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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 mechanism deserves honorable mention as the most misdesigned	528	The epoll mechanism deserves honorable mention as the most misdesigned
392	of the more advanced event mechanisms: mere annoyances include silently	529	of the more advanced event mechanisms: mere annoyances include silently
393	dropping file descriptors, requiring a system call per change per file	530	dropping file descriptors, requiring a system call per change per file
394	descriptor (and unnecessary guessing of parameters), problems with dup and	531	descriptor (and unnecessary guessing of parameters), problems with dup,
		532	returning before the timeout value, resulting in additional iterations
		533	(and only giving 5ms accuracy while select on the same platform gives
395	so on. The biggest issue is fork races, however - if a program forks then	534	0.1ms) and so on. The biggest issue is fork races, however - if a program
396	I<both> parent and child process have to recreate the epoll set, which can	535	forks then I<both> parent and child process have to recreate the epoll
397	take considerable time (one syscall per file descriptor) and is of course	536	set, which can take considerable time (one syscall per file descriptor)
398	hard to detect.	537	and is of course hard to detect.
399		538
400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	539	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
401	of course I<doesn't>, and epoll just loves to report events for totally	540	but of course I<doesn't>, and epoll just loves to report events for
402	I<different> file descriptors (even already closed ones, so one cannot	541	totally I<different> file descriptors (even already closed ones, so
403	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
404	on SMP systems). Libev tries to counter these spurious notifications by	543	(especially on SMP systems). Libev tries to counter these spurious
405	employing an additional generation counter and comparing that against the	544	notifications by employing an additional generation counter and comparing
406	events to filter out spurious ones, recreating the set when required.	545	that against the events to filter out spurious ones, recreating the set
		546	when required. Epoll also erroneously rounds down timeouts, but gives you
		547	no way to know when and by how much, so sometimes you have to busy-wait
		548	because epoll returns immediately despite a nonzero timeout. And last
		549	not least, it also refuses to work with some file descriptors which work
		550	perfectly fine with C<select> (files, many character devices...).
		551
		552	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		553	cobbled together in a hurry, no thought to design or interaction with
		554	others. Oh, the pain, will it ever stop...
407		555
408	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
409	will result in some caching, there is still a system call per such	557	will result in some caching, there is still a system call per such
410	incident (because the same I<file descriptor> could point to a different	558	incident (because the same I<file descriptor> could point to a different
411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	559	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
418	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
419	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
420	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
421	take considerable time and thus should be avoided.	569	take considerable time and thus should be avoided.
422		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
423	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
424	all kernel versions tested so far.	576	a lot of kernel revisions, but probably(!) works in current versions.
425		577
426	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
427	C<EVBACKEND_POLL>.	579	C<EVBACKEND_POLL>.
428		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
429	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	625	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
430		626
431	Kqueue deserves special mention, as at the time of this writing, it	627	Kqueue deserves special mention, as at the time this backend was
432	was broken on all BSDs except NetBSD (usually it doesn't work reliably	628	implemented, it was broken on all BSDs except NetBSD (usually it doesn't
433	with anything but sockets and pipes, except on Darwin, where of course	629	work reliably with anything but sockets and pipes, except on Darwin,
434	it's completely useless). Unlike epoll, however, whose brokenness	630	where of course it's completely useless). Unlike epoll, however, whose
435	is by design, these kqueue bugs can (and eventually will) be fixed	631	brokenness is by design, these kqueue bugs can be (and mostly have been)
436	without API changes to existing programs. For this reason it's not being	632	fixed without API changes to existing programs. For this reason it's not
437	"auto-detected" unless you explicitly specify it in the flags (i.e. using	633	being "auto-detected" on all platforms unless you explicitly specify it
438	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	634	in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a
439	system like NetBSD.	635	known-to-be-good (-enough) system like NetBSD.
440		636
441	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
442	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
443	the target platform). See C<ev_embed> watchers for more info.	639	the target platform). See C<ev_embed> watchers for more info.
444		640
445	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
446	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
447	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
448	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
449	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
450	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
451	cases	647	drops fds silently in similarly hard-to-detect cases.
452		648
453	This backend usually performs well under most conditions.	649	This backend usually performs well under most conditions.
454		650
455	While nominally embeddable in other event loops, this doesn't work	651	While nominally embeddable in other event loops, this doesn't work
456	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
457	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
458	(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
459	(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
460	using it only for sockets.	656	also broken on OS X)) and, did I mention it, using it only for sockets.
461		657
462	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
463	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
464	C<NOTE_EOF>.	660	C<NOTE_EOF>.
465		661
…		…
473	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	669	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
474		670
475	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,
476	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)).
477		673
478	Please note that Solaris event ports can deliver a lot of spurious
479	notifications, so you need to use non-blocking I/O or other means to avoid
480	blocking when no data (or space) is available.
481
482	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
483	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
484	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	676	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
485	might perform better.	677	might perform better.
486		678
487	On the positive side, with the exception of the spurious readiness	679	On the positive side, this backend actually performed fully to
488	notifications, this backend actually performed fully to specification
489	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
490	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.
491		693
492	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
493	C<EVBACKEND_POLL>.	695	C<EVBACKEND_POLL>.
494		696
495	=item C<EVBACKEND_ALL>	697	=item C<EVBACKEND_ALL>
496		698
497	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
498	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
499	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	701	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
500		702
501	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).
502		712
503	=back	713	=back
504		714
505	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,
506	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
507	specified, all backends in C<ev_recommended_backends ()> will be tried.	717	here). If none are specified, all backends in C<ev_recommended_backends
508		718	()> will be tried.
509	Example: This is the most typical usage.
510
511	if (!ev_default_loop (0))
512	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
513
514	Example: Restrict libev to the select and poll backends, and do not allow
515	environment settings to be taken into account:
516
517	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
518
519	Example: Use whatever libev has to offer, but make sure that kqueue is
520	used if available (warning, breaks stuff, best use only with your own
521	private event loop and only if you know the OS supports your types of
522	fds):
523
524	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
525
526	=item struct ev_loop *ev_loop_new (unsigned int flags)
527
528	Similar to C<ev_default_loop>, but always creates a new event loop that is
529	always distinct from the default loop. Unlike the default loop, it cannot
530	handle signal and child watchers, and attempts to do so will be greeted by
531	undefined behaviour (or a failed assertion if assertions are enabled).
532
533	Note that this function I<is> thread-safe, and the recommended way to use
534	libev with threads is indeed to create one loop per thread, and using the
535	default loop in the "main" or "initial" thread.
536		719
537	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.
538		721
539	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	722	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
540	if (!epoller)	723	if (!epoller)
541	fatal ("no epoll found here, maybe it hides under your chair");	724	fatal ("no epoll found here, maybe it hides under your chair");
542		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
543	=item ev_default_destroy ()	737	=item ev_loop_destroy (loop)
544		738
545	Destroys the default loop again (frees all memory and kernel state	739	Destroys an event loop object (frees all memory and kernel state
546	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
547	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
548	responsibility to either stop all watchers cleanly yourself I<before>	742	responsibility to either stop all watchers cleanly yourself I<before>
549	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
550	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
…		…
552		746
553	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
554	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
555	as signal and child watchers) would need to be stopped manually.	749	as signal and child watchers) would need to be stopped manually.
556		750
557	In general it is not advisable to call this function except in the	751	This function is normally used on loop objects allocated by
558	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.
559	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>
560	C<ev_loop_new> and C<ev_loop_destroy>).	758	and C<ev_loop_destroy>.
561		759
562	=item ev_loop_destroy (loop)	760	=item ev_loop_fork (loop)
563		761
564	Like C<ev_default_destroy>, but destroys an event loop created by an
565	earlier call to C<ev_loop_new>.
566
567	=item ev_default_fork ()
568
569	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
570	to reinitialise the kernel state for backends that have one. Despite the	763	to reinitialise the kernel state for backends that have one. Despite
571	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
572	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
573	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
574	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.
575		776
576	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
577	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
578	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).
579		783
580	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
581	it just in case after a fork. To make this easy, the function will fit in	785	it just in case after a fork.
582	quite nicely into a call to C<pthread_atfork>:
583		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	...
584	pthread_atfork (0, 0, ev_default_fork);	797	pthread_atfork (0, 0, post_fork_child);
585
586	=item ev_loop_fork (loop)
587
588	Like C<ev_default_fork>, but acts on an event loop created by
589	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
590	after fork that you want to re-use in the child, and how you do this is
591	entirely your own problem.
592		798
593	=item int ev_is_default_loop (loop)	799	=item int ev_is_default_loop (loop)
594		800
595	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
596	otherwise.	802	otherwise.
597		803
598	=item unsigned int ev_loop_count (loop)	804	=item unsigned int ev_iteration (loop)
599		805
600	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
601	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>
602	happily wraps around with enough iterations.	808	and happily wraps around with enough iterations.
603		809
604	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
605	"ticks" the number of loop iterations), as it roughly corresponds with	811	"ticks" the number of loop iterations), as it roughly corresponds with
606	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.
607		828
608	=item unsigned int ev_backend (loop)	829	=item unsigned int ev_backend (loop)
609		830
610	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
611	use.	832	use.
…		…
620		841
621	=item ev_now_update (loop)	842	=item ev_now_update (loop)
622		843
623	Establishes the current time by querying the kernel, updating the time	844	Establishes the current time by querying the kernel, updating the time
624	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
625	is usually done automatically within C<ev_loop ()>.	846	is usually done automatically within C<ev_run ()>.
626		847
627	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
628	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
629	the current time is a good idea.	850	the current time is a good idea.
630		851
631	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.
632		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
633	=item ev_loop (loop, int flags)	880	=item bool ev_run (loop, int flags)
634		881
635	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
636	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
637	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>.
638		887
639	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
640	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.
641		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
642	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
643	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
644	finished (especially in interactive programs), but having a program	898	finished (especially in interactive programs), but having a program
645	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
646	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
647	beauty.	901	beauty.
648		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
649	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
650	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
651	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
652	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.
653		913
654	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
655	necessary) and will handle those and any already outstanding ones. It	915	necessary) and will handle those and any already outstanding ones. It
656	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
657	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
658	user-registered callback will be called), and will return after one	918	user-registered callback will be called), and will return after one
659	iteration of the loop.	919	iteration of the loop.
660		920
661	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
662	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
663	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
664	usually a better approach for this kind of thing.	924	usually a better approach for this kind of thing.
665		925
666	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):
667		929
		930	- Increment loop depth.
		931	- Reset the ev_break status.
668	- Before the first iteration, call any pending watchers.	932	- Before the first iteration, call any pending watchers.
		933	LOOP:
669	* If EVFLAG_FORKCHECK was used, check for a fork.	934	- If EVFLAG_FORKCHECK was used, check for a fork.
670	- 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.
671	- Queue and call all prepare watchers.	936	- Queue and call all prepare watchers.
		937	- If ev_break was called, goto FINISH.
672	- If we have been forked, detach and recreate the kernel state	938	- If we have been forked, detach and recreate the kernel state
673	as to not disturb the other process.	939	as to not disturb the other process.
674	- Update the kernel state with all outstanding changes.	940	- Update the kernel state with all outstanding changes.
675	- Update the "event loop time" (ev_now ()).	941	- Update the "event loop time" (ev_now ()).
676	- Calculate for how long to sleep or block, if at all	942	- Calculate for how long to sleep or block, if at all
677	(active idle watchers, EVLOOP_NONBLOCK or not having	943	(active idle watchers, EVRUN_NOWAIT or not having
678	any active watchers at all will result in not sleeping).	944	any active watchers at all will result in not sleeping).
679	- 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.
680	- Block the process, waiting for any events.	947	- Block the process, waiting for any events.
681	- Queue all outstanding I/O (fd) events.	948	- Queue all outstanding I/O (fd) events.
682	- 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.
683	- Queue all expired timers.	950	- Queue all expired timers.
684	- Queue all expired periodics.	951	- Queue all expired periodics.
685	- Unless any events are pending now, queue all idle watchers.	952	- Queue all idle watchers with priority higher than that of pending events.
686	- Queue all check watchers.	953	- Queue all check watchers.
687	- 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).
688	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
689	be handled here by queueing them when their watcher gets executed.	956	be handled here by queueing them when their watcher gets executed.
690	- 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
691	were used, or there are no active watchers, return, otherwise	958	were used, or there are no active watchers, goto FINISH, otherwise
692	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.
693		964
694	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
695	anymore.	966	anymore.
696		967
697	... queue jobs here, make sure they register event watchers as long	968	... queue jobs here, make sure they register event watchers as long
698	... 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..)
699	ev_loop (my_loop, 0);	970	ev_run (my_loop, 0);
700	... jobs done or somebody called unloop. yeah!	971	... jobs done or somebody called break. yeah!
701		972
702	=item ev_unloop (loop, how)	973	=item ev_break (loop, how)
703		974
704	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
705	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
706	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
707	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.
708		979
709	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>.
710		981
711	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.
712		984
713	=item ev_ref (loop)	985	=item ev_ref (loop)
714		986
715	=item ev_unref (loop)	987	=item ev_unref (loop)
716		988
717	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
718	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
719	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.
720		992
721	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
722	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>
723	stopping it.	996	before stopping it.
724		997
725	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
726	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
727	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
728	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
729	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
730	(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
731	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).
732		1007
733	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>
734	running when nothing else is active.	1009	running when nothing else is active.
735		1010
736	ev_signal exitsig;	1011	ev_signal exitsig;
737	ev_signal_init (&exitsig, sig_cb, SIGINT);	1012	ev_signal_init (&exitsig, sig_cb, SIGINT);
738	ev_signal_start (loop, &exitsig);	1013	ev_signal_start (loop, &exitsig);
739	evf_unref (loop);	1014	ev_unref (loop);
740		1015
741	Example: For some weird reason, unregister the above signal handler again.	1016	Example: For some weird reason, unregister the above signal handler again.
