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Revision 1.303 by root, Thu Oct 14 04:29:34 2010 UTC vs.
Revision 1.447 by root, Sat Jun 22 16:25:53 2019 UTC

		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
78	with libev.	80	with libev.
79		81
80	Familiarity 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.
82		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
		92
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
87	these event sources and provide your program with events.	97	these event sources and provide your program with events.
…		…
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) >>) event interface
		580	available in post-4.18 kernels.
		581
		582	If this backend works for you (as of this writing, it was very
		583	experimental and only supports a subset of file types), it is the best
		584	event interface available on linux and might be well worth it enabling it
		585	- if it isn't available in your kernel this will be detected and another
		586	backend will be chosen.
		587
		588	This backend can batch oneshot requests and uses a user-space ring buffer
		589	to receive events. It also doesn't suffer from most of the design problems
		590	of epoll (such as not being able to remove event sources from the epoll
		591	set), and generally sounds too good to be true. Because, this being the
		592	linux kernel, of course it suffers from a whole new set of limitations.
		593
		594	For one, it is not easily embeddable (but probably could be done using
		595	an event fd at some extra overhead). It also is subject to various
		596	arbitrary limits that can be configured in F</proc/sys/fs/aio-max-nr>
		597	and F</proc/sys/fs/aio-nr>), which could lead to it being skipped during
		598	initialisation.
		599
		600	Most problematic in practise, however, is that, like kqueue, it requires
		601	special support from drivers, and, not surprisingly, not all drivers
		602	implement it. For example, in linux 4.19, tcp sockets, pipes, event fds,
		603	files, F</dev/null> and a few others are supported, but ttys are not, so
		604	this is not (yet?) a generic event polling interface but is probably still
		605	be very useful in a web server or similar program.
467		606
468	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	607	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
469	C<EVBACKEND_POLL>.	608	C<EVBACKEND_POLL>.
470		609
471	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	610	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
…		…
486		625
487	It scales in the same way as the epoll backend, but the interface to the	626	It scales in the same way as the epoll backend, but the interface to the
488	kernel is more efficient (which says nothing about its actual speed, of	627	kernel is more efficient (which says nothing about its actual speed, of
489	course). While stopping, setting and starting an I/O watcher does never	628	course). While stopping, setting and starting an I/O watcher does never
490	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	629	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
491	two event changes per incident. Support for C<fork ()> is very bad (but	630	two event changes per incident. Support for C<fork ()> is very bad (you
492	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	631	might have to leak fd's on fork, but it's more sane than epoll) and it
493	cases	632	drops fds silently in similarly hard-to-detect cases.
494		633
495	This backend usually performs well under most conditions.	634	This backend usually performs well under most conditions.
496		635
497	While nominally embeddable in other event loops, this doesn't work	636	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	637	everywhere, so you might need to test for this. And since it is broken
…		…
515	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	654	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
516		655
517	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	656	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
518	it's really slow, but it still scales very well (O(active_fds)).	657	it's really slow, but it still scales very well (O(active_fds)).
519		658
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	659	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	660	file descriptor per loop iteration. For small and medium numbers of file
526	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	661	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
527	might perform better.	662	might perform better.
528		663
529	On the positive side, with the exception of the spurious readiness	664	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	665	specification in all tests and is fully embeddable, which is a rare feat
532	OS-specific backends (I vastly prefer correctness over speed hacks).	666	among the OS-specific backends (I vastly prefer correctness over speed
		667	hacks).
		668
		669	On the negative side, the interface is I<bizarre> - so bizarre that
		670	even sun itself gets it wrong in their code examples: The event polling
		671	function sometimes returns events to the caller even though an error
		672	occurred, but with no indication whether it has done so or not (yes, it's
		673	even documented that way) - deadly for edge-triggered interfaces where you
		674	absolutely have to know whether an event occurred or not because you have
		675	to re-arm the watcher.
		676
		677	Fortunately libev seems to be able to work around these idiocies.
533		678
534	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	679	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
535	C<EVBACKEND_POLL>.	680	C<EVBACKEND_POLL>.
536		681
537	=item C<EVBACKEND_ALL>	682	=item C<EVBACKEND_ALL>
538		683
539	Try all backends (even potentially broken ones that wouldn't be tried	684	Try all backends (even potentially broken ones that wouldn't be tried
540	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	685	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
541	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	686	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
542		687
543	It is definitely not recommended to use this flag.	688	It is definitely not recommended to use this flag, use whatever
		689	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		690	at all.
		691
		692	=item C<EVBACKEND_MASK>
		693
		694	Not a backend at all, but a mask to select all backend bits from a
		695	C<flags> value, in case you want to mask out any backends from a flags
		696	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
544		697
545	=back	698	=back
546		699
547	If one or more of the backend flags are or'ed into the flags value,	700	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	701	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	702	here). If none are specified, all backends in C<ev_recommended_backends
550	()> will be tried.	703	()> will be tried.
551		704
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.	705	Example: Try to create a event loop that uses epoll and nothing else.
579		706
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	707	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	708	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	709	fatal ("no epoll found here, maybe it hides under your chair");
583		710
		711	Example: Use whatever libev has to offer, but make sure that kqueue is
		712	used if available.
		713
		714	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		715
		716	Example: Similarly, on linux, you mgiht want to take advantage of the
		717	linux aio backend if possible, but fall back to something else if that
		718	isn't available.
		719
		720	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		721
584	=item ev_default_destroy ()	722	=item ev_loop_destroy (loop)
585		723
586	Destroys the default loop (frees all memory and kernel state etc.). None	724	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	725	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	726	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,	727	responsibility to either stop all watchers cleanly yourself I<before>
590	or cope with the fact afterwards (which is usually the easiest thing, you	728	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).	729	the easiest thing, you can just ignore the watchers and/or C<free ()> them
		730	for example).
592		731
593	Note that certain global state, such as signal state (and installed signal	732	Note that certain global state, such as signal state (and installed signal
594	handlers), will not be freed by this function, and related watchers (such	733	handlers), will not be freed by this function, and related watchers (such
595	as signal and child watchers) would need to be stopped manually.	734	as signal and child watchers) would need to be stopped manually.
596		735
597	In general it is not advisable to call this function except in the	736	This function is normally used on loop objects allocated by
598	rare occasion where you really need to free e.g. the signal handling	737	C<ev_loop_new>, but it can also be used on the default loop returned by
		738	C<ev_default_loop>, in which case it is not thread-safe.
		739
		740	Note that it is not advisable to call this function on the default loop
		741	except in the rare occasion where you really need to free its resources.
599	pipe fds. If you need dynamically allocated loops it is better to use	742	If you need dynamically allocated loops it is better to use C<ev_loop_new>
600	C<ev_loop_new> and C<ev_loop_destroy>.	743	and C<ev_loop_destroy>.
601		744
602	=item ev_loop_destroy (loop)	745	=item ev_loop_fork (loop)
603		746
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	747	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	748	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	749	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	750	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	751	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.	752	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
615		753
		754	In addition, if you want to reuse a loop (via this function or
		755	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		756
616	Again, you I<have> to call it on I<any> loop that you want to re-use after	757	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	758	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	759	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
619	during fork.	760	during fork.
620		761
621	On the other hand, you only need to call this function in the child	762	On the other hand, you only need to call this function in the child
622	process if and only if you want to use the event loop in the child. If you	763	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	764	you just fork+exec or create a new loop in the child, you don't have to
624	it at all.	765	call it at all (in fact, C<epoll> is so badly broken that it makes a
		766	difference, but libev will usually detect this case on its own and do a
		767	costly reset of the backend).
625		768
626	The function itself is quite fast and it's usually not a problem to call	769	The function itself is quite fast and it's usually not a problem to call
627	it just in case after a fork. To make this easy, the function will fit in	770	it just in case after a fork.
628	quite nicely into a call to C<pthread_atfork>:
629		771
		772	Example: Automate calling C<ev_loop_fork> on the default loop when
		773	using pthreads.
		774
		775	static void
		776	post_fork_child (void)
		777	{
		778	ev_loop_fork (EV_DEFAULT);
		779	}
		780
		781	...
630	pthread_atfork (0, 0, ev_default_fork);	782	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		783
639	=item int ev_is_default_loop (loop)	784	=item int ev_is_default_loop (loop)
640		785
641	Returns true when the given loop is, in fact, the default loop, and false	786	Returns true when the given loop is, in fact, the default loop, and false
642	otherwise.	787	otherwise.
643		788
644	=item unsigned int ev_iteration (loop)	789	=item unsigned int ev_iteration (loop)
645		790
646	Returns the current iteration count for the loop, which is identical to	791	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	792	to the number of times libev did poll for new events. It starts at C<0>
648	happily wraps around with enough iterations.	793	and happily wraps around with enough iterations.
649		794
650	This value can sometimes be useful as a generation counter of sorts (it	795	This value can sometimes be useful as a generation counter of sorts (it
651	"ticks" the number of loop iterations), as it roughly corresponds with	796	"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	797	C<ev_prepare> and C<ev_check> calls - and is incremented between the
653	prepare and check phases.	798	prepare and check phases.
654		799
655	=item unsigned int ev_depth (loop)	800	=item unsigned int ev_depth (loop)
656		801
657	Returns the number of times C<ev_loop> was entered minus the number of	802	Returns the number of times C<ev_run> was entered minus the number of
658	times C<ev_loop> was exited, in other words, the recursion depth.	803	times C<ev_run> was exited normally, in other words, the recursion depth.
659		804
660	Outside C<ev_loop>, this number is zero. In a callback, this number is	805	Outside C<ev_run>, this number is zero. In a callback, this number is
661	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	806	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
662	in which case it is higher.	807	in which case it is higher.
663		808
664	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	809	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	810	throwing an exception etc.), doesn't count as "exit" - consider this
666	ungentleman behaviour unless it's really convenient.	811	as a hint to avoid such ungentleman-like behaviour unless it's really
		812	convenient, in which case it is fully supported.
667		813
668	=item unsigned int ev_backend (loop)	814	=item unsigned int ev_backend (loop)
669		815
670	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	816	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
671	use.	817	use.
…		…
680		826
681	=item ev_now_update (loop)	827	=item ev_now_update (loop)
682		828
683	Establishes the current time by querying the kernel, updating the time	829	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	830	returned by C<ev_now ()> in the progress. This is a costly operation and
685	is usually done automatically within C<ev_loop ()>.	831	is usually done automatically within C<ev_run ()>.
686		832
687	This function is rarely useful, but when some event callback runs for a	833	This function is rarely useful, but when some event callback runs for a
688	very long time without entering the event loop, updating libev's idea of	834	very long time without entering the event loop, updating libev's idea of
689	the current time is a good idea.	835	the current time is a good idea.
690		836
691	See also L<The special problem of time updates> in the C<ev_timer> section.	837	See also L</The special problem of time updates> in the C<ev_timer> section.
692		838
693	=item ev_suspend (loop)	839	=item ev_suspend (loop)
694		840
695	=item ev_resume (loop)	841	=item ev_resume (loop)
696		842
697	These two functions suspend and resume a loop, for use when the loop is	843	These two functions suspend and resume an event loop, for use when the
698	not used for a while and timeouts should not be processed.	844	loop is not used for a while and timeouts should not be processed.
699		845
700	A typical use case would be an interactive program such as a game: When	846	A typical use case would be an interactive program such as a game: When
701	the user presses C<^Z> to suspend the game and resumes it an hour later it	847	the user presses C<^Z> to suspend the game and resumes it an hour later it
702	would be best to handle timeouts as if no time had actually passed while	848	would be best to handle timeouts as if no time had actually passed while
703	the program was suspended. This can be achieved by calling C<ev_suspend>	849	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
714	without a previous call to C<ev_suspend>.	860	without a previous call to C<ev_suspend>.
715		861
716	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	862	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
717	event loop time (see C<ev_now_update>).	863	event loop time (see C<ev_now_update>).
718		864
719	=item ev_loop (loop, int flags)	865	=item bool ev_run (loop, int flags)
720		866
721	Finally, this is it, the event handler. This function usually is called	867	Finally, this is it, the event handler. This function usually is called
722	after you have initialised all your watchers and you want to start	868	after you have initialised all your watchers and you want to start
723	handling events.	869	handling events. It will ask the operating system for any new events, call
		870	the watcher callbacks, and then repeat the whole process indefinitely: This
		871	is why event loops are called I<loops>.
724		872
725	If the flags argument is specified as C<0>, it will not return until	873	If the flags argument is specified as C<0>, it will keep handling events
726	either no event watchers are active anymore or C<ev_unloop> was called.	874	until either no event watchers are active anymore or C<ev_break> was
		875	called.
727		876
		877	The return value is false if there are no more active watchers (which
		878	usually means "all jobs done" or "deadlock"), and true in all other cases
		879	(which usually means " you should call C<ev_run> again").
		880
728	Please note that an explicit C<ev_unloop> is usually better than	881	Please note that an explicit C<ev_break> is usually better than
729	relying on all watchers to be stopped when deciding when a program has	882	relying on all watchers to be stopped when deciding when a program has
730	finished (especially in interactive programs), but having a program	883	finished (especially in interactive programs), but having a program
731	that automatically loops as long as it has to and no longer by virtue	884	that automatically loops as long as it has to and no longer by virtue
732	of relying on its watchers stopping correctly, that is truly a thing of	885	of relying on its watchers stopping correctly, that is truly a thing of
733	beauty.	886	beauty.
734		887
		888	This function is I<mostly> exception-safe - you can break out of a
		889	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		890	exception and so on. This does not decrement the C<ev_depth> value, nor
		891	will it clear any outstanding C<EVBREAK_ONE> breaks.
		892
735	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	893	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
736	those events and any already outstanding ones, but will not block your	894	those events and any already outstanding ones, but will not wait and
737	process in case there are no events and will return after one iteration of	895	block your process in case there are no events and will return after one
738	the loop.	896	iteration of the loop. This is sometimes useful to poll and handle new
		897	events while doing lengthy calculations, to keep the program responsive.
739		898
740	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	899	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
741	necessary) and will handle those and any already outstanding ones. It	900	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	901	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	902	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	903	user-registered callback will be called), and will return after one
745	iteration of the loop.	904	iteration of the loop.
746		905
747	This is useful if you are waiting for some external event in conjunction	906	This is useful if you are waiting for some external event in conjunction
748	with something not expressible using other libev watchers (i.e. "roll your	907	with something not expressible using other libev watchers (i.e. "roll your
749	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	908	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
750	usually a better approach for this kind of thing.	909	usually a better approach for this kind of thing.
751		910
752	Here are the gory details of what C<ev_loop> does:	911	Here are the gory details of what C<ev_run> does (this is for your
		912	understanding, not a guarantee that things will work exactly like this in
		913	future versions):
753		914
		915	- Increment loop depth.
		916	- Reset the ev_break status.
754	- Before the first iteration, call any pending watchers.	917	- Before the first iteration, call any pending watchers.
		918	LOOP:
755	* If EVFLAG_FORKCHECK was used, check for a fork.	919	- If EVFLAG_FORKCHECK was used, check for a fork.
756	- If a fork was detected (by any means), queue and call all fork watchers.	920	- If a fork was detected (by any means), queue and call all fork watchers.
757	- Queue and call all prepare watchers.	921	- Queue and call all prepare watchers.
		922	- If ev_break was called, goto FINISH.
758	- If we have been forked, detach and recreate the kernel state	923	- If we have been forked, detach and recreate the kernel state
759	as to not disturb the other process.	924	as to not disturb the other process.
760	- Update the kernel state with all outstanding changes.	925	- Update the kernel state with all outstanding changes.
761	- Update the "event loop time" (ev_now ()).	926	- Update the "event loop time" (ev_now ()).
762	- Calculate for how long to sleep or block, if at all	927	- Calculate for how long to sleep or block, if at all
763	(active idle watchers, EVLOOP_NONBLOCK or not having	928	(active idle watchers, EVRUN_NOWAIT or not having
764	any active watchers at all will result in not sleeping).	929	any active watchers at all will result in not sleeping).
765	- Sleep if the I/O and timer collect interval say so.	930	- Sleep if the I/O and timer collect interval say so.
		931	- Increment loop iteration counter.
766	- Block the process, waiting for any events.	932	- Block the process, waiting for any events.
767	- Queue all outstanding I/O (fd) events.	933	- Queue all outstanding I/O (fd) events.
768	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	934	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
769	- Queue all expired timers.	935	- Queue all expired timers.
770	- Queue all expired periodics.	936	- Queue all expired periodics.
771	- Unless any events are pending now, queue all idle watchers.	937	- Queue all idle watchers with priority higher than that of pending events.
772	- Queue all check watchers.	938	- Queue all check watchers.
773	- Call all queued watchers in reverse order (i.e. check watchers first).	939	- Call all queued watchers in reverse order (i.e. check watchers first).
774	Signals and child watchers are implemented as I/O watchers, and will	940	Signals and child watchers are implemented as I/O watchers, and will
775	be handled here by queueing them when their watcher gets executed.	941	be handled here by queueing them when their watcher gets executed.
776	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	942	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
777	were used, or there are no active watchers, return, otherwise	943	were used, or there are no active watchers, goto FINISH, otherwise
778	continue with step *.	944	continue with step LOOP.
		945	FINISH:
		946	- Reset the ev_break status iff it was EVBREAK_ONE.
		947	- Decrement the loop depth.
		948	- Return.
779		949
780	Example: Queue some jobs and then loop until no events are outstanding	950	Example: Queue some jobs and then loop until no events are outstanding
781	anymore.	951	anymore.
