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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 be shared 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	This flag's behaviour will become the default in future versions of libev.
352		486
353	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	487	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
354		488
355	This is your standard select(2) backend. Not I<completely> standard, as	489	This is your standard select(2) backend. Not I<completely> standard, as
356	libev tries to roll its own fd_set with no limits on the number of fds,	490	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
381	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	515	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
382	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	516	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
383		517
384	=item C<EVBACKEND_EPOLL> (value 4, Linux)	518	=item C<EVBACKEND_EPOLL> (value 4, Linux)
385		519
		520	Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9
		521	kernels).
		522
386	For few fds, this backend is a bit little slower than poll and select,	523	For few fds, this backend is a bit little slower than poll and select, but
387	but it scales phenomenally better. While poll and select usually scale	524	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),	525	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).	526	fd), epoll scales either O(1) or O(active_fds).
390		527
391	The epoll syscalls are the most misdesigned of the more advanced event	528	The epoll mechanism deserves honorable mention as the most misdesigned
392	mechanisms: problems include silently dropping fds, requiring a system	529	of the more advanced event mechanisms: mere annoyances include silently
		530	dropping file descriptors, requiring a system call per change per file
393	call per change per fd (and unnecessary guessing of parameters), problems	531	descriptor (and unnecessary guessing of parameters), problems with dup,
		532	returning before the timeout value, resulting in additional iterations
		533	(and only giving 5ms accuracy while select on the same platform gives
394	with dup and so on. The biggest issue is fork races, however - if a	534	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	535	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	536	set, which can take considerable time (one syscall per file descriptor)
397	course hard to detect.	537	and is of course hard to detect.
398		538
399	Epoll is also notoriously buggy - embedding epoll fds should work, but	539	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	540	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	541	totally I<different> file descriptors (even already closed ones, so
402	even remove them from the set) than registered in the set (especially	542	one cannot even remove them from the set) than registered in the set
403	on SMP systems). Libev tries to counter these spurious notifications by	543	(especially on SMP systems). Libev tries to counter these spurious
404	employing an additional generation counter and comparing that against the	544	notifications by employing an additional generation counter and comparing
405	events to filter out spurious ones.	545	that against the events to filter out spurious ones, recreating the set
		546	when required. Epoll also erroneously rounds down timeouts, but gives you
		547	no way to know when and by how much, so sometimes you have to busy-wait
		548	because epoll returns immediately despite a nonzero timeout. And last
		549	not least, it also refuses to work with some file descriptors which work
		550	perfectly fine with C<select> (files, many character devices...).
		551
		552	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		553	cobbled together in a hurry, no thought to design or interaction with
		554	others. Oh, the pain, will it ever stop...
406		555
407	While stopping, setting and starting an I/O watcher in the same iteration	556	While stopping, setting and starting an I/O watcher in the same iteration
408	will result in some caching, there is still a system call per such incident	557	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	558	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	559	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
411	very well if you register events for both fds.	560	file descriptors might not work very well if you register events for both
		561	file descriptors.
412		562
413	Best performance from this backend is achieved by not unregistering all	563	Best performance from this backend is achieved by not unregistering all
414	watchers for a file descriptor until it has been closed, if possible,	564	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	565	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	566	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	567	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	568	as in libev having to destroy and recreate the epoll object, which can
419	take considerable time and thus should be avoided.	569	take considerable time and thus should be avoided.
420		570
		571	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		572	faster than epoll for maybe up to a hundred file descriptors, depending on
		573	the usage. So sad.
		574
421	While nominally embeddable in other event loops, this feature is broken in	575	While nominally embeddable in other event loops, this feature is broken in
422	all kernel versions tested so far.	576	a lot of kernel revisions, but probably(!) works in current versions.
423		577
424	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	578	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
425	C<EVBACKEND_POLL>.	579	C<EVBACKEND_POLL>.
426		580
		581	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		582
		583	Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<<
		584	io_submit(2) >>) event interface available in post-4.18 kernels (but libev
		585	only tries to use it in 4.19+).
		586
		587	This is another Linux train wreck of an event interface.
		588
		589	If this backend works for you (as of this writing, it was very
		590	experimental), it is the best event interface available on Linux and might
		591	be well worth enabling it - if it isn't available in your kernel this will
		592	be detected and this backend will be skipped.
		593
		594	This backend can batch oneshot requests and supports a user-space ring
		595	buffer to receive events. It also doesn't suffer from most of the design
		596	problems of epoll (such as not being able to remove event sources from
		597	the epoll set), and generally sounds too good to be true. Because, this
		598	being the Linux kernel, of course it suffers from a whole new set of
		599	limitations, forcing you to fall back to epoll, inheriting all its design
		600	issues.
		601
		602	For one, it is not easily embeddable (but probably could be done using
		603	an event fd at some extra overhead). It also is subject to a system wide
		604	limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO
		605	requests are left, this backend will be skipped during initialisation, and
		606	will switch to epoll when the loop is active.
		607
		608	Most problematic in practice, however, is that not all file descriptors
		609	work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds,
		610	files, F</dev/null> and many others are supported, but ttys do not work
		611	properly (a known bug that the kernel developers don't care about, see
		612	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		613	(yet?) a generic event polling interface.
		614
		615	Overall, it seems the Linux developers just don't want it to have a
		616	generic event handling mechanism other than C<select> or C<poll>.
		617
		618	To work around all these problem, the current version of libev uses its
		619	epoll backend as a fallback for file descriptor types that do not work. Or
		620	falls back completely to epoll if the kernel acts up.
		621
		622	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		623	C<EVBACKEND_POLL>.
		624
427	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	625	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
428		626
429	Kqueue deserves special mention, as at the time of this writing, it was	627	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	628	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	629	work reliably with anything but sockets and pipes, except on Darwin,
432	completely useless). For this reason it's not being "auto-detected" unless	630	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	631	brokenness is by design, these kqueue bugs can be (and mostly have been)
		632	fixed without API changes to existing programs. For this reason it's not
		633	being "auto-detected" on all platforms unless you explicitly specify it
		634	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.	635	known-to-be-good (-enough) system like NetBSD.
435		636
436	You still can embed kqueue into a normal poll or select backend and use it	637	You still can embed kqueue into a normal poll or select backend and use it
437	only for sockets (after having made sure that sockets work with kqueue on	638	only for sockets (after having made sure that sockets work with kqueue on
438	the target platform). See C<ev_embed> watchers for more info.	639	the target platform). See C<ev_embed> watchers for more info.
439		640
440	It scales in the same way as the epoll backend, but the interface to the	641	It scales in the same way as the epoll backend, but the interface to the
441	kernel is more efficient (which says nothing about its actual speed, of	642	kernel is more efficient (which says nothing about its actual speed, of
442	course). While stopping, setting and starting an I/O watcher does never	643	course). While stopping, setting and starting an I/O watcher does never
443	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	644	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
444	two event changes per incident. Support for C<fork ()> is very bad (but	645	two event changes per incident. Support for C<fork ()> is very bad (you
445	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	646	might have to leak fds on fork, but it's more sane than epoll) and it
446	cases	647	drops fds silently in similarly hard-to-detect cases.
447		648
448	This backend usually performs well under most conditions.	649	This backend usually performs well under most conditions.
449		650
450	While nominally embeddable in other event loops, this doesn't work	651	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	652	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	653	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	654	(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,	655	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
455	using it only for sockets.	656	also broken on OS X)) and, did I mention it, using it only for sockets.
456		657
457	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	658	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	659	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
459	C<NOTE_EOF>.	660	C<NOTE_EOF>.
460		661
…		…
468	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	669	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
469		670
470	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	671	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
471	it's really slow, but it still scales very well (O(active_fds)).	672	it's really slow, but it still scales very well (O(active_fds)).
472		673
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	674	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	675	file descriptor per loop iteration. For small and medium numbers of file
479	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	676	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
480	might perform better.	677	might perform better.
481		678
482	On the positive side, with the exception of the spurious readiness	679	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	680	specification in all tests and is fully embeddable, which is a rare feat
485	OS-specific backends (I vastly prefer correctness over speed hacks).	681	among the OS-specific backends (I vastly prefer correctness over speed
		682	hacks).
		683
		684	On the negative side, the interface is I<bizarre> - so bizarre that
		685	even sun itself gets it wrong in their code examples: The event polling
		686	function sometimes returns events to the caller even though an error
		687	occurred, but with no indication whether it has done so or not (yes, it's
		688	even documented that way) - deadly for edge-triggered interfaces where you
		689	absolutely have to know whether an event occurred or not because you have
		690	to re-arm the watcher.
		691
		692	Fortunately libev seems to be able to work around these idiocies.
486		693
487	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	694	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
488	C<EVBACKEND_POLL>.	695	C<EVBACKEND_POLL>.
489		696
490	=item C<EVBACKEND_ALL>	697	=item C<EVBACKEND_ALL>
491		698
492	Try all backends (even potentially broken ones that wouldn't be tried	699	Try all backends (even potentially broken ones that wouldn't be tried
493	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	700	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
494	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	701	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
495		702
496	It is definitely not recommended to use this flag.	703	It is definitely not recommended to use this flag, use whatever
		704	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		705	at all.
		706
		707	=item C<EVBACKEND_MASK>
		708
		709	Not a backend at all, but a mask to select all backend bits from a
		710	C<flags> value, in case you want to mask out any backends from a flags
		711	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
497		712
498	=back	713	=back
499		714
500	If one or more of these are or'ed into the flags value, then only these	715	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	716	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.	717	here). If none are specified, all backends in C<ev_recommended_backends
503		718	()> 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		719
532	Example: Try to create a event loop that uses epoll and nothing else.	720	Example: Try to create a event loop that uses epoll and nothing else.
533		721
534	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	722	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
535	if (!epoller)	723	if (!epoller)
536	fatal ("no epoll found here, maybe it hides under your chair");	724	fatal ("no epoll found here, maybe it hides under your chair");
537		725
		726	Example: Use whatever libev has to offer, but make sure that kqueue is
		727	used if available.
		728
		729	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		730
		731	Example: Similarly, on linux, you mgiht want to take advantage of the
		732	linux aio backend if possible, but fall back to something else if that
		733	isn't available.
		734
		735	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		736
538	=item ev_default_destroy ()	737	=item ev_loop_destroy (loop)
539		738
540	Destroys the default loop again (frees all memory and kernel state	739	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	740	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	741	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>	742	responsibility to either stop all watchers cleanly yourself I<before>
544	calling this function, or cope with the fact afterwards (which is usually	743	calling this function, or cope with the fact afterwards (which is usually
545	the easiest thing, you can just ignore the watchers and/or C<free ()> them	744	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
547		746
548	Note that certain global state, such as signal state (and installed signal	747	Note that certain global state, such as signal state (and installed signal
549	handlers), will not be freed by this function, and related watchers (such	748	handlers), will not be freed by this function, and related watchers (such
550	as signal and child watchers) would need to be stopped manually.	749	as signal and child watchers) would need to be stopped manually.
551		750
552	In general it is not advisable to call this function except in the	751	This function is normally used on loop objects allocated by
553	rare occasion where you really need to free e.g. the signal handling	752	C<ev_loop_new>, but it can also be used on the default loop returned by
		753	C<ev_default_loop>, in which case it is not thread-safe.
		754
		755	Note that it is not advisable to call this function on the default loop
		756	except in the rare occasion where you really need to free its resources.
554	pipe fds. If you need dynamically allocated loops it is better to use	757	If you need dynamically allocated loops it is better to use C<ev_loop_new>
555	C<ev_loop_new> and C<ev_loop_destroy>).	758	and C<ev_loop_destroy>.
556		759
557	=item ev_loop_destroy (loop)	760	=item ev_loop_fork (loop)
558		761
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	762	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	763	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	764	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	765	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	766	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.	767	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		768
		769	In addition, if you want to reuse a loop (via this function or
		770	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		771
		772	Again, you I<have> to call it on I<any> loop that you want to re-use after
		773	a fork, I<even if you do not plan to use the loop in the parent>. This is
		774	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		775	during fork.
570		776
571	On the other hand, you only need to call this function in the child	777	On the other hand, you only need to call this function in the child
572	process if and only if you want to use the event library in the child. If	778	process if and only if you want to use the event loop in the child. If
573	you just fork+exec, you don't have to call it at all.	779	you just fork+exec or create a new loop in the child, you don't have to
		780	call it at all (in fact, C<epoll> is so badly broken that it makes a
		781	difference, but libev will usually detect this case on its own and do a
		782	costly reset of the backend).
574		783
575	The function itself is quite fast and it's usually not a problem to call	784	The function itself is quite fast and it's usually not a problem to call
576	it just in case after a fork. To make this easy, the function will fit in	785	it just in case after a fork.
577	quite nicely into a call to C<pthread_atfork>:
578		786
		787	Example: Automate calling C<ev_loop_fork> on the default loop when
		788	using pthreads.
		789
		790	static void
		791	post_fork_child (void)
		792	{
		793	ev_loop_fork (EV_DEFAULT);
		794	}
		795
		796	...
579	pthread_atfork (0, 0, ev_default_fork);	797	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		798
588	=item int ev_is_default_loop (loop)	799	=item int ev_is_default_loop (loop)
589		800
590	Returns true when the given loop is, in fact, the default loop, and false	801	Returns true when the given loop is, in fact, the default loop, and false
591	otherwise.	802	otherwise.
592		803
593	=item unsigned int ev_loop_count (loop)	804	=item unsigned int ev_iteration (loop)
594		805
595	Returns the count of loop iterations for the loop, which is identical to	806	Returns the current iteration count for the event loop, which is identical
596	the number of times libev did poll for new events. It starts at C<0> and	807	to the number of times libev did poll for new events. It starts at C<0>
597	happily wraps around with enough iterations.	808	and happily wraps around with enough iterations.
598		809
599	This value can sometimes be useful as a generation counter of sorts (it	810	This value can sometimes be useful as a generation counter of sorts (it
600	"ticks" the number of loop iterations), as it roughly corresponds with	811	"ticks" the number of loop iterations), as it roughly corresponds with
601	C<ev_prepare> and C<ev_check> calls.	812	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		813	prepare and check phases.
		814
		815	=item unsigned int ev_depth (loop)
		816
		817	Returns the number of times C<ev_run> was entered minus the number of
		818	times C<ev_run> was exited normally, in other words, the recursion depth.
		819
		820	Outside C<ev_run>, this number is zero. In a callback, this number is
		821	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
		822	in which case it is higher.
		823
		824	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
		825	throwing an exception etc.), doesn't count as "exit" - consider this
		826	as a hint to avoid such ungentleman-like behaviour unless it's really
		827	convenient, in which case it is fully supported.
602		828
603	=item unsigned int ev_backend (loop)	829	=item unsigned int ev_backend (loop)
604		830
605	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	831	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
606	use.	832	use.
…		…
615		841
616	=item ev_now_update (loop)	842	=item ev_now_update (loop)
617		843
618	Establishes the current time by querying the kernel, updating the time	844	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	845	returned by C<ev_now ()> in the progress. This is a costly operation and
620	is usually done automatically within C<ev_loop ()>.	846	is usually done automatically within C<ev_run ()>.
621		847
622	This function is rarely useful, but when some event callback runs for a	848	This function is rarely useful, but when some event callback runs for a
623	very long time without entering the event loop, updating libev's idea of	849	very long time without entering the event loop, updating libev's idea of
624	the current time is a good idea.	850	the current time is a good idea.
625		851
626	See also "The special problem of time updates" in the C<ev_timer> section.	852	See also L</The special problem of time updates> in the C<ev_timer> section.
627		853
		854	=item ev_suspend (loop)
		855
		856	=item ev_resume (loop)
		857
		858	These two functions suspend and resume an event loop, for use when the
		859	loop is not used for a while and timeouts should not be processed.
		860
		861	A typical use case would be an interactive program such as a game: When
		862	the user presses C<^Z> to suspend the game and resumes it an hour later it
		863	would be best to handle timeouts as if no time had actually passed while
		864	the program was suspended. This can be achieved by calling C<ev_suspend>
		865	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		866	C<ev_resume> directly afterwards to resume timer processing.
		867
		868	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		869	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		870	will be rescheduled (that is, they will lose any events that would have
		871	occurred while suspended).
		872
		873	After calling C<ev_suspend> you B<must not> call I<any> function on the
		874	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		875	without a previous call to C<ev_suspend>.
		876
		877	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		878	event loop time (see C<ev_now_update>).
		879
628	=item ev_loop (loop, int flags)	880	=item bool ev_run (loop, int flags)
629		881
630	Finally, this is it, the event handler. This function usually is called	882	Finally, this is it, the event handler. This function usually is called
631	after you initialised all your watchers and you want to start handling	883	after you have initialised all your watchers and you want to start
632	events.	884	handling events. It will ask the operating system for any new events, call
		885	the watcher callbacks, and then repeat the whole process indefinitely: This
		886	is why event loops are called I<loops>.
633		887
634	If the flags argument is specified as C<0>, it will not return until	888	If the flags argument is specified as C<0>, it will keep handling events
635	either no event watchers are active anymore or C<ev_unloop> was called.	889	until either no event watchers are active anymore or C<ev_break> was
		890	called.
636		891
		892	The return value is false if there are no more active watchers (which
		893	usually means "all jobs done" or "deadlock"), and true in all other cases
		894	(which usually means " you should call C<ev_run> again").
		895
637	Please note that an explicit C<ev_unloop> is usually better than	896	Please note that an explicit C<ev_break> is usually better than
638	relying on all watchers to be stopped when deciding when a program has	897	relying on all watchers to be stopped when deciding when a program has
639	finished (especially in interactive programs), but having a program	898	finished (especially in interactive programs), but having a program
640	that automatically loops as long as it has to and no longer by virtue	899	that automatically loops as long as it has to and no longer by virtue
641	of relying on its watchers stopping correctly, that is truly a thing of	900	of relying on its watchers stopping correctly, that is truly a thing of
642	beauty.	901	beauty.
643		902
		903	This function is I<mostly> exception-safe - you can break out of a
		904	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		905	exception and so on. This does not decrement the C<ev_depth> value, nor
		906	will it clear any outstanding C<EVBREAK_ONE> breaks.
		907
644	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	908	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
645	those events and any already outstanding ones, but will not block your	909	those events and any already outstanding ones, but will not wait and
646	process in case there are no events and will return after one iteration of	910	block your process in case there are no events and will return after one
647	the loop.	911	iteration of the loop. This is sometimes useful to poll and handle new
		912	events while doing lengthy calculations, to keep the program responsive.
648		913
649	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	914	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
650	necessary) and will handle those and any already outstanding ones. It	915	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	916	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 guarantee that a	917	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	918	user-registered callback will be called), and will return after one
654	iteration of the loop.	919	iteration of the loop.
655		920
656	This is useful if you are waiting for some external event in conjunction	921	This is useful if you are waiting for some external event in conjunction
657	with something not expressible using other libev watchers (i.e. "roll your	922	with something not expressible using other libev watchers (i.e. "roll your
658	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	923	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
659	usually a better approach for this kind of thing.	924	usually a better approach for this kind of thing.
660		925
661	Here are the gory details of what C<ev_loop> does:	926	Here are the gory details of what C<ev_run> does (this is for your
		927	understanding, not a guarantee that things will work exactly like this in
		928	future versions):
662		929
		930	- Increment loop depth.
		931	- Reset the ev_break status.
663	- Before the first iteration, call any pending watchers.	932	- Before the first iteration, call any pending watchers.
		933	LOOP:
664	* If EVFLAG_FORKCHECK was used, check for a fork.	934	- If EVFLAG_FORKCHECK was used, check for a fork.
665	- If a fork was detected (by any means), queue and call all fork watchers.	935	- If a fork was detected (by any means), queue and call all fork watchers.
666	- Queue and call all prepare watchers.	936	- Queue and call all prepare watchers.
		937	- If ev_break was called, goto FINISH.
667	- If we have been forked, detach and recreate the kernel state	938	- If we have been forked, detach and recreate the kernel state
668	as to not disturb the other process.	939	as to not disturb the other process.
669	- Update the kernel state with all outstanding changes.	940	- Update the kernel state with all outstanding changes.
670	- Update the "event loop time" (ev_now ()).	941	- Update the "event loop time" (ev_now ()).
671	- Calculate for how long to sleep or block, if at all	942	- Calculate for how long to sleep or block, if at all
672	(active idle watchers, EVLOOP_NONBLOCK or not having	943	(active idle watchers, EVRUN_NOWAIT or not having
673	any active watchers at all will result in not sleeping).	944	any active watchers at all will result in not sleeping).
674	- Sleep if the I/O and timer collect interval say so.	945	- Sleep if the I/O and timer collect interval say so.
		946	- Increment loop iteration counter.
675	- Block the process, waiting for any events.	947	- Block the process, waiting for any events.
676	- Queue all outstanding I/O (fd) events.	948	- Queue all outstanding I/O (fd) events.
677	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	949	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
678	- Queue all expired timers.	950	- Queue all expired timers.
679	- Queue all expired periodics.	951	- Queue all expired periodics.
680	- Unless any events are pending now, queue all idle watchers.	952	- Queue all idle watchers with priority higher than that of pending events.
681	- Queue all check watchers.	953	- Queue all check watchers.
682	- Call all queued watchers in reverse order (i.e. check watchers first).	954	- Call all queued watchers in reverse order (i.e. check watchers first).
683	Signals and child watchers are implemented as I/O watchers, and will	955	Signals and child watchers are implemented as I/O watchers, and will
684	be handled here by queueing them when their watcher gets executed.	956	be handled here by queueing them when their watcher gets executed.
685	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	957	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
686	were used, or there are no active watchers, return, otherwise	958	were used, or there are no active watchers, goto FINISH, otherwise
687	continue with step *.	959	continue with step LOOP.
