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Revision 1.277 by root, Thu Dec 31 06:50:17 2009 UTC vs.
Revision 1.456 by root, Tue Jul 2 06:07:54 2019 UTC

		1	=encoding utf-8
		2
1	=head1 NAME	3	=head1 NAME
2		4
3	libev - a high performance full-featured event loop written in C	5	libev - a high performance full-featured event loop written in C
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
…		…
26	puts ("stdin ready");	28	puts ("stdin ready");
27	// for one-shot events, one must manually stop the watcher	29	// for one-shot events, one must manually stop the watcher
28	// with its corresponding stop function.	30	// with its corresponding stop function.
29	ev_io_stop (EV_A_ w);	31	ev_io_stop (EV_A_ w);
30		32
31	// this causes all nested ev_loop's to stop iterating	33	// this causes all nested ev_run's to stop iterating
32	ev_unloop (EV_A_ EVUNLOOP_ALL);	34	ev_break (EV_A_ EVBREAK_ALL);
33	}	35	}
34		36
35	// another callback, this time for a time-out	37	// another callback, this time for a time-out
36	static void	38	static void
37	timeout_cb (EV_P_ ev_timer *w, int revents)	39	timeout_cb (EV_P_ ev_timer *w, int revents)
38	{	40	{
39	puts ("timeout");	41	puts ("timeout");
40	// this causes the innermost ev_loop to stop iterating	42	// this causes the innermost ev_run to stop iterating
41	ev_unloop (EV_A_ EVUNLOOP_ONE);	43	ev_break (EV_A_ EVBREAK_ONE);
42	}	44	}
43		45
44	int	46	int
45	main (void)	47	main (void)
46	{	48	{
47	// use the default event loop unless you have special needs	49	// use the default event loop unless you have special needs
48	struct ev_loop *loop = ev_default_loop (0);	50	struct ev_loop *loop = EV_DEFAULT;
49		51
50	// initialise an io watcher, then start it	52	// initialise an io watcher, then start it
51	// this one will watch for stdin to become readable	53	// this one will watch for stdin to become readable
52	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);	54	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
53	ev_io_start (loop, &stdin_watcher);	55	ev_io_start (loop, &stdin_watcher);
…		…
56	// simple non-repeating 5.5 second timeout	58	// simple non-repeating 5.5 second timeout
57	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);	59	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
58	ev_timer_start (loop, &timeout_watcher);	60	ev_timer_start (loop, &timeout_watcher);
59		61
60	// now wait for events to arrive	62	// now wait for events to arrive
61	ev_loop (loop, 0);	63	ev_run (loop, 0);
62		64
63	// unloop was called, so exit	65	// break was called, so exit
64	return 0;	66	return 0;
65	}	67	}
66		68
67	=head1 ABOUT THIS DOCUMENT	69	=head1 ABOUT THIS DOCUMENT
68		70
…		…
75	While this document tries to be as complete as possible in documenting	77	While this document tries to be as complete as possible in documenting
76	libev, its usage and the rationale behind its design, it is not a tutorial	78	libev, its usage and the rationale behind its design, it is not a tutorial
77	on event-based programming, nor will it introduce event-based programming	79	on event-based programming, nor will it introduce event-based programming
78	with libev.	80	with libev.
79		81
80	Familarity with event based programming techniques in general is assumed	82	Familiarity with event based programming techniques in general is assumed
81	throughout this document.	83	throughout this document.
		84
		85	=head1 WHAT TO READ WHEN IN A HURRY
		86
		87	This manual tries to be very detailed, but unfortunately, this also makes
		88	it very long. If you just want to know the basics of libev, I suggest
		89	reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and
		90	look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and
		91	C<ev_timer> sections in L</WATCHER TYPES>.
82		92
83	=head1 ABOUT LIBEV	93	=head1 ABOUT LIBEV
84		94
85	Libev is an event loop: you register interest in certain events (such as a	95	Libev is an event loop: you register interest in certain events (such as a
86	file descriptor being readable or a timeout occurring), and it will manage	96	file descriptor being readable or a timeout occurring), and it will manage
…		…
95	details of the event, and then hand it over to libev by I<starting> the	105	details of the event, and then hand it over to libev by I<starting> the
96	watcher.	106	watcher.
97		107
98	=head2 FEATURES	108	=head2 FEATURES
99		109
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	110	Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll>
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	111	interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	112	mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify>
103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner	113	interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative	114	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	timers (C<ev_timer>), absolute timers with customised rescheduling	115	timers (C<ev_timer>), absolute timers with customised rescheduling
106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status	116	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	change events (C<ev_child>), and event watchers dealing with the event	117	change events (C<ev_child>), and event watchers dealing with the event
108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and	118	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
…		…
124	this argument.	134	this argument.
125		135
126	=head2 TIME REPRESENTATION	136	=head2 TIME REPRESENTATION
127		137
128	Libev represents time as a single floating point number, representing	138	Libev represents time as a single floating point number, representing
129	the (fractional) number of seconds since the (POSIX) epoch (somewhere	139	the (fractional) number of seconds since the (POSIX) epoch (in practice
130	near the beginning of 1970, details are complicated, don't ask). This	140	somewhere near the beginning of 1970, details are complicated, don't
131	type is called C<ev_tstamp>, which is what you should use too. It usually	141	ask). This type is called C<ev_tstamp>, which is what you should use
132	aliases to the C<double> type in C. When you need to do any calculations	142	too. It usually aliases to the C<double> type in C. When you need to do
133	on it, you should treat it as some floating point value. Unlike the name	143	any calculations on it, you should treat it as some floating point value.
		144
134	component C<stamp> might indicate, it is also used for time differences	145	Unlike the name component C<stamp> might indicate, it is also used for
135	throughout libev.	146	time differences (e.g. delays) throughout libev.
136		147
137	=head1 ERROR HANDLING	148	=head1 ERROR HANDLING
138		149
139	Libev knows three classes of errors: operating system errors, usage errors	150	Libev knows three classes of errors: operating system errors, usage errors
140	and internal errors (bugs).	151	and internal errors (bugs).
…		…
148	When libev detects a usage error such as a negative timer interval, then	159	When libev detects a usage error such as a negative timer interval, then
149	it will print a diagnostic message and abort (via the C<assert> mechanism,	160	it will print a diagnostic message and abort (via the C<assert> mechanism,
150	so C<NDEBUG> will disable this checking): these are programming errors in	161	so C<NDEBUG> will disable this checking): these are programming errors in
151	the libev caller and need to be fixed there.	162	the libev caller and need to be fixed there.
152		163
		164	Via the C<EV_FREQUENT> macro you can compile in and/or enable extensive
		165	consistency checking code inside libev that can be used to check for
		166	internal inconsistencies, suually caused by application bugs.
		167
153	Libev also has a few internal error-checking C<assert>ions, and also has	168	Libev also has a few internal error-checking C<assert>ions. These do not
154	extensive consistency checking code. These do not trigger under normal
155	circumstances, as they indicate either a bug in libev or worse.	169	trigger under normal circumstances, as they indicate either a bug in libev
		170	or worse.
156		171
157		172
158	=head1 GLOBAL FUNCTIONS	173	=head1 GLOBAL FUNCTIONS
159		174
160	These functions can be called anytime, even before initialising the	175	These functions can be called anytime, even before initialising the
…		…
164		179
165	=item ev_tstamp ev_time ()	180	=item ev_tstamp ev_time ()
166		181
167	Returns the current time as libev would use it. Please note that the	182	Returns the current time as libev would use it. Please note that the
168	C<ev_now> function is usually faster and also often returns the timestamp	183	C<ev_now> function is usually faster and also often returns the timestamp
169	you actually want to know.	184	you actually want to know. Also interesting is the combination of
		185	C<ev_now_update> and C<ev_now>.
170		186
171	=item ev_sleep (ev_tstamp interval)	187	=item ev_sleep (ev_tstamp interval)
172		188
173	Sleep for the given interval: The current thread will be blocked until	189	Sleep for the given interval: The current thread will be blocked
174	either it is interrupted or the given time interval has passed. Basically	190	until either it is interrupted or the given time interval has
		191	passed (approximately - it might return a bit earlier even if not
		192	interrupted). Returns immediately if C<< interval <= 0 >>.
		193
175	this is a sub-second-resolution C<sleep ()>.	194	Basically this is a sub-second-resolution C<sleep ()>.
		195
		196	The range of the C<interval> is limited - libev only guarantees to work
		197	with sleep times of up to one day (C<< interval <= 86400 >>).
176		198
177	=item int ev_version_major ()	199	=item int ev_version_major ()
178		200
179	=item int ev_version_minor ()	201	=item int ev_version_minor ()
180		202
…		…
191	as this indicates an incompatible change. Minor versions are usually	213	as this indicates an incompatible change. Minor versions are usually
192	compatible to older versions, so a larger minor version alone is usually	214	compatible to older versions, so a larger minor version alone is usually
193	not a problem.	215	not a problem.
194		216
195	Example: Make sure we haven't accidentally been linked against the wrong	217	Example: Make sure we haven't accidentally been linked against the wrong
196	version.	218	version (note, however, that this will not detect other ABI mismatches,
		219	such as LFS or reentrancy).
197		220
198	assert (("libev version mismatch",	221	assert (("libev version mismatch",
199	ev_version_major () == EV_VERSION_MAJOR	222	ev_version_major () == EV_VERSION_MAJOR
200	&& ev_version_minor () >= EV_VERSION_MINOR));	223	&& ev_version_minor () >= EV_VERSION_MINOR));
201		224
…		…
212	assert (("sorry, no epoll, no sex",	235	assert (("sorry, no epoll, no sex",
213	ev_supported_backends () & EVBACKEND_EPOLL));	236	ev_supported_backends () & EVBACKEND_EPOLL));
214		237
215	=item unsigned int ev_recommended_backends ()	238	=item unsigned int ev_recommended_backends ()
216		239
217	Return the set of all backends compiled into this binary of libev and also	240	Return the set of all backends compiled into this binary of libev and
218	recommended for this platform. This set is often smaller than the one	241	also recommended for this platform, meaning it will work for most file
		242	descriptor types. This set is often smaller than the one returned by
219	returned by C<ev_supported_backends>, as for example kqueue is broken on	243	C<ev_supported_backends>, as for example kqueue is broken on most BSDs
220	most BSDs and will not be auto-detected unless you explicitly request it	244	and will not be auto-detected unless you explicitly request it (assuming
221	(assuming you know what you are doing). This is the set of backends that	245	you know what you are doing). This is the set of backends that libev will
222	libev will probe for if you specify no backends explicitly.	246	probe for if you specify no backends explicitly.
223		247
224	=item unsigned int ev_embeddable_backends ()	248	=item unsigned int ev_embeddable_backends ()
225		249
226	Returns the set of backends that are embeddable in other event loops. This	250	Returns the set of backends that are embeddable in other event loops. This
227	is the theoretical, all-platform, value. To find which backends	251	value is platform-specific but can include backends not available on the
228	might be supported on the current system, you would need to look at	252	current system. To find which embeddable backends might be supported on
229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	253	the current system, you would need to look at C<ev_embeddable_backends ()
230	recommended ones.	254	& ev_supported_backends ()>, likewise for recommended ones.
231		255
232	See the description of C<ev_embed> watchers for more info.	256	See the description of C<ev_embed> watchers for more info.
233		257
234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]	258	=item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ())
235		259
236	Sets the allocation function to use (the prototype is similar - the	260	Sets the allocation function to use (the prototype is similar - the
237	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	261	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
238	used to allocate and free memory (no surprises here). If it returns zero	262	used to allocate and free memory (no surprises here). If it returns zero
239	when memory needs to be allocated (C<size != 0>), the library might abort	263	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
245		269
246	You could override this function in high-availability programs to, say,	270	You could override this function in high-availability programs to, say,
247	free some memory if it cannot allocate memory, to use a special allocator,	271	free some memory if it cannot allocate memory, to use a special allocator,
248	or even to sleep a while and retry until some memory is available.	272	or even to sleep a while and retry until some memory is available.
249		273
		274	Example: The following is the C<realloc> function that libev itself uses
		275	which should work with C<realloc> and C<free> functions of all kinds and
		276	is probably a good basis for your own implementation.
		277
		278	static void *
		279	ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
		280	{
		281	if (size)
		282	return realloc (ptr, size);
		283
		284	free (ptr);
		285	return 0;
		286	}
		287
250	Example: Replace the libev allocator with one that waits a bit and then	288	Example: Replace the libev allocator with one that waits a bit and then
251	retries (example requires a standards-compliant C<realloc>).	289	retries.
252		290
253	static void *	291	static void *
254	persistent_realloc (void *ptr, size_t size)	292	persistent_realloc (void *ptr, size_t size)
255	{	293	{
		294	if (!size)
		295	{
		296	free (ptr);
		297	return 0;
		298	}
		299
256	for (;;)	300	for (;;)
257	{	301	{
258	void *newptr = realloc (ptr, size);	302	void *newptr = realloc (ptr, size);
259		303
260	if (newptr)	304	if (newptr)
…		…
265	}	309	}
266		310
267	...	311	...
268	ev_set_allocator (persistent_realloc);	312	ev_set_allocator (persistent_realloc);
269		313
270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]	314	=item ev_set_syserr_cb (void (*cb)(const char *msg) throw ())
271		315
272	Set the callback function to call on a retryable system call error (such	316	Set the callback function to call on a retryable system call error (such
273	as failed select, poll, epoll_wait). The message is a printable string	317	as failed select, poll, epoll_wait). The message is a printable string
274	indicating the system call or subsystem causing the problem. If this	318	indicating the system call or subsystem causing the problem. If this
275	callback is set, then libev will expect it to remedy the situation, no	319	callback is set, then libev will expect it to remedy the situation, no
…		…
287	}	331	}
288		332
289	...	333	...
290	ev_set_syserr_cb (fatal_error);	334	ev_set_syserr_cb (fatal_error);
291		335
		336	=item ev_feed_signal (int signum)
		337
		338	This function can be used to "simulate" a signal receive. It is completely
		339	safe to call this function at any time, from any context, including signal
		340	handlers or random threads.
		341
		342	Its main use is to customise signal handling in your process, especially
		343	in the presence of threads. For example, you could block signals
		344	by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when
		345	creating any loops), and in one thread, use C<sigwait> or any other
		346	mechanism to wait for signals, then "deliver" them to libev by calling
		347	C<ev_feed_signal>.
		348
292	=back	349	=back
293		350
294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	351	=head1 FUNCTIONS CONTROLLING EVENT LOOPS
295		352
296	An event loop is described by a C<struct ev_loop *> (the C<struct>	353	An event loop is described by a C<struct ev_loop *> (the C<struct> is
297	is I<not> optional in this case, as there is also an C<ev_loop>	354	I<not> optional in this case unless libev 3 compatibility is disabled, as
298	I<function>).	355	libev 3 had an C<ev_loop> function colliding with the struct name).
299		356
300	The library knows two types of such loops, the I<default> loop, which	357	The library knows two types of such loops, the I<default> loop, which
301	supports signals and child events, and dynamically created loops which do	358	supports child process events, and dynamically created event loops which
302	not.	359	do not.
303		360
304	=over 4	361	=over 4
305		362
306	=item struct ev_loop *ev_default_loop (unsigned int flags)	363	=item struct ev_loop *ev_default_loop (unsigned int flags)
307		364
308	This will initialise the default event loop if it hasn't been initialised	365	This returns the "default" event loop object, which is what you should
309	yet and return it. If the default loop could not be initialised, returns	366	normally use when you just need "the event loop". Event loop objects and
310	false. If it already was initialised it simply returns it (and ignores the	367	the C<flags> parameter are described in more detail in the entry for
311	flags. If that is troubling you, check C<ev_backend ()> afterwards).	368	C<ev_loop_new>.
		369
		370	If the default loop is already initialised then this function simply
		371	returns it (and ignores the flags. If that is troubling you, check
		372	C<ev_backend ()> afterwards). Otherwise it will create it with the given
		373	flags, which should almost always be C<0>, unless the caller is also the
		374	one calling C<ev_run> or otherwise qualifies as "the main program".
312		375
313	If you don't know what event loop to use, use the one returned from this	376	If you don't know what event loop to use, use the one returned from this
314	function.	377	function (or via the C<EV_DEFAULT> macro).
315		378
316	Note that this function is I<not> thread-safe, so if you want to use it	379	Note that this function is I<not> thread-safe, so if you want to use it
317	from multiple threads, you have to lock (note also that this is unlikely,	380	from multiple threads, you have to employ some kind of mutex (note also
318	as loops cannot be shared easily between threads anyway).	381	that this case is unlikely, as loops cannot be shared easily between
		382	threads anyway).
319		383
320	The default loop is the only loop that can handle C<ev_signal> and	384	The default loop is the only loop that can handle C<ev_child> watchers,
321	C<ev_child> watchers, and to do this, it always registers a handler	385	and to do this, it always registers a handler for C<SIGCHLD>. If this is
322	for C<SIGCHLD>. If this is a problem for your application you can either	386	a problem for your application you can either create a dynamic loop with
323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	387	C<ev_loop_new> which doesn't do that, or you can simply overwrite the
324	can simply overwrite the C<SIGCHLD> signal handler I<after> calling	388	C<SIGCHLD> signal handler I<after> calling C<ev_default_init>.
325	C<ev_default_init>.	389
		390	Example: This is the most typical usage.
		391
		392	if (!ev_default_loop (0))
		393	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
		394
		395	Example: Restrict libev to the select and poll backends, and do not allow
		396	environment settings to be taken into account:
		397
		398	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
		399
		400	=item struct ev_loop *ev_loop_new (unsigned int flags)
		401
		402	This will create and initialise a new event loop object. If the loop
		403	could not be initialised, returns false.
		404
		405	This function is thread-safe, and one common way to use libev with
		406	threads is indeed to create one loop per thread, and using the default
		407	loop in the "main" or "initial" thread.
326		408
327	The flags argument can be used to specify special behaviour or specific	409	The flags argument can be used to specify special behaviour or specific
328	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	410	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
329		411
330	The following flags are supported:	412	The following flags are supported:
…		…
340		422
341	If this flag bit is or'ed into the flag value (or the program runs setuid	423	If this flag bit is or'ed into the flag value (or the program runs setuid
342	or setgid) then libev will I<not> look at the environment variable	424	or setgid) then libev will I<not> look at the environment variable
343	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	425	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
344	override the flags completely if it is found in the environment. This is	426	override the flags completely if it is found in the environment. This is
345	useful to try out specific backends to test their performance, or to work	427	useful to try out specific backends to test their performance, to work
346	around bugs.	428	around bugs, or to make libev threadsafe (accessing environment variables
		429	cannot be done in a threadsafe way, but usually it works if no other
		430	thread modifies them).
347		431
348	=item C<EVFLAG_FORKCHECK>	432	=item C<EVFLAG_FORKCHECK>
349		433
350	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after	434	Instead of calling C<ev_loop_fork> manually after a fork, you can also
351	a fork, you can also make libev check for a fork in each iteration by	435	make libev check for a fork in each iteration by enabling this flag.
352	enabling this flag.
353		436
354	This works by calling C<getpid ()> on every iteration of the loop,	437	This works by calling C<getpid ()> on every iteration of the loop,
355	and thus this might slow down your event loop if you do a lot of loop	438	and thus this might slow down your event loop if you do a lot of loop
356	iterations and little real work, but is usually not noticeable (on my	439	iterations and little real work, but is usually not noticeable (on my
357	GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence	440	GNU/Linux system for example, C<getpid> is actually a simple 5-insn
358	without a system call and thus I<very> fast, but my GNU/Linux system also has	441	sequence without a system call and thus I<very> fast, but my GNU/Linux
359	C<pthread_atfork> which is even faster).	442	system also has C<pthread_atfork> which is even faster). (Update: glibc
		443	versions 2.25 apparently removed the C<getpid> optimisation again).
360		444
361	The big advantage of this flag is that you can forget about fork (and	445	The big advantage of this flag is that you can forget about fork (and
362	forget about forgetting to tell libev about forking) when you use this	446	forget about forgetting to tell libev about forking, although you still
363	flag.	447	have to ignore C<SIGPIPE>) when you use this flag.
364		448
365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	449	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
366	environment variable.	450	environment variable.
367		451
368	=item C<EVFLAG_NOINOTIFY>	452	=item C<EVFLAG_NOINOTIFY>
369		453
370	When this flag is specified, then libev will not attempt to use the	454	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	455	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	456	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.	457	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
374		458
375	=item C<EVFLAG_SIGNALFD>	459	=item C<EVFLAG_SIGNALFD>
376		460
377	When this flag is specified, then libev will attempt to use the	461	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	462	I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API
379	delivers signals synchronously, which makes is both faster and might make	463	delivers signals synchronously, which makes it both faster and might make
380	it possible to get the queued signal data.	464	it possible to get the queued signal data. It can also simplify signal
		465	handling with threads, as long as you properly block signals in your
		466	threads that are not interested in handling them.
381		467
382	Signalfd will not be used by default as this changes your signal mask, and	468	Signalfd will not be used by default as this changes your signal mask, and
383	there are a lot of shoddy libraries and programs (glib's threadpool for	469	there are a lot of shoddy libraries and programs (glib's threadpool for
384	example) that can't properly initialise their signal masks.	470	example) that can't properly initialise their signal masks.
		471
		472	=item C<EVFLAG_NOSIGMASK>
		473
		474	When this flag is specified, then libev will avoid to modify the signal
		475	mask. Specifically, this means you have to make sure signals are unblocked
		476	when you want to receive them.
		477
		478	This behaviour is useful when you want to do your own signal handling, or
		479	want to handle signals only in specific threads and want to avoid libev
		480	unblocking the signals.
		481
		482	It's also required by POSIX in a threaded program, as libev calls
		483	C<sigprocmask>, whose behaviour is officially unspecified.
		484
		485	This flag's behaviour will become the default in future versions of libev.
385		486
386	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	487	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
387		488
388	This is your standard select(2) backend. Not I<completely> standard, as	489	This is your standard select(2) backend. Not I<completely> standard, as
389	libev tries to roll its own fd_set with no limits on the number of fds,	490	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
414	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	515	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
415	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	516	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
416		517
417	=item C<EVBACKEND_EPOLL> (value 4, Linux)	518	=item C<EVBACKEND_EPOLL> (value 4, Linux)
418		519
419	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9	520	Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9
420	kernels).	521	kernels).
421		522
422	For few fds, this backend is a bit little slower than poll and select,	523	For few fds, this backend is a bit little slower than poll and select, but
423	but it scales phenomenally better. While poll and select usually scale	524	it scales phenomenally better. While poll and select usually scale like
424	like O(total_fds) where n is the total number of fds (or the highest fd),	525	O(total_fds) where total_fds is the total number of fds (or the highest
425	epoll scales either O(1) or O(active_fds).	526	fd), epoll scales either O(1) or O(active_fds).
426		527
427	The epoll mechanism deserves honorable mention as the most misdesigned	528	The epoll mechanism deserves honorable mention as the most misdesigned
428	of the more advanced event mechanisms: mere annoyances include silently	529	of the more advanced event mechanisms: mere annoyances include silently
429	dropping file descriptors, requiring a system call per change per file	530	dropping file descriptors, requiring a system call per change per file
430	descriptor (and unnecessary guessing of parameters), problems with dup and	531	descriptor (and unnecessary guessing of parameters), problems with dup,
		532	returning before the timeout value, resulting in additional iterations
		533	(and only giving 5ms accuracy while select on the same platform gives
431	so on. The biggest issue is fork races, however - if a program forks then	534	0.1ms) and so on. The biggest issue is fork races, however - if a program
432	I<both> parent and child process have to recreate the epoll set, which can	535	forks then I<both> parent and child process have to recreate the epoll
433	take considerable time (one syscall per file descriptor) and is of course	536	set, which can take considerable time (one syscall per file descriptor)
434	hard to detect.	537	and is of course hard to detect.
435		538
436	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but	539	Epoll is also notoriously buggy - embedding epoll fds I<should> work,
437	of course I<doesn't>, and epoll just loves to report events for totally	540	but of course I<doesn't>, and epoll just loves to report events for
438	I<different> file descriptors (even already closed ones, so one cannot	541	totally I<different> file descriptors (even already closed ones, so
439	even remove them from the set) than registered in the set (especially	542	one cannot even remove them from the set) than registered in the set
440	on SMP systems). Libev tries to counter these spurious notifications by	543	(especially on SMP systems). Libev tries to counter these spurious
441	employing an additional generation counter and comparing that against the	544	notifications by employing an additional generation counter and comparing
442	events to filter out spurious ones, recreating the set when required.	545	that against the events to filter out spurious ones, recreating the set
		546	when required. Epoll also erroneously rounds down timeouts, but gives you
		547	no way to know when and by how much, so sometimes you have to busy-wait
		548	because epoll returns immediately despite a nonzero timeout. And last
		549	not least, it also refuses to work with some file descriptors which work
		550	perfectly fine with C<select> (files, many character devices...).
		551
		552	Epoll is truly the train wreck among event poll mechanisms, a frankenpoll,
		553	cobbled together in a hurry, no thought to design or interaction with
		554	others. Oh, the pain, will it ever stop...
443		555
444	While stopping, setting and starting an I/O watcher in the same iteration	556	While stopping, setting and starting an I/O watcher in the same iteration
445	will result in some caching, there is still a system call per such	557	will result in some caching, there is still a system call per such
446	incident (because the same I<file descriptor> could point to a different	558	incident (because the same I<file descriptor> could point to a different
447	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed	559	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
…		…
459	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or	571	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
460	faster than epoll for maybe up to a hundred file descriptors, depending on	572	faster than epoll for maybe up to a hundred file descriptors, depending on
461	the usage. So sad.	573	the usage. So sad.
462		574
463	While nominally embeddable in other event loops, this feature is broken in	575	While nominally embeddable in other event loops, this feature is broken in
464	all kernel versions tested so far.	576	a lot of kernel revisions, but probably(!) works in current versions.
465		577
466	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	578	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
467	C<EVBACKEND_POLL>.	579	C<EVBACKEND_POLL>.
468		580
		581	=item C<EVBACKEND_LINUXAIO> (value 64, Linux)
		582
		583	Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<<
		584	io_submit(2) >>) event interface available in post-4.18 kernels (but libev
		585	only tries to use it in 4.19+).
		586
		587	This is another Linux train wreck of an event interface.
		588
		589	If this backend works for you (as of this writing, it was very
		590	experimental), it is the best event interface available on Linux and might
		591	be well worth enabling it - if it isn't available in your kernel this will
		592	be detected and this backend will be skipped.
