libev. While libev fully supports this, they	3084	activate ("feed") events into libev. While libev fully supports this, they
2224	might get executed before other C<ev_check> watchers did their job. As	3085	might get executed before other C<ev_check> watchers did their job. As
2225	C<ev_check> watchers are often used to embed other (non-libev) event	3086	C<ev_check> watchers are often used to embed other (non-libev) event
2226	loops those other event loops might be in an unusable state until their	3087	loops those other event loops might be in an unusable state until their
2227	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3088	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2228	others).	3089	others).
		3090
		3091	=head3 Abusing an C<ev_check> watcher for its side-effect
		3092
		3093	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3094	useful because they are called once per event loop iteration. For
		3095	example, if you want to handle a large number of connections fairly, you
		3096	normally only do a bit of work for each active connection, and if there
		3097	is more work to do, you wait for the next event loop iteration, so other
		3098	connections have a chance of making progress.
		3099
		3100	Using an C<ev_check> watcher is almost enough: it will be called on the
		3101	next event loop iteration. However, that isn't as soon as possible -
		3102	without external events, your C<ev_check> watcher will not be invoked.
		3103
		3104	This is where C<ev_idle> watchers come in handy - all you need is a
		3105	single global idle watcher that is active as long as you have one active
		3106	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3107	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3108	invoked. Neither watcher alone can do that.
2229		3109
2230	=head3 Watcher-Specific Functions and Data Members	3110	=head3 Watcher-Specific Functions and Data Members
2231		3111
2232	=over 4	3112	=over 4
2233		3113
…		…
2273	struct pollfd fds [nfd];	3153	struct pollfd fds [nfd];
2274	// actual code will need to loop here and realloc etc.	3154	// actual code will need to loop here and realloc etc.
2275	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3155	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2276		3156
2277	/* the callback is illegal, but won't be called as we stop during check */	3157	/* the callback is illegal, but won't be called as we stop during check */
2278	ev_timer_init (&tw, 0, timeout * 1e-3);	3158	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2279	ev_timer_start (loop, &tw);	3159	ev_timer_start (loop, &tw);
2280		3160
2281	// create one ev_io per pollfd	3161	// create one ev_io per pollfd
2282	for (int i = 0; i < nfd; ++i)	3162	for (int i = 0; i < nfd; ++i)
2283	{	3163	{
…		…
2357		3237
2358	if (timeout >= 0)	3238	if (timeout >= 0)
2359	// create/start timer	3239	// create/start timer
2360		3240
2361	// poll	3241	// poll
2362	ev_loop (EV_A_ 0);	3242	ev_run (EV_A_ 0);
2363		3243
2364	// stop timer again	3244	// stop timer again
2365	if (timeout >= 0)	3245	if (timeout >= 0)
2366	ev_timer_stop (EV_A_ &to);	3246	ev_timer_stop (EV_A_ &to);
2367		3247
…		…
2396	some fds have to be watched and handled very quickly (with low latency),	3276	some fds have to be watched and handled very quickly (with low latency),
2397	and even priorities and idle watchers might have too much overhead. In	3277	and even priorities and idle watchers might have too much overhead. In
2398	this case you would put all the high priority stuff in one loop and all	3278	this case you would put all the high priority stuff in one loop and all
2399	the rest in a second one, and embed the second one in the first.	3279	the rest in a second one, and embed the second one in the first.
2400		3280
2401	As long as the watcher is active, the callback will be invoked every time	3281	As long as the watcher is active, the callback will be invoked every
2402	there might be events pending in the embedded loop. The callback must then	3282	time there might be events pending in the embedded loop. The callback
2403	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	3283	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2404	their callbacks (you could also start an idle watcher to give the embedded	3284	sweep and invoke their callbacks (the callback doesn't need to invoke the
2405	loop strictly lower priority for example). You can also set the callback	3285	C<ev_embed_sweep> function directly, it could also start an idle watcher
2406	to C<0>, in which case the embed watcher will automatically execute the	3286	to give the embedded loop strictly lower priority for example).
2407	embedded loop sweep.
2408		3287
2409	As long as the watcher is started it will automatically handle events. The	3288	You can also set the callback to C<0>, in which case the embed watcher
2410	callback will be invoked whenever some events have been handled. You can	3289	will automatically execute the embedded loop sweep whenever necessary.
2411	set the callback to C<0> to avoid having to specify one if you are not
2412	interested in that.
2413		3290
2414	Also, there have not currently been made special provisions for forking:	3291	Fork detection will be handled transparently while the C<ev_embed> watcher
2415	when you fork, you not only have to call C<ev_loop_fork> on both loops,	3292	is active, i.e., the embedded loop will automatically be forked when the
2416	but you will also have to stop and restart any C<ev_embed> watchers	3293	embedding loop forks. In other cases, the user is responsible for calling
2417	yourself - but you can use a fork watcher to handle this automatically,	3294	C<ev_loop_fork> on the embedded loop.
2418	and future versions of libev might do just that.
2419		3295
2420	Unfortunately, not all backends are embeddable: only the ones returned by	3296	Unfortunately, not all backends are embeddable: only the ones returned by
2421	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3297	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2422	portable one.	3298	portable one.
2423		3299
…		…
2438		3314
2439	=over 4	3315	=over 4
2440		3316
2441	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3317	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2442		3318
2443	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3319	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2444		3320
2445	Configures the watcher to embed the given loop, which must be	3321	Configures the watcher to embed the given loop, which must be
2446	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3322	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2447	invoked automatically, otherwise it is the responsibility of the callback	3323	invoked automatically, otherwise it is the responsibility of the callback
2448	to invoke it (it will continue to be called until the sweep has been done,	3324	to invoke it (it will continue to be called until the sweep has been done,
2449	if you do not want that, you need to temporarily stop the embed watcher).	3325	if you do not want that, you need to temporarily stop the embed watcher).
2450		3326
2451	=item ev_embed_sweep (loop, ev_embed *)	3327	=item ev_embed_sweep (loop, ev_embed *)
2452		3328
2453	Make a single, non-blocking sweep over the embedded loop. This works	3329	Make a single, non-blocking sweep over the embedded loop. This works
2454	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3330	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2455	appropriate way for embedded loops.	3331	appropriate way for embedded loops.
2456		3332
2457	=item struct ev_loop *other [read-only]	3333	=item struct ev_loop *other [read-only]
2458		3334
2459	The embedded event loop.	3335	The embedded event loop.
…		…
2469	used).	3345	used).
2470		3346
2471	struct ev_loop *loop_hi = ev_default_init (0);	3347	struct ev_loop *loop_hi = ev_default_init (0);
2472	struct ev_loop *loop_lo = 0;	3348	struct ev_loop *loop_lo = 0;
2473	ev_embed embed;	3349	ev_embed embed;
2474		3350
2475	// see if there is a chance of getting one that works	3351	// see if there is a chance of getting one that works
2476	// (remember that a flags value of 0 means autodetection)	3352	// (remember that a flags value of 0 means autodetection)
2477	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3353	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2478	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3354	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2479	: 0;	3355	: 0;
…		…
2493	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3369	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2494		3370
2495	struct ev_loop *loop = ev_default_init (0);	3371	struct ev_loop *loop = ev_default_init (0);
2496	struct ev_loop *loop_socket = 0;	3372	struct ev_loop *loop_socket = 0;
2497	ev_embed embed;	3373	ev_embed embed;
2498		3374
2499	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3375	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2500	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3376	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2501	{	3377	{
2502	ev_embed_init (&embed, 0, loop_socket);	3378	ev_embed_init (&embed, 0, loop_socket);
2503	ev_embed_start (loop, &embed);	3379	ev_embed_start (loop, &embed);
…		…
2511		3387
2512	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3388	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2513		3389
2514	Fork watchers are called when a C<fork ()> was detected (usually because	3390	Fork watchers are called when a C<fork ()> was detected (usually because
2515	whoever is a good citizen cared to tell libev about it by calling	3391	whoever is a good citizen cared to tell libev about it by calling
2516	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3392	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2517	event loop blocks next and before C<ev_check> watchers are being called,	3393	and before C<ev_check> watchers are being called, and only in the child
2518	and only in the child after the fork. If whoever good citizen calling	3394	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2519	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3395	and calls it in the wrong process, the fork handlers will be invoked, too,
2520	handlers will be invoked, too, of course.	3396	of course.
		3397
		3398	=head3 The special problem of life after fork - how is it possible?
		3399
		3400	Most uses of C<fork ()> consist of forking, then some simple calls to set
		3401	up/change the process environment, followed by a call to C<exec()>. This
		3402	sequence should be handled by libev without any problems.
		3403
		3404	This changes when the application actually wants to do event handling
		3405	in the child, or both parent in child, in effect "continuing" after the
		3406	fork.
		3407
		3408	The default mode of operation (for libev, with application help to detect
		3409	forks) is to duplicate all the state in the child, as would be expected
		3410	when I<either> the parent I<or> the child process continues.
		3411
		3412	When both processes want to continue using libev, then this is usually the
		3413	wrong result. In that case, usually one process (typically the parent) is
		3414	supposed to continue with all watchers in place as before, while the other
		3415	process typically wants to start fresh, i.e. without any active watchers.
		3416
		3417	The cleanest and most efficient way to achieve that with libev is to
		3418	simply create a new event loop, which of course will be "empty", and
		3419	use that for new watchers. This has the advantage of not touching more
		3420	memory than necessary, and thus avoiding the copy-on-write, and the
		3421	disadvantage of having to use multiple event loops (which do not support
		3422	signal watchers).
		3423
		3424	When this is not possible, or you want to use the default loop for
		3425	other reasons, then in the process that wants to start "fresh", call
		3426	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3427	Destroying the default loop will "orphan" (not stop) all registered
		3428	watchers, so you have to be careful not to execute code that modifies
		3429	those watchers. Note also that in that case, you have to re-register any
		3430	signal watchers.
2521		3431
2522	=head3 Watcher-Specific Functions and Data Members	3432	=head3 Watcher-Specific Functions and Data Members
2523		3433
2524	=over 4	3434	=over 4
2525		3435
2526	=item ev_fork_init (ev_signal *, callback)	3436	=item ev_fork_init (ev_fork *, callback)
2527		3437
2528	Initialises and configures the fork watcher - it has no parameters of any	3438	Initialises and configures the fork watcher - it has no parameters of any
2529	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3439	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2530	believe me.	3440	really.
2531		3441
2532	=back	3442	=back
2533		3443
2534		3444
		3445	=head2 C<ev_cleanup> - even the best things end
		3446
		3447	Cleanup watchers are called just before the event loop is being destroyed
		3448	by a call to C<ev_loop_destroy>.
		3449
		3450	While there is no guarantee that the event loop gets destroyed, cleanup
		3451	watchers provide a convenient method to install cleanup hooks for your
		3452	program, worker threads and so on - you just to make sure to destroy the
		3453	loop when you want them to be invoked.
		3454
		3455	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3456	all other watchers, they do not keep a reference to the event loop (which
		3457	makes a lot of sense if you think about it). Like all other watchers, you
		3458	can call libev functions in the callback, except C<ev_cleanup_start>.
		3459
		3460	=head3 Watcher-Specific Functions and Data Members
		3461
		3462	=over 4
		3463
		3464	=item ev_cleanup_init (ev_cleanup *, callback)
		3465
		3466	Initialises and configures the cleanup watcher - it has no parameters of
		3467	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3468	pointless, I assure you.
		3469
		3470	=back
		3471
		3472	Example: Register an atexit handler to destroy the default loop, so any
		3473	cleanup functions are called.
		3474
		3475	static void
		3476	program_exits (void)
		3477	{
		3478	ev_loop_destroy (EV_DEFAULT_UC);
		3479	}
		3480
		3481	...
		3482	atexit (program_exits);
		3483
		3484
2535	=head2 C<ev_async> - how to wake up another event loop	3485	=head2 C<ev_async> - how to wake up an event loop
2536		3486
2537	In general, you cannot use an C<ev_loop> from multiple threads or other	3487	In general, you cannot use an C<ev_loop> from multiple threads or other
2538	asynchronous sources such as signal handlers (as opposed to multiple event	3488	asynchronous sources such as signal handlers (as opposed to multiple event
2539	loops - those are of course safe to use in different threads).	3489	loops - those are of course safe to use in different threads).
