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Revision 1.248 by root, Wed Jul 8 04:14:34 2009 UTC vs.
Revision 1.447 by root, Sat Jun 22 16:25:53 2019 UTC

		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
75	While this document tries to be as complete as possible in documenting	77	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	78	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	79	on event-based programming, nor will it introduce event-based programming
78	with libev.	80	with libev.
79		81
80	Familarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	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>.
82		92
83	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
84		94
85	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
86	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
…		…
95	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
96	watcher.	106	watcher.
97		107
98	=head2 FEATURES	108	=head2 FEATURES
99		109
100	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>
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port
102	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>
103	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	with customised rescheduling (C<ev_periodic>), synchronous signals	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	(C<ev_signal>), process status change events (C<ev_child>), and event	115	timers (C<ev_timer>), absolute timers with customised rescheduling
106	watchers dealing with the event loop mechanism itself (C<ev_idle>,	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	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
108	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
109	(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>).
110		121
111	It also is quite fast (see this	122	It also is quite fast (see this
112	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
113	for example).	124	for example).
114		125
…		…
117	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)
118	configuration will be described, which supports multiple event loops. For	129	configuration will be described, which supports multiple event loops. For
119	more info about various configuration options please have a look at	130	more info about various configuration options please have a look at
120	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
121	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
122	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
123	this argument.	134	this argument.
124		135
125	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
126		137
127	Libev represents time as a single floating point number, representing	138	Libev represents time as a single floating point number, representing
128	the (fractional) number of seconds since the (POSIX) epoch (somewhere	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
129	near the beginning of 1970, details are complicated, don't ask). This	140	somewhere near the beginning of 1970, details are complicated, don't
130	type is called C<ev_tstamp>, which is what you should use too. It usually	141	ask). This type is called C<ev_tstamp>, which is what you should use
131	aliases to the C<double> type in C. When you need to do any calculations	142	too. It usually aliases to the C<double> type in C. When you need to do
132	on 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
133	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
134	throughout libev.	146	time differences (e.g. delays) throughout libev.
135		147
136	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
137		149
138	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
139	and internal errors (bugs).	151	and internal errors (bugs).
…		…
163		175
164	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
165		177
166	Returns the current time as libev would use it. Please note that the	178	Returns the current time as libev would use it. Please note that the
167	C<ev_now> function is usually faster and also often returns the timestamp	179	C<ev_now> function is usually faster and also often returns the timestamp
168	you actually want to know.	180	you actually want to know. Also interesting is the combination of
		181	C<ev_now_update> and C<ev_now>.
169		182
170	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
171		184
172	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
173	either it is interrupted or the given time interval has passed. Basically	186	until either it is interrupted or the given time interval has
		187	passed (approximately - it might return a bit earlier even if not
		188	interrupted). Returns immediately if C<< interval <= 0 >>.
		189
174	this is a sub-second-resolution C<sleep ()>.	190	Basically this is a sub-second-resolution C<sleep ()>.
		191
		192	The range of the C<interval> is limited - libev only guarantees to work
		193	with sleep times of up to one day (C<< interval <= 86400 >>).
175		194
176	=item int ev_version_major ()	195	=item int ev_version_major ()
177		196
178	=item int ev_version_minor ()	197	=item int ev_version_minor ()
179		198
…		…
190	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
191	compatible to older versions, so a larger minor version alone is usually	210	compatible to older versions, so a larger minor version alone is usually
192	not a problem.	211	not a problem.
193		212
194	Example: Make sure we haven't accidentally been linked against the wrong	213	Example: Make sure we haven't accidentally been linked against the wrong
195	version.	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
196		216
197	assert (("libev version mismatch",	217	assert (("libev version mismatch",
198	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
199	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
200		220
…		…
211	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
212	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
213		233
214	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
215		235
216	Return the set of all backends compiled into this binary of libev and also	236	Return the set of all backends compiled into this binary of libev and
217	recommended for this platform. This set is often smaller than the one	237	also recommended for this platform, meaning it will work for most file
		238	descriptor types. This set is often smaller than the one returned by
218	returned by C<ev_supported_backends>, as for example kqueue is broken on	239	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
219	most BSDs and will not be auto-detected unless you explicitly request it	240	and will not be auto-detected unless you explicitly request it (assuming
220	(assuming you know what you are doing). This is the set of backends that	241	you know what you are doing). This is the set of backends that libev will
221	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
222		243
223	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
224		245
225	Returns the set of backends that are embeddable in other event loops. This	246	Returns the set of backends that are embeddable in other event loops. This
226	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
227	might be supported on the current system, you would need to look at	248	current system. To find which embeddable backends might be supported on
228	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
229	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
230		251
231	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
232		253
233	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
234		255
235	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
236	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	257	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
237	used to allocate and free memory (no surprises here). If it returns zero	258	used to allocate and free memory (no surprises here). If it returns zero
238	when memory needs to be allocated (C<size != 0>), the library might abort	259	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
244		265
245	You could override this function in high-availability programs to, say,	266	You could override this function in high-availability programs to, say,
246	free some memory if it cannot allocate memory, to use a special allocator,	267	free some memory if it cannot allocate memory, to use a special allocator,
247	or even to sleep a while and retry until some memory is available.	268	or even to sleep a while and retry until some memory is available.
248		269
		270	Example: The following is the C<realloc> function that libev itself uses
		271	which should work with C<realloc> and C<free> functions of all kinds and
		272	is probably a good basis for your own implementation.
		273
		274	static void *
		275	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		276	{
		277	if (size)
		278	return realloc (ptr, size);
		279
		280	free (ptr);
		281	return 0;
		282	}
		283
249	Example: Replace the libev allocator with one that waits a bit and then	284	Example: Replace the libev allocator with one that waits a bit and then
250	retries (example requires a standards-compliant C<realloc>).	285	retries.
251		286
252	static void *	287	static void *
253	persistent_realloc (void *ptr, size_t size)	288	persistent_realloc (void *ptr, size_t size)
254	{	289	{
		290	if (!size)
		291	{
		292	free (ptr);
		293	return 0;
		294	}
		295
255	for (;;)	296	for (;;)
256	{	297	{
257	void *newptr = realloc (ptr, size);	298	void *newptr = realloc (ptr, size);
258		299
259	if (newptr)	300	if (newptr)
…		…
264	}	305	}
265		306
266	...	307	...
267	ev_set_allocator (persistent_realloc);	308	ev_set_allocator (persistent_realloc);
268		309
269	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	310	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
270		311
271	Set the callback function to call on a retryable system call error (such	312	Set the callback function to call on a retryable system call error (such
272	as failed select, poll, epoll_wait). The message is a printable string	313	as failed select, poll, epoll_wait). The message is a printable string
273	indicating the system call or subsystem causing the problem. If this	314	indicating the system call or subsystem causing the problem. If this
274	callback is set, then libev will expect it to remedy the situation, no	315	callback is set, then libev will expect it to remedy the situation, no
…		…
286	}	327	}
287		328
288	...	329	...
289	ev_set_syserr_cb (fatal_error);	330	ev_set_syserr_cb (fatal_error);
290		331
		332	=item ev_feed_signal (int signum)
		333
		334	This function can be used to "simulate" a signal receive. It is completely
		335	safe to call this function at any time, from any context, including signal
		336	handlers or random threads.
		337
		338	Its main use is to customise signal handling in your process, especially
		339	in the presence of threads. For example, you could block signals
		340	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		341	creating any loops), and in one thread, use C<sigwait> or any other
		342	mechanism to wait for signals, then "deliver" them to libev by calling
		343	C<ev_feed_signal>.
		344
291	=back	345	=back
292		346
293	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	347	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
294		348
295	An event loop is described by a C<struct ev_loop *> (the C<struct>	349	An event loop is described by a C<struct ev_loop *> (the C<struct> is
296	is I<not> optional in this case, as there is also an C<ev_loop>	350	I<not> optional in this case unless libev 3 compatibility is disabled, as
297	I<function>).	351	libev 3 had an C<ev_loop> function colliding with the struct name).
298		352
299	The library knows two types of such loops, the I<default> loop, which	353	The library knows two types of such loops, the I<default> loop, which
300	supports signals and child events, and dynamically created loops which do	354	supports child process events, and dynamically created event loops which
301	not.	355	do not.
302		356
303	=over 4	357	=over 4
304		358
305	=item struct ev_loop *ev_default_loop (unsigned int flags)	359	=item struct ev_loop *ev_default_loop (unsigned int flags)
306		360
307	This will initialise the default event loop if it hasn't been initialised	361	This returns the "default" event loop object, which is what you should
308	yet and return it. If the default loop could not be initialised, returns	362	normally use when you just need "the event loop". Event loop objects and
309	false. If it already was initialised it simply returns it (and ignores the	363	the C<flags> parameter are described in more detail in the entry for
310	flags. If that is troubling you, check C<ev_backend ()> afterwards).	364	C<ev_loop_new>.
		365
		366	If the default loop is already initialised then this function simply
		367	returns it (and ignores the flags. If that is troubling you, check
		368	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		369	flags, which should almost always be C<0>, unless the caller is also the
		370	one calling C<ev_run> or otherwise qualifies as "the main program".
311		371
312	If you don't know what event loop to use, use the one returned from this	372	If you don't know what event loop to use, use the one returned from this
313	function.	373	function (or via the C<EV_DEFAULT> macro).
314		374
315	Note that this function is I<not> thread-safe, so if you want to use it	375	Note that this function is I<not> thread-safe, so if you want to use it
316	from multiple threads, you have to lock (note also that this is unlikely,	376	from multiple threads, you have to employ some kind of mutex (note also
317	as loops cannot be shared easily between threads anyway).	377	that this case is unlikely, as loops cannot be shared easily between
		378	threads anyway).
318		379
319	The default loop is the only loop that can handle C<ev_signal> and	380	The default loop is the only loop that can handle C<ev_child> watchers,
320	C<ev_child> watchers, and to do this, it always registers a handler	381	and to do this, it always registers a handler for C<SIGCHLD>. If this is
321	for C<SIGCHLD>. If this is a problem for your application you can either	382	a problem for your application you can either create a dynamic loop with
322	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	383	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
323	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	384	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
324	C<ev_default_init>.	385
		386	Example: This is the most typical usage.
		387
		388	if (!ev_default_loop (0))
		389	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		390
		391	Example: Restrict libev to the select and poll backends, and do not allow
		392	environment settings to be taken into account:
		393
		394	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		395
		396	=item struct ev_loop *ev_loop_new (unsigned int flags)
		397
		398	This will create and initialise a new event loop object. If the loop
		399	could not be initialised, returns false.
		400
		401	This function is thread-safe, and one common way to use libev with
		402	threads is indeed to create one loop per thread, and using the default
		403	loop in the "main" or "initial" thread.
325		404
326	The flags argument can be used to specify special behaviour or specific	405	The flags argument can be used to specify special behaviour or specific
327	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	406	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
328		407
329	The following flags are supported:	408	The following flags are supported:
…		…
339		418
340	If this flag bit is or'ed into the flag value (or the program runs setuid	419	If this flag bit is or'ed into the flag value (or the program runs setuid
341	or setgid) then libev will I<not> look at the environment variable	420	or setgid) then libev will I<not> look at the environment variable
342	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	421	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
343	override the flags completely if it is found in the environment. This is	422	override the flags completely if it is found in the environment. This is
344	useful to try out specific backends to test their performance, or to work	423	useful to try out specific backends to test their performance, to work
345	around bugs.	424	around bugs, or to make libev threadsafe (accessing environment variables
		425	cannot be done in a threadsafe way, but usually it works if no other
		426	thread modifies them).
346		427
347	=item C<EVFLAG_FORKCHECK>	428	=item C<EVFLAG_FORKCHECK>
348		429
349	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	430	Instead of calling C<ev_loop_fork> manually after a fork, you can also
350	a fork, you can also make libev check for a fork in each iteration by	431	make libev check for a fork in each iteration by enabling this flag.
351	enabling this flag.
352		432
353	This works by calling C<getpid ()> on every iteration of the loop,	433	This works by calling C<getpid ()> on every iteration of the loop,
354	and thus this might slow down your event loop if you do a lot of loop	434	and thus this might slow down your event loop if you do a lot of loop
355	iterations and little real work, but is usually not noticeable (on my	435	iterations and little real work, but is usually not noticeable (on my
356	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	436	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
357	without a system call and thus I<very> fast, but my GNU/Linux system also has	437	sequence without a system call and thus I<very> fast, but my GNU/Linux
358	C<pthread_atfork> which is even faster).	438	system also has C<pthread_atfork> which is even faster). (Update: glibc
		439	versions 2.25 apparently removed the C<getpid> optimisation again).
359		440
360	The big advantage of this flag is that you can forget about fork (and	441	The big advantage of this flag is that you can forget about fork (and
361	forget about forgetting to tell libev about forking) when you use this	442	forget about forgetting to tell libev about forking, although you still
362	flag.	443	have to ignore C<SIGPIPE>) when you use this flag.
363		444
364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	445	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
365	environment variable.	446	environment variable.
		447
		448	=item C<EVFLAG_NOINOTIFY>
		449
		450	When this flag is specified, then libev will not attempt to use the
		451	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
		452	testing, this flag can be useful to conserve inotify file descriptors, as
		453	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		454
		455	=item C<EVFLAG_SIGNALFD>
		456
		457	When this flag is specified, then libev will attempt to use the
		458	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
		459	delivers signals synchronously, which makes it both faster and might make
		460	it possible to get the queued signal data. It can also simplify signal
		461	handling with threads, as long as you properly block signals in your
		462	threads that are not interested in handling them.
		463
		464	Signalfd will not be used by default as this changes your signal mask, and
		465	there are a lot of shoddy libraries and programs (glib's threadpool for
		466	example) that can't properly initialise their signal masks.
		467
		468	=item C<EVFLAG_NOSIGMASK>
		469
		470	When this flag is specified, then libev will avoid to modify the signal
		471	mask. Specifically, this means you have to make sure signals are unblocked
		472	when you want to receive them.
		473
		474	This behaviour is useful when you want to do your own signal handling, or
		475	want to handle signals only in specific threads and want to avoid libev
		476	unblocking the signals.
		477
		478	It's also required by POSIX in a threaded program, as libev calls
		479	C<sigprocmask>, whose behaviour is officially unspecified.
		480
		481	This flag's behaviour will become the default in future versions of libev.
366		482
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	483	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		484
369	This is your standard select(2) backend. Not I<completely> standard, as	485	This is your standard select(2) backend. Not I<completely> standard, as
370	libev tries to roll its own fd_set with no limits on the number of fds,	486	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
395	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	511	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
396	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	512	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
397		513
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	514	=item C<EVBACKEND_EPOLL> (value 4, Linux)
399		515
		516	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		517	kernels).
		518
400	For few fds, this backend is a bit little slower than poll and select,	519	For few fds, this backend is a bit little slower than poll and select, but
401	but it scales phenomenally better. While poll and select usually scale	520	it scales phenomenally better. While poll and select usually scale like
402	like O(total_fds) where n is the total number of fds (or the highest fd),	521	O(total_fds) where total_fds is the total number of fds (or the highest
403	epoll scales either O(1) or O(active_fds).	522	fd), epoll scales either O(1) or O(active_fds).
404		523
405	The epoll mechanism deserves honorable mention as the most misdesigned	524	The epoll mechanism deserves honorable mention as the most misdesigned
406	of the more advanced event mechanisms: mere annoyances include silently	525	of the more advanced event mechanisms: mere annoyances include silently
407	dropping file descriptors, requiring a system call per change per file	526	dropping file descriptors, requiring a system call per change per file
408	descriptor (and unnecessary guessing of parameters), problems with dup and	527	descriptor (and unnecessary guessing of parameters), problems with dup,
		528	returning before the timeout value, resulting in additional iterations
		529	(and only giving 5ms accuracy while select on the same platform gives
409	so on. The biggest issue is fork races, however - if a program forks then	530	0.1ms) and so on. The biggest issue is fork races, however - if a program
410	I<both> parent and child process have to recreate the epoll set, which can	531	forks then I<both> parent and child process have to recreate the epoll
411	take considerable time (one syscall per file descriptor) and is of course	532	set, which can take considerable time (one syscall per file descriptor)
412	hard to detect.	533	and is of course hard to detect.
413		534
414	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	535	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
415	of course I<doesn't>, and epoll just loves to report events for totally	536	but of course I<doesn't>, and epoll just loves to report events for
416	I<different> file descriptors (even already closed ones, so one cannot	537	totally I<different> file descriptors (even already closed ones, so
417	even remove them from the set) than registered in the set (especially	538	one cannot even remove them from the set) than registered in the set
418	on SMP systems). Libev tries to counter these spurious notifications by	539	(especially on SMP systems). Libev tries to counter these spurious
419	employing an additional generation counter and comparing that against the	540	notifications by employing an additional generation counter and comparing
420	events to filter out spurious ones, recreating the set when required.	541	that against the events to filter out spurious ones, recreating the set
		542	when required. Epoll also erroneously rounds down timeouts, but gives you
		543	no way to know when and by how much, so sometimes you have to busy-wait
		544	because epoll returns immediately despite a nonzero timeout. And last
		545	not least, it also refuses to work with some file descriptors which work
		546	perfectly fine with C<select> (files, many character devices...).
		547
		548	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		549	cobbled together in a hurry, no thought to design or interaction with
		550	others. Oh, the pain, will it ever stop...
421		551
422	While stopping, setting and starting an I/O watcher in the same iteration	552	While stopping, setting and starting an I/O watcher in the same iteration
423	will result in some caching, there is still a system call per such	553	will result in some caching, there is still a system call per such
424	incident (because the same I<file descriptor> could point to a different	554	incident (because the same I<file descriptor> could point to a different
425	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	555	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
437	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or	567	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
438	faster than epoll for maybe up to a hundred file descriptors, depending on	568	faster than epoll for maybe up to a hundred file descriptors, depending on
439	the usage. So sad.	569	the usage. So sad.
440		570
441	While nominally embeddable in other event loops, this feature is broken in	571	While nominally embeddable in other event loops, this feature is broken in
442	all kernel versions tested so far.	572	a lot of kernel revisions, but probably(!) works in current versions.
		573
		574	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		575	C<EVBACKEND_POLL>.
		576
		577	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		578
		579	Use the linux-specific linux aio (I<not> C<< aio(7) >>) event interface
		580	available in post-4.18 kernels.
		581
		582	If this backend works for you (as of this writing, it was very
		583	experimental and only supports a subset of file types), it is the best
		584	event interface available on linux and might be well worth it enabling it
		585	- if it isn't available in your kernel this will be detected and another
		586	backend will be chosen.
		587
		588	This backend can batch oneshot requests and uses a user-space ring buffer
		589	to receive events. It also doesn't suffer from most of the design problems
		590	of epoll (such as not being able to remove event sources from the epoll
		591	set), and generally sounds too good to be true. Because, this being the
		592	linux kernel, of course it suffers from a whole new set of limitations.
		593
		594	For one, it is not easily embeddable (but probably could be done using
		595	an event fd at some extra overhead). It also is subject to various
		596	arbitrary limits that can be configured in F</proc/sys/fs/aio-max-nr>
		597	and F</proc/sys/fs/aio-nr>), which could lead to it being skipped during
		598	initialisation.
		599
		600	Most problematic in practise, however, is that, like kqueue, it requires
		601	special support from drivers, and, not surprisingly, not all drivers
		602	implement it. For example, in linux 4.19, tcp sockets, pipes, event fds,
		603	files, F</dev/null> and a few others are supported, but ttys are not, so
		604	this is not (yet?) a generic event polling interface but is probably still
		605	be very useful in a web server or similar program.
443		606
444	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	607	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
445	C<EVBACKEND_POLL>.	608	C<EVBACKEND_POLL>.
446		609
447	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	610	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
…		…
462		625
463	It scales in the same way as the epoll backend, but the interface to the	626	It scales in the same way as the epoll backend, but the interface to the
464	kernel is more efficient (which says nothing about its actual speed, of	627	kernel is more efficient (which says nothing about its actual speed, of
465	course). While stopping, setting and starting an I/O watcher does never	628	course). While stopping, setting and starting an I/O watcher does never
466	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	629	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
467	two event changes per incident. Support for C<fork ()> is very bad (but	630	two event changes per incident. Support for C<fork ()> is very bad (you
468	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	631	might have to leak fd's on fork, but it's more sane than epoll) and it
469	cases	632	drops fds silently in similarly hard-to-detect cases.
470		633
471	This backend usually performs well under most conditions.	634	This backend usually performs well under most conditions.
472		635
473	While nominally embeddable in other event loops, this doesn't work	636	While nominally embeddable in other event loops, this doesn't work
474	everywhere, so you might need to test for this. And since it is broken	637	everywhere, so you might need to test for this. And since it is broken
…		…
491	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	654	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
492		655
493	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	656	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
494	it's really slow, but it still scales very well (O(active_fds)).	657	it's really slow, but it still scales very well (O(active_fds)).
495		658
496	Please note that Solaris event ports can deliver a lot of spurious
497	notifications, so you need to use non-blocking I/O or other means to avoid
498	blocking when no data (or space) is available.
499
500	While this backend scales well, it requires one system call per active	659	While this backend scales well, it requires one system call per active
501	file descriptor per loop iteration. For small and medium numbers of file	660	file descriptor per loop iteration. For small and medium numbers of file
502	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	661	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
503	might perform better.	662	might perform better.
504		663
505	On the positive side, with the exception of the spurious readiness	664	On the positive side, this backend actually performed fully to
506	notifications, this backend actually performed fully to specification
507	in all tests and is fully embeddable, which is a rare feat among the	665	specification in all tests and is fully embeddable, which is a rare feat
508	OS-specific backends (I vastly prefer correctness over speed hacks).	666	among the OS-specific backends (I vastly prefer correctness over speed
		667	hacks).
		668
		669	On the negative side, the interface is I<bizarre> - so bizarre that
		670	even sun itself gets it wrong in their code examples: The event polling
		671	function sometimes returns events to the caller even though an error
		672	occurred, but with no indication whether it has done so or not (yes, it's
		673	even documented that way) - deadly for edge-triggered interfaces where you
		674	absolutely have to know whether an event occurred or not because you have
		675	to re-arm the watcher.
		676
		677	Fortunately libev seems to be able to work around these idiocies.
509		678
510	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	679	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
511	C<EVBACKEND_POLL>.	680	C<EVBACKEND_POLL>.
512		681
513	=item C<EVBACKEND_ALL>	682	=item C<EVBACKEND_ALL>
514		683
515	Try all backends (even potentially broken ones that wouldn't be tried	684	Try all backends (even potentially broken ones that wouldn't be tried
516	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	685	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
517	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	686	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
518		687
519	It is definitely not recommended to use this flag.	688	It is definitely not recommended to use this flag, use whatever
		689	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		690	at all.
		691
		692	=item C<EVBACKEND_MASK>
		693
		694	Not a backend at all, but a mask to select all backend bits from a
		695	C<flags> value, in case you want to mask out any backends from a flags
		696	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
520		697
521	=back	698	=back
522		699
523	If one or more of these are or'ed into the flags value, then only these	700	If one or more of the backend flags are or'ed into the flags value,
524	backends will be tried (in the reverse order as listed here). If none are	701	then only these backends will be tried (in the reverse order as listed
525	specified, all backends in C<ev_recommended_backends ()> will be tried.	702	here). If none are specified, all backends in C<ev_recommended_backends
526		703	()> will be tried.
527	Example: This is the most typical usage.
528
529	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
531
532	Example: Restrict libev to the select and poll backends, and do not allow
533	environment settings to be taken into account:
534
535	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
536
537	Example: Use whatever libev has to offer, but make sure that kqueue is
538	used if available (warning, breaks stuff, best use only with your own
539	private event loop and only if you know the OS supports your types of
540	fds):
541
542	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
543
544	=item struct ev_loop *ev_loop_new (unsigned int flags)
545
546	Similar to C<ev_default_loop>, but always creates a new event loop that is
547	always distinct from the default loop. Unlike the default loop, it cannot
548	handle signal and child watchers, and attempts to do so will be greeted by
549	undefined behaviour (or a failed assertion if assertions are enabled).