		593
		594	This backend can batch oneshot requests and supports a user-space ring
		595	buffer to receive events. It also doesn't suffer from most of the design
		596	problems of epoll (such as not being able to remove event sources from
		597	the epoll set), and generally sounds too good to be true. Because, this
		598	being the Linux kernel, of course it suffers from a whole new set of
		599	limitations, forcing you to fall back to epoll, inheriting all its design
		600	issues.
		601
		602	For one, it is not easily embeddable (but probably could be done using
		603	an event fd at some extra overhead). It also is subject to a system wide
		604	limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO
		605	requests are left, this backend will be skipped during initialisation, and
		606	will switch to epoll when the loop is active.
		607
		608	Most problematic in practice, however, is that not all file descriptors
		609	work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds,
		610	files, F</dev/null> and many others are supported, but ttys do not work
		611	properly (a known bug that the kernel developers don't care about, see
		612	L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
		613	(yet?) a generic event polling interface.
		614
		615	Overall, it seems the Linux developers just don't want it to have a
		616	generic event handling mechanism other than C<select> or C<poll>.
		617
		618	To work around all these problem, the current version of libev uses its
		619	epoll backend as a fallback for file descriptor types that do not work. Or
		620	falls back completely to epoll if the kernel acts up.
		621
		622	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		623	C<EVBACKEND_POLL>.
		624
469	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	625	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
470		626
471	Kqueue deserves special mention, as at the time of this writing, it	627	Kqueue deserves special mention, as at the time this backend was
472	was broken on all BSDs except NetBSD (usually it doesn't work reliably	628	implemented, it was broken on all BSDs except NetBSD (usually it doesn't
473	with anything but sockets and pipes, except on Darwin, where of course	629	work reliably with anything but sockets and pipes, except on Darwin,
474	it's completely useless). Unlike epoll, however, whose brokenness	630	where of course it's completely useless). Unlike epoll, however, whose
475	is by design, these kqueue bugs can (and eventually will) be fixed	631	brokenness is by design, these kqueue bugs can be (and mostly have been)
476	without API changes to existing programs. For this reason it's not being	632	fixed without API changes to existing programs. For this reason it's not
477	"auto-detected" unless you explicitly specify it in the flags (i.e. using	633	being "auto-detected" on all platforms unless you explicitly specify it
478	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	634	in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a
479	system like NetBSD.	635	known-to-be-good (-enough) system like NetBSD.
480		636
481	You still can embed kqueue into a normal poll or select backend and use it	637	You still can embed kqueue into a normal poll or select backend and use it
482	only for sockets (after having made sure that sockets work with kqueue on	638	only for sockets (after having made sure that sockets work with kqueue on
483	the target platform). See C<ev_embed> watchers for more info.	639	the target platform). See C<ev_embed> watchers for more info.
484		640
485	It scales in the same way as the epoll backend, but the interface to the	641	It scales in the same way as the epoll backend, but the interface to the
486	kernel is more efficient (which says nothing about its actual speed, of	642	kernel is more efficient (which says nothing about its actual speed, of
487	course). While stopping, setting and starting an I/O watcher does never	643	course). While stopping, setting and starting an I/O watcher does never
488	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	644	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
489	two event changes per incident. Support for C<fork ()> is very bad (but	645	two event changes per incident. Support for C<fork ()> is very bad (you
490	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect	646	might have to leak fds on fork, but it's more sane than epoll) and it
491	cases	647	drops fds silently in similarly hard-to-detect cases.
492		648
493	This backend usually performs well under most conditions.	649	This backend usually performs well under most conditions.
494		650
495	While nominally embeddable in other event loops, this doesn't work	651	While nominally embeddable in other event loops, this doesn't work
496	everywhere, so you might need to test for this. And since it is broken	652	everywhere, so you might need to test for this. And since it is broken
…		…
513	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	669	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
514		670
515	This uses the Solaris 10 event port mechanism. As with everything on Solaris,	671	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
516	it's really slow, but it still scales very well (O(active_fds)).	672	it's really slow, but it still scales very well (O(active_fds)).
517		673
518	Please note that Solaris event ports can deliver a lot of spurious
519	notifications, so you need to use non-blocking I/O or other means to avoid
520	blocking when no data (or space) is available.
521
522	While this backend scales well, it requires one system call per active	674	While this backend scales well, it requires one system call per active
523	file descriptor per loop iteration. For small and medium numbers of file	675	file descriptor per loop iteration. For small and medium numbers of file
524	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	676	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
525	might perform better.	677	might perform better.
526		678
527	On the positive side, with the exception of the spurious readiness	679	On the positive side, this backend actually performed fully to
528	notifications, this backend actually performed fully to specification
529	in all tests and is fully embeddable, which is a rare feat among the	680	specification in all tests and is fully embeddable, which is a rare feat
530	OS-specific backends (I vastly prefer correctness over speed hacks).	681	among the OS-specific backends (I vastly prefer correctness over speed
		682	hacks).
		683
		684	On the negative side, the interface is I<bizarre> - so bizarre that
		685	even sun itself gets it wrong in their code examples: The event polling
		686	function sometimes returns events to the caller even though an error
		687	occurred, but with no indication whether it has done so or not (yes, it's
		688	even documented that way) - deadly for edge-triggered interfaces where you
		689	absolutely have to know whether an event occurred or not because you have
		690	to re-arm the watcher.
		691
		692	Fortunately libev seems to be able to work around these idiocies.
531		693
532	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	694	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
533	C<EVBACKEND_POLL>.	695	C<EVBACKEND_POLL>.
534		696
535	=item C<EVBACKEND_ALL>	697	=item C<EVBACKEND_ALL>
536		698
537	Try all backends (even potentially broken ones that wouldn't be tried	699	Try all backends (even potentially broken ones that wouldn't be tried
538	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	700	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
539	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	701	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
540		702
541	It is definitely not recommended to use this flag.	703	It is definitely not recommended to use this flag, use whatever
		704	C<ev_recommended_backends ()> returns, or simply do not specify a backend
		705	at all.
		706
		707	=item C<EVBACKEND_MASK>
		708
		709	Not a backend at all, but a mask to select all backend bits from a
		710	C<flags> value, in case you want to mask out any backends from a flags
		711	value (e.g. when modifying the C<LIBEV_FLAGS> environment variable).
542		712
543	=back	713	=back
544		714
545	If one or more of the backend flags are or'ed into the flags value,	715	If one or more of the backend flags are or'ed into the flags value,
546	then only these backends will be tried (in the reverse order as listed	716	then only these backends will be tried (in the reverse order as listed
547	here). If none are specified, all backends in C<ev_recommended_backends	717	here). If none are specified, all backends in C<ev_recommended_backends
548	()> will be tried.	718	()> will be tried.
549		719
550	Example: This is the most typical usage.
551
552	if (!ev_default_loop (0))
553	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
554
555	Example: Restrict libev to the select and poll backends, and do not allow
556	environment settings to be taken into account:
557
558	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
559
560	Example: Use whatever libev has to offer, but make sure that kqueue is
561	used if available (warning, breaks stuff, best use only with your own
562	private event loop and only if you know the OS supports your types of
563	fds):
564
565	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
566
567	=item struct ev_loop *ev_loop_new (unsigned int flags)
568
569	Similar to C<ev_default_loop>, but always creates a new event loop that is
570	always distinct from the default loop. Unlike the default loop, it cannot
571	handle signal and child watchers, and attempts to do so will be greeted by
572	undefined behaviour (or a failed assertion if assertions are enabled).
573
574	Note that this function I<is> thread-safe, and the recommended 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.	720	Example: Try to create a event loop that uses epoll and nothing else.
579		721
580	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	722	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
581	if (!epoller)	723	if (!epoller)
582	fatal ("no epoll found here, maybe it hides under your chair");	724	fatal ("no epoll found here, maybe it hides under your chair");
583		725
		726	Example: Use whatever libev has to offer, but make sure that kqueue is
		727	used if available.
		728
		729	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
		730
		731	Example: Similarly, on linux, you mgiht want to take advantage of the
		732	linux aio backend if possible, but fall back to something else if that
		733	isn't available.
		734
		735	struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
		736
584	=item ev_default_destroy ()	737	=item ev_loop_destroy (loop)
585		738
586	Destroys the default loop again (frees all memory and kernel state	739	Destroys an event loop object (frees all memory and kernel state
587	etc.). None of the active event watchers will be stopped in the normal	740	etc.). None of the active event watchers will be stopped in the normal
588	sense, so e.g. C<ev_is_active> might still return true. It is your	741	sense, so e.g. C<ev_is_active> might still return true. It is your
589	responsibility to either stop all watchers cleanly yourself I<before>	742	responsibility to either stop all watchers cleanly yourself I<before>
590	calling this function, or cope with the fact afterwards (which is usually	743	calling this function, or cope with the fact afterwards (which is usually
591	the easiest thing, you can just ignore the watchers and/or C<free ()> them	744	the easiest thing, you can just ignore the watchers and/or C<free ()> them
…		…
593		746
594	Note that certain global state, such as signal state (and installed signal	747	Note that certain global state, such as signal state (and installed signal
595	handlers), will not be freed by this function, and related watchers (such	748	handlers), will not be freed by this function, and related watchers (such
596	as signal and child watchers) would need to be stopped manually.	749	as signal and child watchers) would need to be stopped manually.
597		750
598	In general it is not advisable to call this function except in the	751	This function is normally used on loop objects allocated by
599	rare occasion where you really need to free e.g. the signal handling	752	C<ev_loop_new>, but it can also be used on the default loop returned by
		753	C<ev_default_loop>, in which case it is not thread-safe.
		754
		755	Note that it is not advisable to call this function on the default loop
		756	except in the rare occasion where you really need to free its resources.
600	pipe fds. If you need dynamically allocated loops it is better to use	757	If you need dynamically allocated loops it is better to use C<ev_loop_new>
601	C<ev_loop_new> and C<ev_loop_destroy>.	758	and C<ev_loop_destroy>.
602		759
603	=item ev_loop_destroy (loop)	760	=item ev_loop_fork (loop)
604		761
605	Like C<ev_default_destroy>, but destroys an event loop created by an
606	earlier call to C<ev_loop_new>.
607
608	=item ev_default_fork ()
609
610	This function sets a flag that causes subsequent C<ev_loop> iterations	762	This function sets a flag that causes subsequent C<ev_run> iterations
611	to reinitialise the kernel state for backends that have one. Despite the	763	to reinitialise the kernel state for backends that have one. Despite
612	name, you can call it anytime, but it makes most sense after forking, in	764	the name, you can call it anytime you are allowed to start or stop
613	the child process (or both child and parent, but that again makes little	765	watchers (except inside an C<ev_prepare> callback), but it makes most
614	sense). You I<must> call it in the child before using any of the libev	766	sense after forking, in the child process. You I<must> call it (or use
615	functions, and it will only take effect at the next C<ev_loop> iteration.	767	C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>.
		768
		769	In addition, if you want to reuse a loop (via this function or
		770	C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>.
		771
		772	Again, you I<have> to call it on I<any> loop that you want to re-use after
		773	a fork, I<even if you do not plan to use the loop in the parent>. This is
		774	because some kernel interfaces *cough* I<kqueue> *cough* do funny things
		775	during fork.
616		776
617	On the other hand, you only need to call this function in the child	777	On the other hand, you only need to call this function in the child
618	process if and only if you want to use the event library in the child. If	778	process if and only if you want to use the event loop in the child. If
619	you just fork+exec, you don't have to call it at all.	779	you just fork+exec or create a new loop in the child, you don't have to
		780	call it at all (in fact, C<epoll> is so badly broken that it makes a
		781	difference, but libev will usually detect this case on its own and do a
		782	costly reset of the backend).
620		783
621	The function itself is quite fast and it's usually not a problem to call	784	The function itself is quite fast and it's usually not a problem to call
622	it just in case after a fork. To make this easy, the function will fit in	785	it just in case after a fork.
623	quite nicely into a call to C<pthread_atfork>:
624		786
		787	Example: Automate calling C<ev_loop_fork> on the default loop when
		788	using pthreads.
		789
		790	static void
		791	post_fork_child (void)
		792	{
		793	ev_loop_fork (EV_DEFAULT);
		794	}
		795
		796	...
625	pthread_atfork (0, 0, ev_default_fork);	797	pthread_atfork (0, 0, post_fork_child);
626
627	=item ev_loop_fork (loop)
628
629	Like C<ev_default_fork>, but acts on an event loop created by
630	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
631	after fork that you want to re-use in the child, and how you do this is
632	entirely your own problem.
633		798
634	=item int ev_is_default_loop (loop)	799	=item int ev_is_default_loop (loop)
635		800
636	Returns true when the given loop is, in fact, the default loop, and false	801	Returns true when the given loop is, in fact, the default loop, and false
637	otherwise.	802	otherwise.
638		803
639	=item unsigned int ev_loop_count (loop)	804	=item unsigned int ev_iteration (loop)
640		805
641	Returns the count of loop iterations for the loop, which is identical to	806	Returns the current iteration count for the event loop, which is identical
642	the number of times libev did poll for new events. It starts at C<0> and	807	to the number of times libev did poll for new events. It starts at C<0>
643	happily wraps around with enough iterations.	808	and happily wraps around with enough iterations.
644		809
645	This value can sometimes be useful as a generation counter of sorts (it	810	This value can sometimes be useful as a generation counter of sorts (it
646	"ticks" the number of loop iterations), as it roughly corresponds with	811	"ticks" the number of loop iterations), as it roughly corresponds with
647	C<ev_prepare> and C<ev_check> calls.	812	C<ev_prepare> and C<ev_check> calls - and is incremented between the
		813	prepare and check phases.
648		814
649	=item unsigned int ev_loop_depth (loop)	815	=item unsigned int ev_depth (loop)
650		816
651	Returns the number of times C<ev_loop> was entered minus the number of	817	Returns the number of times C<ev_run> was entered minus the number of
652	times C<ev_loop> was exited, in other words, the recursion depth.	818	times C<ev_run> was exited normally, in other words, the recursion depth.
653		819
654	Outside C<ev_loop>, this number is zero. In a callback, this number is	820	Outside C<ev_run>, this number is zero. In a callback, this number is
655	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),	821	C<1>, unless C<ev_run> was invoked recursively (or from another thread),
656	in which case it is higher.	822	in which case it is higher.
657		823
658	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread	824	Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread,
659	etc.), doesn't count as exit.	825	throwing an exception etc.), doesn't count as "exit" - consider this
		826	as a hint to avoid such ungentleman-like behaviour unless it's really
		827	convenient, in which case it is fully supported.
660		828
661	=item unsigned int ev_backend (loop)	829	=item unsigned int ev_backend (loop)
662		830
663	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	831	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
664	use.	832	use.
…		…
673		841
674	=item ev_now_update (loop)	842	=item ev_now_update (loop)
675		843
676	Establishes the current time by querying the kernel, updating the time	844	Establishes the current time by querying the kernel, updating the time
677	returned by C<ev_now ()> in the progress. This is a costly operation and	845	returned by C<ev_now ()> in the progress. This is a costly operation and
678	is usually done automatically within C<ev_loop ()>.	846	is usually done automatically within C<ev_run ()>.
679		847
680	This function is rarely useful, but when some event callback runs for a	848	This function is rarely useful, but when some event callback runs for a
681	very long time without entering the event loop, updating libev's idea of	849	very long time without entering the event loop, updating libev's idea of
682	the current time is a good idea.	850	the current time is a good idea.
683		851
684	See also L<The special problem of time updates> in the C<ev_timer> section.	852	See also L</The special problem of time updates> in the C<ev_timer> section.
685		853
686	=item ev_suspend (loop)	854	=item ev_suspend (loop)
687		855
688	=item ev_resume (loop)	856	=item ev_resume (loop)
689		857
690	These two functions suspend and resume a loop, for use when the loop is	858	These two functions suspend and resume an event loop, for use when the
691	not used for a while and timeouts should not be processed.	859	loop is not used for a while and timeouts should not be processed.
692		860
693	A typical use case would be an interactive program such as a game: When	861	A typical use case would be an interactive program such as a game: When
694	the user presses C<^Z> to suspend the game and resumes it an hour later it	862	the user presses C<^Z> to suspend the game and resumes it an hour later it
695	would be best to handle timeouts as if no time had actually passed while	863	would be best to handle timeouts as if no time had actually passed while
696	the program was suspended. This can be achieved by calling C<ev_suspend>	864	the program was suspended. This can be achieved by calling C<ev_suspend>
…		…
698	C<ev_resume> directly afterwards to resume timer processing.	866	C<ev_resume> directly afterwards to resume timer processing.
699		867
700	Effectively, all C<ev_timer> watchers will be delayed by the time spend	868	Effectively, all C<ev_timer> watchers will be delayed by the time spend
701	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers	869	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
702	will be rescheduled (that is, they will lose any events that would have	870	will be rescheduled (that is, they will lose any events that would have
703	occured while suspended).	871	occurred while suspended).
704		872
705	After calling C<ev_suspend> you B<must not> call I<any> function on the	873	After calling C<ev_suspend> you B<must not> call I<any> function on the
706	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>	874	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
707	without a previous call to C<ev_suspend>.	875	without a previous call to C<ev_suspend>.
708		876
709	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the	877	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
710	event loop time (see C<ev_now_update>).	878	event loop time (see C<ev_now_update>).
711		879
712	=item ev_loop (loop, int flags)	880	=item bool ev_run (loop, int flags)
713		881
714	Finally, this is it, the event handler. This function usually is called	882	Finally, this is it, the event handler. This function usually is called
715	after you have initialised all your watchers and you want to start	883	after you have initialised all your watchers and you want to start
716	handling events.	884	handling events. It will ask the operating system for any new events, call
		885	the watcher callbacks, and then repeat the whole process indefinitely: This
		886	is why event loops are called I<loops>.
717		887
718	If the flags argument is specified as C<0>, it will not return until	888	If the flags argument is specified as C<0>, it will keep handling events
719	either no event watchers are active anymore or C<ev_unloop> was called.	889	until either no event watchers are active anymore or C<ev_break> was
		890	called.
720		891
		892	The return value is false if there are no more active watchers (which
		893	usually means "all jobs done" or "deadlock"), and true in all other cases
		894	(which usually means " you should call C<ev_run> again").
		895
721	Please note that an explicit C<ev_unloop> is usually better than	896	Please note that an explicit C<ev_break> is usually better than
722	relying on all watchers to be stopped when deciding when a program has	897	relying on all watchers to be stopped when deciding when a program has
723	finished (especially in interactive programs), but having a program	898	finished (especially in interactive programs), but having a program
724	that automatically loops as long as it has to and no longer by virtue	899	that automatically loops as long as it has to and no longer by virtue
725	of relying on its watchers stopping correctly, that is truly a thing of	900	of relying on its watchers stopping correctly, that is truly a thing of
726	beauty.	901	beauty.
727		902
		903	This function is I<mostly> exception-safe - you can break out of a
		904	C<ev_run> call by calling C<longjmp> in a callback, throwing a C++
		905	exception and so on. This does not decrement the C<ev_depth> value, nor
		906	will it clear any outstanding C<EVBREAK_ONE> breaks.
		907
728	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	908	A flags value of C<EVRUN_NOWAIT> will look for new events, will handle
729	those events and any already outstanding ones, but will not block your	909	those events and any already outstanding ones, but will not wait and
730	process in case there are no events and will return after one iteration of	910	block your process in case there are no events and will return after one
731	the loop.	911	iteration of the loop. This is sometimes useful to poll and handle new
		912	events while doing lengthy calculations, to keep the program responsive.
732		913
733	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	914	A flags value of C<EVRUN_ONCE> will look for new events (waiting if
734	necessary) and will handle those and any already outstanding ones. It	915	necessary) and will handle those and any already outstanding ones. It
735	will block your process until at least one new event arrives (which could	916	will block your process until at least one new event arrives (which could
736	be an event internal to libev itself, so there is no guarantee that a	917	be an event internal to libev itself, so there is no guarantee that a
737	user-registered callback will be called), and will return after one	918	user-registered callback will be called), and will return after one
738	iteration of the loop.	919	iteration of the loop.
739		920
740	This is useful if you are waiting for some external event in conjunction	921	This is useful if you are waiting for some external event in conjunction
741	with something not expressible using other libev watchers (i.e. "roll your	922	with something not expressible using other libev watchers (i.e. "roll your
742	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is	923	own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
743	usually a better approach for this kind of thing.	924	usually a better approach for this kind of thing.
744		925
745	Here are the gory details of what C<ev_loop> does:	926	Here are the gory details of what C<ev_run> does (this is for your
		927	understanding, not a guarantee that things will work exactly like this in
		928	future versions):
746		929
		930	- Increment loop depth.
		931	- Reset the ev_break status.
747	- Before the first iteration, call any pending watchers.	932	- Before the first iteration, call any pending watchers.
		933	LOOP:
748	* If EVFLAG_FORKCHECK was used, check for a fork.	934	- If EVFLAG_FORKCHECK was used, check for a fork.
749	- If a fork was detected (by any means), queue and call all fork watchers.	935	- If a fork was detected (by any means), queue and call all fork watchers.
750	- Queue and call all prepare watchers.	936	- Queue and call all prepare watchers.
		937	- If ev_break was called, goto FINISH.
751	- If we have been forked, detach and recreate the kernel state	938	- If we have been forked, detach and recreate the kernel state
752	as to not disturb the other process.	939	as to not disturb the other process.
753	- Update the kernel state with all outstanding changes.	940	- Update the kernel state with all outstanding changes.
754	- Update the "event loop time" (ev_now ()).	941	- Update the "event loop time" (ev_now ()).
755	- Calculate for how long to sleep or block, if at all	942	- Calculate for how long to sleep or block, if at all
756	(active idle watchers, EVLOOP_NONBLOCK or not having	943	(active idle watchers, EVRUN_NOWAIT or not having
757	any active watchers at all will result in not sleeping).	944	any active watchers at all will result in not sleeping).
758	- Sleep if the I/O and timer collect interval say so.	945	- Sleep if the I/O and timer collect interval say so.
		946	- Increment loop iteration counter.
759	- Block the process, waiting for any events.	947	- Block the process, waiting for any events.
760	- Queue all outstanding I/O (fd) events.	948	- Queue all outstanding I/O (fd) events.
761	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	949	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
762	- Queue all expired timers.	950	- Queue all expired timers.
763	- Queue all expired periodics.	951	- Queue all expired periodics.
764	- Unless any events are pending now, queue all idle watchers.	952	- Queue all idle watchers with priority higher than that of pending events.
765	- Queue all check watchers.	953	- Queue all check watchers.
766	- Call all queued watchers in reverse order (i.e. check watchers first).	954	- Call all queued watchers in reverse order (i.e. check watchers first).
767	Signals and child watchers are implemented as I/O watchers, and will	955	Signals and child watchers are implemented as I/O watchers, and will
768	be handled here by queueing them when their watcher gets executed.	956	be handled here by queueing them when their watcher gets executed.
769	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	957	- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
770	were used, or there are no active watchers, return, otherwise	958	were used, or there are no active watchers, goto FINISH, otherwise
771	continue with step *.	959	continue with step LOOP.
		960	FINISH:
		961	- Reset the ev_break status iff it was EVBREAK_ONE.
		962	- Decrement the loop depth.
		963	- Return.
772		964
773	Example: Queue some jobs and then loop until no events are outstanding	965	Example: Queue some jobs and then loop until no events are outstanding
774	anymore.	966	anymore.
775		967
776	... queue jobs here, make sure they register event watchers as long	968	... queue jobs here, make sure they register event watchers as long
777	... as they still have work to do (even an idle watcher will do..)	969	... as they still have work to do (even an idle watcher will do..)
778	ev_loop (my_loop, 0);	970	ev_run (my_loop, 0);
779	... jobs done or somebody called unloop. yeah!	971	... jobs done or somebody called break. yeah!
780		972
781	=item ev_unloop (loop, how)	973	=item ev_break (loop, how)
782		974
783	Can be used to make a call to C<ev_loop> return early (but only after it	975	Can be used to make a call to C<ev_run> return early (but only after it
784	has processed all outstanding events). The C<how> argument must be either	976	has processed all outstanding events). The C<how> argument must be either
785	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	977	C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or
786	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	978	C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return.
787		979
788	This "unloop state" will be cleared when entering C<ev_loop> again.	980	This "break state" will be cleared on the next call to C<ev_run>.
789		981
790	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.	982	It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in
		983	which case it will have no effect.
791		984
792	=item ev_ref (loop)	985	=item ev_ref (loop)
793		986
794	=item ev_unref (loop)	987	=item ev_unref (loop)
795		988
796	Ref/unref can be used to add or remove a reference count on the event	989	Ref/unref can be used to add or remove a reference count on the event
797	loop: Every watcher keeps one reference, and as long as the reference	990	loop: Every watcher keeps one reference, and as long as the reference
798	count is nonzero, C<ev_loop> will not return on its own.	991	count is nonzero, C<ev_run> will not return on its own.
799		992
800	This is useful when you have a watcher that you never intend to	993	This is useful when you have a watcher that you never intend to
801	unregister, but that nevertheless should not keep C<ev_loop> from	994	unregister, but that nevertheless should not keep C<ev_run> from
802	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>	995	returning. In such a case, call C<ev_unref> after starting, and C<ev_ref>
803	before stopping it.	996	before stopping it.
804		997
805	As an example, libev itself uses this for its internal signal pipe: It	998	As an example, libev itself uses this for its internal signal pipe: It
806	is not visible to the libev user and should not keep C<ev_loop> from	999	is not visible to the libev user and should not keep C<ev_run> from
807	exiting if no event watchers registered by it are active. It is also an	1000	exiting if no event watchers registered by it are active. It is also an
808	excellent way to do this for generic recurring timers or from within	1001	excellent way to do this for generic recurring timers or from within
809	third-party libraries. Just remember to I<unref after start> and I<ref	1002	third-party libraries. Just remember to I<unref after start> and I<ref
810	before stop> (but only if the watcher wasn't active before, or was active	1003	before stop> (but only if the watcher wasn't active before, or was active
811	before, respectively. Note also that libev might stop watchers itself	1004	before, respectively. Note also that libev might stop watchers itself
812	(e.g. non-repeating timers) in which case you have to C<ev_ref>	1005	(e.g. non-repeating timers) in which case you have to C<ev_ref>
813	in the callback).	1006	in the callback).
814		1007
815	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	1008	Example: Create a signal watcher, but keep it from keeping C<ev_run>
816	running when nothing else is active.	1009	running when nothing else is active.