		960	FINISH:
		961	- Reset the ev_break status iff it was EVBREAK_ONE.
		962	- Decrement the loop depth.
		963	- Return.
688		964
689	Example: Queue some jobs and then loop until no events are outstanding	965	Example: Queue some jobs and then loop until no events are outstanding
690	anymore.	966	anymore.
691		967
692	... queue jobs here, make sure they register event watchers as long	968	... 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..)	969	... as they still have work to do (even an idle watcher will do..)
694	ev_loop (my_loop, 0);	970	ev_run (my_loop, 0);
695	... jobs done or somebody called unloop. yeah!	971	... jobs done or somebody called break. yeah!
696		972
697	=item ev_unloop (loop, how)	973	=item ev_break (loop, how)
698		974
699	Can be used to make a call to C<ev_loop> return early (but only after it	975	Can be used to make a call to C<ev_run> return early (but only after it
700	has processed all outstanding events). The C<how> argument must be either	976	has processed all outstanding events). The C<how> argument must be either
701	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	977	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
702	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	978	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
703		979
704	This "unloop state" will be cleared when entering C<ev_loop> again.	980	This "break state" will be cleared on the next call to C<ev_run>.
705		981
706	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	982	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		983	which case it will have no effect.
707		984
708	=item ev_ref (loop)	985	=item ev_ref (loop)
709		986
710	=item ev_unref (loop)	987	=item ev_unref (loop)
711		988
712	Ref/unref can be used to add or remove a reference count on the event	989	Ref/unref can be used to add or remove a reference count on the event
713	loop: Every watcher keeps one reference, and as long as the reference	990	loop: Every watcher keeps one reference, and as long as the reference
714	count is nonzero, C<ev_loop> will not return on its own.	991	count is nonzero, C<ev_run> will not return on its own.
715		992
716	If you have a watcher you never unregister that should not keep C<ev_loop>	993	This is useful when you have a watcher that you never intend to
717	from returning, call ev_unref() after starting, and ev_ref() before	994	unregister, but that nevertheless should not keep C<ev_run> from
		995	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
718	stopping it.	996	before stopping it.
719		997
720	As an example, libev itself uses this for its internal signal pipe: It is	998	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	999	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	1000	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	1001	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>	1002	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,	1003	before stop> (but only if the watcher wasn't active before, or was active
726	respectively).	1004	before, respectively. Note also that libev might stop watchers itself
		1005	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		1006	in the callback).
727		1007
728	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	1008	Example: Create a signal watcher, but keep it from keeping C<ev_run>
729	running when nothing else is active.	1009	running when nothing else is active.
730		1010
731	ev_signal exitsig;	1011	ev_signal exitsig;
732	ev_signal_init (&exitsig, sig_cb, SIGINT);	1012	ev_signal_init (&exitsig, sig_cb, SIGINT);
733	ev_signal_start (loop, &exitsig);	1013	ev_signal_start (loop, &exitsig);
734	evf_unref (loop);	1014	ev_unref (loop);
735		1015
736	Example: For some weird reason, unregister the above signal handler again.	1016	Example: For some weird reason, unregister the above signal handler again.
737		1017
738	ev_ref (loop);	1018	ev_ref (loop);
739	ev_signal_stop (loop, &exitsig);	1019	ev_signal_stop (loop, &exitsig);
…		…
759	overhead for the actual polling but can deliver many events at once.	1039	overhead for the actual polling but can deliver many events at once.
760		1040
761	By setting a higher I<io collect interval> you allow libev to spend more	1041	By setting a higher I<io collect interval> you allow libev to spend more
762	time collecting I/O events, so you can handle more events per iteration,	1042	time collecting I/O events, so you can handle more events per iteration,
763	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1043	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
764	C<ev_timer>) will be not affected. Setting this to a non-null value will	1044	C<ev_timer>) will not be affected. Setting this to a non-null value will
765	introduce an additional C<ev_sleep ()> call into most loop iterations.	1045	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		1046	sleep time ensures that libev will not poll for I/O events more often then
		1047	once per this interval, on average (as long as the host time resolution is
		1048	good enough).
766		1049
767	Likewise, by setting a higher I<timeout collect interval> you allow libev	1050	Likewise, by setting a higher I<timeout collect interval> you allow libev
768	to spend more time collecting timeouts, at the expense of increased	1051	to spend more time collecting timeouts, at the expense of increased
769	latency/jitter/inexactness (the watcher callback will be called	1052	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	1053	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
772		1055
773	Many (busy) programs can usually benefit by setting the I/O collect	1056	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	1057	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	1058	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>,	1059	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.	1060	as this approaches the timing granularity of most systems. Note that if
		1061	you do transactions with the outside world and you can't increase the
		1062	parallelity, then this setting will limit your transaction rate (if you
		1063	need to poll once per transaction and the I/O collect interval is 0.01,
		1064	then you can't do more than 100 transactions per second).
778		1065
779	Setting the I<timeout collect interval> can improve the opportunity for	1066	Setting the I<timeout collect interval> can improve the opportunity for
780	saving power, as the program will "bundle" timer callback invocations that	1067	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	1068	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	1069	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	1070	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
784	they fire on, say, one-second boundaries only.	1071	they fire on, say, one-second boundaries only.
785		1072
		1073	Example: we only need 0.1s timeout granularity, and we wish not to poll
		1074	more often than 100 times per second:
		1075
		1076	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		1077	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		1078
		1079	=item ev_invoke_pending (loop)
		1080
		1081	This call will simply invoke all pending watchers while resetting their
		1082	pending state. Normally, C<ev_run> does this automatically when required,
		1083	but when overriding the invoke callback this call comes handy. This
		1084	function can be invoked from a watcher - this can be useful for example
		1085	when you want to do some lengthy calculation and want to pass further
		1086	event handling to another thread (you still have to make sure only one
		1087	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1088
		1089	=item int ev_pending_count (loop)
		1090
		1091	Returns the number of pending watchers - zero indicates that no watchers
		1092	are pending.
		1093
		1094	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1095
		1096	This overrides the invoke pending functionality of the loop: Instead of
		1097	invoking all pending watchers when there are any, C<ev_run> will call
		1098	this callback instead. This is useful, for example, when you want to
		1099	invoke the actual watchers inside another context (another thread etc.).
		1100
		1101	If you want to reset the callback, use C<ev_invoke_pending> as new
		1102	callback.
		1103
		1104	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1105
		1106	Sometimes you want to share the same loop between multiple threads. This
		1107	can be done relatively simply by putting mutex_lock/unlock calls around
		1108	each call to a libev function.
		1109
		1110	However, C<ev_run> can run an indefinite time, so it is not feasible
		1111	to wait for it to return. One way around this is to wake up the event
		1112	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1113	I<release> and I<acquire> callbacks on the loop.
		1114
		1115	When set, then C<release> will be called just before the thread is
		1116	suspended waiting for new events, and C<acquire> is called just
		1117	afterwards.
		1118
		1119	Ideally, C<release> will just call your mutex_unlock function, and
		1120	C<acquire> will just call the mutex_lock function again.
		1121
		1122	While event loop modifications are allowed between invocations of
		1123	C<release> and C<acquire> (that's their only purpose after all), no
		1124	modifications done will affect the event loop, i.e. adding watchers will
		1125	have no effect on the set of file descriptors being watched, or the time
		1126	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1127	to take note of any changes you made.
		1128
		1129	In theory, threads executing C<ev_run> will be async-cancel safe between
		1130	invocations of C<release> and C<acquire>.
		1131
		1132	See also the locking example in the C<THREADS> section later in this
		1133	document.
		1134
		1135	=item ev_set_userdata (loop, void *data)
		1136
		1137	=item void *ev_userdata (loop)
		1138
		1139	Set and retrieve a single C<void *> associated with a loop. When
		1140	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1141	C<0>.
		1142
		1143	These two functions can be used to associate arbitrary data with a loop,
		1144	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1145	C<acquire> callbacks described above, but of course can be (ab-)used for
		1146	any other purpose as well.
		1147
786	=item ev_loop_verify (loop)	1148	=item ev_verify (loop)
787		1149
788	This function only does something when C<EV_VERIFY> support has been	1150	This function only does something when C<EV_VERIFY> support has been
789	compiled in, which is the default for non-minimal builds. It tries to go	1151	compiled in, which is the default for non-minimal builds. It tries to go
790	through all internal structures and checks them for validity. If anything	1152	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	1153	is found to be inconsistent, it will print an error message to standard
…		…
802		1164
803	In the following description, uppercase C<TYPE> in names stands for the	1165	In the following description, uppercase C<TYPE> in names stands for the
804	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1166	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
805	watchers and C<ev_io_start> for I/O watchers.	1167	watchers and C<ev_io_start> for I/O watchers.
806		1168
807	A watcher is a structure that you create and register to record your	1169	A watcher is an opaque structure that you allocate and register to record
808	interest in some event. For instance, if you want to wait for STDIN to	1170	your interest in some event. To make a concrete example, imagine you want
809	become readable, you would create an C<ev_io> watcher for that:	1171	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1172	for that:
810		1173
811	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1174	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
812	{	1175	{
813	ev_io_stop (w);	1176	ev_io_stop (w);
814	ev_unloop (loop, EVUNLOOP_ALL);	1177	ev_break (loop, EVBREAK_ALL);
815	}	1178	}
816		1179
817	struct ev_loop *loop = ev_default_loop (0);	1180	struct ev_loop *loop = ev_default_loop (0);
818		1181
819	ev_io stdin_watcher;	1182	ev_io stdin_watcher;
820		1183
821	ev_init (&stdin_watcher, my_cb);	1184	ev_init (&stdin_watcher, my_cb);
822	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1185	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
823	ev_io_start (loop, &stdin_watcher);	1186	ev_io_start (loop, &stdin_watcher);
824		1187
825	ev_loop (loop, 0);	1188	ev_run (loop, 0);
826		1189
827	As you can see, you are responsible for allocating the memory for your	1190	As you can see, you are responsible for allocating the memory for your
828	watcher structures (and it is I<usually> a bad idea to do this on the	1191	watcher structures (and it is I<usually> a bad idea to do this on the
829	stack).	1192	stack).
830		1193
831	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1194	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
832	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1195	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
833		1196
834	Each watcher structure must be initialised by a call to C<ev_init	1197	Each watcher structure must be initialised by a call to C<ev_init (watcher
835	(watcher *, callback)>, which expects a callback to be provided. This	1198	*, 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	1199	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	1200	time the event loop detects that the file descriptor given is readable
838	is readable and/or writable).	1201	and/or writable).
839		1202
840	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1203	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
841	macro to configure it, with arguments specific to the watcher type. There	1204	macro to configure it, with arguments specific to the watcher type. There
842	is also a macro to combine initialisation and setting in one call: C<<	1205	is also a macro to combine initialisation and setting in one call: C<<
843	ev_TYPE_init (watcher *, callback, ...) >>.	1206	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
866	=item C<EV_WRITE>	1229	=item C<EV_WRITE>
867		1230
868	The file descriptor in the C<ev_io> watcher has become readable and/or	1231	The file descriptor in the C<ev_io> watcher has become readable and/or
869	writable.	1232	writable.
870		1233
871	=item C<EV_TIMEOUT>	1234	=item C<EV_TIMER>
872		1235
873	The C<ev_timer> watcher has timed out.	1236	The C<ev_timer> watcher has timed out.
874		1237
875	=item C<EV_PERIODIC>	1238	=item C<EV_PERIODIC>
876		1239
…		…
894		1257
895	=item C<EV_PREPARE>	1258	=item C<EV_PREPARE>
896		1259
897	=item C<EV_CHECK>	1260	=item C<EV_CHECK>
898		1261
899	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1262	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
900	to gather new events, and all C<ev_check> watchers are invoked just after	1263	gather new events, and all C<ev_check> watchers are queued (not invoked)
901	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1264	just after C<ev_run> has gathered them, but before it queues any callbacks
		1265	for any received events. That means C<ev_prepare> watchers are the last
		1266	watchers invoked before the event loop sleeps or polls for new events, and
		1267	C<ev_check> watchers will be invoked before any other watchers of the same
		1268	or lower priority within an event loop iteration.
		1269
902	received events. Callbacks of both watcher types can start and stop as	1270	Callbacks of both watcher types can start and stop as many watchers as
903	many watchers as they want, and all of them will be taken into account	1271	they want, and all of them will be taken into account (for example, a
904	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1272	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
905	C<ev_loop> from blocking).	1273	blocking).
906		1274
907	=item C<EV_EMBED>	1275	=item C<EV_EMBED>
908		1276
909	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1277	The embedded event loop specified in the C<ev_embed> watcher needs attention.
910		1278
911	=item C<EV_FORK>	1279	=item C<EV_FORK>
912		1280
913	The event loop has been resumed in the child process after fork (see	1281	The event loop has been resumed in the child process after fork (see
914	C<ev_fork>).	1282	C<ev_fork>).
915		1283
		1284	=item C<EV_CLEANUP>
		1285
		1286	The event loop is about to be destroyed (see C<ev_cleanup>).
		1287
916	=item C<EV_ASYNC>	1288	=item C<EV_ASYNC>
917		1289
918	The given async watcher has been asynchronously notified (see C<ev_async>).	1290	The given async watcher has been asynchronously notified (see C<ev_async>).
		1291
		1292	=item C<EV_CUSTOM>
		1293
		1294	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1295	by libev users to signal watchers (e.g. via C<ev_feed_event>).
919		1296
920	=item C<EV_ERROR>	1297	=item C<EV_ERROR>
921		1298
922	An unspecified error has occurred, the watcher has been stopped. This might	1299	An unspecified error has occurred, the watcher has been stopped. This might
923	happen because the watcher could not be properly started because libev	1300	happen because the watcher could not be properly started because libev
…		…
961		1338
962	ev_io w;	1339	ev_io w;
963	ev_init (&w, my_cb);	1340	ev_init (&w, my_cb);
964	ev_io_set (&w, STDIN_FILENO, EV_READ);	1341	ev_io_set (&w, STDIN_FILENO, EV_READ);
965		1342
966	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1343	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
967		1344
968	This macro initialises the type-specific parts of a watcher. You need to	1345	This macro initialises the type-specific parts of a watcher. You need to
969	call C<ev_init> at least once before you call this macro, but you can	1346	call C<ev_init> at least once before you call this macro, but you can
970	call C<ev_TYPE_set> any number of times. You must not, however, call this	1347	call C<ev_TYPE_set> any number of times. You must not, however, call this
971	macro on a watcher that is active (it can be pending, however, which is a	1348	macro on a watcher that is active (it can be pending, however, which is a
…		…
984		1361
985	Example: Initialise and set an C<ev_io> watcher in one step.	1362	Example: Initialise and set an C<ev_io> watcher in one step.
986		1363
987	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1364	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
988		1365
989	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1366	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
990		1367
991	Starts (activates) the given watcher. Only active watchers will receive	1368	Starts (activates) the given watcher. Only active watchers will receive
992	events. If the watcher is already active nothing will happen.	1369	events. If the watcher is already active nothing will happen.
993		1370
994	Example: Start the C<ev_io> watcher that is being abused as example in this	1371	Example: Start the C<ev_io> watcher that is being abused as example in this
995	whole section.	1372	whole section.
996		1373
997	ev_io_start (EV_DEFAULT_UC, &w);	1374	ev_io_start (EV_DEFAULT_UC, &w);
998		1375
999	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1376	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1000		1377
1001	Stops the given watcher if active, and clears the pending status (whether	1378	Stops the given watcher if active, and clears the pending status (whether
1002	the watcher was active or not).	1379	the watcher was active or not).
1003		1380
1004	It is possible that stopped watchers are pending - for example,	1381	It is possible that stopped watchers are pending - for example,
…		…
1024		1401
1025	=item callback ev_cb (ev_TYPE *watcher)	1402	=item callback ev_cb (ev_TYPE *watcher)
1026		1403
1027	Returns the callback currently set on the watcher.	1404	Returns the callback currently set on the watcher.
1028		1405
1029	=item ev_cb_set (ev_TYPE *watcher, callback)	1406	=item ev_set_cb (ev_TYPE *watcher, callback)
1030		1407
1031	Change the callback. You can change the callback at virtually any time	1408	Change the callback. You can change the callback at virtually any time
1032	(modulo threads).	1409	(modulo threads).
1033		1410
1034	=item ev_set_priority (ev_TYPE *watcher, priority)	1411	=item ev_set_priority (ev_TYPE *watcher, int priority)
1035		1412
1036	=item int ev_priority (ev_TYPE *watcher)	1413	=item int ev_priority (ev_TYPE *watcher)
1037		1414
1038	Set and query the priority of the watcher. The priority is a small	1415	Set and query the priority of the watcher. The priority is a small
1039	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1416	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
1040	(default: C<-2>). Pending watchers with higher priority will be invoked	1417	(default: C<-2>). Pending watchers with higher priority will be invoked
1041	before watchers with lower priority, but priority will not keep watchers	1418	before watchers with lower priority, but priority will not keep watchers
1042	from being executed (except for C<ev_idle> watchers).	1419	from being executed (except for C<ev_idle> watchers).
1043		1420
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	1421	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.	1422	you need to look at C<ev_idle> watchers, which provide this functionality.
1051		1423
1052	You I<must not> change the priority of a watcher as long as it is active or	1424	You I<must not> change the priority of a watcher as long as it is active or
1053	pending.	1425	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		1426
1058	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1427	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	1428	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.	1429	or might not have been clamped to the valid range.
		1430
		1431	The default priority used by watchers when no priority has been set is
		1432	always C<0>, which is supposed to not be too high and not be too low :).
		1433
		1434	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
		1435	priorities.
1061		1436
1062	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1437	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1063		1438
1064	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1439	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1065	C<loop> nor C<revents> need to be valid as long as the watcher callback	1440	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>.	1448	watcher isn't pending it does nothing and returns C<0>.
1074		1449
1075	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1450	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1076	callback to be invoked, which can be accomplished with this function.	1451	callback to be invoked, which can be accomplished with this function.
1077		1452
		1453	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1454
		1455	Feeds the given event set into the event loop, as if the specified event
		1456	had happened for the specified watcher (which must be a pointer to an
		1457	initialised but not necessarily started event watcher). Obviously you must
		1458	not free the watcher as long as it has pending events.
		1459
		1460	Stopping the watcher, letting libev invoke it, or calling
		1461	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1462	not started in the first place.
		1463
		1464	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1465	functions that do not need a watcher.
		1466
1078	=back	1467	=back
1079		1468
		1469	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1470	OWN COMPOSITE WATCHERS> idioms.
1080		1471
1081	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1472	=head2 WATCHER STATES
1082		1473
1083	Each watcher has, by default, a member C<void *data> that you can change	1474	There are various watcher states mentioned throughout this manual -
1084	and read at any time: libev will completely ignore it. This can be used	1475	active, pending and so on. In this section these states and the rules to
1085	to associate arbitrary data with your watcher. If you need more data and	1476	transition between them will be described in more detail - and while these
1086	don't want to allocate memory and store a pointer to it in that data	1477	rules might look complicated, they usually do "the right thing".
1087	member, you can also "subclass" the watcher type and provide your own
1088	data:
1089		1478
1090	struct my_io	1479	=over 4
		1480
		1481	=item initialised
		1482
		1483	Before a watcher can be registered with the event loop it has to be
		1484	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1485	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
		1486
		1487	In this state it is simply some block of memory that is suitable for
		1488	use in an event loop. It can be moved around, freed, reused etc. at
		1489	will - as long as you either keep the memory contents intact, or call
		1490	C<ev_TYPE_init> again.
		1491
		1492	=item started/running/active
		1493
		1494	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
		1495	property of the event loop, and is actively waiting for events. While in
		1496	this state it cannot be accessed (except in a few documented ways), moved,
		1497	freed or anything else - the only legal thing is to keep a pointer to it,
		1498	and call libev functions on it that are documented to work on active watchers.
		1499
		1500	=item pending
		1501
		1502	If a watcher is active and libev determines that an event it is interested
		1503	in has occurred (such as a timer expiring), it will become pending. It will
		1504	stay in this pending state until either it is stopped or its callback is
		1505	about to be invoked, so it is not normally pending inside the watcher
		1506	callback.
		1507
		1508	The watcher might or might not be active while it is pending (for example,
		1509	an expired non-repeating timer can be pending but no longer active). If it
		1510	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1511	but it is still property of the event loop at this time, so cannot be
		1512	moved, freed or reused. And if it is active the rules described in the
		1513	previous item still apply.
		1514
		1515	It is also possible to feed an event on a watcher that is not active (e.g.
		1516	via C<ev_feed_event>), in which case it becomes pending without being
		1517	active.
		1518
		1519	=item stopped
		1520
		1521	A watcher can be stopped implicitly by libev (in which case it might still
		1522	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
		1523	latter will clear any pending state the watcher might be in, regardless
		1524	of whether it was active or not, so stopping a watcher explicitly before
		1525	freeing it is often a good idea.
		1526
		1527	While stopped (and not pending) the watcher is essentially in the
		1528	initialised state, that is, it can be reused, moved, modified in any way
		1529	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1530	it again).
		1531
		1532	=back
		1533
		1534	=head2 WATCHER PRIORITY MODELS
		1535
		1536	Many event loops support I<watcher priorities>, which are usually small
		1537	integers that influence the ordering of event callback invocation
		1538	between watchers in some way, all else being equal.
		1539
		1540	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1541	description for the more technical details such as the actual priority
		1542	range.
		1543
		1544	There are two common ways how these these priorities are being interpreted
		1545	by event loops:
		1546
		1547	In the more common lock-out model, higher priorities "lock out" invocation
		1548	of lower priority watchers, which means as long as higher priority
		1549	watchers receive events, lower priority watchers are not being invoked.