782		952
783	... queue jobs here, make sure they register event watchers as long	953	... 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..)	954	... as they still have work to do (even an idle watcher will do..)
785	ev_loop (my_loop, 0);	955	ev_run (my_loop, 0);
786	... jobs done or somebody called unloop. yeah!	956	... jobs done or somebody called break. yeah!
787		957
788	=item ev_unloop (loop, how)	958	=item ev_break (loop, how)
789		959
790	Can be used to make a call to C<ev_loop> return early (but only after it	960	Can be used to make a call to C<ev_run> return early (but only after it
791	has processed all outstanding events). The C<how> argument must be either	961	has processed all outstanding events). The C<how> argument must be either
792	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	962	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
793	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	963	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
794		964
795	This "unloop state" will be cleared when entering C<ev_loop> again.	965	This "break state" will be cleared on the next call to C<ev_run>.
796		966
797	It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.	967	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		968	which case it will have no effect.
798		969
799	=item ev_ref (loop)	970	=item ev_ref (loop)
800		971
801	=item ev_unref (loop)	972	=item ev_unref (loop)
802		973
803	Ref/unref can be used to add or remove a reference count on the event	974	Ref/unref can be used to add or remove a reference count on the event
804	loop: Every watcher keeps one reference, and as long as the reference	975	loop: Every watcher keeps one reference, and as long as the reference
805	count is nonzero, C<ev_loop> will not return on its own.	976	count is nonzero, C<ev_run> will not return on its own.
806		977
807	This is useful when you have a watcher that you never intend to	978	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	979	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>	980	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
810	before stopping it.	981	before stopping it.
811		982
812	As an example, libev itself uses this for its internal signal pipe: It	983	As an example, libev itself uses this for its internal signal pipe: It
813	is not visible to the libev user and should not keep C<ev_loop> from	984	is not visible to the libev user and should not keep C<ev_run> from
814	exiting if no event watchers registered by it are active. It is also an	985	exiting if no event watchers registered by it are active. It is also an
815	excellent way to do this for generic recurring timers or from within	986	excellent way to do this for generic recurring timers or from within
816	third-party libraries. Just remember to I<unref after start> and I<ref	987	third-party libraries. Just remember to I<unref after start> and I<ref
817	before stop> (but only if the watcher wasn't active before, or was active	988	before stop> (but only if the watcher wasn't active before, or was active
818	before, respectively. Note also that libev might stop watchers itself	989	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>	990	(e.g. non-repeating timers) in which case you have to C<ev_ref>
820	in the callback).	991	in the callback).
821		992
822	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	993	Example: Create a signal watcher, but keep it from keeping C<ev_run>
823	running when nothing else is active.	994	running when nothing else is active.
824		995
825	ev_signal exitsig;	996	ev_signal exitsig;
826	ev_signal_init (&exitsig, sig_cb, SIGINT);	997	ev_signal_init (&exitsig, sig_cb, SIGINT);
827	ev_signal_start (loop, &exitsig);	998	ev_signal_start (loop, &exitsig);
828	evf_unref (loop);	999	ev_unref (loop);
829		1000
830	Example: For some weird reason, unregister the above signal handler again.	1001	Example: For some weird reason, unregister the above signal handler again.
831		1002
832	ev_ref (loop);	1003	ev_ref (loop);
833	ev_signal_stop (loop, &exitsig);	1004	ev_signal_stop (loop, &exitsig);
…		…
853	overhead for the actual polling but can deliver many events at once.	1024	overhead for the actual polling but can deliver many events at once.
854		1025
855	By setting a higher I<io collect interval> you allow libev to spend more	1026	By setting a higher I<io collect interval> you allow libev to spend more
856	time collecting I/O events, so you can handle more events per iteration,	1027	time collecting I/O events, so you can handle more events per iteration,
857	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1028	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
858	C<ev_timer>) will be not affected. Setting this to a non-null value will	1029	C<ev_timer>) will not be affected. Setting this to a non-null value will
859	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1030	introduce an additional C<ev_sleep ()> call into most loop iterations. The
860	sleep time ensures that libev will not poll for I/O events more often then	1031	sleep time ensures that libev will not poll for I/O events more often then
861	once per this interval, on average.	1032	once per this interval, on average (as long as the host time resolution is
		1033	good enough).
862		1034
863	Likewise, by setting a higher I<timeout collect interval> you allow libev	1035	Likewise, by setting a higher I<timeout collect interval> you allow libev
864	to spend more time collecting timeouts, at the expense of increased	1036	to spend more time collecting timeouts, at the expense of increased
865	latency/jitter/inexactness (the watcher callback will be called	1037	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	1038	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
890	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1062	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
891		1063
892	=item ev_invoke_pending (loop)	1064	=item ev_invoke_pending (loop)
893		1065
894	This call will simply invoke all pending watchers while resetting their	1066	This call will simply invoke all pending watchers while resetting their
895	pending state. Normally, C<ev_loop> does this automatically when required,	1067	pending state. Normally, C<ev_run> does this automatically when required,
896	but when overriding the invoke callback this call comes handy.	1068	but when overriding the invoke callback this call comes handy. This
		1069	function can be invoked from a watcher - this can be useful for example
		1070	when you want to do some lengthy calculation and want to pass further
		1071	event handling to another thread (you still have to make sure only one
		1072	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
897		1073
898	=item int ev_pending_count (loop)	1074	=item int ev_pending_count (loop)
899		1075
900	Returns the number of pending watchers - zero indicates that no watchers	1076	Returns the number of pending watchers - zero indicates that no watchers
901	are pending.	1077	are pending.
902		1078
903	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1079	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
904		1080
905	This overrides the invoke pending functionality of the loop: Instead of	1081	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	1082	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	1083	this callback instead. This is useful, for example, when you want to
908	invoke the actual watchers inside another context (another thread etc.).	1084	invoke the actual watchers inside another context (another thread etc.).
909		1085
910	If you want to reset the callback, use C<ev_invoke_pending> as new	1086	If you want to reset the callback, use C<ev_invoke_pending> as new
911	callback.	1087	callback.
912		1088
913	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1089	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
914		1090
915	Sometimes you want to share the same loop between multiple threads. This	1091	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	1092	can be done relatively simply by putting mutex_lock/unlock calls around
917	each call to a libev function.	1093	each call to a libev function.
918		1094
919	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1095	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	1096	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>	1097	loop via C<ev_break> and C<ev_async_send>, another way is to set these
922	and I<acquire> callbacks on the loop.	1098	I<release> and I<acquire> callbacks on the loop.
923		1099
924	When set, then C<release> will be called just before the thread is	1100	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	1101	suspended waiting for new events, and C<acquire> is called just
926	afterwards.	1102	afterwards.
927		1103
…		…
930		1106
931	While event loop modifications are allowed between invocations of	1107	While event loop modifications are allowed between invocations of
932	C<release> and C<acquire> (that's their only purpose after all), no	1108	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	1109	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	1110	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	1111	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.	1112	to take note of any changes you made.
937		1113
938	In theory, threads executing C<ev_loop> will be async-cancel safe between	1114	In theory, threads executing C<ev_run> will be async-cancel safe between
939	invocations of C<release> and C<acquire>.	1115	invocations of C<release> and C<acquire>.
940		1116
941	See also the locking example in the C<THREADS> section later in this	1117	See also the locking example in the C<THREADS> section later in this
942	document.	1118	document.
943		1119
944	=item ev_set_userdata (loop, void *data)	1120	=item ev_set_userdata (loop, void *data)
945		1121
946	=item ev_userdata (loop)	1122	=item void *ev_userdata (loop)
947		1123
948	Set and retrieve a single C<void *> associated with a loop. When	1124	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	1125	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
950	C<0.>	1126	C<0>.
951		1127
952	These two functions can be used to associate arbitrary data with a loop,	1128	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	1129	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	1130	C<acquire> callbacks described above, but of course can be (ab-)used for
955	any other purpose as well.	1131	any other purpose as well.
956		1132
957	=item ev_loop_verify (loop)	1133	=item ev_verify (loop)
958		1134
959	This function only does something when C<EV_VERIFY> support has been	1135	This function only does something when C<EV_VERIFY> support has been
960	compiled in, which is the default for non-minimal builds. It tries to go	1136	compiled in, which is the default for non-minimal builds. It tries to go
961	through all internal structures and checks them for validity. If anything	1137	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	1138	is found to be inconsistent, it will print an error message to standard
…		…
973		1149
974	In the following description, uppercase C<TYPE> in names stands for the	1150	In the following description, uppercase C<TYPE> in names stands for the
975	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1151	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
976	watchers and C<ev_io_start> for I/O watchers.	1152	watchers and C<ev_io_start> for I/O watchers.
977		1153
978	A watcher is a structure that you create and register to record your	1154	A watcher is an opaque structure that you allocate and register to record
979	interest in some event. For instance, if you want to wait for STDIN to	1155	your interest in some event. To make a concrete example, imagine you want
980	become readable, you would create an C<ev_io> watcher for that:	1156	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1157	for that:
981		1158
982	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1159	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
983	{	1160	{
984	ev_io_stop (w);	1161	ev_io_stop (w);
985	ev_unloop (loop, EVUNLOOP_ALL);	1162	ev_break (loop, EVBREAK_ALL);
986	}	1163	}
987		1164
988	struct ev_loop *loop = ev_default_loop (0);	1165	struct ev_loop *loop = ev_default_loop (0);
989		1166
990	ev_io stdin_watcher;	1167	ev_io stdin_watcher;
991		1168
992	ev_init (&stdin_watcher, my_cb);	1169	ev_init (&stdin_watcher, my_cb);
993	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1170	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
994	ev_io_start (loop, &stdin_watcher);	1171	ev_io_start (loop, &stdin_watcher);
995		1172
996	ev_loop (loop, 0);	1173	ev_run (loop, 0);
997		1174
998	As you can see, you are responsible for allocating the memory for your	1175	As you can see, you are responsible for allocating the memory for your
999	watcher structures (and it is I<usually> a bad idea to do this on the	1176	watcher structures (and it is I<usually> a bad idea to do this on the
1000	stack).	1177	stack).
1001		1178
1002	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1179	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
1003	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1180	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
1004		1181
1005	Each watcher structure must be initialised by a call to C<ev_init	1182	Each watcher structure must be initialised by a call to C<ev_init (watcher
1006	(watcher *, callback)>, which expects a callback to be provided. This	1183	*, 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	1184	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	1185	time the event loop detects that the file descriptor given is readable
1009	is readable and/or writable).	1186	and/or writable).
1010		1187
1011	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1188	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1012	macro to configure it, with arguments specific to the watcher type. There	1189	macro to configure it, with arguments specific to the watcher type. There
1013	is also a macro to combine initialisation and setting in one call: C<<	1190	is also a macro to combine initialisation and setting in one call: C<<
1014	ev_TYPE_init (watcher *, callback, ...) >>.	1191	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1065		1242
1066	=item C<EV_PREPARE>	1243	=item C<EV_PREPARE>
1067		1244
1068	=item C<EV_CHECK>	1245	=item C<EV_CHECK>
1069		1246
1070	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1247	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1071	to gather new events, and all C<ev_check> watchers are invoked just after	1248	gather new events, and all C<ev_check> watchers are queued (not invoked)
1072	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1249	just after C<ev_run> has gathered them, but before it queues any callbacks
		1250	for any received events. That means C<ev_prepare> watchers are the last
		1251	watchers invoked before the event loop sleeps or polls for new events, and
		1252	C<ev_check> watchers will be invoked before any other watchers of the same
		1253	or lower priority within an event loop iteration.
		1254
1073	received events. Callbacks of both watcher types can start and stop as	1255	Callbacks of both watcher types can start and stop as many watchers as
1074	many watchers as they want, and all of them will be taken into account	1256	they want, and all of them will be taken into account (for example, a
1075	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1257	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1076	C<ev_loop> from blocking).	1258	blocking).
1077		1259
1078	=item C<EV_EMBED>	1260	=item C<EV_EMBED>
1079		1261
1080	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1262	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1081		1263
1082	=item C<EV_FORK>	1264	=item C<EV_FORK>
1083		1265
1084	The event loop has been resumed in the child process after fork (see	1266	The event loop has been resumed in the child process after fork (see
1085	C<ev_fork>).	1267	C<ev_fork>).
		1268
		1269	=item C<EV_CLEANUP>
		1270
		1271	The event loop is about to be destroyed (see C<ev_cleanup>).
1086		1272
1087	=item C<EV_ASYNC>	1273	=item C<EV_ASYNC>
1088		1274
1089	The given async watcher has been asynchronously notified (see C<ev_async>).	1275	The given async watcher has been asynchronously notified (see C<ev_async>).
1090		1276
…		…
1200		1386
1201	=item callback ev_cb (ev_TYPE *watcher)	1387	=item callback ev_cb (ev_TYPE *watcher)
1202		1388
1203	Returns the callback currently set on the watcher.	1389	Returns the callback currently set on the watcher.
1204		1390
1205	=item ev_cb_set (ev_TYPE *watcher, callback)	1391	=item ev_set_cb (ev_TYPE *watcher, callback)
1206		1392
1207	Change the callback. You can change the callback at virtually any time	1393	Change the callback. You can change the callback at virtually any time
1208	(modulo threads).	1394	(modulo threads).
1209		1395
1210	=item ev_set_priority (ev_TYPE *watcher, int priority)	1396	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1228	or might not have been clamped to the valid range.	1414	or might not have been clamped to the valid range.
1229		1415
1230	The default priority used by watchers when no priority has been set is	1416	The default priority used by watchers when no priority has been set is
1231	always C<0>, which is supposed to not be too high and not be too low :).	1417	always C<0>, which is supposed to not be too high and not be too low :).
1232		1418
1233	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1419	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1234	priorities.	1420	priorities.
1235		1421
1236	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1422	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1237		1423
1238	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1424	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1263	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1449	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1264	functions that do not need a watcher.	1450	functions that do not need a watcher.
1265		1451
1266	=back	1452	=back
1267		1453
		1454	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1455	OWN COMPOSITE WATCHERS> idioms.
1268		1456
1269	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1457	=head2 WATCHER STATES
1270		1458
1271	Each watcher has, by default, a member C<void *data> that you can change	1459	There are various watcher states mentioned throughout this manual -
1272	and read at any time: libev will completely ignore it. This can be used	1460	active, pending and so on. In this section these states and the rules to
1273	to associate arbitrary data with your watcher. If you need more data and	1461	transition between them will be described in more detail - and while these
1274	don't want to allocate memory and store a pointer to it in that data	1462	rules might look complicated, they usually do "the right thing".
1275	member, you can also "subclass" the watcher type and provide your own
1276	data:
1277		1463
1278	struct my_io	1464	=over 4
1279	{
1280	ev_io io;
1281	int otherfd;
1282	void *somedata;
1283	struct whatever *mostinteresting;
1284	};
1285		1465
1286	...	1466	=item initialised
1287	struct my_io w;
1288	ev_io_init (&w.io, my_cb, fd, EV_READ);
1289		1467
1290	And since your callback will be called with a pointer to the watcher, you	1468	Before a watcher can be registered with the event loop it has to be
1291	can cast it back to your own type:	1469	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1470	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1292		1471
1293	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1472	In this state it is simply some block of memory that is suitable for
1294	{	1473	use in an event loop. It can be moved around, freed, reused etc. at
1295	struct my_io *w = (struct my_io *)w_;	1474	will - as long as you either keep the memory contents intact, or call
1296	...	1475	C<ev_TYPE_init> again.
1297	}
1298		1476
1299	More interesting and less C-conformant ways of casting your callback type	1477	=item started/running/active
1300	instead have been omitted.
1301		1478
1302	Another common scenario is to use some data structure with multiple	1479	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1303	embedded watchers:	1480	property of the event loop, and is actively waiting for events. While in
		1481	this state it cannot be accessed (except in a few documented ways), moved,
		1482	freed or anything else - the only legal thing is to keep a pointer to it,
		1483	and call libev functions on it that are documented to work on active watchers.
1304		1484
1305	struct my_biggy	1485	=item pending
1306	{
1307	int some_data;
1308	ev_timer t1;
1309	ev_timer t2;
1310	}
1311		1486
1312	In this case getting the pointer to C<my_biggy> is a bit more	1487	If a watcher is active and libev determines that an event it is interested
1313	complicated: Either you store the address of your C<my_biggy> struct	1488	in has occurred (such as a timer expiring), it will become pending. It will
1314	in the C<data> member of the watcher (for woozies), or you need to use	1489	stay in this pending state until either it is stopped or its callback is
1315	some pointer arithmetic using C<offsetof> inside your watchers (for real	1490	about to be invoked, so it is not normally pending inside the watcher
1316	programmers):	1491	callback.
1317		1492
1318	#include <stddef.h>	1493	The watcher might or might not be active while it is pending (for example,
		1494	an expired non-repeating timer can be pending but no longer active). If it
		1495	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1496	but it is still property of the event loop at this time, so cannot be
		1497	moved, freed or reused. And if it is active the rules described in the
		1498	previous item still apply.
1319		1499
1320	static void	1500	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)	1501	via C<ev_feed_event>), in which case it becomes pending without being
1322	{	1502	active.
