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Revision 1.297 by root, Tue Jun 29 11:49:02 2010 UTC vs.
Revision 1.451 by root, Mon Jun 24 00:19:26 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>), Linux eventfd/signalfd (for faster and cleaner	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	timers (C<ev_timer>), absolute timers with customised rescheduling	115	timers (C<ev_timer>), absolute timers with customised rescheduling
106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	change events (C<ev_child>), and event watchers dealing with the event	117	change events (C<ev_child>), and event watchers dealing with the event
108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and	118	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
…		…
124	this argument.	134	this argument.
125		135
126	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
127		137
128	Libev represents time as a single floating point number, representing	138	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (in practise	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	somewhere near the beginning of 1970, details are complicated, don't	140	somewhere near the beginning of 1970, details are complicated, don't
131	ask). This type is called C<ev_tstamp>, which is what you should use	141	ask). This type is called C<ev_tstamp>, which is what you should use
132	too. It usually aliases to the C<double> type in C. When you need to do	142	too. It usually aliases to the C<double> type in C. When you need to do
133	any calculations on it, you should treat it as some floating point value.	143	any calculations on it, you should treat it as some floating point value.
134		144
…		…
165		175
166	=item ev_tstamp ev_time ()	176	=item ev_tstamp ev_time ()
167		177
168	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
169	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
170	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>.
171		182
172	=item ev_sleep (ev_tstamp interval)	183	=item ev_sleep (ev_tstamp interval)
173		184
174	Sleep for the given interval: The current thread will be blocked until	185	Sleep for the given interval: The current thread will be blocked
175	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
176	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 >>).
177		194
178	=item int ev_version_major ()	195	=item int ev_version_major ()
179		196
180	=item int ev_version_minor ()	197	=item int ev_version_minor ()
181		198
…		…
192	as this indicates an incompatible change. Minor versions are usually	209	as this indicates an incompatible change. Minor versions are usually
193	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
194	not a problem.	211	not a problem.
195		212
196	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
197	version (note, however, that this will not detect ABI mismatches :).	214	version (note, however, that this will not detect other ABI mismatches,
		215	such as LFS or reentrancy).
198		216
199	assert (("libev version mismatch",	217	assert (("libev version mismatch",
200	ev_version_major () == EV_VERSION_MAJOR	218	ev_version_major () == EV_VERSION_MAJOR
201	&& ev_version_minor () >= EV_VERSION_MINOR));	219	&& ev_version_minor () >= EV_VERSION_MINOR));
202		220
…		…
213	assert (("sorry, no epoll, no sex",	231	assert (("sorry, no epoll, no sex",
214	ev_supported_backends () & EVBACKEND_EPOLL));	232	ev_supported_backends () & EVBACKEND_EPOLL));
215		233
216	=item unsigned int ev_recommended_backends ()	234	=item unsigned int ev_recommended_backends ()
217		235
218	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
219	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
220	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
221	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
222	(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
223	libev will probe for if you specify no backends explicitly.	242	probe for if you specify no backends explicitly.
224		243
225	=item unsigned int ev_embeddable_backends ()	244	=item unsigned int ev_embeddable_backends ()
226		245
227	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
228	is the theoretical, all-platform, value. To find which backends	247	value is platform-specific but can include backends not available on the
229	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
230	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	249	the current system, you would need to look at C<ev_embeddable_backends ()
231	recommended ones.	250	& ev_supported_backends ()>, likewise for recommended ones.
232		251
233	See the description of C<ev_embed> watchers for more info.	252	See the description of C<ev_embed> watchers for more info.
234		253
235	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	254	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
236		255
237	Sets the allocation function to use (the prototype is similar - the	256	Sets the allocation function to use (the prototype is similar - the
238	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
239	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
240	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
…		…
246		265
247	You could override this function in high-availability programs to, say,	266	You could override this function in high-availability programs to, say,
248	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,
249	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.
250		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
251	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
252	retries (example requires a standards-compliant C<realloc>).	285	retries.
253		286
254	static void *	287	static void *
255	persistent_realloc (void *ptr, size_t size)	288	persistent_realloc (void *ptr, size_t size)
256	{	289	{
		290	if (!size)
		291	{
		292	free (ptr);
		293	return 0;
		294	}
		295
257	for (;;)	296	for (;;)
258	{	297	{
259	void *newptr = realloc (ptr, size);	298	void *newptr = realloc (ptr, size);
260		299
261	if (newptr)	300	if (newptr)
…		…
266	}	305	}
267		306
268	...	307	...
269	ev_set_allocator (persistent_realloc);	308	ev_set_allocator (persistent_realloc);
270		309
271	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	310	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
272		311
273	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
274	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
275	indicating the system call or subsystem causing the problem. If this	314	indicating the system call or subsystem causing the problem. If this
276	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
…		…
288	}	327	}
289		328
290	...	329	...
291	ev_set_syserr_cb (fatal_error);	330	ev_set_syserr_cb (fatal_error);
292		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
293	=back	345	=back
294		346
295	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	347	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
296		348
297	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
298	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
299	I<function>).	351	libev 3 had an C<ev_loop> function colliding with the struct name).
300		352
301	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
302	supports signals and child events, and dynamically created loops which do	354	supports child process events, and dynamically created event loops which
303	not.	355	do not.
304		356
305	=over 4	357	=over 4
306		358
307	=item struct ev_loop *ev_default_loop (unsigned int flags)	359	=item struct ev_loop *ev_default_loop (unsigned int flags)
308		360
309	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
310	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
311	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
312	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".
313		371
314	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
315	function.	373	function (or via the C<EV_DEFAULT> macro).
316		374
317	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
318	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
319	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).
320		379
321	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,
322	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
323	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
324	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
325	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	384	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
326	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.
327		404
328	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
329	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>).
330		407
331	The following flags are supported:	408	The following flags are supported:
…		…
341		418
342	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
343	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
344	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	421	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
345	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
346	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
347	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).
348		427
349	=item C<EVFLAG_FORKCHECK>	428	=item C<EVFLAG_FORKCHECK>
350		429
351	Instead of calling C<ev_loop_fork> manually after a fork, you can also	430	Instead of calling C<ev_loop_fork> manually after a fork, you can also
352	make libev check for a fork in each iteration by enabling this flag.	431	make libev check for a fork in each iteration by enabling this flag.
353		432
354	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,
355	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
356	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
357	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
358	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
359	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).
360		440
361	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
362	forget about forgetting to tell libev about forking) when you use this	442	forget about forgetting to tell libev about forking, although you still
363	flag.	443	have to ignore C<SIGPIPE>) when you use this flag.
364		444
365	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>
366	environment variable.	446	environment variable.
367		447
368	=item C<EVFLAG_NOINOTIFY>	448	=item C<EVFLAG_NOINOTIFY>
369		449
370	When this flag is specified, then libev will not attempt to use the	450	When this flag is specified, then libev will not attempt to use the
371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and	451	I<inotify> API for its C<ev_stat> watchers. Apart from debugging and
372	testing, this flag can be useful to conserve inotify file descriptors, as	452	testing, this flag can be useful to conserve inotify file descriptors, as
373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.	453	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		454
375	=item C<EVFLAG_SIGNALFD>	455	=item C<EVFLAG_SIGNALFD>
376		456
377	When this flag is specified, then libev will attempt to use the	457	When this flag is specified, then libev will attempt to use the
378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API	458	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes it both faster and might make	459	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data. It can also simplify signal	460	it possible to get the queued signal data. It can also simplify signal
381	handling with threads, as long as you properly block signals in your	461	handling with threads, as long as you properly block signals in your
382	threads that are not interested in handling them.	462	threads that are not interested in handling them.
383		463
384	Signalfd will not be used by default as this changes your signal mask, and	464	Signalfd will not be used by default as this changes your signal mask, and
385	there are a lot of shoddy libraries and programs (glib's threadpool for	465	there are a lot of shoddy libraries and programs (glib's threadpool for
386	example) that can't properly initialise their signal masks.	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.
387		482
388	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	483	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
389		484
390	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
391	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,
…		…
419	=item C<EVBACKEND_EPOLL> (value 4, Linux)	514	=item C<EVBACKEND_EPOLL> (value 4, Linux)
420		515
421	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	516	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
422	kernels).	517	kernels).
423		518
424	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
425	but it scales phenomenally better. While poll and select usually scale	520	it scales phenomenally better. While poll and select usually scale like
426	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
427	epoll scales either O(1) or O(active_fds).	522	fd), epoll scales either O(1) or O(active_fds).
428		523
429	The epoll mechanism deserves honorable mention as the most misdesigned	524	The epoll mechanism deserves honorable mention as the most misdesigned
430	of the more advanced event mechanisms: mere annoyances include silently	525	of the more advanced event mechanisms: mere annoyances include silently
431	dropping file descriptors, requiring a system call per change per file	526	dropping file descriptors, requiring a system call per change per file
432	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
433	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
434	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
435	take considerable time (one syscall per file descriptor) and is of course	532	set, which can take considerable time (one syscall per file descriptor)
436	hard to detect.	533	and is of course hard to detect.
437		534
438	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	535	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
439	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
440	I<different> file descriptors (even already closed ones, so one cannot	537	totally I<different> file descriptors (even already closed ones, so
441	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
442	on SMP systems). Libev tries to counter these spurious notifications by	539	(especially on SMP systems). Libev tries to counter these spurious
443	employing an additional generation counter and comparing that against the	540	notifications by employing an additional generation counter and comparing
444	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...
445		551
446	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
447	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
448	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
449	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
…		…
461	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
462	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
463	the usage. So sad.	569	the usage. So sad.
464		570
465	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
466	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) >> but C<<
		580	io_submit(2) >>) event interface available in post-4.18 kernels.
		581
		582	If this backend works for you (as of this writing, it was very
		583	experimental), it is the best event interface available on linux and might
		584	be well worth enabling it - if it isn't available in your kernel this will
		585	be detected and this backend will be skipped.
		586
		587	This backend can batch oneshot requests and supports a user-space ring
		588	buffer to receive events. It also doesn't suffer from most of the design
		589	problems of epoll (such as not being able to remove event sources from the
		590	epoll set), and generally sounds too good to be true. Because, this being
		591	the linux kernel, of course it suffers from a whole new set of limitations.
		592
		593	For one, it is not easily embeddable (but probably could be done using
		594	an event fd at some extra overhead). It also is subject to a system wide
		595	limit that can be configured in F</proc/sys/fs/aio-max-nr> - each loop
		596	currently requires C<61> of this number. If no aio requests are left, this
		597	backend will be skipped during initialisation.
		598
		599	Most problematic in practise, however, is that not all file descriptors
		600	work with it. For example, in linux 5.1, tcp sockets, pipes, event fds,
		601	files, F</dev/null> and a few others are supported, but ttys do not work
		602	properly (a known bug that the kernel developers don't care about, see
		603	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		604	(yet?) a generic event polling interface.
		605
		606	Overall, it seems the linux developers just don't want it to have a
		607	generic event handling mechanism other than C<select> or C<poll>.
		608
		609	To work around the fd type problem, the current version of libev uses
		610	epoll as a fallback for file deescriptor types that do not work. Epoll
		611	is used in, kind of, slow mode that hopefully avoids most of its design
		612	problems and requires 1-3 extra syscalls per active fd every iteration.
467		613
468	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	614	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
469	C<EVBACKEND_POLL>.	615	C<EVBACKEND_POLL>.
470		616
471	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	617	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
…		…
486		632
487	It scales in the same way as the epoll backend, but the interface to the	633	It scales in the same way as the epoll backend, but the interface to the
488	kernel is more efficient (which says nothing about its actual speed, of	634	kernel is more efficient (which says nothing about its actual speed, of
489	course). While stopping, setting and starting an I/O watcher does never	635	course). While stopping, setting and starting an I/O watcher does never
490	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	636	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
491	two event changes per incident. Support for C<fork ()> is very bad (but	637	two event changes per incident. Support for C<fork ()> is very bad (you
492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	638	might have to leak fd's on fork, but it's more sane than epoll) and it
493	cases	639	drops fds silently in similarly hard-to-detect cases.
494		640
495	This backend usually performs well under most conditions.	641	This backend usually performs well under most conditions.
496		642
497	While nominally embeddable in other event loops, this doesn't work	643	While nominally embeddable in other event loops, this doesn't work
498	everywhere, so you might need to test for this. And since it is broken	644	everywhere, so you might need to test for this. And since it is broken
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	661	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		662
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	663	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
518	it's really slow, but it still scales very well (O(active_fds)).	664	it's really slow, but it still scales very well (O(active_fds)).
519		665
520	Please note that Solaris event ports can deliver a lot of spurious
521	notifications, so you need to use non-blocking I/O or other means to avoid
522	blocking when no data (or space) is available.
523
524	While this backend scales well, it requires one system call per active	666	While this backend scales well, it requires one system call per active
525	file descriptor per loop iteration. For small and medium numbers of file	667	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	668	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	669	might perform better.
528		670
529	On the positive side, with the exception of the spurious readiness	671	On the positive side, this backend actually performed fully to
530	notifications, this backend actually performed fully to specification
531	in all tests and is fully embeddable, which is a rare feat among the	672	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	673	among the OS-specific backends (I vastly prefer correctness over speed
		674	hacks).
		675
		676	On the negative side, the interface is I<bizarre> - so bizarre that
		677	even sun itself gets it wrong in their code examples: The event polling
		678	function sometimes returns events to the caller even though an error
		679	occurred, but with no indication whether it has done so or not (yes, it's
		680	even documented that way) - deadly for edge-triggered interfaces where you
		681	absolutely have to know whether an event occurred or not because you have
		682	to re-arm the watcher.
		683
		684	Fortunately libev seems to be able to work around these idiocies.
533		685
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	686	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	687	C<EVBACKEND_POLL>.
536		688
537	=item C<EVBACKEND_ALL>	689	=item C<EVBACKEND_ALL>
538		690
539	Try all backends (even potentially broken ones that wouldn't be tried	691	Try all backends (even potentially broken ones that wouldn't be tried
540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	692	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	693	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		694
543	It is definitely not recommended to use this flag.	695	It is definitely not recommended to use this flag, use whatever
		696	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		697	at all.
		698
		699	=item C<EVBACKEND_MASK>
		700
		701	Not a backend at all, but a mask to select all backend bits from a
		702	C<flags> value, in case you want to mask out any backends from a flags
		703	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		704
545	=back	705	=back
546		706
547	If one or more of the backend flags are or'ed into the flags value,	707	If one or more of the backend flags are or'ed into the flags value,
548	then only these backends will be tried (in the reverse order as listed	708	then only these backends will be tried (in the reverse order as listed
549	here). If none are specified, all backends in C<ev_recommended_backends	709	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	710	()> will be tried.
551		711
552	Example: This is the most typical usage.
553
554	if (!ev_default_loop (0))
555	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
556
557	Example: Restrict libev to the select and poll backends, and do not allow
558	environment settings to be taken into account:
559
560	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
561
562	Example: Use whatever libev has to offer, but make sure that kqueue is
563	used if available (warning, breaks stuff, best use only with your own
564	private event loop and only if you know the OS supports your types of
565	fds):
566
567	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568
569	=item struct ev_loop *ev_loop_new (unsigned int flags)
570
571	Similar to C<ev_default_loop>, but always creates a new event loop that is
572	always distinct from the default loop.
573
574	Note that this function I<is> thread-safe, and one common way to use
575	libev with threads is indeed to create one loop per thread, and using the
576	default loop in the "main" or "initial" thread.
577
578	Example: Try to create a event loop that uses epoll and nothing else.	712	Example: Try to create a event loop that uses epoll and nothing else.
579		713
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	714	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	715	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	716	fatal ("no epoll found here, maybe it hides under your chair");
583		717
		718	Example: Use whatever libev has to offer, but make sure that kqueue is
		719	used if available.
		720
		721	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		722
		723	Example: Similarly, on linux, you mgiht want to take advantage of the
		724	linux aio backend if possible, but fall back to something else if that
		725	isn't available.
		726
		727	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		728
584	=item ev_default_destroy ()	729	=item ev_loop_destroy (loop)
585		730
586	Destroys the default loop (frees all memory and kernel state etc.). None	731	Destroys an event loop object (frees all memory and kernel state
587	of the active event watchers will be stopped in the normal sense, so	732	etc.). None of the active event watchers will be stopped in the normal
588	e.g. C<ev_is_active> might still return true. It is your responsibility to	733	sense, so e.g. C<ev_is_active> might still return true. It is your
589	either stop all watchers cleanly yourself I<before> calling this function,	734	responsibility to either stop all watchers cleanly yourself I<before>
590	or cope with the fact afterwards (which is usually the easiest thing, you	735	calling this function, or cope with the fact afterwards (which is usually
591	can just ignore the watchers and/or C<free ()> them for example).	736	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		737	for example).
592		738
593	Note that certain global state, such as signal state (and installed signal	739	Note that certain global state, such as signal state (and installed signal
594	handlers), will not be freed by this function, and related watchers (such	740	handlers), will not be freed by this function, and related watchers (such
595	as signal and child watchers) would need to be stopped manually.	741	as signal and child watchers) would need to be stopped manually.
596		742
597	In general it is not advisable to call this function except in the	743	This function is normally used on loop objects allocated by
598	rare occasion where you really need to free e.g. the signal handling	744	C<ev_loop_new>, but it can also be used on the default loop returned by
		745	C<ev_default_loop>, in which case it is not thread-safe.
		746
		747	Note that it is not advisable to call this function on the default loop
		748	except in the rare occasion where you really need to free its resources.
599	pipe fds. If you need dynamically allocated loops it is better to use	749	If you need dynamically allocated loops it is better to use C<ev_loop_new>
600	C<ev_loop_new> and C<ev_loop_destroy>.	750	and C<ev_loop_destroy>.
601		751
602	=item ev_loop_destroy (loop)	752	=item ev_loop_fork (loop)
603		753
604	Like C<ev_default_destroy>, but destroys an event loop created by an
605	earlier call to C<ev_loop_new>.
606
607	=item ev_default_fork ()
608
609	This function sets a flag that causes subsequent C<ev_loop> iterations	754	This function sets a flag that causes subsequent C<ev_run> iterations
610	to reinitialise the kernel state for backends that have one. Despite the	755	to reinitialise the kernel state for backends that have one. Despite
611	name, you can call it anytime, but it makes most sense after forking, in	756	the name, you can call it anytime you are allowed to start or stop
612	the child process (or both child and parent, but that again makes little	757	watchers (except inside an C<ev_prepare> callback), but it makes most
613	sense). You I<must> call it in the child before using any of the libev	758	sense after forking, in the child process. You I<must> call it (or use
614	functions, and it will only take effect at the next C<ev_loop> iteration.	759	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
615		760
		761	In addition, if you want to reuse a loop (via this function or
		762	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		763
616	Again, you I<have> to call it on I<any> loop that you want to re-use after	764	Again, you I<have> to call it on I<any> loop that you want to re-use after
617	a fork, I<even if you do not plan to use the loop in the parent>. This is	765	a fork, I<even if you do not plan to use the loop in the parent>. This is
618	because some kernel interfaces *cough* I<kqueue> *cough* do funny things	766	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
619	during fork.	767	during fork.
620		768
621	On the other hand, you only need to call this function in the child	769	On the other hand, you only need to call this function in the child
622	process if and only if you want to use the event loop in the child. If you	770	process if and only if you want to use the event loop in the child. If
623	just fork+exec or create a new loop in the child, you don't have to call	771	you just fork+exec or create a new loop in the child, you don't have to
624	it at all.	772	call it at all (in fact, C<epoll> is so badly broken that it makes a
		773	difference, but libev will usually detect this case on its own and do a
		774	costly reset of the backend).
625		775
626	The function itself is quite fast and it's usually not a problem to call	776	The function itself is quite fast and it's usually not a problem to call
627	it just in case after a fork. To make this easy, the function will fit in	777	it just in case after a fork.
628	quite nicely into a call to C<pthread_atfork>:
629		778
		779	Example: Automate calling C<ev_loop_fork> on the default loop when
		780	using pthreads.
		781
		782	static void
		783	post_fork_child (void)
		784	{
		785	ev_loop_fork (EV_DEFAULT);
		786	}
		787
		788	...
630	pthread_atfork (0, 0, ev_default_fork);	789	pthread_atfork (0, 0, post_fork_child);
631
632	=item ev_loop_fork (loop)
633
634	Like C<ev_default_fork>, but acts on an event loop created by
635	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
636	after fork that you want to re-use in the child, and how you keep track of
637	them is entirely your own problem.
638		790
639	=item int ev_is_default_loop (loop)	791	=item int ev_is_default_loop (loop)
640		792
641	Returns true when the given loop is, in fact, the default loop, and false	793	Returns true when the given loop is, in fact, the default loop, and false
642	otherwise.	794	otherwise.
643		795
644	=item unsigned int ev_iteration (loop)	796	=item unsigned int ev_iteration (loop)
645		797
646	Returns the current iteration count for the loop, which is identical to	798	Returns the current iteration count for the event loop, which is identical
647	the number of times libev did poll for new events. It starts at C<0> and	799	to the number of times libev did poll for new events. It starts at C<0>
648	happily wraps around with enough iterations.	800	and happily wraps around with enough iterations.