2540		3490
2541	Sometimes, however, you need to wake up another event loop you do not	3491	Sometimes, however, you need to wake up an event loop you do not control,
2542	control, for example because it belongs to another thread. This is what	3492	for example because it belongs to another thread. This is what C<ev_async>
2543	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3493	watchers do: as long as the C<ev_async> watcher is active, you can signal
2544	can signal it by calling C<ev_async_send>, which is thread- and signal	3494	it by calling C<ev_async_send>, which is thread- and signal safe.
2545	safe.
2546		3495
2547	This functionality is very similar to C<ev_signal> watchers, as signals,	3496	This functionality is very similar to C<ev_signal> watchers, as signals,
2548	too, are asynchronous in nature, and signals, too, will be compressed	3497	too, are asynchronous in nature, and signals, too, will be compressed
2549	(i.e. the number of callback invocations may be less than the number of	3498	(i.e. the number of callback invocations may be less than the number of
2550	C<ev_async_sent> calls).	3499	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2551		3500	of "global async watchers" by using a watcher on an otherwise unused
2552	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3501	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2553	just the default loop.	3502	even without knowing which loop owns the signal.
2554		3503
2555	=head3 Queueing	3504	=head3 Queueing
2556		3505
2557	C<ev_async> does not support queueing of data in any way. The reason	3506	C<ev_async> does not support queueing of data in any way. The reason
2558	is that the author does not know of a simple (or any) algorithm for a	3507	is that the author does not know of a simple (or any) algorithm for a
2559	multiple-writer-single-reader queue that works in all cases and doesn't	3508	multiple-writer-single-reader queue that works in all cases and doesn't
2560	need elaborate support such as pthreads.	3509	need elaborate support such as pthreads or unportable memory access
		3510	semantics.
2561		3511
2562	That means that if you want to queue data, you have to provide your own	3512	That means that if you want to queue data, you have to provide your own
2563	queue. But at least I can tell you how to implement locking around your	3513	queue. But at least I can tell you how to implement locking around your
2564	queue:	3514	queue:
2565		3515
…		…
2643	=over 4	3593	=over 4
2644		3594
2645	=item ev_async_init (ev_async *, callback)	3595	=item ev_async_init (ev_async *, callback)
2646		3596
2647	Initialises and configures the async watcher - it has no parameters of any	3597	Initialises and configures the async watcher - it has no parameters of any
2648	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3598	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2649	trust me.	3599	trust me.
2650		3600
2651	=item ev_async_send (loop, ev_async *)	3601	=item ev_async_send (loop, ev_async *)
2652		3602
2653	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3603	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2654	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3604	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3605	returns.
		3606
2655	C<ev_feed_event>, this call is safe to do from other threads, signal or	3607	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2656	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3608	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2657	section below on what exactly this means).	3609	embedding section below on what exactly this means).
2658		3610
2659	This call incurs the overhead of a system call only once per loop iteration,	3611	Note that, as with other watchers in libev, multiple events might get
2660	so while the overhead might be noticeable, it doesn't apply to repeated	3612	compressed into a single callback invocation (another way to look at
2661	calls to C<ev_async_send>.	3613	this is that C<ev_async> watchers are level-triggered: they are set on
		3614	C<ev_async_send>, reset when the event loop detects that).
		3615
		3616	This call incurs the overhead of at most one extra system call per event
		3617	loop iteration, if the event loop is blocked, and no syscall at all if
		3618	the event loop (or your program) is processing events. That means that
		3619	repeated calls are basically free (there is no need to avoid calls for
		3620	performance reasons) and that the overhead becomes smaller (typically
		3621	zero) under load.
2662		3622
2663	=item bool = ev_async_pending (ev_async *)	3623	=item bool = ev_async_pending (ev_async *)
2664		3624
2665	Returns a non-zero value when C<ev_async_send> has been called on the	3625	Returns a non-zero value when C<ev_async_send> has been called on the
2666	watcher but the event has not yet been processed (or even noted) by the	3626	watcher but the event has not yet been processed (or even noted) by the
…		…
2669	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3629	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2670	the loop iterates next and checks for the watcher to have become active,	3630	the loop iterates next and checks for the watcher to have become active,
2671	it will reset the flag again. C<ev_async_pending> can be used to very	3631	it will reset the flag again. C<ev_async_pending> can be used to very
2672	quickly check whether invoking the loop might be a good idea.	3632	quickly check whether invoking the loop might be a good idea.
2673		3633
2674	Not that this does I<not> check whether the watcher itself is pending, only	3634	Not that this does I<not> check whether the watcher itself is pending,
2675	whether it has been requested to make this watcher pending.	3635	only whether it has been requested to make this watcher pending: there
		3636	is a time window between the event loop checking and resetting the async
		3637	notification, and the callback being invoked.
2676		3638
2677	=back	3639	=back
2678		3640
2679		3641
2680	=head1 OTHER FUNCTIONS	3642	=head1 OTHER FUNCTIONS
2681		3643
2682	There are some other functions of possible interest. Described. Here. Now.	3644	There are some other functions of possible interest. Described. Here. Now.
2683		3645
2684	=over 4	3646	=over 4
2685		3647
2686	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3648	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
2687		3649
2688	This function combines a simple timer and an I/O watcher, calls your	3650	This function combines a simple timer and an I/O watcher, calls your
2689	callback on whichever event happens first and automatically stops both	3651	callback on whichever event happens first and automatically stops both
2690	watchers. This is useful if you want to wait for a single event on an fd	3652	watchers. This is useful if you want to wait for a single event on an fd
2691	or timeout without having to allocate/configure/start/stop/free one or	3653	or timeout without having to allocate/configure/start/stop/free one or
…		…
2697		3659
2698	If C<timeout> is less than 0, then no timeout watcher will be	3660	If C<timeout> is less than 0, then no timeout watcher will be
2699	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3661	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2700	repeat = 0) will be started. C<0> is a valid timeout.	3662	repeat = 0) will be started. C<0> is a valid timeout.
2701		3663
2702	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3664	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2703	passed an C<revents> set like normal event callbacks (a combination of	3665	passed an C<revents> set like normal event callbacks (a combination of
2704	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3666	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2705	value passed to C<ev_once>. Note that it is possible to receive I<both>	3667	value passed to C<ev_once>. Note that it is possible to receive I<both>
2706	a timeout and an io event at the same time - you probably should give io	3668	a timeout and an io event at the same time - you probably should give io
2707	events precedence.	3669	events precedence.
2708		3670
2709	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3671	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2710		3672
2711	static void stdin_ready (int revents, void *arg)	3673	static void stdin_ready (int revents, void *arg)
2712	{	3674	{
2713	if (revents & EV_READ)	3675	if (revents & EV_READ)
2714	/* stdin might have data for us, joy! */;	3676	/* stdin might have data for us, joy! */;
2715	else if (revents & EV_TIMEOUT)	3677	else if (revents & EV_TIMER)
2716	/* doh, nothing entered */;	3678	/* doh, nothing entered */;
2717	}	3679	}
2718		3680
2719	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3681	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2720		3682
2721	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2722
2723	Feeds the given event set into the event loop, as if the specified event
2724	had happened for the specified watcher (which must be a pointer to an
2725	initialised but not necessarily started event watcher).
2726
2727	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3683	=item ev_feed_fd_event (loop, int fd, int revents)
2728		3684
2729	Feed an event on the given fd, as if a file descriptor backend detected	3685	Feed an event on the given fd, as if a file descriptor backend detected
2730	the given events it.	3686	the given events.
2731		3687
2732	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3688	=item ev_feed_signal_event (loop, int signum)
2733		3689
2734	Feed an event as if the given signal occurred (C<loop> must be the default	3690	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2735	loop!).	3691	which is async-safe.
2736		3692
2737	=back	3693	=back
		3694
		3695
		3696	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3697
		3698	This section explains some common idioms that are not immediately
		3699	obvious. Note that examples are sprinkled over the whole manual, and this
		3700	section only contains stuff that wouldn't fit anywhere else.
		3701
		3702	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3703
		3704	Each watcher has, by default, a C<void *data> member that you can read
		3705	or modify at any time: libev will completely ignore it. This can be used
		3706	to associate arbitrary data with your watcher. If you need more data and
		3707	don't want to allocate memory separately and store a pointer to it in that
		3708	data member, you can also "subclass" the watcher type and provide your own
		3709	data:
		3710
		3711	struct my_io
		3712	{
		3713	ev_io io;
		3714	int otherfd;
		3715	void *somedata;
		3716	struct whatever *mostinteresting;
		3717	};
		3718
		3719	...
		3720	struct my_io w;
		3721	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3722
		3723	And since your callback will be called with a pointer to the watcher, you
		3724	can cast it back to your own type:
		3725
		3726	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3727	{
		3728	struct my_io *w = (struct my_io *)w_;
		3729	...
		3730	}
		3731
		3732	More interesting and less C-conformant ways of casting your callback
		3733	function type instead have been omitted.
		3734
		3735	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3736
		3737	Another common scenario is to use some data structure with multiple
		3738	embedded watchers, in effect creating your own watcher that combines
		3739	multiple libev event sources into one "super-watcher":
		3740
		3741	struct my_biggy
		3742	{
		3743	int some_data;
		3744	ev_timer t1;
		3745	ev_timer t2;
		3746	}
		3747
		3748	In this case getting the pointer to C<my_biggy> is a bit more
		3749	complicated: Either you store the address of your C<my_biggy> struct in
		3750	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3751	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3752	real programmers):
		3753
		3754	#include <stddef.h>
		3755
		3756	static void
		3757	t1_cb (EV_P_ ev_timer *w, int revents)
		3758	{
		3759	struct my_biggy big = (struct my_biggy *)
		3760	(((char *)w) - offsetof (struct my_biggy, t1));
		3761	}
		3762
		3763	static void
		3764	t2_cb (EV_P_ ev_timer *w, int revents)
		3765	{
		3766	struct my_biggy big = (struct my_biggy *)
		3767	(((char *)w) - offsetof (struct my_biggy, t2));
		3768	}
		3769
		3770	=head2 AVOIDING FINISHING BEFORE RETURNING
		3771
		3772	Often you have structures like this in event-based programs:
		3773
		3774	callback ()
		3775	{
		3776	free (request);
		3777	}
		3778
		3779	request = start_new_request (..., callback);
		3780
		3781	The intent is to start some "lengthy" operation. The C<request> could be
		3782	used to cancel the operation, or do other things with it.
		3783
		3784	It's not uncommon to have code paths in C<start_new_request> that
		3785	immediately invoke the callback, for example, to report errors. Or you add
		3786	some caching layer that finds that it can skip the lengthy aspects of the
		3787	operation and simply invoke the callback with the result.
		3788
		3789	The problem here is that this will happen I<before> C<start_new_request>
		3790	has returned, so C<request> is not set.
		3791
		3792	Even if you pass the request by some safer means to the callback, you
		3793	might want to do something to the request after starting it, such as
		3794	canceling it, which probably isn't working so well when the callback has
		3795	already been invoked.
		3796
		3797	A common way around all these issues is to make sure that
		3798	C<start_new_request> I<always> returns before the callback is invoked. If
		3799	C<start_new_request> immediately knows the result, it can artificially
		3800	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3801	example, or more sneakily, by reusing an existing (stopped) watcher and
		3802	pushing it into the pending queue:
		3803
		3804	ev_set_cb (watcher, callback);
		3805	ev_feed_event (EV_A_ watcher, 0);
		3806
		3807	This way, C<start_new_request> can safely return before the callback is
		3808	invoked, while not delaying callback invocation too much.
		3809
		3810	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3811
		3812	Often (especially in GUI toolkits) there are places where you have
		3813	I<modal> interaction, which is most easily implemented by recursively
		3814	invoking C<ev_run>.
		3815
		3816	This brings the problem of exiting - a callback might want to finish the
		3817	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3818	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3819	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3820	other combination: In these cases, a simple C<ev_break> will not work.