1323	struct my_biggy big = (struct my_biggy *)
1324	(((char *)w) - offsetof (struct my_biggy, t1));
1325	}
1326		1503
1327	static void	1504	=item stopped
1328	t2_cb (EV_P_ ev_timer *w, int revents)	1505
1329	{	1506	A watcher can be stopped implicitly by libev (in which case it might still
1330	struct my_biggy big = (struct my_biggy *)	1507	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1331	(((char *)w) - offsetof (struct my_biggy, t2));	1508	latter will clear any pending state the watcher might be in, regardless
1332	}	1509	of whether it was active or not, so stopping a watcher explicitly before
		1510	freeing it is often a good idea.
		1511
		1512	While stopped (and not pending) the watcher is essentially in the
		1513	initialised state, that is, it can be reused, moved, modified in any way
		1514	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1515	it again).
		1516
		1517	=back
1333		1518
1334	=head2 WATCHER PRIORITY MODELS	1519	=head2 WATCHER PRIORITY MODELS
1335		1520
1336	Many event loops support I<watcher priorities>, which are usually small	1521	Many event loops support I<watcher priorities>, which are usually small
1337	integers that influence the ordering of event callback invocation	1522	integers that influence the ordering of event callback invocation
…		…
1464	In general you can register as many read and/or write event watchers per	1649	In general you can register as many read and/or write event watchers per
1465	fd as you want (as long as you don't confuse yourself). Setting all file	1650	fd as you want (as long as you don't confuse yourself). Setting all file
1466	descriptors to non-blocking mode is also usually a good idea (but not	1651	descriptors to non-blocking mode is also usually a good idea (but not
1467	required if you know what you are doing).	1652	required if you know what you are doing).
1468		1653
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 guarantee any specific behaviour in that case.
1474
1475	Another thing you have to watch out for is that it is quite easy to	1654	Another thing you have to watch out for is that it is quite easy to
1476	receive "spurious" readiness notifications, that is your callback might	1655	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	1656	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	1657	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	1658	with a relatively standard program structure. Thus it is best to always
1480	this situation even with a relatively standard program structure. Thus	1659	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
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.	1660	preferable to a program hanging until some data arrives.
1483		1661
1484	If you cannot run the fd in non-blocking mode (for example you should	1662	If you cannot run the fd in non-blocking mode (for example you should
1485	not play around with an Xlib connection), then you have to separately	1663	not play around with an Xlib connection), then you have to separately
1486	re-test whether a file descriptor is really ready with a known-to-be good	1664	re-test whether a file descriptor is really ready with a known-to-be good
1487	interface such as poll (fortunately in our Xlib example, Xlib already	1665	interface such as poll (fortunately in the case of Xlib, it already does
1488	does this on its own, so its quite safe to use). Some people additionally	1666	this on its own, so its quite safe to use). Some people additionally
1489	use C<SIGALRM> and an interval timer, just to be sure you won't block	1667	use C<SIGALRM> and an interval timer, just to be sure you won't block
1490	indefinitely.	1668	indefinitely.
1491		1669
1492	But really, best use non-blocking mode.	1670	But really, best use non-blocking mode.
1493		1671
1494	=head3 The special problem of disappearing file descriptors	1672	=head3 The special problem of disappearing file descriptors
1495		1673
1496	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1674	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1497	descriptor (either due to calling C<close> explicitly or any other means,	1675	a file descriptor (either due to calling C<close> explicitly or any other
1498	such as C<dup2>). The reason is that you register interest in some file	1676	means, such as C<dup2>). The reason is that you register interest in some
1499	descriptor, but when it goes away, the operating system will silently drop	1677	file descriptor, but when it goes away, the operating system will silently
1500	this interest. If another file descriptor with the same number then is	1678	drop this interest. If another file descriptor with the same number then
1501	registered with libev, there is no efficient way to see that this is, in	1679	is registered with libev, there is no efficient way to see that this is,
1502	fact, a different file descriptor.	1680	in fact, a different file descriptor.
1503		1681
1504	To avoid having to explicitly tell libev about such cases, libev follows	1682	To avoid having to explicitly tell libev about such cases, libev follows
1505	the following policy: Each time C<ev_io_set> is being called, libev	1683	the following policy: Each time C<ev_io_set> is being called, libev
1506	will assume that this is potentially a new file descriptor, otherwise	1684	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	1685	it is assumed that the file descriptor stays the same. That means that
…		…
1521		1699
1522	There is no workaround possible except not registering events	1700	There is no workaround possible except not registering events
1523	for potentially C<dup ()>'ed file descriptors, or to resort to	1701	for potentially C<dup ()>'ed file descriptors, or to resort to
1524	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1702	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1525		1703
		1704	=head3 The special problem of files
		1705
		1706	Many people try to use C<select> (or libev) on file descriptors
		1707	representing files, and expect it to become ready when their program
		1708	doesn't block on disk accesses (which can take a long time on their own).
		1709
		1710	However, this cannot ever work in the "expected" way - you get a readiness
		1711	notification as soon as the kernel knows whether and how much data is
		1712	there, and in the case of open files, that's always the case, so you
		1713	always get a readiness notification instantly, and your read (or possibly
		1714	write) will still block on the disk I/O.
		1715
		1716	Another way to view it is that in the case of sockets, pipes, character
		1717	devices and so on, there is another party (the sender) that delivers data
		1718	on its own, but in the case of files, there is no such thing: the disk
		1719	will not send data on its own, simply because it doesn't know what you
		1720	wish to read - you would first have to request some data.
		1721
		1722	Since files are typically not-so-well supported by advanced notification
		1723	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1724	to files, even though you should not use it. The reason for this is
		1725	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1726	usually a tty, often a pipe, but also sometimes files or special devices
		1727	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1728	F</dev/urandom>), and even though the file might better be served with
		1729	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1730	it "just works" instead of freezing.
		1731
		1732	So avoid file descriptors pointing to files when you know it (e.g. use
		1733	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1734	when you rarely read from a file instead of from a socket, and want to
		1735	reuse the same code path.
		1736
1526	=head3 The special problem of fork	1737	=head3 The special problem of fork
1527		1738
1528	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1739	Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()>
1529	useless behaviour. Libev fully supports fork, but needs to be told about	1740	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1530	it in the child.	1741	to be told about it in the child if you want to continue to use it in the
		1742	child.
1531		1743
1532	To support fork in your programs, you either have to call	1744	To support fork in your child processes, you have to call C<ev_loop_fork
1533	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1745	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1534	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1746	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1535	C<EVBACKEND_POLL>.
1536		1747
1537	=head3 The special problem of SIGPIPE	1748	=head3 The special problem of SIGPIPE
1538		1749
1539	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1750	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1540	when writing to a pipe whose other end has been closed, your program gets	1751	when writing to a pipe whose other end has been closed, your program gets
…		…
1622	...	1833	...
1623	struct ev_loop *loop = ev_default_init (0);	1834	struct ev_loop *loop = ev_default_init (0);
1624	ev_io stdin_readable;	1835	ev_io stdin_readable;
1625	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1836	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1626	ev_io_start (loop, &stdin_readable);	1837	ev_io_start (loop, &stdin_readable);
1627	ev_loop (loop, 0);	1838	ev_run (loop, 0);
1628		1839
1629		1840
1630	=head2 C<ev_timer> - relative and optionally repeating timeouts	1841	=head2 C<ev_timer> - relative and optionally repeating timeouts
1631		1842
1632	Timer watchers are simple relative timers that generate an event after a	1843	Timer watchers are simple relative timers that generate an event after a
…		…
1638	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1849	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1639	monotonic clock option helps a lot here).	1850	monotonic clock option helps a lot here).
1640		1851
1641	The callback is guaranteed to be invoked only I<after> its timeout has	1852	The callback is guaranteed to be invoked only I<after> its timeout has
1642	passed (not I<at>, so on systems with very low-resolution clocks this	1853	passed (not I<at>, so on systems with very low-resolution clocks this
1643	might introduce a small delay). If multiple timers become ready during the	1854	might introduce a small delay, see "the special problem of being too
		1855	early", below). If multiple timers become ready during the same loop
1644	same loop iteration then the ones with earlier time-out values are invoked	1856	iteration then the ones with earlier time-out values are invoked before
1645	before ones of the same priority with later time-out values (but this is	1857	ones of the same priority with later time-out values (but this is no
1646	no longer true when a callback calls C<ev_loop> recursively).	1858	longer true when a callback calls C<ev_run> recursively).
1647		1859
1648	=head3 Be smart about timeouts	1860	=head3 Be smart about timeouts
1649		1861
1650	Many real-world problems involve some kind of timeout, usually for error	1862	Many real-world problems involve some kind of timeout, usually for error
1651	recovery. A typical example is an HTTP request - if the other side hangs,	1863	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1726		1938
1727	In this case, it would be more efficient to leave the C<ev_timer> alone,	1939	In this case, it would be more efficient to leave the C<ev_timer> alone,
1728	but remember the time of last activity, and check for a real timeout only	1940	but remember the time of last activity, and check for a real timeout only
1729	within the callback:	1941	within the callback:
1730		1942
		1943	ev_tstamp timeout = 60.;
1731	ev_tstamp last_activity; // time of last activity	1944	ev_tstamp last_activity; // time of last activity
		1945	ev_timer timer;
1732		1946
1733	static void	1947	static void
1734	callback (EV_P_ ev_timer *w, int revents)	1948	callback (EV_P_ ev_timer *w, int revents)
1735	{	1949	{
1736	ev_tstamp now = ev_now (EV_A);	1950	// calculate when the timeout would happen
1737	ev_tstamp timeout = last_activity + 60.;	1951	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1738		1952
1739	// if last_activity + 60. is older than now, we did time out	1953	// if negative, it means we the timeout already occurred
1740	if (timeout < now)	1954	if (after < 0.)
1741	{	1955	{
1742	// timeout occurred, take action	1956	// timeout occurred, take action
1743	}	1957	}
1744	else	1958	else
1745	{	1959	{
1746	// callback was invoked, but there was some activity, re-arm	1960	// callback was invoked, but there was some recent
1747	// the watcher to fire in last_activity + 60, which is	1961	// activity. simply restart the timer to time out
1748	// guaranteed to be in the future, so "again" is positive:	1962	// after "after" seconds, which is the earliest time
1749	w->repeat = timeout - now;	1963	// the timeout can occur.
		1964	ev_timer_set (w, after, 0.);
1750	ev_timer_again (EV_A_ w);	1965	ev_timer_start (EV_A_ w);
1751	}	1966	}
1752	}	1967	}
1753		1968
1754	To summarise the callback: first calculate the real timeout (defined	1969	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	1970	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	1971	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	1972	(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		1973
1761	Note how C<ev_timer_again> is used, taking advantage of the	1974	If this value is negative, then we are already past the timeout, i.e. we
1762	C<ev_timer_again> optimisation when the timer is already running.	1975	timed out, and need to do whatever is needed in this case.
		1976
		1977	Otherwise, we now the earliest time at which the timeout would trigger,
		1978	and simply start the timer with this timeout value.
		1979
		1980	In other words, each time the callback is invoked it will check whether
		1981	the timeout occurred. If not, it will simply reschedule itself to check
		1982	again at the earliest time it could time out. Rinse. Repeat.
1763		1983
1764	This scheme causes more callback invocations (about one every 60 seconds	1984	This scheme causes more callback invocations (about one every 60 seconds
1765	minus half the average time between activity), but virtually no calls to	1985	minus half the average time between activity), but virtually no calls to
1766	libev to change the timeout.	1986	libev to change the timeout.
1767		1987
1768	To start the timer, simply initialise the watcher and set C<last_activity>	1988	To start the machinery, simply initialise the watcher and set
1769	to the current time (meaning we just have some activity :), then call the	1989	C<last_activity> to the current time (meaning there was some activity just
1770	callback, which will "do the right thing" and start the timer:	1990	now), then call the callback, which will "do the right thing" and start
		1991	the timer:
1771		1992
		1993	last_activity = ev_now (EV_A);
1772	ev_init (timer, callback);	1994	ev_init (&timer, callback);
1773	last_activity = ev_now (loop);	1995	callback (EV_A_ &timer, 0);
1774	callback (loop, timer, EV_TIMER);
1775		1996
1776	And when there is some activity, simply store the current time in	1997	When there is some activity, simply store the current time in
1777	C<last_activity>, no libev calls at all:	1998	C<last_activity>, no libev calls at all:
1778		1999
		2000	if (activity detected)
1779	last_activity = ev_now (loop);	2001	last_activity = ev_now (EV_A);
		2002
		2003	When your timeout value changes, then the timeout can be changed by simply
		2004	providing a new value, stopping the timer and calling the callback, which
		2005	will again do the right thing (for example, time out immediately :).
		2006
		2007	timeout = new_value;
		2008	ev_timer_stop (EV_A_ &timer);
		2009	callback (EV_A_ &timer, 0);
1780		2010
1781	This technique is slightly more complex, but in most cases where the	2011	This technique is slightly more complex, but in most cases where the
1782	time-out is unlikely to be triggered, much more efficient.	2012	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		2013
1788	=item 4. Wee, just use a double-linked list for your timeouts.	2014	=item 4. Wee, just use a double-linked list for your timeouts.
1789		2015
1790	If there is not one request, but many thousands (millions...), all	2016	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	2017	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	2044	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	2045	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	2046	off after the first million or so of active timers, i.e. it's usually
1821	overkill :)	2047	overkill :)
1822		2048
		2049	=head3 The special problem of being too early
		2050
		2051	If you ask a timer to call your callback after three seconds, then
		2052	you expect it to be invoked after three seconds - but of course, this
		2053	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2054	guaranteed to any precision by libev - imagine somebody suspending the
		2055	process with a STOP signal for a few hours for example.
		2056
		2057	So, libev tries to invoke your callback as soon as possible I<after> the
		2058	delay has occurred, but cannot guarantee this.
		2059
		2060	A less obvious failure mode is calling your callback too early: many event
		2061	loops compare timestamps with a "elapsed delay >= requested delay", but
		2062	this can cause your callback to be invoked much earlier than you would
		2063	expect.
		2064
		2065	To see why, imagine a system with a clock that only offers full second
		2066	resolution (think windows if you can't come up with a broken enough OS
		2067	yourself). If you schedule a one-second timer at the time 500.9, then the
		2068	event loop will schedule your timeout to elapse at a system time of 500
		2069	(500.9 truncated to the resolution) + 1, or 501.
		2070
		2071	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2072	501" and invoke the callback 0.1s after it was started, even though a
		2073	one-second delay was requested - this is being "too early", despite best
		2074	intentions.
		2075
		2076	This is the reason why libev will never invoke the callback if the elapsed
		2077	delay equals the requested delay, but only when the elapsed delay is
		2078	larger than the requested delay. In the example above, libev would only invoke
		2079	the callback at system time 502, or 1.1s after the timer was started.
		2080
		2081	So, while libev cannot guarantee that your callback will be invoked
		2082	exactly when requested, it I<can> and I<does> guarantee that the requested
		2083	delay has actually elapsed, or in other words, it always errs on the "too
		2084	late" side of things.
		2085
1823	=head3 The special problem of time updates	2086	=head3 The special problem of time updates
1824		2087
1825	Establishing the current time is a costly operation (it usually takes at	2088	Establishing the current time is a costly operation (it usually takes
1826	least two system calls): EV therefore updates its idea of the current	2089	at least one system call): EV therefore updates its idea of the current
1827	time only before and after C<ev_loop> collects new events, which causes a	2090	time only before and after C<ev_run> collects new events, which causes a
1828	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2091	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1829	lots of events in one iteration.	2092	lots of events in one iteration.
1830		2093
1831	The relative timeouts are calculated relative to the C<ev_now ()>	2094	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	2095	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	2096	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	2097	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:	2098	timeout on the current time, use something like the following to adjust
		2099	for it:
1836		2100
1837	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2101	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1838		2102
1839	If the event loop is suspended for a long time, you can also force an	2103	If the event loop is suspended for a long time, you can also force an
1840	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2104	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1841	()>.	2105	()>, although that will push the event time of all outstanding events
		2106	further into the future.
		2107
		2108	=head3 The special problem of unsynchronised clocks
		2109
		2110	Modern systems have a variety of clocks - libev itself uses the normal
		2111	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2112	jumps).
		2113
		2114	Neither of these clocks is synchronised with each other or any other clock
		2115	on the system, so C<ev_time ()> might return a considerably different time
		2116	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2117	a call to C<gettimeofday> might return a second count that is one higher
		2118	than a directly following call to C<time>.
		2119
		2120	The moral of this is to only compare libev-related timestamps with
		2121	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2122	a second or so.
		2123
		2124	One more problem arises due to this lack of synchronisation: if libev uses
		2125	the system monotonic clock and you compare timestamps from C<ev_time>
		2126	or C<ev_now> from when you started your timer and when your callback is
		2127	invoked, you will find that sometimes the callback is a bit "early".
		2128
		2129	This is because C<ev_timer>s work in real time, not wall clock time, so
		2130	libev makes sure your callback is not invoked before the delay happened,
		2131	I<measured according to the real time>, not the system clock.
		2132
		2133	If your timeouts are based on a physical timescale (e.g. "time out this
		2134	connection after 100 seconds") then this shouldn't bother you as it is
		2135	exactly the right behaviour.
		2136
		2137	If you want to compare wall clock/system timestamps to your timers, then
		2138	you need to use C<ev_periodic>s, as these are based on the wall clock
		2139	time, where your comparisons will always generate correct results.