550
551	Note that this function I<is> thread-safe, and the recommended way to use
552	libev with threads is indeed to create one loop per thread, and using the
553	default loop in the "main" or "initial" thread.
554		704
555	Example: Try to create a event loop that uses epoll and nothing else.	705	Example: Try to create a event loop that uses epoll and nothing else.
556		706
557	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	707	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
558	if (!epoller)	708	if (!epoller)
559	fatal ("no epoll found here, maybe it hides under your chair");	709	fatal ("no epoll found here, maybe it hides under your chair");
560		710
		711	Example: Use whatever libev has to offer, but make sure that kqueue is
		712	used if available.
		713
		714	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		715
		716	Example: Similarly, on linux, you mgiht want to take advantage of the
		717	linux aio backend if possible, but fall back to something else if that
		718	isn't available.
		719
		720	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		721
561	=item ev_default_destroy ()	722	=item ev_loop_destroy (loop)
562		723
563	Destroys the default loop again (frees all memory and kernel state	724	Destroys an event loop object (frees all memory and kernel state
564	etc.). None of the active event watchers will be stopped in the normal	725	etc.). None of the active event watchers will be stopped in the normal
565	sense, so e.g. C<ev_is_active> might still return true. It is your	726	sense, so e.g. C<ev_is_active> might still return true. It is your
566	responsibility to either stop all watchers cleanly yourself I<before>	727	responsibility to either stop all watchers cleanly yourself I<before>
567	calling this function, or cope with the fact afterwards (which is usually	728	calling this function, or cope with the fact afterwards (which is usually
568	the easiest thing, you can just ignore the watchers and/or C<free ()> them	729	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
570		731
571	Note that certain global state, such as signal state (and installed signal	732	Note that certain global state, such as signal state (and installed signal
572	handlers), will not be freed by this function, and related watchers (such	733	handlers), will not be freed by this function, and related watchers (such
573	as signal and child watchers) would need to be stopped manually.	734	as signal and child watchers) would need to be stopped manually.
574		735
575	In general it is not advisable to call this function except in the	736	This function is normally used on loop objects allocated by
576	rare occasion where you really need to free e.g. the signal handling	737	C<ev_loop_new>, but it can also be used on the default loop returned by
		738	C<ev_default_loop>, in which case it is not thread-safe.
		739
		740	Note that it is not advisable to call this function on the default loop
		741	except in the rare occasion where you really need to free its resources.
577	pipe fds. If you need dynamically allocated loops it is better to use	742	If you need dynamically allocated loops it is better to use C<ev_loop_new>
578	C<ev_loop_new> and C<ev_loop_destroy>).	743	and C<ev_loop_destroy>.
579		744
580	=item ev_loop_destroy (loop)	745	=item ev_loop_fork (loop)
581		746
582	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.
584
585	=item ev_default_fork ()
586
587	This function sets a flag that causes subsequent C<ev_loop> iterations	747	This function sets a flag that causes subsequent C<ev_run> iterations
588	to reinitialise the kernel state for backends that have one. Despite the	748	to reinitialise the kernel state for backends that have one. Despite
589	name, you can call it anytime, but it makes most sense after forking, in	749	the name, you can call it anytime you are allowed to start or stop
590	the child process (or both child and parent, but that again makes little	750	watchers (except inside an C<ev_prepare> callback), but it makes most
591	sense). You I<must> call it in the child before using any of the libev	751	sense after forking, in the child process. You I<must> call it (or use
592	functions, and it will only take effect at the next C<ev_loop> iteration.	752	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		753
		754	In addition, if you want to reuse a loop (via this function or
		755	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		756
		757	Again, you I<have> to call it on I<any> loop that you want to re-use after
		758	a fork, I<even if you do not plan to use the loop in the parent>. This is
		759	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		760	during fork.
593		761
594	On the other hand, you only need to call this function in the child	762	On the other hand, you only need to call this function in the child
595	process if and only if you want to use the event library in the child. If	763	process if and only if you want to use the event loop in the child. If
596	you just fork+exec, you don't have to call it at all.	764	you just fork+exec or create a new loop in the child, you don't have to
		765	call it at all (in fact, C<epoll> is so badly broken that it makes a
		766	difference, but libev will usually detect this case on its own and do a
		767	costly reset of the backend).
597		768
598	The function itself is quite fast and it's usually not a problem to call	769	The function itself is quite fast and it's usually not a problem to call
599	it just in case after a fork. To make this easy, the function will fit in	770	it just in case after a fork.
600	quite nicely into a call to C<pthread_atfork>:
601		771
		772	Example: Automate calling C<ev_loop_fork> on the default loop when
		773	using pthreads.
		774
		775	static void
		776	post_fork_child (void)
		777	{
		778	ev_loop_fork (EV_DEFAULT);
		779	}
		780
		781	...
602	pthread_atfork (0, 0, ev_default_fork);	782	pthread_atfork (0, 0, post_fork_child);
603
604	=item ev_loop_fork (loop)
605
606	Like C<ev_default_fork>, but acts on an event loop created by
607	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
608	after fork that you want to re-use in the child, and how you do this is
609	entirely your own problem.
610		783
611	=item int ev_is_default_loop (loop)	784	=item int ev_is_default_loop (loop)
612		785
613	Returns true when the given loop is, in fact, the default loop, and false	786	Returns true when the given loop is, in fact, the default loop, and false
614	otherwise.	787	otherwise.
615		788
616	=item unsigned int ev_loop_count (loop)	789	=item unsigned int ev_iteration (loop)
617		790
618	Returns the count of loop iterations for the loop, which is identical to	791	Returns the current iteration count for the event loop, which is identical
619	the number of times libev did poll for new events. It starts at C<0> and	792	to the number of times libev did poll for new events. It starts at C<0>
620	happily wraps around with enough iterations.	793	and happily wraps around with enough iterations.
621		794
622	This value can sometimes be useful as a generation counter of sorts (it	795	This value can sometimes be useful as a generation counter of sorts (it
623	"ticks" the number of loop iterations), as it roughly corresponds with	796	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	797	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		798	prepare and check phases.
625		799
626	=item unsigned int ev_loop_depth (loop)	800	=item unsigned int ev_depth (loop)
627		801
628	Returns the number of times C<ev_loop> was entered minus the number of	802	Returns the number of times C<ev_run> was entered minus the number of
629	times C<ev_loop> was exited, in other words, the recursion depth.	803	times C<ev_run> was exited normally, in other words, the recursion depth.
630		804
631	Outside C<ev_loop>, this number is zero. In a callback, this number is	805	Outside C<ev_run>, this number is zero. In a callback, this number is
632	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	806	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
633	in which case it is higher.	807	in which case it is higher.
634		808
635	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	809	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
636	etc.), doesn't count as exit.	810	throwing an exception etc.), doesn't count as "exit" - consider this
		811	as a hint to avoid such ungentleman-like behaviour unless it's really
		812	convenient, in which case it is fully supported.
637		813
638	=item unsigned int ev_backend (loop)	814	=item unsigned int ev_backend (loop)
639		815
640	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	816	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
641	use.	817	use.
…		…
650		826
651	=item ev_now_update (loop)	827	=item ev_now_update (loop)
652		828
653	Establishes the current time by querying the kernel, updating the time	829	Establishes the current time by querying the kernel, updating the time
654	returned by C<ev_now ()> in the progress. This is a costly operation and	830	returned by C<ev_now ()> in the progress. This is a costly operation and
655	is usually done automatically within C<ev_loop ()>.	831	is usually done automatically within C<ev_run ()>.
656		832
657	This function is rarely useful, but when some event callback runs for a	833	This function is rarely useful, but when some event callback runs for a
658	very long time without entering the event loop, updating libev's idea of	834	very long time without entering the event loop, updating libev's idea of
659	the current time is a good idea.	835	the current time is a good idea.
660		836
661	See also L<The special problem of time updates> in the C<ev_timer> section.	837	See also L</The special problem of time updates> in the C<ev_timer> section.
662		838
663	=item ev_suspend (loop)	839	=item ev_suspend (loop)
664		840
665	=item ev_resume (loop)	841	=item ev_resume (loop)
666		842
667	These two functions suspend and resume a loop, for use when the loop is	843	These two functions suspend and resume an event loop, for use when the
668	not used for a while and timeouts should not be processed.	844	loop is not used for a while and timeouts should not be processed.
669		845
670	A typical use case would be an interactive program such as a game: When	846	A typical use case would be an interactive program such as a game: When
671	the user presses C<^Z> to suspend the game and resumes it an hour later it	847	the user presses C<^Z> to suspend the game and resumes it an hour later it
672	would be best to handle timeouts as if no time had actually passed while	848	would be best to handle timeouts as if no time had actually passed while
673	the program was suspended. This can be achieved by calling C<ev_suspend>	849	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
675	C<ev_resume> directly afterwards to resume timer processing.	851	C<ev_resume> directly afterwards to resume timer processing.
676		852
677	Effectively, all C<ev_timer> watchers will be delayed by the time spend	853	Effectively, all C<ev_timer> watchers will be delayed by the time spend
678	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	854	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
679	will be rescheduled (that is, they will lose any events that would have	855	will be rescheduled (that is, they will lose any events that would have
680	occured while suspended).	856	occurred while suspended).
681		857
682	After calling C<ev_suspend> you B<must not> call I<any> function on the	858	After calling C<ev_suspend> you B<must not> call I<any> function on the
683	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	859	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
684	without a previous call to C<ev_suspend>.	860	without a previous call to C<ev_suspend>.
685		861
686	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	862	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
687	event loop time (see C<ev_now_update>).	863	event loop time (see C<ev_now_update>).
688		864
689	=item ev_loop (loop, int flags)	865	=item bool ev_run (loop, int flags)
690		866
691	Finally, this is it, the event handler. This function usually is called	867	Finally, this is it, the event handler. This function usually is called
692	after you initialised all your watchers and you want to start handling	868	after you have initialised all your watchers and you want to start
693	events.	869	handling events. It will ask the operating system for any new events, call
		870	the watcher callbacks, and then repeat the whole process indefinitely: This
		871	is why event loops are called I<loops>.
694		872
695	If the flags argument is specified as C<0>, it will not return until	873	If the flags argument is specified as C<0>, it will keep handling events
696	either no event watchers are active anymore or C<ev_unloop> was called.	874	until either no event watchers are active anymore or C<ev_break> was
		875	called.
697		876
		877	The return value is false if there are no more active watchers (which
		878	usually means "all jobs done" or "deadlock"), and true in all other cases
		879	(which usually means " you should call C<ev_run> again").
		880
698	Please note that an explicit C<ev_unloop> is usually better than	881	Please note that an explicit C<ev_break> is usually better than
699	relying on all watchers to be stopped when deciding when a program has	882	relying on all watchers to be stopped when deciding when a program has
700	finished (especially in interactive programs), but having a program	883	finished (especially in interactive programs), but having a program
701	that automatically loops as long as it has to and no longer by virtue	884	that automatically loops as long as it has to and no longer by virtue
702	of relying on its watchers stopping correctly, that is truly a thing of	885	of relying on its watchers stopping correctly, that is truly a thing of
703	beauty.	886	beauty.
704		887
		888	This function is I<mostly> exception-safe - you can break out of a
		889	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		890	exception and so on. This does not decrement the C<ev_depth> value, nor
		891	will it clear any outstanding C<EVBREAK_ONE> breaks.
		892
705	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	893	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
706	those events and any already outstanding ones, but will not block your	894	those events and any already outstanding ones, but will not wait and
707	process in case there are no events and will return after one iteration of	895	block your process in case there are no events and will return after one
708	the loop.	896	iteration of the loop. This is sometimes useful to poll and handle new
		897	events while doing lengthy calculations, to keep the program responsive.
709		898
710	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	899	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
711	necessary) and will handle those and any already outstanding ones. It	900	necessary) and will handle those and any already outstanding ones. It
712	will block your process until at least one new event arrives (which could	901	will block your process until at least one new event arrives (which could
713	be an event internal to libev itself, so there is no guarantee that a	902	be an event internal to libev itself, so there is no guarantee that a
714	user-registered callback will be called), and will return after one	903	user-registered callback will be called), and will return after one
715	iteration of the loop.	904	iteration of the loop.
716		905
717	This is useful if you are waiting for some external event in conjunction	906	This is useful if you are waiting for some external event in conjunction
718	with something not expressible using other libev watchers (i.e. "roll your	907	with something not expressible using other libev watchers (i.e. "roll your
719	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	908	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
720	usually a better approach for this kind of thing.	909	usually a better approach for this kind of thing.
721		910
722	Here are the gory details of what C<ev_loop> does:	911	Here are the gory details of what C<ev_run> does (this is for your
		912	understanding, not a guarantee that things will work exactly like this in
		913	future versions):
723		914
		915	- Increment loop depth.
		916	- Reset the ev_break status.
724	- Before the first iteration, call any pending watchers.	917	- Before the first iteration, call any pending watchers.
		918	LOOP:
725	* If EVFLAG_FORKCHECK was used, check for a fork.	919	- If EVFLAG_FORKCHECK was used, check for a fork.
726	- If a fork was detected (by any means), queue and call all fork watchers.	920	- If a fork was detected (by any means), queue and call all fork watchers.
727	- Queue and call all prepare watchers.	921	- Queue and call all prepare watchers.
		922	- If ev_break was called, goto FINISH.
728	- If we have been forked, detach and recreate the kernel state	923	- If we have been forked, detach and recreate the kernel state
729	as to not disturb the other process.	924	as to not disturb the other process.
730	- Update the kernel state with all outstanding changes.	925	- Update the kernel state with all outstanding changes.
731	- Update the "event loop time" (ev_now ()).	926	- Update the "event loop time" (ev_now ()).
732	- Calculate for how long to sleep or block, if at all	927	- Calculate for how long to sleep or block, if at all
733	(active idle watchers, EVLOOP_NONBLOCK or not having	928	(active idle watchers, EVRUN_NOWAIT or not having
734	any active watchers at all will result in not sleeping).	929	any active watchers at all will result in not sleeping).
735	- Sleep if the I/O and timer collect interval say so.	930	- Sleep if the I/O and timer collect interval say so.
		931	- Increment loop iteration counter.
736	- Block the process, waiting for any events.	932	- Block the process, waiting for any events.
737	- Queue all outstanding I/O (fd) events.	933	- Queue all outstanding I/O (fd) events.
738	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	934	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
739	- Queue all expired timers.	935	- Queue all expired timers.
740	- Queue all expired periodics.	936	- Queue all expired periodics.
741	- Unless any events are pending now, queue all idle watchers.	937	- Queue all idle watchers with priority higher than that of pending events.
742	- Queue all check watchers.	938	- Queue all check watchers.
743	- Call all queued watchers in reverse order (i.e. check watchers first).	939	- Call all queued watchers in reverse order (i.e. check watchers first).
744	Signals and child watchers are implemented as I/O watchers, and will	940	Signals and child watchers are implemented as I/O watchers, and will
745	be handled here by queueing them when their watcher gets executed.	941	be handled here by queueing them when their watcher gets executed.
746	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	942	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
747	were used, or there are no active watchers, return, otherwise	943	were used, or there are no active watchers, goto FINISH, otherwise
748	continue with step *.	944	continue with step LOOP.
		945	FINISH:
		946	- Reset the ev_break status iff it was EVBREAK_ONE.
		947	- Decrement the loop depth.
		948	- Return.
749		949
750	Example: Queue some jobs and then loop until no events are outstanding	950	Example: Queue some jobs and then loop until no events are outstanding
751	anymore.	951	anymore.
752		952
753	... queue jobs here, make sure they register event watchers as long	953	... queue jobs here, make sure they register event watchers as long
754	... as they still have work to do (even an idle watcher will do..)	954	... as they still have work to do (even an idle watcher will do..)
755	ev_loop (my_loop, 0);	955	ev_run (my_loop, 0);
756	... jobs done or somebody called unloop. yeah!	956	... jobs done or somebody called break. yeah!
757		957
758	=item ev_unloop (loop, how)	958	=item ev_break (loop, how)
759		959
760	Can be used to make a call to C<ev_loop> return early (but only after it	960	Can be used to make a call to C<ev_run> return early (but only after it
761	has processed all outstanding events). The C<how> argument must be either	961	has processed all outstanding events). The C<how> argument must be either
762	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	962	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
763	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	963	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
764		964
765	This "unloop state" will be cleared when entering C<ev_loop> again.	965	This "break state" will be cleared on the next call to C<ev_run>.
766		966
767	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	967	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		968	which case it will have no effect.
768		969
769	=item ev_ref (loop)	970	=item ev_ref (loop)
770		971
771	=item ev_unref (loop)	972	=item ev_unref (loop)
772		973
773	Ref/unref can be used to add or remove a reference count on the event	974	Ref/unref can be used to add or remove a reference count on the event
774	loop: Every watcher keeps one reference, and as long as the reference	975	loop: Every watcher keeps one reference, and as long as the reference
775	count is nonzero, C<ev_loop> will not return on its own.	976	count is nonzero, C<ev_run> will not return on its own.
776		977
777	If you have a watcher you never unregister that should not keep C<ev_loop>	978	This is useful when you have a watcher that you never intend to
778	from returning, call ev_unref() after starting, and ev_ref() before	979	unregister, but that nevertheless should not keep C<ev_run> from
		980	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
779	stopping it.	981	before stopping it.
780		982
781	As an example, libev itself uses this for its internal signal pipe: It	983	As an example, libev itself uses this for its internal signal pipe: It
782	is not visible to the libev user and should not keep C<ev_loop> from	984	is not visible to the libev user and should not keep C<ev_run> from
783	exiting if no event watchers registered by it are active. It is also an	985	exiting if no event watchers registered by it are active. It is also an
784	excellent way to do this for generic recurring timers or from within	986	excellent way to do this for generic recurring timers or from within
785	third-party libraries. Just remember to I<unref after start> and I<ref	987	third-party libraries. Just remember to I<unref after start> and I<ref
786	before stop> (but only if the watcher wasn't active before, or was active	988	before stop> (but only if the watcher wasn't active before, or was active
787	before, respectively. Note also that libev might stop watchers itself	989	before, respectively. Note also that libev might stop watchers itself
788	(e.g. non-repeating timers) in which case you have to C<ev_ref>	990	(e.g. non-repeating timers) in which case you have to C<ev_ref>
789	in the callback).	991	in the callback).
790		992
791	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	993	Example: Create a signal watcher, but keep it from keeping C<ev_run>
792	running when nothing else is active.	994	running when nothing else is active.
793		995
794	ev_signal exitsig;	996	ev_signal exitsig;
795	ev_signal_init (&exitsig, sig_cb, SIGINT);	997	ev_signal_init (&exitsig, sig_cb, SIGINT);
796	ev_signal_start (loop, &exitsig);	998	ev_signal_start (loop, &exitsig);
797	evf_unref (loop);	999	ev_unref (loop);
798		1000
799	Example: For some weird reason, unregister the above signal handler again.	1001	Example: For some weird reason, unregister the above signal handler again.
800		1002
801	ev_ref (loop);	1003	ev_ref (loop);
802	ev_signal_stop (loop, &exitsig);	1004	ev_signal_stop (loop, &exitsig);
…		…
822	overhead for the actual polling but can deliver many events at once.	1024	overhead for the actual polling but can deliver many events at once.
823		1025
824	By setting a higher I<io collect interval> you allow libev to spend more	1026	By setting a higher I<io collect interval> you allow libev to spend more
825	time collecting I/O events, so you can handle more events per iteration,	1027	time collecting I/O events, so you can handle more events per iteration,
826	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1028	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
827	C<ev_timer>) will be not affected. Setting this to a non-null value will	1029	C<ev_timer>) will not be affected. Setting this to a non-null value will
828	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1030	introduce an additional C<ev_sleep ()> call into most loop iterations. The
829	sleep time ensures that libev will not poll for I/O events more often then	1031	sleep time ensures that libev will not poll for I/O events more often then
830	once per this interval, on average.	1032	once per this interval, on average (as long as the host time resolution is
		1033	good enough).
831		1034
832	Likewise, by setting a higher I<timeout collect interval> you allow libev	1035	Likewise, by setting a higher I<timeout collect interval> you allow libev
833	to spend more time collecting timeouts, at the expense of increased	1036	to spend more time collecting timeouts, at the expense of increased
834	latency/jitter/inexactness (the watcher callback will be called	1037	latency/jitter/inexactness (the watcher callback will be called
835	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1038	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
841	usually doesn't make much sense to set it to a lower value than C<0.01>,	1044	usually doesn't make much sense to set it to a lower value than C<0.01>,
842	as this approaches the timing granularity of most systems. Note that if	1045	as this approaches the timing granularity of most systems. Note that if
843	you do transactions with the outside world and you can't increase the	1046	you do transactions with the outside world and you can't increase the
844	parallelity, then this setting will limit your transaction rate (if you	1047	parallelity, then this setting will limit your transaction rate (if you
845	need to poll once per transaction and the I/O collect interval is 0.01,	1048	need to poll once per transaction and the I/O collect interval is 0.01,
846	then you can't do more than 100 transations per second).	1049	then you can't do more than 100 transactions per second).
847		1050
848	Setting the I<timeout collect interval> can improve the opportunity for	1051	Setting the I<timeout collect interval> can improve the opportunity for
849	saving power, as the program will "bundle" timer callback invocations that	1052	saving power, as the program will "bundle" timer callback invocations that
850	are "near" in time together, by delaying some, thus reducing the number of	1053	are "near" in time together, by delaying some, thus reducing the number of
851	times the process sleeps and wakes up again. Another useful technique to	1054	times the process sleeps and wakes up again. Another useful technique to
…		…
856	more often than 100 times per second:	1059	more often than 100 times per second:
857		1060
858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	1061	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1062	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		1063
		1064	=item ev_invoke_pending (loop)
		1065
		1066	This call will simply invoke all pending watchers while resetting their
		1067	pending state. Normally, C<ev_run> does this automatically when required,
		1068	but when overriding the invoke callback this call comes handy. This
		1069	function can be invoked from a watcher - this can be useful for example
		1070	when you want to do some lengthy calculation and want to pass further
		1071	event handling to another thread (you still have to make sure only one
		1072	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
		1073
		1074	=item int ev_pending_count (loop)
		1075
		1076	Returns the number of pending watchers - zero indicates that no watchers
		1077	are pending.
		1078
		1079	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		1080
		1081	This overrides the invoke pending functionality of the loop: Instead of
		1082	invoking all pending watchers when there are any, C<ev_run> will call
		1083	this callback instead. This is useful, for example, when you want to
		1084	invoke the actual watchers inside another context (another thread etc.).
		1085
		1086	If you want to reset the callback, use C<ev_invoke_pending> as new
		1087	callback.
		1088
		1089	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
		1090
		1091	Sometimes you want to share the same loop between multiple threads. This
		1092	can be done relatively simply by putting mutex_lock/unlock calls around
		1093	each call to a libev function.
		1094
		1095	However, C<ev_run> can run an indefinite time, so it is not feasible
		1096	to wait for it to return. One way around this is to wake up the event
		1097	loop via C<ev_break> and C<ev_async_send>, another way is to set these
		1098	I<release> and I<acquire> callbacks on the loop.
		1099
		1100	When set, then C<release> will be called just before the thread is
		1101	suspended waiting for new events, and C<acquire> is called just
		1102	afterwards.
		1103
		1104	Ideally, C<release> will just call your mutex_unlock function, and
		1105	C<acquire> will just call the mutex_lock function again.
		1106
		1107	While event loop modifications are allowed between invocations of
		1108	C<release> and C<acquire> (that's their only purpose after all), no
		1109	modifications done will affect the event loop, i.e. adding watchers will
		1110	have no effect on the set of file descriptors being watched, or the time
		1111	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
		1112	to take note of any changes you made.
		1113
		1114	In theory, threads executing C<ev_run> will be async-cancel safe between
		1115	invocations of C<release> and C<acquire>.
		1116
		1117	See also the locking example in the C<THREADS> section later in this
		1118	document.