742		1017
743	ev_ref (loop);	1018	ev_ref (loop);
744	ev_signal_stop (loop, &exitsig);	1019	ev_signal_stop (loop, &exitsig);
…		…
764	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.
765		1040
766	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
767	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,
768	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
769	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
770	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).
771		1049
772	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
773	to spend more time collecting timeouts, at the expense of increased	1051	to spend more time collecting timeouts, at the expense of increased
774	latency/jitter/inexactness (the watcher callback will be called	1052	latency/jitter/inexactness (the watcher callback will be called
775	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
…		…
777		1055
778	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
779	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
780	interactive servers (of course not for games), likewise for timeouts. It	1058	interactive servers (of course not for games), likewise for timeouts. It
781	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>,
782	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).
783		1065
784	Setting the I<timeout collect interval> can improve the opportunity for	1066	Setting the I<timeout collect interval> can improve the opportunity for
785	saving power, as the program will "bundle" timer callback invocations that	1067	saving power, as the program will "bundle" timer callback invocations that
786	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
787	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
788	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
789	they fire on, say, one-second boundaries only.	1071	they fire on, say, one-second boundaries only.
790		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
791	=item ev_loop_verify (loop)	1148	=item ev_verify (loop)
792		1149
793	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
794	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
795	through all internal structures and checks them for validity. If anything	1152	through all internal structures and checks them for validity. If anything
796	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
…		…
807		1164
808	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
809	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
810	watchers and C<ev_io_start> for I/O watchers.	1167	watchers and C<ev_io_start> for I/O watchers.
811		1168
812	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
813	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
814	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:
815		1173
816	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)
817	{	1175	{
818	ev_io_stop (w);	1176	ev_io_stop (w);
819	ev_unloop (loop, EVUNLOOP_ALL);	1177	ev_break (loop, EVBREAK_ALL);
820	}	1178	}
821		1179
822	struct ev_loop *loop = ev_default_loop (0);	1180	struct ev_loop *loop = ev_default_loop (0);
823		1181
824	ev_io stdin_watcher;	1182	ev_io stdin_watcher;
825		1183
826	ev_init (&stdin_watcher, my_cb);	1184	ev_init (&stdin_watcher, my_cb);
827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1185	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
828	ev_io_start (loop, &stdin_watcher);	1186	ev_io_start (loop, &stdin_watcher);
829		1187
830	ev_loop (loop, 0);	1188	ev_run (loop, 0);
831		1189
832	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
833	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
834	stack).	1192	stack).
835		1193
836	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>
837	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).
838		1196
839	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
840	(watcher *, callback)>, which expects a callback to be provided. This	1198	*, callback)>, which expects a callback to be provided. This callback is
841	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
842	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
843	is readable and/or writable).	1201	and/or writable).
844		1202
845	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 *, ...) >>
846	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
847	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<<
848	ev_TYPE_init (watcher *, callback, ...) >>.	1206	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
871	=item C<EV_WRITE>	1229	=item C<EV_WRITE>
872		1230
873	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
874	writable.	1232	writable.
875		1233
876	=item C<EV_TIMEOUT>	1234	=item C<EV_TIMER>
877		1235
878	The C<ev_timer> watcher has timed out.	1236	The C<ev_timer> watcher has timed out.
879		1237
880	=item C<EV_PERIODIC>	1238	=item C<EV_PERIODIC>
881		1239
…		…
899		1257
900	=item C<EV_PREPARE>	1258	=item C<EV_PREPARE>
901		1259
902	=item C<EV_CHECK>	1260	=item C<EV_CHECK>
903		1261
904	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
905	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)
906	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
907	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
908	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
909	(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
910	C<ev_loop> from blocking).	1273	blocking).
911		1274
912	=item C<EV_EMBED>	1275	=item C<EV_EMBED>
913		1276
914	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.
915		1278
916	=item C<EV_FORK>	1279	=item C<EV_FORK>
917		1280
918	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
919	C<ev_fork>).	1282	C<ev_fork>).
920		1283
		1284	=item C<EV_CLEANUP>
		1285
		1286	The event loop is about to be destroyed (see C<ev_cleanup>).
		1287
921	=item C<EV_ASYNC>	1288	=item C<EV_ASYNC>
922		1289
923	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>).
924		1296
925	=item C<EV_ERROR>	1297	=item C<EV_ERROR>
926		1298
927	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
928	happen because the watcher could not be properly started because libev	1300	happen because the watcher could not be properly started because libev
…		…
966		1338
967	ev_io w;	1339	ev_io w;
968	ev_init (&w, my_cb);	1340	ev_init (&w, my_cb);
969	ev_io_set (&w, STDIN_FILENO, EV_READ);	1341	ev_io_set (&w, STDIN_FILENO, EV_READ);
970		1342
971	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1343	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
972		1344
973	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
974	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
975	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
976	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
…		…
989		1361
990	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.
991		1363
992	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1364	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
993		1365
994	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1366	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
995		1367
996	Starts (activates) the given watcher. Only active watchers will receive	1368	Starts (activates) the given watcher. Only active watchers will receive
997	events. If the watcher is already active nothing will happen.	1369	events. If the watcher is already active nothing will happen.
998		1370
999	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
1000	whole section.	1372	whole section.
1001		1373
1002	ev_io_start (EV_DEFAULT_UC, &w);	1374	ev_io_start (EV_DEFAULT_UC, &w);
1003		1375
1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1376	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1005		1377
1006	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
1007	the watcher was active or not).	1379	the watcher was active or not).
1008		1380
1009	It is possible that stopped watchers are pending - for example,	1381	It is possible that stopped watchers are pending - for example,
…		…
1029		1401
1030	=item callback ev_cb (ev_TYPE *watcher)	1402	=item callback ev_cb (ev_TYPE *watcher)
1031		1403
1032	Returns the callback currently set on the watcher.	1404	Returns the callback currently set on the watcher.
1033		1405
1034	=item ev_cb_set (ev_TYPE *watcher, callback)	1406	=item ev_set_cb (ev_TYPE *watcher, callback)
1035		1407
1036	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
1037	(modulo threads).	1409	(modulo threads).
1038		1410
1039	=item ev_set_priority (ev_TYPE *watcher, priority)	1411	=item ev_set_priority (ev_TYPE *watcher, int priority)
1040		1412
1041	=item int ev_priority (ev_TYPE *watcher)	1413	=item int ev_priority (ev_TYPE *watcher)
1042		1414
1043	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
1044	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>
1045	(default: C<-2>). Pending watchers with higher priority will be invoked	1417	(default: C<-2>). Pending watchers with higher priority will be invoked
1046	before watchers with lower priority, but priority will not keep watchers	1418	before watchers with lower priority, but priority will not keep watchers
1047	from being executed (except for C<ev_idle> watchers).	1419	from being executed (except for C<ev_idle> watchers).
1048		1420
1049	This means that priorities are I<only> used for ordering callback
1050	invocation after new events have been received. This is useful, for
1051	example, to reduce latency after idling, or more often, to bind two
1052	watchers on the same event and make sure one is called first.
1053
1054	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
1055	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.
1056		1423
1057	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
1058	pending.	1425	pending.
1059
1060	The default priority used by watchers when no priority has been set is
1061	always C<0>, which is supposed to not be too high and not be too low :).
1062		1426
1063	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
1064	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
1065	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.
1066		1436
1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1437	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1068		1438
1069	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
1070	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
…		…
1078	watcher isn't pending it does nothing and returns C<0>.	1448	watcher isn't pending it does nothing and returns C<0>.
1079		1449
1080	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
1081	callback to be invoked, which can be accomplished with this function.	1451	callback to be invoked, which can be accomplished with this function.
1082		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
1083	=back	1467	=back
1084		1468
		1469	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1470	OWN COMPOSITE WATCHERS> idioms.
1085		1471
1086	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1472	=head2 WATCHER STATES
1087		1473
1088	Each watcher has, by default, a member C<void *data> that you can change	1474	There are various watcher states mentioned throughout this manual -
1089	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
1090	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
1091	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".
1092	member, you can also "subclass" the watcher type and provide your own
1093	data:
1094		1478
1095	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)
1096	{	1604	{
1097	ev_io io;	1605	// stop the I/O watcher, we received the event, but
1098	int otherfd;	1606	// are not yet ready to handle it.
1099	void *somedata;	1607	ev_io_stop (EV_A_ w);
1100	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);
1101	};	1613	}
1102		1614
1103	...	1615	static void
1104	struct my_io w;	1616	idle_cb (EV_P_ ev_idle *w, int revents)
1105	ev_io_init (&w.io, my_cb, fd, EV_READ);
1106
1107	And since your callback will be called with a pointer to the watcher, you
1108	can cast it back to your own type:
1109
1110	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1111	{	1617	{
1112	struct my_io *w = (struct my_io *)w_;	1618	// actual processing
1113	...	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);
1114	}	1624	}
1115		1625
1116	More interesting and less C-conformant ways of casting your callback type	1626	// initialisation
1117	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);
1118		1630
1119	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
1120	embedded watchers:	1632	low-priority connections can not be locked out forever under load. This
1121		1633	enables your program to keep a lower latency for important connections
1122	struct my_biggy	1634	during short periods of high load, while not completely locking out less
1123	{	1635	important ones.
1124	int some_data;
1125	ev_timer t1;
1126	ev_timer t2;
1127	}
1128
1129	In this case getting the pointer to C<my_biggy> is a bit more
1130	complicated: Either you store the address of your C<my_biggy> struct
1131	in the C<data> member of the watcher (for woozies), or you need to use
1132	some pointer arithmetic using C<offsetof> inside your watchers (for real
1133	programmers):
1134
1135	#include <stddef.h>
1136
1137	static void
1138	t1_cb (EV_P_ ev_timer *w, int revents)
1139	{
1140	struct my_biggy big = (struct my_biggy *
1141	(((char *)w) - offsetof (struct my_biggy, t1));
1142	}
1143
1144	static void
1145	t2_cb (EV_P_ ev_timer *w, int revents)
1146	{
1147	struct my_biggy big = (struct my_biggy *
1148	(((char *)w) - offsetof (struct my_biggy, t2));
1149	}
1150		1636
1151		1637
1152	=head1 WATCHER TYPES	1638	=head1 WATCHER TYPES
1153		1639
1154	This section describes each watcher in detail, but will not repeat	1640	This section describes each watcher in detail, but will not repeat
…		…
1178	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
1179	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
1180	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
1181	required if you know what you are doing).	1667	required if you know what you are doing).
1182		1668
1183	If you cannot use non-blocking mode, then force the use of a
1184	known-to-be-good backend (at the time of this writing, this includes only
1185	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1186
1187	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
1188	receive "spurious" readiness notifications, that is your callback might	1670	receive "spurious" readiness notifications, that is, your callback might
1189	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
1190	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
1191	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
1192	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
1193	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1194	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1675	preferable to a program hanging until some data arrives.
1195		1676
1196	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
1197	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
1198	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
1199	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
1200	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
1201	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
1202	indefinitely.	1683	indefinitely.
1203		1684
1204	But really, best use non-blocking mode.	1685	But really, best use non-blocking mode.
1205		1686
1206	=head3 The special problem of disappearing file descriptors	1687	=head3 The special problem of disappearing file descriptors
1207		1688
1208	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
1209	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
1210	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
1211	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
1212	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
1213	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,
1214	fact, a different file descriptor.	1695	in fact, a different file descriptor.
1215		1696
1216	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
1217	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
1218	will assume that this is potentially a new file descriptor, otherwise	1699	will assume that this is potentially a new file descriptor, otherwise
1219	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
…		…
1233		1714
1234	There is no workaround possible except not registering events	1715	There is no workaround possible except not registering events
1235	for potentially C<dup ()>'ed file descriptors, or to resort to	1716	for potentially C<dup ()>'ed file descriptors, or to resort to
1236	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1717	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1237		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
1238	=head3 The special problem of fork	1752	=head3 The special problem of fork
1239		1753
1240	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1754	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1241	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
1242	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.
1243		1758
1244	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
1245	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
1246	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1761	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1247	C<EVBACKEND_POLL>.
1248		1762
1249	=head3 The special problem of SIGPIPE	1763	=head3 The special problem of SIGPIPE
1250		1764
1251	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>:
1252	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
…		…
1255		1769
1256	So when you encounter spurious, unexplained daemon exits, make sure you	1770	So when you encounter spurious, unexplained daemon exits, make sure you
1257	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
1258	somewhere, as that would have given you a big clue).	1772	somewhere, as that would have given you a big clue).
1259		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.
1260		1812
1261	=head3 Watcher-Specific Functions	1813	=head3 Watcher-Specific Functions
1262		1814
1263	=over 4	1815	=over 4
1264		1816
…		…
1296	...	1848	...
1297	struct ev_loop *loop = ev_default_init (0);	1849	struct ev_loop *loop = ev_default_init (0);
1298	ev_io stdin_readable;	1850	ev_io stdin_readable;
1299	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);
1300	ev_io_start (loop, &stdin_readable);	1852	ev_io_start (loop, &stdin_readable);
1301	ev_loop (loop, 0);	1853	ev_run (loop, 0);
1302		1854
1303		1855
1304	=head2 C<ev_timer> - relative and optionally repeating timeouts	1856	=head2 C<ev_timer> - relative and optionally repeating timeouts
1305		1857
1306	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
…		…
1311	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
1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1864	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1313	monotonic clock option helps a lot here).	1865	monotonic clock option helps a lot here).
1314		1866
1315	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
1316	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
1317	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).
1318		1874
1319	=head3 Be smart about timeouts	1875	=head3 Be smart about timeouts
1320		1876
1321	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
1322	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,
…		…
1366	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>
1367	member and C<ev_timer_again>.	1923	member and C<ev_timer_again>.