		3821
		3822	The solution is to maintain "break this loop" variable for each C<ev_run>
		3823	invocation, and use a loop around C<ev_run> until the condition is
		3824	triggered, using C<EVRUN_ONCE>:
		3825
		3826	// main loop
		3827	int exit_main_loop = 0;
		3828
		3829	while (!exit_main_loop)
		3830	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3831
		3832	// in a modal watcher
		3833	int exit_nested_loop = 0;
		3834
		3835	while (!exit_nested_loop)
		3836	ev_run (EV_A_ EVRUN_ONCE);
		3837
		3838	To exit from any of these loops, just set the corresponding exit variable:
		3839
		3840	// exit modal loop
		3841	exit_nested_loop = 1;
		3842
		3843	// exit main program, after modal loop is finished
		3844	exit_main_loop = 1;
		3845
		3846	// exit both
		3847	exit_main_loop = exit_nested_loop = 1;
		3848
		3849	=head2 THREAD LOCKING EXAMPLE
		3850
		3851	Here is a fictitious example of how to run an event loop in a different
		3852	thread from where callbacks are being invoked and watchers are
		3853	created/added/removed.
		3854
		3855	For a real-world example, see the C<EV::Loop::Async> perl module,
		3856	which uses exactly this technique (which is suited for many high-level
		3857	languages).
		3858
		3859	The example uses a pthread mutex to protect the loop data, a condition
		3860	variable to wait for callback invocations, an async watcher to notify the
		3861	event loop thread and an unspecified mechanism to wake up the main thread.
		3862
		3863	First, you need to associate some data with the event loop:
		3864
		3865	typedef struct {
		3866	mutex_t lock; /* global loop lock */
		3867	ev_async async_w;
		3868	thread_t tid;
		3869	cond_t invoke_cv;
		3870	} userdata;
		3871
		3872	void prepare_loop (EV_P)
		3873	{
		3874	// for simplicity, we use a static userdata struct.
		3875	static userdata u;
		3876
		3877	ev_async_init (&u->async_w, async_cb);
		3878	ev_async_start (EV_A_ &u->async_w);
		3879
		3880	pthread_mutex_init (&u->lock, 0);
		3881	pthread_cond_init (&u->invoke_cv, 0);
		3882
		3883	// now associate this with the loop
		3884	ev_set_userdata (EV_A_ u);
		3885	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3886	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3887
		3888	// then create the thread running ev_run
		3889	pthread_create (&u->tid, 0, l_run, EV_A);
		3890	}
		3891
		3892	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3893	solely to wake up the event loop so it takes notice of any new watchers
		3894	that might have been added:
		3895
		3896	static void
		3897	async_cb (EV_P_ ev_async *w, int revents)
		3898	{
		3899	// just used for the side effects
		3900	}
		3901
		3902	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3903	protecting the loop data, respectively.
		3904
		3905	static void
		3906	l_release (EV_P)
		3907	{
		3908	userdata *u = ev_userdata (EV_A);
		3909	pthread_mutex_unlock (&u->lock);
		3910	}
		3911
		3912	static void
		3913	l_acquire (EV_P)
		3914	{
		3915	userdata *u = ev_userdata (EV_A);
		3916	pthread_mutex_lock (&u->lock);
		3917	}
		3918
		3919	The event loop thread first acquires the mutex, and then jumps straight
		3920	into C<ev_run>:
		3921
		3922	void *
		3923	l_run (void *thr_arg)
		3924	{
		3925	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3926
		3927	l_acquire (EV_A);
		3928	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3929	ev_run (EV_A_ 0);
		3930	l_release (EV_A);
		3931
		3932	return 0;
		3933	}
		3934
		3935	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3936	signal the main thread via some unspecified mechanism (signals? pipe
		3937	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3938	have been called (in a while loop because a) spurious wakeups are possible
		3939	and b) skipping inter-thread-communication when there are no pending
		3940	watchers is very beneficial):
		3941
		3942	static void
		3943	l_invoke (EV_P)
		3944	{
		3945	userdata *u = ev_userdata (EV_A);
		3946
		3947	while (ev_pending_count (EV_A))
		3948	{
		3949	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3950	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3951	}
		3952	}
		3953
		3954	Now, whenever the main thread gets told to invoke pending watchers, it
		3955	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3956	thread to continue:
		3957
		3958	static void
		3959	real_invoke_pending (EV_P)
		3960	{
		3961	userdata *u = ev_userdata (EV_A);
		3962
		3963	pthread_mutex_lock (&u->lock);
		3964	ev_invoke_pending (EV_A);
		3965	pthread_cond_signal (&u->invoke_cv);
		3966	pthread_mutex_unlock (&u->lock);
		3967	}
		3968
		3969	Whenever you want to start/stop a watcher or do other modifications to an
		3970	event loop, you will now have to lock:
		3971
		3972	ev_timer timeout_watcher;
		3973	userdata *u = ev_userdata (EV_A);
		3974
		3975	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3976
		3977	pthread_mutex_lock (&u->lock);
		3978	ev_timer_start (EV_A_ &timeout_watcher);
		3979	ev_async_send (EV_A_ &u->async_w);
		3980	pthread_mutex_unlock (&u->lock);
		3981
		3982	Note that sending the C<ev_async> watcher is required because otherwise
		3983	an event loop currently blocking in the kernel will have no knowledge
		3984	about the newly added timer. By waking up the loop it will pick up any new
		3985	watchers in the next event loop iteration.
		3986
		3987	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3988
		3989	While the overhead of a callback that e.g. schedules a thread is small, it
		3990	is still an overhead. If you embed libev, and your main usage is with some
		3991	kind of threads or coroutines, you might want to customise libev so that
		3992	doesn't need callbacks anymore.
		3993
		3994	Imagine you have coroutines that you can switch to using a function
		3995	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3996	and that due to some magic, the currently active coroutine is stored in a
		3997	global called C<current_coro>. Then you can build your own "wait for libev
		3998	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3999	the differing C<;> conventions):
		4000
		4001	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4002	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4003
		4004	That means instead of having a C callback function, you store the
		4005	coroutine to switch to in each watcher, and instead of having libev call
		4006	your callback, you instead have it switch to that coroutine.
		4007
		4008	A coroutine might now wait for an event with a function called
		4009	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		4010	matter when, or whether the watcher is active or not when this function is
		4011	called):
		4012
		4013	void
		4014	wait_for_event (ev_watcher *w)
		4015	{
		4016	ev_set_cb (w, current_coro);
		4017	switch_to (libev_coro);
		4018	}
		4019
		4020	That basically suspends the coroutine inside C<wait_for_event> and
		4021	continues the libev coroutine, which, when appropriate, switches back to
		4022	this or any other coroutine.
		4023
		4024	You can do similar tricks if you have, say, threads with an event queue -
		4025	instead of storing a coroutine, you store the queue object and instead of
		4026	switching to a coroutine, you push the watcher onto the queue and notify
		4027	any waiters.
		4028
		4029	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		4030	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		4031
		4032	// my_ev.h
		4033	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4034	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4035	#include "../libev/ev.h"
		4036
		4037	// my_ev.c
		4038	#define EV_H "my_ev.h"
		4039	#include "../libev/ev.c"
		4040
		4041	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4042	F<my_ev.c> into your project. When properly specifying include paths, you
		4043	can even use F<ev.h> as header file name directly.
2738		4044
2739		4045
2740	=head1 LIBEVENT EMULATION	4046	=head1 LIBEVENT EMULATION
2741		4047
2742	Libev offers a compatibility emulation layer for libevent. It cannot	4048	Libev offers a compatibility emulation layer for libevent. It cannot
2743	emulate the internals of libevent, so here are some usage hints:	4049	emulate the internals of libevent, so here are some usage hints:
2744		4050
2745	=over 4	4051	=over 4
		4052
		4053	=item * Only the libevent-1.4.1-beta API is being emulated.
		4054
		4055	This was the newest libevent version available when libev was implemented,
		4056	and is still mostly unchanged in 2010.
2746		4057
2747	=item * Use it by including <event.h>, as usual.	4058	=item * Use it by including <event.h>, as usual.
2748		4059
2749	=item * The following members are fully supported: ev_base, ev_callback,	4060	=item * The following members are fully supported: ev_base, ev_callback,
2750	ev_arg, ev_fd, ev_res, ev_events.	4061	ev_arg, ev_fd, ev_res, ev_events.
…		…
2756	=item * Priorities are not currently supported. Initialising priorities	4067	=item * Priorities are not currently supported. Initialising priorities
2757	will fail and all watchers will have the same priority, even though there	4068	will fail and all watchers will have the same priority, even though there
2758	is an ev_pri field.	4069	is an ev_pri field.
2759		4070
2760	=item * In libevent, the last base created gets the signals, in libev, the	4071	=item * In libevent, the last base created gets the signals, in libev, the
2761	first base created (== the default loop) gets the signals.	4072	base that registered the signal gets the signals.
2762		4073
2763	=item * Other members are not supported.	4074	=item * Other members are not supported.
2764		4075
2765	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4076	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2766	to use the libev header file and library.	4077	to use the libev header file and library.
2767		4078
2768	=back	4079	=back
2769		4080
2770	=head1 C++ SUPPORT	4081	=head1 C++ SUPPORT
		4082
		4083	=head2 C API
		4084
		4085	The normal C API should work fine when used from C++: both ev.h and the
		4086	libev sources can be compiled as C++. Therefore, code that uses the C API
		4087	will work fine.
		4088
		4089	Proper exception specifications might have to be added to callbacks passed
		4090	to libev: exceptions may be thrown only from watcher callbacks, all other
		4091	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4092	callbacks) must not throw exceptions, and might need a C<noexcept>
		4093	specification. If you have code that needs to be compiled as both C and
		4094	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4095
		4096	static void
		4097	fatal_error (const char *msg) EV_NOEXCEPT
		4098	{
		4099	perror (msg);
		4100	abort ();
		4101	}
		4102
		4103	...
		4104	ev_set_syserr_cb (fatal_error);
		4105
		4106	The only API functions that can currently throw exceptions are C<ev_run>,
		4107	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4108	because it runs cleanup watchers).
		4109
		4110	Throwing exceptions in watcher callbacks is only supported if libev itself
		4111	is compiled with a C++ compiler or your C and C++ environments allow
		4112	throwing exceptions through C libraries (most do).
		4113
		4114	=head2 C++ API
2771		4115
2772	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4116	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2773	you to use some convenience methods to start/stop watchers and also change	4117	you to use some convenience methods to start/stop watchers and also change
2774	the callback model to a model using method callbacks on objects.	4118	the callback model to a model using method callbacks on objects.
2775		4119
2776	To use it,	4120	To use it,
2777		4121
2778	#include <ev++.h>	4122	#include <ev++.h>
2779		4123
2780	This automatically includes F<ev.h> and puts all of its definitions (many	4124	This automatically includes F<ev.h> and puts all of its definitions (many
2781	of them macros) into the global namespace. All C++ specific things are	4125	of them macros) into the global namespace. All C++ specific things are
2782	put into the C<ev> namespace. It should support all the same embedding	4126	put into the C<ev> namespace. It should support all the same embedding
…		…
2785	Care has been taken to keep the overhead low. The only data member the C++	4129	Care has been taken to keep the overhead low. The only data member the C++
2786	classes add (compared to plain C-style watchers) is the event loop pointer	4130	classes add (compared to plain C-style watchers) is the event loop pointer
2787	that the watcher is associated with (or no additional members at all if	4131	that the watcher is associated with (or no additional members at all if
2788	you disable C<EV_MULTIPLICITY> when embedding libev).	4132	you disable C<EV_MULTIPLICITY> when embedding libev).
2789		4133
2790	Currently, functions, and static and non-static member functions can be	4134	Currently, functions, static and non-static member functions and classes
2791	used as callbacks. Other types should be easy to add as long as they only	4135	with C<operator ()> can be used as callbacks. Other types should be easy
2792	need one additional pointer for context. If you need support for other	4136	to add as long as they only need one additional pointer for context. If
2793	types of functors please contact the author (preferably after implementing	4137	you need support for other types of functors please contact the author
2794	it).	4138	(preferably after implementing it).
		4139
		4140	For all this to work, your C++ compiler either has to use the same calling
		4141	conventions as your C compiler (for static member functions), or you have
		4142	to embed libev and compile libev itself as C++.
2795		4143
2796	Here is a list of things available in the C<ev> namespace:	4144	Here is a list of things available in the C<ev> namespace:
2797		4145
2798	=over 4	4146	=over 4
2799		4147
…		…
2809	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4157	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2810		4158
2811	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4159	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2812	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4160	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2813	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4161	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2814	defines by many implementations.	4162	defined by many implementations.