		1550
		1551	The less common only-for-ordering model uses priorities solely to order
		1552	callback invocation within a single event loop iteration: Higher priority
		1553	watchers are invoked before lower priority ones, but they all get invoked
		1554	before polling for new events.
		1555
		1556	Libev uses the second (only-for-ordering) model for all its watchers
		1557	except for idle watchers (which use the lock-out model).
		1558
		1559	The rationale behind this is that implementing the lock-out model for
		1560	watchers is not well supported by most kernel interfaces, and most event
		1561	libraries will just poll for the same events again and again as long as
		1562	their callbacks have not been executed, which is very inefficient in the
		1563	common case of one high-priority watcher locking out a mass of lower
		1564	priority ones.
		1565
		1566	Static (ordering) priorities are most useful when you have two or more
		1567	watchers handling the same resource: a typical usage example is having an
		1568	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1569	timeouts. Under load, data might be received while the program handles
		1570	other jobs, but since timers normally get invoked first, the timeout
		1571	handler will be executed before checking for data. In that case, giving
		1572	the timer a lower priority than the I/O watcher ensures that I/O will be
		1573	handled first even under adverse conditions (which is usually, but not
		1574	always, what you want).
		1575
		1576	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1577	will only be executed when no same or higher priority watchers have
		1578	received events, they can be used to implement the "lock-out" model when
		1579	required.
		1580
		1581	For example, to emulate how many other event libraries handle priorities,
		1582	you can associate an C<ev_idle> watcher to each such watcher, and in
		1583	the normal watcher callback, you just start the idle watcher. The real
		1584	processing is done in the idle watcher callback. This causes libev to
		1585	continuously poll and process kernel event data for the watcher, but when
		1586	the lock-out case is known to be rare (which in turn is rare :), this is
		1587	workable.
		1588
		1589	Usually, however, the lock-out model implemented that way will perform
		1590	miserably under the type of load it was designed to handle. In that case,
		1591	it might be preferable to stop the real watcher before starting the
		1592	idle watcher, so the kernel will not have to process the event in case
		1593	the actual processing will be delayed for considerable time.
		1594
		1595	Here is an example of an I/O watcher that should run at a strictly lower
		1596	priority than the default, and which should only process data when no
		1597	other events are pending:
		1598
		1599	ev_idle idle; // actual processing watcher
		1600	ev_io io; // actual event watcher
		1601
		1602	static void
		1603	io_cb (EV_P_ ev_io *w, int revents)
1091	{	1604	{
1092	ev_io io;	1605	// stop the I/O watcher, we received the event, but
1093	int otherfd;	1606	// are not yet ready to handle it.
1094	void *somedata;	1607	ev_io_stop (EV_A_ w);
1095	struct whatever *mostinteresting;	1608
		1609	// start the idle watcher to handle the actual event.
		1610	// it will not be executed as long as other watchers
		1611	// with the default priority are receiving events.
		1612	ev_idle_start (EV_A_ &idle);
1096	};	1613	}
1097		1614
1098	...	1615	static void
1099	struct my_io w;	1616	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	{	1617	{
1107	struct my_io *w = (struct my_io *)w_;	1618	// actual processing
1108	...	1619	read (STDIN_FILENO, ...);
		1620
		1621	// have to start the I/O watcher again, as
		1622	// we have handled the event
		1623	ev_io_start (EV_P_ &io);
1109	}	1624	}
1110		1625
1111	More interesting and less C-conformant ways of casting your callback type	1626	// initialisation
1112	instead have been omitted.	1627	ev_idle_init (&idle, idle_cb);
		1628	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1629	ev_io_start (EV_DEFAULT_ &io);
1113		1630
1114	Another common scenario is to use some data structure with multiple	1631	In the "real" world, it might also be beneficial to start a timer, so that
1115	embedded watchers:	1632	low-priority connections can not be locked out forever under load. This
1116		1633	enables your program to keep a lower latency for important connections
1117	struct my_biggy	1634	during short periods of high load, while not completely locking out less
1118	{	1635	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		1636
1146		1637
1147	=head1 WATCHER TYPES	1638	=head1 WATCHER TYPES
1148		1639
1149	This section describes each watcher in detail, but will not repeat	1640	This section describes each watcher in detail, but will not repeat
…		…
1173	In general you can register as many read and/or write event watchers per	1664	In general you can register as many read and/or write event watchers per
1174	fd as you want (as long as you don't confuse yourself). Setting all file	1665	fd as you want (as long as you don't confuse yourself). Setting all file
1175	descriptors to non-blocking mode is also usually a good idea (but not	1666	descriptors to non-blocking mode is also usually a good idea (but not
1176	required if you know what you are doing).	1667	required if you know what you are doing).
1177		1668
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	1669	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	1670	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	1671	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	1672	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	1673	with a relatively standard program structure. Thus it is best to always
1187	this situation even with a relatively standard program structure. Thus	1674	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
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.	1675	preferable to a program hanging until some data arrives.
1190		1676
1191	If you cannot run the fd in non-blocking mode (for example you should	1677	If you cannot run the fd in non-blocking mode (for example you should
1192	not play around with an Xlib connection), then you have to separately	1678	not play around with an Xlib connection), then you have to separately
1193	re-test whether a file descriptor is really ready with a known-to-be good	1679	re-test whether a file descriptor is really ready with a known-to-be good
1194	interface such as poll (fortunately in our Xlib example, Xlib already	1680	interface such as poll (fortunately in the case of Xlib, it already does
1195	does this on its own, so its quite safe to use). Some people additionally	1681	this on its own, so its quite safe to use). Some people additionally
1196	use C<SIGALRM> and an interval timer, just to be sure you won't block	1682	use C<SIGALRM> and an interval timer, just to be sure you won't block
1197	indefinitely.	1683	indefinitely.
1198		1684
1199	But really, best use non-blocking mode.	1685	But really, best use non-blocking mode.
1200		1686
1201	=head3 The special problem of disappearing file descriptors	1687	=head3 The special problem of disappearing file descriptors
1202		1688
1203	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1689	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1204	descriptor (either due to calling C<close> explicitly or any other means,	1690	a file descriptor (either due to calling C<close> explicitly or any other
1205	such as C<dup2>). The reason is that you register interest in some file	1691	means, such as C<dup2>). The reason is that you register interest in some
1206	descriptor, but when it goes away, the operating system will silently drop	1692	file descriptor, but when it goes away, the operating system will silently
1207	this interest. If another file descriptor with the same number then is	1693	drop this interest. If another file descriptor with the same number then
1208	registered with libev, there is no efficient way to see that this is, in	1694	is registered with libev, there is no efficient way to see that this is,
1209	fact, a different file descriptor.	1695	in fact, a different file descriptor.
1210		1696
1211	To avoid having to explicitly tell libev about such cases, libev follows	1697	To avoid having to explicitly tell libev about such cases, libev follows
1212	the following policy: Each time C<ev_io_set> is being called, libev	1698	the following policy: Each time C<ev_io_set> is being called, libev
1213	will assume that this is potentially a new file descriptor, otherwise	1699	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	1700	it is assumed that the file descriptor stays the same. That means that
…		…
1228		1714
1229	There is no workaround possible except not registering events	1715	There is no workaround possible except not registering events
1230	for potentially C<dup ()>'ed file descriptors, or to resort to	1716	for potentially C<dup ()>'ed file descriptors, or to resort to
1231	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1717	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1232		1718
		1719	=head3 The special problem of files
		1720
		1721	Many people try to use C<select> (or libev) on file descriptors
		1722	representing files, and expect it to become ready when their program
		1723	doesn't block on disk accesses (which can take a long time on their own).
		1724
		1725	However, this cannot ever work in the "expected" way - you get a readiness
		1726	notification as soon as the kernel knows whether and how much data is
		1727	there, and in the case of open files, that's always the case, so you
		1728	always get a readiness notification instantly, and your read (or possibly
		1729	write) will still block on the disk I/O.
		1730
		1731	Another way to view it is that in the case of sockets, pipes, character
		1732	devices and so on, there is another party (the sender) that delivers data
		1733	on its own, but in the case of files, there is no such thing: the disk
		1734	will not send data on its own, simply because it doesn't know what you
		1735	wish to read - you would first have to request some data.
		1736
		1737	Since files are typically not-so-well supported by advanced notification
		1738	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1739	to files, even though you should not use it. The reason for this is
		1740	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1741	usually a tty, often a pipe, but also sometimes files or special devices
		1742	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1743	F</dev/urandom>), and even though the file might better be served with
		1744	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1745	it "just works" instead of freezing.
		1746
		1747	So avoid file descriptors pointing to files when you know it (e.g. use
		1748	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1749	when you rarely read from a file instead of from a socket, and want to
		1750	reuse the same code path.
		1751
1233	=head3 The special problem of fork	1752	=head3 The special problem of fork
1234		1753
1235	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1754	Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()>
1236	useless behaviour. Libev fully supports fork, but needs to be told about	1755	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1237	it in the child.	1756	to be told about it in the child if you want to continue to use it in the
		1757	child.
1238		1758
1239	To support fork in your programs, you either have to call	1759	To support fork in your child processes, you have to call C<ev_loop_fork
1240	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1760	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1241	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1761	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1242	C<EVBACKEND_POLL>.
1243		1762
1244	=head3 The special problem of SIGPIPE	1763	=head3 The special problem of SIGPIPE
1245		1764
1246	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1765	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1247	when writing to a pipe whose other end has been closed, your program gets	1766	when writing to a pipe whose other end has been closed, your program gets
…		…
1250		1769
1251	So when you encounter spurious, unexplained daemon exits, make sure you	1770	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	1771	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).	1772	somewhere, as that would have given you a big clue).
1254		1773
		1774	=head3 The special problem of accept()ing when you can't
		1775
		1776	Many implementations of the POSIX C<accept> function (for example,
		1777	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1778	connection from the pending queue in all error cases.
		1779
		1780	For example, larger servers often run out of file descriptors (because
		1781	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1782	rejecting the connection, leading to libev signalling readiness on
		1783	the next iteration again (the connection still exists after all), and
		1784	typically causing the program to loop at 100% CPU usage.
		1785
		1786	Unfortunately, the set of errors that cause this issue differs between
		1787	operating systems, there is usually little the app can do to remedy the
		1788	situation, and no known thread-safe method of removing the connection to
		1789	cope with overload is known (to me).
		1790
		1791	One of the easiest ways to handle this situation is to just ignore it
		1792	- when the program encounters an overload, it will just loop until the
		1793	situation is over. While this is a form of busy waiting, no OS offers an
		1794	event-based way to handle this situation, so it's the best one can do.
		1795
		1796	A better way to handle the situation is to log any errors other than
		1797	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1798	messages, and continue as usual, which at least gives the user an idea of
		1799	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1800	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1801	usage.
		1802
		1803	If your program is single-threaded, then you could also keep a dummy file
		1804	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1805	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1806	close that fd, and create a new dummy fd. This will gracefully refuse
		1807	clients under typical overload conditions.
		1808
		1809	The last way to handle it is to simply log the error and C<exit>, as
		1810	is often done with C<malloc> failures, but this results in an easy
		1811	opportunity for a DoS attack.
1255		1812
1256	=head3 Watcher-Specific Functions	1813	=head3 Watcher-Specific Functions
1257		1814
1258	=over 4	1815	=over 4
1259		1816
…		…
1291	...	1848	...
1292	struct ev_loop *loop = ev_default_init (0);	1849	struct ev_loop *loop = ev_default_init (0);
1293	ev_io stdin_readable;	1850	ev_io stdin_readable;
1294	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1851	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1295	ev_io_start (loop, &stdin_readable);	1852	ev_io_start (loop, &stdin_readable);
1296	ev_loop (loop, 0);	1853	ev_run (loop, 0);
1297		1854
1298		1855
1299	=head2 C<ev_timer> - relative and optionally repeating timeouts	1856	=head2 C<ev_timer> - relative and optionally repeating timeouts
1300		1857
1301	Timer watchers are simple relative timers that generate an event after a	1858	Timer watchers are simple relative timers that generate an event after a
…		…
1306	year, it will still time out after (roughly) one hour. "Roughly" because	1863	year, it will still time out after (roughly) one hour. "Roughly" because
1307	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1864	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1308	monotonic clock option helps a lot here).	1865	monotonic clock option helps a lot here).
1309		1866
1310	The callback is guaranteed to be invoked only I<after> its timeout has	1867	The callback is guaranteed to be invoked only I<after> its timeout has
1311	passed, but if multiple timers become ready during the same loop iteration	1868	passed (not I<at>, so on systems with very low-resolution clocks this
1312	then order of execution is undefined.	1869	might introduce a small delay, see "the special problem of being too
		1870	early", below). If multiple timers become ready during the same loop
		1871	iteration then the ones with earlier time-out values are invoked before
		1872	ones of the same priority with later time-out values (but this is no
		1873	longer true when a callback calls C<ev_run> recursively).
1313		1874
1314	=head3 Be smart about timeouts	1875	=head3 Be smart about timeouts
1315		1876
1316	Many real-world problems involve some kind of timeout, usually for error	1877	Many real-world problems involve some kind of timeout, usually for error
1317	recovery. A typical example is an HTTP request - if the other side hangs,	1878	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1361	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>	1922	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
1362	member and C<ev_timer_again>.	1923	member and C<ev_timer_again>.
1363		1924
1364	At start:	1925	At start:
1365		1926
1366	ev_timer_init (timer, callback);	1927	ev_init (timer, callback);
1367	timer->repeat = 60.;	1928	timer->repeat = 60.;
1368	ev_timer_again (loop, timer);	1929	ev_timer_again (loop, timer);
1369		1930
1370	Each time there is some activity:	1931	Each time there is some activity:
1371		1932
…		…
1392		1953
1393	In this case, it would be more efficient to leave the C<ev_timer> alone,	1954	In this case, it would be more efficient to leave the C<ev_timer> alone,
1394	but remember the time of last activity, and check for a real timeout only	1955	but remember the time of last activity, and check for a real timeout only
1395	within the callback:	1956	within the callback:
1396		1957
		1958	ev_tstamp timeout = 60.;
1397	ev_tstamp last_activity; // time of last activity	1959	ev_tstamp last_activity; // time of last activity
		1960	ev_timer timer;
1398		1961
1399	static void	1962	static void
1400	callback (EV_P_ ev_timer *w, int revents)	1963	callback (EV_P_ ev_timer *w, int revents)
1401	{	1964	{
1402	ev_tstamp now = ev_now (EV_A);	1965	// calculate when the timeout would happen
1403	ev_tstamp timeout = last_activity + 60.;	1966	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1404		1967
1405	// if last_activity + 60. is older than now, we did time out	1968	// if negative, it means we the timeout already occurred
1406	if (timeout < now)	1969	if (after < 0.)
1407	{	1970	{
1408	// timeout occured, take action	1971	// timeout occurred, take action
1409	}	1972	}
1410	else	1973	else
1411	{	1974	{
1412	// callback was invoked, but there was some activity, re-arm	1975	// callback was invoked, but there was some recent
1413	// the watcher to fire in last_activity + 60, which is	1976	// activity. simply restart the timer to time out
1414	// guaranteed to be in the future, so "again" is positive:	1977	// after "after" seconds, which is the earliest time
1415	w->again = timeout - now;	1978	// the timeout can occur.
		1979	ev_timer_set (w, after, 0.);
1416	ev_timer_again (EV_A_ w);	1980	ev_timer_start (EV_A_ w);
1417	}	1981	}
1418	}	1982	}
1419		1983
1420	To summarise the callback: first calculate the real timeout (defined	1984	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	1985	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	1986	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	1987	(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		1988
1427	Note how C<ev_timer_again> is used, taking advantage of the	1989	If this value is negative, then we are already past the timeout, i.e. we
1428	C<ev_timer_again> optimisation when the timer is already running.	1990	timed out, and need to do whatever is needed in this case.
		1991
		1992	Otherwise, we now the earliest time at which the timeout would trigger,
		1993	and simply start the timer with this timeout value.
		1994
		1995	In other words, each time the callback is invoked it will check whether
		1996	the timeout occurred. If not, it will simply reschedule itself to check
		1997	again at the earliest time it could time out. Rinse. Repeat.
1429		1998
1430	This scheme causes more callback invocations (about one every 60 seconds	1999	This scheme causes more callback invocations (about one every 60 seconds
1431	minus half the average time between activity), but virtually no calls to	2000	minus half the average time between activity), but virtually no calls to
1432	libev to change the timeout.	2001	libev to change the timeout.
1433		2002
1434	To start the timer, simply initialise the watcher and set C<last_activity>	2003	To start the machinery, simply initialise the watcher and set
1435	to the current time (meaning we just have some activity :), then call the	2004	C<last_activity> to the current time (meaning there was some activity just
1436	callback, which will "do the right thing" and start the timer:	2005	now), then call the callback, which will "do the right thing" and start
		2006	the timer:
1437		2007
		2008	last_activity = ev_now (EV_A);
1438	ev_timer_init (timer, callback);	2009	ev_init (&timer, callback);
1439	last_activity = ev_now (loop);	2010	callback (EV_A_ &timer, 0);
1440	callback (loop, timer, EV_TIMEOUT);
1441		2011
1442	And when there is some activity, simply store the current time in	2012	When there is some activity, simply store the current time in
1443	C<last_activity>, no libev calls at all:	2013	C<last_activity>, no libev calls at all:
1444		2014
		2015	if (activity detected)
1445	last_actiivty = ev_now (loop);	2016	last_activity = ev_now (EV_A);
		2017
		2018	When your timeout value changes, then the timeout can be changed by simply
		2019	providing a new value, stopping the timer and calling the callback, which
		2020	will again do the right thing (for example, time out immediately :).
		2021
		2022	timeout = new_value;
		2023	ev_timer_stop (EV_A_ &timer);
		2024	callback (EV_A_ &timer, 0);
1446		2025
1447	This technique is slightly more complex, but in most cases where the	2026	This technique is slightly more complex, but in most cases where the
1448	time-out is unlikely to be triggered, much more efficient.	2027	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		2028
1454	=item 4. Wee, just use a double-linked list for your timeouts.	2029	=item 4. Wee, just use a double-linked list for your timeouts.
1455		2030
1456	If there is not one request, but many thousands (millions...), all	2031	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	2032	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	2059	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	2060	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	2061	off after the first million or so of active timers, i.e. it's usually
1487	overkill :)	2062	overkill :)
1488		2063
		2064	=head3 The special problem of being too early
		2065
		2066	If you ask a timer to call your callback after three seconds, then
		2067	you expect it to be invoked after three seconds - but of course, this
		2068	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2069	guaranteed to any precision by libev - imagine somebody suspending the
		2070	process with a STOP signal for a few hours for example.
		2071
		2072	So, libev tries to invoke your callback as soon as possible I<after> the
		2073	delay has occurred, but cannot guarantee this.
		2074
		2075	A less obvious failure mode is calling your callback too early: many event
		2076	loops compare timestamps with a "elapsed delay >= requested delay", but
		2077	this can cause your callback to be invoked much earlier than you would
		2078	expect.
		2079
		2080	To see why, imagine a system with a clock that only offers full second
		2081	resolution (think windows if you can't come up with a broken enough OS
		2082	yourself). If you schedule a one-second timer at the time 500.9, then the
		2083	event loop will schedule your timeout to elapse at a system time of 500
		2084	(500.9 truncated to the resolution) + 1, or 501.
		2085
		2086	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2087	501" and invoke the callback 0.1s after it was started, even though a
		2088	one-second delay was requested - this is being "too early", despite best
		2089	intentions.
		2090
		2091	This is the reason why libev will never invoke the callback if the elapsed
		2092	delay equals the requested delay, but only when the elapsed delay is
		2093	larger than the requested delay. In the example above, libev would only invoke
		2094	the callback at system time 502, or 1.1s after the timer was started.
		2095
		2096	So, while libev cannot guarantee that your callback will be invoked
		2097	exactly when requested, it I<can> and I<does> guarantee that the requested
		2098	delay has actually elapsed, or in other words, it always errs on the "too
		2099	late" side of things.
		2100
1489	=head3 The special problem of time updates	2101	=head3 The special problem of time updates
1490		2102
1491	Establishing the current time is a costly operation (it usually takes at	2103	Establishing the current time is a costly operation (it usually takes
1492	least two system calls): EV therefore updates its idea of the current	2104	at least one system call): EV therefore updates its idea of the current
1493	time only before and after C<ev_loop> collects new events, which causes a	2105	time only before and after C<ev_run> collects new events, which causes a
1494	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2106	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1495	lots of events in one iteration.	2107	lots of events in one iteration.
1496		2108
1497	The relative timeouts are calculated relative to the C<ev_now ()>	2109	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	2110	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	2111	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	2112	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:	2113	timeout on the current time, use something like the following to adjust
		2114	for it:
1502		2115
1503	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2116	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1504		2117
1505	If the event loop is suspended for a long time, you can also force an	2118	If the event loop is suspended for a long time, you can also force an
1506	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2119	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1507	()>.	2120	()>, although that will push the event time of all outstanding events
		2121	further into the future.
		2122
		2123	=head3 The special problem of unsynchronised clocks
		2124
		2125	Modern systems have a variety of clocks - libev itself uses the normal
		2126	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2127	jumps).
		2128
		2129	Neither of these clocks is synchronised with each other or any other clock
		2130	on the system, so C<ev_time ()> might return a considerably different time
		2131	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2132	a call to C<gettimeofday> might return a second count that is one higher
		2133	than a directly following call to C<time>.
		2134
		2135	The moral of this is to only compare libev-related timestamps with
		2136	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2137	a second or so.