1368		1924
1369	At start:	1925	At start:
1370		1926
1371	ev_timer_init (timer, callback);	1927	ev_init (timer, callback);
1372	timer->repeat = 60.;	1928	timer->repeat = 60.;
1373	ev_timer_again (loop, timer);	1929	ev_timer_again (loop, timer);
1374		1930
1375	Each time there is some activity:	1931	Each time there is some activity:
1376		1932
…		…
1397		1953
1398	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,
1399	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
1400	within the callback:	1956	within the callback:
1401		1957
		1958	ev_tstamp timeout = 60.;
1402	ev_tstamp last_activity; // time of last activity	1959	ev_tstamp last_activity; // time of last activity
		1960	ev_timer timer;
1403		1961
1404	static void	1962	static void
1405	callback (EV_P_ ev_timer *w, int revents)	1963	callback (EV_P_ ev_timer *w, int revents)
1406	{	1964	{
1407	ev_tstamp now = ev_now (EV_A);	1965	// calculate when the timeout would happen
1408	ev_tstamp timeout = last_activity + 60.;	1966	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1409		1967
1410	// if last_activity + 60. is older than now, we did time out	1968	// if negative, it means we the timeout already occurred
1411	if (timeout < now)	1969	if (after < 0.)
1412	{	1970	{
1413	// timeout occured, take action	1971	// timeout occurred, take action
1414	}	1972	}
1415	else	1973	else
1416	{	1974	{
1417	// callback was invoked, but there was some activity, re-arm	1975	// callback was invoked, but there was some recent
1418	// the watcher to fire in last_activity + 60, which is	1976	// activity. simply restart the timer to time out
1419	// guaranteed to be in the future, so "again" is positive:	1977	// after "after" seconds, which is the earliest time
1420	w->again = timeout - now;	1978	// the timeout can occur.
		1979	ev_timer_set (w, after, 0.);
1421	ev_timer_again (EV_A_ w);	1980	ev_timer_start (EV_A_ w);
1422	}	1981	}
1423	}	1982	}
1424		1983
1425	To summarise the callback: first calculate the real timeout (defined	1984	To summarise the callback: first calculate in how many seconds the
1426	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,
1427	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
1428	the callback was invoked too early (C<timeout> is in the future), so	1987	(EV_A)> from that).
1429	re-schedule the timer to fire at that future time, to see if maybe we have
1430	a timeout then.
1431		1988
1432	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
1433	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.
1434		1998
1435	This scheme causes more callback invocations (about one every 60 seconds	1999	This scheme causes more callback invocations (about one every 60 seconds
1436	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
1437	libev to change the timeout.	2001	libev to change the timeout.
1438		2002
1439	To start the timer, simply initialise the watcher and set C<last_activity>	2003	To start the machinery, simply initialise the watcher and set
1440	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
1441	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:
1442		2007
		2008	last_activity = ev_now (EV_A);
1443	ev_timer_init (timer, callback);	2009	ev_init (&timer, callback);
1444	last_activity = ev_now (loop);	2010	callback (EV_A_ &timer, 0);
1445	callback (loop, timer, EV_TIMEOUT);
1446		2011
1447	And when there is some activity, simply store the current time in	2012	When there is some activity, simply store the current time in
1448	C<last_activity>, no libev calls at all:	2013	C<last_activity>, no libev calls at all:
1449		2014
		2015	if (activity detected)
1450	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);
1451		2025
1452	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
1453	time-out is unlikely to be triggered, much more efficient.	2027	time-out is unlikely to be triggered, much more efficient.
1454
1455	Changing the timeout is trivial as well (if it isn't hard-coded in the
1456	callback :) - just change the timeout and invoke the callback, which will
1457	fix things for you.
1458		2028
1459	=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.
1460		2030
1461	If there is not one request, but many thousands (millions...), all	2031	If there is not one request, but many thousands (millions...), all
1462	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
…		…
1489	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
1490	rather complicated, but extremely efficient, something that really pays	2060	rather complicated, but extremely efficient, something that really pays
1491	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
1492	overkill :)	2062	overkill :)
1493		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
1494	=head3 The special problem of time updates	2101	=head3 The special problem of time updates
1495		2102
1496	Establishing the current time is a costly operation (it usually takes at	2103	Establishing the current time is a costly operation (it usually takes
1497	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
1498	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
1499	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
1500	lots of events in one iteration.	2107	lots of events in one iteration.
1501		2108
1502	The relative timeouts are calculated relative to the C<ev_now ()>	2109	The relative timeouts are calculated relative to the C<ev_now ()>
1503	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
1504	of the event triggering whatever timeout you are modifying/starting. If	2111	of the event triggering whatever timeout you are modifying/starting. If
1505	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
1506	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:
1507		2115
1508	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2116	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1509		2117
1510	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
1511	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
1512	()>.	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>).
1513		2185
1514	=head3 Watcher-Specific Functions and Data Members	2186	=head3 Watcher-Specific Functions and Data Members
1515		2187
1516	=over 4	2188	=over 4
1517		2189
1518	=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)
1519		2191
1520	=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)
1521		2193
1522	Configure the timer to trigger after C<after> seconds. If C<repeat>	2194	Configure the timer to trigger after C<after> seconds (fractional and
1523	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
1524	reached. If it is positive, then the timer will automatically be	2196	automatically be stopped once the timeout is reached. If it is positive,
1525	configured to trigger again C<repeat> seconds later, again, and again,	2197	then the timer will automatically be configured to trigger again C<repeat>
1526	until stopped manually.	2198	seconds later, again, and again, until stopped manually.
1527		2199
1528	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
1529	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
1530	trigger at exactly 10 second intervals. If, however, your program cannot	2202	trigger at exactly 10 second intervals. If, however, your program cannot
1531	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
1532	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.
1533		2205
1534	=item ev_timer_again (loop, ev_timer *)	2206	=item ev_timer_again (loop, ev_timer *)
1535		2207
1536	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
1537	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>.
1538		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
1539	If the timer is pending, its pending status is cleared.	2217	=item If the timer is pending, the pending status is always cleared.
1540		2218
1541	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).
1542		2221
1543	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
1544	C<repeat> value), or reset the running timer to the C<repeat> value.	2223	and start the timer, if necessary.
1545		2224
		2225	=back
		2226
1546	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
1547	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.
1548		2241
1549	=item ev_tstamp repeat [read-write]	2242	=item ev_tstamp repeat [read-write]
1550		2243
1551	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
1552	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),
…		…
1578	}	2271	}
1579		2272
1580	ev_timer mytimer;	2273	ev_timer mytimer;
1581	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 */
1582	ev_timer_again (&mytimer); /* start timer */	2275	ev_timer_again (&mytimer); /* start timer */
1583	ev_loop (loop, 0);	2276	ev_run (loop, 0);
1584		2277
1585	// 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":
1586	// reset the timeout to start ticking again at 10 seconds	2279	// reset the timeout to start ticking again at 10 seconds
1587	ev_timer_again (&mytimer);	2280	ev_timer_again (&mytimer);
1588		2281
…		…
1590	=head2 C<ev_periodic> - to cron or not to cron?	2283	=head2 C<ev_periodic> - to cron or not to cron?
1591		2284
1592	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
1593	(and unfortunately a bit complex).	2286	(and unfortunately a bit complex).
1594		2287
1595	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
1596	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
1597	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
1598	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
1599	+ 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
1600	clock to January of the previous year, then it will take more than year	2293	wrist-watch).
1601	to trigger the event (unlike an C<ev_timer>, which would still trigger
1602	roughly 10 seconds later as it uses a relative timeout).
1603		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
1604	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
1605	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
1606	complicated rules.	2305	other complicated rules. This cannot easily be done with C<ev_timer>
		2306	watchers, as those cannot react to time jumps.
1607		2307
1608	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
1609	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
1610	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).
1611		2313
1612	=head3 Watcher-Specific Functions and Data Members	2314	=head3 Watcher-Specific Functions and Data Members
1613		2315
1614	=over 4	2316	=over 4
1615		2317
1616	=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)
1617		2319
1618	=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)
1619		2321
1620	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
1621	operation, and we will explain them from simplest to most complex:	2323	operation, and we will explain them from simplest to most complex:
1622		2324
1623	=over 4	2325	=over 4
1624		2326
1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)	2327	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1626		2328
1627	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
1628	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
1629	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
1630	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.
1631		2334
1632	=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)
1633		2336
1634	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
1635	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
1636	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.
1637		2341
1638	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
1639	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
1640	hour, on the hour:	2344	hour, on the hour (with respect to UTC):
1641		2345
1642	ev_periodic_set (&periodic, 0., 3600., 0);	2346	ev_periodic_set (&periodic, 0., 3600., 0);
1643		2347
1644	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,
1645	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
1646	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
1647	by 3600.	2351	by 3600.
1648		2352
1649	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
1650	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
1651	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.
1652		2356
1653	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
1654	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
1655	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.
1656		2363
1657	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
1658	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
1659	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
1660	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).
1661		2368
1662	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	2369	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1663		2370
1664	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
1665	ignored. Instead, each time the periodic watcher gets scheduled, the	2372	ignored. Instead, each time the periodic watcher gets scheduled, the
1666	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
1667	current time as second argument.	2374	current time as second argument.
1668		2375
1669	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,
1670	ever, or make ANY event loop modifications whatsoever>.	2377	or make ANY other event loop modifications whatsoever, unless explicitly
		2378	allowed by documentation here>.
1671		2379
1672	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
1673	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
1674	only event loop modification you are allowed to do).	2382	only event loop modification you are allowed to do).
1675		2383
…		…
1689		2397
1690	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
1691	equal to the passed C<now> value >>.	2399	equal to the passed C<now> value >>.
1692		2400
1693	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
1694	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
1695	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
1696	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
1697	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).
1698		2424
1699	=back	2425	=back
1700		2426
1701	=item ev_periodic_again (loop, ev_periodic *)	2427	=item ev_periodic_again (loop, ev_periodic *)
1702		2428
…		…
1705	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
1706	program when the crontabs have changed).	2432	program when the crontabs have changed).
1707		2433
1708	=item ev_tstamp ev_periodic_at (ev_periodic *)	2434	=item ev_tstamp ev_periodic_at (ev_periodic *)
1709		2435
1710	When active, returns the absolute time that the watcher is supposed to	2436	When active, returns the absolute time that the watcher is supposed
1711	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.
1712		2440
1713	=item ev_tstamp offset [read-write]	2441	=item ev_tstamp offset [read-write]
1714		2442
1715	When repeating, this contains the offset value, otherwise this is the	2443	When repeating, this contains the offset value, otherwise this is the
1716	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).
1717		2446
1718	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
1719	timer fires or C<ev_periodic_again> is being called.	2448	timer fires or C<ev_periodic_again> is being called.
1720		2449
1721	=item ev_tstamp interval [read-write]	2450	=item ev_tstamp interval [read-write]
…		…
1737	Example: Call a callback every hour, or, more precisely, whenever the	2466	Example: Call a callback every hour, or, more precisely, whenever the
1738	system time is divisible by 3600. The callback invocation times have	2467	system time is divisible by 3600. The callback invocation times have
1739	potentially a lot of jitter, but good long-term stability.	2468	potentially a lot of jitter, but good long-term stability.
1740		2469
1741	static void	2470	static void
1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2471	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1743	{	2472	{
1744	... 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)
1745	}	2474	}
1746		2475
1747	ev_periodic hourly_tick;	2476	ev_periodic hourly_tick;
…		…
1764		2493
1765	ev_periodic hourly_tick;	2494	ev_periodic hourly_tick;
1766	ev_periodic_init (&hourly_tick, clock_cb,	2495	ev_periodic_init (&hourly_tick, clock_cb,
1767	fmod (ev_now (loop), 3600.), 3600., 0);	2496	fmod (ev_now (loop), 3600.), 3600., 0);
1768	ev_periodic_start (loop, &hourly_tick);	2497	ev_periodic_start (loop, &hourly_tick);
1769		2498
1770		2499
1771	=head2 C<ev_signal> - signal me when a signal gets signalled!	2500	=head2 C<ev_signal> - signal me when a signal gets signalled!
1772		2501
1773	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
1774	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
1775	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
1776	normal event processing, like any other event.	2505	normal event processing, like any other event.
1777		2506
1778	If you want signals asynchronously, just use C<sigaction> as you would	2507	If you want signals to be delivered truly asynchronously, just use
1779	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
1780	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.
1781		2511
1782	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
1783	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
1784	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
1785	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
1786	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.
1787	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.
1788		2521
1789	If possible and supported, libev will install its handlers with	2522	If possible and supported, libev will install its handlers with
1790	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2523	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1791	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
1792	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
1793	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>.
1794		2571
1795	=head3 Watcher-Specific Functions and Data Members	2572	=head3 Watcher-Specific Functions and Data Members
1796		2573
1797	=over 4	2574	=over 4
1798		2575
…		…
1814	Example: Try to exit cleanly on SIGINT.	2591	Example: Try to exit cleanly on SIGINT.
1815		2592
1816	static void	2593	static void
1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2594	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1818	{	2595	{
1819	ev_unloop (loop, EVUNLOOP_ALL);	2596	ev_break (loop, EVBREAK_ALL);
1820	}	2597	}
1821		2598
1822	ev_signal signal_watcher;	2599	ev_signal signal_watcher;
1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2600	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1824	ev_signal_start (loop, &signal_watcher);	2601	ev_signal_start (loop, &signal_watcher);
…		…
1830	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
1831	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
1832	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
1833	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.,
1834	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,
1835	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
1836	not.	2613	in the next callback invocation is not.
1837		2614
1838	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
1839	you can only register child watchers in the default event loop.	2616	you can only register child watchers in the default event loop.
1840		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
1841	=head3 Process Interaction	2622	=head3 Process Interaction
1842		2623
1843	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
1844	initialised. This is necessary to guarantee proper behaviour even if	2625	initialised. This is necessary to guarantee proper behaviour even if the
1845	the first child watcher is started after the child exits. The occurrence	2626	first child watcher is started after the child exits. The occurrence
1846	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2627	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1847	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
1848	children, even ones not watched.	2629	children, even ones not watched.