2815		4163
2816	All of those classes have these methods:	4164	All of those classes have these methods:
2817		4165
2818	=over 4	4166	=over 4
2819		4167
2820	=item ev::TYPE::TYPE ()	4168	=item ev::TYPE::TYPE ()
2821		4169
2822	=item ev::TYPE::TYPE (struct ev_loop *)	4170	=item ev::TYPE::TYPE (loop)
2823		4171
2824	=item ev::TYPE::~TYPE	4172	=item ev::TYPE::~TYPE
2825		4173
2826	The constructor (optionally) takes an event loop to associate the watcher	4174	The constructor (optionally) takes an event loop to associate the watcher
2827	with. If it is omitted, it will use C<EV_DEFAULT>.	4175	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2859		4207
2860	myclass obj;	4208	myclass obj;
2861	ev::io iow;	4209	ev::io iow;
2862	iow.set <myclass, &myclass::io_cb> (&obj);	4210	iow.set <myclass, &myclass::io_cb> (&obj);
2863		4211
		4212	=item w->set (object *)
		4213
		4214	This is a variation of a method callback - leaving out the method to call
		4215	will default the method to C<operator ()>, which makes it possible to use
		4216	functor objects without having to manually specify the C<operator ()> all
		4217	the time. Incidentally, you can then also leave out the template argument
		4218	list.
		4219
		4220	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		4221	int revents)>.
		4222
		4223	See the method-C<set> above for more details.
		4224
		4225	Example: use a functor object as callback.
		4226
		4227	struct myfunctor
		4228	{
		4229	void operator() (ev::io &w, int revents)
		4230	{
		4231	...
		4232	}
		4233	}
		4234
		4235	myfunctor f;
		4236
		4237	ev::io w;
		4238	w.set (&f);
		4239
2864	=item w->set<function> (void *data = 0)	4240	=item w->set<function> (void *data = 0)
2865		4241
2866	Also sets a callback, but uses a static method or plain function as	4242	Also sets a callback, but uses a static method or plain function as
2867	callback. The optional C<data> argument will be stored in the watcher's	4243	callback. The optional C<data> argument will be stored in the watcher's
2868	C<data> member and is free for you to use.	4244	C<data> member and is free for you to use.
…		…
2874	Example: Use a plain function as callback.	4250	Example: Use a plain function as callback.
2875		4251
2876	static void io_cb (ev::io &w, int revents) { }	4252	static void io_cb (ev::io &w, int revents) { }
2877	iow.set <io_cb> ();	4253	iow.set <io_cb> ();
2878		4254
2879	=item w->set (struct ev_loop *)	4255	=item w->set (loop)
2880		4256
2881	Associates a different C<struct ev_loop> with this watcher. You can only	4257	Associates a different C<struct ev_loop> with this watcher. You can only
2882	do this when the watcher is inactive (and not pending either).	4258	do this when the watcher is inactive (and not pending either).
2883		4259
2884	=item w->set ([arguments])	4260	=item w->set ([arguments])
2885		4261
2886	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4262	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4263	with the same arguments. Either this method or a suitable start method
2887	called at least once. Unlike the C counterpart, an active watcher gets	4264	must be called at least once. Unlike the C counterpart, an active watcher
2888	automatically stopped and restarted when reconfiguring it with this	4265	gets automatically stopped and restarted when reconfiguring it with this
2889	method.	4266	method.
		4267
		4268	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4269	clashing with the C<set (loop)> method.
		4270
		4271	For C<ev::io> watchers there is an additional C<set> method that acepts a
		4272	new event mask only, and internally calls C<ev_io_modfify>.
2890		4273
2891	=item w->start ()	4274	=item w->start ()
2892		4275
2893	Starts the watcher. Note that there is no C<loop> argument, as the	4276	Starts the watcher. Note that there is no C<loop> argument, as the
2894	constructor already stores the event loop.	4277	constructor already stores the event loop.
2895		4278
		4279	=item w->start ([arguments])
		4280
		4281	Instead of calling C<set> and C<start> methods separately, it is often
		4282	convenient to wrap them in one call. Uses the same type of arguments as
		4283	the configure C<set> method of the watcher.
		4284
2896	=item w->stop ()	4285	=item w->stop ()
2897		4286
2898	Stops the watcher if it is active. Again, no C<loop> argument.	4287	Stops the watcher if it is active. Again, no C<loop> argument.
2899		4288
2900	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4289	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2912		4301
2913	=back	4302	=back
2914		4303
2915	=back	4304	=back
2916		4305
2917	Example: Define a class with an IO and idle watcher, start one of them in	4306	Example: Define a class with two I/O and idle watchers, start the I/O
2918	the constructor.	4307	watchers in the constructor.
2919		4308
2920	class myclass	4309	class myclass
2921	{	4310	{
2922	ev::io io ; void io_cb (ev::io &w, int revents);	4311	ev::io io ; void io_cb (ev::io &w, int revents);
		4312	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2923	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4313	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2924		4314
2925	myclass (int fd)	4315	myclass (int fd)
2926	{	4316	{
2927	io .set <myclass, &myclass::io_cb > (this);	4317	io .set <myclass, &myclass::io_cb > (this);
		4318	io2 .set <myclass, &myclass::io2_cb > (this);
2928	idle.set <myclass, &myclass::idle_cb> (this);	4319	idle.set <myclass, &myclass::idle_cb> (this);
2929		4320
2930	io.start (fd, ev::READ);	4321	io.set (fd, ev::WRITE); // configure the watcher
		4322	io.start (); // start it whenever convenient
		4323
		4324	io2.start (fd, ev::READ); // set + start in one call
2931	}	4325	}
2932	};	4326	};
2933		4327
2934		4328
2935	=head1 OTHER LANGUAGE BINDINGS	4329	=head1 OTHER LANGUAGE BINDINGS
…		…
2954	L<http://software.schmorp.de/pkg/EV>.	4348	L<http://software.schmorp.de/pkg/EV>.
2955		4349
2956	=item Python	4350	=item Python
2957		4351
2958	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4352	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2959	seems to be quite complete and well-documented. Note, however, that the	4353	seems to be quite complete and well-documented.
2960	patch they require for libev is outright dangerous as it breaks the ABI
2961	for everybody else, and therefore, should never be applied in an installed
2962	libev (if python requires an incompatible ABI then it needs to embed
2963	libev).
2964		4354
2965	=item Ruby	4355	=item Ruby
2966		4356
2967	Tony Arcieri has written a ruby extension that offers access to a subset	4357	Tony Arcieri has written a ruby extension that offers access to a subset
2968	of the libev API and adds file handle abstractions, asynchronous DNS and	4358	of the libev API and adds file handle abstractions, asynchronous DNS and
2969	more on top of it. It can be found via gem servers. Its homepage is at	4359	more on top of it. It can be found via gem servers. Its homepage is at
2970	L<http://rev.rubyforge.org/>.	4360	L<http://rev.rubyforge.org/>.
2971		4361
		4362	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4363	makes rev work even on mingw.
		4364
		4365	=item Haskell
		4366
		4367	A haskell binding to libev is available at
		4368	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4369
2972	=item D	4370	=item D
2973		4371
2974	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4372	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2975	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4373	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
2976		4374
2977	=item Ocaml	4375	=item Ocaml
2978		4376
2979	Erkki Seppala has written Ocaml bindings for libev, to be found at	4377	Erkki Seppala has written Ocaml bindings for libev, to be found at
2980	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4378	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4379
		4380	=item Lua
		4381
		4382	Brian Maher has written a partial interface to libev for lua (at the
		4383	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4384	L<http://github.com/brimworks/lua-ev>.
		4385
		4386	=item Javascript
		4387
		4388	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4389
		4390	=item Others
		4391
		4392	There are others, and I stopped counting.
2981		4393
2982	=back	4394	=back
2983		4395
2984		4396
2985	=head1 MACRO MAGIC	4397	=head1 MACRO MAGIC
…		…
2999	loop argument"). The C<EV_A> form is used when this is the sole argument,	4411	loop argument"). The C<EV_A> form is used when this is the sole argument,
3000	C<EV_A_> is used when other arguments are following. Example:	4412	C<EV_A_> is used when other arguments are following. Example:
3001		4413
3002	ev_unref (EV_A);	4414	ev_unref (EV_A);
3003	ev_timer_add (EV_A_ watcher);	4415	ev_timer_add (EV_A_ watcher);
3004	ev_loop (EV_A_ 0);	4416	ev_run (EV_A_ 0);
3005		4417
3006	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4418	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3007	which is often provided by the following macro.	4419	which is often provided by the following macro.
3008		4420
3009	=item C<EV_P>, C<EV_P_>	4421	=item C<EV_P>, C<EV_P_>
…		…
3022	suitable for use with C<EV_A>.	4434	suitable for use with C<EV_A>.
3023		4435
3024	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4436	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3025		4437
3026	Similar to the other two macros, this gives you the value of the default	4438	Similar to the other two macros, this gives you the value of the default
3027	loop, if multiple loops are supported ("ev loop default").	4439	loop, if multiple loops are supported ("ev loop default"). The default loop
		4440	will be initialised if it isn't already initialised.
		4441
		4442	For non-multiplicity builds, these macros do nothing, so you always have
		4443	to initialise the loop somewhere.
3028		4444
3029	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4445	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3030		4446
3031	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4447	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3032	default loop has been initialised (C<UC> == unchecked). Their behaviour	4448	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3049	}	4465	}
3050		4466
3051	ev_check check;	4467	ev_check check;
3052	ev_check_init (&check, check_cb);	4468	ev_check_init (&check, check_cb);
3053	ev_check_start (EV_DEFAULT_ &check);	4469	ev_check_start (EV_DEFAULT_ &check);
3054	ev_loop (EV_DEFAULT_ 0);	4470	ev_run (EV_DEFAULT_ 0);
3055		4471
3056	=head1 EMBEDDING	4472	=head1 EMBEDDING
3057		4473
3058	Libev can (and often is) directly embedded into host	4474	Libev can (and often is) directly embedded into host
3059	applications. Examples of applications that embed it include the Deliantra	4475	applications. Examples of applications that embed it include the Deliantra
…		…
3086		4502
3087	#define EV_STANDALONE 1	4503	#define EV_STANDALONE 1
3088	#include "ev.h"	4504	#include "ev.h"
3089		4505
3090	Both header files and implementation files can be compiled with a C++	4506	Both header files and implementation files can be compiled with a C++
3091	compiler (at least, thats a stated goal, and breakage will be treated	4507	compiler (at least, that's a stated goal, and breakage will be treated
3092	as a bug).	4508	as a bug).
3093		4509
3094	You need the following files in your source tree, or in a directory	4510	You need the following files in your source tree, or in a directory
3095	in your include path (e.g. in libev/ when using -Ilibev):	4511	in your include path (e.g. in libev/ when using -Ilibev):
3096		4512
…		…
3099	ev_vars.h	4515	ev_vars.h
3100	ev_wrap.h	4516	ev_wrap.h
3101		4517
3102	ev_win32.c required on win32 platforms only	4518	ev_win32.c required on win32 platforms only
3103		4519
3104	ev_select.c only when select backend is enabled (which is enabled by default)	4520	ev_select.c only when select backend is enabled
3105	ev_poll.c only when poll backend is enabled (disabled by default)	4521	ev_poll.c only when poll backend is enabled
3106	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4522	ev_epoll.c only when the epoll backend is enabled
		4523	ev_linuxaio.c only when the linux aio backend is enabled
		4524	ev_iouring.c only when the linux io_uring backend is enabled
3107	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4525	ev_kqueue.c only when the kqueue backend is enabled
3108	ev_port.c only when the solaris port backend is enabled (disabled by default)	4526	ev_port.c only when the solaris port backend is enabled
3109		4527
3110	F<ev.c> includes the backend files directly when enabled, so you only need	4528	F<ev.c> includes the backend files directly when enabled, so you only need
3111	to compile this single file.	4529	to compile this single file.