		1119
		1120	=item ev_set_userdata (loop, void *data)
		1121
		1122	=item void *ev_userdata (loop)
		1123
		1124	Set and retrieve a single C<void *> associated with a loop. When
		1125	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		1126	C<0>.
		1127
		1128	These two functions can be used to associate arbitrary data with a loop,
		1129	and are intended solely for the C<invoke_pending_cb>, C<release> and
		1130	C<acquire> callbacks described above, but of course can be (ab-)used for
		1131	any other purpose as well.
		1132
861	=item ev_loop_verify (loop)	1133	=item ev_verify (loop)
862		1134
863	This function only does something when C<EV_VERIFY> support has been	1135	This function only does something when C<EV_VERIFY> support has been
864	compiled in, which is the default for non-minimal builds. It tries to go	1136	compiled in, which is the default for non-minimal builds. It tries to go
865	through all internal structures and checks them for validity. If anything	1137	through all internal structures and checks them for validity. If anything
866	is found to be inconsistent, it will print an error message to standard	1138	is found to be inconsistent, it will print an error message to standard
…		…
877		1149
878	In the following description, uppercase C<TYPE> in names stands for the	1150	In the following description, uppercase C<TYPE> in names stands for the
879	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1151	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
880	watchers and C<ev_io_start> for I/O watchers.	1152	watchers and C<ev_io_start> for I/O watchers.
881		1153
882	A watcher is a structure that you create and register to record your	1154	A watcher is an opaque structure that you allocate and register to record
883	interest in some event. For instance, if you want to wait for STDIN to	1155	your interest in some event. To make a concrete example, imagine you want
884	become readable, you would create an C<ev_io> watcher for that:	1156	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1157	for that:
885		1158
886	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1159	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
887	{	1160	{
888	ev_io_stop (w);	1161	ev_io_stop (w);
889	ev_unloop (loop, EVUNLOOP_ALL);	1162	ev_break (loop, EVBREAK_ALL);
890	}	1163	}
891		1164
892	struct ev_loop *loop = ev_default_loop (0);	1165	struct ev_loop *loop = ev_default_loop (0);
893		1166
894	ev_io stdin_watcher;	1167	ev_io stdin_watcher;
895		1168
896	ev_init (&stdin_watcher, my_cb);	1169	ev_init (&stdin_watcher, my_cb);
897	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1170	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
898	ev_io_start (loop, &stdin_watcher);	1171	ev_io_start (loop, &stdin_watcher);
899		1172
900	ev_loop (loop, 0);	1173	ev_run (loop, 0);
901		1174
902	As you can see, you are responsible for allocating the memory for your	1175	As you can see, you are responsible for allocating the memory for your
903	watcher structures (and it is I<usually> a bad idea to do this on the	1176	watcher structures (and it is I<usually> a bad idea to do this on the
904	stack).	1177	stack).
905		1178
906	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1179	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
907	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1180	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
908		1181
909	Each watcher structure must be initialised by a call to C<ev_init	1182	Each watcher structure must be initialised by a call to C<ev_init (watcher
910	(watcher *, callback)>, which expects a callback to be provided. This	1183	*, callback)>, which expects a callback to be provided. This callback is
911	callback gets invoked each time the event occurs (or, in the case of I/O	1184	invoked each time the event occurs (or, in the case of I/O watchers, each
912	watchers, each time the event loop detects that the file descriptor given	1185	time the event loop detects that the file descriptor given is readable
913	is readable and/or writable).	1186	and/or writable).
914		1187
915	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1188	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
916	macro to configure it, with arguments specific to the watcher type. There	1189	macro to configure it, with arguments specific to the watcher type. There
917	is also a macro to combine initialisation and setting in one call: C<<	1190	is also a macro to combine initialisation and setting in one call: C<<
918	ev_TYPE_init (watcher *, callback, ...) >>.	1191	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
941	=item C<EV_WRITE>	1214	=item C<EV_WRITE>
942		1215
943	The file descriptor in the C<ev_io> watcher has become readable and/or	1216	The file descriptor in the C<ev_io> watcher has become readable and/or
944	writable.	1217	writable.
945		1218
946	=item C<EV_TIMEOUT>	1219	=item C<EV_TIMER>
947		1220
948	The C<ev_timer> watcher has timed out.	1221	The C<ev_timer> watcher has timed out.
949		1222
950	=item C<EV_PERIODIC>	1223	=item C<EV_PERIODIC>
951		1224
…		…
969		1242
970	=item C<EV_PREPARE>	1243	=item C<EV_PREPARE>
971		1244
972	=item C<EV_CHECK>	1245	=item C<EV_CHECK>
973		1246
974	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1247	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
975	to gather new events, and all C<ev_check> watchers are invoked just after	1248	gather new events, and all C<ev_check> watchers are queued (not invoked)
976	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1249	just after C<ev_run> has gathered them, but before it queues any callbacks
		1250	for any received events. That means C<ev_prepare> watchers are the last
		1251	watchers invoked before the event loop sleeps or polls for new events, and
		1252	C<ev_check> watchers will be invoked before any other watchers of the same
		1253	or lower priority within an event loop iteration.
		1254
977	received events. Callbacks of both watcher types can start and stop as	1255	Callbacks of both watcher types can start and stop as many watchers as
978	many watchers as they want, and all of them will be taken into account	1256	they want, and all of them will be taken into account (for example, a
979	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1257	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
980	C<ev_loop> from blocking).	1258	blocking).
981		1259
982	=item C<EV_EMBED>	1260	=item C<EV_EMBED>
983		1261
984	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1262	The embedded event loop specified in the C<ev_embed> watcher needs attention.
985		1263
986	=item C<EV_FORK>	1264	=item C<EV_FORK>
987		1265
988	The event loop has been resumed in the child process after fork (see	1266	The event loop has been resumed in the child process after fork (see
989	C<ev_fork>).	1267	C<ev_fork>).
		1268
		1269	=item C<EV_CLEANUP>
		1270
		1271	The event loop is about to be destroyed (see C<ev_cleanup>).
990		1272
991	=item C<EV_ASYNC>	1273	=item C<EV_ASYNC>
992		1274
993	The given async watcher has been asynchronously notified (see C<ev_async>).	1275	The given async watcher has been asynchronously notified (see C<ev_async>).
994		1276
…		…
1041		1323
1042	ev_io w;	1324	ev_io w;
1043	ev_init (&w, my_cb);	1325	ev_init (&w, my_cb);
1044	ev_io_set (&w, STDIN_FILENO, EV_READ);	1326	ev_io_set (&w, STDIN_FILENO, EV_READ);
1045		1327
1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1328	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1047		1329
1048	This macro initialises the type-specific parts of a watcher. You need to	1330	This macro initialises the type-specific parts of a watcher. You need to
1049	call C<ev_init> at least once before you call this macro, but you can	1331	call C<ev_init> at least once before you call this macro, but you can
1050	call C<ev_TYPE_set> any number of times. You must not, however, call this	1332	call C<ev_TYPE_set> any number of times. You must not, however, call this
1051	macro on a watcher that is active (it can be pending, however, which is a	1333	macro on a watcher that is active (it can be pending, however, which is a
…		…
1064		1346
1065	Example: Initialise and set an C<ev_io> watcher in one step.	1347	Example: Initialise and set an C<ev_io> watcher in one step.
1066		1348
1067	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1349	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1068		1350
1069	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1351	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1070		1352
1071	Starts (activates) the given watcher. Only active watchers will receive	1353	Starts (activates) the given watcher. Only active watchers will receive
1072	events. If the watcher is already active nothing will happen.	1354	events. If the watcher is already active nothing will happen.
1073		1355
1074	Example: Start the C<ev_io> watcher that is being abused as example in this	1356	Example: Start the C<ev_io> watcher that is being abused as example in this
1075	whole section.	1357	whole section.
1076		1358
1077	ev_io_start (EV_DEFAULT_UC, &w);	1359	ev_io_start (EV_DEFAULT_UC, &w);
1078		1360
1079	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1361	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1080		1362
1081	Stops the given watcher if active, and clears the pending status (whether	1363	Stops the given watcher if active, and clears the pending status (whether
1082	the watcher was active or not).	1364	the watcher was active or not).
1083		1365
1084	It is possible that stopped watchers are pending - for example,	1366	It is possible that stopped watchers are pending - for example,
…		…
1104		1386
1105	=item callback ev_cb (ev_TYPE *watcher)	1387	=item callback ev_cb (ev_TYPE *watcher)
1106		1388
1107	Returns the callback currently set on the watcher.	1389	Returns the callback currently set on the watcher.
1108		1390
1109	=item ev_cb_set (ev_TYPE *watcher, callback)	1391	=item ev_set_cb (ev_TYPE *watcher, callback)
1110		1392
1111	Change the callback. You can change the callback at virtually any time	1393	Change the callback. You can change the callback at virtually any time
1112	(modulo threads).	1394	(modulo threads).
1113		1395
1114	=item ev_set_priority (ev_TYPE *watcher, priority)	1396	=item ev_set_priority (ev_TYPE *watcher, int priority)
1115		1397
1116	=item int ev_priority (ev_TYPE *watcher)	1398	=item int ev_priority (ev_TYPE *watcher)
1117		1399
1118	Set and query the priority of the watcher. The priority is a small	1400	Set and query the priority of the watcher. The priority is a small
1119	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1401	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1132	or might not have been clamped to the valid range.	1414	or might not have been clamped to the valid range.
1133		1415
1134	The default priority used by watchers when no priority has been set is	1416	The default priority used by watchers when no priority has been set is
1135	always C<0>, which is supposed to not be too high and not be too low :).	1417	always C<0>, which is supposed to not be too high and not be too low :).
1136		1418
1137	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1419	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1138	priorities.	1420	priorities.
1139		1421
1140	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1422	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1141		1423
1142	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1424	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1151	watcher isn't pending it does nothing and returns C<0>.	1433	watcher isn't pending it does nothing and returns C<0>.
1152		1434
1153	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1435	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1154	callback to be invoked, which can be accomplished with this function.	1436	callback to be invoked, which can be accomplished with this function.
1155		1437
		1438	=item ev_feed_event (loop, ev_TYPE *watcher, int revents)
		1439
		1440	Feeds the given event set into the event loop, as if the specified event
		1441	had happened for the specified watcher (which must be a pointer to an
		1442	initialised but not necessarily started event watcher). Obviously you must
		1443	not free the watcher as long as it has pending events.
		1444
		1445	Stopping the watcher, letting libev invoke it, or calling
		1446	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1447	not started in the first place.
		1448
		1449	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1450	functions that do not need a watcher.
		1451
1156	=back	1452	=back
1157		1453
		1454	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1455	OWN COMPOSITE WATCHERS> idioms.
1158		1456
1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1457	=head2 WATCHER STATES
1160		1458
1161	Each watcher has, by default, a member C<void *data> that you can change	1459	There are various watcher states mentioned throughout this manual -
1162	and read at any time: libev will completely ignore it. This can be used	1460	active, pending and so on. In this section these states and the rules to
1163	to associate arbitrary data with your watcher. If you need more data and	1461	transition between them will be described in more detail - and while these
1164	don't want to allocate memory and store a pointer to it in that data	1462	rules might look complicated, they usually do "the right thing".
1165	member, you can also "subclass" the watcher type and provide your own
1166	data:
1167		1463
1168	struct my_io	1464	=over 4
1169	{
1170	ev_io io;
1171	int otherfd;
1172	void *somedata;
1173	struct whatever *mostinteresting;
1174	};
1175		1465
1176	...	1466	=item initialised
1177	struct my_io w;
1178	ev_io_init (&w.io, my_cb, fd, EV_READ);
1179		1467
1180	And since your callback will be called with a pointer to the watcher, you	1468	Before a watcher can be registered with the event loop it has to be
1181	can cast it back to your own type:	1469	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1470	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1182		1471
1183	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1472	In this state it is simply some block of memory that is suitable for
1184	{	1473	use in an event loop. It can be moved around, freed, reused etc. at
1185	struct my_io *w = (struct my_io *)w_;	1474	will - as long as you either keep the memory contents intact, or call
1186	...	1475	C<ev_TYPE_init> again.
1187	}
1188		1476
1189	More interesting and less C-conformant ways of casting your callback type	1477	=item started/running/active
1190	instead have been omitted.
1191		1478
1192	Another common scenario is to use some data structure with multiple	1479	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1193	embedded watchers:	1480	property of the event loop, and is actively waiting for events. While in
		1481	this state it cannot be accessed (except in a few documented ways), moved,
		1482	freed or anything else - the only legal thing is to keep a pointer to it,
		1483	and call libev functions on it that are documented to work on active watchers.
1194		1484
1195	struct my_biggy	1485	=item pending
1196	{
1197	int some_data;
1198	ev_timer t1;
1199	ev_timer t2;
1200	}
1201		1486
1202	In this case getting the pointer to C<my_biggy> is a bit more	1487	If a watcher is active and libev determines that an event it is interested
1203	complicated: Either you store the address of your C<my_biggy> struct	1488	in has occurred (such as a timer expiring), it will become pending. It will
1204	in the C<data> member of the watcher (for woozies), or you need to use	1489	stay in this pending state until either it is stopped or its callback is
1205	some pointer arithmetic using C<offsetof> inside your watchers (for real	1490	about to be invoked, so it is not normally pending inside the watcher
1206	programmers):	1491	callback.
1207		1492
1208	#include <stddef.h>	1493	The watcher might or might not be active while it is pending (for example,
		1494	an expired non-repeating timer can be pending but no longer active). If it
		1495	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1496	but it is still property of the event loop at this time, so cannot be
		1497	moved, freed or reused. And if it is active the rules described in the
		1498	previous item still apply.
1209		1499
1210	static void	1500	It is also possible to feed an event on a watcher that is not active (e.g.
1211	t1_cb (EV_P_ ev_timer *w, int revents)	1501	via C<ev_feed_event>), in which case it becomes pending without being
1212	{	1502	active.
1213	struct my_biggy big = (struct my_biggy *)
1214	(((char *)w) - offsetof (struct my_biggy, t1));
1215	}
1216		1503
1217	static void	1504	=item stopped
1218	t2_cb (EV_P_ ev_timer *w, int revents)	1505
1219	{	1506	A watcher can be stopped implicitly by libev (in which case it might still
1220	struct my_biggy big = (struct my_biggy *)	1507	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1221	(((char *)w) - offsetof (struct my_biggy, t2));	1508	latter will clear any pending state the watcher might be in, regardless
1222	}	1509	of whether it was active or not, so stopping a watcher explicitly before
		1510	freeing it is often a good idea.
		1511
		1512	While stopped (and not pending) the watcher is essentially in the
		1513	initialised state, that is, it can be reused, moved, modified in any way
		1514	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1515	it again).
		1516
		1517	=back
1223		1518
1224	=head2 WATCHER PRIORITY MODELS	1519	=head2 WATCHER PRIORITY MODELS
1225		1520
1226	Many event loops support I<watcher priorities>, which are usually small	1521	Many event loops support I<watcher priorities>, which are usually small
1227	integers that influence the ordering of event callback invocation	1522	integers that influence the ordering of event callback invocation
…		…
1270		1565
1271	For example, to emulate how many other event libraries handle priorities,	1566	For example, to emulate how many other event libraries handle priorities,
1272	you can associate an C<ev_idle> watcher to each such watcher, and in	1567	you can associate an C<ev_idle> watcher to each such watcher, and in
1273	the normal watcher callback, you just start the idle watcher. The real	1568	the normal watcher callback, you just start the idle watcher. The real
1274	processing is done in the idle watcher callback. This causes libev to	1569	processing is done in the idle watcher callback. This causes libev to
1275	continously poll and process kernel event data for the watcher, but when	1570	continuously poll and process kernel event data for the watcher, but when
1276	the lock-out case is known to be rare (which in turn is rare :), this is	1571	the lock-out case is known to be rare (which in turn is rare :), this is
1277	workable.	1572	workable.
1278		1573
1279	Usually, however, the lock-out model implemented that way will perform	1574	Usually, however, the lock-out model implemented that way will perform
1280	miserably under the type of load it was designed to handle. In that case,	1575	miserably under the type of load it was designed to handle. In that case,
…		…
1294	{	1589	{
1295	// stop the I/O watcher, we received the event, but	1590	// stop the I/O watcher, we received the event, but
1296	// are not yet ready to handle it.	1591	// are not yet ready to handle it.
1297	ev_io_stop (EV_A_ w);	1592	ev_io_stop (EV_A_ w);
1298		1593
1299	// start the idle watcher to ahndle the actual event.	1594	// start the idle watcher to handle the actual event.
1300	// it will not be executed as long as other watchers	1595	// it will not be executed as long as other watchers
1301	// with the default priority are receiving events.	1596	// with the default priority are receiving events.
1302	ev_idle_start (EV_A_ &idle);	1597	ev_idle_start (EV_A_ &idle);
1303	}	1598	}
1304		1599
…		…
1354	In general you can register as many read and/or write event watchers per	1649	In general you can register as many read and/or write event watchers per
1355	fd as you want (as long as you don't confuse yourself). Setting all file	1650	fd as you want (as long as you don't confuse yourself). Setting all file
1356	descriptors to non-blocking mode is also usually a good idea (but not	1651	descriptors to non-blocking mode is also usually a good idea (but not
1357	required if you know what you are doing).	1652	required if you know what you are doing).
1358		1653
1359	If you cannot use non-blocking mode, then force the use of a
1360	known-to-be-good backend (at the time of this writing, this includes only
1361	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1362	descriptors for which non-blocking operation makes no sense (such as
1363	files) - libev doesn't guarentee any specific behaviour in that case.
1364
1365	Another thing you have to watch out for is that it is quite easy to	1654	Another thing you have to watch out for is that it is quite easy to
1366	receive "spurious" readiness notifications, that is your callback might	1655	receive "spurious" readiness notifications, that is, your callback might
1367	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1656	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1368	because there is no data. Not only are some backends known to create a	1657	because there is no data. It is very easy to get into this situation even
1369	lot of those (for example Solaris ports), it is very easy to get into	1658	with a relatively standard program structure. Thus it is best to always
1370	this situation even with a relatively standard program structure. Thus	1659	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1371	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1372	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1660	preferable to a program hanging until some data arrives.
1373		1661
1374	If you cannot run the fd in non-blocking mode (for example you should	1662	If you cannot run the fd in non-blocking mode (for example you should
1375	not play around with an Xlib connection), then you have to separately	1663	not play around with an Xlib connection), then you have to separately
1376	re-test whether a file descriptor is really ready with a known-to-be good	1664	re-test whether a file descriptor is really ready with a known-to-be good
1377	interface such as poll (fortunately in our Xlib example, Xlib already	1665	interface such as poll (fortunately in the case of Xlib, it already does
1378	does this on its own, so its quite safe to use). Some people additionally	1666	this on its own, so its quite safe to use). Some people additionally
1379	use C<SIGALRM> and an interval timer, just to be sure you won't block	1667	use C<SIGALRM> and an interval timer, just to be sure you won't block
1380	indefinitely.	1668	indefinitely.
1381		1669
1382	But really, best use non-blocking mode.	1670	But really, best use non-blocking mode.
1383		1671
1384	=head3 The special problem of disappearing file descriptors	1672	=head3 The special problem of disappearing file descriptors
1385		1673
1386	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1674	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1387	descriptor (either due to calling C<close> explicitly or any other means,	1675	a file descriptor (either due to calling C<close> explicitly or any other
1388	such as C<dup2>). The reason is that you register interest in some file	1676	means, such as C<dup2>). The reason is that you register interest in some
1389	descriptor, but when it goes away, the operating system will silently drop	1677	file descriptor, but when it goes away, the operating system will silently
1390	this interest. If another file descriptor with the same number then is	1678	drop this interest. If another file descriptor with the same number then
1391	registered with libev, there is no efficient way to see that this is, in	1679	is registered with libev, there is no efficient way to see that this is,
1392	fact, a different file descriptor.	1680	in fact, a different file descriptor.
1393		1681
1394	To avoid having to explicitly tell libev about such cases, libev follows	1682	To avoid having to explicitly tell libev about such cases, libev follows
1395	the following policy: Each time C<ev_io_set> is being called, libev	1683	the following policy: Each time C<ev_io_set> is being called, libev
1396	will assume that this is potentially a new file descriptor, otherwise	1684	will assume that this is potentially a new file descriptor, otherwise
1397	it is assumed that the file descriptor stays the same. That means that	1685	it is assumed that the file descriptor stays the same. That means that
…		…
1411		1699
1412	There is no workaround possible except not registering events	1700	There is no workaround possible except not registering events
1413	for potentially C<dup ()>'ed file descriptors, or to resort to	1701	for potentially C<dup ()>'ed file descriptors, or to resort to
1414	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1702	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1415		1703
		1704	=head3 The special problem of files
		1705
		1706	Many people try to use C<select> (or libev) on file descriptors
		1707	representing files, and expect it to become ready when their program
		1708	doesn't block on disk accesses (which can take a long time on their own).
		1709
		1710	However, this cannot ever work in the "expected" way - you get a readiness
		1711	notification as soon as the kernel knows whether and how much data is
		1712	there, and in the case of open files, that's always the case, so you
		1713	always get a readiness notification instantly, and your read (or possibly
		1714	write) will still block on the disk I/O.
		1715
		1716	Another way to view it is that in the case of sockets, pipes, character
		1717	devices and so on, there is another party (the sender) that delivers data
		1718	on its own, but in the case of files, there is no such thing: the disk
		1719	will not send data on its own, simply because it doesn't know what you
		1720	wish to read - you would first have to request some data.
		1721
		1722	Since files are typically not-so-well supported by advanced notification
		1723	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1724	to files, even though you should not use it. The reason for this is
		1725	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1726	usually a tty, often a pipe, but also sometimes files or special devices
		1727	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1728	F</dev/urandom>), and even though the file might better be served with
		1729	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1730	it "just works" instead of freezing.
		1731
		1732	So avoid file descriptors pointing to files when you know it (e.g. use
		1733	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1734	when you rarely read from a file instead of from a socket, and want to
		1735	reuse the same code path.
		1736
1416	=head3 The special problem of fork	1737	=head3 The special problem of fork
1417		1738
1418	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1739	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1419	useless behaviour. Libev fully supports fork, but needs to be told about	1740	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1420	it in the child.	1741	to be told about it in the child if you want to continue to use it in the
		1742	child.
1421		1743
1422	To support fork in your programs, you either have to call	1744	To support fork in your child processes, you have to call C<ev_loop_fork
1423	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1745	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1424	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1746	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1425	C<EVBACKEND_POLL>.
1426		1747
1427	=head3 The special problem of SIGPIPE	1748	=head3 The special problem of SIGPIPE
1428		1749
1429	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1750	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1430	when writing to a pipe whose other end has been closed, your program gets	1751	when writing to a pipe whose other end has been closed, your program gets
…		…
1433		1754
1434	So when you encounter spurious, unexplained daemon exits, make sure you	1755	So when you encounter spurious, unexplained daemon exits, make sure you
1435	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1756	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1436	somewhere, as that would have given you a big clue).	1757	somewhere, as that would have given you a big clue).
1437		1758
		1759	=head3 The special problem of accept()ing when you can't
		1760
		1761	Many implementations of the POSIX C<accept> function (for example,
		1762	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1763	connection from the pending queue in all error cases.
		1764
		1765	For example, larger servers often run out of file descriptors (because
		1766	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1767	rejecting the connection, leading to libev signalling readiness on
		1768	the next iteration again (the connection still exists after all), and
		1769	typically causing the program to loop at 100% CPU usage.
		1770
		1771	Unfortunately, the set of errors that cause this issue differs between
		1772	operating systems, there is usually little the app can do to remedy the
		1773	situation, and no known thread-safe method of removing the connection to
		1774	cope with overload is known (to me).
		1775
		1776	One of the easiest ways to handle this situation is to just ignore it
		1777	- when the program encounters an overload, it will just loop until the
		1778	situation is over. While this is a form of busy waiting, no OS offers an
		1779	event-based way to handle this situation, so it's the best one can do.