649		801
650	This value can sometimes be useful as a generation counter of sorts (it	802	This value can sometimes be useful as a generation counter of sorts (it
651	"ticks" the number of loop iterations), as it roughly corresponds with	803	"ticks" the number of loop iterations), as it roughly corresponds with
652	C<ev_prepare> and C<ev_check> calls - and is incremented between the	804	C<ev_prepare> and C<ev_check> calls - and is incremented between the
653	prepare and check phases.	805	prepare and check phases.
654		806
655	=item unsigned int ev_depth (loop)	807	=item unsigned int ev_depth (loop)
656		808
657	Returns the number of times C<ev_loop> was entered minus the number of	809	Returns the number of times C<ev_run> was entered minus the number of
658	times C<ev_loop> was exited, in other words, the recursion depth.	810	times C<ev_run> was exited normally, in other words, the recursion depth.
659		811
660	Outside C<ev_loop>, this number is zero. In a callback, this number is	812	Outside C<ev_run>, this number is zero. In a callback, this number is
661	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	813	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
662	in which case it is higher.	814	in which case it is higher.
663		815
664	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	816	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
665	etc.), doesn't count as "exit" - consider this as a hint to avoid such	817	throwing an exception etc.), doesn't count as "exit" - consider this
666	ungentleman behaviour unless it's really convenient.	818	as a hint to avoid such ungentleman-like behaviour unless it's really
		819	convenient, in which case it is fully supported.
667		820
668	=item unsigned int ev_backend (loop)	821	=item unsigned int ev_backend (loop)
669		822
670	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	823	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
671	use.	824	use.
…		…
680		833
681	=item ev_now_update (loop)	834	=item ev_now_update (loop)
682		835
683	Establishes the current time by querying the kernel, updating the time	836	Establishes the current time by querying the kernel, updating the time
684	returned by C<ev_now ()> in the progress. This is a costly operation and	837	returned by C<ev_now ()> in the progress. This is a costly operation and
685	is usually done automatically within C<ev_loop ()>.	838	is usually done automatically within C<ev_run ()>.
686		839
687	This function is rarely useful, but when some event callback runs for a	840	This function is rarely useful, but when some event callback runs for a
688	very long time without entering the event loop, updating libev's idea of	841	very long time without entering the event loop, updating libev's idea of
689	the current time is a good idea.	842	the current time is a good idea.
690		843
691	See also L<The special problem of time updates> in the C<ev_timer> section.	844	See also L</The special problem of time updates> in the C<ev_timer> section.
692		845
693	=item ev_suspend (loop)	846	=item ev_suspend (loop)
694		847
695	=item ev_resume (loop)	848	=item ev_resume (loop)
696		849
697	These two functions suspend and resume a loop, for use when the loop is	850	These two functions suspend and resume an event loop, for use when the
698	not used for a while and timeouts should not be processed.	851	loop is not used for a while and timeouts should not be processed.
699		852
700	A typical use case would be an interactive program such as a game: When	853	A typical use case would be an interactive program such as a game: When
701	the user presses C<^Z> to suspend the game and resumes it an hour later it	854	the user presses C<^Z> to suspend the game and resumes it an hour later it
702	would be best to handle timeouts as if no time had actually passed while	855	would be best to handle timeouts as if no time had actually passed while
703	the program was suspended. This can be achieved by calling C<ev_suspend>	856	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
705	C<ev_resume> directly afterwards to resume timer processing.	858	C<ev_resume> directly afterwards to resume timer processing.
706		859
707	Effectively, all C<ev_timer> watchers will be delayed by the time spend	860	Effectively, all C<ev_timer> watchers will be delayed by the time spend
708	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	861	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
709	will be rescheduled (that is, they will lose any events that would have	862	will be rescheduled (that is, they will lose any events that would have
710	occured while suspended).	863	occurred while suspended).
711		864
712	After calling C<ev_suspend> you B<must not> call I<any> function on the	865	After calling C<ev_suspend> you B<must not> call I<any> function on the
713	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	866	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
714	without a previous call to C<ev_suspend>.	867	without a previous call to C<ev_suspend>.
715		868
716	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	869	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
717	event loop time (see C<ev_now_update>).	870	event loop time (see C<ev_now_update>).
718		871
719	=item ev_loop (loop, int flags)	872	=item bool ev_run (loop, int flags)
720		873
721	Finally, this is it, the event handler. This function usually is called	874	Finally, this is it, the event handler. This function usually is called
722	after you have initialised all your watchers and you want to start	875	after you have initialised all your watchers and you want to start
723	handling events.	876	handling events. It will ask the operating system for any new events, call
		877	the watcher callbacks, and then repeat the whole process indefinitely: This
		878	is why event loops are called I<loops>.
724		879
725	If the flags argument is specified as C<0>, it will not return until	880	If the flags argument is specified as C<0>, it will keep handling events
726	either no event watchers are active anymore or C<ev_unloop> was called.	881	until either no event watchers are active anymore or C<ev_break> was
		882	called.
727		883
		884	The return value is false if there are no more active watchers (which
		885	usually means "all jobs done" or "deadlock"), and true in all other cases
		886	(which usually means " you should call C<ev_run> again").
		887
728	Please note that an explicit C<ev_unloop> is usually better than	888	Please note that an explicit C<ev_break> is usually better than
729	relying on all watchers to be stopped when deciding when a program has	889	relying on all watchers to be stopped when deciding when a program has
730	finished (especially in interactive programs), but having a program	890	finished (especially in interactive programs), but having a program
731	that automatically loops as long as it has to and no longer by virtue	891	that automatically loops as long as it has to and no longer by virtue
732	of relying on its watchers stopping correctly, that is truly a thing of	892	of relying on its watchers stopping correctly, that is truly a thing of
733	beauty.	893	beauty.
734		894
		895	This function is I<mostly> exception-safe - you can break out of a
		896	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		897	exception and so on. This does not decrement the C<ev_depth> value, nor
		898	will it clear any outstanding C<EVBREAK_ONE> breaks.
		899
735	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	900	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
736	those events and any already outstanding ones, but will not block your	901	those events and any already outstanding ones, but will not wait and
737	process in case there are no events and will return after one iteration of	902	block your process in case there are no events and will return after one
738	the loop.	903	iteration of the loop. This is sometimes useful to poll and handle new
		904	events while doing lengthy calculations, to keep the program responsive.
739		905
740	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	906	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
741	necessary) and will handle those and any already outstanding ones. It	907	necessary) and will handle those and any already outstanding ones. It
742	will block your process until at least one new event arrives (which could	908	will block your process until at least one new event arrives (which could
743	be an event internal to libev itself, so there is no guarantee that a	909	be an event internal to libev itself, so there is no guarantee that a
744	user-registered callback will be called), and will return after one	910	user-registered callback will be called), and will return after one
745	iteration of the loop.	911	iteration of the loop.
746		912
747	This is useful if you are waiting for some external event in conjunction	913	This is useful if you are waiting for some external event in conjunction
748	with something not expressible using other libev watchers (i.e. "roll your	914	with something not expressible using other libev watchers (i.e. "roll your
749	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	915	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
750	usually a better approach for this kind of thing.	916	usually a better approach for this kind of thing.
751		917
752	Here are the gory details of what C<ev_loop> does:	918	Here are the gory details of what C<ev_run> does (this is for your
		919	understanding, not a guarantee that things will work exactly like this in
		920	future versions):
753		921
		922	- Increment loop depth.
		923	- Reset the ev_break status.
754	- Before the first iteration, call any pending watchers.	924	- Before the first iteration, call any pending watchers.
		925	LOOP:
755	* If EVFLAG_FORKCHECK was used, check for a fork.	926	- If EVFLAG_FORKCHECK was used, check for a fork.
756	- If a fork was detected (by any means), queue and call all fork watchers.	927	- If a fork was detected (by any means), queue and call all fork watchers.
757	- Queue and call all prepare watchers.	928	- Queue and call all prepare watchers.
		929	- If ev_break was called, goto FINISH.
758	- If we have been forked, detach and recreate the kernel state	930	- If we have been forked, detach and recreate the kernel state
759	as to not disturb the other process.	931	as to not disturb the other process.
760	- Update the kernel state with all outstanding changes.	932	- Update the kernel state with all outstanding changes.
761	- Update the "event loop time" (ev_now ()).	933	- Update the "event loop time" (ev_now ()).
762	- Calculate for how long to sleep or block, if at all	934	- Calculate for how long to sleep or block, if at all
763	(active idle watchers, EVLOOP_NONBLOCK or not having	935	(active idle watchers, EVRUN_NOWAIT or not having
764	any active watchers at all will result in not sleeping).	936	any active watchers at all will result in not sleeping).
765	- Sleep if the I/O and timer collect interval say so.	937	- Sleep if the I/O and timer collect interval say so.
		938	- Increment loop iteration counter.
766	- Block the process, waiting for any events.	939	- Block the process, waiting for any events.
767	- Queue all outstanding I/O (fd) events.	940	- Queue all outstanding I/O (fd) events.
768	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	941	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
769	- Queue all expired timers.	942	- Queue all expired timers.
770	- Queue all expired periodics.	943	- Queue all expired periodics.
771	- Unless any events are pending now, queue all idle watchers.	944	- Queue all idle watchers with priority higher than that of pending events.
772	- Queue all check watchers.	945	- Queue all check watchers.
773	- Call all queued watchers in reverse order (i.e. check watchers first).	946	- Call all queued watchers in reverse order (i.e. check watchers first).
774	Signals and child watchers are implemented as I/O watchers, and will	947	Signals and child watchers are implemented as I/O watchers, and will
775	be handled here by queueing them when their watcher gets executed.	948	be handled here by queueing them when their watcher gets executed.
776	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	949	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
777	were used, or there are no active watchers, return, otherwise	950	were used, or there are no active watchers, goto FINISH, otherwise
778	continue with step *.	951	continue with step LOOP.
		952	FINISH:
		953	- Reset the ev_break status iff it was EVBREAK_ONE.
		954	- Decrement the loop depth.
		955	- Return.
779		956
780	Example: Queue some jobs and then loop until no events are outstanding	957	Example: Queue some jobs and then loop until no events are outstanding
781	anymore.	958	anymore.
782		959
783	... queue jobs here, make sure they register event watchers as long	960	... queue jobs here, make sure they register event watchers as long
784	... as they still have work to do (even an idle watcher will do..)	961	... as they still have work to do (even an idle watcher will do..)
785	ev_loop (my_loop, 0);	962	ev_run (my_loop, 0);
786	... jobs done or somebody called unloop. yeah!	963	... jobs done or somebody called break. yeah!
787		964
788	=item ev_unloop (loop, how)	965	=item ev_break (loop, how)
789		966
790	Can be used to make a call to C<ev_loop> return early (but only after it	967	Can be used to make a call to C<ev_run> return early (but only after it
791	has processed all outstanding events). The C<how> argument must be either	968	has processed all outstanding events). The C<how> argument must be either
792	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	969	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
793	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	970	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
794		971
795	This "unloop state" will be cleared when entering C<ev_loop> again.	972	This "break state" will be cleared on the next call to C<ev_run>.
796		973
797	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	974	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		975	which case it will have no effect.
798		976
799	=item ev_ref (loop)	977	=item ev_ref (loop)
800		978
801	=item ev_unref (loop)	979	=item ev_unref (loop)
802		980
803	Ref/unref can be used to add or remove a reference count on the event	981	Ref/unref can be used to add or remove a reference count on the event
804	loop: Every watcher keeps one reference, and as long as the reference	982	loop: Every watcher keeps one reference, and as long as the reference
805	count is nonzero, C<ev_loop> will not return on its own.	983	count is nonzero, C<ev_run> will not return on its own.
806		984
807	This is useful when you have a watcher that you never intend to	985	This is useful when you have a watcher that you never intend to
808	unregister, but that nevertheless should not keep C<ev_loop> from	986	unregister, but that nevertheless should not keep C<ev_run> from
809	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	987	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
810	before stopping it.	988	before stopping it.
811		989
812	As an example, libev itself uses this for its internal signal pipe: It	990	As an example, libev itself uses this for its internal signal pipe: It
813	is not visible to the libev user and should not keep C<ev_loop> from	991	is not visible to the libev user and should not keep C<ev_run> from
814	exiting if no event watchers registered by it are active. It is also an	992	exiting if no event watchers registered by it are active. It is also an
815	excellent way to do this for generic recurring timers or from within	993	excellent way to do this for generic recurring timers or from within
816	third-party libraries. Just remember to I<unref after start> and I<ref	994	third-party libraries. Just remember to I<unref after start> and I<ref
817	before stop> (but only if the watcher wasn't active before, or was active	995	before stop> (but only if the watcher wasn't active before, or was active
818	before, respectively. Note also that libev might stop watchers itself	996	before, respectively. Note also that libev might stop watchers itself
819	(e.g. non-repeating timers) in which case you have to C<ev_ref>	997	(e.g. non-repeating timers) in which case you have to C<ev_ref>
820	in the callback).	998	in the callback).
821		999
822	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	1000	Example: Create a signal watcher, but keep it from keeping C<ev_run>
823	running when nothing else is active.	1001	running when nothing else is active.
824		1002
825	ev_signal exitsig;	1003	ev_signal exitsig;
826	ev_signal_init (&exitsig, sig_cb, SIGINT);	1004	ev_signal_init (&exitsig, sig_cb, SIGINT);
827	ev_signal_start (loop, &exitsig);	1005	ev_signal_start (loop, &exitsig);
828	evf_unref (loop);	1006	ev_unref (loop);
829		1007
830	Example: For some weird reason, unregister the above signal handler again.	1008	Example: For some weird reason, unregister the above signal handler again.
831		1009
832	ev_ref (loop);	1010	ev_ref (loop);
833	ev_signal_stop (loop, &exitsig);	1011	ev_signal_stop (loop, &exitsig);
…		…
853	overhead for the actual polling but can deliver many events at once.	1031	overhead for the actual polling but can deliver many events at once.
854		1032
855	By setting a higher I<io collect interval> you allow libev to spend more	1033	By setting a higher I<io collect interval> you allow libev to spend more
856	time collecting I/O events, so you can handle more events per iteration,	1034	time collecting I/O events, so you can handle more events per iteration,
857	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1035	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
858	C<ev_timer>) will be not affected. Setting this to a non-null value will	1036	C<ev_timer>) will not be affected. Setting this to a non-null value will
859	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1037	introduce an additional C<ev_sleep ()> call into most loop iterations. The
860	sleep time ensures that libev will not poll for I/O events more often then	1038	sleep time ensures that libev will not poll for I/O events more often then
861	once per this interval, on average.	1039	once per this interval, on average (as long as the host time resolution is
		1040	good enough).
862		1041
863	Likewise, by setting a higher I<timeout collect interval> you allow libev	1042	Likewise, by setting a higher I<timeout collect interval> you allow libev
864	to spend more time collecting timeouts, at the expense of increased	1043	to spend more time collecting timeouts, at the expense of increased
865	latency/jitter/inexactness (the watcher callback will be called	1044	latency/jitter/inexactness (the watcher callback will be called
866	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1045	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
872	usually doesn't make much sense to set it to a lower value than C<0.01>,	1051	usually doesn't make much sense to set it to a lower value than C<0.01>,
873	as this approaches the timing granularity of most systems. Note that if	1052	as this approaches the timing granularity of most systems. Note that if
874	you do transactions with the outside world and you can't increase the	1053	you do transactions with the outside world and you can't increase the
875	parallelity, then this setting will limit your transaction rate (if you	1054	parallelity, then this setting will limit your transaction rate (if you
876	need to poll once per transaction and the I/O collect interval is 0.01,	1055	need to poll once per transaction and the I/O collect interval is 0.01,
877	then you can't do more than 100 transations per second).	1056	then you can't do more than 100 transactions per second).
878		1057
879	Setting the I<timeout collect interval> can improve the opportunity for	1058	Setting the I<timeout collect interval> can improve the opportunity for
880	saving power, as the program will "bundle" timer callback invocations that	1059	saving power, as the program will "bundle" timer callback invocations that
881	are "near" in time together, by delaying some, thus reducing the number of	1060	are "near" in time together, by delaying some, thus reducing the number of
882	times the process sleeps and wakes up again. Another useful technique to	1061	times the process sleeps and wakes up again. Another useful technique to
…		…
890	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1069	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
891		1070
892	=item ev_invoke_pending (loop)	1071	=item ev_invoke_pending (loop)
893		1072
894	This call will simply invoke all pending watchers while resetting their	1073	This call will simply invoke all pending watchers while resetting their
895	pending state. Normally, C<ev_loop> does this automatically when required,	1074	pending state. Normally, C<ev_run> does this automatically when required,
896	but when overriding the invoke callback this call comes handy.	1075	but when overriding the invoke callback this call comes handy. This
		1076	function can be invoked from a watcher - this can be useful for example
		1077	when you want to do some lengthy calculation and want to pass further
		1078	event handling to another thread (you still have to make sure only one
		1079	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
897		1080
898	=item int ev_pending_count (loop)	1081	=item int ev_pending_count (loop)
899		1082
900	Returns the number of pending watchers - zero indicates that no watchers	1083	Returns the number of pending watchers - zero indicates that no watchers
901	are pending.	1084	are pending.
902		1085
903	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1086	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
904		1087
905	This overrides the invoke pending functionality of the loop: Instead of	1088	This overrides the invoke pending functionality of the loop: Instead of
906	invoking all pending watchers when there are any, C<ev_loop> will call	1089	invoking all pending watchers when there are any, C<ev_run> will call
907	this callback instead. This is useful, for example, when you want to	1090	this callback instead. This is useful, for example, when you want to
908	invoke the actual watchers inside another context (another thread etc.).	1091	invoke the actual watchers inside another context (another thread etc.).
909		1092
910	If you want to reset the callback, use C<ev_invoke_pending> as new	1093	If you want to reset the callback, use C<ev_invoke_pending> as new
911	callback.	1094	callback.
912		1095
913	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1096	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
914		1097
915	Sometimes you want to share the same loop between multiple threads. This	1098	Sometimes you want to share the same loop between multiple threads. This
916	can be done relatively simply by putting mutex_lock/unlock calls around	1099	can be done relatively simply by putting mutex_lock/unlock calls around
917	each call to a libev function.	1100	each call to a libev function.
918		1101
919	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1102	However, C<ev_run> can run an indefinite time, so it is not feasible
920	wait for it to return. One way around this is to wake up the loop via	1103	to wait for it to return. One way around this is to wake up the event
921	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1104	loop via C<ev_break> and C<ev_async_send>, another way is to set these
922	and I<acquire> callbacks on the loop.	1105	I<release> and I<acquire> callbacks on the loop.
923		1106
924	When set, then C<release> will be called just before the thread is	1107	When set, then C<release> will be called just before the thread is
925	suspended waiting for new events, and C<acquire> is called just	1108	suspended waiting for new events, and C<acquire> is called just
926	afterwards.	1109	afterwards.
927		1110
…		…
930		1113
931	While event loop modifications are allowed between invocations of	1114	While event loop modifications are allowed between invocations of
932	C<release> and C<acquire> (that's their only purpose after all), no	1115	C<release> and C<acquire> (that's their only purpose after all), no
933	modifications done will affect the event loop, i.e. adding watchers will	1116	modifications done will affect the event loop, i.e. adding watchers will
934	have no effect on the set of file descriptors being watched, or the time	1117	have no effect on the set of file descriptors being watched, or the time
935	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1118	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
936	to take note of any changes you made.	1119	to take note of any changes you made.
937		1120
938	In theory, threads executing C<ev_loop> will be async-cancel safe between	1121	In theory, threads executing C<ev_run> will be async-cancel safe between
939	invocations of C<release> and C<acquire>.	1122	invocations of C<release> and C<acquire>.
940		1123
941	See also the locking example in the C<THREADS> section later in this	1124	See also the locking example in the C<THREADS> section later in this
942	document.	1125	document.
943		1126
944	=item ev_set_userdata (loop, void *data)	1127	=item ev_set_userdata (loop, void *data)
945		1128
946	=item ev_userdata (loop)	1129	=item void *ev_userdata (loop)
947		1130
948	Set and retrieve a single C<void *> associated with a loop. When	1131	Set and retrieve a single C<void *> associated with a loop. When
949	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1132	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
950	C<0.>	1133	C<0>.
951		1134
952	These two functions can be used to associate arbitrary data with a loop,	1135	These two functions can be used to associate arbitrary data with a loop,
953	and are intended solely for the C<invoke_pending_cb>, C<release> and	1136	and are intended solely for the C<invoke_pending_cb>, C<release> and
954	C<acquire> callbacks described above, but of course can be (ab-)used for	1137	C<acquire> callbacks described above, but of course can be (ab-)used for
955	any other purpose as well.	1138	any other purpose as well.
956		1139
957	=item ev_loop_verify (loop)	1140	=item ev_verify (loop)
958		1141
959	This function only does something when C<EV_VERIFY> support has been	1142	This function only does something when C<EV_VERIFY> support has been
960	compiled in, which is the default for non-minimal builds. It tries to go	1143	compiled in, which is the default for non-minimal builds. It tries to go
961	through all internal structures and checks them for validity. If anything	1144	through all internal structures and checks them for validity. If anything
962	is found to be inconsistent, it will print an error message to standard	1145	is found to be inconsistent, it will print an error message to standard
…		…
973		1156
974	In the following description, uppercase C<TYPE> in names stands for the	1157	In the following description, uppercase C<TYPE> in names stands for the
975	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1158	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
976	watchers and C<ev_io_start> for I/O watchers.	1159	watchers and C<ev_io_start> for I/O watchers.