1842		2140
1843	=head3 The special problems of suspended animation	2141	=head3 The special problems of suspended animation
1844		2142
1845	When you leave the server world it is quite customary to hit machines that	2143	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?	2144	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1876		2174
1877	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2175	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1878		2176
1879	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2177	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1880		2178
1881	Configure the timer to trigger after C<after> seconds. If C<repeat>	2179	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	2180	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	2181	automatically be stopped once the timeout is reached. If it is positive,
1884	configured to trigger again C<repeat> seconds later, again, and again,	2182	then the timer will automatically be configured to trigger again C<repeat>
1885	until stopped manually.	2183	seconds later, again, and again, until stopped manually.
1886		2184
1887	The timer itself will do a best-effort at avoiding drift, that is, if	2185	The timer itself will do a best-effort at avoiding drift, that is, if
1888	you configure a timer to trigger every 10 seconds, then it will normally	2186	you configure a timer to trigger every 10 seconds, then it will normally
1889	trigger at exactly 10 second intervals. If, however, your program cannot	2187	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	2188	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.	2189	do stuff) the timer will not fire more than once per event loop iteration.
1892		2190
1893	=item ev_timer_again (loop, ev_timer *)	2191	=item ev_timer_again (loop, ev_timer *)
1894		2192
1895	This will act as if the timer timed out and restart it again if it is	2193	This will act as if the timer timed out, and restarts it again if it is
1896	repeating. The exact semantics are:	2194	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2195	timeout to the C<repeat> value and calling C<ev_timer_start>.
1897		2196
		2197	The exact semantics are as in the following rules, all of which will be
		2198	applied to the watcher:
		2199
		2200	=over 4
		2201
1898	If the timer is pending, its pending status is cleared.	2202	=item If the timer is pending, the pending status is always cleared.
1899		2203
1900	If the timer is started but non-repeating, stop it (as if it timed out).	2204	=item If the timer is started but non-repeating, stop it (as if it timed
		2205	out, without invoking it).
1901		2206
1902	If the timer is repeating, either start it if necessary (with the	2207	=item If the timer is repeating, make the C<repeat> value the new timeout
1903	C<repeat> value), or reset the running timer to the C<repeat> value.	2208	and start the timer, if necessary.
1904		2209
		2210	=back
		2211
1905	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2212	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1906	usage example.	2213	usage example.
1907		2214
1908	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2215	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1909		2216
1910	Returns the remaining time until a timer fires. If the timer is active,	2217	Returns the remaining time until a timer fires. If the timer is active,
…		…
1949	}	2256	}
1950		2257
1951	ev_timer mytimer;	2258	ev_timer mytimer;
1952	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2259	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1953	ev_timer_again (&mytimer); /* start timer */	2260	ev_timer_again (&mytimer); /* start timer */
1954	ev_loop (loop, 0);	2261	ev_run (loop, 0);
1955		2262
1956	// and in some piece of code that gets executed on any "activity":	2263	// and in some piece of code that gets executed on any "activity":
1957	// reset the timeout to start ticking again at 10 seconds	2264	// reset the timeout to start ticking again at 10 seconds
1958	ev_timer_again (&mytimer);	2265	ev_timer_again (&mytimer);
1959		2266
…		…
1963	Periodic watchers are also timers of a kind, but they are very versatile	2270	Periodic watchers are also timers of a kind, but they are very versatile
1964	(and unfortunately a bit complex).	2271	(and unfortunately a bit complex).
1965		2272
1966	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2273	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1967	relative time, the physical time that passes) but on wall clock time	2274	relative time, the physical time that passes) but on wall clock time
1968	(absolute time, the thing you can read on your calender or clock). The	2275	(absolute time, the thing you can read on your calendar or clock). The
1969	difference is that wall clock time can run faster or slower than real	2276	difference is that wall clock time can run faster or slower than real
1970	time, and time jumps are not uncommon (e.g. when you adjust your	2277	time, and time jumps are not uncommon (e.g. when you adjust your
1971	wrist-watch).	2278	wrist-watch).
1972		2279
1973	You can tell a periodic watcher to trigger after some specific point	2280	You can tell a periodic watcher to trigger after some specific point
…		…
1978	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2285	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1979	it, as it uses a relative timeout).	2286	it, as it uses a relative timeout).
1980		2287
1981	C<ev_periodic> watchers can also be used to implement vastly more complex	2288	C<ev_periodic> watchers can also be used to implement vastly more complex
1982	timers, such as triggering an event on each "midnight, local time", or	2289	timers, such as triggering an event on each "midnight, local time", or
1983	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2290	other complicated rules. This cannot easily be done with C<ev_timer>
1984	those cannot react to time jumps.	2291	watchers, as those cannot react to time jumps.
1985		2292
1986	As with timers, the callback is guaranteed to be invoked only when the	2293	As with timers, the callback is guaranteed to be invoked only when the
1987	point in time where it is supposed to trigger has passed. If multiple	2294	point in time where it is supposed to trigger has passed. If multiple
1988	timers become ready during the same loop iteration then the ones with	2295	timers become ready during the same loop iteration then the ones with
1989	earlier time-out values are invoked before ones with later time-out values	2296	earlier time-out values are invoked before ones with later time-out values
1990	(but this is no longer true when a callback calls C<ev_loop> recursively).	2297	(but this is no longer true when a callback calls C<ev_run> recursively).
1991		2298
1992	=head3 Watcher-Specific Functions and Data Members	2299	=head3 Watcher-Specific Functions and Data Members
1993		2300
1994	=over 4	2301	=over 4
1995		2302
…		…
2030		2337
2031	Another way to think about it (for the mathematically inclined) is that	2338	Another way to think about it (for the mathematically inclined) is that
2032	C<ev_periodic> will try to run the callback in this mode at the next possible	2339	C<ev_periodic> will try to run the callback in this mode at the next possible
2033	time where C<time = offset (mod interval)>, regardless of any time jumps.	2340	time where C<time = offset (mod interval)>, regardless of any time jumps.
2034		2341
2035	For numerical stability it is preferable that the C<offset> value is near	2342	The C<interval> I<MUST> be positive, and for numerical stability, the
2036	C<ev_now ()> (the current time), but there is no range requirement for	2343	interval value should be higher than C<1/8192> (which is around 100
2037	this value, and in fact is often specified as zero.	2344	microseconds) and C<offset> should be higher than C<0> and should have
		2345	at most a similar magnitude as the current time (say, within a factor of
		2346	ten). Typical values for offset are, in fact, C<0> or something between
		2347	C<0> and C<interval>, which is also the recommended range.
2038		2348
2039	Note also that there is an upper limit to how often a timer can fire (CPU	2349	Note also that there is an upper limit to how often a timer can fire (CPU
2040	speed for example), so if C<interval> is very small then timing stability	2350	speed for example), so if C<interval> is very small then timing stability
2041	will of course deteriorate. Libev itself tries to be exact to be about one	2351	will of course deteriorate. Libev itself tries to be exact to be about one
2042	millisecond (if the OS supports it and the machine is fast enough).	2352	millisecond (if the OS supports it and the machine is fast enough).
…		…
2072		2382
2073	NOTE: I<< This callback must always return a time that is higher than or	2383	NOTE: I<< This callback must always return a time that is higher than or
2074	equal to the passed C<now> value >>.	2384	equal to the passed C<now> value >>.
2075		2385
2076	This can be used to create very complex timers, such as a timer that	2386	This can be used to create very complex timers, such as a timer that
2077	triggers on "next midnight, local time". To do this, you would calculate the	2387	triggers on "next midnight, local time". To do this, you would calculate
2078	next midnight after C<now> and return the timestamp value for this. How	2388	the next midnight after C<now> and return the timestamp value for
2079	you do this is, again, up to you (but it is not trivial, which is the main	2389	this. Here is a (completely untested, no error checking) example on how to
2080	reason I omitted it as an example).	2390	do this:
		2391
		2392	#include <time.h>
		2393
		2394	static ev_tstamp
		2395	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2396	{
		2397	time_t tnow = (time_t)now;
		2398	struct tm tm;
		2399	localtime_r (&tnow, &tm);
		2400
		2401	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2402	++tm.tm_mday; // midnight next day
		2403
		2404	return mktime (&tm);
		2405	}
		2406
		2407	Note: this code might run into trouble on days that have more then two
		2408	midnights (beginning and end).
2081		2409
2082	=back	2410	=back
2083		2411
2084	=item ev_periodic_again (loop, ev_periodic *)	2412	=item ev_periodic_again (loop, ev_periodic *)
2085		2413
…		…
2150		2478
2151	ev_periodic hourly_tick;	2479	ev_periodic hourly_tick;
2152	ev_periodic_init (&hourly_tick, clock_cb,	2480	ev_periodic_init (&hourly_tick, clock_cb,
2153	fmod (ev_now (loop), 3600.), 3600., 0);	2481	fmod (ev_now (loop), 3600.), 3600., 0);
2154	ev_periodic_start (loop, &hourly_tick);	2482	ev_periodic_start (loop, &hourly_tick);
2155		2483
2156		2484
2157	=head2 C<ev_signal> - signal me when a signal gets signalled!	2485	=head2 C<ev_signal> - signal me when a signal gets signalled!
2158		2486
2159	Signal watchers will trigger an event when the process receives a specific	2487	Signal watchers will trigger an event when the process receives a specific
2160	signal one or more times. Even though signals are very asynchronous, libev	2488	signal one or more times. Even though signals are very asynchronous, libev
2161	will try it's best to deliver signals synchronously, i.e. as part of the	2489	will try its best to deliver signals synchronously, i.e. as part of the
2162	normal event processing, like any other event.	2490	normal event processing, like any other event.
2163		2491
2164	If you want signals to be delivered truly asynchronously, just use	2492	If you want signals to be delivered truly asynchronously, just use
2165	C<sigaction> as you would do without libev and forget about sharing	2493	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	2494	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	2498	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	2499	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	2500	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.	2501	the moment, C<SIGCHLD> is permanently tied to the default loop.
2174		2502
2175	When the first watcher gets started will libev actually register something	2503	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	2504	register something with the kernel. It thus coexists with your own signal
2177	you don't register any with libev for the same signal).	2505	handlers as long as you don't register any with libev for the same signal.
2178		2506
2179	If possible and supported, libev will install its handlers with	2507	If possible and supported, libev will install its handlers with
2180	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2508	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	2509	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	2510	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	2513	=head3 The special problem of inheritance over fork/execve/pthread_create
2186		2514
2187	Both the signal mask (C<sigprocmask>) and the signal disposition	2515	Both the signal mask (C<sigprocmask>) and the signal disposition
2188	(C<sigaction>) are unspecified after starting a signal watcher (and after	2516	(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,	2517	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.	2518	and might or might not set or restore the installed signal handler (but
		2519	see C<EVFLAG_NOSIGMASK>).
2191		2520
2192	While this does not matter for the signal disposition (libev never	2521	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	2522	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	2523	C<execve>), this matters for the signal mask: many programs do not expect
2195	certain signals to be blocked.	2524	certain signals to be blocked.
…		…
2209		2538
2210	So I can't stress this enough: I<If you do not reset your signal mask when	2539	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	2540	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.	2541	is not a libev-specific thing, this is true for most event libraries.
2213		2542
		2543	=head3 The special problem of threads signal handling
		2544
		2545	POSIX threads has problematic signal handling semantics, specifically,
		2546	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2547	threads in a process block signals, which is hard to achieve.
		2548
		2549	When you want to use sigwait (or mix libev signal handling with your own
		2550	for the same signals), you can tackle this problem by globally blocking
		2551	all signals before creating any threads (or creating them with a fully set
		2552	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2553	loops. Then designate one thread as "signal receiver thread" which handles
		2554	these signals. You can pass on any signals that libev might be interested
		2555	in by calling C<ev_feed_signal>.
		2556
2214	=head3 Watcher-Specific Functions and Data Members	2557	=head3 Watcher-Specific Functions and Data Members
2215		2558
2216	=over 4	2559	=over 4
2217		2560
2218	=item ev_signal_init (ev_signal *, callback, int signum)	2561	=item ev_signal_init (ev_signal *, callback, int signum)
…		…
2233	Example: Try to exit cleanly on SIGINT.	2576	Example: Try to exit cleanly on SIGINT.
2234		2577
2235	static void	2578	static void
2236	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2579	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2237	{	2580	{
2238	ev_unloop (loop, EVUNLOOP_ALL);	2581	ev_break (loop, EVBREAK_ALL);
2239	}	2582	}
2240		2583
2241	ev_signal signal_watcher;	2584	ev_signal signal_watcher;
2242	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2585	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2243	ev_signal_start (loop, &signal_watcher);	2586	ev_signal_start (loop, &signal_watcher);
…		…
2352		2695
2353	=head2 C<ev_stat> - did the file attributes just change?	2696	=head2 C<ev_stat> - did the file attributes just change?
2354		2697
2355	This watches a file system path for attribute changes. That is, it calls	2698	This watches a file system path for attribute changes. That is, it calls
2356	C<stat> on that path in regular intervals (or when the OS says it changed)	2699	C<stat> on that path in regular intervals (or when the OS says it changed)
2357	and sees if it changed compared to the last time, invoking the callback if	2700	and sees if it changed compared to the last time, invoking the callback
2358	it did.	2701	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2702	happen after the watcher has been started will be reported.
2359		2703
2360	The path does not need to exist: changing from "path exists" to "path does	2704	The path does not need to exist: changing from "path exists" to "path does
2361	not exist" is a status change like any other. The condition "path does not	2705	not exist" is a status change like any other. The condition "path does not
2362	exist" (or more correctly "path cannot be stat'ed") is signified by the	2706	exist" (or more correctly "path cannot be stat'ed") is signified by the
2363	C<st_nlink> field being zero (which is otherwise always forced to be at	2707	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2593	Apart from keeping your process non-blocking (which is a useful	2937	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	2938	effect on its own sometimes), idle watchers are a good place to do
2595	"pseudo-background processing", or delay processing stuff to after the	2939	"pseudo-background processing", or delay processing stuff to after the
2596	event loop has handled all outstanding events.	2940	event loop has handled all outstanding events.
2597		2941
		2942	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2943
		2944	As long as there is at least one active idle watcher, libev will never
		2945	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2946	For this to work, the idle watcher doesn't need to be invoked at all - the
		2947	lowest priority will do.
		2948
		2949	This mode of operation can be useful together with an C<ev_check> watcher,
		2950	to do something on each event loop iteration - for example to balance load
		2951	between different connections.
		2952
		2953	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2954	example.
		2955
2598	=head3 Watcher-Specific Functions and Data Members	2956	=head3 Watcher-Specific Functions and Data Members
2599		2957
2600	=over 4	2958	=over 4
2601		2959
2602	=item ev_idle_init (ev_idle *, callback)	2960	=item ev_idle_init (ev_idle *, callback)
…		…
2613	callback, free it. Also, use no error checking, as usual.	2971	callback, free it. Also, use no error checking, as usual.
2614		2972
2615	static void	2973	static void
2616	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2974	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2617	{	2975	{
		2976	// stop the watcher
		2977	ev_idle_stop (loop, w);
		2978
		2979	// now we can free it
2618	free (w);	2980	free (w);
		2981
2619	// now do something you wanted to do when the program has	2982	// now do something you wanted to do when the program has
2620	// no longer anything immediate to do.	2983	// no longer anything immediate to do.
2621	}	2984	}
2622		2985
2623	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	2986	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2625	ev_idle_start (loop, idle_watcher);	2988	ev_idle_start (loop, idle_watcher);
2626		2989
2627		2990
2628	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2991	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2629		2992
2630	Prepare and check watchers are usually (but not always) used in pairs:	2993	Prepare and check watchers are often (but not always) used in pairs:
2631	prepare watchers get invoked before the process blocks and check watchers	2994	prepare watchers get invoked before the process blocks and check watchers
2632	afterwards.	2995	afterwards.
2633		2996
2634	You I<must not> call C<ev_loop> or similar functions that enter	2997	You I<must not> call C<ev_run> (or similar functions that enter the
2635	the current event loop from either C<ev_prepare> or C<ev_check>	2998	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2636	watchers. Other loops than the current one are fine, however. The	2999	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	3000	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,	3001	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	3002	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2640	called in pairs bracketing the blocking call.	3003	kind they will always be called in pairs bracketing the blocking call.
2641		3004
2642	Their main purpose is to integrate other event mechanisms into libev and	3005	Their main purpose is to integrate other event mechanisms into libev and
2643	their use is somewhat advanced. They could be used, for example, to track	3006	their use is somewhat advanced. They could be used, for example, to track
2644	variable changes, implement your own watchers, integrate net-snmp or a	3007	variable changes, implement your own watchers, integrate net-snmp or a
2645	coroutine library and lots more. They are also occasionally useful if	3008	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	3026	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	3027	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	3028	loop from blocking if lower-priority coroutines are active, thus mapping
2666	low-priority coroutines to idle/background tasks).	3029	low-priority coroutines to idle/background tasks).
2667		3030
2668	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3031	When used for this purpose, it is recommended to give C<ev_check> watchers
2669	priority, to ensure that they are being run before any other watchers	3032	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2670	after the poll (this doesn't matter for C<ev_prepare> watchers).	3033	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3034	watchers).
2671		3035
2672	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3036	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2673	activate ("feed") events into libev. While libev fully supports this, they	3037	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	3038	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	3039	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	3040	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	3041	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2678	others).	3042	others).
		3043
		3044	=head3 Abusing an C<ev_check> watcher for its side-effect
		3045
		3046	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3047	useful because they are called once per event loop iteration. For
		3048	example, if you want to handle a large number of connections fairly, you
		3049	normally only do a bit of work for each active connection, and if there
		3050	is more work to do, you wait for the next event loop iteration, so other
		3051	connections have a chance of making progress.