817		1010
818	ev_signal exitsig;	1011	ev_signal exitsig;
819	ev_signal_init (&exitsig, sig_cb, SIGINT);	1012	ev_signal_init (&exitsig, sig_cb, SIGINT);
820	ev_signal_start (loop, &exitsig);	1013	ev_signal_start (loop, &exitsig);
821	evf_unref (loop);	1014	ev_unref (loop);
822		1015
823	Example: For some weird reason, unregister the above signal handler again.	1016	Example: For some weird reason, unregister the above signal handler again.
824		1017
825	ev_ref (loop);	1018	ev_ref (loop);
826	ev_signal_stop (loop, &exitsig);	1019	ev_signal_stop (loop, &exitsig);
…		…
846	overhead for the actual polling but can deliver many events at once.	1039	overhead for the actual polling but can deliver many events at once.
847		1040
848	By setting a higher I<io collect interval> you allow libev to spend more	1041	By setting a higher I<io collect interval> you allow libev to spend more
849	time collecting I/O events, so you can handle more events per iteration,	1042	time collecting I/O events, so you can handle more events per iteration,
850	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	1043	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
851	C<ev_timer>) will be not affected. Setting this to a non-null value will	1044	C<ev_timer>) will not be affected. Setting this to a non-null value will
852	introduce an additional C<ev_sleep ()> call into most loop iterations. The	1045	introduce an additional C<ev_sleep ()> call into most loop iterations. The
853	sleep time ensures that libev will not poll for I/O events more often then	1046	sleep time ensures that libev will not poll for I/O events more often then
854	once per this interval, on average.	1047	once per this interval, on average (as long as the host time resolution is
		1048	good enough).
855		1049
856	Likewise, by setting a higher I<timeout collect interval> you allow libev	1050	Likewise, by setting a higher I<timeout collect interval> you allow libev
857	to spend more time collecting timeouts, at the expense of increased	1051	to spend more time collecting timeouts, at the expense of increased
858	latency/jitter/inexactness (the watcher callback will be called	1052	latency/jitter/inexactness (the watcher callback will be called
859	later). C<ev_io> watchers will not be affected. Setting this to a non-null	1053	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
865	usually doesn't make much sense to set it to a lower value than C<0.01>,	1059	usually doesn't make much sense to set it to a lower value than C<0.01>,
866	as this approaches the timing granularity of most systems. Note that if	1060	as this approaches the timing granularity of most systems. Note that if
867	you do transactions with the outside world and you can't increase the	1061	you do transactions with the outside world and you can't increase the
868	parallelity, then this setting will limit your transaction rate (if you	1062	parallelity, then this setting will limit your transaction rate (if you
869	need to poll once per transaction and the I/O collect interval is 0.01,	1063	need to poll once per transaction and the I/O collect interval is 0.01,
870	then you can't do more than 100 transations per second).	1064	then you can't do more than 100 transactions per second).
871		1065
872	Setting the I<timeout collect interval> can improve the opportunity for	1066	Setting the I<timeout collect interval> can improve the opportunity for
873	saving power, as the program will "bundle" timer callback invocations that	1067	saving power, as the program will "bundle" timer callback invocations that
874	are "near" in time together, by delaying some, thus reducing the number of	1068	are "near" in time together, by delaying some, thus reducing the number of
875	times the process sleeps and wakes up again. Another useful technique to	1069	times the process sleeps and wakes up again. Another useful technique to
…		…
883	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	1077	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
884		1078
885	=item ev_invoke_pending (loop)	1079	=item ev_invoke_pending (loop)
886		1080
887	This call will simply invoke all pending watchers while resetting their	1081	This call will simply invoke all pending watchers while resetting their
888	pending state. Normally, C<ev_loop> does this automatically when required,	1082	pending state. Normally, C<ev_run> does this automatically when required,
889	but when overriding the invoke callback this call comes handy.	1083	but when overriding the invoke callback this call comes handy. This
		1084	function can be invoked from a watcher - this can be useful for example
		1085	when you want to do some lengthy calculation and want to pass further
		1086	event handling to another thread (you still have to make sure only one
		1087	thread executes within C<ev_invoke_pending> or C<ev_run> of course).
890		1088
891	=item int ev_pending_count (loop)	1089	=item int ev_pending_count (loop)
892		1090
893	Returns the number of pending watchers - zero indicates that no watchers	1091	Returns the number of pending watchers - zero indicates that no watchers
894	are pending.	1092	are pending.
895		1093
896	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))	1094	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
897		1095
898	This overrides the invoke pending functionality of the loop: Instead of	1096	This overrides the invoke pending functionality of the loop: Instead of
899	invoking all pending watchers when there are any, C<ev_loop> will call	1097	invoking all pending watchers when there are any, C<ev_run> will call
900	this callback instead. This is useful, for example, when you want to	1098	this callback instead. This is useful, for example, when you want to
901	invoke the actual watchers inside another context (another thread etc.).	1099	invoke the actual watchers inside another context (another thread etc.).
902		1100
903	If you want to reset the callback, use C<ev_invoke_pending> as new	1101	If you want to reset the callback, use C<ev_invoke_pending> as new
904	callback.	1102	callback.
905		1103
906	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))	1104	=item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ())
907		1105
908	Sometimes you want to share the same loop between multiple threads. This	1106	Sometimes you want to share the same loop between multiple threads. This
909	can be done relatively simply by putting mutex_lock/unlock calls around	1107	can be done relatively simply by putting mutex_lock/unlock calls around
910	each call to a libev function.	1108	each call to a libev function.
911		1109
912	However, C<ev_loop> can run an indefinite time, so it is not feasible to	1110	However, C<ev_run> can run an indefinite time, so it is not feasible
913	wait for it to return. One way around this is to wake up the loop via	1111	to wait for it to return. One way around this is to wake up the event
914	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>	1112	loop via C<ev_break> and C<ev_async_send>, another way is to set these
915	and I<acquire> callbacks on the loop.	1113	I<release> and I<acquire> callbacks on the loop.
916		1114
917	When set, then C<release> will be called just before the thread is	1115	When set, then C<release> will be called just before the thread is
918	suspended waiting for new events, and C<acquire> is called just	1116	suspended waiting for new events, and C<acquire> is called just
919	afterwards.	1117	afterwards.
920		1118
…		…
923		1121
924	While event loop modifications are allowed between invocations of	1122	While event loop modifications are allowed between invocations of
925	C<release> and C<acquire> (that's their only purpose after all), no	1123	C<release> and C<acquire> (that's their only purpose after all), no
926	modifications done will affect the event loop, i.e. adding watchers will	1124	modifications done will affect the event loop, i.e. adding watchers will
927	have no effect on the set of file descriptors being watched, or the time	1125	have no effect on the set of file descriptors being watched, or the time
928	waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it	1126	waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it
929	to take note of any changes you made.	1127	to take note of any changes you made.
930		1128
931	In theory, threads executing C<ev_loop> will be async-cancel safe between	1129	In theory, threads executing C<ev_run> will be async-cancel safe between
932	invocations of C<release> and C<acquire>.	1130	invocations of C<release> and C<acquire>.
933		1131
934	See also the locking example in the C<THREADS> section later in this	1132	See also the locking example in the C<THREADS> section later in this
935	document.	1133	document.
936		1134
937	=item ev_set_userdata (loop, void *data)	1135	=item ev_set_userdata (loop, void *data)
938		1136
939	=item ev_userdata (loop)	1137	=item void *ev_userdata (loop)
940		1138
941	Set and retrieve a single C<void *> associated with a loop. When	1139	Set and retrieve a single C<void *> associated with a loop. When
942	C<ev_set_userdata> has never been called, then C<ev_userdata> returns	1140	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
943	C<0.>	1141	C<0>.
944		1142
945	These two functions can be used to associate arbitrary data with a loop,	1143	These two functions can be used to associate arbitrary data with a loop,
946	and are intended solely for the C<invoke_pending_cb>, C<release> and	1144	and are intended solely for the C<invoke_pending_cb>, C<release> and
947	C<acquire> callbacks described above, but of course can be (ab-)used for	1145	C<acquire> callbacks described above, but of course can be (ab-)used for
948	any other purpose as well.	1146	any other purpose as well.
949		1147
950	=item ev_loop_verify (loop)	1148	=item ev_verify (loop)
951		1149
952	This function only does something when C<EV_VERIFY> support has been	1150	This function only does something when C<EV_VERIFY> support has been
953	compiled in, which is the default for non-minimal builds. It tries to go	1151	compiled in, which is the default for non-minimal builds. It tries to go
954	through all internal structures and checks them for validity. If anything	1152	through all internal structures and checks them for validity. If anything
955	is found to be inconsistent, it will print an error message to standard	1153	is found to be inconsistent, it will print an error message to standard
…		…
966		1164
967	In the following description, uppercase C<TYPE> in names stands for the	1165	In the following description, uppercase C<TYPE> in names stands for the
968	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer	1166	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
969	watchers and C<ev_io_start> for I/O watchers.	1167	watchers and C<ev_io_start> for I/O watchers.
970		1168
971	A watcher is a structure that you create and register to record your	1169	A watcher is an opaque structure that you allocate and register to record
972	interest in some event. For instance, if you want to wait for STDIN to	1170	your interest in some event. To make a concrete example, imagine you want
973	become readable, you would create an C<ev_io> watcher for that:	1171	to wait for STDIN to become readable, you would create an C<ev_io> watcher
		1172	for that:
974		1173
975	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)	1174	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
976	{	1175	{
977	ev_io_stop (w);	1176	ev_io_stop (w);
978	ev_unloop (loop, EVUNLOOP_ALL);	1177	ev_break (loop, EVBREAK_ALL);
979	}	1178	}
980		1179
981	struct ev_loop *loop = ev_default_loop (0);	1180	struct ev_loop *loop = ev_default_loop (0);
982		1181
983	ev_io stdin_watcher;	1182	ev_io stdin_watcher;
984		1183
985	ev_init (&stdin_watcher, my_cb);	1184	ev_init (&stdin_watcher, my_cb);
986	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	1185	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
987	ev_io_start (loop, &stdin_watcher);	1186	ev_io_start (loop, &stdin_watcher);
988		1187
989	ev_loop (loop, 0);	1188	ev_run (loop, 0);
990		1189
991	As you can see, you are responsible for allocating the memory for your	1190	As you can see, you are responsible for allocating the memory for your
992	watcher structures (and it is I<usually> a bad idea to do this on the	1191	watcher structures (and it is I<usually> a bad idea to do this on the
993	stack).	1192	stack).
994		1193
995	Each watcher has an associated watcher structure (called C<struct ev_TYPE>	1194	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
996	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).	1195	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
997		1196
998	Each watcher structure must be initialised by a call to C<ev_init	1197	Each watcher structure must be initialised by a call to C<ev_init (watcher
999	(watcher *, callback)>, which expects a callback to be provided. This	1198	*, callback)>, which expects a callback to be provided. This callback is
1000	callback gets invoked each time the event occurs (or, in the case of I/O	1199	invoked each time the event occurs (or, in the case of I/O watchers, each
1001	watchers, each time the event loop detects that the file descriptor given	1200	time the event loop detects that the file descriptor given is readable
1002	is readable and/or writable).	1201	and/or writable).
1003		1202
1004	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>	1203	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
1005	macro to configure it, with arguments specific to the watcher type. There	1204	macro to configure it, with arguments specific to the watcher type. There
1006	is also a macro to combine initialisation and setting in one call: C<<	1205	is also a macro to combine initialisation and setting in one call: C<<
1007	ev_TYPE_init (watcher *, callback, ...) >>.	1206	ev_TYPE_init (watcher *, callback, ...) >>.
…		…
1030	=item C<EV_WRITE>	1229	=item C<EV_WRITE>
1031		1230
1032	The file descriptor in the C<ev_io> watcher has become readable and/or	1231	The file descriptor in the C<ev_io> watcher has become readable and/or
1033	writable.	1232	writable.
1034		1233
1035	=item C<EV_TIMEOUT>	1234	=item C<EV_TIMER>
1036		1235
1037	The C<ev_timer> watcher has timed out.	1236	The C<ev_timer> watcher has timed out.
1038		1237
1039	=item C<EV_PERIODIC>	1238	=item C<EV_PERIODIC>
1040		1239
…		…
1058		1257
1059	=item C<EV_PREPARE>	1258	=item C<EV_PREPARE>
1060		1259
1061	=item C<EV_CHECK>	1260	=item C<EV_CHECK>
1062		1261
1063	All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts	1262	All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to
1064	to gather new events, and all C<ev_check> watchers are invoked just after	1263	gather new events, and all C<ev_check> watchers are queued (not invoked)
1065	C<ev_loop> has gathered them, but before it invokes any callbacks for any	1264	just after C<ev_run> has gathered them, but before it queues any callbacks
		1265	for any received events. That means C<ev_prepare> watchers are the last
		1266	watchers invoked before the event loop sleeps or polls for new events, and
		1267	C<ev_check> watchers will be invoked before any other watchers of the same
		1268	or lower priority within an event loop iteration.
		1269
1066	received events. Callbacks of both watcher types can start and stop as	1270	Callbacks of both watcher types can start and stop as many watchers as
1067	many watchers as they want, and all of them will be taken into account	1271	they want, and all of them will be taken into account (for example, a
1068	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	1272	C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from
1069	C<ev_loop> from blocking).	1273	blocking).
1070		1274
1071	=item C<EV_EMBED>	1275	=item C<EV_EMBED>
1072		1276
1073	The embedded event loop specified in the C<ev_embed> watcher needs attention.	1277	The embedded event loop specified in the C<ev_embed> watcher needs attention.
1074		1278
1075	=item C<EV_FORK>	1279	=item C<EV_FORK>
1076		1280
1077	The event loop has been resumed in the child process after fork (see	1281	The event loop has been resumed in the child process after fork (see
1078	C<ev_fork>).	1282	C<ev_fork>).
		1283
		1284	=item C<EV_CLEANUP>
		1285
		1286	The event loop is about to be destroyed (see C<ev_cleanup>).
1079		1287
1080	=item C<EV_ASYNC>	1288	=item C<EV_ASYNC>
1081		1289
1082	The given async watcher has been asynchronously notified (see C<ev_async>).	1290	The given async watcher has been asynchronously notified (see C<ev_async>).
1083		1291
…		…
1193		1401
1194	=item callback ev_cb (ev_TYPE *watcher)	1402	=item callback ev_cb (ev_TYPE *watcher)
1195		1403
1196	Returns the callback currently set on the watcher.	1404	Returns the callback currently set on the watcher.
1197		1405
1198	=item ev_cb_set (ev_TYPE *watcher, callback)	1406	=item ev_set_cb (ev_TYPE *watcher, callback)
1199		1407
1200	Change the callback. You can change the callback at virtually any time	1408	Change the callback. You can change the callback at virtually any time
1201	(modulo threads).	1409	(modulo threads).
1202		1410
1203	=item ev_set_priority (ev_TYPE *watcher, int priority)	1411	=item ev_set_priority (ev_TYPE *watcher, int priority)
…		…
1221	or might not have been clamped to the valid range.	1429	or might not have been clamped to the valid range.
1222		1430
1223	The default priority used by watchers when no priority has been set is	1431	The default priority used by watchers when no priority has been set is
1224	always C<0>, which is supposed to not be too high and not be too low :).	1432	always C<0>, which is supposed to not be too high and not be too low :).
1225		1433
1226	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of	1434	See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
1227	priorities.	1435	priorities.
1228		1436
1229	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1437	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1230		1438
1231	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1439	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
…		…
1256	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related	1464	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
1257	functions that do not need a watcher.	1465	functions that do not need a watcher.
1258		1466
1259	=back	1467	=back
1260		1468
		1469	See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR
		1470	OWN COMPOSITE WATCHERS> idioms.
1261		1471
1262	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1472	=head2 WATCHER STATES
1263		1473
1264	Each watcher has, by default, a member C<void *data> that you can change	1474	There are various watcher states mentioned throughout this manual -
1265	and read at any time: libev will completely ignore it. This can be used	1475	active, pending and so on. In this section these states and the rules to
1266	to associate arbitrary data with your watcher. If you need more data and	1476	transition between them will be described in more detail - and while these
1267	don't want to allocate memory and store a pointer to it in that data	1477	rules might look complicated, they usually do "the right thing".
1268	member, you can also "subclass" the watcher type and provide your own
1269	data:
1270		1478
1271	struct my_io	1479	=over 4
1272	{
1273	ev_io io;
1274	int otherfd;
1275	void *somedata;
1276	struct whatever *mostinteresting;
1277	};
1278		1480
1279	...	1481	=item initialised
1280	struct my_io w;
1281	ev_io_init (&w.io, my_cb, fd, EV_READ);
1282		1482
1283	And since your callback will be called with a pointer to the watcher, you	1483	Before a watcher can be registered with the event loop it has to be
1284	can cast it back to your own type:	1484	initialised. This can be done with a call to C<ev_TYPE_init>, or calls to
		1485	C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function.
1285		1486
1286	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)	1487	In this state it is simply some block of memory that is suitable for
1287	{	1488	use in an event loop. It can be moved around, freed, reused etc. at
1288	struct my_io *w = (struct my_io *)w_;	1489	will - as long as you either keep the memory contents intact, or call
1289	...	1490	C<ev_TYPE_init> again.
1290	}
1291		1491
1292	More interesting and less C-conformant ways of casting your callback type	1492	=item started/running/active
1293	instead have been omitted.
1294		1493
1295	Another common scenario is to use some data structure with multiple	1494	Once a watcher has been started with a call to C<ev_TYPE_start> it becomes
1296	embedded watchers:	1495	property of the event loop, and is actively waiting for events. While in
		1496	this state it cannot be accessed (except in a few documented ways), moved,
		1497	freed or anything else - the only legal thing is to keep a pointer to it,
		1498	and call libev functions on it that are documented to work on active watchers.
1297		1499
1298	struct my_biggy	1500	=item pending
1299	{
1300	int some_data;
1301	ev_timer t1;
1302	ev_timer t2;
1303	}
1304		1501
1305	In this case getting the pointer to C<my_biggy> is a bit more	1502	If a watcher is active and libev determines that an event it is interested
1306	complicated: Either you store the address of your C<my_biggy> struct	1503	in has occurred (such as a timer expiring), it will become pending. It will
1307	in the C<data> member of the watcher (for woozies), or you need to use	1504	stay in this pending state until either it is stopped or its callback is
1308	some pointer arithmetic using C<offsetof> inside your watchers (for real	1505	about to be invoked, so it is not normally pending inside the watcher
1309	programmers):	1506	callback.
1310		1507
1311	#include <stddef.h>	1508	The watcher might or might not be active while it is pending (for example,
		1509	an expired non-repeating timer can be pending but no longer active). If it
		1510	is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>),
		1511	but it is still property of the event loop at this time, so cannot be
		1512	moved, freed or reused. And if it is active the rules described in the
		1513	previous item still apply.
1312		1514
1313	static void	1515	It is also possible to feed an event on a watcher that is not active (e.g.
1314	t1_cb (EV_P_ ev_timer *w, int revents)	1516	via C<ev_feed_event>), in which case it becomes pending without being
1315	{	1517	active.
1316	struct my_biggy big = (struct my_biggy *)
1317	(((char *)w) - offsetof (struct my_biggy, t1));
1318	}
1319		1518
1320	static void	1519	=item stopped
1321	t2_cb (EV_P_ ev_timer *w, int revents)	1520
1322	{	1521	A watcher can be stopped implicitly by libev (in which case it might still
1323	struct my_biggy big = (struct my_biggy *)	1522	be pending), or explicitly by calling its C<ev_TYPE_stop> function. The
1324	(((char *)w) - offsetof (struct my_biggy, t2));	1523	latter will clear any pending state the watcher might be in, regardless
1325	}	1524	of whether it was active or not, so stopping a watcher explicitly before
		1525	freeing it is often a good idea.
		1526
		1527	While stopped (and not pending) the watcher is essentially in the
		1528	initialised state, that is, it can be reused, moved, modified in any way
		1529	you wish (but when you trash the memory block, you need to C<ev_TYPE_init>
		1530	it again).
		1531
		1532	=back
1326		1533
1327	=head2 WATCHER PRIORITY MODELS	1534	=head2 WATCHER PRIORITY MODELS
1328		1535
1329	Many event loops support I<watcher priorities>, which are usually small	1536	Many event loops support I<watcher priorities>, which are usually small
1330	integers that influence the ordering of event callback invocation	1537	integers that influence the ordering of event callback invocation
…		…
1373		1580
1374	For example, to emulate how many other event libraries handle priorities,	1581	For example, to emulate how many other event libraries handle priorities,
1375	you can associate an C<ev_idle> watcher to each such watcher, and in	1582	you can associate an C<ev_idle> watcher to each such watcher, and in
1376	the normal watcher callback, you just start the idle watcher. The real	1583	the normal watcher callback, you just start the idle watcher. The real
1377	processing is done in the idle watcher callback. This causes libev to	1584	processing is done in the idle watcher callback. This causes libev to
1378	continously poll and process kernel event data for the watcher, but when	1585	continuously poll and process kernel event data for the watcher, but when
1379	the lock-out case is known to be rare (which in turn is rare :), this is	1586	the lock-out case is known to be rare (which in turn is rare :), this is
1380	workable.	1587	workable.
1381		1588
1382	Usually, however, the lock-out model implemented that way will perform	1589	Usually, however, the lock-out model implemented that way will perform
1383	miserably under the type of load it was designed to handle. In that case,	1590	miserably under the type of load it was designed to handle. In that case,
…		…
1397	{	1604	{
1398	// stop the I/O watcher, we received the event, but	1605	// stop the I/O watcher, we received the event, but
1399	// are not yet ready to handle it.	1606	// are not yet ready to handle it.
1400	ev_io_stop (EV_A_ w);	1607	ev_io_stop (EV_A_ w);
1401		1608
1402	// start the idle watcher to ahndle the actual event.	1609	// start the idle watcher to handle the actual event.
1403	// it will not be executed as long as other watchers	1610	// it will not be executed as long as other watchers
1404	// with the default priority are receiving events.	1611	// with the default priority are receiving events.
1405	ev_idle_start (EV_A_ &idle);	1612	ev_idle_start (EV_A_ &idle);
1406	}	1613	}
1407		1614
…		…
1457	In general you can register as many read and/or write event watchers per	1664	In general you can register as many read and/or write event watchers per
1458	fd as you want (as long as you don't confuse yourself). Setting all file	1665	fd as you want (as long as you don't confuse yourself). Setting all file
1459	descriptors to non-blocking mode is also usually a good idea (but not	1666	descriptors to non-blocking mode is also usually a good idea (but not
1460	required if you know what you are doing).	1667	required if you know what you are doing).
1461		1668
1462	If you cannot use non-blocking mode, then force the use of a
1463	known-to-be-good backend (at the time of this writing, this includes only
1464	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1465	descriptors for which non-blocking operation makes no sense (such as
1466	files) - libev doesn't guarentee any specific behaviour in that case.
1467
1468	Another thing you have to watch out for is that it is quite easy to	1669	Another thing you have to watch out for is that it is quite easy to
1469	receive "spurious" readiness notifications, that is your callback might	1670	receive "spurious" readiness notifications, that is, your callback might
1470	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1671	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1471	because there is no data. Not only are some backends known to create a	1672	because there is no data. It is very easy to get into this situation even
1472	lot of those (for example Solaris ports), it is very easy to get into	1673	with a relatively standard program structure. Thus it is best to always
1473	this situation even with a relatively standard program structure. Thus	1674	use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far
1474	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1475	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1675	preferable to a program hanging until some data arrives.
1476		1676
1477	If you cannot run the fd in non-blocking mode (for example you should	1677	If you cannot run the fd in non-blocking mode (for example you should
1478	not play around with an Xlib connection), then you have to separately	1678	not play around with an Xlib connection), then you have to separately
1479	re-test whether a file descriptor is really ready with a known-to-be good	1679	re-test whether a file descriptor is really ready with a known-to-be good
1480	interface such as poll (fortunately in our Xlib example, Xlib already	1680	interface such as poll (fortunately in the case of Xlib, it already does
1481	does this on its own, so its quite safe to use). Some people additionally	1681	this on its own, so its quite safe to use). Some people additionally
1482	use C<SIGALRM> and an interval timer, just to be sure you won't block	1682	use C<SIGALRM> and an interval timer, just to be sure you won't block
1483	indefinitely.	1683	indefinitely.
1484		1684
1485	But really, best use non-blocking mode.	1685	But really, best use non-blocking mode.
1486		1686
1487	=head3 The special problem of disappearing file descriptors	1687	=head3 The special problem of disappearing file descriptors
1488		1688
1489	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1689	Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1490	descriptor (either due to calling C<close> explicitly or any other means,	1690	a file descriptor (either due to calling C<close> explicitly or any other
1491	such as C<dup2>). The reason is that you register interest in some file	1691	means, such as C<dup2>). The reason is that you register interest in some
1492	descriptor, but when it goes away, the operating system will silently drop	1692	file descriptor, but when it goes away, the operating system will silently
1493	this interest. If another file descriptor with the same number then is	1693	drop this interest. If another file descriptor with the same number then
1494	registered with libev, there is no efficient way to see that this is, in	1694	is registered with libev, there is no efficient way to see that this is,
1495	fact, a different file descriptor.	1695	in fact, a different file descriptor.
1496		1696
1497	To avoid having to explicitly tell libev about such cases, libev follows	1697	To avoid having to explicitly tell libev about such cases, libev follows
1498	the following policy: Each time C<ev_io_set> is being called, libev	1698	the following policy: Each time C<ev_io_set> is being called, libev
1499	will assume that this is potentially a new file descriptor, otherwise	1699	will assume that this is potentially a new file descriptor, otherwise
1500	it is assumed that the file descriptor stays the same. That means that	1700	it is assumed that the file descriptor stays the same. That means that
…		…
1514		1714
1515	There is no workaround possible except not registering events	1715	There is no workaround possible except not registering events
1516	for potentially C<dup ()>'ed file descriptors, or to resort to	1716	for potentially C<dup ()>'ed file descriptors, or to resort to
1517	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.	1717	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1518		1718
		1719	=head3 The special problem of files
		1720
		1721	Many people try to use C<select> (or libev) on file descriptors
		1722	representing files, and expect it to become ready when their program
		1723	doesn't block on disk accesses (which can take a long time on their own).
		1724
		1725	However, this cannot ever work in the "expected" way - you get a readiness
		1726	notification as soon as the kernel knows whether and how much data is
		1727	there, and in the case of open files, that's always the case, so you
		1728	always get a readiness notification instantly, and your read (or possibly
		1729	write) will still block on the disk I/O.