977		1160
978	A watcher is a structure that you create and register to record your	1161	A watcher is an opaque structure that you allocate and register to record
979	interest in some event. For instance, if you want to wait for STDIN to	1162	your interest in some event. To make a concrete example, imagine you want
980	become readable, you would create an C<ev_io> watcher for that:	1163	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1164	for that:
981		1165
982	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1166	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
983	{	1167	{
984	ev_io_stop (w);	1168	ev_io_stop (w);
985	ev_unloop (loop, EVUNLOOP_ALL);	1169	ev_break (loop, EVBREAK_ALL);
986	}	1170	}
987		1171
988	struct ev_loop *loop = ev_default_loop (0);	1172	struct ev_loop *loop = ev_default_loop (0);
989		1173
990	ev_io stdin_watcher;	1174	ev_io stdin_watcher;
991		1175
992	ev_init (&stdin_watcher, my_cb);	1176	ev_init (&stdin_watcher, my_cb);
993	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1177	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
994	ev_io_start (loop, &stdin_watcher);	1178	ev_io_start (loop, &stdin_watcher);
995		1179
996	ev_loop (loop, 0);	1180	ev_run (loop, 0);
997		1181
998	As you can see, you are responsible for allocating the memory for your	1182	As you can see, you are responsible for allocating the memory for your
999	watcher structures (and it is I<usually> a bad idea to do this on the	1183	watcher structures (and it is I<usually> a bad idea to do this on the
1000	stack).	1184	stack).
1001		1185
1002	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1186	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1003	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1187	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1004		1188
1005	Each watcher structure must be initialised by a call to C<ev_init	1189	Each watcher structure must be initialised by a call to C<ev_init (watcher
1006	(watcher *, callback)>, which expects a callback to be provided. This	1190	*, callback)>, which expects a callback to be provided. This callback is
1007	callback gets invoked each time the event occurs (or, in the case of I/O	1191	invoked each time the event occurs (or, in the case of I/O watchers, each
1008	watchers, each time the event loop detects that the file descriptor given	1192	time the event loop detects that the file descriptor given is readable
1009	is readable and/or writable).	1193	and/or writable).
1010		1194
1011	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1195	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1012	macro to configure it, with arguments specific to the watcher type. There	1196	macro to configure it, with arguments specific to the watcher type. There
1013	is also a macro to combine initialisation and setting in one call: C<<	1197	is also a macro to combine initialisation and setting in one call: C<<
1014	ev_TYPE_init (watcher *, callback, ...) >>.	1198	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1065		1249
1066	=item C<EV_PREPARE>	1250	=item C<EV_PREPARE>
1067		1251
1068	=item C<EV_CHECK>	1252	=item C<EV_CHECK>
1069		1253
1070	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1254	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1071	to gather new events, and all C<ev_check> watchers are invoked just after	1255	gather new events, and all C<ev_check> watchers are queued (not invoked)
1072	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1256	just after C<ev_run> has gathered them, but before it queues any callbacks
		1257	for any received events. That means C<ev_prepare> watchers are the last
		1258	watchers invoked before the event loop sleeps or polls for new events, and
		1259	C<ev_check> watchers will be invoked before any other watchers of the same
		1260	or lower priority within an event loop iteration.
		1261
1073	received events. Callbacks of both watcher types can start and stop as	1262	Callbacks of both watcher types can start and stop as many watchers as
1074	many watchers as they want, and all of them will be taken into account	1263	they want, and all of them will be taken into account (for example, a
1075	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1264	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1076	C<ev_loop> from blocking).	1265	blocking).
1077		1266
1078	=item C<EV_EMBED>	1267	=item C<EV_EMBED>
1079		1268
1080	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1269	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1081		1270
1082	=item C<EV_FORK>	1271	=item C<EV_FORK>
1083		1272
1084	The event loop has been resumed in the child process after fork (see	1273	The event loop has been resumed in the child process after fork (see
1085	C<ev_fork>).	1274	C<ev_fork>).
		1275
		1276	=item C<EV_CLEANUP>
		1277
		1278	The event loop is about to be destroyed (see C<ev_cleanup>).
1086		1279
1087	=item C<EV_ASYNC>	1280	=item C<EV_ASYNC>
1088		1281
1089	The given async watcher has been asynchronously notified (see C<ev_async>).	1282	The given async watcher has been asynchronously notified (see C<ev_async>).
1090		1283
…		…
1200		1393
1201	=item callback ev_cb (ev_TYPE *watcher)	1394	=item callback ev_cb (ev_TYPE *watcher)
1202		1395
1203	Returns the callback currently set on the watcher.	1396	Returns the callback currently set on the watcher.
1204		1397
1205	=item ev_cb_set (ev_TYPE *watcher, callback)	1398	=item ev_set_cb (ev_TYPE *watcher, callback)
1206		1399
1207	Change the callback. You can change the callback at virtually any time	1400	Change the callback. You can change the callback at virtually any time
1208	(modulo threads).	1401	(modulo threads).
1209		1402
1210	=item ev_set_priority (ev_TYPE *watcher, int priority)	1403	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1228	or might not have been clamped to the valid range.	1421	or might not have been clamped to the valid range.
1229		1422
1230	The default priority used by watchers when no priority has been set is	1423	The default priority used by watchers when no priority has been set is
1231	always C<0>, which is supposed to not be too high and not be too low :).	1424	always C<0>, which is supposed to not be too high and not be too low :).
1232		1425
1233	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1426	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1234	priorities.	1427	priorities.
1235		1428
1236	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1429	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1237		1430
1238	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1431	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1263	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1456	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1264	functions that do not need a watcher.	1457	functions that do not need a watcher.
1265		1458
1266	=back	1459	=back
1267		1460
		1461	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1462	OWN COMPOSITE WATCHERS> idioms.
1268		1463
1269	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1464	=head2 WATCHER STATES
1270		1465
1271	Each watcher has, by default, a member C<void *data> that you can change	1466	There are various watcher states mentioned throughout this manual -
1272	and read at any time: libev will completely ignore it. This can be used	1467	active, pending and so on. In this section these states and the rules to
1273	to associate arbitrary data with your watcher. If you need more data and	1468	transition between them will be described in more detail - and while these
1274	don't want to allocate memory and store a pointer to it in that data	1469	rules might look complicated, they usually do "the right thing".
1275	member, you can also "subclass" the watcher type and provide your own
1276	data:
1277		1470
1278	struct my_io	1471	=over 4
1279	{
1280	ev_io io;
1281	int otherfd;
1282	void *somedata;
1283	struct whatever *mostinteresting;
1284	};
1285		1472
1286	...	1473	=item initialised
1287	struct my_io w;
1288	ev_io_init (&w.io, my_cb, fd, EV_READ);
1289		1474
1290	And since your callback will be called with a pointer to the watcher, you	1475	Before a watcher can be registered with the event loop it has to be
1291	can cast it back to your own type:	1476	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1477	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1292		1478
1293	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1479	In this state it is simply some block of memory that is suitable for
1294	{	1480	use in an event loop. It can be moved around, freed, reused etc. at
1295	struct my_io *w = (struct my_io *)w_;	1481	will - as long as you either keep the memory contents intact, or call
1296	...	1482	C<ev_TYPE_init> again.
1297	}
1298		1483
1299	More interesting and less C-conformant ways of casting your callback type	1484	=item started/running/active
1300	instead have been omitted.
1301		1485
1302	Another common scenario is to use some data structure with multiple	1486	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1303	embedded watchers:	1487	property of the event loop, and is actively waiting for events. While in
		1488	this state it cannot be accessed (except in a few documented ways), moved,
		1489	freed or anything else - the only legal thing is to keep a pointer to it,
		1490	and call libev functions on it that are documented to work on active watchers.
1304		1491
1305	struct my_biggy	1492	=item pending
1306	{
1307	int some_data;
1308	ev_timer t1;
1309	ev_timer t2;
1310	}
1311		1493
1312	In this case getting the pointer to C<my_biggy> is a bit more	1494	If a watcher is active and libev determines that an event it is interested
1313	complicated: Either you store the address of your C<my_biggy> struct	1495	in has occurred (such as a timer expiring), it will become pending. It will
1314	in the C<data> member of the watcher (for woozies), or you need to use	1496	stay in this pending state until either it is stopped or its callback is
1315	some pointer arithmetic using C<offsetof> inside your watchers (for real	1497	about to be invoked, so it is not normally pending inside the watcher
1316	programmers):	1498	callback.
1317		1499
1318	#include <stddef.h>	1500	The watcher might or might not be active while it is pending (for example,
		1501	an expired non-repeating timer can be pending but no longer active). If it
		1502	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1503	but it is still property of the event loop at this time, so cannot be
		1504	moved, freed or reused. And if it is active the rules described in the
		1505	previous item still apply.
1319		1506
1320	static void	1507	It is also possible to feed an event on a watcher that is not active (e.g.
1321	t1_cb (EV_P_ ev_timer *w, int revents)	1508	via C<ev_feed_event>), in which case it becomes pending without being
1322	{	1509	active.
1323	struct my_biggy big = (struct my_biggy *)
1324	(((char *)w) - offsetof (struct my_biggy, t1));
1325	}
1326		1510
1327	static void	1511	=item stopped
1328	t2_cb (EV_P_ ev_timer *w, int revents)	1512
1329	{	1513	A watcher can be stopped implicitly by libev (in which case it might still
1330	struct my_biggy big = (struct my_biggy *)	1514	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1331	(((char *)w) - offsetof (struct my_biggy, t2));	1515	latter will clear any pending state the watcher might be in, regardless
1332	}	1516	of whether it was active or not, so stopping a watcher explicitly before
		1517	freeing it is often a good idea.
		1518
		1519	While stopped (and not pending) the watcher is essentially in the
		1520	initialised state, that is, it can be reused, moved, modified in any way
		1521	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1522	it again).
		1523
		1524	=back
1333		1525
1334	=head2 WATCHER PRIORITY MODELS	1526	=head2 WATCHER PRIORITY MODELS
1335		1527
1336	Many event loops support I<watcher priorities>, which are usually small	1528	Many event loops support I<watcher priorities>, which are usually small
1337	integers that influence the ordering of event callback invocation	1529	integers that influence the ordering of event callback invocation
…		…
1380		1572
1381	For example, to emulate how many other event libraries handle priorities,	1573	For example, to emulate how many other event libraries handle priorities,
1382	you can associate an C<ev_idle> watcher to each such watcher, and in	1574	you can associate an C<ev_idle> watcher to each such watcher, and in
1383	the normal watcher callback, you just start the idle watcher. The real	1575	the normal watcher callback, you just start the idle watcher. The real
1384	processing is done in the idle watcher callback. This causes libev to	1576	processing is done in the idle watcher callback. This causes libev to
1385	continously poll and process kernel event data for the watcher, but when	1577	continuously poll and process kernel event data for the watcher, but when
1386	the lock-out case is known to be rare (which in turn is rare :), this is	1578	the lock-out case is known to be rare (which in turn is rare :), this is
1387	workable.	1579	workable.
1388		1580
1389	Usually, however, the lock-out model implemented that way will perform	1581	Usually, however, the lock-out model implemented that way will perform
1390	miserably under the type of load it was designed to handle. In that case,	1582	miserably under the type of load it was designed to handle. In that case,
…		…
1464	In general you can register as many read and/or write event watchers per	1656	In general you can register as many read and/or write event watchers per
1465	fd as you want (as long as you don't confuse yourself). Setting all file	1657	fd as you want (as long as you don't confuse yourself). Setting all file
1466	descriptors to non-blocking mode is also usually a good idea (but not	1658	descriptors to non-blocking mode is also usually a good idea (but not
1467	required if you know what you are doing).	1659	required if you know what you are doing).
1468		1660
1469	If you cannot use non-blocking mode, then force the use of a
1470	known-to-be-good backend (at the time of this writing, this includes only
1471	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1472	descriptors for which non-blocking operation makes no sense (such as
1473	files) - libev doesn't guarentee any specific behaviour in that case.
1474
1475	Another thing you have to watch out for is that it is quite easy to	1661	Another thing you have to watch out for is that it is quite easy to
1476	receive "spurious" readiness notifications, that is your callback might	1662	receive "spurious" readiness notifications, that is, your callback might
1477	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1663	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1478	because there is no data. Not only are some backends known to create a	1664	because there is no data. It is very easy to get into this situation even
1479	lot of those (for example Solaris ports), it is very easy to get into	1665	with a relatively standard program structure. Thus it is best to always
1480	this situation even with a relatively standard program structure. Thus	1666	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1481	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1482	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1667	preferable to a program hanging until some data arrives.
1483		1668
1484	If you cannot run the fd in non-blocking mode (for example you should	1669	If you cannot run the fd in non-blocking mode (for example you should
1485	not play around with an Xlib connection), then you have to separately	1670	not play around with an Xlib connection), then you have to separately
1486	re-test whether a file descriptor is really ready with a known-to-be good	1671	re-test whether a file descriptor is really ready with a known-to-be good
1487	interface such as poll (fortunately in our Xlib example, Xlib already	1672	interface such as poll (fortunately in the case of Xlib, it already does
1488	does this on its own, so its quite safe to use). Some people additionally	1673	this on its own, so its quite safe to use). Some people additionally
1489	use C<SIGALRM> and an interval timer, just to be sure you won't block	1674	use C<SIGALRM> and an interval timer, just to be sure you won't block
1490	indefinitely.	1675	indefinitely.
1491		1676
1492	But really, best use non-blocking mode.	1677	But really, best use non-blocking mode.
1493		1678
1494	=head3 The special problem of disappearing file descriptors	1679	=head3 The special problem of disappearing file descriptors
1495		1680
1496	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1681	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1497	descriptor (either due to calling C<close> explicitly or any other means,	1682	a file descriptor (either due to calling C<close> explicitly or any other
1498	such as C<dup2>). The reason is that you register interest in some file	1683	means, such as C<dup2>). The reason is that you register interest in some
1499	descriptor, but when it goes away, the operating system will silently drop	1684	file descriptor, but when it goes away, the operating system will silently
1500	this interest. If another file descriptor with the same number then is	1685	drop this interest. If another file descriptor with the same number then
1501	registered with libev, there is no efficient way to see that this is, in	1686	is registered with libev, there is no efficient way to see that this is,
1502	fact, a different file descriptor.	1687	in fact, a different file descriptor.
1503		1688
1504	To avoid having to explicitly tell libev about such cases, libev follows	1689	To avoid having to explicitly tell libev about such cases, libev follows
1505	the following policy: Each time C<ev_io_set> is being called, libev	1690	the following policy: Each time C<ev_io_set> is being called, libev
1506	will assume that this is potentially a new file descriptor, otherwise	1691	will assume that this is potentially a new file descriptor, otherwise
1507	it is assumed that the file descriptor stays the same. That means that	1692	it is assumed that the file descriptor stays the same. That means that
…		…
1521		1706
1522	There is no workaround possible except not registering events	1707	There is no workaround possible except not registering events
1523	for potentially C<dup ()>'ed file descriptors, or to resort to	1708	for potentially C<dup ()>'ed file descriptors, or to resort to
1524	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1709	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1525		1710
		1711	=head3 The special problem of files
		1712
		1713	Many people try to use C<select> (or libev) on file descriptors
		1714	representing files, and expect it to become ready when their program
		1715	doesn't block on disk accesses (which can take a long time on their own).
		1716
		1717	However, this cannot ever work in the "expected" way - you get a readiness
		1718	notification as soon as the kernel knows whether and how much data is
		1719	there, and in the case of open files, that's always the case, so you
		1720	always get a readiness notification instantly, and your read (or possibly
		1721	write) will still block on the disk I/O.
		1722
		1723	Another way to view it is that in the case of sockets, pipes, character
		1724	devices and so on, there is another party (the sender) that delivers data
		1725	on its own, but in the case of files, there is no such thing: the disk
		1726	will not send data on its own, simply because it doesn't know what you
		1727	wish to read - you would first have to request some data.
		1728
		1729	Since files are typically not-so-well supported by advanced notification
		1730	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1731	to files, even though you should not use it. The reason for this is
		1732	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1733	usually a tty, often a pipe, but also sometimes files or special devices
		1734	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1735	F</dev/urandom>), and even though the file might better be served with
		1736	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1737	it "just works" instead of freezing.
		1738
		1739	So avoid file descriptors pointing to files when you know it (e.g. use
		1740	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1741	when you rarely read from a file instead of from a socket, and want to
		1742	reuse the same code path.
		1743
1526	=head3 The special problem of fork	1744	=head3 The special problem of fork
1527		1745
1528	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1746	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1529	useless behaviour. Libev fully supports fork, but needs to be told about	1747	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1530	it in the child.	1748	to be told about it in the child if you want to continue to use it in the
		1749	child.
1531		1750
1532	To support fork in your programs, you either have to call	1751	To support fork in your child processes, you have to call C<ev_loop_fork
1533	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1752	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1534	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1753	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1535	C<EVBACKEND_POLL>.
1536		1754
1537	=head3 The special problem of SIGPIPE	1755	=head3 The special problem of SIGPIPE
1538		1756
1539	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1757	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1540	when writing to a pipe whose other end has been closed, your program gets	1758	when writing to a pipe whose other end has been closed, your program gets
…		…
1622	...	1840	...
1623	struct ev_loop *loop = ev_default_init (0);	1841	struct ev_loop *loop = ev_default_init (0);
1624	ev_io stdin_readable;	1842	ev_io stdin_readable;
1625	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1843	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1626	ev_io_start (loop, &stdin_readable);	1844	ev_io_start (loop, &stdin_readable);
1627	ev_loop (loop, 0);	1845	ev_run (loop, 0);
1628		1846
1629		1847
1630	=head2 C<ev_timer> - relative and optionally repeating timeouts	1848	=head2 C<ev_timer> - relative and optionally repeating timeouts
1631		1849
1632	Timer watchers are simple relative timers that generate an event after a	1850	Timer watchers are simple relative timers that generate an event after a
…		…
1638	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1856	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1639	monotonic clock option helps a lot here).	1857	monotonic clock option helps a lot here).
1640		1858
1641	The callback is guaranteed to be invoked only I<after> its timeout has	1859	The callback is guaranteed to be invoked only I<after> its timeout has
1642	passed (not I<at>, so on systems with very low-resolution clocks this	1860	passed (not I<at>, so on systems with very low-resolution clocks this
1643	might introduce a small delay). If multiple timers become ready during the	1861	might introduce a small delay, see "the special problem of being too
		1862	early", below). If multiple timers become ready during the same loop
1644	same loop iteration then the ones with earlier time-out values are invoked	1863	iteration then the ones with earlier time-out values are invoked before
1645	before ones of the same priority with later time-out values (but this is	1864	ones of the same priority with later time-out values (but this is no
1646	no longer true when a callback calls C<ev_loop> recursively).	1865	longer true when a callback calls C<ev_run> recursively).
1647		1866
1648	=head3 Be smart about timeouts	1867	=head3 Be smart about timeouts
1649		1868
1650	Many real-world problems involve some kind of timeout, usually for error	1869	Many real-world problems involve some kind of timeout, usually for error
1651	recovery. A typical example is an HTTP request - if the other side hangs,	1870	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1726		1945
1727	In this case, it would be more efficient to leave the C<ev_timer> alone,	1946	In this case, it would be more efficient to leave the C<ev_timer> alone,
1728	but remember the time of last activity, and check for a real timeout only	1947	but remember the time of last activity, and check for a real timeout only
1729	within the callback:	1948	within the callback:
1730		1949
		1950	ev_tstamp timeout = 60.;
1731	ev_tstamp last_activity; // time of last activity	1951	ev_tstamp last_activity; // time of last activity
		1952	ev_timer timer;
1732		1953
1733	static void	1954	static void
1734	callback (EV_P_ ev_timer *w, int revents)	1955	callback (EV_P_ ev_timer *w, int revents)
1735	{	1956	{
1736	ev_tstamp now = ev_now (EV_A);	1957	// calculate when the timeout would happen
1737	ev_tstamp timeout = last_activity + 60.;	1958	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1738		1959
1739	// if last_activity + 60. is older than now, we did time out	1960	// if negative, it means we the timeout already occurred
1740	if (timeout < now)	1961	if (after < 0.)
1741	{	1962	{
1742	// timeout occured, take action	1963	// timeout occurred, take action
1743	}	1964	}
1744	else	1965	else
1745	{	1966	{
1746	// callback was invoked, but there was some activity, re-arm	1967	// callback was invoked, but there was some recent
1747	// the watcher to fire in last_activity + 60, which is	1968	// activity. simply restart the timer to time out
1748	// guaranteed to be in the future, so "again" is positive:	1969	// after "after" seconds, which is the earliest time
1749	w->repeat = timeout - now;	1970	// the timeout can occur.