1849		2630
1850	=head3 Overriding the Built-In Processing	2631	=head3 Overriding the Built-In Processing
…		…
1860	=head3 Stopping the Child Watcher	2641	=head3 Stopping the Child Watcher
1861		2642
1862	Currently, the child watcher never gets stopped, even when the	2643	Currently, the child watcher never gets stopped, even when the
1863	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
1864	callback. Future versions of libev might stop the watcher automatically	2645	callback. Future versions of libev might stop the watcher automatically
1865	when a child exit is detected.	2646	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2647	problem).
1866		2648
1867	=head3 Watcher-Specific Functions and Data Members	2649	=head3 Watcher-Specific Functions and Data Members
1868		2650
1869	=over 4	2651	=over 4
1870		2652
…		…
1928		2710
1929	=head2 C<ev_stat> - did the file attributes just change?	2711	=head2 C<ev_stat> - did the file attributes just change?
1930		2712
1931	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
1932	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)
1933	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
1934	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.
1935		2718
1936	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
1937	not exist" is a status change like any other. The condition "path does not	2720	not exist" is a status change like any other. The condition "path does not
1938	exist" (or more correctly "path cannot be stat'ed") is signified by the	2721	exist" (or more correctly "path cannot be stat'ed") is signified by the
1939	C<st_nlink> field being zero (which is otherwise always forced to be at	2722	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
1997		2780
1998	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
1999	implement this functionality, due to the requirement of having a file	2782	implement this functionality, due to the requirement of having a file
2000	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
2001	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.
2002		2803
2003	=head3 The special problem of stat time resolution	2804	=head3 The special problem of stat time resolution
2004		2805
2005	The C<stat ()> system call only supports full-second resolution portably,	2806	The C<stat ()> system call only supports full-second resolution portably,
2006	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
…		…
2151	Apart from keeping your process non-blocking (which is a useful	2952	Apart from keeping your process non-blocking (which is a useful
2152	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
2153	"pseudo-background processing", or delay processing stuff to after the	2954	"pseudo-background processing", or delay processing stuff to after the
2154	event loop has handled all outstanding events.	2955	event loop has handled all outstanding events.
2155		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
2156	=head3 Watcher-Specific Functions and Data Members	2971	=head3 Watcher-Specific Functions and Data Members
2157		2972
2158	=over 4	2973	=over 4
2159		2974
2160	=item ev_idle_init (ev_signal *, callback)	2975	=item ev_idle_init (ev_idle *, callback)
2161		2976
2162	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
2163	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,
2164	believe me.	2979	believe me.
2165		2980
…		…
2171	callback, free it. Also, use no error checking, as usual.	2986	callback, free it. Also, use no error checking, as usual.
2172		2987
2173	static void	2988	static void
2174	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2989	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2175	{	2990	{
		2991	// stop the watcher
		2992	ev_idle_stop (loop, w);
		2993
		2994	// now we can free it
2176	free (w);	2995	free (w);
		2996
2177	// now do something you wanted to do when the program has	2997	// now do something you wanted to do when the program has
2178	// no longer anything immediate to do.	2998	// no longer anything immediate to do.
2179	}	2999	}
2180		3000
2181	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3001	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
2182	ev_idle_init (idle_watcher, idle_cb);	3002	ev_idle_init (idle_watcher, idle_cb);
2183	ev_idle_start (loop, idle_cb);	3003	ev_idle_start (loop, idle_watcher);
2184		3004
2185		3005
2186	=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!
2187		3007
2188	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:
2189	prepare watchers get invoked before the process blocks and check watchers	3009	prepare watchers get invoked before the process blocks and check watchers
2190	afterwards.	3010	afterwards.
2191		3011
2192	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
2193	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
2194	watchers. Other loops than the current one are fine, however. The	3014	C<ev_check> watchers. Other loops than the current one are fine,
2195	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
2196	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
2197	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
2198	called in pairs bracketing the blocking call.	3018	kind they will always be called in pairs bracketing the blocking call.
2199		3019
2200	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
2201	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
2202	variable changes, implement your own watchers, integrate net-snmp or a	3022	variable changes, implement your own watchers, integrate net-snmp or a
2203	coroutine library and lots more. They are also occasionally useful if	3023	coroutine library and lots more. They are also occasionally useful if
…		…
2221	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
2222	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
2223	loop from blocking if lower-priority coroutines are active, thus mapping	3043	loop from blocking if lower-priority coroutines are active, thus mapping
2224	low-priority coroutines to idle/background tasks).	3044	low-priority coroutines to idle/background tasks).
2225		3045
2226	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
2227	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
2228	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).
2229		3050
2230	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
2231	activate ("feed") events into libev. While libev fully supports this, they	3052	activate ("feed") events into libev. While libev fully supports this, they
2232	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
2233	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
2234	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
2235	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
2236	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.
2237		3077
2238	=head3 Watcher-Specific Functions and Data Members	3078	=head3 Watcher-Specific Functions and Data Members
2239		3079
2240	=over 4	3080	=over 4
2241		3081
…		…
2281	struct pollfd fds [nfd];	3121	struct pollfd fds [nfd];
2282	// actual code will need to loop here and realloc etc.	3122	// actual code will need to loop here and realloc etc.
2283	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	3123	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2284		3124
2285	/* 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 */
2286	ev_timer_init (&tw, 0, timeout * 1e-3);	3126	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2287	ev_timer_start (loop, &tw);	3127	ev_timer_start (loop, &tw);
2288		3128
2289	// create one ev_io per pollfd	3129	// create one ev_io per pollfd
2290	for (int i = 0; i < nfd; ++i)	3130	for (int i = 0; i < nfd; ++i)
2291	{	3131	{
…		…
2365		3205
2366	if (timeout >= 0)	3206	if (timeout >= 0)
2367	// create/start timer	3207	// create/start timer
2368		3208
2369	// poll	3209	// poll
2370	ev_loop (EV_A_ 0);	3210	ev_run (EV_A_ 0);
2371		3211
2372	// stop timer again	3212	// stop timer again
2373	if (timeout >= 0)	3213	if (timeout >= 0)
2374	ev_timer_stop (EV_A_ &to);	3214	ev_timer_stop (EV_A_ &to);
2375		3215
…		…
2404	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),
2405	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
2406	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
2407	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.
2408		3248
2409	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
2410	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
2411	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
2412	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
2413	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
2414	to C<0>, in which case the embed watcher will automatically execute the	3254	to give the embedded loop strictly lower priority for example).
2415	embedded loop sweep.
2416		3255
2417	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
2418	callback will be invoked whenever some events have been handled. You can	3257	will automatically execute the embedded loop sweep whenever necessary.
2419	set the callback to C<0> to avoid having to specify one if you are not
2420	interested in that.
2421		3258
2422	Also, there have not currently been made special provisions for forking:	3259	Fork detection will be handled transparently while the C<ev_embed> watcher
2423	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
2424	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
2425	yourself - but you can use a fork watcher to handle this automatically,	3262	C<ev_loop_fork> on the embedded loop.
2426	and future versions of libev might do just that.
2427		3263
2428	Unfortunately, not all backends are embeddable: only the ones returned by	3264	Unfortunately, not all backends are embeddable: only the ones returned by
2429	C<ev_embeddable_backends> are, which, unfortunately, does not include any	3265	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2430	portable one.	3266	portable one.
2431		3267
…		…
2446		3282
2447	=over 4	3283	=over 4
2448		3284
2449	=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)
2450		3286
2451	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3287	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2452		3288
2453	Configures the watcher to embed the given loop, which must be	3289	Configures the watcher to embed the given loop, which must be
2454	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
2455	invoked automatically, otherwise it is the responsibility of the callback	3291	invoked automatically, otherwise it is the responsibility of the callback
2456	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,
2457	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).
2458		3294
2459	=item ev_embed_sweep (loop, ev_embed *)	3295	=item ev_embed_sweep (loop, ev_embed *)
2460		3296
2461	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
2462	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
2463	appropriate way for embedded loops.	3299	appropriate way for embedded loops.
2464		3300
2465	=item struct ev_loop *other [read-only]	3301	=item struct ev_loop *other [read-only]
2466		3302
2467	The embedded event loop.	3303	The embedded event loop.
…		…
2477	used).	3313	used).
2478		3314
2479	struct ev_loop *loop_hi = ev_default_init (0);	3315	struct ev_loop *loop_hi = ev_default_init (0);
2480	struct ev_loop *loop_lo = 0;	3316	struct ev_loop *loop_lo = 0;
2481	ev_embed embed;	3317	ev_embed embed;
2482		3318
2483	// see if there is a chance of getting one that works	3319	// see if there is a chance of getting one that works
2484	// (remember that a flags value of 0 means autodetection)	3320	// (remember that a flags value of 0 means autodetection)
2485	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3321	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2486	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3322	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2487	: 0;	3323	: 0;
…		…
2501	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3337	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2502		3338
2503	struct ev_loop *loop = ev_default_init (0);	3339	struct ev_loop *loop = ev_default_init (0);
2504	struct ev_loop *loop_socket = 0;	3340	struct ev_loop *loop_socket = 0;
2505	ev_embed embed;	3341	ev_embed embed;
2506		3342
2507	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3343	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2508	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3344	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2509	{	3345	{
2510	ev_embed_init (&embed, 0, loop_socket);	3346	ev_embed_init (&embed, 0, loop_socket);
2511	ev_embed_start (loop, &embed);	3347	ev_embed_start (loop, &embed);
…		…
2519		3355
2520	=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
2521		3357
2522	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
2523	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
2524	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
2525	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
2526	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
2527	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,
2528	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.
2529		3399
2530	=head3 Watcher-Specific Functions and Data Members	3400	=head3 Watcher-Specific Functions and Data Members
2531		3401
2532	=over 4	3402	=over 4
2533		3403
2534	=item ev_fork_init (ev_signal *, callback)	3404	=item ev_fork_init (ev_fork *, callback)
2535		3405
2536	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
2537	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,
2538	believe me.	3408	really.
2539		3409
2540	=back	3410	=back
2541		3411
2542		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
2543	=head2 C<ev_async> - how to wake up another event loop	3453	=head2 C<ev_async> - how to wake up an event loop
2544		3454
2545	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
2546	asynchronous sources such as signal handlers (as opposed to multiple event	3456	asynchronous sources such as signal handlers (as opposed to multiple event
2547	loops - those are of course safe to use in different threads).	3457	loops - those are of course safe to use in different threads).
2548		3458
2549	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,
2550	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>
2551	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
2552	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.
2553	safe.
2554		3463
2555	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,
2556	too, are asynchronous in nature, and signals, too, will be compressed	3465	too, are asynchronous in nature, and signals, too, will be compressed
2557	(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
2558	C<ev_async_sent> calls).	3467	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2559		3468	of "global async watchers" by using a watcher on an otherwise unused
2560	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,
2561	just the default loop.	3470	even without knowing which loop owns the signal.
2562		3471
2563	=head3 Queueing	3472	=head3 Queueing
2564		3473
2565	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
2566	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
2567	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
2568	need elaborate support such as pthreads.	3477	need elaborate support such as pthreads or unportable memory access
		3478	semantics.
2569		3479
2570	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
2571	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
2572	queue:	3482	queue:
2573		3483
…		…
2657	trust me.	3567	trust me.
2658		3568
2659	=item ev_async_send (loop, ev_async *)	3569	=item ev_async_send (loop, ev_async *)
2660		3570
2661	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
2662	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
2663	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,
2664	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
2665	section below on what exactly this means).	3577	embedding section below on what exactly this means).
2666		3578
2667	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
2668	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
2669	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.
2670		3590
2671	=item bool = ev_async_pending (ev_async *)	3591	=item bool = ev_async_pending (ev_async *)
2672		3592
2673	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
2674	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
…		…
2677	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
2678	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,
2679	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
2680	quickly check whether invoking the loop might be a good idea.	3600	quickly check whether invoking the loop might be a good idea.
2681		3601
2682	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,
2683	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.
2684		3606
2685	=back	3607	=back
2686		3608
2687		3609
2688	=head1 OTHER FUNCTIONS	3610	=head1 OTHER FUNCTIONS
2689		3611
2690	There are some other functions of possible interest. Described. Here. Now.	3612	There are some other functions of possible interest. Described. Here. Now.
2691		3613
2692	=over 4	3614	=over 4
2693		3615
2694	=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)
2695		3617
2696	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
2697	callback on whichever event happens first and automatically stops both	3619	callback on whichever event happens first and automatically stops both
2698	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
2699	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
…		…
2705		3627
2706	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
2707	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
2708	repeat = 0) will be started. C<0> is a valid timeout.	3630	repeat = 0) will be started. C<0> is a valid timeout.
2709		3631
2710	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
2711	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
2712	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>
2713	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>
2714	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
2715	events precedence.	3637	events precedence.
2716		3638
2717	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.
2718		3640
2719	static void stdin_ready (int revents, void *arg)	3641	static void stdin_ready (int revents, void *arg)
2720	{	3642	{
2721	if (revents & EV_READ)	3643	if (revents & EV_READ)
2722	/* stdin might have data for us, joy! */;	3644	/* stdin might have data for us, joy! */;
2723	else if (revents & EV_TIMEOUT)	3645	else if (revents & EV_TIMER)
2724	/* doh, nothing entered */;	3646	/* doh, nothing entered */;
2725	}	3647	}
2726		3648
2727	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3649	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2728		3650
2729	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2730
2731	Feeds the given event set into the event loop, as if the specified event
2732	had happened for the specified watcher (which must be a pointer to an
2733	initialised but not necessarily started event watcher).
2734
2735	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3651	=item ev_feed_fd_event (loop, int fd, int revents)
2736		3652
2737	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
2738	the given events it.	3654	the given events.
2739		3655
2740	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3656	=item ev_feed_signal_event (loop, int signum)
2741		3657
2742	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>,
2743	loop!).	3659	which is async-safe.