3112		4530
3113	=head3 LIBEVENT COMPATIBILITY API	4531	=head3 LIBEVENT COMPATIBILITY API
…		…
3139	libev.m4	4557	libev.m4
3140		4558
3141	=head2 PREPROCESSOR SYMBOLS/MACROS	4559	=head2 PREPROCESSOR SYMBOLS/MACROS
3142		4560
3143	Libev can be configured via a variety of preprocessor symbols you have to	4561	Libev can be configured via a variety of preprocessor symbols you have to
3144	define before including any of its files. The default in the absence of	4562	define before including (or compiling) any of its files. The default in
3145	autoconf is documented for every option.	4563	the absence of autoconf is documented for every option.
		4564
		4565	Symbols marked with "(h)" do not change the ABI, and can have different
		4566	values when compiling libev vs. including F<ev.h>, so it is permissible
		4567	to redefine them before including F<ev.h> without breaking compatibility
		4568	to a compiled library. All other symbols change the ABI, which means all
		4569	users of libev and the libev code itself must be compiled with compatible
		4570	settings.
3146		4571
3147	=over 4	4572	=over 4
3148		4573
		4574	=item EV_COMPAT3 (h)
		4575
		4576	Backwards compatibility is a major concern for libev. This is why this
		4577	release of libev comes with wrappers for the functions and symbols that
		4578	have been renamed between libev version 3 and 4.
		4579
		4580	You can disable these wrappers (to test compatibility with future
		4581	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4582	sources. This has the additional advantage that you can drop the C<struct>
		4583	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4584	typedef in that case.
		4585
		4586	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4587	and in some even more future version the compatibility code will be
		4588	removed completely.
		4589
3149	=item EV_STANDALONE	4590	=item EV_STANDALONE (h)
3150		4591
3151	Must always be C<1> if you do not use autoconf configuration, which	4592	Must always be C<1> if you do not use autoconf configuration, which
3152	keeps libev from including F<config.h>, and it also defines dummy	4593	keeps libev from including F<config.h>, and it also defines dummy
3153	implementations for some libevent functions (such as logging, which is not	4594	implementations for some libevent functions (such as logging, which is not
3154	supported). It will also not define any of the structs usually found in	4595	supported). It will also not define any of the structs usually found in
3155	F<event.h> that are not directly supported by the libev core alone.	4596	F<event.h> that are not directly supported by the libev core alone.
3156		4597
		4598	In standalone mode, libev will still try to automatically deduce the
		4599	configuration, but has to be more conservative.
		4600
		4601	=item EV_USE_FLOOR
		4602
		4603	If defined to be C<1>, libev will use the C<floor ()> function for its
		4604	periodic reschedule calculations, otherwise libev will fall back on a
		4605	portable (slower) implementation. If you enable this, you usually have to
		4606	link against libm or something equivalent. Enabling this when the C<floor>
		4607	function is not available will fail, so the safe default is to not enable
		4608	this.
		4609
3157	=item EV_USE_MONOTONIC	4610	=item EV_USE_MONOTONIC
3158		4611
3159	If defined to be C<1>, libev will try to detect the availability of the	4612	If defined to be C<1>, libev will try to detect the availability of the
3160	monotonic clock option at both compile time and runtime. Otherwise no use	4613	monotonic clock option at both compile time and runtime. Otherwise no
3161	of the monotonic clock option will be attempted. If you enable this, you	4614	use of the monotonic clock option will be attempted. If you enable this,
3162	usually have to link against librt or something similar. Enabling it when	4615	you usually have to link against librt or something similar. Enabling it
3163	the functionality isn't available is safe, though, although you have	4616	when the functionality isn't available is safe, though, although you have
3164	to make sure you link against any libraries where the C<clock_gettime>	4617	to make sure you link against any libraries where the C<clock_gettime>
3165	function is hiding in (often F<-lrt>).	4618	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3166		4619
3167	=item EV_USE_REALTIME	4620	=item EV_USE_REALTIME
3168		4621
3169	If defined to be C<1>, libev will try to detect the availability of the	4622	If defined to be C<1>, libev will try to detect the availability of the
3170	real-time clock option at compile time (and assume its availability at	4623	real-time clock option at compile time (and assume its availability
3171	runtime if successful). Otherwise no use of the real-time clock option will	4624	at runtime if successful). Otherwise no use of the real-time clock
3172	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4625	option will be attempted. This effectively replaces C<gettimeofday>
3173	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4626	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3174	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4627	correctness. See the note about libraries in the description of
		4628	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4629	C<EV_USE_CLOCK_SYSCALL>.
		4630
		4631	=item EV_USE_CLOCK_SYSCALL
		4632
		4633	If defined to be C<1>, libev will try to use a direct syscall instead
		4634	of calling the system-provided C<clock_gettime> function. This option
		4635	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4636	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4637	programs needlessly. Using a direct syscall is slightly slower (in
		4638	theory), because no optimised vdso implementation can be used, but avoids
		4639	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4640	higher, as it simplifies linking (no need for C<-lrt>).
3175		4641
3176	=item EV_USE_NANOSLEEP	4642	=item EV_USE_NANOSLEEP
3177		4643
3178	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4644	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3179	and will use it for delays. Otherwise it will use C<select ()>.	4645	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3184	available and will probe for kernel support at runtime. This will improve	4650	available and will probe for kernel support at runtime. This will improve
3185	C<ev_signal> and C<ev_async> performance and reduce resource consumption.	4651	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
3186	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc	4652	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
3187	2.7 or newer, otherwise disabled.	4653	2.7 or newer, otherwise disabled.
3188		4654
		4655	=item EV_USE_SIGNALFD
		4656
		4657	If defined to be C<1>, then libev will assume that C<signalfd ()> is
		4658	available and will probe for kernel support at runtime. This enables
		4659	the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If
		4660	undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4661	2.7 or newer, otherwise disabled.
		4662
		4663	=item EV_USE_TIMERFD
		4664
		4665	If defined to be C<1>, then libev will assume that C<timerfd ()> is
		4666	available and will probe for kernel support at runtime. This allows
		4667	libev to detect time jumps accurately. If undefined, it will be enabled
		4668	if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
		4669	C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled.
		4670
		4671	=item EV_USE_EVENTFD
		4672
		4673	If defined to be C<1>, then libev will assume that C<eventfd ()> is
		4674	available and will probe for kernel support at runtime. This will improve
		4675	C<ev_signal> and C<ev_async> performance and reduce resource consumption.
		4676	If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
		4677	2.7 or newer, otherwise disabled.
		4678
3189	=item EV_USE_SELECT	4679	=item EV_USE_SELECT
3190		4680
3191	If undefined or defined to be C<1>, libev will compile in support for the	4681	If undefined or defined to be C<1>, libev will compile in support for the
3192	C<select>(2) backend. No attempt at auto-detection will be done: if no	4682	C<select>(2) backend. No attempt at auto-detection will be done: if no
3193	other method takes over, select will be it. Otherwise the select backend	4683	other method takes over, select will be it. Otherwise the select backend
…		…
3195		4685
3196	=item EV_SELECT_USE_FD_SET	4686	=item EV_SELECT_USE_FD_SET
3197		4687
3198	If defined to C<1>, then the select backend will use the system C<fd_set>	4688	If defined to C<1>, then the select backend will use the system C<fd_set>
3199	structure. This is useful if libev doesn't compile due to a missing	4689	structure. This is useful if libev doesn't compile due to a missing
3200	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4690	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3201	exotic systems. This usually limits the range of file descriptors to some	4691	on exotic systems. This usually limits the range of file descriptors to
3202	low limit such as 1024 or might have other limitations (winsocket only	4692	some low limit such as 1024 or might have other limitations (winsocket
3203	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4693	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3204	influence the size of the C<fd_set> used.	4694	configures the maximum size of the C<fd_set>.
3205		4695
3206	=item EV_SELECT_IS_WINSOCKET	4696	=item EV_SELECT_IS_WINSOCKET
3207		4697
3208	When defined to C<1>, the select backend will assume that	4698	When defined to C<1>, the select backend will assume that
3209	select/socket/connect etc. don't understand file descriptors but	4699	select/socket/connect etc. don't understand file descriptors but
…		…
3211	be used is the winsock select). This means that it will call	4701	be used is the winsock select). This means that it will call
3212	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4702	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3213	it is assumed that all these functions actually work on fds, even	4703	it is assumed that all these functions actually work on fds, even
3214	on win32. Should not be defined on non-win32 platforms.	4704	on win32. Should not be defined on non-win32 platforms.
3215		4705
3216	=item EV_FD_TO_WIN32_HANDLE	4706	=item EV_FD_TO_WIN32_HANDLE(fd)
3217		4707
3218	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4708	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3219	file descriptors to socket handles. When not defining this symbol (the	4709	file descriptors to socket handles. When not defining this symbol (the
3220	default), then libev will call C<_get_osfhandle>, which is usually	4710	default), then libev will call C<_get_osfhandle>, which is usually
3221	correct. In some cases, programs use their own file descriptor management,	4711	correct. In some cases, programs use their own file descriptor management,
3222	in which case they can provide this function to map fds to socket handles.	4712	in which case they can provide this function to map fds to socket handles.
3223		4713
		4714	=item EV_WIN32_HANDLE_TO_FD(handle)
		4715
		4716	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4717	using the standard C<_open_osfhandle> function. For programs implementing
		4718	their own fd to handle mapping, overwriting this function makes it easier
		4719	to do so. This can be done by defining this macro to an appropriate value.
		4720
		4721	=item EV_WIN32_CLOSE_FD(fd)
		4722
		4723	If programs implement their own fd to handle mapping on win32, then this
		4724	macro can be used to override the C<close> function, useful to unregister
		4725	file descriptors again. Note that the replacement function has to close
		4726	the underlying OS handle.
		4727
		4728	=item EV_USE_WSASOCKET
		4729
		4730	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4731	communication socket, which works better in some environments. Otherwise,
		4732	the normal C<socket> function will be used, which works better in other
		4733	environments.
		4734
3224	=item EV_USE_POLL	4735	=item EV_USE_POLL
3225		4736
3226	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4737	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3227	backend. Otherwise it will be enabled on non-win32 platforms. It	4738	backend. Otherwise it will be enabled on non-win32 platforms. It
3228	takes precedence over select.	4739	takes precedence over select.
…		…
3232	If defined to be C<1>, libev will compile in support for the Linux	4743	If defined to be C<1>, libev will compile in support for the Linux
3233	C<epoll>(7) backend. Its availability will be detected at runtime,	4744	C<epoll>(7) backend. Its availability will be detected at runtime,
3234	otherwise another method will be used as fallback. This is the preferred	4745	otherwise another method will be used as fallback. This is the preferred
3235	backend for GNU/Linux systems. If undefined, it will be enabled if the	4746	backend for GNU/Linux systems. If undefined, it will be enabled if the
3236	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4747	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4748
		4749	=item EV_USE_LINUXAIO
		4750
		4751	If defined to be C<1>, libev will compile in support for the Linux aio
		4752	backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be
		4753	enabled on linux, otherwise disabled.
		4754
		4755	=item EV_USE_IOURING
		4756
		4757	If defined to be C<1>, libev will compile in support for the Linux
		4758	io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's
		4759	current limitations it has to be requested explicitly. If undefined, it
		4760	will be enabled on linux, otherwise disabled.
3237		4761
3238	=item EV_USE_KQUEUE	4762	=item EV_USE_KQUEUE
3239		4763
3240	If defined to be C<1>, libev will compile in support for the BSD style	4764	If defined to be C<1>, libev will compile in support for the BSD style
3241	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4765	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3263	If defined to be C<1>, libev will compile in support for the Linux inotify	4787	If defined to be C<1>, libev will compile in support for the Linux inotify
3264	interface to speed up C<ev_stat> watchers. Its actual availability will	4788	interface to speed up C<ev_stat> watchers. Its actual availability will
3265	be detected at runtime. If undefined, it will be enabled if the headers	4789	be detected at runtime. If undefined, it will be enabled if the headers
3266	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4790	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3267		4791
		4792	=item EV_NO_SMP
		4793
		4794	If defined to be C<1>, libev will assume that memory is always coherent
		4795	between threads, that is, threads can be used, but threads never run on
		4796	different cpus (or different cpu cores). This reduces dependencies
		4797	and makes libev faster.
		4798
		4799	=item EV_NO_THREADS
		4800
		4801	If defined to be C<1>, libev will assume that it will never be called from
		4802	different threads (that includes signal handlers), which is a stronger
		4803	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4804	libev faster.