		1971	ev_timer_set (w, after, 0.);
1750	ev_timer_again (EV_A_ w);	1972	ev_timer_start (EV_A_ w);
1751	}	1973	}
1752	}	1974	}
1753		1975
1754	To summarise the callback: first calculate the real timeout (defined	1976	To summarise the callback: first calculate in how many seconds the
1755	as "60 seconds after the last activity"), then check if that time has	1977	timeout will occur (by calculating the absolute time when it would occur,
1756	been reached, which means something I<did>, in fact, time out. Otherwise	1978	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1757	the callback was invoked too early (C<timeout> is in the future), so	1979	(EV_A)> from that).
1758	re-schedule the timer to fire at that future time, to see if maybe we have
1759	a timeout then.
1760		1980
1761	Note how C<ev_timer_again> is used, taking advantage of the	1981	If this value is negative, then we are already past the timeout, i.e. we
1762	C<ev_timer_again> optimisation when the timer is already running.	1982	timed out, and need to do whatever is needed in this case.
		1983
		1984	Otherwise, we now the earliest time at which the timeout would trigger,
		1985	and simply start the timer with this timeout value.
		1986
		1987	In other words, each time the callback is invoked it will check whether
		1988	the timeout occurred. If not, it will simply reschedule itself to check
		1989	again at the earliest time it could time out. Rinse. Repeat.
1763		1990
1764	This scheme causes more callback invocations (about one every 60 seconds	1991	This scheme causes more callback invocations (about one every 60 seconds
1765	minus half the average time between activity), but virtually no calls to	1992	minus half the average time between activity), but virtually no calls to
1766	libev to change the timeout.	1993	libev to change the timeout.
1767		1994
1768	To start the timer, simply initialise the watcher and set C<last_activity>	1995	To start the machinery, simply initialise the watcher and set
1769	to the current time (meaning we just have some activity :), then call the	1996	C<last_activity> to the current time (meaning there was some activity just
1770	callback, which will "do the right thing" and start the timer:	1997	now), then call the callback, which will "do the right thing" and start
		1998	the timer:
1771		1999
		2000	last_activity = ev_now (EV_A);
1772	ev_init (timer, callback);	2001	ev_init (&timer, callback);
1773	last_activity = ev_now (loop);	2002	callback (EV_A_ &timer, 0);
1774	callback (loop, timer, EV_TIMER);
1775		2003
1776	And when there is some activity, simply store the current time in	2004	When there is some activity, simply store the current time in
1777	C<last_activity>, no libev calls at all:	2005	C<last_activity>, no libev calls at all:
1778		2006
		2007	if (activity detected)
1779	last_activity = ev_now (loop);	2008	last_activity = ev_now (EV_A);
		2009
		2010	When your timeout value changes, then the timeout can be changed by simply
		2011	providing a new value, stopping the timer and calling the callback, which
		2012	will again do the right thing (for example, time out immediately :).
		2013
		2014	timeout = new_value;
		2015	ev_timer_stop (EV_A_ &timer);
		2016	callback (EV_A_ &timer, 0);
1780		2017
1781	This technique is slightly more complex, but in most cases where the	2018	This technique is slightly more complex, but in most cases where the
1782	time-out is unlikely to be triggered, much more efficient.	2019	time-out is unlikely to be triggered, much more efficient.
1783
1784	Changing the timeout is trivial as well (if it isn't hard-coded in the
1785	callback :) - just change the timeout and invoke the callback, which will
1786	fix things for you.
1787		2020
1788	=item 4. Wee, just use a double-linked list for your timeouts.	2021	=item 4. Wee, just use a double-linked list for your timeouts.
1789		2022
1790	If there is not one request, but many thousands (millions...), all	2023	If there is not one request, but many thousands (millions...), all
1791	employing some kind of timeout with the same timeout value, then one can	2024	employing some kind of timeout with the same timeout value, then one can
…		…
1818	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2051	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1819	rather complicated, but extremely efficient, something that really pays	2052	rather complicated, but extremely efficient, something that really pays
1820	off after the first million or so of active timers, i.e. it's usually	2053	off after the first million or so of active timers, i.e. it's usually
1821	overkill :)	2054	overkill :)
1822		2055
		2056	=head3 The special problem of being too early
		2057
		2058	If you ask a timer to call your callback after three seconds, then
		2059	you expect it to be invoked after three seconds - but of course, this
		2060	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2061	guaranteed to any precision by libev - imagine somebody suspending the
		2062	process with a STOP signal for a few hours for example.
		2063
		2064	So, libev tries to invoke your callback as soon as possible I<after> the
		2065	delay has occurred, but cannot guarantee this.
		2066
		2067	A less obvious failure mode is calling your callback too early: many event
		2068	loops compare timestamps with a "elapsed delay >= requested delay", but
		2069	this can cause your callback to be invoked much earlier than you would
		2070	expect.
		2071
		2072	To see why, imagine a system with a clock that only offers full second
		2073	resolution (think windows if you can't come up with a broken enough OS
		2074	yourself). If you schedule a one-second timer at the time 500.9, then the
		2075	event loop will schedule your timeout to elapse at a system time of 500
		2076	(500.9 truncated to the resolution) + 1, or 501.
		2077
		2078	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2079	501" and invoke the callback 0.1s after it was started, even though a
		2080	one-second delay was requested - this is being "too early", despite best
		2081	intentions.
		2082
		2083	This is the reason why libev will never invoke the callback if the elapsed
		2084	delay equals the requested delay, but only when the elapsed delay is
		2085	larger than the requested delay. In the example above, libev would only invoke
		2086	the callback at system time 502, or 1.1s after the timer was started.
		2087
		2088	So, while libev cannot guarantee that your callback will be invoked
		2089	exactly when requested, it I<can> and I<does> guarantee that the requested
		2090	delay has actually elapsed, or in other words, it always errs on the "too
		2091	late" side of things.
		2092
1823	=head3 The special problem of time updates	2093	=head3 The special problem of time updates
1824		2094
1825	Establishing the current time is a costly operation (it usually takes at	2095	Establishing the current time is a costly operation (it usually takes
1826	least two system calls): EV therefore updates its idea of the current	2096	at least one system call): EV therefore updates its idea of the current
1827	time only before and after C<ev_loop> collects new events, which causes a	2097	time only before and after C<ev_run> collects new events, which causes a
1828	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2098	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1829	lots of events in one iteration.	2099	lots of events in one iteration.
1830		2100
1831	The relative timeouts are calculated relative to the C<ev_now ()>	2101	The relative timeouts are calculated relative to the C<ev_now ()>
1832	time. This is usually the right thing as this timestamp refers to the time	2102	time. This is usually the right thing as this timestamp refers to the time
1833	of the event triggering whatever timeout you are modifying/starting. If	2103	of the event triggering whatever timeout you are modifying/starting. If
1834	you suspect event processing to be delayed and you I<need> to base the	2104	you suspect event processing to be delayed and you I<need> to base the
1835	timeout on the current time, use something like this to adjust for this:	2105	timeout on the current time, use something like the following to adjust
		2106	for it:
1836		2107
1837	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2108	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1838		2109
1839	If the event loop is suspended for a long time, you can also force an	2110	If the event loop is suspended for a long time, you can also force an
1840	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2111	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1841	()>.	2112	()>, although that will push the event time of all outstanding events
		2113	further into the future.
		2114
		2115	=head3 The special problem of unsynchronised clocks
		2116
		2117	Modern systems have a variety of clocks - libev itself uses the normal
		2118	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2119	jumps).
		2120
		2121	Neither of these clocks is synchronised with each other or any other clock
		2122	on the system, so C<ev_time ()> might return a considerably different time
		2123	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2124	a call to C<gettimeofday> might return a second count that is one higher
		2125	than a directly following call to C<time>.
		2126
		2127	The moral of this is to only compare libev-related timestamps with
		2128	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2129	a second or so.
		2130
		2131	One more problem arises due to this lack of synchronisation: if libev uses
		2132	the system monotonic clock and you compare timestamps from C<ev_time>
		2133	or C<ev_now> from when you started your timer and when your callback is
		2134	invoked, you will find that sometimes the callback is a bit "early".
		2135
		2136	This is because C<ev_timer>s work in real time, not wall clock time, so
		2137	libev makes sure your callback is not invoked before the delay happened,
		2138	I<measured according to the real time>, not the system clock.
		2139
		2140	If your timeouts are based on a physical timescale (e.g. "time out this
		2141	connection after 100 seconds") then this shouldn't bother you as it is
		2142	exactly the right behaviour.
		2143
		2144	If you want to compare wall clock/system timestamps to your timers, then
		2145	you need to use C<ev_periodic>s, as these are based on the wall clock
		2146	time, where your comparisons will always generate correct results.
1842		2147
1843	=head3 The special problems of suspended animation	2148	=head3 The special problems of suspended animation
1844		2149
1845	When you leave the server world it is quite customary to hit machines that	2150	When you leave the server world it is quite customary to hit machines that
1846	can suspend/hibernate - what happens to the clocks during such a suspend?	2151	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1876		2181
1877	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2182	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1878		2183
1879	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2184	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1880		2185
1881	Configure the timer to trigger after C<after> seconds. If C<repeat>	2186	Configure the timer to trigger after C<after> seconds (fractional and
1882	is C<0.>, then it will automatically be stopped once the timeout is	2187	negative values are supported). If C<repeat> is C<0.>, then it will
1883	reached. If it is positive, then the timer will automatically be	2188	automatically be stopped once the timeout is reached. If it is positive,
1884	configured to trigger again C<repeat> seconds later, again, and again,	2189	then the timer will automatically be configured to trigger again C<repeat>
1885	until stopped manually.	2190	seconds later, again, and again, until stopped manually.
1886		2191
1887	The timer itself will do a best-effort at avoiding drift, that is, if	2192	The timer itself will do a best-effort at avoiding drift, that is, if
1888	you configure a timer to trigger every 10 seconds, then it will normally	2193	you configure a timer to trigger every 10 seconds, then it will normally
1889	trigger at exactly 10 second intervals. If, however, your program cannot	2194	trigger at exactly 10 second intervals. If, however, your program cannot
1890	keep up with the timer (because it takes longer than those 10 seconds to	2195	keep up with the timer (because it takes longer than those 10 seconds to
1891	do stuff) the timer will not fire more than once per event loop iteration.	2196	do stuff) the timer will not fire more than once per event loop iteration.
1892		2197
1893	=item ev_timer_again (loop, ev_timer *)	2198	=item ev_timer_again (loop, ev_timer *)
1894		2199
1895	This will act as if the timer timed out and restart it again if it is	2200	This will act as if the timer timed out, and restarts it again if it is
1896	repeating. The exact semantics are:	2201	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2202	timeout to the C<repeat> value and calling C<ev_timer_start>.
1897		2203
		2204	The exact semantics are as in the following rules, all of which will be
		2205	applied to the watcher:
		2206
		2207	=over 4
		2208
1898	If the timer is pending, its pending status is cleared.	2209	=item If the timer is pending, the pending status is always cleared.
1899		2210
1900	If the timer is started but non-repeating, stop it (as if it timed out).	2211	=item If the timer is started but non-repeating, stop it (as if it timed
		2212	out, without invoking it).
1901		2213
1902	If the timer is repeating, either start it if necessary (with the	2214	=item If the timer is repeating, make the C<repeat> value the new timeout
1903	C<repeat> value), or reset the running timer to the C<repeat> value.	2215	and start the timer, if necessary.
1904		2216
		2217	=back
		2218
1905	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2219	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1906	usage example.	2220	usage example.
1907		2221
1908	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2222	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1909		2223
1910	Returns the remaining time until a timer fires. If the timer is active,	2224	Returns the remaining time until a timer fires. If the timer is active,
…		…
1949	}	2263	}
1950		2264
1951	ev_timer mytimer;	2265	ev_timer mytimer;
1952	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2266	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1953	ev_timer_again (&mytimer); /* start timer */	2267	ev_timer_again (&mytimer); /* start timer */
1954	ev_loop (loop, 0);	2268	ev_run (loop, 0);
1955		2269
1956	// and in some piece of code that gets executed on any "activity":	2270	// and in some piece of code that gets executed on any "activity":
1957	// reset the timeout to start ticking again at 10 seconds	2271	// reset the timeout to start ticking again at 10 seconds
1958	ev_timer_again (&mytimer);	2272	ev_timer_again (&mytimer);
1959		2273
…		…
1963	Periodic watchers are also timers of a kind, but they are very versatile	2277	Periodic watchers are also timers of a kind, but they are very versatile
1964	(and unfortunately a bit complex).	2278	(and unfortunately a bit complex).
1965		2279
1966	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2280	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1967	relative time, the physical time that passes) but on wall clock time	2281	relative time, the physical time that passes) but on wall clock time
1968	(absolute time, the thing you can read on your calender or clock). The	2282	(absolute time, the thing you can read on your calendar or clock). The
1969	difference is that wall clock time can run faster or slower than real	2283	difference is that wall clock time can run faster or slower than real
1970	time, and time jumps are not uncommon (e.g. when you adjust your	2284	time, and time jumps are not uncommon (e.g. when you adjust your
1971	wrist-watch).	2285	wrist-watch).
1972		2286
1973	You can tell a periodic watcher to trigger after some specific point	2287	You can tell a periodic watcher to trigger after some specific point
…		…
1978	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2292	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1979	it, as it uses a relative timeout).	2293	it, as it uses a relative timeout).
1980		2294
1981	C<ev_periodic> watchers can also be used to implement vastly more complex	2295	C<ev_periodic> watchers can also be used to implement vastly more complex
1982	timers, such as triggering an event on each "midnight, local time", or	2296	timers, such as triggering an event on each "midnight, local time", or
1983	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2297	other complicated rules. This cannot easily be done with C<ev_timer>
1984	those cannot react to time jumps.	2298	watchers, as those cannot react to time jumps.
1985		2299
1986	As with timers, the callback is guaranteed to be invoked only when the	2300	As with timers, the callback is guaranteed to be invoked only when the
1987	point in time where it is supposed to trigger has passed. If multiple	2301	point in time where it is supposed to trigger has passed. If multiple
1988	timers become ready during the same loop iteration then the ones with	2302	timers become ready during the same loop iteration then the ones with
1989	earlier time-out values are invoked before ones with later time-out values	2303	earlier time-out values are invoked before ones with later time-out values
1990	(but this is no longer true when a callback calls C<ev_loop> recursively).	2304	(but this is no longer true when a callback calls C<ev_run> recursively).
1991		2305
1992	=head3 Watcher-Specific Functions and Data Members	2306	=head3 Watcher-Specific Functions and Data Members
1993		2307
1994	=over 4	2308	=over 4
1995		2309
…		…
2030		2344
2031	Another way to think about it (for the mathematically inclined) is that	2345	Another way to think about it (for the mathematically inclined) is that
2032	C<ev_periodic> will try to run the callback in this mode at the next possible	2346	C<ev_periodic> will try to run the callback in this mode at the next possible
2033	time where C<time = offset (mod interval)>, regardless of any time jumps.	2347	time where C<time = offset (mod interval)>, regardless of any time jumps.
2034		2348
2035	For numerical stability it is preferable that the C<offset> value is near	2349	The C<interval> I<MUST> be positive, and for numerical stability, the
2036	C<ev_now ()> (the current time), but there is no range requirement for	2350	interval value should be higher than C<1/8192> (which is around 100
2037	this value, and in fact is often specified as zero.	2351	microseconds) and C<offset> should be higher than C<0> and should have
		2352	at most a similar magnitude as the current time (say, within a factor of
		2353	ten). Typical values for offset are, in fact, C<0> or something between
		2354	C<0> and C<interval>, which is also the recommended range.
2038		2355
2039	Note also that there is an upper limit to how often a timer can fire (CPU	2356	Note also that there is an upper limit to how often a timer can fire (CPU
2040	speed for example), so if C<interval> is very small then timing stability	2357	speed for example), so if C<interval> is very small then timing stability
2041	will of course deteriorate. Libev itself tries to be exact to be about one	2358	will of course deteriorate. Libev itself tries to be exact to be about one
2042	millisecond (if the OS supports it and the machine is fast enough).	2359	millisecond (if the OS supports it and the machine is fast enough).
…		…
2072		2389
2073	NOTE: I<< This callback must always return a time that is higher than or	2390	NOTE: I<< This callback must always return a time that is higher than or
2074	equal to the passed C<now> value >>.	2391	equal to the passed C<now> value >>.
2075		2392
2076	This can be used to create very complex timers, such as a timer that	2393	This can be used to create very complex timers, such as a timer that
2077	triggers on "next midnight, local time". To do this, you would calculate the	2394	triggers on "next midnight, local time". To do this, you would calculate
2078	next midnight after C<now> and return the timestamp value for this. How	2395	the next midnight after C<now> and return the timestamp value for
2079	you do this is, again, up to you (but it is not trivial, which is the main	2396	this. Here is a (completely untested, no error checking) example on how to
2080	reason I omitted it as an example).	2397	do this:
		2398
		2399	#include <time.h>
		2400
		2401	static ev_tstamp
		2402	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2403	{
		2404	time_t tnow = (time_t)now;
		2405	struct tm tm;
		2406	localtime_r (&tnow, &tm);
		2407
		2408	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2409	++tm.tm_mday; // midnight next day
		2410
		2411	return mktime (&tm);
		2412	}
		2413
		2414	Note: this code might run into trouble on days that have more then two
		2415	midnights (beginning and end).
2081		2416
2082	=back	2417	=back
2083		2418
2084	=item ev_periodic_again (loop, ev_periodic *)	2419	=item ev_periodic_again (loop, ev_periodic *)
2085		2420
…		…
2123	Example: Call a callback every hour, or, more precisely, whenever the	2458	Example: Call a callback every hour, or, more precisely, whenever the
2124	system time is divisible by 3600. The callback invocation times have	2459	system time is divisible by 3600. The callback invocation times have
2125	potentially a lot of jitter, but good long-term stability.	2460	potentially a lot of jitter, but good long-term stability.
2126		2461
2127	static void	2462	static void
2128	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2463	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2129	{	2464	{
2130	... its now a full hour (UTC, or TAI or whatever your clock follows)	2465	... its now a full hour (UTC, or TAI or whatever your clock follows)
2131	}	2466	}
2132		2467
2133	ev_periodic hourly_tick;	2468	ev_periodic hourly_tick;
…		…
2150		2485
2151	ev_periodic hourly_tick;	2486	ev_periodic hourly_tick;
2152	ev_periodic_init (&hourly_tick, clock_cb,	2487	ev_periodic_init (&hourly_tick, clock_cb,
2153	fmod (ev_now (loop), 3600.), 3600., 0);	2488	fmod (ev_now (loop), 3600.), 3600., 0);
2154	ev_periodic_start (loop, &hourly_tick);	2489	ev_periodic_start (loop, &hourly_tick);
2155		2490
2156		2491
2157	=head2 C<ev_signal> - signal me when a signal gets signalled!	2492	=head2 C<ev_signal> - signal me when a signal gets signalled!
2158		2493
2159	Signal watchers will trigger an event when the process receives a specific	2494	Signal watchers will trigger an event when the process receives a specific
2160	signal one or more times. Even though signals are very asynchronous, libev	2495	signal one or more times. Even though signals are very asynchronous, libev
2161	will try it's best to deliver signals synchronously, i.e. as part of the	2496	will try its best to deliver signals synchronously, i.e. as part of the
2162	normal event processing, like any other event.	2497	normal event processing, like any other event.
2163		2498
2164	If you want signals to be delivered truly asynchronously, just use	2499	If you want signals to be delivered truly asynchronously, just use
2165	C<sigaction> as you would do without libev and forget about sharing	2500	C<sigaction> as you would do without libev and forget about sharing
2166	the signal. You can even use C<ev_async> from a signal handler to	2501	the signal. You can even use C<ev_async> from a signal handler to
…		…
2170	only within the same loop, i.e. you can watch for C<SIGINT> in your	2505	only within the same loop, i.e. you can watch for C<SIGINT> in your
2171	default loop and for C<SIGIO> in another loop, but you cannot watch for	2506	default loop and for C<SIGIO> in another loop, but you cannot watch for
2172	C<SIGINT> in both the default loop and another loop at the same time. At	2507	C<SIGINT> in both the default loop and another loop at the same time. At
2173	the moment, C<SIGCHLD> is permanently tied to the default loop.	2508	the moment, C<SIGCHLD> is permanently tied to the default loop.
2174		2509
2175	When the first watcher gets started will libev actually register something	2510	Only after the first watcher for a signal is started will libev actually
2176	with the kernel (thus it coexists with your own signal handlers as long as	2511	register something with the kernel. It thus coexists with your own signal
2177	you don't register any with libev for the same signal).	2512	handlers as long as you don't register any with libev for the same signal.
2178		2513
2179	If possible and supported, libev will install its handlers with	2514	If possible and supported, libev will install its handlers with
2180	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2515	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2181	not be unduly interrupted. If you have a problem with system calls getting	2516	not be unduly interrupted. If you have a problem with system calls getting
2182	interrupted by signals you can block all signals in an C<ev_check> watcher	2517	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2185	=head3 The special problem of inheritance over fork/execve/pthread_create	2520	=head3 The special problem of inheritance over fork/execve/pthread_create
2186		2521
2187	Both the signal mask (C<sigprocmask>) and the signal disposition	2522	Both the signal mask (C<sigprocmask>) and the signal disposition
2188	(C<sigaction>) are unspecified after starting a signal watcher (and after	2523	(C<sigaction>) are unspecified after starting a signal watcher (and after
2189	stopping it again), that is, libev might or might not block the signal,	2524	stopping it again), that is, libev might or might not block the signal,
2190	and might or might not set or restore the installed signal handler.	2525	and might or might not set or restore the installed signal handler (but
		2526	see C<EVFLAG_NOSIGMASK>).