		1730
		1731	Another way to view it is that in the case of sockets, pipes, character
		1732	devices and so on, there is another party (the sender) that delivers data
		1733	on its own, but in the case of files, there is no such thing: the disk
		1734	will not send data on its own, simply because it doesn't know what you
		1735	wish to read - you would first have to request some data.
		1736
		1737	Since files are typically not-so-well supported by advanced notification
		1738	mechanism, libev tries hard to emulate POSIX behaviour with respect
		1739	to files, even though you should not use it. The reason for this is
		1740	convenience: sometimes you want to watch STDIN or STDOUT, which is
		1741	usually a tty, often a pipe, but also sometimes files or special devices
		1742	(for example, C<epoll> on Linux works with F</dev/random> but not with
		1743	F</dev/urandom>), and even though the file might better be served with
		1744	asynchronous I/O instead of with non-blocking I/O, it is still useful when
		1745	it "just works" instead of freezing.
		1746
		1747	So avoid file descriptors pointing to files when you know it (e.g. use
		1748	libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or
		1749	when you rarely read from a file instead of from a socket, and want to
		1750	reuse the same code path.
		1751
1519	=head3 The special problem of fork	1752	=head3 The special problem of fork
1520		1753
1521	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit	1754	Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()>
1522	useless behaviour. Libev fully supports fork, but needs to be told about	1755	at all or exhibit useless behaviour. Libev fully supports fork, but needs
1523	it in the child.	1756	to be told about it in the child if you want to continue to use it in the
		1757	child.
1524		1758
1525	To support fork in your programs, you either have to call	1759	To support fork in your child processes, you have to call C<ev_loop_fork
1526	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,	1760	()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to
1527	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1761	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1528	C<EVBACKEND_POLL>.
1529		1762
1530	=head3 The special problem of SIGPIPE	1763	=head3 The special problem of SIGPIPE
1531		1764
1532	While not really specific to libev, it is easy to forget about C<SIGPIPE>:	1765	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1533	when writing to a pipe whose other end has been closed, your program gets	1766	when writing to a pipe whose other end has been closed, your program gets
…		…
1536		1769
1537	So when you encounter spurious, unexplained daemon exits, make sure you	1770	So when you encounter spurious, unexplained daemon exits, make sure you
1538	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1771	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1539	somewhere, as that would have given you a big clue).	1772	somewhere, as that would have given you a big clue).
1540		1773
		1774	=head3 The special problem of accept()ing when you can't
		1775
		1776	Many implementations of the POSIX C<accept> function (for example,
		1777	found in post-2004 Linux) have the peculiar behaviour of not removing a
		1778	connection from the pending queue in all error cases.
		1779
		1780	For example, larger servers often run out of file descriptors (because
		1781	of resource limits), causing C<accept> to fail with C<ENFILE> but not
		1782	rejecting the connection, leading to libev signalling readiness on
		1783	the next iteration again (the connection still exists after all), and
		1784	typically causing the program to loop at 100% CPU usage.
		1785
		1786	Unfortunately, the set of errors that cause this issue differs between
		1787	operating systems, there is usually little the app can do to remedy the
		1788	situation, and no known thread-safe method of removing the connection to
		1789	cope with overload is known (to me).
		1790
		1791	One of the easiest ways to handle this situation is to just ignore it
		1792	- when the program encounters an overload, it will just loop until the
		1793	situation is over. While this is a form of busy waiting, no OS offers an
		1794	event-based way to handle this situation, so it's the best one can do.
		1795
		1796	A better way to handle the situation is to log any errors other than
		1797	C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
		1798	messages, and continue as usual, which at least gives the user an idea of
		1799	what could be wrong ("raise the ulimit!"). For extra points one could stop
		1800	the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
		1801	usage.
		1802
		1803	If your program is single-threaded, then you could also keep a dummy file
		1804	descriptor for overload situations (e.g. by opening F</dev/null>), and
		1805	when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
		1806	close that fd, and create a new dummy fd. This will gracefully refuse
		1807	clients under typical overload conditions.
		1808
		1809	The last way to handle it is to simply log the error and C<exit>, as
		1810	is often done with C<malloc> failures, but this results in an easy
		1811	opportunity for a DoS attack.
1541		1812
1542	=head3 Watcher-Specific Functions	1813	=head3 Watcher-Specific Functions
1543		1814
1544	=over 4	1815	=over 4
1545		1816
…		…
1577	...	1848	...
1578	struct ev_loop *loop = ev_default_init (0);	1849	struct ev_loop *loop = ev_default_init (0);
1579	ev_io stdin_readable;	1850	ev_io stdin_readable;
1580	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1851	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1581	ev_io_start (loop, &stdin_readable);	1852	ev_io_start (loop, &stdin_readable);
1582	ev_loop (loop, 0);	1853	ev_run (loop, 0);
1583		1854
1584		1855
1585	=head2 C<ev_timer> - relative and optionally repeating timeouts	1856	=head2 C<ev_timer> - relative and optionally repeating timeouts
1586		1857
1587	Timer watchers are simple relative timers that generate an event after a	1858	Timer watchers are simple relative timers that generate an event after a
…		…
1593	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1864	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1594	monotonic clock option helps a lot here).	1865	monotonic clock option helps a lot here).
1595		1866
1596	The callback is guaranteed to be invoked only I<after> its timeout has	1867	The callback is guaranteed to be invoked only I<after> its timeout has
1597	passed (not I<at>, so on systems with very low-resolution clocks this	1868	passed (not I<at>, so on systems with very low-resolution clocks this
1598	might introduce a small delay). If multiple timers become ready during the	1869	might introduce a small delay, see "the special problem of being too
		1870	early", below). If multiple timers become ready during the same loop
1599	same loop iteration then the ones with earlier time-out values are invoked	1871	iteration then the ones with earlier time-out values are invoked before
1600	before ones of the same priority with later time-out values (but this is	1872	ones of the same priority with later time-out values (but this is no
1601	no longer true when a callback calls C<ev_loop> recursively).	1873	longer true when a callback calls C<ev_run> recursively).
1602		1874
1603	=head3 Be smart about timeouts	1875	=head3 Be smart about timeouts
1604		1876
1605	Many real-world problems involve some kind of timeout, usually for error	1877	Many real-world problems involve some kind of timeout, usually for error
1606	recovery. A typical example is an HTTP request - if the other side hangs,	1878	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1681		1953
1682	In this case, it would be more efficient to leave the C<ev_timer> alone,	1954	In this case, it would be more efficient to leave the C<ev_timer> alone,
1683	but remember the time of last activity, and check for a real timeout only	1955	but remember the time of last activity, and check for a real timeout only
1684	within the callback:	1956	within the callback:
1685		1957
		1958	ev_tstamp timeout = 60.;
1686	ev_tstamp last_activity; // time of last activity	1959	ev_tstamp last_activity; // time of last activity
		1960	ev_timer timer;
1687		1961
1688	static void	1962	static void
1689	callback (EV_P_ ev_timer *w, int revents)	1963	callback (EV_P_ ev_timer *w, int revents)
1690	{	1964	{
1691	ev_tstamp now = ev_now (EV_A);	1965	// calculate when the timeout would happen
1692	ev_tstamp timeout = last_activity + 60.;	1966	ev_tstamp after = last_activity - ev_now (EV_A) + timeout;
1693		1967
1694	// if last_activity + 60. is older than now, we did time out	1968	// if negative, it means we the timeout already occurred
1695	if (timeout < now)	1969	if (after < 0.)
1696	{	1970	{
1697	// timeout occured, take action	1971	// timeout occurred, take action
1698	}	1972	}
1699	else	1973	else
1700	{	1974	{
1701	// callback was invoked, but there was some activity, re-arm	1975	// callback was invoked, but there was some recent
1702	// the watcher to fire in last_activity + 60, which is	1976	// activity. simply restart the timer to time out
1703	// guaranteed to be in the future, so "again" is positive:	1977	// after "after" seconds, which is the earliest time
1704	w->repeat = timeout - now;	1978	// the timeout can occur.
		1979	ev_timer_set (w, after, 0.);
1705	ev_timer_again (EV_A_ w);	1980	ev_timer_start (EV_A_ w);
1706	}	1981	}
1707	}	1982	}
1708		1983
1709	To summarise the callback: first calculate the real timeout (defined	1984	To summarise the callback: first calculate in how many seconds the
1710	as "60 seconds after the last activity"), then check if that time has	1985	timeout will occur (by calculating the absolute time when it would occur,
1711	been reached, which means something I<did>, in fact, time out. Otherwise	1986	C<last_activity + timeout>, and subtracting the current time, C<ev_now
1712	the callback was invoked too early (C<timeout> is in the future), so	1987	(EV_A)> from that).
1713	re-schedule the timer to fire at that future time, to see if maybe we have
1714	a timeout then.
1715		1988
1716	Note how C<ev_timer_again> is used, taking advantage of the	1989	If this value is negative, then we are already past the timeout, i.e. we
1717	C<ev_timer_again> optimisation when the timer is already running.	1990	timed out, and need to do whatever is needed in this case.
		1991
		1992	Otherwise, we now the earliest time at which the timeout would trigger,
		1993	and simply start the timer with this timeout value.
		1994
		1995	In other words, each time the callback is invoked it will check whether
		1996	the timeout occurred. If not, it will simply reschedule itself to check
		1997	again at the earliest time it could time out. Rinse. Repeat.
1718		1998
1719	This scheme causes more callback invocations (about one every 60 seconds	1999	This scheme causes more callback invocations (about one every 60 seconds
1720	minus half the average time between activity), but virtually no calls to	2000	minus half the average time between activity), but virtually no calls to
1721	libev to change the timeout.	2001	libev to change the timeout.
1722		2002
1723	To start the timer, simply initialise the watcher and set C<last_activity>	2003	To start the machinery, simply initialise the watcher and set
1724	to the current time (meaning we just have some activity :), then call the	2004	C<last_activity> to the current time (meaning there was some activity just
1725	callback, which will "do the right thing" and start the timer:	2005	now), then call the callback, which will "do the right thing" and start
		2006	the timer:
1726		2007
		2008	last_activity = ev_now (EV_A);
1727	ev_init (timer, callback);	2009	ev_init (&timer, callback);
1728	last_activity = ev_now (loop);	2010	callback (EV_A_ &timer, 0);
1729	callback (loop, timer, EV_TIMEOUT);
1730		2011
1731	And when there is some activity, simply store the current time in	2012	When there is some activity, simply store the current time in
1732	C<last_activity>, no libev calls at all:	2013	C<last_activity>, no libev calls at all:
1733		2014
		2015	if (activity detected)
1734	last_actiivty = ev_now (loop);	2016	last_activity = ev_now (EV_A);
		2017
		2018	When your timeout value changes, then the timeout can be changed by simply
		2019	providing a new value, stopping the timer and calling the callback, which
		2020	will again do the right thing (for example, time out immediately :).
		2021
		2022	timeout = new_value;
		2023	ev_timer_stop (EV_A_ &timer);
		2024	callback (EV_A_ &timer, 0);
1735		2025
1736	This technique is slightly more complex, but in most cases where the	2026	This technique is slightly more complex, but in most cases where the
1737	time-out is unlikely to be triggered, much more efficient.	2027	time-out is unlikely to be triggered, much more efficient.
1738
1739	Changing the timeout is trivial as well (if it isn't hard-coded in the
1740	callback :) - just change the timeout and invoke the callback, which will
1741	fix things for you.
1742		2028
1743	=item 4. Wee, just use a double-linked list for your timeouts.	2029	=item 4. Wee, just use a double-linked list for your timeouts.
1744		2030
1745	If there is not one request, but many thousands (millions...), all	2031	If there is not one request, but many thousands (millions...), all
1746	employing some kind of timeout with the same timeout value, then one can	2032	employing some kind of timeout with the same timeout value, then one can
…		…
1773	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is	2059	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
1774	rather complicated, but extremely efficient, something that really pays	2060	rather complicated, but extremely efficient, something that really pays
1775	off after the first million or so of active timers, i.e. it's usually	2061	off after the first million or so of active timers, i.e. it's usually
1776	overkill :)	2062	overkill :)
1777		2063
		2064	=head3 The special problem of being too early
		2065
		2066	If you ask a timer to call your callback after three seconds, then
		2067	you expect it to be invoked after three seconds - but of course, this
		2068	cannot be guaranteed to infinite precision. Less obviously, it cannot be
		2069	guaranteed to any precision by libev - imagine somebody suspending the
		2070	process with a STOP signal for a few hours for example.
		2071
		2072	So, libev tries to invoke your callback as soon as possible I<after> the
		2073	delay has occurred, but cannot guarantee this.
		2074
		2075	A less obvious failure mode is calling your callback too early: many event
		2076	loops compare timestamps with a "elapsed delay >= requested delay", but
		2077	this can cause your callback to be invoked much earlier than you would
		2078	expect.
		2079
		2080	To see why, imagine a system with a clock that only offers full second
		2081	resolution (think windows if you can't come up with a broken enough OS
		2082	yourself). If you schedule a one-second timer at the time 500.9, then the
		2083	event loop will schedule your timeout to elapse at a system time of 500
		2084	(500.9 truncated to the resolution) + 1, or 501.
		2085
		2086	If an event library looks at the timeout 0.1s later, it will see "501 >=
		2087	501" and invoke the callback 0.1s after it was started, even though a
		2088	one-second delay was requested - this is being "too early", despite best
		2089	intentions.
		2090
		2091	This is the reason why libev will never invoke the callback if the elapsed
		2092	delay equals the requested delay, but only when the elapsed delay is
		2093	larger than the requested delay. In the example above, libev would only invoke
		2094	the callback at system time 502, or 1.1s after the timer was started.
		2095
		2096	So, while libev cannot guarantee that your callback will be invoked
		2097	exactly when requested, it I<can> and I<does> guarantee that the requested
		2098	delay has actually elapsed, or in other words, it always errs on the "too
		2099	late" side of things.
		2100
1778	=head3 The special problem of time updates	2101	=head3 The special problem of time updates
1779		2102
1780	Establishing the current time is a costly operation (it usually takes at	2103	Establishing the current time is a costly operation (it usually takes
1781	least two system calls): EV therefore updates its idea of the current	2104	at least one system call): EV therefore updates its idea of the current
1782	time only before and after C<ev_loop> collects new events, which causes a	2105	time only before and after C<ev_run> collects new events, which causes a
1783	growing difference between C<ev_now ()> and C<ev_time ()> when handling	2106	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1784	lots of events in one iteration.	2107	lots of events in one iteration.
1785		2108
1786	The relative timeouts are calculated relative to the C<ev_now ()>	2109	The relative timeouts are calculated relative to the C<ev_now ()>
1787	time. This is usually the right thing as this timestamp refers to the time	2110	time. This is usually the right thing as this timestamp refers to the time
1788	of the event triggering whatever timeout you are modifying/starting. If	2111	of the event triggering whatever timeout you are modifying/starting. If
1789	you suspect event processing to be delayed and you I<need> to base the	2112	you suspect event processing to be delayed and you I<need> to base the
1790	timeout on the current time, use something like this to adjust for this:	2113	timeout on the current time, use something like the following to adjust
		2114	for it:
1791		2115
1792	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	2116	ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.);
1793		2117
1794	If the event loop is suspended for a long time, you can also force an	2118	If the event loop is suspended for a long time, you can also force an
1795	update of the time returned by C<ev_now ()> by calling C<ev_now_update	2119	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1796	()>.	2120	()>, although that will push the event time of all outstanding events
		2121	further into the future.
		2122
		2123	=head3 The special problem of unsynchronised clocks
		2124
		2125	Modern systems have a variety of clocks - libev itself uses the normal
		2126	"wall clock" clock and, if available, the monotonic clock (to avoid time
		2127	jumps).
		2128
		2129	Neither of these clocks is synchronised with each other or any other clock
		2130	on the system, so C<ev_time ()> might return a considerably different time
		2131	than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example,
		2132	a call to C<gettimeofday> might return a second count that is one higher
		2133	than a directly following call to C<time>.
		2134
		2135	The moral of this is to only compare libev-related timestamps with
		2136	C<ev_time ()> and C<ev_now ()>, at least if you want better precision than
		2137	a second or so.
		2138
		2139	One more problem arises due to this lack of synchronisation: if libev uses
		2140	the system monotonic clock and you compare timestamps from C<ev_time>
		2141	or C<ev_now> from when you started your timer and when your callback is
		2142	invoked, you will find that sometimes the callback is a bit "early".
		2143
		2144	This is because C<ev_timer>s work in real time, not wall clock time, so
		2145	libev makes sure your callback is not invoked before the delay happened,
		2146	I<measured according to the real time>, not the system clock.
		2147
		2148	If your timeouts are based on a physical timescale (e.g. "time out this
		2149	connection after 100 seconds") then this shouldn't bother you as it is
		2150	exactly the right behaviour.
		2151
		2152	If you want to compare wall clock/system timestamps to your timers, then
		2153	you need to use C<ev_periodic>s, as these are based on the wall clock
		2154	time, where your comparisons will always generate correct results.
1797		2155
1798	=head3 The special problems of suspended animation	2156	=head3 The special problems of suspended animation
1799		2157
1800	When you leave the server world it is quite customary to hit machines that	2158	When you leave the server world it is quite customary to hit machines that
1801	can suspend/hibernate - what happens to the clocks during such a suspend?	2159	can suspend/hibernate - what happens to the clocks during such a suspend?
…		…
1831		2189
1832	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	2190	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
1833		2191
1834	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	2192	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
1835		2193
1836	Configure the timer to trigger after C<after> seconds. If C<repeat>	2194	Configure the timer to trigger after C<after> seconds (fractional and
1837	is C<0.>, then it will automatically be stopped once the timeout is	2195	negative values are supported). If C<repeat> is C<0.>, then it will
1838	reached. If it is positive, then the timer will automatically be	2196	automatically be stopped once the timeout is reached. If it is positive,
1839	configured to trigger again C<repeat> seconds later, again, and again,	2197	then the timer will automatically be configured to trigger again C<repeat>
1840	until stopped manually.	2198	seconds later, again, and again, until stopped manually.
1841		2199
1842	The timer itself will do a best-effort at avoiding drift, that is, if	2200	The timer itself will do a best-effort at avoiding drift, that is, if
1843	you configure a timer to trigger every 10 seconds, then it will normally	2201	you configure a timer to trigger every 10 seconds, then it will normally
1844	trigger at exactly 10 second intervals. If, however, your program cannot	2202	trigger at exactly 10 second intervals. If, however, your program cannot
1845	keep up with the timer (because it takes longer than those 10 seconds to	2203	keep up with the timer (because it takes longer than those 10 seconds to
1846	do stuff) the timer will not fire more than once per event loop iteration.	2204	do stuff) the timer will not fire more than once per event loop iteration.
1847		2205
1848	=item ev_timer_again (loop, ev_timer *)	2206	=item ev_timer_again (loop, ev_timer *)
1849		2207
1850	This will act as if the timer timed out and restart it again if it is	2208	This will act as if the timer timed out, and restarts it again if it is
1851	repeating. The exact semantics are:	2209	repeating. It basically works like calling C<ev_timer_stop>, updating the
		2210	timeout to the C<repeat> value and calling C<ev_timer_start>.
1852		2211
		2212	The exact semantics are as in the following rules, all of which will be
		2213	applied to the watcher:
		2214
		2215	=over 4
		2216
1853	If the timer is pending, its pending status is cleared.	2217	=item If the timer is pending, the pending status is always cleared.
1854		2218
1855	If the timer is started but non-repeating, stop it (as if it timed out).	2219	=item If the timer is started but non-repeating, stop it (as if it timed
		2220	out, without invoking it).
1856		2221
1857	If the timer is repeating, either start it if necessary (with the	2222	=item If the timer is repeating, make the C<repeat> value the new timeout
1858	C<repeat> value), or reset the running timer to the C<repeat> value.	2223	and start the timer, if necessary.
1859		2224
		2225	=back
		2226
1860	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	2227	This sounds a bit complicated, see L</Be smart about timeouts>, above, for a
1861	usage example.	2228	usage example.
1862		2229
1863	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)	2230	=item ev_tstamp ev_timer_remaining (loop, ev_timer *)
1864		2231
1865	Returns the remaining time until a timer fires. If the timer is active,	2232	Returns the remaining time until a timer fires. If the timer is active,
1866	then this time is relative to the current event loop time, otherwise it's	2233	then this time is relative to the current event loop time, otherwise it's
1867	the timeout value currently configured.	2234	the timeout value currently configured.
1868		2235
1869	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns	2236	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1870	C<5>. When the timer is started and one second passes, C<ev_timer_remain>	2237	C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1871	will return C<4>. When the timer expires and is restarted, it will return	2238	will return C<4>. When the timer expires and is restarted, it will return
1872	roughly C<7> (likely slightly less as callback invocation takes some time,	2239	roughly C<7> (likely slightly less as callback invocation takes some time,
1873	too), and so on.	2240	too), and so on.
1874		2241
1875	=item ev_tstamp repeat [read-write]	2242	=item ev_tstamp repeat [read-write]
…		…
1904	}	2271	}
1905		2272
1906	ev_timer mytimer;	2273	ev_timer mytimer;
1907	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	2274	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1908	ev_timer_again (&mytimer); /* start timer */	2275	ev_timer_again (&mytimer); /* start timer */
1909	ev_loop (loop, 0);	2276	ev_run (loop, 0);
1910		2277
1911	// and in some piece of code that gets executed on any "activity":	2278	// and in some piece of code that gets executed on any "activity":
1912	// reset the timeout to start ticking again at 10 seconds	2279	// reset the timeout to start ticking again at 10 seconds
1913	ev_timer_again (&mytimer);	2280	ev_timer_again (&mytimer);
1914		2281
…		…
1918	Periodic watchers are also timers of a kind, but they are very versatile	2285	Periodic watchers are also timers of a kind, but they are very versatile
1919	(and unfortunately a bit complex).	2286	(and unfortunately a bit complex).
1920		2287
1921	Unlike C<ev_timer>, periodic watchers are not based on real time (or	2288	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1922	relative time, the physical time that passes) but on wall clock time	2289	relative time, the physical time that passes) but on wall clock time
1923	(absolute time, the thing you can read on your calender or clock). The	2290	(absolute time, the thing you can read on your calendar or clock). The
1924	difference is that wall clock time can run faster or slower than real	2291	difference is that wall clock time can run faster or slower than real
1925	time, and time jumps are not uncommon (e.g. when you adjust your	2292	time, and time jumps are not uncommon (e.g. when you adjust your
1926	wrist-watch).	2293	wrist-watch).
1927		2294
1928	You can tell a periodic watcher to trigger after some specific point	2295	You can tell a periodic watcher to trigger after some specific point
…		…
1933	C<ev_timer>, which would still trigger roughly 10 seconds after starting	2300	C<ev_timer>, which would still trigger roughly 10 seconds after starting
1934	it, as it uses a relative timeout).	2301	it, as it uses a relative timeout).
1935		2302
1936	C<ev_periodic> watchers can also be used to implement vastly more complex	2303	C<ev_periodic> watchers can also be used to implement vastly more complex
1937	timers, such as triggering an event on each "midnight, local time", or	2304	timers, such as triggering an event on each "midnight, local time", or
1938	other complicated rules. This cannot be done with C<ev_timer> watchers, as	2305	other complicated rules. This cannot easily be done with C<ev_timer>
1939	those cannot react to time jumps.	2306	watchers, as those cannot react to time jumps.
1940		2307
1941	As with timers, the callback is guaranteed to be invoked only when the	2308	As with timers, the callback is guaranteed to be invoked only when the
1942	point in time where it is supposed to trigger has passed. If multiple	2309	point in time where it is supposed to trigger has passed. If multiple
1943	timers become ready during the same loop iteration then the ones with	2310	timers become ready during the same loop iteration then the ones with
1944	earlier time-out values are invoked before ones with later time-out values	2311	earlier time-out values are invoked before ones with later time-out values
1945	(but this is no longer true when a callback calls C<ev_loop> recursively).	2312	(but this is no longer true when a callback calls C<ev_run> recursively).
1946		2313
1947	=head3 Watcher-Specific Functions and Data Members	2314	=head3 Watcher-Specific Functions and Data Members
1948		2315
1949	=over 4	2316	=over 4
1950		2317
…		…
1985		2352
1986	Another way to think about it (for the mathematically inclined) is that	2353	Another way to think about it (for the mathematically inclined) is that
1987	C<ev_periodic> will try to run the callback in this mode at the next possible	2354	C<ev_periodic> will try to run the callback in this mode at the next possible
1988	time where C<time = offset (mod interval)>, regardless of any time jumps.	2355	time where C<time = offset (mod interval)>, regardless of any time jumps.
1989		2356
1990	For numerical stability it is preferable that the C<offset> value is near	2357	The C<interval> I<MUST> be positive, and for numerical stability, the
1991	C<ev_now ()> (the current time), but there is no range requirement for	2358	interval value should be higher than C<1/8192> (which is around 100
1992	this value, and in fact is often specified as zero.	2359	microseconds) and C<offset> should be higher than C<0> and should have
		2360	at most a similar magnitude as the current time (say, within a factor of
		2361	ten). Typical values for offset are, in fact, C<0> or something between
		2362	C<0> and C<interval>, which is also the recommended range.
1993		2363
1994	Note also that there is an upper limit to how often a timer can fire (CPU	2364	Note also that there is an upper limit to how often a timer can fire (CPU
1995	speed for example), so if C<interval> is very small then timing stability	2365	speed for example), so if C<interval> is very small then timing stability
1996	will of course deteriorate. Libev itself tries to be exact to be about one	2366	will of course deteriorate. Libev itself tries to be exact to be about one
1997	millisecond (if the OS supports it and the machine is fast enough).	2367	millisecond (if the OS supports it and the machine is fast enough).
…		…
2027		2397
2028	NOTE: I<< This callback must always return a time that is higher than or	2398	NOTE: I<< This callback must always return a time that is higher than or
2029	equal to the passed C<now> value >>.	2399	equal to the passed C<now> value >>.
2030		2400
2031	This can be used to create very complex timers, such as a timer that	2401	This can be used to create very complex timers, such as a timer that
2032	triggers on "next midnight, local time". To do this, you would calculate the	2402	triggers on "next midnight, local time". To do this, you would calculate
2033	next midnight after C<now> and return the timestamp value for this. How	2403	the next midnight after C<now> and return the timestamp value for
2034	you do this is, again, up to you (but it is not trivial, which is the main	2404	this. Here is a (completely untested, no error checking) example on how to
2035	reason I omitted it as an example).	2405	do this:
		2406
		2407	#include <time.h>
		2408
		2409	static ev_tstamp
		2410	my_rescheduler (ev_periodic *w, ev_tstamp now)
		2411	{
		2412	time_t tnow = (time_t)now;
		2413	struct tm tm;
		2414	localtime_r (&tnow, &tm);
		2415
		2416	tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
		2417	++tm.tm_mday; // midnight next day
		2418
		2419	return mktime (&tm);
		2420	}
		2421
		2422	Note: this code might run into trouble on days that have more then two
		2423	midnights (beginning and end).