		4805
3268	=item EV_ATOMIC_T	4806	=item EV_ATOMIC_T
3269		4807
3270	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4808	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3271	access is atomic with respect to other threads or signal contexts. No such	4809	access is atomic with respect to other threads or signal contexts. No
3272	type is easily found in the C language, so you can provide your own type	4810	such type is easily found in the C language, so you can provide your own
3273	that you know is safe for your purposes. It is used both for signal handler "locking"	4811	type that you know is safe for your purposes. It is used both for signal
3274	as well as for signal and thread safety in C<ev_async> watchers.	4812	handler "locking" as well as for signal and thread safety in C<ev_async>
		4813	watchers.
3275		4814
3276	In the absence of this define, libev will use C<sig_atomic_t volatile>	4815	In the absence of this define, libev will use C<sig_atomic_t volatile>
3277	(from F<signal.h>), which is usually good enough on most platforms.	4816	(from F<signal.h>), which is usually good enough on most platforms.
3278		4817
3279	=item EV_H	4818	=item EV_H (h)
3280		4819
3281	The name of the F<ev.h> header file used to include it. The default if	4820	The name of the F<ev.h> header file used to include it. The default if
3282	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4821	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3283	used to virtually rename the F<ev.h> header file in case of conflicts.	4822	used to virtually rename the F<ev.h> header file in case of conflicts.
3284		4823
3285	=item EV_CONFIG_H	4824	=item EV_CONFIG_H (h)
3286		4825
3287	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4826	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3288	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4827	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3289	C<EV_H>, above.	4828	C<EV_H>, above.
3290		4829
3291	=item EV_EVENT_H	4830	=item EV_EVENT_H (h)
3292		4831
3293	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4832	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3294	of how the F<event.h> header can be found, the default is C<"event.h">.	4833	of how the F<event.h> header can be found, the default is C<"event.h">.
3295		4834
3296	=item EV_PROTOTYPES	4835	=item EV_PROTOTYPES (h)
3297		4836
3298	If defined to be C<0>, then F<ev.h> will not define any function	4837	If defined to be C<0>, then F<ev.h> will not define any function
3299	prototypes, but still define all the structs and other symbols. This is	4838	prototypes, but still define all the structs and other symbols. This is
3300	occasionally useful if you want to provide your own wrapper functions	4839	occasionally useful if you want to provide your own wrapper functions
3301	around libev functions.	4840	around libev functions.
…		…
3306	will have the C<struct ev_loop *> as first argument, and you can create	4845	will have the C<struct ev_loop *> as first argument, and you can create
3307	additional independent event loops. Otherwise there will be no support	4846	additional independent event loops. Otherwise there will be no support
3308	for multiple event loops and there is no first event loop pointer	4847	for multiple event loops and there is no first event loop pointer
3309	argument. Instead, all functions act on the single default loop.	4848	argument. Instead, all functions act on the single default loop.
3310		4849
		4850	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4851	default loop when multiplicity is switched off - you always have to
		4852	initialise the loop manually in this case.
		4853
3311	=item EV_MINPRI	4854	=item EV_MINPRI
3312		4855
3313	=item EV_MAXPRI	4856	=item EV_MAXPRI
3314		4857
3315	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4858	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3323	fine.	4866	fine.
3324		4867
3325	If your embedding application does not need any priorities, defining these	4868	If your embedding application does not need any priorities, defining these
3326	both to C<0> will save some memory and CPU.	4869	both to C<0> will save some memory and CPU.
3327		4870
3328	=item EV_PERIODIC_ENABLE	4871	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4872	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4873	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3329		4874
3330	If undefined or defined to be C<1>, then periodic timers are supported. If	4875	If undefined or defined to be C<1> (and the platform supports it), then
3331	defined to be C<0>, then they are not. Disabling them saves a few kB of	4876	the respective watcher type is supported. If defined to be C<0>, then it
3332	code.	4877	is not. Disabling watcher types mainly saves code size.
3333		4878
3334	=item EV_IDLE_ENABLE	4879	=item EV_FEATURES
3335
3336	If undefined or defined to be C<1>, then idle watchers are supported. If
3337	defined to be C<0>, then they are not. Disabling them saves a few kB of
3338	code.
3339
3340	=item EV_EMBED_ENABLE
3341
3342	If undefined or defined to be C<1>, then embed watchers are supported. If
3343	defined to be C<0>, then they are not. Embed watchers rely on most other
3344	watcher types, which therefore must not be disabled.
3345
3346	=item EV_STAT_ENABLE
3347
3348	If undefined or defined to be C<1>, then stat watchers are supported. If
3349	defined to be C<0>, then they are not.
3350
3351	=item EV_FORK_ENABLE
3352
3353	If undefined or defined to be C<1>, then fork watchers are supported. If
3354	defined to be C<0>, then they are not.
3355
3356	=item EV_ASYNC_ENABLE
3357
3358	If undefined or defined to be C<1>, then async watchers are supported. If
3359	defined to be C<0>, then they are not.
3360
3361	=item EV_MINIMAL
3362		4880
3363	If you need to shave off some kilobytes of code at the expense of some	4881	If you need to shave off some kilobytes of code at the expense of some
3364	speed, define this symbol to C<1>. Currently this is used to override some	4882	speed (but with the full API), you can define this symbol to request
3365	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4883	certain subsets of functionality. The default is to enable all features
3366	much smaller 2-heap for timer management over the default 4-heap.	4884	that can be enabled on the platform.
		4885
		4886	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4887	with some broad features you want) and then selectively re-enable
		4888	additional parts you want, for example if you want everything minimal,
		4889	but multiple event loop support, async and child watchers and the poll
		4890	backend, use this:
		4891
		4892	#define EV_FEATURES 0
		4893	#define EV_MULTIPLICITY 1
		4894	#define EV_USE_POLL 1
		4895	#define EV_CHILD_ENABLE 1
		4896	#define EV_ASYNC_ENABLE 1
		4897
		4898	The actual value is a bitset, it can be a combination of the following
		4899	values (by default, all of these are enabled):
		4900
		4901	=over 4
		4902
		4903	=item C<1> - faster/larger code
		4904
		4905	Use larger code to speed up some operations.
		4906
		4907	Currently this is used to override some inlining decisions (enlarging the
		4908	code size by roughly 30% on amd64).
		4909
		4910	When optimising for size, use of compiler flags such as C<-Os> with
		4911	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4912	assertions.
		4913
		4914	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4915	(e.g. gcc with C<-Os>).
		4916
		4917	=item C<2> - faster/larger data structures
		4918
		4919	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4920	hash table sizes and so on. This will usually further increase code size
		4921	and can additionally have an effect on the size of data structures at
		4922	runtime.
		4923
		4924	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4925	(e.g. gcc with C<-Os>).
		4926
		4927	=item C<4> - full API configuration
		4928
		4929	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4930	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4931
		4932	=item C<8> - full API
		4933
		4934	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4935	details on which parts of the API are still available without this
		4936	feature, and do not complain if this subset changes over time.
		4937
		4938	=item C<16> - enable all optional watcher types
		4939
		4940	Enables all optional watcher types. If you want to selectively enable
		4941	only some watcher types other than I/O and timers (e.g. prepare,
		4942	embed, async, child...) you can enable them manually by defining
		4943	C<EV_watchertype_ENABLE> to C<1> instead.
		4944
		4945	=item C<32> - enable all backends
		4946
		4947	This enables all backends - without this feature, you need to enable at
		4948	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4949
		4950	=item C<64> - enable OS-specific "helper" APIs
		4951
		4952	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4953	default.
		4954
		4955	=back
		4956
		4957	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4958	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4959	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4960	watchers, timers and monotonic clock support.
		4961
		4962	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4963	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4964	your program might be left out as well - a binary starting a timer and an
		4965	I/O watcher then might come out at only 5Kb.
		4966
		4967	=item EV_API_STATIC
		4968
		4969	If this symbol is defined (by default it is not), then all identifiers
		4970	will have static linkage. This means that libev will not export any
		4971	identifiers, and you cannot link against libev anymore. This can be useful
		4972	when you embed libev, only want to use libev functions in a single file,
		4973	and do not want its identifiers to be visible.
		4974
		4975	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4976	wants to use libev.
		4977
		4978	This option only works when libev is compiled with a C compiler, as C++
		4979	doesn't support the required declaration syntax.
		4980
		4981	=item EV_AVOID_STDIO
		4982
		4983	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4984	functions (printf, scanf, perror etc.). This will increase the code size
		4985	somewhat, but if your program doesn't otherwise depend on stdio and your
		4986	libc allows it, this avoids linking in the stdio library which is quite
		4987	big.
		4988
		4989	Note that error messages might become less precise when this option is
		4990	enabled.
		4991
		4992	=item EV_NSIG
		4993
		4994	The highest supported signal number, +1 (or, the number of
		4995	signals): Normally, libev tries to deduce the maximum number of signals
		4996	automatically, but sometimes this fails, in which case it can be
		4997	specified. Also, using a lower number than detected (C<32> should be
		4998	good for about any system in existence) can save some memory, as libev
		4999	statically allocates some 12-24 bytes per signal number.
3367		5000
3368	=item EV_PID_HASHSIZE	5001	=item EV_PID_HASHSIZE
3369		5002
3370	C<ev_child> watchers use a small hash table to distribute workload by	5003	C<ev_child> watchers use a small hash table to distribute workload by
3371	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	5004	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3372	than enough. If you need to manage thousands of children you might want to	5005	usually more than enough. If you need to manage thousands of children you
3373	increase this value (I<must> be a power of two).	5006	might want to increase this value (I<must> be a power of two).
3374		5007
3375	=item EV_INOTIFY_HASHSIZE	5008	=item EV_INOTIFY_HASHSIZE
3376		5009
3377	C<ev_stat> watchers use a small hash table to distribute workload by	5010	C<ev_stat> watchers use a small hash table to distribute workload by
3378	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	5011	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3379	usually more than enough. If you need to manage thousands of C<ev_stat>	5012	disabled), usually more than enough. If you need to manage thousands of
3380	watchers you might want to increase this value (I<must> be a power of	5013	C<ev_stat> watchers you might want to increase this value (I<must> be a
3381	two).	5014	power of two).
3382		5015
3383	=item EV_USE_4HEAP	5016	=item EV_USE_4HEAP
3384		5017
3385	Heaps are not very cache-efficient. To improve the cache-efficiency of the	5018	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3386	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	5019	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3387	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	5020	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3388	faster performance with many (thousands) of watchers.	5021	faster performance with many (thousands) of watchers.
3389		5022
3390	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	5023	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3391	(disabled).	5024	will be C<0>.
3392		5025
3393	=item EV_HEAP_CACHE_AT	5026	=item EV_HEAP_CACHE_AT
3394		5027
3395	Heaps are not very cache-efficient. To improve the cache-efficiency of the	5028	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3396	timer and periodics heaps, libev can cache the timestamp (I<at>) within	5029	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3397	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	5030	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3398	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	5031	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3399	but avoids random read accesses on heap changes. This improves performance	5032	but avoids random read accesses on heap changes. This improves performance
3400	noticeably with many (hundreds) of watchers.	5033	noticeably with many (hundreds) of watchers.
3401		5034
3402	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	5035	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3403	(disabled).	5036	will be C<0>.
3404		5037
3405	=item EV_VERIFY	5038	=item EV_VERIFY
3406		5039
3407	Controls how much internal verification (see C<ev_loop_verify ()>) will	5040	Controls how much internal verification (see C<ev_verify ()>) will
3408	be done: If set to C<0>, no internal verification code will be compiled	5041	be done: If set to C<0>, no internal verification code will be compiled
3409	in. If set to C<1>, then verification code will be compiled in, but not	5042	in. If set to C<1>, then verification code will be compiled in, but not
3410	called. If set to C<2>, then the internal verification code will be	5043	called. If set to C<2>, then the internal verification code will be
3411	called once per loop, which can slow down libev. If set to C<3>, then the	5044	called once per loop, which can slow down libev. If set to C<3>, then the
3412	verification code will be called very frequently, which will slow down	5045	verification code will be called very frequently, which will slow down
3413	libev considerably.	5046	libev considerably.