2191		2527
2192	While this does not matter for the signal disposition (libev never	2528	While this does not matter for the signal disposition (libev never
2193	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2529	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2194	C<execve>), this matters for the signal mask: many programs do not expect	2530	C<execve>), this matters for the signal mask: many programs do not expect
2195	certain signals to be blocked.	2531	certain signals to be blocked.
…		…
2209		2545
2210	So I can't stress this enough: I<If you do not reset your signal mask when	2546	So I can't stress this enough: I<If you do not reset your signal mask when
2211	you expect it to be empty, you have a race condition in your code>. This	2547	you expect it to be empty, you have a race condition in your code>. This
2212	is not a libev-specific thing, this is true for most event libraries.	2548	is not a libev-specific thing, this is true for most event libraries.
2213		2549
		2550	=head3 The special problem of threads signal handling
		2551
		2552	POSIX threads has problematic signal handling semantics, specifically,
		2553	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2554	threads in a process block signals, which is hard to achieve.
		2555
		2556	When you want to use sigwait (or mix libev signal handling with your own
		2557	for the same signals), you can tackle this problem by globally blocking
		2558	all signals before creating any threads (or creating them with a fully set
		2559	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2560	loops. Then designate one thread as "signal receiver thread" which handles
		2561	these signals. You can pass on any signals that libev might be interested
		2562	in by calling C<ev_feed_signal>.
		2563
2214	=head3 Watcher-Specific Functions and Data Members	2564	=head3 Watcher-Specific Functions and Data Members
2215		2565
2216	=over 4	2566	=over 4
2217		2567
2218	=item ev_signal_init (ev_signal *, callback, int signum)	2568	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2233	Example: Try to exit cleanly on SIGINT.	2583	Example: Try to exit cleanly on SIGINT.
2234		2584
2235	static void	2585	static void
2236	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2586	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2237	{	2587	{
2238	ev_unloop (loop, EVUNLOOP_ALL);	2588	ev_break (loop, EVBREAK_ALL);
2239	}	2589	}
2240		2590
2241	ev_signal signal_watcher;	2591	ev_signal signal_watcher;
2242	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2592	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2243	ev_signal_start (loop, &signal_watcher);	2593	ev_signal_start (loop, &signal_watcher);
…		…
2352		2702
2353	=head2 C<ev_stat> - did the file attributes just change?	2703	=head2 C<ev_stat> - did the file attributes just change?
2354		2704
2355	This watches a file system path for attribute changes. That is, it calls	2705	This watches a file system path for attribute changes. That is, it calls
2356	C<stat> on that path in regular intervals (or when the OS says it changed)	2706	C<stat> on that path in regular intervals (or when the OS says it changed)
2357	and sees if it changed compared to the last time, invoking the callback if	2707	and sees if it changed compared to the last time, invoking the callback
2358	it did.	2708	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2709	happen after the watcher has been started will be reported.
2359		2710
2360	The path does not need to exist: changing from "path exists" to "path does	2711	The path does not need to exist: changing from "path exists" to "path does
2361	not exist" is a status change like any other. The condition "path does not	2712	not exist" is a status change like any other. The condition "path does not
2362	exist" (or more correctly "path cannot be stat'ed") is signified by the	2713	exist" (or more correctly "path cannot be stat'ed") is signified by the
2363	C<st_nlink> field being zero (which is otherwise always forced to be at	2714	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2593	Apart from keeping your process non-blocking (which is a useful	2944	Apart from keeping your process non-blocking (which is a useful
2594	effect on its own sometimes), idle watchers are a good place to do	2945	effect on its own sometimes), idle watchers are a good place to do
2595	"pseudo-background processing", or delay processing stuff to after the	2946	"pseudo-background processing", or delay processing stuff to after the
2596	event loop has handled all outstanding events.	2947	event loop has handled all outstanding events.
2597		2948
		2949	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2950
		2951	As long as there is at least one active idle watcher, libev will never
		2952	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2953	For this to work, the idle watcher doesn't need to be invoked at all - the
		2954	lowest priority will do.
		2955
		2956	This mode of operation can be useful together with an C<ev_check> watcher,
		2957	to do something on each event loop iteration - for example to balance load
		2958	between different connections.
		2959
		2960	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2961	example.
		2962
2598	=head3 Watcher-Specific Functions and Data Members	2963	=head3 Watcher-Specific Functions and Data Members
2599		2964
2600	=over 4	2965	=over 4
2601		2966
2602	=item ev_idle_init (ev_idle *, callback)	2967	=item ev_idle_init (ev_idle *, callback)
…		…
2613	callback, free it. Also, use no error checking, as usual.	2978	callback, free it. Also, use no error checking, as usual.
2614		2979
2615	static void	2980	static void
2616	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2981	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2617	{	2982	{
		2983	// stop the watcher
		2984	ev_idle_stop (loop, w);
		2985
		2986	// now we can free it
2618	free (w);	2987	free (w);
		2988
2619	// now do something you wanted to do when the program has	2989	// now do something you wanted to do when the program has
2620	// no longer anything immediate to do.	2990	// no longer anything immediate to do.
2621	}	2991	}
2622		2992
2623	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2993	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2625	ev_idle_start (loop, idle_watcher);	2995	ev_idle_start (loop, idle_watcher);
2626		2996
2627		2997
2628	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2998	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2629		2999
2630	Prepare and check watchers are usually (but not always) used in pairs:	3000	Prepare and check watchers are often (but not always) used in pairs:
2631	prepare watchers get invoked before the process blocks and check watchers	3001	prepare watchers get invoked before the process blocks and check watchers
2632	afterwards.	3002	afterwards.
2633		3003
2634	You I<must not> call C<ev_loop> or similar functions that enter	3004	You I<must not> call C<ev_run> (or similar functions that enter the
2635	the current event loop from either C<ev_prepare> or C<ev_check>	3005	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2636	watchers. Other loops than the current one are fine, however. The	3006	C<ev_check> watchers. Other loops than the current one are fine,
2637	rationale behind this is that you do not need to check for recursion in	3007	however. The rationale behind this is that you do not need to check
2638	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3008	for recursion in those watchers, i.e. the sequence will always be
2639	C<ev_check> so if you have one watcher of each kind they will always be	3009	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2640	called in pairs bracketing the blocking call.	3010	kind they will always be called in pairs bracketing the blocking call.
2641		3011
2642	Their main purpose is to integrate other event mechanisms into libev and	3012	Their main purpose is to integrate other event mechanisms into libev and
2643	their use is somewhat advanced. They could be used, for example, to track	3013	their use is somewhat advanced. They could be used, for example, to track
2644	variable changes, implement your own watchers, integrate net-snmp or a	3014	variable changes, implement your own watchers, integrate net-snmp or a
2645	coroutine library and lots more. They are also occasionally useful if	3015	coroutine library and lots more. They are also occasionally useful if
…		…
2663	with priority higher than or equal to the event loop and one coroutine	3033	with priority higher than or equal to the event loop and one coroutine
2664	of lower priority, but only once, using idle watchers to keep the event	3034	of lower priority, but only once, using idle watchers to keep the event
2665	loop from blocking if lower-priority coroutines are active, thus mapping	3035	loop from blocking if lower-priority coroutines are active, thus mapping
2666	low-priority coroutines to idle/background tasks).	3036	low-priority coroutines to idle/background tasks).
2667		3037
2668	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3038	When used for this purpose, it is recommended to give C<ev_check> watchers
2669	priority, to ensure that they are being run before any other watchers	3039	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2670	after the poll (this doesn't matter for C<ev_prepare> watchers).	3040	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3041	watchers).
2671		3042
2672	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3043	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2673	activate ("feed") events into libev. While libev fully supports this, they	3044	activate ("feed") events into libev. While libev fully supports this, they
2674	might get executed before other C<ev_check> watchers did their job. As	3045	might get executed before other C<ev_check> watchers did their job. As
2675	C<ev_check> watchers are often used to embed other (non-libev) event	3046	C<ev_check> watchers are often used to embed other (non-libev) event
2676	loops those other event loops might be in an unusable state until their	3047	loops those other event loops might be in an unusable state until their
2677	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3048	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2678	others).	3049	others).
		3050
		3051	=head3 Abusing an C<ev_check> watcher for its side-effect
		3052
		3053	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3054	useful because they are called once per event loop iteration. For
		3055	example, if you want to handle a large number of connections fairly, you
		3056	normally only do a bit of work for each active connection, and if there
		3057	is more work to do, you wait for the next event loop iteration, so other
		3058	connections have a chance of making progress.
		3059
		3060	Using an C<ev_check> watcher is almost enough: it will be called on the
		3061	next event loop iteration. However, that isn't as soon as possible -
		3062	without external events, your C<ev_check> watcher will not be invoked.
		3063
		3064	This is where C<ev_idle> watchers come in handy - all you need is a
		3065	single global idle watcher that is active as long as you have one active
		3066	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3067	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3068	invoked. Neither watcher alone can do that.
2679		3069
2680	=head3 Watcher-Specific Functions and Data Members	3070	=head3 Watcher-Specific Functions and Data Members
2681		3071
2682	=over 4	3072	=over 4
2683		3073
…		…
2807		3197
2808	if (timeout >= 0)	3198	if (timeout >= 0)
2809	// create/start timer	3199	// create/start timer
2810		3200
2811	// poll	3201	// poll
2812	ev_loop (EV_A_ 0);	3202	ev_run (EV_A_ 0);
2813		3203
2814	// stop timer again	3204	// stop timer again
2815	if (timeout >= 0)	3205	if (timeout >= 0)
2816	ev_timer_stop (EV_A_ &to);	3206	ev_timer_stop (EV_A_ &to);
2817		3207
…		…
2884		3274
2885	=over 4	3275	=over 4
2886		3276
2887	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3277	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2888		3278
2889	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3279	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2890		3280
2891	Configures the watcher to embed the given loop, which must be	3281	Configures the watcher to embed the given loop, which must be
2892	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3282	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2893	invoked automatically, otherwise it is the responsibility of the callback	3283	invoked automatically, otherwise it is the responsibility of the callback
2894	to invoke it (it will continue to be called until the sweep has been done,	3284	to invoke it (it will continue to be called until the sweep has been done,
2895	if you do not want that, you need to temporarily stop the embed watcher).	3285	if you do not want that, you need to temporarily stop the embed watcher).
2896		3286
2897	=item ev_embed_sweep (loop, ev_embed *)	3287	=item ev_embed_sweep (loop, ev_embed *)
2898		3288
2899	Make a single, non-blocking sweep over the embedded loop. This works	3289	Make a single, non-blocking sweep over the embedded loop. This works
2900	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3290	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2901	appropriate way for embedded loops.	3291	appropriate way for embedded loops.
2902		3292
2903	=item struct ev_loop *other [read-only]	3293	=item struct ev_loop *other [read-only]
2904		3294
2905	The embedded event loop.	3295	The embedded event loop.
…		…
2915	used).	3305	used).
2916		3306
2917	struct ev_loop *loop_hi = ev_default_init (0);	3307	struct ev_loop *loop_hi = ev_default_init (0);
2918	struct ev_loop *loop_lo = 0;	3308	struct ev_loop *loop_lo = 0;
2919	ev_embed embed;	3309	ev_embed embed;
2920		3310
2921	// see if there is a chance of getting one that works	3311	// see if there is a chance of getting one that works
2922	// (remember that a flags value of 0 means autodetection)	3312	// (remember that a flags value of 0 means autodetection)
2923	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3313	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2924	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3314	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2925	: 0;	3315	: 0;
…		…
2939	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3329	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2940		3330
2941	struct ev_loop *loop = ev_default_init (0);	3331	struct ev_loop *loop = ev_default_init (0);
2942	struct ev_loop *loop_socket = 0;	3332	struct ev_loop *loop_socket = 0;
2943	ev_embed embed;	3333	ev_embed embed;
2944		3334
2945	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3335	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2946	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3336	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2947	{	3337	{
2948	ev_embed_init (&embed, 0, loop_socket);	3338	ev_embed_init (&embed, 0, loop_socket);
2949	ev_embed_start (loop, &embed);	3339	ev_embed_start (loop, &embed);
…		…
2957		3347
2958	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3348	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2959		3349
2960	Fork watchers are called when a C<fork ()> was detected (usually because	3350	Fork watchers are called when a C<fork ()> was detected (usually because
2961	whoever is a good citizen cared to tell libev about it by calling	3351	whoever is a good citizen cared to tell libev about it by calling
2962	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3352	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2963	event loop blocks next and before C<ev_check> watchers are being called,	3353	and before C<ev_check> watchers are being called, and only in the child
2964	and only in the child after the fork. If whoever good citizen calling	3354	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2965	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3355	and calls it in the wrong process, the fork handlers will be invoked, too,
2966	handlers will be invoked, too, of course.	3356	of course.
2967		3357
2968	=head3 The special problem of life after fork - how is it possible?	3358	=head3 The special problem of life after fork - how is it possible?
2969		3359
2970	Most uses of C<fork()> consist of forking, then some simple calls to ste	3360	Most uses of C<fork ()> consist of forking, then some simple calls to set
2971	up/change the process environment, followed by a call to C<exec()>. This	3361	up/change the process environment, followed by a call to C<exec()>. This
2972	sequence should be handled by libev without any problems.	3362	sequence should be handled by libev without any problems.
2973		3363
2974	This changes when the application actually wants to do event handling	3364	This changes when the application actually wants to do event handling
2975	in the child, or both parent in child, in effect "continuing" after the	3365	in the child, or both parent in child, in effect "continuing" after the
…		…
2991	disadvantage of having to use multiple event loops (which do not support	3381	disadvantage of having to use multiple event loops (which do not support
2992	signal watchers).	3382	signal watchers).
2993		3383
2994	When this is not possible, or you want to use the default loop for	3384	When this is not possible, or you want to use the default loop for
2995	other reasons, then in the process that wants to start "fresh", call	3385	other reasons, then in the process that wants to start "fresh", call
2996	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3386	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2997	the default loop will "orphan" (not stop) all registered watchers, so you	3387	Destroying the default loop will "orphan" (not stop) all registered
2998	have to be careful not to execute code that modifies those watchers. Note	3388	watchers, so you have to be careful not to execute code that modifies
2999	also that in that case, you have to re-register any signal watchers.	3389	those watchers. Note also that in that case, you have to re-register any
		3390	signal watchers.
3000		3391
3001	=head3 Watcher-Specific Functions and Data Members	3392	=head3 Watcher-Specific Functions and Data Members
3002		3393
3003	=over 4	3394	=over 4
3004		3395
3005	=item ev_fork_init (ev_signal *, callback)	3396	=item ev_fork_init (ev_fork *, callback)
3006		3397
3007	Initialises and configures the fork watcher - it has no parameters of any	3398	Initialises and configures the fork watcher - it has no parameters of any
3008	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3399	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3009	believe me.	3400	really.
3010		3401
3011	=back	3402	=back
3012		3403
3013		3404
		3405	=head2 C<ev_cleanup> - even the best things end
		3406
		3407	Cleanup watchers are called just before the event loop is being destroyed
		3408	by a call to C<ev_loop_destroy>.
		3409
		3410	While there is no guarantee that the event loop gets destroyed, cleanup
		3411	watchers provide a convenient method to install cleanup hooks for your
		3412	program, worker threads and so on - you just to make sure to destroy the
		3413	loop when you want them to be invoked.
		3414
		3415	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3416	all other watchers, they do not keep a reference to the event loop (which
		3417	makes a lot of sense if you think about it). Like all other watchers, you
		3418	can call libev functions in the callback, except C<ev_cleanup_start>.
		3419
		3420	=head3 Watcher-Specific Functions and Data Members
		3421
		3422	=over 4
		3423
		3424	=item ev_cleanup_init (ev_cleanup *, callback)
		3425
		3426	Initialises and configures the cleanup watcher - it has no parameters of
		3427	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3428	pointless, I assure you.
		3429
		3430	=back
		3431
		3432	Example: Register an atexit handler to destroy the default loop, so any
		3433	cleanup functions are called.
		3434
		3435	static void
		3436	program_exits (void)
		3437	{
		3438	ev_loop_destroy (EV_DEFAULT_UC);
		3439	}
		3440
		3441	...
		3442	atexit (program_exits);
		3443
		3444
3014	=head2 C<ev_async> - how to wake up another event loop	3445	=head2 C<ev_async> - how to wake up an event loop
3015		3446
3016	In general, you cannot use an C<ev_loop> from multiple threads or other	3447	In general, you cannot use an C<ev_loop> from multiple threads or other
3017	asynchronous sources such as signal handlers (as opposed to multiple event	3448	asynchronous sources such as signal handlers (as opposed to multiple event
3018	loops - those are of course safe to use in different threads).	3449	loops - those are of course safe to use in different threads).
3019		3450
3020	Sometimes, however, you need to wake up another event loop you do not	3451	Sometimes, however, you need to wake up an event loop you do not control,
3021	control, for example because it belongs to another thread. This is what	3452	for example because it belongs to another thread. This is what C<ev_async>
3022	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3453	watchers do: as long as the C<ev_async> watcher is active, you can signal
3023	can signal it by calling C<ev_async_send>, which is thread- and signal	3454	it by calling C<ev_async_send>, which is thread- and signal safe.
3024	safe.
3025		3455
3026	This functionality is very similar to C<ev_signal> watchers, as signals,	3456	This functionality is very similar to C<ev_signal> watchers, as signals,
3027	too, are asynchronous in nature, and signals, too, will be compressed	3457	too, are asynchronous in nature, and signals, too, will be compressed
3028	(i.e. the number of callback invocations may be less than the number of	3458	(i.e. the number of callback invocations may be less than the number of
3029	C<ev_async_sent> calls).	3459	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3030		3460	of "global async watchers" by using a watcher on an otherwise unused
3031	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3461	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3032	just the default loop.	3462	even without knowing which loop owns the signal.
3033		3463
3034	=head3 Queueing	3464	=head3 Queueing
3035		3465
3036	C<ev_async> does not support queueing of data in any way. The reason	3466	C<ev_async> does not support queueing of data in any way. The reason
3037	is that the author does not know of a simple (or any) algorithm for a	3467	is that the author does not know of a simple (or any) algorithm for a
…		…
3129	trust me.	3559	trust me.
3130		3560
3131	=item ev_async_send (loop, ev_async *)	3561	=item ev_async_send (loop, ev_async *)
3132		3562
3133	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3563	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3134	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3564	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3565	returns.
		3566
3135	C<ev_feed_event>, this call is safe to do from other threads, signal or	3567	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3136	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3568	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3137	section below on what exactly this means).	3569	embedding section below on what exactly this means).
3138		3570
3139	Note that, as with other watchers in libev, multiple events might get	3571	Note that, as with other watchers in libev, multiple events might get
3140	compressed into a single callback invocation (another way to look at this	3572	compressed into a single callback invocation (another way to look at
3141	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3573	this is that C<ev_async> watchers are level-triggered: they are set on
3142	reset when the event loop detects that).	3574	C<ev_async_send>, reset when the event loop detects that).
3143		3575
3144	This call incurs the overhead of a system call only once per event loop	3576	This call incurs the overhead of at most one extra system call per event
3145	iteration, so while the overhead might be noticeable, it doesn't apply to	3577	loop iteration, if the event loop is blocked, and no syscall at all if
3146	repeated calls to C<ev_async_send> for the same event loop.	3578	the event loop (or your program) is processing events. That means that
		3579	repeated calls are basically free (there is no need to avoid calls for
		3580	performance reasons) and that the overhead becomes smaller (typically
		3581	zero) under load.
3147		3582
3148	=item bool = ev_async_pending (ev_async *)	3583	=item bool = ev_async_pending (ev_async *)
3149		3584
3150	Returns a non-zero value when C<ev_async_send> has been called on the	3585	Returns a non-zero value when C<ev_async_send> has been called on the
3151	watcher but the event has not yet been processed (or even noted) by the	3586	watcher but the event has not yet been processed (or even noted) by the
…		…
3168		3603
3169	There are some other functions of possible interest. Described. Here. Now.	3604	There are some other functions of possible interest. Described. Here. Now.
3170		3605
3171	=over 4	3606	=over 4
3172		3607
3173	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3608	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3174		3609
3175	This function combines a simple timer and an I/O watcher, calls your	3610	This function combines a simple timer and an I/O watcher, calls your
3176	callback on whichever event happens first and automatically stops both	3611	callback on whichever event happens first and automatically stops both
3177	watchers. This is useful if you want to wait for a single event on an fd	3612	watchers. This is useful if you want to wait for a single event on an fd
3178	or timeout without having to allocate/configure/start/stop/free one or	3613	or timeout without having to allocate/configure/start/stop/free one or
…		…
3206	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3641	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3207		3642
3208	=item ev_feed_fd_event (loop, int fd, int revents)	3643	=item ev_feed_fd_event (loop, int fd, int revents)
3209		3644
3210	Feed an event on the given fd, as if a file descriptor backend detected	3645	Feed an event on the given fd, as if a file descriptor backend detected
3211	the given events it.	3646	the given events.