2744		3660
2745	=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.
2746		4012
2747		4013
2748	=head1 LIBEVENT EMULATION	4014	=head1 LIBEVENT EMULATION
2749		4015
2750	Libev offers a compatibility emulation layer for libevent. It cannot	4016	Libev offers a compatibility emulation layer for libevent. It cannot
2751	emulate the internals of libevent, so here are some usage hints:	4017	emulate the internals of libevent, so here are some usage hints:
2752		4018
2753	=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.
2754		4025
2755	=item * Use it by including <event.h>, as usual.	4026	=item * Use it by including <event.h>, as usual.
2756		4027
2757	=item * The following members are fully supported: ev_base, ev_callback,	4028	=item * The following members are fully supported: ev_base, ev_callback,
2758	ev_arg, ev_fd, ev_res, ev_events.	4029	ev_arg, ev_fd, ev_res, ev_events.
…		…
2764	=item * Priorities are not currently supported. Initialising priorities	4035	=item * Priorities are not currently supported. Initialising priorities
2765	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
2766	is an ev_pri field.	4037	is an ev_pri field.
2767		4038
2768	=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
2769	first base created (== the default loop) gets the signals.	4040	base that registered the signal gets the signals.
2770		4041
2771	=item * Other members are not supported.	4042	=item * Other members are not supported.
2772		4043
2773	=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
2774	to use the libev header file and library.	4045	to use the libev header file and library.
2775		4046
2776	=back	4047	=back
2777		4048
2778	=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
2779		4083
2780	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
2781	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
2782	the callback model to a model using method callbacks on objects.	4086	the callback model to a model using method callbacks on objects.
2783		4087
2784	To use it,	4088	To use it,
2785		4089
2786	#include <ev++.h>	4090	#include <ev++.h>
2787		4091
2788	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
2789	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
2790	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
…		…
2793	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++
2794	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
2795	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
2796	you disable C<EV_MULTIPLICITY> when embedding libev).	4100	you disable C<EV_MULTIPLICITY> when embedding libev).
2797		4101
2798	Currently, functions, and static and non-static member functions can be	4102	Currently, functions, static and non-static member functions and classes
2799	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
2800	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
2801	types of functors please contact the author (preferably after implementing	4105	you need support for other types of functors please contact the author
2802	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++.
2803		4111
2804	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:
2805		4113
2806	=over 4	4114	=over 4
2807		4115
…		…
2817	=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.
2818		4126
2819	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
2820	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>
2821	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
2822	defines by many implementations.	4130	defined by many implementations.
2823		4131
2824	All of those classes have these methods:	4132	All of those classes have these methods:
2825		4133
2826	=over 4	4134	=over 4
2827		4135
2828	=item ev::TYPE::TYPE ()	4136	=item ev::TYPE::TYPE ()
2829		4137
2830	=item ev::TYPE::TYPE (struct ev_loop *)	4138	=item ev::TYPE::TYPE (loop)
2831		4139
2832	=item ev::TYPE::~TYPE	4140	=item ev::TYPE::~TYPE
2833		4141
2834	The constructor (optionally) takes an event loop to associate the watcher	4142	The constructor (optionally) takes an event loop to associate the watcher
2835	with. If it is omitted, it will use C<EV_DEFAULT>.	4143	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
2867		4175
2868	myclass obj;	4176	myclass obj;
2869	ev::io iow;	4177	ev::io iow;
2870	iow.set <myclass, &myclass::io_cb> (&obj);	4178	iow.set <myclass, &myclass::io_cb> (&obj);
2871		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
2872	=item w->set<function> (void *data = 0)	4208	=item w->set<function> (void *data = 0)
2873		4209
2874	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
2875	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
2876	C<data> member and is free for you to use.	4212	C<data> member and is free for you to use.
…		…
2882	Example: Use a plain function as callback.	4218	Example: Use a plain function as callback.
2883		4219
2884	static void io_cb (ev::io &w, int revents) { }	4220	static void io_cb (ev::io &w, int revents) { }
2885	iow.set <io_cb> ();	4221	iow.set <io_cb> ();
2886		4222
2887	=item w->set (struct ev_loop *)	4223	=item w->set (loop)
2888		4224
2889	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
2890	do this when the watcher is inactive (and not pending either).	4226	do this when the watcher is inactive (and not pending either).
2891		4227
2892	=item w->set ([arguments])	4228	=item w->set ([arguments])
2893		4229
2894	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
2895	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
2896	automatically stopped and restarted when reconfiguring it with this	4233	gets automatically stopped and restarted when reconfiguring it with this
2897	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.
2898		4238
2899	=item w->start ()	4239	=item w->start ()
2900		4240
2901	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
2902	constructor already stores the event loop.	4242	constructor already stores the event loop.
2903		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
2904	=item w->stop ()	4250	=item w->stop ()
2905		4251
2906	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.
2907		4253
2908	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4254	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
2920		4266
2921	=back	4267	=back
2922		4268
2923	=back	4269	=back
2924		4270
2925	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
2926	the constructor.	4272	watchers in the constructor.
2927		4273
2928	class myclass	4274	class myclass
2929	{	4275	{
2930	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);
2931	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4278	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2932		4279
2933	myclass (int fd)	4280	myclass (int fd)
2934	{	4281	{
2935	io .set <myclass, &myclass::io_cb > (this);	4282	io .set <myclass, &myclass::io_cb > (this);
		4283	io2 .set <myclass, &myclass::io2_cb > (this);
2936	idle.set <myclass, &myclass::idle_cb> (this);	4284	idle.set <myclass, &myclass::idle_cb> (this);
2937		4285
2938	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
2939	}	4290	}
2940	};	4291	};
2941		4292
2942		4293
2943	=head1 OTHER LANGUAGE BINDINGS	4294	=head1 OTHER LANGUAGE BINDINGS
…		…
2962	L<http://software.schmorp.de/pkg/EV>.	4313	L<http://software.schmorp.de/pkg/EV>.
2963		4314
2964	=item Python	4315	=item Python
2965		4316
2966	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
2967	seems to be quite complete and well-documented. Note, however, that the	4318	seems to be quite complete and well-documented.
2968	patch they require for libev is outright dangerous as it breaks the ABI
2969	for everybody else, and therefore, should never be applied in an installed
2970	libev (if python requires an incompatible ABI then it needs to embed
2971	libev).
2972		4319
2973	=item Ruby	4320	=item Ruby
2974		4321
2975	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
2976	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
2977	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
2978	L<http://rev.rubyforge.org/>.	4325	L<http://rev.rubyforge.org/>.
2979		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
2980	=item D	4335	=item D
2981		4336
2982	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
2983	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>.
2984		4339
2985	=item Ocaml	4340	=item Ocaml
2986		4341
2987	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
2988	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.
2989		4358
2990	=back	4359	=back
2991		4360
2992		4361
2993	=head1 MACRO MAGIC	4362	=head1 MACRO MAGIC
…		…
3007	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,
3008	C<EV_A_> is used when other arguments are following. Example:	4377	C<EV_A_> is used when other arguments are following. Example:
3009		4378
3010	ev_unref (EV_A);	4379	ev_unref (EV_A);
3011	ev_timer_add (EV_A_ watcher);	4380	ev_timer_add (EV_A_ watcher);
3012	ev_loop (EV_A_ 0);	4381	ev_run (EV_A_ 0);
3013		4382
3014	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,
3015	which is often provided by the following macro.	4384	which is often provided by the following macro.
3016		4385
3017	=item C<EV_P>, C<EV_P_>	4386	=item C<EV_P>, C<EV_P_>
…		…
3030	suitable for use with C<EV_A>.	4399	suitable for use with C<EV_A>.
3031		4400
3032	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4401	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3033		4402
3034	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
3035	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.
3036		4409
3037	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4410	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3038		4411
3039	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
3040	default loop has been initialised (C<UC> == unchecked). Their behaviour	4413	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3057	}	4430	}
3058		4431
3059	ev_check check;	4432	ev_check check;
3060	ev_check_init (&check, check_cb);	4433	ev_check_init (&check, check_cb);
3061	ev_check_start (EV_DEFAULT_ &check);	4434	ev_check_start (EV_DEFAULT_ &check);
3062	ev_loop (EV_DEFAULT_ 0);	4435	ev_run (EV_DEFAULT_ 0);
3063		4436
3064	=head1 EMBEDDING	4437	=head1 EMBEDDING
3065		4438
3066	Libev can (and often is) directly embedded into host	4439	Libev can (and often is) directly embedded into host
3067	applications. Examples of applications that embed it include the Deliantra	4440	applications. Examples of applications that embed it include the Deliantra
…		…
3107	ev_vars.h	4480	ev_vars.h
3108	ev_wrap.h	4481	ev_wrap.h
3109		4482
3110	ev_win32.c required on win32 platforms only	4483	ev_win32.c required on win32 platforms only
3111		4484
3112	ev_select.c only when select backend is enabled (which is enabled by default)	4485	ev_select.c only when select backend is enabled
3113	ev_poll.c only when poll backend is enabled (disabled by default)	4486	ev_poll.c only when poll backend is enabled
3114	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
3115	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4489	ev_kqueue.c only when the kqueue backend is enabled
3116	ev_port.c only when the solaris port backend is enabled (disabled by default)	4490	ev_port.c only when the solaris port backend is enabled
3117		4491
3118	F<ev.c> includes the backend files directly when enabled, so you only need	4492	F<ev.c> includes the backend files directly when enabled, so you only need
3119	to compile this single file.	4493	to compile this single file.
3120		4494
3121	=head3 LIBEVENT COMPATIBILITY API	4495	=head3 LIBEVENT COMPATIBILITY API
…		…
3147	libev.m4	4521	libev.m4
3148		4522
3149	=head2 PREPROCESSOR SYMBOLS/MACROS	4523	=head2 PREPROCESSOR SYMBOLS/MACROS
3150		4524
3151	Libev can be configured via a variety of preprocessor symbols you have to	4525	Libev can be configured via a variety of preprocessor symbols you have to
3152	define before including any of its files. The default in the absence of	4526	define before including (or compiling) any of its files. The default in
3153	autoconf is documented for every option.	4527	the absence of autoconf is documented for every option.
		4528
		4529	Symbols marked with "(h)" do not change the ABI, and can have different
		4530	values when compiling libev vs. including F<ev.h>, so it is permissible
		4531	to redefine them before including F<ev.h> without breaking compatibility
		4532	to a compiled library. All other symbols change the ABI, which means all
		4533	users of libev and the libev code itself must be compiled with compatible
		4534	settings.
3154		4535
3155	=over 4	4536	=over 4
3156		4537
		4538	=item EV_COMPAT3 (h)
		4539
		4540	Backwards compatibility is a major concern for libev. This is why this
		4541	release of libev comes with wrappers for the functions and symbols that
		4542	have been renamed between libev version 3 and 4.
		4543
		4544	You can disable these wrappers (to test compatibility with future
		4545	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4546	sources. This has the additional advantage that you can drop the C<struct>
		4547	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4548	typedef in that case.
		4549
		4550	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4551	and in some even more future version the compatibility code will be
		4552	removed completely.
		4553
3157	=item EV_STANDALONE	4554	=item EV_STANDALONE (h)
3158		4555
3159	Must always be C<1> if you do not use autoconf configuration, which	4556	Must always be C<1> if you do not use autoconf configuration, which
3160	keeps libev from including F<config.h>, and it also defines dummy	4557	keeps libev from including F<config.h>, and it also defines dummy
3161	implementations for some libevent functions (such as logging, which is not	4558	implementations for some libevent functions (such as logging, which is not
3162	supported). It will also not define any of the structs usually found in	4559	supported). It will also not define any of the structs usually found in
3163	F<event.h> that are not directly supported by the libev core alone.	4560	F<event.h> that are not directly supported by the libev core alone.
3164		4561
		4562	In standalone mode, libev will still try to automatically deduce the
		4563	configuration, but has to be more conservative.
		4564
		4565	=item EV_USE_FLOOR
		4566
		4567	If defined to be C<1>, libev will use the C<floor ()> function for its
		4568	periodic reschedule calculations, otherwise libev will fall back on a
		4569	portable (slower) implementation. If you enable this, you usually have to
		4570	link against libm or something equivalent. Enabling this when the C<floor>
		4571	function is not available will fail, so the safe default is to not enable
		4572	this.
		4573
3165	=item EV_USE_MONOTONIC	4574	=item EV_USE_MONOTONIC
3166		4575
3167	If defined to be C<1>, libev will try to detect the availability of the	4576	If defined to be C<1>, libev will try to detect the availability of the
3168	monotonic clock option at both compile time and runtime. Otherwise no use	4577	monotonic clock option at both compile time and runtime. Otherwise no
3169	of the monotonic clock option will be attempted. If you enable this, you	4578	use of the monotonic clock option will be attempted. If you enable this,
3170	usually have to link against librt or something similar. Enabling it when	4579	you usually have to link against librt or something similar. Enabling it
3171	the functionality isn't available is safe, though, although you have	4580	when the functionality isn't available is safe, though, although you have
3172	to make sure you link against any libraries where the C<clock_gettime>	4581	to make sure you link against any libraries where the C<clock_gettime>
3173	function is hiding in (often F<-lrt>).	4582	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
3174		4583
3175	=item EV_USE_REALTIME	4584	=item EV_USE_REALTIME
3176		4585
3177	If defined to be C<1>, libev will try to detect the availability of the	4586	If defined to be C<1>, libev will try to detect the availability of the
3178	real-time clock option at compile time (and assume its availability at	4587	real-time clock option at compile time (and assume its availability
3179	runtime if successful). Otherwise no use of the real-time clock option will	4588	at runtime if successful). Otherwise no use of the real-time clock
3180	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	4589	option will be attempted. This effectively replaces C<gettimeofday>
3181	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	4590	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
3182	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	4591	correctness. See the note about libraries in the description of
		4592	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		4593	C<EV_USE_CLOCK_SYSCALL>.