3414		5047
		5048	Verification errors are reported via C's C<assert> mechanism, so if you
		5049	disable that (e.g. by defining C<NDEBUG>) then no errors will be reported.
		5050
3415	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	5051	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3416	C<0>.	5052	will be C<0>.
3417		5053
3418	=item EV_COMMON	5054	=item EV_COMMON
3419		5055
3420	By default, all watchers have a C<void *data> member. By redefining	5056	By default, all watchers have a C<void *data> member. By redefining
3421	this macro to a something else you can include more and other types of	5057	this macro to something else you can include more and other types of
3422	members. You have to define it each time you include one of the files,	5058	members. You have to define it each time you include one of the files,
3423	though, and it must be identical each time.	5059	though, and it must be identical each time.
3424		5060
3425	For example, the perl EV module uses something like this:	5061	For example, the perl EV module uses something like this:
3426		5062
…		…
3479	file.	5115	file.
3480		5116
3481	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5117	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3482	that everybody includes and which overrides some configure choices:	5118	that everybody includes and which overrides some configure choices:
3483		5119
3484	#define EV_MINIMAL 1	5120	#define EV_FEATURES 8
3485	#define EV_USE_POLL 0	5121	#define EV_USE_SELECT 1
3486	#define EV_MULTIPLICITY 0
3487	#define EV_PERIODIC_ENABLE 0	5122	#define EV_PREPARE_ENABLE 1
		5123	#define EV_IDLE_ENABLE 1
3488	#define EV_STAT_ENABLE 0	5124	#define EV_SIGNAL_ENABLE 1
3489	#define EV_FORK_ENABLE 0	5125	#define EV_CHILD_ENABLE 1
		5126	#define EV_USE_STDEXCEPT 0
3490	#define EV_CONFIG_H <config.h>	5127	#define EV_CONFIG_H <config.h>
3491	#define EV_MINPRI 0
3492	#define EV_MAXPRI 0
3493		5128
3494	#include "ev++.h"	5129	#include "ev++.h"
3495		5130
3496	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5131	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3497		5132
3498	#include "ev_cpp.h"	5133	#include "ev_cpp.h"
3499	#include "ev.c"	5134	#include "ev.c"
3500		5135
3501	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5136	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3502		5137
3503	=head2 THREADS AND COROUTINES	5138	=head2 THREADS AND COROUTINES
3504		5139
3505	=head3 THREADS	5140	=head3 THREADS
3506		5141
…		…
3557	default loop and triggering an C<ev_async> watcher from the default loop	5192	default loop and triggering an C<ev_async> watcher from the default loop
3558	watcher callback into the event loop interested in the signal.	5193	watcher callback into the event loop interested in the signal.
3559		5194
3560	=back	5195	=back
3561		5196
		5197	See also L</THREAD LOCKING EXAMPLE>.
		5198
3562	=head3 COROUTINES	5199	=head3 COROUTINES
3563		5200
3564	Libev is very accommodating to coroutines ("cooperative threads"):	5201	Libev is very accommodating to coroutines ("cooperative threads"):
3565	libev fully supports nesting calls to its functions from different	5202	libev fully supports nesting calls to its functions from different
3566	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5203	coroutines (e.g. you can call C<ev_run> on the same loop from two
3567	different coroutines, and switch freely between both coroutines running the	5204	different coroutines, and switch freely between both coroutines running
3568	loop, as long as you don't confuse yourself). The only exception is that	5205	the loop, as long as you don't confuse yourself). The only exception is
3569	you must not do this from C<ev_periodic> reschedule callbacks.	5206	that you must not do this from C<ev_periodic> reschedule callbacks.
3570		5207
3571	Care has been taken to ensure that libev does not keep local state inside	5208	Care has been taken to ensure that libev does not keep local state inside
3572	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5209	C<ev_run>, and other calls do not usually allow for coroutine switches as
3573	they do not clal any callbacks.	5210	they do not call any callbacks.
3574		5211
3575	=head2 COMPILER WARNINGS	5212	=head2 COMPILER WARNINGS
3576		5213
3577	Depending on your compiler and compiler settings, you might get no or a	5214	Depending on your compiler and compiler settings, you might get no or a
3578	lot of warnings when compiling libev code. Some people are apparently	5215	lot of warnings when compiling libev code. Some people are apparently
…		…
3588	maintainable.	5225	maintainable.
3589		5226
3590	And of course, some compiler warnings are just plain stupid, or simply	5227	And of course, some compiler warnings are just plain stupid, or simply
3591	wrong (because they don't actually warn about the condition their message	5228	wrong (because they don't actually warn about the condition their message
3592	seems to warn about). For example, certain older gcc versions had some	5229	seems to warn about). For example, certain older gcc versions had some
3593	warnings that resulted an extreme number of false positives. These have	5230	warnings that resulted in an extreme number of false positives. These have
3594	been fixed, but some people still insist on making code warn-free with	5231	been fixed, but some people still insist on making code warn-free with
3595	such buggy versions.	5232	such buggy versions.
3596		5233
3597	While libev is written to generate as few warnings as possible,	5234	While libev is written to generate as few warnings as possible,
3598	"warn-free" code is not a goal, and it is recommended not to build libev	5235	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3612	==2274== definitely lost: 0 bytes in 0 blocks.	5249	==2274== definitely lost: 0 bytes in 0 blocks.
3613	==2274== possibly lost: 0 bytes in 0 blocks.	5250	==2274== possibly lost: 0 bytes in 0 blocks.
3614	==2274== still reachable: 256 bytes in 1 blocks.	5251	==2274== still reachable: 256 bytes in 1 blocks.
3615		5252
3616	Then there is no memory leak, just as memory accounted to global variables	5253	Then there is no memory leak, just as memory accounted to global variables
3617	is not a memleak - the memory is still being refernced, and didn't leak.	5254	is not a memleak - the memory is still being referenced, and didn't leak.
3618		5255
3619	Similarly, under some circumstances, valgrind might report kernel bugs	5256	Similarly, under some circumstances, valgrind might report kernel bugs
3620	as if it were a bug in libev (e.g. in realloc or in the poll backend,	5257	as if it were a bug in libev (e.g. in realloc or in the poll backend,
3621	although an acceptable workaround has been found here), or it might be	5258	although an acceptable workaround has been found here), or it might be
3622	confused.	5259	confused.
…		…
3634	I suggest using suppression lists.	5271	I suggest using suppression lists.
3635		5272
3636		5273
3637	=head1 PORTABILITY NOTES	5274	=head1 PORTABILITY NOTES
3638		5275
		5276	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5277
		5278	GNU/Linux is the only common platform that supports 64 bit file/large file
		5279	interfaces but I<disables> them by default.
		5280
		5281	That means that libev compiled in the default environment doesn't support
		5282	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5283
		5284	Unfortunately, many programs try to work around this GNU/Linux issue
		5285	by enabling the large file API, which makes them incompatible with the
		5286	standard libev compiled for their system.
		5287
		5288	Likewise, libev cannot enable the large file API itself as this would
		5289	suddenly make it incompatible to the default compile time environment,
		5290	i.e. all programs not using special compile switches.
		5291
		5292	=head2 OS/X AND DARWIN BUGS
		5293
		5294	The whole thing is a bug if you ask me - basically any system interface
		5295	you touch is broken, whether it is locales, poll, kqueue or even the
		5296	OpenGL drivers.
		5297
		5298	=head3 C<kqueue> is buggy
		5299
		5300	The kqueue syscall is broken in all known versions - most versions support
		5301	only sockets, many support pipes.
		5302
		5303	Libev tries to work around this by not using C<kqueue> by default on this
		5304	rotten platform, but of course you can still ask for it when creating a
		5305	loop - embedding a socket-only kqueue loop into a select-based one is
		5306	probably going to work well.
		5307
		5308	=head3 C<poll> is buggy
		5309
		5310	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5311	implementation by something calling C<kqueue> internally around the 10.5.6
		5312	release, so now C<kqueue> I<and> C<poll> are broken.
		5313
		5314	Libev tries to work around this by not using C<poll> by default on
		5315	this rotten platform, but of course you can still ask for it when creating
		5316	a loop.
		5317
		5318	=head3 C<select> is buggy
		5319
		5320	All that's left is C<select>, and of course Apple found a way to fuck this
		5321	one up as well: On OS/X, C<select> actively limits the number of file
		5322	descriptors you can pass in to 1024 - your program suddenly crashes when
		5323	you use more.
		5324
		5325	There is an undocumented "workaround" for this - defining
		5326	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5327	work on OS/X.
		5328
		5329	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5330
		5331	=head3 C<errno> reentrancy
		5332
		5333	The default compile environment on Solaris is unfortunately so
		5334	thread-unsafe that you can't even use components/libraries compiled
		5335	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5336	defined by default. A valid, if stupid, implementation choice.
		5337
		5338	If you want to use libev in threaded environments you have to make sure
		5339	it's compiled with C<_REENTRANT> defined.
		5340
		5341	=head3 Event port backend
		5342
		5343	The scalable event interface for Solaris is called "event
		5344	ports". Unfortunately, this mechanism is very buggy in all major
		5345	releases. If you run into high CPU usage, your program freezes or you get
		5346	a large number of spurious wakeups, make sure you have all the relevant
		5347	and latest kernel patches applied. No, I don't know which ones, but there
		5348	are multiple ones to apply, and afterwards, event ports actually work
		5349	great.
		5350
		5351	If you can't get it to work, you can try running the program by setting
		5352	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5353	C<select> backends.
		5354
		5355	=head2 AIX POLL BUG
		5356
		5357	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5358	this by trying to avoid the poll backend altogether (i.e. it's not even
		5359	compiled in), which normally isn't a big problem as C<select> works fine
		5360	with large bitsets on AIX, and AIX is dead anyway.
		5361
3639	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5362	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5363
		5364	=head3 General issues
3640		5365
3641	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5366	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3642	requires, and its I/O model is fundamentally incompatible with the POSIX	5367	requires, and its I/O model is fundamentally incompatible with the POSIX
3643	model. Libev still offers limited functionality on this platform in	5368	model. Libev still offers limited functionality on this platform in
3644	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5369	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3645	descriptors. This only applies when using Win32 natively, not when using	5370	descriptors. This only applies when using Win32 natively, not when using
3646	e.g. cygwin.	5371	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5372	as every compiler comes with a slightly differently broken/incompatible
		5373	environment.
3647		5374
3648	Lifting these limitations would basically require the full	5375	Lifting these limitations would basically require the full
3649	re-implementation of the I/O system. If you are into these kinds of	5376	re-implementation of the I/O system. If you are into this kind of thing,
3650	things, then note that glib does exactly that for you in a very portable	5377	then note that glib does exactly that for you in a very portable way (note
3651	way (note also that glib is the slowest event library known to man).	5378	also that glib is the slowest event library known to man).
3652		5379
3653	There is no supported compilation method available on windows except	5380	There is no supported compilation method available on windows except
3654	embedding it into other applications.	5381	embedding it into other applications.
		5382
		5383	Sensible signal handling is officially unsupported by Microsoft - libev
		5384	tries its best, but under most conditions, signals will simply not work.
3655		5385
3656	Not a libev limitation but worth mentioning: windows apparently doesn't	5386	Not a libev limitation but worth mentioning: windows apparently doesn't
3657	accept large writes: instead of resulting in a partial write, windows will	5387	accept large writes: instead of resulting in a partial write, windows will
3658	either accept everything or return C<ENOBUFS> if the buffer is too large,	5388	either accept everything or return C<ENOBUFS> if the buffer is too large,
3659	so make sure you only write small amounts into your sockets (less than a	5389	so make sure you only write small amounts into your sockets (less than a
…		…
3664	the abysmal performance of winsockets, using a large number of sockets	5394	the abysmal performance of winsockets, using a large number of sockets
3665	is not recommended (and not reasonable). If your program needs to use	5395	is not recommended (and not reasonable). If your program needs to use
3666	more than a hundred or so sockets, then likely it needs to use a totally	5396	more than a hundred or so sockets, then likely it needs to use a totally
3667	different implementation for windows, as libev offers the POSIX readiness	5397	different implementation for windows, as libev offers the POSIX readiness
3668	notification model, which cannot be implemented efficiently on windows	5398	notification model, which cannot be implemented efficiently on windows
3669	(Microsoft monopoly games).	5399	(due to Microsoft monopoly games).