		3052
		3053	Using an C<ev_check> watcher is almost enough: it will be called on the
		3054	next event loop iteration. However, that isn't as soon as possible -
		3055	without external events, your C<ev_check> watcher will not be invoked.
		3056
		3057	This is where C<ev_idle> watchers come in handy - all you need is a
		3058	single global idle watcher that is active as long as you have one active
		3059	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3060	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3061	invoked. Neither watcher alone can do that.
2679		3062
2680	=head3 Watcher-Specific Functions and Data Members	3063	=head3 Watcher-Specific Functions and Data Members
2681		3064
2682	=over 4	3065	=over 4
2683		3066
…		…
2807		3190
2808	if (timeout >= 0)	3191	if (timeout >= 0)
2809	// create/start timer	3192	// create/start timer
2810		3193
2811	// poll	3194	// poll
2812	ev_loop (EV_A_ 0);	3195	ev_run (EV_A_ 0);
2813		3196
2814	// stop timer again	3197	// stop timer again
2815	if (timeout >= 0)	3198	if (timeout >= 0)
2816	ev_timer_stop (EV_A_ &to);	3199	ev_timer_stop (EV_A_ &to);
2817		3200
…		…
2884		3267
2885	=over 4	3268	=over 4
2886		3269
2887	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3270	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2888		3271
2889	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3272	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2890		3273
2891	Configures the watcher to embed the given loop, which must be	3274	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	3275	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	3276	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,	3277	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).	3278	if you do not want that, you need to temporarily stop the embed watcher).
2896		3279
2897	=item ev_embed_sweep (loop, ev_embed *)	3280	=item ev_embed_sweep (loop, ev_embed *)
2898		3281
2899	Make a single, non-blocking sweep over the embedded loop. This works	3282	Make a single, non-blocking sweep over the embedded loop. This works
2900	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3283	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2901	appropriate way for embedded loops.	3284	appropriate way for embedded loops.
2902		3285
2903	=item struct ev_loop *other [read-only]	3286	=item struct ev_loop *other [read-only]
2904		3287
2905	The embedded event loop.	3288	The embedded event loop.
…		…
2915	used).	3298	used).
2916		3299
2917	struct ev_loop *loop_hi = ev_default_init (0);	3300	struct ev_loop *loop_hi = ev_default_init (0);
2918	struct ev_loop *loop_lo = 0;	3301	struct ev_loop *loop_lo = 0;
2919	ev_embed embed;	3302	ev_embed embed;
2920		3303
2921	// see if there is a chance of getting one that works	3304	// see if there is a chance of getting one that works
2922	// (remember that a flags value of 0 means autodetection)	3305	// (remember that a flags value of 0 means autodetection)
2923	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3306	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2924	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3307	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2925	: 0;	3308	: 0;
…		…
2939	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3322	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2940		3323
2941	struct ev_loop *loop = ev_default_init (0);	3324	struct ev_loop *loop = ev_default_init (0);
2942	struct ev_loop *loop_socket = 0;	3325	struct ev_loop *loop_socket = 0;
2943	ev_embed embed;	3326	ev_embed embed;
2944		3327
2945	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3328	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2946	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3329	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2947	{	3330	{
2948	ev_embed_init (&embed, 0, loop_socket);	3331	ev_embed_init (&embed, 0, loop_socket);
2949	ev_embed_start (loop, &embed);	3332	ev_embed_start (loop, &embed);
…		…
2957		3340
2958	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3341	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2959		3342
2960	Fork watchers are called when a C<fork ()> was detected (usually because	3343	Fork watchers are called when a C<fork ()> was detected (usually because
2961	whoever is a good citizen cared to tell libev about it by calling	3344	whoever is a good citizen cared to tell libev about it by calling
2962	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3345	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2963	event loop blocks next and before C<ev_check> watchers are being called,	3346	and before C<ev_check> watchers are being called, and only in the child
2964	and only in the child after the fork. If whoever good citizen calling	3347	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2965	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3348	and calls it in the wrong process, the fork handlers will be invoked, too,
2966	handlers will be invoked, too, of course.	3349	of course.
2967		3350
2968	=head3 The special problem of life after fork - how is it possible?	3351	=head3 The special problem of life after fork - how is it possible?
2969		3352
2970	Most uses of C<fork()> consist of forking, then some simple calls to set	3353	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	3354	up/change the process environment, followed by a call to C<exec()>. This
2972	sequence should be handled by libev without any problems.	3355	sequence should be handled by libev without any problems.
2973		3356
2974	This changes when the application actually wants to do event handling	3357	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	3358	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	3374	disadvantage of having to use multiple event loops (which do not support
2992	signal watchers).	3375	signal watchers).
2993		3376
2994	When this is not possible, or you want to use the default loop for	3377	When this is not possible, or you want to use the default loop for
2995	other reasons, then in the process that wants to start "fresh", call	3378	other reasons, then in the process that wants to start "fresh", call
2996	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3379	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	3380	Destroying the default loop will "orphan" (not stop) all registered
2998	have to be careful not to execute code that modifies those watchers. Note	3381	watchers, so you have to be careful not to execute code that modifies
2999	also that in that case, you have to re-register any signal watchers.	3382	those watchers. Note also that in that case, you have to re-register any
		3383	signal watchers.
3000		3384
3001	=head3 Watcher-Specific Functions and Data Members	3385	=head3 Watcher-Specific Functions and Data Members
3002		3386
3003	=over 4	3387	=over 4
3004		3388
3005	=item ev_fork_init (ev_signal *, callback)	3389	=item ev_fork_init (ev_fork *, callback)
3006		3390
3007	Initialises and configures the fork watcher - it has no parameters of any	3391	Initialises and configures the fork watcher - it has no parameters of any
3008	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3392	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
3009	believe me.	3393	really.
3010		3394
3011	=back	3395	=back
		3396
		3397
		3398	=head2 C<ev_cleanup> - even the best things end
		3399
		3400	Cleanup watchers are called just before the event loop is being destroyed
		3401	by a call to C<ev_loop_destroy>.
		3402
		3403	While there is no guarantee that the event loop gets destroyed, cleanup
		3404	watchers provide a convenient method to install cleanup hooks for your
		3405	program, worker threads and so on - you just to make sure to destroy the
		3406	loop when you want them to be invoked.
		3407
		3408	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3409	all other watchers, they do not keep a reference to the event loop (which
		3410	makes a lot of sense if you think about it). Like all other watchers, you
		3411	can call libev functions in the callback, except C<ev_cleanup_start>.
		3412
		3413	=head3 Watcher-Specific Functions and Data Members
		3414
		3415	=over 4
		3416
		3417	=item ev_cleanup_init (ev_cleanup *, callback)
		3418
		3419	Initialises and configures the cleanup watcher - it has no parameters of
		3420	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3421	pointless, I assure you.
		3422
		3423	=back
		3424
		3425	Example: Register an atexit handler to destroy the default loop, so any
		3426	cleanup functions are called.
		3427
		3428	static void
		3429	program_exits (void)
		3430	{
		3431	ev_loop_destroy (EV_DEFAULT_UC);
		3432	}
		3433
		3434	...
		3435	atexit (program_exits);
3012		3436
3013		3437
3014	=head2 C<ev_async> - how to wake up an event loop	3438	=head2 C<ev_async> - how to wake up an event loop
3015		3439
3016	In general, you cannot use an C<ev_loop> from multiple threads or other	3440	In general, you cannot use an C<ev_loop> from multiple threads or other
…		…
3023	it by calling C<ev_async_send>, which is thread- and signal safe.	3447	it by calling C<ev_async_send>, which is thread- and signal safe.
3024		3448
3025	This functionality is very similar to C<ev_signal> watchers, as signals,	3449	This functionality is very similar to C<ev_signal> watchers, as signals,
3026	too, are asynchronous in nature, and signals, too, will be compressed	3450	too, are asynchronous in nature, and signals, too, will be compressed
3027	(i.e. the number of callback invocations may be less than the number of	3451	(i.e. the number of callback invocations may be less than the number of
3028	C<ev_async_sent> calls).	3452	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
3029		3453	of "global async watchers" by using a watcher on an otherwise unused
3030	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3454	signal, and C<ev_feed_signal> to signal this watcher from another thread,
3031	just the default loop.	3455	even without knowing which loop owns the signal.
3032		3456
3033	=head3 Queueing	3457	=head3 Queueing
3034		3458
3035	C<ev_async> does not support queueing of data in any way. The reason	3459	C<ev_async> does not support queueing of data in any way. The reason
3036	is that the author does not know of a simple (or any) algorithm for a	3460	is that the author does not know of a simple (or any) algorithm for a
…		…
3128	trust me.	3552	trust me.
3129		3553
3130	=item ev_async_send (loop, ev_async *)	3554	=item ev_async_send (loop, ev_async *)
3131		3555
3132	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3556	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3133	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3557	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3558	returns.
		3559
3134	C<ev_feed_event>, this call is safe to do from other threads, signal or	3560	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3135	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3561	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3136	section below on what exactly this means).	3562	embedding section below on what exactly this means).
3137		3563
3138	Note that, as with other watchers in libev, multiple events might get	3564	Note that, as with other watchers in libev, multiple events might get
3139	compressed into a single callback invocation (another way to look at this	3565	compressed into a single callback invocation (another way to look at
3140	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3566	this is that C<ev_async> watchers are level-triggered: they are set on
3141	reset when the event loop detects that).	3567	C<ev_async_send>, reset when the event loop detects that).
3142		3568
3143	This call incurs the overhead of a system call only once per event loop	3569	This call incurs the overhead of at most one extra system call per event
3144	iteration, so while the overhead might be noticeable, it doesn't apply to	3570	loop iteration, if the event loop is blocked, and no syscall at all if
3145	repeated calls to C<ev_async_send> for the same event loop.	3571	the event loop (or your program) is processing events. That means that
		3572	repeated calls are basically free (there is no need to avoid calls for
		3573	performance reasons) and that the overhead becomes smaller (typically
		3574	zero) under load.
3146		3575
3147	=item bool = ev_async_pending (ev_async *)	3576	=item bool = ev_async_pending (ev_async *)
3148		3577
3149	Returns a non-zero value when C<ev_async_send> has been called on the	3578	Returns a non-zero value when C<ev_async_send> has been called on the
3150	watcher but the event has not yet been processed (or even noted) by the	3579	watcher but the event has not yet been processed (or even noted) by the
…		…
3167		3596
3168	There are some other functions of possible interest. Described. Here. Now.	3597	There are some other functions of possible interest. Described. Here. Now.
3169		3598
3170	=over 4	3599	=over 4
3171		3600
3172	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3601	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3173		3602
3174	This function combines a simple timer and an I/O watcher, calls your	3603	This function combines a simple timer and an I/O watcher, calls your
3175	callback on whichever event happens first and automatically stops both	3604	callback on whichever event happens first and automatically stops both
3176	watchers. This is useful if you want to wait for a single event on an fd	3605	watchers. This is useful if you want to wait for a single event on an fd
3177	or timeout without having to allocate/configure/start/stop/free one or	3606	or timeout without having to allocate/configure/start/stop/free one or
…		…
3205	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3634	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3206		3635
3207	=item ev_feed_fd_event (loop, int fd, int revents)	3636	=item ev_feed_fd_event (loop, int fd, int revents)
3208		3637
3209	Feed an event on the given fd, as if a file descriptor backend detected	3638	Feed an event on the given fd, as if a file descriptor backend detected
3210	the given events it.	3639	the given events.
3211		3640
3212	=item ev_feed_signal_event (loop, int signum)	3641	=item ev_feed_signal_event (loop, int signum)
3213		3642
3214	Feed an event as if the given signal occurred (C<loop> must be the default	3643	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3215	loop!).	3644	which is async-safe.
3216		3645
3217	=back	3646	=back
		3647
		3648
		3649	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3650
		3651	This section explains some common idioms that are not immediately
		3652	obvious. Note that examples are sprinkled over the whole manual, and this
		3653	section only contains stuff that wouldn't fit anywhere else.
		3654
		3655	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3656
		3657	Each watcher has, by default, a C<void *data> member that you can read
		3658	or modify at any time: libev will completely ignore it. This can be used
		3659	to associate arbitrary data with your watcher. If you need more data and
		3660	don't want to allocate memory separately and store a pointer to it in that
		3661	data member, you can also "subclass" the watcher type and provide your own
		3662	data:
		3663
		3664	struct my_io
		3665	{
		3666	ev_io io;
		3667	int otherfd;
		3668	void *somedata;
		3669	struct whatever *mostinteresting;
		3670	};
		3671
		3672	...
		3673	struct my_io w;
		3674	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3675
		3676	And since your callback will be called with a pointer to the watcher, you
		3677	can cast it back to your own type:
		3678
		3679	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3680	{
		3681	struct my_io *w = (struct my_io *)w_;
		3682	...
		3683	}
		3684
		3685	More interesting and less C-conformant ways of casting your callback
		3686	function type instead have been omitted.
		3687
		3688	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3689
		3690	Another common scenario is to use some data structure with multiple
		3691	embedded watchers, in effect creating your own watcher that combines
		3692	multiple libev event sources into one "super-watcher":
		3693
		3694	struct my_biggy
		3695	{
		3696	int some_data;
		3697	ev_timer t1;
		3698	ev_timer t2;
		3699	}
		3700
		3701	In this case getting the pointer to C<my_biggy> is a bit more
		3702	complicated: Either you store the address of your C<my_biggy> struct in
		3703	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3704	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3705	real programmers):
		3706
		3707	#include <stddef.h>
		3708
		3709	static void
		3710	t1_cb (EV_P_ ev_timer *w, int revents)
		3711	{
		3712	struct my_biggy big = (struct my_biggy *)
		3713	(((char *)w) - offsetof (struct my_biggy, t1));
		3714	}
		3715
		3716	static void
		3717	t2_cb (EV_P_ ev_timer *w, int revents)
		3718	{
		3719	struct my_biggy big = (struct my_biggy *)
		3720	(((char *)w) - offsetof (struct my_biggy, t2));
		3721	}
		3722
		3723	=head2 AVOIDING FINISHING BEFORE RETURNING
		3724
		3725	Often you have structures like this in event-based programs:
		3726
		3727	callback ()
		3728	{
		3729	free (request);
		3730	}
		3731
		3732	request = start_new_request (..., callback);
		3733
		3734	The intent is to start some "lengthy" operation. The C<request> could be
		3735	used to cancel the operation, or do other things with it.
		3736
		3737	It's not uncommon to have code paths in C<start_new_request> that
		3738	immediately invoke the callback, for example, to report errors. Or you add
		3739	some caching layer that finds that it can skip the lengthy aspects of the
		3740	operation and simply invoke the callback with the result.
		3741
		3742	The problem here is that this will happen I<before> C<start_new_request>
		3743	has returned, so C<request> is not set.
		3744
		3745	Even if you pass the request by some safer means to the callback, you
		3746	might want to do something to the request after starting it, such as
		3747	canceling it, which probably isn't working so well when the callback has
		3748	already been invoked.
		3749
		3750	A common way around all these issues is to make sure that
		3751	C<start_new_request> I<always> returns before the callback is invoked. If
		3752	C<start_new_request> immediately knows the result, it can artificially
		3753	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3754	example, or more sneakily, by reusing an existing (stopped) watcher and
		3755	pushing it into the pending queue:
		3756
		3757	ev_set_cb (watcher, callback);
		3758	ev_feed_event (EV_A_ watcher, 0);
		3759
		3760	This way, C<start_new_request> can safely return before the callback is
		3761	invoked, while not delaying callback invocation too much.
		3762
		3763	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3764
		3765	Often (especially in GUI toolkits) there are places where you have
		3766	I<modal> interaction, which is most easily implemented by recursively
		3767	invoking C<ev_run>.
		3768
		3769	This brings the problem of exiting - a callback might want to finish the
		3770	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3771	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3772	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3773	other combination: In these cases, a simple C<ev_break> will not work.
		3774
		3775	The solution is to maintain "break this loop" variable for each C<ev_run>
		3776	invocation, and use a loop around C<ev_run> until the condition is
		3777	triggered, using C<EVRUN_ONCE>:
		3778
		3779	// main loop
		3780	int exit_main_loop = 0;
		3781
		3782	while (!exit_main_loop)
		3783	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3784
		3785	// in a modal watcher
		3786	int exit_nested_loop = 0;
		3787
		3788	while (!exit_nested_loop)
		3789	ev_run (EV_A_ EVRUN_ONCE);
		3790
		3791	To exit from any of these loops, just set the corresponding exit variable:
		3792
		3793	// exit modal loop
		3794	exit_nested_loop = 1;
		3795
		3796	// exit main program, after modal loop is finished
		3797	exit_main_loop = 1;
		3798
		3799	// exit both
		3800	exit_main_loop = exit_nested_loop = 1;
		3801
		3802	=head2 THREAD LOCKING EXAMPLE
		3803
		3804	Here is a fictitious example of how to run an event loop in a different
		3805	thread from where callbacks are being invoked and watchers are
		3806	created/added/removed.
		3807
		3808	For a real-world example, see the C<EV::Loop::Async> perl module,
		3809	which uses exactly this technique (which is suited for many high-level
		3810	languages).
		3811
		3812	The example uses a pthread mutex to protect the loop data, a condition
		3813	variable to wait for callback invocations, an async watcher to notify the
		3814	event loop thread and an unspecified mechanism to wake up the main thread.