		1780
		1781	A better way to handle the situation is to log any errors other than
		1782	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1783	messages, and continue as usual, which at least gives the user an idea of
		1784	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1785	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1786	usage.
		1787
		1788	If your program is single-threaded, then you could also keep a dummy file
		1789	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1790	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1791	close that fd, and create a new dummy fd. This will gracefully refuse
		1792	clients under typical overload conditions.
		1793
		1794	The last way to handle it is to simply log the error and C<exit>, as
		1795	is often done with C<malloc> failures, but this results in an easy
		1796	opportunity for a DoS attack.
1438		1797
1439	=head3 Watcher-Specific Functions	1798	=head3 Watcher-Specific Functions
1440		1799
1441	=over 4	1800	=over 4
1442		1801
…		…
1474	...	1833	...
1475	struct ev_loop *loop = ev_default_init (0);	1834	struct ev_loop *loop = ev_default_init (0);
1476	ev_io stdin_readable;	1835	ev_io stdin_readable;
1477	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1836	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1478	ev_io_start (loop, &stdin_readable);	1837	ev_io_start (loop, &stdin_readable);
1479	ev_loop (loop, 0);	1838	ev_run (loop, 0);
1480		1839
1481		1840
1482	=head2 C<ev_timer> - relative and optionally repeating timeouts	1841	=head2 C<ev_timer> - relative and optionally repeating timeouts
1483		1842
1484	Timer watchers are simple relative timers that generate an event after a	1843	Timer watchers are simple relative timers that generate an event after a
…		…
1490	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1849	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1491	monotonic clock option helps a lot here).	1850	monotonic clock option helps a lot here).
1492		1851
1493	The callback is guaranteed to be invoked only I<after> its timeout has	1852	The callback is guaranteed to be invoked only I<after> its timeout has
1494	passed (not I<at>, so on systems with very low-resolution clocks this	1853	passed (not I<at>, so on systems with very low-resolution clocks this
1495	might introduce a small delay). If multiple timers become ready during the	1854	might introduce a small delay, see "the special problem of being too
		1855	early", below). If multiple timers become ready during the same loop
1496	same loop iteration then the ones with earlier time-out values are invoked	1856	iteration then the ones with earlier time-out values are invoked before
1497	before ones of the same priority with later time-out values (but this is	1857	ones of the same priority with later time-out values (but this is no
1498	no longer true when a callback calls C<ev_loop> recursively).	1858	longer true when a callback calls C<ev_run> recursively).
1499		1859
1500	=head3 Be smart about timeouts	1860	=head3 Be smart about timeouts
1501		1861
1502	Many real-world problems involve some kind of timeout, usually for error	1862	Many real-world problems involve some kind of timeout, usually for error
1503	recovery. A typical example is an HTTP request - if the other side hangs,	1863	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1578		1938
1579	In this case, it would be more efficient to leave the C<ev_timer> alone,	1939	In this case, it would be more efficient to leave the C<ev_timer> alone,
1580	but remember the time of last activity, and check for a real timeout only	1940	but remember the time of last activity, and check for a real timeout only
1581	within the callback:	1941	within the callback:
1582		1942
		1943	ev_tstamp timeout = 60.;
1583	ev_tstamp last_activity; // time of last activity	1944	ev_tstamp last_activity; // time of last activity
		1945	ev_timer timer;
1584		1946
1585	static void	1947	static void
1586	callback (EV_P_ ev_timer *w, int revents)	1948	callback (EV_P_ ev_timer *w, int revents)
1587	{	1949	{
1588	ev_tstamp now = ev_now (EV_A);	1950	// calculate when the timeout would happen
1589	ev_tstamp timeout = last_activity + 60.;	1951	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1590		1952
1591	// if last_activity + 60. is older than now, we did time out	1953	// if negative, it means we the timeout already occurred
1592	if (timeout < now)	1954	if (after < 0.)
1593	{	1955	{
1594	// timeout occured, take action	1956	// timeout occurred, take action
1595	}	1957	}
1596	else	1958	else
1597	{	1959	{
1598	// callback was invoked, but there was some activity, re-arm	1960	// callback was invoked, but there was some recent
1599	// the watcher to fire in last_activity + 60, which is	1961	// activity. simply restart the timer to time out
1600	// guaranteed to be in the future, so "again" is positive:	1962	// after "after" seconds, which is the earliest time
1601	w->repeat = timeout - now;	1963	// the timeout can occur.
		1964	ev_timer_set (w, after, 0.);
1602	ev_timer_again (EV_A_ w);	1965	ev_timer_start (EV_A_ w);
1603	}	1966	}
1604	}	1967	}
1605		1968
1606	To summarise the callback: first calculate the real timeout (defined	1969	To summarise the callback: first calculate in how many seconds the
1607	as "60 seconds after the last activity"), then check if that time has	1970	timeout will occur (by calculating the absolute time when it would occur,
1608	been reached, which means something I<did>, in fact, time out. Otherwise	1971	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1609	the callback was invoked too early (C<timeout> is in the future), so	1972	(EV_A)> from that).
1610	re-schedule the timer to fire at that future time, to see if maybe we have
1611	a timeout then.
1612		1973
1613	Note how C<ev_timer_again> is used, taking advantage of the	1974	If this value is negative, then we are already past the timeout, i.e. we
1614	C<ev_timer_again> optimisation when the timer is already running.	1975	timed out, and need to do whatever is needed in this case.
		1976
		1977	Otherwise, we now the earliest time at which the timeout would trigger,
		1978	and simply start the timer with this timeout value.
		1979
		1980	In other words, each time the callback is invoked it will check whether
		1981	the timeout occurred. If not, it will simply reschedule itself to check
		1982	again at the earliest time it could time out. Rinse. Repeat.
1615		1983
1616	This scheme causes more callback invocations (about one every 60 seconds	1984	This scheme causes more callback invocations (about one every 60 seconds
1617	minus half the average time between activity), but virtually no calls to	1985	minus half the average time between activity), but virtually no calls to
1618	libev to change the timeout.	1986	libev to change the timeout.
1619		1987
1620	To start the timer, simply initialise the watcher and set C<last_activity>	1988	To start the machinery, simply initialise the watcher and set
1621	to the current time (meaning we just have some activity :), then call the	1989	C<last_activity> to the current time (meaning there was some activity just
1622	callback, which will "do the right thing" and start the timer:	1990	now), then call the callback, which will "do the right thing" and start
		1991	the timer:
1623		1992
		1993	last_activity = ev_now (EV_A);
1624	ev_init (timer, callback);	1994	ev_init (&timer, callback);
1625	last_activity = ev_now (loop);	1995	callback (EV_A_ &timer, 0);
1626	callback (loop, timer, EV_TIMEOUT);
1627		1996
1628	And when there is some activity, simply store the current time in	1997	When there is some activity, simply store the current time in
1629	C<last_activity>, no libev calls at all:	1998	C<last_activity>, no libev calls at all:
1630		1999
		2000	if (activity detected)
1631	last_actiivty = ev_now (loop);	2001	last_activity = ev_now (EV_A);
		2002
		2003	When your timeout value changes, then the timeout can be changed by simply
		2004	providing a new value, stopping the timer and calling the callback, which
		2005	will again do the right thing (for example, time out immediately :).
		2006
		2007	timeout = new_value;
		2008	ev_timer_stop (EV_A_ &timer);
		2009	callback (EV_A_ &timer, 0);
1632		2010
1633	This technique is slightly more complex, but in most cases where the	2011	This technique is slightly more complex, but in most cases where the
1634	time-out is unlikely to be triggered, much more efficient.	2012	time-out is unlikely to be triggered, much more efficient.
1635
1636	Changing the timeout is trivial as well (if it isn't hard-coded in the
1637	callback :) - just change the timeout and invoke the callback, which will
1638	fix things for you.
1639		2013
1640	=item 4. Wee, just use a double-linked list for your timeouts.	2014	=item 4. Wee, just use a double-linked list for your timeouts.
1641		2015
1642	If there is not one request, but many thousands (millions...), all	2016	If there is not one request, but many thousands (millions...), all
1643	employing some kind of timeout with the same timeout value, then one can	2017	employing some kind of timeout with the same timeout value, then one can
…		…
1670	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2044	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1671	rather complicated, but extremely efficient, something that really pays	2045	rather complicated, but extremely efficient, something that really pays
1672	off after the first million or so of active timers, i.e. it's usually	2046	off after the first million or so of active timers, i.e. it's usually
1673	overkill :)	2047	overkill :)
1674		2048
		2049	=head3 The special problem of being too early
		2050
		2051	If you ask a timer to call your callback after three seconds, then
		2052	you expect it to be invoked after three seconds - but of course, this
		2053	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2054	guaranteed to any precision by libev - imagine somebody suspending the
		2055	process with a STOP signal for a few hours for example.
		2056
		2057	So, libev tries to invoke your callback as soon as possible I<after> the
		2058	delay has occurred, but cannot guarantee this.
		2059
		2060	A less obvious failure mode is calling your callback too early: many event
		2061	loops compare timestamps with a "elapsed delay >= requested delay", but
		2062	this can cause your callback to be invoked much earlier than you would
		2063	expect.
		2064
		2065	To see why, imagine a system with a clock that only offers full second
		2066	resolution (think windows if you can't come up with a broken enough OS
		2067	yourself). If you schedule a one-second timer at the time 500.9, then the
		2068	event loop will schedule your timeout to elapse at a system time of 500
		2069	(500.9 truncated to the resolution) + 1, or 501.
		2070
		2071	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2072	501" and invoke the callback 0.1s after it was started, even though a
		2073	one-second delay was requested - this is being "too early", despite best
		2074	intentions.
		2075
		2076	This is the reason why libev will never invoke the callback if the elapsed
		2077	delay equals the requested delay, but only when the elapsed delay is
		2078	larger than the requested delay. In the example above, libev would only invoke
		2079	the callback at system time 502, or 1.1s after the timer was started.
		2080
		2081	So, while libev cannot guarantee that your callback will be invoked
		2082	exactly when requested, it I<can> and I<does> guarantee that the requested
		2083	delay has actually elapsed, or in other words, it always errs on the "too
		2084	late" side of things.
		2085
1675	=head3 The special problem of time updates	2086	=head3 The special problem of time updates
1676		2087
1677	Establishing the current time is a costly operation (it usually takes at	2088	Establishing the current time is a costly operation (it usually takes
1678	least two system calls): EV therefore updates its idea of the current	2089	at least one system call): EV therefore updates its idea of the current
1679	time only before and after C<ev_loop> collects new events, which causes a	2090	time only before and after C<ev_run> collects new events, which causes a
1680	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2091	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1681	lots of events in one iteration.	2092	lots of events in one iteration.
1682		2093
1683	The relative timeouts are calculated relative to the C<ev_now ()>	2094	The relative timeouts are calculated relative to the C<ev_now ()>
1684	time. This is usually the right thing as this timestamp refers to the time	2095	time. This is usually the right thing as this timestamp refers to the time
1685	of the event triggering whatever timeout you are modifying/starting. If	2096	of the event triggering whatever timeout you are modifying/starting. If
1686	you suspect event processing to be delayed and you I<need> to base the	2097	you suspect event processing to be delayed and you I<need> to base the
1687	timeout on the current time, use something like this to adjust for this:	2098	timeout on the current time, use something like the following to adjust
		2099	for it:
1688		2100
1689	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2101	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1690		2102
1691	If the event loop is suspended for a long time, you can also force an	2103	If the event loop is suspended for a long time, you can also force an
1692	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2104	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1693	()>.	2105	()>, although that will push the event time of all outstanding events
		2106	further into the future.
		2107
		2108	=head3 The special problem of unsynchronised clocks
		2109
		2110	Modern systems have a variety of clocks - libev itself uses the normal
		2111	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2112	jumps).
		2113
		2114	Neither of these clocks is synchronised with each other or any other clock
		2115	on the system, so C<ev_time ()> might return a considerably different time
		2116	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2117	a call to C<gettimeofday> might return a second count that is one higher
		2118	than a directly following call to C<time>.
		2119
		2120	The moral of this is to only compare libev-related timestamps with
		2121	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2122	a second or so.
		2123
		2124	One more problem arises due to this lack of synchronisation: if libev uses
		2125	the system monotonic clock and you compare timestamps from C<ev_time>
		2126	or C<ev_now> from when you started your timer and when your callback is
		2127	invoked, you will find that sometimes the callback is a bit "early".
		2128
		2129	This is because C<ev_timer>s work in real time, not wall clock time, so
		2130	libev makes sure your callback is not invoked before the delay happened,
		2131	I<measured according to the real time>, not the system clock.
		2132
		2133	If your timeouts are based on a physical timescale (e.g. "time out this
		2134	connection after 100 seconds") then this shouldn't bother you as it is
		2135	exactly the right behaviour.
		2136
		2137	If you want to compare wall clock/system timestamps to your timers, then
		2138	you need to use C<ev_periodic>s, as these are based on the wall clock
		2139	time, where your comparisons will always generate correct results.
		2140
		2141	=head3 The special problems of suspended animation
		2142
		2143	When you leave the server world it is quite customary to hit machines that
		2144	can suspend/hibernate - what happens to the clocks during such a suspend?
		2145
		2146	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		2147	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		2148	to run until the system is suspended, but they will not advance while the
		2149	system is suspended. That means, on resume, it will be as if the program
		2150	was frozen for a few seconds, but the suspend time will not be counted
		2151	towards C<ev_timer> when a monotonic clock source is used. The real time
		2152	clock advanced as expected, but if it is used as sole clocksource, then a
		2153	long suspend would be detected as a time jump by libev, and timers would
		2154	be adjusted accordingly.
		2155
		2156	I would not be surprised to see different behaviour in different between
		2157	operating systems, OS versions or even different hardware.
		2158
		2159	The other form of suspend (job control, or sending a SIGSTOP) will see a
		2160	time jump in the monotonic clocks and the realtime clock. If the program
		2161	is suspended for a very long time, and monotonic clock sources are in use,
		2162	then you can expect C<ev_timer>s to expire as the full suspension time
		2163	will be counted towards the timers. When no monotonic clock source is in
		2164	use, then libev will again assume a timejump and adjust accordingly.
		2165
		2166	It might be beneficial for this latter case to call C<ev_suspend>
		2167	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		2168	deterministic behaviour in this case (you can do nothing against
		2169	C<SIGSTOP>).
1694		2170
1695	=head3 Watcher-Specific Functions and Data Members	2171	=head3 Watcher-Specific Functions and Data Members
1696		2172
1697	=over 4	2173	=over 4
1698		2174
1699	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2175	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1700		2176
1701	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2177	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1702		2178
1703	Configure the timer to trigger after C<after> seconds. If C<repeat>	2179	Configure the timer to trigger after C<after> seconds (fractional and
1704	is C<0.>, then it will automatically be stopped once the timeout is	2180	negative values are supported). If C<repeat> is C<0.>, then it will
1705	reached. If it is positive, then the timer will automatically be	2181	automatically be stopped once the timeout is reached. If it is positive,
1706	configured to trigger again C<repeat> seconds later, again, and again,	2182	then the timer will automatically be configured to trigger again C<repeat>
1707	until stopped manually.	2183	seconds later, again, and again, until stopped manually.
1708		2184
1709	The timer itself will do a best-effort at avoiding drift, that is, if	2185	The timer itself will do a best-effort at avoiding drift, that is, if
1710	you configure a timer to trigger every 10 seconds, then it will normally	2186	you configure a timer to trigger every 10 seconds, then it will normally
1711	trigger at exactly 10 second intervals. If, however, your program cannot	2187	trigger at exactly 10 second intervals. If, however, your program cannot
1712	keep up with the timer (because it takes longer than those 10 seconds to	2188	keep up with the timer (because it takes longer than those 10 seconds to
1713	do stuff) the timer will not fire more than once per event loop iteration.	2189	do stuff) the timer will not fire more than once per event loop iteration.
1714		2190
1715	=item ev_timer_again (loop, ev_timer *)	2191	=item ev_timer_again (loop, ev_timer *)
1716		2192
1717	This will act as if the timer timed out and restart it again if it is	2193	This will act as if the timer timed out, and restarts it again if it is
1718	repeating. The exact semantics are:	2194	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2195	timeout to the C<repeat> value and calling C<ev_timer_start>.
1719		2196
		2197	The exact semantics are as in the following rules, all of which will be
		2198	applied to the watcher:
		2199
		2200	=over 4
		2201
1720	If the timer is pending, its pending status is cleared.	2202	=item If the timer is pending, the pending status is always cleared.
1721		2203
1722	If the timer is started but non-repeating, stop it (as if it timed out).	2204	=item If the timer is started but non-repeating, stop it (as if it timed
		2205	out, without invoking it).
1723		2206
1724	If the timer is repeating, either start it if necessary (with the	2207	=item If the timer is repeating, make the C<repeat> value the new timeout
1725	C<repeat> value), or reset the running timer to the C<repeat> value.	2208	and start the timer, if necessary.
1726		2209
		2210	=back
		2211
1727	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2212	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1728	usage example.	2213	usage example.
		2214
		2215	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
		2216
		2217	Returns the remaining time until a timer fires. If the timer is active,
		2218	then this time is relative to the current event loop time, otherwise it's
		2219	the timeout value currently configured.
		2220
		2221	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		2222	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
		2223	will return C<4>. When the timer expires and is restarted, it will return
		2224	roughly C<7> (likely slightly less as callback invocation takes some time,
		2225	too), and so on.
1729		2226
1730	=item ev_tstamp repeat [read-write]	2227	=item ev_tstamp repeat [read-write]
1731		2228
1732	The current C<repeat> value. Will be used each time the watcher times out	2229	The current C<repeat> value. Will be used each time the watcher times out
1733	or C<ev_timer_again> is called, and determines the next timeout (if any),	2230	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1759	}	2256	}
1760		2257
1761	ev_timer mytimer;	2258	ev_timer mytimer;
1762	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2259	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1763	ev_timer_again (&mytimer); /* start timer */	2260	ev_timer_again (&mytimer); /* start timer */
1764	ev_loop (loop, 0);	2261	ev_run (loop, 0);
1765		2262
1766	// and in some piece of code that gets executed on any "activity":	2263	// and in some piece of code that gets executed on any "activity":
1767	// reset the timeout to start ticking again at 10 seconds	2264	// reset the timeout to start ticking again at 10 seconds
1768	ev_timer_again (&mytimer);	2265	ev_timer_again (&mytimer);
1769		2266
…		…
1773	Periodic watchers are also timers of a kind, but they are very versatile	2270	Periodic watchers are also timers of a kind, but they are very versatile
1774	(and unfortunately a bit complex).	2271	(and unfortunately a bit complex).
1775		2272
1776	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2273	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1777	relative time, the physical time that passes) but on wall clock time	2274	relative time, the physical time that passes) but on wall clock time
1778	(absolute time, the thing you can read on your calender or clock). The	2275	(absolute time, the thing you can read on your calendar or clock). The
1779	difference is that wall clock time can run faster or slower than real	2276	difference is that wall clock time can run faster or slower than real
1780	time, and time jumps are not uncommon (e.g. when you adjust your	2277	time, and time jumps are not uncommon (e.g. when you adjust your
1781	wrist-watch).	2278	wrist-watch).
1782		2279
1783	You can tell a periodic watcher to trigger after some specific point	2280	You can tell a periodic watcher to trigger after some specific point
…		…
1788	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2285	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1789	it, as it uses a relative timeout).	2286	it, as it uses a relative timeout).
1790		2287
1791	C<ev_periodic> watchers can also be used to implement vastly more complex	2288	C<ev_periodic> watchers can also be used to implement vastly more complex
1792	timers, such as triggering an event on each "midnight, local time", or	2289	timers, such as triggering an event on each "midnight, local time", or
1793	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2290	other complicated rules. This cannot easily be done with C<ev_timer>
1794	those cannot react to time jumps.	2291	watchers, as those cannot react to time jumps.
1795		2292
1796	As with timers, the callback is guaranteed to be invoked only when the	2293	As with timers, the callback is guaranteed to be invoked only when the
1797	point in time where it is supposed to trigger has passed. If multiple	2294	point in time where it is supposed to trigger has passed. If multiple
1798	timers become ready during the same loop iteration then the ones with	2295	timers become ready during the same loop iteration then the ones with
1799	earlier time-out values are invoked before ones with later time-out values	2296	earlier time-out values are invoked before ones with later time-out values
1800	(but this is no longer true when a callback calls C<ev_loop> recursively).	2297	(but this is no longer true when a callback calls C<ev_run> recursively).
1801		2298
1802	=head3 Watcher-Specific Functions and Data Members	2299	=head3 Watcher-Specific Functions and Data Members
1803		2300
1804	=over 4	2301	=over 4
1805		2302
…		…
1840		2337
1841	Another way to think about it (for the mathematically inclined) is that	2338	Another way to think about it (for the mathematically inclined) is that
1842	C<ev_periodic> will try to run the callback in this mode at the next possible	2339	C<ev_periodic> will try to run the callback in this mode at the next possible
1843	time where C<time = offset (mod interval)>, regardless of any time jumps.	2340	time where C<time = offset (mod interval)>, regardless of any time jumps.
1844		2341
1845	For numerical stability it is preferable that the C<offset> value is near	2342	The C<interval> I<MUST> be positive, and for numerical stability, the
1846	C<ev_now ()> (the current time), but there is no range requirement for	2343	interval value should be higher than C<1/8192> (which is around 100
1847	this value, and in fact is often specified as zero.	2344	microseconds) and C<offset> should be higher than C<0> and should have
		2345	at most a similar magnitude as the current time (say, within a factor of
		2346	ten). Typical values for offset are, in fact, C<0> or something between
		2347	C<0> and C<interval>, which is also the recommended range.
1848		2348
1849	Note also that there is an upper limit to how often a timer can fire (CPU	2349	Note also that there is an upper limit to how often a timer can fire (CPU
1850	speed for example), so if C<interval> is very small then timing stability	2350	speed for example), so if C<interval> is very small then timing stability
1851	will of course deteriorate. Libev itself tries to be exact to be about one	2351	will of course deteriorate. Libev itself tries to be exact to be about one
1852	millisecond (if the OS supports it and the machine is fast enough).	2352	millisecond (if the OS supports it and the machine is fast enough).
…		…
1882		2382
1883	NOTE: I<< This callback must always return a time that is higher than or	2383	NOTE: I<< This callback must always return a time that is higher than or
1884	equal to the passed C<now> value >>.	2384	equal to the passed C<now> value >>.
1885		2385
1886	This can be used to create very complex timers, such as a timer that	2386	This can be used to create very complex timers, such as a timer that
1887	triggers on "next midnight, local time". To do this, you would calculate the	2387	triggers on "next midnight, local time". To do this, you would calculate
1888	next midnight after C<now> and return the timestamp value for this. How	2388	the next midnight after C<now> and return the timestamp value for
1889	you do this is, again, up to you (but it is not trivial, which is the main	2389	this. Here is a (completely untested, no error checking) example on how to
1890	reason I omitted it as an example).	2390	do this:
		2391
		2392	#include <time.h>
		2393
		2394	static ev_tstamp
		2395	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2396	{
		2397	time_t tnow = (time_t)now;
		2398	struct tm tm;
		2399	localtime_r (&tnow, &tm);
		2400
		2401	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2402	++tm.tm_mday; // midnight next day
		2403
		2404	return mktime (&tm);
		2405	}
		2406
		2407	Note: this code might run into trouble on days that have more then two
		2408	midnights (beginning and end).
1891		2409
1892	=back	2410	=back
1893		2411
1894	=item ev_periodic_again (loop, ev_periodic *)	2412	=item ev_periodic_again (loop, ev_periodic *)
1895		2413
…		…
1933	Example: Call a callback every hour, or, more precisely, whenever the	2451	Example: Call a callback every hour, or, more precisely, whenever the
1934	system time is divisible by 3600. The callback invocation times have	2452	system time is divisible by 3600. The callback invocation times have
1935	potentially a lot of jitter, but good long-term stability.	2453	potentially a lot of jitter, but good long-term stability.