		2138
		2139	One more problem arises due to this lack of synchronisation: if libev uses
		2140	the system monotonic clock and you compare timestamps from C<ev_time>
		2141	or C<ev_now> from when you started your timer and when your callback is
		2142	invoked, you will find that sometimes the callback is a bit "early".
		2143
		2144	This is because C<ev_timer>s work in real time, not wall clock time, so
		2145	libev makes sure your callback is not invoked before the delay happened,
		2146	I<measured according to the real time>, not the system clock.
		2147
		2148	If your timeouts are based on a physical timescale (e.g. "time out this
		2149	connection after 100 seconds") then this shouldn't bother you as it is
		2150	exactly the right behaviour.
		2151
		2152	If you want to compare wall clock/system timestamps to your timers, then
		2153	you need to use C<ev_periodic>s, as these are based on the wall clock
		2154	time, where your comparisons will always generate correct results.
		2155
		2156	=head3 The special problems of suspended animation
		2157
		2158	When you leave the server world it is quite customary to hit machines that
		2159	can suspend/hibernate - what happens to the clocks during such a suspend?
		2160
		2161	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2162	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2163	to run until the system is suspended, but they will not advance while the
		2164	system is suspended. That means, on resume, it will be as if the program
		2165	was frozen for a few seconds, but the suspend time will not be counted
		2166	towards C<ev_timer> when a monotonic clock source is used. The real time
		2167	clock advanced as expected, but if it is used as sole clocksource, then a
		2168	long suspend would be detected as a time jump by libev, and timers would
		2169	be adjusted accordingly.
		2170
		2171	I would not be surprised to see different behaviour in different between
		2172	operating systems, OS versions or even different hardware.
		2173
		2174	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2175	time jump in the monotonic clocks and the realtime clock. If the program
		2176	is suspended for a very long time, and monotonic clock sources are in use,
		2177	then you can expect C<ev_timer>s to expire as the full suspension time
		2178	will be counted towards the timers. When no monotonic clock source is in
		2179	use, then libev will again assume a timejump and adjust accordingly.
		2180
		2181	It might be beneficial for this latter case to call C<ev_suspend>
		2182	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2183	deterministic behaviour in this case (you can do nothing against
		2184	C<SIGSTOP>).
1508		2185
1509	=head3 Watcher-Specific Functions and Data Members	2186	=head3 Watcher-Specific Functions and Data Members
1510		2187
1511	=over 4	2188	=over 4
1512		2189
1513	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2190	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1514		2191
1515	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2192	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1516		2193
1517	Configure the timer to trigger after C<after> seconds. If C<repeat>	2194	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	2195	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	2196	automatically be stopped once the timeout is reached. If it is positive,
1520	configured to trigger again C<repeat> seconds later, again, and again,	2197	then the timer will automatically be configured to trigger again C<repeat>
1521	until stopped manually.	2198	seconds later, again, and again, until stopped manually.
1522		2199
1523	The timer itself will do a best-effort at avoiding drift, that is, if	2200	The timer itself will do a best-effort at avoiding drift, that is, if
1524	you configure a timer to trigger every 10 seconds, then it will normally	2201	you configure a timer to trigger every 10 seconds, then it will normally
1525	trigger at exactly 10 second intervals. If, however, your program cannot	2202	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	2203	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.	2204	do stuff) the timer will not fire more than once per event loop iteration.
1528		2205
1529	=item ev_timer_again (loop, ev_timer *)	2206	=item ev_timer_again (loop, ev_timer *)
1530		2207
1531	This will act as if the timer timed out and restart it again if it is	2208	This will act as if the timer timed out, and restarts it again if it is
1532	repeating. The exact semantics are:	2209	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2210	timeout to the C<repeat> value and calling C<ev_timer_start>.
1533		2211
		2212	The exact semantics are as in the following rules, all of which will be
		2213	applied to the watcher:
		2214
		2215	=over 4
		2216
1534	If the timer is pending, its pending status is cleared.	2217	=item If the timer is pending, the pending status is always cleared.
1535		2218
1536	If the timer is started but non-repeating, stop it (as if it timed out).	2219	=item If the timer is started but non-repeating, stop it (as if it timed
		2220	out, without invoking it).
1537		2221
1538	If the timer is repeating, either start it if necessary (with the	2222	=item If the timer is repeating, make the C<repeat> value the new timeout
1539	C<repeat> value), or reset the running timer to the C<repeat> value.	2223	and start the timer, if necessary.
1540		2224
		2225	=back
		2226
1541	This sounds a bit complicated, see "Be smart about timeouts", above, for a	2227	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1542	usage example.	2228	usage example.
		2229
		2230	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2231
		2232	Returns the remaining time until a timer fires. If the timer is active,
		2233	then this time is relative to the current event loop time, otherwise it's
		2234	the timeout value currently configured.
		2235
		2236	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2237	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2238	will return C<4>. When the timer expires and is restarted, it will return
		2239	roughly C<7> (likely slightly less as callback invocation takes some time,
		2240	too), and so on.
1543		2241
1544	=item ev_tstamp repeat [read-write]	2242	=item ev_tstamp repeat [read-write]
1545		2243
1546	The current C<repeat> value. Will be used each time the watcher times out	2244	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),	2245	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1573	}	2271	}
1574		2272
1575	ev_timer mytimer;	2273	ev_timer mytimer;
1576	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2274	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1577	ev_timer_again (&mytimer); /* start timer */	2275	ev_timer_again (&mytimer); /* start timer */
1578	ev_loop (loop, 0);	2276	ev_run (loop, 0);
1579		2277
1580	// and in some piece of code that gets executed on any "activity":	2278	// and in some piece of code that gets executed on any "activity":
1581	// reset the timeout to start ticking again at 10 seconds	2279	// reset the timeout to start ticking again at 10 seconds
1582	ev_timer_again (&mytimer);	2280	ev_timer_again (&mytimer);
1583		2281
…		…
1585	=head2 C<ev_periodic> - to cron or not to cron?	2283	=head2 C<ev_periodic> - to cron or not to cron?
1586		2284
1587	Periodic watchers are also timers of a kind, but they are very versatile	2285	Periodic watchers are also timers of a kind, but they are very versatile
1588	(and unfortunately a bit complex).	2286	(and unfortunately a bit complex).
1589		2287
1590	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	2288	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	2289	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	2290	(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 ()	2291	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	2292	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	2293	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		2294
		2295	You can tell a periodic watcher to trigger after some specific point
		2296	in time: for example, if you tell a periodic watcher to trigger "in 10
		2297	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		2298	not a delay) and then reset your system clock to January of the previous
		2299	year, then it will take a year or more to trigger the event (unlike an
		2300	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		2301	it, as it uses a relative timeout).
		2302
1599	C<ev_periodic>s can also be used to implement vastly more complex timers,	2303	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	2304	timers, such as triggering an event on each "midnight, local time", or
1601	complicated rules.	2305	other complicated rules. This cannot easily be done with C<ev_timer>
		2306	watchers, as those cannot react to time jumps.
1602		2307
1603	As with timers, the callback is guaranteed to be invoked only when the	2308	As with timers, the callback is guaranteed to be invoked only when the
1604	time (C<at>) has passed, but if multiple periodic timers become ready	2309	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.	2310	timers become ready during the same loop iteration then the ones with
		2311	earlier time-out values are invoked before ones with later time-out values
		2312	(but this is no longer true when a callback calls C<ev_run> recursively).
1606		2313
1607	=head3 Watcher-Specific Functions and Data Members	2314	=head3 Watcher-Specific Functions and Data Members
1608		2315
1609	=over 4	2316	=over 4
1610		2317
1611	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	2318	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1612		2319
1613	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	2320	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1614		2321
1615	Lots of arguments, lets sort it out... There are basically three modes of	2322	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:	2323	operation, and we will explain them from simplest to most complex:
1617		2324
1618	=over 4	2325	=over 4
1619		2326
1620	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2327	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1621		2328
1622	In this configuration the watcher triggers an event after the wall clock	2329	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	2330	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	2331	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.	2332	will be stopped and invoked when the system clock reaches or surpasses
		2333	this point in time.
1626		2334
1627	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	2335	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1628		2336
1629	In this mode the watcher will always be scheduled to time out at the next	2337	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)	2338	C<offset + N * interval> time (for some integer N, which can also be
1631	and then repeat, regardless of any time jumps.	2339	negative) and then repeat, regardless of any time jumps. The C<offset>
		2340	argument is merely an offset into the C<interval> periods.
1632		2341
1633	This can be used to create timers that do not drift with respect to the	2342	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	2343	system clock, for example, here is an C<ev_periodic> that triggers each
1635	hour, on the hour:	2344	hour, on the hour (with respect to UTC):
1636		2345
1637	ev_periodic_set (&periodic, 0., 3600., 0);	2346	ev_periodic_set (&periodic, 0., 3600., 0);
1638		2347
1639	This doesn't mean there will always be 3600 seconds in between triggers,	2348	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	2349	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	2350	full hour (UTC), or more correctly, when the system time is evenly divisible
1642	by 3600.	2351	by 3600.
1643		2352
1644	Another way to think about it (for the mathematically inclined) is that	2353	Another way to think about it (for the mathematically inclined) is that
1645	C<ev_periodic> will try to run the callback in this mode at the next possible	2354	C<ev_periodic> will try to run the callback in this mode at the next possible
1646	time where C<time = at (mod interval)>, regardless of any time jumps.	2355	time where C<time = offset (mod interval)>, regardless of any time jumps.
1647		2356
1648	For numerical stability it is preferable that the C<at> value is near	2357	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	2358	interval value should be higher than C<1/8192> (which is around 100
1650	this value, and in fact is often specified as zero.	2359	microseconds) and C<offset> should be higher than C<0> and should have
		2360	at most a similar magnitude as the current time (say, within a factor of
		2361	ten). Typical values for offset are, in fact, C<0> or something between
		2362	C<0> and C<interval>, which is also the recommended range.
1651		2363
1652	Note also that there is an upper limit to how often a timer can fire (CPU	2364	Note also that there is an upper limit to how often a timer can fire (CPU
1653	speed for example), so if C<interval> is very small then timing stability	2365	speed for example), so if C<interval> is very small then timing stability
1654	will of course deteriorate. Libev itself tries to be exact to be about one	2366	will of course deteriorate. Libev itself tries to be exact to be about one
1655	millisecond (if the OS supports it and the machine is fast enough).	2367	millisecond (if the OS supports it and the machine is fast enough).
1656		2368
1657	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2369	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1658		2370
1659	In this mode the values for C<interval> and C<at> are both being	2371	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	2372	ignored. Instead, each time the periodic watcher gets scheduled, the
1661	reschedule callback will be called with the watcher as first, and the	2373	reschedule callback will be called with the watcher as first, and the
1662	current time as second argument.	2374	current time as second argument.
1663		2375
1664	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2376	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1665	ever, or make ANY event loop modifications whatsoever>.	2377	or make ANY other event loop modifications whatsoever, unless explicitly
		2378	allowed by documentation here>.
1666		2379
1667	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2380	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	2381	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1669	only event loop modification you are allowed to do).	2382	only event loop modification you are allowed to do).
1670		2383
…		…
1684		2397
1685	NOTE: I<< This callback must always return a time that is higher than or	2398	NOTE: I<< This callback must always return a time that is higher than or
1686	equal to the passed C<now> value >>.	2399	equal to the passed C<now> value >>.
1687		2400
1688	This can be used to create very complex timers, such as a timer that	2401	This can be used to create very complex timers, such as a timer that
1689	triggers on "next midnight, local time". To do this, you would calculate the	2402	triggers on "next midnight, local time". To do this, you would calculate
1690	next midnight after C<now> and return the timestamp value for this. How	2403	the next midnight after C<now> and return the timestamp value for
1691	you do this is, again, up to you (but it is not trivial, which is the main	2404	this. Here is a (completely untested, no error checking) example on how to
1692	reason I omitted it as an example).	2405	do this:
		2406
		2407	#include <time.h>
		2408
		2409	static ev_tstamp
		2410	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2411	{
		2412	time_t tnow = (time_t)now;
		2413	struct tm tm;
		2414	localtime_r (&tnow, &tm);
		2415
		2416	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2417	++tm.tm_mday; // midnight next day
		2418
		2419	return mktime (&tm);
		2420	}
		2421
		2422	Note: this code might run into trouble on days that have more then two
		2423	midnights (beginning and end).
1693		2424
1694	=back	2425	=back
1695		2426
1696	=item ev_periodic_again (loop, ev_periodic *)	2427	=item ev_periodic_again (loop, ev_periodic *)
1697		2428
…		…
1700	a different time than the last time it was called (e.g. in a crond like	2431	a different time than the last time it was called (e.g. in a crond like
1701	program when the crontabs have changed).	2432	program when the crontabs have changed).
1702		2433
1703	=item ev_tstamp ev_periodic_at (ev_periodic *)	2434	=item ev_tstamp ev_periodic_at (ev_periodic *)
1704		2435
1705	When active, returns the absolute time that the watcher is supposed to	2436	When active, returns the absolute time that the watcher is supposed
1706	trigger next.	2437	to trigger next. This is not the same as the C<offset> argument to
		2438	C<ev_periodic_set>, but indeed works even in interval and manual
		2439	rescheduling modes.
1707		2440
1708	=item ev_tstamp offset [read-write]	2441	=item ev_tstamp offset [read-write]
1709		2442
1710	When repeating, this contains the offset value, otherwise this is the	2443	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>).	2444	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2445	although libev might modify this value for better numerical stability).
1712		2446
1713	Can be modified any time, but changes only take effect when the periodic	2447	Can be modified any time, but changes only take effect when the periodic
1714	timer fires or C<ev_periodic_again> is being called.	2448	timer fires or C<ev_periodic_again> is being called.
1715		2449
1716	=item ev_tstamp interval [read-write]	2450	=item ev_tstamp interval [read-write]
…		…
1732	Example: Call a callback every hour, or, more precisely, whenever the	2466	Example: Call a callback every hour, or, more precisely, whenever the
1733	system time is divisible by 3600. The callback invocation times have	2467	system time is divisible by 3600. The callback invocation times have
1734	potentially a lot of jitter, but good long-term stability.	2468	potentially a lot of jitter, but good long-term stability.
1735		2469
1736	static void	2470	static void
1737	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2471	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1738	{	2472	{
1739	... its now a full hour (UTC, or TAI or whatever your clock follows)	2473	... its now a full hour (UTC, or TAI or whatever your clock follows)
1740	}	2474	}
1741		2475
1742	ev_periodic hourly_tick;	2476	ev_periodic hourly_tick;
…		…
1759		2493
1760	ev_periodic hourly_tick;	2494	ev_periodic hourly_tick;
1761	ev_periodic_init (&hourly_tick, clock_cb,	2495	ev_periodic_init (&hourly_tick, clock_cb,
1762	fmod (ev_now (loop), 3600.), 3600., 0);	2496	fmod (ev_now (loop), 3600.), 3600., 0);
1763	ev_periodic_start (loop, &hourly_tick);	2497	ev_periodic_start (loop, &hourly_tick);
1764		2498
1765		2499
1766	=head2 C<ev_signal> - signal me when a signal gets signalled!	2500	=head2 C<ev_signal> - signal me when a signal gets signalled!
1767		2501
1768	Signal watchers will trigger an event when the process receives a specific	2502	Signal watchers will trigger an event when the process receives a specific
1769	signal one or more times. Even though signals are very asynchronous, libev	2503	signal one or more times. Even though signals are very asynchronous, libev
1770	will try it's best to deliver signals synchronously, i.e. as part of the	2504	will try its best to deliver signals synchronously, i.e. as part of the
1771	normal event processing, like any other event.	2505	normal event processing, like any other event.
1772		2506
1773	If you want signals asynchronously, just use C<sigaction> as you would	2507	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	2508	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.	2509	the signal. You can even use C<ev_async> from a signal handler to
		2510	synchronously wake up an event loop.
1776		2511
1777	You can configure as many watchers as you like per signal. Only when the	2512	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	2513	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	2514	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	2515	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	2516	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).	2517
		2518	Only after the first watcher for a signal is started will libev actually
		2519	register something with the kernel. It thus coexists with your own signal
		2520	handlers as long as you don't register any with libev for the same signal.
1783		2521
1784	If possible and supported, libev will install its handlers with	2522	If possible and supported, libev will install its handlers with
1785	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2523	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1786	interrupted. If you have a problem with system calls getting interrupted by	2524	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	2525	interrupted by signals you can block all signals in an C<ev_check> watcher
1788	them in an C<ev_prepare> watcher.	2526	and unblock them in an C<ev_prepare> watcher.
		2527
		2528	=head3 The special problem of inheritance over fork/execve/pthread_create
		2529
		2530	Both the signal mask (C<sigprocmask>) and the signal disposition
		2531	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2532	stopping it again), that is, libev might or might not block the signal,
		2533	and might or might not set or restore the installed signal handler (but
		2534	see C<EVFLAG_NOSIGMASK>).
		2535
		2536	While this does not matter for the signal disposition (libev never
		2537	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2538	C<execve>), this matters for the signal mask: many programs do not expect
		2539	certain signals to be blocked.
		2540
		2541	This means that before calling C<exec> (from the child) you should reset
		2542	the signal mask to whatever "default" you expect (all clear is a good
		2543	choice usually).
		2544
		2545	The simplest way to ensure that the signal mask is reset in the child is
		2546	to install a fork handler with C<pthread_atfork> that resets it. That will
		2547	catch fork calls done by libraries (such as the libc) as well.
		2548
		2549	In current versions of libev, the signal will not be blocked indefinitely
		2550	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2551	the window of opportunity for problems, it will not go away, as libev
		2552	I<has> to modify the signal mask, at least temporarily.
		2553
		2554	So I can't stress this enough: I<If you do not reset your signal mask when
		2555	you expect it to be empty, you have a race condition in your code>. This
		2556	is not a libev-specific thing, this is true for most event libraries.
		2557
		2558	=head3 The special problem of threads signal handling
		2559
		2560	POSIX threads has problematic signal handling semantics, specifically,
		2561	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2562	threads in a process block signals, which is hard to achieve.
		2563
		2564	When you want to use sigwait (or mix libev signal handling with your own
		2565	for the same signals), you can tackle this problem by globally blocking
		2566	all signals before creating any threads (or creating them with a fully set
		2567	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2568	loops. Then designate one thread as "signal receiver thread" which handles
		2569	these signals. You can pass on any signals that libev might be interested
		2570	in by calling C<ev_feed_signal>.
1789		2571
1790	=head3 Watcher-Specific Functions and Data Members	2572	=head3 Watcher-Specific Functions and Data Members
1791		2573
1792	=over 4	2574	=over 4
1793		2575
…		…
1809	Example: Try to exit cleanly on SIGINT.	2591	Example: Try to exit cleanly on SIGINT.
1810		2592
1811	static void	2593	static void
1812	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2594	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1813	{	2595	{
1814	ev_unloop (loop, EVUNLOOP_ALL);	2596	ev_break (loop, EVBREAK_ALL);
1815	}	2597	}
1816		2598
1817	ev_signal signal_watcher;	2599	ev_signal signal_watcher;
1818	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2600	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1819	ev_signal_start (loop, &signal_watcher);	2601	ev_signal_start (loop, &signal_watcher);
…		…
1825	some child status changes (most typically when a child of yours dies or	2607	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	2608	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	2609	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.,	2610	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,	2611	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	2612	but forking and registering a watcher a few event loop iterations later or
1831	not.	2613	in the next callback invocation is not.
1832		2614
1833	Only the default event loop is capable of handling signals, and therefore	2615	Only the default event loop is capable of handling signals, and therefore
1834	you can only register child watchers in the default event loop.	2616	you can only register child watchers in the default event loop.
1835		2617
		2618	Due to some design glitches inside libev, child watchers will always be
		2619	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2620	libev)
		2621
1836	=head3 Process Interaction	2622	=head3 Process Interaction
1837		2623
1838	Libev grabs C<SIGCHLD> as soon as the default event loop is	2624	Libev grabs C<SIGCHLD> as soon as the default event loop is
1839	initialised. This is necessary to guarantee proper behaviour even if	2625	initialised. This is necessary to guarantee proper behaviour even if the
1840	the first child watcher is started after the child exits. The occurrence	2626	first child watcher is started after the child exits. The occurrence
1841	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2627	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1842	synchronously as part of the event loop processing. Libev always reaps all	2628	synchronously as part of the event loop processing. Libev always reaps all
1843	children, even ones not watched.	2629	children, even ones not watched.
1844		2630
1845	=head3 Overriding the Built-In Processing	2631	=head3 Overriding the Built-In Processing
…		…
1855	=head3 Stopping the Child Watcher	2641	=head3 Stopping the Child Watcher
1856		2642
1857	Currently, the child watcher never gets stopped, even when the	2643	Currently, the child watcher never gets stopped, even when the
1858	child terminates, so normally one needs to stop the watcher in the	2644	child terminates, so normally one needs to stop the watcher in the
1859	callback. Future versions of libev might stop the watcher automatically	2645	callback. Future versions of libev might stop the watcher automatically
1860	when a child exit is detected.	2646	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2647	problem).
1861		2648
1862	=head3 Watcher-Specific Functions and Data Members	2649	=head3 Watcher-Specific Functions and Data Members
1863		2650
1864	=over 4	2651	=over 4
1865		2652
…		…
1923		2710
1924	=head2 C<ev_stat> - did the file attributes just change?	2711	=head2 C<ev_stat> - did the file attributes just change?