		3815
		3816	First, you need to associate some data with the event loop:
		3817
		3818	typedef struct {
		3819	mutex_t lock; /* global loop lock */
		3820	ev_async async_w;
		3821	thread_t tid;
		3822	cond_t invoke_cv;
		3823	} userdata;
		3824
		3825	void prepare_loop (EV_P)
		3826	{
		3827	// for simplicity, we use a static userdata struct.
		3828	static userdata u;
		3829
		3830	ev_async_init (&u->async_w, async_cb);
		3831	ev_async_start (EV_A_ &u->async_w);
		3832
		3833	pthread_mutex_init (&u->lock, 0);
		3834	pthread_cond_init (&u->invoke_cv, 0);
		3835
		3836	// now associate this with the loop
		3837	ev_set_userdata (EV_A_ u);
		3838	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3839	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3840
		3841	// then create the thread running ev_run
		3842	pthread_create (&u->tid, 0, l_run, EV_A);
		3843	}
		3844
		3845	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3846	solely to wake up the event loop so it takes notice of any new watchers
		3847	that might have been added:
		3848
		3849	static void
		3850	async_cb (EV_P_ ev_async *w, int revents)
		3851	{
		3852	// just used for the side effects
		3853	}
		3854
		3855	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3856	protecting the loop data, respectively.
		3857
		3858	static void
		3859	l_release (EV_P)
		3860	{
		3861	userdata *u = ev_userdata (EV_A);
		3862	pthread_mutex_unlock (&u->lock);
		3863	}
		3864
		3865	static void
		3866	l_acquire (EV_P)
		3867	{
		3868	userdata *u = ev_userdata (EV_A);
		3869	pthread_mutex_lock (&u->lock);
		3870	}
		3871
		3872	The event loop thread first acquires the mutex, and then jumps straight
		3873	into C<ev_run>:
		3874
		3875	void *
		3876	l_run (void *thr_arg)
		3877	{
		3878	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3879
		3880	l_acquire (EV_A);
		3881	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3882	ev_run (EV_A_ 0);
		3883	l_release (EV_A);
		3884
		3885	return 0;
		3886	}
		3887
		3888	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3889	signal the main thread via some unspecified mechanism (signals? pipe
		3890	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3891	have been called (in a while loop because a) spurious wakeups are possible
		3892	and b) skipping inter-thread-communication when there are no pending
		3893	watchers is very beneficial):
		3894
		3895	static void
		3896	l_invoke (EV_P)
		3897	{
		3898	userdata *u = ev_userdata (EV_A);
		3899
		3900	while (ev_pending_count (EV_A))
		3901	{
		3902	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3903	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3904	}
		3905	}
		3906
		3907	Now, whenever the main thread gets told to invoke pending watchers, it
		3908	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3909	thread to continue:
		3910
		3911	static void
		3912	real_invoke_pending (EV_P)
		3913	{
		3914	userdata *u = ev_userdata (EV_A);
		3915
		3916	pthread_mutex_lock (&u->lock);
		3917	ev_invoke_pending (EV_A);
		3918	pthread_cond_signal (&u->invoke_cv);
		3919	pthread_mutex_unlock (&u->lock);
		3920	}
		3921
		3922	Whenever you want to start/stop a watcher or do other modifications to an
		3923	event loop, you will now have to lock:
		3924
		3925	ev_timer timeout_watcher;
		3926	userdata *u = ev_userdata (EV_A);
		3927
		3928	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3929
		3930	pthread_mutex_lock (&u->lock);
		3931	ev_timer_start (EV_A_ &timeout_watcher);
		3932	ev_async_send (EV_A_ &u->async_w);
		3933	pthread_mutex_unlock (&u->lock);
		3934
		3935	Note that sending the C<ev_async> watcher is required because otherwise
		3936	an event loop currently blocking in the kernel will have no knowledge
		3937	about the newly added timer. By waking up the loop it will pick up any new
		3938	watchers in the next event loop iteration.
		3939
		3940	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3941
		3942	While the overhead of a callback that e.g. schedules a thread is small, it
		3943	is still an overhead. If you embed libev, and your main usage is with some
		3944	kind of threads or coroutines, you might want to customise libev so that
		3945	doesn't need callbacks anymore.
		3946
		3947	Imagine you have coroutines that you can switch to using a function
		3948	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3949	and that due to some magic, the currently active coroutine is stored in a
		3950	global called C<current_coro>. Then you can build your own "wait for libev
		3951	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3952	the differing C<;> conventions):
		3953
		3954	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3955	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3956
		3957	That means instead of having a C callback function, you store the
		3958	coroutine to switch to in each watcher, and instead of having libev call
		3959	your callback, you instead have it switch to that coroutine.
		3960
		3961	A coroutine might now wait for an event with a function called
		3962	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3963	matter when, or whether the watcher is active or not when this function is
		3964	called):
		3965
		3966	void
		3967	wait_for_event (ev_watcher *w)
		3968	{
		3969	ev_set_cb (w, current_coro);
		3970	switch_to (libev_coro);
		3971	}
		3972
		3973	That basically suspends the coroutine inside C<wait_for_event> and
		3974	continues the libev coroutine, which, when appropriate, switches back to
		3975	this or any other coroutine.
		3976
		3977	You can do similar tricks if you have, say, threads with an event queue -
		3978	instead of storing a coroutine, you store the queue object and instead of
		3979	switching to a coroutine, you push the watcher onto the queue and notify
		3980	any waiters.
		3981
		3982	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3983	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3984
		3985	// my_ev.h
		3986	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3987	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3988	#include "../libev/ev.h"
		3989
		3990	// my_ev.c
		3991	#define EV_H "my_ev.h"
		3992	#include "../libev/ev.c"
		3993
		3994	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		3995	F<my_ev.c> into your project. When properly specifying include paths, you
		3996	can even use F<ev.h> as header file name directly.
3218		3997
3219		3998
3220	=head1 LIBEVENT EMULATION	3999	=head1 LIBEVENT EMULATION
3221		4000
3222	Libev offers a compatibility emulation layer for libevent. It cannot	4001	Libev offers a compatibility emulation layer for libevent. It cannot
3223	emulate the internals of libevent, so here are some usage hints:	4002	emulate the internals of libevent, so here are some usage hints:
3224		4003
3225	=over 4	4004	=over 4
		4005
		4006	=item * Only the libevent-1.4.1-beta API is being emulated.
		4007
		4008	This was the newest libevent version available when libev was implemented,
		4009	and is still mostly unchanged in 2010.
3226		4010
3227	=item * Use it by including <event.h>, as usual.	4011	=item * Use it by including <event.h>, as usual.
3228		4012
3229	=item * The following members are fully supported: ev_base, ev_callback,	4013	=item * The following members are fully supported: ev_base, ev_callback,
3230	ev_arg, ev_fd, ev_res, ev_events.	4014	ev_arg, ev_fd, ev_res, ev_events.
…		…
3236	=item * Priorities are not currently supported. Initialising priorities	4020	=item * Priorities are not currently supported. Initialising priorities
3237	will fail and all watchers will have the same priority, even though there	4021	will fail and all watchers will have the same priority, even though there
3238	is an ev_pri field.	4022	is an ev_pri field.
3239		4023
3240	=item * In libevent, the last base created gets the signals, in libev, the	4024	=item * In libevent, the last base created gets the signals, in libev, the
3241	first base created (== the default loop) gets the signals.	4025	base that registered the signal gets the signals.
3242		4026
3243	=item * Other members are not supported.	4027	=item * Other members are not supported.
3244		4028
3245	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4029	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3246	to use the libev header file and library.	4030	to use the libev header file and library.
3247		4031
3248	=back	4032	=back
3249		4033
3250	=head1 C++ SUPPORT	4034	=head1 C++ SUPPORT
		4035
		4036	=head2 C API
		4037
		4038	The normal C API should work fine when used from C++: both ev.h and the
		4039	libev sources can be compiled as C++. Therefore, code that uses the C API
		4040	will work fine.
		4041
		4042	Proper exception specifications might have to be added to callbacks passed
		4043	to libev: exceptions may be thrown only from watcher callbacks, all other
		4044	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4045	callbacks) must not throw exceptions, and might need a C<noexcept>
		4046	specification. If you have code that needs to be compiled as both C and
		4047	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4048
		4049	static void
		4050	fatal_error (const char *msg) EV_NOEXCEPT
		4051	{
		4052	perror (msg);
		4053	abort ();
		4054	}
		4055
		4056	...
		4057	ev_set_syserr_cb (fatal_error);
		4058
		4059	The only API functions that can currently throw exceptions are C<ev_run>,
		4060	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4061	because it runs cleanup watchers).
		4062
		4063	Throwing exceptions in watcher callbacks is only supported if libev itself
		4064	is compiled with a C++ compiler or your C and C++ environments allow
		4065	throwing exceptions through C libraries (most do).
		4066
		4067	=head2 C++ API
3251		4068
3252	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4069	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3253	you to use some convenience methods to start/stop watchers and also change	4070	you to use some convenience methods to start/stop watchers and also change
3254	the callback model to a model using method callbacks on objects.	4071	the callback model to a model using method callbacks on objects.
3255		4072
3256	To use it,	4073	To use it,
3257		4074
3258	#include <ev++.h>	4075	#include <ev++.h>
3259		4076
3260	This automatically includes F<ev.h> and puts all of its definitions (many	4077	This automatically includes F<ev.h> and puts all of its definitions (many
3261	of them macros) into the global namespace. All C++ specific things are	4078	of them macros) into the global namespace. All C++ specific things are
3262	put into the C<ev> namespace. It should support all the same embedding	4079	put into the C<ev> namespace. It should support all the same embedding
…		…
3265	Care has been taken to keep the overhead low. The only data member the C++	4082	Care has been taken to keep the overhead low. The only data member the C++
3266	classes add (compared to plain C-style watchers) is the event loop pointer	4083	classes add (compared to plain C-style watchers) is the event loop pointer
3267	that the watcher is associated with (or no additional members at all if	4084	that the watcher is associated with (or no additional members at all if
3268	you disable C<EV_MULTIPLICITY> when embedding libev).	4085	you disable C<EV_MULTIPLICITY> when embedding libev).
3269		4086
3270	Currently, functions, and static and non-static member functions can be	4087	Currently, functions, static and non-static member functions and classes
3271	used as callbacks. Other types should be easy to add as long as they only	4088	with C<operator ()> can be used as callbacks. Other types should be easy
3272	need one additional pointer for context. If you need support for other	4089	to add as long as they only need one additional pointer for context. If
3273	types of functors please contact the author (preferably after implementing	4090	you need support for other types of functors please contact the author
3274	it).	4091	(preferably after implementing it).
		4092
		4093	For all this to work, your C++ compiler either has to use the same calling
		4094	conventions as your C compiler (for static member functions), or you have
		4095	to embed libev and compile libev itself as C++.
3275		4096
3276	Here is a list of things available in the C<ev> namespace:	4097	Here is a list of things available in the C<ev> namespace:
3277		4098
3278	=over 4	4099	=over 4
3279		4100
…		…
3289	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4110	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3290		4111
3291	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4112	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3292	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4113	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3293	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4114	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3294	defines by many implementations.	4115	defined by many implementations.
3295		4116
3296	All of those classes have these methods:	4117	All of those classes have these methods:
3297		4118
3298	=over 4	4119	=over 4
3299		4120
…		…
3361	void operator() (ev::io &w, int revents)	4182	void operator() (ev::io &w, int revents)
3362	{	4183	{
3363	...	4184	...
3364	}	4185	}
3365	}	4186	}
3366		4187
3367	myfunctor f;	4188	myfunctor f;
3368		4189
3369	ev::io w;	4190	ev::io w;
3370	w.set (&f);	4191	w.set (&f);
3371		4192
…		…
3389	Associates a different C<struct ev_loop> with this watcher. You can only	4210	Associates a different C<struct ev_loop> with this watcher. You can only
3390	do this when the watcher is inactive (and not pending either).	4211	do this when the watcher is inactive (and not pending either).
3391		4212
3392	=item w->set ([arguments])	4213	=item w->set ([arguments])
3393		4214
3394	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4215	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4216	with the same arguments. Either this method or a suitable start method
3395	called at least once. Unlike the C counterpart, an active watcher gets	4217	must be called at least once. Unlike the C counterpart, an active watcher
3396	automatically stopped and restarted when reconfiguring it with this	4218	gets automatically stopped and restarted when reconfiguring it with this
3397	method.	4219	method.
		4220
		4221	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4222	clashing with the C<set (loop)> method.
3398		4223
3399	=item w->start ()	4224	=item w->start ()
3400		4225
3401	Starts the watcher. Note that there is no C<loop> argument, as the	4226	Starts the watcher. Note that there is no C<loop> argument, as the
3402	constructor already stores the event loop.	4227	constructor already stores the event loop.
3403		4228
		4229	=item w->start ([arguments])
		4230
		4231	Instead of calling C<set> and C<start> methods separately, it is often
		4232	convenient to wrap them in one call. Uses the same type of arguments as
		4233	the configure C<set> method of the watcher.
		4234
3404	=item w->stop ()	4235	=item w->stop ()
3405		4236
3406	Stops the watcher if it is active. Again, no C<loop> argument.	4237	Stops the watcher if it is active. Again, no C<loop> argument.
3407		4238
3408	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4239	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3420		4251
3421	=back	4252	=back
3422		4253
3423	=back	4254	=back
3424		4255
3425	Example: Define a class with an IO and idle watcher, start one of them in	4256	Example: Define a class with two I/O and idle watchers, start the I/O
3426	the constructor.	4257	watchers in the constructor.
3427		4258
3428	class myclass	4259	class myclass
3429	{	4260	{
3430	ev::io io ; void io_cb (ev::io &w, int revents);	4261	ev::io io ; void io_cb (ev::io &w, int revents);
		4262	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3431	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4263	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3432		4264
3433	myclass (int fd)	4265	myclass (int fd)
3434	{	4266	{
3435	io .set <myclass, &myclass::io_cb > (this);	4267	io .set <myclass, &myclass::io_cb > (this);
		4268	io2 .set <myclass, &myclass::io2_cb > (this);
3436	idle.set <myclass, &myclass::idle_cb> (this);	4269	idle.set <myclass, &myclass::idle_cb> (this);
3437		4270
3438	io.start (fd, ev::READ);	4271	io.set (fd, ev::WRITE); // configure the watcher
		4272	io.start (); // start it whenever convenient
		4273
		4274	io2.start (fd, ev::READ); // set + start in one call
3439	}	4275	}
3440	};	4276	};
3441		4277
3442		4278
3443	=head1 OTHER LANGUAGE BINDINGS	4279	=head1 OTHER LANGUAGE BINDINGS
…		…
3482	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4318	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3483		4319
3484	=item D	4320	=item D
3485		4321
3486	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4322	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3487	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4323	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3488		4324
3489	=item Ocaml	4325	=item Ocaml
3490		4326
3491	Erkki Seppala has written Ocaml bindings for libev, to be found at	4327	Erkki Seppala has written Ocaml bindings for libev, to be found at
3492	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4328	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
…		…
3495		4331
3496	Brian Maher has written a partial interface to libev for lua (at the	4332	Brian Maher has written a partial interface to libev for lua (at the
3497	time of this writing, only C<ev_io> and C<ev_timer>), to be found at	4333	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3498	L<http://github.com/brimworks/lua-ev>.	4334	L<http://github.com/brimworks/lua-ev>.
3499		4335
		4336	=item Javascript
		4337
		4338	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4339
		4340	=item Others
		4341
		4342	There are others, and I stopped counting.
		4343
3500	=back	4344	=back
3501		4345
3502		4346
3503	=head1 MACRO MAGIC	4347	=head1 MACRO MAGIC
3504		4348
…		…
3517	loop argument"). The C<EV_A> form is used when this is the sole argument,	4361	loop argument"). The C<EV_A> form is used when this is the sole argument,
3518	C<EV_A_> is used when other arguments are following. Example:	4362	C<EV_A_> is used when other arguments are following. Example:
3519		4363
3520	ev_unref (EV_A);	4364	ev_unref (EV_A);
3521	ev_timer_add (EV_A_ watcher);	4365	ev_timer_add (EV_A_ watcher);
3522	ev_loop (EV_A_ 0);	4366	ev_run (EV_A_ 0);
3523		4367
3524	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4368	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3525	which is often provided by the following macro.	4369	which is often provided by the following macro.
3526		4370
3527	=item C<EV_P>, C<EV_P_>	4371	=item C<EV_P>, C<EV_P_>
…		…
3540	suitable for use with C<EV_A>.	4384	suitable for use with C<EV_A>.
3541		4385
3542	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4386	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3543		4387
3544	Similar to the other two macros, this gives you the value of the default	4388	Similar to the other two macros, this gives you the value of the default
3545	loop, if multiple loops are supported ("ev loop default").	4389	loop, if multiple loops are supported ("ev loop default"). The default loop
		4390	will be initialised if it isn't already initialised.
		4391
		4392	For non-multiplicity builds, these macros do nothing, so you always have
		4393	to initialise the loop somewhere.