2036		2424
2037	=back	2425	=back
2038		2426
2039	=item ev_periodic_again (loop, ev_periodic *)	2427	=item ev_periodic_again (loop, ev_periodic *)
2040		2428
…		…
2078	Example: Call a callback every hour, or, more precisely, whenever the	2466	Example: Call a callback every hour, or, more precisely, whenever the
2079	system time is divisible by 3600. The callback invocation times have	2467	system time is divisible by 3600. The callback invocation times have
2080	potentially a lot of jitter, but good long-term stability.	2468	potentially a lot of jitter, but good long-term stability.
2081		2469
2082	static void	2470	static void
2083	clock_cb (struct ev_loop *loop, ev_io *w, int revents)	2471	clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2084	{	2472	{
2085	... its now a full hour (UTC, or TAI or whatever your clock follows)	2473	... its now a full hour (UTC, or TAI or whatever your clock follows)
2086	}	2474	}
2087		2475
2088	ev_periodic hourly_tick;	2476	ev_periodic hourly_tick;
…		…
2105		2493
2106	ev_periodic hourly_tick;	2494	ev_periodic hourly_tick;
2107	ev_periodic_init (&hourly_tick, clock_cb,	2495	ev_periodic_init (&hourly_tick, clock_cb,
2108	fmod (ev_now (loop), 3600.), 3600., 0);	2496	fmod (ev_now (loop), 3600.), 3600., 0);
2109	ev_periodic_start (loop, &hourly_tick);	2497	ev_periodic_start (loop, &hourly_tick);
2110		2498
2111		2499
2112	=head2 C<ev_signal> - signal me when a signal gets signalled!	2500	=head2 C<ev_signal> - signal me when a signal gets signalled!
2113		2501
2114	Signal watchers will trigger an event when the process receives a specific	2502	Signal watchers will trigger an event when the process receives a specific
2115	signal one or more times. Even though signals are very asynchronous, libev	2503	signal one or more times. Even though signals are very asynchronous, libev
2116	will try it's best to deliver signals synchronously, i.e. as part of the	2504	will try its best to deliver signals synchronously, i.e. as part of the
2117	normal event processing, like any other event.	2505	normal event processing, like any other event.
2118		2506
2119	If you want signals to be delivered truly asynchronously, just use	2507	If you want signals to be delivered truly asynchronously, just use
2120	C<sigaction> as you would do without libev and forget about sharing	2508	C<sigaction> as you would do without libev and forget about sharing
2121	the signal. You can even use C<ev_async> from a signal handler to	2509	the signal. You can even use C<ev_async> from a signal handler to
…		…
2125	only within the same loop, i.e. you can watch for C<SIGINT> in your	2513	only within the same loop, i.e. you can watch for C<SIGINT> in your
2126	default loop and for C<SIGIO> in another loop, but you cannot watch for	2514	default loop and for C<SIGIO> in another loop, but you cannot watch for
2127	C<SIGINT> in both the default loop and another loop at the same time. At	2515	C<SIGINT> in both the default loop and another loop at the same time. At
2128	the moment, C<SIGCHLD> is permanently tied to the default loop.	2516	the moment, C<SIGCHLD> is permanently tied to the default loop.
2129		2517
2130	When the first watcher gets started will libev actually register something	2518	Only after the first watcher for a signal is started will libev actually
2131	with the kernel (thus it coexists with your own signal handlers as long as	2519	register something with the kernel. It thus coexists with your own signal
2132	you don't register any with libev for the same signal).	2520	handlers as long as you don't register any with libev for the same signal.
2133		2521
2134	If possible and supported, libev will install its handlers with	2522	If possible and supported, libev will install its handlers with
2135	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should	2523	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
2136	not be unduly interrupted. If you have a problem with system calls getting	2524	not be unduly interrupted. If you have a problem with system calls getting
2137	interrupted by signals you can block all signals in an C<ev_check> watcher	2525	interrupted by signals you can block all signals in an C<ev_check> watcher
…		…
2140	=head3 The special problem of inheritance over fork/execve/pthread_create	2528	=head3 The special problem of inheritance over fork/execve/pthread_create
2141		2529
2142	Both the signal mask (C<sigprocmask>) and the signal disposition	2530	Both the signal mask (C<sigprocmask>) and the signal disposition
2143	(C<sigaction>) are unspecified after starting a signal watcher (and after	2531	(C<sigaction>) are unspecified after starting a signal watcher (and after
2144	stopping it again), that is, libev might or might not block the signal,	2532	stopping it again), that is, libev might or might not block the signal,
2145	and might or might not set or restore the installed signal handler.	2533	and might or might not set or restore the installed signal handler (but
		2534	see C<EVFLAG_NOSIGMASK>).
2146		2535
2147	While this does not matter for the signal disposition (libev never	2536	While this does not matter for the signal disposition (libev never
2148	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on	2537	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
2149	C<execve>), this matters for the signal mask: many programs do not expect	2538	C<execve>), this matters for the signal mask: many programs do not expect
2150	certain signals to be blocked.	2539	certain signals to be blocked.
…		…
2160	In current versions of libev, the signal will not be blocked indefinitely	2549	In current versions of libev, the signal will not be blocked indefinitely
2161	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces	2550	unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
2162	the window of opportunity for problems, it will not go away, as libev	2551	the window of opportunity for problems, it will not go away, as libev
2163	I<has> to modify the signal mask, at least temporarily.	2552	I<has> to modify the signal mask, at least temporarily.
2164		2553
2165	So I can't stress this enough I<if you do not reset your signal mask	2554	So I can't stress this enough: I<If you do not reset your signal mask when
2166	when you expect it to be empty, you have a race condition in your	2555	you expect it to be empty, you have a race condition in your code>. This
2167	program>. This is not a libev-specific thing, this is true for most event	2556	is not a libev-specific thing, this is true for most event libraries.
2168	libraries.	2557
		2558	=head3 The special problem of threads signal handling
		2559
		2560	POSIX threads has problematic signal handling semantics, specifically,
		2561	a lot of functionality (sigfd, sigwait etc.) only really works if all
		2562	threads in a process block signals, which is hard to achieve.
		2563
		2564	When you want to use sigwait (or mix libev signal handling with your own
		2565	for the same signals), you can tackle this problem by globally blocking
		2566	all signals before creating any threads (or creating them with a fully set
		2567	sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating
		2568	loops. Then designate one thread as "signal receiver thread" which handles
		2569	these signals. You can pass on any signals that libev might be interested
		2570	in by calling C<ev_feed_signal>.
2169		2571
2170	=head3 Watcher-Specific Functions and Data Members	2572	=head3 Watcher-Specific Functions and Data Members
2171		2573
2172	=over 4	2574	=over 4
2173		2575
…		…
2189	Example: Try to exit cleanly on SIGINT.	2591	Example: Try to exit cleanly on SIGINT.
2190		2592
2191	static void	2593	static void
2192	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)	2594	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
2193	{	2595	{
2194	ev_unloop (loop, EVUNLOOP_ALL);	2596	ev_break (loop, EVBREAK_ALL);
2195	}	2597	}
2196		2598
2197	ev_signal signal_watcher;	2599	ev_signal signal_watcher;
2198	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2600	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
2199	ev_signal_start (loop, &signal_watcher);	2601	ev_signal_start (loop, &signal_watcher);
…		…
2308		2710
2309	=head2 C<ev_stat> - did the file attributes just change?	2711	=head2 C<ev_stat> - did the file attributes just change?
2310		2712
2311	This watches a file system path for attribute changes. That is, it calls	2713	This watches a file system path for attribute changes. That is, it calls
2312	C<stat> on that path in regular intervals (or when the OS says it changed)	2714	C<stat> on that path in regular intervals (or when the OS says it changed)
2313	and sees if it changed compared to the last time, invoking the callback if	2715	and sees if it changed compared to the last time, invoking the callback
2314	it did.	2716	if it did. Starting the watcher C<stat>'s the file, so only changes that
		2717	happen after the watcher has been started will be reported.
2315		2718
2316	The path does not need to exist: changing from "path exists" to "path does	2719	The path does not need to exist: changing from "path exists" to "path does
2317	not exist" is a status change like any other. The condition "path does not	2720	not exist" is a status change like any other. The condition "path does not
2318	exist" (or more correctly "path cannot be stat'ed") is signified by the	2721	exist" (or more correctly "path cannot be stat'ed") is signified by the
2319	C<st_nlink> field being zero (which is otherwise always forced to be at	2722	C<st_nlink> field being zero (which is otherwise always forced to be at
…		…
2549	Apart from keeping your process non-blocking (which is a useful	2952	Apart from keeping your process non-blocking (which is a useful
2550	effect on its own sometimes), idle watchers are a good place to do	2953	effect on its own sometimes), idle watchers are a good place to do
2551	"pseudo-background processing", or delay processing stuff to after the	2954	"pseudo-background processing", or delay processing stuff to after the
2552	event loop has handled all outstanding events.	2955	event loop has handled all outstanding events.
2553		2956
		2957	=head3 Abusing an C<ev_idle> watcher for its side-effect
		2958
		2959	As long as there is at least one active idle watcher, libev will never
		2960	sleep unnecessarily. Or in other words, it will loop as fast as possible.
		2961	For this to work, the idle watcher doesn't need to be invoked at all - the
		2962	lowest priority will do.
		2963
		2964	This mode of operation can be useful together with an C<ev_check> watcher,
		2965	to do something on each event loop iteration - for example to balance load
		2966	between different connections.
		2967
		2968	See L</Abusing an ev_check watcher for its side-effect> for a longer
		2969	example.
		2970
2554	=head3 Watcher-Specific Functions and Data Members	2971	=head3 Watcher-Specific Functions and Data Members
2555		2972
2556	=over 4	2973	=over 4
2557		2974
2558	=item ev_idle_init (ev_idle *, callback)	2975	=item ev_idle_init (ev_idle *, callback)
…		…
2569	callback, free it. Also, use no error checking, as usual.	2986	callback, free it. Also, use no error checking, as usual.
2570		2987
2571	static void	2988	static void
2572	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)	2989	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
2573	{	2990	{
		2991	// stop the watcher
		2992	ev_idle_stop (loop, w);
		2993
		2994	// now we can free it
2574	free (w);	2995	free (w);
		2996
2575	// now do something you wanted to do when the program has	2997	// now do something you wanted to do when the program has
2576	// no longer anything immediate to do.	2998	// no longer anything immediate to do.
2577	}	2999	}
2578		3000
2579	ev_idle *idle_watcher = malloc (sizeof (ev_idle));	3001	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
…		…
2581	ev_idle_start (loop, idle_watcher);	3003	ev_idle_start (loop, idle_watcher);
2582		3004
2583		3005
2584	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	3006	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2585		3007
2586	Prepare and check watchers are usually (but not always) used in pairs:	3008	Prepare and check watchers are often (but not always) used in pairs:
2587	prepare watchers get invoked before the process blocks and check watchers	3009	prepare watchers get invoked before the process blocks and check watchers
2588	afterwards.	3010	afterwards.
2589		3011
2590	You I<must not> call C<ev_loop> or similar functions that enter	3012	You I<must not> call C<ev_run> (or similar functions that enter the
2591	the current event loop from either C<ev_prepare> or C<ev_check>	3013	current event loop) or C<ev_loop_fork> from either C<ev_prepare> or
2592	watchers. Other loops than the current one are fine, however. The	3014	C<ev_check> watchers. Other loops than the current one are fine,
2593	rationale behind this is that you do not need to check for recursion in	3015	however. The rationale behind this is that you do not need to check
2594	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	3016	for recursion in those watchers, i.e. the sequence will always be
2595	C<ev_check> so if you have one watcher of each kind they will always be	3017	C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each
2596	called in pairs bracketing the blocking call.	3018	kind they will always be called in pairs bracketing the blocking call.
2597		3019
2598	Their main purpose is to integrate other event mechanisms into libev and	3020	Their main purpose is to integrate other event mechanisms into libev and
2599	their use is somewhat advanced. They could be used, for example, to track	3021	their use is somewhat advanced. They could be used, for example, to track
2600	variable changes, implement your own watchers, integrate net-snmp or a	3022	variable changes, implement your own watchers, integrate net-snmp or a
2601	coroutine library and lots more. They are also occasionally useful if	3023	coroutine library and lots more. They are also occasionally useful if
…		…
2619	with priority higher than or equal to the event loop and one coroutine	3041	with priority higher than or equal to the event loop and one coroutine
2620	of lower priority, but only once, using idle watchers to keep the event	3042	of lower priority, but only once, using idle watchers to keep the event
2621	loop from blocking if lower-priority coroutines are active, thus mapping	3043	loop from blocking if lower-priority coroutines are active, thus mapping
2622	low-priority coroutines to idle/background tasks).	3044	low-priority coroutines to idle/background tasks).
2623		3045
2624	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	3046	When used for this purpose, it is recommended to give C<ev_check> watchers
2625	priority, to ensure that they are being run before any other watchers	3047	highest (C<EV_MAXPRI>) priority, to ensure that they are being run before
2626	after the poll (this doesn't matter for C<ev_prepare> watchers).	3048	any other watchers after the poll (this doesn't matter for C<ev_prepare>
		3049	watchers).
2627		3050
2628	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not	3051	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
2629	activate ("feed") events into libev. While libev fully supports this, they	3052	activate ("feed") events into libev. While libev fully supports this, they
2630	might get executed before other C<ev_check> watchers did their job. As	3053	might get executed before other C<ev_check> watchers did their job. As
2631	C<ev_check> watchers are often used to embed other (non-libev) event	3054	C<ev_check> watchers are often used to embed other (non-libev) event
2632	loops those other event loops might be in an unusable state until their	3055	loops those other event loops might be in an unusable state until their
2633	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	3056	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
2634	others).	3057	others).
		3058
		3059	=head3 Abusing an C<ev_check> watcher for its side-effect
		3060
		3061	C<ev_check> (and less often also C<ev_prepare>) watchers can also be
		3062	useful because they are called once per event loop iteration. For
		3063	example, if you want to handle a large number of connections fairly, you
		3064	normally only do a bit of work for each active connection, and if there
		3065	is more work to do, you wait for the next event loop iteration, so other
		3066	connections have a chance of making progress.
		3067
		3068	Using an C<ev_check> watcher is almost enough: it will be called on the
		3069	next event loop iteration. However, that isn't as soon as possible -
		3070	without external events, your C<ev_check> watcher will not be invoked.
		3071
		3072	This is where C<ev_idle> watchers come in handy - all you need is a
		3073	single global idle watcher that is active as long as you have one active
		3074	C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop
		3075	will not sleep, and the C<ev_check> watcher makes sure a callback gets
		3076	invoked. Neither watcher alone can do that.
2635		3077
2636	=head3 Watcher-Specific Functions and Data Members	3078	=head3 Watcher-Specific Functions and Data Members
2637		3079
2638	=over 4	3080	=over 4
2639		3081
…		…
2763		3205
2764	if (timeout >= 0)	3206	if (timeout >= 0)
2765	// create/start timer	3207	// create/start timer
2766		3208
2767	// poll	3209	// poll
2768	ev_loop (EV_A_ 0);	3210	ev_run (EV_A_ 0);
2769		3211
2770	// stop timer again	3212	// stop timer again
2771	if (timeout >= 0)	3213	if (timeout >= 0)
2772	ev_timer_stop (EV_A_ &to);	3214	ev_timer_stop (EV_A_ &to);
2773		3215
…		…
2840		3282
2841	=over 4	3283	=over 4
2842		3284
2843	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	3285	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
2844		3286
2845	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	3287	=item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop)
2846		3288
2847	Configures the watcher to embed the given loop, which must be	3289	Configures the watcher to embed the given loop, which must be
2848	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be	3290	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
2849	invoked automatically, otherwise it is the responsibility of the callback	3291	invoked automatically, otherwise it is the responsibility of the callback
2850	to invoke it (it will continue to be called until the sweep has been done,	3292	to invoke it (it will continue to be called until the sweep has been done,
2851	if you do not want that, you need to temporarily stop the embed watcher).	3293	if you do not want that, you need to temporarily stop the embed watcher).
2852		3294
2853	=item ev_embed_sweep (loop, ev_embed *)	3295	=item ev_embed_sweep (loop, ev_embed *)
2854		3296
2855	Make a single, non-blocking sweep over the embedded loop. This works	3297	Make a single, non-blocking sweep over the embedded loop. This works
2856	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	3298	similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most
2857	appropriate way for embedded loops.	3299	appropriate way for embedded loops.
2858		3300
2859	=item struct ev_loop *other [read-only]	3301	=item struct ev_loop *other [read-only]
2860		3302
2861	The embedded event loop.	3303	The embedded event loop.
…		…
2871	used).	3313	used).
2872		3314
2873	struct ev_loop *loop_hi = ev_default_init (0);	3315	struct ev_loop *loop_hi = ev_default_init (0);
2874	struct ev_loop *loop_lo = 0;	3316	struct ev_loop *loop_lo = 0;
2875	ev_embed embed;	3317	ev_embed embed;
2876		3318
2877	// see if there is a chance of getting one that works	3319	// see if there is a chance of getting one that works
2878	// (remember that a flags value of 0 means autodetection)	3320	// (remember that a flags value of 0 means autodetection)
2879	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	3321	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2880	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	3322	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2881	: 0;	3323	: 0;
…		…
2895	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	3337	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2896		3338
2897	struct ev_loop *loop = ev_default_init (0);	3339	struct ev_loop *loop = ev_default_init (0);
2898	struct ev_loop *loop_socket = 0;	3340	struct ev_loop *loop_socket = 0;
2899	ev_embed embed;	3341	ev_embed embed;
2900		3342
2901	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	3343	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2902	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	3344	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2903	{	3345	{
2904	ev_embed_init (&embed, 0, loop_socket);	3346	ev_embed_init (&embed, 0, loop_socket);
2905	ev_embed_start (loop, &embed);	3347	ev_embed_start (loop, &embed);
…		…
2913		3355
2914	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	3356	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
2915		3357
2916	Fork watchers are called when a C<fork ()> was detected (usually because	3358	Fork watchers are called when a C<fork ()> was detected (usually because
2917	whoever is a good citizen cared to tell libev about it by calling	3359	whoever is a good citizen cared to tell libev about it by calling
2918	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the	3360	C<ev_loop_fork>). The invocation is done before the event loop blocks next
2919	event loop blocks next and before C<ev_check> watchers are being called,	3361	and before C<ev_check> watchers are being called, and only in the child
2920	and only in the child after the fork. If whoever good citizen calling	3362	after the fork. If whoever good citizen calling C<ev_default_fork> cheats
2921	C<ev_default_fork> cheats and calls it in the wrong process, the fork	3363	and calls it in the wrong process, the fork handlers will be invoked, too,
2922	handlers will be invoked, too, of course.	3364	of course.
2923		3365
2924	=head3 The special problem of life after fork - how is it possible?	3366	=head3 The special problem of life after fork - how is it possible?
2925		3367
2926	Most uses of C<fork()> consist of forking, then some simple calls to ste	3368	Most uses of C<fork ()> consist of forking, then some simple calls to set
2927	up/change the process environment, followed by a call to C<exec()>. This	3369	up/change the process environment, followed by a call to C<exec()>. This
2928	sequence should be handled by libev without any problems.	3370	sequence should be handled by libev without any problems.
2929		3371
2930	This changes when the application actually wants to do event handling	3372	This changes when the application actually wants to do event handling
2931	in the child, or both parent in child, in effect "continuing" after the	3373	in the child, or both parent in child, in effect "continuing" after the
…		…
2947	disadvantage of having to use multiple event loops (which do not support	3389	disadvantage of having to use multiple event loops (which do not support
2948	signal watchers).	3390	signal watchers).
2949		3391
2950	When this is not possible, or you want to use the default loop for	3392	When this is not possible, or you want to use the default loop for
2951	other reasons, then in the process that wants to start "fresh", call	3393	other reasons, then in the process that wants to start "fresh", call
2952	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying	3394	C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>.
2953	the default loop will "orphan" (not stop) all registered watchers, so you	3395	Destroying the default loop will "orphan" (not stop) all registered
2954	have to be careful not to execute code that modifies those watchers. Note	3396	watchers, so you have to be careful not to execute code that modifies
2955	also that in that case, you have to re-register any signal watchers.	3397	those watchers. Note also that in that case, you have to re-register any
		3398	signal watchers.
2956		3399
2957	=head3 Watcher-Specific Functions and Data Members	3400	=head3 Watcher-Specific Functions and Data Members
2958		3401
2959	=over 4	3402	=over 4
2960		3403
2961	=item ev_fork_init (ev_signal *, callback)	3404	=item ev_fork_init (ev_fork *, callback)
2962		3405
2963	Initialises and configures the fork watcher - it has no parameters of any	3406	Initialises and configures the fork watcher - it has no parameters of any
2964	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	3407	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
2965	believe me.	3408	really.
2966		3409
2967	=back	3410	=back
2968		3411
2969		3412
		3413	=head2 C<ev_cleanup> - even the best things end
		3414
		3415	Cleanup watchers are called just before the event loop is being destroyed
		3416	by a call to C<ev_loop_destroy>.
		3417
		3418	While there is no guarantee that the event loop gets destroyed, cleanup
		3419	watchers provide a convenient method to install cleanup hooks for your
		3420	program, worker threads and so on - you just to make sure to destroy the
		3421	loop when you want them to be invoked.
		3422
		3423	Cleanup watchers are invoked in the same way as any other watcher. Unlike
		3424	all other watchers, they do not keep a reference to the event loop (which
		3425	makes a lot of sense if you think about it). Like all other watchers, you
		3426	can call libev functions in the callback, except C<ev_cleanup_start>.
		3427
		3428	=head3 Watcher-Specific Functions and Data Members
		3429
		3430	=over 4
		3431
		3432	=item ev_cleanup_init (ev_cleanup *, callback)
		3433
		3434	Initialises and configures the cleanup watcher - it has no parameters of
		3435	any kind. There is a C<ev_cleanup_set> macro, but using it is utterly
		3436	pointless, I assure you.
		3437
		3438	=back
		3439
		3440	Example: Register an atexit handler to destroy the default loop, so any
		3441	cleanup functions are called.
		3442
		3443	static void
		3444	program_exits (void)
		3445	{
		3446	ev_loop_destroy (EV_DEFAULT_UC);
		3447	}
		3448
		3449	...
		3450	atexit (program_exits);
		3451
		3452
2970	=head2 C<ev_async> - how to wake up another event loop	3453	=head2 C<ev_async> - how to wake up an event loop
2971		3454
2972	In general, you cannot use an C<ev_loop> from multiple threads or other	3455	In general, you cannot use an C<ev_loop> from multiple threads or other
2973	asynchronous sources such as signal handlers (as opposed to multiple event	3456	asynchronous sources such as signal handlers (as opposed to multiple event
2974	loops - those are of course safe to use in different threads).	3457	loops - those are of course safe to use in different threads).
2975		3458
2976	Sometimes, however, you need to wake up another event loop you do not	3459	Sometimes, however, you need to wake up an event loop you do not control,
2977	control, for example because it belongs to another thread. This is what	3460	for example because it belongs to another thread. This is what C<ev_async>
2978	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you	3461	watchers do: as long as the C<ev_async> watcher is active, you can signal
2979	can signal it by calling C<ev_async_send>, which is thread- and signal	3462	it by calling C<ev_async_send>, which is thread- and signal safe.
2980	safe.
2981		3463
2982	This functionality is very similar to C<ev_signal> watchers, as signals,	3464	This functionality is very similar to C<ev_signal> watchers, as signals,
2983	too, are asynchronous in nature, and signals, too, will be compressed	3465	too, are asynchronous in nature, and signals, too, will be compressed
2984	(i.e. the number of callback invocations may be less than the number of	3466	(i.e. the number of callback invocations may be less than the number of
2985	C<ev_async_sent> calls).	3467	C<ev_async_send> calls). In fact, you could use signal watchers as a kind
2986		3468	of "global async watchers" by using a watcher on an otherwise unused
2987	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not	3469	signal, and C<ev_feed_signal> to signal this watcher from another thread,
2988	just the default loop.	3470	even without knowing which loop owns the signal.
2989		3471
2990	=head3 Queueing	3472	=head3 Queueing
2991		3473
2992	C<ev_async> does not support queueing of data in any way. The reason	3474	C<ev_async> does not support queueing of data in any way. The reason
2993	is that the author does not know of a simple (or any) algorithm for a	3475	is that the author does not know of a simple (or any) algorithm for a
…		…
3085	trust me.	3567	trust me.
3086		3568
3087	=item ev_async_send (loop, ev_async *)	3569	=item ev_async_send (loop, ev_async *)
3088		3570
3089	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3571	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
3090	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3572	an C<EV_ASYNC> event on the watcher into the event loop, and instantly
		3573	returns.
		3574
3091	C<ev_feed_event>, this call is safe to do from other threads, signal or	3575	Unlike C<ev_feed_event>, this call is safe to do from other threads,
3092	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3576	signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the
3093	section below on what exactly this means).	3577	embedding section below on what exactly this means).
3094		3578
3095	Note that, as with other watchers in libev, multiple events might get	3579	Note that, as with other watchers in libev, multiple events might get
3096	compressed into a single callback invocation (another way to look at this	3580	compressed into a single callback invocation (another way to look at
3097	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,	3581	this is that C<ev_async> watchers are level-triggered: they are set on
3098	reset when the event loop detects that).	3582	C<ev_async_send>, reset when the event loop detects that).
3099		3583
3100	This call incurs the overhead of a system call only once per event loop	3584	This call incurs the overhead of at most one extra system call per event
3101	iteration, so while the overhead might be noticeable, it doesn't apply to	3585	loop iteration, if the event loop is blocked, and no syscall at all if
3102	repeated calls to C<ev_async_send> for the same event loop.	3586	the event loop (or your program) is processing events. That means that
		3587	repeated calls are basically free (there is no need to avoid calls for
		3588	performance reasons) and that the overhead becomes smaller (typically
		3589	zero) under load.