1925		2712
1926	This watches a file system path for attribute changes. That is, it calls	2713	This watches a file system path for attribute changes. That is, it calls
1927	C<stat> on that path in regular intervals (or when the OS says it changed)	2714	C<stat> on that path in regular intervals (or when the OS says it changed)
1928	and sees if it changed compared to the last time, invoking the callback if	2715	and sees if it changed compared to the last time, invoking the callback
1929	it did.	2716	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2717	happen after the watcher has been started will be reported.
1930		2718
1931	The path does not need to exist: changing from "path exists" to "path does	2719	The path does not need to exist: changing from "path exists" to "path does
1932	not exist" is a status change like any other. The condition "path does	2720	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	2721	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	2722	C<st_nlink> field being zero (which is otherwise always forced to be at
1935	the stat buffer having unspecified contents.	2723	least one) and all the other fields of the stat buffer having unspecified
		2724	contents.
1936		2725
1937	The path I<must not> end in a slash or contain special components such as	2726	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	2727	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1939	your working directory changes, then the behaviour is undefined.	2728	your working directory changes, then the behaviour is undefined.
1940		2729
…		…
1950	This watcher type is not meant for massive numbers of stat watchers,	2739	This watcher type is not meant for massive numbers of stat watchers,
1951	as even with OS-supported change notifications, this can be	2740	as even with OS-supported change notifications, this can be
1952	resource-intensive.	2741	resource-intensive.
1953		2742
1954	At the time of this writing, the only OS-specific interface implemented	2743	At the time of this writing, the only OS-specific interface implemented
1955	is the Linux inotify interface (implementing kqueue support is left as	2744	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	2745	exercise for the reader. Note, however, that the author sees no way of
1957	of implementing C<ev_stat> semantics with kqueue).	2746	implementing C<ev_stat> semantics with kqueue, except as a hint).
1958		2747
1959	=head3 ABI Issues (Largefile Support)	2748	=head3 ABI Issues (Largefile Support)
1960		2749
1961	Libev by default (unless the user overrides this) uses the default	2750	Libev by default (unless the user overrides this) uses the default
1962	compilation environment, which means that on systems with large file	2751	compilation environment, which means that on systems with large file
…		…
1973	to exchange stat structures with application programs compiled using the	2762	to exchange stat structures with application programs compiled using the
1974	default compilation environment.	2763	default compilation environment.
1975		2764
1976	=head3 Inotify and Kqueue	2765	=head3 Inotify and Kqueue
1977		2766
1978	When C<inotify (7)> support has been compiled into libev (generally	2767	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	2768	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	2769	inotify descriptor will be created lazily when the first C<ev_stat>
1981	change detection where possible. The inotify descriptor will be created	2770	watcher is being started.
1982	lazily when the first C<ev_stat> watcher is being started.
1983		2771
1984	Inotify presence does not change the semantics of C<ev_stat> watchers	2772	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	2773	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	2774	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,	2775	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.	2776	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2777	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2778	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2779	xfs are fully working) libev usually gets away without polling.
1989		2780
1990	There is no support for kqueue, as apparently it cannot be used to	2781	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	2782	implement this functionality, due to the requirement of having a file
1992	descriptor open on the object at all times, and detecting renames, unlinks	2783	descriptor open on the object at all times, and detecting renames, unlinks
1993	etc. is difficult.	2784	etc. is difficult.
		2785
		2786	=head3 C<stat ()> is a synchronous operation
		2787
		2788	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2789	the process. The exception are C<ev_stat> watchers - those call C<stat
		2790	()>, which is a synchronous operation.
		2791
		2792	For local paths, this usually doesn't matter: unless the system is very
		2793	busy or the intervals between stat's are large, a stat call will be fast,
		2794	as the path data is usually in memory already (except when starting the
		2795	watcher).
		2796
		2797	For networked file systems, calling C<stat ()> can block an indefinite
		2798	time due to network issues, and even under good conditions, a stat call
		2799	often takes multiple milliseconds.
		2800
		2801	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2802	paths, although this is fully supported by libev.
1994		2803
1995	=head3 The special problem of stat time resolution	2804	=head3 The special problem of stat time resolution
1996		2805
1997	The C<stat ()> system call only supports full-second resolution portably,	2806	The C<stat ()> system call only supports full-second resolution portably,
1998	and even on systems where the resolution is higher, most file systems	2807	and even on systems where the resolution is higher, most file systems
…		…
2143	Apart from keeping your process non-blocking (which is a useful	2952	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	2953	effect on its own sometimes), idle watchers are a good place to do
2145	"pseudo-background processing", or delay processing stuff to after the	2954	"pseudo-background processing", or delay processing stuff to after the
2146	event loop has handled all outstanding events.	2955	event loop has handled all outstanding events.
2147		2956
		2957	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2958
		2959	As long as there is at least one active idle watcher, libev will never
		2960	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2961	For this to work, the idle watcher doesn't need to be invoked at all - the
		2962	lowest priority will do.
		2963
		2964	This mode of operation can be useful together with an C<ev_check> watcher,
		2965	to do something on each event loop iteration - for example to balance load
		2966	between different connections.
		2967
		2968	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2969	example.
		2970
2148	=head3 Watcher-Specific Functions and Data Members	2971	=head3 Watcher-Specific Functions and Data Members
2149		2972
2150	=over 4	2973	=over 4
2151		2974
2152	=item ev_idle_init (ev_signal *, callback)	2975	=item ev_idle_init (ev_idle *, callback)
2153		2976
2154	Initialises and configures the idle watcher - it has no parameters of any	2977	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,	2978	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
2156	believe me.	2979	believe me.
2157		2980
…		…
2163	callback, free it. Also, use no error checking, as usual.	2986	callback, free it. Also, use no error checking, as usual.
2164		2987
2165	static void	2988	static void
2166	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2989	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2167	{	2990	{
		2991	// stop the watcher
		2992	ev_idle_stop (loop, w);
		2993
		2994	// now we can free it
2168	free (w);	2995	free (w);
		2996
2169	// now do something you wanted to do when the program has	2997	// now do something you wanted to do when the program has
2170	// no longer anything immediate to do.	2998	// no longer anything immediate to do.
2171	}	2999	}
2172		3000
2173	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3001	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2174	ev_idle_init (idle_watcher, idle_cb);	3002	ev_idle_init (idle_watcher, idle_cb);
2175	ev_idle_start (loop, idle_cb);	3003	ev_idle_start (loop, idle_watcher);
2176		3004
2177		3005
2178	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3006	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2179		3007
2180	Prepare and check watchers are usually (but not always) used in pairs:	3008	Prepare and check watchers are often (but not always) used in pairs:
2181	prepare watchers get invoked before the process blocks and check watchers	3009	prepare watchers get invoked before the process blocks and check watchers
2182	afterwards.	3010	afterwards.
2183		3011
2184	You I<must not> call C<ev_loop> or similar functions that enter	3012	You I<must not> call C<ev_run> (or similar functions that enter the
2185	the current event loop from either C<ev_prepare> or C<ev_check>	3013	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2186	watchers. Other loops than the current one are fine, however. The	3014	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	3015	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,	3016	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	3017	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2190	called in pairs bracketing the blocking call.	3018	kind they will always be called in pairs bracketing the blocking call.
2191		3019
2192	Their main purpose is to integrate other event mechanisms into libev and	3020	Their main purpose is to integrate other event mechanisms into libev and
2193	their use is somewhat advanced. They could be used, for example, to track	3021	their use is somewhat advanced. They could be used, for example, to track
2194	variable changes, implement your own watchers, integrate net-snmp or a	3022	variable changes, implement your own watchers, integrate net-snmp or a
2195	coroutine library and lots more. They are also occasionally useful if	3023	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	3041	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	3042	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	3043	loop from blocking if lower-priority coroutines are active, thus mapping
2216	low-priority coroutines to idle/background tasks).	3044	low-priority coroutines to idle/background tasks).
2217		3045
2218	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3046	When used for this purpose, it is recommended to give C<ev_check> watchers
2219	priority, to ensure that they are being run before any other watchers	3047	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2220	after the poll (this doesn't matter for C<ev_prepare> watchers).	3048	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3049	watchers).
2221		3050
2222	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3051	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2223	activate ("feed") events into libev. While libev fully supports this, they	3052	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	3053	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	3054	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	3055	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	3056	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2228	others).	3057	others).
		3058
		3059	=head3 Abusing an C<ev_check> watcher for its side-effect
		3060
		3061	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3062	useful because they are called once per event loop iteration. For
		3063	example, if you want to handle a large number of connections fairly, you
		3064	normally only do a bit of work for each active connection, and if there
		3065	is more work to do, you wait for the next event loop iteration, so other
		3066	connections have a chance of making progress.
		3067
		3068	Using an C<ev_check> watcher is almost enough: it will be called on the
		3069	next event loop iteration. However, that isn't as soon as possible -
		3070	without external events, your C<ev_check> watcher will not be invoked.
		3071
		3072	This is where C<ev_idle> watchers come in handy - all you need is a
		3073	single global idle watcher that is active as long as you have one active
		3074	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3075	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3076	invoked. Neither watcher alone can do that.
2229		3077
2230	=head3 Watcher-Specific Functions and Data Members	3078	=head3 Watcher-Specific Functions and Data Members
2231		3079
2232	=over 4	3080	=over 4
2233		3081
…		…
2273	struct pollfd fds [nfd];	3121	struct pollfd fds [nfd];
2274	// actual code will need to loop here and realloc etc.	3122	// actual code will need to loop here and realloc etc.
2275	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3123	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2276		3124
2277	/* the callback is illegal, but won't be called as we stop during check */	3125	/* the callback is illegal, but won't be called as we stop during check */
2278	ev_timer_init (&tw, 0, timeout * 1e-3);	3126	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2279	ev_timer_start (loop, &tw);	3127	ev_timer_start (loop, &tw);
2280		3128
2281	// create one ev_io per pollfd	3129	// create one ev_io per pollfd
2282	for (int i = 0; i < nfd; ++i)	3130	for (int i = 0; i < nfd; ++i)
2283	{	3131	{
…		…
2357		3205
2358	if (timeout >= 0)	3206	if (timeout >= 0)
2359	// create/start timer	3207	// create/start timer
2360		3208
2361	// poll	3209	// poll
2362	ev_loop (EV_A_ 0);	3210	ev_run (EV_A_ 0);
2363		3211
2364	// stop timer again	3212	// stop timer again
2365	if (timeout >= 0)	3213	if (timeout >= 0)
2366	ev_timer_stop (EV_A_ &to);	3214	ev_timer_stop (EV_A_ &to);
2367		3215
…		…
2396	some fds have to be watched and handled very quickly (with low latency),	3244	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	3245	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	3246	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.	3247	the rest in a second one, and embed the second one in the first.
2400		3248
2401	As long as the watcher is active, the callback will be invoked every time	3249	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	3250	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	3251	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	3252	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	3253	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	3254	to give the embedded loop strictly lower priority for example).
2407	embedded loop sweep.
2408		3255
2409	As long as the watcher is started it will automatically handle events. The	3256	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	3257	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		3258
2414	Also, there have not currently been made special provisions for forking:	3259	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,	3260	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	3261	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,	3262	C<ev_loop_fork> on the embedded loop.
2418	and future versions of libev might do just that.
2419		3263
2420	Unfortunately, not all backends are embeddable: only the ones returned by	3264	Unfortunately, not all backends are embeddable: only the ones returned by
2421	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3265	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2422	portable one.	3266	portable one.
2423		3267
…		…
2438		3282
2439	=over 4	3283	=over 4
2440		3284
2441	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3285	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2442		3286
2443	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3287	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2444		3288
2445	Configures the watcher to embed the given loop, which must be	3289	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	3290	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	3291	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,	3292	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).	3293	if you do not want that, you need to temporarily stop the embed watcher).
2450		3294
2451	=item ev_embed_sweep (loop, ev_embed *)	3295	=item ev_embed_sweep (loop, ev_embed *)
2452		3296
2453	Make a single, non-blocking sweep over the embedded loop. This works	3297	Make a single, non-blocking sweep over the embedded loop. This works
2454	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3298	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2455	appropriate way for embedded loops.	3299	appropriate way for embedded loops.
2456		3300
2457	=item struct ev_loop *other [read-only]	3301	=item struct ev_loop *other [read-only]
2458		3302
2459	The embedded event loop.	3303	The embedded event loop.
…		…
2469	used).	3313	used).
2470		3314
2471	struct ev_loop *loop_hi = ev_default_init (0);	3315	struct ev_loop *loop_hi = ev_default_init (0);
2472	struct ev_loop *loop_lo = 0;	3316	struct ev_loop *loop_lo = 0;
2473	ev_embed embed;	3317	ev_embed embed;
2474		3318
2475	// see if there is a chance of getting one that works	3319	// see if there is a chance of getting one that works
2476	// (remember that a flags value of 0 means autodetection)	3320	// (remember that a flags value of 0 means autodetection)
2477	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3321	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2478	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3322	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2479	: 0;	3323	: 0;
…		…
2493	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3337	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2494		3338
2495	struct ev_loop *loop = ev_default_init (0);	3339	struct ev_loop *loop = ev_default_init (0);
2496	struct ev_loop *loop_socket = 0;	3340	struct ev_loop *loop_socket = 0;
2497	ev_embed embed;	3341	ev_embed embed;
2498		3342
2499	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3343	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2500	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3344	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2501	{	3345	{
2502	ev_embed_init (&embed, 0, loop_socket);	3346	ev_embed_init (&embed, 0, loop_socket);
2503	ev_embed_start (loop, &embed);	3347	ev_embed_start (loop, &embed);
…		…
2511		3355
2512	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3356	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2513		3357
2514	Fork watchers are called when a C<fork ()> was detected (usually because	3358	Fork watchers are called when a C<fork ()> was detected (usually because
2515	whoever is a good citizen cared to tell libev about it by calling	3359	whoever is a good citizen cared to tell libev about it by calling
2516	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3360	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2517	event loop blocks next and before C<ev_check> watchers are being called,	3361	and before C<ev_check> watchers are being called, and only in the child
2518	and only in the child after the fork. If whoever good citizen calling	3362	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2519	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3363	and calls it in the wrong process, the fork handlers will be invoked, too,
2520	handlers will be invoked, too, of course.	3364	of course.
		3365
		3366	=head3 The special problem of life after fork - how is it possible?
		3367
		3368	Most uses of C<fork ()> consist of forking, then some simple calls to set
		3369	up/change the process environment, followed by a call to C<exec()>. This
		3370	sequence should be handled by libev without any problems.
		3371
		3372	This changes when the application actually wants to do event handling
		3373	in the child, or both parent in child, in effect "continuing" after the
		3374	fork.
		3375
		3376	The default mode of operation (for libev, with application help to detect
		3377	forks) is to duplicate all the state in the child, as would be expected
		3378	when I<either> the parent I<or> the child process continues.
		3379
		3380	When both processes want to continue using libev, then this is usually the
		3381	wrong result. In that case, usually one process (typically the parent) is
		3382	supposed to continue with all watchers in place as before, while the other
		3383	process typically wants to start fresh, i.e. without any active watchers.
		3384
		3385	The cleanest and most efficient way to achieve that with libev is to
		3386	simply create a new event loop, which of course will be "empty", and
		3387	use that for new watchers. This has the advantage of not touching more
		3388	memory than necessary, and thus avoiding the copy-on-write, and the
		3389	disadvantage of having to use multiple event loops (which do not support
		3390	signal watchers).
		3391
		3392	When this is not possible, or you want to use the default loop for
		3393	other reasons, then in the process that wants to start "fresh", call
		3394	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
		3395	Destroying the default loop will "orphan" (not stop) all registered
		3396	watchers, so you have to be careful not to execute code that modifies
		3397	those watchers. Note also that in that case, you have to re-register any
		3398	signal watchers.
2521		3399
2522	=head3 Watcher-Specific Functions and Data Members	3400	=head3 Watcher-Specific Functions and Data Members
2523		3401
2524	=over 4	3402	=over 4
2525		3403
2526	=item ev_fork_init (ev_signal *, callback)	3404	=item ev_fork_init (ev_fork *, callback)
2527		3405
2528	Initialises and configures the fork watcher - it has no parameters of any	3406	Initialises and configures the fork watcher - it has no parameters of any
2529	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3407	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2530	believe me.	3408	really.
2531		3409
2532	=back	3410	=back
2533		3411
2534		3412
		3413	=head2 C<ev_cleanup> - even the best things end
		3414
		3415	Cleanup watchers are called just before the event loop is being destroyed
		3416	by a call to C<ev_loop_destroy>.
		3417
		3418	While there is no guarantee that the event loop gets destroyed, cleanup
		3419	watchers provide a convenient method to install cleanup hooks for your
		3420	program, worker threads and so on - you just to make sure to destroy the
		3421	loop when you want them to be invoked.
		3422
		3423	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3424	all other watchers, they do not keep a reference to the event loop (which
		3425	makes a lot of sense if you think about it). Like all other watchers, you
		3426	can call libev functions in the callback, except C<ev_cleanup_start>.
		3427
		3428	=head3 Watcher-Specific Functions and Data Members
		3429
		3430	=over 4
		3431
		3432	=item ev_cleanup_init (ev_cleanup *, callback)
		3433
		3434	Initialises and configures the cleanup watcher - it has no parameters of
		3435	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3436	pointless, I assure you.
		3437
		3438	=back
		3439
		3440	Example: Register an atexit handler to destroy the default loop, so any
		3441	cleanup functions are called.
		3442
		3443	static void
		3444	program_exits (void)
		3445	{
		3446	ev_loop_destroy (EV_DEFAULT_UC);
		3447	}
		3448
		3449	...
		3450	atexit (program_exits);
		3451
		3452
2535	=head2 C<ev_async> - how to wake up another event loop	3453	=head2 C<ev_async> - how to wake up an event loop
2536		3454
2537	In general, you cannot use an C<ev_loop> from multiple threads or other	3455	In general, you cannot use an C<ev_loop> from multiple threads or other
2538	asynchronous sources such as signal handlers (as opposed to multiple event	3456	asynchronous sources such as signal handlers (as opposed to multiple event
2539	loops - those are of course safe to use in different threads).	3457	loops - those are of course safe to use in different threads).
2540		3458
2541	Sometimes, however, you need to wake up another event loop you do not	3459	Sometimes, however, you need to wake up an event loop you do not control,
2542	control, for example because it belongs to another thread. This is what	3460	for example because it belongs to another thread. This is what C<ev_async>
2543	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3461	watchers do: as long as the C<ev_async> watcher is active, you can signal
2544	can signal it by calling C<ev_async_send>, which is thread- and signal	3462	it by calling C<ev_async_send>, which is thread- and signal safe.
2545	safe.
2546		3463
2547	This functionality is very similar to C<ev_signal> watchers, as signals,	3464	This functionality is very similar to C<ev_signal> watchers, as signals,
2548	too, are asynchronous in nature, and signals, too, will be compressed	3465	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	3466	(i.e. the number of callback invocations may be less than the number of
2550	C<ev_async_sent> calls).	3467	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2551		3468	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	3469	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2553	just the default loop.	3470	even without knowing which loop owns the signal.
2554		3471
2555	=head3 Queueing	3472	=head3 Queueing
2556		3473
2557	C<ev_async> does not support queueing of data in any way. The reason	3474	C<ev_async> does not support queueing of data in any way. The reason
2558	is that the author does not know of a simple (or any) algorithm for a	3475	is that the author does not know of a simple (or any) algorithm for a
2559	multiple-writer-single-reader queue that works in all cases and doesn't	3476	multiple-writer-single-reader queue that works in all cases and doesn't
2560	need elaborate support such as pthreads.	3477	need elaborate support such as pthreads or unportable memory access
		3478	semantics.
2561		3479
2562	That means that if you want to queue data, you have to provide your own	3480	That means that if you want to queue data, you have to provide your own
2563	queue. But at least I can tell you how to implement locking around your	3481	queue. But at least I can tell you how to implement locking around your
2564	queue:	3482	queue:
2565		3483
…		…
2649	trust me.	3567	trust me.
2650		3568
2651	=item ev_async_send (loop, ev_async *)	3569	=item ev_async_send (loop, ev_async *)
2652		3570
2653	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3571	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2654	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3572	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3573	returns.
		3574
2655	C<ev_feed_event>, this call is safe to do from other threads, signal or	3575	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2656	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3576	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2657	section below on what exactly this means).	3577	embedding section below on what exactly this means).
2658		3578
2659	This call incurs the overhead of a system call only once per loop iteration,	3579	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	3580	compressed into a single callback invocation (another way to look at
2661	calls to C<ev_async_send>.	3581	this is that C<ev_async> watchers are level-triggered: they are set on
		3582	C<ev_async_send>, reset when the event loop detects that).
		3583
		3584	This call incurs the overhead of at most one extra system call per event
		3585	loop iteration, if the event loop is blocked, and no syscall at all if
		3586	the event loop (or your program) is processing events. That means that
		3587	repeated calls are basically free (there is no need to avoid calls for
		3588	performance reasons) and that the overhead becomes smaller (typically
		3589	zero) under load.
2662		3590
2663	=item bool = ev_async_pending (ev_async *)	3591	=item bool = ev_async_pending (ev_async *)
2664		3592
2665	Returns a non-zero value when C<ev_async_send> has been called on the	3593	Returns a non-zero value when C<ev_async_send> has been called on the
2666	watcher but the event has not yet been processed (or even noted) by the	3594	watcher but the event has not yet been processed (or even noted) by the
…		…
2669	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3597	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,	3598	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	3599	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.	3600	quickly check whether invoking the loop might be a good idea.
2673		3601
2674	Not that this does I<not> check whether the watcher itself is pending, only	3602	Not that this does I<not> check whether the watcher itself is pending,
2675	whether it has been requested to make this watcher pending.	3603	only whether it has been requested to make this watcher pending: there
		3604	is a time window between the event loop checking and resetting the async
		3605	notification, and the callback being invoked.