3546		4394
3547	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4395	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3548		4396
3549	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4397	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3550	default loop has been initialised (C<UC> == unchecked). Their behaviour	4398	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3567	}	4415	}
3568		4416
3569	ev_check check;	4417	ev_check check;
3570	ev_check_init (&check, check_cb);	4418	ev_check_init (&check, check_cb);
3571	ev_check_start (EV_DEFAULT_ &check);	4419	ev_check_start (EV_DEFAULT_ &check);
3572	ev_loop (EV_DEFAULT_ 0);	4420	ev_run (EV_DEFAULT_ 0);
3573		4421
3574	=head1 EMBEDDING	4422	=head1 EMBEDDING
3575		4423
3576	Libev can (and often is) directly embedded into host	4424	Libev can (and often is) directly embedded into host
3577	applications. Examples of applications that embed it include the Deliantra	4425	applications. Examples of applications that embed it include the Deliantra
…		…
3617	ev_vars.h	4465	ev_vars.h
3618	ev_wrap.h	4466	ev_wrap.h
3619		4467
3620	ev_win32.c required on win32 platforms only	4468	ev_win32.c required on win32 platforms only
3621		4469
3622	ev_select.c only when select backend is enabled (which is enabled by default)	4470	ev_select.c only when select backend is enabled
3623	ev_poll.c only when poll backend is enabled (disabled by default)	4471	ev_poll.c only when poll backend is enabled
3624	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4472	ev_epoll.c only when the epoll backend is enabled
		4473	ev_linuxaio.c only when the linux aio backend is enabled
3625	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4474	ev_kqueue.c only when the kqueue backend is enabled
3626	ev_port.c only when the solaris port backend is enabled (disabled by default)	4475	ev_port.c only when the solaris port backend is enabled
3627		4476
3628	F<ev.c> includes the backend files directly when enabled, so you only need	4477	F<ev.c> includes the backend files directly when enabled, so you only need
3629	to compile this single file.	4478	to compile this single file.
3630		4479
3631	=head3 LIBEVENT COMPATIBILITY API	4480	=head3 LIBEVENT COMPATIBILITY API
…		…
3669	users of libev and the libev code itself must be compiled with compatible	4518	users of libev and the libev code itself must be compiled with compatible
3670	settings.	4519	settings.
3671		4520
3672	=over 4	4521	=over 4
3673		4522
		4523	=item EV_COMPAT3 (h)
		4524
		4525	Backwards compatibility is a major concern for libev. This is why this
		4526	release of libev comes with wrappers for the functions and symbols that
		4527	have been renamed between libev version 3 and 4.
		4528
		4529	You can disable these wrappers (to test compatibility with future
		4530	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4531	sources. This has the additional advantage that you can drop the C<struct>
		4532	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4533	typedef in that case.
		4534
		4535	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4536	and in some even more future version the compatibility code will be
		4537	removed completely.
		4538
3674	=item EV_STANDALONE (h)	4539	=item EV_STANDALONE (h)
3675		4540
3676	Must always be C<1> if you do not use autoconf configuration, which	4541	Must always be C<1> if you do not use autoconf configuration, which
3677	keeps libev from including F<config.h>, and it also defines dummy	4542	keeps libev from including F<config.h>, and it also defines dummy
3678	implementations for some libevent functions (such as logging, which is not	4543	implementations for some libevent functions (such as logging, which is not
3679	supported). It will also not define any of the structs usually found in	4544	supported). It will also not define any of the structs usually found in
3680	F<event.h> that are not directly supported by the libev core alone.	4545	F<event.h> that are not directly supported by the libev core alone.
3681		4546
3682	In standalone mode, libev will still try to automatically deduce the	4547	In standalone mode, libev will still try to automatically deduce the
3683	configuration, but has to be more conservative.	4548	configuration, but has to be more conservative.
		4549
		4550	=item EV_USE_FLOOR
		4551
		4552	If defined to be C<1>, libev will use the C<floor ()> function for its
		4553	periodic reschedule calculations, otherwise libev will fall back on a
		4554	portable (slower) implementation. If you enable this, you usually have to
		4555	link against libm or something equivalent. Enabling this when the C<floor>
		4556	function is not available will fail, so the safe default is to not enable
		4557	this.
3684		4558
3685	=item EV_USE_MONOTONIC	4559	=item EV_USE_MONOTONIC
3686		4560
3687	If defined to be C<1>, libev will try to detect the availability of the	4561	If defined to be C<1>, libev will try to detect the availability of the
3688	monotonic clock option at both compile time and runtime. Otherwise no	4562	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3774	If programs implement their own fd to handle mapping on win32, then this	4648	If programs implement their own fd to handle mapping on win32, then this
3775	macro can be used to override the C<close> function, useful to unregister	4649	macro can be used to override the C<close> function, useful to unregister
3776	file descriptors again. Note that the replacement function has to close	4650	file descriptors again. Note that the replacement function has to close
3777	the underlying OS handle.	4651	the underlying OS handle.
3778		4652
		4653	=item EV_USE_WSASOCKET
		4654
		4655	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4656	communication socket, which works better in some environments. Otherwise,
		4657	the normal C<socket> function will be used, which works better in other
		4658	environments.
		4659
3779	=item EV_USE_POLL	4660	=item EV_USE_POLL
3780		4661
3781	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4662	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3782	backend. Otherwise it will be enabled on non-win32 platforms. It	4663	backend. Otherwise it will be enabled on non-win32 platforms. It
3783	takes precedence over select.	4664	takes precedence over select.
…		…
3787	If defined to be C<1>, libev will compile in support for the Linux	4668	If defined to be C<1>, libev will compile in support for the Linux
3788	C<epoll>(7) backend. Its availability will be detected at runtime,	4669	C<epoll>(7) backend. Its availability will be detected at runtime,
3789	otherwise another method will be used as fallback. This is the preferred	4670	otherwise another method will be used as fallback. This is the preferred
3790	backend for GNU/Linux systems. If undefined, it will be enabled if the	4671	backend for GNU/Linux systems. If undefined, it will be enabled if the
3791	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4672	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4673
		4674	=item EV_USE_LINUXAIO
		4675
		4676	If defined to be C<1>, libev will compile in support for the Linux
		4677	aio backend. Due to it's currenbt limitations it has to be requested
		4678	explicitly. If undefined, it will be enabled on linux, otherwise
		4679	disabled.
3792		4680
3793	=item EV_USE_KQUEUE	4681	=item EV_USE_KQUEUE
3794		4682
3795	If defined to be C<1>, libev will compile in support for the BSD style	4683	If defined to be C<1>, libev will compile in support for the BSD style
3796	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4684	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3818	If defined to be C<1>, libev will compile in support for the Linux inotify	4706	If defined to be C<1>, libev will compile in support for the Linux inotify
3819	interface to speed up C<ev_stat> watchers. Its actual availability will	4707	interface to speed up C<ev_stat> watchers. Its actual availability will
3820	be detected at runtime. If undefined, it will be enabled if the headers	4708	be detected at runtime. If undefined, it will be enabled if the headers
3821	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4709	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3822		4710
		4711	=item EV_NO_SMP
		4712
		4713	If defined to be C<1>, libev will assume that memory is always coherent
		4714	between threads, that is, threads can be used, but threads never run on
		4715	different cpus (or different cpu cores). This reduces dependencies
		4716	and makes libev faster.
		4717
		4718	=item EV_NO_THREADS
		4719
		4720	If defined to be C<1>, libev will assume that it will never be called from
		4721	different threads (that includes signal handlers), which is a stronger
		4722	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4723	libev faster.
		4724
3823	=item EV_ATOMIC_T	4725	=item EV_ATOMIC_T
3824		4726
3825	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4727	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3826	access is atomic with respect to other threads or signal contexts. No such	4728	access is atomic with respect to other threads or signal contexts. No
3827	type is easily found in the C language, so you can provide your own type	4729	such type is easily found in the C language, so you can provide your own
3828	that you know is safe for your purposes. It is used both for signal handler "locking"	4730	type that you know is safe for your purposes. It is used both for signal
3829	as well as for signal and thread safety in C<ev_async> watchers.	4731	handler "locking" as well as for signal and thread safety in C<ev_async>
		4732	watchers.
3830		4733
3831	In the absence of this define, libev will use C<sig_atomic_t volatile>	4734	In the absence of this define, libev will use C<sig_atomic_t volatile>
3832	(from F<signal.h>), which is usually good enough on most platforms.	4735	(from F<signal.h>), which is usually good enough on most platforms.
3833		4736
3834	=item EV_H (h)	4737	=item EV_H (h)
…		…
3861	will have the C<struct ev_loop *> as first argument, and you can create	4764	will have the C<struct ev_loop *> as first argument, and you can create
3862	additional independent event loops. Otherwise there will be no support	4765	additional independent event loops. Otherwise there will be no support
3863	for multiple event loops and there is no first event loop pointer	4766	for multiple event loops and there is no first event loop pointer
3864	argument. Instead, all functions act on the single default loop.	4767	argument. Instead, all functions act on the single default loop.
3865		4768
		4769	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4770	default loop when multiplicity is switched off - you always have to
		4771	initialise the loop manually in this case.
		4772
3866	=item EV_MINPRI	4773	=item EV_MINPRI
3867		4774
3868	=item EV_MAXPRI	4775	=item EV_MAXPRI
3869		4776
3870	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4777	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3906	#define EV_USE_POLL 1	4813	#define EV_USE_POLL 1
3907	#define EV_CHILD_ENABLE 1	4814	#define EV_CHILD_ENABLE 1
3908	#define EV_ASYNC_ENABLE 1	4815	#define EV_ASYNC_ENABLE 1
3909		4816
3910	The actual value is a bitset, it can be a combination of the following	4817	The actual value is a bitset, it can be a combination of the following
3911	values:	4818	values (by default, all of these are enabled):
3912		4819
3913	=over 4	4820	=over 4
3914		4821
3915	=item C<1> - faster/larger code	4822	=item C<1> - faster/larger code
3916		4823
…		…
3920	code size by roughly 30% on amd64).	4827	code size by roughly 30% on amd64).
3921		4828
3922	When optimising for size, use of compiler flags such as C<-Os> with	4829	When optimising for size, use of compiler flags such as C<-Os> with
3923	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of	4830	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3924	assertions.	4831	assertions.
		4832
		4833	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4834	(e.g. gcc with C<-Os>).
3925		4835
3926	=item C<2> - faster/larger data structures	4836	=item C<2> - faster/larger data structures
3927		4837
3928	Replaces the small 2-heap for timer management by a faster 4-heap, larger	4838	Replaces the small 2-heap for timer management by a faster 4-heap, larger
3929	hash table sizes and so on. This will usually further increase code size	4839	hash table sizes and so on. This will usually further increase code size
3930	and can additionally have an effect on the size of data structures at	4840	and can additionally have an effect on the size of data structures at
3931	runtime.	4841	runtime.
3932		4842
		4843	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4844	(e.g. gcc with C<-Os>).
		4845
3933	=item C<4> - full API configuration	4846	=item C<4> - full API configuration
3934		4847
3935	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and	4848	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3936	enables multiplicity (C<EV_MULTIPLICITY>=1).	4849	enables multiplicity (C<EV_MULTIPLICITY>=1).
3937		4850
…		…
3967		4880
3968	With an intelligent-enough linker (gcc+binutils are intelligent enough	4881	With an intelligent-enough linker (gcc+binutils are intelligent enough
3969	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by	4882	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3970	your program might be left out as well - a binary starting a timer and an	4883	your program might be left out as well - a binary starting a timer and an
3971	I/O watcher then might come out at only 5Kb.	4884	I/O watcher then might come out at only 5Kb.
		4885
		4886	=item EV_API_STATIC
		4887
		4888	If this symbol is defined (by default it is not), then all identifiers
		4889	will have static linkage. This means that libev will not export any
		4890	identifiers, and you cannot link against libev anymore. This can be useful
		4891	when you embed libev, only want to use libev functions in a single file,
		4892	and do not want its identifiers to be visible.
		4893
		4894	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4895	wants to use libev.
		4896
		4897	This option only works when libev is compiled with a C compiler, as C++
		4898	doesn't support the required declaration syntax.
3972		4899
3973	=item EV_AVOID_STDIO	4900	=item EV_AVOID_STDIO
3974		4901
3975	If this is set to C<1> at compiletime, then libev will avoid using stdio	4902	If this is set to C<1> at compiletime, then libev will avoid using stdio
3976	functions (printf, scanf, perror etc.). This will increase the code size	4903	functions (printf, scanf, perror etc.). This will increase the code size
…		…
4027	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it	4954	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4028	will be C<0>.	4955	will be C<0>.
4029		4956
4030	=item EV_VERIFY	4957	=item EV_VERIFY
4031		4958
4032	Controls how much internal verification (see C<ev_loop_verify ()>) will	4959	Controls how much internal verification (see C<ev_verify ()>) will
4033	be done: If set to C<0>, no internal verification code will be compiled	4960	be done: If set to C<0>, no internal verification code will be compiled
4034	in. If set to C<1>, then verification code will be compiled in, but not	4961	in. If set to C<1>, then verification code will be compiled in, but not
4035	called. If set to C<2>, then the internal verification code will be	4962	called. If set to C<2>, then the internal verification code will be
4036	called once per loop, which can slow down libev. If set to C<3>, then the	4963	called once per loop, which can slow down libev. If set to C<3>, then the
4037	verification code will be called very frequently, which will slow down	4964	verification code will be called very frequently, which will slow down
…		…
4120	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5047	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4121		5048
4122	#include "ev_cpp.h"	5049	#include "ev_cpp.h"
4123	#include "ev.c"	5050	#include "ev.c"
4124		5051
4125	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5052	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4126		5053
4127	=head2 THREADS AND COROUTINES	5054	=head2 THREADS AND COROUTINES
4128		5055
4129	=head3 THREADS	5056	=head3 THREADS
4130		5057
…		…
4181	default loop and triggering an C<ev_async> watcher from the default loop	5108	default loop and triggering an C<ev_async> watcher from the default loop
4182	watcher callback into the event loop interested in the signal.	5109	watcher callback into the event loop interested in the signal.
4183		5110
4184	=back	5111	=back
4185		5112
4186	=head4 THREAD LOCKING EXAMPLE	5113	See also L</THREAD LOCKING EXAMPLE>.
4187
4188	Here is a fictitious example of how to run an event loop in a different
4189	thread than where callbacks are being invoked and watchers are
4190	created/added/removed.
4191
4192	For a real-world example, see the C<EV::Loop::Async> perl module,
4193	which uses exactly this technique (which is suited for many high-level
4194	languages).
4195
4196	The example uses a pthread mutex to protect the loop data, a condition
4197	variable to wait for callback invocations, an async watcher to notify the
4198	event loop thread and an unspecified mechanism to wake up the main thread.
4199
4200	First, you need to associate some data with the event loop:
4201
4202	typedef struct {
4203	mutex_t lock; /* global loop lock */
4204	ev_async async_w;
4205	thread_t tid;
4206	cond_t invoke_cv;
4207	} userdata;
4208
4209	void prepare_loop (EV_P)
4210	{
4211	// for simplicity, we use a static userdata struct.
4212	static userdata u;
4213
4214	ev_async_init (&u->async_w, async_cb);
4215	ev_async_start (EV_A_ &u->async_w);
4216
4217	pthread_mutex_init (&u->lock, 0);
4218	pthread_cond_init (&u->invoke_cv, 0);
4219
4220	// now associate this with the loop
4221	ev_set_userdata (EV_A_ u);
4222	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4223	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4224
4225	// then create the thread running ev_loop
4226	pthread_create (&u->tid, 0, l_run, EV_A);
4227	}
4228
4229	The callback for the C<ev_async> watcher does nothing: the watcher is used
4230	solely to wake up the event loop so it takes notice of any new watchers
4231	that might have been added:
4232
4233	static void
4234	async_cb (EV_P_ ev_async *w, int revents)
4235	{
4236	// just used for the side effects
4237	}
4238
4239	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4240	protecting the loop data, respectively.
4241
4242	static void
4243	l_release (EV_P)
4244	{
4245	userdata *u = ev_userdata (EV_A);
4246	pthread_mutex_unlock (&u->lock);
4247	}
4248
4249	static void
4250	l_acquire (EV_P)
4251	{
4252	userdata *u = ev_userdata (EV_A);
4253	pthread_mutex_lock (&u->lock);
4254	}
4255
4256	The event loop thread first acquires the mutex, and then jumps straight
4257	into C<ev_loop>:
4258
4259	void *
4260	l_run (void *thr_arg)
4261	{
4262	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4263
4264	l_acquire (EV_A);
4265	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4266	ev_loop (EV_A_ 0);
4267	l_release (EV_A);
4268
4269	return 0;
4270	}
4271
4272	Instead of invoking all pending watchers, the C<l_invoke> callback will
4273	signal the main thread via some unspecified mechanism (signals? pipe
4274	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4275	have been called (in a while loop because a) spurious wakeups are possible
4276	and b) skipping inter-thread-communication when there are no pending
4277	watchers is very beneficial):
4278
4279	static void
4280	l_invoke (EV_P)
4281	{
4282	userdata *u = ev_userdata (EV_A);
4283
4284	while (ev_pending_count (EV_A))
4285	{
4286	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4287	pthread_cond_wait (&u->invoke_cv, &u->lock);
4288	}
4289	}
4290
4291	Now, whenever the main thread gets told to invoke pending watchers, it
4292	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4293	thread to continue:
4294
4295	static void
4296	real_invoke_pending (EV_P)
4297	{
4298	userdata *u = ev_userdata (EV_A);
4299
4300	pthread_mutex_lock (&u->lock);
4301	ev_invoke_pending (EV_A);
4302	pthread_cond_signal (&u->invoke_cv);
4303	pthread_mutex_unlock (&u->lock);
4304	}
4305
4306	Whenever you want to start/stop a watcher or do other modifications to an
4307	event loop, you will now have to lock:
4308
4309	ev_timer timeout_watcher;
4310	userdata *u = ev_userdata (EV_A);
4311
4312	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4313
4314	pthread_mutex_lock (&u->lock);
4315	ev_timer_start (EV_A_ &timeout_watcher);
4316	ev_async_send (EV_A_ &u->async_w);
4317	pthread_mutex_unlock (&u->lock);
4318
4319	Note that sending the C<ev_async> watcher is required because otherwise
4320	an event loop currently blocking in the kernel will have no knowledge
4321	about the newly added timer. By waking up the loop it will pick up any new
4322	watchers in the next event loop iteration.