3103		3590
3104	=item bool = ev_async_pending (ev_async *)	3591	=item bool = ev_async_pending (ev_async *)
3105		3592
3106	Returns a non-zero value when C<ev_async_send> has been called on the	3593	Returns a non-zero value when C<ev_async_send> has been called on the
3107	watcher but the event has not yet been processed (or even noted) by the	3594	watcher but the event has not yet been processed (or even noted) by the
…		…
3124		3611
3125	There are some other functions of possible interest. Described. Here. Now.	3612	There are some other functions of possible interest. Described. Here. Now.
3126		3613
3127	=over 4	3614	=over 4
3128		3615
3129	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3616	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)
3130		3617
3131	This function combines a simple timer and an I/O watcher, calls your	3618	This function combines a simple timer and an I/O watcher, calls your
3132	callback on whichever event happens first and automatically stops both	3619	callback on whichever event happens first and automatically stops both
3133	watchers. This is useful if you want to wait for a single event on an fd	3620	watchers. This is useful if you want to wait for a single event on an fd
3134	or timeout without having to allocate/configure/start/stop/free one or	3621	or timeout without having to allocate/configure/start/stop/free one or
…		…
3140		3627
3141	If C<timeout> is less than 0, then no timeout watcher will be	3628	If C<timeout> is less than 0, then no timeout watcher will be
3142	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3629	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3143	repeat = 0) will be started. C<0> is a valid timeout.	3630	repeat = 0) will be started. C<0> is a valid timeout.
3144		3631
3145	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3632	The callback has the type C<void (*cb)(int revents, void *arg)> and is
3146	passed an C<revents> set like normal event callbacks (a combination of	3633	passed an C<revents> set like normal event callbacks (a combination of
3147	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3634	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3148	value passed to C<ev_once>. Note that it is possible to receive I<both>	3635	value passed to C<ev_once>. Note that it is possible to receive I<both>
3149	a timeout and an io event at the same time - you probably should give io	3636	a timeout and an io event at the same time - you probably should give io
3150	events precedence.	3637	events precedence.
3151		3638
3152	Example: wait up to ten seconds for data to appear on STDIN_FILENO.	3639	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3153		3640
3154	static void stdin_ready (int revents, void *arg)	3641	static void stdin_ready (int revents, void *arg)
3155	{	3642	{
3156	if (revents & EV_READ)	3643	if (revents & EV_READ)
3157	/* stdin might have data for us, joy! */;	3644	/* stdin might have data for us, joy! */;
3158	else if (revents & EV_TIMEOUT)	3645	else if (revents & EV_TIMER)
3159	/* doh, nothing entered */;	3646	/* doh, nothing entered */;
3160	}	3647	}
3161		3648
3162	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3649	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3163		3650
3164	=item ev_feed_fd_event (loop, int fd, int revents)	3651	=item ev_feed_fd_event (loop, int fd, int revents)
3165		3652
3166	Feed an event on the given fd, as if a file descriptor backend detected	3653	Feed an event on the given fd, as if a file descriptor backend detected
3167	the given events it.	3654	the given events.
3168		3655
3169	=item ev_feed_signal_event (loop, int signum)	3656	=item ev_feed_signal_event (loop, int signum)
3170		3657
3171	Feed an event as if the given signal occurred (C<loop> must be the default	3658	Feed an event as if the given signal occurred. See also C<ev_feed_signal>,
3172	loop!).	3659	which is async-safe.
3173		3660
3174	=back	3661	=back
		3662
		3663
		3664	=head1 COMMON OR USEFUL IDIOMS (OR BOTH)
		3665
		3666	This section explains some common idioms that are not immediately
		3667	obvious. Note that examples are sprinkled over the whole manual, and this
		3668	section only contains stuff that wouldn't fit anywhere else.
		3669
		3670	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
		3671
		3672	Each watcher has, by default, a C<void *data> member that you can read
		3673	or modify at any time: libev will completely ignore it. This can be used
		3674	to associate arbitrary data with your watcher. If you need more data and
		3675	don't want to allocate memory separately and store a pointer to it in that
		3676	data member, you can also "subclass" the watcher type and provide your own
		3677	data:
		3678
		3679	struct my_io
		3680	{
		3681	ev_io io;
		3682	int otherfd;
		3683	void *somedata;
		3684	struct whatever *mostinteresting;
		3685	};
		3686
		3687	...
		3688	struct my_io w;
		3689	ev_io_init (&w.io, my_cb, fd, EV_READ);
		3690
		3691	And since your callback will be called with a pointer to the watcher, you
		3692	can cast it back to your own type:
		3693
		3694	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
		3695	{
		3696	struct my_io *w = (struct my_io *)w_;
		3697	...
		3698	}
		3699
		3700	More interesting and less C-conformant ways of casting your callback
		3701	function type instead have been omitted.
		3702
		3703	=head2 BUILDING YOUR OWN COMPOSITE WATCHERS
		3704
		3705	Another common scenario is to use some data structure with multiple
		3706	embedded watchers, in effect creating your own watcher that combines
		3707	multiple libev event sources into one "super-watcher":
		3708
		3709	struct my_biggy
		3710	{
		3711	int some_data;
		3712	ev_timer t1;
		3713	ev_timer t2;
		3714	}
		3715
		3716	In this case getting the pointer to C<my_biggy> is a bit more
		3717	complicated: Either you store the address of your C<my_biggy> struct in
		3718	the C<data> member of the watcher (for woozies or C++ coders), or you need
		3719	to use some pointer arithmetic using C<offsetof> inside your watchers (for
		3720	real programmers):
		3721
		3722	#include <stddef.h>
		3723
		3724	static void
		3725	t1_cb (EV_P_ ev_timer *w, int revents)
		3726	{
		3727	struct my_biggy big = (struct my_biggy *)
		3728	(((char *)w) - offsetof (struct my_biggy, t1));
		3729	}
		3730
		3731	static void
		3732	t2_cb (EV_P_ ev_timer *w, int revents)
		3733	{
		3734	struct my_biggy big = (struct my_biggy *)
		3735	(((char *)w) - offsetof (struct my_biggy, t2));
		3736	}
		3737
		3738	=head2 AVOIDING FINISHING BEFORE RETURNING
		3739
		3740	Often you have structures like this in event-based programs:
		3741
		3742	callback ()
		3743	{
		3744	free (request);
		3745	}
		3746
		3747	request = start_new_request (..., callback);
		3748
		3749	The intent is to start some "lengthy" operation. The C<request> could be
		3750	used to cancel the operation, or do other things with it.
		3751
		3752	It's not uncommon to have code paths in C<start_new_request> that
		3753	immediately invoke the callback, for example, to report errors. Or you add
		3754	some caching layer that finds that it can skip the lengthy aspects of the
		3755	operation and simply invoke the callback with the result.
		3756
		3757	The problem here is that this will happen I<before> C<start_new_request>
		3758	has returned, so C<request> is not set.
		3759
		3760	Even if you pass the request by some safer means to the callback, you
		3761	might want to do something to the request after starting it, such as
		3762	canceling it, which probably isn't working so well when the callback has
		3763	already been invoked.
		3764
		3765	A common way around all these issues is to make sure that
		3766	C<start_new_request> I<always> returns before the callback is invoked. If
		3767	C<start_new_request> immediately knows the result, it can artificially
		3768	delay invoking the callback by using a C<prepare> or C<idle> watcher for
		3769	example, or more sneakily, by reusing an existing (stopped) watcher and
		3770	pushing it into the pending queue:
		3771
		3772	ev_set_cb (watcher, callback);
		3773	ev_feed_event (EV_A_ watcher, 0);
		3774
		3775	This way, C<start_new_request> can safely return before the callback is
		3776	invoked, while not delaying callback invocation too much.
		3777
		3778	=head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS
		3779
		3780	Often (especially in GUI toolkits) there are places where you have
		3781	I<modal> interaction, which is most easily implemented by recursively
		3782	invoking C<ev_run>.
		3783
		3784	This brings the problem of exiting - a callback might want to finish the
		3785	main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but
		3786	a modal "Are you sure?" dialog is still waiting), or just the nested one
		3787	and not the main one (e.g. user clocked "Ok" in a modal dialog), or some
		3788	other combination: In these cases, a simple C<ev_break> will not work.
		3789
		3790	The solution is to maintain "break this loop" variable for each C<ev_run>
		3791	invocation, and use a loop around C<ev_run> until the condition is
		3792	triggered, using C<EVRUN_ONCE>:
		3793
		3794	// main loop
		3795	int exit_main_loop = 0;
		3796
		3797	while (!exit_main_loop)
		3798	ev_run (EV_DEFAULT_ EVRUN_ONCE);
		3799
		3800	// in a modal watcher
		3801	int exit_nested_loop = 0;
		3802
		3803	while (!exit_nested_loop)
		3804	ev_run (EV_A_ EVRUN_ONCE);
		3805
		3806	To exit from any of these loops, just set the corresponding exit variable:
		3807
		3808	// exit modal loop
		3809	exit_nested_loop = 1;
		3810
		3811	// exit main program, after modal loop is finished
		3812	exit_main_loop = 1;
		3813
		3814	// exit both
		3815	exit_main_loop = exit_nested_loop = 1;
		3816
		3817	=head2 THREAD LOCKING EXAMPLE
		3818
		3819	Here is a fictitious example of how to run an event loop in a different
		3820	thread from where callbacks are being invoked and watchers are
		3821	created/added/removed.
		3822
		3823	For a real-world example, see the C<EV::Loop::Async> perl module,
		3824	which uses exactly this technique (which is suited for many high-level
		3825	languages).
		3826
		3827	The example uses a pthread mutex to protect the loop data, a condition
		3828	variable to wait for callback invocations, an async watcher to notify the
		3829	event loop thread and an unspecified mechanism to wake up the main thread.
		3830
		3831	First, you need to associate some data with the event loop:
		3832
		3833	typedef struct {
		3834	mutex_t lock; /* global loop lock */
		3835	ev_async async_w;
		3836	thread_t tid;
		3837	cond_t invoke_cv;
		3838	} userdata;
		3839
		3840	void prepare_loop (EV_P)
		3841	{
		3842	// for simplicity, we use a static userdata struct.
		3843	static userdata u;
		3844
		3845	ev_async_init (&u->async_w, async_cb);
		3846	ev_async_start (EV_A_ &u->async_w);
		3847
		3848	pthread_mutex_init (&u->lock, 0);
		3849	pthread_cond_init (&u->invoke_cv, 0);
		3850
		3851	// now associate this with the loop
		3852	ev_set_userdata (EV_A_ u);
		3853	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		3854	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		3855
		3856	// then create the thread running ev_run
		3857	pthread_create (&u->tid, 0, l_run, EV_A);
		3858	}
		3859
		3860	The callback for the C<ev_async> watcher does nothing: the watcher is used
		3861	solely to wake up the event loop so it takes notice of any new watchers
		3862	that might have been added:
		3863
		3864	static void
		3865	async_cb (EV_P_ ev_async *w, int revents)
		3866	{
		3867	// just used for the side effects
		3868	}
		3869
		3870	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		3871	protecting the loop data, respectively.
		3872
		3873	static void
		3874	l_release (EV_P)
		3875	{
		3876	userdata *u = ev_userdata (EV_A);
		3877	pthread_mutex_unlock (&u->lock);
		3878	}
		3879
		3880	static void
		3881	l_acquire (EV_P)
		3882	{
		3883	userdata *u = ev_userdata (EV_A);
		3884	pthread_mutex_lock (&u->lock);
		3885	}
		3886
		3887	The event loop thread first acquires the mutex, and then jumps straight
		3888	into C<ev_run>:
		3889
		3890	void *
		3891	l_run (void *thr_arg)
		3892	{
		3893	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		3894
		3895	l_acquire (EV_A);
		3896	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		3897	ev_run (EV_A_ 0);
		3898	l_release (EV_A);
		3899
		3900	return 0;
		3901	}
		3902
		3903	Instead of invoking all pending watchers, the C<l_invoke> callback will
		3904	signal the main thread via some unspecified mechanism (signals? pipe
		3905	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		3906	have been called (in a while loop because a) spurious wakeups are possible
		3907	and b) skipping inter-thread-communication when there are no pending
		3908	watchers is very beneficial):
		3909
		3910	static void
		3911	l_invoke (EV_P)
		3912	{
		3913	userdata *u = ev_userdata (EV_A);
		3914
		3915	while (ev_pending_count (EV_A))
		3916	{
		3917	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		3918	pthread_cond_wait (&u->invoke_cv, &u->lock);
		3919	}
		3920	}
		3921
		3922	Now, whenever the main thread gets told to invoke pending watchers, it
		3923	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		3924	thread to continue:
		3925
		3926	static void
		3927	real_invoke_pending (EV_P)
		3928	{
		3929	userdata *u = ev_userdata (EV_A);
		3930
		3931	pthread_mutex_lock (&u->lock);
		3932	ev_invoke_pending (EV_A);
		3933	pthread_cond_signal (&u->invoke_cv);
		3934	pthread_mutex_unlock (&u->lock);
		3935	}
		3936
		3937	Whenever you want to start/stop a watcher or do other modifications to an
		3938	event loop, you will now have to lock:
		3939
		3940	ev_timer timeout_watcher;
		3941	userdata *u = ev_userdata (EV_A);
		3942
		3943	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		3944
		3945	pthread_mutex_lock (&u->lock);
		3946	ev_timer_start (EV_A_ &timeout_watcher);
		3947	ev_async_send (EV_A_ &u->async_w);
		3948	pthread_mutex_unlock (&u->lock);
		3949
		3950	Note that sending the C<ev_async> watcher is required because otherwise
		3951	an event loop currently blocking in the kernel will have no knowledge
		3952	about the newly added timer. By waking up the loop it will pick up any new
		3953	watchers in the next event loop iteration.
		3954
		3955	=head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS
		3956
		3957	While the overhead of a callback that e.g. schedules a thread is small, it
		3958	is still an overhead. If you embed libev, and your main usage is with some
		3959	kind of threads or coroutines, you might want to customise libev so that
		3960	doesn't need callbacks anymore.
		3961
		3962	Imagine you have coroutines that you can switch to using a function
		3963	C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro>
		3964	and that due to some magic, the currently active coroutine is stored in a
		3965	global called C<current_coro>. Then you can build your own "wait for libev
		3966	event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note
		3967	the differing C<;> conventions):
		3968
		3969	#define EV_CB_DECLARE(type) struct my_coro *cb;
		3970	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		3971
		3972	That means instead of having a C callback function, you store the
		3973	coroutine to switch to in each watcher, and instead of having libev call
		3974	your callback, you instead have it switch to that coroutine.
		3975
		3976	A coroutine might now wait for an event with a function called
		3977	C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't
		3978	matter when, or whether the watcher is active or not when this function is
		3979	called):
		3980
		3981	void
		3982	wait_for_event (ev_watcher *w)
		3983	{
		3984	ev_set_cb (w, current_coro);
		3985	switch_to (libev_coro);
		3986	}
		3987
		3988	That basically suspends the coroutine inside C<wait_for_event> and
		3989	continues the libev coroutine, which, when appropriate, switches back to
		3990	this or any other coroutine.
		3991
		3992	You can do similar tricks if you have, say, threads with an event queue -
		3993	instead of storing a coroutine, you store the queue object and instead of
		3994	switching to a coroutine, you push the watcher onto the queue and notify
		3995	any waiters.
		3996
		3997	To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two
		3998	files, F<my_ev.h> and F<my_ev.c> that include the respective libev files:
		3999
		4000	// my_ev.h
		4001	#define EV_CB_DECLARE(type) struct my_coro *cb;
		4002	#define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb)
		4003	#include "../libev/ev.h"
		4004
		4005	// my_ev.c
		4006	#define EV_H "my_ev.h"
		4007	#include "../libev/ev.c"
		4008
		4009	And then use F<my_ev.h> when you would normally use F<ev.h>, and compile
		4010	F<my_ev.c> into your project. When properly specifying include paths, you
		4011	can even use F<ev.h> as header file name directly.
3175		4012
3176		4013
3177	=head1 LIBEVENT EMULATION	4014	=head1 LIBEVENT EMULATION
3178		4015
3179	Libev offers a compatibility emulation layer for libevent. It cannot	4016	Libev offers a compatibility emulation layer for libevent. It cannot
3180	emulate the internals of libevent, so here are some usage hints:	4017	emulate the internals of libevent, so here are some usage hints:
3181		4018
3182	=over 4	4019	=over 4
		4020
		4021	=item * Only the libevent-1.4.1-beta API is being emulated.
		4022
		4023	This was the newest libevent version available when libev was implemented,
		4024	and is still mostly unchanged in 2010.
3183		4025
3184	=item * Use it by including <event.h>, as usual.	4026	=item * Use it by including <event.h>, as usual.
3185		4027
3186	=item * The following members are fully supported: ev_base, ev_callback,	4028	=item * The following members are fully supported: ev_base, ev_callback,
3187	ev_arg, ev_fd, ev_res, ev_events.	4029	ev_arg, ev_fd, ev_res, ev_events.
…		…
3193	=item * Priorities are not currently supported. Initialising priorities	4035	=item * Priorities are not currently supported. Initialising priorities
3194	will fail and all watchers will have the same priority, even though there	4036	will fail and all watchers will have the same priority, even though there
3195	is an ev_pri field.	4037	is an ev_pri field.
3196		4038
3197	=item * In libevent, the last base created gets the signals, in libev, the	4039	=item * In libevent, the last base created gets the signals, in libev, the
3198	first base created (== the default loop) gets the signals.	4040	base that registered the signal gets the signals.
3199		4041
3200	=item * Other members are not supported.	4042	=item * Other members are not supported.
3201		4043
3202	=item * The libev emulation is I<not> ABI compatible to libevent, you need	4044	=item * The libev emulation is I<not> ABI compatible to libevent, you need
3203	to use the libev header file and library.	4045	to use the libev header file and library.
3204		4046
3205	=back	4047	=back
3206		4048
3207	=head1 C++ SUPPORT	4049	=head1 C++ SUPPORT
		4050
		4051	=head2 C API
		4052
		4053	The normal C API should work fine when used from C++: both ev.h and the
		4054	libev sources can be compiled as C++. Therefore, code that uses the C API
		4055	will work fine.
		4056
		4057	Proper exception specifications might have to be added to callbacks passed
		4058	to libev: exceptions may be thrown only from watcher callbacks, all other
		4059	callbacks (allocator, syserr, loop acquire/release and periodic reschedule
		4060	callbacks) must not throw exceptions, and might need a C<noexcept>
		4061	specification. If you have code that needs to be compiled as both C and
		4062	C++ you can use the C<EV_NOEXCEPT> macro for this:
		4063
		4064	static void
		4065	fatal_error (const char *msg) EV_NOEXCEPT
		4066	{
		4067	perror (msg);
		4068	abort ();
		4069	}
		4070
		4071	...
		4072	ev_set_syserr_cb (fatal_error);
		4073
		4074	The only API functions that can currently throw exceptions are C<ev_run>,
		4075	C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter
		4076	because it runs cleanup watchers).
		4077
		4078	Throwing exceptions in watcher callbacks is only supported if libev itself
		4079	is compiled with a C++ compiler or your C and C++ environments allow
		4080	throwing exceptions through C libraries (most do).
		4081
		4082	=head2 C++ API
3208		4083
3209	Libev comes with some simplistic wrapper classes for C++ that mainly allow	4084	Libev comes with some simplistic wrapper classes for C++ that mainly allow
3210	you to use some convenience methods to start/stop watchers and also change	4085	you to use some convenience methods to start/stop watchers and also change
3211	the callback model to a model using method callbacks on objects.	4086	the callback model to a model using method callbacks on objects.
3212		4087
3213	To use it,	4088	To use it,
3214		4089
3215	#include <ev++.h>	4090	#include <ev++.h>
3216		4091
3217	This automatically includes F<ev.h> and puts all of its definitions (many	4092	This automatically includes F<ev.h> and puts all of its definitions (many
3218	of them macros) into the global namespace. All C++ specific things are	4093	of them macros) into the global namespace. All C++ specific things are
3219	put into the C<ev> namespace. It should support all the same embedding	4094	put into the C<ev> namespace. It should support all the same embedding
…		…
3222	Care has been taken to keep the overhead low. The only data member the C++	4097	Care has been taken to keep the overhead low. The only data member the C++
3223	classes add (compared to plain C-style watchers) is the event loop pointer	4098	classes add (compared to plain C-style watchers) is the event loop pointer
3224	that the watcher is associated with (or no additional members at all if	4099	that the watcher is associated with (or no additional members at all if
3225	you disable C<EV_MULTIPLICITY> when embedding libev).	4100	you disable C<EV_MULTIPLICITY> when embedding libev).
3226		4101
3227	Currently, functions, and static and non-static member functions can be	4102	Currently, functions, static and non-static member functions and classes
3228	used as callbacks. Other types should be easy to add as long as they only	4103	with C<operator ()> can be used as callbacks. Other types should be easy
3229	need one additional pointer for context. If you need support for other	4104	to add as long as they only need one additional pointer for context. If
3230	types of functors please contact the author (preferably after implementing	4105	you need support for other types of functors please contact the author
3231	it).	4106	(preferably after implementing it).
		4107
		4108	For all this to work, your C++ compiler either has to use the same calling
		4109	conventions as your C compiler (for static member functions), or you have
		4110	to embed libev and compile libev itself as C++.
3232		4111
3233	Here is a list of things available in the C<ev> namespace:	4112	Here is a list of things available in the C<ev> namespace:
3234		4113
3235	=over 4	4114	=over 4
3236		4115
…		…
3246	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.	4125	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
3247		4126
3248	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of	4127	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
3249	the same name in the C<ev> namespace, with the exception of C<ev_signal>	4128	the same name in the C<ev> namespace, with the exception of C<ev_signal>
3250	which is called C<ev::sig> to avoid clashes with the C<signal> macro	4129	which is called C<ev::sig> to avoid clashes with the C<signal> macro
3251	defines by many implementations.	4130	defined by many implementations.
3252		4131
3253	All of those classes have these methods:	4132	All of those classes have these methods:
3254		4133
3255	=over 4	4134	=over 4
3256		4135
…		…
3297	myclass obj;	4176	myclass obj;
3298	ev::io iow;	4177	ev::io iow;
3299	iow.set <myclass, &myclass::io_cb> (&obj);	4178	iow.set <myclass, &myclass::io_cb> (&obj);
3300		4179
3301	=item w->set (object *)	4180	=item w->set (object *)
3302
3303	This is an B<experimental> feature that might go away in a future version.
3304		4181
3305	This is a variation of a method callback - leaving out the method to call	4182	This is a variation of a method callback - leaving out the method to call
3306	will default the method to C<operator ()>, which makes it possible to use	4183	will default the method to C<operator ()>, which makes it possible to use
3307	functor objects without having to manually specify the C<operator ()> all	4184	functor objects without having to manually specify the C<operator ()> all
3308	the time. Incidentally, you can then also leave out the template argument	4185	the time. Incidentally, you can then also leave out the template argument
…		…
3320	void operator() (ev::io &w, int revents)	4197	void operator() (ev::io &w, int revents)
3321	{	4198	{
3322	...	4199	...
3323	}	4200	}
3324	}	4201	}
3325		4202
3326	myfunctor f;	4203	myfunctor f;
3327		4204
3328	ev::io w;	4205	ev::io w;
3329	w.set (&f);	4206	w.set (&f);
3330		4207
…		…
3348	Associates a different C<struct ev_loop> with this watcher. You can only	4225	Associates a different C<struct ev_loop> with this watcher. You can only
3349	do this when the watcher is inactive (and not pending either).	4226	do this when the watcher is inactive (and not pending either).
3350		4227
3351	=item w->set ([arguments])	4228	=item w->set ([arguments])
3352		4229
3353	Basically the same as C<ev_TYPE_set>, with the same arguments. Must be	4230	Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>),
		4231	with the same arguments. Either this method or a suitable start method
3354	called at least once. Unlike the C counterpart, an active watcher gets	4232	must be called at least once. Unlike the C counterpart, an active watcher
3355	automatically stopped and restarted when reconfiguring it with this	4233	gets automatically stopped and restarted when reconfiguring it with this
3356	method.	4234	method.
		4235
		4236	For C<ev::embed> watchers this method is called C<set_embed>, to avoid
		4237	clashing with the C<set (loop)> method.
3357		4238
3358	=item w->start ()	4239	=item w->start ()
3359		4240
3360	Starts the watcher. Note that there is no C<loop> argument, as the	4241	Starts the watcher. Note that there is no C<loop> argument, as the
3361	constructor already stores the event loop.	4242	constructor already stores the event loop.
3362		4243
		4244	=item w->start ([arguments])
		4245
		4246	Instead of calling C<set> and C<start> methods separately, it is often
		4247	convenient to wrap them in one call. Uses the same type of arguments as
		4248	the configure C<set> method of the watcher.
		4249
3363	=item w->stop ()	4250	=item w->stop ()
3364		4251
3365	Stops the watcher if it is active. Again, no C<loop> argument.	4252	Stops the watcher if it is active. Again, no C<loop> argument.
3366		4253
3367	=item w->again () (C<ev::timer>, C<ev::periodic> only)	4254	=item w->again () (C<ev::timer>, C<ev::periodic> only)
…		…
3379		4266
3380	=back	4267	=back
3381		4268
3382	=back	4269	=back
3383		4270
3384	Example: Define a class with an IO and idle watcher, start one of them in	4271	Example: Define a class with two I/O and idle watchers, start the I/O
3385	the constructor.	4272	watchers in the constructor.
3386		4273
3387	class myclass	4274	class myclass
3388	{	4275	{
3389	ev::io io ; void io_cb (ev::io &w, int revents);	4276	ev::io io ; void io_cb (ev::io &w, int revents);
		4277	ev::io io2 ; void io2_cb (ev::io &w, int revents);
3390	ev::idle idle; void idle_cb (ev::idle &w, int revents);	4278	ev::idle idle; void idle_cb (ev::idle &w, int revents);
3391		4279
3392	myclass (int fd)	4280	myclass (int fd)
3393	{	4281	{
3394	io .set <myclass, &myclass::io_cb > (this);	4282	io .set <myclass, &myclass::io_cb > (this);
		4283	io2 .set <myclass, &myclass::io2_cb > (this);
3395	idle.set <myclass, &myclass::idle_cb> (this);	4284	idle.set <myclass, &myclass::idle_cb> (this);
3396		4285
3397	io.start (fd, ev::READ);	4286	io.set (fd, ev::WRITE); // configure the watcher
		4287	io.start (); // start it whenever convenient
		4288
		4289	io2.start (fd, ev::READ); // set + start in one call
3398	}	4290	}
3399	};	4291	};
3400		4292
3401		4293
3402	=head1 OTHER LANGUAGE BINDINGS	4294	=head1 OTHER LANGUAGE BINDINGS
…		…
3441	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.	4333	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
3442		4334
3443	=item D	4335	=item D
3444		4336
3445	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	4337	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
3446	be found at L<http://proj.llucax.com.ar/wiki/evd>.	4338	be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>.