2676		3606
2677	=back	3607	=back
2678		3608
2679		3609
2680	=head1 OTHER FUNCTIONS	3610	=head1 OTHER FUNCTIONS
2681		3611
2682	There are some other functions of possible interest. Described. Here. Now.	3612	There are some other functions of possible interest. Described. Here. Now.
2683		3613
2684	=over 4	3614	=over 4
2685		3615
2686	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3616	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
2687		3617
2688	This function combines a simple timer and an I/O watcher, calls your	3618	This function combines a simple timer and an I/O watcher, calls your
2689	callback on whichever event happens first and automatically stops both	3619	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	3620	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	3621	or timeout without having to allocate/configure/start/stop/free one or
…		…
2697		3627
2698	If C<timeout> is less than 0, then no timeout watcher will be	3628	If C<timeout> is less than 0, then no timeout watcher will be
2699	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3629	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2700	repeat = 0) will be started. C<0> is a valid timeout.	3630	repeat = 0) will be started. C<0> is a valid timeout.
2701		3631
2702	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3632	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2703	passed an C<revents> set like normal event callbacks (a combination of	3633	passed an C<revents> set like normal event callbacks (a combination of
2704	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3634	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2705	value passed to C<ev_once>. Note that it is possible to receive I<both>	3635	value passed to C<ev_once>. Note that it is possible to receive I<both>
2706	a timeout and an io event at the same time - you probably should give io	3636	a timeout and an io event at the same time - you probably should give io
2707	events precedence.	3637	events precedence.
2708		3638
2709	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3639	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2710		3640
2711	static void stdin_ready (int revents, void *arg)	3641	static void stdin_ready (int revents, void *arg)
2712	{	3642	{
2713	if (revents & EV_READ)	3643	if (revents & EV_READ)
2714	/* stdin might have data for us, joy! */;	3644	/* stdin might have data for us, joy! */;
2715	else if (revents & EV_TIMEOUT)	3645	else if (revents & EV_TIMER)
2716	/* doh, nothing entered */;	3646	/* doh, nothing entered */;
2717	}	3647	}
2718		3648
2719	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3649	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2720		3650
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)	3651	=item ev_feed_fd_event (loop, int fd, int revents)
2728		3652
2729	Feed an event on the given fd, as if a file descriptor backend detected	3653	Feed an event on the given fd, as if a file descriptor backend detected
2730	the given events it.	3654	the given events.
2731		3655
2732	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3656	=item ev_feed_signal_event (loop, int signum)
2733		3657
2734	Feed an event as if the given signal occurred (C<loop> must be the default	3658	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2735	loop!).	3659	which is async-safe.
2736		3660
2737	=back	3661	=back
		3662
		3663
		3664	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3665
		3666	This section explains some common idioms that are not immediately
		3667	obvious. Note that examples are sprinkled over the whole manual, and this
		3668	section only contains stuff that wouldn't fit anywhere else.
		3669
		3670	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3671
		3672	Each watcher has, by default, a C<void *data> member that you can read
		3673	or modify at any time: libev will completely ignore it. This can be used
		3674	to associate arbitrary data with your watcher. If you need more data and
		3675	don't want to allocate memory separately and store a pointer to it in that
		3676	data member, you can also "subclass" the watcher type and provide your own
		3677	data:
		3678
		3679	struct my_io
		3680	{
		3681	ev_io io;
		3682	int otherfd;
		3683	void *somedata;
		3684	struct whatever *mostinteresting;
		3685	};
		3686
		3687	...
		3688	struct my_io w;
		3689	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3690
		3691	And since your callback will be called with a pointer to the watcher, you
		3692	can cast it back to your own type:
		3693
		3694	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3695	{
		3696	struct my_io *w = (struct my_io *)w_;
		3697	...
		3698	}
		3699
		3700	More interesting and less C-conformant ways of casting your callback
		3701	function type instead have been omitted.
		3702
		3703	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3704
		3705	Another common scenario is to use some data structure with multiple
		3706	embedded watchers, in effect creating your own watcher that combines
		3707	multiple libev event sources into one "super-watcher":
		3708
		3709	struct my_biggy
		3710	{
		3711	int some_data;
		3712	ev_timer t1;
		3713	ev_timer t2;
		3714	}
		3715
		3716	In this case getting the pointer to C<my_biggy> is a bit more
		3717	complicated: Either you store the address of your C<my_biggy> struct in
		3718	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3719	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3720	real programmers):
		3721
		3722	#include <stddef.h>
		3723
		3724	static void
		3725	t1_cb (EV_P_ ev_timer *w, int revents)
		3726	{
		3727	struct my_biggy big = (struct my_biggy *)
		3728	(((char *)w) - offsetof (struct my_biggy, t1));
		3729	}
		3730
		3731	static void
		3732	t2_cb (EV_P_ ev_timer *w, int revents)
		3733	{
		3734	struct my_biggy big = (struct my_biggy *)
		3735	(((char *)w) - offsetof (struct my_biggy, t2));
		3736	}
		3737
		3738	=head2 AVOIDING FINISHING BEFORE RETURNING
		3739
		3740	Often you have structures like this in event-based programs:
		3741
		3742	callback ()
		3743	{
		3744	free (request);
		3745	}
		3746
		3747	request = start_new_request (..., callback);
		3748
		3749	The intent is to start some "lengthy" operation. The C<request> could be
		3750	used to cancel the operation, or do other things with it.
		3751
		3752	It's not uncommon to have code paths in C<start_new_request> that
		3753	immediately invoke the callback, for example, to report errors. Or you add
		3754	some caching layer that finds that it can skip the lengthy aspects of the
		3755	operation and simply invoke the callback with the result.
		3756
		3757	The problem here is that this will happen I<before> C<start_new_request>
		3758	has returned, so C<request> is not set.
		3759
		3760	Even if you pass the request by some safer means to the callback, you
		3761	might want to do something to the request after starting it, such as
		3762	canceling it, which probably isn't working so well when the callback has
		3763	already been invoked.
		3764
		3765	A common way around all these issues is to make sure that
		3766	C<start_new_request> I<always> returns before the callback is invoked. If
		3767	C<start_new_request> immediately knows the result, it can artificially
		3768	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3769	example, or more sneakily, by reusing an existing (stopped) watcher and
		3770	pushing it into the pending queue:
		3771
		3772	ev_set_cb (watcher, callback);
		3773	ev_feed_event (EV_A_ watcher, 0);
		3774
		3775	This way, C<start_new_request> can safely return before the callback is
		3776	invoked, while not delaying callback invocation too much.
		3777
		3778	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3779
		3780	Often (especially in GUI toolkits) there are places where you have
		3781	I<modal> interaction, which is most easily implemented by recursively
		3782	invoking C<ev_run>.
		3783
		3784	This brings the problem of exiting - a callback might want to finish the
		3785	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3786	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3787	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3788	other combination: In these cases, a simple C<ev_break> will not work.
		3789
		3790	The solution is to maintain "break this loop" variable for each C<ev_run>
		3791	invocation, and use a loop around C<ev_run> until the condition is
		3792	triggered, using C<EVRUN_ONCE>:
		3793
		3794	// main loop
		3795	int exit_main_loop = 0;
		3796
		3797	while (!exit_main_loop)
		3798	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3799
		3800	// in a modal watcher
		3801	int exit_nested_loop = 0;
		3802
		3803	while (!exit_nested_loop)
		3804	ev_run (EV_A_ EVRUN_ONCE);
		3805
		3806	To exit from any of these loops, just set the corresponding exit variable:
		3807
		3808	// exit modal loop
		3809	exit_nested_loop = 1;
		3810
		3811	// exit main program, after modal loop is finished
		3812	exit_main_loop = 1;
		3813
		3814	// exit both
		3815	exit_main_loop = exit_nested_loop = 1;
		3816
		3817	=head2 THREAD LOCKING EXAMPLE
		3818
		3819	Here is a fictitious example of how to run an event loop in a different
		3820	thread from where callbacks are being invoked and watchers are
		3821	created/added/removed.
		3822
		3823	For a real-world example, see the C<EV::Loop::Async> perl module,
		3824	which uses exactly this technique (which is suited for many high-level
		3825	languages).
		3826
		3827	The example uses a pthread mutex to protect the loop data, a condition
		3828	variable to wait for callback invocations, an async watcher to notify the
		3829	event loop thread and an unspecified mechanism to wake up the main thread.
		3830
		3831	First, you need to associate some data with the event loop:
		3832
		3833	typedef struct {
		3834	mutex_t lock; /* global loop lock */
		3835	ev_async async_w;
		3836	thread_t tid;
		3837	cond_t invoke_cv;
		3838	} userdata;
		3839
		3840	void prepare_loop (EV_P)
		3841	{
		3842	// for simplicity, we use a static userdata struct.
		3843	static userdata u;
		3844
		3845	ev_async_init (&u->async_w, async_cb);
		3846	ev_async_start (EV_A_ &u->async_w);
		3847
		3848	pthread_mutex_init (&u->lock, 0);
		3849	pthread_cond_init (&u->invoke_cv, 0);
		3850
		3851	// now associate this with the loop
		3852	ev_set_userdata (EV_A_ u);
		3853	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3854	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3855
		3856	// then create the thread running ev_run
		3857	pthread_create (&u->tid, 0, l_run, EV_A);
		3858	}
		3859
		3860	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3861	solely to wake up the event loop so it takes notice of any new watchers
		3862	that might have been added:
		3863
		3864	static void
		3865	async_cb (EV_P_ ev_async *w, int revents)
		3866	{
		3867	// just used for the side effects
		3868	}
		3869
		3870	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3871	protecting the loop data, respectively.
		3872
		3873	static void
		3874	l_release (EV_P)
		3875	{
		3876	userdata *u = ev_userdata (EV_A);
		3877	pthread_mutex_unlock (&u->lock);
		3878	}
		3879
		3880	static void
		3881	l_acquire (EV_P)
		3882	{
		3883	userdata *u = ev_userdata (EV_A);
		3884	pthread_mutex_lock (&u->lock);
		3885	}
		3886
		3887	The event loop thread first acquires the mutex, and then jumps straight
		3888	into C<ev_run>:
		3889
		3890	void *
		3891	l_run (void *thr_arg)
		3892	{
		3893	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3894
		3895	l_acquire (EV_A);
		3896	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3897	ev_run (EV_A_ 0);
		3898	l_release (EV_A);
		3899
		3900	return 0;
		3901	}
		3902
		3903	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3904	signal the main thread via some unspecified mechanism (signals? pipe
		3905	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3906	have been called (in a while loop because a) spurious wakeups are possible
		3907	and b) skipping inter-thread-communication when there are no pending
		3908	watchers is very beneficial):
		3909
		3910	static void
		3911	l_invoke (EV_P)
		3912	{
		3913	userdata *u = ev_userdata (EV_A);
		3914
		3915	while (ev_pending_count (EV_A))
		3916	{
		3917	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3918	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3919	}
		3920	}
		3921
		3922	Now, whenever the main thread gets told to invoke pending watchers, it
		3923	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3924	thread to continue:
		3925
		3926	static void
		3927	real_invoke_pending (EV_P)
		3928	{
		3929	userdata *u = ev_userdata (EV_A);
		3930
		3931	pthread_mutex_lock (&u->lock);
		3932	ev_invoke_pending (EV_A);
		3933	pthread_cond_signal (&u->invoke_cv);
		3934	pthread_mutex_unlock (&u->lock);
		3935	}
		3936
		3937	Whenever you want to start/stop a watcher or do other modifications to an
		3938	event loop, you will now have to lock:
		3939
		3940	ev_timer timeout_watcher;
		3941	userdata *u = ev_userdata (EV_A);
		3942
		3943	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3944
		3945	pthread_mutex_lock (&u->lock);
		3946	ev_timer_start (EV_A_ &timeout_watcher);
		3947	ev_async_send (EV_A_ &u->async_w);
		3948	pthread_mutex_unlock (&u->lock);
		3949
		3950	Note that sending the C<ev_async> watcher is required because otherwise
		3951	an event loop currently blocking in the kernel will have no knowledge
		3952	about the newly added timer. By waking up the loop it will pick up any new
		3953	watchers in the next event loop iteration.
		3954
		3955	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3956
		3957	While the overhead of a callback that e.g. schedules a thread is small, it
		3958	is still an overhead. If you embed libev, and your main usage is with some
		3959	kind of threads or coroutines, you might want to customise libev so that
		3960	doesn't need callbacks anymore.
		3961
		3962	Imagine you have coroutines that you can switch to using a function
		3963	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3964	and that due to some magic, the currently active coroutine is stored in a
		3965	global called C<current_coro>. Then you can build your own "wait for libev
		3966	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3967	the differing C<;> conventions):
		3968
		3969	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3970	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3971
		3972	That means instead of having a C callback function, you store the
		3973	coroutine to switch to in each watcher, and instead of having libev call
		3974	your callback, you instead have it switch to that coroutine.
		3975
		3976	A coroutine might now wait for an event with a function called
		3977	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3978	matter when, or whether the watcher is active or not when this function is
		3979	called):
		3980
		3981	void
		3982	wait_for_event (ev_watcher *w)
		3983	{
		3984	ev_set_cb (w, current_coro);
		3985	switch_to (libev_coro);
		3986	}
		3987
		3988	That basically suspends the coroutine inside C<wait_for_event> and
		3989	continues the libev coroutine, which, when appropriate, switches back to
		3990	this or any other coroutine.
		3991
		3992	You can do similar tricks if you have, say, threads with an event queue -
		3993	instead of storing a coroutine, you store the queue object and instead of
		3994	switching to a coroutine, you push the watcher onto the queue and notify
		3995	any waiters.
		3996
		3997	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3998	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3999
		4000	// my_ev.h
		4001	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4002	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4003	#include "../libev/ev.h"
		4004
		4005	// my_ev.c
		4006	#define EV_H "my_ev.h"
		4007	#include "../libev/ev.c"
		4008
		4009	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4010	F<my_ev.c> into your project. When properly specifying include paths, you
		4011	can even use F<ev.h> as header file name directly.
2738		4012
2739		4013
2740	=head1 LIBEVENT EMULATION	4014	=head1 LIBEVENT EMULATION
2741		4015
2742	Libev offers a compatibility emulation layer for libevent. It cannot	4016	Libev offers a compatibility emulation layer for libevent. It cannot
2743	emulate the internals of libevent, so here are some usage hints:	4017	emulate the internals of libevent, so here are some usage hints:
2744		4018
2745	=over 4	4019	=over 4
		4020
		4021	=item * Only the libevent-1.4.1-beta API is being emulated.
		4022
		4023	This was the newest libevent version available when libev was implemented,
		4024	and is still mostly unchanged in 2010.
2746		4025
2747	=item * Use it by including <event.h>, as usual.	4026	=item * Use it by including <event.h>, as usual.
2748		4027
2749	=item * The following members are fully supported: ev_base, ev_callback,	4028	=item * The following members are fully supported: ev_base, ev_callback,
2750	ev_arg, ev_fd, ev_res, ev_events.	4029	ev_arg, ev_fd, ev_res, ev_events.
…		…
2756	=item * Priorities are not currently supported. Initialising priorities	4035	=item * Priorities are not currently supported. Initialising priorities
2757	will fail and all watchers will have the same priority, even though there	4036	will fail and all watchers will have the same priority, even though there
2758	is an ev_pri field.	4037	is an ev_pri field.
2759		4038
2760	=item * In libevent, the last base created gets the signals, in libev, the	4039	=item * In libevent, the last base created gets the signals, in libev, the
2761	first base created (== the default loop) gets the signals.	4040	base that registered the signal gets the signals.
2762		4041
2763	=item * Other members are not supported.	4042	=item * Other members are not supported.
2764		4043
2765	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4044	=item * The libev emulation is I<not> ABI compatible to libevent, you need
2766	to use the libev header file and library.	4045	to use the libev header file and library.
2767		4046
2768	=back	4047	=back
2769		4048
2770	=head1 C++ SUPPORT	4049	=head1 C++ SUPPORT
		4050
		4051	=head2 C API
		4052
		4053	The normal C API should work fine when used from C++: both ev.h and the
		4054	libev sources can be compiled as C++. Therefore, code that uses the C API
		4055	will work fine.
		4056
		4057	Proper exception specifications might have to be added to callbacks passed
		4058	to libev: exceptions may be thrown only from watcher callbacks, all other
		4059	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4060	callbacks) must not throw exceptions, and might need a C<noexcept>
		4061	specification. If you have code that needs to be compiled as both C and
		4062	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4063
		4064	static void
		4065	fatal_error (const char *msg) EV_NOEXCEPT
		4066	{
		4067	perror (msg);
		4068	abort ();
		4069	}
		4070
		4071	...
		4072	ev_set_syserr_cb (fatal_error);
		4073
		4074	The only API functions that can currently throw exceptions are C<ev_run>,
		4075	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4076	because it runs cleanup watchers).
		4077
		4078	Throwing exceptions in watcher callbacks is only supported if libev itself
		4079	is compiled with a C++ compiler or your C and C++ environments allow
		4080	throwing exceptions through C libraries (most do).
		4081
		4082	=head2 C++ API
2771		4083
2772	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4084	Libev comes with some simplistic wrapper classes for C++ that mainly allow
2773	you to use some convenience methods to start/stop watchers and also change	4085	you to use some convenience methods to start/stop watchers and also change
2774	the callback model to a model using method callbacks on objects.	4086	the callback model to a model using method callbacks on objects.
2775		4087
2776	To use it,	4088	To use it,
2777		4089
2778	#include <ev++.h>	4090	#include <ev++.h>
2779		4091
2780	This automatically includes F<ev.h> and puts all of its definitions (many	4092	This automatically includes F<ev.h> and puts all of its definitions (many
2781	of them macros) into the global namespace. All C++ specific things are	4093	of them macros) into the global namespace. All C++ specific things are
2782	put into the C<ev> namespace. It should support all the same embedding	4094	put into the C<ev> namespace. It should support all the same embedding
…		…
2785	Care has been taken to keep the overhead low. The only data member the C++	4097	Care has been taken to keep the overhead low. The only data member the C++
2786	classes add (compared to plain C-style watchers) is the event loop pointer	4098	classes add (compared to plain C-style watchers) is the event loop pointer
2787	that the watcher is associated with (or no additional members at all if	4099	that the watcher is associated with (or no additional members at all if
2788	you disable C<EV_MULTIPLICITY> when embedding libev).	4100	you disable C<EV_MULTIPLICITY> when embedding libev).
2789		4101
2790	Currently, functions, and static and non-static member functions can be	4102	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	4103	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	4104	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	4105	you need support for other types of functors please contact the author
2794	it).	4106	(preferably after implementing it).
		4107
		4108	For all this to work, your C++ compiler either has to use the same calling
		4109	conventions as your C compiler (for static member functions), or you have
		4110	to embed libev and compile libev itself as C++.
2795		4111
2796	Here is a list of things available in the C<ev> namespace:	4112	Here is a list of things available in the C<ev> namespace:
2797		4113
2798	=over 4	4114	=over 4
2799		4115
…		…
2809	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4125	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
2810		4126
2811	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4127	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
2812	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4128	the same name in the C<ev> namespace, with the exception of C<ev_signal>
2813	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4129	which is called C<ev::sig> to avoid clashes with the C<signal> macro
2814	defines by many implementations.	4130	defined by many implementations.
2815		4131
2816	All of those classes have these methods:	4132	All of those classes have these methods:
2817		4133
2818	=over 4	4134	=over 4
2819		4135
2820	=item ev::TYPE::TYPE ()	4136	=item ev::TYPE::TYPE ()
2821		4137
2822	=item ev::TYPE::TYPE (struct ev_loop *)	4138	=item ev::TYPE::TYPE (loop)
2823		4139
2824	=item ev::TYPE::~TYPE	4140	=item ev::TYPE::~TYPE
2825		4141
2826	The constructor (optionally) takes an event loop to associate the watcher	4142	The constructor (optionally) takes an event loop to associate the watcher
2827	with. If it is omitted, it will use C<EV_DEFAULT>.	4143	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2859		4175
2860	myclass obj;	4176	myclass obj;
2861	ev::io iow;	4177	ev::io iow;
2862	iow.set <myclass, &myclass::io_cb> (&obj);	4178	iow.set <myclass, &myclass::io_cb> (&obj);
2863		4179
		4180	=item w->set (object *)
		4181
		4182	This is a variation of a method callback - leaving out the method to call
		4183	will default the method to C<operator ()>, which makes it possible to use
		4184	functor objects without having to manually specify the C<operator ()> all
		4185	the time. Incidentally, you can then also leave out the template argument
		4186	list.
		4187
		4188	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		4189	int revents)>.
		4190
		4191	See the method-C<set> above for more details.
		4192
		4193	Example: use a functor object as callback.
		4194
		4195	struct myfunctor
		4196	{
		4197	void operator() (ev::io &w, int revents)
		4198	{
		4199	...
		4200	}
		4201	}
		4202
		4203	myfunctor f;
		4204
		4205	ev::io w;
		4206	w.set (&f);
		4207
2864	=item w->set<function> (void *data = 0)	4208	=item w->set<function> (void *data = 0)
2865		4209
2866	Also sets a callback, but uses a static method or plain function as	4210	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	4211	callback. The optional C<data> argument will be stored in the watcher's
2868	C<data> member and is free for you to use.	4212	C<data> member and is free for you to use.
…		…
2874	Example: Use a plain function as callback.	4218	Example: Use a plain function as callback.
2875		4219
2876	static void io_cb (ev::io &w, int revents) { }	4220	static void io_cb (ev::io &w, int revents) { }
2877	iow.set <io_cb> ();	4221	iow.set <io_cb> ();
2878		4222
2879	=item w->set (struct ev_loop *)	4223	=item w->set (loop)
2880		4224
2881	Associates a different C<struct ev_loop> with this watcher. You can only	4225	Associates a different C<struct ev_loop> with this watcher. You can only
2882	do this when the watcher is inactive (and not pending either).	4226	do this when the watcher is inactive (and not pending either).