3212		3647
3213	=item ev_feed_signal_event (loop, int signum)	3648	=item ev_feed_signal_event (loop, int signum)
3214		3649
3215	Feed an event as if the given signal occurred (C<loop> must be the default	3650	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3216	loop!).	3651	which is async-safe.
3217		3652
3218	=back	3653	=back
		3654
		3655
		3656	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3657
		3658	This section explains some common idioms that are not immediately
		3659	obvious. Note that examples are sprinkled over the whole manual, and this
		3660	section only contains stuff that wouldn't fit anywhere else.
		3661
		3662	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3663
		3664	Each watcher has, by default, a C<void *data> member that you can read
		3665	or modify at any time: libev will completely ignore it. This can be used
		3666	to associate arbitrary data with your watcher. If you need more data and
		3667	don't want to allocate memory separately and store a pointer to it in that
		3668	data member, you can also "subclass" the watcher type and provide your own
		3669	data:
		3670
		3671	struct my_io
		3672	{
		3673	ev_io io;
		3674	int otherfd;
		3675	void *somedata;
		3676	struct whatever *mostinteresting;
		3677	};
		3678
		3679	...
		3680	struct my_io w;
		3681	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3682
		3683	And since your callback will be called with a pointer to the watcher, you
		3684	can cast it back to your own type:
		3685
		3686	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3687	{
		3688	struct my_io *w = (struct my_io *)w_;
		3689	...
		3690	}
		3691
		3692	More interesting and less C-conformant ways of casting your callback
		3693	function type instead have been omitted.
		3694
		3695	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3696
		3697	Another common scenario is to use some data structure with multiple
		3698	embedded watchers, in effect creating your own watcher that combines
		3699	multiple libev event sources into one "super-watcher":
		3700
		3701	struct my_biggy
		3702	{
		3703	int some_data;
		3704	ev_timer t1;
		3705	ev_timer t2;
		3706	}
		3707
		3708	In this case getting the pointer to C<my_biggy> is a bit more
		3709	complicated: Either you store the address of your C<my_biggy> struct in
		3710	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3711	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3712	real programmers):
		3713
		3714	#include <stddef.h>
		3715
		3716	static void
		3717	t1_cb (EV_P_ ev_timer *w, int revents)
		3718	{
		3719	struct my_biggy big = (struct my_biggy *)
		3720	(((char *)w) - offsetof (struct my_biggy, t1));
		3721	}
		3722
		3723	static void
		3724	t2_cb (EV_P_ ev_timer *w, int revents)
		3725	{
		3726	struct my_biggy big = (struct my_biggy *)
		3727	(((char *)w) - offsetof (struct my_biggy, t2));
		3728	}
		3729
		3730	=head2 AVOIDING FINISHING BEFORE RETURNING
		3731
		3732	Often you have structures like this in event-based programs:
		3733
		3734	callback ()
		3735	{
		3736	free (request);
		3737	}
		3738
		3739	request = start_new_request (..., callback);
		3740
		3741	The intent is to start some "lengthy" operation. The C<request> could be
		3742	used to cancel the operation, or do other things with it.
		3743
		3744	It's not uncommon to have code paths in C<start_new_request> that
		3745	immediately invoke the callback, for example, to report errors. Or you add
		3746	some caching layer that finds that it can skip the lengthy aspects of the
		3747	operation and simply invoke the callback with the result.
		3748
		3749	The problem here is that this will happen I<before> C<start_new_request>
		3750	has returned, so C<request> is not set.
		3751
		3752	Even if you pass the request by some safer means to the callback, you
		3753	might want to do something to the request after starting it, such as
		3754	canceling it, which probably isn't working so well when the callback has
		3755	already been invoked.
		3756
		3757	A common way around all these issues is to make sure that
		3758	C<start_new_request> I<always> returns before the callback is invoked. If
		3759	C<start_new_request> immediately knows the result, it can artificially
		3760	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3761	example, or more sneakily, by reusing an existing (stopped) watcher and
		3762	pushing it into the pending queue:
		3763
		3764	ev_set_cb (watcher, callback);
		3765	ev_feed_event (EV_A_ watcher, 0);
		3766
		3767	This way, C<start_new_request> can safely return before the callback is
		3768	invoked, while not delaying callback invocation too much.
		3769
		3770	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3771
		3772	Often (especially in GUI toolkits) there are places where you have
		3773	I<modal> interaction, which is most easily implemented by recursively
		3774	invoking C<ev_run>.
		3775
		3776	This brings the problem of exiting - a callback might want to finish the
		3777	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3778	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3779	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3780	other combination: In these cases, a simple C<ev_break> will not work.
		3781
		3782	The solution is to maintain "break this loop" variable for each C<ev_run>
		3783	invocation, and use a loop around C<ev_run> until the condition is
		3784	triggered, using C<EVRUN_ONCE>:
		3785
		3786	// main loop
		3787	int exit_main_loop = 0;
		3788
		3789	while (!exit_main_loop)
		3790	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3791
		3792	// in a modal watcher
		3793	int exit_nested_loop = 0;
		3794
		3795	while (!exit_nested_loop)
		3796	ev_run (EV_A_ EVRUN_ONCE);
		3797
		3798	To exit from any of these loops, just set the corresponding exit variable:
		3799
		3800	// exit modal loop
		3801	exit_nested_loop = 1;
		3802
		3803	// exit main program, after modal loop is finished
		3804	exit_main_loop = 1;
		3805
		3806	// exit both
		3807	exit_main_loop = exit_nested_loop = 1;
		3808
		3809	=head2 THREAD LOCKING EXAMPLE
		3810
		3811	Here is a fictitious example of how to run an event loop in a different
		3812	thread from where callbacks are being invoked and watchers are
		3813	created/added/removed.
		3814
		3815	For a real-world example, see the C<EV::Loop::Async> perl module,
		3816	which uses exactly this technique (which is suited for many high-level
		3817	languages).
		3818
		3819	The example uses a pthread mutex to protect the loop data, a condition
		3820	variable to wait for callback invocations, an async watcher to notify the
		3821	event loop thread and an unspecified mechanism to wake up the main thread.
		3822
		3823	First, you need to associate some data with the event loop:
		3824
		3825	typedef struct {
		3826	mutex_t lock; /* global loop lock */
		3827	ev_async async_w;
		3828	thread_t tid;
		3829	cond_t invoke_cv;
		3830	} userdata;
		3831
		3832	void prepare_loop (EV_P)
		3833	{
		3834	// for simplicity, we use a static userdata struct.
		3835	static userdata u;
		3836
		3837	ev_async_init (&u->async_w, async_cb);
		3838	ev_async_start (EV_A_ &u->async_w);
		3839
		3840	pthread_mutex_init (&u->lock, 0);
		3841	pthread_cond_init (&u->invoke_cv, 0);
		3842
		3843	// now associate this with the loop
		3844	ev_set_userdata (EV_A_ u);
		3845	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3846	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3847
		3848	// then create the thread running ev_run
		3849	pthread_create (&u->tid, 0, l_run, EV_A);
		3850	}
		3851
		3852	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3853	solely to wake up the event loop so it takes notice of any new watchers
		3854	that might have been added:
		3855
		3856	static void
		3857	async_cb (EV_P_ ev_async *w, int revents)
		3858	{
		3859	// just used for the side effects
		3860	}
		3861
		3862	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3863	protecting the loop data, respectively.
		3864
		3865	static void
		3866	l_release (EV_P)
		3867	{
		3868	userdata *u = ev_userdata (EV_A);
		3869	pthread_mutex_unlock (&u->lock);
		3870	}
		3871
		3872	static void
		3873	l_acquire (EV_P)
		3874	{
		3875	userdata *u = ev_userdata (EV_A);
		3876	pthread_mutex_lock (&u->lock);
		3877	}
		3878
		3879	The event loop thread first acquires the mutex, and then jumps straight
		3880	into C<ev_run>:
		3881
		3882	void *
		3883	l_run (void *thr_arg)
		3884	{
		3885	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3886
		3887	l_acquire (EV_A);
		3888	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3889	ev_run (EV_A_ 0);
		3890	l_release (EV_A);
		3891
		3892	return 0;
		3893	}
		3894
		3895	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3896	signal the main thread via some unspecified mechanism (signals? pipe
		3897	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3898	have been called (in a while loop because a) spurious wakeups are possible
		3899	and b) skipping inter-thread-communication when there are no pending
		3900	watchers is very beneficial):
		3901
		3902	static void
		3903	l_invoke (EV_P)
		3904	{
		3905	userdata *u = ev_userdata (EV_A);
		3906
		3907	while (ev_pending_count (EV_A))
		3908	{
		3909	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3910	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3911	}
		3912	}
		3913
		3914	Now, whenever the main thread gets told to invoke pending watchers, it
		3915	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3916	thread to continue:
		3917
		3918	static void
		3919	real_invoke_pending (EV_P)
		3920	{
		3921	userdata *u = ev_userdata (EV_A);
		3922
		3923	pthread_mutex_lock (&u->lock);
		3924	ev_invoke_pending (EV_A);
		3925	pthread_cond_signal (&u->invoke_cv);
		3926	pthread_mutex_unlock (&u->lock);
		3927	}
		3928
		3929	Whenever you want to start/stop a watcher or do other modifications to an
		3930	event loop, you will now have to lock:
		3931
		3932	ev_timer timeout_watcher;
		3933	userdata *u = ev_userdata (EV_A);
		3934
		3935	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3936
		3937	pthread_mutex_lock (&u->lock);
		3938	ev_timer_start (EV_A_ &timeout_watcher);
		3939	ev_async_send (EV_A_ &u->async_w);
		3940	pthread_mutex_unlock (&u->lock);
		3941
		3942	Note that sending the C<ev_async> watcher is required because otherwise
		3943	an event loop currently blocking in the kernel will have no knowledge
		3944	about the newly added timer. By waking up the loop it will pick up any new
		3945	watchers in the next event loop iteration.
		3946
		3947	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3948
		3949	While the overhead of a callback that e.g. schedules a thread is small, it
		3950	is still an overhead. If you embed libev, and your main usage is with some
		3951	kind of threads or coroutines, you might want to customise libev so that
		3952	doesn't need callbacks anymore.
		3953
		3954	Imagine you have coroutines that you can switch to using a function
		3955	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3956	and that due to some magic, the currently active coroutine is stored in a
		3957	global called C<current_coro>. Then you can build your own "wait for libev
		3958	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3959	the differing C<;> conventions):
		3960
		3961	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3962	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3963
		3964	That means instead of having a C callback function, you store the
		3965	coroutine to switch to in each watcher, and instead of having libev call
		3966	your callback, you instead have it switch to that coroutine.
		3967
		3968	A coroutine might now wait for an event with a function called
		3969	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3970	matter when, or whether the watcher is active or not when this function is
		3971	called):
		3972
		3973	void
		3974	wait_for_event (ev_watcher *w)
		3975	{
		3976	ev_set_cb (w, current_coro);
		3977	switch_to (libev_coro);
		3978	}
		3979
		3980	That basically suspends the coroutine inside C<wait_for_event> and
		3981	continues the libev coroutine, which, when appropriate, switches back to
		3982	this or any other coroutine.
		3983
		3984	You can do similar tricks if you have, say, threads with an event queue -
		3985	instead of storing a coroutine, you store the queue object and instead of
		3986	switching to a coroutine, you push the watcher onto the queue and notify
		3987	any waiters.
		3988
		3989	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3990	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3991
		3992	// my_ev.h
		3993	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3994	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3995	#include "../libev/ev.h"
		3996
		3997	// my_ev.c
		3998	#define EV_H "my_ev.h"
		3999	#include "../libev/ev.c"
		4000
		4001	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4002	F<my_ev.c> into your project. When properly specifying include paths, you
		4003	can even use F<ev.h> as header file name directly.
3219		4004
3220		4005
3221	=head1 LIBEVENT EMULATION	4006	=head1 LIBEVENT EMULATION
3222		4007
3223	Libev offers a compatibility emulation layer for libevent. It cannot	4008	Libev offers a compatibility emulation layer for libevent. It cannot
3224	emulate the internals of libevent, so here are some usage hints:	4009	emulate the internals of libevent, so here are some usage hints:
3225		4010
3226	=over 4	4011	=over 4
		4012
		4013	=item * Only the libevent-1.4.1-beta API is being emulated.
		4014
		4015	This was the newest libevent version available when libev was implemented,
		4016	and is still mostly unchanged in 2010.
3227		4017
3228	=item * Use it by including <event.h>, as usual.	4018	=item * Use it by including <event.h>, as usual.
3229		4019
3230	=item * The following members are fully supported: ev_base, ev_callback,	4020	=item * The following members are fully supported: ev_base, ev_callback,
3231	ev_arg, ev_fd, ev_res, ev_events.	4021	ev_arg, ev_fd, ev_res, ev_events.
…		…
3237	=item * Priorities are not currently supported. Initialising priorities	4027	=item * Priorities are not currently supported. Initialising priorities
3238	will fail and all watchers will have the same priority, even though there	4028	will fail and all watchers will have the same priority, even though there
3239	is an ev_pri field.	4029	is an ev_pri field.
3240		4030
3241	=item * In libevent, the last base created gets the signals, in libev, the	4031	=item * In libevent, the last base created gets the signals, in libev, the
3242	first base created (== the default loop) gets the signals.	4032	base that registered the signal gets the signals.
3243		4033
3244	=item * Other members are not supported.	4034	=item * Other members are not supported.
3245		4035
3246	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4036	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3247	to use the libev header file and library.	4037	to use the libev header file and library.
3248		4038
3249	=back	4039	=back
3250		4040
3251	=head1 C++ SUPPORT	4041	=head1 C++ SUPPORT
		4042
		4043	=head2 C API
		4044
		4045	The normal C API should work fine when used from C++: both ev.h and the
		4046	libev sources can be compiled as C++. Therefore, code that uses the C API
		4047	will work fine.
		4048
		4049	Proper exception specifications might have to be added to callbacks passed
		4050	to libev: exceptions may be thrown only from watcher callbacks, all other
		4051	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4052	callbacks) must not throw exceptions, and might need a C<noexcept>
		4053	specification. If you have code that needs to be compiled as both C and
		4054	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4055
		4056	static void
		4057	fatal_error (const char *msg) EV_NOEXCEPT
		4058	{
		4059	perror (msg);
		4060	abort ();
		4061	}
		4062
		4063	...
		4064	ev_set_syserr_cb (fatal_error);
		4065
		4066	The only API functions that can currently throw exceptions are C<ev_run>,
		4067	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4068	because it runs cleanup watchers).
		4069
		4070	Throwing exceptions in watcher callbacks is only supported if libev itself
		4071	is compiled with a C++ compiler or your C and C++ environments allow
		4072	throwing exceptions through C libraries (most do).
		4073
		4074	=head2 C++ API
3252		4075
3253	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4076	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3254	you to use some convenience methods to start/stop watchers and also change	4077	you to use some convenience methods to start/stop watchers and also change
3255	the callback model to a model using method callbacks on objects.	4078	the callback model to a model using method callbacks on objects.
3256		4079
3257	To use it,	4080	To use it,
3258		4081
3259	#include <ev++.h>	4082	#include <ev++.h>
3260		4083
3261	This automatically includes F<ev.h> and puts all of its definitions (many	4084	This automatically includes F<ev.h> and puts all of its definitions (many
3262	of them macros) into the global namespace. All C++ specific things are	4085	of them macros) into the global namespace. All C++ specific things are
3263	put into the C<ev> namespace. It should support all the same embedding	4086	put into the C<ev> namespace. It should support all the same embedding
…		…
3266	Care has been taken to keep the overhead low. The only data member the C++	4089	Care has been taken to keep the overhead low. The only data member the C++
3267	classes add (compared to plain C-style watchers) is the event loop pointer	4090	classes add (compared to plain C-style watchers) is the event loop pointer
3268	that the watcher is associated with (or no additional members at all if	4091	that the watcher is associated with (or no additional members at all if
3269	you disable C<EV_MULTIPLICITY> when embedding libev).	4092	you disable C<EV_MULTIPLICITY> when embedding libev).
3270		4093
3271	Currently, functions, and static and non-static member functions can be	4094	Currently, functions, static and non-static member functions and classes
3272	used as callbacks. Other types should be easy to add as long as they only	4095	with C<operator ()> can be used as callbacks. Other types should be easy
3273	need one additional pointer for context. If you need support for other	4096	to add as long as they only need one additional pointer for context. If
3274	types of functors please contact the author (preferably after implementing	4097	you need support for other types of functors please contact the author
3275	it).	4098	(preferably after implementing it).
		4099
		4100	For all this to work, your C++ compiler either has to use the same calling
		4101	conventions as your C compiler (for static member functions), or you have
		4102	to embed libev and compile libev itself as C++.
3276		4103
3277	Here is a list of things available in the C<ev> namespace:	4104	Here is a list of things available in the C<ev> namespace:
3278		4105
3279	=over 4	4106	=over 4
3280		4107
…		…
3290	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4117	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3291		4118
3292	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4119	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3293	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4120	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3294	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4121	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3295	defines by many implementations.	4122	defined by many implementations.
3296		4123
3297	All of those classes have these methods:	4124	All of those classes have these methods:
3298		4125
3299	=over 4	4126	=over 4
3300		4127
…		…
3362	void operator() (ev::io &w, int revents)	4189	void operator() (ev::io &w, int revents)
3363	{	4190	{
3364	...	4191	...
3365	}	4192	}
3366	}	4193	}
3367		4194
3368	myfunctor f;	4195	myfunctor f;
3369		4196
3370	ev::io w;	4197	ev::io w;
3371	w.set (&f);	4198	w.set (&f);
3372		4199
…		…
3390	Associates a different C<struct ev_loop> with this watcher. You can only	4217	Associates a different C<struct ev_loop> with this watcher. You can only
3391	do this when the watcher is inactive (and not pending either).	4218	do this when the watcher is inactive (and not pending either).
3392		4219
3393	=item w->set ([arguments])	4220	=item w->set ([arguments])
3394		4221
3395	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4222	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4223	with the same arguments. Either this method or a suitable start method
3396	called at least once. Unlike the C counterpart, an active watcher gets	4224	must be called at least once. Unlike the C counterpart, an active watcher
3397	automatically stopped and restarted when reconfiguring it with this	4225	gets automatically stopped and restarted when reconfiguring it with this
3398	method.	4226	method.
		4227
		4228	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4229	clashing with the C<set (loop)> method.
3399		4230
3400	=item w->start ()	4231	=item w->start ()
3401		4232
3402	Starts the watcher. Note that there is no C<loop> argument, as the	4233	Starts the watcher. Note that there is no C<loop> argument, as the
3403	constructor already stores the event loop.	4234	constructor already stores the event loop.
3404		4235
		4236	=item w->start ([arguments])
		4237
		4238	Instead of calling C<set> and C<start> methods separately, it is often
		4239	convenient to wrap them in one call. Uses the same type of arguments as
		4240	the configure C<set> method of the watcher.
		4241
3405	=item w->stop ()	4242	=item w->stop ()
3406		4243
3407	Stops the watcher if it is active. Again, no C<loop> argument.	4244	Stops the watcher if it is active. Again, no C<loop> argument.
3408		4245
3409	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4246	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3421		4258
3422	=back	4259	=back
3423		4260
3424	=back	4261	=back
3425		4262
3426	Example: Define a class with an IO and idle watcher, start one of them in	4263	Example: Define a class with two I/O and idle watchers, start the I/O
3427	the constructor.	4264	watchers in the constructor.
3428		4265
3429	class myclass	4266	class myclass
3430	{	4267	{
3431	ev::io io ; void io_cb (ev::io &w, int revents);	4268	ev::io io ; void io_cb (ev::io &w, int revents);
		4269	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3432	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4270	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3433		4271
3434	myclass (int fd)	4272	myclass (int fd)
3435	{	4273	{
3436	io .set <myclass, &myclass::io_cb > (this);	4274	io .set <myclass, &myclass::io_cb > (this);
		4275	io2 .set <myclass, &myclass::io2_cb > (this);
3437	idle.set <myclass, &myclass::idle_cb> (this);	4276	idle.set <myclass, &myclass::idle_cb> (this);
3438		4277
3439	io.start (fd, ev::READ);	4278	io.set (fd, ev::WRITE); // configure the watcher
		4279	io.start (); // start it whenever convenient
		4280
		4281	io2.start (fd, ev::READ); // set + start in one call
3440	}	4282	}
3441	};	4283	};
3442		4284
3443		4285
3444	=head1 OTHER LANGUAGE BINDINGS	4286	=head1 OTHER LANGUAGE BINDINGS
…		…
3483	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4325	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3484		4326
3485	=item D	4327	=item D
3486		4328
3487	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4329	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3488	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4330	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3489		4331
3490	=item Ocaml	4332	=item Ocaml
3491		4333
3492	Erkki Seppala has written Ocaml bindings for libev, to be found at	4334	Erkki Seppala has written Ocaml bindings for libev, to be found at
3493	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4335	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3496		4338
3497	Brian Maher has written a partial interface to libev for lua (at the	4339	Brian Maher has written a partial interface to libev for lua (at the
3498	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4340	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3499	L<http://github.com/brimworks/lua-ev>.	4341	L<http://github.com/brimworks/lua-ev>.