3447		4339
3448	=item Ocaml	4340	=item Ocaml
3449		4341
3450	Erkki Seppala has written Ocaml bindings for libev, to be found at	4342	Erkki Seppala has written Ocaml bindings for libev, to be found at
3451	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	4343	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3452		4344
3453	=item Lua	4345	=item Lua
3454		4346
3455	Brian Maher has written a partial interface to libev	4347	Brian Maher has written a partial interface to libev for lua (at the
3456	for lua (only C<ev_io> and C<ev_timer>), to be found at	4348	time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3457	L<http://github.com/brimworks/lua-ev>.	4349	L<http://github.com/brimworks/lua-ev>.
		4350
		4351	=item Javascript
		4352
		4353	Node.js (L<http://nodejs.org>) uses libev as the underlying event library.
		4354
		4355	=item Others
		4356
		4357	There are others, and I stopped counting.
3458		4358
3459	=back	4359	=back
3460		4360
3461		4361
3462	=head1 MACRO MAGIC	4362	=head1 MACRO MAGIC
…		…
3476	loop argument"). The C<EV_A> form is used when this is the sole argument,	4376	loop argument"). The C<EV_A> form is used when this is the sole argument,
3477	C<EV_A_> is used when other arguments are following. Example:	4377	C<EV_A_> is used when other arguments are following. Example:
3478		4378
3479	ev_unref (EV_A);	4379	ev_unref (EV_A);
3480	ev_timer_add (EV_A_ watcher);	4380	ev_timer_add (EV_A_ watcher);
3481	ev_loop (EV_A_ 0);	4381	ev_run (EV_A_ 0);
3482		4382
3483	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,	4383	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
3484	which is often provided by the following macro.	4384	which is often provided by the following macro.
3485		4385
3486	=item C<EV_P>, C<EV_P_>	4386	=item C<EV_P>, C<EV_P_>
…		…
3499	suitable for use with C<EV_A>.	4399	suitable for use with C<EV_A>.
3500		4400
3501	=item C<EV_DEFAULT>, C<EV_DEFAULT_>	4401	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
3502		4402
3503	Similar to the other two macros, this gives you the value of the default	4403	Similar to the other two macros, this gives you the value of the default
3504	loop, if multiple loops are supported ("ev loop default").	4404	loop, if multiple loops are supported ("ev loop default"). The default loop
		4405	will be initialised if it isn't already initialised.
		4406
		4407	For non-multiplicity builds, these macros do nothing, so you always have
		4408	to initialise the loop somewhere.
3505		4409
3506	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>	4410	=item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_>
3507		4411
3508	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the	4412	Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the
3509	default loop has been initialised (C<UC> == unchecked). Their behaviour	4413	default loop has been initialised (C<UC> == unchecked). Their behaviour
…		…
3526	}	4430	}
3527		4431
3528	ev_check check;	4432	ev_check check;
3529	ev_check_init (&check, check_cb);	4433	ev_check_init (&check, check_cb);
3530	ev_check_start (EV_DEFAULT_ &check);	4434	ev_check_start (EV_DEFAULT_ &check);
3531	ev_loop (EV_DEFAULT_ 0);	4435	ev_run (EV_DEFAULT_ 0);
3532		4436
3533	=head1 EMBEDDING	4437	=head1 EMBEDDING
3534		4438
3535	Libev can (and often is) directly embedded into host	4439	Libev can (and often is) directly embedded into host
3536	applications. Examples of applications that embed it include the Deliantra	4440	applications. Examples of applications that embed it include the Deliantra
…		…
3576	ev_vars.h	4480	ev_vars.h
3577	ev_wrap.h	4481	ev_wrap.h
3578		4482
3579	ev_win32.c required on win32 platforms only	4483	ev_win32.c required on win32 platforms only
3580		4484
3581	ev_select.c only when select backend is enabled (which is enabled by default)	4485	ev_select.c only when select backend is enabled
3582	ev_poll.c only when poll backend is enabled (disabled by default)	4486	ev_poll.c only when poll backend is enabled
3583	ev_epoll.c only when the epoll backend is enabled (disabled by default)	4487	ev_epoll.c only when the epoll backend is enabled
		4488	ev_linuxaio.c only when the linux aio backend is enabled
		4489	ev_iouring.c only when the linux io_uring backend is enabled
3584	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	4490	ev_kqueue.c only when the kqueue backend is enabled
3585	ev_port.c only when the solaris port backend is enabled (disabled by default)	4491	ev_port.c only when the solaris port backend is enabled
3586		4492
3587	F<ev.c> includes the backend files directly when enabled, so you only need	4493	F<ev.c> includes the backend files directly when enabled, so you only need
3588	to compile this single file.	4494	to compile this single file.
3589		4495
3590	=head3 LIBEVENT COMPATIBILITY API	4496	=head3 LIBEVENT COMPATIBILITY API
…		…
3616	libev.m4	4522	libev.m4
3617		4523
3618	=head2 PREPROCESSOR SYMBOLS/MACROS	4524	=head2 PREPROCESSOR SYMBOLS/MACROS
3619		4525
3620	Libev can be configured via a variety of preprocessor symbols you have to	4526	Libev can be configured via a variety of preprocessor symbols you have to
3621	define before including any of its files. The default in the absence of	4527	define before including (or compiling) any of its files. The default in
3622	autoconf is documented for every option.	4528	the absence of autoconf is documented for every option.
		4529
		4530	Symbols marked with "(h)" do not change the ABI, and can have different
		4531	values when compiling libev vs. including F<ev.h>, so it is permissible
		4532	to redefine them before including F<ev.h> without breaking compatibility
		4533	to a compiled library. All other symbols change the ABI, which means all
		4534	users of libev and the libev code itself must be compiled with compatible
		4535	settings.
3623		4536
3624	=over 4	4537	=over 4
3625		4538
		4539	=item EV_COMPAT3 (h)
		4540
		4541	Backwards compatibility is a major concern for libev. This is why this
		4542	release of libev comes with wrappers for the functions and symbols that
		4543	have been renamed between libev version 3 and 4.
		4544
		4545	You can disable these wrappers (to test compatibility with future
		4546	versions) by defining C<EV_COMPAT3> to C<0> when compiling your
		4547	sources. This has the additional advantage that you can drop the C<struct>
		4548	from C<struct ev_loop> declarations, as libev will provide an C<ev_loop>
		4549	typedef in that case.
		4550
		4551	In some future version, the default for C<EV_COMPAT3> will become C<0>,
		4552	and in some even more future version the compatibility code will be
		4553	removed completely.
		4554
3626	=item EV_STANDALONE	4555	=item EV_STANDALONE (h)
3627		4556
3628	Must always be C<1> if you do not use autoconf configuration, which	4557	Must always be C<1> if you do not use autoconf configuration, which
3629	keeps libev from including F<config.h>, and it also defines dummy	4558	keeps libev from including F<config.h>, and it also defines dummy
3630	implementations for some libevent functions (such as logging, which is not	4559	implementations for some libevent functions (such as logging, which is not
3631	supported). It will also not define any of the structs usually found in	4560	supported). It will also not define any of the structs usually found in
3632	F<event.h> that are not directly supported by the libev core alone.	4561	F<event.h> that are not directly supported by the libev core alone.
3633		4562
3634	In standalone mode, libev will still try to automatically deduce the	4563	In standalone mode, libev will still try to automatically deduce the
3635	configuration, but has to be more conservative.	4564	configuration, but has to be more conservative.
		4565
		4566	=item EV_USE_FLOOR
		4567
		4568	If defined to be C<1>, libev will use the C<floor ()> function for its
		4569	periodic reschedule calculations, otherwise libev will fall back on a
		4570	portable (slower) implementation. If you enable this, you usually have to
		4571	link against libm or something equivalent. Enabling this when the C<floor>
		4572	function is not available will fail, so the safe default is to not enable
		4573	this.
3636		4574
3637	=item EV_USE_MONOTONIC	4575	=item EV_USE_MONOTONIC
3638		4576
3639	If defined to be C<1>, libev will try to detect the availability of the	4577	If defined to be C<1>, libev will try to detect the availability of the
3640	monotonic clock option at both compile time and runtime. Otherwise no	4578	monotonic clock option at both compile time and runtime. Otherwise no
…		…
3726	If programs implement their own fd to handle mapping on win32, then this	4664	If programs implement their own fd to handle mapping on win32, then this
3727	macro can be used to override the C<close> function, useful to unregister	4665	macro can be used to override the C<close> function, useful to unregister
3728	file descriptors again. Note that the replacement function has to close	4666	file descriptors again. Note that the replacement function has to close
3729	the underlying OS handle.	4667	the underlying OS handle.
3730		4668
		4669	=item EV_USE_WSASOCKET
		4670
		4671	If defined to be C<1>, libev will use C<WSASocket> to create its internal
		4672	communication socket, which works better in some environments. Otherwise,
		4673	the normal C<socket> function will be used, which works better in other
		4674	environments.
		4675
3731	=item EV_USE_POLL	4676	=item EV_USE_POLL
3732		4677
3733	If defined to be C<1>, libev will compile in support for the C<poll>(2)	4678	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3734	backend. Otherwise it will be enabled on non-win32 platforms. It	4679	backend. Otherwise it will be enabled on non-win32 platforms. It
3735	takes precedence over select.	4680	takes precedence over select.
…		…
3739	If defined to be C<1>, libev will compile in support for the Linux	4684	If defined to be C<1>, libev will compile in support for the Linux
3740	C<epoll>(7) backend. Its availability will be detected at runtime,	4685	C<epoll>(7) backend. Its availability will be detected at runtime,
3741	otherwise another method will be used as fallback. This is the preferred	4686	otherwise another method will be used as fallback. This is the preferred
3742	backend for GNU/Linux systems. If undefined, it will be enabled if the	4687	backend for GNU/Linux systems. If undefined, it will be enabled if the
3743	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4688	headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
		4689
		4690	=item EV_USE_LINUXAIO
		4691
		4692	If defined to be C<1>, libev will compile in support for the Linux aio
		4693	backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be
		4694	enabled on linux, otherwise disabled.
		4695
		4696	=item EV_USE_IOURING
		4697
		4698	If defined to be C<1>, libev will compile in support for the Linux
		4699	io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's
		4700	current limitations it has to be requested explicitly. If undefined, it
		4701	will be enabled on linux, otherwise disabled.
3744		4702
3745	=item EV_USE_KQUEUE	4703	=item EV_USE_KQUEUE
3746		4704
3747	If defined to be C<1>, libev will compile in support for the BSD style	4705	If defined to be C<1>, libev will compile in support for the BSD style
3748	C<kqueue>(2) backend. Its actual availability will be detected at runtime,	4706	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
…		…
3770	If defined to be C<1>, libev will compile in support for the Linux inotify	4728	If defined to be C<1>, libev will compile in support for the Linux inotify
3771	interface to speed up C<ev_stat> watchers. Its actual availability will	4729	interface to speed up C<ev_stat> watchers. Its actual availability will
3772	be detected at runtime. If undefined, it will be enabled if the headers	4730	be detected at runtime. If undefined, it will be enabled if the headers
3773	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.	4731	indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
3774		4732
		4733	=item EV_NO_SMP
		4734
		4735	If defined to be C<1>, libev will assume that memory is always coherent
		4736	between threads, that is, threads can be used, but threads never run on
		4737	different cpus (or different cpu cores). This reduces dependencies
		4738	and makes libev faster.
		4739
		4740	=item EV_NO_THREADS
		4741
		4742	If defined to be C<1>, libev will assume that it will never be called from
		4743	different threads (that includes signal handlers), which is a stronger
		4744	assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes
		4745	libev faster.
		4746
3775	=item EV_ATOMIC_T	4747	=item EV_ATOMIC_T
3776		4748
3777	Libev requires an integer type (suitable for storing C<0> or C<1>) whose	4749	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
3778	access is atomic with respect to other threads or signal contexts. No such	4750	access is atomic with respect to other threads or signal contexts. No
3779	type is easily found in the C language, so you can provide your own type	4751	such type is easily found in the C language, so you can provide your own
3780	that you know is safe for your purposes. It is used both for signal handler "locking"	4752	type that you know is safe for your purposes. It is used both for signal
3781	as well as for signal and thread safety in C<ev_async> watchers.	4753	handler "locking" as well as for signal and thread safety in C<ev_async>
		4754	watchers.
3782		4755
3783	In the absence of this define, libev will use C<sig_atomic_t volatile>	4756	In the absence of this define, libev will use C<sig_atomic_t volatile>
3784	(from F<signal.h>), which is usually good enough on most platforms.	4757	(from F<signal.h>), which is usually good enough on most platforms.
3785		4758
3786	=item EV_H	4759	=item EV_H (h)
3787		4760
3788	The name of the F<ev.h> header file used to include it. The default if	4761	The name of the F<ev.h> header file used to include it. The default if
3789	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be	4762	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3790	used to virtually rename the F<ev.h> header file in case of conflicts.	4763	used to virtually rename the F<ev.h> header file in case of conflicts.
3791		4764
3792	=item EV_CONFIG_H	4765	=item EV_CONFIG_H (h)
3793		4766
3794	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	4767	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3795	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	4768	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3796	C<EV_H>, above.	4769	C<EV_H>, above.
3797		4770
3798	=item EV_EVENT_H	4771	=item EV_EVENT_H (h)
3799		4772
3800	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	4773	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3801	of how the F<event.h> header can be found, the default is C<"event.h">.	4774	of how the F<event.h> header can be found, the default is C<"event.h">.
3802		4775
3803	=item EV_PROTOTYPES	4776	=item EV_PROTOTYPES (h)
3804		4777
3805	If defined to be C<0>, then F<ev.h> will not define any function	4778	If defined to be C<0>, then F<ev.h> will not define any function
3806	prototypes, but still define all the structs and other symbols. This is	4779	prototypes, but still define all the structs and other symbols. This is
3807	occasionally useful if you want to provide your own wrapper functions	4780	occasionally useful if you want to provide your own wrapper functions
3808	around libev functions.	4781	around libev functions.
…		…
3813	will have the C<struct ev_loop *> as first argument, and you can create	4786	will have the C<struct ev_loop *> as first argument, and you can create
3814	additional independent event loops. Otherwise there will be no support	4787	additional independent event loops. Otherwise there will be no support
3815	for multiple event loops and there is no first event loop pointer	4788	for multiple event loops and there is no first event loop pointer
3816	argument. Instead, all functions act on the single default loop.	4789	argument. Instead, all functions act on the single default loop.
3817		4790
		4791	Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a
		4792	default loop when multiplicity is switched off - you always have to
		4793	initialise the loop manually in this case.
		4794
3818	=item EV_MINPRI	4795	=item EV_MINPRI
3819		4796
3820	=item EV_MAXPRI	4797	=item EV_MAXPRI
3821		4798
3822	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to	4799	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
…		…
3830	fine.	4807	fine.
3831		4808
3832	If your embedding application does not need any priorities, defining these	4809	If your embedding application does not need any priorities, defining these
3833	both to C<0> will save some memory and CPU.	4810	both to C<0> will save some memory and CPU.
3834		4811
3835	=item EV_PERIODIC_ENABLE	4812	=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
		4813	EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
		4814	EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3836		4815
3837	If undefined or defined to be C<1>, then periodic timers are supported. If	4816	If undefined or defined to be C<1> (and the platform supports it), then
3838	defined to be C<0>, then they are not. Disabling them saves a few kB of	4817	the respective watcher type is supported. If defined to be C<0>, then it
3839	code.	4818	is not. Disabling watcher types mainly saves code size.
3840		4819
3841	=item EV_IDLE_ENABLE	4820	=item EV_FEATURES
3842
3843	If undefined or defined to be C<1>, then idle watchers are supported. If
3844	defined to be C<0>, then they are not. Disabling them saves a few kB of
3845	code.
3846
3847	=item EV_EMBED_ENABLE
3848
3849	If undefined or defined to be C<1>, then embed watchers are supported. If
3850	defined to be C<0>, then they are not. Embed watchers rely on most other
3851	watcher types, which therefore must not be disabled.
3852
3853	=item EV_STAT_ENABLE
3854
3855	If undefined or defined to be C<1>, then stat watchers are supported. If
3856	defined to be C<0>, then they are not.
3857
3858	=item EV_FORK_ENABLE
3859
3860	If undefined or defined to be C<1>, then fork watchers are supported. If
3861	defined to be C<0>, then they are not.
3862
3863	=item EV_ASYNC_ENABLE
3864
3865	If undefined or defined to be C<1>, then async watchers are supported. If
3866	defined to be C<0>, then they are not.
3867
3868	=item EV_MINIMAL
3869		4821
3870	If you need to shave off some kilobytes of code at the expense of some	4822	If you need to shave off some kilobytes of code at the expense of some
3871	speed (but with the full API), define this symbol to C<1>. Currently this	4823	speed (but with the full API), you can define this symbol to request
3872	is used to override some inlining decisions, saves roughly 30% code size	4824	certain subsets of functionality. The default is to enable all features
3873	on amd64. It also selects a much smaller 2-heap for timer management over	4825	that can be enabled on the platform.
3874	the default 4-heap.
3875		4826
3876	You can save even more by disabling watcher types you do not need	4827	A typical way to use this symbol is to define it to C<0> (or to a bitset
3877	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>	4828	with some broad features you want) and then selectively re-enable
3878	(C<-DNDEBUG>) will usually reduce code size a lot.	4829	additional parts you want, for example if you want everything minimal,
		4830	but multiple event loop support, async and child watchers and the poll
		4831	backend, use this:
3879		4832
3880	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to	4833	#define EV_FEATURES 0
3881	provide a bare-bones event library. See C<ev.h> for details on what parts	4834	#define EV_MULTIPLICITY 1
3882	of the API are still available, and do not complain if this subset changes	4835	#define EV_USE_POLL 1
3883	over time.	4836	#define EV_CHILD_ENABLE 1
		4837	#define EV_ASYNC_ENABLE 1
		4838
		4839	The actual value is a bitset, it can be a combination of the following
		4840	values (by default, all of these are enabled):
		4841
		4842	=over 4
		4843
		4844	=item C<1> - faster/larger code
		4845
		4846	Use larger code to speed up some operations.
		4847
		4848	Currently this is used to override some inlining decisions (enlarging the
		4849	code size by roughly 30% on amd64).
		4850
		4851	When optimising for size, use of compiler flags such as C<-Os> with
		4852	gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
		4853	assertions.
		4854
		4855	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4856	(e.g. gcc with C<-Os>).
		4857
		4858	=item C<2> - faster/larger data structures
		4859
		4860	Replaces the small 2-heap for timer management by a faster 4-heap, larger
		4861	hash table sizes and so on. This will usually further increase code size
		4862	and can additionally have an effect on the size of data structures at
		4863	runtime.
		4864
		4865	The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler
		4866	(e.g. gcc with C<-Os>).
		4867
		4868	=item C<4> - full API configuration
		4869
		4870	This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
		4871	enables multiplicity (C<EV_MULTIPLICITY>=1).
		4872
		4873	=item C<8> - full API
		4874
		4875	This enables a lot of the "lesser used" API functions. See C<ev.h> for
		4876	details on which parts of the API are still available without this
		4877	feature, and do not complain if this subset changes over time.
		4878
		4879	=item C<16> - enable all optional watcher types
		4880
		4881	Enables all optional watcher types. If you want to selectively enable
		4882	only some watcher types other than I/O and timers (e.g. prepare,
		4883	embed, async, child...) you can enable them manually by defining
		4884	C<EV_watchertype_ENABLE> to C<1> instead.
		4885
		4886	=item C<32> - enable all backends
		4887
		4888	This enables all backends - without this feature, you need to enable at
		4889	least one backend manually (C<EV_USE_SELECT> is a good choice).
		4890
		4891	=item C<64> - enable OS-specific "helper" APIs
		4892
		4893	Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
		4894	default.
		4895
		4896	=back
		4897
		4898	Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
		4899	reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
		4900	code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
		4901	watchers, timers and monotonic clock support.
		4902
		4903	With an intelligent-enough linker (gcc+binutils are intelligent enough
		4904	when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
		4905	your program might be left out as well - a binary starting a timer and an
		4906	I/O watcher then might come out at only 5Kb.
		4907
		4908	=item EV_API_STATIC
		4909
		4910	If this symbol is defined (by default it is not), then all identifiers
		4911	will have static linkage. This means that libev will not export any
		4912	identifiers, and you cannot link against libev anymore. This can be useful
		4913	when you embed libev, only want to use libev functions in a single file,
		4914	and do not want its identifiers to be visible.
		4915
		4916	To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that
		4917	wants to use libev.
		4918
		4919	This option only works when libev is compiled with a C compiler, as C++
		4920	doesn't support the required declaration syntax.
		4921
		4922	=item EV_AVOID_STDIO
		4923
		4924	If this is set to C<1> at compiletime, then libev will avoid using stdio
		4925	functions (printf, scanf, perror etc.). This will increase the code size
		4926	somewhat, but if your program doesn't otherwise depend on stdio and your
		4927	libc allows it, this avoids linking in the stdio library which is quite
		4928	big.
		4929
		4930	Note that error messages might become less precise when this option is
		4931	enabled.
3884		4932
3885	=item EV_NSIG	4933	=item EV_NSIG
3886		4934
3887	The highest supported signal number, +1 (or, the number of	4935	The highest supported signal number, +1 (or, the number of
3888	signals): Normally, libev tries to deduce the maximum number of signals	4936	signals): Normally, libev tries to deduce the maximum number of signals
3889	automatically, but sometimes this fails, in which case it can be	4937	automatically, but sometimes this fails, in which case it can be
3890	specified. Also, using a lower number than detected (C<32> should be	4938	specified. Also, using a lower number than detected (C<32> should be
3891	good for about any system in existance) can save some memory, as libev	4939	good for about any system in existence) can save some memory, as libev
3892	statically allocates some 12-24 bytes per signal number.	4940	statically allocates some 12-24 bytes per signal number.
3893		4941
3894	=item EV_PID_HASHSIZE	4942	=item EV_PID_HASHSIZE
3895		4943
3896	C<ev_child> watchers use a small hash table to distribute workload by	4944	C<ev_child> watchers use a small hash table to distribute workload by
3897	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	4945	pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3898	than enough. If you need to manage thousands of children you might want to	4946	usually more than enough. If you need to manage thousands of children you
3899	increase this value (I<must> be a power of two).	4947	might want to increase this value (I<must> be a power of two).
3900		4948
3901	=item EV_INOTIFY_HASHSIZE	4949	=item EV_INOTIFY_HASHSIZE
3902		4950
3903	C<ev_stat> watchers use a small hash table to distribute workload by	4951	C<ev_stat> watchers use a small hash table to distribute workload by
3904	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	4952	inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3905	usually more than enough. If you need to manage thousands of C<ev_stat>	4953	disabled), usually more than enough. If you need to manage thousands of
3906	watchers you might want to increase this value (I<must> be a power of	4954	C<ev_stat> watchers you might want to increase this value (I<must> be a
3907	two).	4955	power of two).
3908		4956
3909	=item EV_USE_4HEAP	4957	=item EV_USE_4HEAP
3910		4958
3911	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4959	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3912	timer and periodics heaps, libev uses a 4-heap when this symbol is defined	4960	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3913	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably	4961	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3914	faster performance with many (thousands) of watchers.	4962	faster performance with many (thousands) of watchers.
3915		4963
3916	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4964	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3917	(disabled).	4965	will be C<0>.
3918		4966
3919	=item EV_HEAP_CACHE_AT	4967	=item EV_HEAP_CACHE_AT
3920		4968
3921	Heaps are not very cache-efficient. To improve the cache-efficiency of the	4969	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3922	timer and periodics heaps, libev can cache the timestamp (I<at>) within	4970	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3923	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	4971	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3924	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	4972	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3925	but avoids random read accesses on heap changes. This improves performance	4973	but avoids random read accesses on heap changes. This improves performance
3926	noticeably with many (hundreds) of watchers.	4974	noticeably with many (hundreds) of watchers.
3927		4975
3928	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	4976	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3929	(disabled).	4977	will be C<0>.
3930		4978
3931	=item EV_VERIFY	4979	=item EV_VERIFY
3932		4980
3933	Controls how much internal verification (see C<ev_loop_verify ()>) will	4981	Controls how much internal verification (see C<ev_verify ()>) will
3934	be done: If set to C<0>, no internal verification code will be compiled	4982	be done: If set to C<0>, no internal verification code will be compiled
3935	in. If set to C<1>, then verification code will be compiled in, but not	4983	in. If set to C<1>, then verification code will be compiled in, but not
3936	called. If set to C<2>, then the internal verification code will be	4984	called. If set to C<2>, then the internal verification code will be
3937	called once per loop, which can slow down libev. If set to C<3>, then the	4985	called once per loop, which can slow down libev. If set to C<3>, then the
3938	verification code will be called very frequently, which will slow down	4986	verification code will be called very frequently, which will slow down
3939	libev considerably.	4987	libev considerably.
3940		4988
		4989	Verification errors are reported via C's C<assert> mechanism, so if you
		4990	disable that (e.g. by defining C<NDEBUG>) then no errors will be reported.
		4991
3941	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	4992	The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3942	C<0>.	4993	will be C<0>.
3943		4994
3944	=item EV_COMMON	4995	=item EV_COMMON
3945		4996
3946	By default, all watchers have a C<void *data> member. By redefining	4997	By default, all watchers have a C<void *data> member. By redefining
3947	this macro to a something else you can include more and other types of	4998	this macro to something else you can include more and other types of
3948	members. You have to define it each time you include one of the files,	4999	members. You have to define it each time you include one of the files,
3949	though, and it must be identical each time.	5000	though, and it must be identical each time.
3950		5001
3951	For example, the perl EV module uses something like this:	5002	For example, the perl EV module uses something like this:
3952		5003
…		…
4005	file.	5056	file.