1936		2454
1937	static void	2455	static void
1938	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2456	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
1939	{	2457	{
1940	... its now a full hour (UTC, or TAI or whatever your clock follows)	2458	... its now a full hour (UTC, or TAI or whatever your clock follows)
1941	}	2459	}
1942		2460
1943	ev_periodic hourly_tick;	2461	ev_periodic hourly_tick;
…		…
1960		2478
1961	ev_periodic hourly_tick;	2479	ev_periodic hourly_tick;
1962	ev_periodic_init (&hourly_tick, clock_cb,	2480	ev_periodic_init (&hourly_tick, clock_cb,
1963	fmod (ev_now (loop), 3600.), 3600., 0);	2481	fmod (ev_now (loop), 3600.), 3600., 0);
1964	ev_periodic_start (loop, &hourly_tick);	2482	ev_periodic_start (loop, &hourly_tick);
1965		2483
1966		2484
1967	=head2 C<ev_signal> - signal me when a signal gets signalled!	2485	=head2 C<ev_signal> - signal me when a signal gets signalled!
1968		2486
1969	Signal watchers will trigger an event when the process receives a specific	2487	Signal watchers will trigger an event when the process receives a specific
1970	signal one or more times. Even though signals are very asynchronous, libev	2488	signal one or more times. Even though signals are very asynchronous, libev
1971	will try it's best to deliver signals synchronously, i.e. as part of the	2489	will try its best to deliver signals synchronously, i.e. as part of the
1972	normal event processing, like any other event.	2490	normal event processing, like any other event.
1973		2491
1974	If you want signals asynchronously, just use C<sigaction> as you would	2492	If you want signals to be delivered truly asynchronously, just use
1975	do without libev and forget about sharing the signal. You can even use	2493	C<sigaction> as you would do without libev and forget about sharing
1976	C<ev_async> from a signal handler to synchronously wake up an event loop.	2494	the signal. You can even use C<ev_async> from a signal handler to
		2495	synchronously wake up an event loop.
1977		2496
1978	You can configure as many watchers as you like per signal. Only when the	2497	You can configure as many watchers as you like for the same signal, but
1979	first watcher gets started will libev actually register a signal handler	2498	only within the same loop, i.e. you can watch for C<SIGINT> in your
1980	with the kernel (thus it coexists with your own signal handlers as long as	2499	default loop and for C<SIGIO> in another loop, but you cannot watch for
1981	you don't register any with libev for the same signal). Similarly, when	2500	C<SIGINT> in both the default loop and another loop at the same time. At
1982	the last signal watcher for a signal is stopped, libev will reset the	2501	the moment, C<SIGCHLD> is permanently tied to the default loop.
1983	signal handler to SIG_DFL (regardless of what it was set to before).	2502
		2503	Only after the first watcher for a signal is started will libev actually
		2504	register something with the kernel. It thus coexists with your own signal
		2505	handlers as long as you don't register any with libev for the same signal.
1984		2506
1985	If possible and supported, libev will install its handlers with	2507	If possible and supported, libev will install its handlers with
1986	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2508	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1987	interrupted. If you have a problem with system calls getting interrupted by	2509	not be unduly interrupted. If you have a problem with system calls getting
1988	signals you can block all signals in an C<ev_check> watcher and unblock	2510	interrupted by signals you can block all signals in an C<ev_check> watcher
1989	them in an C<ev_prepare> watcher.	2511	and unblock them in an C<ev_prepare> watcher.
		2512
		2513	=head3 The special problem of inheritance over fork/execve/pthread_create
		2514
		2515	Both the signal mask (C<sigprocmask>) and the signal disposition
		2516	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2517	stopping it again), that is, libev might or might not block the signal,
		2518	and might or might not set or restore the installed signal handler (but
		2519	see C<EVFLAG_NOSIGMASK>).
		2520
		2521	While this does not matter for the signal disposition (libev never
		2522	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2523	C<execve>), this matters for the signal mask: many programs do not expect
		2524	certain signals to be blocked.
		2525
		2526	This means that before calling C<exec> (from the child) you should reset
		2527	the signal mask to whatever "default" you expect (all clear is a good
		2528	choice usually).
		2529
		2530	The simplest way to ensure that the signal mask is reset in the child is
		2531	to install a fork handler with C<pthread_atfork> that resets it. That will
		2532	catch fork calls done by libraries (such as the libc) as well.
		2533
		2534	In current versions of libev, the signal will not be blocked indefinitely
		2535	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
		2536	the window of opportunity for problems, it will not go away, as libev
		2537	I<has> to modify the signal mask, at least temporarily.
		2538
		2539	So I can't stress this enough: I<If you do not reset your signal mask when
		2540	you expect it to be empty, you have a race condition in your code>. This
		2541	is not a libev-specific thing, this is true for most event libraries.
		2542
		2543	=head3 The special problem of threads signal handling
		2544
		2545	POSIX threads has problematic signal handling semantics, specifically,
		2546	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2547	threads in a process block signals, which is hard to achieve.
		2548
		2549	When you want to use sigwait (or mix libev signal handling with your own
		2550	for the same signals), you can tackle this problem by globally blocking
		2551	all signals before creating any threads (or creating them with a fully set
		2552	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2553	loops. Then designate one thread as "signal receiver thread" which handles
		2554	these signals. You can pass on any signals that libev might be interested
		2555	in by calling C<ev_feed_signal>.
1990		2556
1991	=head3 Watcher-Specific Functions and Data Members	2557	=head3 Watcher-Specific Functions and Data Members
1992		2558
1993	=over 4	2559	=over 4
1994		2560
…		…
2010	Example: Try to exit cleanly on SIGINT.	2576	Example: Try to exit cleanly on SIGINT.
2011		2577
2012	static void	2578	static void
2013	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2579	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2014	{	2580	{
2015	ev_unloop (loop, EVUNLOOP_ALL);	2581	ev_break (loop, EVBREAK_ALL);
2016	}	2582	}
2017		2583
2018	ev_signal signal_watcher;	2584	ev_signal signal_watcher;
2019	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2585	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2020	ev_signal_start (loop, &signal_watcher);	2586	ev_signal_start (loop, &signal_watcher);
…		…
2033		2599
2034	Only the default event loop is capable of handling signals, and therefore	2600	Only the default event loop is capable of handling signals, and therefore
2035	you can only register child watchers in the default event loop.	2601	you can only register child watchers in the default event loop.
2036		2602
2037	Due to some design glitches inside libev, child watchers will always be	2603	Due to some design glitches inside libev, child watchers will always be
2038	handled at maximum priority (their priority is set to EV_MAXPRI by libev)	2604	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2605	libev)
2039		2606
2040	=head3 Process Interaction	2607	=head3 Process Interaction
2041		2608
2042	Libev grabs C<SIGCHLD> as soon as the default event loop is	2609	Libev grabs C<SIGCHLD> as soon as the default event loop is
2043	initialised. This is necessary to guarantee proper behaviour even if	2610	initialised. This is necessary to guarantee proper behaviour even if the
2044	the first child watcher is started after the child exits. The occurrence	2611	first child watcher is started after the child exits. The occurrence
2045	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2612	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2046	synchronously as part of the event loop processing. Libev always reaps all	2613	synchronously as part of the event loop processing. Libev always reaps all
2047	children, even ones not watched.	2614	children, even ones not watched.
2048		2615
2049	=head3 Overriding the Built-In Processing	2616	=head3 Overriding the Built-In Processing
…		…
2059	=head3 Stopping the Child Watcher	2626	=head3 Stopping the Child Watcher
2060		2627
2061	Currently, the child watcher never gets stopped, even when the	2628	Currently, the child watcher never gets stopped, even when the
2062	child terminates, so normally one needs to stop the watcher in the	2629	child terminates, so normally one needs to stop the watcher in the
2063	callback. Future versions of libev might stop the watcher automatically	2630	callback. Future versions of libev might stop the watcher automatically
2064	when a child exit is detected.	2631	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2632	problem).
2065		2633
2066	=head3 Watcher-Specific Functions and Data Members	2634	=head3 Watcher-Specific Functions and Data Members
2067		2635
2068	=over 4	2636	=over 4
2069		2637
…		…
2127		2695
2128	=head2 C<ev_stat> - did the file attributes just change?	2696	=head2 C<ev_stat> - did the file attributes just change?
2129		2697
2130	This watches a file system path for attribute changes. That is, it calls	2698	This watches a file system path for attribute changes. That is, it calls
2131	C<stat> on that path in regular intervals (or when the OS says it changed)	2699	C<stat> on that path in regular intervals (or when the OS says it changed)
2132	and sees if it changed compared to the last time, invoking the callback if	2700	and sees if it changed compared to the last time, invoking the callback
2133	it did.	2701	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2702	happen after the watcher has been started will be reported.
2134		2703
2135	The path does not need to exist: changing from "path exists" to "path does	2704	The path does not need to exist: changing from "path exists" to "path does
2136	not exist" is a status change like any other. The condition "path does not	2705	not exist" is a status change like any other. The condition "path does not
2137	exist" (or more correctly "path cannot be stat'ed") is signified by the	2706	exist" (or more correctly "path cannot be stat'ed") is signified by the
2138	C<st_nlink> field being zero (which is otherwise always forced to be at	2707	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2368	Apart from keeping your process non-blocking (which is a useful	2937	Apart from keeping your process non-blocking (which is a useful
2369	effect on its own sometimes), idle watchers are a good place to do	2938	effect on its own sometimes), idle watchers are a good place to do
2370	"pseudo-background processing", or delay processing stuff to after the	2939	"pseudo-background processing", or delay processing stuff to after the
2371	event loop has handled all outstanding events.	2940	event loop has handled all outstanding events.
2372		2941
		2942	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2943
		2944	As long as there is at least one active idle watcher, libev will never
		2945	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2946	For this to work, the idle watcher doesn't need to be invoked at all - the
		2947	lowest priority will do.
		2948
		2949	This mode of operation can be useful together with an C<ev_check> watcher,
		2950	to do something on each event loop iteration - for example to balance load
		2951	between different connections.
		2952
		2953	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2954	example.
		2955
2373	=head3 Watcher-Specific Functions and Data Members	2956	=head3 Watcher-Specific Functions and Data Members
2374		2957
2375	=over 4	2958	=over 4
2376		2959
2377	=item ev_idle_init (ev_idle *, callback)	2960	=item ev_idle_init (ev_idle *, callback)
…		…
2388	callback, free it. Also, use no error checking, as usual.	2971	callback, free it. Also, use no error checking, as usual.
2389		2972
2390	static void	2973	static void
2391	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2974	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2392	{	2975	{
		2976	// stop the watcher
		2977	ev_idle_stop (loop, w);
		2978
		2979	// now we can free it
2393	free (w);	2980	free (w);
		2981
2394	// now do something you wanted to do when the program has	2982	// now do something you wanted to do when the program has
2395	// no longer anything immediate to do.	2983	// no longer anything immediate to do.
2396	}	2984	}
2397		2985
2398	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2986	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2400	ev_idle_start (loop, idle_watcher);	2988	ev_idle_start (loop, idle_watcher);
2401		2989
2402		2990
2403	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2991	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2404		2992
2405	Prepare and check watchers are usually (but not always) used in pairs:	2993	Prepare and check watchers are often (but not always) used in pairs:
2406	prepare watchers get invoked before the process blocks and check watchers	2994	prepare watchers get invoked before the process blocks and check watchers
2407	afterwards.	2995	afterwards.
2408		2996
2409	You I<must not> call C<ev_loop> or similar functions that enter	2997	You I<must not> call C<ev_run> (or similar functions that enter the
2410	the current event loop from either C<ev_prepare> or C<ev_check>	2998	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2411	watchers. Other loops than the current one are fine, however. The	2999	C<ev_check> watchers. Other loops than the current one are fine,
2412	rationale behind this is that you do not need to check for recursion in	3000	however. The rationale behind this is that you do not need to check
2413	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3001	for recursion in those watchers, i.e. the sequence will always be
2414	C<ev_check> so if you have one watcher of each kind they will always be	3002	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2415	called in pairs bracketing the blocking call.	3003	kind they will always be called in pairs bracketing the blocking call.
2416		3004
2417	Their main purpose is to integrate other event mechanisms into libev and	3005	Their main purpose is to integrate other event mechanisms into libev and
2418	their use is somewhat advanced. They could be used, for example, to track	3006	their use is somewhat advanced. They could be used, for example, to track
2419	variable changes, implement your own watchers, integrate net-snmp or a	3007	variable changes, implement your own watchers, integrate net-snmp or a
2420	coroutine library and lots more. They are also occasionally useful if	3008	coroutine library and lots more. They are also occasionally useful if
…		…
2438	with priority higher than or equal to the event loop and one coroutine	3026	with priority higher than or equal to the event loop and one coroutine
2439	of lower priority, but only once, using idle watchers to keep the event	3027	of lower priority, but only once, using idle watchers to keep the event
2440	loop from blocking if lower-priority coroutines are active, thus mapping	3028	loop from blocking if lower-priority coroutines are active, thus mapping
2441	low-priority coroutines to idle/background tasks).	3029	low-priority coroutines to idle/background tasks).
2442		3030
2443	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3031	When used for this purpose, it is recommended to give C<ev_check> watchers
2444	priority, to ensure that they are being run before any other watchers	3032	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2445	after the poll (this doesn't matter for C<ev_prepare> watchers).	3033	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3034	watchers).
2446		3035
2447	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3036	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2448	activate ("feed") events into libev. While libev fully supports this, they	3037	activate ("feed") events into libev. While libev fully supports this, they
2449	might get executed before other C<ev_check> watchers did their job. As	3038	might get executed before other C<ev_check> watchers did their job. As
2450	C<ev_check> watchers are often used to embed other (non-libev) event	3039	C<ev_check> watchers are often used to embed other (non-libev) event
2451	loops those other event loops might be in an unusable state until their	3040	loops those other event loops might be in an unusable state until their
2452	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3041	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2453	others).	3042	others).
		3043
		3044	=head3 Abusing an C<ev_check> watcher for its side-effect
		3045
		3046	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3047	useful because they are called once per event loop iteration. For
		3048	example, if you want to handle a large number of connections fairly, you
		3049	normally only do a bit of work for each active connection, and if there
		3050	is more work to do, you wait for the next event loop iteration, so other
		3051	connections have a chance of making progress.
		3052
		3053	Using an C<ev_check> watcher is almost enough: it will be called on the
		3054	next event loop iteration. However, that isn't as soon as possible -
		3055	without external events, your C<ev_check> watcher will not be invoked.
		3056
		3057	This is where C<ev_idle> watchers come in handy - all you need is a
		3058	single global idle watcher that is active as long as you have one active
		3059	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3060	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3061	invoked. Neither watcher alone can do that.
2454		3062
2455	=head3 Watcher-Specific Functions and Data Members	3063	=head3 Watcher-Specific Functions and Data Members
2456		3064
2457	=over 4	3065	=over 4
2458		3066
…		…
2582		3190
2583	if (timeout >= 0)	3191	if (timeout >= 0)
2584	// create/start timer	3192	// create/start timer
2585		3193
2586	// poll	3194	// poll
2587	ev_loop (EV_A_ 0);	3195	ev_run (EV_A_ 0);
2588		3196
2589	// stop timer again	3197	// stop timer again
2590	if (timeout >= 0)	3198	if (timeout >= 0)
2591	ev_timer_stop (EV_A_ &to);	3199	ev_timer_stop (EV_A_ &to);
2592		3200
…		…
2659		3267
2660	=over 4	3268	=over 4
2661		3269
2662	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3270	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2663		3271
2664	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3272	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2665		3273
2666	Configures the watcher to embed the given loop, which must be	3274	Configures the watcher to embed the given loop, which must be
2667	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3275	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2668	invoked automatically, otherwise it is the responsibility of the callback	3276	invoked automatically, otherwise it is the responsibility of the callback
2669	to invoke it (it will continue to be called until the sweep has been done,	3277	to invoke it (it will continue to be called until the sweep has been done,
2670	if you do not want that, you need to temporarily stop the embed watcher).	3278	if you do not want that, you need to temporarily stop the embed watcher).
2671		3279
2672	=item ev_embed_sweep (loop, ev_embed *)	3280	=item ev_embed_sweep (loop, ev_embed *)
2673		3281
2674	Make a single, non-blocking sweep over the embedded loop. This works	3282	Make a single, non-blocking sweep over the embedded loop. This works
2675	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3283	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2676	appropriate way for embedded loops.	3284	appropriate way for embedded loops.
2677		3285
2678	=item struct ev_loop *other [read-only]	3286	=item struct ev_loop *other [read-only]
2679		3287
2680	The embedded event loop.	3288	The embedded event loop.
…		…
2690	used).	3298	used).
2691		3299
2692	struct ev_loop *loop_hi = ev_default_init (0);	3300	struct ev_loop *loop_hi = ev_default_init (0);
2693	struct ev_loop *loop_lo = 0;	3301	struct ev_loop *loop_lo = 0;
2694	ev_embed embed;	3302	ev_embed embed;
2695		3303
2696	// see if there is a chance of getting one that works	3304	// see if there is a chance of getting one that works
2697	// (remember that a flags value of 0 means autodetection)	3305	// (remember that a flags value of 0 means autodetection)
2698	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3306	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2699	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3307	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2700	: 0;	3308	: 0;
…		…
2714	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3322	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2715		3323
2716	struct ev_loop *loop = ev_default_init (0);	3324	struct ev_loop *loop = ev_default_init (0);
2717	struct ev_loop *loop_socket = 0;	3325	struct ev_loop *loop_socket = 0;
2718	ev_embed embed;	3326	ev_embed embed;
2719		3327
2720	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3328	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2721	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3329	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2722	{	3330	{
2723	ev_embed_init (&embed, 0, loop_socket);	3331	ev_embed_init (&embed, 0, loop_socket);
2724	ev_embed_start (loop, &embed);	3332	ev_embed_start (loop, &embed);
…		…
2732		3340
2733	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3341	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2734		3342
2735	Fork watchers are called when a C<fork ()> was detected (usually because	3343	Fork watchers are called when a C<fork ()> was detected (usually because
2736	whoever is a good citizen cared to tell libev about it by calling	3344	whoever is a good citizen cared to tell libev about it by calling
2737	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3345	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2738	event loop blocks next and before C<ev_check> watchers are being called,	3346	and before C<ev_check> watchers are being called, and only in the child
2739	and only in the child after the fork. If whoever good citizen calling	3347	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2740	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3348	and calls it in the wrong process, the fork handlers will be invoked, too,
2741	handlers will be invoked, too, of course.	3349	of course.
2742		3350
2743	=head3 The special problem of life after fork - how is it possible?	3351	=head3 The special problem of life after fork - how is it possible?
2744		3352
2745	Most uses of C<fork()> consist of forking, then some simple calls to ste	3353	Most uses of C<fork ()> consist of forking, then some simple calls to set
2746	up/change the process environment, followed by a call to C<exec()>. This	3354	up/change the process environment, followed by a call to C<exec()>. This
2747	sequence should be handled by libev without any problems.	3355	sequence should be handled by libev without any problems.
2748		3356
2749	This changes when the application actually wants to do event handling	3357	This changes when the application actually wants to do event handling
2750	in the child, or both parent in child, in effect "continuing" after the	3358	in the child, or both parent in child, in effect "continuing" after the
…		…
2766	disadvantage of having to use multiple event loops (which do not support	3374	disadvantage of having to use multiple event loops (which do not support
2767	signal watchers).	3375	signal watchers).
2768		3376
2769	When this is not possible, or you want to use the default loop for	3377	When this is not possible, or you want to use the default loop for
2770	other reasons, then in the process that wants to start "fresh", call	3378	other reasons, then in the process that wants to start "fresh", call
2771	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3379	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2772	the default loop will "orphan" (not stop) all registered watchers, so you	3380	Destroying the default loop will "orphan" (not stop) all registered
2773	have to be careful not to execute code that modifies those watchers. Note	3381	watchers, so you have to be careful not to execute code that modifies
2774	also that in that case, you have to re-register any signal watchers.	3382	those watchers. Note also that in that case, you have to re-register any
		3383	signal watchers.
2775		3384
2776	=head3 Watcher-Specific Functions and Data Members	3385	=head3 Watcher-Specific Functions and Data Members
2777		3386
2778	=over 4	3387	=over 4
2779		3388
2780	=item ev_fork_init (ev_signal *, callback)	3389	=item ev_fork_init (ev_fork *, callback)
2781		3390
2782	Initialises and configures the fork watcher - it has no parameters of any	3391	Initialises and configures the fork watcher - it has no parameters of any
2783	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3392	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2784	believe me.	3393	really.
2785		3394
2786	=back	3395	=back
2787		3396
2788		3397
		3398	=head2 C<ev_cleanup> - even the best things end
		3399
		3400	Cleanup watchers are called just before the event loop is being destroyed
		3401	by a call to C<ev_loop_destroy>.
		3402
		3403	While there is no guarantee that the event loop gets destroyed, cleanup
		3404	watchers provide a convenient method to install cleanup hooks for your
		3405	program, worker threads and so on - you just to make sure to destroy the
		3406	loop when you want them to be invoked.
		3407
		3408	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3409	all other watchers, they do not keep a reference to the event loop (which
		3410	makes a lot of sense if you think about it). Like all other watchers, you
		3411	can call libev functions in the callback, except C<ev_cleanup_start>.
		3412
		3413	=head3 Watcher-Specific Functions and Data Members
		3414
		3415	=over 4
		3416
		3417	=item ev_cleanup_init (ev_cleanup *, callback)
		3418
		3419	Initialises and configures the cleanup watcher - it has no parameters of
		3420	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3421	pointless, I assure you.
		3422
		3423	=back
		3424
		3425	Example: Register an atexit handler to destroy the default loop, so any
		3426	cleanup functions are called.
		3427
		3428	static void
		3429	program_exits (void)
		3430	{
		3431	ev_loop_destroy (EV_DEFAULT_UC);
		3432	}
		3433
		3434	...
		3435	atexit (program_exits);
		3436
		3437
2789	=head2 C<ev_async> - how to wake up another event loop	3438	=head2 C<ev_async> - how to wake up an event loop
2790		3439
2791	In general, you cannot use an C<ev_loop> from multiple threads or other	3440	In general, you cannot use an C<ev_loop> from multiple threads or other
2792	asynchronous sources such as signal handlers (as opposed to multiple event	3441	asynchronous sources such as signal handlers (as opposed to multiple event
2793	loops - those are of course safe to use in different threads).	3442	loops - those are of course safe to use in different threads).
2794		3443
2795	Sometimes, however, you need to wake up another event loop you do not	3444	Sometimes, however, you need to wake up an event loop you do not control,
2796	control, for example because it belongs to another thread. This is what	3445	for example because it belongs to another thread. This is what C<ev_async>
2797	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3446	watchers do: as long as the C<ev_async> watcher is active, you can signal
2798	can signal it by calling C<ev_async_send>, which is thread- and signal	3447	it by calling C<ev_async_send>, which is thread- and signal safe.
2799	safe.
2800		3448
2801	This functionality is very similar to C<ev_signal> watchers, as signals,	3449	This functionality is very similar to C<ev_signal> watchers, as signals,
2802	too, are asynchronous in nature, and signals, too, will be compressed	3450	too, are asynchronous in nature, and signals, too, will be compressed
2803	(i.e. the number of callback invocations may be less than the number of	3451	(i.e. the number of callback invocations may be less than the number of
2804	C<ev_async_sent> calls).	3452	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2805		3453	of "global async watchers" by using a watcher on an otherwise unused
2806	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3454	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2807	just the default loop.	3455	even without knowing which loop owns the signal.
2808		3456
2809	=head3 Queueing	3457	=head3 Queueing
2810		3458
2811	C<ev_async> does not support queueing of data in any way. The reason	3459	C<ev_async> does not support queueing of data in any way. The reason
2812	is that the author does not know of a simple (or any) algorithm for a	3460	is that the author does not know of a simple (or any) algorithm for a
2813	multiple-writer-single-reader queue that works in all cases and doesn't	3461	multiple-writer-single-reader queue that works in all cases and doesn't
2814	need elaborate support such as pthreads.	3462	need elaborate support such as pthreads or unportable memory access
		3463	semantics.