4323		5114
4324	=head3 COROUTINES	5115	=head3 COROUTINES
4325		5116
4326	Libev is very accommodating to coroutines ("cooperative threads"):	5117	Libev is very accommodating to coroutines ("cooperative threads"):
4327	libev fully supports nesting calls to its functions from different	5118	libev fully supports nesting calls to its functions from different
4328	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5119	coroutines (e.g. you can call C<ev_run> on the same loop from two
4329	different coroutines, and switch freely between both coroutines running	5120	different coroutines, and switch freely between both coroutines running
4330	the loop, as long as you don't confuse yourself). The only exception is	5121	the loop, as long as you don't confuse yourself). The only exception is
4331	that you must not do this from C<ev_periodic> reschedule callbacks.	5122	that you must not do this from C<ev_periodic> reschedule callbacks.
4332		5123
4333	Care has been taken to ensure that libev does not keep local state inside	5124	Care has been taken to ensure that libev does not keep local state inside
4334	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5125	C<ev_run>, and other calls do not usually allow for coroutine switches as
4335	they do not call any callbacks.	5126	they do not call any callbacks.
4336		5127
4337	=head2 COMPILER WARNINGS	5128	=head2 COMPILER WARNINGS
4338		5129
4339	Depending on your compiler and compiler settings, you might get no or a	5130	Depending on your compiler and compiler settings, you might get no or a
…		…
4423	=head3 C<kqueue> is buggy	5214	=head3 C<kqueue> is buggy
4424		5215
4425	The kqueue syscall is broken in all known versions - most versions support	5216	The kqueue syscall is broken in all known versions - most versions support
4426	only sockets, many support pipes.	5217	only sockets, many support pipes.
4427		5218
		5219	Libev tries to work around this by not using C<kqueue> by default on this
		5220	rotten platform, but of course you can still ask for it when creating a
		5221	loop - embedding a socket-only kqueue loop into a select-based one is
		5222	probably going to work well.
		5223
4428	=head3 C<poll> is buggy	5224	=head3 C<poll> is buggy
4429		5225
4430	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>	5226	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4431	implementation by something calling C<kqueue> internally around the 10.5.6	5227	implementation by something calling C<kqueue> internally around the 10.5.6
4432	release, so now C<kqueue> I<and> C<poll> are broken.	5228	release, so now C<kqueue> I<and> C<poll> are broken.
4433		5229
4434	Libev tries to work around this by neither using C<kqueue> nor C<poll> by	5230	Libev tries to work around this by not using C<poll> by default on
4435	default on this rotten platform, but of course you cna still ask for them	5231	this rotten platform, but of course you can still ask for it when creating
4436	when creating a loop.	5232	a loop.
4437		5233
4438	=head3 C<select> is buggy	5234	=head3 C<select> is buggy
4439		5235
4440	All that's left is C<select>, and of course Apple found a way to fuck this	5236	All that's left is C<select>, and of course Apple found a way to fuck this
4441	one up as well: On OS/X, C<select> actively limits the number of file	5237	one up as well: On OS/X, C<select> actively limits the number of file
4442	descriptors you can pass in to 1024 - your program suddenyl crashes when	5238	descriptors you can pass in to 1024 - your program suddenly crashes when
4443	you use more.	5239	you use more.
4444		5240
4445	There is an undocumented "workaround" for this - defining	5241	There is an undocumented "workaround" for this - defining
4446	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>	5242	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
4447	work on OS/X.	5243	work on OS/X.
…		…
4450		5246
4451	=head3 C<errno> reentrancy	5247	=head3 C<errno> reentrancy
4452		5248
4453	The default compile environment on Solaris is unfortunately so	5249	The default compile environment on Solaris is unfortunately so
4454	thread-unsafe that you can't even use components/libraries compiled	5250	thread-unsafe that you can't even use components/libraries compiled
4455	without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,	5251	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
4456	isn't defined by default.	5252	defined by default. A valid, if stupid, implementation choice.
4457		5253
4458	If you want to use libev in threaded environments you have to make sure	5254	If you want to use libev in threaded environments you have to make sure
4459	it's compiled with C<_REENTRANT> defined.	5255	it's compiled with C<_REENTRANT> defined.
4460		5256
4461	=head3 Event port backend	5257	=head3 Event port backend
4462		5258
4463	The scalable event interface for Solaris is called "event ports". Unfortunately,	5259	The scalable event interface for Solaris is called "event
4464	this mechanism is very buggy. If you run into high CPU usage, your program	5260	ports". Unfortunately, this mechanism is very buggy in all major
		5261	releases. If you run into high CPU usage, your program freezes or you get
4465	freezes or you get a large number of spurious wakeups, make sure you have	5262	a large number of spurious wakeups, make sure you have all the relevant
4466	all the relevant and latest kernel patches applied. No, I don't know which	5263	and latest kernel patches applied. No, I don't know which ones, but there
4467	ones, but there are multiple ones.	5264	are multiple ones to apply, and afterwards, event ports actually work
		5265	great.
4468		5266
4469	If you can't get it to work, you can try running the program with	5267	If you can't get it to work, you can try running the program by setting
4470	C<LIBEV_FLAGS=3> to only allow C<poll> and C<select> backends.	5268	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5269	C<select> backends.
4471		5270
4472	=head2 AIX POLL BUG	5271	=head2 AIX POLL BUG
4473		5272
4474	AIX unfortunately has a broken C<poll.h> header. Libev works around	5273	AIX unfortunately has a broken C<poll.h> header. Libev works around
4475	this by trying to avoid the poll backend altogether (i.e. it's not even	5274	this by trying to avoid the poll backend altogether (i.e. it's not even
4476	compiled in), which normally isn't a big problem as C<select> works fine	5275	compiled in), which normally isn't a big problem as C<select> works fine
4477	with large bitsets, and AIX is dead anyway.	5276	with large bitsets on AIX, and AIX is dead anyway.
4478		5277
4479	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5278	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4480		5279
4481	=head3 General issues	5280	=head3 General issues
4482		5281
…		…
4484	requires, and its I/O model is fundamentally incompatible with the POSIX	5283	requires, and its I/O model is fundamentally incompatible with the POSIX
4485	model. Libev still offers limited functionality on this platform in	5284	model. Libev still offers limited functionality on this platform in
4486	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5285	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4487	descriptors. This only applies when using Win32 natively, not when using	5286	descriptors. This only applies when using Win32 natively, not when using
4488	e.g. cygwin. Actually, it only applies to the microsofts own compilers,	5287	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4489	as every compielr comes with a slightly differently broken/incompatible	5288	as every compiler comes with a slightly differently broken/incompatible
4490	environment.	5289	environment.
4491		5290
4492	Lifting these limitations would basically require the full	5291	Lifting these limitations would basically require the full
4493	re-implementation of the I/O system. If you are into this kind of thing,	5292	re-implementation of the I/O system. If you are into this kind of thing,
4494	then note that glib does exactly that for you in a very portable way (note	5293	then note that glib does exactly that for you in a very portable way (note
…		…
4588	structure (guaranteed by POSIX but not by ISO C for example), but it also	5387	structure (guaranteed by POSIX but not by ISO C for example), but it also
4589	assumes that the same (machine) code can be used to call any watcher	5388	assumes that the same (machine) code can be used to call any watcher
4590	callback: The watcher callbacks have different type signatures, but libev	5389	callback: The watcher callbacks have different type signatures, but libev
4591	calls them using an C<ev_watcher *> internally.	5390	calls them using an C<ev_watcher *> internally.
4592		5391
		5392	=item null pointers and integer zero are represented by 0 bytes
		5393
		5394	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5395	relies on this setting pointers and integers to null.
		5396
		5397	=item pointer accesses must be thread-atomic
		5398
		5399	Accessing a pointer value must be atomic, it must both be readable and
		5400	writable in one piece - this is the case on all current architectures.
		5401
4593	=item C<sig_atomic_t volatile> must be thread-atomic as well	5402	=item C<sig_atomic_t volatile> must be thread-atomic as well
4594		5403
4595	The type C<sig_atomic_t volatile> (or whatever is defined as	5404	The type C<sig_atomic_t volatile> (or whatever is defined as
4596	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5405	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
4597	threads. This is not part of the specification for C<sig_atomic_t>, but is	5406	threads. This is not part of the specification for C<sig_atomic_t>, but is
…		…
4605	thread" or will block signals process-wide, both behaviours would	5414	thread" or will block signals process-wide, both behaviours would
4606	be compatible with libev. Interaction between C<sigprocmask> and	5415	be compatible with libev. Interaction between C<sigprocmask> and
4607	C<pthread_sigmask> could complicate things, however.	5416	C<pthread_sigmask> could complicate things, however.
4608		5417
4609	The most portable way to handle signals is to block signals in all threads	5418	The most portable way to handle signals is to block signals in all threads
4610	except the initial one, and run the default loop in the initial thread as	5419	except the initial one, and run the signal handling loop in the initial
4611	well.	5420	thread as well.
4612		5421
4613	=item C<long> must be large enough for common memory allocation sizes	5422	=item C<long> must be large enough for common memory allocation sizes
4614		5423
4615	To improve portability and simplify its API, libev uses C<long> internally	5424	To improve portability and simplify its API, libev uses C<long> internally
4616	instead of C<size_t> when allocating its data structures. On non-POSIX	5425	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4619	watchers.	5428	watchers.
4620		5429
4621	=item C<double> must hold a time value in seconds with enough accuracy	5430	=item C<double> must hold a time value in seconds with enough accuracy
4622		5431
4623	The type C<double> is used to represent timestamps. It is required to	5432	The type C<double> is used to represent timestamps. It is required to
4624	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5433	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4625	enough for at least into the year 4000. This requirement is fulfilled by	5434	good enough for at least into the year 4000 with millisecond accuracy
		5435	(the design goal for libev). This requirement is overfulfilled by
4626	implementations implementing IEEE 754, which is basically all existing	5436	implementations using IEEE 754, which is basically all existing ones.
		5437
4627	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5438	With IEEE 754 doubles, you get microsecond accuracy until at least the
4628	2200.	5439	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5440	is either obsolete or somebody patched it to use C<long double> or
		5441	something like that, just kidding).
4629		5442
4630	=back	5443	=back
4631		5444
4632	If you know of other additional requirements drop me a note.	5445	If you know of other additional requirements drop me a note.
4633		5446
…		…
4695	=item Processing ev_async_send: O(number_of_async_watchers)	5508	=item Processing ev_async_send: O(number_of_async_watchers)
4696		5509
4697	=item Processing signals: O(max_signal_number)	5510	=item Processing signals: O(max_signal_number)
4698		5511
4699	Sending involves a system call I<iff> there were no other C<ev_async_send>	5512	Sending involves a system call I<iff> there were no other C<ev_async_send>
4700	calls in the current loop iteration. Checking for async and signal events	5513	calls in the current loop iteration and the loop is currently
		5514	blocked. Checking for async and signal events involves iterating over all
4701	involves iterating over all running async watchers or all signal numbers.	5515	running async watchers or all signal numbers.
4702		5516
4703	=back	5517	=back
4704		5518
4705		5519
4706	=head1 PORTING FROM LIBEV 3.X TO 4.X	5520	=head1 PORTING FROM LIBEV 3.X TO 4.X
4707		5521
4708	The major version 4 introduced some minor incompatible changes to the API.	5522	The major version 4 introduced some incompatible changes to the API.
4709		5523
4710	At the moment, the C<ev.h> header file tries to implement superficial	5524	At the moment, the C<ev.h> header file provides compatibility definitions
4711	compatibility, so most programs should still compile. Those might be	5525	for all changes, so most programs should still compile. The compatibility
4712	removed in later versions of libev, so better update early than late.	5526	layer might be removed in later versions of libev, so better update to the
		5527	new API early than late.
4713		5528
4714	=over 4	5529	=over 4
4715		5530
4716	=item C<ev_loop_count> renamed to C<ev_iteration>	5531	=item C<EV_COMPAT3> backwards compatibility mechanism
4717		5532
4718	=item C<ev_loop_depth> renamed to C<ev_depth>	5533	The backward compatibility mechanism can be controlled by
		5534	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5535	section.
4719		5536
4720	=item C<ev_loop_verify> renamed to C<ev_verify>	5537	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5538
		5539	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5540
		5541	ev_loop_destroy (EV_DEFAULT_UC);
		5542	ev_loop_fork (EV_DEFAULT);
		5543
		5544	=item function/symbol renames
		5545
		5546	A number of functions and symbols have been renamed:
		5547
		5548	ev_loop => ev_run
		5549	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5550	EVLOOP_ONESHOT => EVRUN_ONCE
		5551
		5552	ev_unloop => ev_break
		5553	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5554	EVUNLOOP_ONE => EVBREAK_ONE
		5555	EVUNLOOP_ALL => EVBREAK_ALL
		5556
		5557	EV_TIMEOUT => EV_TIMER
		5558
		5559	ev_loop_count => ev_iteration
		5560	ev_loop_depth => ev_depth
		5561	ev_loop_verify => ev_verify
4721		5562
4722	Most functions working on C<struct ev_loop> objects don't have an	5563	Most functions working on C<struct ev_loop> objects don't have an
4723	C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is	5564	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5565	associated constants have been renamed to not collide with the C<struct
		5566	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5567	as all other watcher types. Note that C<ev_loop_fork> is still called
4724	still called C<ev_loop_fork> because it would otherwise clash with the	5568	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
4725	C<ev_fork> typedef.	5569	typedef.
4726
4727	=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4728
4729	This is a simple rename - all other watcher types use their name
4730	as revents flag, and now C<ev_timer> does, too.
4731
4732	Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4733	and continue to be present for the foreseeable future, so this is mostly a
4734	documentation change.
4735		5570
4736	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>	5571	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4737		5572
4738	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different	5573	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4739	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile	5574	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
…		…
4746		5581
4747	=over 4	5582	=over 4
4748		5583
4749	=item active	5584	=item active
4750		5585
4751	A watcher is active as long as it has been started (has been attached to	5586	A watcher is active as long as it has been started and not yet stopped.
4752	an event loop) but not yet stopped (disassociated from the event loop).	5587	See L</WATCHER STATES> for details.
4753		5588
4754	=item application	5589	=item application
4755		5590
4756	In this document, an application is whatever is using libev.	5591	In this document, an application is whatever is using libev.
		5592
		5593	=item backend
		5594
		5595	The part of the code dealing with the operating system interfaces.
4757		5596
4758	=item callback	5597	=item callback
4759		5598
4760	The address of a function that is called when some event has been	5599	The address of a function that is called when some event has been
4761	detected. Callbacks are being passed the event loop, the watcher that	5600	detected. Callbacks are being passed the event loop, the watcher that
4762	received the event, and the actual event bitset.	5601	received the event, and the actual event bitset.
4763		5602
4764	=item callback invocation	5603	=item callback/watcher invocation
4765		5604
4766	The act of calling the callback associated with a watcher.	5605	The act of calling the callback associated with a watcher.
4767		5606
4768	=item event	5607	=item event
4769		5608
…		…
4788	The model used to describe how an event loop handles and processes	5627	The model used to describe how an event loop handles and processes
4789	watchers and events.	5628	watchers and events.
4790		5629
4791	=item pending	5630	=item pending
4792		5631
4793	A watcher is pending as soon as the corresponding event has been detected,	5632	A watcher is pending as soon as the corresponding event has been
4794	and stops being pending as soon as the watcher will be invoked or its	5633	detected. See L</WATCHER STATES> for details.
4795	pending status is explicitly cleared by the application.
4796
4797	A watcher can be pending, but not active. Stopping a watcher also clears
4798	its pending status.
4799		5634
4800	=item real time	5635	=item real time
4801		5636
4802	The physical time that is observed. It is apparently strictly monotonic :)	5637	The physical time that is observed. It is apparently strictly monotonic :)
4803		5638
4804	=item wall-clock time	5639	=item wall-clock time
4805		5640
4806	The time and date as shown on clocks. Unlike real time, it can actually	5641	The time and date as shown on clocks. Unlike real time, it can actually
4807	be wrong and jump forwards and backwards, e.g. when the you adjust your	5642	be wrong and jump forwards and backwards, e.g. when you adjust your
4808	clock.	5643	clock.
4809		5644
4810	=item watcher	5645	=item watcher
4811		5646
4812	A data structure that describes interest in certain events. Watchers need	5647	A data structure that describes interest in certain events. Watchers need
4813	to be started (attached to an event loop) before they can receive events.	5648	to be started (attached to an event loop) before they can receive events.
4814		5649
4815	=item watcher invocation
4816
4817	The act of calling the callback associated with a watcher.
4818
4819	=back	5650	=back
4820		5651
4821	=head1 AUTHOR	5652	=head1 AUTHOR
4822		5653
4823	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5654	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5655	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4824		5656

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