3670		5400
3671	A typical way to use libev under windows is to embed it (see the embedding	5401	A typical way to use libev under windows is to embed it (see the embedding
3672	section for details) and use the following F<evwrap.h> header file instead	5402	section for details) and use the following F<evwrap.h> header file instead
3673	of F<ev.h>:	5403	of F<ev.h>:
3674		5404
…		…
3681	you do I<not> compile the F<ev.c> or any other embedded source files!):	5411	you do I<not> compile the F<ev.c> or any other embedded source files!):
3682		5412
3683	#include "evwrap.h"	5413	#include "evwrap.h"
3684	#include "ev.c"	5414	#include "ev.c"
3685		5415
3686	=over 4
3687
3688	=item The winsocket select function	5416	=head3 The winsocket C<select> function
3689		5417
3690	The winsocket C<select> function doesn't follow POSIX in that it	5418	The winsocket C<select> function doesn't follow POSIX in that it
3691	requires socket I<handles> and not socket I<file descriptors> (it is	5419	requires socket I<handles> and not socket I<file descriptors> (it is
3692	also extremely buggy). This makes select very inefficient, and also	5420	also extremely buggy). This makes select very inefficient, and also
3693	requires a mapping from file descriptors to socket handles (the Microsoft	5421	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3702	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5430	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3703		5431
3704	Note that winsockets handling of fd sets is O(n), so you can easily get a	5432	Note that winsockets handling of fd sets is O(n), so you can easily get a
3705	complexity in the O(n²) range when using win32.	5433	complexity in the O(n²) range when using win32.
3706		5434
3707	=item Limited number of file descriptors	5435	=head3 Limited number of file descriptors
3708		5436
3709	Windows has numerous arbitrary (and low) limits on things.	5437	Windows has numerous arbitrary (and low) limits on things.
3710		5438
3711	Early versions of winsocket's select only supported waiting for a maximum	5439	Early versions of winsocket's select only supported waiting for a maximum
3712	of C<64> handles (probably owning to the fact that all windows kernels	5440	of C<64> handles (probably owning to the fact that all windows kernels
3713	can only wait for C<64> things at the same time internally; Microsoft	5441	can only wait for C<64> things at the same time internally; Microsoft
3714	recommends spawning a chain of threads and wait for 63 handles and the	5442	recommends spawning a chain of threads and wait for 63 handles and the
3715	previous thread in each. Great).	5443	previous thread in each. Sounds great!).
3716		5444
3717	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5445	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3718	to some high number (e.g. C<2048>) before compiling the winsocket select	5446	to some high number (e.g. C<2048>) before compiling the winsocket select
3719	call (which might be in libev or elsewhere, for example, perl does its own	5447	call (which might be in libev or elsewhere, for example, perl and many
3720	select emulation on windows).	5448	other interpreters do their own select emulation on windows).
3721		5449
3722	Another limit is the number of file descriptors in the Microsoft runtime	5450	Another limit is the number of file descriptors in the Microsoft runtime
3723	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5451	libraries, which by default is C<64> (there must be a hidden I<64>
3724	or something like this inside Microsoft). You can increase this by calling	5452	fetish or something like this inside Microsoft). You can increase this
3725	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5453	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3726	arbitrary limit), but is broken in many versions of the Microsoft runtime	5454	(another arbitrary limit), but is broken in many versions of the Microsoft
3727	libraries.
3728
3729	This might get you to about C<512> or C<2048> sockets (depending on	5455	runtime libraries. This might get you to about C<512> or C<2048> sockets
3730	windows version and/or the phase of the moon). To get more, you need to	5456	(depending on windows version and/or the phase of the moon). To get more,
3731	wrap all I/O functions and provide your own fd management, but the cost of	5457	you need to wrap all I/O functions and provide your own fd management, but
3732	calling select (O(n²)) will likely make this unworkable.	5458	the cost of calling select (O(n²)) will likely make this unworkable.
3733
3734	=back
3735		5459
3736	=head2 PORTABILITY REQUIREMENTS	5460	=head2 PORTABILITY REQUIREMENTS
3737		5461
3738	In addition to a working ISO-C implementation and of course the	5462	In addition to a working ISO-C implementation and of course the
3739	backend-specific APIs, libev relies on a few additional extensions:	5463	backend-specific APIs, libev relies on a few additional extensions:
…		…
3746	Libev assumes not only that all watcher pointers have the same internal	5470	Libev assumes not only that all watcher pointers have the same internal
3747	structure (guaranteed by POSIX but not by ISO C for example), but it also	5471	structure (guaranteed by POSIX but not by ISO C for example), but it also
3748	assumes that the same (machine) code can be used to call any watcher	5472	assumes that the same (machine) code can be used to call any watcher
3749	callback: The watcher callbacks have different type signatures, but libev	5473	callback: The watcher callbacks have different type signatures, but libev
3750	calls them using an C<ev_watcher *> internally.	5474	calls them using an C<ev_watcher *> internally.
		5475
		5476	=item null pointers and integer zero are represented by 0 bytes
		5477
		5478	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5479	relies on this setting pointers and integers to null.
		5480
		5481	=item pointer accesses must be thread-atomic
		5482
		5483	Accessing a pointer value must be atomic, it must both be readable and
		5484	writable in one piece - this is the case on all current architectures.
3751		5485
3752	=item C<sig_atomic_t volatile> must be thread-atomic as well	5486	=item C<sig_atomic_t volatile> must be thread-atomic as well
3753		5487
3754	The type C<sig_atomic_t volatile> (or whatever is defined as	5488	The type C<sig_atomic_t volatile> (or whatever is defined as
3755	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5489	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3764	thread" or will block signals process-wide, both behaviours would	5498	thread" or will block signals process-wide, both behaviours would
3765	be compatible with libev. Interaction between C<sigprocmask> and	5499	be compatible with libev. Interaction between C<sigprocmask> and
3766	C<pthread_sigmask> could complicate things, however.	5500	C<pthread_sigmask> could complicate things, however.
3767		5501
3768	The most portable way to handle signals is to block signals in all threads	5502	The most portable way to handle signals is to block signals in all threads
3769	except the initial one, and run the default loop in the initial thread as	5503	except the initial one, and run the signal handling loop in the initial
3770	well.	5504	thread as well.
3771		5505
3772	=item C<long> must be large enough for common memory allocation sizes	5506	=item C<long> must be large enough for common memory allocation sizes
3773		5507
3774	To improve portability and simplify its API, libev uses C<long> internally	5508	To improve portability and simplify its API, libev uses C<long> internally
3775	instead of C<size_t> when allocating its data structures. On non-POSIX	5509	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3778	watchers.	5512	watchers.
3779		5513
3780	=item C<double> must hold a time value in seconds with enough accuracy	5514	=item C<double> must hold a time value in seconds with enough accuracy
3781		5515
3782	The type C<double> is used to represent timestamps. It is required to	5516	The type C<double> is used to represent timestamps. It is required to
3783	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5517	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3784	enough for at least into the year 4000. This requirement is fulfilled by	5518	good enough for at least into the year 4000 with millisecond accuracy
		5519	(the design goal for libev). This requirement is overfulfilled by
3785	implementations implementing IEEE 754 (basically all existing ones).	5520	implementations using IEEE 754, which is basically all existing ones.
		5521
		5522	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5523	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5524	is either obsolete or somebody patched it to use C<long double> or
		5525	something like that, just kidding).
3786		5526
3787	=back	5527	=back
3788		5528
3789	If you know of other additional requirements drop me a note.	5529	If you know of other additional requirements drop me a note.
3790		5530
…		…
3852	=item Processing ev_async_send: O(number_of_async_watchers)	5592	=item Processing ev_async_send: O(number_of_async_watchers)
3853		5593
3854	=item Processing signals: O(max_signal_number)	5594	=item Processing signals: O(max_signal_number)
3855		5595
3856	Sending involves a system call I<iff> there were no other C<ev_async_send>	5596	Sending involves a system call I<iff> there were no other C<ev_async_send>
3857	calls in the current loop iteration. Checking for async and signal events	5597	calls in the current loop iteration and the loop is currently
		5598	blocked. Checking for async and signal events involves iterating over all
3858	involves iterating over all running async watchers or all signal numbers.	5599	running async watchers or all signal numbers.
3859		5600
3860	=back	5601	=back
3861		5602
3862		5603
		5604	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5605
		5606	The major version 4 introduced some incompatible changes to the API.
		5607
		5608	At the moment, the C<ev.h> header file provides compatibility definitions
		5609	for all changes, so most programs should still compile. The compatibility
		5610	layer might be removed in later versions of libev, so better update to the
		5611	new API early than late.
		5612
		5613	=over 4
		5614
		5615	=item C<EV_COMPAT3> backwards compatibility mechanism
		5616
		5617	The backward compatibility mechanism can be controlled by
		5618	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5619	section.
		5620
		5621	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5622
		5623	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5624
		5625	ev_loop_destroy (EV_DEFAULT_UC);
		5626	ev_loop_fork (EV_DEFAULT);
		5627
		5628	=item function/symbol renames
		5629
		5630	A number of functions and symbols have been renamed:
		5631
		5632	ev_loop => ev_run
		5633	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5634	EVLOOP_ONESHOT => EVRUN_ONCE
		5635
		5636	ev_unloop => ev_break
		5637	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5638	EVUNLOOP_ONE => EVBREAK_ONE
		5639	EVUNLOOP_ALL => EVBREAK_ALL
		5640
		5641	EV_TIMEOUT => EV_TIMER
		5642
		5643	ev_loop_count => ev_iteration
		5644	ev_loop_depth => ev_depth
		5645	ev_loop_verify => ev_verify
		5646
		5647	Most functions working on C<struct ev_loop> objects don't have an
		5648	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5649	associated constants have been renamed to not collide with the C<struct
		5650	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5651	as all other watcher types. Note that C<ev_loop_fork> is still called
		5652	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5653	typedef.
		5654
		5655	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5656
		5657	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5658	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5659	and work, but the library code will of course be larger.
		5660
		5661	=back
		5662
		5663
		5664	=head1 GLOSSARY
		5665
		5666	=over 4
		5667
		5668	=item active
		5669
		5670	A watcher is active as long as it has been started and not yet stopped.
		5671	See L</WATCHER STATES> for details.
		5672
		5673	=item application
		5674
		5675	In this document, an application is whatever is using libev.
		5676
		5677	=item backend
		5678
		5679	The part of the code dealing with the operating system interfaces.
		5680
		5681	=item callback
		5682
		5683	The address of a function that is called when some event has been
		5684	detected. Callbacks are being passed the event loop, the watcher that
		5685	received the event, and the actual event bitset.
		5686
		5687	=item callback/watcher invocation
		5688
		5689	The act of calling the callback associated with a watcher.
		5690
		5691	=item event
		5692
		5693	A change of state of some external event, such as data now being available
		5694	for reading on a file descriptor, time having passed or simply not having
		5695	any other events happening anymore.
		5696
		5697	In libev, events are represented as single bits (such as C<EV_READ> or
		5698	C<EV_TIMER>).
		5699
		5700	=item event library
		5701
		5702	A software package implementing an event model and loop.
		5703
		5704	=item event loop
		5705
		5706	An entity that handles and processes external events and converts them
		5707	into callback invocations.
		5708
		5709	=item event model
		5710
		5711	The model used to describe how an event loop handles and processes
		5712	watchers and events.
		5713
		5714	=item pending
		5715
		5716	A watcher is pending as soon as the corresponding event has been
		5717	detected. See L</WATCHER STATES> for details.
		5718
		5719	=item real time
		5720
		5721	The physical time that is observed. It is apparently strictly monotonic :)
		5722
		5723	=item wall-clock time
		5724
		5725	The time and date as shown on clocks. Unlike real time, it can actually
		5726	be wrong and jump forwards and backwards, e.g. when you adjust your
		5727	clock.
		5728
		5729	=item watcher
		5730
		5731	A data structure that describes interest in certain events. Watchers need
		5732	to be started (attached to an event loop) before they can receive events.
		5733
		5734	=back
		5735
3863	=head1 AUTHOR	5736	=head1 AUTHOR
3864		5737
3865	Marc Lehmann <libev@schmorp.de>.	5738	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5739	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3866		5740

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