2815		3464
2816	That means that if you want to queue data, you have to provide your own	3465	That means that if you want to queue data, you have to provide your own
2817	queue. But at least I can tell you how to implement locking around your	3466	queue. But at least I can tell you how to implement locking around your
2818	queue:	3467	queue:
2819		3468
…		…
2903	trust me.	3552	trust me.
2904		3553
2905	=item ev_async_send (loop, ev_async *)	3554	=item ev_async_send (loop, ev_async *)
2906		3555
2907	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3556	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2908	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3557	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3558	returns.
		3559
2909	C<ev_feed_event>, this call is safe to do from other threads, signal or	3560	Unlike C<ev_feed_event>, this call is safe to do from other threads,
2910	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3561	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
2911	section below on what exactly this means).	3562	embedding section below on what exactly this means).
2912		3563
2913	Note that, as with other watchers in libev, multiple events might get	3564	Note that, as with other watchers in libev, multiple events might get
2914	compressed into a single callback invocation (another way to look at this	3565	compressed into a single callback invocation (another way to look at
2915	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3566	this is that C<ev_async> watchers are level-triggered: they are set on
2916	reset when the event loop detects that).	3567	C<ev_async_send>, reset when the event loop detects that).
2917		3568
2918	This call incurs the overhead of a system call only once per event loop	3569	This call incurs the overhead of at most one extra system call per event
2919	iteration, so while the overhead might be noticeable, it doesn't apply to	3570	loop iteration, if the event loop is blocked, and no syscall at all if
2920	repeated calls to C<ev_async_send> for the same event loop.	3571	the event loop (or your program) is processing events. That means that
		3572	repeated calls are basically free (there is no need to avoid calls for
		3573	performance reasons) and that the overhead becomes smaller (typically
		3574	zero) under load.
2921		3575
2922	=item bool = ev_async_pending (ev_async *)	3576	=item bool = ev_async_pending (ev_async *)
2923		3577
2924	Returns a non-zero value when C<ev_async_send> has been called on the	3578	Returns a non-zero value when C<ev_async_send> has been called on the
2925	watcher but the event has not yet been processed (or even noted) by the	3579	watcher but the event has not yet been processed (or even noted) by the
…		…
2942		3596
2943	There are some other functions of possible interest. Described. Here. Now.	3597	There are some other functions of possible interest. Described. Here. Now.
2944		3598
2945	=over 4	3599	=over 4
2946		3600
2947	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3601	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
2948		3602
2949	This function combines a simple timer and an I/O watcher, calls your	3603	This function combines a simple timer and an I/O watcher, calls your
2950	callback on whichever event happens first and automatically stops both	3604	callback on whichever event happens first and automatically stops both
2951	watchers. This is useful if you want to wait for a single event on an fd	3605	watchers. This is useful if you want to wait for a single event on an fd
2952	or timeout without having to allocate/configure/start/stop/free one or	3606	or timeout without having to allocate/configure/start/stop/free one or
…		…
2958		3612
2959	If C<timeout> is less than 0, then no timeout watcher will be	3613	If C<timeout> is less than 0, then no timeout watcher will be
2960	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3614	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2961	repeat = 0) will be started. C<0> is a valid timeout.	3615	repeat = 0) will be started. C<0> is a valid timeout.
2962		3616
2963	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3617	The callback has the type C<void (*cb)(int revents, void *arg)> and is
2964	passed an C<revents> set like normal event callbacks (a combination of	3618	passed an C<revents> set like normal event callbacks (a combination of
2965	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3619	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
2966	value passed to C<ev_once>. Note that it is possible to receive I<both>	3620	value passed to C<ev_once>. Note that it is possible to receive I<both>
2967	a timeout and an io event at the same time - you probably should give io	3621	a timeout and an io event at the same time - you probably should give io
2968	events precedence.	3622	events precedence.
2969		3623
2970	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3624	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2971		3625
2972	static void stdin_ready (int revents, void *arg)	3626	static void stdin_ready (int revents, void *arg)
2973	{	3627	{
2974	if (revents & EV_READ)	3628	if (revents & EV_READ)
2975	/* stdin might have data for us, joy! */;	3629	/* stdin might have data for us, joy! */;
2976	else if (revents & EV_TIMEOUT)	3630	else if (revents & EV_TIMER)
2977	/* doh, nothing entered */;	3631	/* doh, nothing entered */;
2978	}	3632	}
2979		3633
2980	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3634	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2981		3635
2982	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2983
2984	Feeds the given event set into the event loop, as if the specified event
2985	had happened for the specified watcher (which must be a pointer to an
2986	initialised but not necessarily started event watcher).
2987
2988	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3636	=item ev_feed_fd_event (loop, int fd, int revents)
2989		3637
2990	Feed an event on the given fd, as if a file descriptor backend detected	3638	Feed an event on the given fd, as if a file descriptor backend detected
2991	the given events it.	3639	the given events.
2992		3640
2993	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3641	=item ev_feed_signal_event (loop, int signum)
2994		3642
2995	Feed an event as if the given signal occurred (C<loop> must be the default	3643	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
2996	loop!).	3644	which is async-safe.
2997		3645
2998	=back	3646	=back
		3647
		3648
		3649	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3650
		3651	This section explains some common idioms that are not immediately
		3652	obvious. Note that examples are sprinkled over the whole manual, and this
		3653	section only contains stuff that wouldn't fit anywhere else.
		3654
		3655	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3656
		3657	Each watcher has, by default, a C<void *data> member that you can read
		3658	or modify at any time: libev will completely ignore it. This can be used
		3659	to associate arbitrary data with your watcher. If you need more data and
		3660	don't want to allocate memory separately and store a pointer to it in that
		3661	data member, you can also "subclass" the watcher type and provide your own
		3662	data:
		3663
		3664	struct my_io
		3665	{
		3666	ev_io io;
		3667	int otherfd;
		3668	void *somedata;
		3669	struct whatever *mostinteresting;
		3670	};
		3671
		3672	...
		3673	struct my_io w;
		3674	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3675
		3676	And since your callback will be called with a pointer to the watcher, you
		3677	can cast it back to your own type:
		3678
		3679	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3680	{
		3681	struct my_io *w = (struct my_io *)w_;
		3682	...
		3683	}
		3684
		3685	More interesting and less C-conformant ways of casting your callback
		3686	function type instead have been omitted.
		3687
		3688	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3689
		3690	Another common scenario is to use some data structure with multiple
		3691	embedded watchers, in effect creating your own watcher that combines
		3692	multiple libev event sources into one "super-watcher":
		3693
		3694	struct my_biggy
		3695	{
		3696	int some_data;
		3697	ev_timer t1;
		3698	ev_timer t2;
		3699	}
		3700
		3701	In this case getting the pointer to C<my_biggy> is a bit more
		3702	complicated: Either you store the address of your C<my_biggy> struct in
		3703	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3704	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3705	real programmers):
		3706
		3707	#include <stddef.h>
		3708
		3709	static void
		3710	t1_cb (EV_P_ ev_timer *w, int revents)
		3711	{
		3712	struct my_biggy big = (struct my_biggy *)
		3713	(((char *)w) - offsetof (struct my_biggy, t1));
		3714	}
		3715
		3716	static void
		3717	t2_cb (EV_P_ ev_timer *w, int revents)
		3718	{
		3719	struct my_biggy big = (struct my_biggy *)
		3720	(((char *)w) - offsetof (struct my_biggy, t2));
		3721	}
		3722
		3723	=head2 AVOIDING FINISHING BEFORE RETURNING
		3724
		3725	Often you have structures like this in event-based programs:
		3726
		3727	callback ()
		3728	{
		3729	free (request);
		3730	}
		3731
		3732	request = start_new_request (..., callback);
		3733
		3734	The intent is to start some "lengthy" operation. The C<request> could be
		3735	used to cancel the operation, or do other things with it.
		3736
		3737	It's not uncommon to have code paths in C<start_new_request> that
		3738	immediately invoke the callback, for example, to report errors. Or you add
		3739	some caching layer that finds that it can skip the lengthy aspects of the
		3740	operation and simply invoke the callback with the result.
		3741
		3742	The problem here is that this will happen I<before> C<start_new_request>
		3743	has returned, so C<request> is not set.
		3744
		3745	Even if you pass the request by some safer means to the callback, you
		3746	might want to do something to the request after starting it, such as
		3747	canceling it, which probably isn't working so well when the callback has
		3748	already been invoked.
		3749
		3750	A common way around all these issues is to make sure that
		3751	C<start_new_request> I<always> returns before the callback is invoked. If
		3752	C<start_new_request> immediately knows the result, it can artificially
		3753	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3754	example, or more sneakily, by reusing an existing (stopped) watcher and
		3755	pushing it into the pending queue:
		3756
		3757	ev_set_cb (watcher, callback);
		3758	ev_feed_event (EV_A_ watcher, 0);
		3759
		3760	This way, C<start_new_request> can safely return before the callback is
		3761	invoked, while not delaying callback invocation too much.
		3762
		3763	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3764
		3765	Often (especially in GUI toolkits) there are places where you have
		3766	I<modal> interaction, which is most easily implemented by recursively
		3767	invoking C<ev_run>.
		3768
		3769	This brings the problem of exiting - a callback might want to finish the
		3770	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3771	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3772	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3773	other combination: In these cases, a simple C<ev_break> will not work.
		3774
		3775	The solution is to maintain "break this loop" variable for each C<ev_run>
		3776	invocation, and use a loop around C<ev_run> until the condition is
		3777	triggered, using C<EVRUN_ONCE>:
		3778
		3779	// main loop
		3780	int exit_main_loop = 0;
		3781
		3782	while (!exit_main_loop)
		3783	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3784
		3785	// in a modal watcher
		3786	int exit_nested_loop = 0;
		3787
		3788	while (!exit_nested_loop)
		3789	ev_run (EV_A_ EVRUN_ONCE);
		3790
		3791	To exit from any of these loops, just set the corresponding exit variable:
		3792
		3793	// exit modal loop
		3794	exit_nested_loop = 1;
		3795
		3796	// exit main program, after modal loop is finished
		3797	exit_main_loop = 1;
		3798
		3799	// exit both
		3800	exit_main_loop = exit_nested_loop = 1;
		3801
		3802	=head2 THREAD LOCKING EXAMPLE
		3803
		3804	Here is a fictitious example of how to run an event loop in a different
		3805	thread from where callbacks are being invoked and watchers are
		3806	created/added/removed.
		3807
		3808	For a real-world example, see the C<EV::Loop::Async> perl module,
		3809	which uses exactly this technique (which is suited for many high-level
		3810	languages).
		3811
		3812	The example uses a pthread mutex to protect the loop data, a condition
		3813	variable to wait for callback invocations, an async watcher to notify the
		3814	event loop thread and an unspecified mechanism to wake up the main thread.
		3815
		3816	First, you need to associate some data with the event loop:
		3817
		3818	typedef struct {
		3819	mutex_t lock; /* global loop lock */
		3820	ev_async async_w;
		3821	thread_t tid;
		3822	cond_t invoke_cv;
		3823	} userdata;
		3824
		3825	void prepare_loop (EV_P)
		3826	{
		3827	// for simplicity, we use a static userdata struct.
		3828	static userdata u;
		3829
		3830	ev_async_init (&u->async_w, async_cb);
		3831	ev_async_start (EV_A_ &u->async_w);
		3832
		3833	pthread_mutex_init (&u->lock, 0);
		3834	pthread_cond_init (&u->invoke_cv, 0);
		3835
		3836	// now associate this with the loop
		3837	ev_set_userdata (EV_A_ u);
		3838	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3839	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3840
		3841	// then create the thread running ev_run
		3842	pthread_create (&u->tid, 0, l_run, EV_A);
		3843	}
		3844
		3845	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3846	solely to wake up the event loop so it takes notice of any new watchers
		3847	that might have been added:
		3848
		3849	static void
		3850	async_cb (EV_P_ ev_async *w, int revents)
		3851	{
		3852	// just used for the side effects
		3853	}
		3854
		3855	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3856	protecting the loop data, respectively.
		3857
		3858	static void
		3859	l_release (EV_P)
		3860	{
		3861	userdata *u = ev_userdata (EV_A);
		3862	pthread_mutex_unlock (&u->lock);
		3863	}
		3864
		3865	static void
		3866	l_acquire (EV_P)
		3867	{
		3868	userdata *u = ev_userdata (EV_A);
		3869	pthread_mutex_lock (&u->lock);
		3870	}
		3871
		3872	The event loop thread first acquires the mutex, and then jumps straight
		3873	into C<ev_run>:
		3874
		3875	void *
		3876	l_run (void *thr_arg)
		3877	{
		3878	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3879
		3880	l_acquire (EV_A);
		3881	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3882	ev_run (EV_A_ 0);
		3883	l_release (EV_A);
		3884
		3885	return 0;
		3886	}
		3887
		3888	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3889	signal the main thread via some unspecified mechanism (signals? pipe
		3890	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3891	have been called (in a while loop because a) spurious wakeups are possible
		3892	and b) skipping inter-thread-communication when there are no pending
		3893	watchers is very beneficial):
		3894
		3895	static void
		3896	l_invoke (EV_P)
		3897	{
		3898	userdata *u = ev_userdata (EV_A);
		3899
		3900	while (ev_pending_count (EV_A))
		3901	{
		3902	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3903	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3904	}
		3905	}
		3906
		3907	Now, whenever the main thread gets told to invoke pending watchers, it
		3908	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3909	thread to continue:
		3910
		3911	static void
		3912	real_invoke_pending (EV_P)
		3913	{
		3914	userdata *u = ev_userdata (EV_A);
		3915
		3916	pthread_mutex_lock (&u->lock);
		3917	ev_invoke_pending (EV_A);
		3918	pthread_cond_signal (&u->invoke_cv);
		3919	pthread_mutex_unlock (&u->lock);
		3920	}
		3921
		3922	Whenever you want to start/stop a watcher or do other modifications to an
		3923	event loop, you will now have to lock:
		3924
		3925	ev_timer timeout_watcher;
		3926	userdata *u = ev_userdata (EV_A);
		3927
		3928	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3929
		3930	pthread_mutex_lock (&u->lock);
		3931	ev_timer_start (EV_A_ &timeout_watcher);
		3932	ev_async_send (EV_A_ &u->async_w);
		3933	pthread_mutex_unlock (&u->lock);
		3934
		3935	Note that sending the C<ev_async> watcher is required because otherwise
		3936	an event loop currently blocking in the kernel will have no knowledge
		3937	about the newly added timer. By waking up the loop it will pick up any new
		3938	watchers in the next event loop iteration.
		3939
		3940	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3941
		3942	While the overhead of a callback that e.g. schedules a thread is small, it
		3943	is still an overhead. If you embed libev, and your main usage is with some
		3944	kind of threads or coroutines, you might want to customise libev so that
		3945	doesn't need callbacks anymore.
		3946
		3947	Imagine you have coroutines that you can switch to using a function
		3948	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3949	and that due to some magic, the currently active coroutine is stored in a
		3950	global called C<current_coro>. Then you can build your own "wait for libev
		3951	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3952	the differing C<;> conventions):
		3953
		3954	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3955	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3956
		3957	That means instead of having a C callback function, you store the
		3958	coroutine to switch to in each watcher, and instead of having libev call
		3959	your callback, you instead have it switch to that coroutine.
		3960
		3961	A coroutine might now wait for an event with a function called
		3962	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3963	matter when, or whether the watcher is active or not when this function is
		3964	called):
		3965
		3966	void
		3967	wait_for_event (ev_watcher *w)
		3968	{
		3969	ev_set_cb (w, current_coro);
		3970	switch_to (libev_coro);
		3971	}
		3972
		3973	That basically suspends the coroutine inside C<wait_for_event> and
		3974	continues the libev coroutine, which, when appropriate, switches back to
		3975	this or any other coroutine.
		3976
		3977	You can do similar tricks if you have, say, threads with an event queue -
		3978	instead of storing a coroutine, you store the queue object and instead of
		3979	switching to a coroutine, you push the watcher onto the queue and notify
		3980	any waiters.
		3981
		3982	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3983	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3984
		3985	// my_ev.h
		3986	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3987	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3988	#include "../libev/ev.h"
		3989
		3990	// my_ev.c
		3991	#define EV_H "my_ev.h"
		3992	#include "../libev/ev.c"
		3993
		3994	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3995	F<my_ev.c> into your project. When properly specifying include paths, you
		3996	can even use F<ev.h> as header file name directly.
2999		3997
3000		3998
3001	=head1 LIBEVENT EMULATION	3999	=head1 LIBEVENT EMULATION
3002		4000
3003	Libev offers a compatibility emulation layer for libevent. It cannot	4001	Libev offers a compatibility emulation layer for libevent. It cannot
3004	emulate the internals of libevent, so here are some usage hints:	4002	emulate the internals of libevent, so here are some usage hints:
3005		4003
3006	=over 4	4004	=over 4
		4005
		4006	=item * Only the libevent-1.4.1-beta API is being emulated.
		4007
		4008	This was the newest libevent version available when libev was implemented,
		4009	and is still mostly unchanged in 2010.
3007		4010
3008	=item * Use it by including <event.h>, as usual.	4011	=item * Use it by including <event.h>, as usual.
3009		4012
3010	=item * The following members are fully supported: ev_base, ev_callback,	4013	=item * The following members are fully supported: ev_base, ev_callback,
3011	ev_arg, ev_fd, ev_res, ev_events.	4014	ev_arg, ev_fd, ev_res, ev_events.
…		…
3017	=item * Priorities are not currently supported. Initialising priorities	4020	=item * Priorities are not currently supported. Initialising priorities
3018	will fail and all watchers will have the same priority, even though there	4021	will fail and all watchers will have the same priority, even though there
3019	is an ev_pri field.	4022	is an ev_pri field.
3020		4023
3021	=item * In libevent, the last base created gets the signals, in libev, the	4024	=item * In libevent, the last base created gets the signals, in libev, the
3022	first base created (== the default loop) gets the signals.	4025	base that registered the signal gets the signals.
3023		4026
3024	=item * Other members are not supported.	4027	=item * Other members are not supported.
3025		4028
3026	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4029	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3027	to use the libev header file and library.	4030	to use the libev header file and library.
3028		4031
3029	=back	4032	=back
3030		4033
3031	=head1 C++ SUPPORT	4034	=head1 C++ SUPPORT
		4035
		4036	=head2 C API
		4037
		4038	The normal C API should work fine when used from C++: both ev.h and the
		4039	libev sources can be compiled as C++. Therefore, code that uses the C API
		4040	will work fine.
		4041
		4042	Proper exception specifications might have to be added to callbacks passed
		4043	to libev: exceptions may be thrown only from watcher callbacks, all other
		4044	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4045	callbacks) must not throw exceptions, and might need a C<noexcept>
		4046	specification. If you have code that needs to be compiled as both C and
		4047	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4048
		4049	static void
		4050	fatal_error (const char *msg) EV_NOEXCEPT
		4051	{
		4052	perror (msg);
		4053	abort ();
		4054	}
		4055
		4056	...
		4057	ev_set_syserr_cb (fatal_error);
		4058
		4059	The only API functions that can currently throw exceptions are C<ev_run>,
		4060	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4061	because it runs cleanup watchers).
		4062
		4063	Throwing exceptions in watcher callbacks is only supported if libev itself
		4064	is compiled with a C++ compiler or your C and C++ environments allow
		4065	throwing exceptions through C libraries (most do).
		4066
		4067	=head2 C++ API
3032		4068
3033	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4069	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3034	you to use some convenience methods to start/stop watchers and also change	4070	you to use some convenience methods to start/stop watchers and also change
3035	the callback model to a model using method callbacks on objects.	4071	the callback model to a model using method callbacks on objects.
3036		4072
3037	To use it,	4073	To use it,
3038		4074
3039	#include <ev++.h>	4075	#include <ev++.h>
3040		4076
3041	This automatically includes F<ev.h> and puts all of its definitions (many	4077	This automatically includes F<ev.h> and puts all of its definitions (many
3042	of them macros) into the global namespace. All C++ specific things are	4078	of them macros) into the global namespace. All C++ specific things are
3043	put into the C<ev> namespace. It should support all the same embedding	4079	put into the C<ev> namespace. It should support all the same embedding
…		…
3046	Care has been taken to keep the overhead low. The only data member the C++	4082	Care has been taken to keep the overhead low. The only data member the C++
3047	classes add (compared to plain C-style watchers) is the event loop pointer	4083	classes add (compared to plain C-style watchers) is the event loop pointer
3048	that the watcher is associated with (or no additional members at all if	4084	that the watcher is associated with (or no additional members at all if
3049	you disable C<EV_MULTIPLICITY> when embedding libev).	4085	you disable C<EV_MULTIPLICITY> when embedding libev).
3050		4086
3051	Currently, functions, and static and non-static member functions can be	4087	Currently, functions, static and non-static member functions and classes
3052	used as callbacks. Other types should be easy to add as long as they only	4088	with C<operator ()> can be used as callbacks. Other types should be easy
3053	need one additional pointer for context. If you need support for other	4089	to add as long as they only need one additional pointer for context. If
3054	types of functors please contact the author (preferably after implementing	4090	you need support for other types of functors please contact the author
3055	it).	4091	(preferably after implementing it).
		4092
		4093	For all this to work, your C++ compiler either has to use the same calling
		4094	conventions as your C compiler (for static member functions), or you have
		4095	to embed libev and compile libev itself as C++.
3056		4096
3057	Here is a list of things available in the C<ev> namespace:	4097	Here is a list of things available in the C<ev> namespace:
3058		4098
3059	=over 4	4099	=over 4
3060		4100
…		…
3070	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4110	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3071		4111
3072	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4112	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3073	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4113	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3074	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4114	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3075	defines by many implementations.	4115	defined by many implementations.
3076		4116
3077	All of those classes have these methods:	4117	All of those classes have these methods:
3078		4118
3079	=over 4	4119	=over 4
3080		4120
3081	=item ev::TYPE::TYPE ()	4121	=item ev::TYPE::TYPE ()
3082		4122
3083	=item ev::TYPE::TYPE (struct ev_loop *)	4123	=item ev::TYPE::TYPE (loop)
3084		4124
3085	=item ev::TYPE::~TYPE	4125	=item ev::TYPE::~TYPE
3086		4126
3087	The constructor (optionally) takes an event loop to associate the watcher	4127	The constructor (optionally) takes an event loop to associate the watcher
3088	with. If it is omitted, it will use C<EV_DEFAULT>.	4128	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3121	myclass obj;	4161	myclass obj;
3122	ev::io iow;	4162	ev::io iow;
3123	iow.set <myclass, &myclass::io_cb> (&obj);	4163	iow.set <myclass, &myclass::io_cb> (&obj);
3124		4164
3125	=item w->set (object *)	4165	=item w->set (object *)
3126
3127	This is an B<experimental> feature that might go away in a future version.
3128		4166
3129	This is a variation of a method callback - leaving out the method to call	4167	This is a variation of a method callback - leaving out the method to call
3130	will default the method to C<operator ()>, which makes it possible to use	4168	will default the method to C<operator ()>, which makes it possible to use
3131	functor objects without having to manually specify the C<operator ()> all	4169	functor objects without having to manually specify the C<operator ()> all
3132	the time. Incidentally, you can then also leave out the template argument	4170	the time. Incidentally, you can then also leave out the template argument
…		…
3144	void operator() (ev::io &w, int revents)	4182	void operator() (ev::io &w, int revents)
3145	{	4183	{
3146	...	4184	...
3147	}	4185	}
3148	}	4186	}
3149		4187
3150	myfunctor f;	4188	myfunctor f;
3151		4189
3152	ev::io w;	4190	ev::io w;
3153	w.set (&f);	4191	w.set (&f);
3154		4192
…		…
3165	Example: Use a plain function as callback.	4203	Example: Use a plain function as callback.
3166		4204
3167	static void io_cb (ev::io &w, int revents) { }	4205	static void io_cb (ev::io &w, int revents) { }
3168	iow.set <io_cb> ();	4206	iow.set <io_cb> ();
3169		4207
3170	=item w->set (struct ev_loop *)	4208	=item w->set (loop)
3171		4209
3172	Associates a different C<struct ev_loop> with this watcher. You can only	4210	Associates a different C<struct ev_loop> with this watcher. You can only
3173	do this when the watcher is inactive (and not pending either).	4211	do this when the watcher is inactive (and not pending either).