2883		4227
2884	=item w->set ([arguments])	4228	=item w->set ([arguments])
2885		4229
2886	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4230	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4231	with the same arguments. Either this method or a suitable start method
2887	called at least once. Unlike the C counterpart, an active watcher gets	4232	must be called at least once. Unlike the C counterpart, an active watcher
2888	automatically stopped and restarted when reconfiguring it with this	4233	gets automatically stopped and restarted when reconfiguring it with this
2889	method.	4234	method.
		4235
		4236	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4237	clashing with the C<set (loop)> method.
2890		4238
2891	=item w->start ()	4239	=item w->start ()
2892		4240
2893	Starts the watcher. Note that there is no C<loop> argument, as the	4241	Starts the watcher. Note that there is no C<loop> argument, as the
2894	constructor already stores the event loop.	4242	constructor already stores the event loop.
2895		4243
		4244	=item w->start ([arguments])
		4245
		4246	Instead of calling C<set> and C<start> methods separately, it is often
		4247	convenient to wrap them in one call. Uses the same type of arguments as
		4248	the configure C<set> method of the watcher.
		4249
2896	=item w->stop ()	4250	=item w->stop ()
2897		4251
2898	Stops the watcher if it is active. Again, no C<loop> argument.	4252	Stops the watcher if it is active. Again, no C<loop> argument.
2899		4253
2900	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4254	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2912		4266
2913	=back	4267	=back
2914		4268
2915	=back	4269	=back
2916		4270
2917	Example: Define a class with an IO and idle watcher, start one of them in	4271	Example: Define a class with two I/O and idle watchers, start the I/O
2918	the constructor.	4272	watchers in the constructor.
2919		4273
2920	class myclass	4274	class myclass
2921	{	4275	{
2922	ev::io io ; void io_cb (ev::io &w, int revents);	4276	ev::io io ; void io_cb (ev::io &w, int revents);
		4277	ev::io io2 ; void io2_cb (ev::io &w, int revents);
2923	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4278	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2924		4279
2925	myclass (int fd)	4280	myclass (int fd)
2926	{	4281	{
2927	io .set <myclass, &myclass::io_cb > (this);	4282	io .set <myclass, &myclass::io_cb > (this);
		4283	io2 .set <myclass, &myclass::io2_cb > (this);
2928	idle.set <myclass, &myclass::idle_cb> (this);	4284	idle.set <myclass, &myclass::idle_cb> (this);
2929		4285
2930	io.start (fd, ev::READ);	4286	io.set (fd, ev::WRITE); // configure the watcher
		4287	io.start (); // start it whenever convenient
		4288
		4289	io2.start (fd, ev::READ); // set + start in one call
2931	}	4290	}
2932	};	4291	};
2933		4292
2934		4293
2935	=head1 OTHER LANGUAGE BINDINGS	4294	=head1 OTHER LANGUAGE BINDINGS
…		…
2954	L<http://software.schmorp.de/pkg/EV>.	4313	L<http://software.schmorp.de/pkg/EV>.
2955		4314
2956	=item Python	4315	=item Python
2957		4316
2958	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	4317	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	4318	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		4319
2965	=item Ruby	4320	=item Ruby
2966		4321
2967	Tony Arcieri has written a ruby extension that offers access to a subset	4322	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	4323	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	4324	more on top of it. It can be found via gem servers. Its homepage is at
2970	L<http://rev.rubyforge.org/>.	4325	L<http://rev.rubyforge.org/>.
2971		4326
		4327	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		4328	makes rev work even on mingw.
		4329
		4330	=item Haskell
		4331
		4332	A haskell binding to libev is available at
		4333	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		4334
2972	=item D	4335	=item D
2973		4336
2974	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4337	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2975	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4338	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
2976		4339
2977	=item Ocaml	4340	=item Ocaml
2978		4341
2979	Erkki Seppala has written Ocaml bindings for libev, to be found at	4342	Erkki Seppala has written Ocaml bindings for libev, to be found at
2980	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4343	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4344
		4345	=item Lua
		4346
		4347	Brian Maher has written a partial interface to libev for lua (at the
		4348	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4349	L<http://github.com/brimworks/lua-ev>.
		4350
		4351	=item Javascript
		4352
		4353	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4354
		4355	=item Others
		4356
		4357	There are others, and I stopped counting.
2981		4358
2982	=back	4359	=back
2983		4360
2984		4361
2985	=head1 MACRO MAGIC	4362	=head1 MACRO MAGIC
…		…
2999	loop argument"). The C<EV_A> form is used when this is the sole argument,	4376	loop argument"). The C<EV_A> form is used when this is the sole argument,
3000	C<EV_A_> is used when other arguments are following. Example:	4377	C<EV_A_> is used when other arguments are following. Example:
3001		4378
3002	ev_unref (EV_A);	4379	ev_unref (EV_A);
3003	ev_timer_add (EV_A_ watcher);	4380	ev_timer_add (EV_A_ watcher);
3004	ev_loop (EV_A_ 0);	4381	ev_run (EV_A_ 0);
3005		4382
3006	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4383	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3007	which is often provided by the following macro.	4384	which is often provided by the following macro.
3008		4385
3009	=item C<EV_P>, C<EV_P_>	4386	=item C<EV_P>, C<EV_P_>
…		…
3022	suitable for use with C<EV_A>.	4399	suitable for use with C<EV_A>.
3023		4400
3024	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4401	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3025		4402
3026	Similar to the other two macros, this gives you the value of the default	4403	Similar to the other two macros, this gives you the value of the default
3027	loop, if multiple loops are supported ("ev loop default").	4404	loop, if multiple loops are supported ("ev loop default"). The default loop
		4405	will be initialised if it isn't already initialised.
		4406
		4407	For non-multiplicity builds, these macros do nothing, so you always have
		4408	to initialise the loop somewhere.
3028		4409
3029	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4410	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3030		4411
3031	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4412	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3032	default loop has been initialised (C<UC> == unchecked). Their behaviour	4413	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3049	}	4430	}
3050		4431
3051	ev_check check;	4432	ev_check check;
3052	ev_check_init (&check, check_cb);	4433	ev_check_init (&check, check_cb);
3053	ev_check_start (EV_DEFAULT_ &check);	4434	ev_check_start (EV_DEFAULT_ &check);
3054	ev_loop (EV_DEFAULT_ 0);	4435	ev_run (EV_DEFAULT_ 0);
3055		4436
3056	=head1 EMBEDDING	4437	=head1 EMBEDDING
3057		4438
3058	Libev can (and often is) directly embedded into host	4439	Libev can (and often is) directly embedded into host
3059	applications. Examples of applications that embed it include the Deliantra	4440	applications. Examples of applications that embed it include the Deliantra
…		…
3099	ev_vars.h	4480	ev_vars.h
3100	ev_wrap.h	4481	ev_wrap.h
3101		4482
3102	ev_win32.c required on win32 platforms only	4483	ev_win32.c required on win32 platforms only
3103		4484
3104	ev_select.c only when select backend is enabled (which is enabled by default)	4485	ev_select.c only when select backend is enabled
3105	ev_poll.c only when poll backend is enabled (disabled by default)	4486	ev_poll.c only when poll backend is enabled
3106	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4487	ev_epoll.c only when the epoll backend is enabled
		4488	ev_linuxaio.c only when the linux aio backend is enabled
		4489	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)	4490	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)	4491	ev_port.c only when the solaris port backend is enabled
3109		4492
3110	F<ev.c> includes the backend files directly when enabled, so you only need	4493	F<ev.c> includes the backend files directly when enabled, so you only need
3111	to compile this single file.	4494	to compile this single file.
3112		4495
3113	=head3 LIBEVENT COMPATIBILITY API	4496	=head3 LIBEVENT COMPATIBILITY API
…		…
3139	libev.m4	4522	libev.m4
3140		4523
3141	=head2 PREPROCESSOR SYMBOLS/MACROS	4524	=head2 PREPROCESSOR SYMBOLS/MACROS
3142		4525
3143	Libev can be configured via a variety of preprocessor symbols you have to	4526	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	4527	define before including (or compiling) any of its files. The default in
3145	autoconf is documented for every option.	4528	the absence of autoconf is documented for every option.
		4529
		4530	Symbols marked with "(h)" do not change the ABI, and can have different
		4531	values when compiling libev vs. including F<ev.h>, so it is permissible
		4532	to redefine them before including F<ev.h> without breaking compatibility
		4533	to a compiled library. All other symbols change the ABI, which means all
		4534	users of libev and the libev code itself must be compiled with compatible
		4535	settings.
3146		4536
3147	=over 4	4537	=over 4
3148		4538
		4539	=item EV_COMPAT3 (h)
		4540
		4541	Backwards compatibility is a major concern for libev. This is why this
		4542	release of libev comes with wrappers for the functions and symbols that
		4543	have been renamed between libev version 3 and 4.
		4544
		4545	You can disable these wrappers (to test compatibility with future
		4546	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4547	sources. This has the additional advantage that you can drop the C<struct>
		4548	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4549	typedef in that case.
		4550
		4551	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4552	and in some even more future version the compatibility code will be
		4553	removed completely.
		4554
3149	=item EV_STANDALONE	4555	=item EV_STANDALONE (h)
3150		4556
3151	Must always be C<1> if you do not use autoconf configuration, which	4557	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	4558	keeps libev from including F<config.h>, and it also defines dummy
3153	implementations for some libevent functions (such as logging, which is not	4559	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	4560	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.	4561	F<event.h> that are not directly supported by the libev core alone.
3156		4562
		4563	In standalone mode, libev will still try to automatically deduce the
		4564	configuration, but has to be more conservative.
		4565
		4566	=item EV_USE_FLOOR
		4567
		4568	If defined to be C<1>, libev will use the C<floor ()> function for its
		4569	periodic reschedule calculations, otherwise libev will fall back on a
		4570	portable (slower) implementation. If you enable this, you usually have to
		4571	link against libm or something equivalent. Enabling this when the C<floor>
		4572	function is not available will fail, so the safe default is to not enable
		4573	this.
		4574
3157	=item EV_USE_MONOTONIC	4575	=item EV_USE_MONOTONIC
3158		4576
3159	If defined to be C<1>, libev will try to detect the availability of the	4577	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	4578	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	4579	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	4580	you usually have to link against librt or something similar. Enabling it
3163	the functionality isn't available is safe, though, although you have	4581	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>	4582	to make sure you link against any libraries where the C<clock_gettime>
3165	function is hiding in (often F<-lrt>).	4583	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3166		4584
3167	=item EV_USE_REALTIME	4585	=item EV_USE_REALTIME
3168		4586
3169	If defined to be C<1>, libev will try to detect the availability of the	4587	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	4588	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	4589	at runtime if successful). Otherwise no use of the real-time clock
3172	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4590	option will be attempted. This effectively replaces C<gettimeofday>
3173	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4591	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3174	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4592	correctness. See the note about libraries in the description of
		4593	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4594	C<EV_USE_CLOCK_SYSCALL>.
		4595
		4596	=item EV_USE_CLOCK_SYSCALL
		4597
		4598	If defined to be C<1>, libev will try to use a direct syscall instead
		4599	of calling the system-provided C<clock_gettime> function. This option
		4600	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4601	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4602	programs needlessly. Using a direct syscall is slightly slower (in
		4603	theory), because no optimised vdso implementation can be used, but avoids
		4604	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4605	higher, as it simplifies linking (no need for C<-lrt>).
3175		4606
3176	=item EV_USE_NANOSLEEP	4607	=item EV_USE_NANOSLEEP
3177		4608
3178	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4609	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 ()>.	4610	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3195		4626
3196	=item EV_SELECT_USE_FD_SET	4627	=item EV_SELECT_USE_FD_SET
3197		4628
3198	If defined to C<1>, then the select backend will use the system C<fd_set>	4629	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	4630	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	4631	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	4632	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	4633	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	4634	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3204	influence the size of the C<fd_set> used.	4635	configures the maximum size of the C<fd_set>.
3205		4636
3206	=item EV_SELECT_IS_WINSOCKET	4637	=item EV_SELECT_IS_WINSOCKET
3207		4638
3208	When defined to C<1>, the select backend will assume that	4639	When defined to C<1>, the select backend will assume that
3209	select/socket/connect etc. don't understand file descriptors but	4640	select/socket/connect etc. don't understand file descriptors but
…		…
3211	be used is the winsock select). This means that it will call	4642	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,	4643	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	4644	it is assumed that all these functions actually work on fds, even
3214	on win32. Should not be defined on non-win32 platforms.	4645	on win32. Should not be defined on non-win32 platforms.
3215		4646
3216	=item EV_FD_TO_WIN32_HANDLE	4647	=item EV_FD_TO_WIN32_HANDLE(fd)
3217		4648
3218	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4649	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	4650	file descriptors to socket handles. When not defining this symbol (the
3220	default), then libev will call C<_get_osfhandle>, which is usually	4651	default), then libev will call C<_get_osfhandle>, which is usually
3221	correct. In some cases, programs use their own file descriptor management,	4652	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.	4653	in which case they can provide this function to map fds to socket handles.
3223		4654
		4655	=item EV_WIN32_HANDLE_TO_FD(handle)
		4656
		4657	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4658	using the standard C<_open_osfhandle> function. For programs implementing
		4659	their own fd to handle mapping, overwriting this function makes it easier
		4660	to do so. This can be done by defining this macro to an appropriate value.
		4661
		4662	=item EV_WIN32_CLOSE_FD(fd)
		4663
		4664	If programs implement their own fd to handle mapping on win32, then this
		4665	macro can be used to override the C<close> function, useful to unregister
		4666	file descriptors again. Note that the replacement function has to close
		4667	the underlying OS handle.
		4668
		4669	=item EV_USE_WSASOCKET
		4670
		4671	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4672	communication socket, which works better in some environments. Otherwise,
		4673	the normal C<socket> function will be used, which works better in other
		4674	environments.
		4675
3224	=item EV_USE_POLL	4676	=item EV_USE_POLL
3225		4677
3226	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4678	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	4679	backend. Otherwise it will be enabled on non-win32 platforms. It
3228	takes precedence over select.	4680	takes precedence over select.
…		…
3232	If defined to be C<1>, libev will compile in support for the Linux	4684	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,	4685	C<epoll>(7) backend. Its availability will be detected at runtime,
3234	otherwise another method will be used as fallback. This is the preferred	4686	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	4687	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.	4688	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4689
		4690	=item EV_USE_LINUXAIO
		4691
		4692	If defined to be C<1>, libev will compile in support for the Linux aio
		4693	backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be
		4694	enabled on linux, otherwise disabled.
		4695
		4696	=item EV_USE_IOURING
		4697
		4698	If defined to be C<1>, libev will compile in support for the Linux
		4699	io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's
		4700	current limitations it has to be requested explicitly. If undefined, it
		4701	will be enabled on linux, otherwise disabled.
3237		4702
3238	=item EV_USE_KQUEUE	4703	=item EV_USE_KQUEUE
3239		4704
3240	If defined to be C<1>, libev will compile in support for the BSD style	4705	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,	4706	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	4728	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	4729	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	4730	be detected at runtime. If undefined, it will be enabled if the headers
3266	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4731	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3267		4732
		4733	=item EV_NO_SMP
		4734
		4735	If defined to be C<1>, libev will assume that memory is always coherent
		4736	between threads, that is, threads can be used, but threads never run on
		4737	different cpus (or different cpu cores). This reduces dependencies
		4738	and makes libev faster.
		4739
		4740	=item EV_NO_THREADS
		4741
		4742	If defined to be C<1>, libev will assume that it will never be called from
		4743	different threads (that includes signal handlers), which is a stronger
		4744	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4745	libev faster.
		4746
3268	=item EV_ATOMIC_T	4747	=item EV_ATOMIC_T
3269		4748
3270	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4749	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	4750	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	4751	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"	4752	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.	4753	handler "locking" as well as for signal and thread safety in C<ev_async>
		4754	watchers.
3275		4755
3276	In the absence of this define, libev will use C<sig_atomic_t volatile>	4756	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.	4757	(from F<signal.h>), which is usually good enough on most platforms.
3278		4758
3279	=item EV_H	4759	=item EV_H (h)
3280		4760
3281	The name of the F<ev.h> header file used to include it. The default if	4761	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	4762	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.	4763	used to virtually rename the F<ev.h> header file in case of conflicts.
3284		4764
3285	=item EV_CONFIG_H	4765	=item EV_CONFIG_H (h)
3286		4766
3287	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4767	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	4768	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3289	C<EV_H>, above.	4769	C<EV_H>, above.
3290		4770
3291	=item EV_EVENT_H	4771	=item EV_EVENT_H (h)
3292		4772
3293	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4773	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">.	4774	of how the F<event.h> header can be found, the default is C<"event.h">.
3295		4775
3296	=item EV_PROTOTYPES	4776	=item EV_PROTOTYPES (h)
3297		4777
3298	If defined to be C<0>, then F<ev.h> will not define any function	4778	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	4779	prototypes, but still define all the structs and other symbols. This is
3300	occasionally useful if you want to provide your own wrapper functions	4780	occasionally useful if you want to provide your own wrapper functions
3301	around libev functions.	4781	around libev functions.
…		…
3306	will have the C<struct ev_loop *> as first argument, and you can create	4786	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	4787	additional independent event loops. Otherwise there will be no support
3308	for multiple event loops and there is no first event loop pointer	4788	for multiple event loops and there is no first event loop pointer
3309	argument. Instead, all functions act on the single default loop.	4789	argument. Instead, all functions act on the single default loop.
3310		4790
		4791	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4792	default loop when multiplicity is switched off - you always have to
		4793	initialise the loop manually in this case.
		4794
3311	=item EV_MINPRI	4795	=item EV_MINPRI
3312		4796
3313	=item EV_MAXPRI	4797	=item EV_MAXPRI
3314		4798
3315	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4799	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3323	fine.	4807	fine.
3324		4808
3325	If your embedding application does not need any priorities, defining these	4809	If your embedding application does not need any priorities, defining these
3326	both to C<0> will save some memory and CPU.	4810	both to C<0> will save some memory and CPU.
3327		4811
3328	=item EV_PERIODIC_ENABLE	4812	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4813	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4814	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3329		4815
3330	If undefined or defined to be C<1>, then periodic timers are supported. If	4816	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	4817	the respective watcher type is supported. If defined to be C<0>, then it
3332	code.	4818	is not. Disabling watcher types mainly saves code size.
3333		4819
3334	=item EV_IDLE_ENABLE	4820	=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		4821
3363	If you need to shave off some kilobytes of code at the expense of some	4822	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	4823	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	4824	certain subsets of functionality. The default is to enable all features
3366	much smaller 2-heap for timer management over the default 4-heap.	4825	that can be enabled on the platform.
		4826
		4827	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4828	with some broad features you want) and then selectively re-enable
		4829	additional parts you want, for example if you want everything minimal,
		4830	but multiple event loop support, async and child watchers and the poll
		4831	backend, use this:
		4832
		4833	#define EV_FEATURES 0
		4834	#define EV_MULTIPLICITY 1
		4835	#define EV_USE_POLL 1
		4836	#define EV_CHILD_ENABLE 1
		4837	#define EV_ASYNC_ENABLE 1
		4838
		4839	The actual value is a bitset, it can be a combination of the following
		4840	values (by default, all of these are enabled):
		4841
		4842	=over 4
		4843
		4844	=item C<1> - faster/larger code
		4845
		4846	Use larger code to speed up some operations.
		4847
		4848	Currently this is used to override some inlining decisions (enlarging the
		4849	code size by roughly 30% on amd64).
		4850
		4851	When optimising for size, use of compiler flags such as C<-Os> with
		4852	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4853	assertions.
		4854
		4855	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4856	(e.g. gcc with C<-Os>).
		4857
		4858	=item C<2> - faster/larger data structures
		4859
		4860	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4861	hash table sizes and so on. This will usually further increase code size
		4862	and can additionally have an effect on the size of data structures at
		4863	runtime.
		4864
		4865	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4866	(e.g. gcc with C<-Os>).
		4867
		4868	=item C<4> - full API configuration
		4869
		4870	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4871	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4872
		4873	=item C<8> - full API
		4874
		4875	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4876	details on which parts of the API are still available without this
		4877	feature, and do not complain if this subset changes over time.
		4878
		4879	=item C<16> - enable all optional watcher types
		4880
		4881	Enables all optional watcher types. If you want to selectively enable
		4882	only some watcher types other than I/O and timers (e.g. prepare,
		4883	embed, async, child...) you can enable them manually by defining
		4884	C<EV_watchertype_ENABLE> to C<1> instead.
		4885
		4886	=item C<32> - enable all backends
		4887
		4888	This enables all backends - without this feature, you need to enable at
		4889	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4890
		4891	=item C<64> - enable OS-specific "helper" APIs
		4892
		4893	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4894	default.
		4895
		4896	=back
		4897
		4898	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4899	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4900	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4901	watchers, timers and monotonic clock support.
		4902
		4903	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4904	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4905	your program might be left out as well - a binary starting a timer and an
		4906	I/O watcher then might come out at only 5Kb.
		4907
		4908	=item EV_API_STATIC
		4909
		4910	If this symbol is defined (by default it is not), then all identifiers
		4911	will have static linkage. This means that libev will not export any
		4912	identifiers, and you cannot link against libev anymore. This can be useful
		4913	when you embed libev, only want to use libev functions in a single file,
		4914	and do not want its identifiers to be visible.