3500		4342
		4343	=item Javascript
		4344
		4345	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4346
		4347	=item Others
		4348
		4349	There are others, and I stopped counting.
		4350
3501	=back	4351	=back
3502		4352
3503		4353
3504	=head1 MACRO MAGIC	4354	=head1 MACRO MAGIC
3505		4355
…		…
3518	loop argument"). The C<EV_A> form is used when this is the sole argument,	4368	loop argument"). The C<EV_A> form is used when this is the sole argument,
3519	C<EV_A_> is used when other arguments are following. Example:	4369	C<EV_A_> is used when other arguments are following. Example:
3520		4370
3521	ev_unref (EV_A);	4371	ev_unref (EV_A);
3522	ev_timer_add (EV_A_ watcher);	4372	ev_timer_add (EV_A_ watcher);
3523	ev_loop (EV_A_ 0);	4373	ev_run (EV_A_ 0);
3524		4374
3525	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4375	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3526	which is often provided by the following macro.	4376	which is often provided by the following macro.
3527		4377
3528	=item C<EV_P>, C<EV_P_>	4378	=item C<EV_P>, C<EV_P_>
…		…
3541	suitable for use with C<EV_A>.	4391	suitable for use with C<EV_A>.
3542		4392
3543	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4393	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3544		4394
3545	Similar to the other two macros, this gives you the value of the default	4395	Similar to the other two macros, this gives you the value of the default
3546	loop, if multiple loops are supported ("ev loop default").	4396	loop, if multiple loops are supported ("ev loop default"). The default loop
		4397	will be initialised if it isn't already initialised.
		4398
		4399	For non-multiplicity builds, these macros do nothing, so you always have
		4400	to initialise the loop somewhere.
3547		4401
3548	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4402	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3549		4403
3550	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4404	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3551	default loop has been initialised (C<UC> == unchecked). Their behaviour	4405	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3568	}	4422	}
3569		4423
3570	ev_check check;	4424	ev_check check;
3571	ev_check_init (&check, check_cb);	4425	ev_check_init (&check, check_cb);
3572	ev_check_start (EV_DEFAULT_ &check);	4426	ev_check_start (EV_DEFAULT_ &check);
3573	ev_loop (EV_DEFAULT_ 0);	4427	ev_run (EV_DEFAULT_ 0);
3574		4428
3575	=head1 EMBEDDING	4429	=head1 EMBEDDING
3576		4430
3577	Libev can (and often is) directly embedded into host	4431	Libev can (and often is) directly embedded into host
3578	applications. Examples of applications that embed it include the Deliantra	4432	applications. Examples of applications that embed it include the Deliantra
…		…
3618	ev_vars.h	4472	ev_vars.h
3619	ev_wrap.h	4473	ev_wrap.h
3620		4474
3621	ev_win32.c required on win32 platforms only	4475	ev_win32.c required on win32 platforms only
3622		4476
3623	ev_select.c only when select backend is enabled (which is enabled by default)	4477	ev_select.c only when select backend is enabled
3624	ev_poll.c only when poll backend is enabled (disabled by default)	4478	ev_poll.c only when poll backend is enabled
3625	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4479	ev_epoll.c only when the epoll backend is enabled
		4480	ev_linuxaio.c only when the linux aio backend is enabled
3626	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4481	ev_kqueue.c only when the kqueue backend is enabled
3627	ev_port.c only when the solaris port backend is enabled (disabled by default)	4482	ev_port.c only when the solaris port backend is enabled
3628		4483
3629	F<ev.c> includes the backend files directly when enabled, so you only need	4484	F<ev.c> includes the backend files directly when enabled, so you only need
3630	to compile this single file.	4485	to compile this single file.
3631		4486
3632	=head3 LIBEVENT COMPATIBILITY API	4487	=head3 LIBEVENT COMPATIBILITY API
…		…
3670	users of libev and the libev code itself must be compiled with compatible	4525	users of libev and the libev code itself must be compiled with compatible
3671	settings.	4526	settings.
3672		4527
3673	=over 4	4528	=over 4
3674		4529
		4530	=item EV_COMPAT3 (h)
		4531
		4532	Backwards compatibility is a major concern for libev. This is why this
		4533	release of libev comes with wrappers for the functions and symbols that
		4534	have been renamed between libev version 3 and 4.
		4535
		4536	You can disable these wrappers (to test compatibility with future
		4537	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4538	sources. This has the additional advantage that you can drop the C<struct>
		4539	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4540	typedef in that case.
		4541
		4542	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4543	and in some even more future version the compatibility code will be
		4544	removed completely.
		4545
3675	=item EV_STANDALONE (h)	4546	=item EV_STANDALONE (h)
3676		4547
3677	Must always be C<1> if you do not use autoconf configuration, which	4548	Must always be C<1> if you do not use autoconf configuration, which
3678	keeps libev from including F<config.h>, and it also defines dummy	4549	keeps libev from including F<config.h>, and it also defines dummy
3679	implementations for some libevent functions (such as logging, which is not	4550	implementations for some libevent functions (such as logging, which is not
3680	supported). It will also not define any of the structs usually found in	4551	supported). It will also not define any of the structs usually found in
3681	F<event.h> that are not directly supported by the libev core alone.	4552	F<event.h> that are not directly supported by the libev core alone.
3682		4553
3683	In standalone mode, libev will still try to automatically deduce the	4554	In standalone mode, libev will still try to automatically deduce the
3684	configuration, but has to be more conservative.	4555	configuration, but has to be more conservative.
		4556
		4557	=item EV_USE_FLOOR
		4558
		4559	If defined to be C<1>, libev will use the C<floor ()> function for its
		4560	periodic reschedule calculations, otherwise libev will fall back on a
		4561	portable (slower) implementation. If you enable this, you usually have to
		4562	link against libm or something equivalent. Enabling this when the C<floor>
		4563	function is not available will fail, so the safe default is to not enable
		4564	this.
3685		4565
3686	=item EV_USE_MONOTONIC	4566	=item EV_USE_MONOTONIC
3687		4567
3688	If defined to be C<1>, libev will try to detect the availability of the	4568	If defined to be C<1>, libev will try to detect the availability of the
3689	monotonic clock option at both compile time and runtime. Otherwise no	4569	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3775	If programs implement their own fd to handle mapping on win32, then this	4655	If programs implement their own fd to handle mapping on win32, then this
3776	macro can be used to override the C<close> function, useful to unregister	4656	macro can be used to override the C<close> function, useful to unregister
3777	file descriptors again. Note that the replacement function has to close	4657	file descriptors again. Note that the replacement function has to close
3778	the underlying OS handle.	4658	the underlying OS handle.
3779		4659
		4660	=item EV_USE_WSASOCKET
		4661
		4662	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4663	communication socket, which works better in some environments. Otherwise,
		4664	the normal C<socket> function will be used, which works better in other
		4665	environments.
		4666
3780	=item EV_USE_POLL	4667	=item EV_USE_POLL
3781		4668
3782	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4669	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3783	backend. Otherwise it will be enabled on non-win32 platforms. It	4670	backend. Otherwise it will be enabled on non-win32 platforms. It
3784	takes precedence over select.	4671	takes precedence over select.
…		…
3788	If defined to be C<1>, libev will compile in support for the Linux	4675	If defined to be C<1>, libev will compile in support for the Linux
3789	C<epoll>(7) backend. Its availability will be detected at runtime,	4676	C<epoll>(7) backend. Its availability will be detected at runtime,
3790	otherwise another method will be used as fallback. This is the preferred	4677	otherwise another method will be used as fallback. This is the preferred
3791	backend for GNU/Linux systems. If undefined, it will be enabled if the	4678	backend for GNU/Linux systems. If undefined, it will be enabled if the
3792	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4679	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4680
		4681	=item EV_USE_LINUXAIO
		4682
		4683	If defined to be C<1>, libev will compile in support for the Linux
		4684	aio backend. Due to it's currenbt limitations it has to be requested
		4685	explicitly. If undefined, it will be enabled on linux, otherwise
		4686	disabled.
3793		4687
3794	=item EV_USE_KQUEUE	4688	=item EV_USE_KQUEUE
3795		4689
3796	If defined to be C<1>, libev will compile in support for the BSD style	4690	If defined to be C<1>, libev will compile in support for the BSD style
3797	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4691	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3819	If defined to be C<1>, libev will compile in support for the Linux inotify	4713	If defined to be C<1>, libev will compile in support for the Linux inotify
3820	interface to speed up C<ev_stat> watchers. Its actual availability will	4714	interface to speed up C<ev_stat> watchers. Its actual availability will
3821	be detected at runtime. If undefined, it will be enabled if the headers	4715	be detected at runtime. If undefined, it will be enabled if the headers
3822	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4716	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3823		4717
		4718	=item EV_NO_SMP
		4719
		4720	If defined to be C<1>, libev will assume that memory is always coherent
		4721	between threads, that is, threads can be used, but threads never run on
		4722	different cpus (or different cpu cores). This reduces dependencies
		4723	and makes libev faster.
		4724
		4725	=item EV_NO_THREADS
		4726
		4727	If defined to be C<1>, libev will assume that it will never be called from
		4728	different threads (that includes signal handlers), which is a stronger
		4729	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4730	libev faster.
		4731
3824	=item EV_ATOMIC_T	4732	=item EV_ATOMIC_T
3825		4733
3826	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4734	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3827	access is atomic with respect to other threads or signal contexts. No such	4735	access is atomic with respect to other threads or signal contexts. No
3828	type is easily found in the C language, so you can provide your own type	4736	such type is easily found in the C language, so you can provide your own
3829	that you know is safe for your purposes. It is used both for signal handler "locking"	4737	type that you know is safe for your purposes. It is used both for signal
3830	as well as for signal and thread safety in C<ev_async> watchers.	4738	handler "locking" as well as for signal and thread safety in C<ev_async>
		4739	watchers.
3831		4740
3832	In the absence of this define, libev will use C<sig_atomic_t volatile>	4741	In the absence of this define, libev will use C<sig_atomic_t volatile>
3833	(from F<signal.h>), which is usually good enough on most platforms.	4742	(from F<signal.h>), which is usually good enough on most platforms.
3834		4743
3835	=item EV_H (h)	4744	=item EV_H (h)
…		…
3862	will have the C<struct ev_loop *> as first argument, and you can create	4771	will have the C<struct ev_loop *> as first argument, and you can create
3863	additional independent event loops. Otherwise there will be no support	4772	additional independent event loops. Otherwise there will be no support
3864	for multiple event loops and there is no first event loop pointer	4773	for multiple event loops and there is no first event loop pointer
3865	argument. Instead, all functions act on the single default loop.	4774	argument. Instead, all functions act on the single default loop.
3866		4775
		4776	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4777	default loop when multiplicity is switched off - you always have to
		4778	initialise the loop manually in this case.
		4779
3867	=item EV_MINPRI	4780	=item EV_MINPRI
3868		4781
3869	=item EV_MAXPRI	4782	=item EV_MAXPRI
3870		4783
3871	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4784	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3885	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,	4798	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3886	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.	4799	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3887		4800
3888	If undefined or defined to be C<1> (and the platform supports it), then	4801	If undefined or defined to be C<1> (and the platform supports it), then
3889	the respective watcher type is supported. If defined to be C<0>, then it	4802	the respective watcher type is supported. If defined to be C<0>, then it
3890	is not. Disabling watcher types mainly saves codesize.	4803	is not. Disabling watcher types mainly saves code size.
3891		4804
3892	=item EV_FEATURES	4805	=item EV_FEATURES
3893		4806
3894	If you need to shave off some kilobytes of code at the expense of some	4807	If you need to shave off some kilobytes of code at the expense of some
3895	speed (but with the full API), you can define this symbol to request	4808	speed (but with the full API), you can define this symbol to request
…		…
3907	#define EV_USE_POLL 1	4820	#define EV_USE_POLL 1
3908	#define EV_CHILD_ENABLE 1	4821	#define EV_CHILD_ENABLE 1
3909	#define EV_ASYNC_ENABLE 1	4822	#define EV_ASYNC_ENABLE 1
3910		4823
3911	The actual value is a bitset, it can be a combination of the following	4824	The actual value is a bitset, it can be a combination of the following
3912	values:	4825	values (by default, all of these are enabled):
3913		4826
3914	=over 4	4827	=over 4
3915		4828
3916	=item C<1> - faster/larger code	4829	=item C<1> - faster/larger code
3917		4830
3918	Use larger code to speed up some operations.	4831	Use larger code to speed up some operations.
3919		4832
3920	Currently this is used to override some inlining decisions (enlarging the roughly	4833	Currently this is used to override some inlining decisions (enlarging the
3921	30% code size on amd64.	4834	code size by roughly 30% on amd64).
3922		4835
3923	When optimising for size, use of compiler flags such as C<-Os> with	4836	When optimising for size, use of compiler flags such as C<-Os> with
3924	gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of	4837	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3925	assertions.	4838	assertions.
3926		4839
		4840	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4841	(e.g. gcc with C<-Os>).
		4842
3927	=item C<2> - faster/larger data structures	4843	=item C<2> - faster/larger data structures
3928		4844
3929	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4845	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3930	hash table sizes and so on. This will usually further increase codesize	4846	hash table sizes and so on. This will usually further increase code size
3931	and can additionally have an effect on the size of data structures at	4847	and can additionally have an effect on the size of data structures at
3932	runtime.	4848	runtime.
		4849
		4850	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4851	(e.g. gcc with C<-Os>).
3933		4852
3934	=item C<4> - full API configuration	4853	=item C<4> - full API configuration
3935		4854
3936	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4855	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3937	enables multiplicity (C<EV_MULTIPLICITY>=1).	4856	enables multiplicity (C<EV_MULTIPLICITY>=1).
…		…
3969	With an intelligent-enough linker (gcc+binutils are intelligent enough	4888	With an intelligent-enough linker (gcc+binutils are intelligent enough
3970	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4889	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3971	your program might be left out as well - a binary starting a timer and an	4890	your program might be left out as well - a binary starting a timer and an
3972	I/O watcher then might come out at only 5Kb.	4891	I/O watcher then might come out at only 5Kb.
3973		4892
		4893	=item EV_API_STATIC
		4894
		4895	If this symbol is defined (by default it is not), then all identifiers
		4896	will have static linkage. This means that libev will not export any
		4897	identifiers, and you cannot link against libev anymore. This can be useful
		4898	when you embed libev, only want to use libev functions in a single file,
		4899	and do not want its identifiers to be visible.
		4900
		4901	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4902	wants to use libev.
		4903
		4904	This option only works when libev is compiled with a C compiler, as C++
		4905	doesn't support the required declaration syntax.
		4906
3974	=item EV_AVOID_STDIO	4907	=item EV_AVOID_STDIO
3975		4908
3976	If this is set to C<1> at compiletime, then libev will avoid using stdio	4909	If this is set to C<1> at compiletime, then libev will avoid using stdio
3977	functions (printf, scanf, perror etc.). This will increase the codesize	4910	functions (printf, scanf, perror etc.). This will increase the code size
3978	somewhat, but if your program doesn't otherwise depend on stdio and your	4911	somewhat, but if your program doesn't otherwise depend on stdio and your
3979	libc allows it, this avoids linking in the stdio library which is quite	4912	libc allows it, this avoids linking in the stdio library which is quite
3980	big.	4913	big.
3981		4914
3982	Note that error messages might become less precise when this option is	4915	Note that error messages might become less precise when this option is
…		…
3986		4919
3987	The highest supported signal number, +1 (or, the number of	4920	The highest supported signal number, +1 (or, the number of
3988	signals): Normally, libev tries to deduce the maximum number of signals	4921	signals): Normally, libev tries to deduce the maximum number of signals
3989	automatically, but sometimes this fails, in which case it can be	4922	automatically, but sometimes this fails, in which case it can be
3990	specified. Also, using a lower number than detected (C<32> should be	4923	specified. Also, using a lower number than detected (C<32> should be
3991	good for about any system in existance) can save some memory, as libev	4924	good for about any system in existence) can save some memory, as libev
3992	statically allocates some 12-24 bytes per signal number.	4925	statically allocates some 12-24 bytes per signal number.
3993		4926
3994	=item EV_PID_HASHSIZE	4927	=item EV_PID_HASHSIZE
3995		4928
3996	C<ev_child> watchers use a small hash table to distribute workload by	4929	C<ev_child> watchers use a small hash table to distribute workload by
…		…
4028	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4961	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4029	will be C<0>.	4962	will be C<0>.
4030		4963
4031	=item EV_VERIFY	4964	=item EV_VERIFY
4032		4965
4033	Controls how much internal verification (see C<ev_loop_verify ()>) will	4966	Controls how much internal verification (see C<ev_verify ()>) will
4034	be done: If set to C<0>, no internal verification code will be compiled	4967	be done: If set to C<0>, no internal verification code will be compiled
4035	in. If set to C<1>, then verification code will be compiled in, but not	4968	in. If set to C<1>, then verification code will be compiled in, but not
4036	called. If set to C<2>, then the internal verification code will be	4969	called. If set to C<2>, then the internal verification code will be
4037	called once per loop, which can slow down libev. If set to C<3>, then the	4970	called once per loop, which can slow down libev. If set to C<3>, then the
4038	verification code will be called very frequently, which will slow down	4971	verification code will be called very frequently, which will slow down
…		…
4042	will be C<0>.	4975	will be C<0>.
4043		4976
4044	=item EV_COMMON	4977	=item EV_COMMON
4045		4978
4046	By default, all watchers have a C<void *data> member. By redefining	4979	By default, all watchers have a C<void *data> member. By redefining
4047	this macro to a something else you can include more and other types of	4980	this macro to something else you can include more and other types of
4048	members. You have to define it each time you include one of the files,	4981	members. You have to define it each time you include one of the files,
4049	though, and it must be identical each time.	4982	though, and it must be identical each time.
4050		4983
4051	For example, the perl EV module uses something like this:	4984	For example, the perl EV module uses something like this:
4052		4985
…		…
4121	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5054	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4122		5055
4123	#include "ev_cpp.h"	5056	#include "ev_cpp.h"
4124	#include "ev.c"	5057	#include "ev.c"
4125		5058
4126	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5059	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4127		5060
4128	=head2 THREADS AND COROUTINES	5061	=head2 THREADS AND COROUTINES
4129		5062
4130	=head3 THREADS	5063	=head3 THREADS
4131		5064
…		…
4182	default loop and triggering an C<ev_async> watcher from the default loop	5115	default loop and triggering an C<ev_async> watcher from the default loop
4183	watcher callback into the event loop interested in the signal.	5116	watcher callback into the event loop interested in the signal.
4184		5117
4185	=back	5118	=back
4186		5119
4187	=head4 THREAD LOCKING EXAMPLE	5120	See also L</THREAD LOCKING EXAMPLE>.
4188
4189	Here is a fictitious example of how to run an event loop in a different
4190	thread than where callbacks are being invoked and watchers are
4191	created/added/removed.
4192
4193	For a real-world example, see the C<EV::Loop::Async> perl module,
4194	which uses exactly this technique (which is suited for many high-level
4195	languages).
4196
4197	The example uses a pthread mutex to protect the loop data, a condition
4198	variable to wait for callback invocations, an async watcher to notify the
4199	event loop thread and an unspecified mechanism to wake up the main thread.
4200
4201	First, you need to associate some data with the event loop:
4202
4203	typedef struct {
4204	mutex_t lock; /* global loop lock */
4205	ev_async async_w;
4206	thread_t tid;
4207	cond_t invoke_cv;
4208	} userdata;
4209
4210	void prepare_loop (EV_P)
4211	{
4212	// for simplicity, we use a static userdata struct.
4213	static userdata u;
4214
4215	ev_async_init (&u->async_w, async_cb);
4216	ev_async_start (EV_A_ &u->async_w);
4217
4218	pthread_mutex_init (&u->lock, 0);
4219	pthread_cond_init (&u->invoke_cv, 0);
4220
4221	// now associate this with the loop
4222	ev_set_userdata (EV_A_ u);
4223	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4224	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4225
4226	// then create the thread running ev_loop
4227	pthread_create (&u->tid, 0, l_run, EV_A);
4228	}
4229
4230	The callback for the C<ev_async> watcher does nothing: the watcher is used
4231	solely to wake up the event loop so it takes notice of any new watchers
4232	that might have been added:
4233
4234	static void
4235	async_cb (EV_P_ ev_async *w, int revents)
4236	{
4237	// just used for the side effects
4238	}
4239
4240	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4241	protecting the loop data, respectively.