3174		4212
3175	=item w->set ([arguments])	4213	=item w->set ([arguments])
3176		4214
3177	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4215	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4216	with the same arguments. Either this method or a suitable start method
3178	called at least once. Unlike the C counterpart, an active watcher gets	4217	must be called at least once. Unlike the C counterpart, an active watcher
3179	automatically stopped and restarted when reconfiguring it with this	4218	gets automatically stopped and restarted when reconfiguring it with this
3180	method.	4219	method.
		4220
		4221	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4222	clashing with the C<set (loop)> method.
3181		4223
3182	=item w->start ()	4224	=item w->start ()
3183		4225
3184	Starts the watcher. Note that there is no C<loop> argument, as the	4226	Starts the watcher. Note that there is no C<loop> argument, as the
3185	constructor already stores the event loop.	4227	constructor already stores the event loop.
3186		4228
		4229	=item w->start ([arguments])
		4230
		4231	Instead of calling C<set> and C<start> methods separately, it is often
		4232	convenient to wrap them in one call. Uses the same type of arguments as
		4233	the configure C<set> method of the watcher.
		4234
3187	=item w->stop ()	4235	=item w->stop ()
3188		4236
3189	Stops the watcher if it is active. Again, no C<loop> argument.	4237	Stops the watcher if it is active. Again, no C<loop> argument.
3190		4238
3191	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4239	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3203		4251
3204	=back	4252	=back
3205		4253
3206	=back	4254	=back
3207		4255
3208	Example: Define a class with an IO and idle watcher, start one of them in	4256	Example: Define a class with two I/O and idle watchers, start the I/O
3209	the constructor.	4257	watchers in the constructor.
3210		4258
3211	class myclass	4259	class myclass
3212	{	4260	{
3213	ev::io io ; void io_cb (ev::io &w, int revents);	4261	ev::io io ; void io_cb (ev::io &w, int revents);
		4262	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3214	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4263	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3215		4264
3216	myclass (int fd)	4265	myclass (int fd)
3217	{	4266	{
3218	io .set <myclass, &myclass::io_cb > (this);	4267	io .set <myclass, &myclass::io_cb > (this);
		4268	io2 .set <myclass, &myclass::io2_cb > (this);
3219	idle.set <myclass, &myclass::idle_cb> (this);	4269	idle.set <myclass, &myclass::idle_cb> (this);
3220		4270
3221	io.start (fd, ev::READ);	4271	io.set (fd, ev::WRITE); // configure the watcher
		4272	io.start (); // start it whenever convenient
		4273
		4274	io2.start (fd, ev::READ); // set + start in one call
3222	}	4275	}
3223	};	4276	};
3224		4277
3225		4278
3226	=head1 OTHER LANGUAGE BINDINGS	4279	=head1 OTHER LANGUAGE BINDINGS
…		…
3265	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4318	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3266		4319
3267	=item D	4320	=item D
3268		4321
3269	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4322	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3270	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4323	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3271		4324
3272	=item Ocaml	4325	=item Ocaml
3273		4326
3274	Erkki Seppala has written Ocaml bindings for libev, to be found at	4327	Erkki Seppala has written Ocaml bindings for libev, to be found at
3275	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4328	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		4329
		4330	=item Lua
		4331
		4332	Brian Maher has written a partial interface to libev for lua (at the
		4333	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
		4334	L<http://github.com/brimworks/lua-ev>.
		4335
		4336	=item Javascript
		4337
		4338	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4339
		4340	=item Others
		4341
		4342	There are others, and I stopped counting.
3276		4343
3277	=back	4344	=back
3278		4345
3279		4346
3280	=head1 MACRO MAGIC	4347	=head1 MACRO MAGIC
…		…
3294	loop argument"). The C<EV_A> form is used when this is the sole argument,	4361	loop argument"). The C<EV_A> form is used when this is the sole argument,
3295	C<EV_A_> is used when other arguments are following. Example:	4362	C<EV_A_> is used when other arguments are following. Example:
3296		4363
3297	ev_unref (EV_A);	4364	ev_unref (EV_A);
3298	ev_timer_add (EV_A_ watcher);	4365	ev_timer_add (EV_A_ watcher);
3299	ev_loop (EV_A_ 0);	4366	ev_run (EV_A_ 0);
3300		4367
3301	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4368	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3302	which is often provided by the following macro.	4369	which is often provided by the following macro.
3303		4370
3304	=item C<EV_P>, C<EV_P_>	4371	=item C<EV_P>, C<EV_P_>
…		…
3317	suitable for use with C<EV_A>.	4384	suitable for use with C<EV_A>.
3318		4385
3319	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4386	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3320		4387
3321	Similar to the other two macros, this gives you the value of the default	4388	Similar to the other two macros, this gives you the value of the default
3322	loop, if multiple loops are supported ("ev loop default").	4389	loop, if multiple loops are supported ("ev loop default"). The default loop
		4390	will be initialised if it isn't already initialised.
		4391
		4392	For non-multiplicity builds, these macros do nothing, so you always have
		4393	to initialise the loop somewhere.
3323		4394
3324	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4395	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3325		4396
3326	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4397	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3327	default loop has been initialised (C<UC> == unchecked). Their behaviour	4398	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3344	}	4415	}
3345		4416
3346	ev_check check;	4417	ev_check check;
3347	ev_check_init (&check, check_cb);	4418	ev_check_init (&check, check_cb);
3348	ev_check_start (EV_DEFAULT_ &check);	4419	ev_check_start (EV_DEFAULT_ &check);
3349	ev_loop (EV_DEFAULT_ 0);	4420	ev_run (EV_DEFAULT_ 0);
3350		4421
3351	=head1 EMBEDDING	4422	=head1 EMBEDDING
3352		4423
3353	Libev can (and often is) directly embedded into host	4424	Libev can (and often is) directly embedded into host
3354	applications. Examples of applications that embed it include the Deliantra	4425	applications. Examples of applications that embed it include the Deliantra
…		…
3394	ev_vars.h	4465	ev_vars.h
3395	ev_wrap.h	4466	ev_wrap.h
3396		4467
3397	ev_win32.c required on win32 platforms only	4468	ev_win32.c required on win32 platforms only
3398		4469
3399	ev_select.c only when select backend is enabled (which is enabled by default)	4470	ev_select.c only when select backend is enabled
3400	ev_poll.c only when poll backend is enabled (disabled by default)	4471	ev_poll.c only when poll backend is enabled
3401	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4472	ev_epoll.c only when the epoll backend is enabled
		4473	ev_linuxaio.c only when the linux aio backend is enabled
3402	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4474	ev_kqueue.c only when the kqueue backend is enabled
3403	ev_port.c only when the solaris port backend is enabled (disabled by default)	4475	ev_port.c only when the solaris port backend is enabled
3404		4476
3405	F<ev.c> includes the backend files directly when enabled, so you only need	4477	F<ev.c> includes the backend files directly when enabled, so you only need
3406	to compile this single file.	4478	to compile this single file.
3407		4479
3408	=head3 LIBEVENT COMPATIBILITY API	4480	=head3 LIBEVENT COMPATIBILITY API
…		…
3434	libev.m4	4506	libev.m4
3435		4507
3436	=head2 PREPROCESSOR SYMBOLS/MACROS	4508	=head2 PREPROCESSOR SYMBOLS/MACROS
3437		4509
3438	Libev can be configured via a variety of preprocessor symbols you have to	4510	Libev can be configured via a variety of preprocessor symbols you have to
3439	define before including any of its files. The default in the absence of	4511	define before including (or compiling) any of its files. The default in
3440	autoconf is documented for every option.	4512	the absence of autoconf is documented for every option.
		4513
		4514	Symbols marked with "(h)" do not change the ABI, and can have different
		4515	values when compiling libev vs. including F<ev.h>, so it is permissible
		4516	to redefine them before including F<ev.h> without breaking compatibility
		4517	to a compiled library. All other symbols change the ABI, which means all
		4518	users of libev and the libev code itself must be compiled with compatible
		4519	settings.
3441		4520
3442	=over 4	4521	=over 4
3443		4522
		4523	=item EV_COMPAT3 (h)
		4524
		4525	Backwards compatibility is a major concern for libev. This is why this
		4526	release of libev comes with wrappers for the functions and symbols that
		4527	have been renamed between libev version 3 and 4.
		4528
		4529	You can disable these wrappers (to test compatibility with future
		4530	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4531	sources. This has the additional advantage that you can drop the C<struct>
		4532	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4533	typedef in that case.
		4534
		4535	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4536	and in some even more future version the compatibility code will be
		4537	removed completely.
		4538
3444	=item EV_STANDALONE	4539	=item EV_STANDALONE (h)
3445		4540
3446	Must always be C<1> if you do not use autoconf configuration, which	4541	Must always be C<1> if you do not use autoconf configuration, which
3447	keeps libev from including F<config.h>, and it also defines dummy	4542	keeps libev from including F<config.h>, and it also defines dummy
3448	implementations for some libevent functions (such as logging, which is not	4543	implementations for some libevent functions (such as logging, which is not
3449	supported). It will also not define any of the structs usually found in	4544	supported). It will also not define any of the structs usually found in
3450	F<event.h> that are not directly supported by the libev core alone.	4545	F<event.h> that are not directly supported by the libev core alone.
3451		4546
3452	In stanbdalone mode, libev will still try to automatically deduce the	4547	In standalone mode, libev will still try to automatically deduce the
3453	configuration, but has to be more conservative.	4548	configuration, but has to be more conservative.
		4549
		4550	=item EV_USE_FLOOR
		4551
		4552	If defined to be C<1>, libev will use the C<floor ()> function for its
		4553	periodic reschedule calculations, otherwise libev will fall back on a
		4554	portable (slower) implementation. If you enable this, you usually have to
		4555	link against libm or something equivalent. Enabling this when the C<floor>
		4556	function is not available will fail, so the safe default is to not enable
		4557	this.
3454		4558
3455	=item EV_USE_MONOTONIC	4559	=item EV_USE_MONOTONIC
3456		4560
3457	If defined to be C<1>, libev will try to detect the availability of the	4561	If defined to be C<1>, libev will try to detect the availability of the
3458	monotonic clock option at both compile time and runtime. Otherwise no	4562	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3522	be used is the winsock select). This means that it will call	4626	be used is the winsock select). This means that it will call
3523	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	4627	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3524	it is assumed that all these functions actually work on fds, even	4628	it is assumed that all these functions actually work on fds, even
3525	on win32. Should not be defined on non-win32 platforms.	4629	on win32. Should not be defined on non-win32 platforms.
3526		4630
3527	=item EV_FD_TO_WIN32_HANDLE	4631	=item EV_FD_TO_WIN32_HANDLE(fd)
3528		4632
3529	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	4633	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3530	file descriptors to socket handles. When not defining this symbol (the	4634	file descriptors to socket handles. When not defining this symbol (the
3531	default), then libev will call C<_get_osfhandle>, which is usually	4635	default), then libev will call C<_get_osfhandle>, which is usually
3532	correct. In some cases, programs use their own file descriptor management,	4636	correct. In some cases, programs use their own file descriptor management,
3533	in which case they can provide this function to map fds to socket handles.	4637	in which case they can provide this function to map fds to socket handles.
3534		4638
		4639	=item EV_WIN32_HANDLE_TO_FD(handle)
		4640
		4641	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		4642	using the standard C<_open_osfhandle> function. For programs implementing
		4643	their own fd to handle mapping, overwriting this function makes it easier
		4644	to do so. This can be done by defining this macro to an appropriate value.
		4645
		4646	=item EV_WIN32_CLOSE_FD(fd)
		4647
		4648	If programs implement their own fd to handle mapping on win32, then this
		4649	macro can be used to override the C<close> function, useful to unregister
		4650	file descriptors again. Note that the replacement function has to close
		4651	the underlying OS handle.
		4652
		4653	=item EV_USE_WSASOCKET
		4654
		4655	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4656	communication socket, which works better in some environments. Otherwise,
		4657	the normal C<socket> function will be used, which works better in other
		4658	environments.
		4659
3535	=item EV_USE_POLL	4660	=item EV_USE_POLL
3536		4661
3537	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4662	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3538	backend. Otherwise it will be enabled on non-win32 platforms. It	4663	backend. Otherwise it will be enabled on non-win32 platforms. It
3539	takes precedence over select.	4664	takes precedence over select.
…		…
3543	If defined to be C<1>, libev will compile in support for the Linux	4668	If defined to be C<1>, libev will compile in support for the Linux
3544	C<epoll>(7) backend. Its availability will be detected at runtime,	4669	C<epoll>(7) backend. Its availability will be detected at runtime,
3545	otherwise another method will be used as fallback. This is the preferred	4670	otherwise another method will be used as fallback. This is the preferred
3546	backend for GNU/Linux systems. If undefined, it will be enabled if the	4671	backend for GNU/Linux systems. If undefined, it will be enabled if the
3547	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4672	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4673
		4674	=item EV_USE_LINUXAIO
		4675
		4676	If defined to be C<1>, libev will compile in support for the Linux
		4677	aio backend. Due to it's currenbt limitations it has to be requested
		4678	explicitly. If undefined, it will be enabled on linux, otherwise
		4679	disabled.
3548		4680
3549	=item EV_USE_KQUEUE	4681	=item EV_USE_KQUEUE
3550		4682
3551	If defined to be C<1>, libev will compile in support for the BSD style	4683	If defined to be C<1>, libev will compile in support for the BSD style
3552	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4684	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3574	If defined to be C<1>, libev will compile in support for the Linux inotify	4706	If defined to be C<1>, libev will compile in support for the Linux inotify
3575	interface to speed up C<ev_stat> watchers. Its actual availability will	4707	interface to speed up C<ev_stat> watchers. Its actual availability will
3576	be detected at runtime. If undefined, it will be enabled if the headers	4708	be detected at runtime. If undefined, it will be enabled if the headers
3577	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4709	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3578		4710
		4711	=item EV_NO_SMP
		4712
		4713	If defined to be C<1>, libev will assume that memory is always coherent
		4714	between threads, that is, threads can be used, but threads never run on
		4715	different cpus (or different cpu cores). This reduces dependencies
		4716	and makes libev faster.
		4717
		4718	=item EV_NO_THREADS
		4719
		4720	If defined to be C<1>, libev will assume that it will never be called from
		4721	different threads (that includes signal handlers), which is a stronger
		4722	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4723	libev faster.
		4724
3579	=item EV_ATOMIC_T	4725	=item EV_ATOMIC_T
3580		4726
3581	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4727	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3582	access is atomic with respect to other threads or signal contexts. No such	4728	access is atomic with respect to other threads or signal contexts. No
3583	type is easily found in the C language, so you can provide your own type	4729	such type is easily found in the C language, so you can provide your own
3584	that you know is safe for your purposes. It is used both for signal handler "locking"	4730	type that you know is safe for your purposes. It is used both for signal
3585	as well as for signal and thread safety in C<ev_async> watchers.	4731	handler "locking" as well as for signal and thread safety in C<ev_async>
		4732	watchers.
3586		4733
3587	In the absence of this define, libev will use C<sig_atomic_t volatile>	4734	In the absence of this define, libev will use C<sig_atomic_t volatile>
3588	(from F<signal.h>), which is usually good enough on most platforms.	4735	(from F<signal.h>), which is usually good enough on most platforms.
3589		4736
3590	=item EV_H	4737	=item EV_H (h)
3591		4738
3592	The name of the F<ev.h> header file used to include it. The default if	4739	The name of the F<ev.h> header file used to include it. The default if
3593	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4740	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3594	used to virtually rename the F<ev.h> header file in case of conflicts.	4741	used to virtually rename the F<ev.h> header file in case of conflicts.
3595		4742
3596	=item EV_CONFIG_H	4743	=item EV_CONFIG_H (h)
3597		4744
3598	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4745	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3599	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4746	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3600	C<EV_H>, above.	4747	C<EV_H>, above.
3601		4748
3602	=item EV_EVENT_H	4749	=item EV_EVENT_H (h)
3603		4750
3604	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4751	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3605	of how the F<event.h> header can be found, the default is C<"event.h">.	4752	of how the F<event.h> header can be found, the default is C<"event.h">.
3606		4753
3607	=item EV_PROTOTYPES	4754	=item EV_PROTOTYPES (h)
3608		4755
3609	If defined to be C<0>, then F<ev.h> will not define any function	4756	If defined to be C<0>, then F<ev.h> will not define any function
3610	prototypes, but still define all the structs and other symbols. This is	4757	prototypes, but still define all the structs and other symbols. This is
3611	occasionally useful if you want to provide your own wrapper functions	4758	occasionally useful if you want to provide your own wrapper functions
3612	around libev functions.	4759	around libev functions.
…		…
3617	will have the C<struct ev_loop *> as first argument, and you can create	4764	will have the C<struct ev_loop *> as first argument, and you can create
3618	additional independent event loops. Otherwise there will be no support	4765	additional independent event loops. Otherwise there will be no support
3619	for multiple event loops and there is no first event loop pointer	4766	for multiple event loops and there is no first event loop pointer
3620	argument. Instead, all functions act on the single default loop.	4767	argument. Instead, all functions act on the single default loop.
3621		4768
		4769	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4770	default loop when multiplicity is switched off - you always have to
		4771	initialise the loop manually in this case.
		4772
3622	=item EV_MINPRI	4773	=item EV_MINPRI
3623		4774
3624	=item EV_MAXPRI	4775	=item EV_MAXPRI
3625		4776
3626	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4777	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3634	fine.	4785	fine.
3635		4786
3636	If your embedding application does not need any priorities, defining these	4787	If your embedding application does not need any priorities, defining these
3637	both to C<0> will save some memory and CPU.	4788	both to C<0> will save some memory and CPU.
3638		4789
3639	=item EV_PERIODIC_ENABLE	4790	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4791	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4792	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3640		4793
3641	If undefined or defined to be C<1>, then periodic timers are supported. If	4794	If undefined or defined to be C<1> (and the platform supports it), then
3642	defined to be C<0>, then they are not. Disabling them saves a few kB of	4795	the respective watcher type is supported. If defined to be C<0>, then it
3643	code.	4796	is not. Disabling watcher types mainly saves code size.
3644		4797
3645	=item EV_IDLE_ENABLE	4798	=item EV_FEATURES
3646
3647	If undefined or defined to be C<1>, then idle watchers are supported. If
3648	defined to be C<0>, then they are not. Disabling them saves a few kB of
3649	code.
3650
3651	=item EV_EMBED_ENABLE
3652
3653	If undefined or defined to be C<1>, then embed watchers are supported. If
3654	defined to be C<0>, then they are not. Embed watchers rely on most other
3655	watcher types, which therefore must not be disabled.
3656
3657	=item EV_STAT_ENABLE
3658
3659	If undefined or defined to be C<1>, then stat watchers are supported. If
3660	defined to be C<0>, then they are not.
3661
3662	=item EV_FORK_ENABLE
3663
3664	If undefined or defined to be C<1>, then fork watchers are supported. If
3665	defined to be C<0>, then they are not.
3666
3667	=item EV_ASYNC_ENABLE
3668
3669	If undefined or defined to be C<1>, then async watchers are supported. If
3670	defined to be C<0>, then they are not.
3671
3672	=item EV_MINIMAL
3673		4799
3674	If you need to shave off some kilobytes of code at the expense of some	4800	If you need to shave off some kilobytes of code at the expense of some
3675	speed, define this symbol to C<1>. Currently this is used to override some	4801	speed (but with the full API), you can define this symbol to request
3676	inlining decisions, saves roughly 30% code size on amd64. It also selects a	4802	certain subsets of functionality. The default is to enable all features
3677	much smaller 2-heap for timer management over the default 4-heap.	4803	that can be enabled on the platform.
		4804
		4805	A typical way to use this symbol is to define it to C<0> (or to a bitset
		4806	with some broad features you want) and then selectively re-enable
		4807	additional parts you want, for example if you want everything minimal,
		4808	but multiple event loop support, async and child watchers and the poll
		4809	backend, use this:
		4810
		4811	#define EV_FEATURES 0
		4812	#define EV_MULTIPLICITY 1
		4813	#define EV_USE_POLL 1
		4814	#define EV_CHILD_ENABLE 1
		4815	#define EV_ASYNC_ENABLE 1
		4816
		4817	The actual value is a bitset, it can be a combination of the following
		4818	values (by default, all of these are enabled):
		4819
		4820	=over 4
		4821
		4822	=item C<1> - faster/larger code
		4823
		4824	Use larger code to speed up some operations.
		4825
		4826	Currently this is used to override some inlining decisions (enlarging the
		4827	code size by roughly 30% on amd64).
		4828
		4829	When optimising for size, use of compiler flags such as C<-Os> with
		4830	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4831	assertions.
		4832
		4833	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4834	(e.g. gcc with C<-Os>).
		4835
		4836	=item C<2> - faster/larger data structures
		4837
		4838	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4839	hash table sizes and so on. This will usually further increase code size
		4840	and can additionally have an effect on the size of data structures at
		4841	runtime.
		4842
		4843	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4844	(e.g. gcc with C<-Os>).
		4845
		4846	=item C<4> - full API configuration
		4847
		4848	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4849	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4850
		4851	=item C<8> - full API
		4852
		4853	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4854	details on which parts of the API are still available without this
		4855	feature, and do not complain if this subset changes over time.
		4856
		4857	=item C<16> - enable all optional watcher types
		4858
		4859	Enables all optional watcher types. If you want to selectively enable
		4860	only some watcher types other than I/O and timers (e.g. prepare,
		4861	embed, async, child...) you can enable them manually by defining
		4862	C<EV_watchertype_ENABLE> to C<1> instead.
		4863
		4864	=item C<32> - enable all backends
		4865
		4866	This enables all backends - without this feature, you need to enable at
		4867	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4868
		4869	=item C<64> - enable OS-specific "helper" APIs
		4870
		4871	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4872	default.
		4873
		4874	=back
		4875
		4876	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4877	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4878	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4879	watchers, timers and monotonic clock support.
		4880
		4881	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4882	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4883	your program might be left out as well - a binary starting a timer and an
		4884	I/O watcher then might come out at only 5Kb.
		4885
		4886	=item EV_API_STATIC
		4887
		4888	If this symbol is defined (by default it is not), then all identifiers
		4889	will have static linkage. This means that libev will not export any
		4890	identifiers, and you cannot link against libev anymore. This can be useful
		4891	when you embed libev, only want to use libev functions in a single file,
		4892	and do not want its identifiers to be visible.
		4893
		4894	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4895	wants to use libev.
		4896
		4897	This option only works when libev is compiled with a C compiler, as C++
		4898	doesn't support the required declaration syntax.
		4899
		4900	=item EV_AVOID_STDIO
		4901
		4902	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4903	functions (printf, scanf, perror etc.). This will increase the code size
		4904	somewhat, but if your program doesn't otherwise depend on stdio and your
		4905	libc allows it, this avoids linking in the stdio library which is quite
		4906	big.
		4907
		4908	Note that error messages might become less precise when this option is
		4909	enabled.
		4910
		4911	=item EV_NSIG
		4912
		4913	The highest supported signal number, +1 (or, the number of
		4914	signals): Normally, libev tries to deduce the maximum number of signals
		4915	automatically, but sometimes this fails, in which case it can be
		4916	specified. Also, using a lower number than detected (C<32> should be
		4917	good for about any system in existence) can save some memory, as libev
		4918	statically allocates some 12-24 bytes per signal number.
3678		4919
3679	=item EV_PID_HASHSIZE	4920	=item EV_PID_HASHSIZE
3680		4921
3681	C<ev_child> watchers use a small hash table to distribute workload by	4922	C<ev_child> watchers use a small hash table to distribute workload by
3682	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4923	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3683	than enough. If you need to manage thousands of children you might want to	4924	usually more than enough. If you need to manage thousands of children you
3684	increase this value (I<must> be a power of two).	4925	might want to increase this value (I<must> be a power of two).