		4594
		4595	=item EV_USE_CLOCK_SYSCALL
		4596
		4597	If defined to be C<1>, libev will try to use a direct syscall instead
		4598	of calling the system-provided C<clock_gettime> function. This option
		4599	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		4600	unconditionally pulls in C<libpthread>, slowing down single-threaded
		4601	programs needlessly. Using a direct syscall is slightly slower (in
		4602	theory), because no optimised vdso implementation can be used, but avoids
		4603	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		4604	higher, as it simplifies linking (no need for C<-lrt>).
3183		4605
3184	=item EV_USE_NANOSLEEP	4606	=item EV_USE_NANOSLEEP
3185		4607
3186	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	4608	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
3187	and will use it for delays. Otherwise it will use C<select ()>.	4609	and will use it for delays. Otherwise it will use C<select ()>.
…		…
3203		4625
3204	=item EV_SELECT_USE_FD_SET	4626	=item EV_SELECT_USE_FD_SET
3205		4627
3206	If defined to C<1>, then the select backend will use the system C<fd_set>	4628	If defined to C<1>, then the select backend will use the system C<fd_set>
3207	structure. This is useful if libev doesn't compile due to a missing	4629	structure. This is useful if libev doesn't compile due to a missing
3208	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	4630	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3209	exotic systems. This usually limits the range of file descriptors to some	4631	on exotic systems. This usually limits the range of file descriptors to
3210	low limit such as 1024 or might have other limitations (winsocket only	4632	some low limit such as 1024 or might have other limitations (winsocket
3211	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	4633	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3212	influence the size of the C<fd_set> used.	4634	configures the maximum size of the C<fd_set>.
3213		4635
3214	=item EV_SELECT_IS_WINSOCKET	4636	=item EV_SELECT_IS_WINSOCKET
3215		4637
3216	When defined to C<1>, the select backend will assume that	4638	When defined to C<1>, the select backend will assume that
3217	select/socket/connect etc. don't understand file descriptors but	4639	select/socket/connect etc. don't understand file descriptors but
…		…
3219	be used is the winsock select). This means that it will call	4641	be used is the winsock select). This means that it will call
3220	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4642	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3221	it is assumed that all these functions actually work on fds, even	4643	it is assumed that all these functions actually work on fds, even
3222	on win32. Should not be defined on non-win32 platforms.	4644	on win32. Should not be defined on non-win32 platforms.
3223		4645
3224	=item EV_FD_TO_WIN32_HANDLE	4646	=item EV_FD_TO_WIN32_HANDLE(fd)
3225		4647
3226	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4648	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3227	file descriptors to socket handles. When not defining this symbol (the	4649	file descriptors to socket handles. When not defining this symbol (the
3228	default), then libev will call C<_get_osfhandle>, which is usually	4650	default), then libev will call C<_get_osfhandle>, which is usually
3229	correct. In some cases, programs use their own file descriptor management,	4651	correct. In some cases, programs use their own file descriptor management,
3230	in which case they can provide this function to map fds to socket handles.	4652	in which case they can provide this function to map fds to socket handles.
3231		4653
		4654	=item EV_WIN32_HANDLE_TO_FD(handle)
		4655
		4656	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4657	using the standard C<_open_osfhandle> function. For programs implementing
		4658	their own fd to handle mapping, overwriting this function makes it easier
		4659	to do so. This can be done by defining this macro to an appropriate value.
		4660
		4661	=item EV_WIN32_CLOSE_FD(fd)
		4662
		4663	If programs implement their own fd to handle mapping on win32, then this
		4664	macro can be used to override the C<close> function, useful to unregister
		4665	file descriptors again. Note that the replacement function has to close
		4666	the underlying OS handle.
		4667
		4668	=item EV_USE_WSASOCKET
		4669
		4670	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4671	communication socket, which works better in some environments. Otherwise,
		4672	the normal C<socket> function will be used, which works better in other
		4673	environments.
		4674
3232	=item EV_USE_POLL	4675	=item EV_USE_POLL
3233		4676
3234	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4677	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3235	backend. Otherwise it will be enabled on non-win32 platforms. It	4678	backend. Otherwise it will be enabled on non-win32 platforms. It
3236	takes precedence over select.	4679	takes precedence over select.
…		…
3240	If defined to be C<1>, libev will compile in support for the Linux	4683	If defined to be C<1>, libev will compile in support for the Linux
3241	C<epoll>(7) backend. Its availability will be detected at runtime,	4684	C<epoll>(7) backend. Its availability will be detected at runtime,
3242	otherwise another method will be used as fallback. This is the preferred	4685	otherwise another method will be used as fallback. This is the preferred
3243	backend for GNU/Linux systems. If undefined, it will be enabled if the	4686	backend for GNU/Linux systems. If undefined, it will be enabled if the
3244	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4687	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4688
		4689	=item EV_USE_LINUXAIO
		4690
		4691	If defined to be C<1>, libev will compile in support for the Linux
		4692	aio backend. Due to it's currenbt limitations it has to be requested
		4693	explicitly. If undefined, it will be enabled on linux, otherwise
		4694	disabled.
3245		4695
3246	=item EV_USE_KQUEUE	4696	=item EV_USE_KQUEUE
3247		4697
3248	If defined to be C<1>, libev will compile in support for the BSD style	4698	If defined to be C<1>, libev will compile in support for the BSD style
3249	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4699	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3271	If defined to be C<1>, libev will compile in support for the Linux inotify	4721	If defined to be C<1>, libev will compile in support for the Linux inotify
3272	interface to speed up C<ev_stat> watchers. Its actual availability will	4722	interface to speed up C<ev_stat> watchers. Its actual availability will
3273	be detected at runtime. If undefined, it will be enabled if the headers	4723	be detected at runtime. If undefined, it will be enabled if the headers
3274	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4724	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3275		4725
		4726	=item EV_NO_SMP
		4727
		4728	If defined to be C<1>, libev will assume that memory is always coherent
		4729	between threads, that is, threads can be used, but threads never run on
		4730	different cpus (or different cpu cores). This reduces dependencies
		4731	and makes libev faster.
		4732
		4733	=item EV_NO_THREADS
		4734
		4735	If defined to be C<1>, libev will assume that it will never be called from
		4736	different threads (that includes signal handlers), which is a stronger
		4737	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4738	libev faster.
		4739
3276	=item EV_ATOMIC_T	4740	=item EV_ATOMIC_T
3277		4741
3278	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4742	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3279	access is atomic with respect to other threads or signal contexts. No such	4743	access is atomic with respect to other threads or signal contexts. No
3280	type is easily found in the C language, so you can provide your own type	4744	such type is easily found in the C language, so you can provide your own
3281	that you know is safe for your purposes. It is used both for signal handler "locking"	4745	type that you know is safe for your purposes. It is used both for signal
3282	as well as for signal and thread safety in C<ev_async> watchers.	4746	handler "locking" as well as for signal and thread safety in C<ev_async>
		4747	watchers.
3283		4748
3284	In the absence of this define, libev will use C<sig_atomic_t volatile>	4749	In the absence of this define, libev will use C<sig_atomic_t volatile>
3285	(from F<signal.h>), which is usually good enough on most platforms.	4750	(from F<signal.h>), which is usually good enough on most platforms.
3286		4751
3287	=item EV_H	4752	=item EV_H (h)
3288		4753
3289	The name of the F<ev.h> header file used to include it. The default if	4754	The name of the F<ev.h> header file used to include it. The default if
3290	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4755	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3291	used to virtually rename the F<ev.h> header file in case of conflicts.	4756	used to virtually rename the F<ev.h> header file in case of conflicts.
3292		4757
3293	=item EV_CONFIG_H	4758	=item EV_CONFIG_H (h)
3294		4759
3295	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4760	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3296	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4761	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3297	C<EV_H>, above.	4762	C<EV_H>, above.
3298		4763
3299	=item EV_EVENT_H	4764	=item EV_EVENT_H (h)
3300		4765
3301	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4766	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3302	of how the F<event.h> header can be found, the default is C<"event.h">.	4767	of how the F<event.h> header can be found, the default is C<"event.h">.
3303		4768
3304	=item EV_PROTOTYPES	4769	=item EV_PROTOTYPES (h)
3305		4770
3306	If defined to be C<0>, then F<ev.h> will not define any function	4771	If defined to be C<0>, then F<ev.h> will not define any function
3307	prototypes, but still define all the structs and other symbols. This is	4772	prototypes, but still define all the structs and other symbols. This is
3308	occasionally useful if you want to provide your own wrapper functions	4773	occasionally useful if you want to provide your own wrapper functions
3309	around libev functions.	4774	around libev functions.
…		…
3314	will have the C<struct ev_loop *> as first argument, and you can create	4779	will have the C<struct ev_loop *> as first argument, and you can create
3315	additional independent event loops. Otherwise there will be no support	4780	additional independent event loops. Otherwise there will be no support
3316	for multiple event loops and there is no first event loop pointer	4781	for multiple event loops and there is no first event loop pointer
3317	argument. Instead, all functions act on the single default loop.	4782	argument. Instead, all functions act on the single default loop.
3318		4783
		4784	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4785	default loop when multiplicity is switched off - you always have to
		4786	initialise the loop manually in this case.
		4787
3319	=item EV_MINPRI	4788	=item EV_MINPRI
3320		4789
3321	=item EV_MAXPRI	4790	=item EV_MAXPRI
3322		4791
3323	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4792	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3331	fine.	4800	fine.
3332		4801
3333	If your embedding application does not need any priorities, defining these	4802	If your embedding application does not need any priorities, defining these
3334	both to C<0> will save some memory and CPU.	4803	both to C<0> will save some memory and CPU.
3335		4804
3336	=item EV_PERIODIC_ENABLE	4805	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4806	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4807	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3337		4808
3338	If undefined or defined to be C<1>, then periodic timers are supported. If	4809	If undefined or defined to be C<1> (and the platform supports it), then
3339	defined to be C<0>, then they are not. Disabling them saves a few kB of	4810	the respective watcher type is supported. If defined to be C<0>, then it
3340	code.	4811	is not. Disabling watcher types mainly saves code size.
3341		4812
3342	=item EV_IDLE_ENABLE	4813	=item EV_FEATURES
3343
3344	If undefined or defined to be C<1>, then idle watchers are supported. If
3345	defined to be C<0>, then they are not. Disabling them saves a few kB of
3346	code.
3347
3348	=item EV_EMBED_ENABLE
3349
3350	If undefined or defined to be C<1>, then embed watchers are supported. If
3351	defined to be C<0>, then they are not. Embed watchers rely on most other
3352	watcher types, which therefore must not be disabled.
3353
3354	=item EV_STAT_ENABLE
3355
3356	If undefined or defined to be C<1>, then stat watchers are supported. If
3357	defined to be C<0>, then they are not.
3358
3359	=item EV_FORK_ENABLE
3360
3361	If undefined or defined to be C<1>, then fork watchers are supported. If
3362	defined to be C<0>, then they are not.
3363
3364	=item EV_ASYNC_ENABLE
3365
3366	If undefined or defined to be C<1>, then async watchers are supported. If
3367	defined to be C<0>, then they are not.
3368
3369	=item EV_MINIMAL
3370		4814
3371	If you need to shave off some kilobytes of code at the expense of some	4815	If you need to shave off some kilobytes of code at the expense of some
3372	speed, define this symbol to C<1>. Currently this is used to override some	4816	speed (but with the full API), you can define this symbol to request
3373	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4817	certain subsets of functionality. The default is to enable all features
3374	much smaller 2-heap for timer management over the default 4-heap.	4818	that can be enabled on the platform.
		4819
		4820	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4821	with some broad features you want) and then selectively re-enable
		4822	additional parts you want, for example if you want everything minimal,
		4823	but multiple event loop support, async and child watchers and the poll
		4824	backend, use this:
		4825
		4826	#define EV_FEATURES 0
		4827	#define EV_MULTIPLICITY 1
		4828	#define EV_USE_POLL 1
		4829	#define EV_CHILD_ENABLE 1
		4830	#define EV_ASYNC_ENABLE 1
		4831
		4832	The actual value is a bitset, it can be a combination of the following
		4833	values (by default, all of these are enabled):
		4834
		4835	=over 4
		4836
		4837	=item C<1> - faster/larger code
		4838
		4839	Use larger code to speed up some operations.
		4840
		4841	Currently this is used to override some inlining decisions (enlarging the
		4842	code size by roughly 30% on amd64).
		4843
		4844	When optimising for size, use of compiler flags such as C<-Os> with
		4845	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4846	assertions.
		4847
		4848	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4849	(e.g. gcc with C<-Os>).
		4850
		4851	=item C<2> - faster/larger data structures
		4852
		4853	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4854	hash table sizes and so on. This will usually further increase code size
		4855	and can additionally have an effect on the size of data structures at
		4856	runtime.
		4857
		4858	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4859	(e.g. gcc with C<-Os>).
		4860
		4861	=item C<4> - full API configuration
		4862
		4863	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4864	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4865
		4866	=item C<8> - full API
		4867
		4868	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4869	details on which parts of the API are still available without this
		4870	feature, and do not complain if this subset changes over time.
		4871
		4872	=item C<16> - enable all optional watcher types
		4873
		4874	Enables all optional watcher types. If you want to selectively enable
		4875	only some watcher types other than I/O and timers (e.g. prepare,
		4876	embed, async, child...) you can enable them manually by defining
		4877	C<EV_watchertype_ENABLE> to C<1> instead.
		4878
		4879	=item C<32> - enable all backends
		4880
		4881	This enables all backends - without this feature, you need to enable at
		4882	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4883
		4884	=item C<64> - enable OS-specific "helper" APIs
		4885
		4886	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4887	default.
		4888
		4889	=back
		4890
		4891	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4892	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4893	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4894	watchers, timers and monotonic clock support.