4242
4243	static void
4244	l_release (EV_P)
4245	{
4246	userdata *u = ev_userdata (EV_A);
4247	pthread_mutex_unlock (&u->lock);
4248	}
4249
4250	static void
4251	l_acquire (EV_P)
4252	{
4253	userdata *u = ev_userdata (EV_A);
4254	pthread_mutex_lock (&u->lock);
4255	}
4256
4257	The event loop thread first acquires the mutex, and then jumps straight
4258	into C<ev_loop>:
4259
4260	void *
4261	l_run (void *thr_arg)
4262	{
4263	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4264
4265	l_acquire (EV_A);
4266	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4267	ev_loop (EV_A_ 0);
4268	l_release (EV_A);
4269
4270	return 0;
4271	}
4272
4273	Instead of invoking all pending watchers, the C<l_invoke> callback will
4274	signal the main thread via some unspecified mechanism (signals? pipe
4275	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4276	have been called (in a while loop because a) spurious wakeups are possible
4277	and b) skipping inter-thread-communication when there are no pending
4278	watchers is very beneficial):
4279
4280	static void
4281	l_invoke (EV_P)
4282	{
4283	userdata *u = ev_userdata (EV_A);
4284
4285	while (ev_pending_count (EV_A))
4286	{
4287	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4288	pthread_cond_wait (&u->invoke_cv, &u->lock);
4289	}
4290	}
4291
4292	Now, whenever the main thread gets told to invoke pending watchers, it
4293	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4294	thread to continue:
4295
4296	static void
4297	real_invoke_pending (EV_P)
4298	{
4299	userdata *u = ev_userdata (EV_A);
4300
4301	pthread_mutex_lock (&u->lock);
4302	ev_invoke_pending (EV_A);
4303	pthread_cond_signal (&u->invoke_cv);
4304	pthread_mutex_unlock (&u->lock);
4305	}
4306
4307	Whenever you want to start/stop a watcher or do other modifications to an
4308	event loop, you will now have to lock:
4309
4310	ev_timer timeout_watcher;
4311	userdata *u = ev_userdata (EV_A);
4312
4313	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4314
4315	pthread_mutex_lock (&u->lock);
4316	ev_timer_start (EV_A_ &timeout_watcher);
4317	ev_async_send (EV_A_ &u->async_w);
4318	pthread_mutex_unlock (&u->lock);
4319
4320	Note that sending the C<ev_async> watcher is required because otherwise
4321	an event loop currently blocking in the kernel will have no knowledge
4322	about the newly added timer. By waking up the loop it will pick up any new
4323	watchers in the next event loop iteration.
4324		5121
4325	=head3 COROUTINES	5122	=head3 COROUTINES
4326		5123
4327	Libev is very accommodating to coroutines ("cooperative threads"):	5124	Libev is very accommodating to coroutines ("cooperative threads"):
4328	libev fully supports nesting calls to its functions from different	5125	libev fully supports nesting calls to its functions from different
4329	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5126	coroutines (e.g. you can call C<ev_run> on the same loop from two
4330	different coroutines, and switch freely between both coroutines running	5127	different coroutines, and switch freely between both coroutines running
4331	the loop, as long as you don't confuse yourself). The only exception is	5128	the loop, as long as you don't confuse yourself). The only exception is
4332	that you must not do this from C<ev_periodic> reschedule callbacks.	5129	that you must not do this from C<ev_periodic> reschedule callbacks.
4333		5130
4334	Care has been taken to ensure that libev does not keep local state inside	5131	Care has been taken to ensure that libev does not keep local state inside
4335	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5132	C<ev_run>, and other calls do not usually allow for coroutine switches as
4336	they do not call any callbacks.	5133	they do not call any callbacks.
4337		5134
4338	=head2 COMPILER WARNINGS	5135	=head2 COMPILER WARNINGS
4339		5136
4340	Depending on your compiler and compiler settings, you might get no or a	5137	Depending on your compiler and compiler settings, you might get no or a
…		…
4351	maintainable.	5148	maintainable.
4352		5149
4353	And of course, some compiler warnings are just plain stupid, or simply	5150	And of course, some compiler warnings are just plain stupid, or simply
4354	wrong (because they don't actually warn about the condition their message	5151	wrong (because they don't actually warn about the condition their message
4355	seems to warn about). For example, certain older gcc versions had some	5152	seems to warn about). For example, certain older gcc versions had some
4356	warnings that resulted an extreme number of false positives. These have	5153	warnings that resulted in an extreme number of false positives. These have
4357	been fixed, but some people still insist on making code warn-free with	5154	been fixed, but some people still insist on making code warn-free with
4358	such buggy versions.	5155	such buggy versions.
4359		5156
4360	While libev is written to generate as few warnings as possible,	5157	While libev is written to generate as few warnings as possible,
4361	"warn-free" code is not a goal, and it is recommended not to build libev	5158	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4397	I suggest using suppression lists.	5194	I suggest using suppression lists.
4398		5195
4399		5196
4400	=head1 PORTABILITY NOTES	5197	=head1 PORTABILITY NOTES
4401		5198
		5199	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5200
		5201	GNU/Linux is the only common platform that supports 64 bit file/large file
		5202	interfaces but I<disables> them by default.
		5203
		5204	That means that libev compiled in the default environment doesn't support
		5205	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5206
		5207	Unfortunately, many programs try to work around this GNU/Linux issue
		5208	by enabling the large file API, which makes them incompatible with the
		5209	standard libev compiled for their system.
		5210
		5211	Likewise, libev cannot enable the large file API itself as this would
		5212	suddenly make it incompatible to the default compile time environment,
		5213	i.e. all programs not using special compile switches.
		5214
		5215	=head2 OS/X AND DARWIN BUGS
		5216
		5217	The whole thing is a bug if you ask me - basically any system interface
		5218	you touch is broken, whether it is locales, poll, kqueue or even the
		5219	OpenGL drivers.
		5220
		5221	=head3 C<kqueue> is buggy
		5222
		5223	The kqueue syscall is broken in all known versions - most versions support
		5224	only sockets, many support pipes.
		5225
		5226	Libev tries to work around this by not using C<kqueue> by default on this
		5227	rotten platform, but of course you can still ask for it when creating a
		5228	loop - embedding a socket-only kqueue loop into a select-based one is
		5229	probably going to work well.
		5230
		5231	=head3 C<poll> is buggy
		5232
		5233	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5234	implementation by something calling C<kqueue> internally around the 10.5.6
		5235	release, so now C<kqueue> I<and> C<poll> are broken.
		5236
		5237	Libev tries to work around this by not using C<poll> by default on
		5238	this rotten platform, but of course you can still ask for it when creating
		5239	a loop.
		5240
		5241	=head3 C<select> is buggy
		5242
		5243	All that's left is C<select>, and of course Apple found a way to fuck this
		5244	one up as well: On OS/X, C<select> actively limits the number of file
		5245	descriptors you can pass in to 1024 - your program suddenly crashes when
		5246	you use more.
		5247
		5248	There is an undocumented "workaround" for this - defining
		5249	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5250	work on OS/X.
		5251
		5252	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5253
		5254	=head3 C<errno> reentrancy
		5255
		5256	The default compile environment on Solaris is unfortunately so
		5257	thread-unsafe that you can't even use components/libraries compiled
		5258	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5259	defined by default. A valid, if stupid, implementation choice.
		5260
		5261	If you want to use libev in threaded environments you have to make sure
		5262	it's compiled with C<_REENTRANT> defined.
		5263
		5264	=head3 Event port backend
		5265
		5266	The scalable event interface for Solaris is called "event
		5267	ports". Unfortunately, this mechanism is very buggy in all major
		5268	releases. If you run into high CPU usage, your program freezes or you get
		5269	a large number of spurious wakeups, make sure you have all the relevant
		5270	and latest kernel patches applied. No, I don't know which ones, but there
		5271	are multiple ones to apply, and afterwards, event ports actually work
		5272	great.
		5273
		5274	If you can't get it to work, you can try running the program by setting
		5275	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5276	C<select> backends.
		5277
		5278	=head2 AIX POLL BUG
		5279
		5280	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5281	this by trying to avoid the poll backend altogether (i.e. it's not even
		5282	compiled in), which normally isn't a big problem as C<select> works fine
		5283	with large bitsets on AIX, and AIX is dead anyway.
		5284
4402	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5285	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5286
		5287	=head3 General issues
4403		5288
4404	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5289	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4405	requires, and its I/O model is fundamentally incompatible with the POSIX	5290	requires, and its I/O model is fundamentally incompatible with the POSIX
4406	model. Libev still offers limited functionality on this platform in	5291	model. Libev still offers limited functionality on this platform in
4407	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5292	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4408	descriptors. This only applies when using Win32 natively, not when using	5293	descriptors. This only applies when using Win32 natively, not when using
4409	e.g. cygwin.	5294	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5295	as every compiler comes with a slightly differently broken/incompatible
		5296	environment.
4410		5297
4411	Lifting these limitations would basically require the full	5298	Lifting these limitations would basically require the full
4412	re-implementation of the I/O system. If you are into these kinds of	5299	re-implementation of the I/O system. If you are into this kind of thing,
4413	things, then note that glib does exactly that for you in a very portable	5300	then note that glib does exactly that for you in a very portable way (note
4414	way (note also that glib is the slowest event library known to man).	5301	also that glib is the slowest event library known to man).
4415		5302
4416	There is no supported compilation method available on windows except	5303	There is no supported compilation method available on windows except
4417	embedding it into other applications.	5304	embedding it into other applications.
4418		5305
4419	Sensible signal handling is officially unsupported by Microsoft - libev	5306	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4447	you do I<not> compile the F<ev.c> or any other embedded source files!):	5334	you do I<not> compile the F<ev.c> or any other embedded source files!):
4448		5335
4449	#include "evwrap.h"	5336	#include "evwrap.h"
4450	#include "ev.c"	5337	#include "ev.c"
4451		5338
4452	=over 4
4453
4454	=item The winsocket select function	5339	=head3 The winsocket C<select> function
4455		5340
4456	The winsocket C<select> function doesn't follow POSIX in that it	5341	The winsocket C<select> function doesn't follow POSIX in that it
4457	requires socket I<handles> and not socket I<file descriptors> (it is	5342	requires socket I<handles> and not socket I<file descriptors> (it is
4458	also extremely buggy). This makes select very inefficient, and also	5343	also extremely buggy). This makes select very inefficient, and also
4459	requires a mapping from file descriptors to socket handles (the Microsoft	5344	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4468	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5353	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4469		5354
4470	Note that winsockets handling of fd sets is O(n), so you can easily get a	5355	Note that winsockets handling of fd sets is O(n), so you can easily get a
4471	complexity in the O(n²) range when using win32.	5356	complexity in the O(n²) range when using win32.
4472		5357
4473	=item Limited number of file descriptors	5358	=head3 Limited number of file descriptors
4474		5359
4475	Windows has numerous arbitrary (and low) limits on things.	5360	Windows has numerous arbitrary (and low) limits on things.
4476		5361
4477	Early versions of winsocket's select only supported waiting for a maximum	5362	Early versions of winsocket's select only supported waiting for a maximum
4478	of C<64> handles (probably owning to the fact that all windows kernels	5363	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4493	runtime libraries. This might get you to about C<512> or C<2048> sockets	5378	runtime libraries. This might get you to about C<512> or C<2048> sockets
4494	(depending on windows version and/or the phase of the moon). To get more,	5379	(depending on windows version and/or the phase of the moon). To get more,
4495	you need to wrap all I/O functions and provide your own fd management, but	5380	you need to wrap all I/O functions and provide your own fd management, but
4496	the cost of calling select (O(n²)) will likely make this unworkable.	5381	the cost of calling select (O(n²)) will likely make this unworkable.
4497		5382
4498	=back
4499
4500	=head2 PORTABILITY REQUIREMENTS	5383	=head2 PORTABILITY REQUIREMENTS
4501		5384
4502	In addition to a working ISO-C implementation and of course the	5385	In addition to a working ISO-C implementation and of course the
4503	backend-specific APIs, libev relies on a few additional extensions:	5386	backend-specific APIs, libev relies on a few additional extensions:
4504		5387
…		…
4510	Libev assumes not only that all watcher pointers have the same internal	5393	Libev assumes not only that all watcher pointers have the same internal
4511	structure (guaranteed by POSIX but not by ISO C for example), but it also	5394	structure (guaranteed by POSIX but not by ISO C for example), but it also
4512	assumes that the same (machine) code can be used to call any watcher	5395	assumes that the same (machine) code can be used to call any watcher
4513	callback: The watcher callbacks have different type signatures, but libev	5396	callback: The watcher callbacks have different type signatures, but libev
4514	calls them using an C<ev_watcher *> internally.	5397	calls them using an C<ev_watcher *> internally.
		5398
		5399	=item null pointers and integer zero are represented by 0 bytes
		5400
		5401	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5402	relies on this setting pointers and integers to null.
		5403
		5404	=item pointer accesses must be thread-atomic
		5405
		5406	Accessing a pointer value must be atomic, it must both be readable and
		5407	writable in one piece - this is the case on all current architectures.
4515		5408
4516	=item C<sig_atomic_t volatile> must be thread-atomic as well	5409	=item C<sig_atomic_t volatile> must be thread-atomic as well
4517		5410
4518	The type C<sig_atomic_t volatile> (or whatever is defined as	5411	The type C<sig_atomic_t volatile> (or whatever is defined as
4519	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5412	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4528	thread" or will block signals process-wide, both behaviours would	5421	thread" or will block signals process-wide, both behaviours would
4529	be compatible with libev. Interaction between C<sigprocmask> and	5422	be compatible with libev. Interaction between C<sigprocmask> and
4530	C<pthread_sigmask> could complicate things, however.	5423	C<pthread_sigmask> could complicate things, however.
4531		5424
4532	The most portable way to handle signals is to block signals in all threads	5425	The most portable way to handle signals is to block signals in all threads
4533	except the initial one, and run the default loop in the initial thread as	5426	except the initial one, and run the signal handling loop in the initial
4534	well.	5427	thread as well.
4535		5428
4536	=item C<long> must be large enough for common memory allocation sizes	5429	=item C<long> must be large enough for common memory allocation sizes
4537		5430
4538	To improve portability and simplify its API, libev uses C<long> internally	5431	To improve portability and simplify its API, libev uses C<long> internally
4539	instead of C<size_t> when allocating its data structures. On non-POSIX	5432	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4542	watchers.	5435	watchers.
4543		5436
4544	=item C<double> must hold a time value in seconds with enough accuracy	5437	=item C<double> must hold a time value in seconds with enough accuracy
4545		5438
4546	The type C<double> is used to represent timestamps. It is required to	5439	The type C<double> is used to represent timestamps. It is required to
4547	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5440	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4548	enough for at least into the year 4000. This requirement is fulfilled by	5441	good enough for at least into the year 4000 with millisecond accuracy
		5442	(the design goal for libev). This requirement is overfulfilled by
4549	implementations implementing IEEE 754, which is basically all existing	5443	implementations using IEEE 754, which is basically all existing ones.
		5444
4550	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5445	With IEEE 754 doubles, you get microsecond accuracy until at least the
4551	2200.	5446	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5447	is either obsolete or somebody patched it to use C<long double> or
		5448	something like that, just kidding).
4552		5449
4553	=back	5450	=back
4554		5451
4555	If you know of other additional requirements drop me a note.	5452	If you know of other additional requirements drop me a note.
4556		5453
…		…
4618	=item Processing ev_async_send: O(number_of_async_watchers)	5515	=item Processing ev_async_send: O(number_of_async_watchers)
4619		5516
4620	=item Processing signals: O(max_signal_number)	5517	=item Processing signals: O(max_signal_number)
4621		5518
4622	Sending involves a system call I<iff> there were no other C<ev_async_send>	5519	Sending involves a system call I<iff> there were no other C<ev_async_send>
4623	calls in the current loop iteration. Checking for async and signal events	5520	calls in the current loop iteration and the loop is currently
		5521	blocked. Checking for async and signal events involves iterating over all
4624	involves iterating over all running async watchers or all signal numbers.	5522	running async watchers or all signal numbers.
4625		5523
4626	=back	5524	=back
4627		5525
4628		5526
4629	=head1 PORTING FROM LIBEV 3.X TO 4.X	5527	=head1 PORTING FROM LIBEV 3.X TO 4.X
4630		5528
4631	The major version 4 introduced some minor incompatible changes to the API.	5529	The major version 4 introduced some incompatible changes to the API.
4632		5530
4633	At the moment, the C<ev.h> header file tries to implement superficial	5531	At the moment, the C<ev.h> header file provides compatibility definitions
4634	compatibility, so most programs should still compile. Those might be	5532	for all changes, so most programs should still compile. The compatibility
4635	removed in later versions of libev, so better update early than late.	5533	layer might be removed in later versions of libev, so better update to the
		5534	new API early than late.
4636		5535
4637	=over 4	5536	=over 4
4638		5537
4639	=item C<ev_loop_count> renamed to C<ev_iteration>	5538	=item C<EV_COMPAT3> backwards compatibility mechanism
4640		5539
4641	=item C<ev_loop_depth> renamed to C<ev_depth>	5540	The backward compatibility mechanism can be controlled by
		5541	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5542	section.
4642		5543
4643	=item C<ev_loop_verify> renamed to C<ev_verify>	5544	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5545
		5546	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5547
		5548	ev_loop_destroy (EV_DEFAULT_UC);
		5549	ev_loop_fork (EV_DEFAULT);
		5550
		5551	=item function/symbol renames
		5552
		5553	A number of functions and symbols have been renamed:
		5554
		5555	ev_loop => ev_run
		5556	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5557	EVLOOP_ONESHOT => EVRUN_ONCE
		5558
		5559	ev_unloop => ev_break
		5560	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5561	EVUNLOOP_ONE => EVBREAK_ONE
		5562	EVUNLOOP_ALL => EVBREAK_ALL
		5563
		5564	EV_TIMEOUT => EV_TIMER
		5565
		5566	ev_loop_count => ev_iteration
		5567	ev_loop_depth => ev_depth
		5568	ev_loop_verify => ev_verify
4644		5569
4645	Most functions working on C<struct ev_loop> objects don't have an	5570	Most functions working on C<struct ev_loop> objects don't have an
4646	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is	5571	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5572	associated constants have been renamed to not collide with the C<struct
		5573	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5574	as all other watcher types. Note that C<ev_loop_fork> is still called
4647	still called C<ev_loop_fork> because it would otherwise clash with the	5575	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4648	C<ev_fork> typedef.	5576	typedef.
4649
4650	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4651
4652	This is a simple rename - all other watcher types use their name
4653	as revents flag, and now C<ev_timer> does, too.
4654
4655	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4656	and continue to be present for the forseeable future, so this is mostly a
4657	documentation change.
4658		5577
4659	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5578	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4660		5579
4661	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5580	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4662	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5581	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4669		5588
4670	=over 4	5589	=over 4
4671		5590
4672	=item active	5591	=item active
4673		5592
4674	A watcher is active as long as it has been started (has been attached to	5593	A watcher is active as long as it has been started and not yet stopped.
4675	an event loop) but not yet stopped (disassociated from the event loop).	5594	See L</WATCHER STATES> for details.
4676		5595
4677	=item application	5596	=item application
4678		5597
4679	In this document, an application is whatever is using libev.	5598	In this document, an application is whatever is using libev.
		5599
		5600	=item backend
		5601
		5602	The part of the code dealing with the operating system interfaces.
4680		5603
4681	=item callback	5604	=item callback
4682		5605
4683	The address of a function that is called when some event has been	5606	The address of a function that is called when some event has been
4684	detected. Callbacks are being passed the event loop, the watcher that	5607	detected. Callbacks are being passed the event loop, the watcher that
4685	received the event, and the actual event bitset.	5608	received the event, and the actual event bitset.
4686		5609
4687	=item callback invocation	5610	=item callback/watcher invocation
4688		5611
4689	The act of calling the callback associated with a watcher.	5612	The act of calling the callback associated with a watcher.
4690		5613
4691	=item event	5614	=item event
4692		5615
…		…
4711	The model used to describe how an event loop handles and processes	5634	The model used to describe how an event loop handles and processes
4712	watchers and events.	5635	watchers and events.
4713		5636
4714	=item pending	5637	=item pending
4715		5638
4716	A watcher is pending as soon as the corresponding event has been detected,	5639	A watcher is pending as soon as the corresponding event has been
4717	and stops being pending as soon as the watcher will be invoked or its	5640	detected. See L</WATCHER STATES> for details.
4718	pending status is explicitly cleared by the application.
4719
4720	A watcher can be pending, but not active. Stopping a watcher also clears
4721	its pending status.
4722		5641
4723	=item real time	5642	=item real time
4724		5643
4725	The physical time that is observed. It is apparently strictly monotonic :)	5644	The physical time that is observed. It is apparently strictly monotonic :)
4726		5645
4727	=item wall-clock time	5646	=item wall-clock time
4728		5647
4729	The time and date as shown on clocks. Unlike real time, it can actually	5648	The time and date as shown on clocks. Unlike real time, it can actually
4730	be wrong and jump forwards and backwards, e.g. when the you adjust your	5649	be wrong and jump forwards and backwards, e.g. when you adjust your
4731	clock.	5650	clock.
4732		5651
4733	=item watcher	5652	=item watcher
4734		5653
4735	A data structure that describes interest in certain events. Watchers need	5654	A data structure that describes interest in certain events. Watchers need
4736	to be started (attached to an event loop) before they can receive events.	5655	to be started (attached to an event loop) before they can receive events.
4737		5656
4738	=item watcher invocation
4739
4740	The act of calling the callback associated with a watcher.
4741
4742	=back	5657	=back
4743		5658
4744	=head1 AUTHOR	5659	=head1 AUTHOR
4745		5660
4746	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5661	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5662	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4747		5663

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