3685		4926
3686	=item EV_INOTIFY_HASHSIZE	4927	=item EV_INOTIFY_HASHSIZE
3687		4928
3688	C<ev_stat> watchers use a small hash table to distribute workload by	4929	C<ev_stat> watchers use a small hash table to distribute workload by
3689	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4930	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3690	usually more than enough. If you need to manage thousands of C<ev_stat>	4931	disabled), usually more than enough. If you need to manage thousands of
3691	watchers you might want to increase this value (I<must> be a power of	4932	C<ev_stat> watchers you might want to increase this value (I<must> be a
3692	two).	4933	power of two).
3693		4934
3694	=item EV_USE_4HEAP	4935	=item EV_USE_4HEAP
3695		4936
3696	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4937	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3697	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4938	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3698	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4939	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3699	faster performance with many (thousands) of watchers.	4940	faster performance with many (thousands) of watchers.
3700		4941
3701	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4942	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3702	(disabled).	4943	will be C<0>.
3703		4944
3704	=item EV_HEAP_CACHE_AT	4945	=item EV_HEAP_CACHE_AT
3705		4946
3706	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4947	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3707	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4948	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3708	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4949	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3709	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4950	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3710	but avoids random read accesses on heap changes. This improves performance	4951	but avoids random read accesses on heap changes. This improves performance
3711	noticeably with many (hundreds) of watchers.	4952	noticeably with many (hundreds) of watchers.
3712		4953
3713	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4954	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3714	(disabled).	4955	will be C<0>.
3715		4956
3716	=item EV_VERIFY	4957	=item EV_VERIFY
3717		4958
3718	Controls how much internal verification (see C<ev_loop_verify ()>) will	4959	Controls how much internal verification (see C<ev_verify ()>) will
3719	be done: If set to C<0>, no internal verification code will be compiled	4960	be done: If set to C<0>, no internal verification code will be compiled
3720	in. If set to C<1>, then verification code will be compiled in, but not	4961	in. If set to C<1>, then verification code will be compiled in, but not
3721	called. If set to C<2>, then the internal verification code will be	4962	called. If set to C<2>, then the internal verification code will be
3722	called once per loop, which can slow down libev. If set to C<3>, then the	4963	called once per loop, which can slow down libev. If set to C<3>, then the
3723	verification code will be called very frequently, which will slow down	4964	verification code will be called very frequently, which will slow down
3724	libev considerably.	4965	libev considerably.
3725		4966
3726	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4967	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3727	C<0>.	4968	will be C<0>.
3728		4969
3729	=item EV_COMMON	4970	=item EV_COMMON
3730		4971
3731	By default, all watchers have a C<void *data> member. By redefining	4972	By default, all watchers have a C<void *data> member. By redefining
3732	this macro to a something else you can include more and other types of	4973	this macro to something else you can include more and other types of
3733	members. You have to define it each time you include one of the files,	4974	members. You have to define it each time you include one of the files,
3734	though, and it must be identical each time.	4975	though, and it must be identical each time.
3735		4976
3736	For example, the perl EV module uses something like this:	4977	For example, the perl EV module uses something like this:
3737		4978
…		…
3790	file.	5031	file.
3791		5032
3792	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5033	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
3793	that everybody includes and which overrides some configure choices:	5034	that everybody includes and which overrides some configure choices:
3794		5035
3795	#define EV_MINIMAL 1	5036	#define EV_FEATURES 8
3796	#define EV_USE_POLL 0	5037	#define EV_USE_SELECT 1
3797	#define EV_MULTIPLICITY 0
3798	#define EV_PERIODIC_ENABLE 0	5038	#define EV_PREPARE_ENABLE 1
		5039	#define EV_IDLE_ENABLE 1
3799	#define EV_STAT_ENABLE 0	5040	#define EV_SIGNAL_ENABLE 1
3800	#define EV_FORK_ENABLE 0	5041	#define EV_CHILD_ENABLE 1
		5042	#define EV_USE_STDEXCEPT 0
3801	#define EV_CONFIG_H <config.h>	5043	#define EV_CONFIG_H <config.h>
3802	#define EV_MINPRI 0
3803	#define EV_MAXPRI 0
3804		5044
3805	#include "ev++.h"	5045	#include "ev++.h"
3806		5046
3807	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5047	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3808		5048
3809	#include "ev_cpp.h"	5049	#include "ev_cpp.h"
3810	#include "ev.c"	5050	#include "ev.c"
3811		5051
3812	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5052	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
3813		5053
3814	=head2 THREADS AND COROUTINES	5054	=head2 THREADS AND COROUTINES
3815		5055
3816	=head3 THREADS	5056	=head3 THREADS
3817		5057
…		…
3868	default loop and triggering an C<ev_async> watcher from the default loop	5108	default loop and triggering an C<ev_async> watcher from the default loop
3869	watcher callback into the event loop interested in the signal.	5109	watcher callback into the event loop interested in the signal.
3870		5110
3871	=back	5111	=back
3872		5112
		5113	See also L</THREAD LOCKING EXAMPLE>.
		5114
3873	=head3 COROUTINES	5115	=head3 COROUTINES
3874		5116
3875	Libev is very accommodating to coroutines ("cooperative threads"):	5117	Libev is very accommodating to coroutines ("cooperative threads"):
3876	libev fully supports nesting calls to its functions from different	5118	libev fully supports nesting calls to its functions from different
3877	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5119	coroutines (e.g. you can call C<ev_run> on the same loop from two
3878	different coroutines, and switch freely between both coroutines running the	5120	different coroutines, and switch freely between both coroutines running
3879	loop, as long as you don't confuse yourself). The only exception is that	5121	the loop, as long as you don't confuse yourself). The only exception is
3880	you must not do this from C<ev_periodic> reschedule callbacks.	5122	that you must not do this from C<ev_periodic> reschedule callbacks.
3881		5123
3882	Care has been taken to ensure that libev does not keep local state inside	5124	Care has been taken to ensure that libev does not keep local state inside
3883	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5125	C<ev_run>, and other calls do not usually allow for coroutine switches as
3884	they do not call any callbacks.	5126	they do not call any callbacks.
3885		5127
3886	=head2 COMPILER WARNINGS	5128	=head2 COMPILER WARNINGS
3887		5129
3888	Depending on your compiler and compiler settings, you might get no or a	5130	Depending on your compiler and compiler settings, you might get no or a
…		…
3899	maintainable.	5141	maintainable.
3900		5142
3901	And of course, some compiler warnings are just plain stupid, or simply	5143	And of course, some compiler warnings are just plain stupid, or simply
3902	wrong (because they don't actually warn about the condition their message	5144	wrong (because they don't actually warn about the condition their message
3903	seems to warn about). For example, certain older gcc versions had some	5145	seems to warn about). For example, certain older gcc versions had some
3904	warnings that resulted an extreme number of false positives. These have	5146	warnings that resulted in an extreme number of false positives. These have
3905	been fixed, but some people still insist on making code warn-free with	5147	been fixed, but some people still insist on making code warn-free with
3906	such buggy versions.	5148	such buggy versions.
3907		5149
3908	While libev is written to generate as few warnings as possible,	5150	While libev is written to generate as few warnings as possible,
3909	"warn-free" code is not a goal, and it is recommended not to build libev	5151	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
3945	I suggest using suppression lists.	5187	I suggest using suppression lists.
3946		5188
3947		5189
3948	=head1 PORTABILITY NOTES	5190	=head1 PORTABILITY NOTES
3949		5191
		5192	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5193
		5194	GNU/Linux is the only common platform that supports 64 bit file/large file
		5195	interfaces but I<disables> them by default.
		5196
		5197	That means that libev compiled in the default environment doesn't support
		5198	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5199
		5200	Unfortunately, many programs try to work around this GNU/Linux issue
		5201	by enabling the large file API, which makes them incompatible with the
		5202	standard libev compiled for their system.
		5203
		5204	Likewise, libev cannot enable the large file API itself as this would
		5205	suddenly make it incompatible to the default compile time environment,
		5206	i.e. all programs not using special compile switches.
		5207
		5208	=head2 OS/X AND DARWIN BUGS
		5209
		5210	The whole thing is a bug if you ask me - basically any system interface
		5211	you touch is broken, whether it is locales, poll, kqueue or even the
		5212	OpenGL drivers.
		5213
		5214	=head3 C<kqueue> is buggy
		5215
		5216	The kqueue syscall is broken in all known versions - most versions support
		5217	only sockets, many support pipes.
		5218
		5219	Libev tries to work around this by not using C<kqueue> by default on this
		5220	rotten platform, but of course you can still ask for it when creating a
		5221	loop - embedding a socket-only kqueue loop into a select-based one is
		5222	probably going to work well.
		5223
		5224	=head3 C<poll> is buggy
		5225
		5226	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5227	implementation by something calling C<kqueue> internally around the 10.5.6
		5228	release, so now C<kqueue> I<and> C<poll> are broken.
		5229
		5230	Libev tries to work around this by not using C<poll> by default on
		5231	this rotten platform, but of course you can still ask for it when creating
		5232	a loop.
		5233
		5234	=head3 C<select> is buggy
		5235
		5236	All that's left is C<select>, and of course Apple found a way to fuck this
		5237	one up as well: On OS/X, C<select> actively limits the number of file
		5238	descriptors you can pass in to 1024 - your program suddenly crashes when
		5239	you use more.
		5240
		5241	There is an undocumented "workaround" for this - defining
		5242	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5243	work on OS/X.
		5244
		5245	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5246
		5247	=head3 C<errno> reentrancy
		5248
		5249	The default compile environment on Solaris is unfortunately so
		5250	thread-unsafe that you can't even use components/libraries compiled
		5251	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5252	defined by default. A valid, if stupid, implementation choice.
		5253
		5254	If you want to use libev in threaded environments you have to make sure
		5255	it's compiled with C<_REENTRANT> defined.
		5256
		5257	=head3 Event port backend
		5258
		5259	The scalable event interface for Solaris is called "event
		5260	ports". Unfortunately, this mechanism is very buggy in all major
		5261	releases. If you run into high CPU usage, your program freezes or you get
		5262	a large number of spurious wakeups, make sure you have all the relevant
		5263	and latest kernel patches applied. No, I don't know which ones, but there
		5264	are multiple ones to apply, and afterwards, event ports actually work
		5265	great.
		5266
		5267	If you can't get it to work, you can try running the program by setting
		5268	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5269	C<select> backends.
		5270
		5271	=head2 AIX POLL BUG
		5272
		5273	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5274	this by trying to avoid the poll backend altogether (i.e. it's not even
		5275	compiled in), which normally isn't a big problem as C<select> works fine
		5276	with large bitsets on AIX, and AIX is dead anyway.
		5277
3950	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5278	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5279
		5280	=head3 General issues
3951		5281
3952	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5282	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3953	requires, and its I/O model is fundamentally incompatible with the POSIX	5283	requires, and its I/O model is fundamentally incompatible with the POSIX
3954	model. Libev still offers limited functionality on this platform in	5284	model. Libev still offers limited functionality on this platform in
3955	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5285	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
3956	descriptors. This only applies when using Win32 natively, not when using	5286	descriptors. This only applies when using Win32 natively, not when using
3957	e.g. cygwin.	5287	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5288	as every compiler comes with a slightly differently broken/incompatible
		5289	environment.
3958		5290
3959	Lifting these limitations would basically require the full	5291	Lifting these limitations would basically require the full
3960	re-implementation of the I/O system. If you are into these kinds of	5292	re-implementation of the I/O system. If you are into this kind of thing,
3961	things, then note that glib does exactly that for you in a very portable	5293	then note that glib does exactly that for you in a very portable way (note
3962	way (note also that glib is the slowest event library known to man).	5294	also that glib is the slowest event library known to man).
3963		5295
3964	There is no supported compilation method available on windows except	5296	There is no supported compilation method available on windows except
3965	embedding it into other applications.	5297	embedding it into other applications.
3966		5298
3967	Sensible signal handling is officially unsupported by Microsoft - libev	5299	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
3995	you do I<not> compile the F<ev.c> or any other embedded source files!):	5327	you do I<not> compile the F<ev.c> or any other embedded source files!):
3996		5328
3997	#include "evwrap.h"	5329	#include "evwrap.h"
3998	#include "ev.c"	5330	#include "ev.c"
3999		5331
4000	=over 4
4001
4002	=item The winsocket select function	5332	=head3 The winsocket C<select> function
4003		5333
4004	The winsocket C<select> function doesn't follow POSIX in that it	5334	The winsocket C<select> function doesn't follow POSIX in that it
4005	requires socket I<handles> and not socket I<file descriptors> (it is	5335	requires socket I<handles> and not socket I<file descriptors> (it is
4006	also extremely buggy). This makes select very inefficient, and also	5336	also extremely buggy). This makes select very inefficient, and also
4007	requires a mapping from file descriptors to socket handles (the Microsoft	5337	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4016	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5346	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4017		5347
4018	Note that winsockets handling of fd sets is O(n), so you can easily get a	5348	Note that winsockets handling of fd sets is O(n), so you can easily get a
4019	complexity in the O(n²) range when using win32.	5349	complexity in the O(n²) range when using win32.
4020		5350
4021	=item Limited number of file descriptors	5351	=head3 Limited number of file descriptors
4022		5352
4023	Windows has numerous arbitrary (and low) limits on things.	5353	Windows has numerous arbitrary (and low) limits on things.
4024		5354
4025	Early versions of winsocket's select only supported waiting for a maximum	5355	Early versions of winsocket's select only supported waiting for a maximum
4026	of C<64> handles (probably owning to the fact that all windows kernels	5356	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4041	runtime libraries. This might get you to about C<512> or C<2048> sockets	5371	runtime libraries. This might get you to about C<512> or C<2048> sockets
4042	(depending on windows version and/or the phase of the moon). To get more,	5372	(depending on windows version and/or the phase of the moon). To get more,
4043	you need to wrap all I/O functions and provide your own fd management, but	5373	you need to wrap all I/O functions and provide your own fd management, but
4044	the cost of calling select (O(n²)) will likely make this unworkable.	5374	the cost of calling select (O(n²)) will likely make this unworkable.
4045		5375
4046	=back
4047
4048	=head2 PORTABILITY REQUIREMENTS	5376	=head2 PORTABILITY REQUIREMENTS
4049		5377
4050	In addition to a working ISO-C implementation and of course the	5378	In addition to a working ISO-C implementation and of course the
4051	backend-specific APIs, libev relies on a few additional extensions:	5379	backend-specific APIs, libev relies on a few additional extensions:
4052		5380
…		…
4058	Libev assumes not only that all watcher pointers have the same internal	5386	Libev assumes not only that all watcher pointers have the same internal
4059	structure (guaranteed by POSIX but not by ISO C for example), but it also	5387	structure (guaranteed by POSIX but not by ISO C for example), but it also
4060	assumes that the same (machine) code can be used to call any watcher	5388	assumes that the same (machine) code can be used to call any watcher
4061	callback: The watcher callbacks have different type signatures, but libev	5389	callback: The watcher callbacks have different type signatures, but libev
4062	calls them using an C<ev_watcher *> internally.	5390	calls them using an C<ev_watcher *> internally.
		5391
		5392	=item null pointers and integer zero are represented by 0 bytes
		5393
		5394	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5395	relies on this setting pointers and integers to null.
		5396
		5397	=item pointer accesses must be thread-atomic
		5398
		5399	Accessing a pointer value must be atomic, it must both be readable and
		5400	writable in one piece - this is the case on all current architectures.
4063		5401
4064	=item C<sig_atomic_t volatile> must be thread-atomic as well	5402	=item C<sig_atomic_t volatile> must be thread-atomic as well
4065		5403
4066	The type C<sig_atomic_t volatile> (or whatever is defined as	5404	The type C<sig_atomic_t volatile> (or whatever is defined as
4067	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5405	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4076	thread" or will block signals process-wide, both behaviours would	5414	thread" or will block signals process-wide, both behaviours would
4077	be compatible with libev. Interaction between C<sigprocmask> and	5415	be compatible with libev. Interaction between C<sigprocmask> and
4078	C<pthread_sigmask> could complicate things, however.	5416	C<pthread_sigmask> could complicate things, however.
4079		5417
4080	The most portable way to handle signals is to block signals in all threads	5418	The most portable way to handle signals is to block signals in all threads
4081	except the initial one, and run the default loop in the initial thread as	5419	except the initial one, and run the signal handling loop in the initial
4082	well.	5420	thread as well.
4083		5421
4084	=item C<long> must be large enough for common memory allocation sizes	5422	=item C<long> must be large enough for common memory allocation sizes
4085		5423
4086	To improve portability and simplify its API, libev uses C<long> internally	5424	To improve portability and simplify its API, libev uses C<long> internally
4087	instead of C<size_t> when allocating its data structures. On non-POSIX	5425	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4090	watchers.	5428	watchers.
4091		5429
4092	=item C<double> must hold a time value in seconds with enough accuracy	5430	=item C<double> must hold a time value in seconds with enough accuracy
4093		5431
4094	The type C<double> is used to represent timestamps. It is required to	5432	The type C<double> is used to represent timestamps. It is required to
4095	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5433	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4096	enough for at least into the year 4000. This requirement is fulfilled by	5434	good enough for at least into the year 4000 with millisecond accuracy
		5435	(the design goal for libev). This requirement is overfulfilled by
4097	implementations implementing IEEE 754, which is basically all existing	5436	implementations using IEEE 754, which is basically all existing ones.
		5437
4098	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5438	With IEEE 754 doubles, you get microsecond accuracy until at least the
4099	2200.	5439	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5440	is either obsolete or somebody patched it to use C<long double> or
		5441	something like that, just kidding).
4100		5442
4101	=back	5443	=back
4102		5444
4103	If you know of other additional requirements drop me a note.	5445	If you know of other additional requirements drop me a note.
4104		5446
…		…
4166	=item Processing ev_async_send: O(number_of_async_watchers)	5508	=item Processing ev_async_send: O(number_of_async_watchers)
4167		5509
4168	=item Processing signals: O(max_signal_number)	5510	=item Processing signals: O(max_signal_number)
4169		5511
4170	Sending involves a system call I<iff> there were no other C<ev_async_send>	5512	Sending involves a system call I<iff> there were no other C<ev_async_send>
4171	calls in the current loop iteration. Checking for async and signal events	5513	calls in the current loop iteration and the loop is currently
		5514	blocked. Checking for async and signal events involves iterating over all
4172	involves iterating over all running async watchers or all signal numbers.	5515	running async watchers or all signal numbers.
4173		5516
4174	=back	5517	=back
4175		5518
4176		5519
		5520	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5521
		5522	The major version 4 introduced some incompatible changes to the API.
		5523
		5524	At the moment, the C<ev.h> header file provides compatibility definitions
		5525	for all changes, so most programs should still compile. The compatibility
		5526	layer might be removed in later versions of libev, so better update to the
		5527	new API early than late.
		5528
		5529	=over 4
		5530
		5531	=item C<EV_COMPAT3> backwards compatibility mechanism
		5532
		5533	The backward compatibility mechanism can be controlled by
		5534	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5535	section.
		5536
		5537	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5538
		5539	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5540
		5541	ev_loop_destroy (EV_DEFAULT_UC);
		5542	ev_loop_fork (EV_DEFAULT);
		5543
		5544	=item function/symbol renames
		5545
		5546	A number of functions and symbols have been renamed:
		5547
		5548	ev_loop => ev_run
		5549	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5550	EVLOOP_ONESHOT => EVRUN_ONCE
		5551
		5552	ev_unloop => ev_break
		5553	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5554	EVUNLOOP_ONE => EVBREAK_ONE
		5555	EVUNLOOP_ALL => EVBREAK_ALL
		5556
		5557	EV_TIMEOUT => EV_TIMER
		5558
		5559	ev_loop_count => ev_iteration
		5560	ev_loop_depth => ev_depth
		5561	ev_loop_verify => ev_verify
		5562
		5563	Most functions working on C<struct ev_loop> objects don't have an
		5564	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5565	associated constants have been renamed to not collide with the C<struct
		5566	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5567	as all other watcher types. Note that C<ev_loop_fork> is still called
		5568	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5569	typedef.
		5570
		5571	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5572
		5573	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5574	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5575	and work, but the library code will of course be larger.
		5576
		5577	=back
		5578
		5579
4177	=head1 GLOSSARY	5580	=head1 GLOSSARY
4178		5581
4179	=over 4	5582	=over 4
4180		5583
4181	=item active	5584	=item active
4182		5585
4183	A watcher is active as long as it has been started (has been attached to	5586	A watcher is active as long as it has been started and not yet stopped.
4184	an event loop) but not yet stopped (disassociated from the event loop).	5587	See L</WATCHER STATES> for details.
4185		5588
4186	=item application	5589	=item application
4187		5590
4188	In this document, an application is whatever is using libev.	5591	In this document, an application is whatever is using libev.
		5592
		5593	=item backend
		5594
		5595	The part of the code dealing with the operating system interfaces.
4189		5596
4190	=item callback	5597	=item callback
4191		5598
4192	The address of a function that is called when some event has been	5599	The address of a function that is called when some event has been
4193	detected. Callbacks are being passed the event loop, the watcher that	5600	detected. Callbacks are being passed the event loop, the watcher that
4194	received the event, and the actual event bitset.	5601	received the event, and the actual event bitset.
4195		5602
4196	=item callback invocation	5603	=item callback/watcher invocation
4197		5604
4198	The act of calling the callback associated with a watcher.	5605	The act of calling the callback associated with a watcher.
4199		5606
4200	=item event	5607	=item event
4201		5608
4202	A change of state of some external event, such as data now being available	5609	A change of state of some external event, such as data now being available
4203	for reading on a file descriptor, time having passed or simply not having	5610	for reading on a file descriptor, time having passed or simply not having
4204	any other events happening anymore.	5611	any other events happening anymore.
4205		5612
4206	In libev, events are represented as single bits (such as C<EV_READ> or	5613	In libev, events are represented as single bits (such as C<EV_READ> or
4207	C<EV_TIMEOUT>).	5614	C<EV_TIMER>).
4208		5615
4209	=item event library	5616	=item event library
4210		5617
4211	A software package implementing an event model and loop.	5618	A software package implementing an event model and loop.
4212		5619
…		…
4220	The model used to describe how an event loop handles and processes	5627	The model used to describe how an event loop handles and processes
4221	watchers and events.	5628	watchers and events.
4222		5629
4223	=item pending	5630	=item pending
4224		5631
4225	A watcher is pending as soon as the corresponding event has been detected,	5632	A watcher is pending as soon as the corresponding event has been
4226	and stops being pending as soon as the watcher will be invoked or its	5633	detected. See L</WATCHER STATES> for details.
4227	pending status is explicitly cleared by the application.
4228
4229	A watcher can be pending, but not active. Stopping a watcher also clears
4230	its pending status.
4231		5634
4232	=item real time	5635	=item real time
4233		5636
4234	The physical time that is observed. It is apparently strictly monotonic :)	5637	The physical time that is observed. It is apparently strictly monotonic :)
4235		5638
4236	=item wall-clock time	5639	=item wall-clock time
4237		5640
4238	The time and date as shown on clocks. Unlike real time, it can actually	5641	The time and date as shown on clocks. Unlike real time, it can actually
4239	be wrong and jump forwards and backwards, e.g. when the you adjust your	5642	be wrong and jump forwards and backwards, e.g. when you adjust your
4240	clock.	5643	clock.
4241		5644
4242	=item watcher	5645	=item watcher
4243		5646
4244	A data structure that describes interest in certain events. Watchers need	5647	A data structure that describes interest in certain events. Watchers need
4245	to be started (attached to an event loop) before they can receive events.	5648	to be started (attached to an event loop) before they can receive events.
4246		5649
4247	=item watcher invocation
4248
4249	The act of calling the callback associated with a watcher.
4250
4251	=back	5650	=back
4252		5651
4253	=head1 AUTHOR	5652	=head1 AUTHOR
4254		5653
4255	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5654	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5655	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4256		5656

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