		4895
		4896	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4897	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4898	your program might be left out as well - a binary starting a timer and an
		4899	I/O watcher then might come out at only 5Kb.
		4900
		4901	=item EV_API_STATIC
		4902
		4903	If this symbol is defined (by default it is not), then all identifiers
		4904	will have static linkage. This means that libev will not export any
		4905	identifiers, and you cannot link against libev anymore. This can be useful
		4906	when you embed libev, only want to use libev functions in a single file,
		4907	and do not want its identifiers to be visible.
		4908
		4909	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4910	wants to use libev.
		4911
		4912	This option only works when libev is compiled with a C compiler, as C++
		4913	doesn't support the required declaration syntax.
		4914
		4915	=item EV_AVOID_STDIO
		4916
		4917	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4918	functions (printf, scanf, perror etc.). This will increase the code size
		4919	somewhat, but if your program doesn't otherwise depend on stdio and your
		4920	libc allows it, this avoids linking in the stdio library which is quite
		4921	big.
		4922
		4923	Note that error messages might become less precise when this option is
		4924	enabled.
		4925
		4926	=item EV_NSIG
		4927
		4928	The highest supported signal number, +1 (or, the number of
		4929	signals): Normally, libev tries to deduce the maximum number of signals
		4930	automatically, but sometimes this fails, in which case it can be
		4931	specified. Also, using a lower number than detected (C<32> should be
		4932	good for about any system in existence) can save some memory, as libev
		4933	statically allocates some 12-24 bytes per signal number.
3375		4934
3376	=item EV_PID_HASHSIZE	4935	=item EV_PID_HASHSIZE
3377		4936
3378	C<ev_child> watchers use a small hash table to distribute workload by	4937	C<ev_child> watchers use a small hash table to distribute workload by
3379	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4938	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3380	than enough. If you need to manage thousands of children you might want to	4939	usually more than enough. If you need to manage thousands of children you
3381	increase this value (I<must> be a power of two).	4940	might want to increase this value (I<must> be a power of two).
3382		4941
3383	=item EV_INOTIFY_HASHSIZE	4942	=item EV_INOTIFY_HASHSIZE
3384		4943
3385	C<ev_stat> watchers use a small hash table to distribute workload by	4944	C<ev_stat> watchers use a small hash table to distribute workload by
3386	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4945	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3387	usually more than enough. If you need to manage thousands of C<ev_stat>	4946	disabled), usually more than enough. If you need to manage thousands of
3388	watchers you might want to increase this value (I<must> be a power of	4947	C<ev_stat> watchers you might want to increase this value (I<must> be a
3389	two).	4948	power of two).
3390		4949
3391	=item EV_USE_4HEAP	4950	=item EV_USE_4HEAP
3392		4951
3393	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4952	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3394	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4953	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3395	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4954	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3396	faster performance with many (thousands) of watchers.	4955	faster performance with many (thousands) of watchers.
3397		4956
3398	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4957	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3399	(disabled).	4958	will be C<0>.
3400		4959
3401	=item EV_HEAP_CACHE_AT	4960	=item EV_HEAP_CACHE_AT
3402		4961
3403	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4962	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3404	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4963	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3405	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4964	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3406	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4965	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3407	but avoids random read accesses on heap changes. This improves performance	4966	but avoids random read accesses on heap changes. This improves performance
3408	noticeably with many (hundreds) of watchers.	4967	noticeably with many (hundreds) of watchers.
3409		4968
3410	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4969	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3411	(disabled).	4970	will be C<0>.
3412		4971
3413	=item EV_VERIFY	4972	=item EV_VERIFY
3414		4973
3415	Controls how much internal verification (see C<ev_loop_verify ()>) will	4974	Controls how much internal verification (see C<ev_verify ()>) will
3416	be done: If set to C<0>, no internal verification code will be compiled	4975	be done: If set to C<0>, no internal verification code will be compiled
3417	in. If set to C<1>, then verification code will be compiled in, but not	4976	in. If set to C<1>, then verification code will be compiled in, but not
3418	called. If set to C<2>, then the internal verification code will be	4977	called. If set to C<2>, then the internal verification code will be
3419	called once per loop, which can slow down libev. If set to C<3>, then the	4978	called once per loop, which can slow down libev. If set to C<3>, then the
3420	verification code will be called very frequently, which will slow down	4979	verification code will be called very frequently, which will slow down
3421	libev considerably.	4980	libev considerably.
3422		4981
		4982	Verification errors are reported via C's C<assert> mechanism, so if you
		4983	disable that (e.g. by defining C<NDEBUG>) then no errors will be reported.
		4984
3423	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4985	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3424	C<0>.	4986	will be C<0>.
3425		4987
3426	=item EV_COMMON	4988	=item EV_COMMON
3427		4989
3428	By default, all watchers have a C<void *data> member. By redefining	4990	By default, all watchers have a C<void *data> member. By redefining
3429	this macro to a something else you can include more and other types of	4991	this macro to something else you can include more and other types of
3430	members. You have to define it each time you include one of the files,	4992	members. You have to define it each time you include one of the files,
3431	though, and it must be identical each time.	4993	though, and it must be identical each time.
3432		4994
3433	For example, the perl EV module uses something like this:	4995	For example, the perl EV module uses something like this:
3434		4996
…		…
3487	file.	5049	file.
3488		5050
3489	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5051	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3490	that everybody includes and which overrides some configure choices:	5052	that everybody includes and which overrides some configure choices:
3491		5053
3492	#define EV_MINIMAL 1	5054	#define EV_FEATURES 8
3493	#define EV_USE_POLL 0	5055	#define EV_USE_SELECT 1
3494	#define EV_MULTIPLICITY 0
3495	#define EV_PERIODIC_ENABLE 0	5056	#define EV_PREPARE_ENABLE 1
		5057	#define EV_IDLE_ENABLE 1
3496	#define EV_STAT_ENABLE 0	5058	#define EV_SIGNAL_ENABLE 1
3497	#define EV_FORK_ENABLE 0	5059	#define EV_CHILD_ENABLE 1
		5060	#define EV_USE_STDEXCEPT 0
3498	#define EV_CONFIG_H <config.h>	5061	#define EV_CONFIG_H <config.h>
3499	#define EV_MINPRI 0
3500	#define EV_MAXPRI 0
3501		5062
3502	#include "ev++.h"	5063	#include "ev++.h"
3503		5064
3504	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5065	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3505		5066
3506	#include "ev_cpp.h"	5067	#include "ev_cpp.h"
3507	#include "ev.c"	5068	#include "ev.c"
3508		5069
3509	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5070	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3510		5071
3511	=head2 THREADS AND COROUTINES	5072	=head2 THREADS AND COROUTINES
3512		5073
3513	=head3 THREADS	5074	=head3 THREADS
3514		5075
…		…
3565	default loop and triggering an C<ev_async> watcher from the default loop	5126	default loop and triggering an C<ev_async> watcher from the default loop
3566	watcher callback into the event loop interested in the signal.	5127	watcher callback into the event loop interested in the signal.
3567		5128
3568	=back	5129	=back
3569		5130
		5131	See also L</THREAD LOCKING EXAMPLE>.
		5132
3570	=head3 COROUTINES	5133	=head3 COROUTINES
3571		5134
3572	Libev is very accommodating to coroutines ("cooperative threads"):	5135	Libev is very accommodating to coroutines ("cooperative threads"):
3573	libev fully supports nesting calls to its functions from different	5136	libev fully supports nesting calls to its functions from different
3574	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5137	coroutines (e.g. you can call C<ev_run> on the same loop from two
3575	different coroutines, and switch freely between both coroutines running the	5138	different coroutines, and switch freely between both coroutines running
3576	loop, as long as you don't confuse yourself). The only exception is that	5139	the loop, as long as you don't confuse yourself). The only exception is
3577	you must not do this from C<ev_periodic> reschedule callbacks.	5140	that you must not do this from C<ev_periodic> reschedule callbacks.
3578		5141
3579	Care has been taken to ensure that libev does not keep local state inside	5142	Care has been taken to ensure that libev does not keep local state inside
3580	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5143	C<ev_run>, and other calls do not usually allow for coroutine switches as
3581	they do not call any callbacks.	5144	they do not call any callbacks.
3582		5145
3583	=head2 COMPILER WARNINGS	5146	=head2 COMPILER WARNINGS
3584		5147
3585	Depending on your compiler and compiler settings, you might get no or a	5148	Depending on your compiler and compiler settings, you might get no or a
…		…
3596	maintainable.	5159	maintainable.
3597		5160
3598	And of course, some compiler warnings are just plain stupid, or simply	5161	And of course, some compiler warnings are just plain stupid, or simply
3599	wrong (because they don't actually warn about the condition their message	5162	wrong (because they don't actually warn about the condition their message
3600	seems to warn about). For example, certain older gcc versions had some	5163	seems to warn about). For example, certain older gcc versions had some
3601	warnings that resulted an extreme number of false positives. These have	5164	warnings that resulted in an extreme number of false positives. These have
3602	been fixed, but some people still insist on making code warn-free with	5165	been fixed, but some people still insist on making code warn-free with
3603	such buggy versions.	5166	such buggy versions.
3604		5167
3605	While libev is written to generate as few warnings as possible,	5168	While libev is written to generate as few warnings as possible,
3606	"warn-free" code is not a goal, and it is recommended not to build libev	5169	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3642	I suggest using suppression lists.	5205	I suggest using suppression lists.
3643		5206
3644		5207
3645	=head1 PORTABILITY NOTES	5208	=head1 PORTABILITY NOTES
3646		5209
		5210	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5211
		5212	GNU/Linux is the only common platform that supports 64 bit file/large file
		5213	interfaces but I<disables> them by default.
		5214
		5215	That means that libev compiled in the default environment doesn't support
		5216	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5217
		5218	Unfortunately, many programs try to work around this GNU/Linux issue
		5219	by enabling the large file API, which makes them incompatible with the
		5220	standard libev compiled for their system.
		5221
		5222	Likewise, libev cannot enable the large file API itself as this would
		5223	suddenly make it incompatible to the default compile time environment,
		5224	i.e. all programs not using special compile switches.
		5225
		5226	=head2 OS/X AND DARWIN BUGS
		5227
		5228	The whole thing is a bug if you ask me - basically any system interface
		5229	you touch is broken, whether it is locales, poll, kqueue or even the
		5230	OpenGL drivers.
		5231
		5232	=head3 C<kqueue> is buggy
		5233
		5234	The kqueue syscall is broken in all known versions - most versions support
		5235	only sockets, many support pipes.
		5236
		5237	Libev tries to work around this by not using C<kqueue> by default on this
		5238	rotten platform, but of course you can still ask for it when creating a
		5239	loop - embedding a socket-only kqueue loop into a select-based one is
		5240	probably going to work well.
		5241
		5242	=head3 C<poll> is buggy
		5243
		5244	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5245	implementation by something calling C<kqueue> internally around the 10.5.6
		5246	release, so now C<kqueue> I<and> C<poll> are broken.
		5247
		5248	Libev tries to work around this by not using C<poll> by default on
		5249	this rotten platform, but of course you can still ask for it when creating
		5250	a loop.
		5251
		5252	=head3 C<select> is buggy
		5253
		5254	All that's left is C<select>, and of course Apple found a way to fuck this
		5255	one up as well: On OS/X, C<select> actively limits the number of file
		5256	descriptors you can pass in to 1024 - your program suddenly crashes when
		5257	you use more.
		5258
		5259	There is an undocumented "workaround" for this - defining
		5260	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5261	work on OS/X.
		5262
		5263	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5264
		5265	=head3 C<errno> reentrancy
		5266
		5267	The default compile environment on Solaris is unfortunately so
		5268	thread-unsafe that you can't even use components/libraries compiled
		5269	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5270	defined by default. A valid, if stupid, implementation choice.
		5271
		5272	If you want to use libev in threaded environments you have to make sure
		5273	it's compiled with C<_REENTRANT> defined.
		5274
		5275	=head3 Event port backend
		5276
		5277	The scalable event interface for Solaris is called "event
		5278	ports". Unfortunately, this mechanism is very buggy in all major
		5279	releases. If you run into high CPU usage, your program freezes or you get
		5280	a large number of spurious wakeups, make sure you have all the relevant
		5281	and latest kernel patches applied. No, I don't know which ones, but there
		5282	are multiple ones to apply, and afterwards, event ports actually work
		5283	great.
		5284
		5285	If you can't get it to work, you can try running the program by setting
		5286	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5287	C<select> backends.
		5288
		5289	=head2 AIX POLL BUG
		5290
		5291	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5292	this by trying to avoid the poll backend altogether (i.e. it's not even
		5293	compiled in), which normally isn't a big problem as C<select> works fine
		5294	with large bitsets on AIX, and AIX is dead anyway.
		5295
3647	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5296	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5297
		5298	=head3 General issues
3648		5299
3649	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5300	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3650	requires, and its I/O model is fundamentally incompatible with the POSIX	5301	requires, and its I/O model is fundamentally incompatible with the POSIX
3651	model. Libev still offers limited functionality on this platform in	5302	model. Libev still offers limited functionality on this platform in
3652	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5303	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3653	descriptors. This only applies when using Win32 natively, not when using	5304	descriptors. This only applies when using Win32 natively, not when using
3654	e.g. cygwin.	5305	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5306	as every compiler comes with a slightly differently broken/incompatible
		5307	environment.
3655		5308
3656	Lifting these limitations would basically require the full	5309	Lifting these limitations would basically require the full
3657	re-implementation of the I/O system. If you are into these kinds of	5310	re-implementation of the I/O system. If you are into this kind of thing,
3658	things, then note that glib does exactly that for you in a very portable	5311	then note that glib does exactly that for you in a very portable way (note
3659	way (note also that glib is the slowest event library known to man).	5312	also that glib is the slowest event library known to man).
3660		5313
3661	There is no supported compilation method available on windows except	5314	There is no supported compilation method available on windows except
3662	embedding it into other applications.	5315	embedding it into other applications.