		4915
		4916	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4917	wants to use libev.
		4918
		4919	This option only works when libev is compiled with a C compiler, as C++
		4920	doesn't support the required declaration syntax.
		4921
		4922	=item EV_AVOID_STDIO
		4923
		4924	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4925	functions (printf, scanf, perror etc.). This will increase the code size
		4926	somewhat, but if your program doesn't otherwise depend on stdio and your
		4927	libc allows it, this avoids linking in the stdio library which is quite
		4928	big.
		4929
		4930	Note that error messages might become less precise when this option is
		4931	enabled.
		4932
		4933	=item EV_NSIG
		4934
		4935	The highest supported signal number, +1 (or, the number of
		4936	signals): Normally, libev tries to deduce the maximum number of signals
		4937	automatically, but sometimes this fails, in which case it can be
		4938	specified. Also, using a lower number than detected (C<32> should be
		4939	good for about any system in existence) can save some memory, as libev
		4940	statically allocates some 12-24 bytes per signal number.
3367		4941
3368	=item EV_PID_HASHSIZE	4942	=item EV_PID_HASHSIZE
3369		4943
3370	C<ev_child> watchers use a small hash table to distribute workload by	4944	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	4945	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	4946	usually more than enough. If you need to manage thousands of children you
3373	increase this value (I<must> be a power of two).	4947	might want to increase this value (I<must> be a power of two).
3374		4948
3375	=item EV_INOTIFY_HASHSIZE	4949	=item EV_INOTIFY_HASHSIZE
3376		4950
3377	C<ev_stat> watchers use a small hash table to distribute workload by	4951	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>),	4952	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>	4953	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	4954	C<ev_stat> watchers you might want to increase this value (I<must> be a
3381	two).	4955	power of two).
3382		4956
3383	=item EV_USE_4HEAP	4957	=item EV_USE_4HEAP
3384		4958
3385	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4959	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	4960	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	4961	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3388	faster performance with many (thousands) of watchers.	4962	faster performance with many (thousands) of watchers.
3389		4963
3390	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4964	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3391	(disabled).	4965	will be C<0>.
3392		4966
3393	=item EV_HEAP_CACHE_AT	4967	=item EV_HEAP_CACHE_AT
3394		4968
3395	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4969	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	4970	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>),	4971	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,	4972	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	4973	but avoids random read accesses on heap changes. This improves performance
3400	noticeably with many (hundreds) of watchers.	4974	noticeably with many (hundreds) of watchers.
3401		4975
3402	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4976	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3403	(disabled).	4977	will be C<0>.
3404		4978
3405	=item EV_VERIFY	4979	=item EV_VERIFY
3406		4980
3407	Controls how much internal verification (see C<ev_loop_verify ()>) will	4981	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	4982	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	4983	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	4984	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	4985	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	4986	verification code will be called very frequently, which will slow down
3413	libev considerably.	4987	libev considerably.
3414		4988
		4989	Verification errors are reported via C's C<assert> mechanism, so if you
		4990	disable that (e.g. by defining C<NDEBUG>) then no errors will be reported.
		4991
3415	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4992	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3416	C<0>.	4993	will be C<0>.
3417		4994
3418	=item EV_COMMON	4995	=item EV_COMMON
3419		4996
3420	By default, all watchers have a C<void *data> member. By redefining	4997	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	4998	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,	4999	members. You have to define it each time you include one of the files,
3423	though, and it must be identical each time.	5000	though, and it must be identical each time.
3424		5001
3425	For example, the perl EV module uses something like this:	5002	For example, the perl EV module uses something like this:
3426		5003
…		…
3479	file.	5056	file.
3480		5057
3481	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5058	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:	5059	that everybody includes and which overrides some configure choices:
3483		5060
3484	#define EV_MINIMAL 1	5061	#define EV_FEATURES 8
3485	#define EV_USE_POLL 0	5062	#define EV_USE_SELECT 1
3486	#define EV_MULTIPLICITY 0
3487	#define EV_PERIODIC_ENABLE 0	5063	#define EV_PREPARE_ENABLE 1
		5064	#define EV_IDLE_ENABLE 1
3488	#define EV_STAT_ENABLE 0	5065	#define EV_SIGNAL_ENABLE 1
3489	#define EV_FORK_ENABLE 0	5066	#define EV_CHILD_ENABLE 1
		5067	#define EV_USE_STDEXCEPT 0
3490	#define EV_CONFIG_H <config.h>	5068	#define EV_CONFIG_H <config.h>
3491	#define EV_MINPRI 0
3492	#define EV_MAXPRI 0
3493		5069
3494	#include "ev++.h"	5070	#include "ev++.h"
3495		5071
3496	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5072	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3497		5073
3498	#include "ev_cpp.h"	5074	#include "ev_cpp.h"
3499	#include "ev.c"	5075	#include "ev.c"
3500		5076
3501	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5077	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3502		5078
3503	=head2 THREADS AND COROUTINES	5079	=head2 THREADS AND COROUTINES
3504		5080
3505	=head3 THREADS	5081	=head3 THREADS
3506		5082
…		…
3557	default loop and triggering an C<ev_async> watcher from the default loop	5133	default loop and triggering an C<ev_async> watcher from the default loop
3558	watcher callback into the event loop interested in the signal.	5134	watcher callback into the event loop interested in the signal.
3559		5135
3560	=back	5136	=back
3561		5137
		5138	See also L</THREAD LOCKING EXAMPLE>.
		5139
3562	=head3 COROUTINES	5140	=head3 COROUTINES
3563		5141
3564	Libev is very accommodating to coroutines ("cooperative threads"):	5142	Libev is very accommodating to coroutines ("cooperative threads"):
3565	libev fully supports nesting calls to its functions from different	5143	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	5144	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	5145	different coroutines, and switch freely between both coroutines running
3568	loop, as long as you don't confuse yourself). The only exception is that	5146	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.	5147	that you must not do this from C<ev_periodic> reschedule callbacks.
3570		5148
3571	Care has been taken to ensure that libev does not keep local state inside	5149	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	5150	C<ev_run>, and other calls do not usually allow for coroutine switches as
3573	they do not call any callbacks.	5151	they do not call any callbacks.
3574		5152
3575	=head2 COMPILER WARNINGS	5153	=head2 COMPILER WARNINGS
3576		5154
3577	Depending on your compiler and compiler settings, you might get no or a	5155	Depending on your compiler and compiler settings, you might get no or a
…		…
3588	maintainable.	5166	maintainable.
3589		5167
3590	And of course, some compiler warnings are just plain stupid, or simply	5168	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	5169	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	5170	seems to warn about). For example, certain older gcc versions had some
3593	warnings that resulted an extreme number of false positives. These have	5171	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	5172	been fixed, but some people still insist on making code warn-free with
3595	such buggy versions.	5173	such buggy versions.
3596		5174
3597	While libev is written to generate as few warnings as possible,	5175	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	5176	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3634	I suggest using suppression lists.	5212	I suggest using suppression lists.
3635		5213
3636		5214
3637	=head1 PORTABILITY NOTES	5215	=head1 PORTABILITY NOTES
3638		5216
		5217	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5218
		5219	GNU/Linux is the only common platform that supports 64 bit file/large file
		5220	interfaces but I<disables> them by default.
		5221
		5222	That means that libev compiled in the default environment doesn't support
		5223	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5224
		5225	Unfortunately, many programs try to work around this GNU/Linux issue
		5226	by enabling the large file API, which makes them incompatible with the
		5227	standard libev compiled for their system.
		5228
		5229	Likewise, libev cannot enable the large file API itself as this would
		5230	suddenly make it incompatible to the default compile time environment,
		5231	i.e. all programs not using special compile switches.
		5232
		5233	=head2 OS/X AND DARWIN BUGS
		5234
		5235	The whole thing is a bug if you ask me - basically any system interface
		5236	you touch is broken, whether it is locales, poll, kqueue or even the
		5237	OpenGL drivers.
		5238
		5239	=head3 C<kqueue> is buggy
		5240
		5241	The kqueue syscall is broken in all known versions - most versions support
		5242	only sockets, many support pipes.
		5243
		5244	Libev tries to work around this by not using C<kqueue> by default on this
		5245	rotten platform, but of course you can still ask for it when creating a
		5246	loop - embedding a socket-only kqueue loop into a select-based one is
		5247	probably going to work well.
		5248
		5249	=head3 C<poll> is buggy
		5250
		5251	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5252	implementation by something calling C<kqueue> internally around the 10.5.6
		5253	release, so now C<kqueue> I<and> C<poll> are broken.
		5254
		5255	Libev tries to work around this by not using C<poll> by default on
		5256	this rotten platform, but of course you can still ask for it when creating
		5257	a loop.
		5258
		5259	=head3 C<select> is buggy
		5260
		5261	All that's left is C<select>, and of course Apple found a way to fuck this
		5262	one up as well: On OS/X, C<select> actively limits the number of file
		5263	descriptors you can pass in to 1024 - your program suddenly crashes when
		5264	you use more.
		5265
		5266	There is an undocumented "workaround" for this - defining
		5267	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5268	work on OS/X.
		5269
		5270	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5271
		5272	=head3 C<errno> reentrancy
		5273
		5274	The default compile environment on Solaris is unfortunately so
		5275	thread-unsafe that you can't even use components/libraries compiled
		5276	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5277	defined by default. A valid, if stupid, implementation choice.
		5278
		5279	If you want to use libev in threaded environments you have to make sure
		5280	it's compiled with C<_REENTRANT> defined.
		5281
		5282	=head3 Event port backend
		5283
		5284	The scalable event interface for Solaris is called "event
		5285	ports". Unfortunately, this mechanism is very buggy in all major
		5286	releases. If you run into high CPU usage, your program freezes or you get
		5287	a large number of spurious wakeups, make sure you have all the relevant
		5288	and latest kernel patches applied. No, I don't know which ones, but there
		5289	are multiple ones to apply, and afterwards, event ports actually work
		5290	great.
		5291
		5292	If you can't get it to work, you can try running the program by setting
		5293	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5294	C<select> backends.
		5295
		5296	=head2 AIX POLL BUG
		5297
		5298	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5299	this by trying to avoid the poll backend altogether (i.e. it's not even
		5300	compiled in), which normally isn't a big problem as C<select> works fine
		5301	with large bitsets on AIX, and AIX is dead anyway.
		5302
3639	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5303	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5304
		5305	=head3 General issues
3640		5306
3641	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5307	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	5308	requires, and its I/O model is fundamentally incompatible with the POSIX
3643	model. Libev still offers limited functionality on this platform in	5309	model. Libev still offers limited functionality on this platform in
3644	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5310	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3645	descriptors. This only applies when using Win32 natively, not when using	5311	descriptors. This only applies when using Win32 natively, not when using
3646	e.g. cygwin.	5312	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5313	as every compiler comes with a slightly differently broken/incompatible
		5314	environment.
3647		5315
3648	Lifting these limitations would basically require the full	5316	Lifting these limitations would basically require the full
3649	re-implementation of the I/O system. If you are into these kinds of	5317	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	5318	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).	5319	also that glib is the slowest event library known to man).
3652		5320
3653	There is no supported compilation method available on windows except	5321	There is no supported compilation method available on windows except
3654	embedding it into other applications.	5322	embedding it into other applications.
		5323
		5324	Sensible signal handling is officially unsupported by Microsoft - libev
		5325	tries its best, but under most conditions, signals will simply not work.
3655		5326
3656	Not a libev limitation but worth mentioning: windows apparently doesn't	5327	Not a libev limitation but worth mentioning: windows apparently doesn't
3657	accept large writes: instead of resulting in a partial write, windows will	5328	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,	5329	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	5330	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	5335	the abysmal performance of winsockets, using a large number of sockets
3665	is not recommended (and not reasonable). If your program needs to use	5336	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	5337	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	5338	different implementation for windows, as libev offers the POSIX readiness
3668	notification model, which cannot be implemented efficiently on windows	5339	notification model, which cannot be implemented efficiently on windows
3669	(Microsoft monopoly games).	5340	(due to Microsoft monopoly games).
3670		5341
3671	A typical way to use libev under windows is to embed it (see the embedding	5342	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	5343	section for details) and use the following F<evwrap.h> header file instead
3673	of F<ev.h>:	5344	of F<ev.h>:
3674		5345
…		…
3681	you do I<not> compile the F<ev.c> or any other embedded source files!):	5352	you do I<not> compile the F<ev.c> or any other embedded source files!):
3682		5353
3683	#include "evwrap.h"	5354	#include "evwrap.h"
3684	#include "ev.c"	5355	#include "ev.c"
3685		5356
3686	=over 4
3687
3688	=item The winsocket select function	5357	=head3 The winsocket C<select> function
3689		5358
3690	The winsocket C<select> function doesn't follow POSIX in that it	5359	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	5360	requires socket I<handles> and not socket I<file descriptors> (it is
3692	also extremely buggy). This makes select very inefficient, and also	5361	also extremely buggy). This makes select very inefficient, and also
3693	requires a mapping from file descriptors to socket handles (the Microsoft	5362	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 */	5371	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3703		5372
3704	Note that winsockets handling of fd sets is O(n), so you can easily get a	5373	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.	5374	complexity in the O(n²) range when using win32.
3706		5375
3707	=item Limited number of file descriptors	5376	=head3 Limited number of file descriptors
3708		5377
3709	Windows has numerous arbitrary (and low) limits on things.	5378	Windows has numerous arbitrary (and low) limits on things.
3710		5379
3711	Early versions of winsocket's select only supported waiting for a maximum	5380	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	5381	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	5382	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	5383	recommends spawning a chain of threads and wait for 63 handles and the
3715	previous thread in each. Great).	5384	previous thread in each. Sounds great!).
3716		5385
3717	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5386	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	5387	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	5388	call (which might be in libev or elsewhere, for example, perl and many
3720	select emulation on windows).	5389	other interpreters do their own select emulation on windows).
3721		5390
3722	Another limit is the number of file descriptors in the Microsoft runtime	5391	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	5392	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	5393	fetish or something like this inside Microsoft). You can increase this
3725	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5394	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	5395	(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	5396	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	5397	(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	5398	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.	5399	the cost of calling select (O(n²)) will likely make this unworkable.
3733
3734	=back
3735		5400
3736	=head2 PORTABILITY REQUIREMENTS	5401	=head2 PORTABILITY REQUIREMENTS
3737		5402
3738	In addition to a working ISO-C implementation and of course the	5403	In addition to a working ISO-C implementation and of course the
3739	backend-specific APIs, libev relies on a few additional extensions:	5404	backend-specific APIs, libev relies on a few additional extensions:
…		…
3746	Libev assumes not only that all watcher pointers have the same internal	5411	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	5412	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	5413	assumes that the same (machine) code can be used to call any watcher
3749	callback: The watcher callbacks have different type signatures, but libev	5414	callback: The watcher callbacks have different type signatures, but libev
3750	calls them using an C<ev_watcher *> internally.	5415	calls them using an C<ev_watcher *> internally.
		5416
		5417	=item null pointers and integer zero are represented by 0 bytes
		5418
		5419	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5420	relies on this setting pointers and integers to null.
		5421
		5422	=item pointer accesses must be thread-atomic
		5423
		5424	Accessing a pointer value must be atomic, it must both be readable and
		5425	writable in one piece - this is the case on all current architectures.
3751		5426
3752	=item C<sig_atomic_t volatile> must be thread-atomic as well	5427	=item C<sig_atomic_t volatile> must be thread-atomic as well
3753		5428
3754	The type C<sig_atomic_t volatile> (or whatever is defined as	5429	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	5430	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3764	thread" or will block signals process-wide, both behaviours would	5439	thread" or will block signals process-wide, both behaviours would
3765	be compatible with libev. Interaction between C<sigprocmask> and	5440	be compatible with libev. Interaction between C<sigprocmask> and
3766	C<pthread_sigmask> could complicate things, however.	5441	C<pthread_sigmask> could complicate things, however.
3767		5442
3768	The most portable way to handle signals is to block signals in all threads	5443	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	5444	except the initial one, and run the signal handling loop in the initial
3770	well.	5445	thread as well.
3771		5446
3772	=item C<long> must be large enough for common memory allocation sizes	5447	=item C<long> must be large enough for common memory allocation sizes
3773		5448
3774	To improve portability and simplify its API, libev uses C<long> internally	5449	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	5450	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3778	watchers.	5453	watchers.
3779		5454
3780	=item C<double> must hold a time value in seconds with enough accuracy	5455	=item C<double> must hold a time value in seconds with enough accuracy
3781		5456
3782	The type C<double> is used to represent timestamps. It is required to	5457	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	5458	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	5459	good enough for at least into the year 4000 with millisecond accuracy
		5460	(the design goal for libev). This requirement is overfulfilled by
3785	implementations implementing IEEE 754 (basically all existing ones).	5461	implementations using IEEE 754, which is basically all existing ones.
		5462
		5463	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5464	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5465	is either obsolete or somebody patched it to use C<long double> or
		5466	something like that, just kidding).
3786		5467
3787	=back	5468	=back
3788		5469
3789	If you know of other additional requirements drop me a note.	5470	If you know of other additional requirements drop me a note.
3790		5471
…		…
3852	=item Processing ev_async_send: O(number_of_async_watchers)	5533	=item Processing ev_async_send: O(number_of_async_watchers)
3853		5534
3854	=item Processing signals: O(max_signal_number)	5535	=item Processing signals: O(max_signal_number)
3855		5536
3856	Sending involves a system call I<iff> there were no other C<ev_async_send>	5537	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	5538	calls in the current loop iteration and the loop is currently
		5539	blocked. Checking for async and signal events involves iterating over all
3858	involves iterating over all running async watchers or all signal numbers.	5540	running async watchers or all signal numbers.
3859		5541
3860	=back	5542	=back
3861		5543
3862		5544
		5545	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5546
		5547	The major version 4 introduced some incompatible changes to the API.
		5548
		5549	At the moment, the C<ev.h> header file provides compatibility definitions
		5550	for all changes, so most programs should still compile. The compatibility
		5551	layer might be removed in later versions of libev, so better update to the
		5552	new API early than late.
		5553
		5554	=over 4
		5555
		5556	=item C<EV_COMPAT3> backwards compatibility mechanism
		5557
		5558	The backward compatibility mechanism can be controlled by
		5559	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5560	section.
		5561
		5562	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5563
		5564	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5565
		5566	ev_loop_destroy (EV_DEFAULT_UC);
		5567	ev_loop_fork (EV_DEFAULT);
		5568
		5569	=item function/symbol renames
		5570
		5571	A number of functions and symbols have been renamed:
		5572
		5573	ev_loop => ev_run
		5574	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5575	EVLOOP_ONESHOT => EVRUN_ONCE
		5576
		5577	ev_unloop => ev_break
		5578	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5579	EVUNLOOP_ONE => EVBREAK_ONE
		5580	EVUNLOOP_ALL => EVBREAK_ALL
		5581
		5582	EV_TIMEOUT => EV_TIMER
		5583
		5584	ev_loop_count => ev_iteration
		5585	ev_loop_depth => ev_depth
		5586	ev_loop_verify => ev_verify
		5587
		5588	Most functions working on C<struct ev_loop> objects don't have an
		5589	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5590	associated constants have been renamed to not collide with the C<struct
		5591	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5592	as all other watcher types. Note that C<ev_loop_fork> is still called
		5593	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5594	typedef.
		5595
		5596	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5597
		5598	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5599	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5600	and work, but the library code will of course be larger.
		5601
		5602	=back
		5603
		5604
		5605	=head1 GLOSSARY
		5606
		5607	=over 4
		5608
		5609	=item active
		5610
		5611	A watcher is active as long as it has been started and not yet stopped.
		5612	See L</WATCHER STATES> for details.
		5613
		5614	=item application
		5615
		5616	In this document, an application is whatever is using libev.
		5617
		5618	=item backend
		5619
		5620	The part of the code dealing with the operating system interfaces.
		5621
		5622	=item callback
		5623
		5624	The address of a function that is called when some event has been
		5625	detected. Callbacks are being passed the event loop, the watcher that
		5626	received the event, and the actual event bitset.
		5627
		5628	=item callback/watcher invocation
		5629
		5630	The act of calling the callback associated with a watcher.
		5631
		5632	=item event
		5633
		5634	A change of state of some external event, such as data now being available
		5635	for reading on a file descriptor, time having passed or simply not having
		5636	any other events happening anymore.
		5637
		5638	In libev, events are represented as single bits (such as C<EV_READ> or
		5639	C<EV_TIMER>).
		5640
		5641	=item event library
		5642
		5643	A software package implementing an event model and loop.
		5644
		5645	=item event loop
		5646
		5647	An entity that handles and processes external events and converts them
		5648	into callback invocations.
		5649
		5650	=item event model
		5651
		5652	The model used to describe how an event loop handles and processes
		5653	watchers and events.
		5654
		5655	=item pending
		5656
		5657	A watcher is pending as soon as the corresponding event has been
		5658	detected. See L</WATCHER STATES> for details.
		5659
		5660	=item real time
		5661
		5662	The physical time that is observed. It is apparently strictly monotonic :)
		5663
		5664	=item wall-clock time
		5665
		5666	The time and date as shown on clocks. Unlike real time, it can actually
		5667	be wrong and jump forwards and backwards, e.g. when you adjust your
		5668	clock.
		5669
		5670	=item watcher
		5671
		5672	A data structure that describes interest in certain events. Watchers need
		5673	to be started (attached to an event loop) before they can receive events.
		5674
		5675	=back
		5676
3863	=head1 AUTHOR	5677	=head1 AUTHOR
3864		5678
3865	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5679	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5680	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3866		5681

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