4006		5057
4007	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	5058	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4008	that everybody includes and which overrides some configure choices:	5059	that everybody includes and which overrides some configure choices:
4009		5060
4010	#define EV_MINIMAL 1	5061	#define EV_FEATURES 8
4011	#define EV_USE_POLL 0	5062	#define EV_USE_SELECT 1
4012	#define EV_MULTIPLICITY 0
4013	#define EV_PERIODIC_ENABLE 0	5063	#define EV_PREPARE_ENABLE 1
		5064	#define EV_IDLE_ENABLE 1
4014	#define EV_STAT_ENABLE 0	5065	#define EV_SIGNAL_ENABLE 1
4015	#define EV_FORK_ENABLE 0	5066	#define EV_CHILD_ENABLE 1
		5067	#define EV_USE_STDEXCEPT 0
4016	#define EV_CONFIG_H <config.h>	5068	#define EV_CONFIG_H <config.h>
4017	#define EV_MINPRI 0
4018	#define EV_MAXPRI 0
4019		5069
4020	#include "ev++.h"	5070	#include "ev++.h"
4021		5071
4022	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	5072	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4023		5073
4024	#include "ev_cpp.h"	5074	#include "ev_cpp.h"
4025	#include "ev.c"	5075	#include "ev.c"
4026		5076
4027	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES	5077	=head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT
4028		5078
4029	=head2 THREADS AND COROUTINES	5079	=head2 THREADS AND COROUTINES
4030		5080
4031	=head3 THREADS	5081	=head3 THREADS
4032		5082
…		…
4083	default loop and triggering an C<ev_async> watcher from the default loop	5133	default loop and triggering an C<ev_async> watcher from the default loop
4084	watcher callback into the event loop interested in the signal.	5134	watcher callback into the event loop interested in the signal.
4085		5135
4086	=back	5136	=back
4087		5137
4088	=head4 THREAD LOCKING EXAMPLE	5138	See also L</THREAD LOCKING EXAMPLE>.
4089
4090	Here is a fictitious example of how to run an event loop in a different
4091	thread than where callbacks are being invoked and watchers are
4092	created/added/removed.
4093
4094	For a real-world example, see the C<EV::Loop::Async> perl module,
4095	which uses exactly this technique (which is suited for many high-level
4096	languages).
4097
4098	The example uses a pthread mutex to protect the loop data, a condition
4099	variable to wait for callback invocations, an async watcher to notify the
4100	event loop thread and an unspecified mechanism to wake up the main thread.
4101
4102	First, you need to associate some data with the event loop:
4103
4104	typedef struct {
4105	mutex_t lock; /* global loop lock */
4106	ev_async async_w;
4107	thread_t tid;
4108	cond_t invoke_cv;
4109	} userdata;
4110
4111	void prepare_loop (EV_P)
4112	{
4113	// for simplicity, we use a static userdata struct.
4114	static userdata u;
4115
4116	ev_async_init (&u->async_w, async_cb);
4117	ev_async_start (EV_A_ &u->async_w);
4118
4119	pthread_mutex_init (&u->lock, 0);
4120	pthread_cond_init (&u->invoke_cv, 0);
4121
4122	// now associate this with the loop
4123	ev_set_userdata (EV_A_ u);
4124	ev_set_invoke_pending_cb (EV_A_ l_invoke);
4125	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
4126
4127	// then create the thread running ev_loop
4128	pthread_create (&u->tid, 0, l_run, EV_A);
4129	}
4130
4131	The callback for the C<ev_async> watcher does nothing: the watcher is used
4132	solely to wake up the event loop so it takes notice of any new watchers
4133	that might have been added:
4134
4135	static void
4136	async_cb (EV_P_ ev_async *w, int revents)
4137	{
4138	// just used for the side effects
4139	}
4140
4141	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
4142	protecting the loop data, respectively.
4143
4144	static void
4145	l_release (EV_P)
4146	{
4147	userdata *u = ev_userdata (EV_A);
4148	pthread_mutex_unlock (&u->lock);
4149	}
4150
4151	static void
4152	l_acquire (EV_P)
4153	{
4154	userdata *u = ev_userdata (EV_A);
4155	pthread_mutex_lock (&u->lock);
4156	}
4157
4158	The event loop thread first acquires the mutex, and then jumps straight
4159	into C<ev_loop>:
4160
4161	void *
4162	l_run (void *thr_arg)
4163	{
4164	struct ev_loop *loop = (struct ev_loop *)thr_arg;
4165
4166	l_acquire (EV_A);
4167	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
4168	ev_loop (EV_A_ 0);
4169	l_release (EV_A);
4170
4171	return 0;
4172	}
4173
4174	Instead of invoking all pending watchers, the C<l_invoke> callback will
4175	signal the main thread via some unspecified mechanism (signals? pipe
4176	writes? C<Async::Interrupt>?) and then waits until all pending watchers
4177	have been called (in a while loop because a) spurious wakeups are possible
4178	and b) skipping inter-thread-communication when there are no pending
4179	watchers is very beneficial):
4180
4181	static void
4182	l_invoke (EV_P)
4183	{
4184	userdata *u = ev_userdata (EV_A);
4185
4186	while (ev_pending_count (EV_A))
4187	{
4188	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
4189	pthread_cond_wait (&u->invoke_cv, &u->lock);
4190	}
4191	}
4192
4193	Now, whenever the main thread gets told to invoke pending watchers, it
4194	will grab the lock, call C<ev_invoke_pending> and then signal the loop
4195	thread to continue:
4196
4197	static void
4198	real_invoke_pending (EV_P)
4199	{
4200	userdata *u = ev_userdata (EV_A);
4201
4202	pthread_mutex_lock (&u->lock);
4203	ev_invoke_pending (EV_A);
4204	pthread_cond_signal (&u->invoke_cv);
4205	pthread_mutex_unlock (&u->lock);
4206	}
4207
4208	Whenever you want to start/stop a watcher or do other modifications to an
4209	event loop, you will now have to lock:
4210
4211	ev_timer timeout_watcher;
4212	userdata *u = ev_userdata (EV_A);
4213
4214	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
4215
4216	pthread_mutex_lock (&u->lock);
4217	ev_timer_start (EV_A_ &timeout_watcher);
4218	ev_async_send (EV_A_ &u->async_w);
4219	pthread_mutex_unlock (&u->lock);
4220
4221	Note that sending the C<ev_async> watcher is required because otherwise
4222	an event loop currently blocking in the kernel will have no knowledge
4223	about the newly added timer. By waking up the loop it will pick up any new
4224	watchers in the next event loop iteration.
4225		5139
4226	=head3 COROUTINES	5140	=head3 COROUTINES
4227		5141
4228	Libev is very accommodating to coroutines ("cooperative threads"):	5142	Libev is very accommodating to coroutines ("cooperative threads"):
4229	libev fully supports nesting calls to its functions from different	5143	libev fully supports nesting calls to its functions from different
4230	coroutines (e.g. you can call C<ev_loop> on the same loop from two	5144	coroutines (e.g. you can call C<ev_run> on the same loop from two
4231	different coroutines, and switch freely between both coroutines running	5145	different coroutines, and switch freely between both coroutines running
4232	the loop, as long as you don't confuse yourself). The only exception is	5146	the loop, as long as you don't confuse yourself). The only exception is
4233	that you must not do this from C<ev_periodic> reschedule callbacks.	5147	that you must not do this from C<ev_periodic> reschedule callbacks.
4234		5148
4235	Care has been taken to ensure that libev does not keep local state inside	5149	Care has been taken to ensure that libev does not keep local state inside
4236	C<ev_loop>, and other calls do not usually allow for coroutine switches as	5150	C<ev_run>, and other calls do not usually allow for coroutine switches as
4237	they do not call any callbacks.	5151	they do not call any callbacks.
4238		5152
4239	=head2 COMPILER WARNINGS	5153	=head2 COMPILER WARNINGS
4240		5154
4241	Depending on your compiler and compiler settings, you might get no or a	5155	Depending on your compiler and compiler settings, you might get no or a
…		…
4252	maintainable.	5166	maintainable.
4253		5167
4254	And of course, some compiler warnings are just plain stupid, or simply	5168	And of course, some compiler warnings are just plain stupid, or simply
4255	wrong (because they don't actually warn about the condition their message	5169	wrong (because they don't actually warn about the condition their message
4256	seems to warn about). For example, certain older gcc versions had some	5170	seems to warn about). For example, certain older gcc versions had some
4257	warnings that resulted an extreme number of false positives. These have	5171	warnings that resulted in an extreme number of false positives. These have
4258	been fixed, but some people still insist on making code warn-free with	5172	been fixed, but some people still insist on making code warn-free with
4259	such buggy versions.	5173	such buggy versions.
4260		5174
4261	While libev is written to generate as few warnings as possible,	5175	While libev is written to generate as few warnings as possible,
4262	"warn-free" code is not a goal, and it is recommended not to build libev	5176	"warn-free" code is not a goal, and it is recommended not to build libev
…		…
4298	I suggest using suppression lists.	5212	I suggest using suppression lists.
4299		5213
4300		5214
4301	=head1 PORTABILITY NOTES	5215	=head1 PORTABILITY NOTES
4302		5216
		5217	=head2 GNU/LINUX 32 BIT LIMITATIONS
		5218
		5219	GNU/Linux is the only common platform that supports 64 bit file/large file
		5220	interfaces but I<disables> them by default.
		5221
		5222	That means that libev compiled in the default environment doesn't support
		5223	files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
		5224
		5225	Unfortunately, many programs try to work around this GNU/Linux issue
		5226	by enabling the large file API, which makes them incompatible with the
		5227	standard libev compiled for their system.
		5228
		5229	Likewise, libev cannot enable the large file API itself as this would
		5230	suddenly make it incompatible to the default compile time environment,
		5231	i.e. all programs not using special compile switches.
		5232
		5233	=head2 OS/X AND DARWIN BUGS
		5234
		5235	The whole thing is a bug if you ask me - basically any system interface
		5236	you touch is broken, whether it is locales, poll, kqueue or even the
		5237	OpenGL drivers.
		5238
		5239	=head3 C<kqueue> is buggy
		5240
		5241	The kqueue syscall is broken in all known versions - most versions support
		5242	only sockets, many support pipes.
		5243
		5244	Libev tries to work around this by not using C<kqueue> by default on this
		5245	rotten platform, but of course you can still ask for it when creating a
		5246	loop - embedding a socket-only kqueue loop into a select-based one is
		5247	probably going to work well.
		5248
		5249	=head3 C<poll> is buggy
		5250
		5251	Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
		5252	implementation by something calling C<kqueue> internally around the 10.5.6
		5253	release, so now C<kqueue> I<and> C<poll> are broken.
		5254
		5255	Libev tries to work around this by not using C<poll> by default on
		5256	this rotten platform, but of course you can still ask for it when creating
		5257	a loop.
		5258
		5259	=head3 C<select> is buggy
		5260
		5261	All that's left is C<select>, and of course Apple found a way to fuck this
		5262	one up as well: On OS/X, C<select> actively limits the number of file
		5263	descriptors you can pass in to 1024 - your program suddenly crashes when
		5264	you use more.
		5265
		5266	There is an undocumented "workaround" for this - defining
		5267	C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
		5268	work on OS/X.
		5269
		5270	=head2 SOLARIS PROBLEMS AND WORKAROUNDS
		5271
		5272	=head3 C<errno> reentrancy
		5273
		5274	The default compile environment on Solaris is unfortunately so
		5275	thread-unsafe that you can't even use components/libraries compiled
		5276	without C<-D_REENTRANT> in a threaded program, which, of course, isn't
		5277	defined by default. A valid, if stupid, implementation choice.
		5278
		5279	If you want to use libev in threaded environments you have to make sure
		5280	it's compiled with C<_REENTRANT> defined.
		5281
		5282	=head3 Event port backend
		5283
		5284	The scalable event interface for Solaris is called "event
		5285	ports". Unfortunately, this mechanism is very buggy in all major
		5286	releases. If you run into high CPU usage, your program freezes or you get
		5287	a large number of spurious wakeups, make sure you have all the relevant
		5288	and latest kernel patches applied. No, I don't know which ones, but there
		5289	are multiple ones to apply, and afterwards, event ports actually work
		5290	great.
		5291
		5292	If you can't get it to work, you can try running the program by setting
		5293	the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
		5294	C<select> backends.
		5295
		5296	=head2 AIX POLL BUG
		5297
		5298	AIX unfortunately has a broken C<poll.h> header. Libev works around
		5299	this by trying to avoid the poll backend altogether (i.e. it's not even
		5300	compiled in), which normally isn't a big problem as C<select> works fine
		5301	with large bitsets on AIX, and AIX is dead anyway.
		5302
4303	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	5303	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
		5304
		5305	=head3 General issues
4304		5306
4305	Win32 doesn't support any of the standards (e.g. POSIX) that libev	5307	Win32 doesn't support any of the standards (e.g. POSIX) that libev
4306	requires, and its I/O model is fundamentally incompatible with the POSIX	5308	requires, and its I/O model is fundamentally incompatible with the POSIX
4307	model. Libev still offers limited functionality on this platform in	5309	model. Libev still offers limited functionality on this platform in
4308	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	5310	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4309	descriptors. This only applies when using Win32 natively, not when using	5311	descriptors. This only applies when using Win32 natively, not when using
4310	e.g. cygwin.	5312	e.g. cygwin. Actually, it only applies to the microsofts own compilers,
		5313	as every compiler comes with a slightly differently broken/incompatible
		5314	environment.
4311		5315
4312	Lifting these limitations would basically require the full	5316	Lifting these limitations would basically require the full
4313	re-implementation of the I/O system. If you are into these kinds of	5317	re-implementation of the I/O system. If you are into this kind of thing,
4314	things, then note that glib does exactly that for you in a very portable	5318	then note that glib does exactly that for you in a very portable way (note
4315	way (note also that glib is the slowest event library known to man).	5319	also that glib is the slowest event library known to man).
4316		5320
4317	There is no supported compilation method available on windows except	5321	There is no supported compilation method available on windows except
4318	embedding it into other applications.	5322	embedding it into other applications.
4319		5323
4320	Sensible signal handling is officially unsupported by Microsoft - libev	5324	Sensible signal handling is officially unsupported by Microsoft - libev
…		…
4348	you do I<not> compile the F<ev.c> or any other embedded source files!):	5352	you do I<not> compile the F<ev.c> or any other embedded source files!):
4349		5353
4350	#include "evwrap.h"	5354	#include "evwrap.h"
4351	#include "ev.c"	5355	#include "ev.c"
4352		5356
4353	=over 4
4354
4355	=item The winsocket select function	5357	=head3 The winsocket C<select> function
4356		5358
4357	The winsocket C<select> function doesn't follow POSIX in that it	5359	The winsocket C<select> function doesn't follow POSIX in that it
4358	requires socket I<handles> and not socket I<file descriptors> (it is	5360	requires socket I<handles> and not socket I<file descriptors> (it is
4359	also extremely buggy). This makes select very inefficient, and also	5361	also extremely buggy). This makes select very inefficient, and also
4360	requires a mapping from file descriptors to socket handles (the Microsoft	5362	requires a mapping from file descriptors to socket handles (the Microsoft
…		…
4369	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */	5371	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4370		5372
4371	Note that winsockets handling of fd sets is O(n), so you can easily get a	5373	Note that winsockets handling of fd sets is O(n), so you can easily get a
4372	complexity in the O(n²) range when using win32.	5374	complexity in the O(n²) range when using win32.
4373		5375
4374	=item Limited number of file descriptors	5376	=head3 Limited number of file descriptors
4375		5377
4376	Windows has numerous arbitrary (and low) limits on things.	5378	Windows has numerous arbitrary (and low) limits on things.
4377		5379
4378	Early versions of winsocket's select only supported waiting for a maximum	5380	Early versions of winsocket's select only supported waiting for a maximum
4379	of C<64> handles (probably owning to the fact that all windows kernels	5381	of C<64> handles (probably owning to the fact that all windows kernels
…		…
4394	runtime libraries. This might get you to about C<512> or C<2048> sockets	5396	runtime libraries. This might get you to about C<512> or C<2048> sockets
4395	(depending on windows version and/or the phase of the moon). To get more,	5397	(depending on windows version and/or the phase of the moon). To get more,
4396	you need to wrap all I/O functions and provide your own fd management, but	5398	you need to wrap all I/O functions and provide your own fd management, but
4397	the cost of calling select (O(n²)) will likely make this unworkable.	5399	the cost of calling select (O(n²)) will likely make this unworkable.
4398		5400
4399	=back
4400
4401	=head2 PORTABILITY REQUIREMENTS	5401	=head2 PORTABILITY REQUIREMENTS
4402		5402
4403	In addition to a working ISO-C implementation and of course the	5403	In addition to a working ISO-C implementation and of course the
4404	backend-specific APIs, libev relies on a few additional extensions:	5404	backend-specific APIs, libev relies on a few additional extensions:
4405		5405
…		…
4411	Libev assumes not only that all watcher pointers have the same internal	5411	Libev assumes not only that all watcher pointers have the same internal
4412	structure (guaranteed by POSIX but not by ISO C for example), but it also	5412	structure (guaranteed by POSIX but not by ISO C for example), but it also
4413	assumes that the same (machine) code can be used to call any watcher	5413	assumes that the same (machine) code can be used to call any watcher
4414	callback: The watcher callbacks have different type signatures, but libev	5414	callback: The watcher callbacks have different type signatures, but libev
4415	calls them using an C<ev_watcher *> internally.	5415	calls them using an C<ev_watcher *> internally.
		5416
		5417	=item null pointers and integer zero are represented by 0 bytes
		5418
		5419	Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and
		5420	relies on this setting pointers and integers to null.
		5421
		5422	=item pointer accesses must be thread-atomic
		5423
		5424	Accessing a pointer value must be atomic, it must both be readable and
		5425	writable in one piece - this is the case on all current architectures.
4416		5426
4417	=item C<sig_atomic_t volatile> must be thread-atomic as well	5427	=item C<sig_atomic_t volatile> must be thread-atomic as well
4418		5428
4419	The type C<sig_atomic_t volatile> (or whatever is defined as	5429	The type C<sig_atomic_t volatile> (or whatever is defined as
4420	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different	5430	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
…		…
4429	thread" or will block signals process-wide, both behaviours would	5439	thread" or will block signals process-wide, both behaviours would
4430	be compatible with libev. Interaction between C<sigprocmask> and	5440	be compatible with libev. Interaction between C<sigprocmask> and
4431	C<pthread_sigmask> could complicate things, however.	5441	C<pthread_sigmask> could complicate things, however.
4432		5442
4433	The most portable way to handle signals is to block signals in all threads	5443	The most portable way to handle signals is to block signals in all threads
4434	except the initial one, and run the default loop in the initial thread as	5444	except the initial one, and run the signal handling loop in the initial
4435	well.	5445	thread as well.
4436		5446
4437	=item C<long> must be large enough for common memory allocation sizes	5447	=item C<long> must be large enough for common memory allocation sizes
4438		5448
4439	To improve portability and simplify its API, libev uses C<long> internally	5449	To improve portability and simplify its API, libev uses C<long> internally
4440	instead of C<size_t> when allocating its data structures. On non-POSIX	5450	instead of C<size_t> when allocating its data structures. On non-POSIX
…		…
4443	watchers.	5453	watchers.
4444		5454
4445	=item C<double> must hold a time value in seconds with enough accuracy	5455	=item C<double> must hold a time value in seconds with enough accuracy
4446		5456
4447	The type C<double> is used to represent timestamps. It is required to	5457	The type C<double> is used to represent timestamps. It is required to
4448	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	5458	have at least 51 bits of mantissa (and 9 bits of exponent), which is
4449	enough for at least into the year 4000. This requirement is fulfilled by	5459	good enough for at least into the year 4000 with millisecond accuracy
		5460	(the design goal for libev). This requirement is overfulfilled by
4450	implementations implementing IEEE 754, which is basically all existing	5461	implementations using IEEE 754, which is basically all existing ones.
		5462
4451	ones. With IEEE 754 doubles, you get microsecond accuracy until at least	5463	With IEEE 754 doubles, you get microsecond accuracy until at least the
4452	2200.	5464	year 2255 (and millisecond accuracy till the year 287396 - by then, libev
		5465	is either obsolete or somebody patched it to use C<long double> or
		5466	something like that, just kidding).
4453		5467
4454	=back	5468	=back
4455		5469
4456	If you know of other additional requirements drop me a note.	5470	If you know of other additional requirements drop me a note.
4457		5471
…		…
4519	=item Processing ev_async_send: O(number_of_async_watchers)	5533	=item Processing ev_async_send: O(number_of_async_watchers)
4520		5534
4521	=item Processing signals: O(max_signal_number)	5535	=item Processing signals: O(max_signal_number)
4522		5536
4523	Sending involves a system call I<iff> there were no other C<ev_async_send>	5537	Sending involves a system call I<iff> there were no other C<ev_async_send>
4524	calls in the current loop iteration. Checking for async and signal events	5538	calls in the current loop iteration and the loop is currently
		5539	blocked. Checking for async and signal events involves iterating over all
4525	involves iterating over all running async watchers or all signal numbers.	5540	running async watchers or all signal numbers.
4526		5541
4527	=back	5542	=back
4528		5543
4529		5544
		5545	=head1 PORTING FROM LIBEV 3.X TO 4.X
		5546
		5547	The major version 4 introduced some incompatible changes to the API.
		5548
		5549	At the moment, the C<ev.h> header file provides compatibility definitions
		5550	for all changes, so most programs should still compile. The compatibility
		5551	layer might be removed in later versions of libev, so better update to the
		5552	new API early than late.
		5553
		5554	=over 4
		5555
		5556	=item C<EV_COMPAT3> backwards compatibility mechanism
		5557
		5558	The backward compatibility mechanism can be controlled by
		5559	C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING>
		5560	section.
		5561
		5562	=item C<ev_default_destroy> and C<ev_default_fork> have been removed
		5563
		5564	These calls can be replaced easily by their C<ev_loop_xxx> counterparts:
		5565
		5566	ev_loop_destroy (EV_DEFAULT_UC);
		5567	ev_loop_fork (EV_DEFAULT);
		5568
		5569	=item function/symbol renames
		5570
		5571	A number of functions and symbols have been renamed:
		5572
		5573	ev_loop => ev_run
		5574	EVLOOP_NONBLOCK => EVRUN_NOWAIT
		5575	EVLOOP_ONESHOT => EVRUN_ONCE
		5576
		5577	ev_unloop => ev_break
		5578	EVUNLOOP_CANCEL => EVBREAK_CANCEL
		5579	EVUNLOOP_ONE => EVBREAK_ONE
		5580	EVUNLOOP_ALL => EVBREAK_ALL
		5581
		5582	EV_TIMEOUT => EV_TIMER
		5583
		5584	ev_loop_count => ev_iteration
		5585	ev_loop_depth => ev_depth
		5586	ev_loop_verify => ev_verify
		5587
		5588	Most functions working on C<struct ev_loop> objects don't have an
		5589	C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and
		5590	associated constants have been renamed to not collide with the C<struct
		5591	ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme
		5592	as all other watcher types. Note that C<ev_loop_fork> is still called
		5593	C<ev_loop_fork> because it would otherwise clash with the C<ev_fork>
		5594	typedef.
		5595
		5596	=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
		5597
		5598	The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
		5599	mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
		5600	and work, but the library code will of course be larger.
		5601
		5602	=back
		5603
		5604
4530	=head1 GLOSSARY	5605	=head1 GLOSSARY
4531		5606
4532	=over 4	5607	=over 4
4533		5608
4534	=item active	5609	=item active
4535		5610
4536	A watcher is active as long as it has been started (has been attached to	5611	A watcher is active as long as it has been started and not yet stopped.
4537	an event loop) but not yet stopped (disassociated from the event loop).	5612	See L</WATCHER STATES> for details.
4538		5613
4539	=item application	5614	=item application
4540		5615
4541	In this document, an application is whatever is using libev.	5616	In this document, an application is whatever is using libev.
		5617
		5618	=item backend
		5619
		5620	The part of the code dealing with the operating system interfaces.
4542		5621
4543	=item callback	5622	=item callback
4544		5623
4545	The address of a function that is called when some event has been	5624	The address of a function that is called when some event has been
4546	detected. Callbacks are being passed the event loop, the watcher that	5625	detected. Callbacks are being passed the event loop, the watcher that
4547	received the event, and the actual event bitset.	5626	received the event, and the actual event bitset.
4548		5627
4549	=item callback invocation	5628	=item callback/watcher invocation
4550		5629
4551	The act of calling the callback associated with a watcher.	5630	The act of calling the callback associated with a watcher.
4552		5631
4553	=item event	5632	=item event
4554		5633
4555	A change of state of some external event, such as data now being available	5634	A change of state of some external event, such as data now being available
4556	for reading on a file descriptor, time having passed or simply not having	5635	for reading on a file descriptor, time having passed or simply not having
4557	any other events happening anymore.	5636	any other events happening anymore.
4558		5637
4559	In libev, events are represented as single bits (such as C<EV_READ> or	5638	In libev, events are represented as single bits (such as C<EV_READ> or
4560	C<EV_TIMEOUT>).	5639	C<EV_TIMER>).
4561		5640
4562	=item event library	5641	=item event library
4563		5642
4564	A software package implementing an event model and loop.	5643	A software package implementing an event model and loop.
4565		5644
…		…
4573	The model used to describe how an event loop handles and processes	5652	The model used to describe how an event loop handles and processes
4574	watchers and events.	5653	watchers and events.
4575		5654
4576	=item pending	5655	=item pending
4577		5656
4578	A watcher is pending as soon as the corresponding event has been detected,	5657	A watcher is pending as soon as the corresponding event has been
4579	and stops being pending as soon as the watcher will be invoked or its	5658	detected. See L</WATCHER STATES> for details.
4580	pending status is explicitly cleared by the application.
4581
4582	A watcher can be pending, but not active. Stopping a watcher also clears
4583	its pending status.
4584		5659
4585	=item real time	5660	=item real time
4586		5661
4587	The physical time that is observed. It is apparently strictly monotonic :)	5662	The physical time that is observed. It is apparently strictly monotonic :)
4588		5663
4589	=item wall-clock time	5664	=item wall-clock time
4590		5665
4591	The time and date as shown on clocks. Unlike real time, it can actually	5666	The time and date as shown on clocks. Unlike real time, it can actually
4592	be wrong and jump forwards and backwards, e.g. when the you adjust your	5667	be wrong and jump forwards and backwards, e.g. when you adjust your
4593	clock.	5668	clock.
4594		5669
4595	=item watcher	5670	=item watcher
4596		5671
4597	A data structure that describes interest in certain events. Watchers need	5672	A data structure that describes interest in certain events. Watchers need
4598	to be started (attached to an event loop) before they can receive events.	5673	to be started (attached to an event loop) before they can receive events.
4599		5674
4600	=item watcher invocation
4601
4602	The act of calling the callback associated with a watcher.
4603
4604	=back	5675	=back
4605		5676
4606	=head1 AUTHOR	5677	=head1 AUTHOR
4607		5678
4608	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.	5679	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael
		5680	Magnusson and Emanuele Giaquinta, and minor corrections by many others.
4609		5681

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