		5316
		5317	Sensible signal handling is officially unsupported by Microsoft - libev
		5318	tries its best, but under most conditions, signals will simply not work.
3663		5319
3664	Not a libev limitation but worth mentioning: windows apparently doesn't	5320	Not a libev limitation but worth mentioning: windows apparently doesn't
3665	accept large writes: instead of resulting in a partial write, windows will	5321	accept large writes: instead of resulting in a partial write, windows will
3666	either accept everything or return C<ENOBUFS> if the buffer is too large,	5322	either accept everything or return C<ENOBUFS> if the buffer is too large,
3667	so make sure you only write small amounts into your sockets (less than a	5323	so make sure you only write small amounts into your sockets (less than a
…		…
3672	the abysmal performance of winsockets, using a large number of sockets	5328	the abysmal performance of winsockets, using a large number of sockets
3673	is not recommended (and not reasonable). If your program needs to use	5329	is not recommended (and not reasonable). If your program needs to use
3674	more than a hundred or so sockets, then likely it needs to use a totally	5330	more than a hundred or so sockets, then likely it needs to use a totally
3675	different implementation for windows, as libev offers the POSIX readiness	5331	different implementation for windows, as libev offers the POSIX readiness
3676	notification model, which cannot be implemented efficiently on windows	5332	notification model, which cannot be implemented efficiently on windows
3677	(Microsoft monopoly games).	5333	(due to Microsoft monopoly games).
3678		5334
3679	A typical way to use libev under windows is to embed it (see the embedding	5335	A typical way to use libev under windows is to embed it (see the embedding
3680	section for details) and use the following F<evwrap.h> header file instead	5336	section for details) and use the following F<evwrap.h> header file instead
3681	of F<ev.h>:	5337	of F<ev.h>:
3682		5338
…		…
3689	you do I<not> compile the F<ev.c> or any other embedded source files!):	5345	you do I<not> compile the F<ev.c> or any other embedded source files!):
3690		5346
3691	#include "evwrap.h"	5347	#include "evwrap.h"
3692	#include "ev.c"	5348	#include "ev.c"
3693		5349
3694	=over 4
3695
3696	=item The winsocket select function	5350	=head3 The winsocket C<select> function
3697		5351
3698	The winsocket C<select> function doesn't follow POSIX in that it	5352	The winsocket C<select> function doesn't follow POSIX in that it
3699	requires socket I<handles> and not socket I<file descriptors> (it is	5353	requires socket I<handles> and not socket I<file descriptors> (it is
3700	also extremely buggy). This makes select very inefficient, and also	5354	also extremely buggy). This makes select very inefficient, and also
3701	requires a mapping from file descriptors to socket handles (the Microsoft	5355	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
3710	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5364	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3711		5365
3712	Note that winsockets handling of fd sets is O(n), so you can easily get a	5366	Note that winsockets handling of fd sets is O(n), so you can easily get a
3713	complexity in the O(n²) range when using win32.	5367	complexity in the O(n²) range when using win32.
3714		5368
3715	=item Limited number of file descriptors	5369	=head3 Limited number of file descriptors
3716		5370
3717	Windows has numerous arbitrary (and low) limits on things.	5371	Windows has numerous arbitrary (and low) limits on things.
3718		5372
3719	Early versions of winsocket's select only supported waiting for a maximum	5373	Early versions of winsocket's select only supported waiting for a maximum
3720	of C<64> handles (probably owning to the fact that all windows kernels	5374	of C<64> handles (probably owning to the fact that all windows kernels
3721	can only wait for C<64> things at the same time internally; Microsoft	5375	can only wait for C<64> things at the same time internally; Microsoft
3722	recommends spawning a chain of threads and wait for 63 handles and the	5376	recommends spawning a chain of threads and wait for 63 handles and the
3723	previous thread in each. Great).	5377	previous thread in each. Sounds great!).
3724		5378
3725	Newer versions support more handles, but you need to define C<FD_SETSIZE>	5379	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3726	to some high number (e.g. C<2048>) before compiling the winsocket select	5380	to some high number (e.g. C<2048>) before compiling the winsocket select
3727	call (which might be in libev or elsewhere, for example, perl does its own	5381	call (which might be in libev or elsewhere, for example, perl and many
3728	select emulation on windows).	5382	other interpreters do their own select emulation on windows).
3729		5383
3730	Another limit is the number of file descriptors in the Microsoft runtime	5384	Another limit is the number of file descriptors in the Microsoft runtime
3731	libraries, which by default is C<64> (there must be a hidden I<64> fetish	5385	libraries, which by default is C<64> (there must be a hidden I<64>
3732	or something like this inside Microsoft). You can increase this by calling	5386	fetish or something like this inside Microsoft). You can increase this
3733	C<_setmaxstdio>, which can increase this limit to C<2048> (another	5387	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3734	arbitrary limit), but is broken in many versions of the Microsoft runtime	5388	(another arbitrary limit), but is broken in many versions of the Microsoft
3735	libraries.
3736
3737	This might get you to about C<512> or C<2048> sockets (depending on	5389	runtime libraries. This might get you to about C<512> or C<2048> sockets
3738	windows version and/or the phase of the moon). To get more, you need to	5390	(depending on windows version and/or the phase of the moon). To get more,
3739	wrap all I/O functions and provide your own fd management, but the cost of	5391	you need to wrap all I/O functions and provide your own fd management, but
3740	calling select (O(n²)) will likely make this unworkable.	5392	the cost of calling select (O(n²)) will likely make this unworkable.
3741
3742	=back
3743		5393
3744	=head2 PORTABILITY REQUIREMENTS	5394	=head2 PORTABILITY REQUIREMENTS
3745		5395
3746	In addition to a working ISO-C implementation and of course the	5396	In addition to a working ISO-C implementation and of course the
3747	backend-specific APIs, libev relies on a few additional extensions:	5397	backend-specific APIs, libev relies on a few additional extensions:
…		…
3754	Libev assumes not only that all watcher pointers have the same internal	5404	Libev assumes not only that all watcher pointers have the same internal
3755	structure (guaranteed by POSIX but not by ISO C for example), but it also	5405	structure (guaranteed by POSIX but not by ISO C for example), but it also
3756	assumes that the same (machine) code can be used to call any watcher	5406	assumes that the same (machine) code can be used to call any watcher
3757	callback: The watcher callbacks have different type signatures, but libev	5407	callback: The watcher callbacks have different type signatures, but libev
3758	calls them using an C<ev_watcher *> internally.	5408	calls them using an C<ev_watcher *> internally.
		5409
		5410	=item null pointers and integer zero are represented by 0 bytes
		5411
		5412	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5413	relies on this setting pointers and integers to null.
		5414
		5415	=item pointer accesses must be thread-atomic
		5416
		5417	Accessing a pointer value must be atomic, it must both be readable and
		5418	writable in one piece - this is the case on all current architectures.
3759		5419
3760	=item C<sig_atomic_t volatile> must be thread-atomic as well	5420	=item C<sig_atomic_t volatile> must be thread-atomic as well
3761		5421
3762	The type C<sig_atomic_t volatile> (or whatever is defined as	5422	The type C<sig_atomic_t volatile> (or whatever is defined as
3763	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5423	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
3772	thread" or will block signals process-wide, both behaviours would	5432	thread" or will block signals process-wide, both behaviours would
3773	be compatible with libev. Interaction between C<sigprocmask> and	5433	be compatible with libev. Interaction between C<sigprocmask> and
3774	C<pthread_sigmask> could complicate things, however.	5434	C<pthread_sigmask> could complicate things, however.
3775		5435
3776	The most portable way to handle signals is to block signals in all threads	5436	The most portable way to handle signals is to block signals in all threads
3777	except the initial one, and run the default loop in the initial thread as	5437	except the initial one, and run the signal handling loop in the initial
3778	well.	5438	thread as well.
3779		5439
3780	=item C<long> must be large enough for common memory allocation sizes	5440	=item C<long> must be large enough for common memory allocation sizes
3781		5441
3782	To improve portability and simplify its API, libev uses C<long> internally	5442	To improve portability and simplify its API, libev uses C<long> internally
3783	instead of C<size_t> when allocating its data structures. On non-POSIX	5443	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
3786	watchers.	5446	watchers.
3787		5447
3788	=item C<double> must hold a time value in seconds with enough accuracy	5448	=item C<double> must hold a time value in seconds with enough accuracy
3789		5449
3790	The type C<double> is used to represent timestamps. It is required to	5450	The type C<double> is used to represent timestamps. It is required to
3791	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5451	have at least 51 bits of mantissa (and 9 bits of exponent), which is
3792	enough for at least into the year 4000. This requirement is fulfilled by	5452	good enough for at least into the year 4000 with millisecond accuracy
		5453	(the design goal for libev). This requirement is overfulfilled by
3793	implementations implementing IEEE 754 (basically all existing ones).	5454	implementations using IEEE 754, which is basically all existing ones.
		5455
		5456	With IEEE 754 doubles, you get microsecond accuracy until at least the
		5457	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5458	is either obsolete or somebody patched it to use C<long double> or
		5459	something like that, just kidding).
3794		5460
3795	=back	5461	=back
3796		5462
3797	If you know of other additional requirements drop me a note.	5463	If you know of other additional requirements drop me a note.
3798		5464
…		…
3860	=item Processing ev_async_send: O(number_of_async_watchers)	5526	=item Processing ev_async_send: O(number_of_async_watchers)
3861		5527
3862	=item Processing signals: O(max_signal_number)	5528	=item Processing signals: O(max_signal_number)
3863		5529
3864	Sending involves a system call I<iff> there were no other C<ev_async_send>	5530	Sending involves a system call I<iff> there were no other C<ev_async_send>
3865	calls in the current loop iteration. Checking for async and signal events	5531	calls in the current loop iteration and the loop is currently
		5532	blocked. Checking for async and signal events involves iterating over all
3866	involves iterating over all running async watchers or all signal numbers.	5533	running async watchers or all signal numbers.
3867		5534
3868	=back	5535	=back
3869		5536
3870		5537
		5538	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5539
		5540	The major version 4 introduced some incompatible changes to the API.
		5541
		5542	At the moment, the C<ev.h> header file provides compatibility definitions
		5543	for all changes, so most programs should still compile. The compatibility
		5544	layer might be removed in later versions of libev, so better update to the
		5545	new API early than late.
		5546
		5547	=over 4
		5548
		5549	=item C<EV_COMPAT3> backwards compatibility mechanism
		5550
		5551	The backward compatibility mechanism can be controlled by
		5552	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5553	section.
		5554
		5555	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5556
		5557	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5558
		5559	ev_loop_destroy (EV_DEFAULT_UC);
		5560	ev_loop_fork (EV_DEFAULT);
		5561
		5562	=item function/symbol renames
		5563
		5564	A number of functions and symbols have been renamed:
		5565
		5566	ev_loop => ev_run
		5567	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5568	EVLOOP_ONESHOT => EVRUN_ONCE
		5569
		5570	ev_unloop => ev_break
		5571	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5572	EVUNLOOP_ONE => EVBREAK_ONE
		5573	EVUNLOOP_ALL => EVBREAK_ALL
		5574
		5575	EV_TIMEOUT => EV_TIMER
		5576
		5577	ev_loop_count => ev_iteration
		5578	ev_loop_depth => ev_depth
		5579	ev_loop_verify => ev_verify
		5580
		5581	Most functions working on C<struct ev_loop> objects don't have an
		5582	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5583	associated constants have been renamed to not collide with the C<struct
		5584	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5585	as all other watcher types. Note that C<ev_loop_fork> is still called
		5586	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5587	typedef.
		5588
		5589	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5590
		5591	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5592	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5593	and work, but the library code will of course be larger.
		5594
		5595	=back
		5596
		5597
		5598	=head1 GLOSSARY
		5599
		5600	=over 4
		5601
		5602	=item active
		5603
		5604	A watcher is active as long as it has been started and not yet stopped.
		5605	See L</WATCHER STATES> for details.
		5606
		5607	=item application
		5608
		5609	In this document, an application is whatever is using libev.
		5610
		5611	=item backend
		5612
		5613	The part of the code dealing with the operating system interfaces.
		5614
		5615	=item callback
		5616
		5617	The address of a function that is called when some event has been
		5618	detected. Callbacks are being passed the event loop, the watcher that
		5619	received the event, and the actual event bitset.
		5620
		5621	=item callback/watcher invocation
		5622
		5623	The act of calling the callback associated with a watcher.
		5624
		5625	=item event
		5626
		5627	A change of state of some external event, such as data now being available
		5628	for reading on a file descriptor, time having passed or simply not having
		5629	any other events happening anymore.
		5630
		5631	In libev, events are represented as single bits (such as C<EV_READ> or
		5632	C<EV_TIMER>).
		5633
		5634	=item event library
		5635
		5636	A software package implementing an event model and loop.
		5637
		5638	=item event loop
		5639
		5640	An entity that handles and processes external events and converts them
		5641	into callback invocations.
		5642
		5643	=item event model
		5644
		5645	The model used to describe how an event loop handles and processes
		5646	watchers and events.
		5647
		5648	=item pending
		5649
		5650	A watcher is pending as soon as the corresponding event has been
		5651	detected. See L</WATCHER STATES> for details.
		5652
		5653	=item real time
		5654
		5655	The physical time that is observed. It is apparently strictly monotonic :)
		5656
		5657	=item wall-clock time
		5658
		5659	The time and date as shown on clocks. Unlike real time, it can actually
		5660	be wrong and jump forwards and backwards, e.g. when you adjust your
		5661	clock.
		5662
		5663	=item watcher
		5664
		5665	A data structure that describes interest in certain events. Watchers need
		5666	to be started (attached to an event loop) before they can receive events.
		5667
		5668	=back
		5669
3871	=head1 AUTHOR	5670	=head1 AUTHOR
3872		5671
3873	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5672	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5673	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
3874		5674

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